ammonia manual

389
Ammonia Plant Operating Manual 1 AMMONIA PLANT The ammonia plant has a capacity of 1100 MT per day of liquid anhydrous ammonia. After revamping the plant capacity raised to 1260 MT per day. The plant is a single stream unit, comprising of the following process steps. 1) Hydro fining of Naphtha based on IIP - IFP process. 2) Primary reforming of naphtha based on ICI process. 3) Secondary Reforming. 4) CO Conversion. 5) CO 2 removal by Giammarco-Vetrocoke process. 6) Methanation. 7) Ammonia synthesis is based on ICI process. 8) Ammonia Recovery and Storage. 9) Hydrogen Recovery from loop purge gas designed and supplied by Nippon Sanso K.K. In addition to the above, the ammonia plant has the following utilities integrated with it. 1) Tank farm for storing raw naphtha, sweet naphtha, fuel oil and high aromatic fuel naphtha. 2) Cooling tower. 3) Inert gas generation unit. 4) Auxiliary boiler and Additional Steam Generation Unit 5) Instrumentation system 6) Imported Ammonia Storage station. 7) Captive Power Plant.

Upload: ahmed

Post on 08-Apr-2016

1.175 views

Category:

Documents


165 download

DESCRIPTION

Ammonia Manual

TRANSCRIPT

Page 1: Ammonia Manual

Ammonia Plant Operating Manual 1

AMMONIA PLANT

The ammonia plant has a capacity of 1100 MT per day of liquid anhydrous ammonia. After revamping the plant capacity raised to 1260 MT per day. The plant is a single stream unit, comprising of the following process steps.

1) Hydro fining of Naphtha based on IIP - IFP process.

2) Primary reforming of naphtha based on ICI process.

3) Secondary Reforming.

4) CO Conversion.

5) CO2 removal by Giammarco-Vetrocoke process.

6) Methanation.

7) Ammonia synthesis is based on ICI process.

8) Ammonia Recovery and Storage.

9) Hydrogen Recovery from loop purge gas designed and supplied by Nippon Sanso K.K.

In addition to the above, the ammonia plant has the following utilities integrated with it.

1) Tank farm for storing raw naphtha, sweet naphtha, fuel oil and high aromatic fuel naphtha.

2) Cooling tower.

3) Inert gas generation unit.

4) Auxiliary boiler and Additional Steam Generation Unit

5) Instrumentation system

6) Imported Ammonia Storage station.

7) Captive Power Plant.

Page 2: Ammonia Manual

Ammonia Plant Operating Manual 2

CONTENTS

Chapter one DESIGN BASIS

Chapter two PROCESS DESCRIPTION

2 Principles of steam reforming

2.2 Carbon formation

2.3 Catalyst for reforming

2.4 Description of Reforming section

2.5 Description of Furnace and waste heat recovery system

2.6 Secondary reforming

2.7 Description of 106 ATA steam generating system

2.8 Conversion

2.9 CO2 removal

2.10 Methanation

2.11 Ammonia synthesis

2.12 Synloop - General

2.13 Synthesis loop

2.14 Casale insert cartridge converter layout

2.15 Refrigeration system

2.16 Ammonia recovery

2.17 Ammonia storage and Refrigeration

2.18 Process condensate system

2.19 Polished water and BFW system

2.20 Steam system

2.21 Nitrogen system

2.22 Instrument Air and Service Air system

2.23 Heavy water plant.

Chapter three STARTUP

Page 3: Ammonia Manual

Ammonia Plant Operating Manual 3

Preliminary Operations before start-up

Introduction

Preparation for start-up

Light primary reformer burners

Turn in steam

Reduce Primary reformer catalyst

Naphtha introduction

Introduction of Process Air

Put Methanator on line

Degassing of process condensate

Synthesis

Recovery

Naphtha Introduction after plant trip

Start Up Schedule

Chapter four BOILERS

Auxiliary Boiler (South) & (North)

General

Description

Trip system

Checks to be done before Light up

Filling up of the boiler

Making ready the burner system

Control room pre start up checks.

FD fan start up

Firing the boiler

Raising the pressure

Page 4: Ammonia Manual

Ammonia Plant Operating Manual 4

Operation checks during pressure raising

Shutting down of boilers

Emergency shut down

Normal Operation

Additional steam generating unit

Boiler specifications

Steam system

Steam system commissioning

Preparation for start up

Deaerator commissioning

Boiler feed water pump start up

Lining up BFW heater

Filling up the boiler

Make ready the burner system

FD fan start up

Regenerative Air Pre Heater

Boiler Start up

Raising the pressure

Operations checks while raising the pressure

Lining up steam

Boiler normal Shut down

Normal Operation

Drum Preheater

Chapter five PROCESS AIR COMPRESSOR

Outline of the Machine

Page 5: Ammonia Manual

Ammonia Plant Operating Manual 5

Start up procedure

Start-up and loading

Operation during emergency

Limitation of operating conditions for turbine compressor and others

Normal shut down

Chapter Six SYNTHESIS GAS COMPRESSOR, DRIVER,CIRCULATOR AND RECYCLE HYDROGEN BLEED

Outline of machine

Compressor

Turbine

Governor System

Anti Surge systems

Turbine Auxiliaries

Turbine accessories

Start up procedure

Compressor loading/lining up syn loop

Shut down

Trip actions

Chapter seven LOOP REFRIGERATION COMPRESSOR

Lube oil system

Seal oil system

Main Compressor

Main Turbine

Start up

Limitations for operations

Normal shut down procedure

Page 6: Ammonia Manual

Ammonia Plant Operating Manual 6

Emergency Shut down procedure

Chapter eight INERT GAS PLANT

Design

Description

Dissociator

Generator

Compressor

Deoxo Rector

After cooler

Humid drier

Start up procedure

Normal shut down procedure

Normal operation

Dissociation Catalyst Reduction

Chapter nine FLARE SYSTEM

Description

Lighting up procedure

Chapter Ten COOLING WATER PUMPS

Page 7: Ammonia Manual

Ammonia Plant Operating Manual 7

OGT 101 A Condensing turbine

Start-up procedure

Stopping up procedure

Normal running

Alarm and trip values

General

Back pressure turbine OGT 101 B

Start - up procedure

Stopping procedure

Normal running

Alarm / trip values

General

Chapter eleven HYDROFINING

Introduction

Fundamental reactions

Unit description

Start-up procedure

Normal shut down

Emergency shut down procedure

1431 decoking and 1101 catalyst regeneration

Page 8: Ammonia Manual

Ammonia Plant Operating Manual 8

Chapter twelve TRIP SYSTEM

Trip Initiators and Automatic Trip Actions

Total Plant Trip

Fuel Naphtha Trip

Secondary Reformer Trip

Methanator Trip

Hydro finer Trip

Product Ammonia Shut down

Degassed Condensate Trip

Boilers Trip

Ammonia Converter Start up Heater Trip

Synthesis Loop Shut down PGL 3 & 4

PGL 2

Electric Power Failure

Synthesis Gas Compressor Shut down

Reformer ID / FD Trip

Semi Lean solution Low flow Trip

Lean solution Low flow Trip

1432 & 1433 Flame Failure

Lean Sump & Semi Lean Sump Low Level Trip

HWP Shut down

Features of Trip Panel relevant for operation

Trip Panel Reset procedure

Taking Trips in Line

Guidelines to be followed for Restart

Emergency Trip Actions

Instrument Air pressure low trip

Cooling Water low pressure trip

Page 9: Ammonia Manual

Ammonia Plant Operating Manual 9

Boiler Feed Water low pressure trip

Control Room push button on trip ‘A’

Furnace top push button / Fuel Naphtha / Feed stock trips.

One set of ID / FD Fans trip

Secondary reformer trip

Methanator trip

Power failure

Chapter thirteen SHUT DOWN

Normal shut down

Emergency shut down

Shut Down Schedule

Chapter fourteen NORMAL OPERATION

General

Reforming section

Fired heaters

Shift conversion

Methanation

Co2 removal

Synthesis

Tank farm and Hydro fining

Control room

Compressor house

Chapter fifteen TANK FARM

Page 10: Ammonia Manual

Ammonia Plant Operating Manual 10

Introduction

Tank Details

Salient Features of the Naphtha Tanks

Fuel Oil System

Safety Features of Naphtha & fuel oil storage yard

Naphtha Specifications and its importance

Chapter sixteen HYDROGEN RECOVERY UNIT

Design basis

Process description

Start up procedure

Purge gas system

Shut down procedures

Chapter seventeen CAPTIVE POWER PLANT

Introduction

Description

Control Systems

Protective Device

Operation

TG I Start up procedure

TG II Start up procedure

Precautions

Trip and Alarm schedule

Chapter eighteen APPENDIXES

Electrical Power Distribution System

Ammonia plant control power network after DCS installation

Page 11: Ammonia Manual

Ammonia Plant Operating Manual 11

Procedure for decoking 1432

1432 lighting up procedure

LT Catalyst reduction [C-18-HC]

Ammonia Synthesis Catalyst reduction

Procedure of Silica wash of Syn gas compressor for turbine

LRC / PAC turbine silica washing procedure

Loading of ammonia in tankers

Ammonia plant catalysts

List of storage tanks present in Ammonia plant

Ammonia plant UPS system

18.12a Analysis in CTIG Area

Safety

Ammonia plant Alarm & Trip set values

Page 12: Ammonia Manual

Ammonia Plant Operating Manual 12

CHAPTER I - BASIS OF DESIGN

The existing Ammonia Plant of SPIC is designed to produce 1100 TPD of anhydrous ammonia using naphtha as feedstock. The plant is being revamped to produce 1260 TPD of ammonia. The higher target capacity would call for a proportional increase in the quantity of synthesis gas (H2 + N2) being made available to the ammonia synthesis loop.

The larger hydrogen requirement is met by two means: by increased hydrogen production in the front-end of the plant to 110% of original design; and by recycling recovered hydrogen equivalent to approximately 50 TPD of ammonia from the Purge Gas Hydrogen Recovery Unit to the synthesis loop.

The larger nitrogen demand is met by increasing process air intake in the Secondary reformer and adjusting the process conditions suitably.

The process in the CO2 Removal section has been modified to incorporate a dual pressure regeneration system instead of the existing scheme having solution regeneration at a single pressure. Further the revamped unit will feature an activated carbonate solution using glycine instead of arsenic, which is used presently.

Some new equipment was added as a result of the modified process. The adequacy of existing equipment has been checked for the post-revamp duty and wherever necessary these are being modified, replaced or supplemented by additional equipment.

PRODUCT SPECIFICATIONS

Ammonia:

NH3 99.5% by wt. minimumMoisture 0.5% by wt. maximumOil 5 ppm by wt. maximum

Carbon dioxide:

41127 Nm3/h of carbon dioxide is produced of the following purity:

CO2 99.38% by volume on dry basisH2 0.53% by volume on dry basisN2 0.09% by volume on dry basis

Page 13: Ammonia Manual

Ammonia Plant Operating Manual 13

FEED SPECIFICATION

The design feed specification for revamp and the range in values that the plant is capable of handling are specified below.

TYPE REVAMP RANGE

Feedstock type Naphtha Naphtha

Specific Gravity (15/15) 0.7348 0.65-0.75

Density at 25C (kg/m3) 732.7 640.7-742.1

ASTM Distillation (C)

Initial Boiling Point 38-55 38-55

10vol.% over 45-97 45-97

50vol.% over 60-115 60-115

90vol.% over 110-160 110-160

Final Boiling Point 175 130-200

Residue mg/100ml 1.5 1-5

PONA Analysis (Vol%)

Paraffin 56.0 75 max

Olefins 0.5 0.1-2.0

Naphthenes 31.5 10-36

Aromatics 11.0 10-15

Sulphur Content (ppm wt.) 0.5 0.2-0.5

Chlorides (ppb wt.) 3 0-5

C/H Ratio (wt./atomic) 5.78 5.5-6.0

Mean average boiling point (C) 94.0

Molecular weight (kg/kgmol) 100 100

Higher heating value (kcal/kg) 11250 11000-11500

Lower heater value (kcal/kg) 10350 10200-10500

Page 14: Ammonia Manual

Ammonia Plant Operating Manual 14

UTILITIES SPECIFICATIONSUTILITIES - WATER

Type of water Fire & service water

5)

Cooling Water

Steam turbine

condensate

Drinking Water

Boiler Feed Water

Less than 60 kg/cm2

More than 60 kg/cm2

Appearance Clean/ Colourless

Clean/ Colourless

Clean/ Colourless

Clean/

Colourless

Clean/ Colourless

Clean/ Colourless

GH m val/kg 1) 2-3 7 Nil 0.0004

KG m val/kg 1) 1-2 0.5 Nil -

NKH m val/kg 1) 2-3 6.5 Nil -

MgH m val/kg 1) 0.5-1.0 2.6 Nil 0.0002

CaH m val/kg 1) 1-2 4.4 Nil 0.0004

SO4-- mg/kg 100 1000 Nil Nil

Cl- ppm wt. 100 200 Nil 0.02

pH at 25C 6.5-7.0 6.5-7.0 10 8.8-9.2

p-Value mval/l Nil Nil 0.2 0.6

m-Value mval/l 2 0.5 0.2 0.6

Conductivitymicro S/cm 150-300 3000 25 - 40 2) 30 3)

Solids ppm wt. 90-180 2000 <1 <1

O2 ppm wt. 5 5 Nil <0.005

SiO2 ppm wt. 25 50 <0.02 <0.02

Fe ppm wt. <0.03 1.0 12 ppb 0.01

Cu ppm wt. 0.05 Nil 0.01

KMnO4 ppm wt. Nil Nil Nil Nil

Oil ppm wt. Nil Nil Nil Nil

Phosphate as PO4 ppm Nil Total: 4-6Ortho: 2-3

Nil Nil

Page 15: Ammonia Manual

Ammonia Plant Operating Manual 15

Type of water Fire & service water

5)

Cooling Water

Steam turbine

condensate

Drinking Water

Boiler Feed Water

Less than 60 kg/cm2

More than 60 kg/cm2

Appearance Clean/ Colourless

Clean/ Colourless

Clean/ Colourless

Clean/

Colourless

Clean/ Colourless

Clean/ Colourless

Min. Temperature C 28 29 4) 50 100 6)

Normal Temperature C 31 32 (supply)4)

56 109 6)

Max. Temperature C 35 Normal return 40

4)

80 111 6)

Fouling FactorKcal/hm2C

5000 3333 5000 5000

Turbidity ppm wt. <50 30 as SiO2 Nil

Mg, Ca, C1, SO4 ppm wt.

<1000 0.1

Chromate as CrO4 ppm wt.

30-35 Nil

Zinc as Zn ppm wt. 2-3 Nil

Ammoniacal nitrogen ppm wt.

250 13 20

Chloride ppm wt. 200 20 ppb

Aluminium ppm wt. 1 1 25 ppb 10 ppb

Sodium ppm wt. 50 200 10 ppb 10 ppb

Notes:1) Hardness types: G H = Total; KH = Permanent; NKH = Temporary;

MgH = Magnesium hardness; CaH = Calcium hardness.1 mval/kg = 50 ppm wt. CaCO3; (1 mval/l = 28 ppm wt. CaO).

2) Depending on ammonia dosage to steam drum.3) Point of measurement is downstream of dosing chemicals injection.4) Temperature figures specified above are applicable only to new heat exchangers

using cooling water.

Page 16: Ammonia Manual

Ammonia Plant Operating Manual 16

5) Fire water and service water specification are the same.6) Temperature measured at pump suction.

Page 17: Ammonia Manual

Ammonia Plant Operating Manual 17

UTILITIES - STEAM

Extra High Pressure Steam - EHPHigh Pressure Steam - HPMedium Pressure Steam - MPLow Pressure Steam - LP

TYPE EHP HP MP LP service

steam

LP*

VGB RATING kg/cm2a > 60 30-60 10-30 3-10 3-10

Normal Pressure kg/cm2a 106 45 12 2.1 12 4.8

Normal Temperature C 482 365 278 243 187 151

* ex new LP boiler 1550

Page 18: Ammonia Manual

Ammonia Plant Operating Manual 18

UTILITIES - FUEL GAS

TYPE OF FUEL GAS PGHRU TAIL GAS

H2 mol. % 14.0

CH4 mol. % 28.7

C2H6 mol. % -

C3H8 mol. % -

C4H10 mol. % -

CO mol. % -

Argon mol. % 12.7

N2 mol. % 44.5

H2O mol. % -

Sulphur Content (as H2S) ppm wt. Nil

Molecular Weight kg/mol 22.4

LHV @ 15C kcal/kg 2694

Wobbe Index (on LHV) kcal/Nm3 3081

Normal Pressure kg/cm2a 2.3

Normal Temperature C 35

Page 19: Ammonia Manual

Ammonia Plant Operating Manual 19

UTILITIES - FUEL NAPHTHA

TYPE REVAMP RANGE

ASTM Distillation:

IBP C

41 38-45

50 vol.% C 72

FBP C 175 130-175

Molecular Weight kg/kmol 100 100

C/H Ratio (atomic) 5.78 5.5-6.0

Sulphur ppm wt 800 800-1500

Vanadium wt. % NT NT

Density @ 15 C kg/m3 700 650-750

LHV at 15C kcal/kg 10200 10200-10500

Viscosity at 38C 0.46 centi poise

Coke particles > 100 micron wt. % n.a.

Basic Sediment Water wt. % nil nil

Residue mg/100 ml 5

Chloride ppb (wt) 200

Page 20: Ammonia Manual

Ammonia Plant Operating Manual 20

UTILITIES - AIR

TYPE COMBUSTIONAIR

INSTRUMENTAIR

PLANT/SERVICE

AIR

Quality oil-free dust/oil-free oil-free

Composition

N2 vol. %

78.11 78.11 78.11

O2 vol. %

20.95 20.95 20.95

A vol. %

0.94 0.94 0.94

Relative Humidity % 65/ 85 - 65

Dew point C -12

Minimum Pressurekg/cm2a * 100 mmwc 7.0 2

Normal Pressure kg/cm2a * 170-180 mmwc

8 4

Maximum Pressurekg/cm2a * 535 mmwc 11 10

* Pressure is measured at fan discharge

Page 21: Ammonia Manual

Ammonia Plant Operating Manual 21

UTILITIES - NITROGEN

COMPOSITION

Nitrogen purity, minimum : 99.5 vol. %

CO + CO2 : Nil

Source : Cracked ammonia

O2 : 200 ppm wt.

Hydrogen : <0.3 vol. %

Dew point : -40 C

Ammonia : 200 ppm wt.

Normal Pressure : 2-31* kg/cm2a

Normal Temperature : 32 C

* Depends on the use of nitrogen.

Page 22: Ammonia Manual

Ammonia Plant Operating Manual 22

UTILITIES - HYDROGEN

COMPOSITION

Source Cracked ammonia

Hydrogen purity, minimum: 75.0 vol. %

Nitrogen : 25.0 vol. %

Ammonia : <100 ppm wt.

Normal Pressure : 35 kg/cm2a

Normal Temperature : 32 C

Page 23: Ammonia Manual

Ammonia Plant Operating Manual 23

SITE CONDITIONS

Elevation Above Sea Level 2.7 m

Minimum Barometric Pressure 1005 mbar

Average (Process Design) Barometric Pressure 1013 mbar

Maximum Ambient Temperature 41.0 C

Minimum Ambient Temperature 16 C

Average (Process Design) Ambient Temperature 35 C

Average Relative Humidity 70 %

Average wind speed for mechanical design 120 miles/h

Average Wind Speed (Process Design) m/s

Prevailing Wind Direction

Airborne Materials (Process/ Mechanical Design *Salt/ Sand

* SO2 - 0.02 ppmNO2 - 0.01 ppmNH3 - 0.72 ppmH2S - 10 ppbCl2 - 50 ppbSPM - < 200 µgm/m³

Page 24: Ammonia Manual

Ammonia Plant Operating Manual 24

PURGE GAS HYDROGEN RECOVERY UNIT

This unit is designed to recover hydrogen from 8400 Nm3/h of syn loop purge gas. Product hydrogen from this unit is delivered at 48.5 kg/cm2a with a purity of 94%. The unit also yields a tail gas stream suitable for use in the primary reformer.

Product hydrogen:

Flow (Nm3/h) 4404Pressure (kg/cm2 g) 49.5Temperature C 40

Composition (mole%):

H2 94.2N2 4.82CH4 0.39Ar 0.59NH3 NT

Tail Gas :

Flow (Nm3/h) 2938Pressure (kg/cm2 a) 2.3Temperature C 40

Composition (mole%):

H2 13.96N2 44.45CH4 28.71Ar 12.66NH3 0.21

Page 25: Ammonia Manual

Ammonia Plant Operating Manual 25

CHAPTER II - PROCESS DESCRIPTION

2.1 REFORMING SECTION

Sweet naphtha containing up to a maximum of 5.0 weight ppm sulphur is stored in the Sweet naphtha storage tank(1203). It is pumped from the tank at a pressure of 44.0 kg/cm2 a by Process Naphtha pump -3204-001/002. This is a eight stage pump with a normal flow of 26818 kg/h. A MFCV is provided from the pump to the tank to prevent over-heating in the pump due to low flow.

Sweet naphtha flow is controlled by FC-1203. Recycle gas from the first stage of Synthesis Gas compressor 3102 is mixed with the naphtha under flow ratio control from FFRC-1204 and fed to Process Naphtha Vaporizer (1432). During start-up and plant upsets recycle gas would not be available. During such periods hydrogen is supplied from Inert Gas Generation Plant through XCV-1205. During normal operation when recycle gas is available from syn gas compressor, this valve would remain closed. In order to meet emergency situations it is necessary to maintain the hydrogen receiver in I.G. Plant at a pressure of 43.5 kg/cm2 a. This is done by drawing necessary quantities of gas from syn gas compressor through a bypass line of XCV-1205.

The Process Naphtha Vaporizer is a fired heater in which the naphtha is vaporized and superheated. Recycle gas is mixed with naphtha before the heater because the hydrogen present in the gas forms a film in the heater coils and inhibits naphtha from coking. The outlet temperature of vaporized naphtha from 1432 is controlled at 375C by TRCA-1205, which regulates fuel flow to the burners. TRCA-1205 gives a low temperature alarm at 370C to ensure meeting the minimum temperature required for the desulphurizer catalyst. It also has a high temperature alarm at 430C to avoid over-heating of the coil and temperature run-away in the desulphurizer.

The naphtha, recycle gas mixture is passed over a Sud chemie manufactured COMOX bed (C-20-6) and John Matthey manufactured two zinc oxide beds (C-7-2) in Desulphurisation tower to remove traces of H2S to a level of less than 0.5 ppm. Though C-20-6 can operate over a range of 300C to 450C, C-7-2 operates most efficiently in the temperature range 370C to 400C. Hence 1104 is operated in the temperature of 370C to 400C.

There is a six point alarm TRA-1206 in the COMOX bed, which is set at 450C(HH). Any slip of carbon oxides into this bed will lead to methanation reaction and temperature rise will be about 60 to 70C for every percent of carbon oxides. Temperature indicators TI 1/1205 and TI 1/1206 are provided in the zinc oxide bed.

There is a provision for sampling at the outlet of each bed. There is a purge nitrogen connection provided at the outlet of 1104 with double block and bleed protection.

The vessel itself has a bypass line, which has two valves and a bleed in-between. When the plant is under normal operation both the bypass valves are kept closed and the bleed is open to flare. Because of this arrangement passing of the bypass valve cannot contaminate the vapour exit 1104 with sulphur.

Page 26: Ammonia Manual

Ammonia Plant Operating Manual 26

The feed vapour line to reformer exit the Desulphurizer 1104 has PIC-1208, which is the cascade element for the flow controller in the liquid naphtha line to 1432. Because of this arrangement flow measurement to the reformer is done at a steady pressure of 39.3 kg/cm2a, which is necessary for measuring steam to carbon ratio accurately. Vapour naphtha to reformer at 375C is controlled by FC-1303 and it is mixed with superheated process steam at 471C by flow ratio controller FFRC-1304. Efficient mixing is ensured by a mixing orifice (Diff. Pr.=4.9 ksca ) before feeding to the reformer. After the revamp the ratio of steam to naphtha + recycle gas would be maintained normally at 4.06 wt/wt which corresponds to a steam to carbon mole ratio of 3.25. There is a trip to cut off feedstock to the reformer if the ratio of steam to naphtha + recycle gas falls below 3.42 wt/wt.

Superheated process steam is used here to avoid the possibility of condensation at the inlet of the reformer. Firing in the reformer can be reduced by having higher degree of superheat in the steam. However this would increase the cost of the process steam super heater. Therefore the process steam temperature has been fixed at 471C. This yields a mixed reformer feed temperature of 445C.

The mixture of vaporized naphtha, recycle gas and steam is fed to the reformer tubes through a new feed mains line and manifold system. The latter consists of a main header feeding eight sub-headers corresponding to the eight rows of tubes. Symmetrical arrangement of sub-headers and main header has been made in order to uniformly distribute feed through all the reformer tubes.

The reformer consists of 264 tubes of 102 (105.4) mm internal diameter arranged in eight rows. The length of each tube is 12.2 metres and is filled with catalyst to a height of 12.5 meters. The Reformer catalysts are Sud chemie manufactured C11NK and G90LDP.

Reformed gas leaving the tubes would be at a temperature of 787C and has the following analysis on a dry basis:

H2 = 62.37 Mole %N2 = 0.44 Mole %CH4 = 9.98 Mole %CO = 11.55 Mole %CO2 = 15.65 Mole %

Reformed gas from the tubes is collected through an outlet system consisting of four sub-headers. Each outlet sub-header is located beneath and receives gas from two rows of reformer tubes. The four outlet sub-headers in turn feed the reformed gas mains through four spun-cast cones. The outlet sub-headers and spun-cast cones are fabricated from alloy 800H suitable for the high design pressure and temperature. On the other hand the reformed gas mains is a refractory lined pipe made of carbon steel.Connection between the reformer tubes and the inlet and outlet sub-headers is done using small-bore flexible tubing called pigtails. Pigtails are located outside the firebox. This has the following advantages:

Page 27: Ammonia Manual

Ammonia Plant Operating Manual 27

* The pigtails are subjected only to the process fluid temperature and can be insulated against heat loss. They would experience higher metal temperatures if they were positioned inside the firebox. * They are easily accessible for inspection and maintenance.* In the event of a reformer tube failure the plant need not be shutdown. The inlet and outlet pigtails are fabricated from ductile materials, which enable the pigtails to be nipped, thereby isolating the defective tube.

Inlet pigtails are designed to accommodate the thermal movements of reformer tube, feedstock header and their own thermal expansion. They are made of SA335 Gr P11 (1.25 Cr 0.5 Mo). Outlet pigtails are designed to accommodate thermal movement of outlet sub-headers, reformed gas mains and their own thermal expansion.

2.2 FURNACE AND WASTE HEAT RECOVERY SYSTEM

The reformer in the SPIC plant is a top-fired unit. In the revamped plant ninety new burners located in nine rows with ten burners per row provide the necessary heat of reaction. Desirable temperature profiles along the length of the tubes are achieved by the co-current flow of process gas inside the tubes and flue gas in the firebox.

The reformer uses naphtha and tail gas as fuel. The burners located in the four and sixth row are dual fuel burners whereas the burners in the other rows consume only naphtha. Burners in the first row and ninth row are rated for a lower capacity (about 55 %) than the burners in the other rows. This is because these burners see only one row of tubes and have refractory wall on the other side. Burners in rows two to eight are all of equal firing capacity and are referred as 100 % burners. The dual fuel burners can supply the rated capacity by either firing a combination of naphtha and tail gas or naphtha alone.

Fuel grade naphtha is pumped from the Raw Naphtha Tanks (1202A/B/C/D) by Fuel Naphtha Pump(3205-001/002) at 17 kg/cm2 a. This pump is driven by a steam turbine. A spill-back line is provided from pump discharge to the tank. The naphtha is filtered and divided into two lines: one supplying fuel to the naphtha-only burners and the other to the dual fuel burners.

Fuel flow to the naphtha only burners is controlled by PIC-1305. This in turn is set by operator through HIC-1304. In the event of a partial trip HIC-1304 is over-ridden and a pre-set value is fed to PIC-1305. In the event of a total trip valves XCV-1303 and PCV-1305 close and provide a double-block.

Naphtha to the dual fuel burners is supplied through PIC-1319 and trip valve XCV-1307.

Tail gas is supplied to the dual fuel burners at 3.0 kg/cm2 a by PIC-1303. The controller vents excess gas to flare. Required flow to the burners is controlled by HIC-1302 and measured by FIA-1301.

The furnace is provided with a tertiary air door upstream of the convection box. This door may be opened during emergencies to protect the convection box from excess temperatures.

Page 28: Ammonia Manual

Ammonia Plant Operating Manual 28

2.3 CONVECTION SECTION

Flue gas leaves the radiant section of the reforming furnace at a temperature of 940C. A major portion of the heat carried by the flue gas is recovered in the convection section. It consists of the following sections:

Flue Gas Boiler 1510High Temperature Turbine Super heater 1536AProcess Steam Super heater 1537Low Temperature Turbine Super heater 1536BCombustion Air Preheater 1511

As part of the revamp the H.T Turbine Super heater, L.T Turbine Super heater, Process Steam Super heater and the Combustion Air Preheater have been replaced. In addition the ductwork between the Flue Gas Boiler and Combustion Air Preheater has also been replaced.

The Flue Gas Boiler (1510) is the first heat transfer section in the flue gas path after the radiant section. It is connected to the Steam Drum 1106 by down comers and risers. Steam is raised inside the coils of 1510 at 112.5 ata and 318C.

Flue gas from 1510 flows over the coils of the High Temperature Turbine Superheater 1536A. Partially superheated steam from 1536B is further heated in this section and then sent to the 106 kg/cm2 a steam header.

The Process Steam Superheater 1537 forms the third heat recovery section in the convection section. The function of this section is to supply superheated process steam for blending with process naphtha upstream of the reformer. Necessary amount of steam for this purpose is extracted at 45 kg/cm2 a from Syn Gas Compressor turbine.

Flue gas leaving 1537 next flows over the Low Temperature Turbine Superheater 1536B. Saturated steam from 1106 is heated in these coils before it is fed to the High Temperature Turbine Superheater.

The flue gas leaving 1536B enters the new plate type Combustion Air Preheater 1511 which replaces the old rotary air preheater. Combustion air at ambient temperature from the fans is preheated to 277C in the air preheater while flue gas temperature is reduced from 335C to 158C. The heat exchanger consists of a large number of closely spaced parallel plates that form lanes for flow of flue gas and air. The exchanger is a cross-flow type of unit constructed of Corten steel. The unit is designed in such a way as to reduce the air side heat transfer coefficient in the cold end of the exchanger and thereby avoid dew-point corrosion problems. In addition the Air Preheater is provided with an air-side bypass for use during start-up. Flue gas leaving 1511 flows to the chimney while the preheated combustion air is sent to the revamped burner air distribution manifold.

Page 29: Ammonia Manual

Ammonia Plant Operating Manual 29

2.4 PROCESS AIR COMPRESSOR

Process air flow to the Secondary Reformer is set by the operator through FIC-1401. The air is obtained from the Process Air Compressor 3107 which is a four stage centrifugal compressor driven by steam turbine. The compressor discharge pressure is controlled by a PIC which has the turbine speed control cascaded under it. In addition anti-surge kick-back lines to the suction of the compressor as well as a blow-off valve are provided to ensure that enough flow is always maintained through the machine to keep it well above the surge limit. 3107 also mets the instrument air requirement of the plant. For this purpose a bleed of 1200 Nm3/hr is taken from the compressor discharge.

The capacity of 3107 is not sufficient to meet the revamp process air load. The shortfall in capacity will be met by adding a new, smaller compressor 3110 to operate in parallel with 3107.

The new Process Air compressor will be a reciprocating machine driven by an electric motor. It will have step-wise loading / unloading. The discharge pressure of both compressors will be controlled by the earlier mentioned PIC varying 3107 speed. Normally the reciprocating compressor will be run at its full load and continuous capacity control will be on the centrifugal compressor.

In the event that the plant has to operate at turndown for prolonged periods the reciprocating compressor can be manually unloaded or stopped.

2.5 SECONDARY REFORMER

Gas from the primary reformer contains a large amount of methane; in the secondary reformer this methane is converted to CO and H2. This requires a higher temperature and additional heat for the reaction. It is obtained by burning the process gas with air in the secondary reformer. In this manner the nitrogen required in the synthesis section is introduced conveniently into the process stream.

With proper mixing of air and primary reformer gas the theoretical flame temperature obtained will be about 1200C. Secondary reformer catalyst must be able to tolerate temperature of about 1300C without breakage or shrinkage.

After the revamp the secondary reformer is proposed to be filled with ICI 54-8, which is a four hole, shaped nickel oxide catalyst on calcium aluminate ceramic support. The reactor vessel is refractory lined and has a water jacket on the outside of the shell. The water jacket should always have a visible overflow to drain. An alarm is provided to warn the operator of low-level in the jacket. The top of the vessel where gas enters is Incolloy lined. As part of the revamp the existing burner will be replaced by a new larger capacity burner designed to have a lower flame length.

The top of the catalyst is protected against excessive temperatures by a bed of 450 mm deep, 19 to 50 mm graded alumina lumps. On top of these refractory tiles having suitably sized holes to allow passage of process gas will be arranged during the revamp.

Page 30: Ammonia Manual

Ammonia Plant Operating Manual 30

The reaction in the secondary reformer is endothermic and gas temperature falls as reaction proceeds down the height of the bed. As part of the revamp a new outlet collection pipe (of higher thickness) will be installed in the bottom of the secondary reformer. Also the existing bed of alumina lumps in the bottom of the vessel on which the catalyst rests will be removed and replaced by alumina spheres having the required diameter and hardness. There is provision for nitrogen purge at the base of the vessel.

Process air from the process air compressors is preheated to 490C in Process Air Preheater 1433 and flow controlled by FIC-1401. Further downstream a trip valve XCV-1406 is provided. Differential pressure between process air and process gas is maintained at more than 1.5 kg/cm2 to ensure positive flow of air into the secondary reformer. There is also a provision to admit HP sealing steam through XCV-1405 at 45 ata in-between. Whenever the interlock system closes FCV-1401 and XCV-1406, XCV-1405 would automatically open to admit sealing steam and thus effectively isolate the process airline from the secondary reformer as a safety measure.

Gas temperature leaving Secondary Reformer is monitored by TRA-1405 with high and low alarms and high temperature trip. The exit gas has the following composition on a dry basis:

H2 = 51.53 Mole %N2 = 22.29 Mole %CH4 = 0.27 Mole %Ar = 0.27 Mole %CO = 14.94 Mole %CO2 = 10.70 Mole %

Gas from Secondary Reformer is cooled to 380C in the tube side of Reformed Gas Boiler 1509 and the released heat is used to generate steam at 106 ata. For this purpose a down comer from the Steam Drum 1106 supplies circulating water to the shell of the reformed gas boiler while three risers of 12 inch diameter and two of 16 inch diameter carry steam-water mixture from 1509 back to 1106. Within the Reformed Gas Boiler the hot gas first flows through a hot compartment and then through a cold compartment. An internal gas bypass line is provided for the cold compartment. The bypass line is equipped with a valve whose opening can be set by the control room operator through a HIC.

Process gas from 1509 is sent to High Temperature Shift Converter Guard vessel. A provision has been made for automatically quenching the gas at 1509 outlet using quench water in order to prevent excessively hot gas from entering the H.T.Shift during an upset.

2.6 106 ATA STEAM GENERATING SYSTEM

Extra high-pressure steam at 106 ata is generated in the ammonia plant:

1) In the process waste heat recovery boilers2) In the Auxiliary Boiler 1702

Detailed description of Auxiliary Boiler is given in a later section.

Page 31: Ammonia Manual

Ammonia Plant Operating Manual 31

Steam is raised in two process waste heat boilers. These are Flue Gas Boiler (1510) mentioned in the description of the convection section and the Reformed Gas Boiler (1509). Both boilers are connected to the steam drum 1106 by a system of down comers and risers. The steam drum is located at a higher elevation and some distance away from both boilers. The down comers and risers are separated by an arrangement of internal baffles within the steam drum. The baffles ensure even distribution along the length of the drum thus avoiding unnecessary fluctuations in the water level.

Effective separation of steam and water is achieved by a system of cyclone separators and stainless steel demister pads paced inside the steam drum.

Boiler feed water at 126 kg/cm2 a and 238C is fed to the steam drum from Boiler Feed water Heater 1539. Saturated steam from 1106 at 112.5 ata and 318C flows in series through the revamped Low Temperature Turbine Super heater (1536B) and High Temperature Turbine Super heater (1536A) before it is sent to the 106 kg/cm2 a steam header.

Steam temperature at the exit of 1536A is controlled at 485C by means of a spray water type attemperator utilizing high pressure boiler feed water. This attemperator is situated in the cross-over pipe between the L.T. and H.T. sections of the super heater.

2.7 CONVERSION SECTION

Gas from the Reforming section contains a large amount of CO which is converted into useful CO2

and H2 in the Shift conversion section. This is carried out by the water-gas shift reaction

CO + H2O == CO2 + H2

Equilibrium of this reaction is independent of pressure. The reaction is highly exothermic and high conversions are achieved at low temperature; however the rate of reaction increases with temperature.

For this reason shift conversion is done in two stages. In the first stage most of the CO is converted to CO2 at high temperature. In the second stage the reaction is performed at a low temperature to bring down the co concentration to a low level. The first step uses Fe3O4 as catalyst while the second step employs CuO - ZnO.

High Temperature Shift

The H.T.Shift Guard vessel is provided upstream of the H.T.Shift reactor in order to protect the shift catalyst from potash. The vessel is packed with 2” Raschig rings. Nitrogen purge and provision for D.M water or steam flushing is made at the bottom of the vessel. When pressure drop across the vessel goes up, the vessel can be bypassed and washed free of potash without disturbing normal plant operation.

Page 32: Ammonia Manual

Ammonia Plant Operating Manual 32

The H.T. Shift reactor consists of two beds of Fe2O3 catalyst. The first bed catalyst is C12-4, 2nd bed catalyst if SK 201-2. The top of each bed is provided with a 150 mm layer of 25 m x 25 mm ceramic Raschig rings. In the first bed the gas temperature rises to 449C and has the following composition on a dry basis:

H2 = 56.10 Mole %N2 = 20.19 Mole %CH4 = 0.25 Mole %Ar = 0.24 Mole %CO = 4.09 Mole %CO2 = 19.13 Mole %

The gas from the first bed should be cooled in order to obtain higher conversion. This is achieved by cooling it against high-pressure boiler feed water in H.P BFW Heater 1539. The existing heat exchanger is not adequate for the post-revamp heat duty and has been replaced by a new unit.

The gas is cooled to 350C in 1539 while the boiler feed water is heated from 181C to 238C.

A waterside bypass valve is provided for 1539. However this should be used selectively and carefully, as there may be a tendency for water hammering in 1539 because of inadequate water flow.

Cooled gas from 1539 is returned to the second catalyst bed of H.T.Shift Reactor. Conversion proceeds in this bed with a corresponding temperature rise to 363C. The converted gas has the following composition on dry basis:

H2 = 56.91 Mole %N2 = 19.82 Mole %CH4 = 0.24 Mole %Ar = 0.24 Mole %CO = 2.17 Mole %CO2 = 20.62 Mole %

Gas leaving the second bed of H.T.Shift is cooled in two stages before the Low Temperature Shift Reactor. It first passes through the tube side of Methanation Heat Exchanger No. 2 (1514) wherein it heats the feed to the Methanator. A hot bypass is provided around 1514; the bypass rate is controlled by TIC-1506 located on the Methanator feed gas downstream of 1514.

The partly cooled gas leaves 1514 at 302.5C and enters Quench Drum 1111. Two water spray nozzles are provided in the gas line to 1111. Water is added to cool and de-superheat the gas to 205C. Desuperheating water is supplied from the process condensate collected in drum 1115 through Quench water pump 3215. There is also a provision to use BFW from LP Desuperheating header for this purpose. The amount of water sprayed is controlled by TRCA-1509 located downstream of the spray nozzles.

Page 33: Ammonia Manual

Ammonia Plant Operating Manual 33

The mixing of gas and water, even if not completed in the pipeline, will get completed in the Quench Drum. This vessel is packed with 38 mm stainless steel Raschig rings. The gas at the outlet of vessel 1111 can be vented to the vent header through PCV-1504, thus enabling the reforming section to be kept on stream if there is any problem in the downstream section.

Gas at 205C enters the Low temperature shift vessel with a bed of C18-HC catalyst. At the top of the bed there is a 500 mm layer of 25 mm x 25 mm Raschig rings. A six-point temperature indicator TRA-1511 with high alarm monitors the temperature rise across the catalyst. There is a total bypass around the vessel for start-up and trip situations and there is a separate loop for heating up and reduction. A hydrogen injection point is provided for use during start-up.

The exit gas is at 217C and has the following analysis on a moisture-free basis:

H2 = 57.71 Mole %N2 = 19.45 Mole %CH4 = 0.24 Mole %Ar = 0.23 Mole %CO = 0.27 Mole %CO2 = 22.10 Mole %

Low temperature shift catalyst is a very sensitive catalyst and is susceptible to sulphur and chlorine poisoning. Its temperature should never be allowed to exceed 240C to avoid thermal sintering. Water should never be allowed to condense over the catalyst. Apart from the possibility of water entering the catalyst pores and damaging it, small amounts of dissolved ammonia, if present, may react with the reduced copper.

2.8 CO2 REMOVAL SECTION

Gas leaving the Low temperature shift is cooled to 173C in a new LP Steam Boiler 1550. This exchanger is a kettle type unit in which the gas is cooled and partly condensed in the tube side while low pressure steam is generated in the shell side. For this purpose boiler feed water at 50 kg/cm2 a is supplied from battery limits.

The boiler is controlled by a three element level control system which consists of FC-1551 for BFW flow control, LICA-1551 for drum level control and FI-1553 for steam flow rate measurement.

Steam from the LP Boiler is divided into two portions: one portion is fed to H.P. Vetrocoke Regenerator 1117A as live steam while the balance is sent to 4 ata steam header. LP Boiler steam pressure is controlled by PICA-1550 which manipulates steam flow to the 4 ata header. Steam injection into 1117A is done under flow control from FIC-1650.

The LP Boiler is provided with a hot gas bypass line fitted with a manually operable valve. The mixture of gas and condensate from 1550 is fed to Condensate Knock-out Drum 1114. The gas from 1114 is sent as heating medium to the tube side of Vetrocoke Regenerator Reboiler 1517A/B while the condensate is sent under level control from LC-1502 to Condensate Degasser.

Page 34: Ammonia Manual

Ammonia Plant Operating Manual 34

As mentioned above the gas from 1114 is the source of reboiling heat for the Vetrocoke Regenerator; moreover a part of the steam generated in 1550 is injected into 1117A. Therefore it is very important to maintain good control over the heat duty of LP Boiler. If too much heat is withdrawn from the gas in 1550 there may not be enough heat content left in it to provide the necessary heat duty in the reboiler. This could be partly compensated by increasing live steam injection in 1117A but that would result in larger water blowdown requirements in the CO2 Removal section. On the other hand if the LP Boiler duty is too low then it could result in insufficient steam generation and/or excess reboiling.

The heat duty of 1550 can be controlledin two ways:

a) By manually opening/closing the hot bypass valve

b) By varying steam generation pressure by adjusting the set-point of PICA-1550. Raising or lowering the steam generation pressure would correspondingly increase or decrease the shell side temeprature and thereby affect LMTD and heat duty.

Process gas is cooled to 135C and partly condensed in the reboilers 1517 A/B. It then enters the DMW preheater II 1513 where it is further cooled down to 126C. The process condensate from 1517 A/B and 1513 is separated in 1115 and fed to the process condensate stripper 3603. The process gas feeds the absorber 1116 where the CO2 is absorbed by the solution flowing countercurrently.

In the GV hot potassium carbonate (HPC) dual activated solution, the CO2 is chemically combined with the potassium carbonate via formation of potassium bicarbonate, a thermally unstable salt, according to the equilibrium equation represented by 1) [Fig. 1]. The reaction rate of 4) is determined by the sum of the rates of 2) and 3), where 2) - formation of bicarbonate ion - repre-sents the slow step of the absorption reaction localised in the resistence for transfer of the CO2

molecules from the gas phase to the liquid phase.

CO2 + H2O + K2CO3 <====> 2KHCO3 1)

CO2 + H2O <====> HCO3- + H+ 2)

CO3= + H2O <====> HCO3

- + OH- 3)

-------------------------------------------------------------------

CO2 + H2O + CO3= <===> 2HCO3

- 4)

H2NCH2COO- + CO2 <===> -OOCHNCH2COO- + H+ 5)

-OOCHNCH2COO- + H2O <===> H2NCH2COO- + HCO3- 6)

--------------------------------------------------------------------------- CO2 + H2O <===> HCO3

- + H+ 7)

Page 35: Ammonia Manual

Ammonia Plant Operating Manual 35

Fig 1 - CO2 absorption mechanism

Glycine (amino acetic acid) works as a CO2 carrier by rapidly introducing the CO2 into the liquid phase via formation of glycine carbamate 5) since the amino group acts as a Lewis base which is very effective for linking an acid component like the CO2 molecule. At high temperature and in the presence of OH- ion, the glycine carbamate is hydrolized and the activator is restored with formation of bicarbonate ion according to reaction 6). Reactions 5) and 6) take place continuously (shuttle mechanism) and 7), the sum of the two reaction rates, represents reaction 2) which anyway occurs very quickly thanks to the enhanced mass transfer rate induced by glycine activation. The addition of a secondary amine is effective to further enhance the rate of glycine to act as a CO2 carrier ac-cording to a synergistic effect in promoting the rate of hydrolisis of carbamate 6) which represents the slower step of the shuttle chemistry of reactions 5) plus 6).

Basically, a secondary amine has an activation mechanism similar to that of glycine (carbamate formation). But, glycine having a much higher reaction rate than amine, it will prevail reacting much faster with CO2 via glycine carbamate formation while amine will do it only partially resulting largely free to catalyse the glycine carbamate hydrolisis according to the model in Fig. 2.

GAS PHASE CO2 (g)

GAS/LIQUID INTERFACE

CarbamateFormation

-------------------------------------------------------------------------------------------------Free Glycine H2O - OOCNHCH2COO-

NH2CH2COO- Glycine carbamate

CarbamateHydrolysis

LIQUID PHASE HCO3

-

CO3= / HCO3

- R2NHR2NH FREE SECONDARY AMINENH2CH2COO-

Fig 2 - Dual activation model

A much reduced amine content is sufficient to effectively improve the overall absorbing/desorbing efficiency, allowing in the meantime less glycine content than the mono-activated solution. So, the chemicals make-up is drastically reduced and the solution stability increased.

Page 36: Ammonia Manual

Ammonia Plant Operating Manual 36

The absorption is carried out in two stages: at the first stage, the bulk of CO2 is absorbed; at the second a reduced stream of strongly regenerated cold solution is utilized to get very low CO2

slippages due to the very low CO2 vapour pressure of the dual-activated solution. At the regeneration phase, the dual activation improves the fractional conversion of bicarbonate to carbonate [right to left in reaction 1) of Fig. 1] This way, it gets a lower CO2 vapour pressure in the solution compared to the conventional mono-activated solutions allowing a reduction in the CO2 slip from the absorption step and a reduction in the amount of stripping steam.

The rich solution leaving the absorber 1116 at 113C is expanded through the hydraulic turbine 3708 connected to an alternator and is divided into two streams which feed the regenerators top. The rich solution feeding the top of 1117-B is regulated by HCV-1605 while the balance feeds 1117-A through HCV-1607.

The regeneration is performed according to the GV two-pressure-level technology which provides that the pressure in 1117-A (controlled by means of the adjustable nozzle needle of the regenerator 1117-A) is regulated to obtain a temperature increase in the solution leaving the bottom of the regenerator 1117-A with respect to the solution entering the top.

Conventional technology uses an isothermal cycle so that the temperature at the absorber bottom is approximately the same as at the regenerator bottom. The main disadvantage of this cycle is the development by flash of a remarkable amount of steam which permanently exits the cycle and is lost. Instead, the GV technology, giving rise to a considerable difference in temperature between the absorber bottom and the HP regenerator bottom, strongly reduces the amount of steam otherwise lost by flash and exploits the steam produced at the bottom of the regenerator 1117-A in a substantially different way.

In fact, almost the total amount of steam exceeding the equilibrium conditions is used along the whole column to preheat the down coming solution to reach therefore a high temperature at the regenerator bottom. The heat so stocked in the lean and semilean solutions allows to recover energy by flashing into 1117-B.

The semilean solution extracted from the intermediate tray of 1117-A at 124C is flashed across the level control valve and enters 1117-B operating at about 0.22 kg/cm2g. The solution is collected on the take-off tray of 1117-B and feeds the semilean solution pump 3207. The level on the tray is controlled by the flash valve located on the Semilean solution line feeding 1117-B. An interlock trip for very low level on the tray stops the circulation pump to avoid the damage consequent to a lack of liquid.

The lean solution extracted from the bottom of 1117-A at 128C is flashed across the level control valve and enters the bottom of 1117-B to feed the lean solution pump 3206. The level on the bottom is controlled by the flash valve located on the lean solution line feeding 1117-B. An interlock trip for low level at the bottom of 1117-B stops the circulation pump to avoid the damage consequent to a lack of liquid. The steam developed by flash from the lean and semi lean solutions (which is practically pure steam) is used as stripping steam to regenerate the rich solution fed to the top of 1117-B.

Page 37: Ammonia Manual

Ammonia Plant Operating Manual 37

The lean solution drawn from the bottom of 1117-B at 111C feeds the cooler 1521, where it cools to about 70C. Then, by means of the circulation pump 3206, the lean solution feeds the top of 1116. The semi lean solution drawn from the intermediate take-off tray of 1117-B at 108C, after cooling to 102.5C in the cooler 1520 upstream the circulation pump 3207, feeds the middle of 1116.

The overhead condensate is introduced by means of pumps 3216 and 3221 to the CO2 removal unit and the water make-up balance is performed by exporting the excess OH condensate to the condensate header. In case the OH condensate is not sufficient for the water make-up balance, an injection of DMW through the absorber overhead K.O. drum 1131 is provided.

The CO2/steam mixture leaving the top of 1117-A feeds X-100 as motive stream. The CO2/steam mixture leaving the top of 1117-B is partially condensed in 1551 and its heat is transferred to the cold DMW coming from the B.L. The condensate separated in 1150 is recycled to 3206 suction or partly fed to the condensate header, according to the water make-up balance, by means of the condensate pump 3221. The CO2/steam mixture cooled to about 77C feeds X-100 and is recompressed at about 0.41 kg/cm2g by the CO2/steam mixture coming out of 1117-A. The CO2/steam mixture coming from X-100 is cooled to about 80C in 1519 and the condensate separated in 1118 is totally recycled to 3206 suction by means of the condensate pump 3216. The final cooling to 40C is performed by direct contact with cooling water in 1119.

The gas from 1131 has the following analysis (in dry basis) and is fed to Methanation section:

H2 = 73.99 Mole %N2 = 24.96 Mole %CH4 = 0.31 Mole %Ar = 0.30 Mole %CO = 0.34 Mole %CO2 = 0.10 Mole %

2.9 METHANATION SECTION

The stripped gas from the absorber contains CO and CO2, both of which are poisons to the synthesis catalyst. These components are converted to methane in the Methanator by the following reactions:

CO + 3H2 ===> CH4 + H2OCO2 + 4H2 ===> CH4 + 2H2O

As part of the revamp the heat recovery scheme around the Methanator has been modified. This has been done to meet the following objectives:

a) Meet Methanator preheat duty for revamp situation using only waste heat available from H.T. Shift outlet gas and Methanator outlet gas

b) Increase heat recovery and decrease heat rejection to cooling water in Final Cooler 1516

Page 38: Ammonia Manual

Ammonia Plant Operating Manual 38

c) Avoid the recurring problems in 1516 related to tube-side (cooling water) plugging

In the new design two heat exchangers have been added, namely H.P. BFW Preheater (1553) and Methanation Heat Exchanger No. 1 (1554). Two existing exchangers have been scrapped. These are Methanation Heat Exchanger No. 1 (1512) and H.P. BFW Preheater (1515).

Gas from the absorber is heated first to 179C against Methanator outlet gas in the new Methanation Heat Exchanger No. 1 (1554) and subsequently to 305C against H.T.Shift outlet gas in exchanger 1514. Stripped gas from 1514 is then fed to the Methanator. The lower Methanator inlet temperature (305C as compared to the previous figure of 315C) is a result of the constraints imposed by the lower H.T.Shift outlet gas temperature and the surface area, geometry of 1514. However 305C would still be sufficient to meet the required maximum CO and CO2 slip from the reactor.

The Methanator has a trip valve at the inlet and a six-point temperature recorder TRA 1516. Gas may be sampled between the two catalyst beds. There is a nitrogen purge point at the outlet of the vessel. The vessel also has a bypass line sized for 100 % bypass and fitted with a double block and bleed arrangement. This prevents contamination of Methanator outlet gas in case the bypass valve is passing.

The gas from Methanator at 335C is cooled first against H.P.BFW in the new exchanger H.P.BFW Preheater 1553. Here the gas temperature is lowered to 220C while BFW is heated from 181C to 218C before sending it to the Auxiliary Boiler.

The gas from 1553 is further cooled to 111C in Methanation Heat Exchanger No. 1 and then sent to Final Cooler 1516. The gas is cooled to 40C and partly condensed in the Final Cooler against cooling water. Condensate is separated out in Condensate Knock-out drum No. 3 (1113).

Vapour from 1113 is sent as make-up gas to Syn Gas Compressor in the synthesis loop. A small bleed stream of approximately 300 Nm3/h is taken to the Hydro finer section. The overhead pressure of 1113 is controlled by the suction pressure controller of Syn Gas compressor. When the gas is not taken to syn loop pressure is controlled by venting through PCV 1509.

Synthesis gas make-up has the following composition in dry basis:

H2 = 73.61 Mole %N2 = 25.32 Mole %CH4 = 0.76 Mole %Ar = 0.30 Mole %CO+CO2 = 1.0 ppm v

2.11 AMMONIA SYNTHESISSynthesis of Ammonia from the gaseous mixture of Nitrogen and Hydrogen is an exothermic process. Iron Oxide is used as the catalyst. This is active in the metallic form, so it has to be reduced prior to using it.

Page 39: Ammonia Manual

Ammonia Plant Operating Manual 39

THERMODYNAMICS OF THE PROCESS

The reaction is :

N2 + 3H2 <===> 2NH3 + 26 Kcal/gm Mole @ 5000C

From Le-Chatelier's principle, the following conclusions can be drawn :

1. High pressure favors the forward reaction. 2. Low temperature also favors the forward reaction.

In practice, over the last 50 years the optimum pressure for economic operation has been in the range of 150-350 atm. Higher-pressure processes upto 1000 atm are in operation, but normally the equilibrium advantage of very high pressure is more than off set by the higher cost of compression and by higher capital costs of the plant.

The temperature of operation is directly connected with the characteristics of the catalyst. The metallic iron catalyst is active above 3500C. The kinetics demands a higher temperature for better rate of conversion whereas the thermodynamics demand as low temperature as possible for best equilibrium conditions. Therefore, an optimum has to be worked out. Normally the conversion reaction is carried out in the temperature range of 400 - 5000C.

PROCESS VARIABLES

The process variables at the disposal of the designer, to economizes ammonia Synthesis are:

a. Operating pressureb. Operating temperaturec. Space velocityd. Ratio of H2: N2e. Concentration of inerts andf. Concentration of NH3 inlet to Converter.

OPERATING PRESSURE

As the synthesis of NH3 involves a decrease in the number of moles, the equilibrium percentage of Ammonia will increase with pressure. Increasing the pressure accelerates the reaction rate. As the catalyst activity declines, the operating pressure has to be maintained at higher level to maintain the same level of efficiency.

OPERATING TEMPERATURE

The effect of a change in temperature is a double one, as it affects both equilibrium percentage and reaction rate. As the Synthesis reaction is exothermic a rise in temperature lowers the equilibrium percentage of Ammonia and at the same time accelerates the reaction. This means that under conditions far away from equilibrium a temperature rise will lead to higher conversion, while on the other hand a synthesis system operating near equilibrium, will give a lower conversion for any increase in operating temperature.

SPACE VELOCITY

Page 40: Ammonia Manual

Ammonia Plant Operating Manual 40

The Ammonia concentration in the gas leaving the Converter decreases with longer contact time i.e. lower space velocity. However the production rate per unit time increases with space velocity, although the Ammonia concentration in the exit gas is somewhat lower. The Ammonia production rate will be substantially increased by an increase in circulation rate. With increasing space velocities additional capital and operating costs are incurred, i.e. the Converter must be designed for higher-pressure drop and the power required for circulation will be higher. Further the space velocity should maintain the temperature profile across the converter. The optimum design will include an economic balance of such factors.

RATIO OF HYDROGEN TO NITROGEN

Stoichiometry indicates that a ratio of 3:1 for H2 and N2 mixture is required. However, it is interesting to note that not only is the efficiency lowest at the proportion of 3:1, but the maximum conversion percentage is actually obtained at a ratio of Hydrogen to Nitrogen of 2.5. CONCENTRATION OF INERTS

CH4 and Argon take no part in the Synthesis reaction and hence their concentration (as inerts) keeps building. Since the effective pressure for Ammonia Synthesis is the partial pressure of Hydrogen and Nitrogen, inerts in the system lower this effective pressure and so the conversion is reduced. The inerts in the recycled gas are always much higher than the inerts in the make-up gas, as in the Synthesis process only Hydrogen and Nitrogen get converted to Ammonia while the inerts go on accumulating. Hence the inerts must be maintained at the designed value by purging a small portion of gas from the loop, which is equivalent to the inerts in the make up gas.

CONCENTRATION OF INLET AMMONIA TO CONVERTER

The outlet Ammonia from the Converter is fixed by conditions of temperature pressure and space velocity. The inlet-recycled gas also contains some Ammonia, generally about 4% decreasing the conversion of synthesis gas in the converter to that extent. The higher the inlet Ammonia the lesser will be the conversion in the Converter.

2.12 SYN LOOP - General

In general outline, the Synthesis Loop consists of the Converter 1121, Loop Boiler Feed water Heater 1523, Loop Cooler Condenser 1524, Converter Feed Interchanger 1525, Primary and Secondary Chillers 1526 and 1527 and the Ammonia Catch Pot 1122. These items affect catalytic synthesis of Ammonia, gas cooling, Ammonia condensation and liquid Ammonia separation. Also associated with the high-pressure loop are the Synthesis Gas Compressor and Synthesis Gas Circulator. The refrigeration system consists of the Refrigeration Compressor 3104, Refrigeration Condenser 1528 Refrigeration Receiver 1127, and HP suction drum 1128, together with the two Refrigeration Chillers referred to above.

Product let down is effected in the Let Down vessel 1123 and recovery of Ammonia vapors from purge and flash gases in the Ammonia recovery section, consisting of an Absorber and still with associated heat exchangers and pumps.

2.13 SYNTHESIS LOOP

Gas from the discharge of the Synthesis Gas Compressor, at 227 Kg/cm2g, goes to the Heavy Water Plant for deuterium recovery, and returns as make up gas to the Synthesis Loop. The

Page 41: Ammonia Manual

Ammonia Plant Operating Manual 41

Make Up Gas joins the Circulating Gas at the inlet to the tube side of Primary Chiller 1526. The introduction of synthesis gas into the loop gas at a point where liquid ammonia is present has the effect of reducing the loop gas temperature from 23.50C to 21.10C and the gas enters 1526 at this temperature. This unit cools the gas to 80C. At 4.65 ATA, ammonia vapor leaves the shell side to the refrigeration compressor for recompression and condensation. A relief valve has been provided on the shell as a protection against a burst tube. The circulating or loop gas, which contains ammonia, is then finally cooled to -2.50C in the tube side of the Secondary Chiller 1527. Evaporation of liquid ammonia in the shell side occurs at -11.50C and 2.8 ATA. The shell is protected with a relieve valve.

The two-phase gas/liquid mixture from the Secondary Chiller passes to the Ammonia Catch pot 1122 for separation and removal of liquid from the circulating gas. The gas/liquid mixture enters through the central top inlet and flows down a down pipe, which expands in diameter. The mixture is thrown against a conically shaped deflector, which disengages the liquid from the gas. The gas then reverses direction and flows upwards through a nozzle in the vessel head. Disengaged liquid drops into the bottom where it accumulates and contacts with a bed of 1" carbon steel ranching rings installed to ensure good disengagement of entrained gases from the liquid, and also to prevent vortex formation.

Liquid leaves the vessel through one of two outlets, both of which are fitted with temporary strainers, to a letdown vessel 1123 (dealt with separately). Gas from the catch pot then flows to the shell side of converter feed interchanger 1525 where it is heated to 300C by interchange of heat with the effluent gas from the loop cooler condenser 1524. It enters the circulator where pressure losses around the loop are made up prior to admission to the converter. The circulator, previously described, compresses the gas from 208.5 ATA to 230 ATA and has a Flow sheet capacity of 531, 120 Nm3/hr measured on FI 1809.

The loop gas of following composition enters the synthesis Converter (1121)

NH3 - 3.96 Mole% H2 - 63.03 Mole% N2 - 21.01 Mole% CH4 - 8.18 Mole% Ar - 3.81 Mole% Synthesis of ammonia from hydrogen and nitrogen in the circulating loop gases takes place in this vessel. 2.14 CASALE INSERT CARTRIDGE CONVERTER LAYOUT

The cartridge configuration is 3 bed with 1 quench between the I and II bed, 1 interchanger between the II and III bed and one bottom exchanger. The interchanger and the bottom exchanger are placed in central position respectively inside the II and III bed. All three beds are of axial radial type with outwards flow direction in the I bed and inward flow direction in the II and III bed.

In each bed the following items are inserted, two cylindrical walls, one external, near the cartridge wall and one internal. Each wall is made up of an embossed and perforated wall and a wire net lining in contact with the catalyst. The external perforated wall has the main function to secure an even gas distribution and support the catalyst net, while the wire net contains the catalyst. The wire net is supported by the embossment of the perforated wall. The

Page 42: Ammonia Manual

Ammonia Plant Operating Manual 42

supporting system ensures that the requested gas distribution is obtained in all directions between the perforated wall and the wire net.

A low linear velocity of the gas characterizes the axial radial converters. In fact the bed arrangement offers a large cross sectional area to the gas passage, so that the pressure drop across the catalyst beds is strongly reduced; on the other hand the gas distribution is a critical factor. The process design takes into account the difference of temperature existing at full capacity between the points of the same cross sectional area. This difference will increase at reduced capacity, i.e., at reduced flow rate across the converter. Therefore, it is better to keep this flow rate across converter always higher and in the mean time it should maintain the temperature profile across the converter.

GAS FLOW PATH

The main stream of feed gas enters through HCV 1809 at the bottom of the converter. A part of the inlet gas enters the converter at the top through HCV 1807 in between the top cover and inner cartridge cover and travels down through the annular space between inner cartridge and the shell. This flush gas is useful in maintaining the inner cartridge and HP shell temperature uniformly. During normal operating conditions this flush gas flow should be always maintained above 50,000 Nm3/hr. The inlet gas stream and the flush gas stream are mixed together at the bottom of the converter and passed to the tube side of the bottom exchanger placed in the center of the III bed, where it is heated by the product gas that leaves the III bed. In this process the gas outlet of III bed is cooled.

The bottom interchanger exit feed gas temperature is controlled by the direct addition of the III quench through HCV 1808. This feed gas is then passes through the tube side of the interchanger placed in the center of the II bed. Here the feed gas is heated by cooling the reacted gas in the II bed. Thus addition of III quench through HCV 1808 increase the heat transfer in the II bed exit exchanger by reduced inlet temperature and increased mass flow rate. This reduces the III bed inlet temperature. This will also reduce the I bed inlet temperature since the feed gas at the bottom exchanger outlet is cooled.

The feed gas at the outlet of II bed interchanger is fed to the I bed as the feed. The inlet temperature is further controlled by the direct addition of circulator discharge gas through HCV 1801. This gas is coming through the 1434 coil. This can be utilized for the catalyst bed heating during startup using the startup heater 1434. The gas now enters the I bed where its flow pattern is outward. After leaving the I bed, the II bed inlet temperature is controlled by quenching this stream with the quench gas through HCV 1806. Then the gas flows through the II bed in an inward direction and crosses the interchanger shell side. The gas enters the III bed where the inlet temperature is controlled by HCV 1808 as discussed earlier. In the III bed gas flows in an inward direction. After leaving the III bed, in the bottom exchangers it preheats the feed gas to the converter and leaves the converter at the top by means of a long central pipe.

A total bypass HCV 1810 is provided for the converter, which is used to regulate the flow through the converter during initial startup and any upset conditions. During full load normal running condition this valve is in closed condition.

The axial radial gas distribution in catalytic beds is controlled by the following parameter:

* Pressure drop in the catalytic bed. * Concentrated pressure drop in inlet and outlet bed walls.

Page 43: Ammonia Manual

Ammonia Plant Operating Manual 43

* Height of the imperforated zone in top portion of outlet bed wall. This height is fixed taking also into account the catalyst shrinkage that will occur mainly during catalyst reduction phase. Because of this of 100% catalyst utilization efficiency is practically obtained.

To monitor the catalyst performance and degree of reaction two sets of thermocouple are provided in each catalyst bed and exit. The catalyst used is a magnetite catalyst activated with K2O, CIO, Al2O3 and Mao. The total catalyst volume is 51 M3, the I bed containing 7.3 M3, II bed 15.5 M3 and the III bed 28.2 M3.

The Converter shell has an I’d. of 2700 mm and 14175 mm clear height. The vessel has a "full bore" top closure to enable removal of converter internals. The cartridge is supported on a pad in the bottom head so designed as to ensure accurate concentricity of the cartridge within the H.P. shell. The main joint between the top cover and the shell is a self-sealing double cone joint, the seal being formed between opposed conical surfaces between vessel and cover using aluminum gaskets inserted between; the opposing surfaces. By its construction this type of joint utilizes the internal pressure to maintain the joint. The internal interchangers are constructed of austenitic stainless steel and is of conventional shell and tube construction. The cartridge is a completely separate unit and hence the interchangers can be removed for maintenance. The interchangers are of rod baffle type exchangers to have minimum pressure drop across the shell side.

1121 Exit Gas Analysis NH3 - 19.70 Mole% H2 - 49.86 Mole% N2 - 16.62 Mole% CH4 - 9.46 Mole% Ar - 4.35 Mole%

The effluent gas leaving the converter is cooled to 123.40C in the tube side of Low pressure Boiler Feed Water Heater 1523 which preheats boiler water from pump 3214 from 1090C to 181.60C. A pressure relief valve is mounted on the shell. Downstream of this exchanger is a high-pressure vent for depressurizing the loop. Further cooling of the loop gas to 35.5 0C is effected in the tube side of the Loop Cooler Condenser (1524), which is split into 2 shells. TI 1/1807 measures the temperature at the outlet. The dew point of the gas is reached in this unit and condensation of ammonia is started in this exchanger itself.

The converter effluent is now cooled to 20.30C in the tube side of Converter Feed Interchanger 1525 by heat exchange with cold gas returning to the circulator from the catalyst. Converter feed flows on the shell side and is warmed from -6.50C to 300C prior to recompression in the synthesis gas circulator. The gas leaving 1525 shows the highest concentration of inerts since the make-up gas is introduced just before entering the Primary Chiller. Accordingly the voluntary loop purge is taken off at this point. Liquid Ammonia is also present and the purge gas is separated from it in a simple disengagement device, which consists of a vertical section of 12" M.S. pipe containing a demister pad. The purge gas is taken to the Hydrogen Recovery Unit. Immediately after purge gas removal, fresh make-up synthesis gas from the discharge of SGC, at 198.3ATA is added before it is circulated through the chillers. The liquid ammonia separated from the circulating gases in the Ammonia Catch Pot 1122 is passed under level control LC 1811 or hand control HC 1811 to Let Down Vessel 1123 which operates at 21.1 ate. Pressure let down causes gases dissolved in the product ammonia to flash off, together with some ammonia (and separation of flashed gas

Page 44: Ammonia Manual

Ammonia Plant Operating Manual 44

occurs in the let down vessel from where they join the purge gas). This vessel is sized both to give adequate `buffer’ storage of liquid ammonia, and separation of the flashed gases. Removal of liquid ammonia is by level control valve LCV 1813 with a flow meter FQ 1808 upstream. A demister is incorporated in the vessel to effect final disengagement of liquid from the flash gas.

The product ammonia from ammonia recovery section is also introduced into this vessel. Two relief valves are fitted to the vessel, connected by a 3-way valve designed so that one relief valve will always be in use. This allows maintenance on one relief valve without shutting down the plant and purging the Let Down Vessel. The valves are sized for possible blow through of the synthesis gas from the Catch Pot.

2.15 REFRIGERATION SYSTEM

(Refer to Drug. 1160/2001/18 & Vendors drawings for Compressor 3104)

The Loop Refrigeration System is designed to reduce the temperature of the circulating loop gases -2.50C at the entrance for the Ammonia Catch Pot. It is conventional mechanical refrigeration system, using ammonia as the working medium and incorporating two levels of refrigeration.

The Refrigeration Compressor 3104 is a single casing two stage centrifugal machine driven by a condensing steam turbine. The speed of the compressor (and hence capacity of the refrigeration system) is controlled by a pressure signal taken on the L.P. suction of the compressor. In this way, the L.P. suction pressure is maintained constant and hence the degree of refrigeration achieved in the loop maintained at a constant level.

Starting at the outlet of the Refrigeration Receiver 1127 the flow scheme is as follows: -

Liquid Ammonia leaves the Refrigeration Receiver 1127 at 17.4 ate and 430C and flows to the shell of the Primary Chiller 1526. A level control valve over which the pressure is reduced to the operating pressure of the shell controls the rate of admission, 4.65 ate. Reduction in pressure causes the temperature to drop to 20C and some vapor to flash off. The liquid/liquid mixture enters the shell side of lathe exchanger where a certain amount of liquid evaporates. The combined evaporated plus flashed liquid leave the exchangers. The liquid droplets carried along with the vapor system are knocked out in the HP suction pot 1128 and it joins the side stream inlet of the refrigeration compressor. Liquid Ammonia, which has not evaporated, flows to the Secondary Chiller shell 1527 again through a level control valve. This liquid all evaporates at 2.79 ate and -11.50C and the combined evaporated plus flash vapors flow to the low-pressure inlet of the Refrigeration Compressor 3104. The entrained liquid is separated in the demisters of liquid separator kept horizontally over secondary chiller.

A further gas circuit is employed round the Refrigeration Compressor and consists of two anti-surge bypass round the H.P. and stages. The H.P. Stage anti-surge bypass takes superheated gas from the compressor discharge, under flow control, and recycles it to the H.P. Gas inlet via the H.P. Suction Pot. To avoid a build up in temperature within the compressor, liquid ammonia from the Receiver or feed pump discharge is injected to the gas prior to the Suction Pot using TCV1811. This saturates the superheated gas, thus cooling it and controls the compressor discharge temperature.

The L.P. stage anti-surge bypass takes saturated gas from between the suction pot and the compressor H.P. liquid inlet and recycles it to the L.P. inlet under flow control. Superheated

Page 45: Ammonia Manual

Ammonia Plant Operating Manual 45

Ammonia liquid at 1900C from the Refrigeration Compressor flows to the shell side of the Refrigeration Condensers 1528 where it is de-superheated and condensed at 430C by cooling water on the tube side. There are three exchangers operating in parallel. A pressure relief valve is mounted on each shell to guard against excessive shell pressures. Each shell can be completely Isolated and each has a drain. A vent is fitted to the shell of each exchanger.

Liquid Ammonia from the Condensers flows by gravity into the Refrigeration Receiver 1127. This vessel provides a "buffer" in the system and evens out flow surges. It is a horizontal vessel fitted with a level gauge, level indicator alarm and pressure indicator. Make up Ammonia can be introduced into the vessel from Ammonia storage either in liquid form (for initial pressurization) or in liquid form (for make-up). From this make-up line is a branch for injection of Ammonia in the anti-surge line from compressor discharge to H.P.Suction Drum. When the refrigeration system is in operation, a separate line from the liquid outlet of 1127 supplies Ammonia and the line from the make-up is closed. TC 1811 is set at just above Ammonia saturation temperature at the prevailing H.P. suction pressure to ensure complete evaporation of the injected Ammonia.

Liquid from the Primary Chiller 1526 passes back to the compressor via 1128 H.P. Suction Drum, in which entrained liquid Ammonia is disengaged. L.P. anti-surge bypass gas, having been first saturated by liquid Ammonia injection, also has any liquid Ammonia in the vessel is removed by a level control valve LCV 1807 which passes the liquid to the Secondary Chiller shell 1527.

LI 1807 transmits the liquid level in 1128 to the control room, together with high and low level alarms. Should the level control fail to operate for any reason the refrigeration compressor is protected against liquid carry over by a high liquid level trip on the suction pot, which trips the compressor drive turbine. Inerts introduced into the refrigeration system with the liquid ammonia make up will tend to accumulate. A higher discharge pressure on the compressor and slightly abnormal temperatures will notice this in the system. The inerts may be purged off from the shell of the refrigeration condenser 1528. The purge gas is passed through 1529, the Inerts Purer in which there are two coils. Through these coils liquid ammonia from 1127 is passed. Some ammonia is evaporated and the liquid/liquid leaves the coils and passes to the shell side of Secondary Chiller 1527/ Outside the coils, the ammonia in the purge gas is condensed and returned under gravity to 1127, while the inert gases are vented to a safe location.

Prior to filling the refrigeration system with its first charge of ammonia the system is evacuated by means of the Vacuum Pump 3105, which is connected, to the refrigeration condenser shells. The pump is driven by an electric motor.

2.16 AMMONIA RECOVERY

The Ammonia Absorber 1124 in conjunction with the Ammonia, Still 1125, is designed to strip out NH3 from purge gas & flash gas as 15%. NH3 liquor, which is distilled to produce the required grade of Ammonia.

The Ammonia Absorber contains 4 beds of 50 mm carbon steel ranching rings. There are two liquid feeds, one at the top of the column and one to the middle.15% liquor from the base of the column at 600C and 20.7 ata is pumped by motor driven Absorber bottom pump 3211 in two directions:

a. As recycle via water-cooled exchanger 1530 back to Absorber at the rate of 5950 Kg/Hr (FI 1903). The cooler reduces the liquor temperature to 400C (TI 1/1902).

Page 46: Ammonia Manual

Ammonia Plant Operating Manual 46

b. To the Ammonia Still via liquor interchanger 1531 at a flow rate of 3558 Kg/Hr (TI 1/1901) by heat exchange with hot liquor from the Still base. Both flows FI 1903 and FI 1904 Are manually controlled.

Liquor from the base of the Still (which is almost pure water) at 2230C (TC 1904) is cooled in Liquor Interchanger 1531 to 750C (TI 1902) and again cooled to 400C in a water-cooled Absorber Feed Cooler 1532 (TI 1/1903). About 1 tph of this liquor is taken as scrubbing water to the Wash Water Tower in PGHRU section. Remaining liquor is fed to the top of the Absorber under Still level control valve LCV 1904 at a flow rate of 3049 kg/hr (FI 1902). Return liquor from Wash Water Tower of PGHRU section joins the recycle water before 1531.

The rate of purge gas from the top of the Absorber is measured by FI 1902. When Hydrogen Recovery Unit is in line, the flash gas, which comes out of 1124 top, is then taken to Hydrogen Recovery section. Heat required for the NH3 still reboiler 1534 is supplied by 45 ATA steam. The overheads from the still at 520C, (TI 1903) are cooled in water-cooled still condenser 1533 A, 1533 B and pass to still overhead receiver 1126, where Ammonia and gas are separated. The gas is returned to the inlet of absorber under pressure control of PC 1905.

The liquor from 1126 is pumped by motor driven still Reflex pump 3212 to the still top as reflex liquor at a flow rate of 14 T/hr, FC 1905. The water content of the product ammonia is governed by the reflex ratio on the ammonia still.

The level in the still overhead receiver 1126 controls the flow of recovered ammonia returned to the let down vessel 1123. There is a N2 purge at 1126. Whenever purge gas hydrogen recovery section is not run, loop purge gas, flash gas are routed through 1124. Rate of purge gas from top of 1124 is measured by FI 1901, 6848 Nm3/hr and its composition is

NH3 - 0.1 Mole% H2 - 61.985 Mole% N2 - 21.01 Mole% CH4 - 11.25 Mole% Ar - 5.543 Mole%

This gas is fed towards the reformer burners at 400C and PC 1301 at 20 Kg/cm2 controls pressure of absorber 1124.

2.17 AMMONIA STORAGE & REFRIGERATION

The main function of the Storage Refrigeration Unit is to maintain the contents of Ammonia Storage Sphere at a constant pressure of 4.5ATA and temperature 00C. The sphere is of 3000 tons capacity to hold nearly 3 days production of our plant. Pressure change in the sphere is very slow. Sphere pressure is maintained by condensing ammonia liquid and purging out inerts from the system.

This SR Unit consists of mainly compressors, condenser, separator and a purge pot. Ammonia liquid along with inerts come to Storage Refrigeration Compressor suction through a Knock Out Pot. There is a 12 ATA saturated steam coil in the knock out pot. The Compressor then compresses liquid ammonia to 32.2 ATA.

This compressor is of two stage horizontal reciprocating type. Gas from knock out pot comes to I suction through a damper and filter. In the first stage it is compressed to 12 ATA after which

Page 47: Ammonia Manual

Ammonia Plant Operating Manual 47

the gas is cooled to 450C in the intercooler. Second stage suction high gas temp alarm and trip are set to 500C and 550C respectively. In the second stage gas is compressed to 32.3 ATA. This pressure depends on the setting of PIC 2002. The hot liquid from the compressor is condensed in the water-cooled Condenser and the liquid ammonia condensed is separated in the Ammonia Receiver. The flash gas from the Receiver and non-condensable gases from the Condenser are further cooled in the shell side of the Purge Pot. Liquid Ammonia separated in the Receiver goes through LCV 2006 to Purge Pot where it passes through the coil. Cooling the non-condensable gas on the shell-side to 40C. Purge pot shell side pressure is controlled by PCV 2002. Liquor ammonia condensed in the shell side of the purge pot again passes through the purge pot coil along with liquor. NH3 from receiver and goes to sphere. Non-condensable gases are vented out at the top of the sphere to atmosphere by PCV 2002. Storage Refrigeration System

Start-up Procedure:

1. Purge the system with N2. 2. Line up gas from the sphere to compressor; charge service steam to K.O pot coil. 3. Line up cooling water to intercooler and primary condenser. Bleed off if necessary. 4. Fill up cylinder jacket cooling thermo siphon system with cooling water. 5. Line up gland cooling water to comp. From D.M. water source. 6. Isolate Suction & Discharge N2 line valves and provide slip plate upstream of these valves. 7. Check crank case oil level. 8. Bar the machine if it is started after a long shut down. 9. Set PIC 2002 at 4 Kg/cm2g. 10. Start comp. And check lube oil pressure. Comp. Low lube oil trip is set at 0.87 Kg/cm2g. 11. Slowly increase PIC 2002 set point to 30 Kg/cm2g. 12. Check comp. Suction and discharge temp. 13. Watch ammonia receiver level glass. When level comes up commission LCV 2006. 14. When LCV 2006 is commissioned purge pot temp will come down and level will go up. When level comes up commission LCV 2002.

2.18 PROCESS CONDENSATE SYSTEM

Process Condensate is recovered from condensate knock out drums 1, 2 and 3 (1114, 1115 and 1113). Part of the condensate from 1115 is pumped by quench water pump to quench the gas inlet L.T. shift vessel and the gas exit RG Boiler. This pump also provides wash water to stripped gas wash pot 1131,as a back-up to BFW supplied from ASGU and flow is controlled by FCV 1610. This is recently commissioned to enrich the deuterium concentration in feed gas to HWP. Process condensate from 1115 may be used as emergency make-up to Regenerators. Rest of the condensate from 1115 and condensate from 1114 and 1113 are treated for reusing as make-up D M Water. The condensate contains dissolved CO2, Ammonia and Methanol. Other impurities present are likely to be Ferrous Iron and Silica.

CO2 - from process gas 1500 ppm NH3 - formed over H.T. shift catalyst 1000 ppm CH3OH- formed over L.T. shift catalyst 2000 ppm Fe - from pipe work and HT shift catalyst 1 ppm SiO2 - from catalyst & Secondary Reformer 0.1 ppm

Page 48: Ammonia Manual

Ammonia Plant Operating Manual 48

The condensate from the three sources is collected and passed to the degassed 3603.001. This is a vertical column containing 15 valve trays. The condensate is introduced at the top of the column and passes down against a counter current flow of steam. This steam is available from the turbine of cooling water pump. The degasser operates at low pressure of 2 ate in order to remove as much of dissolved gases as possible. The stripped condensate leaving the bottom of the column is expected to contain about 40 ppm CO2, 20 ppm NH3 and 50 ppm CH3OH.

This condensate is pumped by degassed condensate pump 3603.003/004 cooled by cooler 3603-002 and sent to the condensate polisher. It is necessary to cool the condensate to 400C to avoid damaging the resin in the polisher. The duty of the polisher is to reduce NH3 and CO2 to less than 1 ppm and to reduce the iron content to less than 0.1 ppm. This condensate is sent to DM water storage.

For the RG mains cooling, a part of SCC is diverted and the return is cooled in cooler and pumped to degassed condensate system for purification at water treatment plant.

2.19 DM WATER & BFW SYSTEM

DM Water

DM Water is supplied to Ammonia plant from WTP. The flow is indicated and integrated by FQ 0201. DM Water is supplied to the following:

1. De-aerator2. Flushing connection to 11083. Ammonia Recovery System for priming the section during startup.4. Storage tank and Make-up tank in Vetrocoke and a hose connection point near Vetrocoke filter set. (Water to Vetrocoke area is normally supplied from steam condensate header but a jump over from DM water header also is available).5. Auxiliary Boiler6. Make-up to Dosing Tanks.7. SRC’s gland cooling water.

Low Pressure Boiler Feed Water

Flow of water to Deaerator is controlled by LCV 0202-A operated by Deaerator level control and downstream of this it is joined by steam condensate from various condensing type turbines. This combined feed water called as low-pressure boiler feed water is preheated in 1513 by gases from the L.T. shift vessel. The preheated water passes to the Deaerator. Stripping stream is provided to deaerator from 2.1 ata steam header. Pressure of Deaerator is controlled by vent valve PCV 0212. Steam condensate from 1534 is fed to Deaerator directly. Deaerator has a storage capacity for 30 minutes at 100 % plant throughout.

De-aerated Water De-aerated water from 1703 feeds -1. Under gravity the Vetrocoke seal water tank via a water cooler. 2. Water jacket on 1105.3. Boiler Feed Water Pumps.

The boiler feed water develops a pressure of 134.5 Kg/cm2 and there is a special compensating bypass check valve at the discharge of the pump to pass a flow of 100 TPH back to Deaerator at a low loads of the pump. Hydrazine and Ammonia are dosed at the suction of BFW Pump.

Page 49: Ammonia Manual

Ammonia Plant Operating Manual 49

High Pressure Boiler Feed Water

High-pressure boiler feed water from the pump discharge is supplied to the following:1. 1523, the loop boiler feed water heater. The water is preheated to 1810C and water is split into two streams.2. It is further heated in 1515 to 2030C and fed to Auxiliary boilers.3. It is preheated in 1539 and the water at 2330C is fed to steam drum (1106).

High Pressure Desuperheater HeaderThe H.P. Desuperheater header feeds the following:

1. Water (at BFW pump discharge pressure) to TCV 1311, the Temperature upstream of 1536-A (turbine steam Superheated- HT section) in the Convection Box of Reformer.2. The pressure is let down to 55 ate by PC 0209 and water is fed to L.P. Desuperheater header.

Low Pressure Desuperheater Header

The L.P. Desuperheater headers feed the following four Desuperheater via various TCVs.1. Desuperheater for the start up steam to 1517 A & B.2. Desuperheater for the 45 ata / 12 ata Let Down station.3. Desuperheater for 106 ata / 45 ata Let Down station.4. Desuperheater for 12-ata super to 12 ata steam.

L.P. Desuperheater water is further used in the following sources when necessary:

1. As Make-up water to recovery Absorber 1124.2. As seal water when seal water pressure is low, through a finned cooler in the process condensate line exit 1115.3. To build up liquid seal in 1115 during startup.4. When quench water header pressure falls, PC 0207, which is downstream of PC 0209, lets down the pressure to 34-ata and supplies water to TCV 1509, TCV 1407 and 1131.

There is a spillback downstream PCV 0209 back to deaerator.Seal Water to Low Pressure Desuperheater Header Jump Over

There is a jump over from seal water header to low pressure desuperheater header to charge the low pressure desuperheater header when BFW pump is not running e.g.: during steam system charging.

When the jump over is in line PCV 0209 should be isolated to avoid the seal water backing up into BFW header. Spillback of PCV 0209 to Aerator also should be isolated. If these are not isolated, pressure of Desuperheater header will be very low.

During the period which this jump over is in line, Desuperheater header pressure is only about 25 Kg/cm2 and hence TCV 0104 (desuperheater for 45 ata steam header) should positively be isolated to eliminate the possibility of 45-ata stream backing up to seal water header.

Steam Cooled Condensate Header

Page 50: Ammonia Manual

Ammonia Plant Operating Manual 50

This header is fed by the steam condensate from the condensers of the following turbines:

1. Syn Gas Compressor Turbine2. Process Air Compressor Turbine3. Refrigeration Compressor Turbine4. Cooling Water Pump Turbine5. ID/FD Fans (A) Turbines6. ID/FD Fans (B) Turbines7. Condensate from Steam Air Heater of Auxiliary Boilers All the steam-cooled condensate are cooled in a cooler and sent to Water treatment plant for purification. To meet the heat balance in the system a part of polished water received is heated up in a heater using 4-ata steam. In case of polished water shortage SCC can be diverted to our Deaerator at the down stream ohm of LCV 0202 A.

An additional polished water line from CPP header is also joining at the downstream of LCV 0202 A to meet the make up purpose. Part of the SCC is used in the water jackets on R.G. mains and at The neck of RGB and 1105. This is recycled to degassed condensate header.

SCC connections are available to Vetrocoke solution storage tank, Make-up tank and filter set. When SCC is not available, DM Water can be used at these places through a jump over.

2.20 STEAM SYSTEM

There are seven interconnected steam systems namely:

1. Extra high pressure steam: 106 Kg/cm2a 4750C2. HP steam: 45 Kg/cm2a 3650C3. MP steam: 12 Kg/cm2a 2780C4. Service Steam: 12 Kg/cm2a saturated 1880C5. Atomizing Steam: 4 Kg/cm2a6. LP steam: 2.1 Kg/cm2a 2430C7. Export steam: 4 Kg/cm2a

Extra High Pressure Steam System to 106 ATA 4750C

Waste heat recovery System, Auxiliary Boilers, and ASGU feed this header. Almost the entire steam from this header passes to the Sin Gas Compressor turbine 3701. There is a pressure-controlled vent PC 0105. This steam can be let down through PC 0104 to the 45 ata steam main when the demand of the 45 ata steam header is more than the extraction stream supplied by 3701 to 45 ata header. E.H.P Steam from ASGU is controlled a HCV 202 C.

High Pressure Steam System 45 ata 3650C

Supply sources: 1. Extraction steam from 37012. Let Down through PC 01043. Import steam from OSB via FC 0101

Page 51: Ammonia Manual

Ammonia Plant Operating Manual 51

Consumers

1. 1. Semi lean solution pumps, lean solution pumps, BFW pumps, auxiliary boiler fans and let down to 12-ata steam header.2. Refrigeration Compressor Turbine C.W. pump turbine-A and ID/FD fans' turbines to respective condensers.3. C W pump turbine-B to export steam header degasser and 2.1 ata header.4. Process steam to Reformer.5. Steam to H.T. Shift Vessel.6. Ammonia Still Reboiler 1534 from which condensate is returned to Deaerator.7. Startup Steam to 1517 A & B.8. Startup steam to 1536-B.9. Startup steam to 1509 & 1510.10. Blanketing steam on the process airline to 1105.11. Decoking steam to 1511.

PC 0104 maintains the pressure of the header, which is a split range controller. Under normal operating conditions, varying the steam flows through the high pressure and low-pressure sections of the Sin Gas Turbine controls the pressure. The turbine control system adjusts the turbine inlet regulating valve and the extraction value to maintain at the required pressure and turbine speed. If the pressure cannot be maintained at the required level, PCV 0104 in the let down station opens to restore the pressure.

If the Syn Gas Compressor turbine should trip, the pressure in 45-ata steam main will start to drop rapidly. As there is no cushion available to take care of the immediate fluctuations, a special flow follower system is fitted. During normal operation, FX 0107 measures the extraction steam flow from 3701. This transmits a signal to FCV 0107 in the bypass line between 106 and 45 ata mains and in parallel with PCV 0104. Hence, the position of the value FCV 0107 changes as the extraction steam flow changes. If the turbine trips the trip valve in series with FCV 0107 that is XCV 0102 A & B, which remain normally closed, open and steam is admitted to the 45 ata main at exactly the same rate at just previous to the trip. As soon as the trip occurs, FCV 0107 drifts to close at such a rate that PRCA 0104 can take over control of the steam pressure.

There is a provision to give steam to ASGU during start-up

Medium Pressure Steam

Source of supply

1. BFW Pump turbines2. Lean solution pump turbine3. Semi lean solution pump turbines4. Auxiliary boiler fan turbine5. Let Down through PCV 0103-A.

MP steam system Consumers:

1. The following drives which exhaust into the 2.1 ata LP header.a. Fuel oil pump turbinesb. Fuel Naphtha pump turbinesc. Process Naphtha pump turbines2. Pressure let down to 2.1 ata via PCV 0102-A.

Page 52: Ammonia Manual

Ammonia Plant Operating Manual 52

3. Service steam main via a Desuperheater.4. Decoking stream to 1432.5. Ejectors, condensate pump turbines, lube oil pump turbines 6. And seal oil pump turbines of -a. Sin Gas Compressor turbine.b. Process Air Compressor turbinec. Refrigeration Compressor turbined. C W pump turbines ande. ID/FD fan turbine.

Any excess steam not consumed is vented by PCV 0103-B to maintain 12-ata-header pressure. There is an interconnection to give steam ASGU.

Service Steam 12 ata SaturatedThis is supplied from 12 ata 2780C steam main via a Desuperheater. It supplies steam to the following:

1. Steam coils ina. Vetrocoke solution storage tankb. Vetrocoke solution make-up tankc. Ammonia flash vesseld. F O Day Tank2. Fuel Oil Preheated 15023. Steam Air Heater of Auxiliary Boilers. `4. Soot blowing steam to 1431 and 1433.5. Ejectors for the rain water pit and Hydro finer.6. Snuffing steam to 1431, 1432, 1433, 1434 and vent headers.7. To the Flare stack.8. Decoking steam to 1431.9. Steam out for 1108.10. Steam tracing of FO lines, instruments on Vetrocoke solution serviced and suction of 3101.11. Atomizing steam for burners in Auxiliary Boiler.

Atomizing Steam 4 ata

This is supplied from service steam 12-ata header via pressure let down PCV 0109. It supplies the burners of 1431, 1432, 1433, 1434 and Primary Reformer.

Low Pressure Steam 2.1 ata

FO pump turbines, FN pump turbines and Process Naphtha Pump turbines exhaust into this header. Leak off steam from Lean solution pump turbines, Semi lean solution pump turbines and BFW pump turbines also is connected to this header.

Steam is let down from MP steam main via PCV 0102-A to maintain the pressure in the LP main. Any excess steam is vented by PCV 0102-B to maintain the pressure. Exhaust steam from the backpressure turbine of C.W. Pump is connected to this header through a HIC.

2.1 Ata steam main supplies stripping steam to the Deaearator.

Export Steam Header 4 ata

Page 53: Ammonia Manual

Ammonia Plant Operating Manual 53

The backpressure turbine of CW pump feeds this. This steam is consumed by -

1. Process Condensate Degasser2. 2.1 Ata steam header through a HCV.Exhaust steam available, if any, can be vented to atmosphere by the vent control valve available at the turbine exhaust.

2.21 NITROGEN SYSTEM

Nitrogen is supplied at 43.4 ata by the Inert Gas generating plant. This high pressure Nitrogen is connected by double block and bleeds arrangement to the following:

1. Upstream of Process Naphtha Vaporizer in the Process Naphtha header, downstream of FCV 1203.2. At the inlet of Reformer, downstream of FCV 1303.

High pressure Nitrogen is let down via PC 0205 and supplied to various purge points of the plant:

1. To base of 11082. To base of 11093. To base of 11104. To base of 11125. To 15426. To 11247. To 11268. To 11299. To 360210. To 120411. To 152512. To 143413. To discharge of Circulator14. To suction of Refrigeration Compressor15. To 151316. To various oil consoles and degassers in Compr.House.17. To base of 110418. To base of 110519. To Fuel Naphtha header20. To 143121. To 110122. To 3101

2.22 INSTRUMENT AIR AND SERVICE AIR SYSTEM

During the normal course of running, Process Air Compressor supplies instrument air and service air requirement of the plant. Process air from 4th stage suction of the compressor is let down through PCV 0223 (normally set at 10 Kg/cm2g) to Wet Air Receiver 1137-B. Instrument Air is then supplied to various consumer points at 70C through PCV 0229. Wet air from the receiver is supplied as such at 7 Kg/cm2g pressure for service air requirement of the plant. Service air header supply is controlled by means of a HIC operated from control room. Before this HIC, one branch is taken for supply of service air to 1511 air motor. This ensures that 1511 air motor gets necessary air at required pr. Discharge of Instrument Air Compressor (S) can directly join the

Page 54: Ammonia Manual

Ammonia Plant Operating Manual 54

Service Air header downstream of HIC. Following alarm provisions have been made for taking corrective action.

1. High pr. alarm of Wet Air Receiver set at 10.5 Kg/cm2g.2. Wet air receiver low-pressure alarm, set at 9.5 Kg/cm2g.3. Dry air receiver (Instrument Air Receiver) low-pressure alarm, set at 8.5 Kg/cm2g.4. Instrument Air header low-pressure alarm, set at 6.7 Kg/cm2g.5. Trouble alarm is also provided for instrument air drier system on Main panel.

Auto-start provisions are given for starting/loading operations of IAC (N) and IAC (M). Instrument air for Urea, OSB and SA PA/DAP plants are also supplied from Ammonia Plant Inkster header through HIC 2720 installed at Western battery limit on the main pipe rack.

Data Sheet for Instrument Air Dryer (Mirch-Mirew Ltd) Service Condition

1. Gas to be dried Air2. Composition Atmospheric3. Flow rate 1600-2000 Nm3/hr4. Dryer Cycle 16 hrs.a. Adsorption 8 hrs.b. Reactivation 8 hrs.5. Inlet pressure 8-10 Kg/cm2g.6. Inlet temperature 400C7. Inlet moisture content Saturated8. Outlet moisture content & -400C dew point at atmospheric 9. Connected Power 31.5 Kw.10. Cooling water flow 60.0 ppm. At 330C

The Dryer is designed to dry the air by physical adsorption. The adsorbent used is silica gel, a white highly porous substance, which has a strong affinity for water. The water liquid present in the air will be adsorbed on the silica gel and will be desorbed when the gel is heated. The adsorbing capacity of silica gel is thereby restored. About 750 kg. Of silica gel are used in each of 2 vessels.

A ceramic candle-type profiler is provided before the two-adsorber vessels to remove dust particles, water and oil droplets if any. The two adsorber filled with silica gel are interconnected by 4-way change-over plug valves which are operated at regular intervals by a power piston actuated by a 2-way solenoid valve and a process timer. A ceramic candle-type after filter is provided to remove the silica gel dust if carried over by dried air. The main airflow is divided in a distributor where a portion of air is passed through reactivation system before rejoining the main stream in the distributor.

The compressed air after being passed through profiler is taken to one of the adsorption towers. The silica gel in the tower adsorbs the water liquid present in the air. The process is exothermic and hence the temp. Have the bed and air raised and becomes steady at a certain point. The dry air leaves the adsorption tower and is passed through an after filter. Simultaneously, the adsorbent bed in the other adsorber vessel is being regenerated in closed circuit. A part of the main stream of compressed air is taken from distributor and is passed through an electric heater. The air after being heated is passed through adsorbent bed. The adsorbent gets heated the regeneration temperature and the water adsorbed during adsorption is liberated. The regenerated gas is then passed through a cooler where the moisture is condensed and the gas is

Page 55: Ammonia Manual

Ammonia Plant Operating Manual 55

cooled to ambient temperature. The gas is then passed through a moisture separator, a trap and an air filter where the water droplets are separated out. The regeneration gas is then mixed with mainstream in the distributor before the main stream enters the vessel under adsorption. After the heating period is over, the heater is cut off. But the regeneration is continued and gas continues to be passed though bed for cooling. After the cooling period is over the bed is completely regenerated and ready for adsorption cycle. At the same time the bed under adsorption gets saturated and is ready for regeneration. At this point, the 4-way change over valves are operated through the pneumatic power piston, 2-way solenoid valve and a programmed timer so that the compressed wet gas passes through the regenerated bed and the regeneration gas through the saturated bed. The operation is completely automatic.

2.22 HEAVY WATER PLANT

The fertilizer complex at Tuticorin includes a Heavy Water Plant. This plant is, of course, completely outside the scope of Dab Power Gas. However, as there are a number of interconnections between this plant and the Ammonia Plant, it is intended here to give a brief description of the plant for operator information. Synthesis gas contains traces of deuterium, which is an isotope of hydrogen. The purpose of the Heavy Water Plant is to extract this deuterium and to covert it to deuterium oxide (heavy water).

Synthesis gas from the discharge of the Synthesis Gas Compressor 3102 is passed to the Heavy Water Plant where the pressure is boosted by a booster compressor. The gas then passes via a drier to an isotope exchange tower where the deuterium is extracted by contact with liquid ammonia. The depleted synthesis gas then passes to an ammonia synthesis unit (supplied by Toyo Engineering Corporation) where the ammonia required for isotope exchange is produced. The unrelated synthesis gas, which now contains a trace of ammonia liquid, is returned from the TEC synthesis unit to the SPIC Ammonia Loop.

The enriched ammonia from the isotope exchange tower after contact with synthesis gas is passed to an ammonia cracker. Part of the cracked gas is returned to the isotope exchange tower for contact with enriched ammonia as explained above and the rest is treated further to produce heavy water.

The quantity of synthesis gas lost in the Heavy Water Plant is small and the booster compressor makes up the pressure loss in the plant. This means that when the Heavy Water Plant is on line, make up gas is supplied to the SPIC. Ammonia Loop at substantially the same conditions as when the HWP is not in line.

Page 56: Ammonia Manual

Ammonia Plant Operating Manual 56

1 Chapter three STARTUP

3.1 PRELIMINARY OPERATIONS BEFORE START-UP

Start Motor Driven Cooling Water Pump

1. Fill up the cooling tower sump with make-up water and start the sump pump.

2. Line up cooling water to vacuum pump and also to either side of the cooling water pump seals.

3. Line up both the valves in the priming line to vacuum pump. Ensure priming line to steam ejector is closed. Start vacuum pump.

4. Check oil level in bearings and line up cooling water to bearings of OGT 101 C.

5. When water level starts raising in sight glass in the priming lines, start the motor . When the discharge pressure raises to 5 Kg/cm²g, close the priming valve of the pump and stop the vacuum pump. Stop sump pump after isolating water to seals.

6. Open the discharge valve by about 25%. Keep the high point vents in CWS and CWR linesopen till air stops coming from them. Keep cooling water supply to cooling water return jump over at hydrofining section in open condition.

7. Keep the cooling tower cells in line.

8. Depending upon the availability, line up a few exchangers (preferably those at the terminus of the cooling water lines like ID/FD condensers, HF coolers, PAC inter coolers, 1119 etc.) one by one. While lining up heat exchangers watch the cooling water pump motor amperage and limit it to 100 amps. Vent the air in each exchanger.

9. By suitably adjusting the cooling water discharge valve and cooling tower cell isolation valves, keep the CWS pressure at 4 Kg/cm²g and CWR pressure at 2 Kg/cm²g.

10. If the cooler 1524 is in line, check the CWS temp. Start CT fans as and when required.

11. After lining up cooling water to few exchangers, cooling water supply to cooling water return jump over may be closed.

START IAC

1. Line up cooling water to IAC intercoolers and cylinders.

2. Check oil level in the sump.Ensure valve in the impulse line to discharge pressure switches and that to suction valve unloaders is open.

3. Keeping the discharge valve open, start the machine and check whether it gets loaded up to 100 %. Put the machine in "auto".

Page 57: Ammonia Manual

Ammonia Plant Operating Manual 57

4. Allow the pressure in the wet air receiver to rise and check for 50 % unloading, 100 % unloading and stopping of the machine.

5. Line up one of the IAD & open cooling water to IAD cooler. After ensuring sufficient flow through the drier, put the other drier in regeneration by switching on the heater. Check the proper working of the thermostat.

6. Check the dew point of instrument air.

7. Check instrument air is open to all instruments.

8. Line up PCV 0209 for instrument air. Frequently check wet air receiver for any water collection.

Check Control Valves & Check Trip System

1. Keep all the trip initiators in bypass condition. Keep hydrogen gas compressors trip in bypassed condition with Instrument help.

2. Reset trips A to L.

3. Reset trip actions 1 to 24.

4. Give "50% open" output to all the control valves connected with trip system and check their actual position in the field. Check for healthy condition in fired heaters, ID, FD, lean and semilean pumps. In SGC, keep all other trip initiations (except those coming from trip panel) healthy by suitable arrangements.

5. Initiate trip A & check whether all trip actions have taken place properly.

6. Now reset A & then trip actions 1 to 24.

7. In the above manner initiate all trips one by one and check for trip actions.

8. When trip checking is over, reset all trip actions and stroke check all control valves in both opening and closing directions.

9. Now initiate trip A.

Steam Charging

44 Kg/cm²g, 11 Kg/cm²g (superheated and saturated)) and 1.1 Kg/cm²g steam headers shall be charged simultaneously.

Page 58: Ammonia Manual

Ammonia Plant Operating Manual 58

1. Check that the isolation valve at all points consuming steam from or supplying steam to the above 3 headers is closed.

2. Keep 1537 inlet valve and FCV 1304 and HCV 1306 block valves and its bypass valve closed. Keep PCV 0104 isolation valve closed. Keep 1537 vent full open.

3. Keep FCV 0101 and PCV 0104 full close and PCV 0102 B and PCV 0103 B full open.

4. Take PCV 0103 A control to PAM 0103 A and keep it open by about 20% on manual.

5. Open PCV 0102 A through PAM 0102 A by about 20% on manual.

6. Keep all drains in the above 3 headers full open.

7. Slowly open the west battery limit isolation valve's integral bypass valve and charge steam up to FCV 0101.

8. Crack open FCV 0101 and allow steam to enter all the 3 headers slowly. Ensure there is no steam hammering.

9. When steam starts coming through the 1.1 Kg/cm²g header drains in tank farm slowly close PCV 0102 B through PAM 0102 B so that pressure in this header rises to about 0.5 Kg/cm²g.

10. Slowly close the drains one by one when dry steam starts coming out.

11. Slowly raise the 1.1 Kg/cm² header pressure to normal value by raising the set point and put the PAM 0102 B on Auto.

12. Raise the 11 Kg/cm²g header pressure gradually by closing PCV 0103B. Open FCV 0101 also gradually. This will increase the 44 Kg/cm²g header pressure and in turn will supply more steam into the 11 Kg/cm²g header through PCV 0103 A. When 11 Kg/cm²g header reaches normal value put PAM 0103 B on auto.

13. Now raise the 44 Kg/cm²g header pressure to normal value by gradually opening FCV 0101 to 100 %. Now all steam coming into the plant (as indicated by FI 0101) is being vented through PCV 0103 B and PCV 0102 B and this steam flow can be increased or decreased by opening or closing PCV 0103 A by PAM 0103 A.

14. Close the following valves in the desuper heating header. Isolation valves of TCV 0105, TCV 0102, TCV 0103, TCV 0104, PCV 0209, valve in spill back line to deaerator and make up valve to ammonia absorber. Fill up seal water tank with water from deaerator and put its LCV on auto. Start seal water pump after isolating all seal water supply valves. Put seal water discharge pressure controller in auto at 27 Kg/cm²g. Open the jump over valve from seal water header to desuperheating header. Line up TCV 0105 and TCV 0103 and control TI 0105 at 200 0C and TI 0103 at 278 0C and put the instruments on auto.

15. When one of the 44 Kg/cm²g to 11 Kg/cm²g let down turbines is started, slowly close PCV 0103 A through PAM 0103 A watching that PCV 0103 B is always open. When PCV 0103 A comes to 0% opening, switch over PAM 0103 A to auto mode so that PC 0103 will start the controlling function.

Page 59: Ammonia Manual

Ammonia Plant Operating Manual 59

Similarly when one of the 11 Kg/cm²g to 1.1 Kg/cm²g let down turbines is started, slowly close PCV 0102 A through PAM 0102 A watching that PCV 0102 B is always open. When PCV 0102 A comes to 0% opening switch over PAM 0102 A to auto mode so that PC 0102 will start the controlling function.

START IG PLANT

Press reset 1 in trip panel and allow liquid ammonia flow to IG plant. Start IG plant and fillup Nitrogen receiver after checking nitrogen quality. Refer IG plant section for start up.

START BOILER FEED WATER PUMP

1. Build up level in Deaerator with polished water. Put LCV 0202 on auto. Ensure that LCV 0202 A is always open (by keeping open the 2" deaerator drain partly) and allow a continuous water flow into the deaerator.

2. Keep deaerator vent fully open and PC 0212 (deaerator pressure control valve) full close in manual.

3. After opening the block valves of PCV 0212, crack open PCV 0212 and allow steam into the deaerator gradually. Check there is no hammering in the polished water line to deaerator. Gradually raise PI 0212 to normal value and put PC 0212 on auto with set at 0.5 Kg/cm²g.

4. When there is sufficient consumption of deaerated water, close the 2" drain line.

Ensure that the following BFW consuming points are isolated :

1. Steam drum level control valve and steam temperature control valve in both the boilers.

2. BFW inlet 1539.

3. TCV 1311 isolation valve.

4. PCV 0209 isolation valve.

Now start BFW pump and open the pump discharge valve, keep the standby pump available. Line up desuperheater water header pressure control valve PCV 0209 and isolate seal water jump over.

FUEL OIL SYSTEM

Build up 60 % level in FO day tank 1201. Open suction and discharge valves of the three FO pumps. Keep PCV 0206 and its isolation valves full open. Ensure FO supply valves to both the boilers isolated. Start turbine driven FO pump. Slowly close PCV 0206 and build up FO header pressure to the normal operating value of 12 Kg/cm²g and confirm the auto start pressure values. Put the controller on auto and put the other two pumps on auto.

Charge steam to 1502 and set TIC 1002 at 120 0C. Check that both the steam traps at the exit of 1502 are functioning well. Ensure that the day tank temperature never exceeds 105 0C and falls below 70 0C.

3.2 NORMAL START-UP PROCEDURE

Page 60: Ammonia Manual

Ammonia Plant Operating Manual 60

A. INTRODUCTION

The start-up circulation loop consists of 1432, 1104 (on bypass) primary and secondary reformers, RG Boiler with bypass in full open condition, 1108, 1109, 1110(on bypass), 1111, 1112 (on by pass) & start-up compressor. This closed loop circuit is established to bring up the temperature of the various sections of the plant and to carry out operations of various system.

B. PREPARATION FOR START-UP

I. The entire loop is to be purged with Nitrogen, free of Oxygen & Hydrogen to less than 0.2 % each. Pressurise the entire loop to 24 ATA with Nitrogen. The vessels on bypass as 1110 and 1112 also are to be pressurised with Nitrogen to maintain higher pressure than the equipments in the start-up loop to avoid moisture / steam entry. 1104 is to be kept at a pressure lower than the feedstock header to avoid hydrocarbons carry over into reformer.

II. Check whether the following valves are in open condition :

1. Suction block valves of 3109.

2. Discharge block valves of 3109 at the compressor and at the line joining the process naphtha header to 1432 and Ball valve downstream.

3. bypass valve of 1104.

4. Block valve of FCV1303.

5. Bypass valve RGB.

6. FCV 1401 downstream drain.

7. Inlet and exit valve of 1108.

8. 1539 gas and water bypass valves.

9. TCV 1506. Provide 'DO NOT CLOSE' operation mark on the face plate.

10. Bypass valve of 1110.

11. Inlet butterfly valves of 1517 A & B.

12. Methanator bypass valves.

13. Startup block valves at 1113 exit.

14. HCV 1308, 1309 & their block valves.

15. HCV 1408.

16. Drains of superheaters, 106 Kg/cm²g header from superheater and vents on steam drum.

17. Drains upstream of FCV 1203 and FCV 1501.

Page 61: Ammonia Manual

Ammonia Plant Operating Manual 61

18. HCV 1306 upstream drain and FCV 1304 downstream drain.

III. Check whether the following valves are in closed condition:

1. Vent and drain between discharge block valve of 3109 and downstream ball valve.

2. Block valves of FCV 1203, isolation valves of process naphtha header upstream FCV 1203 and discharge valves of process naphtha pumps.

3. Block valves in the Hydrogen line from syn gas compressor and from Hydrogen receiver.

4. Inlet and exit block valves and the bypass line bleed valve of 1104.

5. Vent valves in-between FCV 1303 and its block valve.

6. PCV 1208 isolation valve.

7. Inlet block valve of 1537 and its integral bypass valve.

8. Block valve and integral bypass valve of FCV 1304 and block valve of HCV 1306.

9. Mixing orifice downstream drain isolation valve and drain valves on feedstock headers at reformer inlet after checking for any condensate.

10. Process air block valves at 1433 and 1105 inlet.

11. Block valves on blanketing steam line to secondary reformer.

12. Drain valves of secondary reformer and its jacket (slip plate to be introduced downstream of these valves).

13. Block valves of TCV 1407.

14. RGB HT & LT compartment drains & vents.

15. Bypass, drain & vent valves of 1108.

16. FCV 1501 block valves.

17. Drain & vent valves of 1109.

18. TCV 1509 A & B upstream block valves.

19. 1539 water inlet isolation valve and 1514 inlet butterfly valve.

20. 1111 drain valve.

21. 1110 inlet and exit block valves.

22. LCV 1502, LCV 1504 and LCV 1606 block and bypass valves and drain valve of 1114 & 1115.

Page 62: Ammonia Manual

Ammonia Plant Operating Manual 62

23. Drains of various pressure indicators.

24. 1” line from 1115 to finned seal water cooler and 1” block valve of XCV 1610.

25. Block valves in the air inlet line to absorber.

26. 1517 A & B bypass valves.

27. All the valves in the start-up steam line to 1517 A & B.

28. Suction, discharge and spill back isolation valves of both 3215.

29. Water make-up from 1115 to 1117 A & B.

30. Block valve in the rich solution line exit 1116.

31. Discharge block valves, spill back valves, drains and vents of lean and semilean solution pumps 32. Valves in the branch from lean solution header to side stream filter and vice versa.

33. Block and bypass valves of LCV 1604 A & B.

34. Block and bypass valves of LCV 1602, drain valve of 1131 and block valves on the condensate line to 1131.

35. 2” drain valve on rich solution line exit absorber to HP drain header.

36. Lean and semilean duplex filters drains and vents.

37. 2” globe valve on rich solution line to concentration tank.

38. Drains at the check valves on lean and semilean solution pumps & headers and 1517 A & B solution drains.

39. Inlet, exit, bleed in the bypass line, vent and drain valves of 1112.

40. Drain valves at the inlet of 1554, 1514 & exit of 1553.

41. LT vessel heating line isolation valve at the exit of 1112 and 1113.

42. Block and bypass valves of ESV 101.

43. Bypass valve of PCV 1509.

44. Block valves in the make-up line from 1113 to Hydrofiner near PCV 0201.

45. 1113 to flash gas compressor line isolation valve near FGC.

46. Block valve of TCV 1311.

47. CCJT system isolation valves.

Page 63: Ammonia Manual

Ammonia Plant Operating Manual 63

48. FCV 1304, HCV 1306, FCV 1203, FCV 1204, FCV 1401, XCV 1406, TCV 1407, TCV 1509 A & B, XCV 1501 A&B, FCV 1501, LCV 1502, LCV 1504, LCV 1602, LCV 1606, PCV 1504, PCV 1509, ESV 101, TCV 1311, HCV 1701, HCV 1702, HCV 1606, HCV 1608, HCV 1605, HCV 1607, FCV 1602, FCV 1603, XCV 1602 & XCV 1604.

49. The following Nitrogen points are all to be closed with their bleeds open :

FCV 1203 downstream, mixing orifice, secondary reformer drain, 1108 inlet, 1109, 1110, 1112, 1513, startup compressor suction.

IV. Start rinsing the CCJT system with BFW. Ensure that pH and Hydrazine concentration are normal.

V. Check the trip system and ensure that actions for various trip initiators are OK. Check stroking of control valves.

VI. Complete pneumatic leak check on fuel naphtha header and get all the leaks attended.

VII. Start flue gas fan A and then combustion air fan A. Start ID, FD fans B also and put both fans on auto at field. Set PRCA 1313 at -1.27 mmWC on auto. Maintain combustion air pressure at about 100 mmWC. Take furnace pressure and ID, FD interlock trips in line after checking PLC trip initiators lamp.

VIII.Check ignitors for proper functioning.

IX. Keep the combustion air bypass damper wide open. Check that all the individual isolation valves of burners are in shut position and establish fuel naphtha circulation. Start raw naphtha pump and set PC 1324 at 0.5 Kg/cm²g lower than fuel naphtha header PV (in PC 1305). Ensure that FCV 1103 is blocked and bleed open and stripper circulation valves are isolated.

X. Check isolation valves on 1431, 1432 1433 and 1434. Charge atomising steam header of reformer.

XI. Start lube oil pump of startup compressor. Drain the suction and discharge snubbers.

XII.Before establishing circulation, check all low point drains.

XIII.Open FCV 1303 and start the start-up compressor in unloaded condition. Keep PCV 1206 at the discharge of compressor in open condition and load the valve plates.

XIV.Close PCV 1206 gradually and establish circulation. Take PIC 1206 on auto and keep the set point close to the actual pressure so that PCV 1206 opens quickly in case of any trip leading closure of FCV 1303. (If pressurising of start-up loop continues after starting the compressor, set point of PCV 1206 should be raised from time to time to avoid PCV 1206 opening and reducing the circulation rate).

XV. Establish water flow at 2 TPH to 1131 and drain locally.

XVI.Admit SCC to the RG mains jacket before TI 1314 temperature reaches 80 0C and maintain the required level.

Page 64: Ammonia Manual

Ammonia Plant Operating Manual 64

XVII.Admit DM water to the jacket of secondary reformer and ensure visual overflow.

XVIII.Test the furnace with standard explosive meter and confirm that there is no explosive atmosphere.

C. LIGHT PRIMARY REFORMER BURNERS

1. Light a couple of burners initially and then raise TRA 1314 at the rate of 30 0C per hour. Burners chosen should not be adjacent to each other. They should be spaced such that uniform heating of the furnace is achieved.

2. Burner rotation is to be given at regular intervals to prevent local overheating. Leak check all burners after lighting. Ensure that all 90 burners are lit atleast once and leak checked before steam introduction. Avoid lighting burners at wall side.

3. Start circulating Lean solution around regenerator.

4. Admit startup steam to the risers of 1510 and RGB, ensuring no hammering and gradually raise the pressure of waste heat recovery system. When the pressure comes to 3 Kg/cm²g and steam is issuing freely through all the vents, close the vents and drains in waste heat recovery system.

5. Monitor skin temperatures of 1536 A & B and flue gas temperatures inlet 1511.

6. Admit start-up steam to 1536 B when the skin temperature is about 250 0C. Open the gate valve fully and throttle the globe valve. Ensure that till the time the pressure of steam drum is raised gradually with start-up steam through risers, start-up steam through superheaters should not create back pressure at the steam drum. Otherwise natural circulation in the boilers will be affected.

7. To keep 1537 cool, crack open 1537 inlet isolation valve, its integral bypass valve and vent steam to atmosphere via HCV 1309. The pressure of the steam in 1537 should be kept below the circulating Nitrogen pressure to prevent ingress of moisture to the reformer catalyst. Check mixing orifice drain frequently for any condensate.

8. If the flue gas temperature inlet 1511 exceeds 400 0C, increase steam flow through 1536 and 1537 not deviating from the conditions mentioned earlier. Air dampers of burners not in line may be closed to reduce the flue gas temperature inlet 1511. Adjust the bypass of 1511 ensuring that the stack temperature below 150 0C.

9. Open the block valves of TCV 1311 and take the controller in line as decided by the flue gas temperature inlet 1511 and skin temperature of 1536. In no case should the temperature inlet 1536 A be less than the saturation temperature of steam at the existing pressure of superheater. This is to avoid boiling inside the superheater.

10. Slowly pressurise CCJT system by throttling HCV 1308, watching 1536 A & B skin temperatures. Start up steam is to be isolated only after steam cut in.

11. Hold PRO temperature at 480 0C and wait for TC 1509 A to rise. When it crosses the maximum temperature of any of the LT temperature, line up LT for heating up after draining away the condensate thoroughly, if any.

Page 65: Ammonia Manual

Ammonia Plant Operating Manual 65

12. Reduce 3109 suction pressure to about 18 Kg/cm²g to accommodate steam and hydrogen.

13. Light up 1432 and increase TC 1205 at 50 0C per hour until it reaches 400 0C. Reduce firing in primary reformer to maintain temperature at 480 0C.

14. When LT bed temperatures (all the six points) reach 200 0C, bypass LT and pressurise to 20 Kg/cm²g.

D. GV SECTION START UP

1. PRELIMINARY PROCEDURES

1.1.1 K2CO3 wash

Wash the plant with a 5% wt K2CO3 solution at 90°C. During this washing, foaming tests (see Appendix -2) shall be frequently carried out - at least four times a day - to control the washing operation on the basis of the foaming tendency (collapse time and foam height) of the solution. If, after 48 hours, no remarkable formation of foam is oberserved, the alkaline washing can be considered over and if the arsenic content is about 1 g/l, the solution shall be used for the plant passivation after addition of vanadium. Instead, if there is a progressive increase in the solution foaming, the washing must be continued till the increase in the foaming tendency is stopped and stabilised for 12 hours minimum. The solution is then discharged.

If the foams are remarkable and lasting, the solution must be discharged and a further washing must be started with a fresh alkaline solution.

Clean the strainers at the pump suction as well as the mechanical filter carefully to remove the same and deposits coming from the cleaning procedures.

Plant passivation

The passivation follows the alkaline washing immediately.

Static passivation (for the reboilers)

Prepare a solution made of 20% w/w K2 CO3 and 0.5 w/w V2O5 as per the solution preparation procedure.

Flood the bottom of 1117-A with solution introduced by means of 3208 so that reboilers 1517 A/B up to solution/steam return lines are completely filled.

Pressurize 1117-A with N2 up to about 0.5 Kg/cm2 g.

Heat-up the solution gradually by introducing MP steam through the proper line into reboilers 1517 A/B and adjusting the steam flowrate so as to maintain the solution temperature at about 110 °C. To obtain the best consistency of the passivation film, the temperature has to be kept as high as

Page 66: Ammonia Manual

Ammonia Plant Operating Manual 66

possible yet without reaching the boiling point in order to avoid the risk of internals failure. LIC 1606 on 1115 has to be operating in order to remove the steam condensed in 1517 A/B.

Go ahead with the operation for two days regularly checking the columns pressure and the solution temperature.

During the operation, roughly every eight hours, analyse the K2CO3 and V2O5 to check that the solution concentration remains approximately constant. Add V2O5 if this falls below 0.3%.

Dynamic passivation (for the whole plant)

It follows the static passivation immediately. The same solution is used.

Circulate the solution in accordance with the procedures described in “Start-up procedures”, avoiding the presence of the process gas and pressurizing 1116 with nitrogen to set up this circulation.

Pressurize with N2 1117-A to 0.5 kg/cm2 g and 1117-B to 0.35-kg/cm2 g to allow the free flow of the solution from 1117-A to 1117-B.

Carry out the passivation maintaining the solution flow rates at the design value (min. 80% of design).

Adjust the quenched MP steam flow to 1517 A/B to maintain the boiling temperature (114-111 °C) at the bottom of 1117-A and 1117-B without solution cooling (except when this is required for the smooth operation of the pumps). Continue this operation for about four days regularly checking the columns pressure and the solution temperature. The steam temperature at 1517 A/B inlet must not exceed 180 °C.

During the operation, roughly every eight hours, analyse the K2CO3 and V2O5 to check that the solution concentration remains approximately constant. Add V2O5 if this falls below 0.3%.

At the end of the operation, stop the steam flow to 1517 A/B. When the solution has cooled down below 105 °C, depressurize 1117-A and 1117-B to 0.20/0.05 kg/cm2 g respectively keeping a reduced solution circulation until introduction of the process gas.Manholes are not to be opened in order to prevent the protective film on the metal surface from altering.

Repassivation after a plant shut-down

a) Short shut-down

In the case of a short shut-down during which the process gas feeding is stopped maintaining 1116 under pressurization and the solution circulation, the plant can be started up again without repassivation.

b) Long shut-down

In the case of a long shut-down, repassivation is necessary.

The GV solution, which was regenerated and stored in 1204 before the shut-down, is used for the above-mentioned operation at the standard concentration. For this operation, V5+ has not to be less than 40% of the total vanadium.

Page 67: Ammonia Manual

Ammonia Plant Operating Manual 67

The solution in 1204 tends to oxidize, but it is possible to save time oxidizing the solution in 1206 according to the procedures described in the “Filtration/Oxidation unit section”.

The solution must circulate according to the modalities described under Dynamic passivation, but pressurizing 1117A/1117B with N2 to 0.20/0.05 kg/cm2 g respectively.

Adjust the steam flowrate to maintain the boiling temperature of about 109-105 °C at the bottom of 1117-A and 1117-B respectively. Go ahead with the passivation for 2-3 days (minimum 36 hours), checking the columns pressure and the solution temperature from time to time. It is very important to notice that if the operation is not uninterruptedly performed for at least 36 hours, the passivation film cannot form.

During the operation, about every eight hours, analyse the K2CO3 and V2O5 to check that the solution concentration remains approximately constant.

At the end of the operation, stop the steam flow to 1517 A/B maintaining a reduced solution circulation until introduction of the process gas.

Manholes are not to be opened to prevent the protective film on the metal surface from altering.

c) Shut-down with insertion of new equipment

If new carbon steel equipment was added during the plant shut-down, the passivation operation will be performed according to the modalities described in Subpara. b) above, going on with the operation for about four days.

GV solution preparation

Prepare the solution with demineralized water fed to the preparation tank up to about 3/4 of its capacity.

Heat the water to about 80 °C. Maintain this temperature by introducing steam into the heating coil.

Start up the mixer adding the chemicals. Keep stirring the solution at 80 °C for about two hours and then send it to the storage tank through the mechanical filter by means of the preparation pump. The solution can be prepared at a concentration up to 40-50% w/w, diluted in the storage tank with demineralized water and homogenized through a recycle with the preparation pump.

At the end of the passivation activities, take off part of the solution from the plant, feed it to the preparation tank, heat it up to 80 °C. Add glycine and diethanolamine at a temperature not below 80 °C. The operation will be repeatedly performed until the following solution composition is reached:

K2CO3 27.0 % w/wGlycine 1.0 % w/w

Page 68: Ammonia Manual

Ammonia Plant Operating Manual 68

Diethanolamine 1.0 % w/wV2O5 0.4 % w/w

During the normal plant operation it might be necessary to add chemicals. This can be done according to the above-mentioned modalities by feeding some solution taken off from the regenerator bottom to the preparation tank.

2. START UP PROCEDURE

1. Vent the process gas upstream of the LT shift conversion 1110 through PCV 1504. Isolate the absorber 1116 by closing the isolation valve upstream 1110 with its bypass and the valves XCV 1501 A/B on the methanator 1112 inlet with its bypass.2. Check 1114, 1115, 1131 and 1116 bottom a certain amount of water is present for hydraulic seal and that 1114/1115/1131 level control valves LCV 1502/LCV 1606 A/B and LCV 1602 A/B with their by-pass along with the vessels bottom drain and LG/LI drains are closed. 3. Keep closed the samples connections of 1116 and the valves FV 1602 and FV 1603 on the solution lines feeding 1116.4. Isolate 3708 by closing the block valve in/out.5. Put the level controller LICA 1604 on manual with control valve LCV 1604 B/C closed.6. Purge the air from 1116 with nitrogen introduced by means of the proper line downstream 1110.7. Keep 1116 pressurised by nitrogen at about 10 kg/cm2g.8. Check that 1117A and 1117B drains, sample connections and LG/LI drains are closed.9. Check that the following valves are in close position: HCV1605/1607 on the rich solution lines feeding 1117B/1117ALCV 1653 on the semilean solution line from 1117A to 1117B with its by-passLCV 1654 on the lean solution line from 1117A to 1117B with its by-pass. 10. By means of pump 3208 transfer the solution from the storage tank 1204 to 1117B until reaching the maximum level on the stripper bottom. 11. The strainers on the suction of the lean and semilean solution pumps 3206/3207 will be already positioned. 12. Check that the line connecting 1117B bottom to 3206 A/B suction is free from air pockets by opening and soon after closing the pumps drains to verify that the solution is flowing freely. Start the sealing water flushing according to the pump supplier’s prescriptions. 3206A is put into operation and the solution circulation starts by feeding the lean solution to 1116 top. 13. Put into operation the flow controller FRCA 1603 at 50% of the normal flow rate. 14. Carefully check the correct pressurization of 1116 and the level on 1117B bottom. 15. Transfer additional solution from 1204 by means of 3208 to keep the level constant. 16. The solution feeding 1116 top is distributed on the packing and is collected on 1116 bottom. 17. When the normal level on 1116 bottom is reached, put into operation the level controller LICA 1604B.18. Isolate the ejector X-100 by closing the block valves in/out and the valve on the 20” by-pass line. 19. Keep closed the block valve on the CO2 lines at B.L., the vent valve HCV 1705 on the CO2 line and XCV 1702 on the cooling water line both feeding 1119.20. Check that on 1118, 1119, 1150 and 1120 bottom a certain amount of water is present for hydraulic seal and that 1118, 1119, 1150 level control valves LCV 1702, LCV 1704, LCV 1650 with its by-pass along with the vessels bottom drains and LG/LI drains are closed.21. Purge the air from 1117A and the downstream equipment pressurizing and depressurizing by nitrogen introduced through the proper line and operating with PCV 1705.22. Purge the air from 1117B and the downstream equipment pressurizing and depressurizing by nitrogen introduced through the proper line and operating with PCV 1663B.

Page 69: Ammonia Manual

Ammonia Plant Operating Manual 69

23. Pressurize 1117A by nitrogen setting PCV 1705 at 0.5 kg/cm2g in order to allow the transfer of solution from 1117A to 1117B. 24. Set PCV 1663B at 0.1 kg/cm2g. Open HCV 1607 to feed the stripper 1117A. 25. The solution is distributed on beds no 4 and no 3, collected on the semilean solution take-off tray, fed to beds no 2 and no 1 and finally collected on 1117A bottom passing through 1517 A/B. 26. Open LCV1654 to transfer the solution from 1117A to 1117B bottom keeping LICA 1654 on manual. 27. Transfer additional solution from 1204 by means of the pump 3208, as required. Await the stabilization of the levels in 1116, 1117A and 1117B. Then put LCV 1654 on automatic.28. The flow controller FRCA 1603 is gradually increased to 60-70% of the normal flow. 29. The level controller LICA 1653, acting on the LCV 1653 on the line connecting the semilean solution take-off tray of 1117A with the intermediary tray of 1117B, is put into operation on manual. When the normal level is reached, the controller LICA 1653 is put on automatic. 30. Start the semilean solution pump 3207 according to the same procedure described for 3206. 31. 3207 is put into operation and the semilean solution feeds the middle of the absorber 1116. 32. The flow controller FRCA 1602 is put into operation at 50% of the normal flow rate and slowly increased to 60-70% giving the plant time to reach the normal levels and refilling additional solution from 1204, as required. 33. When stable operating conditions are reached, start to feed the solution to 1117B by opening HCV 1605 at 50% of the normal flow rate (FR 1606). 34. The solution is distributed on the beds no 4 and 3 and collected on 1117B intermediary take-off tray mixing with the solution coming from 1117A semi lean solution take-off tray. 35. If necessary, additional solution is taken from 1204 to reach the levels stabilization and the steady solution circulation on the whole plant. 36. The circulating solution is gradually heated at the rate of about 10-15 °C/h. 37. The heating is performed by feeding conditioned steam to 1517 A/B through the proper line. 38. The level controller LICA 1606 on the separator 1115 is put into operation to remove the condensate separated. 39. During the solution circulation, water enters through the pump sealings. It is therefore advisable that the solution heating be brought up to the boiling point in 1117B. 40. Cooling water is fed to 1520/1521 in order to have a correct suction temperature for the smooth operation of pump 3207/3206. 41. An excessive solution concentration, shown by a level decrease on 1117B bottom, is controlled by putting into operation 1519 and 1551 respectively on the gas streams coming out of 1117A and 1117B top. 42. The overhead K.O. drum level controls LIC 1650 and LXC 1702 are put on automatic control. 43. 3216 A/B and 3221 A/B are prepared for the start-up according to the supplier’s prescriptions in order to recycle to the plant the condensate separated in 1150 and 1118 and control the water balance by stabilizing the columns bottom levels.44. Fill LP boiler 1550 with BFW up to the normal level putting LX 1551 into operation.45. The vent valve is open in order to evacuate the steam developed by 1550 to the atmosphere.46. Start the operation to introduce into 1116 the process gas previously vented upstream of the LT shift conversion 1110.47. Keeping closed the block valve XCV 1501 A/B upstream of the methanator 1112, progressively open the MOV valve upstream of 1110.48. Stop the nitrogen injection into 1116 and the steam injection into 1517 A/B.49. Start to open the methanator bypass venting the gas through PCV 1509, progressively closing PCV 1504 according to 1112 start up procedure, in order to have gas flow through 1550, 1517 A/B, 1513 and finally through 1116.50. Close the valve venting the LP steam from 1550 regulating the PICA 1550 in order to feed 1117 A bottom X-100 is put into operation according to the supplier’s prescriptions. Open the block valves in/out X-100 and put in service PCV 1662 and PCV 1663 A/B.

Page 70: Ammonia Manual

Ammonia Plant Operating Manual 70

51. The pressure in 1117 B is progressively increased by setting the set-point of PICA 1662 at about 1.0 kg/cm2g while PICA 1663 acting in split range on PCV 1663 and PCV 1663A is set at about 0.15 kg/cm2g.52. The CO2 removed is totally fed to the battery limit putting in service the final cooling on 1119 and setting PIC 1705 according to the downstream requirements. The solution flow rates are progressively increased and adjusted according to the process gas flow rate.53. The plant is slowly brought to the normal operating conditions with regard to flow rates, temperatures and pressures.54. Check the solution composition making corrections, if necessary.

E. TURN IN STEAM

1. Before taking steam to reformer, the plant position should be :

a) LT heating up is complete and is bypassed.

b) HT bed temperatures are above saturation temperature atleast by 30 0C.

c) 1432 is in line, TC 1205 at 400 0C.

d) TRA 1314 is at 480 0C. All the burners in reformer are available.

e) Steam system is stable.

f) PAC supplies instrument air.

g) Turbine driven cooling water pump is in line.

h) ID/FD trips, PAC trip, PC 1313 trip should be in line.

2. Build up pressure in 1537 by opening the upstream block valve. Warm up line downstream HCV 1306 and FCV 1304.

3. Ensure that wash water pump is circulating water.

4. Establish lean solution circulation around absorber at the rate of about 300 TPH and line up LCV 1604 C.

5. Ensure that LT shift vessel is under Nitrogen pressure greater than the system pressure.

6. Keep the drain valves on feedstock subheaders open.

7. Open the block valve of HCV 1306 and crack open HCV 1306. Allow the steam to enter the tubes slowly.

8. Light sufficient burners in reformer, avoid cycling of temperature in reformer.

9. When sufficient steam flow is maintained, start closing HCV 1309 keeping a watch on skin temperature and boiler load.

Page 71: Ammonia Manual

Ammonia Plant Operating Manual 71

10. Line up PCV 0207. Set PC 0207 at a pressure 5 Kg/cm²g above 1109 exit pressure. Line up TCV 1509 A & B. Set TC 1509 at 206 0C. Open 1514 inlet butterfly valve. Remove “do not close” operation mark from TC 1506 face plate.

11. When the drains at the feedstock sub headers are free of condensate, close the drain valves.

12. Check the drain points at 1109 first bed exit, 1539 gas exit, 1109 second bed exit frequently for any condensate. Keep the drain on 1539 gas exit open as this will issue condensate continuously.

13. Line up LCV 1502, 1504 & 1606.

14. Start acid gas condensate pump when level builds up in 1118.

15. Gradually increase the steam flow rate to 45 TPH. Increase firing rate in reformer to maintain a steady increase of 50 0C per hour at TI 1314 upto 725 0C. Avoid cycling of temperature. Transfer the flow of steam to FCV 1304 and take FC 1304 on auto. Close HCV 1309 isolation valves keeping watch on boiler load.

16. Adjust RGB bypass and maintain 392 0C at the exit.

17. Adjust 1539 gas side bypass and maintain 365 0C at the inlet of second bed of 1109. (Do not close water bypass valve of 1539 at this stage as this will lead to more condensation on the gas side)

18. Start quench water pump after ensuring copper, etc in the condensate and line up. PCV 0207 will close now. Set PC 0207 very close to the actual pressure so that it will open quickly in case pressure drops.

19. Open the block valve on the blanketing steam line to secondary reformer. Transfer process air venting partly from compressor house to HCV 1408. While transferring the vent, flow through PAC casing should be carefully watched to avoid any surging. If venting is not transferred immediately after lining up blanketing steam, steam might back up into 1433, condense and lead to hammering.

20. Close start-up steam to vetrocoke reboilers if opened earlier.

21. Open cooling water valves of lean solution cooler to allow adequate flow through the cooler. Use the solution side bypass to control the temperature at 70 0C. Do not allow the cooling water return temperature to pick up more than about 45 0C.

22. Raise PRO temperature at the rate of 55 0C/hr and hold TI 1314 at 725 0C for a period of 6 to 8 hours. This is for the potash to recombine with the catalyst 46/3.

F. REDUCE PRIMARY REFORMER CATALYST

It is necessary to drop the plant pressure to accommodate the increase in pressure due to addition of Hydrogen. Very slowly depressurise the system by opening PCV 1509 to 15 Kg/cm²g at suction of start-up compressor. Hydrogen to the start-up compressor loop can be added soon after lining up blanketing steam to secondary reformer. IG units should run on cracked gas service.

Page 72: Ammonia Manual

Ammonia Plant Operating Manual 72

1. Ensure that the ball valve on Hydrogen line to 1432 remains open.

2. Open the block valve on the Hydrogen line from storage and allow the flow through FCV 1204. Keep Hydrogen flow at maximum possible, always maintaining a steady pressure of 38 Kg/cm²g in the Hydrogen receiver.

3. Check the circulating gas for Hydrogen content and then calculate the Hydrogen circulation rate. From this value and the steam flow rate, the ratio of steam to Hydrogen can be calculated. The reducing conditions are achieved at a ratio in between 4 & 8. Though the reformer catalyst is not affected by a ratio less than 4, such a low ratio will lead to over reduction of HT shift catalyst vessel to elemental Fe.

4. After stabilisation period of catalyst at 725 0C, raise TI 1314 at the rate of 15 0C/hr and take up to 760 0C.

5. Maintain reducing conditions for 8 hours.

6. Reduce Hydrogen flow to the start-up loop to maintain the ratio.

7. Pressurise 1104 to system pressure and start raising the temperature at the rate of 50 0C/hr to 400 0C. Open both the inlet and outlet valves fully and close the bypass valves. Keep the bleed in the bypass line full open.

8. Ensure that all the six points in TI 1206, TI 1/1205 and TI 1/1206 are above a minimum temperature of 377 0C.

9. Build up levels in regenerators and start semilean pump. Provide adequate cooling water to the coolers for the cooling water return temperature not to be more than 10 - 12 0C above the cooling water supply temperature. Use solution bypass to control the solution temperature at 90 0C.

For the next stage of cutting in naphtha, though semilean circulation need not be established, this is done in parallel at this stage itself to cut down the time required for Methanator lining up at the later stage.

G. NAPHTHA INTRODUCTION

1. At this time the condition of the plant is as follows :

a) The reduction of reformer catalyst is complete.

b) Steam flow to reformer is 40 % of design flow rate ie., about 50 TPH.

c) Start-up compressor is circulating in H2, N2 mixture.

d) Reformer tube outlet temperature is 760 0C.

e) Lean solution circulation to the absorber is established at 300 TPH.

Page 73: Ammonia Manual

Ammonia Plant Operating Manual 73

f) Semilean solution circulation to the absorber is established at 800 TPH.

g) On the feedstock line to reformer, FCV 1303 is full open. FCV 1203 is kept on manual with the block valves isolated.

h) Process Naphtha pump has been started and running on spillback, the discharge pressure being less than the discharge pressure of start-up compressor.

2. Keep PCV 1705 full open on manual.

3. Keep PCV 1504 and PCV 1509 closed on manual.

4. Introduce maximum quantity of Hydrogen available from IG plant through FCV 1204. Maintain receiver pressure.

5. Start closing the vapourised feedstock control valve FCV 1303. The pressure controller PC 1206 on the discharge of the start-up compressor will bypass the excess gas back to the suction. As the flow rate through the process naphtha vapouriser 1432 is reduced., the firing rate should be cut down to maintain 400 0C at TC 1205. Continue to close FCV 1303 until the circulating gas rate is at the minimum value required to give good temperature control on TC 1205 without flame failure of 1432 and ensure steam carbon ratio is above 5.

6. Speed up the process naphtha pump to 40 Kg/cm²g discharge pressure and line up FCV 1203. Close the bleed valve upstream of FCV 1203.

7. Crack open FCV 1203 and introduce a small flow of naphtha, say 2 TPH. Reduce opening of FCV 1303 to 10%. The initial steam/carbon ratio at the reformer inlet should be between 6 & 10.

8. With the introduction of naphtha, the temperature at the outlet of 1432 will tend to drop, increase the firing rate to maintain the temperature at 400 0C.

9. Increase firing rate in reformer and maintain exit temperature of reformer steadily at 7600C.

10. When PC 1509 registers a sharp rise in pressure, unload the start-up compressor and stop it. This is necessary to prevent carbon oxides being circulated back from 1113 to 1104 and to avoid methanation reaction over COMOX catalyst. Isolate the discharge and suction block valves of start-up compressor. Provide slip plates immediately.

11. Use the vent valve PCV 1509 to vent the gas now being produced and control the system pressure. Raise PC 1509 pressure to 21 Kg/cm²g.

12. Increase steam rate to reformer to about 50 % design flow rate. Increase naphtha rate in stages to 10 TPH, maintaining a steam carbon ratio of about 5.

13. Adjust FCV 1303 so that all the times vapour naphtha flow rate in Nm3/Hr = 300 x liquid naphtha flow rate in TPH, and to maintain a steady pressure of about 30 Kg/cm²g on PC 1208.

14. Adjust RGB bypass valve to get an exit temperature of 392 0C.

15. Adjust 1539 gas side bypass to get 365 0C on the top of second bed of 1109. Keep the water bypass of 1539 wide open and drain on 1539 gas exit line open to drain away any condensate.

Page 74: Ammonia Manual

Ammonia Plant Operating Manual 74

16. Adjust 1513 bypass valve to keep the LP BFW temperature less than 78 0C.

17. When liquid naphtha and vapour naphtha flow rates are steady, take the controllers on auto. Take steam carbon ratio trip in line.

18. Gradually bring up the CO2 pressure exit 1120 to about 0.1 Kg/cm²g and take the PC 1705

on auto.

19. Admit air to absorber at the rate of 5 Nm3/Hr.

20. Heat up LT catalyst if not done earlier and line up. (For proceeding to next stage of cutting in air, LT catalyst need not be in line and lining up can continue in parallel).

H. INTRODUCTION OF PROCESS AIR

1. The position of the plant at this time is as follows :

a) Naphtha rate is at 40 % design.b) Steam rate is at 50 % design.c) Process gas is being vented at PCV 1509.d) Process air is being vented through HCV 1408. e) LT shift vessel is being lined up.f) PAC trip, PDI 1405 trip, ID/FD trips, PC 1313 trip and steam carbon ratio trip should be in line.

2. Ensure that the temperature of gas exit primary reformer is about 760 0C. This is absolutely essential for the secondary reformer burner to get lit and on no account should an attempt be made to light the secondary reformer if the outlet temperature is less than 750 0C. (Auto ignition temperature of H2 is 585 0C).

3. Speed up process air compressor and check that the process air pressure upstream of FCV 1401 is atleast 2 Kg/cm²g above the pressure in secondary reformer. Take PIC & FIC ofPAC on auto. The operator should be available near the local panel of PAC when air to secondary reformer is cut in.

4. Drain the blanketing steam condensate downstream of FCV 1401 thoroughly. Open process air block valve inlet 1105 and check that people are away from secondary reformer.

5. Press reset 9, 10 & 11 in trip panel and open FCV 1401 by 5 % on manual.

6. Observe closely the temperature trend TI 1405 at the outlet of secondary reformer for the expected temperature rise. If there is no temperature increase within 7 minutes, trip out the air from the control panel.

7. Increase the air flow gradually. As the air flow to secondary reformer is increased, HCV 1408 may be gradually closed.

8. When TI 1405 settles at 920 0C drain the impulse lines of FC 1401 free of condensate and take FC 1401 on auto.

Page 75: Ammonia Manual

Ammonia Plant Operating Manual 75

9. Adjust RGB bypass and 1539 gas bypass to get design inlet temperature to the beds of HT shift vessel.

10. Adjust the air flow now further to get the correct ratio of syn. gas watching the Hydrogen analyser.

11. Line up TCV 1311 if not lined up earlier. Pressurise CCJT system using HCV 1308. Watch superheater skin temperatures and 1511 flue gas inlet temperature. When PI 1321 matches with PC 0105, line up CCJT isolation valve fully and close HCV 1308 gradually ensuring the required load to boilers.

I. PUT METHANATOR ON LINE

1. Check gas analysis exit 1116 for CO & CO2. The concentration of CO & CO2 should be equal

to or less than the design figures of 0.26 % and 0.1 % respectively.

2. Open the outlet block valve of 1112 to equalise the pressure. The valve should be opened carefully to avoid disturbing the catalyst.

3. Reset 12 opens XCV 1501 A & B and crack open the inlet block valve and allow the gas to pass through the catalyst vessel.

4. Slowly open the inlet block valve and close the bypass valves. Open up the bleed valve in between the bypass valves. Rate of heating of catalyst bed should be controlled at 40 - 50 0C per hour.

5. Adjust the catalyst inlet temperature to 315 0C. Open 1512 bypass valves so as to close TCV 1506 maintaining the inlet temperature of 1112 as well. Opening of 1512 bypass will maximise the temperature of high pressure boiler feedwater to Auxiliary Boiler.

6. Analyse gas exit 1112 for CO & CO2.

7. Check whether the slip plate is inserted downstream of start-up line (to 3109) isolation valve at 1110 exit, lest there is a chance of syn gas contamination.

If it is desired to put the Methanator on line before lining up at the LT shift vessel, it can be done with more careful temperature control. Normally it should be possible to establish operation at an inlet temperature of 230 - 250 0C. The CO content exit conversion section can be minimised by high steam/carbon ratio, to achieve a CO content of less than 2 % inlet the Methanator.

J. DEGASSING OF PROCESS CONDENSATE

1. Keep PCV 0221 full open on the vent.

2. Establish level in the condensate degasser and start the degassed condensate pump on spill-back.

3. Open the pump discharge and pass the condensate to LCV 0203 A, through the cooler and to the drain at the exit of the cooler.

Page 76: Ammonia Manual

Ammonia Plant Operating Manual 76

4. Make sure that steam line right up to degasser is drained of condensate. Crack open the globe valve on the steam inlet line and pass the steam to degasser.

5. Raise pressure and put PC 0221 on auto.

6. Analyze the degassed condensate and adjust the steam flow to the degasser to reduce methanol, CO2 and Ammonia to design levels. Analyse for other impurities like silica and iron.

When the degassed condensate needs a design specification, pass on the condensate to WTP.

K. SYNTHESIS

1. Before admitting quality syn gas to the synthesis loop, the loop must be pressure tested to the maximum pressure possible using Nitrogen.

2. Check the following valve positions :

HCV 1810 converter bypass and its : Open block valve

HCV 1809 converter inlet : Close

HCV 1806 quench to Bed II : Close

HCV 1807 Converter Shell cooling : Open

HCV 1808 quench to Bed III : Close

HCV 1801 heater inlet and its : Open block valve

XCV 1814 heater outlet and its : Open block valve

HCV 1811 catch pot level hand : Close control valve and its block valve

LCV 1811 catch pot level control : Closevalve and its block valve

LCV 1813 letdown vessel level : Close control valve and its block valve

Flash gas (from 1123 to 1124) lines : Open isolation valve.

HCV 1812 purge gas control valve : Close

Block valve of HCV 1812 : Open

Isolation valves on the 1434 side : Close in the LT catalyst reduction loop.

Page 77: Ammonia Manual

Ammonia Plant Operating Manual 77

These lines should have slip plates introduced at the appropriate places.

HP vent valves on the line exit 1523 : Close

Block valve in the purge gas line : Open exit 1124

Block valves in the liquid Ammonia : Close line from HWP to 1123

Block valves in the liquid Ammonia : Close from 1122 to HWP

Block valves in the start-up line : Close from recirculator suction to HWP

HWP gas bypass valve downstream of ESV : Open in Compressor House.

PCV 1301 : Open

PCV 1303 : Open

HCV 1302 and its block valve : Close

Cooling water to 1524 : Open

Cooling water to 1528 A,B & C : Open

3. Start syngas compressor as per the instructions in the chapter on SGC start up. Keep the barrel vents slightly open to purge out the barrel.

4. Adjust syngas machine to have a discharge pressure of 120 Kg/cm²g. Keep open all the drains in the gas lines till they are free of oil and moisture.

5. Analyse for CO + CO2 in the barrel.

6. When CO + CO2 in the barrel is less than 10ppm, start pressurising the synloop by crack opening the bypass valve of ESV 104, to a pressure of 120 Kg/cm²g.

7. Rate of pressurisation should not exceed 1-2.5 Kg/cm²g/min. (See catalyst activation procedure).

8. Charge atomising steam to 1434 and warm up the line.

9. Charge ammonia to refrigeration loop through 2" vapour ammonia line from sphere to 1127, start refrigeration compressor and bring it to minimum governor speed.

10. When synloop pressure is 120 Kg/cm²g, check whether circulator discharge pressure and loop pressure are same by opening the bypass of ESV 104 fully.

Page 78: Ammonia Manual

Ammonia Plant Operating Manual 78

11. When the pressures are equal, close HCV 1810 to 5% and establish circulation in the loop, by opening ESV 102, ESV 103 and ESV 104.

12. Close bypass of ESV 104 as soon as circulation is established.

13. Watch the catch pot level carefully. If it increases abnormally, close circulator suction valve immediately. Check 1122 and then establish circulation when conditions are normalised.

14. Through converter inlet sample point check the gas is free of oil and moisture.

15. When circulation is established, establish levels in chillers and load the refrigeration compressor. Control second suction temperature with quench through TCV 1811. Watch levels in 1128 and 1527. Too much of quench will lead to build up of level in 1128 and 1527. Remember that high level in 1128 or 1527 will trip out refrigeration compressor.

16. Throttle HCV 1810 and HCV 1809 to get:

adequate flow (38,000 Nm3/hr) FI 1810 , through 1434 start up heater.

adequate flow (about 50,000 Nm3/hr) FI 1803, through converter shell.

17. Light 1434 and adjust the firing rate and or gas rate through 1434 to get a steady increase in temperature at the rate of about 1 0C/min in the first bed inlet.

18. Do not increase heater exit temperature more than 500 0C. Remember that a temperature of 520 0C will trip out the heater.

19. Normally the reaction picks up when inlet temperature of I bed is about 300-350 0C. When reaction picks up in I bed, the exit temperature will tend to rise fast. If the rate of rise is too much, do not hesitate to open even fastly the converter main inlet HCV 1809 and / or HCV 1807.

20. The opening of converter inlet will drop the flow both through the heater and converter shell flushing; therefore close HCV 1810 to keep about constant flush gas flow FI 1810 and flow through startup heater FI 1803.

21. If reaction picks up in II bed because of rise in I bed exit temperature, HCV 1806 shall be operated to maintain heating up rate. An excessive quench rate will result in a decrease of heat recovery, due to the internal exchangers bypassing. Therefore at all stages during the heat up, it is necessary to limit the quench gas rate to that which will allow the inlet temperature of I bed to continue to rise at the proper rate. It is good practice to refer at quench ratio (FI 1802/FI 1809), increasing gradually this ratio from zero to normal value.

22. When converter inlet flow is sufficient enough (when HCV 1809 is open more than 50%), 1434 exit temperature may be reduced gradually by fuel decreasing. When additional heat from1434 is no longer important, start reducing 1434 exit temperature at the rate of 50 0C/hr to 150 0C.

23. Throttle HCV 1801 to allow the coil cooling down at a low rate. At the same time, to get an appropriate control of I bed temperature, start open the local bypass valve of 1434. If the local bypass valve is not available, use directly HCV 1801 as first bed controller adjusting the fuel to cool down the coil.

Page 79: Ammonia Manual

Ammonia Plant Operating Manual 79

24. When the ammonia formation begins, maintain the loop pressure at about 120 Kg/cm²g by loading the syngas compressor.

25. Start open HCV 1812 reaching initially a purge of 3,000 Nm3/hr.

26. When the III bed inlet temperature reaches about 420 0C start open HIC 1808 increasing the ratio FI 1804 / FI 1809 to normal value.

27. When the beds temperature are approaching the normal values, increase the loop pressure further.

28. Maintain catchpot temperature at -5 0C to minimise ammonia concentration in the gas inlet converter and to maximise condensation of ammonia in the circulation gas.

29. When levels build up, line up LCVs of 1122 and 1113. Open the block valves of LCV 1811 to make it available for any emergency.

30. At the time when production is expected, if there is no level build up in catchpot, watch suction and discharge temperature of circulator and I bed exit temperature of converter carefully.

31. Any drop in temperature must be viewed seriously and level in 1122 should be checked. If necessary, circulator must be unloaded totally and isolated.

32. Increase the loop pressure and circulation rate to take all the syngas into the loop so as to close PCV 1509. Adjust the loop purge rate according to the inerts level and loop pressure.

33. Take care of Hydrogen/Nitrogen ratio by adjusting the process air flow.

34. When the start up heater exit temperature comes down to recirculator discharge temperature, trip heater and close the block valves of HCV 1801 and XCV 1814.

L. RECOVERY

1. Fill up 1124 with LP desuperheating make up line at 1530 to about 50% level. Line up cooling water to 1530, 1532 & 1533.

2. Open PC 1905 on manual to pressurise 1125.

3. Start absorber bottom pump and establish 4 TPH flow through 1530 and back to absorber.

4. Open the globe valve at 1531 inlet to have about 3 TPH to stripper and make up to 1124 to be increased further for maintaining the level in absorber.

5. Once the level in absorber and stripper comes to about 50%, make up to 1124 and flow to stripper are to be kept at minimum.

6. Close PC 1905 and put it on auto at 25 Kg/cm²g. Drain 1126 completely to 1132.

Page 80: Ammonia Manual

Ammonia Plant Operating Manual 80

7. Slowly open steam to 1534 and increase the temperature 223 0C. As the pressure in 1125 increases more than absorber, flow from 1125 to 1124 is established through the stripper LCV 1904. The flow from absorber to stripper is to be slowly increased to 3.5 TPH.8. As soon as the level comes up within the gauge glass range in 1126, start the reflux pump and keep very little flow of about 2 Kg/hr. At the time of starting the pump, current taken by the reflux pump motor will be high (about 9-10 amps) since the liquid in 1126 will have only very little Ammonia. Only when reflux to 1125 is established the liquid in 1126 will be enriched with Ammonia. Otherwise, draining 1126 again and filling up will not have higher concentration of Ammonia. The reason to start and establishing reflux as soon as the level appears in gauge glass is the holdup volume of lean ammonia liquor will be minimum, at the time of starting.

9. As Ammonia concentration builds up the current taken by reflux pumps also comes down. The reflux flow is gradually increased by FC 1905 to 14 Kg/hr. Steam to 1534 is also increased further to maintain still bottom temperature at 225 0C.

10. Test for the purity of Ammonia at 1126 and product lined up through LCV 1906 to let down vessel.

3.3 NAPHTHA INTRODUCTION AFTER PLANT TRIP

For the case where a reformer trip has occurred and the plant has to be restarted without rereduction of the primary reformer catalyst the following procedure has to be adopted.

Stabilise the Primary reformer exit temperature at 760 0C with about 50 TPH of process steam and about 30 burners in line well distributed. Maintain midstream pressure at 20.5 Kg/cm²g.

After resetting the appropriate trips, establish a flow of about 600 Nm3/hr. of cracked gas from the IG plant through 1432 and 1104 bypass, venting the gas through PCV 1208 at the upstream of FCV 1303. Maintain the pressure in PC 1208 at about 25 Kg/cm²g . Equalise the pressure in 1104 with that of PC 1208. Ensure that cracked gas receiver pressure maintains above 35 Kg/cm²g. Light the flare.

After stabilising the flow and pressure, light one burner in 1432 keeping the ring header pressure at the minimum (4 Kg/cm²g). On the panel , start monitoring all the parameters concerning 1432 flue gas temperatures, skin temperatures, process temperature and flow etc. for any abnormal change.

Line up Sweet naphtha to 1432, when the highest skin temperature crosses 200 0C , admit about 2 TPH of naphtha to 1432. Gradually increase the flow to 4 TPH and also raise the firing on the burner. Maintain PC 1208 at the same pressure as the flow through 1432 and the exit temperature increases.

When the temperature on TC 1205 reaches 300 0C, line up 1104 completely, line up vapor naphtha to reformer and light the second burner in 1432. Maintain ring header pressure initially at 4 Kg/cm²g and increase the sweet naphtha throughput to continue raising TC 1205 to 400 0C.

Start introducing vapour naphtha to reformer gradually. Close PC 1208 watching the pressure. Control the vapour naphtha rate depending on the reformer exit temperature. Light more burners in the reformer as more feed stock is introduced.

Gradually increase Sweet naphtha rate to 10 TPH and stabilise 1432 exit temperature at 400 0C.

Page 81: Ammonia Manual

Ammonia Plant Operating Manual 81

START UP SCHEDULE

Sly. No.

Normal Start-up Probable time (Hrs.)1. Light first burner in Reformer, raise TRA 1314 at 30 0C/hr. 0

2. Commission SCC to RG mains/RGB/20 Reformer Water jackets. 1.003. Cut in bubbling steam to RGB riser. 2.004. Put start up steam to super heater coils, pressurise 1106

gradually. 8.00

5. Light 1432, hold reformer temperature at 480 0C 16.006. Warp up process steam line. 16.007. Bring up reformer temperature from 480 to 500 0C 18.009. Reduce system pressure to 14 Kg/cm². Cut in steam to

reformer. raise TRA 1314 at 50 C/hr rate.

20.00

10. Divert lean solution circulation to Absorber. 19.0011. Divert process air vent to HCV 1408, line up sealing steam to

110524.00

12. Cut in Hydrogen. 24.3014. Start OGA 101 B. 26.0015. Raise TRA 1314 at 15 0C/hr rate at 760 0C. 32.0016. Run 3204 on spill back. 32.0017. Hold reformer temperature at 760 0C for 8 hrs. 35.0018. Line up 1104. 36.0019. Start semi lean pump. 39.0020. Cut in Process Naphtha, Stop 3109. 43.0021. Raise Naphtha rate to 10 TPH. 45.0022. Drain condensate in Process Air Line, Cut in Process Air. 45.3023. Line up CCJT. 46.0024. Line up LT. 47.0025. Slow roll SGC. Heat up Methanator. 48.0026. Line up Methanator fully, reach min. Governor speed in SGC. 52.0027. Line up recycle Hydrogen, start Hydrofining section.

section. 52.30

28. Start pressurising syn loop at 50 Kg/hr rate. 53.0029. Reach 125 Kg/cm² in syn loop, leak test critical flanges. 55.3030. Establish loop circulation, light up 1434 & heat converter at

500C/hr 56.30

31. Start PGRU section 57.0032. Slow roll LRC 57.3033. Reach min Governor speed in LRC, load the machine 60.3034. Stabilise Converter as reaction picks up, cut off 1434

gradually. 67.00

Page 82: Ammonia Manual

Ammonia Plant Operating Manual 82

35. Line up production. 67.3036. Start Ammonia recovery section. 68.00

2 Chapter four BOILERS

4.1 GENERAL

No. of units 3 Nos.

Equipment SOUTH NORTH ASGU

Registration No. (As per IBR) T-4338 T-4337 T-4737

I. AUXILIARY BOILER (SOUTH) & (NORTH)

4.2 DESCRIPTION

Capacity 90 TPH each, for 1702 South & North at 106.5 Kg/cm²g and 482 0C at superheater outlet respectively.

The boilers, 1702 (S) & (N) are vertical, water tube, two drum, natural circulation, oil fired, pressurised furnace, type. The heat liberation is high compared to other conventional type boilers. They are designed for easy maintenance and high reliability.

Each boiler is self supported and does not require a structural support. Membrane type walls are adopted on the water wall of combustion chamber and all welded skin casings are used on cageside water walls. Downcomers are provided at the rear of No. 2 generating tubes and sufficient water circulation is maintained even at low loads. Superheaters are provided behind No. 1 screen tubes in two stages. In between the stages to control the superheater outlet steam temperature within design limits, a desuperheater has been provided. The steam temperature is controlled by direct quenching of feed water by temperature control valve.

Feedwater is preheated in two stages in the economiser located in the convection zone. Tubular air Preheater are also provided for recovering heat from the outgoing flue gas.

A steam air heater of radiator type has been provided at the FD fan outlet for preheating the air entering the gas air heater. Before that superheated steam is used, now saturated steam. This helps to minimize low temperature acid corrosion problems in tubular air heaters (particularly in cold air heater).

Each boiler has been provided with a turbine driven FD fan to supply the required quantity of air for combustion. 12 Nos. of soot blowers for each boiler have been provided at various locations such as superheaters, bank tubes region, economisers and air heaters to remove soot formation on heating surfaces using high pressure steam (this is controlled by a PCV the pressure is varied depending up on the soot deposition it gets varied from 20 ksc to 12 ksc).

Page 83: Ammonia Manual

Ammonia Plant Operating Manual 83

At the top of economiser part an explosion door has been provided which will open if the flue gas pressure in that region rises above normal values. (now it is in welded condition).

The firing system comprises six steam atomised fuel oil /LSHS burners provided in the auxiliary boilers. Pilot burners using LPG have been provided for initial starting. Oil firing is controlled by the master pressure controller through a fuel oil flow control valve so as to keep the outlet steam pressure constant under variable load conditions. At full load conditions, oil consumption is 6.3 TPH. Peepholes have been provided on either side of the furnace to check the flame conditions. Three element level controllers have been provided for keeping the steam drum level constant even during sudden load variations.

Mountings : Three safety valves, one at superheater outlet and two on steam drum have been provided to keep the boiler pressure below design limits in case of emergencies. Two level gauge glasses have been provided for each boiler one on either side of the steam drum for checking the actual water level in the drum.

Provision for chemical dosing in steam drum to maintain boiler water quality has been given. Continuous blowdown facility provided in steam drum helps to maintain boiler water quality, especially silica, within limits. In addition to this, blow down provisions from low points of water wall panels and mud drum have been given for removal of sludge, if any. The water holding

capacity of the entire boiler is 38.5 M3.

4.3 TRIP SYSTEM

The following trips have been provided for ensuring safe operating conditions :

1. Drum level low alarm followed by very low trip. Level low alarm = -50 mm Level low trip = -150 mm

Bypass for this trip has been provided for momentary emergencies. Boiler should be hand tripped when the level indication reaches -150 mm, even if the trip is bypassed..

2. Air flow low alarm followed by air flow very low trip.

Low alarm = 56000 Nm3/hr

Very low trip = 12000 Nm3/hr

Bypass has been provided to enable maintenance on the instrument. This trip otherwise remains on line.

3. FD fan trip for failure of FD fan. Actuated at regulating oil pressure of 5 Kg/cm²g. 4. Fuel Oil pressure very low :- Set for 2 Kg/cm²g.

Bypass provided for fluctuating conditions such as pump changeover. Common low pressure alarm provided at 10 Kg/cm²g.

5. Atomising steam pressure low alarm followed by very low pressure trip. Low alarm set at 8 Kg/cm²g. Very low trip set at 4 Kg/cm²g.

Page 84: Ammonia Manual

Ammonia Plant Operating Manual 84

6. Furnace pressure high followed by very high trip. High alarm set at 300 mmWC. Very high trip set at 360 mmWC.7. Plant J & K trip initiated from trip panel.

8. Boiler hand trip.

4.4 CHECKS TO BE DONE BEFORE LIGHTING UP

1. Close all blowdown valves connected to blowdown header.

2. Open all air vents at roof including start-up vent and economiser air vent fully.

3. Open damper at flue gas outlet duct.(not in line now it is in welded condition)

4. Open drain valves provided before and after main steam stop valve.

5. Close main steam (motor operated) stop valve and its bypass valves.

6. Close feedwater drain valves before and after feedwater flow control valve.

7. Close injection line isolation valves.

8. Open attemperator drain valve.

9. Check whether both the gauge glasses are in line.

10. Check whether all manhole doors, peepholes, inspection doors are in closed condition. All foreign materials should be removed from inside before closing the same.

11. Box up the hopper drain dummies.

12. Confirm that the retractable soot blowers are in pulled out condition.

13. Confirm all pressure gauges are available and keep them on line.

14. Check oil level in FD fan bearings and turbine oil sump.

15. Check whether all pilot ignitors are properly fixed.

16. Make ready all burner guns.

17. Check the availability of sufficient LPG gas cylinders.

18. Check the availability of service air and open air to gland seals of soot blowers.

19. Proceed further after getting instruction from Shift-in-charge for lighting up.

4.5 FILLING UP OF THE BOILER

1. Confirm the availability of feed water pressure and quality.

Page 85: Ammonia Manual

Ammonia Plant Operating Manual 85

2. Ammonia dosing and hydrazine dosing should be done in feedwater.3. Open air vent in feed line before FCV and release air lock.

4. Open the equalizing valves of the economiser block valve.

5. Start feeding by opening the integral bypass valve of the FCV bypass valve.

6. Adjust the feed rate to 10 - 12 tons per hour so that the working level can be reached in 3 hours.

7. Close the economiser air vent when there is steady and continuous water flow.

8. Feed the boiler upto -50 mm in the gauge glass.

9. Start the boiler rinsing operation keeping the level constant. Rinsing may be done by opening the mud drum blow off and other low point header drains alternately.

10. Check the gauge glass for its correct functioning by raising/lowering the level and by draining the glass a few times.

11. Stop rinsing when the required quality of water is obtained in the Boiler.

Silica - 0.5 ppm pH - same as feed water.

4.6 MAKING READY THE BURNER SYSTEM

1. Switch on the supply to the BCC panel.

2. Confirm the isolation valves in oil lines for individual burners are closed.

3. Oil circulation is to be established through the burner front about 2 hours before lighting up the boiler. Better to start initial circulation through mass flow meter bypass and FCV bypass.

4. Open the fuel oil main trip valve bypass and the oil return valve and establish the oil circulation. Keep the oil pressure around 5 KSCG.

5. After establishing oil circulation in boiler front, isolate spillback valve on the common header at No. 1 platform level.

6. Co-ordinate with the Hydrofining section operator and bring the fuel oil temperature to 120 0C at the burner front.

4.7 CONTROL ROOM PRE START-UP CHECKS

1. Check instrument air supply pressure. Normal 7 Kg/cm²g.

2. Check the electrical supply to panel, annunciators and controllers and put them "ON" with the help of the Instrument staff.

3. Stroke check all the control valves.

Page 86: Ammonia Manual

Ammonia Plant Operating Manual 86

4. After stroke check keep all the control valves in close condition.

5. Record the initial readings of all instruments in the log sheet.

6. Keep FD fan "NORMAL"/"TRIP" switch in NORMAL position.

7. Keep drum level "very low trip" on bypass "ON" position.

8. Check Main steam stop valve operation from the Control Room and from the local station.

9. Check all the indications, alarms and hooters.

10. Check all trip interlocks for the correct functioning.

11. Reset trip J & K.

4.8 FD FAN START UP

1. Keep FD fan suction damper in close condition.

2. Check the power cylinder and keep it ready for control room operation.

3. Open turbine casing drain, spindle leakoff drain and drain before exhaust isolation valve.

4. Keep the chest valve in closed condition by hand and warm up control chamber by opening the 45 Kg/cm²g. steam isolation valve slightly and blowing through the control chamber drain.

5. Before opening the 45 Kg/cm²g mains, confirm that there is no condensate in the line by opening the drain trap bypass. Keep the trap on line.

6. Open the exhaust isolation gate valve in 12 Kg/cm²g steam line and steam inlet isolation valve fully.

7. Reset the overspeed/hand trip device.

8. Start the Starting oil pump by opening the steam inlet to Starting oil pump turbine.

9. The governor/regulating oil pressure should be about 9 Kg/cm²g and lube oil pressure should be above 0.5 Kg/cm²g.

10. press FD start button.

11. Then press F2 button to reach the minimum governor speed in auto. we have to ensure the speed raising and the conform the governor action to control the speed, if not immediately stop the FD fan by pedestal trip.

12. When the speed reaches 600 rpm, the starting oil pump should be stopped.

13. Adjust the speed governor from control room depending upon the boiler load. (normal 980 rpm).

Page 87: Ammonia Manual

Ammonia Plant Operating Manual 87

14. Check all the pressure gauges for normal values and check the temperatures of various bearings.

15. The rotary oil filter is to be operated frequently so as to keep a steady regulating oil pressure.

16. The normal governor oil pressure is 10 Kg/cm²g and lube oil pressure is 4 Kg/cm²g.

17. All the drains should be closed completely (i.e., in turbine casing, chest valve and drain before exhaust isolation valve).

18. Open the suction air damper slightly from the control room.

19. Check for the minimum and maximum air flow of the FD fan.

20. Commission the steam air heater.

4.9 FIRING THE BOILER

1. Establish oil circulation through the mass flow meter and the flow control valve. Establish a flow of 4 TPH at a pressure of 5 Kg/cm²g.

2. Warm up atomising steam line and charge it. Adjust the pressure to about 9 Kg/cm²g (pressure should be more than the fuel oil pressure for about 2 ksc).

3. By this time, all the six guns should be fixed in position and the hose connections should be given.

4. Position the bottom three guns and open the atomising steam to these burners.

5. Open the suction damper of FD fan and establish about 30 % of the rated flow. Confirm the draft losses in each region and ensure that they are normal.

6. All air doors to individual burners should be in open condition. Open the service air to all pilot burners.

7. Check the BCC panel for "OK START" indication after resetting the reset button. If any trip indication persists, rectify the parameters and restore normality.

8. On confirming "OK START" signal, open the Main trip valve from BCC panel and then closed the bypass valve of main Trip valve after ensuring the flow.

9. Boiler running indication will appear in BCC and control panels.

10. Charge the LPG gas header (about 2 Kg/cm²g). Open the pilot gas valve to No. 2 burner (or the burner to be lighted : No. 2 is preferred normally) and isolation valve on the header.

11. Press the "IGNITOR ON" button for No. 2 burner. Ignition on lamp indication will appear.

Page 88: Ammonia Manual

Ammonia Plant Operating Manual 88

12. Confirm the pilot flame through the peepholes and press the "BURNER START" push button for No. 2 burner. Burner "ON" indication will appear.

13. Confirming the existence of pilot flame, open the oil isolation valve to the No. 2 burner slowly. Main flame will be established. If the main flame does not get established, the next attempt to light up the burner should be made after purging the furnace.

14. Adjust the oil pressure, atomising steam pressure and air flow to have a small and a non-smoky flame.

15. The pilot ignitor should cut out automatically within about 20 secs. of putting it on. This should be confirmed.

16. Check the rate of temperature rise at various points in temperature trend. Any abnormal temperature rise, should be noted and necessary action should be taken immediately. The rate of temperature rise should be around 60 0C/hr.

17. Watch the drum level in the local gauge glass (the panel indication will be wrong during the initial condition) and operate the IBD if the level goes above + 150 mm.

18. Water wall air vents can be closed when continuous steaming is noticed (from 30 min. to one hour depending on BFW temperature).

19. Once the firing is established, close the pilot gas isolation valve and main pilot gas isolation valve to avoid gas loss due to passing of the valves.

20. Close the air vents when the pressure reaches about 4 to 5 Kg/cm²g. Raise the pressure by increasing the firing.

21. Hot tightening of manholes/flanges should be carried out when the pressure is within 5 - 10 Kg/cm²g.

22. It is very important to record the initial and start-up readings in the log sheet.

4.10 RAISING THE PRESSURE

1st Hour : No pressure. All vents should be open.

2nd Hour : 3 - 5 Kg/cm²G pressure. Water wall air vent is closed.

3rd hour : 20 Kg/cm²G pressure. All vents in closed condition. Steam line drains throttled. Gradually increase firing to raise pressure.

4th hour : 45 Kg/cm²g steam line drains to be throttled. Firing is to be increased to have a steady pr. rise. Line up CBD and sampling coolers. Start warmingup main steam line through main steam stop valve bypass.

5th hour : 80 Kg/cm²g. Second burner may be cut in. Other conditions are the same as the above. Open TCV isolation valves.

6th hour : 100 Kg/cm²g. Ready for lining up. Line up feed FCV.

Page 89: Ammonia Manual

Ammonia Plant Operating Manual 89

4.11 OPERATION CHECKS DURING PRESSURE RAISING

1. Since the furnace is cold and only one burner is initially in line, the flame condition should be checked very frequently.

2. Check whether the boiler expansion is normal and free in all directions.

3. Watch the drum level frequently in the gauge glass.

4. When the boiler pressure raises up to 50 Kg/cm²g, start warming up the main steam line.

Open the drains in the 106 Kg/cm²g line. The air vent also to be opened.

Open PCV 0105 about 5 to 10%.

Start gradually opening the main stop valve bypass valve. (This can be opened fully within 15 minutes).

5. After starting warming up of 106 Kg/cm²g line, second burner may be lit. After lighting up second burner, the total firing rate should be kept minimum so as to maintain the rate of temperature and pressure rise.

6. The firing rate to be adjusted by throttling the oil return valve or by opening the FCV.

7. Feeding of the boiler has to be done intermittently through the bypass valve to maintain the drum level.

8. At 40 - 50 Kg/cm²g pressure, CBD and sampling system can be lined up.

9. Do injection backwashing once or twice between 50 - 80 Kg/cm²g pressure range.

10. Start phosphate dosing to steam drum and maintain normal phosphate and pH values in boiler water.

11. When the exit steam temperature goes above 400 C, open the isolation valves of attemperator TCV.

12. When the steam line pressure equals the boiler pressure, main steam stop valve can be opened fully. Confirm the opening of main steam stop valve physically. During the pressure equalising, PCV 0105 may have to be throttled. After opening the main stop valve fully, close the integral bypass valve.

13. Main steam line drains can be throttled to minimum.

14. At 80 Kg/cm²g pressure, IBD is to be operated once.

15. Bring the exit steam temperature to near normal values.

16. All the burner guns are to be locked in position and atomising steam should be lined up to all burners.

17. Line up feedwater FCV.

Page 90: Ammonia Manual

Ammonia Plant Operating Manual 90

18. When pressure reaches about 100 Kg/cm²g, take load gradually.

19. Close the start-up vent gradually after confirming the load taken. All the drains can be closed fully.

20. Adjust the firing rate. Cut in more burners as per the requirement so as to keep the steam pressure steady and the oil pressure below 8 Kg/cm²g. Adjust air flow as per the requirement.

21. Open injection control valve to keep the exit steam temperature within limits. Do not allow the temperature to exceed 490 0C.

22. When the boiler load is about 35 % of the rated load, close the fuel oil return valve gradually and adjust the FCV simultaneously, keeping the fuel oil header pressure constant (minimum four burners to be on line).

23. Take the firing system to cascade control mode.

24. Drum level controller can also be switched over to cascade control.

25. Keep injection control on "MANUAL" mode until the boiler feedwater temperature inlet economiser reaches 150 0C.

26. Keep the air flow controller in MANUAL.

27. Adjust CBD to minimum.

28. The condition of each part of the boiler should be constantly watched during pressurising and if any abnormality is found, suitable action should be taken.

29. Pilot gas system to be kept isolated, cylinders to be closed and delinked.

30. Top row burners should be cut in only after lining up all the bottom row burners. To ensure uniform heat distribution, middle burner should be cut in first.

31. Take all trips excluding drum level low trip on line.

32. Check the gauge glass indication once more and ensure the level is OK by raising and lowering the level.

4.12 SHUTTING DOWN OF BOILERS

1. Reduce the load on both boilers to less than 50 % of the rated load.

2. After reducing the boiler's load, transfer the load from the boiler to be shutdown to the other boiler by reducing the firing rate in the former. If only one boiler is in line and that has to be shutdown, this is not necessary.

3. Cut out two burners in the top row one by one and purge the same.

Page 91: Ammonia Manual

Ammonia Plant Operating Manual 91

4. Take the fuel oil controller to manual operation. Open the oil return valve watching the oil pressure( adjust FCV and oil return valve to have a flow of around 4 TPH). (note: don’t take master pressure control in manual if two boilers are running)

5. Cut out two more burners one by one. Adjust the oil return valve again to have a comfortable oil flow through the control valve. Burners to be steam purged immediately.

6. Take temperature controller and drum level controller to manual mode.

7. Open start-up vent gradually to about 50 % and close the main steam stop valve. (Confirm physically that the main steam valve and its integral valve are closed).

8. If the other boiler is on line, final adjustment of the load is to be done.

9. Cut out one more burner and purge it. Only one burner is in line. Reduce the firing rate to minimum. Adjust the air flow accordingly.

10. Before putting out the last burner, it is preferable to operate the soot blowers in air heater region.

11. Attemperator TCV should be isolated when the exit steam temperature falls down to 400 C, the TCV in closed condition.

12. Injection backwashing may be done, if necessary.

13. Bring down the Boiler pressure to the required level (as described below) by adjusting the start-up vent.

For natural cooling, prolonged shutdown, the boiler can be boxed up at around 80 Kg/cm²g.

If it is necessary to bring the boiler on line after a few hours, the boiler can be boxed up at 90 -95 Kg/cm²g pressure.

If the boiler is to be cooled down urgently for maintenance work etc., the boiler can be boxed up at 40 - 45 Kg/cm²g pressure. 14. If Ammonia injection in flue gas is open, this should be closed before cutting out the last burner.(now this line is disconnected).

14. Cut out the last burner also by tripping from the BCC panel or from the Control Room. LAST BURNER SHOULD NOT BE STEAM PURGED.

15. Isolate the feed line FCV with a level of + 200 mm in the steam drum.

16. Close CBD and other sampling systems. Close start-up vent.

17. Bring air flow to minimum and cut off steam to steam air heater.

18. Establish oil circulation in burner front as per the given procedure or isolate the complete system depending on the situation.

19. Trip FD fan after about 15 minutes of tripping the boiler for purging out the explosion mixture out of the boiler.

Page 92: Ammonia Manual

Ammonia Plant Operating Manual 92

20. Close the suction damper of fan.

21. Line up the starting oil pump and keep it running till the bearing temperature of the turbine unit comes down to 65-70 C.

22. Isolate the 45 Kg/cm²g and 12 Kg/cm²g steam lines to FD fan, after stopping the starting oil pump.

23. Open drains in turbine and 12 Kg/cm²g line before the isolation valve on the turbine side and check that there is no passing of steam.

24. Cut off atomising steam to all the burners and isolate the main.

25. Pull out all the burner guns and clean them immediately. Oil is to be drained from the last cut out burner for proper disposal.

26. Feeding of the boiler is to be done intermittently whenever the level falls to -200 mm.

27. When the steam pressure reaches to about 5 Kg/cm²g all the vents can be opened.

28. Feeding of the boiler should be done until the temperature (max. recorded) of boiler reaches 125 - 150 C.

29. Boiler can be handed over for maintenance after satisfying all safety precautions.

4.13 EMERGENCY SHUT DOWN

Emergency shutdown of one Auxiliary Boiler with the other on line

1. Reduce the steam load.

2. Transfer all the load to the running boiler.

3. Take the fuel oil controller to manual mode and reduce firing.

4. Cut out all burners except one burner in the bottom row and steam purge one by one.

5. Open the oil return valve in-between to reduce the firing.

6. Open start-up vent to about 50 % and close the main steam stop valve.

7. Isolate the injection control valve when the steam temperature starts dropping below 4000 C.

8. Bring down air flow to minimum (about 35 % of the rated flow).

9. Feed the boiler to +200 mm. Close CBD and sampling.

10. Isolate the feedwater system.

11. Trip the boiler and box up the same as per the required condition.

Page 93: Ammonia Manual

Ammonia Plant Operating Manual 93

12. Isolate all individual burner valves and put oil circulation if necessary depending upon the condition.

13. Isolate atomising steam, pull out and clean the guns.

Emergency Operation when one boiler trips while both units are running on load

1. See the cause of the trip in Trip annunciator and acknowledge the alarm.

2. Take the running boiler on "MANUAL" control. Keep oil at 6.3 TPH (Max) and air flow at maximum.

3. Reduce the steam load to maximum possible extent.

4. If the trip cause is known and boiler can be restarted immediately, main steam valve need not be closed.

5. Isolate TCV to avoid temperature dropping due to passing of TCV.

6. Maintain the drum level within normal range. If water level goes high, isolate feed water system.

7. Open start-up vent, if there is any pressure rise.

8. If there is any delay in starting up close the Main stop valve and box up the boiler at slightly lower pressure than the working pressure.

9. CBD also can be isolated if there is any delay in lighting up.

10. Isolate all individual burner oil valves and put oil circulation around the boiler front by opening the main trip valves bypass.

11. Take more care of the running boiler's FD fan exit steam temperature, drum level etc.

12. After rectifying the defect, line up the boiler as per normal start up. Open Main Steam valve when the boiler pressure is about 3-5 Kg/cm²g less than the main steam header pressure. Before opening the main steam valve, ensure that exit steam temperature has attained its normal value, by venting for some time through the start-up vent.

NOTE :

If both the boilers have got tripped, close both steam stop valves immediately and box up the boilers as described above. Start and line up the boilers one by one at the earliest not neglecting any of the above procedure. If any one of the boiler is on line and it trips suddenly, box up the boiler immediately. Close main steam valve, open start-up vent if pressure tends to increase. Isolate TCV & CBD. Maintain drum level. Start the boiler after getting clearance from the Shift Engineer. Before opening the main steam valve, bring steam temperature to the normal value.

Page 94: Ammonia Manual

Ammonia Plant Operating Manual 94

4.14 NORMAL OPERATION

1. Phosphate dosing to be done twice or more in each shift to maintain phosphate and pH in the boiler water.

Phosphate : 3 - 10 ppm pH : 9.5 - 10.5

2. Soot blowing to be done once in each shift or as per instructions.

3. CBD is to be adjusted so as to have silica in boiler water less than 1 ppm and Iron 0.1 ppm.

4. Gun cleaning to be done once in 15 days and also whenever a gun is suspected to be choked.

5. Mass flow meter filter is to be cleaned periodically. (DP across the filter should not exceed 2 Kg/cm²g).

6. IBD of all panels to be operated twice a week and also depending upon the analysis report.

7. Draft values and temperatures at various points are to be watched carefully and any abnormality is to be reported.

8. Gauge glass is to be kept on line always and checked frequently. Only gauge glass level is to be taken as the correct level. Boiler should never be operated without atleast one of the gauge glasses on line.

9. Control Room level indication is to be adjusted as per the local gauge glass indication (if the difference is significant).

10. Flame checking is to be done frequently.

11. Boiler should be tripped if the water level cannot be maintained within the gauge glass even if the drum level very low trip is kept on bypass, the boiler should never be operated without level indication in the panel.

Operations to be done in case there is a sudden load increase(Caused by offsite boilers tripping or problems in Ammonia Plant)

1. This will be immediately indicated by steam flow increase. "Master pressure Low" will also appear.

2. Take the Master pressure controller on manual operation and keep the fuel oil flow to the individual boilers at maximum limit, however not exceeding 6.3 TPH.

3. Raise air flow to maximum depending on furnace pressure.

4. Bypass the Drum level low trip. (Do not operate the boiler without visible level indication in the field and the panel)

5. If the feed water pressure is low it should be increased. Inform control room or field operator.

Page 95: Ammonia Manual

Ammonia Plant Operating Manual 95

6. Have a glance at the chimney. If it smokes black slightly reduce the oil flow. Find out which boiler smokes black using O2 analyser. If the chimney is clear, fuel flow can be increased slightly until smoke in the chimney is observed.

7. If necessary, take injection control on manual. Do not allow the temperature to go beyond 490 0C. Boiler should not be operated at 490 0C even for a short duration.

8. Have a close watch on the FD fan speed. While decreasing air flow do it slowly. Otherwise it may cause over speed trip.

9. Have a close watch over the other parameters and physical conditions. If any abnormality is found, limit the load accordingly.

10. Suspend all auxiliary operations such as soot blowing etc.

11. If necessary, take the feed water flow controller to manual operation.

12. After normal conditions are achieved, put back all the controllers on AUTO mode one by one.

Operations in case if there is a sudden decrease in load :

1. Steam flow will fall down "Master Pressure High" alarm will appear.

2. Bypass the drum level very low trip.

3. Adjust the air flow. Reduce slightly and keep 50 to 60% of rated air flow (ie., above low flow alarm level).

4. Firing rate will be reduced by Master pressure controller if it is not sufficient, reduce it manually.

5. Cut out two burners in each boiler.

6. If the load is very low ie., 35 % of the rated load, take one of the boiler fuel control valves to MANUAL and reduce the load in that boiler to minimum by opening the oil return valve.

7. Get instructions from the shift in-charge and proceed further accordingly.

II ADDITIONAL STEAM GENERATING UNIT

4.15 BOILER SPECIFICATIONS

1. Steaming capacity : 120 tph2. Pressure at superheater exit : 106.5 Kg/cm²a3. Temperature at superheater exit : 482 ± 5 0C4. Boiler Feed water consumption : 124.8 TPH5. Fuel oil consumption : 8.2 TPH6. Number of burners : 47. Number of soot blowers : 6 (rotary cum retractable)

Page 96: Ammonia Manual

Ammonia Plant Operating Manual 96

8. Thermal efficiency : 92.5% min9. Salient features Single drum Drum Preheated Tubular Air preheated. 4.16 STEAM SYSTEM

ASGU is designed to produce 106.5 Kg/cm²a steam which is mainly utilised for Captive power production in TG I. TG I exhaust is 45Kg/cm²g steam and it is used again for captive power production in TG II as well as to meet the requirement of 48 Kg/cm²a steam demand.

106.5 Kg/cm²a steam

Supplier : ASGU

Consumer :

1. TG I2. To ammonia header through HC 202C3. Through PCV 2600 to 48 Kg/cm²a header4. Through MFCV 2600 to 48 Kg/cm²a header in case of TG I turbine or generator trip.

48 Kg/cm²a steam

Supplier :

1. TG I exhaust2. 106 Kg/cm²a to 48 Kg/cm²a let down PCV 26003. MFCV 26004. From OSB through FCV 26035. From ammonia plant 48 Kg/cm²a header.

Consumer :

1. ASGU Boiler feed water pump turbines.2. ASGU FD fan turbines.3. ASGU main soot blowers.4. TG II5. CPP cooling water pump turbine.6. 48 / 12 Kg/cm²a let down through PCV 26267. TG II Condensate extraction turbine.8. To OSB header through FCV 2603.9. To Ammonia plant 45 Kg/cm²g header

12 Kg/cm²a steam

Supplier :

1. ASGU FD fan turbine exhaust.2. ASGU BFWP turbines exhaust.3. 48/12 Kg/cm²a let down through PCV 2626

Page 97: Ammonia Manual

Ammonia Plant Operating Manual 97

4. From Ammonia plant 12 Kg/cm²a header.

Consumer:

1. ASGU Steam air Preheater.2. ASGU Fuel oil pump turbines.3. ASGU BFW Heater.4. ASGU Fuel oil heater.5. 12/2.1 Kg/cm²a let down through PC 26146. Service steam header.7. Atomising steam.8. TG II Steam ejectors. 2.1 Kg/cm²a steam

Supplier :

1. ASGU FOP Turbines exhaust.2. TG II CEP exhaust.3. TG I leak off 4. 12/ 2.1 Kg/cm²a let down through PC 26145. CBD flash steam 6. 2.1 ata steam from ammonia plant through HC 2628.

Consumer :

1. To Deaerator through PC 26172. Vent PC 2610.

Desuper heating

From the boiler feed pump discharge through PC 2662 pressure is let down to 60 Kg/cm²g and is fed to all desuperheaters.

For 48 Kg/cm²a desuperheating TCV 2600 For 12 Kg/cm²a desuperheating TCV 2626 For 2.1 Kg/cm²a desuperheating TCV 2614 For Service steam desuperheating TCV 2660 For TGI leak off steam desuperheating TCV 2657 For Atomising steam desuperheating TCV 213C

There is a provision to give make up water to 1131.

4.17 STEAM SYSTEM COMMISSIONING

When the ASGU is to be run to supply steam for power generation, all systems and utilities will be made independent of Ammonia Plant.

Steam will be charged to the unit from OSB to enable start up of FD fan, BFW pump, FO pump and to supply to Deaerator, FO Header Atomising Steam etc., until the Boiler generates steam to make it self-sufficient for these and other requirements.

Page 98: Ammonia Manual

Ammonia Plant Operating Manual 98

PROCEDURE FOR STEAM CHARGING

1. Following valves to be kept closed:

45 Kg/cm²g and 12 Kg/cm²g isolation valves at Ammonia Plant battery limit.

Inlet and Exhaust isolation valves of FD Fan Turbine, BFW Pump Turbines, FO Pump Turbines and TG-II Condensate Pump Turbine.

Inlet valves of TG-II and CW Pump Turbines.

FO Preheater TCV isolation valve.

48/12 Kg/cm²a letdown PCV 2626 and its isolation valve.

12/2.1Kg/cm²a letdown PCV 2614 and its isolation valve.

BFW Heater inlet PCV and its isolation valve.

Atomising steam isolation valve.

Soot Blower steam (48 and 12 Kg/cm²a) isolation valves.

Steam - Air Heater TCV isolation valve and its bypass valve.

Leak off steam isolation valve from TG I to 2.1 Kg/cm²a header.

CBD flash steam isolation valve to 2.1 Kg/cm²a Header.

All Desuperheater station TCV's and their isolation valves.

Deaerator steam isolation valves.

48 Kg/cm²a Header vent PCV and its isolation valve.

FCV isolation valves and bypass valve.

106.5 to 48 Kg/cm²a letdown PCV 2600 and MFCV isolation valves.

2. Following valves to be kept open:

12 Kg/cm²a vent PCV 2609 and its isolation valve.

2.1 Kg/cm²a vent PCV 2628 and its isolation valve.

Isolation valve of 12 Kg/cm²a Header Relief Valve.

All PI isolation valves and PT and FT impulse line isolation valves.

Page 99: Ammonia Manual

Ammonia Plant Operating Manual 99

All drains and trap bypasses in the system.

Ensure that instrument signal for FX 2603 is reversed, to enable steam flow from OSB to be measured. (after steam system stablised by receiving steam from ASGU FX 2603 should be normalized back).

3. Ensure that instrument air system of CPP is stabilised, IA from Ammonia Plant is isolated and IA from CPP lined up to all Boiler are instruments.

4. Stoke check all control valves.

5. Ensure that 48 Kg/cm²a Header isolation valve at OSB has been opened and the line warmed up and pressurised upto CPP battery limit isolatiion valve (FCV 2603 downstream isolation valve).

6. Open FCV 2603 downstream isolation valve.

7. Open FCV 2603 by 5% and its upstream isolation valve integral bypass valve and start warming up the 48 Kg/cm²a header.

8. After condensate has stopped issuing from all drains, start pressurising the header slowly by opening battery limit valve. Throttle the drains as the pressure increases.

9. When the pressure is about 10 Kg/cm²g, open isolation valve on 48-12 Kg/cm²a letdown, open PCV 2626 slightly and start warming up 12 Kg/cm²a header.

10. When condensate stops issuing out of the drains, start pressurising 12 Kg/cm²a header by throttling the vent PCV.

11. When the pressure is about 5 Kg/cm²g, put the vent controller on "AUTO" and continue raising the pressure.

12. Start warming up the 2.1 Kg/cm²a header through the 12-12.1 Kg/cm²a letdown as done above.

13. Gradually bring up 12 and 12.1 Kg/cm²a header to normal pressure, keeping letdown PCV's on "MANUAL" and vent PCV's on "AUTO". Allow 48 Kg/cm²a header pressure to come up and float with OSB header pressure.

14. Desuperheaters need not be lined up if the 12 and 12.1 Kg/cm²a header temperature are not much higher than normal. If required water has to be drawn from Ammonia plant until BFW pump is started.

4.18 PREPARATION FOR START UP

1. All equipment and boiler heating sections should be checked for rags, tools and any other foreign matter and they should be removed. The heating surface should be kept clean.

2. Check inside the steam drum for any foreign materials and close the drum manhole.

3. Check air duct and flue gas duct for any foreign materials and close the manhole covers.

4. Close all access doors and peepholes.

Page 100: Ammonia Manual

Ammonia Plant Operating Manual 100

5. Line up level gauges of steam drum, CBD tank and IBD Tank. (now CBD tank is shifted to main plant for use of 12 ksc to 2.1 ksc flash drum).

6. Line up all instrument tapping connections.

7. Open all air vent valves.

8. Close all drain valves of the headers and CBD / IBD Valves.

9. Check Instrument air pressure and maintain at 7 Kg/cm²g.

10. Stroke check the following control valves.

FCV 201C – Feed water FCV 203C - Fuel oil TCV 203C - Attemperator. HCV 202C - Steam to Ammonia HCV 203C - Start-up Vent FCV 204C - FD Fan Suction damper TCV 209C - SAPH

11. Check the operations of MOV on the following lines.

Main steam line to ammonia. Main steam line to CPP Start-Up Vent.

12. Check oil levels in bearing / sump of FD fan, FD fan turbine, boiler feed water turbine make-up the level if required,

13. Line up cooling water to

FD Fan bearings FD Fan Turbine oil cooler Sample coolers Boiler Feed water turbine oil coolers and seal water coolers.

14. Open the drain valve upstream and downstream of HCV 202 C.

15. Open the Start -up Isolation valve and its MOV.

16. Confirm that all the soot blowers are kept at pulled out condition.

17. Check whether all the pilot igniters are properly fixed.

18. Make ready all burner guns.

19. Check the availability of LPG cylinders.

Page 101: Ammonia Manual

Ammonia Plant Operating Manual 101

4.19 DEAERATOR COMMISSIONING

1. If Deaerator is taken in line after prolonged shut down it has to be inspected inside for collection of any foreign material. This is to be done for storage tank also.

2. After thorough inspection / cleaning, the system is to be filled up with polished water and to be flushed several times. If inlet and outlet water quality is the same, flushing can be stopped. (Check for Silica and Iron.) The Deaerator and storage tank must be drained fully and drain valve to be closed.

3. Ensure that all the instruments and control valves are available. Stroke check all the valves related to Deaerator.

4. Keep open all the vents including the control vent provided with an isolation valve.

5. Admit steam through the startup steam line provided in the storage and allow the system to warm up slowly. Temperature of the steam to be kept at 200 0C. If all the entrapped gases are released and adequate temperature is attained, slowly close the controlled vent isolation valve. Pressure of the unit must be controlled at 0.4 Kg/cm²g. Check all the pipe lines, manholes, flanges etc for any leak. All the instruments connected with pressure must be in service. Check them for any malfunctioning.

6. Admit water gradually through the LCV since in this line only strainer is available. Watch for any hammering, which must be avoided. Slowly increase the water quantity to reach the normal level in the storage. Initially the drain valve in the storage may have to be used to have a continuous water flow till the BFW pump is started and water is used in Boiler. In that case, establish a flow rate of about 10 to 15 TPH through drain and stabilise the Deaerator.Check oxygen content in deaerated water after achieving the design conditions of 0.4 Kg/cm²g and 109 0C.

SOURCES OF WATER TO DEAERATOR

1. Polished water through LCV from WTP.2. Condensate from TG-II and CWPT condenser.3. SAPH condensate.4. BFW Heater condensate also joins directly to storage tank.

4.20 BOILER FEED WATER PUMP START UP

1. Ensure that 24 V DC power is available. LO Auxiliary Pump must be started as a first step before warming up of casing is done. For starting Auxiliary Oil Pump, the level in the LO Reservoir should be above alarm level. After starting the pump, ensure that all the lines are filled up and normal flow is observed in the slight glasses provided on LO return lines. Ensure that the priming valve provided for main oil pump, to fill its suction line, is in open condition.

2. Line up suction isolation valve of the pump (before this, the Deaerator system must be in line and adequate water make up available). Prime the pump thoroughly and check the suction pressure. It should be about 1.5 Kg/cm²g. The minimum allowed pressure is 1.0 Kg/cm²g. Ensure that spill back valve is full open and that discharge valve is fully closed.

Page 102: Ammonia Manual

Ammonia Plant Operating Manual 102

3. Initially turbine is warmed up thoroughly through casing drains by opening the exhaust isolation valve slowly. (Care to be taken not to pressurise the line and casing suddenly).

4. Reset the manual trip latch and over speed trip latch. Reset the trip throttle value by closing it fully. Finally reset the panel reset provided in the local panel. Open the main steam isolation valve and pressurise the line upto trip valve. Ensure that the first nozzle valve is kept open fully.

5. Slightly open the trip throttle valve and roll the turbine. Set it at 100 rpm and watch for any abnormal noise or bearing temperature rise. Allow the casing to warm up thoroughly. Once the casing is warmed up and inlet temperature starts picking up above 280 0C, increase the speed to 500 rpm. Allow the turbine to run at 500 rpm for 5 minute, check vibration and temperature. Turbine speed can be taken up in steps of 500 rpm, allowing the turbine to run for 5 minutes at every stage before raising the speed. Once minimum Governor speed is reached, open the trip throttle valve fully. (Keep it half turn closed to enable it to close at the time of trip.) Slowly rise the speed using Governor speed change knob and line up the pump at required pressure (100 Kg/cm² for start up). After reaching the minimum governor speed the leak off steam is lined up to the 2.1 ksc header.

4.21 LINING UP BFW HEATER

The BFW heater provided with the BFW pumps in a 'U' tube type. BFW passes through the tubes and on the shell side, 12 Kg/cm²a superheated steam is used as a heating medium. The shell side pressure is controlled to achieve in the shell which enables condensate level to be maintained. The condensed water is directly fed to Deaerator storage tank.

After starting the BFW pump and before lining up the heater, ensure that priming vent is kept open slightly and heater is primed thoroughly before lining up. Once circulation is established through the heater, shell side steam isolation valve to be opened slightly and steam must be admitted slowly through the PCV. Initial liquid collection in the shell can be drained locally.

Once the system is warmed up thoroughly and checked for leaks in the flanges, the shell side can be pressurised slowly to get the exit BFW temperature of 185 0C. Line up LCV after checking the quality of condensates to Deaerator Storage Tank.

Shell Side Relief Valve set pressure - 14 Kg/cm²gTube side Relief Valve set pressure - 175 Kg/cm²g

4.22 FILLING UP THE BOILER

1. Ammonia dosing and Hydrazine dosing should be done in the feed water.

2. Open air vent in feed water line before FCV 201C and release the air lock.

3. Keep FCV 201C Isolation valves and by pass valve in closed condition.

4. Open all panel drain valves. Keep economiser drain valve and common drain valve to IBD tank closed.

5. Open the boiler filling isolation valves and start filling the boiler through all panel IBD.

6. Adjust the feed rate to about 15 tph so that working level may be reached in about three hours.

Page 103: Ammonia Manual

Ammonia Plant Operating Manual 103

7. Feed the boiler upto 50mm in gauge glass. Close filling up line valves and line up feed through FCV 203 C.

8. Start rinsing the boiler keeping the level constant . Rinsing shall be done by opening the drain valves in the water wall panel bottom headers. Rinse through all panels.

9. Check the gauge glass for its correct functioning by raising or lowering the level through the drains.

10. Stop rinsing when the quality of water is obtained.

Silica > 0.5 ppm pH = 9.5 to 10.0

4.23 MAKE READY THE BURNER SYSTEM

1. Ensure oil lines isolation valves for individual burners are kept closed.

2. Ensure the fuel gas line isolation valves are in closed condition.

3. Establish oil circulation in the burner front atleast 8 hours before lighting the boiler.

4. Inform CPP to start Fuel oil pump. Line up PCV and put it in auto at 15 Kg/cm²g.

5. Ensure that oil recirculation valve after fuel oil heater is kept partially opened and line up steam to fuel oil heater . slowly raise the oil temperature to 120 0C.

6. Check all drains and Vents in boiler area are kept closed. Open Isolation valves of Mass flow meter and FCV 203 C.

7. Confirm steam tracing lines are energized .(Not in line)

8. Open Fuel oil return valve to cpp day tank.

9. Open the Isolation valve in fuel oil supply line. Open FCV 203C and its bypass valve and adjust so as to have a flow of about 8 TPH, and pressure of about 10 Kg/cm²g.

10. Energise burner control panel.

4.24 FD FAN START UP

1. Check oil level in turbine oil sump and fan bearings. Keep cooling water to oil cooler closed and water to bearing jackets open.

2. Check position of auxiliary oil pump auto/local switch in control Room. Keep the switch on 'Local'.

3. Start the aux. oil pump using the start - stop PB station near the turbine. Ensure that it develops a minimum of 1.8 Kg/cm²g, Oil pressure (the 'low lube oil' trip switch gets reset at a pressure of 1.7 Kg/cm²g). Put the auto/local switch on 'auto'.

Page 104: Ammonia Manual

Ammonia Plant Operating Manual 104

4. Check that the governor speed knob is set at the minimum position (turned fully counter-clockwise from the top).

5. Ensure that the steam inlet and exhaust lines upto the turbine isolation valves are thoroughly warmed up and that no condensate issues from the drains.

6. Open the turbine exhaust valve slowly and gradually pressurise the turbine casing. Keep the turbine casing drain sufficiently open to drain all condensate and warm up the casing. Also open the gate valve in the steam inlet line.

7. Ensure that the fan suction damper is fully closed .

8. Check the turbine 'handtrip' and ensure that it is pushed in (reset).

9. Push the 'start' PB in the control Room to open the hydraulic stop valve in the steam inlet.

10. Inform the concerned department for requirement of steam. Slowly open the globe valve at the turbine inlet. Allow the turbine speed to pick up such that the lube oil pressure increases to 3.8 Kg/cm²g and the auxiliary lube oil pump can be stopped and put it in auto. In the control panel, watch 12 ata header pressure and ensure that it is steady.

11. When the governor starts controlling the speed at minimum setting (about 600 rpm), slowly open the steam inlet valve fully.

12. Check the fan bearings for adequate oil level, any abnormal temperature rise, vibration, etc.

13. Open water to turbine oil cooler and maintain the oil exit temperature at about 45 0C. Backflush the cooler for sometime before taking it in line.

14. Raise the speed to 980 rpm using the governor speed changer knob (turn clockwise).

15. The fan suction damper can be opened at this stage for further start up activities.

SHUT DOWN

1. Close the fan suction damper fully.

2. Speed down the turbine to the governor minimum.

3. Close the globe valve on the steam inlet. Check that the aux.oil pump starts on auto when the oil pressure reaches 1.7 Kg/cm²g.

4. Press the ‘stop' PB in control Room to close the hydraulic valve. Also pull the hand trip knob to the trip position.

5. Check that the aux.oil pump runs for half an hour before stopping.

6. Isolate and drain water to oil cooler and fan bearing jackets.

Page 105: Ammonia Manual

Ammonia Plant Operating Manual 105

4.25 BOILER START UP

1. Fix all the four guns in position and connect them with respective hoses.

2. Open atomising steam to burner No.4.

3. Open the suction damper of FD fan and establish about 30% of rated air flow. Check the draft losses at each section of the boiler and verify with the normal values. Check for any abnormal air leakage.

4. Ensure the air to soot blowers for gland sealing is on.

5. Ensure service air supply to all pilot burners and flame scanners.

6. Charge the LPG header by opening the cylinders valves and check the header pressure.

7. Line up the gas header pressure regulating valve and maintain a pressure of 2 Kg/cm²g at the gas header.

4.26 RAISING THE PRESSURE

1. Steam will be found to issue freely out of the vents in about half an hour after lighting up. Close all air vents. Throttle the start up vent control valve PCV 203 C gradually to about 30% opening to raise the boiler pressure.

2. Pressure at the end of the one hour will be about 10 Kg/cm²g. Throttle drains in steam. Continue raising the pressure by increasing fule oil firing.

3. Pressure at the end of the second hour will be about 45 Kg/cm²g.

4. Light up burner #3 and maintain oil pressure of 5 Kg/cm²g on both burners.

5. Line up desuperheater TCV 203 C and control steam temperature to limit superheater metal temperatures.

6. Continue raising boiler pressure by increasing firing, to achieve 90 Kg/cm²g at the end of the third hour.

7. Gradually close FO FCV bypass value and take control on FCV.

8. Close FO return valve watching the FO pressure.

4.27 OPERATION CHECKS WHILE RAISING THE PRESSURE

1. Frequently check the flame condition through the peepholes.

2. Regularly check the boiler expansion and ensure that it is normal.

3. Keep a watch on the superheater coil skin temperatures. The temperature should be kept below 500 0C, by using the attemperator to control exit steam temperature.

4. Check the drum level on the gauge glasses and the remote level indicator frequently.

Page 106: Ammonia Manual

Ammonia Plant Operating Manual 106

5. Line up the CBD and the sample coolers when the boiler pressure is about 50 Kg/cm²g.

6. Operate the IBD and all the bottom header drains once at about 60 Kg/cm²g pressure.

7. Start warming up the main steam line when the boiler pressure is about 80 Kg/cm²g (if steam is to be supplied to CPP). Inform CPP Operator and ensure that all interbattery drains are kept open. Slightly open integral bypass of MOV to CPP.

8. If steam is to be supplied to Ammonia plant, ensure that isolation valve at hook up point is kept closed, open drains downstream of MOV and downstream of HCV 202 C. Then slightly open integral bypass of MOV.

9. Line up the feed water FCV and take drum level control on cascade auto.

10. Start dosing phosphate to the steam drum and maintain normal PO4 and pH.

4.29 LINING UP STEAM

I. If lining up steam to Ammonia plant

1. Check the master pressure controller PC 201 setting and increase the pressure of the III boiler to this value.

2. After warming up the 106 ata header to Ammonia plant, gradually pressurise the header and equalise with III boiler (also with boilers I & II). Throttle all drains.

3. Open the isolation valve at the hook up point.

4. Ensure that the master pressure controller PC 201 C change over switch is set to receive signal from PC of boilers I & II.

5. Open the MOV on the steam line to Ammonia plant. Close the integral bypass.

6. Gradually close the start up vent PCV 203 C and feed steam to Ammonia plant. Loads on auxiliary boilers are to be adjusted without any upset.

7. After the start up vent is fully closed, increase the firing gradually (either raise FO pressure or light another burner).

8. When steam flow to Ammonia plant is established (minimum 40 TPH), put 'Combustion Control' on cascade auto. Adjust ratio contact to share load as required.

9. Stabilise exit steam temperature and put controller in 'auto'.

II. If lining up steam to CPP

1. Inform CPP Operator, check that all interbattery drains are kept open and slightly open integral bypass valve of MOV to CPP.

Page 107: Ammonia Manual

Ammonia Plant Operating Manual 107

2. After the header is completely warmed up (as confirmed by CPP Operator), gradually pressurise the header and equalise with boiler pressure (105.5 Kg/cm²g).

3. Open the MOV fully. Close the integral bypass.

4. Line up 106-48 letdown station PCV 2600 and FCV 2600 and also the desuperheater TCV 203 C.

5. Inform OSB Operator and gradually open PCV 2600. Import steam from OSB will get reduced. Close start up vent to maintain boiler load at same value (about 30 TPH).

6. Export steam to OSB and put PCV 2600 on 'auto'.

7. Put start up vent PCV on auto with set point slightly higher than boiler pressure.

8. Put 48 ata vent PCV 2627 on auto.

9. Take ASGU on cascade auto.

10. Give clearance to CPP Operator to draw steam.

4.30 BOILER NORMAL SHUT DOWN

In case of steam supply to Ammonia plant

1. Take the combustion control on 'manual'.

2. Reduce boiler load gradually by reducing oil firing. Watch other boiler loads. Cut off burners depending on FO pressure. (Cut off top row burners first).

3. Open FO return valve when the flow drops below 4 TPH.

4. When the boiler load drops below 30%, start closing the MOV on main steam line slowly. Simultaneously open the start up vent to maintain the drum pressure. Keep a watch on superheater coil skin temperatures.

5. Take attemperator TC 203 C and drum level controllers on 'manual'.

6. After the MOV is fully closed (and start up vent proportionately opened), reduce firing further to bring down the pressure to 90 Kg/cm²g.

In case of steam supply to CPP

7. As TG-I and TG-II load are reduced, allow boiler load to come down. Cut off burners as necessary.

8. When the load is about 30%, take the combustion control on 'manual' and reduce firing. Open FO return.

Page 108: Ammonia Manual

Ammonia Plant Operating Manual 108

9. Open start up vent to maintain the steam header pressure. Watch superheater coils skin temperature.

10. When TG-I / TG-II are shut down, 45 ata steam will be required for boiler and CPP auxiliaries only (about 25 TPH). Inform OSB regarding this requirement. Gradually close 106 - 48 ata letdown PCV 2600 and draw steam from OSB. When letdown is closed, isolate letdown station and close MOV at boiler exit to CPP. Keep start up vent open to maintain boiler pressure at the same firing.

11. Take attemperator TC and drum level control on 'manual'.

12. Reduce steam pressure to 90 Kg/cm²g.

13. In both cases, box up the boiler at 90 Kg/cm²g pressure.

14. Stop FD fan after purging the furnace for about 5 minutes. Isolate steam to SAPH.

15. Close and isolate FCV 201 C when the drum level is + 150 mm.

16. Close CBD and sampling system.

17. Continue fuel oil circulation at the burner front.

18. Cut off atomising steam to all burners and isolate the main.

19. Take out all 4 burners and clean them immediately.

20. Keep the drum level not less than - 150 mm by intermittently supplying feed water to drum.

21. Allow the boiler to cool naturally. When the pressure reaches about 5 Kg/cm², all vents can be opened.

22. Feeding of the boiler should be done until the temperature of boiler reaches 125-150 0C.

23. Boiler can be taken up for any maintenance, if necessary.

4.31 NORMAL OPERATION

1. Phosphate dosing is to be done in each shift to maintain PO4 and pH in the boiler feed water.

PO4 - 3 to 10 ppm

pH - 9.5 to 10.5 ppm

2. Hydrazine and Ammonia are to be dosed to boiler feed water to maintain the following values:

pH N2H4

BFW 9.5 -CBD 9.5-10.5 0.08 max

Page 109: Ammonia Manual

Ammonia Plant Operating Manual 109

3. Steam soot blowing is to be done once in each shift or more frequently depending on boiler conditions.

4. CBD to be adjusted so as to have silica in boiler water less than 1 ppm.

5. Gun cleaning is to be done once in 15 days minimum and also whenever a gun is suspected choked. Also clean the Y-strainer in the FO line to each burner.

6. Check FD fan turbine and boiler feed water pump turbine oil level.

7. IBD (all panels) to be operated twice in a week for about 4 seconds each.

8. Draft values and temperature at various points are to be watched carefully and any change to be reported.

9. Gauge glasses should be kept on line always and are to be checked frequently. Only gauge glass level is to be taken as the correct level.

10. Closely monitor the flame condition through peephole.

11. Check LPG cylinder availability once in a week.

12. The superheater coils are provided with skin thermocouples at 12 locations. The temperature at any point should not exceed 517 0C. Any abnormal increase should be immediately reported.

13. Conduct 'Walk Down Check' of the entire boiler atleast once every shift.

4.32 DRUM PREHEATER

Normally the boiler feed water supply temperature will be 185 0C. In case boiler feed water is available at 105 0C only a drum Preheater is provided to minimise or prevent corrosion in Economiser and TAPH.

Water temperature is raised from 105 C to 155 0C in the drum coil heater and fed to the drum through economiser.

Open the isolation valve in the line to drum Preheater (located downstream of FCV 201 C) in boiler feed water line and close the isolation valve for the economiser. Circulation of boiler feed water is established through drum Preheater.

While the boiler load is being raised, keep a watch on economiser exit water temperature. If the temperature increases beyond 260 0C, open economiser inlet valve slightly to control the temperature below this value.

Page 110: Ammonia Manual

Ammonia Plant Operating Manual 110

3 Chapter Five PROCESS AIR COMPRESSOR

5.1 OUTLINE OF THE MACHINE

Compressor

Compressor train consists of two casings. A step up gear is provided in between the casings with the gear ratio of 1:1.47. Rated speed of the LP casing is 7500 rpm and HP casing is 11000 rpm.

Lube oil system

Main lube oil pump driven by turbine, takes oil from reservoir (capacity 6300 liters) and pressurises to 6 KSCG. This is cooled to 40 0C in oil cooler, filtered to 25 microns, letdown to 2.2 KSCG by lube oil pressure control valve and further reduced 1.5 KSCG to journal bearings and 1 KSCG to thrust bearing, through adjustable restriction orifices. A part of the oil discharged from the pump is branched off at the upstream of the oil filter and supplied to the governing system. Oil drain from the lubrication and governing system returns to oil reservoir across the flow sights.

This system is provided with the following devices :

1. Auxiliary lube oil pump driven by motor. If the lube oil pressure drops to 1.2 KSCG due to any trouble, this pump will start automatically and deliver the lube oil to the main line.

2. Accumulator : If the lube oil pump fails, the accumulators will prevent the oil pressure from dropping during the startup of Auxiliary oil pump.

3. Standby oil cooler and oil filter are provided. This filter is to be lined up when the filter on-line differential pressure increases to 2 KSC.

4. Nitrogen gas connection for oil reservoir is given for purging the reservoir and to keep under Nitrogen atmosphere during normal operation.

Roll-O-Matic filter

This is fixed inside a Plenum chamber with suction on one side through a suction tower, the outlet connected to the compressor first suction. The filter roll is fixed on the top and filter cloth passes through chamber and it is rolled up in the bottom. This is driven by a motor. The rolling of the filter is done manually depending upon the suction pressure and filter differential pressure.

Turbine

Hitachi condensing turbine having 6 stages, double flow at the exhaust and multi-control valve. The turbine uses 12 ata steam, about 53 TPH at normal full load conditions.

Page 111: Ammonia Manual

Ammonia Plant Operating Manual 111

Condenser

Surface condenser is designed to condense about 57 TPH of the turbine exhaust steam at 56.2 0C and -635 mmHg pressure. The condensate is collected at the hotwell and is pumped out by the condensate extraction pump. The cooling water is on the tube side. It is divided into two halves to enable isolation of one side for cleaning while the turbine is in operation.

Ejector

This is for maintaining vacuum at the turbine exhaust. There are two sets of Primary & Secondary Ejectors. One set will normally function and the other set is kept as standby. This takes suction from the surface condenser above the hotwell. The ejector outlet steam is condensed in the intercondenser and put back into the surface condenser. A startup ejector is provided for additional capacity during startup. Gland ejector is provided to remove the leakoff steam from the main turbine. The leakoff steam will pass through gland condenser and the condensate is drained. The gland ejector outlet is put into the aftercondenser. The non-condensable from aftercondenser is put into atmosphere through vent.

Condensate Pump

The main pump is turbine driven and the standby is motor driven. It takes suction from surface condenser hotwell and pumps condensate to the SCC header.

5.2 START-UP PROCEDURE

Preparation for start-up

1. Confirm that sufficient steam is available.

2. Prepare and check instruments : Ensure that instrument air to all instruments has been lined up. Obtain clearance from Instruments Maintenance for completion of jobs.

3. Line up all pressure gauges, flowmeters and level gauges.

Inspection before starting lube oil pump

1. Check the reservoir level. Ensure that sufficient oil is available for filling up oil coolers, filters, accumulators and piping.

2. Line up pump suction. Close the pump discharge. Line up one cooler and one filter to the system.

3. Check Nitrogen pressure in accumulator is 4 KSCG.

Start lube oil pump

1. Start the motor driven lube oil pump.

2. Open the discharge to get 6 KSCG at the cooler inlet pressure gauge.

3. Adjust the lube oil pressure to 2.2 KSCG (now the lube oil control is set for correct pressure).

Page 112: Ammonia Manual

Ammonia Plant Operating Manual 112

4. Check the oil pressure to the journal bearings and gear box is more than 1.5 KSCG and for thrust bearing is more than 1 KSCG.

5. Confirm the lube oil circulation in close sights and the drain piping of the compressor gear box and turbine.

6. Vent the trapped air in the oil cooler filter and gauges through the vent valves.

7. Check the cooling water to main oil cooler. Vent any air from both the shell and tube side of the oil cooler. Adjust the water flow to have the outlet temperature of the cooler within the range of 35-40 0C. Maximum allowable oil temperature is 51.7 0C at the exit of oil cooler.

Start-up of the condensate pump

1. Open the surface condenser hotwell drain.

2. Open the DM water make-up valve.

3. Flush the condenser by filling up and draining repeatedly till the water is clear from the drain. Then close the drain.

4. Build up level in the surface condenser. Line up motor driven pump suction valve and close the discharge. Keep the vapour equalising line from the pump to surface condenser in the open condition.

5. Start the condensate pump and line up the level control valve isolation valves. Keep the local drain open and isolate the line to SCC header till analysis is OK. The condensate may be lined up to SCC header at a convenient time after analysing the condensate for Silica and Iron.

6. Line up the seal water to all the valve glands and lines under vacuum to prevent air leakage into the system. Line up seal water to condensate pump gland seal.

Inspection of compressor before start-up

1. Keep the coolers and separators drains full open.

2. Check the governor oil pressure is normal (more than 5 KSCG) and lube oil pressure is 2.2 KSCG.

3. Keep all the casing drains full open.

4. Check the Roll-o-matic filter is in good condition.

5. Check sealing air valves remain in open condition.

Inspection of the turbine before start-up

1. Start warming up of the steam line atleast half an hour before the startup to ensure that the steam temperature is 100 0C above the saturation.

Page 113: Ammonia Manual

Ammonia Plant Operating Manual 113

2. Line up cooling water to surface condenser. This is to be done in co-ordination with Control Room. Vent any air locked up in the cooling water chamber of the surface condenser.

3. The following drain valves in the main steam line shall be kept open.

drain downstream of main isolation valve.

drain downstream main stop valve.

4. Charge the steam upto to MSV by opening the bypass valve around the main isolation valve.

5. Then open the main isolation valve. The drain may be throttled if excessive steam is blowing out.

6. For warming up the steam line, the startup ejector steam line shall be kept fully opened. For this charge the steam to ejector and keep the start-up ejector steam fully opened.

5.3 START-UP AND LOADING

1. Reset the Control Room panel reset-9A. (PAC shutdown, PDI 1405, FIA 1401 are on bypass)

2. Pull vacuum in the surface condenser (if the turbine is hot, seal steam shall be admitted before pulling vacuum and immediately turbine shall be put on roll) To do this, close the vacuum breaker valve. Check the startup ejector steam is opened.

3. Open the air valve to start-up ejector. Now the vacuum in the surface condenser will come to -500 mmHg. One set of Primary and Secondary Ejectors also shall be lined up by lining up the steam to the ejectors first and then opening the air valve from surface condenser to the ejector.

4. Reset the pedestal trip. Governor oil pressure will increase to 5 KSCG in the local panel.

5. Now the turbine driven lube oil pump and condensate pump shall be started and lined up. When opening the turbine driven lube oil pump discharge valve, the motor driven lube oil pump discharge valve shall be closed to maintain the lube oil header pressure in the header.

6. Then the motor driven pump shall be stopped and put on auto start service. To do this "STOP", "AUTO" & "START". Switch on the local panel shall be turned to STOP position and then to auto.

7. Check the auto starting of the standby lube oil pump by stopping the turbine driven pump.

Low pressure alarm and auto-start of standby pump is at 1.2 KSCG.

8. Check the auto start of the standby condensate pump by increasing the condenser level. Stop and keep it as standby on auto start position. Discharge valves on the standby pump shall be kept open during normal run. Keep the standby lube oil pump discharge throttled to avoid overloading of the motor.

9. Check the extra-low lube oil pressure trip by actuating the pedestal trip, and governor oil pressure indicating and the local panel to go down.

Page 114: Ammonia Manual

Ammonia Plant Operating Manual 114

Extra low pressure trip = 0.8 KSCG

10. Check PIC 1-201 and FIC 1-201 outputs are kept at zero. Check the LP casing hand control vent is kept fully opened. Physically check the valves in the field and ensure that they are full open.

11. Check the Woodward governor speed control knob is set at minimum position.

NOW THE TURBINE IS READY FOR ROLLING

12. Start opening the main steam stop valve. When the rotor starts rotating, throttle the MSV, to avoid the rotor speeding up. Maintain the speed at 500 rpm for about one hour.

13. As soon as the rotor starts rotating, line up sealing steam by opening the steam valve to seal steam regulator and the bypass valve of the seal steam regulator if necessary.

14. Line up the gland ejector and maintain 20 mmHg in the gland condenser, by throttling the steam to gland ejector. Line up gland ejector drain to the surface condenser.

15. Check for any rubbing noise from the turbine and compressor.

16. Do not allow the condenser pressure to go below -700 mmHg. This will damage exhaust wheel blade. Now check the turbine driven lube oil pump and condensate pumps are in service and motor driven pumps are on "AUTO" before increasing the speed.

17. Speed up the turbine to 1000 rpm according to the start-up diagram.

18. Check the physical tripping of the machine at 1000 rpm by actuating the pedestal trip. Reset and start continue to run at 1000 rpm. Increase the speed according to the startup diagram for PAC.

19. At 6600 rpm :

close all the drains in the compressor casings.

close all the drains of the intercoolers.

close the separator drains bypass valves.

close all the steam line drains.

isolate start-up ejector.

close LP case start-up hand control valve.

close DM water make-up to surface condenser.

adjust lube oil temperature to 40-45 0C at the cooler exit.

adjust seal steam to 0.2 - 0.5 KSCG.

Page 115: Ammonia Manual

Ammonia Plant Operating Manual 115

observe for vibrations or any abnormal noise.

check oil flow through the flow sights.

To load up, reset the push button "BLOW OFF", then start closing FIC 1-201 manually to build up the pressure. Check the minimum flow required to prevent surging and keep the flow above this value.

Increase the speed to 7500 rpm. Load up the machine to 32.5 KSCG and put FIC & PIC on Auto control.

Line up process air to instrument air.

When the process air is being lined up to Secondary Reformer, the operator shall be present to take action in case any problem.

Adjust the seal air pressure by throttling isolation valves. Use the pressure gauges provided on the seal air lines and keep the header pressure about 0.5 KSCG above the seal pressure.

5.4 OPERATION DURING EMERGENCY

Secondary Reformer Trip

In this case, DPG trip-2 will appear on the local panel. Compressor anti surge valve FIC 1-201 will open full.

take PIC 1-201 on manual and stabilize at 7000 rpm speed.

bring down the air signal on FIC 1-201 to zero.

wait for the Control Room to reset the Trip Panel Reset No. 9-A.

reset the local panel.

reset the "BLOW OFF" valve. Start closing FIC 1-201 manually to get pressure to 20 KSCG on the discharge so that instrument air supply is ensured. Wait for the instruction from Shift Engineer for further loading.

Total Plant Trip: DPG Trip-1

This will cause a shutdown of Process Air Compressor.

Immediately put PIC and FIC 1-201 on manual and bring down the signal to zero.

Page 116: Ammonia Manual

Ammonia Plant Operating Manual 116

Open the LP case hand control vent valve.

Inform the Control Room that the compressor is ready for start-up.

In case the compressor is to be started immediately, enquire about the steam load.

Open the MSV and bring it upto minimum governor speed gradually but without any delay. Then load up the PIC 1-201 and FIC 1-201 to get 32.5 KSCG at the final discharge. Put both the controls on auto.

If the compressor has to be stopped, open all the drains. Break the vacuum, isolate the steam line, stop the condensate pump and keep only the lube oil pump (motor) running. This shutdown shall be done systematically.

In case of vibration and noise

If the vibration slightly goes up or a slight noise is heard, we can try to reduce the load and see the vibration or noise comes down. Inform the Shift Engineer first. But if the trend is on the increasing, it is better to take a planned shutdown.

If the vibration or noise is heavy, use the pedestal trip and stop the machine immediately.

5.5 LIMITATION OF OPERATING CONDITIONS FOR TURBINE, COMPRESSOR AND OTHERS

Turbine Max. Rated Normal

Output (KW) 9550 8570 8270Speed (RPM) 7875 7500 7380

1st critical speed 4217 RPMTrip speed 8700 RPMGovernor control range 5580 to 7875 RPM

No. of stages 4 + (1 X 2)

Steam consumption 52.72 TPHSteam pressure/temp.(Normal)12 Kg/cm²g/278 C Max. continuous 12.6 Kg/cm²g/286 C Max. Momentary 15.6 Kg/cm²g/290 C

Compressor LP case HP case

Max. Operating pressure 10 Kscg 41 KscgMax. Operating temperature 240 0C 180 0CNo. Of wheels 5 6Critical speed 4500 RPM 6050 RPM

Surge flow 35600Nm3/Hr 37600 Nm3/Hr

Page 117: Ammonia Manual

Ammonia Plant Operating Manual 117

Capacity normal/rated 42609/44800 Nm3/Hr

Minimum duty 29820 Nm3/Hr

Compressor shall be operated at 35600 Nm3/Hr for a minimum duty of 29820 Nm3/Hr and rest shall be vented.

Lube oil system

Filter mesh 25 micronsGovernor oil pressure Normal 5 Kg/cm²gLube oil pressure Normal 2-2.5 Kg/cm²gLow lube oil Pr. alarm 1.2 Kg/cm²gLow oil pressure trip 0.8 Kg/cm²gOil pr. to journal brg. and gear box 1.5 Kg/cm²gOil. pr. to thrust brg. 1.0 Kg/cm²gLube oil filter max. DP 2.0 Kg/cm²gRoll-o-matic filter Max. DP 12 mmAq

Vibration

Permissible 14 micronsAxial displacement 600 - 650 microns manual trip value Axial displacement ± 375 microns permissible

5.6 NORMAL SHUT DOWN

1. Inform Control Room.

2. Take FIC 1-201 and PIC 1-201 on manual.

3. Open FIC 1-201 full (gradually).

4. Bring down the speed to minimum governor speed.

5. Open the LP case hand control valve.

6. Use the pedestal trip and shutdown the machine.

7. Open the DM water make-up to the condenser.

8. Open all the cooler drains, compressor casing drains, separator drain trap bypass valves.

9. Start motor driven lube oil pump and condensate pump. Stop the turbine driven pumps.

10. Cut off the air valve to air ejector and isolate steam to air ejector.

11. Open the vacuum breaker and wait for the vacuum to come down to absolute zero.

Page 118: Ammonia Manual

Ammonia Plant Operating Manual 118

12. Cut off the sealing steam. Isolate gland ejector air line and steam.

13. After 15 minutes, stop the condensate pump. Isolate the DM water make-up. Drain the surface condenser and leave the drain in open condition.

14. Isolate the main steam valve. Open all the steam line drains.

15. Keep only the motor driven lube oil pump running till the turbine and the compressor are cooled down below 90 0C.

16. Once the turbine metal temperature cools down below 90 0C, stop the lube oil pump. Isolate the cooling water lines and drain the water from the cooler. Leave the cooling water chamber drain and vent in open condition.

Page 119: Ammonia Manual

Ammonia Plant Operating Manual 1

Page 120: Ammonia Manual

Ammonia Plant Operating Manual 1

4 Chapter six SYNTHESIS GAS COMPRESSOR, DRIVER, CIRCULATOR AND HYDROGEN RECYCLE BLEED

The turbine 3701 drives the Syn Gas Compressor 3102 and the compressor 3103 which circulates the Synthesis Gas round the loop.

6.1 OUTLINE OF THE MACHINE

Compressor

The Compressor is a three casing machine, the final wheel of the third casing forming the circulator. The first casing is split into two sections, gas being cooled between the sections. This gives a more efficient stage.

The normal suction capacity of the Synthesis Gas Compressor is 130522 Nm3/Hr. A bleed is taken off after the first casing and this gas is mixed with product hydrogen and sent to the Naphtha desulphurisation section. The rest of the gas is delivered to the Ammonia loop at 190

Kg/cm²A (128,700 Nm3/Hr). The actual make-up requirement of the loop is 127,573 Nm3/Hr. The difference between these two figures is the allowance for losses from compressor seals and loop flanges.

The Circulator has a capacity of 531,120 Nm3/Hr and its suction and discharge pressures are 185 and 195 ATA respectively.

Turbine

The driver is an Extraction Condensing Turbine 3701-001 powered by 268 tph of 106 ATA steam at 475 0C, developing 19035 KW AT 10,309 rpm (at normal rated point). The turbine has a passout connection into the HP 45 ATA steam main and exhausts at 0.17 ATA in the condenser, and it comprises basically the following equipment:-

3701 - 002 Condenser.

3701 - 003 Main condensate Extraction pump.

3701 - 004 Main Condensate Extraction Turbine driver.

3701 - 005 Standby Condensate Extraction pump.

3701 - 006 Standby by Condensate Extraction pump driver.

3701 - 007 1st stage ejector.

3701 - 008 1st stage ejector standby. 3701 - 009 2nd stage ejector

3701 - 011 Start up ejector.

3701 - 012 Ejector Condenser. The auxiliaries are driven by MP 12 ATA, 278 0C

Page 121: Ammonia Manual

Ammonia Plant Operating Manual 2

steam and the auxiliary turbines exhaust into the condenser of the main turbine.

Governor System

Governor system consist of speed control device and extraction control device to maintain speed and extraction constant even when load and extraction flow are changed.

Functioning of the System

When the compressor load is decreased with constant extraction flow, turbine speed goes up. Woodward governor driven by turbine shaft end pushes up its folk to push up point "K" of the main lever. As the extraction flow is constant, point "C" at the extraction control oil cylinder becomes fix point. When point "K" is pushed up, main lever turns upward to pull reset lever as these two levers are connected at point "B" and "D". Reset lever is pulled up with point "F" as a fix point to pull up pilot valve for regulating valve at point "D".

At the inlet port of the regulating valve oil pilot valve, governor oil is introduced. When the pilot valve is pulled up, pressure oil flows into the upper port of regulating valve oil cylinder to pull down connecting lever. By the above, regulating valve is closed to decrease speed.

When the connecting lever is pulled down, point "F" of the reset lever is pushed down to reset regulating oil pilot valve.

Meantime, when the main lever is pushed up by governor, point "A" is also pushed up. With this action, extraction control oil pilot valve is pulled upto lead pressure oil at the bottom port of extraction control oil cylinder. Then the extraction control valve is closed to decrease steam flow into low pressure part to maintain same extraction flow. Reset of the extraction control oil pilot valve is also made by the reset lever mechanism.

When more extraction flow is required for plant use, signal air pressure from the flow controller increases. With higher pressure, bellow in the askania extraction controller is pushed to shift oil jet sideway. Pressure oil is then led to the top part of the extraction control oil cylinder. As the compressor load is constant, point "K" becomes fix point when the main lever is turned. By the above action, point "B" is pulled down and point "A" is pushed up.

Therefore, inlet steam is increased and the extraction flow also is increased since extraction control valve is closed to reduce steam flow into low pressure part.

Critical Operation

In case that the extraction flow is too large or too small for the turbine load, extraction control is locked with stopper and governor only is used for turbine operation.

Page 122: Ammonia Manual

Ammonia Plant Operating Manual 3

When extraction flow requirement is too large for a output, lift of the extraction control valve cylinder is limited by the upper stopper to keep minimum flow for low pressure part. Under such condition, when load on the turbine is further reduced, regulating valve is closed to reduce load however, extraction flow becomes less than the plant requirement. In this case, steam by-pass valve in plant steam piping shall be opened to maintain steam flow.

When extraction flow requirement is too small for the output, lift of the extraction control valve oil cylinder is limited by the lower stopper to protect lower pressure turbine blades. Under such condition, when the load is increased further, regulating valve is opened to increase output however, extraction flow increases since the control valve does not move.

Then the excessive steam flow must be led to the lower pressure line or vent to atmosphere via relief valve.

Speed change equipment

Pneumatic speed change equipment

This is a device for adjusting the turbine speed by changing air pressure to the Woodward Governor.

For example, in case it is desirable to drop the turbine speed, signal air pressure to the governor shall be decreased. If air pressure falls, the lever turns upward with point "C" as fulcrum, through the pneumatic speed change equipment incorporated in the governor. As a result the governor valve oil pilot valve is pulled up, and the turbine speed is dropped by the same action as in the case of an increase in the turbine speed due to a decrease in the load.

In case it is desirable to raise the turbine speed, the action goes on in the direction opposite to that described above. Further, the relationship between control air pressure and turbine speed is as follows:

Control pressure Speed

1.0 Kg/cm² (15 psig) 10920 rpm 0.2 Kg/cm² (3 psig) 7216 rpm

Manual speed change equipment (control at site)

By turning the speed change knob provided at top of the governor it is possible to adjust the required speed in the same way as described in (a) above.

For details, refer to the Woodward Governor instruction manual.

The adjusting range is as follows:

Maximum 10920 rpm

Minimum 7216 rpm

Page 123: Ammonia Manual

Ammonia Plant Operating Manual 4

Moreover, in the case of changer over from manual control to pneumatic control, be sure to maintain the speed at 7216 rpm by means of the speed change knob provided on top of the Woodward Governor and then introduce pressure air at 0.2 Kg/cm².

If the above procedure is neglected a balance between signal air pressure and turbine revolution is lost, so sufficient attention must be given to this point.

Anti-surge control:

The phenomenon of surge in a centrifugal compressor occurs when flow is reduced sufficiently to cause a momentary reversal of flow in the compressor. This reversal tends to lower the pressure in the discharge line. Normal compression resumes and the cycle is repeated. This cycling or surging can vary in intensity from an audible rattle to a violent shock. Intense surges are capable of causing complete destruction of the components such as blades and seals. Therefore, for different speeds there are points of corresponding pressure head and flow where this phenomenon occurs and this is called the surge line as shown on the compressor performance curves. To prevent this occurring, valves between the suction and discharge of the compressor casings open to maintain sufficient flow through the casing and the anti-surge control system is programmed to open those valves at a set point line to the right of the surge line.

On the first casing of the machine the suction pressure PI 101, discharge pressure PT 104 and discharge flow FIC 101T are monitored and out put signals are fed to FIC 101. The output from this controller actuates the surge valve FCV 101 across the 1st casing.

The second casing is similar. The suction pressure is monitored by PT 105, the discharge pressure by PT 106 and the discharge flow by FIC 102 which in turn send a computed signal to the anti-surge valve FCV 102 across the second casing.

The third casing is more complex as the circulator is in the same casing. For the synthesis gas section, the suction pressure is monitored by PT 107, the discharge pressure by PT 108, the flow by FIC 103 which sends an out put to the anti-surge valve across the compressor section FCV 103. Across the circulator there is a similar system.

Suction pressure PT 109 Discharge pressure PT 110 Discharge flow FIC 104T Controller FIC 104 Anti-surge valve FCV 104

The recycled gas in the circulator is cooled between suction and discharge by a water cooled exchanger.

6.2 TURBINE AUXILIARIES

Lube Oil System

Main lube oil pump driven by turbine takes oil from the reservoir and pressurises it to about 10 Kg/cm²g. This oil is cooled to about 43 0C in oil cooler filtered to 25 microns by oil filter controlled to 1.4 Kg/cm²g by pressure control valve (PCV 144) and flows into bearings and couplings for the compressors and turbine for lubrication. A part of oil discharged from the lube

Page 124: Ammonia Manual

Ammonia Plant Operating Manual 5

oil pump is branched off at the upstream of oil cooler, filtered to 60 microns and supplied to the governing system of the turbine as governor oil.

Oil drain from the lubrication and governing systems returns to the oil reservoir across the flow sights.

This system is provided with the following devices :

1. Auxiliary lube oil pump driven by motor.

If the governor oil or lube oil pressure drops due to any trouble in lube oil pump, this pump will be started automatically and deliver the oil to the main header.

2. Accumulators :

If the main lube oil pump fails these accumulators will prevent the oil pressure from dropping during the startup of Auxiliary Pump and rise it to the normal pressure. The bladder inside the accumulator is kept under 5.8 Kg/cm²g Nitrogen pressure.

Standby lube oil cooler and oil filter are provided in this stream.

3. Steam heaters for oil reservoir.

This is used to raise the oil temperature to 30 0C at only startup if it is cold.

4. Nitrogen gas injection for oil reservoir :

This is for injecting Nitrogen into the oil reservoir for purging out air completely and for providing nitrogen atmosphere inside the reservoir.

Seal oil system

Two seal oil sources are provided in this system. One of them is low pressure seal oil source for low pressure compressor (463-B5/4) and the other is high pressure source for medium pressure compressor (2 BF9) and high pressure compressor (2 BF 9-7). The low pressure seal oil is pressurised to 65 Kg/cm²g from downstream of lube oil filter by main low pressure oil pump driven by steam turbine (common drive along with the lube oil pump) filtered to 10 microns by low pressure seal oil filter and reaches the low pressure seal oil tank to level control valve (LCV 108). The high pressure seal oil is pressurised to 230 Kg/cm²g from downstream of lube oil filter by main pressure seal oil pump driven by a steam turbine, filtered to 10 microns by high pressure seal oil filter and sent to medium and high pressure seal oil tanks through level control valves (LCV 109 and LCV 110).

Seal oil supply pressure at the compressor is based on the seal oil reference pressure and is always kept 0.35 Kg/cm²g higher than the gas pressure.

Seal oil head tanks are mounted at a level about 4570 mm higher than the shaft centre of compressor to provide about 0.35 Kg/cm²g oil head. The tops of the tanks are connected to seal oil reference pressure and oil level in each is controlled by LCV's 108, 109 & 110.

Page 125: Ammonia Manual

Ammonia Plant Operating Manual 6

In this way, the seal oil supplied is kept at a pressure of seal reference pressure + 0.35 Kg/cm²g under any operating conditions. Most of the oil flowing into the seal port of the compressor flows out to the bearing chamber through the outer seal ring and returns to the lube oil reservoir along with the lube oil drain.

A small amount of oil (80-160 lits/day per casing) flows into the leakage gas port through the inner seal ring and flows out to seal traps with leakage gas.

The mixed flow of oil and gas separated at seal oil traps, the gas is blown off outside the system and the oil is returned to the oil reservoir after it is degassed in the degassing tank.

The following are provided in the Seal Oil system :

Auxiliary low pressure seal oil pump (motor driven) :

If the oil level in LP seal oil head tank drops due to any trouble in the main LP seal oil pump, this pump will start automatically to deliver oil. This pump will also be running when the lube oil pump starts because their driver is common.

During the initial start, LP seal oil seal pump should take suction from the oil reservoir directly. For this a bypass line with a valve is provided between LP seal oil pump suction and oil reservoir. A few minutes after the lube oil pump has reached the rated speed, the valve can be closed slowly.

Auxiliary High Pressure Seal Oil Pump (Motor driven)

If the oil level in MP or HP seal oil head tank drops due to any trouble in the main HP seal oil pump, this pump will be started automatically.

Accumulators :

These are provided to absorb the pulsation due to HP seal pump which is of axial plunger type. They consist of a steel cylinder with a bladder inside. Nitrogen is filled into the space between the bladder and the cell at the following pressure.

a. HPSO pump suction accumulator - 5.6 Kg/cm²g b. HPSO pump discharge accumulator - 138 Kg/cm²g c. Desurger - 160 Kg/cm²g

Spare seal oil filter and HP oil filter are provided in this system. Two seal oil traps are usually operated for each compressor. If one of them fails, operation can be kept with one trap.

Degassing tank :

This is mounted on the top of the oil reservoir, it collects sour oil from the seal oil traps and strips off the dissolved gases, by bubbling Nitrogen into the coil and heating it to 70-80 C using steam in the steam coil.

6.3 TURBINE ACCESSORIES

Page 126: Ammonia Manual

Ammonia Plant Operating Manual 7

Turbine exhaust steam condenses on the surface condenser tube external surface and collects at the hot well. The condensate extraction pump (Main pump driven by turbine) takes the condensate from the hot well and pumps into the SCC header through the inner and after condensers where the ejected out steam from surface condenser is condensed. The level in the surface condenser hot well is maintained by an LIC. Seal water supply is taken from the condensate recovery pump discharge to the valve glands operating under vacuum. A standby motor driven pump is provided which will start automatically when the hot well level increases for any reason.

Gland condenser and ejector :

These are provided in this system to remove the leak off steam from the outermost part of the turbine seal. Cooling water is used in the gland condenser for this purpose.

Turning device :

Turning device is provided on the compressor side pedestal. Before and after turbine operation, the rotor has to be turned with this device to minimise rotor deflection due to non-uniform heating and cooling.

6.4 STARTUP PROCEDURE

Preparation and check for startup

Confirm that sufficient steam is available.

Check that CO & CO2 content in the compressor suction gas is less than the following values

:

CO + CO2 - 10 ppm

CO2 - 5 ppm

Check all instruments before startup and confirm all the instruments are available.

Open fully the isolation valve of each pressure gauge, flow meter and level gauge.

Restart inspection of lube, seal oil system

1. Confirm that oil level in the oil reservoir is at normal level or higher. Additional quantity of oil is required for filling up of oil coolers, filters, accumulators, head tanks and other equipments. The oil required for initial charge is approximately 13000 litres.

2. Confirm that valves are opened or closed as indicated below :

open all the valves on the main flow line.

open the gauges, valves and close the drain valves and vent valves.

Page 127: Ammonia Manual

Ammonia Plant Operating Manual 8

open the valve on suction line of low pressure oil pump connected to oil reservoir.

close the bypass valve of PCV 144 (lube oil pressure control valve).

adjust the bypass valve on LP seal oil header to about 1/6 opened and set the pressure controller at 30 Kg/cm²g.

open the bypass valve of PCV 151 (HPSO header pressure controller).

close the inlet valves and bypass valves of LCV 108, 109 & 110. (control valves for the 3 overhead tanks level)

3. Charge instrument air to all instruments and check the set pressure of all the pressure regulators.

4. Charge nitrogen to all the accumulators and desurgers and set the following pressure using hand pump. 3102 - 31 A, B, C & D 58 Kg/cm²g 3102 - 035 & 036 131 Kg/cm²g 3103 - 033 & 034 5.6 Kg/cm²g 3102 - 037, 038 & Desurger 160 Kg/cm²g Accumulator for PCV 111 A & 111 B 104 Kg/cm²g

Start up lube oil and seal oil system

1. On the steam turbines (3102 - 011 & 017) check lube oil level in the bearing chamber and drain each port.

2. Start the steam turbine for lube oil pump and LP seal oil pump with the exhaust lined up to the atmosphere.

3. Adjust the lube oil pressure at 1.4 Kg/cm²g by pressure control valve (PCV 144) and confirm the lube oil circulation in close sights and drain piping of the compressors and turbine.

4. Vent the trapped air in all the coolers, oil filters and gauges through vent valves.

5. Close the block valve gradually and adjust the LP seal oil pressure controller to normal operating pressure of 63 Kg/cm²g by closing the bypass valve.

6. Charge the cooling water to the main oil cooler and vent away any air from the water chamber of oil cooler. Adjust to keep the oil outlet temperature in the range of 35 - 45 C by controlling the cooling water flow. Maximum allowable temperature from the oil cooler is 51.7 0C.

7. Open the valve (VF 544 and VF 547) for seal oil supply to PCV 11 A & B (steam bypass valve station).

8. Start the main high pressure seal oil pump (turbine driven). This turbine exhaust also shall be lined up to atmosphere and the valve on the exhaust line to the surface condenser shall remain closed, till cooling water is lined up to the surface condenser.

Page 128: Ammonia Manual

Ammonia Plant Operating Manual 9

9. Vent the trapped air in the high pressure oil filters.

10. Vent the trapped air in instruments and their piping through vent valves.

11. Pressurise gradually through bypass valve of pressure control valve (PCV 151). Adjust the pressure controller PIC 151 to about 100 Kg/cm²g and put the controller on auto.

13. Check the following valves :

Valves on seal oil reference line - to be closed.

Common inlet valve of oil traps - to be closed.

Valves on normal flowing line - to be opened.

14. Charge oil into the seal oil head tank according to the following procedure.

Pressurise the compressor casing to 0.5 Kg/cm²g with Nitrogen.

Line up the seal oil overhead tank LCVs 108, 109 & 110.

Open them manually to charge seal oil into the seal oil head tanks. Watch the level into the gauge glass.

When the oil level has been charged approximately, to the normal level, put the controllers on auto.

Check the sour oil traps for oil. When the pressure in the compressor is lower, the seal oil from the traps does not return to the reservoir. So the pressure in the compressor should be increased. Expected value of sour oil quantity is about 80 - 110 lits/day per casing.

(The maximum sour oil drain quantity is 500 lits/day per casing)

CAUTION : Do not charge the seal oil into the head tank when there is no pressure in the casing. The oil will flow into the casing.

15. Measure the oil quantity periodically and check whether there is any change or not. Measurement of sour oil can be done by filling in the drums from the trap drain.

16. Pressurise the HP seal oil pump discharge according to the pressure in the compressor casing by adjusting PIC 151. In normal operation, the pressure shall be at 230 Kg/cm²g.

17. Sour oil drain is returned to oil reservoir after degassing. Suitable temperature for degassing is 70 - 80 0C and suitable volume of the Nitrogen is twice the sour oil volume. Never raise the temperature above 90 0C. Charge new oil into the system if the oil contains more than 5 ppm of ammonia.

18. Check the actuation of all of the safety devices, such as alarm circuit, pump cut in circuit and compressor shutdown circuit before startup of the compressor.

Page 129: Ammonia Manual

Ammonia Plant Operating Manual 10

19. Turning of the compressor shall not be done without lube oil and seal oil circulation. To begin turning,

Open lube oil to gear. Connect the turning gear. Switch on the turning motor.

NOTE : Do not line up cooling water to lube oil cooler until the temperature reaches 40 0C.

Startup of Condensate Pump

Open the surface condenser DM water make-up valve. Flush the condenser through hot well drain. Open the suction valve to both the pumps. Keep the turbine driven pump discharge closed. Open the equalising valve from the pumps to the surface condenser to prime the pumps. (Motor driven pump discharge shall be kept open).

Line up the isolation valve of FCV 105 and LCV 105. Keep the SCC local drain open and the valve on the line leading to SCC header closed.

Line up the turbine exhaust to atmosphere. Keep the line to surface condenser closed. Open the sealing steam to turbine. Check oil level in the bearing cups.

Reset the steam trip valve. Open the steam isolation valve. Start the turbine by pulling the minimum steam lever. When the turbine picks up speed, allow the lever to go back to original position. Now the turbine comes to 2900 rpm (Governor set speed). Open the pump discharge and line up seal water to glands of valves operating under vacuum.

Maintain the hot well level with make-up DM water. Confirm that water circulates through inter and after condenser and through FCV 105. Now cooling water to the surface condenser shall be lined up in co-ordination with the cooling tower operator. Open the vents and the cooling water chamber to vent air.

Cautions for startup of Compressor & Turbine

Before startup, carry out the protection device test for lube and seal oil.

Lube oil and governor oil :

By throttling the lube oil pump turbine steam check the following :

i. Low lube oil pressure alarm : 0.84 Kg/cm²gii. Low lube oil pressure autostart : 0.84 Kg/cm²giii. Extra low oil pressure trip : 0.56 Kg/cm²giv. Governor oil low pressure alarm : 7 Kg/cm²gv. Governor oil low autostart : 7 Kg/cm²g

In this test check the following :

a) The governor pressure does not drop below 6 Kg/cm²g and lube oil pressure does not drop below 0.6 Kg/cm²g before repressurising to normal condition by startup of Auxiliary Pump.

Page 130: Ammonia Manual

Ammonia Plant Operating Manual 11

b) At turbine trip confirm the following :

i. Main stop valve Closeii. Governor lever Rapid movementiii. Regulating valve Closeiv. Extraction regulating valve Closev. Emergency oil cylinder for MSV Rapid movement and trip gear actuationvi. Extraction check valve Closevii. Pressure switch (PAC 145) Actuation c) Seal oil head tank: High-level alarm Low-level alarm Low level Aux.pump start Low-level trip

d) When the turning gear is running, do not stop seal oil and lube oil supply.

e) Do not start compressor if the following requirements are not met :

i. Oil reservoir level Normal or aboveii. Lube oil pressure 1 - 1.4 Kg/cm²giii. Governor oil pressure 7 Kg/cm²giv. Oil temperature exit cooler 45 0Cv. Auxiliary LO, LPSO & HPSO On autovi. Seal oil head tank level Normal ± 50vii. Seal oil DP 0.25 - 0.4 Kg/cm²gviii. Seal oil filter DP Maximum 1.75 Kg/cm²gix. Gas pressure in the casing Normal

f). Rapid change of pressure upsets the head tank level and it overflows into the casing.

g) In case compressor trips, all emergency valves ESV 101, 102, 103 & 104 will close and JCV 101, 102 & 103 will open.

Trip values :

i. Low lube oil pressure : 0.56 Kg/cm²gii. SO head tank level low : - 200 mmiii. Balance piston high DP : 4.6 Kg/cm²giv. Excess axial movement : 25 Mils(manual trip)

v. Overspeed trip : 12012 ± 1%vi. PGL trip I : From main panel

h) Never supply seal oil into compressor when compressor casing is at atmospheric pressure. If oil is flown into the casing, it should be drained out from the drain line of the casing and gas piping.

i) Data for operation of turbine :

Page 131: Ammonia Manual

Ammonia Plant Operating Manual 12

When starting or stopping turbine the following are to be measured :

i. Main steam pressure and temperature.ii. Exhaust pressure and temperature.iii. Thermal expansion of casing in all directions.iv. Load, time at which operation was stopped and period of turning after stop, in a previous operation.v. Period of warm-up, acceleration and increase in load at starting time.vi. Period of decrease in load, speed, stop and turning at stopping time. Limit values at starting, during operation and stopping :

i. Main steam temperature : Saturation temperature + 50 0Cii. Main steam temperature raising period maximum 135 0C/hr and falling temperature maximum 42 0C/hr.iii. Expansion of turbine casing : To be uniform on right and left within 0.5 mm by difference.

Preparation of the Compressor for startup

Valve positions :

The following valves to be opened :

FCV 101, 102, 103, 104 & JCV 103. The following valves to be closed : ESV 101, 102, 103, 104 JCV 101 & 102. All drain valves and vent valves.

Purge the compressor with Nitrogen by venting the gas in all suction and discharge pipings, separators and through JCV 101 & 102. Then close all the drains and vents. Keep a pressure of 1 - 2 Kg/cm²g with Nitrogen till synthesis gas is admitted for pressurising the compressor.

Cooling water to all gas coolers should be lined up and air vented from the vent on the CWR line.

Check CO + CO2 in the process gas is less than 10 ppm and gradually introduce syn. gas into

the compressor through the bypass valve of ESV 101 on the first suction line.

CAUTION : If syn gas is introduced rapidly the rotor will rotate and the compressor would be damaged.

Pressurise upto to normal pressure (23 Kg/cm²g) and check for oil and water in the compressor casings, pipelines, separators and drain if found.

Check that the suction compressor pressure is above the design value. The minimum reference gas pressure specified by vendors for

II case - 27.2 Kg/cm²g

III case - 34.0 Kg/cm²g

Page 132: Ammonia Manual

Ammonia Plant Operating Manual 13

Preparation of turbine for startup

1. Confirm that the condenser and condensate system is functioning normally. Put the rotor on turning with the turning device as follows :

turn system cover to remove stopper.

remove spindle cap.

apply ratchet lever at the end of the spindle and turn worm until worm wheel comes in contact with the shaft.

open lube oil supply valve.

start turning motor and turn the rotor.

2. Check the following valves are fully closed :

main steam gate valve.

main stop valve.

extraction check valve.

extraction gate valve.

regulating valve.

extraction control valve.

condenser atmospheric relief valve.

air inlet of ejector.

main stop valve leak off valve.

gland steam leak off valve.

vacuum breaker valve.

hogging ejector air valve.

signal air valve for extraction controller.

gland steam valve to gland condenser.

seal and ejector steam header valve.

seal and ejector steam valves VT 121, 122, 123, 125 & 126.

Page 133: Ammonia Manual

Ammonia Plant Operating Manual 14

valve on leak off steam to 12 ATA steam header.

3. Check that the reservoir level is higher than normal.

4. Fully open ejector drain valves.

5. Line up cooling water to gland condenser.

6. Start gland condenser ejector and maintain - 200 mmHg in the shell.

7. Open gland steam valve to gland condenser.

Startup of Turbine and Compressor Train

a) Open bypass of main steam gate valve. Open startup vent and drain valves of main steam pipe to warm up piping.

b) Open bypass valve of extraction steam gate valve. Open vent and drain valves of extraction piping for warm up.

c) Open the following valves :

main stop valve drain.

main stop valve gland.

gland steam leak.

main steam line drain.

regulating valve steam line drain.

casing drain.

gland leak of steam.

extraction line drain to condenser.

extraction check valve drain.

vent valve on the 12 ATA steam leak off line.

d) Open extraction gate valve gradually confirming temperature rise of the line is steady and not abrupt. Do not use this valve to control flow and pressure. Leave it fully open.

e) Open main steam gate valve gradually to the full open position. Confirm thermal expansion of main line does not twist the casing.

f) Open seal air supply valves slightly to supply seal air into oil slinger of each pedestal.

Page 134: Ammonia Manual

Ammonia Plant Operating Manual 15

g) Line up seal steam pressure control valve (put water into header at the top of the control valve to protect the diaphragm).

h) Open the startup seal steam valve slightly and confirm the seal steam header pressure is above 0.2 Kg/cm²g.

i) Close the casing the drain valve.

j) Start hogging ejector by opening the air valve and drive steam valve. Evacuate until condenser shell pressure reaches -500 mmHg and then maintain it.

k) Start second stage ejector opening air valves and drive steam. As the steam entering the condenser is only from seal steam line, second ejector is sufficient. Stop hogging ejector. Close air valve and then steam valve.

l) Stop the turning motor :

apply ratched lever and turn spindle to loosen the worm gear.

Install stopper. Be sure that the stopper cover pushes the limit switch. (turning motor on lamp in the panel will disappear.)

Install spindle cap. Shut the lube oil supply valve. Do not open the main steam valve until every part of turning device is in right position.

m) Press "START OK" push button on the panel.

n) Reset the pedestal reset lever. Now the regulating valve will open.

o) Ensure that casing pressure has equalised with pressure on PIC 1509 and open ESV 101 (ESV 101 bypass close).

p) After confirming all pipes are completely warmed up and the steam temperature comes within the range of safe operation, turn the reset lever. When the unit starts to rotate, close main stop valve and let the unit run with inertia. Use sound detecting rod to confirm that there is no unusual sound from the internals. If everything is alright, open main stop valve again and maintain the speed between 300 & 500 rpm. Confirm all the systems are working normally.

q) Push trip button after removing safety piece and confirm the following :

main stop valve is fully closed.

regulating vale is fully closed.

extraction control valve is fully closed.

extraction check valve is fully closed.

Page 135: Ammonia Manual

Ammonia Plant Operating Manual 16

turbine speed start to decrease.

r) Turn the pedestal reset and then reset main stop valve by pulling return lever. Reset of main stop valve should be done after closing the valve wheel to the fully set position. Open main stop valve again and continue warming up at 300 - 500 rpm. Refer to startup diagram for duration. Check casing expansion with expansion gauges.

s) Increase speed in accordance with startup diagram. Pay attention to the following items : Pass the critical speed band as quickly as possible and do not stop speeding up within this range. watch bearing oil supply temperature and control oil temperature around 45 0C.

confirm casing expansion is symmetrical.

vibration and unusual sound.

exhaust temperature does not exceed 120 0C.

t) At the end of the warm up start raising vacuum by operating drive steam valves of air ejector. For detailed steps refer to startup diagram.

u) During speedup, first stage pressure starts increasing. When this pressure becomes higher than atmospheric pressure, start closing the seal steam supply valve. At this stage also, close the following valves.

main steam drain valve.

main steam line drain and vent valve.

regulating valve piping drain.

extraction piping drain, do not close the drain to flush chamber.

v) When the speed reaches minimum governor speed, governor starts to control the unit. Confirm that the system is functioning and the manual control knob is in the position "MINIMUM". At this stage, if extraction controller is set at a positive value, extraction comes out suddenly to fluctuate the steam line pressure. Therefore set Askania signal at 0.2 Kg/cm²g until speed reaches minimum governor speed. As the regulating valve is now controlling the speed, fully open the main stop valve. Turn the handle back half, turn after fully opening, to avoid the sticking due to heat. Line up the first gland leak off steam to 12 ATA steam header and close the vent.

w) Introduce air signal of 0.2 Kg/cm²g to the governor and observe speed. If the speed increases higher than the predetermined value, reduce the pressure and set the manual knob to minimum position.

x) Increase speed and extraction in accordance with the plant requirement. Increase signal air pressure as gradually as possible to avoid shock load.

Page 136: Ammonia Manual

Ammonia Plant Operating Manual 17

y) After starting extraction, close the following valves

Extraction drain to flush chamber.

extraction check valve drain.

extraction piping drain and vent.

6.5 COMPRESSOR LOADUP AND LINING UP SYN LOOP

a) Start increasing the speed by increasing the air signal into governor.

b) Watch the flow quantity and manually close FCV 101, 102 & 103 to build up pressure. When the second stage pressure reaches 40 Kg/cm²g, inform the Control Room for lining up recycle Hydrogen.

c) As soon as the main panel reset button No. 17 is reset, open PCV 0224 manually to pressurise the recycle Hydrogen header and put the controller on auto after pressurising. (Raise the set point of PCV 0224 to 43 Kg/cm²g when the second stage pressure rises)

d) Check that LP seal oil header pressure is at 65 Kg/cm²g and HP seal oil pressure is at a minimum of 150 Kg/cm²g (minimum required for operation of steam bypass valve). Then raise the speed of the compressor and load upto 100 Kg/cm²g pressure at circulator discharge. When the pressure rises, the HP seal oil pressure should always be kept at 10 Kg/cm²g above the fourth stage suction pressure.

e) Confirm synthesis loop is ready for pressurising and open ESV 104 bypass lightly and pressurise the loop at the rate of 50 Kg/cm²g. When syn loop pressure is equal to that of circulator discharge, open ESV 102, 103 & 104 one by one and close JCV103.

f) Further increase in compressor load depends upon the syn loop startup.

Operational control of compressor and oil system

a) Prevention of ammonium carbamate /ammonium carbanate.

Compressor might be damaged by the scales produced from reaction of NH3, CO, CO2 and H2O.

So check the Methanator gas periodically for CO & CO2.

b) Prevent condensation of gas due to low temperature.

Do not operate the compressor at lower gas suction temperature than the design value. Drain the separators periodically.

Page 137: Ammonia Manual

Ammonia Plant Operating Manual 18

c) Observe the performance of the compressor, gas flow rate, compression ratio, suction and discharge temperature and Nitrogen : Hydrogen ratio etc.

d) Shaft vibration and axial displacement, bearing temperature, seal oil and gas differential pressure, seal sour oil quantity to be watched carefully.

6.6 SHUTDOWN PROCEDURE

a) Open the FCV 104, 103, 102 & 101 very gradually, watching the seal oil reference pressure, to full open position. (if the gas pressure is rapidly changed, seal oil will flow into the compressor).

b) Decrease the speed to minimum governor speed while opening the FCVs.

c) Line up recycle Hydrogen from IG plant before second stage pressure drops below 40 Kg/cm²g.

d) Slowly reduce the extraction flow to zero.

e) Close ESV 102, 103 & 104 and open JCV 103 manually.

f) Line up startup sealing steam to main turbine and open make-up DM water to surface condenser before stopping the turbine.

g) Trip the unit by means of manual trip knob or signal from control panel. Check main stop valve is fully closed and extraction gate valve is closed. h) Open the following valves.

vent and drain of main steam line.

main stop valve drain.

casing drain for the turbine.

extraction piping drain and regulating piping drain.

extraction check valve drain.

extraction piping drain to flash chamber.

vent valve on 12 ATA leak off steam line and close the header isolation valve.

i) Shutdown of Surface Condenser :

start motor drive lube oil and LPSO pump, HPSO pump and condensate recovery pump and stop the turbine driven pumps.

open FCV 105 bypass valve to allow condensate to circulate. Close the air valve to the ejector and open the vacuum breaker.

Stop the drive steam to first stage ejector and then to second stage ejector. Allow the

Page 138: Ammonia Manual

Ammonia Plant Operating Manual 19

ejector condenser to cool down and stop the condensate pump.

Close the seal water valves and the seal water lines to valve glands operating under vacuum.

Confirm the pressure in the surface condenser to Absolute Zero and only then the sealing steam is to be isolated. After isolating the sealing steam, gland ejector drive steam shall be isolated.

As soon as the unit comes down to a complete stop, put the rotor on turning. Maintain minimum 7 Kg/cm²g gas pressure in the barrels. This is to be done in the same way as it was done before startup of turbine.

Keep the turning for about 4 hrs. and stop turning motor. Even after turning is over, do not stop supplying oil to the bearings until the unit cools off to the safe temperature.

j) Now fully close the following.

Main steam isolation valve.

Isolation valve on the ejector and seal steam header.

Pedestal sealing air valve.

All the drains in the steam lines and turbine casing.

k) On Compressor side :

- Decrease the pressure in the casing. - If Nitrogen is available, replace syn gas with Nitrogen in compressor casing.

l) Stopping the lube oil and seal oil system :

- Lube oil can be stopped only when the turbine metal temperature cools down to 100 0C. A minimum of 24 hrs. of oil circulation is required for cooling the turbine.

- If bearing motor is in line, stop it and fix the stopper. (barring case may be stopped 4 hrs. after stopping the turbine. In that case hand barring should be done every half an hour for atleast for 4 hrs.

- Reduce the pressure in the barrel. A minimum pressure to push the sour oil from the traps to reservoir shall be maintained till all the seal oil is drained.

- Bring down the levels in the seal oil head tanks and isolate the LCVs. If the seal oil head tank LCVs are not isolated, the governor oil may pass through the HPSO pump and then LCV to fill up the overhead tank. Finally oil would enter the barrel. (Keep the JCV 101 and 102 isolation valves closed)

- When the oil level drops from the head tank, depressurise the casing and drain the oil from sour seal oil traps using the local drain into the drums.

Page 139: Ammonia Manual

Ammonia Plant Operating Manual 20

- Check separators/gas pipe lines/barrel drains for any oil/water and drain them.

- Stop HP seal oil pump first and isolate the pump and the drive. Stop lube oil and LPSO pump and isolate the pump and the drive.

- Isolate water to lube oil cooler and drain the water to prevent contamination oil in case of tube leakage.

Page 140: Ammonia Manual

Ammonia Plant Operating Manual 1

Page 141: Ammonia Manual

Ammonia Plant Operating Manual 1

6.7 TRIP ACTIONS

A. PGL 1 trip

This is a total compressor trip due to non-availability of syn gas from the front end. This occurs whenever feedstock to the primary reformer is cut. Also for local trips such as

- Lube oil extra low pressure

- Seal oil head tank level very low

- Extra high extraction pressure

- overspeed trip

- MP & HP balance piston DP.

It causes a complete shutdown of the machine. It will close ESVs 101, 102, 103 & 104 and open FCVs 101, 102, 103 & 104 and JCV 103. In case of lube oil and seal oil head tank level trips, this will open JCV 101 & 102 also.

Actions to be taken

a) A very important and immediate action is to use the pedestal trip and make sure the machine trips, if the trip indication appears in the local panel and the machine has not actually tripped.

b) Check with the Control Room whether to isolate the machine or it is to be restarted immediately.

c) If it is to be stopped.

- close the main stop valve fully

- bring down signal on the speed controller and FCV 101, 102, 103 & 104 to zero.

- watch the seal oil head tank level and adjust the seal oil header pressure. Usually it is required to reduce HP seal oil pressure in case the casing pressure is dropping.

- Check JCV 103 opens. When the turbine stops, put it on barring and proceed with the normal shutdown.

d) If the machine is to be started ask the Control Room to reset the trip panel. Reset the local panel by pushing START OK push button.

- open FCVs 101, 102, 103 & 104 on manual. Bring PIC signal to zero.

- reset the pedestal reset lever.

- open ESV 101 (Check the casing pressure is equal to that of the methanator exit). Keep ESV 102, 103, 104, JCV 101 & 102 closed and JCV 103 open.

Page 142: Ammonia Manual

Ammonia Plant Operating Manual 2

- close MSV to reset the MSV.

- pull the reset on the main stop valve.

- open the MSV to get minimum governor speed gradually.

- Load up the machine as before.

B. PGL 2 trip

This trip is caused by trip H (1113 extra high level) which will close ESV 101 and open FCVs 101,102,103 and 104 and JCV 103.

Action : Adjust refrigeration load - Close ESV 102, 103 and 104 - Check JCV 103 is open

- Bring down FIC s 101,102,103 and 104 output to zero

- Reset the trip after reducing level in 1113

- Load back

Note: Recycle H2 cannot be supplied if the trouble is not rectified immediately

C. PGL 3 Trip

This is caused by all Secondary Reformer, Methanator and Refrigeration trips. This will close ESV 102 and open FCV 101, 102, 103, 104 & JCV 103. Actions to be taken

- Close ESV 103 & 104.

- Bring down FICs 101, 102, 103 & 104 signal to zero.

- Reset the trip.

- Loadup for recycle Hydrogen duty if possible and contact Control Room for further instructions.

In case of Methanator trip, recycle Hydrogen cannot be supplied to desulphuriser.

Page 143: Ammonia Manual

Ammonia Plant Operating Manual 3

In case of Secondary Reformer trip, recycle Hydrogen can be provided for a short period. But seal oil DP has to be watched for hunting, as hunting indicates the partial surging of the machine due to higher Hydrogen concentration in the make-up gas.

D. PGL 4 trip

Catch pot level high, 1128, 1527 high level, refrigeration trips will cause this trip.

This will cause closing of ESV 103 and opening of FCVs 101, 102, 103 & 104 and JCV 103.

Actions to be taken

-Adjust refrigeration compressor load if the trip is because of 1122 high level.

-Zero the signal on FICS 101, 102, 103 & 104.

-Start refrigeration compressor if it has tripped on 1128/1517 high level, after normalising the condition.

-Reset trip.

-Load up in consultation with Control Room.

E. HWP Trip

This will cause sudden increase in Compressor discharge pressure. As soon as the lamp appears on the local panel, check for circulator discharge pressure and restrict at 228 KSCG.

F. Trip due to axial displacement , seal oil head tank level low and lube oil failure

These trips causes a complete shutdown of the machine. ESV 102, 103 & 104 will close. FCV 101, 102, 103 & 104 will open. JCV 101, 102 & 103 will open full to depressurise the casing.

a) JCV 101 & 102 isolation valves are usually kept throttled to avoid the sudden depressurising of the barrel and the consequent upsets. So check that the barrel gets depressurised before all the oil in the head tank is lost.

b) Introduce Nitrogen into the casing to replace the syn gas.

c) Proceed with the other shutdown activities.

d) In case of oil level is lost or lube oil is lost, try to resume the oil supply and head tank level as soon as possible. Pressurise the barrel slightly with Nitrogen and keep the rotor turning.

e) If the trip is due to axial displacement, balance piston high pressure drop, the machine has to be cooled for maintenance and inspection.

Page 144: Ammonia Manual

Ammonia Plant Operating Manual 4

G In case of vibration or noise

If the vibration is slightly goes up or a slight noise is heard, we can try to reduce the load and see the vibration or noise comes down. Inform Shift Engineer first.

But if the trend is on the increasing, it is better to takeup planned shutdown. If the vibration or noise is heavy, use the pedestal trip and stop the machine immediately.

SPEED

RPM

FIC 101 FIC 102 FIC 103 FIC 104

SURGE

15% MOR

E

SURGE

15% MOR

E

SURGE

15% MOR

E

SURGE

15% MOR

E

72106179

9 71069 68373 78629 62438 7180442548

248930

4

8240 70917 81555 77101 88666 73245 84232 38911

644748

3

103009725

811184

7 9601311041

5 9485810908

730911

135547

8

10815 104349

120002

100377

115434

100862

115991

272745

313657

These flows are corrected to the pressure:

FIC 101 - 69 Kg/cm²g FIC 102 - 143 Kg/cm²g FIC 103 - 217 Kg/cm²g FIC 104 - 229 Kg/cm²g

Page 145: Ammonia Manual

Ammonia Plant Operating Manual 5

5 Chapter Seven LOOP REFRIGERATION COMPRESSOR

7.1 LUBE OIL SYSTEM

The main pump driven by turbine takes oil from lube oil reservoir (capacity - 4000 lits) and pressurises it to 6 Kg/cm²g. The oil is cooled to 40-45 0C in an oil cooler and filtered to 25 microns before being reduced to 2-2.5 Kg/cm²g for lube oil service by a pressure control valve. This oil pressure is further reduced to 1.5 Kg/cm²g for journal bearings & couplings and to 1 KSC for thrust bearings through adjustable restriction orifices.

A part of the oil is trapped at the upstream of the oil filter and supplied to governor. This system is also provided with the following :

1) Stand by auxiliary pump driven by motor.2) Stand by lube oil cooler.3) Stand by lube oil filter.4) N2 connection to oil reservoir.

5) Governor oil accumulator.6) A degasser for degassing the return lube oil.

7.2 SEAL OIL SYSTEM

The system is provided with a turbine driven seal oil pump which takes oil from seal oil reservoir and pressurises to the required pressure (Max. pressure 20 Kg/cm²g, Normal pressure is at 5 Kg/cm²g). The oil is cooled to 40-45 0C in an oil cooler and filtered to 25 microns and supplied to seal oil overhead tank. Level of the overhead tank controls the spill back flow to reservoir tapped upstream of the seal oil filter in the seal oil line.

The sour oil from the casing is collected in the sour oil trap and then send to degassing tank on the top of the seal oil reservoir. The sour oil is degassed to < 0.5 ppm of ammonia content and allowed to overflow into the seal oil reservoir. The gas from the sour oil trap is returned to the first suction.

The sweet seal oil returns to the seal oil reservoir directly.

This system is provided with the following :

1) Standby oil pump driven by motor.2) Standby oil cooler.3) Stand by oil filter.4) N2 connection to oil reservoir and to degasser.

5) Steam coil and 12 ATA service steam to degasser.6) Sour oil traps (2 Nos.) - normally both are in line.7) Seal oil transfer barriers (4Nos.) to prevent the contaminated oil entering the seal port.

7.3 MAIN COMPRESSOR

Page 146: Ammonia Manual

Ammonia Plant Operating Manual 6

This compressor has 8 wheels on the rotor. It takes suction at 1.4 Kg/cm²g at the first stage. A sidestream at 3.4 Kg/cm²g (from primary chiller) enters the third impeller. At normal operation, discharge pressure is 17.5 Kg/cm²g. A gas balance is taken from the side stream and given to both sides of the compressor.

7.4 MAIN TURBINE

Turbine has six stages. It is driven by 45 ATA steam and all the steam is condensed at the exhaust. The condensate from the surface condenser hotwell is removed by a turbine-driven condensate extraction pump. This condensate is used for cooling the air ejector inter & after condensers and gland condensers before joining SCC header. A sealing steam regulator is provided to regulate the pressure of seal steam.

The vacuum unit is provided with the following :

1) Startup hogging ejector.2) Standby air ejectors and gland ejectors.3) Standby condensate recovery pump driven by motor.4) Atmospheric relief valve set for 0.5 Kg/cm²g.

7.5 START-UP

Preparation and Startup of Lube Oil System

1) Open the suction valves of lube oil pumps. Keep the discharge valves closed for both the pumps.

2) Line up one cooler and filter.

3) Line up the lube oil pressure control isolation valve.

4) Check the oil reservoir level is normal. Additional quantity of oil for filling up the coolers, filters and pipelines will be required.

5) Start the motor driven lube oil pump.

6) Open the discharge to get 6 Kg/cm²g at upstream of oil filter.

7) Vent air from cooler and filter.

8) Check and adjust lube oil pressure to 2-2.5 Kg/cm²g.

9) Check the oil return flow for good oil circulation (through sight glass).

10)Open the cooling water return line to oil cooler and vent the air from the water chamber.

Seal Oil Pump Preapration & Start up

1) Line up the pump suction and discharge valves.

2) Check oil level in the reservoir is above normal and prepare additional quantity of oil for start up, filling up of coolers, filters, overhead tank and piping.

Page 147: Ammonia Manual

Ammonia Plant Operating Manual 7

3) Line up one cooler and filter and open all the valves in the normal oil flow line.

4) Line up both swivel traps; trap vent valve to atmosphere shall be opened and the valve on the line to first suction shall remain closed.

5) Pressurise the casing with N2 to 0.5 Kg/cm²g.

6) Open the LCV bypass fully and LCV isolation valves. Line up the LIC instrument and instrument air to all the instruments and valves.

7) Start the motor driven pump. Vent air from coolers and filters.

8) Open the transfer barriers isolation valves and the bypass fully.

9) Start building up level in the seal oil head tank by closing the LCV bypass.

10)When the level comes to the normal value, LCV will start opening to maintain the level. Now slowly close the bypass and leave the LCV to control the level.

11)Close the transfer barrier bypass valve fully.

12)Check the seal oil DP around 0.6 Kg/cm²g.

13)Open the suction isolation valve and pressurise the casing to normal pressure.

14)Open side stream and final discharge isolation valves.

15) Keep the anti surge valves fully open.

16)Open cooling water outlet valve to oil cooler and vent air from water chamber.

Preparation of main Turbine for start up

Same as for Process Air Compressor.

Pre start inspection

1) Check both antisurge valves are in open position. FIC - 2-201 and FIC - 2-202 shall be kept at minimum signal.

2) Check the air signal to speed control is at minimum. (PIC -2-201 at zero).

3) Check seal oil DP is steady at about 0.6 Kg/cm²g and seal oil flows through the flow sights.

4) Check lube oil flow, pressure at 2 - 2.5 Kg/cm²g. Governor oil pressure 5 Kg/cm²g. Lube oil temperature about 30 0C. Do not line up cooling water to oil coolers now. The oil temperature shall be allowed to increase during start-up.

5) Check lube oil and seal oil reservoir level.

Page 148: Ammonia Manual

Ammonia Plant Operating Manual 8

7) Check condensate recovery system is normal.

8) Keep the gas balance line open to seals.

9) Check seal oil trap levels and line up the drain to degasser.

10) Line up steam and Nitrogen to degasser. Degassing temperature shall be maintained at about 80 0C and shall not exceed 90 0C at any time.

11)Check overhead tank level.

12) Line up the TCV 1811 quench Ammonia upto TCV 1811 and keep one isolation atleast closed till the time the Ammonia quench is required. Quench shall be taken from Ammonia feed pumps.

13)Check the level in 1526 and 1527.

14) Line up cooling water to 1528 A, B & C and prime the coolers.

Turbine Start up

Reset the panel. Warming of the turbine and rolling of the turbine shall be done in the same manner as that of the process air turbine. For further details refer to START-UP DIAGRAM.

Speed up the machine according to the start-up diagram to minimum governor speed. Close the seal oil trap vent to atmosphere and line up to first suction. When the flow indications on FIC - 2-201 and FIC - 2-202 starts increasing, start closing them watching the minimum flow required to prevent surging.

Line up the Ammonia quench through TCV 1811 and control the gas temperature. At the discharge, the temperature shall not exceed 190 0C. While using TCV 1811, watch 1128 level and 1527 level (too much of quench and low rate vapourisation in 1128 will lead to dumping of too much of liquid from 1128 to 1527). Further loading shall be done after establishing level in 1526 and 1527. Wait for start of syn loop circulation. Once the synthesis unit is started, more vapour is produced in 1526 and 1527 to give increased load on the machine. Further loading is done to maintain the suction pressure for the required refrigeration. Changeover quench from pump to 1127 after obtaining a discharge pressure of 10 - 12 Kg/cm²g on the compressor.

Normal conditions are

Temperature Pressure Flow

0C Kg/cm²g Nm3/Hr

First suction -11.5 1.37 23450Side stream 2.0 3.37 -Discharge 161.0 17.22 56724Speed 8930 rpm

Page 149: Ammonia Manual

Ammonia Plant Operating Manual 9

When the compressor flows are well established and the antisurge valve FIC - 2-202 is closed, quench will not be required. TCV 1811 can be isolated.

7.5 LIMITATIONS FOR OPERATION

1) The compressors shall be operated with the minimum flow requirements according to the performance curve given. FIC - 2-201 and 202 may be put on auto control once a steady condition is reached.

2) Suction pressure of the compressor shall be maintained by loading up / unloading to give the required refrigeration.

3) The discharge temperature shall not exceed 190 0C.

4) Lube oil and seal oil supply temperature shall be maintained around 40 - 45 0C. Normally the oil temperature at the bearing outlet is 60 - 70 0C.

Limitations in Operating Conditions

Lube oil pressure : 2 - 2.5 Kg/cm²g

Governor oil pressure : 5 Kg/cm²g

Seal oil pressure normal : 4.5 Kg/cm²g

Seal oil DP normal : 0.6 Kg/cm²g

Lube & seal oil temperature : 42 0C Normal

Lube & seal oil temperature : 51.6 CMaximum

Rated speed : 9000 rpm

Maximum speed : 9450 rpm

Trip speed : 10400 rpm

Governor control range : 6615 - 9450 rpm

Condenser high pressure alarm : - 575 mmHg

Condenser high pressure trip : - 508 mmHg

Turbine 1st critical speed : 5214 rpm

Compressor 1st critical speed : 5400 rpm

7.6 NORMAL SHUTDOWN PROCEDURE

Page 150: Ammonia Manual

Ammonia Plant Operating Manual 10

1) Line up Ammonia to TCV 1811 and open the isolation valves.

2) Check 1128 LCV is also lined up to 1527.

3) Start opening the FCV 2-201 and FCV 2-202. Use TCV 1811 to maintain discharge temperature below 190 0C.

4) Bring down the speed watching the minimum flow required to prevent surging.

5) Open all FCVs and speed control output are brought to minimum, inform the Control Room and trip the machine using the pedestal trip. Close the MSV fully.

6) Isolate TCV 1811.

7) Open DM water make-up to surface condenser.

8) Start motor driven lube oil, seal oil and condensate pumps and stop turbine driven auxiliary pumps.

9) Isolate air valve to ejector and cut off dry steam to air ejectors.

10)Open vacuum breaker.

11)Wait for the vacuum to come to zero.

12) In the meantime, line up seal sour oil trap vent to atmosphere and close the valve to first suction.

13)Once the condenser pressure comes to zero, cut off seal steam and gland condenser and ejector.

14)Open all steam line drains.

15) Isolate the main steam line isolation valve.

16) Stop DM water make-up to surface condenser.

17) Stop condensate recovery pump.

18)Drain the surface condenser.

If it is required to isolate the compressor,

a) Close suction, side stream and discharge valves. b) Isolate 1128 LCV. c) Depressurise the casing slowly to 0.5 Kg/cm²g. d) Replace the gas with Nitrogen.

Seal oil circulation shall be maintained atleast for 4 hours after stopping of the compressor. Then bring down Nitrogen pressure in the casing below 0.5 Kg/cm²g and stop seal oil pump. Close the transfer barrier bottom valve. Isolate cooling water to oil cooler and drain the cooling water.

Page 151: Ammonia Manual

Ammonia Plant Operating Manual 11

Once the turbine metal temperature drops below 90 0C, stop lube oil pump. Isolate the cooling water to cooler and drain the cooling water.

7.7 EMERGENCY SHUTDOWN PROCEDURE

1. SGC unloading or tripping

In this case, the load on LRC comes down.

Actions to be taken.

a) Open FIC - 2-201 and 202 on manual and maintain the required flow.

b) Bring down the speed.

c) Line up liquid Ammonia to TCV 1811.

d) Control the gas temperature using the Ammonia quench. The discharge temperature shall be less than 190 0C.

2. Loss of both seal oil pumps

Machine automatically trips on extra low overhead tank level.

Actions to be taken,

a) Open FIC 2-201 & 202.

b) Isolate suction side stream and discharge valves of the compressor.

c) Open the casing vent and depressurise the casing.

d) Put Nitrogen into the casing (if available).

e) Proceed with the rest of the shutdown procedure to isolate the machine.

f) Try to stabilise the level as soon as possible to protect the seals.

For other trips such as low lube oil pressure and condenser pressure high, action is to proceed with the normal shutdown. If the system which had failed comes back, start the machine.

In case of lube oil failure, try to establish oil flow as soon as possible to save the bearings from overheating from the turbine / compressor metal temperature.

3. The 1527 high level push button trip on the main panel will give "MAIN PANEL TRIP" indication on the local panel. For this trip, compressor shall be restarted after draining 1527. This trip may be initiated for other reasons even as reduction in steam demand etc. Proceed with normal shutdown actions but do not break the vacuum until instructed by the Shift Engineer.

4. In case of vibration and noise,

Page 152: Ammonia Manual

Ammonia Plant Operating Manual 12

If the vibration slightly goes up or a slight noise is heard, we can try to reduce the load and see the vibration or noise comes down. Inform Shift Engineer first.

But if the trend is on the increase, it is better to take a planned shutdown. If the vibration or noise is heavy, use the pedestal trip and stop the machine immediately.

Page 153: Ammonia Manual

Ammonia Plant Operating Manual 1

Page 154: Ammonia Manual

Ammonia Plant Operating Manual 1

6 Chapter Eight INERT GAS PLANT

8.1 DESIGN

The IG plant produces Hydrogen or Nitrogen using Ammonia as the raw material. This plant

makes available at battery limit 1200 Nm3/Hr of cracked gas ( H2 + N2 ) of the following

quantity, in three streams

H2 : 75%

N2 : 25%

O2 : less than 10 ppm

NH3 : less than 100 ppm

Alternatively this plant can produce maximum of 1950 Nm3/Hr of N2 of the following quality, in

three streams.

N2 : not less than 99.5 %

H2 : less than 0.3 %

O2 : less than 200 ppm

NH3 : less than 200 ppm

Each stream can be run independently either on cracked gas or Nitrogen service or in parallel. Further it is possible to run one stream on Nitrogen at low throughput and transfer Hydrogen available as excess to the other unit, if running on cracked gas, to the extent of the capacity of the compressor.

8.2 DESCRIPTION

Each of the three streams in the plant consists of two Ammonia dissociators, Nitrogen generator, dual duty reciprocating compressors, deoxopreheater, aftercooler and humid dryer.

A. Dissociator

There are two dissociators per stream. Each dissociator consists of a furnace, dissociator chamber and vapouriser. Liquid ammonia from the bulk storage is vapourised in the shell side of the vapouriser by the sensible heat of dissociator exit gas passing through the vapouriser coil. The vapouriser has a relief valve set at 13.5 Kg/cm²g.

The vapourised ammonia is passed through the bundle of tubes (9 Nos) containing the catalyst. A pressure regulator controls the pressure at 0.4 Kg/cm²g. There is a pressure relief valve set at 0.42 Kg/cm²g to protect the dissociator tubes against pressure.

The tubes are mounted vertically within the furnace chamber. ICI 27/2 Nickel catalyst supported on grid is employed as the catalyst. It operates over a temperature of 850 - 1000 0C. The tube is housed within the furnace which consists of cylindrical casing lined with refractory,

Page 155: Ammonia Manual

Ammonia Plant Operating Manual 2

backed up by graded insulation. The furnace chamber is heated electrically. The heating elements are arranged in two zones with automatic temperature control in each zone. When the furnace temperature in any zone falls below the set value, the furnace heating element in that zone are switched on. The cracked gas after giving away the sensible heat is fed to the suction of the compressor or sent to the Nitrogen generator depending upon the service of the stream. There is manually operated flow control valve at the exit of the vapouriser to regulate the dissociated product gas flow which is measured at the exit of the vapouriser. In addition a manual vent valve is also provided to vent the cooled product gas when necessary. Each

dissociator produces 212.5Nm3/Hr of cracked gas. Each dissociator consumes approximately 82 Kg/hr of liquid ammonia at full throughput.

B. Generator

There are three nitrogen generators in the plant, one in each stream. Each generator produces

675Nm3/Hr of nitrogen from 425 Nm3/Hr of cracked gas at maximum throughput. Each generator consists of combustion air fan, fuel gas, air; regulating and metering equipment, a pilot burner and a main burner firing into a refractory lined combustion chamber and a direct contact cooler.

The Nitrogen gas is produced by a combustion process in which cracked gas is burned with air to consume the Oxygen in air. By running with slightly less than the theoretical air requirement for complete combustion, the product gas will contain residual Hydrogen in addition to water and

Nitrogen. The ratio of air to gas is maintained at 1.8 Nm3/Nm3 by a proportionating valve.

The combustion is carried out in a refractory lined combustion chamber, mounted horizontally from which the gases pass into and cooled in a vertically mounted direct contact cooler. This cooler is in effect, a counter flow heat exchanger where the gas passes vertically upward first through stainless steel pall rings and through ceramic saddle packings with water sprayed at the top. Cool gas pass through a stainless steel demister to the buffer receiver and suction of compressor through a separator to knockout any moisture.

There are provisions to shut off the unit in case of :

a) gas failureb) water flow failurec) air failured) flame failure & e) high gas pressure.

C. Compressors

There are three compressors one in each stream. These are four stage reciprocating compressors developing 43.4 Kg/cm²g from suction pressure of 250 mmWC. These are dual duty compressors, specified to run either on Nitrogen or on Hydrogen. There is a vent control valve at suction chamber of the compressor to maintain the suction pressure by venting gas to atmosphere when the pressure increases higher than a preset value.

There is an another control valve which feeds cooled gas from the discharge of compressor to the suction in case the suction pressure falls below a preset value.

Page 156: Ammonia Manual

Ammonia Plant Operating Manual 3

The compressor has the following protections :

a) low lube oil pressure.b) high lube oil temperature.c) high discharge temperature.d) high level in separator &e) low suction pressure.

In addition, if the control valve feeding suction of the compressor fully opens, the compressor trips out automatically.

D. Deoxo reactor

The compressed gas, if hydrogen is passed to an aftercooler bypassing the deoxo preheater and deoxo reactor. If the compressed gas is Nitrogen, it is initially preheated in the deoxo preheater.

Each heater is rated for a minimum flow of 200 Nm3/Hr. Each gas heater is capable of heating

675 Nm3/Hr of Nitrogen from 110 0C to 230 0C. When the compressor is stopped or tripped, the heater is cut off automatically.

The gas is then passed over a deoxo catalyst in deoxo reactor. The catalyst used is GRIDLER G-43 which is a Platinum-Nickel bearing Alumina. The recommended quantity of Hydrogen in the gas stream is 1 % by volume of the process flow rate. The temperature rise across the catalyst bed will be approximately 140 0C for each percentage of Oxygen plus Nitrogen Oxide reacted. Therefore with design inlet figure of 0.615 % by volume of Nitrogen Oxides, the temperature rise across catalyst will be approximately 86 0C.

E . After cooler

Each aftercooler will continuously lower the temperature of gas stream to 40 0C.

F. Humid drier

Each Humid drier will continuously and automatically dry up 425 Nm3/Hr of cracked ammonia gas (inclusive of purge requirement) to an outlet dew point equivalent to 10 ppm moisture. In addition to the inlet ammonia content of 0.5 % volume will be lowered to below 100 ppm.

Alternatively, it will continuously and automatically dry up 675 Nm3/Hr of Nitrogen gas entering

Humidrier saturated with water vapour to an outlet dew point of 5 0C. 25Nm3/Hr of process gas will be required for the purge. Hence Nitrogen availability from the receiver from each stream at

maximum throughput is 650 Nm3/Hr. Hydrogen to receiver from each unit at maximum

throughput is 400 Nm3/Hr. The process gas enters the top of the absorption tower and flows down through molecular seive where the drying operation is completed and the gas flows out through the nozzle at the bottom of the tower. It flows further to dust afterfilter where any desiccant dust particles which may have carried over from the absorber towers are removed.

The two absorber towers are operated cyclically with one absorber tower in service while the other is being reactivated and cooled. The drier operation is fully automatic and works in the same manner regardless of which gas stream is being processed. At the end of drying and purification period, the freshly reactivated absorber tower is brought into service and the spent tower begins its reactivation cycle. The tower is first depressurised to approximately atmospheric

Page 157: Ammonia Manual

Ammonia Plant Operating Manual 4

pressure by opening the pressure blowdown valve and allowing the gas contents of the vessel to exhaust to atmosphere. The pressure blowdown then closes and the reactivation purge valve opens allowing purified process gas from downstream of the dust filter to flow into the terminal chamber at the top of the absorber tower. At the same time, as the purge valve opens, the reactivation heater is switched on. The purge gas then flows from the terminal chamber down through the heater sheath in direct contact with heater elements and out at bottom of sheaths and flows upward through the bed and exhaust through the reactivation purge valve to atmosphere. The closed terminal chamber ensures that only dry process gas is in contact with the electrical heater terminal. Although the internal heaters are the main source of reactivation heat, bypassing the purge gas over them, a more efficient, reverse flow reactivation is achieved.

At the end of the reactivation heating period, the internal heaters are switched off and the bed is cooled by the purge gas flow. This continues until just before the changeover of the towers when the valve closes and allows the tower to be repressurised by the purified process gas still taken from downstream of dust afterfilter.

In the event of compressor shutdown or failure, an absorber tower which is in reactivation phase will carry on reactivating by drawing purge gas through the emergency reactivation control valve which opens in case of compressor stoppage and feeds gas either from Nitrogen receiver or Hydrogen receiver as the case may be. Hence when regeneration is interrupted, receiver isolation valve should not be closed as closing the isolation valve will prevent drawal of purge gas from receiver through the emergency valve.

On completion of regeneration, "Safe to Stop Drier" lamp appears in the drier local panel and sounds in the annunciator panel. On acknowledging it, receiver may be isolated as regeneration is completed.

NOTE : When H2 receiver and N2 receiver are under a pressure of 43.5 Kg/cm²g, capacity of the

receiver is 25 m3 and 36 m3 respectively.

8.3 START - UP PROCEDURE

A. Nitrogen service

i. Bring dissociator in line

Condition of dissociators is as follows:

a) Temperature controllers in both zones are set at 800 0C and OTC are set at 850 0C.

b) Liquid ammonia valve inlet vapouriser is open.

c) Vapourised ammonia valve exit vapouriser is opened but upstream of pressure regulating valve is closed.

d) Vapourised ammonia valve downstream of pressure regulator is open.

e) Vent valve to atmosphere and valve feeding the compressor/generator and the manual flow control valve are in closed position.

Page 158: Ammonia Manual

Ammonia Plant Operating Manual 5

To bring dissociator in line,

a) Raise the setting of TC to 850 0C and OTC to 900 0C and allow the temperature to raise to 900 0C.

b) Line up vent valve.

c) Open the vapouriser exit valve and check for proper functioning of regulator. If it is not OK, throttle the vapouriser exit valve and maintain the pressure at 0.4 Kg/cm²g. Remember there is a relief valve to pop at 0.42 Kg/cm²g.

d) Open the manual control valve and adjust the record flow.

e) At the exit of dissociator, check the gas for ammonia slip. In case of ammonia slip, more than 500 ppm gradually take up the temperature in steps, not forgetting to raise the OTC setting at +50 0C above the TC. Do not raise the controller set point above 950 0C.

ii. Bring generator in line

a) Open the vent valve at the exit of dissociator.

b) Close all valves on cracked gas line to compressor.

c) Close the butterfly valve at the exit of generator to the compressor and open the local vent valve at the upstream of butterfly valve.

d) Switch on generator panel. Set the switches to START and ZERO position.

e) Open the isolation valve at the inlet of generator and check that the "GAS FAILURE " lamp disappears. Increase incoming pressure if necessary.

f) Admit cooling water to the water jacket of combustion chamber and water to the direct contact cooler, check that the "WATER FAILURE" disappears. Ensure that water does not back up into the combustion chamber.

g) Start the combustion air fan and check that "AIR FAILURE" alarm disappears.

h) Audible alarm should sound and this is silenced by turning the control switch from START to Normal position.

i) Leave the fan running for few minutes to purge out the combustion chamber.

j) Maintain adequate flow by opening the Selas proportionating valve and ensure that all the air is vented locally, upstream of Nitrogen butterfly valve and not through the vent stack. This is to avoid the possibility of a fire in the vent stack, which is venting cracked gas from dissociators already.

j) Turn the control switch to Position 1 from Position 0. Check that ignition lamp illuminates. The Solenoid valve on the Pilot gas line opens and pilot flame is established. Check whether a stable pilot flame is established. "FLAME ON" lamp should now illuminate and "FLAME FAILURE"

Page 159: Ammonia Manual

Ammonia Plant Operating Manual 6

lamp should be extinguished. If the pilot flame is not established within a set time after turning the control switch to Position 1, combustion air fan will be tripped and the Solenoid valve on pilot gas line is closed and the startup procedure should be repeated.

l) Ensure that the plug valve on the main gas line is closed and turn control switch to Position 2 and check the IGNITION ON lamp goes out.

m) Reset the main gas Solenoid valve by operating the reset button from the bottom.

n) Slowly open the main gas burner valve and establish main flame. Slowly open the Selas valve further to the desired output watching the gas pressure. Vent valve, if opened at the exit of dissociators, should be fully shut. In case of flame failure during Step (m) total shutdown of generator occurs and all the steps from Step A are to be repeated.

o) On establishing the main flame, turn the control switch position to 3. This will cut off pilot gas by closing the Solenoid valve.

p) On starting Nitrogen generation, open the butterfly valve exit generator and feed the gas to the compressor suction. On transferring the gas to suction part of compressor, the vent control valve opens and maintains the pressure of the suction chamber.

o) By now, cracked gas venting from dissociators also would have been stopped and hence close the local vent upstream of butterfly valve.

q) If the suction pressure is not controlled by venting, manual venting may be resorted to. Check the generator through the view glass for normal conditions. Check the direct contact cooler shell and ensure that there is no hot spot.

iii. Start the Compressor

a) Start lube oil pump of the compressor and ensure that the DP across the filter is less than 1 Kg/cm²g. If necessary, clean the filter.

b) Ensure adequate water flow to the cylinder jackets and glands. Clean the filter if necessary.

c) Bar the compressor and ensure that it is moving freely.

d) Ensure that inlet and exit valves of Deoxoreactor are closed and bypass valve is opened. Check that the drier valves are in the correct positions.

e) Check that the line downstream of drier upto receiver isolation valve is through. Keep the receiver isolation valves closed and open the vent upstream receiver isolation valve.

f) Check the inter-stage separators for any liquid level, drain them thoroughly. Ensure that cooling water is flowing to all the intercoolers, lube oil cooler and aftercooler.

g) Open the block valve of MASONEILAN control valve near the suction chamber and near drier.

h) Analyse the gas at suction chamber for Hydrogen and Oxygen. If Hydrogen is too much, check the Hydrogen valve from dissociators to compressor. Till the situation is made OK, do not start compressor.

Page 160: Ammonia Manual

Ammonia Plant Operating Manual 7

i) Check the liquid seal at the suction of the compressor.

j) Start the compressor and watch the suction pressure. If there is a tendency for sharp falling, take Masonielan valve on manual and admit more recycle gas till suction pressure is stabilised. Manual vent from suction chamber should have been fully shut by now. While operating Masonielan, remember that if the valve is wide open compressor will trip.

k) On starting the compressor, check the interstage pressures and interstage temperatures. Check the PCV at the discharge of compressor for proper operation. Set the suction pressure controller at 250 mmWC and take it on AUTO.

iv. Bring Drier in line

Switch on the drier after checking the various valve positions for the proper cycle of operation.

v. Bring Deoxo reactor in line

Till this time, the gas at high pressure is being dried and vented upstream of receiver. Before lining up the gas to receiver, the Oxygen content should be brought to less than 10 ppm to meet the specification.

a) Crack open the inlet of deoxo unit and pressurise slowly, not exceeding 2 Kg/cm²g/min.

b) When the pressure has equalised with compressor discharge, open the outlet valve also and close the bypass valve.

c) Switch on the deoxo unit local panel and raise the temperature gradually not exceeding 100 0C/hr. Remember that OTC has to be set always at +50 0C above the set point of TC.

vi. Line up Nitrogen to Nitrogen receiver

When the deoxo catalyst bed temperature has come up and reaction has picked up as indicated by rise in temperature at the exit of reactor, analyse for Nitrogen quality downstream of drier.

If it meets the required specification, line-up the gas to the Nitrogen receiver. Ensure that both block valves at the discharge of the compressor to Hydrogen receiver are shut and the bleed is opened fully. Remember that Hydrogen receiver is always under a pressure of 43 Kg/cm²g when the plant is running but Nitrogen receiver pressure is variable. If the double block and bleed system is not made use of, there is every chance of Nitrogen being contaminated with Hydrogen.

B. CRACKED GAS SERVICE

i. Bring Dissociator in line

Condition of dissociators is as follows:

a) Temperature controllers in both zones are set at 800 0C and OTC are set at 850 0C.

b) Liquid ammonia valve inlet vapouriser is open.

Page 161: Ammonia Manual

Ammonia Plant Operating Manual 8

d) Vapourised ammonia valve exit vapouriser is opened but upstream of pressure regulating valve is closed.

d) Vapourised ammonia valve downstream of pressure regulator is open.

e) Vent valve to atmosphere and valve feeding the compressor/generator and all Nitrogen feed the suction at compressors should remain closed.

To bring dissociator in line,

a) Raise the setting of TC to 850 0C and OTC to 900 0C and allow the temperature to raise to 900 0C.

b) Line up vent valve.

c) Open the vapouriser exit valve and check for proper functioning of regulator. If it is not OK, throttle the vapouriser exit valve and maintain the pressure at 0.4 Kg/cm²g. Remember there is a relief valve to pop at 0.42 Kg/cm²g.

d) Open the manual control valve and adjust the flow.

e) At the exit of dissociator, check the gas for ammonia slip. In case of ammonia slip, more than 500 ppm gradually take up the temperature in steps, not forgetting to raise the OTC setting at +50 0C above the TC. Do not raise the controller set point above 950 0C.

f) After stabilising, line up dissociator exit gas to compressor suction.

ii. Start the Compressor

a) Start lube oil pump of the compressor and ensure that the DP across the filter is less than 1 Kg/cm²g. If necessary, clean the filter.

b) Ensure adequate water flow to the cylinder jackets and glands. Clean the filter if necessary.

c) Bar the compressor and ensure that it is moving freely.

d) Ensure that inlet and exit valves of Deoxoreactor are closed and bypass valve is opened. Check that the drier valves are in the correct positions.

e) Check that the line downstream of drier upto receiver isolation valve is through. Keep the receiver isolation valves closed and open the vent upstream receiver isolation valve.

f) Check the inter-stage separators for any liquid level, drain them thoroughly. Ensure that cooling water is flowing to all the intercoolers, lube oil cooler and aftercooler.

g) Open the block valve of MASONEILAN control valve near the suction chamber and near drier.

Page 162: Ammonia Manual

Ammonia Plant Operating Manual 9

h) Check the liquid seal at the suction of the compressor.

i) Start the compressor and watch the suction pressure. If there is a tendency for sharp falling, take Masonielan valve on manual and admit more recycle gas till suction pressure is stabilised. Manual vent from suction chamber should have been fully shut by now. While operating Masonielan, remember that if the valve is wide open compressor will trip.

j) On starting the compressor, check the interstage pressures and interstage temperatures. Check the PCV at the discharge of compressor for proper operation. Set the suction pressure controller at 250 mmWC and take it on AUTO.

iii. Bring the Drier in line

Switch on the drier after checking the various valve positions for the proper cycle of operation.

iv. Line up to Hydrogen receiver

Check the quality of Hydrogen exit drier and line up to Hydrogen receiver. Ensure that block valves at the discharge of compressor to Nitrogen receiver are shut and bleed in-between is opened as there is every chance of Hydrogen entering Nitrogen receiver and contaminating the quality Nitrogen.

8.4 NORMAL SHUTDOWN

1. NITROGEN SERVICE

a) Isolate receiver . Open the manual vent upstream of receiver isolation valve and close the receiver block valves.

b) Isolate deoxo unit. Switch off the heater of Deoxopreheater. Open the bypass valve of deoxo unit. Do not close inlet and exit of deoxo unit immediately.

c) Stop drier operation. If the regeneration of the tower is complete "SAFE TO STOP DRIER" alarm would appear and receiver isolation valves can be closed. Switch off drier panel. If the regeneration of any of the towers is incomplete and heating cycle is on, receiver should not be isolated so that the emergency valve will feed gas to the drier for regeneration from the receiver. Wait for "SAFE TO STOP DRIER" alarm appears.

d) Stop compressor.

Stop the compressor and watch the suction pressure. If the pressure is not controlled by vent control valve, at suction, manual vent may be opened.

e) Stop generator.

Open the local vent upstream of butterfly valve and close the butterfly valve. Close the plug valve on gas line and change the position of switch to 0 from 3.

Page 163: Ammonia Manual

Ammonia Plant Operating Manual 10

When gas to generator is cut off because of decrease of drawal rate from dissociators, the vapourised ammonia pressure will go up. If the pressure regulators on the vapourised ammonia line do not function properly, relief valve may lift. When there is a tendency for pressure to go up, the valve upstream of pressure regulator may be throttled to control the pressure and local vent of the dissociator may also be opened. If after cutting off gas to generator, run the fan for about 10 minutes to purge out the combustion chamber completely.

Close water to jacket of combustion chamber when it is cooled down. Close water to direct contact cooler when it is not necessary.

f) Isolate dissociators.

Close vapourised Ammonia isolation valve upstream of pressure regulator.

Close the manual flow control valve, vent valve and the valve to the compressor / generator.

Reduce the set point of the temperature controllers to 800 0C and set OTC at 850 0C.

2. HYDROGEN SERVICE

Same as Nitrogen service except (b) & (e) which are to be deleted.

8.5 NORMAL OPERATION

a. Dissociators

OTC should be set always at + 50 0C above the set point of temperature controller whenever the set point of temperature controller is changed, set point of OTC also should be changed correspondingly. Same setting for OTC for onload and offload conditions should not be kept.

Whenever any earth fault or OTC trip occurs, power to dissociator is cut off and hence though "heater on" lamps glow in the local panel, dissociator heaters are not switched on actually. The reset button in the panel has to be pressed for switching on the heaters after power is made available.

When the main contacter of the panel is switched on, reset button should be pressed, as power is not supplied to heaters though heater on lamp appears.

Whenever the dissociator is not in service, set point of temperature controllers should be brought down to 800 0C.

b. Generators

Shell of the direct contact cooler should be checked often for any hot spot and water jacket on the combustion chamber should have adequate flow always.

Before lighting the generator and after putting out the flame, generator should be purged with air for adequate period.

Page 164: Ammonia Manual

Ammonia Plant Operating Manual 11

When there is no air / gas flow to generator and when water is flowing to direct contact cooler, it should be checked that there is no back flow of water to combustion chamber.

Before lighting the furnace, the purge air should be vented locally and it should not be vented through vent stack.

After stopping water flow to the direct contact cooler, the drain from the top of the direct contact cooler should be opened and any residual water in the compartment around the demister should be drained out.c. Compressors

Keep a close watch on inter stage pressures and temperatures.

Check lube oil pressure and clean the filter.

Check the gland cooling water filter frequently.

Open the bypass of various traps provided in the separators to drain out any condensate. Do not wait for the alarm to appear and do not depend upon the traps.

Check for gland leaks on the compressor.

Ensure that the crossovers at the suction of the compressor are properly isolated when the machine runs on Nitrogen to prevent any Hydrogen ingress.

Check the liquid seal at compressor suction.

Check the opening of Masoneilan valve feeding the suction from final discharge. Increase in opening indicates starvation of suction.

Check the suction pressure. Any increase indicates deterioration in performance which has to be confirmed by amperage of compressors.

d. Deoxo Unit

Heater should be switched off manually, immediately after stoppage of compressor. Though there is an automatic cut out on high temperature and interlock with compressor

trip.

Check for any abnormal temperature rise in the bed which indicates off quality gas at inlet.

e. Drier Unit

The inlet temperature of gas to drier unit should not exceed 43 0C.

Various vent valves, blowdown valves etc., should be checked for correct position as

Page 165: Ammonia Manual

Ammonia Plant Operating Manual 12

malfunctioning of these will lead to loss of gas or pressure build-up.

8.6 DISSOCIATOR CATALYST REDUCTION

1) Maintain positive Nitrogen pressure in the vapouriser/retard before commencing heating operation.

2) Heat the catalyst at the rate of 25 0C/hr till the catalyst attains temperature of 100 0C. For heating raise the set point of TC by 25 0C each hour maintain the set point of OTC above the set point of TC by 50 0C always.

3) After attaining 100 0C, the rate of heating may be increased to 50 0C/hr raise the set point of temperature controller by 25 0C every half an hour.

4) On attaining 950 0C, maintain the temperature for two hours.

5) Remove the slip plate at vapouriser inlet and disconnect Nitrogen hose from the drain.

6) Admit Ammonia to vapouriser slowly. (10 % of normal flow rate of Ammonia)

7) Analyse for moisture and Ammonia content exit dissociator once in two hours.

8) When there is a drop in moisture and Ammonia slip exit dissociator, raise the Ammonia input by another 10 %.

9) Continue the process till the output is raised to 100%.

10) As the catalyst is fresh, higher operating temperature is not required and set points of 950 0C on TC and 1000 0C on OTC are expected to be adequate. After checking ammonia slip at 100 % throughput, operating temperature may be increased if necessary.

7 Chapter Nine FLARE SYSTEM

9.1 DESCRIPTION

Flaring is employed to dispose the waste gases without polluting the atmosphere.

The major components of a flare system includes the flare tip, flare pilot, flare seal, ignition system, base drum etc.

The water seal is located at the base of the flare to provide a solid water barrier to prevent passage of flame from the flare back towards process area. This water seal can also serve as a back pressure device to maintain positive pressure in the relief header. It should be ensured that no air enters the flare seal drum in case of water failure.

Page 166: Ammonia Manual

Ammonia Plant Operating Manual 13

Explosions in the flare system are prevented with a patented molecular seal in which the design utilises minimum purge gas to prevent air entering the flare.

The operating principle of the molecular seal, when using purge gas having molecular weight of less than 28, uses of buoyancy of the purge gas to create a zone of greater than atmospheric pressure at the tip of the flare in an area protected from wind action. Air cannot flow to higher pressure thus air cannot enter the flare. Following are some of the possibilities for air to enter otherwise:

1. Rapid closure of relief valves and creation of low pressure zone behind the column of gas.

2. Thermal contraction can draw in air when flaring stops and gas cools rapidly. This problem is aggravated by rainfall which accelerates the cooling process.

3. Wind is a major factor causing introduction of high velocity air which is countered by purge gas.

A molecular seal is a gas seal which functions as a dynamic flame arrestor. In order to prevent push back the molecular seal requires purging at a minimum rate.

Three pilots are used to ensure that flame covers the tip and guarantees ignition at all rates of design flame. This pilot should remain alright and cater for any contingency and to retain the flame at high velocity.

Flare top is one of the key components in any system. There are two injection points in the flare tip. One through the upper outer steam injector which jets to produce smokeless combustion and the second into the core of the flare tip to maintain the tip in a cool condition and to prevent burn back. Steam injected into the flare causes a shift reaction and changes the burning characteristics of the gas eliminating smoke.

Steam tips are set away from the flare gas discharge to prevent flame impingement and provide long life. Remote placement also provides the distance necessary to draw in adequate combustion air for smokeless operation. Vortex steam action of this design keeps the flare gas flame erect, even in high winds and prevents the flame from missing the steam mixing zone which could cause smoke.

Upper end of stack is lined with high temperature refractory anchored with SS expanded metal.

When the drain from molecular seal is used for any water removal, it must be closed after use. Open drains have been responsible for internal flare explosions because of oxygen drawn through the drain valve into a lower pressure zone.

9.2 LIGHTING UP PROCEDURE

1. Admit water to flare seal drum and ensure visible overflow.

2. Charge the pilot gas header.

3. Charge seal gas line.

4. Keep a pressure of 0.5 Kg/cm² in the gas line to ignitor and maintain 0.5 Kg/cm² in the air line to ignitor.

Page 167: Ammonia Manual

Ammonia Plant Operating Manual 14

5. Just press the ignitor and leave it. Prolonged pressing of ignitor button should not be done as it might damage the ignitor transformer.

6. Check through the view glass that the spark is produced. Do not look at the view glass directly.

7. If the flame is not getting established, change over the 3 way valves and try with other pilots. While changing over, check that the gas and air pressures do not increase. Increase in pressure indicates choke in the line.

8. After establishing a flame, admit steam to the outer ring and inner core through 2" and 1½" steam line to stabilise the flare to make it smokeless and to make it free from wind disturbances.

8 Chapter Ten COOLING WATER PUMPS AND TURBINES

I. OGT 101 A CONDENSING TURBINE

10.1 START-UP PROCEDURE

1) Check the oil level in the lube oil reservoir. Also in main turbine governor, bearings of cooling water pump and auxiliary machines.

2) Ensure cooling water to auxiliaries like gland condenser, gland ejector condenser and main condenser. Cooling water to oil cooler need not be opened. This is to be done only after the initial increase in the lube oil temperature has been observed.

3) 12 Kg/cm²g & 45 Kg/cm²g steam valves at battery limit should be opened gradually keeping the drain valves open for warming up the lines. The steam trap bypass and the common header drain should be kept open till the steam coming out from the drain is free of any condensate.

4) Motor driven lube oil pump is to be started. Pressure to be maintained are

Lube oil pressure : 1 - 1.2 Kg/cm²g Control oil pressure : 4 - 4.2 Kg/cm²g

5) Warm up lube oil pump turbine and condensate pump turbine.

Page 168: Ammonia Manual

Ammonia Plant Operating Manual 15

6) The shaft turning motor should be started after engaging the clutch provided. The lamp indications provided in the panel should indicate "ON".

Note : If the lube oil pressure is not to the required value, the turning motor cannot be started. Gland sealing steam from 12 Kg/cm²g header should be opened slightly to maintain the sealing steam pressure at 0.2 Kg/cm²g.

7) Hogging ejector should be started (steam valve should be opened first and then air valve).

8) Steam valve to gland condenser ejector of main turbine should be opened such that the pressure is about 5 Kg/cm²g.

9) Pump gland sealing line valve should be opened keeping its own cooling water line in closed condition for initial starting up. Put the pump priming ejector in service. Check that the valves in the bearing cooling water inlet and outlet are kept in opene condition. Bearing cooler drain should be kept in closed condition.

10) The bypass to condensing turbine steam inlet line should be opened very little for warming up keeping open the drain before turbine for 10 minutes.

11)Check the opening of inlet and exhaust valve for lube oil pump turbine. Then warm up the turbine by screwing down the handle of emergency stop valve. After screwing down, the handle should be screwed off for emergency stop. After screwing up them, locking pin should be introduced. After warming up, slowly increase the speed by screwing the butterfly valve nut. After attaining full speed and checking the pump stop the Motor Driven Oil Pump. The panel switch (knob) is to be turned to "Auto" start position.

12)All the drain tanks are to be checked and drained by isolating the incoming valves and opening the air vent and tank drain. After draining, put the drain tank into service.

13) If the vacuum is about 600 mm Hg, change over to Main ejector. Following are the procedure in case of 1st and 2nd stage ejector. Open the valve nearer to the ejector cooler. Open the steam valve to that particular ejector. Open the air valve. If the left side first stage ejector was put on service the corresponding left side second stage ejector should be put on service. If the vacuum is okay cut out the starting ejector.

Attention : Close first air valve and then the steam valve. If there is a drop out on vacuum, start the other set of ejectors. Even then there is a trouble, cut in starting up ejector. While running, if there is any drop in vacuum, put on the starting up ejector till vacuum is restored.

14)Check all the equipment such as Lub oil pump turbine, condensing pump turbine for bearing temperature, speed, inlet steam pressure and temperature, vacuum etc. Condenser level should be checked.

15)Open the main valve of turbine keeping a watch on the colour of the steam. It should be colourless. Open fully the main valve.

Page 169: Ammonia Manual

Ammonia Plant Operating Manual 16

16)Check that the water is coming out through the priming line of the pump. Check the reset button in the panel and the level handle in the emergency main valve. Keep the knob of the governor in the minimum position.

17) If priming is okay, start rolling by opening the emergency valve. (When the turbine starts rolling, turning gear gets disengaged automatically) Maintain 100-200 rpm for about 45 mts. If everything is okay increase the speed to minimum governor speed (i.e.) 385 rpm. Check allbearing temperature, and maintain the speed for 15 mts.

Attention : Speed increase should be done quickly in the range 200-350 rpm since the critical speed of the machine is 280 rpm. Check the bearing temperatures of pump turbine and the discharge pressure of pump.

18)Then increase the speed to normal (i.e.) 485 rpm and check all point temperatures. Cooling water to pump gland should be changed over from sealing steam line. Change the turbine sealing steam to its own source.

19) Put "ON" the automatic level controller for condenser and close the recirculation. Check the condensate pump performance and open the discharge. Maintain discharge pressure around 5.2 Kg/cm²g.

20)Open discharge valve of main pump gradually keeping the header presure constant (when one pump is in service). Close the pump priming valves and ejector steam.

21)All temperatures, pressure and vacuum are to be checked. Readings are to be written every one hour.

22) Lube oil temperature is to be maintained between 35 0C and 40 C. Vacuum above 700 mmHg (Normal 635 mmHg). Max. bearing temperature 75 0C. Turbine is to be stopped at 80 0C.

Attention : The emergency valve should not be closed tightly and also should not be opened to the tight condition.

10.2 STOPPING UP PROCEDURE

1) Close the pump discharge.

2) Bring down the speed by turning the knob anticlockwise to 385 rpm.

3) Close the emergency valve and watch for decrease in speed.

4) After the speed comes to zero put "ON" the turning motor, close the sealing steam, close the ejector (gland condenser ejector) steam valve and finally the main valve. Open the drains fully for casing.

5) Stop the condensing pump and open the casing drains.

6) Stop the lube oil pump turbine after starting the motor driven pump. If the auto start for motor is to be checked then turning motor would have got tripped due to low oil pressure. So again it has to be started.

Page 170: Ammonia Manual

Ammonia Plant Operating Manual 17

7) Lube oil pump turbine turning motor should be in service for minimum four hours after stopping the turbine.

10.3 NORMAL RUNNING

1) Reading are to be taken once in every hour.

2) Oil filter DP to be checked. If it is more than 0.6 Kg/cm²g, change over to the other filter and clean it.

3) Only one oil cooler should be in service. The cooling water should be opened or closed according to the required temperature of lube oil, i.e., 35-40 C.

4) Drain tank drains are to be operated once in a shift (for operation see previous instruction).

5) Condenser level to be checked.

6) Once in a week the spindle movement for control valve and emergency valve to be checked by closing the emergency valve to some extent and increasing the speed to 500 rpm. After that they should be brought to the original position.

10.4 ALARM & TRIP VALUES

Alarm Trip

Low lub oil pressure 0.70 0.49

Overspeed 540 rpm

Exhaust pressure high 460 mmHg

Condenser level - High 250 + 100 70 % level trol Low 250 - 100 30 % level trol

Turbine trouble hand trip

Accumulator charging pressure 0.9 Kg/cm²g 3.6 Kg/cm²g

10.5 GENERAL

Page 171: Ammonia Manual

Ammonia Plant Operating Manual 18

When both the condensing and back pressure turbine are stopped close the 45 Kg/cm²g line battery limit valve to avoid passing of steam to turbine. If only one pump is running the body temperature of the other turbine to be checked. If it is hot put on the turning motor in continuous service.

There are two condensate pumps. The condensate pump should be changed once in a month.

II BACK PRESSURE TURBINE OGT 101 B

10.6 START UP

If the condensing turbine pump is already in service, the warming up of steam lines, running of lube oil pump all would have been taken care of. Or else follow the instruction for warming up.

1) Check the oil level in the pump bearing and in turbine governor.

2) Check cooling water to gland condenser.

3) Line up water for gland sealing and start priming of the pump.

4) Open the casing drain for main turbine.

5) Open all the drain in 3 Kg/cm²g line venting system. Open the exhaust valves in 3 Kg/cm²g. line and venting system.

6) Switch "ON" the turning motor after putting the clutch in "ON" position.

7) Open steam valve to ejector of gland condenser.

8) Open gradually the main valve 45 Kg/cm²g line and warm up the turbine. Colour of the steam should be watched. It should be colourless.

9) Check the priming of the pump.

10)Check the reset button in control panel. Check the level of the emergency valve. Keep the governor knob in the minimum position.

11) If everything is okay start rolling the turbine by opening the emergency valve. Maintain 100-200 rpm for 30 mts. Check all points, temperature, pressure etc.

12) If everything is okay increase the speed 385 rpm - minimum governor speed. Maintain for 15 mts. Check bearing temperature for pump and turbine. Check the discharge pressure of pump.

Attention: Pump critical speed is 300 rpm. So increase speed quickly 220 to 350 rpm.

13) Increase the speed to 485 rpm. Change gland sealing water to cooling water of its own.

14) Put the PCV in the venting system on auto. Maintain pressure to 2.8-2.9 Kg/cm²g and close the drains. Safety valves are set to 3.1 and 3.25 Kg/cm²g.

Page 172: Ammonia Manual

Ammonia Plant Operating Manual 19

15)Open the discharge valve gradually keeping the header pressure constant and take the pump into service. Close the pump priming valve and ejector valve.

16) If steam is to be supplied to off site boiler deaerator, open the valve near the condensate stripper after informing the offsite boiler. Check for all the points for any abnormality.

17)Oil temperature to be maintained at 35 to 45 0C. Accordingly close or open the water inlet valve to oil cooler.

18)Max bearing temperature is 75 0C. Turbine to be stopped at 80 0C.

Attention : Emergency stop valve should not be kept opened or closed in tight condition.

10.7 STOPPING PROCEDURE

1) Close the discharge valve of the pump. Before that change over the steam from offsite boiler to venting system after informing offsite boiler control room.

2) Bring down the speed to minimum by turning the knob to anti-clockwise direction of governor control.

3) Close the emergency valve and watch for decreasing the speed.

4) After speed comes to zero put "ON" the turning motor after switching "ON" the clutch. Check for lamp indication in panel.

5) Close the main steam valve and open the casing drains.

6) Lub oil and turning motor should be in service for min 4 hrs.

10.8 NORMAL RUNNING

1) All temperature, pressure readings are to be taken once in an hour.

2) Lube oil filter DP to be checked. DP not more than 0.6 Kg/cm²g. If it is more change over to the other filter and clean that.

3) Lube oil temperature to be maintained at 35 0C to 40 0C.

4) Bearing temperature maximum 75 0C.

5) Once in a week the handle to be checked for emergency valve and by increasing the speed to 500 rpm for control valve. Then bring back to original positions.

10.9 ALARM & TRIP VALUES

Alarm Trip

Lub oil pressure - Low 0.68 0.5 Kg/cm²g

Overspeed 540 rpm

Page 173: Ammonia Manual

Ammonia Plant Operating Manual 20

Bearing temperature - High 75 0C Hand trip at 80 0C

Oil tank level low level - 50 mm

Turbine trouble Hand trip

10.10 GENERAL

When both the condensing and back pressure turbine are stopped close the 45 Kg/cm²g line battery limit valve to avoid passing of steam to turbine.

If only one pump is running, the body temperature of the other turbine to be checked. If it is hot put on the turning motor in continuous service.

Page 174: Ammonia Manual

Ammonia Plant Operating Manual 21

9 Chapter Eleven HYDROFINING

11.1 INTRODUCTION

The Naphtha contains impurities that could be detrimental to steam naphtha-reforming catalyst. These impurities are variable in nature and in quantity depending on the origin of the crude petroleum. The most important amongst them is Sulphur, Nitrogen, Oxygen and metals. The aim of the hydro-desulphurisation is to eliminate these impurities by catalytic treatment in presence of hydrogen.

11.2 FUNDAMENTAL REACTIONS

As there are wide ranges of susceptible compounds in the naphtha products to be treated, it is difficult to give precise examples of chemical reactions.

Nevertheless, one can draw out of the following families:

a) Hydrofining reactions.

Desulphurisation.

Denitrogenation.

Other reactions: Hydrodeoxygenation, hydrodemetalisation etc.

b) Hydrogenation reactions:

Aromatic saturation.

The Hydrofining reactions are essentially characterised by the breaking of the C-S; C-O & C-N bond. They lead to the formation of hydrocarbons and the elimination of S, N & O in the form of H2S, ammonia and water respectively. These reactions are slightly exothermic.

The parallel reactions of saturation of double bonds by hydrogen are more strongly exothermic.

Hydrofining Reaction

1. Desulphurisation

The Mercaptons, sulphides and disulphide react easily to give saturated hydrocarbons and corresponding aromatics.

Mercaptons: RSH + H2 RH + H2S

Disulphide: R-S-S-R' + 3H2 RH + R'H + 2 H2S

The removal of combined sulphur in the Aromatic ring such as Thiophene (mainly in the case of Benzothiophenic and dibenzothiophenic derivatives) becomes more difficult. The main reaction is constituted by the opening of heterocycle ring resulting in a phenyl mercaptan and finally sulphur

Page 175: Ammonia Manual

Ammonia Plant Operating Manual 22

is removed as Hydrogen Sulphide. These reactions could be accompanied by the cracking of the lateral chain or rings after Hydrogenation. The desulphurisation reactions are exothermic in nature, 12-17 KCal/hr per mole of Hydrogen being the energy released.

Denitrification

Of all the reactions accompanying the desulphurisation, the denitrogenation is the most important. R-NH2 + H2 RH + NH3

The denitrogenation reaction is obviously less rapid than the desulphurisation reaction. It is particularly slow in the case of aromatic hetrocyclic compounds. Other reactions

These reactions are essentially those of demetallisation and deoxygenation.

Alcohol : R-OH + H2 RH + H2O

Hydrogenation reactions-Saturation of aromatics

The saturation reactions of the aromatics are partial in the normal conditions of hydrodesulphurisation.

In general, only the poly nuclear aromatics are affected in the presence of Cobalt catalyst.

11.3 UNIT DESCRIPTION

Feed gas and preheating section

Raw naphtha feed from the storage enters the unit by means of a Motor driven raw naptha pump 3203, , it's flow being controlled by a flow controller FC 1103. 3203 E having the VFD control to regulate the discharge pressure (PC1112). This feed is blended with a mixture of recycle and make-up gases discharged by the Hydrogen gas compressors 3101 North & South. Both the liquid feed and gases are heated in the heat exchangers 1505 A, B & C in the shell side while the hot reactor effluent passes through the tube side. This hot mixture of vapour naphtha and gas arrives at the fired heater 1431.

At the startup

Naphtha is directly sent to the stripper column by means of 3" line. The bottom liquid of this stripper is sent to the storage tank by a 3”slops line. This is to avoid the starvation of the reboiler due to tube side hot fluid flow during startup.

Page 176: Ammonia Manual

Ammonia Plant Operating Manual 23

Furnace and reactor section

Preheated naphtha and hydrogen are brought to the reaction temperature (330-355) at furnace 1431. In this furnace, feed has to pass both in the radiation and convection section. Symmetrical arrangement of inlet, outlet and tube bundles of the furnace helps in a good distribution of the process stream. The heated feed then flows across the reactor 1101 filled with Cobalt Molybdenum catalyst (HR 103) wherein the desulphurisation reactions take place. There are twelve thermocouples spread out in the catalyst bed of the reactor to found the carbon deposition in the catalyst vessel. Normal operation and regeneration of the catalyst can therefore be controlled accurately. A differential pressure gauge PDI 1105 is used to indicate the pressure drop across the catalyst bed. The reactor inlet temperature is controlled by means of TC 1102, which in turn acts upon the fuel quantity to the furnace burners.

Effluent Cooling Section

The effluent from reactor is cooled and partially condensed in a series of heat exchangers as follows:

In the tube side of 1507 wherein the recovered heat is made use of to boil the stripper Column bottoms.

In the tube side of 1505 C, B & A, the recovered heat being utilised to preheat the feed.

In the shell side of the cooler 1506, water is used as coolant.

Finally this effluent is sent to the separator 1102.

Separator, make-up and recycle gases section

The reactor effluent is split into two phases in the separator 1102. The liquid phase is sent to the stripper column 1103, to strip out the dissolved H2S. One part of the vapor gas is recycled

while the rest is sent as purge to 1431 and fired. The purge can also be taken to flare.

The liquid level in the separator is controlled by a controller LC 1102. In addition, it is provided with a high level alarm LI 1108 (70%). At the top of the separator, a wire mesh demister is placed to prevent liquid entrainment along with the gas to the compressor.

The unit pressure is controlled by the pressure controller PC 0201 of make-up gas located at the reforming section. FC 1105 allows control of purge gas flow and thereby indirectly the make-up gas flow. The recycle gas along with the make-up gas is compressed by two reciprocating compressors 3101 N & S working in parallel having capacity of 5000 NM3 each. Before mixing with recycle gas, the make-up gas passes through a knockout drum 1133. The compressed gas is then mixed with the Naphtha feed after metering the flow. A low flow alarm is provided in gas line. (225 NM3)

Page 177: Ammonia Manual

Ammonia Plant Operating Manual 24

The compressors will trip on the following indicators ;

very high level in separator 1102.

low lube oil pressure.

high discharge temperature.

high lube oil temperature.

Stripping section

Before being fed to the stripper column 1103, the liquid from the separator 1102 is heated in exchangers 1540 A & B, passing through the shell side, recovering heat from the treated Naphtha from stripper on the tube side.

The column consists of 30 ballast trays, single pass type. Feed enters at the 21st tray. A part of the stripper bottom is boiled in the heat exchanger 1507 on the shell side, recovering heat from the reactor effluent passing through the tube side. TC 1118 acting on the reactor effluent controls the bottom temperature of the stripper.

Hot sweet naphtha from the stripper bottom is cooled and sent to the storage tank 1203. Cooling is carried out first, in the tube side of the heat exchangers 1540 B & A and finally in the water cooler 1504.

The stripper bottom level is controlled by means of the controller LC 1106 acting on the product flow. The stripper overheads are cooled and Naphtha / water is condensed and separated in the integral condenser 1508. The stripped gas from the top is sent to the flare/fired in 1431. The liquid is totally refluxed back to the column. A down comer at the bottom of the integral condenser withdraws condensed water and sends it to the collector 1135. Corrosion inhibitor is pumped by means of a pump 3218 and introduced at the top of the column. A differential pressure gauge is provided to indicate the pressure drop across the stripper column (not now in operation). Both the off gases from the stripper and the naptha knockout drum can vent to flare by PC1111 or by a separate isolation valves

11.4 START-UP PROCEDURE

I. Purging of reactor and stripper section

Reactor and stripper sections are to be purged free of Oxygen before charging Hydrogen to the system. Whenever hydro fining section is shutdown for maintenance job or for decoking operations, system gets exposed to atmosphere. Therefore after a shutdown, the reactor and stripper sections are to be purged with Nitrogen.

1) Check the circuit consisting of 3101 N & S, 1505 A, B and C, 1431, 1101, 1507, 1506 & 1102. Ensure that all the flange joints opened out during shutdown have been boxed up.

2) "Swing elbows" at 1431 inlet, 1101 outlet should be linked up to the normal operating lines. Process lines used for decoking should be blinded.

Page 178: Ammonia Manual

Ammonia Plant Operating Manual 25

3) Check the slip plates on the LP Nitrogen line at 3101 N & S inlet have been removed for taking Nitrogen.

4) Pressurize the system with Nitrogen to about 0.5 - 1.0 Kg/cm²g. Observe for any major leak. If so, get it attended. Depressurize the system through all possible drains and vents. Pressurizing and depressurizing can be done several times till O2 content in the reactor loop

comes down to 0.2 %. If the catalyst has not been oxidized, purging operation should ensure forward flow of Nitrogen i.e., the section exposed to atmospheric oxygen shall not contaminate the reactor, which was on Nitrogen blanket.

5) Once reactor section is free of O2, pressurize the system with Nitrogen to 5-17 Kg/cm²g.

Attend to the flange/gland leaks, if any, in the system.

6) Use the Nitrogen in the reactor section to purge the stripper column. For this 1" startup line exit 1102 to 1103 can be used. Once stripper section is also purged free of Oxygen both reactor and stripper section can be boxed up under Nitrogen atmosphere at a convenient pressure.(say 5 ksc)

II. Hydrogen introduction

1) Cracked gas from IG unit will be available only if it is not used in the reformer. However, process gas from 1113 exit is normally used as long as Methanator is in line. Purge gas from recovery unit is not being used as Hydrogen source. Line is kept isolated permanently. Due to formation of ammonium sulphate which will form sludge.

2) Inform Control Room operator and line up PCV 0201. Set it at 18 KSCG pressure on AUTO.

3) Take Hydrogen feed through 1133 into the system. Drain up condensate at 1133-drain flow indication. Pressurize the system to 15(18) Kg/cm²g.

4) Check FC 1105 opening and keep it on neutral position to facilitate to operate at hand jack and from control room.

5) Commission PCV 1110 and put the controller on AUTO.(manual mode)

III. Establishing stripper circulation

1) Confirming that FCV 1103 isolation valves are closed and the drain upstream FCV 1103 is kept open to prevent premature entry of naphtha into the reactor.

2) Close 1102 liquid outlet isolation valve.

3) Close the isolation valve at the sweet naphtha product line going to 1203.

4) Open isolation valve on slop naphtha line downstream of LCV 1106 : Can be done even after getting level in stripper.

5) LCV 1106 to be kept closed manually in field.

6) Line up CWS/CWR to 1504.

Page 179: Ammonia Manual

Ammonia Plant Operating Manual 26

7) Start raw naphtha pump and take naphtha to stripper through start-up circulation line upstream of FCV 1103. Adjust the valve opening to get 10 TPH of flow (slop line capacity is 10 tph). Once level appears in 1103 gauge glass, commission LCV 1106 and send the naphtha to slops. Unless stripper pressure is maintained above 4 KSCG, naphtha will not flow back to the tank.

8) Check FQ 1103 for flow indication.

IV. Hydrogen Circulation and reactor bed heating up

A. Hydrogen Compressor (3101) Start-up

1) Check that oil level in the crankcase is above refill mark.

2) Line up CWS/CWR for lube oil cooler, cylinder jacket cooling and gland cooling. Ensure that enough cooling water flow is maintained in glands. If necessary, clean the filter elements.

3) Start the lube oil pump. Maintain lube oil filter DP less than 1 KSCG.

4) Inform Control Room and ask the Control Room operator to reset the hydrofiner trip condition (Reset No 3). HC 1118 shall be kept open.

5) Pull the commissioning button in the local panel for start-up of the compressor. Check that all trip conditions are healthy.

6) Open compressor suction and discharge valves. Open block valve downstream of FX 1104 in the Hydrogen line.

7) Keep the manual loaders of the cylinder in unloaded condition and start the compressor. Load the valves. Check for flow in FI 1104.

8) Line up cooling water to 1506 after the shell side pressure reached 4 kscg

B. Catalyst bed heating up

1) Line up atomizing steam and purge the individual burners and ensure the draft is established.

2) Keep TCV 1102 in 50 % open condition.

3) Keep the chimney damper full open .(now it is always in open condition).

4) Light one burner, adjust the firing rate to get 40 C per hour heating up rate.

V. Naphtha feed introduction

1) Catalyst bed temperature shall be raised at 40 C per hour.

2) Watch the bed temperatures.

Page 180: Ammonia Manual

Ammonia Plant Operating Manual 27

3) When all the 12 points in the bed and 1101 outlet temperature also reach 270 C, the catalyst is ready to receive naphtha.

4) Open block valves of FCV 1103. Close the drain valve upstream of FCV 1103.

5) Light additional burner in 1431. Open FCV 1103 on manual and introduce feed to 1101 at slow rate (2 tph). Do not allow the catalyst bed temperature to drop below 270 C at any point. It will cause the naphtha to condense inside the catalyst bed, naphtha saturation temp is 250 c.

6) Once level appears in 1102, LCV 1104 can be lined up.

7) When the feed rate to reactor reaches more than 50% of the design flow, close the globe valve on the startup line to stripper by matching the initial flow through the LC 1106.

8) Stripper bottom product is sent back to raw naphtha tank through slop line till attain the quality.

9) Maintain a minimum of 60 % of the normal flow rate to the reactor. If the catalyst is fresh, it takes 24 - 48 hours for the desulphurisation to attain its activity fully. It also depends on the Sulphur content of the feed.

10) Stripper column reboiling temperature is adjusted by TCV 1118 B. While adjusting TCV 1118 B and HCV 1118 ensure that pressure exit 1101 does not increase.

11) Start corrosion inhibitor pump after establishing level in the tank. About 500 ml of corrosion inhibitor is required for every 24 hours. Use the agitator to mix the corrosion inhibitor with naphtha.

11.5 NORMAL SHUTDOWN

1) Reduce the naphtha feed rate to 12 TPH gradually. While doing so, one burner in 1431 may have to be cut off.

2) Cut off feed to hydrofiner. Close FCV 1103 manually. Inform the field operator to close FCV 1103 block valves and open the drain valve upstream of FCV 1103.

3) Isolate the valve in the product line to 1203.

4) Open the 3" valve in the start-up line to the stripper and maintain stripper circulation rate at 10 TPH through slops.

5) Continue to circulate Hydrogen gas across the reactor and keep one burner in 1431 and gradually reduce the bed temperature of 1101. Bed temperature shall not be reduced unless FCV 1103 is positively isolated and bleed open.

6) Residual naphtha in the reactor section will be removed during circulation and it will be collected in 1102. As LCV 1102 is in control, collected naphtha will be pushed back to raw naphtha tank through 1103.

7) Once 1101 bed temperature drops below 170 0C all burners in 1431 may be cut off and reactor cooling is further continued with Hydrogen circulation.

Page 181: Ammonia Manual

Ammonia Plant Operating Manual 28

8) After cutting off all burners in 1431, purge out all burners with steam. After purging out, isolate atomizing steam.

9) When bed temperature of 1101 comes below 70 0C, Hydrogen circulation may be stopped.

10) Before starting depressurizing of the system, push out remaining liquid naphtha from 1102 and 1103.

11)After confirming that liquid naphtha from 1102 has been pushed out fully, close LCV 1102 on manual and isolate it.

12) Stop corrosion inhibitor pump (3218) and isolate it.

13) Stop stripper circulation and push the stripper bottom naphtha, to tank under column pressure.

14)After stopping hydrogen compressor, allow the lube oil pump to run for an hour, to cool the bearing, cross head, distance piece, etc.

15) If it is required to depressurize the system for maintenance job or decoking of 1101, proceed as follows :

isolate cooling water to 1504, 1506 & 1508.

depressurize 1101 through FCV 1105 to about 0.5 KSCG.

depressurize stripper section through PCV 1110 to about 0.5 Kg/cm²g.

Remove the slip plate in Nitrogen inlet line to 1431/ Hydrogen gas compressor 3101.

Purge the entire unit with Nitrogen till hydro carbon content is less than 500 ppm and Hydrogen concentration comes below 0.2 %.

keeping a small Nitrogen bleed through 1101 "From 1431 outlet Nitrogen connection" provide slip plates at 1101 inlet and outlet flanges. Then the equipment other than 1101 can be released for maintenance jobs.

for decoking operation, refer to decoking procedure.

Note : Without reoxidation of the catalyst, 1101 catalyst shall not be exposed to atmosphere, since it is pyrophoric.

11.6 EMERGENCY SHUTDOWN PROCEDURE

1. Electric Power Failure

This causes the shutdown of raw naphtha pumps and Hydrogen compressors, in effect tripping the entire section. Following actions occur automatically :

1) Flame in 1431 is cut off. 2) TCV 1102 & XCV 1101 closes.3) FCV 1103 closes.

Page 182: Ammonia Manual

Ammonia Plant Operating Manual 29

4) XCV1102 & XCV 1111 closes.5) FCV 1105 closes.

Actions :

Control Room Operator has to take TCV 1102, FCV 1103 & FCV 1105 on manual and bring the air signal to zero. Field operator has to isolate FCV 1103 and open the drain upstream FCV 1103. Isolate fuel to 1431. Raw naphtha to fuel naphtha jump over block isolation valves, sweet naphtha product to 1203, LCV 1102 isolation valves are also to be closed. Lube oil pumps of Hydrogen compressor should be started when emergency power becomes available. Compressor should be unloaded.

If power failure is of short duration, then quickly establish start-up circulation in 1103 and Hydrogen circulation across reactor section. This avoids condensation of naphtha inside 1101. Light up one burner in 1431 after getting clearance from Control Room. If power failure is prolonged, then depressurize the reactor section slowly through FCV 1105 (open on hand jack) to keep a purge through reactor 1101.

2. Total Plant trip (plant A trip CW failure , FN trip & IA failure)

Unless the cause of these trips is not rectified, Hydrogen compressors cannot be started. Raw naphtha pump continues to run. If IA fails and it is not resumed soon, open FCV 1105 on hand jack to keep a purge through 1101. Other actions are similar to electric power failure trip. After restoring normality in the trip initiations, proceed as before.

Since Main Plant has also tripped, no feed gas is available for restarting. Proceed as per normal shutdown procedure.

3. Hydrofiner push button trip G

This is an emergency trip on hydrofiner alone. The trip actions are similar to Case of electrical power failure. If Hydrogen circulation cannot be established for any reason keep a purge through 1101, if possible.

4. Hydrogen Compressor Trip

Cause of this trip are :

a) Naphtha K.O drum level high - Trips both the compressors. (80%)

b) Gas discharge temperature high - Trips individual compressors. (95 C)

c) Lube oil pressure low - Trips individual compressors. (0.8 ksc)

d) Lube oil temperature high - Trips individual compressors. (75 C)

e) All Process trips as mentioned above.

When only one compressor trips, reduce the feed input to 16 TPH. Do not maintain high feed rate (more than 70 % of the feed rated capacity) as the Hydrogen partial pressure required for Sulphur removal may not be adequate.

Page 183: Ammonia Manual

Ammonia Plant Operating Manual 30

When both the compressor trips, following actions take place automatically :

a) FCV 1103 is closed.b) FCV 1105 is closed.c) XCV 1101 and TCV 1102 are closed. d) XCV 1102 & XCV Actions are similar to Case 1.

If compressors had tripped on 1102 high level, bring down the level. Quickly start back the compressors and establish Hydrogen circulation and stripper circulation. Get the concurrence of Control Room Operator and light 1431.

V. 1431 Flame Failure

For this trip, only XCV 1101 and TCV 1102 close.

Actions :

Field operator should quickly relight and establish atleast one burner. If the trip is due to defects in flame scanner circuit/burner etc., proceed with normal shutdown procedure.

Control Room operator can reduce feed rate immediately to the required extent but never less than 50 %. If bed temperature cannot be maintained above 260 0C and/or if heater outlet temperature has dropped to 260 0C, cut off the feed completely.

11.7 1431 DECOKING AND 1101 CATALYST REGENERATION

1. Preparatory Jobs

Instrument

Check calibration of following instruments :

a) Flowmeter in service air line 0-160 Nm3/hr

b) Flowmeter in process air line (Dual range)

Low range 0-840 Nm3/hr

High range 0-4200 Nm3/hr

c) Flowmeter in steam line.

d) PCV 1122 in process air line and FCV 1101 in steam line and FCV 1102 in air line must be stroke checked.

Mechanical

Slip plates to be removed from Nitrogen lines at 1431 inlet and reactor inlet.

Elbows are to be swung in the following places.

Page 184: Ammonia Manual

Ammonia Plant Operating Manual 31

a) 1431 inlet line swing elbow.

b) 1101 outlet swing elbow.

2) Blinds are to be fixed in the open flanges.

3) Slip plate is to be put in FCV 1103 isolation valve downstream flange.

4) 1431 guns are to be cleaned.

5) Sampling provision is to be made at the reactor oulet line drain point.

II. Procedure for regeneration

1) Cut off feed to reactor and cool down the reactor to ambient conditions using Hydrogen compressors.

2) Purge the reactor and stripper sections using Nitrogen.

3) Keeping a Nitrogen purge to reactor, swing elbows at 1431 inlet and 1101 outlet for regeneration. Blinds are to be fixed in open flanges.

4) Line up circuit for regeneration. Admit Nitrogen at maximum possible rate through reactor / heater circuit to vent and light 1431. Bring up bed temperature above 125 0C at the bottom most point.

5) Introduce CW through the spray nozzles located in the inlet line to quench separator.

6) Cut in steam and keep a flow rate of 4 TPH and cut off Nitrogen completely. Increase the bed temperatures to 400 0C at 40 C/hr. Keep reactor inlet temperature at 400 0C maximum.

7) Slowly introduce air at the rate of 100 Nm3/hr through the service air line. Watch catalyst bed temperature. If temperature at any point tends to increase beyond 480 0C, reduce or cut off air flow. Analyse combustion gases for O2, CO & SO2 contents every hour. 1431 coil skin

temperature are to be monitored and visual observations of the coils are to be made for any local hot spot.

8) If temperature raise is under control, increase air flow in small increments of 50 Nm3/hr limiting maximum temperature of 480 0C.

9) Line up process air header and keep a pressure of 3 KSCG in the header downstream of PCV 1110.

10) Switch over air feed from service air to process air. Keep the low range flow meter ( 0

- 840 Nm3 ) in line.

11) Keep air flow of 250 Nm3/hr (corresponding to 1 % O2 with 4 TPH steam flow). If reactor

bed temperature decrease, gradually increase bed temperature to 450 0C at 40 0C C/hr, keeping the maximum bed temperature at 480 0C.

Page 185: Ammonia Manual

Ammonia Plant Operating Manual 32

12) Slowly increase air rate to 1000 Nm3/hr( 3% O2 )and steam rate to 5 TPH. If CO2 content in

the exit gas is 0.2 % increase the inlet temperature to 480 C confirming that there is no temperature increase in bed. Whenever bed temperature exceeds 480 0C, reduce/cutoff air flow to control the temperature.

13) If there is no fresh combustion, increase air flow to 2400 Nm3/hr(8% O2) for oxidation.

Keep air flow of 3500 Nm3/hr and 480 0C inlet temperature for 4 hours and confirm analysis of CO2/O2/SO2 etc. Until oxidation is completed limit maximum temperature to 500 0C.

14)Decrease reactor temperature at the rate of 40 C/hr to 250 0C. Cut off heater and cut off steam. Slowly cool the reactor to ambient temperature keeping the air flow.

Note : Max. bed temperature during regeneration is 480 0C. Max. bed temperature for oxidation is 500 0C. 15) After cooling down, clearance can be given to open the reactor top manhole for inspection of the catalyst.

Page 186: Ammonia Manual

Ammonia Plant Operating Manual 33

10 Chapter Twelve EMERGENCY TRIP SYSTEM

The Emergency Trip System in Ammonia Plant automatically shuts down the plant or sections of the plant, when process conditions deviate from normal operating values to such an extent that hazardous conditions can arise or damage can be done to the plant / personnel.

Generally, trip initiation is preceded by an alarm, which alerts the operator to take corrective action and rectify the situation before the trip takes place. Following are the details described in this section :

1. Description of the trip interlock system.

2. The various trip initiators in the trip panel (totally 64 Nos) and corresponding trip actions that will take place automatically. Related reset groupings also are indicated.

3. Certain features of trip panel relevant to operation.

4. The various emergency actions to be taken immediately after a trip by various area operators.

5. Reset procedure.

6. Guide lines to be followed in case a restart is possible, immediately, after rectifying the cause, which must be read in conjunction with the appropriate sections of normal start-up procedure.

12.2 TRIP INITIATORS AND AUTOMATIC TRIP ACTIONS

A.Total Plant Trip

Initiators

1. Instrument air pressure low - PA 0217

2. Cooling water pressure low - PA 0222

3. Push button trip 'A'.

Trip Actions Corresponding Reset No.

1. a) XCV 1902 closed Ammonia exit sphere 1 b) XA 1905 A & B Amm feed pumps stopped 1

Page 187: Ammonia Manual

Ammonia Plant Operating Manual 34

Trip Actions Corresponding Reset No.

2.a) XA 1107 A & B H2 Compressors stopped 3

b) XA 1104 Tripped fuel to 1431 3

c) FCV 1105 closed hydrofiner off gas 3

d) FCV 1103 closed Raw naphtha to Hydrofiner 3

3.a) XA 0112 Aux Boiler 'A' shutdown 4

b) XA 0113 Aux.Boiler 'B' shutdown 4

(Will not occur for C.W low pr. and push button 'A')

4.a) XA 1616 lean pump stopped 5

b) XA 1618 letdown turbine stopped 5

c) XA 1617 Semilean pump stopped 5

d) Closed solution to letdown turbine 5

e) FCV 1602 closed semilean solution to absorber 5

f) HCV 1702 closed water to 1119 5

g) FCV 1603 closed lean solution to absorber 5

5.a) XA 1320 ID north stopped 6

b) XA 1318 FD north stopped 6

c) XA 1321 ID south stopped 6

d) XA 1319 FD south stopped 6

e) XCV 1303/XCV 1307 closed fuel to furnace 6

6.a) XA 1204 tripped fuel to 1432 7

b) FCV 1304 cut back process steam 7

(This action will take place only for

Page 188: Ammonia Manual

Ammonia Plant Operating Manual 35

Instrument Air pressure low trip)

Trip Actions Corresponding Reset No.

c) FCV 1204 closed recycle H2 to 1432 7

d) FCV 1203 closed liquid feedstock to 1432 7

e) FCV 1303 closed vapour naphtha to reformer 7

7. XA 0205 degassed process cond. to drain 8

8.a) XA 0114 PAC shutdown 9

b) HCV 1408 opened process air to vent 9

c) XA 1404 tripped fuel to 1433 9

d) PCV 0223 closed process/Inst. air system 9

9. XCV 1602/4 closed & XCV 1603 opened 10 air to Absorber

10.a) FCV 1501 closed steam to HT shift 11

b) FCV 1401/XCV 1406 closed. XCV 1405 11 opened. Air to Sec Reformer isolated and blanketted.

11. XCV 1501 A/B closed gas to methanator 12

12. XA 1804 tripped fuel to 1434 13

13. XA 1819 LRC stopped 14

14. PCV 0104/FCV 0107 steam system actuated 15

(It is actuated through XA 0107 and SGC trip system)

15. XA 0115 SGC stopped 16

16. PCV 0224 closed recycle H2 from SGC 17

Trip Actions Corresponding

Page 189: Ammonia Manual

Ammonia Plant Operating Manual 36

Reset No.

17. HCV 1801/XCV 1814 closed 18 gas to 1434 isolated

18. HCV 1302 closed purge gas to reformer 19

19. XA 1820 HWP shutdown 21

20. PGHRU section tripped 22

21. Ammonia Importation section tripped 23

(This will not occur for CW low pressure trip)

B.Fuel Naphtha Trip

Initiators

1. Furnace top push button trip. - XA 1316 (Provided at three places namely Furnace top, peepholes floor and at the bottom of 1510

southern side.)

2. Furnace pressure high - PXH 1313

3. Fuel naphtha flow to furnace low - FXL 1302

4. Combustion air pressure low - PXL 1310

5. Atomising steam pressure low - PXL 1320

6. Steam drum level low - LXL 1306

7. Steam feed stock ratio low - FFXL 1303

8. Liquid feedstock flow low - FXL 1203

9. Process naphtha vapouriser - TXL 1205 outlet temperature low

10. Primary reformer outlet - TXL 1314 gas temperature low

11. Recycle H2 to 1432 flow low - FXL 1204

12. Push button trip B

Page 190: Ammonia Manual

Ammonia Plant Operating Manual 37

As PXL 1310, PXL 1320, LXL 1306, TXL 1205, TXL 1314 and FXL 1204 are normally kept in bypass, manual trip must be taken when conditions reach trip value.

Fuel Naphtha Trip Actions Corresponding Reset No.

1.a) XA 1107 A & B H2 Compressors stopped 3

b) XA 1104 Tripped fuel to 1431 3

c) FCV 1105 closed hydrofiner off gas 3

d) FCV 1103 closed R.naphtha to Hydrofiner 3

2. XA 1303, XA 1307 closed fuel to furnace 6

3. a) XA 1204 tripped fuel to 1432 7

b) FCV 1204 closed recycle H2 to 1432 7

c) FCV 1203 closed liquid feedstock to 1432 7

d) FCV 1303 closed vapour naphtha to reformer 7

4.a) HCV 1408 opened process air to vent 9

b) XA 1404 tripped fuel to 1433 9

c) PCV 0223 closed process/Inst air system 9

5. XCV 1602/4 closed & XCV 1603 opened 10 air to Absorber

6.a) FCV 1501 closed steam to HT shift 11

b) FCV 1401/XCV 1406 closed XCV 1405 opened 11 Air to sec. reformer isolated.

7. XCV 1501 A/B closed gas to methanator 12

8. PCV 0104/ FCV 0107 steam system actuated 15 (Actuated through XA 0107 and SGC trip system)

Fuel Naphtha Trip Actions Corresponding Reset No.

Page 191: Ammonia Manual

Ammonia Plant Operating Manual 38

9. XA 0115 SGC stopped 16

10. PCV 0224 closed recycle H2 from SGC 17

11. HCV 1302 closed purge gas to 1400 19

12. XA 1820 HWP shutdown 21

13. PGHRU section tripped 22

C.Secondary Reformer Trip

Initiators

1. Process Air Compressor shutdown - XA 0108

2. Gas exitsecondary reformer high temperature - TXH 1405

3. Sec.reformer air inlet differential pressure low - PDXL 1405

4. Process air to secondary reformer low flow - FXL 1401

5. Push button trip 'C'.

6. Vapour Naphtha flow to 1400 low - FXL 1303

FXL 1303 is kept on bypass normally.PDXL 1405 is kept in line during air cut in and at lower plant load. FXL 1401 is taken in line when plant load is more than 18 TPH and PDXL 1405 is bypassed.

Trip Actions Corresponding Reset No. 1.a) HCV 1408 opened process air to vent 9

b) XA 1404 tripped fuel to 1433 9

c) PCV 0223 closed process/Inst. air system 9

2. XCV 1602/4 closed & XCV 1603 opened 10 air to Absorber

(This gets reset by pressing 9 itself for secondary reformer trips alone)

Trip Actions Corresponding Reset No.

3. FCV 1401/XCV 1406 closed XCV 1405 opened 11 Air to sec. reformer isolated.

Page 192: Ammonia Manual

Ammonia Plant Operating Manual 39

4. XA 1804 tripped fuel to 1434 13 5. XA 0117 gas from SGC stopped 16

6. XA 1820 HWP shutdown 21

7. PGRU section tripped 22

When Secondary reformer trip is initiated through initiators other than PAC , then reset 9A is to be pressed for loading PAC for instrument air service.

D.Methanator Trip

Initiators

1. Methanator high temperature - TXH 1516

2. Push button trip 'D'.

3. Absorber level low - LXL 1605

LXL 1605 is kept bypassed normally. Push button trip 'D' to be taken when situation warrants.

Trip Actions Corresponding Reset No.

1. XCV 1602/4 closed & XCV 1603 opened 10 air to Absorber

2. XCV 1501 A/B Gas to methanator closed 12

3. XA 1804 tripped fuel to 1434 13

4. XA 0117 Gas from SGC stopped 16

5.a) PCV 0224 closed recycle H2 from SGC 17

b) XCV 1205 opened H2 from storage 17

Trip Actions Corresponding Reset No.

6. XA 1820 HWP shutdown 21

7. PGHRU section tripped 22

E.Hydrofiner Trip

Page 193: Ammonia Manual

Ammonia Plant Operating Manual 40

Initiators

1. Both Hydrogen compressors shutdown - XA 1105

2. Electric power failure I - XA 0109A

3. 1431 flame failure - XA 1104

4. Push button trip 'G'.

XA 1104 is normally kept on bypass. But fuel cut off to 1431 takes place even if it is bypassed, with 5 seconds time delay.

Trip Actions Corresponding Reset No.

a) XA 1107 A & B Hydrogen compressors stopped 3

b) XA 1104 tripped fuel to 1431 3

c) FCV 1105 Closed Hydrofiner off gas 3

d) FCV 1103 Closed R.Naphtha to Hydrofiner 3

After trip 'G' initiation and XA 0109A initiation, when the initiation is made healthy, Reset No : 3 is to be pressed to start H2 compressor. Then XA 1105 vanishes. No. 3 has to be reset again to

open control valves.

F.Product Ammonia shutdown

Initiator

a) Push button trip 'F '

Trip Actions Corresponding Reset No.

a) XCV 1902 Closes NH3 exit sphere 1

b) XCV 1905 A & B NH3 feed pump stopped 1

c) Push button trip 'F ' Used in case of emergency arising out of ammonia leak downstream Horton Sphere. Separate push button trips are provided to take shut down of ammonia importation site also.

Page 194: Ammonia Manual

Ammonia Plant Operating Manual 41

G.Degassed Condensate Trip

Initiators

1. Push button trip 'I'.

2. Degassed condensate temp. high - TXH 0209.

Trip Actions Corresponding Reset No.

a) XCV 0205 Opened condensate to CT sump 8

Trip 'I' shall be taken as a part of fuel naphtha trip actions.

H. Boilers trip

Initiators

Push Button Trip 'J, K, L'

This provision is given to trip both Auxiliary Boilers (S) & (N) and ASGU respectively. This will be useful during failure in BFW system and during emergencies in boiler which requires remote trip.

I.Ammonia Converter Start-up Heater Trips

Initiators

1. Gas to Ammonia converter start-up heater low - FXL 1810.

2. Start-up heater flue gas temperature high - TXH 1801

3. Start-up heater exit gas temperature high - TXH 1802

4. Flame failure - XA 1804

5. Push button trip - H

6. Local push button trip - XA 1818

Trip Actions Corresponding Reset No.For all the initiators

XA 1804 Fuel to 1434 cut off 13

In addition to the above,for TXH 1801, trip H and local trip.HCV 1801/ XCV 1814 closed Gas to 1434 isolated 18

Note : For flame failure XA 1805, Rest 13 is not required. FXL 1810 is normally kept on bypass.

Page 195: Ammonia Manual

Ammonia Plant Operating Manual 42

J.Synthesis loop shutdown : PGL 3 & 4

Initiators

1. LRC shutdown - XA 1816

2. Push button trip 'E' (for LRC shut down through LXH 1803)

3. Secondary chiller level high - LXH 1803

4. Ammonia catch pot level high - LXH 1812

5. HP suction pot level high - LXH 1808

6. Local PGL - 3 trip

Trip Actions Corresponding Reset No.

a) XA 0117 Gas from SGC stopped 16

b) XA 0118 Gas to circulator stopped 16

c) XA 1820 HWP shutdown 21

e) PGHRU section tripped 22

In addition to the above, for LXH 1803 and LXH 1808

XA 1819 LRC stopped also will be initiated 4

K.PGL 2

Initiator

1113 High level high - LXH 1505

Trip Actions Corresponding Reset No.1. XA 1804 tripped fuel to 1434 13

2.a) XA 0116 Gas to SGC stopped 16

b) PCV 0224 Closed recycle H2 from SGC 17

Page 196: Ammonia Manual

Ammonia Plant Operating Manual 43

c) XCV 1205 Opened H2 from storage 17

d) XA 1820 HWP shutdown 21

e) PRHRU section tripped 22

L.Electric Power failure - XA 0109A & XA 0109B

When there is no power available in TP 30, TP 31 and TP 32 transformer secondaries, the under voltage relays in TP 30, TP 31, TP 32 senses undervoltage. If all the three senses the undervoltage of 144 V simultaneously XA 0109A Electric failure is initiated.

Trip Actions Corresponding Reset No.

a) XA 1107 A & B H2 Compressors stopped 3

b) XA 1104 Tripped fuel to 1431 3

c) FCV 1105 Closed Hydrofiner off gas 3

d) FCV 1103 Closed R.Naphtha to Hydrofiner 3

e) HCV 1702 Closed water to 1119 5

These above trips are initiated by XA 0109A

f) XA 1819 LRC stopped 14 *

g) XA 1804 tripped fuel to 1434 13 *

h) XA 0117 Gas from SGC stopped 16 *

Trip Actions Corresponding Reset No.

i) XA 0118 Gas to circulator stopped 16 *

j) XA 1820 HWP shut down 21

k) PGHRU section tripped 22

* Important Note

There is a provision to bypass XA 0109B. It is normally kept bypassed due to availability of 830 KVA DG set. Even if the trip is in line, these actions occur only after one minute time delay. If bypass is removed after one minute, actions will instantaneously occur . Trip initiator lamps will

Page 197: Ammonia Manual

Ammonia Plant Operating Manual 44

appear irrespective of the bypass key position. In case both 830 KVA DG set and TG-I are not available during power failure, this trip must be taken in line.

M.Synthesis Gas Compressor Shutdown XA 0107

Trip Actions Corresponding Reset No.

PCV 0104 / FCV 0107 Steam system actuated 15

Apart from this, ESVs and FCVs action will occur as described in SGC section.

N.Reformer ID or FD fan trip

For any ID or FD fan trip, corresponding FD or ID fan will be tripped. Dampers of both tripped fans will be closed.

PCV 1305 cut back naphtha to furnace will be actuated. The plant load should be reduced immediately to 14 TPH sweet naphtha rate and stabilised.

For above actions Reset No : 6

HCV 1302 Closed purge gas to reformer Reset No. 19

O.Semi lean solution flow low trip - FXL 1602

Trip Actions Corresponding Reset No.

a) Semilean solution pump stopped 21

b) FCV 1602 closed 21 (This trip is normally kept bypassed)

P.Lean solution flow low trip - FXL 1603

Trip Actions Corresponding Reset No.

a) Lean solution pump stopped 22

b) FCV 1603 closed 22 (This trip is normally kept bypassed)

Q.1432 & 1433 Flame Failure

When the scanner senses no flame for 5 seconds, fuel valves will be closed. No reset is required from trip panel. Pressing 'Main Flame Start' at local panel, relighting can be done.

R.Lean sump low level trip - LXL 1611

Page 198: Ammonia Manual

Ammonia Plant Operating Manual 45

This trip is provided to save the lean pump from starvation and hence to avoid CO2 slippage from absorber because of lean flow failure.

Semilean sump level low trip - LXL 1612

This trip is provided to save the semilean pump from starvation and hence to avoid CO2 slippage from absorber and because of semilean solution failure. Further this prevents lower part of the LP regenerator running dry.

Trip Actions Corresponding Reset No.

1.a) XA 1616 lean solution pump stopped 5

b) XA 1618 led down turbine tripped 5

c) XA 1617 standby semilean solution pump stopped 5

d) Closed solution to letdown turbine 5

e) FCV 1602 closed semilean solution to absorber 5 f) FCV 1603 closed lean solution to absorber 5

2. XCV 1602/4 closed & XCV 1603 opened 10 air to Absorber

3. XCV 1501 A & B closed gas to methanator 12

Trip Actions Corresponding Reset No.

4. XA 1804 tripped fuel to 1434 13

5. XA 0117 gas from syn compressor stopped 16

6. a) PCV 0224 closed recycle from SGC 17

b) XCV 1205 opened H2 from storage 17

7. XA 1820 HWP plant shut down 21

8. PGHRU section tripped 22

Normally these trips are provided with bypass key provision and they are kept on bypass mode.

S.HWP Shutdown

Page 199: Ammonia Manual

Ammonia Plant Operating Manual 46

Only annunciation will occur at trip panel. No action by trip panel.

T. HF make up gas low flow - FXL 1107 Reformer purge gas fuel low flow - FXL 1301 Boiler feed water pressure low - PXL 0228 Let down turbine shut down - XA 1613

The above trips are kept bypassed normally.

Thus, various trip actions that will automatically take place for 64 initiators are described above. Manual actions to be taken immediately after trip are described in the table under "Emergency Actions during Plant trips".

12.3 FEATURES OF TRIP PANEL RELAVENT FOR OPERATION

1. Two limit switches are provided in FCV 1303. One switch is used for trip output lamp indication. The other switch is connected in series in the signal to close FCV 1304 during total plant trips. Thus availability of FCV 1304 is ensured, if FCV 1303 fails to close protecting reformer from low steam/carbon ratio.

2. PXH 1313 - Annunciation will occur as soon as the furnace pressure reaches trip value. Actions will occur, if it persists for 5 seconds.

3. seconds time delay is provided in the signal to close XCV 1406, to purge out air by blanketing steam in the air inlet line.

4. A limit switch at ESV 102 will initiate HWP shutdown whenever the valve closes.

5. Steam system Actuated - Reset 15.

XCV 0102 A & B opening is initiated by PAL 145, Governor oil low pressure switch of SGC, whereas FCV 0107 closing will be initiated by XA 0107. FCV 0107 closing will take 80 seconds from the present opening. Similarly, XCVs will get reset when PAL 145 is healthy, and FCV 0107 by pressing Reset 15. It is wise to take, XA 0107 trip in line as soon as SGC reached MGS.

It may be relevant here to know the function of PAL 145. Whenever SGC shutdown is initiated by main trip panel (PGL I) or local panel. Solenoid valve No. 100 is de-energised. This leads to draining of governor oil through a pneumatic actuator. Oil draining leads to closure of MSV and initiation of PAL 145. PAL 145 sends signal to close all ESVs, open all FCVs, open JCV 103, open XCV 0102 A & B and send signal to main trip panel to initiate XA 0107, which will actuate closure of FCV 0107 in a slow mode. Because of this 45 Kg/cm²g steam header pressure will be controlled smoothly by PC 0104 during SGC trips.

6. To prevent compressors from possible surging, due to remote resetting, local reset buttons also have been provided in series, in SGC and PAC panels. Ensure signals to FCVs are zero, before attempting local reset. FCVs can be operated only after this local reset.

7. When local push button trip for Ammonia Converter start-up heater was used, Reset 'H' shall be used to cancel the initiator.

Page 200: Ammonia Manual

Ammonia Plant Operating Manual 47

8. For all trips leading to the closure of FCV 1303 will close HCV 1306 also. This action can be reset by pressing reset 7.

12.4 TRIP PANEL RESET PROCEDURE

1. Never reset trip panel without clearance from shift engineer.

2. Remember reset is a planned action and never do it in hurry, without ensuring completion of secondary actions.

3. But 'Reset 9 A' can be pressed at the earliest, whenever a trip initiates unloading of PAC, so that, compressor operator can load back PAC for instrument air service. 'Reset 9 A Actuated' annunciation will appear in PAC local panel, when 9A is reset. After blowoff valve reset, machine can be loaded. This reset makes PCV 0223 also available for operation.

Remember 'Reset 9 A' can be used for only loading PAC when it runs unloaded on a trip. It cannot be used to restart PAC, during total plant trips. When 'Reset 9' is pressed, Reset 9A will get cancelled with one second off time delay circuit.

4. To enable reset, get the initiation cancelled, by one of the following three ways :

a) Press push button reset to cancel push button trip initiation.

b) Normalise the process parameter, to normal value for trips like high temperature or high pressure, etc.

c) Use the bypass key to cancel the initiation wherever recommended, like low flow trips.

5. When initiation is made healthy as described above, reset is to be done in the numerical sequence in which they got initiated. (Refer Section I). Reset shall be done one by one, or as required as per the progress in start-up.

6. There is a bypass key provision to bypass the reset sequence interlock. There will be no necessity to use it, for routine trip check and shutdown maintenance. Ensure it is always in line. Under special circumstances, get clearance from Shift Engineer for operation of this key.

12.5 TAKING TRIPS IN LINE

1. Never take a trip in line, without clearance from the Shift Engineer.

2. Before commencing start-up activities of the plant, do the "Trip Check of Trip panel" for various initiators. Check actuation of control valves, annunciation at Control Room, Boiler and Compressor House, trip output lamp indications and timer operations wherever applicable. Maintain close co-ordination with Instrument Department during trip check.

In most of the occasions, Trip check may have to be done when following sections of the plant are alive.

a) Boilers running, to keep steam system alive.

b) PAC running to keep instrument air system alive.

Page 201: Ammonia Manual

Ammonia Plant Operating Manual 48

c) Ammonia feed pumps running to meet requirement of DAP plants.

Relevant actions may have to be bypassed to keep these sections alive without tripping, during Trip check.

To simulate certain initiations, instrument connections may have to be disconnected. Scanners action in fired heaters will be bypassed during Trip check, to facilitate actuation of fuel valves in fired heaters.

Ensure all these connections are normalised on completion of Trip check and before commencing start-up activities.

Before taking the trip do the lamp test. If the lamp is healthy during test condition alone, it indicates that the trip initiator has become healthier. Ensure that the trip initiator is reasonably above the trip value and take the trip in line. In case of triple redundant trip initiator ensure that all the inputs are above trip value.

3. Among the 64 initiators in Trip panel, 30 initiators have bypass key provision. Rest of the trips must be in line before starting the plant. Generally, following will be the sequence of taking trips in line during plant start-up.

Take 'XA 0108 - PAC shutdown' trip in line as soon as PAC reaches its minimum governor speed.

Take ID & FD fans trip in line as soon as the corresponding set is paralleled.

c)PXH 1313 trip must be taken in line before lighting the reformer.

Before lighting reformer, ensure following trips are in line :

1. XA 1311, 2. XA 1312, 3. XA 1313, 4. XA 1314, 5. PXH 1313 6) XA 0108.

4. Take FFXL 1303 steam/feedstock ratio Trip in line when start-up compressor is stopped, after admitting naphtha to reformer. In case of a immediate restart without start-up compressor, this trip can be taken in line, before admitting naphtha to reformer.

5. Take FXL 1302 fuel naphtha to furnace low flow trip in line, when feedstock rate is stabilised at 40 % plant load and fuel naphtha spill back at reformer is closed fully.

6. Take PDXL 1405 trip in line before cutting in air to secondary reformer.

7. Take FXL 1203 Liquid feedstock low trip in line when feedstock rate is stable above 40 % plant load.

8. Take XA 0107 trip in line as soon as SGC reaches its minimum governor speed.

9. Take XA 1816 trip in line as soon as LRC reaches its minimum governor speed.

10. When plant load is above 18 TPH, and 1433 exit temperature is above 400 C, take FXL 1401 trip in line after checking impulse lines of the flow transmitter. PDXL 1415 shall be bypassed after taking FXL 1401 in line.

Page 202: Ammonia Manual

Ammonia Plant Operating Manual 49

12.6 GUIDELINES TO BE FOLLOWED FOR RESTART

A.CONTROL ROOM PUSH BUTTON TRIP A

1. Reformer Exit temperature more than 500oC Rereduction not required.

a) Ensure that cooling water pressure is normal. Start PAC and line up for instrument air service. Reset the trip panel Reset 1 and get XCV 1902 opened for running IG plant. Start Ammonia feed pump, in case there is any consumption by the downstream plants.

b) Reset trip panel and start ID/FD fans and set PC 1313 at -1.27 mmWC. Note that flue gas fan should be started before combustion air fan. Note, while resetting trip panel for ID/FD fans, that vetrocoke section would have been reset already. Run the wash water pump. Further fuel naphtha valves are also reset while resetting the panel for ID/FD fans. All the control valves should be in "Tripped" position before resetting trip panel.

c) Open the spillback on the fuel naphtha return header and establish fuel naphtha circulation (all the valves for individual burners are in closed condition). Ensure that isolation valves for the rows at both inlet and outlet are wide open especially for 4th and 6th rows for which the return header isolation valves would have been closed while the plant is running.

d) Relight some burners in a staggered pattern and bring the flue gas temperature up 50 C per hour. If auto ignition is not possible, switch over to ignitors immediately.

e) While taking up the reformer temperature, take up process steam to reformer to about 45 TPH. There should not be any sudden increase in steam flow to reformer as this might lead to quenching of the tubes.

f) Take up the temperature exit reformer to 760 C and check the furnace visually.

g) Before resetting the trip panel for cutting in feedstock, ensure that all the valves are in tripped condition. In the field, vapour naphtha block valve should be in closed condition and the bleed in-between FCV 1303 & its block valve should be in full open condition. Desulphuriser should have been depressurised to avoid any entry of naphtha to reformer.

h) Stabilise the primary reformer exit temperature at 760 C with about 50 TPH of process steam and about 30 burners in line well distributed, maintain midstream pressure at 20.5 Kg/cm²g.

After reset 7, establish a flow of about 600 Nm3/Hr of cracked gas from the IG plant through 1432 and 1104 bypass venting the gas at the PCV 1208 vent upstream of FCV 1303. Maintain the pressure in PC 1208 at 25 Kg/cm²g by throttling the PCV 1208. Equalise the pressure in 1104 with that in PC 1208. Ensure that cracked gas receiver pressure maintains above 35 Kg/cm²g. Light the flare.

After stabilising the flow and pressure, light one burner in 1432, keeping the ring header pressure at the minimum (about 4 Kg/cm²g). On the panel, start monitoring all the parameters

Page 203: Ammonia Manual

Ammonia Plant Operating Manual 50

concerning 1432 - flue gas temperatures, skin temperatures, process temperature and flow etc. for any abnormal change.

Line up sweet naphtha to 1432, when the highest skin temperature crosses 200 C, admit about 2 TPH of naphtha to 1432. Gradually increase the flow to 4 TPH and also raise the firing on the burner. Maintain PC 1208 at the same pressure by PCV 1208, as the flow through 1432 and the exit temperature increases.

When the temperature on TC 1205 reaches 380 C, line up 1104 completely, line up vapour naphtha to reformer and light the second burner in 1432 if necessary. Maintain ring header pressure initially at 4 Kg/cm²g and increase the sweet naphtha throughout to continue raising TC 1205 to 400 C. Ensure that all the points in 1104 and TI 1/1301 (exit of 1104) is above 377 C. 1104 bypass is fully closed and bleed should be kept opened.

Start introducing vapour naphtha to reformer gradually. PC 1208 pressure should be maintained. Control the vapour naphtha rate depending on the reformer exit temperature. Light more burners in the reformer as more and more feedstock is introduced and maintained the reformer exit temperature at 760 C throuthout.

Gradually increase sweet naphtha rate to 10 TPH and stabilise 1432 exit temperature at 400 C and reformer exit temperature at 760 C.

i) The process gas is vented through PCV 1504.

j) Vetrocoke solution circulation should have been commenced by now.

k) Transfer venting of process gas to PCV 1509.

l) Bring rest of the plant in line in accordance with the normal start-up procedure.

2. Rereduction required : Steam on to reformer.

If reformer exit temperature could not be brought up to 760 C within 4 hours after cutting of feedstock, because of steaming without feed stock, the catalyst in Primary Reformer, Secondary Reformer and HT shift catalyst get oxidised. It should be rereduced to regain its full activity.

a) The reformer exit temperature should be above 500 C and bring this temperature to 760 C and stabilise.

b) Vent process steam through PCV 1504.

c) Keep inlet, exit and bypass valves of LT shift vessel in closed condition.

d) Purge the section from LT exit to syn gas compressor suction free of H2 to less than 0.2 %

(The residual process gas before purging may be used for purging the section from FCV 1203 to FCV 1303 via start-up compressor bypassing 1104. For this the slip plates in Start up Compressor suction and discharge is to be removed).

e) Purge the feedstock header from FCV 1203 to FCV 1303 free of hydrocarbons, and hydrogen to less than 1 ppm and 0.2 % respectively.

Page 204: Ammonia Manual

Ammonia Plant Operating Manual 51

f) Do not use the process gas for purging 1104. Purge 1104 independently with Nitrogen.

g) When all the sections in start-up loop except the section from reformer inlet to PCV 1504 has been purged, pressurise with nitrogen and analyse.

h) Establish lean solution circulation.

i) Open LT shift vessel bypass and establish start-up circulation through 1112 bypass; light 1432 and bring up the exit temperature.

j) Keep the circulation rate initially to minimum possible to avoid cold nitrogen condensing steam at reformer inlet.

k) Watch reformer inlet temperature and keep the drains on feed stock header on reformer inlet open for sometime to blow out any condensate.

l) Ensure that the pressure of 1104 is less than the system pressure to prevent the possibility of hydrocarbons entering the system.

m) Inject Ammonia to Primary reformer inlet watching mixed feed temperature and PRO temperature. Cut off Ammonia if PRO drops below 760°C. Build up ammonia in steps to carry out reduction. Parallely admit recycle hydrogen from IG plant and build up enough concentration.

n) Bring up the bed temperature of 1104 above 350 C and line up.

o) After a re-reduction period of about 2-6 hours naphtha can be cut into reformer.

p) For further operations, appropriate sections in normal start up can be referred to.

3. Steam cut off to reformer :

After a trip caused by P.B. trip 'A' if reformer exit temperature has fallen below 500 C, before relighting the furnace, process steam to reformer should be cut off and further cooling should be done by nitrogen only.

After cutting off steam to reformer, steam should positively be isolated and the pressure of 1537 should be reduced below plant pressure.

Purging of the entire plant should be carried out till Hydrogen and Oxygen are less than 0.2 % respectively. Hydrocarbons should be purged away from the feedstock header, after draining, to less than 1 ppm.

After building up the system pressure with N2 circulation may be established at a minimum rate.

Keep the feed stock header drains and other low point drain in the pipe work open to blow out accumulated condensate. Circulation rate may be increased gradually.

All the steps as mentioned in the normal shutdown procedure should be carried out to cool down the plant, by starting the startup compressor. When possible to relight the furnace, normal start-up procedure should be adopted.

B.Instrument air failure

Page 205: Ammonia Manual

Ammonia Plant Operating Manual 52

The occasions when this trip occurs should be rare as there are effectively two sources of instrument air namely the process air compressor and instrument air compressor. However, there are possibilities for this trip to occur, e.g. tripping of auxiliary boilers after power failure or any other steam system upset leading to non-running process air compressor and non-availability of power to run instrument air compressors. Consequences for this trip are the same as for control room manual plant trip A but in addition there is the air failure action of the valves to consider. All the control valves fail shut on air failure except the following which fall open :

TCV 1118, PCV 1206, PCV 1205, PCV 1303, XCV 1405, HCV 1408, HCV 1605, HCV 1606, HCV 1607, HCV 1608, PCV 1705, HCV 1810, PCV 1903, LCV 0203 B, LCV 0202 B, PCV 0229, XCV 1603, PCV 2101, PCV 2111, PCV 2106, PCV 2107, PCV 2108, PCV 2109, PCV 1208, PCV 1111.

Further both Auxiliary Boilers will also trip.

Restarting procedure is same as for Plant A trip on resumption of I.A. supply. But the following points also are to be considered.

a) for taking OSB steam, FCV 0101 is to be opened on handjack.

b) for maintaining 12 ATA and 2.1 ATA steam header pressure vent control valves have to be adjusted on hand jack.

c) Water to deaerator should be through the bypass of LCV 0202 A.

d) CW supply pressure should be restored, if lost. If necessary coolers can be isolated.

C. Cooling water low pressure

This is a total plant trip as Trip 1 and actions for restarting the plant are the same as Trip 1. If there is a common fault on turbine driven units, motor driven pump should be started and coolers should be isolated to maintain 4 Kg/cm²g pressure (Aux boilers continue operation with fire water lined to L.O. cooler). BFWPs & IACs will run with fire water back up. However ASGU has to to be stopped as there is no back up for its FD fan.

D. Boiler feedwater low pressure trip

The procedure for restart of the plant is same as Trip 1 except that the first objective before restart is to establish levels in waste heat recovery system steam drum and auxiliary boiler steam drums. If level in steam drum (1106) cannot be established, steam to reformer should be cut off to conserve water in CCJT system.

E. Fuel naphtha trips

Ensure instrument air pressure, cooling water pressure, steam system and BFW system are stable. Restarting procedure is same as in Trip 1.

F.Secondary reformer trip

Possible causes :

Page 206: Ammonia Manual

Ammonia Plant Operating Manual 53

a) Process air compressor shutdown.

b) Excess air rate, or reduced vapour naphtha flow to reformer leading to high temperature at secondary reformer exit.

c) Surge in process air compressor leading to low flow trip.

d) Failure of control valves as follows :

FCV 1401 close, XCV 1406 close, HCV 1408 open or FCV-2-201 open. All these will lead to low flow trip.

Restart procedure

a) Ensure trip actions by trip panel.

b) Ensure completion of secondary actions.

c) Determine and rectify the cause.

d) Re-establish flow of process air to instrument air system and stop IACs.

e) Cut in air to secondary reformer as per normal start-up procedure (Reset 9 to 11).

f) Adjust TC 1509 back to its previous value.

g) Put air to absorber as required.

h) Stop IG units and FGC if they are running on recycle H2 duty.

i) Establish synthesis loop circulation and line up converter (Reset 16). Line up production.

j) Start PGHRU unit and recovery section.

k) Raise plant load and light up 1433.

G.Methanator Trips

Possible causes :

a) Excessive CO2 slip exit Absorber, due to one of the following reasons.

i) Poor regeneration ii) Low system pressure iii)Low specific gravity of the solution iv) Low solution circulation rate v) Foaming vi) Flooding vii)High differential pressure across absorber.

Page 207: Ammonia Manual

Ammonia Plant Operating Manual 54

b) Failure of lean or semilean pump.

c) Loss in level control at Absorber.

d) Drop in temperature of LT and possible CO slip

e) 1514 exchanger leak.

Restart procedure

a) Ensure trip actions by trip panel.

b) Ensure completion of secondary actions.

c) Determine and rectify the cause.

d) Bypass methanator and transfer venting to PCV 1509 ensuring solution circulation.

e) When CO2 analysis is satisfactory, take methanator in line and close bypass valves. Open

bleed (Reset 12)

f) Line up recycle H2 from SGC (Reset 16 & Reset 17). Stop IG units. Start Hydrofining

section.

g) Establish synthesis lop circulation after checking CO, CO2 at SGC 4th suction.

h) Line up production.

i) Start PGHRU unit and recovery section.

j) Raise plant load.

H.Power failure

Possible causes :

a) Grid failure preceded by drop in voltage or frequency resulting in unloading of Turbogenerators on reverse power or under frequency.

b) Grid failure when Turbogenerators are not running.

Restart Procedure

If TGS are running in unloaded condition, power can be made available in a short time.

The main factors which affect the operation is the rise in cooling water temperature because of trip of CT fans.

Page 208: Ammonia Manual

Ammonia Plant Operating Manual 55

Rise in cooling water temperature will result in the lowering of surface condenser vaccum, vetrocoke solution temperatures, compressors suction and discharge temperature and refrigeration duty of the loop. This further rises the CWS temperature and thus a vicious circle is formed.

If both 1100 KVA and 830 KVA DG sets are available, all emergency loads and 5 CT fands (E,F,G,H,I) have to be started immediately. With this the plant load can be stabilised at 18 TPH at a cooling water temperature of 35 C above which the CWS temperature should not be allowed to rise.

If TG is coming in line immediately, the load reduction can be started after the cooling water temperature reaches 35 C in such a way that the cooling water temperature is maintained at 35 C.

If either 830 KVA DG set power or TG power is not resuming within one minute, take power failure trip in line and LRC will trip and SGC will get unloaded. This removes major heat load for the cooling tower. The front end load should be stabilised at 18 TPH when power resumes plant load is to be raised.

Page 209: Ammonia Manual

Ammonia Plant Operating Manual 56

11 Chapter Thirteen SHUTDOWN

13.1 NORMAL SHUTDOWN

A.Precautions

1) The rate of cooling down of the reformer brick work should not exceed 50 0C/hr.

2) It is essential at all times to avoid condensate deposition on the low temperature shift catalyst as this causes deactivation. Since the low temperature shift catalyst operates fairly close the gas dew point, a constant check should be carried out so that the gas temperature to this unit does not at any point fall below its dew point. The L.T. shift vessel is taken off line fairly early in the shutdown procedure, purged with nitrogen and left under nitrogen pressure higher than the adjacent plant pressure.

3) As for L.T. shift catalyst, liquid water must not be allowed to contact the reforming catalyst. When the temperature in any part of the reforming system drops to 50 0C above the saturation temperature of the steam at the tube inlet pressure, all steam should be purged out with Nitrogen.

4) Gas containing CO should not be allowed to stay in contact with Nickel containing catalyst or construction materials of primary reformer and secondary reformer at low temperatures. This is because significant amount of extremely poisonous Nickel Carbonyl will be formed at temperatures below 150 0C. Apart from the dangers of poisoning, this reaction will tend to remove Nickel from the catalyst thus causing deactivation.

5) At the plant, downstream of the reformer tubes, steam will condense from the gas. This condensate should be drained off immediately from the drain points on exchangers, vessel and pipe work to avoid possible bulk carry-over of condensate directly into any catalyst at a later stage.

6) If the plant is to be depressurised prior to entering the process vessels, all toxic gases must be purged out with Nitrogen.

7) Depressurisation of the plant must be carried out very slowly as the catalyst are porous and sufficient time must be allowed for gas diffusion to take place or severe catalyst damage may result. A rate of depressurisation not exceeding 7 ATA per hour is always recommended.

8) One of the primary concerns of shutdown should be the prevention of carbon deposition on the reforming catalyst due to momentary low steam/feedstock ratios. This can be and is often caused by leaky valves. It is therefore essential that immediately following a shutdown, the feedstock should be manually isolated by the block valve provided. The line between the valve

Page 210: Ammonia Manual

Ammonia Plant Operating Manual 57

and the control valve should be vented and then pressurised using HP Nitrogen. This prevents both forward leakage of the feedstock and backward leakage of process gas, either of which cause carbon formation in the absence of steam.

9) Two items of equipment in the flue gas duct should receive special consideration on shutdown. These are the process steam superheater and turbine steam superheater. The steam flows, through these, should be high enough to prevent design metal temperatures being exceeded.

10)Depressurisation of the Ammonia loop should not exceed 50 ATA per hour.

B.Plant load reduction

The plant capacity is reduced in 5 % steps to 70 % capacity by reducing the settings on the controllers in the following order :

a) Process air flow FC 1401.

b) Reduce simultaneously :-

1) Feedstock vapour naphtha FC 1303, then feedstock FC 1203 and then FC 1204 to maintain the pressure in PC 1208.

2) Fuel naphtha rate by reducing the set point on PC 1305. The reformer outlet temperature should be maintained at the normal value.

3) Purge gas fuel rate to reformer dual fired burners by closing HCV 1302.

c) Steam rate FC 1304.

d) Vetrocoke solution flows.

e) Reduce the speed of the synthesis gas compressor and circulation in the Ammonia loop to maintain suction pressure PC 1509.

Get clearance from HWP, open HWP bypass valve and the discharge of the syn gas compressor and close all the valves on the lines to and from HWP namely liquid Ammonia lines to and from HWP and 1" recycle gas line to HWP.

C. SGC Shutdown

Start I.G plant on cracked gas service to supply recycle hydrogen to 1432. Isolate recycle H2from syn gas compressor. Take syn gas compressor off line as per the procedure described in the section on Syn gas compressor. Check PC 1509 and ensure that PDXL 1405 trip does not get initiated.

D. LRC Shutdown

Page 211: Ammonia Manual

Ammonia Plant Operating Manual 58

Load on LRC will reduce as SGC is unloaded. on stopping the circulation in Syn loop stop refrigeration compressor according to the procedure described in the section on refrigeration compressor.

Watch the chiller pressures and drain NH3 from 1526, 1527 and 1127 sphere. In case the

pressure in 1526, 1527 is inadequate, pressurise them with Ammonia from 1127 and then depressurise to sphere. Carefully watch the pressures to avoid relief valves lifting or liquid from sphere backing up into the chillers on the other extreme.

Isolate the inert purger.

E. Synthesis Loop Shutdown

The procedure for a controlled shutdown of the synthesis loop depends to some extent on whether maintenance on the loop is required. If the shutdown is of a short duration with no maintenance required, the loop may be left under syn gas pressure. If maintenance is required, the loop is depressurised and purged with Nitrogen.

a) Shut down - No maintenance required

1) Open direct bypass HCV 1801 gradually so that the first bed inlet temperature is reduced by 10 OC in not less than half an hour.

2) As bed temperatures fall, adjust and finally reduce quench rates to zero.

3) Stop circulation (or use converter bypass HCV 1810 to achieve the same effect).

4) Empty ammonia from catchpot and isolate HCV 1811 and LCV 1812.

5) Blow down loop.

6) Purge converter and the loop with Nitrogen. Open all control valves from around the converter and purge through quench lines etc. Purge systematically to all drains and vents.

7) Maintain loop and converter under small positive pressure of Nitrogen.

8) If the loop shutdown duration is small, proceed upto Pt. No. 3.

b) Shutdown - Converter Requiring Maintenance

1) Proceed as under (1) and (2) above.

2) Reduce circulation rate by opening HCV 1810. Do not cool down more than 10 OC in half an hour.

3) When ammonia production ceases, drain catch pot and isolate LCV 1812 and HCV 1811. Inorder to cool down the converter reasonably quickly, it is necessary to maintain a circulation rate, allowing the converter to cool down at a rate not more than 50 0C/hr.

Page 212: Ammonia Manual

Ammonia Plant Operating Manual 59

4) When the temperature is down to 50 - 60 OC stop circulation and blow down loop.

5) Sweep out with Nitrogen as done earlier under (4) above.

6) When loop is completely purged, disconnect converter exit piping whilst continuing to purge.

7) Connect a Nitrogen hose to the converter exit and sweep out in the reverse direction.

8) When the converter is opened, the surface of the catalyst should be covered as much as possible but use Nitrogen purge through the opening. Make sure that the converter is not opened at the top and the bottom at the same time.

c) Shutdown with Catalyst Discharge

1) Proceed as under (1) to (6) above.

2) Make sure there are no openings at the top of the converter - other than for Nitrogen purge connection.

3) Remove HP covers from catalyst discharge nozzles and connect slide valves and water washed catalyst discharged chutes. Discharge catalyst (keeping it wet) into a wagon and tip on waste ground and spread out evenly.

13.2 EMERGENCY SHUTDOWN

A. Converter shell gas failure

In the new Ammonia Converter, a shell gas flow of around 50000 - 70000 Nm 3 / hr has to be maintained necessarily through HCV 1807 to cool the HP shell. The shell temperature shall be monitored periodically, using contact thermometer and shall be recorded.

In case of no shell gas flow due to valve problem etc., the following actions are to be followed:

1) Confirm the reduction in shell gas flow (FI 1803 ) as indicated in loop circulation flow (FI1809) for any momentary sharp drop in flow.

2) Isolate synloop immediately and take trip actions.

3) Close HCV 1806, 1808, 1809 and 1810. Open HCV 1807 to 5% (if it cannot be opened, do it with handjack and open HCV 1812 to 1% and maintain forward flow through the converter.)

4) If HCV 1807 could not be opened in any means, depressurise the loop as per normal rate through HCV1812.

B. Converter temperatures dropping

The following method of shutdown can be used in cases where converter temperatures are dropping in an uncontrolled manner. This situation should be avoided as too rapid cooling of the converter can cause cartridge bending and other internals damage. The procedure may be used

Page 213: Ammonia Manual

Ammonia Plant Operating Manual 60

to cover other emergencies on the loop except that in some circumstances the compressor/circulator may be tripped out as the first step.

1) Close direct bypass control valve HCV 1801.

2) Close both quench control valves HCV 1806 and HCV 1808.

3) Stop circulation and isolate make-up gas to loop.

4) Provided the above instructions are carried out quickly it should be found that loss of temperature will have been checked, and restart can be made from the appropriate point in the start-up procedure.

5) If shutdown is prolonged, a small purge should be taken from the loop. This provides some gas flow in the converter sheath and prevent overheating of the shell. Drain ammonia from the catch pot and close isolation valves.

C. Front End Shutdown

1) When syn loop is isolated, open water side bypass of 1539 fully.

2) Stop purge gas flow to reformer burners. Vent any purge gas still flowing from ammonia loop to flare via PCV 1303. Increase naphtha fuel rate to dual fuel reformer burners to maintain same burner heat output.

3) Reduce process air, naphtha feedstock, naphtha fuel and process steam flows in the sequence described previously. Air and feedstock should be reduced to 40 % steam to 50 %. Increase temperature inlet L.T. shift to maintain this temperature 28 0C above gas dewpoint.

4) Bypass and isolate the Methanator. Purge the vessel with nitrogen and leave under nitrogen pressure greater than adjacent plant pressure.

5) Bypass and isolate the LT shift vessel. Purge the vessel with nitrogen to remove the steam containing process gas and leave under nitrogen pressure greater than the adjacent plant pressure.

D. Cut off air

6) Reduce the process air flow to just above the trip value and then trip the air flow by pressing trip B. Stop firing on process air preheater. Isolate all valves at 1433 inlet and 1105 inlet.

7) Isolate air to the Vetrocoke Absorber.

8) Isolate the process air supply to the instrument air system and stop the process air compressor. (This may be done later if desired if there is no problem.)

9) Trip degassed condensate to drain downstream of the degasser. Turn off steam to the degasser. Stop quench water pump after lining up PCV 0207.

Page 214: Ammonia Manual

Ammonia Plant Operating Manual 61

E. Cut off naphtha

10)Reduce the flow of naphtha feedstock to a minimum. Cut off fuel to Reformer furnace and take Fuel Naphtha trip. Isolate fuel to 1432. Close the block valve on the liquid feedstock line downstream of FCV 1203 and the block valve on the recycle gas line downstream of FCV 1204. Close the block valve on the vapourised naphtha line downstream of FCV 1303 and open vent upstream isolation valve. Open 2" vent upstream FCV 1303 slightly to prevent pressure rise in 1104. Throughout the above steps, keep on adjusting the I & II bed temperatures of the HT shift vessel.

11)Open the low point drains at various points and drain away condensate.

12)Maintain steam flow to reformer at about 45 TPH.

13) Ensure that all burners in reformer are isolated. Re-establish fuel naphtha circulation and relight about 18 burners to hold reformer exit temperature TI 1314 at 760 0C.

14)When feedstock to reformer is stopped, transfer the venting to PCV 1504 from PCV 1509.

15) Stop Process Naphtha Pump.

16)Maintain levels in 1113, 1114, 1115, 1116 & 1131 and isolate LCVs at appropriate time.

17) Stop semilean solution pump and change over lean circulation to regenerators. Drain the regenerators and maintain levels at about 60 %. Isolate side stream filter from system.

18) Isolate LCV 1604 B.

19) Stop the quench water supply to TCV 1509 A & B. Close the block valve on the quench water supply line.

20) Isolate and bypass 1104. Depressurise the vessel to about 0.5 KSCG pressure.

21)Drain the naphtha from FCV 1203 to 1432 free of liquid naphtha.

F. Vetro solution regeneration

22)Open bypass valve of LT shift vessel slightly to divert the steam partially to reboilers to regenerate the vetrocoke solution. Maintain HP regenerator pressure more than 1.0 kscg with nitrogen to continue lean and semi lean circulation across absorber.

23)Analyse lean and semi lean solution FC once in an hour. Stop regeneration when solution FC comes down below 0.18.

24)Close the bypass valve of LT shift vessel after regeneration completion.

25)Drain the solution from the system to storage tank, if is a long shutdown.

Page 215: Ammonia Manual

Ammonia Plant Operating Manual 62

G. Purging the plant.

26) Line up section from LT shift vessel exit to feedstock header via the bypass of Methanator and 3109.

27)Use the gas available in Absorber section to purge the feedstock header section from FCV 1203 to FCV 1303 free of hydrocarbon to less than 1 ppm. Nitrogen can be used later if the hydrocarbon content has not come down. Check for Hydrogen and Oxygen to be less than 0.2 % and pressurise with Nitrogen.

Note : Gases from absorber section should not be used to purge 1104. 1104 should be purged with Nitrogen separately.

24) When Absorber section is fully depressurised, feed Nitrogen into this section via 1513 LP Nitrogen point, purge and pressurise to get Hydrogen and Oxygen less than 0.2 %.

H. Cool down furnace and establish Nitrogen circulation

25)The process of furnace temperature reduction in the reformer should be taken up in such a way that the system is ready for Nitrogen circulation when primary reformer exit temperature has come down to 500 O C

In other words, temperature exit reformer (process side) should be reduced such that the back end will be purged and pressurised with Nitrogen in the next 5 hours. Ensure that steam is not cut off without Nitrogen circulation and reformer is not held anywhere in between 500 & 700 C. 26. When primary reformer exit temperature (Process side) has come down to 500 C, open the bypass valve of LT shift vessel, open the block valve of FCV 1303, close the vents open for purging and establish Nitrogen circulation with start-up compressor.RGB & 1539 bypass valves will remain open. Maintain 1104 at a pressure less than plant pressure.

26)Maintain circulation rate as low as possible initially to avoid cold nitrogen condensing steam at inlet of reformer. Check the circulating gas for hydrogen, oxygen, CO, CO2 and hydrocarbons.

27)Check all the drain points to be free of condensate.

I. Cut off steam

29)After establishing Nitrogen circulation, cut off steam to primary reformer. When steam to reformer is cut off, system pressure will drop. Adjust conditions such that rate of depressurisation of 7 ATA is not exceeded.

30) Isolate block valves of FCV 1304 and close inlet block valve of 1537 to reduce 1537 pressure less than plant pressure.

31)Check raw naphtha to fuel naphtha jump over system and isolate all burners in reformers and purge.

32) Stop fuel naphtha pump after isolating raw naphtha to fuel naphtha jump over.

Page 216: Ammonia Manual

Ammonia Plant Operating Manual 63

33) Isolate air inlet valve of 1433 and cut off blanketing steam to 1105. Keep HCV 1408 open. Without closing air valve inlet 1433 and keeping HCV 1408 open, blanketing steam should never be isolated.

34)Continue to feed Nitrogen into loop to build up loop pressure to about 18 Kg/cm²g. Open the combustion air bypass on 1511.

35) Stop 3216 and 3210 when there is no boiling in regenerators.

36)Depending on steam demand, stop auxiliary boilers.

37) Isolate coolers not in line in compressor house, vetrocoke and synthesis areas and stop OGT 101 A.

38)When the circulating gas temperatures inlet 1517 drops to about 80 0C, stop lean solution circulation and drain regenerators, reboilers, pumps, filters, coolers and pipings.

39)Drain and flush all level gauges. Flush the solution pump casing with seal water.

40)Maintain vetrocoke storage tank temperature around 70 - 80 0C.

41)When the gas temperature exit primary reformer and secondary reformer has come down less than 70 0C, stop water to jackets of RGB, RGM & secondary reformer.

42)When gas temperature exit secondary reformer drops to 40 0C, stop gas circulation and isolate start-up compressor.

43) Isolate block valves of FCV 1303, 1108 inlet, LT bypass, 1112 bypass and 1113 exit.

44) Stop ID, FD fans and 1511.

45) Start instrument air compressors and stop PAC.

46) Stop auxiliary boiler and maintain steam system with steam from OSB.

47)Maintain Nitrogen pressure in all catalyst vessels.

48)Check the trip system to see that all trip valves are in tripped position.

SHUT DOWN SCHEDULE

Page 217: Ammonia Manual

Ammonia Plant Operating Manual 64

Probable Probable Sl. S h u t D o w n A c t i v i t y time of time of No. starting completion hrs. hrs. 1) Cut off feed stock, Hold Reformer temperature 0 - at 730 0C. 2) Remove slip plates in start up loop and HP - 2.00 N2 line at liquid feed stock header 3) Drain liquid Naphtha from liquid feed stock 2.00 4.00 header. 4) Line up LT bypass slightly and commence Solution regeneration. 2.00 6.00

5) Purge feed stock header with back end gas, 6.00 8.00 push out liquid Ammonia from 1122 & 1123 6) Purge back end section free of H2, CO & CO2 7.00 10.00 7) Pressurise back end section with N2 10.00 16.00 8) Purge feed stock header free of Hydrocarbons 10.00 14.00 9) Reduce Reformer temperature from 730 0C to 520 0C 12.00 16.00 10) Cut off process steam to Reformer Cut off 16.30 16.30 burners in Reformer 11) Start lean circulation to regenerator 15.00 15.30 12) Line up start up loop and establish circulation 16.00 16.30 for cooling Reformer 12) Establish short loop and depressurise 17.00 17.00 absorber section.Cool down Reformer section till SRO reaches 90°C

Probable Probable Sl. S h u t D o w n A c t i v i t y time of time of

Page 218: Ammonia Manual

Ammonia Plant Operating Manual 65

No. starting completion

hrs. hrs.

14) Purge 1104, LT, Methanator; Stop OGA 101 B 18.00 24.00 15) Drain solution from regenerators & coolers 17.00 25.00 to storage tank. 16) Stop Nitrogen circulation, isolate 1108 36.00 40.00 depressurise Reformer section. Stop Second Auxiliary Boiler 17) Purge syn gas barrel free of Hydrogen; Stop LO 36.00 40.00 & SO circulation 18) Purge synthesis section & recovery section; 38.00 50.00 Start IAC and Stop PAC. 19) Purge hydrofining section free of Hydrogen & 40.00 48.00 hydro carbons. 20) Defrost cold box of PGHRU. 48.00 64.00

Page 219: Ammonia Manual

Ammonia Plant Operating Manual 66

12 Chapter fourteen NORMAL OPERATION

14.1 GENERAL

In case of any doubt/trouble, Shift Engineer/Asst. Shift Engineer should be contacted immediately.

1. Check all the running machinery for

a) Suction pressureb) Discharge pressurec) Lubricationd) Lubeoil for quality (colour, contamination, foaming etc.)e) Bearing temperaturef) Vibrationg) Abnormal noiseh) Amperage in case of motor driven unitsi) Steam leaks leading to heating up of bearings.j) Gland leaks / seal leaksk) Adequate seal water flow for vetrocoke solution pumps.

2) Check the stand by machinery for availability for use with reference to relevant points mentioned under (1).

3) Check the level glasses and confirm that they match with level trols or DP transmitters.

4) Check the control valve openings in the field and confirm they match with the output from Control Room.

5) In case of any maintenance job by Instrumentation staff, efficient co-ordination should be maintained between the Control Room Operator, field operator and instrumentation technician. Use walkie talkie sets for quick communication.

6) Check for adequate cooling water flow to cylinder jackets of compressors, glands, bearing housings, etc. Periodic cleaning of Duplex filter in cooling water lines to machinery should be done.

7) Check D.P. across lube oil filters and change over when warranted.

8) Watch for any leaks and get them attended at the earliest. Leaks of hazardous fluids should be blanketed with steam.

9) Double block and bleed system in the nitrogen points should be checked and bleed valves should be kept open. In case of excessive passing, slip plates may be inserted or RSP may be removed.

10) Passing drains on hazardous piping (e.g. Naphtha service) should be piped away to a safe area. They should not be allowed to contaminate the effluent leading to safety hazard.

11)Drains of vent headers should be kept open to avoid liquid accumulation and hammering.

Page 220: Ammonia Manual

Ammonia Plant Operating Manual 67

12)Good house keeping should be ensured. Any oil spills, etc should be cleaned immediately.

13)No block valve should be kept throttled normally unless absolutely necessary.

14) There are services where two block valves in series are provided for positive isolation. e.g IBD from RGB/FGB, drain from RGB, drain from separators of SGC etc.

When these are put into service, high pressure valve (first valve in the flow direction) should be opened fully and the second valve only should be throttled to get the required flow. Throttling both the valves should never be practiced as this leads to passing of both valves.

15) Process conditions on both sides of exchangers should be monitored during shutdown periods also. e.g. (i) Cooling water can leak into syn loop if the loop is under pressure < 4 KSC and if 1524 is leaking. (ii) Spare lube oil coolers of turbines can lead to contamination of stagnant oil.

16)Highly volatile fluids should not be locked up by isolating valves at both ends as this can lead to thermal pressurisation. In case of necessity to isolate at both ends drain/vent should be kept open as a measure of thermal relief e.g naphtha lines, ammonia lines etc.

17)Hot side of any exchanger should not be isolated, unless the possibility of freezing because of cold fluid on the other side is eliminated. e.g. cooling water to 1528 should not be isolated unless ammonia on shell side is fully eliminated.

18)Record the various parameters regularly in the log sheets. Any abnormal condition should be brought to the notice of Shift Engineers/Asst Shift Engineers immediately. Existence of anabnormal condition already doesn't mean normality.

14.2 REFORMING SECTION

a) Reforming furnace

Regular visual checks must be made on the furnace for uniform firing, flame geometry, tube conditions etc. Any burner having the tendency to impinge on to the tubes must be attended and the situation rectified. Throttling may be done but it should be followed by change of gun if adjustment of air/steam doesn't help. Throttling the burners and leaving them as such will build the pressure in the fuel naphtha header and conditions of many other flames will become worse. Burners which have bad flames even after trying all possible adjustments must be noted down in a defect register for taking up the jobs during any shutdown. Furnace walls and furnace roof must be inspected regularly, any tendency for hot spot to develop on furnace wall and bulging of furnace wall or peepholes must be attended to immediately. Furnace roof must be checked on the top as well as inside the furnace. The areas where there is any tendency for the bricks to fall down must be watched more carefully and brought to the attention of Shift Engineer/Asst Shift Engineer. Packing of gaps in refractory bricks and reformer roof or gaps around tube collars may be done with Kaowool to prevent the support materials on the top of the furnace being exposed to radiation. Various supporting rods, hooks etc on the hanging roof cannot stand the high temperature of the furnace and they are cooled by Ambient conditions on reformer top. It is essential that reformer top is absolutely free from all debris, loose materials, loose insulation. Loose insulation may cover the support materials leading to the overheating and failure. Debris and other loose materials can catch fire under the hot condition on the top.

Page 221: Ammonia Manual

Ammonia Plant Operating Manual 68

If spill-back valve and fuel naphtha header on reformer top is opened because of load reduction, it should be done gently and very carefully. Otherwise there is a possibility of flames getting put out by sudden drop in fuel naphtha pressure.

Whenever a new burner is lit, check with explosive meter. Any leak should be attended. Otherwise the burner should be put out. Keep naphtha valve full open and keep the combustion air damper in locked position. Close the ignition port with the cap. Burners with passing valves should be noted down in the register for attending them later. If a combination burner burns only gas and not naphtha, steam to burner should be on to keep the tip cool.

When the plant is in normal operation, burner should be checked with explosive meter regularly, say one row of burners per day.

Keep steam lances available on reformer top always charged and free from condensate. Fire hydrants should never be used to put out fire on reformer top.

b) RG Mains

All the jackets in the RG mains should be visually checked for correctness of level and visual overflow from the jacket. Water flow at the inlet of jacket should be adjusted to have overflow only through the overflow pipe of the jacket and not through the walls of the jackets. If the water splashes along the walls of the jackets especially the ones near the outlet pigtails, there is a possibility of water spray on the outlet pigtails and consequent damage. Whenever there is an upset in the plant leading to upset in the water system, jackets should be checked more carefully. Check the skin temperatures of RG mains regularly.

c) Reformer tubes

Visual checks of the tubes should be done frequently as this is the best guide for conditions inside the tubes. This should be done especially after each change in feedstock load and firing rate in addition to regular inspection. If the catalyst is working satisfactorily all the tubes should be approximately at the same temperature. The tubes will appear to be colder normally over about the top two metre of the length than over the rest of the tubes which will be at a higher temperature. Overheating occurs when the amount of steam reforming reaction is insufficient to remove the heat input at that point in the tubes. The faults which cause this may often be identified by the appearance of that particular tube.

Tiger Tailing

If clear well-defined hot bands develop at random on individual tubes, this is usually associated with a void in the catalyst bed at that position and is normally known as tiger tailing. If care is not taken and filling the catalyst a bridge can be formed in the tube by catalyst rings locking together and will lead to this problem later. The tube should be recharged and refilled at the next opportunity.

Hot zones

Page 222: Ammonia Manual

Ammonia Plant Operating Manual 69

Hot zones are not as well defined as the hot bands described above. Generally the cause for hot zones is deactivation of the catalyst caused by general fall in activity or masking with carbon or some other deposit. If steaming does not remove the problem, affected tubes should be discharged and refilled at the earliest opportunity.

Giraffe necking

This is the term used to describe the tube showing a number of uneven hot zones. It may occur for three reasons. It may be an extreme type of hot zone, it may also be because of channeling caused by broken catalyst and dust or by accumulation of carbon. Lastly especially in case of old catalyst it may indicate that the catalyst requires changing as it is nearing the end of its active life.

Hot tubes

Where the carbon deposition or the catalyst breakdown mentioned in the section on Girrafi necking it is extensive enough to restrict the flow of gas through the tubes, the whole tube will become overheated. It may be possible to regenerate catalyst in these tubes by steaming but this is often ineffective because the steam will flow preferentially through the unaffected tubes. Usually the tube is discharged and recharged at the next opportunity. If all the catalyst tubes are hotter than anticipated and no overall restriction in flow is observed, there are two possible explanations.

I. The catalyst activity is low throughout the catalyst bed. This will probably show up in the exit gas analysis. If this occurs immediately after a start-up it may indicate an incomplete catalyst reduction and further period of reduction is required.

II. It is possible that the temperature of the reformer exit is reading too low and reformer is being run at too higher temperature as a result. This should be indicated by higher firing rate than usual and the relevant thermocouples should be checked. If all the tubes are hotter than anticipated and an overall restriction in flow is observed as indicated by high D.P., this indicates that some plant malfunction has occurred which has deposited carbon more or less evenly in all tubes or has caused catalyst breakdown throughout the furnace. If steaming and rereduction doesn't remove the problem, the catalyst change at the next shutdown is indicated.

Determination of concentration of aromatics in the product gas provides a convenient measure of catalyst activity. The effect of any poisons in the feedstock can be deducted by an increase in the benzene and toluene concentration before any change in methane content of the product gas is noted.

Whenever any change is made in firing rate, response in both the flue gas temperature exit reformer and process gas temperature exit reformer should be taken into care before making any further move. Contrasting responses require immediate attention lest the possibility of overheating exists.

When increasing the plant throughput, steam is always first increased followed by feedstock and then air. While it is advantageous to have high inlet temp at reformer to reduce heat duty of furnace inlet temperature should not exceed design temperature of 457 0C as otherwise the inlet pigtails are in danger.

Page 223: Ammonia Manual

Ammonia Plant Operating Manual 70

While reformer is being heated up prior to cutting in steam till the time the plant conditions have been brought up to the required level, the pressure of process steam superheater should be maintained at a value less than the reformer inlet pressure to avoid premature entry of steam inside reformer.

After cutting off steam to reformer if steam flow to process steam superheater is maintained to keep it cool, the pressure of superheater should be less than reformer inlet pressure. This is to avoid contact of steam with magnesia in catalyst below 500 0C, when magnesia can hydrate under some conditions leading to weakening and disintegration of catalyst.

Check reformer tubes for any bowing and inform. This occurs because of uneven firing conditions or improper supports.

Check the pigtails for normal expansion, any abnormal expansion which may lead to fouling with pigtails or support columns in the vicinity should be intimated immediately. Skin temperature of reformer tubes should be measured regularly say one row per day and record along with steam rate and process temperature.

Skin temperature should be checked during the catalyst reduction period when the tube exit temperature is the normal operating temperature, but when there is no endothermic reaction for good heat transfer in the tubes.

Steam/Carbon Measurement

A measurement problem arises from the variable physical characteristics of different naphthas since orifice plates are calibrated for a particular set of conditions including pressure, temperature and fluid density. Pressure of desulphuriser should be maintained at the design value always irrespective of the load. Variations in the naphtha/hydrogen ratio should not occur. For example if a deficiency of Hydrogen exists this will tend to higher figure of vapour naphtha flow measured.

Heat Recovery System

Natural circulation should be ensured always :

1) While operating IBD, it should be done carefully not to affect the natural circulation. It should not be kept open more than 5 seconds.

2) During start up of the plant when the system has inadequate heat input for establishing natural circulation, start up steam must be introduced through the risers of RGB and FGB to establish circulation. Rate of temperature rise on saturated steam should not be more than 66.6 0C/hr.

3) When start up steam is introduced to steam superheaters, it should be ensured that there is not too much back pressure on steam drum which can affect natural circulation.

Skin temperature of the superheater coils should not be allowed to exceed the design values at any period of operation. The temperature of steam inlet high temperature superheater should be higher than saturation temperature at the working pressure by 100 0C. Attemperator should be adjusted for fulfilling this requirement.

Page 224: Ammonia Manual

Ammonia Plant Operating Manual 71

At low load operation, combustion air bypass of 1511 is to be adjusted to get flue gas temperature of 150 0C at the stack.

Skin temperature of RGB shell should be checked regularly.

Secondary Reformer

1) Check skin temperature of Secondary Reformer shell regularly..

2) Ensure adequate water flow to the jacket in Secondary Reformer confirmed by the visual overflow.

3) Rate of steaming from vents of jacket should be watched for any abnormal boiling.

4) Drain from the jacket of Secondary Reformer should never be opened while the plant is in operation as this will lead to starvation of water. Slip plate may be inserted downstream of drain valve for positive isolation.

5) Slip plate may be inserted downstream of drain valve of Secondary Reformer in the nitrogen line, to avoid the valve becoming heated up in case of any passing.

14.3 FIRED HEATERS

1) Check the flames regularly for any impingement and correct. Adjust air registers and stack dampers to get good flames and to maintain slight excess of air.

2) Check the skin temperature of shell regularly. Whenever air inlet block valve of 1433 is closed, blanketing steam to Secondary Reformer may be isolated to avoid steam baking up and condensing in the coil.

3) Whenever blanketing steam to process air line is charged, air inlet valve of 1433 should be opened and process air venting should be transferred to HCV 1408; otherwise steam will condense inside 1433 and the condensate will get carried over to Secondary Reformer catalyst when process air is admitted.

4) Whenever there is any trip leading to unloading to PAC, HCV 1408 should be opened fully on manual before resetting trip panel. Otherwise in case of immediate resetting, HCV 1408 will close and build up pressure in 1433 (higher than compressor discharge) and the relief valve exit 1433 is likely to pop.

5) The operation problem with any process naphtha vapouriser is a tendency to lay down a carbonaceous deposit usually on the region where final vapourisation occurs. This is especially so in the vertical legs where refluxing of heavy ends increases the residence time of heavy ends which can crack. To prevent overheating of coil, because of poor heat transfer through these deposits, close observation of metal skin temperature must be maintained. When high temperature are observed, deposits can be removed by a high temperature steaming process with traces of air added to the steam.

6) Keep the auxiliary units required for lighting up of fired heater, as pilot gas torch, LPG cylinder etc., available always. Check the gas cylinder for availability of gas. Ensure that pilot gas header is kept charged.

Page 225: Ammonia Manual

Ammonia Plant Operating Manual 72

Hydrodesulphurisation

Sulphur removal is basically due to a catalytic decomposition reaction, rather than to a hydrogenolysis reaction. Hence the main effect of increasing the hydrogen pressure is to decrease the hydrocarbon partial pressure. The hydrocarbon feedstock inhibits the hydrogenolysis reaction, probably by adsorption on the catalytic surface, thereby reducing the fraction of surface available for hydrogen and sulphur compounds. Analysis of product should be carried out more frequently when the available hydrogen is less compared with what is required to meet the naphtha : H2 ratio spec.

Bed temperature of C-20-6 should not be allowed to exceed 430 0C (alarm value) as shortly after this hydrocracking reaction which is highly exothermic sets in.

Sulphur slip exit HDS reactor should be monitored regularly as this is the guide to predict the life of ZnO catalyst.

Sulphur slippage in extreme cases can upset the kinetic balance between the carbon formation and carbon removing reactions and carbon can be deposited on reforming catalyst.

Any possibility of oxides of carbon entering the reactor should be prevented especially during start-ups, as methanation reaction starts and temperature rises rapidly.

Ammonia is a poison to the catalyst and hence special care should be taken with regard to recycle H2 quality if the source is ammonia.

During start-ups it is suggested to keep 1104 under lower pressure than system pressure till the time it is lined up to avoid any hydrocarbon in the vessel entering the start up loop in case of inlet/exit valve passing.

14.4 SHIFT CONVERSION

Keep a regular watch on the D.P. of catalyst vessels and HT shift guard vessel. Any abnormal increase needs immediate attention. At low load operation, drain valve on the gas line exit 1539 should be kept open to drain away all the condensate and to prevent this being carried over to II bed of H.T. shift vessel.

Check 1111 for any accumulation of condensate and drain it out.

Set point of PC 0207 should be kept very close to the discharge pressure of quench water pump so that the temperature of LT shift vessel is not affected and wash water to stripper gas washpot is ensured. When there is a change in plant pressure, PC 0207 should be adjusted accordingly.

Start up lines inlet and exit of L.T. shift vessel should be isolated for main process lines by slip plates. Passing of start up valve on the exit line can lead to contamination of quality of syn gas exit 1113. Passing of inlet start up valve will lead to build up of off-quality gas in 1434 and may lead to contamination of syn loop when start-up circulation is established.

During start-up when LT shift vessel and Methanator are on bypass, they should be maintained at a pressure higher than plant pressure.

Page 226: Ammonia Manual

Ammonia Plant Operating Manual 73

When LT shift vessel and Methanator are bypassed after a shutdown, catalyst should be purged free of process gas and pressurised with N2 above plant pressure. Remember that steam and

CO2 in process gas from ZnCO3 in the catalyst below 160 0C and lead to disintegration of

catalyst. CO at temperatures below 150 0C can form Ni(CO)4 on Methanator catalyst.

Check the drains on gas lines exit 1515 and 1539 for any boiler feed water.

Check 1113 for any abnormal increase in level which may indicate malfunctioning of control valve, leak in 1516 etc.

LT shift catalyst loses activity because of poisons by sulphur, chlorine and thermal sintering. Special care should be taken to prevent sulphur entry especially during start-ups when Reformer and HTS catalyst are being reduced. Temperature of about 240 0C should never be exceeded to protect the catalyst from thermal sintering.

14.5 METHANATION

There should be no carry over of Vetrocoke solution to the methanation catalyst ; blocking of pores of catalyst occurs by evaporation of K2CO3 solution. AS2O3 also is a poison and catalyst

activity is lost.

Methanator catalyst being a nickel catalyst, sulphur is a poison to the catalyst. Because of low temperature of operation (compared to Reformer) subsequent operation with sulphur free gas will not restore the activity, as it will in case of Reformer. Hence the adverse effect of sulphur on a Methanation catalyst is permanent.

14.6 CO2 REMOVAL

The solution circuit being a closed loop, no solution escape from the system because of the poisonous nature of arsenic trioxide in the solution.

Periodic analyses for arsenic should be made in the acid gas leaving the regenerator and process gas leaving the stripped gas washpot.Any solution which may escape from the solution system due to pump gland leaks, leaking valves, etc., must be collected in the make up tank and returned to the solution circuit through side-stream filter. The regenerator base levels should be watched carefully to ensure that

the levels do not rise above the top of the level gauges ;

the levels do not drip sufficiently to cause cavitation in the pump or even loss of suction. The level in the base of regenerators must be maintained constant for any load by adjusting the water balance in the system to maintain the concentration of the solution.

The suction strainers of solution pumps tend to block slowly over a considerable length of time after the start up of the plant and, in fact due to the excessive heating and cooling of the absorber and regenerator equipment there will be a certain amount of ceramic packing breakages which will eventually be carried through to the suction strainer of pumps.

Page 227: Ammonia Manual

Ammonia Plant Operating Manual 74

The level gauges and level controllers in the base of absorber and regenerators should be periodically blown down and flushed with seal water. The washings should be collected in make up tank. Operator in the control room must be advised before the instrument is blown down.

No piping or equipment should at any time stand full of static solution. After closing down the solution pumps, they should be drained and washed and washings collected in make up tank.

Air Injection

Once in the solution iron forms complexes with the plant chemicals. In the ferrous form, these compounds can under certain conditions be insoluble above a concentration of 50 mg/l (at 80 0C). Since the iron content of the complex is only of the order of 10 - 15%, a very small amount of iron can precipitate a considerable amount of sludge. In order to prevent sludge formation, the iron is maintained in the oxidised ferric form which is soluble upto about 3 g/litre. Addition of air, preferably at the base of the Absorber, control the ferrous content of the solution at less than 1 ppm. An approximate guide on the amount of air addition is to achieve a steady arsenate increase 0.01 g/litre/day (as AS2O3).

During start up and restarts of the plant sufficient air should be injected into the Absorber base to give 10 - 15 ppm oxygen in the stripped gas. As the rate of increase of total iron content of the solution levels out of the air may be cut back to give between 5-10 ppm oxygen; but maintain ferrous content at less than 2 ppm.

Total iron concentration should be maintained at 400 - 500 mg/litre.

Side stream filter should be kept in line always filtering a portion from lean pump discharge and feeding back at lean solution pump suction. The filter should be primed to release any vapour lock at least once a day. The maximum allowable D.P. across the filter is 1.8 Kg/cm²g. Since arsenate is not effective in the absorption of CO2 at arsenate concentration of over 30 g/litre,

action should be taken to reduce the arsenate concentration by batch ammoniation and precipitation when the arsenate level reaches 25 gm/litre.

Ratio of K2O to As2O3

The ratio of total K2O to total arsenic (expressed as As2O3) should be maintained at a minimum

1.33. Lower ratios than this could give rise to precipitation f arsenic salts. Higher ratios than 1.33 are not serious but it is suggested that the ratio be maintained between 1.33 and 1.43.

Index of Carbonation

This indicates the extent of regeneration.

Free moles of CO2 I.C. = -------------------

Page 228: Ammonia Manual

Ammonia Plant Operating Manual 75

Mole of K2O

The exact indices required on lean and semilean solutions at any time will be dependent on obtaining the required performance from the Absorber. The values should be in the following ranges:

Semilean index = 1.0 - 1.2 Lean index = 0.85 - 1.0

Foaming

As well as the foam tests, gradual increase in tower pressure drops may be an indication that the solution is starting to foam. UCON HB - 5100 anti-foam agent should be injected into the solution when there is foaming tendency. Over enthusiastic addition will destroy all the foam leading to decrease in absorption efficiency.

Temperature of CO2 exit 1118 should be maintained above 81.4 0C always as carbon steel

cannot stand wet CO2 below this temperature. It should be strictly ensured that there is no

possibility of oil or grease or any other organic material entering the solution loop especially during maintenance of equipment. Maintenance crew should be instructed clearly on this. Various conditions in the plant should be guarded against any foreign material entering the system.

Rain water pit level should be maintained at minimum level possible always especially during rainy seasons. There should not be any back flow from effluent header into rain water pit. Any contamination of contents of make up tank by rain water pit contents should be prevented.

Pressure drop across LCV 1604 B should be checked regularly. It should not exceed the design value. If this happens, it may create excessive vibration and flashing across the valve and result in valve failure.

Any pump handling Vetrocoke solution should have seal water to its seals, even if it is not running. Seal water should be charged to seals before opening the suction valve and filling up pump casing itself.

Equal loading of 1117 A & B and 1517 A & B should be ensured always unless the situation warrants otherwise.

While running the make up pump to fill up the system during any start up, the filter exit valve should be lined up to Regenerators so that reboilers are filled up before building up levels in Regenerators.

14.7 SYNTHESIS

1. Operating Variables

The main variables to be considered in the operation of the loop are as follows :

Ammonia concentration inlet converter.

Page 229: Ammonia Manual

Ammonia Plant Operating Manual 76

Inerts concentration inlet converter.

H2 : N2 ratio inlet converter.

Total circulation and quench rates & pressure.

a) Ammonia concentration inlet converter - As the loop is cooled by refrigeration, the catchpot temperature and hence the ammonia returned to the converter, will remain fairly constant at constant loop pressure.

b) Methane and Argon take no part in the synthesis reaction and hence their concentration keeps building. Since the effective pressure for ammonia synthesis is the partial pressure of Hydrogen and Nitrogen, inerts in the system lowers this effective pressure and so the conversion is reduced. The inerts in the recycled gas are always much higher than the inerts in the make up gas, as in the process only Hydrogen and Nitrogen get converted into Ammonia while the inerts keep on accumulating. Hence the inerts must be maintained at the designed values by purgingout a small portion of the gas from the loop which is equivalent to the inerts in the make up gas.

c) H2 : N2 ratio :

A thorough understanding of the way make up gas composition and circulating gas composition are controlled is necessary for the efficient operation of the loop. It is essential that the H2 : N2ratio in the MUG and circulating gas be known at any time, that all gas analysers be maintained in good order and reliable laboratory gas analyses be available as required.

The object of the operator is to maintain the circulating gas H2 : N2 ratio constant at the

optimum value by suitable adjustment of the process air rate. The optimum value corresponds to approximately 63 % H2 in circulating gas containing 12 % inerts. In practice it is not

necessary to keep the ratio exactly constant, nor is it possible since the effect of slight variation on the make up gas composition is greatly magnified in the circulating gas. Therefore the operator should only make an adjustment to the make up gas when circulating gas composition is 1 - 2 % away from normal e.g. 64 - 65 % or 61 - 62 % H2 and this causes the previous drift in

composition to be reversed. Thus the trace on the H2 recorder will be a wavy line whose mean

position is the 63 % H2 line. The period of the oscillation depends on the skill of the operator

but could commonly be of the order of one hour.

It is often not realised that the circulating gas H2 : N2 ratio does not have to be 3 : 1. It can be

controlled at any value desired widely different 3 : 1.

It is possible that the ratio of circulating gas gets upset because of the change in the make up gas quality due to following reasons.

a) Lighting of 1433 and improper adjustment on process air flow.

b) Flame failure of 1433.

Page 230: Ammonia Manual

Ammonia Plant Operating Manual 77

c) Change in 1104 pressure (probably because of 1432 flame failure). Care should be taken to maintain converter bed temperature and stabilise.

There is a possibility of converter losing temperature even with normal ratio in make up gas, because of coupling of HWP at low loads of SPIC Ammonia Plant, reducing the effective load on SPIC converter. The ammonia converter can operate auto-thermally upto a minimum load of 30% only.

d) Converter temperature

Once the high initial activity of the catalyst has been gained, the converter should be operated at the lowest temperatures consistent with stable operation. During early life of the catalyst it may be possible to operate with bed inlets in the region 370 - 390 C. In later life 420 - 430 0C may be necessary. Temperatures should be adjusted upwards if there is a tendency towards a slow continuous fall, although the reason for this could be, for example, incorrect H2 : N2 ratio,

increase in inerts level or inlet ammonia level.

e) Total circulation and quench rates

As mentioned above, the converter should be run at the lowest temperature consistent with stable operation and therefore at the highest total circulation rate. Also, in order to achieve low 2nd and 3rd bed inlet temperature it is necessary to use as high as possible quench rates.

f) Pressure

The loop should be run as close as possible to design pressure as described in (b) above ; this means that high inerts can be tolerated in the circulating as during early catalyst life. Alternatively, during early life, design output can be achieved at lower than design pressure and inerts level.

2. Catalyst Life and Poisons Level

The converter is designed to produce the rated plant output two years catalyst life. The design also assumes a total of 1 ppm CO + CO2 in the make up gas. Provided the design poisons level

is not exceeded and the catalyst is not run at a temperature in excess of 530 0C, a significantly greater life may be expected, although it may be necessary to run at low inerts level when the catalyst has aged considerably.

3. Causes of Abnormal Operation

I) High Methane in Make up Gas.

a) Primary Reformer exit temperature too low. b) Steam/Carbon ratio inlet Primary Reformer too low. c) Channeling in Secondary Reformer bed. d) Change in air rate to Secondary Reformer or an air trip. e) Methanation of excessive quantities of CO and CO2.

Page 231: Ammonia Manual

Ammonia Plant Operating Manual 78

II. Converter Catalyst Temperature Dropping out of Control

a) Catalyst poisoned. b) Internal leak in cartridge. c) Carry over of liquefied ammonia to converter. d) Excessive use of quenches. e) High inerts. f) Bad H2/N2 ratio.

III. High CO + CO2 in make-up gas

a) Loss of activity of Methanation Catalyst. b) Channeling in Methanation Catalyst. c) Gas bypassing methanator vessel.

IV. High Converter Temperature

a) Inerts level falling due to loss of purge control. b) Return ammonia level falling due to loss of refrigeration control. c) Loss of quench control.

I bed of catalyst should be operated at high allowable temperature to take advantage of low NH3inlet of the bed and high reaction rate and high temperature. Subsequent beds may be operated at low temperature to obtain the equilibrium.

The maximum operating temperature for the converter is 530 0C (limited to 510 0C as a safe practice in our plant) but if for some reason the temperature rise above this to say 540-550 0C, do not take "panic measures" to reduce the temperature but at the same time do not run for more than a few hours at temperature of 540 - 550 0C and do not operate at all above 550 0C as this will lead to a greatly increased rate of catalyst deactivation.

Adequate flow must be ensured through the annulus of converter shell and internal cartridge to keep the shell cool from the radiation from the cartridge.

In case the relief valves at discharge of circulator blow and fail to reset, there is a possibility of syn loop getting depressurised by reverse flow through the converter. Reverse flow through the converter can damage the internals. To prevent this occurring, Syn gas compressor should be isolated from the syn loop immediately and converter inlet valve should be closed. A positive flow of syn gas should be established through the HP vent downstream of 1523. While depressurising the syn loop for any reason, DP across the converter should not exceed the design value.

Whenever syn loop pressure is less than BFW header pressure especially during a shutdown or start-up gas drain exit 1523 should be checked for any water to prevent water entering the converter.

Page 232: Ammonia Manual

Ammonia Plant Operating Manual 79

During shut down when no work is being done in the loop, drain the catchpot free of liquid ammonia and leave the loop boxed up under nitrogen pressure 5 - 10 Kg/cm²g topping up when necessary, leaving the total bypass open with the converter inlet valve and quench valves closed. This will prevent nitrogen containing some oxygen passing continuously over the catalyst and so slowly reoxidising it.

14.8 TANK FARM AND HYDROFINING

1) Check the seals on the floating roof of naphtha tanks.

2) Check the breathers on the floating roof, for any abnormal issue of gas/vapour.

3) Keep the water level in the naphtha tanks at minimum say 2 - 4 cm.

4) Centre drain disposing water from floating roof is to be kept open to avoid any water accumulation on the roof.

5) Temperature in a day tank should not exceed 70 0C.

6) Drain 1135 fully once a day in II shift.

7) Though reboiler exit temperature is 186 0C as per design, it may be possible to obtain the required quality of naphtha with less temperature. When unit is running normal, reduce the temperature gradually, observe the results and stabilise.

8) As 355 0C is the design temperature for catalyst bed at end of life, operation at about 320 0C may be tried initially. Temperature may be taken up at later stages, when necessary.

9) During any upset like power dip/failure, entry of naphtha inside reactor at temperatures less than 270 0C should positively be prevented by blocking the control valve FCV 1103 and keeping drain open.

14.9 CONTROL ROOM

1) Maintain efficient co-ordination with field operators and other panel operator.

2) Whenever any instrument maintenance job is taken up, close co-ordination with field operator and instrument technician should be maintained. Otherwise there is a chance of a plant upset.

3) Test the trip panel and hardware annunciator panel.

4) Use the memory points in the controllers to indicate the output signal. Check for change in output requiring action.

Page 233: Ammonia Manual

Ammonia Plant Operating Manual 80

5) Check whether all controllers are on auto. In case any controller is on manual, pay special attention to them. When plant conditions change rapidly, especially during an emergency controllers on manual should be monitored continuously to control the parameters within normal values.

6) Check the alarms and their values present in the alarm summary panel and take corrective action. Ensure that remedial action in the field or panel is adequate to cancel out the alarm.

7) Check all the parameters indicated in the control room, whether there is any change from the normal values. Existence of an abnormal value, though present for quite sometime, does not mean that a normal condition exists.

8) Check whether `fire alarm' and `electrical power status' panels are OK.

9) Take special care when there is a pump change over to avoid a process upset/trip.

10)Confirm all the control valves having hanjack provision are on neutral, eg. the quench valves on converter. Fix tags for valves on handjack.

11) If vetrocoke solution flow rate comes down to zero, close FCV on manual and do not open if unless flow can be established. While checking for flow by opening the valve slightly if no flow is obtained, close the valve again.

Same procedure is to be adopted for FCV 0101 also.

12) Keep the set points of vent controllers such as PC 0105, PC 1504, PC 1509 etc. close to the process point to avoid `overshoot'. Do not keep the set point too close leading to unnecessary venting.

13) Set Fuel Naphtha jump over controller close to the actual header pressure. Do not keep it too close, leading to fluctuation in FN header pressure because of jump over cutting in and out.

14) Set `FN high flow alarm' at a value more than the actual value by 0.4 TPH. Set TI 1313 high alarm at a value more than the actual value by about 15 C. Vary the set points for those alarms as process conditions change.

15)Cross-check the panel indication with the receiver gauge in the field or with the duplicate instrument whenever provided.16)Cross-check the actual valve openings in the field with controller outputs.

17)Rhythmic fluctuation in catchpot exit temperature may be an indication to liquid carry over to LRC.

18)When there is an alarm from trip panel, note the alarm which is flickering. The flickering alarm is the first trip initiator. Any other trip lamps appearing alongwith the first cause alarm might have got initiated as a consequence of or subsequent to the first trip.

19)After a trip, when a restart is possible, never reset the trip panel without moving the control valve position to the `trip' positions (`Close' or `Open' as the case may be).

Page 234: Ammonia Manual

Ammonia Plant Operating Manual 81

20)Whenever a trip leading to unloading of SGC or PAC occurs, do not reset without getting concurrence from Compressor House operator. Though the cause initiating the trip might have been corrected, flow controllers, pressure controllers etc., of the centrifugal machines might not have been taken on manual to keep the machine beyond surge condition.

21)Avoid bypassing of sequence in the trip panel. If sequence is bypassed, before removing the sequence bypass, ensure that the required reset buttons are pressed.

22) Inform Urea Plant, OSB & HWP whenever an action is taken which might affect conditions at their end.

14.10 COMPRESSOR HOUSE

Operating Notes

While bringing up speed :

1) Steam temperature should be above the saturation temperature. Warming up the steam line should be done gradually to keep the thermal stress as low as possible.

2) Watch the critical speed range.

3) Check vibration and listen for rubbing.

4) The turbine should not be operated below the low vacuum alarm limit except for warming up run.

5) Bearing oil temperature : Allow the oil temperature to rise with speed. The oil temperature should atleast be 38 C by the time machine speed is raised after the speed after warming up.

6) It is essential to check the lube oil failure trip before every start. A periodic check up is necessary for the emergency speed governor.

7) Check the oil pressure and temperature. The temperature rise should not be more than 20 0C.

8) While increasing the speed maintain the initial load until the exhaust hood cools down to saturation temperature.

9) Check that compressor casing, inter coolers and separators do not have any water liquid level.

During normal operation :

1) Check oil level in the tank.

2) Oil pressure should be as specified.

3) Check oil sight discharge from bearings, to ensure that there is adequate flow from each bearing.

Page 235: Ammonia Manual

Ammonia Plant Operating Manual 82

4) Bearing oil temperature are to be maintained as specified. The oil temperature rise across the bearing should not exceed 20 C.

5) Steam pressure : Compare initial and present steam stage pressure as they may indicate abnormal pressure drop which should be investigated.

6) Watch turbine exhaust temperature.

7) An increase in the vibration can be controlled by reducing the speed. If the vibration cannot be controlled by the reduction in speed the machine should be stopped and the cause investigated.

8) On the compressors : interstage temperature should not exceed specified values. Check the intercooler water is lined up fully and the water chamber is primed.

9) The balance piston DP of SGC should be watched. An increase in pressure drop indicates labyrinth seal damage. This will increase axial load on the thrust bearing.

10) Seal oil flow through the seal exit line sight glasses should be watched. An increased flow indicates the seal is getting worn out. The normal seal oil flow from each casing is 75 - 150 lit/day. If this flow exceeds 500 lit/day it would cause serious problems.

11)Abnormal trend of any parameter should be investigated.

Shutdown :

1) In general shutdown should be done by unloading as fast as practically possible reducing the speed to minimum governor and tripping the turbine. This way the turbine is not cooled down and remains hot for restart.

While restarting it may be difficult to match the steam temperature with a high turbine temperature.

2) After tripping the unit, start the motor driven oil pumps and stop turbine driven oil pumps.

3) Sealing steam should be in service as long as vacuum exists in the turbine to prevent cold air being pulled in along the shaft.

4) As the speed decreases the oil temperature shall be brought down to 27 to 32 C by the time the rotor slows down.

5) In process air compressor open out all the casing, intercooler and separator drains.

6) Open wide all the steam drains to surface condensers.

7) Break vacuum and cut off seal steam.

8) As soon as the rotor stops in SGC engage the barring gear and put the rotor on slow roll.

9) In case the rotor cannot be immediately be rolled by barring motor or if it is found that the turning gear will not turn the shaft, never admit steam to the turbine to try to turn the shaft. If the problem is only with motor, try hand barring.

Page 236: Ammonia Manual

Ammonia Plant Operating Manual 83

10) Steam or water should not enter the turbine when it is out of service.

11) Keep the barring gear in service as long as possible or atleast till the unit is thoroughly cooled. However, barring motor should be run after stopping Lube Oil circulation.

12) In the compressor casing keep a minimum pressure until the seal circulation is stopped to prevent the seal oil entering the casing. Casing drains should be opened and checked for any oil, when the seal oil is in circulation.

To complete the shutdown

1) To stop the seal oil circulation the over head levels should be dropped below the gauge glass indication. Casing should be depressurised. The seal oil pump should be stopped. The remaining oil in the sour seal oil traps shall be collected in drums with a hose. The sour seal oil traps shall be completely drained by this way to prevent the oil in the seal oil supply line entering into the casing.

2) Lock out the electrical power supply.

3) Shut off all the water to the coolers. Vent and drains of cooler and separators should remain open.

4) Keep the condenser hot well drain opened.

5) Keep the vent and drain points at the downstream of Main Stop Valve and isolation valve in open condition.

13 Chapter fifteen TANK FARM

15.1 INTRODUCTION

The feedstock and the Fuels used in Ammonia Plant are received from Indian Oil Corporation Limited. IOC receives Naphtha and Fuel Oil through Shipments and store them at their Terminals situated at Tuticorin Harbor. Shipment composite sample is taken and analysed for the acceptable level, then unloaded to their Tanks. IOC has totally six tanks, three tanks for Naphtha and three tanks for Fuel Oil. Their capacities are:

Page 237: Ammonia Manual

Ammonia Plant Operating Manual 84

Fuel Oil Tanks

T1: 8923 KLT2: 8896 KLT3: 8639 KL

Naphtha Tanks

T4: 13550 KLT5: 13400 KLT6: 13590 KL

IOC has three Fuel Oil Pumps and three Naphtha pumps each with a pumping capacity of approximately 250 KL/Hr

IOC Naphtha tanks samples are collected (Top, Middle & Bottom) and analysed for allowable limits. Depending on the requirement, tank opening stock will be taken prior to transfer. Naphtha and fuel oil are transferred through pipelines to our tanks.

15.2 TANK DETAILS

Our tank farm consists of the following tanks:

..11 TTaannkk Numbers Capacity in KL

Raw Naphtha (1202 A & B) 2 8750

Fuel Naphtha (1202 C & D) 2 6150

Sweet Naphtha (1203) 1 8750

Fuel Oil (FO - I & II) 2 3800

15.3 SALIENT FEATURES OF THE NAPHTHA TANKS

1. All the Naphtha tanks are Floating Roof Type to minimize the evaporation loss and to eliminate explosive mixture formation inside the tank.

2. Adjustable supporting legs are provided which are normally kept at 2 Mts height. They rest the roof at 2 Mts height facilitating maintenance inside the tank.

3. Neoprene seals are provided to seal the gap between roof and tank. It also prevents the direct contact between the roof and tank eliminating the possibility of spark production due to friction. Zinc made whether plates are used to protect the seals.

4. All the naphtha tanks are provided with double seal arrangement to minimize the vapourisation loss of naphtha.

5. Two numbers of breather vents are provided for each tanks which open at 2.25 Mts height and avoid vacuum formation side the tank while pumping is carried out after the roof is seated.

Page 238: Ammonia Manual

Ammonia Plant Operating Manual 85

6. One number Rim Vent is provided for each tank to release the vapour naphtha formed between the Pantoon and the Neoprene seal.

7. To drain the rainwater from the roof, a roof center drain with swivel joints, emergency drain plug, and a siphon drain are provided. An NRV at the top of roof drain to avoid naphtha reaching the roof through the drainpipe in case of drainpipe leak.

8. Tank drain is provided to drain the water collected at the bottom. The source is generally seawater, which is used for line flushing after ship unloading.

9. Each tank is provided with a Level Indicator. Control room indication also available.

10. Wind Girders are provided for giving stiffness to overcome the wind velocity. (120 km/hr)

11. Level measurements are done through dip leg, which is provided with holes to eliminate the capillary effect.

12. The floating roof is electrically earthed to shell and the ladder to avoid static electricity.

13. Naphtha tanks are earthed to avoid static electricity accumulation.

14. Naphtha tanks are Aluminium painted while to reflect away radiation heat thereby minimizing evaporation loss.

15.4 FUEL OIL SYSTEM

1. Fuel oil storage tanks are fixed roof tanks.

2. Fuel oil tanks are painted black to absorb radiation heat thereby reducing its viscosity for each pumping.

3. Fuel oil tanks are earthed to avoid static electricity accumulation.

4. Three fuel oil transfer pumps (Gear type) are used to transfer oil to consumer ends like Auxiliary Boilers Day Tank, ASGU Day Tank, Off Site Boilers Day Tank and to DAP Plants.

5. Auxiliary boilers day tank has the capacity of 216 KL. (license obtained for 246 kl)

6. There are three Fuel oil pumps for delivering oil to auxiliary boilers. From the day tank normally one screw pump of turbine driven runs for oil supply to the boilers and other two pumps are kept as standby on auto. Out of these two one is motor driven, it is provided with spill back arrangement to facilitate the operation during the trial run etc..,

7. Fuel oil pump takes suction from the day tank through a strainer and delivers oil through a heater 1502 and discharge strainer. Oil is at 16 kg/cm2g and at 120oC before entering the boilers.

8. PC 0206 controls fuel header pressure and return oil is sent back to the day tank thereby maintaining the tank temperature.

15.5 SAFETY FEATURES OF NAPHTHA & FUEL OIL STORAGE YARD

1. All naphtha line flanges are provided with “C” clamps to eliminate static electricity accumulation in pipes.

Page 239: Ammonia Manual

Ammonia Plant Operating Manual 86

2. Dyke walls are provided around to tanks to avoid spreading of Naphtha / Fuel Oil in case of damage/leakage in the tanks. They have the capacity to hold the largest capacity tank. To hold up the small leaks, Bund walls / Firewalls are provided.

3. Flame Traps are provided for the drainage system.

4. Fire monitors and fire hydrants are provided inside the tank farm. A separate central hose station with foam cane, hoses and foam nozzles is installed near the security booth.

5. Tank farm is fended and is guarded by security personnel. A separate entry register is maintained.

6. A dedicated Foam pourer system and Medium velocity water curtains are installed for the Naphtha tanks.

7. For Emergency communications, a flameproof Phone is provided inside the tank farm.

8. Four nos of “Fire Alarm” Push button is provided around the tank farm, which initiates an alarm in the main control room as well as in Fire Station.

9. Electrical fittings inside the tank farm are flame and explosion proof.

10. A ring road is laid for easier movement of Fire Tender and Fire Trolleys.

11. Floor in and around the storage yard dyke wall is covered with concrete slabs to avoid vegetation, which is a potential source of fire.

15.6 NAPHTHA SPECIFICATIONS AND ITS IMPORTANCE

Steam reforming of Naphtha is a sensitive process and is suitable only for certain specification of naphtha. The Naphtha should be straight run naphtha obtained by straight distillation of virgin crudes. Use of cracked naphtha is seldom attempted, as desulphurisation of cracked naphtha is difficult. The crudes processed by various refineries are different and the import naphtha also is of wide variations. Each fertilizer unit is designed for a particular grade of naphtha and there is no standard specification on national basis. A typical specification of naphtha is given below:

Typical specification of naphtha

Specific Gravity: 0.65 – 0.75

Distillation - 10 % - 45 – 97oC

- 50 % - 60 – 115oC

- FBP - 130 – 200oC

PONA Analysis

Paraffins - 75 % Min

Olefins - 2 % Max

Naphthenes - 36 % Max

Aromatics - 15 % Max

Sulphur - 0.15 % Max

C/H Ratio - 5.5 – 6.0

Reid Vapour Pressure - 10 psi

Page 240: Ammonia Manual

Ammonia Plant Operating Manual 87

Residue on evaporation - 5 kg/100 ml max.

The various characteristics of naphtha and their limiting values are discussed below:

BOILING POINT RANGE

The final boiling point is indicative of the presence of high molecular weight hydrocarbons in the naphtha. Although the amount of high boiling hydrocarbon is small in comparison to the bulk, they tend to lay down carbon resulting in lowering of the activity of the reforming catalyst. Further, higher molecular weight hydrocarbons contain sulphur compounds, which are difficult to remove.

TOTAL SULPHUR CONTENT

Normally naphtha contains sulphur as received and is desulphurised at the ammonia plant before reforming, bringing down the sulphur content to less than 0.5 ppm. The specification for raw naphtha includes a maximum limit of 1500 ppm of sulphur of which not more than 100 ppm is ‘unreactive sulphur’ that is sulphur compounds other than sulphur, Hydrogen sulphide, mercaptans, Disulphides and Thioethers. Sulphur lowers the activity of Nickel based reforming catalyst.

OLEFINS

Olefin content in straight run naphtha is normally very low. To ensure that the product is straight run naphtha, a nominal value of 2 % is specified. However, the presence of Olefins beyond limit is not desirable because of the tendency to thermal cracking and laying down carbon in vapouriser and over catalyst bed.

NAPHTHENES

The naphthenes are more susceptible to dehydrogenation and deposition of carbon over the catalyst bed. However, naphthenes have been successfully reformed if present within the limit specified.

AROMATICS

Aromatics are normally difficult to reform. Aromatic content in the naphtha is one of the factors deciding the catalyst loading and higher aromatic content than design results in reduction of throughput.

Further, operation of the plant with high aromatic naphtha will lead to higher hydrocarbon slip and continuous operation under these conditions could lead to progressive carbon lay down on the catalyst as high aromatic feedstocks are prone to deposit carbon under even slightly adverse conditions leading to severe pressure drop and loss of catalyst activity.

Higher aromatic content further implies higher amount of thiophenic sulphur, which is difficult to be converted in the desulphuriser unit.

1133..11..11 CCAARRBBOONN // HHYYDDRROOGGEENN RRAATTIIOO

The Carbon / Hydrogen ratio normally increases with rise in FBP. As C/H ratio increases, H2 yield per tonne of naphtha comes down and specific consumption of feedstock increases. As high C/H

Page 241: Ammonia Manual

Ammonia Plant Operating Manual 88

ratio is indicative of higher boiling hydrocarbons, severe operating conditions are required in Reformer.

1133..11..22 RREEIIDD VVAAPPOOUURR PPRREESSSSUURREE

RVP provides a guide to the amount of extremely light fractions present in the naphtha, either as dissolved gases or as low boiling hydrocarbons. Naphtha with high RVP leads to increased storage losses and risk in storage, increased NSPH requirement of pumps and losses in stripper section of hydrodesulphurisation, in a tropical country like India.

1133..11..33 RREESSIIDDUUEE OONN EEVVAAPPOORRAATTIIOONN

ROE is monitored in any naphtha parcel to ensure that the naphtha is not contaminated with high boiling hydrocarbons, which will deposit carbon over reforming catalyst.

ROE is limited to 5-mg/100 ml as determined by the method ASTM-D-1353.

Though the method ASTM-D-381 also is in use to determine ROE, it may be noted that ASTM-D-381 (Jet Evaporation Method) is a measure of existent gum in fuels and is a guide to possible fouling tendency of fuels in engines only. This method found to be inadequate to detect any contamination of naphtha with high boiling hydrocarbons, which will result in carbon deposition on the reforming catalyst. However, the method ASTM-D-1353 is found to be a sensitive and consistent method to detect any contamination of naphtha with high boiling hydrocarbons.

IINNOORRGGAANNIICCSS

1133..11..44 LLEEAADDThere is a possibility of contamination of naphtha by lead particularly during storage and transportation in multi product installation and tankers/tank wagons, etc., which handle petrol containing the anti-knocking agent called Tetra Ethyl Lead. Normally lead concentration upto 50 PPB is tolerated in the naphtha.

With the presence of lead in Naphtha, there is an increased tendency for carbon formation in the vapouriser and desulphuriser catalyst. Further, Lead can also cause fluxing of the corrosion resistant oxide film on the outer tube wall when naphtha is used as fuel.

1133..11..55 VVAANNAADDIIUUMMThis must not be present as it can cause severe corrosion of the tubes by reforming a low melting slag, which fluxes the protective oxide film.

1133..11..66 SSOODDIIUUMMParticularly in association with vanadium, this can cause severe corrosion as above. A limiting concentration of 0.03 ppm is specified.

Page 242: Ammonia Manual

Ammonia Plant Operating Manual 89

1133..11..77 CCOOPPPPEERRThis must not be present.

1133..11..88 CCHHLLOORRIIDDEESS,, BBRROOMMIIDDEESSThey are usually associated with Lead. Chloride may also be found in feedstocks transported by sea. These can deactivate the reforming catalyst and LT shift catalyst by sintering. Chloride may also cause stress corrosion cracking.

1133..11..99 AARRSSEENNIICCGenerally naphtha contains arsenic less than 0.01 ppm. Poisoning action is delayed while it accumulates in the catalyst. Loss of activity of catalyst is shown by increase in the level of higher hydrocarbons slip. This results in deactivation of catalyst and development of hot tubes.

Arsenic impregnated on the reformer tube can poison the fresh catalyst also, even if the poisoned catalyst is discharged.

.oOOo.

Chapter Sixteen HYDROGEN RECOVERY UNIT

16.1 DESIGN BASIS

1. Raw Material

a) Purge Gas (tapped off from Synthesis loop purge point)

Flow (Nm3/Hr) 7900Pressure (Kg/cm²g) 215.3Temperature ( 0C) 23.5

Composition (mole %)

H2 57.57N2 19.65Ar 5.05CH4 9.77NH3 7.96

b) Flash gas (tapped off from the 1124 exit gas line)

Flow (Nm 3/hr) 600Pressure (Kg/cm²g) 19.4 Temperature (0C) 40.0

Composition (mole %)

Page 243: Ammonia Manual

Ammonia Plant Operating Manual 90

H2 56.23N2 18.96Ar 6.27CH4 18.44NH3 0.10

2. Products

a) Product Hydrogen (joining the SGC II suction seperator after I stge cooler)

Flow (Nm 3/Hr) 4725Pressure (Kg/cm²g) 47 Temperature ( 0C) 35

Composition (mole %) H2 94.19N2 4.85 Ar 0.60 CH4 0.36NH3 -

b) Tail gas (Joining the fuel gas header of Reformer)

Flow (Nm3/Hr) 3006Pressure (Kg/cm²g) 2 Temperature (0C) 30 Composition (mole %) H2 12.81N2 47.28Ar 13.17CH4 26.74NH3 -

16.2 PROCESS DESCRIPTION

1. Main Process Stream

Synthesis loop purge gas at a pressure of 215.3 Kg/cm²g and temperature of 23.5 0C is tapped off after converter feed interchanger at the rate of 7900 Nm3/Hr the loop purge gas has the following composition.

H2 57.57 % (All mole %)N2 19.65 %Ar 5.05 %

Page 244: Ammonia Manual

Ammonia Plant Operating Manual 91

CH4 9.77 %NH3 7.96 %

Loop purge gas enters the tube side of No. 1 Precooler and the temperature is brought down to 5 0C by heat exchange with Freon R22 which evaporates at 0 0C at a pressure of 4 Kg/cm²g. The pressure at the shell side of HEA 101 is controlled by PIC 2112. The level of the refrigerant in HEA 101 is controlled by LIC 2105 provided at the liquid Freon to the exchanger. The shell side is protected by the relief valve SV 2111-2 provided at the vapour outline. A high temperature alarm TI 2102 set at 7 0C and a low temperature alarm TI 2102 set at 0 0C are provided, on the gas line exit HEA 101.

The cooled purge gas with condensed ammonia is fed to the ammonia separator. The condensed ammonia at the rate of 250 kg/hr after separation is sent to the let-down vessel 1123 through LCV 2101. The separator is provided with high and low level alarms. The pressure of the purge gas from the separator is let down to 60 Kg/cm²g through FCV 2101.The flash gas from the ammonia absorber at a pressure of 19.4 Kg/cm²g and at 40 0C is fed to the suction of the flash gas compressor HGB 101 A/B. The flash gas has the following composition. mole %

H2 56.23 % N2 18.96 % Ar 6.27 % CH4 18.44 % NH3 0.1 %

The pressure of the flash gas is boosted up to 60 Kg/cm²g by means of flash gas compressor HGB 101. The suction pressure of the compressor is controlled at 19.4 Kg/cm²g by PIC 2111 by recycling the gas from the discharge. A low suction pressure alarm PS 2141at 17 Kg/cm²g is provided. The delivery of the flash gas from the compressor is at 43 0C and a high temperature alarm TI 2105 set at 50 0C is provided. The flash gas from the compressor discharge mixes with the purge gas down stream of FCV 2101 and the feed gas enters the bottom of the water scrubbing tower.

The water scrubbing tower has 5 beds of 1" Ceramic Raschig rings. The remaining ammonia in the feed gas is reduced to 100 ppm in this tower by means of scrubbing with water. The normal source of the scrubbing water is from the ammonia recovery unit, tapped off from the exit of 1532. A quantity fo 1350 kg/hr tapped off from 1532 at a pressure of 24 Kg/cm²g is pumped to the scrubbing tower by water pump at a pressure of 62.5 Kg/cm²g. A low flow trip for the scrubbing water measured at the pump suction is provided. To ensure a sustained operation of the PGHRU in the event of any upset in ammonia recovery section, an alternate source of scrubbing water is provided from the seal water header.

The aqueous ammonia solution from the bottom of the scrubbing tower containing 15.9 % by weight of ammonia is returned to the ammonia still at the rate of 1592 kg/hr through LCV 2102. Both high and low level alarms are provided for the scrubbing tower.

The feed gas from the scrubbing tower at 45 0C is cooled to 35 0C by heat exchange with product hydrogen from cold box, in feed product heat exchanger. The feed gas flow is through the tube side whereas the product hydrogen flow is in the shell side. The feed gas temperature is further brought down to 15 0C in No. 2 pre-cooler by means of evaporation of Freon R22 in the shell side at 0 0C and 4 Kg/cm²g. The level of refrigerant in HEA 102 is controlled by LCV

Page 245: Ammonia Manual

Ammonia Plant Operating Manual 92

2106 provided in the liquid Freon line to the exchanger. The shell side of HEA 102 is protected by the relief valve SV 2111-1 set at 20 Kg/cm²g.

The evaporating pressure for Freon in both HEA 101 and HEA 102 is controlled at a value of 4 Kg/cm²g corresponding to a saturation temperature of 0 0C by means of a pressure controller. The Freon vapour from HEA 101 & 102 (approximately 5800 kg/hr is taken to the No. 1 Cryo compressor suction through the PCV 2112. The pressure and temperature conditions at the suction end of the compressors are 3.9 Kg/cm²g and 8-10 0C respectively. The oil carried over along with liquid freon to HEA 101 & 102 is continuously drained off to the accumulator provided at the suction of the compressor. The freon vapour is compressed to 15 Kg/cm²g and leaves for condensation at 80 0C. The condensation of the vapour takes place at a pressure of 14.8 Kg/cm²g and 40 0C in the condenser E 101. Relief valves SV 2112 and SV 2113 set at 26 Kg/cm²g are provided at the discharge of HGC 101 A & B respectively. Also the condenser shell side is protected by SV 2114 set at 21 Kg/cm²g.

The feed gas from HEA 102 enters the water separator HFA 102 where the saturated moisture content of the gas is knocked off and drained through LCV 2103. The drain liquor (9 kg/hr) containing maximum of 1 % ammonia is sent to the ammonia flash vessel. A low temperature alarm set at 5 0C is provided for the feed gas at the exit of HEA 102 to protect against the possibility of freezing of moisture in the separator and associated piping.

The feed gas from the water separator is fed to the drying system consisting of two molecular sieve adsorbers operating in a cycle. The final traces of moisture and ammonia are adsorbed in molecular sieve as these components if present, would freeze in cold box and could lead to operational problems. The adsorber cycle is 12 hours on stream and 12 hours on reactivation, in which heating operation takes 5 hours cooling operation 6 hours and change over operation 1 hour.

A part of tail gas (700 Nm3/Hr) from the cold box heating in the shell side of regenerating heat exchanger HEA 103 by 45 ata steam, is passed through adsorbent bed for reactivation. This gas rejoins the balance of the tail gas through the regenerating gas cooler HEA 105. After completion of 5 hrs. of heating operation in the reactivation cycle, off line adsorber is cooled down to the operating temperature by passing tail gas for a period of 6 hrs. with the regenerating heat exchanger off the line.

The dry feed gas exit M.S. adsorber unit enters the cold box consisting of two heat exchangers and two separators. The heat exchangers are of plate fin type and constructed of aluminum alloy. The separators are also made of alumimium alloy. The drain separator and associated piping and control valves are insulated with Rockwool whereas the rest of the cold box unit is filled with Perlite insulation. There is a provision to purge the cold box continuously with dry Nitrogen (dew point -70 0C) at a flow rate of 1 Nm3/Hr and Pressure 0.5 Kg/cm²g. The purge nitrogen from the top of the cold box is let off to atmosphere through an oil seal. The main purpose of purging cold box with dry N2 is to drive out all residual air and prevent moisture/other impurities from entering the cold box and to facilitate detection of any leak by constant analysis of purge nitrogen at the inlet of oil seal pot. A relief valve set is provided at the top of the cold box to ensure safety of the equipment. The feed gas at 20 0C from the M.S. adsorber is cooled down to -38.5 0C by heat exchange with product hydrogen and tail gas in No. 1 heat exchanger HEC 101.

The feed gas leaves cold box and is further cooled down to -40 0C in No. 3 heat exchanger located outside cold box unit by evaporating liquid freon in the shell side at -45 0C and corresponding pressure of -130 mmHg. The level of refrigerant in HEC 103 is controlled by LCV

Page 246: Ammonia Manual

Ammonia Plant Operating Manual 93

2107 provided in the liquid freon inlet line. The evaporating pressure of freon in HEC is controlled by PIC 2113 at a value of 130 mmHg corresponding to a saturation temperature of -45 0C. The freon vapour from HEC 103 enters the compressor through PCV 2113 at -22 0C and -130 mmHg pressure. Similar to the drain provision for HEA 101 & 102, provision is made for HEC 103 also for draining off oil into the accumulator at the compressor I stage suction.

The vapour is discharged from the I stage of 1.87 Kg/cm²g and 40 0C and gets cooled to -60 0C by mixing with the freon from the oil cooler. In the second stage the vapour is compressed to 14.8 Kg/cm²g at a temperature of 80 0C. The vapour discharged from the II stage after oil separation is condensed at 14 Kg/cm²g and 36 0C in the condenser E 201 provided with a relief valve in the shell side set at 21 Kg/cm²g.

The feed gas from HEC 103 enters back cold box and is further cooled down to -193 0C with partial condensation by heat exchange with product Hydrogen and tail gas in No. 2 heat exchanger. The partially condensed feed gas is introduced into the drain separator in a state of gas liquid mixture. The hydrogen gas is separated from the liquid and discharged as product hydrogen through a pressure control valve PC 2106 which controls the system pressure at 57.5 Kg/cm²g. High and low pressure alarms are provided for the system pressure at 63 Kg/cm²g and 45 Kg/cm²g respectively. The system is protected against excess pressurisation by SV 2101 and SV 2102 set at 66 Kg/cm²g located at the inlet of the scrubbing tower and on the drain separator HFA 103 respectively. The product Hydrogen gets cooled to -194.2 0C after expansion through PCV 2106 (from 57.5 Kg/cm²g to 47.5 Kg/cm²g) and exchanges cold with incoming fed gas in exchangers HEC 102 & 101 thereby getting heated upto -47.5 0C and + 17 0C respectively and leaves the cold box for further heating in HEA 104. Composition of the produce hydrogen is as follows : mole % H2 94.19 % N2 4.85 % Ar 0.60 % CH4 0.36 %

The liquid condensed and separated in the drain separator is expanded at 2.5 Kg/cm²g through LCV 2104 which results in lowering of temperature due to Joule-Thomson Effect. HFA 103 has both high and low level alarm provisions. The flashed liquid gas mixture enters the phase separator HFA 105 at -194.8 0C. There is a provision to inject product hydrogen from HFA 103 to the inlet of HFA 105 through HCV 2101 to effect lowering the evaporating temperature of liquid from HEA 103 by way of reducing the partial pressure of the gas which would inturn improve the prouduct purity by the resultant temperature drop at the inlet of HFA 103. The liquid from HFA 105 after evaporation mixes with the gas stream in HEC 102 and the tail gas stream leaves cold box through HEC 102 and 101 and -42.5 0C and + 17 0C respectively, effecting cooling incoming feed gas.

The tail gas pressure is controlled by PC 2108 Kg/cm²g. The quantity of tail gasleaving cold box is about 3006 Nm3/Hr. A part of the tail gas 700 Nm3/Hr required for reactivation of M.S. adsorber is tapped upstream of PCV 2108 and joins back the tail gas header downstream of PCV 2108. There is a pressure controller PC 2109 set at 2 Kg/cm²g on the tail gas header to relieve the tail gas to vent gas header. The tail gas header joins the primary reformer fuel gas header downstream of PCV 1301. The composition of the tail gas joining the fuel gas header is as follows : Mole % H2 12.81 %

Page 247: Ammonia Manual

Ammonia Plant Operating Manual 94

N2 47.28 % Ar 13.17 % CH4 26.74 %

The product hydrogen leaving the cold box at the rate of 4725 Nm3/Hr enters the shell side of HEA 104 and gets warmed upto 35 0C. An analyser with an alarm is provided in the product hydrogen line to monitor the hydrogen purity. The product hydrogen header pressure is controlled at 47.5 Kg/cm²g by PCV 2107 which relieves any excess pressure into the tail gas header. The product hydrogen is fed at the upstream of II suction separator of syn gas compressor.2. UTILITES

a) The following are the utilities required for operations of the Hydrogen Recovery Unit.

1. Steam 2. Cooling water 3. Instrument air 4. Nitrogen 5. Electic power

1) Steam

The requirement of steam is for the purpose of preheating of the tail gas during the reactivation cycle of the M.S. adsorbers. The quantity required is about 1003 Kg/hr at a pressure of 42 Kg/cm²g and temperature 380 0C. The quantity of steam is made available to the unit from the 45 Kg/cm²g steam line to the still reboiler 1534. The same source of steam is used for the purpose of heating up of the cold box unit during shutdown, using HEA 103.

2) Cooling Water

The total requirement of cooling water at a pressure of 4 Kg/cm²g and at 33 0C is 94 M3/hr with the following break-up.

Cryo compressor No. 1 : 66 M3/Hr Cryo compressor No. 2 : 18 M3/Hr Flash gas compressor : 4.5 M3/Hr Regenerating gas cooler : 5.6 M3/hr

This requirement is met from the branch off line from the C.W. supply mains going to the ammonia refrigeration condensers. The cooling water return from each of the above units is collectively joined back to the C.W.R header of the refrigeration condensers.

3) Instrument air

The total requirement of instrument air at a pressure of 7 Kg/cm²g with a dew point of -35 0C is 42 Nm3/Hr. This is met from the main instrument air header.

4) Nitrogen

Dry nitrogen at 7 Kg/cm²g with a dew point of -70 0C for diluting the leakage gas from the piston rod seal of flash gas compressor a the rate of 29 Nm3/Hr and 1 Nm3/Hr for purging the interior of the cold box unit. This quantity of dry nitrogen is from HWP. Alternatively it is made

Page 248: Ammonia Manual

Ammonia Plant Operating Manual 95

available from the Nitrogen receiver through a pressure control valve followed by a dryer unit of 30 Nm3/Hr capacity operating on a 12 hrs cycle.

The Nitrogen requirement for start-up defrosting etc., is as follows :

700 Nm3/Hr at 30 0C and 7 Kg/cm²g to purge out air in piping and equipment.

700 Nm3/Hr at 80 0C and 7 Kg/cm²g to defrost the cold box unit before any long shutdown. The temperature of 80 0C is achieved by heating Nitrogen with steam in HEA 103.

500 Nm3/Hr at 30 0C and 7 Kg/cm²g to dilute the vent gas rich in methane from drainage liquid tank HFA 104.

75 Nm3/Hr at 80 0C and 7 Kg/cm²g to warm up the vent gas during short shutdown if required.The requirement of N2 for the above is met from the LP N2 header.

5) Electric Power

The total power requirement at 415 V is 162.5 KW. The break up is as follows :

No. 2 cryo compressor : 84 KW (for each) No. 2 cryo compressor : 18 KW ( do ) Scrubbing Water pump : 5.5. KW ( do ) Flash gas compressor : 55 KW The above power requirement is met from the urea plant sub-station.

16.3 START UP PROCEDURE

1. Sequence of start-up

a. Purging the system with Nitrogen.

b. Total heating of the cold box unit.

c. Reactivation of both molecular sieve adsorbers.

d. Purging of cold box interior with dry Nitrogen.

e. Introduction of purge gas and pressurisation of the purge gas system to synthesis loop pressure.

f. Line up water pump to scrubbing tower and stabilise scrubbing tower level and pressure.

Page 249: Ammonia Manual

Ammonia Plant Operating Manual 96

g. Cooling down operation.

h. Line up product hydrogen to the main plant.

i. Start flash gas compressor and line up flash gas to scrubbing tower.

2. Purging of the system :

i) Ensure the positive isolation of the total system from the main plant by closing the following valves :

A. Purge Gas System :

a. First isolation valve at the battery limit.

b. Drain valves in between the battery limit isolation valves.

c. Isolation vale of the sample point at the battery limit.

d. Purge gas vent control valve PCV 2101 (The controller PC 2101 to be on manual).

e. Block valves in the N2 line to HEA 101. (Ensure taht the spectacle blind provided in between the block valves is in "Open" position).

B. Liquid Ammonia System

a. First isolation valve at the battery limit.

b. Drain valves in between the two battery limit block valves.

c. Isolation valve of the sample point at the battery limit.

d. Drain valves at the bottom of HFA 101.

e. Drain valves in between LCV 2101 and its block valve.

C. Flash Gas System

a. Block valve at the battery limit (Spectacle blind to be in "Open" position).

b. Drain valve down stream of block valve at the battery limit.

c. Isolation valve of the sample point at the battery limit.

d. Block valves of nitrogen line to flash gas compresor (Spectacle blind to be in "Open" position.

e. Drain valves of suction and discharge snubbers of HGB 101.

D. Wash Water System

a. Isolation valve at the battery limit (Spectacle blind to be in "Open" position).

Page 250: Ammonia Manual

Ammonia Plant Operating Manual 97

b. Isolation valve of the sample point at the battery limit.

c. Drain valves at the suction and discharge lines of HGA 101 A & B.E. Aqueous Ammonia System

a. Isolation valve at the battery limit (Spectacle blind to be in "Open" position).

b. Vent valve at the battery limit.

c. Isolation valve of the sample poiint at the battery limit.

d. Bypass valve of the strainer exit HDA 101.

e. Drain valve exit HDA 101.

F. Feed Gas System

a. Isolation valve of LCV 2103 and drain valve of HFA 102.

b. Isolation valve of sample point at the inlet of MS adsorbers HDA 102 A & B.

c. Blow down valves of MS adsorbers.

d. Drain valve on the shell side of HEA 105.

e. Isolation valve on the Nitrogen Line to HEA 105.

f. Isolation valves on the Nitrogen line to HEA 103 (spectacle blind to be in "Open" position).

g. Isolatoin valve on the Nitrogen heating line downstream of HEA 103.

h. Isolation valve of the sample point in the feed gas line exit MS adsorbers.

i. Bypass valve of the strainer exit MS adsorber and drain valve of the strainer.

j. Isolation valve on the Nitrogen heating line to the feed gas line at the inlet of cold box.

k. Isolation valves of pressure points in tubeside inlet and outlet of HEC 103.

l. Start-up isolation valve exit HEC 103.

G. Product Hydrogen System

a. Isolation valve on the nitrogen heating line at the exit of cold box.

b. Isolation valve of the pressure point on the product hydrogen line exit cold box.

c. Vent control valve PCV 2107.

d. Isolation valve of the sample point at the battery limit.

Page 251: Ammonia Manual

Ammonia Plant Operating Manual 98

e. Drain valves at the battery limit.

f. First isolation valve at the battery limit.

H. Tail gas system

a. Drain valve in the line from HFA 103 to HFA 104.

b. Isolation valve on the Nitrogen heating at the exit of the cold box. c. Isolation valve of the sample point exit cold box.

d. Vent control valve PCV 2109.

e. Isolation valve of the sample point at the battery limit.

f. Drain valve at the battery limit.

g. First isolation valve at the battery limit. (Spectacle blind to be in "Open" position).

ii) Ensure the system is "through" for purging by keeping the following valves in "Open condition"

A. Purge Gas System a. Second isolation valve at the battery limit.

b. Isolation valve of FCV 2101.

c. FCV 2101 (FCV 2101 to be on manual in fully "Open" position)

d. Isolation valve of SV 2101 at the inlet of HDA 101.

B. Liquid Ammonia System

a. Second isolation valve at the battery limit.

b. LCV 2101 (LC 2101 to be on manual in full "Open condition).

c. Isolation valve of LCV 2101.

C. Flash Gas System

a. Suction and discharge isolation valves of flash gas compressor.

b. PCV 2111 (PIC 2111 to be on manual in full "Open" position).

D. Wash Water System

a. Isolation valves on the spill back line of HGA 101 A & B.

Page 252: Ammonia Manual

Ammonia Plant Operating Manual 99

b. Suction valves of HGB 101 A & B.

c. Discharge valves of HGB 101 A & B.

E. Aqueous Ammonia System

a. LCV 2102 of HDA 101 (LC on manual)

b. Isolation valves of the strainer exit HDA 101.

F. Feed gas system

a. Isolation valves of the strainer exit MS adsorber.

G. Product Hydrogen System

a. PCV 2106 on HFA 103 (PC 2106 to be on manual)

b. HCV 2101.

c. Second isolation valve at the battery limit.

d. Isolation valve of SV 2102 on HFA 103.

e. Isolation valve of SV 2103 downstream PCV 2106.

H. Tail gas system

a. LCV 2104 (LC 2104 to be on manual)

b. Isolation valve of SV 2104 at the inlet of HEC 102.

c. Isolation valve at the inlet of HEA 103.

d. PCV 2108 to be on manual.

3. Nitrogen Sources of Purging :

1. The following are the Nitrogen Purge points provided :

a. 1" line at the inlet fo HEA 101 in the purge gas line.

b. 3/4" line at the suction of flash gas compressor.

2.Ensure the charging of LP Nitrogen header and availability of Nitrogen for purging.

3.Admit Nitrogen into the purge gas line at the inlet fo HEA 101 and into the suction line of HGB 101.

4. Pressurise the whole system of 2 Kg/cm²g.

Page 253: Ammonia Manual

Ammonia Plant Operating Manual 100

5. Keep Nitrogen pressure in the system at 2 Kg/cm²g for about 10 minutes.

6. Depressurise the system through PCV 2109 to the atmosphere.

7. Repeat the pressure swing operation for 3 times.

8.Check for oxygen content in the system by analysing the samples from the following points

a) AP 2101 - at battery limit in the purge gas line.

b) AP 2107 - at battery limit in the product hydrogen line.

c) AP 2108 - at the battey limit in the tail gas line.

d) AP 2109 - at the battery limit in the liquid ammonia line.

10. Repeat the purging operations till the oxygen content in the system comes down to less than 0.2 % as confirmed by 2 successive analysis.

11. Carryout the total heating of cold box unit as per the detailed description given under "Shutdown Procedures".

3. Reactivation of M.S. Adsorbers

To ensure both M.S. adsorbers are ready to take up the feed gas, manual reactivation of both the adsorbes prior to introduction of the feed gas is necessary. The reactivation of the adsorbers is done in following following steps.

1. Ensure that the adsorber system is totally isolated from the rest of the system by Closing the following valves :

a. Isolation valve in the tail gas line to HEA 103.

b. Isolation valve on the Nitrogen heating line to cold box.

c. Isolation valve on deriming N2 line to MS adsorber. d. Isolation valve on N2 line to HEA 103.

e. Isolation valve on N2 line to MS adsorber.

2. To take up regeneration of Tower A set the cam timer at 13 hrs. Put the tower on 'RUN' for 2 minutes and put tower back on 'STOP'. Then check that the following valves are in CLOSED position.

a. Blow down valves of MS adsorber.

b. Equalising valve.

c. Heating and precooling valves of adsorber B.3. Check that the following valves are in Open position.

Page 254: Ammonia Manual

Ammonia Plant Operating Manual 101

Heating and precooling valves of Adsorber A.

4. Set PIC 2109 at 2 Kg/cm²g on "auto".

5. Admit Nitrogen to the heater HEA 103 by opening the valves in the Nitrogen line. Establish flow fo 700 Nm3/Hr of Nitrogen through the heater and adsorber by maintaining a pressure of 2.3 Kg/cm²g on PI 2104.

6. Open isolation valve in the steam inlet ine of HEA 103 after lining up the stream trap.

7. Adjust the heating rate such that the adsorbent bed temperatures reach 200 - 250 0C in a duration of 5 hrs. of heating.

8. After ensuring the uniform temperature in the adsorber bed as indicated by the two TIs provided cut off steam to the heater HEA 103.

9. Allow the same quantity of Nitrogen through the circuit for a period of 6 hrs to effect cooling of the bed to ambient.

10. To regenerate tower B Set the can timer at 1 hr. Put of tower on 'RUN' for 2 minutes and put the toewr on 'STOP' check that the heating / precooling valves of HDA 102 B are open.

11. Check that the heating/precooling valves of HDA 102 A are closed.

12. Carry out the reactivation of HDA 102 B similar to the procedure adopted for HDA 102 A.

13. After completion of reactivatoin of HDA 102 B cut off N2 to adsorber check that PIC 2109 has closed on auto.

4. Purging of Cold Box interior with dry nitrogen

1. Charge the import N2 header from HWP.

2. Check for the dew point of Nitrogen at the battery limit to be -70 0C.

3. Open the inlet valve of cold box.

4. Ensure that the regulating valve controls the nitrogen pressure at 0.5 Kg/cm²g at the inlet of cold box, with a flow of about 1Nm3/Hr.

5. Check for the presence of any impurity like Oxygen and moisture in the Purge Nitrogen by analysing the gas from the sample point at the inlet of seal pot.

6. Check the level of oil in the seal pot.

7. Continue the purging.

8. Purging of cold box should be started atleast 4 days before the commencement of cooling down operations.

Page 255: Ammonia Manual

Ammonia Plant Operating Manual 102

5. Introduction of purge gas

1. Ensure that the following valves are in "closed" condition.

A. Purge Gas System

a. First isolation valve at the battery limit.

b. Drain valves inbetween battery limit isolation valves.

c. Isolation valve of the sample point at the battery limit.

d. Purge gas vent control valve PCV 2101.

e. Block valves in nitrogen to HEA 101 (keep the bleed valve in "Open" condition).

f. FCV 2101 (FC 2101 to be on manual)

B. Liquid Ammonia System

a. First isolation valve A 522 at the battery limit.

b. Drain valves inbetween the two battery limit block valves.

c. Isolation valve of sample point at battery limit.

d. Drain valve at the bottom of HEA 101.

e. Drain valve in between LCV 2101 and its block valve.

f. Isolation valve of LCV 2101.

g. LCV 2101 (LC 2101 on manual)

C. Wash Water System

a. Isolation valve at the battery limit.

b. Isolation valve of the sample point at the battery limit.

c. Drain valves at the suction and discharge lines of HGA 101 A & B.

d. Suction and discharge valves of HGA 101 A & B.

e. Spill back valves of HGA 101 A & B.

D. Aqueous Ammonia System

Page 256: Ammonia Manual

Ammonia Plant Operating Manual 103

a. Isolation valve at the battery limit.

b. Vent valve at the battery limit.

c. Isolation valve of the sample point at the battery limit.

d. Bypass valve of the strainer exit HDA 101.

e. Drain valve exit HDA 101.

f. Isolation valve A 523 upstream of strainer exit HDA 101.

g. LCV 2102 (LC 2102 to be on manual).

E. Feed Gas System

a. Isolation valve of LCV 2103 and drain valve of HFA 102.

b. Isolation valve of sample points.

c. Blow down valves of MS adsorbers.

d. Equalizing valve of HDA 102 A & B. e. Drain valve on shell side of HEA 105.

f. Isolation valve on Nitrogen line to HEA 105.

g. Isolation valve in Nitrogen line (Bleed open).

h. Isolation valve on Nitrogen heating line downstream of HEA 108.

i. Isolation valve of the sample point in the feed gas line exit MS adsorbers.

j. Bypass valve of the strainer exit MS adsorbers.

k. Drain valve of the strainer.

l. Isolation valve on Nitrogen heating line to the feed gas line at the inlet of the cold box.

m. Isolation valves of pressure points at tube side inlet and outlet of HEC 103.

n. Start-up isolation valve exit HEC 103.

F. Product Hydrogen System

a. Isolation valve on Nitrogen heating line at the exit of cold box.

Page 257: Ammonia Manual

Ammonia Plant Operating Manual 104

b. Isolation valve of the pressure point on the product hydrogen line exit cold box.

c. Pressure control valve PCV 2106 (PC on manual).

d. HCV 2101.

e. Vent control valve PCV 2107 (PC on manual) f. Isolation valve of the sample point at the battery limit.

g. Drain valves at battery limit.

h. First isolation valve at battery limit.

G. Tail Gas System

a. Drain valve in the line from HFA 103 to HFA 104.

b. LCV 2104 of HFA 103 (LC 2104 on manual).

c. Isolation valve of sample point exit cold box.

d. Isolation valve oon Nitrogen heating line at the exit of cold box.

e. PCV 2108 (PC 2108 to be on manual).

f. Vent control valve PCV 2109 (PIC 2109 to be on manual).

g. Isolation valve of sample point at the battery limit.

h. Drain valve at the battery limit.

i. First isolation valve at the battery limit.

2. Ensure the following valves are in OPEN condition :

A. Purge Gas System

a. Second isolation valve at the battery limit.

b. Isolation valve of FCV 2101.

c. Isolation valve of SV 2101 at the inlet of HDA 101.

B. Liquid Ammonia System

a. Second isolation valve at the battery limit.

C. Flash Gas System

Page 258: Ammonia Manual

Ammonia Plant Operating Manual 105

a. PCV 2111 (PC 2111 to be on manual).

D. Wash Water System

Nil.

E. Aqueous Ammonia System

Downstream isolation valve of the strainer exit HDA 101.

F. Feed Gas System

Isolation valves of the strainer exit MS adsorbers.

G. Product Hydrogen System

a. Second isolation valve at the battery limit.

b. Isolation valve of SV 2102 on HFA 103.

c. Isolation valve of SV 2103 downstream PCV 2106.

H. Tail Gas System

a. Isolation valve of SV 2104 at the inlet of HEC 102.

b. Isolation valve at the inlet of HEA 103.

3. OPEN the following pressure control valves fully on manual :

a. PCV 2109 - Vent control tail gas.

b. PCV 2108 - Line control on tail gas.

c. PCV 2107 - Vent control on product hydrogen.

4. Open gradually the block valve at the battery limit in the purge gas line after getting clearance from the control room.

5. Pressurise the purge gas line upto FCV 2101 at the rate of 50 Kg/cm²g hr as indicated by PC 2101, till the line pressure gets equalised to the synthesis loop pressure. Open the block valve fully.

6. Put the FCV 2101 trip action, on bypass and gradually open FCV 2101 on "Manual" admitting about 1000 Nm3/Hr. Reduce the syn loop purge rate through HCV 1812 accordingly. Adjust firing in 4 & 6 rows of primary reformer burners to maintain reformer exit temperature.

7. Pressurise gradually the feed gas system to 45 Kg/cm²g upto PCV 2106 as indicated by PC 2106 (at 50 Kg/cm²g per hour).

Page 259: Ammonia Manual

Ammonia Plant Operating Manual 106

8. Stabilise the system pressure at 45 Kg/cm²g and get PC 2106 on "Auto".

9. Open the battery limit isolation valve in the wash water line and check the header pressure to be 24 Kg/cm²g.

10. Line up HGA 101 A

a. Open the suction valves of HGA 101 & 101 B.

b. Prime both the pumps through the respective vents.

c. Open the discharge valve of HGA 101 A.

d. Check the pump for free rotation by turning V Pulley 5-6 times by hand.

e. Confirm the correct direction of rotation and check for any abnormality by kick start.

f. Run the pump on no load for 10 minutes after starting.

g. During no load running check whether valve and gear sounds are normal.

h. Ensure once again the complete removal of locket up gas by opening the priming vent.

11. Close the spillback valve of the pump fully and establish water flow in scrubbing tower.

12. Open fully the battery limit block valve in aqueous ammonia header.

13. Open fully the isolation valve upstream of the strainer in aqueous ammonia line from HDA 101.

14. Line up LCV 2102 of HDA 101 and set LC 2102 on "Auto" at 60 %.

15. Open the discharge valve of standby pump and set it on auto.

16. Take up the pressure gradually in the feed gas system to 57.5 Kg/cm²g PC 2106.

6. COOLING DOWN OPERATION

1. Start-up of No. 2 Cryo Compressor HGC 102 A & B

i. Ensure that the freon refrigerant is adequately charged into the system.

ii. Switch on the crank case heaters for both the compressors atleast 12 hrs before starting the compressors.

Page 260: Ammonia Manual

Ammonia Plant Operating Manual 107

iii.Check the oil level in the crank case.

iv. Ensure that the following valves are in closed condition :

a. Isolation valves of charging dryer Y 201.

b. Refrigerant charging valve.

c. Drain valve of HEC 103.

d. Drain valve of common accumulator at the suction.

e. Suction valves of HGC 102 A & B. f. Evacuation valves.

g. Oil drain valves of HGC 102 A & B.

h. Vent and drain valves of the condenser E 201.

i. LCV 2107 of HEC 103 (LC 2107 on manual)

j. PCV 2113 (PC 2113 on manual)

v. Ensure that the following valves are in OPEN condition :

a. Liquid freon valve exit the condenser E 201.

b. Bypass valve of the charging dryer Y 202.

c. Isolation valve on the freon line from the condenser to the oil coolers of HGC 102 A & B.

d. Isolation valve of LCV 2107.

e. Isolation valve of PCV 2113.

f. Discharge valves of HGC 102 A & B.

g. Oil drain valves from oil separator V 201.

h. Isolation valve at the vapour inlet to condenser E 201.

i. Isolation valve of SV 2116 on condenser E 201.

j. CWS & CWR valves to the condenser.

vi. Ensure that the following valves are in SLIGHTLY OPEN position :

a. Blow down valve from HEA 103.

b. Drain valve from oil separator of HGC 102 A & B.

vii.Crack open the suction valve and start the compressor HGC 102 A.

viii.Bring down gradually the suction pressure to about -470 mmHG by adjusting the suction valve. Ensure that the amperage of the motor does not exceed 30.

Page 261: Ammonia Manual

Ammonia Plant Operating Manual 108

ix. As the amperage reduces, open PCV 2113 gradually watching the amperage. When PCV 2113 is open fully, set PC 2113 on auto @ 0.5 Kg/cm²g.

x. Open gradually LCV 2107 on manual, watching the suction pressure of the compresor and amperage of the motor.

xi.Close PCV 2107 gradually and set the controller on "auto" at 5 Kg/cm²g..

xii.Close PCV 2108 gradually and set the controller on "AUTO" at 2.3 Kg/cm²g.

xiii.Close PCV 2100 gradually and set the controller on "Auto" at 2 Kg/cm²g.

xiv.Take up the purge gas flow gradually, following the differential temperatures flow rate curve. Ensure that the purge rate through HCV 1812 is accordingly adjusted. Simultaneously stabilise the ammonia recovery section and firing in 4th and 6th rows burners of primary reformer.

xv.Open gradually and manually LCV 2104 of HFA 103. Allow minimum required flow only through PCV 2106.

xvi.Open tail gas isolation valve and line up tail gas to fuel gas header. Set PC 2108 @ 0.35 Kg/cm²g higher than a real pressure indicated by PIC 2109.

xvii.When continuous flow through PCV 2108 is observed set cam timer at 10 hrs. and put the tower on 'RUN'.

xviii.When the purge gas flow is increased to about 3700 Nm3/Hr, start Cryo Compressor No. 1.

2. Start-up of No. 1 Cryo Condenser HGC 101 A

i. Ensure that the freon refrigerant is adequately charged in the system.

ii. Switch on the crankcase heater of HGC 101 A and ensure that it is on for a minimum period of 12 hrs before start-up of the compressor.

iii.Check the oil level in the crank case.

iv. Ensure that the following valves are in CLOSED condition :

a. Inlet and outlet valves of charging dryer Y 101.

b. Refrigerant charging valve.

c. Drain valve downstream of LCV 2105 of HEA 101.

d. Drain valve of HEA 101.

e. Drain valve downstream of LCV 2106 of HEA 102.

f. Drain valve of HEA 102.

Page 262: Ammonia Manual

Ammonia Plant Operating Manual 109

g. Drain valve upstream. of PCV 2112.

h. Drain valve of the common suction accumulator V 102.

i. Suction valves of HGC 101 A & B.

j. Evacuation valves of HGC 101 A & B.

k. Oil drain valves of HGC 101 A & B.

l. Vent and drain valves of the condenser E 101.

m. LCV 2105 of HEA 101 (LC 2105 on manual).

n. LCV 2106 of HEA 102 (LC 2105 on manual).

o. PCV 2112 (PC 2112 on manual).

p. Discharge valve of HGC 101 B.

q. Oil drain valve on the line from oil separator.

v) Ensure the following valves are in OPEN position

a. Liquid Freon valve exit the condenser E 101.

b. Bypass valve of charging dryer Y 101.

c. Isolation valve on the freon line from the condenser to the oil coolers of HGC 101A&B

d. Isolation valve on the vapour freon line from oil coolers to compressor suction line. e. Isolation valve of LCV 2105 of HEA 101.

f. Isolation valve of LCV 2106.

g. Isolation valve of PCV 2112.

h. Discharge valve of HGC 101 A.

i. Isolatoin valve at the vapour inlet to the condenser E 101.

j. CWS & CWR valves to the condenser E 1001.

k. Isolation valves of SV 2112 & SV 2113 at the discharge of HGC 101 A & B.

l. Isolation valve of the SV 2114 at condenser E 101.

m. Oil drain valve from oil separator to HGC 101 A.

Page 263: Ammonia Manual

Ammonia Plant Operating Manual 110

n. Isolation valves of SV 2111-1 SV 2111-2 on HEA 101 & HEA 102.

vi. Ensure that the following valves are in SLIGHT OPEN position.

a. Blow down valves from HEA 101 & HEA 102.

b. Drain valve from oil separator to HGC 101 A & B.

vii. Crack open the suction valve to get a suction pressure of 3.5 - 4.0 Kg/cm²g downstream of the valve.

viii. Start the compressor HGC 101 A and maintain the suction pressure at 3.5 to 4 Kg/cm²g by throttling the suction valve as and when required. Never allow the amperage of the motor to exceed 80.

ix. When the suction valve is opened fully, open PCV 2112 gradually on manual watching the suction pressure and amperage.

x. Set PC 2112 on "Auto" to get a pressure of 4 Kg/cm²g at the shell side of the precoolers.

10. Observe the level of the liquid ammonia in the ammonia separator. Line up LCV 2101 by opening isolation valve of battery limit isolation rate A 522 and set LC 2101 on auto at 50 %.

11. Line up LCV 2103 of HFA 102 by opening the isolation valve A 193. Set the controller on auto at 50 %.

12. Increase purge rate through FCV 2101 till HCV 1812 is fully shut. Allow the cooling process by means of Joule Thomson effect across PCV 2106 in the feed gas system and LCV 2104 of the drain separator HFA 103 to continue further. When the inlet temperature of drain seperator HFA 103 reaches - 150 0C, a portion of the methane in the feed gas will start liquifying.

13. When the temperature of tail gas inlet phase separator reaches -195 0C, start closing LCV 2104 gradually on manual not allowing the temperature to fall further. Stabilise the level of HFA 103 at 50 % and set LC 2104 on "Auto".

14.Raise gradually the pressure of the product hydrogen line with PC 2107 (which is on auto) to the specified pressure of 47.5 Kg/cm²g. It is to be noted that the cooling by way of Joule Thomson Effect across PCV 2106 comes down while pressurising the product hydrogen line to 47.5 Kg/cm²g. Hence care has to be taken to ensure that the pressurisation is carried out gradually without affecting the cold box, temperature and the degree of condensation of methane in HFA 103.

15.Check for the purity of product hydrogen through the sample point AP 2107 and through the on-line analyser AH2RA 2100. Ensure that the purity of hydrogen reaches the specified value of 93 % by stabilising the temperatures in the cold box unit at design values.

7. LINING UP PRODUCT HYDROGEN

Page 264: Ammonia Manual

Ammonia Plant Operating Manual 111

1. Set PC 2107 at a pressure equal to the I discharge pressure of SGC. Take PC 2107 on manual.

2. Open gradually the battery limit block valve of the product hydrogen header.

3. Check there is no change in hydrogen header pressure before and after opening the valve hydrogen.

4. If the hydrogen header pressure increases, isolate the block valve immediately and inform control room.

5. On confirming that there is the change in H2 pressure start closing PIC 2101 gradually. Increase the requirred amount of air to secondary reformer and load syn gas compressor.

6. It is to be noted that the product hydrogen from recovery unit at a relatively cold condition( 30 - 35 0C) is joining the main stream of make up gas (40-45 0C) at the inlet of the II suction separator of syn gas compressor. This would in effect bring down the average temperature of the gas at the suction of II stage. Hence a close watch has to be kept on the water level of II suction separator.

7. As hydrogen is lined up to SGC, available tail gas to fuel gas header comes down. Adjust the firing rate in 4th and 6th row of burners.

8. Check that PCV 2107 & PCV 2109 are in closed poisiton on "Auto". Keep the set points of both the contrtollers slightly above the actual pressures to avoid unnecessary venting of the gas.

8. LINING UP OF FLASH GAS COMPRESSOR HGB 101

1. Ensure the system remains purged with Nitrogen.

2. Ensure the following valves remain in CLOSED condition.

a. Isolation valve at the battery limit. b. Drain valve at the battery limit.

c. Suction and discharge isolation valves of HGB 101.

d. Isolatoin valve of sample point AP 2106.

e. Drain valves of suction and discharge snubbers.

f. Vent valves of suction and discharge snubbers.

g. Isolation valve of sealing nitrogen line to the compressor HGB 101.

Page 265: Ammonia Manual

Ammonia Plant Operating Manual 112

h. Vents and drain valves of CWR lines of HGB 101.

3. Ensure the following valves are in OPEN position

a. PCV 2111 (PC 2111 on manual).

b. CWS & CWR valves.

4. Line up seal nitrogen to the compressor by opening the isolation valve in the dry nitrogen line to the compressor.

5. Open the battery limit isolation valve and check the pressure to be 19.4 Kg/cm²g as indicated by PC 2111.

6. Open suction and discharge valves of the compressor.

7. Check the oil level in the crank case.

8. Check for free rotation of the rotor by hand.

9. Check for the direction of rotationof the motor by kick start. Check for any abnormality also during kick start.

10. Start the compressor and run it on no load for 30 minutes with PC 2111 on manual and full open position.

11. Watch the compressor performance (vibration abnormal sound, temperature etc)

12. Start loading the compressor gradually by closing the PCV 2111 on manual, till PCV 1301 just closes fully. During loading observe the downstream parameters like cooler exit temperature, levels in HFA 102, HFA 101, HEA 102, temperature condition in cold box etc. Set PC 2111 on ""Auto".

13. Stabilise the hydrogen recovery unit to cope up with additional load by way of flash gas.

9. START UP PROCEDURE(After short stoppage)

1. Put 'FCV 2101 trip action, on bypass.

2. Open FCV 2101 slightly and raise the system pressure to 45 Kg/cm²g.

3. When PI 2103 low alarm cancels, start the scrubbing water pump.

4. Continue to raise the system pressure and stabilise PC 2106 @ 57.5 Kg/cm²g.

5. Keep PCV 2107 open fully on manual.

6. Increase purge gas rate gradually.

7. As the cold box would not have lost the temperature, there will be condensation and HFA 103 level would tend to rise.

8. Set LC 2104 on auto @ 60 %.

9. When there is continuous flow that PCV 2108, line up tail gas to the fuel gas leader of

Page 266: Ammonia Manual

Ammonia Plant Operating Manual 113

main plant.

10. Check that the differential of 0.3 Kg/cm²g is maintained between PC 2108 and PC 2109.

11. Switch on M.S. adsorber, setting the cam timer at suitable position.

12. When the purge gas flow is increased to 3700 Nm3/Hr, start No. 1 Cryo Compressor. Remove "FCV trip action" bypass.

13. Line up ammonia to 1123 and drain water to flash vessel 1132.

14. Start No. 3 Cryo Compressor.

15. Continue the cooling down process and watch hydrogen puerly.

16. When the hydrogen purely is about 93 %, raise PC 2107 gradually to II suction pressure of synthesis gas compressor.

17. Line up product hydrogen to SGC.

18. Start flash gas compressor and stabilise.

16.4 PURGE GAS SYSTEM

1. Ensure that PCV 2101 is closed on manual always. This is to ensure that there is no venting pf purge gas through the PCV 2101 on normal operation. During start up also, unless there is positive flow through the tail gas line from cold box, PCV 2101 should not be used for venting.

2. Whenever any change in the purge gas flow through FCV 2101 is effected, ensure that suitable adjustment is made in purge rate through HCV 1812 and in the air rate to secondary reformer. Also ensure the primary reformer exit gas temperature is maintained by suitable adjustment of firing in 4th & 6th row of burners. Recovery system also is to be stabilised whenever changes are effected in the purge gas flow through FCV 2101.

3. Have a continuous monitoring of the purge gas temperature at the exit of HEA 101. The normal value to be maintained in 5 0C for effecting maximum condensation of ammonia. An alarm provision is given when the temperature increases above 7 0C. In case increase in the temperature check the following :

a. The refrigerant freon level in HEA 101 through local level gauge and LC 2105.

b. Shell side pressure of HEA 101.

c. Adequacy of oil blow down from HEA 101 to compressor suction accumulator.

4. Double check the level of HFA 101 with LG 2101 as well as LC 2101 as otherwise it would lead to either carryover of liquid ammonia into the scrubbing tower or entry of gas into the liquid ammonia line.

Page 267: Ammonia Manual

Ammonia Plant Operating Manual 114

Flash Gas System

1. Ensure that the suction pressure of the flash gas compressor is maintained by PC 2111 without affecting the letdown vessel pressure. In normal course it is expected that PCV 2111 would remain partly closed on auto and PCV 1301 closed on auto.

2. Close monitoring checking of the following is required to ensure a smooth and normal operation of flash gas compressor.

a. Lube oil level in the crank case.

b. Colour and turbidity of lube oil.

c. Abnormal sound around the cylinder and crank case.

d. Compressor discharge pressure and temperature.

e. Vibration level.

f. Bearing temperature and cylidner head cover temperature.

g. Amperage of the motor.

h. Steady flow of cooling water to the glands and after cooler as seen through the sight glasses.

i. Periodical draining of suction and discharge snubbers for removal of any accumualated condensate.

Feed Gas System

Scrubbing Tower

1. Normal operation of scrubbing tower depends upon the ammonia recovery unit as the water is from the ammonia still 1125. Hence any upsets in the recovery system would lead to a probable upset in the scribbing tower operation. Hence in the event of any upset in either of the systems the operator should take care of the other unit immediately.

2. A low trip is provided for the water flow to the suction of water pumps. In the event of any upset in the ammonia recovery system, and subsequent fall in 1125 pressure or level the water to the suction of HGA 101 A & B to immediately changed over to the alternate source provided from LP desuperheating water header to avoid the occurrence "Low flow trip". However this would result in higher water input to the recovery system. Hence open the drain upstream of LCV 1904 accordingly to maintain water balance in ammonia recovery system.

3. A low pressure trip is provided at the scrubbing tower exit gas line. The possibilities of occurrence of this trip are :

i. Mal function of PCV 2106. ii. Flooding in the scrubbing tower. iii. Mal function of the LCV 2102 of the scrubbing tower. iv. Damage to the packing of the scrubbing tower.

Page 268: Ammonia Manual

Ammonia Plant Operating Manual 115

4. Close monitoring of the pressure at the exit of the scrubbing tower is necessary. In the event of any fall observed in the pressure check for normal operation of the following :

i. LC/LCV 2102 ii. PC/PCV 2106 iii. LC/LCV 2101

5. Monitor the % opening of LCV 2102 to know the extent of choking in the upstream strainer. In case of choking of the strainer, bypass the strainer and clean the same.

6. An alarm provision is given for high pressure at the scrubbing tower exit in the feed gas system. This is likely to happen in the event of the following upsets.

i. Mal function of PC/PCV 2106. ii. Mal function of MS adsorber change over system.

As soon as the high pressure alarm appears in the panel take FC 2101 on manual and close the FCV 2101 (otherwise sensing FC 2101 would open more on auto causing further pressure increase which would result in popping of SV 2101 at the inlet of scrubbing tower and or SV 2102 on the vessel HFA 103).

Water pumps

i. The following are to be checked with regard to the normal operation of HGA 101 A/B.

a. Noise in valve plate and gear.

b. Amperage of the motor.

c. Speed of the pump with respect of belt slippage.

d. Discharge pressure of the pump.

e. Pulsations in the discharge.

f. Contamination in the lube oil by appearance and oil level.

g. Temperature of plunger and bearings.

h. Vibration in the pump.

ii.Change over the pumps once in 750 hrs without fail. Do not fail to operate the stand- by pumps once a day for 5 minutes.

iii.Continuously monitor the suction pressure of the pump. In the event of low suction pressure change over the pump and clean suction strainer.

Page 269: Ammonia Manual

Ammonia Plant Operating Manual 116

3. A low temperature alarm is provided for the feed gas at the exit of HEA 102 to avoid freezing of condensate in the downstream piping and vessels.

On the other hand higher temperature would lead to moisture carryover into the M.S. adsorbers. Hence the temperature at the exit of HEA 102 has to be maintained at 150 C by controlling the following parameters.

a. Shell side pressure of HFA 102 through PCV 2112.

b. Level of liquuid freon the shell side of HEA 102 through LIC 2106.

c. Oil blow down from HEA 102 to the suction accumulator of the compressor.

4. Cryo Compressor HGC 101 A & B, HGC 102 A & B

1. The following are to be closely checked/monitored to ensure a normal operation of the compressor.

a. Oil level in the crank case.

b. Lube oil temperature. c. Pressure drops across the lube oil filter. If it exceeds 0.5 Kg/cm²g change over the filter and clean it.

d. Pressure drop across the suction strainer. If this exceeds 0.5 Kg/cm²g change over the compressor and charge the filter element.

e. Discharge pressure of the compressor.

f. Amperage of the motor.

g. Vibration levels.

h. Abnormal noise in the crank case.

i. Discharge temperature (A high discharge temperature trip is provided as it would lead to decomposition of freon).

M.S. Adsorbers

1.The operation of the M.S. adsorbers is on 12 hrs cycle consisting of 5 hrs of heating 6 hrs of cooling and 1 hr of changeover operations which are to be carried out in the following sequence.

H D A 102 A H D A 102 B __________________ _______________ Time Valves Valves Valves Valves Open lose Open Close

Page 270: Ammonia Manual

Ammonia Plant Operating Manual 117

0 hrs Inlet Heating/ Heating/ Inlet A 112(Begining of Outlet precooling pre- Outlet A 114heating cycle) A 111 A 331 & cooling Blowdown 102 A in service A 113 A 333 A 332 A 116

Blowdown A 334 A 115.

102 B in Equaliser A 117 is in closed condition.reactivation Heating valve A 335 on heating side.

5 hrs - do - - do - - do - - do -(End of heatingcycle & begining Equaliser A 117 is closed condition.of cooling cycle) Heating valve A 335 cooling cycle.

11 hrs - do - - do - - do - - do -(End of cooling cycle and begining A 117 - closeof cooling operation) A 335 - On cooling side

11.02 hrs - do - - do - Nil Heating/(Isolation of precooling.HDA 102 B) A 332& A 334, inlet A 114 A 117 - Close outlet A 114 A 335 - Cooling side. Blow down A 116.

11.04 hrs - do - - do - Nil - do -(Begining of equalising) A 335 - Cooling side. A 117 - Open.

11.19 hrs - do - - do - Nil Heating/(End of lining precoolingup HDA 102 B) A 332 & A 334 Blow down A 117 - Close A 116. A 335 - On cooling side H D A 102 A H D A 102 BTime Valves Valves Valves Valves Open Close Open Close 11.21 hrs - do - - do - Inlet - do -(Begining of A 112

Page 271: Ammonia Manual

Ammonia Plant Operating Manual 118

parallel operation) Outlet A 114 11.36 hrs Nil Inlet A 111 - do - - do -(End of parallel Outlet A 113operation & Heating /isolation of HDA precooling AA 102 A) 331 & A 333 Blowdown A 115

A 117 - Close A 335 - On cooling side

11.38 hrs Blow Inlet A 111 Inlet Heating/(Begining of down Outlet 113 A 112 precoolingdepressurisation) A 115 Heating / Outlet A 332 & precooling A 114 A 335. A 331 & A 333 Blowdown A 116 A 117 - Close A 335 - On cooling side

11.56 hrs Nil A 111, A 113 - do - - do -(End of A 331, A 333depressurisation) & A 115

A 117 - Close A 335 - On cooling side. H D A 102 A H D A 102 BTime Valves Valves Valves Valves Open Close Open Close

11.58 hrs A 331 A 111, A 113 - do - - do -(Preparations for A 333 A 115regeneration ofTower A) A 117 - Close A 335 - On cooling side

12.01 hrs Heating/ Inlet - do - - do -(Begining of precooling A 111regeneration of A 331 & Outlet A 113Tower A) A 333 Blowdown A 115

A 117 - Close

Page 272: Ammonia Manual

Ammonia Plant Operating Manual 119

A 335 - On heating cycle 2. In the event of any stoppage of "Reactivation cycle" within 4 hours after commencement of heating cycle, the reactivation cycle has to be once again started back from the beginning.

3. Close monitoring of the pressure drop across the strainer s-104 is necessary.

4. Analysis of moisture and ammonia slip from the adsorber unit is necessary to take corrective actions to avoid choking in cold box.

Operation of Cold Box Unit

1. Ensure that dry Nitrogen purge in "ON" to the interior of cold box to avoid any ingress.

2. Check the oil level in the oil seal pot.

3. Analyse the dry purge Nitrogen at the inlet of oil seal to check for any leaks.

4. Closely monitor the temperatures. The temperature difference between feed gas inlet and product hydrogen exit cold box and tail gas exit cold box is normally maintained at 2 0C. Any increase in DT is an indication of poor transfer in cold box suggesting a probably choking of the heat exchangers HEC 101 & HEC 102.

5. The control of temperature at the inlet of HFA 103 at -193 0C and at the inlet of HFA 105 at -194.8 0C is most essential. Any further reduction in these temperatures may leak to freezing of methane causing plugging in the cold box. However, any increase in these parameters would lower the recovery efficiency and purity of the product. Hence it is necessary to meticulosly control these temperatures in the cold box by suitably adjusting hydrogen injection through HCV 2101 and the tail gas header pressure through PC 2108.

6. Never open the heating valves A644, A645 & A646 during normal operation.

7. In case of any suspected ammonia blockage inside cold box warming up of cold box must be carried out to bring up temperature TI-2108 and 9 to -40 0C.

8. In case of any upset leading to closure of FCV 2101, LCV 2104 should be closed immediately on manual. Otherwise with no incoming as to cold box, cold generated by the liquid flashed will not be dissipated and the temperature of tail gas / product H2 line will drop to negative temperature.

9. During normal run as well as start up and shutdowns, ensure that the temperature TI 2105, 10 & 11 are always more than 0 0C.

10. In case LCV 2104 stucks up to open position during any shutdown, tail gas / product H2 temperature will fall less than 0 0C. To prevent this happening, open the drain valve A 391 and drain away all the liquid to the disposal tank and depresurise the system gradually watching the various temperatures.

Page 273: Ammonia Manual

Ammonia Plant Operating Manual 120

11. During disposing operations, hydrogen, methane, etc., are discharged through the vent line provided over the drain tank HFA 104. It must be made as a practice to use the provision of 'nitrogen purge' into the interior of the vent line to prevent the formation of explosive gas mixture in the stock.

12. Do not drain liquid from drain separator and phase separator if there is a fire near cold box.

16.5 SHUTDOWN PROCEDURE

Planned Stoppage (Long Duration)

1. Close the isolation valves at the battery limit in the product hydrogen line. While isolating, check with local gauge and ensure that the product hydrogen system pressure and tail gas pressure do not exceed the specified values 47.5 and 2.0 Kg/cm²g. Reduce air flow to secondary reformer accordingly.

2. Close the isolation valve at the battery limit in the tail gas line. Adjust firing in 4th & 6th row burners of primary reformer to maintain the primary reformer exit temperature.

3. Take PC 2111 on manual and open PCV 2111 gradually watching the pressure of the let down vessel system PC 1301. Unload the flash gas compressor fully.

4. Stop the flash gas compressor and close the suction and discharge valves and the battery limit isolation valve A 413 in the flash gas line.

5. Reduce the purge gas flow gradually and increase purge acordingly through HCV 1812 to maintain the parameter of the synthesis loop. Cut off the flow through FCV 2101. Put back the controller FC 2101 on manual in closed condition.

6. Put back LC 2104 on manual and close the LCV 2104.

7. Ensure that the PCV 2106 is in fully closed position, with PC 2106 on auto at a setting of 57.5 Kg/cm²g.

8. Stabilise ammonia recovery section during the above operation.

9. Close the isolation valve of FCV 2101 and the battery limit isolation valves.

10. Open LCV 2101 on manual and drain liquid Ammonia to 1123. Watch lip Ammonia header pressure at PGHRU battery limit valve and upstream isolation valve.

11. Stop Cryo Compressor No. 1 HGC 101 A

a) Close the liquid freon valve from E 101 to HEA 101 & 102 and allow the liquid freon to get stored in the condenser E 101.

b) Observe a fall in the suction pressure of the compressor gradually from 4 Kg/cm²g due to the stoppage of the process load in the precoolers No. 1 & No. 2 HEA 101 & 102 and the fall in the liquid freon level in HEC 101 & 102.

c) Stop the compressor HGC 101 A and close the suction and discharge valve.

Page 274: Ammonia Manual

Ammonia Plant Operating Manual 121

d) Put back LC 2105, LC 2106, LC 2112 on manual and close LCV 2105, LCV 2106 & PCV 2112.

e) Close the isolation valves of LCV 2105, LCV 2106 & PCV 2112.

f) Close the blow down valves from HEA 101 and HEA 102.

g) Close the drain valve from oil separator to HGC 101 A & B.

12. Stop the Cryo Compressor No. 2 HGC 102 A

a) Close liquid freon valve from E 201 to HEC 103 and allow the liquid freon to get stored in the condenser with compressor running.

b) Observe the fall in the suction pressure of the compressor gradually from -130 mmHG to -400 mmHG due to the stoppage of the process load in the precooler No. 3 and the fall in the liquid freon level in HEC 103.

c) Stop the compresspor HEC 102 A and close the suction and discharge valves.

d) Put back LC 2107 and PC 2113 on manual and close LCV 2107 and PCV 2113.

e) Close the isolation valves of LCV 2107 and PCV 2113.

f) Close blow down valve from HEA 103.

g) Close the drain valves from oil separator to HGC 102 A & B.

13. Close the upstream isolation valve of LCV 2103.

14. Changeover MS adsorber unit HDA 102 A & B from "RUN" to Stop.

15. Stop the water pump HGA 101. 16. Close suction and discharge valves.

17. Close the battery limit isolation valve on the scrubbing water line.

18. Close the upstream isolation valve of the LCV 2102 and the battery limit isolation valve A 528 in the aqueous ammonia header.

19. Depressurise the feed gas system, the product hydrogen line and the tail gas line through PCV 2106, PCV 2107, PCV 2108 and PCV 2109. Put back PC 2106, PC 2107, PC 2108 & PIC 2109 to about 2Kg/cm²g.

20. Drain the entire liquid hold-up from the drain separtor HFA 103 to the liquified gas disposed tank HFA 104 by opening the drain valve. Ensure that nitrogen seal is also simultaneously.

21. Admit Nitrogen to the vent header by opening Nitrogen valves A 657 and A 654 in the Nitrogen purge line.

22. Confirm absence of liquid in drain separator with LC 2104.

23. Ensure that the drain valve from HFA 103 in HFA 104 is fully open.

Page 275: Ammonia Manual

Ammonia Plant Operating Manual 122

24. Open the isolation valves of the Purge Nitrogen to HEA 101 and feed dry N2 to cold box.

25. Continue this operation till the temperature inlet of HFA 103 increases to -60 0C. Ensure that the heating rate does not exceed 40 0C/hr by adjusting the nitrogen flow.

26. Set M.S. adsorber in heating position.

27. Admit N2 to M.S. adsorber through heating/precooling valve and take the dry N2 to cold box by opening heating valve. Check that PCV 2109 and PCV 2108 are closed.

28. Open PCV 2106 fully manually.

29. Open Nitrogen heating valve in product hydrogen system.

30. Carry out heating of the product hydrogen system similar to the feed gas system by venting throught the drain valve.

31. Open LCV 2104 fully, when drain valve A 391 is defrosted.

32. Open Nitrogen heating valve intail gas system and close fully heating valve in product hydrogen system.

33. Carrying out heating of the tail gas system similar to the feed gas and product hydrogen systems till TI 2109 reads 40 0C.

34. Open Nitrogen heating valves A 646 and 644 in the product hydrogen and feed gas system and continue heating operation through the drain of HFA 103.

35. Complete the total heating of the cold box unit, when all the thermometers indicate about 40 0C.

36. After ensuring the comletion of total heating close the following valves :

a. Drain valve from HFA 103 to HFA 104.

b. Nitrogen valve to the vent header exit HFA 104.

c. PCV 2106 & LCV 2104.

d. Isolation valve in the steam line.

e. Isolation valves in the Nitrogen heating line to feed gas system, tail gas system and product hydrogen system.

f. Isolation valves in the Nitrogen line to HEA 103.

g. Isolation valve in the Nitrogen line exit HEA 103.

37. Purge the flash gas system independantly and box up under N2 atmosphere.

Short Stoppage

Page 276: Ammonia Manual

Ammonia Plant Operating Manual 123

1. Isolate the product H2 block valves. Check the local PI while isolating and ensure that the pressure does not shoot up. Simultaneously, adjust the opening of PCV 2107 on auto.

2. Stop flash gas compressor.

3. Reduce purge gas flow gradually and close FCV 2101 fully.

4. Stop Cryo Compressor No. 1.

5. When continuous flow through PCV 2108 ceases, isolate tail gas header from fuel gas header of main plant. Ensure that PCV 2109 controls the tail gas header pressure.

6. Close LCV 2104 on manual.

7. When ammonia separator level come down, isolate the LCV and its block valve.

8. Stop M.S. Adsorber.

9. Monitor the temperatures TI 2105, 10 & 11 and ensure that they are above 0 0C.

Instrument Air Failure

In case of instrument failure the following actions are to be taken immediately.

1. Close the block valves on purge gas line. This is necessary to avoid depressurisation of synthesis loop through PCV 2101 which trip open on instrument air failure.

2. LCV 2104 of drain separator and FCV 2101 trip close on failure of instrument air. But PCV 2106, PCV 2107, PCV 2108 & PCV 2109 trip open to depressurise the cold box. Temperature TR 2105, 10 & 11 should be closesly monitored to check that the temperature do not go down below 0 0C.

3. The LCVs in the freon line to precoolers and PCVs on the suction of cryo compressors trip close on failure of instrument air. Hence cryo compressor should be manually stopped.

4. LCV 2102 trip closes cutting off aqueous ammonia flow from scrubbing tower to main plant. Stop the scrubbing water pump to build up level in the tower.

DEFROSTING OPERATION FOR COLD BOX

1. Close the isolation valves at the battery limit in the product hydrogen line. While isolating, check with local gauge and ensure that the product hydrogen system pressure and tail gas pressure do not exceed the specified values 47.5 and 2.0 Kg/cm²g. Reduce air flow to secondary reformer accordingly.

2. Close the isolation valve at the battery limit in the tail gas line. Adjust firing in 4th & 6th row burners of primary reformer to maintain the primary reformer exit temperature.

3. Take PC 2111 on manual and open PCV 2111 gradually watching the pressure of the let down vessel system PC 1301. Unload the flash gas compressor fully.

Page 277: Ammonia Manual

Ammonia Plant Operating Manual 124

4. Stop the flash gas compressor and close the suction and discharge valves and the battery limit isolation valve A 413 in the flash gas line.

5. Reduce the purge gas flow gradually and increase purge acordingly through HCV 1812 to maintain the parameter of the synthesis loop. Cut off the flow through FCV 2101. Put back the controller FC 2101 on manual in closed condition.

6. Put back LC 2104 on manual and close the LCV 2104.

7. Ensure that the PCV 2106 is in fully closed position, with PC 2106 on auto at a setting of 57.5 Kg/cm²g.8. Stabilise ammonia recovery section during the above operation.

9. Close the isolation valve of FCV 2101 and the battery limit isolation valves.

10. Open LCV 2101 on manual and drain liquid Ammonia to 1123. Watch liq Ammonia header pressure at PGHRU battery limit valve and upstream isolation valve.

11.Stop the Cryo Compressor No. 2 HGC 102 A

a) Close liquid freon valve from E 201 to HEC 103 and allow the liquid freon to get stored in the condenser with compressor running.

b) Observe the fall in the suction pressure of the compressor gradually from -130 mmHG to -400 mmHG due to the stoppage of the process load in the precooler No. 3 and the fall in the liquid freon level in HEC 103.

c) Stop the compresspor HEC 102 A and close the suction and discharge valves.

d) Put back LC 2107 and PC 2113 on manual and close LCV 2107 and PCV 2113.

e) Close the isolation valves of LCV 2107 and PCV 2113.

f) Close blow down valve from HEA 103.

g) Close the drain valves from oil separator to HGC 102 A & B.

12. Stop Cryo Compressor No. 1 HGC 101 A

a) Close the liquid freon valve from E 101 to HEA 101 & 102 and allow the liquid freon to get stored in the condenser E 101.

b) Observe a fall in the suction pressure of the compressor gradually from 4 Kg/cm²g due to the stoppage of the process load in the precoolers No. 1 & No. 2 HEA 101 & 102 and the fall in the liquid freon level in HEC 101 & 102.

c) Stop the compressor HGC 101 A and close the suction and discharge valve.

d) Put back LC 2105, LC 2106, LC 2112 on manual and close LCV 2105, LCV 2106 & PCV 2112.

e) Close the isolation valves of LCV 2105, LCV 2106 & PCV 2112.

Page 278: Ammonia Manual

Ammonia Plant Operating Manual 125

f) Close the blow down valves from HEA 101 and HEA 102.

g) Close the drain valve from oil separator to HGC 101 A & B.

13. Close the upstream isolation valve of LCV 2103.

14. Changeover MS adsorber unit HDA 102 A & B from "RUN" to Stop. 15. Stop the scrubbing water pump HGA 101.

15. Close scrubbing water pump suction and discharge valves.

16. Close the battery limit isolation valve on the scrubbing water line.

17. Close the upstream isolation valve of the LCV 2102 and the battery limit isolation valve A 528 in the aqueous ammonia header.

18. Depressurise the feed gas system, the product hydrogen line and the tail gas line through PCV 2106, PCV 2107, PCV 2108 and PCV 2109. Put back PC 2106, PC 2107, PC 2108 & PC 2109 to about 2 Kg/cm²g.

19. Drain the entire liquid hold-up from the drain separtor HFA 103 to the liquified gas disposed tank HFA 104 by opening the drain valve. Ensure that nitrogen seal is also simultaneously used.

20. Admit Nitrogen to the vent header by opening Nitrogen valves A 657 and A 654 in the Nitrogen purge line.

21. Confirm absence of liquid in drain separator with LICA 2104.

22. Ensure that the drain valve from HFA 103 in HFA 104 is fully open.

23. Open the isolation valves of the Purge Nitrogen to HEA 101 and feed dry N2 to cold box.

24. Continue this operation till the temperature inlet of HFA 103 increases to -60 C. Ensure that the heating rate does not exceed 40 C/hr by adjusting the nitrogen flow.

25. Set M.S. adsorber in heating position.

26. Admit N2 to M.S. adsorber through heating/precooling valve and take the dry N2 to cold box by opening heating valve. Check that PCV 2109 and PCV 2108 are closed.

27. Open PCV 2106 fully manually.

28. Open Nitrogen heating valve in product hydrogen system.

29. Carry out heating of the product hydrogen system similar to the feed gas system by venting throught the drain valve. Analyse for dew point in the exit gas.

30. Open LCV 2104 fully, when drain valve A 391 is defrosted.

Page 279: Ammonia Manual

Ammonia Plant Operating Manual 126

31. Open Nitrogen heating valve intail gas system and close fully heating valve in product hydrogen system.

32. Carrying out heating of the tail gas system similar to the feed gas and product hydrogensystems till TI 2109 reads 40 0C.

33. Open Nitrogen heating valves A 646 and 644 in the product hydrogen and feed gas system and continue heating operation through the drain of HFA 103.

34. Complete the total heating of the cold box unit, when all the thermometers indicate about 40 0C.

35. After ensuring the comletion of total heating close the following valves :

a. Drain valve from HFA 103 to HFA 104.

b. Nitrogen valve to the vent header exit HFA 104.

c. PCV 2106 & LCV 2104.

d. Isolation valve in the steam line.

e. Isolation valves in the Nitrogen heating line to feed gas system, tail gas system and product hydrogen system.

f. Isolation valves in the Nitrogen line to HEA 103.

g. Isolation valve in the Nitrogen line exit HEA 103.

37. Purge the flash gas system independantly and box up under N2 atmosphere.

Page 280: Ammonia Manual

Ammonia Plant Operating Manual 127

14 Chapter seventeen CAPTIVE POWER PLANT

17.1 INTRODUCTION

The Captive Power Plant has the capacity to generate 18.4 MW. There are two Turbo Generators viz TG-I with a capacity of 5.4 MW and TG-II with a capacity of 13.0 MW. TG-I is driven by a back pressure turbine while TG-II is driven by a condensing type turbine.

17.2 DESCRIPTION

Tubrines are of NKK-ALSTHOM impulse, multistage (TG-I is back pressure, TG-II is condensing) turbines with single reduction gear mounted on the common bed.

The steam admitted to the turbine through the main stop valve, the emergency stop valves and through steam control valves.

The reduction gear is of horizontal, single reduction and single helical type. The input shaft is coupled to the turbine rotor with a diaphragm coupling, while the output shaft to the generator shaft with a gear coupling lubricated by packed oil.

The after end of the pinion shaft is coupled with the turning device by way of movable teeth clutch and the fore end of wheel shaft drives the main oil pump of gear type.

In order to control the turbine speed and ouput power in various operating conditions, speed control and fuel limit is provided. The control system of the turbine consists of Woodward Electric Governor, EGP 10 P Actuator with hydro-mechanical back-up governor, hydraulic servomoter and steam control valves.

The oil unit is installed in the mezzanine of turbine house which comprises the circuits of lube oil, control oil and servomotor oil.

The gland condenser installed in the first floor of turbine house, condenses the gland leak steam of turbine.

The turning device is used to heat and cool the turbine rotor uniformly during warming up and after stop so as to avoid the deformation of rotor and is equipped to the after end of pinion shaft.

This device is driven by an AC motor and it has also the manual operating mechanism.

The turning device is disengaged automatically for the safe and easy operation.

17.3 CONTROL SYSTEMS

Control system is composed of Electric Governor, Servo Motor, Steam Control Valves, Lever Mechanism.

1) Electric Governor

Page 281: Ammonia Manual

Ammonia Plant Operating Manual 128

This electric governor is Woodward 2301 type which performs three funtions - precise turbine speed control, load control and load sharing with another tubro generator. If the magnetic pickup signal fails, the turbine will be shut down with fail safe signal.

This governor is composed of following modules:

a. A magnetic pick up is equipped to the fore end of turbine as a speed detector. This magnetic pick up generates an AC voltage whose frequency is proportional to turbine speed. F/V transformer converts this frequency signal into a DC voltage inversely proportional to turbine speed and sends it to speed controller.

b. Load sensor

Generator's load is measured by Potential transformer and Current transformer is sent to the load sensor. The load sensor converts these signals into a DC voltage proportional to generators' load.

c. External speed trim

The turbine speed is set with DIGITAL REFERENCE for speed setting. By using this module the setting speed can be changed between 85% and 109% of rated speed.

The setting speed is changed by using a switch on the turbine start up panel in the turbine room and also on supervisory control panel. The setting speed returns to the lower limit automatically by the signal that the emergency stop valve is shut.

d. Speed Controller

The voltage sent from speed sensor is compared at the control amplifier with the speed setting voltage sent from the external speed trim. Then the control amplifier sends an appropriate voltage to Actuator.

For example, if the speed were greater than the speed setting, the control amplifier would decrease its output and actuator would decrease the steam to the turbine.

2) Load Limit

a. Load limitter

It is a module which receives an actuator signal from speed controller and then sends an appropriate signal to the actuator.

The signal sent from the speed controller is compared with signal sent from the DIGITAL REFERENCE for KW setting and then lower signal is sent to actuator.

In case of operating parallelly with bus, this module prevents sudden increase of load caused by fluctuation of the bus.

b. External load trim

The setting of load limit valve is performed by the DIGITAL REFERENCE for KW setting. This module will set the limit value of load limitter by the same way speed setting.

17.4 PROTECTIVE DEVICE

Page 282: Ammonia Manual

Ammonia Plant Operating Manual 129

Functions

Refer to the safety interlocking diagram. Emergency stop signals caused by the troubles indicated in this diagram are sent to the following protective devices and stop the turbine.

Solenoid Valve for Emergency Stop

When the trip causes arises or somebody pushes the emergency button, 3-way solenoid valve assumes the non-excited condition. The safety oil supplied to the oil chamber of protection relay is then cut off and discharged to the oil tank via said solenoid valve. With this result, the trip oil supplied to the emergency stop valve is discharged and the emergency stop valve is closed instantly.

Hydromechanical Over Speed Detector

Hydromechanical overspeed trip device mounted at the fore end of turbine rotor actuates at the set speed to discharge the safety oil supplied to the protection relay and the emergency stop valve is closed instantly.

The oil exhaust vane is pressed to vane seat by the compression spring (D). The centre of gravity of (B) is "X" distant from turbine rotor centre. At rated speed the force of compression spring (D) is larger than the centrifugal force of oil exhaust vane (B). So the oil exhaust vane closes and holds the safety oil pressure.

When the turbine speed is increased, the centrifugal force of the oil exhaust vane overcomes the force of compression spring (D) and the oil exhaust vane moves outside separating from the vane seat (C). At this time safety oil is discharged to the oil tank. The set speed is adjustable by the adjusting screw (E).

Protection Relay

The protection relay is a device that stops the turbine by detecting directly the pressure drop of the lubricating oil or by lowering the safety oil pressure by the action of solenoid valve or overspeed detector.

The protection relay comprises a turbine stop part (AG) consisting of trip oil exhaust vane, compression spring and piston, a turbine stop holding part (HJ) consisting of the stopper, compression spring and reset knob and a turbine start interlocking part (KL) consisting of stopper and compression spring. The port (O) is connected with safety oil line. The port (P) is connected with lubricatory oil main line. The interlock oil supply port (Q) is connected with the lower port of servomotor power piston.

The trip oil supply port (R) is connected with the rapid oil exhaust device in the emergency stop valve. At the normal operating condition, the force between the lubricating oil pressure and compressiion spring (G) are equalised. The balancing piston (F) settles down in the position where it close the port (S). The piston (E) is lifted up by the force of the safety oil pressure supplied through the port (O). The trip oil exhaust vane (A) is lifted up by compression spring (B). Consequently the exhaust port (M) is closed.Action of Turbine stop device

The pressure drop of safety oil occurs in the following cases:

Page 283: Ammonia Manual

Ammonia Plant Operating Manual 130

1. The push button for emergency stop is pushed.2. Hydro mechanical over speed detector acts.3. Oil pump is troubled.4. Oil piping is clogged.5. 3 way solenoid valve for emergency stop is not excited caused by some troubles.

In the above each case, the safety oil pressure supplied through the port (O) drops. The force of the safety oil pressure on the piston (E) becomes smaller than the force of compression spring (O). Consequently the piston (E) pushes the trip oil exhaust vane (A) downward, and the exhaust port (M) is opened. The trip oil connected to the rapid oil exhaust device in the emergency stop valve is discharged via exhaust port (M). The emergency stop valve is closed by acting the rapid oil exhaust device.

In the Case of Pressure drop of Lubricating Oil

In the case of hydromechanical LO pressure low trip, the action of the device is same as above mentioned.

In the case of pushing stop button

By pushing the turbine stop button on TSP or SCP, the 3-way solenoid valve for the emergency stop assumes the non-excited and lower the safety oil pressure. In the case of pushing the push button on protection relay directly, safety oil pressure drops, the balancing piston (E) is pushed downward and the emergency stop valves are closed by the same actons above mentioned.

Action of turbine stop holding device

At normal operation, the compression spring (I) pushes the stopper (H) to the side of piston (E). When the piston moves downward, the stopper (H) gets into the upper part of the piston (E) by the compression spring (I). Even if the safety oil pressure and lubricating oil pressure are restored to normal condition and the balancing piston (E) is forced to normal position, the oil exhaust port (M) continue to open because the piston (E) is stopped with the stopper (H).

When the operator resets the protection relay, should pull out the reset knob after confirming the safety oil pressure. So the oil exhaust port (M) is closed and the trip oil pressure connected to the port (R) is restored. Consequently the emergency stop valve open.

Turbine starting interlocking device

In case of turbine start, the steam control valves should be closed whenever the emergency stop valve is tried to open in order to avoid the turbine run out. The protection relay is equipped with the interlocking device for said reason. If the steam control valve opens, it does not make emergency stop valve open.

The turbine starting interlock device acts as follows:

The port (Q) is connected with the lower part of the power cylinder in the servomotor. The servomotor oil is suppled for the port (Q) as the interlocking oil. When the steam turbine is operating normally, the reset stopper (K) is pushed to the side of stopper (H). Because the force

Page 284: Ammonia Manual

Ammonia Plant Operating Manual 131

of reset stopper (K) by the oil pressure overcomes the force of compression spring (L). If the protection relay acts, the piston (E) moves down, the stopper (H) rushes out by the force of spring. Consequently the reset stopper (K) sticks into the groove of stopper (H) by the force of servomotor oil pressure.

Accordingly, in order to pull out the reset knob (J) and open the ESV the reset stopper (K) wants being released. For the purpose of doing it, the servomotor power piston must be let to lower limit. So it makes the interlocking oil pressure lower. Emergency Stop Valve

The emergency stop valve mounted at the steam inlet part of upper turbine casing close the steam inlet valve rapidly and stop the turbine after receiving the emergency stop signal from the protection relay.

Stem Freedom knob

The stem freedom knob is mounted at the lower part of ESV Servomotor cylinder. The action of ESV stem freedom is as follows:

* The Operator pushes the stem freedom knob (I)

* Port (S) is opened.

* The Servomotor oil in the ESV Servomotor cylinder is discharged.

* The oil pressure in the ESV Servomotor is lowered.

* The piston (F) is pushed to the direction of ESV shutting by the force of compression spring (E).

The moving distance of the piston (F) is about 10 mm in the stem freedom action. So there is no trouble by the ESV stem freedom during the turbine operation.

The stick of the piston (F) is prevented by performing the periodic stem freedom (one time/week) the ESV should be shut certainly in case of emergency.

INTERLOCKING DEVICE

Turbine Starting Interlock

When the ESV is opened at the turbine starting, the steam control valves should be closed certainly lest the turbine should run away abruptly. Accordingly the protection relay is equipped with the hydromechanical turbine starting interlocking device. The operator cannot open ESV if Steam control valve are not closed.

Turning motor starting interlock

The turning motor start interlocking is that turning motor cannot start if the turning motor is not engaged and the lubricating oil does not have rated pressure.

Page 285: Ammonia Manual

Ammonia Plant Operating Manual 132

So each bearing metal is protected from the seizure and the claw clutch is prevented from damage. In the case of automatic disengagement of turning device, the turning motor is stopped automatically.

AUTOMATIC DEVICE

Auxiliary Oil Pump (AOP) Auto start

In case of lube oil pressure having dropped under the set value because of main pump trouble and turbine low speed, the auxiliary oil pump driven by AC motor will start automatically with a signal from the pressure switch.

Emergency Oil Pump (EOP) Auto Start

When the AOP cannot start becuase of pump trouble or no AC power -As the pressure of LO becomes under the setting value of EOP, EOP starts in 'auto'.Keep the change over switches of AOP and EOP in 'AUTO' position during TG operation.

17.5 OPERATION

The smooth operation and life of the turbine depends on the care for warming up, loading and stopping the turbine. Therefore, it is necessary to be familiar with construction, the fabrication and the control system of turbine and also necessary to grasp the condition of operating the boiler and auxiliary equipments, for example oil unit, gland condenser in turbine house.

The important matters in the turbine operations are thermal stress, thermal deformation and vibration caused by sudden fluctuations of steam condition and load or rapidly starting up and suddenly stopping the turbine. So operate the turbine paying attention for these matters all time.

During operation, a constant care should be taken to keep all equipments and instruments in normal condition and daily periodical records of operation shall be carried out to perform operation management. Even if an emergency happens deal with it by a suitable judgement.

The control of the turbo generator is carried out by the electric governor which controls the turbine speed or generator load. Isolated Parallel with Parallel with Parallel with TG Grid TG & with grid TG-I Speed Speed control Load limit Load limit control & load sharing control control

TG-II Speed Speed control Load limit Load limit control & load sharing control control & APC control. Speed Control Operation

Speed control is achieved by controlling the steam control valves via the speed control governor. In case of parallel running with BUS, BUS frequency is dominant over the turbine speed, therefore, the steam control valves are kept open constant as long as BUS frequency does not vary, which results in constant steam inlet flow and constant output.

Page 286: Ammonia Manual

Ammonia Plant Operating Manual 133

A variation of plant electric power demand is compensated by a variation of receiving power from BUS.

While in case of isolated running, plant electric power demand is all covered by TG output, a variation of plant electric power demand changes turbine speed, then speed governor working to maintain turbine speed constant, consequently opening of speed constrol valves follows a change of turbine output depending on plant power demand.

Load Limit Operation

Load limiter (fuel limiter) limits the rotation angle of the output terminal of the governor actuator to keep the lift of the steam control valves below the limit value.

While the parallel running with BUS, if speed control is selected, the turbine speed or the lift of the control valves fluctuates according to the frequency of BUS. In order to achieve the stable running, fuel limit operation should be selected.

Because the fuel limiter keeps the lift of the steam control valves and load constant in constant steam condition.

17.6 TG I START-UP PROCEDURE

Sl.No PROCEDURE OPERATION MANUAL

A. Starting the Oil System

1. Check the oil level Check the oil level in the oil tank by means of the oil level gauge. When starting up the auxiliary oil pump, if an alarm "OIL LEVEL LOW" is given, make up oil.

Check the minglement of water in oil.

Check the colour of oil and the necessity of replacement or replenishment.

2. Check the open and close Fully open the main valves in the oil of valves in of valves in the oil tank the oil line.

Close the drain valves, air vent valves and globe valves of differential pressure gauge.

Page 287: Ammonia Manual

Ammonia Plant Operating Manual 134

3. Check the oil temp in Do not start the auxiliary oil pump in oil tankwhile the oil the oil tank temperature is less than 10 0C.

If necessary, raise the oil temperature by the oil heater of the oil purifier.

4. Start the oil purifier Check the open and close of valves on the oil purifier unit.

Check the oil level of the oil tanks.

Start the oil purifier and the oil heater.

After the motor speed reaches rated speed open the water charge water and shut the water valve.

5. Start the auxiliary Start the auxiliary oil pump manually oil pump by the switch on the TSP.

Make sure that the switch is put in "AUTO" position.

Make sure that the outlet pressure is more than 16.3 Kg/cm²g.

Draw out air from the oil cooler, the oil strainer and so on.

Check the oil level of the oil tank again.

6. Start the oil mist Start the oil mist extract fan by the extract fanthe switch on extract fan TSP.

Set the internal pressure of the oil tank between -30 and -50 mmAq by adjusting the damper valve. 7. Check the pressure of Make sure that the oil pressure in each oil line each line is rated on the turbine gauge board.

LO pressure : 2.0 Kg/cm²g Control oil pressure : 12.5 Kg/cm²g S/M oil pressure : 16.5 Kg/cm²g Diff pr of LO filter : <0.8 Kg/cm²g (Primary pressure : 3.5 Kg/cm²g Diff pr of CO filter : <1.0 Kg/cm²g

Note:

If the indicated pressures are different from above, check again the open and close of valves in the oil line.

Page 288: Ammonia Manual

Ammonia Plant Operating Manual 135

If the difference is much, adjust the setting of pressure control valves.

Final setting of pressure is carried out while the turbine is running.

8. Let the CW run through Check the LO temperature. the oil cooler When the LO temperature rises above 30 0C, let the CW run through the oil cooler.

Open the CW inlet valve and outlet valve, and draw out air from the water chamber. Note If the LO temperature rises above 30 C after turning the

turbine, it is desirable to let the CW run through the oil cooler.

B. Start the Turning

1. Start the turning For the cold start: More than 2 hours before the steam runs to the emergency stop For the warm start: Continuous turningvalves.from the turbine valves stop.

For the hot start : Continuous turning from the turbine stop.

2. Make sure that the LO Make sure that the LO pressure ispressure is more than indicated more than 0.9 Kg/cm² by the the rated valuepressure gauge on the TSP.

3. Put the turning clutch Push the turning clutch lever to the lever in "ENGAGE" "ENGAGE" direction until the lever stops position. Set the handle to the shaft, and push the lever while turning the handle to the same direction of the turning.

Check the engagement of the turning gears and the lighting of "ENGAGE" on the TSP. And turn the handle until it

becomes heavy to turn.

4. Start the turning motor Start the turning motor manually by and begin the turning the switch on the turbine starting up panel.

Note Remove the handle from the shaft before starting.C. Check for the actuation of the Control Device

1. Reset the turbine Reset the turbine by the switch on the TSP.

2. Check the setting Check the TSP to make sure that the

Page 289: Ammonia Manual

Ammonia Plant Operating Manual 136

values of the governor setting values are equal to following ones a) Speed setting ... minimum b) Load limit ... minimum

3. Draw out air from Let the servomotor piston move up and the servomotor down by the turbine starting handle draw out air from the

servomotor.

4. Check the opening and Let the steam control valves open and shutting action of close fully by the starting handle to the steam control make sure that they move smoothly valves without sticking and so on.

5. Set the valves at the Turn the starting handle to left until lower limit position it is stopped. by turning the starting handle Make sure that the servomotor stroke is -12 mm.

6. Draw out air from the Open the air vent valve and draw out inlet pipe and the air until the oil overflow. outlet pipe of main oil pump. Make sure that the inlet and the outlet pressure of the pump is about 2 to 3 Kg/cm²g.

D Starting the gland steam condenser

1. Check the open and close Close the drain valve, the air vent of valves around the valve and the gate valve of the spare gland steam condenser ejector (SV-3095, SV-402S, SV-311S,

SV-346N, SV-312S, SV-345N) Make sure that the other valves are open.

2. Start the gland steam Make sure that the CW is running condenser. through the gland steam condenser.

Open the inlet valve of the ejector (SV-310S) gradually to start.

Set the suction pressure between -300 and -400 mmAq by the steam inlet valve (SV-310S).

Check the vibration and noise.

E Warming up the steam line & the Turbine

1. Warm up sufficiently Warming up the boiler side steam line between the boiler from the stop valve (SV-001N) starts & the main steam stop at the same time when the boiler valve from when the starts.

Page 290: Ammonia Manual

Ammonia Plant Operating Manual 137

boiler starts. So now this line is warmed up enough and the drain valves (SV-012S, NV- 013N) are opened. 2. Make sure that the Main steam pressure: above the main steam pressure & pressure low alarm point of inlet temperature are rated. steam pressure.

Main steam temperature: above the saturated temperature.

3. Close the steam control Close the steam control valves by valves. means of manual starting handle.

4. Open the drain valves Let the drain valves (SV-016NF, SV- of the turbine. 025NF, SV-014N, SV-015N) fully open.

5. Open the drain valve of Open the drain valve (SV-147N) the exhaust line.

6. Check the close of the emergency stop valves.

7. Open the bypass valve Warm up the steam line to the of the main steam emergency stop valves by opening the stop valve to warm up bypass valve of the main steam stop the steam line to the valve (SV-001N) gradually. emergency stop valves.

8. Open the main steam Open the main steam stop valve (SV-001N) gradually stop valve (SV-001N) Shut the bypass valve of the mainsteam stop valve.

9. Reset the 3-way Make sure that there is no trip soleniod valve for factor. emergency stop. Reset the 3-way solenoid valve for emergency stop by pushing reset button on the TSP.

10. Pull the reset knob Pull the reset knob on the protection on the protection relay. relay and fully open the emergency stop S.O. and trip oil pressure rise. valve. The emergency stop valve is fully opened. 11. Warm up the steam The steam runs to the steam chambers chambrs of the turbine and warms up them. 12. Warm up the turbine Open the drain valve (SV-115N). casing & exhaust piping. Open the bypass valve of the exhaust steam stop valve (SV-114N) to warm up

Page 291: Ammonia Manual

Ammonia Plant Operating Manual 138

the exhaust line.

Open the drain valve (SV-147N). Open the exhaust steam stop valve (SV-101N).

Open the bypass valve of the exhaust non-return valve (SV- 102N) gradually to warm up the turbine casing and the exhaust line.

F Rubbing Check

1. Warm up the turbine Follow the starting up curve. & steam piping enough. Make sure that the main steam temperature is more than 360 0C.

2. Close the bypass valve Make sure that this bypass valve (SV- of the exhaust check 102N) is closed. valve (SV-102N).

3. Open the steam control Make sure again that the drain valves vlave slightly. around the turbine are opened.

Open the steam control valve gradually by means of manual starting handle.

4. When the turbine speed When the turbine speed exceeds the exceeds the turning turning speed, the turning device is speed, the turning disengaged automatically. device is disengaged & stopped automatically. Check the automatically stopping of

the turning device.

Check the lever position of the turning device. (Set it in the "DISENGAGE" position).

Check the lamp on the TSP.

5. Open the steam control Open the steam control valve by valve further. turning the manual starting handle gradually with checking the turbine speed and warming up state of turbine casing.

Stop the turbine manually by pushing the hand trip button on the protection

relay.

Page 292: Ammonia Manual

Ammonia Plant Operating Manual 139

While the turbine is running by the inertia force of the rotor, make sure that the turbine rotor has no unusual state. Note

Carry out the turning if it needs a long interval to start up the turbine again.

G Starting up the Turbine

1. Check the steam Main steam pressure : 101 Kg/cm²g conditions. Main steam temperature : above 380 C

2. Reset the governor Check the TSP to make sure that the setting values are equal to following ones:

a. Speed setting ... Minimum b. Load limit ... Minimum

3. Turn down the starting Shut the steam control valve by handle to the lower turning the manual starting handle. limit position. Make sure that the servomotor stroke is -12 mm.

4. Reset the 3-way Make sure that there is no trip soleniod valve for factor. emergency stop. Reset the 3-way soleniod valve for emergency stop by pushing reset button on the TSP.

5. Pull the reset knob Pull the reset knob on the protection on the protection relay relay. and fully open the emergency stop valves. SO pressure rise and the pressure of trip oil for the emergency stop valves rise. The emergency stop valves are fully opened.

6. Start the turbine Open the steam control valves gradually to start the turbine by turning the manual starting handle.

Starting up and raising the turbine speed according to the turbine starting up curve. Carry out the warming up of the turbine at low speed (about 300 rpm).

7. Pass the turbine In the critical zone the turbine critical speed zone becomes unstable and the vibration is swiftly. increased.

Page 293: Ammonia Manual

Ammonia Plant Operating Manual 140

Therefore, let the turbine pass the critical zone swiftly.

The critical zone: 900 rpm - 1200 rpm

8. Check the operation Further increase the turbine speed by of the Governor means of manual starting handle.

Make sure the turbine speed is controlled by the speed governor at about 85% of the rated speed (about 1275 rpm). 9. Set the manual starting Set the manual starting handle at its handle at its upper highest position by turning it limit position. gradually.

The turbine speed is not increased because it is controlled by the speed governor.

10. Set the turbine speed Check the lighting of "Lower limit at the synchronous speed" on the TSP. speed (the rated speed) by raising the speed Set the turbine speed at the rated setting. speed by raising the speed setting of speed governor on the TSP.

11. Stop the auxiliary Stop the auxiliary oil pump manually oil pump. by the switch on the TSP.

Make sure that the switch is set at "AUTO" and "SCP" position after stopping.

12. Inspect the state of Check the operation state of the each part. turbine in raising the turbine speed.

Check the vibration of the turbine by not only the monitor but also your hand.

Make sure that there is no abnormal sound.

Check the main steam pressure, temperature and exhaust pressure.

Check the Lube Oil pressure, temperature and bearing temperature.

Check the Servomotor oil pressure and Safety oil pressure.

Take other datum of the operation records and make sure that there is no other unusual state.

H Synchronising

Page 294: Ammonia Manual

Ammonia Plant Operating Manual 141

1. The operation location is SCP.

2. Adjust the turbine speed Adjust the turbine speed at the rated at the synchronised one by means of operating the switch one. of electric governor.

3. Establish the voltage Check the establishment of voltage.

Check the main circuit voltage, field voltage and field current.

Adjust the voltage at the rated one.

4. Synchronise the turbine Set the synchronising switch. and throw in. The synchroniser starts automatically.

The voltage and the speed are adjusted automatically, and the Circuit breaker is thrown in automatically.

Check the lamp.

The turbo generator is set in the parallel operation.

Note

Before automatically synchronising, adjust the voltage and the speed manually.

5. Throw on an initial Raise the speed reference of electric load. governor by means of the switch on the SCP, and give initial load (about 600 KW) to the turbine.

6. Close all the drain Close the drain vales of the emergency valvestop valves, the steam chambers and the first stage (SV-016N to SV-025N).

Close the drain valves of the main steam stop valve and the exhaust stop valve (SV-012N, SV-015N) (SV-114N, SV-147N).

7. Raise the speed setting Raise the speed setting manually by to the upper limit the switch on the SCP. gradually. Check the lamp.

Make sure that the output is constant.

Page 295: Ammonia Manual

Ammonia Plant Operating Manual 142

8. Raise the laod Turn the KW setting switch of the electic governor toward "INCREASE", and raise the generator's load gradually.

The time for raising the load follows the start up curve.

While raising the load, pay attention to the following items:

a. Lowering of the main steam pressure. b. Sudden fluctuations of the exhaust pressure and

temperature. c. Vibration and noise. d. Bearing temperature. e. Generator coil temperature. f. Make sure that there is no other abnormal items.

9. The turbo generator is set in the state of parallel load controller operation.

I Stopping the Turbine

1. Lower the KW set point Decrease the turbine output by of electric governor lowering the set point of electric and decrease the turbine governor with the electric governor output power. operation switch on the SCP.

Decrease it according to the turbine stop curve. 2. Decrease the turbine output power to the initial load (about 600 KW).

3. Unload the turbine Unload the turbine by opening the generator circuit breaker.

The turbine is operated in no load running at the rated speed.

4. Open the drain valves Open the drain valves of the emergency around the turbines. stop valves, the steam chambers and the first stage (SV-016N, SV-025N). Open the drain valves of the main steam stop valve and the

exhaust stop valve (SV-012N, SV-015N, SV-114N,

Page 296: Ammonia Manual

Ammonia Plant Operating Manual 143

SV-147N).

Note: Don't forget to make sure that the bypass check valve of the exhaust valve is closed.

5. Lower the turbine speed. Avoid the long no load running after unloading as far as possible.

Lower the speed setting of the electric governor to the lower limit by means of the switch on the TSP.

Check the lamp.

The turbine speed is lowered to about 1275 rpm.

6. Shut the emergency Shut the emergency stop valves by stop valve. means of emergency stop button the TSP or hand trip button on the protection relay.

Check the lamp.

7. Start the turning Make sure that the turbine rotor stops rotating.

Engage the turning device immediately after the turbine rotor stops, and check the lighting of "ENGAGE" lamp on the TSP.

Start the turning motor by means of the start switch on the TSP.

Perform the turning after the turbine stops sufficiently to cool down the turbine rotor evenly and prevent the deformation.

8. Close the exhaust stop Close the exhaust stop valve (SV-101N) valve. Open the drain valve (SV-114N).

9. Close the main steam Close the main steam stop valve (SV- stop valve.001N)

Open the drain valves of the main steam pipe (SV-014N, SV 3/4, SV-015N)

10. Stop the gland ejector. Close the inlet valve of the ejector to stop the gland condenser.

Close the inlet and outlet valves of CW perfectly, and open the drain valve.

Page 297: Ammonia Manual

Ammonia Plant Operating Manual 144

11. After finishing the Stop the turning motor manually by the turning, stop the switch on the TSP. turning motor. Make sure that the clutch lever is put in the "DISENGAGE" position.

12. Stop the oil unit Turn the switch of the emergency oil pump to "MAN" from "AUTO".

Stop the auxiliary pump manually.

Stop the gas extractor fan of the oil tank.

Close the inlet and outlet valves of the oil coolers and open their drain valves.

Check the oil level of the oil tank.

Chock the discolouration of oil and the minglement of water.

Close the main valve of the oil purifier.

17.7 TG II START UP PROCEDURE

A. Starting the oil system Procedure is same as TG-I

B. Starting the turbine Procedure is same as TG-I Device

C. Check for Actuation of Procedure is same as TG-I Control Device

D. Starting the Gland Steam Condenser

1. Check the open and Close the drain valve, the air-vent close of valves around valve and the gate valve of the spare the gland steam ejector (SV-313S, SV-404S, SV-315S, condenser SV-348N, SV-314S, SV-316S)

Make sure that the other valves are open.

2. Start the gland steam Make sure that the CW is running condenser through the gland steam condenser.

Page 298: Ammonia Manual

Ammonia Plant Operating Manual 145

Open the ejector driving steam inlet valve (SV-314S) gradually to start.

Set the action pressure between -300 and -400 mmAq by the steam inlet valve (SV-314S).

Check the vibration and noise.

E. Starting the gland seal steam line 1. Check the open and Close the following valves SV-301S, close of valves in SV-303S, SV-306N. the gland seal steam line. Open the following valves SV-302S, SV-304S, SV-305N, SV-307S, SV-308N, SV-338N.

2. Admit the gland seal Check the steam condition of 12 steam to the turbine Kg/cm²g steam line. gland. Check the instrument air pressure. Open the inlet valve (SV-301S) gradually.

Make sure that the gland seal steam pressure is rated value of 0.2-0.3 Kg/cm²g.

F. Starting the main air ejector

1. Check the open and Close the following valves entirely: closes of valves around the ejectors. SV-321S, SV-501S, SV-502S, SV-317S, SV-318S,

SV-319S,SV-320S,SV-513N,SV-510N, SV-344N

Open the following vavles:

SV-503N, SV-512N, SV-343N, Gauge valves.

2. Check the steam Make sure that ejector driving steam conditions condition is rated value.

3. Start up the starting Open the steam inlet valve (SV-321S) ejector gradually.

4. Check the vacuum Make sure that the vacuum pressure is pressure about 500 mmHg.

5. Start up the main air Make sure that CW is running through jector the main air ejector.

Open the II stage ejector driving steam inlet valve (SV-318S).

Page 299: Ammonia Manual

Ammonia Plant Operating Manual 146

Open the I stage ejector driving steam inlet valve (SV-320S).

Open the I stage air inlet valve (SV-502N) gradually.

6. Stop the starting Make sure that the vacuum pressure is ejector. above 500 mmHg.

Close the air inlet valve (SV-503N).

Close the steam inlet valve (SV-321S) gradually.

7. Check the vacuum Make sure that the vacuum pressure is pressure 675 mmHg.

G. Warming up the Main Steam Line and Turbine

1. Make sure that the main Main steam pressure : about 46 Kg/cm²g steam pressure and temperature in the Main steam temp : about 376 C 48 Kg/cm²g header are rate.

2. Close the steam control Close the steam control valves by valves of the turbine means of manual starting handle.

3. Open the drain valves Open the following drain valves: of the turbine or on SV-115N, SV-117N, SV-118 NF the maint steam line SV-119NF, SV-120NF, SV-121 NF

4. Check the close of the Check the indicator on the emergency emergency stop valve stop valve.

5. Open the bypass valve Warm up the steam line to the of the main steam emergency stop valve by opening the stop valve to warm up bypass valve of the main steam stop the steam line between valve (SV-104N) gradually. that valve to the emergency stop valve.

6. Open the main stop Open the main stop valve (SV-104N) valve (SV-104N) gradually.

Shut the bypass valve of the main steam stop valves.

7. Reset the 3-way Make sure that there is no trip soleniod valve for factor. Emergency stop.

Reset the 3-way solenoid valve for emergency stop by pushing reset button on the TSP.

8. Pull the reset knob Pull the reset knob on the

Page 300: Ammonia Manual

Ammonia Plant Operating Manual 147

on the protection relay protection relay. and fully open the emergency stop valve. S.O. and trip oil pressure rise.

The emergency stop valve is fully opened. 9. Warm up the steam The steam runs to the steam chambers chambers of the and warms up them. turbine

H. Rubbing check

1. Warm up the turbine Follow the starting up curve. and the steam piping enough. Make sure that the main steam temperature is more than 310 0C.

2. Open the steam control Make sure again that the drain valves valve slightly. around the turbine are opened. Open the steam control valves gradually by means of manual starting handle.

3. When the turbine speed When the turbine speed exceeds the exceeds the turning turning speed, the turning device is speed, the turning disengaged automatically. device is disengaged and stopped Check the automatically stopping of automatically the turning device.

Check the lever position of the turning device (set it in the "DISENGAGE" position).

Check the lamp on the TSP.

4. Open the steam control Open the steam control valve by valve further. turning the manual starting handle gradually with checking the turbine speed and warming up state of turbine casing.

Stop the turbine manually by pushing the hand trip button on the protection relay.

While the turbine is running by the inertia force of the rotor, make sure that the turbine rotor has no unusual state.

Note Carry out the turning if it needs a long interval to start up the turbine again.

Page 301: Ammonia Manual

Ammonia Plant Operating Manual 148

I Starting up the Turbine

1. Check the steam Main steam pressure : about 36 Kg/cm²g condition Main steam temperature : about 376 0C 2. Reset the governor Check the TSP to make sure that the setting valves are equal to following one:

a. Speed setting ... minimum b. Load limit ... minimum

3. Turn down the starting Shut the steam control valve by handle to the lower turning the manual starting handle. limit position

Make sure that the servomotor stroke is -12mm.

4. Reset the 3-way Make sure that there is no trip solenoid valve for factor. emergency stop.

Reset the 3-way solenoid valves for emergency stop by pushing reset button on the TSP.

5. Pull the reset knob on Pull the reset knob on the protection the protection relay relay. and fully open the emergency stop valve. Safety oil trip oil pressure rise. The emergency stop valve is fully opened.

6. Start the turbine Open the steam control valves gradually to start the turbine by turning the manual starting handle.

Starting up and raising the turbine speed according to the turbine start up curve.

Carry out the warming up of the turbine at low speed (about 300 rpm).

7. Pass the turbine In the critical zone the turbine critical speed zone becomes unstable and the vibration swiftly. is increased.

Therefore, let the turbine pass the critical zone switfly.

The critical zone : 600 - 900 rpm

8. Check the operation Further increase the turbine speed by of the governor means of manual starting handle. Make sure that the turbine speed is controlled by the speed governor at about 85% of the rated speed (about 1275 rpm).

Page 302: Ammonia Manual

Ammonia Plant Operating Manual 149

9. Set the manual starting Set the manual starting handle at its handle at its upper highest position by turning it limit position gradually.

The turbine speed does not increase because it is controlled by the speed governor.

10. Set the turbine speed Check the lamp of "Lower-limit speed" at the synchronous on the TSP. speed (the rated speed) by raising the speed Set the turbine speed at the rated setting. speed by raising the speed setting of speed governor on the TSP.

11. Stop the auxiliary oil Stop the auxiliary pump manually by pump the switch on the TSP. Make sure that the switches are set at "AUTO" and "SCP" position after stopping.

12. Inspect the condition Check the condition of the turbine in of each position raising the turbine speed. Check the vibration of the turbine by not only the monitor but also by your hand.

Make sure that there is no abnormal sound.

Check the main steam pressure, temperature and exhaust pressure.

Check the LO pressure, temperature and bearing temperature.

Check the SMO pressure and SO pressure.

Take other data of the operation records and make sure that there is no other unusual state.

J Synchronising

1. The operation location is the SCP.

2. Adjust the turbine Adjust the turbine speed at the rated speed at the one by means of operating the switch synchronous one. of electric governor.

3. Establish the voltage Check the establishment of voltage.

Check the main circuit voltage, field voltage and field current.

Page 303: Ammonia Manual

Ammonia Plant Operating Manual 150

Adjust the voltage at the rated one.

4. Synchronise the turbine Set the synchronising switch. and throw in. The synchroniser starts automatically.

The voltage and the speed are adjusted automatically, and the CB is thrown if automatically.

Check the lamp.

The turbine generator is set in the parallel operation.

Note: Before automatically synchronising, adjust the voltage and the speed manually.

5. Throw on an initial Raise the speed reference of electric load governor by means of the switch on the SCP, and give initial load (about 1300 KW) to the turbine.

6. Close all the drain Close the drain valves of the valves emergency stop valve, the steam chambers and the I stage. SV-118NF, SV-119NF, SV-112NF, SV-121NF.

Close the drain valves of the main steam line. SV-115N,SV- 117N.

7. Raise the speed setting Raise the speed setting manually by to the upper limit the switch on the SCP. gradually. Check the lamp.

Make sure that the output is constant. 8. Raise the load Turn the KW setting switch of the electric governor toward

"INCREASE", and raise the generator's load gradually.

The time for raising the load follows the starting up curves.

While raising the load, pay attention to following items: a. Lowering of the main steam pressure. b. Sudden fluctuations of the exhaust pressure and

temperature. c. Vibration and noise. d. Bearing temperature. e. Generator coil temperature. f. Make sure that there is no other abnormal items.

9. The turbo generator is set in the state

Page 304: Ammonia Manual

Ammonia Plant Operating Manual 151

of parallel operation.

K. Stopping the Turbine

1. Lower the KW setting Decrease the turbine output by of electric governor lowering the setting of electric and decrease the governor with the electric governor turbine output operation switch on the SCP. power. Decrease it according to the turbine stop curve.

2. Decrease the turbine output power to the initial load (about 1300 KW).

3. Unload the turbine Unload the turbine by opening the generator circuit breaker.

The turbine is operated in no load running at the rated speed.

4. Open the drain valves Open the drain valves of the emergency around the turbine. stop valve, the steam chambers and the I stage. SV-118NF,

SV-119NF, SV-120NF, SV-121NF

5. Lower the turbine Avoid the long no load running after speed unloading as far as possible. Lower the speed setting of the electric governor to the

minimum by means of the switch on the TSP.

Check the lamp.

The turbine speed is lowered to about 1275 rpm.

6. Shut the emergency Shut the emergency stop valve by means stop valve of emergency stop button on the turbine TSP or hand trip

button on the protection relay.

Check the lamp.

7. Make sure that the Make sure that the A.O.P. starts A.O.P. starts automatically when the LO pressure automatically becomes less than 0.9 Kg/cm²g.

8. Start the turning Make sure that the turbine rotor stops rotating. Engage the turning device immediately after the turbine rotor stops, and check the lamp of "ENGAGE", on the TSP.

Start the turning motor by means of the start switch on the TSP.

Page 305: Ammonia Manual

Ammonia Plant Operating Manual 152

Perform the turning after the turbine stops sufficiently to cool down the turbine rotor evenly and prevent the deformation.

9. Close the main stop Close the main steam stop valve valve (SV-104N)

10. Stop the air ejector Make sure that no steam is admitted to the main condenser without gland seal steam.

Close the I stage air inlet valve (SV-520N)

Close the I stage driving steam inlet valve (SV-320S).

Close the II stage air inlet valve, (SV-512N).

Close the II stage driving steam inlet valve (SV-318S).

11. Break the vacuum in Open the vacuum breaking valve (SV- the main condenser 510N) gradually.

Make sure that the pressure in the main condenser is equal to atmosphere.

12. Stop the gland seal Close the gland seal steam inlet valve steam to the turbine (SV-301S). gland. Make sure that the pressure in the gland seal reservoir is equal to atmosphere.

13. Stop the gland steam Close the ejector driving steam inlet condenser. valve (SV-314S).

14. Stop the condensate Stop the condensate pump according to pump. the manual of condensate pump and steam turbine.

Close the steam inlet valve (SV-107N) and 48 Kg/cm²g header outlet valve (SV-106N).

15. After finishing the Make sure that the turbine is cooled turbine, stop the enough to stop the turning. turning motor.

Stop the turning motor manually by means of the switch on the TSP.

Make sure that the clutch lever is put in the "DISENGAGE" position.

16. Stop the oil unit Turn the switch of the emergency oil pump to "MAN" from "AUTO".

Stop the auxiliary oil pump manually.

Page 306: Ammonia Manual

Ammonia Plant Operating Manual 153

Stop the gas extractor fan of the oil tank.

Close the cooling water inlet and outlet valves of the oil coolers and open their drain valves.

Check the oil level of the oil tank.

Check the discolouration of oil and the minglement of water.

Close the main valve of the oil purifier.

17.8 PRECAUTIONS

General

1. Keep the steam condition of turbine inlet and outlet at the rated state as far as possible.

2. Make sure that there is no rapid change of measuring value by taking operation data periodically every day.

3. Check the oil level of oil tank and replenish the oil if necessary.

4. Keep the lubricating oil clean and pay attention to the intrude of water, foreign matters. Perform the oil analysis periodically and change it if necessary.

5. Supply the oil some times to the sliding part of control lever mechanism.

6. Pay attention always to the noise and vibration of turbine inside. Stop the turbine if any unusual sound or vibration occurs.

7. Pay attention to the invasion of drain to the turbine. Open the drain valve and bypass valve of steam trap if the steam involves much water.

8. Avoid the continuous no-load running as for as possible because of preventing the LP side of turbine casing from excessive heating. (It is recommended that the lowest load for running be 10% of the rated power)

9. Always put the switch of A.O.P., E.O.P. in position "AUTO". Always keep open the inlet and outlet valves of the pumps.

In case of Start-up and Stop

1. Warming up the pipes and turbine sufficiently paying attention to the invasion of drain on turbine start up.

2. Perform the sufficient turning in turbine start up and stop.

3. Operate the equipments according to the start up curve in order to prevent the equipments from deformation.

In Case of Speed Control

Page 307: Ammonia Manual

Ammonia Plant Operating Manual 154

1. Adjust the TG output paying attention to the main steam pressure exhaust pressure and flow.

2. Avoid the rapid change of TG output and obey the start up curve.

In case of Isolated running with Bus

1. Pay attention especially to the steam pressure and flow.

2. Pay attention to the generator frequency. If it is changed by variation of electrical load, adjust the set point of the electrical govenor so that it keeps constant.

In case of Stopping Turning

When the turbine is stopped and there is no flow of steam in its casing, each part in the turbine casing is cooled gradually, while the lower part is more cooled than the upper part.

If the turbine rotor is put in such condition, it gets deformed immediately. Therefore, after stopping the turbine it is necessary to keep the turbine rotor rotating continuously by carrying out the turning until the temperature in the turbine casing is lowered and uniformed enough. By carrying out the turning sufficiently the turbine rotor is prevented from deforming and the turning period for the next start-up can be shortened.

Before starting up the turbine, it is necessary to take more than 2 hours for the turning.

In the case of Short-Term Stop (within 12 hours)

The turning should be carried out continuously until the next start-up.

In the case of Long-Term Stop (More than 12 hours)

The turning should be carried out continuously until the temperature in the casing is lowered and uniformed enough. (It takes more than 24 hours to cool the turbine casing sufficiently)

In the case of Emergency

When the turbine trips by one factor and is stopped still, the turning should be started immediately.

However, if the turning can not be started because of a failure of the power source for the turning motor or troubes of both the auxiliary pump and the emergency pump, the turbine rotor left in such condition is deformed immediately.

In this case, it should set the turning handle on the end of the motor shaft and rotate the turbine rotor 180 , i.e., rotate the generator shaft 30 , every 5 minutes. (45 for TG-II).

And at this time one should also send LO to the turbine by the hand pump.

Page 308: Ammonia Manual

Ammonia Plant Operating Manual 155

By carrying out this procedure, the turbine rotor is prevented from service deformation and it becomes easy to start up next.

17.9 TRIP AND ALARM SCHEDULE

TG-I TURBINE ALARM

Decription TAG No. Normal Value Set point

Exhaust steam pressure PS 2504 47 Kg/cm²g 49.0 Kg/cm²g HiHigh and Low PS 2505 45.0 Kg/cm²g Lo

Inlet steam pressure low PIA 2501 101 Kg/cm²g 95 Kg/cm²g 48 ata line steam pressure FPTR 2502 47 Kg/cm²g 49Kg/cm²g

Page 309: Ammonia Manual

Ammonia Plant Operating Manual 156

High and Low PS 2620 45Kg/cm²g

L O Pressure Low PIA 2559 1.5 Kg/cm²g 0.9 Kg/cm²g

L O Filter DP high DPIA 2562 0.3 0.8

L O Temperature High TRA 2546 45 0C 51 0C

L O Tank Level Low LA 2503 4.7 M 3.25 M

C O pressure low PIA 2551 12 Kg/cm²g 9 Kg/cm²g

C O filter DP high DPIA 2553 0.4 Kg/cm²g 1.0Kg/cm²g

Safety Oil pressure low PS 2548 9 Kg/cm²g 5.5 Kg/cm²g

Abnormal Rotor vibration VIA 2502 < 55 µ 55 µ VIA 2503

Excessive Axial Movement DIA 2501 0 mm + 0.3 mmof rotor - 0.7 mm

Excessive Acceleration VIA 2506 < 0.5 0.5

Bearing temperature rise TRA 2546 60 0C 78 0C

CW pressure low PS 2541 3.5 Kg/cm²g

TG-I TURBINE TRIP SETTING

Decription TAG No. Normal Value Set point

Over speed SIA 2502 1500 1665 Elec 1692 Mech

L O pressue low PS 2560 1.5 Kg/cm²g 0.7 Kg/cm²g (Elec) 0.55 Kg/cm²g (Mech)

C O pressure low PS 2550 12 Kg/cm²g 8 Kg/cm²g

Page 310: Ammonia Manual

Ammonia Plant Operating Manual 157

Governor Power Failure 24 V DC 17 V DC

Abnormal Rotor Vibration VIA 2502 < 55 µ 85 VIA 2503

Excessive Axial movement DIA 2501 0 + 0.5of Rotor - 0.9

Inlet steam pressure PS 2501 101 Kg/cm²g 80 Kg/cm²g

Emergency Stop 5E

Boiler trip & others

TG-II TURBINE ALARM SETTING

Decription TAG No. Normal Value Set point

L O Pressure Low PIA 2576 1.5 Kg/cm²g 0.9 Kg/cm²g

L O Temperature High TRA 2564 45 0C 51 0C

L O Tank Level Low LIA 2505 8.5 M 4.9 M

L O filter DP high DPIA 2579 0.3 0.8

Bearing temperature high TRA 2564 < 70 0C 78 0C

C O pressure low PIA 2568 12 9

Page 311: Ammonia Manual

Ammonia Plant Operating Manual 158

C O filter DP high DPIA 2570 0.4 Kg/cm²g 1.0Kg/cm²g

Safety Oil pressure low PS 2505 9 Kg/cm²g 5.5 Kg/cm²g

Condenser Hot well level LICA 2501 0 + 150 mm Hi - 150 mm Lo

Vacuum low PS 2511 686 mmHg 576 mmHg

Condenser pressure low PS 6.8

Condensate conductivity high CIA 2501 -

Condensate pH high PHIA 2501

Abnormal Rotor vibration VIA 2504 < 75 µ 75 µ VIA 2510

Excessive Axial Movement DIA 2502 0 mm + 0.3 mmof rotor - 0.8 mm

Excessive Acceleration VIA 2513 < 0.5 0.5

Exhaust steam temperatue high TIA 2506 45 0C 80 0CSealing steam pressure low PS 2515 0.2 Kg/cm²g 0.1 Kg/cm²g CW pressure low PS 2546 3.5 Kg/cm²g

TG-II TURBINE TRIP SETTING

Decription TAG No. Normal Value Set point

Over speed SIA 2505 1500 rpm 1665 Elec 1695 Mech

L O pressue low PS 2572 1.5 Kg/cm²g 0.7 Kg/cm²g (Elec) 0.55 Kg/cm²g (Mech)

C O pressure low PS 2567 12 Kg/cm²g 8 Kg/cm²g

Governor Power Failure 80 EG 24 V DC 17 V DC

Abnormal Rotor Vibration VIA 2504 < 75 µ 125 VIA 2510

Page 312: Ammonia Manual

Ammonia Plant Operating Manual 159

Excessive Axial movement DIA 2510 0 + 0.5 mmof Rotor - 1.0 mm

Vacuum low PS 2510 686 503 mmHg

Emergency Stop 5E

TG- I & II GENERATOR ALARM

Rotor Earth Fault 648 - -

Generator bearing temp rise 26 BH 65 0C 71 0C

Generator winding temp rise 26 WH 120 0C 125 0C

Generator cooling air temp 26 CAH 43 0C 47 0C inlet 69 0C 74 0C outlet

Generator Abnormal vibration 33VH <55 55Generator CW leak 33CW

Fire fighting operate

Grid I isolated

Tripping selecct operated 5 FX

AVR light fault 30 AVRL

----------------------------------------------------------------------------------------------------------------

TG-I&II GENERATOR & TRIP

Trip OperationDecription TAG No. -------------------- Trip set Turbine C B Exit trip trip trip

Differential 87

Earth Fault 64

Diode Failure 71 E

Generator abnormal vibration 33 VHH 85

Pole slipping 78

Loss of excitation 40 T

Page 313: Ammonia Manual

Ammonia Plant Operating Manual 160

Negative sequence over 46current

Under frequency 95 LT 47.5Hz

Over Voltage 59 130%

Reverse power 67 RT

Over current 51 V

P T fuse failure 98

Under Voltage 27 75%

AVR Heavy Fault 30 AVRH

15 Chapter Eighteen APPENDIX

18.1 ELECTRICAL POWER DISTRIBUTION SYSTEM

Our Ammonia Plant is designed based on "Total Energy Concept" and most of the drives in this plant are turbine driven, utilising the heat recovered from the process stream in the various stages. To augment the steam available from the process, Auxiliary Boilers are available. Hence the requirement of electrical power is for

1) Instrumentation2) Lighting3) Non essential drives

There are four sources of electrical power sources for our plant.

1) TNEB2) Captive Power Plant3) Inverter supply with associated batteries and battery charger.

Page 314: Ammonia Manual

Ammonia Plant Operating Manual 161

4) DG sets

1. TNEB POWER SUPPLY

SPIC requires about 27 MVA (Maximum Demand ) of power and this is supplied by TNEB at 110 KV. Supply to SPIC is received from TNEB sub station located at north of Construction Road. Two lines from TNEB substation comes to SPIC main substation. TNEB auto substation is connected to TNEB grid by 230 KV feeders. One feeder comes from Kayathar which in turn is connected Edaman-Kerala and two feeders from TTPS which in turn connected to Pasumalai. The 230 KV is stepped down to 110 KV through 50 MVA auto transformers connected in parallel. From Arumuganeri, one 110 KV feeder is connected at 110 KV bus.

2. CAPTIVE POWER PLANT

To augment the power supply in case of power cut posed by TNEB, Captive Power Plant of 18.4 MW capacity is installed with two turbo generators. The installed capacity of TG-I is 5.4 MW and TG-II is 13 MW. Our CPP is conceived as a co-generation plant with TG-I generating power and its exhaust steam at 48 Kg/cm²g being used to cater the demand of process requirements. Both the turbo generators can be run (i) independently (ii) in parallel with another TG or in parallel with grid.

The transformers in main substation step down the voltage to 11 KV for distribution inside the factory. There is a limit to which we can make use of 11 KV directly after which we have to go for lower KV. Generally, motors upto 160 KW are supplied power at 415 volts. 3.3 KV supply is given to motors ranging from 150 KW to 1000 KW. Some deviations are exceptions.

The supply voltage at 110 KV can be varied ± 12 % from rated voltage and 3 % from rated frequency. Though this variation is permitted as per Indian Electricity Act, a standard motor cannot withstand to this variation. To limit the variation in supply voltage to 1.5 %, automatic "ON LOAD" tap changers are provided on the main transformers. 'OFF LOAD' tap changers are provided in the individual transformers for 11 KV / 3.3 KV and 11 KV / 415 volts.

The total installed capacity of Ammonia Plant is 3.4 MW which includes the 11 KV, 1880 KW cooling tower pump and 825 KW, 3.3 KV start-up compressor motors. Normally both the motors will be in idle condition and will be used during shutdown only. Hence the actual maximum demand of Ammonia Plant will be about 2 MW. The electrical distribution of Ammonia Plant is given in the enclosed drawing.

The Ammonia Plant receives power supply from MSS and CPP through 3 Nos. of 2 MVA 11 KV/ 440 volts step down transformers viz., TP 30, TP 31 & TP 32 and out of which TP 30 (PCC 1A) receives power from CPP 11 KV panel.

The critical loads of Ammonia Plant are fed by MCC 2 panel which normally receives power either from PCC 1A or PCC 1B. In case of power failure,this panel will receive emergency power from 1100 KVA, automatically within 18 seconds.

There are 3 Diesel generators provided to cater the demand in case of total power failure including failure of TG sets. When the under voltage relay in Ammonia substation senses 144 volts in 230 volts single phase supply, power dip annunciation appears in the main substation

Page 315: Ammonia Manual

Ammonia Plant Operating Manual 162

and it gives signal for power failure trip initiation . 1100 KVA DG set is started automatically on getting signal from one of the low voltage sensing relay from MCC 1,MCC 2, MCC 3 & PCC 3C From the time the power failure sensed, within 15 seconds, DG sets builds up voltage and is available for emergency use.

If normal power supply has not resumed within 18 seconds, this DG set starts supplying the essential loads on MCC 2. When the DG set is on load, 'EMERGENCY POWER SUPPLY ON' appears in the Control Room. Till that time, this lamp does not appear even if DG set is started. If MCC 2 does not get emergency power within one minute from the time of power failure, "EMERGENCY POWER FAILURE" alarm will come in Main Control Room.

MCC 11 panel gets power from PCC 1B and feeding supply to 5 CT fans and effluent pump. In case of power failure, Ammonia 830 KVA DG set will start automatically on getting signal from MCC 11 low voltage sensing relay and it feeds emergency power.

MCC 18 panel gets power from PCC 9A and feeding supply to critical loads to critical loads of CPP. In case of power failure in MCC 18 , CPP 830 KVA DG set will start automatically on sensing low voltage in MCC 18 and feeds power.

Ammonia Plant has sufficient points for lighting to have good illumination. Due to the importance of lighting, emergency power is used to light about 50 % of the plant lighting. Normally these emergency lights will glow on main power supply. During power failure, emergency power will be automatically supplied to these lamps. To avoid the plant to be under total darkness during power failure, incandescent lamps are used on emergency power. In addition to this, chargeable battery operated emergency incandescent lamps are fixed in Control Room and in critical locations.

18.2 AMMONIA PLANT CONTROL POWER NETWORK AFTER DCS INSTALLATION

115V AC UPS POWER SOURCE

40 KVA Gutor redundant UPS receives power from MCC-11 and MCC-18. UPS-A receives power from MCC-11 and UPS-B from MCC-18. Normally both the UPS will be in-line sharing the load. In case of single UPS failure, other UPS will take the full load. Apart from this, there is a total bypass main fed from MCC-2 for UPS, which will come on line in case of failure of both the UPS. Each UPS is provided with independent 220VDC battery bank,designed for an hour back-up.

CONSUMING POINTS

a) All PLC and DCS system cabinets kept inside the partitioned enclosure at the control room.

b) All operator stations, utility consoles, engineering work station and printers for log, alarm and events.

c) Long term trend PC, Trilogger, PLC work station and their printers operate on 230V AC stepped up from 115V AC UPS power.

Page 316: Ammonia Manual

Ammonia Plant Operating Manual 163

d) All field transmitters, though operate on 24V DC derives power from system cabinets supplied with UPS power.

e) Flame scanners of all fired heaters operate on this UPS power.

f) Field instruments like mass flow meters and digital tachometer are operating on UPS power.

UPS POWER FAILURE

In case of UPS power failure following will be the consequences:

a) All control station will stop functioning and electronic signals received by all the I/P converters will be Zero. Thus all the control valves will reach their fail safe condition irrespective of the availability of instrument air. This is achieved by suitable closed loop configuration to have the same state of valve for both signal failure and air failure.

b) All operator station will not be available for control and monitoring. Stations will become available after 20 seconds after the resumption of power. 20 seconds being the initialisation process of EOPS.

c) PLC will stop working. All solenoids will be deenergised because of null output from the system. Thus all trip valves connected to PLC will reach their trip state.

d) The software has to be necessarily reloaded for PLC to resume operation. However once EPROM of final software are fitted, reloading from workstation will not be required for the PLC to resume operation.

e) Total plant trip action in the field shall be carried out, monitoring the process parameters from the field mounted pressure gauges and temperature gauges. On resumption of EOPS, all control valves shall be kept in the required status, as all controller status would have changed to MAN mode, with zero MV.

f) 5.In case the power failure was more than 72 hours, all the control station images have to be loaded from the engineering station, as the battery in EFCD is expected to last for 72hours only. Check for control station images, as a check for battery performance, even if the power interruption is for shorter duration.

g) Similarly PLC processor images shall be checked, and loaded from engineering station if required.

110V DC POWER

SOURCE

There are two sources for 110V DC power, which is mainly used to power all the solenoids in the plant except a few solenoids as detailed below under consumption. Ammonia plant battery chargers C and D receive power from PCC-1A and MCC-2 respectively, supplies Ammonia plant 110V DC. There is one battery charger for ASGU which receives power from MCC-18 and supplies to the ASGU 110V DC feeder.

Page 317: Ammonia Manual

Ammonia Plant Operating Manual 164

At DCS control room, there is a provision to interconnect these two 110V DC power feeders for switch over of source for both the consuming categories.

CONSUMING POINTS

AMMONIA 110V DC Distribution

1. All solenoids connected with PLC system.

2. Deaerator dump valve solenoid for which interlock execution is from DCS on energised to trip concept.

3. There is a separate cable running to compressor house for auxiliary motors auto start circuit execution.

4. Aux.Boilers main trip valve solenoids.

5. FO pumps auto start XCVs solenoids.

6. control circuit for air motor auto start.

ASGU 110V DC Distribution

1. ASGU, PGHRU, and AIS solenoids.

2. MFCV2600, ASGU deaerator drain, BFW heater PCV,and CPP FOP auto start XCVs are operating on 110V DC which were earlier operated on 24V DC.

110V DC Failure

All the solenoids connected to the relevant source will go to trip state leading to plant trip. Alternative source can be lined up, if available, for restart of the plant.

Non UPS,115V AC power from GUTOR 5KVA inverter

Source

Battery chargers A and B receives power from MCC-2. Bypass mains for these inverters is also from MCC2. Inverter A and B are connected to these battery chargers. These units feed power to CSA 2A panel.

Consuming points for CSA 2A panel

1 exit CO2, 1113 exit hydrogen, 1121 exit hydrogen, PGHRU product hydrogen, analysers.

2 IAC control circuit.

3 IG control circuit.

4 SRC control circuit.

5 New control room utility sockets,at marshaling area.

Page 318: Ammonia Manual

Ammonia Plant Operating Manual 165

6 ID/FD panel lamp circuits.

7 Distribution panel at CH for compressor house instruments, and fired heaters lamp annunciation. Barriers at compressor house operate on this power.

8 Aux.Boilers BCC panel lamp annunciation and individual burner solenoid valves.

9 ASGU BCC panel lamp circuit.

10 CWPT panel for lamp annunciation.

11 SCPU bypass XCV solenoid.

12 PGHRU local panels.

13 Fired heaters and BCC panels ignition transformer circuits.

14 Boiler FD fan trip solenoids which are energised to trip.

15 RGAH soot blowing panel control circuit.

115V AC Non-UPS power failure

1. All local panel annunciation will not work.

2. IAC, IG, SRC, could not be started.

3. Aux.boilers individual burners could not be tripped, however main trip valve can be operated with, 110V DC and UPS power availability.

4. Ignition transformers of Boiler and fired heaters will not work.

5. Analysers will not work.

6. Boiler FD fans can not be tripped from control room.

7. RGAH soot blowing can not be operated.

8. Compressor house, temperature and vibration monitors will not work.

230V AC power from CSA 2 with source from MCC2 - consumers

1. IAD control circuit.

2. Reformer ignitors.

3. Paging units.

Page 319: Ammonia Manual

Ammonia Plant Operating Manual 166

4. Super phones.

5. 24V DC battery charger.

6. Flare ignitor.

7. Cathodic protection units near RGB, sub station, and IG units.

8. DCS control room fire alarm system.

24V DC power

One 40amps battery charger feeds 24V DC distribution, getting source power from CSA 2. Following are the consuming points:

1. Sub station smoke detector units.

2. Area fire call points.

3. MCC2 power failure alarm circuit.

4. Compressor house annunciation circuits and call hooter.

18.3 PROCEDURE FOR DECOKING 1432

Preparations

1. Position of swing elbows :

a) Swing elbow at 1432 inlet to be connected to 6"P12017.

b) Swing elbow at 1432 exit to be connected to 6"P12016.

c) Swing elbow to be connected between 6"P12016 and P12018 for forward flow.

d) All the open flanges to be blinded (3 Nos.)

2. Inspect 1432 thoroughly, clean the furnace, remove any foreign matter and box up manholes and burners.

3. Decoking steam is to be charged.

4. Atomising steam is to be charged.

5. Pilot gas is to be made available.

6. Fuel naphtha is to be charged upto battery limit.

7. Service air is to be available.

OPERATION

Page 320: Ammonia Manual

Ammonia Plant Operating Manual 167

Limits of temperatureFlue gas exit radiation section - Decoking maximum 677 0C Decoking minimum 566 0CSkin temperature (Radiation zone) Operating design 539 0C Decoking maximum 760 0C

1. Establish cooling water to quench separator to allow a minimum flow of live steam through vent.

2. Purge the coil with steam for about 10 minutes in the forward direction. Ensure that 1432 is warmed up gradually avoiding hammering. Check CW from quench separator for hydrocarbons.

3. Light 1432 and raise flue gas temperature exit radiation section TI-1/1201 at a rate not exceeding 150 C/hr. Adjust steam flow and maintain tube skin temperatures less than 690 C. When conditions are steady, note the position of the steam valve spindle.

4. Open steam valve fully to effect a quick temperature reduction of the tube metal causing spalling of coke. Do not adjust firing rate while increasing steam flow. Maximum steam flow to be kept for about 5 minutes and flow to be reduced to the previous value.

5. Repeat the above operation 3 times to complete spalling. During this check, check the quench water for colour change. As the spalling proceeds, colour changes from milky white to gray and to black.

6. After completion of spalling, adjust steam flow (to approx. 1 TPH) and maintain tube skin temperature at 567 0C by adjusting firing.

7. Inject air at very slow rate and initiate combustion. Once combustion begins, tube temperature is reduced to 539 0C.

8. Combustion is to be controlled by varying steam and air flow and adjusting firing. In any case, the highest skin temperature should not exceed 690 0C - 760 0C.

9. CO2 in the exit gases should not exceed 10 %. Any higher figure indicates that combustion

is too rapid and the proportion of air in the steam flow should be reduced.

10. Progress of decoking is monitored by CO2 in the exit gas, appearance of quench water and

exit vapour and VISUAL observation of the tubes. When the combustion starts, the quench water will be gray or milky. As the conditions become more rapid, the quench water darkens in appearance.

11. Completion of decoking is decided by the absence of CO2 in the exit gas, clean exit vapours

and disappearance of hot zones of combustion.

12. When this condition is reached, the air flow is shut off. Steam rate is increased to flush out the tubes.

13. Shut the burners off, but continue a steam flow to cool the tubes. Cut off steam and connect inlet elbow. Admit N2 to the coil . Light 1432 and dry out for 15 minutes. Give clearance for connecting outlet elbow.

Page 321: Ammonia Manual

Ammonia Plant Operating Manual 168

14. Leak check 1432 at 40 Kg/cm²g N2 pressure.

18.4 1432 LIGHTING UP PROCEDURE

1. Open the stack damper fully.

2. Check the local panel control power availability.

3. Check the guns are fixed properly and close it's combination valves. Check pilot gas availability.

4. Open all the air registers and allow for natural purging of the furnace.

5. Charge atomising steam after warming up the line.

6. Check fule naphtha header pressure. Ensure 1432 ball vales (remote & local) and individual ball valves are in closed condition.

7. Check whether cap are provided in TCV 1205 upstream drain.

8. Slowly open the remote ball valve and charge naphtha upto 1432 ball valve.

9. Inform CR to reset and keep open the TCV 1205 at 30% opening on manual.

10. Open the isolation valve upstream of pilot XCV. Press pilot start push button to open XCV. Now the ignitor will come in line and also XCV will open after a time lag of 60 secs.

11. Pilot flame is established and PILOT ON lamp will glow. In case the pilot flame does not get established within 15 secs, pilot XCV will close automatically and ignitor will be cut off.

12. After ensuring pilot flame is on, press MAIN FLAME START push button to open XCV & TCV 1205. Holding the push button in press condition, open the fuel naphtha ball valve of main burner gradually to establish main flame. Keep the ring header pressure 4.0 Kg/cm²g.

13. Ensure the FLAME ON indication in the panel and release the push button and inform CR. Closly monitor the stack and tube skin temperature and the rate of temperature raise should not exceed 50 0C/hr.

18.5 LT CATALYST REDUCTION [C-18-HC]

1. C-18-HC is a low temperature, shift conversion catalyst having a copper oxide content of a minimum of 38%.

2. Reduction of CuO to Cu is required for activating the catalyst. This is achieved by a specific reduction procedure as follows.

a) Copper oxide is reduced to copper by reacting with hydrogen.

CuO + H2 Cu + H2O

Page 322: Ammonia Manual

Ammonia Plant Operating Manual 169

The H2O thus formed is knocked out from the circulating gas during reduction.

b) Check and calibrate all the thermocouple points, temperature indicators/recorders in the LTS reduction loop and converter.

c) Check and calibrate the inert gas (IG) flow meter. Hydrogen flow meter precalibration may be done. However, a calibration during the heating up of catalyst bed will have to be done.

d) Loop is to be checked for system leaks, if any and rectified.

e) Log all temperatures, pressures, flow rates and analyse every 15 minutes, except otherwise specified from start of reduction till completion.

f) Laboratory analyses required are as given below:

i) IG 1) H2 and O2 every 30 minutes.

2) As, S, Cl, Co, CO2 and NH3 before start of circulation.

3) NH3 once in 2 hours.

ii) Loop 1) O2 once in one hour.

2) H2 inlet and exit of LTS once in 15 minutes.

iii) H2 (cracked gas)

1) S, Cl once in a day. 2) Ammonia once in four hours.

3. a. IG quality may be controlled for oxygen and hydrogen as follows:

O2 less than 500 ppm

H2 less than 500 ppm

However do not exceed maximum of O2 1500 ppm maximum and H2 500 ppm maximum.

b) Further Ammonia content of IG should be controlled close to Nil ppm. This should not exceed 0-10 ppm.

c) The traces of CO and CO2 in IG may not exceed 1000 ppm and 2000 ppm respectively.

d) Cl- should not be present in IG.

4. Ammonia cracked gas as source of hydrogen is used for this reduction. There should not be any S and Cl in cracked gas.

Page 323: Ammonia Manual

Ammonia Plant Operating Manual 170

5. LTS reduction

a) Purge the LTS loop and converter with IG to bring down the oxygen content to less than 1000 ppm. Also analyse the loop for hydrogen concentration. It should be less than 500 ppm specified.

b) Establish a flow of IG to a space velocity of a minimum of 200 hrs. Space velocity is defined as IG flow Nm3/hr divided by catalyst quantity in cm. Based on available gas flow of 27500 Nm3/hr, the space velocity will be 270 hrs.

c) Eventhough a linear velocity of around 0.2 ft/sec is preferred for the reduction, based on above circulating flow rate of 27500 Nm3/hr, the linear velocity achievable will be around 0.12 ft/sec.

Gas flow rate M3/hr Linear velocity = ------------------------------------------------ Cross sectional area of LTS catalyst bed

d) Start heating the LTS catalyst bed with inlet gas temperature at a rate not exceeding 50 0C per hour.

e) The difference between the inlet gas temperature and minimise catalyst bed temperature should not exceed 200 0C at any time during heating up or reduction. However, limit the inlet gas temperature to 250 0C unless otherwise specified.

f) Calibrate the hydrogen flow meter when the maximum catalyst bed temperature reaches 700 C as follows:

Crack open hydrogen needle valve and inject hydrogen for 2 to 3 minutes noting down flow rate.

After 5 minutes draw gas samples at inlet and exit of LTS and check hydrogen concentration. Repeat the above operation at different calibrations of the flow meter and calibrate the flow meter with laboratory analysis. During this operation ensure;

i) Temperature of catalyst bed should not exceed 70 C. ii) H2 concentration should not exceed 0.3% in the loop.

g) Continue heating at the rate specified to bring up maximum catalyst bed temperature to 180 0C. Keep analysing hydrogen at inlet and exit of LTS to check for hydrogen consumption.

h) If hydrogen consumption is noticed, then inject hydrogen in small quantities. However, keeping a close watch on temperature and hydrogen analysis.

i) If the temperatures are within specified limits (as below) and hydrogen consumption is continuously confirmed, keep hydrogen needle valve crack opened continuously.

j) Limit maximum hot spot anywhere in catalyst bed to 210 C. If there is a tendency of run away temperature, cut down or cut off hydrogen as necessary to limit temperature to less than 210 C maximum.

Page 324: Ammonia Manual

Ammonia Plant Operating Manual 171

k) Reduction is an exothermic reduction. There will be approximately 25 C rise in temperature per percent hydrogen consumed. In order to keep hot spot in catalyst bed less than 210 C maximum, hydrogen at inlet should not exceed 1% maximum during major portion of catalyst reduction.

l) Adjust needle valve opening to come to a hydrogen concentration level such as to limit hot spot anywhere in catalyst bed to less than 210 C maximum. Keep hydrogen flow continuously at this level for a steady reduction.

m) During reduction each TI in catalyst bed from top to bottom progressively will rise and fall in temperature indicating completion of reduction at each point.

n) As the last point, the LTS outlet temperature rises and falls to near inlet temperature, the hydrogen concentration at outlet starts building up.

o) At this point, there is a tendency for hydrogen build up in the loop. Therefore, out down inlet hydrogen to keep inlet hydrogen concentration at 1% level.

p) Slowly, the outlet hydrogen concentration will be more or less the same as inlet hydrogen concentration. At this point, start increasing inlet temperature to bring all bed temperature to 200 0C.

q) Increase hydrogen flow and bring up hydrogen concentration to about 5% in three hours. Watch forsudden rise in temperature anywhere in catalyst bed. If so, cut down hydrogen or cut off hydrogen and if necessary, purge the loop free of hydrogen to bring the temperature within hot spot limits.

r) Continue raising hydrogen concentration to about 15% in a further prior of three hours.

s) At this point with hydrogen around 15%, all bed temperature around 200 C reduction is essentially considered complete.

t) Continue circulation for about 6 hours. Purge free of hydrogen with quality IG and box up LTS vessel under pressure.

N o t e:

1. In case of power failure or tripping of circulating gas compressor, cut off hydrogen completely.

2. In case of any run away temperature indicating, cut down or cut off hydrogen as may be necessary.

3. Consult UCIL representative for variation in procedure if any.

18.6 AMMONIA SYNTHESIS CATALYST REDUCTION

GENERAL

Ammonia synthesis catalyst is activated by circulating syn gas through catalyst beds by slowly increasing the temperature.

Page 325: Ammonia Manual

Ammonia Plant Operating Manual 172

The catalyst reduction is the formation of water vapour by reduction of Iron Oxide and separating the water in the down stream of the converter. The water formation due to the reduction is about 30 Kg/Ton of pre-reduced catalyst and 280 Kg/Ton of oxidised catalyst.

The main control criterion for the reduction of catalyst is thus maintaining a steady syn gas flow with a steady heat input, giving a well controlled, moderate temperature rise in the beds.

START OF CATALYST REDUCTION

1. Stroke check all the control valves.

2. Ensure that all the temperature indication in the synthesis loop and refregeration loop are available in DCS. Trip check 1434.

3. Analyse for IV suction CO + CO2, when CO + CO2 is less than 1 ppm, take gas to synthesis

loop by opening bypass of ESV 104.

4. Ensure cooling water flow to loop cooler condersors(1524).

5. Pressurise syn loop to 20 Kg/cm²g and leak check all the flanges opened during the shutdown. This procedure is to be repeated at 40 Kg/cm²g, 80 Kg/cm²g and 100 Kg/cm²g.

Pressurise and depressurise rate:

0 - 40 Kg/cm²g 1 Kg/cm²g/min 40 - 80 Kg/cm²g 2 Kg/cm²g/min 80 - 120 Kg/cm²g 2.5 Kg/cm²g/min

6. Keep the XCV 1809 Valve open and HC 1810 closed. To remove the dust from the catalyst, slightly open HP vent at the outlet of 1523 without allowing the loop pressure to decrease (by adjusting the antisurge valves of SGC). Watch closely the closure of PC1509. HP vent isolation valve is to be opened till PC 1509 is 10% opening. Watch the vent stack for dust. The dusting operation should be continued minimum for one hour till the vent stack is visibly clear of dust. Once the dedusting operation is completed, slowly close the HP vent isolation valve without surging the machine.

7. Control valves in the loop shall be in the following position:

a) HC 1810 converter bypass full open. b) XCV 1809 converter inlet closed. c) HC 1806 closed - II bed inlet quench.

d) HC 1807 (Flush gas) kept open. Flush gas flow is about 50,000 Nm3/hr. e) HC 1808 III BED Quench kept closed. f) HC 1801 1434 inlet and its Isolation valve open.

Page 326: Ammonia Manual

Ammonia Plant Operating Manual 173

g) XCV 1814 1434 outlet and its isolation valve open. h) HC 1812, LCV 1811, HC 1811, LC 1813 kept closed.

8. Open ESV 102, ESV 103, ESV 104 and close JCV 103 to establish the circulation. Close ESV 104 bypass isolation valve.

9. Adjust converter bypass and heater inlet valves to achieve about 50,000 Nm3/hr in FI 1810

(1434 inlet) and 50,000 Nm3/hr in FI1803/B (Flush gas through HC 1807).

10. Remember that an alteration of any flow in the converter will affect all the flows to some extent. Care should be taken to ensure that while increasing another flow, the FI 1810 is steady.

11. The loop refrigeration system should operate in such a way as to ensure the temperature in the secondary chiller 10 C higher than freezing point of aqua ammonia solution separated in 1122. To achieve this, primary chiller is to be operated at 5 Kg/cm²g and secondary chiller level control valve should be isolated. Care should be taken to avoid build up in level of 1128.

12. Light up 1434 and raise the outlet temperature as per heating rate. Keep a careful check of heater outlet temperature, skin temperature and condition of burner firing.

REDUCTION OF I BED:

1. This bed is charged with 18320 Kg of pre reduced catalyst. The temperature increase should be as per the following rate.

Ambient to 150 C (First bed inlet) 50oC/hr (max)

150oC to 200oC ( " ) 25oC/hr (max)

200oC to 250oC ( " ) 20oC/hr (max)

250oC to 350oC ( " ) 10oC/hr (max)

350oC to 470oC (hot spot) 6oC /hr

2. Take reading in the log every half an hour.

3. When the I bed inlet temperature reaches 200 oC inform lab to analyse for the following

Converter outlet moisture Once in an hour

Converter outlet ammonia Once in four hour

Converter inlet moisture Once in four hour

Converter inlet ammonia Once in hour for first eight hours afterwards once in four hours. Concentration of 1122 Ammonia as and when required.

4. During the heating up and the reduction of the converter the converter inlet flow rate is minimum. Hence converter shell temperatures should be watched.

Page 327: Ammonia Manual

Ammonia Plant Operating Manual 174

5. Converter inlet and outlet gas samples should be analysed for moisture and ammonia every

hour from 200oC (at I bed), some water will be detected initially (at 200oC) due to the catalyst drying out.

6. The temperature in the chiller should not be allowed to fall below the freezing point.

Freezing Point % Ammonia w/w

0oC 0

- 5oC 4.0

-10oC 7.0

-15oC 9.5

-20oC 12.0

-25oC 14.3

-30oC 16.0

-33oC 17.0

Once the ammonia concentration is surely more than 10%, the risk of freezing is over.

7. When the I bed temperature is at about 350oC (in the range of 350oC-400oC), the rate of increase if I bed outlet temperature will be more than the rate of increase of inlet temperature, indicating the formation of ammonia.

8. When the I bed exit temperature exceeds 360oC, the II bed inlet temperature should be controlled by opening HCV 1806. (Remember to keep steady FI 1810 and FI 1803/B).

9. The I bed outlet temperature is controlled by increasing the flow to the converter inlet (through HCV 1807). Care should be taken to avoid swinging of the bed temperature.

10. When the I bed outlet temperature is 400oC, the concentration of aqua ammonia in 1122 is expected to reach 10%. The secondary chiller can be lined up very slowly (to avoid any upset in the I bed).

11. should be drained often and water should be collected in drums. Care should be taken to avoid build up of level in 1122.

12. Converter outlet moisture should not exceed 1000 ppm v/v. In case of increase of moisture above the limit, the rate of increase in I bed inlet temperature should be reduced.

13. When ammonia formation takes place, the loop pressure tends to decrease. Maintain the loop pressure at 100 Kg/cm²g and the loop pressure can be increased by 1-2 Kg/cm²g/hr up to 150 Kg/cm²g.

Page 328: Ammonia Manual

Ammonia Plant Operating Manual 175

14. II bed inlet temperature can be raised by 1-2oC/hr upto maximum of 400oC till the I bed reduction is complete. Converter outlet moisture will slightly increase due to this.

15. When the I bed outlet temperature reaches 470oC the I bed reduction is said to be complete.

I bed outlet temperature is increased to 495oC (505oC max) and maintained.

16. Water content in the converter inlet should be below 100 ppm.

17. A small purge through HCV 1812 is required to ensure correct ratio.

CIRCULATOR TRIP

In case of stoppage of circulation, the loop should be depressurised at rate same as

pressurisation till the temperature of the bed which is getting reduced to decrease by 35oC.

Even after depressurisation if the reducing bed temperature does not reduces by 35oC, nitrogen / syngas to be admitted to cool down.

1434 TRIP

1434 to be lighted up with in few minutes. If it is not possible HCV 1801 is to be closed and minimum flow through bed to be maintained through HCV 1807.

REDUCTION OF II BED

1. This bed is charged with 47550 kg of oxidised catalyst. When the I bed outlet temperature

is increased to 495oC, the II bed inlet temperature is at 400oC.

2. Increase the II bed inlet temperature to 420 oC at the rate of 3-4 oC/hr by reducing the quench gas flow through HCV 1806. II bed activation begins when the temperature is at about

430oC. Increase the II bed outlet temperature (hot spot) at the rate of 2-3oC by increasing the inlet flow to the converter (By opening HCV 1807, if necessary also open XCV 1809).

3. II bed reduction is completed when the bed outlet temperature reaches 470oC and quench valve HC 1806 is about closed.

4. Open HCV 1808 III bed quench gas to maintain the III bed inlet temperature at 360oC.

5. The converter outlet moisture during the reduction of II bed and III bed should not exceed 2500 ppm.

6. Raise the III bed inlet temperature from 360oC to 400oC (max) at the rate of 1-2oC per hour during the reduction of II bed.

7. should be kept in line and flow through the 1434 should be maintained till the converter reaction is autothermic.

III BED CATALYST REDUCTION

1. This bed is charged with 87950 Kg of oxidised catalyst.

Page 329: Ammonia Manual

Ammonia Plant Operating Manual 176

2. When the II bed reduction is complete, III bed inlet temperature should have been raised to

400oC. Raise the temperature of the III bed inlet to 420oC at the rate at the rate of 2-3oC/hr by

reducing the gas flow through HCV 1808. Catalyst activation is expected at about 430oC.

3. Increase the III bed outlet temperature to 480 oC at the rate of 2-3oC/hr by increasing the inlet gas flow (By opening inlet gas flow).

4. III BED reduction is complete when the bed temperature 470oC.

5. When the first bed inlet temperature is steady, reduce the 1434 out let temperature and flow. Cut off 1434 and reset the trip panel and maintain minimum flow through HC1801 to control the first bed inlet temperature.

6. The design Optimum temperatures of the beds after the reduction at full capacity of the plant is as follows:

INLET OUTLET

I BED oC 378 504

II BED oC 405 478

III BED oC 394 444

At reduced capacity the bed inlet temperature shall be increased; for instance at 60 % Load the

increase shall be around 30 oC.

7. The loop pressure after the reduction would be about 150 Kg/cm²g.

8. When catalyst reduction is considered complete the converter can be increased by raising the front end load.

9. Although the purity of the product over 99% full activity of the catalyst will not be achieved for a few days.

PROCEDURE FOR LINING OF CONVERTER WITHOUT LIGHTING 1434

1. After trip out, if the loop pressure is lower than 100 Kg/cm²g, pressurise the loop with quality syngas to 100 Kg/cm²g as per normal rate.

2. Ensure the following before establishing loop circulation.

a) Circular d/c and loop pressure is same. b) HC 1801 - Close. c) HC 1806 - Close. d) HC 1807 - 5% (therefore this valve must have been opened already during trip out). e) HC 1808 - Close. f) HC 1809 - Close.

Page 330: Ammonia Manual

Ammonia Plant Operating Manual 177

g) HC 1810 - 75%. h) HC 1812 - 0.1%.

3. Ensure LRC is on MGS with normal levels in chillers.

4. Establish loop circulation and close ESV 104 bypass.

5. Slowly open HC 1807 to 25% and get a flow of 9 KNm3/Hr as indicated by FI 1803.

6. Watch for sharp increase in 1121 exit temperature than other points; maintain purge rate of

around 2000 Nm3/Hr through HC 1812.

7. Control the rise in I bed exit temperature by opening HC 1807 further.

8. Once HC 1807 opening is 70% (flow 75.2 KNm3/Hr) throttle HC 1810 gradually to 50%.

9. To control further the rise in I bed exit temperature. Open HC 1809 by 0.5% and ensure a

flow of 215 KNm3/Hr as indicated by FR 1809.

Slowly open HC 1809 up to 10% watching I bed exit. Following are likely to prevail.

HC 1809 - 10% Loop pressure - 110K

HC 1807 - 70% FI 1809 - 229 KNm3/Hr

10. Once the level is built up in 1122, line up HCV 1811 and LCV 1811. Put LCVB 1811 on auto.

11. Gradually open the HC 1809 and simultaneously increasing the loop pressure. Watch PC 1509 opening.

12. Once there is no delta T increase further, open HC 1806 to get reaction in II bed. Maintain

II bed inlet at 460oC. Throttle HC 1810 suitably. Maintain a loop purge of 3000 Nm3/Hr.

13. Slowly load the converter further.

14. Maintain I bed inlet temperature not lower than 380oC by operating HC 1801.

18.7 PROCEDURE FOR SILICA WASH OF SYN GAS COMPRESSOR TURBINE

HOT WATER WASHING METHOD

Preparation

1. Hook up 1" drain near TCV 0103 in the desuperheating water header near 45/12 Kg/cm²a let down station and 1" drain line from the main stream piping of SGC between MSV and regulating valves, near flush chamber with a 60 mesh strainer.

2. Additional supports (temporary) for the main steam and extraction steam pipe work to take up the additional load due to weight of water. Provision for thermal expansion should be there.

3. Removal of inspection cover of the LP casing and fixing up with a temporary cover having provision for venting air and also a water outlet pipe with a sample point and temperature indication.

Page 331: Ammonia Manual

Ammonia Plant Operating Manual 178

4. Gland condenser inlet pipe to be disconnected and left open with a provision for sampling.

5. Temporary level indication provisions on extraction steam line and on the condenser.

OPERATION

1. The temporary water line inlet to main steam line should be thoroughly flushed, after charging the desuperheating water header and line to be connected back.

2. Shut all drain lines around the unit.

3. Start lube oil system and maintain normal lube oil pressure.

4. Confirm the following trips are bypassed locally.

- PGL - 1 trip. - Head tank level low. - Low lube oil trip.

5. Keep regulating valves and extraction control valves full open. (Keep MSV and block valves in main steam line and extraction line shut).

6. Keep sealing air to pedestals open.

7. Before filling deaerated water into the turbine casing,. check the following :

- MSV and its block valve in extraction line are fully shut.

- Condensate pump suction and its spillback valves are shut.

- Check all other drain valves & vent valves for a possible leakage and loss of water.

8. Fill condenser with make up water until level comes to the height of exhaust flange of the turbine. (Keep condensate pump suction and spillback shut).

9. Keep the drain in the extraction steam line partly open.

10. Start the turning motor.

11. Slowly admit hot water into the casing.

12. Maintain level in the casing slightly above the axis of the rotor.

13. Sampling of water to be done at the following points (silica and conductivity).

Interval a) Supply 1 hr. b) Extraction line 10 - 15 minutes c) Casing outlet - do -

Page 332: Ammonia Manual

Ammonia Plant Operating Manual 179

d) Gland condenser line - do - e) Condenser 1 hr.

14. Compare conductivity of supply water and the outlet water to judge whether scale in the turbine is soluble in water.

15. When conductivity of outlet water reaches saturation, stop hot water supply and drain out water from the casing and pipe work.

16. Repeat washing as above till the conductivity of outlet water comes to almost the same level of supply. Thus the washing is considered complete.

17. All the preparatory jobs are to be removed and normal connections to be given.

18. Turbine to be started as early as possible to avoid rusting. A longer warning up period has to be followed to ensure complete evaporation of water inside the casing.

18.8 LRC / PAC TURBINE SILICA WASHING PROCEDURE

Preparation

1. Introduce a slip plate at the gland condenser gas inlet flange.

2. Condensate water connection from desuperheating water header is given through HP hoses to the inlet steam PI point.

3. A sampling hose is provided and it syphons out the sample continuously through the Inspection door.

4. Turbine has to be decoupled and manual barring provision is provided at the turbine coupling end.

5. Lube oil to the turbine side to be isolated by slip plates.

6. All the interconnection lines are positively isolated.

7. Fill up the condenser upto the shaft level with polished water and then admit desuperheating water.

Once hot water is admitted;

a) Maintain constant barring.b) Never allow the level to raise beyond the shaft level. Excessive condensate leak through the labyrinth soals may damage the same.c) Collect the overflow samples and analyse at every 30 minutes.d) The hot well sample is to be analysed once in two hours.e) Stop the condensate addition when three or more valves of silica remains constant.f) Continue the Lube Oil circulation until all bearing temperature falls down to 60 C. Drain the condenser totally and stop the lube oil circulation.

18.9 LOADING OF AMMONIA IN TANKERS

Page 333: Ammonia Manual

Ammonia Plant Operating Manual 180

1. Ensure that tanker is parked at right place to connect liquid and vapour line hoses easily.

2. Ensure tanker wheel stopped blocks are positioned.

3. Check tanker pressure, temperature and level and record.

4. Ensure earthing cable is connected to tanker.

5. Get the keys of the tanker tractor.

6. Connect vapour and liquid line hoses to the tanker liquid inlet and vapour outlet line. Hoses are provided with 'Quick Fix' snap joints and they can be fixed easily.

7. Ensure that tanker liquid and vapour and vapour line bleed valves are kept closed.

8. Close drain valves in the liquid and vapour lines down stream of isolation valves in our side.

9. Fill up Ammonia loading clearance form and send it to Shift Engineer along with tractor key.

10. After getting clearance from Shift Engineer, open tanker liquid and vapour isolation valve (keep both the valves full open).

11. Open vapour side MOV fully, slowly open the vapour line isolation valve at outside and equalise the tanker pressure with sphere pressure.

12. Open the liquid line MOV fully.

13. Open feed pump discharge isolation valve (when there is no ammonia receipt from AIT) in such a way that PCV 1903 in 25% open.

14. Check open the liquid loading line globe valve, now liquid Ammonia starts flowing into the tanker.

15. Check the level and pressure of the tanker. If the pressure increasing rate is faster, throttle liquid inlet globe valve further.

16. When the level comes to pre-marked position in the dip rod, close liquid inlet gate valve.

17. Close liquid MOV. Put water over the liquid line hose and push the liquid by vapourisation. Close tanker side liquid isolation valve.

18. Close vapour side isolation valves.

19. Drain the Ammonia if any entrapped in the hoses.

20. Open the bleed in the liquid and vapour line on the tanker side.

21. After ensuring that there is no vapour/liquid in the hose, disconnect both the hoses at the tanker side.

22. Keep the hoses on the loading platform.

Page 334: Ammonia Manual

Ammonia Plant Operating Manual 181

23. Remove earthing cables.

24. Fill up loading clearance form and send it to Shift Engineer.

Note

1. Keep liquid and vapor side MOV’s on remote mode during loading.

2. Wear safety goggles and ensure the availability of service water hose nearby.

3. Monitor the wind direction.

15.1.1 AMMONIA PLANT CATALYSTS

Page 335: Ammonia Manual

Ammonia Plant Operating Manual 182

LIST OF STORAGE TANKS PRESENT IN AMMONIA PLANT

TANK VOLUME KL/CM SAFE PRESSURE TEMP. DEAD

M3 STORAGE Kg/cm²g 0C STOCK 1202 A 8800 9.085 988 Atm Amb. 3000 1202 B 8800 9.085 988 " " 3000 1203 8800 9.085 988 " " 3000 1202 C 6150 6.15 980 " " 2000 1202 D 6150 6.15 980 " " 2000 FO-I 3800 5.31 710 " " 1200 FO-II 3800 5.31 710 " " 1200 FO DAY TANK 216 - - " 90 - (AMMONIA) FO DAY TANK(CPP) 216 - - " 90 - 1204 (VETRO STORAGE 510 - - " - - TANK) 1209 VETRO DISP.TANK 450 1205 VETRO M/U TANK 10.5 1206 CONCN TANK 11.4 HORTON 3000 MT - 2500 MT 3.4 0 - SPHERE NITROGEN RECEIVER 36 - - 40 amb. -

Page 336: Ammonia Manual

Ammonia Plant Operating Manual 183

CRACKED 25 - - 43 amb. - GAS RECEIVER

18.12AMMONIA PLANT UPS SYSTEM

The Ammonia Plant UPS power supply is fed from three sources:

1. UPS 'A' from MCC-11 with 220 DC battery back up.2. UPS 'B' from MCC-18 with 220 DC battery back up.3. Total bypass mains MCC-2 through an auto transformer which step down the voltage from 415 V to 115 V AC.

In normal condition, MCC-11 (UPS 'A') and MCC-18 (UPS'B') share the total load of Ammonia UPS power. Our UPS system is known as 'parallel redundant system'.

UPS OUTPUT

Make Gutor 40 KVA Inverter

Voltage 115 VI 1%

Frequency 50 Hz to 0.1%

Current At 100% load - 347.8 A At 125% load - 425.8 A (for maximum 10 minutes) At 150% load - 521.7 A (for maximum 1 minute)

Cells Sulphuric Acid and Lead type

Temperature 0-40 0C (during operation)

-25 to 70 0C (during storage condition)

Humidity > 90%

Noise level > 65 dB

MTBF 1,85,000 hrs

In normal operation load of each inverter is 14.4 KVA (18% of total load). Amps is 398 A. To compensate for loss in voltage of battery the current taken is only 1-2A.

1. If MCC-11 fails

a) UPS 'A' rectifier fail alarm will appear in DCS panel.b) will take the full load.c) outlet breaker will open to prevent the use of batteries in MCC-11.d) After MCC-11 comes in line UPS'A' rectifier fail recover alarm will appear. MCC-11 breaker will close and share the total load on UPS with MCC-18.

Page 337: Ammonia Manual

Ammonia Plant Operating Manual 184

2. MCC-11 Failure followed by MCC-18 failure

a) & MCC-18 both battery (220 V DC) will come in line sharing the total load on UPS.

b) Now if MCC-11 battery or MCC-18 battery or both MCC-11 & MCC-18 battery fails, the monitor provided at the outlet of battery senses the lesser voltage and MCC-2 bypass main will come in line. During this MCC-2 both static switch will come in line. If one static switch fails the another static switch will take up the load.

c) MCC 11 & MCC-18 failure followed by Grid frequency reduces to 47 Hz

Static switch will open and the power fed to UPS will stop.

d) Control Power Unit Power Supply Failure

For UPS Auxiliaries, power was taken from safe bus itself. For UPS'A' and UPS'B' separate control units are provided. If the control unit with power supply fails, the another MCC-11 / MCC-18 will take up the fuel load.

e) Rectifier Input Voltage Nil (Cable failure)

For R,Y,B cables, earthing is done. If cable disconnected, the monitors at the line senses lesser voltage and the another unit will come in line (MCC-11 or MCC-18).

18.12 ANALYSIS IN CTIG AREA

1.Boiler feed water analysis (main plant & ASGU )

2.Boiler water analysis (1106,Auxillary boilers & ASGU)

3.Converter inlet & exit ammonia analysis

4.SGC Fourth suction CO & CO2 analysis

5.Aux.Boiler flue gas analysis

6.IG Oxygen & Hydrogen analysis

7.1127 Inerts analysis

In water analysis,

a.pH value b.M-Alakalinity c.Silica d.Phosphate e.Hydrazine are measured.

Page 338: Ammonia Manual

Ammonia Plant Operating Manual 185

SPECIFICATIONS

BOILER FEED WATER

pH - 8.5-9.0

Total hardness as CaCO3 - Nil

Turbidity - Nil

Silica as SiO2 - 0.02 ppm

Total dissolved solids - 1.0 ppm

Dissolved Oxygen - 0.005 ppm

Oil - Nil

Hydrazine - 0.05-1 ppm

Conductivity - 50 micro mho/cm

BOILER WATER (CBD)

pH - 9.5-10.5

Total hardness as CaCO3 - Nil

Silica as SiO2 - 1.0 ppm

Total dissolved solids - Nil

Phosphate as PO4 - 3-10 ppm

Hydrazine - 0.05 ppm

1.WATER ANALYSIS a. pH VALUE

Principle of the method:

pH is a measure of the relative acidity or alkalinity of water. The determination is carried out by electromeric method or the indicator method. However determination by electromeric method is accurate and more reliable.

Electromeric method:

Page 339: Ammonia Manual

Ammonia Plant Operating Manual 186

The pH is measured by determining with a potentiometer, the voltage developed by two electrodes , which are on contact with the solution. The voltage of one electrode known as a calomel half-cell is fixed,while the voltage of other electrode varies with pH of the sample.

Apparatus:

pH meter.

Procedure:

The pH meter is standardised under conditions of temperature and concentrations by using 9.2 buffer solution. The electrode shall then be washed free of buffer solution by distilled water and finally with sample. The electrode shoulld be left in the sample for several minutes to obtain a stable reading.

Precautions:

1.The electrode should be always in wetted condition.2.Before starting analysis standardise it with buffer.

b. M- ALKALINITY

Principle of the method

The alkalinity of water is mainly due to the presence of carbonates and hydroxides and less frequently due to borates,silicates and phosphates. Alkalinity is determined by titration with a standard solution of a strong acid to certain end points as given by the indicator solution.

Reagents:

1.0.02 N H2SO42.Mixed indicator

Procedure

Take 50ml of the sample in conical flask, add 2 drops of mixed indicator which is titrated against 0.02N H2SO4 taken in burrette.

Calculation

M-Alkalinity as V x N x 50,000ppm of CaCO3 = ------------------- Vol. of sampleWhere,

V-Vol. of H2SO4N-Normality of H2SO4

c. SILICA ANALYSIS

General

Page 340: Ammonia Manual

Ammonia Plant Operating Manual 187

The presence of silca in BFW may be lead to the formation of dense scale on boiler tubes consequently reduce the heat transfer . In addition, a very serious problem encountered in high pressure operations is deposition of silica in turbine blades and superheater coils.

Principle of the method

Colorimetric estimation of silica.

Procedure

Take 100ml of the sample in PVC conical flask. To this add 2ml of ammonium molybdate for silica. Wait for 5 minutes. Small amount of oxalic acid is added. Shake well.After one minute add 2ml of reducing agent for silica. Mix well & Wait for 5 min. Simultaneously conduct a reagent blank. Read the absorbance using colorimeter with 660 filter.

Calculation

Absorbance value x Factorppm of SiO2 = -------------------------------- Vol. of sample

d. PHOSPHATE ANALYSIS

Principle of the method

The test is based on the formation of phosphomolybdic acid through the reaction of the molybdate reagent with phosphate present in water. The phosphomolybdic acid is then reduced by 1-amino 2-naphtho l4 -sulphonic acid to give a blue color,(Molybdenum Blue). The colour intensity is proportional to the amount of phosphate present.

Reagents

1.Ammonium molybdate for phosphate2.Reducing agent for phosphate

Procedure

Take 50 ml of the sample to which add 2ml of ammonium molybdate reagent and after 5min. add 2ml of reducing agent. Wait for 5min. Find the absorbance using 660 filter in colorimeter.

Calculation

Absorbance x FactorPhosphate as ppm = -------------------- Vol. of sample

e. HYDRAZINE ANALYSIS

General

Hydrazine is dosed in HP boiler feed water to remove dissolved oxygen from water.

Page 341: Ammonia Manual

Ammonia Plant Operating Manual 188

N2 H2 + O2 N2 + 2H2 O

Reagents

1.PDAB (Para Dimethyl Amino Benzaldehyde)2.2N HCl

Procedure

Take 25 ml of sample in a 50 ml standard measuring flask. Add 15 ml of 2N HCl and 10 ml of PDAB. Wait for 15 min and take absorbance reading using 470 filter in colorimeter.

Calculation Absorbance x Factor Hydrazine as ppm = --------------------- Vol. of sample

2. CONVERTER INLET/EXIT AMMONIA ANALYSIS

Principle of the method

The stream of converter inlet/exit gas is passed through a known volume of standard sulphuric acid solution.

Apparatus & Reagents

1.Gas flow meter2.Glass bubblers3.0.5N H2SO44.Mixed indicator

Procedure

Take 50 ml of 0.5N H2SO4 and 100 ml of 0.5N H2SO4 in two seperate glass bubblers for

converter inlet/exit respectively.To this add 100 ml of polished water and 2 drop of mixedindicator.The bubblers are connected to gas flow meter. The stream of gas containing ammonia is passed through the bubblers slowly (bubble by bubble) until the colour changes . Note the gas flow meter reading. i.e vol. of gas passed.

Calculation V1 x N x 22.4 x 100% of NH3 = ------------------------------------------------

V2 x (P/760x273/273+t)x(1-Ps/760) + V1 x N x22.4

Where,

Page 342: Ammonia Manual

Ammonia Plant Operating Manual 189

V1-Vol. of H2SO4 in ml

V2-Vol. of gas passed * FM FactorN -Normality of H2SO4P -Barometric pressure in mmHgPs-Vapour pressure of water at t in mmHgt -Temperature of gas

Temperature Vapour pressure in 0C mm Hg

32 35.733 37.7 34 39.935 42.236 44.6

4.DETERMINATION OF OXIDES OF CARBON INMETHANATED GAS SAMPLES

SCOPE: The method decscribes the procedure for determining CO and CO2 in ppm range for

methanated gas samples (eg. SGC IV suction)

Principle

CO and CO2 are determined by first oxidising the CO present to CO2 in presence of a catalyst

and then absorbing the CO2 in Ba(OH)2 solution. The amount of CO2 absorbed is determined

tritimetically.

Apparatus :

Reagents: 0.01N Ba(OH)2 (Baryta)

0.01N HCl Phenolphthalene indicator I2O5 catalyst.

Procedure:Purge a gas bubbler with the sample gas. Take 25 ml of 0.01N Baryta in the bubbler and half fill the bubbler with CO2 free distilled water. Purge the train with the sample gas for

about 5 minutes. Then connect the Baryta bubbler in the train.

Pass 50 litres of gas throgh the train at the rate of around 60 L/hr. Disconnect the baryta bubbler from the train & close both the ends with a rubber tube.

Take the bubbler to the lab and titrate with 0.01N HCl until the pink color disappear. Note the volume of 0.01N HCl .

Blank Titrate 25 ml of 0.01N Baryta using phenolphthalein indicator with 0.01N HCl. Note the volume of 0.01N HCl.

Page 343: Ammonia Manual

Ammonia Plant Operating Manual 190

Calculation

(A-B) x N x 11.2 x 1000 -------------------------- = PPM of CO + CO2 L x 0.9 x F.F Where A - ml of 0.01N HCl for blank B - ml of 0.01 N HCl after passing gas L - liter of gas passed 0.9 - NTP correction F.F - flow meter factor.

5. BOILER FLUE GAS ANALYSIS

General

In order to have proper control on combustion process an idea about the complete or incomplete combustion of fuel is made by the analysis of flue gas . Thus

1. If the flue gas contain considerable amount of carbon monooxide ,it indicates that the incomplete combustion is occuring .i.e wastage of fuel and it also indicates the short supply of oxygen for combustion.

2.If the flue gas contain a considerable amount of oxygen it indicates the air supply is excess.

Apparatus

Orstat's apparatus

Construction

It consist of water jacketed measuring burette, connected in series to a set of three absorption bulbs through stop-cocks. The other end is provided with three-way stop-cock.The graduated pipette is surrounded by a water jacket to keep the temperature of gas constant during the experiment. The lower end of the burette is connected to an aspirator bottle containing acidified saturated solution of NaCl with 4 or 5 drops of methyl red indicator by means of a long rubber tubing. The absorption bottles have solutions for the absorption of O2 and CO2.

Potassium hydroxide - it absorbs CO2 only

Alkaline pyrogallol - it absorbs CO2 & O2

Hence it is necessary that the flue gas is passed first through potassium hydroxide bulb, where CO2 is absorbed then through alkaline pyrogallol bulb bottle where only O2 will be absorbed.

Working

Step1: The three way stopcock is opened to the atm. and aspirator bottle is raised, till the burette is completely filled with confining solution and air is excluded from the burette . The three way stopcock is now connected to the flue gas supply and the reservoir is lowered to draw

Page 344: Ammonia Manual

Ammonia Plant Operating Manual 191

the gas to be analysed in the burette . The flue gas volume is adjusted to 100 ml then the three way stopcock is closed.

Step2: The stopper of the absorption bulb containing KOH is opened and all the gas is forced into the bulb by raising the aspirating bottle . The gas is again sent to the burette . The process is repeated several times to ensure complete absorption of CO2 . The unabsorbed gas is finally

taken back to the burette till the level of solution in the CO2 absorption bulbs stands at the fixed

mark. The levels of containing solution in the burette and aspirator bottle are equalised and the vol. of residual gas is noted. The decrease in volume gives the volume of CO2 in 100ml of gas

sample.

Step3: The volume of O2 is similarly determined by passing the remaining gas in alkaline

pyrogallol bulb. The gas remaining in burette after absorption of CO2,O2 is taken as N2.

6.a.IG OXYGEN ANALYSIS

In IG oxygen analyser, sample gas is directly sent to the pyrogallol absorption bulb. The difference in volume gives the % of oxygen present in the given volume of the gas.

b. IG HYDROGEN ANALYSIS

Initially take 50 ml of air in the bottle of Orsat apparatus. Transfer the 50 ml of air to the combustion pipette which is having a small heating coil. Heat the coil by giving 4-6 volts power supply through a Dimmerstat. Cover the combustion pipette with a wire gauze.

Take 50 ml of sample gas in the burette. Then slowly pass the gas into the combustion pipette in which the heating coil is glown.

Then again take the gas into the burette using the aspirator bottle. Repeat this operation for 4 to 5 times. In the combustion pipette Hydrogen in the sample gas reacts with oxygen in air which is initially taken and it is converted to water.

Note the contraction in volume in the burette.Calculation: a x 2/3 x 100/A = % of H2 V/V present in the gas.Where A vol. of sample taken in mla vol. of contraction in ml. 7.1127 INERTS ANALYSIS

DETERMINATION OF INERT GASES DISSOLVED IN LIQUID AMMONIA

Principle

The liquid ammonia is allowed to vapourise and react with 50% H2SO4 acid. The unreached

quantity of gas is determined.

Apparatus: Gas scrubbing apparatus.

Reagents: 50% H2SO4

Page 345: Ammonia Manual

Ammonia Plant Operating Manual 192

Procedure

Open the sample point and purge the sample point. Connect the scrubbing apparatus to the sample point with both the stopcocks 1 and 2 in open condition. Now the ammonia vapour enter into the apparatus. Allow the vapour to purge through the apparatus for some time. Then close the stop cock 2 and immediately close the stop cock 1 (Two way cock). Close the sample point valve and disconnect the apparatus from the sample point. Equalise the pressure inside the apparatus to atmospheric pressure by flash opening and closing of stopcock 2. Repeat this operation for 2 or 3 times. Then slowly open the stop cock 1 (Two way stop cock) and raise the aspirator bottle so that the 50% H2SO4 enter in to the apparatus and react with the ammonia

vapour present.The volume of the apparatus is 100 cc. The unreacted volume of gas is measured from the apparatus itself which is already calibrated. The unreacted volume in cc will give the percentage of inerts directly.

NOTE: Care should be taken while opening the sample point in which line pressure is around 15.0 Kg/cm²g. Use single tube for sampling. Face along the wind direction when analysis is done.

18.13 SAFETY

The following safety regulations cover operations of particular concern to the personnel responsible for the operation of the Ammonia Plant. They are intended to supplement, not supercede, any existing general plant regulations which cover all units, and reference should be made to the latter for all points not mentioned below. Mechanical craftsmen working on the unit will be governed, in addition, by their own departmental regulations, but the unit operators should see to it that not one of the regulations presented here is violated by a mechanical craftsman.

1. Fire Fighting and Protective Equipment

a) All personnel must know the location and use of all fire extinguishers, fire hoses and hydrants, fire blankets, gas masks and respirators and other protective equipments as hard hats, rubber gloves etc.

b) Foam type extinguishers and water streams must not be used on fires around electrical equipment because the water solution will conduct electricity and may aggrevate the difficulty or result in the electrocution of personnel.

c) Carbondioxide or dry powder extinguishers may be used safely on electrical fires. The carbon tetrachloride extinguishers liberate poisonous fumes and should not be used.

d) Carbondioxide, dry chemical or foam type extinguishers are suitable for oil fires. For large oil fires, steam hose equipment or fog nozzles on the end of a water hose are suitable.

e) Gas masks must be worn whenever poisonous fumes are encountered such as HS.

f) Safety hats are to be worn around the plant when repairs are being made and there is a possibility of falling tools or materials.

g) Gloves and goggles or face shields are recommended for use where hot oil samples are being withdrawn.

Page 346: Ammonia Manual

Ammonia Plant Operating Manual 193

h) Steam hoses and water hoses should be checked weekly.

i) If there is a fire or other emergency, since persons not concerned in fighting the fire or handling the emergency should stay away from the area involved.

2. Fire Protection

The plant is engaged in making Ammonia from naphtha. Practically all of the materials are highly inflammable and extreme precautions are needed to prevent fires and explosions. Each person must remember this whilst carrying out his work.

a) Smoking is absolutely forbidden within the plant area.

b) Matches are prohibited within the plant areas.c) Become thoroughly familiar with fire protection equipment in the location.

d) Fire fighting equipment must be kept in designated accessible places which are well identified at all times.

e) Positively no one shall light a fire, or otherwise cause a possible source of ignition in the plant area except under the authorisation of a work permit.

f) Do not use light distillates such as gasoline or naphtha to clean machinery or for any other cleaning purpose. Use a heavier oil instead. Carbon tetrachloride is toxic and should not be used.

g) Fire fighting equipment will only be used to fight fires. It is forbidden to tamper with this equipment. If fire protection equipment is used, notify the supervisor immediately.

h) Good housekeeping is an important part of the fire prevention programme. Keep all areas free of waste papers. Oil rags and oily clothes should not be left in lockers or tool boxes.

3. Maintenance of equipment and housekeeping

a) Fire extinguishers must be re-charged or replaced immediately after use. All steam and water hose equipment must be put back in place after use. Access to such equipment must not be obstructed.

b) Gas masks must have fresh cartridge installed after use.

c) Operating equipment should be checked frequently for signs of leakage, overheating or corrosion so that unsafe conditions may be corrected before they result in serious consequences. Unusual conditions should be reported at once.

d) Guards around moving shafts, couplings, belts, etc which have been removed for repairs to the equipment must be replaced when repair work is completed.

Page 347: Ammonia Manual

Ammonia Plant Operating Manual 194

e) Tools, pieces of pipes etc., should never be left lying on platforms or railings of operating equipment where they can be knocked off and injure someone below.

f) Access to ladders and fire escapes must be kept clear. Waste material and refuse must be put in proper locations where they will not cause a fire or will not be stumbled over.g) Liquid spills must be cleaned up immediately.

h) In the event that electrical equipment does not function properly, notify the electrical department and stay clear of the equipment until the electrician arrives.

i) Gas cylinders should be stores so that they cannot fall over. Guard caps must remain in place over the valves of cylinder which are not connected up.

4. Repair Work

a) Mechanical work around an operating unit must be carried out with minimum number of persons.

b) No mechanical work on the equipment is to be done without a properly authorised work permit.

c) No burning, welding, open fires or other hot work shall be allowed in the area unless authorised by a work permit.

d) No personnel shall enter a vessel for any purpose whatsoever until it has been adequately purged, blanked off as required and tested to ensure freedom from noxious or inflammable gases.

e) Non sparking tools must be used for making emergency repairs where hydrocarbon gases, hydrogen or naphtha and other inflammable gases are present.

f) When flushing equipment with fire hoses, the fire hose must be equipped with a non return valve.

5. Thermal Expansion in Exchangers

Because of serious accidents caused by thermal expansion of liquid trapped in exchangers, the following procedure is outlined in an effort to eliminate these accidents.

a) When the cold side of an exchanger is to be bypassed with hot material is passing through the other side, the drain or vent should be tried before bypassing to see that it is not plugged.

b) When the exchanger is bypassed, the bleeder or vent should be arranged so that the pressure can be dissipated at a suitable place.

c) It is advised that warning signs be installed on all exchangers where it is possible to block in the cold side of an exchanger with hot liquid going through the other side. (Note that even in the absence of hot liquid flow chances in ambient temperature can cause failure and warning signs should be posted.)

Page 348: Ammonia Manual

Ammonia Plant Operating Manual 195

Sign

CAUTION

Have you established circulation or drained this equipment ?

Thermal expansion of a trapped liquid can cause failure of the equipment and an explosion.Do not trap liquid in this equipment

6. Canister Type mask

a) Only used in open air, not any tank or other confined space, except for rescue purpose. This mask does not protect the user against a deficiency of oxygen.

b) The type of canister mask used must be suitable for the gas present.

c) When a seal is removed from a canister, the date should be marked on the canister and after one year the canister should be discarded regardless of how little it has been used.

d) A record of the length of time that the canister is used must be kept on a tag attached to the canister and the permissible time limit for the particular should not be exceeded.

7. Use of Fresh Air Mask (Hose type and Tank type)

a. Hose Type

When an employees is required to enter any tank, sewer, manhole or other confined area in which the atmosphere contains 20% or more of the lower explosive limit of a combustive gas or if there is evidence of H2S or toxic chemicals a fresh air mask be used. The blower on a hose pipe must be placed where only fresh air may enter the hose. Do not use more than 100 ft hose.

Be sure that the harness is buckled close to the wearer's body so that it will not slip over his shoulders and pull off if a rope rescue is required.

A life belt and rope should always be used with the end fixed so that it will not fall into the tank or enclosure.

b. Tank type (self contained)

Used only by specially instructed employees.Use only in emergencies.After use they should be recharged.

8. General

a) When using any type of gas mask, be sure that the mask fits the face properly. Test by squeezing hose with the hand and inhaling. If the face piece collapses, the mask fits properly.

Page 349: Ammonia Manual

Ammonia Plant Operating Manual 196

b) Care must be taken in the use of canister mask for rescue purposes, as it will not protect you against a deficiency of oxygen. It should be used only where there is adequate ventilation.

c) The shift fireman is always available for information concerning the use of masks.

d) Become familiar with the accepted method of artifical respiration in order that you may render assistance to anyone overcome by gas, electric stock or drawing.

e) If anyone is overcome by gas, the rescuer should proceed as follows:

Protest himself before attempting rescue. Get the patient to the fresh air at once. Give artificial respiration Call a doctor

9. Chemicals

a. Hydrogen

Under normal conditions, hydrogen exits as a colourless, odourless testeless diatomic gas, H2. It

is the lightest known substance. Hydrogen is not toxic or poisonous in the sense that H2S and

Carbon monoxide are toxic.

However, gaseous hydrogen in large enough quantities can cause asphyxiation by replacing the oxygen normally in air that is needed to sustain life. If is much lighter than air and raises to the top of any room or container in which it is present. Since gaseous hydrogen is colourless, tasteless and odourless the risk of asphyxiation is seldom realised by the victim. The wide explosive limits of hydrogen make exposure of humans, except under closely controlled conditions, to air / hydrogen atmosphere extremely inadvisable.

The following constants apply to pure Hydrogen. Melting point -260 0C, boiling point at atmospheric pressure -253 0C molecular weight 2.016, gas specific gravity (air - 1200) 0.0695, solubility in water at 0 0C and 25 Kg/cm²a. 0.45 ml H2 per grain (H2O mm).

Limits of flammability (Explosive limits)

Lower limit Upper limit

Hydrogen in air Vol % 4 74 Hydrogen in oxygen Vol % 5 94 Methane in air Vol % 5 15

Net Heat of Combustion

K Cal/Kg K Cal/Nm3

Hydrogen H2 28,600 2,500

Methane CH4 11,950 8,500

Page 350: Ammonia Manual

Ammonia Plant Operating Manual 197

Methane is given as a comparison. Flame velocity for hydrogen-air is about eight times that of methane-air mixtures. Make up gas and recycle gas in the unit will contain about 75% H2 with

25% N2. A hydrogen-air flame is light blue colour and is non-luminous. A small fire stemming

from a straight recycle gas leak would have a slight bluish tinge and could be seen quite readily at night. The fire would not be readily apparent in strong sunlight.

Hydrogen has rather high theoretical flame temperatures, but special burner designs are necessary to produce a compact, intense, high temperature hydrogen flame. Due to the low heat of combustion per cubic metre of hydrogen, normal hydrogen fires run relatively cool and do surprisingly little damage. There have been pinhole leaks in catalytic reformer furnace fittings. The fires resulting from the pinhole leaks have been allowed to burn for months with no apparent damage to the furnace or tubes.

Leaks

Hydrogen gas leaks relatively easily. It will leak through smaller holes than most other gases. High concentrations usually prevent coke deposits that can seal off a leak. Under some conditions, hydrogen can remove graphite deposits and carbide formation usually found in metal walls and thus from its own leak holes. There is some technical evidence that molecular hydrogen H2, has a significant diffusion rate through normal walls. The rate is so small as to be negligible in commercial installations.

Molecular hydrogen can decompose to form atomic hydrogen. The following reaction expresses the idea.

H2 H + H

The atomic H2 is the same as the material called 'nascent' hydrogen in acid corrosion attacks or

in hydrogen blistering. However, the temperature must be extremely high before there is much atomic hydrogen present in a hydrogen atmosphere. There is considerable technical evidence that 'Nascent' or atomic hydrogen will diffuse through metal walls at an appreciable rate.

Practical Precautions

From a practical point of view, the harmful qualities hydrogen stem from its extreme lightness, its wide explosive limits, and its rapid flame transmission.

Lightness

Hydrogen floats on top of any gas. Be sure vessels are thoroughly steamed and vented. Watch out for the top of rooms where hydrogen might be present. There may be an explosive mixture up by the ceiling unless there is good roof venting.

Wide explosive limits

Treat all hydrogen steams containing more than 10 or 20 Vol % hydrogen as though the steam were pure hydrogen. If you suspect air is present and there is more than 4 Vol % hydrogen, treat the situation immediately.

Page 351: Ammonia Manual

Ammonia Plant Operating Manual 198

The 74 Vol% upper explosive limit means that any air-hydrogen mixture that has more than 5.2 Vol% oxygen is explosive.

b. Hydrogen Sulphide

Hydrogen Sulphide is extremely toxic with concentration above 20 parts per million in the air considered unsafe for breathing. In very low concentration, the gas has an odour resembling rotten eggs, this warning of its presence must be heeded immediately because the gas has the property of paralysing the sense of smell. Therefore the apparent absence of this characteristic odour is no proof that hydrogen sulphide is not present. Men entering areas where H2S is present must wear approved canister type gas masks. Where fresh air mask or a self-contained oxygen breathing apparatus must be worn. The rules set down for inspecting, entering and working on vessels that contain H2S must be strictly adhered to for the personal safety of employees.

c. Catalyst

The catalyst are listed in appendix 1 of this manual. They are not toxic in nature but when handling them, it is necessary to wear dust respirators and goggles. Special precautions are required for unloading spent catalyst. These are listed elsewhere. At temperatures below 500 0C Nickel containing catalyst (reforming and methanation) react with Carbon monoxide to form a poisonous gas Nickel Carbonyl.

No Nickel containing catalyst should be allowed to remain in contact with gases containing Carbon monoxide at temperatures lowere than this (see g).

d. Ammonia

Ammonia is a poison giving an alkaline action with serious irritation of the eyes, skin and upper respiratory system. Fortunately, the concentration at which the odour is detectable is below the safe limit for prolonged exposure. Ammonia is moderately combustible with explosive limits of 16 to 25 percent with air.

Lowest concentration detectable by odour 53 ppm Lowest concentration causing eye irritation 700 ppm Maximum concentration for prolonged exposure 85-100 ppm Maximum concentration for short exposure 300-500 ppm (½ - 1 hr) If liquid Ammonia comes in contact with the skin, flush with water immediately. A gas mask should be worn whenever the odour of Ammonia is strong.

Mercury and Ammonia can under certain conditions, from explosive compounds. The use of mercury on instruments likely to come into contact with Ammonia gas or liquid should be avoided.

e. Potassium Carbonate

Potassium Carbonate is a strong alkali and is extremely caustic. Care should be taken therefore to prevent all parts of the body from contact with the solution. In case of contact with the skin

Page 352: Ammonia Manual

Ammonia Plant Operating Manual 199

or eyes the affected part should be repeatedly flushed with large quantities of water and the area kept wet until the physician arrives, or for atleast 2 hours.

f. Arsenic Trioxide

Extreme care must be taken in handling the Arsenic Trioxide which is used in the Vetrocoke plant. Protective clothing including gloves, masks and goggles should be worn when handling this chemical. At all times great care must be taken to ensure that the atmosphere does not become laden with arsenical dust.

Arsenical poisoning in Industry results from the absorption into the bed of arsenical compounds, usually by inhalling arsenical dust over a long period. The dust alights on exposed skin and mucous membranes and therefore acts as a local irritant, causing inflamation or ulceration. Thus, when such losions are seen on a worker known to be working among arsenical compounds, it is sometimes difficult to say at once poisoning. Arsenical dust alightiing on the skin, especially where there are creases or wrinkles, or where there are moist patches, tends to set up dermatitis which may assume on acneic form or an exzematous aspect and which, if untreated, is prone to advance to ulceration. Some losions are commonly seen on the face where the edge of a respirator causes friction on the skin surface which is creased, warm and moist. They may be accompanied by evidence of simultaneous damage to mucous membranes such as conjunctivitis, blepharitis, rhinitis, pharyngitis and laryngitis. Hoarseness is also a prominent sympton. Ulceration of nasal septum not infrequently going on to perforation is usually painless and does not result in deformity, for only the cartilagious part of the septum is involved.The above diseases, due to arsenic/poisoning are most common to operators who are continually handling arsenic and its compounds and even then very rarely when appropriate precautions have been taken. The danger of arsenical poisoning is, therefore, very remote where operators only handle arsenic occasionally, as in the case with the Giammarco Vetrocoke Plant.General Action

On absorption however, by whatever route, arsenic tends to cause gastric-intestinal symptons (vomiting, abdominal cramp and purging) but chronic cases generally show skin losions as well which may be due, atleast in part, to the systematic poisoning. Possitive manifestations are deramatitis, ulcers, seleroderma, bronzing, trophic changes in the nails loss of hair etc. Arsenical bronzing in slight cases is best seen in the eye lids, temples, neck and nipples. In more marked cases there may be extensive bronzing of the trunk.

Treatment

In the event of any personnel being suspected of being poisoned by arsenic a medical practitioner should be consulted immediately. The following is suggested as first aid measure where arsenic has been taken internally.

1) Dilute the poison by giving 4 to 7 glass full of any one of the following emetics:Salt and lukewarm water (a cupful of common salt in one quarter of water).Soapy warm water.2) Wash out the poison (empty the stomach) by having the patient stick his finger down his throat to produce vomiting. Warning: Only a physician should use a stomach tube.3) Repeat the above procedure atleast three times.4) Give the known antidote.

Page 353: Ammonia Manual

Ammonia Plant Operating Manual 200

5) After the stomach has been emptied and cleaned of the poison, give a soothing (demulcent) drink such as milk, raw eggs, flour or starch and water.6) If the patient feels weak or faint and to prevent collapse and shock, he should lie down without a pillow and should be kept quiet and warm and given strong coffee or tea. Smelling salts or aromatic spirits of Ammonia may be inhaled.

g. Nickel Carbonyl

This section summarises the known information about the toxicity of Nickel Carbonyl and outlines the circumstances under which it may be formed. Fatal cases of poisoning by Nickel Carbonyl are known and atleast one of these in the United States was caused by the entry into a vessel in which Nickel Carbonyl had accumulated because of the cooling of plant containing Nickel in the presence of Carbon monoxide.

Clearly, in order to avoid poisoning accidents, it is necessary to ensure that a reformer is cooled down in the presence of gases not containing carbon monoxide. If for any reason, this instruction is not followed, then any vessel it is intended to enter should be thoroughly cleaned by steaming or other suitable means. The absence of Nickel Carbonyl must be established by chemical test before entry is made.

1) Formation of Nickel Carbonyl

Nickel Carbonyl may be formed by the contact of carbon monoxide containing gases with Nickel by the reaction:

NiS + 4 CO (g) Ni(CO)4 (g)

At normal steam reforming temperature of 750 0C or above the formation of Nickel Carbonyl is thermodynamically impossible. At temperature below 500 0C significant quantities of Nickel Carbonyl may be formed. Therefore, should a reformer be cooled down in the presence of reformed or other Carbonmonoxide containing gas, the formation of potentially dangerous and lethal quantities of Nickel Carbonyl may be expected.

2) The properties of Nickel Carbonyl

Specific gravity 1.32 Boiling point 43 0C Freezing point -25 0C Vapour pressure at 15 0C 261 mmHg

It is possible that Nickel Carbonyl formed in cooling a reformer in the presence of Carbon monoxide could condense in cold parts of the system, for e.g., waste best boilers, knock out pots with subsequent danger of poisoning if the vessel is opened. Due to relatively high vapour pressure of Nickel Carbonyl it will be practically impossible to prevent inhalation of the vapour.

Page 354: Ammonia Manual

Ammonia Plant Operating Manual 201

Carmicheal (1) reports a poisoning case where worker opened a vessel containing Carbon monoxide and spilling possibly 1 or 3 ounces of Nickel Carbonyl. In this case poisoning was caused by inhalation, but another possible cause was absorption of liquid through the skin.

3) Recommended maximum allowable concentration of Nickel Carbonyl in the atmosphere

ICI Industrial Products and Health Research Committee state 1 ppm. American Conference of Governmental Industrial Hygieniets state 0.001 ppm for continuous daily exposure.

4) Symptoms of Nickel Carbonyl poisoning

The initial symptoms which frequently develop during exposure include headache, giddiness and nausea. These symptoms which could also be in part due to Carbon monoxide, usually disappear within an hour of removal of fresh air.

The delayed symptom usually appear after 24 hours and include headache, nausea, sleeplessness and pains in the chest. In severe cases, respiratory distress increases and delirium occurs frequently. Oedema and haemorrhages in the lungs and brain injur have also been found in fatal cases.In fatal cases, death occurs between 4 and 11 days after exposure.Case histories and treatment are described in medical literature in reference (2) & (3).

5) Detection

Nickel Carbonyl may be detected quantitatively in inflammable gas by burning in a glass jet burner a visible Nickel deposit forming at the top of the jet. Approximately 0.02 ppm can be detected in this way.

A quantitative detemination may be carried out by absorption on Iodine monochloride in glacial acetic acid. This is probably the only reliable method of detection.

The detection of Carbon monoxide in a relatively cold reformer would be sufficient evidence to investigate the presence of Nickel Carbonyl preventation of Nickel Carbonyl formation cooling down of the Steam Reformer.

6) Nickel Carbonyl should not be formed provided all parts of the reformer are purged of Carbon monoxide with Nitrogen or steam before the Reformer or other Nickel containing part of the plant is cooled to below 500 C.

7) Reference

a) Carmichael J L 'Nickel Carbonyl Poisoning'. Archieves Industrial Hygiene and Occupational Medicine 8143 (1953).

b) Kineaid J F, Strong J S, Sunderman F W, 'Nickel Poisoning'. Archieves Industrial Hygience and Occupational Medicine 8 4848 (1953).

Page 355: Ammonia Manual

Ammonia Plant Operating Manual 202

c) Sunderman F W, Kincaid J F, 'Nickel Poisoning' Journal American Medical Association 155 899 (1954).

10) Repairing Process Equipment

As soon as possible after equipment has been pumped out, steamed, purged or flushed out sufficiently, all pipe lines should be disconnected and blanked from the vessel in which hot work is to be done. All pipe connections shall be blanked as close to the equipment as is feasible. It may be advantageous to prepare and block several pieces of equipment as one unit rather than one particular vessel. This procedure applies only providing the same tests are made and the same precautions taken in all pieces of equipment. It is the responsibility of the process foreman to determine how many pieces of equipment can be considered as one unit. Any deviation from the above prescribed procedure should be brought to the attention of the shift foreman. Before allowing anyone to enter equipment, every effort must be made to free it off all oil and vapours and gas tests shall be made by operator in order to be certain it is safe to enter.When hot work is done, observe the following precautions:

Inspect all manholes, catch basins or other openings to sewers in the proximity of the hot work area and it necessary flush them out with water. See that the tops of such basins or manholes are covered with burlap or other suitable materials and see that atleast three inches of earth are placed on top of the covering to prevent the escape of gases or the entrance of sparks. Before any hallow object is heated, make sure that the free escape of air or gas can be obtained. Authorised persons must issue hot work permits before hot work is started. quipment preparation provisions as outlined in the hot work permit shall be followed.

11) Opening Equipment

The opening of equipment such as pipelines, drums presents a very special problem and unless the proper precautions are taken in preparing the equipment, mishaps may occur. A particular risk is present if the equipment to be opened is in corrosive or toxic chemical service.

a) To ensure safety in jobs of opening equipment, it is good practice to treat the equipment as if it were under considerable pressure, even though you have taken all steps to relieve the pressure.

b) In opening flanges or coverplates, employees should be cautioned to first loosen and remove the bolts on the far side away from the downwind of the person doing the work, with a sufficient number of bolts allowed to remain tight on the near side until the connection can be wedged open. Any unanticipated pressure then will be released in a direction away from the person doing the work.

c) See that workers wear special protectiive equipment when opening lines, valves or vessels containing corrosive or toxic chemicals or hot or cold materials. If special protective equipment is required, this information should be indicated on the work permit.

12) Entering tanks, drums or other vessels

Necessary work permits must be issued before anyone enters a tank drum or other vessel. Should there be any doubt about excessive amounts of gas at any time mechanical work is being performed, the operator should stop the work immediately. Additional gas tests shall then be made to ensure that combustible materials are not present. Every reasonable step should be taken to remove the maximum amounts of oil and gas.

Page 356: Ammonia Manual

Ammonia Plant Operating Manual 203

Before allowing a person to enter a vessel, combustible gas tests must be taken at various points throughout the vessel to determine whether or not any combustibles are present. The general rule is that the vessel must be completely free of combustibles and toxic gases. An exception to this general rule can be made in the case of tanks or drums. These vessels have little internal equipment. Entry into such vessels may be permitted with concentration of combustible gas upto 20% of the lower explosive limit (a reading of 0.2 on the combustible gas indicator) if the following conditions are met.

a) The vessel shall have contained nothing other than regular petroleum hydrocarbons.

b) Measure must be taken to ensure that changing conditions do not cause any increase in concentration. This procedure may necessitate that the gas tester remain in constant attendance and periodically check the atmosphere within the vessel.

c) Good ventilation shall be provided.

d) The work shall involve no possibility of striking sparks or causing ignition.

e) There must be no Hydrogen Sulphide or other toxic gases present.

f) Employees entering the vessel must wear fresh air masks if the gas concentration builds up higher than 20% of the lower explosive limit. Even when equipped with fresh air masks, none must be allowed inside vessels having a concentration of combustible gas greater than 50% of the lower explosive limit (a reading of 0.5 on the combustion gas indicator).

g) Maximum ventilation must be provided in all cases. This provision shall include removing cover plates from vessels and may also include installing mechanical ventilation equipment.

h) In some cases, when work is done within a vessel, it may be considered necessary to station someone outside the vessel so that he will be available to take action in an emergency. This precaution is taken to warn the employees working in the vessel in case light hydrocarbons escape in the area, or some other recognised condition occurs which might jeopardise their study. Tank or vessels which may contain self-ignition scales or other deposits must be kept wet until such materials have been removed or changed in such a manner that they will no longer ignite.

Westing House Tubrine, Model E-125 Orifice Governor type Steam Turbines

This type of tubrines are employed for ID/FD sets. The lubrications and control system of Hydrauctic Orifice Governor are described here.

Oil is drawn from the reservoir, though a strainer, by a gear type oil pump which is an integral part of the governor and is driven by the turbine. The pump discharges initially into the governor after which the major portion of the oil flow continues to the lubricating zone.

Governing System

Page 357: Ammonia Manual

Ammonia Plant Operating Manual 204

The maximum oil pressure to the governor is controlled by the safety relief valve which discharge into the lubricating zone. Governor Control is proportional to the oil pump pressure. Variation in speed control is a accomblished by varying the orifice area which relives the pressure above the operating piston.

Lubrication System

Oil discharge from the governor passes through a renewable cartridge type filter and then an oil cooler, to the turbine bearings and where applicable to a gear unit and for driver equipment.

Oil filter

A continuous flow change over valve is provided to enable the cartridge clement to be repalced while the turbine is in operation.

Oil Cooler

The amount of water circulated through the cooler should be regulated to maintain the temperature of the leaving the cooler between 110 F (43 0C) and 120 F (49 0C). The correct criterion for oil cooler water should be of course the temperature of the oil leaving the hottest bearing. This temperature will vary with different unit and operating conditions. However in general oil return temperature of 140 F (60 0C) to 160 F (72 0C) are considered good practice. When starting the turbine the oil cooler water supply should not be turned on until the oil temperature has increased to the approximate limits given above.

Reservoir

A baseplate type reservoir of rigid construction is provided with a sloping bottom for complete drainage.

Reservoir is having the followiing features.

a. Oil level indicator b. Filter breather c. Water-Siphon and drain connections d. Sealed openings e. Hand holes f. Three minute retention time

Over Speed trip

A Centrifugal over speed trip device (a spring loaded weight eccentrically mounted in a transverse hole in the turbine shaft) operates by striking a trip lever which actuates the over speed trip mechanism.

Page 358: Ammonia Manual

Ammonia Plant Operating Manual 205

The standard butterfly type trip valve in mechanically unlatched by the over speed trip linkage and in spring closed when the over speed trip device operates.

The simultaneous closing of both trip valve and governor valve, when the trip device operates, provides the unique 'dual - protection' feature of weating house steam turbines.

Oil Failure Trip

The oil failure trip is connected to the lubricatiing oil system and when the pressure decreases to approximately 3 PSIG, operates the overspeed trip linkage, causing the trip valve and governor valve to close, thus shutting down the turbine.

Solenoid Trip

The solenoid trip operates through the oil failure trip and usually is provided to facilitate remote shut down of the turbine.

Governor (Orifice type direct acting)

Being driven by turbine shaft and controlled by an orifice, the pressure deliveryed by the governing pump varies as the square of the turbine speed and thus provides a positive governing force. The discharge pressure acting against the spring loaded operating piston, causes the piston and hence the governing valve to move in response to change in speed. Therefore, if the speed increases the oil pressure acting against the piston increases, thus moving the piston outward to close the governing valve. Conversely, if the speed decreases, the oil pressure acting against the piston decreases, thus allowing the spring to move the piston inward and allowing the governing valve to open.

Speed Changer

The speed maintained by the governor can be varied while the unit is in operation by means of the speed changer. This consists of the hand-operated, sleeve-type valve which is located adjacent to the operating cylinder and is arranged to control a passage from the operating cyclinder.

In normal operation, when this passage is adjusted to effect an increased orifice the oil pressure in the operating cylinder would momentarily decrease and cause the steam admission valve to open thus increasing the speed until equilibrium is re-established by the oil pressure in the operating cylinder again attaining its proper valve. Closing the speed changer valve results in a momentary increased oil pressure in the operating cylinder and therefore decreased the operating speed.

Westing House Turbines, Vertical Oil Relay Governor Type(Model EH - 125 VOR Governor type)

This type of governor system is employed for the following turbines.

1. 3704 - N & S BFWPT 2. 3705 - K & E Lean pump turbine

Page 359: Ammonia Manual

Ammonia Plant Operating Manual 206

3. 3709 - W & E Semilean pump turbine

Governing Oil System

This system basically comprises of a vertical oil relay governor which houses the speed sensing governor elements and control valve and speed adjusting knob. Governor oil is passed through rotary and edge type oil filter and then divides into two separate routes. The first route enters the VOR governor which reduces the pressure to a predetermined value before passing the oil to the control section of the servomotor which operates the governor steam valve.

This second steam passes through the overspeed oil trip device and then to the high pressure section of the servomotor. The provision of speed adjusting knob helps to vary the speed of the machine on line as and when required.

Governor controlling action is actuated by manipulating the clearance between the cup valve and its seat housed inside the VOR Governor. Arrangements are given to move the position of the cup valve by changing the position of the speed adjusting knob and the same clearance can be varied by changing the position of the valve seat by the governor action. On either case the clearance between the cup valve and it seat changes thereby chaning the control oil pressure which is led to the servo piston top chamber to manipulate the opening of the steam chest valve. When the speed adjusting knob is screwed inside it allows the cup valve to raise through its stem thereby increasing the clearance between the cup valve and its seat. This drains more governor oil into the sump and decrease the control oil pressure. Since the servo piston is exposed to constant high pressure as it bottom the decreases in control oil pressure allows the servo piston to go tup thereby opening the steam valve more. Similarly the steam valve can be closed more by increased controlled oil pressure. A constant governor oil pressure is maintained by a fixed orifice at the oil inlet to the VOR governor.

Lubrication Oil System

The VOR Governor houses a gear type pump at its bottom driven by the main shaft. Oil is taken from the reservoir through the strainer. The oil is then discharged into two streams. The first steam passes through the edge type rotary filter to the governing system while the next stream passes through a twin oil filter/cooler arrangement to the lubrication system. The oil filter is a 25 micron cartridge type one. A continuous flow change over value is provided to enable the cartridge element to be replaced while the turbine is in operation. This arrangement also facilitates the maintenance of coolers while the turbine is in operation. The cooled lubrication oil at 45 to 50 0C is supplied to the turbine bearings and governor drive gear spray.

Two oil coolers are provided which are of shell and tube side. One cooler provided in series with each filter. It is designed to handle oil of 60 to 65 0C and cools the same to about 45 to 52 0C. Generally while starting the turbine the cooling water supply to the coolers should not be turned in until the temperature raises upto the given limits above. A relief valve has been provided which maintains the pressure in the lubrication zone at about 0.6 Kg/cm2.

Overspeed Oil System High pressure oil passes through the overspeed trip piston to the servo motor relay piston. The trip piston is actuated by the overspeed trip linkage which closes the piston and shuts off high pressure oil to the servomotor when the turbine overspeeds. This relieves the pressure under the servomotor operating piston which moves downwards to close the govenor steam valve and

Page 360: Ammonia Manual

Ammonia Plant Operating Manual 207

shuts down the turbine. The standard butterfly type trip valve is mechanically unlatched by the overspeed trip linkage and is spring closed when the overspeed device operates.

The simultaneous closing of both trip valve and governor valve when the trip device operates provides unique dual protection feature of Westinghouse steam turbines.

Lubrication Oil Trip System

The oil failure trip is connected to the lubrication oil system and when the pressure decreases approximaely to 0.2 Kg/cm2, it operates the trip linkage, causing trip valve and governor valve to close simultaneously thus shutting down the turbine.Accessories

Pressure gauges have been supplied across the cartridge filters to check the healthy condition of the filter element. Also pressure gauges have been provided to check the governor oil, control oil and lubrication oil pressures.

Temperature indicators have been provided across the coolers evaluate their performance.

18.14 AMMONIA PLANT - ALARM & TRIP SET VALUES

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET ------------------------------------------------------------------------------------------------------------------------------ 1. PI 206 Boiler feed water pressure 117 115

2. PHI 202 A CBD (S) pH 11 9 0

3. CI 202 A CBD (S) conductivity 80 0 0

4. SI FDS FD (S) speed 1000 700 0

5. LI 1003 Day tank level 70 40 0

6. PHI 201 Boiler feed water pH 11 9 0

7. CI 201 BFW conductivity 160 80 0

8. PHI 202 B CBD (N) pH 11 9 0

9. CI 202 B CBD (N) conductivity 80 0 0

10. SI FDN FD (N) speed 1000 700 0

11. DI 205 B Economiser inlet (N) 250 0 0

Page 361: Ammonia Manual

Ammonia Plant Operating Manual 208

12. DI 206 B GAH inlet (N) 250 0 0

13. SI 3202 E FOP (E) speed 1300 0

14. SI 3202 W FOP (W) speed 1300 0

15. PI 204 A FO pressure (S) 10 5 4 2.0 2.2

16. PI 207 A Atomising steam pressure (S) 7 6 4.0 4.2

17. PI 215 A Furnace pressure (S) 330 300 0 0 350 346

18. LI 202 A Drum level (S) 100 50 -50 -100 -150 -144

19. PI 204 B FO pressure (N) 10 5 4 2.0 2.2

20. PI 207 B Atomising steam pressure (N) 16 7 6 4.0 4.2

21. PI 215 B Furnace pressure (N) 330 300 0 0 350 342

22. LI 202 B Drum level (N) 250 250 -50 -150 -150 -143

23. PC 0105 EHP steam pressure 106 90 0

24. PC 0206 FO header pressure 16 14.5 12 11.5

25. PC 203 A Start up steam vent (S) 108 106 95 0 -------------------------------------------------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET ----------------------------------------------------------------------------------------------------------------------------------

26. PC203B Start up steam vent (N) 108 106 95 0

27. PC208 Soot blower pressure 18 0 0

28. LI201A Drum level (S) 100 50 -50 -100

Page 362: Ammonia Manual

Ammonia Plant Operating Manual 209

29. PI202A Drum pressure (S) 110 115 0 0

30. LC201A Drum level (S) 100 50 -50 -100

31. PC201 Master Pressure 107 100 90

32. LSR203A FC203A Low Selector 4 0

33. HSR203A FC204A SV SEL 4 0

34. FC204A Air flow (S) 100 56 50 10,000

35. TC203A Steam after injector (S) 350 335 290

36. TC202A Exit steam temperature (S) 492 490 475 460

37. LI201B Drum level (N) 100 50 -50 -100

38. PI202B Drum pressure (N) 115 110 0 0

39. LC201B Drum level (N) 100 50 -50 -100

40. LSR203B FC203B low SEL 4 0

41. HSR203B FC204B SV SEL 4 0

42. FC204B Air flow (N) 56 50 10,000 Nm3/hr

43. TC202B Exit steam temperature (N) 492 490 475 465

44. PI204C FO pressure 20 20 6 4.5 2.5 Kg/cm2g

45. PI206C ASGU BFW pressure 135 130 120 115

46. PI207C ASGU atomising stream pressure 8.5 6 3.9 Kg/cm2g

47. PI215C Furnace pressure 350 335 0 0

48. FI202C ASGU steam flow 133 60 0

49. LI201C Drum level 100 50 -50 -100

50. PHI201C CBD pH ASGU 10.5 9.0

51. PHI202C Steam pH 10.5 9.0 -------------------------------------------------------------------------------------------------------------------------------

Page 363: Ammonia Manual

Ammonia Plant Operating Manual 210

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

52. CI201C CBD conductivity 80 0 0

53. PI2602 48 Kg/cm2g steam pressure 48 42 0

54. PI2607 12 Kg/cm2g steam pressure 11.5 9 0

55. PI2635 Boiler feed water pressure 120 116

56. PI2728 Instrument air receiver pr 10.5 7.9 0

57. FI2750 Polished water flow 120 60 0

58. LI2740 Fuel oil day tank level 75 55 0

59. PI216C Furnace pressure 350 300 0 0

60. LI202C Drum level 100 50 -50 -100 -200.4

61. PC203C Exit steam pressure 108 106 100 90

62. PC2600 106/48 Kg/cm2G Let down 47.5 43 0

63. PC2609 12 Kg/cm2g steam vent 12 10 5

64. PC2610 2.1 Kg/cm2g vent 1.7 0.7 0

65. PC2613 HP heater pressure 13 0 0

66. PC2614 12/2.1 Kg/cm2g let down 1.7 0.7 0

67. PC2617 Deaerator pressure 0.7 0.2 0

68. PC2626 48/12 Kg/cm2g let down 12 10 0

69. PC2627 48 Kg/cm2g steam vent 48 42 0

70. PC2662 Spray control 70 50 0

71. PC2722 Instrument air pressure 8 6.5 6 4 Kg/cm2g 72. PC2748 FO pressure 16 12.5 0

Page 364: Ammonia Manual

Ammonia Plant Operating Manual 211

73. TC209C FG temperature stack 155 0

74. TC213C Atomising stream temperature 250 200 0

75. TC2600 48 Kg/cm2g steam pressure 400 350 0

76. TC2609 FO heater exit temperature 130 110 0

77. TC2626 12 Kg/cm2g steam temperature 300 250 0

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

78. TC2660 Service steam temperature 250 190 0

79. LC2651 Deaerator level 90 70 50 0

80. LC2654 HP heater level 65 35 0

81. FC2603 Steam to OSB - - -

82. FC201C BFW flow ASGU 60 0

83. PI202C Drum pressure ASGU 115 110 0 0

84. LC201C Drum level ASGU 100 50 -50 -100

85. FI202C Steam flow ASGU 133 60 0

86. PC201C Master pressure ASGU 108 106 100 95

87. LSR203C Low SEL relay 4 0

88. FC203C Fuel oil flow ASGU 9.3 2.5 0

89. HSR203C High SEL relay 4 0

90. FC204C Air flow ASGU 50 40

91. TC202C Exit steam temperature 500 490 475 465

Page 365: Ammonia Manual

Ammonia Plant Operating Manual 212

92. TI209A FO temperature (S) 140 100

93. TI221A SH skin temp N-B (S) 540 0

94. TI222A SH skin temp M-B (S) 540 0

95. TI223A SH skin temp S-B (S) 540 0

96. TI224A SH skin temp N-B (S) 540 0

97. TI225A SH skin temp N-B (S) 540 0

98. TI226A SH skin temp S-B (S) 540 0

99. TI227A SH skin temp S-B (S) 540 0

100. TI1003 Exit temp 1502 130 95

101. TI209B FO temp (N) 135 100

102. TI221B SH skin temp N-B (N) 540 0

103. TI222B SH skin temp M-B (N) 540 0

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

104. TI223B SH skin temp S-B (N) 540 0

105. TI224B SH skin temp N-B (N) 540 0

106. TI225B SH skin temp N-B (N) 540 0

107. TI226B SH skin temp S-B (N) 540 0

108. TI227B SH skin temp S-B (N) 540 0

109. TI201C Oil temperature 130 110

110. TI2607 Day tank temperature 95 0

111. SIOGAA OGT101A speed 400 0

Page 366: Ammonia Manual

Ammonia Plant Operating Manual 213

112. SIOGAB OGT101B speed 400 0

113. PI0228 BFW pump discharge 114 0 99 102

114. FI0210 Polished water from CPP 30 0

115. LI0202A Deaerator level 100 80 35 0

116. PHI0222 CW pH 7.5 6 0

117. CI0203 SCC conductivity 100 0 0

118. ZI Grid Grid frequency 53 47.8 45

119. FI1104 Recycle gas 6000 4000

120. FI1107A Makeup gas 650 650 225 200

121. PI0217 Inst air header pressure 10 8 6.5 6 5.25 KSCG

122. PI0222 CW pressure 5 5 3.5 3 2.575 KSCG

123. TI0209A Degasser exit temp 50 60 0C

124. FI1203A SN to 1432 10 8 6 TPH

125. FI1203B SN to 1432 0 6 6 TPH

126. TI1205A 1432 exit temp 430 370 355 350*C

127. PC0109 Atm steam pressure 6 4.1 2.0 1.5 0.7 KSCG

128. PC0209 LP desup. 46 0

-------------------------------------------------------------------------------------------------------------------------------

Page 367: Ammonia Manual

Ammonia Plant Operating Manual 214

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

129. PC0212 Deaerator pressure 0.6 0.35 0

130. PC0223 PA to inst air let down 11 9 0

131. PC0229 Inst air header 8 6.3 6

132. PC1110 Stripper pressure 14 0 0

133. TC0103 MP steam temp 310 250 0

134. TC0104 HP steam temp 400 350 0

135. TC0105 Service stm temp 210 0 0

136. TC1102 1431 exit temp 350 330 300 0

137. TC1205 1432 exit temp 430 370 350 350 0C

138. FC0101 Steam from OSB 15 0

139. FC1103 RN feed 10 0

140. FC1204 Recycle H2 flow 800 700 600

141. FC1203 SN to 1432 10 8

142. LC1102 1102 level 65 35 0

143. LC1106 1103 level 65 35 0

144. LC0202 Deaerator level 90 65 35 20

145. PC0102 LP steam pressure 4 1.5 0.7 0

146. PC0103 MP steam pressure 12 9 0

147. PC0104 HP steam pressure 44 41 0

148. LI0201 CW cump level 70 60

149. PI1304 FN filter exit 13 12.5 Kg/cm2g

Page 368: Ammonia Manual

Ammonia Plant Operating Manual 215

150. PI1310 CA pressure 300 300 75 50 50 mmwc

151. PI1312 1537 exit pressure 44 43 40 0

152. PI1321 CCJT exit pressure 106 0 0

153. FI1301 Fuel gas flow 6000 2000 - 3000 Nm3/hr

154. PDI1405 Sec Ref diff pressure 2.5 1.5 1 0.3

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

155. QI1504 1131 exit CO2 0.4 0.125 0 0

156. PI1313A Furnace pressure 1.0 0.5 -3 -4 +3 mmWC

157. PI1313B Furnace pressure 1.0 0.5 -3.5 -5 +3 mmWC

158. FI1302 Fuel naphtha to 1400 11 10 5 4 2.25 TPH

159. FI1302A Fuel naphtha to 1400 11 10 5 4 2.25 TPH

160. FI1302B Fuel naphtha to 1400 - 4 3.8 3.5 2.25 TPH

161. FI1303A Vap naphtha to 1400 - 6000 - 1500 Nm3/hr

162. FI1303B Vap naphtha to 1400 - 6000 5000 1500 Nm3/hr

163. FI1401A Air to 1105 20000 16000 10000 Nm3/hr

164. FI1401B Air to 1105 20000 16000 10000 Nm3/hr

Page 369: Ammonia Manual

Ammonia Plant Operating Manual 216

164. LI1306A 1106 level 100 75 -50 -100 17.5% (-198)

165. LI1306B 1106 level 150 100 -50 -82 17.5% (-198)

166. TI1314 Primary Ref exit temp 775 770 755 750 730 0C

167. TI1314A Primary Ref exit temp 780 750 730 730 0C

168. TI1314B Primary Ref exit temp 780 750 730 730 0C

169. TI1405 Sec Ref exit temp 970 960 920 900 1020 0C

170. TI1405A Sec Ref exit temp 960 955 920 900 1020 0C

171. TI1405B Sec Ref exit temp 960 955 920 900 1020 0C

172. TI1516-1 1112 bed temp 370 350 400 0C

173. TI1516-2 1112 bed temp 370 350 400 0C

174. TI1516-3 1112 bed temp 370 350 400 0C

175. TI1516-4 1112 bed temp 370 350 400 0C

176. TI1516-5 1112 bed temp 370 350 400 0C

177. TI1516-6 1112 bed temp 370 350 400 0C

178. PC1301 1124 exit gas 20 18

179. PC1303 Fuel gas pressure 3 1

-------------------------------------------------------------------------------------------------------------------------------

Page 370: Ammonia Manual

Ammonia Plant Operating Manual 217

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

180. PC1313 Furnace pressure 1.0 0 -2.0 -5.0

181. PC1324 FN jump over 13 -

182. PC1504 Midstream vent 29 28 20 -

183. PC1509 Final vent 26 25 23 22.5

184. PC1208 1104 exit pressure 40 39 0 0

185. TC1311 CCJT exit steam temp - 510 428 -

186. TC1407 RGB exit temp 425 420 350 340

187. TC1506 1112 inlet temp - 370 270 -

188. LC1502 1114 level - 75 25 -

189. LC1504 1113 level 85 65 35 - On line switch

190. PC1305 FN to Reformer - 4 -

191. LC1306 1106 level - 65 35 25 17.5%

192. FC1401 Air to 1105 - 20000 16000 10000 Nm3/hr

193. TC1509 LT inlet temp 230 220 190 -

194. FC1303 Vap naphtha to 1400 - 7600 6000 5000 1500 Nm3/hr

195. TI1312 1537 steam out - 510 0 -

196. PDI1400 1400 diff pressure 5 4.5 - -

197. DF1306 RGB diff water flow 10 8 - -

198. PDI1607 1116 total DP 0.6 0.3 - -

199. PDI1608 1116 I bed DP - 0.3 - -

Page 371: Ammonia Manual

Ammonia Plant Operating Manual 218

200. LI1604A 1116 level - 68 35 20

201. LI1609 1117A level - 70 35 -

202. LI1611 1117B level - 70 35 -

203. SI3702 PAC speed - 6000 -

204. PI1808 1121 inlet - 230 - -

205. PI1809 1121 exit - 230 - -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET ------------------------------------------------------------------------------------------------------------------------------

206. PI1814 1123 pressure 23 21 - -

207. LI1802A Sec chiller level 15 5 - Switch on line

208. LI1809 1127 level - 65 35 -

209. LI1814 1123 level - 66 35 -

210. FI1803 1121 flush gas - - 50 -

211. FI1810 Gas inlet 1434 - 42000 40000 20000 15000 Nm3/hr

212. PI1807 HC1809 upstream pressure - 230 - -

213. TI1801A 1434 stack temp 880 850 - - 880 *C

214. TI1802A 1434 exit gas temp 520 500 500 - 520 *C

215. LI1812 1122 level - 65 25 - 73%

216. LC1602 1131 level - 65 35 -

Page 372: Ammonia Manual

Ammonia Plant Operating Manual 219

217. LC1702 1118 level - 65 35 -

218. LC1704 1119 level - 65 35 -

219. LC1802 Sec chiller level 65 55 35 -

220. LC1805 Pri chiller level - 65 35 -

221. LC1807 1128 level 30 20 - - 90%

222. LC1811 1122 level - 65 35 -

223. LC1813 1123 level - 65 35 -

224. FC1602 Semilean flow - 1500 800 - 485 TPH

225. FC1603 Lean flow - 490 300 - 175 TPH

226. LC1604 1116 level - 65 35 10

227. LC1606 1115 level - 63 35 -

228. PC1705 CO2 exit 1120 0.3 0.2 0.08 0.05

229. PDI1805 Converter pr drop 4

230. PI1908 Sphere pr 4 3.85 3 -

231. LI1902 1124 level 90 65 35 -

-------------------------------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET -------------------------------------------------------------------------------------------------------------------------------

232. PI2103 Adsorber inlet - 65 50 -

233. TI2102 HEA101 exit gas - 15 0 -

234. TI2104 HEA102 outlet - 20 5 -

235. QI2100 Product H2 % - - 90 -

Page 373: Ammonia Manual

Ammonia Plant Operating Manual 220

236. PI2211 CCL pressure - 28 - -

237. TI2208 Amm Heater exit cond - 30 15 8 8

238. TI2211 CCL Amm - 50 -28 -30 -30

239. PC2106 HFA103 pressure - 65 50 -

240. PC2107 Product H2 pressure - 50 - -

241. PC2108 Tail gas pressure - 3 - -

242. PC2201 T-201 pressure - 4 - -

243. FC1905 Reflux to 1125 - 2 0.7 -

244. LC1904 1127 level - 65 35 -

245. LC1906 1126 level - 65 35 -

246. LC2002 SRC purge pot level 50 20 - -

247. LC2006 SRC receiver level - 65 35 -

248. LC2101 Amm separator - 65 35 -

249. LC2104 HFA 103 level - 65 35 -

250. LC2201 T201 level 85 65 35 10 85%

251. TC2202 E-201 exit temp - 20 -5 -10 -10

252. TI1-1103 1431 skin - 470 - -

253. TI1-1104 1431 skin - 470 - -

254. TI1-1105 1101 bed temp - 350 - -

255. TI1-1106 1101 bed temp - 350 - -

256. TI1-1107 1101 bed temp - 350 - -

257. TI1-1108 1101 bed temp - 350 - -

-------------------------------------------------------------------------------------------------------------------------------

Page 374: Ammonia Manual

Ammonia Plant Operating Manual 221

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET --------------------------------------------------------------------------------------------------------------------------------

258. TI1-1109 1101 bed temp - 350 - -

259. TI1-1110 1101 bed temp - 350 - -

260. TI1-1111 1101 bed temp - 350 - - 261. TI1-1112 1101 bed temp - 350 - -

262. TI1-1113 1101 bed temp - 350 - -

263. TI1-1114 1101 bed temp - 350 - -

264. TI1-1115 1101 bed temp - 350 - -

265. TI1-1116 1101 bed temp - 350 - -

266. TI1-1117 1101 bed temp - 350 - -

267. TI1-1119 1103 off gas - 50 - -

268. TI1-1101 1431 stack - 450 - -

269. TI1-1202 1433 skin (E) - 500 - -

270. TI1-1204 1432 skin (W) - 500 - -

271. TI1-1205 1104 Mid bed - 430 - -

272. TI1-1211 1432 outskin (E) - 430 - -

273. TI1-1212 1432 outskin (W) - 430 - -

274. TI2-1210 1432 skin (W) - 500 - -

275. TI1266 1432 (W) RAD IN - 250 - -

276. TI1267 1432 (E) RAD IN - 250 - -

277. TI2-1211 1432 skin (E) - 500 - -

278. TI1204 1432 stack - 300 - -

279. TI1206-1/6 1104 bed (top) - 430 - -

Page 375: Ammonia Manual

Ammonia Plant Operating Manual 222

280. TI1310 steam to 1536 A - - 335 -

281. TI1313 FG exit 1400 - 900 - -

282. TIA03 Pigtail temp - 815 650 -

283. TIA07 Pigtail temp - 815 650 -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET --------------------------------------------------------------------------------------------------------------------------------

284. TIA11 Pigtail temp - 815 650 -

285. TIA15 Pigtail temp - 815 650 -

286. TIA19 Pigtail temp - 815 650 -

287. TIA23 Pigtail temp - 815 650 -

288. TIA27 Pigtail temp - 815 650 -

289. TIA31 Pigtail temp - 815 650 -

290. TIB 5/9/17/ Pigtail temp - 815 650 - 21/25/29/33

291. TIC 3/7/11/ Pigtail temp - 815 650 - 18/19/23/27/31

292. TID 1/5/9/13 Pigtail temp - 815 650 - /21/25/29/33

293. TIE 3/7/11/ Pigtail temp - 815 650 - 15/19/23/27/31

294. TIF 1/5/9/13 Pigtail temp - 815 650 - /21/25/29/33

295. TIG 3/7/11/ Pigtail temp - 815 650 - 15/19/23/27/31

296. TIH 1/5/9/17 Pigtail temp - 815 650 - /21/25/29/33

Page 376: Ammonia Manual

Ammonia Plant Operating Manual 223

297. TI N 1-9 Coffin temp - 980 - -

298. TI S 1-9 Coffin temp - 980 - -

299. TI1-1401 1433 skin - 600 - -

300. TI1-1402 1433 skin - 600 - -

301. TI1-1403 1433 skin - 600 - -

302. TI1-1404 1433 FG Radiation outlet - 600 - -

303. TI1-1405 1433 skin - 600 - -

304. TI1-1406 1433 skin - 600 - -

305. TI1-1407 1433 skin - 600 - -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET --------------------------------------------------------------------------------------------------------------------------------

306. TI1401 1433 stack - 450 - -

307. TI1406 RGB mid temp - 650 - -

308. TI1-1505 1109 I bed temp - 460 - -

309. TI1-1506 1109 gas exit - 390 - -

310. TI1-1509 LT exit gas temp - 235 - -

311. TI1-1510 Gas exit 1114 - 200 - -

312. TI1-1511 1112 exit gas - 350 - -

313. TI1-1515 3214 N bearing - 50 - -

314. TI1-1516 3214 S bearing - 80 - -

315. TI1-1517 Gas exit 1115 - 130 - -

316. TI1-1502 Gas in HT II bed - 400 - -

Page 377: Ammonia Manual

Ammonia Plant Operating Manual 224

317. TI1-1505 Gas exit 1113 - 50 - -

318. TI1-1507 1111 bottom - - 190 -

319. TI1-1511 1-6 LT shift bed temp - 235 - -

320. TI2-1501 1109 I bed top - 400 - -

321. TI2-1502 1109 I bed bottom - 460 - -

323. TI2-1503 1109 II bed top - 400 - -

324. TI2-1504 1109 II bed bottom - 400 - -

325. TI1513 BFW exit 1513 - 85 - -

326. TI1661 SL pump (E) C/E brg - 75 - -

327. TI1662 SL pump (E) F/E brg - 75 - -

328. TI1663 SL pump (W) C/E brg - 75 - -

329. TI1664 SL pump (W) F/E brg - 75 - -

330. TI1610 Lean out 1521 - 85 65 -

331. TI1-1702 1120 exit CO2 - 40 - -

332. TI1801 1434 stack - 850 200 -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------ Sl TAG NO. COMMENT HH PH PL LL TRIP RESET ------------------------------------------------------------------------------------------------------------------------------

333. TI1-1801 1121 I bed in - 500 - -

334. TI1-1802 1121 I bed out - 520 - -

335. TI1-1803 1121 II bed in - 520 - -

336. TI1802 1434 exit gas - 500 - -

337. TI1803-8 1434 exit gas - 400 - -

Page 378: Ammonia Manual

Ammonia Plant Operating Manual 225

338. VI101A SGC LP free end 4 2 - -

339. VI102A SGC LP coupling end 4 2 - -

340. VI103A SGC LP comp C/E 4 2 - -

341. VI104A SGC MP comp C/E 4 2 - -

342. VI105A SGC MP barrel TCE 4 2 - -

343. VI106A SGC MP HP CE 4 2 - -

344. VI107A SGC HP MP CE 4 2 - -

345. VI108A SGC HP barrel FE 4 2 - -

346. VI101B SGC LP FE 4 2 - -

347. VI102B SGC LP coupling end 4 2 - -

348. VI103B SGCT LP compr CE 4 2 - -

349. VI104B SGCT compr CE 4 2 - -

350. VI105B SGC MP brl TCE 4 2 - -

351. VI106B SGC MP HP CE 4 2 - -

351. VI107B SGC HP MP CE 4 2 - -

352. VI108B SGC HP barrel FE 4 2 - -

353. ADXI109 SGC LP barrel FE 20 10 -10 -20

354. ADXI110 SGC LP T side 20 10 -10 -20

355. ADXI111 SGC MP HP CE 20 10 -10 -20

356. ADXI112 SGC HP barrel FE 20 10 -10 -20

357. VI201A PAC T FE 4 3 - -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET

Page 379: Ammonia Manual

Ammonia Plant Operating Manual 226

-------------------------------------------------------------------------------------------------------------------------------

358. VI202A PAC T CE 4 2.5 - -

359. VI203A PAC LP barrel CE 4 2.5 - -

360. VI204A PAC LP barrel GBCE 4 2.5 - - 361. VI205A PAC GB LP CE 4 2.5 - -

362. VI206A PAC GB HP CE 4 2.5 - -

363. VI207A PAC HP barrel CE 4 2.5 - -

364. VI208A PAC HP FE 4 2.5 - -

365. VI201B PAC T FE 4 2.3 - -

366. VI202B PAC T CE 4 2.5 - -

367. VI203B PAC LP barrel CE 4 2.5 - -

368. VI204B PAC LP barrel GBCE 4 2.5 - -

369. VI205B PAC GB LP CE 4 2.5 - -

370. VI206B PAC GB HP CE 4 2.5 - -

371. VI207B PAC HP barrel CE 4 2.5 - -

372. VI208B PAC LP barrel FE 4 2.5 - -

373. AXDI209 PAC T AX disp 20 10 -10 -20

374. AXDI210 PAC LP AX disp 20 10 -10 -20

375. AXDI211 PAC GB AX disp 20 10 -10 -20

376. AXDI212 PAC HP AX disp 15 7 -7 - 15

377. AXDI305 LRC T AX disp 15 7 -7 -15

378. AXDI306 LRC Compr Ax Disp 15 7 -7 -15

379. VI301A LRC compr Ax Disp 15 7 -7 -15

380. VI301B LRC T FE 4 2 - -

381. VI302A LRC T CE 4 2.5 - -

382. VI302B LRC T CE 4 2.5 - -

Page 380: Ammonia Manual

Ammonia Plant Operating Manual 227

383. VI303A LRC B CE 4 2 - -

-------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- Sl TAG NO. COMMENT HH PH PL LL TRIP RESET --------------------------------------------------------------------------------------------------------------------------------

384. VI303B LRC B CE 4 2 - -

385. VI304A LRC B FE 4 2 - -

386. VI304B LRC B FE 4 2 - -

387. PI0104A HP steam pressure - 44 40 -

388. FI1002 FO return flow 5.0

389. PI0103A MP steam pressure 12 10 -

390. TC1404 1433 air exit 540 460 -

391. FI1809 Syn loop circulation 250000 -

392. PC1903 Product ammonia pressure 20 17

393. FI0107A SGC extraction 220

394. PI1601 1117A exit 0.6

395. PI1602 1117B exit 0.6

396. FI1307 FN to 4th & 6 th row 2.8 1.2

397. PC2201 T 201 press. 5.0 4.0

398. LC2201 T 201 level 85 65 35 10 10

399. TC2202 Exit amm. temp. 20 20 -5 -10

400. TI2208 Amm. heater exit condensate 30 30 15 8

401. TI2211 CCL Amm. temp. low -28 -30

Page 381: Ammonia Manual

Ammonia Plant Operating Manual 228

402. PI2211 CCL press. high 40 26

403. FI 1606 Rich solution to 1117A 1100 900

404. FI 1608 Rich solution to 1117B 1100 900

405. FI 1204A Recycle Hydrogen flow 900

-------------------------------------------------------------------------------------------------------------------------------

AMMONIA PLANT LOCAL PANEL ALARM AND TRIP VALUES

S.NO. DESCRIPTION TAG NO ALARM TRIP

1 HYDROGEN COMPRESSOR

1. Lube oil pressure low 2. Lube oil temp high 3. Gas delivery temp high 4. Separator level high 2 IAD PANEL 1. Intrument air header pr low 2. Intrument air receiver pr low 3. Reactivation temp high 3 IAC (SOUTH) 1. Lube oil pressure low 2. CW flow low 3. Unloading pressure 4. Loading pressure

4 IAC (M) & (N)

1. CW low pressure 2. LO low pressure 3. 100 % loading pressure 4. 50 % loading pressure

5 START-UP COMPRESSOR

Page 382: Ammonia Manual

Ammonia Plant Operating Manual 229

1. LO pressure low 2. LO temp high 3. Gas delivery temp high CYL No.1 4. Gas delivery temp high CYL No.2 5. Separator level high 6 ID/FD

1. LO low pressure alarm ID 2. LO low pressure alarm FD 3. LO low pressure trip ID 4. LO low pressure trip FD 5. Condensor pressure high alarm (N) 6. Condensor pressure high alarm (S) 7. Condensor level high alarm (N) 8. Condensor level high alarm (S) 7. Condensor level high trip (N) 8. Condensor level high trip (S) 9. Aux condensate pump start pressure 10. Panel pressure low alarm

7 I G

1. Compressor (E) LO press low alarm 2. Compressor (E) LO press low trip 3. Compressor (E) suc press low alarm 4. Compressor (E) suc press low trip 5. Compr (E) condensor I level high alarm 6. Compr (E) condensor I level high trip 7. Compr (E) condensor II level high alarm 8. Compr (E) condensor II level high trip 9. Compr (E) condensor III level high alarm 10. Compr (E) condensor III level high trip 11. Compr (E) LO temp high alarm 12. Compr (E) LO temp high trip 13. Compr (E) gas temp high alarm 14. Compr (E) gas temp high trip 15. Compressor (W) LO press low alarm 16. Compressor (W) LO press low trip 17. Compressor (W) suc press low alarm 18. Compressor (W) suc press low trip 19. Compr (W) condensor I level high alarm 20. Compr (W) condensor I level high trip 21. Compr (W) condensor II level high alarm 22. Compr (W) condensor II level high trip 23. Compr (W) condensor III level high alarm 24. Compr (W) condensor III level high trip 25. Compr (W) LO temp high alarm 26. Compr (W) LO temp high trip

Page 383: Ammonia Manual

Ammonia Plant Operating Manual 230

27. Compr (W) gas temp high alarm 28. Compr (W) gas temp high trip

8 DEOXO (E) & (W)

1. Over temp trip 2. 22.5 KW heater 'on' temp 3. 7.5 KW heater 'on' temp

9 IG GENERATOR

1. Gas pressure high trip 2. Water flow low trip

10 III IG

1. I stage i/l pressure low alarm 2. I stage i/l pressure low trip 3. LO oil pressure low alarm 4. LO oil pressure low trip 5. I stage suc separator level high alarm 6. II stage suc separator level high alarm 7. III stage suc separator level high alarm 8. IV stage suc separator level high alarm 9. I stage suc separator level high trip 10. II stage suc separator level high trip 11. III stage suc separator level high trip 12. IV stage suc separator level high trip 13. IV stage d/c temp high alarm 14. IV stage d/c temp high trip 15. IV stage d/c pressure high trip 16. CW pressure low trip 17. LO temp high trip 18. CW return manifold temp high 19. I stage d/c temp high alarm 20. II stage d/c temp high alarm 21. III stage d/c temp high alarm

11 CRYO COMPRESSOR II

NORTH

1. Oil pressure low alarm 2. Oil pressure low trip 3. CW low trip 4. D/c pressure too high trip 5. D/c temp too high trip 6. Unloading set pressure

Page 384: Ammonia Manual

Ammonia Plant Operating Manual 231

SOUTH

1. Oil pressure low alarm 2. Oil pressure low trip 3. CW low trip 4. D/c pressure too high trip 5. D/c temp too high trip 6. Unloading set pressure

12 CRYO COMPRESSOR I

EAST

1. Oil pressure low alarm 2. Oil pressure low trip 3. CW low trip 4. D/c pressure too high trip 5. D/c temp too high trip 6. Unloading set pressure 7. Suc pressure low alarm 8. Suc pressure low trip

WEST

1. Oil pressure low alarm 2. Oil pressure low trip 3. CW low trip 4. D/c pressure too high trip 5. D/c temp too high trip 6. Unloading set pressure 7. Suc pressure low alarm 8. Suc pressure low trip

13 SRC

1. High gas temp trip 2. LO pressure low trip

14 LRC

1. LO pressure low (pump auto start) 2. Condensor level low 3. Reservoir seal oil level low 4. Local panel pressure low 5. LO pressure extra low 6. Condensor pressure extra high 7. Axial displacement of T high

Page 385: Ammonia Manual

Ammonia Plant Operating Manual 232

8. Seal tank level high 9. Axial displacement of T extra high 10. Axial displacement of Compr high 11. Seal tank level low (pump auto start) 12. LO filter DP high 13. Axial dispalcement of compr extra high 14. condenser press high 15. 1128 level high 16. Seal oil filter DP high 17. 1128 level extra high 18. Condensor level high (pump auto start) 19. Reservoir LO level low 20. Vibration high 15 PAC

1. LO pressure low(pump start) 2. Condenser press high 3. I separator level high 4. II separator level high 5. III separator level high 6. Vibration high 7. Axial displacement of turbine high 8. Condenser level high(pump auto start) 9. Air filter DP high 10. Aux. disp. of gear high 11. Condensor level low 12. Lube oil filter DP high 13. Aux. disp. of H compr. high 14. I separator level high 15. Reservoir oil level low 16. Local panel pressure low 17. Axial disp. of L compr. high 18. II separator level high 19. Solenoid valve box press low 20. Lube oil press extra low 21. Axial disp. of turbine extra high 22. Axial disp. of L compr. extra high 23. Axial disp. of gear extra high 24. Condensor press. extra high

16 SGC

1. I suction press low PAL 101 2. M/G discharge temp. high TIA 101 3. R/G discharge temp. high IA 101,10 4. I separator level high LAH 101-1 5. II separator level high LAH 101-2 6. III separator level high LAH 101-3 7. IV separator level high LAH 101-4 8. MP Balance piston Dp high PDAH 101-1 9. HP Balance piston Dp high PDAH 102-1 10. HP comp. diaphragm Dp high PDAH 103

Page 386: Ammonia Manual

Ammonia Plant Operating Manual 233

11. Main steam temp. high TAH 111 12. Extra steam press high PAH 115-1 13. Condenser vacuum failure PAH 117-1 14. Shaft vibration high VIA 101~108 15. Shaft displacement high AXDA 109~112 16. Oil cooler outlet temp. high TIA 101~23 17. Bearing temp. high TIA 101~22 18. Oil reservoir level low LAL 106 19. Lube oil filter Dp high PDAH 104 20. LP seal oil filter Dp high PDAH 105 21. HP seal oil filter Dp high PDAH 106 22. Governor oil pressure low PAL 143 23. Lube oil press. low PAL 144-1 24. Condenser level high LAH 105 25. Condenser level low LAL 105 26. LPSO head tank level high LAH 108 27. LPSO head tank level low LAH 108-1 28. MPSO head tank level high LAH 109 29. MPSO head tank level low LAH 109-1 30. HPSO head tank level high LAH 110 31. MPSO head tank level low LAH 110-1 32. LPSO trap level high LAH 111 33. LPSO trap level high LAH 112 34. MPSO trap level high LAH 113 35. MPSO trap level high LAH 114 36. HPSO trap level high LAH 115 37. HPSO trap level high LAH 116 38. Main steam pressure low PAL 111B 39. Panel purge air low PAL 151 40. Relay and SOV purge air low PAL 152 41. Instrument purge air low PAL 153 42. SOV 112 & 113 purge air low PAL 154 43. LPSO head tank level low LAL 108-2 44. MPSO head tank level low LAL 109-2 45. HPSO head tank level low LAL 110-2 46. MP Balance piston Dp high PDAH 101-2 47. HP Balance piston Dp high PDAH 102-2 48. Shaft displacement excess AXDA 109-112 49. Lube oil press. low PAL 144-2 50. Compressor speed high SIA 101 51. Steam press. high PAH 115-2 52. Condenser vacuum failure PAH 117-2 53. I separator level high LAH 101-2 54. IIseparator level high LAH 102-2 54. III separator level high LAH 103-2 55. IV separator level high LAH 104-2

17 CPP COOLING WATER PUMP(TURBINE)

1. Lube oil press. very low PALL 2646A 2. Lube oil press. low PAL 2644 A 3. Exhaust pres. very high PAHH 2631

Page 387: Ammonia Manual

Ammonia Plant Operating Manual 234

4. Exhaust press. high PAH 2631 5. Lube oil press. very low PALL 2646 B 6. Condenseer level low LAL 2656 7. Aux. oil pump start press. 8. CEP auto start pressure

18 CPP IAD 1. Cooler outlet temp. high 2. Heater outlet temp. high 3. Bed temp. high

19 CPP IAC

1. Lube oil press. low alarm 2. Lube oil press. very low trip 3. CW flow low alarm 4. CW flow very low trip 5. Air receiver press. low alarm 6. Air temp. before after cooler high alarm 7. Cyl. jacket CW temp. of HP cylinder high alarm

20 TG I

1. AOP start press. 2. EOP start press. 3. Lube oil press. low alarm PAL 2559 4. Lube oil press. low trip PAL 2560 5. Lube oil temp. high TAH 2546-10 6. LO filter Dp high DPAH 2562 7. Safety oil press. low PAL 2548 8. Control oil press. low alarm PAL 2551 9. Control oil press. low trip PAL 2550 10. Lube oil tank level low LAL 2503 11. Control oil press Dp high DPAH 2553 12. Inlet steam press. low alarm PAL 2501 13. Inlet steam press. low trip PALL 2502 14. Exhaust steam press high PAH 2504 15. Exhaust steam press. low PAL 2505 16. Bearing temp. high TAH 2546 17. Excessive axial movement alarm DAH 2501 18. Excessive axial movement trip DAHH 2501 19. Over speed trip SAH 2501 20. Abnormal vibration alarm VAH 2502/2503 21. Abnormal vibration trip VAHH 2502/2503 22. Excessive acceleration VAH 2506 23. Instrument air press. low 24. CW press low PAL 2541 25. 48 KSCG steam press. high PAH 2602 26. 48 KSCG steam press. low PAL 2602 27. Packing steam press. low PAL 2515 28. CEP auto start PAL 2539

Page 388: Ammonia Manual

Ammonia Plant Operating Manual 235

29. Condensate conductivity high CAH 2501 30. Condenser press. high PAHH 2501 31. Condenser hot well level high LAH 2501 32. Condenser hot well level low LAL 2501 33. Condenser vacuum low alarm PAH 2511 34. Condenser vacuum low trip PAHH 2510 35. Exhaust steam temp. high TAH 2506 36. CW press. low PAL 2546

21 TG II

1. Lube oil press. low alarm PAL 2576 2. Lube oil press. low trip PAL 2577 3. Lube oil temp. high TAH 2564-10 4. LO filter Dp high DPAH 2579 5. Safety oil press. low PAL 2565 6. Control oil press. low alarm PAL 2568 7. Control oil press. low trip PAL 2567 8. Lube oil tank level low LAL 2505 9. Control oil press. Dp high DPAH 2570 10. Bearing temp. high TAH 2564 11. Excessive axial movement alarm DAH 2502 12. Excessive axial movement trip DAHH 2502 13. Over speed trip SAH 2505 14. Abnormal vibration alarm VAH 2509/2510 15. Abnormal vibration trip VAHH 2509/2510 16. CW pH high 17. FOTP auto start press. 18. CW sump level low 19. Debris filter Dp high 20. FO day tank level high

22 AUXILIARY BOILER(SOUTH)

1. Air flow low trip 2. Furnace press high 3. HFO press low 4. Atomising steam press. low 5. Drum level low

23 AUXILIARY BOILER(NORTH)

1. Air flow low trip 2. Furnace press high 3. HFO press low 4. Atomising steam press. low 5. Drum level low

24 AMMONIA COOLING WATER PUMP

Page 389: Ammonia Manual

Ammonia Plant Operating Manual 236

1. Low lube oil press trip 2. Low lube oil press. alarm 3. Oil tank level low 4. LOP auto start press.