ash handling system for eet-r3

8/11/2019 Ash Handling System for EET-r3

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15 September 1

Ash HandlingSystem


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WHY ASH HANDLING?Ash content of Indian coal used in power station is about 30 to 40 %.

A typical 2000 MW station produce around 9000T to 12000T of ash per day.This huge amount of ash needs to be disposed off continuously.

Necessary care to be taken for preventing pollution

Ash Handling system takes care the above requirement

Typical Ash Data

210 MW 500 MW 660 MW

TOTAL ASH 75 180 240

BOTTOM ASH 11.25 28 36

ECONOMISER ASH 2.25 6 7

AIR PREHEATERASH

1.5 4 5

ESP ASH 60 144 192


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WHAT HAPPENS TO THE ASH

PRODUCED?20 % Of the ash falls at the bottom of the furnace known

as Bottom Ash (BA).

80 % of the ash carried away with flue gas known as Fly

Ash.BA can form slag and clinker depending on the temp.

of the combustion zone and environment inside.

reducing environment (Less O2) reduces ash MP.BA is disposed off through BA disposal system.

FA is collected through ESP and disposed through FA

disposal system.


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15 September 5

Coal Seam

Surge Pile

Pulverize (-150)

Overburden

Fly Ash

Flue Gas

Electrostatic Precipitator

Flue Gas

Boiler

Fly AshBottom Ash

SmokeStack

Fly AshBottom

Ash

Schematics of Ash Generation


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15 September 6

Ash volumes and properties

ESP

Pulverized

Coal

Furnace

(1300 - 1500C)

Electrostatic

Precipitator

Sta

geA:80%

Sta

geB:17%

80-90 %

Sta

geC:3%

Fly ash

Air

preheater

APH

Economizer

Eco Ash APH Ash

1 % 1 %

Stack

Fineness

Bottom AshCoal

10-20 %100 % Ash


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Bottom Ash HandlingSystem

Wet Type

Continuous

ScrapperConveyor

ScrewConveyor

Intermittent

Jet Pump /Ejector

Dry type

Pneumatic Conveyor


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15 September 8

BA Handling SystemBA can be collected at furnace bottom as Wet or Dry form.

Wetbottom ash system consists of i)Trough seal, ii)BA

gate, iii)Hopper, iv)Scrapper Conveyer, v)Clinker grinder,

vi)BA trench, vii)BA tank, viii)BA pump, ix)BA pond.

DryBA consists of i)Trough seal, ii)BA gate, iii)Hopper,iv)Scrapper Conveyer, v)Clinker grinder, vi)Silo.

Trough seal: A channel around the furnace bottom

filled with water where the furnace bottom end is

immersed in water. This is to prevent air ingression in the

boiler during operation.


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15 September 9

BA Handling System

BA Gate: Each hopper has separate gate to isolate Scrapper conveyorfrom running furnace for any repairing at scrapper.

Scrapper Conveyer : Consists of number of scrapper bars fasten atboth the ends with two chain which can run on chain pulley and drivenby scrapper conveyor motor. The whole conveyor is submerged inwater for wet BA system. Bottom ash after falling on scrapper isscrapped away by the running conveyor to one end of the conveyor toclinker grinder.


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SCRAPER CHAIN CONVEYOR

ONE REFRACTORY-LINED TRANSITION HOPPER WITH ISOLATION GATES FOR EMERGENCYSTORAGE OF ASH FOR 3 TO 4 HOURS

2 X 100% ( ONE WORKING + ONE STANDBY) , OR 2 X 50% (TWO WORKING + TWO STANDBY)DEPENDING ON SUPPLIERS CAPABILITY

WATER SUPPLIED CONTINUOUSLY

FOR SPRAY-QUENCHING OF ASH IN TRANSITION HOPPER

FOR COOLING OF ASH IN TROUGH. OVERFLOW WATER FROM TROUGH RECYCLED IN ASHHANDLING PLANT AFTER SETTLING OUT CARRY OVER ASH

DEWATERED ASH FALLING FROM SSC SLUICED THROUGH TRENCH TO LOCAL BOTTOM ASH

SLURRY SUMP BOTTOM ASH

SLURRY PUMPED OUT BY HEAVY DUTY CENTRIFUGAL PUMPS TO MAIN SLURRY DISPOSAL

PUMPHOUSE


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15 September 11

Wet Bottom Ash System with Scrapper Conveyor


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15 September 12


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BA Handling SystemClinker grinder : Any big size ash clinker is crushed to enable to becarried away by water jet through BA trench.

BA trench : Through water jet ash slurry is carried awayto BA tank


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SCREW CONVEYOR

ONE TRANSITION HOPPER PER UNIT

WATER SPRAYED ON BOTTOM ASH FALLING THROUGHHOPPER FOR QUENCHING

ASH FALLS INTO TROUGH BELOW HOPPER

ONE SCREW CONVEYOR ,INCLINED UPWARDS,PROVIDED IN TROUGH TO REMOVE THE ASH

CONTINUOUSLY DEWATERED ASH SLUICED VIA TRENCH TO SLURRY

DISPOSAL PUMPHOUSE


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WATER IMPOUNDED HOPPER WITH JET PUMPS

HOPPER EVACUATED ONCE IN 4 HOURS OR 8 HOURSUSING JET PUMPS SUPPLIED WITH HIGH PRESSURE

WATER FROM DEDICATED PUMPS. ASH SLUICED VIA

PIPELINES TO MAIN SLURRY PUMPHOUSE.

LOWER CAPITAL COST

EASIER MAINTENANCE- FEWER MOVING PARTS

HOPPER DISCHARGE GATES LEAKAGEPRONE

HIGHER WATER AND POWER CONSUMPTION OVERALL OF ASHPLANT DUE TO UNEVEN WATER AND SLURRY FLOWS

WIDELY EMPLOYED

PROS AND CONS


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15 September 17

Dry BA Handling System

DryBA collection system after clinker grinder collect ash

to silo through a transport mechanism for further transportthrough road system.


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15 September PMI Revision 00 18


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ECONOMISER ASH HANDLING SYSTEMS

WET TYPE

- FLUSHING BOX

- FEEDER EJECTOR

DRY TYPE

VACUUM TYPE PNEUMATIC CONVEYING PRESSURE TYPE PNEUMATIC CONVEYING


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ECO ASH SYSTEMS

FLUSHING BOX BASED SYSTEMS CONTINUOUS ASH REMOVAL

CAN BE COMBINED WITH CONTINUOUS -TYPE BOTTOM ASHREMOVAL SYSTEMS( SSC , SCREW CONVEYOR) TO OPTIMISEWATER AND POWER CONSUMPTION AND LAYOUT

PREFERRED , AS HOT ASH IS CONTINUOUSLY COOLED AND

REMOVED

FEEDER EJECTOR BASED SYSTEMS INTERMITTENT ASH REMOVAL

CAN BE COMBINED WITH INTERMITTENT TYPE BOTTOM ASH

REMOVAL SYSTEMS (WIH) TO OPTIMISE WATER AND POWERCONSUMPTION AND LAYOUT


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AIR PREHEATER ASH REMOVAL

SYSTEMS

SIMILAR TO ECONOMISER ASH REMOVAL SYSTEMS

RELATIVELY EASIER DUE TO LOWER ASH

TEMPERATURE( 150-200 DEG. C)

MAY BE COMBINED WITH ESP DRY ASH REMOVAL

SYSTEM


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15 September 22

Dry FA Handling System

Hydrobackter is a vacuum device to collect ash from thehopper.

Water jet ejectors used for creating vacuum.

Dry ash thus collected to silo through belt conveyor.

Dry ash is disposed through road transport to a dry ash

disposal system. Part of it sold for commercial purpose


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ESP ASH REMOVAL SYSTEMS

ESP AshRemoval

Wet

Continuous Intermittent

Dry

DryExtractionfrom Silo

PressureType


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15 September 24

FA Handling SystemFA is collected from Air heater hopper, Eco hopper andESP hopper.

Either through flushing apparatus or hydrobactur system.

In Flushing apparatus system ash is allowed to fall influshing apparatus under gravitation.

Water jet in flushing apparatus carries away the ash to FAtrench

High pressure jets further carries it to FA sump.Series pumping carries the ash slurry to FA pond.


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CONTINUOUS TYPE

- FLUSHING BOX AND TRENCH SLUICE (WET

SYSTEM)

- PNEUMATIC TYPE (DRY SYSTEM)

INTERMITTENT TYPE

- FEEDER EJECTOR AND TRENCH SLUICE (WETSYSTEM)


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(AS PER STATUTORY REQUIREMENTS)

DRY ASH EXTRACTION FROM ESP

PROVISION OF ASH SILOS FOR SALE OF ASH


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ESP ASH EXTRACTION

SYSTEMS

DRY CONVEYING FROM ESP HOPPERS , AND

FURTHER REMOVAL EITHER BY WET SYSTEM AS

SLURRY FOR ONWARD DISPOSAL TO ASH POND OR BY

DRY SYSTEM TO STORAGE SILO FOR SALE

PNEUMATIC SYSTEMS

- VACUUM TYPE- PRESSURE TYPE


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VACUUM TYPE SYSTEMS

- SUITED FOR REMOVING MATERIAL FROM MANYCOLLECTION POINTS AND DISCHARGE TO ONEPOINT(ESP)

- MATERIAL CONVEYED AS A SUSPENSION IN THE PIPEAT HIGH VELOCITIES

- VACUUM PRODUCED USING

- LIQUID-RING VACUUM PUMP, IF ASH IS TO BE CONVERTEDTO SLURRY FOR DISPOSAL

- LOBE-TYPE AS VACUUM PUMPS IF ASH IS TO BE HANDLEDDRY


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VACUUM TYPE SYSTEMS PROS AND CONS

SIMPLE LAYOUTDOES NOT REQUIRE MUCH HEADROOM BELOWESP

SIMPLE IN OPERATION

NO LEAKAGE OF ASH

EASY TO MAINTAIN

HIGH WEAR AND TEAR ,ESPECIALLY AT VALVES AND BENDS

RESTRICTION ON CONVEYING RATE/DISTANCEMAX. 60 TPH/150 M.


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PRESSURE SYSTEMS

LOW

PRESSURE

MEDIUM

PRESSURE

HIGH

PRESSURE

MATERIALTRANSPORT MODE

SUSPENSION PARTLY INSUSPENSION,

PARTLY ASMOVING BED

SLUG (DUNE ORPLUGS FILLINGWHOLE PIPESECTION)

TYPICALCONVEYING AIRPRESSURE (BAR)

1-1.5 1.5-3 >3

TYPICAL AIR/ASHRATIO BY WT.

10-15 20-30 >50

TYPICALCONVEYINGVELOCITIES(M/S)

20-25 10-15 5-8

TYPICAL AIRSOURCE

BLOWER/COM-PRESSOR

SINGLE-STAGESCREWCOMPRESSOR

TWO-STAGESCREWCOMPRESSOR


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ESP ASH HANDLING

SINGLE STAGE CONVEYING TO SILO BY

VACUUM SYSTEM IF TONNAGE IS WITHIN 60 TPHAND/OR DISTANCE IS WITHIN 150 M

OTHERWISE, PRESSURE SYSTEM FOR DISTANCEWITHIN 400M FROM ESP

TWO-STAGE CONVEYING SYSTEM FOR DISTANCE MORETHAN 400M

VACUUM EXTRACTION+PRESSURE TRANSPORTATION

PRESSURE EXTRACTION+PRESSURETRANSPORTATION


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ASH SLURRY DISPOSAL

BOTTOM ASH AND FLY ASH DISPOSED OFF AS COMBINEDSLURRY

ASH PUMPED AS LEAN SLURRY MAX. 25% FOR BA/BA+FA

MAX. 30% FOR FA ONLY

HORIZONTAL, CENTRIFUGAL ,SLURRY DUTY PUMPS USED PUMPS COUPLED IN SERIES TO ACHIEVE DESIRED TOTAL HEAD

TYPICALLY FOUR PUMPS PER SERIES TO PUMP UPTO 10KM

TOTAL NO. OF DISPOSAL SERIES IS NO. OF UNITS +2

GARLANDING OF ASH POND FOR EFFECTIVE FILLING ANDCONSTRUCTION AND OPERATIONAL FLEXIBILITY


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Ash Pipe line System


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ASH WATER SYSTEM

RAW WATER,CW BLOWDOWN, RECYCLED WATER FROM

ASH POND USED FOR ASH SLUICING

CLARIFIED WATER FOR SEALING/COOLING

HORIZONTAL, CENTRIFUGAL PUMPS WIDELY USED LESSER COST

EASIER TO INSPECT AND MAINTAIN

ASH POND WATER RECYCLED TO SAVE ON WATERCONSUMPTION AND FROM ENVIRONMENT ANGLE


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15 September 37

BA Handling System

BA pump : Ash slurry handling pump. It carries ash to the BA pond.Depending on the distance of BA pond two or more BA pumpsconnected in series.

BA pond : Finally ash is discharged to ash pond. It is a large areasurrounded by embankment. Ash mixed with water is allowed to settle

for considerable time. Water from top surface is allowed to go out fromthe pond through a designed escape route. Quality of water discharge isalways monitor for turbidity and heavy metal. Piezo meter is used formonitoring the slope stability of the embankment.

BA Supporting water pumpsLP BA pump : Supply water to trough seal, scrapper conveyor sump,BA sump and LP jets.

HP BA pump : HP jets in BA trench and line cleaning.


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Typical Ash Dyke Design


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Typical Ash Dyke Design


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Ash Pond in Google Map


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Initially in an endeavor to utilize around 100 MMT of ashgenerated in the country Ministry of Environment and Forest

(MoEF) came up with a notification (S.O. 763(E) Dt.

14.9.1999)(Annexue-5) which allows the ash users (e.g.-

Cement companies, Asbestos manufacturing companies,

brick manufacturers etc.) to take ash "Free of cost" from

power generating companies till Sep-2009. During the period of ten years, ash utilization has increased

from 12% to 40% and is growing at fast rate. Ash user

companies especially Cement, and Asbestos sheet

manufacturing companies used this opportunity and

exploited pozzolanic properties of ash by using ash as a raw

material in the manufacturing of their products. In line with the practices followed in western countries, like

USA and Europe, in April -2007 Ministry of Environment and

Forest (MoEF) came up with a draf t not i f icat ion w hich allow

sale of Ash

Ash Utilization Govt Initiatives


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ASH UTILISATIONMajor usage of ash

Fly ash bricks / blocks

Cellular concrete products

Light weight aggregates

Concrete and mortar

In manufacture of cementIn manufacture of asbestos products

Road construction

Embankment/back fills/land development

Controlled low strength material (CLSM)In agriculture

Mine filling

Manufacture of fertilizer


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Other usageManufacture of distemper

Floor and wall tiles

Refractory bricks

Manufacture of ceramics

Use with Ferro cement

Recovery of metalsUse in grouting

Manufacture of alum

Extraction of Cenospheres

Domestic cleaning powderIn synthetic wood


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THANK YOU


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Direct Disposal

ash handling system for eet-r3

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