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United Arab Emirates University College of Engineering

Training and Graduation Projects Unit Graduation Project II

Advisor:Advisor: Dr. Marcelo Castier

Done by:Basma Ali 200211743 Fatima Rashid 200212000  Latifa Obaid 200203237 

Sheikh AL thahry 200202742

Liquefied Natural Liquefied Natural GasGas

Liquefied Natural Liquefied Natural GasGas

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Outline:Outline:Outline:Outline:• Back ground Gp1Back ground Gp1

• Introduction to Liquefied Natural Gas project

• Main objectives & challenges

• Process Descriptions of the co production plant

• Equipments sizing & Design parameters

• HAZOP study & Process Modifications

• Economic evaluation

• Site layout & location

• Conclusions

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Background GPIBackground GPIBackground GPIBackground GPI Process Selection

Material Balance Calculation.

Energy Balance Calculation.

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Process of Liquefaction of Natural Gas

Double Mixed Refrigerant

Co-production.

Hybrid cycle.

HYSIS simulation

CompressionLoop

HYSIS simulation

Compression Loop

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Project description: Project description:

• Project objective: The main technical challenge of this project is to cool

natural gas into very low temperature (approximately -163 0C), what requires

several interlinked refrigeration cycles.

• Raw Feed Materials Specifications

• Tools and Methods

Conditions

StreamTemperature (oC)Pressure (kPa)Mass flow rate (kg/sec)

Natural gas318860129.515

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Project challenge:Project challenge:

• Setup the process model in a commercial simulator (HYSYS) and obtain numerical convergence.

• Design a unusual distillation column with multiple feeds and products and, more importantly, with a liquid recycle structure at the top of the column that does not occur via a conventional condenser.

• Design a liquid expander, which exists in the plant to recover mechanical work from liquid expansion.

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Important definitions:Important definitions:

• Natural gas is a mixture of hydrocarbon gases and acid gases with varying molecules and amount of impurities.

• NGL is removal of certain components, such as dust, helium, water, and heavy hydrocarbons and then condensed into a

liquid at close to atmospheric pressure.

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Introduction to equipment design Introduction to equipment design Introduction to equipment design Introduction to equipment design

•Design mean is to formulate a plan for devise designed.

•Important of equipment design:-

Checking new process designs

Providing equipment size and performance estimates

Helping to troubleshoot problems with operating systems

Verifying the reasonableness of results of computer calculations and simulations

Obtaining approximate costs for process units

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15 Equipment Design 15 29-May-2008

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High-Pressure Phase Separator:High-Pressure Phase Separator:

• From heuristics of separator:-

Rule 1 → Vertical Vessel Rule 1 → L/D between 2.5 and 5 with optimum at 3.0 Rule 3 → liquid hold-up time is 5 min based on ½ volume of vessel Rule 4 → Gas velocity u (m/s) is given by

where k = 0.0305 for vessels without mesh entrainers

• Data provided from HYSYS:-Vapor flow, Liquid flow, ρv and ρl

1v

lku

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Heat Exchanger DesignHeat Exchanger Design

•Heat exchanger is device that is used to transfer thermal energy from one fluid to another without mixing the two fluids.

•Main parameter of designing heat exchanger: determining its type, area and duty.

•The type of heat exchangers in the LNG plant are shell and tube heat exchangers.

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Expander DesignExpander Design::Expander DesignExpander Design::

Liquid expanders offer the potential to improve process efficiency by recovering otherwise unused energy.

Type of Liquid Expander:

– Cryogenic Liquid Expander– Joule Thompson (JT) Valve– Hydraulic turbine.– Flashing liquid expander.

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Expander Design:Expander Design:

Assumptions:– Adiabatic.– Reversible.– ΔS = 0, isentropic process.– Ideal gas.

Equations:– dH = T ds + V dP– Δ H = V dP.

– Rackett equation: Vsat = Vc Zc (1-Tr) 0.2857

19)(

)(

2

.

12

1 hhMW

HMW

PPVKGmol

KJH

o

S

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CompressorCompressorCompressorCompressor

• Mechanical device that increases the pressure of a gas by reducing its volume. Compression of a gas naturally increases its temperature.

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Types of compressors:

Recipcating rotary van compressors

Centrifugalcompressors

Axial flow compressors

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Compressors designCompressors design::Compressors designCompressors design::

Determination of:– Type of compressor.

V. = m./ρCR = Pout/Pin ; <3

Poptimum = Pout √Pin/Pout

– Efficiency.

– Power & actual power.R.A.P = n. Z. R. T. [(Pout/Pin)a - 1)]/a,

a = Cp/Cv, A = (k-1)kActual power = R.A.P / ζ

– Outlet temperature.

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Tr = T/TcPr = P/Pc

Determination of compressibility factor:Determination of compressibility factor:

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Valves designValves designValves designValves design

• A device that regulates the flow of substances like gases, fluidized solids, slurries or liquids, by opening or closing.

• Valves applications:• Used for safety purposes.• Used for controlling applications.

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Valves design parameterValves design parameterValves design parameterValves design parameter

a)  The process requirements (pressure and flow) downstream.

b)  The service (regular flow line, intermittent, blow-down, depressurizing).

c)  The variations in the flow and pressure with time.

d)  Fluid characteristics (composition, solids, Newtonian or non-Newtonian).

e)  Phase behavior (single phase, two phase, water contain).

f) The suitable diameter for the suitable pipe with stand

the range of velocity between 5 – 10 ft.25 29-May-2008

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Distillation Column DesignDistillation Column Design::Distillation Column DesignDistillation Column Design::

•Distillation is a process in which a liquid or vapor mixture of two or more substances is separated into its component.

Determination of relative volatility:

Rault’s Law:

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BB

AA

/xy

/ xy AB

B

A

P

P AB

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Cont; Relative VolatilityCont; Relative VolatilityCont; Relative VolatilityCont; Relative Volatility

• Minimum number of stages by using Fenske equation :

• Nmin = Log [ (XLD/XHD)

(XHW/XLW) ] /Log (αavg.)

• Actual Reflux Ratio:(R-Rmin)/(R+1)27 29-May-2008

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Diameter & Height of towerDiameter & Height of tower::Diameter & Height of towerDiameter & Height of tower::

ρvap= ( avg.Mw *P) / (R/T)

Volume flow rate = (Top flow * Mwav.)/(vap.ρ *3600)

Diameter (m) = ((4*Volume flow rate)/(π*v))0.5

Velocity = (1.35)/(top ρ) 0.5

Refer to recommended tray table:

Hmin = (NAS + 1)*plate spacing

Hmax = (NAS – 1)*plate spacing+(1+3)

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Definition of HAZOP:Definition of HAZOP:

• An analysis of the hazards which could occur

at step in the process, and a description and implementation of the measures to be taken for their control.

• Invented by the BCI "British chemical industry" in the United Kingdom.

• Officially adopted in 1974 after flixborough explosion.

• This chemical plant explosion killed twenty eight people and injured scores of others:

• the public living nearby

• Lack of a systematic review of the qualified personnel. 29-May-2008

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Benefits of using HAZOP techniques:Benefits of using HAZOP techniques:

• easy to learn.

• can be easily adapted to almost all industrial operations

• No special level of academic qualification is required. 

• The HAZOP Study is an opportunity to correct these before such changes become too expensive, or 'impossible' to accomplish.

• HAZOP methodology is perhaps the most widely used aid to loss prevention.

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Procedure setup:Procedure setup:

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HAZOP Analysis:HAZOP Analysis:

3. Subdivide the system or activity and develop deviations

2.0 Define the problems of interest for the analysis

4. Conduct HAZOP reviews

1.0 Define the system or activity

5. Use the results in decision making

2. Define the problems of interest for the analysis

1. Define the system or activity

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Process Modification:Process Modification:

Studying the special concern of these conditions are important to provide conditions that allow effective process performance.

Specific Condition:

Temperature Pressure Flow

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Special Concern Area of Equipments : Special Concern Area of Equipments :

Type of EquipmentsConditions

Separators

High temperature (T>250OC) or pressure (P>10 bar)Low temperature (T<40OC) or pressure (P<1 bar)

CompressorsPout/Pin > 3High Temperature inlet gas

Heat exchangersΔTIn>100oC

ValvesLarge ΔP across valve

Mixers

Streams of greatly differing temperatures mixStreams of greatly differing composition mix 29-May-2008

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Distillation Column:There are a special concern.

Heat Exchanger:

Δ TIn= 105.9 oC -30 oC

= 75.9 oC <100 oC

Special Concern areas:Special Concern areas:

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Introduction to equipments cost Introduction to equipments cost

Cost Estimation:Cost estimation models are mathematical algorithms or parametric equations used to determine the costs of plant.

The results of the models are typically necessary to measure approval to proceed, and are factored into business plans, budgets, and other financial planning and tracking mechanisms.

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Total module and Grass root cost:Total module and Grass root cost:

– Total module cost can be evaluated from:

– And Grass root cost can be evaluated from:

n

iiBM

n

iiTMTM CCC

1,

1, 18.1

n

i

iBMo

TMGR CCC1

,5.0

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Cost Estimation for Coolers:Cost Estimation for Coolers:

2103102110 )()(

:cost Purchased

ALogKALogKKCpLog o

BMo

BM

PBM

P

FCpC

FBBF

PLogCPLogCCFLog

M21

2103102110

F

)()(

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Cost estimation for distillation column:Cost estimation for distillation column:Cost estimation for distillation column:Cost estimation for distillation column:

Cost equations for tower and trays.Cost equations for tower and trays.

Volume = π D2 L / 4

Area for trays = V / L

0063.0

00315.0)1(6.08502

)1(

PDP

FP

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Raw material CostRaw material CostRaw material CostRaw material Cost

The cost of raw materials can be estimated by using the current price listed in such publications as the Chemical Market Reporter (CMR).

Factor Conversion TimeFactor Stream/$12.1)rate flow stream (Gas Natural Raw ofCost Yearly kgraw

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Labor Operating Cost:Labor Operating Cost:

The technique used to estimate operating labor requirements is based on data obtained from five chemical companies and correlated by Alkayat and Gerrard.

5.02 )23.07.3129.6( npOL NPN

vesselsand pumpsexcept Equipment,npN

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Equipment Type:Number of

Equipment: Nnp:

Exchangers 99

Compressors 44

Expanders33

Tower11

Vessel1-

Total 17

Shift)Operators/()23.07.3129.6( 5.02npOL NPN

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Utilities Cost (CuT)Utilities Cost (CuT)

• Specific difficulties emerge when estimating the cost of fuel like electricity, stream and thermal fluid.

• Costs of utility streams required by process includes:– Fuel gas, oil and coal.– Electric power.– Stream.– Cooling water.– Process water.– Boiler feed water.– Instrument air.– Inert gas.– Refrigeration. Factor Conversion TimeFactor Stream($/GJ)Cost Utilitiy (GJ/h)Duty CostYearly

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Changes in Fuel prices:Changes in Fuel prices:

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Compression between coal and NGCompression between coal and NG

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Plant Layout:Plant Layout:

• It is necessary to make a preliminary study on the layout of the plant equipments.

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Layout depending factor:

• Main rooms as control room and offices should sit away from areas that have high accident risk and upstream of the current winds.

• Reactors, boilers, etc., Should build up away from the chemical storage tanks.

• Storage tanks should be easy access and choice on whether all tanks (of raw materials and products) should be located together or dispersed throughout the site

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• Availability of plant requirement.

• Minimizing plant piping systems.

• Suitable access to equipment that usual require maintenance or repair and keep a space between equbments.

• Access to the plant in the case of an accident.

• Availability of source of cooling place for equipments need cooling water close.

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The aim of minimizing the layout of plant equipment

• avoid damage to persons and property due to fire or explosion.

• decrease Maintenance costs.

• reduce number of worker in the plant.

• decrease operating costs.

• reduce construction costs.

• Reduce cost of expansion or modifications on plant.

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Piping and Instrumental Diagram (P&ID) Designs

• The piping and instrumentation diagram (P&ID) provides information need by engineers to begin planning for the construction of the plant.

Mechanical engineers and civil engineers will design and install pieces of equipment.

Instrument engineers will specify, install and check control system.

Piping engineers will develop plant layout and elevation drawings.

Project engineers will develop plant and construction schedules.

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For equipments, show every piece including spare units, parallel units and summary details of each unit.

For piping, include all lines including drains, sample connections and specify size, schedule, materials of construction and insulation.

For instruments, identify indicators, recorders, controllers and show instrument line.

For utilities, identify entrance utilities, exist utilities and exist to waste treatment facilities.

Conventions in constructing P&D

diagram:

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Conclusion:

• Total Module Cost and Grass Roots Cost

• Cost of operating labor (COL)

• Utility costs (CUT)

Total utilities cost = 4.685*107 $/yr

• Raw materials costs (CRM)

• Capital Cost of Manufacturing (COMd)

r750,000$/y 50,000$ 15(2008)Cost Operating

yr/$10689.6Gas Natural Raw ofCost Yearly 9

yrCOM d /$10832.8 1029-May-2008

88GR

77

102.1397

412.998$ 10095.22008@C

108.98397

412.998$10667.82008@

TMC

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Qatar Conference of LNG :

Important Dates:

Full Paper Submission June 16, 2008        Paper Acceptance  August 8, 2008        Final Submission August 24, 2008

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