Coal to Liquid Process

8/10/2019 Coal to Liquid Process

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COAL TO LIQUIDPROCESS USINGFISCHER TROPSCHSYNTHESIS

Faheem Shereef

Parnil Singh

Shubam Gupta


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INTRODUCTION

There is a great dearth of liquid fuel in the world

To meet this, the process of coal to liquid was discove

Converting coal to liquid allows coal to be used as an afuel to oil

The scarcity of fuel has led to considerable interest in msynthetic fuels from coalso called coal-to-liquid (CTLlight of coals relatively low prices and the abundance

Moreover, the synthetic fuels provided would be cleancrude oil products displaced


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BENEFITSOF THEPROCESS

Coal is affordable and available worldwide enabling caccess domestic coal reserves and a well-supplied imarket - and decrease reliance on oil imports, imprsecurity.

Coal liquids can be used for transport, cooking, statiogeneration, and in the chemicals industry.

Coal-derived fuels are sulphur-free, low in particulanitrogen oxides.

Liquid fuels from coal provide ultra-cleancooking fuhealth risks from indoor air pollution


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SOMEEXISTINGPROCESSES

Hydrogenation process: In this process, dry coal is mheavy oil recycled from the process.

Pyrolysis and Carbonation process: The carbonizatiooccurs through pyrolysis or destructive distillation.

Direct liquefaction: It works by dissolving the coal in

high temperature and pressure. This process is highly the liquid products require further refining to achieve fuel characteristics.


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THEPROCESS

The process used by us is CTL-RC-CCS: Coal to Liquid

CCS, that is coal is converted to liquid fuel with recycCO2 produced is sequestered.

The main two steps in this process is Coal GasificatioFischer-Tropschprocess

Coal gasification is the process of producing syngasconsisting of methane, carbon-monoxide, hydrogendioxide and water-vapor by reacting coal with a cont

amount of oxygen and steam at high temperatures.


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The reactions involved in the combustion process are:

C+0.5O2COC+ O2CO2

The main gasification reaction occurring is:

C + H2OCO+H2

The Fischer-Tropschprocess is a collection of chemical converts a mixture of carbon-dioxide and hydrogen to liqhydrocarbons. The general reaction can be expressed as

(2n+1)H2 + nCOCnH(2n+2) + nH2O

REACTIONS


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F-T REACTOR

A slurry-phase reactor is used the feed syngas is buban inert oil in which catalyst particles are suspended.

High release rates of reaction heat are accommodateeffective reactor cooling by boiler tubes immersed in t

The vigorous mixing, intimate gas-catalyst contact,

temperature distribution enable a high conversion of fliquids in a relatively small reactor volume.

Conversion by slurry-phase F-T synthesis can achieve fractional conversion of CO to FTL as high as 80%


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PROCESSSTEPS

A coal/water slurry is fed with oxygen from a dedicatcryogenic air separation unit (ASU) into the coal gas

The syngas leaving the reactor is scrubbed with watesome of it enters a single-stage (adiabatic) water gareactor.

CO+H2O CO2+H2

A syngas bypass around the WGS reactor is adjustedthat a molar H2:CO ratio of 1:1 is realized. In this mecaptured CO2 is vented out to the atmosphere.


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For all systems the acid gases CO2, H2S, and COS contsyngas are removed to improve the kinetics and econodownstream synthesis process.

Most of syngas following acid gas removal travels to th

Most of the unconverted syngas and light gases generhydrocarbon recovery step are compressed and recyclthrough the synthesis reactor

The reformed gas stream is mixed with the fresh syng

upstream of the acid gas removal island. A small portiogases leaving the hydrocarbon recovery unit are drawnpurge stream to avoid the build up of inert gases in the

PROCESS STEPS(Cont..)


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COAL-GRADE=ILLINOIS #6

COAL


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DESIGNDESCRIPTION

Equipment

ID

Equipment type Equipment specifications

DECOMP

GASIFIER

T = 25oC, P = 1 atm

GASIFIER Pressure maintained at 30 atm,

ASHREMO

V

CYCLONE (ASH

REMOVAL

SECTION)

Absolute solid separation (solid split f

REFORME

R

STOIC. REACTOR

(WGS SECTION)

Tincalculated from Gasifier outlet, Touisothermally)

COOL1

2-SHIFT WATER

GAS SHIFTREACTION

SECTION

T = 423oC, P = 30 atm

WGS1 T = 423o

C, P = 30 atm; 0o

C temp. appr

COOL2 T = 230oC, P = 30 atm

WGS2 T = 230oC, P = 30 atm; 0oC temp. appr

COND1 CONDENSER T = 37oC, P = 30 atm; water decanted

DESULFUR DESULFURIZER

SEPARATOR

Split fractions of 1 for H2S and NH3rem

PSA MEA ADSORBER S lit f ti f f CO d


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PSA MEA-ADSORBER

(PRESSURE

SWING)

Split fractions of 1 for CO2and rem

mixture

P1 PUMP Pin= 1 atm, Pout= 30 atm; type: cen

efficiency = 0.95

COMP1 COMPRESSOR P = 25 atm;

polytropic efficiency = 0.9, adiabatXE1 HEAT

EXCHANGER

Shell-and-tube heat exchanger wit

FT-REACT FISCHER-

TROPSCH

REACTOR

CSTR reactor to simulate slurry con

loading of 4 kg in vessel volume of

atm; Used Cu-Fe-K catalyst

COOL4 COOLER T = 40oC, P = 30 bar

FLASH FLASH DRUM P = 24 bar; Isothermal flash at 40oC

COMP2 COMPRESSOR P = 27 bar

polytropic efficiency = 0.9, adiabat

ATR AUTO-THERMAL

REFORMER

P = 30 bar, T = 900oC; Gibbs Reacto

COOL3 COOLER T = 40oC, P = 28 bar

DESIGNDESCRIPTION


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PROCESSLIMITATIONS

The product quality is very sensitive to the coal qualityand low carbon content gave very poor outputs

H2:CO ratio should be equal to 1:1 in syngas entering tsynthesis reactor. However this is not ensured and leavariations later

There are some simulation limitations. Fluidization in FT synthesis are not properly accounted for and simul


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PROCESSASSUMPTIONS

No reactions of coke formation are assumed

Heat Capacity is a function of temperature only & not p

100% heat exchange across any units, reactors or heat

No leakage in the system, therefore law of mass conseracross all units.

+=0 &

Heat of reaction is not considered in the energy balanc

100% CO2 absorbed in the absorption tower

Only iso-octane production is taken care of in FT reactoavailability of data


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ENERGYBALANCEFOR GASIFIER

Mass Flow kg/hr Cp

1000.0 300.0kj/kg.k kj/kg.k Kj/h

H2 44.0 0.0 14.42

O2 117.0 300.0 0.92 0.915938

N2 13.0 0.0 1.04

H2O 105.0 0.0 4.19CO 0.0 0.0 0

CO2 0.0 0.0 0

H2S 0.0 0.0 0

H3N 0.0 0.0 0

Total

Mass Flow kg/hr Cp E

1300.0kj/kg.k K

H2 0.0 0

O2 0.0 0

N2 trace 0

H2O 492.0 4.997222

CO 497.8 1.235

CO2 163.5 1.298636

H2S 11.7 1.459706

H3N 13.0 3.708824

Delta H = 4050192 kJ/h


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MASSBALANCEFOR WGS

SECTION

WGS1 WGS2 TH

Stream WG1IN WG1OUT WG2IN WG2OUT IN

Temperature C 972.0 623.0 423.0 230.0 10

Pressure bar 30.4 30.4 30.4 30.4 Mass Flow

kg/hr 2300.0 2300.0 2300.0 2300.0 23

H2 0.3 10.4 10.4 98.3

O2 trace trace trace trace trac

H2O 482.8 311.0 311.0 213.2 15

CO 404.4 386.0 386.0 249.0 5

CO2 163.5 192.4 192.4 407.7 2

H2S 11.7 11.7 11.7 11.7

H3N 13.0 13.0 13.0 13.0


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ENERGYBALANCEFOR WGS

SECTION

Mass Flow kg/hr Cp Inlet

2300.0Kj/kg.k Kj/h

H2 0.3 15.63

O2 trace 0.00

H2O 482.8 5.36

CO 404.4 1.23CO2 163.5 1.29

H2S 11.7 1.44

H3N 13.0 3.65

Mass Flow kg/hr Cp Outl

2300.0Kj/kg.k Kj/h

H2 98.3 14.63

O2 trace 0.00H2O 213.2 4.65

CO 230.6 1.07

CO2 407.7 1.01

H2S 11.7 1.09

H3N 13.0 2.47

Delta H = -2602757.92 kJ/h


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FISCHER-TROPSCHREACTORAND FINAL

SEPARATION Fischer-Tropsch Reactor converts CO and H2to associate

hydrocarbons

Catalyst used was activated Cu-Fe-K/ -Al2O3

Loading of 0.4 kg of catalyst based on catalyst literature

Reference: YN Wang et al, Kinetics modelling of FischerTropsch synthesis over

Cu

K catalyst, 2003


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ENERGYBALANCEFOR FTREACTOR

m (kg/h) Cp (kJ/kgK) Inle

H2 254.40 14.64

O2 trace 0.97

H2O 50.10 4.65

CO 158.90 1.07

CO2 trace 1.02 CH4 0.00 2.96

C2H6 0.00 2.46

I-OCT-01 0.00 2.05

m (kg/h) Cp (kJ/kgK)

Ou

(kJ

H2 4.40 14.65

O2 trace 0.98

H2O 284.40 4.65

CO trace 1.07

CO2 15.70 1.03

CH4 98.80 3.02

C2H6 32.60 2.64

I-OCT-01 35.64 2.05

Delta H = -1146189.05 kJ/h


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AUTO-THERMALREACTOR

Converts light gases (primarily CH4and C2H6) to H2an

high temperatures

Oxygen and Steam input must be optimized for givena fixed temperature


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MASSBALANCEFOR AUTOTHERMAL

REACTOR

ATR-IN ATR-IN THEO OXYGEN OPT STEAM OPT A

Temperature C 40.0 40.0 245.0 185.0

Pressure bar 24.0 24.0 38.0 30.0 Mass Flow kg/hr 435.9 365.6 500.0 220.0

H2 4.4 19.6 0.0 0.0

O2 trace 0.0 500.0 0.0 t

H2O 284.4 212.7 0.0 220.0

CO trace trace 0.0 0.0

CO2 15.7 37.4 0.0 0.0

CH4 98.8 74.6 0.0 0.0

C2H6 32.6 54.4 0.0 0.0


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ENERGYBALANCEFOR AUTOTHERMAL

REFORMER

Mass flow rate Cp

Kg/h Kj/kg.k

H2 4.4 0.0 0.0 14.45 14.64 14.61 19

O2 trace 500.0 0.0 0.00 0.96 0.96

H2O 284.4 0.0 220.0 4.19 4.66 4.42

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CO trace 0.0 0.0 0.00 0.00 0.00

CO2 15.7 0.0 0.0 0.85 1.01 0.96 4

CH4 98.8 0.0 0.0 2.23 0.00 0.00 690

Mass flow rate Cp Out

kg/h Kj/kg.k KjH2 131.29 15.50

O2 trace 0.00

H2O 114.20 5.14

CO 442.30 1.22

CO2 468.11 1.28

CH4 0.00 0.00Delta E=3295199 kJ/h


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OPTIMIZATIONOF AUTO-THERMALREFORMER

Source: Ekaterini Ch. Vagia, Angeliki A. Lemonidou,Thermodynamic analysis of hydrogen production via

steam reforming

Source: Ekaterini Ch. Vagia,Thermodynamic analysis of hsteam reforming


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HEATEXCHANGENETWORKOPTIMIZATION

Stream

No. Type Ts(oC) Tt(

oC) Cp (Mj/h.K) T (oC

1 Hot 623 423 2.93 -200

2 Hot 423 230 0.30 -193

3 Cold 27.3 245 4.24 217.7

4 Hot 260 73.7 2.20 -186.3

5 Hot 912.7 40 3.94 -872.7

H = (Flow Rate x (Cpt. TtCps. Ts))


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ECONOMICANALYSIS

The sixth-tenths rule is used for ca

costs varying with the capacity

To calculate the cost at a particula

the value at some particular year w

This is done to correct for inflation


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% of equipment


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INDIRECT COST

Sno. Indirect cost% of equipmentcost

1.Engineering andsupervision

2.

Construction expenses

3. Legal expenses

4. Contractors fee

5. Contingency

6. Total indirect costs 1

7. Fixed capital investment 4


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MATERIALSCOST

Cost Cost($)

Operating cost (15% of fixed capital inv

From calculations 1033620

From Aspen 954309

Raw material Cost 39892

Product Cost 184573.2


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CALCULATIONS

Economic Potential = Cost of product-Cost of raw mater

E.P = $144681.2

Economic potential is positive which implies the produeconomically viable

However, Product Cost-Operating Cost= (-$849046.8

Hence our process is infeasible because operating coscovered by the product cost.

The main reason is the large energy requirements of t


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Coal to Liquid Process

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