Aspen IGCC Model

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Aspen Plus IGCC Model

Aspen Plus



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Contents iii

Contents1 Introduction.........................................................................................................1

2 Components .........................................................................................................2

3 Process Description..............................................................................................4

4 Physical Properties...............................................................................................6

5 Chemical Reactions ..............................................................................................7

Coal Gasification ..............................................................................................7Desulfuration...................................................................................................8

Power Generation.............................................................................................8WGS...............................................................................................................8

Methanation ....................................................................................................9

6 Simulation Approaches.......................................................................................10

7 Simulation Results .............................................................................................13

8 Conclusions ........................................................................................................15





1 Introduction 1

1 Introduction

Global warming and global politics are driving the US and other countriestowards the development of new energy technologies which avoid the use of

petroleum and which allow for carbon capture and sequestration.

This model simulates an Integrated Coal Gasification Combined-Cycle Power

(IGCC) process with different sections of the plant modeled as hierarchy

blocks (model templates).

The model includes the following sections:

Sizing of the coal

Gasification unit

Air Separation (ASU)

Gas cleaning unit

Water-gas shift unit

Ammonia unit

Methanizer

Combined cycle power generation



2 2 Components

2 Components

The table below lists the components modeled in the simulation.

Component ID Type Component name Formula

N2 CONV NITROGEN N2

O2 CONV OXYGEN O2

AR CONV ARGON AR

COAL NC

BIOMASS NC

H2O CONV WATER H2O

CO CONV CARBON-MONOXIDE CO

CO2 CONV CARBON-DIOXIDE CO2

C SOLID CARBON-GRAPHITE C

COALASH NC

S CONV SULFUR S

COS CONV CARBONYL-SULFIDE COS

H3N CONV AMMONIA H3NH2S CONV HYDROGEN-SULFIDE H2S

O2S CONV SULFUR-DIOXIDE O2S

O3S CONV SULFUR-TRIOXIDE O3S

H2 CONV HYDROGEN H2

CH4 CONV METHANE CH4

CL2 CONV CHLORINE CL2

HCL CONV HYDROGEN-CHLORIDE HCL

S-S SOLID SULFUR S

NH4+ CONV NH4+ NH4+

H3O+ CONV H3O+ H3O+

HCLO CONV HYPOCHLOROUS-ACID HCLO

NH4CL(S) SOLID AMMONIUM-CHLORIDE NH4CL

CLO- CONV CLO- CLO-

CL- CONV CL- CL-

OH- CONV OH- OH-

NH4CL CONV AMMONIUM-CHLORIDE NH4CL

AMMON(S) SOLIDAMMONIUM-HYDROGEN-SULFITE NH4HSO3



2 Components 3

Component ID Type Component name Formula

NH4HS(S) SOLIDAMMONIUM-HYDROGEN-SULFIDE NH4HS

SALT1 SOLID AMMONIUM-SULFITE-HYDRATE (NH4)2SO3*W

SALT2 SOLID AMMONIUM-SULFITE (NH4)2SO3

HSO3- CONV HSO3- HSO3-

HS- CONV HS- HS-

SO3-- CONV SO3-- SO3-2

S-- CONV S-- S-2

S2 CONV SULFUR-DIATOMIC-GAS S2

S3 CONV SULFUR-TRIATOMIC-GAS S3

S4 CONV SULFUR-4-ATOMIC-GAS S4




S8 CONV SULFUR-8-ATOMIC-GAS S8MEOH CONV METHANOL CH4O

Of the 45 components specified, COAL, BIOMASS and COALASH are

nonconventional solid components. The only properties calculated fornonconventional components are enthalpy and density. Aspen Plus includes

special models for estimating these properties for coal and coal-derived

materials. See section 4 Physical Properties for more details.



4

3 Process

Figure 1 shows t

Figure 1: IGCC P

1 The coal feed

crushing and

resulting coal

shown in Tab

3 P

Description

e process flowsheet of the IGCC process.

ocess Flowsheet

is mixed with water in the Sizing section and

screening. The PSD of BITUMOUS feed strea

slurry FUELOUT product stream in the Sizing

le 1.

rocess Description

undergoes

and the

section is



3 Process Description 5

Table 1

IntervalLowerlimit Upper limit

Weight fraction inBITUMOUS

Weight fractionin FUELOUT

1 0 20 0.11323618 0.19917354

2 20 40 0.04219685 0.09034502

3 40 60 0.05991239 0.1036473

4 60 80 0.09682933 0.1340567

5 80 100 0.1459255 0.17447921

6 100 120 0.1079199 0.12620008

7 120 140 0.0523056 0.06557651

8 140 160 0.04586571 0.0438711

9 160 180 0.0584937 0.02871873

10 180 200 0.27731484 0.03393179

2 The air separation unit (ASU) uses air to reach nearly pure Oxygen and

Nitrogen. Using Radfrac-rigorous method to separate the air afterpretreatment. The resulting Nitrogen product is 99.83 mole % pure, and

the Oxygen product is 95 mole % pure.

3 The coal-water slurry is mixed with 95% O2 separated from air in the coalgasification section and converted into middle-low heating value syngas.

4 Corrosive components such as sulfide, nitride and dust are removed from

the raw syngas in the cleaning section. The H2S-rich regeneration gasfrom the acid gas removal system is then fed into the Claus plant,producing elemental sulfur.

5 The Desulfuration section converts the hydrogen sulfide into sulfur.

6 To capture the carbon dioxide, a WGS reactor containing a two sections inseries with intercooling converts a nominal 96% of the carbon monoxide

to carbon dioxide.7 The plant will operate at extremely low emissions of regulated air

pollutants and will isolate carbon dioxide so that it can be captured.

Ammonia is produced from Hydrogen and Nitrogen.

8 The carbon monoxide and Hydrogen are synthesized here into methane(by-product) in the Methanation section.

9 Following the cleaning section, the syngas is fed into the Combined CyclePower Generation section, where the combustion energy is converted in

electric energy at high efficiency.



6 4 Physical Properties

4 Physical Properties

The global property method used in this model is Peng-Rob. This method isused for the gasification and downstream unit operations. The SOLIDS

property method is used for the coal crushing and screening section. TheIDEAL property method is used in the CLAUS Hierarchy (Desulfuration

section). The BWRS property method is used in the NH3 Hierarchy (the

previous step of Methanation). The PR-BM property method is used in thePower Generation section.

The enthalpy model for COAL, BIOMASS and COALASH is HCOALGEN and the

density model for all components is DCOALIGT. The HCOALGEN modelincludes a number of empirical correlations for heat of combustion, heat of formation and heat capacity. You can select one of these correlations by

specifying an option code in the Properties | Advanced | NC Props form

The table below lists the specifications for this model:

Model Parameter

COAL BIOMASS COALASH

CodeValue

CorrelationCodeValue

CorrelationCodeValue

Correlation

Enthalpy

Heat of Combustion

1Boiecorrelation

1

The sameas those forCOAL

1

The sameas those forCOAL

StandardHeat of

Formation

1

Heat-of-combustion-basedcorrelation

1 1

HeatCapacity

1Kirovcorrelation

1 1

EnthalpyBasis

1

Elements intheirstandardstates at

298.15K and1 atm

1 1

The density method DCOALIGT is specified on the Properties | Advanced |

NC Props form. This model is based on equations from IGT (Institute of Gas

Technology). The Aspen Properties User Guide, Chapter 6 gives moredetails on this.



5 Chemical Reactions 7

5 Chemical Reactions

The chemical reactions in this process are very complex. This model uses arelatively simple approach to represent the reactions. There are some

reactions of by-products in this model. The reactors are modeled with thebuilt-in models RStoic, REquil and RGibbs.

Reactions in each reactor and their specifications in the Aspen Plus model are

listed as follows:

Coal Gasification

Reactions in the COMB (RStoic) block

RxnNo.

Specificationtype Stoichiometry Fraction

BaseComponent

1Frac.Conversion

COAL H2O+O2+N2+C(Cisolid)+

COALASH+S-S(Cisolid)+CL2+H2 0.95 COAL

2Frac.Conversion

BIOMASSH2+O2+N2+C(Cisolid)+

COALASH+S-S(Cisolid)+CL2+H2 1 BIOMASS

Reactions in COSHYDR (RStoic) block

RxnNo.


BaseComponent

1Frac.Conversion COS + H2O CO2 + H2S 0.9 COS

Coal gasification is modeled using the Gibbs free energy minimization method

in the RGibbs model named GASIFIER. The option “RGibbs considers allcomponents as products in Products sheet” is selected so the model can

determine the phase of each of the products as fluid or solid based on their

properties.

Note: The component yield of the coal decomposition product depends on the

coal ULTANAL attributes, not on the yield specification. Calculator blocksBCONVRT and CCONVRT set up the appropriate coefficients to establish the

yield.



8 5 Chemical Reactions

Desulfuration

Reactions in BURNER (RStoic) block

Rxn

No.

Specification

type Stoichiometry Fraction

Base

Component

1Frac.Conversion H2S + 0.5 O2 H2O + S 0.65 O2

2Frac.Conversion H2S + 1.5 O2 O2S + H2O 1 O2

In this model, H2S are converted to S and SO2, and finally S will become

Sulfur.

Power Generation

Reactions in the COMB-A (RStoic) block

RxnNo.


BaseComponent

1Frac.Conversion CO + 0.5 O2 CO2 1 CO

2Frac.Conversion H2 + 0.5 O2 H2O 1 H2

Reactions in the BURNER (RStoic) block

Rxn

No.

Specification

type Stoichiometry Fraction

Base

Component

1Frac.Conversion CH4 + 2 O2 CO2 + 2 H2O 1 CH4

At very high temperature, it is assumed that components H2, CO and CH4

burn completely.

WGS

Reactions in SHFT (REquil) and SHFT2 (REquil) blocks

Rxn No. Specification type Stoichiometry

1 Temp. approach CO + H2O CO2 + H2

The water gas shift (WGS) reactor converts most of the CO contained in the

syngas into CO2 and H2



5 Chemical Reactions 9

Methanation

Reactions in the METHANZR (REquil) block

Rxn No. Specification type Stoichiometry

1 Temp. approach CO + 3 H2 H2O + CH4



10 6 Simulation Approaches

6 Simulation Approaches

Unit Operations – The major unit operations are represented by Aspen Plusmodels as shown in the following table (excludes reactor units):

Aspen Plus Unit Operation Models Used in the Model

Unit Operation Aspen Plus Model Comments / Specifications

Coal Sizing Crusher, Screen, Mixer Reduce coal particle size

Air Separation Flash2, Sep, Compr, HeatX,MHeatX, RadFrac, Heater

Separate Air into Oxygen and Nitrogen

Coal Gasification RStoic, RGibbs, HeatX,Sep, Mixer, Flash2, Heater

Decompose coal to produce coal gas

Syngas Clean-up RadFrac, Flash2, HeatX,Sep, Compr, Heater

Remove the corrosive components from theraw syngas

Desulfuration RStoic, RGibbs, Flash2 Removal of the Sulfur

Power Generation Compr, Mixer, Heater,Flash2, HeatX, Pump

Generate electrical power by utilizing thecoal gas

Methanation Mixer, REquil Produce Methane

WGS REquil, Flash2, HeatX,RadFrac

Convert the carbon monoxide to carbondioxide, and then capture carbon dioxide.

NH3 RGibbs, HeatX, Sep, Mixer,Heater, Flash2

Produce ammonia



6 Simulation Approaches 11

Streams - Streams represent the material and energy flows in and out of the

process. For the nonconventional solid components in the coal feed stream

FEEDCOAL, the specification of PSD and component attributes is required. Thevalues used are:

PSD SpecificationInterval Lower limit Upper limit Weight fraction

1 0 20 0.11323618

2 20 40 0.04219685

3 40 60 0.05991239

4 60 80 0.09682933

5 80 100 0.1459255

6 100 120 0.1079199

7 120 140 0.0523056

8 140 160 0.04586571

9 160 180 0.058493710 180 200 0.27731484

Component Attributes

PROXANAL ULTANAL SULFANAL

Element Value Element Value Element Value

MOISTURE 9.535 ASH 9.66 PYRITIC 100

FC 50.9091914 CARBON 74.455 SULFATE 0

VM 39.4517217 HYDROGEN 4.955 ORGANIC 0

ASH 9.63908694 NITROGEN 1.585

CHLORINE 0.065SULFUR 2.44

OXYGEN 6.84

Design-Specs, Calculator Blocks and Convergence - The simulation isaugmented with a combination of flowsheeting capabilities such as

Convergence, Design Specs and Calculator Blocks.

The following tables outlines the key flowsheeting capabilities used in thismodel:

Design-Specs Used in the IGCC Model

Spec Name Spec (Target) Manipulated Variables

ASU-DS-1Sets the Heat-Duty of stream NET-DUTY to 0 Watt HX-2 hot temperature

GASFR-CSCBFWSets the temperature of streamCSCSYN1 to 700 F CSC1BFW mass flow

GASFR- RSCBFWSets the temperature of stream B to1400 F RAD-BFW mass flow



12 6 Simulation Approaches

Calculators Used in the IGCC Model

Hiearachy Name(Calculator name)

Purpose

SIZING

(PC-SLD1)

Sets the value of water stream to corresponding to solidstream

ASU

(COOLANT)

Sets the temperature of streams with the same value of TCW1

ASU

(F-1)

Specify the pressure of TURB-1, VALVE-1 and VALVE-3

ASU

(HUMIDITY)

Sets the water flow and temperature according to streamAIR-A.

GASFR

(BCONVRT)

Modify the stoichiometric coefficient of each component inreaction 2.

GASFR

(CCONVRT)

Modify the stoichiometric coefficient of each component inreaction 1.

CLAUS

(AIRFEED)

Sets the flow of stream BURNAIR to corresponding to flow of

H2S

WGS

(STEAM)

Sets the flow of H2O in stream SYNGAS equal with the flowof CO in stream STEAM



7 Simulation Results 13

7 Simulation Results

The Aspen Plus simulation main flowsheet is shown in Figure 2.

Figure 2. IGCC Flowsheet in Aspen Plus

No errors occur in the simulation. Warnings occur due to physical propertyparameters PC and Freeze Point of carbon being outside the normal range.

Key simulation results are shown in the following table:



14 7 Simulation Results

Key Stream Simulation Results

Main Flowsheet Variable Value Unit

Feed

Coal Feed 277431 lb/hr

Water for crushing 149386 lb/hr

O2 for Gasification 243840 lb/hr

Air for Separation 1053143 lb/hr

Air for Combustion 2993175 lb/hr

RAD-BFW 410000 lb/hr

Water for Water-gas-shift 30352 lb/hr

Water for Methanation 18015 lb/hr

Product

Sulfur 1747 lb/hr

Methane 11827 lb/hr

Ammonia 3625 lb/hr

Power 447003 hp

Key Process Simulation results

Process Variable Value Unit

Coal Moisture before entering into

Gasification furnace 44.8%

Coal Particle Size 80% of coal < 120 mu

Gasification Furnace Temperature 1451

Combuster Temperature 1395

Air/fuelgas mole Ratio in combustor 6.84



8 Conclusions

The IGCC model provides a useful description of the process. The simulationtakes advantage of Aspen Plus’s capabilities for modeling solid components.

This includes tracking component attributes and particle size distribution, andestimating properties for coal. It also produces Methane, Sulfur and Ammonia

as by-products.

The model may be used as a guide for understanding the process and theeconomics, and also as a starting point for more sophisticated models for

plant design and specifying process equipment.

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Aspen IGCC Model

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