Mamoon Asif || Zubia Saleem|| Mubeen Kamran

Project Supervisor: Dr. Arshad Hussain Department of Chemical Engineering. SCME (NUST), Islamabad

Abstract

As Pakistan is moving deeper into the clutches of energy and natural gas cri-sis, it has become crucial to search for new sources to meet our increasing de-mands. Coal is believed to be the future energy carrier for the world; however, due to environmental hazards the pro-duction of electricity from coal is not being commercialized on a large scale. Integrated Gasification Combined Cycle(IGCC) process is the solution for this problem. Lignite is the most abundant coal present in Pakistan which has a very lower heating value. To utilize the full capacity of lignite, the coal-water slurry feed is converted into Coal-CO2 Slurry by the PHICCOS Process. This process increases the Net IGCC and Cold Gas Efficiency by 15%. IGCC uses the Pre-Combustion Technique to remove CO2 hence protecting the environment.

Motivation

Coal is an alternative source for electricity production and with igcc less harm is done to the environment as copared to the con-ventional gasification processes.

Entrained Flow Gasification is Environmen-tal Friendly.

IGCC reduces the waste (clean and healthy Pakistan)

Chemistry of Gasification

C + 0.5O2 →CO

C + H2O →CO + H2

C + 2H2 →CH4

CH4 +1.5O2 →CO + 2H2O

CO + H2O→CO2 + H2

CO + 0.5O2 →CO2

S + H2 →H2S

S + O2→SO2

CO + H2S →COS + H2

N2 + 3H2 →2 NH3

Selection Criteria

Entrained Flow Gasifier

Material Input

Coal-CO2 Slurry (kmol/ 10846.02

Oxygen Rich Stream 1677.63

Steam (kmol/hr) 524.63

Total 13048.28

Energy Input Materials Energy (kcal) Coal (CV) 3 x108

Enthalpy of steam in gasifier 2.735 x 106

Sensible Heat of CO2 3.35 x 107

Total Energy of the input Feed 3.36 x 108

Thermal Efficiency 77%

Cold Gas Efficiency 74.4%

Hot Gas Efficiency 97.2%

Syngas Composition Composition Mol %

CO 6.68 CO2 32.3 O2 13.7 N2 0.448 H2 38.5

CH4 1.52 H2S 0.025 COS 0.1362 SO2 0.17 NH3 0.2605

H2O 5.86 Total 100

Selected Processes

SECTION UNIT KEY FOCUS METHOD ASSISTANCE

Entrained Flow Gasifi-er

Process To convert the Coal-CO2 Slurry into syngas and slag

Gasification Flame Fired

Air Separation Unit

Operation

To separate air into N2 and O2 to ensure supply into Entrained Flow Gasifier and Combustor

Cryogenic Distillation

Carbon Molecular Sieves

Shift Conversion

Process

Convert CO to CO2 and maximum hy-drogen production

Catalytic Shift Conversion

Iron Oxide Catalyst,

Copper Oxide Catalyst, Steam

CO2 and H2 S Removal (AGR)

Process

To reduce concentration of CO2 and H2S is also removed.

Absorption

SELEXOL Solvent

COS Hydrolysis

Process

Conversion of COS to H2S and CO2

Catalytic Bed Reactor

Catalyst

(Nickel Based)

Combustor

Process

To combust the clean syngas in order to run the gas turbine

Complete Combustion

Clean Syngas as fuel

Process Flow Diagram

Results & Analysis

Cost Estimation

The major advantages of this project scheme are the efficient production of power using environmentally harm-free processes by re-ducing the emissions of sulfur dioxide, par-ticulates and carbon dioxide and efficient utilization of recovered heat from syngas cooling system and minimal waste produc-tion as the by-products are marketable.

Conclusions

References

1) SIMULATION AND ECONOMIC EVALUATION OF COAL

GASIFICATION WITH SETS REFORMING PROCESS FOR POW-ER PRODUCTION by Zachary Hoffman

2) Technical Documentation: Integrated Gasification Com-

bined Cycle Systems (IGCC) with Carbon Capture and Storage (CCS) Authors Edward S. Rubin, Michael B. Berkenpas, H. Christopher Frey, Chao Chen, Sean T. McCoy, and Constance

EQUIPMENT COST (K$)

Entrained Flow Gasifier

23000.11

ASU & Compressor 4000.68

HTSC

27.4

LTSC

13.682

AGR (Absorber) 4064

Convective Cooler

9661.7

Process Condensate Han-dling Section

16708.05

Energy Output Materials Energy (Kcal) Syngas (CV) 250 x 106

Enthalpy of H2 O 8.81 x 106

Sensible heat of Syngas 67.7 x 106

Heat Loss 9.49 Total Output of Energy (KW) 3.36 x 108

Material Output

Slag ((kmol/hr) 170.196 Syngas (kmol/hr) 12877.844

Total 13048.04

•Feed rate of 10,846 kmol/hr (80%-20%) Coal-CO2 slurry results in a production of 267 mw Power.

•The CO2 that has been sequestered from the process is used in the preparation of CO2-Coal Slurry hence optimizing the process.

•Pre-Combustion technique is more effi-cient than Post-combustion since CO2 is at high partial pressure and is easily re-movable.

•Entrained flow gasifier is the ideal choice for this gasification since the temperature is above ash slagging tem-perature and proper mechanism is avail-able for ash removal. Moreover, it can gasify all types of coal regardless of coal rank, caking characteristics or coal fines’ amount.

Net Efficiency of the plant calculated is about 66% which is enough to meet the desired electricity needs.

Capital cost is high but due to the modifications done and also less mar-ginal cost the process becomes feasible.

Power Production Using Syngas From Coal-Water Slurry

Calorifiic value of coal

HHV (kJ/kg) 14551.161

LHV (kJ/kg) 12689.798 Net Plant Effi-ciency 66%