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Reduced Integration Optimization Model for Coupled Elevated-Pressure Air Separation Unit and Gas Turbine in Oxy-combustion and Gasification Power Plant

  • Maojian Wang
  • Qinli Liu
  • Yingzong Liang
  • Chi Wai HuiEmail author
  • Guilian LiuEmail author
Original Research Paper
  • 156 Downloads

Abstract

For the promising and green oxy-combustion and gasification power plant, the most efficient and assessable approach for further improvements on the current situation with less investment turned to be process optimization and integration. In this work, the gap of systematic analysis of air separation unit (ASU) and gas turbine (GT) integrations in integrated gasification combined cycle (IGCC) power plant has been fulfilled in the elevated-pressure ASU operation conditions beyond discrete case studies. Based on the conventional rigorous mathematical simulation, a series of model reductions have been proposed and applied to increase the computational flexibility. To validate the reduced model, a base case is built and settled as the benchmark, which is consistent with the industrial experiences. Afterwards, based on the reduced model, the effects of air integration on the thermal performance of IGCC power plant have been explored under the conditions of various nitrogen injection levels. The individual influences of nitrogen injection level on IGCC plant efficiency have been explored as well. To achieve best IGCC performance, the optimization of coupled air integration and nitrogen injection as a whole is completed. Based on the proposed reduced model, the three dimensional figure about systematics analysis of integration optimization for IGCC power plant is generated for the first time. Based on its two-dimensional top view, the feasible regions are identified and optimal solution is generated through nonlinear programming problem solver based on enhanced generalized reduced gradient method.

Keywords

Optimization Reduced model Integrated gasification combined cycle Air separation unit 

Nomenclature

FRair, GT

Flow rate of air injection to GT compressor.

FRair, cooling

Flow rate of the compressed air for GT cooling.

FRair, com

Flow rate of compressed air for GT combustion.

FRn, ST

Flow rate of stream going through steam turbine.

\( {G}_f^0 \)

Standard Gibbs free energy of formation.

Gsystem

Total Gibbs free energy of the system.

Hf ‐ coal

Enthalpy of formation for feed coal.

Hf, i

Enthalpy of formation for feed component i.

\( {H}_{298.15}^o \)

Standard enthalpy of formation at 298.15 K and 1 atm.

LHVcoal

Lower heating value of the feed coal.

ncoal

Total mole flow rate of feed coal.

PMAC

Discharge pressure of main air compressor.

PGTC

Discharge pressure of GT compressor.

PGTT

Discharge pressure of GT turbine.

PGT, 0

Inlet air pressure of GT compressor.

PGT, com

Inlet combusted gas’s pressure.

PHPC

Operation pressure of high-pressure column.

PST,out

Total power output of steam turbine.

rcom

Isentropic index of exhausted combusted gas.

SGT

GT compressor surge margin.

Tout

The outlet syngas temperature.

TGT, com

Inlet combusted gas’s temperature.

TGT, 0

Inlet air temperature of GT compressor.

TGTC, isen

Outlet temperature after isentropic process from GT compressor.

TGTT, isen

Outlet temperature after isentropic process from GT turbine.

THPC, con

Temperature of high-pressure column condenser.

TLPC, reb

Temperature of low-pressure column reboiler.

TMAC, isen`

Outlet temperature after isentropic process from MAC.

WMAC

Main air compressor’s work consumption.

WGTT

The work generation of GT turbine.

ηis, GTC

Isentropic efficiency of the GT compressor.

ηis, GTT

Isentropic efficiency of the GT turbine.

ηis

Isentropic efficiency of the main air compressor.

Notes

Funding information

Financial supports provided by RGC-GRF Grant No. 16211117 is gratefully acknowledged. The National Natural Science Foundation of China (U1662126) and (21476180) are gratefully acknowledged as well.

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Copyright information

© Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  1. 1.Xi’an Jiao Tong UniversityXi’anChina
  2. 2.Hong Kong University of Science and TechnologyKowloonHong Kong

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