Analysis of Gas Turbine Performance in IGCC Plants Considering Compressor Operating Condition and Turbine Metal Temperature

Abstract

An IGCC (integrated gasification combined cycle) plant couples a power block to a gasification block. The method of integrating a gas turbine with a gasification process is the major design option. Matching between the gas turbine and the air separation unit is especially important. This study analyzes the influences of IGCC design options on the operability and performance of the gas turbine. Another research focus is given to the estimation of the change of turbine metal temperature in the IGCC operating environment. For this purpose, a full off-design analysis of the gas turbine is used with the turbine blade cooling model. Four different syngas fuels are considered. As the integration degree becomes lower, the gas turbine power and efficiency increase. However, a lower integration degree causes a reduction of the compressor surge margin and overheating of the turbine metal. Only near 100% integration degree designs are almost free of those two problems. The syngas property also affects the gas turbine operation. As the heating value gets lower, the problems of surge margin reduction and metal overheating become more severe. Modifications of the compressor (adding a couple of stages) and the turbine (increasing gas path area) could solve the compressor surge problem. However, the turbine overheating problem still exists. In particular, the turbine modification is predicted to overheat turbine metal considerably.