Performance Analysis of Integrated Gasification Combined Cycle considering Turbine Modification

초록

In IGCC plants, the operating environment of the gas turbine changes from its designed condition due to its integration with the gasifier block, especially with the air separation unit. The theoretical IGCC power and efficiency enhances as the integration degree becomes lower. However, low integration degree designs would reduce the compressor surge margin and cause overheating of turbine metal considerably. The main reason for these problems is that turbine inlet gas flow increases considerably because the heating value of the syngas is much lower than that of natural gas and also additional air is supplied by the auxiliary compressor. The problems can be mitigated by modulating gas turbine operating parameters. However, the problems can better be overcome through modifications of gas turbine components. This study analyzed the modification of the turbine to accommodate the increased turbine flow. The entire IGCC plant was modeled and a full offdesign operation of the gas turbine was simulated. The performances of the IGCC plant with and without the turbine modification were compared. The limitations of the compressor surge margin and the turbine blade temperature were applied in both cases. The turbine modification enables a larger net power output in the low integration degree regime. The net plant efficiency does not depend very much on the integration degree.