Parametric study of GT and ASU integration in case of IGCC with CO2 removal

One of the most promising technologies for coal-to-electricity conversion considering CO2 removal is coal gasification process integrated with a combined cycle (IGCC). One of the ideas for IGCC efficiency increase is process integration including well-known ASU-GT coupling by compressed air and nitrogen streams. In this case, the integration idea is based on supplying of the compressed air from the GT compressor to ASU where it replaces air compressed in electrical-driven compressors. From the energy effectiveness point of view, the integration should reduce the electricity consumption in ASU and energy losses in auxiliary transformer. It should also be noted, that the polytropic efficiency of large compression stages like for GT compressor is usually higher than for smaller units as for ASU compressors. The main goal of the present paper is to check if the air-side ASU-GT integration has a positive impact on the IGCC efficiency, assuming that the GT unit is a syngas-dedicated machine and massive CO2 removal is applied. The general conclusion is that in case of dedicated GT unit, where the compressor pressure ratio is relatively high, the ASU-GT integration is not recommended from the efficiency point of view.

► For syngas-dedicated GT units the air-side ASU-GT integration is not an optimal solution from thermodynamic point of view.
► Overall integration benefits may come only from possible reduction of the equipment capital costs.
► The newer GT – the lower possible benefits from integration.