The implications of choice between sour and sweet shift on process design and operation of an IGCC power plant integrated with a dual-stage selexol unit

In this study, it was sought to design and evaluate two process configurations of an Integrated Gasification Combined Cycle (IGCC) integrated with a dual-stage Selexol unit in which they differ in that one IGCC is configured with sour shift and the other is based on sweet shift. Incorporating water gas shift reactors consuming vast amount of shift steam into an IGCC involves significant alternations to the associated steam cycle, in addition to simply changing the location of the H2S removal step around the shift reactors. It turned out that the sweet shift case would require approximately 4.6 times more shift steam than the sour shift case, as the syngas after H2S removal did not have much steam in it. However, the energy penalties incurred by the carbon capture integration were estimated almost identical regardless of the choice between the sour and sweet shift. This is because the sour shift case would also undergo considerable reduction in power generation at steam cycle due to water quenching. In both shift cases, the high and low temperature shift reactors were sized using the reaction rate models reported in literature.