Process simulation of a dual-stage Selexol process for 95% carbon capture efficiency at an integrated gasification combined cycle power plant

It was aimed to simulate a conventional dual-stage Selexol process for removing CO2 and H2S simultaneously from a synthesis gas (syngas) originated from a typical Integrated Gasification Combined Cycle (IGCC) power plant driven by a dry-coal fed gasifier using Honeywell UniSim R400. The solubilities of syngas components on Selexol were predicted by temperature-dependant Henry's law constants being newly evaluated in this study based on the experimental data in Xu et al. (1992). The operating conditions of the dual-stage Selexol unit were determined so as to meet simultaneously various performance targets, such as 99+% H2 recovery, 90% CO2 recovery, 99+% H2S recovery, and less than 20 ppm H2S in CO2 product. By and large the resulting energy consumptions of the Selexol process were in good agreement with those reported in DOE NETL (2010) that this study was based on. It was shown that the integrated dual-stage Selexol unit could achieve 95% carbon capture rate as well as 90% by simply changing the operating conditions. By contrast a CO2 removal Selexol process having not an input of lean solvent generated by thermal regeneration could not achieve 95% carbon capture rate due to a pinch point formed at the top of the CO2 absorber.