Simulation of H2S and CO2 removal from IGCC syngas by cryogenic distillation

Abstract

The H2S and CO2 through absorption methods absorbed at low temperature and high pressure, while desorption was operated at high temperature and low pressure, presenting repeated lifting temperatures, that is, the cold fever. The captured CO2 required the further drying and compression to meet the requirements for transport and storage, existing repeated work. The cryogenic distillation used the difference of boiling point of IGCC syngas components to achieve H2S and CO2 removal through a range of multicompression, condensation and separation steps. The cryogenic distillation process was simulated by Aspen Plus, which removed water by flash, then H2S by desulfurization tower, and CO2 by decarburization tower. The tower parameters, such as reflux ratio, stage number and feed stage, were optimized to study their effect on H2S and CO2 removal rate. Under the optimal conditions, the simulated results of cryogenic distillation were compared with absorption methods (Rectisol, Selexol, Purisol and MDEA), it removed 85% of CO2 from the syngas, 98.2% of H2S and 100% of NH3 and could achieve the integration of carbon capture and storage without repeated work. The CO2 purity by cryogenic distillation process was as high as 99.94% to completely meet the requirements for transport and storage. It required no absorbent, hence avoiding solvent regeneration and loss. Its process was simple with two towers to achieve gas separation and reduce the operation cost. It is a potential to achieve H2S and CO2 removal from IGCC syngas with simple operation process and without repeated work and solvent consumption to reduce energy and cost.