An SO2 tolerant process for CO2 capture

The presence of SO2 in flue gas has a negative impact on typical CO2 capture processes utilising aqueous amines. For countries like Australia, that do not have flue gas desulphurisation, retrofitting such equipment to existing coal fired power stations is of the order of 100s of millions of dollars. In this work a new process configuration is described in which SO2 is absorbed into a fraction of the absorbent used for CO2 capture. SO2 absorption is carried out in the bottom of the absorber column into a bleed stream from the bulk solvent, and a recycle flow allows the absorbent to be near saturation in SO2. This high concentration allows a number of low cost options for sulphur removal from the absorbent such as chemical treatment and precipitation, with predicted capital and operating costs in the range of 100s of thousands for a full scale plant. The principles underlying the concept, specifically kinetic selectivity of SO2 absorption over CO2 and reactivity with amines, have been studied in the laboratory. Also a rate based model of an absorber column has been used to model the behaviour of SO2 from the application of the process concept to CSIRO's CO2 capture pilot plant at Loy Yang power station. The laboratory and modelling results support both its feasibility and utility. (C) 2014 Published by Elsevier Ltd.