Effects of SO2 on CO2 capture using a hollow fiber membrane contactor

Membrane gas absorption technology is a promising alternative to conventional technologies for the mitigation of acid gases. In this study, with a polypropylene (PP) hollow fiber membrane contactor as absorber and a packed column as stripper, the influence of SO2 on the CO2 capture from coal-fired power plant flue gas was investigated in an absorption–desorption experimental set-up using aqueous monoethanolamine (MEA) as the absorbent. The experimental results showed that the MEA loss per ton captured CO2 increased with the addition of SO2, resulting in sharp decreases in CO2 removal efficiency and mass transfer rate of CO2 after initial several days of operation. This tendency is mainly attributed to the promotional effect of SO2 on the degradation of MEA by the formation of sulfate. Thus, it is necessary to regenerate MEA using a reclaimer in this case. The respective SO2 concentrations at the outlets of absorber and stripper remained constant values of 24 and 120 ppb throughout the operation although the CO2 removal efficiency decreased dramatically with time. This co-capture of CO2 and SO2 could play an important role in further desulfuration, thus alleviating the burden of desulfuration to some extent and benefiting the subsequent CO2 purification and storage. More progresses are greatly needed in high-efficiency and stable absorbents, high-efficiency reclaimer, and methods to reduce MEA loss by evaporation.

Graphical abstractMEA loss and the formation of different degradation species for CO2 capture with the impurity of SO2.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► SO2 resulted in sharp decreases in removal efficiency and mass transfer rate of CO2. ► Sulfate showed the biggest contribution to the MEA loss followed by evaporation. ► SO2 concentrations at the outlets of absorber and stripper remained 24 and 120 ppb.