Assessment of Membrane Performance for Post-Combustion CO2 Capture

This work investigates the separation performance of a commercial carbonized polyimide hollow fiber membrane module for post-combustion CO2 capture applications. In particular, the resilience to water and sulfur and nitrogen oxides (SO x and NO x ) as gas impurities was examined. The membrane exhibited a CO2 permeance of 660 Gas Permeance Units (GPU) and a CO2/N2 permselectivity of 20 at 50 °C when the permeate side was controlled at 0.2 bar absolute pressure. With an increase in water vapor in the feed stream, this CO2 permeance decreased slightly, while the CO2/N2 selectivity increased slightly, due to the combination of competitive sorption and concentration polarization. The water vapor permeance was high, which made accurate measurement difficult due to the concentration polarization but a value of 1090 ± 200 GPU was recorded. The membrane was then examined under three mixed gas conditions (i.e. SO2/CO2/O2/N2, NO/CO2/N2, and NO/NO2/N2) for a time frame of 30 days. The permeances of SO2, O2, NO, and NO2 were 650 ± 50, 155 ± 5, 125 ± 10, and 70 ± 5 GPU at 30 °C, respectively. All of these minor components had a marginal impact on the membrane separation performance during the testing period, indicating strong commercial potential. The higher permeance of SO2 and NO relative to nitrogen meant that these penetrants were concentrated in the permeate stream, which might lead to issues with downstream corrosion in a humid environment. Conversely, the permeance of NO2 was low.