Pulverized coal (PC) power plants emit CO2 in flue gas at atmospheric pressure with a volume concentration of 10-15%. Post-combustion capture of CO2 is a challenging application but has the greatest near-term potential , because it can be retrofitted to existing state-of-the-art power plants. Membrane-based separation is a promising technology for post-combustion CO2 capture. Our study explored sub-ambient temperature conditions for CO2/N2 separation with Matrimid® asymmetric hollow fiber membranes. Due to the lower permeation activation energy for CO2 , a decrease in operating temperature reduced N2 permeance more than CO2 , resulting in high CO2/N2 selectivity. We found that skin morphology had great influence on hollow fiber membrane’s separation performance. Fibers with two kinds of skins were successfully spun: fused nodular skins and isotropic dense skins. At -50 °C , the nodular-skinned hollow fiber membranes displayed CO2/N2 selectivity higher than 150 with CO2 permeance higher than 100 GPU. However , the CO2/N2 selectivity and CO2 permeance for dense-skinned samples were much lower. This was hypothesized to be the synergistic effect of increased diffusivity selectivity and solubility selectivity in nodular-skinned hollow fiber membranes at sub-ambient temperatures.
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