(111e) Membranes for Heat Integrated CO2 Capture Via Sub-Ambient Temperature Operation

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.