Influence of Skin Morphology On CO2/N2 Separation At Sub-Ambient Temperature

NAMS 2013, Boise, ID, USA

 

Influence of skin morphology on CO₂/N₂ separation at sub-ambient temperature

Lu Liu¹, William J. Koros²，Edgar S. Sanders³

 ¹Georgia Institute of Technology, Atlanta, GA, USA, 30332, lliu66@gatech.edu

²Georgia Institute of Technology, Atlanta, GA, USA, 30332, bill.koros@chbe.gatech.edu

³American Air Liquide, Newark, DE, USA, 19702, ed.sanders@airliquide.com

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 activation energy for permeation for CO₂, a decrease in operating temperature reduced N₂ permeance more than CO_2. At sub-ambient temperature, we achieved a high CO₂/N₂ selectivity. We also 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. The nodular-skinned fibers displayed much higher CO₂/N₂ selectivity as well as higher CO₂ permeance than dense-skinned fibers at sub-ambient temperature. This was hypothesized to be due to the introduction of added Langmuir sorption sites in the less consolidated nodular skins by CO₂ swelling. At low temperatures, due to intrinsically higher affinity constants, CO₂ molecules occupied most of such additional sorption sites, resulting in higher CO₂/N₂ selectivity.