Removal and Enrichment of CO2 by Novel Facilitated Transport Membrane Using Capillary Membrane Module with Permeation of Carrier Solution

Publisher Summary Facilitated transport membranes attract attention because very high selectivity is obtained compared to conventional polymeric membranes. However, due to their instability and rather low permeability, they have not been employed in commercial gas separation processes. A novel facilitated transport membrane module is proposed for separation and enrichment of CO2 in which an aqueous amine solution (carrier solution) is forced to permeate the membrane. Both a model flue gas (5–15% CO2 in N2) and a carrier solution are supplied to the lumen side (high-pressure side, feed side) of the capillary ultrafiltration membrane at atmospheric pressure. Most of the carrier solution containing dissolved CO2 permeates the membrane to the permeate side (low pressure side, shell side) maintained at about 10 kPa, where the solution releases dissolved CO2 to form a lean solution. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO2. CO2 in the feed gas was successfully concentrated from 5–15 % to more than 98%. The membrane was very stable and no deterioration was observed over a discontinuous one-month testing period. Furthermore, because the membrane is always contacting with the carrier solution, the membrane becomes very stable with no open pores or liquid-unfilled pores through which gas flows to the low pressure side of the membrane unselectively.