CO2 Absorption/Desorption on Gas-Liquid Membrane Contactors Using Monoethanolamine Solvent: Comparison of Porous and Composite Hollow Fibers

Abstract

The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO2 absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO2 mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO2 absorption, because they allow to remove more than 90 % of CO2 from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO2 desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO2 fluxes (0.12-(STP)/(m2·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO2 absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.