CO_2 Absorption/Desorption on Gas-Liquid Membrane Contactors Using Monoethanolamine Solvent: Comparison of Porous and Composite Hollow Fibers

摘要

The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO_2 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 CO_2 mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO_2 absorption, because they allow to remove more than 90 % of CO_2 from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO_2 desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO_2 fluxes (0.12-0.14 m~3(STP)/(m~2h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO_2 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 um increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.