Separation and concentration of CO 2 by capillary-type facilitated transport membrane module with permeation of carrier solution

Abstract

A novel facilitated transport membrane module for gas separation is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high-pressure side, feed side) of the capillary ultrafiltration membrane module and flow upward. Most of the carrier solution which contains dissolved solute gas, CO 2 in the present case, permeates the membrane to the permeate side (low-pressure side, shell side), where the solution liberates dissolved gas to become a lean solution, and the lean solution is returned to the lumen of the capillary module by a pump. This type of capillary membrane module was applied to the separation of CO 2 from model flue gases consisting of CO 2 and N 2 using various amines as carriers or absorbents of CO 2. The feed side pressure was atmospheric and the permeate side pressure was controlled at 9–27 kPa. CO 2 in the feed was successfully concentrated from 1.5–15 to 98.5–99.8 mol%. When the CO 2 mole fraction in the feed was 0.1 and the mean residence time of gas in the module was 0.28 s, the CO 2 permeance was 3.8×10 −4 mol m −2 s −1 kPa −1 (1.1×10 −3 cm 3 cm −2 s −1 cmHg −1) and the CO 2 recovery was 76%. The selectivity of CO 2 over N 2 was in the range from about 800 to 8000. The membrane was very stable over a discontinuous 4-month testing period. The energy consumption was found to be much smaller than those of conventional chemical absorption and membrane separation processes.