| Global warming caused by greenhouse gas emissions from human activities is increasing gradually, and CO2emission issue is attractive especially due to its great contribution to greenhouse effect. Membrane contactor is a new potential technology for the CO2emission reduction as a consequence with numerous advantages, such as, less investment, low energy consumption, easy operation and non-polluting.This paper investigated the separation of CO2from simulated flue gas(CO2/N2) employing polypropylene (PP) hollow fiber membrane contactor. Absorbents used herein were water (H2O), aqueous solution of sodium hydroxide (NaOH), aqueous solutions of potassium glycinate (GLY), complex aqueous solutions of potassium glycinate and piperazine (GLY+PZ). The effects of various factors, including type of absorbent, concentration&temperature of absorbent, velocity of absorbent&feeding gas flow, flow pattern, on the CO2removal efficiency and overall mass transfer coefficient were investigated. Comparing with cococurrent flow mode, the countercurrent flow showed higher separation efficiency. The order of the removal efficiency and total mass transfer coefficient of different absorbents was:NaOH> GLY+PZ> GLY> H2O. When flow rate and concentration of absorbents were fixed, CO2removal efficiency decreased with velocity of feeding gas and total mass transfer coefficient increased with velocity of feeding gas. CO2removal efficiency and mass transfer coefficient decreased with concentration of feeding gas while increased with flow rate and concentration of absorbent. Absorbent temperature was a sensitive factor for membrane absorption, both removal efficiency and overall mass transfer coefficient increased firstly and then decreased with temperature. The optimum absorbent temperatures were30℃and25℃for NaOH and GLY, GLY+PZ resepctively. Additionaly, uneven distribution of hollow fibers in shell side increased the mass transfer resistance and deteriorated absorption. |
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