Rigorous non-isothermal modeling approach for mass and energy transport during CO2 absorption into aqueous solution of amino acid ionic liquids in hollow fiber membrane contactors

Abstract

In the current study, a rigorous modeling approach was used to develop a mathematical model for the non-isothermal absorption process of CO2 in hollow fiber membrane contactors (HFMC). Four amino acid-based ionic liquids (ILs) namely, tetramethylammonium glycinate [N1111][Gly], 1-ethyl-3-methylimidazolium glycinate [C2mim][Gly], 1-butyl-3-methylimidazolium glycinate [C4mim][Gly] and 1-hexyl-3-methylimidazolium glycinate [C₆mim][Gly] were used as absorbents. These ILs have never been implemented for the membrane contactor CO2 absorption operations both on the lab scale and industrial scale. Wide ranges of operating conditions were investigated for freshly unloaded absorbents and partial conversion of absorbents considering steady-state conditions for the model. Non-wetting conditions were adopted by keeping very low transmembrane pressure. The non-isothermal model predicted a significant temperature rise along the contactor length, ranging from 10 to 25 K, which further affected the absorption and reaction kinetics. Simulations confirmed the strong influence of absorbent concentration and mild influence of process temperature on the separation performance of ILs, CO2 boundary flux, and reaction kinetics between CO2 and ILs. Very fast absorption of CO2 near the interface justified the dominancy of the chemisorption for the current absorption. Finally, the comparison with experimental data evidenced the identical trends and hence validated the model.