Mathematical modeling of CO2 absorption with ionic liquids in a membrane contactor, study of absorption kinetics and influence of temperature

Abstract

AbstractBACKGROUNDThis work presents a comprehensive study of carbon dioxide (CO2) capture from CO2/N2 mixtures in a hollow fiber membrane contactor (HFMC). The absorbents considered were three different ionic liquids (ILs): 1‐ethyl‐3‐methylimidazolium acetate ([emim][OAc]), 1‐ethyl‐3‐methylimidazolium ethylsulfate ([emim][EtSO4]) and 1‐ethyl‐3‐methylimidazolium methyl sulfate ([emim][MeSO4]). A comprehensive two‐dimensional (2D) mathematical model for the transport of CO2 was developed and solved for steady‐state and pseudo steady‐state modes. For pseudo steady‐state mode, the 2D model was linked with a dynamic model applied on a tank from which the IL was recirculated into the shell side of the HFMC.RESULTSThe model showed excellent agreement between the simulations and experimental data within the range of 2 to 5% standard deviation. Initially, overall mass transfer coefficients of 7.6 × 10−6 (m s−1), 1.6 × 10−6 (m s−1) and 3.7 × 10−6 (m s−1) were obtained for [emim][OAc], [emim][EtSO4] and [emim][MeSO4], respectively. Solubility, diffusivity and absorption efficiency of CO2 in ILs showed strong dependence on the temperature. Furthermore, concentration drop in the wetted portion of the membrane, effect of porosity, tortuosity, gas and absorbent flow rates were systematically studied.CONCLUSIONFindings of both experimental and modeling work suggests that in spite of the difference of extraction efficiency, these ILs are potential absorbents for CO2 in membrane contactors. Moreover, the modeling approach was found very effective to predict the absorption behavior of CO2 in ILs and to study the wetting phenomena and parametric effects. © 2019 Society of Chemical Industry