Ionic liquids are promising CO2 absorbents due to their excellent CO2 selective absorbability, non-volatile and chemically stable properties. In this study, a CO2 absorption system using ionic liquids in a microchannel was developed, and the effect of the flow rate ratio between CO2 gas and ionic liquid on the CO2 absorption performance was investigated. Visualization of the two-phase flow revealed that CO2 bubbles shrank in the flow owing to CO2 absorption. Image analysis of the bubble size enabled the quantification of the amount of CO2 absorbed and the absorption rate in this system. The results showed that increasing the flow rate ratio of CO2 gas to ionic liquid enhanced the amount of CO2 absorbed in ionic liquid. In addition, the CO2 mass transfer coefficient was evaluated using the two-film theory. The CO2 mass transfer coefficient exhibited an optimum value with respect to the flow rate ratio. Two-dimensional numerical simulation of the two-phase flow revealed that the effective circulation inside the liquid during advection was highest under the optimal condition.
SHUTO et al. (Sun,) studied this question.