Numerical simulation of CO2-ionic liquid flow in a stirred tank

Ionic liquids (ILs) are new solvents that represent a breakthrough for absorption and conversion of CO2. However, there has been little research on the hydrodynamics of gas-IL systems in stirred tanks, and this has become a bottleneck for development of IL-based reactors. In the present study, a CO2-IL ([bmim][BF4]) flow in a stirred tank was studied using computational fluid dynamics (CFD). A new drag coefficient model that is specific to a gas-ionic liquid system and a population balance model (PBM) were adopted to describe the bubble behavior, such as gas holdup and bubble size evolution, precisely. The predicted results for the total gas holdup and local Sauter diameter agree well with the experimental data. The influences of the gassing rate, agitation speed, and temperature on local gas holdup, bubble size distribution, and interfacial area for the CO2-[bmim][BF4] system were also investigated. The results of this study provide fundamental information for designing gas-IL systems for stirred tanks.