Numerical simulations of bubble behavior and mass transfer in CO2 capture system with ionic liquids

Abstract

Ionic liquids (ILs) have exhibited excellent performance on CO2 capture. However, the lack of research on transport properties has become a bottleneck of industrial application. In order to understand the bubble behavior and mass transfer performance in CO2 capture systems with ILs, a computational fluid dynamics (CFD) method with two improvements is developed in this paper. One improvement is that a drag force equation suitable for IL systems is introduced into the hydrodynamics model, and the other one is that the influence of CO2 concentration in liquid phase on viscosity of ILs is considered in the mass transfer model. Based on the developed CFD method, the bubble behavior and mass transfer properties are accurately described. The simulation results of bubble diameter, velocity and aspect ratio agree well with the experimental data with the overall deviation of 7.52%, 12.17% and 5.17%, respectively. The bubble coalescence phenomenon is illustrated by pressure gradient field analysis rather than conventional pressure field analysis, which can represent the drag force and lift force directly. The simulation results also show that the CO2 mass transfer is kinetic-controlled in pure ILs and thermodynamic-controlled in aqueous ILs, respectively.