Computational fluid dynamics investigation of gas–liquid two-phase flow in aerated stirred reactors

An extensive investigation of multiphase flow and mass transfer in aerated stirred reactors will provide methods for improving reactor performance. In this study, a computational fluid dynamics (CFD) model that characterizes gas–liquid two-phase flow in a reactor equipped with a dual-impeller and a gas sparger was developed. The numerical simulations were performed to predict the gas and liquid flow fields, gas holdup, and volumetric mass transfer coefficient (kLa). Experiments were conducted to determine bubble size distribution, bubble diameter, gas holdup and kLa with respect to impeller speed, gas flow rate and temperature. The CFD model was validated against the measured kLa and gas holdup, and then five mass transfer models were examined to propose an appropriate one that would best predict the kLa. Moreover, the effects of agitation and aeration on the overall gas holdup, the kLa, and the power consumption were evaluated. The results demonstrate that reactors with a rounded-bottom work better than those with a flat-bottom in terms of hydrodynamic performance and mass transfer efficiency, that the optimal number of holes in a gas sparger is determined by the mixing scenarios of a reactor, and that the mass transfer coefficient increases with the increase in impeller speed and operating temperature.