PBM-CFD Investigation of the Gas Holdup and Mass Transfer in a Lab-Scale Internal Loop Airlift Reactor

This paper investigated the problem of overall gas holdup and the oxygen mass transfer in the internal loop airlift reactor by numerical modeling and experimental validation. The population balance model (PBM) was introduced as the general model to characterize the bubble behaviors, i.e., bubble breakage and coalescence. Bubble coalescence, as a result of fluid turbulent eddy, bubble rise difference, and bubble wake entrainment, was considered in the PBM kernels. Meanwhile, bubble breakage, owing to eddy collision and large bubble instability, was included in the PBM kernels. A class method was applied to numerically solve the population balance equations. Based on the lab-scale internal loop airlift reactor, experiments and CFD simulations have been carried on simultaneously. The comparison between them demonstrated that CFD simulation results had good agreement between the experimental data and validated the effectiveness of the PBM model indirectly. Therefore, the PBM-CFD modeling provides an effective method for the problem of scale up. Finally, the flow regime transition of gas holdup difference and small bubble volume fraction are investigated in an internal loop airlift reactor.