CFD-PBM simulations on hydrodynamics and gas-liquid mass transfer in a gas-liquid-solid circulating fluidized bed

The bubble size distribution, phase holdups and mass transfer characteristics in a gas-liquid-solid circulating fluidized bed (GLSCFB) riser were simulated through the three-fluid (Euler-Euler-Euler) approach, the population balance model (PBM) and the gas-liquid mass transfer models. The three-fluid approach coupled with the PBM included the effect of bubble coalescence and breakage on the interphase forces, and gave good predictions on the bubble size distribution and the phase holdups. The bubble size distribution obtained from the PBM, together with the gas holdup, was used to calculate the gas-liquid interfacial area. For the mass transfer coefficient k(l), the penetration model, the surface renewal model and the eddy cell model were tested and compared under varied superficial gas velocities, among which the eddy cell model provided the most reasonable prediction fork. The effects of superficial gas, liquid velocities and particle circulating rate on the bubble size distribution, the phase holdups, the gas-liquid interfacial area, the mass transfer coefficient and the volumetric mass transfer coefficient were investigated numerically. It is concluded that the CFD-PBM coupled model, together with the eddy cell model could predict the hydrodynamics and mass transfer in a GLSCFB riser reasonably. (C) 2019 Elsevier B.V. All rights reserved.