Simulation of mass transfer in downer fluidized beds with a structure-based consideration

The gas-solid mass transfer in the downer fluidized bed is analyzed theoretically in this work. Compared to the homogeneous assumption in each calculating grid, a structure-based model was proposed that the process was divided into the mass transfer in the cluster and dispersed phases. Simulations were performed with the cooperation of the Euler-Euler two-fluid method. The model predictions are in good agreement with the previous reported experimental measurements under a wide range of operating conditions. Simulated ozone profiles show a sharp conversion in the acceleration region, and a gentle conversion in the fully developed region. The transition point is well consistent with the boundary measured experimentally. These results show that the consideration of the heterogeneous structure results in a better understanding and prediction of mass transfer in downers. (C) 2019 Elsevier Ltd. All rights reserved.