Effects of drag force correlations on the mixing and segregation of polydisperse gas‐solid fluidized bed by CFD‐DEM simulation

Abstract

Abstract The dense gas‐solid fluidized beds with polydisperse particles are commonly encountered in the chemical industry. In this study CFD‐DEM simulation of ternary particles in a bubbling fluidized bed were studied to assess four polydisperse drag correlations, using experimental data from Olaofe et al.[1] as the benchmark. The following was shown: (i) the drag force models of Sarkar et al.,[2] Cello et al.,[3] and Rong et al.[4] can correctly predict the minimum fluidization velocity of the mixture of ternary particles, but Gidaspow's model significantly over‐predicts this;[5] (ii) no model can accurately predict the experimental segregation degree at different gas velocity, but for the cases that were studied, the models from Cello et al.[3] and Sarkar et al.[2] correlated relatively better with Olaofe et al.'s[1] experimental data than others; and (iii) detailed force analysis found that the collisional force of each type of particles is on average not equal to zero, especially for a system that is strongly segregated. In addition, the differences of drag force for different sizes of particles are the key reason for size segregation rather than pressure gradient force.