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

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.