CFD modeling the hydrodynamics of binary particle mixtures in bubbling fluidized beds: Effect of wall boundary condition

The hydrodynamics of binary particle mixtures differing in size and density in low gas velocity bubbling fluidized beds were simulated by a multi-fluid Eulerian model incorporating the kinetic theory of granular flow. Parametric studies of the particle–wall restitution coefficient and specularity coefficient were performed to investigate the influence of wall boundary condition on the predicted segregation and mixing behavior in terms of jetsam concentration and velocity distribution. The predicted axial and radial concentration distributions were compared with available experimental data. The results demonstrate that the particle–wall restitution coefficient only plays a minor role in predicting the segregation and mixing of binary particle mixtures in bubbling fluidized beds. For the segregation process, the predicted segregation is significantly affected by the specularity coefficient. No segregation can be predicted for small specularity coefficients, while for the mixing process, the predicted jetsam concentration distributions are almost unaffected by the specularity coefficient, although the jetsam velocity distributions are significantly influenced.