| In this work a multiphase computational fluid dynamic (CFD) model was applied to a commonly used industrial experiment known as the collapsing fluidized bed experiment. The collapsing bed experiment involves several hydrodynamic regimes including the bed expansion, bubbling, sedimentation and consolidation of the fluidized bed. Simulation of the collapsing bed experiment provides a through test of the CFD model. The three Geldart Groups C, A, and B particles were simulated in a bubbling and subsequently collapsing fluidized bed.; Detailed studies were done on grid size convergence, hydrodynamic Model A vs. Model B, various drag functions, bubble sizes of each Geldart group, sedimentation characteristics, and the role of the solids elasticity modulus, G.; Results show that hydrodynamic Models A and B, and the use of the modified Ergun equation or the MFIX code drag model have limited impact on the bubbling and collapsing bed. However the solids elasticity modulus, G, is the controlling parameter during consolidations. The simulated bubble sizes and bed collapse rate for all Geldart groups were found to be within reported experimental error.; It is also demonstrated that the traditional separate stages of the collapsing bed are not separate events and that the bubble escape and sedimentation stages are occurring simultaneously. |
