Improvement,validation and application of CFD/DEM model to dense gas-solid flow in a fluidized bed

Dense gas-solid flow with solid volume fraction greater than 10%and at moderate Reynolds number is important in many industrial facilities such as fluidized beds.In this work,the Euler-Lagrange approach in combination with a deterministic collision model is applied to a laboratory-scale fluidized bed.The fluid-particle interaction is studied using a new procedure called the offset method,which results in several numbers of spatial displacements of the fluid grid.The proposed method is highly precise in determining porosity and momentum transfer,thus improving simulation accuracy.A validation study was carried out to assess the results using this in-house CFD/DEM code against 5-s operation of a Plexiglas spouted-fluidized bed,showing good qualitative correlation of solid distribution in the bed and acceptable quantitative agreement of pressure drops at different positions in the bed.In view of high computing cost,special emphasis is placed on effective program design,such as application of advanced detection algorithm for particle-particle/wall collisions,the multi-grid method and parallel calculation.In this context,the influence of increasing the processor number,up to 36,on calculation efficiency was investigated.