Extended CFD/DEM model for the simulation of circulating fluidized bed

The Euler–Lagrange approach combined with a deterministic collision model, so-called discrete element method, is investigated. In this work, the physical values of fluid and particle phases are determined in separated grids. The proposed procedure allows the variation of the fluid grid resolution independent of the particle size and consequently improves the calculation accuracy. A validation study has been performed to assess the results obtained from an in-house CFD/DEM code and a quasi-2D spouted–fluidized bed of Plexiglas®. The results suggest that the extended CFD/DEM model can predict accurately the particles motion and the pressure gradients in the bed. In view of the high computing cost, special emphasis is put on an effective program design such as the application of the multi-grid method and the parallel calculation. Hence, the influence of increasing the processor numbers (up to 36) on the calculation efficiency of the extended CFD/DEM model will be analysed. Finally, the improved CFD/DEM model is applied to simulate relevant engineering equipments but in small scale with relative large particles and thus less number of particles. In this context, the hydrodynamic behaviour of gas–solid flow in a 3D circulating fluidized bed with a particle separator (cyclone) will be estimated.

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► Variation of fluid grid resolution independent of particle size improves the calculation accuracy.
► Parallelise CFD/DEM simulation should not exceed the critical number of domain decomposition.
► Precise DEM simulation requires exact properties of heterogeneous material pairing.