Mixing quality in mono- and bidisperse systems under the influence of particle shape: A numerical and experimental study
Mixing processes in fluidized beds involving spherical particles have been extensively studied with the discrete element method (DEM) coupled with computational fluid dynamics (CFD) in the past. However spherical particles can represent the behavior of real, complex shaped particles only to a limited degree. In this study DEM-CFD simulations relying on drag force models that consider particle shape and orientation, of four different particle groups, including spheres, cubes, elongated cuboids and plates have been carried out. The Lacey mixing index was determined and the results compared with analogously conducted experiments.
Results indicate very good agreement for the majority of the examined mixtures. Both the individual mixing processes as well as the relationships between them were accurately reproduced. Limitations of the DEM-CFD arise for bidisperse mixtures of spherical and complex shaped particles, as here particle accumulations on the outer walls occurred in the simulations which were not observed in the experiments. Analysis showed that this may be attributed to restrictions in the particle fluid force models.
Keywords: fluidised bed, DEM-CFD, experiments, mixing, Lacey mixing index, complex shaped particles.