CFD-DEM modelling of mixing and segregation of binary mixtures of ellipsoidal particles in liquid fluidizations

Abstract

Solid-liquid fluidized beds of binary mixtures are widely used in many industries. Particle segregation may occur as particles can differ in size, density, or shape. Extensive studies have been conducted in the past to understand the effects of particles size and density on the mixing and segregation, but the effect of particle shape has not been well addressed. Therefore, in the present work, CFD-DEM approach is employed to perform a numerical analysis of the effect of particle shape on the particle mixing and segregation phenomenon in liquid fluidization system. Different particle shapes from oblate to prolate are produced by varying aspect ratio of ellipsoids from 0.25 to 3, and eight binary mixtures of spheres and ellipsoids are examined. The results show that when oblate or prolate particles are added to spheres, the segregation takes place. The segregation degree increases with particle aspect ratio diverging from 1.0 and also liquid superficial velocity. The relationship of mixing index with aspect ratio under different liquid velocities is established, and a detailed explanation is given. It is revealed that increasing the projected area and hence the drag force results in the separation of ellipsoidal particles from spheres.