DEM study of mixing performance of superquadric particles in an industrial-scale ribbon mixer

Abstract

Horizontal ribbon mixers with a U-shaped vessel are widely used to mix non-spherical particles, yet the accurate characterisation of particle morphology and in-depth elucidation of the mixing mechanisms are still lacking. In this study, a superquadric DEM model is developed to study the mixing behaviours of non-spherical particles in an industrial U-shaped ribbon mixer. The model of superquadric particle mixing is first validated against experiments. Then the influences of two key particle shape-related parameters (i.e., aspect ratio and surface blockiness) on the mixer performance are comprehensively evaluated in terms of Lacey mixing index, velocity distribution, dispersion coefficient and force analysis. The results show a weak dependence of mixing behaviours on the variation of particle aspect ratio. The case of aspect ratio of 1.0 indicates the minimum degree of mixing, followed by the cases of aspect ratios of 0.5, 2.0 and 4.0. On the other hand, with the increase of surface blockiness from 2 to 7, the degree of mixing at the quasi-steady state decreases from 0.886 to 0.875, and the proportion of particles having larger contact forces also slightly decreases. This work provides a cost-effective tool to evaluate the superquadric particle mixing in an industrial U-shaped ribbon mixer.