Super-quadric DEM study of cylindrical particle behaviours in a rotating drum

Abstract

Rotating drum is a common reactor for particle processing, yet an in-depth understanding of the fundamental physics of non-spherical particle behaviours is still lacking. Accordingly, this work established a super-quadric DEM model to accurately describe the motion of non-spherical particles, and study the solid transportation mechanisms of cylindrical particles in the active and passive regions of a rotating drum under different particle aspect ratio (AR) and rotation speed (Ω). The results show that increasing AR enhances the interlocking and stacking effects of cylindrical particles, resulting in higher lifting heights and steeper bed inclination angles. There are three mechanisms of mixing in the drum: macroscopic convection mixing caused by the internal circulation of particles, mesoscopic shear mixing caused by the mutual motion of active and passive zones, and microscopic diffusion mixing caused by particle diffusion. The time-averaged mixing index of cylindrical particles is the highest at AR = 2 but is the lowest at AR = 4 under the given conditions. The rotation speed is the primary factor affecting the mixing rate of cylindrical particles. Increasing AR reduces the residence time of cylindrical particles in the active region and cylindrical particles with an AR of 2 show the smallest residence time in the passive region. Increasing the rotation speed intensifies particle motion and slowly increases the axial time-averaged particle dispersion coefficient. The orientation between the cylindrical particles in the active zone and the horizontal direction is concentrated at 0– 30°, and the cylindrical particles in the drum tend to be perpendicular to the axis direction of the drum.