Analysis of the mixing of solid particles in a plowshare mixer via discrete element method (DEM)

Mixing of powders is an important unit operation in many industries. Discrete element method (DEM) was employed in this study to characterize the mixing of the solid particles in a plowshare mixer. To validate the model, the simulation results were compared to the Positron Emission Particle Tracking (PEPT) data reported in the literature by Laurent and Cleary for a plowshare mixer. The parameters used for validation were the mean square of axial and radial displacements of particles. The simulation results were in good agreement with the experimental data. The validated DEM was then utilized to calculate the mixing index as a function of the initial loading, rotational speed of impeller, fill level, and particle size for a six-blade plowshare mixer. In order to employ the Lacey index for the assessment of the degree of mixing, the mixing domain was discretized using a mesh system and the variance of the mixture was calculated. Moreover, the mixing time, which is the time required to reach a homogeneous mixture, was presented as a function of the operating conditions. (C) 2015 Elsevier B.V. All rights reserved.