Numerical study on the elucidation of powder mixing mechanism in a container blender

Numerical simulations by the discrete element method (DEM) and DEM-computational fluid dynamics (CFD) have greatly facilitated the investigation of mixing kinetics in various particle mixing systems, including the common container blender. Recently, airflow within the container blender has been found to remarkably improve the mixing efficiency of fine particles. Nevertheless, a wide range of particle sizes has not been examined regarding the airflow effect. Thus, to comprehensively understand the particle size dependence of the airflow impact on powder mixing, this study aims to investigate the relationship of various particle diameters and powder mixing in an industrial container blender. An advanced mathematical-statistical method, named proper orthogonal decomposition-analysis of variance (POD-ANOVA), is used to clarify the complex mixing mechanisms. Numerical results show that airflow has different impacts on the mixing efficiency determined by the particle size range. The mixing of coarse particles with diameters above 1.000 mm is not significantly influenced by airflow, whereas medium-sized particles, ranging from 0.5000 to 1.000 mm, display reduced mixing efficiency as particle size decreases. Conversely, for small particles (0.2000–0.5000 mm), the mixing efficiency improves when decreasing the particle size. The underlying variations of powder mixing mechanisms have been well elucidated, and the convection mixing mechanism is found to be crucial in determining the mixing efficiency via POD-ANOVA analysis. Consequently, this work provides critical insights into the airflow effect during powder mixing, which has been verified to be highly dependent on particle size and is dominated by the convection mechanism.