Continuum Analysis of DEM Simulations of Mixing Processes

Mixing of particulate solids is one of the most important unit operations in many industries including chemical, food processing and pharmaceutical. A low mixing quality can compromise the final product and may result in loss of production and increased costs in the manufacturing process. There exists an extensive variety of mixers that can be mainly grouped into two categories depending on their main mixing mechanism: tumbling mixers (diffusion) and convective mixers (convection). Discrete Element Method (DEM) has been proved as useful modelling methodology to model the mixing process due to its ability to simulate the dynamics of the particles during the process. Nevertheless, the mixing process can involve complex dynamics that have not been fully resolved yet.

We present a numerical study on the analysis of solids mixing in different mixers including tumbling and convective mixers. The mixing process is modelled using DEM simulations and different operating conditions of the process are investigated. The particle and contact data generated by DEM simulation are post-processed using of coarse-graining technique [1,2]. This technique computes the bulk quantities of the particulate material and projects them onto a continuum field. The results of the analysis are used to investigate the flow patterns and diffusion of the particulate material and how they correlate with the mixing performance and quality [3]. Furthermore, it also helps to easily spot problematic zones of the mixer where poor mixing or segregation is happening.

[1] C. Labra, J.Y. Ooi, and J. Sun, “Spatial and temporal coarse-graining for DEM analysis”, AIP Conference Proceedings, 1542, 1258-1261 (2013).

[2] T. Weinhart, C. Labra, S. Luding and J.Y. Ooi, “Influence of coarse-graining parameters on the analysis of DEM simulations of silo flow”, Powder Technology, 293, 138-148 (2016).

[3] S. Pantaleev, S. Yordanova, A. Janda, M. Marigo and J.Y.Ooi, “An experimentally validated DEM study of powder mixing in a paddle blade mixer”, Powder Technology, 311, 287-302 (2017).