Analysis and modelling of bead contacts in wet-operating stirred media and planetary ball mills with CFD–DEM simulations. (29th September 2015) - Beinert, S.
Abstract: Wet fine grinding is an important unit process in various industries. In the present work two different stirred media mills (one with a cylindrical stirrer; one with a disc stirrer) and a planetary ball mill are investigated using coupled CFD (computational fluid dynamics) and DEM (discrete element method) simulations. While the DEM takes the grinding media into account, the CFD is used for the calculation of the fluid flow. With these coupled simulations the grinding media movement and the resulting contacts per time unit as well as their kinetic energy at the start of the contact can be tracked. In a first step these values are compared to an analytical model that was originally developed for wet operating stirred media mills. To compare different types of mills the type of contact along the stress energy spectrum, which is based on the kinetic energy of the grinding media, is important. Therefore, in the present work an extended contact analysis was developed that enables the description of normal impact and torsion, shearing and rolling induced by rotational and translational velocities. The extended analysis enables the complete characterisation of the energy spectrum for different mill types and operating conditions. Abstract : Highlights: We investigated the grinding media movement in wet operating mills with CFD–DEM simulations. The influence of mesh size, steady state and reproducibility were discussed. An existing analytical model for stirred media mills was compared with the simulative results. An extended contact analysis was developed (consider impact, torsion, shearing and rolling). This analysis was used to quantify the contact type for the entire stress energy spectrum.