Multiscale simulation of fine grinding and dispersing processes: Stressing probability, stressing energy and resultant breakage rate

Abstract

Wet grinding is an important unit operation in many industrial fine grinding and dispersing processes. The main aim of this study is the development of a multiscale modelling method to predict and optimize grinding and dispersing processes in wet operated stirred media mills. In the first part of this paper, numerical CFD-DEM studies on the meso and macro scale were carried out with the focus on the acting forces, stressing probability, grinding media motion and the stressing energy distribution of a stirred media mill. The stressing probability of product particles between the grinding media was investigated at varying relative velocities in normal direction as well as at different conditions of grinding bead rotation. The determination of the stressing energy distribution on the macro scale is discussed exemplarily for a disc stirrer at three different rotational velocities. Thus, the increase in stressing frequency and energy at higher rotational speed was quantified. Moreover, the transfer of the results on an overall process simulation using population balance equations was studied. In the second part of this study the effect of the drag coefficient and the fracture processes of aggregates with various fractal dimension and solid bond properties are discussed numerically.