Strategies for multi-scale simulation of fine grinding and dispersing processes: Drag coefficient and fracture of fractal aggregates

摘要

Wet grinding is an important unit operation in many industrial fine grinding and dispersing processes. The main aim of this study was the development of a multi-scale modelling method to predict and improve grinding and dispersing processes in wet operated stirred media mills. In the first part of the study "Multiscale simulation of fine grinding and dispersing processes" macro and process scale, e.g. stressing probability, stressing energy and resultant breakage rate, were discussed. To describe those scales in sufficient manner information of the micro and meso scale which affect the macro and process scale are important. In this second part, numerical studies on the micro scale were carried out regarding the effect of different particle sizes and morphologies on the drag coefficient and the mechanical stressing during grinding and dispersing processes in stirred media mills. The fracture processes during compression between two surfaces or grinding beads on the micro scale were investigated numerically as function of the aggregate structure and solid bond properties for aggregates with a linear gradient in fractal dimension using DEM-CFD simulations. Beside the fractal dimension, the inertia tensor was introduced as another decisive aggregate characteristic which has to be taken into account. In the first part of this study the meso and macro scale simulation will be discussed taken the acting forces, stressing probability, grinding media motion and the stress energy distribution of the stirred media mill into account. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.