Predicting effects of operating condition variations on breakage rates in stirred media mills

Abstract

In order to model predictively the breakage kinetics in stirred media mills, it is required to determine the effect of operating conditions on the breakage rate. In this study specific breakage rates are measured for grinding experiments in wet-operated stirred media mills for various operating parameters. The experimental specific breakage rates are compared against two different models using yeast cells and limestone as test materials. A simple stressing energy model is able to predict the effect of changes in grinding bead size, grinding bead material, stirrer speed and mass concentration on the specific breakage rate. A more detailed model, which takes stressing energy distributions achieved by mill simulations and material breakage energy distributions from material tests as input, shows promising results. However, the latter is less robust and needs precise input data. Yeast cells prove to be a good test material for the purpose of model validation because of its well described breakage behaviour.