A DEM based scale-up model for tumbling ball mills

Abstract

Scale-up of mills is critical to the design and operation of industrial grinding circuits. This paper presented a scale-up model based on the discrete element method (DEM) simulation to predict the performance of tumbling ball mills. The mills of different sizes partially filled with steel balls and ground particles were operated at different loading and speeds. The breakage energy characterized by the damping energy on the ground particles were analysed. In particular, a breakage model was adopted to link the breakage energy with particle mechanical properties to predict particle breakage in the mills. The predicted grinding rates of the particles under different conditions were comparable to experimental measurements. Results indicated that while particle-particle contacts were dominant in the flow, particle-ball contacts were the main breakage mechanism of particles. Power draw and grinding rate were not always positive correlated. Excessive mill speeds caused more power consumption but resulted in reduced grinding rate. Based on the simulation data, two scale-up models were proposed to predict power draw and grinding rate. The models were tested with larger mills and show excellent prediction on power draw and reasonable accuracy on grinding rate. • Tumbling mills filled with grinding balls and particles were simulated using DEM. • The damping energy on particles is more suitable than power draw to characterise mill efficiency. • Grinding rate of mills can be calculated by linking the damping energy and powder properties. • Scale-up models to predict power draw and grinding rate of mills were developed and validated.