A discrete element method investigation of the charge motion and power draw of an experimental two-dimensional mill

The Discrete Element Method (DEM) has the potential to be a powerful tool f or the design and optimisation of mills. However, for DEM to gain acceptanc e within the minerals processing industry, it is necessary to show that the results obtained from a DEM simulation are valid, and that this validity e xtends over a wide range of mill operating conditions. Real grinding mills are complex multi-phase devices with a range of particle dynamics and mater ial processes that depend on the exact operating point of the mill. Mill co nditions will generally vary statistically over time. It is therefore diffi cult in this type of environment to systematically verify DEM, where some d egree of precision in the mill operation is required. With these considerat ions in mind a programme of both experimental and DEM simulation work was d eveloped. A " two-dimensional" laboratory mill was built in such a way that precise power measurement and monitoring of charge motion was possible. DE M simulation runs were matched to the experimental conditions. In this acco unt of the work, particular attention is given to the effect of mill speed on power and charge motion, and also of particle behaviour at mill speeds a bove the critical. DEM predicts the power draft and charge motion of the mi ll well at speeds below the critical speed. At super-critical speeds, the c entrifuging of material in the load was predicted, but power predictions we re not as accurate. (C) 2001 Elsevier Science B.V. All rights reserved.