Verification of Polyhedral DEM with Laboratory Grinding Mill Experiments

Abstract

The simulation of grinding mills with the discrete element method (DEM) has been advancing. First, it emerged as a method for studying charge motion with spherical balls and predicting the power draw of the mill. Subsequently, studies on liner wear, charge motion with ellipsoidal and polyhedral shaped particles simulated with three dimensional DEM followed. Further, the impact energy spectra computed in the DEM algorithm is leading to the development of models for the breakage of brittle particles in mills. The core elements in such simulations are the shape of particles in the mill charge and the power draw of the mill due to operating variables. To advance the field, we present a set of experimental data and the corresponding DEM validation results for a 90 × 13 cm mill. The DEM algorithm uses the volume-overlap method which is more realistic for multifaceted irregular particle collisions. Further, we use the scanned shape of the rock media and multifaceted spherical shape for the grinding media to represent as close as possible the actual charge in the mill. First, we present DEM validation for spherical grinding media-only experiments, rock-only experiments, and a mixture of spherical grinding media and rocks, as well as aluminum cubes only to represent the theme of particle shape. Finally, a discussion of the contact mechanics parameters in the four modes of experiments is given. Since the feed ore to plant scale mills can vary in shape, mill simulations with scanned shape of typical particles are the future for more accurate results.

Effect of grinding media shape on the particle size distribution of UG2 ore using the response surface methodology central composite design

“…Several researchers have studied the effect of grinding media shapes in ball milling using cylpebs, cubes, ellipsoids, spheres, and other media. 5–8 Khumalo et al, 9 investigated the effect of cubes, spheres, and ellipsoids on particle breakage using the population balance model and attainable region technique which showed that spheres and ellipsoids give higher values of the required product size than cubes. Simba and Moys, 10 also used the same media shapes to investigate their effect on milling kinetics and found that a mixture of the shapes can increase the breakage rates in some mill environments though spherical media proved to be the best.…”