An Investigation of Various Particle Shapes Load Structure in Tumbling Mills by DEM Method

Load movement in tumbling mills involving spherical particles has been extensively studied with the discrete element method (DEM) in the past. This assumption is legitimized by the added complexity of non-spherical shape representation, contact detection and computational cost. Simulation of particles with realistic shape helps to capture the essential aspects of mechanical behavior of the particulate material. In this research, an in-house developed DEM software called KMPCDEM© was used to simulate the charge movement with spherical and non-spherical particles. At the first to calibrate the model parameters, a model tumbling mill (100 cm diameter and 10.8 cm length) with one transparent end was used. The tests were performed with steel balls and wood cubes. After calibration, a number of mill simulations were performed with the different shape of particles (spherical, cubical, and tetrahedron) to study the effect of particle shape. Comparison of the simulation and experimental results showed that the difference between the measured and predicted impact toe, shoulder angle and bulk toe angles were within 3˚-5˚ of the measured values in the model mill. The amount of in-flight of charge when using spherical and non-spherical particles was significantly different (17%). The marked difference was attributed to higher interlocking of non-spherical particles in comparison to spherical balls. The results showed that the elongation of charge was increased (5o) by considering the non-spherical shape of particles. The simulation computation time increased by 35 times when the shape of particles changed from spherical to cubical.