A preliminary model of high pressure roll grinding using the discrete element method and multi-body dynamics coupling

Abstract

The HPGR is properly regarded as one of the most important recent developments in the field of size reduction. This success is mainly associated to its improved energy efficiency, grinding capacity, lower sensitivity to grindability variations and higher metal recovery in downstream processes compared with conventional grinding technologies such as ball mills and cone crushers. It comprises two counter-rotating rolls mounted on a sturdy frame, one of which is allowed to float and is positioned using hydraulic springs. Comminution in the HPGR is largely determined by the pressure exerted on the bed of particles by the hydraulic system. The paper describes how the coupling of the multi-body dynamic simulation with the discrete element method can be effectively used to describe the performance of the HPGR. The model considers important variables, including the HPGR rolls geometry and design, the hydraulic spring system start-up parameters and the material loading response, to describe key operational outputs as material throughput, operating gap and roller pressure distribution. The preliminary version of the model has been used to demonstrate qualitatively the effect of material properties on the operating gap, the pressure and the energy consumption of a laboratory-scale HPGR. Predictions using the model have been compared to those from phenomenological models, showing good agreement, but also limitations in the DEM approach with the current simple particle replacement model to predict the working gap at high initial nitrogen pressures.