Modeling flow in pulp lifter channels of grinding mills with computational fluid dynamics

The current study is aimed at improving the performance of autogenous grinding and semiautogenous grinding mills. In particular, the material transport issue is the focus since the efficiency of mill discharge via grate, pulp lifter channels, and discharge trunnion determines the mill throughput. The objective of this study is to develop a computational tool, and a simulation model which is built on fundamental physics of the process. Mainly, the simulation model is expected to give reasonably accurate predictions of free surface profiles inside the pulp lifter channels and volumetric flow rate out of the pulp lifter channels. Employing the computational fluid dynamics as the central component, the study puts forward the mathematical modeling of the pulp flow in the pulp lifter channels along with experimental validation of simulation results. First, past modeling studies of grinding mills are reviewed, with the focus on the material transport. Then the experimental methodology is presented. The explanations of flow dynamics are given from a theoretical point of view. Primarily, the free surface profiles and the dynamic discharge profiles are captured experimentally. The proposed model that includes rotation of the pulp lifter channel is validated by comparing the predictions of the model to experimental results. Having proved the pulp flow dynamics by the experimental study, the computational fluid dynamics methodology is employed for the prediction of plant scale mill data. The free surface profiles inside the mill are well captured by the CFD methodology, giving insight into understanding the pulp flow. The volumetric flow rate predictions conform to the experimental data as well as the plant scale mill survey data. Modeling of pulp flow in the pulp lifter channel by computational fluid dynamics is beneficial in the sense that it yields comprehensive information about the specifics of the operation, making it possible to investigate in detail such phenomena as flow back and carry over flow in semiautogenous grinding mill pulp lifter channels.