Development of models relating charge shape and power draw to SAG mill operating parameters and their use in devising mill operating strategies to account for liner wear

Abstract

A set of 22 three-dimensional DEM simulations are used to understand and quantify the relationship between key charge locations and three important operating parameters – fill level, lifter height and mill speed for a generic SAG mill. The charge shape and location are characterised by the shoulder, head, bulk and impact toe positions and are assessed by analysis of particle trajectories and the spatial variation of the pressure on the liner. Parametric models, created as a best fit to the DEM mill data, are used to relate these charge shape characteristics and the power draw to these operating parameters. They also allow inverse prediction of the fill level and lifter height (or wear state) from measurements of the charge structure and the mill speed. Such models can then be used to interpret experimental measurement data for SAG mills and to infer charge structure. The paper will also explore how such parametric models can be used to create operational management strategies (in terms of how to vary control variables such as target mill fill level and mill speed) in order to maintain chosen performance attributes over the wear life cycle of the liner. Examples of development of strategies that preserve for example, the bulk toe or the power draw of the mill are demonstrated.