Auto-SEM particle shape characterisation: Investigating fine grinding of UG2 ore

Abstract

For processing low grade complex ores there is a need to improve operation efficiency to maintain profitability. This may be done by introducing more efficient equipment or improving the understanding and modelling of minerals processing circuits. Particle shape can have an impact on numerous processes through its effect on drag coefficients, rheology, and particle bubble interactions. Understanding these effects in greater detail could significantly improve model capabilities. Automated scanning electron microscopy (Auto-SEM) can provide two dimensional particle shape measurements for thousands of particles, complemented by mineralogical information. These measurements are readily available from previous mineralogical studies and have the potential to be very useful.This study shows how Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN) can be used to differentiate between shape characteristics of specific mineral particles within a sample. The strengths and weaknesses of various shape descriptors were investigated including effects of image resolution and particle orientation. Roundness was found to be better than perimeter dependent descriptors such as angularity, and is recommended for studies of fine grinding which are limited by resolution. A novel approach for shape characterisation using roundness and aspect ratio in conjunction was developed and demonstrated. The potential value of the mineral specific shape characterisation enabled by Auto-SEM is demonstrated with a comparison of the major components of Upper Group 2 chromitite (UG2) platinum ore comminuted with different mill types.