Analysis of the size–dependency of relevant mineralogical and textural characteristics to particles strength

Abstract

In developing a geometallurgical characterisation for comminution, the geological information, usually captured from drill core with a resolution of down to micrometre scale, is compared with the results of comminution tests. These tests require several kilograms of material and are empirical tests that do not focus on understanding the effect of ore characteristics separately from the machine functioning.The resultant particles from the comminution process depend upon the operating conditions of the comminution devices (i.e., ball size and load, rotational speed, mill specifications) and the heterogeneity of the rock characteristics (i.e., texture and mineralogy) that influence the mechanical properties of particles which are being reduced in scale from metres to micrometres. A newer approach for comminution modelling and characterisation considers the measurement of the particle strength and minimum required energy to break them at different sizes and its application as a parameter to characterise the breakage behaviour of the ores. However, the relationship between particle strength and minimum energy with the ore characteristics that may link this information to ore' comminution potential has not been explored yet.This study focuses on selecting variables that have been previously identified as relevant for strength at the core scale (i.e., mineralogy, mineral association, grain size, grain shape and porosity) and quantifying their variation as the particle size decreases from 30 to 3 mm. The results show that for a set of ten different rock types, the median value of ore characteristics such as modal mineralogy, mineral association and grain shape does not change with particle size. However, as the particle size is reduced over that size range, these characteristics do become more variable. This behaviour is similar to the variation observed in the strength values of samples, which shows size independence within the studied particle size range, but it is not clear which characteristic has more relevance to the strength results.Detailed geological characterisation information is rarely used to predict how the geological variability may affect the plant's operation. The results from this work indicate that mineralogical and textural features might be controlling the strength of particles formed during comminution. By understanding the physics of the fracture process, these characteristics may be identified. So, a novel link between the detailed mineralogical and textural characterisation at different particle scales and the strength of particles could be developed, which would be helpful in the connection of geological data with the newest developments in comminution research.