The Effect of Particle Size Distribution on the BWI and Energy Consumption of Harder Ores

When it comes to fragmentation, the grinding process is the most significant in terms of energy consumption and can directly affect the viability of mining activities, especially in this new context of energy transition and hard minerals. Over the years, several researchers have presented various procedures for determining grindability. However, in practice, the Bond test remains one of the most widely used methods. The aim is to determine the Bond Work Index (BWI), which would describe the energy consumption to reduce a particle of infinite size to the so-called P80 (80% passing through 100 µm). However, the Bond test is time-consuming and does not take into account the particle size distribution of the ore during the test; it is only used when passing through the test mesh. Therefore, this study proposed a test similar to Bond, but carried out with a maximum of three grinding cycles, in addition to determining the SWI (Simplified Work Index) by means of a granulometric factor. The Reduction Ratios (RR) or A80/P80 were correlated with the SWI and the SWIop (Simplified Operational Work Index)/SWI ratios or (RWI—Relationship between Work Index: SWIop/SWI). The effect of the particle size distribution of the feed in restricted size ranges was also verified. The results showed that the SWI estimated by the new methodology showed relative differences of less than 12% when compared to the BWI values. And that the particle size distribution of the feed influenced the results. The correlations (RR, SWI) and (RR, RWI) are strong, with R2 very close to 1.