The effect of ore heterogeneity on the net value of a grinding/flotation product

Abstract

Ore heterogeneity (e.g., head grade, hardness, density and lithology) represents an important preoccupation for any given mine. The actual consequence of this variability is not always clear on the bottom line, especially when the average value remains constant over time. This paper examines the effect of random variations of two feed particle characteristics, namely the size index and grindability, on the net value of a grinding/flotation plant product. The simulated plant consists of rougher flotation cells processing the ore ground by a 2-stage semi-autogenous/ball mill circuit. Normal Gaussian distributions model the centered heterogeneity over time for three level of standard deviations (low, moderate and high) generating 32 possible scenarios. The high variability case reduces the product net value compared to the low variability one, equivalent to 1.5 M$/year loss. The additional revenues come from the ability to process more ore on average, while achieving the desired product size index in narrow variability situations. Conversely, high standard deviations lead to a slightly coarser ground product. The proposed simulation setting provides a quantitative basis to assess the financial benefits of regulatory control, and ore blending systems.