Scale-up of batch grinding data for simulation of industrial milling of platinum group minerals ore

• Milling parameters of a UG2 ore were measured in the laboratory.
• The milling parameters were scaled-up to industrial mill using empirical models.
• The simulated PSD displayed a close match with the actual one from a bigger mill.
• The validated model was used to optimise the bigger mill from an AR perspective.
• Optimal operating conditions were determined.

The attainable region analysis of batch grinding is a graphical method of establishing limits of performance of possible outcomes of any defined process. When applied to batch grinding, the results have often come into conflict with traditionally acceptable milling practice under which most concentrators operate (Metzger et al., 2011). This novel technique has not been tested on an industrial scale and thus, application of the scheme to full scale industrial mill is naturally the next step.This research entailed scaling-up data obtained from laboratory batch milling of a platinum ore using empirical models. Using the parameters obtained in the laboratory tests, the authors applied a scheme developed by Austin et al. (1984) to predict the selection function and breakage function parameters for an operational industrial mill on which some plant survey had been conducted. It was found that the simulated product size distributions based on this scale up-procedure displayed a close match with the actual obtained from an operational industrial mill.The attainable region plots from the scaled-up data showed that a finer product is achieved by using small balls. This is in agreement with initial findings based on laboratory batch tests only. It is also anticipated that pilot tests, industrial tests or simulations should be the next step in the quest for bridging the gap between the attainable region methodology and industrial experience. It has also been validated on industrial scale that less powder and grinding balls are needed to achieve finer grinding. However, it was interesting to note that the factors that produced a coarser product when analysed from a particle point of view were the same as those that yield the greatest amount of the desired size class when viewed from an attainable region perspective.

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