Abstract:
Since the advent of sulphide flotation over a century ago, the processing of sulphide ores by grinding and flotation to concentrate the economic minerals into a low-bulk product suitable for smelting and refining has become common practice. This choice places the concentrator as a key lever in the business case of the mining company, however, the final tailings produced by the concentrator carry the highest and most variable amount of paymetal loss in the entire production chain of saleable metals (Cramer, 2001). For decades, the flotation process was operated by empirical heuristics and was limited by incomplete understanding. Quite often this metals loss to the final tailings could be considerably reduced with more appropriate flowsheet design and optimisation.
Since the 1980s, there has been much advancement in the technology used to diagnose the causes and find possible flowsheeting solutions to this problem, starting with the milestone work of Henley, 1983, in which he proposed the integration of geology, mineralogy, and mineral processing to synergise the processing information and develop more effective flowsheeting solutions. This was followed by the development and commercialisation of quantitative mineral measurement systems such as QEMSCAN, MLA and TIMA. Sampling practice, using the methods published by Pierre Gy in 1979, was also introduced for obvious reasons. There are now many publications on this modern integrated practice, which is called Process Mineralogy. In the best practice of Process Mineralogy, it is possible to quantify the process entitlement of performance. This gives a benchmark against which to compare existing plant performance and leads to an operations improvement programme that will close this performance gap.
Moving forward into the mining and milling of future orebodies, the challenge becomes more a matter of how to treat these difficult and complex ores, since the older, simpler and richer orebodies have already been discovered and treated. Additionally, the paymetal grades of these future orebodies are lower than was the case with the older ones, implying that more efficient processing will be necessary in order to profitably treat these future ores. It is thus critical in a greenfield project to establish the performance entitlement for the ore and to develop a flowsheet that will deliver that entitlement so as to assure the project of the maximum financial return on the investment.
This paper presents a summary of the modern toolbox and discusses some case studies in which successful flowsheeting solutions were found for both existing operations and greenfield projects.
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