Development of ore sorting and its impacts on mineral processing economics


Ore sorting technology represents a step-change improvement in eco-efficient comminution strategies. Sorting equipment offers the benefit of greatly reducing the comminution energy required per tonne of mineral processed by identifying stones that contain ore and separating them from stones that do not contain ore so that barren stones are not milled. The paper submitted with this application is the first of its kind to identify, quantify, and explain the operational and economic benefits to ore sorting in a traditional mineral processing circuit.

To date, most members of the mining and mineral processing industry have been aware of ore sorting and the benefits it offers. Introduced nearly thirty years ago, sorting was first adopted by the diamond and precious metal industries. In these sectors, the value of the minerals sorted was so high that the capital payback could be easily justified. Similarly, the throughput tonnages across the first generations of sorters were relatively low in these industries. However, sorting was not as readily adopted in other mining sectors because the sensors could not sort at the throughput required in higher volume minerals. Therefore, many miners rejected sorting as a pipe dream that could not deliver. Advances in sensor technology over the past decade have dramatically improved the capabilities of sorters: they can now sort at higher throughputs, identify smaller grains of mineralization, and offer even greater economic benefit. However, because the technology was introduced and rejected so long ago, it is finding it difficult to make in-roads to the hard rock mining industry.

This resistance has cultivated a knowledge gap between the mining industry and the sorter manufacturers. Both parties understand that real economic benefits exist with functional sorters capable of meeting a mine's demands. To date, vague "hand waving" arguments for sorting have been the norm. However, it is impossible for a miner to commit to a technology and make serious investment on qualitative guarantees of process improvements and equipment performance. The typical argument follows these lines: sorters reject stones not bearing mineralization, which means you have to mill less, which means you save money! Lacking in this explanation is the "how much;" how much does it cost to run these equipment, and how much money does one save.

Development of ore sorting and its impacts on mineral processing economics addresses these exact questions by chronicling a detailed pilot study on sorting equipment of an operating molybdenum mine's ore. The perfonnance of the equipment was then used to build mass balance models of a typical comminution circuit. The model generated power consumption details to allow the authors to study how different sorting efficiencies impacted the operating cost of the milling plant. In the end, it was found that sorting could reduce comminution costs by over 60% while increasing throughput in the mill. (The exact numbers and assumptions are contained in the paper.) Anned with these data, the authors propose future studies investigating the upstream ( e.g. at the mine site concerning mine life and mine schedule) and downstream (e.g. flotation perfonnance and waste handling) impacts of sorting; this study is currently underway by Lessard and McHugh with others.

The critical value of this paper is that it presents quantifiable data on how ore sorters improve comminution efficiency. In speaking with sorter manufacturers, the authors learned that the equipment manufacturers had never seen this type of data and realized it had been lacking for the past decade. This work has been well­ received by the industry and is part of the reason why miners are becoming more receptive to sorting technology. Implementation of ore sorting is one component of a comprehensive strategy to facilitate more eco-efficient, more productive , and less costly comminution installations. The authors here have laid the important foundations for realistic, objective evaluation of ore sorting for interested parties.


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