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Waste Liberation: Improving Mill Feed from a Miner's Perspective

Bob McCarthy, Dr. Bern Klein
Wednesday, May 9, 2018
First presented: 
Mine Waste

Over the decades, with decreasing ore deposit grades, miners have turned to economies of scale and bulk mining to gain advantage. This has resulted in an inherent diluting of ore feed to the mill. However, a point is being reached for most ore deposits where the mill feed grades for the larger selective mining unit (SMU) sizes are too low to be deemed economic. So what can we do to improve the quality of mill feed? Mineral processors have long had to consider “mineral liberation”. The smaller the grain size, the more likely a particle will contain pure or near pure mineral, which can then be separated and retrieved by various methods. However, what now needs to be considered by both mineral processors and miners is “waste liberation”. At what size does a particle or batch of mined material have insufficient mineralization to exceed the cut-off grade and can no longer be deemed “ore”? That is the key to improving the quality of mill feed. This paper explores methods of gaining orebody knowledge, such as assessing heterogeneity, rock hardness and mineral size deportment, so that informed decisions can be made on SMU sizes, grade control strategies, and ore sorting (batch and particle) strategies.

Feature Author

Bob McCarthy

Bob McCarthy is a professional mining engineer with 30 years of experience in mine operations and engineering, asset management, technology design and implementation, and consulting. He has worked at numerous mines in western Canada, gaining experience in roles across the spectrum of mine functions and to the level of department manager.

Bob’s technical strengths lie in mine design and planning, due diligence and technical reviews, technology selection and implementation, project and change management, and mine financial analysis. Bob is particularly knowledgeable about In-Pit Crushing and Conveying (IPCC) and ore sorting, having completed multiple studies on the subject and presented at several international conferences.

Principal Mining Engineer
SRK Vancouver
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