Development of ore sorting and its impact on mineral processing economics

• Run-of-mine molybdenum ore was sorted using a dual energy X-ray transmission array.
• Sorting thresholds permit optimization of Mo recovery and waste rejection.
• Mo recoveries of 65.6–93.4% and waste rejection of 40.2–93.7% were achieved.
• Two comminution circuits were proposed to evaluate ore sorting impact on operations.
• Grinding models suggest potential energy savings of >60% due to waste rejection.

Several factors contribute to an often bleak outlook for mining and mineral processing projects in the current market: rising energy costs, falling ore body head grades, and lower profit margins on added value products have all made it more difficult to operate economically. Ore sorting is a class of technologies that offers potential solutions to these problems by identifying the metal values in a run-of-mine stream and separating the stones containing valuable mineralization from barren stones. This separation reduces the amount of material that must be processed to produce a given amount of value added metal, which has significant impact on the total mine and plant economics. To date, ore sorting has been studied extensively and several technologies have been identified as suitable for industrial application; however, very little quantitative discussion has been made about the impact of these technologies. Dual-energy X-ray transmission has been used to sort ore from different mines, and an analysis identifying the economic impact of these results is presented. Significant energy savings in milling have been realized, and capital and operating cost advantages to using ore sorting have been identified.