Over the last 30 years the average grade of ore bodies has significantly decreased while the proportion of waste removal has in many cases more than doubled. This in turn has led to a major increase in energy consumption and decrease in productivity across mining operations.
Metal preconcentration at coarse scale (10–100 mm) by screening has the potential to reverse decreasing mining productivity trends through early rejection of uneconomic grade material prior to energy intensive comminution. Metal preconcentration of feed grades using screening exploits the propensity of certain ores to preferentially deport metal into specific size fractions during breakage. This phenomenon is referred as preferential grade by size deportment. The exploitation of preferential grade by size response involves generation of multiple streams with different metal content post screening. Streams can be engineered for different grade characteristics suitable for different processing destination (eg: as waste, leach, and mill).
Preferential grade by size data obtained by an extensive belt cut sampling campaign after primary crushing has been used to develop a method to define samples that are amenable for metal preconcentration by size. This amenability changes depending on cut-off grade, magnitude of preferential grade by size response and the proportion of mass contained in individual screen products. Outcomes of this work will support the short term preferential grade by size operational implementation.
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