The Influence of Near-Dense Material on the Separation Efficiency of Dense-Medium Processes

Abstract

Near-dense (also termed near-gravity) material is material that has a relative density that is close to that of the separating liquid or dense medium used to separate coal and the impurities contained in raw coal. Near-dense material makes the separation more difficult because it settles very slowly in the dense-medium due to the fact that its density is close to that of the medium. This increases the probability that material that should have reported to floats wrongly reports to sinks and vice versa, hence increasing the amount of misplaced material. Data is presented that show how the amount of misplaced material increases with an increase of near-dense material in the feed coal. The data furthermore illustrates the influence of near-dense material on the separation efficiency of dense-medium washers. A new definition for near-dense material is proposed.