Effects of Fine Coal Particles on the Recovery of Coarse Coal in Collectorless Coal Flotation

The effects of fine coal (<74 mu m) of four density fractions, namely <1.4, 1.4-1.6, 1.6-1.8, and >1.8 g/cm(3), on the recovery of coarse coal (-500 + 250 mu m) in collectorless flotation were studied in this article. It was found that the fine coal of all density fractions increased the coarse coal recovery except for the fine coal of <1.4 g/cm(3) density fraction with the low mixing ratio in the feed. By analyzing the coarse coal yield, water recovery, concentrate weight composition, froth gray value, and froth height over weir, two mechanisms of increasing the coarse coal recovery by fine coal particles were, respectively, put forward for hydrophobic and hydrophilic particles. The hydrophobic particles mainly affected the dynamic froth stability by hydrophobicity and the overflowing froth volume by the amount of floatable particles, while the hydrophilic particles affected water drainage by the entrained particles in the froth network.