Effects of surface chemistry and particle size and density on froth flotation of fine coal

Abstract

This paper reports the effects of surface chemistry and particle size and density on the froth flotation of fine coal. It is shown that froth flotation of very fine coal particles (up to 12 μm) can be readily accomplished in a mechanical-type flotation cell. In addition, the coal particle surface, though primarily hydrophobic, consists of hydrophilic sites such as minerals, hydroxyl and carboxyl groups. The flotability of the coal increases as the surface hydrophobicity increases, but decreases as more hydrophilic sites become ionized. The lower flotability for particles of high mineral content is further attributed to the density effect. Thus, clean coal particles can be selectively froth floated while leaving particles of a high mineral content in the tailings. The selectivity deteriorates as the average particle sizes are reduced from 75 to 12 μm. The selectivity problem can be partially overcome, however, through the use of an anionic collector and staged froth flotation.