Effects of particle size on coal flotation
In the operation of industrial coal processing plants it is conventional to screen the crushed coal at typically 0.5 mm, with the coarse coal product being processed using some form of gravity or heavy media stage and the fine coal processed by flotation for the removal of mineral matter. This is to generate a combined product of suitable characteristics to comply with an agreed specification. In the present study, several flotation tests were conducted on a plant slurry using a laboratory batch flotation cell and the results subjected to a kinetic analysis as a function of particle size. The results obtained showed high combustible and mineral matter recoveries and first order rate constants in the coarse (> 300 µm) fraction compared to intermediate size fractions that are traditionally considered to be the fastest floating. This was associated with lower mineral matter contents in these coarse fractions, hence combustible flotation was enhanced by the greater exposure of the carbonaceous phases in the coarse size fractions compared to the higher mineral matter intermediate and fine size fractions.