Patents
Flotation technology is commercially utilised for beneficiation of 0 to 500 micron coal fines. But in general, performance of coal flotation plants in India has not been satisfactory. Ash content of the clean coal is on the higher side and with low yield. Studies on particle size effects and flotation kinetics have shown that poor flotation results are due to low recovery of coarse particles at a specified target ash of 17%. The invention provides an improved process for beneficiation of coking coal fines. The new process comprises of split processing involving spiral concentration of the coarser fraction (100 to 500 micron) and flotation of 0 to100 micron fine fraction using pneumatic column type flotation cell. The new process resulted in overall improvement in recovery of combustibles. Substantial improvement in yield of clean coal at same target ash (17%) could be achieved for high ash coking coal fines by split processing in comparison to the conventional flotation technique. The process can be adopted for new coal washeries or may be implemented at existing washeries. The process of the present invention describes the strategy for splitting the feed coal into two size fractions based on particle size effects and flotation kinetics and processing them through novel beneficiation scheme resulting in optimum recovery of combustible. Use of sodium silicate as dispersant particularly for siliceous gangues improves selectivity of separation between coal and gangue mineral particles.