Flotation Behaviors of Coal Particles and Mineral Particles of Different Size Ranges in Coal Reverse Flotation

Reverse flotation is conducted as an alternative method for cleaning of fine coal. In the present study, dextrin and Lilaflot D817M (a complex amine) were used as a coal depressant and mineral collector, respectively. Dextrin can be adsorbed by coal particles through hydrophobic bonds, while Lilaflot D817M can be adsorbed by minerals (mainly silica) through electrostatic interactions. The effects of reagent dosages on the flotation performance of coal and mineral particles at different size ranges were examined. The average particle size of all of the concentrates (sink) was much larger than that of the tailings (float). Dextrin has weak depression effects on coal particles of below 38 mu m because they become entrained easily to the froth phase. Coal particles -74 + 53 mu m respond to dextrin best. More than 80% of minerals -38 mu m were recovered when 1 kg/t collector was used, while coarser minerals needed more collectors. For the mineral particles larger than 38 mu m, those of -104 + 74 mu m have the best flotation performance. When the collector dosage increased from 1 to 6 kg/t, the combustible matter recovery in concentrates decreased from 78.65 to 59.35% because coal particles can also interact with the amine collector and are lost in the froth product. A concentrate with 25.45% ash reduction can be achieved with 4 kg/t dextrin and 6 kg/t collector.