improvement of concentrate quality in flotation of low-rank coal

Percentage of high-rank coal with low content of ash, moisture, and sulfur in total coal production output is low. most of the produced coal has a low quality (lignite, bituminous coal: long-flame and fiery). under increasing requirements for ecological cleanness of coal, the efficient use of coal products is only possible after improvement of their processing properties. the authors discuss the enhancement of flotation efficiency of low-rank coal using the mechanism of physisorption of a collecting agent in particle – bubble attachment. it is explained why the yield of concentrate with low ash content increases as a result of combination of collectors having different physical properties. it is shown that the surface activity of a heteropolar agent relative to the gas – liquid interface and the adsorption density of the agent govern its collecting properties. based on the recovery – surface activity relationship, the correlation is found between the collecting activity of a chemical compound and the structure of its molecules. the combination of the collectors with different surface activity enables adjusting collectability and selectivity of the blend. the physisorption mechanism of collectors can be a framework for developing recommendations on modification of concentrate yield and ash content, and on selection of optimized ratios of surface activities of miscible collectors relative to the gas – liquid interface.