Status quo of the research work on low-rank coal flotation and future outlook

For stepping up the progress of industrialization of low-rank coal flotation, following an analysis of the surface property of low-rank coal, the author presents a general overview of the achievements obtained by both domestic and overseas workers in research on low-rank coal pretreatment, optimization of flotation agents, and flotation process intensification, together with an introduction to the low-rank coal flotation processes currently in industrial application. It is concluded that having the low-rank coal pretreated by heating, microwave, ultrasonic wave, pore compression and pulp conditioning means can result in a better flotation result due to improvement of surface hydrophobicity of the coal; the use of surfactant and composite and synthetic agents can likewise produce an improved flotation effect; and a much improved flotation effect can be expected by applying the oil-bubble, agent emulsification and carrier flotation intensification processes. It is pointed out that the industrialization of low-rank coal flotation process is currently just in a starting stage and further research work should be directed towards mechanism of action of agents, development of high-efficiency, green and environmentally-friendly agents suitable for use in flotation of low-rank coal; stepping up the study on low-rank coal surface modification technology and its industrial application; and the optimal approaches for utilization of low-rank coal flotation concentrate and tailings products.