Research progress in lignite flotation intensification

With the increasing exhaustion of high quality coals, it is important to utilize lignite efficiently, which is a resource with abundant reserves. Flotation, as an efficient method for fine particles separation, however, is making slow progress for use with lignite, which basically remains in the laboratory stage. In this article, we briefly describe the characteristics of lignite and explain why lignite is hard to separate. Meanwhile, we review progress in lignite flotation in recent years. In addition, we analysed lignite flotation methods, including grinding, reverse flotation, heating, microwaving, ultrasonic, oily-bubbles flotation and modification of collectors. The advantages and difficulties of the methods above are discussed from a molecular level. Finally, we provide an outlook for the future of lignite flotation.