Effect of ultrasonic-hydraulic coupling cavitation pretreatment on carbon extraction from coal gasification coarse slag by flotation

Coal gasification coarse slag represents a type of low-value solid waste produced in coal gasification. This study investigated how the pretreatment of the pulp obtained from coal gasification coarse slag affects carbon extraction by flotation. Ultrasonic treatment can promote carbon ash separation. Flotation results revealed that at an ultrasonic action time of 15 min, the ultrasonic power was 90 W and the microbubble generator flow rate was 300 ml/min. Moreover, the best flotation effect was observed under these conditions. Compared with the results obtained for conventional flotation, the concentrate ash content decreased from 36.88 % to 25.51 % and the combustible substance recovery index increased from 79.84 % to 92.91 %. After coupled cavitation treatment, coal gasification coarse slag exhibited a reduced particle size, an increased specific surface area, a smooth and clean surface, a reduced number of surface inorganic elements, an increased number of pores and a remarkable carbon ash separation effect. This study can provide a reference for special methods such as ultrasonic-hydraulic coupling cavitation to strengthen the flotation of coal gasification coarse slag.