Ultrasonic simoltaneous flotation of coal fines

In view of various problems faced by the current fine coal slime flotation,the ultrasonic flotation could improve the flotation rate and flotation effect of fine coal,which could be used as an effective flotation method. In order to explore the effect of simultaneous ultrasound on the flotation process of fine coal slime,some ultrasonic simultaneous flotation experiments were carried out on fine coal slimes at different ultrasonic frequencies in a standing wave ultrasonic flotation device. The surface morphology of clean coal collected from conventional flotation and 100 kHz ultrasonic flotation was observed by scanning electron microscope (SEM). The pH and tem-perature changes of liquid during ultrasonic treatment at 100 kHz were measured by a pH meter. The particle size distributions of clean coal and coal tailing from ultrasonic flotation (80,100 and 120 kHz) and conventional flotation were measured by an OMEC laser particle size analyzer. The behavior of gas phase in the standing wave ultrasonic field was observed in a bubble observation device. The results show that the ultrasonic simultaneous flotation was superior to conventional flotation,and the ultrasonic flotation was best at 100 kHz. Compared with conventional flotation,the cleaned coal yield,combustible recovery and flotation complete index were increased by 6. 82% ,7. 83% and 2. 79% , respectively, meanwhile the cleaned coal ash increased slightly. The surface of coal particles treated by ultrasound was cleaner than those treated by conventional flotation. Besides,the ultrasonic treatment made the surface of coal particles cleaner,the ultrasonic cleaning and emulsification increased the content of fine particles in flotation clean coal,and the ultrasonic treatment had weaker crushing effect as the raw coal had small particle size. During ultrasonic treatment,the pH and temperature of liquid rose,and the coal particles were easy to be floated in slightly alkaline environment. In the standing wave ultrasonic field,bubbles formed bubble aggregation,which was beneficial for the collection of fine coal slimes and the flotation rate,however,the flotation selectivity become worse,leading to the increase of fine mud in the coal tailing.Therefore,the ultrasonic frequency affected the formation of bubble aggregation,resulting in different ultrasonic flotation results at different frequencies.