Effect of Gas Input Conditions and Ultrasound on the Dynamic Behavior of Flotation Bubbles

Ultrasonic flotation is useful for fine low-rank coal purification; however, the efficiency of ultrasonic flotation still needs to be improved. Because the dynamic behavior of flotation bubbles has significant effects on their flotation efficiency, it was investigated under different gas input conditions with and without ultrasound using the volume of fluid method and h-speed imaging. The results indicated that the gas input method can influence the final kinetic behavior of the flotation bubbles by changing the morphology of the initial bubble. With an increase in the size and aspect ratio of the bubble, the bubble deformation and velocity increased, and the range of motion of the bubble increased and then decreased. Meanwhile, the size of the bubble increased with an increase in the thickness of the vibrating plate of the ultrasonic transducer owing to the aggregation of the bubbles under the influence of ultrasound.