Effect of gas injection rate on bubble generation characteristics and coal flotation

Abstract

Using a high-speed motion acquisition system, the effect of gas injection rate on dynamic bubble characteristics in the presence of flotation reagents was investigated, and the force analysis during the bubble generation was performed. The corresponding coal flotation tests were conducted to discuss the relationship of the bubble characteristics and the coal recovery. According to a partition criterion of contact angle as 90° between the bubble and the capillary, the bubble generation process was divided into formation, expansion and contraction stages, and the generation time was majorly allocated to the expansion stage. As the gas injection rate increased, the bubble aspect ratio decreased, the bubble size increased and the bubble generation time decreased. The surface tension was analyzed as the main force for adhering the bubble on the capillary, and the buoyancy was deemed as the main force detaching the bubble from the capillary. Furthermore, the increase in net force was analyzed as the essential factor for the increase in bubble generation rate during the expansion stage. The combustible matter recovery increased as the gas injection rate increased, and the flotation rate constant was analyzed closely related to the bubble deformation. The results can provide valuable insights into the development of technology for mineral flotation.