School of Chemical & Environmental Engineering,China University of Mining & Technology-Beijing

The study of particle⁃bubble interaction behavior is essential for understanding the mechanism of flotation.Based on the theory of particle⁃bubble mechanics,the Discrete Element Method(DEM)was used to build a simulationsystem for particle⁃bubble interaction behavior. The interaction behavior between spherical coal particles with the par⁃ticle size of 0.1 mm and densities of -1.3,1.3-1.4,1.4-1.5,1.5-1.6,1.6-1.7,+1.7 g/ cm3,and fixed bubbles in astill water environment was simulated. The various stages of particle bubble interaction behavior and the variation lawof particle velocity in each stage,the relationship between particle density and critical collision angle between particleand bubble,and the relationship between particle density and particle capture probability were studied. The simulationresults show that the particle⁃bubble interaction behavior can be divided into five stages:free settlement,flow about abubble,sliding with a liquid film,liquid film rupture & three⁃phase contact line(TPC)formation,and sliding with a TPC. The particle approaches the bubble at terminal velocity and will flow about a bubble and the motion trajectorywill change. When a particle collides with bubbles,its velocity decreases to the minimum. After the collision,the parti⁃cle slide on the bubble surface. The sliding speed first increases gradually,then decreases sharply,and then contin⁃ues to increase. When the particle reaches the “equator” of the bubble,its speed reaches the maximum. After cross⁃ing the “equator”,the speed begins to decrease gradually and finally stays at the bottom of the bubble. The sliding ve⁃locity of particles on the bubble surface is approximately symmetrical about the “ equator” of the bubble.When the density of particles increases from -1.3 g/ cm3 to +1.7 g/ cm3,the critical collision angle between particlesand bubbles decreases from 50.77° to 31.93°,and the capture probability of bubbles to particles decreases from51.74% to 22.04%.