Simulation of particle-bubble interaction behavior based on Discrete Element Method

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 simulation system for particle-bubble interaction behavior. The interaction behavior between spherical coal particles with the particle 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 a still water environment was simulated. The various stages of particle bubble interaction behavior and the variation law of particle velocity in each stage, the relationship between particle density and critical collision angle between particle and bubble, and the relationship between particle density and particle capture probability were studied. The simulation results show that the particle-bubble interaction behavior can be divided into five stages: free settlement, flow about a bubble, 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 trajectory will change. When a particle collides with bubbles, its velocity decreases to the minimum. After the collision, the particle slide on the bubble surface. The sliding speed first increases gradually, then decreases sharply, and then continues to increase. When the particle reaches the “equator” of the bubble, its speed reaches the maximum. After crossing the “equator”,the speed begins to decrease gradually and finally stays at the bottom of the bubble. The sliding velocity 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 particles and bubbles decreases from 50.77° to 31.93°,and the capture probability of bubbles to particles decreases from 51.74% to 22.04%.