Experimental Study On Motion Characteristic Of Single Particle-loaded Bubble In Surfactant Solution

Flotation is an efficient solid-liquid separation technology,which is widely used in many industrial fields such as mineral processing and oil extraction.In the flotation process,the bubbles collide and adhere to the mineral particles in the slurry,and then load the particles to float under the action of buoyancy.It can be said that the essence of flotation is that the bubbles move upwards with the particles.In recent years,the development of computational fluid dynamics provides another method for research on flotation.Usually fluid dynamics(particle-bubble movement)and flotation dynamics(particle-bubble action)are used to simulate the flotation process.Movement and action are mutually restricted and affect each other,so the numerical study of the multiphase flow problem in the flotation process cannot bypass the selection of the terminal velocity prediction model and drag coefficient prediction model,it is necessary to accurately express the influence of particles on bubble movement,and it is also necessary to establish the relationship between particle load and bubble movement characteristics to provide a theoretical basis for mineral flotation.In this experiment,PMMA particles are selected to simulate mineral particles,and the surfactant is MIBC.First,a high-speed dynamic analysis system is used to record the rising movement of a single bubble loaded with particles in a static solution,and then the image processing software i-SPEED 3 suite and Image-Pro Plus 7.0 are used to obtain parameters such as the equivalent diameter,aspect ratio,trajectory and terminal velocity of the bubble,and the particle coverage is processed by Auto CAD software.The main conclusions of the paper are as follows:In the surfactant solution,the relative movement between the bubble and the solution will cause the concentration of the surfactant at the bottom of the bubble higher than that at the top of the bubble,resulting in Marangoni shear stress,which is opposed to the pressure difference that causes bubble deformation;As for bubbles loaded with particles,the gravity on the particles is also opposed to the pressure difference that causes bubble deformation,and part of the gas-liquid interface is transformed into solidliquid interface,and the surface tension decreases.Therefore,both the increase of the concentration of surfactant and the particle coverage would cause the bubble shape tends to be spherical and the bubble movement trajectory tends to a straight line.The instantaneous velocity of a single bubble loaded with particles fluctuates periodically in the terminal velocity section,and the terminal velocity of the bubble decreases with the increase of particle coverage and surfactant concentration.When the particle coverage is less than 50%,the average aspect ratio of the bubbles increases with the increase of the particle coverage,and the terminal velocity decreases with the increase of the particle coverage;when the particle coverage reaches 50%,the bubbles are more like a rigid ball,both the average aspect ratio and the terminal velocity reaches a relatively stable value.Based on the experimental values,terminal velocity prediction model and drag coefficient prediction model of particle-loaded bubble suitable for MIBC solution are obtained: Based on the Tomiyama bubble rising velocity model,the dimensionless number Eo and the particle coverage ratio ? are introduced,and a model suitable for predicting the velocity of particle-loaded bubble is obtained by fitting.The ratio of the predicted value to the experimental value can be controlled between 0.9 and 1.1.The maximum relative error within 10%;Based on the Schiller&Naumann drag coefficient model,the average aspect ratio E of the bubble,the dimensionless number Eo and the particle coverage ? are introduced to obtain a drag coefficient prediction formula for particle-loaded bubble,the maximum average relative error is 5.39%.