| In the flotation process,bubbles carry particles,and the movement behavior of bubbles directly affects the flotation effect of flotation equipment.The properties of particles and coverage rate of bubbles have a great influence on the movement state and shape of bubbles.There are a wide variety of minerals in flotation.It is of great significance for the structure optimization of flotation equipment and the improvement of separation effect to clarify the influence law of property of particles and coverage rate of bubbles on bubbles movement and establish the prediction model of movement velocity and deformation of particles-laden bubbles.Glass beads modified by Trimethylchlorosilane(TMCS)were selected to simulate real minerals.The average diameter of the glass beads was 84.89 μm,and the contact angle was controlled between 40° and 90°.The bubble size ranges from 2.99 mm to4.75 mm.The high-speed dynamic camera system was used to photograph the shape and upward movement of modified bubbles loaded glass beads.Image processing software I-Speed 3 Suite,Image-Pro Plus 7.0,Adobe Illustrator 2021 and MATLAB are used to obtain the data of bubble equivalent diameter,aspect ratio,surface tension and terminal velocity after Image processing.The main conclusions are as follows:Based on the profile data of static bubble before and after loading particles,the bubble surface tension and the curvature radius of the bubble vertex were obtained by solving Young-Laplace equation.The results show that the bubble surface tension does not change when the particle coverage rate,particle contact angle,bubble size and solution environment are changed.The reason is that the microparticles are different from the nanoparticles that carry out Brownian movement at the fluid interface.They keep the force balance and are in a stable state at the fluid interface,and do not produce dynamic pressure on the bubble surface.When the particle coverage rate is lower than 50 %,the average terminal velocity decreases with the increase of the coverage rate,while the aspect ratio increases with the increase of the coverage rate,and the terminal velocity is synchronous with the aspect ratio.When the particle coverage rate is more than 50 %,the bubble terminal velocity and aspect ratio are basically stable.The reason is that the particles are loaded in a compact hexagonal pattern on the surface of the bubble.With the increase of the load,the stiffness of the bubble increases,and the bubble is more and more spherical,and the average aspect ratio gradually increases.When the coverage rate exceeds 50 %,the aspect ratio is between 0.8 and 0.9 and no longer increases.The bubble floating velocity is closely related to the aspect ratio of the bubble.In order to predict the bubble velocity,a prediction model of the aspect ratio of the bubble carrying particles is established.The relative errors of bubbles of different sizes between the predicted results and the experimental values are 3.22 % and 4.47 %,respectively.The bubble aspect ratio prediction model was substituted into Tomiyama bubble terminal rising velocity calculation model,and the model was modified based on the experimental data.The prediction model can accurately calculate terminal rising velocity of the particle-laden bubbles,and the relative errors of bubbles of different sizes between the predicted results and the experimental values are 2.72 % and 4.17 %,respectively.The calculation of drag coefficient shows that the drag coefficient can be predicted by Yan’s model,and the average relative error is less than 1 %.This thesis contains 34 figures,12 tables and 98 references. |
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