Study On The Preparation Of Nano-bubbles And Their Effect On Coal Slime Flotation

In recent years,the research of nanobubbles in the field of froth flotation has become a hot spot.Based on previous research,this thesis explores the method and conditions for the generation of nano-bubbles,and systematically examines the effects of nano-bubbles on the flotation of low-ash coal,the entrainment of kaolin,and coalkaolin mixed ore coating phenomenon.The influence of nano-bubbles on the flotation mechanism of coal slime was studied by means of sedimentation tests,Zeta potential measurements,rheological analysis and SEM.The research on the preparation of nano-bubbles shows that the effect of preparing the nano-bubbles by the hydraulic cavitation method is better than that of the decompression method.The concentration and particle size of the nano-bubbles are related to the production method.When the nano-bubbles were prepared by the decompression method,the optimal decompression time was 20 min,the concentration of nano-bubbles in the solution was the largest at this time,which was 2.87 × 107 cells / m L,and the average particle size was 85 nm.When the hydraulic cavitation method is used,the optimal cavitation time is 5 min.At this time,the concentration of nanobubbles in the solution is the 5.39 × 107 cells / m L,and the average size is 180 nm.The mechanism of nano-bubbles promoting low-ash coal flotation is that nanobubbles are adsorbed on the surface of low-ash coal,and promote the formation of larger aggregates between fine-grained coal particles,thereby increasing the probability of collision between particles and bubbles.Experimental research on low ash coal flotation shows that nanobubbles promote better flotation of fine-grained coal(-38 μm).Under the same conditions,the recovery rate of combustible bodies of nanobubble flotation is higher than that of conventional flotation,and the flotation rate is faster.Kaolinite entrained flotation experiments show that under the same conditions,the nanobubble flotation entrainment recovery rate is higher than that of conventional flotation,and in both flotation systems,the kaolinite entrainment recovery rate and the foam water recovery rate have a linear relationship.The mechanism analysis shows that the nano-bubbles promote the formation of the end-to-end three-dimensional network structure of kaolin,which makes it difficult for kaolin to sink smoothly,and it is easy to enter the flotation product through the entrainment of foam water.Coal-kaolin mixed ore flotation studies show that the lower the pH value,the more severe the kaolin is on the coal surface,and the lower the combustible recovery rate.The introduction of nano-bubbles in coal-kaolin mixed ore flotation can reduce the phenomenon of kaolin coating on the surface of coal particles and improve the effect of kaolin on coal flotation to a certain extent.