Study On Coal Flotation Kinetics Of High Intensity Conditioning

In this paper,the advantages of high shear slurry adjustment are illustrated by comparing high shear slurry adjustment test with conventional flotation test.Compared with conventional flotation,Bailong coal,Zhongxing coal,Xinzhi coal and Xiqu coal can increase concentrate yield by 2%-5%,combustible recovery by 3%-6%and flotation efficiency by 40%-60%under the same dosage of reagent.Compared with conventional flotation,collector dosage can be saved by15%-35%and foaming agent dosage can be saved by 40%-60%.It is found that with the increase of slurry speed and slurry time,the concentrate yield,combustible recovery and flotation kinetics constants of the four kinds of slimes show similar changes.Flotation speed is lower than that of conventional flotation when the slurry speed and slurry time are too large or too small,and the slurry time and slurry speed are too short.Suitable slurry mixing conditions can significantly improve the yield of clean coal and flotation speed.Combining with image analysis,the aggregate size of fine coal produced by conventional flotation is larger than that under low slurry adjusting speed(<800r/min).In the process of slurry adjusting speed from low to high,the coal particles in slurry change from uniform dispersion,small aggregate size,small number to large aggregate size,large number to small aggregate size and small number.The change process of agglomeration is similar to that of pulping speed under pulping time.According to the classical first-order kinetic constants k,k_f and k_s,the flotation speed of the fast flotation is much faster than that of the slow flotation.For the fast flotation,at medium speed of slurry adjustment(1600-2000 r/min),the shorter time of slurry adjustment(1min),the more amount of collector and the lower rate of the slow flotation are needed.The mixing speed(800-1200r/min),longer mixing time(3min)and less dosage of collector are needed.Both the classical first-order and fractional-velocity kinetic models can explain the variation of flotation speed,but the fractional-velocity dynamic model describes the flotation speed in more detail,and its fitting accuracy is about 0.994 or more.According to the flotation kinetics test of different particle sizes of the flotation products,the values of the first-order kinetics constant K and the fast-floating mechanics constant k_f of three kinds of coal with different particle sizes under the optimum slurry-mixing conditions are larger than those of conventional flotation,that is,under the optimum slurry-mixing conditions,the flotation speed of coal with different particle sizes is faster than that of conventional flotation.The suitable mixing speed and time(not the best mixing conditions)are different among different particle sizes.That is to say,for particles of+0.25mm size,at lower rotational speed(400-1200r/min),shorter time(1-2min);0.25-0.074mm size,at lower rotational speed(400-1200r/min),shorter time(1-2min);0.074-0.045mm size,at medium rotational speed(1200-2000r/min),medium time(2-3min);and-0.045mm size,at higher rotational speed(2000-2400r/min).The recovery rate and k value of combustible matter for a long time(3-4min)are higher than those of conventional flotation.Fluent software was used to simulate the high shear pulping equipment,and the data were extracted to correlate with the flotation effect.Turbulence dissipation rate in fluid,stirring power per unit volume and shear rate all have important effects on flotation efficiency.The yield and flotation speed of clean coal are lower when the value is too large or too small.Selecting the appropriate value can greatly improve the quality of clean coal and lower the cost and energy consumption.