| With the deepening of coal mining and the development of mechanized coal mining technology,the content of fine coal in raw coal has gradually increased,and fine coal separation has gradually become a research hotspot in the industry.Flotation is an effective method for separating fine coal.The commonly used flotation equipment in the industry includes mechanical agitation flotation machine,jet flotation machine and flotation column.Combined with the characteristics of the traditional flotation device,an annular jet flotation device was designed,which uses the jet to intake and the gas jet drives the impeller to stir to improve the flotation efficiency of the fine coal.The structural design and laboratory model parameters of the device were introduced.The mechanism of intaking and driving impeller were analyzed by fluid mechanics theory.On this basis,the energy test system was built to study the energy conversion process of the annulus jet flotation device.The I-speed camera system and measuring cylinder method were used to study the effects of frother system,energy input and air intake on the bubble characteristics and dispersion effect in the device.The corresponding relationship between bubble characteristics,dispersion effect and flotation recovery was studied by coal flotation tests.The aim is to find the best operating conditions to improve flotation efficiency,and provide a reference for the improvement of this new flotation device.The main research conclusions are as follows:The energy conversion process of the annulus jet flotation device was ascertained.In the jet suction section,the slurry pressure energy and initial kinetic energy generated by the feed pump were converted into slurry jet flow energy and air kinetic energy.In the impact stirring section,the slurry jet flow energy,air kinetic energy and potential energy were converted into impeller mechanical energy and slurry end kinetic energy.The effective input energy in the flotation cell included the effective power of the impeller stirring and the end kinetic energy of slurry.The energy conversion efficiency of the device decreased and the effective input energy in the flotation cell increased with the input frequency increased.The bubble characteristics of the annulus jet flotation device were disclosed.The size of bubble decreased with frother concentration increased,the inflection point occurs at the Critical Coalescence Concentration(CCC),after which the bubble sizes tend to be stable.The increase of the effective input energy in the flotation cell caused the bubble size to decrease.When the bubble reaches the same decay degree,the input energy power was larger,and the required frother concentration was lower.The bubble surface area flux increased with the input energy power increased.The increase of air intake cause the increase of bubble size.The optimum air intake is 3.0 L/min,and the bubble surface area flux is the largest at 9.590 s-1.The air dispersion characteristics of the annulus jet flotation device were described.The increase of frother concentration cause the increase of aeration rate in the flotation cell.The increase of input energy not only caused the increase of aeration rate,but also promoted air dispersion.The increase of air intake caused the increase of aeration rate in the flotation cell and the decrease of air dispersion degree.The optimal operating factors of the annulus jet flotation device were explored through the coal flotation flotation tests.The flotation recovery increased with frother concentration increased,and the flotation recovery rate tended to the maximum with the frother concentration reached the Critical Coalescence Concentration.The optimal concentration of the agent is 0.1078 mmol/L(CCC).The energy input in the flotation cell can effectively increase the flotation recovery of coal.The optimal input energy is 9.39 W,and the input frequency of the corresponding feed pump is 50 Hz.The optimal air intakes were 2.5.3.0,and 3.0 L/min for the frother concentrations of 0.0770,0.1078 and 0.1386 mmol/L,respectively,and the flotation recoveries were 75.36%,77.89%and 81.72%,respectively.Figure[48]table[13]reference[109]... |
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