| Coal preparation is the first step to achieve clean utilization of coal, which has some merits, firstly, improving the quality of coal to decrease amount of contaminant emission; Secondly, enhancing the efficiency of coal utilization to save energy; Thirdly, optimizing the product structure to raise product competitiveness and reduce waste of transportation. Flotation is one of the types of coal washing, it is the most effective way to deal with fine particle coal. Among the ways of improving the efficiency of the flotation, the most cost-effective is to improve flotation reagents. Conventional coal flotation agents is mostly petroleum products or by-products which is limited by the shortage of petroleum resource, looking for new and highly efficient flotation reagent to replace traditional reagents is imperative.In this paper, preparing the polystyrene nano-emulsions by emulsion polymerization methods, analyzing its nature. Selecting nanoemulsion as flotation collectors and flotation accelerator for four different metamorphic slime flotation, designing flotation experiments to find the optimum amount. Through the role of slime around the nanoemulsion ζ- potential testing, researching the impact of nano-emulsion slime nature, exploring its mode of action. The main contents of the following aspects:1.Obtaining different types of polystyrene prepared nano-emulsion by changing the experimental conditions of emulsion polymerization. Selecting 61nm,80nm,89nm,93nm,108nm,157nm,234nm nano-emulsion has selected as flotation collectors through testing the nanoemulsion particle size, particle size distribution and potential.2.Determining the flotation yield and floatability of four different degrees of metamorphism slime flotation by step releasing experiments and conventional kerosene flotation experiment. The result is that Dongqu coal slime is very easy to float, Zhangcun coal slime is easy to float, Pangpangta coal slime is medium to float, Pingshuo coal slime is difficult to float.3.The polystyrene nano-emulsion was used as flotation collector for 4 kinds of different metamorphosing range coal slime flotation, the flotation complete index and combustible recovery were used to evaluate the efficacy of the flotation. Nano-emulsion has showed a better performance than Kerosene as flotation collector on various flotation indicators for 4 coal slime. As the coal slime which used in the experiments, it turned out that the smaller size of nanoparticle showed a better effectiveness for coal slime that very easy to float and easy to float. The larger size of nanoparticle showed a better effectiveness for coal slime that medium to float and difficult to float.4.Selecting kerosene as collector and polystyrene nano-emulsions as accelerator for flotation of the four kinds of different metamorphosing range coal slime. The experiment results are that the addition of polystyrene nano-emulsion can save more than half of kerosene dosage in the same clean coal yielding. And among the experimental coal slime, Polystyrene nano-emulsion shows better promoting performance on the coal slime that medium to float and difficult to float.5.Through testing the ζ-potential of coal and polystyrene before and after the effect of nano-emulsions,we found coal surface shows electronegativity, the higher metamorphic grade coal, the weaker surface electricity negative. The surface electronegativity weakened with the effect of nanoemulsion, and the degree relates to the polystyrene nanoemulsion itself ζ-potential.6.Theoretical analysis the role of polystyrene nanoparticles in coal surface, research the mechanism of action of nano-emulsion collector.What makes polystyrene nanoparticles different from traditional oil collertor is that traditional oil collertor formed hydrophobic oil slick on the coal surface to improve hydrophobicity of coal, but polystyrene nanoparticles loaded on the coal surface to micro-roughening the coal surface.Enlarge hydrophobicity of the coal surface,so as to achieve its flotability. |
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