| With the increase of the degree of mechanization of coal mining and the change of geological conditions,the quality of raw coal tends to deteriorate gradually,and the output of coal slime has gradually increased.As a by-product of coal washing and beneficiation,coal slime is a low-grade fuel with limited applications.The large accumulation of coal slime will not only waste coal resources,but also cause serious environmental pollution problems.Flotation is an important method to achieve efficient and low pollution utilization of coal slime.However,due to the fine particle size of coal slime and its large specific surface area,the consumption amount of the collector is high,and the results of flotation are unsatisfactory,which severely limits the development and utilization of coal slime.Therefore,it has great academic and industry significance to develop high-efficiency and low-cost collectors for flotation of fine coal slime with high ash content.In this paper,the bituminous coal slime with average particle sizes of 48-72 ?m and ash content of57% was taken as the research object.In addition,the microemulsion with good stability was prepared based on research methods such as Shah titration and pseudo-ternary phase diagram.Besides,Dynamic light scattering(DLS),Cryo Transmission Electron Microscope(Cryo-TEM),X-ray diffractometer(XRD),Fourier transform infrared spectrometer(FT-IR)and contact angle methods were carried out to compare the effects of kerosene and microemulsion in coal slime flotation.The particle size distribution,droplet morphology,and dispersion degree of the microemulsion were studied by DLS and Cryo-TEM.The fluidity and dispersion in water of the microemulsion were analyzed by rotational rheometer and surface tensionmeter.The results showed that the average particle size of the microemulsion is 92.50 nm,and the droplet morphology is close to spherical and dispersed.In addition,the microemulsion has good fluidity,good dispersion effect in water,and foaming effect.In coal smile flotation,the microemulsion was used as a collector,and flotation results of kerosene and microemulsion were compared by using cleaned coal ash,combustible recovery and flotation perfection index as evaluation indexes.The result showed that the microemulsion can save the amount of reagent,but the selectivity of microemulsion is easily influenced by the amount of reagent.Based on the above research,in this paper,an innovative approach according to the flotation effect of coal slime to select reagent formulations was proposed.Moreover,the three main factors of surfactant blending HLB value,ratio of surfactant to kerosene and the co-surfactant content were discussed and the stabilityof agents was verified.The result showed that the formula of the microemulsion collector with best flotation performance is kerosene:(Span80+Tween80):MIBC:water=64.50:12.90:19.35:3.25.After fourteen days,the flotation efficiency of the microemulsion collector was not decreased.In addition,the effects of the amount of foaming agent and collector on the optimized microemulsion and kerosene were investigated by the coal slime flotation test,and the economic benefits were evaluated under their respective optimal reagent systems.The results showed that the reagent cost of microemulsion collector for flotation of 1 ton of dry coal slime is60.19% of the reagent cost of kerosene,which has great application value.The adsorption behavior of kerosene and microemulsion collector on the surface of coal slime was analyzed by FT-IR and contact angle.The results showed that the adsorption types of kerosene and microemulsion collectors on the surface of coal slime are both physical adsorption.Contact angle experiments showed that microemulsion collectors could significantly improve the hydrophobicity of coal slime surface compared to kerosene. |
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