Preparation Of High Internal Phase Water-in-oil Emulsion And Its Application In Flotation

High-ash fine-grained slime particles have poor flotability and large specific surface area,and traditional hydrocarbon oil collectors are not easy to form adsorption on their surface,which leads to high-ash and fine-grained slime flotation.The dosage of chemicals is large and the flotation recovery rate is low,thereby affecting economic efficiency.The development of new and efficient flotation reagents is of great significance for improving the recovery rate of clean coal combustibles in high-ash fine-grained slime flotation,reducing the dosage of reagents and efficient recovery and utilization of slime.In view of the characteristics of high ash content,fine particle size,and high chemical consumption of steam coal,two high internal phase water-in-oil emulsions(FDJ-HIP and kerosene-HIP)were prepared by using collector FDJ and kerosene as base fluids respectively.It was used as a collector in thermal coal flotation,and the flotation of the new emulsion collector was compared with conventional flotation.In this paper,the experimental optimization of the emulsion collector was carried out by changing the test conditions such as organic liquid mass ratio,surfactant and inorganic salt solution,and at the same time,the flotation process was further optimized by "one coarse and one refined",and finally the optimal emulsion slime flotation was obtained.Test conditions and results.In addition,the physical and chemical properties of high internal phase water-in-oil emulsions were characterized by microscopy analysis,stability analysis,electrical conductivity analysis,rheological analysis and particle size analysis,and infrared spectroscopy analysis and molecular dynamics simulation were carried out to obtain the results.Explain the influence mechanism of emulsion on thermal coal flotation from a microscopic perspective,and provide a theoretical basis for realizing thermal coal flotation cost reduction and efficiency increase.The main research results of this paper are as follows:(1)The properties of the high internal phase water-in-oil emulsion were characterized by microscopy analysis,stability analysis,electrical conductivity analysis,rheological analysis and particle size analysis.,a large number of small emulsion droplets are closely packed in a polyhedral shape inside;Span80 has the most obvious improvement effect on the stability of high internal phase water-in-oil emulsions compared with other surfactants;inorganic salts have little effect on emulsion stability,however With the increase of the inorganic salt concentration,the stability of the emulsion tends to decrease;the high internal phase water-in-oil emulsion is a pseudoplastic fluid and has shear thinning phenomenon,and the apparent viscosity of the FDJ-HIP emulsion is higher than that of the kerosene-HIP emulsion.At the same time,the emulsion viscosity increases with the increase of the surfactant mass ratio;the addition of surfactant can reduce the emulsion particle size,while the type of base liquid(FDJ and kerosene)has little effect on the emulsion particle size.(2)The effect of high internal phase water-in-oil emulsion on coal slime flotation was investigated.The coal slime flotation experiments were carried out using kerosene-HIP and FDJ-HIP emulsions as flotation collectors respectively.The test results show that the high internal phase water-in-oil emulsion as collectors can significantly reduce the dosage of chemicals and improve the flotation performance.Compared with conventional flotation,FDJHIP emulsion flotation can save 80% of organic liquid consumption,while kerosene-HIP emulsion flotation can save more than 90% of organic liquid consumption.(3)By changing the types of surfactants,the mass ratio of collectors and surfactants,the types and concentrations of inorganic salts in the internal water phase,the effects of the structure and composition of the high internal phase emulsion on coal slime flotation were investigated.The results show that in the FDJ-HIP emulsion flotation,the emulsion flotation effect is the best when the surfactant is Span80,the FDJ:Span80 is 2:1,and the internal water phase inorganic salt solution is 0.1 mol/L AlCl3,and the clean coal is obtained.The ash content is 20.17%,and the recovery rate of combustibles and the flotation perfection index can reach 80.10% and51.93%,respectively.In the kerosene-HIP emulsion system,the emulsion flotation effect is the best when the surfactant is Span80,the kerosene:Span80 is 2.61:1,and the inorganic salt solution in the inner water phase is 0.3 mol/L NaCl,and the obtained clean coal ash content is18.04%,the recovery rate of combustibles and the flotation perfection index were 82.49% and57.90%,respectively.(4)The flotation index is further optimized through the "one coarse and one fine" flotation process.The results show that "one coarse and one fine" can significantly reduce the ash content of flotation clean coal and improve the flotation efficiency.When the dosage of FDJ-HIP emulsion is 320 g/t,the flotation clean coal with ash content of 9.52% and combustible recovery rate of 72.95% can be obtained,and the flotation perfection index is 62.27%.When the dosage of kerosene-HIP emulsion is 1009 g/t,the flotation clean coal ash content is 10.07%,the recovery rate of combustibles is 77.50%,and the flotation perfect index is 65.74%.(5)Infrared spectral analysis showed that no new peaks or peaks disappeared on the coal surface after the action of kerosene,kerosene-HIP emulsion,FDJ,and FDJ-HIP emulsion,only the peak area and intensity changed,which indicated that the four agents were The adsorption methods on the coal surface are all physical adsorption,and the oxygen-containing functional groups(-OH)on the coal surface are reduced after the action of kerosene and kerosene-HIP emulsion,and the hydrophobicity of the coal is enhanced.However,the aromatic hydrocarbons on the coal surface increased after the action of FDJ and FDJ-HIP emulsions,which enhanced the hydrophobicity of coal.(6)By comparing the molecular dynamics simulation results of pure kerosene and kerosene-Span80 mixed collector on the coal surface,the microscopic mechanism of keroseneSpan80 mixed agent to enhance coal slime flotation is revealed.The results show that there are a large number of polar ends on the coal surface,and Span80 can better adsorb on the polar ends;the distance between pure kerosene and coal surface is about 0.8 nm farther than that of kerosene-Span80 mixed collector.When the collector is kerosene,the van der Waals energy is very low,but the electrostatic energy is almost zero.The addition of Span80 to the mixture increases the van der Waals energy and electrostatic energy between four different molecules,which greatly reduces the electrostatic energy,so the total energy of the system is lower and more stable.By calculating the slope of the MSD diagram,it can be seen that the diffusion coefficient of the kerosene-Span80 mixture on the coal surface is lower,and it is more closely combined with the coal.