Experimental Research Of Low Rank Coal Flotation On Synergistic Enhancement Of Inorganic Salts And Surfactants

In this paper,the raw coal and the filter press slime of final coal system concentrator low flow in a power coal preparation plant in Ordos City are taken as the research object.Aiming at the problems of strong surface hydration ability and low flotation efficiency,the study of using inorganic salts and surfactants to coordinately regulate the low rank coal surface properties and strengthen the low rank coal flotation efficiency is carried out,and the influence of inorganic salts and surfactants on low rank coal flotation behavior is deeply explored.Through the coal sample properties analysis,it can be seen that the coal sample ash content is 32.05%,fixed carbon content is 43.29%and fine grained material content is more.XRD and XPS analysis show that quartz and kaolinite are main gangue minerals in coal.Infrared spectrum analysis shows that the coal samples surface contains more hydrophilic oxygen-containing functional groups,so its hydrophobicity and floatability are poor.Coal samples wetting heat is-40.922J/g.The effects of inorganic salts and surfactants on the low rank coal surface modification were studied.The results show that surfactants can enhance the hydrophobicity of low rank coal surface,and the intervention of inorganic salts can enhance the ability of surfactants to improve the hydrophobicity of coal surface.Under the synergistic action of PEG and AlCl₃,the hydrophobicity of coal surface is the strongest.At this time,its contact angle is 71.3°and the wetting heat is-7.441 J/g.Scanning electron microscopy images of coal samples show that the effect of inorganic salts and surfactants can reduce the fine particles content on the low rank coal surface and make the surface smooth.The effects of inorganic salts and surfactants on the solution environment and bubble properties were studied.The results showed that the adsorption behavior of surfactants at the gas-liquid interface would be changed by inorganic salts and there is a surface tension switch point.Surfactants can improve bubbles deformability so that the bubbles tend to be spherical,and the bubbles final rising velocity decreases.The addition of inorganic salts can reduce the deformability and the motion final velocity of bubbles.That is to say,inorganic salts regulate the bubble movement in the synergistic system by affecting the adsorption behavior of surfactants at the gas-liquid interface.The stability of gas-liquid two phase foam is improved obviously by adding inorganic salts in water.The higher valence state of inorganic cation,the stronger stability of two phase foam layer.Surfactant can enhance the stability of gas-liquid two phase foam.SDS has the highest ability to enhance foam stability.The effects of inorganic salts and surfactants on the field low rank coal slime flotation were studied.The results show that in a single flotation test,Al³⁺and PEG can effectively improve the flotation clean coal yield.At the same time,the clean coal ash content is low and the comprehensive effect is better.When NaCl,CaCl₂ and AlCl₃ are added to the surfactant solutions,the flotation efficiency decreases in SDS solution.SDS neutralizes or reacts with inorganic cations to form complex precipitation,the effect of SDS on low rank coal is inhibited.Three inorganic salts can promote flotation in DTAC and PEG solutions,and the flotation effect of Al³⁺combined with PEG is the best.Under this condition,the flotation combustible recovery rate increased by 8.66%,the clean coal ash content increased by only 1.64%.In the flotation test of low rank coal pure minerals,the combustible recovery rate of pure minerals in deionized water is 77.47%,and its clean coal ash is 4.34%.In the synergistic system of AlCl₃ and PEG,when the flotation combustible recovery rate increased by 20.03%,the clean coal ash content increased by only 0.4%.It can be seen that the selectivity of collector to clean coal can still be maintained in the synergistic system of AlCl₃ and PEG.The conclusion is the same as that of field low rank coal slime flotation experiment.This paper contains 55 figures,11 tables and 106 references.