The Effect Of The Synergism Adsorption Of Non-Ionic Surfactant And Kerosene On The Wettability Of Low-Rank Coal

The reserves of low rank coal are abundant in China.With the continuous growth of energy demand in China,how to efficiently and cleanly exploit and utilize low rank coal is very important.Because of low rank coal metamorphism,low degree of coalification,high porosity of particle surface and many hydrophilic groups in side chain,the surface hydrophobicity of low rank coal is poor and the drug consumption is high.Therefore,conventional flotation reagents can not efficiently recover low rank coal.Nonionic surfactant plays an increasingly important role in the flotation of low rank coal with its good adsorption selectivity.It can improve the surface floatability of low rank coal,reduce the flotation reagent consumption and improve the flotation efficiency.In this paper,the properties of the mixture of nonpolar hydrocarbon oil collectors（kerosene,n-dodecane）and C₁₂EO₄ in aqueous solution were studied;The adsorption characteristics of nonpolar hydrocarbon oil collector,C₁₂EO₄ and their mixtures on the surface of low rank coal and their effects on wettability were discussed;The flotation experiment was carried out to verify the effect of compound reagents on the flotation results of different kinds of low rank coal.The main conclusions are as follows:According to the interaction parameters and mixing energy data of n-dodecane and C₁₂EO₄,they are compatible in theory.The addition of C₁₂EO₄ has little effect on the surface tension of kerosene and n-dodecane.The collector can form oil in water emulsion in aqueous solution and has good stability.The dispersion of the complex collector in aqueous solution is enhanced,and the particle size of oil drops in water is smaller,which is beneficial to improve the contact and collision probability between the collector and coal particles.At the same time,with the increase of C₁₂EO₄ ratio,the surface electrical properties of the oil droplets gradually move to the positive direction.The decrease of the surface electronegativity of the oil droplet weakens the electrostatic repulsion between the oil droplet and the negatively charged low-order coal particles,which is beneficial to the interaction between the oil droplet and the particles.Therefore,the wetting heat release between the complex collector and low rank coal is more significant,and the maximum wetting heat value is obtained when the volume ratio of kerosene（n-hexadecane）:C₁₂EO₄ is 100:30.Within the experimental concentration range,the adsorption amount of kerosene on the surface of low-rank coal increases with the increase of kerosene concentration;under the same kerosene concentration,the adsorption amount of kerosene basically does not change with the extension of time,and can be adsorbed on the lower-rank coal in a relatively short time Coal surface.The adsorption capacity of kerosene increased with the increase of p H value;Comparing the zeta potential of low rank coal before and after adsorption of kerosene,it can be seen that the adsorption of kerosene on the surface of low rank coal is helpful to reduce the surface electronegativity of low rank coal.Inorganic salt ions have a significant influence on the adsorption of kerosene on the surface of low-order coal:low concentration Na Cl promotes the adsorption of kerosene on the surface of low-order coal,and high concentration Na Cl will inhibit the adsorption of kerosene,while Mg Cl₂ shows the opposite trend,which may be due to the presence of inorganic salt affecting the surface properties of low-order coal.The adsorption capacity of C₁₂EO₄ on the surface of low-order coal increases with the increase of initial concentration,and the moisture heat value between C₁₂EO₄ and water decreases with the increase of solution concentration.Oil soluble surfactant C₁₂EO₄ can significantly enhance the hydrophobicity of low rank coal surface,enhance the interaction between low rank coal and kerosene,and enhance the adsorption capacity of low rank coal surface to kerosene.It is also found that the order of adding reagents can affect the adsorption of kerosene on the surface of low rank coal:the adsorption effect of kerosene by C₁₂EO₄ and kerosene miscible reagent is better than that by C₁₂EO₄ first and then kerosene.Through the flotation experiments of HEWS 1#and 2#coal samples and HLS coal,it is found that the combination of C₁₂EO₄ and kerosene（dodecane）as collector can greatly improve the flotation effect of low rank coal,and when the volume fraction of C₁₂EO₄ is 30%,it is consistent with the wetting law of low rank coal surface under the condition of compound reagent,The results show that the combined reagent can reduce the amount of non-polar hydrocarbon oil collector and improve the flotation effect of low rank coal.Compared with the flotation experiment results of HEWS 1#and gangue,the addition of C₁₂EO₄ can not only improve the yield of clean coal,but also improve the selectivity of non-polar hydrocarbon oil collector for organic matter and inorganic matter of coal,and promote the flotation separation of organic matter and inorganic matter.