Study On Micro Wetting Mechanism And Compound Optimization Of Surfactant On Coal

A large amount of dust will be generated during the efficient production of coal mines.In most mines,various surfactants are added to the water injection process to reduce the dust concentration generated during the coal mining process,but their wetting effect on the coal surface is not ideal.Compared with the single surfactant,the compound surfactant can greatly improve the wetting ability of the solution to coal.Based on this,in order to deeply study the influence mechanism of surfactant on coal surface wettability,this paper selects three different coal rank coals as the research objects,and conducts research on the microscopic wetting mechanism and compound optimization of surfactants on coal.By means of molecular simulation and experiment,the micro-wetting mechanism and influence law of compound surfactants on coal of different rank were revealed.The research results are of great significance to the application of coal seam water injection and dust reduction.The main research results are as follows:Through industrial elemental analysis,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,and nuclear magnetic resonance（13C NMR）combined spectroscopic experiments,the elemental composition and content and surface functional group distribution of the three coal samples were determined.and content,the degree of polycondensation of the benzene ring.The bridge carbon and peripheral carbon ratios of lignite,bituminous coal and anthracite were obtained,and the arrangement of aromatic rings and the connection of aliphatic hydrocarbons in lignite,bituminous and anthracite were determined.The positions of oxygen-containing functional groups and heteroatoms in the molecular structure of the three coal samples were clarified,and the planar structure models of lignite,bituminous coal and anthracite were constructed.Using quantum mechanics as the theoretical basis,the dipole moment values of different ionic surfactants were determined by simulation,and the polarity relationship of different ionic surfactants was obtained.The influence of the charge distribution of different groups on their polarity was clarified.The electrostatic potential relationship between different rank coal bodies and surfactant aqueous solution was clarified,and the wetting performance parameters were obtained.Molecular dynamics simulation was used to carry out the optimal adsorption configuration of water molecules in different oxygen-containing functional groups and Benzene-CH₃,and the optimal adsorption distance and adsorption energy of water molecules in oxygen-containing functional groups and Benzene-CH₃ were determined.According to the optimal adsorption conformation distance and adsorption energy,the order of the binding ability of water molecules to functional groups was obtained:Benzene-COOH>Benzene-OH>Benzene-O-CH₃>Benzene-CH₃.The molecular simulation of adsorbed water of different coal ranks was carried out by Monte Carlo method,and the absolute adsorption of water adsorbed by coal of different coal ranks in the pressure range of P=1-10MPa was obtained at T=288.15K,298.15K,303.15K It is clear that the adsorption law of the absolute adsorption capacity curve conforms to the Langmuir curve.It was obtained that the adsorption of water by different coal rank coals inhibited with the increase of temperature,and the increase of external pressure promoted the adsorption.When the external pressure of water was P=4MPa,an inflection point appeared,and the adsorption effect gradually tended to increase with the increase of pressure.in peace.The adsorption methods of water in three different rank coals were clarified,and the adsorption methods of lignite were mainly chemical adsorption,supplemented by physical adsorption.The adsorption of bituminous coal is supplemented by chemical adsorption and mainly by physical adsorption.The adsorption of anthracite is physical adsorption.Molecular dynamics simulations of coal/water,coal/surfactant/water,coal/complex surfactant/water under 500ps were carried out by molecular dynamics simulation.By analyzing the interaction energy of the system,the contribution distribution along the Z axis and the mean square displacement of the water molecule.The interaction energy,the wetting range of water molecules and the diffusion rate parameters of water molecules in the system without surfactant,water in single surfactant,and water in compound surfactant system were obtained.Microscopic wetting mechanism and influence law under the action of active agent.Using the surface tension and contact angle measurement experimental system,the optimal compounding methods and compounding concentrations of monomeric surfactants and compounded surfactants in different coal rank coals were studied.Optimum compounding concentration of different ionic surfactants.When the compound solution titrated lignite and anthracite,the minimum contact angle angle combination was anionic surfactant SDBS+nonionic surfactant CDEA,and the compound solution titrated bituminous coal with the minimum contact angle angle combination was anionic surfactant SDBS+zwitterionic surfactant LAD-40.It has a good synergistic effect in the way of compounding,thereby increasing the wettability of coal.Through the coal dust sedimentation experiment and the water retention performance experiment,the diffusion law of the compound surfactant in the coal body of different coal ranks was determined,and the reliability of the compound method was verified.Based on the research on the wetting mechanism and compounding optimization of the molecular simulated surfactant on the coal body,a field test of coal seam water injection was carried out in the 10105 fully mechanized working face of Baozigou Coal Mine.According to the actual working conditions on site,the water injection method,drilling length,advance water injection time and distance are determined.According to the research results of molecular simulation and compound experiment,the compound method of the best surfactant for bituminous coal was obtained,and the industrial experiment of coal seam water injection was carried out by using 0.5%anionic active agent SDBS and 0.5%zwitterionic active agent LAD-40 as the water injection medium.The field test results show that the total dust and exhalation dust reduction efficiency after pure water injection are 41.3%and 29.5%,respectively.After injecting the compound surfactant solution,the dust reduction efficiency of total dust and exhaled dust was 76.7%and 52.7%.Using the compound surfactant as the water injection medium can significantly improve the working face environment and achieve a good water injection and dust reduction effect.The dissertation has 90 figures,58 tables,and 213 references.