Construction Of Molecular Model Of Anthracite Dust Phase And Study On Its Wettability

Judging from the current development trend of the country,by the middle of this century,coal demand still accounts for more than 50%of China's total energy demand.As coal mines move towards green,environmental protection,intelligence,mechanization,large-scale,and intensification development,there are higher requirements for the prevention and control of coal dust.Looking at all countries,so far,more than 140 molecular structures of coal have been constructed all over the world,but there are only more than 10 molecular structure models of anthracite,and the molecular structure model of anthracite coal dust in southern china has not been constructed.The Bijie area of Guizhou Province and the Longyan area of Fujian Province are the main anthracite production bases in south of our country.The anthracite in this area is harder,and the coal dust produced is usually 2 to 3 times that of bituminous coal and lignite.Therefore,the construction of molecular structure model of Bijie Guizhou and Longyan Fujian anthracite not only fills the blank of southern china anthracite without molecular structure model,but also has profound significance to understand and solve the coal dust suppression,coal dust explosion and air pollution in these two areas by deeply understanding their molecular structure model and studying their wettability.This article takes BJ and LY anthracite coal dust as the research object,the structure of BJ and LY anthracite coal dust was characterized by proximate analysis,ultimate analysis,solid-state nuclear magnetic resonance carbon spectroscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy and X-ray diffraction,and the structural parameters of coal dust were obtained.Then the planar macromolecular structure model and single chain energy model of BJ and LY anthracite coal dust were constructed.The wettability of coal dust was studied by interaction energy,relative concentration distribution and mean square displacement molecular simulation technology,and the wettability of coal dust was studied by contact angle experiment,permeability experiment and improved sedimentation experiment.The main conclusions are as follows:(1)Through proximate analysis and ultimate analysis,it is found that BJ and LY coal dust belong to anthracite(volatile matter<10%),and the atomic ratios of H/C,O/C,N/C and S/C of BJ and LY anthracite structure are obtained.The 12 parameters of the molecular structure skeleton of coal dust and the bridge carbon ratio of BJ and LY were obtained by¹³C-NMR test to be 0.16 and 0.29;using FTIR test,the types and contents of hydroxyl group,oxygen-containing functional group and aromatic group in the molecular structure of BJ and LY coal dust were found;The structural forms of carbon,nitrogen and sulfur in BJ and LY anthracite coal dust samples were obtained by XPS technology.They all contain aromatic carbon,aliphatic carbon,oxygen-bonded carbon,pyrrole type nitrogen and mercaptan thiophenol;In addition,BJ coal dust contains quaternary nitrogen and sulfoxide sulfur,while LY coal dust contains nitrogen oxides and sulfoxide sulfur;the microcrystalline structure parameters of BJ and LY anthracite coal dust are obtained by XRD technology,and the distribution on two-dimensional horizon is regular and similar,which is considered to be"graphitization".(2)The relevant structural parameters of BJ and LY anthracite coal dust volume phase molecular models.1)The aromatic structure of BJ anthracite coal dust molecular structure is benzene ring,naphthalene and pyrrole,the numbers of which are 7,8,and 1,respectively;the aliphatic carbon structure is composed of oxygen-bonded carbon and methyl,and the numbers are 4,5;The heteroatom structure is composed of phenolic hydroxyl group,carbonyl group,carboxyl group,pyrrole,thiophenol and 4 ethers,all of which are 1.2)The aromatic structure of LY anthracite dust is benzene ring,naphthalene,anthracene,phenanthrene,and pyrrole,the numbers are 1,5,4,1,and 1,respectively;the aliphatic carbon structure is composed of oxygen-bonded carbon and methyl,and the numbers are in order 2and 1;the heteroatom structure is composed of carbonyl,ether,pyrrole,phenolic hydroxyl and thiophenol,and the corresponding numbers are 2,2,1,1,and 1.(3)The plane structure model of BJ and LY anthracite coal dust macromolecules was preliminarily constructed,the molecular formulas of which are C₁₄₈H₇₅O₈NS and C₁₅₂H₇₇O₅NS in sequence.On the basis of the BJ and LY anthracite coal dust macromolecular plane structure model,after geometric optimization,annealing simulation and relaxation,the lowest energy three-dimensional structure model of BJ and LY coal dust was constructed,and then the BJ and LY anthracite coal was constructed.Dust single-phase and two-phase system aggregation model.(4)The wettability molecular simulation was performed on the aggregation model of BJ and LY anthracite coal dust/water two-phase system.Through the adsorption configuration,it is found that the aqueous solution adsorbs,spreads and aggregates on the surface of the anthracite coal dust,and the hydrophobic carbon chain is also entangled.Even a few water molecules pass through the surface of the anthracite coal dust and are adsorbed near the inner oxygen-containing groups of the anthracite coal dust;From the interaction energy,the total interaction energy between BJ anthracite coal dust and aqueous solution is greater than the total interaction energy between LY anthracite coal dust and aqueous solution,indicating that the adsorption of BJ anthracite coal dust on the surface is stronger than that of LY;The concentration distribution shows that the overlapping range of BJ anthracite coal dust and water is larger than that of LY,so BJ anthracite coal dust is easier to wet than LY.From the mean square displacement,it is found that the water molecule MSD of BJ anthracite coal dust/water two-phase system is better than that of LY.This is because the hydrophobic carbon chain in the BJ anthracite coal dust structure repels water molecules weaker than LY.From the mean square displacement,it can also be found that the water molecule diffusion coefficient of BJ anthracite coal dust/water two-phase system is smaller than that of LY,indicating that LY anthracite coal dust is more hydrophobic than BJ.(5)Through the contact angle experiment,the contact angles of coal dust and water in BJ and LY are 47.7°and 54.2°,respectively.The wettability of BJ coal dust is better than that of LY;From the permeability experiment,it is found that the coals of BJ and LY have better wettability than LY.The dust penetration depths are 4.2 cm and 3.8 cm,respectively,indicating that the permeability of BJ coal dust is better than that of LY coal dust;By improving the settlement experiment,it is found that the coal dust immersion speed of BJ is faster than that of LY,but the overall difference is not very large.It shows that the coal dust in BJ and LY can be wetted and the wettability is similar.