Study On Microscopic Differences Of Tectonic Coal In Pingdingshan Mining Area And Bituminous Coal Organic Small Molecule Model Building

Coal plays a very important role in China’s energy structure under the current rapid economic development,and China is the third largest coal resource country in the world.However,due to the particularity of coal seam structure,mine disasters are very serious,among which coal and gas outburst accident is the most serious.In coal seam structure,tectonic region more easily cause accidents of coal and gas outburst,and this phenomenon has not been given a clear scientific conclusion.Therefore,for Pingdingshan mining area with typical outburst risk,this paper used industrial analysis,elemental analysis,Fourier infrared spectroscopy（FT-IR）,nuclear magnetic resonance carbon spectrum（13C-NMR）and other test methods to carry out the study on the microscopic differences of primary coal（PT）,fault coal（D）and soft stratified coal（R）in the mining area,and built the organic small molecule model of Pingdingshan bituminous coal based on the microstructure information.The results obtained are of great significance for predicting the tectonic area of coal seam and studying the pore structure and gas adsorption and analytical characteristics of coal structure.（1）Fourier infrared spectroscopy can qualitatively analyze the composition of functional groups in coal;nuclear magnetic resonance carbon spectrum can accurately and quantitatively determine the type and proportion of carbon atoms in coal;meanwhile industrial analysis and elemental analysis give the overall structure information of coal.（2）The above experimental results show that the calculated results of tectonic coal in elemental analysis of H_daf and infrared characteristic parameter Ii are both greater than that of primary coal,so the degree of hydrogen enrichment in the two tectonic coals is greater and the hydrocarbon generation capacity is stronger.The values of O_daf in elemental analysis,infrared characteristic parameter I2 and nuclear magnetic parameter falO are all greater than the primary coal sample,indicating that there are more oxygen-containing functional groups in the tectonic coal structure.In terms of structural condensation degree,it can be concluded from the calculation results of infrared characteristic parameters I3 and I4,as well as the aromatic degree fa and ratio X_BP of aromatic carbon bridge to cyclic carbon in the carbon spectrum that the primary coal has a higher degree of condensation and a deeper degree of aromatization than the tectonic coal.（3）Calculation of ether bond content in coal structure:R is 1.439;D is 1.244;PT is 0.768;The aromatic degree measured by the nuclear magnetic carbon spectrum is D<R<PT.Oxygen-containing fat carbon:D-f（al）^O>R-f（al）^O>PT-fatO;The ratio of aromatic bridge carbon to cyclic carbon was 0.27 for R-X_BP,0.23 for D-X_BP and 0.53 for PT-X_BP.Based on the above（2）results and other experts’ studies on coal with different coal ranks,it can be concluded that the tectonic coal samples in the same geological unit show a phenomenon of "delayed coalification" in terms of ether bond content,aromaticity,number of oxygen-containing functional groups and ratio of aromatic bridged carbon to cyclic carbon.That is,compared with the primary coal in the same geological unit,the tectonic coal shows the characteristics of low-order coal.Therefore,according to the changes of the microscopic properties of the coal slag discharged from different positions of the leading borehole on the mining face,the tectonic area in front of the mining face can be detected in advance.（4）According to the above microstructure information and based on the molecular mechanics and molecular dynamics of Material Studio software,the organic small-molecule structure model of Pingdingshan bituminous coal was constructed,Molecular formula is C₁₀₈H₇₁O₄N.This model can better simulate the density and porosity of coal structure,and the error between the gas isothermal adsorption amount and the real coal isothermal adsorption amount in the high-pressure stage is less than 5%,so this model has certain research value and application value.