Research On Spontaneous Combustion Characteristics Of Lignite Based On Macro-meso

Coal spontaneous combustion is one of the main disasters in mines.Systematically analyzing the characteristics of coal spontaneous combustion and studying the corresponding relationship between coal molecular structure and macro-products during spontaneous combustion are helpful to understand the occurrence and development of coal spontaneous combustion,to explore the mechanism of coal spontaneous combustion,and to provide theoretical guidance for fire prevention and extinguishing.In this paper,by combining theoretical analysis with experimental study,the intrinsic relationship between the macro-characterization of coal spontaneous combustion,the characteristics of gas release and micro-characteristics,and the evolution law of surface functional groups of coal molecule is explored.Firstly,by analyzing the micro-mechanism of coal spontaneous combustion,the active structure of coal molecule which is easily attacked by oxygen is determined.and the source of main gas products in the process of coal spontaneous combustion is inferred.On this basis,the oxidation process of coal samples between 30?300? was simulated by using a temperature programmed experimental system.The variation of the concentration of CO,CO2,CH4,C2H4 and C2H6 with temperature was obtained.The CO gas with good correlation with coal temperature is selected as the index gas.and the characteristic temperature points of coal samples are calculated by the index gas growth rate analysis method.The experimental results show that the concentration of carbon and oxygen gases increases sharply after the critical temperature,and the concentration of hydrocarbon gases increases rapidly after the dry cracking temperature.Then.seven groups of coal samples treated at different oxidation temperatures were tested by FTIR.According to the attribution characteristics of main absorption peaks of coal,and taking absorbance as an index,the variation of 17 main functional groups in coal molecular structure with temperature was quantitatively analyzed.The results show that with the increase of oxidation temperature,the content of hydroxyl and aliphatic hydrocarbon functional groups in coal samples decreases,the oxygen functional groups increase continuously,and the aromatic hydrocarbons increase first and then decrease.Finally,SPSS software was used to analyze the correlation between the characteristics of gas release at macro level and the evolution of functional groups at micro level in the process of coal spontaneous combustion.It was found that aliphatic hydrocarbons and oxygen-containing functional groups had a good correlation with the main gas products.On this basis.the intrinsic relationship between surface functional groups of coal molecule and main gas products is analyzed.It is proposed that the generation of carbon and oxygen gases is mainly attributed to the oxidation and decomposition of active structures such as methylene bridge bonds in coal molecule.Hydrocarbon gases mainly come from the oxidation and fracture of alkyl side chains.