Experimental Study On Spontaneous Combustion Characteristics In Low-Temperature Oxidation Process Of Jurassic Coal And Its Index Gases

Spontaneous combustion of coal constitutes a great harm to mine safety production.The Jurassic coal reserves in China are large and the tendency of spontaneous combustion of it is strong.The characteristics of spontaneous combustion of coal low-temperature oxidation,the critical value of the index gas and its influence factors were studied in this article.The research results have important scientific significance and practical value for prediction of the Jurassic coal spontaneous combustion and coal fire disaster.First,the kinetics of oxidation reaction of two stages were studied by TG of four different heating rates during low-temperature oxidation process,which from normal temperature to critical temperature then to dry cracking temperature.The finding indicates that the overall reaction process of coal spontaneous combustion is similar.The characteristic temperature of coal sample is lagged with the increase of the degree of metamorphism,which means that it is not easy to oxidize and combust under the same condition.During the low-temperature oxidation process,the chemical reaction of coal samples is accelerated,so it is mainly controlled by the three stage chemical reaction equation.Then,the change rules of main functional groups at critical temperature and dry cracking temperature during low-temperature oxidation process of coal samples were studied by FTIR.The finding indicates that aliphatic hydrocarbons and oxygenated functional groups are the main participants in oxidation reaction,while aromatic hydrocarbons are not.The higher the degree of metamorphism of coal sample is,the more the substituent benzene that reflects the stability of the aromatic nucleus is,and the shorter the alkyl side chain connected to the aromatic nucleus is,which indicate that the coal molecular structure is relatively stable.Moreover,the less the oxidizable-OH is.These mean coal samples with higher metamorphism degree are more difficult for oxidation and spontaneous combustion.At last,the macro characteristics of gas concentration,oxygen consumption rate and the critical value of CO during low-temperature oxidation of coal samples were studied by programmed temperature experiments under different experimental conditions.The finding indicates that CO and C2H4 with the approximate exponential growth trend can be used as index gases for coal spontaneous combustion,but CO2,CH4 and C2H6 stored in coal samples are not.Particle size,air supply and oxygen concentration can affect the oxidation and spontaneous combustion of coal.The smaller the particle size is,the stronger the character of oxidation and spontaneous combustion of coal sample is.The suitable air supply can promote the oxidation of coal samples.The lower the oxygen concentration is,the more difficult the interaction of coal and oxygen is.The multiple linear regression model of CO critical value is established,which can predict the CO critical value,thus providing a scientific evidence for the prevention and control of coal spontaneous combustion.