Experimental Study On Characteristics Of C₂H₄ Production From Low Temperature Oxidation Of Coal

At this stage, the spontaneous combustion of coal mine is inevitable in coal mine production,this disaster has been for a long time, scholars had done some research in terms of spontaneous combustion of coal in recent years, that the reasons for spontaneous combustion is largely due to of coal low-temperature oxidation, low-temperature oxidation of coal will produce a variety of gases, some of which gas plays a big role in mine fire forecast, scholars on the part of indicators such as gas formation mechanism of CO, CO2 with a certain understanding, but the formation mechanism of C₂H₄ to generate in spontaneous combustion of coal reports rarely,this text present systems of coal-based low-temperature oxidation mechanism, build basic theory of low-temperature oxidation of coal, coal mechanism of low temperature oxidation of ethylene design experiments, aimed to predict coal spontaneous combustion and suppress acts of help to establish the theoretical basis of spontaneous combustion of coal.This text selects four kinds of different rank coals for the study with Ximeng（XM） lignite, Shendong（SD） long-flame coal, Yima（YM） gas coal, Zaozhuang（ZZ） coking coal by temperature programming, defining an enclosed environment thermostat, Fourier transform infrared spectroscopy,to use these three kinds of experimental conditions to study variation of different rank coal with the oxidation of C₂H₄ oxidation temperature, simultaneous analysis of different temperature history, different coal particle size, different reactor volume and other factors effect of C₂H₄ emission; at the same time using the infrared spectroscopy to analyze microscopic structure of coal, designed to generate ethylene gas in this macro performance during low-temperature oxidation of coal and generation of microstructure change during the coal ethylene molecules were association, the following main conclusions are obtained:（1）Through four kinds of different coal rank for XM lignite, SD long-flame coal, YM gas coal, ZZ coking doing temperatureprogrammed experiments showed that low temperature oxidation of coal with coal released of C₂H₄ increases with the temperature exponentially, regularity is very good, in line with the principle of selecting indicators gases. Also by the four coal samples isothermal oxidation in defining an enclosed environment, the display as the temperature increases, the concentration of C₂H₄ exponentially.（2）The degree of coal metamorphism decide coal release of C₂H₄ in low temperature oxidation process, C₂H₄ release of coal with temperature changes had a trend of exponential.（3） The temperature in detecting of C₂H₄ earlier than the programmed temperature within an enclosed environment; because energy coal oxide emission can be gathered in defining a closed condition,in turn, coal-oxygen activation to release C₂H₄ occurs, C₂H₄ release of coal will decrease as the particle size increases, after reaching a certain particle size, to further reduce the particle size of coal will inhibit the release of coal samples C₂H₄, because as the particle diameter decreases to some extent, the porosity of the coal particles is too small, the effects of oxygen diffusion and gas generated by the reaction, and thus impacts the coal react with oxygen.（4）Temperature played a decisive role in the process of lowtemperature oxidation of coal, coal-oxygen complex capacity was positively correlated with temperature; the larger reactor volume, the greater the total amount generated C₂H₄, because with the increase of the volume of the reaction vessel and oxygen content in the coal and oxygen will increase the contact area, it is conducive to coal-oxygen reaction.（5）To research the three coal by Fourier infrared spectroscopy, there is a big difference can be found in three coal infrared absorption spectrum, which shows the type and content of the functional groups largely by coal metamorphism level decisions, coal intramolecular chemical structure of these functional groups because of the differences occur. Infrared spectra can exhibit a difference in time oxidized functional group type and quantity changes,the change of the oxidation process each reactive functional groups can be more clearly reflected.（6）Through two levels of XM lignite and ZZ coke in different metamorphism coals isothermal oxidation at four different temperature points, we can get an aliphatic C-H component content at 100℃ have decreased, when the temperature reaches 125 ℃, the tendency to reduce the content thereof is more obvious, and with increasing oxidation temperature and oxidation time, the aliphatic C-H component content decreased rapidly, but with the oxidation time, component content of the aliphatic C-H the rate of decrease slowed down, which is good correspondence of coal under defined confinement release of the C₂H₄. In addition, we can be found in various temperature points, with the oxidation time, the reduction of aliphatic C-H component content in XM lignite is slower than coke of ZZ XM, it also proves that the rate of release of C₂H₄ in XM lignite is more fast.（7） The release of C₂H₄ as a consequence of the gradual change of spontaneous combustion of coal functional groups generated, namely coal of different functional groups activation reaction at different temperatures, and only at this temperature, the number of the functional groups will vary further into a gas product, specifically in coal lowtemperature oxidation process, with oxidation temperature rises, O2 attack benzene ring side chain aliphatic C-H bond, lead to the formation of ethylene oxide and other products, in using of experimental research to establish the mechanism of ethylene obtained in this paper,the spontaneous combustion of coal gas generated by the general rules of indicators were well explained.