Study On Prediction Method Of Coal Spontaneous Combustion In Xichuan Coal Mine With Native CO

Mine fire is one of the main disasters in the normal course of coal mining.CO gas in the early stage of spontaneous combustion of coal produces earlier and greater concentration, so as the main indicator of coal spontaneous combustion prediction.But in recent years, the domestic part of the mine, which have a high concentration of CO gas was not accompanied by the phenomenon of spontaneous combustion of coal.Some people think that this part of the CO gas is a kind of coal gas, which means that the coalbed with native CO gas. This view has not been effectively confirmed at present. For seam containing native of CO, CO whether as coal spontaneous combustion index gas needs in-depth study.This paper studied Xichuan coal mine also had a similar phenomenon. Studying the CO genetic types and exploring new coal spontaneous combustion prediction method to Xichuancoal arevery important for the efficient production of coal mine safety.This paper study the isotope variation of Xichuan coal in different reaction atmosphere with increasing temperature by exploring the methods of detecting isotopes in low concentrations of CO and CO₂. The CO isotope test results show that δ¹⁸O of the CO produced in different reaction atmosphere become smaller with the increasing temperature.It shows that low temperature reaction of coal does not belong to a single reaction sequence. Furthermore, δ¹⁸O of CO producedinargon atmosphere is heavier 9 ‰than in air atmosphere, which prove that CO produced in different atmosphere have different sources of oxygen atoms. The CO₂ isotope test results show that the variation of δ¹⁸O in CO₂ is complex. And itdose not change significantly at 75℃ before, then the variation of δ¹⁸O has down- up- and reduce features after 75℃.The inflection temperatures are 130 ℃ and 160 ℃. δ¹⁸O increases suddenly after 130℃,which shows that the oxygen atom of CO₂ comes from coal mainly.And the temperature is the coal cracking temperature.By testing the δ¹⁸O in COfrom 1109 ventilation roadway, 1111 and 1109 upper-cornerworking face, we found δ¹⁸O in CO of coalmine and δ¹⁸O in CO produced in air are quite different. It shows that the part of the oxygen in CO comes from Xichuan Coalbed. Based on geological structures and sedimentary characteristics of Xichuan coalmine further analysis, we think that the native CO in coalbed comes from the shedding of functional groups in the process of metamorphism. The roof and floor of Xichuan 4-2 Coalbed are all muddy siltstone or mudstone, and the content of oxygen in coal is higher, which provide favorable conditions for native COformation and occurrence.Combining with the actual situation of Xichuan coalmine, We further explores the prediction method of coal spontaneous combustion. The result shows that if C₂H₄ gas is detected during normal coal mining, we should pay attention to it, and we should continuously detect the concentration changes of C₂H₄ gas. At the same time, we should detect the ratio of ethylene oxide,R3 and isotope values of CO₂. If C₂H₄ gas concentration is increasing, and the ratio of ethylene oxide is more than 0.1%, and the R3 values is over 10%, and oxygen isotope values of CO₂ is less than-5‰, and carbon isotope value of CO₂ is less than-19‰,it can be sure that the temperature of coal spontaneous combustion has reached more than 70℃. Therefore, we should stop the normal production at once, and adopt the method of injecting nitrogen, filling slurry and so on, to prevent the occurrence of coal spontaneous combustion.