Spontaneous Combustion Characteristics And Fire-Fighting Technology For Coal In High Ground Temperature Environment In Tengnan Mining Area

The mining depth is increasing in the east mining area and the groundtemperature gradually increased, leading to more frequent occurrence of coalspontaneous combustion hazard. The coal mining elevation of TianChen, TengDongmine in TengNan mining area have reached-900m and the ground temperaturereached more than40℃, coal spontaneous combustion disaster is particularly acute.But now there is little research about low temperature oxidation characteristics of coalin high ground temperature and fire suppression technology.Ground temperature is the initial oxidation temperature of the coal. This papersimulated the coal oxidation process with temperature-programmed method under thestarting temperature of20℃,30℃,40℃, and respectively obtained the variation ofthe oxygen consumption, oxygen consumption rate and junction temperature duringthe process of coal oxidation. Studies show that：the higher the initial oxidationtemperature, the larger oxygen consumption and oxygen consumption rate of coal,and this difference increases with increasing temperature; the higher initial oxidationtemperature, the lower temperature of junction temperature, and with the startingtemperature increased, the degree of increase of junction temperature decreasesgradually; the higher initial temperature, the more active groups react with oxygenunder the process of low-temperature oxidation of coal in any temperature, whichleads to higher oxygen consumption and oxygen consumption rate, higher heatproduction, quicker temperature rise rate, lower crossing point temperature.Low-temperature oxidation of coal heat is the root cause of spontaneouscombustion of coal, and activation energy and pre-exponential factor are the majordeterminant of low-temperature oxidation rate of coal. This paper used high-precisionmicro-calorimeter C80to test the thermal behavior of the oxidation process of coalsamples in three different temperatures rising rate, and accurately solved the changingrule of the kinetic parameters (activation energy and pre-exponential factor) in theprocess of low-temperature oxidation of coal. And also used kinetics based simulationmethod assess the risk of spontaneous combustion of coal in different groundtemperature environments. Researches show that: With the increase of groundtemperature, the time for coal to reach70℃during adiabatic oxidation quicklyreduces, and the risk of spontaneous combustion of coal gradually changes from noteasy spontaneous combustion to spontaneous combustion, and spontaneous combustion to easy spontaneous combustion; Based on accurately solving kineticparameters and the heat balance equation of coal in adiabatic environment, theself-heating process of coal from different temperature can be accurately simulatedusing the kinetics based simulation method, which can accurately judge the risk ofself-heating of coal in different ground temperature, and overcomes the drawbacks ofadiabatic oxidation experiment which tends to consume for long time and has lowsuccess rate.The effective prevention of spontaneous fire is based on the early recognitionand prediction of coal spontaneous combustion, and the gas analysis method is themost widely used in early prediction and forecasting of coal spontaneous combustion.This paper simulates the programmed oxidation process of coal respectively with20℃,30℃,40℃as the starting temperature, and obtains the variation of gas productsin the process of coal oxidation temperature rising with different initial temperature.The results show that: In the process of coal oxidation temperature rising withdifferent initial temperature, the higher the incipient oxidation temperature is, thelower the concentration of CO which coal releases at anytemperature(20℃>30℃>40℃); When using the absolute amount of CO production asthe index-gas to predict coal spontaneous combustion, we need to reduce the criticaldecision index value with the increase of mine ground temperature, otherwise the firepoint temperature of coal spontaneous combustion will be assessed too low and we’lldelay the best time to put out a fire; In the oxidation process of coal with differentinitial temperature, the coal lower incipient oxidation temperature is, the higher theGray Hamm Coefficient R2is at any temperature. With the underground temperatureincreasing, we need to reduce the critical decision index value. If we still uses the oldcritical indicators when underground temperature increasing, it will lead to prematurealarm and unnecessary panic.To achieve mining safety in high geothermal in TengNan mining area, theprevention of coal spontaneous combustion accident and governance of internal fireneed to take measures from the two aspects of the inhibition of heat production andpromote heat radiation. With the theoretical analysis and experimental research, thispaper determined the performance of the inerting-technology inhibit low-temperatureoxidation process of coal and the cooling performance of various governancetechnology of internal fire. Based on that, to make high-temperature mine miningsafely in TengNan mining area, this paper put forward integrated high efficiency comprehensive prevention and control technology which use foam to cooling rapidlyas the core, to plugging for oxygen reduction and inert replacement as assist. Theresults show that: When using the inerting technology to prevent coal spontaneouscombustion disasters, the oxygen concentration of coal left in the surroundingenvironment is needed to reduce to the following of5%. When the left ambientoxygen concentration around the coal is higher than5%, the reduction of oxygenconcentration can’t inhibit the oxidation process of coal obviously. Using liquidcarbon dioxide or nitrogen filling technique to governance coal spontaneouscombustion disaster, the cooling effect of the high temperature region is extremelylimited, the main effect is inerting and suppression on fire area. But the three-phasefoam flowing through high temperature point with the vaporization of water whichwill absorb a lot of heat, the cooling effect is very obvious, and it can coolinghigh-temperature fire area rapidly; The integrated high efficiency comprehensiveprevention and control technology which use foam to cooling rapidly as the core andto plugging for oxygen reduction and inert replacement as assist is promoted to use inTengNan mining area smoothly, and the effect test verify the validity andpracticability of the comprehensive fire prevention and extinguishing technologyintegrated system.