Research On The Method Of Determining The Critical Value Of CO Of Spontaneous Combustion Marker Gas In Qinan Coal Mine

Spontaneous coal combustion is one of coal mine disasters,which seriously threatens the safety of coal mine production.CO gas is an important indicator of coal spontaneous combustion warning.Among them,CO gas is an important marker gas as a coal spontaneous combustion sign prediction.According to the Coal Mine Safety Regulations（2022）version,when mining coal seams prone to spontaneous combustion and spontaneous combustion,natural coal seam fire marker gases and critical values must be determined.However,there are various methods for determining the critical value of the marker gas CO,which are not yet uniform,and a method for determining the critical value of the marker gas that combines the actual situation of the site needs to be established.In this thesis,based on the characteristics of coal mine spontaneous combustion and the law of CO and temperature change in the mine area,a new method is proposed to determine the critical value of marker gas CO,and further determine the critical value of marker gas CO in the working face corner,return air flow and mine extraction pipeline.The details are as follows.First,the low-temperature oxidation characteristics of the coal sample were studied by the programmed warming experiment,and the critical temperature for spontaneous combustion of the coal sample at this working face was determined to be53°C by analyzing the change of activation energy during the low-temperature oxidation of the coal sample.Secondly,the mathematical model for the variation of CO concentration with temperature was obtained by field measurements of CO gas and temperature in Qinan7₂43 coal mine,in which the highest value of 34 ppm was obtained during the rising CO concentration and the corresponding temperature was 29.2°C.According to this model,when the coal temperature in the mining area rises to the critical temperature of53°C,the CO concentration in the mining area will reach 110.84 ppm,which is the critical value of CO,the marker gas of coal spontaneous combustion in the mining area.Since the natural fire prediction at the backface is usually monitored at the backwind flow,upper corner and extraction pipeline of the mining area.Therefore,in this thesis,numerical simulation analysis of CO gas transport law in the mining area was carried out to analyze the CO concentration in the corner of the working face,the return air flow and the extraction pipeline of the mining area are 31.25 ppm,11.26 ppm and 56.91 ppm respectively when the CO concentration in the mining area reaches the critical value,which is the critical value of CO,the marker gas of coal spontaneous combustion,at the corresponding location.When the concentration of CO at the corresponding location exceeds the critical value,it indicates that there is a risk of coal spontaneous combustion in the mining area,and countermeasures need to be taken to prevent the occurrence of spontaneous combustion disaster in the mining area.The method of determining the CO threshold value of coal spontaneous combustion marker gas proposed in this thesis combines the oxidation characteristics of coal samples from the working face and the spontaneous combustion characteristics of coal in the mine were studied under normal back mining conditions,and obtains the CO threshold values at different locations of the working face,which makes the determination of CO threshold values more scientific,thus facilitating the sampling and testing of the marker gas on site,and playing an important role in preventing coal spontaneous combustion disasters in the mining area.This thesis has 50 figures,4 tables,and 72 references.