Prediction method of gas explosion risk induced by coal mine fire

The gas explosion often occurs during the sealing and opening of the high gas and spontaneous combustion prone zone.The gas explosion limit under the conditions of ambient temperature (25-200 ℃) and CO volume fraction (1%-10%) was studied experimentally by using 20 aL explosive device.It was found that the CO volume fraction increases,the upper and lower limits of gas explosion decrease,and the temperature increases,the upper explosion limit increases and the lower limit decreases.Under the coupling effect of temperature and CO gas,the upper limit of gas explosion increases and the lower limit decreases,and the risk of gas explosion increases.The upper and lower explosion limits show a quadratic polynomial change trend with temperature and CO gas concentration.The coupling effect of initial temperature and CO gas on the explosion limit is greater than that of a single factor,and the impact on the upper explosion limit is more significant.Based on the changes in the gas explosion triangle and curve fitting theory,the risk of induced secondary gas explosion in the process of the fire area closed was studied.According to the principle of curve intersection,the CH4 concentration and O2 concentration were determined.Combining with CH4 concentration and O2 concentration with time,the possible gas explosion time t was found out.If the O2 concentration of the potential explosion point M (XM(CH4),YM(O2)) is less than the O2 concentration of critical point E,namely YM(O2)YE(O2),that is the O2 concentration is sufficient,the gas explosion time is determined according to the explosion time t(CH4) of CH4 concentration change. The study analyzed the gas explosive point monitoring location and the change trend.Taking the fire hazard at the floor of a horizontal roadway as an example,based on the numerical model of the rectangular roadway 50 m×4 m×3 m(length×width×height),width and height of 50,4,and 3 m established in the previous stage,the gas explosion time was estimated by the gas and O2 fitting curve and the change explosion triangle theory,and the time of gas explosion was obtained,which was instructive for on-site emergency rescue.