煤矿火灾诱发瓦斯爆炸危险性预测

Hazard prediction of gas explosion induced by coal mine fire

针对高瓦斯易自燃煤层火区封闭与启封过程中常发生的瓦斯爆炸问题,采用20 L爆炸装置,在实验研究环境温度为25~200℃和CO体积分数为1%~10%的条件下进行瓦斯爆炸极限测定,发现CO体积分数升高,瓦斯爆炸上限、下限均下降,温度升高,爆炸上限升高、下限下降;温度与CO气体耦合作用下,瓦斯爆炸上限升高、下限下降,瓦斯爆炸危险性增加,爆炸上限、下限与温度和CO气体体积分数呈二次多项式变化趋势。初始温度和CO气体对爆炸极限的耦合影响比单一因素影响大,其对爆炸上限的影响更为显著。在此基础上,基于变化瓦斯爆炸三角形与曲线拟合理论,研究了火区封闭过程中次生瓦斯爆炸危险性演化过程,根据曲线相交原则反演求出CH4体积分数与O2体积分数,结合CH4体积分数与O2体积分数随时间变化关系,求出可能发生瓦斯爆炸时间t。若可能爆炸点M(XM(CH4),YM(O2))点的O2体积分数小于临界点E的O2体积分数,即YM(O2)<YE(O2),则O2体积分数不足,不爆炸。若O2体积分数大于临界点E的O2体积分数YM(O2)>YE(O2),O2充足,发生瓦斯爆炸时间依据CH4体积分数变化的爆炸时间t(CH4)确定,并分析了瓦斯易爆点监测位置及变化趋势。以水平巷道煤巷底板火灾事故为例,在前期建立50 m×4 m×3 m(长×宽×高)的长方体巷道数值模型基础上,应用瓦斯、O2拟合曲线与变化爆炸三角形理论对火区封闭过程中瓦斯爆炸时间进行估算,得到了瓦斯爆炸发生时间,为现场应急抢险救援提供借鉴。

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 L 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),the O2 concentration is insufficient and the gas does not explode.If the O2 concentration is greater than the critical YE(O2)concentration,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 cuboid roadway 50 m×4 m×3 m(length×width×height)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.