遗煤二次氧化对复合采空区气体浓度场影响

Influence of coal secondary oxidation on the concentration field of composite goaf

复合采空区内氧化遗煤发生二次氧化是近年来引发煤矿内因火灾的重要原因之一。从气体浓度场的角度定量分析遗煤二次氧化对复合采空区自然发火的影响,是制定重复采动影响下复合采空区防灭火方案的理论基础,对于煤矿安全生产具有重要意义。以内蒙古平庄能源股份有限公司六家煤矿近距离煤层开采的SIIN_(2)6-9工作面为工程背景,现场采集本煤层原始遗煤与上覆煤层垮落氧化遗煤并制备实验煤样,利用等温差引领升温方法实验测试了2种煤样的宏观自燃特性。实验结果表明:现场采集氧化遗煤二次氧化过程处于激活阶段,煤氧反应更加活跃;相同温度与氧浓度条件下,氧化遗煤耗氧与CO生成速率更高。根据现场采集煤样的宏观自燃特性实验结果,提出采空区多种遗煤氧化情况的煤氧反应源项计算方法,建立了动态推进条件下采空区多种遗煤自然发火过程的数值预测模型。通过对比氧气与CO体积分数的束管监测数据与数值模拟结果,验证了所建立数值模型的可靠性。数值模拟结果显示:上覆采空区遗煤二次氧化增加了采空区遗煤耗氧和CO生成速率,在遗煤二次氧化作用下采空区内氧化带位置较单一煤层采空区向工作面移动约27 m,最大CO体积分数提高了30%。上覆采空区氧化遗煤二次氧化是不可忽略的自燃火灾潜在威胁。

The secondary oxidation of oxidized residual coal in composite goaf is one of the important causes of coal mine fire in recent years.A quantitative analysis of the impact of secondary oxidation on the spontaneous combustion in the composite goaf from the perspective of gas concentration field is of great significance to the safe production of coal mine.It is conducive to putting forward the fire prevention scheme when the condition of re-mining is considered.In this study,the SIIN_(2)6-9 working face of the Liujia coal mine in Inner Mongolia Pingzhuang Energy Co.,Ltd.was taken as the engineering background.The constant temperature difference guidance method was employed to measure the macroscopic spontaneous combustion characteristics of original and oxidized residual coal that were both collected from the Liujia coal mine.The experimental results showed that the secondary oxidation process of the collected residual coal was more active.Under the conditions of the same temperature and oxygen concentration,the rate of oxygen consumption and CO generation was higher for oxidized residual coal.According to the measured macroscopic spontaneous combustion characteristics,a method to determine the coal-oxygen reaction source term was developed which considered various kinds of residual coals in the goaf.Subsequently,a numerical model to predict the spontaneous combustion in goaf under dynamic advance condition was established.The developed model was validated by comparing the numerical results and field measurements.The numerical results showed that the secondary oxidation had a significant effect on increasing the rates of oxygen consumption and CO generation.In comparison with the goaf with a single coal seam,the oxidizing zone of the composite goaf with secondary oxidation process moved toward to the working face at a distance of about 27 m,and the maximum CO concentration increased 30%.The secondary oxidation of residual coal is a potential threat of coalmine fire that cannot be ignored.