采空区遗煤自燃过程及其规律的数值模拟研究

基于非均质多孔介质中的连续性方程、多相气体渗流———扩散方程和综合传热方程,建立了工作面动态推进下的采空区自燃数值模型。结合实例,从理论上描绘了工作面开采过程中采空区的漏风流态、氧、CO、瓦斯和温度等分布状态及其动态过程。计算中考虑了瓦斯涌出对自燃的耦合作用;工作面动态推进对自燃的影响,以及沿边界冒落非压实性对漏风供氧、自燃高温区产生的影响。从理论上重点讨论了采空区自燃与各因素的定量化关系,得出自然发火期与煤氧化速度、工作面风量二者均呈显著的反比例关系;对于综放工作面采场漏风供氧系统,自然发火期主要取决于煤的耗氧能力,提高工作面风量仅能扩大自燃高温区的范围,增大自燃的发生几率;提高推进度能显著延长采空区自然发火期,呈指数变化。

Numerical Simulation of Spontaneous Combustion Process of Residual Coal in Goaf

Based on air leakage seepage equation of heterogeneous porous media, seepage flow-diffusion-consumption equation of gas concentration and heat transfer equation, a unsteady numerical model of spontaneous combustion in goaf is established; and these equations are combined and solved by windward finite element based numerical simulation method. Referring to an example, air leakage seepage flow, oxygen, CO gas, methane concentration distribution, and temperature distribution in goaf, their variation processes are all described theoretically. In calculation, the coupling effect of gas surging and the dynamic advance of working surface on spontaneous combustion are fully considered, and the impact of incompactness of the falling along the border on oxygen supply due to seepage and on high temperature zone of spontaneous combustion is also taken into account. The quantification relationship between spontaneous combustion and various factors is emphatically and theoretically discussed. As a result, the self-ignition period of spontaneous combustion is significantly and inversely proportional to both the oxidation rate of coal and volume of ventilation at working face. The spontaneous combustion in goaf could be retarded obviously if the advancing speed is increased with exponential relationship. More input air in working surface has little influence on shortening the spontaneous combustion period, but it could expand the high temperature zone and enhance the probability of spontaneous combustion.