采空区矸石热弛豫作用下的自然发火多场耦合理论建模研究

The main reason for coal spontaneous combustion is the result of continued temperature rise by that the generated heat is more than the dissipated heat. The previous studies has been established a number of theoretical models for predicting the spontaneous combustion of goaf, but without considering the thermal relaxation process of waste rock, so that there is a big difference between the predicted temperature and the actual temperature of goaf. This project plans to solve it by theoretical analysis, experiment and numerical simulation. The physical model of gas-solid dual medium of goaf is established to analyze the relaxation process of heat transfer in the waste rock. In order to solve the problem that the temperature field of waste rock in goaf with the changing distribution is different to be modeled, which is caused by the thermal relaxation of waste rock, one scheme that an internal temperature field of waste rock is superimposed on any point of the continuous and smooth surface temperature field of waste rock is put forward to establish the four-dimensional temperature field model of waste rock. And the equivalent radius of heat transfer of some kinds of waste rock is researched. Finally, combining with our workgroup’s previous research about the multi-field coupling of spontaneous combustion of goaf, a new mathematical model of spontaneous combustion based on the moving coordinate system can be established, which incorporates four-dimensional solid temperature, three-dimensional gas temperature, oxygen concentration, gas pressure, air leakage rate, CO concentration, oxidative heat generation as a whole. A piece of computing software will be compiled to reveal that the space-time evolution regularity of coal spontaneous combustion in goaf with the influence of thermal relaxation of waste rock. The new model will be verified and improved by the in-site observation about the temperature variation in goaf.

煤矿采空区自然发火是产热大于散热而持续升温所导致的。前人提出了多个自然发火理论模型，但矸石吸热弛豫过程作为重要的散热途径却一直没被考虑进去，使采空区温度的预测结果与实际存在较大差异。本项目拟通过理论、实验及仿真等方法，构建采空区气固双重介质模型，分析其中矸石的传热及弛豫过程，提出在连续光滑的采空区矸石表面温度场上任一空间点处叠加一个矸石内部温度场的方案，以解决热弛豫作用下采空区矸石温度场分布的起伏变化，建立由三维矸石表面温度场和矸石球一维温度场组成的采空区固体“四维”温度场数学模型，确定各类形状矸石的当量传热半径，结合课题组前期的自然发火多场耦合研究，最终建立基于移动坐标集采空区“四维”固体温度、三维气体温度、氧浓度、气体压力、漏风速度、氧化生热等多物理量为一体的采空区自然发火新模型，编制耦合解算软件，揭示矸石热弛豫作用下采空区发火时空演化规律，并现场观测采空区温度变化来验证和完善新模型。

项目针对采空区自然发火过程中的矸石热弛豫问题，阐述了矸石热弛豫作用下的采空区自然发火多场耦合机制，推导煤自燃过程的了标准耗氧速率和标准一氧化碳生成方程，构建了包括一氧化碳浓度场在内的采空区自然发火多场耦合数学模型，开发了“采空区自然发火三维仿真解算系统”软件，实现了采空区各物理场量的图形化显示，研究了推进速度、漏风量、遗煤厚度、工作面停采等因素对采空区然发火时空演化的影响，总结出调整开采工艺参数抑制自然发火的具体方案，提出了以工作面上隅角CO定量化预报采空区发火程度的基本方法，建立了定量化预测函数模型，还研制了矿用干冰相变发生器，完成了停采面采空区自燃火灾的干冰相变惰化现场工业性试验，形成了一整套煤矿停采面煤自燃防控技术及关键装备体系。项目在采空区自然发火机理、定量化预测预报基本理论以及现场自燃火灾高效精准治理等方面取得一定进展，为采空区发自然发火的科学防控提供了理论支撑和技术手段。