综放采空区自然发火规律动态数值模拟

Laws of coal spontaneous combustion in the goaf of long wall caving face by means of dynamic modeling

数值模拟是研究煤层自燃规律,实现自燃预测预报的重要方法.建立了含自然对流、强制对流及扩散的传质、传热与煤氧化相耦合的采空区自燃数学模型;通过现场监测确定了陈家沟煤矿下分层综放开采时,采空区自燃数值模拟相关区域的范围及其边界条件;实验测定了陈家沟矿煤样在不同温度时的耗氧速度和氧化放热强度,并按照Arrhenius定律拟合出其函数关系式;在此基础上实现了采空区自燃的动态数值模拟.开展了系列数值模拟实验,得到了不同工作面推进速度时采空区空气渗流速度场、浓度场及温度场随时间的变化规律.研究得到不发生煤层自燃的工作面最小推进度为3m/d,当工作面推进度长期小于3 m/d时,采空区进风侧首先出现煤层自燃.

Numeric simulation is a very important method to study the laws and predict coal spontaneous combustion. A mathematical model was set up to depict coupled fields of heat and mass transfer together with coal oxidation, it was taken into consideration natural convection, forced convection and diffusion. Through mining site observation, domain and boundary conditions of spontaneous combustion in lower sub - layer long wall caving mining workface in Chenjiagou mine was determined. Oxygen consumption and heat production rate of the coal at different temperatures were tested with coal spontaneous combustion modeling experiments, and the function relation were fitted according to Arrhenius law. Based on the above study, dynamic numeric simulations of coal spontaneous combustion in the goaf were conducted to find the laws of air flow velocity, oxygen concentration and temperature fields varied with mining workface moving velocity and time. It proved that the minimum welocity of the workface movement to prevent spontaneous combustion is 3 m/d, if the workface movement velocity is smaller than 3In/d for a long time, coal spontaneous combustion will take place at the air inlet side in the gob.