半“O”型冒落采空区注CO_2防灭火的数值模拟

Numerical simulation of fire prevention in gob area with half O-ring risked falling by CO_2 injection

为确定采空区注入CO_2防灭火的相关技术参数,研究注CO_2过程中多组分气体浓度场分布、扩散及自燃温度场变化的规律,基于实测数据,建立采空区非均质多孔介质3D数值模型。运用FLUENT软件,解算按半"O"型圈描述冒落岩层碎胀系数分布的数学公式、通用控制方程、遗煤耗氧与放热公式。模拟结果表明:未注入CO_2时,CO_2浓度及O_2浓度随距工作面距离的增加而逐渐降低,采空区最高温度出现在回风侧;注入CO_2时,CO_2浓度随着注入口距工作面距离的增加和注入量的增大而逐步升高,O_2浓度则反之。采空区CO_2注入口的最佳位置在进风侧距工作面20~30 m处,合理注入流量为540~720 m^3/h,此时采空区氧化带最大宽度稳定在64 m,最高温度下降13℃。模拟结果与现场标志气体监测数据相符。

In order to determine related technical parameters of fire prevention by injecting CO2 into gob, and study variations in both gases＇concentration fields and spontaneous combustion temperature field during CO2 injection process, a 3D numerical model was built for heterogeneous porous media on the basis of the practical statistics. A mathematical formula was given for describing distribution of falling rock expansion coefficient according to half O-ring. The formula, general control equation, modified non-uniform oxygen consumption and oxidative exothermic mathematical equations were solved by FLUENT. The results show that concentrations of CO2 and O2 decrease gradually with increase in the distance to the working face while the high temperature area appears on the return side when no CO2 injection, that concentrations of CO2 increase gradually with increase in the injection CO2 position distance to the working face, but the concentrations of O2 decrease at the same time, and that the maximum width of oxidation zone is stabilized at 64 m, and the highest temperature is reduced by 13 ℃ when CO2 is injected from a position 20 -30 m away from the intake side working face, and the injection flow rate is 540 - 720 m^3/h. The results of simulation conform to the data obtained from the field monitoring.