Study on the Equilibrium Point of Coordinated Control of Gas and Fire in Fully Mechanized Goaf with High Gas Content

In order to solve the problem of coordinated prevention and control of gas and fire in fully mechanized goaf with high gas content, by using the method of numerical simulation, a physical model of buried pipe extraction and nitrogen injection to prevent fire in the upper corner of goaf was built. The concept of “equilibrium point”, which can balance the contradiction between the two, was introduced. Air distribution, gas extraction and nitrogen injection were selected as test factors, and the maximum width of oxidation zone was taken as test index, based on the design of Box-Behnken response surface in Design Expert software, an experiment of three factors and three levels was established. Different values of test indexes were determined through field observation and FLUENT numerical simulation, response surface model was established, and optimal process parameters were obtained through optimization. The results show that the P value of the model is 0.009 5, the quadratic regression model is significant, the lack of fit is 0.050 1, not significant, the regression model is accurate and reliable; the influence of the one degree term on the maximum width of the oxidation zone is air distribution quantity > gas extraction volume > nitrogen injection volume, and there is no interaction between the two factors. The model is used to calculate the “equilibrium point” of coordinated prevention and control of gas and fire in 206 fully mechanized working face of Tingnan Coal Mine, that is, air distribution quantity is 1 168.10 m³/min, gas extraction volume is 162.94 m³/min and nitrogen injection volume is 800.01 m³/h, which is consistent with site observation. It can guide mine practice under similar conditions.