“Trinity” treatment technology for fire area of joint mining in close coal seam groups

In view of the problem of spontaneous combustion prevention and control during the mining of close coal seam groups, taking the fire point disposal in the fault area of 2110 and 3108 working faces of Xinwei Coal Mine as an example, the detection and comprehensive treatment technology of hidden fire points was carried out by combining experimental research and field practice. The results of the simulation experiment of spontaneous combustion in 3^# coal seam show that the volume fraction CO and C₂H₄ is a quadratic function relationship with coal temperature, which can be used for forecasting of spontaneous combustion in coal seam. The decrease of oxygen volume fraction can effectively inhibit the spontaneous combustion oxidation process of coal, and it is most obvious when the oxygen volume fraction is 7%, so it is set as the critical oxygen volume fraction of the spontaneous combustion of 3^# coal seam. Through the analysis of spontaneous combustion hidden dangers combined with drilling exploration, the F₉ fault area with 80 m longth and 10 m width in the west of 3110 track lane was delineated as a spontaneous combustion hidden danger area, and a fire area treatment idea of liquid-colloid-gas “trinity” with grouting and cooling as the guide, rubber injection plugging as the core, and nitrogen injection and explosion prevention as the means was proposed, and a total of 180 t of cement slurry and 504 m³ of colloidal injection were injected into the hidden danger area, and the nitrogen injection flow rate in the goaf area of 2110 working face was maintained at 810 m³/h, which realized the effective treatment of the fire area. It ensures the smooth unsealing and safe recovery of the two working faces.