缓倾斜煤层采空区CO2-N2混合惰化"三带"分布规律研究OA

To address the problem of spontaneous combustion of residual coal in goaf of gently inclined coal seams,a numerical model of gas migration in goaf was established based on the porous medium model and gas component transport equation.The influ-ences of injection position and flow rate of pure CO2 and CO2-N2 mixture on the distribution range of the"three zones"in goaf were investigated,and the gas migration law under CO2-N2 mixed inertization was analyzed.The results show that when CO2 is injected from the intake air side to inertize the goaf,the area of the oxidation zone first decreases and then increases with the increase of the distance between the CO2 injection position and the working face.With the increase of CO2 injection rate,the oxidation zone area de-creases,and the CO2 migration pattern presents a"trumpet shape",forming"inertization blind zones"near the working face on the intake air side and in the middle of the goaf.When CO2 is injected on the intake air side and N2 on the return air side for mixed inert-ization,the oxidation zone area first decreases and then increases with the increase of the distance between the N2 injection position and the working face.With the increase of N2 injection rate,the oxidation zone area decreases,and the N2 migration pattern shows a"wave shape",which reduces the area of the"inertization blind zone"in the goaf.The optimal inertization effect is achieved when the CO2 injection position is 40 m from the working face with an injection rate of 750 m3/h,and the N2 injection position is 50 m from the working face with an injection rate of 750 m3/h.Under these conditions,the CO2 volume fraction in the return airway does not exceed 1.5%,the oxidation zone area decreases from 4 100.445 m2 to 2 463.205 m2,which is 14.84%lower than that under single CO2 inertization.An"isolation zone"is formed in the middle of the goaf,which effectively restrains the migration of O2 to the deep goaf.