Research On Classcification Of Spontaneous Combustion Areas In Compound Goaf And Parameter Optimization Of Nitrogen Infusion

The air leakage from the lower goaf of the compound goaf of the 31114 working face of Lijiahao Mine to the overlying goaf caused the oxygen concentration in the overlying goaf to be too high,which increased the possibility of spontaneous combustion of the remaining coal in the goaf.Therefore,combined with numerical simulation,this paper studied the leakage flow field,oxygen concentration field and temperature change in the compound goaf through procedural heating experiment,field air leakage measurement and the tube bundle monitoring system,and the spontaneous combustion dangerous areas in the compound goaf were divided.On this basis,the nitrogen injection parameters in the goaf were optimized.First of all,the critical oxygen concentration of coal spontaneous combustion was tested by procedural heating experiment,and the critical oxygen concentration was determined to be 7%,which provided the basis for the division of the spontaneous combustion dangerous areas in the goaf.This paper adopted the SF₆tracer gas air leakage detection technology to detect and found that there was an air leakage channel between the upper and lower coal seam goaf and the direction of the leakage was from the upper to the lower.And the air leakage in the goaf was279.28 m³/min by the section element measurement.According to the relevant theory of"three belts"of coal spontaneous combustion in the goaf,the critical oxygen concentration of remaining coal spontaneous combustion and the tube bundle monitoring system,the spontaneous combustion dangerous areas in the goaf were divided.Based on the actual situation of the compound goaf of the 31114 working face of Lijiahao Mine and the relevant mathematical model theory of fluid mechanics,the leakage flow field,oxygen concentration field and temperature change of the compound goaf were studied by adopting the numerical simulation method.And this paper compared the field measured air leakage and oxidation zone distribution in the lower goaf,and found that they were basically consistent.Through the use of nitrogen injection fire extinguishing technology,the spontaneous combustion dangerous areas in the compound goaf were studied,and the design of the nitrogen injection pipeline was completed at a distance of 20 meters from the working face of the intake air side in the lower goaf.The reasonable amount of nitrogen injection was determined by comparative analysis to be 1200m³/h.And after taking nitrogen injection fire extinguishing technology measures,the oxidation condition of the remaining coal in the goaf was monitored by the tube bundle monitoring system,and the actual effect of nitrogen injection fire extinguishing technology in 31114 working face was analyzed.This thesis has 35 figures,7tables,72 references.