| The mined-out area is one of the places where most coal mines ignite spontaneously,and it is also a key area for fire prevention control in underground coal mines.Spontaneous fire in the goaf not only affects the normal mining of the underground working face,but also brings heavy economic losses and even casualties.This article takes Yuandian 7222 working face as the research object,aiming at the problem of slow mining speed and coal loss due to faults and shortening of working face during mining of 7222 working face,it points out that there may be dangerous areas of coal spontaneous combustion.This research is a practical guide to the prevention and control of coal spontaneous combustion during the period when the 7222 fully mechanized mining face is mining and withdrawing from the fault.The main research results are as follows:1 Through temperature-programmed experimental research,the spontaneous combustion parameters of 72 coal were measured,and the law of the concentration of 72 coal oxidation gas with temperature was obtained,and the various stages and critical temperatures of coal oxidation were determined,combined with the optimization of landmark gases,and determined that CO and C2H4 were the main ones.Iconic gases,the alkane ratio φ(C2H6)/φ(CH4),and the alkane ratio φ(C2H4)/φ(C2H6)are used as auxiliary indicator gases to establish an early prediction index system for coal spontaneous combustion;2 Analyzed the influencing factors of coal spontaneous combustion in the mining process of 7222 working face,using dual tracer gas technology to test and analyze the air leakage channel and air leakage flow field of 7222 working face.The results show that due to the isolation effect of the 7221F2 fault,The mined-out area constitutes a return air channel in the local area of the inlet side of the working face,and the air leakage intensity of the outer closed wall of the 7222 old air lane is greater than the air leakage intensity of the upper corner of the working face;3 Combining on-site measurement,theoretical research and gas chromatography analysis,the dangerous area of 7222 working face is judged,and it is concluded that the dangerous area of 7222 working face goaf is mainly near the faults and the "remaining coal triangle" at the junction of old and new wind tunnels.Oxidation zone near and in the goaf.According to the beam tube monitoring,based on the measured O2 concentration change trend of the inlet and return air lanes,combined with the limit oxygen concentration method,it is determined that the oxidation zone on the inlet and return air sides are 21～58m and 28～68m respectively,and the minimum safety is calculated.The advancing speed is 1.65m/d;4 Proposed the prevention and control technology of coal spontaneous combustion in the goaf of the 7222 working face while mining and withdrawing from the goaf of the fault,and through the implementation of the "legacy coal triangle" and the pre-embedded beam tube monitoring near the fault,reducing air leakage in the goaf and gel atomization injection,Continuous nitrogen injection and two-phase foam injection and other comprehensive prevention and control technologies for coal spontaneous combustion have eliminated the hidden dangers of spontaneous combustion in the working face.Figure[41]Table[26]Reference[72]... |
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