| There are external air leakage and internal air leakage around the mining of surface cracks in most coal mines in western China,especially the top mining of shallow deep coal seam,which leads to more coal in goaf.Meanwhile,influenced by mining,the large air leakage in goaf leads to a large amount of oxygen entering,leading to the serious problem of spontaneous combustion in goaf.In particular,the ignition probability accounts for 76.3%of the whole working face during the stop-harvest period.Aiming at this problem,the 507 working face of Madiliang in Inner Mongolia is taken as the research object to seek efficient and reasonable fire prevention technology.This article acquisition ma liang mine 5#coal samples,the laboratory analysis of industrial experiment of coal samples,coal sample temperature programmed heating rate,oxygen consumption rate,gas product and heat emission intensity,flammability limit parameters,selection of CO gas for indicators,establish calculation model,draw a goaf return corner,return,scattered tropical,oxidation zone CO gas critical value.The"three zones"of goaf were divided according to the standard of oxygen concentration.The O2and CO concentration data inside goaf were measured by the embedded temperature probe and beam tube in goaf,and the distribution of the"three zones"of goaf under normal mining and nitrogen injection conditions was obtained as follows:the dispersing zone on the inlet side was 0-24.4m,the oxidation zone was 24.4-58.8m,and the suffocating zone was>58.8m.The scatter zone on the return wind side is 0-5m,the oxidation zone is 5-14m,and the asphyxia zone is>14m.The minimum safe propulsion speed is 1.90m/d.The normal advancing speed of the working face is 2.5m/d,and the possibility of spontaneous combustion is low under the existing fire prevention measures.The correctness and reliability of the model were verified by the simulation results of Fluent software and the measured data,and the distribution of oxidation zone after 14 iterations of goaf stoppage under different air supply rates was simulated.The optimal air supply rate was determined to be 900m3/min,with a range of 31-126m and a maximum width of 95m.The floating coal in the goaf will spontaneously ignite for about 20 days,which will threaten the working face retreat,and further fire prevention measures are needed.When the air supply volume is determined to be 900m3/min,nitrogen injection simulation with different flow rates is carried out.It is concluded that the goaf oxidation zone range is 12-59m and the width is reduced to 47m at1200m3/h nitrogen injection flow rate.The risk of spontaneous ignition is reduced.According to the simulation and monitoring results,special fire prevention measures are formulated for 507 working face to adjust air volume,inject nitrogen grouting,set beam tube to monitor coal oxidation state,and monitor CO overlimit in the later stage of rack removal.By injecting high solid water material measures,the CO overlimit problem is eliminated to ensure the safe withdrawal of 507 working face.Figure 53 Table 19 Reference 86... |
