Study On The Mechanism And Prevention Technology Of Low Oxygen In Thick Coal Seam Working Face

At present,in a full-height or fully mechanized caving mining of a thick coal seam of3.5m and above,during the mining process,there is often a phenomenon of low oxygen in the coal face.In order to study the cause mechanism of low oxygen in thick coal seam mining face and propose prevention technology,based on the background of Madaotou Mine 8105fully mechanized caving face,systematic research is carried out through theoretical analysis,field testing,experimental research and numerical simulation.The specific content is:The possible factors of low oxygen phenomenon in thick coal seam mining face are analyzed.Determine the reason for the decrease of oxygen concentration in the working face;determine the main factors that cause hypoxia in the working face.Through the analysis of the characteristics and mechanism of low-temperature oxygen consumption of large-dose raw coal in the goaf,it is concluded that large-dose raw coal consumes oxygen at a low temperature at 40?.With the consumption of oxygen,gaseous products such as CO_x and C₂H₆ are generated;When it is constant,with the extension of the oxygen supply time,the gas-phase product generation and the generation rate show an upward trend.In the process of low-temperature oxygen consumption of the original remnant coal,asymmetric methyl and methylene are more likely to undergo oxidation reactions to produce carbonyl-containing compounds;during the oxidation process,CO_x gas is mainly decomposed by aromatic ketones,aromatic quinones and aromatic acid compounds.When the temperature is lower than 50°C,the generation amount of these three types of compounds is less than the decomposition amount,and when the temperature is higher than 50°C,the generation amount of these three types of compounds is greater than the decomposition amount.Based on the FLUENT numerical simulation,the influence mechanism of low-temperature oxidation of large-dose original coal in the goaf,the amount of nitrogen injection,the amount of coal,and the amount of air intake on the low-oxygen in the working face are revealed.With the increase of the amount of nitrogen injected in the goaf,the hypoxic phenomenon in the working face will be first relieved and then severely changed.The optimal nitrogen injection rate is determined to be 1500-1900m³/h;with the increase in the amount of coal remaining,the working face will be hypoxic.The problem is serious;increasing the air intake will increase the oxygen concentration in the return airway and solve the hypoxia problem in the tail area of the working face.At the same time,it will aggravate the hypoxia in the upper corner.The optimal air intake is determined to be about 2100m³/min.Determine the influence of different working conditions on the oxygen concentration of the working face and the upper corner;during the mining,due to the fracture of the coal body,the N₂ and CO₂stored in the coal seam will cause the reduction of the oxygen concentration of the working face,and the top coal mining is better than the shearer Coal cutting has a great influence on the oxygen concentration of the working face.Determine the cause mechanism of multi-factor coupling hypoxia in thick coal mining face and the area where hypoxia occurs is mainly within 50m of the upper corner of the face,the back slip area and the tail of the face;the upper corner of the oxygen concentration is in the three-dimensional space The distribution is uneven,and the oxygen concentration changes in the upper corner of the horizontal and vertical directions are parabolic,and the oxygen concentration in the space far away from the coal wall is greater than the oxygen concentration in the space near the coal wall.On the basis of the hypoxia-causing mechanism of thick coal mining face,the lower corner plugging,nitrogen-inhibited fine water mist to inhibit coal oxidation technology is proposed to replace the 24h open nitrogen injection technology,and the air guide curtain-jet combined technology to control Hypoxia in the working face.This paper systematically studies the cause mechanism of hypoxia in thick coal seam mining face,and puts forward effective prevention and control techniques to provide guidance for safe production in mines.