Study On The Formation Regularity And Prevention Of Toxic And Harmful Gases With Low Oxygen In The Near Coal Seam Mining Face Of Shaping Mine

Due to the close distance between coal seams,mining-induced fractures formed in upper and lower goaf under the influence of working face mining develop into air leakage channels,which provide a way for air leakage in goaf.In the process of mining in the lower coal seam working face,the toxic and harmful gases in the overlying goaf will be discharged to the goaf of the coal seam through the air leakage channel,and then together with the toxic and harmful gases in the goaf of the coal seam will surge to the working face,threatening the life and health of the underground workers.Therefore,it is of great significance to study the formation rules of toxic and harmful gases in close coal seam mining for ensuring coal mine safety production and preventing safety accidents.In this paper,shaping Coal mine is taken as the research object,and the main conclusions are as follows by setting measuring points to sample and analyze gas concentration in fully mechanized mining face,laying beam tubes to monitor gas concentration in goaf and overlying goaf of the coal seam,normal temperature oxidation experiment of coal in laboratory sealed device,theoretical calculation,etc.:(1)Through the analysis of the gas collected in the working face,it can be concluded that the main components of the toxic and harmful gases in the working face are CO,CO2 and CH4,and the oxygen concentration in the working face is low,especially the oxygen concentration in the corner of the return air is sometimes lower than 18%.Toxic and harmful gases come from coal seam residual coal oxidation,mined-out area residual coal oxidation,coal mining of shearer and tail gas emission of rubber wheel car.Among them,CO mainly comes from minedout area residual coal oxidation,CO2 mainly comes from original coal seam residual coal oxidation and mined-out area residual coal oxidation,and CH4 mainly comes from coal seam residual coal oxidation.And "U" type negative pressure ventilation way cause pressure difference between goaf and coal face,toxic or harmful gases from pressure large mined-out area flock to face less pressure.(2)The amount and rate of oxygen consumption,as well as the amount and rate of toxic and harmful gas generation were obtained through the normal temperature oxidation experiment of coal in a laboratory closed device,which laid a foundation for the subsequent calculation of the proportion of the gas in the goaf from the upper and lower coal seams.(3)According to the on-site situation,samples were drilled into the overlying goaf in the return air lane of 1818 working face and analyzed to obtain the gas concentration distribution in the overlying goaf.Meanwhile,sampling points were arranged in the goaf and the working face to obtain the gas distribution law.Through the theoretical calculation,the proportion of the gas migration from the overlying goaf to the goaf of the coal seam and the proportion of the gas migration from the goaf of the coal seam to the working face are obtained,and the proportion of the toxic and harmful gas from the goaf of the coal seam and the overlying goaf is calculated.(4)Comprehensive prevention and control technology is put forward for the toxic and harmful gases in working face mainly come from the overlying goaf and the coal seam goaf.Establishing early warning surveillance mechanism,putting prevention in the monitoring of atmospheric pressure and return air corner gas concentration change,from the working face,the production management control and mined-out area three aspects put forward relevant measures of prevention and cure constitute a comprehensive control technical measures for prevention and control,through field application,will face the oxygen concentration is low and the problems of higher concentration of poisonous and harmful gases is greatly improved.The oxygen consumption and oxygen consumption rate of coal at a certain temperature,the amount and generation rate of toxic and harmful gases were obtained through the normal temperature oxidation experiment of coal,which laid the foundation for the subsequent calculation of the gas source ratio in the goaf.