Research And Application Of Low Oxygen Prevention And Control Technology Based On The Principle Of Piloting In The Corner Of The Return Wind Of The Working Face

In recent years,the frequency and severity of the phenomenon of hypoxia has gradually increased in some low gas mines in northern Shaanxi during the normal recovery of the working face,with serious effects on the breathing of underground personnel during operations.There has been little systematic research in this area,so it is necessary to investigate the causes and influencing factors,and to propose targeted prevention and control measures.In this paper,the causes and main areas of low oxygen at the working face were identified using a combination of theoretical analysis,field observations,experimental tests and numerical simulations,and in this way,a prevention and control technique for low oxygen at the working face based on the priming principle was proposed,as follows.Through field observation,it was found that the low oxygen area of the working face is mainly in the corner of the return wind,and its oxygen concentration is in the range of 15.5%-17.5%,and it decreases with the increase of surface temperature.Through theoretical analysis,it was found that the direct cause of low oxygen in the return comer of the working face is due to the influence of the pressure difference between the mining area and the working face,the ventilation method,etc.,and the gas gushing out from the mining area and accumulating there.The relationship between the influence of the oxidation of the coal remnants and the outgassing of the fugitive gases in the seam and the variation of the oxygen concentration in the extraction zone was analysed by means of programmed warming and adsorption and desorption tests of the fugitive gases in the primary seam,and the importance was ranked by combining the results of field observations.The results show that the oxidation of coal relics in the mining area is in the initial stage,and the release of CO and CO2 and the oxygen consumption rate are low.112207 working face belongs to the CO2-N2 zone of the coal seam gas partition,and the influences of coal fragmentation and pressure changes during the back mining,the influx of CO2 and N2 gas in the coal seam is the main reason for the decrease of oxygen concentration.Based on the causes and main influencing factors of low oxygen in 112207 working face,the advantages and disadvantages of the existing means of low oxygen prevention and control are analyzed.On the premise of maintaining the full air pressure ventilation method of the working face,the prevention and control idea of changing the flow field distribution of the return corner with the principle of piloting is proposed.Numerical simulations and experimental studies were carried out using the ZYX-150 induced draft system platform to study the change of induced draft under different pressure parameters.The results show that the main stream pressure has the greatest influence on the induced air flow,and when the induced air flow is at its highest efficiency,the main stream pressure is 0.4 MPa,and when the induced air flow is at its highest,the main stream pressure is 0.5 MPa.In the process of induced injection,the inlet static pressure and the outlet back pressure both have extreme values,and when the pressure is greater than this value,the efficiency of induced injection is greatly reduced.The extreme value of the inlet static pressure is related to the main stream pressure,and the maximum value of the inlet static pressure is about 1.5 kPa when the main stream pressure is 0.4 MPa,and the extreme value of the outlet back pressure is about 0.14 MPa.Using numerical simulation software,the variation of wind speed and oxygen concentration at the working face under different induced air flow conditions was analysed.The results show that the induced air flow has a good effect on improving the low oxygen environment in the corner of the return air at the working face,and the best effect is achieved when the direction of the induced air flow is set at a certain angle 30° with the return air tunnel.Based on the results of the above study,the field application and effect test of the pilot jet was carried out in conjunction with the actual situation on the 112207 working face.After a week of normal operation of the equipment,the oxygen concentration in the corner of the return wind of the working face was maintained at more than 18.5%,which is a significant effect of treatment.