Low-oxygen Distribution Characteristics And Optimal Control In A Fully Mechanized Mining Face With Shallow Depth

The large mining height fully mechanized mining technology is rapidly popularized in the Yushen mining area.However,due to the combined effects of geological conditions,ventilation methods and other factors,many coal face The airflow distribution has changed,which affects the low-oxygen distribution on the working face and the safety of personnel.This paper mainly uses the combination of on-site measurement,theoretical data analysis and numerical simulation to study the distribution and change trend of hypoxic gas at the breathing belt of the working face,the sidewalk of the hydraulic support and the corner of the return air,and determine the key points of hypoxia prevention and treatment based on this.Regional and optimized measures provide a theoretical basis for the prevention and control of hypoxia hazards.The main results are as follows.First of all,through field observation of a fully mechanized mining face of a mine in Dongsheng,the composition and co.ncentration of low-oxygen gas at various locations in the space have been determined,indicating that low-oxygen gas mainly comes from the goaf.The micrrostructure analysis of coal samples and the temperature-programmed oxidation experiment show that,The oxidation of leftover coat in the goaf and the nitrogen released from the coal seam are the main causes of low oxygen in the working face;the main factors affecting the distribution of low oxygen gas include geological conditions,ventilation methods,surface fissures,large-scale goafs,and pressure changes.Based on this,the spatial diffusion and distribution law of low-oxygen gas in fully mechanized mining face was determined,and three key hypoxic prevention and control areas,namely,the return air corner,the sidewalk and the tail of the machine were determined.Secondly,based on the field measured data of the gas phase flow theory,using CFD software to model,analyze the basic properties of low-oxygen gas in the downhole working and the mathematical model of its movement with the wind,and propose the Euler model as a suitable numerical solution method;reasonable settings With boundary conditions and continuous phase parameters,numerical simulations were carried out on the spatial low-oxygen migration law of the fully mechanized coal mining face,and the airflow distribution and low-level airflow at various locations in the space were studied when the wind speed was 0.95 m/s and the air leakage degree was 0.1 m/s.The law of oxygen transport and diffusion and the relationship between the two,that is,the distribution of low oxygen is obviously affected by the changes of turbulence and wind current.Again,adjust the parameters to simulate the effects of 5 different wind speeds and 3 different air leakage degrees on the hypoxic distribution of the breathing zone,sidewalk and return air corner.The dual factors of preventing the diffusion of low-oxygen gas and the key experimental areas for prevention and control have been determined.The specific parameters of the comprehensive prevention and control plan are determined by optimizing the two factors,that is,the best comprehensive hypoxia prevention and control plan for the working face is that the inlet wind speed is 1.5 m/s and the air leakage degree is 0.01 m/s.Finally,according to the simulation parameters,the proposal and implementation of comprehensive prevention measures for coal mines are determined.And put forward the comprehensive prevention and control measures of hypoxia in fully mechanized mining face.Increasing the wind speed in a small range can accelerate the excretion of low-oxygen gas and is beneficial to recover the oxygen concentration in key areas.Focus on prevention and detection in key prevention and control areas,establish ground atmospheric pressure monitoring and working face gas monitoring to form an early warning monitoring system,and adopt separate prevention and control of working face and goaf area.The working face can prevent and control the emergence of low-oxygen gas in the fully mechanized mining face by locally increasing the air flow and partial leaking;the goaf is prevented and prevented from the gas gushing in the goaf through the surface landfilling and leakage plugging and the valve discharge air pressure.When the pressure difference between the goaf and the working face is too large,the use of equalized pressure ventilation can effectively solve the problem of hypoxia.The various measures complement each other to form a set of feasible and effective comprehensive hypoxic prevention and control programs.After field practice,the effect of hypoxic problem treatment is remarkable.