Principle and technology of precise and quantitative gas traceability in coal seam group mining face

Quantitative analysis of the source and proportion of gas emission from longwall face of coal seams is an important prerequisite for mine gas drainage design and management. The stable hydrocarbon isotope method is based on the principle that the total amount of carbon and hydrogen isotopes remain unchanged before and after the gas is mixed. It can quantitatively calculate the proportion of each source of gas in the working face and become an effective method for accurate and quantitative traceability of the gas at the working face. The necessary condition for the realization of stable hydrocarbon isotope analysis is that the concentration of gas mixture is not less than 10%. In this regard, the principle of accurate and quantitative gas traceability at the coal mining face was firstly proposed,and a method for efficiently separating low-concentration gas was constructed.The separation law of methane, oxygen and nitrogen in the adsorption column was compared and the optimized adsorbent and the size of the adsorption column were compared and determined. The ultra-low concentration gas in the upper corner, return airway and other places was separated and further measured for carbon and hydrogen isotopes.hen, based on the measued carbon and hydrogen isotope values of methane in the end-member gas of each coal seam and the mixed gas at different positions of the longwall face,the proportion and regularity of gas sources in each position of the four tested longwall faces (Dongqu mine and Tunlan mine in Xishan mining area) were quantitatively analyzed using the linear mixing model of two and three end members. Finally, the key gas drainage targets for the working face of the short-distance coal seams were determined: Only 5% of the gas in the upper corners come from the upper adjacent seam, and the current coal seam accounts for 78%, indicating that efforts should be made to increase the gas drainage intensity of the current coal seam. The gas in the gob, upper corner and return airway mainly comes from the pressure relief gas in the current coal seam, and the proportion of gas from the upper adjacent layer shows an upward trend from the goaf to the upper corner and return airway. The ratio of each source in the gob and upper corner gas is less affected by the advancement of the working face and remains basically stable. The technology of precise and quantitative traceability of gas in coal seam mining face is easy to implement and has significant effects. It effectively solves the major engineering problems of precise and quantitative traceability in places such as upper corners and return airways.