Study On Adsorption And Desorption Of CH₄ In 3^# Coal Seam Of Guojiahe Coal Mine In Yonglong Mining Area

Guojiahe coal mine is located in the middle of Yonglong mining area in the west of Huanglong Jurassic coal field.The structure of the mine is medium.The coal mine mainly excavates 3#coalseem wich the thickness is 0.55-26.83m with an average thickness of 11.57m.which is most of the minable coal seams.The average maximum vitrinite reflectance(Rmax)of 3#coal seam is 0.52%-0.58%,which belongs to low metamorphism long flame coal.Guojiahe coal mine is a high gas mine,and the absolute gas emission of the mine is up to 77.91m3/min,which has a certain impact on the mine production.Therefore,it is of great significance to study the adsorption and desorption of CH4 in the 3#coal seam of Guojiahe coal mine in Yonglong mining area and the gas occurrence law,which can provide an important basis for the gas prevention and development in the post mine production.Based on the analysis of the original geological data,this paper collected the coal samples of Guojiahe coal mine,carried out mercury injection experiment,coal quality analysis,adsorption/desorption experiment,and calculated the adsorption capacity and equivalent adsorption heat.Finally,it studied the gas geological characteristics of guojiahe coal mine and the desorption characteristics and mechanism of low rank coal CH4,The results show that:(1)The gas occurrence in Guojiahe coal mine is mainly controlled by the thickness of overlying bedrock,followed by geological structure,and the thickness,buried depth and volatile content of coal seam have little influence on it.(2)The isotherm adsorption curves of the whole coal sample and mirror coal conform to Langmuir curve,and the saturated adsorption capacity of mirror coal is slightly greater than that of the whole coal sample.The desorption curve of low rank coal does not coincide with the adsorption curve,desorption lags behind adsorption,and there is "Desorption Hysteretic Effect";(3)The pressure of low rank coal is linearly related to the adsorption capacity in the range of pressure approaching to zero.(4)when the pressure is constant,the adsorption capacity decreases with the increase of temperature,because the increase of temperature makes the molecular kinetic energy increase,and the original adsorption/desorption equilibrium goes in the direction conducive to desorption,making the adsorption capacity decrease,which is consistent with the maximum adsorption capacity decreasing with the increase of temperature.(5)The equal adsorption heat of low rank coal increases with the increase of adsorption capacity,which indicates that the adsorption process is a continuous exothermic process.The research results discussed the gas geological law and the energy change mechanism of the adsorption and desorption process of low-order methane in Guojiahe coal mine,providing theoretical reference for the gas control and innovation of high-efficiency development technology of coalbed methane in the research area.