Study On The Displacement Effect Of Methane In Coal By He

A series of experiments about adsorption-desorption of CH4,、He and injecting He into coal seam to displace coal methane in different conditions have been conducted on the basis of the measurement method of methane adsorption capacity. The laws of the coal adsorption-desorption of CH4,、He single gas were studied and the influence of pressure changes on the displacement effect In the process of high injection gas was verified.For the coal samples from the No.15 coal seam of Yangquan area, the experimental results of adsorption-desorption about single component CH4, and He show that the CH4, adsorption quantity can be neglected,the analysis results through molecular polarity、critical temperature and molecular diameter can also demonstrate that He is non-adsorptive gas,only has displacement effect. From the angle of groove,pore size distribution and adsorption potential explains the hysteresis of the coal of CH4, adsorption curve. According to the replacement experiment of He to CH4, in the coal,the replacement effect were analyzed from the angle of qualitative and quantitative,the results indicated that the adsorption equilibrium pressure remained unchanged after the injection of He in the high-pressure gas injection condition,and amount of free gas and gas concentration have less changed, but the replacement quantity and replacement rate increased at first and then decreased with increasing of gas pressure,the replacement quantity and replacement rate reached the maximum as 0.02cm3/g and 0.1% when equilibrium pressure is 0.84 MPa,but the two values are all very small,and reached 0 when equilibrium pressure is 2.5MPa. In the condition of the diffusion of constant pressure,the equilibrium pressure、replacement quantity and replacement rate increased with injection pressure,the replacement quantity and replacement rate reached the maximum as 2.45cm3/g、8.17% when equilibrium pressure is 2.5 MPa.The replacement effect of He on methane in coal under the condition of high pressure was analyzed through Dalton’s Law of Partial Pressures and extended-Langmuir equation,the results indicated that high-pressure injection He is very weak in the displacement effect for coal methane desorption,and the effect is not because He reducing the partial pressure of methane,but He will be absolutely not adsorbed by coal,which leads to methane having less desorption. The replacement effect of He on methane in coal under the condition of isobaric diffusion was analyzed through macro perspectives and extended-Langmuir equation,the results indicated that under the constant pressure He and methane’s diffusion because of the concentration difference dilutes the dissociation of methane concentration,which reduces the partial pressure of methane and has the desorption. Under the condition of isobaric diffusion He has substitution effect on methane in coal, the substitution effect caused by gass diffusion reduces the partial pressure of methane.