Experimental Study On Anisotropic Characteristics And Mechanism Of Adsorption And Desorption Of Coal

In view of the anisotropic problems of coal deformation which are caused by gas adsorption and desorption,using the independently developed adsorption/desorption deformation test platform,taking coal with nitrogen as the research object and using the method of laboratory simulation test and theoretical analysis,and under different conditions researching the anisotropic characteristics of coal adsorption/desorption deformation,analysing the mechanism of coal adsorption and expansion deformation preliminarily.Through the experimental research,the paper reveals the anisotropic rules of coal adsorption/desorption deformation under different conditions,and more accurately calculates the adsorption/desorption deformation value of coal,which provides a very important reference index for the identification of coal outburst danger.The research results of this paper are as follows:(1)The adsorption/desorption deformation test of Hebi lean coal under different nitrogen pressures was carried out by using a self developed adsorption/desorption deformation test platform.The test results show that the coal adsorption/desorption deformation is anisotropic,the vertical bedding direction is the largest,the parallel bedding vertical face cleat direction is the second,the parallel bedding vertical butt cleat direction is the smallest.In the process of adsorption and desorption of coal,the greater the gas pressure,the greater the deformation quantity.With the increase of the gas pressure,the ratio of the strain of the vertical face cleat direction to the vertical butt cleat direction gradually reduce,and the anisotropy decrease in the parallel bedding.The adsorption and desorption process of coal sample under different nitrogen pressure has the same rule,that is,the vacuum contraction deformation stage,the inflatable instantaneous compression deformation stage,the elastic recovery deformation stage,the adsorption expansion deformation stage,the unloading expansion deformation stage,the elastic recovery deformation stage and the absorption contraction deformation stage.(2)Comparative analysis of the deformation regularity of adsorption process of different rank,under different temperatures,the anisotropy was found after gas adsorption performance than anthracite coal is more significant.The deformation of coal adsorbed gas increases first and then decreases with the increase of temperature.As the temperature increases,the specific surface area of coal increases and the frequency of gas molecules collide with the surface of coal increases,so that the amount of gas adsorption increases and the deformation of coal increases.With the temperature increasing,the kinetic energy of gas molecules increases,the adsorbed gas molecules that have enough energy to escape from the bondage of coal matrix and migration from the state,caused by coal deformation decreased.(3)The adsorption / desorption of coal is an irreversible process.There is a certain residual deformation after adsorption / desorption of coal under different gas pressures.The greater the gas pressure,the greater the residual deformation and the linear relationship with the gas pressure.