Study On Gas Adsorption Law And Adsorption Model Of Coal Under Gas Pressure Temperature Stress

Coal has complex pore structure,which makes the process of gas adsorption extremely complex,and is affected by gas pressure,environmental temperature,formation stress and other factors.With the increase of coal mining depth year by year,the response of deep coal seam high temperature,high gas pressure and high stress environment to coal seam gas adsorption is more obvious.Taking lump coal as the research object,this paper studies the law of gas adsorption by coal under the action of gas pressure,temperature and stress.Aiming at the problem of inaccurate measurement of adsorption capacity caused by the change of adsorption space of coal under stress loading,a triaxial constant volume adsorption chamber was designed and improved,and a constant volume,variable temperature,variable load and variable pressure coal adsorption test system was built.By using the test system,the experiments of gas adsorption by coal under different gas pressure,temperature and stress were designed,and the law of gas adsorption by coal under different factors was obtained.The experimental results show that the gas adsorption of lump coal conforms to the Langmuir adsorption law,and the relationship between Langmuir adsorption constant and temperature and stress conforms to the quadratic function.The variation range of the two is different.The adsorption constant a decreases with the increase of temperature,decreases first and then increases with the increase of stress,and the adsorption constant b decreases first and then increases with the increase of temperature,and decreases with the increase of stress.When the adsorption equilibrium pressure is fixed,the gas adsorption capacity of coal decreases with the increase of stress.The influence of gas pressure,temperature and stress on gas adsorption capacity of coal is as follows: the influence of gas pressure on adsorption is better than that of stress,and the influence of stress on adsorption is better than that of temperature.Based on the test results,a gas adsorption model of coal under the action of gas pressure,temperature and stress was established,and the adsorption law under the action of different gas pressure,temperature and stress was numerically solved by COMSOL multiphysics software.This paper reveals the law of gas adsorption by coal under the action of gas pressure,temperature and stress,and puts forward the adsorption model,which provides a reference for the test of gas content in deep high stress coal seam,the study of protective layer protection mechanism,the determination of coal seam gas drainage radius,and the design of coal seam gas surface drainage scheme.This paper has 39 pictures,29 tables and 76 references.