Theoretical study on adsorption heat of methane in coal

Abstract：Microscopic mechanism of adsorption heat＇s generation was expounded systematically.On the basis of the potential energy model,two-energy-state model was got and the computational formula of the corresponding adsorption heat was deduced.On the basis of the grand canonical ensemble theory,the Langmuir monolayer model of statistical mechanics was got,and the computational formula of the corresponding adsorption heat was deduced.This paper cited De Broglie thermal average wavelength,and got the approximate computational formula of adsorption heat based on the Langmuir monolayer model.To compare the two models,it shows that adsorption heat is much affected by the adsorption capacity,adsorption centers and the average distance between molecules,and that we should use different physical models for analysis towards the outer layer of methane（relative to the coal surface） and the inner methane.On the basis of the Langmuir monolayer model,from perspective of adsorption,the fractal features of pore structure and fracture structure was studied,the two-dimensional flat surface adsorption to the fractal surface adsorption was extended,and a fractal dimension based on De Broglie thermal average wavelength was got.