Coal deformation characteristics in gas adsorption and desorption

Abstract

Experimental analysis and numerical calculation are used to study the characteristics of axial strain and circumferential strain during adsorption and desorption process of coal and the volumetric strain-time model.The results show that the axial strain and circumferential strain are anisotropic,and the axial strain changes faster than the circumferential strain.There are several stages,for example,adsorption swelling strain increase,adsorption equilibrium,pressure relief strain decrease,and desorption equilibrium in the variation of axial strain and circumferential strain of briquette.However,there are several stages in the variation of circumferential strain of raw coal,for instance,gas compression strain reduction,adsorption swelling strain increment,adsorption equilibrium,pressure relief strain reduction,and desorption equilibrium.Under the same pressure,the briquette is reach the adsorption equilibrium state earlier than the raw coal,and the desorption rate of briquette and raw coal are bigger than adsorption rate.Furthermore,the original Langmuir model is improved,and fitted by MATLAB.Compared with other models,the modified Langmuir model is optimal.

Keywords

• adsorption and desorption
• axial strain and circumferential strain
• anisotropy
• improved langmuir model