Pore structure and its impact on CH4 adsorption capability and diffusion characteristics of normal and deformed coals from Qinshui Basin

In this study, the pore structure, adsorption/desorption kinetics and thermodynamics of normal and deformed coals are compared. The total pore volume and porosity of deformed coal are 2.84 to 2.91 times greater than those of normal coal, whereas the micropore volume and specific surface area of normal coal are 1.15 to 1.35 times greater than those of deformed coal. Langmuir volume of normal coal is greater than that of deformed coal. Delta sigma of normal coal is slightly greater than that of deformed coal which indicates that the unit area of normal coal CH4 adsorption capacity is also greater than that of deformed coal. At the early stage of the desorption process, the mass diffusivity of deformed coal is ten times greater than that of normal coal. Then it decreases rapidly, while that of normal coal decreases very slowly. At last, it will be less than that of normal coal.