Nanoscale Pore Structures of Medium and High Rank Tectonic Deformed Coal and Their Influence on Methane Adsorption

Based on vitrinite reflectance test, maceral determination, liguid nitrogen and isothermal adsorption test, nanoscale pore structures and adsorption characteristics of six tectonic deformed medium and high rank coal at typical mining field in the north central of Henan were studied. Results show that the pore volume and the specific surface area are respectively controlled by transitional pores (10 mm to 100 nm) and micropores (1.5 nm to 10 nm)．Nanoscale pore volume, specific surface area and transitional pore volume increased gradually from cataclastic structure coal, granulated coal in brittle deformation coal to mylonitic structure coal in ductile deformation coal; the relationship of Langmuir volume content with nanoscale pore entrance and the surface area of medium and high rank tectonic deformed coal was linear regression; the distribution relationship of transitional pores and micropores has important influence on the coalbed methane desorption characteristics, and the bigger the transitional pore’s volume, the easier the methane desorption.