Research On The Pore Structure Of Soft Coal And Its Adsorption Characteristics To CH₄

Due to the low strength of coal mass, worse permeability and strong ability in methane diffusion of soft coal, it is easily induced in gas accident, pore structure characteristics of soft coal and gas delivery law are not only the premise of studying the gas emission law in soft coal seam, but the foundation of coal and gas safety mining. This paper summarizes and reviews the achievements of the characteristics of hole and fracture structure and gas adsorption characteristics, the basic characteristics of porous media and the influencing factors of coal porosity are analyzed in theory, taking the soft coal in Chenghe coalmine for research object, using the pressured-mercury testing, low- temperature nitrogen adsorption method, SEM experiments, X-ray diffraction experiment. The results show that keyhole and microporous are the chief in soft coal's pore system, the additive effect of adsorption force field in microporous has enhanced the adsorption potential, airtight pores with a close end and ink-botttle pores are benefit to gas aggregation, but go against the gas diffusion and migration, tectonic stress improves the connectivity of mesopore and macroporous. The aromatic nucleus interlayer spacing(d002) less than hard coal, but the diameter(La) and the stack height(Lc) of basic structural unit are opposite. Analysing the pore structure characteristics of soft coal, elaborating soft coal's characteristic fractional dimension and its change laws are summarized.The characteristics of methane adsorption in soft coal are studied by the physics experiments and molecular simulation method, the fractal adsorption model is constructed, soft coal is more sensitive to temperature, the change range of adsorption constants of soft coal more than hard coal under the same condition of change of temperature gradient, the change law of isosteric heat of adsorption and adsorption quantity are analysed to verify the energy unevenness of coal surface. Based on the gas flow theory in coal seam, seepage field mathematical model of gas suction by drilling is established, using numerical simulation method to study gas delivery law in drainage hole, the layout parameter of gas drilling is determined. The research results provide certain theoretical basis and technical support for optimizing gas control technology and realizing coal and gas safety mining.