Effection Of Displace Methane In Coal By Weakly Adsorbed Nitrogen

From the viewpoint of the effect of injection N₂ to coal mine promoting gas extraction/ gas emission and the safety in production of coal mine, this article have conducted a series of injecting weakly adsorption N₂ into coal particles to displace coal methane experiments under the condition of high injection pressure gas and isobaric diffusion on the determine method of methane adsorption capacity in coal, and studied the laws and mechanisms of N₂ displace coal methane in two experiment conditions.The result of adsorption-desorption experiment of coal samples from the No.15 coal seam of Yangquan area showes that the coal’s adsorption ability of CH₄ is stronger than N₂. From the the laws of N₂ displace coal methane in two experiment conditions, we can find that the amount of CH₄’s displacement is every small at the condition of high injection pressure gas, it increases first and decreases then with the increasing of CH₄ adsorption equilibrium pressure, and it’s maxium is 0.56 cm3/g at CH₄ adsorption equilibrium pressure is 0.84 MPa, it incerses with the increasing of N₂ gas injection pressure at the same CH₄ adsorption equilibrium pressure; the amount of CH₄ displacement increases with the the increasing of CH₄ adsorption equilibrium pressure under the condition of isobaric diffusion; the amount of CH₄ displacement under the condition of isobaric diffusion is always greater than it’s under the condition of high injection pressure gas.at the same CH₄ adsorption equilibrium pressure. For the amount of N₂ adsorption, it increases first and decrease then with the increasing of CH₄ adsorption equilibrium pressure, and it is always greater under the condition of isobaric diffusion than it’s under the condition of high injection pressure gas.at the same CH₄ adsorption equilibrium pressure.Analyzing the N₂ displace coal methane mechanisms under two experiment conditions, we can find that N₂ displace coal methane mechanisms is high pressure N₂’s injection increases the total pressure of coal that lead to the CH₄ dessorption under the condition of high injection pressure gas; N₂ displace coal methane mechanisms are the diffusion of gases, methane partial pressure decreased and N₂ partial pressure increased by the diffusion of gases and under the condition of isobaric diffusion, so the amount of CH₄ displacement under the condition of isobaric diffusion is larger than it’s under the condition of high injection pressure gas. Analyzing the mechanisms of injection N₂ under coal mine promoting gas extraction/ gas emission technology combined with experiment results, we can find that the mechanisms of this technology are the carrying effects of gas injection flow, the diffusion of gases, it include the effection of increase permeability by gas injection flow and a little effection of high pressure N₂’s injection increases the total pressure of coal that lead to the CH₄ dessorption.