Study on gas seepage characteristics of loose coal

Abstract

In order to study the influence of temperature on the gas seepage law in loose coal bodies in goaf, gas seepage characteristics experiments were conducted on three types of coal samples, namely anthracite, bituminous coal, and lignite, under different temperature conditions using a self-developed loose coal temperature seepage comprehensive experimental platform, and COMSOL Multiphysics was used to simulate the gas seepage process through bituminous coal under constant temperature and continuous heating conditions. By studying the gas seepage law when there is a local heat source in the loose coal body in the goaf, a temperature based on gas seepage model for the loose coal body was established. Under constant temperature conditions ranging from 30 ℃ to 80 ℃, when air passes through loose and broken anthracite, bituminous coal, and lignite at a speed of less than 1.0 cm/s, it follows the linear Darcy flow law, and the pressure gradient gradually increases with the increase of specific flow rate; the permeability of coal decreases with increasing temperature, and the permeability changes of different coal samples vary with increasing temperature, and brown coal>bituminous coal>anthracite; as the temperature increases, the temperature distribution and permeability distribution inside the coal pillar can be approximated as an “ellipsoidal shell” near the gas outlet.

Keywords

• goaf
• gas seepage model
• loose coal body
• temperature
• permeability
• local heat source