Physical kinetics of coal-methane system: Mass transfer, pre-outburst events

Abstract

The article gives the review of the present-day development in the physical kinetics of coal-methane system. The Gibbs thermodynamic potential is derived for this system as the function of methane density (persisting order parameter) and coal jointing (non-persisting order parameter). The authors put forward epy diffusion-filtration mechanism of mass transfer in porous material on two time scales and substantiate the concept of “quick” and “slow” methane. Based on the nonequilibrium thermodynamic potential, kinetic equations are derived for gas pressure and jointing in coal (bed). The first equation solution explains the physical effect of temporal gas pressure growth at the maximum of the external rock (bearing) pressure, the second equation enables generalization of the Griffiths failure criterion for a set of gas-filled joints. Mechanism of pre-outburst spalling of gas-saturated coal is analyzed.