Forms of Methane and Gas Releases from Coal Beds

Abstract

Generally, in underground mining, coking coal beds are gas-bearing and require degassing. Therefore, the gas dynamics of the bed is a key aspect in the development of coal–methane deposits. The prevailing standards are based on sorption theory, but current requirements are associated with new approaches to understanding gas liberation. New results based on the hypothesis of a coal–gas solid solution indicate that the irreversible decomposition of that solid solution due to the relaxation of the mine pressure provokes gas liberation from the bed in the appropriate conditions. Given the steady increase in the speed of face movement, it is clear that ideas from the past (1950s–1970s) regarding the properties of the coal bed and the processes that occur there do not meet current requirements. Since the breakdown of some part of the coal–gas solid solution changes the gas structure of the bed, we may determine the gas flow into the bed’s filtration volume by analysis of that breakdown. The gas balance equation in terms of the forms of methane in the bed takes account of the influence of methane in solid form on the sorptional potential of coal and permits quantitative assessment of changes in the gas structure within the bed under the influence of geomechanical mining processes.