By Dr. Jürgen F. Brune, Colorado School of Mines

Longwall coal mining sections may develop spontaneous combustion or explosive mixtures of methane-air in the gob. Both phenomena are related to the depth to which oxygen from the active mining entries can penetrate into the gob. If the longwall panel is operated as a bleederless or sealed gob, progressive sealing along the gate roads as the longwall face retreats limits the flow of fresh air into the gob and thus deprives potentially explosive atmospheres or sponcom of oxygen. In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), researchers at the Colorado School of Mines have used computational fluid dynamics (CFD) modeling to simulate the flow of methane, oxygen and nitrogen in longwall gobs. Modeling indicates that targeted injection of nitrogen through the seals along the gate roads inby the face can be used to control the size and location of methane-air mixtures as well as the oxygen concentration within the gob and minimize or eliminate the hazards of spontaneous combustion and methane explosions within the gob.