Mining Publication: Modeling the Effect of Seal Leakage on Spontaneous Heating in a Longwall Gob Area

Federal regulations provide that mines with a demonstrated history of spontaneous combustion or that are located in a coal seam determined to be susceptible to spontaneous combustion may use a bleederless ventilation system as a spontaneous combustion control measure. Currently, three coal mines in the U.S. are utilizing a bleederless system to prevent spontaneous combustion. In a bleederless ventilation system, one of the headgate entries is used as the tailgate entry of the succeeding panel and is isolated from the gob of the active panel by gob seals constructed in each crosscut inby the active face. Air is coursed across the face area and outby in the tailgate entry into a return entry instead of inby through the gob. As the longwall progresses, some seals may leak. When the headgate entry is ventilated, such as in a Y-type bleederless system, the air leakage through the seals into the gob may lead to spontaneous heating in the gob behind the seals. In this study, a computational fluid dynamics (CFD) model developed in our previous work is used to model the effect of seal leakage on spontaneous heating of coal in longwall gob behind the seal. A single longwall panel using a Y-type bleederless ventilation system was simulated. With typical bleederless ventilation conditions, the simulation results demonstrate that the effect of seal leakage on the spontaneous heating process depends on both seal leakage rate and gob permeability.