A model for assessing the compound risk represented by spontaneous coal combustion and methane emission in a gob

Abstract

In recent years, the spontaneous combustion of coal has led to numerous gas explosions in mines that have resulted in hundreds of fatalities and very substantial damage to facilities. The present work developed a fully coupled model capable of simulating spontaneous coal combustion and carbon monoxide (CO) release together with methane (CH4) desorption rates, concentration distributions and migration. The aim was to evaluate the combined hazard posed by spontaneous coal combustion and CH4 build-up in mine as a result of the heat release generated by coal oxidation. The results show that the zone representing the highest degree of compound hazard is in the shape of an inclined strip located between 75 and 115 m from the working face on the inlet airway side but closer to the working face on the return airway side. Increases in the CH4 concentration in the return corner decrease as the ventilation flux increases, while the potential danger zone moves deeper into the gob. A greater initial CH4 release rate from the coal increases the size of the danger zone and moves this zone closer to the working face. The danger zone also moves away from the working face with decreases in the residual coal thickness and in the coal oxidation rate. Multivariate functions were developed to predict the positions of the gas explosive zone and the oxidation zone in the gob, and a model for assessing the risk of the compound hazard was established based on evaluating the index gas concentrations in the return corner.