Identification and control of spontaneous combustion of coal pillars: a case study in the Qianyingzi Mine, China

Spontaneous combustion of coal is a natural hazard during mining. In China, more than 60 % of cases of spontaneous combustion of coal in China result from coal pillars in goafs. In this paper, the plastic deformation of a coal pillar was simulated and, based on the simulated vertical and horizontal displacement, the distribution of surface porosity was deduced. Mathematical models of oxygen consumption together with air diffusion and leakage were incorporated as user-defined functions in a FLUENT simulation to obtain the air flow and oxygen consumption during a 6-month interruption of mining in the Qianyingzi Mine, China. The simulated oxygen concentration was used as an indicator to identify areas of potential spontaneous coal combustion. The application of a foam slurry to the identified potential coal combustion areas proved to be an effective measure to prevent spontaneous coal combustion as carbon monoxide concentration remained at 20 ppm in the air return flow and at 10 ppm in the gas drainage line.