Coupling Treatment of Gas Drainage and Nitrogen Injection for Fire Prevention in the First Stratified Mining goaf:Theoretical Calculation and Field Experiment

In order to solve gas and spontaneous combustion in high gassy and combustible coal seam, in this work, the hazard control of gas and spontaneous combustion was studied by numerical simulation and on-site experiments, combining data from the first stratified mining working-face in Gushan Mine, China. Fracture variation in roof and floor of the coal were simulated by the UDEC software with the influence of mining operations. The on-site experiments and COMSOL Multiphysics numerical simulation method were carried out to study the width variation of oxidation zone in goaf with buried pipe extraction and nitrogen injection. The results showed that the combined use of high position borehole drilling, buried pipe in goaf and downward floor hole could reduce the amount of gas extraction, but the stereoscopic gas extraction would enlarge the width of oxidation zone. However, the nitrogen injection measures in goaf could reduce the amount of gas extraction and width of the oxidation zone at the same time, while it also increased the pumping capacity of downwards hole. Besides, the goaf nitrogen injection had a good inhibitory effect on both residual coal seam spontaneous combustion and bottom stratification gas emission.

Automated summary

The research showed that the combination of high position borehole drilling, buried pipe in goaf, and nitrogen injection can effectively reduce gas extraction, while stereoscopic gas extraction can increase the width of the oxidation zone. Nitrogen injection in goaf not only reduces gas extraction and oxidation zone width, but also increases the pumping capacity of downwards hole, with good inhibitory effects on spontaneous combustion and gas emission.