Investigation of spontaneous heating zones and proactive inertisation of longwall goaf in Fenguangshan Mine

To understand the spatial distribution of spontaneous combustion zones under a Y ventilation scheme, field tests and numerical modelling studies were carried out on a longwall face in Fenghuangshan mine. Computational fluid dynamics models were developed and base model results validated using tube bundle gas monitoring data. A three dimensional high oxygen concentration zone where spontaneous combustion was most likely to occur was predicted behind the longwall face. Parametric studies were conducted to develop proactive goaf inertisation strategies to minimise the spontaneous combustion zones. Results indicated that effective goaf inertisation can be achieved by injecting inert gas on the belt road side at least 100 m behind the face, and, if underground access becomes prohibitive, injection can be carried out via surface wells/boreholes. Injection behind the retaining wall is only effective for localised heating(s) around the injection point(s), as much of the injected inert gas will be dispersed by air leakage along the unconsolidated goaf boundary