spontaneous heating; coal; gob area; modelling; Fluent

A commercial CFD (Computational Fluid Dynamics) software program, Fluent, was used to study spontaneous combustion processes of the coal left in the longwall mined-out (gob) area. A three-dimensional model of the gob with an advancing coal face has been developed. For the model, typical behaviour of a bituminous coal exposed to oxygen, obtained from laboratory investigations, was incorporated. The longwall gob area was designed on the basis of the actual longwall face district. Main attention was paid to model the effect of grain size of the coal left in the mined-out area on the oxidation heat and evolution of gases. Numerical simulations confirmed the existence of an ?optimal? zone for intense development of the spontaneous heating process in the gob area. This zone was found to shift towards the longwall face if the coal grain size in the gob decreases.