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One of the main reasons for coal mine fire is spontaneous combustion of residual coal in gob. As the difference of compaction degree of coal and rock, the underground gob can be considered as a porous medium and divided into “three zones” in accordance with the criteria. The “three zones” are “heat dissipation zone”, “oxidation zone” and “choking zone”, respectively. Temperature programming experiments are taken and numerical simulation with obtained experimental data is utilized to analyze the distribution of “three zones” in this paper. Different width and depth of “oxidation zone” are obtained when the inlet air velocity is changed. As the nitrogen injection has inhibition effect on spontaneous combustion of residual coal in gob, nitrogen is injected into the gob. The widths of “oxidation zone” are compared before and after nitrogen injection. And ultimately the optimum location and volume of nitrogen injection are found out.

Tracer gas technology is an effective way to evaluate underground coal mine ventilation system, especially in stope, air leakage from working face to gob can be quickly detected by this method. While tracer gas distribution characteristics may be different with the variation of ventilation parameters, therefore, ascertaining the uniform distributed location as sampling point is essential to improve the measuring accuracy of tracer gas technology. This study conducts simulations of tracer gas distribution in four ventilation models with different parameters, aiming to analyze the effects of gob and height difference between roadway and working face on tracer gas distribution uniformity. The result shows the porous characteristics of gob is not conductive to tracer gas uniform distribution, the height difference between roadway and working face increases the turbulence intensity of airflow and promotes the uniform distribution of tracer gas. In no height difference stope, tracer gas and airflow can be mixed uniformly at 5D of return roadway, but in height difference stope, only 1D is required. Finally, a practical case study is conducted to verify the validity of simulation.