Abstract:

In order to study the effect of different nitrogen injection conditions on the spontaneous combustion of residual coal, the three zones in the goaf of a working face were measured, with the beam tube monitoring system of mines utilized. A migration model for the three zones, which featured spontaneous combustion in the goaf of the working face under different nitrogen injection conditions, was established, and Fluent simulation software was adopted. The optimal nitrogen injection location, temperature, and flow rate were determined by the model. Field experiments were carried out at the Cuncaota No.2 mine, so as to verify the scientificity and effectiveness of the model. The results show that the nitrogen injection effect is the best when the outlet of nitrogen injection is 30 m from the working face. The minimum width of the oxidized zone on the wind return side is 25 m. In addition, the width of the oxidized zone decreases as the nitrogen injection flow rate increases. The oxidized zone in the goaf is better controlled when the flow rate reaches 900 m³/h. As the nitrogen injection temperature drops, the oxidized zone covers more areas and has a cooling effect on the goaf. During the field application of nitrogen injection for fire prevention in this working face, the maximum width of the oxidized zone is reduced from 40.4 m to 15.2 m. The maximum width of the oxidized zone is reduced by 61.4%, which indicates a significant effect on fire prevention.

Key words: nitrogen injection location, nitrogen injection temperature, nitrogen injection flow rate, fire prevention, numerical simulation, width of oxidized zone