Suppressive effect of nitrogen injection against smoldering combustion in model coal seams. Study on neutralization with nitrogen to counter spontanious combustion in coal mines.

To obtain the fundamental data on suppressive effect of nitrogen injection against spontanious combustion in coal mines, some extinguishing experiments were carried out by using intermediate scale model coal seams in a test gallery. The results obtained through experiments and discussion are summerized as follows:(1) The upper limit of oxygen concentration in sealing area to suppress smoldering combustion of coal was about 5% in case of the early heating stage, and under 1% in case of its growing stage.(2) Temperatures in model coal seams during the nitrogen injection dropped rapidly according with the decrease rate of oxygen concentration, and so early extinguishment can be expected in case of lower oxygen concentration in sealing area.(3) Gas composition in sealing area has some relation with temperatures in coal seams under suppression process of combustion.