Experimental Study on Extinguishing Spontaneous Combustion of Residual Coal in Goaf by Nitrogen-water Mist two-phase Flow

In order to clarify the effect of nitrogen-water mist two-phase flow on extinguishing spontaneous combustion of residual coal, experiments were carried out in similarity model of mine goaf by using self-designed device. The experimental results indicated that the average cooling rates of 1–6# K type thermocouple temperatures in goaf were 24.6°C/min, 8.3°C/min, 4.2°C/min, 12.3°C/min, 8.1°C/min and 19.2°C/min during the period of 55–80 min when nitrogen-water mist was applied to combustion area. After the application of nitrogen-water mist, the consumption rate of O2 in the experiment was reduced from 3.16 × 10–4 m3/s to 1.41 × 10–4 m3/s; the generation rates of CO, CO2 were reduced from 3.91 × 10–5 m3/s, 1.74 × 10–4 m3/s to 1.69 × 10–6 m3/s, 6.57 × 10–6 m3/s, respectively; the generation rate of H2 was reduced from 1.41 × 10–5 m3/s to 3.6 × 10–8 m3/s; the emission rate of CH4 was reduced from 1.05 × 10–5 m3/s to 7.78 × 10–7 m3/s. The experimental results suggested that nitrogen-water mist could effectively suppress the burning of coal and reduce the generation amount of toxic and harmful gas in mine goaf.