Dispersion patterns of spontaneous coal combustion fumes in deep open-pit mines effects of wind direction and speed

To explore the smoke dispersion patterns of spontaneous coal combustion in deep open-pit mines, the 13^# coal seam mining bench at Hequ open-pit mine was studied using FDS software. The analysis focused on smoke dispersion and visibility around the fire source under three wind directions and four wind speeds. A similar experiment was conducted to verify the smoke dispersion patterns. The results indicate: FDS is suitable for analyzing smoke dispersion in open-pit mines. The angle between the smoke flow and the bench surface decreases with increasing wind speed, and reverse flow occurs with leeward bench winds. The distribution range of different CO concentrations around the fire source was quantitatively analyzed. The ranges where CO concentration exceeds 200 ppm in the wind direction and vertical wind directions are as follows: 0 to 12 m, 10 m (wind facing the bench); - 3 m to 15 m, 5 m (leeward bench wind); 3 m to - 30 m, 4 m (parallel bench wind). The impact range of visibility around the smoke source decreases with increasing wind speed. The threshold wind speed for visibility impact is 0.1 m/s. Below 0.1 m/s, the impact range is similar for all three wind directions, while above 0.1 m/s, there are significant differences.