The initial signs of spontaneous combustion of coal are as follows:
(1) The coal generates heat during the low-temperature oxidation process. Due to the accumulation of heat, the temperature of the coal body is increased, and the water is evaporated. Therefore, the humidity in the roadway increases, and the water vapor agglomerates in the air to form a mist, on the surface of the bracket and the roadway wall. Water droplets are formed, and workers call this phenomenon “the sweat on the coal wallâ€. However, it should be noted that the place where this phenomenon occurs is not necessarily the initial sign of coal spontaneous combustion, because in the place where the two hot and cold air streams meet, fog and “sweating†phenomenon will appear in the roadway.
(2) If the smell of kerosene, gasoline and turpentine smells in the roadway, especially when smelling the odor of coal tar, it indicates that the spontaneous combustion of coal has developed to a serious extent.
(3) The temperature of the air near the underground fire zone and the temperature of the water flowing out of the fire zone are higher than the normal temperature.
(4) Carbon monoxide and carbon dioxide are produced during the spontaneous combustion of coal, which makes people feel sultry, suffocating, headache, limb weakness, fatigue and other symptoms.
(5) When shallow coal is mined, it can be seen that water vapor escapes from the surface collapse and can smell the coal tar; in winter, the snow in the surface subsidence area can be melted first.
In a man-ventilated mine, if there is a fire in the goaf, the signs are not obvious and it is not easy to find it in time.
In order to find the spontaneous combustion fire in the underground as accurately and reliably as possible, the air sample should be taken in the well for testing to analyze the change of air composition. If a trace of carbon monoxide is found and it persists, and its concentration gradually increases with time, it can be concluded that the coal has Self-ignition.
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