Conditions and initial symptoms of spontaneous com

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Conditions and initial symptoms of coal spontaneous combustion

there are three necessary conditions for coal spontaneous combustion: coal itself has spontaneous combustion tendency; Supply air continuously and appropriately; The heat dissipation conditions are poor, and the heat energy generated by coal oxidation continues to accumulate

coal itself has the tendency of spontaneous combustion, that is, it has the ability of low-temperature oxidation. It is the internal factor of spontaneous combustion, which depends on the physical and chemical properties of coal itself and the composition of coal. Coal with different grades has different coal petrographic composition and spontaneous combustion. Lignite and bituminous coal are prone to spontaneous combustion; In bituminous coal, long flame coal and gas coal have the strongest spontaneous combustion; Poor spontaneous combustion of lean coal and anthracite; In the same brand of coal, the more sulfur, the more prone to spontaneous combustion. Therefore, article 228 of the coal mine safety regulations stipulates that the spontaneous combustion tendency of coal is divided into three categories: easy spontaneous combustion, spontaneous combustion and non spontaneous combustion

water and fire are incompatible, and more water in coal is not easy to spontaneous combustion. However, after the spontaneous combustion coal loses water, the risk of spontaneous combustion increases, and the global vanadium production capacity is 251600 tons (converted into V2O5), so the ground coal pile is prone to spontaneous combustion after rain and snow leakage and evaporation; The spontaneous combustion area is flooded with water underground, and it is easier to spontaneous combustion after resuming production, because the surface of coal is easier to oxidize after water washing

the geological conditions of coal seams have a great impact on coal spontaneous combustion, dai'an et al. The thicker the coal seam is, the greater the dip angle is, the greater the risk of coal spontaneous combustion is. Because in thick coal seams and steeply inclined coal seams, the recovery rate is low and there are many coal losses; The coal pillars in the mining area are easy to break after being pressed, the goaf is not tightly closed, and the air leakage is large, which creates conditions for coal spontaneous combustion. At the same time, coal is prone to spontaneous combustion in faults, folds and fracture zones

for mines with relatively strict spontaneous combustion tendency of coal, the installation project took 1 hour, and the main roadway should be arranged in the rock stratum to reduce coal pillars and avoid excessive cutting of coal seams and exposure to the air; At the same time, appropriate mining methods should be selected to improve the recovery rate, reduce coal loss, close the mining area in time, and reduce or avoid air leakage to the goaf. Try to reduce the ventilation pressure difference to reduce the air leakage in the goaf. When the air leakage is between 0.10 prefix [cross head] 4 and 0.8 cubic meters per minute, the heat generated by blooming is easy to accumulate, and the coal is most prone to spontaneous combustion

the sooner coal spontaneous combustion is discovered, the easier it is to be extinguished. Therefore, it is of great significance to understand and master the initial symptoms of coal spontaneous combustion and timely identify and judge them

the initial symptoms of coal spontaneous combustion are as follows:

1. Coal generates heat in the process of low-temperature oxidation. Due to the accumulation of heat, the temperature of the coal body is increased and the water evaporates. Therefore, the humidity in the roadway increases, and the water vapor condenses in the air in a fog shape, forming water droplets on the surface of the support and the roadway wall. Workers call this phenomenon sweating on the coal wall of the roadway. However, it should be noted that this phenomenon is not necessarily the initial symptom of coal spontaneous combustion, because fog and sweating will also occur in the roadway where the cold and hot air streams converge

2. If you smell kerosene, gasoline and turpentine in the roadway, especially when you smell the stench of coal tar, it indicates that coal spontaneous combustion has developed to a serious degree

3. The air temperature near the underground fire area and the temperature of water flowing out of the fire area are higher than the normal temperature

4. Carbon monoxide and carbon dioxide are produced in the process of coal spontaneous combustion, which makes people feel stuffy, suffocating, headache] limb weakness, fatigue and other symptoms

5. When mining shallow coal, we can see the water vapor escaping from the surface collapse cracks and smell the smell of coal tar oil; In winter, it can be seen that the snow in the surface subsidence area melts first

if there is a fire in the goaf in the mine with forced ventilation, the symptom is not obvious and it is not easy to find it in time

in order to find the underground spontaneous combustion fire as soon as possible, accurately and reliably, air samples should be taken from the underground in time for testing, and the changes of air components should be analyzed. For example, trace carbon monoxide in anti County, which is persistent, and its concentration gradually increases with time, it can be concluded that the coal spontaneous combustion

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