Coal quality has a significant impact on coal spontaneous combustion
1. The grade of coal. The grade of coal indicates the degree of metamorphism of coal, expressed as the amount of volatiles commonly used and the amount of coal contained. The low-grade pure coal has high self-ignition heat sensitivity, and its self-ignition sensitivity decreases as the coal product energy increase. So the dry lignite is most susceptible to self-heating and anthracite is hardly self-igniting. However, lignite containing the most moisture is less prone to spontaneous combustion than pure lignite.
2. The moisture content of coal. The moisture content of coal has a great influence on the spontaneous combustion of coal. Coal with saturated moisture content, especially before the lignite and sub-bituminous coal with high moisture content are mined and dried, the coal body no longer adsorbs moisture and thus cannot release the heat of wetting. The heat released by the oxidation of coal generally increases the temperature of the internal moisture. On the other hand, the chemical reaction at the time of self-heating requires a small amount of water to participate. The moisture content of low-grade coal is much greater than the amount required for chemical reactions. Thus, for low grade coal, the moisture is actually a self-heating inhibitor of coal.
3. Minerals. The mineral component of coal is also called ash. It can react with oxygen to exotherm and increase coal temperature, and decompose coal to increase the surface area of coal contact with air, such as pyrite, which can absorb part of the heat released by oxidation reaction to reduce the oxidation reaction process of coal; high ash of coal makes The heat of oxidation per unit mass is reduced.
Environmental factors for mining and storage
The influence of environmental factors on coal self-heating is the moisture content of coal can be changed; the contact condition of coal oxygen is changed: the heat generated is diffused.
1. Geological factors. Faults and fissures facilitate the contact of air and moisture with coal. Therefore, the heat dissipation is not significantly increased, but the chance of oxidation of coal and the adsorption of water is increased. That is to say, faults and fissures increase the risk of spontaneous combustion of coal. There is less air leakage on the buried coal seam. The coal in the goaf (especially for thick coal seams) increases the risk of spontaneous combustion of coal due to incomplete recovery.
2. Mining factors. There are two main aspects of the impact of mining factors on coal spontaneous combustion, ventilation and coal crushing. Where there is no ventilation or adequate ventilation, the possibility of spontaneous combustion of coal is low. However, the possibility of spontaneous combustion of coal in places with insufficient ventilation is greater. Fracture leakage is an insufficient leakage, which creates conditions for further oxidation of the coal, and the heat dissipation conditions are not improved. Therefore, any air leakage is very dangerous for coal spontaneous combustion.
3. Storage and transportation factors. In the process of storage and transportation, the factors affecting coal spontaneous combustion are heat dissipation caused by insufficient rain and spray water for low-grade ventilated and dry low-grade coal.
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