Coal Mine Fire
A mine fire can occur either from natural causes or by human accidents. There are two types of fires: near surface fires and underground fires. The fires that are close to the surface are usually generated by the oxygen which comes from the atmosphere while the underground fires are started by oxygen which comes from the ventilation.
Industrial accidents resulting from gas explosions or negligence of irresponsible people, who are burning the waste in the rubbish dumps placed near the abandoned mines, also can cause mine fires. Besides the human error factor there are natural causes which also can lead to mine coal fires. Sometimes coal may auto-combust, a phenomenon which appears at temperatures of 40 degrees. The fire usually starts inside the coal, but only if it has the proper amount of oxygen from outside.
Coal fire usually depends on two major factors: the grain size and the ambient temperature. If the temperature is high, the oxidation reaction releases heat into the grain. If the grain size is large, the burning process is slow. This means spontaneous combustion. Before the coal burns there is a special process that takes place: the oxygen from the air reacts with the coal, generating the released heat which is transported by the air circulation. When the temperature reaches 80 degrees, some gases like carbon monoxide, carbon dioxide or water vapours are released.
There are multiple factors which influence the coal burning such as: air ventilation, the quality of the coal, low carbon composition and volatile components which encourage the combustion. The particles size, the geological conditions, the human mining activities are also major factors in the coal burning process.
In order to determine the best solution for fire extinguishing, some studies are first needed. The experts must measure the temperature of land surface, by using pyrometers. They need to describe the combustion reactions by taking gas measurements in order to characterize the air ventilation. Geophysical measurements are also needed in order to see the possible fire extent or the magnetic rock characteristics caused by the heat. In order to prevent such fires, the mine can be equipped with warning sensor systems.
Coal fires, whether natural or accidental in nature, have a major impact on the environment. They destroy the flora and fauna in the proximity areas. They also release gasses such as carbon dioxide, carbon monoxide, sulphur dioxide or methane which speed up the global warming process. The fires can be extinguished by cooling the area with large volumes of water inserted, even if this procedure is highly dangerous because the humidity can increase the heat. Drilling holes near the fire is also a solution. All in all the environment needs to be protected as the effects can be dire.
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