Explosive gases

EXPLOSIVE GASES WITHIN THE UNDERGROUND MINES (EN: detonating gas; DE: sprengbare Gase, Schlagwetter; FR: gas explosifs; ES: gases detonantes; RU: взрывчатые газы) are the gases (methane, higher hydrocarbons, hydrogen, carbon monoxide, and others), which are able to explode in case of the mixing with the air in the determined proportions.

The mixture of methane with the atmospheric air explodes in case of the content of methane from 5% (the lower limit of the explosiveness) to 16% (the upper limit of the explosiveness). The explosion of the greatest strength is observed in case of the concentration of methane of approximately 9.5%, when there enter into the reaction all methane and oxygen completely. The ignition of the methane-air mixture proceeds at the temperature of 650-750 degrees Celsius. The possibility of the ignition increases with the increasing of the time of the impact from the source of the high temperature, with the increasing of the pressure of the gaseous mixture, in case of the existence of the catalysts, and depends on the character of the igniter. During the explosion of the methane-air mixture, there proceeds the reaction, which is accompanied with the significant emission of the heat:

CH4 + 2O2 = CO2 + 2H2O.

The temperature of the products of the explosion reaches 2000-2500 degrees Celsius; the final pressure under the underground mine conditions, in association with the preliminary compression of the gaseous mixture, is the tens of the atmospheres.

There can also yield the explosive mixtures with the air the carbon monoxide, which is formed during the underground fires, hydrogen, vapours of gasoline, and of other easily flammable liquids. For the prevention of the explosions of the gaseous mixtures, it is necessary to exclude the possibility of the accumulation of the combustible gases at the concentrations, which are dangerous because of the explosion, and also to prevent the existence of any sources of the ignition within the zone of the possible accumulation of the explosive mixture.