Firedamp

The firedamp (the word comes from Greek) is a Gaz natural which is released from the layers of coal and of the country rocks.

Composition of the firedamp

The composition of the firedamps of the basins Houille rs britannico-free-belgo-Rhenish varies between the following limits:

  • Methane (CH4): from 93,0 to 99,5%
  • Ethane (C2H6): from 0,02 to 2,8%
  • Hydrogen: from 0,00 to 0,23%
  • Nitrogen: from 0,00 to 3,5%
  • Carbonic gas CO2: from 0,03 to 3,4%

In theory, one can thus compare this firedamp to methane, gas extrèmement dangerous. It is in the beginning many mining catastrophes (firedamp explosions), especially before the invention of the lamp of Davy.

Properties of the firedamp

Its Density is of 0,72 kg/m ³ and its Densité of 0,558. Moreover, it is Inodore and Incolore.

With Pressure and ordinary Temperature, the limiting contents of inflammability are 5,6 and 14%. The Combustion takes an explosive form between 6 and 12%.

The ignition of a gas Volume made up of a mixture of Air and firedamp, in underground work, involves:

  • the production of a flame whose expansion is limited enough,
  • the formation of a Wave of high pressure which is propagated very far at speeds of about 250 m/s,
  • the gas release flarings (CO2 and CO),
  • the combustion of methane can put fire at easily flammable matters, in particular with coal dusts raised by the breath of the flame.

The equation of combustion of methane is the following one: CH4 + 2 O2 → CO2 + 2:00 2O

Recovery of the firedamp

With Plane and Divion in old the field of the Pas-de-Calais like to Lourches (old Desired pit it Naville) close to Valencian, the firedamp is recovered, purified and injected into the public network of distribution of Natural gas.

Since March 1st, 2007 Gazonor is the single one exploiting of the three sites developing 12 térawatts-hour per annum gas is the equivalent of the consumption of a town of 60.000 inhabitants. With him only the site of Plane develops 8 térawatts-hour per annum.

The Firedamp explosion

The firedamp explosion is a gas accidental explosion in a mine, related to its exploitation. It is about an often fatal, and very dreaded accident of the minors; it is in general worsened by a collapse of the tunnels, and sometimes by a Dust explosion.

Prevention of the firedamp explosions

The first measurement consists in avoiding the naked flames and the sparks. The miner's lamps with flame quickly evolved to a protected flame: the air enters by a special sieve to feed the flame, the total atmosphere is not in contact with it. It is for this reason also that the mechanization of the mines was done, at the beginning, by using the Compressed air. The routing and the use of electricity in the gassy mines require special precautions. The electrical motors and other generators of electric sparks, such as the contactors, must be locked up in “explosion-proof enclosures” which prevent the propagation towards the surrounding air of a possible ignition of the perhaps gassy atmosphere contained in the explosion-proof enclosure.

On the other hand, one cannot exclude the sparks produced by friction from the Métal (Pioche S, then power picks), in particular with the Pyrite S.

The second measurement consists in detecting the firedamp, which is colorless and practically odorless. For that, one took along formerly oisillons in cages at the bottom of the mines; when they stopped singing and would die, it was the sign which the atmosphere became unbreathable and thus contained of the firedamp or lacked oxygen (the oisillon is much more fragile than the man). The miner's lamps to flame protected also made it possible to detect the firedamp: if the air entering by the explosion-proof sieve were charged with gas, it occurred a visible combustion (known as “aureole”) of the firedamp around the normal flame, which made it possible to appreciate the content of firedamp of the air.

One uses now Détecteur S called “fire-damp detectors”, based on the catalytic combustion of the firedamp on a allied platinum wire. The first apparatus was developed by general engineer Leon in 1900, improved in the Années 1950 by the research and studies Center of Charbonnages de France (CERCHAR) to lead to the series of the “Verneuil 52” of which a few hundreds of specimens were usually used in the French mines until their closing towards the Années 2000. Other physical characteristics of the firedamp (Index of refraction, selective absorption in the infra-red one, etc) were also used, to produce recording telegrisoumeters in particular making it possible to supervise surface automatically, with automatic alarms, the gassy atmosphere in many points of a mine.

List firedamp explosions

Abbreviations of the countries: BE: Belgium. CA: Canada. CN: China. OF: Germany. FR: France. GB: Great Britain. IN: India. JP: Japan. RU: Russia. UKR: Ukraine.

  • March 10th 1906: the most important mining catastrophe of France, known as Catastrophe of Courrières, the name of the mining Company which exploited then the layer of coal; it makes 1  099 died on the territories of Billy-Montigny (pit 2 known as “Auguste Lavaurs”), Méricourt (pit 3 known as “Lavaleresse”) and Sallaumines (pit 4 known as “Holy-Bores”); however, the generally allowed cause is the Poussier and not the firedamp; the emotion which followed is at the origin of a vast movement of Grève which led to the introduction of the weekly rest; as from this time, the lamps with naked fire will be banished.

In the Years 2000, it is the China which counts the most mining accidents, with 80% of the world deaths for only 35% of the world production of coal; 6.000 people died in the Chinese mines in 2004.

According to a recent article of the Company of mineral industry, appeared for the centenary of the catastrophe of Courrières, on the whole, one could estimate in March 2005 at 42.614 the number of minors killed at the time of the various catastrophes (c.a.d. having made more than 50 victims, floods and fires included/understood) which occurred between 16th and the 21e century.

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