Gas outbreak (mining)

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In mining and tunneling, gas outbreaks are the sudden and intensified leaks of gases from the mountains . In the event of an underground gas eruption, very large amounts of gas are released in a very short time that cannot be diverted quickly enough by the weather stream . This leads to a high concentration of the outflowing gas in a limited area.

Gas formation and release

When hard coal was formed, the mine gas methane was also created in addition to the hard coal . This gas is normally bound in the coal and in the adjacent rock. When degradation of the coal mined in the particular is not only seam resulting mine gas released, but also included in the host rocks and in the neighboring seams gas. Due to the mountain pressure , the pressure in the gas can rise to 40 bar and sometimes even higher. As long as the coal is firmly enclosed by the adjacent rock, this has no effect. If the coal is no longer firmly enclosed by the adjacent rock due to the construction of pits, the structure of the coal can be worn down at the exposed area due to the high gas pressure of the methane enclosed in the coal. This then leads to a sudden outbreak of the trapped gas. The outbreaks are particularly violent when tied to coal dust nests. In addition to the gas eruption, large amounts of coal are also ejected. These coals are then suddenly hurled into the open pit. The amount of coal thrown in is so great that the stretches affected are often filled with coal over a greater length. The tendency to such eruptions and their number increases with increasing depth .

The coalification process has not yet been completed in lignite seams . Certain seams are still in a state of carbonic acid fermentation. For this reason, the gas carbon dioxide , which is also enclosed in the coal, is formed here. Since lignite has a high level of humidity, the carbon dioxide then turns into carbonic acid . Here, too, a gas outbreak occurs under certain conditions. In the Kali Mountains there are large carbon dioxide deposits in the mineral in some places. Although the gas is normally bound in the mineral, it can suddenly e.g. B. be released by an explosion. With such a gas outbreak, several thousand cubic meters of carbonic acid are released within a few minutes.

impact

A gas outbreak can lead to serious accidents. In 1865, a gas eruption from a coal seam broke out at the Midi de Dour coal mine at a depth of 468 meters. The amount of gas released was so great that the gas mixture flowing out of the delivery shaft ignited in a fire and an explosion occurred. During this gas eruption, two miners who were on site were thrown several meters away by the gas stream. 121 people were killed in a gas eruption at the Agrappe pit in 1879. The rescue teams are particularly at risk if they act hastily in the event of an incident. Several rescuers have already died in chopping down or in the form of rash actions.

prevention

In mines that suffer from gas eruptions due to their geology , it is hardly possible to avoid such eruptions. However, the risk of gas outbreak can be better assessed using certain parameters. Measures such as the targeted extraction of mine gas can significantly reduce gas outbreaks. In addition to gas extraction, the dismantling of so-called protective seams to combat the risk of outbreak has proven its worth. Here, harmless seams in the hanging wall or in the lying of the endangered seam are first dismantled. This relieves the pressure on the seam at risk of eruption and, as a result, pre-degassing. This protects the mining in this seam. Another measure is the targeted avoidance of cross cuts in the endangered areas. As soon as the endangered seam has been approached, the pressure in the seam is loosened by vibration shooting. These measures can significantly reduce or even combat the risk of gas outbreaks. Compressed air emergency breathing air dispensers will be installed for the miners who work in these areas.

Individual evidence

  1. ^ A b c d Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining encyclopedia. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  2. ^ A b c d e Carl Hellmut Fritzsche: Textbook of mining science. First volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1961.
  3. ↑ Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1 .
  4. ↑ a b c Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. First volume, published by Julius Springer, Berlin 1908.
  5. ↑ a b c Moritz Ferdinand Gätzschmann: Complete guide to the art of mining. Third part; The mining theory, published by JG Engelhardt, Freiberg 1846.
  6. ↑ Dräger Review 384: Protection for the City Underground. February 2010 Online (accessed February 29, 2016; PDF; 3.2 MB).
  7. ↑ Guidelines of the State Mining Authority of North Rhine-Westphalia on the defense against the dangers of the sudden release of large amounts of mine gas with or without the ejection of coal or rock (gas outbreak guidelines) of May 29, 1996, Section 5.1.3 Protective measures online (accessed on September 10, 2012) .