Rock dust scattering

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In mining, rock dust scattering is a measure that serves to combat explosive deposits of coal dust. The process is used in hard coal mining in drifts and in blind shafts . It is part of the rock dust process. The scattering of rock dust is intended to prevent the occurrence of a coal dust explosion; it is not very suitable for rendering a coal dust explosion that is already taking place harmless.

Basics

Deposited coal dust can, under certain conditions, lead to a coal dust explosion. Through the targeted use of rock dust , it is possible to prevent the occurrence of coal dust explosions or to minimize their effects. However, the rock dust must be scattered in such large quantities that the combustible portion of the deposited coal dust does not exceed 20 percent. In addition, in order to be able to achieve an effective explosion-inhibiting effect, the coal dust must be well mixed with the rock dust. The disadvantage of the process is that this mixing can only be carried out very inadequately in practice. For this reason, other methods such as the dust binding method are often used.

History

As early as the second half of the 19th century, studies to prevent coal dust explosions were being carried out in the English and French coal mines. After a pure coal dust explosion in 1887 at the Altofts coal mine in England, the director general of the Royal Commission on Coal-dust proposed the use of shale dust in certain stretches to prevent coal dust explosions. After the method had been tested several times in a small test section on the mine, the scattering of rock dust was introduced throughout the mine building from 1910 . It was not until 1920 that the first colliery in the German coal mining industry was released from the sprinkling requirement that was then prescribed in German coal mining. Instead of irrigation, the Dortmund Oberbergamt has allowed the mine to use rock dust to prevent explosions in some of the mine workings.

Application and problems with application

During the process, the rock dust is generously scattered on the coal dust accumulations. Such a large amount of rock dust has to be scattered on the coal dust that the entire dust mixture does not contain more than 20 percent combustible components. In order to be able to accomplish this, a correspondingly large amount of rock dust must be stored at all points in the mine building where coal dust is deposited. The rock dust is collected in storage containers on site and transferred to a carrying case for use. From there it is blown onto the coal dust accumulation using a compressed air nozzle attached to a 20 meter long hose. This measure is necessary so that as soon as new coal dust collects, it can be sprinkled with rock dust again immediately. This gradually creates an alternating stratification of coal dust and rock dust. However, the alternating stratification does not result in an intimate mixing of the two types of dust. This means that there is a risk that the rock dust will lose its protective effect. To avoid this, rock dust would have to be continuously scattered in particularly dust-intensive areas. In addition , there is an additional risk of the lighter coal dust becoming explosive again in the mining section , in particular on the weathered side of struts with a lot of dust.

Individual evidence

  1. ↑ a b c d e Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 .
  2. ^ A b Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  3. ↑ a b c d e f Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
  4. ↑ a b c d Wimplinger: The causes of mine explosions and their control. In: Polytechnisches Journal . 340, 1925, pp. 75-76.
  5. ↑ Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. First volume, fifth improved edition, published by Julius Springer, Berlin 1923.
  6. ↑ K. Hatzfeld: The development of measures to combat coal dust . In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Dortmund Upper Mining District (Ed.), No. 44, 61st year, October 31, 1925, pp. 1385–1398.
  7. ↑ a b H. Schultze Ronhof: The rock dust process introduced on a mine in the Ruhr district and its economic efficiency . In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Oberbergamtsiertel Dortmund (Ed.), No. 42, 57th year, June 21, 1921, pp. 1010-1016.

See also