Longwall (mining)

from Wikipedia, the free encyclopedia
Scheme of longwall with offset
(green: strike sections, gray: seam, orange: old man, red: mining face; the space between gray and orange is the longwall)
In the face of a coal mine
Shearer loader in action on the face, view of the leading roller
Shield extension with chain conveyor
Coal plane

In mining, the term longwall is used to describe a narrow, long mining area. The longwall mining method is called longwall mining . When coal mining longwall is in the downhole operation of the part of a seam , in which the coal is mined.

Basics and dimensions

The face of the longwall is bounded by the deposit . This side is called the excavation front, where the perpendicular or oblique excavation joint advances. On the opposite side, the face is bounded by the old man . This results in a strut width of up to six meters. Due to the fact that the longwall follows the mining front, this width changes during ongoing operations. Depending on the operating condition, the longwall sometimes becomes narrower and then widens again to its normal size. The lower ( lying ) boundary of the strut is the sole , the upper ( hanging ) boundary is the roof . During extraction , the longwall migrates to the front at right angles to its longitudinal direction , depending on the progress of mining . Here also the old man walking with in the working direction by the unneeded portion of the longwall with waste rock ( tailings ) are added is to keep low to the Nachstürzen. The side boundaries of the longwall form the two mining stretches . The lateral boundaries of the mining route to the seam and to the Alten Mann are called the route seams . The transition area between the longwall and the mining section is known as the face burn. The face burn is an area in which the miners are particularly at risk from falling rocks. The area known as the machine shed, in which the drive system is housed, is also located in the face burn area .

The distance between the two mining stretches also determines the length of the longwall. Further determining factors for the face length are the technical equipment, the extraction method, the type of backfill and geological influences. When it comes to technical equipment, the face conveyor has the greatest influence on the length of the face. The breaking strength of the armored chains sets a maximum limit for the length of the face. In terms of geological influences, it is the nature of the adjacent rock, the seam thickness and the respective storage of the deposit that limit the length of the face. In addition, there is a guarantee of adequate ventilation and, in the case of coal extraction, the permissible methane content in the weather . The length of a longwall is between 100 and 300 meters. In individual cases, face lengths of 400 meters and more are feasible. With strong pressure , the length of the face can be reduced to 50 to 80 meters. Which face length is ultimately chosen after prior planning and calculation depends primarily on economic factors. Here it is not absolutely necessary that the economically most favorable face length corresponds to the technically feasible face length.

Technical equipment

The longwall houses the technical equipment necessary for the extraction, loading and extraction of the minerals. In addition, the longwall contains the equipment required to secure the tusks in the longwall . Until the middle of the 20th century, extraction was still carried out manually using a pick hammer and shooting . This type of coal extraction was supplemented by cutting machines . In modern operations there is a coal plow or a shearer loader in the face , with which the coal is extracted and loaded onto the face conveyor. From 1920 onwards, the shaking slide was used as a means of conveyance for the conveyance in the face . From the mid-1950s, scraper chain conveyors were used as face conveyors . These funds were initially powered by compressed air and later also electrically. In modern mining, face conveyors with a width of up to 1.5 meters are used in the face. These face conveyors are driven by electric motors that have a drive power of up to 1200 kilowatts . To secure the hanging wall , individual stamps in combination with caps were used until the 20th century . In modern mining, the strut support in the form of shield support is used as an extension . Due to the problem (risk of falling rocks), special face defoliation is used today in the face burn area. In order to be able to work the face burn area better, special face burn machines are used. In modern mining, the extraction machine, the conveyor and the longwall mining form a technical unit in the struts. In the case of struts with a blow offset, this unit also includes the blow offset device. All equipment in the face is controlled by the face control room .

Individual evidence

  1. ^ A b c d e f g h i 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 Tilo Cramm, Joachim Huske: Miners' language in the Ruhr area. 5th revised and redesigned edition, Regio-Verlag, Werne 2002, ISBN 3-929158-14-0 .
  3. ^ A b c Wirtschaftsvereinigung Bergbau eV: The mining manual . 5th edition, Verlag Glückauf GmbH, Essen, 1994, ISBN 3-7739-0567-X .
  4. ↑ a b c d e f Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962
  5. ↑ a b Heinz Kundel: coal production. 6th edition, Verlag Glückauf GmbH, Essen, 1983, ISBN 3-7739-0389-8 .
  6. ↑ F. Freise: Alignment, device and mining of hard coal deposits. Publishing house by Craz & Gerlach, Freiberg in Sachsen 1908
  7. ↑ a b c d Ulrich Lange: Shearer longwall mining simulation. Approved dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen 2009, pp. 25–29
  8. ↑ Ernst-Ulrich Reuther: Introduction to mining . 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1 .

Web links