Coal mixer

About the sound

In the coal mixer of the colliery Prosper-Haniel (Ruhrkohle AG) the mined coal is mixed in order to provide a consistent quality of coal for further uses. This is a necessary measure, because the coal comes from different mining areas and therefore has varying properties. The facility is located in the so-called mixing hall, which, with a length of 94 meters and a height of 26 meters, represents the largest hall on the colliery site. Up to 30.000 tons of coal can be stored there.
The pit coal is transported into the center of the hall by means of underground conveyors. It is directed to the top level of the processing facility by another system of conveyors. Here, variations in the quality of the coal, for example in the ash content or in the granular size, are balanced out, first, by dumping the unmixed pit coal into a stockpile. This work is done by the fully automated run-of-mine stockpiling and homogenization plant. During this homogenizing, the processing facility moves slowly along a circular rail built around the center of the hall.
In the next step the coal is loosened from the coal stockpile with a so called „harrow“. It does this in a regular combing motion perpendicular to the dumping direction. The coal trickles down the sides of the stockpile. At the foot of the dump, the second part of the homogenization plant, a bucket chain, directs the freshly mixed coal back to the center of the hall. From there, conveyor belts carry the coal to the processing facility.
The sounds heard here are the tumbling of the coal, after the „harrow“ has loosened it, and the coal being dumped out of the transport buckets onto the conveyor belts. These sounds will be heard at the Prosper-Haniel colliery until 2018. Then, anthracite coal mining in Germany will come to an end.

Sound recordist: Konrad Gutkowski
Photographer: Klaus Pirsig