Wet stone
A wet stone is a molding made of lignite (forerunner of the coal briquette ) with which the earthy coal particles and dusts produced during mining and processing can be used as fuel for heating purposes.
The process was already used at the beginning of the 19th century. At that time, a coal paste was made by mixing the coal with water and, similar to brick production, was shaped by hand by painting into molding boxes and then air-dried. Five stones measuring 21 cm × 10.5 cm × 6 cm were simultaneously formed in one mold. The performance of a worker in a 10-hour shift, including the preparatory work and transport, was 1200 stones. These stones are also referred to as "hand-held stones" to differentiate them from machine-made ones. In the Rhenish lignite mining district , such manually produced pellets in the conical shape customary there were known as " Klütten ".
Wet formed stones shrink strongly when drying and become cracked. They are therefore sensitive to mechanical influences and moisture. Due to the high water content of the air-dried stones of up to 30% they have a low calorific value . Therefore, dry pressing processes for the production of briquettes were developed . The first machines for the production of wet press blocks are developed around 1830. The breakthrough in large-scale implementation was achieved in 1863 with the Hertel-Schmelzer coal press .
Meyer's Konversationslexikon in the edition from 1905 to 1909 describes machines for the production of wet press blocks:
“A coal press is used to produce the wet press blocks, on which the coal passes a pair of rollers, then a mashing device with a rotating knife shaft, is moistened with water, then goes through a fine rolling mill and is driven into a press hull from which it emerges in the form of a strand that is finally cut by wires. The stones obtained are air-dried. They retain a lot of water even after drying, which reduces their calorific value and increases transport costs "
Drying in open drying sheds takes a few days up to three weeks and is only possible in summer, as the wet stones are shattered by ice formation in winter. Artificial drying was then rejected as not being economical.
In the period after the Second World War, wet pressed bricks were also produced in Germany, some in brickworks.
literature
- Hans Otto Gericke: wet molded bricks - wet pressed bricks - briquettes. From the early history of lignite molded bricks in Central Germany. In: History of Technology. 67, 2000, p. 177.
Individual evidence
- ↑ Lausitzer und Mitteldeutsche Bergbau-Verwaltungs GmbH: Briquette factories and Brieske power station
- ↑ a b c Otto Lueger (Ed.) Lexicon of all technology 2nd edition 1904–1920 online version