Oker lead works
The lead works Oker (BHO), also Blei-Kupfer-Hütte Oker (BKO), formerly Frau-Marien- (Saiger-) Hütte , was a location for the early modern to industrial heavy and non-ferrous metal extraction in the Harz Mountains . It was operated from 1527 to 1970. In a successor company, lead was smelted from secondary raw materials until January 31, 2001 . The hut was located at the exit of the Okertal on Hüttenberg in today's Oker district of the city of Goslar . The Harz-Metall GmbH operations are still located on the extensive factory premises .
History and technology
Time before the founding of the Okerhütte - the medieval hikers' hut
The Harz metallurgy goes back to the silver , heavy and non-ferrous metal mining in the Upper and Lower Harz. Only the possibility of extracting the metals from the Harz ores and their further development made economic mining possible. The Harz was one of the most important mining areas in Europe in the early modern period and mining, in the case of the Rammelsberg, dates back around 3000 years.
Until the end of the Middle Ages , there were hardly any permanent smelter sites. The processes in the time of so-called traveling smelting were associated with a high consumption of charcoal as a reducing agent and energy supplier. The high-quality hardwoods required for this (e.g. beech) could not grow back in the amount that was needed. In addition, transporting the ore to the forests was seen as easier than transporting the required wood to the raw material. Around 200 slag sites in the Harz are known from this time.
Foundation of the Frau-Marien-Hütte - transition to permanent hut locations
The reason for the establishment of permanent smelter locations was the use of water power to drive machines, for example for the bellows for the combustion air in the melting furnaces. From the end of the 15th century, the smelters were preferably built on the Harz rivers such as Oker , Grane , Innerste and Sieber , where the stamping works for crushing and enriching the ores were also located. In the Oker valley, the water of the Oker was also dammed up in order to transport the wood required to the huts by rafting . This means that the trunks were allowed to drift downstream and later fished out of the river bed at weirs . At that time, the cabin tom somber Ford was built in such a place . The Frau-Marien-Hütte was mentioned for the first time in 1527. It was founded by Duke Heinrich d. J. von Braunschweig-Lüneburg and was named after his wife. The Duke and his son Julius were responsible for the renewed upswing in mining and metallurgy from 1520 and for the freedom of the mountains . At the Frau-Marien-Hütte, silver and lead were produced from silver-containing lead ores based on Rammelsberg ores. The silver was used directly as currency in coins, the value corresponded to the coin weight. Lead was handcrafted into sheet metal and pipes, the metallic lead (lead oxide), a residue of silver production, was sold to glassworks. From the 17th century, copper was also extracted in parallel. After the Braunschweig-Wolfenbüttel line died out, the manorial hut fell to a Guelf community of heirs, the Communion . The division 3/7 to 4/7 remained important until the complete takeover by Preussag in 1967.
Early modern mining of silver from Rammelsberg ores until 1850
The Rammelsberg ores were extremely finely fused together. A treatment was until the early 20th century hardly possible. It was limited to the pre-sorting of certain types of ore in the mine (e.g. galena , gray ore , Kniest ) and crushing by stamp mills. As a result, smelting in the Okerhütte was extraordinarily complicated and its essential process hardly changed until the middle of the 19th century.
Until the age of the railway, ore was transported from the Rammelsberg mines to the lead-copper smelter in Oker with two-wheeled horse carts, the cave wagons . The ore was piled up in layers with wood to form several 10 m long and 2-3 m high barns in the open air. After lighting, the heap roasting fires burned down for several months, thereby removing the sulfur from the sulphidic ores.
The roasting gases escaping caused considerable environmental damage. At the end of the roasting process , the caked heap was removed with shovels, pickaxes and heavy hand hammers. The subsequent melting took place in so-called Krummöfen , simple shaft furnaces of 1.5 m height with only one wind form (air nozzle). With a constant supply of air, the metal oxides reacted with the charcoal to form metallic lead containing silver and separated from the gangue .
The lead and slag poured through a tap opening into a depression in the hallway of the hut. The solidified slag was lifted off with forks. Copper ores were similarly smelted into black copper . To recover the silver contained therein, it was removed from the copper with lead in a two-stage process is extracted . The silver-containing lead from the lead smelting process and copper desilvering was selectively oxidized in the blowing furnace so that the metallic silver ( eye silver ) remained. For this purpose, hot gases generated in a combustion chamber were passed over the melt. The burned lead, the smoothness, was permanently pulled off the hallway with the smoothing hook. When all the lead was oxidized, the surface of the melt pool reflected for a brief moment, that was the silver look . Then the process was stopped so as not to burn the valuable silver. The silver was left to solidify in the stove and the block ( Regulus ) was handed over to the mint in Zellerfeld . There, the gold was also separated using nitric acid , a method that was secret at the time .
Obtaining the considerable zinc content was not possible before the industrial age. The zinc got into the slag and significantly disrupted the smelting process. It was only later that it was possible to manufacture brass from zinc-containing furnace batches ( furnace gall = zinc carbonate ) and copper in a sister smelter . In the 16th to 18th In the 19th century, around 30–40 tons of copper were produced each year. Figures for lead and silver are not available for this period. In the 19th century, copper production rose from an initial 67 t (1815) to 211 t in 1850, and lead from 41 t (1818) to 65 t in 1850. There were 1,818,529 kg of silver and 1,850,908 kg Silver creates.
Extraction of lead, copper and sulfuric acid as well as precious metals in the industrial age 1850–1945
At the end of the 19th century, significant procedural improvements were developed, which led to the expansion of the Frau-Marien-Hütte into an efficient and modern steelworks. Steam engines and electricity were available as additional drive energy . From then on, roasting (desulphurisation) took place in roasting shaft ovens in Kilns . These were also no longer in the open and the roasting gases were recorded in order to obtain salable sulfuric acid using the lead chamber process . In the 20th century, roasting ovens based on the Dwight-Lloyd process were used, which enabled continuous and mechanized roasting. The shaft furnaces for reducing smelting became ever larger in terms of cross-section, height and thus throughput. The separation of metal and slag now took place in the lower part of the furnace, in the crucible, through different densities . Lead or copper and slag were tapped through holes made at different heights. In order to simplify the extraction of precious metals from copper and to reduce losses, the copper extraction process was changed: a so-called copper stone (copper-iron sulfide) made from partially roasted ore was melted in the shaft furnace . The raw copper was created in the converter by blowing air into the melt. Raw copper was refined in the electrolysis process , i.e. H. freed from impurities. The residue ( anode sludge ) contained the precious metal contents.
In the lead refinery , the lead was cleaned in externally heated boiler stoves by adding certain reagents or by selective oxidation . The silver was also removed by stirring in zinc metal . The rich foam containing silver was freed from zinc by distillation in the Faber-du-Faur oven . Since the First World War , the hut was connected to the mine by a narrow-gauge steam train . From 1935 ore concentrates processed by the Rammelsberg project were available. The zinc was obtained in the new Harlingerode zinc works . The lead smelter's facilities were expanded to double the capacity and essential parts were rebuilt. The barite content of the gray ores could be extracted in a new hot spar plant. The owner was Unterharzer Berg- und Hüttenwerke GmbH , founded in 1941, and since 1923 Preussag 4/7 and Braunschweig GmbH 3/7 owned shares in the mine and the smelters as shareholders. A dark chapter in the history of the Oker lead-copper works is the employment of Eastern European forced laborers during World War II .
Post-war period and decline of the Oker lead-copper smelter 1945–1970
After the Second World War, the reconstruction and the increased consumption of raw materials led to a further expansion and modernization of the lead copper smelter until the end of the 1950s. Work on the Rammelsberg project that was not completed due to the war was ended. For example, a slag blowing plant to recover previously lost zinc and a new lead refinery were built. Internal transports were carried out with forklifts and shovel loaders . The transport route to Rammelsberg was expanded for standard gauge diesel locomotives. Material cycles between the Harz huts were closed, so from 1960 onwards no more slag was piled up. It could be completely recycled in the zinc oxide smelter . The workforce reached almost 1,000 men. From the 1960s onwards, world market prices for metals fell inexorably. Therefore the production of copper and silver was given up first. Kupferstein and Reichschaum were sold directly to other smelters. In 1967, all shares in the Unterharzer smelters were completely taken over by Preussag AG. Rationalization measures began, which meant the loss of independence for the lead smelter and the conversion of the raw material base. The ore smelting ended on June 30, 1970 when the roasting and shaft furnace facilities were closed. The barite plant was in operation until the end of the Rammelsberg mining on June 30, 1988. Up until 2001, commercial lead was still produced in the refinery on the basis of accumulator scrap and lead-containing waste. The lead came from the rotary kilns of the former zinc oxide smelter in Oker until 1993 , after which it was produced exclusively in a short drum furnace in the vicinity of the refinery.
Smelting works building from 1845 on the mountain
Heavy spar plant building, historically roasting hut, condition before demolition in 2002
Former silver mining furnace building
Interior of the former shaft furnace, as it was in 2004
Current condition (2009)
The buildings no longer needed were gradually demolished and converted into green spaces in the years after 1970. A larger part of the buildings on the mountain have been preserved , such as the smelter operated from 1845 to 1935 , the green furnace house , the airborne dust leaching plant (formerly the Kiln building), the hydropower plant and the precious metal works (today the training workshop of a non-profit educational institution). In particular, the smelter building with its neoclassical style is a technical monument . In the lower part of the factory there is the laboratory , administration , main workshop , the more modern smelter building from 1935, the lead refinery, coal grinding plant , locomotive shed and the masticatory building that was last used . The complex around the smelter is threatened with demolition; this part of the factory premises is earmarked for sale and other development.
See also
- Zinkhütte Harlingerode , Zinkoxydhütte Oker , Herzog-Julius Hut
- List of steelworks in Germany
- Lead smelter , metallurgy
- Harz-Metall GmbH , Preussag AG
literature
- Jürgen Feiser: Chronicle of the Okerhütte 1527 - 1970 . Manuscript, Goslar 1971 (unpublished).
- Kunibert Hanusch: The lower Harz metal works in the 19th and 20th centuries - Chronicle of a change . 1st edition. World Heritage Rammelsberg, Goslar 2005, ISBN 3-9809704-1-8 .
- Lothar Klappauf et al .: On the trail of an early industrial landscape . Lower Saxony State Office for Monument Preservation, Hameln 2000.
- Wolfgang Mehner: History of lead and copper production on the lower Harz . Harz-Metall GmbH, Goslar 1993.
- Franz Pawlek: Metallurgy . Walter de Gruyter & Co., Berlin 1982, ISBN 3-11-007458-3 .
- Franz Rosenhainer: The history of the Lower Harz metallurgy from its beginnings to the establishment of Communion in 1635 . Contributions to the history of the city of Goslar, Goslar 1968.
- unknown: Zinc "Harz" - zinc production at the Harlingerode zinc works . Unterharzer Berg- und Hüttenwerke, Goslar 1956.
Individual evidence
- ↑ Kunibert Hanusch: The Lower Harz Metalworks in the 19th and 20th Century - Chronicle of Change . 1st edition. World Heritage Rammelsberg, Goslar 2005, ISBN 3-9809704-1-8 .
- ↑ a b Franz Rosenhainer: The history of the Lower Harz metallurgy from its beginnings to the establishment of Communion in 1635 . Contributions to the history of the city of Goslar, Goslar 1968.
- ↑ a b Jürgen Feiser: Chronicle of the Okerhütte 1527–1970 . Manuscript, Goslar 1971 (unpublished).
Web links
Coordinates: 51 ° 54 ′ 11 ″ N , 10 ° 29 ′ 12 ″ E