Zinc oxide smelter Oker

Northwest view of Melting Cyclone, 2018

View of some of the company buildings of the zinc oxide smelter 2004

The Oker zinc oxide smelter was an industrial company in what is now the Oker district of the city of Goslar in the Harz region of Lower Saxony . There, zinc oxide was produced from the slag and residues from the surrounding metalworks . The zinc oxide sold served both as a raw material for paints and chemical products and for the extraction of metallic zinc .

With the loss of independence and the merging with the lead works Oker and zinc works Harlingerode to form the Harz ironworks in 1968, the name Zinkoxydhütte Oker was lost. The Harz iron and steel works were converted into the Harz-Metall GmbH , which still exists today .

History and technology

initial situation

Use and production of the zinc oxide smelter Oker 1909–1985

The ores from the Rammelsberg contained lead , silver and copper as well as between 8 and 24% zinc. The minerals were very finely grown together in the ore and could not be separated from one another by processing methods until the 1930s . With the boom in mining in the 15th century, steelworks were built on the northern edge of the Harz to extract the metals that were usable at the time, especially silver. The zinc content was neither recoverable nor of economic interest and was therefore slagged. Over the centuries, the huts in Oker , the Herzog-Julius-Hütte and the Frau-Sophien-Hütte in Langelsheim developed into the most important locations. Large amounts of zinc-containing slag with an average of 20% zinc accumulated in their surroundings .

With the beginning of the industrial production and use of zinc at the turn of the 19th and 20th centuries, the value of these artificial zinc deposits was recognized .

The production of colored zinc oxide from lead slag 1909 to 1945

Depiction of a Pape or slot oven (1907)

The so-called fire dump - residues of the Pape plant 1909 to 1945

The Hamburg zinc smelter entrepreneur Hermann Pape , together with other engineers, had developed a process for the enrichment of zinc from low-zinc ores and secondary raw materials . In order to be able to better supply his company in Billwerder with zinc raw materials, he joined forces with the Communion Hüttenamt (jointly Prussian and Braunschweigische Hüttenverwaltung) to build a plant. Construction work on the Oker zinc oxide plant (later Plant I) began in 1907 on a plot of land between the road from Oker to Harlingerode and the Röseckenbach in the vicinity of the Oker lead smelter. After initial difficulties, 45,000 tons of old and fresh slag were determined by the so-called after the official opening on April 1, 1909 year Pape- or slot furnace process processed. This resulted in a mixed oxide with around 71% zinc and a low-zinc slag with around 4% zinc. In addition, steam for energy generation could be obtained through downstream boiler systems.

In 1911 there was a fire in the residue dump for the first time due to spontaneous combustion. Further fires occurred more frequently in the period that followed, polluting the environment and local residents. The cause was the high residual sulfur content .

After the First World War , the company became the sole property of Unterharzer Berg- und Hüttenwerke GmbH . By optimizing the composition of the Möller , a quarter of the amount of zinc oxide produced could be used as a starting material for the production of zinc paint. It was marketed by Zinkfarben AG, founded in 1923 in Oker.

In order to make the previously lost precious metal content of the lead smelter slag recoverable, another plant (= Plant II ) was built in 1930 . A further developed type of furnace, the Wenzel blow shaft furnace, was used there. In this process, a crucible was used instead of a grate and side tuyeres for the combustion air. This created a completely melted slag and it was also possible to separate a precious metal-containing copper-iron-stone ( metal sulfide mixture ). The stone phase was sold to the Norddeutsche Affinerie . Steam was also obtained from this plant. The higher charging column in the oven resulted in an unsaleable color quality. For this reason, from then on, colored zinc oxide was primarily produced from low-lead raw materials in Plant I and mixed oxide for the extraction of metallic zinc from copper-rich slag in Plant II . From 1936 the mixed oxide was also processed in the newly built, own zinc smelter in Harlingerode in the immediate vicinity. From 1937 on, the sales group for Harzer Zinkoxide (VHZ) in Osterwieck took care of the sale of the color pigments .

This first operating period ended with the collapse at the end of the Second World War .

The zinc oxide smelter as a recycling company in the material cycle of the Unterharzer Hüttenwerke 1945 to 1988

Material cycles of the Unterharzer smelters with the zinc oxide smelter as of the 1960s

Operating building of the melting cyclone plant, as it was in 1989

Operations in the zinc oxide smelter could be resumed very early in May 1945. However, the situation had changed significantly in the post-war years: On the one hand, the demand for lead-containing zinc oxide was due to other competing products, e.g. B. Lithopone decreased. On the other hand, the New Jersey retorts of the zinc smelter produced steadily increasing amounts of carbon , zinc and lead-containing clearing ash . At the same time, significantly less fresh lead smelter slag was created because the Herzog-Julius-Hütte and Frau-Sophien-Hütte were shut down in 1940/1941. Therefore, a new type of furnace was 1946 designed initially Bastard oven called that combined the advantages of both the old method. By the end of the 1940s, both plants were converted to the so-called half - shaft furnace , also known as the Hellwig process after its inventor . Due to the constant expansion of the Harlingerode zinc smelter, the use of clearing ash rose sharply in the 1950s to 1960s. Most of the mixed oxide obtained was returned to the zinc smelter. The proportion of lead in the mixed oxide was so high due to the large proportion of clearing flaps that the oxide produced had to be processed. It was initially discharged in a rotary kiln plant commissioned in 1953 in the clinker process (= volatilization of the lead content and recovery as filter dust ). In order to obtain a sellable colored oxide, a migrating east plant was built in 1959 using the Wetherill process for post-treatment.

In 1967 Preussag took over the Unterharzer Berg- und Hüttenwerke completely and on April 1, 1968 merged the Oker zinc oxide smelter with the Oker lead smelter and the Harlingerode zinc smelter to form the Harz smelting works . From then on, the zinc oxide smelter was only an operating department (= ZOH ) of the newly organized plant. In the meantime, white inks containing lead were no longer in demand, and titanium dioxide , an even “whiter” pigment, competed on the market. In addition, lead extraction from Rammelsberg ores was abandoned in 1970. Therefore, zinc white production was temporarily stopped in 1971, with the simultaneous shutdown of Plant I and the traveling grate plant.

Since 1974, lead-free zinc white has been produced by today's sister company Norzinco Harzer Zinkoxide GmbH in Harlingerode using a completely different process.

At a cost of around DM 37 million, a completely new process was built for the processing of the scraper, and the trial operation began on March 27, 1977. The smelting cyclone plant should replace all existing half- shaft furnaces in one unit and continue to make the waste heat usable for energy generation. However, it turned out that the technology was not mature. The company only ran by the hour with long repair and improvement stoppages. Nevertheless, the last old ovens in Plant II were switched off on November 16, 1977. When it turned out that economic operation was impossible, the melting cyclone was abandoned in 1985 and the project declared a failure. Since there was no longer a suitable process, 1.1 million tons of unprocessed clearing ash accumulated by the time the zinc smelter was closed in 1988.

Zinc oxides purchased from the mid-1970s to 1988 were clinkered in the rotary kiln in order to maintain the supply of the zinc smelter. Among them were zinc ashes containing chlorine from hot-dip galvanizing plants and the exhaust gases from the rotary kiln were cleaned in a dechlorination system. Furthermore, the released capacity was used to extract lead from battery scrap with the addition of soda . After the end of the official zinc smelting, only work lead was produced. This ended the zinc oxide smelter's second operating period.

The rolling operation since 1989

Exterior view of the rolling plant of Harz-Metall GmbH (formerly clinker plant)

The third operating period for processing zinc-containing residues is the operation of the rotary kiln using the rolling process . Originally, from 1989 to 2000, clearing ashes were used with other zinc carriers such as steel mill fly ash . This should ensure the continued existence of the plant for 30 years, since lead work had to be stopped for environmental reasons. The operation proved to be permanently uneconomical. The reasons were high costs for dismantling the caked-up heap and transporting the clearing ash. The zinc-lead mixed oxide with only about 40% zinc was difficult to settle. At the same time, the volume of steel mill fly ash that had to be paid for was comparatively low. After 2000, the operation was switched to the sole use of steel mill dust and similar foreign materials with petroleum coke and sand. A public discussion about dioxins and furans in the exhaust gases led to the construction of the so-called dioxin filter .

Since 2005, the Waelz furnace has been operated based on the SHDL process . By lime as a slag, a preparation of the burden and a modified technique of air supply, the throughput could be increased even further. The residues of the waelz process were used for a number of years to cover and secure the old slag heaps, including the paper slag from the fire heaps of Plant I.

Current condition (2009)

The site of the former Oker zinc oxide smelter extends east-northeast-west-southwest between the Oker- Vienenburg railway line and the road from Oker to Harlingerode. In the far north is the dump site with the slag residue and the so-called fire dump. Almost nothing has survived from the eastern area of the railway line with the former Plant I. At the western border to Plant II there are still some outbuildings, such as the Kaue and the former electrical workshop. The administration building, which today houses the management of Harz-Metall GmbH, already belongs to Plant II. In contrast to Plant I, this part of the plant has largely been preserved and continues to be used. The main production buildings are located on Landstrasse. In the north, the former mill and briquetting building with the clearing ash bunker serves as an operating building for battery scrap processing . This is followed from north to south by the rotary kiln system of the rolling plant with crane and bunker system and filter systems. This is followed by the former furnace house for the half-shaft furnaces, which today serves as a warehouse. To the west of it is the crane hall of the traveling grate system, today a high-rise bunker system for steel mill fly ash. The melting cyclone plant in the very south now houses the dry dust intake and pelletizing of the rolling plant. Different outbuildings are used for different tasks, e.g. B. the oxide storage shed for the wastewater treatment plant .

literature

Wolfgang Mehner: History of zinc metallurgy on the Harz: a chronicle of zinc production from 1900 to 1990 . 2nd Edition. Harz-Metall GmbH, Goslar 1995.
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 .

Individual evidence

↑ Unknown: 1000 years of Harz ores and metals . Preussag AG, Clausthal-Zellerfeld 1968.

Web links

51.904166666667 10.491666666667Coordinates: 51 ° 54 ′ 15 ″ N , 10 ° 29 ′ 30 ″ E

[1000_Jahre_Harzer_Erze-1] Unknown: 1000 years of Harz ores and metals . Preussag AG, Clausthal-Zellerfeld 1968.