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Extracting zinc through steel mill dust recycling at Rönnskär

Extracting zinc from steel mill dust is just one way Boliden’s Rönnskär smelter in northern Sweden contributes to a circular economy.

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Boliden’s innovative zinc extraction solution
Boliden is currently the only company in the copper/zinc industry that uses a fuming process to extract zinc from steel mill dust. Rönnskär uses the process to annually produce approximately 35,000 tonnes of zinc clinker that is virtually free from halogens. Approximately 10-15% of the produced clinker originates from steel mill dust.

“Our process at Rönnskär involves melting the dust to form a slag and the removal of halogens in a clinker furnace to produce clinker,” explains Anders Öhrvall, Head of Strategy & Planning at Rönnskär. “Our product is virtually halogen free, which allows more of the zinc to be extracted.”

The clinker is sent to either Boliden’s Odda smelter in Norway or Kokkola smelter in Finland to be refined into pure zinc.

A circular economy pioneer
Boliden Rönnskär has been processing steel mill dust since the 1980s – long before the term circular economy was coined.

“At Boliden, we source materials that suit and benefit our processes, while dealing with them responsibly and according to all relevant environmental standards,” says Öhrvall. “Some such materials promote the circular economy, and we are happy to contribute – steel mill dust is one such material.”

“Our work to recycle dust from the steel industry has been driven by both financial and environmental benefit over the years,” says Öhrvall. “We work with three dust suppliers in Sweden and constantly refine and improve our processes. We are even looking into the potential to further increase our capacity to process zinc bearing materials.”

Optimal and safe transport
“Sourcing from Swedish suppliers enables the dust to be transported efficiently by train in custom-made containers,” says Öhrvall. “This ensures that the loading, transport and unloading of the dust has minimal environmental impact, with no dust escaping into the environment.”

The train between Helsingborg and Skelleftehamn (Rönnskär) runs seven days a week and ensures low-cost transportation.

Rönnskär – at the heart of the circular economy
Extracting zinc from steel mill dust and finding uses for the resulting slag is only part of the story how Rönnskär contributes to a circular economy. The smelter finds uses for a variety of other societal end-of-life materials, which also helps avoid the need to source virgin materials.

“At Rönnskär, we are at the heart of the circular economy by recycling various metals from secondary materials coming from various industries,” says Öhrvall. “But we are perhaps best known for being a world leader in recycling electronics, thanks to our capacity of 120,000 tonnes each year.”

About steel mill dust

Steel mill dust containing zinc is formed when galvanized scrap iron is recycled in steel mills. As the dust easily leaches, it should not be landfilled and is typically processed in waelz kiln furnaces around the world. However, waelz processing does not remove halogens, such as fluorine, which can limit how much zinc can be extracted.

At Boliden’s Rönnskär smelter the fuming technology is used for recycling steel mill dust – to extract a zinc product containing almost no halogens.

Contact

Boliden Head Office

Boliden Group
Klarabergsviadukten 90
P.O. Box 44, SE-101 20 Stockholm
Tel: + 46 8 610 15 00
Fax: + 46 8 654 80 90