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More from the same amount

Extracting more from the material processed by the smelters not only increases profitability – it also guarantees environmental benefits.

Smelters are facing a new challenge. An increasing amount of the incoming raw material we use contains substances that interfere with the process used by the smelters to produce their principal metals. These substances have until now been regarded as impurities, but are in fact often valuable materials in their own right. With the aid of new technology and improved processes, these materials could also be utilised, providing new and profitable products.

Development engineer Risto Alapiha at Boliden Kokkola inspects the new process for extracting silver from zinc concentrate.

Extracting more metals from the same amount of raw material is not just financially profitable; it also benefits the environment. Once the smelters have processed the raw material and extracted the metal that will be turned into a saleable product, any residual products and waste must be dealt with in a sustainable way. Extracting more metal from the same amount of material may therefore maximise the number of valuable products, while also minimising the amount of waste produced.

There is a lot to be gained here, and Boliden constantly works to develop technologies and processes that increase the ability of smelters to handle complex materials.

One example of process development along these lines can be found at Boliden Kokkola in Finland. Here, the main products are zinc and zinc alloys, but in 2014 the smelter also began extracting silver from the zinc concentrate.

The new process has been integrated into the existing production flow, with the silver content being extracted using a chemical process called flotation, and filtration.

Someone who works on the silver extraction process is development engineer Risto Alapiha. “Flotation technology is new to us and so learning how it works and how best to manage it has been extremely interesting. The process also brings new demands to my role, and I have to draw on my specialist knowledge within the field of chemistry,” he explains.

The end-product is a silver concentrate, which is sold to external customers or turned into pure silver at Boliden’s own smelters. “Silver concentrate is set to become one of Boliden Kokkola’s most valuable byproducts. The new process is very important for us because it increases profitability and means that we can better utilise the raw material,” says Jarmo Herronen, General Manager at Boliden Kokkola.

Text: Maarit Frilund, Photo: Päivi Karjalainen

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