New use for roasted by-product
In the production of zinc, a sulphur-rich by-product is formed which is normally disposed of. Reworking the material into a usable product offers economic and environmental gains for industry and society.
Boliden Kokkola is Europe's second largest zinc producer. The company produces 315,000 tonnes annually, and around half of all zinc produced is used as an anti-corrosion agent in steel.
100 000 tonnes of by-product
The production of zinc usually involves five stages: roasting, leaching, purification, electrolysis, and finished zinc is finally cast into ingots. During production, approximately 100,000 tonnes of a sulphur-rich by-product is formed which is not currently used.
Boliden Kokkola conducted pilot testing in Swerea's fluidised bed plant, with a view to utilising the by-product. The material is granulated (atomised) and roasted in the plant, which creates a product containing high levels of precious metals such as zinc, lead, copper and silver – materials which can be then processed further.
A win-win for industry and environment
Using the by-product in this way is environmentally friendly and increases the recovery rate of metals. It will ultimately benefit both industry and the environment.
"For us it is very important to be able to utilise residual materials and it's something we work diligently with. The collaboration between Boliden Kokkola and Swerea succeeded in resolving this issue," says Jens Nyberg, Manager R&D Strategic Projects at Boliden.