AFRY and Boliden in Finland turns sulphur concentrate into value
Driving circular economy with sulphur concentrate processing
Boliden Kokkola, Finland, operates a world-class zinc production facility, delivering high-quality zinc through fully integrated operations. Together with AFRY, they are developing a concept for treating sulphur concentrate to improve material sustainability at the site.
Project highlights
Project
Feasibility study of Sulphur concentrate project
Client
Boliden Kokkola Oy
Start—end dates
April 2024-November 2025
Project location
Kokkola, Finland
AFRY scope of services
Multidisciplinary feasibility study
Historically, sulphur-rich concentrate from the direct leaching process has been stored in the plant’s backyard and directed to a tailings pond in the landfill area. The facility includes two roasters and a direct leaching process, with residues from these operations combined, stabilized, and landfilled as a single waste stream.
Boliden has a strong tradition of creating value from waste and side streams. In line with its circular economy strategy, Boliden has been working closely with AFRY and technology suppliers to develop a concept for treating sulphur concentrate. Over the past five years, this concept has evolved into a detailed and robust process. Treating the sulphur concentrate enables CO₂-free electricity generation, sulphuric acid production, and recovery of valuable metals — significantly improving material sustainability at the site.
Unlocking energy and metals through pyrometallurgy
The goal is to recover energy and metal content from sulphur concentrate using pyrometallurgical methods, such as:
- Traditional roasting with a fluid bed roaster
- Indirectly heated electric rotary kiln
All outputs are intended to be utilized either as final products or as raw materials for other processes. Various options have been evaluated based on mass and energy balances, lab and pilot tests, and CAPEX/OPEX assessments. The treatment routes have now been narrowed down to two main options: Fluid bed roasting and electric rotary kiln with indirect heating.
Long term sustainable improvement of material utilization at Boliden Kokkola site is one of the key elements in our way of operating nowadays. Sulphur concentrate project has been a good cooperation effort from the initial concept development phase through to the start of detailed engineering.
– Markus Pohjonen, Project manager at Boliden.
AFRY’s role in advancing sustainable zinc production
I am thrilled to be involved with this novel technology and long-term relationship with the world-class Boliden. The development of this process concept has been on the AFRY–Boliden shared table for five years and is now moved into a feasibility study, with the next steps focused on detailed engineering.
– Virpi Leinonen, Technology Manager at AFRY.
The plant’s capacity is designed for three raw material bases across different phases:
- 110 000 tpa of sulphur concentrate
- 300 000 tpa of combined residue
- 250 000 tpa of jarosite in the final phase
Next steps include an investment decision and possibly additional pilot-scale tests for final verification. While all process units are based on proven technologies, introducing sulphur concentrate or combined residue into the system represents a novel application.
Strategic importance for circular economy
The innovation centers on low-CO₂ treatment of sulphur concentrate and zinc production residues, turning waste into valuable resources and setting a new benchmark for sustainable zinc production.
