Higher value and quality of blast furnace sludge with Linde's OXYFINES technology
20 October, 2020
Reduced waste and optimized utilization of residual materials mean positive economic and environmental effects, in line with agendas such as the UN's sustainable development goals and the concept of circular economy. The steel industry is working constantly to increase the degree of utilization of residual materials; but some of these by-products, such as blast furnace sludge, which despite high iron and carbon content, have not yet been fully utilized.
In the Optifines research project we have built a pilot plant and successful pilot trials have been conducted with Linde's OXYFINES technology. The aim is to develop and demonstrate a concept for 100-percent recovery and use of blast furnace sludge. This has included verification and optimization of the OXYFINES technology for separating zinc from blast furnace sludge on-site at the steelmill to make an internally recyclable zinc-free product and a zinc-rich dust that can be used as a raw material in external zinc production.
“The project has successfully shown how new engineering solutions can generate higher quality and value in residual materials and thereby contribute to increased utilization and improved resource efficiency,” explains Katarina Lundkvist, senior research engineer at metals research institute Swerim and project manager for the Optifines project.
Results from the project show that the OXYFINES technology is very stable, easily controlled and flexible at different moisture contents. Zinc separation of up to 97 percent was demonstrated in the conducted pilot trials, whereby a refined, practically zinc-free and iron-rich sinter product and a dry zinc-bearing dust were produced. However, the desired zinc concentration in generated dust was not obtained in these pilot trials, but may be achievable if adjustments to the process are made. In addition, in the project, a hypothetical OXYFINES concept was assessed in full-scale to determine the effects of implementation of the concept in steel production with respect to process efficiency, economy, energy and CO2 emissions. Results show that the OXYFINES concept has positive sustainability effects, mainly in terms of material efficiency and a reduced amount of waste. Use of generated OXYFINES products also means reduced need for virgin raw materials. An industrial implementation will contribute to sustainable energy and material supply when the OXYFINES concept is developed to enable optimal recovery and upgrading of valuable components in residual material.
The two-year project has had a budget of just over 15 million kronor. Swerim has managed the project and industry partners have included Linde Gas, SSAB Europe and SSAB Merox in Luleå and Boliden Mineral. Funding has been provided by the Swedish Energy Agency programme RE:Source.
/Photo/ A gathering in Swerim's experimental hall during trials to optimize Linde's OXYFINES technology. From left: Katarina Lundkvist, Swerim, Fredrik Nyman, Linde and Daniel Söderström from SSAB Europe. Photo: André Pettersson, Sveriges Radio.