Slags from decarbonised steel production suitable for cement

New slags generated in the smelter during the production of decarbonised steel taking the direct reduction route are suitable as latent hydraulic binders in cement production – this is the result of the “SAVE CO2” research project.

The investigations carried out at laboratory and pilot-plant scale show that, with suitable process control and targeted chemical adjustments, the electric pig iron slag produced on the basis of sponge iron (DRI) could replace conventional granulated blast furnace slag. For steel and cement production – if supplied with renewable energy – this would mean a total savings potential of around two thirds of today’s CO2 emissions in the future.
Blast furnace slag has been used as a high-quality, resource-conserving and climate-friendly secondary raw material in the cement industry for decades. However, neither empirical data nor industrial applications existed for slags from DRI-based processes. Accordingly, a fundamental understanding of the chemical-mineralogical composition, glass formation, environmental impact and hydraulic activity of these new types of slag was lacking. The research project therefore focused on investigating the dependence of slag properties on variable raw materials and process parameters as well as evaluating the technical and economic prerequisites for full utilisation as a main component of cement.
David Algermissen, Head of the Secondary Raw Materials/Slag Metallurgy Department at the FEhS Institute, which coordinated the project, says, “The work conducted with this great consortium was very successful. We were able to establish basic knowledge about electric pig iron slag and to run pilot projects around granulated blast furnace slag production 2.0 at industrial scale and testing in cement and concrete. The next steps are normative and legal frameworks so that the material can be brought to market quickly once slag is generated at thyssenkrupp.”
The “SAVE CO2” research project, launched in 2021 by thyssenkrupp Steel, Heidelberg Materials, the Department for Technologies of Metals at the University of Duisburg-Essen, Fraunhofer Umsicht and the FEhS Institute, was funded by the German Federal Ministry of Research, Technology and Space and the European Union/NextGenerationEU as part of the KlimPro-Industrie funding programme; the project was managed by project management agency DLR Projektträger.
Source: FEhS