Project SlagCEM - High quality cements and pig iron from steelmaking slags

12/01/2022

• Description
• Objectives
• Methods
• Partners

In Germany, more than 5 million tons of steelmaking slag are produced each year. This steelmaking slag is currently used mainly in road construction, earthworks and hydraulic engineering. The iron contained in the slag is lost in this application. The process used in SlagCEM enables the iron to be recovered. In addition, a material similar to Portland cement clinker is produced during the process, which can be used as a binder in the cement industry.

SlagCEM aims to recycle steelmaking slag as completely as possible. The iron is to be recovered and the mineral material is to be made usable as a hydraulic binder. The process thus contributes to saving primary raw materials and reducing greenhouse gas emissions in the cement industry.

The largely oxide-bound iron in the steelmaking slag is reduced to metallic iron in the molten slag at high temperatures. To make this process profitable on an industrial scale, it must be carried out directly on the liquid slag at ~1600 °C in the steel mill. For this purpose, the chemical composition of the slag has to be modified so that their melting temperature and viscosity are in a technically suitable range.

Project coordination
Bundesanstalt für Materialforschung und -prüfung (BAM)
Thermochemical Residues Treatment and Resource Recovery division

Partners
ArcelorMittal Eisenhüttenstadt
Technische Universität Berlin
Deutsches Zentrum für Luft- und Raumfahrt e.V.
FEhS - Institut für Baustoff-Forschung e.V.
thyssenkrupp Industrial Solutions
Öko-Institut e.V.
LTB Lasertechnik Berlin

Steelmaking slags - a by-product with potential

German crude steel production generates over 5 million tons of steelmaking slag per year. This by-product still contains a mass fraction of up to 30% iron oxide, which is lost for further use in the current common use of the slags in road construction.

The SlagCEM project is investigating the recovery of crude iron from steelmaking slags. By separating the iron from the slag, its chemical and mineralogical composition is closely matched to that of the Portland cement clinker. This makes it possible to produce a hydraulic binder for the cement industry in the same process.

Implementation of the high-temperature process

In a high-temperature process, the largely oxide-bound iron can be recovered by reducing it to metallic iron in the molten slag at ~1800 °C. These temperatures are uneconomical in a large-scale process and problematic with regard to the refractory material.

In SlagCEM, the process is to be adapted in such a way that large-scale implementation is feasible under economic conditions. To this end, the composition of the slag is to be modified in order to bring the viscosity into a technically suitable range and to enable iron recovery at lower temperatures. The goal is to perform the reduction on liquid steelmaking slags directly in the steel mill at ~1600 °C. At the same time, a mineral product with good cementitious properties is to be produced.

Project team consisting of research institutes, steel and cement industry

With expertise from research institutes, the steel and the cement industry, a technically, logistically and economically manageable process is to be developed that will generate marketable products. To this end, the Bundesanstalt für Materialforschung und -prüfung (BAM), the Technical University of Berlin (TUB), the German Aerospace Center (DLR) and the FEhS - Institut für Baustoff-Forschung are investigating the effects of a chemical modification on the melting behavior of steelmaking slags from ArcelorMittal Eisenhüttenstadt and on the cementitious properties of the binder produced. By means of online LIBS (Laser Induced Breakdown Spectroscopy) from LTB Lasertechnik Berlin, it will be possible to analyze occurring changes already during the experiments. The collaborating partners CEMEX Deutschland AG and Spenner GmbH & Co. KG evaluate the performance of the product as a binder.

Based on the project results, ArcelorMittal will plan a large-scale demonstrator with which the process can be tested and integrated in a steel mill. A final assessment of the ecological impact of the process, for both the steel and cement industries, will be made possible by a life cycle assessment (LCA) of the entire recycling process prepared by Öko-Institut e.V.

Project coordination

Bundesanstalt für Materialforschung und -prüfung (BAM)

Partners

Bundesanstalt für Materialforschung und -prüfung (BAM)
Thermochemical Residues Treatment and Resource Recovery division
ArcelorMittal Eisenhüttenstadt
TUB Technische Universität Berlin
DLR Deutsches Zentrum für Luft- und Raumfahrt e.V.
FEhS Institut für Baustoff-Forschung e.V.
thyssenkrupp Industrial Solutions
Öko-Institut e.V.
LTB Lasertechnik Berlin

Funding

The SlagCEM project is funded by the German Federal Ministry of Education and Research (BMBF) under the funding guideline „Resource-efficient circular economy - Building and mineral cycles (ReMin)“, which is part of the FONA framework program.