CO2 emissions in steel production

How can the steel industry contribute to reducing CO₂ emissions? More precisely: How can CO₂ emissions be reduced by up to 95 percent as efficiently as possible in the production of crude steel? Answers to these questions are provided by the MACOR project, funded by the German Federal Ministry of Education and Research (BMBF) and undertaken by the Fraunhofer Institutes IKTS, ISI and UMSICHT as well as Salzgitter AG. Fraunhofer IKTS in Dresden contributed its expertise in process simulation and high-temperature electrolysis and coordinated the project.

By 2050, Salzgitter AG plans to have completed a conversion to virtually CO₂-free crude steel production within the framework of the SALCOS^® project (Salzgitter Low CO₂ Steelmaking). Until now, the iron oxide in the ore has been reduced with coal, which is associated with high CO₂ emissions - steel production accounts for around seven percent of global CO₂ emissions. If instead green hydrogen, produced by electrolysis using electricity from renewable energies, is used in place of coal in a so-called direct reduction process, up to 95 percent of CO₂ can be saved on the way to crude steel production. Of course, this cannot be achieved overnight, as the conversion is not only associated with high investment costs but is also technically demanding.

Feasibility study MACOR

But how do you assess the transition of steel production to a more climate-friendly process? What exactly does it mean in concrete terms for the integrated steel mill of Salzgitter Flachstahl GmbH? How much renewable energy is required, for example, to save one ton of CO₂? These and other questions were clarified by the "Feasibility study on the reduction of CO₂ emissions in the steel mill using renewable energies", MACOR for short. The BMBF-sponsored study was carried out by the three Fraunhofer Institutes IKTS, ISI and UMSICHT, as well as the Salzgitter subsidiaries Salzgitter Flachstahl and Salzgitter Mannesmann Forschung. Fraunhofer IKTS focused primarily on process simulation, while Fraunhofer ISI analysed the economic efficiency of several process variants. The staff of Fraunhofer UMSICHT examined the processes involved in direct reduction as well as the properties of the reduced iron. For the Salzgitter subsidiaries, the emphasis was on the preparation of an implementation plan for SALCOS^®, technical analyses of the direct-reduced iron and the ecological balance.

An important parameter is the energy required per ton of reduced CO₂. This is because energy from renewable sources is limited - their share of the total energy market in Germany is currently a mere 15 percent. The question therefore arises: Where does their use bring the greatest benefit? The result of the study: avoiding CO₂ in crude steel production is four times more efficient than capturing the CO₂ and using it for other purposes, such as the production of chemicals. Hydrogen-based steel production offers the greatest CO₂ savings potential of almost 100 percent compared to conventional processes, such as hydrogen injection in the blast furnace. Simulated calculations by IKTS also show that high-temperature electrolysis is a very efficient and economical process for supplying the hydrogen required for direct reduction in the integrated steel mill. In the follow-up project "Accompanying Research Hydrogen in Steel Production", in short BeWiSe – also funded by the BMBF – the established consortium now dedicates itself to further research to optimize the hydrogen-based steel production route investigated in MACOR.