Project CircSmeltSteel

The European steel industry is undergoing a transition from the CO₂-intensive blast furnace–basic oxygen furnace route (BF-BOF) to electrically based steel production. This decarbonization effort is driven by the EU Green Deal, the Clean Industrial Deal, and increasing CO₂ certificate costs. However, this transformation creates a critical gap. Iron-rich by-products that are currently recycled internally via sinter plants and blast furnaces will require alternative utilization pathways once sinter plants are phased out.

CircSmeltSteel directly addresses this challenge. The project develops, validates, and scales two low-CO₂ electric melting routes – the Electric Smelting Furnace (ESF, also referred to as Smelter, Submerged Arc Furnace, or Open Slag Bath Furnace) and the Electric Arc Furnace (EAF). Both technologies can process a broad portfolio of metallurgical by-products as secondary raw materials. Therefore, the CircSmeltSteel project is investigating blast furnace dust, BOF slag, EAF dust, iron-rich process sludge from an in-house steel mill wastewater treatment plant, and the iron-rich fraction of pig iron desulfurization slag, which has an average iron content of approximately 40 wt-%. Target by-product shares amount to up to 50% in the ESF and 20% in the EAF. This approach enables a significant CO₂ reduction compared to the conventional BF-BOF route, which will be demonstrated within the project.

A distinguishing feature of CircSmeltSteel is its holistic consideration of the entire process chain. The project covers by-product characterization and processing (e.g., agglomeration of dusts), melting trials, secondary metallurgy, casting, hot and cold rolling, and finally the evaluation of end-product properties. The increased use of residues as secondary materials inevitably raises the input of so-called tramp elements such as nitrogen, phosphorus, sulfur, copper, molybdenum, and tin. CircSmeltSteel systematically investigates how these elements affect the formation of non-metallic inclusions, surface quality, microstructure, and mechanical properties, and develops process strategies to minimize their impact.

The combination of physics-based models and reduced-order models (ROMs) will be utilized for Level-2 process automation in the two application cases of hot rolling and annealing after cold rolling. All experimental results and models will be integrated into a common digital platform based on FAIR data principles, which will remain accessible to the steel research community beyond the project duration. Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) will quantify the environmental and economic benefits, with initial estimates indicating potential product cost reductions of up to 15%.