Energieeffizientes Recycling von Stahlwerkstäuben durch Abwärmenutzung

To reduce the CO₂ emissions of the iron and steel sector, the development and integration of emission-reducing processes are of central importance. A key technology in this context is the electric arc furnace (EAF), whose use can reduce specific CO₂ emissions from about 2.32 t CO₂ per tonne of steel to around 0.7 t CO₂ per tonne of steel (Blanco Perez et al., 2025)However, with the increasing use of this technology, the amount of process residues generated is also rising. A major component of these residues is electric arc furnace dust (EAFD), which is characterized by a high content of zinc and iron compounds. The recovery of these metals and their use as secondary raw materials is fundamentally established. The most widely used process worldwide is the Waelz kiln process; however, it has the disad-vantage that landfill-bound residues are also produced. The Two-Step Dust Recycling pro-cess (2sDR) represents an alternative recycling route that pursues a zero-waste strategy and enables higher product purities. Since this process has so far only been at laboratory scale, the aim of the present work is to scale up the 2sDR process to an industrially relevant throughput of 150 t/h of agglomerated EAFD pellets. For this purpose, detailed mass and en-ergy balances were created for the individual process steps. The analysis of these balances showed considerable potential for the utilization of the waste heat generated. Based on this, a total of thirteen different waste heat utilization scenarios were developed and investigated us-ing the simulation software EBSILON®Professional (Iqony GmbH, 2025). In addition, an eco-nomic evaluation of the scenarios was carried out, consisting of an estimation of investment costs (CAPEX) as well as ongoing operating costs and revenues (OPEX). To account for market uncertainties, three different price scenarios were defined for each scenario, reflect-ing fluctuating energy and revenue prices. The economic evaluation was carried out using four key performance indicators: levelized cost of energy (LCOE), specific benefit, payback period, and return on investment (ROI). The results show that the economically most attrac-tive scenario is the use of the waste heat from the reduction furnace for air preheating of the upstream process steps. Furthermore, it was found that hydrogen-based process variants are not economical under current market conditions, which is attributable to a combination of high hydrogen prices and comparatively low CO₂ prices. Finally, a break-even analysis for hydro-gen-based scenarios was conducted by comparing projected developments in hydrogen and CO₂ prices with a methane-based reference scenario. The results indicate that an economi-cally viable transition to hydrogen-based concepts in the worst-case hydrogen price scenario is likely to be expected at the earliest from the year 2041, assuming declining hydrogen prices and further rising CO₂ costs.