RESycling – Climate-friendly solutions for processing and recycling hot metal desulfurization slag

An innovative processing strategy for hot metal desulfurization slag is designed to sustainably promote resource efficiency and climate protection in three industrial sectors by harnessing previously unused raw materials.

The focus of the "RESycling" project is on the processing of hot metal desulfurization slag from iron and steel production. The processing results in valuable raw materials. These previously unused raw material potentials are to be made available and usable by means of a novel and innovative processing strategy.
The recovered valuable materials are to replace primary materials in three relevant industrial sectors - the steel, cement and fertilizer industries - and also reduce climate-relevant process emissions. The RESycling project thus makes an important contribution to climate protection and increased resource efficiency in the industrial sectors addressed.

During steel production in integrated steel mills, the desulfurization of molten pig iron produces pig iron desulfurization slag. Every year, around 450,000 tons of hot metal desulfurization slag are made available in Germany in this way, but much of it is stored in increasingly scarce landfills and remains unused. By completely processing and using the previously unused hot metal desulfurization slag components, such as iron, sulfur and mineral waste, and by optimizing the process steps, climate-relevant process emissions can be reduced by substitution and closing the loop.

Practical solution for the treatment and recyclability of hot metal desulfurization slag

Specifically, the treatment of hot metal desulfurization slag with high-voltage pulses in the nanosecond range is intended to initially separate iron contained in the slag and thus make it usable again as a high-quality raw material for the steel industry. In a subsequent wet chemical process, raw materials for the fertilizer and cement industries are to be selectively produced. The process will initially be optimized in an application-oriented manner and evaluated later in the course of the project in a pilot plant, i.e. a test facility for the development of production plants. In parallel, an ecological and economic analysis will be carried out for further process optimization.

In addition, the effects of substituting primary materials and the savings in climate-relevant process emissions are quantified in order to derive ecological potentials. Based on the comparison of running costs and revenues, an economic feasibility study will be prepared for the novel reprocessing strategy.

The REScycling project coordinated by the Fraunhofer Institute for Building Physics (IBP) is being funded with approximately 2 million euros as part of the BMBF funding measure "Avoidance of climate-relevant process emissions in industry (KlimPRo-Industrie)".


Project coordination

Dr. Sebastian Dittrich
Fraunhofer Institute for Building Physics IBP
Fraunhoferstrasse 10
83626 Valley

Phone: +49 8024 643209

REScycling Website

Project partners

  • Fraunhofer Center for Chemical-Biotechnological Processes CBP
  • Weihenstephan-Triesdorf University of Applied Sciences
  • Südbayerisches Portland-Zementwerk Gebr. Wiesböck & Co. GmbH
  • thyssenkrupp MillServices & Systems GmbH

Last updated on