Presentation Information
[O8-4]Hydrogen plasma assisted recycling process of end-of-life Nd-Fe-B based permanent magnets
*Rafael Gitti Tortoretto Fim1, Nartai Chimed1, Tim Schwartz1, Ilya Radulov2, Oliver Diehl2, Jürgen Gassman2, Dierk Raabe1, Matic Jovičević-Klug1 (1. Max-Planck-Institute for Sustainable Materials (MPI SusMat) (Germany), 2. IWKS Fraunhofer Research Institution for Materials Recycling and Resources Strategies (Germany))
Keywords:
Recycling,Nd-Fe-B bulk waste,Permanent magnets recycling,Sustainability
Nd-Fe-B based permanent magnets are one of the key building blocks in the transition to more sustainable technologies, from green energy production and energy conversion to fossil-free mobility. The annual demand for Rare-Earth (RE)-based permanent magnets is expected to increase up to 4.5% until the end of this decade (2020 – 2030), for which 37.8% of the total REE demand is dedicated for permanent magnets manufacturing [1]. Major share of this demand is related to critical REEs, that have very low recyclability (1 – 2 wt.%) and high carbon footprint (up to 100s of kg CO2-eq/kg), such as neodymium (Nd), dysprosium (Dy) and terbium (Tb). Highly efficient recycling and a low environmental impact process are critical to the long-term availability and improved sustainability of the growing Nd-Fe-B based magnets market [2]. So far, there have been few Nd-Fe-B recycling strategies reported in the literature exploring the reuse of end-of-life (EoL) magnet waste for permanent magnet production. The so-called magnet-to-magnet approach focuses on the pulverization of the EoL magnets through the hydrogen decrepitation (HD) process, which allows the reintroduction of the base Nd-Fe-B material into the production chain. Although simplifying of the recycling loop can reduce the environmental impact of the magnet production chain by up to 96%. The increased amount of contamination by oxygen and other elements (e.g. carbon and nitrogen) is a limiting factor in obtaining high-performance sintered magnets through multiple reuse cycles [3]. In this context, the Hydrogen-based Plasma Smelting Reduction (HPSR) process emerges as a candidate to overcome several of the mentioned limitations of existing Nd-Fe-B recycling methods. The potential of the HPSR for green steel production has been reported using a hydrogen lean thermal plasma (Ar – 10% H2) to reduce iron ores [4] and to extract iron from bauxite refining waste residue [5]. The outcome of this process was a high purity Fe with a negligible impurity content and demonstrated purification of the feed from volatile and intrusive elements through evaporation. The HPSR process is versatile in many aspects: the use of hydrogen as the reducing element eliminates carbon-based emissions, the high-energy plasma enables the reduction/decontamination step within minutes, and there are practically no limitations regarding the input material. As mentioned above, the HPSR provides the unique potential opportunity to overcome the key issues regarding Nd-Fe-B, the performance of recycled magnets and their multiple reuse. In this research study, we test the potential of the HPSR process as an alternative recycling process of commercial grade Nd-Fe-B waste magnets and provide insight into its potential influence on selected figure of merits. References[1] Roskill Information Services Ltd, Rare Earths: Outlook to 2029, 2019.[2] Crownhart, C. (2024, August 21). This rare earth metal shows us the future of our planet’s resources. MIT Technology Review. https://www.technologyreview.com/2024/08/21/1096469/neodymium-rare-earth-materials-supply-chain/ [3] Schönfeldt, M., Rohrmann, U., Schreyer, P., Hasan, M., Opelt, K., Gassmann, J., Weidenkaff, A., & Gutfleisch, O. (2023). Magnetic and structural properties of multiple recycled and sustainable sintered Nd-Fe-B magnets. Journal of Alloys and Compounds, 939, 168709.[4] Souza Filho, I. R., Ma, Y., Kulse, M., Ponge, D., Gault, B., Springer, H., & Raabe, D. (2021). Sustainable steel through hydrogen plasma reduction of iron ore: Process, kinetics, microstructure, chemistry. Acta Materialia, 213, 116971. [5] Jovičević-Klug, M., Souza Filho, I. R., Springer, H., Adam, C., & Raabe, D. (2024). Green steel from red mud through climate-neutral hydrogen plasma reduction. Nature, 625(7996), 703–709.