Analysis of induction-based thermal demagnetization of a permanent magnet rotor in the context of recycling

Rare Earth (RE) Magnets are a key for many green technologies causing continuously increasing demand in the European Union (EU). Alongside motors for e-mobility and generators in wind turbines, compressors in domestic heat pumps represent a potential lever for slowing climate change. On the other hand, the dominant market power of the PR China results in a high supply chain risk. Therefore, the EU has declared these elements as critical raw materials of the highest category and plans a compulsory recycling share of 15% until 2030. Currently, no systematic recycling activities for RE magnets are operated on an industrial scale. In the present paper a concept for the extraction of RE magnets from rotors of HVAC compressors is presented. The focus is set on the thermal in-situ demagnetization by induction which is crucial for the disassembly of the magnets. This process ensures efficient heating to temperatures above the individual Curie temperatures so that interfering reaction forces are eliminated. Systematic test series are carried out based on an experimental set-up to identify the main process parameters and restrictions. The achieved results are analyzed and are evaluated regarding the transferability to a potential series process.