Abstract
NdFeB permanent magnets have different life cycles, depending on the applications: from as short as 2–3 years in consumer electronics to 20–30 years in wind turbines. The size of the magnets ranges from less than 1 g in small consumer electronics to about 1 kg in electric vehicles (EVs) and hybrid and electric vehicles (HEVs), and can be as large as 1000–2000 kg in the generators of modern wind turbines. NdFeB permanent magnets contain about 31–32 wt% of rare-earth elements (REEs). Recycling of REEs contained in this type of magnets from the End-of-Life (EOL) products will play an important and complementary role in the total supply of REEs in the future. However, collection and recovery of the magnets from small consumer electronics imposes great social and technological challenges. This paper gives an overview of the sources of NdFeB permanent magnets related to their applications, followed by a summary of the various available technologies to recover the REEs from these magnets, including physical processing and separation, direct alloy production, and metallurgical extraction and recovery. At present, no commercial operation has been identified for recycling the EOL NdFeB permanent magnets and the recovery of the associated REE content. Most of the processing methods are still at various research and development stages. It is estimated that in the coming 10–15 years, the recycled REEs from EOL permanent magnets will play a significant role in the total REE supply in the magnet sector, provided that efficient technologies will be developed and implemented in practice.
Highlights
Neodymium–iron–boron (Nd2Fe14B, or NdFeB for short) permanent magnets are considered as the best available magnets since their introduction on the market in 1984, due to their superior energy product, which makes them highly efficient and suitable for lightweight mobile applications [1].J
They are widely used in wind turbines, hybrid and electric vehicles (HEVs and EVs), household electrical appliances, computer hard disk drives (HDDs), and many small consumer electronic devices
Dissolution of magnet scrap can be performed in three different ways: (1) complete dissolution of the NdFeB magnet, (2) roasting followed by selective leaching of the rare-earth elements (REEs), and (3) selective conversion of REEs in solid magnet or magnet scrap directly to a new solid phase
Summary
Neodymium–iron–boron (Nd2Fe14B, or NdFeB for short) permanent magnets are considered as the best available magnets since their introduction on the market in 1984, due to their superior energy product (with a theoretical maximum of 512 kJ/m3), which makes them highly efficient and suitable for lightweight mobile applications [1]. REMANENCE (http://www.project-remanence.eu/) have demonstrated that it is possible to extract 5 kg of magnets from ‘real’ scrap hard disk drives provided by Stena Metal in Sweden using the HPMS process, outlined in ‘‘Hydrogen Decrepitation of Pre-dismantled Computer HDDs’’ section, After jet milling, blending, pressing and resintering the maximum energy product of the final magnets was shown to vary by only ±5 kJ/m3 respectively [68]. This level of variation is similar to that observed in primary magnet production despite the mixed compositional feed which was presented to the process [68]. A total materials recovery from EOL products (containing REE magnets) would be the direction for future research and development, in parallel with magnet pre-dismantling approach
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