Birmingham pilot plant first to trial rare earth recovery process

A PILOT plant using a new process to recover rare earth alloys from scrap magnets will be built at the UK’s University of Birmingham following a €4m (US$4.4m) grant from the EU.

The pilot plant will be the first to use a patented process called HPMS (hydrogen processing of magnet scrap). This uses hydrogen to decrepitate magnets containing the rare earth element neodymium which are used in a range of hi-tech applications including in electric cars and hard disk drives.

While demand for rare earth elements is increasing and there are concerns about China’s dominance of supply, less than 1% of the elements used today are recycled. The barriers preventing this are complex but include fluctuating prices and challenges in recovering the small amounts of metals used in products.

The technology that will be applied in Birmingham was first developed there in the 1980s and has been under further development with partners across Europe in the last 15 years. The plant, which will process 50 kg batches in around 4–-6 hours, is expected to begin production within about a year.

The process involves adding pre-processed scrap material into a reaction vessel that is purged of air and hydrogen added. In the pre-processing stage a portion of the coating that protects the neodymium-iron-boron alloy from readily corroding during service is removed from the magnet. The hydrogen is absorbed through the non-coated section and enters the rare-earth-rich grain boundary phase causing the lattice structure to expand and degrade. This produces a friable demagnetised alloy powder which can then be separated using an agitated porous reactor from the rest of the material such as plastics or screws leftover from the original scrapped product.

University of Birmingham researcher Vicky Mann said the process uses equipment already in commercial use; it avoids the solvents used in other processing techniques; and is set up in a way to only react with neodymium-iron-boron magnets so can reliably handle mixed waste streams.

“It’s cheap and there’s not really any negative environmental footprint associated with it,” Mann said, adding that the hydrogen used in the process is captured and reused.

The €4m grant from the EU-funded SUSMAGPRO (Sustainable Recovery, Reprocessing and Reuse of Rare-Earth Magnets in a Circular Economy) project will fund the development of a European supply chain that will prevent 20 t of magnets reaching landfill. This will involve the construction of two other pilot plants in Germany and Slovenia. The project is also investigating how the resulting magnets can be used to produce magnets through processes including metal-injection moulding.

Allan Walton, from the School of Metallurgy and Materials at the University of Birmingham, is one of the inventors of the process. He said: “Rare earth magnets are used in practically every application that uses electricity to produce motion, and underpin industries that are worth more than £1trn worldwide.  However, both the price and supply have fluctuated considerably over recent years. This means there is considerable opportunity for cost-efficient technologies, which make recycling viable in the long-term.”