Applying underwater explosion for the liberation of neodymium magnet rotor followed by thermal treatment for recycling

Prior to applying metallurgical processes for the recovery of rare earth elements from neodymium magnets in used rotors, it is necessary to separate the neodymium magnets from the rotors as effectively as possible. Due to the characteristics of the rotors such as hard steel cover, complex inner structure, and strong magnetic fields of neodymium magnet, it is difficult to disintegrate the neodymium magnet rotors by traditional mechanical crushing methods. This research letter presents the result of a preliminary experiment on applying underwater explosion for the liberation of neodymium magnet rotor followed by thermal treatment for recycling. The neodymium magnet rotor used in the compressor unit of an air conditioner can be effectively disintegrated by underwater explosion. The crushed products contain several steel pieces with neodymium magnet powder attached to their surfaces. After the crushed products are heated above the Curie temperature of the neodymium magnet, the neodymium magnet powder is demagnetized. After it is sieved, the neodymium magnet powder can be separated from the steel pieces. The separated powder can be subsequently treated by developed metallurgical processes for rare earth elements recovery.