#Industry News
Processing of magnet recyclate
Recycling and the sustainable use of valuable raw materials is playing an increasingly important role in the area of rare earth magnets
Rare earth alloys and the permanent magnets made from them are becoming increasingly important as the use of electromobility grows. These materials are of crucial importance for the efficiency and performance of electric motors, generators, and other industrial applications. To ensure the sustainable use of these valuable raw materials and at the same time protect the environment, recycling is also playing an increasingly important role in this area.
Recycled magnets can be divided into two main categories: On the one hand, waste is generated during the production of magnets, and on the other hand, classic returns from electric motors, generators or other applications are recycled.
Magnet waste from production is usually cutting waste from the mechanical processing of magnets. To be able to reincorporate this material into the production process, it is crucial to remove any impurities such as oxides and carbides.
Electric motors and generators generally have a service life of around 10 years. As a result, a considerable number of used magnets is already produced today, as a wind turbine, for example, uses around 600 kg of rare earth magnets per megawatt.
Processing of magnet recyclate
However, magnetic recyclate contains a high proportion of impurities with oxygen, nitrogen or carbon, which accumulate primarily in the fines. These have a negative effect on the magnetic properties and must therefore be removed before reuse. To achieve an effective reduction in the oxygen content, the hydrogen-brittle powder must first be ground. Subsequently, the ultrafine particles and thus the impurities are reliably separated from the recycled magnetic powder using the high-performance ultrafine separator M-CLASS and a reusable magnetic powder is obtained (Fig. 1).
Theoretical decrease in oxygen impurities in the recyclate as a function of d90 in the fines and the coarse material content in wt.% (good product)
With the diagram shown in Fig. 2, one can estimate the anticipated decrease in oxygen content within the recyclate. To effectively reduce the oxygen content, the hydrogen-embrittled powder must undergo grinding initially. It's essential to attain a slightly finer d50 value than the intended target particle size, as the value tends to shift slightly coarser during subsequent classification processes.
To achieve the most effective reduction of impurities at maximum yield, the d90 to be aimed for in the fines should be between 3 µm and 3.5 µm. For example, to obtain a good product (GG) with a d50 of 3.5 µm, a d50 of 3.0 µm should be aimed for in the feed material. To achieve the most effective reduction of impurities, the feed material must contain a high proportion of particles < 1 -2 µm. For this purpose, it is necessary to carry out pregrinding at pressures between 8 bar(g) and 9 bar(g).
The degree of impurity removal in the recyclate after the classification process varies depending on the yield of coarse material. The following application example shown in Fig. 2 illustrates this: Starting from a concentration of 0.65 wt.% in the feed material, reducing the oxygen content by 0.55 wt.% would result in a coarse material yield of about 85%.
The material obtained in this way can be reused to produce new permanent magnets. The recycling of rare earth alloys and permanent magnets therefore contributes to sustainable and resource-efficient production.
