Seversk Technological Institute of National Research Nuclear University “MEPhI”, Seversk, Russia

V. L. Sofronov, Professor, Assistant Professor of the Technological Faculty, e-mail: sofronov@ssti.ru
A. S. Buynovskiy, Professor
V. V. Dogaev, Post-graduate Student
A. Yu. Makaseev, Assistant Professor, Deputy Administrator
Yu. N. Makaseev, Assistant Professor

The article presents the results of research on the decarburization of waste from grinding sintered high-energy permanent magnets on the basis of Nd – Fe – B. Waste from grinding except metal components, that fall into them from the magnets, contain 5–14% (wt.) of oxygen, 5–7% (wt.) by weight of carbon (in the form of oil), 10–30% (wt.) by weight of moisture and a small amount, up to 1.5% (wt.) impurities of silicon and aluminum. For decarbonization of waste from grinding there have been tested methods for their cleaning by alkaline solutions and organic solvents, as well as the method of thermal decarbonization. There have been found optimal conditions for decarburization of waste from grinding by alkaline solutions: a solution containing NaOH, NaH₂PO₄, Na₂SiO₃; temperature range from 50 to 90 ^oC. It is shown that the efficiency of decarburization of waste from grinding with organic solvents is much lower than with alkaline solutions. The best results are achieved by heat treatment of waste from grinding by drying and decarburization in the mode of self-propagating high temperature synthesis, so this method is promising for industrial use, as it makes it easy and cheap to obtain metal oxides which are suitable for further processing. Mathematical processing of experimental data of the drying process of waste from grinding determined the apparent activation energy, which is equal to 9800 J/mol, oxidation process is limited by diffusion of waste from grinding.

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