Recycling Process for Rare-Earth Magnet Sludge with Chlorine Circulating Cycle

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 14550719
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Metal making engineering
• Research Institution: Tohoku University
• Principal Investigator: KOMAROV Sergey Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Associate Professor, 多元物質科学研究所, 助教授 (20252257)
• Co-Investigator(Kenkyū-buntansha): HIRASAWA Masahiro Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Professor, 多元物質科学研究所, 教授 (90126897) ; KAMEDA Tomohito Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Research Associate, 多元物質科学研究所, 助手 (60333895)
• Project Period (FY): 2002 – 2003
• Keywords: recycling / sludge / selective chlorination / high temperature reaction / vacuum distillation / rare earth magnet / lanthanoid

Research Abstract

The present research is aimed at development of an effective recycling process of rare earth elements in magnet sludge that is formed in the manufacturing processes of rare earth magnets and is heavily polluted by oxygen.
In the first stage of the present research, basic trial experiments were made concerning the selective chlorination and vacuum distillation for rare earth elements in sludge of Fe -Nd -Dy -B magnet On the basis of the trials, selective chlorination with FeCl_2 was performed of rare earth elements in the sludge of Fe -Nd -Dy -B magnet, and the chlorides of trivalent rare earth elements were distilled under appropriate vacuum distillation conditions. According to the quantitative analysis, the condensates obtained at 853 -1123 K had the composition of 82.4 % Nd, 16.8 % Dy, and, 0.8 % Fe with 〜 0 % B, while the condensates obtained at 413 -853 K had the composition of 98.7 % Fe, 0.7 % Nd, and, 0.3 % Dy with 0.2 % B. The residual materials in the carbon crucible consisted of Fe with impurities of small amounts of Nd, Dy, and, very slight amounts of Co and Cl. The efficiency of distillation of Nd and Dy from initial sludge was ca. 95 % in the present study.
The possibility of utilization of waste poly-vinyl chloride, PVC, as chlorination reagent was also investigated. Powders of various rare earth oxides were mixed with PVC powder, and the mixture was heated at 1073 K under He flow. From the experiments, it was found that considerably high percentage of Nd_2O_3 and La_O_3 powders were transformed to oxy-chiorides, LnOCl. This indicates the positive possibility of PVC wastes as chlorine source for the chlorination of rare earth elements in the magnet sludge.