Recovery of Nd and Dy from Magnet Scrap by Utilizing Molten Salt

Transcription

1 Recovery of Nd and Dy from Magnet Scrap by Utilizing Molten Salt Sakae Shirayama 1 and Toru H. Okabe 2 1 Department of Materials Engineering, School of Engineering, the University of Tokyo, Japan 2 Institute of Industrial Science, the University of Tokyo, Japan

2 Nd Fe B magnet Production amount of Nd Fe B magnet in Japan, W / kt : Other : Communication equipment : Audio equipment : MRI : Hard disk drive : Motors for industry Year Fig. Production amount of Nd Fe B magnet in Japan. Nd Fe B rare earth magnet is the strongest permanent magnet. Applications: Hard Disk Drive (HDD) Motors for air conditioner generator electric vehicle Large amount of magnet scrap will be produced in the future _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 2

3 Supply of REE Worlds 97 % supply is dominated by China. Prices of REE are escalating especially for Dy. Dy is very scarce and limited. 180 Other 3 kt (3%) Total 123 kt China 120 kt (97%) Fig. World share in supply of REE in (USGS Mineral Commodity Summaries (2007)) Price US$ / kg Dy Year. Month Price of Dy is still high even after the economic collapse in Nd Fig. Change in prices of Nd and Dy. (Industrial rare metals (2007): Arum Ltd.) Development of new recycling process is important _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 3

4 Aim of this study Nd Fe B magnet Efficient recovery of rare earth compounds Motor for driving Nd & Dy flow This study Rare earth compounds Electric vehicle Motor for driving (Scrap) Reaction with molten salt Discarded Development of effective recovery process by utilizing molten salt as a rare earth extracting agent _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 4

5 Flowchart of recycling of the magnet scrap Dy-containing Nd Fe B magnet scrap MX n (l) (MX n : MgCl 2 ZnI 2 ) Nd and Dy extraction by molten MX n Step 1: Extraction NdXn (s, l) + DyXn (s, l) + M(l) + MX n (l) + Fe B(s) Solid / liquid separation L S Fe B(s) NdXn (s, l) + DyXn (l) + M(l) + MX n (l) Step 2: Separation Vacuum distillation / separation NdXn (s, l) DyXn (s, l) M(g) MX n (l, g) Refining / reduction Nd(s) Dy(s) _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 5

6 Experimental procedure (extraction) Selective extraction of Nd and Dy by immersing the magnet alloy into molten salt Extracting agent MgCl 2 ZnI 2 Reaction temp K 740 K Reaction time 3 ~ 12 h 12 h Alumina tube Stainless-steel tube Stainless-steel wire Stainless-steel foil Molten salt (MgCl 2, ZnI 2 ) Dy-containing Nd Fe B alloy Stainless-steel chamber Thermocouple Heating element Fe crucible Ti sponge (N 2, O 2 getter) Fig. Schematic illustration of experimental setup for the extraction experiments _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 6

7 Experimental procedure (separation) Separation and recovery of rare earth compounds by vacuum distillation Extracting agent MgCl 2 ZnI 2 Reaction temp K 1073 K Reaction time 6 h 1 h Quartz tube Ti foil Heating element Salt obtained after extraction exp. Evacuate Ti sponge Thermocouple Stainless-steel crucible Fig. Schematic illustration of experimental setup for the separation experiments _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 7

8 Development of novel recovery process Recovery of Nd and Dy by utilizing molten MgCl 2. Recovery of Nd and Dy by utilizing molten ZnI 2. 2 Nd (in magnet alloy, s) + 3 MgCl 2 (l) 2 NdCl 3 (l) + 3 Mg(l) 2 Dy (in magnet alloy, s) + 3 MgCl 2 (l) 2 DyCl 2 (l) + 3 Mg(l) _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 8

9 Results (extraction) Composition analysis: XRD analysis: Extraction ratio, w i, salt R i = w 100 (%) i, Nd Fe B w i, salt w i, Nd Fe B Extraction ratio, R i (%) : mass of element i in salt after exp. : initial mass of element i in alloy : Dy : Nd : Fe : B Reaction time, t / h Intensity, I (a. u.) Salt obtained after exp. (1273 K, 6 h) MgCl 2 NdCl 3 PDF# PDF# Angle, 2θ / degree (Cu-Kα) 2 Nd(s) + 3 MgCl 2 (l) 2 NdCl 3 (l) + 3 Mg(l) ΔG = kj at 1273 K Nd and Dy were selectively extracted into molten MgCl _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 9

10 Results (vacuum distillation) Deposition of samples after vacuum distillation Deposit obtained after exp. 1-(A) 1-(B) 1-(C) Remained sample in the crucible Vacuum Sample : Temperature during exp. T 0 T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 T 9 1-(A) : 500 K ~ 900 K Temperature, T / K (B) 1-(C) : 1050 K : 1273 K Distance from the open end of quartz tube, L / mm _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 10

11 Results (vacuum distillation) 1-(A): 500 K ~ 900 K : MgCl 2 # : MgCl 2 # : NdCl 3 # : NdOCl # Deposit obtained after exp., 1-(A) Intensity, I (a.u.) 1-(B): 1050 K 1-(C): 1273 K MgCl 2 + NdCl 3 Deposit obtained after exp., 1-(B) NdCl 3 Remained sample in the crucible, 1-(C) Angle, 2θ / degree (Cu-Kα) NdOCl Fig. XRD patterns of the samples obtained after vacuum distillation _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 11

12 Summary of recovery exp. by utilizing MgCl 2 In the extraction step: Selective extraction of Nd and Dy was experimentally demonstrated. In the separation step: MgCl 2 was removed from mixed salt. NdCl 3 were recovered by gas phase transportation. MgCl 2 + NdCl 3 NdCl 3 NdOCl Generation of NdOCl is probably due to the hydration of the salt during handling. 500~900 K 1050 K 1273 K _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 12

13 Development of novel recovery process Recovery of Nd and Dy by utilizing molten MgCl 2. Recovery of Nd and Dy by utilizing molten ZnI 2. 2 Nd (in magnet alloy, s) + 3 ZnI 2 (l) 2 NdI 3 (l) + 3 Zn(l) 2 Dy (in magnet alloy, s) + 3 ZnI 2 (l) 2 DyI 3 (l) + 3 Zn(l) _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 13

14 Results (vacuum distillation) Small pieces of the magnet alloy were used in the extraction experiment. (740 K, 12 h) Substance obtained after extraction exp. was distilled under vacuum.(1073 K 1 h) Deposit obtained after exp. 2-(W) 2-(X) 2-(Y) 2-(Z) Remained sample in the crucible Temperature, T / K T 0 T 1 T 2 T 3 T T 5 T 6 T 7 T 8 2-(W) 2-(X) 2-(Y) 2-(Z) : 410 K ~ 640 K : 500 K ~ 700 K : 920 K : 1073 K Distance from the open end of quartz tube, L / mm _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 14 T 9 Sample : Temperature during exp.

15 Results (vacuum distillation) (a) 2-(W) (410~640 K) : ZnI 2 # : Zn # : NdI 1.95 # Deposit obtained after exp., 2-(W) Intensity, I (a.u.) (b) 2-(X) (410~640 K) (c) 2-(Y) (920 K) ZnI 2 Deposit obtained after exp., 2-(X) Zn Deposit obtained after exp., 2-(Y) NdI Angle, 2θ / degree (Cu-Kα) Fig. XRD patterns of the samples obtained after vacuum distillation _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 15

16 Summary of recovery exp. by utilizing ZnI 2 ZnI 2 Zn NdI (Z) Obtained residue 2-(Z) Leaching by distilled water 410~640 K 920 K 1073 K Dissolved portion Residue after leaching 2 Nd(s) + 3 ZnI 2 (l) 2 NdI 3 (s) + 3 Zn(l) ΔG = kj at 740 K NdI x, DyI x Fe-B Selective extraction of Nd and Dy by ZnI 2 is feasible. NdI 1.95 was recovered by gas phase transportation _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 16

17 Conclusion Recovery of Nd and Dy from magnet alloy by utilizing molten MgCl 2 or ZnI 2 was investigated. Extraction experiment By utilizing MgCl 2 and ZnI 2, selective extraction of Nd and Dy was experimentally verified. Separation experiment Excess extracting agent was removed by vacuum distillation. Gas phase transportation of rare earth compounds was experimentally verified. Effective recovery process can be established by utilizing molten salt _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 17

18 Aim of this study Nd Fe B magnet Efficient recovery of rare earth compounds Motor for driving Nd & Dy flow This study Rare earth compounds Electric vehicle Motor for driving (Scrap) Reaction with molten salt Discarded Development of effective recovery process by utilizing molten salt as a rare earth extracting agent _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 18

19 Acknowledgement Travel expense of the author (Sakae Shirayama) was supported by the grant from the Foundation for the Promotion of Industrial Science (FPIS). The authors are grateful to Okabe s Lab. members for providing technical assistance and various support _16:40-17:00_Workshop on Materials Process Engineering, San Francisco, California 19