© 2016 Toshiba Corporation
Hisao OHMURAToshiba Corp.Dec 8, 2016
Recycle of rare earth magnet with pyrochemical process
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Background
Industrial device@ 2015
Automobile@ 2019
Home electronics@ 2018
43%
22%
35%General Industry(Small, Middle motor)
Elevator Hoisting machine(Large motor)
508 t/y Air conditioner
39.4%
36.4%
23.6%
Others 0.6%
Amount of rare earth magnet embedded each product (estimate)
Breakdown
• 【Rare Earth(RE) magnet】Recycle of RE magnet from home electronics has been focused in JAPAN.– Amount of RE magnet embedded in industrial device is comparable to
home electronics. (508 ton/year)– Simple distribution route → Easy collection of waste product
(for product maker)
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Concept• 【RE magnet recycle system】
– Solution to uneven distribution of RE and high environmental load in RE production from ore
– RE recycle system from urban mine to product– Less-waste and economical process by applying nuclear technology
Hoisting Machine(motor)
Coil(Copper)
Used RE magnet
Other parts(Steel)
High purityRE alloy
Recycled RE magnet
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Outline and Features of TSB process
- Processing capacity: 3000 motors/year (motor weight: 230kg/unit)- Recovered RE alloy to recycled RE magnet,
other metal parts (steel, copper) to raw material for product- No liquid waste (acid, alkaline and organic solvent) process with molten salt*1
Recovery of 99%-component of industrial motor
*1Molten salt: Conductive melted salt, such as NaCl, at high temperature
Copper: 62 t/yearSteel: 621 t/year
Magnet : 7 t/year
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Analysis of RE magnetElement composition analysis by XRF, ICP-AES, IR and TCD
The composition of RE magnet recovered from industrial motor was almost equal to from compressor.
The RE magnet was not almost oxidized.
The RE magnet contained additive substances such as Al, Co and Cu.
Element composition RE magnet (wt%)
Element Industrialmotor Compressor
Fe 65.4 65.4Nd 24.6 26.2Dy 5.6 5B 1 0.97Al 0.19 0.23Si 0.08 0.15Co 2.2 1.5Cu 0.13 0.23O 0.21 0.25N 0.005 0.01C 0.071 0.066
RE magnet recovered from industrial motor (after thermal demagnetization)
33 mm
33 mm
Thickness: 4 mm
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RE metal recovery from RE magnet
温度:400~900℃
RE magnet
Extraction
Extractant
Molten salt extraction
Residue
RE3+
(Nd3+, Dy3+, Pr3+)
Molten salt electrolysis
Cathode Anode
RE3+Molten salt
Electrolysis
RE-Fe liquid alloy
Formation of RE-Fe liquid alloy
T > 685 ºC
Selective Extraction of RE ions from RE magnet by extractant addition
Electrowinning of RE-Fe liquid alloy from molten salt after extraction
Conc
entr
atio
n of
RE
ions
Time
Extraction Electrolysis Extraction Electrolysis
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Principle of molten salt extraction
NdDyMolten
salt
MClx
RE magnet
Nd3+, Dy3+
• Extraction of RE ions from RE magnet• Elimination of undesirable elements by volatilization
Volatilization
LiCl
CaCl2
NdCl3
MgCl2 DyCl3
MnCl2
FeCl2NiCl2
FeCl3
Candidate extractant
AlCl3e.g. FeCl3, NiCl2, FeCl2, AlCl3, MnCl2, MgCl2
Extraction ReactionxNd(in magnet) + 3MClx
= xNd3+ + 3xCl- + 3Me.g. M= Fe, Mg
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Molten salt extraction(1)
Extraction ratio = Mass of RE ion in molten salt
Mass of RE metal in initial RE magnet×100
After extraction (2 hours)
Before extraction
•RE ions were extracted by addition of MClx.•There were no differences in the extraction behavior of RE ions.•Al ion was also extracted into the melt.
Molten salt: LiCl-KCl (59:41mol%)Temperature: 500 ºCExtractant: MClx (Mole ratio; MClx/RE=1-3)Atmosphere: ArAgitation: No
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Molten salt extraction(3)
•RE ions were extracted into CaCl2 melt by addition of MClx•Al ion was not detected in the melt.→ Al ion was eliminated as AlCl3 by volatilization.
Molten salt extraction is applicable to RE recovery from RE magnet.
Molten salt: CaCl2Temperature: 850 ºCExtractant: MClx (Mole ratio; MClx/RE=1.8)Atmosphere: ArAgitation: No
B, Al, Co ions were not detected.
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Principle of molten salt electrolysis
Molten salt
Cathode(Fe)Anode(C)
Crucible
Liquid alloy(RE-Fe)
Formation of RE-Fe liquid alloyT > 685 ºC
Eutectic pointT = 685 ºC, XNd = 0.795
Expected reactionRE3+ 3e- + = RE-Fe alloy
Molten salt electrolysis with fluoride melt is applied to Nd-Fe metal production on a commercial scale.
Is it possible to product RE-Fe metal in the chloride melts after molten salt extraction ?
G. Schneider, E.T. Henig, G. Petzow, and H.H. Stadelmaier, Z. Metallkd., 78(10), 694-696 (1987).
Fe Nd
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Molten salt electrolysis
wt% mol%
Nd 89.04 75.88
Fe 10.96 24.12
O ND ND
Ca ND ND
Cl ND NDΣ 100 100
wt% mol%
Nd 21.66 9.59
Fe 78.06 89.27
O 0.29 1.14
Ca ND ND
Cl ND ND
Σ 100 100
wt% mol%
Nd ND ND
Fe 99.64 99.94
O ND ND
Ca ND ND
Cl 0.36 0.56
Σ 100 100
Fe electrodeNd-Fe alloy
Molten salt: CaCl2 - NdCl3Temperature: 850 ºCPotential: 0.27 V vs. Ca2+/CaElectrolysis time: 6 hoursAtmosphere: Ar
High pure Nd-Fe metal was obtained from CaCl2 melt.
Image of the cathode after electrolysis
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Demonstration test with actual used RE magnet(1)
温度:400~900℃
RE magnet
Extraction
Extractant
Molten salt extraction
Residue
RE3+
(Nd3+, Dy3+, Pr3+)
Molten salt electrolysis
Cathode Anode
RE3+Molten salt
Electrolysis
RE-Fe liquid alloy
Formation of RE-Fe liquid alloy
T > 685 ºC
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Demonstration test with actual used RE magnet(2)
NdDy
Molten salt
• Molten salt: CaCl2• Temperature: 850 ºC• Extractant: MClx (Mole ratio; MClx/RE=1-3)• RE magnet: NdFeB + Dy• Atmosphere: Ar• Agitation: No
RE magnet
MClx
B, Al, Co ions were not detected.
RE ions were extracted selectively from actual used RE magnet.
RE magnet crushed under Ar atmosphere
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Demonstration test with actual used RE magnet(3)
Molten salt
Cathode(Fe)Anode(C)
Crucible
Liquid alloy(RE-Fe)
• Molten salt: CaCl2 containing extracted RE ions
• Temperature: 850 ºC• Current density: 1-3 A cm-2
• Atmosphere: Ar
Reference(Ag+/Ag)
Obtained RE-Fe alloy
RE-Fe metal was obtained from the melts after molten salt extraction.
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Demonstration test with actual used RE magnet(4)
Element composition (wt%)Fe Nd Dy B Al Si Co Cu N C
Actual used RE magnet
65.4 24.6 5.6 1.0 0.19 0.08 2.2 0.13 0.005 0.071
Recovered RE-Fe metal
9.8 63 14 N.D.<0.1
N.D.<0.1
N.D.<0.1
N.D.<0.1
N.D.<0.1
N.D.<0.02
N.D.<0.05
Actual used RE magnet Recovered RE-FE metal
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Summary
•High purity RE-Fe alloy was recovered from actual used RE magnet by pyrochemical process.
•RE recovery test was conducted using actual used RE magnet by pyrochemical process.
•RE ions were selectively extracted from RE magnet into chloride melts by addition of MClx.
•RE-Fe alloy was obtained by molten salt electrolysis from the melts containing extracted RE ions.
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Acknowledgment
This presentation is partly based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).