Dry Recycling Process of Rare Earth Elements

from Alloy Magnets Keigo Nishimura1, Toru H. Okabe2

1Freshman, Division of The College of Arts and Sciences, The University of Tokyo, Japan; 2Institute of Industrial Science, The University of Tokyo, Japan.

Introduction

Experimental

Results Conclusion

Total

109 kt

Rare earth elements Production of

rare earth ore

Nd-Fe-B magnets

Application of Nd-Fe-B magnet

China China

87%

India

2.6%

Other

4.2%

India

Other

United States

1985 1980 1990 1995 2010 2000

140

120

100

80

60

40

20

0

Am

ou

nt o

f p

rod

uctio

n o

f R

E o

xid

es, W

/ k

t

Year

Change in amount of production of REE

United

States

6.4%

2005

Current recycling process

Nd-Fe-B magnet alloys were reacted

with Molten Mg at 1000℃ for 24 hours.

(Nd, Dy)-rich phase Top view of

sectioned crucible

Fig. Samples obtained after the extraction experiment.

Magnet

phase

Reaction

phase

Mg-rich

phase

Demand for Nd-Fe-B sintered magnet by use in Japan (2008).

VCM 31%

MRI 5%

Other 19%

In 2010, China accounts for 97% of

world rare earth production.

Almost all rare earth are produced in China. Used for Nd-Fe-B alloy magnet

Nd-Fe-B magnet is

the strongest permanent magnet in the world.

Demand for Nd-Fe-B magnet

Alloy magnet used in this study

Experimental procedure

Nd is an essential element for high performance alloy magnet.

Addition of Dy or Tb improves heat resistance of magnet.

Nd and Dy are vital elements for strong magnets. Ion clay which contains large amount of Dy and

other heavy rare earth exsist only in China.

Large amount of scraps will be

generated in the future.

Supply of REE in 2012

Serious environmental pollution occurs.

But·····

Change in prices of Nd, Dy. (Industrial rare metals (2007))

Year. Month 2005.1 2006.1 2006.12

0

20

40

60

80

100

120

Pri

ce

U

S$ ・

kg

-1 Dy

Nd

Price chart of Nd and Dy

Price of Nd and Dy is increasing

Recycling of Nd from scraps is important.

Concept of our new process

Development of environmentally

friendly dry recycling process for

rare earth.

Stable supply of rare earth.

1. Experimental setup

2. Nd extraction at elevated temperature.

TIG welding

Fe lid

Mg shot

Nd-Fe-B magnet

alloy lump

Iron crucible

Stainless steel vessel

Ti sponge

SEM-EDS analysis of sample

ICP-AES analysis of sample

95 kt

Total supply

of China

自動車生産に必要なNd磁石量(保有台数から)

0.00

5000.00

10000.00

15000.00

20000.00

25000.00

30000.00

1 6 11 16 21

Dy Nd

他

0.0

5.0

10.0

15.0

20.0

1 3 5 7 9 11 13 15 17 19 21 23 25

自動車保有台数(百万台)

系列1

0

5

10

15

20

25

30

De

ma

nd

fo

r N

d-F

e-B

ma

gn

et a

nd

the

ra

tio

of m

ate

ria

ls fo

r E

V, W

/ k

t

0

2

4

10

12

18

20

6

8

14

16

Year

Pro

du

ctio

n o

f E

V,

N (

mill

ion

)

2006 2010 2015 2020 2025 2030

: Nd

: Dy

: other materials

(Annual Energy Outlook 2008: US DOE EIA, http://www.eia.doe.gov/oiaf/ieo/)

Extract only Nd and Dy from

Nd-Fe-B alloy magnet by using

molten Mg.

Nd

Fe

Nd Mg

Nd-Mg alloy

Mg as an

extractant

Nd-Fe-B

magnet

1,000 ℃

High affinity

between

Nd and Mg

Fe

49%

Nd

44%

Dy

6%

B

1%

Most of Nd was extracted from alloy

phase to Mg phase.

On the other hand, Fe was not

extracted into molten Mg.

Over 90 % of Nd was extracted from

Nd-Fe-B alloy magnet.

• Nd was extracted directly

from Nd-Fe-B magnet by

dry recycling process.

• Not any highly toxic waste

solution was generated by

this dry process.

Discarding large amount of

highly toxic waste solutions

×

The representative component of

rare earth ore La Ce

Y

Pr

Sm

Dy

Mt. Pass (USA)

Baiyun Obo (China)

Mt. Weld (Australia)

Rongnan (China)

Xinfeng(China)

Xunwu(China)

Ion clay

Bastnaesite

Bastnaesite

Monasite

Ion clay

Ion clay

7 kt

4 kt

Nd

Motor

31%

Nd2Fe14B magnet scrap

Pulverization

Oxidation

Acid dissolution

L S

Filtration

Nd, Fe (in solution)

FeOx, abrasives, etc.

Fractional precipitation Fractional precipitation

Filtration Filtration

Calcination Calcination

Nd2O3

HF

Fe (in solution) Nd2(C2O4)3 NdF3・nH2O

Fe (in solution)

NdF3

H2C2O4

Objectives

Fig. Composition of alloy magnet (mass%)

Mg shot Magnet alloy lump

A 1 1.5

B 1 2.0

C 1 2.5

Weight ratio of alloy magnet lump and Mg shot

Mg SEM

Nd Fe

Composition, Ci (mass%)

Mg Fe Nd

A 0.82 96.1 3.07

B 1.11 93.7 5.19

C 0.64 92.6 6.75

Composition, Ci (mass%)

Mg Fe Nd

A 62.65 0.87 35.79

B 62.38 0.00 36.97

C 53.35 0.35 45.41

Result in magnet alloy phase

Result in Mg phase

Extraction rate of Nd (On assumption that Mg is not flowing

outside as gaseous phase)

Sample A B C

Extracted Nd ratio (%)

93.2 88.5 85.0

now

~$1,000/kg Dy metal

*1 The value was

determined from the

composition of

magnet alloy after

extraction.

Keigo Nishimura is expert of Taido, martial arts.

Nd can be extracted and separated

directly from magnet alloy

Other heavy REE

(Eu, Gd, Tb, Ho, Er, Yb, Lu)

Total

10400 t