高純度金属バナジウムの新製造法の開発Development of New Production Process of High Purity Vanadium MetalAkihiko Miyauchi1, Toru H. Okabe2 　　　　　　　　　　　　　　

1Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo; 2Institute of Industrial Science, The University of Tokyo.

Introduction

Experimental

Results Current status

Future work

V2O5 (s)

+ Al (s)

( + Fe (s))V － Al (l)

(Fe － V － Al (l))

Slag

Electron beam melting

Alloying process

Fe － V alloy

V metal

Flux V2O5

1273 K

Vanadium?

Resources and production Application

Flowchart of our processThermodynamic analysis Preform reduction process (PRP)

Reduction process

Sintered preform

Mixing / casting

Feed preform

Calcination

Reduction

Reductant (Ca, Mg)

Reduced preform

Leaching and rinsing

Solid

Vacuum drying

Waste solution

V metal powder

Special steel

In the primary use, vanadium is consumed as an alloy

element of steel.

High thermal stability and tensile strength

Ti-V hydrogen storing alloy

Vanadium has high hydrogen storage ability. Ti-V alloy

draws attention as a negative electrode material of nickel

hydride battery, and has a potential to be used for

lower-cost and higher-capacity battery.

It is important to develop

a new production process

of pure vanadium metal

and vanadium alloy.

Commercial production process

◎ Simple and economic process

○ First batch type process with rich scalability

× Difficult to control the purity

× Repeated removal of Al by the electron

　　 beam melting for some applications 　

Features

Aluminothermic process

3 V2O5 (s) + 10 Al (s) (+ Fe (s))

→ 6 V (in Al (l)) + 5 Al2O3 (s)

(Fe-V-Al (l))

Reduction by reductant vapor

MxOy ＋ Flux ＋ Binder Preform

Casting Forming

V2O5 + 5 R → 2 V + 5 ROx 　

Features ◎ Suitable for uniform reduction ◎ Flexible scalability

○ Possible to control the morphology of the powder by varying the flux content in the preform○ Possible to prevent the contamination from the reaction container and to control the purity ○ Amount of waste solution is minimized.○ Molten salt as a flux can be reduced in comparison with the other direct reduction process.× Difficult to produce reductant and to control its vapor

PRP is simple and low-cost processfor high purity products.

Stainless steel reaction vessel

Ti sponge getter

Feed preform(V2O5, Flux)

TIG welding

Stainless steel cover

Stainless steel holder

Reductant (Ca, Mg)

Problem 　 The melting point of vanadium pentoxide (V2O5) is low (963 K), and it is difficult to fabricate mechanically strong solid preform. Reduction has to be carried out at temperature higher than 1173 K to maintain enough vapor pressure of Ca or Mg.

The feasibility of the preform reduction

process (PRP), based on the thermal

reduction of V2O5, was demonstrated.

・ Complex oxide containing V2O5 was

synthesized by the calcination process in

order to increase the mechanical strength of

feed preform.

・ Vanadium powder with 99.7 mass% purity

was obtained by magnesiothermic reduction

of feed preform.

・ Investigation of residual oxygen concentration,

and evaluation of total vanadium yield.

・ Development of production process of Ti-V

alloys.

・ Analysis of reduction mechanism by utilizing

the chemical potential diagram for the system

involving oxygen, calcium, magnesium, and

vanadium.

Calcination process

Liquid

Binder

Vapor pressure of metals

(Ref. Iron and Steel Institute of Japan)

(Ref. Matsushita Electric Industrial Co., Ltd)

Sta

ndar

d G

ibbs

ene

rgy

of fo

rmat

ion,

Gﾟ

f /

kJ m

ol-1

2 Ca + O2 = 2 CaO

3/2 Fe + O2 = 1/2 Fe3O4

Ti + O2 = TiO2

2 Mg + O2 = 2 MgO

4/5 V + O2 = 2/5 V2O5

Temperature, T / K

-1400

-1200

-1000

-800

-600

-400

-200

0

800 900 1000 1100 1200 1300

-30

-25

-20

-15

-10

-5

0

800 900 1000 1100 1200 1300

Vap

or p

ress

ure

log

p° (

atm

)

Mg

Ca

Fe

Ti

V

Temperature, T / K

1173 K

CaO or MgO was added to feed preform in order to

synthesize complex oxides (CaxVyOz, MgxVyOz) during

calcination. The obtained feed preform has a mechanical

strength at elevated temperature and suitable for

handling during processing.

X-ray diffraction pattern Appearance

・ Complex oxides (Ca2V2O7 or Mg2V2O7) was

synthesized after calcination.

・ Calcined sample maintained its shape form.

m.p.(V2O5)

963 KReaction

temperature

-4

1273 K

Condition for calcination

The calcination temperature was raised from 873 K

to 1173 K during 2 hr of calcination period.

Weight change of the samples

X-ray diffraction pattern

Development of simple and

low-cost process for high purity

vanadium metal or alloys

Aim of this study

20 % HCl aq.,Distilled water,

Isopropanol,

Tred. = 1273 K

tred. = 6 hr

1173 K

Ⅰ A Ⅱ A ⅢB ⅣB ⅤB ⅥB ⅦB Ⅰ A Ⅱ A ⅢA ⅣA ⅤA ⅥA ⅦA ⅧAHydrogen Helium

1 H 2 HeLithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

3 Li 4 Be 5 B 6 C 7 N 8 O 9 F 10 NeSodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon

11 Na 12Mg 13 Al 14 Si 15 P 16 S 17 Cl 18 ArPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

19 K 20 Ca 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 KrRubidium Strontium Yttrium Zirconium Niobium MolybdnumTechnetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 Te 53 I 54 XeCaesium Barium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

55 Cs 56 Ba 71 Lu 72 Hf 73 Ta 74 W 75 Re 76 Os 77 Ir 78 Pt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 RnFrancium Radium LawrenciumRutherfordiumDubnium Seaborgium Bohrium Hassium Meitnerium

87 Fr 88 Ra 103 Lr 104 Rf 105 Db 106 Sg 107 Bh 108 Hs 109 Mt

The periodic table of the elementsⅧB

Ellingham diagram of oxides

→ This can be used as a feed preform for

reduction experiment.

V metal・・・

Crustal abundance (ppm) 　　Element

> 105 　 O, Si

Al, Fe, Ca, Na, K, Mg

Ti, H, P

　 V, Mn, S, C, Cl,　　 　・・・ Cu, Ni, Zn, Nb, Co, Pb,　 　 　 　・・・

　 Hg, Ag, Pd, Se　 　　 Pt, Au, Rh,　・・・

105 ～ 104

104 ～ 103

103 ～ 102

10-1 ～ 10-2

102 ～ 101

10-2 ～ 10-3

・・・

15 ～ 25 mass% Al

Feature of vanadium

　・ Low density(6.11 g/cm3) and high melting point (2188 K).

　・ The 20th largest crustal abundances among the all

elements . 　

　・ Average abundance of vanadium in the earth’s crust;

120ppm. (cf. Common (or base) metals such as

Ni: 84ppm, Cu: 60ppm, Zn: 70ppm, Pb: 14ppm).

Table Abundance of elements in the earth’s crust.

Total6.42×103 t (pure V)

Steel

86.0%

Catalyst

12.9 %

Others1.1 %Amount of production Price

(103 ton / year) ($ ・ kg-1)

V 58 39

Fe 1,100,000 0.06

Al 29,000 3

Cu 15,000 7

Ni 1,600 40

Zn 11,000 3

Element

Table Amount of production and price of some metal elements in 2007.

Vanadium production

in Japan

China

31.1 %

South Africa

39.1 %

Russia

26.8 %

Other3.0 %

Total56.3×103 t(pure V)

China

38.3 %

South Africa

23.0 %

Russia

38.3 %

Other0.4 %

Total13.0×106 t (pure V)

China

20.1 %

South Africa

43.9 %

Russia

14.9 %

U.S.A

12.4 %

Japan

2.0 %

Other6.7 %

Total46.0×103 t (pure V)

China

15.2 %

South Africa30.5 %

Australia

14.2 %

Other

40.1 %

Total36.6×103 t (pure V)

Ores productionConfirmed reserve

V2O5 production Fe-V production

Tcal. = 873 K → 1173 Ktcal. = 2 hr

50 %

CH3COOH aq.,

Acetone

20 30 40 50 60 70 80

Angle, 2θ (degree)

MgO JCPDS # 77-2364

Inte

nsity

, I

(a.u

.)

Mg2V2O7 JCPDS # 70-1163

Ca2V2O7 JCPDS # 72-2312

CaO JCPDS # 77-2010

20 40 60 80Angle, 2θ (degree)

V

MgO

Mg2V2O7

(1) After calcination

(2) After reduction

(3) After leaching

Inte

nsity

, I (

a.u.

)

ex.1 Flux : CaO, Reductant : Ca

Inte

nsity

, I (

a.u.

)

Ca2V2O7

CaO

(1) After calcination

(2) After reduction

(3) After leaching

CaV2O4

20 40 60 80Angle, 2θ (degree)

ex.4 Flux : MgO, Reductant : Mg

X-ray fluorescence spectrometry

Table Analytical results of vanadium powder obtained by PRP.

Table Experimental condition and mass of samples after each step.

aDetermined by XRF ; value excludes carbon and gaseous elements.

Condition for reduction

・ Temperature :1273 K, Time : 6 hr

・ When using Mg vapor as a reductant, pure vanadium metal was obtained. The purity of the obtained vanadium powder was 99.7 mass%.

・ When using Ca vapor as a reductant, Ca2V2O7 in

thepreform was reduced to CaV2O4 after reduction. At this stage, vanadium metal was not obtained.

The reason for incomplete reduction when using Ca vapor is not well understood. The difference of the results between Mg and Ca reductant is partially due to the difference of their vapor pressure. The vapor pressure of Mg (0.458 atm) is 26 times larger than Ca (0.018 atm) at 1273 K.

ex.1

Mass of sample

after leaching,

w3 / g

Mass of sample

after reduction,

w2 / g

Mass of reductant,

wR / g

Ca

Mg

ex.2

ex.3

3.642

5.086

3.976

3.345

4.906

2.573

3.955

4.435

1.805

0.729

0.981

1.071

Reductant

Ca

Mg

Ca

Mg

Flux

CaO

MgO

MgO

CaO

Ex. #

Mass of preform,

wpre / g

V2O5 + 3CaO

V2O5 + 3MgO

4.537

4.158

4.226

4.478

Mass of sample

after calcination,

w1 / g

3.474

3.937

3.670

3.604

V Ca Mg

79.0 20.4 －

99.7

86.0 2.4 10.6

85.4 13.0

0.2

Ex. #Composition of sample (mass%)

ex.1

－ex.4

ex.3

ex.2

Reductant

Ca

Mg

Ca

Mg

Flux

CaO

MgO

MgO

CaO

Fe Cr

0.1 0.4

0.50.3

0.5

0.01 0.03

－

0.2

ex.4