Current Research Activities on the Titanium Reduction ... Institute of Industrial Science The...

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Institute of Industrial Science The University of Tokyo

Current Research Activitieson the

Titanium Reduction Process in Japan

Toru H. Okabe


Euchem 2002, Sept. 2, Oxford

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Ornate table centerpiece crafted for Napoleon III in 1858.Aluminum was seen as a precious metal, worthy of an emperor. (Carnegie Museum of Art, Pittsburgh, Pennsylvania, cover page of JOM, Nov. 2000)

Innovation Changes Rare Metal to Common Metal


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1 8O 49.502 14Si 25.803 13Al 7.564 26Fe 4.705 20Ca 3.396 11Na 2.637 19K 2.408 12Mg 1.939 1H 0.8710 22Ti 0.4611 17Cl 0.1912 25Mn 0.0913 15P 0.0814 6C 0.0815 16S 0.0316 7N 0.0317 9F 0.0318 39Rb 0.0319 56Ba 0.0220 40Zr 0.0221 24Cr 0.0222 38Sr 0.0223 23V 0.0224 28Ni 0.0125 29Cu 0.0126 74W 6×10-3

27 3Li 6×10-3

28 58Ce 4.5×10-3

29 27Co 4×10-3

30 50Sn 4×10-3

Rank Element Clark #.

Titanium is the 10th most abundant element in the earth’s crust

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1791First discovered by William Gregor, a clergyman and amateur geologist in Cornwall, England 1795Klaproth, a German chemist, gave the name titanium to an element re-discovered in Rutile ore. 1887Nilson and Pettersson produced metallic titanium containing large amounts of impurities1910M. A. Hunter produced titanium with 99.9% purity by the sodiothermic reduction of TiCl4 in a steel vessel.(119 years after the discovery of the element)

1946W. Kroll developed a commercial process for the production of titanium: Magnesiothermic reduction of TiCl4...

History of Titanium

Titanium was not purified until 1910, and was not produced commercially until the early 1950s.

5


Annual production of Ti Sponge

117,500 ton(2001)

Production capacity

Japan has about 40 ％％％％ of the market share

sponge

Japan

USA

Russia

China

65,000 ton (2001)

Kazakhstan

Japan

USA

Russia

China

Kazakhstan

Capacity

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Production volume of titanium mill products in Japan

0

2000

4000

6000

8000

10000

12000

14000

16000

6364

6566

6768

6970

7172

7374

7576

7778

7980

8182

8384

8586

8788

8990

9192

9394

9596

9798

9900

01

14,700 ton　　（　　（　　（　　（2001））））

(ton)

The Japanese titanium industry is expanding rapidly

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Export 58%

Aircraft 7%

Architecture/ Civil and ocean engineering

5%

General products 3%

Automobile 4%plant 6%

USA21,600 t

Industry 25%

Others 11%

Military aircraft 14%

Application of titanium mill products:in US (1999) and Japan (2001)

Commercial aircraft

50%

Japan14,434 t

Medical treatment 7%

Electric power

Chemical industry 10%

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Mg & TiCl4 feed port

Fig. Reactor for reducing titanium by the Kroll process.

TiCl4 + 2 Mg → Ti + MgCl2

The Kroll Process

Huge exothermic reaction:→It requires several days to produce

titanium in large (ton) scale

Mg & MgCl2 recovery port

Metallic reaction vessel

MgCl2 recovery port

Sponge titanium

Ti / Mg / MgCl2 mixtureFurnace

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Flowchart of titanium production by the Kroll process.

Ti feed (TiO2)

Crude TiCl4

Pure TiCl4

Sponge Ti + MgCl2 + Mg

Sponge Ti

Ti Ingot

Reductant (C)

CO2

MgCl2 + Mg

Chlorine (Cl2)

FeClx, AlCl3・・・

Other compounds

MgCl2

Chlorination

Distillation

Reduction

Vacuum distillation

Crushing / Melting

Electrolysis

H2S etc.

Mg

The Kroll Process

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TiO2 + C + 2 Cl2→ TiCl4 + CO2

MgCl2→ Mg + Cl2

Chlorination

Reduction

Electrolysis

TiO2 + C → Ti + CO2

Overall reaction


(TiCl4, Mg, MgCl2,…)

The Kroll Process

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Representative analytical result of sponge titanium

Titanium sponge containslarge amounts of oxygen

→ Amount of oxygen increases in the following processes

Commercial product contains500～1000 mass ppm O

Fe Ni Cr Al Mn O N C

17 3 <1 2 <1 290 20 50

Impurity concentration (mass ppm)

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Past Research Activitieson the



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Thermocouple

Ceramic pipe

Fused CaCl２２２２bath

TiO2 powder

Electric furnace

Alumina crucible

Graphite crucible ( anode )

Anode lead wire ( W )

Cathode (stainless steel )

Alumina pipe

T. Oki, and H. Inoue: “Reduction of Titanium Dioxide by Calcium in Hot Cathode Spot”, Mem. Fac. Eng., Nagoya Univ., 19, (1967) 164-166.

Electrochemical reduction of TiO2 in CaCl2

TiO2 (CaCl2) + 4 e-→ Ti + 2 O2- (CaCl2)

Obtained titanium was heavily contaminated

Oki and Inoue, 1967

or + 2 Ca + 2 CaO

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Calciothermic reduction TiO2

TiO2 + 2 Ca → Ti + CaO

Obtained titanium was contaminated;mainly with oxygen

(molten salt)

Production of highly pure Ti directly from oxide was considered impossible

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O (in Ti) + Ca → CaO (in CaCl2)

Developed an oxygen removal technique which utilizes CaCl2molten salt to remove oxygen directly from titanium metal with less than 100 mass ppm O

Possibility of a new titanium refining process was demonstrated

T. H. Okabe, T. Oishi, and K. Ono: 'Preparation and Characterization of Extra-Low-Oxygen Titanium',

J. Alloys and Compounds, 184 (1992) pp.43-56.

Calcium-halide flux deoxidation method

Okabe et al., 1992

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(b) Deoxidation by Metal / Metal Oxide Equilibrium

(c) Calcium-Halide Flux Deoxidation

(d) Electrochemical Deoxidation

R

O Metal

RO x

(R=Ca, Y, Er...)

Ca

CaO (in halide flux, aCaO <<1)

e-

O2- (in molten salt)

(e) Deoxidation by Oxyhalide Formation

R, RCl x

ROCl (in molten salt)

(a) Solid State Electrotransport (SSE)

O Metal

e-

O Metal

O Metal

O Metal

Fig. Principles of some solid state purification methods which are capable of reducing oxygen in reactive metals down to ppm level.

Various deoxidation processes

'Removal of Oxygen in Reactive Metals', T. H. Okabe, K. T. Jacob and Y. Waseda: in "Purification Process and Characterization of Ultra High Purity Metals" edited by Y. Waseda and M. Isshiki, Springer, Berlin (2001) pp.3-37.

1990s

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+

Cl2

Cl-

Cl-

COx

CaCl2

O2-

Ca2+

O2-

Ca

CaCa2+

[O]in TiTi

C

e-

-

e-

TiO2

+

-

Ca[O] O2-

Molten salt

Carbon anode Titanium cathode

[O] in Ti + Cain flux= O2-in flux + Ca2+

in flux

Ca2+in flux + 2e- = Ca (on Ti cathode →in flux)

[O]in Ti + 2e- = O2-

O2-in flux+ C(carbon anode) = CO (gas)↑ + 2e-

+)

Electrochemical deoxidation method was demonstrated to be effective for removing oxygen directly from titanium-oxygen system.

Electrochemical deoxidation methodOkabe et al., 1993

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O (in Ti) + 2 e-→ O2- (in CaCl2)

Direct removal of oxygen from titanium with below 10 mass ppm becomes possible by this electrochemical method

'Electrochemical Deoxidation of Titanium', T. H. Okabe, M. Nakamura, T. Oishi, and K. Ono: Met. Trans. B, vol.24B, June (1993) pp.449-455.

Electrochemical deoxidation method

Okabe et al., 1993

C + x O2-(in CaCl2)→ COx + 2x e-Anodic reaction (Oxidation)

Cathodic reaction (Reduction)

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Current Research Activitieson the



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Nature, vol. 407, no. 21, September (2000) p.361.


FFC Cambridge ProcessChen et al., 2000

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Titanium ore

Chlorination orsulfate method

Titanium oxide

Mixing withBinder

Cathodeformation

Calcination

Titanium reduction by FFC process

Recovery oftitanium electrode

Crushingand leaching

FFC titanium

AnodeCathode

Molten saltTiO2

(TiO2 electrode)

TiO2 CCOx


Chen et al., 2000

TiO2 + 4 e- → Ti + 2 O2-

CaCl2

FFC Cambridge Process

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TiO2 + 4 e- → Ti + 2 O2-

Direct electrochemical reduction of TiO2, and simultaneous deoxidation of obtained titanium

CaCl2

C + 2 O2- → CO2 + 4 e-

Cathodic reaction (Reduction/Deoxidation)

Anodic reaction (Oxidation)

CaCl2

2 O2- → O2 + 4 e-


Chen et al., 2000



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Scanning Electron Micrograph of metallised titanium dioxide.The oxygen has been stripped out leaving titanium metal sponge. The structure is typical of materials produced by electrolysis. Total original width of the picture is 50 microns.

http://www.britishtitanium.co.uk/Euchem 2002, Sept. 2, Oxford

Chen et al., 2000


Pure titanium Pure titanium was producedwas produceddirectly from TiOdirectly from TiO22


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The extensive research work by Fray and co-workers on the direct electrochemical reduction of titanium dioxide (TiO2) to titanium in molten calcium chloride (CaCl2) has inspired not only Japanese research activity but has also stimulated the Japanese government and the titanium industry

Impact on the Japanese titanium society

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1) 小野勝敏、鈴木亮輔：まてりあ 41[1](2002) 2) K.Ono and R.O. Suzuki ：JOM, Feb. (2002).3) (CaCl2+CaO)溶融塩電解による酸化チタンの還元と新製錬法

鈴木亮輔、寺沼考、井上修一、福井慎次、小野勝敏、日本鉄鋼協会春季大会概要（2002）

OS Process (Kyoto Univ. Process)Ono & Suzuki, 2002

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1) 小野勝敏、鈴木亮輔：まてりあ 41[1](2002) 2) K.Ono and R.O. Suzuki ：JOM, Feb. (2002).3) (CaCl2+CaO)溶融塩電解による酸化チタンの還元と新製錬法

鈴木亮輔、寺沼考、井上修一、福井慎次、小野勝敏、日本鉄鋼協会春季大会概要（2002）

Ono & Suzuki, 2002

C + x O2- → COx + 2x e-Anode:

TiO2 + 2 Ca→ Ti + 2 O2- + Ca2+

Cathode: Ca2+ + 2 e-→ CaElectrolysis

(a)

(b)(c)

TiO2 powder

CaCl2molten salt

Carbon anode

Ca

Calciothermic reduction of TiO2

OS Process (Kyoto Univ. Process)

e-

27Fig. 4 Comparison of various reduction processes of

titanium oxide in molten calcium chloride medium.

(a) FFC processe-

CaCl2molten salt

TiO2 preform

(b) OS processe-TiO2 powder

CaCl2molten salt

Carbon anode

Carbon anode

Ca


Oxide reduction cellChen et al., 2000

Ono & Suzuki, 2002

Ono & Suzuki are currently developing a commercial process with an aluminum smelting companyin Japan.

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Pow

er

sourc

e

Electrode holder

Graphite electrode

Water cooled mold

Molten salt

Molten metal pool

Casted titnaium ingot

Takenaka et al., 1999

T. Takenaka, T. Suzuki, M. Ishikawa, E. Fukasawa, M. Kawakami: ‘New Concept for Electrowinning Process of Liquid Titanium Metal in Molten Salt’, Electrochemistry (The Electrochemical Society of Japan) 67, (1999) pp.661-668.

DC-ESR process

TiO2 + 4 e- → Ti + 2 O2-

Molten salt

Solidified titanium ingot

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Takenaka et al., 1999

T. Takenaka, T. Suzuki, M. Ishikawa, E. Fukasawa, M. Kawakami: ‘New Concept for Electrowinning Process of Liquid Titanium Metal in Molten Salt’, Electrochemistry (The Electrochemical Society of Japan) 67, (1999) pp.661-668.

DC-ESR process

Ti4+ + 4 e- → Ti (l) + 2 O2-

Molten salt

e-

TiO2 powder

Liquid titanium

Carbon anode

Solidified titanium ingot

Molten salt( CaO-CaF2-TiO2)

Analytical result of the obtained　titanium by electro slag remelting process

Analytical Method Elements (at%)Ti Cu Si Al O C

EPMA 95.0 n.d. 2.3 2.8 n.d. n.d.Chemical analysis bal. 0.10 0.57 0.80 4.0 0.8

Current efficiency: max. 18 %

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Application of Electrochemical Methods

to Metallothermic Reduction

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FeedTiO2 Ca

Reductant

Ti

CaOO-2-

Tie-

e-

Ca+

Metal deposit

Molten salt


TiO2

Ca

Reductant

Feed material Reaction product

Metal deposit

Ti

CaO

Electronically Mediated Reaction (EMR)Okabe & Sadoway, 1997

'Metallothermic Reduction as an Electronically Mediated Reaction', T. H. Okabe and D. R. Sadoway: J. Materials Research, vol.13, no.12 (1998) pp.3372-3377.

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'Direct Evidence of Electronically Mediated Reaction during TiCl4Reduction by Magnesium', T. Uda, T. H. Okabe, E. Kasai, and Y. Waseda: J. Japan Inst. Metals, vol.61, no.7 (1997) pp.602-609.

Uda et al., 1997

TiCl4 + 4 e-→ Ti + 4 Cl-

Anode: 2 Mg → 2 Mg2+ + 4 e-

(a)

(b)

e-

TiCl4 feed

Molten salt(e.g. MgCl2)

Mg-X (X = Al, Ni, Ag) liquid alloy

Electrochemical reduction of TiCl4 in molten salt

molten salt

A

e-

Electronically Mediated Reaction (EMR)

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Reduction TiCl4 + 2 Mg → Ti + MgCl2

Kroll Process (Kroll, 1945)

2 Mg → 2 Mg2- + 4 e-Anode:

Cathode: TiCl4 + 4 e-→ Ti + 4 Cl-

EMR Process (Okabe & Sadoway, 1997Uda et al.,1997)

Application of electrochemical reactions during metallothermic reductionReduction

(1)

(2)

(3)

Fig. Reactions of the Kroll process, and electrochemicalreactions during metallothermic reduction.



Electronically Mediated Reaction (EMR)

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Reduction of oxide in molten CaCl2Okabe et al., 1999

'Production of Niobium Powder by Electronically Mediated Reaction (EMR)Using Calcium as a Reductant',

T. H. Okabe, Il Park, K. T. Jacob, and Yoshio Waseda.: J. Alloys and Compounds, vol.288 (1999) pp.200-210.

Nb2O5 + 10 e-→ 2 Nb + 5 O2-

Anode: 5 Ca (Ca-X alloy)→ 5 Ca2+ + 10 e-

(a)

(b)

e-Nb2O5 powder

CaCl2molten salt

Ca-X (X = Al, Ni, Ag) liquid alloy

Electrochemical reduction of Nb2O5 in CaCl2

CaCl2

A

e-

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(a) Conventional representation of metallothermic reduction

(b) Electronically mediated reaction

(c) Reduction by using Rm+/R(m+1)+ redox couple

(d) Reduction by using electronically conductive molten salt

TiCl4

Ti

2 Mg

2 MgCl2

Physical contact

TiCl4

Ti

4 e-

4 Cl-

Metal

Moltensalt

4 e-

2 Mg2+

2 Mg

Tin+

Ti

n Rm+

n R(m+1)

Molten saltcontainingRm+, R(m+1)+

n/2 Mg

n/2 Mg2+

TiCln

Ti

n e-

n Cl-

Electronicallyconductivemolten salt

n e-

n Na+

n Na

Various types of EMR

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Potential forMetallic titanium production

Potential region forreaction mediator salt

which has reducing ability

Reduction potential

E (v.s. Mg / Mg2+) / V

Tin+

Ti

n Dy2+

n Dy3+

n2 Mg

n2 Mg2+

(b)

(a)

Ti3+ / Ti4+

Ti2+ / Ti3+

Ti / Ti2+

Dy2+ / Dy3+

Mg / Mg2+

Dy / Dy2+ -0.36

0

0.50

0.67

0.930.98

Halidothermic reductionUda et al., 1998

'ハライド熱還元法による粉末チタンの製造', 宇田哲也、岡部徹、早稲田嘉夫: 日本金属学会誌, vol.62, no.9 (1998) pp.796-802.

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Ti (Ti (Ti (Ti (s))))

DyDyDyDy2+2+2+2+

DyDyDyDy3+3+3+3+ n/2 Mgn/2 Mgn/2 Mgn/2 Mg2+2+2+2+

n/2 Mg (n/2 Mg (n/2 Mg (n/2 Mg (l))))TiTiTiTin+n+n+n+

Effective titanium powder production process which utilizes reaction mediator with reducing ability

mediator


Uda et al., 1998

Halidothermic reduction

Homogeneous reduction takes place which is suitable for fast reaction

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Reduction cell(Titanium reduction by EMR)

Molten Salt Electrolysis cell(Production of reductant)

Application of EMR to titanium reduction.Cell for magnesium reductant (1)

Electrolysis cell Molten salt

Current / potential controller

Anode carbon

CathodeReduction housing(Feed material electrode)

Reductant Separator

Seal wallFeed tube / electrode

Gas recovery chamber

DC power source

Cooling chamber


Titanium feed

Magnesiothermic Reduction by EMR+MSE

e-e- e-

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Application of EMR to titanium reduction.Cell for calcium reductant (2)

Current / potential controller

Anode carbon

Reduction housing(Feed material electrode)

Reductant alloy Separator

Seal wall

Gas recovery chamber

DC power source

Cooling chamber

Reduction cell(Titanium reduction by EMR)

Molten Salt Electrolysis cell(Production of reductant)

Titanium feed

Feed tube / electrode

Molten salt


Calciothermic Reduction by EMR + MSE

e-e- e-

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TiO2 + C → Ti + CO2

Over all reaction


Cathode: TiO2 + 4 e-→ Ti + 2 O2-

FFC Process (Fray et al., 2000)


TiO2 + 2 Ca→ Ti + 2 O2- + Ca2+OS Process (Ono & Suzuki, 2002)

Cathode: Ca2+ + 2 e-→ Ca

Ca → Ca2+ + 2 e-Anode:

Cathode: TiO2 + 4 e-→ Ti + 2 O2-

EMR / MSE Process (Okabe, 2002)

C + x O2- → COx + 2x e-

Ca2+ + 2 e-→ Ca Cathode:Anode:

Electrolysis

Electrolysis

Electrolysis

(3a)(3b)

(4a)

(4b)(4c)

(5d)

(5a)

(5b)

(5c)

(6)

Various types of reactions during the currently investigated direct reduction process of titanium oxides.

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Fig. Comparison of various reduction processes of titanium oxide in molten calcium chloride medium.

(a) FFC processe-

CaCl2molten salt

TiO2 preform

(b) OS process

e- Carbon anode

CaCl2 molten saltTiO2

(c) EMR / MSE process (Oxide system)

e-TiO2 powder

e-

Current monitor / controller

Ca-X alloy

CaCl2molten salt

Carbon anode

Carbon anode

Ca


Various types of oxide reduction cells are currently under investigation

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FFC Process

OS Process

EMR / MSE Process

Kroll Process◎◎◎◎High purity titanium available◎◎◎◎Easy metal / salt separation○Established chlorine circulation○Utilizes efficient Mg electrolysis○Reduction and electrolysis operation　

can be carried out independently

×Complicated process××××Slow production speed××××Batch type process

×Difficult metal / salt separation ×Reduction and electrolysis have

to be carried out simultaneously△△△△Sensitive to carbon and iron

contamination△Low current efficiency

◎◎◎◎Simple process○Semi-continuous process

×Difficult metal / salt separation△△△△Sensitive to carbon and iron

contamination△Low current efficiency

◎Resistant to iron and carbon contamination

○Semi-continuous process ○Reduction and electrolysis

operation can be carried out independently

×Difficult metal / salt separationwhen oxide system

××××Complicated cell structure△Complicated process

◎◎◎◎Simple process○Semi-continuous process

Features of various reduction processes.

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Stainless protection tube

Molten salt and

molten metal mixture

TiClTiClTiClTiCl 4444 + Ar + Ar + Ar + Ar

Flat blade mixer

Thermocouple

Magnesium metal

Power supply for electrochemical

potent ial control

Deposit scraper

/ Potential lead

Carbon injection nozzle

Gas outlet

Gas inlet

V

Example of an electrochemical method for preventing feed tube clogging bytitanium deposition.

Application of EMR

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Ultra-high speed reduction by utilizingreaction mediator

TiCl 4

EEEE

（第2章）

TiCl 4

（第3章）

TiCl 4(s)

（第4章）

(a) (b) (c)

Reaction mediator salt

Stirrer Well typemixer

'Reduction of TiCl4 in Molten Salt/Liquid Metal Mixtures', N. Michishita, T. H. Okabe, N. Sakai, J. Tanaka, K. Nikami, and Y. Umetsu: J. Japan Inst. Metals, vol.64, no.10 (2000) pp.940-947. 'New Titanium Production Process with Molten Salt Mediator',J. Tanaka, T. H. Okabe, N. Sakai, T. Fujitani, K. Takahashi, N. Michishita, Y. Umetsu, and K. Nikami:J. Japan Inst. Metals, vol.65, no.8 (2001) pp.659-667.

Michishita et al., 2000

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Molten salt and

molten metal mixture

TiCl4 (s)

Thermocouple

Iron crucible

Stainless steel

reaction tube

Ar gas Ar gas

Well type m ixer

Apparatus for high speed reduction byinjecting solid TiCl4 directly into reaction mediator

Euchem 2002, Sept. 2, Oxford Euchem 2002, Sept. 2, Oxford

'Reduction of TiCl4 in Molten Salt/Liquid Metal Mixtures', N. Michishita, T. H. Okabe, N. Sakai, J. Tanaka, K. Nikami, and Y. Umetsu: J. Japan Inst. Metals, vol.64, no.10 (2000) pp.940-947.

Ultra-high speed reduction by utilizingreaction mediator Michishita et al., 2000

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Key factors for the development of anew titanium reduction process

Low cost reduction process

Continuous /high speed system

Morphology &reaction sitecontrol

Impurity control

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Can Ti be a common metal ?

(Carnegie Museum of Art, Pittsburgh, Pennsylvania, cover page of JOM, Nov. 2000)

Innovation Changes Rare Metal to Common Metal


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Titanium Aluminum Iron

Ti Al FeMelting point 1660 1660 1660 1660 ℃℃℃℃ 660 660 660 660 ℃℃℃℃ 1540 1540 1540 1540 ℃℃℃℃

Density (g/cc @25℃℃℃℃) 4.54.54.54.5 2.72.72.72.7 7.97.97.97.9

Specific strength((kgf/mm2)/(g/cc))

8888～～～～10101010 3333～～～～6666 4444～～～～7777

Price (¥/kg) 3,0003,0003,0003,000 600600600600 50505050

100,000100,000100,000100,000 20,000,00020,000,00020,000,00020,000,000 800,000,000800,000,000800,000,000800,000,000

Symbol

Production volume

1/2001/2001/2001/200

1/80001/80001/80001/8000


Comparison with common metals

(t/year・・・・world)

49

Less common metal～～～～104 ton / year

Common metal～～～～106 ton / year

Incubation of key technology

Large scale / energy saving/ environmentally soundtechnology

New process development


Innovation Changes the Future of Titanium

(Carnegie Museum of Art, Pittsburgh, Pennsylvania., cover page of JOM, 1999)

Current Research Activities on the Titanium Reduction ... Institute of Industrial Science The...

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