1 資源･素材 2005( 室蘭 ); september 25, 2005 電気化学的な手法を用いた...

1資源･素材 2005( 室蘭 ); September 25, 2005

電気化学的な手法を用いたチタン鉱石からの脱鉄

尾花勲 1 ・岡部徹 2

1 東京大学大学院工学系研究科1 Graduate School of Engineering,

The University of Tokyo

Iron removal from titanium oreby electrochemical method

Isao Obana1, Toru. H. Okabe2

2 東京大学生産技術研究所2 Institute of Industrial Science,

The University of Tokyo


AircraftSpacecraftChemical plantImplantArtificial bone

etc.

ApplicationLightweightand high-strengthCorrosion resistantBiocompatibilitySome titanium alloys ： shape-memory effect super elasticity

Feature of titanium

Introduction

Ti ore + C + 2 Cl2 → TiCl4 (+ FeClx) + CO2

Chlorination

TiCl4 + 2 MgReduction

MgCl2

Electrolysis

The Kroll process: Current Ti production process

Mg & TiCl4 feed port

Sponge titanium

→ Ti + 2 MgCl2

→ Mg + Cl2

Reaction container

MgCl2


(CaCl2)

Ti ore (Ilmenite, FeTiOx) Upgraded Ilmenite (UGI)

TiOx

FeOx Others

TiOxFeOx

Others UpgradeChloridewastes

Discarded

Upgrading of Ti ore

Ti metal

Ti smelting

This studyLow grade Ti ore

Upgraded Ti ore FeClx(+AlCl3)

(FeTiOX)

(TiO2)

MClx

Chlorine recoverySelective chlorination

Fe

FeClx

TiCl4

Ti scrap

Advantages:1. Material cost can be reduced

by using low grade ore.

2. Chlorine circulation in the Kroll process can be improved.

3. This process can also be applied tothe new Ti production processes, e.g. ,the direct electrochemical reduction of TiO2.


Previous study

Ref. R. Matsuoka and T. H. Okabe: 　 Symposium on Metallurgical　　　 Technology for Waste Minimization at the 2005　　　 TMS Annual Meeting, [San Francisco, California] (2005.2.13-17).

FeOx (s, in Ore) + MgCl2 (s, l )

　　 → FeClx (l, g) + MgO (s)

CaCl2 (s, l) + H2O (g)

→ HCl (g) + CaO (s)

FeOx (in Ore) + HCl (g)

　　　　　　→ FeClx (l, g) + H2O (g)

The selective-chlorination of Ti ore by MgCl2 or CaCl2 is found to be feasible.

Susceptor

RF coil

Vacuum pump

Quartz flange

Deposit

Mixture ofTi oreand MClx

N2 or N2+H2O gas

Pyrometallurgical de-Fe process

Condenser

(FeClx)

T = 973 ~ 1373 K


Objective

Application of electrochemical method

Ti powder

Reduction

Low grade Ti ore

TiO2 + flux

(FeTiOx)

Iron removal byselective chlorination

1. Thermodynamic analysis of selective chlorination

2. Fundamental experiments of selective chlorination by electrochemical methods

Electrochemical reduction・・・・・or

Calciothermic reduction


TiCl4 (g)

TiCl3 (s)

-40

-10

-30

-20

-50

-60

0

-40 -10-30 -20 0

CaO (s) / CaCl2 (l) eq.aCaO = 0.1

Fig. Chemical potential diagram for Fe-Cl-O　　　 and Ti-Cl-O system at 1100 K.

Fe-Cl-O and Ti-Cl-O system, T = 1100 KPotential regionfor selective 　chlorination of iron from titanium ore

Potential region for chlorinationOf titanium

Oxy

gen

part

ial p

ress

ure,

lo

g p

O2 (

atm

)

Chlorine partial pressure, log pCl2 (atm)

C / CO eq.CO / CO2 eq.

The selective-chlorination of Ti ore by controlling chlorine partial pressuremight be possibleusing an electrochemical technique.

Thermodynamic analysis (Ti ore chlorination)

Ti ore : mixture of TiOx and FeOx.

H2O (g) / HCl (g) eq.

MgO (g) / MgCl2 (l) eq.

TiCl2 (s)

FeO (s)

Fe2O3 (s)

FeCl2 (l)

Fe3O4 (s)

FeCl3 (g)Fe (s)

TiO (s)

TiO2 (s)

Ti (s)


2 Cl- (in CaCl2) → Cl2 + 2 e-Anode:

Chlorine chemical potentialat anode in molten CaCl2

can be increased electrochemically.

Cathode ：Ca2+ + 2 e- → Ca

Electrolysis

Fen+ + n e- → Fe

FeOx + Cl2 → FeClX↑ + O2-

Refining process using FeClx

e-

Molten salt (CaCl2, MgCl2, etc.)

DC power source

Ti ore or upgraded Ti ore(e.g. FeTiOx)

FeCl ３ , AlCl ３ , O2, CO2 gas


Experimental apparatus

Electrochemicalinterface

Reaction chamber

Fig. Schematic illustration of experimental apparatus in this experiment.

Ceramic insulator

Thermocouple

Heater

Rubber plug

Ar inlet

Wheel flange

Stainless steel tube (Electrode)

Molten salt (CaCl2)

Potential lead (Ni wire)

Nickel electrode

Mild steel crucible (Cathode)

V1V2

A1A2

Carbon crucible (Anode)

Ti ore

10 APowerSource

Electrochemicalcontrol unit

100 mm


Experimental condition ：Temp.: 1100 KAtmosphere: ArMolten salt: CaCl2 (800 g)Cathode: Mild steel crucible (O.D 102 mm)Anode: Carbon crucible (O.D 19 mm)

Experiment 1

Sample

Molten CaCl2


Carbon cruciblecontaining Ti ore (Anode)

e- Voltage monitor / controller

Mass of Ti ore(Ilmenite), w / g

Exp. A 4.00

Exp. B 4.00

4.00Exp. C

Voltage,E / V

Time,t’ / h

2.5

2.0

1.5

6

3

12


Result 1

XRF analysis

After the electrochemical treatment, Fe was selectivelychlorinated and removed.

Table Analytical results of titanium ore (starting sample) and the sample obtained after electrochemical selective chlorination.

Concentration of element i, Ci (mass %)

VTi Fe Si Al

Ti ore (init.) 0.642.6 48.7 2.2 2.2

Exp. A 0.964.5 29.7 1.8 1.0

Fe / Ti (%)

114

49.5

To proceed iron removal reaction

Ti ore (Ilmenite, FeTiOx)

Molten CaCl2

Carbon crucible (Anode)

e-

Observed unreacted portion

Lower half of sample was unreacted.

Exp. B 1.464.3 29.4 1.3 1.4 45.6

Exp. C 3.157.1 24.7 1.6 0.9 47.4


Experiment 2

Sample

Molten CaCl2


Carbon crucible containingTi ore + CaCl2 mixture (Anode)

e- Voltage monitor / controller

Mass of element i, Ci (g)Ti ore

(Ilmenite)CaCl2

Carbonpowder

4.00 ーーーExp. C

Ti ore : CaCl2

Exp. D

Exp. E

0.74

0.74

2.17

2.17

ー0.18

Voltage,E / V

Time,t” / h

1 : 4

1 : 4

1.5

1.5

1.5

12

3

3

Experimental condition ：Temp.: 1100 KAtmosphere: ArMolten salt: CaCl2 (800 g)Cathode: Mild steel crucible (O.D 102 mm)Anode: Carbon crucible (O.D 19 mm)


Result 2

XRF analysisIn this stage, it is successfully demonstrated that Fe / Ti ratio decreased to 7.2%.

Table Analytical results of titanium ore (starting sample) and the sample obtained after electrochemical selective chlorination.


VTi Fe Si Al

0.642.6 48.7 2.2 2.2

Fe / Ti (%)

114

94% of Fe was successfully removed.

Exp. C 3.157.1 24.7 1.6 0.9 47.4

Exp. D 0.690.8 6.5 0.0 0.1 7.2

Exp. E 0.252.9 13.1 0.6 0.3 24.7

XRD analysisIn Exp. D, the Ilmenite sample changed from FeTiO3 to CaTiO3 and TiO2 after experiment.

Fig. XRD pattern of the sample obtained after Exp. D.

10 20 30 40 50 60 70 80 90 100

Inte

nsity

, I(a

. u.)

:CaTiO3

:TiO2

Angle, 2 θ (degree)

Ti ore (init.)


FeTiO3 (s) + CaCl2 (l) → CaTiO3 (s) + FeClx (l, g)

Fe in FeTiO3 was selectively removed in carbon crucible.

2 Cl- (in CaCl2) → Cl2 + 2 e-Anode :

Cathode : Ca2+ + 2 e- → CaFen+ + n e- → Fe

Disccusion

Increase in the chlorine potential facilitates selective chlorination reaction of Ti ore.

CaTiO3 can be utilized for material ofdirect TiO2 reduction processes(e.g. FFC, OS, EMR-MSE processes).

Ae-

TiO2 Ti

e-

e- O2-

Ca-X alloy

Molten CaCl2-CaO

Carbon electrode

Ti crucible （ Cathode ）

Ti reduction Production of reductantFig. Apparatus of EMR-MSE process.


Summary and future work

Selective chlorination of Ti oreby the electrochemical methodwas investigated, and94 mass% Fe was successfullyremoved from low-grade Ti ore.

・ A more efficient process for producing Fe-free Ti ore by the electrochemical method will be investigated.

・ Behavior of chlorine during selective chlorination will be investigated.

・ Low-cost Ti production directly from low-grade Ti ore will be established.

Summary

Future work


以下　質問対策


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...Titanium was not purified until 1910,

and was not produced commercially until the early 1950s.

History of Titanium


・非常に遅い生産速度　（反応容器一基あたりの生産は～ 1 t /day ）・エネルギー大量消費プロセス

× バッチ（回分）式プロセス× 工程が複雑× 還元反応が大きな発熱反応

◎ 高純度のチタンが得られる◎ 塩素サイクルが確立している○ 効率の良いＭｇの電解を利用○Ti と MgCl2/Mg の分離が容易○ 還元と電解は同時に行う必要はない

チタンの新しい製造プロセスの開発が必要⇒

Features of the Kroll process


FFC Process (Fray et al., 2000)

C + x O2- → COx + 2x e-Anode:Cathode: TiO2 + 4 e- → Ti + 2 O2- Electrolysis

(a1)(a2)

OS Process (Ono & Suzuki, 2002)

C + x O2- → COx + 2x e-Anode:

TiO2 + 2 Ca → Ti + 2 O2- + Ca2+

Cathode: Ca2+ + 2 e- → CaElectrolysis

(b1)

(b2)(b3)

e-

CaCl2 molten salt

TiO2 preform

Carbon anode

e-

TiO2 powder

CaCl2 molten salt

Carbon anode

Ca

実用化研究中の製造法


EMR / MSE Process(Electronically Mediated Reaction / Molten Salt Electrolysis)

(a) TiO2 reduction (b) Reductant production

e-

Carbon anode

TiO2

e-

Ca-X alloy (X = Ag, Ni, Cu, ・・・ )

e-

e-

CaCl2 -CaO molten salt

Current monitor / controller

TiO2 + C → Ti + CO2

Over all reaction

(d)

Ca → Ca2+ + 2 e-Anode:

Cathode: TiO2 + 4 e- → Ti + 2 O2-

C + x O2- → COx + 2x e-Ca2+ + 2 e- → Ca Cathode:

Anode:

Electrolysis

(c4)

(c1)

(c2)

(c3)

開発中の製造法


◎ 炭素や鉄などの汚染を防止できる○ 還元と電解は同時に行う必要はない○ プロセスの連続化が可能

FFC Process

OS Process

EMR / MSE Process

× 電解と還元を同時に行う必要あり× メタルと反応浴の分離が困難△ 炭素や鉄などの汚染に敏感△ 電流効率が低い

◎ プロセスがシンプル○ プロセスの連続化が可能

× メタルと反応浴の分離が困難△ 炭素や鉄などの汚染に敏感△ 電流効率が低い

× 酸化物系の場合、メタルと反応浴の分離が困難× セルの構造が複雑△ プロセスが複雑

◎ プロセスがシンプル○ プロセスの連続化が可能

電力の安価な夜に還元剤を製造し、日中に TiO2 を還元することが可能

各直接還元プロセスの特徴


Stainless steel cover

Stainless steel plate

R reductant

Stainless steel reaction vessel

Ti sponge getter

Feed preform (MO ｘ + flux)

TIG weld

Fig. Schematic illustration of the experimental apparatus for producing titanium powder by means of the preform reduction process (PRP).

MOx + R → M + RO

1. Amount of flux (molten salt) is small.

2. Easy to prevent contamination from reaction vessel and reductant.

3. Highly scalable.

M = Nb, Ta, TiR = Mg, Ca…

Preform Reduction Process (PRP)


Reduction (in kiln)

Fe2+ / TFe = 80~95%

145C° (2.5 kg/cm2) *4 hr*2 step

(90% purity)

Ilmenite Reductant (Heavy oil etc.)

Reduced ore HCl vapor

Leached ilmenite Water Spray acid Fuel

(Synthetic rutile)95% TiO2

1% TiFe

TiO2 HCl aq.

Leaching (in digestor)

Filtration Roasting

HClSol.TiO2 Iron oxide

Calcination Absorber

HCl aq.(18~20% HCl)

Fig. Flowsheet of the Benilite process.

The Benilite process


Gas + particle Particle

Ilmenite

Gas

Reduced ilmenite

TiO2

(Synthetic rutile)TiO2 92~93%TiFe 2.0~3.5%

TiO2

TiO2

Reduction (in kiln)

Leaching

WasteMag. separator

Acid Leaching

Filtering / Drying

Screen

-1 mm+1 mm

Cyclone

Reduced ore

Coal (low ash) Air

NH4Cl

H2SO4 aq.

Air

Iron oxide + Sol.

Iron oxide Sol.

Thickener

Fig. Flowchart of the Beacher process.

(Non. mag.)

The Beacher process (WLS)


FeOx (s) + MgCl2 (l) = FeClx (l) + MgO (s)

T = 1100 K, t’ = 1 h, Atmosphere : N2,Ti ore (UGI) : 4 g, MgCl2 : 2 g

Experimental condition

Fig. Experimental apparatus for selective-chlorination of titanium ore using MgCl2 as a chlorine source.

Carbon crucible

Stainless steel susceptor

Glass beads

Stainless steel net

RF coil

Ceramic tube

Glass flange

Vacuum pump

Quartz flange

Deposit

Mixture ofTi oreand MgCl2

ChloridesCondenser

ChlorinationReactor

(FeClx ．．． )

(Fe-free Ti ore)

N2 or N2+H2O gas

Selective chlorination using MgCl2


FeOx (s) + MgCl2 (l) = FeClx (l,g) + MgO (s)

Inte

nsity

, I (

a. u

.)

10 30 40 50 60 70 8020

Fig. XRD pattern of the deposit at chlorides condenser.The sample powder was sealed in Kapton film before analysis.

XRD analysisDeposit obtained after selective-chlorination.→ FeCl2 was generated.

90 100

: FeCl2

XRF analysisResidue after selective-chlorination.→ Fe was selective chlorinated.

Angle, 2θ (deg.)

Table Analytical results of titanium ore, the residue after selective chlorination, and the sample after reduction. These values are determined by XRF analysis.


Ti ore (UGI from Ind.)

After heating sample

V

0.75

1.50

Ti

95.10

96.45

Fe

2.29

0.43

Si

0.41

0.44

Al

0.12

0.37

98.30 0.05 0.38 0.12 0.52After reduction sample

Results of previous study


Fig. Experimental apparatus for chlorination of titanium using FeCl2 as a chlorine source.

Heater

Quartz tube

Sample deposits(on Si rubber, NaOH gas trap and quartz tube)

Carbon crucible

Sample mixture:(e.g., FeCl2+Ti powder)

Ti (s) + 2 FeCl2 (s) = TiCl4 (g) + 2 Fe (s)

XRF analysis

Table Analytical results of the samples before and after heating and the sample deposited on quartz tube and Si rubber. These values are determined by XRF analysis.


Residue before heating

Residue after heating

Ti

18.4

9.8

Fe

45.3

80.1

Cl

36.2

9.0

Dep. on quartz tube after heating

Dep. on Si rubber after heating

3.5 50.4 46.1

64.9 0.9 34.1

Chlorination of Ti using FeCl2


@1100 K2CaCl2 + O2 → 2CaO ＋ 2Cl2

2MgCl2 + O2 → 2MgO ＋ 2Cl2

4HCl + O2 → 2H2O ＋ 2Cl2

2CO + O2 → 2CO2

FeO + MgCl2 → FeCl2 + MgO

2C + O2 → 2CO

log pCl22 　 / 　 pO2

= -

8.29

log pO2 = -17.74

log pO2 = -19.85

e.g.

ΔG = -0.28 kJ < 0


= 1.49


=

0.48

各反応のポテンシャル


e.g.

-40

-10

-30

-20

-50

-60

0

-40 -10-30 -20 0

Fe-Cl-O system, T = 1100 K

CaO (s) / CaCl2 (l) aCaO = 0.1


Oxy

gen

part

ial p

ress

ure,

lo

g p

O2 (

atm

)


FeO (s)

Fe2O3 (s)

FeCl2 (l)

Fe3O4 (s)

FeCl3 (g)

Fig. Chemical potential diagram for Fe-Cl-O system at 1100 K.

FeOx can be chlorinated by controlling oxygen and chlorine partial pressure.


H2O (g) / HCl (g)


Fe (s)

FeOX (s) + MgCl2 (l) → FeClX (l, g)↑ + MgO (s, l)

Thermodynamic analysis (FeOx chlorination)


Fig. Chemical potential diagram for Ti-Cl-O system at 1100 K.

-40

-10

-30

-20

-50

-60

0

-40 -10-30 -20 0

TiO (s)

TiO2 (s)

TiCl4 (g)

Ti2O3 (s)

TiCl3 (s)

Ti3O5 (s)

Oxy

gen

part

ial p

ress

ure,

lo

g p

O2 (

atm

)

Ti-Cl-O system, T = 1100 K


CaO (s) / CaCl2 (l) aCaO = 0.1


Fe / FeCl2 eq.


Since TiCl4 is highly volatile species,chlorine partial pressure must be kept in the oxide stable region.

TiCl2 (s)

H2O (g) / HCl (g)


Ti4O7 (s)

Ti (s)

Thermodynamic analysis (TiOx chlorination)


Importance 1. Reduction of disposal cost of chloride wastes 2. Minimizing chlorine loss in the Kroll process 3. Improvement of environmental burden 4. Reduction of material cost using low grade ore

Upgrading Ti ore for minimizing chloride wastes

Ti ore (eg. Ilmenite) Up-graded Ilmenite (UGI)

TiOx

FeOxOthers

TiOxFeOx

Others UpgradeChloridewastes

Discarded

1. A large amount of chloride wastes (e.g., FeClx) are produced in the Kroll process.

2. Chloride waste treatment is costly, and it causes chlorine loss in the Kroll process.


Refining process using FeClx

Advantages:1. Utilizing chloride wastes from the Kroll process

2. Low cost Ti chlorination

3. Minimizing chlorine loss in the Kroll process

caused by generation of chloride wastes

Development of a new environmentally sound chloride metallurgy

Effective utilization of chloride wastes

Ti metal or TiO2 production

TiCl4 feed FeClx (+AlCl3)

Carbo-chlorination

COx

This study

Low-grade Ti ore

Upgraded Ti ore FeClx(+AlCl3)

(FeTiOX)

(TiO2)

MClX

Chlorine recoverySelective chlorination(Cl2)

Fe

FeClx

TiCl4

Ti scrap


反応媒体である CaCl2-CaO 溶融塩の電気的性質を調べることが必要

サイクリックボルタンメトリー (CV) 法を用いる

Fig. Structure of cyclic voltammetry.

V

Counter electrode(Fe or C rod)

Working electrode(Fe or C rod)

Reference electrode(Ca/Ca2+ ref.)

Electrolysis cell(Fe crucible)

Molten salt(CaCl2 (-CaO) )

A

Electrochemical Interface(Potentiostat / Galvanostat)

サイクリックボルタンメトリー (CV) 法


Iron removal process by electrochemical method

Direct reduction process from Ti oreto Ti metal can be achieved.

Establishment of a new up-grading process of Ti ore by electrochemical method.

Ae-

TiO2 Ti

e-

e- O2-

Ca-X alloy

Molten CaCl2-CaO

Carbon electrode

Ti crucible（Cathode）

Ti reduction Production of reductant

Ti ore（TiO2 + FeOｘ）

Molten CaCl2

V

Mild steel crucible（Cathode）

Carbon crucible(Anode)

A

TiFeOX

Reference electrode

e-

2. TiO2 reduction process

TiO2 + 4 e- → Ti + O2-

Ca（or Ca-X）Cathode：Anode ：

(e.g. EMR-MSE process)

→ Ca2+ + 2 e-

Selective chlorination・Iron removal process

Fen+ + n e- → Fe

2 Cl- → Cl2 + 2 e-

FeOx + Cl2

Cathode：

Anode ：Ca2+ + 2 e- → Ca

→ FeClｘ(l, g) + O


Iron removal process

Low cost Ti production and Increase new application

Available Low-grade Ti ore and Directly reduction method

Ti ore （ TiO2 + FeO ｘ）

Molten CaCl2

V

Mild steel crucible （ Cathode ）

Carbon crucible(Anode)

A

FeTiOX

Ae-

TiO2 Ti

e-

e- O2-

Reference electrode

Ca-X alloy

Molten CaCl2-CaO

Carbon electrode

e-

Ti crucible （ Cathode）

Ti reduction Production of reductant

Selective chlorination ・ Iron removal process

Fen+ 　 + 　 n e- 　 →　Fe

2 Cl- 　→　 Cl2 　 + 　2 e-FeOx + C + Cl2

Cathode ：

Anode 　：Ca2+ 　 + 　 2 e- 　 →　

Ca

→ 　 FeCl ｘ (l, g) + COx

2. TiO2 reduction process

TiO2 　 + 　 4 e- 　→　 Ti 　+ 　 O2-Ca （ or Ca-X ）

Cathode：Anode 　：

(e.g. EMR-MSE process)

→ Ca2+ 　 + 　2 e-

1 資源･素材 2005( 室蘭 ); september 25, 2005 電気化学的な手法を用いた...

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