?? ?1

1
???????????? ??????????
Iron removal from titanium oreby electrochemical
method
?? ?1?? ?2
Isao Obana1, Toru. H. Okabe2
1 ???? ????????? 1 Graduate School of
Engineering, The University of Tokyo
2 ???? ??????? 2 Institute of Industrial
Science, The University of Tokyo
2
Introduction
Application
Feature of titanium
Lightweight and high-strength Corrosion
resistant Biocompatibility Some titanium alloys
shape-memory effect super elasticity
Aircraft Spacecraft Chemical plant Implant Artific
ial bone etc.
The Kroll process Current Ti production process
Mg TiCl4 feed port
Reaction container
Sponge titanium
MgCl2
Chlorination
Ti ore C 2 Cl2 ? TiCl4 ( FeClx) CO2
Reduction
TiCl4 2 Mg
? Ti 2 MgCl2
Electrolysis
MgCl2
? Mg Cl2
3
Upgrading of Ti ore
FeOx
Others
Others
Chloride wastes
TiOx
TiOx
FeOx
Ti ore (Ilmenite, FeTiOx)
Upgraded Ilmenite (UGI)
Discarded
This study
Low grade Ti ore
MClx
Ti scrap
(CaCl2)
(FeTiOX)
Chlorine recovery
Selective chlorination
Fe
Upgraded Ti ore
FeClx
TiCl4
(AlCl3)
(TiO2)
Ti smelting
Ti metal
Advantages 1. Material cost can be reduced by
using low grade ore.
2. Chlorine circulation in the Kroll process
can be improved.

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

4
Previous study
Pyrometallurgical de-Fe process
Vacuum pump
FeOx (s, in Ore) MgCl2 (s, l ) ?
FeClx (l, g) MgO (s)
Condenser
Deposit
(FeClx)
Susceptor
CaCl2 (s, l) H2O (g) ? HCl (g) CaO (s)
Mixture of Ti ore and MClx
FeOx (in Ore) HCl (g) ? FeClx (l, g)
H2O (g)
RF coil
Quartz flange
T 973 1373 K
N2 or N2H2O gas
The selective-chlorination of Ti ore by MgCl2 or
CaCl2 is found to be feasible.
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).
5
Objective
Low grade Ti ore
(FeTiOx)
Application of electrochemical method
Iron removal by selective chlorination
TiO2 flux

Electrochemical reduction
Reduction
or
Ti powder
Calciothermic reduction
1. Thermodynamic analysis of selective
chlorination 2. Fundamental experiments of
selective chlorination by electrochemical
methods
6
Thermodynamic analysis (Ti ore chlorination)
Ti ore mixture of TiOx and FeOx.
Fe-Cl-O and Ti-Cl-O system, T 1100 K
Potential region for selective chlorination of
iron from titanium ore
Fe2O3 (s)
Fe3O4 (s)
CO / CO2 eq.
C / CO eq.
TiO2 (s)
H2O (g) / HCl (g) eq.
FeO (s)
Oxygen partial pressure, log pO2 (atm)
MgO (g) / MgCl2 (l) eq.
CaO (s) / CaCl2 (l) eq. aCaO 0.1
FeCl2 (l)
TiO (s)
Potential region for chlorination Of titanium
FeCl3 (g)
Fe (s)
TiCl4 (g)
TiCl3 (s)
Ti (s)
TiCl2 (s)
Chlorine partial pressure, log pCl2 (atm)
Fig. Chemical potential diagram for Fe-Cl-O
and Ti-Cl-O system at 1100 K.
The selective-chlorination of Ti ore by
controlling chlorine partial pressure might be
possible using an electrochemical technique.
7
Refining process using FeClx
Electrolysis
Cathode
Fen n e- ? Fe
Ca2 2 e- ? Ca
2 Cl- (in CaCl2) ? Cl2 2 e-
Anode
FeOx Cl2 ? FeClX? O2-
Chlorine chemical potential at anode in molten
CaCl2 can be increased electrochemically.
DC power source
FeCl3, AlCl3, O2, CO2 gas
e-
Ti ore or upgraded Ti ore (e.g. FeTiOx)
Molten salt (CaCl2, MgCl2, etc.)
8
Experimental apparatus
Electrochemical interface
10 A Power Source
Electrochemical control unit
Reaction chamber
100 mm
Potential lead (Ni wire)
Stainless steel tube
(Electrode)
Ar inlet
Rubber plug
Wheel flange
Thermocouple
Heater
Mild steel crucible (Cathode)
Nickel electrode
Carbon crucible (Anode)
Ti ore
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of experimental
apparatus in this experiment.
9
Experiment 1
Experimental condition Temp. 1100 K Atmosphere
Ar Molten salt CaCl2 (800 g) Cathode Mild
steel crucible (O.D 102 mm) Anode Carbon
crucible (O.D 19 mm)
Mass of Ti ore (Ilmenite), w / g
Voltage, E / V
Time, t / h
Exp. A
4.00
2.5
6
Exp. B
4.00
2.0
3
4.00
Exp. C
1.5
12
Voltage monitor / controller
e-
Mild steel crucible (Cathode)
Molten CaCl2
Sample
Carbon crucible containing Ti ore (Anode)
10
Result 1
XRF analysis
Table Analytical results of titanium ore
(starting sample) and the sample
obtained after electrochemical
selective chlorination.
Concentration of element i, Ci (mass )
V
Ti
Fe
Si
Al
Fe / Ti ()
Ti ore (init.)
0.6
42.6
48.7
2.2
2.2
114
Exp. A
0.9
64.5
29.7
1.8
1.0
49.5
Exp. B
1.4
64.3
29.4
1.3
1.4
45.6
Exp. C
3.1
57.1
24.7
1.6
0.9
47.4
After the electrochemical treatment, Fe was
selectively chlorinated and removed.
To proceed iron removal reaction
Lower half of sample was unreacted.
e-
Ti ore (Ilmenite, FeTiOx)
Carbon crucible (Anode)
Observed unreacted portion
Molten CaCl2
11
Experiment 2
Experimental condition Temp. 1100 K Atmosphere
Ar Molten salt CaCl2 (800 g) Cathode Mild
steel crucible (O.D 102 mm) Anode Carbon
crucible (O.D 19 mm)
Mass of element i, Ci (g)
Voltage, E / V
Time, t / h
Ti ore (Ilmenite)
Carbon powder
Ti ore CaCl2
CaCl2
4.00
?
?
?
Exp. C
1.5
12
Exp. D
0.74
2.17
?
1 4
1.5
3
Exp. E
0.74
2.17
0.18
1 4
1.5
3
Voltage monitor / controller
e-
Mild steel crucible (Cathode)
Molten CaCl2
Sample
Carbon crucible containing Ti ore CaCl2 mixture
(Anode)
12
Result 2
XRF analysis
In 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.
Concentration of element i, Ci (mass )
V
Ti
Fe
Si
Al
Fe / Ti ()
0.6
42.6
48.7
2.2
2.2
114
Ti ore (init.)
Exp. C
3.1
57.1
24.7
1.6
0.9
47.4
Exp. D
0.6
90.8
6.5
0.0
0.1
7.2
Exp. E
0.2
52.9
13.1
0.6
0.3
24.7
94 of Fe was successfully removed.
XRD analysis
In Exp. D, the Ilmenite sample changed from
FeTiO3 to CaTiO3 and TiO2 after experiment.
CaTiO3
TiO2
Angle, 2 ? (degree)
Fig. XRD pattern of the sample obtained after
Exp. D.
13
Disccusion
Fe in FeTiO3 was selectively removed in carbon
crucible.
Cathode
Ca2 2 e- ? Ca
Fen n e- ? Fe
2 Cl- (in CaCl2) ? Cl2 2 e-
Anode
FeTiO3 (s) CaCl2 (l) ? CaTiO3 (s) FeClx (l, g)
Increase in the chlorine potential facilitates
selective chlorination reaction of Ti ore.
Fig. Apparatus of EMR-MSE process.
CaTiO3 can be utilized for material of direct
TiO2 reduction processes (e.g. FFC, OS, EMR-MSE
processes).
14
Summary and future work
Summary
Selective chlorination of Ti ore by the
electrochemical method was investigated, and 94
mass Fe was successfully removed from low-grade
Ti ore.
Future work
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.
15
?? ????
16
History of Titanium
1791 First discovered by William Gregor, a
clergyman and amateur geologist in Cornwall,
England 1795 Klaproth, a German chemist, gave
the name titanium to an element re-discovered in
Rutile ore. 1887 Nilson and Pettersson produced
metallic titanium containing large amounts of
impurities 1910 M. 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) 1946 W. 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.
17
Features of the Kroll process
????????? ( ?????????????1 t /day
) ?????????????
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?
18
??????????
FFC Process (Fray et al., 2000)
e-
Carbon anode
TiO2 preform
CaCl2 molten salt
OS Process (Ono Suzuki, 2002)
TiO2 powder
e-
Carbon anode
Ca
CaCl2 molten salt
(b1)
TiO2 2 Ca ? Ti 2 O2- Ca2
Electrolysis
Cathode
Ca2 2 e- ? Ca
(b2)
C x O2- ? COx 2x e-
Anode
(b3)
19
EMR / MSE Process(Electronically Mediated
Reaction / Molten Salt Electrolysis)
???????
Carbon anode
Current monitor / controller
e-
e-
e-
e-
TiO2
Ca-X alloy (X Ag, Ni, Cu,)
CaCl2 -CaO molten salt
(a) TiO2 reduction
(b) Reductant production
(c1)
Cathode
TiO2 4 e- ? Ti 2 O2-
(c2)
Ca ? Ca2 2 e-
Anode
Electrolysis
Cathode
(c3)
Ca2 2 e- ? Ca
(c4)
C x O2- ? COx 2x e-
Anode
Over all reaction
(d)
TiO2 C ? Ti CO2
20
????????????
FFC Process
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????
?????????? ????????????
OS Process
????????????? ????????????? ????????
?????????? ????????????
EMR / MSE Process
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???????????????? ????????????????? ????????????
???????????????? ???TiO2 ??????????
21
Preform Reduction Process (PRP)
M Nb, Ta, Ti R Mg, Ca
MOx R ? M RO
TIG weld
Stainless steel cover
Stainless steel reaction vessel
Feed preform (MOx flux)
Stainless steel plate
R reductant
Ti sponge getter
Fig. Schematic illustration of the experimental
apparatus for producing titanium powder by means
of the preform reduction process (PRP).

1. Amount of flux (molten salt) is small.
2. Easy to prevent contamination from reaction
   vessel and reductant.
3. Highly scalable.

22
The Benilite process
Fe2 / TFe 8095
(1820 HCl)
145C (2.5 kg/cm2) 4 hr 2 step
HCl
Sol.
TiO2
Iron oxide
(90 purity)
(Synthetic rutile) 95 TiO2 1 TiFe
Fig. Flowsheet of the Benilite process.
23
The Beacher process (WLS)
Ilmenite
Air
Coal (low ash)
Reduction (in kiln)
Gas particle
Particle
Reduced ore
Cyclone
Gas
Screen
1 mm
-1 mm
Waste
Mag. separator
(Non. mag.)
Reduced ilmenite
NH4Cl
Air
Leaching
TiO2
H2SO4 aq.
Acid Leaching
TiO2
Iron oxide
Sol.
Filtering / Drying
(Synthetic rutile) TiO2 9293 TiFe 2.03.5
TiO2
Fig. Flowchart of the Beacher process.
24
Selective chlorination using MgCl2
FeOx (s) MgCl2 (l) FeClx (l) MgO (s)
Vacuum pump
Glass flange
Glass beads
Chlorides Condenser
Stainless steel net
Deposit
(FeClx...)
Stainless steel susceptor
Carbon crucible
Chlorination Reactor
Mixture of Ti ore and MgCl2
(Fe-free Ti ore)
RF coil
Quartz flange
Ceramic tube
N2 or N2H2O gas
Fig. Experimental apparatus for
selective-chlorination of titanium ore
using MgCl2 as a chlorine source.
Experimental condition
T 1100 K, t 1 h, Atmosphere N2, Ti ore
(UGI) 4 g, MgCl2 2 g
25
Results of previous study
FeOx (s) MgCl2 (l) FeClx (l,g) MgO (s)
XRD analysis
Deposit obtained after selective-chlorination. ?
FeCl2 was generated.
FeCl2
Intensity, I (a. u.)
10
30
40
50
60
70
80
20
90
100
Angle, 2? (deg.)
Fig. XRD pattern of the deposit at chlorides
condenser. The sample powder was sealed in Kapton
film before analysis.
XRF analysis
Residue after selective-chlorination. ? Fe was
selective chlorinated.
26
Chlorination of Ti using FeCl2
Ti (s) 2 FeCl2 (s) TiCl4 (g) 2 Fe (s)
Quartz tube
Sample mixture (e.g., FeCl2Ti powder)
Sample deposits (on Si rubber, NaOH gas trap and
quartz tube)
Heater
Carbon crucible
Fig. Experimental apparatus for chlorination
of titanium using FeCl2 as a chlorine
source.
XRF analysis
27
??????????
_at_1100 K
2CaCl2 O2 ? 2CaO 2Cl2
log pCl22 / pO2 -8.29
2MgCl2 O2 ? 2MgO 2Cl2
log pCl22 / pO2 0.48
4HCl O2 ? 2H2O 2Cl2
log pCl22 / pO2 1.49
2CO O2 ? 2CO2
log pO2 -17.74
2C O2 ? 2CO
log pO2 -19.85
e.g.
FeO MgCl2 ? FeCl2 MgO
?G -0.28 kJ lt 0
28
Thermodynamic analysis (FeOx chlorination)
Ti ore mixture of TiOx and FeOx.
Fe-Cl-O system, T 1100 K
CaO (s) / CaCl2 (l) aCaO 0.1
Fe2O3 (s)
Fe3O4 (s)
H2O (g) / HCl (g)
CO / CO2 eq.
C / CO eq.
FeO (s)
Oxygen partial pressure, log pO2 (atm)
MgO (g) / MgCl2 (l) eq.
FeCl2 (l)
FeCl3 (g)
Fe (s)
Chlorine partial pressure, log pCl2 (atm)
Fig. Chemical potential diagram for Fe-Cl-O
system at 1100 K.
FeOX (s) MgCl2 (l) ? FeClX (l, g)? MgO (s,
l)
e.g.
FeOx can be chlorinated by controlling oxygen and
chlorine partial pressure.
29
Thermodynamic analysis (TiOx chlorination)
Ti ore mixture of TiOx and FeOx.
Fe / FeCl2 eq.
Ti-Cl-O system, T 1100 K
CaO (s) / CaCl2 (l) aCaO 0.1
TiO2 (s)
H2O (g) / HCl (g)
CO / CO2 eq.
C / CO eq.
Ti4O7 (s)
Ti3O5 (s)
Oxygen partial pressure, log pO2 (atm)
Ti2O3 (s)
MgO (g) / MgCl2 (l) eq.
TiO (s)
TiCl3 (s)
Ti (s)
TiCl4 (g)
TiCl2 (s)
Chlorine partial pressure, log pCl2 (atm)
Fig. Chemical potential diagram for Ti-Cl-O
system at 1100 K.
Since TiCl4 is highly volatile species, chlorine
partial pressure must be kept in the oxide stable
region.
30
Upgrading Ti ore for minimizing chloride wastes
Others
FeOx
Upgrade
Chloride wastes
TiOx
Up-graded Ilmenite (UGI)
Ti ore (eg. Ilmenite)
Discarded
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
31
Refining process using FeClx
This study
Low-grade Ti ore
MClX
FeClx
Ti scrap
(FeTiOX)
(Cl2)
Chlorine recovery
Selective chlorination
Upgraded Ti ore
FeClx
Fe
TiCl4
(AlCl3)
(TiO2)
Carbo-chlorination
TiCl4 feed
FeClx
COx
(AlCl3)
Ti metal or TiO2 production

• Advantages
• 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

Effective utilization of chloride wastes
Development of a new environmentally sound
chloride metallurgy
32
??????????????(CV)?
??????? CaCl2-CaO ???? ??????????????
??????????????(CV) ?????
Fig. Structure of cyclic voltammetry.
33
Iron removal process by electrochemical method
Establishment of a new up-grading process of Ti
ore by electrochemical method.
Direct reduction process from Ti ore to Ti metal
can be achieved.
34
Iron removal process
Selective chlorinationIron removal process
Fen n e- ? Fe
Cathode
Ca2 2 e- ? Ca
2 Cl- ? Cl2 2 e-
Anode
FeOx C Cl2
? FeClx(l, g) COx
A
e-
Ti ore(TiO2 FeOx)
V
Reference electrode
Mild steel crucible(Cathode)
FeTiOX
Molten CaCl2
Carbon crucible(Anode)
A
e-
e-
2. TiO2 reduction process
O2-
e-
(e.g. EMR-MSE process)
Carbon electrode
TiO2
Ti
TiO2 4 e- ? Ti O2-
Cathode
Ti crucible(Cathode)
Molten CaCl2-CaO
Ca(or Ca-X)
Anode
?
Ca2 2 e-
Ca-X alloy
Ti reduction
Production of reductant
Available Low-grade Ti ore and
Directly reduction method
Low cost Ti production and
Increase new application