Iron Removal from Titanium Ore

1
Iron Removal from Titanium Ore by Electrochemical
Method
Isao Obana1 and Toru H. Okabe2
1Graduate School of Engineering, The University
of Tokyo 2International Research Center for
Sustainable Materials, Institute of Industrial
Science, The University of Tokyo
2
Introduction
Applications
Features of titanium
Aircraft Spacecraft Chemical plants Implants Artif
icial bones, etc.
Lightweight and high strength Corrosion
resistant Biocompatible Some titanium alloys
shape memory effect
superelasticity
The Kroll process Currently employed Ti
production process
Mg TiCl4 Feed port
Chlorination
Ti ore C 2 Cl2 ? TiCl4 ( FeClx) CO2
Reaction Container
Reduction
TiCl4 2 Mg
? Ti 2 MgCl2
Sponge Titanium
Electrolysis
MgCl2
MgCl2
? Mg Cl2
3
Upgrading Ti ore
FeOx
Others
Others
Chloride wastes
TiOx
TiOx
FeOx
Discarded
Ti ore (Ilmenite, FeTiOx)
Upgraded Ilmenite (UGI)
Advantages
Low grade Ti ore
MClx
1. Material cost can be reduced by using
low-grade ore.
(CaCl2)
(FeTiOX)
Selective chlorination
2. Chlorine circulation in the Kroll process
can be improved.
Upgraded Ti ore
FeClx
Ti scrap
(AlCl3)
(TiO2)
Ti smelting
Chlorine recovery

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

Ti metal
Fe
TiCl4
4
Previous study
Vacuum pump
Pyrometallurgical de-Fe process
FeOx (s, in Ti ore) MgCl2 (s, l) ? FeClx (l, g)
MgO (s)
Condenser
Deposit
CaCl2 (s, l) H2O (g) ? HCl (g)
CaO (s)
(FeClx)
Susceptor
FeOx (s, in Ti ore) HCl (g) ? FeClx (l, g)
H2O (g)
Mixture of Ti ore and MClx
T 9731373 K
The selective chlorination of Ti ore by MgCl2 or
CaCl2 is found to be feasible.
RF coil
Quartz Tube
Ref. R. Matsuoka and T. H. Okabe Symposium on
Metallurgical Technology for Waste
Minimization at the 2005 TMS Annual Meeting,
San Francisco, California (2005.2.1317).
N2 or N2H2O gas
5
Study objectives
Low-grade Ti ore
(FeTiOx)
Fe removal by selective chlorination
Application of electrochemical method using
molten salt
TiO2 flux
Direct reduction of TiO2 obtained after Fe
removal
Ti powder
1. Thermodynamic analysis of selective
chlorination 2. Fundamental experiments of
selective chlorination by electrochemical
methods 3. Reduction experiment for the sample
obtained by selective chlorination
6
Thermodynamic analysis (Ti ore chlorination)
Fe-Cl-O and Ti-Cl-O system, T 1100 K
Potential region for selective chlorination of
iron from titanium ore
TiO2 ? Stable FeOx ? FeClx (g)
Fe2O3 (s)
Fe3O4 (s)
CO/CO2 eq.
Ti ore FeTixOy For simplicity, it is assumed to
be a mixture of TiOx and FeOx
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)
The selective chlorination of Ti ore by
controlling chlorine partial pressure may be
possible using an electrochemical technique.
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 systems at 1100 K
7
Chlorination by increasing Cl2 potential
Electrolysis
Cathode
DC power source
FeCl3, AlCl3, O2, CO2 gas
Fen n e ? Fe
e
Ca2 2 e ? Ca
Anode
2 Cl (in CaCl2) ? Cl2 2 e
FeOx Cl2 ? FeClx? O2
Molten salt (CaCl2, MgCl2, etc.)
Upgraded or low-grade Ti ore (e.g., FeTiOx)
Chlorine chemical potential in molten CaCl2 at
anode can be increased electrochemically.
8
Theoretical decomposition voltage
Table Standard Gibbs energy of decomposition and
theoretical voltage of that in several chemical
species at 1100 K.
Reactions
o
o
D
D
G
/kJ mol-1a
E
/Va
CaCl2 (l) Ca (l) Cl2 (g)
629
3.26
FeO (s) Fe (s) 1/2 O2 (g)
201
1.04
FeO (s) 1/2 C (s) Fe (s) 1/2 CO2 (g)
3
0.02
FeO (s) CaCl2 (l) C (s) FeCl2 (l) CO (g)
Ca (l)
409
2.23
FeTiO3 (s) CaCl2 (l) 1/2 C (s) TiO2 (s)
FeCl2 (l) Ca (l) 1/2 CO2 (g)
438
2.34
a I. Barin Thermochemical Data of Pure
Substances, 3rd ed. (Weinheim, Federal
Republic of Germany, VCH Verlagsgesellschaft mbH,
1997)
Under a certain condition, the selective
chlorination of Fe in Ti ore may proceed below
the theoretical decomposition voltage of CaCl2.
9
Low-grade Ti ore
(FeTiOx)
Iron removal by selective chlorination using an
electrochemical method
Fe removal by selective chlorination
TiO2 flux
Direct reduction of TiO2 obtained after Fe
removal
Ti powder
10
Experimental apparatus
(a) Reaction chamber
(b) Reaction cell
V
Potential lead (Nickel wire)
A
(a)
(b)
Stainless steel tube
(Electrode)
O.D. 19 mm
I.D. 17 mm
Ar inlet
Support rod (Stainless steel tube)
Rubber plug
Wheel flange
Air hole
Thermocouple
Screw (Stainless steel)
Heater
Surface of molten salt
Mild steel crucible (Cathode)
Graphite crucible (Anode)
Holes for molten salt diffusion
Sample
Molten salt (CaCl2)
Graphite crucible
Ceramic insulator
Sample (Ti ore, CaCl2, etc.)
Height 40 mm
11
Selective chlorination experiments
Experimental conditions Temperature
Atmosphere Molten salt Cathode Anode
1100 K Ar CaCl2 (800 g) Mild steel crucible (I.D.
96 mm) Graphite crucible (I.D. 17 mm)
Voltage monitor /controller
Sample
e
Mass of sample i, wi/g
Voltage, E/V
Time, t/h
Ti ore
Carbon powder
CaCl2
Exp. No.
Ilmenite
UGI
4.00
?
?
A
1.5
12
?
Molten CaCl2
B
0.74
2.17
?
1.5
3
?
C
0.74
2.17
0.18
1.5
3
?
Mild steel crucible (Cathode)
Graphite crucible containing Ti ore (Anode)
D
1.59
1.27
?
1.5
3
?
E
1.59
1.27
2.0
3
?
?
Low initial Fe content
12
Results of the selective chlorination experiments
XRF analysis
Table Analytical results of the samples
obtained after electrochemical
selective chlorination
Concentration of element i, Ci (mass)
Fe/Ti ratio,
Sample
Fe/Ti ratio decreased from 114 to 7.2
(ilmenite) and from 2.00 to 0.18 (UGI).
V
Ti
Fe
Ca
Si
RFe/Ti ()
0.6
42.6
48.7
0.3
2.2
114
Ilmenite
Exp. A
2.7
45.7
21.7
12.3
1.4
47.4
Exp. B
0.4
47.2
3.4
47.9
0.0
7.2
94 of Fe in ilmenite and 92 of Fe in UGI were
successfully removed.
Exp. C
0.1
30.2
7.5
42.7
0.3
24.7
Exp. X
0.1
45.1
5.8
40.6
0.5
12.9
0.2
95.9
1.9
0.1
0.1
2.00
UGI
Exp. D
0.5
98.0
0.2
0.1
0.3
0.18
Exp. E
0.2
96.9
0.3
0.2
0.5
0.28
a Average values of the samples obtained from
the upper and lower parts of the graphite
crucible
13
Result of a selective chlorination experiment
XRD analysis
Discussion
Ilmenite FeTiO3
FeTiO3 (s) CaCl2 (l) ? CaTiO3 (s) FeClx (l,
g)
Intensity, I(a. u.)
CaTiO3
FeTiO3 (s) CaCl2 (l) C (s) ? TiO2 (s)
FeClx (l, g) COx (g) Ca (s)
TiO2
CaTiO3 can be utilized as a feed material of
direct TiO2 reduction processes (e.g., FFC, OS,
EMR-MSE processes).
Angle, 2? (degree)
Fig. XRD pattern of the start sample and
the sample obtained after Fe removal (Exp. B)
A mixture of CaTiO3 and TiO2 was obtained after
Fe removal.
14
Low-grade Ti ore
Direct reduction of TiO2 after Fe removal by
electrochemical method
(FeTiOx)
Fe removal by selective chlorination
TiO2 flux
Direct reduction of TiO2 obtained after Fe
removal
Ti powder
15
Reduction experiment apparatus
Direct reduction by electrochemical method was
applied.
Carbon anode
Electrolysis
Cathode
TiO2 4 e ? Ti 2 O2
Anode
CaCl2 molten salt
C x O2 ? COx 2x e
Ti crucible
TiO2 feed
Fig. Schematic illustration of the experimental
apparatus in this study.
16
Reduction experiments
Experimental conditions Temperature 1100
K Atmosphere Ar Molten salt CaCl2 (800
g) Cathode Ti crucible
(I.D. 18 mm) Anode Graphite
rod (O.D. 3 mm)
Table Analytical results of the sample obtained
after electrochemical selective
chlorination
Fe/Ti ratio,
Concentration of element i, Ci (mass)
Sample
V
Ti
Ca
Si
Fe
RFe / Ti ()
0.2
95.9
1.9
0.1
0.1
2.00
UGI
Exp. D
0.5
98.0
0.2
0.1
0.3
0.18
Exp. E
0.2
96.9
0.3
0.2
0.5
0.28
Mass of element i, wi / g
Voltage, E/V
Time, t/h
Ti ore
CaCl2
CaTiO3
Exp.
2.50
R-1
1.5
3
1.50
?
R-2
2.50
3.0
3
1.50
?
R-3
0.79
2.50
3.0
3
?
R-4
2.50
3.0
3
0.76
?
17
Result of the reduction experiments
XRD analysis
Ti reduction by EMR
Ti2O
Ti JCPDS 44-1294
CaTiO3
(a.u.)
I
Intensity, I(a. u.)
Intensity,
90
70
50
30
10
40
60
80
100
20
Angle, 2q (degree)
Fig. XRD pattern (Cu-K?) of the obtained
powder sample after reduction at 1173 K
using the EMR process.
Angle, 2? (degree)
Fig. XRD pattern of the sample obtained
after the reduction experiment (Exp. R-2)
2500 ppm O
CaTiO3 was changed into Ti2O during this
reduction experiment.
In a previous study, low oxygen titanium
powder was obtained.
A complete reduction was not achieved in this
study.
Ref. T. Abiko, I. Park, and T.H. Okabe,
Proceedings of 10th World Conference on
Titanium, Ti-2003, (Hamburg, Germany, 1318 July
2003), 253260.
18
Summary
Low-grade Ti ore
The selective chlorination of Ti ore by using
an electrochemical method was investigated,
and 94 of Fe was successfully removed
directly from low-grade Ti ore.
(FeTiOx)
Iron removal by selective chlorination
TiO2 flux
Reduction by electrochemical method
The feasibility of Ti smelting process for
directly producing metallic Ti from low-grade
Ti ore was demonstrated.
Ti powder
Development of an industrial scale process for
producing low-cost titanium
19
QuestionandAnswer
20
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.
21
Titanium Production
(a) Production of titanium sponge in the world
(2003).
(b) Transition of production volume of
titanium mill products in Japan.
17.4 kt (2004)
USA 8 kt
China 4 kt
Total 65.5 kt
Kazakhstan 9 kt
Amount of titanium mill products kt
Japan 18.5 kt (28 share)
Russia 26 kt
Year
Fig. Current status of titanium production,
(a) production of titanium sponge in the world
(2003),
(b) transition of production volume of titanium
mill products in Japan.
22
Table Comparison between common metals
and titanium.
Titanium
Aluminum
Iron
Symbol
Ti
Al
Fe
Melting point (K)
1943
933.3
1809
Density (g / cc _at_298 K)
4.5
2.7
7.9
Specific strength ((kgf / mm2) / (g / cc))
8 10
3 6
4 7
Clarke numbera
0.46 (rank 10)
7.56 (rank 3)
4.7 (rank 4)
Price (Yen / kg)
3000
600
50
Production volume (106 ton / yearworld)
0.1
20
800
a Values in parentheses are the existence rank
in the earths crust.
23
Flowchart of the titanium production
Ti feed (TiO2)
Reductant (C)
Chlorine (Cl2)
CO2, FeClx,AlCl3 etc.
Chlorination
Other compounds
Distillation
H2S etc.
Pure TiCl4
Reductant, Mg
Reduction
Vacuum distillation
MgCl2 Mg
Sponge Ti
MgCl2
Electrolysis
Fig. Flowchart of the titanium
production based on the Kroll process.
Crushing / Melting
Ti ingot
24
Composition of titanium ore
(a) Low grade titanium ore (ilmenite)
(b) Up-graded titanium ore (UGI)
Others 10
Others 3
FeOx 2
TiOx 45
FeOx 45
TiOx 95
Fig. (a) Composition of low grade titanium ore
(ilmenite), and (b) that of up-graded
titanium ore (up-graded ilmenite, UGI).
25
Upgrading Ti ore for minimizing chloride wastes
FeOx
Others
Others
Chloride wastes
TiOx
TiOx
FeOx
Discarded
Ti ore (Ilmenite, FeTiOx)
Upgraded Ilmenite (UGI)
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.
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
26
Refining process using FeClx
This study

• Advantages
• Utilizing chloride wastes
• from the Kroll process
• 2. Low cost Ti chlorination
• Minimizing chlorine loss
• in the Kroll process
• caused by generation
• of chloride wastes

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
Effective utilization of chloride wastes
Development of a new environmentally sound
chloride metallurgy
27
The Benilite process
Fe2 / TiFe 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.
28
The Beacher process (WLS)
Ilmenite
Coal (low ash)
Air
Reduction (in kiln)
Gas particle
Particle
Reduced ore
Cyclone
Screen
1 mm
Gas
-1 mm
Waste
Mag. separator
(Non. mag.)
Reduced ilmenite
NH4Cl
Air
Leaching
H2SO4 aq.
Iron oxide Sol.
TiO2
Acid Leaching
TiO2
Iron oxide
Sol.
Fig. Flowchart of the Beacher process.
(Synthetic rutile) TiO2 9293
TiFe 2.03.5
TiO2
Filtering / Drying
29
Thermocouple
Cathode (stainless steel)
Ceramic tube
Alumina tube
Anode lead wire (W)
TiO2 (CaCl2) 4 e- ? Ti 2 O2- (CaCl2)
Fused CaCl2 bath
or TiO2 (CaCl2) 2 Ca ? Ti 2 CaO
Alumina crucible
TiO2 powder
Graphite crucible (anode)
Electric furnace
Fig. Electrochemical reduction of TiO2 in
CaCl2. (Ref. Mem. Fac. Eng., Nagoya
Univ., 19, (1967) 164-166.)
30
Carbon anode
Ti cathode
e-
Cl2
COX
e-
Ca2
O O2-
O2-
Cl-
Ca
Ca
O (in Ti) 2 e- ? O2- (in CaCl2)
Ca2
C
Ti
O2-
Ca
Cl-
Ca2
O2-
Ca2
O
in Ti
Ca2
Cl-
Ti
CaCl2 molten salt
Fig. The principle of electrochemical
deoxidization of titanium. (Ref. Met.
Trans. B, 24B, June, (1993) 449-455.)
31
TiO2 4 e- ? Ti 2 O2 (in CaCl2)
Fig. Schematic illustration of the
procedure of the FFC process. (Ref.
Nature, 407, 21, Sep. (2000) 361.)
32
Production process under investigation
OS Process (Ono Suzuki, 2002)
FFC Process (Fray et al., 2000)
TiO2 powder
e-
e-
Carbon anode
Carbon anode
Ca
TiO2 preform
CaCl2 molten salt
CaCl2 molten salt
(b1)
TiO2 2 Ca ? Ti 2 O2- Ca2
Electrolysis
Electrolysis
Cathode
Cathode
TiO2 4 e- ? Ti 2 O2-
(a1)
Ca2 2 e- ? Ca
(b2)
Anode
Anode
C x O2- ? COx 2x e-
(a2)
C x O2- ? COx 2x e-
(b3)
33
EMR / MSE Process (Electronically Mediated
Reaction / Molten Salt Electrolysis)
Production process under investigation
Cathode
TiO2 4 e- ? Ti 2 O2-
(c1)
Anode
Ca ? Ca2 2 e-
(c2)
Electrolysis
Cathode
Ca2 2 e- ? Ca
(c3)
Anode
C x O2- ? COx 2x e-
(c4)
Over all reaction
(d)
TiO2 C ? Ti CO2
34
(a) FFC Process (Fray et al., 2000)
(b) OS Process (Ono Suzuki, 2002)
(C) EMR / MSE Process (Okabe et al., 2002)
TiO2 powder
Current monitor / controller
e-
Carbon anode
Carbon anode
e-
e-
e-
e-
Carbon anode
Ca
CaCl2 molten salt
CaCl2 molten salt
TiO2 preform
TiO2 2 Ca ? Ti 2 O2- Ca2
(b1)
CaCl2 molten salt
TiO2 feed
Ca-X alloy
EMR
MSE
Electrolysis
Electrolysis
Cathode
TiO2 4 e- ? Ti 2 O2-
(c1)
Cathode
Cathode
Ca ? Ca2 2 e-
Anode
(c2)
TiO2 4 e- ? Ti 2 O2-
(a1)
Ca2 2 e- ? Ca
(b2)
Electrolysis
Anode
Anode
Ca2 2 e- ? Ca
C x O2- ? COx 2x e-
(a2)
C x O2- ? COx 2x e-
(b3)
Cathode
(c3)
C x O2- ? COx 2x e-
Anode
(c4)
Fig. Schematic illustration of experimental
apparatus for titanium smelting in the
future.
Over all reaction
TiO2 C ? Ti CO2
(d)
35
Features of several titanium production process
Advantages
Disadvantages
Kroll Process
?
High purity titanium available

Complicated process
?
Easy metal / salt separation
Slow production speed

?
Established chlorine circulation
Batch type process

?
Utilizes efficient Mg electrolysis
?
Reduction and electrolysis operation
can be carried out independently
FFC Process
?
Simple process
Difficult metal / salt separation

?
Semi-continuous process
Reduction and electrolysis have to be

carried out simultaneously
?
Sensitive to carbon and iron contamination
?
Low current efficiency
OS Process
?
Simple process
Difficult metal / salt separation

?
Semi-continuous process
?
Sensitive to carbon and iron contamination
?
Low current efficiency
PRP (Preform
?
Effective control of purity

Difficult recovery of reductant
and morphology
Reduction
?
Flexible scalability
Process)
?
Resistant to contamination
?
Small amount of fluxes necessary
Environmental burden by leaching
?
Resistant to iron and carbon

EMR / MSE Process
Difficult metal / salt separation when oxide

contamination
?
Semi-continuous process
system
Complicated cell structure
?
Reduction and electrolysis operation

?
Complicated process
can be carried out independently
36
Product Ti pellets Ti ( CaO CaCl2)
Carbon anode
Feed preform (TiO2 CaCl2)
A
Current monitor / controller
V
COx gas
Vn
e-
e-
e-
A
CaCl2-CaO
e-
CaCl2-CaO molten salt
Ca
Fig. Conceptual image of the new
titanium reduction process currently
under investigation (EMR / MSE
process, Oxide system).
O2- , Ca2
Ca-X reductant alloy
Ca (Ca-X alloy)
TiO2 4 e- Ti 2 O2-
C x O2- COx 2x e-
Ca (Ca-X alloy) Ca2 2 e-
Ca2 2 e- Ca (Ca-X alloy)
Daytime reduction
Nighttime electrolysis
37
Preform Reduction Process (PRP)
TIG weld
Stainless steel cover
MOx R ? M RO
Stainless steel reaction vessel
Feed preform (MOx flux)
M Nb, Ta, Ti R Mg, Ca
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).

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

38
(a) Conventional Metallothermic Reduction
(b) Preform Reduction Process (PRP)
Feed preform
Feed powder
Reductant vapor
Reductant vapor
Reductant (R Ca, Mg)
Reductant (R Ca, Mg)
Fig. Metal powder production process
(a) conventional metallothermic reduction,
(b) preform reduction process (PRP).
39
Selective chlorination using MgCl2
Vacuum pump
Glass flange
FeOx (s) MgCl2 (l) FeClx (l) MgO
(s)
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)
Experimental condition
RF coil
T 1100 K, t 1 h, Atmosphere N2, Ti ore
(UGI) 4 g, MgCl2 2 g
Quartz flange
Ceramic tube
N2 or N2H2O gas
Fig. Experimental apparatus for
selective-chlorination of titanium ore using
MgCl2 as a chlorine source.
40
Results of previous study
FeOx (s) MgCl2 (l) FeClx (l, g) MgO (s)
XRD analysis
XRF analysis
Deposit obtained after selective -chlorination. ?
FeCl2 was generated.
Residue after selective-chlorination. ? Fe was
selective chlorinated.
Table Analytical results of titanium ore,
the residue after selective chlorination,
and the sample after reduction.
These values are determined by XRF analysis.
FeCl2
Intensity, I (a. u.)
Concentration of element i, Ci (mass )
V
Ti
Fe
Si
Al
10
30
40
50
60
70
80
20
90
100
Ti ore (UGI from Ind.)
0.75
95.10
2.29
0.41
0.12
Angle, 2? (deg.)
1.50
0.43
0.44
0.37
After heating sample
96.45
Fig. XRD pattern of the deposit at
chlorides condenser. The sample powder was
sealed in Kapton film before analysis.
98.30
0.05
0.38
0.12
0.52
After reduction sample
41
Chlorination of Ti using FeCl2
Quartz tube
Sample mixture (e.g., FeCl2Ti powder)
Ti (s) 2 FeCl2 (s) TiCl4 (g) 2 Fe (s)
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
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.
Concentration of element i, Ci (mass )
Ti
Fe
Cl
Residue before heating
18.4
45.3
36.2
Residue after heating
9.8
80.1
9.0
Dep. on quartz tube after heating
3.5
50.4
46.1
Dep. on Si rubber after heating
64.9
0.9
34.1
42
This study
Low-grade Ti ore
MClx
FeClx
Ti scrap
(CaCl2)
(FeTiOx)
Selective chlorination by electrochemical method
Chlorine recovery
Upgraded Ti ore
FeClx
Fe
TiCl4
( AlCl3)
(TiO2)
Ti smelting by electrochemical method
Ti metal
Fig. Flowchart of new titanium smelting process
from titanium ore discussed in this
study.
43
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.
44
(a) Iron removal process
(b) FFC process (Fray et al., 2000)
e-
Carbon crucible containing Ti ore CaCl2 mixture
(Anode)
e-
Carbon anode
CaCl2 molten salt
Sample
Molten CaCl2
Mild steel crucible (Cathode)
TiO2 preform
Electrolysis
Electrolysis
Cathode
Ca2 2 e- ? Ca
(a1)
Cathode
TiO2 4 e- ? Ti 2 O2-
(b1)
2 Cl- ? Cl2 2 e- FeOx Cl2
C ? FeClx COx
Anode
(a2)
C x O2- ? COx 2x e-
Anode
(b2)
(a3)
Fig. Schematic illustrations of the processes
investigated in this study.
45
Potential of several reaction
_at_1100 K
log pCl22 / pO2 -8.29
2CaCl2 O2 ? 2CaO 2Cl2
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
46
Table Gibbs energy change of formation in the
Fe-Ti-O system.
47
Temperature, T / K
TiCl4 (l)
Region suitable for vaporization of chlorides
TiCl2 (s)
TiCl3 (s)
FeCl3 (s,l)
CaCl2 (s, l)
Vapor pressure, log pi (atm)
Ti (s,l)
Fe (s,l)
FeCl2 (s,l)
MgCl2 (s, l)
Fig. Vapor pressure of iron, calcium,
magnesium and titanium chlorides as a
function of reciprocal temperature.
Reciprocal temperature, 1000 T-1 / K-1
48
Thermodynamic analysis (FeOx chlorination)
Fe-Cl-O system, T 1100 K
CaO (s) / CaCl2 (l) aCaO 0.1
Fe2O3 (s)
Ti ore mixture of TiOx and FeOx.
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)
FeOX (s) MgCl2 (l) ? FeClX (l,
g)? MgO (s, l)
FeCl3 (g)
Fe (s)
e.g.
FeOx can be chlorinated by controlling oxygen and
chlorine partial pressure.
Chlorine partial pressure, log pCl2 (atm)
Fig. Chemical potential diagram for Fe-Cl-O
system at 1100 K.
49
Thermodynamic analysis (TiOx chlorination)
Ti-Cl-O system, T 1100 K
Fe / FeCl2 eq.
CaO (s) / CaCl2 (l) aCaO 0.1
Ti ore mixture of TiOx and FeOx.
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)
Since TiCl4 is highly volatile species, chlorine
partial pressure must be kept in the oxide stable
region.
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.
50
(No Transcript)
51
This chapter
Low-grade Ti ore
MClx
FeClx
Ti scrap
(CaCl2)
(FeTiOx)
Selective chlorination by electrochemical method
Chlorine recovery
Upgraded Ti ore
FeClx
Fe
TiCl4
( AlCl3)
(TiO2)
Ti smelting by electrochemical method
Ti metal
Fig. Flowchart of the new titanium smelting
process discussed in this study.
52
Ti ore
Flux
Binder
Flux CaCl2, MgCl2
Binder Collodion
Preform fabrication
Feed preform
FeClx
Sintered feed preform
Fig. Flowchart of the procedure of preform
fablication supplied for Fe removal
experiment.
53
Table Composition of titanium ore (ilmenite)
and up-graded ilmenite (UGI) used this
study.
54
Table Starting materials used in this study.
Purity or conc. ()
Form
Supplier
Materials
Liquid
5.0
Collodiona
Wako Pure Chemical., Inc.
Powder
95.0up
CaCl2
Kanto Chemicals, Inc.
Chip
98.0up
Ca
Osaka Tokusyu Goukin Co., Ltd.
Ti
Sponge
98.0up
Toho Titanium Co., Ltd.
CH3COOH
Liquid
99.7
Kanto Chemicals, Inc.
HCl
Liquid
35
Kanto Chemicals, Inc.
2-Propanol
Liquid
99.5up
Kanto Chemicals, Inc.
Aceton
99.0up
Liquid
Kanto Chemicals, Inc.
Graphite
99.98
Crucible
Kanto Chemicals, Inc.
a 5 mass nitro cellulose, 23.75 mass ethanol,
71.25 mass diethylether.
55
Experimental apparatus
Electrochemical interface
Voltage monitor / controller
Sample
e-
Furnace
Holes on crucible
Molten CaCl2
Mild steel crucible (Cathode)
Graphite crucible containing Ti ore (Anode)
10 A power source
Electrochemical control unit
56
Potential lead (Nickel wire)
Stainless steel tube
Ar inlet
Rubber plug
Wheel flange
Reaction chamber
Thermocouple
Heater
Mild steel crucible
Graphite crucible
Ti ore, sample
Preform containing Ti ore
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of the experimental
apparatus in a voltage measurement.
57
(a)
(b)
Support rod (Stainless steel tube)
O.D. 19 mm
I.D. 17 mm
Air hole
Screw (Stainless steel)
Surface of molten salt
40 mm
Inlet of molten salt
Graphite crucible
Sample (Ti ore, CaCl2 etc.)
Fig. Schematic illustration of the graphite
crucible used in this experiment, (a)
appearance, (b) inner content.
58
Fig. Variation of the external current from the
dipped preform to the graphite crucible.
59
Fig. Electromotive force between the dipped
preform and the graphite crucible.
60
Table Analytical results of various samplesa.
Concentration of element i, Ci (mass)b
Fe / Ti ratioc,
Fe
Ti
Ca
RFe / Ti ()
Al
Si
Cl
Cr
Sample
33.7
50.6
7.1
66.6
0.0
5.3
2.7
0.6
A
41.4
41.9
9.6
98.8
0.0
4.3
2.5
0.3
B
50.1
42.2
0.1
84.3
0.0
4.0
3.3
0.3
C
42.4
50.4
0.2
84.1
0.9
0.0
3.7
2.4
D
E
40.7
36.1
10.8
88.7
8.7
2.0
1.3
0.3
a Ilmenite (FeTiOx) produced in China. b
Determined by X-ray fluorescence analysis.
This value excludes carbon and gaseous elements.
c Indicator of iron removal from titanium ore.
61
800
782?
Liquid
700
674?
Temperature, T / ?
592?
600
0
100
20
40
60
80
CaCl2
FeCl2
FeCl2 content, xFeCl2 (mol)
Fig. Phase diagram for the CaCl2-FeCl2 system
2.
62
Potential lead (Nickel wire)
A
Stainless steel tube
Ar inlet
Rubber plug
Wheel flange
Reaction chamber
Thermocouple
Heater
Mild steel crucible (working)
Nickel quasi-reference electrode
Graphite crucible (counter)
Ti ore
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of the experimental
apparatus for cyclic voltammetry in
molten CaCl2.
63
(a)
2
1
0
-1
Current, i / A
(b)
2
Ca2 2 e- Ca (on Fe)
1
0
3.2 V
-1
2 Cl- Cl2 2 e- (on C)
Fig. Cyclic voltammograms for molten CaCl2 at
1100 K (a) before pre-electrolysis, (b)
after pre-electrolysis, cathode sweep
working Fe rod counter C rod, anode
sweep working C rod counter Fe rod,
scan rate 100 mV / s, immersion length 4 cm.
-2
-1
0
1
2
Potential (vs Ni quasi-ref.), E / V
64
Table Standard Gibbs energy of formation and
theoretical voltage for reactions in
this study.
65
(a)
2
Ca2 2 e- Ca (on Fe)
1
0
3.0 V
-1
2 Cl- Cl2 2 e- (on C)
(b)
Ca2 2 e- Ca (on Fe)
2
1
Current, i / A
0
1.7 V
-1
C x O2- COx 2x e- (on C)
Fig. Cyclic voltammograms for molten CaCl2
at 1100 K after Ca deposition using
various carbon electrode, (a) C rod,
scan rate 100 mV / s, (b) C crucible,
scan rate 100 mV / s, (c) Ti ore
holding C crucible, scan rate 20
mV / s, cathode sweep working Fe rod
counter Carbon, anode sweep working
Carbon counter Fe rod, immersion
length 2 cm.
(c)
2
Ca2 2 e- Ca (on Fe)
1
0
1.7 V
-1
C x O2- COx 2x e- (on C)
-1
0
1
2
-2
3
Potential (vs Ca / Ca2 ref.), E / V
66
Liq.
Two liquids
Temperature, T / C
825
828
767
CaCl2
Ca
Ca content, xCa (mol)
Fig. Phase diagram for the CaCl2Ca system 3.
67
e-
Mild steel crucible (Cathode)
Carbon crucible containing Ti ore CaCl2
mixture (Anode)
Sample
Molten CaCl2
Fig. Schematic illustration of experimental
apparatus for iron removal by
electrochemical method.
68
V
Potential lead (Nickel wire)
A
Stainless steel tube
Ar inlet
Rubber plug
Wheel flange
Stainless steel reaction chamber
Thermocouple
Heating element
Mild steel crucible (Cathode)
Graphite crucible (Anode)
Ti ore
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of the experimental
apparatus for iron removal by
electrochemical method.
69
Ti ore ( Fe2O3 etc)
Electrochemical iron removal
CaCl2
TiO2 CaCl2
CaCl2
Separation
Distilled water
TiO2
CH3COOH aq., HCl aq., Distilled
water, Isopropanol, Acetone
Leaching
S L
Waste solution
Vacuum drying
TiO2 powder
Fig. Flowchart of the procedure for iron removal
experiment by electrochemical method.
70
Experiment 1
Experimental condition Temperature 1100
K Atmosphere Ar Molten salt CaCl2 (800
g) Cathode Mild steel crucible (I.D 96
mm) Anode Graphite crucible (I.D 17 mm)
Voltage monitor / controller
Sample
e-
Mass of Ti ore (Ilmenite), w / g
Voltage, E / V
Time, t / h
Exp. No.
Molten CaCl2
A
4.00
2.5
6
B
4.00
2.0
3
Mild steel crucible (Cathode)
Graphite crucible containing Ti ore (Anode)
4.00
C
1.5
12
71
Result 1
XRF analysis
Disscussion
Table Analytical results of the sample obtained
after the electrochemical selective
chlorination.
Ti ore (Ilmenite, FeTiOx)
Concentration of element i, Ci (mass )
Fe / Ti ratio,
Sample
e-
V
Ti
Fe
Ca
Si
RFe / Ti ()
Ti ore
0.6
42.6
48.7
2.2
2.2
114
Exp. A
0.9
64.2
29.6
0.5
1.8
49.5
Exp. B
1.2
55.4
25.3
13.8
1.1
45.6
Molten CaCl2
Exp. C
2.7
45.7
21.7
12.3
1.4
47.4
a Average of the samples obtained from the
upper part and lower part of the graphite
crucible.
Graphite crucible (Anode)
Unreacted part
After the electrochemical treatment, Fe in the
Ti ore was selectively chlorinated and removed.
Unreacted part was remained at the bottom of the
graphite crucible.
72
Table Experimental condition for iron removal
from Ti ore by electrochemical methodc.
Exp.
Voltage, V / volts
Reaction time, t / hr
Exp.
Reaction time, t / hr
Mass of feed materials i, wi / g
Mass of feed materials i, wi / g
Voltage, V / volts
UGIa
Ilmeniteb
UGIa
Ilmeniteb
2.76
2.0
1.0
A
I
4.00
2.5
3.0
B
2.82
1.2
1.0
J
4.03
1.5
3.0
C
2.92
1.0
1.0
K
4.01
1.5
6.0
D
2.91
0.5
1.0
L
3.99
1.0
6.0
E
2.88
2.0
3.0
M
4.00
0.5
6.0
F
2.81
1.0
6.0
N
3.93
6.0
?
G
2.75
0.5
0.5
O
4.01
1.5
9.0
H
1.42
1.2
1.0
4.00
2.0
13.0
P
a Upgrade ilmenite by the Benilite process (see
Fig.1-6 ). The ore was produced in India (see
Table 3-1). b Ilmenite (FeTiOx) produced in
China. c Temperature 1100 K, Ar atmosphere.
73
10 A Power Source
20 cm
Fig. Schematic illustration of electrochemical
interface in this experiment.
74
Exp. K
Current, I / A
Exp. L
Exp. M
Exp. N
Time, t / second
Fig. Current generated by imposed each voltage.
75
Table Analytical results of the samples obtained
after iron removal by electrochemical method.
76
100 mm
Potential lead (Ni wire)
Stainless steel tube
(Electrode)
Ar inlet
Rubber plug
Wheel flange
Thermocouple
Heater
Mild steel crucible (Cathode)
Graphite crucible (Anode)
Ti ore CaCl2 mixture
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of experimental
apparatus in this experiment.
77
Fig. Current value passed by imposed certain
voltage, and voltage in this
experiment, Exp. F.
78
CaTiO3 (JCPDS 42-0423)
TiO2 (JCPDS 21-1276)
Intensity, I (a. u.)
Angle, 2? (degree)
Fig. XRD pattern of the obtained sample
after selective chlorination experiment.
79
Table Experimental condition and analytical
results of the chlorination experiment using
ilmenite.
80
Table Experimental conditions and analytical
results of the chlorination experiment using UGI.
81
Low-grade Ti ore
MClx
FeClx
Ti scrap
(CaCl2)
(FeTiOx)
Selective chlorination by electrochemical method
Chlorine recovery
Upgraded Ti ore
FeClx
Fe
TiCl4
( AlCl3)
(TiO2)
Ti smelting by electrochemical method
Ti metal
This chapter
Fig. Flowchart of new titanium smelting process
from titanium ore discussed in this
chapter.
82
V
Potential lead (Nickel wire)
A
Stainless steel tube
Ar inlet
Rubber plug
Wheel flange
Reaction chamber
Thermocouple
Heater
Mild steel crucible
Ti crucible (Cathode)
Graphite rod (Anode)
Mixture of Ti ore after Fe removal and CaCl2
Molten salt (CaCl2)
Ceramic insulator
Fig. Schematic illustration of the experimental
apparatus for electrochemical reduction
of Ti ore after Fe removal.
83
Ti ore (Fe2O3 etc)
CaCl2
Mixing
Mixture
CaCl2
Electrochemical reduction
Ti CaCl2
CH3COOH aq., HCl aq., Distilled
water, Isopropanol, Acetone
Leaching
S L
Waste solution
Vacuum drying
Ti powder
Fig. Flowchart of the experimental procedure for
electrochemical reduction of Ti ore after
Fe removal.
84
Table Experimental conditions for electrochemical
reduction of Ti ore after Fe removal.
Mass of feed material i, Ci / g
Exp. No.
Voltage, E / V
Time, t / h
Ti ore
CaCl2
CaTiO3
2.50
R1
1.5
3
1.50
?
R2
2.50
3.0
3
1.50
?
R3
0.79a
2.50
3.0
3
?
R4
2.50
3.0
3
0.76b
?
a The sample obtained by selective chlorination
exp. A.
b The sample obtained by selective chlorination
exp. D.
85
1150 K
Temperature, T / C
10
20
30
0
CaCl2
CaO content, xCaO (mol)
CaO
Fig. Phase diagram for the CaCl2CaO system.