Transcript Document

Direct Production of Titanium Powder from Titanium Ore
by Preform Reduction Process
Haiyan Zheng
1
and Toru H. Okabe
1
1 Institute of Industrial Science, University of Tokyo,  Graduate Student
Introduction
The Kroll process
Direct reduction of TiO2
Current commercial Ti production process
Current status of
industrial production of Ti
Mg & TiCl4 feed port
Preform reduction process (PRP)
(a) FFC process (Fray et al.)
e–
Feed preform
(TiO2 feed + flux)
World production of Ti sponge (2003)
China
4 kt
Metallic reaction vessel
USA
8 kt
Ti/Mg/MgCl2 mixture
(b) OS process (Ono & Suzuki) ○Simple process
Furnace
TiO2
powder
e–
Mg & MgCl2 recovery port
Comparison with common metals
Metal
Iron
Aluminum Titanium
Symbol
Fe
Al
Ti
Melting point (K)
1809
933
1939
Density
7.9
2.7
4.5
(g/cm3 at 298 K)
Specific strength
4~7
3~6
8~10
((kgf/mm2)/(g/cm3))
Clarke no.
4
3
9
Price (\/kg)
50
600
3000
Production volume 9.6 x 108 2.2 x 107 6.6 x 104
(t/world in 2003)
1/300
1/15000
Research work
Chlorination
Ti ore + C + 2 Cl2 → TiCl4 (+ MClx) + CO2
Reduction
TiCl4 + 2 Mg
→ Ti + 2 MgCl2
Electrolysis
MgCl2
→ Mg + Cl2
Features of the Kroll process:
◎High-purity Ti can be obtained.
◎Metal/salt separation is simple.
○Chlorine circulation is established.
○Efficient Mg electrolysis can be utilized.
○Reduction and electrolysis can be
carried out independently.
×Process is complicated.
×Reduction process is batch type.
×Production speed is low.
×Chloride wastes are produced.
Production cost of Ti is high
and its application is limited.
Typical experimental apparatus
for the reduction process
Flowchart of the PRP
Flux
Binder
Mixing
TIG welding
Stainless steel
reaction vessel
Stainless steel
cover
Feed preform
after Fe removal
Stainless steel net
Stainless steel
holder
Reductant (Ca)
Ti sponge getter
Ti ore: Rutile
Flux: CaCl2
Binder: Collodion
Slurry
Carbon anode
Ca
CaCl2 molten salt
(c) EMR/MSE process
(Okabe et al.)
e–
e–
Feed preform
TiO2 + CaCl2 + Binder
(2)
Preform after calcination
1 cm
Sintered feed preform
(2)
Reduction
Ca vapor
(3)
Reduced preform
Leaching
Acid
Waste
solution
Vacuum drying
Powder
(4)
Experimental results 3
(4)
(4)
Ti powder obtained
after leaching
5 m
20
40
60
80
100
Table Analytical results of the obtained sample.
Step
Experimental conditions
Preform
after reduction
A
B
Cc
Dc
0.2
0.3
0.2
0.3
Calcination
Temp.
Time
Concentration of element i, Ci a (mass %)
Ti
Fe
Al
Ca
Cl
(1)
67.64
1.36
0.50
10.20
20.29
(2)
65.99
0.13
0.08
11.65
22.15
(3)
18.79
0.10
(0.00)
67.98
13.09
(4)
98.23
0.23
0.56
0.98
(0.00)
a: Determined by X-ray fluorescence analysis,
and the value excludes carbon and gaseous elements.
Temp.
Time
Tcal./K
t'cal./h
Tred./K
t'red./h
1273
1273
1273
1273
1
1
2
2
1273
1273
1273
1273
6
6
9
9
SEM images
: TiO2
: CaCl2
: CaCl2 (H2O)4
JCPDS # 21-1276
JCPDS # 74-0522
JCPDS # 01-0989
: TiO2
: CaCl2
: CaCl2 (H2O)4
JCPDS # 21-1276
JCPDS # 74-0522
JCPDS # 01-0989
Concentration of
Cationic
Iron
Ti and Fe in
Exp. molar the obtained Ti powder removal Yield
c
No.
ratio
ratio
(%)
b
C
(mass
%)
RCat./Ti a
(%)
Ti
Fe others
A
0.2
98.16 0.88 1.76
59
B
0.3
99.10 0.03 0.87
56
C
0.2
98.23 0.23 1.54
90
79
D
0.3
98.44 0.14 1.42
65
88
a: Cationic molar ratio, RCat./Ti = NCat./NTi, where NCat. and NTi are the
mole amounts of the cations in the flux and Ti, respectively.
b: Determined by X-ray fluorescence analysis,
and the value excludes carbon and gaseous elements.
c: Iron removal ratio: (CFe/CTi (Before) – CFe/CTi (After))/(CFe/CTi (Before))
・High-purity metallic Ti powder was obtained
directly from natural Ti ore.
・Ti powder with a yield of 88% was obtained.
(1) Feed preform
: Ti
: Ca
: CaO
(3)
JCPDS # 44-1294
JCPDS # 23-0430
JCPDS # 48-1467
TiO2 + CaO + Ca
: Ti
20
40
60
80
100
Angle, 2 (deg.)
Metallic Ti was successfully obtained
after the experiment.
Mechanism of iron removal (Ti ore chlorination)
Fe2O3(s)
Fe3O4(s)
–10
TiO2(s) FeO(s)
Fe(s)
–20
Ti2O3(s)
–30 TiO(s)
–50
Ti(s)
5 m
Ti powder
5 m
Concentration of element i, Ci a (mass %)
Ti
Fe
Al
Ca
Cl
(1)
68.00
1.07
0.44
11.66
18.83
(2)
60.68
0.42
0.33
14.88
23.70
(3)
17.74
0.07
(0.00)
67.42
14.76
(4)
99.10
0.03
0.30
0.58
(0.00)
a: Determined by X-ray fluorescence analysis,
and the value excludes carbon and gaseous elements.
・Metallic Ti exhibiting a coral-like structure
was obtained.
・Purity of Ti was greater than 99 mass %.
Conclusion
Discussion
–40
(4) Sample obtained
after leaching
JCPDS # 44-1294
Sample obtained
after leaching
0
5 m
TiO2 + CaCl2
Table Analytical results of the obtained sample.
(4)
Ti powder
5 m
(3) Preform after reduction
TiO2 + CaO +Ca
(4)
(2) Preform
after calcination
TiO2 + CaCl2 + Binder
Step
a: Natural rutile ore produced in South Africa after pulverization.
b: Cationic molar ratio, RCat./Ti = NCat./NTi, where NCat. and NTi are
the mole amounts of the cations in the flux and Ti, respectively.
c: C powder was added to the preform during the fabrication step
in experiments C and D.
・Iron removal ratio was enhanced
when C powder was added to the preform.
Iron removal efficiency was improved
when C powder was added to the preform.
(2)
Exp. B, RCat./Ti = 0.3
Reduction
Table Composition of the samples obtained after
leaching and yield of Ti powder
SEM image
: Ti JCPDS # 44-1294
(3)
Experimental results 4
Exp. C, RCat./Ti = 0.2, C powder: 0.2 g
XRD pattern
TiO2 + CaCl2
Cationic
molar
Exp.
ratio
No. a
RCat./Ti b
Experimental results 2
Exp. A, RCat./Ti = 0.2
Photographs
XRD patterns
Table Experimental conditions in this study.
FeClx
Development of a new smelting process
for producing Ti with high purity and
productivity and low cost
Experimental results 1
(1)
TiO2(s) + Ca(g) → Ti(s) + CaO(s)
Features: → Simple and low-cost process
◎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 control purity
○Amount of waste solution is minimized
○Molten salt as a flux can be reduced
in comparison with the other direct
reduction process
△Leaching is required
×Difficult to produce calcium and control
its vapor
Purpose of this study:
Feed preform
(TiO2 feed + flux)
Reductant vapor
Reductant
(R = Ca or Ca-X alloy)
log pO2 (atm)
Calcination/iron removal
(1)
×Difficult to control
the purity
×Large amount of
molten salt
(d) PRP
(1)
Reductant
(R = Ca or Ca-X alloy)
Common features:
Current monitor/
controller
Carbon anode
CaCl2-CaO
molten salt
TiO2
Ca-X alloy
Preform fabrication
Feed preform
Reductant vapor
○Semi-continuous
process
Intensity, I (a.u.)
Japan
18.5 kt
(28% share)
Ti ore
TiO2 preform
CaCl2 molten salt
Ti sponge
Russia
Total 26 kt
65.5 kt
Kazakhstan
9 kt
Carbon anode
CaO(s)/CaCl2(l) eq.
Region for Selective
chlorination of iron
CO(g)/CO2(g) eq.
C(s)/CO(g) eq.
Ti4O7(s)
Ti3O5(s)
FeCl3(g)
FeCl2(g)
H2O(g)/HCl(g) eq.
MgO(g)/MgCl2(g) eq.
TiCl4(g)
TiCl3(g)
–60
–40 –30 –20 –10 0
log pCl2 (atm)
Fig. Combined chemical potential diagram of
the Fe-Cl-O (dotted line) and Ti-Cl-O (solid line)
systems at 1300 K.
FeOx (FeTiOx,s) + HCl(g)
→ FeClx(g)↑ + H2O(g)
FeOx (FeTiOx,s) + CaCl2(l)
→ FeClx(g)↑ + CaO (CaTiOx,s)
aCaO << 1
・FeOx can be chlorinated using CaCl2 + H2O.
・TiOx cannot be chlorinated using CaCl2 or
CaCl2 + H2O.
The feasibility of the preform reduction
process (PRP), based on the
calciothermic reduction of natural Ti ore,
was demonstrated.
・ 90% of iron was successfully removed
by selective chlorination
during the calcination step.
・ When C powder was added to
the preform, iron was removed more
efficiently, and Ti powder with a purity
of 98% and yield of 88% was obtained.
・ It was experimentally demonstrated
that high-purity metallic Ti powder
(greater than 99 mass %) was obtained
directly from natural Ti ore (rutile ore)
by the PRP.
Currently, the development of a more
effective method for the direct removal
of iron from Ti ore, analysis of the
detailed mechanism of selective
chlorination, and development of an
efficient recycling system of CaCl2 flux
and the residual Ca reductant are under
investigation.