Direct Production of Titanium Powder from Titanium Ore

1
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 Current commercial Ti
production process
Direct reduction of TiO2
Preform reduction process (PRP)
(a) FFC process (Fray et al.)
Current status of industrial production of Ti
Mg TiCl4 feed port
e
Feed preform (TiO2 feed flux)
Metallic reaction vessel
World production of Ti sponge (2003)
Carbon anode
Reductant vapor
Mg MgCl2 recovery port
TiO2 preform
China 4 kt
Reductant (R Ca or Ca-X alloy)
CaCl2 molten salt
Common features ?Simple process ?Semi-continuous
process Difficult to control the
purity Large amount of molten salt
Ti sponge
Ti/Mg/MgCl2 mixture
(b) OS process (Ono Suzuki)
USA 8 kt
Russia 26 kt
TiO2(s) Ca(g) ? Ti(s) CaO(s)
TiO2 powder
Furnace
Total 65.5 kt
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
Chlorination Ti ore C 2 Cl2 ? TiCl4 (
MClx) CO2 Reduction TiCl4 2 Mg ? Ti 2
MgCl2 Electrolysis MgCl2 ? Mg Cl2
e
Kazakhstan 9 kt
Carbon anode
Ca
Japan 18.5 kt (28 share)
CaCl2 molten salt
(c) EMR/MSE process (Okabe et al.)
Comparison with common metals
Current monitor/ controller
e
e
Metal Iron Aluminum Titanium
Symbol Fe Al Ti
Melting point (K) 1809 933 1939
Density (g/cm3 at 298 K) 7.9 2.7 4.5
Specific strength ((kgf/mm2)/(g/cm3)) 47 36 810
Clarke no. 4 3 9
Price (\/kg) 50 600 3000
Production volume (t/world in 2003) 9.6 x 108 2.2 x 107 6.6 x 104
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.
Carbon anode
CaCl2-CaO molten salt
TiO2
Ca-X alloy
(d) PRP
Purpose of this study Development of a new
smelting process for producing Ti with high
purity and productivity and low cost
Feed preform (TiO2 feed flux)
Reductant vapor
Production cost of Ti is high and its
application is limited.
Reductant (R Ca or Ca-X alloy)
1/300
1/15000
Research work
Experimental results 1
Experimental results 2
Typical experimental apparatus for the reduction
process
Exp. A, RCat./Ti 0.2
Exp. B, RCat./Ti 0.3
Flowchart of the PRP
Photographs
XRD patterns
SEM images
TIG welding
(1)
(1)
(1)
(2)
TiO2 CaCl2 CaCl2 (H2O)4
JCPDS 21-1276 JCPDS 74-0522 JCPDS 01-0989
Stainless steel reaction vessel
Feed preform TiO2 CaCl2 Binder
Preform after calcination TiO2 CaCl2
Feed preform TiO2 CaCl2 Binder
Ti ore
Flux
Binder
Ti ore Rutile Flux CaCl2 Binder Collodion
Stainless steel cover
Feed preform after Fe removal
Mixing
Stainless steel net
JCPDS 21-1276 JCPDS 74-0522 JCPDS 01-0989
TiO2 CaCl2 CaCl2 (H2O)4
Stainless steel holder
(2)
(2)
Slurry
(3)
(4)
Preform after reduction TiO2 CaO Ca
Sample obtained after leaching Ti powder
Preform after calcination TiO2 CaCl2
Reductant (Ca)
Ti sponge getter
Preform fabrication
Intensity, I (a.u.)
Feed preform
(1)
Experimental conditions
Ti Ca CaO
JCPDS 44-1294 JCPDS 23-0430 JCPDS 48-1467
(3)
(3)
Preform after reduction TiO2 CaO Ca
Table Analytical results of the obtained sample.
Calcination/iron removal
FeClx
Table Experimental conditions in this study.
Step Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass )
Step 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)
Exp. No. a Cationic molar ratio Calcination Calcination Reduction Reduction
Exp. No. a Cationic molar ratio Temp. Time Temp. Time
Exp. No. a RCat./Ti b Tcal./K t'cal./h Tred./K t'red./h
A 0.2 1273 1 1273 6
B 0.3 1273 1 1273 6
C c 0.2 1273 2 1273 9
D c 0.3 1273 2 1273 9
Sintered feed preform
(2)
JCPDS 44-1294
Ti
(4)
(4)
Reduction
Ca vapor
Sample obtained after leaching Ti powder
(3)
Reduced preform
100
80
60
40
20
Angle, 2? (deg.)
Leaching
Acid
Waste solution
a Determined by X-ray fluorescence analysis,
and the value excludes carbon and gaseous
elements.
Vacuum drying
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.
Metallic Ti exhibiting a coral-like structure
was obtained. Purity of Ti was greater than 99
mass .
Metallic Ti was successfully obtained after the
experiment.
Powder
(4)
Conclusion
Experimental results 3
Experimental results 4
Discussion
Exp. C, RCat./Ti 0.2, C powder 0.2 g
Mechanism of iron removal (Ti ore chlorination)
Table Composition of the samples obtained after
leaching and yield of Ti powder
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.
0
CaO(s)/CaCl2(l) eq.
Fe2O3(s)
SEM image
XRD pattern
Exp. No. Cationic molar ratio RCat./Ti a Concentration of Ti and Fe in the obtained Ti powder C b (mass ) Concentration of Ti and Fe in the obtained Ti powder C b (mass ) Concentration of Ti and Fe in the obtained Ti powder C b (mass ) Iron removal ratio c () Yield ()
Exp. No. Cationic molar ratio RCat./Ti a Ti Fe others Iron removal ratio c () Yield ()
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
Region for Selective chlorination of iron
Fe3O4(s)
10
FeO(s)
TiO2(s)
Ti powder obtained after leaching
CO(g)/CO2(g) eq.
(4)
(4)
Ti
JCPDS 44-1294
Fe(s)
C(s)/CO(g) eq.
20
Ti4O7(s)
Ti2O3(s)
Ti3O5(s)
log pO2 (atm)
TiO(s)
30
FeCl3(g)
FeCl2(g)
5 ?m
40
H2O(g)/HCl(g) eq.
20
40
60
80
100
MgO(g)/MgCl2(g) eq.
Ti(s)
50
TiCl4(g)
Table Analytical results of the obtained sample.
TiCl3(g)
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))
Step Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass ) Concentration of element i, Ci a (mass )
Step 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)
60
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 ltlt 1
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.
High-purity metallic Ti powder was obtained
directly from natural Ti ore. Iron removal ratio
was enhanced when C powder was added to the
preform. Ti powder with a yield of 88 was
obtained.
a Determined by X-ray fluorescence analysis,
and the value excludes carbon and gaseous
elements.
FeOx can be chlorinated using CaCl2 H2O. TiOx
cannot be chlorinated using CaCl2 or CaCl2
H2O.
Iron removal efficiency was improved when C
powder was added to the preform.