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
Current status of industrial production of Ti
Metal Iron Aluminum TitaniumSymbol Fe Al TiMelting point (K) 1809 933 1939Density (g/cm3 at 298 K)
7.9 2.7 4.5
Specific strength((kgf/mm2)/(g/cm3))
4~7 3~6 8~10
Clarke no. 4 3 9Price (\/kg) 50 600 3000Production volume (t/world in 2003)
9.6 x 108 2.2 x 107 6.6 x 104
1/150001/300
Comparison with common metals
World production of Ti sponge (2003)
China4 kt
USA8 kt
Russia26 ktTotal
65.5 ktKazakhstan9 kt
Japan18.5 kt (28% share)
Introduction
Chlorination Ti ore + C + 2 Cl2 → TiCl4 (+ MClx) + CO2
Reduction TiCl4 + 2 Mg → Ti + 2 MgCl2
Electrolysis MgCl2 → Mg + Cl2
The Kroll process Current commercial Ti production process
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.
Mg & TiCl4 feed port
Mg & MgCl2 recovery port
Ti sponge
Ti/Mg/MgCl2 mixture
Furnace
Metallic reaction vessel
Production cost of Ti is high and its application is limited.
Direct reduction of TiO2
e–
CaCl2 molten salt
TiO2 preform
Carbon anode
(a) FFC process (Fray et al.)
TiO2 powder
Carbon anode
e–
CaCl2 molten salt
Ca
(b) OS process (Ono & Suzuki)
CaCl2-CaO molten salt
Current monitor/controller
e–
Carbon anode
TiO2
e–
Ca-X alloy
(c) EMR/MSE process (Okabe et al.)
(d) PRP
Reductant vaporReductant(R = Ca or Ca-X alloy)
Feed preform(TiO2 feed + flux)
Common features:
○Simple process○Semi-continuous process
×Difficult to control the purity×Large amount of molten salt
Preform reduction process (PRP)
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
TiO2(s) + Ca(g) → Ti(s) + CaO(s)
Purpose of this study:Development of a new smelting process for producing Ti with high purity and productivity and low cost
Reductant vapor
Feed preform(TiO2 feed + flux)
Reductant(R = Ca or Ca-X alloy)
Flowchart of the PRP
Powder
Feed preform
Reduced preform
Mixing
Vacuum drying
Ca vapor
Acid Waste solution
Slurry
Preform fabrication
Ti ore Flux Binder
FeClx
Reduction
Ti ore: Rutile Flux: CaCl2Binder: Collodion
Sintered feed preform
Leaching
Calcination/iron removal
(1)
(2)
(3)
(4)
Research work
Exp.No. a
Cationicmolar ratio
Calcination Reduction
Temp. Time Temp. Time
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
Experimental conditions
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.
Table Experimental conditions in this study.
Stainless steel net
Reductant (Ca)
Stainless steel reaction vessel
Ti sponge getter
Feed preformafter Fe removal
TIG welding
Stainless steel cover
Stainless steel holder
Experimental results 1Exp. A, RCat./Ti = 0.2
Photographs(1)
(2)
(3)
(4)
Inte
nsity
, I
(a.u
.)
: TiO2
: CaCl2: CaCl2 (H2O)4
JCPDS # 21-1276JCPDS # 74-0522JCPDS # 01-0989
JCPDS # 44-1294: Ti
Angle, 2 (deg.)10080604020
(1)
(2)
(3)
(4)
XRD patterns: TiO2
: CaCl2: CaCl2 (H2O)4
JCPDS # 21-1276JCPDS # 74-0522JCPDS # 01-0989
: Ti: Ca: CaO
JCPDS # 44-1294JCPDS # 23-0430JCPDS # 48-1467
Metallic Ti was successfully obtained after the experiment.
Feed preform
TiO2 + CaCl2 + Binder
Preform after calcination
TiO2 + CaCl2
Preform after reduction
TiO2 + CaO +Ca
Sample obtainedafter leaching
Ti powder
Experimental results 2Exp. B, RCat./Ti = 0.3
・ Metallic Ti exhibiting a coral-like structure was obtained.・ Purity of Ti was greater than 99 mass %.
Table Analytical results of the obtained sample.
a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements.
5 m
(1)
(3)
(2)
(4)
SEM images
5 m
5 m5 m
StepConcentration 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)
Feed preform
TiO2 + CaCl2 + Binder
Preform after calcination
TiO2 + CaCl2
Preform after reduction
TiO2 + CaO + Ca
Sample obtainedafter leaching
Ti powder
Experimental results 3
SEM image
Exp. C, RCat./Ti = 0.2, C powder: 0.2 g
5 m
Table Analytical results of the obtained sample.
a: Determined by X-ray fluorescence analysis, and the value excludes carbon and gaseous elements.
Iron removal efficiency was improved when C powder was added to the preform.
StepConcentration 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)
XRD pattern(4)
20 40 60 80 100
JCPDS # 44-1294: Ti(4)
Experimental results 4
・ 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.
Exp. No.
Cationic molar ratio
RCat./Ti a
Concentration of Ti and Fe in
the obtained Ti powderC b (mass %)
Iron removal ratio c
(%)
Yield(%)
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
Table Composition of the samples obtained after leaching and yield of Ti powder
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))
Discussion
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.
Mechanism of iron removal (Ti ore chlorination)
Fig. Combined chemical potential diagram of the Fe-Cl-O (dotted line) and Ti-Cl-O (solid line) systems at 1300 K.
TiCl4(g)TiCl3(g)
–40
–10
–30
–20
–50
–60–40 –10–30 –20 0
CaO(s)/CaCl2(l) eq.
H2O(g)/HCl(g) eq.MgO(g)/MgCl2(g) eq.
log pCl2 (atm)
FeCl3(g)Ti3O5(s)Ti4O7(s)
FeCl2(g)
Fe2O3(s)
Fe3O4(s)FeO(s)TiO2(s)Fe(s)
Ti2O3(s)
TiO(s)
Ti(s)
Region for Selective chlorination of iron
log
p O2 (
atm
)
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.
Conclusion
Ti powder obtained after leaching
Typical experimental apparatusfor the reduction process
0
1 cm
C(s)/CO(g) eq.CO(g)/CO2(g) eq.
