Polar™ Titanium – Development of the
BHP Billiton Titanium Metal Production
Process
G.D. Rigby, I.P. Ratchev, R.I. Olivares, K. Mukunthan,
S.A. Bliznyukov, and A.A. Shook
Titanium 2005 – Emerging Technologies session
21st Annual ITA Conference
25-27 September 2005, Scottsdale, AZ, USA
The Polar™ Titanium process is based on reduction of
TiO2 to Ti using molten salt electrochemistry
Cathodic reactions
CaO(in salt) + 2e- = CaMet (in salt) + O2TiO2 + 2Ca(in salt) = Ti + 2CaO(in salt)
e- _ +
Anodic reactions
O2- + C(anode) = CO(gas) + 2e-
Cathode
2O2- + C(anode) = CO2(gas) + 4e-
e-
TiO2 + C = Ti + {CO(gas) + CO2 (gas)}*
Kinetics of the reaction are
important – key parameters for
investigation include:
• Reactor temperature,
• Applied voltage,
• Electrolyte composition
• Feed properties
[O]Ti
TiO2
*
Molten salt
O2-
CaO
Ca2+
CO
CO2
CO
CO2
CaCl2
(& CaO)
Stoichiometry not shown, CO/CO2 ratio varies with
process conditions
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Carbon
anode
Polar™ Titanium
- Project history
2001 - 2002
Gram-scale
fundamentals
2001
2002
2003 - 2004
Design, construction, commissioning
2003
2004
2004 - 2005
kg-scale operation
2005
2006
Fundamental program
• Elucidated the key reaction mechanisms and provided an IP portfolio base.
• Provided key understanding of reduction kinetics as a function of electrode design, current
densities, process voltage, temperature, salt composition, feed morphology & properties.
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Attributes of the experimental facilities – main reactor
REACTORS
• Containment of up to 1 t of molten salt
(CaCl2).
• CaCl2 preheating and melting plant for
reactor startup (patented).
• Molten CaCl2 salt temperature up to
150°C of salt superheat (i.e. to 930°C
in-salt temperature).
• Variable reduction power to 4800 A,
or to a potential of 16 V.
• Off gas handling facilities and reactor
shrouding to 28 m3 min-1 (1000 cfm).
Off gas scrubbing facilities for HCl,
Cl2, and CaCl2 fume.
• Inert gas (Ar) shielding for mitigation
of metal re-oxidation.
PROCESS CONTROL & MONITORING
• Cascaded, multi-zone, flux-limited control
for near isothermal furnace heating.
• Individual current and voltage monitoring
for every electrode.
• Real-time product gas analysis (CO,
CO2, and O2).
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Titanium produced in recent reactor trials for a range of
feed types
5.0
14
4.0
10
3.0
8
6
2.0
4
1.0
2
0.0
March 2005
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
0
August 2005
Cumulative Titanium (kg)
Titanium produced (kg)
12
1.0
5.0
0.8
4.0
0.6
3.0
0.4
2.0
0.2
1.0
0.0
0.0
March 2005
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
August 2005
Titanium produced (kg)
Oxygen (%)
Oxygen content in reduced titanium during experimental
program
0.10
5.0
0.08
4.0
0.06
3.0
0.04
2.0
0.02
1.0
0.00
March 2005
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
0.0
August 2005
Titanium produced (kg)
Carbon (%)
Carbon content in reduced titanium during experimental
program
A range of TiO2 feed morphologies have been tested
Micrographs show fracture surfaces of TiO2 feed forms.
Increasing sintering temperature
Increasing BET surface area (m2/g)
Increasing reactivity
Increasing physical integrity
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Final titanium metal product - morphology changes
throughout the reduction process
Feed stock (TiO2)
Ti metal (low O)
CaTiO3
Ti metal (high O)
• The morphology of the final
titanium develops to the final
form as the oxygen content is
progressively reduced.
TiO
Scale
10 µm
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Typical product chemistry
• Quality achieved to date
Oxygen < 0.05%;
Carbon < 0.02%;
Nitrogen < 0.009%
Hydrogen < 0.01%
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
20
100
18
90
16
80
14
70
12
60
10
50
8
40
6
30
4
20
2
10
0
0
1
2
3
O
4
Ca
5
Cl
C
6
Ti
7
Ti, [wt.%]
• Potential for a range of products:
ingot, sheet, or powder.
• Product quality from the reactor can be varied
to suit market requirements.
O, Ca, Cl, C, [wt%]
Product analysis comments
• As reduction reactions proceed, the feed form progressively attains final product
specifications, moving through a series of transitions to produce Ti:
TiO2 ⇒Ti4O7 ⇒ Ti3O5 ⇒ Ti2O3 ⇒ CaxTiyOz ⇒ TiO ⇒ Ti metal (0 to 15% O)
Titanium metal produced in the Polar™ reactor has been
amenable to milling to powder
0.5 -1.0 mm
0.25-0.50 mm
0.05-0.25 mm
-0.05 mm
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
• Milling of Ti product
accomplished using standard
hammer and disc mill equipment
with inert gas shroud.
• Milled shape is encouraging for
all size distributions.
• Pre-milling morphology of
uniformly-distributed microscale
pores is preserved within
individual particles.
Process and commercial development
• BHP Billiton have committed significant resources to the experimental program
for Polar™ Titanium development.
• There has been promising experimental process development, from gram to
kilogram scale at BHP Billiton’s Newcastle Technology Centre.
• A program of product characterisation work is underway for all product forms.
• Operation at 10kg/day scale is planned by end of calendar year 2005, with a
0.25 t/day scale demonstration plant under design, dependent upon success of
the 10kg/day pilot.
• BHP Billiton interest is ultimately aimed at commodity level production of
titanium, and work is continuing to prove the commercial viability of the
process.
• A collaboration strategy is being considered, but will be based on all
collaborating parties adding value to the business.
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
(Spare slide) Decomposition potentials of titanium oxides
in the presence of solid carbon
• If the reduction process takes place via calcium, only negligible rates of reduction
will be observed under voltages below ~1.2V.
Ti3O5
Decomposition potential, V
0.5
TiO2
TiOx+xC=Ti+xCO(gas)
0
α+TiO
-0.5
α+β
-1
Ca=0.00001wt.%
Ca=0.0001wt.%
Ti2O3
-1.5
CaO+C=Ca+CO
-2
0.001
Ca=0.01wt.%; CaO=0.2 wt.%
0.01
0.1
Oxygen, wt %
Titanium 2005 – 21st Annual ITA Conference, Scottsdale, AZ, USA – 25-27 September 2005
© BHP Billiton Innovation Pty Ltd – September 2005
1
10
100