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Molten Oxide Electrolysis: Towards “Green” Steelmaking
& Lunar in situ Resource Utilization
3rd Reactive Metals Workshop,
MIT, Cambridge, MA
Mar. 3, 2007
Dihua Wang Department of Materials Science & Engineering
Massachusetts Institute of Technology
Steel:
the most commonly used material
Steel production
2Fe2O3 + 3C =
Pyrometallurgy for steel making
4Fe(l) + 3CO2 (g)2Fe2O3 + 3C =
Pyrometallurgy for steel making
4Fe(l) + 3CO2 (g)
annual production 1.2 billion tonnes (2006)increasing at 8.8% per year
~2.1 billion tonnes CO2 / yr by world’s steel industry
Molten Oxide Electrolysis (MOE)
Sadoway MIT Process
Where should steel industry go?
Innovation
Molten Oxide Electrolysis (MOE)
Processes emitting only products- Gordon Forward, Chaparral Steel
2 Fe2+ + 4 e 2 Fe( ) 2 O2- O2(g) + 4 e
1550-1700oC
Sadoway MIT Process
e e
cathode anode
Fe2+
O= O= O= O=Fe2+
molten oxide electrolyte
Schematic of electrolysis cell for Sadoway Process (proposed)
Oxygen
Iron
FeO
Carbon-free electricity
Supporting electrolyte(CaO-MgO-SiO2)
Electrochemical reduction of iron cation in molten oxide at 1575oC
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4-1.2
-0.8
-0.4
0.0
0.4
0.8
i (A
cm
-2)
E (V vs. Mo)
Deposition of Si
Oxidation of Mo
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4-1.2
-0.8
-0.4
0.0
0.4
0.8
i (A
cm
-2)
E (V vs. Mo)
reduction of Fe2+
stripping of deposited iron
2 Fe2+ + 4 e 2 Fe( )
Electrolysis product
e e
cathode anode
Fe2+
O= O= O= O=Fe2+
molten oxide electrolyte
Constant-current electrolysis at 1575oC(Current density: ~1A cm-2)
Current efficiency: ~ 40% Theoretical: 85%
akingron
echnology
Another great challenge for human sustainability:limited resources living off the land
Sadoway Process forin situ Resource Utilization NASA “ISRU”
Composition of JSC-1a (lunar regolith simulant)
Major Element Composition % by Weight
Silicon Oxide (SiO2) 46-49
Aluminum Oxide (Al2O3) 14.5-15.5
Ferric Oxide (Fe2O3) 3-4
Iron Oxide (FeO) 7-7.5
Magnesium Oxide (MgO) 8.5-9.5
Calcium Oxide (CaO) 10-11
Sodium Oxide (Na2O) 2.5-3
Titanium Dioxide (TiO2) 1-2
Potassium Oxide (K2O) 0.75-0.85
Manganese Oxide (MnO) 0.15-0.20
Chromium III Oxide (Cr2O3) 0.02-0.06
Diphosphorus Pentoxide (P2O5) 0.6-0.7
Mined from a volcanic ash deposit in a commercial cinder quarry located in the San Francisco volcano field.
Closely matches the chemical composition, mineralogy, particle size distribution, and engineering properties of lunar mare soil.
Direct electrolysis lunar soil to in situproduce metals and oxygen on moon
cathodic product ( JSC-1a electrolyte)
Cathode withdrawn from electrolyte
Same minus frozen electrolyte
Constant-current electrolysis at 1350oC
SEM and EDS confirmed iron deposition
50 µm
Elem ent
-------------------Iron M olybdenu m -------------------
Atom. C [a t.-%]
70.12 29.88
-8.0E-02
-6.0E-02
-4.0E-02
-2.0E-02
0.0E+00
2.0E-02
4.0E-02
-200 -100 0 100 200 300 400 500 600 700 800
Cur
rent
(A)
Elapsed Time (s)
Determination of current efficiency by two-step chronoamperometry
- 0.5V deposition
0.3V stripping
Stable background current (0.0024A)obtained by a separate experiment
%100%100, ×−
=×=red
backgroundox
red
netox
QQQ
CE
Current efficiency: ~60%
-0.50 -0.45 -0.40 -0.35 -0.300
20
40
60
80
100
Cur
rent
Effi
cien
cy %
Potential / V
Summary
• For the first time liquid iron was produced in conjunction with oxygen gas by molten oxide electrolysis, demonstrating Sadoway process a first step towards “green” steelmaking.
• Iron and oxygen were extracted by directelectrolysis of lunar regolith simulant.
Acknowledgments
Prof. Sadoway and members of Sadoway group, especially
Dr. Chanaka de Alwis, Dr. Bing Li, Mr. Andrew J. Gmitter, Mr. Guenter Arndt, Ms. Hilary Sheldon
Thank you
