Microsoft PowerPoint - Sadoway RMW3pMassachusetts Institute of Technology Cambridge, Massachusetts
The Principles of Oxygen
electrolyte chemistry
cell feed
current density
current efficiency
voltage efficiency
consumables
renewables
Ionic Liquids
+
Ionic Liquids power supply
T ≈ room temp.
0.99 V
1.35 V
1.71 V
1.84 V
1.92 V
2.28 V
2.48 V
2.68 V
850°C
Molten Fluorides power supply
Si4+ + 4 e Si(s)
oxide solubility in fluorides is not universal
TiO2 + 3 F- = TiOF3 -
Sadoway 3rd Reactive Metals Workshop March 2, 2007
electrochemical stability: EMF series
Molten Fluorides power supply
Si4+ + 4 e Si(s)
Molten Chlorides power supply
Fe2+ + 2 e Fe(s)
Si4+ + 4 e Si(s)
Sadoway 3rd Reactive Metals Workshop March 2, 2007
electrochemical stability: EMF series
calciothermic reduction of regolith
Ca + FeO = Fe + CaO
3 Ca + Al2O3 = 2 Al + 3 CaO
Sadoway 3rd Reactive Metals Workshop March 2, 2007
power supply
(solvent + feed)
(flux + regolith)
molten CaCl2 – CaO
Molten Chlorides: FFC / British Ti
(flux + regolith)
O2- ½ O2(g) + 2 e FeO + 2 e Fe(s) + O2-
SiO2 + 4 e Si(s) + 2 O2-
consolidated regolith
Fluxed Molten Oxides power supply
(solvent + feed)
Na+ + e Na(l)
electrochemical stability: EMF series
electrolyte chemistry: regolith + flux
crucible material: Mo, carbon
current efficiency: 80%
voltage efficiency: 50%
Sadoway 3rd Reactive Metals Workshop March 2, 2007
previous work at MIT
Viton O-ring
tube furnace
alumina beads
cell design
• 6 mm ø planar
counter electrode • carbon crucible
cell design
• Fe rod in melt of 10% FeO - supporting electrolyte
• alumina tube capped with hot-pressed BN
• contact via drill hole 0.4 mm ø
Sadoway 3rd Reactive Metals Workshop March 2, 2007
needs for steady-state operation fluxed oxide
consumables anode? flux?
control of electrolyte level partial extraction of metal value
control of electrolyte composition staying molten as composition shifts
containment crucible lined with frozen electrolyte
power supply
(solvent + feed)
Molten Oxide Electrolysis
molten regolith
electrochemical stability: EMF series
electrolyte chemistry: regolith
cell feed: regolith
crucible material: Mo or regolith
operating parameters / figures of merit
current density: 5 A cm-2
current efficiency: 60%
voltage efficiency: 30%
_
+ to oxygen sensor
Schematic of experimental setup
Sadoway 3rd Reactive Metals Workshop March 2, 2007
Electrolysis of JSC-1a on Mo electrodes
Working electrode: Mo rod
Reference electrode: Fe rod
Counter electrode: Mo rod
Heat source: carbon tube furnace WERECE
JSC-1a
Mo rod
Cathode after removing the
The product with Mo rod held by a magnetic vertically
Cross section of the cathode
Mo rod
Cathode after removing the
The product with Mo rod held by a magnetic vertically
Cross section of the cathode
Electrodeposit on Mo suspended from magnet
Cathode withdrawn from electrolyte
Same minus frozen electrolyte
SEM and EDS confirmed iron deposition
Element Series unn. C norm. C Atom. C [wt.-%] [wt.-%] [at.-%] ------------------------------------------------ Iron K-series 59.92 57.74 70.12 Molybdenum L-series 43.86 42.26 29.88 ------------------------------------------------
Sample 1116
50 µm
needs for steady-state operation molten oxide
consumables anode?
renewables electrolyte
control of electrolyte level partial extraction of metal value
control of electrolyte composition staying molten as composition shifts
containment crucible lined with frozen electrolyte
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250 300 grams O2 produced
D is
so ci
at io
n Po
te nt
ia l (
relative amounts of regolith constituents and energy cost associated with electrowinning of each
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250 300 grams O2 produced
D is
so ci
at io
n Po
te nt
ia l (
variation in electrolyte solidification temperature under galvanostatic electrolysis
Sadoway 3rd Reactive Metals Workshop March 2, 2007
status report
production of oxygen repeatedly verified
much to be learned by analogy with Al smelting
capacity for metal & semiconductor extraction
technical questions remain: electrode life, separation of cell products, management of electrolyte composition, start-up, thermal management
need data from self-heating cell
The End