ELECTROCHEMICAL PATHWAYS TOWARDS CARBON-FREE METALS PRODUCTION Donald R. Sadoway Department of Materials Science & Engineering Massachusetts Institute of Technology Cambridge, Massachusetts
The message
The road to sustainability is paved with advanced materials.
Sadoway
GCEP Carbon Management in Manufacturing Industries
April 15, 2008
problems with metals extraction
unfavorable by-products steelmaking makes CO2 2 FeO + C = 2 Fe + CO2 ( kg C / kg Fe) x 1.2 billion tonnes
sundry HAPs including Mn & Pb, polycyclic organics, benzene, & CS2 Sadoway
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Why is metal production so dirty?
many processes are over 100 years old
attitude then of indifference towards the environment Sadoway
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Why is metal production so dirty?
“Where there’s smoke, there’s money.” Sadoway
GCEP Carbon Management in Manufacturing Industries
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We’re all just temporarily visiting this planet
Towards sustainability
Green technology Sadoway
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April 15, 2008
ELECTROCHEMICAL PATHWAYS TOWARDS CARBON-FREE METALS PRODUCTION Donald R. Sadoway Department of Materials Science & Engineering Massachusetts Institute of Technology Cambridge, Massachusetts
Where do metals come from? occur naturally as compounds beneficiated high-purity feed reducing agents: H, C, M, e options for sustainability?
Sadoway
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April 15, 2008
beyond the blast furnace most metals are found in nature as oxides “like dissolves like” e- is the best reducing agent
molten oxide electrolysis: extreme form of molten salt electrolysis where pure oxygen gas is the by-product
Sadoway
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April 15, 2008
aluminum produced by electrolytic reduction of Al2O3 world capacity: ~40 million tons/year 1886 Charles Martin Hall, USA Paul Héroult, France
decompose Al2O3 dissolved in Na3AlF6 (T = 960°C) liquid Al (-) and CO2 (+) find an inert anode & molten oxide electrolyte
green ironmaking: cell schematic x
(FeOx) Fe(l) + O2
iron
iron
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Technology Needs: dateline 2050
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Technology Taxonomy: Reducing Agents
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kg CO2/tls
GJ net energy
Environmental Impact & Energy Savings
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GCEP Carbon Management in Manufacturing Industries
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Environmental Impact & Energy Savings
CO2 emissions reduced from 1750 kg/tonne liquid steel for benchmark blast furnace technology to 345 kg/tonne liquid steel: a five-fold reduction 90 g CO2/kWh for generation of electric power equivalent energy consumption: MOE vs benchmark
Sadoway
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Other Benefits
tonnage oxygen
Sadoway
GCEP Carbon Management in Manufacturing Industries
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scientific and technical challenges
molten oxides of transition metals exhibit electronic conduction inert anode operable at temperatures as high as 1700°C in an oxide melt
Sadoway
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some of the relevant engineering science:
electrical conductivity measurements transference number measurements voltammetry process kinetics electrolysis testing Sadoway
GCEP Carbon Management in Manufacturing Industries
April 15, 2008
conductivity measurements
inventing two new techniques for aggressive
melts at high temperatures: moveable coaxial cylinders 4-point crucible
Sadoway
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moveable coaxial cylinders
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GCEP Carbon Management in Manufacturing Industries
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effect of FeO addition: = (T, c) 1425 T(ºC) 0
1650
1579
1513
1451
1394
1340
1.000 0.606
ln / S cm-1
-0.5
20% 15%
-1.0
0.367 0.223
-1.5
10% 0.135
-2.0
Sadoway
5%
S1
-2.5 50
/ S cm-1
1727
52
54
56 105/T
58
0.082 60
62
(K)
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FeO greatly raises conductivity 0.45
= 2.0766 XFeO + 0.0897
0.40
R2 = 0.9796
/ S cm-1
0.35 0.30 0.25 0.20 0.15
T = 1425ºC
0.10 0.05 0
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
XFeO in S1 Sadoway
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regression of conductivity data 0.45 0.40
y = x R2 = 0.8918
0.35
/ S cm-1
0.30 0.25
T = 1425ºC
0.20 0.15 0.10
= ai*Xi
0.05 0 0
0.10
0.20
0.30
0.40
0.50
= - 0.138 - 0.361*SiO2 + 1.186*FeO + 0.917*(FeO+MgO+CaO) Sadoway
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electrochemistry at white heat
CaO - MgO - SiO2 scan rate = 50 mV s-1 T = 1575°C
electrochemistry at white heat add 5% FeO to CaO - MgO - SiO2 scan rate = 50 mV s-1 T = 1575°C
--- supporting electrolyte --- 5 wt% FeO
electrolytic production of molten iron:
cathode: Mo anode: Pt electrolyte: CaO - MgO - SiO2 feed: FeO crucible: Mo reactor tube: Al2O3
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constant-current electrolysis at 1575oC current density: ~1 A cm-2
Mo crucible
electrolyte
iron
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more electrolytic production of molten iron:
iron
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SEM and EDX analysis
let’s now raise our sights oxygen generation on the moon by molten oxide electrolysis: sustaining human life rocket propellant
Oxygen Extraction From Regolith
Lab-scale Cell for Regolith Electrolysis furnace power supply Ar in Ar out
potentiostat and impedance spectrometer
Ar bubblers water chiller (for cell cap) hot zone
Sadoway
University of Michigan
April 4, 2008
Lab-scale Cell for Regolith Electrolysis furnace power supply Ar in Ar out
potentiostat and impedance spectrometer
Ar bubblers water chiller (for cell cap) hot zone
Sadoway
University of Michigan
April 4, 2008
Sadoway
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April 15, 2008
Sadoway
University of Michigan
April 4, 2008
Sadoway
University of Michigan
April 4, 2008
O2 evolution rate vs. optical basicity
i = FAk°CO e-F/RT 2-
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April 15, 2008
O2 evolution rate vs. optical basicity
i = FAk° e-F/RT
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cyclic voltammetry in titanates at 1550ºC
supporting electrolyte
WE: Mo RE: Ti CE: Mo
melt containing TiO2
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April 15, 2008
cyclic voltammetry in titanates at 1550ºC
Current
WE: Ti supporting electrolyte
RE: Ti CE: Mo
melt containing TiO2
electrolytic production of liquid titanium T = 1725°C (above m.p. of Ti)
Mo crucible
frozen electrolyte
titanium puddle cathode: Mo anode: C current density 1 A/cm2 Sadoway
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analysis of metal pool indicates titanium CP titanium titanium made by the Sadoway Process
Sadoway
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what have we learned? deposition of Fe, Ti, Ni, & Cr in oxide melts from oxide feedstock
very high current densities are sustainable 5 A cm-2 observed; maybe higher! c.f. 0.7 A cm-2 in Hall-Héroult cell 15 productivity of aluminum smelting capable of tonnage productivity Sadoway
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what else have we learned?
first evidence of inert anode full realization of the concept of molten oxide electrolysis carbon-free metal making with tonnage industrial oxygen as by-product
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workshop questions
How would low- or zero-cost CO2
sequestration change the game, and what barriers to separating and capturing carbon would remain?
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workshop questions
If carbon-free or carbon-neutral energy
carriers were cost competitive with current feedstocks, what technical and economic challenges would prevent the switch to those fuels?
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workshop questions
What are the opportunities for disparate
industries to collaborate on carbon management?
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workshop questions
How can industry's specialized
knowledge of process engineering and material handling address the grand challenge of reducing carbon emissions?
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workshop questions
What are the research priorities in your
area of investigation and why?
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workshop questions
What barriers exist to successful
research and what breakthroughs are needed?
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workshop questions
What are the opportunities for
fundamental, academic research to develop pathways for technologies to overcome the barriers?
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workshop questions
Where do you feel that a contribution by
a project such as GCEP could have the most impact?
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towards carbon-free metallurgy
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GCEP Carbon Management in Manufacturing Industries
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The End
