ELECTROCHEMICAL PATHWAYS TOWARDS CARBON-FREE … · Sadoway GCEP Carbon Management in Manufacturing Industries April 15, 2008 problems with metals extraction steelmaking makes CO

ELECTROCHEMICAL PATHWAYS

TOWARDS

CARBON-FREE

METALS PRODUCTION

Department of Materials Science

& Engineering

Massachusetts Institute of Technology

Cambridge, Massachusetts

Donald R. Sadoway

GCEP Carbon Management in Manufacturing Industries April 15, 2008 Sadoway

The message

The road to sustainability is paved

with advanced materials.


problems with metals extraction

� 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

� unfavorable by-products �


Why is metal production so dirty?

� many processes are over

100 years old

� attitude then of indifference

towards the environment


Why is metal production so dirty?

“Where there’s smoke, there’s money.”


We’re all just temporarily visiting this planet

Towards sustainability

� Green technology

ELECTROCHEMICAL PATHWAYS

TOWARDS

CARBON-FREE

METALS PRODUCTION

Department of Materials Science

& Engineering

Massachusetts Institute of Technology

Cambridge, Massachusetts

Donald R. Sadoway


Where do metals come from?

� occur naturally as compounds

� beneficiated � high-purity feed

� reducing agents: H, C, M, e-

� options for sustainability?


beyond the blast furnace

extreme form of molten salt electrolysis

� molten oxide electrolysis:

where pure oxygen gas is the by-product

��

� most metals are found in nature as oxides

� “like dissolves like”

� e- is the best reducing agent

world capacity: ~40 million tons/year

aluminum produced by electrolytic reduction of Al2O3

decompose Al2O3 dissolved in Na3AlF6 (T = 960°C)

� liquid Al (-) and CO2 (+)

� find an inert anode & molten oxide electrolyte

Charles Martin Hall, USAPaul Héroult, France

1886


(FeOx) � Fe(l) + � O2

iron

iron

green ironmaking: cell schematic

x


Technology Needs: dateline 2050


Technology Taxonomy: Reducing Agents


Environmental Impact & Energy Savings

kg

CO

2/t

ls

GJ n

et

en

erg

y


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


Other Benefits

tonnage oxygen


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


some of the relevant engineering science:

� electrical conductivity measurements

� transference number measurements

� voltammetry � process kinetics

� electrolysis testing

�

�

�

�


conductivity measurements

� inventing two new techniques for aggressive

melts at high temperatures:

� moveable coaxial cylinders

� 4-point crucible


moveable coaxial cylinders


effect of FeO addition: � = �(T, c)

-2.5

-2.0

-1.5

-1.0

-0.5

0

50 52 54 56 58 60 62

105/T (K)

S1

20%

5%

10%

15%

1.000

0.606

0.367

0.223

0.135

0.082

1727 1650 1579 1513 1451 1394 1340

T(ºC)

� /

S c

m-1

ln �

/ S

cm

-1

1425


FeO greatly raises conductivity

0

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

� / S

cm

-1

T = 1425ºC

XFeO in S1

� = 2.0766 XFeO + 0.0897

R2 = 0.9796


regression of conductivity data

y = x

R2 = 0.8918

0

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.10 0.20 0.30 0.40 0.50

� = - 0.138 - 0.361*SiO2 + 1.186*FeO + 0.917*(FeO+MgO+CaO)

� / S

cm

-1

T = 1425ºC

0

� = � ai*X

i

electrochemistry at white heat

CaO - MgO - SiO2

T = 1575°C

scan rate = 50 mV s-1

electrochemistry at white heat

CaO - MgO - SiO2

T = 1575°C

scan rate = 50 mV s-1

--- supporting electrolyte

--- 5 wt% FeO

add 5% FeO to


electrolytic production of molten iron:

cathode: Mo

anode: Pt

electrolyte:

CaO - MgO - SiO2

feed: FeO

crucible: Mo

reactor tube: Al2O3


constant-current electrolysis at 1575oC

current density: ~1 A cm-2

iron

electrolyte

Mo crucible


more electrolytic production of molten iron:

iron

SEM and EDX analysis

oxygen generation on the moon

by molten oxide electrolysis:

� sustaining human life

� rocket propellant

let’s now raise our sights

Oxygen Extraction From Regolith

University of Michigan April 4, 2008 Sadoway

Lab-scale Cell for Regolith Electrolysis

water chiller (for cell cap)

Ar in

Ar out

potentiostat and

impedance spectrometer

furnace power supply

hot zone

Ar bubblers


Lab-scale Cell for Regolith Electrolysis

water chiller (for cell cap)

Ar in

Ar out

potentiostat and

impedance spectrometer

furnace power supply

hot zone

Ar bubblers





O2 evolution rate vs. optical basicity

i = FAk°CO2-e-�F�/RT


O2 evolution rate vs. optical basicity

i = FAk°�e-�F�/RT


cyclic voltammetry in titanates at 1550ºC

WE: Mo

RE: Ti

CE: Mo

supporting electrolyte

melt containing TiO2

WE: Ti

RE: Ti

CE: Mo

cyclic voltammetry in titanates at 1550ºC

supporting electrolyte

melt containing TiO2

Cu

rre

nt


electrolytic production of liquid titanium

frozen electrolyte

titanium puddle

Mo crucible

cathode: Mo

anode: C

current density �1 A/cm2

T = 1725°C (above m.p. of Ti)


analysis of metal pool indicates titanium

CP titaniumtitanium

made by theSadowayProcess


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


what else have we learned?

� first evidence of inert anode

� carbon-free metal making with tonnage

industrial oxygen as by-product

� full realization of the concept of

molten oxide electrolysis


workshop questions

� How would low- or zero-cost CO2

sequestration change the game, and

what barriers to separating and capturing

carbon would remain?


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?


workshop questions

� What are the opportunities for disparate

industries to collaborate on carbon

management?


workshop questions

� How can industry's specialized

knowledge of process engineering and

material handling address the grand

challenge of reducing carbon emissions?


workshop questions

� What are the research priorities in your

area of investigation and why?


workshop questions

� What barriers exist to successful

research and what breakthroughs are

needed?


workshop questions

What are the opportunities for

fundamental, academic research to

develop pathways for technologies to

overcome the barriers?


workshop questions

Where do you feel that a contribution by

a project such as GCEP could have the

most impact?


towards carbon-free metallurgy

The End

Documents

ELECTROCHEMICAL PATHWAYS TOWARDS CARBON-FREE … · Sadoway GCEP Carbon Management in Manufacturing Industries April 15, 2008 problems with metals extraction steelmaking makes CO