Steelmaking
by
Molten Oxide Electrolysis
Department of Materials Science
& Engineering
Massachusetts Institute of Technology
Cambridge, Massachusetts
Donald R. Sadoway
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
goal of the research
develop a carbon-free technology for the production of iron by molten oxide electrolysis
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
(FeOx) Fe(l) + ½ O2iron
iron
green ironmaking: cell schematic
x
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 L.T. Héroult, France
1886
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Technology Needs: dateline 2050
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Technology Taxonomy: Reducing Agents
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Environmental Impact & Energy Savings
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Environmental Impact & Energy Savings
what did the European study conclude?
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
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Environmental Impacts & Other Benefits
zero GHG emissions when electricity is carbon-free
byproduct tonnage oxygen
no coke ovens, blast furnace, BOF
treatment of hazardous waste,
e.g., chromate sludge
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
Technical Challenges & Barriers
suitable electrolyte: no electronic conductivityinert anodeoperational stability of cell
service life of cell components
metal purity
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
progress to date:
designed, constructed, and operated laboratory-scale cell up to 1750ºC
conducted electrochemical testing on candidate electrolyte melts
demonstrated production of liquid iron and oxygen gas by electrolysis in laboratory-scale cell
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
electrolytic production of molten iron:
cathode: Mo
anode: Pt
electrolyte:
CaO - MgO - SiO2
feed: FeOcrucible: Moreactor tube: Al2O3
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
constant-current electrolysis at 1575oC
current density: ~1 A cm-2
iron
electrolyte
Mo crucible
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
more electrolytic production of molten iron:
iron
SEM and EDX analysis
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
what have we learned?
deposition of iron is feasible in these
meltsvery high current densities are sustainable
5 A cm-2 observed; maybe higher!
c.f. 0.7 A cm-2 in Hall-Héroult cell15⋅ productivity of aluminum smelting
4 capable of producing tonnage metal
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
what else have we learned?
first evidence of inert anode
full realization of the molten oxide electrolysis concept
carbon-free steelmaking with tonnage industrial oxygen as by-product
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
next steps: phase 2
design, build, & operate pre-pilot cell
- current: 4000 A = 100⋅ today’s lab cell
- externally heated
- operating temperature: 1675ºC
- daily productivity: 67 kg Fe & 29 kg O2
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
acknowledgments
Dr. Aislinn SirkMr. Andrew GmitterVisiting Professor Dihua Wang Dr. Chanaka DeAlwis
Thank you for your attention!
AISI Annual Meeting, Phoenix, AZ May 6, 2008Sadoway
towards carbon-free steelmaking