steelmaking by molten oxide...

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


(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


Technology Needs: dateline 2050


Technology Taxonomy: Reducing Agents


Environmental Impact & Energy Savings


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


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


Technical Challenges & Barriers

suitable electrolyte: no electronic conductivityinert anodeoperational stability of cell

service life of cell components

metal purity


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


electrolytic production of molten iron:

cathode: Mo

anode: Pt

electrolyte:

CaO - MgO - SiO2

feed: FeOcrucible: Moreactor 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


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


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


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


acknowledgments

Dr. Aislinn SirkMr. Andrew GmitterVisiting Professor Dihua Wang Dr. Chanaka DeAlwis

Thank you for your attention!


towards carbon-free steelmaking

steelmaking by molten oxide...

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