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

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