MIT researchers observe CO2 emissions-free steel production process

Sources: Massachusetts Institute of Technology, Cambridge; CP staff

As researchers at the MIT Department of Civil and Environmental Engineering-hosted Concrete Sustainability Hub seek methods of lowering carbon dioxide emissions in portland cement milling—based on lower kiln temperatures and shorter clinker phases—campus peers have a tandem effort involving another vital commodity whose production is synonymous with high carbon footprint.

In a paper for the journal Nature, Professor of Materials Chemistry Donald Sadoway and Professor of Metallurgy Antoine Allanore describe molten oxide electrolysis, a steel milling process hinging on an inexpensive iron oxide source. Research leading to their observation was backed by the American Iron and Steel Institute and U.S. Department of Energy.

Faced with the challenge of experimenting at the high temperatures attendant with steel production, they turned to electrochemistry, plus an alloy of chromium and iron, that naturally forms a thin metallic oxide film—thick enough to prevent further attack by oxygen, but thin enough to allow electric current flow. In addition to producing no emissions other than pure oxygen, the process lends itself to smaller-scale production: a few hundred thousand tons per year versus the million-plus ton figure conventional steel plants must maintain for economical viability.

Apart from eliminating CO2 emissions, molten oxide electrolysis yields metal of exceptional purity, Professor Sadoway contends, and could be adapted to carbon-free production of other metals and alloys including nickel, titanium and ferromanganese. The researchers and a former student have formed a company to develop the concept, still at the laboratory scale, to a commercially viable prototype electrolysis cell. They project about three years to design, build and test such a reactor.