MIT process promises cheaper steel, no CO2

01 June 2013

An MIT team has found a process that could lead to cheaper, higher-quality steel-making without the baggage of greenhouse gases.

A paper co-authored by Antoine Allanore, the Thomas B King assistant professor of metallurgy at MIT, and former postdoc Lan Yin (now a postdoc at the University of Illinois at Urbana-Champaign), has been published in the journal Nature.

David L Chandler of MIT News Office,  in a report, quotes Donald Sadoway, the John F Elliott professor of materials chemistry at MIT and senior author of a new paper describing the process, as saying this could be a significant “win, win, win” proposition.

The prevailing process makes steel from iron ore — which is mostly iron oxide — by heating it with carbon; the process forms carbon dioxide as a byproduct. Production of a tonne of steel generates almost two tonnes of CO2 emissions, according to steel industry figures, accounting for as much as 5 per cent of the world’s total greenhouse-gas emissions.
The idea for the new method, Sadoway says, arose when he received a grant from Nasa to look for ways of producing oxygen on the moon.

Sadoway found that a process called molten oxide electrolysis could use iron oxide from the lunar soil to make oxygen in abundance, with no special chemistry. He tested the process using lunar-like soil from Meteor Crater in Arizona — which contains iron oxide from an asteroid impact thousands of years ago — finding that it produced steel as a byproduct.

Sadoway’s method used an iridium anode, but since iridium is expensive and supplies are limited, that was not a viable approach for bulk steel production on Earth. But after more research and input from Allanore, the MIT team identified an inexpensive metal alloy that can replace the iridium anode in molten oxide electrolysis.

The problem was solved using an alloy that naturally forms a thin film of metallic oxide on its surface: thick enough to prevent further attack by oxygen, but thin enough for electric current to flow freely through it. The answer turned out to be an alloy of chromium and iron — constituents that are “abundant and cheap,” according to Sadoway.

In addition to producing no emissions other than pure oxygen, the process lends itself to smaller-scale factories.

Sadoway, Allanore and a former student have formed a company to develop the concept, which is still at the laboratory scale. The research was supported by the American Iron and Steel Institute and the US Department of Energy.

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