Electrolysis may one day provide 'green iron' -

Producing iron by electrolysis rather than conventional smelting could prevent the emission of a billion tonnes of carbon dioxide into the atmosphere every year.
So concludes Donald Sadoway, a materials scientist at MIT in the US who has developed a way producing iron by electrolysing a molten iron oxide in the lab. If the process can be scaled up, it could eliminate the need for conventional smelting, which releases almost a tonne of CO2 for every tonne of steel produced.
In conventional smelting, iron ore is combined with a coal-derived carbon called coke. The coke reacts with the iron, producing CO2 and carbon monoxide, leaving pure iron behind.
Electrolysis produces iron a different way. The iron ore is dissolved in a solvent of silicon dioxide and calcium oxide at 1600°C and an electric current passed through it. Negatively-charged oxygen ions migrate to the positively charged anode, and the oxygen bubbles off. Positively-charged iron ions migrate to the negatively-charged cathode where they are reduced to elemental iron which collects in a pool at the bottom of the cell and is siphoned off.
Leadership position
A similar process is routinely used to produce aluminium, whose oxide is so stable that it cannot be practically reduced by conventional carbon reduction in a blast furnace, the reactor in which iron is produced. The steel industry has never had any reason to switch to electrolysis, since iron oxide is easily reduced by carbon to produce molten iron.
If governments begin to impose serious carbon emission taxes however, the new process may become more attractive, according to the American Iron and Steel Institute, which has provided $500,000 in funds for Sadoway’s work.
"Things are going to take 10 to 15 years to develop and get to a commercial scale. Now is the time to be working on them," says Lawrence Kavanagh, vice president of manufacturing and technology for the institute.
Material quest
Sadoway says that the technology has a number of hurdles to overcome. The biggest is finding practical anode material. In his experiments, he used an anode made of graphite, similar to baked carbon anodes used for making aluminium.
Unfortunately, the carbon reacts with the oxygen, releasing about as much carbon dioxide into the air as the conventional iron-making process. Platinum anodes can be used, but are too expensive for large-scale manufacturing.
Possibilities include metal alloys that form an oxide on the outer layer but still conduct electricity, or conductive ceramics.
Carbon tax
Another problem is that the process uses a lot of electricity – about 2000 kilowatt hours per tonne of iron produced.
Richard Fruehan, a metallurgical researcher at Carnegie Mellon University in Pittsburgh, does not think the method will ever make economic and environmental sense. He says that the process uses so much electricity that it would actually result in more carbon in the atmosphere from the increased demand on power generating stations.
Fruehan is also sceptical about the likelihood of a practical carbon-free anode, since the aluminium industry has been trying for years to develop one and still has not. Even Sadoway admits that the method would require a source of clean electricity.
"The economics are just not there under the present circumstances. Carbon is cheap, and there's no [financial] cost associated with venting carbon dioxide. And electricity's expensive. So if you put those three factors on the table, this just isn't economically viable," he says.
But if a carbon tax comes into the play the economics change entirely.
Kavanagh agrees and argues that there are other factors in favour of electrolysis. For one thing, it would cut out the energy-intensive coke-making process, which requires baking coal at high temperatures. But he says more development work is needed before the industry can decide whether the process will be economical or not.