Cool smelting option to help reduce global warming?

Aluminium is an energy-intensive industry, consuming as much as 15 per cent of Australia’s electricity, which contributes to the nation’s greenhouse gas emissions.

Over the past decade, the industry has gone some way towards reducing greenhouse gas emissions from its smelter potlines and improving its energy efficiency.

Now, the industry is working with the Light Metals Flagship – a national research program led by CSIRO – to investigate the use of ionic liquids in reducing the very high temperatures needed for aluminium smelting.

The Flagship’s ionic liquids research project leader, Dr Theo Rodopoulos, says the key to ionic liquids is their low melting point.

“Aluminium is currently produced through electro-deposition, where the alumina is dissolved in a molten cryolite bath at 1000°C and an electric current is applied to separate aluminium from oxygen,” Dr Rodopoulos says.

“By contrast, ionic liquids typically melt below 100°C. If they can be used instead of molten cryolite, they could dramatically reduce a smelter’s energy needs.”

The Flagship is working with CSIRO Minerals and mining company Rio Tinto to develop ionic liquids for aluminium production.

Rio Tinto’s technology support general manager, Dr Ray Shaw, says that although research on ionic liquids is still in its early days, it is a novel approach that the company is monitoring closely.

Dr Shaw says ionic liquids could reduce the electricity used in aluminium production by 20-30 per cent.

“Whether that’s achievable or not is uncertain at this early stage, but if there’s an opportunity to improve, then we’re interested in exploring it,” Dr Shaw says.

Ionic liquids could be used as alternative media for reprocessing nuclear fuel and waste in the nuclear power industry, and as catalysts or solvents in a host of other industrial processes.

CSIRO is also exploring their use as electrolytes in lithium batteries, because the organic solvents used in lithium battery manufacture are volatile and flammable. Other potential uses include carbon dioxide recapture in power plants, desulfurisation of fuels and even perfume production.

Dr Rodopoulos believes these unusual liquids have significant commercial potential. They are often called designer solvents because they can be tailored to meet the needs of specific applications.

“An almost infinite number of combinations is possible,” Dr Rodopoulos says.