A man in yellow safety gear operating carbothermic reduction equipment.

Mr Michael Nagle operating the Light Metals Flagship's nozzle rig for carbothermal reduction of magnesium.

Carbothermal production of magnesium

The Minerals Down Under Flagship is investigating carbothermal reduction as an alternative to current silicothermic and electrolytic processes for the direct production of magnesium metal.

  • 6 May 2011 | Updated 19 January 2012

Carbothermal reduction has the potential to produce magnesium more efficiently and more cost effectively than the other methods which are currently used.

The process is also environmentally friendlier, producing up to 70 per cent less CO2-equivalent emissions than the silicothermic Pidgeon process.

The process involves the reaction of carbon and magnesium oxide which, at temperatures of 1500 °C or above, produce magnesium metal vapour and carbon monoxide gas.

The challenge to producing magnesium in this way is that, as the vapours cool, the magnesium and carbon dioxide revert to magnesium oxide and carbon. This has limited the success of the commercial application of this process in the past.

Supersonic nozzle

CSIRO's MagSonic technology uses a supersonic nozzle to rapidly cool the magnesium vapour, preventing the reversion reaction.

Flagship researchers are engineering a system that allows ultra-rapid quenching (cooling) of magnesium vapour as it is produced.

To do this, high-temperature magnesium vapour and carbon monoxide gas is passed through a Laval nozzle at four times the speed of sound. This cools the vapour at a rate greater than 1 000 000 °C per second.

Magnesium vapour is passed through the nozzle at four times the speed of sound.

Magnesium powder may be recovered directly from the process, or high-purity ingot produced after distillation.

It is now being optimised through high-temperature experimentation and advanced mathematical modelling in order to move towards pilot plant operation and commercialisation.

Outcomes

The MagSonic™ technology received the 2011 Institution of Chemical Engineers (IChemE) innovation and excellence award for Sustainable Technology. 

The project team, led by CSIRO's Dr Leon Prentice, has demonstrated production of both powder and purified magnesium in the laboratory. The team is now focused on improving product quality and yield, and is preparing to scale up to pilot plant construction and operation.

Find out more about the Minerals Down Under Flagship.