Supersonic technology enables low-emission magnesium

CSIRO has partnered with Canadian chemicals company Enirgi Group in a move to develop and commercialise an affordable and efficient technology for producing magnesium — a metal that is in rising demand from car manufacturers looking to make lightweight, low-emission vehicles.

The technology, known as MagSonic, uses carbothermal reduction and a supersonic nozzle to produce the high-quality magnesium. It is likely to produce magnesium almost twice as efficiently as today’s conventional process and could reduce greenhouse gas emissions from production by 50–85%, depending on the electricity source.

The method involves heating magnesia with carbon to extreme temperatures (above 1700°C) to produce magnesium vapour and carbon monoxide. The vapour and carbon monoxide are passed through a supersonic nozzle — similar to a rocket engine — at four times the speed of sound to cool the gases in milliseconds, preventing the re-oxidation of the magnesium.

The magnesium condenses, much like the steam from a kettle forming droplets of metal. At this point the droplets, still moving faster than the speed of sound, continue to cool, travelling through a series of sonic shocks as they slow down. They soon freeze into metal powder particles that travel into a large chamber, which gives them time to completely cool and solidify.

From this chamber the mixture of powder and cooled gas is drawn towards a cyclone. A swirling motion separates the powder, which travels downward in a spiral, while the gases are removed. The cool, solid magnesium powder is collected at the bottom of this cyclone, before being purified and cast into slabs.

CSIRO’s Dr Mark Cooksey holds a wheel casting made out of lightweight magnesium metal.

CSIRO and Enirgi Group’s Innovation Division will work together to further develop and validate the MagSonic technology. Once it is ready for commercialisation, Enirgi Group has the option to take up an exclusive global licence that would see the company initially build a commercial-scale magnesium production facility in Australia.

“We are pleased to be working with CSIRO on this exciting opportunity to bring reliable supply of magnesium metal to the global market in an environmentally sustainable way,” said Enirgi Group’s vice president of corporate development, Anthony Deal.

“We are confident that this process is capable of commercial production.

“The flow-through benefits to emerging industries like electric vehicle manufacturing are enormous, not to mention a substantial reduction in carbon emissions when compared to current magnesium production processes.”

Dr Mark Cooksey, who leads CSIRO’s sustainable process engineering group, added that commercialisation would help take advantage of Australia’s abundant reserves of magnesite ore that remain largely untapped.

“The growth of magnesium use has been limited because it’s been too expensive and labour-intensive to produce the metal from ore using traditional processes,” Dr Cooksey said.

“Our MagSonic technology offers an economically viable solution to overcome these issues and make clean magnesium more available and affordable to manufacturers.”