Little gem It will cut your car's emissions, and make diamonds as you go
AUSTRALIAN engineers have invented a device that blasts the noxious gases in car exhausts with microwaves, eliminating up to 70 per cent of harmful emissions. Better still, the process can double as a source of industrial-grade diamond.
Their device, called a microwave emissions converter, is about the size of a wine bottle. It microwaves the exhaust gas, heating its core to as much as 5000 kelvin, more than three times the melting point of steel. At this temperature, molecular bonds in the gases break, creating a plasma of free ions.
As the mix cools, the ions recombine to form less harmful substances. "Under ideal lab conditions, we get up to a 90 per cent reduction in carbon monoxide, carbon dioxide and hydrocarbons. On the road, it will probably fall to around 70 per cent," says Elias Siores at Swinburne University of Technology in Melbourne, who developed the converter with Carlos Destefani. They have filed a patent on the device.
Although the converter works on diesel and petrol engines, and can be used downstream of a catalytic converter to further reduce emissions, it has a downside. It increases the number of tiny carbon particles spewed out in the exhaust. To combat this, the pair have developed a way of harvesting the carbon and producing industrial diamond from it.
An electrostatic filter lining the exhaust pipe attracts the carbon particles. These particles are collected and used to feed a separate process called microwave plasma spray deposition, in which microwaves heat up and ionise an inert gas such as argon or helium. The ionised gas reacts with the carbon to create a volatile liquid. This is then sprayed onto a glass surface, producing industrial-grade diamond. "Every time you have your car serviced, you'd have the filter taken out and it would be sent to the factory and used to make industrial diamond," says Siores. The diamond could be used as a protective coating for lenses, CDs, artificial hip joints, and electronic components, he says.
Plasma exhaust cleaner If their prototype makes it to the production line, cleaner exhausts would have an immediate impact on people's health, and help cut levels of greenhouse gases.
The same technology could be used to clean up emissions from factories, chemicals plants and power stations. "There are lots of manufacturing processes that give off hydrocarbons. We are going to look at using this technology to reduce these," says David Galvin, executive director of the Cooperative Research Centre for Intelligent Manufacturing Systems and Technologies in Melbourne.
Rachel Nowak
>From New Scientist magazine, 07 October 2000.