The technology, which is known as dry slag granulation (DSG), has been developed over the past decade by CSIRO in collaboration with a number of steel industry partners.
According to CSIRO’s group leader of sustainable process engineering, Mark Cooksey, steel manufacturing produces more than 300 million tonnes of the waste product known as slag every year.
The current acceptable methods of handling the by-product are to either dump it on the ground or to add water to produce granules that can be used to make cement. However, Cooksey indicated these options were far from efficient.
“[By dumping the slag] you waste a large amount of material that could be [put to] another use and you lose all the heat, a gigajoule of heat for every tonne of slag,” he explained. “[With granulation,] the trouble is you use 1000 litres of water for every tonne of slag, so that’s a large environmental cost.”
CSIRO’s new DSG technology, which can be fitted to blast furnaces, separates molten slag into droplets under centrifugal forces, uses air to quench and solidify the droplets, and extracts a granulated slag product that is ideal for cement manufacture – without the high levels of greenhouse gas emissions associated with cement produced via conventional methods.
“If you use our products to produce cement for each tonne you use you basically save 800kg of CO2 emissions,” Cooksey stated.
In addition to creating a useful, “glassy” cement product from the waste slag, the new process is also said to save water and extract heat that can be recycled for on-site drying, preheating or steam generation.
“The benefits each year from full commercialisation and adoption of DSG technology are in the order of 60 billion litres of water, 800 petajoules of heat energy and 60 million tonnes of greenhouse gas emissions,” Jonathan Law, director of CSIRO’s Mineral Resources Flagship, explained. “Those savings are equivalent to 14 per cent of Australia’s energy use and about 10 per cent of our greenhouse gas emissions each year.”
The technology is currently being trialled for commercialisation in China.