10 May 2013

When the humble car tyre has lost its tread and is no longer safe on the family car it is often thrown to landfill or stockpiled with no apparent means of re-use. In some cases we improvise; how often have you seen a child's swing or a planting barrel, or even a tyre swan, made from discarded tyres?

While such individual solutions reuse a few of the twenty million or so tyres that would have otherwise been consigned to dumps across Australia every single year, an innovative, new process developed by a University of New South Wales (UNSW) researcher has shown car tyres can be reused within industry to the benefit of the environment and a business's bottom line.

Using her expertise in the iron and steel industry Professor Veena Sahajwalla, Director of the UNSW's Centre for Sustainable Materials Research and Technology, developed a new "green steel" making process which has, to date, diverted over 1.6 million waste tyres from landfill.

With support from grants under the ARC Discovery and Linkage Projects schemes, Professor Veena Sahajwalla discovered that in extremely reactive high-temperature environments (greater than 1500 degrees Celcius)—in which liquids/solids behave aggressively—transformations to the molecular structure of carbonaceous materials occur rapidly. This new knowledge won her the Australian Museum Eureka Prize.

Combining her deep understanding of carbonaceous materials and high-temperature reactions, Professor Sahajwalla realised that exposing carbon-rich rubber/plastics to rapid, high-temperature conditions would produce solid carbon-bearing materials and clean gases such as Hydrogen and Carbon Monoxide. She hypothesised that the slag layer in electric arc steel making furnaces would provide this rapid heating environment and injecting these end-of-life materials could reduce the amount of coke being used. This was confirmed using her unique research facility at UNSW.

This technique is called Polymer Injection Technology, and its commercial viability was only established after extensive laboratory and industrial scale testing and development in partnership with Australia's largest manufacturer of long steel products, Arrium Ltd (formerly OneSteel).

"When I first looked into a laboratory furnace and realised my idea was actually working I was so excited I couldn't sleep that night. I still had to 'do the science'—and establish exactly why it was working and how this could be practically applied in industry—but that was the Eureka moment," she said.

Not only did OneSteel play a crucial role in research and testing through ARC Linkage Projects grants, but OneSteel then licensed the technology from New South Innovations—the commercialisation arm of UNSW. The technology has since been commercialised internationally and is improving EAF (electric arc furnace) steelmaking in Australia and overseas.

In trials at OneSteel's mini-mill, coke mixed with polymers such as rubber sourced from waste tyres and HDPE (high-density polyethylene) plastic waste performed better than metallurgical coke alone in electric arc furnaces.

Using end of life polymers as a replacement for coke in the EAF steelmaking process increases the volume of 'foamy slag', and as a consequence, reduces the total cost of steel production and improves productivity. It does this through:

  • a lower quantity of inject material required per heat
  • reduced power consumption
  • lower Iron losses;
  • increased furnace productivity resulting from reduced power-on time
  • reduced consumption of coking coal

This technology has the potential to cut the amount of power used by the world's 300 electric-arc furnace steelmaking plants, which account for 30% of crude-steel output globally.

One typical EAF steel mill using this technology has the potential to divert 300,000 car tyres from landfill each year.

And while this innovative approach is the result of years of research by Professor Sahajwalla, it's the strong collaborative relationship that was established between researchers and the business delegates at OneSteel that has assured the long-term success of the project.

"Our partnership with OneSteel through the ARC Linkage programme has been critical to getting our research out of the lab and into industry and in continuing to promote its application worldwide," she said.

"My discovery was only going to make a contribution in Australia and the world if I could get it into industrial scale trials and through the commercialisation process. OneSteel and UNSW collaborated through several stages of research, and OneSteel opened up its own plants for industrial trials as well as sponsoring a number of extra PhD students to support the research process."

As well as leading SMaRT@UNSW, Professor Sahajwalla holds an ARC Future Fellowship. As an international award-winning scientist and engineer she presents on her research and experiences throughout the world. This innovative technology in the steel making process has been the subject of numerous invited/keynote addresses including the Royal Institution of Great Britain, London and the prestigious 'Howe Memorial Lecture', USA.

The partnership with OneSteel has now gone beyond 'green steel'. The result is a productive 10-year relationship and collaboration with other industry partners to cross-pollinate ideas and concepts to help improve productivity within the business.

The next chapter for this innovative team is to use a new ARC Linkage Projects grant to focus on the recycling of automotive glass and plastics. The glass used in automobiles includes two types of safety glasses: laminated and tempered. Automotive windshield and window glass are difficult to dispose of waste materials that necessitate ingenious recycling solutions.