Te Whare Wānanga o Waitaha | ˴Ƭ (UC) Chemical and Process Engineering master’s student Josh McArdle’s research takes a circular economy approach using a waste material to decrease the CO₂ emissions of the industry.
In collaboration with the Robinson Research Institute at Victoria University of Wellington, his research explores using precipitated iron residue (PIR), a common waste material from mineral processing for iron production. Global research efforts are currently focussed on using green hydrogen to reduce ironmaking emissions, and McArdle’s research has created a pellet feedstock suitable for these new green hydrogen processes through blending PIRs with ironsand.
“Currently considered waste, these residues are produced at a scale of 100 million tonnes per year and are expected to increase as renewable energy systems and technologies like electric vehicles expand,” McArdle says.
These PIRs are often stored in waste ponds and landfills or disposed of in countries with poor environmental regulations without suitable environmental protection measures. McArdle says there is significant scope for improved utilisation of these waste materials.
McArdle blended PIRs with New Zealand’s titanomagnetite ironsand to create pellets. He demonstrated that his blending approach is beneficial for green hydrogen powered ironmaking, most notably when using a 5% blend of PIR. This novel approach not only diverts waste disposal but can also enhance the speed and efficiency of existing iron production streams.
His supervisor, UC , says, “blending is a good idea because, while these byproducts contain iron from other minerals processes, there isn’t enough of them to completely replace all of the iron ore that’s used today. It creates value from a waste product by blending it into an existing process.”
McArdle says a key focus for his research was on sustainability, which is also a major theme within the Chemical and Process Engineering department. “The world uses an extraordinary amount of material, for example from the mining and refining of rocks and minerals, however, we need to adapt such processes to eliminate negative consequences for the environment and people.”
The global increase in demand for mineral processing also decreases the quality of mined iron ores such as titano-magnetite ironsand. “Inherently lower quality iron ores mean you'll need more electricity to heat them up. These ores also contain more gangue (worthless) material, which doesn’t produce iron metal,” McArdle says.
Using an X-ray diffractometer with a temperature-controlled hydrogen environment, McArdle heated his samples to 900 °C to test their suitability for iron making. “There’s some pretty neat techniques that Josh was using, and he was the first to do them here at UC with this new capability that we have, which is cool,” Professor Watson says.
While this research is promising, Professor Watson says the steel industry is hundreds of years old and requires careful steering, suggesting further research is required to demonstrate how using PIRs might work at a larger scale.
Sustainable Development Goal (SDG) 9 - Industry, innovation and infrastructure.
