1.6 Using physics to boost New Zealand’s milk powder export industry – Annual Report 2017

Unlike most of us, when physicist Dr Geoff Willmott thinks about milk, he thinks about droplets, surfaces and heat.

And he’s eager to use surface interactions to solve problems in the dairy industry.

“I’m pretty big on this type of thing – supporting New Zealand industry with our research – and often we, as university researchers, aren’t doing this.”

To make milk powder, heated milk is sprayed into the top of large spray dryers – silos up to 20 storeys high. The milk droplets, which are about 200°C at the top of the silo, fall through the spray dryer to form milk powder at the bottom.

However, milk droplets can stick to the side of the silo, causing fouling, and incurring losses due to cleaning costs and production downtime.

Dr Willmott is using his expertise to study drop impact and the effects of surfaces on this.

“We’re looking at surfaces and spraying conditions. We’ll study closely exactly how milk drops hit the surface of the silo and figure out when they stick and why.

“By altering the drop size of the milk, and the temperature, we can figure out how to improve efficiency of spraying conditions. We can also look at specific drop interactions and which products are easier to dry.”

He is taking his fundamental research in microfabrication and high-speed photography (developed over the past few years while on a Marsden grant – looking at the high-speed surface interactions of water drops with PhD student Matheu Broom) and has now won a $1 million MBIE grant to apply this to the dairy industry.

Dr Willmott says the aim is to help the dairy industry understand the types of surfaces they currently use, how best to tweak them, and what spray settings (such as drop size and temperature) are ideal.

At first glance, this seems a bit removed from his day job teaching physics at the University of Auckland. But it’s something he’s keen to do more of.

“It’s great to see this flow from fundamental research to applied technology. It’s also a nice opportunity to get out of the lab and talk to industry people.

“The infant formula industry is a big deal for New Zealand, with exports of infant formula growing, especially to China. It’s an interesting premium foods opportunity for New Zealand.”

He is now working with the dairy industry, including equipment manufacturers and producers. “We have the engineering capability to make these giant spray dryers in New Zealand.”

Dr Willmott says that one of the best things he did to obtain the MBIE funding was to take up MacDiarmid Institute funding to attend a GetFunded workshop – although he nearly didn’t go.

“The MacDiarmid Institute had to twist my arm to get me there. I was busy and wasn’t too keen, but it was there that I spent two days developing the idea and really got started on it.

“The MacDiarmid Institute supports me as an individual researcher extremely strongly. With all the collaborations – we learn from each other – this is what enables us to do high- quality fundamental research, says Dr Willmott.

“More specifically for this research, my students learn about microfabrication from people like [MacDiarmid Associate Investigator] Volker Nock at Canterbury and have access to fabrication and characterisation equipment through facilities like the Photon Factory.”