College of Agriculture, Engineering
and Science (CAES)

Professor Indresan Govender.

A New Theory of Granular Flow for SA Mining Industry

During his inaugural lecture in 2017, UKZN’s Professor Indresan Govender, argued that a theory published in Nature Letters [NATURE Vol 441] failed to match the high-quality nuclear imaging measurements that his Particle Technology Group (PTG) were obtaining for complex industrial flows typical of South African mining systems.

The argument was settled when Govender co-published an article this year in the prestigious Physical Review Letters [123, 048001 (2019)] on a new granular flow theory.

Unlike the theory published in Nature Letters that works only for a limited and simplified range of flows, the new theory is valid for wet, dry and multidirectional flows that span industrial, natural and even biological flow systems.

‘Since its publication, the attention has been overwhelming and has culminated in several invited lectures, most notably to the Department of Applied Mathematics and Theoretical Physics (DAMTP) at Cambridge University in England,’ said Govender.

During the various invited lectures he gave around the world – including in China, North America and Europe – Govender said he became aware of two interesting facts: (i) this was the first time a South African chemical engineer had published in Physical Review Letters, and (ii) there were sadly no other research groups on the continent working on granular flows at the continuum scale.

‘These simple observations speak volumes about the lack of homegrown technologies for maximising local benefit from a rich, naturally resourced continent,’ said Govender.

Govender, however, is very positive about the future and notes that the new theory, underpinned by a new dimensionless number, will ‘reshape the way we think about mixing, flow and size reduction in the mining, pharmaceutical and agricultural processing industries’.

According to Govender, this is only the beginning of a long road to testing the theory rigorously and proving its value to industry. Fortunately, the PTG is uniquely positioned to make in-situ measurements of complex flows using the nuclear imagine technique of Positron Emission Particle Tracking.

Govender’s laboratory is the only one in the world with the ability to measure non-invasively the flow of complex, often opaque, granular systems to sub-millimetre accuracy at sub-millisecond sampling resolutions.

The PTG is funded almost entirely through generous partnerships with the mining, pharmaceutical and manufacturing industries across the globe, and Govender expects those partnerships to grow with the recent theoretical breakthrough.

Beyond the excitement of developing a new theory, Govender argues that the theory can be used to improve the energy efficiency of mining equipment, such as tumbling mills, which currently consume up to 10 percent of South Africa’s power.

Optimistically, it might even be possible to design new equipment that produces paradigm shifts in energy efficient mining and extraction of precious metals for the South African economy.

Words: Ndabaonline

Photograph: Supplied