French-press coffee maker press inspires ‘drying’ discovery

Removing water from liquid-solid mixtures rapidly and effectively has long been a particular challenge for industries such as papermaking, wastewater treatment and mining.

But now, researchers from UBC and the University of Cambridge have developed an important building block for designing powerful machines that can “dewater” dense suspensions, like paper pulp, sludge or mine tailings.

“Drying is a very expensive operation, requiring significant amounts of energy. By formulating a theoretical model that predicts how the suspension will behave under pressure, we now know exactly how much compression speed to apply to get the best results,” explained study co-author Daniel Paterson, PhD student in chemical and biological engineering at UBC.

The mathematical model built by Paterson and his colleagues predicts how the solid part of a suspension transmits and responds to stress, which in turn influences how the suspension as a whole reacts to pressure.


Daniel Paterson, far right, explains his discovery at the Pulp and Paper Centre’s 30th Anniversary Open House on May 28, 2016

To put their model to the test, the group placed two different suspensions–nylon fibers and cellulose fibers–in a set-up that mimicked the design of a traditional French coffee-making press.

Their model successfully predicted how the fibers behaved when pressure was applied rapidly from one direction–and they also found that natural fibers performed better.

“The poorer dewatering performance of the nylon fiber was due to the fibre’s solid structure,” explained Paterson. “This solid structure resulted in a tight, compact region of fibres near the compressing piston, which required a higher load to continue to squeeze the suspension’s liquid through. With the cellulose fibres’ hollow structure, more uniform fibre distribution occurred throughout the suspension, meaning less load was needed to squeeze the liquid out.”

The findings has implications for equipment and process optimization used in existing drying operations, and industries that are exploring the use of biomass, or plant materials, such as cosmetics and nutraceuticals.

“Biomass provides an exciting alternative to oil-based plastics, however possess difficult drying challenges making production difficult. By understanding the drying of natural fibres, we can contribute to these developing industries,” said Paterson.

The group is working with industrial partners to develop simulation tools for designing industrial machinery



Dewatering of Fibre Suspension by Pressure Filtration was published in Volume 28, Issue 6, June 2016 in Physics of Fluids.


Official Press Release on AIP Publishing site here

Additional media coverage:
Science Daily here
EurekAlert here




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