Fibre dewatering wakes up and smells the coffee

The physics of so many people’s indispensible morning gadget, the cafetiere or French Press coffee maker, could be a key tool for improving the efficiency of an increasingly important industrial process – removing water from natural fibres. An Anglo-Canadian team from the Universities of Cambridge and British Columbia has discovered how the microscopic structure of a suspension of natural fibres influences how it behaves when it is compressed, which they believe will help to optimise industrial processes involving dense suspensions, such as papermaking, waste treatment and an increasing number of processes based around making new materials from cellulose.

The behaviour of fibrous suspensions, where the volume of the suspension is much larger than the size of an individual fibre, is complex, as the fibres and the fluid in which they are suspended interact with each other. Particularly complex is the way that the fibres react to and transmit stress, explained Duncan Hewitt of the department of applied mathematics and theoretical physics at Cambridge. Using an analogy to a cafetiere was vital to the groups modelling, he added. “Using these devices, we were able to measure all of the empirical relationships required for the two-phase model," Hewitt said. "Then we tested the model under industrially relevant, but not widely studied, conditions of rapid compression using a French press geometry.” The team describes their work in the American Institute of Physics journal, Physics of Fluids.