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Low Consistency Refining

My research in low-consistency refining is a collaboration with Tom Lundin, a researcher in the Laboratory of Fibre and Cellulose Technology at Abo Akademi University in Finland.  As part of this collaboration, I am now a Docent in Fibre Physics  in the laboratory

We are interested in the process of fibre trapping in refining.  In order for the fibres to to be mechanically treated in refiner they must be first be trapped between the surfaces of the rotor and stator bars.  This fibre trapping has never been considered in any of the theories of refining.  For example, the Specific Edge Load theory measures the energy consumed when a metre of rotor bar edge crosses over a metre of stator bar edge, without considering if there are any  fibres actually there to absorb this energy. 

We think that this fibre trapping process is a hidden variable in refining that explains why, for example, refining becomes less efficient when the bar edges go blunt as the refiner plates become worn.  Other refining variables that can influence refining efficiency through fibre trapping are stock consistency, and the refiner plate design.

The method we have developed to characterise refiner trapping efficiency is to measure refiner power as a function of plate gap- known as a loadability curve.  The diagram below shows that fibre trapping can be characterised by the fraction of the bar edge that trap fibres and the thickness of the mat that is trapped.  By comparing loadability curves obtained under different conditions, we can determine relative changes in fibre trapping.

Presentations and publications

  • The refiner loading measurements are described in Tom's presentation from the University of British Columbia Pulp and Paper Centre Refining seminar in 2003. 
  • Our initial analysis of the results was also presented at this seminar. (PDF of presentation)
  • The method was further developed and presented at the 2006 PIRA International Refining Conference (PDF of presentation) and the 2007 Refining seminar at the Helsinki University of Technology (PDF of presentation).
  • An article on the method has been published in Tappi Journal and another article will shortly be published.
  • The complete list of publications in refining is given here.