Low Consistency Refining
The research in low-consistency refining is done in 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.
Batchelor, W. and T. Lundin (2003). Effects of consistency on bar coverage in refining, Progress in Pulp Refining Research Seminar in Victoria, BC, Canada 12th September 2003.
Lundin, T. and Batchelor, W. (2006). Evaluating studies in refiner load-ability, 9th Pira International Refining Conference, 10-12 February 2006, Vienna, Austria.
Lundin, T., Batchelor, W., Fardim, P. (2007). Estimation of fibre trapping from refiner loadability measurements, International Pulp Refining Seminar, 4 June 2007, Otaniemi, Espoo, Finland. Proceedings, pp. 31-36.
Lundin, T., Batchelor, W. and Fardim, P. (2008). Fibre trapping in low consistency refining: new parameters to describe the refining process, Tappi J., 7(7): 14-19 (Appendix II).
Batchelor, W.J. and Lundin, T. (2006). A method to estimate fibre trapping in low consistency refining, TAPPI J., 5(8):31.
Batchelor, W.J. (2001). Effects of flocculation and floc trapping on fibre treatment in low-consistency refining, J. Pulp Paper Sci., 27(7):249.