Fiber trapping in low-consistency refining: New parameters to describe the refining process

Tom Lundin, Warren Batchelor, Pedro Fardim

Research output: Contribution to specialist publicationArticleOther

1 Citation (Scopus)


Fiber trapping in refining has been defined by the fraction f of the bar edges that trap fibers as they cross, and by the number of fibers i trapped under each section of bar. From these parameters, equations were derived to calculate the number of impacts that a fiber undergoes during refining and the maximum force experienced during each impact. Refiner power versus gap was measured for a conical laboratory refiner at maximum peripheral speeds ranging from 4 m/s to 27 m/s and consistencies ranging from 1% to 6% for one softwood kraft pulp. The data were used to calculate relative changes in i and f as a function of consistency and speed. It was found that fwas extremely sensitive both to an increase in refiner rotational speed and to a reduction in pulp consistency. A reduction in consistency from 4% to 2% at 20 m/s (3000 rpm) led to a decrease in the trapping fraction, f, by approximately 80%. The number of fibers trapped under each section of bar also decreased, although to a lesser extent. The reduction in fiber trapping greatly increased the forces on the fibers, leading to enhanced fiber shortening and reduced refining efficiency.

Original languageEnglish
Number of pages7
Specialist publicationTAPPI Journal
Publication statusPublished - Oct 2009

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