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Licensed Unlicensed Requires Authentication Published by De Gruyter September 16, 2020

Development of fibre properties in mill scale high- and low consistency refining of thermomechanical pulp (Part 1)

Rita Ferritsius, Christer Sandberg, Olof Ferritsius, Mats Rundlöf, Geoffrey Daniel, Kathrin Mörseburg and Dinesh Fernando


The aim of this study was to evaluate changes in fibre properties with high (HC)- and low consistency (LC) refining of TMP and determine how these contribute to tensile index. Two process configurations, one with only HC refining and another with HC refining followed by LC refining were evaluated in three TMP mainline processes in two mills using Norway spruce. An increase in tensile index for a given applied specific energy was similar for all LC refiners in the three lines, despite differences in the fibre property profiles of the feed pulps. Compared with only HC refined pulps at a given tensile index, HC+LC refined pulps had greater fibre wall thickness, similar fibre length, strain at break and freeness, but lower light scattering coefficient, fibre curl and external fibrillation. The degree of internal fibrillation, determined by Simons’ stain measurements, was similar for both configurations at a given tensile index. The results indicate that the increase in tensile index in LC refining is largely influenced by a decrease in fibre curl and in HC refining by peeling of the fibre walls. Compared at a given tensile index, the shive content (Somerville mass fraction) was similar for both HC+LC and HC refining.

Funding statement: The study was supported by the KK-foundation and The Swedish Energy Agency.


The KK-foundation, The Swedish Energy Agency, StoraEnso, Holmen Paper, SCA and Inovocell are gratefully acknowledged for considerable experimental help and financial support. This work was carried out within the energy efficient pulping programme (e2mp) in Sweden.

  1. Conflict of interest: The authors declare no conflicts of interest.


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Received: 2020-03-25
Accepted: 2020-08-09
Published Online: 2020-09-16
Published in Print: 2020-11-18

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