On the application of grits to thermomechanical pulp refining

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Doctoral thesis (article-based)
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Date
2009
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Degree programme
Language
en
Pages
Verkkokirja (3738 KB, 52 s.)
Series
TKK reports in forest products technology, Series A, 7
Abstract
The objective of this thesis was to develop a mechanical pulping process capable of producing good-quality pulp, while consuming less electrical energy. The study focused on applying of grits to TMP refining to enhance the breaking of the fiber cell wall promoting faster development of pulp fibers to the desired quality for papermaking. The study comprises tests at laboratory scale and development of an application for industrial, including trials at pilot scale. A preliminary trial with the grit application in TMP refining was conducted at laboratory scale. The results showed that the grits should be introduced between the first and second stages in TMP refining. The grit treatment on the TMP fibers caused disruption of the wall structure, opening of the outer layers and peeling-off of the cell wall. The efficient disruption with minimal shortening and weakening of fibers was found to be operated at a low-intensity and high-frequency of treatment. According to an experiment with first-stage TMP pulp, the disrupted pulp developed faster during subsequent refining, while the energy consumption was reduced by up to 30% without a significant loss of pulp quality. With the aim of developing an industrial application, the refiner segments were modified by applying grits on the refiner segment surfaces. The grits were made from self-fluxing tungsten-carbide powder and a Ni-base alloy powder, which were laser-clad onto the surface of breaker bars, the inner part of a segment. Trials with grit segments were carried out on a pilot refiner. The grit segments were applied in first-stage TMP refining, followed by treatment with base segments operated under normal mill conditions. The grit segments were found to have no negative effects on the refining system. A refiner equipped with grit segments, operated at a speed of 2400 rpm, produced pulp with a higher level of disruption of fiber cell walls than a refiner equipped with the reference segments. According to the results, the energy consumption can be reduced by at least 10% with minimal negative impacts on pulp and paper properties.
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Keywords
thermomechanical pulp, refining, segments, grits, disruption, energy consumption
Other note
Parts
  • [Publication 1]: Phichit Somboon and Tuomo Pynnönen. 2008. Performance of abrasive segments in mechanical pulp refining. A review. Paperi ja Puu – Paper and Timber, volume 90, number 5, pages 41-45. © 2008 Metsäkustannus Oy. By permission.
  • [Publication 2]: Phichit Somboon and Hannu Paulapuro. Determination of wet fiber strength. TAPPI Journal, accepted for publication. © 2009 by authors and © 2009 Technical Association of the Pulp and Paper Industry (TAPPI). By permission.
  • [Publication 3]: Phichit Somboon and Hannu Paulapuro. 2008. Surface mechanical treatment of TMP pulp fibers using grit material. TAPPI Journal, volume 7, number 12, pages 4-9. © 2008 Technical Association of the Pulp and Paper Industry (TAPPI). By permission.
  • [Publication 4]: P. Somboon, T. Kang, and H. Paulapuro. 2007. Disrupting the wall structure of high-freeness TMP pulp fibres and its effect on the energy required in the subsequent refining. Pulp and Paper Canada, volume 108, number 10, pages 30-34. © 2007 Pulp and Paper Technical Association of Canada (PAPTAC). By permission.
  • [Publication 5]: Phichit Somboon, Kaarlo Nieminen, and Hannu Paulapuro. 2008. Finite element analysis of the fatigue behavior of wood fiber cell walls. BioResources, volume 3, number 4, pages 983-994. © 2008 by authors.
  • [Publication 6]: Phichit Somboon, Juha Vuorela, Tuomo Pynnönen, and Hannu Paulapuro. 2009. Grit segments in TMP refining. Part 1: Operating parameters and pulp quality. Appita Journal, volume 62, number 1, pages 37-41. © 2009 Australian and New Zealand Pulp and Paper Industry Technical Association (Appita). By permission.
  • [Publication 7]: Phichit Somboon, Juha Vuorela, Tuomo Pynnönen, and Hannu Paulapuro. 2009. Grit segments in TMP refining. Part 2: Potential for energy reduction. Appita Journal, volume 62, number 1, pages 42-45, 59. © 2009 Australian and New Zealand Pulp and Paper Industry Technical Association (Appita). By permission.
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