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Improved refining energy efficiency in thermo-mechanical pulping by means of collimated wood chipping – from solid mechanics to full scale evaluation
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. (FSCN - High Yield Pulping Research Profile)ORCID iD: 0000-0003-1881-6473
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (FSCN - High Yield Pulping Research Profile)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (FSCN High Yield Pulping Research Profile)
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (FSCN)ORCID iD: 0000-0002-3622-4247
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2016 (English)In: PaperWeek Canada 2016 Conference February 1 to 5, 2016, Montreal: Technical Track Program / [ed] Greg Hay, 2016Conference paper, Abstract (Refereed)
Abstract [en]

The wood chipping process was never optimized with regard to high yield pulping processes as thermomechanical pulping (TMP) and chemithermomechanical pulping (CTMP). It is generally believed that wood chips for pulping should be produced in such a way that the degree of damage is minimized and that the chip dimensional distribution should be as narrow as possible. Since the TMP and CTMP processes were developed in the 60-ies and 70-ies, compression screw as well as roll nip equipment have been developed to pretreat wood chips as a way to reduce refining energy consumption to given fiber and pulp properties and also in order to improve impregnation. The general conclusions are that a combination of shear and compression in the tangential or radial direction of the wood initiates cracks that later in the refiner will enhance and optimize fiber separation and also fiber property development. The idea with the collimated chipping technology is to utilize the wood chipper as a tool, combining cutting of wood logs to wood chips with a pretreatment of the chips by creating cracks that would enhance fiber separation, fiber surface development as well as chip-impregnation. In this case the compression is performed in the wood fiber direction, in which direction wood actually is weakest when it comes to compression induced cracking. The maximization of the amount of cracks in wood-chips is performed by optimizing the knife angle (or spout angle) in the chipper, to what we call collimated chipping (according to a patent owned by CCT AB). This presentation describes a theoretical background and two demonstration scale studies performed by SCA Forest Products at their Ortviken mill. One conclusion drawn, based on two-month test period with three weeks of collimated chipping, was that specific refining energy reduction was around 100 kWh/adt of the 1400 kWh/adt used in primary stage double disc refining. Most probably the potential is higher if the whole system is optimized. Tests were performed at constant production rate and energy was reduced by reducing power to constant freeness, leading to similar tensile and light scattering levels. The deliberately increased forces created in the wood chipper by means of an optimized (increased) edge angle caused more problems with knife holder equipment than normally, as well as increased vibrations. These problems will have to be solved for future long-term implementation of the technique.

Place, publisher, year, edition, pages
2016.
Keyword [en]
chipping, mechanical pulping, energy reduction
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:miun:diva-29474OAI: oai:DiVA.org:miun-29474DiVA: diva2:1053004
Conference
PaperWeek Canada 2016 Conference, Montreal, February 1-5, 2016
Projects
e2mp forskningsprofil
Funder
Knowledge Foundation, 2010/0178VINNOVA, 2012-00786
Available from: 2016-12-07 Created: 2016-12-07 Last updated: 2017-02-07Bibliographically approved

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http://www.paperweekcanada.ca/pwc2016/program.html

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Engstrand, PerGradin, PerHellström, LisbethCarlberg, Torbjörn
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CiteExportLink to record
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Citation style
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