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Dewatering properties of low grammage handsheets softwood kraft pulps modified to minimize the need for refining
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. SCA R & D Centre, Sundsvall.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.ORCID iD: 0000-0003-1881-6473
SCA R & D Centre, Sundsvall.
Karlstad University, Karlstad.
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 3, p. 397-403Article in journal (Refereed) Published
Abstract [en]

Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.

Place, publisher, year, edition, pages
2018. Vol. 33, no 3, p. 397-403
Keywords [en]
dwell time, hemicellulose, refining, solid content, suction box dewatering, tensile index, thermoporosimetry, water retention value
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-32836DOI: 10.1515/npprj-2018-3037ISI: 000450923900005Scopus ID: 2-s2.0-85052642839OAI: oai:DiVA.org:miun-32836DiVA, id: diva2:1182127
Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2018-12-11Bibliographically approved
In thesis
1. Modifying kraft pulping to produce a softwood pulp requiring less energy in tissue paper production
Open this publication in new window or tab >>Modifying kraft pulping to produce a softwood pulp requiring less energy in tissue paper production
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Modification of softwood kraft pulp by the addition of either polysulfide (PS) or sodium borohydride (NaBH4) has been shown to increase the pulp yield due to a higher retention of glucomannan.  The pulps with higher yield gave a paper with higher tensile index than reference pulp, especially at lower degrees of refining. The higher yield pulps also showed a greater porosity of the fibre wall, indicating an increase in the swelling potential of the fibres. This can lead to increased fibre flexibility and increased joint strength between the fibres and to the higher handsheet tensile index. However, the swelling increase associated with the higher hemicellulose content could also make dewatering more challenging because of the higher water retention of the pulp. The results of this study show however that the positive influence of the increase in yield (fewer fibres and a more open sheet structure) dominates over the negative influence of the higher hemicellulose content on the dewatering properties, especially at lower refining energy levels. Studies simulating full-scale tissue machine dewatering conditions showed that pulps with a higher yield and a higher hemicellulose content had a higher tensile index at the same dryness. Moreover, the same dryness level was achieved in a shorter dwell-time. A given tensile index was also achieved with less refining energy.

Increasing the yield and hemicellulose content by the addition of either an oxidizing or a reducing agent in the softwood kraft pulping process thus has a potential for giving high quality fibres for tissue paper production with less refining energy and lower drying energy costs.

 

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2018. p. 40
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 137
Keywords
Modifying kraft pulp, tissue dewatering, polysulfide, sodium borohydride, tensile index, hemicellulose
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-32833 (URN)978-91-88527-42-4 (ISBN)
Presentation
2018-03-22, M102, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Funder
Knowledge Foundation
Note

Vid tidpunkten för framläggningen av avhandlingen var följande delarbeten opublicerade: delarbete 2 inskickat.

At the time of the defence the following papers were unpublished: paper 2 submitted.

Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2018-02-12Bibliographically approved

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Rahman, HafizurEngstrand, Per

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