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Sub project 3: Effect of sulphite pre-treatment and high intensity refining on spruce TMP pulps produced at the Braviken mill

Fernando, Dinesh and Daniel, Geoffrey and Bardage, Stig and Hafrén, Jonas and Ander, Paul and Nelsson, Erik and Olsson, Ann-Mari and Salmén, Lennart and Sandström, Peter (2012). Sub project 3: Effect of sulphite pre-treatment and high intensity refining on spruce TMP pulps produced at the Braviken mill. Uppsala: (S) > Dept. of Forest Products, Sveriges lantbruksuniversitet. Rapport (SLU, Institutionen för skogens produkter) ; 7
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Abstract

The effects of pressurized compressive chip and low dosage sulphite pretreatments were evaluated for production of thermomechanical pulp in mill scale trials using Norway spruce (Picea abies) at the Braviken paper mill (Holmen Paper AB, Sweden). The aim of the study was to provide knowledge leading to the improvement of energy efficiency during the production of mechanical pulps suitable for news and improved new grade papers. Pulps produced in the mill trials were characterized using conventional pulp and paper testing and by advanced methods including image analysis, FTIR with multivariate analysis, Simons staining with statistical analysis, spectral imaging and HCL fibre cleavage.

Sulphite pre-treatment gave a linear dose response in tensile index and light scattering with addition of sulphite (≥ 1.2% Na2SO3). The maximum in tensile index and light scattering at a sulphur content of 0.2% (as Na2SO3) reported previously was not found in this mill study. Low dosage sulphite pre-treatment increased delamination/internal fibrillation of fibres indicating increased fibre flexibility. These fibres produced denser
sheets with higher tensile index and slightly reduced light scattering at certain specific energy consumption. The specific energy consumption needed to produce pulp at a
certain tensile index was reduced by 320 kWh/BDT (15%) for chips pre-treated with ~1.2% Na2SO3 compared with untreated chips. This gave a reduction in light scattering for sulphite pre-treated pulps when compared at equal tensile index.

Image analysis of fibre cross-sections provided information of the composition of the total fibre population, fibre cross-sectional compactness as well as effects of sulphite
treatment. Results showed a fairly constant fibre population (40% early-/60% latewood) existing in all samples and for higher energy to cause greater fibre
splitting of untreated fibres particularly of latewood fibres. Increasing the amount of sulphite reduced fibre splitting with less severe fibre delamination for pulps refined at 1820 and 1850 KWh/ADT. Sulphite treatment seemed in general to induce more refining of early- than latewood fibres. SEM observation on fibres revealed high degree of deformation along the fibre axis that could also be seen on the fibre crosssections analyzed.

FTIR analyses indicated that the highest degree of sulphonation (10 kg/BDT) gave rise to different fibre separation mechanisms during refining compared with the
reference unsulphonated pulps providing a different fibre surface and thereby mechanical properties. Multivariate analysis of FTIR spectra suggested the exposed fibre surface to be richer in hemicellulose for sulphonated pulped fibres. This could provide for a better binding surface and higher strength for paper. However, no clear
pattern of differences in the distribution images and therefore the microdistribution of xylan were determined.
Statistical analysis of the Simons´ staining of fibres indicated that both the energy input and chip pre-treatment significantly induced wall delamination and internal
fibrillation (D/IF) of pulp fibres. It was shown that the fibre development of pulp 10(1580) (with lowest SEC) gained via improved wall D/IF was almost similar to that shown for pulp 00(1850) (with highest SEC). This indicates that an energy efficient refining can be obtained with 10 kg/BDT sulfite pre-treatment prior to refining and will produce the most flexible fibres.

Spectral imaging showed sulphite treatment of impressarefiner chips to improve the optical properties of pulps with a clear dose-response shown at both higher and
lower SEC levels, the former having the largest effect on whiteness. Photochemical effects of sulfonation using reflectance intensities showed complex results regarding lignocellulosic autofluorescence. Unlike wood, impressarefiner chips and pulp fibres showed a clear blue-shifted fluorescence maximum characteristic
for a shortened conjugated system indicating that both the chipping and Impressafiner pretreatment induced a minor degradation of the lignocellulosic matrix that can be measured using spectral imaging. Refining however, increased
the red edge fluorescence of the sulfonated whole long fibre fraction with a similar effect on the lignin fluorescence of wood.

Using the HCL method of fibre analysis no significant trend for the effect of sulphite treatment was noted and only minor differences in fibre length were detected.

Authors/Creators:Fernando, Dinesh and Daniel, Geoffrey and Bardage, Stig and Hafrén, Jonas and Ander, Paul and Nelsson, Erik and Olsson, Ann-Mari and Salmén, Lennart and Sandström, Peter
Title:Sub project 3: Effect of sulphite pre-treatment and high intensity refining on spruce TMP pulps produced at the Braviken mill
Series/Journal:Rapport (SLU, Institutionen för skogens produkter) (1654-1383)
Year of publishing :2012
Number:7
Number of Pages:53
Place of Publication:Uppsala
Publisher:Institutionen för skogens produkter
ISSN:1654-1383
Language:English
Publication Type:Report
Article category:Other scientific
Full Text Status:Public
Agris subject categories.:K Forestry > K01 Forestry - General aspects
K Forestry > K50 Processing of forest products
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Wood Science
Keywords:mechanical pulps, energy ifficiency, sulphite pre-treatment, high intensity refining, spruce TMP pulps, forest products
URN:NBN:urn:nbn:se:slu:epsilon-e-1611
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1611
ID Code:10770
Department:(S) > Dept. of Forest Products
Deposited By: SLUpub Connector
Deposited On:29 Aug 2013 10:55
Metadata Last Modified:03 Jan 2015 10:28

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