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Halden, Norway

Fernando D.,Swedish University of Agricultural Sciences | Gorski D.,University of British Columbia | Gorski D.,Norske Skog Saugbrugs AS | Daniel G.,Swedish University of Agricultural Sciences
International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference | Year: 2014

In order to unravel fundamental mechanisms governing property development during high- consistency (HC) and low-consistency (LC) refining of thermo-mechanical pulping (TMP), characterization of pulp fibre development at the cell wall level was carried out. Both HC and LC refining significantly enhance the internal fibre development (IFD) with the latter being more energy-efficient. The IFD was identical between HC and LC pulps when compared at the targeted tensile strength 40 Nm/g of handsheets providing the basis for energy efficiency of LC refining. External fibre development and the resulting fines development were very different between the two processes. Mechanisms of fibre development during HC and LC refining were explored which appear to govern most physical and optical properties of the pulps. Source


Hafren J.,Swedish University of Agricultural Sciences | Fernando D.,Swedish University of Agricultural Sciences | Gorski D.,Pulp and Paper Research Institute of Canada | Gorski D.,Norske Skog Saugbrugs AS | And 2 more authors.
Wood Science and Technology | Year: 2014

High-yield pulping of wood chips using low-consistency (LC) refining in combination with primary-stage high-consistency (HC) refining has previously been shown to produce paper with quality parameters (tensile strength and light-scattering coefficient) commonly targeted for newsprint with significantly less refining energy input than using only HC refining. However, questions remain on the differences in the refining action between the two refiner types and for high-yield pulping, the refiner energy demand is a crucial process parameter. Therefore, fines- and fiber-fraction development in HC and LC refining has been studied in detail using Bauer-McNett fractionation, and the respective tensile strengths of the different fractions have been compared. Quantitative and qualitative (morphological) characteristics of the isolated fine fractions have also been analyzed in detail using a newly developed automated fluorescence microscopy method and scanning electron microscopy. The results suggest the difference in LC/HC pulp properties (strength and optical) is partly derived from deviating fiber and fines morphologies and mass balances. The quality of the fines generated during HC and LC refining also differs. LC-refined pulps contain thinner fibrillar fines (thread-like) and HC-refined pulps broader fibrils such as lamellae-type fines. Flake-like fines from the outer fiber wall decreased in relative amount with energy input. © 2014 Springer-Verlag Berlin Heidelberg. Source


Enberg S.,Norske Skog Saugbrugs AS | Enberg S.,Mid Sweden University | Rundlof M.,Mid Sweden University | Paulsson M.,Mid Sweden University | And 3 more authors.
Nordic Pulp and Paper Research Journal | Year: 2013

The aim of this work was to study the influence of process conditions (time, pH, temperature and consistency) on the optical properties of mechanical pulps during storage in a clean system as a reference for further work. Laboratory storage trials were performed with unbleached and hydrogen-peroxide bleached well-washed Norway spruce pulps. In general, the pulp darkened during storage due to an increase in light absorption, especially at shorter wavelengths. After long storage times, the light absorption coefficient, k had increased also at longer wavelengths. No specific peaks were seen in Δk-spectra. The increase in light absorption was most rapid initially, during the first four hours, for all pulps when stored at high temperature (80°C), and then proceeded more slowly. The corresponding change in colour, measured as a* and b*, was shifted towards red and somewhat towards yellow, and over longer periods of storage, the shift towards yellow became greater. Time and temperature were found to have the largest impact. The effects were similar regardless of the starting pH (4.3-9.7) and pulp consistency (5%-25%). The hydrogen-peroxide bleached pulps were more sensitive to storage compared to the unbleached pulp at temperatures above 50°C. At storage times of up to four hours, the unbleached pulp showed no loss of brightness at either of the storage temperatures. A slightly less bleached pulp darkened more than a highly bleached pulp at all wavelengths. The only difference measured between the two pulps was that the less bleached pulp had a higher content of iron. This higher iron content may be at least part of the reason for the more extensive darkening. Source

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