Norrköping, Sweden
Norrköping, Sweden

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Nelsson E.,Holmen AB | Paulsson M.,Akzo Nobel | Paulsson M.,Mid Sweden University | Sandberg C.,Holmen Paper AB | And 2 more authors.
Nordic Pulp and Paper Research Journal | Year: 2017

The effects of low dosage sodium sulfite (Na2SO3) pretreatment (0, 0.6 and 1.2% on bone dry wood, pH 9) at two different refining temperatures (4.6 and 6.4 bar(g) refiner housing pressure) were evaluated for production of thermomechanical pulp with a double disc refiner in mill scale using Norway spruce wood at Braviken paper mill (Holmen Paper AB, Sweden). The sulfonate content of the pulps was not affected by the different refining temperatures and was 0.29% (as Na2SO3 equivalents) for the highest sulfite addition. Tensile index at constant SEC was increased by 3.2 Nm/g when the refining temperature was increased, and by 8.6 Nm/g when 1.2% sodium sulfite was added. The effects were additive and led to an increase in tensile index of ∼12 Nm/g at constant SEC when combined and would enable a reduction in SEC of 380 kWh/bdt (∼20%) to similar tensile index. The degree of delamination and internal fibrillation of the fibers was increased by both increased refining temperature and sulfite addition. Pulp brightness was slightly reduced (≤0.4% ISO) by increased refining temperature and increased (2-3% ISO), when sodium sulfite was added. Spectra of reflectance factors (360-740 nm) were used to study the optical properties of produced pulps.

Fernando D.,Swedish University of Agricultural Sciences | Muhic D.,Holmen Paper AB | Engstrand P.,Mid Sweden University | Daniel G.,Swedish University of Agricultural Sciences
Holzforschung | Year: 2011

The morphological and chemical characteristics of cell walls govern the response of wood fibre to mechanical pulping processes and thereby influence the energy efficiency of the process and determine most pulp and paper properties. A study has been carried out at the microstructural/ultrastructural level of fibre cell walls by means of a newly developed Simons' staining (SS) method and scanning electron microscopy to characterize thermomechanical pulps (TMPs) produced under different refining conditions. The SS method allows assessment and quantification of pulp fibre development during the process in terms of cell wall delamination/internal fibrillation (D/IF) under different process conditions, and the degree of D/IF can be statistically evaluated for different TMP types. In focus was never-dried Norway spruce TMP from primary stage double-disc refining running in a full-scale mill, where specific refining energy was varied at different refining pressure levels. Improved energy efficiency was gained at the same tensile index level when applying high pressure (temperature). Under conditions of high pressure and refining energy, a significant enhancement of the degree of D/IF of pulp fibres was observed. The surface ultrastructure of these fibres exhibited an exposed S2 layer with long ribbon-type fibrillation compared to pulps produced with lower pressure and energy input. A given TMP type can be classified in the categories of high-severity and low-severity changes and quasi-untreated concerning the degree of D/IF of its fibres. The relative proportions of these are important for the development of pulp properties such as tensile strength. The presence of higher amounts of fibre fractions in the categories high D/IF and low D/IF will improve the tensile index of a TMP. © 2011 by Walter de Gruyter Berlin Boston.

Nelsson E.,Holmen AB | Sandberg C.,Holmen Paper AB | Svensson-Rundlof E.,Holmen Paper AB | Engstrand P.,Mid Sweden University | And 2 more authors.
Nordic Pulp and Paper Research Journal | Year: 2015

The effects of low dosage sulfite pretreatment combined with modern high consistency double disc refining were evaluated for production of thermomechanical pulp in a mill scale trial using Norway spruce wood at the Braviken paper mill (Holmen Paper AB, Sweden). Spruce wood chips were mechanically pretreated in an Impressafiner before impregnation with different dosages (0-1.2%) of sodium sulfite (Na2SO3) at pH 9. Approximately 23% of the added sulfite was converted to sulfonate groups in pulp, resulting in a sulfonate content of 0-0.28% (as Na2SO3). The low dosage sulfite addition increased tensile index, elongation, density, brightness and decreased shive content, light scattering and light absorption coefficients when compared at equal specific energy consumption (SEC). The increase in tensile index was proportional to dosage of sulfite. Further analyses showed that low dosage sulfite addition did not affect the distribution of the Bauer-McNett fractions nor the fibre length for pulps refined with equal SEC. However, the low dosage sulfite addition increased fibre delamination/internal fibrillation (D/IF). With the addition of 1.2% Na2SO3, it was possible to produce pulp with a tensile index of 47 Nm/g using ∼320 kWh/bdt (∼15%) lower refining energy, compared with pulps produced without sulfite addition.

Andersson S.,Holmen Paper AB | Sandberg C.,Holmen Paper AB | Engstrand P.,Mid Sweden University
Nordic Pulp and Paper Research Journal | Year: 2012

The aim of this study was to investigate the influence of long fibre concentration on loadability and pulp properties during LC refining of mechanical pulp. Long fibre concentration was adjusted to three different levels by screen fractionation of the pulp. The three pulps were refined in a single disc pilot scale LC refiner at similar process conditions. Increased long fibre concentration supported a larger refiner gap and resulted in less fibre cutting at a given specific energy consumption. The higher long fibre concentration probably contributed to a stronger fibre network that maintained a larger refining gap at certain specific energy consumption. Increased long fibre concentration also enabled a higher tensile index increase in the LC refiner at certain fibre length reduction. The study supports a process combining LC refining with screen fractionation, where the long fibre fraction is recycled to the refiner feed. This enables a higher loadability and a more effective utilisation of the LC refiner. By using this technology, overall specific energy consumption can be reduced if a larger share of the refining is performed in LC rather than HC refining.

Fernando D.,Swedish University of Agricultural Sciences | Muhic D.,Holmen Paper AB | Engstrand P.,Mid Sweden University | Daniel G.,Swedish University of Agricultural Sciences
Holzforschung | Year: 2012

Refining during mechanical pulping causes delamination and internal fibrillation (D/IF) of the fibre wall and changes the surface ultrastructure. Fundamental knowledge about these phenomena at the fibre cell wall level helps our understanding of the development of pulp and paper properties, which in turn facilitates the optimization of processes, helping to save energy and improve the characteristics of final products. In the present study, pulps were produced by double-disc (DD) refined thermomechanical processes (DD-TMP) and have been characterized at the fibre cell wall micro/ultrastructural level based on Fernando and Daniel's method (2010) of Simons ' staining and scanning electron microscopy (SEM). The pulps studied were never-dried Norway spruce DD-TMP from a full-scale mill trial running under different process conditions; a) varying refining intensity, achieved by using a high-intensity turbine segment (HTS) and a standard (Ref) segment from Metso, and b) varying specific energy consumption (SEC). Improved energy efficiency was obtained with HTS segments, giving adequate or better pulp properties with respect to elongation, light scattering, Canadian Standard Freeness (CSF) at a similar tensile index level and lower energy consumption. Energy efficiency was gained through an elevated degree of D/IF and S2 fibrillation with low energy input. Both the SEC and segment designs had a significant impact on elevating the degree of D/IF. Statistical evaluation of fibre development with respect to D/IF gave evidence for improved energy efficiency in HTS refining. Ultrastructural studies on fibre surfaces showed that HTS refining produced better external fibrillation and leads to exposing the secondary S2 wall as fibre outer layer with different ribbon-type S2 fibrillation. Information obtained at the fibre wall level concerning D/IF and surface ultrastructure contribute to the fundamental knowledge about the pulp and handsheet properties and the energy efficiency of TMP processing. Copyright © by Walter de Gruyter·Berlin·Boston.

Hafren J.,Swedish University of Agricultural Sciences | Muhic D.,Holmen Paper AB | Muhic D.,Metso Paper Inc. | Gerritsen H.C.,University Utrecht | Bader A.N.,University Utrecht
Nordic Pulp and Paper Research Journal | Year: 2011

Norway spruce wood pulps were produced in full industrial scale trials at different thermomechanical pulp refining conditions, such as plate gap, housing pressures and energy consumption levels. To investigate the effects of these refining conditions on the lingocellulosic matrix in fines and fibers, we applied high-resolution spectral imaging in a two-photon fluorescence microscope and compared with conventional pulp and paper analyses (strength, freeness etc.). The fluorescence spectra of lignin in native wood and fibersand fines from pulps showed that spatial- and spectral heterogeneities can be observed using two-photon autofluorescence spectral imaging, and successfully probed on a microscopic level. Moreover, it was shown that wood autofluorescence depends on fiber morphology and becomes red-shifted by increased temperature, but the fluorescence spectrum of TMP long fiber fraction shifted towards blue by increased refining pressure.

Hafren J.,Swedish University of Agricultural Sciences | Nelsson E.,Holmen Paper AB | Gerritsen H.C.,University Utrecht | Bader A.N.,University Utrecht
Holzforschung | Year: 2012

Chips of Norway spruce have been impregnated with Na2SO 3 and refined at two specific energy consumptions levels at full mill scale. The optical properties of thermomechanical pulps (TMPs) obtained were analyzed in terms of brightness, light scattering, opacity, and autofluorescence by spectral imaging. Even at low sulfite dosage (0.24% sulfite by dry weight) light absorption was reduced, and the brightness was elevated, and a clear dose-response effect was observed. Two-photon spectral imaging (TPSI) showed that sulfonation, impregnation, and refining affect the fluorescence properties differently. Compared to native wood, both processed wood chips and pulp fibers revealed blue-shifted fluorescence maxima, a characteristic of shortened conjugated systems. Two subpopulations of fibers with different optical properties were observed, and the fluorescence of one fiber population was red shifted. Copyright © by Walter de Gruyter.

Nelsson E.,Holmen Paper AB | Sandberg C.,Holmen Paper AB | Hilden L.,Holmen Paper AB | Daniel G.,Swedish University of Agricultural Sciences
Nordic Pulp and Paper Research Journal | Year: 2012

Mill scale trials were performed to evaluate pressurised compressive chip pre-treatment with the Impressafiner installed in one of the thermomechanical pulp lines at Braviken paper mill (Holmen Paper AB). The aim of the study was to determine if earlier reported effects of the Impressafiner pre-treatment on spruce chips from pilot scale trials (i.e. energy reduction and extractives removal) could also be attained with the mill scale Impressafiner. The mill scale Impressafiner pre-treatment resulted in partial disintegration of chips into a material consisting of fragmented chips with cracks running along the longitudinal fibre axis. Splits or evidence for weaknesses were observed between the primary and secondary fibre walls of pre-treated chips. An increase in water uptake for pre-treated chips was also observed. The extractive content was reduced by up to 24% for pulps produced with pre-treated chips compared to pulps from untreated chips. Pulp produced from pre-treated chips had higher tensile- and tear indices, elongation and light scattering and lower freeness compared to pulps from untreated chips produced with the same total specific energy consumption. The total specific energy needed to reach a tensile index of 47 Nm/g was reduced by 120 kWh/bone dry ton (6%) with Impressafiner pre-treatment. A smaller refiner plate gap was needed to reach the same specific energy consumption for pre-treated chips compared to untreated chips.

Lindqvist H.,Åbo Akademi University | Holmback J.,Holmen Paper AB | Rosling A.,Åbo Akademi University | Salminen K.,VTT Technical Research Center of Finland | And 3 more authors.
BioResources | Year: 2013

Native galactoglucomannans (GGMs), which were isolated from thermomechanical pulping waters of Norway spruce, were modified through cationization, carboxymethylation, and imination at the reducing end with a primary long-chain hydrocarbon amine. The derivatives were tested for their papermaking properties. The native GGMs increased the wet tensile strength as a result of the dispersion of fibrils in the wet fibre web. In wood-containing paper, GGMs increased the retention of fines and extractives without a decrease in paper strength. The GGMs also flocculated fillers effectively. The cationic GGMs were able to interact between fibrous fine material and fibres, as well as with fillers. Therefore, an electrostatic mechanism of action is suggested. Carboxymethylated GGMs are believed to bind to fibres and fines through divalent metal ions present in wood. For the amphiphilic amine-modified GGMs, the alkane chain attached to the reducing end appeared to play a key role. The tail was orientated towards the hydrophobic particles; the resulting paper was the most hydrophilic, since the hydrophobic particles were covered with the polysaccharide. Based on the present results, it can be concluded that galactoglucomannans can be modified to yield new and interesting functionalities to wet-end additives for papermaking and other purposes.

Andersson S.,Holmen Paper AB | Sandberg C.,Holmen Paper AB
Appita Annual Conference | Year: 2010

In this work, a traditional two stage single disc (SD) high consistency (HC) mechanical pulping line was compared with a line consisting of a combination of high consistency double disc (DD) and low consistency (LC) refining. Trials were performed in full scale at Holmen Paper, Braviken Paper Mill, Sweden. The purpose was to compare pulp quality and electrical energy consumption between the two process configurations. A difference in electrical energy consumption of 500 kWh/adt was demonstrated to similar tensile strength and freeness. At a tensile index of 45 Nm/g, a number of pulp characteristics were compared for both refining concepts. Fibre length was shorter after DD refining than after SD refining. However, fibre length was somewhat better preserved in second stage LC refining than in second stage SD refining. Light scattering was higher after DD-LC refining than SD-SD refining while the development in the second refining stage was better for SD-SD pulp than for DD-LC pulp. Long fibre bonding was slightly higher for DD-LC pulp than SD-SD, although the long fibre bonding development was similar for both pulp types. Shive level was significantly lower for DD-LC pulp than for SD-SD pulp.

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