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  • 1.
    Dyhr, Kurt
    et al.
    Luleå tekniska universitet.
    Sterte, Johan
    Use of zeolites in hydrogen peroxide bleaching of pulp1998In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 13, no 4, p. 257-262Article in journal (Refereed)
    Abstract [en]

    The use of zeolites for inhibition of transition metal catalyzed decomposition of hydrogen peroxide was evaluated. A number of zeolite types (A, P, Y, and mordenite 10A), with different crystal structures and ion-exchange characteristics, were tested as additives in bleaching experiments using a mechanical (TMP) pulp and a chemical (kraft) pulp. For the mechanical pulp, addition of zeolites A and P at a moderate alkali charge resulted in a significant improvement of the bleaching performance as signified by an increase in both brightness and residual peroxide content of the bleaching liquor. The other zeolite types studied did not give any positive effects at the bleaching conditions used. For the chemical pulp, no significant improvements were obtained at any alkali charge using zeolite A as an additive. At high alkali charges, addition of zeolite A resulted in a substantially lower brightness than that reached in a zeolite free reference experiment. The effects of zeolite addition upon the bleaching of pulp are complex and dependent upon a number of factors. Parameters of great importance are the bleaching pH, consistency and the zeolite type and charge

  • 2.
    Edin, M.
    et al.
    Luleå tekniska universitet.
    Ödberg, Lars
    Luleå tekniska universitet.
    Sterte, Johan
    Hot melt adhesion of liner sized with alkylketene dimer2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, no 4, p. 395-400Article in journal (Refereed)
    Abstract [en]

    The effect of the sizing agent alkylketene dimer (AKD) on hot melt adhesive joint strength was studied. By varying the amount of AKD added, and varying the degrees of beating and calendering, sheets with different surface energies, surface structures, and strength properties, were obtained. The sheets were adhesively bonded using a commercial packaging machine, and the adhesive joints were tested in T-peel and creep tests. Contact angles, water absorptivity, delamination strength, density, and surface roughness were measured to study the way in which the addition of AKD, beating, and calendering influence these paper properties. The results indicate that neither sizing with AKD nor calendering or beating have any pronounced effect on the adhesive joint strength, at least not under the conditions used. Most of the differences observed are within the limits of the experimental error. The greatest influence on the joint strength was observed when samples had been stored at low temperature.

  • 3. Hafrén, Johan
    et al.
    Westermark, Ulla
    Distribution of acidic and esterified polygalacturonans in sapwood of spruce, birch and aspen2001In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 16, no 4, p. 284-290Article in journal (Refereed)
    Abstract [en]

    The distribution and degree of esterification of polygalacturonans have been studied in spruce, birch and aspen using immunolocalization. Monoclonal antibodies against acidic and methyl esterified polygalacturonan were localized by fluorescence- and transmission electron microscopy.

  • 4.
    Hellström, Lisbeth M.
    et al.
    Mid Sweden University, Fibre Science and Communication Network, FSCN, Department of Natural Science.
    Isaksson, Per
    Mid Sweden University, Fibre Science and Communication Network, FSCN, Department of Natural Science.
    Gradin, Per A.
    Mid Sweden University, Fibre Science and Communication Network, FSCN, Department of Natural Science.
    Eriksson, Kjell
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    An analytical and numerical study of some aspects of the wood chipping process2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 2, p. 225-230Article in journal (Refereed)
    Abstract [en]

    In order to model the wood chipping process, the primary process parameters have been identified and their first order interaction studied. The model is analytical and incorporates, in particular, the influence of sliding friction between the wood chipping tool and the log. To estimate the accuracy of the analytical model, a Finite Element (FE) analysis of the problem considered was also performed. The analytical model and the FE analysis are both restricted to small deformations and linear elastic orthotropic material behaviour. The most severe limitation with both the analytical and the FE model is the assumption of linearly elastic material. On the other hand it is felt that existing models of anisotropic plasticity in metals are lacking too much of physical relevance, if applied to wood. The analytical model predicts the normal and shear strain distribution in the crack-plane prior to crack initiation. The analytical distributions are in reasonable agreement with the corresponding distribution of the FE analysis. Based on experimental findings, it is suggested that the stress field over the entire crack-plane, in conjunction with the stress field close to the tip of the chipping tool, are critical for chip creation, rather than just the latter.

  • 5.
    Håkansson, Mikael
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Carlson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Multivariate prediction of key kraft paper properties from designed experiments in a pilot plant2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 258-264Article in journal (Refereed)
    Abstract [en]

    A two-level factorial design was set up where five factors in a kraft paper process were varied, from wood chip origin to paper machine roll pressure. Nine paper properties were selected for a more in-depth analysis. This paper shows how these 9 responses can be modeled as a function of the experimental factors. The model, a full interaction model, was estimated using Partial Least-Squares Regression. The resulting model shows that there is a strong correlation between the experimental factors and the measured paper properties. The paper also presents a careful analysis of how the uncertainties of the measured values propagate through the model and contribute to the final model uncertainty. Finally, the interpretations and application of the resulting model is discussed. Specifically, having access to a good model enables the plant operators to simulate the effect of changing the process variables, either for training purposes or to test new production scenarios

  • 6.
    Håkansson, Mikael
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Carlson, Johan E.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Factorial study of connections between process variables and kraft paper quality properties2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 2, p. 286-293Article in journal (Refereed)
    Abstract [en]

    By investigating how properties of a finished paper product are related to different process variables as well as pulp characteristics throughout the fiber line, the understanding of the process will increase. In this paper we investigate the correlation between some key paper quality parameters and five tunable process variables, along the entire fiber production line. A full two-level factorial experiment has been conducted, where five factors were varied. The factor settings were based on a laboratory replica of a specific kraft mill’s paper product. The mill replicate was then used as a center point in the factorial design and appropriate levels of the factors were set based on these center points. Several experimental runs could be simulated via a Monte Carlo approach making it possible to get a reliable estimate of the significance of each factor effect. Analysis of the results shows that there are interaction effects present between variables, and that these interaction effects can be utilized to achieve similar paper properties using different variable settings.

  • 7.
    Höhn, Patrick
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dynamic model and simulation for a high consistency refining process2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 1, p. 88-101Article in journal (Refereed)
    Abstract [en]

    A novel dynamic model for the behavior inside of the gap of a high consistency refiner in the pulp and paper industry is presented. As the original entropy model gives additional information about the work split between thermodynamic effects and fiber changes inside the refining zone, it is used as a base for a dynamic model to describe the efficiency of the refining process. This model is derived for the mass flow rates of steam and water, changes of the work distribution and consistency as a function of radius and time. The temperature distribution inside the refining zone, specific energy, inlet consistency and total mass flow rate are used as input signals. After a general presentation in continuous-time, the spatial discrete model is also discretized in temporal dimension. Both discretizations are dependent on each other as the ratio can be considered as a flow speed of the fluid elements and it affects the residence time inside the refining zone. Thereafter, results from a simulation with assumed input parameters using the discrete model are presented and compared with the output of previously published models. Other dynamic models exhibit similar oscillations when applying changes to the inputs. Furthermore, the overall general trend is consistent with other published steady-state models. Hence, we expect the newly proposed model to be reliable and more efficient to describe the behavior inside the refining zone.

  • 8.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    The significance of glucomannan for the condensation of cellulose and lignin under kraft pulping conditions1997In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 12, no 2, p. 90-Article in journal (Refereed)
  • 9.
    Li, Shiming
    et al.
    Chalmers University of Technology.
    Lundquist, Knut
    Chalmers University of Technology.
    Westermark, Ulla
    Cleavage of arylglycerol β-aryl ethers under neutral and acid conditions2000In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 15, no 4, p. 292-299Article in journal (Refereed)
    Abstract [en]

    Arylglycerol β-aryl ethers constitute a major type of structure in lignins. Experiments with model compounds representative of such ethers show that the β-ether linkage is broken homolytically on heating under neutral and weakly acid conditions. Cleavage via a benzylic carbocation becomes important when the acidity level is raised.

  • 10.
    Li, Shiming
    et al.
    Department of Organic Chemistry, Chalmers University of Technology.
    Lundqvist, Knut
    Chalmers University of Technology, Department of Forest Products and Chemical Engineering.
    Westermark, Ulla
    Cleavage of syringylglycerol β-syringyl ethers during soda cooking2000In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 15, no 3, p. 205-210Article in journal (Refereed)
    Abstract [en]

    The degradation of model compounds of the syringylglycerol β-syringyl ether type [2-(2,6-dimethoxyphenoxy)-1-(4-hydroxy-3,5-dimethoxyphenyl)-1, 3-propanediol and 2-(2,6-dimethoxy-4-methylphenoxy)-1-(4-hydroxy-3,5-dimethoxyphen yl)-1, 3-propanediol] on soda cooking under comparatively mild conditions was studied. The formation of the degradation products detected, can be envisioned to proceed via a homolytic cleavage of the β-ether bond in an intermediate quinone methide. 2,6-Dimethoxyphenol, sinapyl alcohol, syringaldehyde, 1,2-bis(4-hydroxy-3,5-dimethoxyphenyl)ethanedione, bis(4-hydroxy-3,5-dimethoxyphenyl)methanone and traces of syringyl alcohol were detected in the reaction product obtained from 2-(2,6-dimethoxyphenoxy)-1-(4-hydroxy-3,5-dimethoxyphenyl)-1,3-p ropanediol. 2,6-Dimethoxy-4-methylphenol, sinapyl alcohol, 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone, 1-(4-hydroxy-3,5-dimethoxyphenyl)-2-propen-1-one, syringaldehyde and syringyl alcohol were detected in the reaction product obtained from 2-(2,6-dimethoxy-4-methylphenoxy)-1-(4-hydroxy-3,5-dimethoxyphen yl)-1, 3-propanediol. Traces of sinapaldehyde, 2-aryloxyacroleins and, possibly, syringaresinol were present in the reaction mixtures from both model compounds. Reaction routes that explain the differences in product patterns of the two model compounds are presented. The reactions of phenolic arylglycerol β-aryl ethers under the conditions prevailing during alkaline pulping are discussed on the basis of the results

  • 11.
    Linder, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Löfqvist, Torbjörn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Anisotropic light propagation in paper2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 500-506Article in journal (Refereed)
    Abstract [en]

    We investigate anisotropic light propagation in paper using both a theoretical model and experiments. The theoretical model utilizes the Monte Carlo method to solve the photon transport equation numerically. It is assumed that wood fibres are represented by infinitely long, homogeneous and straight cylinders. The layer-like microstructure and anisotropic orientation of the fibres is considered in the model. The conical scattering by cylindrical objects, the wood fibres, is argued as the main source of anisotropic scattering. Simulations revealed that laterally resolved transmittance exhibits directional dependence. Experiments on light transmitted through a standard kraft liner product confirmed that light in fact do propagate more in the machine direction than in the cross direction. Reasonably good agreement was obtained between experimentally and numerically obtained iso-intensity patterns.

  • 12.
    Mattsson, Rosa
    et al.
    Kappa Kraftliner, Piteå.
    Sterte, Johan
    Ödberg, Lars
    AssiDomän Corporate R&D, Stockholm.
    Sizing with pre-flocculated alkylketene dimer (AKD) dispersions.2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, no 3, p. 240-245Article in journal (Refereed)
    Abstract [en]

    Pre-flocculated AKD dispersions were used to size laboratory sheets. The cationic AKD dispersion was pre-flocculated in a Britt Dynamic Drainage Jar. Carboxymethylcellulose and white water from a linerboard mill were used as flocculating agents. The particle size distribution was determined to verify the flocculation. Laboratory sheets sized with pre-flocculated AKD dispersions were made in a dynamic sheet former. The sizing efficiency was evaluated with the 60-second Cobb value, contact angle measurements and quantitative analysis of the total AKD content in the laboratory sheets. The results show that sizing with pre-flocculated AKD improved the sizing efficiency significantly, due to an increased retention. This clearly indicates that agglomerates can be used for internal sizing provided that the flocculation process is controlled. (14 refs.)

  • 13.
    Nohlgren, Ingrid
    et al.
    Luleå tekniska universitet.
    Zhuang, Qianlin
    Theliander, Hans
    Heiningen, Adriaan Van
    Direct causticization using titanates in a fluidized bed reactor2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, no 3, p. 246-253Article in journal (Refereed)
    Abstract [en]

    Experiments were carried out in a fluidized bed reactor operated in a semi-batch mode using TiO2 or sodium trititanate to causticize either sodium carbonate or the sodium carbonate in kraft black liquor at temperatures between 800-825°C. Conversions of sodium carbonate of up to 88% were obtained, with the main product being sodium penta-titanate. Sodium hexatitanate and sodium tri-titanate are reaction intermediates formed when TiO2 is used. The BET surface area of the reacted solids decreased with increasing formation of sodium penta-titanate. Upon leaching of the final product, the surface area is regained. The high surface area of the leached material allows for good mixing with black liquor when the solids are recycled to the reactor. EDX analysis along the cross-section of TiO2 particles showed that sodium diffuses into the TiO2 particle, forming a very sharp front. This indicates that the direct causticization reaction proceeds according to the shrinking-core model, i.e. the reaction at the reaction front is fast compared to the diffusion of Na2CO3 into the reaction interface

  • 14.
    Parkås, Jim
    et al.
    Chalmers University of Technology.
    Paulsson, Magnus
    Chalmers University of Technology.
    Li, Shiming
    Chalmers University of Technology.
    Lundquist, Knut
    Chalmers University of Technology.
    Westermark, Ulla
    Photoyellowing behavior of non-phenolic lignin models representative of end groups and β-ether structures2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 2, p. 146-154Article in journal (Refereed)
    Abstract [en]

    Lignin model compounds representative of etherified end groups [(E)-3-(3,4-dimethoxyphenyl)-2-propenl-ol (1), (E)-3-(3,4-dimethoxyphenyl) propenal (2)] and βethers, [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxy- phenoxy)-1-propanone (3), erythiro-1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)- 1,3-propanediol (4)] have been applied to filter paper and subjected to accelerated photoaging with UV/VIS-light. The changes in optical properties were monitored. In case of all the models, the brightness decreased and the b*-value increased as a result of irradiation, which shows that they are sensitive to light simulating sunlight behind window-glass. In the case of the end group models, the photo-products identified were veratraldehyde and veratric acid together with the Z-isomers of the starting materials. In the case of the cinnamyl alcohol 1, photo-oxidation to the cinnamaldehyde 2 was observed. The irradiation of the αt-carbonylic βether 3 resulted in the homolytic cleavage of the CβO bond and a recombination that led to a β-5 dimer [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-hydroxy-3-methoxyphenyl)- 1-propanone] and a β-1 dimer [1-(3,4-dimethoxyphenyl)-3-hydroxy-2-(4- hydroxy-3-methoxyphenyl)-l-propanone]. The monomeric products veratraldehyde, vanillin, acetoveratrone, and 1-(3,4-dimethoxyphenyl)-3-hydroxy-l-propanone were also formed. The only photoproduct conclusively identified in experiments with the arylglycerol-β-aryl ether 4 was veratraldehyde and most of the starting material was unaffected by the irradiation. The addition of a photosensitizer (acetoveratrone) to this type of model prior to irradiation resulted in some increase in discoloration

  • 15.
    Parkås, Jim
    et al.
    Chalmers University of Technology.
    Paulsson, Magnus
    Chalmers University of Technology.
    Terashima, Noritsugo
    Chalmers University of Technology.
    Westermark, Ulla
    Ralph, Sally
    US Forest Products Laboratory.
    Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs): Part 1. Side-chain 13C-enriched DHP (α-, β-, and γ-13C)2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 1, p. 29-36Article in journal (Refereed)
    Abstract [en]

    Light-induced yellowing has been studied using side-chain (α, β, and γ) 13C-enriched DHP (dehydrogenation polymer) and quantitative solution state 13C NMR spectroscopy. The DHP was formed from 13C-enriched coniferin using an enzymatic system consisting of β-glucosidase, glucose oxidase, and peroxidase in a pH 6 buffer solution. The DHP was applied to filter paper, irradiated with UV/VIS light and the photodegraded DHP was extracted and analyzed. The NMR study revealed a drastic decrease in the amount of coniferyl alcohol end groups with the formation of end groups of the vanillin type and small amounts of end groups of the vanillic acid type. The results indicated a moderate formation of αcarbonyls, however, no significant decrease in the amount of βO-4 structures in the extractable part of the irradiated DHP could be established, based on difference spectra corresponding to the 13C-enriched DHP.

  • 16.
    Parkås, Jim
    et al.
    Chalmers University of Technology.
    Paulsson, Magnus
    Chalmers University of Technology.
    Terashima, Noritsugo
    Chalmers University of Technology.
    Westermark, Ulla
    Ralph, Sally
    US Forest Products Laboratory.
    Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs): Part 2. NMR assignments and photoyellowing of aromatic ring 1-, 3-, 4-, and 5-13C DHPs2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 1, p. 44-52Article in journal (Refereed)
    Abstract [en]

    Light-induced yellowing of lignocellulosic materials has been studied using 13C-enriched DHP (dehydrogenation polymer), selectively 13C-enriched at positions 1, 3, 4, and 5 in the aromatic ring, and quantitative solution state 13C NMR spectroscopy. The NMR study confirmed the results of previous studies using side-chain labeled DHP, mainly that coniferyl alcohol end groups are degraded with the subsequent formation of α-carbonylic structures, e.g. vanillin end groups. The developed technique renders the potential to follow chemical changes of aromatic carbons 1, 3, 4, and 5, independently from each other. Although a drastic photoyellowing of the sheets was observed, definitive chemical shifts corresponding to quinoid carbons could not be discerned in the spectra. The reasons for this may be that the amount of quinoid carbons formed was too low to be detected, with the experimental setup used, or that the quinoid photo-products, if formed, were not extractable with the solvent used or had reacted further forming non-quinoid structures.

  • 17.
    Richards, Tobias
    et al.
    Chalmers University of Technology.
    Nohlgren, Ingrid
    Luleå tekniska universitet.
    Warnqvist, Björn
    ÅF-IPK AB, Stockholm.
    Theliander, Hans
    Chalmers University of Technology.
    Mass and energy balances for a conventional recovery cycle and for a recovery cycle using borates or titanates2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, no 3, p. 213-221Article in journal (Refereed)
    Abstract [en]

    Mass and energy flows for different methods to recover the cooking chemicals in a kraft pulp mill have been studied. It was revealed that recovery using titanates is the most energy effective method, followed by conventional recovery and, finally, recovery using borates.

  • 18. Sand, Anders
    et al.
    Toivakka, Martti
    Åbo Akademi.
    Hjelt, Tuomo
    KCL.
    Influence of Drying Strategy on Coating Layer Structure Formation2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 46-51Article in journal (Refereed)
  • 19. Sand, Anders
    et al.
    Toivakka, Martti
    Åbo Akademi.
    Hjelt, Tuomo
    KCL.
    Small Particle Mobility in Consolidating Coating Layers2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 52-56Article in journal (Refereed)
  • 20.
    Sedin, Peter
    et al.
    Luleå tekniska universitet.
    Theliander, Hans
    Chalmers University of Technology, Department of Forest Products and Chemical Engineering.
    Filtration properties of green liquor sludge2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 1, p. 67-74Article in journal (Refereed)
    Abstract [en]

    The filtration properties of green liquor sludge were investigated. Three different experimental set-ups were used: one for low pressure (up to 3 bars), one for high pressure (up to 100 bars) and one for washing and lime mud addition experiments (1 bar). Green liquor sludge from four different pulp mills was investigated in the low pressure tests. The influence of pressure and the addition of calcium, magnesium and aluminium ions were investigated. The low pressure filtration tests showed that green liquor sludge is relatively compressible (the compressibility coefficient is approximately 0.6), and that the average specific filtration resistance could differ by one order of magnitude between different mills (1012-1013 m/kg). It was found that the addition of both aluminium and calcium ions improved the filtration properties, whilst the addition of magnesium has the opposite effect. The high pressure tests showed that a considerable amount of water could be squeezed out of the filter cakes at high pressures. The addition of lime mud to the green liquor decreased the average specific filtration resistance to a large extent. In the washing experiments, breakthrough curves were calculated. These curves showed considerable deviations from ideal displacement washing. The dispersion model was fitted to the experiments and a fair fit was obtained.

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