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  • 201.
    Persson, Johan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Granfeldt, Thomas
    Valmet AB.
    Feeding of double disc refiners - modeling of particle flow2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    Improvements to the energy efficiency of double disk refiners are hampered by the feeding rate in tothe machine. This study aims to evaluate parameters towards a complete model, which will help tobring clarity to the limiting factors in feeding rate. A combined computational fluid dynamic anddiscrete element model is used to evaluate the flowrate of a hopper discharge unaided, and aided by agas flow with varying density. The results of the study shows that it is essential to capture the exactgeometry of the double disk feeding in relation to the woodchips in the complete model. The resultsalso shows that while it is essential to include the gas phase in the full model, the model is not sensitiveto small variance in the density of the gas.

  • 202.
    Persson, Johan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Isaksson, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A particle-based method for mechanical analyses of planar fiber-based materials2013In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 93, no 11, p. 1216-1234Article in journal (Refereed)
    Abstract [en]

    A new discrete element model to deal with rapid deformation and fracture of flat fibrous materials is derived. The method is based on classical mechanical theories and is a combination of traditional particle dynamics and nonlinear engineering beam theory. It is assumed that a fiber can be seen as a beam that is represented by discrete particles, which are moving according to Newton's laws of motion. Damage is dealt with by fracture of fiber-segments and fiberfiber bonds when the potential energy of a segment or bond exceeds the critical fracture energy. This allows fractures to evolve as a result of material properties only. To validate the model, four examples are shown and compared with analytical results found in literature. Copyright (c) 2013 John Wiley & Sons, Ltd.

  • 203.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    KTH, Stockholm.
    The use of polyelectrolyte multilayers of cationic starch and CMC to enhance strength properties of papers formed from mixtures of unbleached chemical pulp and CTMP: Part I2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 1, p. 115-121Article in journal (Refereed)
    Abstract [en]

    The construction of alternating multilayers of cationic potato starch and anionic carboxymethylcellulose(CMC) was investigated in two parts. In the first part, stagnation point adsorption reflectometry (SPAR) showed that the chosen chemicals formed polyelectrolyte multilayers (PEM)upon adsorption to the silicon oxide surface. This was in accordance with earlier work. The chosen polyelectrolytes adsorbed to similar extents on the silicon oxide surface and recharged the surface enough to allow for adsorption of a consecutive layer. In the second part, the multilayer concept was tested on 80/20,20/80% of total in mixture of mixed spruce CTMP and bleached chemical pulp in order to enhance the sheet strength properties of a typical packaging board furnish.. The multilayers yielded a significant improvement in Scott Bond values and tensile index and a marginal improvement in tensile stiffness index. The Scott Bond values were improved more than 150% for papers prepared from a furnish consisting of 80% spruce CTMP and 20% chemical pulp. Polyelectrolyte multilayers treatment also led to a slight densification of the sheets, but the polyelectrolyte multilayers treatment resulted in a more favourable density/strength relationship than that achieved with a change in the amount of chemical pulp.

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  • 204.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    KTH.
    The use of polyelectrolyte multilayers of cationic starch and CMC to enhance strength properties of papers formed from mixtures of unbleached chemical pulp and CTMP-II: Part II: Influnence of addition strategy, fibre treatment and fibre type2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 1, p. 122-128Article in journal (Refereed)
    Abstract [en]

    Polyelectrolyte multilayers (PEM) consisting of cationic starch and anionic carboxymethylcellulose (CMC) have been applied to different pulp fibres in order to enhance the out-of-plane sheet strength properties of a typical packaging board furnish. An unbleached softwood chemical pulp was treated with multilayers consisting of two layers of cationic starch and one layer of CMC, and then mixed with different mechanical and chemimechanical pulps. Hand sheets were prepared with the aid of the Rapid Köthen sheet former from stocks consisting of 20% treated chemical pulp and 80% mechanical or chemimechanical pulp, which was either PGW from spruce, HT-CTMP from spruce or birch, or a standard spruce CTMP. Multilayer treatment significantly improved Scott Bond values and in some cases improved the tensile index, with the achieved effects being significantly larger than the effects of applying starch alone. Positive effects were obtained by treating only 20% of the furnish, showing a very high efficiency of the adsorbed multilayers. Compared to earlier work, one important finding was that the PEM treatment should preferably be applied only to the chemical pulp and not on the entire stock. It was possible to increase the out-of-plane strength properties, measured as Scott Bond values, with just a very small increase in density of the sheets. Multilayer treatment of the chemical pulp improved the joint strength between the fibres while maintaining the high bulk of the sheets prepared from the stiff mechanical and chemimechanical fibres.

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  • 205.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    MoRe Res, Box 70, SE-89122 Örnsköldsvik, Sweden..
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Capisco, Mariehov Kanalbyn 108, SE-61492 Soderkoping, Sweden..
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Aspects on bond strength in sheet structures from TMP and CTMP - a review2021In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, no 2, p. 177-213Article, review/survey (Refereed)
    Abstract [en]

    High yield pulps (HYP), manufactured in mechanical and chemimechanical pulping processes, are mainly used in graphic papers and paper grades where a high bulk is preferable, like in paperboards. Moreover, packaging papers with very high demands on both dry and wet strength could be manufactured from HYP in a near future. Preferred bonds between fibre components (long fibres, shortened fibres and fines) in the various paper grades are quite different. In the review, plausible effects of mechanical interlocking, intermolecular interactions ("physical bonding"), hydrogen bonds, intermixing of polymers, additives and possible specific interactions in the formation of strong bonds in sheet structures from HYP are discussed. A required condition for high bond strength in sheets from HYP furnishes is that fibre components are forced into sufficiently close contact. This is to a great extent impeded if the fibre walls are too stiff. Consequently, the current review focuses on both how fibre fractions should preferably be developed for different end uses and how suitable bonds might be achieved in different paper grades. The ideal type of bonds is certainly different depending on the demands on the final paper quality.

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  • 206.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sjöberg, Jessica
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Averheim, Andreas
    Luleå University of Technology.
    Increased joint-forming ability of ductile kraft pulp fibres by polyelectrolyte multilayer treatment-Influence of refining and drying strategies2007In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 2, p. 228-235Article in journal (Refereed)
    Abstract [en]

    In this study a sack paper furnish was used. It consisted of a high-consistency kraft pulp refined in either an atmospheric pressure or a pressurized system. The pulps were subsequently low-consistency refined in an Escher-Wyss laboratory refiner to 17.5-20.5 SR. Ordinary ISO sheets and freely dried sheets were manufactured from these pulp samples to serve as reference sheets. The laboratory sheets made of pulp from the pressurized system had a higher strain at break and tensile energy adsorption index but a lower tensile index than sheets made of pulp from a conventional atmospheric highconsistency refiner. These sheets were subject to a polyelectrolyte multilayer treatment to increase the interaction between the fibres, thus enhancing the paper strength properties. The polyelectrolyte multilayers (PEM) were applied by sequentially treating fibres from an unbleached kraft pulp for sack paper production with cationic starch and anionic carboxymethyl cellulose. The multilayer treatment was only applied to 50% of the stock and both ordinary ISO sheets and freely dried sheets were prepared with one and three layers of polyelectrolyte. Evaluation of the strength properties of the sheets showed that the addition of only one layer of starch increased strain at break, tensile index, tensile energy adsorption index, and out-of-plane properties measured as Scott-bond values. Using the multilayer technique created large increases in Scott-bond, a measure of the internal bonding of the sheets. The achieved effects were significantly larger than those usually achieved by applying starch alone to enhance the out-of plane strength properties. Also, the density increased considerably when the third layer was applied, for both ISO and freely dried sheets, though the tensile strength was enhanced significantly only in the freely dried sheets.

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  • 207. Provatas, N.
    et al.
    Uesaka, Tetsu
    Modelling paper structure and paper-press interactions2003In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 29, no 10, p. 332-340Article in journal (Refereed)
  • 208.
    Ragauskas, Arthur J.
    et al.
    Georgia Inst Technol, Sch Chem, Inst Paper Sci & Technol, Atlanta, GA 30332 USA.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Akzo Nobel Pulp & Performance Chem AB, Bohus, Sweden.
    Goyal, Gopal
    Corp Technol Ctr, Loveland, OH, USA.
    Editorial perspective on bleaching: Today and tomorrow2013In: TAPPI Journal, ISSN 0734-1415, Vol. 12, no 10, p. 5-6Article in journal (Other academic)
  • 209.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Aspects of optimizing pulp fibre properties for tissue and packaging materials2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To improve the competitive advantages of pulp fibre-based materials for tissue and packaging over fossil-based products, it is essential to increase knowledge of the selectivity of the cooking and the chemimechanical processes by optimizing the unit operations of impregnation, cooking and refining. A general goal in pulping processes is to achieve as efficient and even fibre separation as possible. A key to achieving this is to improve impregnation uniformity. In the case of chemical pulping, we need to study how a more even distribution of lignin at the fibre level via easily impregnated wood chips can be achieved using classic measures such as equalized hydroxide ion concentration, increased initial sulphide ion concentration, low sodium ion concentration and a low cooking temperature combined with an oxidative and reductive environment. In the case of chemithermomechanical pulp (CTMP) manufacturing, we need to achieve as even a degree of sulphonation as possible at the level of the individual fibres by means of improved sulphite ion distribution within the wood chips before they are pre-heated prior to entering the refiner. 

    Firstly, we have studied selective cooking systems for sulphate pulp manufacturing in oxidative (polysulfide) and reductive (sodium borohydride) environments. The yield increased from 48% to a maximum of 53%, which resulted in faster dewatering when mimicking a tissue papermaking process. This could explain how the advantage of the increased yield (fewer fibres and a more open sheet structure) outweighs the negative effects of the higher hemicellulose content on the dewatering properties. Moreover, the increased proportion of hemicellulose in the fibre walls resulted in improved bonding and increased tensile index at a certain refining energy. 

    Secondly, we have studied the uniformity of impregnation at the fibre level by developing an accurate way of measuring sulphur and sodium content in measuring points that are 5-10 µm in diameter with miniaturized X-ray-based technology. This technology is considered cheap and efficient enough to be introduced in industrial labs and/or in online equipment. Our newly built miniaturized energy dispersive X-ray fluorescence (ED-XRF) demonstrates the capability of imaging sulphur and possibly sodium distribution in wood chip fibres or individual fibres on a micro scale. 

    In parallel, to the above research we have studied a new catalytic lignin-selective cooking method where a substantial portion of the dissolved lignin can be extracted as vanillin, creating significant value and opportunities for new cost-efficient wood biorefinery systems. 

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  • 210.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modify or optimize the Kraft pulping process to produce more refining energy efficient fibers at the final functional product properties of Tissue Papers2015In: Cellulose Materials Doctoral Students Summer Conference 2015 / [ed] Hauhio, Leena, Aalto University, Finland, 2015Conference paper (Refereed)
  • 211.
    Rahman, Hafizur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    An, Siwen
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Persson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Measurement of S and Na distribution in impregnated wood chip by XRF2021In: TAPPICon Virtual 2021, TAPPI Press, 2021, p. 547-553Conference paper (Refereed)
    Abstract [en]

    As there are increasing demands to replace plastics especially as packaging material with renewable, easy to recycle and compostable materials as those produced by paper industry, there is an increasing demand also to improve the fundamental scientific understanding of pulp and paper manufacturing systems. High yield pulping (HYP) processes, such as CTMP, are increasingly interesting for packaging material as well as manufacturing of hygiene paper. The yield from wood chips to final fiber is about 90%-98% and due to that, the lignin (28% of coniferous wood) plays a key role when designing properties of packing materials. A key unit operation when producing CTMP is the pre-treatment of wood chips before defibration. In order to separate the wood to individual fibers with a minimum amount of electricity it is necessary to soften the lignin. The lignin is softened by means of a combination of sulphonation at high pH and elevated temperatures in the preheater and in the refiner, where the fiber separation occurs. As the size of wood chips is normally about 20 mm in length, 3-4 mm in thickness at the same time the fiber size is 20-40 μm in width with 1.5-5 mm in length, it is challenging to create a process technology that gives an even distribution across the wood chips of the sodium sulphite (Na2SO3) containing liquid used for impregnation. In order to improve the impregnation technology, it is valuable to measure the sulphonation degree on a detailed level. Our XRF imaging system using a collimated X-Ray source and an energy-dispersive X-Ray spectroscopy can make an image of sulphur (S) and sodium (Na) across wood chips or in individual fibers. 

  • 212.
    Rahman, Hafizur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    An, Siwen
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. Lund University.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Persson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Zeeshan, Faisal
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Granfeldt, T.
    Slavicek, Tomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. Czech Technical University.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    On-Site X-ray Fluorescence Spectrometry Measurement Strategy for Assessing the Sulfonation to Improve Chemimechanical Pulping Processes2022In: ACS Omega, E-ISSN 2470-1343, Vol. 7, no 51, p. 48555-48563Article in journal (Refereed)
    Abstract [en]

    Minimizing the fiber property distribution would have the potential to improve the pulp properties and the process efficiency of chemimechanical pulp. To achieve this, it is essential to improve the level of knowledge of how evenly distributed the sulfonate concentration is between the individual chemimechanical pulp fibers. Due to the variation in quality between pulpwood and sawmill chips, as well as the on-chip screening method, it is difficult to develop an impregnation system that ensures the even distribution of sodium sulfite (Na2SO3) impregnation liquid. It is, therefore, crucial to measure the distribution of sulfonate groups within wood chips and fibers on a microscale. Typically, the degree of unevenness, i.e., the amount of fiber sulfonation and softening prior to defibration, is unknown on a microlevel due to excessively robust or complex processing methods. The degree of sulfonation at the fiber level can be determined by measuring the distribution of elemental sulfur and counterions of sulfonate groups, such as sodium or calcium. A miniaturized energy-dispersive X-ray fluorescence (ED-XRF) method has been developed to address this issue, enabling the analysis of sulfur distributions. It is effective enough to be applied to industrial laboratories for further development, i.e., improved image resolution and measurement time. 

  • 213.
    Reyier, Sofia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Bonding Ability Distribution of Fibers in Mechanical Pulp Furnishes2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a method of measuring the distribution of fiber bonding ability in mechanical pulp furnishes. The method is intended for industrial use, where today only average values are used to describe fiber bonding ability, despite the differences in morphology of the fibers entering the mill. Fiber bonding ability in this paper refers to the mechanical fiber’s flexibility and ability to form large contact areas to other fibers, characteristics required for good paper surfaces and strength.

     

    Five mechanical pulps (Pulps A-E), all produced in different processes from Norway spruce (Picea Abies) were fractionated in hydrocyclones with respect to the fiber bonding ability. Five streams were formed from the hydrocyclone fractionation, Streams 1-5. Each stream plus the feed (Stream 0) was fractionated according to fiber length in a Bauer McNett classifier to compare the fibers at equal fiber lengths (Bauer McNett screens 16, 30, 50, and 100 mesh were used).

     

    Stream 1 was found to have the highest fiber bonding ability, evaluated as tensile strength and apparent density of long fiber laboratory sheets. External fibrillation and collapse resistance index measured in FiberLabTM, an optical measurement device, also showed this result. Stream 5 was found to have the lowest fiber bonding ability, with a consecutively falling scale between Stream 1 and Stream 5. The results from acoustic emission measurements and cross-sectional scanning electron microscopy analysis concluded the same pattern. The amount of fibers in each hydrocyclone stream was also regarded as a measure of the fibers’ bonding ability in each pulp.

     

    The equation for predicted Bonding Indicator (BIN) was calculated by combining, through linear regression, the collapse resistance index and external fibrillation of the P16/R30 fractions for Pulps A and B. Predicted Bonding Indicator was found to correlate well with measured tensile strength. The BIN-equation was then applied also to the data for Pulps C-E, P16/R30, and Pulp A-E, P30/R50, and predicted Bonding Indicator showed good correlations with tensile strength also for these fibers.

     

    From the fiber raw data measured by the FiberLabTM instrument, the BIN-equation was used for each individual fiber. This made it possible to calculate a BIN-distribution of the fibers, that is, a distribution of fiber bonding ability.

     

    The thesis also shows how the BIN-distributions of fibers can be derived from FiberLabTM measurements of the entire pulp without mechanically separating the fibers by length first, for example in a Bauer McNett classifier. This is of great importance, as the method is intended for industrial use, and possibly as an online-method. Hopefully, the BIN-method will become a useful tool for process evaluations and optimizations in the future.

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  • 214.
    Reyier, Sofia
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Ferritsius, Olof
    BIN - a method of measuring the distribution of Bonding Indicator of fibers in mechanical pulp furnishesManuscript (Other academic)
  • 215.
    Reyier, Sofia
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Ferritsius, Olof
    Shagaev, Oleg
    Measuring the bonding ability distribution of fibers in mechanical pulps2008In: TAPPI Journal, ISSN 0734-1415, Vol. 7, no 12, p. 26-32Article in journal (Refereed)
    Abstract [en]

    Currently, the pulp and paper industry mainly uses average values of   mechanical pulp properties to characterize fibers, while printing paper   grammages keep decreasing, making every fiber more important for   strength, surface, and structure properties. Because fibers are   inhomogeneous, average values of the whole pulp may not be enough for   proper fiber characterization. This paper reports results from the   development of a method to measure the distribution of fiber bonding   ability in mechanical pulps.   Fibers from two commercial TMPs were fractionated into five   hydrocyclone streams, using a four-stage hydrocyclone system. The fiber   bonding ability of Bauer McNett fractions R16, P16/R30 and P30/R50   collected from each stream was analyzed. Five different methods of   evaluating fiber bonding ability all showed that fibers were separated   in the hydrocyclones according to their bonding ability.   Long fiber handsheets of the highest bonding fibers had up to 2.5 times   higher tensile strength for the P16/1330 fraction than handsheets from   the lowest bonding fibers. We also found that both the degree of   fibrillation and collapse resistance index (CRI) of the fibers obtained   from optical measurements are sufficient to predict quite accurately   the tensile strength of handsheets made from fiber fractions. Further,   we propose how to describe the distribution in fiber bonding ability   for mechanical pulps, by combining some of these five different   methods. A method to calculate fracture toughness of long fiber   handsheets based on acoustic emission is also illustrated.   A more rapid way to characterize fibers in mechanical pulps with   respect to their bonding ability distribution needs to be developed in   the future. It appears that it is time to move on from characterizing   pulp suspensions and handsheet properties using conventional approaches   based on average values.

  • 216.
    Reza, Salim
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thim, Jan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Non-Destructive Method to Resolve the Core and the Coating on Paperboard by Spectroscopic X-ray Imaging2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 3, p. 439-442Article in journal (Refereed)
    Abstract [en]

    Quality control is an important issue in the paperboard industry. A typical sheet of paperboard contains a core of cellulose fibers [C6H10O5], coated on one or both sides with layers of calcium carbonate [CaCO3] or Kaolin [Al2Si2O5(OH)4]. One of the major properties of a good quality paperboard is the consistency of the expected ratio between the thickness of the core and the coating layers. A measurement system to obtain this ratio could assist the paperboard industry to monitor the quality of their products in an automatic manner. In this work, the thicknesses of the core and the coating layers on a paperboard with coating layer on only one side were measured using an X-ray imaging technique. However, the limited spectral and spatial resolution offered by the measurement system being used led to the measured thicknesses of the layers being lower than their actual thicknesses in the paperboard sample. Suggestions have been made in relation to overcoming these limitations and to enhance the performance of the method. A Monte Carlo N-particle code simulation has been used in order to verify the suggested method.

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  • 217.
    Reza, Salim
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Pelzer, Georg
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Weber, Thomas
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bayer, Florian
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Anton, Gisela
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Rieger, Jens
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Thim, Jan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Michel, Thilo
    University of Erlangen-Nuremberg, ECAP-Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany .
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Investigation on the directional dark-field signals from paperboards using a grating interferometer2014In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 9, p. Art. no. C04032-Article in journal (Refereed)
    Abstract [en]

    Recent advancements in the grating interferometer based Phase Contrast X-ray Imag- ing (PCXI) technique enables high quality dark-field images to be obtained using conventional X-ray tubes. The dark-field images map the scattering inhomogeneities inside objects. Since, the dark-field image is constructed by considering only those photons which are scattered while pass- ing through the objects, it can reveal useful information about the object inner structures, such as, the fibre structures inside paperboards.

    The end-use performance of paperboards, such as the printing quality and the stiffness de-pends on the uniformity in the thickness and the structures of the coating layer of the paperboards. The uniformity in the coating layer is determined by the coating techniques, the coating materials and the topography of the base sheet. In this article, the dark-field signals from four paperboard samples with different quality indices are analysed. The isotropic and the anisotropic scattering coefficients for all of the samples have been calculated. Based on the correlation between the isotropic coefficients and the quality indices of the paperboards, a new method for paperboard quality measurement has been suggested.

  • 218.
    Rezasson, Reza
    et al.
    Högskolan i Gävle.
    Zhou, Tunhe
    Stockholms Universitet.
    Burvall, Anna
    KTH.
    Lindgren, Johan
    Holmen Iggesund.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Hertz, Hans M.
    KTH.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    A fast and non-destructive alternative to the burnout method for paperboard quality inspections using phase-contrast X-ray imaging2023In: TAPPI Journal, ISSN 0734-1415, Vol. 22, no 2, p. 99-106Article in journal (Refereed)
    Abstract [en]

    An X-ray based quality inspection method for paperboard was implemented and tested as a fast and non-destructive alternative to the burnout method. An argument against X-ray imaging for inspection of paper and paperboard has been that X-ray absorption is low in paper. To overcome this limitation, we used phase-contrast X-ray imaging (PCXI), which gives higher contrast than conventional attenuation-based imaging for low-absorbing materials such as paper. The suggested PCXI method was applied to previously prepared and quality rated samples using the burnout method. A strong similarity between the burnout images and the PCXI images was observed. In conclusion, further development of the phase-contrast X-ray method would provide an interesting option for replacing or complementing the standard burnout method.

  • 219.
    Rubiano Berna, Jorge Enrique
    et al.
    University of British Columbia, Vancouver, Canada.
    Sandberg, Christer
    Holmen Paper AB, Bravikens pappersbruk, Norrköping, Sweden.
    Martinez, D. Mark
    University of British Columbia, Vancouver, Canada.
    Olson, James A.
    University of British Columbia, Vancouver, Canada.
    Theoretical Study of Systems Composed of Low Consistency Refining and Pressure Screening2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    The main objective of this work is to study the LC rening of mechanical pulps from system-design point of view. Mathematical models that describe bre length distribution changes were used to develop aframework capable of simulating LC rening { pressure screening systems. Specically, pressure screening models and comminution models for LC rening that are available in literature together with heuristic and a developed correlation to predict rening power were implemented in MATLAB Simulink toolbox.Later on, this same environment was used to simulate three basic rening systems found in TMP mills. In this study, each considered system was composed of a single rener and single pressure screen arranged in dierent congurations. Performance curves of length-weighed mean bre length were generated from simulation results andused to assess each system behaviour in terms of rener gap, reject ratio and rener power. The impact of some design aspects such as rener size, recirculation and reject ratio were also described. Furthermore,comparisons between systems and some basic recommendations and suggested applications are made. This theoretical framework was compared to industrial-scale data from a TMP mill sub-system. Simulation results showed good agreement with real data, where relative errors between 6-18% on the predicted variables were observed.

  • 220. Salmi, Ari
    et al.
    Salminen, Lauri I.
    Montonen, Risto
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Björkqvist, Tomas
    Haeggström, E.
    Lucander, Mikael
    Cyclic impacting of wood results in localized fatigue2011In: Proceedings of International Mechanical Pulping Conference 2011 (Xi'an, China 2011), 2011Conference paper (Other academic)
  • 221. Salminen, Lauri
    et al.
    Salmi, Ari
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Björkqvist, Tomas
    Haeggström, Edward
    Lucander, Mikael
    Cyclic loading and fatigue of wood2011In: Progress in Paper Physics Seminar2011: Conference Proceedings / [ed] U. Hirn, 2011, p. 243-245Conference paper (Other academic)
  • 222.
    Samuelsson, Tove
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. MoRe Research Örnsköldsvik AB.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Svedberg, Anna
    MoRe Research Örnsköldsvik AB.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Development of strong and water resistant packaging materials from high yield pulps – fundamental aspects2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    This work is focused on fundamental aspects of the densification of paper sheets during hot-pressing under conditions where the lignin in the fibre walls is softened. In this study light microscope and scanning electron microscope (SEM) techniques were used to reveal the mechanisms in the fibre network structure within the paper sheets that arises due to densification and the impact of lignin. UV and staining methods and spectrometric observations of the ultrastructure of cross section of paper sheets and fibre surfaces will highlight the changes that occur in the fibre structures. This study improves the understanding of how fibres collapse and how internal fibre-fibre bonds in lignin-rich mechanical pulp affect the physical properties of the final paper sheet. To demonstrate this, paper sheets from five different pulps containing different concentration of natural lignin were produced. Handsheets of 150 g/m2 were prepared in a Rapid Köthen (RK) laboratory sheet former, where the sheets were press-dried at 100 kPa and ca 90oC to a dry content of 45-50% d.c. After 24 hours in room temperature the hand sheets were hot-pressed in a temperature interval from 20 – 200oC at a constant pressure in a cylinder-press at a speed of 1 m/min. The results show that remarkable improvements on paper sheets, based lignin-rich pulps, can be achieved in terms of increased tensile index (up to 85 kNm/kg), compression strength, SCT, (up to 38 kNm/kg) and wet strength (up to 10 kNm/kg), which depends on the densification of the fibre structure at high temperature and pressure in the load nip. It is concluded that this to a major extent is related to that the lignin rich fibres are compressed at high enough temperature to both softened and develop tacky surfaces so that the fibres are locked into their positions within the highly densified sheets. The SEM evaluation shows how the surface structure get dense at pressing at 200oC for the CTMP based paper sheets. The light microscopy studies of the sheet cross sections reveal how the fibres collapse in the case of CTMP based sheets while fibres from bleached kraft pulp based sheets are quite well collapsed already at room temperature.

  • 223.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen paper.
    Fibre development in an intensified mechanical pulping process2021In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 75, no 9, p. 824-837, article id 0242Article in journal (Refereed)
    Abstract [en]

    Mechanical pulp for printing paper can be produced with a process that involve much less equipment and that require much lower specific energy compared to conventional processes. Even though common evaluation methods, e.g. handsheet testing, have shown that the pulp quality is similar for the simplified and the conventional processes, it is not known how fibre properties, at the microscopic level, is developed with the simplified process. In this mill scale study, the fibre properties attained with an "intensified"mechanical pulping process, consisting of single stage high consistency double disc refining followed by two stage low consistency refining and no reject treatment was investigated. The simplified process was compared to a process with a reject system. The simplified process rendered fibres with higher degree of fibrillation, higher share of axial splits, lower fibre wall thickness but slightly lower length than the conventional process. The fibrillar fines size distribution of the two processes was different. The conventional process generated more of small fibrillar fines which probably explains the higher tensile index at given density for that process. The results show that it is possible to simplify the production process for mechanical pulp and reduce the specific energy with over 700 kWh/adt.

  • 224.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Process intensification in mechanical pulping: Reduced process complexity and improved energy efficiency2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work shows that, for newsprint quality grades, the production processes for mechanical pulp can be simplified, and the specific electrical energy demand can be reduced with around 600 kWh/ton (30%). The purpose of the work is to demonstrate how the production cost for mechanical pulps can be decreased through increased energy efficiency and reduced number of unit operations. The idea was to improve the main line refining conditions so that no additional fibre development or shive reduction is needed and thereby, the normal screening and rejects treatment system could be omitted.

    Mechanical pulp is used to produce a variety of products, where the two largest categories are printing papers and paperboard for packaging. The pulp is mainly produced by the breakdown of wood chips between rotating metal discs in machines called refiners with the product and process generally referred to as thermomechanical pulp(ing) (TMP). The refiner process requires high specific electrical energy to separate and develop the fibres to a pulp intended for the production of printing papers. Today, many processes need over 2000 kWh/ton of refining energy plus 200-300 kWh/ton of auxiliary energy (to drive pumps, agitators, screw conveyors, screens, presses, etc.).

    During the last two decades of the 20th century, the chemical processing industry underwent a transformation. The process development changed from being unit operation focused to function focused. The result is more compact processes with less equipment, higher yield and lower energy demand. When the development is made in an innovative way with such large effects on process performance, it is referred to as process intensification. My work is inspired by the concepts of process intensification, especially the striving for more compact processes with higher efficiency. 

    This work is focused on mechanical pulp, intended for the manufacture of printing paper, produced in refiners with Norway spruce (Picea abies) as raw material. However, this approach could also be applied to mechanical pulp production in integrated paperboard mills and also using other raw materials e.g., pines or hardwoods. The investigated pulps and processes in this work are mainly intended for uncoated paper grades (newsprint, improved newsprint and book paper) printed by the offset printing process. In all studies, the pulps have been produced with full scale mill equipment and evaluated using laboratory measurements. However, in two studies, the produced pulps were evaluated on paper machines and at printing houses.

    A large number of process concepts have been evaluated in which different approaches have been used to reduce the specific energy and, in some cases, improve pulp quality. The approaches include:

    1.     Impressafiner chip pretreatment 

    2.     Primary high consistency (HC) refiner type (DD, RTS, CD, SD)

    3.     Addition of low doses of sodium sulphite 

    4.     Increased refining temperature (housing pressure)

    5.     Refiner segments and centre plate design

    6.     Increased production rate

    7.     Low consistency (LC) refining in different process positions and in combination with different HC refiner types

    The separate effects of all these techniques have not been evaluated systematically neither have potential synergistic effects of all possible combinations been investigated. Even though a large number of combinations of unit operations have been studied, the emphasis has been on trying to do as much fibre development as possible in a single HC refining stage.

    The mill trials with spruce as raw material have shown that a low shive content and appropriate fibre development can be attained in a process without separate treatment of long fibres. High intensity primary stage refining (RTS and DD) was necessary to reach a low shive content at a low specific refining energy (SRE), with DD refiners appearing to be the most suitable for simplified processes. DD and RTS refining produced pulps with fibres exhibiting a higher degree of external fibrillation and share of split fibres than SD refining. DD refining produced fibres with lower cell wall thickness and higher light scattering at given fibre length than RTS refining. The lowest specific refining energy was attained for one of the trials using the process, denoted as S:HT:DD-LC-LC, consisting of DD refining at increased production rate, 18 adt/h, increased housing pressure, 6.6 bar(g), and with 5 kg/adt sodium sulphite added to the chips immediately  before the refiner. After DD refining the pulp was refined in two LC refining stages. This process required only 1280 kWh/adt SRE to reach a tensile index of 52 Nm/g (Rapid-Köthen). This is 900 kWh/adt lower than the final pulp for newsprint based on SD HC refining, and over 500 kWh/adt lower than Scandinavian BAT processes (2014). Additionally, the auxiliary energy was around 150 kWh/adt lower for the processes without a conventional rejects treatment system. At 52 Nm/g tensile index, the light scattering coefficient was 2-3 m2/kg higher, and the length-weighted average fibre length was around 0.1 mm lower for this process than for SD TMP final pulp. The fibre bonding, indicated by density, tensile index and Z-strength of fibre fraction handsheets, was similar or higher for the S:HT:DD-LC-LC process than the reference SD TMP process with a rejects treatment system. 

    Other interesting process configurations, with somewhat lower efficiencies, included:

    1.     Impressafiner pretreatment of the chips with sodium sulphite before DD refining, with or without subsequent LC refining. Chip pretreatment with the Impressafiner enabled operating the DD refiner at higher intensity (feeding segments and increased production rate) without significant loss of quality and LC refining enabled increased production rate which increased the overall efficiency.

    2.     RTS-SD refining with sodium sulphite added before the second stage SD refiner referred to as RTS-S:SD. The pulp from the RTS-S:SD process had similar fibre length as the S:HT:DD-LC-LC process but lower light scattering coefficient.

    3.     A single-stage DD refiner operating at 15.5 adt/h and 4 bar(g) housing pressure (no sodium sulphite addition), which produced pulp with lower fibre length but higher light scattering coefficient than the S:HT:DD-LC-LC process. 

    Two simplified processes were evaluated on paper machines and in printing houses. The first, denoted DD-LC-F, involved a combination of DD primary refining followed by LC refining and fractionation (screening). The screen rejects were mixed with the main line DD pulp before the LC refiner. The second process was the CPT:S-DD-LC process (№1 above). Good runnability was attained both on the paper machines and in the offset printing presses and the paper quality was similar to the reference paper.

    For printing paper applications, the proportion of fibre development in LC refining should preferably be relatively low, since it was shown that LC refiners have limited capacity to reduce fibre wall thickness and thereby develop light scattering and fibre fraction Z-strength.

    Explicit effects on the number of unit operations and production cost have not been evaluated in this work, but clearly both investment and variable costs as well as fixed costs can be reduced with a simplified process.

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  • 225.
    Sandberg, Christer
    et al.
    Holmen Paper AB.
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    LC refining combined with screen fractionation – Reduction of system complexity for mechanical pulping2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    Process intensification - a process development method used in the chemical process industry has been appliedto mechanical pulping process design. Process intensification is characterized by significant reduction of energyconsumption and process complexity.A process with single stage high consistency (HC) refining followed by low consistency (LC) refining andscreening was evaluated in mill trials at the Holmen Paper Braviken mill, Sweden. After LC refining, pulp wasscreened and the reject was fed back to LC refining. The process is called HC-LC-S. Two different HC primaryrefiner types were evaluated – single disc (SD) and double disc (DD).High intensity DD chip refining was more suitable than single disc refining for the process due to higher lightscattering and lower shives content of the final pulp. It was also easier to reach high enough tensile index beforeLC refining with the DD refining. The DD-LC-S process required 1940 kWh/adt total specific energy for newsgrade TMP, which was 300 kWh/adt lower than the reference TMP line; DD chip refining and HC rejectrefining. The auxiliary specific energy was reduced with 100 kWh/adt.Six unit operations and three chests with agitators and pumps were omitted compared to a conventional TMPline.

  • 226.
    Sandberg, Christer
    et al.
    Holmen Paper AB, Norrköping.
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Process intensification in mechanical pulping2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 4, p. 615-622Article in journal (Refereed)
    Abstract [en]

    Process intensification is a term used in the chemical process industry for major improvements in the process design leading to radical changes in process complexity, equipment size and efficiency. We suggest that a similar approach is applied in the pulp and paper industry. We have focused on the production of mechanical pulp, but a similar approach can be applied to other areas within the pulp and paper industry. Inspired by process intensification methodology, we suggest five principles for development of the mechanical pulping process. Three fundamental principles; 1. Break up the wood and fibre wall structure in the right positions. 2. Give each fibre, of certain morphology, the same processing experience. 3. Optimize the applied mechanical forces and the physiochemical state of the wood and fibre material.  and two system oriented principles; 1. Select wood raw material based on final product specifications. 2. Design the process to facilitate observability, controllability and maintenance. Implications of these principles on process design and future challenges for mechanical pulping are discussed.

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  • 227.
    Sandberg, Christer
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. StoraEnso.
    Energy efficiency in mechanical pulping2017Conference paper (Refereed)
  • 228.
    Sandberg, Christer
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen paper.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso.
    Energy efficiency in mechanical pulping-definitions and considerations2021In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, no 3, p. 425-434, article id 0013Article in journal (Refereed)
    Abstract [en]

    Production of mechanical pulps requires high specific electrical energy compared to many other attrition processes. In Scandinavia, the lowest specific refining energy for production of thermomechanical pulp is around 1800 kWh/t for newsprint quality, which is roughly 60 times higher than for crushing of stone to a similar size distribution. The high specific energy demand for refining has naturally motivated large efforts in the search for improved efficiency. It is always practical to be able to quantify improvements in efficiency for comparison of process designs and of different machine types. However, there is no commonly accepted definition of efficiency for mechanical pulping processes. In published work within mechanical pulping, energy efficiency has been presented in different ways. In this paper, we discuss definitions of energy efficiency and aspects that ought to be considered when energy efficiency is presented. Although focus of this work is on energy efficiency for refiner processes, the principles can be applied to other types of mechanical pulping processes such as stone groundwood. 

  • 229.
    Sandberg, Christer
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper, Norrköping.
    Hill, Jan
    QualTech, Tyringe.
    Jackson, Michael
    Michael Jackson Consulting Inc., Vancouver, Canada.
    On the development of the refiner mechanical pulping process - A review2020In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 35, no 1Article in journal (Refereed)
    Abstract [en]

    This paper is a review of the development of the mechanical pulping process with focus on refiner-based processes. The intention is to provide an overview of the trends and the major advances in the development of the mechanical pulping (MP) process. The focus is on the development of the entire MP process, rather than the refiner as such. However, when discussing the MP process development, it is inevitable to consider the development of the refiner unit operation briefly. Processes for printing papers based on softwood is mainly discussed, but board processes are discussed briefly as well. 

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  • 230. Shigetani, Tsunehisa
    et al.
    Yamana, Takao
    Kamiya, Masahiro
    Uesaka, Tetsu
    Support sheet for photographic paper1990Patent (Other (popular science, discussion, etc.))
  • 231.
    Sikter, David
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Quality Control of a Newsprint TMP Refining Process based on Rifining Zone Temperature Measurements2007Licentiate thesis, comprehensive summary (Other academic)
  • 232.
    Sikter, David
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Karlström, Anders
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Czmaidalka, Josef
    Using the refining zone temperature profile for quality control2007In: International Mechanical Pulping Conference 2007, TAPPI, Atlanta, GA: TAPPI Press, 2007, Vol. 2, p. 894-902Conference paper (Refereed)
    Abstract [en]

    ABSTRACT To achieve good quality control in TMP refining, relevant information about the process is needed. In this paper, the refining zone temperature profile has been studied to investigate if this information can be used to stabilize the pulp quality. The studied system is a commercial RTS primary refiner at Hallsta Paper mill. The response of the temperature profile was examined and compared with the pulp quality disturbances after both the first and second stage. The disturbances in the radial position of the temperature peak were found to be strongly correlated with the disturbances in freeness and mean fiber length. Based on these results, a new control strategy was designed to keep the peak position constant by changing the inlet pressure. This new control strategy decreased the freeness disturbances compared to the mill�s normal strategy, and analysis suggests that the disturbances could be further reduced by including also the maximum temperature in the control concept. The potential of improvement in terms of reduced standard deviation of CSF was estimated to 11% or more. The comparison indicates that temperature parameters are better than the commonly used specific energy when it comes to predicting and reducing these quality disturbances.

  • 233.
    Sikter, David
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Karlström, Anders
    Sandberg, Christer
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Economic perspectives on quality control in TMP refining processes2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 3, p. 305-314Article in journal (Refereed)
    Abstract [en]

    Many Studies have been carried out with the goal of improving pulp quality control in TMP refining processes. While it is intuitively clear that minimizing the deviations from the target quality is desirable, the economic value Of Such reduced quality variations is complicated to estimate. So far not much research has been done in this area related to the pulp and paper industry. This Study has been performed to address this issue and to increase the knowledge, in economic terms, of the different mechanisms involved. The focus lies in controlling the pulp quality stability of the refining stage. Several areas in which economic benefits arise from improved quality control are analyzed in more detail. A generic model for estimating the economic Value of improved quality optimization is developed. Applied to freeness variability reduction, the model indicates notable economic savings, partly in terms of energy. The connection between pulp quality variations and web-breaks in the paper machine has been Studied in a full scale trial. The results indicate that a reduction of web breaks may yield a significant contribution to the profit. Improving the quality control may also enable a production rate increase. In this case there are some energy savings due to improved refiner efficiency at higher throughput. The major economic profit contribution from production increase does however come from the additional Volume of paper.

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  • 234.
    Sjöberg, Jessica C
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Häggquist, M
    Wikström, M
    Lindström, T
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Effects of pressurised high consistency refining on sheet density2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 1, p. 39-45Article in journal (Refereed)
    Abstract [en]

    This study investigates the possibility of decreasing the sheet density of paper made from unbleached kraft pulp for the middle layer in board production. The objective was to evaluate how treatments in a compressive screw equipment pressure expansion (PREX) plug screw feeder, atmospheric (HCatm) and pressurised high-consistency refining (HCpress refining) affect both fibre and paper properties and, in particular, how fibre curl affects sheet density.The plug screw pre-treatments and HC refining were performed under atmospheric and steam-pressurised conditions at 100 degrees C, 125 degrees C and 175 degrees C. Even though fibre curl increased considerably during plug screw treatment and HCatm and HCpress refining, the density of the paper sheets did not decrease, as had been expected. A possible explanation for this result may be that the fibres become more flexible during curl treatment, resulting in increased sheet density.In order to obtain fibres that were both very curly and stiff, three ways of improving the fibre stiffness were tested: 1) lowering the pH during refining, 2) drying the fibres (hornification) and 3) treating the fibres with 1,2,3,4-ButaneTetraCarboxylic Acid (BTCA). If the fibres are dried (hornified), there is a lowering effect on sheet density. However, fibre curl does not have any lowering effect on sheet density. If the pH is decreased during plug screw treatment, the sheet density may be reduced but, again, the fibre curl does not have any positive effect on sheet density. Fibres treated with BTCA had a marked lowering effect on sheet density. With this treatment, the fibre curl does have a positive effect on sheet density. The BTCA-treated fibres were also used to lower sheet density. A mixture of 15% by weight BTCA- treated fibres resulted in an approximately 9% density reduction.

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  • 235.
    Sjöberg, Jessica
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Refining system for sack paper pulp: Part I HC refining under pressurised conditions and subsequent LC refining2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 3, p. 320-328Article in journal (Refereed)
    Abstract [en]

    Unbleached kraft pulp for sack paper is usually refined in a high consistency process followed by low consistency refining in order to achieve the desired paper properties, such as a high strain at break and high tensile energy absorption at low airflow resistance. In this study, conventional atmospheric high consistency refining is compared to pressurised high consistency refining after preheating to 125C and 175C. After high the consistency refining stage, the pulp samples were refined in a low consistency process in a laboratory Escher-Wyss refiner. The results show that the highest levels of tensile energy absorption and strain at break were achieved with curled and kinked fibres refined in a pressurised refiner at 175C at a relatively low refining energy input, before the low consistency refining stage. These results were obtained at low airflow resistance, which is advantageous for sack paper. The disadvantage of the pressurised high consistency refining process is a loss in tensile strength. Paper properties were evaluated on freely dried as well as ISO sheets.

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  • 236. Solberg, D.
    et al.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    On the mechanism of GCC filler particle retention during dewatering - New techniques and initial findings2000Conference paper (Refereed)
    Abstract [en]

    The main objective of this present investigation was to clarify the mechanism of ground calcium carbonate (GCC) retention during dewatering through a thick pad of pulp fibers. It has earlier been claimed that mechanical filtration of aggregated filler particles during dewatering and the deposition of filler particles onto the fiber surface prior to dewatering, are the main filler retention mechanisms. In the present study, the effect of filtration was studied by examining the filler particle size distribution before and after filtration of a filler suspension through a thick pad of pulp fibers. Changes in the wet-web pore size distribution in beds with and without filler were measured by liquid porosimetry. The filler distribution through the bed was obtained from SEM micrographs. The results indicate that deposition on fibers is the dominant process for the retention of commercial GCC particles with a mean particle size of 0,6 and 0,8 μm. Only a marginal fraction of these particles are retained by filtration even though the experimental conditions (laminar flow and a very high grammage) were chosen to favour such process. These results are valid for well-dispersed, non-flocculated GCC particles.

  • 237.
    Sund, Johan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen paper.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen paper.
    Karlström, Anders
    Chalmers.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The effect of process design on refiner pulp quality control performance2021In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, no 4, p. 594-607Article in journal (Refereed)
    Abstract [en]

    In this study, the effect of process- and online analyser configuration on pulp quality control is explored. The following parameters were included: analyser sampling interval, time delay, measurement error magnitude, and latency chest residence time. Using different values of parameters in a process model, a range of configurations were constructed. For each configuration, the achievable control performance was evaluated using an optimization approach. PI controller settings were chosen based on minimization of the integrated absolute error (IAE) in pulp quality after an input step disturbance. The results show that reducing the sampling interval improves performance also when the interval is smaller than the chest residence time or the analyser delay. Moreover, reducing the chest residence time can reduce the IAE by up to 40 %. However, reducing the residence time to lower than 1/3 of the sampling interval does not improve performance. Further improvement is possible if the analyser delay is reduced. The compromise between reducing the IAE and avoiding creating variation by acting on measurement error has a strong influence on the results. In conclusion, pulp quality control performance can be improved significantly by making changes to the studied configuration parameters. 

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  • 238.
    Thim, Jan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Simulating the Impact of Topographical Microstructures on Triangulation Measurement Setups using Matlab2008In: Proceedings of Nordic MATLAB User Conference, 2008Conference paper (Refereed)
    Abstract [en]

    The paper manufacturing industry is currently exploring the possibility of measuring micro structural topography online in a paper manufacturing machine, which is intended to lead to a more precise measure of the paper quality reel to reel and a more efficient use of raw material. This paper presents a Matlab simulation model that can be used to configure such measurement readout systems, and includes a demonstration of the model in use. The model will also be used for research purposes in order to assist in gaining a better understanding of both the limitations and possibilities of such measurement systems. In this regard the angular shading of microstructures and Centre of Gravity (CoG) functions are included in the attributes that require further exploration.

     

  • 239.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Complex matters: Things that matter2015Conference paper (Refereed)
  • 240. Uesaka, Tetsu
    DIMENSIONAL STABILITY OF PAPER - UPGRADING PAPER PERFORMANCE IN END USE1991In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 17, no 2, p. J39-J46Article in journal (Refereed)
  • 241.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Mechanics and Physics of Wet Fibre Network2011In: Fundamental and Applied Pulp and Paper Modelling Symposium / [ed] R.Gaudreault, 2011Conference paper (Other academic)
  • 242.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Page'S Theory Of Tensile Strength And The Stress-Strain Properties Of Paper2018In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 6, no 6, p. 13-17Article in journal (Refereed)
    Abstract [en]

    One of the most well-known theories in the area of paper is probably Page's theory of tensile strength. The article was published in Tappi Journal in 1969 [1], and written, in a very articulate way, to explain how tensile strength is determined by fibre properties and inter-fibre bond properties. Because this is the area of great interest to papermakers and pulp manufacturers, the theory has attracted great attention since then. In particular, many paper chemists were fascinated by this intuitive way of describing the relationships between bond and fibre parameters so that the theory became a theoretical foundation for many investigations of dry/wet strength agents. Interestingly, Derek himself was not completely happy with the popularity of the theory. As he noted in his paper, it is a semi-empirical theory, intended to provide a picture of the essential factors affecting tensile strength, but not as an analytical equation to predict some of the model parameters. (We will briefly touch upon Derek's concerns later.) In the late 70s, Derek and his colleague, Raj Seth, another legendary scientist from Pulp and Paper Research Institute of Canada (PAPRICAN, currently, FPlnnovations), launched investigations of the tensile stress-strain curves of paper [2,3,4]. The work depicted complex interplays among network structures, fibre properties and inter-fibre bond properties, again, in a very articulate way. This paper has also influenced a number of studies by younger researchers in the areas of paper mechanics and network mechanics. In this short article, I will try to describe how Derek tackled the problem of understanding the tensile properties of paper in the simplest and most articulate way. Based on this review, I will comment on how far we have gone from his ideas, and try to define some outstanding questions.

  • 243.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Particle-level Simulation in Paper Science2009In: Hannu Paulapuro Symposium, Helsinki, Finland: KCL , 2009, p. 54-60Conference paper (Other academic)
  • 244.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Performance-based Design of Corrugated Board and Box2013Conference paper (Other academic)
    Abstract [en]

    Currently corrugated box and board are designed and manufactured according to the strength specs, such as BCT, SCCT, RCT and SCT. As the market moves toward greener packaging (less-waste, less-cost, and less carbon footprint), the box and board manufacturers are trying to meet both these demands and the strength specs. However, the task is becoming increasingly difficult, because this subject is not new and the industry in fact has already worked on it for decades. The basic question today is what else we can do to improve/maintain strength with reduced weight (and reduced cost).

  • 245.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Variability, non-uniformity, and complexity: From product to process2013In: Advances in pulp and paper research, Cambridge 2013, Bury, UK: Pulp and Paper Fundamental Research Society , 2013Conference paper (Refereed)
    Download full text (pdf)
    Variability Complexity FRS 2013
  • 246. Uesaka, Tetsu
    et al.
    Murakami, Koji
    Imamura, Rikizou
    BIAXIAL TENSILE BEHAVIOR OF PAPER1979In: TAPPI Journal, ISSN 0734-1415, Vol. 62, no 8, p. 111-114Article in journal (Refereed)
  • 247. Uusi-Tarkka, E. -K
    et al.
    Levanič, J.
    Heräjärvi, H.
    Kadi, N.
    Skrifvars, M.
    Haapala, Antti
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    All-Cellulose Composite Laminates Made from Wood-Based Textiles: Effects of Process Conditions and the Addition of TEMPO-Oxidized Nanocellulose2022In: Polymers, E-ISSN 2073-4360, Vol. 14, no 19, article id 3959Article in journal (Refereed)
    Abstract [en]

    All-cellulose composites (ACCs) are manufactured using only cellulose as a raw material. Biobased materials are more sustainable alternatives to the petroleum-based composites that are used in many technical and life-science applications. In this study, an aquatic NaOH-urea solvent system was used to produce sustainable ACCs from wood-based woven textiles with and without the addition of TEMPO-oxidized nanocellulose (at 1 wt.-%). This study investigated the effects of dissolution time, temperature during hot press, and the addition of TEMPO-oxidized nanocellulose on the mechanical and thermal properties of the composites. The results showed a significant change in the tensile properties of the layered textile composite at dissolution times of 30 s and 1 min, while ACC elongation was the highest after 2 and 5 min. Changes in hot press temperature from 70 °C to 150 °C had a significant effect: with an increase in hot press temperature, the tensile strength increased and the elongation at break decreased. Incorporating TEMPO-oxidized nanocellulose into the interface of textile layers before partial dissolution improved tensile strength and, even more markedly, the elongation at break. According to thermal analyses, textile-based ACCs have a higher storage modulus (0.6 GPa) and thermal stabilization than ACCs with nanocellulose additives. This study highlights the important roles of process conditions and raw material characteristics on the structure and properties of ACCs. 

  • 248.
    Vesterlind, Eva-Lotta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A method to optimise birch CTMP pre-treatments by direct measurement of brightness on birch wood2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 3, p. 419-425Article in journal (Refereed)
    Abstract [en]

    It is challenging and quite difficult to optimise the pre-treatment of birch CTMP with respect to brightness in large-scale trials. Because of the complexity of the system, it is necessary to go beyond a two-dimensional experimental approach (where not more than two variables are varied at the same time) to find optimal conditions. This paper presents a straightforward laboratory technique that may be used to study the effects on the brightness of wood by various pre-treatments. Combining this methodology with multivariate data analysis provides a powerful tool for optimising birch CTMP pre-treatment with respect to brightness. Recommendations within the experimental domain are given.

    Download full text (pdf)
    FULLTEXT01
  • 249.
    Vesterlind, Eva-Lotta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Chemitermomechanical pulp made from birch at high temperature2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 2, p. 216-221Article in journal (Refereed)
    Abstract [en]

    The inherent stiffness of birch wood-fibres makes birch an excellent raw material in the manufacture of high bulk pulp. By a combination of chemical impregnation of birch chips and pre-heating of the chips to high temperature prior to refining, it is possible to manufacture CTMP with very high bulk using a low energy input. Trials revealed that the high pre-heating temperature lowers the energy consumption considerably. At 500 ml CSF an increase in the pre-heating temperature from 110C to 160C reduced the energy consumption by more than 40 %. Despite the low energy input, the shive content remained low or was even reduced and the internal bond strength, in terms of Scott-Bond, compared favourably with Spruce CTMP. In summary, a high pre-heating temperature can be used to manufacture birch CTMP with very high bulk, at a low energy consumption.

    Download full text (pdf)
    FULLTEXT01
  • 250.
    Vesterlind, Eva-Lotta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    High Temperature Birch CTMP2005In: Proceedings. SPCI International Conference 2005, Stockholm, Sweden, June 14-16, 2005Conference paper (Other academic)
    Abstract [en]

    The inherent stiffness of birch wood-fibres makes it an excellent raw material in the manufacture of high bulk pulp. By a combination of chemical impregnation of birch chips and pre-heating of the chips to a high temperature prior to refining, it is possible to manufacture CTMP with very high bulk with a low energy input. The bulky pulp obtained is low in shive content and is a suitable choice for the middle-layer of multi-ply board.

23456 201 - 250 of 274
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