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  • 151. Holmgren, Anders
    et al.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zhang, Liming
    Henriksson, Gunnar
    On the role of the monolignol gamma-carbon functionality in lignin biopolymerization2009Inngår i: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 70, nr 1, s. 147-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to investigate the importance of the monomeric γ-carbon chemistry in lignin biopolymerization and structure, synthetic lignins (dehydrogenation polymers; DHP) were made from monomers with different degrees of oxidation at the γ-carbon, i.e., carboxylic acid, aldehyde and alcohol. All monomers formed a polymeric material through enzymatic oxidation. The polymers displayed similar sizes by size exclusion chromatography analyses, but also exhibited some physical and chemical differences. The DHP made of coniferaldehyde had poorer solubility properties than the other DHPs, and through contact angle of water measurement on spin-coated surfaces of the polymeric materials, the DHPs made of coniferaldehyde and carboxylic ferulic acid exhibited higher hydrophobicity than the coniferyl alcohol DHP. A structural characterization with 13C NMR revealed major differences between the coniferyl alcohol-based polymer and the coniferaldehyde/ferulic acid polymers, such as the predominance of aliphatic double bonds and the lack of certain benzylic structures in the latter cases. The biological role of the reduction at the γ-carbon during monolignol biosynthesis with regard to lignin polymerization is discussed.

  • 152.
    Holmin, Susanne
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Permascand AB, Ljungaverk, Sweden .
    Näslund, Lars-Ake
    Department of Physics, Chemistry, and Biology (IFM), Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Ingason, Arni S.
    Department of Physics, Chemistry, and Biology (IFM), Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Rosen, Johanna
    Department of Physics, Chemistry, and Biology (IFM), Thin Film Physics Division, Linköping University, Linköping, Sweden.
    Zimmerman, Erik
    Permascand AB, Ljungaverk, Sweden .
    Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents2014Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 146, nr 10, s. 30-36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A reverse current obtained during power shutdowns in industrial processes, such as chlor-alkali production or alkaline water electrolysis, is deleterious for hydrogen evolving ruthenium dioxide (Ru02) based cathodes. It has been observed that RuO2 coatings after a power shutdown, necessary for e.g. maintenance, are severely damaged unless polarization rectifiers are employed. In this work we show why these types of cathodes are sensitive to reverse currents, i.e. anodic currents, after hydrogen evolution. RuO2 coatings deposited on nickel substrates were subjected to different electrochemical treatments such as hydrogen evolution, oxygen evolution, or reverse currents in 8 M NaOH at 90 degrees C. Polarity inversion was introduced after hydrogen evolution to simulate the effect of reverse currents. Because of chemical interaction with hydrogen, a significant amount of the RuO2 coating was transformed into hydroxylated species during cathodic polarization. Our study shows that these hydroxylated phases are highly sensitive to electrochemical corrosion during anodic polarization after extended hydrogen evolution. (C) 2014 Elsevier Ltd. All rights reserved.

  • 153.
    Holmvall, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Nip Mechanics, Hydrodynamics and Print Quality in Flexo Post-Printing2010Doktoravhandling, med artikler (Annet vitenskapelig)
  • 154.
    Holmvall, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Striping on flexo post-printed corrugated board2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Striping is the most common print non-uniformity on corrugated board. It is defined as periodic print density and/or print gloss variations parallel to the flutes. Corrugated boards are mainly printed with flexography, making striping a major concern for the flexographic post-printing industry. In spite of its long history, the basic mechanisms of striping have not been fully understood, and no concrete solution has been provided. The objective of this thesis is to obtain an understanding of the fundamental mechanisms behind and a solution to striping. Both experimental and numerical approaches have been taken in thiswork. Nonlinear finite element models have been constructed in both corrugated board and halftone dot scales to determine the pressure distributions in the printing nip. Ink transfer experiments have been performed to determine the print density vs. pressure relations. Parametric studies have been done for the effects of printing system variables and deformations. The results showed that striping is predominantly print density variations caused by pressure variations in the printing nip. The pressure variations are inherent to the corrugated board structure. Washboarding was shown to play a minor part in causing print density variations, but might contribute to gloss striping. A new printing plate design has been proposed to eliminate the pressure variations and hence the print density striping.

  • 155.
    Holmvall, Martin
    et al.
    SCA R&D Ctr, SE-85121 Sundsvall, Sweden.
    Lindström, Stefan
    Royal Inst Technol, Dept Fibre & Polymer Technol, S-10044 Stockholm, Sweden.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Simulation of two-phase flow with moving immersed boundaries2011Inngår i: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 67, nr 12, s. 2062-2080Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-dimensional model for immiscible binary fluid flow including moving immersed objects is presented. The fluid motion is described by the incompressible Navier-Stokes equation coupled with a phase-field model based on van der Waals’ free energy density and the Cahn-Hilliard equation. The immersed boundary method has been utilised to handle moving immersed objects and the phase-field boundary conditions have been adapted accordingly. Numerical stability and execution time was significantly improved by the use of a new boundary condition which implements minimisation of the free energy in a direct way. Convergence toward the analytical solution was demonstrated for equilibrium contact angle, the Lucas-Washburn theory and Stefan’s problem. The proposed model may be used for two-phase flow problems with moving boundaries of complex geometry, such as the penetration of fluid into a deformable, porous medium.

  • 156.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nip Mechanics of Flexo Post-Printing on Corrugated Board2006Inngår i: Euromech Colloquium 486, 2006Konferansepaper (Annet vitenskapelig)
  • 157.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nip Mechanics of Flexo Post-Printing on Corrugated Board.2007Inngår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, nr 17, s. 2129-2145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A finite element model of a flexo printing press has been developed and the material and geometrical properties of the sustem has been investigated. The results showed that it is the photopolymer and the top liner that have the biggest impact on the printing pressure variations.

  • 158.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Print Uniformity of Corrugated Board in Flexo Printing: Effects of Corrugated Board and Halftone Dot Deformations.2008Inngår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 21, nr 7, s. 385-394Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Print non-uniformity problems are a major concern for flexo post-printers. Many of these non-uniformities are suspected to be caused by the corrugated board structure itself. Striping is the most obvious one, but also other print quality problems might be structure-related. This work focuses on how deformations of the board might lead to print non-uniformities, and if the deformation of halftone dots is the mechanism behind striping in halftone flexo post-printing. The problems were analysed by using finite element models to simulate deformed board and halftone dot compression in the printing nip. Distortions of the board due to non-uniform hygro-thermal strains were shown to be a potential cause of print non-uniformities. Striping in halftone prints was found to be caused by differences in dot gain between ridge and valley areas above the flute structure.

  • 159.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Striping of Corrugated Board in Flexo Post-Printing2006Inngår i: International Printing and Graphic Arts Conference proceedings 2006, 2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    By doing ink transfer experiments and measuring reflectance variations on corrugated boards it was found that striping mainly consists of print density variations and not print gloss variations.

  • 160.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Striping of Corrugated Board in Full-tone Flexo Post-Printing2008Inngår i: Appita journal, ISSN 1038-6807, Vol. 61, nr 1, s. 35-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Striping is a print defect that is often seen in flexo post-printing on corrugated board. It appears as lines parallel to the flutes of the corrugated medium (fluting). These lines are generally thought to be print density and/or print gloss variations. The objective of this Paper is to obtain fundamental understanding of the striping mechanism. Print density and print gloss have been determined as a function of printing pressure. Typical printing pressure variations have also been determined by a non-linear finite element method. A 2D reflectance mapping has been performed for printed corrugated boards. The results showed that striping is dominated by print density variations for uncoated board, and the print density variations are, in turn, caused by the printing pressure variations. The extent to which the pressure variations appear as print density variations depends on the ink transfer characteristics of the liner board.

  • 161.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Striping of Corrugated Board in Halftone Flexo Post-printing2007Inngår i: 61st Appita annual conference and exhibition, Gold Coast, Australia, 6-9 May 2007, 2007 International paper physics conference, 6pp, 2007Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A fintie element model has been used to simulate how halftone dots deform during printing. Another finite element model has also been used for simulating how the pressure distribution in the nip changes when the corrugated board is deformed before printing by e.g. moisture induced warp. The simulations showed that striping in halftone prints can be explained by the deformation of halftone dots leading to more "dot gain" above flute ridges than between. When the corrugated board is deformed over a few flutes, the pressure distribution is affected which might cause print non-uniformities.

  • 162.
    Holmvall, Martin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Drolet, Francois
    FPInnovations-Paprican, 570 boul. St-Jean, Pointe-Claire, Québec, Canada.
    Lindström, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Transfer of a microfluid to a stochastic fibre network2011Inngår i: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 27, nr 7, s. 937-946Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transfer of a microscopic fluid droplet from a flat surface to a deformable stochastic fibre network is investigated. Fibre networks are generated with different levels of surface roughness, and a two-dimensional, two-phase fluid-structure model is used to simulate the fluid transfer. In simulations, the Navier-Stokes equations and the Cahn-Hilliard phase-field equations are coupled to explicitly include contact line dynamics and free surface dynamics. The compressing fibre network is modelled as moving immersed boundaries. The simulations show that the amount of transferred fluid is approximately proportional to the contact area between the fluid and the fibre network. However, areas where the fluid bridges and never actually makes contact with the substrate must be subtracted.

  • 163.
    Hossain, Shakhawath
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bergström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sarangi, S.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Computational Design of Fibre Network by Discrete Element Method2017Inngår i: Advancedin Pulp and Paper Research, Proceedings of the 16th Fundamental Research Symposium (Peer-reviewed), Oxford, UK, September 3rd-8th,2017, 2017Konferansepaper (Fagfellevurdert)
  • 164.
    Hossain, Shakhawath
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bergström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    A Particle-based Model to Investigate the Mechanics of Soft Fibre Network2016Konferansepaper (Fagfellevurdert)
  • 165.
    Hossain, Shakhawath
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bergström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Non-Affine Deformation Of Soft Fibre Network2017Konferansepaper (Fagfellevurdert)
  • 166.
    Hossain, Shakhawath
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bergström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Nonlinear Compression of Soft Fibre Network2017Inngår i: Book Of Abstracts Deformation And Damage Mechanisms Of Woodfibre Network- Materials And Structures, 2017Konferansepaper (Fagfellevurdert)
  • 167.
    Hossain, Shakhawath
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik. Uppsala university, Uppsala.
    Bergström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Uniaxial Compression of Three-Dimensional Entangled Fibre Networks: Impacts of Contact Interactions2019Inngår i: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 27, nr 1, artikkel-id 015006Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This paper concerns uniaxial compression of anisotropic fibre network, as typically seen in the end use of nonwoven and textile fibre assemblies. The constitutive relationship and deformation mechanism have been investigated by using a bead-model to represent the complex structures of the constituent fibres and the fibre networks. The compression stress shows a power-law dependency on the density with a threshold density for both experimental and numerical fibre networks. Unlike the widely studied tri-axial compression of the initially isotropic network, it was found that the contact interaction between the fibres, especially the fibre-fibre contact stiffness (or the transverse compression properties of fibres), has a large impact on all the constitutive parameters. In particular, the exponent values computed based on the softer contact stiffnesses agreed very well with the experimental values reported in the literature. The internal deformation mechanism was similar to the earlier studies that at low compression, the deformation is dominated by the low-energy-mode deformations (i.e. bending and shear), whereas at higher compression, the difference appears: the compression of fibre-fibre contacts, instead of the deformation in the fibre axial direction, takes over.

  • 168.
    Hu, Junhao
    et al.
    Huazhong Univ Sci & Technol, Peoples R China.
    Shao, Jingai
    Huazhong Univ Sci & Technol, Peoples R China.
    Yang, Haiping
    Huazhong Univ Sci & Technol, Peoples R China.
    Lin, Guiying
    Huazhong Univ Sci & Technol, Peoples R China.
    Chen, Yingquan
    Huazhong Univ Sci & Technol, Peoples R China.
    Wang, Xianhua
    Huazhong Univ Sci & Technol, Peoples R China.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Chen, Hanping
    Huazhong Univ Sci & Technol, Peoples R China.
    Co-gasification of coal and biomass: Synergy, characterization and reactivity of the residual char2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 244, s. 1-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)(3) is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.

  • 169.
    Hyll, K.
    et al.
    Innventia AB, Drottning Kristinas väg 61, Stockholm, Sweden.
    Björk, Elisabeth
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Innventia AB, Drottning Kristinas väg 61, Stockholm, Sweden.
    Vomhoff, H.
    Innventia AB, Drottning Kristinas väg 61, Stockholm, Sweden.
    Flow imaging characterisation of morphological changes of chemical pulp due to refining2016Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 3, s. 411-421Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of the refining process on the morphological changes of a chemical softwood pulp was investigated. The Voith LR40 industrial-like laboratory low consistency refiner was used, where the pulp was refined with five refining segments with differences in bar widths, groove widths, and cutting angles. The refined pulp was characterized with a fibre analyser with a spatial resolution of approximately 4 μm/pixel and a wide size range. The fines fraction of the refined pulp was also characterized with an imaging flow cytometer with a spatial resolution of 0.33 μm/pixel and a narrower size range. The fibre analyser measurements showed that the mean length, width, and aspect ratio of the fines decreased monotonically with accumulated refining energy. The imaging flow cytometer with its higher spatial resolution showed little change in fines morphology with accumulated refining energy. The morphology of the fines was more dependent on the applied specific refining energy than the design of the refining segment. However, a segment with much finer grooves and bars, initially designed for hardwood, gave significantly less fibre shortening, fines generation, external fibrillation, kink, and fines that were more fibrillar, compared to the other segments.Grant: The authors of this work would like to thank Prof. Lars Mattsson, Thomas Grahn, and Eva Ålander for fruitful discussions. The discussions with Lorentzen & Wettre were of great assistance. The financial support of the Swedish Energy Agency and the Önnesjöstiftelsen to the PhD project, and of the Fibre and Stock Design research programme to this evaluation study is gratefully acknowledged.

  • 170.
    Högberg, Ida
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Zasadowski, Dariusz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Karlsson, Anette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Wikman, Bengt
    SCA Rand D Centre, Box 716, SE-851 21 Sundsvall, Sweden.
    Andersson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Brightness development of a hydrogen peroxide bleached spruce TMP. Comparisons of pre-treatments with DTPA and a separable chelating surfactant2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 1, s. 50-55Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this investigation a new type of recoverable complexing agent (chelating surfactant) has been compared with a conventional complexing agent; diethylenetriamine pentaacetic acid (DTPA), in the metal ion sequestering of thermomechanical pulps (TMP) to be hydrogen peroxide bleached. After different degrees of washing of the pulps, bleaching experiments at different total alkali charges were performed with and without sodium silicate additions, and the ISO brightness of hand-made sheets was measured. The residual hydrogen peroxide in the bleaching liquor was also determined. No significant difference in either the brightness development or the residual hydrogen peroxide content could be detected between the pulps treated with equivalent molar ratios of the different complexing agents. Furthermore, the recovery of the chelating surfactant-manganese complexes from laboratory made white water by froth flotation was also studied. Two different foaming agents; sodium dodecyl sulphonate (SDS) and dimethyldodecylamine oxide (DDAO), were tested in the froth generation. After an addition of 160 ppm of DDAO, more than 80% of the manganese chelates could be recovered in the foam, containing 3% of the initial water mass.

  • 171.
    Högberg, Ida
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zasadowski, Dariusz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Karlsson, Anette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Wikman, Bengt
    SCA R&D, Sundsvall, Sweden.
    Andersson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Use of chelating surfactants as complexing agents for removal of manganese from mechanical pulp fibres prior to hydrogen peroxide bleaching.2011Inngår i: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC / [ed] Wang, L.; Kuang, S.; Hou, Q.; Cao, C.;Si, C.; Zhang, H., Tianjin: China Light Industry Press , 2011, s. 682-686Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this investigation a new type of recoverable complexing agent (chelating surfactant) has been compared with a conventional complexing agent (DTPA) in the metal ion management of thermomechanical pulps (TMP) to be hydrogen peroxide bleached. After different degrees of washing of the pulps, bleaching experiments at different total alkali charges were performed with and without sodium silicate additions, and the ISO brightness of hand-made sheets was measured. The residual hydrogen peroxide in the bleaching liquor was also determined. No significant difference in either the brightness development or the residual hydrogen peroxide content could be detected between the pulps treated with equivalent molar ratios of the different complexing agents. Furthermore, the recovery of the surfactant-manganese complexes from laboratory made white water by foam flotation was also studied. Two different foaming agents, SDS and DDAO, were tested. After an addition of 160 ppm of the latter surfactant, about 80% of the manganese chelates could be recovered in the foam, containing 3% of the initial water mass.

  • 172.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Mechanical Pulping2009Inngår i: Pulping Chemistry and Technology / [ed] Ek, M., Gellerstedt, G., Henriksson, G., Stockholm: KTH Royal Institute of Technology, 2009, s. 57-90Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 173.
    Isaksson, Per
    et al.
    Uppsala Univ, Angstrom Lab, SE-75121 Uppsala, Sweden.
    Gradin, Per A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hellström, Lisbeth M.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    A numerical and experimental study regarding the influence of some process parameters on the damage state in wood chips2013Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, nr 6, s. 691-696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The specific energy consumption during mechanical refining operation can be reduced by choosing the optimal process parameters in the wood chipping process such that a beneficial pretreatment is obtained. In the case of the utilization of a larger knife-edge angle, which is one such process parameter, the energy reduction is presumably due to the increased compressive loading parallel to the wood fibers. In the present article, a chip damage parameter D of spruce is in focus, which is relevant for cracking parallel to the fibers. D is defined and its dependence on the chip length and edge angle of the chipping knife is analyzed numerically by means of finite element analyses (FEA). The cutting force was measured in a pilot wood chipper for a number of knife-edge angles. There is a good correlation between the experimental results and those of FEA.

  • 174.
    Jiang, X.
    et al.
    School of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China.
    Song, X.
    School of Forestry, Central South University of Forestry and Technology, Changsha 410004, China.
    Chen, Y.
    School of Forestry, Central South University of Forestry and Technology, Changsha 410004, China.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Research on biogas production potential of aquatic plants2014Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 69, s. 97-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is to explore the biogas production potential of wetland aquatic biomass plants. 7 species of wetland aquatic biomass plants are used in the study, which include 4 plants with more fiber carbohydrate, Acorus calamus Linn, Typha orientalis Presl, Pontederia cordata and Canna indica, and 3 plants with more starch carbohydrate, Colocasia tonoimo Nakai, Thalia dealbata and Hydrocotyle vulgaris. In the experiment, these plants were treated by anaerobic fermentation in batch mode at 37°C. The results show that the anaerobic biogas production potential (ABP, mL·g-1VS) of aquatic biomass plants is different for different components content (%TS). The correlation between ABP and hemicellulose content is significant and negative (R=-0.784, 0.01<p<0.05), and the correlation between ABP and starch carbohydrate content is significant and positive (R=0.767, 0.01<p<0.05). The multiple stepwise regression equation with cross variable can roughly meet the statistical model to reflect the coeffect of hemicellulose, cellulose, starch carbohydrate and lignin on ABP of aquatic biomass plants, y=238.62+2.60x1+28.55x2-2.08x2x3+12.67x3, (Adj-R2=0.962, p(intercept)=0.034, p(x1)=0.101, p(x2)=0.036, p(x2x3)=0.066, p(x3)=0.031, p=0.025, SD=9.95), y represents ABP (mLg-1VS), x1, x2 and x3 represents the cellulose, lignin and starch carbohydrate content (%TS) respectively.

  • 175.
    Jiang, Yan
    et al.
    Stockholm University, Stockholm.
    Deiana, Luca
    Stockholm University, Stockholm.
    Zhang, Keihang
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lin, Shuangzheng
    Stockholm University, Stockholm.
    Córdova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Total Asymmetric Synthesis of Quinine, Quinidine, and Analogues via Catalytic Enantioselective Cascade Transformations2019Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 35, s. 6016-6023Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A catalytic asymmetric strategy for the total synthesis of quinuclidine natural products, which includes the completed enantioselective synthesis of the classical targets quinine and quinidine is disclosed. It is based on catalytic asymmetric cascade transformations, which paves the road for the synthesis of both enantiomers of the crucial C4 stereocenter with high enantioselectivity (up to 99 % ee) in one pot. Next, developing a route to all possible stereoisomers of a common early-stage intermediate sets the stage for the total synthesis of different enantiomers or epimers of quinine, quinidine and analogues with high selectivity. 

  • 176. Johansson, E
    et al.
    Lingström, R
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, L
    Evaluation of Adhesion between Polyelectrolyte Multilayers using AFM. : Poster - Veeco Scandinavian User Meeting2007Konferansepaper (Annet vitenskapelig)
  • 177.
    Johansson, O.
    et al.
    InovoCell, Inc., Brookfield, United States.
    Fernando, D.
    SLU, Uppsala.
    Fenitsius, R.
    Stora Enso AB, Borlänge.
    Daniel, G.
    SLU, Uppsala.
    Ferritsius, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Advancements in optical analysis yields new insight to mechanical pulping processes in an efficient and inexpensive way2016Inngår i: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, s. 267-276Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Operating costs, pulp quality, and loss of markets continue to dominate the concern of mechanical pulp producers. The search for process improvements, new products, and cost reductions requires significant amount of pulp testing to find out how improvements or new products can be achieved. Unfortunately, the required testing comes at a significant cost due to the time consuming and labor intensive preparation of each sample. For example, a detailed analysis which requires fractionation, hot disintegration, hand sheets, etc. may cost in excess of a thousand dollars. Thus, for an in-depth study where one compares different processes or operating conditions, the cost is significant. At the IMPC conference in Helsinki 2010, 2014 Fernando & Daniel showed how a modern variation of Simon staining can be used to gain information about the fiber wall conditions. This idea has now been expanded further by combining traditional fiber morphology measurements with the information gained from the measurement of color and intensities. In this paper, we will demonstrate a new approach to evaluate mechanical pulps using a special optical analyzer with the ability to process images in color or image intensities. The additional information gained from the color of the images is discussed. For the study, we have been comparing results from three modem commercial installations. The results from these trials are discussed using traditional testing methods in an earlier paper by Ferritsius et al., (2016). We will continue the discussion and show how these pulp samples were analyzed with a new optical device involving minimal sample preparations.

  • 178.
    Karlsson, Anette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    High consistency hydrogen peroxide bleaching of a Norway spruce stone groundwood pulp: Influence of heat treatment and iron content2011Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 2, s. 186-196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this work was to improve the understanding on how thermal treatments of mechanical pulps containing iron influence the unbleached brightness and hydrogen peroxide bleachability at high brightness levels. An unbleached Norway spruce stone groundwood (SGW) pulp was subjected to heat and iron (Fe3+) treatments followed by a chelating stage and a high consistency hydrogen peroxide bleaching stage. The hydrogen peroxide bleachability was studied on pulps as a function of pre-treatment at elevated temperatures and strongly bound iron content prior to bleaching and the alkali charge during bleaching. The evaluation was done using an experimental design based on the MODDE software (Umetrics AB).

    Heat treatment of the unbleached SGW pulp at 110 or 140 degrees C did not induce a significant increase in light absorption coefficient. Increasing the heat treatment temperature to 170 degrees C did, however, result in an increased light absorption coefficient corresponding to a brightness loss of 3.5% ISO. The light scattering coefficient was found to be essentially unchanged regardless of the heat-treatment conditions applied. The brightness loss resulting from the heat treatment could only partly be regained by hydrogen peroxide bleaching.

    An increased amount of strongly bound iron in the unbleached SGW pulp increased the light absorption coefficient. This increase was slightly higher when heat pre-treatment was performed at 140 and 170 degrees C compared to when heating at 110 degrees C. Hydrogen peroxide bleaching was found to reduce the iron content of the pulps and thus regain some of the brightness that was lost. This effect was most pronounced at the higher alkali charge levels. It is thus important to minimise the processing temperature, the time at high temperature and the iron content of the pulp in order to improve the unbleached brightness and bleachability of mechanical pulps.

  • 179.
    Karlsson, Anette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    High consistency hydrogen peroxide bleaching of Norway spruce mechanical pulps2010Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 180.
    Karlsson, Anette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Improved hydrogene peroxide bleaching of mechanical pulps through fundamental understanding of the influence of heat, iron, fines and chemical treatment on chromophore content2013Doktoravhandling, med artikler (Annet vitenskapelig)
  • 181.
    Karlsson, Anette
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Agnemo, Roland
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    High consistency hydrogen peroxide bleaching of mechanical pulps with varying amounts of fines2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 3, s. 256-268Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogen peroxide is a widely used bleaching chemical for mechanical pulps and is particularly useful when high brightness levels are required. The objective of this work was to study fines as a limiting factor for reaching higher brightness levels in high consistency hydrogen peroxide bleaching of Norway spruce (Picea abies) thermomechanical (TMP) and stone groundwood (SGW) pulps. The hydrogen peroxide bleaching efficiency (i.e. light absorption coefficient reduction) was studied as a function of temperature, alkali charge and fines content using an experimental design based on MODDE software (Umetrics AB).It is known that all types of fines contain more lignin, hemicelluloses, pectins, metals and less cellulose than long fibres. The light absorption coefficient was greater for unbleached TMP than for unbleached SGW pulp and an increased quantity of fines increased the light absorption coefficient for both pulp types. The increase was, however, most pronounced for the TMP. Furthermore, the data suggests that both the fibre fraction and the fines fraction are more coloured in the thermomechanical pulp. In most cases, increased amounts of fines in the pulp had a negative impact on the bleached pulp brightness in spite of the improved light scattering ability accompanying the addition of fines. A level of fines exceeding 50% was especially detrimental resulting in lower pulp brightness due to a higher light absorption coefficient.Increasing the bleaching temperature did not improve the bleaching efficiency. The optimal bleaching temperature at a hydrogen peroxide charge of 4.5% was found to be 70°C within the tested interval of 70-110°C. For a fines content of 25%, the stone groundwood pulp displayed a brightness of 83% whereas the thermomechanical pulp achieved a brightness of 79%.

  • 182.
    Karlsson, Anette
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Enberg, Sofia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Rundlöf, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Determining optical properties of mechanical pulps: Sheetmaking procedure and investigation of different ways to evaluate light absorption2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 3, s. 531-541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method to produce representative sheets for determination of optical properties of mechanical pulps has been developed. It reduces the risk of contamination and discoloration and can be used with small pulp quantities. The deviation from the expected linear behaviour of the light scattering coefficient, s, at wavelengths corresponding to strong light absorption, has been studied using the Kubelka-Munk model and the angular resolved DORT2002 radiative transfer solution method. This decrease in s could not be explained by errors introduced in the Kubelka-Munk modelling by anisotropic scattering. Linear extrapolation of s can therefore not be justified as a way to obtain a more correct light absorption coefficient, k. For thepulps studied, the decrease in s at short wavelengths had little effect on k at 457 nm.

  • 183.
    Karlsson, Anette
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Reduced heat-induced darkening and enhanced bleachability of mechanical pulps studied using the UV-visible absorption spectraManuskript (preprint) (Annet vitenskapelig)
  • 184.
    Karlsson, Anette
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. SCA R and D Centre AB, SE-851 21 Sundsvall, Sweden.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. AkzoNobel Pulp and Performance Chemicals, SE-445 80 Bohus, Sweden.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Strategies to reduce heat-induced darkening for enhanced bleachability of mechanical pulps2014Inngår i: Appita journal, ISSN 1038-6807, Vol. 67, nr 1, s. 50-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Under mechanical pulping conditions, elevated temperature initiates reactions in the wood constituents resulting in the formation of coloured structures. In an attempt to reduce the formation of colour, a number of additives have been examined to assess their ability to inhibit heat-induced darkening of a Norway spruce (Picea abies) stone groundwood (SGW) pulp. SGW pulp was used as a model pulp with the purpose of imitating a thermomechanical pulp (IMP). The heat-treated SGW pulp, both with and without additives present, was subsequently bleached with 4.5% hydrogen peroxide at high pulp consistency and with varying alkali charges in order to examine the hydrogen peroxide bleachability of such pulps. Heat treatment at 170 °C resulted in a loss of brightness of about 4% ISO after heating for 60 seconds. The reduction in brightness could only partly be regained through high consistency hydrogen peroxide bleaching; the SGW pulp displayed a brightness of 83.7% ISO whereas the heat-treated SGW pulp reached a brightness of 80.4% ISO. Heat treatment with a low addition rate (1 %) of alkaline hydrogen peroxide, sodium bisulfite or sodium sulfite, with a subsequent hydrogen peroxide bleaching stage, resulted in an improved bleached brightness of about 81.6% ISO, i.e. the loss of brightness due to heat was still approximately 2% ISO. Sodium borohydride (1 %) did not suppress the thermal darkening but improved the bleached brightness by approximately 2% ISO compared to the heat-treated SGW pulp and resulted in a brightness of 82.6% ISO. Addition of a chelating agent (DTPA, 0.11 and 0.45%) and the radical scavengers phthalic hydrazide (1 %) and 1 -hexanol (1 %) suppressed the heat-induced darkening somewhat but did not improve the hydrogen peroxide bleachability to any noticeable extent. Addition of citric acid (0.6%) did not suppress the thermal darkening and resulted in impaired bleachability.

  • 185.
    Karlsson, S.
    et al.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Friman, R.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Björkqvist, M.
    Laboratory of Industrial Physics, Department of Physics, University of Turku, FI-20014 Turku, Finland.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Backlund, S.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, FI-20500 Turku, Finland.
    Phase behavior and characterization of the system acetic acid-dodecylamine-water2001Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, nr 12, s. 3573-3578Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase behavior of carboxylic acid/alkylamine mixtures in water is largely dictated by a proton transfer from the acid to the amine, which will lead to charged species. If the distribution of carbon atoms is unequal between the acid and the amine, the result will be an ionic surfactant with an organic counterion. In this work the phase diagram for the ternary system acetic acid-dodecylamine-water at 298.2 K has been determined. Dodecylamine forms a lamellar phase with water, but when,acetic acid is added up to an equimolecular ratio between acid and amine, three new phases appear. These phases are an isotropic solution phase, a hexagonal liquid crystalline phase, and a cubic liquid crystalline phase. These three phases are not able to incorporate any excess amine. The solution phase shows the existence of micelles, which are spherical at high dilution, but show an elongation close to the phase border to the hexagonal phase.

  • 186.
    Karlsson, S.
    et al.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Friman, R.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Lindström, Birger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Backlund, S.
    Department of Physical Chemistry, Åbo Akademi University, Porthaninkatu 3-5, Turku, FI-20500, Finland.
    Self-assembly in the system decanoic acid-butylamine-water2001Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 243, nr 1, s. 241-247Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase behavior of alkanoic acid-alkylamine mixtures in water is mainly dictated by a proton transfer from the acid to the amine. For an asymmetric distribution of carbon atoms in the alkyl chains, the result will be an ionic surfactant with an organic counter-ion. In this study the phase diagram at 298.2 K for the ternary system decanoic acid-butylamine-water has been determined. The phase diagram is dominated by a large isotropic solution region. The selfdiffusion, viscosity, and conductivity measurements in the solution phase for an equimolecular ratio between the acid and the amine indicate a continuous transition from aqueous spherical mixed micelles to highly interacting hydrated acid-amine complexes passing through a bicontinuous region. One liquid crystalline lamellar phase, existing at excess acid, has been found. The small angle Xray scattering results indicate that the amine, due to its slightly amphiphilic character, is distributed between water and the bilayer.

  • 187.
    Karlström, A.
    et al.
    Chalmers University of Technology, Göteborg.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Refining efficiency for future CTIVIP and TMP systems co-optimizing fundamental wood material knowledge with a soft sensor control approach2016Inngår i: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, s. 304-316Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Internal variables in (C)TMP-refining processes (e.g. temperature, consistency, fiber residence time, backward flowing steam and forces acting upon the chips and pulp) are defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e.g. dilution water feed rate, load and gap distance) which are not available as distributed variables from refining zone measurements. The internal variables are the backbone of physical models and such models can be used for on-line implementation of soft sensors and advanced process control. Of special interest are the temperature and consistency profiles together with fiber residence time, which are the internal variables in focus of (in) this study. Moreover, they are directly linked to pulp and handsheet property development. To illustrate the capability to use a modeling strategy, two examples are given; one where it is shown how to reach a 40% reduction in specific energy in a CD82-refiner using a new control strategy without violating the pulp properties studied and one example where the consistency can be controlled individually in two parallel Twin refining zones. Hence, the article comprises both temperature and consistency control to reach optimal process conditions.We believe that increased fundamental understanding of the role of the spatially dependent viscosity in refining in general will be a key factor to find ways to further improve energy efficiency of refining.

  • 188.
    Karlström, A.
    et al.
    Chalmers University of Technology, Göteborg, Sweden .
    Hill, J.
    QualTech AB, Tyringe, Sweden.
    Ferritsius, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Ferritsius, Rita
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Stora Enso Kvarnsveden, Borlänge, Sweden.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Can we increase the proportion of electrical energy into fibre development in existing HC-refiners?2014Inngår i: International Mechanical Pulping Conference, IMPC 2014, Paper Engineers' Association (PI) , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Currently some 5 % of the electrical energy input in high consistency refining can be attributed to fibre development work. The rest is related to thermo- dynatnical steam generation. Can this unfavourable relation between fibre development and heat generation eventually be improved? A pre-requisite to consistent improvement is a stable process, controlled to targets deduced from profound process evaluations. This statement is elaborated based on two case studies and extensive refiner modelling. It is indicated that a well designed process including its basic process control can with proper refiner control reach energy reductions in excess of 20 %. Proper selections of process targets aligned with choice of segments can further increase the energy reduction in existing lines. These drastic energy reductions will demand concurrent observations and process modelling based on spatial measurements in the refining zone rather than slow, inadequate feedback control from pulp property measurements downstream. This will furthermore stress the need for more advanced control schemes if the full potential is to be captured. Additionally this approach will be a key element in the development of novel process approaches with even larger potential of energy reduction.

  • 189.
    Karlström, Anders
    et al.
    Chalmers University of Technology, Göteborg.
    Hill, Jan
    QualTech AB, Tyringe.
    Ferritsius, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Ferritsius, Rita
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pulp property development Part III: Fiber residence time and consistency profile impact on specific energy and pulp properties2016Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 2, s. 300-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper focuses on the pulp properties obtained from ThermoMechanical Pulp (TMP) CD refiners. Undersampled pulp variables are expanded into an oversampled set of process data, which makes it possible to analyze pulp properties in a dynamic time frame. It is shown that, in order to gain deeper insight into the defibration/fibrillation at a specific energy input, one needs to know the fiber residence time and the consistency profile. Moreover, the fiber residence time in the flat zone (FZ) and conical zone (CD) are intertwined with the consistency out from FZ and CD. Together with an external variable (production), these internal variables are essential for predicting the pulp properties. It is also shown that internal process conditions from different test series can be manipulated in the operating window using a low-frequency gain description obtained from an ARX model. The same mapping procedure can be applied to pulp and handsheet properties (in this paper represented by the tensile index), and this opens for implementation of new optimization routines to find more energy efficient operating points while maintaining prespecified pulp quality.

  • 190.
    Karlström, Anders
    et al.
    Chalmers University of Technology, Göteborg, Sweden.
    Hill, Jan
    QualTech AB, Tyringe, Sweden.
    Ferritsius, Rita
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Ferritsius, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pulp property development Part I: Interlacing under-sampled pulp properties and TMP process data using piece-wise linear functions2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 4, s. 599-608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermo-Mechanical Pulp (TMP) refiners served in this work as an example of how to combine oversampled and undersampled variables on a common timeframe for further analysis.To get more information from the refining process, temperature measurement arrays in the refining zones were studied alongside process measurements such as motor load, production rates, plate gaps, dilution waters, pulp properties and manually measured blow-line consistency.The undersampled data set consisted of 63 laboratory samples obtained at a Swedish TMP mill, which were tested for tensile index, mean fiber length and Somerville shives content. The pulp samples were obtained at five different periods during three months to cover a large dynamic operating window.The data set was expanded using a piece-wise linear approach. The measurements inside the refining zone were shown to be important variables when interlacing the undersampled pulp properties with the oversampled process data set, consisting of 350 000 samples.Use of an extended entropy model provided a palette of information about the process conditions inside the refining zone. Particularly, the residence time and the consistency in the refining zones were essential for the pulp property development, as a link between the refining segment pattern used and the current state of refiner operation.

  • 191.
    Karlström, Anders
    et al.
    Chalmers University of Technology, Göteborg.
    Hill, Jan
    QualTech AB, Tyringe.
    Ferritsius, Rita
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Ferritsius, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pulp property development Part II: Process non-linearities and their influence on pulp property development2016Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 2, s. 287-299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is shown in this paper that knowledge of the spatially measured temperatures inside the refining zone in TMP refiners is essential in describing non-linear dynamics of high consistency refining. By expanding the pulp and handsheet properties using piece-wise linear functions into the time domain, an auto-regressive model can be applied to verify that the tempera-ture and the consistency profiles, in combination with the motor load and production rate, are key input candidates when modeling changes in different pulp properties. The model accuracy is analyzed using process information captured at different time and operating conditions. It is also shown that it is more complex to estimate and validate the tensile index than the mean fiber length and Somerville shives content, especially close to refiner operating limits where a shift in the process gain may occur. This type of switched dynamics in tensile index estimation at a specific consistency is related to non-linear behaviors where the fiber pad distribution most likely undergoes a local collapse.

  • 192.
    Klinga, Niklas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The influence of fibre characteristics on bulk and strength properties of TMP and CTMP from spruce2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is intended to contribute to an increased knowledge about the influence of fibre characteristics on bulk and strength properties of thermomechanical pulp (TMP) and chemithermomechanical pulp (CTMP) from spruce. It deals with laboratory sheet properties and how they are affected by the conditions during pressing and drying, e.g. pressure, temperature and what dryness level the sheets have once pressing and drying is terminated. Further on it deals with how sheet properties depend on fibre properties, such as fibre length, fibre flexibility and fibre surface characteristics. The thesis is part of a long term project with the goal of increasing bending stiffness of paperboard, hence bulk and internal bond strength properties are of main interest. Apart from standard methods (ISO, TAPPI and Rapid Köthen), sheets have been pressed and dried in a modified Rapid Köthen dryer which has the capacity to press the sheets at higher pressure compared to a standard Rapid Köthen dryer. The results illustrated that there are large differences in mechanical pulp sheet properties depending on how the sheets have been pressed and dried. The main factors contributing to the bulk and strength levels achieved are a combination of pressure, temperature and to what dryness level the sheets are pressed. Sheets made from stiff fibres sprung back more when only wet pressed, and appeared to be less sensitive to pressure than sheets made from flexible fibres. The situation was the other way around when sheets were pressed and dried until dry at high temperature; pulps with stiff fibres were affected more by temperature and pressure than pulps with flexible fibres. When looking at strength development with respect to what dryness level the sheets had been pressed at high temperature, the most interesting finding was that the increase in strength was not continuous, especially when looking at the Z-strength development for high freeness pulps and long fibre fractions. There was a distinct inflection of the strength-dryness curve when dryness reached a level of ~50% and the most important dryness interval for internal strength development was found between 50 and 80%. This result combined with the fact that most paper and board machines only press the sheet to ~50% dryness, before the sheet is fed into the drying section, show that much of the inherent strength potential of mechanical pulps is unexploited. There are commercial techniques for pressing to higher dryness levels available, such as Condebelt drying and press drying. These techniques have however only been implemented to a limited extent. Further research on pressing to higher dryness levels will in the future be continued at FSCN at Mid Sweden University. Pilot refining trials with HTCTMP from spruce showed that densification and strength development were achieved by two different mechanisms: by making fibres flexible with gentle high consistency refining (HC refining) or by reducing fibre length with intense low consistency refining (LC refining). It was found that a high bulk at a very high Z-strength was achieved with LC refining even though the fibre length was reduced and at extremely low energy input. The results showed that fibres with extremely high content of sulphonated lignin on surfaces with low degree of fibrillation bond well as long as the surfaces get into contact during pressing and drying. This can be achieved by either making fibres flexible or by reducing fibre length. LC post-refining of spruce HTCTMP was found to be a very interesting process concept for production of high quality pulps intended for paperboard at a very low total energy input of ~800 kWh/admt.

  • 193.
    Klinga, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Sandberg, C
    Energy efficient high quality CTMP for paperboard2008Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 34, nr 2, s. 98-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper discusses the relationship between bulk and internal bond strength in paper sheets and their dependency on fibre length, fibre flexibility and fibre surface properties. It also discusses an interesting process concept for manufacturing of energy efficient high quality CTMP for paperboard. Post-refining pilot trials of spruce HTCTMP with an initial freeness of 740 ml were carried out at Metso Paper R&D in Sundsvall, Sweden. Both gentle high consistency and severe low consistency post-refining were performed. High consistency post-refining, at high energy input, gave freeness levels below 70 ml and still preserved the fibre length. These fibres were characterised by a very high flexibility giving sheets with a tensile index as high as 64 kNm/kg. Long fibres can however cause formation problems on a board machine which in turn can lead to poor surface properties, hence shorter fibres are from that perspective desirable. The low consistency post-refining resulted in a rapid drop in freeness due to fibre cutting. This was achieved at an extremely low specific energy input, which probably preserved most of the original fibre stiffness. In spite of this low energy input it was possible to reach the same Z-strength at a given bulk, as for the high consistency post-refined pulp. This implied that high bulk at certain internal bond strength could be achieved with stiff fibres even though the content of long fibres was low. Energy efficient low consistency post-refining of spruce HTCTMP yields high quality pulp at a total energy input of ~800 kWh/admt and is an interesting process concept for production of pulps intended for paperboard.

  • 194.
    Klinga, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sandberg, C
    Sheet properties of high yield pulps related to different pressing and drying conditions - part IIManuskript (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    This paper discusses how sheet properties of different mechanical pulps and chemithermomechanical pulps and their respective long fibre fractions depend on the level of dryness to which the sheets are wet pressed before being dried. This was performed with the aim of evaluating the consolidation and evolution of strength properties with respect to dryness. The results show that the development of strength, i.e. tensile strength and internal bond strength measured as Z-strength, is most pronounced in the dryness interval between 50 and 80% for the long fibre fractions.

  • 195.
    Klinga, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sandberg, Christer
    Paper properties of TMP and CTMP handsheets from spruce, as affected by the press load and temperature during sheet drying2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 4, s. 468-474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this investigation was to evaluate how physical properties of laboratory sheets, made from different thermomechanical and chemithermomechanical pulps, depend on the pressure and temperature levels during pressing and drying. Sheets were formed from long fibre fractions, defined as the pulp retained on a 50 mesh wire in a Britt Dynamic Drainage Jar, and pressed and dried according to a number of different pressure and temperature settings. The results showed that there were large differences in the sheet properties depending on what type of method was used for pressing and drying. High freeness pulps were more sensitive than low freeness pulps to the methods used for pressing and drying. The results indicate that the difference in sheet properties between ISO and Rapid Kothen sheets may be explained by the fact that ISO sheets are wet pressed only at room temperature, the fibres are then allowed to spring back when pressure is released whereas the fibres in Rapid Kothen sheets are locked in their positions as the sheets are pressed and dried at high temperature until dry.

  • 196.
    Klinga, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sandberg, Christer
    Paper properties of TMP and CTMP handsheets from spruce, as affected by the solids content from pressing2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 4, s. 475-480Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper discusses how the properties of dry handsheets from two different mechanical pulps and one chemithermomechanical pulp and their respective long fibre fractions depend on the level of dryness to which the sheets are pressed at high temperature. Sheets were pressed and dried to different dryness levels at 400 kPa and 93 degrees C in a modified Rapid Kothen dryer. Prior to testing of the physical properties, the sheets were dried without pressure at, room temperature to full dryness and kept in a conditioning room. This was performed with the aim of evaluating the consolidation and development of final strength properties with respect to dryness after a press section in a paper machine.The most interesting finding from these trials was that the increase in density and strength were far from linear with increased press dryness, especially for the long fibre fractions when looking at the Z-strength development. There was a distinct inflection of the curve when the sheets reached a press dryness level of some 50%. The most important dryness interval for internal strength development was found between 50 and 80%.The fact that most paper and board machines press the sheet to only some 50% dryness, before feeding it into the drying section, implies that much of the inherent strength potential of mechanical pulps may be unexploited. Further research on pressing to higher dryness levels will in the future be continued at FSCN at Mid Sweden University.

  • 197.
    Klinga, Niklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sandberg, C
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sheet properties of high yield pulps related to different pressing and drying conditions - part I2005Inngår i: International Mechanical Pulping Conference: IMPC 2005, Oslo, Norway, 7-9 June 2005, Oslo: Pappersindustriens tekniske forening , 2005, s. 344-348Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The objective of this investigation was to evaluate how physical properties of laboratory sheets, made from different thermomechanical and chemithermomechanical pulps, depend on the pressure and temperature levels during pressing and drying. Sheet were formed from long fibre fractions, defined as the pulp retained on a 50 mesh wire in a Britt Dynamic Drainage Jar, and pressed and dried according to a number of different pressure and temperature settings. The results showed that there were large differences in the sheet properties depending on what type of method that were used for pressing and drying. High freeness pulps were more sensitive to the type of method used for pressing and drying than low freeness pulps. The results indicate that the difference in sheet properties between ISO and Rapid Köthen sheets might be explained by the fact that ISO sheets are only wet pressed, the fibres are then allowed to spring back when pressure is released whereas the fibres in Rapid Köthen sheets are locked in their positions as the sheets are pressed and dried till over dry.

  • 198.
    Kulachenko, Artem
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Printing Press Paper Web Mechanics2004Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 199.
    Kulachenko, Artem
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Lindström, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Reinventing mechanics of fibre network2008Inngår i: Progress in Paper Physics Seminar, Helsinki: Helsinki University Press, 2008, s. 185-193Konferansepaper (Annet vitenskapelig)
  • 200.
    Kumar, V.
    et al.
    Åbo Akad Univ, Turku, Finland.
    Forsberg, S.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engström, A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Nurmi, M.
    Åbo Akad Univ, Turku, Finland.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Toivakka, Martti
    Åbo Akad Univ, Turku, Finland.
    Conductive carbon-nanocellulose coatings on paper2017Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 16, nr 6, s. 310-311Artikkel i tidsskrift (Annet vitenskapelig)
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