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  • 1.
    Abbaszad Rafi, Abdolrahim
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Alimohammadzadeh, Rana
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Avella, Angelica
    Mõistlik, Tanel
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Jűrisoo, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Kaaver, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Tai, Cheuk -Wai
    Lo Re, Giada
    Cordova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis2023Inngår i: Scientific Reports, E-ISSN 2045-2322, Vol. 13, nr 1, artikkel-id 14730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers. 

  • 2.
    Alimadadi, Majid
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Foam-formed Fiber Networks: Manufacturing, Characterization, and Numerical Modeling: With a Note on the Orientation Behavior of Rod-like Particles in Newtonian Fluids2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Fiber networks are ubiquitous and are seen in both industrial materials (paper and nonwovens) and biological materials (plant cells and animal tissues). Nature intricately manipulates these network structures by varying their density, aggregation, and fiber orientation to create a variety of functionalities.

    In conventional papermaking, fibrous materials are dispersed in water to form a sheet of a highly oriented two-dimensional (2D) network. In such a structure, the in-plane mechanical and transport properties are very different from those in the out-of-plane direction. A three-dimensional (3D) network, however, may offer unique properties not seen in conventional paper products.

    Foam, i.e., a dispersed system of gas and liquid, is widely used as the suspending medium in different industries. Recently, foam forming was studied extensively to develop the understanding of foam-fiber interactions in order to find potential applications of this technology in papermaking.

    In this thesis, a method for producing low-density, 3D fiber networks by utilizing foam forming is investigated and the structures and mechanical properties of such networks are studied. Micro-computed tomography is used to capture the 3D structure of the network and subsequently to reproduce artificial networks. The finite element method is utilized to model the compression behavior of both the reproduced physical network and the artificial networks in order to understand how the geometry and constitutive elements of the foam-formed network affect its bulk mechanical properties. Additionally, a method was studied in order to quantify the orientation behavior of particles in a laminar Newtonian flow based on the key parameters of the flow which control the orientation.

    The resulting foam-formed structures were extremely bulky. Yet despite this high bulk, the fiber networks retained good structural integrity. The compression behavior in the thickness direction was characterized by extreme compressibility and high strain recovery after compression. The results from the modeling showed that the finite-deformation mechanical response of the fiber network in compression was satisfactorily captured by the simulation. However, the artificial network shows higher stiffness than the simulated physical network and the experiment. This discrepancy in stiffness was attributed to macroscopic structural non-uniformities in the physical network, which result in increased local compliance. It was also found that the friction between the fibers, as well as the fiber curvature, had a negligible impact on the compression response of the fiber network, while defects (in the form of kinks) had an effect on the response in the last stages of compression. The study of the orientation behavior of particles at different flow velocities, particle sizes, and channel geometries suggests that it might be possible to utilize the flow shear rate as a means to quantify the orientation behavior.

    Fulltekst (pdf)
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  • 3.
    Alimadadi, Majid
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Lindström, Stefan B.
    Division of Solid Mechanics, Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Kulachenko, Artem
    Department of Solid Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks2018Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, nr 44, s. 8945-8955, artikkel-id C7SM02561KArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, we are able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

  • 4.
    Alimadadi, Majid
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    3D-oriented fiber networks made by foam forming2016Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, ISSN 1572-882X, Vol. 23, nr 1, s. 661-671Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In industrial applications, such as paper and nonwovens, cellulose fibers are used in the form of a network where the fibers are oriented more or less in the sheet-plane direction. However, in many biological systems, fibers are instead oriented in a three-dimensional (3D) space, creating a wide variety of functionalities. In this study we created a 3D-oriented fiber network on the laboratory scale and have identified some unique features of its structure and mechanical properties. The 3D fiber network sheets were prepared by using foam-forming as well as modifying consolidation and drying procedures. The fiber orientation and tensile/compression behavior were determined. The resulting sheets were extremely bulky (above 190 cm3/g) and had extremely low stiffness (or high softness) compared to the reference handsheets. Despite this high bulk, the sheets retained good structural integrity. We found that a 3D-oriented fiber network requires much less fiber-fiber contact to create a connected (“percolated”) network than a two-dimensionally oriented network. The compression behavior in the thickness direction was also unique, characterized by extreme compressibility because of its extreme bulk and a long initial increase in the compression load as well as high strain recovery after compression because of its fiber reorientation during compression.

    Fulltekst (pdf)
    fulltext
  • 5.
    Alimadadi, Majid
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Exploring One-more Dimension of Paper: Properties of 3D-Orieneted Fiber Network2014Inngår i: Progress in Paper Physics Proceedings 2014, 2014Konferansepaper (Annet vitenskapelig)
    Fulltekst (pdf)
    fulltext
  • 6.
    Alimohammadzadeh, Rana
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Osong, Sinke H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Abbaszad Rafi, Abdolrahim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Cordova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sustainable Surface Engineering of Lignocellulose and Cellulose by Synergistic Combination of Metal‐Free Catalysis and Polyelectrolyte Complexes2019Inngår i: Global Challenges, E-ISSN 2056-6646, Vol. 3, artikkel-id 1900018Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A sustainable strategy for synergistic surface engineering of lignocellulose and cellulose fibers derived from wood by synergistic combination of metal‐free catalysis and renewable polyelectrolyte (PE) complexes is disclosed. The strategy allows for improvement and introduction of important properties such as strength, water resistance, and fluorescence to the renewable fibers and cellulosic materials. For example, the “green” surface engineering significantly increases the strength properties (up to 100% in Z‐strength) of chemi‐thermomechanical pulp (CTMP) and bleached sulphite pulp (BSP)‐derived sheets. Next, performing an organocatalytic silylation with a nontoxic organic acid makes the corresponding lignocellulose and cellulose sheets hydrophobic. A selective color modification of polysaccharides is developed by combining metal‐free catalysis and thiol‐ene click chemistry. Next, fluorescent PE complexes based on cationic starch (CS) and carboxymethylcellulose (CMC) are prepared and used for modification of CTMP or BSP in the presence of a metal‐free catalyst. Laser‐scanning confocal microscopy reveals that the PE‐strength additive is evenly distributed on the CTMP and heterogeneously on the BSP. The fluorescent CS distribution on the CTMP follows the lignin distribution of the lignocellulosic fibers.

    Fulltekst (pdf)
    fulltext
  • 7.
    Alimohammadzadeh, Rana
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Osong, Sinke H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Cordova, Armando
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Scalable Improvement of the Strength Properties of Chemimechanical Pulp Fibers by Eco-Friendly Catalysis2018Inngår i: IMPC 2018, Trondheim, Norway, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The sustainable improvement of the strength properties of chemimechanical pulp by eco-friendlycatalysis is disclosed. Significant research activities have been performed on the use of cationic starchand polyelectrolyte complexes for improving the strength properties of cellulose-based materials. Herewe apply an eco-friendly strategy based on catalysis for significantly improving the strength propertiesof sheets made from chemimechanical pulp (CTMP) and bleeched sulphite pulp (BSP) using sustainablepolyelectrolyte complexes as the strength additives and organocatalysis. This surface engineeringstrategy significantly increased the strength properties of the assembled sheets (up to 100% in the caseof Z-strength). We also developed a catalytic selective colour marking of the cationic potato starch (CS)and carboxymethylcellulose (CMC) in order to elucidated how the specific strength additives aredistributed on the sheets. It revealed that the strength additives were more evenly distributed on thesheets made from CTMP as compared to BSP sheets. This is most likely attributed to the presence oflignin in the former lignocellulosic material. It also contributes to the increase in strength (up to 100%,Z-strength) for the CTMP derived sheets. The selective colour marking method also revealed that morestrength additives had been bound to the pulps in the presence of the catalyst.

  • 8.
    Andersson, Kerstin
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Pranovich, Andrey
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Eriksson, Marie
    Holmbom, Bjarne
    Effects of biological treatment on the chemical structure of dissolved lignin-related substances in effluent from thermomechanical pulping2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 2, s. 164-171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effluent from a TMP-based pulp and paper mill was collected at the inlet and outlet of the mill's biological treatment plant and fractionated by sorption on XAD-8 resin and MTBE precipitation. Fractionation indicated that the refractory dissolved organic material in biologically treated effluent was mainly composed of lignin-related substances. Characterisation of the lignin-related substances by chromatographic and spectrometric methods confirmed the similarities of the isolated material and milled wood lignin. Fractionation and characterisation of alkali-extracted material from solids (biosludge) in biologically treated effluent found evidence of lignin-related material. Results indicated that biological treatment had altered the chemical structure and molar-mass distribution of dissolved lignin-related substances.

    Fulltekst (pdf)
    FULLTEXT01
  • 9.
    Andersson, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Low consistency refining of mechanical pulp: process conditions and energy efficiency2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis is focussed on low consistency (LC) refining of mechanical pulp. Theresearch included evaluations of energy efficiency, development of pulpproperties, the influence of fibre concentration on LC refining and effects of rotorposition in a two-zoned LC refiner.

    Trials were made in mill scale in a modern TMP line equipped with an MSDImpressafiner for chip pre-treatment, double disc (DD) first stage refining and aprototype 72-inch TwinFlo LC refiner in the second stage. Tensile index increasedby 8 Nm/g and fibre length was reduced by 10 % in LC refining at 140 kWh/adtgross specific refining energy and specific edge load 1.0 J/m. Specific lightscattering coefficient did not develop significantly over the LC refiner.

    The above mentioned TMP line was compared with a two stage single disc highconsistency Twin 60 refiner line. The purpose was to evaluate specific energyconsumption and pulp properties. The two different process solutions were testedin mill scale, running similar Norway spruce wood supply. At the same tensileindex and freeness, the specific energy consumption was 400 kWh/adt lower in theDD-LC concept compared with the SD-SD system. Pulp characteristics of the tworefining concepts were compared at tensile index 47 Nm/g. Fibre length was lowerafter DD-LC refining than after SD-SD refining. Specific light scattering coefficientwas higher and shive content much lower for DD-LC pulp.

    The effects of sulphite chip pre-treatment on second stage LC refining were alsoevaluated. No apparent differences in fibre properties after LC refining werenoticed between treated and untreated pulps. Sulphite chip pre-treatment iniiicombination with LC refining in second stage, yielded a pulp without screeningand reject refining with tensile index and shives content that were similar to nonpre-treated final pulp after screening and reject refining.

    A pilot scale study was performed to investigate the influence of fibreconcentration on pulp properties in LC refining of mechanical pulps. MarketCTMP was utilised in all trials and fibre concentrations were controlled by meansof adjustments of the pulp consistency and by screen fractionation of the pulp. Inaddition, various refiner parameters were studied, such as no-load, gap and baredge length. Pulp with the highest fibre concentration supported a larger refinergap than pulp with low fibre concentration at a given gross power input. Fibreshortening was lower and tensile index increase was higher for long fibre enrichedpulp. The results from this study support the interesting concept of combiningmain line LC refining and screening, where screen reject is recycled to the LCrefiner inlet.

    It has been observed that the rotor in two-zoned refiners is not always centred,even though pulp flow rate is equal in both refining zones. This leads to unequalplate gaps, which renders unevenly refined pulp. Trials were performed in millscale, using the 72-inch TwinFlo, to investigate differences in pulp properties androtor positions by means of altering the pressure difference between the refiningzones. In order to produce homogenous pulp, it was found that uneven plate gapscan be compensated for in LC refiners with dual refining zones. Results from thedifferent flow rate adjustments indicated that the control setting with similar plategap gave the most homogenous pulp.

    Fulltekst (pdf)
    Lic Stefan Andersson
  • 10.
    Andersson, Stefan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Sandberg, Christer
    Holmen Paper AB, Braviken Paper Mill, SE-60188 Norrkoping, Sweden .
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Comparison of mechanical pulps from two stage HC single disc and HC double disc - LC refining2012Inngår i: Appita journal, ISSN 1038-6807, Vol. 65, nr 1, s. 57-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mechanical pulping line consisting of high consistency (HC) double disc (DD) and low consistency (LC) refining was compared with a two stage single disc (SD) high consistency twin refiner line. The purpose of this study was to evaluate specific energy consumption and pulp properties. The two different process solutions were tested running similar Norway spruce wood supply. At similar tensile index and freeness, the DD-LC concept reduced the electric energy consumption by 400 kWh/adt compared with the traditional two-stage SD-SD system. Pulp characteristics of the two refining concepts were compared at tensile index 47 Nm/g. Fibre length was reduced more after DD-LC refining than after SD-SD refining. Specific light scattering coefficient was higher after DD-LC refining than SD-SD refining, while the development in second stage refining was better for SD-SD pulp than for DD-LC pulp. Shive level was significantly lower for DD-LC pulp than for SD-SD pulp.

  • 11.
    Andersson, Stefan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Sandberg, Christer
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Effect of fibre length distribution on low consistency refining of mechanical pulpManuskript (preprint) (Annet vitenskapelig)
  • 12.
    Andersson, Stefan
    et al.
    Holmen Paper AB, Bravikens Pappersbruk, SE-601 88 Norrköping, Sweden.
    Sandberg, Christer
    Holmen Paper AB, Bravikens Pappersbruk, SE-601 88 Norrköping, Sweden.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Effect of long fibre concentration on low consistency refining of mechanical pulp2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 4, s. 702-706Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

    Fulltekst (pdf)
    fulltext
  • 13.
    Andersson, Stefan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Sandberg, Christer
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    The effect of rotor position on pulp properties in a two-zoned low consistency refiner2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 3, s. 525-530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earlier studies have shown that plate gaps are sometimes unequal in two-zoned low consistency refiners and that unequal gaps render unevenly refined pulp. It is also known that optimisation of plate gap in low consistency refining leads to improved energy efficiency. In this work, trials were made in mill scale in a modern TMP line equipped with a prototype 72 inch TwinFlo low consistency refiner in second stage. The study was designed to investigate the development of pulp properties from different rotor positions by means of altering the outlet flow rate ratio. The specific energy consumption was calculated for each refining zone and setting, based on flow rate and temperature increase. In order to produce homogenous pulp, it was found that uneven plate gaps need to be compensated in low consistency refiners with dual refining zones. Results from the different flow rate adjustments indicated that the control setting with similar plate gap gave the most homogenous pulp. However, further studies are needed to find an adequate rotor control strategy. The temperature increase in each refining zone seems to correlate well with the applied specific energy consumption in each refining zone.

    Fulltekst (pdf)
    fulltext
  • 14. Andreasson, B
    et al.
    Forsström, Jennie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Determination of fibre pore structure: influence of salt, pH and conventional wet strength resins2005Inngår i: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 12, nr 3, s. 253-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.

  • 15.
    Berg, Jan-Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Persson, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Hellstadius, Börje
    Billerud Korsnäs AB, SE-80181 Gävle, Sweden..
    Edlund, Henrik
    Billerud Korsnäs AB, SE-71880 Frövi, Sweden..
    Granfeldt, Thomas
    Lundfors, Mikael
    Valmet AB, Refiner Segments, Vretenvagen 11, SE-17154 Solna, Sweden..
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Refining gentleness - a key to bulky CTMP2022Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 37, nr 2, s. 349-355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemithermomechanical pulp (CTMP) is often used in middle layers of multiply paperboards due to its high bulk at specified strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to examine the effect of refining on bulk, taking into account conditions such as temperature, sulphonation, refining gap and refiner size. First stage CTMP made from Norway spruce (Picea abies) were produced in pilot and mill scale trials. Two new parameters, Equivalent temperature related to softness and Refining gentleness are introduced that take into account refining conditions as actual temperature, softening temperature, bound sulphonate content, refining gap and refiner diameter. The results show that bulk increases linearly with refining gentleness.

  • 16. Bijok, Nicolaus
    et al.
    Fiskari, Juha
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Gustafson, Richard R.
    Alopaeus, Ville
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-). Aalto University, Finland.
    Chip scale modelling of the kraft pulping process by considering the heterogeneous nature of the lignocellulosic feedstock2023Inngår i: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 193, s. 13-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article focuses on a multiscale modelling approach to describe the delignification of softwood during the kraft pulping process. A framework for modelling the lignocellulosic feedstock on a fibre scale which considered the fundamental chemical components of wood as a distributed variable is re-assessed and extended to include chip-level phenomena such as diffusion limitations and initial component distributions within a softwood chip mixture. A new description of the wood chip is presented using a finite volume discretisation along one spatial dimension by simultaneously considering the anisotropic structural differences of the wood. Additionally, based on literature data, a distinction between the softwood chips' early- and latewood regions with their differences in densities and chemical composition is suggested. The presented model framework uses published sub-models for kinetics, diffusion etc. The validation and estimation of the remaining parameters are conducted from experimental data that quantifies the kappa number distribution of individual softwood fibres after kraft pulping. The investigation hypothesises a Gaussian distribution for the initial chemical component distribution within wood chips from a well-defined region. In contrast, a Log-normal distribution is used to describe the initial chemical distribution within a softwood chip mixture. The established sub-models for the kraft pulping process's kinetics and mass transfer phenomena could not predict the experimental data satisfactorily. However, modifying the sub-models by including a change in lignin reactivity and a temperature dependency of the lignin reactivity decline during the delignification progress could predict the essence of the observed experimental kappa number distribution. 

  • 17. Bijok, Nicolaus
    et al.
    Fiskari, Juha
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Gustafson, Richard R.
    Alopaeus, Ville
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik. Aalto University, Finland.
    Modelling the kraft pulping process on a fibre scale by considering the intrinsic heterogeneous nature of the lignocellulosic feedstock2022Inngår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 438, artikkel-id 135548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Renewable raw materials such as lignocellulose are inherently complex and demanding in chemical processing compared to petroleum-based feedstocks. This article addresses the challenge of developing a general model framework for modelling lignocellulosic feedstock on a fibre scale, considering its inherent heterogeneous nature in terms of the fundamental chemical component distribution in addition to its anisotropic structural properties. The presented model is tested and validated for the well-established kraft pulping process. Simulations and parameter estimation are carried out to investigate the kappa number distribution of softwood fibres during kraft pulping by using experimental data from the literature showing non-uniform delignification. A moving grid discretisation method for the distributed concentration variables is used to predict the reaction of the wood solids. The results suggest that an inherent fundamental chemical component distribution can be hypothesised as one source of the non-uniform delignification. The model indicates that a Gaussian distribution can be assumed for the initial lignin concentration within softwood. In addition, an investigation of the lignin kinetics suggests that the reactivity of lignin during kraft pulping decreases as the delignification progresses. 

  • 18.
    Björk, Elisabeth
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier.
    Production and application of fine fractions made of chemical pulp for enhanced paperboard strength2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For all kinds of paperboard packages, the bending stiffness of the paperboard is a crucial property. In multi-ply folding boxboard (FBB) grades, this is obtained by placing different stocks in the outer and centre plies of the board. In the outer plies, a stock with a high tensile stiffness is used, typically made from refined kraft pulp fibres. In the middle ply/plies a stock with more bulky properties is placed, typically comprising of a high proportion of CTMP (chemi-thermomechanical pulp). CTMP fibres are stiffer and more inflexible with poor bonding abilities resulting in low strength properties. To increase the bonding strength in the middle ply, broke, containing chemical pulp is added, and sometimes refined chemical kraft pulp as well. Both fibres and fines, i.e. smaller fibre fragments, in a pulp have a significant contribution to the properties of the product. Fines produced during refining of chemical pulp are especially beneficial for increasing the strength.

    To achieve pulp fraction with higher fines content the pulp can be fractionated with a micro-perforated screen basket; a fine fraction produced from a screen with very small holes will contain a large proportion of fines. By adding such a fine fraction to a middle ply stock, the bulk properties of the main pulp, for example a CTMP, can be conserved as less refining of this pulp is required to achieve the targeted strength properties. However, a drawback is that the fine fraction usually has a very low mass concentration after the screening process as a lot of water pass through the screen together with the fines and fibre fragments. The excess water must be removed to maintain the water balance of the papermaking process. Further, the larger volumes require extra pumping capacity. A resource-efficient production of a fine fraction must target a high fine fraction mass concentration and a high content of fines and short fibre fragments in order to be implemented industrially.

    The focus of the present work was on separation efficiency (i.e. the difference in fibre length distribution caused by screening) and process efficiency (i.e. the concentration of the fine fraction) for production of a fine fraction of chemical pulp by screening, and the utilisation of the fine fraction as strength agent.

    Pilot-scale fractionation trials with a pressure screen with different microperforated screen baskets were performed in order to evaluate how the separation efficiency and process efficiency were affected by parameters such as feed concentration, pulp type (hardwood or softwood kraft pulp), hole size of the screen, and refining treatment prior to screening. The trials were evaluated using fibre length distributions, flow rates and concentrations of viii the feed flow and the fractions. Here, two complementary quantitative measures, Proportion in fine fraction (for process efficiency) and Fine fraction enrichment (for separation efficiency), were developed. To evaluate the strength enhancing effect of the obtained fine fraction, a lab scale study was performed where the fine fraction of a highly refined pulp was compared with the highly refined pulp as strength agent for a CTMP. The results of this study were verified in a pilot paper machine trial. In a second pilot paper machine trial, sheets with different CTMP proportions in the middle ply were studied in order to find out if the bulk could be increased while maintaining strength, by using a fine fraction made from refined chemical pulp.

    Regarding process efficiency, it was found that the most important parameter to obtain a high fine fraction concentration was a high feed concentration. Further, a higher fine fraction concentration for a given screening process was also obtained when using hardwood pulp and refining the pulp prior to the screening process. A higher feed concentration also had a positive effect on the separation efficiency. Small holes and a smooth surface of the screen basket were also important to improve the separation efficiency.

    It was shown that, when used as a strength agent in a CTMP pulp, the fine fraction of highly refined kraft pulp was twice as efficient as the highly refined kraft pulp, when added at equal mass proportion. However, both in the lab and pilot trial the strength increase was accompanied by a decreased bulk. This was expected, and to avoid this the proportion of the bulky CTMP had to be increased. The pilot paper machine trial with an increased CTMP proportion in the middle ply and a fine fraction of refined kraft pulp as strength agent demonstrated that it was possible to produce sheets with an increased bulk and maintained z-strength.

    Fulltekst (pdf)
    fulltext
  • 19.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Bouveng, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi.
    Vomhoff, Hannes
    Holmen AB.
    Fines-enriched pulp as a strength agent in a CTMP middle ply2018Inngår i: PaperCon 2018: Shaping the future through innovation, TAPPI Press, 2018, artikkel-id PA5.2Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of this pilot scale trial, was to evaluate fines-enriched pulp (FE-pulp) as a strength agent in amiddle ply of a board product.A typical CTMP-based middle ply was produced on the FEX pilot paper machine. The stock consisted of CTMP,refined hardwood and softwood pulp, and filler. FE-pulp as strength agent was compared with glue pulp, ahighly refined chemical pulp. FEX sheets and hand sheets made of pulp mixtures were evaluated. Also, thedewatering and pressing conditions on the paper machine were compared.The results confirmed the results of earlier experiments with handsheets; FE-pulp used as strength agent showedto be twice as efficient as glue pulp regarding strength properties without impairing the bulk. Further, thedewatering conditions and press dryness's on the paper machine was comparable at these additions. Thus, allthese results imply that addition of FE-pulp can replace the double amount of glue pulp as a strength agent.

  • 20.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Bouveng, Mikael
    RISE - Research Institutes of Sweden, Bioekonomi.
    Vomhoff, Hannes
    Holmen AB.
    Production of pulps with an extremely high fines content for use as strength agent2018Inngår i: PaperCon 2018: Shaping the future through innovation, TAPPI Press, 2018, artikkel-id PA5.1Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective was to optimize the production of fines-enriched pulp (FE-pulp) from chemical pulp.The first trial was a continuous production of FE-pulp with unbleached and bleached never-dried softwood. Thepulp was refined using a JC00 equipped with SF filling, and screened with a micro-perforated screen basket with250 μm diameter holes, but the produced FE-pulp got low concentration, below 3 g/l.The second trial aimed at optimised conditions, using dried bleached softwood. Three fillings, microbar, AA andFF were evaluated in a JC01 refiner, where microbar was most energy efficient. Microbar and AA reachedtargeted FE-pulp concentration, 10 g/l. The refined pulps were screened with different hole diameters, where, asexpected, larger hole diameters resulted in higher concentration but also lower fines content in the FE-pulps.The last trial, the microbar filling was evaluated for never-dried softwood pulp, unbleached and bleached. Now,the refining of unbleached softwood gave 3 times more fines per kWh/ton compared with first trial.These trials demonstrated the importance of the right refining conditions regarding effect of refiner and type offilling to achieve glue-pulp with high enough fines content. With the right conditions, it was possible to produceFE-pulp with high concentration at moderate energy consumption.

  • 21.
    Björk, Elisabeth
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik. RISE Res Inst Sweden, Pulp Papermaking & Packaging, Stockholm, Sweden.
    Bouveng, Mikael
    RISE Res Inst Sweden, Pulp Papermaking & Packaging, Stockholm, Sweden..
    Vomhoff, Hannes
    Holmen AB, Stockholm, Sweden..
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Use of fines-enriched chemical pulp to increase CTMP strength2021Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 20, nr 4, s. 255-263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, fines-enriched pulp (FE-pulp)-the fine fraction of highly-refined kraft pulp-was benchmarked against highly-refined kraft pulp (HRK-pulp) as a strength agent in eucalyptus chemithermomechanical pulp (CTMP). Both the FE-pulp and the HRK-pulp were produced from unbleached softwood kraft pulp, and equal amounts of those strength agents were added to the original CTMP, as well as to washed CTMP, where most of the fines had been removed. The effects of the added strength agents were evaluated with laboratory handsheets. The FE-pulp proved to be twice as effective as HRK-pulp. Both HRK-pulp and FE-pulp increased the strength of the CTMP handsheets. The bulk of the handsheets decreased, however, as well as the drainability. The addition of 5% FE-pulp resulted in the same strength increase as an addition of 10% HRK-pulp, as well as the same decrease in bulk and CSF. For the handsheets of washed CTMP, the strengths were not measurable; the CTMP lost the sheet strength when the CTMP-fines content was reduced through washing. The reduced strength properties were compensated for by the addition of chemical pulp fines that proved to be an efficient strength agent. The addition of 5% FE-pulp restored the strength values, and at a higher bulk and higher drainability. Application: In this study, we show how the strength of a CTMP sheet can be improved by adding fine material from kraft pulp.

  • 22.
    Björk, Elisabeth
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik. Rise.
    Vomhoff, Hannes
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Production of fines from refined kraft pulp by fractionation with micro-perforated screens2021Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, nr 3, s. 456-464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective in this work was to obtain a fine fraction of kraft pulp, with as high concentration as possible, in a pilot-scale fractionation with micro-perforated screen baskets. The influence of screen basket surface, hole size, feed concentration, pulp type and refining segment design was investigated. The results showed that a smooth screen basket surface improved the fractionation efficiency of the unrefined pulp compared to a profiled screen basket, despite a larger hole size. A significantly higher fine fraction concentration was obtained when using refined hardwood pulp compared to when using softwood pulp, which was explained with its lower average fibre length and narrower and thus more flexible fibre fragments. The pilot trials also showed that the screening process could be operated at feed concentrations similar to those directly after a refiner, 30-40 g/l. This was demonstrated in a process layout with partial recirculation where a refiner and a micro-perforated screen basket were operated in series in pilot scale. 

  • 23.
    Bohlin, Erik
    et al.
    Karlstad Universitet.
    Gustafsson Coppel, Ludovic
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Johansson, Caisa
    Karlstads Universitet.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Modelling of brightness decrease in coated cartonboard as an effect of calendering: Microroughness and effective refractive index aspects2010Inngår i: 11th Advanced Coating Fundamentals Symposium Proceedings: The Latest Advances in Coating Research and Development, Norcross, GA, USA: TAPPI Press, 2010, s. 51-65Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Calendering of coated paper leads to a brightness decrease. The mechanism for this is not clear, although it has been discussed in the past. One common explanation is that the porosity of the coating layer decreases and hence scattering. By comparing simulated and measured results this paper shows that modifications of the surface properties account for the brightness decrease of GCC coated substrates with calendering. The effect of a deformable cartonboard substrate is investigated here and compared to a less deformable plastic film substrate. From simulations based on a two-layer Kubelka-Munk model, it is shown that the brightness decrease of the cartonboard due to calendering has a negligible contribution to the brightness decrease of the coated cartonboard. The brightness decrease was similar for coated plastic film and coated cartonboard. The thickness of GCC coated plastic films was not affected by calendering irrespectively of the pigment and latex size distribution. Monte Carlo light scattering simulations, taking into account the measured decrease of surface microroughness and increased effective refractive index, showed that surface modifications accounted for most of the observed brightness decrease of the GCC coated substrate, whereas the bulk scattering and absorption coefficients were not affected by calendering. It is also shown that the scattering coefficient is significantly dependent on the coat weight whereas the physical absorption coefficient is not.

  • 24. Borrega, M.
    et al.
    Hinkka, V.
    Hörhammer, H.
    Kataja, K.
    Kenttä, E.
    Ketoja, Jukka A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Palmgren, R.
    Salo, M.
    Sundqvist-Andberg, H.
    Tanaka, A.
    Utilizing and Valorizing Oat and Barley Straw as an Alternative Source of Lignocellulosic Fibers2022Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, nr 21, artikkel-id 7826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transition to sustainable, biodegradable, and recyclable materials requires new sources of cellulose fibers that are already used in large volumes by forest industries. Oat and barley straws provide interesting alternatives to wood fibers in lightweight material applications because of their similar chemical composition. Here we investigate processing and material forming concepts, which would enable strong fiber network structures for various applications. The idea is to apply mild pretreatment processing that could be distributed locally so that the logistics of the raw material collection could be made efficient. The actual material production would then combine foam-forming and hot-pressing operations that allow using all fractions of fiber materials with minimal waste. We aimed to study the technical features of this type of processing on a laboratory scale. The homogeneity of the sheet samples was very much affected by whether the raw material was mechanically refined or not. Straw fibers did not form a bond spontaneously with one another after drying the sheets, but their effective bonding required a subsequent hot pressing operation. The mechanical properties of the formed materials were at a similar level as those of the conventional wood-fiber webs. In addition to the technical aspects of materials, we also discuss the business opportunities and system-level requirements of using straw as an alternative source of lignocellulosic fibers. 

  • 25.
    Brugés Martelo, Javier Mauricio
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Thim, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Liguori, Consolatina
    Department of Industrial Engineering (DIIn), University of Salerno, Fisciano, SA, Italy .
    Three-dimensional scanning electron microscopy used as a profilometer for the surface characterization of polyethylene-coated paperboard2021Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 36, nr 2, s. 276-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In food packaging, low-density polyethylene (PE) coating is applied to paperboards to act as a functional barrier and to provide the smoothness required to enhance printability. These characteristics are related to the material’s surface roughness, the parameter monitored during the manufacturing process. Measurement of surface roughness using optical profilometry has gained importance in the paper industry. The optical instruments used to measure surface roughness are limited spatially by the relationship with the light wavelength at which they operate. A scanning electron microscope (SEM) is an alternative for overcoming the spatial resolution limitation, and the use of stereo-photogrammetry on SEM images can be seen as an alternative profilometry technique to measure surface roughness. In this investigation, the surface topography of industrially manufactured high-quality PE-coated paperboard was studied, comparing the SEM stereo-photogrammetry technique with a reference profilometry method, i. e., chromatic confocal microscopy (CCM). We found close agreement between the calculated surface roughness and the results of the techniques used and compared them according to the new ISO 25178 Geometric Product Specifications. We concluded that SEM stereo-photogrammetry provides comparable accurate alternative profilometry method for characterizing the surface roughness of PE-coated paperboard in the micrometer scale.

    Fulltekst (pdf)
    fulltext
  • 26. Bäckström, Marie
    et al.
    Hammar, Lars-Åke
    Htun, Myat
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Beatability and runnability studies of ion-exchanged unbleached kraft pulps on a pilot scale2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 1, s. 94-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has earlier been shown that the counter-ion to the charged groups in the fibre has a significant effect on the beatability of fibres, but large-scale investigations of this effect are scarce in the literature. The objectives of the present study were therefore to develop a technique to ion-exchange large quantities of industrial pulp into the Na+-form using complexing agents and to study the effect of industrial-scale refining on pulp fibres in the Na+-form and how the fibres respond to industrial-like papermaking. The results show that ion-exchange can indeed be conducted on a pilot-scale using complexing agents such as DTPA. The study further indicates that an energy reduction of 50% at a given WRV or tensile index may be achieved if the fibres are converted to Na+-form prior to pilot-scale refining. By applying these techniques in full-scale production, it should thus be possible to save significant amount of energy, especially in the case of papers made from unbleached pulp that usually demands a higher degree of beating to achieve sufficient strength.

    Fulltekst (pdf)
    Bäckström et al: Beatability and runnability studier os ion-exchanged unbleached kraft pulps on a pilot scale. NJPPR 2009 Vol 24 Vol 24 1 pp 094-100
  • 27. Cortes Ruiz, Maria F.
    et al.
    Brusentsev, Yury
    Lindström, Stefan B
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för ingenjörsvetenskap, matematik och ämnesdidaktik (2023-).
    Xu, Chunlin
    Wågberg, Lars
    Shape-recovering nanocellulose networks: Preparation, characterization and modeling2023Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 315, artikkel-id 120950Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Development of strong cellulose nanofibril (CNF) networks for advanced applications, such as in the biomedical field, is of high importance owing to the biocompatible nature and plant-based origin of cellulose nanofibrils. Nevertheless, lack of mechanical strength and complex synthesis methods hinder the application of these materials in areas where both toughness and manufacturing simplicity are required. In this work, we introduce a facile method for the synthesis of a low solid content (< 2 wt%), covalently crosslinked CNF hydrogel where Poly (N-isopropylacrylamide) (NIPAM) chains are utilized as crosslinks between the nanofibrils. The resulting networks have the capability to fully recover the shape in which they were formed after various drying and rewetting cycles. Characterization of the hydrogel and its constitutive components was performed using X-ray scattering, rheological investigations and uniaxial testing in compression. Influence of covalent crosslinks was compared with networks crosslinked by the addition of CaCl2. Among other things the results show that the mechanical properties of the hydrogels can be tuned by controlling the ionic strength of the surrounding medium. Finally, a mathematical model was developed based on the experimental results, which describes and predicts to a decent degree the large-deformation, elastoplastic behavior, and fracture of these networks.

  • 28.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Quantitative microscopy of coating uniformity2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Print quality demands for coated papers are steadily growing, and achieving coating uniformity is crucial for high image sharpness, colour fidelity, and print uniformity. Coating uniformity may be divided into two scales: coating thickness uniformity and coating microstructure uniformity, the latter of which includes pigment, pore and binder distributions within the coating layer. This thesis concerns the investigation of both types of coating uniformity by using an approach of quantitative microscopy.First, coating thickness uniformity was analysed by using scanning electron microscope (SEM) images of paper cross sections, and the relationships between local coating thickness variations and the variations of underlying base sheet structures were determined. Special attention was given to the effect of length scales on the coating thickness vs. base sheet structure relationships.The experimental results showed that coating thickness had a strong correlation with surface height (profile) of base sheet at a small length scale. However, at a large length scale, it was mass density of base sheet (formation) that had the strongest correlation with coating thickness. This result explains well the discrepancies found in the literature for the relationship between coating thickness variation and base sheet structure variations. The total variance of coating thickness, however, was dominated by the surface height variation in the small scale, which explained around 50% of the variation. Autocorrelation analyses were further performed for the same data set. The autocorrelation functions showed a close resemblance of the one for a random shot process with a correlation length in the order of fibre width. All these results suggest that coating thickness variations are the result of random deposition of particles with the correlation length determined by the base sheet surface textures, such as fibre width.In order to obtain fundamental understandings of the random deposition processes on a rough surface, such as in paper, a generic particle deposition model was developed, and systematic analyses were performed for the effects of particle size, coat weight (average number of particles), levelling, and system size on coating thickness variation. The results showed that coating thickness variation3grows with coat weight, but beyond a certain coat weight, it reaches a plateau value. A scaling analysis yielded a universal relationship between coating thickness variation and the above mentioned variables. The correlation length of coating thickness was found to be determined by average coat weight and the state of underlying surfaces. For a rough surface at relatively low coat weight, the correlation length was typically in the range of fibre width, as was also observed experimentally.Non-uniformities within the coating layer, such as porosity variations and binder distributions, are investigated by using a newly developed method: field emission scanning electron microscopy (FESEM) in combination with argon ion beam milling technique. The combination of these two techniques produced extremely high quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method was also developed by using marker-controlled watershed segmentation (MCWS) of the secondary electron images (SEI).The high resolution imaging revealed that binder enrichment, a long disputed subject in the area, is present in a thin layer of a 500 nm thickness both at the coating surface and at the base sheet/coating interface. It was also found that the binders almost exclusively fill up the small pores, whereas the larger pores are mainly empty or depleted of binder.

    Fulltekst (pdf)
    Doctoral Thesis 129
  • 29.
    Dahlström, Christina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Allem, Rafik
    FPInnovations, Pointe Claire, PQ, Canada.
    Uesaka, Tetsu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    New Method for Characterizing Paper Coating Structures Using Argon Ion Beam Milling and Field Emission Scanning Electron Microscopy2011Inngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 241, nr 2, s. 179-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have developed a new method for characterizing microstructures of paper coating using argon ion beam milling technique and field emission scanning electron microscopy. The combination of these two techniques produces extremely high-quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method has been developed by using marker-controlled watershed segmentation technique of the secondary electron images. The high-quality secondary electron images with well-defined pores makes it possible to use this semi-automatic segmentation method. One advantage of using secondary electron images instead of backscattered electron images is being able to avoid possible overestimation of the porosity because of the signal depth. A comparison was made between the new method and the conventional method using greyscale histogram thresholding of backscattered electron images. The results showed that the conventional method overestimated the pore area by 20% and detected around 5% more pores than the new method. As examples of the application of the new method, we have investigated the distributions of coating binders, and the relationship between local coating porosity and base sheet structures. The technique revealed, for the first time with direct evidence, the long-suspected coating non-uniformity, i.e. binder migration, and the correlation between coating porosity versus base sheet mass density, in a straightforward way.

  • 30.
    Dahlström, Christina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Coating Uniformity and its Effect on Supercapacitor Capacitance2014Konferansepaper (Annet vitenskapelig)
  • 31.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Radiative transfer i pappersindustriella tillämpningar2010Inngår i: Thule: Kungl. Skytteanska Samfundets Årsbok 2010 / [ed] R. Jacobsson, Umeå: Kungl. Skytteanska Samfundet , 2010, s. 115-124Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 32.
    Edvardsson, Sverker
    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.
    Papermaking Research symposium (PRS): Web tension variations and runnability of the open draw section2009Inngår i: PRS 2009 Papermaking Research Symposium, Kuopio, 2009, , s. 11Konferansepaper (Fagfellevurdert)
  • 33.
    Edvardsson, Sverker
    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.
    System dynamics of the open draw with web adhesion: Particle approach2010Inngår i: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 77, nr 2, s. 1-11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work we propose a particle approach, which is designed

    to treat complex mechanics and dynamics of the open-draw sections that

    are still present in many of today's paper machines. First, known

    steady-state continuous solutions are successfully reproduced. However,

    it is shown that since the boundary conditions depend on the solution

    itself, the solutions for web strain and web path in the open-draw

    section are generally time-dependent. With a certain set of system

    parameters, the nonsteady solutions are common. A temporal fluctuation

    of Young's modulus, for example, destabilizes the system irreversibly,

    resulting in the continuous growth of web strain, i.e., break. Finally

    we exemplify with some strategic draw countermeasures how to prevent a

    dangerous evolution in the web strain.

     

  • 34.
    Edvardsson, Sverker
    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.
    System stability of the open draw section and paper machine runnability2009Inngår i: ADVANCES IN PULP AND PAPER RESEARCH, OXFORD 2009, VOLS 1-3 / [ed] IAnson, SJ, 2009, s. 557-575Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The present work is concerned with the system dynamics and stability of the open draw sections of paper machines where web breaks occur most frequently. We have applied a novel particle-based system dynamics model that allows the investigation of complex interactions between web property fluctuations and system parameters, without any constraints of a particular geometrical web shape or boundary conditions assumed a priori. The result shows that, at a given machine draw and web property parameters, the open draw section maintains its steady-state until it reaches a certain machine speed limit. At this speed the system looses its stability and the web strain starts growing without any limit, and thus leading to a web break. A similar instability can also be triggered when web properties suddenly fluctuate during steady-state operation. The parametric sensitivity studies indicate that, among the web property parameters studied, the elastic modulus of the wet web has the largest impact on the critical machine speed as well as on the detachment point where the web is released from the first roll. Further analysis shows that the decrease in dryness has a (negative) synergistic effect causing an increased risk of system instability. It is, therefore, most important to control, not only average dryness, but also its variations in order to enhance paper machine runnability.

  • 35.
    Edvardsson, Sverker
    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.
    The correlation between web breaks and defectsManuskript (Annet vitenskapelig)
  • 36.
    Eivazihollagh, Alireza
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Svanedal, Ida
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    On chelating surfactants: Molecular perspectives and application prospects2019Inngår i: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 278, s. 688-705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chelating agents, molecules that very strongly coordinates certain metal ions, are used industrially as well as in consumer products to minimize disturbances and increase performance of reactions and applications. The widely used sequestering agents, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) belong to this branch of readily water-soluble compounds. When these chemical structures also have hydrophobic parts, they are prone to adsorb at air-water interfaces and to self-assemble. Such bifunctional molecules can be called chelating surfactants and will have more extended utilization prospects than common chelating agents or ordinary ionic surfactants. The present review attempts to highlight the fundamental behavior of chelating surfactants in solution and at interfaces, and their very specific interactions with metal ions. Methods to recover chelating surfactants from metal chelates are also described. Moreover, utilization of chelating surfactants in applications for metal removal in environmental engineering and mineral processing, as well as for metal control in the fields of biology, chemistry and physics, is exemplified and discussed.

  • 37.
    Enberg, Sofia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Norske Skog Saugbrugs.
    Storage of Hydrogen Peroxide Bleached Mechanical Pulp: Reduction in Reflectance over the Visible Spectrum2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The objective of this thesis is to determine possible causes of the darkening of hydrogen peroxide bleached mechanical pulp over the visible spectrum and their relative contributions. It focuses on both process conditions and the composition of the pulp and the dilution water, including additions or losses of material along the process line from the bleach tower to the paper machine.

    A mapping of the optical properties of the pulp along the process showed that the fine fraction of the pulp darkened more than the long fibre fraction. Simulation of retention times of different fractions showed that the main part of the fine material is retained in the paper within a few hours, a small part might circulate for considerably longer time and may therefore be strongly coloured.

    Storage trials were mainly performed using a hydrogen peroxide bleached mechanical pulp intended for SC paper made of Norway spruce (Picea abies), sampled on one occasion and stored in a freezer. Unwashed or well-washed pulp was stored in distilled water or in different process waters. Some complementary trials were included, e.g. unbleached pulp.

    Time and temperature were the process variables that gave the strongest darkening of the pulp, as expected, both in a clean and a more process-like system, whereas pH only had an effect in the presence of process waters; the highest brightness stability was seen at a pH around 5.5–6.0.

    The darkening was due to an increase in the light absorption coefficient (k) beginning at short wavelengths, but after longer storage times the increase in kλ also became noticeable at longer wavelengths. The colour (CIE L*, a*, b*) of the pulp changed towards red and yellow, initially more towards red and then more towards yellow. These changes were clearly visible.

    Washing of the bleached pulp made it less sensitive to storage; possibly due to the removal of extractives, lignin-like substances, metals and pulp fines. This washing had little effect before storage and the amount of material removed was small.

    The pulp darkened more when stored in process waters compared to distilled water. Apart from fibres, most of the colour was associated with pulp fines or filler but some colour was also found in the dissolved and colloidal fractions. At an increased pulp consistency, the increase in k460 was smaller.

    Storage in white water from the paper machine gave extensive discolouration with a shoulder in the absorption spectrum around 550–650 nm, which increased with time. The addition of ferric ions increased the light absorption coefficient during storage, but could not explain the increased absorption at 550–650 nm nor could it be the only cause of the darkening in the mill system. A cationic basic violet dye gave a shoulder in the absorption spectrum similar to that of the mill system, but the absorption of the dye did not increase during storage. Model calculations indicate, but do not prove, that ferric ions together with violet and red dyes could have played a major, but not exclusive role in the colour observed in the mill system after storage. The darkening not accounted for, at longer wavelengths and around 550–650 nm, is suggested to be related to fines and fillers including dissolved and colloidal substances associated with these particles.

    A method to produce representative sheets for determination of optical properties of mechanical pulps was developed. The new method makes it possible to follow changes in light absorption and light scattering coefficients over the visible range of wavelengths. It is approximately six times faster than standard methods, reduces the risk of additional darkening of the sample 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. The decrease in s could not be explained by errors introduced in the Kubelka-Munk modelling by anisotropic scattering.

    Fulltekst (pdf)
    fulltext
  • 38.
    Enberg, Sofia
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Opdal, Øivind
    Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Axelsson, Patrik
    Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Eriksen, Øyvind
    Paper & Fibre Res Inst, NO-7491 Trondheim, Norway.
    Rundlöf, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Capisco Sci & Art, SE-60234 Norrkoping, Sweden.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Mapping and modelling of optical properties from pulp to super calendered paper2015Inngår i: Appita journal, ISSN 1038-6807, Vol. 68, nr 2, s. 128-138-Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    During production of mechanical pulp based paper, the pulp darkenswithin the process which represents a significant cost for the mill. Amapping of the optical properties of the pulp was conducted along theprocess, from pulp mill to paper machine, at a mill producing supercalendered (SC) paper on three paper machines. The focus was to evaluateat which positions in the mill the discolouration occurs and also whichfraction of the pulp darkens the most.The fine fraction of the pulp darkened more than the long fibrefraction. Bleached pulp diluted with white water from the paper machinedarkened more during storage than pulp diluted with clear filtrate. Thewhite water contains a considerable amount of suspended solids, i.e.pulp fines and clay. There was a tendency for a shoulder in absorptionspectra of the pulp stored in white water from the paper machine in theregion 550 to 650 nm, both for fibres and for fines. This is in the sameregion where the added dyes have their absorption maxima and also somecomplexes between iron and some of the components among lignin and theextractives. Simulation of retention times of different fractions showedthat, although the main part of the fine material is retained in thepaper within a few hours, a small part might circulate for considerablylonger time.

  • 39.
    Engberg, Birgitta A.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    Fiskari, Juha
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för kemiteknik.
    New Sustainable Method to Produce Pulp Fibres ‐ Deep Eutectic Solvent‐Assisted Mechanical Pulping2021Inngår i: Accelerating the progress towards the 2030 SDGs in times of crisis / [ed] Catrin Johansson, Volker Mauerhofer, Östersund: Mittuniversitetet , 2021, s. 2131-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mechanical pulps are widely used in the manufacture of printing paper grades and also to a lesser extent in packaging materials and hygiene products. An advantage of mechanical pulps in general is the high yield (95‐97%) of the production processes, which implies a resource efficient way of producing fibre‐based products. A major drawback when producing mechanical pulps for printing qualities is the high electric energy consumption needed. However, the mechanical action associated with the liberation of fibres from the wood matrix can be facilitated if the middle lamella lignin is softened, leading to lower energy input and less fibre damages. The lignin can be softened by chemicals and high process temperatures, like in the chemi‐thermomechanical process (CTMP) and the high‐temperature‐chemi‐thermomechanical process (HT‐CTMP), where sodium sulphite is utilized. The pulps from these processes are best suited for packaging materials and tissue products. In this study, an alternate chemical treatment using deep eutectic solvents (DES) was explored. The DES used was bio‐based, non‐toxic, non‐corrosive, and could be recycled. The main goal was to facilitate the refining process and possibly create a new quality of mechanical pulp, not to remove lignin or hemicellulose. Wood chips were pre‐steamed and then soaked in DES, to ensure a sufficient impregnation. The conditions of the DES treatment were much less severe than those of a chemical pulping process, i.e. low temperature, neutral or nearly‐neutral pH, and a short residence time. The excess DES was removed by washing the chips with water before the chips where fed into a refiner. According to fibre quality analyses, the DES‐treated fibres were longer and less damaged than the control. The DES‐treated fibres also demonstrated significantly higher dewatering capacity than fibres without DES‐treatment produced at the same specific energy input in the refiner. These facts indicate that the fractures during fibre liberation to a higher extent occurred in the middle lamella, similar to when producing CTMP. A maintained high yield of the DES‐treated pulp was confirmed by chemical analysis. In conclusion, this initial study show that DES‐assisted mechanical pulping appears to be an interesting alternative for producing a mechanical pulp with different fibre properties. An aim for future work would be to tailor the DES‐treatment to alter fibre properties in a more controlled manner preferably so that market shares could be taken from the today dominating low‐yield (<50%) processes.

  • 40.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Energy efficient mechanical pulping – summary of the Scandinavian industry initiative research work 2011 - 20152016Inngår i: 2016 International Mechanical Pulping Conference, Jacksonville, Florida, USA  September 28-30, 2016: SESSION 11: INDUSTRY INITIATIVE FOR ENERGY REDUCTION / [ed] Robert Lanouette, Georgia 30092 USA: TAPPI Press, 2016, s. 288-303Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A research program funded by the Swedish Energy Agency, the Swedish Knowledge Foundation and the Research Council of Norway was initiated by the companies; Holmen, Norske Skog, SCA and Stora Enso during 2008 with the objective to demonstrate techniques to reduce electrical energy demand by 50% for production of TMP and CTMP within a 10-year period starting 2011, while retaining similar final product characteristics of printing paper and paperboard. A gap analysis was performed to summarize different options to reach the goal at similar final product quality properties. The gap analysis indicated that some different approaches based on earlier research work both in pilot and demonstration scale together with improved process and product quality control should make it possible to reach the very tough goal. The very thorough benchmarking study was performed during 2012 including 16 TMP and CTMP-lines in Norway and Sweden showed the best production lines had the following electrical energy demands to certain final product properties; 900 kWh/t for CTMP optimized for paperboard, 1800 kWh/t for TMP optimized for newsprint and 2800 kWh/t for TMP optimized for SC-paper. The best results reached in industrial demonstration tests until 2015 showed potential to reduce the energy demand from 900 to 700 kWh/t for paperboard CTMP, from 1800 to 1400 kWh/t for newsprint TMP and from 2800 to 2400 for SC-paper TMP. In addition the results from other research within the program in the form of pilot and demonstration trials indicates that it could be possible to reach the goal of 50% reduced energy demand within a 10-year period provided that the industry and the research funds will continue to finance a continuation of the research program. 

  • 41.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Carlberg, T.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hellström, Lisbeth M.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kvalitetsteknik, maskinteknik och matematik.
    Gregersen, Øyvind Weiby
    NTNU - Norges teknisk-naturvitenskapelige universitet.
    Method for producing and processing wood chips [Förfarande för framställning av flis]2012Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    This patent application describes a method to produce wood chips with the intention of reducing the energy consumption in the subsequent process steps for pulp production. With the present method wood chipping is done in a wood chipper where the chipping tool (3) has an angle γ (4) within the interval of 75° to 105° between the fibre direction of the log and the side of the tool which faces the chip (2). Angles in this interval will cause an axially directed compression of the chip which will cause a cracking of the wood during chipping.

  • 42.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hellström, Lisbeth
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Carlberg, Torbjörn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Sandström, Peter
    SCA Reseach.
    Liden, Joar
    SCA Ortviken.
    Söderberg, Mats
    SCA Research.
    Mats, Egnell
    Andritz Iggesund Tools.
    Improved refining energy efficiency in thermo-mechanical pulping by means of collimated wood chipping – from solid mechanics to full scale evaluation2016Inngår i: PaperWeek Canada 2016 Conference February 1 to 5, 2016, Montreal: Technical Track Program / [ed] Greg Hay, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The wood chipping process was never optimized with regard to high yield pulping processes as thermomechanical pulping (TMP) and chemithermomechanical pulping (CTMP). It is generally believed that wood chips for pulping should be produced in such a way that the degree of damage is minimized and that the chip dimensional distribution should be as narrow as possible. Since the TMP and CTMP processes were developed in the 60-ies and 70-ies, compression screw as well as roll nip equipment have been developed to pretreat wood chips as a way to reduce refining energy consumption to given fiber and pulp properties and also in order to improve impregnation. The general conclusions are that a combination of shear and compression in the tangential or radial direction of the wood initiates cracks that later in the refiner will enhance and optimize fiber separation and also fiber property development. The idea with the collimated chipping technology is to utilize the wood chipper as a tool, combining cutting of wood logs to wood chips with a pretreatment of the chips by creating cracks that would enhance fiber separation, fiber surface development as well as chip-impregnation. In this case the compression is performed in the wood fiber direction, in which direction wood actually is weakest when it comes to compression induced cracking. The maximization of the amount of cracks in wood-chips is performed by optimizing the knife angle (or spout angle) in the chipper, to what we call collimated chipping (according to a patent owned by CCT AB). This presentation describes a theoretical background and two demonstration scale studies performed by SCA Forest Products at their Ortviken mill. One conclusion drawn, based on two-month test period with three weeks of collimated chipping, was that specific refining energy reduction was around 100 kWh/adt of the 1400 kWh/adt used in primary stage double disc refining. Most probably the potential is higher if the whole system is optimized. Tests were performed at constant production rate and energy was reduced by reducing power to constant freeness, leading to similar tensile and light scattering levels. The deliberately increased forces created in the wood chipper by means of an optimized (increased) edge angle caused more problems with knife holder equipment than normally, as well as increased vibrations. These problems will have to be solved for future long-term implementation of the technique.

  • 43.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Hammar, Lars Åke
    Innventia (STFI).
    Htun, Myat
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Rune
    STFI.
    Method of reducing the energy consumption at the refining of cellulose containing material [Sätt att reducera energikonsumtionen vid raffinering av cellulosahaltigt material]1987Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Method of reducing the energy consumption at the refining/beating of cellulose-containing material by the addition of alkali to the material for neutralizing acid groups bonded to the fibre wall. According to the invention, the pH-value in the pulp suspension is measured at the refiner outlet, the alkali is added in an amount depending on the measured pH value for neutralization without excess in the beating zone or immediately before the material enters the same, in an amount of 0.05-9 kg/ton, preferably 0.5-5 kg/ton, suitably 1-4 kg/ton, calculated as NaOH.

  • 44.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Hammar, Lars Åke
    Innventia (STFI).
    Sjögren, Birger
    STFI (Innventia).
    Svensson, Börje
    Innventia (STFI).
    Htun, Myat
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    A method of producing cellulosic pulp1991Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Mechanical and chemimechanical cellulose pulp, particularly paper pulp, is produced at a low energy input by disintegrating and beating wood material in one or more stages. Acccording to the invention, a substance capable of forming complexes with polyvalent metal ions, particularly calcium ions, so-called complexing agent, is added to the wood material prior to the beating process in order to replace said calcium or other polyvalent metal ions with sodium ions, therewith a further reduction in the energy input is obtained.

  • 45.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Johansson, B.
    Paper recycling2009Inngår i: Pulping Chemistry and Technology, Walter de Gruyter, 2009, s. 391-427Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 46.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Karlström, Anders
    Chalmers.
    System for continuously measuring pressure and temperature in the beating zones of refiners [System för att kontinuerligt mäta tryck och temperatur i malzonen hos raffinörer]1996Patent (Annet (populærvitenskap, debatt, mm))
  • 47.
    Engstrand, Per
    et al.
    Mittuniversitetet.
    Karlström, Anders
    Nilsson, Lennart
    The impact of chemical addition on refining parameters1995Inngår i: International Mechanical Pulping Conference 1995, Ottawa/St Paul, Canada, Ottawa,: Ontario Technical Section, CPPA , 1995, s. 281-286Konferansepaper (Annet vitenskapelig)
  • 48. Engstrand, Per
    et al.
    Lindgren, Johan
    Iggesund Paperboard AB.
    Agnemo, Roland
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    A method for increasing the stability of fluorescent whitening agent [Metod för att öka stabiliteten hos fluorescerande vitmedel]2004Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The present invention relates to a method for increasing the stability of fluorescent whitening agent after its preparation and during its use either on its own or mixed with other chemicals. The method is characterised in that the whitening agent is supplied with an organic acid containing aromatic group and/or can be esterified internally forming lactone, or the salt of the acid (additive A) and reducing chemical (additive B).

  • 49.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Rune
    STFI.
    Htun, Myat
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Hammar, Lars Åke
    Innventia (STFI).
    Svensson, Börje
    Innventia (STFI).
    Method of making mechanical and chemi-mechanical papermaking pulp [Framställning av mekanisk och kemimekanisk massa i två steg]1989Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The invention relates to a method of manufacturing mechanical and chemi-mechanical papermaking pulp with low energy input by disintegrating and beating wood material in at least two steps. According to the invention, the material is coarse-disintegrated in a first step at a concentration exceeding 20 %, acid groups in the wood material are neutralized, the material is diluted to a concentration of 1-10 % and beaten in one or several steps.

  • 50.
    Engstrand, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Sandberg, Christer
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Jonsson, Jonas
    Holmen Paper AB.
    Starck, Göran
    Holmen Paper aB.
    Wahlgren, Mikael
    Holmen Paper AB.
    Wancke-Ståhl, Charlotte
    Method of producing bleached thermomechanical pulp (tmp) or bleached chemithermomechanical pulp (ctmp) [Förfarande för framställning av blekt termomekanisk massa (TMP) eller blekt kemitermomekanisk massa (CTMP)]2003Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    There is a need for a cheaper method of producing bleached TMP and CTMP without impairing the properties of the pulp. This is made possible by the present invention, which relates to a method of producing said pulps in which finely divided lignocellulosic material is defibrated after pretreatment and the resultant pulp is bleached in the form of a suspension with bleaching agent that increases the anionic charge of the pulp fibres, whereafter the pulp suspension is cleaned and then possibly further treated, for instance bleached, characterised in that the defibration is effected with the aid of a) a refiner that has counter-rotating refining discs while using an extra high temperature (HTDD), or b) a refiner that has a single rotating refining disc(s) having a single refining zone or two parallel refining zones, while using an extra high temperature and while rotating the disc(s) at an extra high speed (RTS), and in that the cleaning treatment comprises first screeming the pulp suspension and them hydrocyclone cleaning said suspension, wherewith the reject obtained with each cleaning process is treated individually and the treated reject is returned to the advancing pulp suspension.

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