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  • 51.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Nilsson, Carl, Fredrik
    FN Engineering AB.
    A method for selective removal of ray cells from cellulose pulp [Förfarande för selektivt avlägsnande av märgstråleceller ur cellulosamassa]2004Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The content of ray cells in cellulose pulp causes problems and therefore these ray cells should be removed from the cellulose pulp to improve the pulp quality. The present invention makes this possible and comprises a method wherein at first an advancing pulp suspension is screened or vortex cleaned, (3) leading to the formation of an accept pulp fraction (4) and a reject pulp fraction (5) and that the reject pulp fraction is cleaned and divided, and that accepted material (pulp fibres and valuable fine material) is brought to further treatment and/or use. The invention is characterized in that the cleaning and division of the reject pulp suspension is carried out so that substantially all ray cells are present in the apex fraction of a fractionating cyclone (6) (if that is the kind of device used) and in that said fraction as such constitutes a very limited material stream, or in that a very limited material stream, predominantly containing ray cells is selected from the apex fraction, and in that this very limited material stream is brought to a disposal stage.

  • 52.
    Eriksson, K.
    et al.
    CIT (Chalmers industriteknik).
    Karlström, A.
    CTH (Chalmers tekniska högskola).
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. StoraEnso.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hill, Jan
    QualTech AB.
    Recent advances in modelling and control of TMP refining processes2015Conference paper (Refereed)
  • 53. Eriksson, Malin
    et al.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Application of polymeric multilayers of starch onto wood fibres to enhance strength properties of paper2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 3, p. 270-275Article in journal (Refereed)
    Abstract [en]

    Polyelectrolyte multilayers of cationic and anionic starch have been used to enhance the strength properties of paper. All starches used in this investigation had a degree of substitution around 0.065. Optical reflectometry showed that a combination of cationic and anionic starch could form polyelectrolyte multilayers onto silicon oxide surfaces. The same combination of starches was then applied to unbeaten, bleached softwood kraft fibres to form three layers, i.e. a cationic/anionic/cationic starch combination. The results showed a significant increase in the paper strength properties in terms of tensile index, strain at break, and Scott Bond. The adsorbed amount of starch in the sheets, determined using an enzymatic method, was found to increase with each successive starch treatment. The increased paper strength was not only due to the increase in adsorbed amount of starch; rather, the chemical composition of the starch was also important. Cationic starch with high amylose content had a more positive effect on the paper strength properties. Furthermore, it was observed that anionic starch, despite being adsorbed in large amounts, did not contribute to the increase in tensile strength or strain at break to the same extent as did cationic starch. However, the out-of-plane properties, measured as Scott Bond properties, increased with the adsorbed amount, regardless of the chemical composition of the starch used in the outermost layer.

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  • 54.
    Fallahjoybari, Nima
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engberg, Birgitta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Persson, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Investigation of pulp flow helicity in rotating and non-rotating grooves2021In: Proceedings of the Institution of mechanical engineers. Part E, journal of process mechanical engineering, ISSN 0954-4089, E-ISSN 2041-3009, Vol. 235, no 6, p. 2045-2058Article in journal (Refereed)
    Abstract [en]

    Numerical simulation of pulp flow in rotating and non-rotating grooves is carried out to investigate the effect of pulp rheological properties and groove geometry on the rotational motion of the pulp flow. The eucalyptus pulp suspension is considered as a working fluid in the present study whose apparent viscosity correlation is available from the experimental measurements reported in the literature. The simulations are carried out with OpenFoam for different values of pulp material, fiber concentrations, and groove cross-section. Helicity is introduced to measure the turnover rate of pulp flow in the groove due to the importance of such motion on the final properties of the pulp flow. A measurement of helicity magnitude and its distribution along the groove revealed that a change in the pulp material would significantly affect the flow structures within the groove. Further investigation on the effects of fiber concentration, c, showed that this parameter does not have a significant effect on the averaged helicity magnitude for c = 2.0 and 2.5, whereas the helicity distribution over the groove cross-section changes clearly for c = 1.5. The results showed that the helicity level is negligible for almost half of the cavity cross-section in the non-rotating groove simulations, which can be considered as a shortcoming of the original geometry of the groove. Therefore, a smaller cross-section for the groove is considered through which an enhancement in the helicity magnitude is observed. 

  • 55.
    Fallahjoybari, Nima
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Engberg, Birgitta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Persson, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Berg, Jan-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Lundstrom, T. Staffan
    Luleå Univ Technol, Div Fluid Mech, S-97187 Luleå, Sweden..
    An investigation of forces on a representative surface in a pulp flow through rotating and non-rotating grooves2023In: Journal of the Brazilian Society of Mechanical Sciences and Engineering, ISSN 1678-5878, E-ISSN 1806-3691, Vol. 45, no 5, article id 280Article in journal (Refereed)
    Abstract [en]

    Softwood pulp flow in rotating and non-rotating grooves is numerically simulated in the present study to investigate the fluid flow and the forces acting on a representative surface mounted in the groove. The viscosity of softwood pulp with various consistencies is available from the measurements reported in the literature providing the opportunity to examine the effects of fiber consistency on the velocity and pressure distribution within the groove. The simulations are carried out in OpenFOAM for different values of gap thickness, angular velocity and radial positions from which the pressure coefficient and shear forces values are obtained. It is found that the shear forces within the gap increase linearly with the angular velocity for all fiber consistencies investigated and in both grooves. Also, this behavior can be successfully predicted by modeling the gap flow as a Couette flow in a two-dimensional channel. Meanwhile, a more detailed analysis of the flow kinetic energy close to the stagnation point using Bernoulli's principle is carried out to provide a better understanding of the pressure coefficient variation with angular velocity in the non-rotating groove. A comparison of pressure coefficients obtained numerically with those calculated by considering the compression effects revealed that the comparison effects are dominating in the pulp flow within the groove.

  • 56.
    Ferritsius, Olof
    et al.
    STORA Corporate Research.
    Ferritsius, Rita
    STORA Corporate Research.
    Improved quality control and process design in production of mechanical pulp by use of factor analysis1997In: Proceedings International Mechanical Pulping Conference, 1997, p. 111-125Conference paper (Refereed)
    Abstract [en]

    In 1963, Forgacs showed that at least two quality variables are needed in order to characterize the quality of mechanical pulps. Later, Strand came to asimilar conclusion by introducing two independent common factors through the use of factor analysis. Both Forgacs and Strand showed that handsheet properties can be predicted from these two factors. This paper shows how STORA, on the basis of Strand’s approach, examines the two independent common factors directly, instead of examining a large amount of conventional measured pulp and handsheet properties. The factors are called F1, fibrebonding, and F2, long fibre influence. The independent factors are controlled to a great extent by independent process parameters; F1 correlates more strongly to specific energy than does freeness while F2 is mainly controlled by conditions in the defibration stage. In order to produce a uniform pulp quality, F1 and F2 should be kept inside a specified quality window. Since July 1995 a quality window in terms of F1 and F2 has been used at STORA Kvarnsveden TMP plant and thus has given a more stable pulp quality. The quality window gives a rapid overview of the status of the quality. Another advantage of applying F1 and F2 is that not only refiners, but also screens and cleaners can be evaluated in terms of the same quality variables. New parameters for evaluation of screens and cleaners are suggested. By examining all process stages from chip refiner, screen room to final pulp we can get a quality map in terms of F1 and F2. From this map it is quite obvious how the pulp quality is influenced by chip refiner stage and rejects refining. The F1/F2-map can simplify the work to find reasons for producing off-spec pulp and also mee tone big challenge: to produce a product of more uniform quality. To attain more uniform quality we have to think and speak daily in terms of factors like F1 and F2.

  • 57.
    Ferritsius, Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Johanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Capisco.
    Heterogeneity2019In: Heterogeneity, 2019Conference paper (Other academic)
    Abstract [en]

    Heterogeneity may be a most proper word to describe paper and board. Wood, the raw material to produce mechanical pulps, is almost as heterogeneous a material as the products. Looking in a microscope at a mechanical pulp it is obvious that it consists of a huge amount of small particles, which vary very much in several aspects: length, curl, width, wall thickness, fibrillation etc. In spite of that, we (scientists, mill employees, suppliers, consultants, researchers) commonly describe a pulp in terms of collective properties such as averages of fibre dimensions, hand sheet properties, dewatering ability etc. In other words: we describe mechanical pulp as a continuum. This may be more common than we believe. A review of the variables used in the more than 5,000 graphs in the preprints of the 23 International Mechanical Pulping Conferences (IMPC) between 1973 and 2018 showed that 97% of the variables described mechanical pulp as a continuum. Hence, only 3% of the variables reflected the heterogeneous nature of mechanical pulps.   Many authors point out the benefits of describing the character of a material by as few and as independent properties as possible. In 1957, Steenberg stated: “Any valuable theory must be supposed to include a number of independent factors”. However, within the mechanical pulping area it is common practise to evaluate the character of pulp with respect to a wide range of more or less correlated measured pulp and fibre properties. In the review of the last 23 IMPCs we found that more than 96% of the variables examined in the articles where of that kind. In our efforts to describe a mechanical pulp with respect to its highly heterogeneous nature we have among others been inspired by Forgacs who worked with independent common factors in order to characterize mechanical pulps. He presented a paper in 1963 where he states that at least two independent factors are needed to describe a mechanical pulp. They reflect shape and length of the particles. Also Strand has inspired us with his work in the 80’s where he used factor analysis on a huge database to derive two independent common factors reflecting “bonding” (Factor 1) and “fibre length” (Factor 2). Examining a few independent common factors instead of several conventionally measured properties, which are more or less correlated, makes it easier to get an overview of the status of the processed material. Therefore, it is a little surprising that independent common factors constitute only 4% of the variables presented at the IMPCs since 1973. Strands approach was tested in a long-term evaluation in two mills. It was possible to produce a paper product more uniform in quality, compared to common practise. However, none of the above-mentioned independent factors reflects the heterogeneity of the pulp.   Paper and pulp makers commonly agree that, within certain limits, uniformity is the most important characteristic of both the pulp and the paper. If we know how to perform uniformly, we may also be able to move into other operating areas (or volumes) in a controlled way. However, there is no common agreement on how to define "uniformity". Papermakers are still to a great extent specifying their demands on the pulp in terms of dewatering ability and average length-weighted fibre length although the correlation to product quality is vague and weak and varies over time. Almost since the advent of mechanical pulping processes, the operators have for process control had readings of dewatering ability of a pad consisting of billions of particles expressed as mL of water and average length-weighted fibre length of the pulp, which are far from being independent factors. Variations in any of these two properties may depend on variations in a combination of several more underlying factors. Therefore, it is hard to know what actions the operators should take to avoid running off spec. So far, the main development in the concept with dewatering and length to assist the operators have been firstly, to get time trends of these variables on a DCS screen instead of on a piece of paper in the control room, and secondly to get the readings more frequently with on-line analysers. During the same period, there have been an immense development of refiner concepts, fractionation, process design, modelling, use of raw material, fibre characterization, and new products.   By putting more attention to reality and describing mechanical pulp as a heterogeneous material, which the mechanical pulps truly are, we hope to be able to get a more profound understanding how wood particles are developed along the process all the way to product. We also hope to give the operators in the mechanical pulping plant a more realistic description of the material they are supposed to deliver to the paper and board makers in order to facilitate their possibilities to produce a more uniform product quality at minimum cost.  The aim of our presentation is to share some of our insights and reflections how to describe the heterogeneous nature of mechanical pulps to the mill operators.

    We have applied factor analysis on particle level based on measurements in an optical analyser of fibre diameter, fibre wall thickness, fibre length, and fibre fibrillation. Examples will be presented of how the raw material and the process have set characteristic fingerprints in terms of the distribution of an independent common bonding factor on particle level. It is fascinating to see how much that may be hidden behind averages, c.f. Rosling et al. (2018) who warn against comparing averages, which often obstruct a more profound understanding of a subject.   In our presentation, we intend also to discuss how a description of the heterogeneity of the material may be used to get measures of energy efficiency of the process, separation efficiency of fractionation equipment, and how to link fibre characteristics to properties of products. Some reflections will also be shared on what we think is further required to get a more realistic description of the heterogeneous material we call mechanical pulp. Reference:  Rosling H., Rosling Rönnlund A., Rosling O., (2018), ”Factfulness”, Natur & Kultur,  ISBN 978-91-27-14994-6

  • 58.
    Ferritsius, Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. StoraEnso.
    Hill, Jan
    QualTech AB.
    Ferritsius, Johanna
    Some insights regarding standards and common practice2015Conference paper (Refereed)
  • 59.
    Ferritsius, Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. StoraEnso Paper Kvarnsveden Mill.
    Rundlöf, Mats
    Capisco.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The Independent State of Fibres in Relation to the Mechanical Pulping World2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    Paper and wood are highly inhomogeneous materials. When describing the mechanical pulp itself, we allcommonly ignore that it is an inhomogeneous material. We have realized that just a very small fraction of stifffibres are enough to impair the printability of the product. In this paper we share some of our reflections andattempts how to describe the inhomogeneous nature of mechanical pulps. A method denoted BIN is underdevelopment based on independent common factors and paying attention to the inhomogeneity of the material.The method may give the possibility to describe the nature of TMP/CTMP/SGW in a more relevant way comparedto todays practice. Hence the paper and board makers may be able to deliver more uniform products at “goodenough” level at lower costs. We have realized that because a method or opinion is well spread (sometimes usedby almost everybody) it does not necessarily mean that it is relevant. A couple of myths have been reflected uponand in our opinion they remain just myths. By putting more attention to reality and describing mechanical pulp asan inhomogeneous material we hope to be able to rid ourselves and the mechanical pulping community of someother myths circulating (some still to be discovered).

  • 60.
    Ferritsius, Olof
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso Kvarnsveden.
    Rundlöf, Mats
    Capisco.
    Reyier Österling, Sofia
    Dalarna University.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Heterogeneity of Thermomechanical and Chemi-thermomechanical Pulps described with distributions of an independent common bonding factor on particle level2022In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 17, no 1, p. 763-784Article in journal (Refereed)
    Abstract [en]

    Particles in mechanical pulp show a wide variety but are commonly described using averages and/or collective properties. The authors suggest using distributions of a common bonding factor, BIND (Bonding INDicator), for each particle. The BIND-distribution is based on factor analysis of particle diameter, wall thickness, and external fibrillation of several mechanical pulps measured in an optical analyser. A characteristic BIND-distribution is set in the primary refiner, depending on both wood and process conditions, and remains almost intact along the process. Double-disc refiners gave flatter distributions and lower amounts of fibres with extreme values than single-disc refiners. More refining increased the differences between fibres with low and high BIND. Hence, it is more difficult to develop fibres with lower BIND. Examples are given of how BIND-distributions may be used to assess energy efficiency, fractionation efficiency, and influence of raw material. Mill scale operations were studied for printing-grade thermomechanical pulp (TMP), and board-grade chemi-thermomechanical pulp (CTMP), both from spruce.

  • 61.
    Ferritsius, Rita
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso Paper Kvarnsveden Mill.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Capisco, Norrköping.
    Daniel, Geoffrey
    SLU, Dept. of Forest Products/Wood Science, Uppsala.
    Mörseburg, Kathrin
    Paper and Fibre Research Institute (PFI), Trondheim Norway.
    Fernando, Dinesh
    SLU, Dept. of Forest Products/Wood Science, Uppsala.
    Development of Fiber Properties in Full Scale HC and LC Refining2016In: TAPPI conference proceedings, TAPPI Press, 2016Conference paper (Refereed)
  • 62.
    Ferritsius, Rita
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso Paper Kvarnsveden Mill, Borlänge.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper, Norrköping.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Daniel, Geoffrey
    Mörseburg, Kathrin
    Fernando, Dinesh
    Development of fibre properties in mill scale high- And low consistency refining of thermomechanical pulp (Part 1)2020In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 35, no 4, p. 589-599Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate changes in fibre properties with high (HC)- and low consistency (LC) refining of TMP and determine how these contribute to tensile index. Two process configurations, one with only HC refining and another with HC refining followed by LC refining were evaluated in three TMP mainline processes in two mills using Norway spruce. An increase in tensile index for a given applied specific energy was similar for all LC refiners in the three lines, despite differences in the fibre property profiles of the feed pulps. Compared with only HC refined pulps at a given tensile index, HC+LC refined pulps had greater fibre wall thickness, similar fibre length, strain at break and freeness, but lower light scattering coefficient, fibre curl and external fibrillation. The degree of internal fibrillation, determined by Simons' stain measurements, was similar for both configurations at a given tensile index. The results indicate that the increase in tensile index in LC refining is largely influenced by a decrease in fibre curl and in HC refining by peeling of the fibre walls. Compared at a given tensile index, the shive content (Somerville mass fraction) was similar for both HC+LC and HC refining. 

  • 63.
    Fiskari, Juha
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Derkacheva, Olga
    St Petersburg State Univ Ind Technol & Design, Mgher Sch Technol & Energy, Str Ivana Chernikh 4, St Petersburg, Russia..
    Kulomaa, Tuomas
    Univ Helsinki, Dept Chem, Chem Sci, AI Virtasen Aukio 1, FI-00014 Helsinki, Finland..
    Quick non-destructive analysis of condensed lignin by ftir. part 2. pulp samples from acid sulfite cooking2021In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 55, no 3-4, p. 263-270Article in journal (Refereed)
    Abstract [en]

    In our previous work, we demonstrated how lignin condensation and precipitation taking place in kraft pulping can be detected and even quantified by Fourier Transform Infrared (FTIR) spectroscopy. Because lignin reactions in acid sulfite pulping are very different from those occurring during kraft cooking, a new analysis method is proposed to rapidly analyze the condensed lignin in acid sulfite pulp. This kind of analysis is useful for sulfite pulp mills to detect the elevated risk of black cook. This paper presents and discusses the novel method using FTIR spectroscopy to rapidly analyze lignin condensation in softwood pulp samples from acid sulfite processes. Several softwood pulp samples from acid sulfite pulping at varying levels of condensation were included in this research. According to the results, FTIR spectroscopy allows indirect quantification of lignin condensation in a difficult matrix of wood constituents, such as in incompletely delignified acid sulfite pulp.

  • 64.
    Fiskari, Juha
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Valmet.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso.
    Osong, Sinke H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Persson, A.
    Höglund, T.
    Immerzeel, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Deep eutectic solvent delignification to low-energy mechanical pulp to produce papermaking fibers2020In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 15, no 3, p. 6023-6032Article in journal (Refereed)
    Abstract [en]

    A novel process based on low-energy mechanical pulp and deep eutectic solvents (DESs) was evaluated with the goal of producing fibers suitable for papermaking. Ideally, these fibers could be produced at much lower costs, especially when applied to an existing paper mill equipped with a thermomechanical pulp (TMP) production line that was threatened with shutdown due to the decreasing demand for wood-containing paper grades. The efficiency of DES delignification in Teflon-coated autoclaves and in a specially designed non-standard flow extractor was evaluated. All tested DESs had choline chloride ([Ch]Cl) as the hydrogen bond acceptor. Lactic acid, oxalic acid, malic acid, or urea acted as hydrogen bond donors. The temperatures and times of the delignification tests were varied. Chemical analysis of the pulp samples revealed that DESs containing lactic acid, oxalic acid, or urea decreased the lignin content by approximately 50%. The DES delignification based on [Ch]Cl and urea exhibited good hemicellulose retention while DES systems based on organic acids resulted in varying hemicellulose losses. The [Ch]Cl / urea mixture did not appear to be corrosive to stainless steel, which was another advantage of this DES system. 

  • 65.
    Fiskari, Juha
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Valmet AB.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Stora Enso Paper, Kvarnsvedens Mill.
    Osong, Sinke H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Persson, Anders
    Valmet AB.
    Höglund, Tomas
    Valmet AB.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Deep Eutectic Solvent Treatment to Low-Energy TMP to Produce Fibers for Papermaking2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    The aim of this research was to gain a better understanding on whether a novel process based on low-energy thermo-mechanical pulp (TMP) process followed by a chemical treatment with deep eutectic solvents (DESs) could produce fibers suitable for papermaking. In full scale production, these fibers could be produced at a much lower capital and operational costs, especially when utilizing existing TMP plants which are under the threat to be shut down or have already been shut down due to a decreasing demand for newsprint and other wood-containing papers.The efficiency of several DES treatments under various temperatures and times were evaluated by carrying out experiments in standard Teflon-lined autoclaves. A few tests were also performed in a unique nonstandard flow extractor. Pulp samples were characterized for their cellulose, hemicellulose and lignin contents. Moreover, tensile index was measured both before and after pulp refining. Depending on the solvent, the response of mechanical pulp varied, especially in terms of hemicellulose dissolution. Lactic acid, oxalic acid and urea, all in combination with choline chloride ([Ch]Cl) as the hydrogen bond acceptor, dissolved about 50% of the lignin of the low-energy TMP fibers under the tested conditions. The mixture of malic acid and [Ch]Cl was less effective in lignin dissolution. The mixture of urea and [Ch]Cl exhibited only a minor loss in hemicellulose content, when compared to the other tested DESs. Although 50% of the lignin was dissolved with minor loss in hemicellulose no improvement in tensile strength was observed, as it was rather the opposite. Another benefit with the mixture of urea and [Ch]Cl was that this DES did not appear to be corrosive to stainless steel. All other tested DESs—which were also quite acidic—were observed to be corrosive. Moreover, this DES-related corrosion was found to intensify at elevated temperatures.When chips were used as starting material with otherwise the same conditions almost no lignin was dissolved. This suggests that low-energy mechanical pulp is likely to be a good starting material for extracting lignin using DESs.

  • 66.
    Fiskari, Juha
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Kilpeläinen, Petri
    Acid sulfite pulping of Acacia mangium and Eucalyptus pellita as a pretreatment method for multiproduct biorefineries2021In: Asia-Pacific Journal of Chemical Engineering, ISSN 1932-2135, E-ISSN 1932-2143, Vol. 16, no 6Article in journal (Refereed)
    Abstract [en]

    Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries. 

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  • 67.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Green materials for inkjet printing of 2D materials and transparent electronics2018Conference paper (Other (popular science, discussion, etc.))
  • 68.
    Forsström, Jennie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Eriksson, Malin
    Wågberg, Lars
    A new technique for evaluating ink–cellulose interactions: initial studies of the influence of surface energy and surface roughness2005In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 19, no 9, p. 783-798Article in journal (Refereed)
    Abstract [en]

    Ink–cellulose interactions were evaluated using a new technique in which the adhesion properties between ink and cellulose were directly measured using a Micro-Adhesion Measurement Apparatus (MAMA). The adhesion properties determined with MAMA were used to estimate the total energy release upon separating ink from cellulose in water. The total energy release was calculated from interfacial energies determined via contact angle measurements and the Lifshitz–van der Waals/acid–base approach. Both methods indicated spontaneous ink release from model cellulose surfaces, although the absolute values differed because of differences in measuring techniques and different ways of evaluation. MAMA measured the dry adhesion between ink and cellulose, whereas the interfacial energies were determined for wet surfaces. The total energy release was linked to ink detachment from model cellulose surfaces, determined using the impinging jet cell. The influences of surface energy and surface roughness were also investigated. Increasing the surface roughness or decreasing the surface energy decreased the ink detachment due to differences in the molecular contact area and differences in the adhesiom properties.

  • 69.
    Fridén, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Stattin, Andreas
    Löfgren, Göran
    Online operator decision support and optimization for sack paper production by PAT based process automation2008In: Third pan-European PAT conference: Oct 7-8, Gothenburg, Sweden, 2008Conference paper (Other academic)
  • 70.
    Friman, Linda
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The influence of Iron and Some Other Metals on the Optical Properties of Thermomechanical Pulps2004Licentiate thesis, comprehensive summary (Other academic)
  • 71.
    Friman, Linda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Agnemo, Roland
    Tannin-iron impregnated thermomechanical pulp: Part I: Effects of extractions and heat on brightness2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 2, p. 229-236Article in journal (Refereed)
    Abstract [en]

    Tannins are polyphenolic compounds found mainly in bark. When reacting with iron, they form strongly coloured complexes, which through contamination from the bark may induce a brightness decrease of mechanical pulps. Wood itself contains phenolic compounds, which can form coloured complexes with iron. We have investigated gallotannin as a model for metal-binding sites in the pulp. The behaviour of tannin-iron complexes in solution and in pulp has been studied. In aqueous solution, the tannin-iron complexes can be decolourised by the addition of diethylenetriaminepentaacetic acid (DTPA). The colour of the tannin-iron complexes was very pH-dependent. Thus in solution, these were decolourised at low pH and at high pH the spectral characteristics were changed substantially. We have studied the effects on brightness and heatinduced brightness loss of the impregnation of thermomechanical pulp (TMP) with 30 parts per million iron (ppm i.e. mg/kg) either as iron or tannin-iron as well as the possibility to decrease such effects by using various solvent extractions. The tannin-iron impregnation causes a decrease in ISO-brightness of approximately 3% and an increase in the light absorption coefficient (k) by approximately 2 m(2)/kg at the tannin-iron absorbance maximum. 565 run. These effects are approximately ten times higher than those observed for the Pulp only impregnated with iron. Extraction with 1% by weight of DTPA provides a way to reduce the brightness decrease induced by the tanniniron complexes and the observed decrease can be attributed to removal of iron from the pulp. Acid extraction was the most efficient way to reduce the iron content in the pulps and to decoulorise the tannin-iron impregnated pulp. However, after acid extraction of iron impregnated Pulps, new chromophores were evidently formed. Addition of the reducing agent, sulphite, to extractions had no effect on the iron removal or the brightness of the impregnated pulps. The heat-induced brightness loss is not influenced by the addition of tannin-iron or iron. The brightness loss caused by heat was lower for pulps extracted with DTPA.

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  • 72.
    Friman, Linda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Högberg, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Agnemo, Roland
    Tannin-iron impregnated thermomechanical pulp: Part II: Bleachability and brightness reversion2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 4, p. 525-531Article in journal (Refereed)
    Abstract [en]

    Tannins are polymeric, phenolic constituents found in the bark of pine and spruce. When reacting with iron ions, tannins form strongly coloured complexes. Thus, the presence of bark in the mechanical pulping process leads to decreased brightness of the pulp. In order to evaluate the effects of the presence of iron on the properties of pulp, we have impregnated thermomechanical pulp (TMP) with 30 parts per million (ppm i.e. mg/kg) iron either as Fe3+ or as tannin-iron complexes and studied how such treatments affect bleachability and heat-induced brightness reversion. The bleaching agents studied are hydrogen peroxide and sodium dithionite. Treatment of the tannin-iron impregnated pulp with 1% by weight of diethylenetriaminepentaacetic acid (DTPA) before bleaching with 4% hydrogen peroxide almost eliminated the brightness loss caused by the impregnation. Such a treatment also removed all of the added iron from both the tannin-iron and FeCl3 impregnated pulps. Approximately 5% more of the added peroxide was required for oxidation of the tannins in the tannin-iron impregnated pulp. Contrary to what was observed with peroxide bleaching, dithionite bleaching did not reduce the amount of iron in the pulps. Instead, the added iron and tannin-iron negatively affected the dithionite bleaching, even if the pulps were extracted with DTPA before bleaching. It should therefore be advantageous to first bleach with peroxide, which removes most of the iron, and then with dithionite. Compared with dithionite, peroxide yields a more efficient bleaching. The reason for this is that the former reduces the light absorption coefficient, the k-value, more efficiently in the whole visible spectrum, whereas dithionite reduces it mainly at shorter wavelengths. In our experiments, the addition of tannin-iron or FeCl3 to the untreated pulp did not increase heat-induced brightness reversion. This is Supported by the fact that although extraction of the samples with DTPA before bleaching lowered the iron content slightly, it-did not affect the brightness reversion. The initial brightness reversion of the dithionite bleached pulps was larger than that observed for the peroxide bleached pulps.

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  • 73.
    Fält, Susanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Model Studies of Cellulose Fibers and Films and Their Relation to paper Strenght2003Licentiate thesis, comprehensive summary (Other academic)
  • 74.
    Fält, Susanna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Vesterlind, Eva-Lotta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Swellling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers2003In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, no 19, p. 7895-7903Article in journal (Refereed)
    Abstract [en]

    Cellulose model films with different charge densities were prepared by spin-coating dissolved cellulose in N-methylmorpholine-N-oxide onto SiO2 surfaces. The swelling of the model cellulose films due to exposure to solutions of different electrolytes and at different ionic strengths and pH values were studied using QCM-D (quartz crystal microbalance with dissipation monitoring). Results show that at pH 5, there is a swelling of the film at a low electrolyte concentration (10(-4)-10(-2) M), whereas the deswelling of the film was observed at a high electrolyte concentration (10(-1)-1 M). A considerable swelling of the films is seen when they are treated with deionized water with an increasing pH. The swelling of the films is accompanied by an increase in dissipation, that is, a softening of the material, and the deswelling by a decrease in dissipation, that is, a stiffening of the material. Furthermore, exposure of the films to solutions of different electrolytes affected the swelling of the layer. In this respect, the swelling response of Na2SO4 differs from that of NaCl and CaC1(2) by showing simultaneously high swelling and low dissipation values. The results also show that the rate of swelling reaches its lowest value as the electrolyte concentration reaches the detected limit for the deswelling. The QCM-D results are compared to the swelling of the corresponding carboxymethylated fibers, where a similar behavior was found. However, for the fibers a marked deswelling occurred at a high electrolyte concentration, but only a minor deswelling of the cellulose film was observed. This difference between the materials can be ascribed to noncovalent bonds within the film that will not reform when the swelling forces are decreased at high electrolyte concentrations. A direct measurement of the thickness changes was performed using atomic force microscopy, which shows that the change in frequency measured with QCM-D for the films treated with different NaCl electrolyte concentrations corresponds to changes of 1-2%.

  • 75.
    Fält, Susanna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Vesterlind, Eva-Lotta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Larsson, P.T.
    Model films of cellulose II - Improved preparation method and characterization of the cellulose film2004In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 2, p. 151-162Article in journal (Refereed)
    Abstract [en]

    An optimization study of the preparation of spin-coated cellulose model films from the NMMO/DMSO system on silicon wafers has been made. The study shows that the cellulose concentration in the solution determines the cellulose film thickness and that the temperature of the solution affects the surface roughness. A lower solution temperature results in a lower surface roughness at cellulose concentrations below 0.8%. Using the described method, it is possible to prepare films with thicknesses of 30-90 nm with a constant surface roughness by changing the cellulose concentration, i.e. by dilution with DMSO. On these films, water has a contact angle less than 20degrees and about 50% of the material can, according to CP/MAS C-13-NMR spectroscopy on corresponding fibrous material, be considered to consist of crystalline cellulose II type material. It has further been shown that AFM can be used to determine the thickness of cellulose films, in both dry and wet states. In this method, the difference in height between the top surface and the underlying wafer has been measured at an incision made into the cellulose film. The cellulose films have also been spin-coated with the same technique as on the silicon oxide wafer onto the crystal in a quartz crystal microbalance (QCM). These model films were found to be suitable for swelling measurements with the QCM. The films were very stable during this type of measurement and films with different amounts of charges gave different swelling responses depending on their charges. As expected, films with a higher charge showed a higher swelling.

  • 76.
    Gaynullin, Bakhram
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. SenseAir AB.
    Implementation of low cost methane sensing IR-technology in bio refinery industry2015Conference paper (Refereed)
  • 77.
    Gorski, Dmitri
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    ATMP Process: Improved Energy Efficiency in TMP Refining Utilizing Selective Wood Disintegration and Targeted Application of Chemicals2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on the novel wood chip refining process called AdvancedThermomechanical Pulp (ATMP) refining. ATMP consists of mechanical pretreatmentof chips in Impressafiner and Fiberizer prior to first stage refining atincreased intensity. Process chemicals (this study was concentrated on hydrogenperoxide and magnesium hydroxide) are introduced into the first stage refiner.It is known that the use of chemicals in TMP process and first stage refining atelevated intensity can reduce the energy demands of refining. The downside is thatthey also alter the character of the produced pulp. Reductions in fibre length andtear index are usually the consequences of refining at elevated intensity. Additionof chemicals usually leads to reduction of the light scattering coefficient. Usingstatistical methods it was shown that it is possible to maintain the TMP character ofthe pulp using the ATMP process. This is explained by a separation of thedefibration and the fibre development phases in refining. This separation allowsdefibration of chips to fibres and fibre bundles without addition of chemicals orincrease in refining intensity. Chemicals are applied in the fibre developmentphase only (first stage refiner). The energy demand in refining to reach tensileindex of 25 Nm/g was reduced by up to 1.1 MWh/odt (42 %) using the ATMPprocess on Loblolly pine. The energy demand in refining of White spruce, requiredto reach tensile index of 30 Nm/g, was reduced by 0.65 MWh/odt (37%).Characterizations of individual fibre properties, properties of sheets made fromlong fibre fractions and model fibre sheets with different fines fractions werecarried out. It was established that both the process equipment configuration (i.e.the mechanical pre‐treatment and the elevated refining intensity) and the additionof process chemicals in the ATMP process influence fibre properties such as external and internal fibrillation as well as the amount of split fibres. Improvementof these properties translated into improved properties of sheets, made from thelong fibre fractions of the studied pulps. The quality of the fines fraction alsoimproved. However, the mechanisms of improvement in the fines quality seem tobe different for fines, generated using improved process configuration andaddition of process chemicals. The first type of fines contributed to better bondingof model long fibre sheets through the densification of the structure. Fines whichhave been influenced by the addition of the process chemicals seemed in additionto improve bonding between long fibres by enhancing the specific bond strength.The improved fibre and fines properties also translated into better airpermeability and surface roughness of paper sheets, properties which areespecially important for supercalendered (SC) printing paper. The magnitude offibre roughening after moistening was mainly influenced by the processequipment configuration while the addition of process chemicals yielded lowestfinal surface roughness due to the lowest initial surface roughness. There was nodifference in how fines fractions from the studied processes influenced the fibreroughening. However, fines with better bonding yielded model fibre sheets withhigher PPS, probably due to their consolidation around fibre joints. Hence, thedecrease in PPS can probably be attributed to the improvements in the long fibrefraction properties while the improvement of fines quality contributed to thereduction of air permeability.The process chemicals, utilized in the ATMP process (Mg(OH)2 and H2O2) alsoproved to be an effective bleaching system. Comparable increases in brightnesscould be reached using the ATMP process and conventional tower bleaching.Maximum brightness of the pulp was reached after approximately 10 minutes ofhigh‐consistency storage after refining or 40 minutes of conventional bleaching.This study was conducted using a pilot scale refiner system operated as a batchprocess. Most of the experiments were performed using White spruce (Piceaglauca). In Paper I, Loblolly pine (Pinus taeda) was used. It is believed that theresults presented in this thesis are valid for other softwood raw materials as well,but this limitation should be considered.

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  • 78.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hill, J
    Axelsson, P
    Johansson, L
    Mg(OH)(2)-based hydrogen peroxide refiner bleaching: influence of extractives content in dilution water on pulp properties and energy efficiency2010In: Appita journal, ISSN 1038-6807, Vol. 63, no 3, p. 218-225Article in journal (Refereed)
    Abstract [en]

    Two refiner bleaching trials on TMP and SGW rejects using magnesium hydroxide and hydrogen peroxide were conducted in a reject refiner. Clear filtrate from a disc filter was used as dilution water during the first trial (normal mill operation) and fresh water was used during the second trial. Refiner bleached pulp had approximately nine %ISO higher brightness than reference pulps in both trials using a peroxide charge of 25 kg/t pulp. The brightness gain increased to 12 %ISO after high consistency storage at 755 degrees C for 30 minutes. The bleached pulp from the first trial had 10% lower tensile index compared to reference at similar refining energy. The extractives content on the surfaces of the bleached fibres (surface coverage measured by ESCA) was 20% higher compared to the unbleached reference pulp when clear filtrate was used as dilution water. Within this surface extractives content increase, the increase of triglycerides and steryl esters was largest, almost doubling in value. Acetone extraction of the pulps led to higher apparent sheet strength. The increase was equal for both the reference and the bleached samples but the bleached pulp still had inferior strength properties compared to the reference pulp. When a second trial was carried out with fresh water as dilution, much less difference in the strength properties of bleached and unbleached pulp was observed.

    It is suggested that addition of alkali to the refiner caused extractives in the clear filtrate to destabilise and re-deposit onto fibre surfaces. The fact that removal of extractives with acetone did not bring the strength of bleached pulp up to the level of the reference pulp suggests that extractives may have influenced the fibre development process of the bleached pulp fibres in the refiner.

  • 79.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Johansson, L
    Paper and Fibre Research Institute (PFI), Trondheim, Norway.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Refiner bleaching in a peroxide-based ATMP process compared with conventional bleaching2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 3, p. 275-281Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare refiner bleaching with conventional laboratory bleaching by means of hydrogen peroxide and magnesium hydroxide. Refiner bleaching in this study was a part of the ATMP (advanced thermo mechanical pulping) process, in which bleaching chemicals are added to the first stage refiner. Unbleached reference pulp which underwent similar mechanical treatment as refiner bleached pulp was used for laboratory bleaching. Bleaching efficiency was found to be almost equal for pilot scale refiner bleaching and conventional laboratory bleaching. A brightness increase of 10 ISO was reached with addition of 26 kg t -1 hydrogen peroxide leading to a final brightness of 66 ISO using both methods. Slightly more COD (52kg t -1 compared with 46 kg t -1) was generated in refiner bleaching compared with conventional laboratory bleaching to equal brightness with the same chemicals added. © 2012 by Walter de Gruyter Berlin Boston 2012.

  • 80.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Johansson, Lars
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Bleaching efficiency in peroxide-based ATMP process compared to conventional bleachingManuscript (preprint) (Other academic)
  • 81.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Kure, Kjell-Arve
    Hill, Jan
    Using ATMP Technology to Improve Energy Efficiency and Pulp Quality in Production of SC magazine PaperManuscript (preprint) (Other (popular science, discussion, etc.))
  • 82.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Mörseburg, Kathrin
    Paper & Fibre Res Inst PFI, NO-7491 Trondheim, Norway.
    Axelsson, Patrik
    Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Peroxide-based ATMP refining of spruce: energy efficiency, fibre properties and pulp quality2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 1, p. 47-63Article in journal (Refereed)
    Abstract [en]

    Pilot scale refining of White spruce using a modified TMP refining process (ATMP - Advanced Thermomechanical Pulp) was studied. ATMP combines selective wood disintegration by mechanical pretreatment and refining at elevated intensity with chemical treatment after defibration (in this study hydrogen peroxide, alone and in combination with alkali). The electrical energy efficiency and pulp quality using ATMP were evaluated and compared to a conventional TMP process. One goal was to retain the combination of optical properties and strength of typical TMP. Fibre properties (structural dimensions, external and internal fibre development) as well as the amount of split fibres resulting from TMP and ATMP processes were compared. The results indicate an electrical energy efficiency improvement potential of 0.65 MWh/odt (34%) at tensile index 30 N.m/g of ATMP compared to reference TMP. All ATMP pulps retained their TMP character, i.e. the relationships between light scattering coefficient, density, elongation properties and strength that are important for printing paper. ATMP had a significantly lower content of shives and higher external and internal fibre development compared to TMP at equal energy application. The long fibre fraction of ATMP also contained significantly higher amount of split fibres. The brightness of ATMP produced with addition of hydrogen peroxide (28 kg/odt) and magnesium hydroxide (14 kg/odt) was 14 ISO % higher compared to TMP.

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  • 83.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Mörseburg, Kathrin
    Paper & Fibre Res Inst PFI, NO-7491 Trondheim, Norway.
    Johansson, Lars
    Paper & Fibre Res Inst PFI, NO-7491 Trondheim, Norway.
    Role of equipment configuration and process chemicals in peroxide-based ATMP refining of spruce2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 2, p. 232-247Article in journal (Refereed)
    Abstract [en]

    Pilot scale refining of White spruce using ATMP (Advanced Thermomechanical Pulp) process was studied. Conventional TMP process, where first stage refiner was equipped with low-intensity segments, was the first reference used in the trial. Another reference was a TMP process with modified equipment configuration (ATMP (aq.)). Modifications consisted of mechanical pre-treatment of chips in Impressafiner and Fiberizer prior to first stage relining at elevated intensity. TMP and ATMP (aq.) references were compared to the ATMP (Mg+P) process which had the same equipment configuration as the ATMP (aq.) and where fibre development in refining was further enhanced using hydrogen peroxide and magnesium hydroxide. The main goal of the trial was to separate the effects of equipment configuration from the effects of process chemicals in ATMP refining. Impact on the development of individual fibre properties. properties of fines fraction. whole pulp properties and laboratory sheet properties was studied and linked to the energy efficiency in refining Electrical energy demand, needed to reach the tensile index of 30 Nm/g could be reduced by 0.42 MWh/odt (28 %) compared to conventional TMP process when mechanical pre-treatment and refining at elevated intensity (ATMP (aq.)) were utilized. Relining energy reduction was 0.49 MWh/odt (33 %) when ATMP (Mg+P) concept was used. The content of shives was considerably lower for ATMP and ATMP (aq.) pulps compared to the TMP reference. ATMP (Mg+P) also had higher brightness compared to the references, an increase by 10 ISO % for a 26 kg/odt hydrogen peroxide charge.

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  • 84.
    Gradin, Per A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Isaksson, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Nyström, Staffan K
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Graham, D
    Kao, D
    Knight, B
    Acoustic Emission applied to mechanically loaded Paper2004In: EWGAE (European Working Group on Acoustic Emission) 2004 proceedings, 2004, p. 423-431Conference paper (Refereed)
  • 85.
    Granberg, Hjalmar
    et al.
    Innventia AB.
    Gustafsson Coppel, Ludovic
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Eita, M.
    Innventia AB, Box 5604, 104 86 Stockholm, Sweden.
    de Mayolo, E. A.
    Innventia AB, Box 5604, 104 86 Stockholm, Sweden.
    Arwin, Hans
    Innventia AB, Box 5604, 104 86 Stockholm, Sweden.
    Wågberg, Lars
    Innventia AB, Box 5604, 104 86 Stockholm, Sweden.
    Dynamics of moisture interaction with polyelectrolyte multilayers containing nanofibrillated cellulose2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 496-499Article in journal (Refereed)
    Abstract [en]

    Recent findings have shown that it is possible to use the Layer-by-Layer technique to create nanofibrillated cellulose / polyethyleneimine interference films whose colour change with relative humidity. This study uses different optical models to describe spectral ellipsometry measurements data of interference films and how the film properties alter in dry and humid environments. The results indicate that water condensation initially is filling the surface pores within seconds whereas relaxation of the film to adjust to the added water is a slower process that reaches a steady state after ≈20 min. The maximum swelling ratio of the LbL films is almost independent of the number of layers within the film, but decreases considerably by crosslinking via heat treatment. The films show a distinct birefringence with optical axis perpendicular to the surface. Analysis of the moisture response with different optical models indicates that the films swell uniformly in the thickness direction with no separate water film on top. The results provide important understanding for the design of NFC based LbL films for visual moisture sensors and interactive security paper. 

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  • 86. Gurnagul, Norayr
    et al.
    Howard, R.C.
    Zou, Xuejun
    Uesaka, Tetsu
    Page, Derek
    THE MECHANICAL PERMANENCE OF PAPER - A LITERATURE-REVIEW1993In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 19, no 4, p. J160-J166Article in journal (Refereed)
  • 87.
    Gustafsson Coppel, Ludovic
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Measuring and producing high perceived whiteness2011In: Paper Technology, ISSN 0306-252X, Vol. 52, no 1, p. 15-17Article in journal (Other academic)
  • 88.
    Gustafsson Coppel, Ludovic
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Whiteness and Fluorescence in Layered Paper and Board: Perception and Optical Modelling2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is about modelling and predicting the perceived whiteness of plain paper from the paper composition, including fluorescent whitening agents. This involves psychophysical modelling of perceived whiteness from measurable light reflectance properties, and physical modelling of light scattering and fluorescence from the paper composition.

    Existing models are first tested and improvements are suggested and evaluated. A colour appearance model including simultaneous contrast effects (CIECAM02-m2), earlier tested on coloured surfaces, is successfully applied to perceived whiteness. An extension of the Kubelka-Munk light scattering model including fluorescence for turbid media of finite thickness is successfully tested for the first time on real papers. It is extended to layered constructions with different layer optical properties and modified to enable parameter estimation with conventional d/0° spectrophotometers used in the paper industry. Lateral light scattering is studied to enable simulating the spatially resolved radiance factor from layered constructions, and angle-resolved radiance factor simulations are performed to study angular variation of whiteness.

    It is shown that the linear CIE whiteness equation fails to predict the perceived whiteness of highly white papers with distinct bluish tint. This equation is applicable only in a defined region of the colour space, a condition that is shown to be not fulfilled by many commercial office papers, although they appear white to most observers. The proposed non-linear whiteness equations give to these papers a whiteness value that correlates with their perceived whiteness, while application of the CIE whiteness equation outside its region of validity overestimates perceived whiteness.

    It is shown that the fluorescence efficiency of FWA is essentially dependent only on the ability of the FWA to absorb light in its absorption band. Increased FWA concentration leads accordingly to increased whiteness. However, since FWA absorbs light in the violet-blue region of the electromagnetic spectrum, the reflectance factor decreases in that region with increasing FWA amount. This violet-blue absorption tends to give a greener shade to the paper and explains most of the observed greening and whiteness saturation at larger FWA concentrations. A red-ward shift of the quantum efficiency is observed with increasing FWA concentration, but this is shown to have a negligible effect on the whiteness value. The results are directly applicable to industrial applications for better instrumental measurement of whiteness and thereby optimising the use of FWA with the goal to improve the perceived whiteness.

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  • 89.
    Gustafsson Coppel, Ludovic
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Open source Monte carlo simulation platform for particle level simulation of light scattering from generated paper structures2009In: Papermaking Research Symposium, 2009Conference paper (Refereed)
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  • 90.
    Gustafsson Coppel, Ludovic
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Neuman, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lateral light scattering in paper - MTF simulation and measurement2011In: Optics Express, E-ISSN 1094-4087, Vol. 19, no 25, p. 25181-25187Article in journal (Refereed)
    Abstract [en]

    The modulation transfer function (MTF) of 22 paper samples is computed using Monte Carlo simulations with isotropic or strongly forward single scattering. The inverse frequency at half maximum of the MTF (kp) is found inappropriate as a single metric for the MTF since it is insensitive to the shape of the modeled and simulated MTF. The single scattering phase function has a significant impact on the shape of the MTF, leading to more lateral scattering. However, anisotropic single scattering cannot explain the larger lateral scattering observed in paper. It is argued that the directional inhomogeneity of paper requires a light scattering model with both the phase function and scattering distances being dependent on the absolute direction.

  • 91. Gustafsson, Per- Johan
    et al.
    Niskanen, Kaarlo
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Paper as an engineering material2021In: Mechanics of Paper Products, Walter de Gruyter, 2021, p. 5-28Chapter in book (Other academic)
  • 92.
    Hellström, Lisbeth
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    On the wood chipping process: a study on basic mechanisms in order to optimize chip properties for pulping2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In both the chemical and mechanical pulping process, the logs are cut into wood chips by a disc chipper before fibre separation. To make the wood chipping process more efficient, one have to investigate in detail the coupling between process parameters and the quality of the chips. One objective of this thesis was to obtain an understanding of the fundamental mechanisms behind the creation of wood chips. Another objective with the thesis was to investigate whether it was possible to, in a way tailor the chipping process so as to reduce the energy consumption in a following mechanical refining process.

    Both experimental and analytical/numerical approaches have been taken in this work. The first part of the experimental investigations, were performed with an in-house developed chipping device and a digital speckle photography equipment.

    The results from the experimental investigation showed that the friction between the log and chipping tool is probably one crucial factor for the chip formation. Further more it was found that the indentation process is approximately self-similar, and that the stress field over the entire crack-plane is critical for chip creation.

    The developed analytical model predicts the normal and shear strain distribution and to be more specific, the model can predict the compressive stresses parallel to the fibre direction for an assumed linear elastic and orthotropic material. The analytical distributions were found to be in reasonable agreement with the corresponding distributions obtained from a finite element analysis.

    To be able to study the chipping process under realistic conditions, which for example means to use chipping rates representative for a real wood chipper, a laboratory chipper was developed. Details regarding the chipper and how to evaluate the force measurements are given together with an example of how the force on the cutting tool (the knife) varies with time during cutting.

    To investigate the influence of a certain chipping process parameter, the chips were after production in the laboratory chipper, refined in a pilot refiner during conditions optimized for TMP (thermomechanical pulp) and CTMP (chemithermomechanical pulp) processes. It was concluded that the details concerning the chip process had a large impact on e.g. the energy consumption in both first stage and second stage refining. Results showing this are given in this thesis.

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  • 93.
    Hellström, Lisbeth M
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A device for studying wood chipping under realistic conditions2009In: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, p. 252-254Conference paper (Refereed)
    Abstract [en]

    It seems to be a consensus in the papermaking society that chip quality is very much a matter of a narrow thickness distribution. Much effort has been spent on studying the influence of certain process parameters on the thickness distribution of chips. However, when these studies have been performed in a laboratory environment, the conditions have been far from realistic when it comes to for instance cutting rates. In this paper a laboratory chipper is presented, which has been developed to admit chipping at rates used in the industry. The knife holder is instrumented in such a way that moments and forces in three directions can be measured. Results from tests, where the cutting rate is varied, is presented and it is concluded that the laboratory chipper is a versatile tool in the process of increasing the understanding of the chipping process.

     

     

  • 94.
    Hellström, Lisbeth M
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A Method for Experimental Investigation of the Wood Chipping Process2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 3, p. 339-342Article in journal (Refereed)
    Abstract [en]

    SUMMARY: To be able to formulate criteria’s for determining the onset of the creation of a wood chip; it is desirable to be able to study the deformation fields in a vicinity of the edge of the chipping tool. To that end, an experimental setup has been developed in which the chipping can be performed under very well defined conditions. In this setup it is possible to control the rate of indentation of the chipping tool and also to measure the force on the tool. The setup admits also that the angle of the wood specimen with respect to the cutting plane can be varied in both a horizontal and a vertical plane. To determine the deformations, a Digital Speckle Photography (DSP) equipment is used, which together with image processing software makes it possible to determine the strain field on the surface of the wood specimen. One observation that can be made in these studies is that prior to the creation of a chip, there is a localization of strains in a thin region starting from the edge of the tool and directed parallel to the grain. Another observation made during the experimental work is that there exist different types of fracture processes, each giving different chip thicknesses.

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  • 95.
    Hellström, Lisbeth M
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Isaksson, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Eriksson, Kjell
    Luleå University of Technology.
    An Analytical and Numerical Study of some aspects of the Wood Chipping Process2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 2, p. 225-230Article in journal (Refereed)
    Abstract [en]

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

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    Hellström et al: An analytical and numerical study of some aspects of the wood chipping process. NPPRJ 2009 24 2 pp 225-230
  • 96.
    Hellström, Lisbeth Maria
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A Study of Fracture processes in Wood Chipping2008In: 6th Fundamental Mechanical Pulp Research Seminar, Espoo: KCL Oy Keskuslaboratorio - Centrallaboratorium AB , 2008Conference paper (Refereed)
  • 97.
    Hellström, Pia
    et al.
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Heijnesson-Hultén, Anette
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Håkansson, Helena
    Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden.
    Germgård, Ulf
    Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden.
    Fenton pre-treated microfibrillated cellulose evaluated as a strength enhancer in the middle ply of paperboard2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 732-740Article in journal (Refereed)
    Abstract [en]

    Microfibrillated celluloses (MFCs), produced by various pre-treatments of a fully bleached birch kraft pulp, were evaluated as strength enhancers in test sheets representing the middle ply of paperboard. The furnish consisted of hydrogen peroxide bleached high temperature spruce chemithermomechanical pulp (HT-CTMP), MFC and a retention system containing cationic starch and an anionic silica sol. The MFC was prepared via a mechanical treatment in a colloid mill after pretreatment with Fenton's reagent, monocomponent endoglucanase or acidic hydrogen peroxide. Addition of 5% MFC, produced with Fenton pre-treatment, resulted in improved HT-CTMP properties with respect to increased tensile index (similar to 35%), z-directional strength (similar to 50%), tensile stiffness index (similar to 25%) compared to HT-CTMP test sheets prepared without MFC addition. The strength improvement was linearly correlated to the density of the tests sheet, to the surface area (BET) and to the surface charge of the enzymatic or chemically pre-treated MFCs.

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  • 98.
    Hemmingsson, Bengt-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Aspects of predicting fracture in paper with the cohesive zone model combined with an elastic-plastic material model with kinematical hardening2004Report (Other academic)
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  • 99.
    Hemmingsson, Bengt-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Determination of the cohesive stress-displacement relation aimed at prediction of fracture in paper2003Report (Other academic)
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  • 100. Henriksson, Marielle
    et al.
    Berglund, Lars A.
    Isaksson, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Lindström, Tom
    Nishino, Takashi
    Cellulose nanopaper structures of high toughness2008In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 9, no 6, p. 1579-1585Article in journal (Refereed)
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