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  • 1.
    Abbaszad Rafi, Abdolrahim
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Deiana, Luca
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Granfeldt, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Nyström, Staffan K.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Mathematics, and Science Education (2023-).
    Birch-Bark-Inspired Synergistic Fabrication of High-Performance Cellulosic Materials2024In: ACS Sustainable Resource Management, ISSN 2837-1445Article in journal (Refereed)
    Abstract [en]

    There is a growing demand for the utilization of sustainable materials, such as cellulose-based alternatives, over fossil-based materials. However, the inherent drawbacks of cellulosic materials, such as extremely low wet strength and resistance to moisture, need significant improvements. Moreover, several of the commercially available wet-strength chemicals and hydrophobic agents for cellulosic material treatment are toxic or fossil-based (e.g., epichlorohydrin and fluorocarbons). Herein, we present an eco-friendly, high-yield, industrially relevant, and scalable method inspired by birch bark for fabricating hydrophobic and strong cellulosic materials. This was accomplished by combining simple surface modification of cellulosic fibers in water using colloidal particles of betulin, an abundant triterpene extracted from birch bark, with sustainable chemical engineering (e.g., lignin modification and hot-pressing). This led to a transformative process that not only altered the morphology of the cellulosic materials into a more dense and compact structure but also made them hydrophobic (contact angles of up to >130°) with the betulin particles undergoing polymorphic transformations from prismatic crystals (betulin III) to orthorhombic whiskers (betulin I). Significant synergistic effects are observed, resulting in a remarkable increase in wet strength (>1400%) of the produced hydrophobic cellulosic materials.

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  • 2.
    Abdulgadir, Alamin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. MoRe Research.
    Norgren, Sven
    MoRe Research.
    Persson, Johan
    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.
    Performance Simulation of a Composite Filter Material Containing Mechanical Pulp Fibers, Microfibrillated Cellulose, and Cellulose Nanofibers2022In: Proceedings of the International Mechanical Pulping Conference, 2022, p. 160-Conference paper (Other academic)
    Abstract [en]

    Nonwoven fibrous materials with reticular support of an interconnected fiber network and a tortuous airflow pathway have been commonly used in filtration applications. To meet the criteria of filter efficiency and performance, the filter materials are recommended to contain different types of fibers such as mechanical pulp fibers, microfibrillated cellulose, cellulose nanofibers, and other polymer or synthetic fibers with a range of dimensions, i.e., length and diameter. Cellulose fibers in filter media possess irregular and complex structures with hollow or collapsed lumen structures owing to their refinement or pulping method. The development of an appropriate filter media model requires information on actual fiber characteristics. In this study, a simulation method was used to investigate the complex microstructures of filter media. The physical parameters such as fiber wall thickness, diameter, length, cross-section shapes, and curliness were obtained from fiber analyzers and scanning electron microscopy. Based on the experimental findings, GeoDict database comprising different types of common fiber models was constructed. 3-Dimensional fibrous models corresponding to the wet-laid binderless filter material were generated. Using the GeoDict modules, the pore size distributions, average pore sizes, air permeability, pressure drop and initial filter efficiency simulations were performed. The simulation results appear to be in close agreement with the experimental results. The incorporation of cellulose nanofibers resulted in reduced average pore sizes and air permeability of the filter material, thus enhancing the initial filter efficiency. The filter media developed a biobased material derived from pulp fibers for advanced applications such as medical facemask, and air filtration purposes.

  • 3.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Henshaw Osong, Sinke
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Tai, Cheuk-Wai
    The Arrhenius Laboratory, Stockholm University.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Eco-friendly design for scalable direct fabrication of nanocelluloseManuscript (preprint) (Other academic)
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  • 4.
    Afewerki, Samson
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Osong, Sinke H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Tai, Cheuk-Wai
    The Arrhenius Laboratory, Stockholm University.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sustainable Design for the Direct Fabrication and Highly Versatile Functionalization of Nanocelluloses2017In: Global Challenges, E-ISSN 2056-6646, Vol. 1, no 7, article id 1700045Article in journal (Refereed)
    Abstract [en]

    This study describes a novel sustainable concept for the scalable direct fabrication and functionalization of nanocellulose from wood pulp with reduced energy consumption. A central concept is the use of metal-free small organic molecules as mediators and catalysts for the production and subsequent versatile surface engineering of the cellulosic nanomaterials via organocatalysis and click chemistry. Here, “organoclick” chemistry enables the selective functionalization of nanocelluloses with different organic molecules as well as the binding of palladium ions or nanoparticles. The nanocellulosic material is also shown to function as a sustainable support for heterogeneous catalysis in modern organic synthesis (e.g., Suzuki cross-coupling transformations in water). The reported strategy not only addresses obstacles and challenges for the future utilization of nanocellulose (e.g., low moisture resistance, the need for green chemistry, and energy-intensive production) but also enables new applications for nanocellulosic materials in different areas.

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  • 5.
    Alimohammadzadeh, Rana
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Abbaszad Rafi, Abdolrahim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Persson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Marksted, Kajsa
    Hilden, Lars
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Improving the mechanical properties of CTMP fibers by combining synergistic organocatalytic/polyelectrolyte complex surface engineering with sulfite pretreatment2022In: Proceedings of the International Mechanical Pulping Conference, 2022, p. 149-Conference paper (Other academic)
    Abstract [en]

    Fabrication of paper-based packaging materials is increasing and the challenge is developing a sustainable process to manufacture the materials that can compete with plastics. Employing stronger fiber in production of fiber-based materials improves the efficiency of fabrication process by using a reduced amount of biomass. Cationic starch is a well-known polysaccharide that has been introduced to paper and paperboard fibers to improve the mechanical properties of lignocellulosic fibers. The polyelectrolyte (PE) multilayer method has been popularized as a new and interesting technique to enhance the adsorption of cationic starch on the fiber for improving the strength properties of chemi-thermomechanical pulp (CTMP), chemical and kraft pulps. We have shown in our previous work that the synergistic combination of organocatalysis and PE complexes improved the mechanical properties of CTMP and TMP. In this work, we chose to expand this concept by integrating it with low-dose sulfite pretreatment of wood chips in preparation of CTMP. Thus, CTMP produced by initial sulfite pre-treatment was next surface engineered by synergistic combination of organocatalysis and PE complexes using organic acids as catalysts. The CTMP pulps, which contains 0.1-0.24 wt.% sulfur, produced by our novel pulp-engineering strategy shows a dramatic strength increase (Z- strength: up to 100 %) as compared to no surface engineering. While only sulfite pre-treatment and PE-complex surface engineering were able to improve the strength properties, it was only when the organic catalysts was present that the highest strength improvements were reached. Thus, a clear synergistic effect of the catalyst was observed.

  • 6.
    Andersson, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Sandberg, Christer
    Holmen Paper AB, Braviken Paper Mill, SE-60188 Norrkoping, Sweden .
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Comparison of mechanical pulps from two stage HC single disc and HC double disc - LC refining2012In: Appita journal, ISSN 1038-6807, Vol. 65, no 1, p. 57-62Article in journal (Refereed)
    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.

  • 7.
    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
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Effect of long fibre concentration on low consistency refining of mechanical pulp2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 4, p. 702-706Article in journal (Refereed)
    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.

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  • 8.
    Andersson, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Sandberg, Christer
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    The effect of rotor position on pulp properties in a two-zoned low consistency refiner2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 3, p. 525-530Article in journal (Refereed)
    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.

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  • 9.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hellstadius, Börje
    BillerudKorsnäs.
    Lundfors, Mikael
    Valmet.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Low-consistency refining of CTMP targeting high strength and bulk: effect of filling pattern and trial scale2021In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, no 1, p. 33-41, article id 61Article in journal (Refereed)
    Abstract [en]

    Chemithermomechanical pulp (CTMP) is often used in central layers of multiply paperboards due to its high bulk and strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to optimize process conditions in low-consistency (LC) refining, i. e. to select or ultimately develop new optimal LC refiner filling patterns, in order to produce fibrillar fines and improve the separation of fibres from each other while preserving the natural fibre morphology as much as possible. Furthermore, the aim is to evaluate if this type of work can be done at laboratory-scale or if it is necessary to run trials in pilot- or mill-scale in order to get relevant answers. First stage CTMP made from Norway spruce (Picea abies) was LC refined in mill-, pilot- and laboratory-scale trials and with different filling patterns. The results show that an LR1 laboratory refiner can favourably be used instead of larger refiners in order to characterize CTMP with regard to tensile index and z-strength versus bulk. A fine filling pattern resulted in CTMP with higher tensile index, z-strength and energy efficiency at maintained bulk compared to a standard filling pattern.

  • 10.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Persson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    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
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Refining gentleness - a key to bulky CTMP2022In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 37, no 2, p. 349-355Article in journal (Refereed)
    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.

  • 11.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sandberg, Christer
    Braviken Paper Mill, Holmen Paper, SE-60188 Norrkoping, Sweden.
    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.
    Low-consistency refining of mechanical pulp in the light of forces on fibres2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 225-229Article in journal (Refereed)
    Abstract [en]

    The aim of this investigation was to find new approaches to evaluate the performance of low-consistency refiners. Data from a paper mill producing TMP from Norway spruce was used in order to find a possible way to calculate the power split between the zones in a TwinFlo refiner. An assumption of equal amount of fibres captured between overlapping bars was found successful in order to develop equations for the power split. The equations predicted equal power in both zones at equal disc gaps. The power was found to increase approximately linearly with decreasing disc gap over the range, 0.1-0.2 mm. The power split was essential to know for calculating refining intensities expressed as specific edge load and forces on fibres in the two zones. The reduction in fibre length was about 5% at 0.17 mm disc gap or at 0.03 N forces on fibres or at 0.7 J/m specific edge load. Disc gap, forces on fibres and specific edge load was found to predict fibre shortening approximately equally upon changes in power and flow rate through the refiner.

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  • 12.
    Berg, Jan-Erik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sandberg, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Holmen Paper, Braviken Paper Mill, Sweden.
    Engberg, Birgitta
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    LC Refining Intensity In The Light Of Forces On Fibres2014In: International Mechanical Pulping Conference, IMPC 2014, Espoo: Paper Engineers' Association (PI) , 2014Conference paper (Refereed)
    Abstract [en]

    The aim of this investigation was to find new approaches to evaluate the performance of a full sized two-zoned low-consistency refiner i.e. a refiner with two stators and one rotor in between. Data from a paper mill producing TMP from Norway spruce was used in order to find a possible way to calculate the power split between the two zones. An assumption of equal amount of fibres captured between overlapping bars was found successful in order to develop equations for the power split. The equations predicted equal power in both zones at equal disc gaps. The power was found to correlate approximately linearly with the disc gap. The power split was essential to know for calculating refining intensity expressed as specific edge load and forces on fibres in the two zones. The reduction in fibre length was about 5% at 0.17 mm disc gap corresponding to 0.03 N force on fibres and 0.7 J/m specific edge load. Disc gap, force on fibres and specific edge load was found to predict the fibre shortening with approximately equal sufficiency upon changes in power and flow rate through the refiner.

  • 13.
    Björk, Elisabeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. 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
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Use of fines-enriched chemical pulp to increase CTMP strength2021In: TAPPI Journal, ISSN 0734-1415, Vol. 20, no 4, p. 255-263Article in journal (Refereed)
    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.

  • 14.
    Björk, Elisabeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Rise.
    Vomhoff, Hannes
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Production of fines from refined kraft pulp by fractionation with micro-perforated screens2021In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 36, no 3, p. 456-464Article in journal (Refereed)
    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. 

  • 15.
    Björkqvist, Olof
    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.
    Fridén, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Concepts of Steam Recovery from LC-Refining by Increase Temperature2009In: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, p. 190-194Conference paper (Refereed)
    Abstract [en]

    In a mechanical pulping process, (TMP) wood is refined to pulp in a process with very high wood utilization. However, the power demand in the process is high. Thus efficient energy recovery, especially steam recov-ery, is very important. In high consistency (HC) refining the pulp wood is refined at high temperature (140°C) and pressure. The high temperature makes it possible to recover process heat with usable steam properties.

    One strategy to decrease the power consumption is to split the refining into two stages, one HC-stage and one low consistency (LC) refining stage. This kind of sys-tem is quite common today. One drawback with LC-refining is that it operates at a low temperature normally below 100°C. Hence, the steam recovery potential from conventional LC-refining is limited.

    In this project, we analyse three concepts of steam re-covery in LC-refining by increasing the temperature in the LC-stage. Two base cases: Conventional HC refin-ing only and conventional HC/LC refining is compared with three steam recovery cases: Pulp/Pulp heat ex-changing, Screw Press Dewatering combined with proc-ess water re-circulation and finally Pulp/Water Heat Exchanging.

    The study shows that it is possible to recover steam from the LC-stage and, hence, increase the energy effi-ciency of a combined HC/LC refining system. The screw press case has the highest steam recovery poten-tial of the HC/LC configurations. An initial economic estimate indicates that steam recovery in LC-refining is profitable compared to a conventional HC/LC-configuration.

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  • 16.
    Björkqvist, Olof
    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.
    Fridén, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Energiåtervinning vid LC-raffinering – Förstudie2008Report (Other academic)
    Abstract [en]

    Normally, steam recovery from a conventional low consistency (LC) mechanical pulprefining system is not possible. This is due to the fact that the temperature level in theLC-refiner is less than 100°C. The steam with such a low temperature and associatedpressure has limited value in the mill. In this project, we study a concept of increasingthe temperature in the refiner to a level were process steam with higher quality can berecovered. The temperature level can be increased by transferring heat from outgoingpulp or drainage to incoming pulp or water. This makes it possible to recover heat fromthe process.An initial estimate indicates that steam recovery from LC-refining systems may have agood economic potential. Three cases have been analyzed: Case A: Steam recovery incombination with pulp/pulp heat exchanging, Case B: Steam recovery in combinationwith a pressurized screw press and finally Case C: steam recovery in combination withpump/water heat exchanging.Case B show the best specific steam recovery, 87% kWh recovered steam per kWh usedelectricity. This concept has a lower technological uncertainty compared to cases A andC as it does not need heat exchanging from pulp.The specific heat recovery from case A and C is 78% and 82% respectively. However,the suggested heat exchangers used in these cases do not exist on the market today.There is hence a need for development of exchangers that can handle pulp with highviscosity. The technological risk associated with the screw press scenario is lower and itis likely that this concept is easier to implement.

  • 17.
    Björkqvist, Olof
    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.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    FORE – Ett nytt industrikombinat baserat på mekaniska massaprocesser2010In: Svensk papperstidning, Nordisk cellulosa, ISSN 1101-766X, no 2, p. 24-25Article in journal (Other (popular science, discussion, etc.))
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  • 18.
    Cordova, Armando
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sanhueza, Italo
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Tai, Cheuk-Wai
    Stockholm University, Stockholm.
    Osong, Sinke H.
    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.
    Ibrahem, Ismail
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    A sustainable strategy for production and functionalization of nanocelluloses2019In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075, Vol. 91, no 5, p. 865-874Article in journal (Refereed)
    Abstract [en]

    A sustainable strategy for the neat production and surface functionalization of nanocellulose from wood pulp is disclosed. It is based on the combination of organocatalysis and click chemistry ("organoclick" chemistry) and starts with nanocellulose production by organic acid catalyzed hydrolysis and esterification of the pulp under neat conditions followed by homogenization. This nanocellulose fabrication route is scalable, reduces energy consumption and the organic acid can be efficiently recycled. Next, the surface is catalytically engineered by "organoclick" chemistry, which allows for selective and versatile attachment of different organic molecules (e.g. fluorescent probes, catalyst and pharmaceuticals). It also enables binding of metal ions and nanoparticles. This was exemplified by the fabrication of a heterogeneous nanocellulose-palladium nanoparticle catalyst, which is used for Suzuki cross-coupling transformations in water. The disclosed surface functionalization methodology is broad in scope and applicable to different nanocelluloses and cellulose based materials as well.

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  • 19.
    Enberg, Sofia
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Rundlöf, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. AkzoNobel Pulp & Performance Chem, SE-85170 Bohus, Sweden.
    Axelsson, Patrik
    Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Eriksen, Oyvind
    Paper & Fibre Res Inst, NO-7491 Trondheim, Norway.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Some causes of formation of colour during storage of hydrogen-peroxide bleached Norway spruce mechanical pulp2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 2, p. 356-366Article in journal (Refereed)
    Abstract [en]

    The discolouration of hydrogen-peroxide bleached Norway spruce mechanical pulp during storage in mill systems was studied and the contributions of process water, iron and dyes were evaluated over the visible spectrum. Washing of the pulp made it less sensitive to storage, possibly due to the removal of extractives, lignin-like substances, iron and pulp fines. Storage in white water gave extensive discolouration with a shoulder in the absorption spectrum at around 550-650 nm. Most of the colour was associated with pulp fines or filler but some colour was also found in smaller fractions and in the water phase. The addition of ferric ions increased the light absorption coefficient during storage, initially at short wavelengths and then over the whole spectrum, but could not explain the increased absorption at 550-650 nm and could not 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 in the mill system, but the absorption in this area did not increase during storage. Model calculations indicate that ferric ions together with violet and red dyes could explain a major part, but not all, of 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.

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  • 20.
    Enberg, Sofia
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Axelsson, Patrik
    Norske Skog Saugbrugs, NO-1756 Halden, Norway.
    Eriksen, Oyvind
    Paper & Fibre Res Inst, NO-7491 Trondheim, Norway.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The influence of process waters on optical properties during storage of hydrogen-peroxide bleached Norway spruce mechanical pulp2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 2, p. 344-355Article in journal (Refereed)
    Abstract [en]

    To evaluate the causes behind the formation of colour in mill systems, the effect of different process waters on the optical properties of hydrogen-peroxide bleached Norway spruce mechanical pulp during storage was studied. The influence of process water type, temperature, time, pulp consistency and pH was evaluated over the visible range of wavelengths. The darkening was more pronounced when pulp was stored in process waters compared to in distilled water. Increased temperature and prolonged storage times increased the darkening as expected, whereas a higher storage consistency gave less darkening than a lower storage consistency (15% compared to 5%). The pH value that gave the lowest brightness reduction and a minimum in Delta k(460) was found to be 5.5-6.0. Storage of pulp in white water from the paper machine resulted in a broad shoulder in the k spectra indicating colour formation related to the particles in this water. Part of this shoulder in absorption spectra was related to added dyes, but the increase in absorption with time is likely to be caused by some other colour formation. The colour measured as a*, b* showed that the storage changed the colour of the pulp towards red and yellow, and initially more towards red.

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  • 21.
    Engberg, Birgitta
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Logenius, Louise
    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.
    Mechanical properties of sulphonated wood in relation to wing refiner properties2014In: International Mechanical Pulping Conference, IMPC 2014, Espoo: Paper Engineers' Association (PI) , 2014Conference paper (Other academic)
    Abstract [en]

    To reach maximum effect of different pretreatments we need to know how wood properties can be changed and how this can be related to both refining conditions and pulp characteristics. To understand how the material properties were affected, sulphonated wood samples were tested using several new testing techniques. The data was correlated to pulp properties of batch refined chips to learn more how the initial defibration mechanisms and pulp properties were affected by the pretreatments.

  • 22.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Energy efficient mechanical pulping – summary of the Scandinavian industry initiative research work 2011 - 20152016In: 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, p. 288-303Conference paper (Refereed)
    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. 

  • 23.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    FILLING THE GAP – IMPROVED ENERGYEFFICIENCY AND QUALITY STABILITYIN MECHANICAL PULP REFINING2011Conference paper (Refereed)
    Abstract [en]

    As energy prices will continue to rise long term itis very important to come up with suggestions toefficiency-improving solutions based on modificationsof the existing refining technology without largeinvestments. There are several suggestions torelatively large modifications in design of refiner platepatterns, chip pre-treatment and chip feed strategies toexisting refiners, but these suggestions are difficult toimplement, as the knowledge of the mechanismsprevalent in the refiner gap is insufficient.To solve this problem FSCN and CIT have startedresearch project, “Filling the Gap”, together with thecompanies; Dametric, Holmen, Metso, Norske Skog,Pöyry, SCA and Stora-Enso co-financed by theSwedish authorities; Vinnova and Swedish EnergyAgency. The objective of this research project is toshow how to improve the electric energy efficiency ofchip refining by means of utilizing the fundamentalknowledge of wood material properties relevant forchip refining i.e. refining hypotheses in combinationwith output variable knowledge from new andimproved refining zone measurement methods as;exact gap distance, temperature-, force- and fibrematerial radial distributions combined with thetraditional out/in-put variables used. These data will beutilized in two ways:1) Optimize refining conditions in a static way, i.e. ofconditions to maximize energy efficiency to reach thefunctional fibre properties aimed for.2) Maximize process stability and minimize qualityvariations to these functional fibre properties.This paper reports a general overview from thepreliminary results of these evaluations.

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  • 24.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Produkter från växande skogar ersätter fossilbaserade material2022In: Skogens värden: forskares reflektioner / [ed] Catrin Johansson, Hans-Erik Nilsson, Peter Öhman, Bengt-Gunnar Jonsson, Birgitta Engberg, Oskar Englund, Per Simonsson och Inger Axbrink, Sundsvall: Mittuniversitetet , 2022, p. 154-155Chapter in book (Other academic)
  • 25.
    Engstrand, Per
    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.
    Rundlöf, Mats
    Capisco AB.
    Paulsson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Decrease in strengthalong a process line for SC paper2019In: Fundamental Mechanical Pulp Research Seminar, FMPRS2019, Norrköping, SwedenArranged by Mid Sweden University in cooperatrion with Holmen AB, Valmet AB, AF AB and Treesearch., 2019Conference paper (Refereed)
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  • 26.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hellström, Lisbeth
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    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 evaluation2016In: PaperWeek Canada 2016 Conference February 1 to 5, 2016, Montreal: Technical Track Program / [ed] Greg Hay, 2016Conference paper (Refereed)
    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.

  • 27.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hammar, Lars Åke
    Innventia (STFI).
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    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 (Other (popular science, discussion, etc.))
    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.

  • 28.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hammar, Lars Åke
    Innventia (STFI).
    Sjögren, Birger
    STFI (Innventia).
    Svensson, Börje
    Innventia (STFI).
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    A method of producing cellulosic pulp1991Patent (Other (popular science, discussion, etc.))
    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.

  • 29.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Johansson, B.
    Paper recycling2009In: Pulping Chemistry and Technology, Walter de Gruyter, 2009, p. 391-427Chapter in book (Other academic)
  • 30.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    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 (Other (popular science, discussion, etc.))
  • 31. Engstrand, Per
    et al.
    Lindgren, Johan
    Iggesund Paperboard AB.
    Agnemo, Roland
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A method for increasing the stability of fluorescent whitening agent [Metod för att öka stabiliteten hos fluorescerande vitmedel]2004Patent (Other (popular science, discussion, etc.))
    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).

  • 32.
    Engstrand, Per O.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engberg, Birgitta A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Filling the Gap - Final Report2014Report (Other academic)
    Abstract [en]

    Executive Summary

    As energy prices continue to rise long-term it is very important to come up with suggestions toefficiency-improving solutions based on modifications of the existing refining technology withoutlarge investments. There are several suggestions to relatively large modifications of processsolutions, in design of refiner plate patterns, chip pre-treatment and chip feed strategies to existingrefiners, but these suggestions are often expensive and difficult to implement as the knowledge ofthe mechanisms prevalent in the refiner gap is still insufficient.

    To help solving this problem FSCN and CIT initiated the research project “Filling the Gap” togetherwith the companies Dametric, Holmen, Metso Paper, Norske Skog, Pöyry, SCA and Stora Enso cofinancedby the Swedish authorities Vinnova and the Swedish Energy Agency. The research projectwas designed with the intension to show how to improve the electric energy efficiency of chiprefining by means of utilizing fundamental knowledge of wood material properties relevant for chiprefining in relation to refining hypotheses and in combination with output variables from new andimproved refining zone measurement methods as; exact gap distance, temperature-, force- and fibrematerial radial distributions combined with the traditional out/in-put variables normally used. Thepotential of the above mentioned ideas as well as the specific goal of this project was to show how toreach 25% efficiency improvement in existing refiners and at the same time reduce refiner causedstops by >50% and plate wear also by >50%.

    The data produced within the project was utilized in two ways:

    1. To optimize refining conditions in a static way, i.e. optimization of conditions to maximizeenergy efficiency to reach the functional fibre properties aimed for.

    2. To maximize process stability and minimize quality variations at the functional fibreproperties aimed for.

    The general conclusion from the project is that we can show that there are great opportunities toimprove electric energy efficiency in refining according to the goal by means of using the abovementioned measurement techniques. More specifically the full-scale trials performed during theperiod 2010 – beginning of 2013 showed the possibility to improve the electric energy efficiency by25% at similar functional properties of the pulp, i.e. a reduction in electricity consumption by 20%. Inorder to implement similar strategies in other TMP or CTMP lines it will just as in this case benecessary to use the same measurement system and evaluation techniques together with verythorough and statistically well controlled pulp/fibre evaluation techniques. It would of course beinteresting to implement the same techniques on as many other production lines as possible withinthe participating companies, but it must be emphasized that the procedure is very demanding. Eachproduction line needs to perform a corresponding detailed process analysis as the one performed inthe mill case study of this research project. Furthermore it would also be necessary to utilize therefiner gap measurement techniques, especially the combination of temperature profile and gapdistance measurements, in a modern but still simple process control system making it easier for theoperator to continuously run the process in a more energy efficient mode. Implementation of thetechniques evaluated in pilot scale within this research project, i.e. fibre distribution and force3distribution measurements, would of course have potential to further improve the process efficiencyas well as improve the fibre property level.

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  • 33.
    Engstrand, Per O.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Ferritsius, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Björkqvist, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Johansson, Lars
    PFI.
    Johansson, Örjan
    Luleå Tekniska Universitet.
    Daniel, Geoffrey
    Sveriges Lantbruks Universitet.
    Ferritsius, Rita
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Karlström, Anders
    Chalmers.
    Karlsson, Anette
    SCA Forest Products AB, Ortviken.
    Sandberg, Christer
    Holmen Paper, Braviken.
    Mekmassainitiativet för energieffektivitet, e2mp-i2015Report (Other academic)
    Abstract [sv]

    Projektet har drivits som ett program för finansiering av forskning som ska utveckla ochdemonstrera tekniker som reducerar elenergiförbrukningen med 50% vid tillverkning avTMP och CTMP med bibehållna slutproduktegenskaper hos tryckpapper och kartong.Programmet är en del av skogsindustrins initiativ att under en tioårsperiod tillsammansmed svenska och norska finansiärer investera minst 200 Mkr för att nå detta radikalaeffektiviseringsmål. Ett uttalat mål för industriinitiativet är också att befästaforskningsnoderna vid FSCN i Sundsvall och PFI i Trondheim.

    Parallellt med Energimyndighetens finansiering, 30 Mkr, har Norges Forskningsråd satsat25 MNOK (2010‐14) i industriinitiativet, KK‐stiftelsen 36 MSEK (2011‐17) ochMittuniversitetet har finansierat12 MSEK. Industrins totala satsning kommer att överstiga100 MSEK redan vid utgången av 2017.

    Resultat från benchmarkingstudien BAT2012 av industrins modernaste TMP‐ och CTMPlinjersamt från demonstrationsskaleprojekt visas i rapporten. Projekten baseras delvis pågrundläggande forskningsprojekt genomförda inom FSCN´s KK‐stiftelse‐finansieradeforskningsprofil och projektet ”Filling the Gap” 31676‐, ISSN 1650‐5387 2014:57. Resultaten visar följande reduktionsnivåer; 28% TMP för news (Braviken), 14% TMP för SC(Kvarnsveden) och 21% CTMP för kartong (Skoghall).

    Utöver demoprojekten finns ytterligare tydliga potentialer beskrivna i övriga delprojekt:

    Processintensifiering och processmodifiering > 15%

    Processtabilitet via avancerad processanalys och reglering > 15%

    Kombinera effektivaste processavsnitt från benchmarking ca 25%Detta gör det troligt att det kommer att gå att i fullskaliga demonstrationsförsök validera50% elenergireduktion inom de tre produktområdena, förutsatt att fortsattforskningsfinansiering finns tillgänglig. Tre av de idéer till avknoppningsprojekt somframkommit under projektets gång har redan erhållit beslut om finansiering frånEnergimyndigheten 2015. Ytterligare projektförslag baserade på den här redovisadeforskningen kommer att ingå i ansökningar under 2016. Utöver energireduktion i själva TMP‐ och CTMP‐processerna har forskare vid FSCN lagt forskningsgrunden för hur manska kunna tillverka mycket starka förpackningsmaterial från dessa massatyper på ettenergieffektivt sätt. Även inom detta område kommer en ansökning omuppskalningsprojekt att skickas in.

  • 34.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Rune
    STFI.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    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 (Other (popular science, discussion, etc.))
    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.

  • 35.
    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.
    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 (Other (popular science, discussion, etc.))
    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.

  • 36.
    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.

  • 37.
    Fernando, D.
    et al.
    Department of Forest Products/Wood Science, Wood Ultrastructure Research Centre (WURC), Swedish University of Agricultural Sciences, P.O. Box 7008, SE-750 07 Uppsala, Sweden.
    Muhic, D
    Holmen Paper AB, Braviken Mill, Norrköping, Sweden.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Daniel, G
    Department of Forest Products/Wood Science, Wood Ultrastructure Research Centre (WURC), Swedish University of Agricultural Sciences, P.O. Box 7008, SE-750 07 Uppsala, Sweden.
    Surface and internal micro/ultrastructure of TMP fibres produced during high-intensity refining elucidate the development of pulp and paper properties2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 4, p. 467-475Article in journal (Refereed)
    Abstract [en]

    Refining during mechanical pulping causes delamination and internal fibrillation (D/IF) of the fibre wall and changes the surface ultrastructure. Fundamental knowledge about these phenomena at the fibre cell wall level helps our understanding of the development of pulp and paper properties, which in turn facilitates the optimization of processes, helping to save energy and improve the characteristics of final products. In the present study, pulps were produced by double-disc (DD) refined thermomechanical processes (DD-TMP) and have been characterized at the fibre cell wall micro/ultrastructural level based on Fernando and Daniel’s method (2010) of Simons ’ staining and scanning electron microscopy (SEM). The pulps studied were never-dried Norway spruce DD-TMP from a full-scale mill trial running under different process conditions; a) varying refining intensity, achieved by using a high-intensity turbine segment (HTS) and a standard (Ref) segment from Metso, and b) varying specific energy consumption (SEC). Improved energy efficiency was obtained with HTS segments, giving adequate or better pulp properties with respect to elongation, light scattering, Canadian Standard Freeness (CSF) at a similar tensile index level and lower energy consumption. Energy efficiency was gained through an elevated degree of D/IF and S2 fibrillation with low energy input. Both the SEC and segment designs had a significant impact on elevating the degree of D/IF. Statistical evaluation of fibre development with respect to D/IF gave evidence for improved energy efficiency in HTS refining. Ultrastructural studies on fibre surfaces showed that HTS refining produced better external fibrillation and leads to exposing the secondary S2 wall as fibre outer layer with different ribbon-type S2 fibrillation. Information obtained at the fibre wall level concerning D/IF and surface ultrastructure contribute to the fundamental knowledge about the pulp and handsheet properties and the energy efficiency of TMP processing. Copyright © by Walter de Gruyter·Berlin·Boston.

  • 38.
    Fernando, Dinesh
    et al.
    Wood Ultrastructure Research Centre (WURC), Department of Forest Products/Wood Science, Swedish University of Agricultural Sciences, Uppsala.
    Muhic, Dino
    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.
    Daniel, Geoffrey
    Wood Ultrastructure Research Centre (WURC), Department of Forest Products/Wood Science, Swedish University of Agricultural Sciences, Uppsala.
    Fundamental understanding of pulp property development under different thermomechanical pulp refining conditions as observed by a new Simons' staining method and SEM observation of the ultrastructure of fibre surfaces2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 6, p. 777-786Article in journal (Refereed)
    Abstract [en]

    The morphological and chemical characteristics of cell walls govern the response of wood fibre to mechanical pulping processes and thereby influence the energy efficiency of the process and determine most pulp and paper properties. A study has been carried out at the microstructural/ultrastructural level of fibre cell walls by means of a newly developed Simons' staining (SS) method and scanning electron microscopy to characterize thermomechanical pulps (TMPs) produced under different refining conditions. The SS method allows assessment and quantification of pulp fibre development during the process in terms of cell wall delamination/internal fibrillation (D/IF) under differentprocess conditions, and the degree of D/IF can be statistically evaluated for different TMP types. In focus was never-dried Norway spruce TMP from primary stage double-disc refining running in a full-scale mill, where specific refining energy was varied at different refining pressure levels. Improved energy efficiency was gained at the same tensile index level when applying high pressure (temperature). Under conditions of high pressure and refining energy, a significant enhancement of the degree of D/IF of pulp fibres was observed. The surface ultrastructure of these fibres exhibited an exposed S2 layer with long ribbon-type fibrillation compared to pulps produced with lower pressure and energy input. A given TMP type can be classified in the categories of high-severity and low-severity changes and quasi-untreated concerning the degree of D/IF of its fibres. The relative proportions of these are important for the development of pulp properties such as tensile strength. The presence of higher amounts of fibre fractions in the categories high D/IF and low D/IF will improve the tensile index of a TMP. © 2011 by Walter de Gruyter Berlin Boston.

  • 39.
    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).

  • 40.
    Ferritsius, Rita
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Moberg, Anders
    Stora Enso.
    Hallgren, Hans
    Stora Enso.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rundlöf, Mats
    Capisco.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engberg, Birgitta A.
    Water Absorption and Wet Strength in Hot-pressed Paper2022In: Proceedings of the International Mechanical Pulping Conference, 2022, p. 168-170Conference paper (Other academic)
    Abstract [en]

    Effects of hot-pressing on anisotropic sheets with less good formation was here investigated. The main objective was to study water absorption capacity in relation to the wet strength of hot-pressed paper. A pilot paper machine was used to produce papers from TMP and CTMP furnishes. The results indicate that it is not only the high dry content after wetting that contributes to the high wet strength of the paper hot-pressed at 200C. If it is required to have a paper with both low absorption of water and high wet strength, hot-pressing at 200C seems to be more desirable than using con-ventional drying and adding wet chemical agents to the furnish.

  • 41.
    Fjellström, Helena
    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.
    Granfeldt, T.
    Metso Paper Sundsvall AB, SE-851 94, Sundsvall, Sweden.
    Logenius, Louise
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Predicting CTMP bleachability using wood shavings2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC, 2011, Vol. 1, p. 613-616Conference paper (Refereed)
    Abstract [en]

    To predict the brightness reduction in a chemithermomechanical process as well as the bleachability of pulps produced from different species of wood raw materials there are, at present, no shortcuts available. Pulps have to be manufactured in pilot or mill scale and bleached; evaluating and predicting the bleachability has consequently been very resource consuming and thus expensive - until now! Due to this, we have used a laboratory method based on 60 × 60 mm wood shavings making it possible to predict the bleachability of primarily chemithermomechanical pulps but also other mechanical pulps. Our experiments showed that retention time and impregnation temperature appears to have no impact on the final brightness of birch shavings. When being subjected to a simulated chemithermomechanical pulp process, eucalyptus exhibited an increase in chromophore content before the bleaching stage. In addition, eucalyptus suffered from severe alkaline darkening. After the bleaching stage, the alkaline darkening diminished. A higher retention temperature resulted in lower brightness of the eucalyptus shavings compared to when using a lower retention temperature. Birch reached the highest final brightness levels and had a higher overall yield too.

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  • 42.
    Fjellström, Helena
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Aspects of fibre wall swelling in high-yield pulp.2012In: PROCEEDING OF THE 4TH INTERNATIONAL CONFERENCE ON PULPING, PAPERMAKING AND BIOTECHNOLOGY (ICPPB '12), VOLS. I AND II, 2012, p. 1183-1186Conference paper (Refereed)
    Abstract [en]

    When producing mechanical pulps the fibre separation will take place in the weakest part of the wood matrix. A prerequisite to swelling in wood and mechanical pulps is that the wood matrix is softened. The position of where the weakest part of the wood matrix is situated can to a large extent be controlled by adjustment of the swelling and softening properties of each of the wood polymers (lignin, hemicelluloses and cellulose). Most probably the efficiency of the external and internal fibrillation of the fibre walls is also influenced by how the swelling and softening properties are controlled. The combination of position of fibre-fibre separation together with the efficiency of the external and internal fibrillation will to a large extent determine the energy demand to produce mechanical pulps. Refining of wood chips with different state of softening and swelling will give rise to fibres with different optical and physical properties. The most important parameters that influence the wood matrix and wood fibres’ ability to swell are temperature, pH, ionic form of and the amount of charged groups in the hemicelluloses and lignin of the cell walls. In order to improve the level of knowledge on how to influence the degree of wood matrix and fibre wall swelling of mechanical pulps we have undertaken to study the swelling properties of wood and fibres produced by means of different mechanical pulping processes.

    It was found that pulps not containing sulphonic acid groups need to be heated above the softening temperature of lignin in order to be able to swell to their full capacity. Introduction of sulphonic acid groups also opens up the rigid structure of lignin which lowers the softening temperature and increases the swelling potential even at lower temperatures. The effect of valence of the counter ion was also shown to be more pronounced after adding more carboxylic acid groups to a pulp. Depending on the number and type of anionic acid groups in the fibres, high-yield pulps will have different combinations of properties in different ionic conditions. The preliminary conclusions from this study are that the ability to control swelling properties of mechanical pulps is an important feature to take into account when producing pulp and paper.

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  • 43.
    Fjellström, Helena
    et al.
    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.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    On the relationship between charged groups, chemical environment and delamination during refining.2013Conference paper (Refereed)
    Abstract [en]

    Improved understanding regarding how to optimise the degree of swelling in the wood fibre wall may be a way to reduce the energy demand in the refining process. The forces necessary to achieve fibrillation (internal as well as external) are greatly influenced by the swelling properties of the fibre wall. The degree and position of swelling is also the main cause to where in the wood matrix the fibre separation will take place. Refining of wood chips in different state of swelling will result in mechanical pulp fibres with different optical and mechanical properties.

     

    The typical parameters that influence the wood fibres’ ability to swell are temperature, pH, ionic form, amount of charged groups and ionic strength. Water retention value is one way to measure the pulp´s capacity to retain water after centrifugation and is strongly correlated to the swelling ability of wood fibres.

     

    A blowline-sample of Norway spruce thermomechanical pulp (TMP) taken out directly after the chip-refining step was used as reference material for this study. The sample was treated with sodium sulphite under different conditions to introduce a range of very low to very high degrees of sulphonic acid groups in the cell walls. In a similar way alkaline hydrogen peroxide was used to introduce a range of very low to very high degrees of carboxylic acid groups. Each sample was then ion-exchanged into proton, sodium, calcium and aluminium form.

     

    The effect of the amount of sulphonic and carboxylic acid groups in combination with the effect of counter ion, on the swelling capacity of mechanical pulp fibres was investigated. In addition, all samples were measured in a temperature interval between 25°C and 95°C to monitor changes in the softening temperature due to lignin structure modifications.

  • 44.
    Fjellström, Helena
    et al.
    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.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    ON THE RELATIONSHIP BETWEEN WOOD FIBRE WALL SWELLING, CHARGED GROUPS, AND DELAMINATION DURING REFINING2013In: J-FOR-JOURNAL OF SCIENCE & TECHNOLOGY FOR FOREST PRODUCTS AND PROCESSES, ISSN 1927-6311, Vol. 3, no 4, p. 30-34Article in journal (Refereed)
    Abstract [en]

    The influence of sulphonic and carboxylic acid groups in combination with the effect of counter ion form, on the swelling capacity of mechanical pulp fibres was studied by means of water retention value (WRV) measured in the temperature range from 25 to 95oC. Mechanical pulp fibres (TMP) were treated with hydrogen peroxide and/or sodium sulphite during conditions resembling those used in chemimechanical and bleaching processes commonly used in the industry. In conventional chemimechanical processes sulphite treatment is used before refining while peroxide treatment can be utilized both before and after refining. In this study we did however also use sulphite after peroxide treatment. When subjecting sodium sulphite treated pulps to a subsequent hydrogen peroxide step, all pulps show a decrease in sulphonic acid groups, which could be owed to dissolution of highly charged lignin. Pulps treated with a high hydrogen peroxide charge (4%), showed a loss in carboxylic acid groups during subsequent treatment with sodium sulphite. This loss is probably due to dissolution of highly charged fibre material such as demethylated pectins. Both increased degree of sulphonation and carboxylation of the lignin reduces the softening temperature by means of reducing the degree of cross-linking in the lignin matrix. This softening probably improves the compressibility of the fibre pads in the sample holders of the WRV centrifuge, which would counteract an otherwise expected increasing WRV-value due to increased swelling potential. This makes it difficult to see clear trends in WRV as a function of increase in degree of sulphonation and carboxylation. When changing counter ion form from proton or calcium form to sodium form there is however always a clear increase in WRV in the range from 20 to 30%.

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  • 45.
    Fjellström, Helena
    et al.
    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.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    On the relationship between wood fibre wall swelling, charged groups, and delamination during refining2013In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 3, no 4, p. 30-34Article in journal (Refereed)
    Abstract [en]

    The influence of sulphonic and carboxylic acid groups in combination with the effect of counter-ion form on the swelling capacity of mechanical pulp fibres was studied by means of water retention value (WRV) measured in the temperature range from 25oC to 95oC. Mechanical pulp fibres (TMP) were treated with hydrogen peroxide, sodium sulphite, or both under conditions resembling those used in chemi-thermomechanical and bleaching processes commonly used in the industry. In conventional chemi-thermo-mechanical processes, sulphite treatment is used before refining, whereas peroxide treatment can be used both before and after refining. However, in this study, sulphite was also used after peroxide treatment. When sodium sulphite-treated pulps are subjected to a subsequent hydrogen peroxide step, all pulps show a decrease in sulphonic acid groups, which can be attributed to dissolution of highly charged lignin. Pulps treated with a high hydrogen peroxide charge (4%) show a loss in carboxylic acid groups during subsequent treatment with sodium sulphite. This loss is probably due to dissolution of highly charged fibre material such as demethylated pectins. Both the increased degree of sulphonation and carboxylation of lignin reduce the softening temperature reducing the degree of cross-linking in the lignin matrix. This softening probably improves the compressibility of the fibre pads in the sample holders of the WRV centrifuge, which would counteract the otherwise expected increase in WRV due to increased swelling potential. This phenomenon makes it difficult to see clear trends in WRV as a function of increasing degrees of sulphonation and carboxylation. When changing the counter-ion form from proton or calcium form to sodium form, there is, however, always a clear increase in WRV in the range from 20% to 30%.

  • 46.
    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.

  • 47.
    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
    Johansson, L
    Review: Reduction of energy consumption in refining through mechanical pretreatment of wood chips2009In: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, p. 17-21Conference paper (Refereed)
    Abstract [en]

    Refining of thermomechanical pulp is a very energy-intensive process. Mechanical pretreatment of wood chips prior to refining has been shown to be able to reduce total energy consumption, facilitate removal of extractives, have positive synergies with chemical and enzymatic pretreatments and improve impregnation of chips. There are a number of publications dealing with different aspects of mechanical pretreatment but few of them give a comprehensive overview of what has been done in this field. No review articles dealing with the subject have been written. Today, mechanical pretreatment is becoming more and more common and therefore a review is important.

     

     

  • 48.
    Gorski, Dmitri
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Hill, J
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Johansson, Lars
    Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips2010In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, no 2, p. 156-161Article, review/survey (Refereed)
    Abstract [en]

    This review covers the effect of mechanical pre-treatment of wood chips on the energy consumption in refining and the quality of pulp. To understand the mechanisms of mechanical pre-treatment, a short description of relevant refining theory and reported effects of pre-treatment on wood morphology is given. Mechanical pre-treatment offers a chance to utilize the energy needed to defibrate chips in a more efficient way, minimizing the cyclic elastic deformations which are the main defibration mechanism in refining. Studies of fibre morphology indicate that compressive pretreatment mechanically introduces favorable weak points in the S1 and S2 fibre walls where defibration proceeds easier upon subsequent refining.Published results which cover the effect of the pretreatment on energy consumption and pulp properties are reviewed. Energy reduction of between 10% and 30% is reported in the literature. High ratio of volumetric compression is necessary. Pressurized conditions are required to ensure that the fibres are not damaged during the pre-treatment. Other effects of compressive pretreatment include a more uniform chip size and moisture content, better penetration of chemicals and removal of extractives from the chips. A list of equipment used for chip pre-compression is provided together with published results of pilot-scale and mill-scale operation.

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    Gorski et al: Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips. JNPPR 2010 Vol 25 2 pp 156-161
  • 49.
    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.

  • 50.
    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)
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