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  • 51.
    Balakshin, Mikhail
    et al.
    Aalto University, Finland.
    Capanema, Ewellyn A
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Huang, Zeen
    FP Innovations, Cananda.
    Sulaeva, Irina
    BOKU, Austria.
    Rojas, Orlando
    Aalto University, Finland.
    Feng, Martin
    FP Innovations, Canada.
    Rosenau, Thomas
    BOKU, Austria.
    Potthast, Antje
    BOKU, Austria.
    Recent achievement in the valorization of technical lignins2018In: The 8th Nordic Wood Biorefinery Conference: NWBC 2018 : proceedings / [ed] Hytönen Eemeli, Vepsäläinen Jessica, Espoo, 2018, p. 151-156Conference paper (Refereed)
  • 52. Barbier, C.
    et al.
    Rättö, Peter
    RISE, Innventia.
    Hornatowska, Joanna
    RISE, Innventia.
    Coating models for an analysis of cracking behavior between folded paper and creased board2012Conference paper (Refereed)
  • 53. Bellani, G.
    et al.
    Lundell, F.
    Söderberg, L. Daniel
    RISE, STFI-Packforsk.
    Experimental study of the forming process: Fluid velocity and fluid-fiber interaction measurements2008In: Paper Conference and Trade Show, PaperCon '08, TAPPI Press, 2008, Vol. 2, p. 1145-1176Conference paper (Refereed)
    Abstract [en]

    A study of the flow in the direct vicinity of a forming wire and a fiber network during forming is reported. The measurements are performed with Particle Image Velocimetry in a scaled system. Index-of-refraction matching is used to gain optical access to the flow. Time resolved measurements of the flow velocity in the vertical and horizontal direction is obtained in a plane with a size of 60 × 40 fiber diameters. The spatial resolution is 2 fiber diameters. Data is obtained for three drainage velocities and two different lengths of the fibers. The relative level of the velocity fluctuations are found to decrease with drainage velocity and is higher in the flow above a network mat of shorter fibers compared to the network made of longer fibers. The size of the flow structures is obtained by spectral analysis and compared for the six cases.

  • 54.
    Bengtsson, Andreas
    et al.
    KTH Royal Institute of Technology, Sweden.
    Bengtsson, Jenny
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Sedin, Maria
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Sjöholm, Elisabeth
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Carbon Fibers from Lignin-Cellulose Precursors: Effect of Stabilization Conditions2019In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 7, no 9, p. 8440-8448Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for lightweight composites reinforced with carbon fibers (CFs). Due to its high availability and carbon content, kraft lignin has gained attention as a potential low-cost CF precursor. CFs with promising properties can be made from flexible dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood kraft lignin and fully bleached softwood kraft pulp. This study focused on reducing the stabilization time, which is critical in CF manufacturing. The impact of stabilization conditions on chemical structure, yield, and mechanical properties was investigated. It was possible to reduce the oxidative stabilization time of the PFs from about 16 h to less than 2 h, or even omitting the stabilization step, without fusion of fibers. The main reactions involved in the stabilization stage were dehydration and oxidation. The results suggest that the isothermal stabilization at 250 °C override the importance of having a slow heating rate. For CFs with a commercial diameter, stabilization of less than 2 h rendered in tensile modulus 76 GPa and tensile strength 1070 MPa. Impregnation with ammonium dihydrogen phosphate significantly increased the CF yield, from 31-38 to 46-50 wt %, but at the expense of the mechanical properties.

  • 55.
    Bengtsson, Andreas
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy. KTH Royal institute of technology, Sweden.
    Sjöholm, Elisabeth
    RISE - Research Institutes of Sweden, Bioeconomy, Biobased Materials.
    Conditions for the stabilisation of lignin-cellulose prefibres for carbon fibre production2018In: 15th European workshop on lignocellulosics and pulp: Proceedings for poster presentations, 2018, p. 111-114Conference paper (Other academic)
    Abstract [en]

    Stabilisation of the prefibre is a time-consuming step in carbon fibre (CF) production. In this paper the stabilisation condition of dry-jet wet-spun lignin-cellulose (LC) prefibres (70:30  t%) are reported. The impact of prefibre-impregnation by ammonium dihydrogen phosphate (ADHP) and various thermal conditions were evaluated by measuring the yield and mechanical properties of the final CFs. The addition of ADHP improved the CF yields from 32-40 wt% to 45-47 wt% but had a slight negative impact on the tensile modulus (TM) whereas no significant difference in tensile strength (TS) was observed. The absence of fibre fusion and glass transition temperature (Tg) indicate successful stabilisation of all prefibres. This implies possibilities of using short stabilisation times of LC prefibres in CF production.

  • 56.
    Bengtsson, Jenny
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Olsson, Carina
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Idström, Alexander
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Köhnke, Tobias
    RISE - Research Institutes of Sweden, Materials and Production, IVF.
    Impact of non-solvents in the tetrabutylammonium acetate: dimethyl sulfoxide-cellulose system2016In: The 7th Workshop on cellulose, regenerated cellulose and cellulose derivatives, 2016, p. 19-22Conference paper (Other academic)
    Abstract [en]

    This work examines the potential of tetrabutylammonium acetate: dimethyl sulfoxide (TBAAc:DMSO) as a solvent used in a process for producing man-made cellulose fibers. The tolerance towards nonsolvents is an important step to evaluate the recyclability of the solvent. TBAAc:DMSO was in this work further confirmed to be an efficient solvent for cellulose. Non-solvent tolerance depended on cellulose concentration, TBAAc:DMSO ratio and type of non-solvent. There was no significant change in mechanical properties for filaments regenerated from solutions containing 2 wt% non-solvent compared to those spun from virgin solvent. With 4 wt% ethanol present in solution very brittle filaments were produced, not suitable for use as textile fibers.

  • 57.
    Berglin, N.
    et al.
    RISE, Innventia.
    Lovell, A.
    RISE, Innventia.
    Delin, L.
    Tormala, J.
    The 2010 reference mill for kraft market pulp2011Conference paper (Refereed)
  • 58.
    Berglin, Niklas
    et al.
    RISE, Innventia.
    Tomani, Per
    RISE, Innventia.
    Olowson, P.
    Hultberg, T.
    Persson, S.
    Experiences from feeding and co-firing of lignin powder in a lime kiln2010In: International Chemical Recovery Conference, 2010, Vol. 1, p. 175-187Conference paper (Refereed)
    Abstract [en]

    A significant part of the fossil fuel oil consumption at a pulp mill today is related to combustion in the lime kiln. Therefore, replacing fuel oil with lignin in this application has been one of the most important issues in the FRAM2 (Future Resource-Adapted Mill) research program coordinated by Innventia (formerly STFl-Packforsk) and funded by Sodra and other partners. A full-scale trial to fire lignin powder in a lime kiln was carried out at the Sodra Cell Monsteras mill, as part of the research program. In total 37 tonnes of lignin was co-fired with fuel oil. For part of the trial the kiln was operated on 100 % lignin. The experiences from the trial imply that it is possible to achieve stable and continuous operation of a lime kiln when lignin is used as the main fuel. The temperature levels in the kiln are of the same order of magnitude as when firing fuel oil or wood powder. Sulfur capture by the lime is very efficient, but there is a threshold above which S02 emissions increase rapidly. In the trial this step change occurred when going from 90 % to 100 % lignin firing. Based on the trial results, it is possible to produce lime with consistent quality when firing lignin, and the temperature reached in the burner zone is sufficient for proper sintering of the lime nodules. White liquor can be produced from the lime with the same causticizing efficiency and at the same rate as during normal operation. The mill operators also commented that it was easier to control the performance of the kiln when co-firing lignin and oil compared to the normal operation with co-firing of bark and oil.

  • 59.
    Berglin, Niklas
    et al.
    RISE, STFI-Packforsk.
    Tomani, Per
    RISE, STFI-Packforsk.
    Salman, H.
    Svärd, S. H.
    Amand, L. -E
    Pilot-scale combustion studies with kraft lignin as a solid biofuel2008In: Engineering, Pulping and Environmental Conference 2008, TAPPI Press, 2008, Vol. 4, p. 2571-2580Conference paper (Refereed)
    Abstract [en]

    Processing of kraft lignin precipitated from black liquor to produce a solid biofuel with high energy density and low ash content has been developed in research programs by STFI-Packforsk and partners. In preparation for full-scale combustion trials, tests were carried out on pilot scale in a 150 kW powder burner and in a 12 MWfluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the airflows to reduce swirl. Lignin dried to 10 % moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than wood/bark powder. In the CFB boiler lignin was easily handled and co-fired together with bark. Although the filter cake was broken into smaller pieces and fines the combustion was not disturbed. When co-firing lignin with bark, the sulfur emission increased compared to bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture with addition of limestone to the bed was also demonstrated. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk.

  • 60.
    Berglin, Niklas
    et al.
    RISE, Innventia.
    Tomani, Per
    RISE, Innventia.
    Salman, H.
    Svärd, S.H.
    Ąmand, L.-E.
    Pilot-scale combustion studies with kraft lignin in a powder burner and a CFB boiler2010In: TAPPI Journal, ISSN 0734-1415, Vol. 9, no 6, p. 24-30Article in journal (Refereed)
    Abstract [en]

    Processes have been developed to produce a solid biofuel with high energy density and low ash content from kraft lignin precipitated from black liquor. Pilot-scale tests of the lignin biofuel were carried out with a 150 kW powder burner and a 12 MW circulating fluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the air flows to reduce swirl. Lignin dried to 10% moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than did wood/ bark powder. In the CFB boiler, lignin was easily handled and cofired together with bark. Although the filter cake was broken into smaller pieces and fines, the combustion was not disturbed. When cof ¡ring lignin with bark, the sulfur emission increased compared with bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture also occurred with addition of limestone to the bed. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk. Application: This research is of interest for pulp and paper and energy and utilities companies that want to understand how kraft lignin can be used to replace fuel oil or coal in many combustion applications.

  • 61.
    Berglin, Niklas
    et al.
    RISE, Innventia.
    von Schenck, Anna
    RISE, Innventia.
    Hoffstedt, Christian
    RISE, Innventia.
    Co-production of renewable polymers and ethanol from eucalyptus-based pulp mills2012Conference paper (Refereed)
  • 62.
    Bernstad Saraiva, Anna
    et al.
    COPPE UFRJ, Brazil.
    Valle, Rogerio A. B.
    COPPE UFRJ, Brazil.
    Bosque, A.E.S., Jr.
    Fibria CElulose SA, Brazil.
    Berglin, Niklas
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    von Schenck, A.
    ÅF AB, Sweden.
    Provision of pulpwood and short rotation eucalyptus in Bahia, Brazil: Environmental impacts based on lifecycle assessment methodology2017In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 105, p. 41-50Article in journal (Refereed)
    Abstract [en]

    Environmental impacts from cultivation of eucalyptus pulpwood and short rotation eucalyptus in northeast Brazil were investigated using lifecycle assessment methodology. The assessment considers all relevant inputs and outputs, as well as direct land use changes, assuming conversion of grassland (pasture) to areas for eucalyptus plantation. Results show that production of pulpwood eucalyptus is beneficial compared to short rotation eucalyptus in relation to all assessed impact categories, except for climate change (greenhouse gas emissions = 47 kg CO2-eq. t DM−1 pulpwood eucalyptus and 35 kg CO2-eq. t DM−1 short rotation eucalyptus). Excluding emissions from direct land use changes would increase overall GWP from investigated systems with around 5–6%, and changing the assumed land-use prior to land conversion is of decisive character for overall GWP-results from the assessed eucalyptus production systems. Modeling of nutrient balances in the short rotation production system shows a potential need to increase the input of mineral fertilizer in order to compensate for nutrient losses. This would increase environmental impacts from the short rotation system, making pulpwood eucalyptus preferable in relation to all assessed impact categories.

  • 63.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Björklund Jansson, Marianne
    RISE, Innventia.
    Törngren, Per
    RISE, Innventia.
    Influence of wood extractives on calcium balance during kraft cooking2014Conference paper (Refereed)
  • 64.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Hoffstedt, Christian
    RISE, Innventia.
    Björklund Jansson, Marianne
    RISE, Innventia.
    Samuelsson, Åsa
    RISE, Innventia.
    Wadsborn, Rickard
    RISE, Innventia.
    Increasing the availability of the kraft pulp mill by the use of process simulation2012Conference paper (Refereed)
  • 65.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Jensen, Anna
    RISE, Innventia.
    Ahlroth, Mikael
    RISE, Innventia.
    New challenges regarding nonprocess elements in the liquor and lime cycle2015In: TAPPI Journal, ISSN 0734-1415, Vol. 14, no 7, p. 421-429Article in journal (Refereed)
    Abstract [en]

    Optimal performance of the green liquor plant, recausticizing plant, and lime cycle is vital for adequate white liquor availability and quality as well as for a mill's energy efficiency. Recently, various problems in the liquor and lime cycle have been frequently reported by our industrial partners, including poor performance of green liquor filters or sludge filters, decreased filterability of lime mud, increased lime kiln dead load, and poorquality white liquor. Those problems are most likely caused by an accumulation of nonprocess elements in the liquor and lime cycle due to increased mill closure, increased use of biofuels, or both. Data from the literature and earlier studies have been analyzed with regard to the occurrence and concentration of nonprocess elements in various process streams, including filtered green liquor, green liquor sludge, lime mud, and white liquor. The mineral forms in which nonprocess elements often precipitate were also studied, together with the common knowledge and rules of thumb used by mills for dealing with the problems. The literature data are compared with the newest analytical results from a sampling campaign involving several mills with varying process solutions with respect to nonprocess elements. The consequences and possible recommendations for the mills are presented. Application: Kraft pulp mills can use this information to diagnose and possibly solve problems related to nonprocess elements in day-to-day mill operation.

  • 66.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Jensen, Anna
    RISE, Innventia.
    Ahlroth, Mikael
    RISE, Innventia.
    New challenges regarding non-process elements in the liquor/lime cycle2014Conference paper (Refereed)
  • 67.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Jensen, Anna
    RISE, Innventia.
    Kulander, Ida
    RISE, Innventia.
    Scaling of manganese in kraft pulping process2014Conference paper (Refereed)
  • 68.
    Bialik, Marta
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Jensen, Anna
    RISE - Research Institutes of Sweden, Bioeconomy.
    Rahman, Haribur
    Chalmers university of technology, Sweden.
    Langer, Vratislav
    Chalmers university of technology, Sweden.
    Na2CO3-Na2SO4-double salt scaling in black liquor evaporators: solubility experiments in model solutions2017In: International chemical recovery conference, May 24-26, 2017, Halifax, Canada, 2017Conference paper (Refereed)
    Abstract [en]

    Scaling by Na2CO3-Na2SO4-type solids counts among the most common problems in black liquor evaporation. Previous studies have identified two double salts precipitating from Na-CO3-SO4 solutions: burkeite, Na2CO3·2Na2SO4 and (sodium sulphate) dicarbonate, Na2SO4·2Na2CO3. The latter is believed to be more prone to cause scaling. However, it has long been suspected that other double salts, with largely unknown properties, may form in this system. This work summarizes the results of precipitation studies in the Na2CO3-Na2SO4-(additive) system targeting the transition zone between burkeite and dicarbonate formation. At least one additional double salt has been identified by X-ray diffraction in both bulk crystals and in the scale. The solubility data and the equilibrium liquor compositions have been compared with earlier models

  • 69.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Moosavifar, A.
    Sedin, M.
    Theliander, H.
    Using the pitzer method to estimate the boiling point rise in black liquor solutions2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 2, p. 172-182Article in journal (Refereed)
    Abstract [en]

    The boiling point rise (elevation) of aqueous industrial solutions is often of significant importance for the design of process conditions, equipment, heat balances, etc. However, few rigorous methods exist for predicting boiling point elevation in complex, multicomponent, electrolyte solutions. An example of such a solution is the black liquor obtained in kraft pulp production: a complex mixture of organic and inorganic ions including Na +, K + OH -, HS - C0 3 2- S0 4 2- S 20 3 2- CH 3COO - various phenolates and many more. This work shows one application of the semi-empirical Pitzer method to the theoretical prediction of the boiling point rise in industrial black liquor solutions. The values of the boiling point elevation were measured in two series of black liquors from representative Swedish mills, including both the original and lignin-lean black liquor at different solid contents. The results show a good agreement between experimental and predicted values at low to moderate solid content, and good qualitative prediction at high solid content.

  • 70.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Sedin, Maria
    Theliander, H.
    Application of the pitzer method in estimating the properties of black liquor solutions: A summary2010In: International Chemical Recovery Conference, 2010, Vol. 2, p. 16-23Conference paper (Refereed)
    Abstract [en]

    The Pitzer method for calculating activity coefficients in aqueous electrolyte solutions has been widely applied to modeling the properties of numerous industrial systems. Its use in hot, concentrated solutions, an example being black liquor from kraft pulping process, has nevertheless been limited mainly due to a lack of suitable interaction parameters. This paper summarizes our work in implementing the Pitzer method into modeling of double salt solubilities and boiling point rise in industrial black liquors. Two solubility models: for burkeite, Na 2Co 22Na 2S0 4 and for (sodium sulfate) dicarbonate, 2Na 2CO 3Na 2S0 4 were developed based on literature and experimental data, respectively. Boiling point rise was modeled in two types of black liquor: ordinary and lignin-lean after a lignin precipitation stage. The paper also presents our study on a method for estimating new Pitzer interaction parameters in hot solutions of sodium lactate using the boiling point rise data.

  • 71.
    Bialik, Marta
    et al.
    RISE, Innventia.
    Wadsborn, Rickard
    RISE, Innventia.
    Karlholm, Ingeli
    RISE, Innventia.
    Berglin, Niklas
    RISE, Innventia.
    Assessment of scaling risk in a pressurized black liquor gasification pilot plant2010In: International Chemical Recovery Conference, 2010, Vol. 1, p. 279-286Conference paper (Refereed)
    Abstract [en]

    Black liquor gasification is considered as an interesting alternative to the recovery boiler-based process of green liquor production. Although the handling of the smelt in the two separate processes is similar, the final concentration and temperature of the green liquor from gasification might both be higher. This, together with the S/Na split acquired by the gasification unit, may increase the risk of scaling of slightly soluble salts during green liquor handling. This work uses a previously developed solubility model for sodium carbonate, calcium carbonate and pirssonite, CaCO 3·Na 2CO 3·H 20 in order to evaluate the scaling risk in green liquor obtained from the gasification process. The model, originally based on both gasification green liquor and regular green liquor data, was verified against new samples of green liquor from an experimental gasification unit in Sweden. During the conducted sampling campaign, the following process parameters were varied in order to establish their influence on the final liquor composition: temperature and load of the gasifier, mixing rate in the smelt dissolver, and composition of the dilution water. It has been found that varying the process parameters within the normal operational limits has a relatively small influence, on the composition of the green liquor. The risk for pirssonite precipitation in gasification green liquor was estimated as relatively low, which is consistent with earlier findings. The calculated values of the apparent solubility product were also consistent with previous results.

  • 72. Bjurhager, I.
    et al.
    Olsson, Anne-Mari
    RISE, Innventia.
    Zhang, B.
    Gerber, L.
    Kumar, M.
    Berglund, Lars A.
    Burgert, I.
    Sundberg, B.
    Salmen, Lennart
    RISE, Innventia.
    Ultrastructure and mechanical properties of populus wood with reduced lignin content caused by transgenic down-regulation of cinnamate 4-hydroxylase2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 9, p. 2359-2365Article in journal (Refereed)
    Abstract [en]

    Several key enzymes in lignin biosynthesis of Populus have been down-regulated by transgenic approaches to investigate their role in wood lignification and to explore their potential for lignin modification. Cinnamate 4-hydroxylase is an enzyme in the early phenylpropanoid pathway that has not yet been functionally analyzed in Populus. This study shows that down-regulation of cinnamate 4-hydroxylase reduced Klason lignin content by 30% with no significant change in syringyl to guaiacyl ratio. The lignin reduction resulted in ultrastructural differences of the wood and a 10% decrease in wood density. Mechanical properties investigated by tensile tests and dynamic mechanical analysis showed a decrease in stiffness, which could be explained by the lower density. The study demonstrates that a large modification in lignin content only has minor influences on tensile properties of wood in its axial direction and highlights the usefulness of wood modified beyond its natural variation by transgene technology in exploring the impact of wood biopolymer composition and ultrastructure on its material properties.

  • 73.
    Bjärestrand, Annika
    RISE, Innventia.
    Upgrading of recycled pulp quality by fractionation and selective refining2016Conference paper (Other academic)
  • 74.
    Bjärestrand, Annika
    et al.
    RISE, Innventia.
    Vomhoff, Hannes
    RISE, Innventia.
    Upgrading recycled pulp quality by fractionation and selective refining2016In: International Paperworld IPW, ISSN 1615-1720, Vol. 2016-January, no 12, p. 40-44Article in journal (Other academic)
    Abstract [en]

    As recycling rates increase and the consumption of graphic papers decrease it becomes more and more difficult to maintain the recycled fibre quality. Also, increasing ash content in the recycled pulp contributes to the strength challenge ahead for the paper and board producers. The fractionation of recycled fibre in this study was made in order to investigate possible routes for upgrading the recycled pulp strength. A recycled pulp for containerboard was fractionated in pilot scale using a pressure screen and hydrocydones. The pulp was first fractionated using a micro-perforated screen basket into a short fraction, with high ash and fines content, and a long fibre fraction. The following hydrocyclone fractionation of the screen short fraction resulted in a fine fraction with fibrillar fines and a coarse fraction containing low bonding fines and fibre fragments together with most of the ash. The short coarse fraction also had a high dirt content. When the screen long fibre fraction was split in the hydrocyclone fractionation, a fine fibre fraction containing good bonding fibres and fines and a coarse fibre fraction with coarse low bonding fibres were obtained. The coarse long fibre fraction was upgraded, to a strength level comparable to the good bonding fine fraction, by refining with an energy input of only 24 kWh/t calculated on the whole pulp. This selective refining of the coarse long fibre fraction resulted in an improvement of the pulp strength by 20 % when the pulp fractions were mixed back together in the same proportion as they had been separated. Further strength was gained when the low bonding short coarse fraction with high ash content was removed. This study showed that a recycled pulp can be upgraded by selective and appropriate treatment of the different streams, with different properties, produced in a fractionation process.

  • 75.
    Björk, Elisabeth
    et al.
    RISE, Innventia.
    Athley, Karin
    RISE, Innventia.
    Thomsson, Lars
    RISE, Innventia.
    Advanced techniques to study filler flocs in high shear environments2012Conference paper (Refereed)
  • 76.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Bouveng, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Vomhoff, Hannes
    Holmen AB, Sweden.
    Fines-enriched pulp as a strength agent in a CTMP middle ply2018In: PaperCon 2018: Shaping the future through innovation, TAPPI , 2018, p. 741-760, article id PA5.2Conference paper (Refereed)
    Abstract [en]

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

  • 77.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Bouveng, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy, Papermaking and Packaging.
    Vomhoff, Hannes
    Holmen AB, Sweden.
    Production of pulps with an extremely high fines content for use as strength agent2018In: PaperCon 2018: Shaping the future through innovation, TAPPI , 2018, article id PA5.1Conference paper (Refereed)
    Abstract [en]

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

  • 78.
    Björk, Elisabeth
    et al.
    RISE, Innventia.
    Vomhoff, Hannes
    RISE, Innventia.
    Bouveng, Mikael
    RISE, Innventia.
    Production of a fine fraction using micro-perforated screens2015In: Paper Conference and Trade Show (PaperCon 2015), TAPPI Press, 2015, Vol. 1, p. 543-560Conference paper (Refereed)
  • 79.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy.
    Vomhoff, Hannes
    RISE - Research Institutes of Sweden, Bioeconomy.
    Bouveng, Mikael
    RISE - Research Institutes of Sweden, Bioeconomy.
    Usage of Fines-enriched pulp to increase strength in CTMP2017In: Paper Conference and Trade Show, PaperCon 2017: Renew, Rethink, Redefine the Future, TAPPI Press, 2017, Vol. 3, p. 1607-1631Conference paper (Other academic)
    Abstract [en]

    Fines-enriched pulp (FE-pulp) was benchmarked against glue pulp as strength agent in eucalypt CTMP. FE-pulp was produced by combining high intensity multiple-pass refining with a fractionation in a microperforated screen basket. The fraction passing through the holes of the screen is the FE-pulp. The FE-pulp comprises of secondary fines, created in the refiner, and flexible, fibrillated highly-refined fibres or fibre fragments. Glue pulp is highly refined kraft pulp, commonly added as a strength agent in middle plies of board products, or between plies to increase the plybond. Equal amounts of FE-pulp and glue pulp were added to the original CTMP as well as to washed CTMP, where most of the CTMP-fines had been removed. The effects of the strength agents were evaluated using laboratory sheets. Both glue pulp and FE-pulp increased the strength of the CTMP sheets. The bulk of the sheets decreased however. When 5 % FE-pulp was added, the tensile index increased by more than 50 %, and the tensile energy absorption and z-strength increased by more than 100 %. FE-pulp proved to be twice as effective as glue pulp. The addition of 5 % FE-pulp resulted in the same relative strength increase as an addition of 10 % glue pulp. The washed CTMP lost all strength when the CTMP-fines content was reduced from 17 % to 3% through washing. The addition of 5 % FE-pulp restored the strength values, and at a higher bulk. The drainability in terms of CSF of that stock was much higher when compared to the original pulp.

  • 80.
    Björk, Elisabeth
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Vomhoff, Hannes
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Lindgren, Margareta
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    Single-stage hydrocyclone fractionation of refined bleached softwood pulp2017In: PaperCon 2017, 2017Conference paper (Other academic)
    Abstract [en]

    Refined bleached chemical softwood was fractionated using a hydrocyclone in a fine and a coarse fraction. The trials were done at three inject concentrations, three coarse fraction volume ratios, and with pulps refined with two refining levels.

    A large difference in sheet properties between fine and coarse fraction was observed. Compared with the feed pulp, the relative change in the sheet properties increased more in the fine fractions than it decreased in the coarse fractions. Increased fines proportion had a positive effect on all properties up to a certain level when a further improvement could not be observed. Interestingly, the fine fractions of both refining levels reached the same absolute strength level, both for the tensile properties and z-strength. The fine fractions at the highest coarse fraction mass ratios contained more fines, and the mean fibre was shorter and narrower. This led to higher density but also a decrease of the stretch-at-break and z-strength values.

    When comparing these results with previous fractionation results for unrefined pulp, it was found that inject concentration did not have a large effect on thickening in the present study. As for the refined pulp, the tensile index increased with fines proportion for the unrefined pulp, however, only up to a certain fines proportion where a maximum values was reached. The increase was larger for the refined pulps which had higher fines proportion.

  • 81.
    Björk, Elisabeth
    et al.
    RISE, Innventia.
    Vomhoff, Hannes
    RISE, Innventia.
    Lindgren, Margareta
    RISE, Innventia.
    Single-stage hydrocyclone fractionation of refined bleached softwood pulp2017In: Paper Conference and Trade Show: Renew, Rethink, Redefine the Future, PaperCon 2017, TAPPI Press, 2017, Vol. 2, p. 878-905Conference paper (Other academic)
    Abstract [en]

    Refined bleached chemical softwood was fractionated using a hydrocyclone in a fine and a coarse fraction. The trials were done at three inject concentrations, three coarse fraction volume ratios, and with pulps refined with two refining levels. A large difference in sheet properties between fine and coarse fraction was observed. Compared with the feed pulp, the relative change in the sheet properties increased more in the fine fractions than it decreased in the coarse fractions. Increased fines proportion had a positive effect on all properties up to a certain level when a further improvement could not be observed. Interestingly, the fine fractions of both refining levels reached the same absolute strength level, both for the tensile properties and z-strength. The fine fractions at the highest coarse fraction mass ratios contained more fines, and the mean fibre was shorter and narrower. This led to higher density but also a decrease of the stretch-at-break and z-strength values. When comparing these results with previous fractionation results for unrefined pulp, it was found that inject concentration did not have a large effect on thickening in the present study. As for the refined pulp, the tensile index increased with fines proportion for the unrefined pulp, however, only up to a certain fines proportion where a maximum values was reached. The increase was larger for the refined pulps which had higher fines proportion.

  • 82.
    Björklund Jansson, Marianne
    et al.
    RISE, Innventia.
    Bialik, Marta
    RISE, Innventia.
    Törngren, Per
    RISE, Innventia.
    New insights into soap solubility and separation during kraft cooking2014Conference paper (Refereed)
  • 83. Bohlin, E.
    et al.
    Coppe, L.
    RISE, Innventia.
    Johansson, C.
    Edström, P.
    Modelling of brightness decrease of coated cartonboard as an effect of calendering: Microroughness and effective refractive index aspects2010In: 11th Advanced Coating Fundamentals Symposium Proceedings: The Latest Advances in Coating Research and Development, 2010, p. 51-65Conference paper (Refereed)
    Abstract [en]

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

  • 84.
    Borrega, Marc
    et al.
    Aalto university, Finland ; VTT Technical Research Centre of Finland Ltd, Finland.
    Larsson, Per Tomas
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Ahvenainen, Patrik
    University of Helsinki, Finland.
    Ceccherini, Sara
    Aalto university, Finland.
    Maloney, Thaddeus
    Aalto university, Finland.
    Rautkari, Lauri
    Aalto university, Finland.
    Sixta, Herbert
    Aalto university, Finland.
    Birch wood pre-hydrolysis vs pulp post-hydrolysis for the production of xylan-based compounds and cellulose for viscose application2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 190, p. 212-221Article in journal (Refereed)
    Abstract [en]

    Hydrothermal treatments of birch wood and kraft pulp were compared for their ability to extract the xylan and produce viscose-grade pulp. Water post-hydrolysis of kraft pulp produced a high-purity cellulosic pulp with lower viscosity but higher cellulose yield than traditional pre-hydrolysis kraft pulping of wood. Post-hydrolysis of pulp also increased the crystallite dimensions and degree of crystallinity in cellulose, and promoted a higher extent of fibril aggregation. The lower specific surface area in post-hydrolyzed pulps, derived from their larger fibril aggregates, decreased the accessibility of –OH groups. However, this lower accessibility did not seem to decrease the pulp reactivity to derivatizing chemicals. In the aqueous side-stream, the xylose yield was similar in both pre- and post-hydrolysates, although conducting post-hydrolysis of pulp in a flow-through system enabled the recovery of high purity and molar mass (∌10 kDa) xylan for high-value applications.

  • 85. Bradley, E. L.
    et al.
    Honkalampi-Hämäläinen, U.
    Weber, A.
    Andersson, M. A.
    Bertaud, F.
    Castle, L.
    Dahlman, O.
    RISE, STFI-Packforsk.
    Hakulinen, P.
    Hoornstra, D.
    Lhuguenot, J. -C
    Mäki-Paakkanen, J.
    Salkinoja-Salonen, M.
    Speck, D. R.
    Severin, I.
    Stammati, A.
    Turco, L.
    Zucco, F.
    von Wright, A.
    The BIOSAFEPAPER project for in vitro toxicity assessments: Preparation, detailed chemical characterisation and testing of extracts from paper and board samples2008In: Food and Chemical Toxicology, ISSN 0278-6915, E-ISSN 1873-6351, Vol. 46, no 7, p. 2498-2509Article in journal (Refereed)
    Abstract [en]

    Nineteen food contact papers and boards and one non-food contact board were extracted following test protocols developed within European Union funded project BIOSAFEPAPER. The extraction media were either hot or cold water, 95% ethanol or Tenax, according to the end use of the sample. The extractable dry matter content of the samples varied from 1200 to 11,800 mg/kg (0.8-35.5 mg/dm2). According to GC-MS the main substances extracted into water were pulp-derived natural products such as fatty acids, resin acids, natural wood sterols and alkanols. Substances extracted into ethanol particularly, were diisopropylnaphthalenes, alkanes and phthalic acid esters. The non-food contact board showed the greatest number and highest concentrations of GC-MS detectable compounds. The extracts were subjected to a battery of in vitro toxicity tests measuring both acute and sublethal cytotoxicity and genotoxic effects. None of the water or Tenax extracts was positive in cytotoxicity or genotoxicity assays. The ethanol extract of the non-food contact board gave a positive response in the genotoxicity assays, and all four ethanol extracts gave positive response(s) in the cytotoxicity assays to some extent. These responses could not be pinpointed to any specific compound, although there appeared a correlation between the total amount of extractables and toxicity.

  • 86. Brelid, H.
    et al.
    Bogren, J.
    Dang, B.
    Lundqvist, F.
    RISE, Innventia.
    Saltberg, A.
    Theliander, H.
    Kraft delignification: Recent findings regarding the impact of non-reacting ions in the cooking liquor2011Conference paper (Refereed)
  • 87. Brodin, F.W.
    et al.
    Sonavane, Y.
    Sedin, M.
    RISE, Innventia.
    Displacement washing of TEMPO-oxidized softwood kraft pulp:: Effects of change in fiber properties2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, no 3, p. 366-376Article in journal (Refereed)
  • 88. Brodin, Ida
    et al.
    Sjöholm, Elisabeth
    RISE, STFI-Packforsk.
    Gellerstedt, Göran
    RISE, STFI-Packforsk.
    Kraft lignin as feedstock for chemical products: The effects of membrane filtration2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 3, p. 290-297Article in journal (Refereed)
    Abstract [en]

    The use of technical lignins as feedstock for chemical products will require improvements in purity, molecular mass distribution, and thermal behavior. Therefore, industrial black liquors from kraft pulping of softwood (spruce/pine) and hardwood (birch and Eucalyptus globulus) have been subjected to fractionation according to molecular mass by ceramic membranes. After acidification and isolation of the lignin fractions, a variety of analytical methods have been applied to help understand their structure - property relationships. From all types of lignin, the chemical and polymeric properties of fractions isolated from the membrane permeates were more homogeneous. This demonstrates that technical kraft lignins, irrespective of origin, may constitute an interesting feedstock for products, such as carbon fibers, adhesives, and phenol-based polymers.

  • 89.
    Brodin, Ida
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sjöholm, Elisabeth
    RISE, Innventia.
    Gellerstedt, Göran
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    The behavior of kraft lignin during thermal treatment2010In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 87, no 1, p. 70-77Article in journal (Refereed)
    Abstract [en]

    Purified kraft lignin fractions from technical pulping liquors of softwood and hardwood have been subjected to step-wise analytical pyrolysis in the temperature interval 200-900 °C. The heterogenic structure of kraft lignin was revealed by the formation of pyrolysis products throughout the entire temperature interval although the majority of products were formed at 500-600 °C. Beyond 700 °C, no further pyrolysis products could be detected but a substantial portion of the lignin was shown to be converted into thermally stable products (char) not accessible by analytical pyrolysis. With pre-oxidation of the lignin with air at 250 °C prior to pyrolysis, a shift towards higher pyrolysis temperature was observed with a concomitant change in product composition. Thermal gravimetric analysis on such lignins also showed an improved stability against degradation. Methylation of the lignin prior to pyrolysis did not induce any significant changes in behavior, except for much lower Tg values.

  • 90.
    Brännvall, Elisabet
    RISE - Research Institutes of Sweden, Bioeconomy. RISE, Innventia.
    The limits of delignification in kraft cooking2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 1, p. 2081-2107Article in journal (Refereed)
    Abstract [en]

    The perspective of the article is to explore kraft cooking at the limits of delignification, i.e. what degree of delignification is needed to obtain fibre liberation and what is the maximum degree of delignification possible in the kraft pulping stage. The reasons for the quite narrow boundaries for sufficient and maximum delignification are explained, and the differences between the behaviour of hardwood and softwood kraft pulping are clarified.

  • 91.
    Brännvall, Elisabet
    et al.
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Bäckström, Marie
    RISE, Innventia.
    Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 11, p. 1031-1037Article in journal (Refereed)
    Abstract [en]

    A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali (EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.

  • 92.
    Brännvall, Elisabet
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Kulander, Ida
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Consequences in a softwood kraft pulp mill of initial high alkali concentration in the impregnation stage2019In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 1, p. 28-35Article in journal (Refereed)
    Abstract [en]

    Impregnation with high initial concentration is fast and efficient, leading to a homogeneous delignification in the subsequent cook, resulting in improved screened pulp yield. To obtain high initial alkali concentration, the white liquor flow needs to be significantly increased. The moisture content of the wood chips and the alkali concentration of the white liquor limit the initial alkali concentration of the impregnation liquor that can be reached. It is therefore of interest to evaluate the possibility to implement high alkali impregnation (HAI) industrially and the consequences this would have on the mill system. The effect of HAI on mass and energy balances in a kraft pulp mill has been studied using mill model simulations. The sensitivity to disturbances in important parameters for process control has been compared to impregnation scenarios used industrially. It was shown that high initial alkali concentration can be achieved on industrial scale by increased white liquor flow. HAI has a positive effect on recovery flows and reduces the need for make-up chemicals. The HAI concept is less sensitive to variations in process parameters, such as chip moisture and white liquor concentration, thus diminishing the risk of alkali depletion in chip cores. © 2019 Brännvall and Kulander.

  • 93.
    Bäckström, M.
    et al.
    RISE, Innventia.
    Bolivar, S.
    Paltakari, J.
    Effect of ionic form on fibrillation and the development of the fibre network strength during the refining of the kraft pulps2012In: O Papel, ISSN 0031-1057, no 7, p. 57-65Article in journal (Refereed)
  • 94.
    Bäckström, Marie
    et al.
    RISE, STFI-Packforsk.
    Drotz, Mattias
    RISE, STFI-Packforsk.
    Tubek-Lindblom, Anna
    RISE, STFI-Packforsk.
    Blohm, Erik
    RISE, STFI-Packforsk.
    Improved product quality and increased production capacity with impulse technology2009In: Pulp and Paper Canada, ISSN 03164004, Vol. 110, no 2, p. 33-36Article in journal (Refereed)
    Abstract [en]

    Impulse technology is a high-intensity web consolidation technique in which water is removed from a wet paper web by the combined action of mechanical pressure and intense heat. Pilot trials show that impulse technology is a feasible technique for the production of linerboard, paperboard and fine paper. Improved dewatering, combined with enhanced mechanical and surface properties, are benefits that can be obtained.

  • 95.
    Bäckström, Marie
    et al.
    RISE, Innventia.
    Hammar, Lars-Åke
    RISE, Innventia.
    The influence of the counter-ions to the charged groups on the refinability of never-dried bleached pulps2010In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 5, no 4, p. 2751-2764Article in journal (Refereed)
    Abstract [en]

    Refining of bleached hardwood pulps and bleached softwood pulps having different counter-ions to the charged groups within the fibres was studied. The results show that an energy reduction of 50% for the hardwood pulps and 20% for the softwood pulp can be achieved if 1he fibres are converted into the Na +-form prior to refining. The results also show that the amount of charged groups in the fibres is important for the refinability, which explains why the refining efficiency is much lower for bleached softwood fibres, which have a much smaller amount of charged groups than the bleached hardwood pulp.

  • 96.
    Bäckström, Marie
    et al.
    RISE, STFI-Packforsk.
    Hammar, Lars-Åke
    RISE, STFI-Packforsk.
    Htun, Myat
    RISE, STFI-Packforsk.
    Beatability and runnability studies of ion-exchanged unbleached kraft pulps on a pilot scale2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 1, p. 94-100Article in journal (Refereed)
    Abstract [en]

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

  • 97.
    Bäckström, Marie
    et al.
    RISE, Innventia.
    Jensen, Anna
    RISE, Innventia.
    Brännvall, Elisabet
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Influence of chip presteaming conditions on kraft pulp composition and properties2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 5, p. 393-399Article in journal (Refereed)
    Abstract [en]

    Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.

  • 98.
    Bäckström, Marie
    et al.
    RISE, STFI-Packforsk.
    Kolar, Marie-Claude
    RISE, STFI-Packforsk.
    Htun, Myat
    RISE, STFI-Packforsk.
    Characterisation of fines from unbleached kraft pulps and their impact on sheet properties2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 5, p. 546-552Article in journal (Refereed)
    Abstract [en]

    Fines are an essential component in the papermaking process because they have a profound influence on the behaviour of the wet web and on the mechanical properties of the final sheet. Primary fines are present in the pulp prior to refining, and secondary fines are produced during refining. In the present investigation, two commercially manufactured unbleached pulps with kappa numbers of 45 and 90 were studied in terms of how they responded to refining with respect to the quality of fibre and fines. Primary and secondary fines were collected and characterised and their impact on sheet strength was evaluated by addition of known amounts to a refined and decrilled pulp. All the measured paper strength properties improved when primary and secondary fines were added. The strength improvement was generally somewhat higher in the second case. The effect was more pronounced at a higher level of addition. We attribute the main strength improvements associated with fines to improved consolidation by the creation of capillary forces between the surfaces.

  • 99.
    Bäckström, Marie
    et al.
    RISE, Innventia.
    Melander, E.
    Brännvall, Elisabet
    RISE, Innventia.
    Study of the influence of charges on refinability of bleached softwood kraft pulp2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, no 4, p. 588-595Article in journal (Refereed)
  • 100.
    Bäckström, Marie
    et al.
    RISE, Innventia.
    Tubek-Lindblom, Anna
    RISE, Innventia.
    Wågberg, Lars
    RISE, Innventia.
    Studies of the influence of deflocculants and flocculants on the refining efficiency on a pilot scale2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 3, p. 319-326Article in journal (Refereed)
    Abstract [en]

    The objective of the present investigation was to study the influence of flocculants and deflocculants on refining efficiency. The refining was performed with the aid of a conical refiner at EuroFEX, and the refining response was evaluated as the change in fibre properties and in the mechanical properties of handsheets. Using the same furnish, an unbleached neverdried softwood pulp, the effect of fibre dimensions on floc strength was excluded as much as possible. The degree of flocculation was changed by addition of APAM, CPAM, guar gum and CMC. The floc strength was characterized using a parallel plate rheometer. The added chemicals, except for APAM, affected the relation between power input and gap clearance. To reach a certain power the fibres treated with guar gum, CMC or CPAM required a narrower gap clearance than the reference pulp or when APAM was added to the fibres. Refining at a narrower gap clearance increased the refining efficiency in terms of WRV and paper property development, as long as fibre length reduction could be avoided.

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