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  • 1.
    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.

  • 2.
    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.

  • 3.
    Björk, Elisabeth
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Bouveng, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Vomhoff, Hannes
    Engstrand, Per
    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 chemithermomech. 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 chem. 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.

  • 4.
    Björk, Elisabeth
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging. Mittuniversity, Sweden.
    Bouveng, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Vomhoff, Hannes
    Holmen AB, Sweden.
    Engstrand, Per
    Mittuniversity, Sweden.
    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.

  • 5. Bruun, H
    et al.
    Friberg, S
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Studies on the interaction between tetrahydroabietic acid and ferric salt solutions1968In: TAPPI Journal, ISSN 0734-1415, Vol. 51, p. 482-488Article in journal (Refereed)
  • 6.
    Carlsson, Per
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Marklund, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Furusjö, Erik
    Wiinikka, Henrik
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Gebart, Rikard
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energy Technology Center.
    Experiments and mathematical models of black liquor gasification: Influence of minor gas components on temperature, gas composition, and fixed carbon conversion2010In: TAPPI Journal, ISSN 0734-1415, Vol. 9, no 9, p. 15-24Article in journal (Refereed)
    Abstract [en]

    In this work, predictions from a reacting Computational Fluid Dynamics (CFD) model of a gasification reactor are compared to experimentally obtained data from an industrial pressurized black liquor gasification plant. The data consists of gas samples taken from the hot part of the gasification reactor using a water cooled sampling probe. During the considered experimental campaign, the oxygen-to-black liquor equivalence ratio (λ was varied in three increments, which resulted in a change in reactor temperature and gas composition. The presented numerical study consists of CFD and thermodynamic equilibrium calculations in the considered λ-range using boundary conditions obtained from the experimental campaign. Specifically, the influence of methane concentration on the gas composition is evaluated using both CFD and thermodynamic equilibrium. The results show that the main gas components (H 2, CO, CO2) can be predicted within a relative error of 5% using CFD if the modeled release of H2S and CH4 are specified a priori. In addition, the calculations also show that the methane concentration has large influence on the reactor outlet temperature and final carbon conversion.

  • 7.
    De San Pio, Ignacio
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Johansson, Klas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Krochak, Paul
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    A novel predictive method for filler coflocculation with cellulose microfibrils2020In: TAPPI Journal, ISSN 0734-1415, Vol. 18, no 11, p. 653-664Article in journal (Refereed)
    Abstract [en]

    Different strategies aimed at reducing the negative impact of fillers on paper strength have been the objective of many studies during the past few decades. Some new strategies have even been patented or commercialized, yet a complete study on the behavior of the filler flocs and their effect on retention, drainage, and formation has not been found in literature. This type of research on fillers is often limited by difficulties in simulating high levels of shear at laboratory scale similar to those at mill scale. To address this challenge, a combination of techniques was used to compare preflocculation (i.e., filler is flocculated before addition to the pulp) with coflocculation strategies (i.e., filler is mixed with a binder and flocculated before addition to the pulp). The effect on filler and fiber flocs size was studied in a pilot flow loop using focal beam reflectance measurement (FBRM) and image analysis. Flocs obtained with cationic polyacrylamide (CPAM) and bentonite were shown to have similar shear resistance with both strategies, whereas cationic starch (CS) was clearly more advantageous when coflocculation strategy was used. The effect of flocculation strategy on drainage rate, STFI formation, ash retention, and standard strength properties was measured. Coflocculation of filler with CPAM plus bentonite or CS showed promising results and produced sheets with high strength but had a negative impact on wire dewatering, opening a door for further optimization.

  • 8.
    Deshpande, R.
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Sundvall, Lars
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Grundberg, Hans
    RISE Research Institutes of Sweden, Bioeconomy and Health, Biorefinery and Energy.
    Lawoko, M.
    KTH Royal Institute of Technology, Sweden.
    Henriksson, G.
    KTH Royal Institute of Technology, Sweden.
    Lignin carbohydrate complex studies during kraft pulping for producing paper grade pulp from birch2020In: TAPPI Journal, ISSN 0734-1415, Vol. 19, no 9, p. 447-460Article in journal (Refereed)
    Abstract [en]

    Paper grade pulp production across the globe is dominated by the kraft process using different lig-nocellulosic raw materials. Delignification is achieved around 90% using different chemical treatments. A bottleneck for complete delignification is the presence of residual covalent bonds that prevail between lignin and carbohydrate even after severe chemical pulping and oxygen delignification steps. Different covalent bonds are present in native wood that sustain drastic pulping conditions. In this study, 100% birch wood was used for producing paper grade pulp, and the lignin carbohydrate bonds were analyzed at different stages of the kraft cook. The lignin carbohydrate bonds that were responsible for residual lignin retention in unbleached pulp were compared and analyzed with the original lignin-carbohydrate complex (LCC) bonds in native birch wood. It was shown that lignin remaining after pulping and oxygen delignification was mainly bound to xylan, whereas the lignin bound to glucomannan was for the most part degraded. Application: One central problem for the pulp and paper industry is efficiency in delignification during the chemical pulping and bleaching processes. It has been believed that one limiting factor is the covalent bonds between lignin and polysaccharides. We present data on presence of such LCC bonds in paper grade birch pulp and its development during the processes. Hopefully, this research data will be useful for the development of more effi-cient processes. 

  • 9. Engström, G
    et al.
    Norrdahl, P
    Ström, G
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Studies of the drying and its effect on binder migration and offset mottling1987In: TAPPI Journal, ISSN 0734-1415, Vol. 70, p. 45-49Article in journal (Refereed)
  • 10. Francey, S.
    et al.
    Tran, H.
    Berglin, N.
    RISE, Innventia.
    Global survey on lime kiln operation energy consumption and alternative fuel usage2011In: TAPPI Journal, ISSN 0734-1415, no 8, p. 19-26Article in journal (Refereed)
  • 11. Fälth, F
    et al.
    Jönsson, A-S
    Brinck, J
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Wimmerstedt, R
    Ultrafiltration of bleach plant filtrate when using evaporation condensate as washing liquor2000In: TAPPI Journal, ISSN 0734-1415, Vol. 83, p. 74-Article in journal (Refereed)
  • 12.
    Hagman, Anton
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rydefalk, Cecilia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging. KTH Royal Institute of Technology, Sweden.
    Z-directional testing of paperboard in combined tensile and compression loading2024In: TAPPI Journal, ISSN 0734-1415, Vol. 23, no 5, p. 268-284Article in journal (Refereed)
    Abstract [en]

    The out-of-plane properties of paperboard are important in several converting applications such as printing, sealing, creasing, and calendering. A juxtaposed tensile and compression curve in the z direction (ZD) will, however, appear to have a kink or discontinuity at 0 stress. The purpose of the present work is to capture the continuous transition between tension and compression and to increase the understanding of the complex ZD properties of paperboard by cyclic testing. In this attempt to unify the ZD tensile and compressive behavior of paperboard, samples were laminated to the testing platens using heat seal laminate film. The method for adhering the samples was compared to samples that were laminated and glued to the testing platens. The edge effects of the cutting method were evaluated in compression testing with samples not attached to the testing platens. The flat slope seen in the initial part of the pure compression curve disappeared when the samples were laminated to the testing platens. The flat slope was instead replaced by a continuous response in the transition across 0 N. The stiffness in the transition region resembled the response in tensile testing. When the testing is cycled, the material exhibits a history dependence. Starting the cycle in either compression or tensile will show an effect on the stiffness at the transition, as well as the compressive stiffness. However, the ultimate tensile strength is unaffected. © TAPPI Press 2024.

  • 13.
    Jour, Pia
    et al.
    Akzo Nobel Pulp and Performance Chemicals, Sweden.
    Lindgren, Karin
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Gutke, Katarina
    Akzo Nobel Pulp and Performance Chemicals, Sweden.
    Walllinder, Johan
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Decreased water usage in a softwood ECF bleaching sequence: full mill simulations2018In: TAPPI Journal, ISSN 0734-1415, Vol. 17, no 6, p. 353-360Article in journal (Refereed)
    Abstract [en]

    In this study, an elemental chlorine free (ECF) bleach plant with a D0(EOP)D1(EP)D2 sequence was studied with the aim of identifying options for significantly decreasing (fresh) water usage in the bleach plant and decreasing the effluent volume. A base-case simulation model for a softwood kraft market pulp mill was made based on a reference model representing the best available techniques as well as data produced in an extensive  laboratory pulp bleaching study. This model was used to evaluate increased closure within the bleach plant and the recirculation of bleach plant effluent to the brownstock system and their effects on both the bleach plant and the recovery cycle. The results indicate that it is possible to reduce the fresh water consumption from 15 metric tons/a.d. metric ton in the base case to about 2 metric tons/a.d. metric ton, without increasing the carryover of chemical  oxygen demand (COD) to the pulp machine. Nonprocess elements in wood contribute to the levels of metals found in the bleach plant and thus to the risk of  precipitates such as calcium oxalate, barium sulfate, and calcium carbonate. The risk of precipitates forming is a key factor determining the possible degree of closure. In addition, chloride concentration in the black liquor is another important factor that is affected by recirculating bleach plant filtrate to the brownstock washer and by the grade of the sodium hydroxide used in the mill.

  • 14. Järnström, L
    et al.
    Ström, G
    Stenius, P
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    The adsorption of dispersing and thickening polymers and their effect on the rheology of coating colors1987In: TAPPI Journal, ISSN 0734-1415, Vol. 70, p. 101-107Article in journal (Refereed)
  • 15.
    Krochak, Paul
    et al.
    RISE, Innventia.
    Fasci, Giuseppe Carmini
    KTH Royal Institute of Technology, Sweden.
    Norman, Bo
    RISE, Innventia.
    Prahl Wittberg, Lisa
    KTH Royal Institute of Technology, Sweden.
    Bridging chemical dosage, mixing quality, and variability in paper sheets2015In: TAPPI Journal, ISSN 0734-1415, Vol. 14, no 5, p. 311-320Article in journal (Refereed)
    Abstract [en]

    In the first part of this work, a series of paper production trials were performed on a forming experimental (FEX) pilot machine to investigate the distribution of additives in the final product. In these trials, a blue color was dosed into the stock before the headbox instead of a retention aid. Fine paper sheets were produced using twin-wire forming. Visual inspection of the sheets revealed surprisingly high levels of variability of the blue color. In the second part, the effect of different dosage nozzle configurations on downstream mixing quality of a single-component, polyacrylamide retention aid was studied using two-phase computational fluid dynamics. A non-Newtonian model for this phase was implemented using rheological parameters obtained through a combination of numerical and experimental analysis. Dosage was made into a turbulent pipe flow under typical industrial approach flow conditions. The effect of the number of dosage points, impingement angle, dosage location, and dosage speed on mixing uniformity was investigated qualitatively and quantitatively. Results from these studies indicate the existence of optimal dosage configurations and point toward strong coupling between chemical addition strategy, mixing quality, and chemical variability in final products. Application: Mills can gain valuable information, including dosage nozzle configuration and dosage conditions, for optimizing mixing of retention aids in the approach flow during paper production.

  • 16.
    Krochak, Paul
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Johansson, Klas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    De San Pio, Ignacio
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    The effect of contact time between CPAM and colloidal silica on the flocculation behavior in the approach flow2021In: TAPPI Journal, ISSN 0734-1415, Vol. 20, no 1, p. 39-47Article in journal (Refereed)
    Abstract [en]

    Multicomponent wet-end systems have become increasingly common in papermaking, with the objective of improving the retention-formation-dewatering relationship. It is quite common to use at least a cationic polymer, often in combination with an anionic microparticle. In some cases, a fixative is also used. However, there is still debate on the optimal implementation of these systems. In particular, optimizing the contact time of the cationic polymer prior to addition of the anionic microparticle is still poorly understood. In this work, we investigate the effect of the contact time of a cationic polyacrylamide (CPAM) prior to addition of colloidal silica on the flocculation response in a flowing fiber suspension. The effect of using a fixative is also investigated. Focused beam reflectance measurements (FBRM) are combined with zeta-potential measurements for optimizing the addition levels of a two- and three-component system, as well as for elucidating the effect of contact time on CPAM performance. Trials are then performed on a pilot scale flow loop, where the time between addition of these two components is varied and the resulting flocculation response is characterized using high-speed filming and image anal. techniques. It is shown that the efficacy of CPAM can be improved through use of a fixative and that a longer CPAM contact time may be beneficial in terms of immediate flocculation; however, hydrodynamic shear tends to dominate the flocculation response regardless of contact time due to floc rupture.

  • 17.
    Marin, Gustav
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Nygårds, Mikael
    RISE Research Institutes of Sweden.
    Östlund, S.
    KTH Royal Institute of Technology, Sweden.
    Stiffness and strength properties of five paperboards and their moisture dependency2020In: TAPPI Journal, ISSN 0734-1415, Vol. 19, no 2, p. 71-85Article in journal (Refereed)
    Abstract [en]

    Five commercial multiply folding boxboards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and because the bending stiffness and grammage varies, the performance of the packages will differ. Finite element simulations can be used to predict these differences, but for this to occur, the stiffness and strength properties need to be determined. For efficient determination of the three-dimensional properties in the machine direction (MD), cross direction (CD), and Z direction (ZD), it is proposed that the paperboard should be characterized using in-plane tension, ZD-tension, shear strength profiles, and two-point bending. The proposed setups have been used to determine stiffness and strength properties at different relative humidity (20,% 50%, 70%, and 90% RH), and the mechanical properties have been evaluated as a function of moisture ratio. There was a linear relation between mechanical properties and moisture ratio for each paperboard. When the data was normalized with respect to the standard climate (50% RH) and plotted as a function of moisture ratio, it was shown that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants. Consequently, it is possible to obtain the mechanical properties of a paperboard by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50% RH and 23°C).

  • 18.
    Moon, R. J.
    et al.
    USDA Forest Service, USA.
    Hensdal, C. L.
    Stora Enso Pulp & Paper Asia AB, Sweden.
    Beck, S.
    Calgary, Canada.
    Fall, Andreas
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Costa, J.
    WebTech Pulp & Paper Technologies, Brazil.
    Kojima, E.
    Nanocellulose Japan, Japan.
    Abitbol, Tiffany
    EPFL Institute of Materials, Switzerland.
    Raghuwanshi, V.
    Monash University, Australia.
    Walker, C.
    University of Maine, USA.
    Batchelor, W.
    Monash University, USA.
    Setting priorities in CNF particle size measurement: What is needed vs. what is feasible2023In: TAPPI Journal, ISSN 0734-1415, Vol. 22, no 2, p. 116-137Article in journal (Refereed)
    Abstract [en]

    Measuring the size of cellulose nanomaterials can be challenging, especially in the case of branched and entangled cellulose nanofibrils (CNFs). The International Organization for Standardization, Technical Committee 6, Task Group 1—Cellulosic Nanomaterials, is exploring opportunities to develop standard methods for the measurement of CNF particle size and particle size distribution. This paper presents a summary of the available measuring techniques, responses from a survey on the measurement needs of CNF companies and researchers, and outcomes from an international workshop on cellulose nanofibril measurement and standardization. Standardization needs differed among groups, with Japanese companies mostly requiring measurements for product specification and production control, and other companies mostly needing measurements for safety/regula-tory purposes and for grade definitions in patents. Among all the companies, average length and width with percen-tiles (D(10), D(50), D(90)) were the most desired measurands. Workshop participants concurred that defining the location(s) on the CNF at which to measure the width and the length is an urgent and complex question. They also agreed that methods are needed for rapid particle size measurement at the nanoscale. Our recommendation within ISO is to start work to revise the definition of CNFs and develop sample preparation and measurement guidelines. It was also recommended that further research be done to reproducibly prepare hierarchical branched CNF structures and characterize them, develop automated image analysis for hierarchical branched CNF structures, and develop a classification system encompassing measurements at multiple size ranges from micro-to nanoscale to fully characterize and distinguish CNF samples. 00327-2022 

  • 19. Preston, J.
    et al.
    Hiorns, A. G.
    Elton, N.
    Ström, Göran
    RISE, STFI-Packforsk.
    Application of imaging reflectometry to studies of print mottle on commercially printed coated papers2008In: TAPPI Journal, ISSN 0734-1415, Vol. 7, no 1, p. 11-18Article in journal (Refereed)
    Abstract [en]

    It has been well documented that homogeneous coating structures are necessary for obtaining good, mottle-free printed papers. Methods such as mercury intrusion porosimetry are widely used in the paper industry, but will deliver a bulk porosity measure, which contains contributions from both the surface layers and the bulk of the coating. One way of assessing the surface porosity is to measure its effective refractive index (Rl) because the Rl measured is a combination of the material Rl and air. In this work three papers coated with PCC, kaolin, and GCC were Rl mapped using an imaging reflectometer. The data were then treated with a mathematical transform in order to be able to quantify the degree of variation that was taking place at each length scale. These results were then compared to the print mottle, which was evident after both lab scale printing and full scale sheetfed printing of the pilot coated papers. The commercial mottle was quantified both visually and using image analysis and there was a reasonable correlation between these two methods. In the halftone printed area, the propensity for mottle correlated with the degree of porosity variation of the coating. However, the rankings for the full tone print areas better correlated with the short time water absorbency of the coatings. FFT band-pass analysis confirmed that the same spatial distribution of unevenness occurred in the basepaper, coating layer and printed areas.

  • 20.
    Ragauskas, Arthur J.
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Lindström, Tom
    RISE, Innventia, Material Processes. KTH Royal Institute of Technology, Sweden.
    Nanocellulose and the future2014In: TAPPI Journal, ISSN 0734-1415, Vol. 13, no 5, p. 5-6Article in journal (Refereed)
  • 21.
    Roberts, K
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Österlund, R
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Axberg, C
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Liquid crystals in systems of rosin and fatty acids : implications for talloil recovery1976In: TAPPI Journal, ISSN 0734-1415, Vol. 59, p. 156-159Article in journal (Refereed)
  • 22. Rättö, Peter
    et al.
    Junel, Kristina
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Valtakari, Dimitar
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Impact of different calendering strategies on barrier coating pickup2023In: TAPPI Journal, ISSN 0734-1415, Vol. 22, no 11, p. 665-673Article in journal (Refereed)
    Abstract [en]

    Paper was pre-calendered in a pilot scale configuration with a traditional soft nip calender and a metal belt calender. All calendering strategies reduced surface roughness and permeability of the samples, but dif-ferent strategies affected the surface roughness and permeability differently. The metal belt calender seemed to have a larger effect on the large-scale variations compared to the soft nip calender.Six test points from the pilot calendered papers were chosen for laboratory coating studies. Uncalendered paper was included as reference samples. The calendered samples and the reference were pre-coated with a regular pig-mented coating consisting of a ground calcium carbonate (GCC) pigment and a styrene acrylate (SA) latex. Both uncoated and pre-coated substrates were barrier coated with a polyvinyl alcohol (PVOH) in one and two layers. The coating pickup was determined gravimetrically, and the barrier properties were evaluated with TAPPI Standard Test Method T 454 grease resistance test.All samples needed two PVOH coating layers to form a grease barrier. The uncalendered sheets showed the best results with one coating layer, but this was at the expense of a higher coating pickup compared to the calendered sheets. The barrier coating pickup could be reduced by a combination of high temperature metal belt calendering and pre-coating. The high temperature and long residence time in the nip enabled plasticization of the fibers. This led to an irreversible deformation, even after water application. This meant that the smoothness obtained during cal-endering would be less affected by water-induced roughening during the coating operation.Application: Most works on barrier research have previously focused on either coating formulations or coating processes. This work complements earlier research by demonstrating that the amount of required coating color can be reduced through an appropriate calendering strategy and use of pre-coating.

  • 23.
    Rättö, Peter
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Junel, Kristina
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Valtakari, Dimitar
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Impact of different calendering strategies on barrier coating pickup2023In: TAPPI Journal, ISSN 0734-1415, Vol. 22, no 11, p. 665-673Article in journal (Refereed)
    Abstract [en]

    Paper was pre-calendered in a pilot scale configuration with a traditional soft nip calender and a metal belt calender. All calendering strategies reduced surface roughness and permeability of the samples, but dif-ferent strategies affected the surface roughness and permeability differently. The metal belt calender seemed to have a larger effect on the large-scale variations compared to the soft nip calender.Six test points from the pilot calendered papers were chosen for laboratory coating studies. Uncalendered paper was included as reference samples. The calendered samples and the reference were pre-coated with a regular pig-mented coating consisting of a ground calcium carbonate (GCC) pigment and a styrene acrylate (SA) latex. Both uncoated and pre-coated substrates were barrier coated with a polyvinyl alcohol (PVOH) in one and two layers. The coating pickup was determined gravimetrically, and the barrier properties were evaluated with TAPPI Standard Test Method T 454 grease resistance test.All samples needed two PVOH coating layers to form a grease barrier. The uncalendered sheets showed the best results with one coating layer, but this was at the expense of a higher coating pickup compared to the calendered sheets. The barrier coating pickup could be reduced by a combination of high temperature metal belt calendering and pre-coating. The high temperature and long residence time in the nip enabled plasticization of the fibers. This led to an irreversible deformation, even after water application. This meant that the smoothness obtained during cal-endering would be less affected by water-induced roughening during the coating operation.Application: Most works on barrier research have previously focused on either coating formulations or coating processes. This work complements earlier research by demonstrating that the amount of required coating color can be reduced through an appropriate calendering strategy and use of pre-coating.

  • 24.
    Stenius, P
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Kuortti, J
    Kronberg, B
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Competitive adsorption phenomena in paper coatings1984In: TAPPI Journal, ISSN 0734-1415, Vol. 67, no 5, p. 56-59Article in journal (Refereed)
  • 25.
    Sterner, Marion
    et al.
    Research and Development for Gruppo X di X Gruppo Srl, Italy.
    Magnusson, Mikael
    RISE - Research Institutes of Sweden (2017-2019), Bioeconomy. RISE, Innventia.
    Innovative technology for making improved paper from the poorest fibers2017In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 11, p. 633-637Article in journal (Refereed)
    Abstract [en]

    The trademarked Papermorphosis technology, consisting of two novel units for separately increasing cross direction (CD) and machine direction (MD) elongation over purely mechanical processes, has been successfully tested on recycling fiber, reaching high elongation values in each direction of over 15% in CD or 20% in MD. Increase of elongation has also had a positive influence on the relative tensile energy absorption (TEA) values in CD and MD. It is well known that mechanical properties in paper basically depend on fiber choice, headbox properties, and refining. With the novel system, elongations in cross direction (CD) and machine direction (MD) can be individually customized, even in paper grades with lower strength deriving from recycled fiber. Customizing elongations also has the effect of improving or better balancing TEA values in both directions. The aim is to improve existing recycling papers and to broaden the use of recycling fiber with respect to the past.

  • 26.
    Thorman, Sofia
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Rydefalk, Cecilia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Hagman, Anton
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Granlöf, Lars
    RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging.
    Dynamic out-of-plane compression of paperboard — Influence of impact velocity on the surface2024In: TAPPI Journal, ISSN 0734-1415, Vol. 2024-February, p. 113-122Article in journal (Refereed)
    Abstract [en]

    Processes that convert paperboard into finished products include, for example, printing, where the paperboard is subjected to rapid Z-directional (ZD) compression in the print nip. However, measuring and evaluating the relevant properties in the thickness direction of paperboard are not necessarily straightforward or easy. Measuring at relevant, millisecond deformation rates further complicates the problem. The aim of the present work is to elucidate some of the influences on the compressive stiffness. Both the initial material response and the overall compressibility of the paperboard is studied. In this project, the effect on the material response from the surface structure and the millisecond timescale recovery is explored. The method utilized is a machine called the Rapid ZD-tester. The device drops a probe in freefall on the substrate and records the probe position, thus acquiring the deformation of the substrate. The probe is also allowed to bounce several times on the surface for consecutive impacts before being lifted for the next drop. To investigate the time dependent stiffness behavior, the probe is dropped several times at the same XY position on the paperboard from different heights, thus achieving different impact velocities. The material response from drops and bounces combined allows study of the short-term recovery of the material. The material in the study is commercial paperboard. The paperboard samples are compared to material where the surface has been smoothed by grinding it. Our study shows that there is a non-permanent reduction in thickness and a stiffening per bounce of the probe, indicating a compaction that has not recovered in the millisecond timescale. Additionally, a higher impact velocity has an initial stiffening effect on the paperboard, and this is reduced by smoothing the surface.

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  • 27.
    Vähä-Savo, Niklas
    et al.
    Åbo Akademi University, Finland.
    Demartini, Nikolai
    Åbo Akademi University, Finland.
    Ziesig, Rufus
    RISE, Innventia.
    Tomani, Per
    RISE, Innventia.
    Theliander, Hans
    Chalmers University of Technology, Sweden.
    Välimäki, Erkki
    Valmet Power Oy, Finland.
    Hupa, Mikko
    Åbo Akademi University, Finland.
    Combustion properties of reduced-lignin black liquors2014In: TAPPI Journal, ISSN 0734-1415, Vol. 13, no 8, p. 81-90Article in journal (Refereed)
    Abstract [en]

    The growing interest in production of green chemicals and biofuels from biomass provides an incentive for pulp mills to identify new possibilities in recovering more wood components from the pulping process. One possibility is to use lignin, separated from black liquor. We undertook this work to determine the combustion properties of reduced-lignin black liquors-two kraft liquors and one soda liquor-in a laboratory-scale, single-particle furnace. The combustion times, maximum swollen volume, nitric oxide formation, cyanate formation, and sulfur release were measured for the original liquors, the filtrates, and intermediate levels of lignin reduction. Combustion experiments were conducted at 900°C in 10% oxygen. Cyanate formation experiments were carried out by pyrolyzing the droplets at 800°C in 100% nitrogen to form a char. The chars were then gasified at 800°C in a 13% carbon dioxide/87% nitrogen atmosphere to obtain the smelt. Sulfur release was studied by pyrolyzing the samples at temperatures ranging from 300°C to 900°C. Liquors with the lowest lignin content had a smaller maximum swollen volume than the original sample. The devolatilization time was not affected by the lignin removal to any great extent, but lignin removal did have a clear effect on the char burning time. The amount of formed nitric oxide (g N/kg black liquor solids) remained constant or decreased slightly with increasing lignin removal in the kraft liquor samples, while for the soda samples the amount of nitric oxide formed increased. The amount of cyanate decreased clearly when comparing the samples with lowest lignin content to the original liquor samples. The peak sulfur release occurred at 500°C for both kraft liquors. In almost all experiments, the share of sulfur released was highest for the original samples and lowest for the sample with lowest lignin content. These results provide new data on combustion properties for reduced-lignin black liquors and indicate that for lignin removal levels up to about 20%, no significant changes are expected in the combustion behavior. Application: This work will help mills identify the effect of lignin precipitation on combustion properties of black liquor.

  • 28.
    Ziesig, Rufus
    et al.
    RISE, Innventia.
    Tomani, Per
    RISE, Innventia.
    Schweinebarth, Hannah
    RISE, Innventia.
    Norberg, Lars
    RISE, Innventia.
    Theliander, Hans
    Chalmers University of Technology, Sweden.
    Production of a pure lignin product, part 1: Distribution and removal of inorganics in Eucalyptus globulus kraft lignin2014In: TAPPI Journal, ISSN 0734-1415, Vol. 13, no 3, p. 65-72Article in journal (Refereed)
    Abstract [en]

    Future high-value, lignin-based products, such as carbon fibers, are expected to require a lignin raw material essentially free from inorganic impurities. Lignin of low inorganic content can be separated from kraft black liquor by the LignoBoost process. This laboratory scale study focuses on the effect of different process parameters, such as final precipitation pH and resuspension pH, on the content of inorganic impurities in the processed lignin. Black liquor from pulping of Eucalyptus globulus was used in this study. Specific attention has been paid to the distribution of the inorganics aluminum (Al), calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), potassium (K), silicon (Si), and sodium (Na). By lowering the resuspension pH and wash pH to 1.5, the ash content could be greatly reduced, primarily because of the dissolution of calcium-oxalate (Ca-oxalate) particles present in the lignin. By slightly increasing the retention time in the resuspension stage, the content of Al, Fe, Mg, Mn, and Si could be reduced by approximately 50%. Repeated resuspension followed by washing resulted in a lignin with very low Na and K content. The total amount of inorganics could be reduced from 5.7 g/kg lignin to 0.6 g/kg lignin by combining a low resuspension/wash pH and a repeated resuspension and wash. Application: The results of this study can be used as guidelines on how to design and operate lignin separation plants to produce lignin that is more pure.

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