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  • 1.
    Andersson, Niclas
    et al.
    BTG Instruments AB, Saffle, Sweden..
    Wilke, Caroline
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Biazzo, Tom
    BTG Instruments AB, Saffle, Sweden..
    Van Fleet, Rick
    BTG Instruments AB, Saffle, Sweden..
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A new sensor and a novel control concept for optimized fiber line operation2014In: TAPPI Journal, ISSN 0734-1415, Vol. 13, no 10, p. 39-45Article in journal (Refereed)
    Abstract [en]

    Kraft and sulfite pulp mills use several consecutive process stages for pulp production. However, usually only one key pulp parameter is used for process control and that is the lignin content in the fibers, typically expressed as the kappa number. Even so, to improve process efficiency, more variables need to be monitored. To do that, a new sensor was developed, the dissolved lignin transmitter (DLT), along with a new control concept. The DLT measures the dissolved lignin content in the pulp slurry using a unique principle based on optical measurements. The device can measure the dissolved lignin inline at low consistency and at medium consistency. The sensor has two major applications: 1) improving the efficiency in washing stages and 2) optimizing chemical charges. Results from several mill trials have shown that the contribution from dissolved lignin in the filtrate portion of the pulp is up to 30% of the total bleach load, i.e., fiber and filtrate kappa number combined into the bleach plant. Hence, chemical savings can be achieved taking this component into account compared to only measuring the washed fiber kappa number. Application: The results of this study can help mills understand how to better control the pulping stages, which might lead to significant economic savings and better pollution control.

  • 2.
    Bohlin, Erik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Johansson, Caisa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lestelius, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Flexographic ink-coating interactions: Effects of latex variations in coating layers2016In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 4, p. 253-262Article in journal (Refereed)
  • 3.
    Engström, Gunnar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Causes of back-trap mottle in lithographic offset prints on coated papers2016In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 2, p. 91-101Article in journal (Refereed)
    Abstract [en]

    Back-trap mottle is a common and serious print quality problem in lithographic offset printing of coated papers. It is caused by nonuniform ink retransfer from an already printed surface when it passes through a subsequent printing nip with the print in contact with the rubber blanket in that nip. A nonuniform surface porosity gives rise to mottle. A key parameter in mottling contexts is the coating mass distribution, which must be uniform. Good relationships between mottle and mass distribution have also been reported; the mottle pattern coincides with that of the coating mass distribution. High blade pressures, compressible base papers, and high water pick-up between application and metering, which plasticizes the paper, yield uniform mass distributions, but these parameters might have a detrimental effect on the runnability in blade coating in terms of web breaks. The general opinion has been that nonuniform surface porosity is caused by binder migration and enrichment of binder in the coating surface, more in the high coat weight areas and less in the low coat weight areas. Recent research has suggested that a more probable mechanism is depletion of binder in the coating surface. Nonuniform shrinkage of the pigment matrix (filter cake) formed during the consolidation between the first critical concentration (FCC) and the second critical concentration (SCC) is another possible mechanism. Relevant relaxation times for latex and the time scales for consolidation show that the high coat weight areas shrink more than the low coat weight areas in the coating layer. A recent pilot-scale experiment has shown that the drying strategy did not affect the differences in shrinkage between high and low coat weight areas. The drying strategy has a pronounced impact on mottle. A high evaporation rate at the beginning of the evaporation results in less mottle than a low evaporation rate. The least mottle is obtained if the drying is performed with a gap in the course of evaporation between the FCC and the SCC.

  • 4.
    Hellström, Pia
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Akzo Nobel Pulp & Paper Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden..
    Heijnesson-Hulten, Anette
    Akzo Nobel Pulp & Paper Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden..
    Paulsson, Magnus
    Akzo Nobel Pulp & Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden.;Mid Sweden Univ, Sundsvall, Sweden..
    Håkansson, Helena
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A comparative study of enzymatic and Fenton pretreatment applied to a birch kraft pulp used for MFC production in a pilot scale high-pressure homogenizer2016In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 6, p. 375-381Article in journal (Refereed)
    Abstract [en]

    Microfibrillated cellulose (MFC) was produced in pilot scale from a bleached birch (Betula verrucosa) kraft pulp that was pretreated with either Fenton's reagent or with a combined mechanical and enzymatic method used at the Centre Technique du Papier (CTP; Grenoble, France). The change in fiber fibrillation during the homogenization treatment was monitored by analyzing the fiber and the fines content, size fractionation, rheological properties and visualization by light-and scanning electron microscopy (SEM). The Fenton pretreatment resulted in MFC suspensions that contained a high amount of small sized elements. After five passes through the high-pressure homogenizer, the amount of particles smaller than 20 mu m was 37% for the Fenton pretreated MFC compared to 13% for the enzymatically (endoglucanase) pretreated MFC. Altogether, the Fenton pretreatment enabled preparation of MFC with a higher degree of fibrillation after the same number of passes through the high-pressure homogenizer. Another option is to produce MFC of the same amount of fibrillation as after an enzymatic stage, but at significantly lower energy consumption.

  • 5.
    Johansson, Kristin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Christophliemk, Hanna
    Energy and Process Engineering, Tampere University of Technology.
    Johansson, Caisa
    Karlstad University, Faculty of Technology and Science, Paper Surface Centre. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Jönsson, Leif J.
    Kemiska institutionen, Department of Chemistry, Umeå Universitet.
    Järnström, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Paper Surface Centre.
    The effects of coating structure and water-holding capacity on the oxygen-scavenging ability of enzymes embedded in the coating layer2013In: TAPPI Journal, ISSN 0734-1415, Vol. 12, no 6, p. 43-52Article in journal (Refereed)
    Abstract [en]

    Enzymes catalyzing oxygen scavenging were embedded in latex-based coatings with and without barrier kaolin clay to produce material for active packages. The clay was used to create a porous structure, and the closed-structure matrix consisted of a biopolymer comprising either starch or gelatin to increase the water uptake of the coating. The effects of the porous open structure and of the water uptake of the coated layer on the oxygen-scavenging ability of the embedded enzymes were examined at both 75% and 100% relative humidity. The results showed that the porous clay structure led to higher oxygen-scavenging capacity than that of a closed structure at both test conditions by enabling a high diffusion rate for oxygen and glucose to the active sites of the enzymes. The addition of a water-holding biopolymer did not always significantly affect the oxygen-scavenging capacity. However for a less-porous layer at 100% relative humidity, an increase in the amount of biopolymer resulted in an increase in oxygen-scavenging capacity. The results were treated statistically using multiple-factor analysis where the most important factor for the oxygen-scavenging ability was found to be the addition of clay. The coatings were also characterized with respect to water vapor uptake, overall migration, porosity, and scanning electron microscopy images.

  • 6.
    Jonhed, Anna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Järnström, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Influence of polymer charge, temperature and surfactants on surface sizing of liner and greaseproof with hydrophobically modified starch2009In: TAPPI Journal, ISSN 0734-1415, no February, p. 33-38Article in journal (Refereed)
  • 7.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013), Paper Surface Centre.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Abaca as a reinforcement fibre for softwood pulp2007In: TAPPI Journal, ISSN 0734-1415, Vol. 6, no 10, p. 25-32Article in journal (Refereed)
  • 8.
    Kjellgren, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science.
    Engström, Gunnar
    Karlstad University, Faculty of Technology and Science.
    The relationship between energy requirement and barrier properties in the production of greaseproof paper2005In: TAPPI Journal, ISSN 0734-1415, Vol. 4, no 8, p. 7-11Article in journal (Refereed)
  • 9.
    Kvarnlöf, Niklas
    et al.
    Karlstad University, Faculty of Technology and Science.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science.
    Jönsson, Leif J.
    Karlstad University, Faculty of Technology and Science.
    Söderlund, Carl-Axel
    Svenska Rayon AB.
    Optimization of the enzymatic activation of a dissolving pulp before viscose manufacture2007In: TAPPI Journal, ISSN 0734-1415, Vol. 6, no 6, p. 14-19Article in journal (Refereed)
  • 10.
    Land, Cecilia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Modeling of bagginess due to storage of paper reels with ridges2009In: TAPPI Journal, ISSN 0734-1415, Vol. 8, no 9, p. 18-22Article in journal (Refereed)
    Abstract [en]

    Paper is subjected to stress relaxation during storage in reels. Ridges in the paper reel subject the paper in the ridge to a higher strain than the paper adjacent to the ridge. The strain difference can become a permanent strain difference, resulting in a baggy web after unwinding. Researchers used a geometrical model based on stress relaxation test results to determine when the bagginess is substantial enough to cause problems. The results showed that runnability problems will appear if the ridge is about 1–2 mm high. This applies for a reel with a diameter of 1.2–1.8 m stored for 1 week.

  • 11.
    Magnusson, Hans
    et al.
    Swedish Forest Products Research Laboratory.
    Mörk, Karin
    Swedish Forest Products Research Laboratory.
    Can magnesium build-up be a problem in a kraft mill with oxygen bleaching?1980In: TAPPI Journal, ISSN 0734-1415, Vol. 63, no 5, p. 121-123Article in journal (Refereed)
    Abstract [en]

    The material balance of magnesium for one mill and some important data from two other mills show that the build-up of magnesium will not be a problem. This conclusion is supported by laboratory studies and thermodynamic calculations which explain the chemical basis for the behavior of magnesium in the mill system. The main input of magnesium are the wood chips and the magnesium inhibitor. The main outputs are the effluent from the conventional bleaching and the dregs and grits. The magnesium concentrationdoes not form a closed loop, and the white liquor contains only neglectible amounts of magnesium.

  • 12.
    Mesic, Behudin
    et al.
    Scion Res, Wood & Biofiber Technol, Rotorua, New Zealand..
    Kugge, Christian
    SCA R&D Ctr, Sundsvall, Sweden..
    Järnström, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science.
    Superhydrophobic paper coating containing nonconventional clay2010In: TAPPI Journal, ISSN 0734-1415, Vol. 9, no 11, p. 33-40Article in journal (Refereed)
    Abstract [en]

    Hydrophobic clay fillers have not been widely used in dispersion coatings for linerboard because of the difficulty of dispersing them in water. This work investigated whether hydrophobic clay can be used as filler in barrier dispersion coatings. Hydrophobic clay was compared with conventional clay in terms of coating consolidation, structure, wetting, and barrier performance. All coatings were applied to linerboard sheets made using a laboratory dynamic sheet former. The coated linerboards were examined using scanning electron microscopy and Raman spectroscopy, and were characterized with respect to water absorption, vapor transmission rate, and contact angles. The results show that a coating containing hydrophobic clay provides a superhydrophobic character to paper; i.e., a high water contact angle (150 degrees) and relatively low water absorption. Raman mapping of cross-sections revealed that the latex distribution is uniform in the presence of either conventional clay or hydrophobic clay, and that the distribution of hydrophobic clay tends to be more uniform than conventional clay, which might reflect good mixing and consolidation of hydrophobic clay.

  • 13.
    Sjöstrand, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Barbier, Christophe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Modeling the influence of forming fabric structure influence on vacuum box dewatering2017In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 8, p. 477-483Article in journal (Refereed)
    Abstract [en]

    This investigation used numerical models to describe forming section sheet dewatering at the high vacuum suction boxes. Three different fabric structures were examined with numerical models for single-phase flow of air and for two-phase flow of air and water. This was done to evaluate how forming fabric structure influences sheet dewatering. The numerical models were compared with an experimental study of the same fabrics investigated on a laboratory suction box. The small differences in dewatering rate in the experimental study could be simulated with the models, which confirmed the validity of the models. This implies that these numerical models can be used to describe new fabrics and how they will respond in the papermaking process.

  • 14.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Andersson, Niclas
    BTG Instruments AB.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Impact of dissolved matter in the oxygen delignification stage2017In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 5, p. 275-284Article in journal (Refereed)
    Abstract [en]

    The presence of dissolved matter in the pulp suspension in an oxygen (O-2) delignification stage, consisting mainly of dissolved lignin, is normally considered to negatively affect the delignification rate due to the competing reactions between the fiber bound lignin and the lignin dissolved in the filtrate. Recirculated oxidized filtrate from the post-O-2 washing is usually considered to be less harmful to the delignification efficiency than unoxidized dissolved matter originating from the cooking stage. To develop a better understanding of the mechanisms of the dissolved matter's reactions and impact on the O-2 stage performance, laboratory oxygen delignification experiments with varying levels of unoxidized and oxidized dissolved matter were conducted. The results showed that unoxidized dissolved matter had a negative impact on the delignification in the O-2 stage, whereas oxidized dissolved matter actually had a positive effect. The delignification efficiency of the laboratory experiments thus depends on both the amount of dissolved matter and its origin. The pulp viscosity decreased with increasing dissolved matter content irrespective of its origin but at higher COD levels; however, the viscosity drop was larger for the unoxidized dissolved matter. In terms of selectivity, the oxidized filtrate had a similar impact as additional NaOH charge. Both types of filtrates consumed hydroxide and the final pH decreased with increasing dissolved matter content. The final pH was significantly lower in the unoxidized filtrate experiments at higher COD levels, indicating a high reactivity between the unoxidized dissolved matter and the oxygen in the reactor. Based on the results, further understanding is achieved about the relation between pre-O-2 washing performance and process configuration in an actual mill case, as well as the impact of dissolved matter on delignification. The importance of efficient removal of harmful unoxidized dissolved matter is verified, but the results also suggest that the oxidized dissolved matter that is recirculated from post-O-2 washing actually has a significant positive impact on the delignification and is not just a potential problem in case of carryover to the bleach plant. Subsequently, pulp washing efficiency is critical both pre- and post-O-2.

  • 15.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. BTG Instruments AB, Saffle, Sweden..
    Andersson, Niclas
    BTG Instruments AB, R&D & Business Dev, Saffle, Sweden..
    Van Fleet, Rick
    BTG Amer Inc, Fiber Line, Norcross, GA USA..
    Mathur, Akhlesh
    BTG Instruments, BTG Asia Fiber Segment & SEA, Singapore, Singapore..
    Germgard, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Impact of dissolved lignin in oxygen delignification and chlorine dioxide stages2016In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 3, p. 167-174Article in journal (Refereed)
    Abstract [en]

    While carryover of dissolved lignin between stages in the pulp mill fiber line is a well-known problem, it is still typically seen only as a minor disturbance factor or bias in the control of oxygen (O-2) delignification and bleaching stages. The present study, however, reveals that it plays a larger role than anticipated, and that it should be properly analyzed in order to correctly control the process stages. This is especially important for the O-2 and D-0 stages as the lignin content is still high in these positions. The results of the study show that dissolved lignin carried over between stages may have a significant impact on the bleaching chemical consumption and, indirectly, on the pulp quality. Mill investigations have shown very large variations in the dissolved lignin content in the pulp before the oxygen delignification stage and before the D-0 stage that have significantly influenced the bleaching chemical demand and, subsequently, the degree of delignification. In order to develop a better understanding of the mechanisms of the dissolved lignin's reactions, laboratory O-2 and D-0 experiments with controlled levels of dissolved lignin were conducted. It was anticipated that a better feedforward control could be achieved using an online dissolved lignin measurement, and results from mill trials are presented. Chlorine dioxide laboratory experiments using different levels of carryover (i.e., different dissolved lignin contents) were conducted. It was concluded that the filtrate kappa number provides a relevant measure of the bleach demand due to the dissolved lignin and that, subsequently, the combined fiber and filtrate kappa number provides an appropriate measure for optimum feedforward control of the stages. Mill results support these findings, which show that the chemical consumption is reduced significantly using the total kappa number. The post-D or post-DE kappa number feedback control can most probably be eliminated by using this technology.

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