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  • 1.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Enzyme treatment of dissolving pulps as a way to improve the following dissolution of the fibres2012Konferansepaper (Annet vitenskapelig)
  • 2.
    Annergren, Göran
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Instability of acidic sulfite cooking of softwoods2013Annet (Annet vitenskapelig)
  • 3.
    Barbier, Christophe
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Rättö, Peter
    Hornatowska, Joanna
    Coating models for an analysis of cracking behavior between folded paper and creased board2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Creasing coated carton board or folding coated magazine paper, result in large strains in the surface layer of the paper product and might result in surface cracks, which decrease the quality of the products. A better understanding of the mechanical properties of coated layers increases the knowledge needed to reduce crack formation in coated fiberbased materials.The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and a Ground Calcium Carbonate (GCC) pigment were used. The binder was either an S/B latex or an S/B latex combined with starch.

  • 4. Beder- Miller, Sandra
    et al.
    Andersson, Niclas
    Wilke, Caroline
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Biazzo, Tom
    van Fleet, Rick
    Germgård, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Is Conductivity the Best Measurement of Bleach Plant Carryover?2014Konferansepaper (Fagfellevurdert)
  • 5.
    Broms, Helen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Tillverkning av högviskös viskos i laboratorieskala: Effekter av enzymatisk behandling på dissolvingmassans viskositet och reaktivitet2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

     I viskosprocessens inledande merceriseringssteg behandlas cellulosa (dissolvingmassa) med natriumhydroxid (NaOH) varvid cellulosan omvandlas till alkalicellulosa. Därpå följer en sulfidering med koldisulfid (CS2) som omvandlar alkalicellulosa till natriumxantogenat. Xantatet löses i en alkalisk lösning och en trögflytande vätska, viskos, bildas. Vid tillverkning av spinnviskos är sista steget i processen en surgörning där koldisulfiden spjälkas av och cellulosan återbildas i form av en tråd. Vid tillverkning av högviskös viskos (Freudenberg HP) sker regenereringen i basisk miljö men vid förhöjd temperatur (100°C), och återbildningen av cellulosa ger då en cellulosabaserad bädd. Genom att öka dissolvingmassans reaktivitet skulle förbrukningen av koldisulfid i sulfideringssteget kunna minskas. Med en ökad reaktivitet menas att fler hydroxylgrupper på cellulosan blir tillgängliga för vidare reaktioner med natriumhydroxid och koldisulfid. Detta skulle kunna möjliggöras med en enzymatisk förbehandling av massan.

    Det första delmålet i projektet var att producera en viskos med hög viskositet i laboratorieskala. Projektets andra mål var att undersöka effekterna av en enzymatisk behandling, med enzymet Carezyme®, på massans viskositet och reaktivitet.

    En studie gjordes för att se hur olika tider i viskosprocessens andra steg, pressteget, påverkade cellulosahalten och luthalten för alkalicellulosa. Resultaten tydde på att en längre presstid gav en högre cellulosahalt upp till en viss tidpunkt. Vid 195 sekunder avklingade kurvan och effekten av en längre presstid minskade. Resultatet visade också på att mängden lut i alkalicellulosaprovet var relativt konstant och att luthalten inte påverkas nämnvärt av pressningen.

    Vidare genomfördes försök kring viskosprocessens sulfideringssteg. Det fanns under projektets gång stora svårigheter i att uppnå samma höga nivå på gammatalet vid produktion av viskos i laborativ skala (52-58 %) som vid produktion i fabriksskala (68-70 %). Gammatalet är ett mått på hur väl koldisulfid har reagerat med cellulosa under sulfideringen. I ett försök att öka gammatalet satsades en större mängd koldisulfid, med förhoppningen att kunna kompensera för den relativt stora andel koldisulfid som befann sig i gasfas under reaktionen och som därmed inte var aktiv under sulfideringen. Den ökade mängden koldisulfid resulterade dock inte i en ökning av gammatalet. I ett annat försök tillsattes en svag natriumhydroxidlösning direkt till sulfideringskärlet vid avslutad reaktion, utan att någon effekt på gammatalet kunde påvisas. Det undersöktes även om ett ökat förhållande mellan luthalt och cellulosahalt i alkalicellulosan kunde ge någon positiv effekt på gammatalet. Denna förändring gav dock inget ökat gammatal.   

    Dissolvingmassaprover behandlades med enzymet Carezyme® för att kunna studera dess inverkan på massans reaktivitet och viskositet.  Resultaten visade på en tydlig nedgång i viskositet med högre koncentrationer av enzym. Reaktiviteten på den enzymbehandlade massan ökade i jämförelse med den obehandlade massan. Då viskos producerades med en enzymbehandlad massa kunde ingen effekt av enzymbehandlingen noteras, med avseende på gammatalet.

     

  • 6.
    Christophliemk, Hanna
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Ullsten, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Johansson, Caisa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Järnström, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Starch-poly(vinyl alcohol) barrier coatings for flexible packaging paper and their effects of phase interactions2017Inngår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 111, s. 13-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Starch and poly(vinyl alcohol) based barrier coatings for flexible packaging papers were studied. Both octenyl succinate modified and hydroxypropylated corn and potato starches were blended with regular and ethylene modified poly(vinyl alcohol) to increase the water vapor barrier properties and enhance the flexibility of the starch coatings, in order to accomplish superior barrier performance. Phase separation between starch and poly (vinyl alcohol) was studied in detail, both in the solution and in dry draw-down coatings on paper. The barrier performance of the coated paper was evaluated with respect to water vapor transmission rate. Conditions for the creation of a thin surface layer consisting of only one of the pure polymers were identified and discussed in terms of phase separation in solution migration of poly(vinyl alcohol) to the uppermost surface layer. The phase separation promoted low water vapor transmission rates also with a rather high fraction of starch in the coatings

  • 7.
    Ekbåge, Daniel
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Håkansson, Helena
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Time series analysis of refining conditions and estimated pulp properties in a chemi-thermomechanical pulp process2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 3, s. 5451-5466Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Frequently sampled process data from a conical disc refiner and infrequently sampled pulp data from a full scale chemi-thermomechanical pulp (CTMP) mill were evaluated to study autocovariance with aspects of potential dynamic modelling applicability. Two trial measurements with an online pulp analyzer at decreased sampling intervals were performed. For variability analysis, time-series containing up to one day of operational data were used. At the chip refiner, the clearest significant autocovariance was identified for the specific electricity consumption, based on the longer sequences. Most of the estimated pulp properties indicated low or non-significant autocovariance, limiting applicability of a specific dynamic model. A mill trial was conducted to investigate the impact from an increase in the conical disc gap on the specific electricity consumption and the resulting freeness. The response time from the gap change in the refiner to measured change in freeness was estimated at 19 min, which was approximately the hydraulic residence time in the latency chest. The relevance of this study lies in applicability of mill-data-driven modelling to capture the dynamics of a specific refining process. Through mill trials the sampling speed of pulp properties was more than doubled to gain insights into short term systematic variations by applying time-series-analysis.

  • 8.
    Ekbåge, Daniel
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Trial measurements in a CTMP-process to perform time-series analysis of refining conditions and estimated pulp properties2017Konferansepaper (Annet vitenskapelig)
  • 9.
    Erhardsson, Erik
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Aktivering av en dissolvingmassa med enzymer före en konventionell viskosprocess2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In conventional viscose manufacturing, a large amount of carbondisulfide is consumed. This amount has to be decreased to keep the production cost down and to reduce the environmental impact. The purpose with this work was to show if an enzyme treatment of a dissolving pulp could increase the degree of substitution in the viscose so that the amount of carbon disulfide consumed in the process could be decreased. Previous investigations by Kvarnlöf (2007), Engström et.al. (2006) and Henriksson et.al. (2005) has shown that the reactivity of a dissolving pulp (the cellulose raw material) increased when it was pre-treated with endoglucanase (enzyme). Kvarnlöf (2007) also showed that the amount of carbon disulfide that is needed to produce an ordinary viscose (in this work a more viscous viscose has been investigated) could be reduced with one third because of the enzyme treatment.

     

    In this thesis, viscose has been manufactured in a laboratory where the process has been adapted to look like the industrial as far as possible. Analyses were done on the viscose viscosity and degree of substitution. A reference curve was made with the percentage carbon disulfide load versus the viscose gamma number (degree of substitution). Then it was investigated how an enzyme treatment of the dissolving pulp affected the viscose. After the enzyme treatment, the manufacturing process for viscose was done in the exact same way as when the reference tests were done. The enzyme used in this thesis was Carezyme which contents endoglucanase. Then the results from the analyses of the viscose manufactured from enzyme treated dissolving pulp and the reference curve was compared. A positive result would have been that viscose manufactured with enzyme treatment gets a higher gamma number than viscose, with the same load of carbon disulfide, manufactured in the regular way.

     

    The results showed that the degree of substitution had no effect at all; the viscose that has been manufactured from enzyme treated dissolving pulp resulted in gamma numbers on or very close to the reference curve. The only effect that could be shown was a decrease in viscosity, which unfortunately was an unwanted effect. The enzyme treatment has also hampered the process, where shorter fibres among other things have given poorer dewatering properties. Analyses on the viscose manufactured in the laboratory showed that it didn't have the same characteristics as viscose manufactured in a plant.

  • 10.
    Frodeson, Stefan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Henriksson, Gunnar
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Berghel, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Effects of moisture content during densification of biomass pellets, focusing on polysaccharide substances2019Inngår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 122, s. 322-330Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we pelletized four different pure polysaccharides represented cellulose - Avicel, hemicelluloses - locus bean gum mannan and beech xylan and other polysaccharides - apple pectin, and three woods - pine, spruce and beech. All were pelletized at 100° in a single pellet press unit with different level of moisture content from 0 to 15%. The maximal friction force and work required for compression and friction was analyzed together with the pellet density and hardness. The results showed that xylan pellets completely changed in color at 10% moisture content, and this also occurred to some extent with pectin pellets. The color of both Avicel and locus bean gum pellets were not affected at all. During compression, the results showed that water does not affect compression up to 5 kN, while above 5 kN water decreases the energy need for densification of Avicel, locus bean gum and woods. Above 5 kN the energy needs for compressing xylan and pectin increases with increased moisture content. The hardest pellets were produced from Avicel, while locus bean gum produced the weakest pellets. The study concludes that there is a significant difference in how water affects the two hemicelluloses, glucomannan and xylan, during densification.

  • 11.
    Frodeson, Stefan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Henriksson, Gunnar
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Berghel, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Pelletizing pure biomass substances to investigate the mechanical properties and bonding mechanisms2018Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, nr 1, s. 1202-1222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solid fuel for heating is an important product, and for sustainability reasons, it is important to replace nonrenewable fuels with renewable resources. This entails that the raw material base for pellet production has to increase. A broader spectrum of materials for pelleting involves variation in biomass substances. This variation, due to lack of knowledge, limits the possibilities to increase the pellet production using new raw materials. In this study, pellets were produced with a single pellet press from 16 different pure biomass substances representing cellulose, hemicellulose, other polysaccharides, protein, lignin, and extractives, and five different wood species, representing softwoods and hardwoods. All pellets were analyzed for the work required for compression and friction, maximum force needed to overcome the backpressure, pellet hardness, solid density, and moisture uptake. The results showed that the hardest pellets were produced from the group of celluloses, followed by rice xylan and larch arbinogalactan. The weakest pellets were from the group of mannans. Conclusions are that the flexible polysaccharides have a greater impact on the pelletizing process than previously known, and that the differences between xylan and glucomannan may explain the difference in the behavior of pelletizing softwoods and hardwoods.

  • 12.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Aspects on the reactivity of dissolving pulps prior to viscose preparation2012Konferansepaper (Annet vitenskapelig)
  • 13.
    Hallbäck, Nils
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Korin, Christer
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Barbier, Christophe
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Nygårds, Mikael
    KTH.
    Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board2014Inngår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 27, nr 9, s. 701-712Artikkel i tidsskrift (Fagfellevurdert)
  • 14.
    Henriksson, Lisa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Frodeson, Stefan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Berghel, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Andersson, Simon
    Emerging Cooking Solutions Sweden AB.
    Ohlson, Mattias
    Emerging Cooking Solutions Sweden AB.
    Bioresources for Sustainable Pellet Production in Zambia: Twelve Biomasses Pelletized at Different Moisture Content2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 2, s. 2550-2575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of charcoal and firewood for cooking is common in Zambia,and its utilization is suchthat the deforestation rate is high, energy utilization is low, and unfavorable cooking methods lead to high death rates due to indoor air pollution mainly from particulate matter and carbon monoxide.Byusing an alternative cooking method, such as pellet stoves, it is possible to offer a sustainable solution, provided that sustainable pelletproduction can be achieved. In this study, 12different available biomaterials were pelletizedina single pellet unitto investigate their availability as raw materials for pellet production in Zambia. The study showedthat sicklebush and pigeon pea generatedthe same pelleting properties correlated withcompression and frictionand that both materials showedlow moisture uptake. The study also identifiedtwo groups of materials that broadenedthe raw material base and helpedto achieve sustainable pellet production.Group 1consisted of materials with equal pelletingabilities (miombo, peanut shell, pigeon pea,and sicklebush) andGroup 2 consistedof materialsthat showed low impact of varying moisture content(eucalyptus, miombo, peanut shell, pigeon pea, and sicklebush). The hardest pellet was made from Tephrosia, which wasfollowed by Gliricidia.

  • 15.
    Hubbe, Martin A.
    et al.
    North Carolina State Univ, Dept Forest Biomat,.
    Alen, Raimo
    University Jyvaskyla, Finland.
    Paleologou, Michael
    FPInnovations, Canada.
    Kannangara, Miyuru
    Natl Res Council Canada.
    Kihlman, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lignin Recovery from Spent Alkaline Pulping Liquors Using Acidification, Membrane Separation, and Related Processing Steps: A Review2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 1, s. 2300-2351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomena have potential to enable higher-value uses of black liquor components, including biorefinery options, alternative ways to recover the chemicals used to cook pulp, and debottlenecking of kraft recovery processes.

  • 16.
    Hämäläinen, Pyry
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    On the determination of transverse shear properties of paper using the short span compression test2017Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 107, s. 22-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko-Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young's modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko-Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose.

  • 17.
    Jireskog, Elin
    Karlstads universitet.
    Påverkan av spädvätskans pH och renhet på sulfatmassans blekbarhet: Laborativa försök och fabriksförsök för att minska kemikalieförbrukningen2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 18.
    Johansson, Caisa
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Going through the barrier2012Inngår i: Food Science & Technology, ISSN 1475-3324, Vol. 26, nr 3, s. 32-34Artikkel, forskningsoversikt (Annet vitenskapelig)
  • 19.
    Johansson, Caisa
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Bras, Julien
    France.
    Mondragon, Inaki
    Spain.
    Nechita, Petronela
    Romania.
    Plackett, David
    Danmark.
    Simon, Peter
    Slovakia.
    Gregor Svetec, Diana
    Slovenia.
    Virtanen, Sanna
    Finland.
    Giacinti Baschetti, Marco
    Italy.
    Breen, Chris
    UK.
    Clegg, Fransic
    UK.
    Aucejo, Susana
    Spain.
    Renewable fibers and bio-based materials for packaging applications-a reveiw of recent developments2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 2, s. 2506-2552Artikkel, forskningsoversikt (Fagfellevurdert)
  • 20.
    Karlsson, Hanna
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Strength Properties of Paper produced from Softwood Kraft Pulp: Pulp Mixture, Reinforcement and Sheet Stratification2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For paper producers, an understanding of the development of strength properties in the paper is of uttermost importance. Strong papers are important operators both in the traditional paper industry as well as in new fields of application, such as fibre-based packaging, furniture and light-weight building material. In the work reported in this thesis, three approaches to increasing paper strength were addressed: mixing different pulps, multilayering and reinforcement with man-made fibres. In specific:

    The effects of mixing Swedish softwood kraft pulp with southern pine or with abaca (Musa Textilis) were investigated. Handsheets of a softwood kraft pulp with the addition of abaca fibres were made in a conventional sheet former. It was seen that the addition of abaca fibres increased the tearing resistance, fracture toughness, folding endurance and air permeance. Tensile strength, tensile stiffness and tensile energy absorption, however, decreased somewhat. Still it was possible to add up to about 60% abaca without any great loss in tensile strength. As an example, with the addition of 30% abaca, the tear index was increased by 36%, while the tensile index was decreased by 8%.

    To study the effect of stratification, a handsheet former for the production of stratified sheets, the LB Multilayer Handsheet Former was evaluated. The advantage of this sheet former is that it forms a stratified sheet at low consistency giving a good ply bond. It was shown to produce sheets with good formation and the uniformity, evaluated as the variation of paper properties, is retained at a fairly constant level when the number of layers in the stratified sheets is increased. The uniformity of the sheets produced in the LB Multilayer Handsheet Former is generally at the same level as of those produced in conventional sheet formers.

    The effects of placing southern pine and abaca in separate layers, rather than mixing them homogeneously with softwood pulp were studied. Homogeneous and stratified sheets composed of softwood and southern pine or softwood and abaca were produced in the LB Multilayer Handsheet Former. It was found that by stratifying a sheet, so that a pulp with a high tear index and a pulp with a high tensile index are placed in separate layers, it was possible to increase the tear index by approximately 25%, while the tensile index was decreased by 10-20%. Further, by mixing a pulp with less conformable fibres and no fines with a pulp with more flexible fibres and fines, a synergy in tensile strength (greater strength than that predicted by linear mass fraction additivity) was obtained.

    The effects of stratifying sheets composed of softwood and abaca were compared to the effects of refining the softwood pulp. Homogeneous and stratified sheets composed of softwood with three different dewatering resistances and abaca were also produced in the LB Multilayer Handsheet Former. It was found that by stratifying the sheets the tear index was retained while the tensile index was increased by the refining.

    The effects of reinforcing softwood pulp of different dewatering resistances with man-made fibres with low bonding ability were also investigated. Man-made fibres (i.e. regenerated cellulose, polyester and glass fibres) were added in the amounts 1, 3, or 5 wt% to softwood pulp of three different dewatering resistances. It was found that with refining of a softwood pulp and subsequent addition of long fibres with low bonding ability the tensile-tear relationship can be shifted towards higher strength values. The bonding ability of the man-made fibres was evaluated by pull-out tests and the results indicated that, in relation to the fibre strength, regenerated cellulose (lyocell) was most firmly attached to the softwood network while the glass fibres were most loosely attached.

  • 21.
    Khan, Kashif
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Development and evaluation of a puncture strength test method for sterilization paper2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main objective of this research project, carried out at Karlstad University was to investigate which paper property has the best correlation with the package integrity failure (puncture hole). To achieve this goal, a simple equipment was designed at Karlstad University. This research project was divided into two phases, more precisely first a test design with investigation of suitable parameters to carry out the tests with the newly designed equipment and secondly with the help of those parameters the investigation of paper properties which will have direct connection with puncture strength. Results showed that Tensile Energy Absorption (TEA) has the best correlation with puncture strength as compared to other paper properties used in this research project i.e. burst strength, strain at break, tear strength, and tensile strength. In real it seems to be reasonable as tensile energy absorption (TEA) is the amount of energy absorbed during straining until it breaks. Higher the tensile energy absorption, higher will be the resistance against puncture. Furthermore sack paper proved to be the type of paper grade that has the strongest resistance against package integrity failure, as it has the highest tensile energy absorption (TEA) as compared to other paper grades used in this research project. It was also observed that paper in a package should be stretched in order to minimize the risk of puncture hole.

  • 22.
    Kihlman, Martin
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Dissolvingmassa baserat på soda-AQ kokning: Potential för ökat förädlingsvärde av svensk skogsråvara2009Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Detta examensarbete genomfördes från begäran av två företag, Pöyry Sweden AB, Karlstad och Kiram AB. Arbetet var uppdelat i två delar, en litteraturstudie samt en experimentell del. I litteraturstudien kartlades olika processer för framställning av dissolvingmassa och olika processer för beredning av viskosfiber. Utöver det sammanställdes även några av de ledande aktörerna av joniska vätskor samt applikationer för cellulosabaserade produkter. Fokus genom hela arbetet har legat på svavelfria processer som t.ex. användandet av joniska vätskor för upplösning av cellulosa. I den experimentella delen undersöktes det om man via en förhydrolys följt av ett soda-AQ kok, en svavelfri process, kunde producera dissolvingmassa. Utöver produktion av dissolvingmassa undersöktes också filtratet som drogs av efter förhydrolysen.

    Under den experimentella delen varierades olika parametrar för att se hur det påverkade kvaliteten av massan. De parametrar som varierades vid förhydrolysförsöken var tid och antrakinon (AQ), för soda-AQ koket varierades tid, AQ och effektiv alkali (EA) halt. För ett förhydrolysförsök varierades även vätske/vedförhållandet. Vilka betingelser som skulle användas samt de mål som skulle uppnås fick man fram under litteraturstudien.

    För att nå målet med ett utbyte på ca 85 % efter förhydrolysen krävdes en temperatur på 160°C och tid på 1 timme för en förhydrolys med enbart vatten. Hypotesen om att en AQ tillsats redan vid förhydrolysen skulle sänka utbytet visades inte stämma, man fick då istället ett ökat utbyte. Målet för massorna efter soda-AQ koket var ett utbyte på ca 40 %, ett kappatal runt 30 och en viskositet > 1000 ml/g. Utförde man en förhydrolys som beskrivits ovan följt av ett soda-AQ kok med dessa betingelser: temperatur 160°C, tid ≥ 2 h, EA sats > 21 % och en AQ halt ≥ 1 kg/ton, fick man en dissolvingmassa som uppfyllde kraven.

    Kolhydratanalysen på filtratet visade att mestadels glukomannan brutits ner och lösts ut under förhydrolysen. Däremot skedde det ingen nedbrytning av cellulosa. Utförde man förhydrolysen på ett sådant sätt som beskrivits ovan bröt man ner en hemicellulosa mängd på ca 72 kg/ton flis. Det får ses som en ganska rejäl mängd eftersom man enbart använder vatten under förhydrolysen.

  • 23.
    Kihlman, Martin
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Medronho, Bruno
    University of Coimbra, Portugal; University of Algarve, Portugal.
    Romano, Anabela
    University of Coimbra, Portugal.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Lindman, Björn
    University of Coimbra, Portugal; Lund University, Sweden.
    Kinetic and Thermodynamic Effects on Cellulose Fibre Dissolution in an Alkali Based Solvent: Influence of Additives and Pretreatments2012Manuskript (preprint) (Annet vitenskapelig)
  • 24.
    Kihlman, Martin
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Wawro, Dariusz
    Perzon, Erik
    Hedlund, A
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Preparation of cellulosic fibres in semi-pilot scale from NaOH-solutions2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Cellulose is a highly interesting polymer for bio-based products and can be utilized in a wide variety of products, either in its native form or derivatized. One application for cellulose that is predicted to grow remarkably is textile fibers. It is believed that in the future a number of forest based raw materials can play a major role in replacing fossil oil based fibers and cotton to new ecological man-made fibers in both woven and nonwoven end applications.[p]The CelluNova project was initiated in early 2010 with the objective of developing a new environmentally friendly process for production of cellulose-based textile fibers. Cellulose fibers based on dissolving pulp have so far successfully been prepared from semi-pilot scale trials in a stepwise procedure. The solvent systems used were the NaOH/urea/thiourea system and the NaOH/ZnO system, at a temperature below 0°C, and a cellulose concentration as high as 6-8%.

  • 25.
    Konradsson, Rikard
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Produktionsökning i sileriet vid Rottneros Bruk2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 26.
    Kvarnlöf, Niklas
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Aspects on the reactivity of dissolving pulps prior to viscose preparation2012Konferansepaper (Annet vitenskapelig)
  • 27.
    Land, Cecilia
    Karlstads universitet, Institutionen för kemi.
    Laboratory method for the study of moisture-induced waviness in paper2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Paper that is subjected to moisture undergoes dimensional changes. It expands during moistening and shrinks during drying. When the paper is under tension between rollers, the effects are complex since shrinkage and expansion are restricted in the width direction. Waves can then appear on the paper web. This can be a problem in heatset web offset printing. The problem is known as waviness or fluting. The printed papers exhibit a wavy shape, which is visually disturbing due to light reflections which create glossy streaks. The aim of the work described in this thesis was to develop a method suitable for studying the moisture- and tension-induced waviness. Experiments were carried out on a laboratory scale to study how such waves develop during moistening and drying. The experimental setup was based on a modified tensile tester. A CCD camera and image analysis based on the STFI-OptiTopo technique was used to characterise the waviness. Moistening and drying were achieved by changing the surrounding air humidity. The method was used to study the effect of moisture uptake by the paper, and to evaluate the effect of tension on the waviness. It was found that increasing moisture resulted in a higher waviness amplitude, but that the web tension controlled the wavelength of the waviness. A high tension gave rise to a shorter wavelength. The measured wavelength was compared with a previously suggested model and the predicted wavelength was about twice as high as the measured wavelength.

  • 28.
    Land, Cecilia
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Stolpe, Lennart
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Beghello, Luciano
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Modeling of bagginess due to storage of paper reels with ridges2009Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 8, nr 9, s. 18-22Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29.
    Land, Cecilia
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Wahlström, Torbjörn
    Stora Enso, Karlstad, Sweden.
    Stolpe, Lennart
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Moisture streaks and their relation to baggy paper webs2008Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 34, nr 4, s. 234-239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Significant and controlled wet streaks were imparted to laboratory-made kraft paper sheets having an initial moisture content of 50 %. The sheets were then dried under a specified strain according to different drying strategies. Both the wet streaks and the drying strain were applied in the CD in order to amplify the observed effects. The bagginess of the paper sheet, or the length profile, was measured after drying and relaxation. Moisture streaks remaining after unloading resulted in short streaks in the paper. Drying of the paper beyond moisture equilibrium also led to an uneven paper length, particularly when the paper was allowed to shrink during drying. No correlation was found between the tensile stiffness profile and the permanent length profile.

  • 30.
    Land, Cecilia
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Wahlström, Torbjörn
    Stora Enso, Karlstad, Sweden.
    Stolpe, Lennart
    Beghello, Luciano
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Plastic strain of moisture streaks at different moisture contents2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 4, s. 481-487Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An uneven moisture profile in the paper web during drying can cause runnability problems due to slack areas in the paper web. This study aims at indentifying the moisture level at which it is most important to keep the moisture even. This was evaluated with a laboratory study of plastic strain after loading wet paper samples to strains between 0.3-4% and unloading. The papers tested were made from softwood bleached kraft pulp and the moisture content varied between 9 and 50%. The plastic strain was highest at a moisture content of 20-30%, but the sensitivity to moisture variations was highest at a moisture content of 10-20%. The paper was also sensitive to moisture variations above a moisture content of 30%.

    According to calculations based on the laboratory results, moist streaks appearing at a high moisture content would turn into short streaks, and moist streaks appearing at a low moisture content would turn into long streaks. A machine trial with moist streaks applied at high moisture resulted in short streaks in the paper, confirming the qualitative results of the laboratory study.

  • 31.
    Larsson, Markus
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Kullander, Johan
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Utbytets och malningens inverkan på NSSC-massans egenskaper2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Neutralsulfitkokning av björk möjliggör ett högt utbyte av hemicellulosa, vilket bidrar positivt till flutingens egenskaper och minskar vedkostnaden. Neutralsulfitkoket ska avbrytas när delignifieringen nått tillräckligt långt för att veden ska kunna defibreras skonsamt med en rimlig energiinsats, men innan nedbrytningen av hemicellulosa hunnit accelerera. Syftet med detta examensarbete var att undersöka utbytets och malningens inverkan på NSSC-massans egenskaper.

    En laboratoriestudie genomfördes där massan kokades till olika utbyten och maldes vid olika insatser. Resultatet av den studien användes sedan för att ställa om kokaren och raffinörerna på lämpligt sätt vid fabriksförsöken. Massaprover togs ut efter det andra kvarnsteget och skickades för analys. De mest väsentliga egenskaperna för fluting testades genom CCT (Corrugated Crush Test), CMT (Concora Medium Test) och SCT (Short Span Compression test) men övriga konventionella egenskaper testades likväl. En avgörande egenskap för fluting är också dess krypstyvhet som undersöktes på laboratorie genom isokrona kryptester. För att få en djupare förståelse för NSSC-massans egenskaper samt kokningens och malningens inverkan på dessa utfördes även fiberkaraktärisering.

    Resultatet visar att styrkan på NSSC-massan kan påverkas genom att variera både utbytet och effekten i raffinörerna. För att åstadkomma en signifikant styrkeökning krävs ett lågt utbyte tillsammans med en hög effekt i raffinörerna. Kraftiga ändringar av dessa parametrar leder dessvärre till att papperets egenskaper förändras i den grad att körbarheten på maskin kan påverkas. Studien visar även att fluting som uppfyller dagens riktvärden kan framställas kostnadseffektivt genom ett högt utbyte i kokaren och en hög insats i raffinörerna. Samtidigt erhålls då en ljusare massa, vilket kan vara betydande i vissa fall. Krypmätningarna visar samtidigt att malningen i positiv bemärkelse påverkar krypstyvheten medan utbytets inverkan är mer svårtolkat. Ett allt för högt utbyte verkar dock vara negativt ur krypstyvhetssynpunkt.

  • 32.
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Ytbehandling av papper och papper som leder ström2012Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 33.
    Lestelius, Magnus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Järnström, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013), Paper Surface Centre.
    Carlsson, Gunilla
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Bonnerup, Chris
    Govindarajan, Venkatesh
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Oxygen permeabilityand economic-environmental impact studies of some polyvinyl alcohol dispersionbarrier coatings for packaging applications2017Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Purposes of employing barrier coatings in packaging, and in particular food packaging, can be to increase the shelf life, preserve colour, odour, and taste, and to protect from a harmful environment in general. Barrier coatings can thus help to reduce food waste along the value chain until end use. Including both materials choice for packaging and the possible fates of the used package, even further steps to provide greater knowledge for decisions on choices of packaging solutions. To that end, we have conducted several experimental and transport modeling studies on oxygen barrier coatings performance. The coating system of choice    has been dispersion coatings of poly vinyl alcohol (PVOH), with additions of kaolin. Physical and chemical features of the coatings were characterized to obtain information on polymer crystallinity, free volume and filler orientation as these characteristics are influential to the oxygen mass transport performance. In turn, the oxygen mass transport was also measured, both in steady state and dynamically. In so doing, we obtained information    useful for developing a general model to describe the oxygen permeability taking into account the physical and chemical features, described above, of the coating layer. Attempts on describing the interdependence and impact, for instance between crystalline and amorphous polymer regions and moisture, was added to the model. The model showed agreement to experimental data for PVOH-kaolin coating in this particular case. However, the basic permeability model has been applied to  many different polymers.

    To further explore the potential of these types of coating, which are technically possible to    produce in paperboard production, an economic-environmental impact comparison to other existing material solutions was made. Four barrier material alternatives – starch, polyethylene, ethyl vinyl alcohol (chosen as an alternative for PVOH, where data was difficult to obtain) and kaolin, and latex and kaolin, were analyzed with respect to cost and global warming potential. Weighting and comparing cost to environmental aspect, weighting    factors based on interviews with experts in the packaging value chain, starch emerges as the most sustainable alternative. However, previous coating and mass transport studies also shows how these renewable materials require some further technical development to be competitive.

    The mass transport model can serve as a tool for customizing barrier coatings and to predict the barrier performance, as permeability is obtained and thus shelf-life estimation is    possible. The overall concept, the combination of assessment of structural performance and the environmental studies, can be employed to find sustainable food packaging solutions.

  • 34.
    Lin, Wamei
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013). Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Malutta, Raffaelle
    Waste heat recovery by organic rankine cycle (ORC) for moist exhaust gases from paper industry2017Inngår i: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), American Society of Mechanical Engineers (ASME) , 2017, Vol. 6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Large potential exists in recovering waste heat from paper industry processes and machinery. If the overall energy efficiency would be increased, it could lead to significant fuel savings and greenhouse gas emission reduction. The organic Rankine cycle (ORC) system is a very strong candidate for converting low-grade waste heat into power. However, there is a lot of water vapor containing latent heat in the exhaust gases from the drying process in the paper industry. Thus, the aim of this research work is to increase the efficiency of the ORC system by recovering not only the sensible heat but also the latent heat from the exhaust gases in the paper drying process. In order to recover the latent heat from the moist exhaust gases, one idea of this article is to introduce a direct contact condensing unit into the ORC system. The performance of ORC system with the direct contact condensing unit was analyzed by using the CHEMCAD software. A case study was conducted based on data of the exhaust gases from a tissue production / drying machine. Latent heat will be recovered when the evaporating temperature of the ORC working fluid is lower than the dew point of the water vapor in the exhaust gases. The results showed that the available heat load was increased when the evaporating temperature was reduced. Furthermore, a performance comparison of the ORC systems with and without the direct contact condensing unit was carried out in the case study as well. The results showed that the ORC system with the direct contact condensing unit not only could recover latent heat from the water vapor in the exhaust gases but also could have a small size and small volume evaporator in the ORC system.

  • 35.
    Marques da Silva Näsman, Aline Fernanda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Effects of refining energy, pH and different types of fibers on the strength of paper2011Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    This report is the result of an examination work at Karlstad University. This thesis was performed in cooperation with Billerud Gruvön. The purpose of this project was to investigate how refining energy, pH and different types of fibers affect the strength of the final paper. A laboratory study was performed where softwood and hardwood unbeaten pulps and broke had their pH adjusted after disintegration and then they were refined with different energy inputs in a laboratory pulp refiner. Mixtures containing softwood and broke or hardwood and broke were prepared to produce hand sheets. As reference, refined pulp and broke from Billerud Gruvön were taken and hand sheets were also produced. The results indicate that it is possible to affect the strength properties of paper by varying pH, different types of fibers and energy input in the refiner.

  • 36.
    Montibon, Elson
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Modification of Paper into Conductive Substrate for Electronic Functions: Deposition, Characterization and Demonstration2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis investigates the modification of paper into an ion- and electron-conductive material, and as a renewable material for electronic device. The study stretches from investigating the interaction between the cellulosic materials and the conducting polymer to demonstrating the performance of the conductive paper by printing the electronic structure on the surface of the conductive paper. Conducting materials such as conducting polymer, ionic liquids, and multi-wall carbon nanotubes were deposited into the fiber networks.

    In order to investigate the interaction between the conducting polymer and cellulosic material, the adsorption of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(4-styrene sulfonate) (PEDOT:PSS) onto microcrystalline cellulose (MCC) was performed. Electroconductive papers were produced via dip coating and rod coating, and characterized. The Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS) images showed that the conducting polymer was deposited in the fiber and in fiber-fiber contact areas. The X-ray Photoelectron Spectroscopy (XPS) analysis of dip-coated paper samples showed PEDOT enrichment on the surface. The effects of fiber beating and paper formation, addition of organic solvents and pigments (TiO2, MWCNT), and calendering were investigated. Ionic paper was produced by depositing an ionic liquid into the commercial base paper. The dependence to temperature and relative humidity of the ionic conductivity was also investigated. In order to reduce the roughness and improve its printability, the ionic paper was surface-sized using different coating rods.  The bulk resistance increased with increasing surface sizing. The electrochemical performance of the ionic paper was confirmed by printing PEDOT:PSS on the surface. There was change in color of the polymer when a voltage was applied. It was demonstrated that the ionic paper is a good ionic conductor that can be used as component for a more compact electronic device construction.

    Conductive paper has a great potential to be a flexible substrate on which an electronic structure can be constructed. The conduction process in the modified paper is due to the density of charge carriers (ions and electrons), and their short range mobility in the material. The charge carrying is believed to be heterogeneous, involving many charged species as the paper material is chemically heterogeneous.

  • 37.
    Montibon, Elson
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Preparation of Electroconductive Paper by Deposition of Conducting Polymer2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis describes an investigation into the interaction between the conducting polymer and cellulosic materials, and the preparation of electroconductive paper. The adsorption behavior of the conducting polymer onto cellulosic materials was characterized. Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrene sulfonate) (PEDOT:PSS) was used as conducting polymer because of its attractive properties in terms of conductivity, water solubility, and environmental stability. The model substrate used for adsorption was microcrystalline cellulose (MCC). Various pH levels and salt concentrations were explored to completely understand the adsorption behavior of PEDOT:PSS. The variation in surface charge characteristics when the pH and salt concentration were changed was monitored by polyelectrolyte titration and zeta potential measurement. The adsorption isotherm showed a broad molecular distribution of the conducting polymer and considerable interaction between the polymer and MCC. As the pH of the solution was increased, the adsorbed amount decreased. With varying salt concentrations, the adsorption passed through a maximum. The extent of deposition of PEDOT:PSS on the surface of cellulosic fibers was investigated using X-ray Photoelectron Spectroscopy (XPS) with a commercial base paper as substrate. XPS analysis of dip-coated paper samples showed PEDOT enrichment on the surface. The degree of washing the dip-coated paper with acidic water did not significantly affect the PEDOT enrichment on the surface.

     

    A base paper was coated with PEDOT:PSS blends to produce electroconductive papers. The bulk conductivities (σdc) of the coated papers were measured using a four-probe technique and impedance spectroscopy. One-side and two-side coating gave comparable conductivity levels. Various organic solvents added to the PEDOT:PSS dispersion at different concentrations showed various effects on the bulk conductivity of the coated paper. Blends containing sorbitol and isopropanol did not enhance the bulk conductivity of the coated paper, and at high concentrations these organic solvents lowered the conductivity. Paper samples coated with a PEDOT:PSS blend containing N-methylpyrrolidinone (NMP) and dimethyl sulfoxide (DMSO) exhibited a higher conductivity than when coated with pure PEDOT:PSS, due to conformational changes and their plasticizing effect. The effect of calendering was investigated and only the sample subjected to 174 kN/m line load after coating showed significant conductivity enhancement. The addition of TiO2 pigment lowered the bulk conductivity of the paper. Contact angle measurements were made to monitor the effect of coating the paper with PEDOT:PSS blends on the hydrophilicity of the paper samples. The amount of PEDOT:PSS deposited in the fiber network was determined using total sulfur analysis. Thus, this study makes use of conventional paper surface treatment as method for achieving bulk conductivity of paper in the semi-conductor range without significantly decreasing the paper strength.

  • 38.
    Naqvi, Muhammad
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013). Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Dahlquist, E.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Yan, J.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden & Department of Chemical Engineering, Royal Institute of Technology (KTH), Sweden.
    Naqvi, S. R.
    School of Chemical & Materials Engineering, NUST, Pakistan.
    Nizami, A. S.
    Center of Excellence in Environmental Studies, King Abdulaziz University, Saudi Arabia.
    Salman, C. A.
    Department of Energy, Building, and Environment, Mälardalen University, Sweden.
    Danish, M.
    State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, ECUST, China.
    Farooq, U.
    State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, ECUST, China.
    Rehan, M.
    Center of Excellence in Environmental Studies, King Abdulaziz University, Saudi Arabia.
    Khan, Z.
    Systems Power and Energy, School of Engineering, University of Glasgow, UK.
    Qureshi, A. S.
    Institute of Biotechnology and Genetic Engineering, University of Sindh, Pakistan.
    Polygeneration system integrated with small non-wood pulp mills for substitute natural gas production2018Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 224, s. 636-646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to examine the potential substitute natural gas (SNG) production by integrating black liquor gasification (BLG) island with a small wheat straw-based non-wood pulp mills (NPM), which do not employ the black liquor recovery cycle. For such integration, it is important to first build knowledge on expected improvements in an overall integrated non-wood pulp mill energy system using the key performance indicators. O2-blown circulating fluidized bed (CFB) gasification with direct causticization is integrated with a reference small NPM to evaluate the overall performance. A detailed economic analysis is performed together with a sensitivity analysis based on variations in the rate of return due to varying biomass price, total capital investment, and natural gas prices. The quantitive results showed considerable SNG production but significantly reduced electricity production. There is a substantial CO2 abatement potential combining CO2 capture and CO2 mitigation from SNG use replacing compressed natural gas (CNG) or gasoline. The economic performance through sensitivity analysis reflects significant dependency on both substitute natural gas production and natural gas market price. Furthermore, the solutions to address the challenges and barriers for the successful commercial implementation of BLG based polygeneration system at small NPMs are discussed. The system performance and discussion on the real application of integrated system presented in this article form a vital literature source for future use by large number of small non-wood pulp industries.

  • 39.
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper2014Inngår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, nr 13, s. 1587-1597Artikkel i tidsskrift (Fagfellevurdert)
  • 40.
    Nilsson, Lars
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Stenström, Stig
    Lunds universitet.
    Predicting water removal during vacuum dewatering from fundamental fibre property data2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 2, s. 265-271Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Control of the solids content after vacuum dewatering is vital for efficient control and energy use of the paper machine. Dewatering is a complex function of many parameters such as fibre and pulp properties as well as settings on the paper machine and a predictive model for dewatering will require extensive and detailed studies of the occurring physical phenomena. The hypothesis investigated in the present study is that fibre width and fibre length density measured for fibres suspended in water can be used for estimating the achievable dryness in vacuum dewatering. The hypothesis was tested by comparing model predictions to experimental data for 11 different pulps. The results show that the dryness after vacuum dewatering can be estimated from the fibre length density and the fibre width for the fresh pulps using an elliptical fibre cross-section model with a ratio of 0.48 between the short and long axes. For the dried pulps a lower value was needed to reach a good agreement.

  • 41.
    Nilsson, Lars
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Tysén, Aron
    Innventia AB.
    Vomhoff, Hannes
    Innventia AB.
    The influence of grammage and pulp type on through air drying2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 4, s. 651-659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of grammage and pulp type on through air drying was studied. The temperature of a sample was measured during the drying process and the observed temperature changes were used to evaluate the drying process. Laboratory sheets with grammages 15- 60 g/m², from two softwood and two hardwood bleached chemical pulps were used. All samples were analysed with respect to formation, flow resistance, modified permeability, mean drying time, non-uniformity of drying time, and area- and mass-specific drying rate. The pulps had different modified permeabilities but showed similar behaviour when analysed as a function of grammage. A constant value was found for higher grammages, while an increase in modified permeability was found at decreasingly low grammages. Almost all pulp and grammage combinations had similar area-specific drying rates, but the mass-specific drying rates decreased with grammage. However, the samples with lower grammages had mass specific drying rates independent of modified permeability, where samples with increasing grammage showed an increasing dependency. This implies that the drying efficiency at low grammages was not controlled by the volume flow of the drying air. A good correlation was found between energy needed to evaporate water and energy supplied by the drying air as estimated from the surface temperature and air flow measurement. The surface temperature can therefore be used to quantify the drying process.

  • 42.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Development of an Image Processing Tool for Fluorescence Microscopy Analysis of Paper Chemistry2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Paper making today is, to some extent, based on empirical knowledge. It is wellknown that fines, pH, charge and ion strength affect the manufacture of paper. One way of extending knowledge of the mechanisms of paper chemistry is to follow the trajectories of fines and additives in the paper suspension to gather information as to the manner in which they react. Four tracking algorithms adapted to the needs of this particular problem were implemented in order to track particles effciently. The tracking algorithms include two variants of the well-known "Lucas-Kanade algorithm" and template matching techniques based on cross-correlation and least squares matching. Although these techniques are similar in principle, the actual tracking can nevertheless differ; the Lucas-Kanade algorithms were found to be more invariant to noise, whereas the cross-correlation and least squares methods are more rapid to execute in Matlab. The tracking methods have been evaluated using a simulator to generate image sequences of synthetic particles moving according to Brownian motion. Tracking has also been evaluated on microscope images of real latex particles where the results have been compared to manual tracking. Tracking of both the simulated particles and the latex particles resulted in similar results when compared to known position and manual tracking, respectively.

  • 43.
    Nyflött, Åsa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Structure-Performance Relations of Oxygen Barriers for Food Packaging2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Food packaging should ensure the safety and quality of food, minimize spoilage and provide an easy way of storing and handling it. Barrier coatings are generally used to meet the demands placed on fibre-based food packages, as these have the ability to regulate the amount of gases that can enter them. Some gases are detrimental to food quality: oxygen, for example, initiates lipid oxidation in fatty foods. Using both experimental data and computer modelling, this thesis explains some aspects of how the structure of barrier coatings influences the mass transport of oxygen with the aim of obtaining essential knowledge that can be used to optimize the performance of barriers.

    Barrier coatings are produced from polyvinyl alcohol and kaolin blends that are coated onto a polymeric support. The chemical and physical structures of these barriers were characterized according to their influence on permeability in various climates. At a low concentration of kaolin, the crystallinity of polyvinyl alcohol decreased; in the thinner films, the kaolin particles were orientated in the basal plane of the barrier coating. The experimental results indicated a complex interplay between the polymer and the filler with respect to permeability.

    A computer model for permeability incorporating theories for the filled polymeric layer to include the polymer crystallinity, addition of filler, filler aspect ratio and surrounding moisture was developed. The model shows that mass transport was affected by the aspect ratio of the clay in combination with the clay concentration, as well as the polymer crystallinity. The combined model agreed with the experiments, showing that it is possible to combine different theories into one model that can be used to predict the mass transport.

    Four barrier coatings: polyethylene, ethylene vinyl alcohol + kaolin, latex + kaolin and starch were evaluated using the parameters of greenhouse gas emissions and product costs. After the production of the barrier material, the coating process and the end-of-life handling scenarios were analysed, it emerged that starch had the lowest environmental impact and latex + kaolin had the highest.

  • 44.
    Rahman, H.
    et al.
    Mittuniversitetet.
    Engstrand, P.
    Mittuniversitetet.
    Sandström, P.
    SCA R&D.
    Sjöstrand, Björn
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Dewatering properties of low grammage handsheets of softwood kraft pulps modified to minimize the need for refining2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 3, s. 397-403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.

  • 45.
    Rixen, Alexandra
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Energieffektivisering i ett reningsverk för skogsindustriellt avloppsvatten genom förfällning av extraktivämnen2011Independent thesis Basic level (university diploma), 20 poäng / 30 hpOppgave
    Abstract [en]

    Pulp- and papermills expend vast amounts of water in order to produce pulp, paper and cardboard. Hence, they alsocreate vast amounts of waste water which has to be cleaned before it can be released into the receiving body of water. Insuch a wastewater treatment plant, tremendous amounts of energy are expended by the aeration in the biologicalcleaning process. This aeration is necessary to supply the microorganisms that shall decompose organic material withoxygen, which they need for their metabolism. The transfer of oxygen from the gas phase to the liquid phase isprimarily inhibited by surface-active substances in the waste water like resin acids or fatty acids. The purpose of thisthesis has been to determine if the surface-active substances can be removed by means of chemical pre-precipitationbefore the waste water enters the biological cleaning step. Thus, the efficiency of the aeration shall be improved.In the laboratory, aeration tests were performed for plain water, water with added surface-active substances and CTMPwastewaterfrom Stora Enso Skoghalls Bruk. The test for water with added surface-active substances showed clearlythat these substances have a big influence on the aeration efficiency, which was impaired considerably compared withplain water.In order to determine how chemical precipitation influences the content of surface-active substances, screening trialswere performed with the CTMP waste water. The concentration of surface-active substances was estimated bymeasuring the surface tension of the waste water. The surface tension sinks with increasing concentration of thesesubstances. 250 ml CTMP-wastewater was precipitated with three different chemicals: PAX-XL60, PGA and AVR. Inorder to determine the optimal dosing as well as the optimal pH-value for goal-oriented precipitation of the surfaceactivesubstances, the precipitation was performed with different pH-values between 4 and 8 as well as for differentdoses of the precipitation chemicals. It was discovered that the optimal pH-value for precipitation with PAX-XL60 is7,5 while the precipitation with PGA had the optimal pH-value of 6. The optimal dosage for PAX-XL60 was 10 g/cm3,while the optimal dosage for PGA could not be determined because of the small waste water volume used in thescreening trials. The screening trials showed that the surface tension increased after precipitation with both PAX-XL60and PGA which leads to the assessment that the concentration of surface-active substances has decreased.Precipiation- and aeration trials in big lab-scale were performed at pH 7,5 and the optimal dosage of PAX-XL60. ForPGA, the precipitation and aeration trials were performed at pH 6 and the lowest dosage of the screening trials. Theaeration trials showed that precipitated CTMP-wastewater could be aerated more energy efficient than the samewastewater without precipitation.Calculations showed that energy costs can be reduced by nearly 90% by using the tested precipitation chemical PAXXL60respectively nearly 65% by using the tested precipitation chemical PGA according to the lab-scale trials. Thecosts for the chemicals are not included.

  • 46. Rättö, Peter
    et al.
    Hornatowska, Joanna
    Barbier, Christophe
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Influence of the distribution of the shape and size distribution of pigment particles on cracking in coating layers during creasing2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 4, s. 714-720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and two Ground Calcium Carbonate (GCC) pigments were used. The GCC pigments differed in their particle size distribution. The binder was either an S/B latex or an S/B latex combined with starch. The type of pigment seemed to have the greatest influence on the crack area in creased and folded board. Clay showed a larger crack area than the GCC with a broad particle size distribution. The GCC with a narrow particle size distribution showed a considerably larger crack area than both the clay pigment and the GCC with a broad particle size distribution. The coatings containing starch generally showed a larger crack area than the coatings that only contained the S/B latex. After the folding of the copy paper, the crack area showed a slightly different pattern. Here, it seemed that the binder was of greater importance than the type of pigment, with the coatings containing only latex showing a considerably lower crack area than the coatings containing starch. The coatings that were based on the clay pigment showed similar values as the coatings based on the GCC pigment with the broad particle size distribution. The coatings based on the GCC with the narrow particle size distribution showed displayed considerably higher crack areas than the coatings based on the other two pigments. The cracking tendency of the coatings, based on the GCC with the narrow particle size distributions was probably due to a greater demand for latex, i.e. smaller particles in the GCC with broad particle size distribution would probably fill in the voids and the GCC with the broad particle size distribution will therefore demand less binder. It was further suggested that the different loadings on the coating layer during the creasing and folding of the board, compared to the folding of copy paper, explain the different results obtained with the two base-substrates. 

  • 47.
    Sandberg, Maria
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för energi-, miljö- och byggteknik.
    Rixen, Alexandra
    Chemical flocculation as pretreatment for energy efficient biological treatment2012Inngår i: 10th IWA Symposium on Forest Industry Wastewater and 8th International Conference on the fate and effect of Pulp and Paper Mill Effluents, 2012, s. 42-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biological treatment of forest industry wastewaters uses large amounts of electrical energy. For many mills aeration is the single most energy intensive process in the wastewater treatment plant. The oxygen transfer from bubbles into the water volume is quite slow with low aeration efficiency as result. If the oxygen transfer can be improved, the efficiency can be improved and less compressed air will be needed for aeration with decreased energy costs as the result. It has been shown that surface-active extractives, such as fatty acids and resin acids, have a large impact on oxygen transfer in diffuser aeration systems. With chemical flocculation, extractives can be removed from the process streams. Trials have been made where pulp-mill process streams were pretreated with chemical flocculation before the oxygen transfer tests. When the chemical flocculation conditions were optimized to increase surface tension in the process stream, extractives were removed and the oxygen transfer rate increased in the following oxygen transfer tests. With the pretreatment also COD concentration decreased. The effect will be less need for oxygen for degradation in the following biological process. With decreased COD concentration and increased oxygen-transfer rate, energy can be saved in the biological treatment. Energy savings resulted in greater economic return than the cost for flocculating chemicals. If waste sludge can be used as energy source, one can even achieve a better result.

    Acknowledgements. This work was supported by ÅF-forskningsstiftelse and Stora Enso Skoghall mill.

  • 48. Schenzel, Karla
    et al.
    Almlöf Ambjörnsson, Heléne
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Two new methods determining the degree of substitution of carboxymethyl cellulose by utilizing NIR FT Raman and FT IR (ATR) spectroscopy2012Konferansepaper (Annet vitenskapelig)
  • 49.
    Sjöstrand, Björn
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Barbier, Christophe
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Nilsson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Rewetting after high vacuum suction boxes in a pilot paper machine2015Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, nr 4, s. 667-672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increased energy efficiency is a major concern for all companies today. Not only does the cost efficiency follow energy efficiency but also environmental and sustainability aspects motivate more energy efficient production lines. A study has been made on a pilot paper machine with the purpose to show the magnitude and time of rewetting after high vacuum suction box dewatering. The grammages used in this study were 20 and 100 g/m2 to cover both tissue and printing paper grades. Machine speed was varied from 400 to 1600 m/min and the maximum pressure drop in the suction box was 32 kPa. The pulp used was unbeaten, chemical, fully bleached softwood from Sweden. Rewetting is observed when the dewatering in the suction box is sufficiently high. No rewetting takes place when the dewatering in the suction box is limited due to insufficient pressure drop and dwell time. The time for the rewetting is in the range of 10-50 ms and in this study the maximum rewetting observed is 180 g/m2, or 6.1% decrease in dryness. The mechanisms behind the phenomenon are believed to be capillary forces caused by sufficiently low sheet moisture and expansion of the network. This study shows that rewetting is so fast that it would be difficult to prevent it without changing major machine parameters.

  • 50.
    Stahl, Magnus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Berghel, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Granstrom, Karin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Improvement of Wood Fuel Pellet Quality Using Sustainable Sugar Additives2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 2, s. 3373-3383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The global production and use of wood fuel pellets has increased significantly in recent years. The raw material and the energy required to dry it are the main production costs. Therefore, it is crucial to minimize energy consumption, production costs, and the environmental impact associated with wood pellets. However, these changes should not negatively affect the quality of the pellets. One way to achieve these goals is to use additives. This work investigates how different types of sugar additives affect both the energy needed by the pellet press and the durability and oxidation of the produced pellets. When sugar was used as an additive, the energy use was practically unaffected. When molasses and SSL were added, a small decrease in energy use was observed (6 to 8%) for admixtures up to 1 wt.%; however, when more molasses was added, the energy use increased. Using these additives increased the bulk density (7 to 15 %) and durability (10 to 20 %) of the pellets. The storage of the pellets also caused a small increase in durability (1 to 3 %). Volatile organic compounds were produced as oxidation peaks within the first two months of storage; thereafter, the peaks tapered off.

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