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  • 1.
    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.

  • 2.
    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)
  • 3.
    Germgård, Ulf
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Acid Hydrolysis of pulps2003Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 4.
    Germgård, Ulf
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Östberg, Linda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Activation of Dissolving Pulp with Enzymes Prior to Preparation of High Viscosity Viscose2009Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 5.
    Germgård, Ulf
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Östberg, Linda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Enzyme Activation of Pulp and its Influence on the Gamma Number of Viscose2011Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 6.
    Germgård, Ulf
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Östberg, Linda
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Lab Scale Preparation of High Viscosity Viscose at Karlstad University2011Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 7.
    Hellstrom, Pia
    et al.
    AkzoNobel Pulp & Performance Chem, S-44580 Bohus, Sweden.;Karlstad Univ, Dept Chem Sci & Engn, S-65188 Karlstad, Sweden..
    Heijnesson-Hulten, Anette
    AkzoNobel Pulp & Performance Chem, S-44580 Bohus, Sweden..
    Paulsson, Magnus
    AkzoNobel Pulp & Performance Chem, S-44580 Bohus, Sweden.;Mid Sweden Univ, FSCN, S-85170 Sundsvall, Sweden..
    Hakansson, Helena
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    The effect of Fenton chemistry on the properties of microfibrillated cellulose2014Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, nr 3, s. 1489-1503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully bleached birch kraft pulp was treated with acidic hydrogen peroxide in the presence of ferrous ions (Fenton's reagent) and thereafter treated mechanically in a colloid mill to produce a product containing microfibrillated cellulose (MFC). The produced MFC products were chemically and morphologically characterized and compared with MFC products produced without pretreatment as well as with enzymatic hydrolysis. Fenton treatment resulted in an increase in total charge and number of carbonyl groups while the intrinsic viscosity decreased. The Fenton treated pulps were easier to process mechanically i.e. they reached a higher specific surface area at a given mechanical treatment time and the MFC produced had a stable water-fibre suspension for at least 8 weeks compared to enzymatic pretreated pulps and pulps not subjected to any pretreatment.

  • 8.
    Hellstrom, Pia
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (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
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Germgard, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (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 homogenizer2016Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 15, nr 6, s. 375-381Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Hellstrom, Pia
    et al.
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.;Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    Heijnesson-Hulten, Anette
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden..
    Paulsson, Magnus
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.;Mid Sweden Univ, FSCN, SE-85170 Sundsvall, Sweden..
    Håkansson, Helena
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper. Karlstad Univ, Dept Chem Sci & Engn, S-65188 Karlstad, Sweden..
    Germgård, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Fenton pre-treated microfibrillated cellulose evaluated as a strength enhancer in the middle ply of paperboard2014Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, nr 4, s. 732-740Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microfibrillated celluloses (MFCs), produced by various pre-treatments of a fully bleached birch kraft pulp, were evaluated as strength enhancers in test sheets representing the middle ply of paperboard. The furnish consisted of hydrogen peroxide bleached high temperature spruce chemithermomechanical pulp (HT-CTMP), MFC and a retention system containing cationic starch and an anionic silica sol. The MFC was prepared via a mechanical treatment in a colloid mill after pretreatment with Fenton's reagent, monocomponent endoglucanase or acidic hydrogen peroxide. Addition of 5% MFC, produced with Fenton pre-treatment, resulted in improved HT-CTMP properties with respect to increased tensile index (similar to 35%), z-directional strength (similar to 50%), tensile stiffness index (similar to 25%) compared to HT-CTMP test sheets prepared without MFC addition. The strength improvement was linearly correlated to the density of the tests sheet, to the surface area (BET) and to the surface charge of the enzymatic or chemically pre-treated MFCs.

  • 10.
    Hellström, Pia
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper. AkzoNobel.
    Heijnesson- Hultén, Anette
    AkzoNobel.
    Paulsson, Magnus
    AkzoNobel, Mid Sweden University.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    The effect of Fenton chemistry on the properties of microfibrillated cellulose (MFC)2013Annet (Annet vitenskapelig)
  • 11. Hellström, Pia
    et al.
    Heijnesson-Hultén, Anette
    Paulsson, Magnus
    3FSCN, Mid Sweden University, SE-851 70 Sundsvall, Sweden.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    The effect of Fenton chemistry on the production of microfibrillated cellulose - characterization and paper board application2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A fully bleached birch (Betula verucosa) sulphate pulp was treated with acidic hydrogen peroxide in the presence of ferrous iron (i.e. Fenton's reagent) and thereafter treated mechanically in a colloid mill to produce microfibrillated cellulose (MFC). The produced MFCs were chemically and morphologically characterized and compared with MFCs produced with enzymatic (monocomponent endoglucanase) pre-treatment (Figure 1). As a reference MFC produced with only acid pre-treatment was also included in the study.

    The Fenton pre-treatment increased the total charge of the fibres, decreased the viscosity and introduced new carbonyl groups. Addition of 10 and 50 kg/t hydrogen peroxide resulted in a yield loss of 2 and 4%, respectively. The enzymatic hydrolysis did not substantially change the total charge or the carbonyl group content of the pulp and did not release any organic material. The Fenton pre-treated pulps were easier to process mechanically, i.e. they reached a higher specific surface (BET) area and thereby a higher surface charge at a given mechanical treatment time, indicating a potential to reduce the energy demand in the final mechanical processing stage. The Fenton pre-treatment produced microfibrillated cellulose that in a water suspension (0.5% consistency) was stable with respect to sedimentation for at least eight weeks (Figure 2). Further, the Fenton pre-treatment gave a MFC product that contained a higher amount of small well fibrillated particles, as indicated by fractionation and scanning electron microscopy, compared with the enzymatic and acid pre-treatment methods studied.

  • 12.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Ethanol Pulping of Reed Canary Grass1995Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The aim of this study was to investigate the possibility of processing an agricultural crop grown in Sweden to usable pulp. A further purpose was to study ethanol pulping applied to a non-wood raw material.



    The first part of this thesis deals with the criteria for selecting a fibre crop for further studies. Based on the content of fibres and the harvested yield reed canary grass was found to be the most interesting crop. The effect on fibre content of the amount of leaves was investigated and it was found that leaves contain a very small amount of fibres. If the amount of leaves in the crop is 25 % or less they have a rather small influence, however.



    In the second part of the thesis the studies of ethanol-alkali pulping and autocatalysed acidic ethanol pulping of reed canary grass are reported. The effects of the pulping conditions in the two methods were investigated using a response surface methodology. In ethanol-alkali pulping, the results were compared at the point of fibre liberation, which occurred at a kappa number of about 13. The shortest cooking time (80 min) required to reach kappa number 13 was obtained at an ethanol concentration of about 32 %, a liquor-to-raw material ratio of 4 l/kg and an alkali charge of 25 %. The highest pulp yield at kappa number 13 was obtained at about 38 % ethanol, 15 % alkali and any of the investigated liquor-to-raw material ratios (4 to 10 l/kg). In autocatalysed ethanol pulping, the results were compared at the end of the bulk delignification. The lowest possible kappa number (about 35) was obtained using 60 % ethanol at a liquor-to-raw material ratio of 10 l/kg.



    Some paper properties were investigated on an unbleached soda pulp from reed canary grass,

    an unbleached ethanol-alkali pulp from reed canary grass, an unbleached ethanol pulp from reed canary grass and a bleached (ODED) ethanol pulp from reed canary grass. For comparison, the properties of an unbleached and a bleached industrial birch kraft pulp were tested. The strength properties of the reed canary grass pulps are generally lower than those of the birch pulps.



    The investigated ethanol pulping techniques can be used for the pulping of reed canary grass. The pulps are not suitable in products where strength is important. They may be useful, however, as e.g. a component in printing paper.

  • 13.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Preparation and Characterization of Chemical Pulps from Wood and Reed Canary Grass2005Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis presents laboratory results from ethanol pulping of reed canary grass for the production of paper pulp. The focus was on the influence of cooking pa-rameters on the delignification. The strength of the grass pulps was found to be low and the use of such pulps will therefore be limited to a few products.



    The use of reed canary grass pulp for the preparation of microcrystalline cellulose by acid hydrolysis was also studied.



    The degradation of cellulose in different pulps during acid hydrolysis was investi-gated mainly through the levelling-off degree of polymerization (LODP) and the weight loss. The effect of hydrolysis conditions on the LODP and on the weight loss was studied, and a method for determining LODP was established.



    Pulps from birch, eucalyptus and reed canary grass with different hemicellulose contents were prepared. The hemicellulose content was reduced either by a prehy-drolysis step before kraft pulping or by alkali treatment of the bleached pulps. The crystallite size, as determined by LODP, of the pulps was strongly affected by the xylan content in the pulps after acid hydrolysis. A mechanism for the degradation of cellulose in pulps with different hemicellulose content was suggested.



    The size of the fiber fragments after acid hydrolysis was also influenced by the xy-lan content. At a given xylan content the fiber fragments from reed canary grass were smaller than those from the hardwoods.

  • 14.
    Håkansson, Helena
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Ahlgren, Per
    Acid Hydrolysis of Some Industrial Pulps: Effect of Hydrolysis Conditions and Raw Material2005Inngår i: Cellulose, vol 12, 2 (2005)Artikkel i tidsskrift (Fagfellevurdert)
  • 15.
    Håkansson, Helena
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Ahlgren, Per
    Germgård, Ulf
    The Degree of Disorder in Hardwood Kraft Pulps Studied by Means of LODP2005Inngår i: (accepted for publication in Cellulose, 2005)Artikkel i tidsskrift (Fagfellevurdert)
  • 16.
    Håkansson, Helena
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Ahlgren, Per
    Sjöberg, Lars-Arne
    Ethanol-Alkali Pulping of Reed Canary Grass1994Inngår i: Nordic Pulp & Paper Research Journal, vol. 9, 4 (1994)Artikkel i tidsskrift (Fagfellevurdert)
  • 17.
    Håkansson, Helena
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Sjöberg, Lars-Arne
    Ahlgren, P.
    Autocatalysed Ethanol Pulping of Reed Canary Grass1996Inngår i: Nordic Pulp and Paper ResearchJournal. 11, 2:100Artikkel i tidsskrift (Fagfellevurdert)
  • 18.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Håkansson, Helena
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Some aspects of the reactivity of pulp intended for high-viscosity viscose2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 1, s. 743-755Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The original objective of this study was to reduce the consumption of carbon disulphide in the preparation of high-viscosity viscose by pre-treating two softwood pulps with enzymes prior to the viscose stages. Reactivity can, however, be measured in different ways and the methods used in this study are Fock´s test of the pulp and the gamma number of the viscose solution prior to regeneration. It was found that whilst the reactivity of a pulp that had been subjected to enzyme pretreatment increased according to Fock´s test, it did not increase when the gamma number obtained in a standardized viscose preparation process was used. This unexpected difference that was discovered between the two reactivity tests made it difficult to analyze the impact of the enzyme stage on reactivity; the underlying reasons for the different reactivity results obtained were therefore investigated first. The conclusion that may be drawn from this investigation is that Fock´s test measures the extent to which carbon disulphide reacts with a pulp sample during a standardized test whereas the gamma number measures the resulting degree of xanthate substitution on the cellulose backbone. These two reactivity tests are thus not totally correlated. It was concluded that the gamma number was the more relevant of the two tests since it reflects the dissolution ability of a pulp in the viscose preparation, which is a very basic property of viscose. A higher gamma number also means that the coagulation time in the spinning process is prolonged; this is beneficial as it can be used to increase the tenacity of the viscose fibres. Measuring the reactivity according to Fock´s test, on the contrary, provides more dubious results as the test has no undisputed correlation to the viscose preparation process.

1 - 18 of 18
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