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  • 1.
    Germgård, Ulf
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Dan
    Kinetik för utlösning av cellulosa och hemicellulosa under sulfatkok (Kinetics and dissolution of cellulose and hemicellulose during kraft cooking)2005Conference paper (Other (popular science, discussion, etc.))
  • 2. Greschik, Thomas
    et al.
    Guo, Sanchuan
    Basta, Jiri
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Dan
    Optimization of the cooking conditions when producing high quality eucalyptus pulps using a design of experiments (DoE) approach2008Conference paper (Other (popular science, discussion, etc.))
  • 3. Johansson, Dan
    Carbohydrate degradation and dissolution2008Licentiate thesis, monograph (Other academic)
  • 4.
    Johansson, Dan
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Carbohydrate degradation and dissolution during Kraft cooking: Modelling of kinetic results2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions.

    Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples.

    For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.

  • 5. Johansson, Dan
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A kinetic model describing the carbohydrate dissolution during softwood kraft cooking2006Conference paper (Other (popular science, discussion, etc.))
  • 6.
    Johansson, Dan
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A kinetic study of softwood Kraft cooking: carbohydrate dissolution as a function of cooking conditions2008In: Appita journal, ISSN 1038-6807, Vol. 61, no 3, p. 229-234Article in journal (Refereed)
  • 7. Johansson, Dan
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A kinetic study of softwood kraft cooking- carbohydrate dissolution as a function of the cooking conditions2006Conference paper (Refereed)
  • 8. Johansson, Dan
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A Kinetic Study of Softwood Kraft Cooking: Carbohydrate Dissolution as a Function of the Cooking Conditions2008In: Appita Journal, Vol. 61(2008)3,228-233Article in journal (Refereed)
  • 9.
    Johansson, Dan
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Carbohydrate degradation during softwood Kraft cooking: influence on cellulose viscosity, carbohydrate composition and hexenuronic acid content2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 3, p. 292-298Article in journal (Refereed)
    Abstract [en]

    A kinetic model, including the variables temperature as well as hydroxide ion, sulphide ion and sodium ion concentrations, was fitted to laboratory data from kraft cooking of industrial Norway spruce chips. The model described well the data for carbohydrates, for hexenuronic acids and for the intrinsic viscosity. 

  • 10. Johansson, Dan
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    The Relationship Between Xylan and Hexenuronic Acid in Eucalyptus Kraft Pulping2006In: O Papel, Vol. 67(2006)10,84-91Article in journal (Refereed)
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