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  • 1.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pettersson, B.
    Westermark, Ulla
    Linkages between residual lignin and carbohydrates in bisulphite (magnefite) pulps2001In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, no 9, p. 310-316Article in journal (Refereed)
    Abstract [en]

    The presence of bonds between residual lignin and carbohydrates in bisulphite pulps from hardwoods and softwoods was studied. Results showed that a fraction of the residual lignin was bonded to cellulose in bisulphite pulps of softwood. The treatment with xylanase indicated the existence of alkali-stable lignin-xylan bonds in softwood bisulphite pulps.

  • 2.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pettersson, B.
    Westermark, Ulla
    The use of cellulases and hemicellulases to study lignin-cellulose as well as lignin-hemicellulose bonds in kraft pulps2001In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, no 6, p. 196-201Article in journal (Refereed)
    Abstract [en]

    The combination of carbohydrate-degrading enzymes and size-exclusion chromatography (SEC) has been used to analyze the existence of covalent bonds between lignin and cellulose and/or hemicelluloses in pulps. Cellulases and xylanase were used for degradation of cellulose and xylan, respectively. Analysis of the molecular weight profiles of lignin and carbohydrates before and after enzymic hydrolysis were performed by dissolution of the pulps in LiCl/dimethylacetamide (DMAC). The results indicate that a considerable part of the residual lignin in unbleached pine kraft pulp is bond to cellulose. Bonding of lignin to xylan in the pine kraft pulp could also be detected. Analysis of birch kraft pulp shows that most of the residu lignin in birch kraft pulps is covalently linked to xylan. The combination of carbohydrate-degrading enzymes and SEC in LiCl/DMAC seems to be an excellent way of characterizing bonds between lignin and carbohydrates in chemical pulps.

  • 3.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    Evidence for chemical bonds between lignin and cellulose in kraft pulps1996In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 22, no 10, p. J397-401Article in journal (Refereed)
    Abstract [en]

    The cellulose solvent system LiCl-dimethylacetamide has been used to dissolve kraft pulps prepared from pine and birch. The dissolved polymers were analyzed using size-exclusion chromatography combined with both RI- and UV-detection systems in order to monitor simultaneously the major wood polymers (cellulose, hemicellulose and lignin). Kraft pulps from birch were completely soluble in the solvent system and the pine kraft pulp about 80% soluble. Analyses of the kraft pulps strongly suggest that a considerable amount of the residual lignin is chemically linked to the high molecular weight cellulose in pine but not in birch. The presence of stable lignin-cellulose bonds will reduce the possibility of achieving a low kappa number by cooking. For comparison, sulphite and bisulphite pulps were also examined. Both pulps were soluble in the solvent system and analyses indicated that lignin-cellulose bonds also exist in these pulps although to a significantly lesser extent than in the pine kraft pulp

  • 4.
    Lif, J.O.
    et al.
    STFI.
    Fellers, C.
    Söremark, C.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Characterizing the in-plane hygroexpansivity of paper by electronic speckle photography1995In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 21, no 9, p. J302-J308Article in journal (Refereed)
    Abstract [en]

    A newly developed electronic speckle photographic system is used to investigate the hygroexpansion of paper. By using a spray-paint technique for the creation of the speckle pattern, two applications of the system are demonstrated on different machine-made papers. The first one is the determination of the displacement field after the exposure of a sheet to a moisture change. The second is the determination of hygroexpansion orientation. Lastly, an investigation of the correspondence between hygroexpansion and tensile stiffness orientations determined by an ultrasonic technique is presented.

  • 5.
    Mattsson, Rosa
    et al.
    Development Department, Kappa Kraftliner Piteå.
    Lindström, Dan
    Luleå tekniska universitet.
    Sterte, Johan
    Ödberg, Lars
    AssiDomän Corporate R&D, Stockholm.
    Influence of abietic acid, betulinol, sodium oleate and tripalmitine on the migration of akd in paper2003In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 29, no 8, p. 281-Article in journal (Refereed)
    Abstract [en]

    The migration of alkylketene dimer (AKD) wax through untreated paper and through paper sheets impregnated with extractives was investigated at temperatures above themelting point of the wax. The migration was studied at 80and 105°C by using various combinations of untreated paper sheets, paper sheets impregnated with AKD and sheets impregnated with extractives. The migration was observed by measuring contact angles with distilled water. There is no indication that extractives such as betulinol, oleate or tripalmitine interfere with the migration of AKD. The diffusion coefficient for AKD in paper was estimated to be of the order of 10–11 m2/s at the temperatures investigated.

  • 6.
    Nohlgren, Ingrid
    et al.
    Luleå tekniska universitet.
    Sricharoenchaikul, V.
    Singuefield, S.
    Frederick, W.J. Jr
    Theliander, Hans
    Black liquor gasification with direct causticization using titanates in a pressurized entrained-flow reactor: Part I: kinetics of the causticization reaction2003In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 29, no 4, p. 107-113Article in journal (Refereed)
    Abstract [en]

    The kinetics of the direct causticization reaction between sodium tri-titanate and sodium carbonate in a pressurized entrained-flow reactor has been studied using both pure sodium carbonate and black liquor solids. The experiments were carried out at 900, 950 and 1000°C, at pressures of 0.5 and 1 MPa, in pure nitrogen and in 2% carbon dioxide in nitrogen. The experimental results showed that sodium penta-titanate formation is faster with black liquor than with sodium carbonate, and that the rate increases with temperature. Furthermore, carbon dioxide in the reaction gases slows down the reaction rate and no clear influence of pressure was seen on the reaction rate. The reaction rates for the direct causticization reaction between sodium tri-titanate and sodium carbonate was found to be fast enough to be carried out in an entrained-flow reactor system, e.g. a Chemrec gasification system

  • 7.
    Nohlgren, Ingrid
    et al.
    Luleå tekniska universitet.
    Sricharoenchaikul, V.
    Institute of Paper Science Technology.
    Singuefield, S.
    Institute of Paper Science Technology.
    Frederick, W.J. Jr
    Institute of Paper Science Technology.
    Theliander, Hans
    Chalmers University of Technology.
    Black liquor gasification with direct causticization using titanates in a pressurized entrained-flow reactor: Part II: carbon and carbon species transitions2003In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 29, no 10, p. 348-355Article in journal (Refereed)
    Abstract [en]

    Experiments on black liquor conversion in the presence of sodium titanates were carried out in a pressurized entrained-flow reactor, at temperatures of 900, 950 and 1000°C, at pressures of 0.5 and 1 MPa and in atmospheres of pure nitrogen (N2) or N2 with 2% carbon dioxide (CO2). Up to 80-90% conversion of the carbon in black liquor to gases was obtained within 5 s at these conditions. This is a very promising result for industrial scale gasifiers. Char carbon was gasified two to four times faster in N2 with 2% CO2 than in N2 alone. Overall, carbon conversion increased with increasing temperature, but the gasification rate decreased with increasing temperature. CO was found to be the main carbon-containing gas formed

  • 8.
    Olofsson, Kenneth
    et al.
    Luleå tekniska universitet.
    Kyösti, Anders
    Stiffness and stiffness variation in paper measured by laser-generated and laser-recorded bending waves1994In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 20, no 11, p. 328-332Article in journal (Refereed)
    Abstract [en]

    Stiffness in paper is measured by holographic interferometry. The displacement field is numerically evaluated using a phase-stepping and phase-unwrapping reconstruction technique. Transient bending waves in the paper sample are generated and recorded by the same pulsed laser. The proposed method can be developed into a commercial on-line measuring device to measure paper stiffness. A number of defects, like variations in thickness, stiffness or density, are identified using this technique.

  • 9. Pantze, Anna
    et al.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    A model system to study esterification reactions in cellulosic or lignocellulosic material2007In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 33, no 4, p. 177-183Article in journal (Refereed)
    Abstract [en]

    The formation of natural ester cross-linkages in cellulosic or lignocellulosic composite materials during drying and heating is of interest for the production of paper and of wood composite boards and in giving cotton materials improved characteristics. A model system has been developed to study quantitatively the esterification of cellulosic material during drying and heating when solid-state conditions can be said to predominate. In the experiments, hexanoic acid and 3-hydroxybutyric acid were added to ordinary filter paper. Moisture content was adjusted, and samples were heated to temperatures ranging from 85 degrees C to 180 degrees C for between 15 and 45 minutes. Quantitative analysis of ester,formation, in this case between the monocarboxylic acids and the cellulose's hydroxyl groups, was performed using aminolysis/gas chromatography. The 3-hydroxybutyric acid was surprising v effective in ester formation. The results indicate that direct esterification of monocarboxylic acid can be an important reaction in lignocellulosic material at elevated temperatures.

  • 10. Pettersson, Patrik
    et al.
    Wikström, T.
    Metso Paper Sundsvall.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Method for measuring permeability of pulp suspension at high basis weights2008In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 34, no 4, p. 191-197Article in journal (Refereed)
    Abstract [en]

    During the formation of pulp to paper, a large amount of water is added to dilute the pulp in order to obtain a homogenous material. This water call be mechanically and/or thermodynamically removed by different process solutions. The pulp suspension flows through various process equipment that influence the pulp suspension by changing its properties before the pulp suspension finally becomes paper. It is important to understand the mechanisms behind the transport path of water in this process in order to reduce cost and to increase the production rate of pulp and paper. The resistance to flow must be known in order to describe the flow path and the corresponding pressure drop in dewatering equipment in a pull.? mill. For networks with a complex geometry, a reliable method is to measure the resistance to flow at discrete points and to fit suitable resistance models to the results obtained. The objective of this study is to investigate how the history of pulp suspensions affects their permeability. A device for measuring the permeability of various pulp suspensions at high basis weights is developed and validated. Then the permeability of a number of virgin pulp species is measured. Some of the suspensions are then circulated in a closed flow loop and permeability is measured as a function of the number of loops. The results from two separate test's show that a basis weight variation and a different process treatment of the pulp suspension do not influence permeability.

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