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  • 101.
    Forsström, Jennie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of different deinking efficiency of waterbased flexographic ink from model cellulose surfaces and sheets2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 250-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of UV-light, temperature, atmospheric

    environment and storage time on the ink detachment of

    water-based flexographic ink printed on model cellulose surfaces

    was investigated using an impinging jet cell equipment. The

    printed surfaces were deinked using a NaOH solution (pH = 10)

    and the deinking process was monitored using a microscope

    equipped with a CCD camera. Images were collected at different

    time intervals during the detachment process and image

    analysis was used to quantify the ink detachment from the surface.

    Hand sheets, (the same pulp as used for model surface

    preparation) were also printed and stored under the same conditions,

    after which they were reslushed and deinked. The deinking

    efficiency of the recycled sheets was evaluated using

    brightness and ERIC (Effective Residual Ink Concentration)

    values. It was shown that UV-light had a negative effect on ink

    detachment both from the model cellulose surfaces and from

    the hand sheets. At storage temperatures of 55°C, (dark conditions

    were used) a large negative effect was observed for the

    cellulose surfaces while only a small effect on the ink detachment

    could be seen for the hand sheets. Ink detachment from

    the hand sheets became more difficult when increasing the storage

    temperature above 55°C, as detected as a decrease in

    brightness of the recycled and deinked sheets. A further increase

    in the storage temperature to 105°C gave poorer ink detachment

    efficiency than storage under UV-light for the hand sheets.

    Air had a more negative effect on ink detachment than nitrogen.

  • 102. Freyhult, E
    et al.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Tamas, I
    Moulton, Vincent
    Poole, AM
    Fisher: a program for the detection of H/ACA snoRNAs using MFE secondary structure prediction and comparative genomics - assessment and update2008Inngår i: BMC Research Notes, ISSN 1756-0500, E-ISSN 1756-0500, Vol. 1, nr 49, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BackgroundThe H/ACA family of small nucleolar RNAs (snoRNAs) plays a central role in guiding the pseudouridylation of ribosomal RNA (rRNA). In an effort to systematically identify the complete set of rRNA-modifying H/ACA snoRNAs from the genome sequence of the budding yeast, Saccharomyces cerevisiae, we developed a program - Fisher - and previously presented several candidate snoRNAs based on our analysis [1].

     

    FindingsIn this report, we provide a brief update of this work, which was aborted after the publication of experimentally-identified snoRNAs [2] identical to candidates we had identified bioinformatically using Fisher. Our motivation for revisiting this work is to report on the status of the candidate snoRNAs described in [1], and secondly, to report that a modified version of Fisher together with the available multiple yeast genome sequences was able to correctly identify several H/ACA snoRNAs for modification sites not identified by the snoGPS program [3]. While we are no longer developing Fisher, we briefly consider the merits of the Fisher algorithm relative to snoGPS, which may be of use for workers considering pursuing a similar search strategy for the identification of small RNAs. The modified source code for Fisher is made available as supplementary material.

     

    ConclusionOur results confirm the validity of using minimum free energy (MFE) secondary structure prediction to guide comparative genomic screening for RNA families with few sequence constraints.

     

  • 103.
    Fält, Susanna
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of electrolytes on the swelling and strength of kraft-liner pulps2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 1, s. 69-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present paper, the effect of common process electrolytes NaCl, Na2SO4 and CaCl2 on fibre swelling and paper strength has been investigated. Results show that there is an initial increase in the water retention value (WRV) of the fibres when the salt concentration is increased at a pH of 5 in the solution surrounding the fibres. At higher salt concentrations, the WRV decreases. This behaviour is most pronounced for Na2SO4 and smaller for NaCl and CaCl2.The increase in swelling is explained as being due to an increase in pH in the fibre wall and a subsequent increased dissociation of the carboxyl groups during the initial increase in ionic strength. When the electrolyte concentration is further increased, the difference in osmotic pressure between the interior of the fibre wall and the surrounding solution decreases and eventually the pressure difference drops to zero. It is also found that there is no unique relationship between the WRV and the strength of paper formed from the fibres treated with different electrolyte concentrations.

  • 104. Gernandt, Renate
    et al.
    Wågberg, Lars
    Gärdlund, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dautzenberg, Herbert
    Polyelectrolyte complexes for surface modification of wood fibres I: Preparation and characterisation of complexes for dry and wet strength improvement of paper2003Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 213, nr 1, s. 15-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyelectrolyte complexes (PEC) were formed between a cationic polyamideamine epichlorohydrine condensate (PAE) and an anionic carboxymethylcellulose (CMC) at different ratios between the polymers, orders of mixing, salt concentrations and polymer concentrations. Firstly the polymers were characterised by polyelectrolyte titration (charge), static light scattering (molecular weight, radius of gyration) and measurements with a scanning interferometric refractometer (refractive index). The complexes were characterised by ocular inspection and static light scattering in combination with a special evaluation algorithm allowing an estimation of the geometric form of the complexes. The results show that the initial complexes have a spherical form and that the size is fairly constant over a large range of charge ratios between the polymers, provided the complexes are formed in deionised water. When the charge mixing ratio exceeded neutrality a secondary agglomeration of the initially formed complexes occurred. The presence of salt during PEC formation caused a dependence of the level of aggregation on the mixing ratio, whereby small amounts of NaCl drastically lowered the particle mass at lower mixing ratios. Subsequent addition of salt to PECs formed in water led to a strong swelling of the complex particles and at a critical salt concentration to dissolution.

  • 105.
    Gorski, Dmitri
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Hill, J
    Johansson, L
    Review: Reduction of energy consumption in refining through mechanical pretreatment of wood chips2009Inngår i: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, s. 17-21Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Refining of thermomechanical pulp is a very energy-intensive process. Mechanical pretreatment of wood chips prior to refining has been shown to be able to reduce total energy consumption, facilitate removal of extractives, have positive synergies with chemical and enzymatic pretreatments and improve impregnation of chips. There are a number of publications dealing with different aspects of mechanical pretreatment but few of them give a comprehensive overview of what has been done in this field. No review articles dealing with the subject have been written. Today, mechanical pretreatment is becoming more and more common and therefore a review is important.

     

     

  • 106.
    Gorski, Dmitri
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Hill, J
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Johansson, Lars
    Review: Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 2, s. 156-161Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    This review covers the effect of mechanical pre-treatment of wood chips on the energy consumption in refining and the quality of pulp. To understand the mechanisms of mechanical pre-treatment, a short description of relevant refining theory and reported effects of pre-treatment on wood morphology is given. Mechanical pre-treatment offers a chance to utilize the energy needed to defibrate chips in a more efficient way, minimizing the cyclic elastic deformations which are the main defibration mechanism in refining. Studies of fibre morphology indicate that compressive pretreatment mechanically introduces favorable weak points in the S1 and S2 fibre walls where defibration proceeds easier upon subsequent refining.Published results which cover the effect of the pretreatment on energy consumption and pulp properties are reviewed. Energy reduction of between 10% and 30% is reported in the literature. High ratio of volumetric compression is necessary. Pressurized conditions are required to ensure that the fibres are not damaged during the pre-treatment. Other effects of compressive pretreatment include a more uniform chip size and moisture content, better penetration of chemicals and removal of extractives from the chips. A list of equipment used for chip pre-compression is provided together with published results of pilot-scale and mill-scale operation.

  • 107.
    Gorski, Dmitri
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Hill, Jan
    QualTech AB (Previously Norske Skog ASA), SE-282 21, Tyringe, Sweden.
    Improved quality of SC magazine paper through enhanced fibre development using the ATMP process2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 1, s. 35-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A pilot scale refining trial was conducted using the ATMP (Advanced Thermomechanical Pulp) refining concept with White spruce as raw material. Low-intensity TMP and high-intensity TMP with mechanical pre-treatment of chips were compared to ATMP (Mg+P), where development of fibres was enhanced using hydrogen peroxide and magnesium hydroxide. The main goal of the trial was to evaluate the potential of using ATMP process for production of SC (supercalendered) magazine paper. SC paper is especially demanding when it comes to the paper surface structure which is strongly influenced by the development of fibre properties.

    Improvement in individual fibre properties such as flexibility, fibre split index and fibre surface area index achieved using ATMP process was found to translate into decreased surface roughness and air permeability of calendered laboratory sheets. Both the refining process configuration and the addition of process chemicals were found to have significant impacts though the process configuration had major role. The influence of process chemicals on PPS was mainly pronounced after second stage refining. The magnitude of surface roughening (fibre rising) was found to be influenced mainly by the process configuration.

  • 108.
    Gradin, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Graham, D
    University of Greenwich, UK.
    Nygård, P
    Paper and Fibre Research Institute, Norway.
    Vallen, H
    Vallen-Systeme GmbH, Germany.
    The use of acoustic emission monitoring to rank paper materials with respect to their fracture toughness2008Inngår i: Proceedings of the Society for Experimental Mechanics, Inc., Society for experimental mechanics , 2008, Vol. 65, s. 133-137Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, a simplified Acoustic Emission (AE) equipment, in essence an AE signal conditioner and a USB (Universal Serial Bus) data acquisition system, is used to study what happens in paper structures during mechanical loading. By the use of such equipment, some parameters that can be extracted are e.g. the stress and strain at onset of AE, the stress and strain at the onset of rapid AE defined as some numerical factor (larger then one) times the initial emission rate, the emission rate at the first stage of loading and the stress and strain at final failure i.e. when the specimen loses its load carrying ability.In this study however, the interest is focused on one particular parameter i.e. the elastic strain energy density Wc at onset of AE. This is a parameter with a clear physical meaning and in this study, the correlation between this parameter and a fracture toughness measure, is investigated.The conclusion is that when nine different paper materials (with a large span regarding properties) are considered, there is a correlation (however not linear) between these two parameters.

  • 109.
    Gradin, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Graham, D
    Nygård, P
    Vallen, H
    The Use of Acoustic Emission Monitoring to Rank Paper Materials With Respect to their Fracture Toughness2008Inngår i: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 48, nr 1, s. 133-137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, simplified Acoustic Emission (AE) equipment, in essence an AE signal conditioner and a USB (Universal Serial Bus) data acquisition system, are used to study what happens in paper structures during mechanical loading. By the use of such equipment, some parameters that can be extracted are e.g. the stress and strain at onset of AE, the stress and strain at the onset of rapid AE (defined in some appropriate way), the emission rate at the first stage of loading and the stress and strain at final rupture. In this study however, the interest is focused on one particular parameter i.e. the elastic strain energy density Wc at onset of AE. This is a parameter with a clear physical meaning and in this study, the correlation between this parameter and a fracture toughness measure, is investigated. The conclusion is that when nine different paper materials (with a large span regarding properties) are considered, there is a correlation (however not linear) between these two parameters.

  • 110.
    Gärdlund, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Polyelectrolyte Complexes: Their Characterization and use for Modification of Wood Fibre Surfaces2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For economical reasons filler particles and less expensive fibre raw materials are more frequently used in papermaking. This influences the mechanical properties of the formed papers in a negative way and it is therefore necessary to add strength-enhancing agents to the papermaking furnish. Traditionally cationic starch has been the dominating additive used for strength enhancement but new techniques are continuously being developed and in the present work the use of polyelectrolyte complexes (PEC) for improvements of different paper strength properties has been evaluated. Large focus has also been given to evaluating the properties of the polyelectrolyte complexes since these properties are largely dependant on molecular mass of the polyelectrolytes, the mixing conditions and ionic strength of the polyelectrolyte solutions. The PEC formation was studied between chemicals already used for strength enhancing purposes in real papermaking systems, i.e. poly (amido-amine) epichlorohydrin (PAE) and carboxymethylcellulose (CMC). The PEC formation was studied with respect to fundamental characteristics and the ability for use as strength additives. The PEC formation was also studied using model polyelectrolytes (PEL) poly(allylamine hydrochloride) (PAH), as the cationic component, and poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA), as the anionic components. The fundamental studies involve the PEC formation by varying the mixing ratio between the polyelectrolytes, the charge density or molecular weight of a component, structure of the one polyelectrolyte component, the mixing order, together with solution conditions. The main techniques used for these purposes were the static and dynamic light scattering, AFM tapping mode and Cryo-TEM. The adsorption of PECs onto surfaces of silica and lignin was investigated, using the stagnation point adsorption reflectometry (SPAR) and QCM-D (quartz crystal microgravimetry with dissipation). With these two techniques the amount of adsorbed chemical is obtained an also the viscoelastic properties of the adsorbed layer. The stability of PECs towards an increase in salt concentrations was investigated and the PECs were stable up to 0.2-0.4 M NaCl before complete dissolution, suggesting that the driving force for the formation of the PECs (from CMC-PAE) is a combination of the entropic effect of the released counterions and an enthalpy contribution from the interaction between the polymer segments. The PECs did not change their 3D-structure upon drying. It was also found that the swollen 3D structure of the complexes is achieved by an incorporation of a large amount of water into the complexes. Calculations based on the collected results show that the complexes consist of between 60 % and 95 % water. The PECs formed from PAA and PAH displayed higher water content when formed from low PEL concentration and salt concentrations up to 0.1 M NaCl than the PMAA-PAH PECs. At high PEL concentration and high salt concentration the opposite was observed. The use of the complexes as dry strength additives has two large benefits. First of all the 3D structure of the complexes allows for an efficient bridging between the microscopically rough fibre surfaces. Secondly the complexes allows for a higher saturation adsorption of polyelectrolytes on the fibre surface compared with a single polyelectrolyte addition. The PEC addition also leads to an increase in density, but the PECs showed the same benefits as beating when added to the unbeaten fibres. The effect on the fibre material, with regard to paper properties, varies depending on the pulp used.

  • 111.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsström, Jennie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andreasson, Bo
    Wågberg, Lars
    Influence of polyelectrolyte complexes on strength properties of papers made from unbleached kraft pulps with different yields2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 1, s. 36-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of the materials combined in corrugated

    board are set to give the board its strength, flexibility

    and protection towards impact and pressure. The raw material is

    of course the single fibre but additives that enhance e.g. the wet

    and dry paper strength are also added. As the strength

    enhancing additives used today are most efficient between pH 4

    and pH 7 there is a need for new types of additives that can be

    used under alkaline conditions. In the present report polyallylamine

    hydrochloride (PAH) and polyelectrolyte complexes

    (PEC) of PAH and polyacrylic acid (PAA) were investigated as

    strength enhancing additives. The components can be used

    under alkaline conditions and results showed that PAH alone or

    incorporated into a PEC gave different effects regarding

    strength properties of sheets from kraft pulps of different yields.

    The results showed that by treating the fibres with PEC´s of

    PAH and PAA it was possible to considerably increase the

    tensile properties, the Z-strength and the compression strength

    of papers made from the treated fibres. The results showed an

    increase of as much as 54 % to 180 % in dry Z-strength and 14

    % to 53 % in compression strength, when using the PEC as an

    additive, indicating an increase in inter-fibre joint strength. It

    was also found that a heat treatment of the non-treated papers

    and of the papers from the PAH treated fibres gave a large

    improvement in tensile properties as well as Z-strength properties

    for the different pulps. For the PEC treated fibres it was not

    necessary to heat-treat the paper to achieve a higher dry

    strength. The molecular mechanism behind the large improvements

    is not identified in the present work but the problem is

    currently being investigated in the lab of the authors.

  • 112.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    KTH.
    Marklund, Ann
    The use of polyelectrolyte complexes (PEC) as strength additives for different pulps used for production of fine paper2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 2, s. 210-216Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work the application of polyelectrolyte complexes (PEC) to different pulps, to improve the strength of papers produced from them, is compared with conventional pulp beating. The pulps chosen for the investigation were a fully bleached chemical hardwood pulp (HBK), a fully bleached chemical softwood pulp (SBK), and a peroxide-bleached chemi-thermomechanical pulp (BCTMP). The polyelectrolytes used were a polyamideamine epichlorohydrine condensate (PAE), traditionally used as a wet-strength additive, and carboxymethylcellulose. Since the complexes prepared from these chemicals bear an anionic charge, they can only be used after fibre pre-treatment with the cationic PAE. Results indicate that the addition of 2% PAE and 2% PEC can improve all the measured tensile strength properties of the sheets as much as is commonly achieved by mechanically beating the pulps. In fact, for the chemical pulps, PEC addition at the chosen level produced better results than did traditional beating, since the improved tensile index and tensile energy absorption could be achieved without any significant deterioration in the light scattering coefficient of the papers produced. However, with the BCTMP a significant decrease in light scattering could be detected, especially following the addition of PEC. Adding the chemicals (especially the PEC) increased the sheet density, so chemical treatment left the bending stiffness of the sheets unaffected. However, based on the results, it was suggested that a combination of unbeaten HBK and BCTMP treated with PAE and PEC should be used as the fibre components of a typical fine paper furnish.

  • 113.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    KTH, Fiber and Polymer Technology Department, Fibre Technology, S-100 44, Stockholm, Sweden.
    Gernandt, Renate
    Polyelectrolyte complexes for surface modification of wood fibres II: Influence of complexes on wet and dry strength of paper2003Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 218, nr 1-3, s. 137-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current paper presents a way of enhancing paper strength by the use of polyelectrolyte complexes (PEC) of cationic poly (amide, amine) epichlorohydrin condensate (PAE) and anionic carboxymethylcellulose (CMC). In this study the complexes were pre-formed in different mixing ratios, but with an overall anionic charge. The complexes were characterized by means of size, charge, and adsorption properties both to fibres and to model silica surfaces. Finally the PEC�s were applied as strength additive in paper sheet preparation. The main findings are that by changing polymer weight-ratios when preparing the complexes the charge and the amount adsorbed could be altered. Addition of the complexes to the fibres before sheet preparation led to a significant increase in strength of the paper, compared to sheets prepared with only the PAE. The strength improvement depended upon the mixing ratio and a maximum in dry strength was found for complexes where the anionic charge of the CMC had been neutralized to 60%. Paper strength; Polyelectrolyte Complexes; PAE; CMC; Strength additive

  • 114.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Royal Institute of Technology, Stockholm.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    New insights into the structure of polyelectrolyte complexes2007Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, nr 2, s. 237-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of polyelectrolyte complexes (PECs) prepared from oppositely charged linear polyelectrolytes (PELs) was studied by static light scattering at various salt concentrations. The PELs used were poly(allylamine hydro chlorid) (PAH) and the two polyanions poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Physical characteristics such as radii of gyration and molecular weights as well as water content of the PECs were determined at various molar mixing ratios. In spite of the relatively small difference in chemical structure between PAA and PMAA, fairly large differences in the mentioned parameters were detected. Generally, PECs consisting of PMAA were larger and contained more water. Moreover, by using cryogenic transmission electron microscopy, transmission microscopy and atomic force microscopy, shape and structure of the prepared PECs were investigated both in solution and after drying. The PECs were found to be spherical in solution and the shape was retained after freeze-drying. PECs adsorbed on silica surfaces and dried in air at room-temperature still showed a three-dimensional structure. However, from the relatively low aspect ratios determined, the PECs were found to be significantly collapsed due to interactions with the silica surface during the adsorption and drying processes.

  • 115.
    Göransson, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Internal Tar/CH4 Reforming in Biomass Dual Fluidised Bed Gasifiers towards Fuel Synthesis2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Production of high-quality syngas from biomass gasification in a dual fluidised bed gasifier (DFBG) has made a significant progress in R&D and Technology demonstration. An S&M scale bio-automotive fuel plant close to the feedstock resources is preferable as biomass feedstock is widely sparse and has relatively low density, low heating value and high moisture content. This requires simple, reliable and cost-effective production of clean and good syngas. Indirect DFBGs, with steam as the gasification agent, produce a syngas of high content H2 and CO with 12-20 MJ/mn3 heating value. The Mid Sweden University (MIUN) gasifier, built for research on synthetic fuel production, is a dual fluidised bed gasifier. Reforming of tars and CH4 (except for methanation application) in the syngas is a major challenge for commercialization of biomass fluidised-bed gasification technology towards automotive fuel production. A good syngas from DFBGs can be obtained by optimised design and operation of the gasifier, by the use of active catalytic bed material and internal reforming. This thesis presents a series of experimental tests with different operation parameters, reforming of tar and CH4 with catalytic bed material and reforming of tar and CH4 with catalytic internal reformer.

     

    The first test was carried out to evaluate the optimal operation and performance of the MIUN gasifier. The test provides basic information for temperature control in the combustor and the gasifier by the bed material circulation rate.

     

     After proven operation and performance of the MIUN gasifier, an experimental study on in-bed material catalytic reforming of tar/CH4 is performed to evaluate the catalytic effects of the olivine and Fe-impregnated olivine (10%wtFe/olivine Catalyst) bed materials, with reference to non-catalytic silica sand operated in the mode of dual fluidised beds (DFB). A comparative experimental test is then carried out with the same operation condition and bed-materials but when the gasifier was operated in the mode of single bubbling fluidised bed (BFB). The behaviour of catalytic and non-catalytic bed materials differs when they are used in the DFB and the BFB. Fe/olivine and olivine in the BFB mode give lower tar and CH4 content together with higher H2+CO concentration, and higher H2/CO ratio, compared to DFB mode. It is hard to show a clear advantage of Fe/olivine over olivine regarding tar/CH4 catalytic reforming. 

     

    In order to significantly reduce the tar/CH4 contents, an internal reformer, referred to as the FreeRef reformer, is developed for in-situ catalytic reforming of tar and CH4 using Ni-catalyst in an environment of good gas-solids contact at high temperature.  A study on the internal reformer filled with and without Ni-catalytic pellets was carried out by evaluation of the syngas composition and tar/CH4 content. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases from 25 g/m3 down to 5 g/m3 and the CH4 content from 11% down below 6% in the syngas.

     

    The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. The novel design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas composition. 

     

  • 116.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    An experimental study on catalytic bed materials in a biomass dual fluidised bed gasifier2015Inngår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 81, s. 251-261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study on in-bed material catalytic reforming of tar/CH4 has been performed in the 150 kW allothermal gasifier at Mid Sweden University (MIUN). The major challenge in biomass fluidised-bed gasification to produce high-quality syngas, is the reforming of tars and CH4. The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. This paper evaluates the catalytic effects of olivine and Fe-impregnated olivine (10%wtFe/olivine Catalyst) with reference to silica sand in the MIUN dual fluidised bed (DFB) gasifier. Furthermore, a comparative experimental test is carried out with the same operation condition and bed-materials when the gasifier is operated in the mode of single bubbling fluidised bed (BFB), in order to detect the internal regeneration of the catalytic bed materials in the DFB operation. The behaviour of catalytic and non-catalytic bed materials differs when they are used in the DFB and the BFB. Fe/olivine and olivine in the BFB mode give lower tar and CH4 content together with higher H-2 + CO concentration, and higher H-2/CO ratio, compared to DFB mode. It is hard to show a clear advantage of Fe/olivine over olivine regarding tar/CH4 catalytic reforming. (C) 2015 Elsevier Ltd. All rights reserved.

  • 117.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Henschel, Till
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Internal tar/CH4 reforming in a biomass dual fluidised bed gasifier2014Inngår i: Proceeding of 4th International Symposium on Gasification and its Applications, 2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    An internal reformer is developed for in-situ catalytic reforming of tar and methane (CH4) in allothermal gasifiers. The study has been performed in the 150 kW dual fluidised bed (DFB) biomass gasifier at Mid Sweden University (MIUN). The MIUN gasifier is built for research on synthetic fuel production. Reduction of tars and CH4 (except for methanation application) in the syngas is a major challenge for commercialization of biomass fluidised-bed gasification technology towards automotive fuel production. The MIUN gasifier has a unique design with an internal reformer, where intensive contact of gas and catalytic solids improves the reforming reactions. This paper presents a study on the internal reformer operated with and without Ni-catalytic pellets, by evaluation of the syngas composition and tar/CH4 content. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6% in the syngas. The novel design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality

  • 118.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Henschel, Till
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Internal tar/CHreforming in a biomass dual fluidised bed gasifier.2015Inngår i: Biomass Conversion and Biorefinery, ISSN 2190-6815, Vol. 5, s. 355-366Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An internal reformer is developed for in situ catalyticreforming of tar and methane (CH4) in allothermal gasifiers.The study has been performed in the 150 kW dual fluidised bed (DFB) biomass gasifier at Mid Sweden University(MIUN). The MIUN gasifier is built for research onsynthetic fuel production. Reduction of tars and CH4 (exceptfor methanation application) in the syngas is a major challengefor commercialization of biomass fluidised-bed gasificationtechnology towards automotive fuel production. The MIUN gasifier has a unique design with an internal reformer, where intensive contact of gas and catalytic solids improves the reforming reactions. This paper presents an initial study on the internal reformer operated with and without Ni-catalytic pellets, by evaluation of the syngas composition and tar/CH4 content. A novel application of Ni-catalyst in DFB gasifiers is proposed and studied in this work. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6 % in the syngas. The tar content can be decreased further to lower levels, with increased gas contact to the specific surface area of the catalyst and increased catalyst surface-to-volume ratio. The new design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality.

  • 119.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Biogas production from biological methanation of syngas2018Inngår i: European Biomass Conference and Exhibition Proceedings, ETA-Florence Renewable Energies , 2018, nr 26thEUBCE, s. 512-515Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biogas to be used as gas vehicle fuel is a highly potential source to meet transport fuel demand and give a significant contribution to the Swedish target: vehicle fleet independent of fossil fuels by 2030. At present the biogas market is limited by the amount of available organic waste and the associated infrastructure. To overcome these issues, biomass could either be gasified into syngas and synthesized into bio-SNG (Synthetic Natural Gas) through catalytic methanation, or biomass gasification could be integrated into the biogas system to produce methane through biological methanation. Biomass gasification integrated in biological methanation is a relatively new idea and technology. Syngas conversion to methane by anaerobic cultures is practically unexplored, and few reports are available on this subject. Nevertheless, the pathway has been receiving intensive attractions and R&D recent years. For this purpose, a novel pathway by integrating biomass gasification into biogas system is studied in detail. This paper reviews the whole process from integration of biomass gasification into the biogas system to methane production through biological methanation: Biomass gasification > H2+CO > Biogas digester > Upgrading > Natural gas network. 

  • 120.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    CATALYTIC REDUCTION OF TAR/CH4 BY AN INTERNAL REFORMER IN A DFB GASIFIER2014Inngår i: European Biomass Conference & Exhibition Proceedings, 2014, s. 620-625Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    An internal reformer is developed for in-situ catalytic reforming of tar and methane (CH4) in allothermal gasifiers. Reduction of tars and CH4 in the syngas is a challenge for commercialization of biomass fluidised-bed gasification technology towards advanced automotive fuel production. This paper presents an initial study on the internal reformer operated with and without Ni-catalytic pellets in the Mid Sweden University (MIUN) DFB (Dual Fluidised Bed) gasifier, by evaluation of the syngas composition and tar/CH4 content. The novelty with the application of Ni-catalyst in this paper is the selected location where intensive gas to catalytic-material and bed-material contacts improve the reforming reactions. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6% in the syngas. The tar content will be decreased further to lower levels, with increased gas contact to the specific surface area of the catalyst and increased catalyst surface-to-volume ratio. The new design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality.  

  • 121.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Experimental test on a novel dual fluidised bed biomass gasifier for synthetic fuel production2011Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 90, nr 4, s. 1340-1349Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents a preliminary test on the 150 kWth allothermal biomass gasifier at MIUN (Mid Sweden University) in Härnösand, Sweden. The MIUN gasifier is a combination of a fluidised bed gasifier and a CFB riser as a combustor with a design suitable for in-built tar/CH4 catalytic reforming. The test was carried out by two steps: 1) fluid-dynamic study; 2) measurements of gas composition and tar. A novel solid circulation measurement system which works at high bed temperatures is developed in the presented work. The results show the dependency of bed material circulation rate on the superficial gas velocity in the combustor, the bed material inventory and the aeration of solids flow between the bottoms of the gasifier and the combustor. A strong influence of circulation rate on the temperature difference between the combustor and the gasifier was identified. The syngas analysis showed that, as steam/biomass (S/B) ratio increases, CH4 content decreases and H2/CO ratio increases. Furthermore the total tar content decreases with increasing steam/biomass ratio and increasing temperature.  The biomass gasification technology at MIUN is simple, cheap, reliable, and can obtain a syngas of high CO+H2concentration with sufficient high ratio of H2 to CO, which may be suitable for synthesis of Methane, DME, FT-fuels or alcohol fuels. The measurement results of MIUN gasifier have been compared with other gasifiers. The main differences can be observed in the H2 and the CO content, as well as the tar content. These can be explained by differences in the feed systems, operating temperature, S/B ratio or bed material catalytic effect etc..

  • 122.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Internal Tar/CH4 Reforming using a Novel Design in a Biomass Dual Fluidised Bed Gasifier2013Inngår i: 21st European Biomass Conference and Exhibition: Setting the course for a biobased ecomomy, Florence, Italy: ETA-Florence Renewable Energies , 2013, s. 2038-2042Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Reforming of tars and methane (CH4) in syngas is a significant challenge for low-temperature biomass gasification. For a dual fluidised bed gasifier (DFBG), catalytic bed materials are usually used to promote the reforming reactions. Intensive contact between gas and catalytic bed material at high temperature enhances the internal tar/CH4 reforming. The MIUN gasifier, built for research into synthetic fuel production, is a dual fluidised bed gasifier (DFBG). The results with different bed materials (silica sand, olivine and Fe-impregnated olivine) give roughly equivalent amounts of methane and gravimetric tar in the raw untreated syngas, and need to be reduced to an acceptably low level. The gasification research group at MIUN investigates a novel design in the MIUN gasifier, to increase the gasification efficiency, suppress the tar generation and to upgrade the syngas quality. The first step is taken towards a novel design in the MIUN gasifier. The application is expected to significantly enhance the syngas quality.

  • 123.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Preliminary Test on the Allothermal Gasifier at Mid Sweden University2009Inngår i: 17th European Biomass Conference: FROM RESEARCH TO INDUSTRY AND MARKETS / [ed] G. F. DE SANTI, J. F. DALLEMAND, H. OSSENBRINK, A. GRASSI and P. HELM, Florence, Italy: ETA-Florence Renewable Energies , 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper presents a preliminary test on the 150 kW allothermal biomass gasifier at MSU (Mid Sweden University) in Härnösand, Sweden. The MSU gasifier is a combination of a fluidized bed gasifier and a CFB riser as a combustor with an unique design suitable for in-built tar/CH4 catalytic reforming. The test was carried out by two steps, 1) fluid-dynamic study and 2) measurements of gas composition. The results show the dependency of bed material circulation rate on the superficial gas velocity in the combustor, the bed material inventory and the aeration of solids flow between the bottoms of the gasifier and the combustor. A strong influence of circulation rate on the temperature difference between the combustor and the gasifier was identified. The syngas analysis showed that, as steam/biomass ratio increases, CH4 content decreases and H2/CO ratio increases. The biomass gasification technology developed at MSU is simple, cheap, reliable, and can obtain a syngas of high CO+H2 concentration with sufficient high ratio of H2 to CO, suitable for synthesis of Methane, DME, FT-fuels or alcohol fuels This development work is expected to help for developing an effective and a reliable BTL technology in S&M scales under 200 MW, possibly for biorefinery integration.

  • 124.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Tar/CH4 Reforming by Catalytic Bed Materials in a Biomass Fluidised Bed Gasifier2012Inngår i: 20th European Biomass Conference & Exhibition: Proceedings of the International Confernce held in Milano, Italy, 18 - 22 June 2012, 2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A study on in-bed catalytic material reforming of tar/methane (CH4) has been performed in the 150 kW allothermal biomass gasifier at Mid Sweden University (MIUN). The MIUN gasifier, built for research on synthetic fuel production, is a dual fluidised bed gasifier (DFBG). The syngas for automotive fuels synthesis has a strict specification of impurities. The biggest challenge for biomass fluidised-bed gasification is the reforming of tars and CH4. Internal reforming should be considered before downstream reforming. The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. The experimental tests are carried out in three cases: 1) basic condition with silica sand (no catalytic activity), 2) calcinated olivine, and 3) Fe-impregnated olivine (10%wtFe/Olivine Catalyst). The measurement results have been evaluated by comparing tar/CH4 content in the syngas from the gasifier operated under different operation conditions. These results in BFB mode have initiated the ongoing investigations of the catalytic effects and regeneration in DFB mode. It can be concluded that the Fe-impregnated olivine showed a surprising low reactivity for tar and CH4 reforming in the BFB model. 

  • 125.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    TAR/CH4 REFORMING BY CATALYTICALLY ACTIVE MATERIALS IN A BIOMASS DUAL FLUIDISED BED GASIFIER 2010Inngår i: The second International Symposium on Gasification and Its Application (ISGA 2010), December 5-8, Fukuoka, Japan, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a study on the effects of catalytically active materials, before tests in the 150 kW allothermal biomass gasifier at Mid Sweden University (MIUN). The gasifier has been built up in 2008 for research on synthetic fuel production, and is a combination of a circulating fluidised bed (CFB) riser as combustor and a fluidised bed (FB) as steam gasifier. The MIUN gasifier has a unique design suitable for in-built tar/methane (CH4) catalytic reforming. The lifetime of the catalyst can be prolonged using a dual fluidised bed gasifier (DFBG) with continuously internal regeneration of the catalyst. The catalytic effects of 1) basic condition with silica sand (no catalytic activity), 2) commercial catalyst, 3) development metal-catalyst (high surface area support), and 4) olivine catalyst will be evaluated by comparing tar/CH4 content in the syngas from the gasifier operated under different conditions. Silica sand and commercial catalyst can be considered as extremes for comparing the activity of the chosen conditions.

  • 126.
    Hafrén, Jonas
    et al.
    Sveriges lantbruksuniversitet (SLU).
    Nelsson, Erik
    Gerritsen, Hans C.
    Utrecht university, The Nederlands.
    Bader, Arjen N.
    Utrecht university, The Nederlands.
    Optical properties of thermomechanical pulp (TMP) obtained from sulfite-pretreated Norway spruce with focus on two-photon spectral imaging (TPSI)2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, ISSN 0018-3830, Vol. 66, nr 7, s. 817-824Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chips of Norway spruce have been impregnated with Na2SO3 and refined at two specific energy consumptions levels at full mill scale. The optical properties of thermomechanical pulps (TMPs) obtained were analyzed in terms of brightness, light scattering, opacity, and autofluorescence by spectral imaging. Even at low sulfite dosage (0.24% sulfite by dry weight) light absorption was reduced, and the brightness was elevated, and a clear dose-response effect was observed. Two-photon spectral imaging (TPSI) showed that sulfonation, impregnation, and refining affect the fluorescence properties differently. Compared to native wood, both processed wood chips and pulp fibers revealed blue-shifted fluorescence maxima, a characteristic of shortened conjugated systems. Two subpopulations of fibers with different optical properties were observed, and the fluorescence of one fiber population was red shifted.

  • 127.
    Halvarsson, Sören
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Manufacture of straw MDF and fibreboards2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels.  The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps.

    1. 1.       Size-reduction (hammer-milling) and screening of straw
    2. 2.       Wetting and heating of straw
    3. 3.       Defibration
    4. 4.       Resination of straw fibre
    5. 5.       Mat forming
    6. 6.       Pre-pressing
    7. 7.       Hot-pressing

     

     

     

    The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization.

    A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible.

  • 128.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Manufacture of High-Performance Rice-Straw Fiberboards2010Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, nr 3, s. 1428-1435Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rice straw, a waste agriculture material grown and harvested in Willows, CA, was used,is a raw material in the production of thin medium- and high-density fiberboards (MDFs and HDFs). The rice straw was cleaned, size-reduced, and soaked in water before being refined. Defibration was performed in it pressurized pilot-plant single-disk refiner, OHP 20". The fiber production capacity reached a level of 63 kg/h. and the proper fiber quality for MDF/HDF production was established. Analysis of the produced fiber showed an average fiber length of approximately 0.9 mm, in average fiber width of 31 mu m, a shive weight of below 24%, and a dust content of less than 30%. Production of fiberboards was performed by addition of 3%, 4%, and 5% methylene diphenyl diisocyanate (MDI). The flexural properties, internal bond strength, and thickness swelling of the produced fiberboards were evaluated according to ASTM methods. The finished fiberboards based on rice straw and MDI resin showed excellent properties. The internal bond (IB) reached levels of 2.6 MPa, and the modulus of rupture (MOR) and modulus of elasticity (MOE) showed levels comparable to those of wood-based fiberboards and were acceptable according to the requirements or medium-density fiberboard (MDF) for interior applications (American National Standards Institute, ANSI A208.2-2002). The water-repelling properties of the 3-min rice-straw fiberboards were encouraging; the thickness swelling, (TS) was in the range of 15-30%. Two different methods to avoid adhesion between the press plates and the resinated fiber material during hot pressing were investigated: protective paper sheets were placed between the fiber mat and press plates, or a press-release agent was sprayed oil steel plates that were then placed ill the press before pressing Satisfactory results were obtained with both methods, and no adhesion was observed between the fiberboard and the steel plates. The method of using press-release agent during pressing had no notable negative effects oil the fiberboard properties.

  • 129.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Manufacture of non-resin wheat straw fibreboards2009Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 29, nr 2-3, s. 437-445Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheat straw was used as raw material in the production of fibreboards. The size-reduced straw was pretreated with steam, hot water and sulphuric acid before the defibration process to loosen its physical structure and reduce the pH. No synthetic binder was added. Adhesive bonding between fibres was initiated by activation of the fibre surfaces by an oxidative treatment during the defibration process. Fenton’s reagent (ferrous chloride and hydrogen peroxide) was added. Two different levels of hydrogen peroxide (H2O2), 2.5% or 4.0% were used. The resulting fibres were characterized in terms of fibre length distribution, shive content, pH and pH-buffering capacity. The properties of finished fibreboards were compared with medium-density fibreboard (MDF) with density above 800 kg/m3 produced from straw and melamine modified UF resin. The modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) were lower than those of conventional manufactured wheat straw fibreboards but close to the requirements of the MDF standard (EN 622-5: 2006). The water absorption properties for the H2O2 activated straw fibreboards were relatively high, but were reduced by 25% with the addition of CaCl2 into the defibrator system as a water-repelling agent. Increased levels of hydrogen peroxide improved the mechanical and physical properties of the straw fibreboard.

  • 130.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Properties of Medium Density Fibreboard (MDF) based on Wheat straw and Melamine Modified Urea Formaldehyde (UMF) Resin2008Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 28, nr 1, s. 37-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheat straw was investigated as a raw material for manufacturing of medium density fibreboard (MDF) in a fully equipped pilot-plant. Commercial urea melamine formaldehyde (UMF) and a mixture of UMF-resin and urea melamine phenol formaldehyde (UMPF) adhesives were used as binders in manufacturing of high performance MDF. The study evaluated the quality of MDF produced of straw (i.e., SMDF). Different qualities of wheat straw and different resin contents (14–17%) were used. Moreover, the SMDF was produced at different thicknesses of 9 and 16 mm and densities of 750–1000 kg/m3. The properties of the resulting SMDF were evaluated by analysing mechanical and water absorption (anti-swelling) properties as a function of density. Internal bond (IB), modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling (TS), and water absorption (WABS) were the properties analysed. SMDF-panels produced with densities above 780 kg/m3 and resin contents above 14% met the requirements for wood-based MDF standard EN 622-5:1997.

  • 131.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Manufacturing of fiber composite Medium Density Fiberboard (MDF) based on annual plant fiber and Urea Formaldehyde Resin2004Inngår i: Proceedings of ICECFOP1: 1st International Conference on Environmentally-Compatible Forest Products, EDICOES UNIV FERNANDO PESSOA , 2004, s. 131-147Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Production of fiber composite materials such as Medium Density Fiberboard (MDF) and particleboard (PB) is in general based on wood as a raw material. However, cereal straws and other annual agriculture waste materials have regained an interest as a potential raw material for production of MDF. The cereal straws are among the most common lignocellulosic materials that are easily accessible, non-expensive and renewable. The aim of this investigation was to produce high performance MDF based on wheat straw and urea formaldehyde (UF) resin. The usage of UF-resin for wheat straw MDF-panels has so far resulted in acceptable strength properties but poor moisture resistance and thickness swelling (TS). Application of melamine modified UF-resin for wood based MDF has improved the moisture resistance of produced MDF panels. In this investigation two commercial melamine modified UF-resins were used as binders (adhesives) in the production of wheat straw MDF. Hammer milled wheat straw was treated with water and sulfuric acid (0.6 %) before refining. The reason was to improve the curing, conditions of the UF-resins by a reduction of the pH and the pH-buffering capacity of refined wheat straw fiber. Refining of wheat straw was performed at slightly lower pressure and retention time compared with refining of wood material. However, a lot of fines and dust (wheat straw fibers < 0.5 mm) were generated during refining. A hi-h resin content of the melamine modified UF-resin was necessary (15 %) to compensate for the high ratio of wheat straw fines and dust. Final panel properties of wheat straw MDF could meet the requirements of the MDF standard (EN 622-5:1997), including the TS. Strength properties as internal bond (IB) and modulus of rupture (MOR) were increased as a function of density. Thickness swelling was reduced as a function of density. The usage of wheat straw as a raw material in combination with a melamine modified UF-resin, as an adhesive, is a possible route for manufacturing of high performance Medium Density Fiberboard.

  • 132.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Manufacturing of Non-Resin Wheat Straw MDF/HDF2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wheat straw was used as raw material in production of medium density fibreboard (MDF) and high-density fibreboard (HDF). The straw fibreboard process was performed without addition of synthetic binders. Adhesive bonding between fibers was initiated by activation of the fibre surfaces by an oxidative pre-treatment in the defibration process. Hydrogen peroxide was added into the blowline to get a fast and effective process. Adhesive bonding between the activated fibres were later formed when pressing. The fiber quality and pH and pH buffering capacity was analysed at different hydrogen peroxide loadings. The effects of mechanical and physical properties of the non-resin wheat straw MDF/HDF were evaluated. Mechanical bending properties, Modulus of Rupture (MOR), Modulus of Elasticity (MOE), and Internal Bond (IB) were generally lower than conventional wood-based MDF/HDF but close to the requirements of the MDF-standard. Modulus of Elongation (MOE) was surprisingly high and exceeded the levels in the MDF-standard. Moreover, the thickness swelling of the non-resin wheat straw MDF was high but was reduced by the addition of a hydrophobic agent (metallic ion). Increased level of hydrogen peroxide improved the panel properties and the usage of the hydrophobic agent reduced the thickness swelling.

  • 133.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Processing of Wheat Straw Materials for Production of Medium Density Fiberboard (MDF) 2005Inngår i: 59th Appita Annual Conference, Aukland, New Zealand 16-19 May 2005, Brunswick East Victoria 3057, Australia: New Genaration Print & Copy , 2005, s. 623-629Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wheat straw waste materials were processed in a fully equipped pilot-scale MDF-process. Hammermilled wheat straw was used as a raw material in combination with a commercial melamine modified Urea Formaldehyde (UF) resin. Approximately 15 wt % of the wheat straw particles smaller than 0.7 mm was removed in a sifting operation. Medium density fiberboard was produced in the range of 790 to 860 kg/m3 average densities and at a resin content of 12.5, 13.1 and 14 wt %. The panels produced were approved according to the European Standard for MDF (EN 622-5:1997). Four different wheat straw fractions were investigated and sifted at 1.0 mm, 0.6 mm and 0.2 mm screen hole diameter, including the fine particles less than 0.2 mm. The ash content of the four wheat straw fractions varied between 7 wt % and 15 wt %. The maximum level of ash (15 wt %) was observed for the finest particle fraction based on materials less than 0.2 mm. The silicone (Si) content in corresponding ash samples of the sifted wheat straw was analysed by Energy Dispersive X-ray analysis, EDX. The silicone content increased from 18 % to 24 % at a reduced particle size. Moreover, the pH-buffering capacity of the four wheat straw fractions was reduced as the particle size of the specific fractions was increased.

  • 134.
    He, Jie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Gasification-based Biorefinery for Mechanical Pulp Mills2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The modern concept of “biorefinery” is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various bio-based products. It includes thermochemical processes such as gasification and fast pyrolysis. In thermo-mechanical pulp (TMP) mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, bio-sludges and other available fuels such as peat, recycled wood and paper products. On the other hand, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. The huge amount of purchased electricity can be compensated for by self-production of electricity from gasification, or the involved cost can be compensated for by extra revenue from bio-transport fuel production. This work is to study co-production of bio-automotive fuels, bio-power, and steam via gasification of the waste biomass streams in the context of the mechanical pulp industry. Ethanol and substitute natural gas (SNG) are chosen to be the bio-transport fuels in the study. The production processes of biomass-to-ethanol, SNG, together with heat and power, are simulated with Aspen Plus. Based on the model, the techno-economic analysis is made to evaluate the profitability of bio-transport fuel production when the process is integrated into a TMP mill.The mathematical modelling starts from biomass gasification. Dual fluidized bed gasifier (DFBG) is chosen for syngas production. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150

    KWth Mid Sweden University (MIUN) DFBG. As a reasonable result, the tar content in the syngas decreases with the gasification temperature and the steam to biomass (S/B) ratio. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass or product gas needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming.For ethanol production, a stand-alone thermo-chemical process is designed and simulated. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost. The calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built over 200 MW.In TMP mills, wood and biomass residues are commonly utilized for electricity and steam production through an associated CHP plant. This CHP plant is here designed to be replaced by a biomass-integrated gasification combined cycle (BIGCC) plant or a biomass-to-SNG (BtSNG) plant including an associated heat & power centre. Implementing BIGCC/BtSNG in a mechanical pulp production line might improve the profitability of a TMP mill and also help to commercialize the BIGCC/BtSNG technologies by taking into account of some key issues such as, biomass availability, heat utilization etc.. In this work, the mathematical models of TMP+BIGCC and TMP+BtSNG are respectively built up to study three cases: 1) scaling of the TMP+BtSNG mill (or adding more forest biomass logging residues in the gasifier for TMP+BIGCC); 2) adding the reject fibres in the gasifier; 3) decreasing the TMP SEC by up to 50%.The profitability from the TMP+BtSNG mill is analyzed in comparison with the TMP+BIGCC mill. As a major conclusion, the scale of the TMP+BIGCC/BtSNG mill, the prices of electricity and SNG are three strong factors for the implementation of BIGCC/BtSNG in a TMP mill. A BtSNG plant associated to a TMP mill should be built in a scale above 100 MW in biomass thermal input. Comparing to the case of TMP+BIGCC, the NR and IRR of TMP+BtSNG are much lower. Political instruments to support commercialization of bio-transport fuel are necessary.

     

  • 135.
    He, Jie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    GASIFICATION-BASED BIOREFINERY FOR MECHANICAL PULP MILLS2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The modern concept of "biorefinery" is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various biobased products. It includes thermochemical processes such as gasification and fast pyrolysis. In mechanical pulp mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, biosludges and other available fuels such as peat, recycled wood, and paper products. This work is to study co-production of bio-automotive fuels, biopower, and steam via gasification in the context of the mechanical pulp industry.

     

    Biomass gasification with steam in a dual-fluidized bed gasifier (DFBG) was simulated with ASPEN Plus. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150 KWth Mid Sweden University (MIUN) DFBG. The model predicts that the content of char transferred from the gasifier to the combustor decreases from 22.5 wt.% of the dry and ash-free biomass at gasification temperature 750 ℃ to 11.5 wt.% at 950 ℃, but is insensitive to the mass ratio of steam to biomass (S/B). The H2 concentration is higher than that of CO under normal DFBG operating conditions, but they will change positions when the gasification temperature is too high above about 950 ℃, or the S/B ratio is too far below about 0.15. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming. Tar content in the syngas can also be predicted from the model, which shows a decreasing trend of the tar with the gasification temperature and the S/B ratio. The tar content in the syngas decreases significantly with gasification residence time which is a key parameter.

     

    Mechanical pulping processes, as Thermomechanical pulp (TMP), Groundwood (SGW and PGW), and Chemithermomechanical pulp (CTMP) processes have very high wood-to-pulp yields. Producing pulp products by means of these processes is a prerequisite for the production of printing paper and paperboard products due especially to their important functional properties such as printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant. Integration of a BIGCC plant into a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when the flow of biomass (such as branches and tree tops) from the forest is increased. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency of the system is further improved. A TMP+BIGCC mathematic model is developed based on ASPEN Plus. By means of this model, three cases are studied:

     

    1) adding more forest biomass logging residues in the gasifier,

    2) adding a reject fraction of low quality pulp fibers to the gasifier, and

    3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%.

     

    For the TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profit and the internal rate of return (IRR) are calculated. The results quantify the economic benefit from the TMP+BIGCC mill.

     

    Bio-ethanol has received considerable attention as a basic chemical and fuel additive. It is currently produced from sugar/starch materials, but can also be produced from lignocellulosic biomass via a hydrolysis--fermentation or thermo-chemical route. In terms of the thermo-chemical route, a few pilot plants ranging from 0.3 to 67 MW have been built and operated for alcohols synthesis. However, commercial success has not been achieved. In order to realize cost-competitive commercial ethanol production from lignocellulosic biomass through a thermo-chemical pathway, a techno-economic analysis needs to be done.

     

    In this work, a thermo-chemical process is designed, simulated, and optimized mainly with ASPEN Plus. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost.

     

    Calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built at around 200 MW. Cost-competitive ethanol production can be realized with efficient equipments, optimized operation, cost-effective syngas cleaning technology, inexpensive raw material with low pretreatment cost, high-performance catalysts, off-gas and methanol recycling, optimal systematic configuration and heat integration, and a high-value byproduct.

  • 136.
    He, Jie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Björkqvist, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Techno-economic evaluation of a mechanical pulp mill with gasification2013Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 3, s. 349-357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical pulping processes, including thermomechanical pulp (TMP), groundwood (SGW andPGW), and chemithermomechanical pulp (CTMP) processes, each have a very high wood-to-pulp yield. Producing pulp by means of these processes is a prerequisite for paper (such as printing paper and paperboard) grades requiring high printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost.

    In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant.

    Implementing BIGCC in a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when more biomass from forest (such as branches and tree tops) is available. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency will be further improved. A TMP+BIGCC mathematical model is developed with ASPEN Plus. By means of modeling, three cases are studied:

    1) adding more forest biomass logging residues in the gasifier,2) adding the reject fibres in the gasifier, and3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%.

    For a TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profits are evaluated.

  • 137.
    He, Jie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bio-SNG production in a TMP Mill in comparison with BIGCC2014Inngår i: Energy Procedia, Elsevier, 2014, Vol. 61, s. 2894-2897Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biorefinery as a concept for polygeneration of various bio-based materials, fuels and chemicals has been more and more attractive. This concept is applied to the thermomechanical pulp (TMP) and paper industry in the present study to evaluate the possibility of co-production of substitute natural gas (SNG), electricity and district heating (DH) in addition to mechanical pulp and paper. In TMP mills, wood and biomass residues are commonly utilized for electricity and steam production through an associated combined heat and power (CHP) plant. This CHP plant is designed to be replaced by a biomass-T o-SNG (BtSNG) plant including an associated heat and power centre. Implementing BtSNG in a mechanical pulp production line might improve the profitability of a TMP mill and also help to commercialize the BtSNG technology by taking into account of some key issues such as, biomass availability, heat utilization etc. A TMP+BtSNG mathematical model is developed with ASPEN Plus.

  • 138.
    He, Jie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Research on ethanol synthesis from syngas2008Inngår i: Journal of Zhejiang University - Science A, ISSN 1673-565X, Vol. 9, nr 5, s. 714-719Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is a very fine substitutable energy technology to synthesize ethanol from biomass-derived syngas. This paper summarized the development of preparing ethanol from syngas, and especially elaborated on the research status of catalysts for the process. Based on the relative researches on the reaction mechanism, structure and performance of the catalysts, the optimumdesign of catalysts with high activity was presented in this review, which set the theoretical and application foundation for the industrial production of ethanol from syngas.

  • 139.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andersson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Sjöberg, Natalia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Eltz, Thomas
    Ruhr University Bochum, Bochum, Germany.
    6-(4-Methylpent-3-en-1-yl)naphthalene-1,4-dione, a behaviorally active semivolatile in tibial perfumes of orchid bees2018Inngår i: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 28, nr 4-5, s. 131-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Male neotropical orchid bees (Euglossini) collect volatiles from varied sources in their environment to compile complex, species-specific tibial perfumes, which are later released at mating sites. A major compound prominent in tibial extracts of Euglossa allosticta was purified, as well as isolated and its structure was elucidated by analytical methods including GC–MS, GC–FTIR, HRMS and 1H and 13C NMR. After synthesis, the compound with the proposed structure was finally identified as 6-(4-methylpent-3-en-1-yl)naphthalene-1,4-dione. At field sites in Panama and Costa Rica, the synthetic compound attracted males of E. allosticta, but no other euglossines. This strengthens the view that semivolatiles play an important role in conveying specificity to perfume signals of orchid bees. 

  • 140.
    Hellström, Lisbeth
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Energy Efficiency Improvement Potential in TMP and CTMP by Axial Precompression of Wood During ChippingManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    It has recently been shown that there is a possibillity to improve the energy efficiency during first stage TMP (thermomechanical pulp) refining by performing the wood chipping so as to increase the compressive damage in the chips and hence breaking up the wood structure. The parameter that was varied was the spout angle i.e. the angle between the fibre direction of the wood specimen and the cutting plane. In this article is investigated how the refining of chips produced at two different spout angles i.e. 30 and 50, influenced the properties of CTMP (chemithermomechanical pulp). It was found that the specific energyinput for a certain CSF (Canadian Standard Freeness) value was lower for chips produced at the spout angle of 50 but that the addition of chemicals (NaHSO3) to the dilution water had no influence on the specific energy value for a given CSF value. However, the tensile index and specific light scattering coefficient was substantially higher for handsheets made of the pulp refined from chips produced at the spout angle 50 and with NaHSO3 added compared to handsheets from pulp made from 30 and 50 chips without chemicals added.

  • 141.
    Hellström, Lisbeth
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Carlberg, Torbjörn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Gregersen, Øyvind
    Department for Chemical Engineering, NTNU, Norway.
    Evaluation Of Collimated Chipping Technology For Reducing Energy Consumption In Mechanical Pulping2012Inngår i: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 2, nr 3, s. 6-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has recently been shown that the energy efficiency during first-stage TMP (thermo-mechanical pulp) refining can be improved using amodified chipping method (collimated chipping), where the angle between the fibre direction of the wood specimen and the cutting plane is increased. This paper reports the differences in properties of TMP refined from wood chips produced at two different spout angles, 30° and 50°, with and without the addition of sodium bisulphite (NaHSO3) to the dilution water. It was found that the specific energy input for a certain CSF (Canadian Standard Freeness) value was lower for chips produced at spout 50°, but that the addition of chemicals to the dilution water had no influence on the specific energy value for a given CSF value. However, the tensile index and specific light-scattering coefficient were substantially higher for handsheets made from the pulp refined from chips produced at spout angle 50° and with NaHSO3 added compared to handsheets from pulp made from 30° and 50° chips without chemicals added.

  • 142.
    Hellström, Lisbeth
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    The effect on the energy consumption in mechanical pulping of different wood chipping conditions2010Inngår i: Proceedings of 7th International Seminar of Fundamental Mechanical Pulp Research (IFMPRS 2010), 2010, s. 124-126Konferansepaper (Annet vitenskapelig)
  • 143.
    Hellström, Lisbeth
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Gregersen, Øyvind
    Department for Chemical Engineering, NTNU, Trondheim, Norway.
    Properties of wood chips for thermomechanical pulp (TMP) production as a function of spout angle2011Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, nr 6, s. 805-809Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spruce woodchipswere produced under well-controlled conditions in a laboratory woodchipper at spout angles of 30°, 40°, and 50° at a cutting rate of 20 m s-1 and with a nominalchip length of 25 mm. Thechips were then refined under thermomechanical pulp (TMP) conditions in a pilot refiner plant. The pulpproperties such as freeness, average fiber length, and shives content were determined and evaluated as a function of specific energy consumption. For a first stage refining and for a freeness value of 350 ml, a decrease in specific electrical energy consumption could be achieved by performing thewood chipping at a spout angle of 50° as compared to 30° which is the spout angle commonly used. A patent application regarding this method has been filed and is pending. It is realized that a freeness value is not directly indicative of any quality measure, such as, for example tensile index and light scattering coefficient but the obtained results can be interpreted to be promising. Further studies are needed regarding the impact of the modified chipping process.

  • 144.
    Hellström, Lisbeth M.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Biller, Sven-Olov
    Andritz Iggesund Tools AB, Iggesund, Sweden.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gradin, Per A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    A theoretical and experimental study of the circular sawing process2014Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, nr 3, s. 307-312Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To gain further insight into the energy dissipation during the wood sawing process, a theoretical model has been developed. The model is based on the assumption that there are two basic causes for energy dissipation during sawing: the creation of a new surface and the compression of material below a saw tooth. It is assumed that both contributions can be dependent on the cutting angle (the angle between the fiber direction and the tangent to the path followed by a saw tooth) because a saw tooth changes its angle of attack during its way through a log. To determine this dependence of the dissipation on the cutting angle, a series of experiments with pine plank sawing were performed by means of different feeding rates and cutting angles while the electrical power supplied to the saw was measured. The parameters in the theoretical model were derived from the experimental findings. Finally, two tests were carried out under different conditions with respect to thickness and cutting angles and the validity of the model was confirmed concerning the prediction of the electrical power consumption.

  • 145.
    Hellström, P.
    et al.
    AkzoNobel Pulp and Performance Chemicals, 445 80 Bohus, Sweden.
    Heijnesson-Hultén, A.
    AkzoNobel Pulp and Performance Chemicals, 445 80 Bohus, Sweden.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. AkzoNobel Pulp and Performance Chemicals, 445 80 Bohus, Sweden.
    Håkansson, H.
    Department of Engineering and Chemical Sciences, Karlstad University, 651 88 Karlstad, Sweden .
    Germgård, U.
    Department of Engineering and Chemical Sciences, Karlstad University, 651 88 Karlstad, Sweden .
    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. © 2014 Springer Science+Business Media Dordrecht.

  • 146.
    Hellström, Pia
    et al.
    Akzo Nobel Pulp & Paper Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden.;Karlstad Univ, Karlstad, Sweden.
    Heijnesson-Hulten, Anette
    Akzo Nobel Pulp & Paper Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. Akzo Nobel Pulp & Performance Chem AB, Bleaching Chem Applicat RD&I, Bohus, Sweden.
    Hakansson, Helena
    Karlstad Univ, Chem Engn, Karlstad, Sweden.
    Germgard, Ulf
    Karlstad Univ, Pulp Technol, Karlstad, Sweden.
    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.

  • 147.
    Hellström, Pia
    et al.
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Heijnesson-Hultén, Anette
    AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Paulsson, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik. AkzoNobel Pulp & Performance Chem, SE-44580 Bohus, Sweden.
    Håkansson, Helena
    Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden.
    Germgård, Ulf
    Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden.
    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.

  • 148.
    Henschel, Till
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    A study on the pyrolysis behaviour of different biomass fuels using thermogravimetry and online gas analysis2016Inngår i: European Biomass Conference and Exhibition Proceedings, ETA-Florence Renewable Energies , 2016, Vol. 24thEUBCE, nr 24thEUBCE, s. 1290-1293Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fuel availability and flexibility are important issues for biomass-based heat/power and advanced biofuel plants. The physical and chemical properties of biomass feedstocks vary from one to others to a great degree, which must be taken care of for the reactor design/operation, system optimization and blend feedstock application. In this work, the biomass property is evaluated based on pyrolysis behavior of biomass fuels by means of TGA and online gas analysis. Wood, pine bark, peat, straw, black liquor and microalgae are chosen as the biomass feedstocks for the pyrolysis study. The measurement results show high volatile content for algae and black liquor (around 85%) and low volatile content for pine bark and peat (around 69%). Differently from woody biomass, the DTG curve of straw has a single dominant peak at much lower temperature, which suggests a dominant component of hemicellulose in biomass, while algae and peat have a broader temperature specturm of devolatilization but much lower peak temperature. CO2 is released first and H2 later in the pyrolysis process for all biomass feedstocks, whileas the peak of CO formation follows CO2 formation trend for most feedstocks used, except for peat and pine bark which give a peak later at high temperature. This indicates secondary reactions of tar cracking, steam reforming and char gasification.

  • 149.
    Henshaw Osong, Sinke
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Engström, Ann-Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Development of CTMP-based nanofibrillated Cellulose /nanographite composites for paper applications2015Konferansepaper (Annet vitenskapelig)
  • 150.
    Henshaw Osong, Sinke
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Pettersson, Gunilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    The use of cationic starch and microfibrillated cellulose to improve strength properties of CTMP-based paperboardManuskript (preprint) (Annet vitenskapelig)
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