| 1. |
- Ahlbom, Anders, 1993, et al.
(författare)
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Using guaiacol as a capping agent in the hydrothermal depolymerisation of kraft lignin
- 2023
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 38:4, s. 619-631
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Tidskriftsartikel (refereegranskat)abstract
- The depolymerisation of softwood kraft lignin was investigated, under hydrothermal conditions at 290 °C and 250 bar, with guaiacol in the reactor feed to evaluate its impact on the formation of char and on the molecular weights of the products. The effect of residence time was investigated in the time span 1-12 min. Lignin is depolymerised during the process and guaiacol is both formed and consumed during the reaction, with clearly noticeable changes as early as in the first minute of reaction. Although the addition of guaiacol in the reactor feed causes a reduction in the weight average molecular weight of the products, the yield of char increases. Longer residence times result in repolymerisation of the reaction products as well as a further increase in the yield of monoaromatic components and char.
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| 2. |
- Al-Dajani, W. W., et al.
(författare)
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On the isolation and structure of softwood residual lignins
- 2002
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 17:2, s. 193-198
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Tidskriftsartikel (refereegranskat)abstract
- Different softwood residual lignins were isolated by acid hydrolysis of kraft and soda Pulps. Complete isolation of lignin Could not be achieved in one hydrolysis step. The yield of lignin varied between 35 and 55%. A more acidic, second hydrolysis step was therefore necessary to isolate almost all the lignin remaining in the Pulp residue, giving a total lipin yield of 91%. Alkaline extraction of the pulp was almost as efficient as acid hydrolysis in isolating residual lignins. However, alkaline extraction gave less pure lignin fractions and there was a clear indication of the existence of lignin-carbohydrate bonds. Pine wood meal was acid-hydrolyzed in the same way as the pulps. After two-stage acid hydrolysis, the combined lignin yield was only 45% of the Klason lignin content, which means that native lignin is more difficult to isolate front wood than residual lignin front a chemical pulp. It is Concluded that the difficulty encountered in isolating residual lignin by acid hydrolysis is a problem of limited accessibility due to a complex carbohydrate network surrounding the lignin.
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| 3. |
- Alam, Anzar, et al.
(författare)
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Online surface roughness characterization of paper and paperboard using a line of light triangulation technique
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:3, s. 662-670
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Tidskriftsartikel (refereegranskat)abstract
- Within both the paper and paperboard industries, real time monitoring and measurement of surface roughness of a paper moving at high velocities is an important and challenging area of research. The uniform surface, for an entire production, can be effectively achieved by monitoring and controlling the paper surface roughness, in real time during the manufacturing steps. Presently the majority of paper industries rely on traditional laboratory profilometers. The obvious limitations of lab profilometers are that these are slow, do not measure the quality of entire reels but rather deal with only a few small pieces of samples taken from the end of the reels and it is difficult to make any possible correction in the productionlines without knowing the online roughness data. To eradicate the disadvantages associated with conventional measurements, an online prototype instrument has been developed that measures the surface roughness during the manufacturing steps, and is based on a line of lighttriangulation technique. The prototype technique will be of assistance in ensuring tight process control in order to maintain both a better and auniform quality throughout the entire production. It measures the whole reel, meter by meter, in traditional units of roughness and is also capable of characterizing the topography in a wide range of wavelength spectra. The article presents the online analyses results obtained from the developed prototype. The real time measurements, in a paperboard pilot mill, have successfully characterized and distinguished 16 different grades of newspaper and paperboard reels including reels which have the same family of quality grades and materials.
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| 4. |
- Alam, Mohammad Anzar, et al.
(författare)
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Investigation of the surface topographical differences between the Cross Direction and the Machine Direction for newspaper and paperboard
- 2011
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 26:4, s. 468-475
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Tidskriftsartikel (refereegranskat)abstract
- Paper and paperboard surface quality is constantly being improved by the industry. This improvement work deals with the essential fact that the surface topography must be measured, both in relation to offline and online measurements for the manufactured products. Most measurements relating to surface topography (especially online) are performed either in the machine direction (MD) or in the cross direction (CD). It has been the opinion of SCA Ortviken AB and Iggesund Paperboard AB that the surface topography amplitudes are almost always higher in the CD than in the MD, for their products which consist of newspaper and paperboard. This article aims to investigate the rela-tionship between the CD and the MD surface topography amplitudes for a wide range of spatial wavelength for both newspaper and paperboard. The tests and investiga-tions have been conducted using an FRT Microprof profilometer within the range 20 μm up to 8 mm, and the results confirm that the surface topography amplitudes are higher in the CD for most of the shorter spatial wavelength within this range. The results also show significant differences between measurements for different paper qualities, suggesting a requirement to investigate the relationship between the CD and the MD topography for all paper and paperboard qualities of interest for a paper or paperboard mill, before a decision is made in relation to a measurement method.
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| 5. |
- Aldaeus, Fredrik, et al.
(författare)
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Miniaturized determination of ash content in kraft lignin samples using oxidative thermogravimetric analysis
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:2, s. 280-282
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Tidskriftsartikel (refereegranskat)abstract
- A study has been made of several aspects of determination of ash content in kraft lignin samples using thermogravimetric analysis (TGA). Three different methods were used; with the main differences between the methods being that two have a temperature hold at 250 deg C to remove volatiles and that the three methods use different maximum temperatures, namely 525, 550 and 575 deg C, respectively. The three kraft lignins used were produced using the LignoBoost lignin isolation process. It has been demonstrated that the results obtained by the different temperature programmes showed no significant difference. The results were comparable with those from using oven ignition. Moreover, the limit of quantification was several orders of magnitude lower than when using oven ignition. It has been recommended that if TGA is used for determination of ash content, a temperature programme from a standard method should be used, which should be mentioned together with the results. The temperature programme in method one (corresponding to ISO 1762) was the shortest and the preferable method. A well as requiring less labour due to fewer movements in the analytical protocol, the TGA methods enabled a high sample throughput due to autosampling possibilities.
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| 6. |
- Alfthan, Johan
(författare)
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Experimental study of non-linear stress relaxation and creep of paper materials and the relation between the two types of experiments
- 2010
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:3, s. 351-357
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Tidskriftsartikel (refereegranskat)abstract
- The non-linear time-dependent mechanical behaviour of three different commercial paper grades was investigated. Stress relaxation and creep tests were carried out in MD and CD using different load levels. The strain in each test was split in a linear part and a non-linear part. From the stress and the linear part of the strain in the test, a stress relaxation modulus or a creep compliance was calculated. The stress relaxation moduli and creep compliances determined in this way were observed to be independent of the load level. The stress relaxation moduli and creep compliances for each paper were further independent of the loading direction (MD/CD) when scaled by the elastic modulus. It was also shown that the stress relaxation modulus was approximately equal to the inverse of the creep compliance, which is what would have been expected if linear viscoelastic theory had been applicable.
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| 7. |
- Ali, Silvia, et al.
(författare)
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From wood shavings to mechanical pulp - a new raw material?
- 2005
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 20:4, s. 418-422
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Tidskriftsartikel (refereegranskat)abstract
- Wood chips used in the thermomechanical pulping (TMP) process were originally designed to suit the chemical pulping process. The production of small wood pieces more suitable for the TMP process could lead to an energy saving in this energy-intensive process. This paper discusses the potential benefits of using wood shavings instead of chips as the raw material for TMP production. In some exploratory trials, wood shavings with a thickness of about 2 mm and wood chips were refined in two steps under normal TMP process conditions in a pilot refiner. The first-stage refining was performed under pressurized conditions at 130°C. The second-stage refining was performed at atmospheric pressure at approximately 100°C at four different energy levels. The quality of the pulp produced from wood shavings was found to be better than that of the pulp produced from wood chips, with respect to both strength properties (except tear index) and optical properties at comparable energy levels. The potential for energy savings at a given tensile index using wood shavings instead of the traditional chips is estimated to be about 25%.
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| 8. |
- Alm, Hajer Kamal, et al.
(författare)
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Effect of excess dispersant on surface properties and liquid interactions on calcium carbonate containing coatings
- 2010
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 25:1, s. 82-92
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to identify what effects excess amount of sodium polyacrylate, a commonly used dispersant, has on the coating properties and the interaction between ink and the paper coating in offset printing. Since polyacrylate strongly interacts with calcium ions, soluble calcium salt was added to some coating colours to illustrate the impact of charge neutralization by calcium ions. It was found that the coating structure was only slightly affected by the extra addition of polyacrylate, showing some weak flocculation, whereas the surface chemistry was strongly influenced. The coatings became more polar and interacted more strongly with water. This resulted in slower ink setting and reduced ink-paper coating adhesion, especially in the presence of applied water/dampening solution, which are identified as contributory factors in ink piling and print mottle.
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| 9. |
- Andersson, Christian, et al.
(författare)
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Evaluation of the stress-strain properties in the thickness direction : Particularly for thin and strong papers
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 287-294
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Tidskriftsartikel (refereegranskat)abstract
- The performance of the paper in a number of converting operations such as creasing, bending, printing, and plastic coating put great demands on the mechanical properties in the thickness direction of the material. The knowledge of strength, elastic- and plastic behavior in tension and compression in the thickness direction is needed for a comprehensive description of the performance of the material in these operations. In spite of its importance, very few publications deal with the evaluation of the entire tensile stress-strain curve of paper in the thickness direction. A likely reason for this is the intrinsic difficulty of testing a thin, uneven, porous, fibrous and compressible material such as paper with sufficient precision and testing time efficiency. The z-directional strength test is usually performed by fastening the paper by means of double-adhesive tape to metal platens. The platens are fastened in a testing machine and strained to break. The adhesion of the tape is the limiting factors for how strong papers that can be tested. The tape-based method also is expected to have a lower limit in grammage due to the penetration of the adhesive. The aim of the present publication was to show a procedure how to evaluate the entire stress-elongation curve in the z-direction of papers, using a lamination method for fastening the paper to the metal platens. From this curve the z-strength, z-modulus, z-strain at break, zenergy at break and z-fracture energy could be extracted. Such information is, so far, non-existing in the literature.
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| 10. |
- Andersson, Henrik, et al.
(författare)
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Contacting paper-based supercapacitors to printed electronics on paper substrates
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 476-480
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid printed electronics, in which printed structures and silicon-based components co-exist will likely be among the first commercial solutions. In this case the paper substrate acts much in the same way as circuit boards, containing conductive tracks and acting as a carrier for the electrical components. It is important to consider the contacting of the components to be able to produce low resistance electrical contacts to the conductive tracks. Supercapacitors are able to deliver a large amount of current in a short time and are a good option for short term energy storage and if the printed product is to be used only one, or a few times, it can be the only power source needed. When manufacturing printed electronics, the overall resistance of the printed tracks as well as the contact resistance of the mounted components will add up to the total resistance of the system. A high resistance will cause a voltage drop from the power source to the component. This will waste power that goes to Joule heating and also the voltage and current available to components may be too low to drive them. If the intention is to use a power supply such as batteries or solar cells this becomes a limitation. In this article have been tested several conductive adhesives used to contact paper based supercapacitors to ink jet printed silver tracks on paper. The best adhesive gives about 0.3 Ω per contact, a factor 17 better compared to the worst which gave 5 Ω. The peak power that is possible to take out from a printed system with a flexible battery and super capacitors is about 10 times higher than compared with the same system with only the battery.
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| 11. |
- Andersson, Kerstin, et al.
(författare)
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Effects of biological treatment on the chemical structure of dissolved lignin-related substances in effluent from thermomechanical pulping
- 2008
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 23:2, s. 164-171
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Tidskriftsartikel (refereegranskat)abstract
- Effluent from a TMP-based pulp and paper mill was collected at the inlet and outlet of the mill's biological treatment plant and fractionated by sorption on XAD-8 resin and MTBE precipitation. Fractionation indicated that the refractory dissolved organic material in biologically treated effluent was mainly composed of lignin-related substances. Characterisation of the lignin-related substances by chromatographic and spectrometric methods confirmed the similarities of the isolated material and milled wood lignin. Fractionation and characterisation of alkali-extracted material from solids (biosludge) in biologically treated effluent found evidence of lignin-related material. Results indicated that biological treatment had altered the chemical structure and molar-mass distribution of dissolved lignin-related substances.
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| 12. |
- Andersson, Kerstin I., et al.
(författare)
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Effects of biological treatment on the chemical structure of dissolved lignin-related substances in effluent from thermomechanical pulping
- 2008
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 23:2, s. 164-171
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Tidskriftsartikel (refereegranskat)abstract
- Effluent from a TMP-based pulp and paper mill was collected at the inlet and outlet of the mill's biological treatment plant and fractionated by sorption on XAD-8 resin and MTBE precipitation. Fractionation indicated that the refractory dissolved organic material in biologically treated effluent was mainly composed of lignin-related substances. Characterisation of the lignin-related substances by chromatographic and spectrometric methods confirmed the similarities of the isolated material and milled wood lignin. Fractionation and characterisation of alkali-extracted material from solids (biosludge) in biologically treated effluent found evidence of lignin-related material. Results indicated that biological treatment had altered the chemical structure and molar-mass distribution of dissolved lignin-related substances.
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| 13. |
- Andersson, Stefan, et al.
(författare)
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Effect of long fibre concentration on low consistency refining of mechanical pulp
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:4, s. 702-706
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the influence of long fibre concentration on loadability and pulp properties during LC refining of mechanical pulp. Long fibre concentration was adjusted to three different levels by screen fractionation of the pulp. The three pulps were refined in a single disc pilot scale LC refiner at similar process conditions. Increased long fibre concentration supported a larger refiner gap and resulted in less fibre cutting at a given specific energy consumption. The higher long fibre concentration probably contributed to a stronger fibre network that maintained a larger refining gap at certain specific energy consumption. Increased long fibre concentration also enabled a higher tensile index increase in the LC refiner at certain fibre length reduction. The study supports a process combining LC refining with screen fractionation, where the long fibre fraction is recycled to the refiner feed. This enables a higher loadability and a more effective utilisation of the LC refiner. By using this technology, overall specific energy consumption can be reduced if a larger share of the refining is performed in LC rather than HC refining.
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| 14. |
- Andersson, Stefan, et al.
(författare)
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The effect of rotor position on pulp properties in a two-zoned low consistency refiner
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:3, s. 525-530
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have shown that plate gaps are sometimes unequal in two-zoned low consistency refiners and that unequal gaps render unevenly refined pulp. It is also known that optimisation of plate gap in low consistency refining leads to improved energy efficiency. In this work, trials were made in mill scale in a modern TMP line equipped with a prototype 72 inch TwinFlo low consistency refiner in second stage. The study was designed to investigate the development of pulp properties from different rotor positions by means of altering the outlet flow rate ratio. The specific energy consumption was calculated for each refining zone and setting, based on flow rate and temperature increase. In order to produce homogenous pulp, it was found that uneven plate gaps need to be compensated in low consistency refiners with dual refining zones. Results from the different flow rate adjustments indicated that the control setting with similar plate gap gave the most homogenous pulp. However, further studies are needed to find an adequate rotor control strategy. The temperature increase in each refining zone seems to correlate well with the applied specific energy consumption in each refining zone.
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| 15. |
- Andres, Britta, et al.
(författare)
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Supercapacitors with graphene coated paper electrodes
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 481-485
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Tidskriftsartikel (refereegranskat)abstract
- Paper based supercapacitors are prepared by stacking a paper between two graphene electrodes and soaking these in an aqueous electrolyte. We demonstrate that supercapacitors can easily be manufactured by using proven paper technologies. Several different electrode materials were compared and two types of contacting material, silver and graphite foil were tested. The influence of the paper used as separator was also investigated. The supercapacitors with a graphene-gold nanoparticle composite as electrodes showed a specific capacitance of up to 100 F/g and an energy density of 1.27 Wh/kg. The energy density can further be increased by using other electrolytes. The silver contacts showed a pseudo capacitance, which the graphite contacts did not. The papers tested had a minor effect on the capacitance, but they have an influence on the weight and the volume of the supercapacitor.
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| 16. |
- Ankerfors, Caroline, et al.
(författare)
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A comparison of polyelectrolyte complexes and multilayers : Their adsorption behaviour and use for enhancing tensile strength of paper
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:1, s. 77-86
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Tidskriftsartikel (refereegranskat)abstract
- This paper compares the adsorption behaviour and paper-strength-enhancing properties of polyelectrolyte complexes (PECs) and polyelectrolyte multilayers (PEMs) of polyallylamine hydrochloride and polyacrylic acid. Model adsorption experiments using SPAR (stagnation point adsorption reflectometry) and QCM-D (quartz crystal microbalance with dissipation) showed that the amount of complexes adsorbed was lower than the amount adsorbed when forming a multilayer using the same polymer system. From these experiments, in combination with AFM and ESEM imaging, it was concluded that the PEC adsorption stopped before full surface coverage was reached. Tensile testing of handsheets treated with PECs and PEM showed a significant increase in both tensile index and strain-at-break using both systems. The largest strength improvement was achieved with the fibres treated with the largest number of PEMs, but the largest effect per adsorbed amount of polymer was achieved by PEC treatment.
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| 17. |
- Ankerfors, Mikael, et al.
(författare)
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Multilayer assembly onto pulp fibres using oppositely charged microfibrillated celluloses, starches, and wetstrength resins : Effect on mechanical properties of CTMP-sheets
- 2016
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:1, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- The effects of multilayering of microfibrillar cellulose (MFC) onto a chemi-thermomechanical pulp (CTMP), from which the fines material had been removed, were investigated with regard to the mechanical properties of hand-sheets. In one series of experiments, the CTMP was multilayered with cationic MFC/anionic MFC (C-MFC/A-MFC) at various addition levels and sheets made in a conventional sheet former, pressed, and dried at room temperature. This experimental series was complemented with a second series, where sheets were made in a Rapid Köthen sheet former. In a third series of experiments, the CTMP was multilayered using a cationic polyamideamine epichlorohydrine resin (PAE) and an AMFC. Sheets were formed using the Rapid Köthen sheet former. Finally, in a fourth series of experiments, the MFC multilayering experiments were compared with multilayering experiments using cationic starch/anionic starch (C-starch/A-Starch). MFC-multilayering (C-MFC/A-MFC) gave inferior strength gain at a low addition level compared to starch multilayering, but (compared on a weight basis) the strength seemed to level off using starches at high addition levels, whereas there were a continuous increase in strength using MFC multilayering. Multilayering using PAE/A-MFC was found to give a higher strength gain than both C-MFC/A-MFC and C-starch/A-starch multilayering. Sheet density was slightly affected (<14%) by the multilayering techniques used in these experiments.
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| 18. |
- Ankerfors, Mikael, et al.
(författare)
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The effects of different types of wet-end added microfibrillated celluloses on the properties of paper made from bleached kraft pulp
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:3, s. 336-345
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Tidskriftsartikel (refereegranskat)abstract
- Research has been undertaken to compare the effects of different types of microfibrillated cellulose (MFC) on the mechanical properties of paper. Three types of MFC were produced: Enzyme MFC (low anionic charge density), Carboxymethylated MFC (high anionic charge density) and cationic MFC (high cationic charge density). The different MFCs required different retention aid strategies. The simplest retention strategy was selected to secure a high retention of MFC. Some experiments also focused on dewatering and pressability of wet webs with carboxymethylated MFC. Conventional isotropic laboratory handsheets were made using a never-dried unrefined elemental chlorine free (ECF)-bleached softwood kraft pulp. It has been shown that the evolution of the mechanical properties and scattering coefficients when plotted versus MFC content was very similar for the three types. However, Enzyme MFC gave a significantly better reinforcement effect. All three types of MFC had a similar effect on the sheet consolidation, reflected in sheet density. Evaluation of the dewatering and pressability of the wet sheets showed that if the MFC was aggregated by an appropriate retention strategy, the dewatering and pressability were not detrimental to the practical applicability of MFC.
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| 19. |
- Ankerfors, Mikael, et al.
(författare)
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The use of microfibrillated cellulose in fine paper manufacturing : Results from a pilot scale papermaking trial
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 29:3, s. 476-483
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Tidskriftsartikel (refereegranskat)abstract
- In this work the strength enhancing capabilities of microfibrillated cellulose (MFC) in highly filled papers was studied. Both the MFC production and the paper making were done in pilot scale under realistic industrial conditions. The results clearly show that MFC (2.5 - 5.0wt-%) could improve the mechanical properties of highly filled papers (20 - 35 wt-% filler contents). All studied dry mechanical properties were improved and the improvements were most pronounced for Z-strength and fracture toughness. By combining the MFC with a C-starch dosage further improvements in mechanical properties could be achieved. The improvements in mechanical properties enabled increased filler content with retained properties. The filler increase could be achieved at the same time as the sheet formation and the dry content after pressing were improved.
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| 20. |
- Ankerfors, Mikael, et al.
(författare)
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The use of microfibrillated cellulose in fine paper manufacturing : Results from a pilot scale papermaking trial
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 29:3, s. 476-483
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Tidskriftsartikel (refereegranskat)abstract
- In this work the strength enhancing capabilities of microfibrillated cellulose (MFC) in highly filled papers was studied. Both the MFC production and the paper making were done in pilot scale under realistic industrial conditions. The results clearly show that MFC (2.5-5.0 wt-%) could improve the mechanical properties of highly filled papers (20-35 wt-% filler contents). All studied dry mechanical properties were improved and the improvements were most pronounced for Z-strength and fracture toughness. By combining the MFC with a C-starch dosage further improvements in mechanical properties could be achieved. The improvements in mechanical properties enabled increased filler content with retained properties. The filler increase could be achieved at the same time as the sheet formation and the dry content after pressing were improved.
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| 21. |
- Ankerfors, Mikael, et al.
(författare)
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Topo-chemical modification of fibres by grafting of carboxymethyl cellulose in pilot scale
- 2013
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; :1, s. 6-14
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to graft carboxymethyl cellulose (CMC) on to bleached softwood kraft pulp at temperatures below 100°C and to do a pilot paper machine trial in order to examine the influence of the CMC on dewatering, sheet formation and mechanical properties. During the pilot trial, one CMC grafted pulp was compared to a pulp with 3 different refining degrees. It was shown that CMC-grafting improves the mechanical properties of paper with only a minor effect on the sheet density. It was also shown that the CMC grafting is less detrimental to dewatering than refining and at a certain tensile index a higher dry content after pressing could be reached. The formation number of the paper produced in the FEX trial was not significantly affected by the addition of CMC.
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| 22. |
- Antonsson, S., et al.
(författare)
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A comparative study of the impact of the cooking process on oxygen delignification
- 2003
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 18:4, s. 388-394
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Tidskriftsartikel (refereegranskat)abstract
- The impact of oxygen delignification on chemical pulps of a given kappa number manufactured in different ways (using kraft, prehydrolysis kraft and magnesium sulphite cooking) has been investigated. The prehistory of the pulps proves to be a very important factor in determining the response to oxygen delignification, i.e. the degree of delignification. It is shown that this is not due to different amounts of hexenuronic acid (HexA) in the different pulps, although this is an important factor behind the high residual kappa number after oxygen delignification of birch kraft pulp. Oxygen delignification of sulphite pulps proves to be efficient even at kappa numbers significantly lower than 10. These pulps show the greatest yield loss over the oxygen delignification. It is likely that Lignin Carbohydrate Complexes (LCC) complexes play a very important role in limiting the speed of reaction of oxygen delignification. Due to the very different prehistories of the pulps investigated, it is probable that the LCC:s are native and not formed during cooking.
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| 23. |
- Antonsson, Stefan, et al.
(författare)
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Applying a novel cooking technique to produce high kappa number pulps : the effects on physical properties
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:4, s. 415-420
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Tidskriftsartikel (refereegranskat)abstract
- A recently developed kraft cooking technique, with a longer impregnation time at lower temperatures to facilitate diffusion over consumption of active cooking chemicals, makes it possible to produce kraftliner pulp without inline refining. This technique was applied to prepare two pulps with different lignin contents, which were compared with two industrial pulps from conventional kraft cooks in order to evaluate the physical properties of the pulps. It was demonstrated that pulps with lower lignin content can increase tensile stiffness, decrease hygroexpansion, and decrease the mechano-sorptive creep of handsheets. However, no difference in SCT and tensile energy absorption values due to different lignin contents was observed. It was further demonstrated that pulps made with Extended Impregnation Cooking (EIC) results in straighter pulp fibres with higher cellulose content. These pulps tended to have lower mechano-sorptive creep than conventional pulps. A higher brightness of the pulp sheets can also be obtained by choosing a higher alkali profile.
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| 24. |
- Antonsson, Stefan, et al.
(författare)
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Comparison of the physical properties between hardwood and softwood pulps
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:4, s. 409-414
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Tidskriftsartikel (refereegranskat)abstract
- High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechano-sorptive creep properties.The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps.The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.
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| 25. |
- Antonsson, S., et al.
(författare)
-
Comparison of the physical properties of hardwood and softwood pulps
- 2009
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:4, s. 409-414
-
Tidskriftsartikel (refereegranskat)abstract
- High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechanosorptive creep properties. The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps. The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.
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| 26. |
- Antonsson, Stefan, et al.
(författare)
-
The influence of lignin and xylan on some kraftliner pulp properties
- 2009
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:4, s. 403-408
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the influence of lignin and hemicellulose content on the mechanical and physical properties of softwood kraft liner pulp. Tensile properties, hygroexpansion, and mechano-sorptive creep properties were measured. The lignin and hemicellulose contents were modified by chlorite delignification and xylanase treatment. After treatment, the chemical composition of the pulps was 3-14% Klason lignin, 69-77% cellulose, 16-21% hemicellulose, and 4-7% xylan. In the tested pulps, low lignin content tended to decrease hygroexpansion as well as increase tensile stiffness and mechano-sorptive creep stiffness. Xylan contributed less to the pulp sheet properties, but at equal lignin contents, higher xylan content tended to give increased hygroexpansion and worse mechano-sorptive creep properties.
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| 27. |
- Areskogh, Dimitri, et al.
(författare)
-
Fenton's reaction : a simple and versatile method to structurally modify commercial lignosulphonates
- 2011
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 26:1, s. 90-98
-
Tidskriftsartikel (refereegranskat)abstract
- Treatment of lignosulphonates with hydrogen peroxide and Fe (II) acetate under mild conditions can be used to increase the molecular weight and content of carboxylic acids. Such Fenton's oxidation can produce, in some of the conditions of and lignosulphonate concentration, a two-fold increase in the molecular weight and a 6-7 fold increase in the carboxylic acid content. The structural modifications of lignosulphonate may increase the technical performance of the product in several applications. Possible reaction mechanisms of the Fenton system are proposed and discussed.
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| 28. |
- Asadollahzadeh, Mohammadtaghi, et al.
(författare)
-
Using spent sulfite liquor for valuable fungal biomass production by Aspergilus oryzae
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:4, s. 630-638
-
Tidskriftsartikel (refereegranskat)abstract
- The recent and increasing interest in bioconversion of lignocellulosic wastes into value-added products has led to extensive research on various microorganisms and substrates. In this study, filamentous fungus Aspergillus oryzae was cultivated on spent sulfite liquor (SSL) from a pulp mill. The process using an airlift bioreactor (3.5 L working volume) was successfully carried out in 48 h with an airflow of 0.85 vvm (volume air per volume culture per minute) at 35°C and pH 5.5. The cultivation results showed that the fungal biomass concentration was higher in more diluted SSL. The highest and lowest fungal biomass concentrations when spore inoculation was used were 10.2 and 6.5 g/l SSL, in diluted SSL to 60 and 80%, respectively. The range of crude protein and total fat of the fungal biomass was 0.44 – 0.48 and 0.04 – 0.11 g/g biomass dry weight, respectively. All essential amino acids were present in acceptable quantities in the fungal biomass. The results obtained in this study have practical implications in that the fungus A. oryzae could be used successfully to produce fungal biomass protein using spent sulfite liquor for animal feed.
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| 29. |
- Athley, Karin, et al.
(författare)
-
Mechanical retention - Influence of filler floc size and grammage of the fibre web
- 2012
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 202-207
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation of the impact of particle size on the mechanical retention of particles in a fibre network has been conducted. The particles used were five sets of quartz particle fractions having fairly narrow particle size distributions with average particle size ranging from a few μm to around 100 μm. The particles were used to model flocculated filler aggregates as part of a larger study of the effect of pre-flocculation on mechanical retention. Pre-flocculation of the filler is a possible strategy to increase the filler content of paper without deterioration of strength properties. A modified laboratory hand sheet former, known as the Rapid Drainage Device (RDD) was used. The major modification consisted of a long pipe that acted as a suction leg, which provides a dewatering vacuum at the same level as on a paper machine. The experimental results showed that mechanical filler retention increased linearly with particle size and grammage of the fibre layer above a critical grammage which depended on particle size. The linear relation was also seen in a pilot scale trial on the FEX pilot-paper machine at Innventia. During this trial fine paper was produced using pre-flocculated filler where the mean particle size of the flocs and fibres was measured in the flow to the headbox. The results from this pilot trial show that mechanical retention is an important part of the total filler retention. Drainage time and therefore drainage resistance increased with the grammage of the fibre layer and amount of quartz particle added. Drainage time, compared at total grammage (i.e. the sum of fibre and quartz particle grammage) was lowest for a fraction of medium-sized particles, with a median size of 35 μm. There was no obvious effect on retention or drainage resistance of a change in the dewatering pressure from 27.5 to 41.5 kPa.
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| 30. |
- Athley, Karin, et al.
(författare)
-
Mechanical retention – Influence of filler floc size and grammage of the fibre web
- 2012
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 27:2
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation of the impact of particle size on the mechanical retention of particles in a fibre network has been conducted. The particles used were five sets of quartz particle fractions having fairly narrow particle size distributions with average particle size ranging from a few μm to around 100 μm. The particles were used to model flocculated filler aggregates as part of a larger study of the effect of pre-flocculation on mechanical retention. Pre-flocculation of the filler is a possible strategy to increase the filler content of paper without deterioration of strength properties. A modified laboratory hand sheet former, known as the Rapid Drainage Device (RDD) was used. The major modification consisted of a long pipe that acted as a suction leg, which provides a dewatering vacuum at the same level as on a paper machine. The experimental results showed that mechanical filler retention increased linearly with particle size and grammage of the fibre layer above a critical grammage which depended on particle size. The linear relation was also seen in a pilot scale trial on the FEX pilot-paper machine at Innventia. During this trial fine paper was produced using pre-flocculated filler where the mean particle size of the flocs and fibres was measured in the flow to the headbox. The results from this pilot trial show that mechanical retention is an important part of the total filler retention. Drainage time and therefore drainage resistance increased with the grammage of the fibre layer and amount of quartz particle added. Drainage time, compared at total grammage (i.e. the sum of fibre and quartz particle grammage) was lowest for a fraction of medium-sized particles, with a median size of 35 mm. There was no obvious effect on retention or drainage resistance of a change in the dewatering pressure from 27.5 to 41.5 kPa.
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| 31. |
- Aulin, Christian, et al.
(författare)
-
Enhanced mechanical and gas barrier performance of plasticized cellulose nanofibril films
- 2022
-
Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 37:1, s. 138-148
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils (CNF) are mixed with plasticizers; sorbitol and glycerol, through high-pressure homogenization to prepare multifunctional biohybrid films. The resulting plasticized films obtained after solvent evaporation are strong, flexible and demonstrate superior toughness and optical transparency. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials. The sorbitol-plasticized CNF films possess excellent oxygen barrier properties, 0.34 cm3·μm/m2·day·kPa at 50 % relative humidity, while significantly enhancing the toughness and fracture strength of the films. CNF films plasticized by 20 wt.% of sorbitol and glycerol could before rupture, be strained to about 9 % and 12 %, respectively. The toughness of the plasticized films increased by ca. 300 % compared to the pristine CNF film. Furthermore, the water vapor barrier properties of the biohybrid films were also preserved by the addition of sorbitol. CNF films plasticized with sorbitol was demonstrated to simultaneously enhance fracture toughness, work of fracture, softening behavior while preserving gas barrier properties. Highly favorable thermomechanical characteristics were found with CNF/sorbitol combinations and motivate further work on this material system, for instance as a thermoformable matrix in biocomposite materials. The unique combination of excellent oxygen barrier behavior, formability and optical transparency suggest the potential of these CNF-based films as an alternative in flexible packaging of oxygen sensitive devices like thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in packaging applications, including free-standing films as aluminium-replacement in liquid board and primary packaging, as replacement for polyethylene (PE) in wrapping paper, e. g. sweats and confectionary.
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| 32. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
-
Increased capacity in kraft pulp mills: Lignin separation and reduced steam demand compared with recovery boiler upgrade
- 2006
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 21:4, s. 485-492
-
Tidskriftsartikel (refereegranskat)abstract
- For increased production in pulp mills, the recoveryboiler is often a bottleneck. Two different approaches todebottleneck the recovery boiler have been investigated in twomodel mills that represent typical Scandinavian pulp mills. As areference approach, the recovery boiler was upgraded. Inconnection with this, the turbine system was also upgraded toenable increased electricity production. As an alternative to thisconventional approach, the load of the boiler was kept constantby extracting lignin from the black liquor in proportion to theproduction increase. To keep the steam balance, the specificsteam consumption at the mill was reduced through steamsavingmeasures to such an extent that the amount of steamproduced from burning the lignin-lean black liquor was sufficient.Consequently, the extracted lignin was not needed in-houseand could be sold as a biofuel. The net profit of implementinglignin separation was calculated for different conditions. Theresult was that, depending on the conditions, the lignin pricehad to be 2-17 /MWh for lignin separation to be equallyprofitable as boiler upgrade. With an assumed lignin price ofabout 15 /MWh, the conclusion is that lignin separationshould be an economically attractive alternative for debottleneckingthe recovery boiler. With a high power price and along-term investment strategy, however, upgrading the recoveryboiler and the turbine system can be more profitable.
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| 33. |
- Axelsson, Maria, et al.
(författare)
-
Estimation of the pore volume at the interface between paper web and press felt
- 2006
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 21:3, s. 395-402
-
Tidskriftsartikel (refereegranskat)abstract
- A method for determining the water content at the interface between a press felt and a paper web has been developed. The water content was obtained by subtracting the estimated volume of the indented fibre web from the measured felt surface porosity of the press felt. The felt surface porosity was calculated from a topography map that was imaged with a Confocal Laser Scanning Microscope (CLSM) method. Here, the press felt was compressed against a smooth surface using a stress in the range of 0 to 10 MPa. Artefacts in the CLSM images were reduced using an image analysis method. The indentation of paper webs into the measured felt surface pores at different applied pressures was estimated using another image analysis method, simulating a rolling ball, with different radii of curvature for the different pressures and grammages, rolling over the felt surface. The ball radii were determined for a low and a high grammage web using the STFI-Packforsk Dewatering model. The method was evaluated in a case study with four press felts that had batt fibre diameters in a range between 22 and 78 μm. The indentation was calculated for webs with a low (15 g/m2) and a high grammage (105 g/m2), respectively. The evaluation showed that a considerable amount of porespace is available at the interface between the web and the felt. In most cases, the volume of the water-filled pores accounted for approximately 50% of the total surface porosity of the felt. Assuming a complete water saturation of the web/felt interface, approximately 10 g/m2 of water for the finest felt surface up to 40 g/m2 for the coarsest felt surface, could be located at the interface between the press felt and the paper web at a load of 10 MPa. This implies that a considerable amount of water is available for separation rewetting.
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| 34. |
- Axelsson, P., et al.
(författare)
-
Influence of alkali profiling in birch kraft pulping on QPQP bleachability
- 2004
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 19:1, s. 37-43
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of different aspects of alkali profiling in the kraft cook on QPQP bleachability of oxygen-delignified birch pulp was investigated. The use of a levelled-out alkali profile was compared to a conventional, and different modifications to the levelled-out alkali profile, like alkali charge, degree of delignification and amount of dissolved organic substance and ionic strength in the cooking liquor were studied. The alkali profile itself was found to have a significant effect where a levelled-out alkali profile showed a superior bleachability compared to a conventional one. The bleachability improved with an increased alkali charge towards the end of the cook, a high kappa number after cooking or by a cooking liquor exchange in order to decrease the amount of dissolved organic substance and the ionic strength towards the end of the cook. When a levelled-out alkali profile was used, the bleachability correlated well with the light-absorption of the lignin in the unbleached pulp, where a pulp with a brighter lignin consumed less peroxide in the QPQP sequence, for the pulp to reach 89% brightness.
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| 35. |
- Axelsson, Patrik, et al.
(författare)
-
Influence of the conditions during birch kraft cooking on unbleached brightness, and on ECF- and TCF-bleachability
- 2004
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 19:3, s. 309-317
-
Tidskriftsartikel (refereegranskat)abstract
- The influences on ECF and TCF bleachability of the hydroxide ion, hydrogen sulphide ion and sodium ion concentrations as well as of the amount of dissolved wood components (DWC) in a birch kraft cook were investigated. The pulping was carried out using a so-called constant composition cooking technique, where a high liquor-to-wood ratio enables an almost constant concentration of the cooking chemicals during the entire cook. This cooking method also renders possible to vary each cooking variable separately. The pulps were oxygen-delignified and bleached in a D(EOP)DD and a Q(OP)Q(PO) sequence. The presence of DWC caused a significant rate increasing effect on the delignification. An increase in hydroxide ion concentration, an increase in hydrogen sulphide ion concentration or a decrease in sodium ion concentration improved both the ECF and the TCF bleachability, but the DWC had no significant effect on the bleachability. Further a correlation was found between the bleachability and the brightness of the oxygen-delignified pulp.
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| 36. |
- Axelsson, P., et al.
(författare)
-
The influence of alkali charge and temperature in the kraft cook on the QPQP bleachability and the kappa number composition of birch pulp
- 2002
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 17:3, s. 206-212
-
Tidskriftsartikel (refereegranskat)abstract
- The main objective of this investigation was to study how the alkali charge and the temperature in the kraft cook influence the QPQP bleachability of oxygen-delignified birch pulp. The bleachability was evaluated as the normalised consumption of bleaching chemicals required to reach a certain light absorption coefficient of the pulp. All the pulps had a kappa number of about 17 after the cook and a kappa number of about 10 after oxygen delignification. The alkali charge significantly affected the bleachability and the best bleachability was obtained for an intermediate level alkali charge ([HO-](initial)=1,35 mol/L, corresponding to an effective alkali charge of 21.6% on wood). An increase in cooking temperature gave only a slight increase in bleachability. The contributions to the kappa number of lignin, hexenuronic acids (HexA) and other non-lignin structures were also investigated. Lignin contributed to about 60% of the kappa number in pulps after the cook, to about 40% in pulps after the oxygen delignification, and to about 30% after QPQP bleaching. Hexenuronic acids contributed between 3.7 to 4.7 kappa number units in all pulps, which makes them the largest contributors to the kappa number in oxygen-delignified and QPQP bleached pulps. Other non-lignin structures, were contributing about 3 kappa number units in pulps after the cook, but decreased to less than I kappa number unit after QPQP bleaching. No great differences in the composition of the kappa number could be seen between pulps produced under different pulping conditions, except that there was a somewhat lower hexenuronic acid content in the pulps produced with the highest alkali charge or at the highest cooking temperature.
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| 37. |
- Back, EL, et al.
(författare)
-
Effect of modifiers on wax properties and on dispersibility under hot alkaline conditions
- 1995
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 10, s. 122-128
-
Tidskriftsartikel (refereegranskat)abstract
- This paper is one in a series of papers presenting a process for the removal of modified waxes from old corrugated containers by washing after alkaline hot dispersion of the recycled pulp. It presents experiments for selection of the most useful dispersants to be incorporated as wax modifiers already before the wax application. Criteria for selection were their effect on wax properties such as water and moisture resistance and their efficiency for dispersion to minimum size under hot alkaline conditions. The dispersants must also permit simple coagulation of the wax dispersion for its removal from a closed white water system. The dispersion experiments were carried out on a laboratory scale in the absence of fibers at 90°C and pH 9 to 11. Evaluated was the turbidity both at that temperature and after cooling to 20°C. For the final selection, the particle size distribution at 20°C was also measured. A few per cent of a commercial stearic acid with a minor addition of a nonionic fatty alcohol ethoxylate formula R-O-(CH2)2-O-]nH, was found to be a most suitable and economic wax additive.
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| 38. |
- Backa, Stefan, et al.
(författare)
-
Pulp bleaching with peracetic acid generated from acetylated polymeric carbohydrates and hydrogen peroxide - Proof of principle
- 2007
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 22:4, s. 409-414
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of peracetic acid in the pulp mill may open up new opportunities to use this bleaching chemical. The generation of peracetic acid from acetylated carbohydrates and hydrogen peroxide followed by bleaching of pulp in a T stage was therefore studied with special emphasis on the COD content in the bleaching effluent from this stage. This preliminary work demonstrates that peracetic acid can be generated from acetylated polymeric carbohydrates and hydrogen peroxide, and that this peracetic acid will bleach pulp fibres as effectively as distilled peracetic acid. It is also shown that most of the deacetylated polymeric carbohydrate (in this case cationic starch) adsorbs to the fibre and does not affect the COD content of the filtrate after the T stage. The peracetic acid has been generated with and without pulp present. The peracetic acid yield from polymeric activators and hydrogen peroxide was lower than that from acetylated glucose. The peracetic acid yield can be further be optimised with respect to the acetylated polymer structure, process parameters and added peracetic acid stabilisers. No effect on the tensile strength was observed when cationic starch was used as an acetyl carrier in a TCF sequence with a final (PO) stage. Most of the cationic starch was probably removed in the washing after the (PO) stage pulp. To avoid this, the (PO) stage should be exchanged for a neutral or acidic bleaching stage or the cationic starch should be exchanged to a carbohydrate that better adsorbs to the fibre under alkaline conditions.
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| 39. |
- Barbier, Christophe, 1974-, et al.
(författare)
-
Experimental investigation of damage at folding of coated papers
- 2002
-
Ingår i: Nordic Pulp & Paper Research Journal. - Sundsvall : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 17:1, s. 34-
-
Tidskriftsartikel (refereegranskat)abstract
- To achieve a better understanding of the folding properties of coated papers pertinent to the mechanical behaviour, a microscopic investigation was performed. The influence on the damage levels in the coating from such features as delamination, humidity and paper thickness have been studied
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| 40. |
- Barbier, Christophe, et al.
(författare)
-
Experimental investigation of damage at folding of coated papers
- 2002
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 17:1, s. 34-38
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation of damage occuring at folding of coated paper has been performed. For this purpose an experimental device was constructed in such a way that close resemblance with an industrial situation was achieved. During the experiments the influence on the damage levels in the coating from such features as delamination, humidity and paper thickness have been studied using an optical microscope. The behaviour of two different paper materials has been investigated. A stress (or strain) based fracture criterion is relevant for the present problem but biaxiality of stresses as well as in-plane anisotropy must be taken into account. It was observed that cracking of the coating would not lead to subsequent cracking of the paper substrate and that delamination occurred during folding, in the base stock and not at the paper/coating interface, but its quantitative influence as regards cracking could not be determined. The influence from sheet grammage was investigated and it was found that the only case when (visible) cracks did not appear was at low values. High humidity did not affect the cracking.
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| 41. |
- Barros, Gustavo Gil, et al.
(författare)
-
Prediction of UnCovered Area occurrence in flexography based on topography : A feasibility study
- 2006
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 21:2, s. 172-179
-
Tidskriftsartikel (refereegranskat)abstract
- This investigation concerns the development and prediction of uncovered areas (UCA) in flexographic full-tone prints based purely on substrate topographic information. Four different predictive models based on topography thresholding were proposed and tested using two independent quality judgement criteria.
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| 42. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
-
Modeling of tensile index using uncertain data sets
- 2020
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 35:2, s. 231-242
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this investigation is to analyze and model tensile index. Two approaches are used, one based on training and validation data, while the other novel approach tests models using all possible combinations of data points. This approach is focused on small data sets which have here been obtained from nineteen pulp samples at different refining conditions in a full-scale TMP production line with a CD-76 refiner as a primary stage. From each pulp sample twenty handsheet strips for tensile index measurements were performed. Initially, specific energy and the external variables (dilution water feed rates and plate gaps) are used as predictors in a modeling approach based on an adjusted R 2 {R^{2}} approach. Thereafter, the resulting models are compared with a combination of specific energy and internal variables (primarily consistencies) obtained from temperature measurements inside the refining zones using a soft sensor concept. It is found that specific energy and internal variables as predictors outperform the external variables when estimating tensile index.
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| 43. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
-
On the modeling of pulp properties in CTMP processes
- 2021
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 36:2, s. 234-248
-
Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.
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| 44. |
- Berg, Jan-Erik, 1957-, et al.
(författare)
-
Low-consistency refining of CTMP targeting high strength and bulk : effect of filling pattern and trial scale
- 2021
-
Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open. - 0283-2631 .- 2000-0669. ; 36:1, s. 33-41
-
Tidskriftsartikel (refereegranskat)abstract
- Chemithermomechanical pulp (CTMP) is often used in central layers of multiply paperboards due to its high bulk and strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to optimize process conditions in low-consistency (LC) refining, i. e. to select or ultimately develop new optimal LC refiner filling patterns, in order to produce fibrillar fines and improve the separation of fibres from each other while preserving the natural fibre morphology as much as possible. Furthermore, the aim is to evaluate if this type of work can be done at laboratory-scale or if it is necessary to run trials in pilot- or mill-scale in order to get relevant answers. First stage CTMP made from Norway spruce (Picea abies) was LC refined in mill-, pilot- and laboratory-scale trials and with different filling patterns. The results show that an LR1 laboratory refiner can favourably be used instead of larger refiners in order to characterize CTMP with regard to tensile index and z-strength versus bulk. A fine filling pattern resulted in CTMP with higher tensile index, z-strength and energy efficiency at maintained bulk compared to a standard filling pattern.
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| 45. |
- Berg, Jan-Erik, et al.
(författare)
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Low-consistency refining of mechanical pulp in the light of forces on fibres
- 2015
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 30:2, s. 225-229
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this investigation was to find new approaches to evaluate the performance of low-consistency refiners. Data from a paper mill producing TMP from Norway spruce was used in order to find a possible way to calculate the power split between the zones in a TwinFlo refiner. An assumption of equal amount of fibres captured between overlapping bars was found successful in order to develop equations for the power split. The equations predicted equal power in both zones at equal disc gaps. The power was found to increase approximately linearly with decreasing disc gap over the range, 0.1-0.2 mm. The power split was essential to know for calculating refining intensities expressed as specific edge load and forces on fibres in the two zones. The reduction in fibre length was about 5% at 0.17 mm disc gap or at 0.03 N forces on fibres or at 0.7 J/m specific edge load. Disc gap, forces on fibres and specific edge load was found to predict fibre shortening approximately equally upon changes in power and flow rate through the refiner.
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| 46. |
- Berg, Jan-Erik, 1957-, et al.
(författare)
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Refining gentleness - a key to bulky CTMP
- 2022
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 37:2, s. 349-355
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Tidskriftsartikel (refereegranskat)abstract
- Chemithermomechanical pulp (CTMP) is often used in middle layers of multiply paperboards due to its high bulk at specified strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to examine the effect of refining on bulk, taking into account conditions such as temperature, sulphonation, refining gap and refiner size. First stage CTMP made from Norway spruce (Picea abies) were produced in pilot and mill scale trials. Two new parameters, Equivalent temperature related to softness and Refining gentleness are introduced that take into account refining conditions as actual temperature, softening temperature, bound sulphonate content, refining gap and refiner diameter. The results show that bulk increases linearly with refining gentleness.
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| 47. |
- Bergström, Jonas, et al.
(författare)
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Application of a pitometer to measure the tangential velocity in a cylindrical through-flow hydrocyclone operated with a fiber suspension
- 2005
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 20:1, s. 30-35
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Tidskriftsartikel (refereegranskat)abstract
- This investigation evaluates a novel fluid velocity measurement method to measure the tangential velocity in a hydrocyclone. The hydrocyclone was operated with an opaque fiber suspension in order to investigate the influence of fiber presence on the tangential velocity distribution. The tangential velocity was measured with a one-hole pitometer, 0.9 mm in diameter, that was equipped with a micro pressure transducer. The pitometer was kept clean with a continuous purge flow. The probe was tested in a cylindrical through-flow hydrocyclone operated with water and 0.4 g/l and 0.8 g/l (0 %, 0.04 % and 0.08 %) addition of a bleached softwood kraft pulp. The velocity profiles measured in pure water agreed qualitatively with velocity distributions that are found in the literature. The outer section had a free vortex-like distribution and the inner section had a solid body rotation. The addition of small amounts of fibers changed the tangential velocity profile significantly. The radius of solid body rotation increased, the maximum tangential velocity decreased and the transition from solid body rotation to free vortex rotation was smoothened.
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| 48. |
- Bergström, Roger, et al.
(författare)
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A twin-wire model gap former : design and evaluation methods
- 2006
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 21:1, s. 54-58
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Tidskriftsartikel (refereegranskat)abstract
- A one-sided model twin wire gap former, the KTH-former has been developed. The former consists of headbox with transparent gables, forming unit, including a forming roll with a transparent surface and outer forming wire and a reservoir system for water/fibre suspension handling. To allow the study of blade forming, a blade can be introduced against the outer wire to generate a pressure pulse. Two measurement techniques have been utilized to study the flow mechanisms of fibre suspension flow in the forming zone; A pressure sensor has been used to study the dewatering pressure along the forming zone. A high speed video system was used to visually study the suspension flow. The study was made with pulp fibres. Fibre floes were introduced in the center of the headbox at the beginning of the linear nozzle contraction, by an introduction tube with an inner diameter of 10 mm. The acceleration in the nozzle contraction was used to separate the fibre floes in the Suspension making them move individually, thus making the visualisations easier. To avoid the problem of floc break-down at nozzle exit when using a conventional linear nozzle with parrot's beak outlet, two Curved contraction blocs were inserted, giving a more constant acceleration profile, letting the floes keep their integrity in the emerging jet. The high speed video system had two main arrangements, for the Study of floc behaviour in the forming zone. A mirror installed on the machine structure visualised a certain area of the forming zone. Alternatively, a mirror fastened to the back plate of the forming roll followed a specific area of the wire (and roll), making it possible to follow the floes through the entire forming zone. It is then possible to detect any relative motion between floes and wire.
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| 49. |
- Bialik, Marta Anna, 1978, et al.
(författare)
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Using the Pitzer method to estimate the boiling point rise in black liquor solutions
- 2009
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 24:2, s. 172-182
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Tidskriftsartikel (refereegranskat)abstract
- The b.p. rise (elevation) of aq. industrial solns. is often of significant importance for the design of process conditions, equipment, heat balances, etc. However, few rigorous methods exist for predicting b.p. elevation in complex, multicomponent, electrolyte solns. An example of such a soln. is the black liquor obtained in kraft pulp prodn.: a complex mixt. of org. and inorg. ions including Na+, K+, OH-, HS-, CO32-, SO42-, S2O32-, CH3COO-, various phenolates and many more. This work shows one application of the semi-empirical Pitzer method to the theor. prediction of the b.p. rise in industrial black liquor solns. The values of the b.p. elevation were measured in two series of black liquors from representative Swedish mills, including both the original and lignin-lean black liquor at different solid contents. The results show a good agreement between exptl. and predicted values at low to moderate solid content, and good qual. prediction at high solid content.
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| 50. |
- Bialik, Marta, et al.
(författare)
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Using the pitzer method to estimate the boiling point rise in black liquor solutions
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:2, s. 172-182
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Tidskriftsartikel (refereegranskat)abstract
- The boiling point rise (elevation) of aqueous industrial solutions is often of significant importance for the design of process conditions, equipment, heat balances, etc. However, few rigorous methods exist for predicting boiling point elevation in complex, multicomponent, electrolyte solutions. An example of such a solution is the black liquor obtained in kraft pulp production: a complex mixture of organic and inorganic ions including Na +, K + OH -, HS - C0 3 2- S0 4 2- S 20 3 2- CH 3COO - various phenolates and many more. This work shows one application of the semi-empirical Pitzer method to the theoretical prediction of the boiling point rise in industrial black liquor solutions. The values of the boiling point elevation were measured in two series of black liquors from representative Swedish mills, including both the original and lignin-lean black liquor at different solid contents. The results show a good agreement between experimental and predicted values at low to moderate solid content, and good qualitative prediction at high solid content.
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