| 1. |
- 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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| 2. |
- 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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| 3. |
- 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
-
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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| 4. |
- Asadollahzadeh, Mohammadtaghi, et al.
(författare)
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Using spent sulfite liquor for valuable fungal biomass production by Aspergilus oryzae
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:4, s. 630-638
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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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| 5. |
- Berg, Jan-Erik, et al.
(författare)
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Low-consistency refining of mechanical pulp in the light of forces on fibres
- 2015
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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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| 6. |
- Borodulina, Svetlana
(författare)
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Extracting fiber and network connectivity data using microtomography images of paper
- 2016
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Ingår i: Nordic Pulp & Paper Research Journal. - Stockholm : Arbor Publishing AB. - 0283-2631 .- 2000-0669. ; 31:3, s. 469-478
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Tidskriftsartikel (refereegranskat)abstract
- We apply image analysis methods based on micro-computed tomography (μCT) to extract the parameters that characterize the structure and bonding parameters in the fiber network of paper. The scaling and variational properties of μCT images are examined by analyzing paper structural properties of two 1 × 1 mm2 test pieces, which have been cut out from a low-grammage handsheet. We demonstrate the applicability of the methods for extracting the free fiber length, fiber cross-sectional data, the distances between the fibers, and the number of fiber-to-fiber bonds, which are the key properties required for the adequate representation of the network in numerical models. We compare the extracted connectivity data with the early reported analytical estimations and conclude that the number of contacts in three-dimensional networks is controlled by the fiber aspect ratio. In addition, we compare the cross-sectional data with those measured by the fiber morphology characterization tools and estimate the fiber shrinkage from completely wet to dry state to be nearly 20%.
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| 7. |
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| 8. |
- Brodin, Fredrik Wernersson, et al.
(författare)
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Preparation of individualised lignocellulose microfibrils based on thermomechanical pulp and their effect on paper properties
- 2015
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Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 30:3, s. 443-451
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Tidskriftsartikel (refereegranskat)abstract
- Although mechanical pulp can be considered as a potential raw material for preparation of microfibrils, suitable pre-treatment methods have been missing. Consequently, the objectives of this study were firstly to find a suitable procedure to prepare lignocellulose microfibrils (LCMF) from fractionated thermo-mechanical pulp (TMP) and secondly to evaluate if these TMP-based materials could be used as paper additives to increase paper strength. Carboxymethylation was found to be a suitable pretreatment for both TMP fines and TMP fibres to enable preparation of individualised LCMF after subsequent homogenisation treatment. After air drying, this material formed dense continuous films in conformity with films prepared from cellulose microfibrils (CMF) originating from chemical pulp. Homogenisation only or sulphonation followed by homogenisation did not fibrillate the TMP samples into individualised LCMF. Analysis of paper properties showed that addition of 20% LCMF to a standard TMP furnish improved tensile strength index by 15%. The LCMF-containing papers were also more brittle (less elongation) than the other paper sheets in this study. Similar tensile strength index was also obtained for TMP fines treated by sulphonation followed by homogenisation.
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| 9. |
- Brännvall, Elisabet, et al.
(författare)
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Consequences in a softwood kraft pulp mill of initial high alkali concentration in the impregnation stage
- 2019
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 34:1, s. 28-35
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Tidskriftsartikel (refereegranskat)abstract
- Impregnation with high initial concentration is fast and efficient, leading to a homogeneous delignification in the subsequent cook, resulting in improved screened pulp yield. To obtain high initial alkali concentration, the white liquor flow needs to be significantly increased. The moisture content of the wood chips and the alkali concentration of the white liquor limit the initial alkali concentration of the impregnation liquor that can be reached. It is therefore of interest to evaluate the possibility to implement high alkali impregnation (HAI) industrially and the consequences this would have on the mill system. The effect of HAI on mass and energy balances in a kraft pulp mill has been studied using mill model simulations. The sensitivity to disturbances in important parameters for process control has been compared to impregnation scenarios used industrially. It was shown that high initial alkali concentration can be achieved on industrial scale by increased white liquor flow. HAI has a positive effect on recovery flows and reduces the need for make-up chemicals. The HAI concept is less sensitive to variations in process parameters, such as chip moisture and white liquor concentration, thus diminishing the risk of alkali depletion in chip cores. © 2019 Brännvall and Kulander.
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| 10. |
- Chen, Chao, et al.
(författare)
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Antibacterial evaluation of CNF/PVAm multilayer modified cellulose fiber and cellulose model surface
- 2018
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Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 33:3, s. 385-396
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have shown that 3-layer-modified cellulose fibers with poly(acrylic acid) (PAA) as the middle layer between two cationic polyelectrolyte polyvinylamine (PVAm) layers have strong antibacterial efficacy in terms of both bacteria adsorption and bacterial growth inhibition. In the present work, the fossil-based PAA middle layer was replaced by sustainable wood-based cellulose nano-fibrils (CNF), i. e., the fibers were modified by a 3-layer PVAm/CNF/PVAm system. Interestingly, the antibacterial efficacy of this system was greater than that of the previous PVAm/PAA/PVAm system. A higher salt concentration and lower assembly pH in the multilayer build-up resulted in better bacterial reduction. As the surface of a cellulose fiber is heterogeneous, making it difficult to characterize and visualize at high resolution, more homogeneous cellulose model surfaces were prepared by spin coating the dissolved cellulose fiber onto a silica surface to model the fiber surface. With increasing ionic strength, more aggregated and heterogeneous structures can be observed on the PVAm/CNF/PVAm modified model surfaces. The adsorbed bacteria distributed on the structured surfaces were clearly seen under fluorescence microscopy. Adsorbed amounts of bacteria on either aggregate or flat regions were quantified by scanning electron microscopy (SEM). More adsorbed bacteria were clearly seen on aggregates than on the flat regions at the surfaces. Degrees of bacteria deformation and cell damage were also seen under SEM. The surface roughness of the modified model surfaces was examined by atomic force microscopy (AFM), and a positive correlation was found between the surface roughness and the bacterial adhesion. Thus, an additional factor that controls adhesion, in addition to the surface charge, which is probably the most dominant factor affecting the bacteria adhesion, is the surface structures, such as roughness.
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| 11. |
- de Souza, Gustavo B., et al.
(författare)
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Enhancement of eucalypt pulp yield through extended impregnation cooking
- 2018
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 33:2, s. 175-185
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Tidskriftsartikel (refereegranskat)abstract
- The improvement caused by eucalypt chip impregnation on kraft pulping performance was assessed for terminating the cook at kappa in the range of 15-27 and at controlled residual effective alkali (REA) of 6-8 g/L NaOH. Extended impregnation cooking of eucalypt chips (EIC) increased about 10/0 lignin- and HexA-free screen yield gains in relation to conventional cooking (CC), regardless of kappa number in the range of 15-27. The EIC technology allows for cooking eucalypt wood to kappa number up to 27, without rejects production, but without significant improvement in lignin- and HexA-free screen yield and with larger chlorine dioxide (ClO2) consume during bleaching. The optimum kappa number for both CC and EIC cooking was about 19 with similar refinability and strength properties for both technologies, CC and EIC. It was concluded that extended impregnation cooking is an attractive technique for enhancing bleached eucalypt Kraft pulp yield.
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| 12. |
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| 13. |
- Deshpande, Raghu, 1979-, et al.
(författare)
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Some process aspects on single-stage bisulfite pulping of pine
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 31:3, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Sulfite pulping of pine is well-known to be a risky process because problematic lignin conden-sation reactions can occur resulting in poor pulp quality. However, sulfite pulping of pine is interesting of economic reasons as pine wood is cheaper than spruce. Therefore it has become interesting to investigate sulfite pulping again to determine if old data are still valid. Thus sodium bisulfite pulping of pine was carried out to investigate the influence of time, temperature and cooking acid quality. A small comparison of spruce pulping was also included. By using different cooking temperatures the activation energies for delignification and for degradation of cellulose and hemicelluloses could be determined. The results showed no lignin condensation reactions, thus it was not problematic to carry out these pine cooking experiments. It was found that glucomannan had higher activation energy than xylan and the activation energies of these hemicelluloses were lower than the corresponding value for the lignin degradation. It was found that the activation energy for bisulfite pulping of pine was slightly lower than the activation energy for bisulfite pulping of spruce.
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| 14. |
- Deshpande, Roghe, et al.
(författare)
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Some process aspects on single-stage bisulfite pulping of pine
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 31:3, s. 379-385
-
Tidskriftsartikel (refereegranskat)abstract
- Sulfite pulping of pine is well-known to be a risky process because problematic lignin conden-sation reactions can occur resulting in poor pulp quality. However, sulfite pulping of pine is interesting of economic reasons as pine wood is cheaper than spruce. Therefore it has become interesting to investigate sulfite pulping again to determine if old data are still valid. Thus sodium bisulfite pulping of pine was carried out to investigate the influence of time, temperature and cooking acid quality. A small comparison of spruce pulping was also included. By using different cooking temperatures the activation energies for delignification and for degradation of cellulose and hemicelluloses could be determined. The results showed no lignin condensation reactions, thus it was not problematic to carry out these pine cooking experiments. It was found that glucomannan had higher activation energy than xylan and the activation energies of these hemicelluloses were lower than the corresponding value for the lignin degradation. It was found that the activation energy for bisulfite pulping of pine was slightly lower than the activation energy for bisulfite pulping of spruce.
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| 15. |
- Deshpande, Raghu, 1979-, et al.
(författare)
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The Initial Phase of Sodium Bisulfite Pulping of Pine, Part II
- 2016
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Ingår i: Nordic Pulp & Paper Research Journal. - Härnösand : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 31:3, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Single stage sodium bisulfite cooking of pine was carried out to investigate the influence of time and temperature in the initial phase of the cook. The cooking experiments were carried out using either a lab or a mill prepared cooking acid and the initial stage of the cook was extended up to 5 h cooking time. The impact of temperature on wood components and side reactions was analyzed between 142°C and 165°C. Arrhenius equation was used to determine the influence of temperature on wood components during the initial phase of bisulfite cooking and the activation energy was calculated for delignification rate, cellulose degradation and hemicellulose dissolution with regard to glucomannan and xylan. The extent of extractives removal at different temperature and time was also analyzed.
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| 16. |
- Durruty, Julie, 1988, et al.
(författare)
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Filtration properties of kraft lignin : The influence of xylan and precipitation conditions
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 32:4, s. 508-526
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Tidskriftsartikel (refereegranskat)abstract
- LignoBoost lignin powder was dissolved together with xylan and re-precipitated. The influence of the (i) precipitation temperature, (ii) rate of acidification and (iii) final pH of the slurries on the resulting material and its filtration properties was investigated. In the case of slow acidification, larger agglomerates were obtained for slurries with higher precipitation temperatures as well as with higher ionic strengths. Fast acidification led to a more heterogeneous formation of particles, having a broader particle size distribution, compared to slow acidification. Chemical analysis of different layers of the filter cakes formed revealed that xylan was distributed evenly on the solid lignin, reinforcing the hypothesis that xylan is sorbed onto the lignin agglomerates when precipitated together with lignin. Furthermore, the resulting lignin-xylan mixtures were found to be more difficult to filter in the case of a higher final pH of the slurry (pH 4), close to the pKa values of the carboxylic acid groups of xylan, compared to lower pH values (pH 1-3). This is likely the result of an increase in electrostatic repulsive interactions between the particles/agglomerates at higher pH: a locally more porous solid structure is formed, leading to a larger solid/liquid surface area during filtration.
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| 17. |
- Durruty, Julie, 1988, et al.
(författare)
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Local and average filtration properties of kraft softwood lignin
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 30:1, s. 132-140
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Tidskriftsartikel (refereegranskat)abstract
- The extraction of lignin from black liquor is of interest in order to increase the overall material yield when producing paper pulp by the kraft process. The extracted lignin can be used either as a solid biofuel or a potential alternative raw material to fossil oil for the production of various green chemicals and high valuable products such as carbon fibres. The LignoBoost process is a new approach in which the kraft lignin extracted reaches a high level of purity. In this study, the local and average dead-end filtration properties during dewatering of a softwood lignin extracted from black liquor using the LignoBoost process were investigated; the material was also characterized. It was found that the investigated lignin was an easy to filter material that formed weakly compressible filter cakes in the solid compressive pressure range of 0.03 to 1.5 MPa. The concentration of the lignin slurry did not influence the filtration properties; the resulting cakes final heights were in the industrial size range. Moreover, the two different filter media used yielded similar results. Semi-empirical relationships were fitted successfully to the experimental local data and a good estimation of the average filtration properties was also obtained using the relationships fitted parameters. This indicates a good agreement between the local and average experimental data.
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| 18. |
- Ekbåge, Daniel, et al.
(författare)
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Potential energy improvements in a multiple-effect evaporation system : Case studies of heat recovery
- 2016
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Ingår i: Nordic Pulp & Paper Research Journal. - : Mittuniversitetet. - 0283-2631 .- 2000-0669. ; 31:4, s. 583-591
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Tidskriftsartikel (refereegranskat)abstract
- The primary objective of this study was to quantify the amount of excess energy that is present in the evaporation system of an integrated pulp and paper-board mill and to analyze a number of energy recovery cases. These focus on improving the energy efficiency in the evaporation plant and are mainly based on the process data of performance tests from the full-scale production site. A computer script was developed in order to analyze the process streams and can be used to construct the Grand Composite Curve (GCC) of the evaporation system. In addition, the study identified seasonal variations in the potential excess of energy (higher in warmer weather and lower, or even non-existent, in colder) and suggestions are made as to how this energy may be used in a thermodynamically optimal way. In the case studies, the thermodynamically optimal method of recovering heat involved a combination of sensible heat and flash evaporation, indicating the maximum reduction in steam consumption. For the case of only utilizing sensible heat outside the evaporator system to pre-heat one of the liquor flows, the results indicated a lower reduction in steam but also a lower capital cost.
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| 19. |
- Ferritsius, Olof, et al.
(författare)
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Average fibre length as a measure of the amount of long fibres in mechanical pulps - ranking of pulps may shift
- 2018
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:3, s. 468-481
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the applicability of different ways of calculating the average fibre length based on length measurements of individual particles of mechanical pulps. We have found that the commonly used average length-weighted fibre length, which is based on the assumption that coarseness is constant for all particles, as well as the arithmetic average, may lead to erroneous conclusions in real life as well as in simulations when used as a measure of the amount of long fibres. The average length-length-weighted fibre length or a weighting close to that, which to a larger extent suppresses the influence of shorter particles, is a relevant parameter of the "length" factor, i. e. amount of long fibres. Our findings are based on three studies: refining of different assortments of wood raw material in a mill; data from LC refining in mill of TMP, including Bauer McNett fractionation; mixing of pulps with different fibre length distributions. If the acceptable average fibre length for different products can be lowered, the possibility of reducing the specific energy input in refining will increase. Therefore, we need a reliable and appropriate way to assess the "length" factor.
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| 20. |
- Ferritsius, Olof, et al.
(författare)
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Process considerations and its demands on TMP property measurements - A study on tensile index
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- As a vital component in the strive towards improved energy efficiency in the operation of TMP refining processes, this work highlights the importance of well- designed procedures when collecting and analysing pulp properties with respect to process conditions. Process data and pulp from a CD82 chip refiner have been used to show that tensile index has strong covariance with fibre residence time calculated by the extended entropy model. A combination of theoretical and practical analysis methods has shown that, in order to assure representative, reliable results, pulp sampling procedures should comprise composite pulp samples collected during a sampling period of about three minutes. In addition, at least four subsequently collected composite pulp samples should be included in the analysis to effectively dampen effects from fast process variations as well as from slow process drift. An in-depth study on tensile index measurements clarifies that 40-60 strips should be used in the case we studied regardless if machine made paper or handsheets are considered.
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| 21. |
- Ferritsius, Rita, et al.
(författare)
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TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II: Comparison of the five tests
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 82-94
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Tidskriftsartikel (refereegranskat)abstract
- This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.
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| 22. |
- Ferritsius, Rita, et al.
(författare)
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TMP properties and refining conditions in a CD82 chip refiner. Part I: Step changes of process variables, description of the tests
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- The study explores how changes in process variables, residence time and pulp consistency in refining influence the pulp properties. The equipment utilized in this study was a conical disc chip refiner (RGP82CD) producing thermomechanical pulp (TMP). The focus was on the ratio between tensile index and specific energy consumption. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. This showed that the CD-refiner, with the flat and conical refining zone, has a process performance similar to that of a two-stage refiner set-up, and that the consistency in both refining zones is of high importance. Comparing different periods revealed that even if the values of measured blow line consistency are similar, significant differences in the estimated consistency in the flat zone can prevail. Therefore, only monitoring blow line consistency is not enough. Specifically, it was found that the pulp consistency after the flat zone could be very high, considerably higher than in the blow line, and this could have negative effects on tensile index and fibre length.
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| 23. |
- Germgård, Ulf, 1950-
(författare)
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The Arrhenius Equation is Still a Useful Tool in Chemical Engineering
- 2017
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter. - 0283-2631 .- 2000-0669. ; 32:1, s. 21-24
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Tidskriftsartikel (refereegranskat)abstract
- The Arrhenius equation correlates the rate of a chemical reaction with the corresponding activation energy, reaction time and reaction temperature, where the latter is measured in Kelvin. Although the equation is rather simple it can be used to summarize the kinetics of most chemical reactions in a surprisingly good manner. The activation energy is an interesting parameter that can be seen as an energy barrier which the reacting chemicals have to pass before a chemical reaction is initiated. Thus, the higher the activation energy, the lower is the rate of the chemical reaction. Moreover, the equation can also be used, for example, to forecast the influence of a higher temperature on the composition of a product consisting of components with different activation energies. In such a case, a component with higher activation energy will increase its rate of reaction more than a component with lower activation energy. The composition of the original product will thus obtain a shrinking fraction of the fast reacting component. The report gives some guidelines of how to calculate the activation energy for a given case in a pulp mill.
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| 24. |
- Giummarella, Nicola, et al.
(författare)
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On the effect of hemicellulose removal on cellulose-lignin interactions
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 32:4, s. 542-549
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Tidskriftsartikel (refereegranskat)abstract
- In a recent study, it was suggested that there could be direct associations between cellulose and lignin in mild alkaline cooked pulps. The observation was based on studies showing that the molecular straining of lignin was similar to that of cellulose. This finding has serious ramifications for technical production of pulps as it could expand on what is known about recalcitrant lignin removal during pulping. Herein, we investigate the possible interaction between cellulose and lignin discussing possible mechanisms involved at the nano- and molecular-scales, and present support for that the removal of hemicellulose by hot water extraction or mild kraft pulping causes strong interactions between lignin and cellulose.
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| 25. |
- Giummarella, Nicola, et al.
(författare)
-
On the effect of hemicellulose removal on celluloselignin interactions
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 32:4, s. 542-549
-
Tidskriftsartikel (refereegranskat)abstract
- In a recent study, it was suggested that there could be direct associations between cellulose and lignin in mild alkaline cooked pulps. The observation was based on studies showing that the molecular straining of lignin was similar to that of cellulose. This finding has serious ramifications for technical production of pulps as it could expand on what is known about recalcitrant lignin removal during pulping. Herein, we investigate the possible interaction between cellulose and lignin discussing possible mechanisms involved at the nano- and molecularscales, and present support for that the removal of hemicellulose by hot water extraction or mild kraft pulping causes strong interactions between lignin and cellulose.
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| 26. |
- Hagman, Anton, et al.
(författare)
-
Short compression testing of multi-ply paperboard, influence from shear strength
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB Svensk Papperstidning. - 0283-2631 .- 2000-0669. ; 31:1, s. 123-134
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of the through-thickness shear strength profiles on the short span compression test was examined. This was done both with experiments and finite element simulations on five industrial produced paperboards. It was concluded that the short span compression test is governed by in-plane stiffness and through thickness delamination The delamination damage was in turn dependent on the local transverse shear strength and in-plane stiffness gradients. Furthermore, it was concluded that the pre-delamination mechanisms were elastic. Finally it was possible to alter the results from the test by altering the shear strength of the paperboard; this should be done uniformly over the entire middle ply of the board if an increased SCT value was what was sought after.
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| 27. |
- Hedlund, Artur, et al.
(författare)
-
Coagulation of EmimAc-cellulose solutions : Dissolution-precipitation disparity and effects of non-solvents and cosolvent
- 2015
-
Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 30:1, s. 32-42
-
Tidskriftsartikel (refereegranskat)abstract
- Coagulation values (CVs) of cellulose/1-ethyl-3-methylimidazolium acetate (EmimAc)/dimethyl-sulfoxide (DMSO) solutions for water, ethanol (EtOH) and 2-propanol (2-PrOH) were measured by using a light-scattering technique. Expressed in moles per mole, CVs of H2O were roughly twice as high as the CVs of EtOH and 2-PrOH at equal cellulose concentration for EmimAc solutions without the addition of a cosolvent. We explain this observation mainly in terms of alcohol alkyl chains efficiently obstructing EmimAc anions, preventing anions from simultaneously interacting with cellulose hydroxyls. DMSO was found to mitigate the coagulating effect of water and, to a lesser extent, the effect of alcohols. The explanation may be the different enthalpies of mixing for water and alcohols, with DMSO. An explanation on a more practical level, is based on how the solvatochromic α and β parameters change due to small amounts of the different non-solvents. Small additions of methanol induce disproportionately large changes from basic towards acidic properties for DMSO, meanwhile, the same stoichiometric addition of water induces only minor changes. Precipitation occurred at concentrations of non-solvent much higher than the concentrations that limit dissolution. The most likely explanation for this is a metastable region in the phase diagram. It was also seen that the typically observed inhibitive effect of high Mw on solubility during dissolution did not apply to precipitation.
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| 28. |
- Hedlund, Artur, 1984, et al.
(författare)
-
Coagulation of EmimAc-cellulose solutions: dissolution-precipitation disparity and effects of non-solvents and cosolvent
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 30:1, s. 32-42
-
Tidskriftsartikel (refereegranskat)abstract
- Coagulation values (CVs) of cellulose/1-ethyl-3-methylimidazolium acetate (EmimAc)/dimethyl-sulfoxide (DMSO) solutions for water, ethanol (EtOH) and 2-propanol (2-PrOH) were measured by using a light-scattering technique. Expressed in moles per mole, CVs of H2O were roughly twice as high as the CVs of EtOH and 2-PrOH at equal cellulose concentration for EmimAc solutions without the addition of a cosolvent. We explain this observation mainly in terms of alcohol alkyl chains efficiently obstructing EmimAc anions, preventing anions from simultaneously interacting with cellulose hydroxyls. DMSO was found to mitigate the coagulating effect of water and, to a lesser extent, the effect of alcohols. The explanation may be the different enthalpies of mixing for water and alcohols, with DMSO. An explanation on a more practical level, is based on how the solvatochromic a and beta parameters change due to small amounts of the different non-solvents. Small additions of methanol induce disproportionately large changes from basic towards acidic properties for DMSO, meanwhile, the same stoichiometric addition of water induces only minor changes. Precipitation occurred at concentrations of non-solvent much higher than the concentrations that limit dissolution. The most likely explanation for this is a metastable region in the phase diagram. It was also seen that the typically observed inhibitive effect of high M-w on solubility during dissolution did not apply to precipitation.
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| 29. |
- Heldin, Magnus, et al.
(författare)
-
Initiation of wood defibration in groundwood pulping, single asperity indentation and scratching
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 31:3, s. 401-406
-
Tidskriftsartikel (refereegranskat)abstract
- To understand how the energy requirements of the mechanical pulping process can be reduced, the fundamental mechanisms behind fiber separation in Norway spruce were studied experimentally and analytically. Single tip scratching in heated water was used to reproduce initial defibration mechanisms found industrially. The resulting scratches were then compared with surfaces ground in a real industrial process. Moreover, the mechanical behavior of the wood microstructure was monitored with X-ray computed microtomography as a single hard tip was pressed into it. Subsequent digital image correlation was applied to estimate the strain field in the region around the indenting tip. Regions in the wood with high tensile or shear strains were identified, i.e. where cracking and fiber separation is believed to initiate.
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| 30. |
- Henriksson, Gunnar
(författare)
-
What are the biological functions of lignin and its complexation with carbohydrates?
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:4, s. 527-541
-
Tidskriftsartikel (refereegranskat)abstract
- This critical review discusses how lignin can fulfill its biological functions with a focus on the potential importance of covalent bonds between lignin and polysaccharides. Biological function and definition of lignin are discussed. There are several direct and indirect indications that covalent bonds between lignin and polysaccharides are common in wood, and there are mechanistic explanations for the formation of these bonds, with the exception of phenyl glycosides. Grasses might have a unique pathway for formation of links between lignin and hemicellulose. The monolignol structures might be evolutionary "designed" for forming covalent bond to polysaccharides during polymerization, and hemicelluloses might have the ability to some extent control the lignin structure and frequency of covalent bonds between lignin and polysaccharides. These bonds represent both technical problems and possibilities.
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| 31. |
- Hill, Jan, et al.
(författare)
-
ATMP pulping of Norway spruce : Pulp property development and energy efficiency
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:1, s. 70-86
-
Tidskriftsartikel (refereegranskat)abstract
- ATMP pilot refining trials on Norway spruce were conducted. The ATMP configuration consists of selective wood disintegration and targeted application of chemicals when defibration already is initiated in order to achieve energy-efficient final fibre separation and development. ATMP was compared to TMP and RTS. The TMP like character was maintained despite of differences in pre-treatment, chemicals and primary stage refining energies. The fractional composition of the pulps was, however, altered. Bauer McNett R14 fraction exhibited the largest differences followed by P200 fraction. Thus different process alternatives produced pulps with different fingerprints. The amount of the R14 fibres is important as these tend to cause surface roughness impairing printability. Regardless of strategy, the ATMP pulp properties at equal tensile index (44 Nm/g) were equal or superior to those achieved by TMP or RTS refining. The main difference was the required specific energy input, ranging from 1.71 (TMP) to 1.05 MWh/BDT (ATMP with bisulphite addition). Primary stage refining was explored from multiple trials with the same process configuration and chemistry. The higher the specific energy applied the better is the energy efficiency. Furthermore established refining theories appear inadequate in describing the differences between process alternatives with respect to energy efficiency and pulp property development.
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| 32. |
- Hyll, Kari, et al.
(författare)
-
Comparison of optical instruments for fines and filler characterisation
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 32:1, s. 97-109
-
Tidskriftsartikel (refereegranskat)abstract
- A laser diffractometer and three image-based instruments with spatial resolutions between 0.33 and 10 mu m/pixel were compared through measurements on calibration spheres and fine fractions comprising pulp fines of various types, neat PCC filler, and a mixture of fines and fillers. The laser diffractometer was highly sensitive to the keyed in refractive index of the samples, which was calculated based on volume-based mixing rules. A high-resolution flow cytometer and a high-resolution fibre analyser were found to be complimentary for measurements on neat fines and fines/filler mixtures, and superior to the laser diffractometer. When measuring on fillers, the laser diffractometer performed as well as the high-resolution flow cytometer, which was capable of resolving single filler particles. The sizes of the calibration spheres were overestimated by the image-based instruments, and the measurement uncertainty was high. The uncertainty was mainly attributed to the unrestricted particle motion, and the low accuracy to the dissimilar optical properties of the calibration material, compared to fines. Thus, calibration materials with shape and optical properties more similar to fines should be developed.
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| 33. |
- Hyll, Kari, et al.
(författare)
-
Flow imaging characterisation of morphological changes of chemical pulp due to refining
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 31:3, s. 411-421
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of the refining process on the morphological changes of a chemical softwood pulp was investigated. The Voith LR40 industrial-like laboratory low consistency refiner was used, where the pulp was refined with five refining segments with differences in bar widths, groove widths, and cutting angles. The refined pulp was characterized with a fibre analyser with a spatial resolution of approximately 4 μm/pixel and a wide size range. The fines fraction of the refined pulp was also characterized with an imaging flow cytometer with a spatial resolution of 0.33 μm/pixel and a narrower size range. The fibre analyser measurements showed that the mean length, width, and aspect ratio of the fines decreased monotonically with accumulated refining energy. The imaging flow cytometer with its higher spatial resolution showed little change in fines morphology with accumulated refining energy. The morphology of the fines was more dependent on the applied specific refining energy than the design of the refining segment. However, a segment with much finer grooves and bars, initially designed for hardwood, gave significantly less fibre shortening, fines generation, external fibrillation, kink, and fines that were more fibrillar, compared to the other segments.Grant: The authors of this work would like to thank Prof. Lars Mattsson, Thomas Grahn, and Eva Ålander for fruitful discussions. The discussions with Lorentzen & Wettre were of great assistance. The financial support of the Swedish Energy Agency and the Önnesjöstiftelsen to the PhD project, and of the Fibre and Stock Design research programme to this evaluation study is gratefully acknowledged.
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| 34. |
- Hyll, Kari
(författare)
-
Size and shape characterization of fines and fillers : A review
- 2015
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 30:3, s. 466-487
-
Tidskriftsartikel (refereegranskat)abstract
- Many properties of fines and fillers are dependent on their size and shape. This review is on the literature on size and shape characterization of fines and fillers. It takes into account measurement techniques of particle width, length, equivalent diameter, area, and shape/morphology. The advantages and limitations of different methods are discussed. Measurement of other particles properties, e.g., optical, chemical or rheological, were not included in the review. Size and shape characterization methods can be roughly divided into gravimetric and non-gravimetric methods. Gravimetric measurements methods account for all particles in the sample, but give only indicative size and shape information. Non-gravimetric methods usually give more direct size and shape information, but only account for particles larger than the resolution of the instrument. Additionally, measuring both larger and smaller particles simultaneously is rarely possible. An implication is that current analysers fail to measure a larger share of the sample, for example fibrils, which have a high impact on product properties. Of the reviewed measurement techniques, flow microscopy had the highest potential. Based on instruments found in other application areas, possible developments for flow microscopes include multiwavelength illumination and sensors, fluorescent staining, and hydrodynamic focusing.
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| 35. |
- Håkansson, Mikael, et al.
(författare)
-
Multivariate prediction of key kraft paper properties from designed experiments in a pilot plant
- 2015
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 30:2, s. 258-264
-
Tidskriftsartikel (refereegranskat)abstract
- A two-level factorial design was set up where five factors in a kraft paper process were varied, from wood chip origin to paper machine roll pressure. Nine paper properties were selected for a more in-depth analysis. This paper shows how these 9 responses can be modeled as a function of the experimental factors. The model, a full interaction model, was estimated using Partial Least-Squares Regression. The resulting model shows that there is a strong correlation between the experimental factors and the measured paper properties. The paper also presents a careful analysis of how the uncertainties of the measured values propagate through the model and contribute to the final model uncertainty. Finally, the interpretations and application of the resulting model is discussed. Specifically, having access to a good model enables the plant operators to simulate the effect of changing the process variables, either for training purposes or to test new production scenarios
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| 36. |
- Hämäläinen, Pyry, et al.
(författare)
-
Development and evaluation of a high-speed creping simulator for tissue
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 31:3, s. 448-458
-
Tidskriftsartikel (refereegranskat)abstract
- An innovative creping simulator for tissue has been developed to meet the requirements set by both industrial needs, such as speed and process step duration, and research ambitions, such as flexibility for modifications and efficient operation. Some of these factors can be difficult to achieve with the previously introduced simulators. Lower speeds and much longer process step times can jeopardize results when, for instance, the drying time of chemicals is longer and the speed of creping is slower than in a tissue mill. The newly developed simulator has been used to investigate the effects of paper grammage, creping angle, temperature of dryer, speed and the horizontal force experienced during tissue creping. Results show good agreement with results of industrial-scale tissue production, with the exception of shrinkage which was greater. It was observed that the grammage influences the final thickness and the shrinkage of creped sheets, and that creping speed affects the creping frequency, thickness and shrinkage. The temperature of the surface of a sled mimicking the Yankee cylinder was shown to influence creping frequency and thickness. The horizontal friction force during creping appears to increase if drying temperature is lowered.
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| 37. |
- Höhn, Patrick
(författare)
-
Dynamic model and simulation for a high consistency refining process
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:1, s. 88-101
-
Tidskriftsartikel (refereegranskat)abstract
- A novel dynamic model for the behavior inside of the gap of a high consistency refiner in the pulp and paper industry is presented. As the original entropy model gives additional information about the work split between thermodynamic effects and fiber changes inside the refining zone, it is used as a base for a dynamic model to describe the efficiency of the refining process. This model is derived for the mass flow rates of steam and water, changes of the work distribution and consistency as a function of radius and time. The temperature distribution inside the refining zone, specific energy, inlet consistency and total mass flow rate are used as input signals. After a general presentation in continuous-time, the spatial discrete model is also discretized in temporal dimension. Both discretizations are dependent on each other as the ratio can be considered as a flow speed of the fluid elements and it affects the residence time inside the refining zone. Thereafter, results from a simulation with assumed input parameters using the discrete model are presented and compared with the output of previously published models. Other dynamic models exhibit similar oscillations when applying changes to the inputs. Furthermore, the overall general trend is consistent with other published steady-state models. Hence, we expect the newly proposed model to be reliable and more efficient to describe the behavior inside the refining zone.
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| 38. |
- Iselau, Frida, 1979, et al.
(författare)
-
Parameters influencing hydrophobization of paper by surface sizing
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 95-104
-
Tidskriftsartikel (refereegranskat)abstract
- Paper surface hydrophobization, also referred to as "surface sizing", is often necessary for printing and packaging purposes. Typically, hydrophobic polymeric nanoparticles, in combination with starch are applied on the paper surface at the dry-end of the paper machine. In the surface sizing process, the nature of the nanoparticles, starch type, starch concentration and ratio between starch and nanoparticles, paper quality, ionic strength, and application as well as drying temperature are parameters that influence the result. The aim of this work was to systematically evaluate these parameters in order to create knowledge to be used for optimization of the process. Laboratory scale surface sizing trials were performed and the results from the trials showed that cationic particles gave superior performance compared to anionic particles. Both the starch type and the concentration of the oxidized starch had an impact on the performance. The effect of the ionic strength was found to depend on the particle charge: for cationic particles, the addition of salt was detrimental while for the anionic particles it was beneficial. An increase of the application or the drying temperature was found to enhance the performance up to a temperature around the glass transition temperature of the polymer.
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| 39. |
- Javed, Asif, 1982-, et al.
(författare)
-
Crack analysis of barrier coatings based on starch and starch-PVOH with and without plasticizer
- 2018
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:2, s. 336-347
-
Tidskriftsartikel (refereegranskat)abstract
- Barrier coatings based on starch and starch-PVOH plasticized with glycerol and without plasticizer were applied to two different paperboard substrates, a triple coated board and duplex board, in order to investigate the tendency for cracks to develop in the barrier coating layers during creasing and folding. Tensile properties of films based on the starch and starch-PVOH blend were determined to investigate the relationship between the flexibility of the films and the cracking in the barrier coating layers. Furthermore, the oxygen transmission rate through the barrier-coated paperboard was measured before and after creasing and folding. The oxygen transmission rate through the barrier-coated samples was over the measurable range i. e. OTR > 10000 cm 3 / m 2 day\text{OTR}>10000\hspace{0.1667em}{\text{cm}}^{3}/{\text{m}}^{2}\hspace{0.1667em}\text{day} after creasing and folding, which indicated failure in the barrier coating layers. Optical microscopy revealed small cracks in the barrier coating layers, probably related to an increase in flexibility of the barrier coating layers. It was observed in scanning electron micrographs that cracks in the barrier coating layers seemed to follow the fibers when the barrier coating was applied on the rear side of the duplex board. Scanning electron micrographs and surface profiler images revealed that cracks in the barrier coating layers might have originated from the mineral coating layer when the starch and starch/PVOH coating layers were applied on the mineral-coated side of the triple coated board. An increase in the thickness of the barrier coating layer did not seem to increase the resistance to failure.
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| 40. |
- Javed, Asif, 1982-, et al.
(författare)
-
Lignin-containing coatings for packaging materials
- 2018
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 33:3, s. 548-556
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties and chemical stability in water of self-supporting films made from aqueous solutions of starch and lignin, and the barrier properties of paperboard coated with solutions of these polymers have been studied. The dissolution of starch from the starch-lignin films in contact with the model liquids was decreased significantly when lignin was added to the starch films. The addition of ammonium zirconium carbonate (AZC) to the formulations as a crosslinking agent substantially increased the storage modulus of the starch-lignin films, which indicated that crosslinking had occurred. The addition of AZC to the formulations also led to a decrease in dissolution of both starch and lignin from the starch-lignin films in contact with model liquids. The effect of AZC on the water stability of the films was greater when the pH of the starch-lignin-AZC solution was adjusted with ammonia rather than NaOH. The addition of NH4Cl solution as a presumed catalyst to the recipe when the pH adjustment was performed with NaOH did not improve the effect of AZC on the water stability of the films. The water vapour transmission rate of the coated paperboard decreased slightly when AZC was added to the coating formulation.
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| 41. |
- Javed, Asif, 1982-, et al.
(författare)
-
Study of starch and starch-PVOH blends and effects of plasticizers on mechanical and barrier properties of coated paperboard
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Swedish Association of Pulp and Paper Engineers. - 0283-2631 .- 2000-0669. ; 31:3, s. 499-510
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties of self-supporting films based on starch-plasticizer and starch-PVOH-plasticizer and the barrier properties of paperboard coated with solutions of these polymers have been studied. The plasticizers used were glycerol, polyethylene glycol and citric acid. It was shown that the addition of a plasticizer and PVOH to starch substantially increases the flexibility of starch films. It was seen that curing the self-supporting films led to a decrease in flexibility. After heat-treatment, a substantial increase in storage modulus was observed only in the starch-PVOH-citric-acid blend films. Tensile tests on the films indicate that citric acid did not cause any noticeable phase separation. Citric acid acted as a compatibilizer for starch-PVOH blends even though a similar enrichment of PVOH at the air-solid interface was observed with both citric acid and polyethylene glycol as plasticizer. The properties of barrier coatings greatly reflected the compatibility of starch-PVOH blends containing citric acid. The only plasticizer that resulted in a lower water vapour transmission rate through the starch and starch-PVOH coatings was citric acid, which suggests that cross-linking took place. With four layers, coatings based of starch-PVOH possessed the same oxygen- transmission rate with citric acid as without citric acid.
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| 42. |
- Johnson, Tomas, 1979, et al.
(författare)
-
A Multi-Scale Simulation Method for the Prediction of Edge Wicking in Multi-Ply Paperboard
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 30:4, s. 640-650
-
Tidskriftsartikel (refereegranskat)abstract
- When liquid packaging board is made aseptic in the filling machine the unsealed edges of the board are exposed to a mixture of water and hydrogen peroxide. A high level of liquid penetration may lead to aesthetic as well as functional defects. To be able to make a priori predictions of the edge wicking properties of a certain paperboard material is therefore of great interest to the paper industry as well as to packaging manufacturers. In this paper an extended multi-scale model of edge wicking in multi-ply paperboard is presented. The geometric and physical properties of the paperboard are modeled on the micro-scale, and include fillers and fines. The absolute air permeabilities and pore size distributions are validated with experimental and tomographic values. On the macro-scale random porosity and sizing distributions, time and sizing dependent contact angles, and inter-ply dependence are modeled. Arbitrary shapes of the paperboard are handled through an unstructured 3D surface mesh. Stationary and transient edge wicking simulations are validated against experiments with excellent agreement. The simulations show that the diffusive menisci between the liquid and air phases together with the two-ply model is necessary to achieve good agreement with the transient edge wicking experiments.
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| 43. |
- Karlsson, Erik, 1983, et al.
(författare)
-
Separation and recirculation of bulk crystals to potentially mitigate sodium salt scaling in black liquor evaporators
- 2016
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 31:4, s. 592-599
-
Tidskriftsartikel (refereegranskat)abstract
- Black liquor contains high concentrations of sodium carbonate and sodium sulfate. In black liquor concentrators, these salts begin to crystallize and have the potential to rapidly form scales on the surfaces of heat exchangers. The highest potential for scaling is when a supersaturated liquor begins to nucleate, which occurs when no crystals are available in the bulk. A mitigation strategy used in some mills is to recirculate thick liquor, which increases the bulk crystal concentration. However, a more efficient solution would be to separate bulk crystals and add them selectively to mitigate scaling directly.This study investigated the separation of bulk crystal from black liquor using a hydrocyclone. Separation was shown to be possible and was proven for a dry solids content of up to 65%, which corresponded to a viscosity of 20 mPa·s at 120°C. The two most important parameters relating to separation were viscosity and flow velocity. The cyclone Reynolds number encompasses both of these parameters and can be used to estimate the degree of separation. An implementation strategy for bulk crystal recirculation has also been developed and discussed. The recirculation of bulk crystals is most beneficial when operating close to critical solids and when reseeding crystals after cleaning.
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| 44. |
- Karlsson, Erik, 1983, et al.
(författare)
-
The Effect of Bulk Crystals on Sodium Salt Scaling in Black Liquor Evaporators
- 2017
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 32:2, s. 299-308
-
Tidskriftsartikel (refereegranskat)abstract
- Black liquor evaporation is an essential unit operation in the chemical recovery cycle of a pulp mill. The high concentrations of sodium carbonate and sodium sulphate in black liquor cause crystallization fouling, or scaling, in the concentrator effect, which affects the operation negatively.The focus of this work was to evaluate the effect the content and size of the bulk crystals had on the scaling rate of the sodium salts. This was done experimentally by evaporating both pure sodium carbonate solution (to crystallize anhydrous sodium carbonate) and black liquor.It was found that bulk crystals were required to suppress rapid scaling during primary nucleation (when passing the metastable limit), which was tenfold higher than scaling during continuous crystallization under steady-state operation. The amount of bulk crystals did not, however, affect the scaling rate during continuous crystallization. It was also found that the scaling rate increased when the largest crystals were removed, in this case by a hydrocyclone. The results were similar for both sodium carbonate solutions and black liquor, although the latter had a finer crystal size and scale structure.
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| 45. |
- Karlström, Anders, 1958, et al.
(författare)
-
Control strategies for refiners Part I: Soft sensors for CD-refiner control
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 28-43
-
Tidskriftsartikel (refereegranskat)abstract
- Internal variables in (C)TMP-refining processes (e. g. temperature, consistency, fiber residence time, backward flowing steam and forces acting upon the chips and pulp) are defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e. g. dilution water feed rate and specific energy) which are not obtained from measurements or physical models of the process in the refining zone. The internal variables are the backbone of physical models and are used in this paper as soft sensors for advanced process control. Besides the shape of the temperature profile, the position of the maximum temperature and the shape of the consistency profiles inside the refining zones are important to control as they are directly linked to the development of different pulp and handsheet properties. To illustrate the capability when using combined modeling and control strategies, the concept is applied on a full scale CD82 refiner. This means both temperature and consistency control in the flat zone and the conical zone, together with an overall estimator for fiber development. Finally, in this paper it is shown that the production can be increased significantly without changing the refiner motor load nor violating the pulp property specification.
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| 46. |
- Karlström, Anders, 1958, et al.
(författare)
-
Control strategies for refiners Part II: Consistency control in twin-disc refining zones using temperature profile information
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 44-57
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Tidskriftsartikel (refereegranskat)abstract
- Consistency profiles in the refining zones of twin-disc refiners have always been cumbersome to estimate with good accuracy. To overcome such challenges, this paper shows that it is vital to measure temperature profiles between the refining discs to estimate uneven chip/pulp feed distribution. It is also shown that the plate clearance, measured by plate gap measurement devices, is changed dramatically when changing the amount of dilution water to the refining zones asymmetrically. At the same time, the inlet temperature will change as well while the maximum temperature is rather stable. This makes the maximum temperature a good candidate for use when estimating the split of the pulp mass flow rates to the refining zones. This also opens for a new consistency control concept for each refining zone. The findings in this paper have been validated in a commercial TMP production line with two serially linked twin-disc refiners, and it is shown that the pulp and handsheet property variations, in terms of mean fiber length and tensile index, between the refining zones can be reduced considerably when running the refiners with similar consistency in each refining zone.
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| 47. |
- Karlström, Anders, 1958, et al.
(författare)
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CTMP process optimization Part I: Internal and external variables impact on refiner conditions
- 2017
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 32:1, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, internal variables (e. g. temperature, consistency and fiber residence time) are introduced and defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e. g. dilution water feed rate and specific energy), which are not available as distributed variables from refining zone measurements. The internal variables can be seen as the backbone of physical models and we illustrate that based on a model for a CD-82 refiner in a CTMP production line. Such a model can be used for on-line implementation of soft sensors for advanced process control and it is shown that the refining segment pattern affects the temperature profile. It is particularly interesting to study how the segment parameters in terms of the distributed width of the bars and grooves together with the segment taper affect the back-flowing steam, the cross-sectional area and thereby the fiber residence time. To illustrate the capability to use a modeling strategy it is shown how to reach a 40% reduction in specific energy without violating the required pulp properties.
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| 48. |
- Karlström, Anders, 1958, et al.
(författare)
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CTMP Process Optimization Part II: Reliability in Pulp and Handsheet Measurements
- 2017
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 32:2, s. 253-265
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this investigation is to analyze and model pulp and handsheet properties using two different approaches based on a reduced set of binomial coefficients for small data sets and constrained linear functions for larger data sets.The properties are linked to process data from the daily CTMP operation in a CD-82 refiner. From a laboratory test program perspective, the test series was extensive and covered 80 pulp samples at different process conditions.In this paper, external variables (dilution water feed rate, specific energy and plate clearance) are compared with internal variables (consistency and fiber residence time) as predictors.It is shown that internal variables as predictors seem to outperform the external variables when estimating CSF Freeness, sheet density, tensile strength, tensile index, elongation to rupture, tensile energy absorption, tensile energy absorption index, tensile stiffness, tensile stiffness index, tear strength, tear index, short-span compressive test index, ISO brightness, Scott-Bond, Z-strength, shives(>= 0.3mm), long fibers and fines.It is important to cover all important dynamics to select the best possible models. Here, the absolute differences between the measured and estimated pulp and handsheet properties are ranked in ascending order, followed by a selection procedure before the polynomial fitting. Moreover, three different sets of chip mixtures were analyzed, and the results shown in this paper indicate that only one model is required for each pulp and handsheet property when using internal variables as predictors.Finally, at a given threshold of shives, it is shown that both Scott-Bond and sheet density can be optimized by changing the consistency and fiber residence time in the refining zones individually. This opens for implementation of new control strategies based on soft sensors.
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| 49. |
- Karlström, Anders, 1958, et al.
(författare)
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CTMP Process Optimization Part III: On the Predicition of Scott-Bond, Z-strength and Tensile index
- 2017
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 32:2, s. 266-279
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Tidskriftsartikel (refereegranskat)abstract
- Here, the objective is to analyze estimates of the handsheet properties Scott-Bond, Z-strength and tensile index. It is shown that temperature profile measurements from the refining zones make it is possible to derive hidden physical phenomena that are impossible to measure inside the refining zones. Such measures are typical internal variables (consistency and fiber residence time) which can be used as predictors in multilinear models. The analysis is based on process data comprises three different chip mixtures. It is shown that the selected internal variables as predictors outperform the external variables (such as dilution water and plate clearance) in the polynomial fit. This is even more pronounced when validating the models using a holdout set. The methodology outlined in this paper makes it possible to model Scott-Bond, Z-strength and tensile index independently of the type of chip mixture when internal variables are used. It is also shown that the use of mean values of the handsheet properties can deteriorate the final model prediction considerably. Only about 60 % of all handsheet property samples were acceptable for modeling purposes. However, due to the extended laboratory test procedures a ranked and assured database as well as on-line models where possible to derive.
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| 50. |
- Karlström, Anders, 1958, et al.
(författare)
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On the modeling of tensile index from larger data sets
- 2019
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Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 34:3, s. 289-303
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to analyze and foresee potential outliers in pulp and handsheet properties for larger data sets. The method is divided into two parts comprising a generalized Extreme Studentized Deviate (ESD) procedure for laboratory data followed by an analysis of the findings using a multivariable model based on internal variables (i. e. process variables like consistency and fiber residence time inside the refiner) as predictors. The process data used in this has been obtained from CD-82 refiners and from a laboratory test program perspective, the test series were extensive. In the procedure more than 290 samples were analyzed to get a stable outlier detection. Note, this set was obtained from pulp at one specific operating condition. When comparing such "secured data sets" with process data it is shown that an extended procedure must be performed to get data sets which cover different operating points. Here 100 pulp samples at different process conditions were analyzed. It is shown that only about 60 percent of all tensile index measurements were accepted in the procedure which indicates the need to oversample when performing extensive trials to get reliable pulp and handsheet properties in TMP and CTMP processes.
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