| 1. |
- Antonsson, Stefan, et al.
(författare)
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The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps
- 2010
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Ingår i: Appita journal. - 1038-6807. ; 63:1, s. 231-
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Tidskriftsartikel (refereegranskat)abstract
- Hygroexpansion coefficient and tensile stiffness are important parameters in many paper applications. This study compares several bleached industrial hardwood kraft pulps, comprising five eucalypt pulps from South America, Europe, and Africa as well as an acacia pulp from Asia and a birch pulp from Scandinavia. Refined and unrefined pulps are compared. The results indicate significant differences in hygroexpansion but smaller differences in tensile stiffness index at comparable densities. No single factor offering a reasonable explanation of these differences in hygroexpansion coefficient, such as carbohydrate composition, fibre dimensions, or fibre form, was found. However, correlation between hygroexpansion coefficient and the mechano-sorptive creep stiffness was observed. We suggest that the hygroexpansion coefficient at a given tensile stiffness level can be used to rank pulps in terms of their mechano-sorptive creep properties.
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| 2. |
- Bijok, Nicolaus, et al.
(författare)
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Chip scale modelling of the kraft pulping process by considering the heterogeneous nature of the lignocellulosic feedstock
- 2023
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Ingår i: Chemical engineering research & design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 193, s. 13-27
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Tidskriftsartikel (refereegranskat)abstract
- This article focuses on a multiscale modelling approach to describe the delignification of softwood during the kraft pulping process. A framework for modelling the lignocellulosic feedstock on a fibre scale which considered the fundamental chemical components of wood as a distributed variable is re-assessed and extended to include chip-level phenomena such as diffusion limitations and initial component distributions within a softwood chip mixture. A new description of the wood chip is presented using a finite volume discretisation along one spatial dimension by simultaneously considering the anisotropic structural differences of the wood. Additionally, based on literature data, a distinction between the softwood chips' early- and latewood regions with their differences in densities and chemical composition is suggested. The presented model framework uses published sub-models for kinetics, diffusion etc. The validation and estimation of the remaining parameters are conducted from experimental data that quantifies the kappa number distribution of individual softwood fibres after kraft pulping. The investigation hypothesises a Gaussian distribution for the initial chemical component distribution within wood chips from a well-defined region. In contrast, a Log-normal distribution is used to describe the initial chemical distribution within a softwood chip mixture. The established sub-models for the kraft pulping process's kinetics and mass transfer phenomena could not predict the experimental data satisfactorily. However, modifying the sub-models by including a change in lignin reactivity and a temperature dependency of the lignin reactivity decline during the delignification progress could predict the essence of the observed experimental kappa number distribution.
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| 3. |
- Bijok, Nicolaus, et al.
(författare)
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Modelling the kraft pulping process on a fibre scale by considering the intrinsic heterogeneous nature of the lignocellulosic feedstock
- 2022
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 438
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Tidskriftsartikel (refereegranskat)abstract
- Renewable raw materials such as lignocellulose are inherently complex and demanding in chemical processing compared to petroleum-based feedstocks. This article addresses the challenge of developing a general model framework for modelling lignocellulosic feedstock on a fibre scale, considering its inherent heterogeneous nature in terms of the fundamental chemical component distribution in addition to its anisotropic structural properties. The presented model is tested and validated for the well-established kraft pulping process. Simulations and parameter estimation are carried out to investigate the kappa number distribution of softwood fibres during kraft pulping by using experimental data from the literature showing non-uniform delignification. A moving grid discretisation method for the distributed concentration variables is used to predict the reaction of the wood solids. The results suggest that an inherent fundamental chemical component distribution can be hypothesised as one source of the non-uniform delignification. The model indicates that a Gaussian distribution can be assumed for the initial lignin concentration within softwood. In addition, an investigation of the lignin kinetics suggests that the reactivity of lignin during kraft pulping decreases as the delignification progresses.
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| 4. |
- Deb, Somdatta, et al.
(författare)
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Application of mild autohydrolysis to facilitate the dissolution of wood chips in direct-dissolution solvents
- 2016
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 18:11, s. 3286-3294
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Tidskriftsartikel (refereegranskat)abstract
- Wood is not fully soluble in current non-derivatising direct-dissolution solvents, contrary to the many reports in the literature quoting wood 'dissolution' in ionic liquids. Herein, we demonstrate that the application of autohydrolysis, as a green and economical wood pre-treatment method, allows for a massive increase in solubility compared to untreated wood. This is demonstrated by the application of two derivitising methods (phosphitylation and acetylation), followed by NMR analysis, in the cellulose-dissolving ionic liquids 1-allyl-3-methylimidazolium chloride ([amim]Cl) and 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]. In addition, the non-derivitising tetrabutylphosphonium acetate ([P-4444][OAc]) : DMSO-d6 electrolyte also allowed for dissolution of the autohydrolysed wood samples. By combination of different particle sizes and P-factors (autohydrolysis intensity), it has been clearly demonstrated that the solubility of even wood chips can be drastically increased by application of autohydrolysis. The physiochemical factors affecting wood solubility after autohydrolysis are also discussed.
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| 5. |
- Engberg, Birgitta A., Docent, 1975-, et al.
(författare)
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New Sustainable Method to Produce Pulp Fibres ‐ Deep Eutectic Solvent‐Assisted Mechanical Pulping
- 2021
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Ingår i: Accelerating the progress towards the 2030 SDGs in times of crisis. - Östersund : Mittuniversitetet. - 9789189341173 ; , s. 2131-
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Konferensbidrag (refereegranskat)abstract
- Mechanical pulps are widely used in the manufacture of printing paper grades and also to a lesser extent in packaging materials and hygiene products. An advantage of mechanical pulps in general is the high yield (95‐97%) of the production processes, which implies a resource efficient way of producing fibre‐based products. A major drawback when producing mechanical pulps for printing qualities is the high electric energy consumption needed. However, the mechanical action associated with the liberation of fibres from the wood matrix can be facilitated if the middle lamella lignin is softened, leading to lower energy input and less fibre damages. The lignin can be softened by chemicals and high process temperatures, like in the chemi‐thermomechanical process (CTMP) and the high‐temperature‐chemi‐thermomechanical process (HT‐CTMP), where sodium sulphite is utilized. The pulps from these processes are best suited for packaging materials and tissue products. In this study, an alternate chemical treatment using deep eutectic solvents (DES) was explored. The DES used was bio‐based, non‐toxic, non‐corrosive, and could be recycled. The main goal was to facilitate the refining process and possibly create a new quality of mechanical pulp, not to remove lignin or hemicellulose. Wood chips were pre‐steamed and then soaked in DES, to ensure a sufficient impregnation. The conditions of the DES treatment were much less severe than those of a chemical pulping process, i.e. low temperature, neutral or nearly‐neutral pH, and a short residence time. The excess DES was removed by washing the chips with water before the chips where fed into a refiner. According to fibre quality analyses, the DES‐treated fibres were longer and less damaged than the control. The DES‐treated fibres also demonstrated significantly higher dewatering capacity than fibres without DES‐treatment produced at the same specific energy input in the refiner. These facts indicate that the fractures during fibre liberation to a higher extent occurred in the middle lamella, similar to when producing CTMP. A maintained high yield of the DES‐treated pulp was confirmed by chemical analysis. In conclusion, this initial study show that DES‐assisted mechanical pulping appears to be an interesting alternative for producing a mechanical pulp with different fibre properties. An aim for future work would be to tailor the DES‐treatment to alter fibre properties in a more controlled manner preferably so that market shares could be taken from the today dominating low‐yield (<50%) processes.
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| 6. |
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| 7. |
- Fiskari, Juha, 1967-, et al.
(författare)
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Acid sulfite pulping of Acacia mangium and Eucalyptus pellita as a pretreatment method for multiproduct biorefineries
- 2021
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Ingår i: Asia-Pacific Journal of Chemical Engineering. - : Wiley. - 1932-2135 .- 1932-2143. ; 16:6
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.
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| 8. |
- Fiskari, Juha, 1967-, et al.
(författare)
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Deep eutectic solvent delignification to low-energy mechanical pulp to produce papermaking fibers
- 2020
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Ingår i: BioResources. - 1930-2126. ; 15:3, s. 6023-6032
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Tidskriftsartikel (refereegranskat)abstract
- A novel process based on low-energy mechanical pulp and deep eutectic solvents (DESs) was evaluated with the goal of producing fibers suitable for papermaking. Ideally, these fibers could be produced at much lower costs, especially when applied to an existing paper mill equipped with a thermomechanical pulp (TMP) production line that was threatened with shutdown due to the decreasing demand for wood-containing paper grades. The efficiency of DES delignification in Teflon-coated autoclaves and in a specially designed non-standard flow extractor was evaluated. All tested DESs had choline chloride ([Ch]Cl) as the hydrogen bond acceptor. Lactic acid, oxalic acid, malic acid, or urea acted as hydrogen bond donors. The temperatures and times of the delignification tests were varied. Chemical analysis of the pulp samples revealed that DESs containing lactic acid, oxalic acid, or urea decreased the lignin content by approximately 50%. The DES delignification based on [Ch]Cl and urea exhibited good hemicellulose retention while DES systems based on organic acids resulted in varying hemicellulose losses. The [Ch]Cl / urea mixture did not appear to be corrosive to stainless steel, which was another advantage of this DES system.
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| 9. |
- Fiskari, Juha, et al.
(författare)
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Deep Eutectic Solvent Treatment to Low-Energy TMP to Produce Fibers for Papermaking
- 2018
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Ingår i: IMPC 2018. - Trondheim, Norway.
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Konferensbidrag (refereegranskat)abstract
- The aim of this research was to gain a better understanding on whether a novel process based on low-energy thermo-mechanical pulp (TMP) process followed by a chemical treatment with deep eutectic solvents (DESs) could produce fibers suitable for papermaking. In full scale production, these fibers could be produced at a much lower capital and operational costs, especially when utilizing existing TMP plants which are under the threat to be shut down or have already been shut down due to a decreasing demand for newsprint and other wood-containing papers.The efficiency of several DES treatments under various temperatures and times were evaluated by carrying out experiments in standard Teflon-lined autoclaves. A few tests were also performed in a unique nonstandard flow extractor. Pulp samples were characterized for their cellulose, hemicellulose and lignin contents. Moreover, tensile index was measured both before and after pulp refining. Depending on the solvent, the response of mechanical pulp varied, especially in terms of hemicellulose dissolution. Lactic acid, oxalic acid and urea, all in combination with choline chloride ([Ch]Cl) as the hydrogen bond acceptor, dissolved about 50% of the lignin of the low-energy TMP fibers under the tested conditions. The mixture of malic acid and [Ch]Cl was less effective in lignin dissolution. The mixture of urea and [Ch]Cl exhibited only a minor loss in hemicellulose content, when compared to the other tested DESs. Although 50% of the lignin was dissolved with minor loss in hemicellulose no improvement in tensile strength was observed, as it was rather the opposite. Another benefit with the mixture of urea and [Ch]Cl was that this DES did not appear to be corrosive to stainless steel. All other tested DESs—which were also quite acidic—were observed to be corrosive. Moreover, this DES-related corrosion was found to intensify at elevated temperatures.When chips were used as starting material with otherwise the same conditions almost no lignin was dissolved. This suggests that low-energy mechanical pulp is likely to be a good starting material for extracting lignin using DESs.
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| 10. |
- Fiskari, Juha, 1967-, et al.
(författare)
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Evaluation of the potential of Acacia Mangium and Eucalyptus pellita as feedstock for biorefinery
- 2019
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Ingår i: Proceedings of the 20<sup>th</sup> ISWFPC. - Tokyo, Japan. ; , s. P-44-
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Konferensbidrag (refereegranskat)abstract
- This laboratory research was undertaken to gain a better understanding of Acacia mangium and Eucalyptus pellita and their feasibility as feedstock in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The wood samples were analyzed for carbohydrates, lignin and extractives. The cooking experiments were carried out in 2L autoclaves with temperatures of 130°C and 140°C, with varied chemical charges, after which the resulting pulp samples were characterized for kappa number and fiber quality. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, even more severe cooking conditions would be needed. This kind of pulp and the resulting lignin may be well used as intermediate products in biorefineries.
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