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BETA
Håkansson, Helena
Alternative names
Publications (10 of 18) Show all publications
Ekbåge, D., Nilsson, L. & Håkansson, H. (2019). Time series analysis of refining conditions and estimated pulp properties in a chemi-thermomechanical pulp process. BioResources, 14(3), 5451-5466
Open this publication in new window or tab >>Time series analysis of refining conditions and estimated pulp properties in a chemi-thermomechanical pulp process
2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 3, p. 5451-5466Article in journal (Refereed) Published
Abstract [en]

Frequently sampled process data from a conical disc refiner and infrequently sampled pulp data from a full scale chemi-thermomechanical pulp (CTMP) mill were evaluated to study autocovariance with aspects of potential dynamic modelling applicability. Two trial measurements with an online pulp analyzer at decreased sampling intervals were performed. For variability analysis, time-series containing up to one day of operational data were used. At the chip refiner, the clearest significant autocovariance was identified for the specific electricity consumption, based on the longer sequences. Most of the estimated pulp properties indicated low or non-significant autocovariance, limiting applicability of a specific dynamic model. A mill trial was conducted to investigate the impact from an increase in the conical disc gap on the specific electricity consumption and the resulting freeness. The response time from the gap change in the refiner to measured change in freeness was estimated at 19 min, which was approximately the hydraulic residence time in the latency chest. The relevance of this study lies in applicability of mill-data-driven modelling to capture the dynamics of a specific refining process. Through mill trials the sampling speed of pulp properties was more than doubled to gain insights into short term systematic variations by applying time-series-analysis.

Place, publisher, year, edition, pages
North Carolina State University, 2019
Keywords
Chemi-thermomechanical pulp (CTMP); Freeness; Dynamic modelling; conical disc refiner; Specific electricity consumption; Energy efficiency; Autocovariance
National Category
Paper, Pulp and Fiber Technology
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-65734 (URN)10.15376/biores.14.3.5451-5466 (DOI)000473204700036 ()
Funder
Knowledge Foundation
Note

Artikeln ingick som manuskript i Ekbåges licentiatuppsats (2018) Process modelling based on data from an evaporation and a CTMP process

Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2019-08-06Bibliographically approved
Ekbåge, D., Nilsson, L. & Håkansson, H. (2017). Trial measurements in a CTMP-process to perform time-series analysis of refining conditions and estimated pulp properties. In: : . Paper presented at 10th Fundamental Mechanical Pulp Research Seminar.
Open this publication in new window or tab >>Trial measurements in a CTMP-process to perform time-series analysis of refining conditions and estimated pulp properties
2017 (English)Conference paper, Oral presentation with published abstract (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kau:diva-65786 (URN)
Conference
10th Fundamental Mechanical Pulp Research Seminar
Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2018-02-02Bibliographically approved
Hellstrom, P., Heijnesson-Hulten, A., Paulsson, M., Håkansson, H. & Germgard, U. (2016). A comparative study of enzymatic and Fenton pretreatment applied to a birch kraft pulp used for MFC production in a pilot scale high-pressure homogenizer. TAPPI Journal, 15(6), 375-381
Open this publication in new window or tab >>A comparative study of enzymatic and Fenton pretreatment applied to a birch kraft pulp used for MFC production in a pilot scale high-pressure homogenizer
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2016 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 6, p. 375-381Article in journal (Refereed) Published
Abstract [en]

Microfibrillated cellulose (MFC) was produced in pilot scale from a bleached birch (Betula verrucosa) kraft pulp that was pretreated with either Fenton's reagent or with a combined mechanical and enzymatic method used at the Centre Technique du Papier (CTP; Grenoble, France). The change in fiber fibrillation during the homogenization treatment was monitored by analyzing the fiber and the fines content, size fractionation, rheological properties and visualization by light-and scanning electron microscopy (SEM). The Fenton pretreatment resulted in MFC suspensions that contained a high amount of small sized elements. After five passes through the high-pressure homogenizer, the amount of particles smaller than 20 mu m was 37% for the Fenton pretreated MFC compared to 13% for the enzymatically (endoglucanase) pretreated MFC. Altogether, the Fenton pretreatment enabled preparation of MFC with a higher degree of fibrillation after the same number of passes through the high-pressure homogenizer. Another option is to produce MFC of the same amount of fibrillation as after an enzymatic stage, but at significantly lower energy consumption.

Place, publisher, year, edition, pages
TAPPI Press, 2016
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-46239 (URN)000380267900004 ()
Available from: 2016-09-21 Created: 2016-09-21 Last updated: 2019-06-10Bibliographically approved
Hellstrom, P., Heijnesson-Hulten, A., Paulsson, M., Håkansson, H. & Germgård, U. (2014). Fenton pre-treated microfibrillated cellulose evaluated as a strength enhancer in the middle ply of paperboard. Nordic Pulp & Paper Research Journal, 29(4), 732-740
Open this publication in new window or tab >>Fenton pre-treated microfibrillated cellulose evaluated as a strength enhancer in the middle ply of paperboard
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2014 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 732-740Article in journal (Refereed) Published
Abstract [en]

Microfibrillated celluloses (MFCs), produced by various pre-treatments of a fully bleached birch kraft pulp, were evaluated as strength enhancers in test sheets representing the middle ply of paperboard. The furnish consisted of hydrogen peroxide bleached high temperature spruce chemithermomechanical pulp (HT-CTMP), MFC and a retention system containing cationic starch and an anionic silica sol. The MFC was prepared via a mechanical treatment in a colloid mill after pretreatment with Fenton's reagent, monocomponent endoglucanase or acidic hydrogen peroxide. Addition of 5% MFC, produced with Fenton pre-treatment, resulted in improved HT-CTMP properties with respect to increased tensile index (similar to 35%), z-directional strength (similar to 50%), tensile stiffness index (similar to 25%) compared to HT-CTMP test sheets prepared without MFC addition. The strength improvement was linearly correlated to the density of the tests sheet, to the surface area (BET) and to the surface charge of the enzymatic or chemically pre-treated MFCs.

Keywords
Microfibrillated cellulose, Fenton's reagent, Enzymatic hydrolysis, Tensile strength, Z-directional strength, Bending stiffness index, Bending resistance, Dewatering
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-41572 (URN)000346146900020 ()
Available from: 2016-04-25 Created: 2016-04-11 Last updated: 2017-10-31Bibliographically approved
Hellstrom, P., Heijnesson-Hulten, A., Paulsson, M., Hakansson, H. & Germgård, U. (2014). The effect of Fenton chemistry on the properties of microfibrillated cellulose. Cellulose (London), 21(3), 1489-1503
Open this publication in new window or tab >>The effect of Fenton chemistry on the properties of microfibrillated cellulose
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2014 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 3, p. 1489-1503Article in journal (Refereed) Published
Abstract [en]

A fully bleached birch kraft pulp was treated with acidic hydrogen peroxide in the presence of ferrous ions (Fenton's reagent) and thereafter treated mechanically in a colloid mill to produce a product containing microfibrillated cellulose (MFC). The produced MFC products were chemically and morphologically characterized and compared with MFC products produced without pretreatment as well as with enzymatic hydrolysis. Fenton treatment resulted in an increase in total charge and number of carbonyl groups while the intrinsic viscosity decreased. The Fenton treated pulps were easier to process mechanically i.e. they reached a higher specific surface area at a given mechanical treatment time and the MFC produced had a stable water-fibre suspension for at least 8 weeks compared to enzymatic pretreated pulps and pulps not subjected to any pretreatment.

Place, publisher, year, edition, pages
Springer, 2014
Keywords
Microfibrillated cellulose, Fenton chemistry, Enzymatic hydrolysis, Carbonyl groups, Carbohydrate composition, Total and surface charge, Suspension stability
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-41526 (URN)10.1007/s10570-014-0243-1 (DOI)000336322800036 ()
Available from: 2016-04-25 Created: 2016-04-11 Last updated: 2017-10-31Bibliographically approved
Hellström, P., Heijnesson-Hultén, A., Paulsson, M., Håkansson, H. & Germgård, U. (2013). The effect of Fenton chemistry on the production of microfibrillated cellulose - characterization and paper board application. In: : . Paper presented at The Nordic Wood Biorefinery Workshop Chalmers october 2013.
Open this publication in new window or tab >>The effect of Fenton chemistry on the production of microfibrillated cellulose - characterization and paper board application
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2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

A fully bleached birch (Betula verucosa) sulphate pulp was treated with acidic hydrogen peroxide in the presence of ferrous iron (i.e. Fenton's reagent) and thereafter treated mechanically in a colloid mill to produce microfibrillated cellulose (MFC). The produced MFCs were chemically and morphologically characterized and compared with MFCs produced with enzymatic (monocomponent endoglucanase) pre-treatment (Figure 1). As a reference MFC produced with only acid pre-treatment was also included in the study.

The Fenton pre-treatment increased the total charge of the fibres, decreased the viscosity and introduced new carbonyl groups. Addition of 10 and 50 kg/t hydrogen peroxide resulted in a yield loss of 2 and 4%, respectively. The enzymatic hydrolysis did not substantially change the total charge or the carbonyl group content of the pulp and did not release any organic material. The Fenton pre-treated pulps were easier to process mechanically, i.e. they reached a higher specific surface (BET) area and thereby a higher surface charge at a given mechanical treatment time, indicating a potential to reduce the energy demand in the final mechanical processing stage. The Fenton pre-treatment produced microfibrillated cellulose that in a water suspension (0.5% consistency) was stable with respect to sedimentation for at least eight weeks (Figure 2). Further, the Fenton pre-treatment gave a MFC product that contained a higher amount of small well fibrillated particles, as indicated by fractionation and scanning electron microscopy, compared with the enzymatic and acid pre-treatment methods studied.

Keywords
Microfibrillated cellulose, birch sulphate pulp, Fenton chemistry, enzymatic hydrolysis, carbonyl groups, total and surface charge, fractionation, suspension stability
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-31653 (URN)
Conference
The Nordic Wood Biorefinery Workshop Chalmers october 2013
Projects
Akzo Nobel och VIPP FORSKARSKOLA: Values created in fibre-based processes and products
Available from: 2014-03-06 Created: 2014-03-06 Last updated: 2014-07-01Bibliographically approved
Hellström, P., Heijnesson- Hultén, A., Paulsson, M., Håkansson, H. & Germgård, U. (2013). The effect of Fenton chemistry on the properties of microfibrillated cellulose (MFC).
Open this publication in new window or tab >>The effect of Fenton chemistry on the properties of microfibrillated cellulose (MFC)
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2013 (English)Other (Other academic)
Keywords
Fenton, microfibrillated cellulose
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-29181 (URN)
Available from: 2013-09-25 Created: 2013-09-25 Last updated: 2017-12-11Bibliographically approved
Östberg, L., Håkansson, H. & Germgård, U. (2012). Some aspects of the reactivity of pulp intended for high-viscosity viscose. BioResources, 7(1), 743-755
Open this publication in new window or tab >>Some aspects of the reactivity of pulp intended for high-viscosity viscose
2012 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 1, p. 743-755Article in journal (Refereed) Published
Abstract [en]

The original objective of this study was to reduce the consumption of carbon disulphide in the preparation of high-viscosity viscose by pre-treating two softwood pulps with enzymes prior to the viscose stages. Reactivity can, however, be measured in different ways and the methods used in this study are Fock´s test of the pulp and the gamma number of the viscose solution prior to regeneration. It was found that whilst the reactivity of a pulp that had been subjected to enzyme pretreatment increased according to Fock´s test, it did not increase when the gamma number obtained in a standardized viscose preparation process was used. This unexpected difference that was discovered between the two reactivity tests made it difficult to analyze the impact of the enzyme stage on reactivity; the underlying reasons for the different reactivity results obtained were therefore investigated first. The conclusion that may be drawn from this investigation is that Fock´s test measures the extent to which carbon disulphide reacts with a pulp sample during a standardized test whereas the gamma number measures the resulting degree of xanthate substitution on the cellulose backbone. These two reactivity tests are thus not totally correlated. It was concluded that the gamma number was the more relevant of the two tests since it reflects the dissolution ability of a pulp in the viscose preparation, which is a very basic property of viscose. A higher gamma number also means that the coagulation time in the spinning process is prolonged; this is beneficial as it can be used to increase the tenacity of the viscose fibres. Measuring the reactivity according to Fock´s test, on the contrary, provides more dubious results as the test has no undisputed correlation to the viscose preparation process.

Keywords
Carbon disulphide, endoglucanase, Fock test, Gamma number, Viscose, Xylanase
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-13244 (URN)000304041200058 ()
Available from: 2012-05-07 Created: 2012-05-07 Last updated: 2017-12-07Bibliographically approved
Germgård, U., Östberg, L. & Håkansson, H. (2011). Enzyme Activation of Pulp and its Influence on the Gamma Number of Viscose. Paper presented at Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011. Paper presented at Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011.
Open this publication in new window or tab >>Enzyme Activation of Pulp and its Influence on the Gamma Number of Viscose
2011 (English)Conference paper, Published paper (Other (popular science, discussion, etc.))
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-10768 (URN)
Conference
Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2013-06-12Bibliographically approved
Germgård, U., Östberg, L. & Håkansson, H. (2011). Lab Scale Preparation of High Viscosity Viscose at Karlstad University. Paper presented at Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011. Paper presented at Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011.
Open this publication in new window or tab >>Lab Scale Preparation of High Viscosity Viscose at Karlstad University
2011 (Swedish)Conference paper, Published paper (Other (popular science, discussion, etc.))
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-10769 (URN)
Conference
Poster presented at the IAWS 2011 conference, Augusti 31 - September 2, 2011
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2013-06-12Bibliographically approved
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