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Publications (10 of 44) Show all publications
Ekbåge, D., Nilsson, L., Håkansson, H. & Lin, P.-I. (2020). Multiple linear regression modelling of pulp and handsheet properties based on fiber morphology measurements and process data. BioResources, 15(1), 654-676
Open this publication in new window or tab >>Multiple linear regression modelling of pulp and handsheet properties based on fiber morphology measurements and process data
2020 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 15, no 1, p. 654-676Article in journal (Refereed) Published
Abstract [en]

A multiple regression model was evaluated to predict pulp and handsheet properties including z-directional tensile strength (z-strength) and Scott bond values. One hypothesis that was central for the model evaluation was that the crill content, as measured with ultraviolet and infrared lights, would improve the statistical models. A chemi-thermomechanical pulp (CTMP) mill designed with two parallel primary refining lines and a reject refiner was the basis for this study, and all process data and pulp samples were gathered from the specific process. Pulp was extracted from the process for an extended period from a position after the latency chest (primary refined pulp) and from the pulp-stream exiting the mill to the board machine (accept pulp). The crill content was positively correlated to the z-strength of the accept pulp, explaining 55% of the variance with a linear regression model with the drill content as the sole predictor. The estimation model of the z-strength of accept pulp was based on a combination of the crill content, freeness, fibril perimeter for longer fibers, and mean kink angle, and resulted in an R-2 of 0.79. When applying cross-validation to determine the predictive model performance, the highest R-2 obtained was 0.67. This latter model included the crill content, fibril perimeter, and mean kink angle as predictors.

Place, publisher, year, edition, pages
North Carolina State University, 2020
Keywords
CTMP, Fiber morphology, Multiple regression modelling, Handsheet, Z-strength, Scott bond, Crill
National Category
Chemical Engineering
Research subject
Chemical Engineering; Public Health Science
Identifiers
urn:nbn:se:kau:diva-77086 (URN)10.15376/biores.15.1.654-676 (DOI)000511129100050 ()
Funder
Stora Enso
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2020-05-04
Sjöstrand, B., Nilsson, L., Barbier, C. & Ullsten, H. (2020). Numerical model of water removal and air penetration during vacuum dewatering. Drying Technology
Open this publication in new window or tab >>Numerical model of water removal and air penetration during vacuum dewatering
2020 (English)In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300Article in journal (Refereed) Epub ahead of print
Place, publisher, year, edition, pages
Taylor & Francis, 2020
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-75959 (URN)10.1080/07373937.2020.1745825 (DOI)000523132300001 ()
Note

Artikeln ingick som manuskript i Sjöstrands doktorsavhandling (2020): Vacuum Dewatering of Cellulosic Materials: New insights into transport phenomena in the papermaking process

Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2020-04-24Bibliographically approved
Sjöstrand, B., Barbier, C., Ullsten, H. & Nilsson, L. (2019). Dewatering of Softwood Kraft Pulp with Additives of Microfibrillated Cellulose and Dialcohol Cellulose. BioResources, 14(3), 6370-6383
Open this publication in new window or tab >>Dewatering of Softwood Kraft Pulp with Additives of Microfibrillated Cellulose and Dialcohol Cellulose
2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 3, p. 6370-6383Article in journal (Refereed) Published
Abstract [en]

The addition of nano-and micro-fibrillated cellulose to conventional softwood Kraft pulps can enhance the product performance by increasing the strength properties and enabling the use of less raw material for a given product performance. However, dewatering is a major problem when implementing these materials to conventional paper grades because of their high water retention capacity. This study investigated how vacuum dewatering is affected by different types of additives. The hypothesis was that different types of pulp additions behave differently during a process like vacuum suction, even when the different additions have the same water retention value. One reference pulp and three additives were used in a laboratory-scaled experimental study of high vacuum suction box dewatering. The results suggested that there was a linear relationship between the water retention value and how much water that could be removed with vacuum dewatering. However, the linear relationship was dependent upon the pulp type and the additives. Additions of micro-fibrillated cellulose and dialcohol cellulose to the stock led to dewatering behaviors that suggested their addition in existing full-scale production plants can be accomplished without a major redesign of the wire or high vacuum section.

Place, publisher, year, edition, pages
NORTH CAROLINA STATE UNIV DEPT WOOD & PAPER SCI, 2019
Keywords
Vacuum dewatering, Dewatering, Microfibrillated cellulose, Dialcohol cellulose, Papermaking, Strength additives, Retention aids, Drainage, Water retention value
National Category
Chemical Engineering
Research subject
Chemical Engineering; Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-74224 (URN)10.15376/biores.14.3.6370-6383 (DOI)000473204700100 ()
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2019-12-19Bibliographically approved
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: 2020-05-04Bibliographically approved
Tysén, A., Vomhoff, H. & Nilsson, L. (2018). Through air drying assisted by infrared radiation: The influence of radiator power on drying rates and temperature. Nordic Pulp & Paper Research Journal, 33(4), 581-591
Open this publication in new window or tab >>Through air drying assisted by infrared radiation: The influence of radiator power on drying rates and temperature
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 4, p. 581-591Article in journal (Refereed) Published
Abstract [en]

The use of infrared radiation for heating the web in the through air drying process was investigated in lab scale. The hypothesis was that infrared radiation should be a more efficient method to transfer drying energy to the wet web compared to hot air, but that a certain air flow is still required as a transport medium for the evaporated water. A trial program comprising handsheets made of two types of bleached chemical pulps, five grammages (15, 22, 30 and 60 g/m2), and dried with five radiator power levels was performed on a lab scale through air drying equipment. Drying times of the samples were determined from temperature data recorded with an infrared camera. The use of infrared radiation shortened drying times, especially for low grammage samples. The shortening of the drying time ranged between 10 and 45 %. The most substantial shortenings were obtained for the lowest grammages and the highest radiator power level. However, the increase of power did not linearly shorten drying time. After an initial shortening at the lowest power level, the positive effect of the IR heating decreased as the power was further increased. © 2018 Walter de Gruyter GmbH, Berlin/Boston.

Place, publisher, year, edition, pages
De Gruyter Open, 2018
Keywords
drying, infrared, pulp, TAD, thermography, tissue, Chemical equipment, Infrared radiation, Radiators, Solar dryers, Thermography (temperature measurement), Bleached chemical pulps, Drying rates, Drying time, Infra-red cameras, Power levels, Temperature data, Through air drying, Through-air-drying process, Infrared drying
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-70244 (URN)10.1515/npprj-2018-2002 (DOI)000451437900001 ()2-s2.0-85054212752 (Scopus ID)
Note

Artikeln ingick i doktorsavhandlingen Through air drying: Thermographic studies of drying rates, drying non-uniformity and infrared assisted drying som manuskript.

Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2020-01-16Bibliographically approved
Ottosson, A., Nilsson, L. & Berghel, J. (2017). A mathematical model of heat and mass transfer in Yankee drying of tissue. Drying Technology, 35(3), 323-334
Open this publication in new window or tab >>A mathematical model of heat and mass transfer in Yankee drying of tissue
2017 (English)In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 35, no 3, p. 323-334Article in journal (Refereed) Published
Abstract [en]

Final dewatering in the production of dry creped tissue is performed by Yankee drying, which includes hot pressing followed by simultaneous contact and impingement drying. The present study models Yankee drying and compares simulation results to the data obtained from trials on a pilot tissue machine. It advances models published previously by the representations developed for the transport of heat in the pressing stage and for the heat transfer involved in the dehydration of the cylinder coating spray. The model predicts an average specific drying rate within 4% in the range of the experimental data used.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
Keywords
Heat and mass transfer, mathematical model, tissue drying
National Category
Energy Engineering
Research subject
Chemical Engineering; Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-63896 (URN)10.1080/07373937.2016.1170697 (DOI)000395033700006 ()
Available from: 2017-09-22 Created: 2017-09-22 Last updated: 2020-05-25Bibliographically approved
Sjöstrand, B., Nilsson, L. & Barbier, C. (2017). Modeling the influence of forming fabric structure influence on vacuum box dewatering. TAPPI Journal, 16(8), 477-483
Open this publication in new window or tab >>Modeling the influence of forming fabric structure influence on vacuum box dewatering
2017 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 8, p. 477-483Article in journal (Refereed) Published
Abstract [en]

This investigation used numerical models to describe forming section sheet dewatering at the high vacuum suction boxes. Three different fabric structures were examined with numerical models for single-phase flow of air and for two-phase flow of air and water. This was done to evaluate how forming fabric structure influences sheet dewatering. The numerical models were compared with an experimental study of the same fabrics investigated on a laboratory suction box. The small differences in dewatering rate in the experimental study could be simulated with the models, which confirmed the validity of the models. This implies that these numerical models can be used to describe new fabrics and how they will respond in the papermaking process.

National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kau:diva-47598 (URN)000413824000005 ()
Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2020-01-16Bibliographically 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: 2020-05-04Bibliographically approved
Lin, W., Nilsson, L. & Malutta, R. (2017). Waste heat recovery by organic rankine cycle (ORC) for moist exhaust gases from paper industry. In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE): . Paper presented at ASME 2017 International Mechanical Engineering Congress and Exposition, IMECE 2017, 3 - 9 November 2017, Tampa, USA. American Society of Mechanical Engineers (ASME), 6
Open this publication in new window or tab >>Waste heat recovery by organic rankine cycle (ORC) for moist exhaust gases from paper industry
2017 (English)In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), American Society of Mechanical Engineers (ASME) , 2017, Vol. 6Conference paper, Published paper (Refereed)
Abstract [en]

Large potential exists in recovering waste heat from paper industry processes and machinery. If the overall energy efficiency would be increased, it could lead to significant fuel savings and greenhouse gas emission reduction. The organic Rankine cycle (ORC) system is a very strong candidate for converting low-grade waste heat into power. However, there is a lot of water vapor containing latent heat in the exhaust gases from the drying process in the paper industry. Thus, the aim of this research work is to increase the efficiency of the ORC system by recovering not only the sensible heat but also the latent heat from the exhaust gases in the paper drying process. In order to recover the latent heat from the moist exhaust gases, one idea of this article is to introduce a direct contact condensing unit into the ORC system. The performance of ORC system with the direct contact condensing unit was analyzed by using the CHEMCAD software. A case study was conducted based on data of the exhaust gases from a tissue production / drying machine. Latent heat will be recovered when the evaporating temperature of the ORC working fluid is lower than the dew point of the water vapor in the exhaust gases. The results showed that the available heat load was increased when the evaporating temperature was reduced. Furthermore, a performance comparison of the ORC systems with and without the direct contact condensing unit was carried out in the case study as well. The results showed that the ORC system with the direct contact condensing unit not only could recover latent heat from the water vapor in the exhaust gases but also could have a small size and small volume evaporator in the ORC system.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME), 2017
Keywords
Emission control, Energy efficiency, Engineering research, Fuel economy, Gas emissions, Gases, Greenhouse gases, Latent heat, Machinery, Paper and pulp industry, Rankine cycle, Recovery, Waste heat, Waste heat utilization, Water vapor, Evaporating temperature, Greenhouse gas emission reduction, Low-grade waste heat, Organic Rankine Cycle(ORC), Overall energy efficiency, Paper industries, Performance comparison, Tissue production, Exhaust gases, Exhaust Gas, Paper Industry
National Category
Energy Systems Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kau:diva-66199 (URN)10.1115/IMECE2017-71326 (DOI)000428485500012 ()2-s2.0-85040927064 (Scopus ID)9780791858417 (ISBN)
Conference
ASME 2017 International Mechanical Engineering Congress and Exposition, IMECE 2017, 3 - 9 November 2017, Tampa, USA
Available from: 2018-02-09 Created: 2018-02-09 Last updated: 2019-08-02Bibliographically approved
Rezk, K., Forsberg, J., Nilsson, L. & Berghel, J. (2016). Characterizing flow resistance in 3-dimensional disordered fibrous structures based on Forchheimer coefficients for a wide range of Reynolds numbers. Applied Mathematical Modelling, 40(21-22), 8898-8911
Open this publication in new window or tab >>Characterizing flow resistance in 3-dimensional disordered fibrous structures based on Forchheimer coefficients for a wide range of Reynolds numbers
2016 (English)In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 40, no 21-22, p. 8898-8911Article in journal (Refereed) Published
Abstract [en]

The flow resistance in 3-dimensional fibrous structures are investigated in particle Reynolds number representing flow characteristics with strong inertia. The resistance coefficients are established based on steady state simulations of single-phase processes of water numerically. An automatized simulation process in COMSOL is developed with a MATLAB algorithm in which production runs could be carried for various 3-dimensional fibrous structures. Simulation of flow processes ranging from Reynolds numbers at creeping flow levels to high Reynolds number at approximately 1000 are calculated and a numerical data set is established in order to estimate Forchheimer coefficients which are used to correlate a dimensionless friction factor to a modified Reynolds expression for porous media.

The friction factor and dimensionless permeability are calculated for fibrous structures with (i) disordered unidirectional fibers (ii) an isotropic fiber orientation in-plane perpendicular to the flow, and (iii) an isotropic fiber structure in a the 3-dimensional space. Empirical correlations of the friction factor and Reynolds number are used to compare our simulation data in order to assess the validity of our models and flow resistance estimations. The dimensionless permeability is moreover compared to other numerical simulations of flow through fibrous structures in order to assess flow resistance at low Reynolds number.

It is concluded that flow resistance in the isotropic fiber arrangement in space is lower than the in-plane isotropic orientation and disordered unidirectional fiber arrangements at creeping flow conditions, however, all friction actors converges towards the same value at higher Reynolds numbers indicating that fiber orientation is independent at high inertia flow regimes. Overall, our numerical simulations agree well to classical empirical formulations for a wide range of Reynolds number. However, the comparison differs considerably depending on the porosity level.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Flow resistance; Volume-averaging; Porous media; Forchheimer coefficients; Friction factor; Fibrous structure
National Category
Fluid Mechanics and Acoustics
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-46411 (URN)10.1016/j.apm.2016.05.036 (DOI)000384853900005 ()
Note

This article was published as manuscript in Kamal Rezk thesis.

Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2019-09-19Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5864-4576

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