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BETA
Engberg, Birgitta A.ORCID iD iconorcid.org/0000-0003-3381-5516
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Publications (10 of 36) Show all publications
Sandberg, C., Nelsson, E., Engberg, B. A., Berg, J.-E. & Engstrand, P. (2018). Effects of chip pretreatment and feeding segments on specific energy and pulp quality in TMP production. Nordic Pulp & Paper Research Journal, 33(3), 448-459
Open this publication in new window or tab >>Effects of chip pretreatment and feeding segments on specific energy and pulp quality in TMP production
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2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 3, p. 448-459Article in journal (Refereed) Published
Abstract [en]

Increased wood softening and refining intensity have earlier been utilized to improve refining efficiency in mechanical pulping. We have evaluated a combination of increased softening by low dose sulphite chip pretreatment and increased intensity by feeding segment design in a TMP line for production of high quality printing papers. Norway spruce wood chips were preheated, compressed in an Impressafiner and impregnated with water or sodium sulphite solutions (Na2SO3 charges 3.6 and 7.2 kg/t). Chips were refined in two parallel 68" double disc refiners using two different refining conditions: standard bidirectional segments at normal production rate (9 t/h) and feeding segments at increased production rate (11.1-12.1 t/h). The feeding segments enabled a 30 % increase in production rate. Refining with feeding segments at 12.1 t/h production rate combined with chip pretreatment with 3.6 kg/t sodium sulphite reduced the specific energy 360 kWh/t (19 %) compared to refining with standard segments and no pretreatment. Pulp properties were similar for the two configurations. The combination of feeding segments and chip pretreatment with water reduced the specific energy 180 kWh/t (9 %). Implementation of most of the technology presented has reduced the electrical energy use for the mill by approximately 80 GWh/year.

Keywords
chip pretreatment, double disc refiner, energy efficiency, mechanical pulping, refining intensity, sodium sulphite
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-34604 (URN)10.1515/npprj-2018-3052 (DOI)000450923900011 ()2-s2.0-85053157973 (Scopus ID)
Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-12-11Bibliographically approved
Persson, J., Engberg, B. A. & Granfeldt, T. (2018). Feeding of double disc refiners - modeling of particle flow. In: IMPC 2018: . Paper presented at International Mechanical Pulping Conference (IMPC) 2018, May 27-30, 2018, Trondheim, Norway. Trondheim, Norway
Open this publication in new window or tab >>Feeding of double disc refiners - modeling of particle flow
2018 (English)In: IMPC 2018, Trondheim, Norway, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Improvements to the energy efficiency of double disk refiners are hampered by the feeding rate in tothe machine. This study aims to evaluate parameters towards a complete model, which will help tobring clarity to the limiting factors in feeding rate. A combined computational fluid dynamic anddiscrete element model is used to evaluate the flowrate of a hopper discharge unaided, and aided by agas flow with varying density. The results of the study shows that it is essential to capture the exactgeometry of the double disk feeding in relation to the woodchips in the complete model. The resultsalso shows that while it is essential to include the gas phase in the full model, the model is not sensitiveto small variance in the density of the gas.

Place, publisher, year, edition, pages
Trondheim, Norway: , 2018
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34676 (URN)
Conference
International Mechanical Pulping Conference (IMPC) 2018, May 27-30, 2018, Trondheim, Norway
Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-10-09Bibliographically approved
Ferritsius, O., Ferritsius, R., Rundlöf, M., Engberg, B. A. & Engstrand, P. (2018). The Independent State of Fibres in Relation to the Mechanical Pulping World. In: IMPC 2018: . Paper presented at International Mechanical Pulping Conference (IMPC) 2018, May 27-30, 2018, Trondheim, Norway. Trondheim, Norway
Open this publication in new window or tab >>The Independent State of Fibres in Relation to the Mechanical Pulping World
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2018 (English)In: IMPC 2018, Trondheim, Norway, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Paper and wood are highly inhomogeneous materials. When describing the mechanical pulp itself, we allcommonly ignore that it is an inhomogeneous material. We have realized that just a very small fraction of stifffibres are enough to impair the printability of the product. In this paper we share some of our reflections andattempts how to describe the inhomogeneous nature of mechanical pulps. A method denoted BIN is underdevelopment based on independent common factors and paying attention to the inhomogeneity of the material.The method may give the possibility to describe the nature of TMP/CTMP/SGW in a more relevant way comparedto todays practice. Hence the paper and board makers may be able to deliver more uniform products at “goodenough” level at lower costs. We have realized that because a method or opinion is well spread (sometimes usedby almost everybody) it does not necessarily mean that it is relevant. A couple of myths have been reflected uponand in our opinion they remain just myths. By putting more attention to reality and describing mechanical pulp asan inhomogeneous material we hope to be able to rid ourselves and the mechanical pulping community of someother myths circulating (some still to be discovered).

Place, publisher, year, edition, pages
Trondheim, Norway: , 2018
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34680 (URN)
Conference
International Mechanical Pulping Conference (IMPC) 2018, May 27-30, 2018, Trondheim, Norway
Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-10-09Bibliographically approved
Moilanen, C., Björkqvist, T., Ovaska, M., Koivisto, J., Miksic, A., Engberg, B. A., . . . Alava, M. (2017). Influence of strain rate, temperature and fatigue on the radial compression behaviour of Norway spruce. Holzforschung, 71(6), 505-514
Open this publication in new window or tab >>Influence of strain rate, temperature and fatigue on the radial compression behaviour of Norway spruce
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2017 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 6, p. 505-514Article in journal (Refereed) Published
Abstract [en]

A dynamic elastoplastic compression model of Norway spruce for virtual computer optimization of mechanical pulping processes was developed. The empirical wood behaviour was fitted to a Voigt-Kelvin material model, which is based on quasi static compression and high strain rate compression tests (QSCT and HSRT, respectively) of wood at room temperature and at high temperature (80-100 degrees C). The effect of wood fatigue was also included in the model. Wood compression stress-strain curves have an initial linear elastic region, a plateau region and a densification region. The latter was not reached in the HSRT. Earlywood (EW) and latewood (LW) contributions were considered separately. In the radial direction, the wood structure is layered and can well be modelled by serially loaded layers. The EW model was a two part linear model and the LW was modelled by a linear model, both with a strain rate dependent term. The model corresponds well to the measured values and this is the first compression model for EW and LW that is based on experiments under conditions close to those used in mechanical pulping.

Keywords
radial compression behaviour, dynamic modelling of defibration, earlywood, high strain rate test, latewood, moist Norway spruce, split-Hopkinson pressure bar, Voigt-Kelvin material model
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-30841 (URN)10.1515/hf-2016-0144 (DOI)000401835900007 ()2-s2.0-85020476071 (Scopus ID)
Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2017-08-18Bibliographically approved
Moilanen, C. S., Björkqvist, T., Engberg, B. A., Salminen, L. I. & Saarenrinne, P. (2016). High strain rate radial compression of Norway spruce earlywood and latewood. Cellulose (London), 23(1), 873-889
Open this publication in new window or tab >>High strain rate radial compression of Norway spruce earlywood and latewood
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2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 1, p. 873-889Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of Norway spruce were studied and a compression model for mechanical pulping was developed. The split-Hopkinson pressure bar technique was combined with high-speed photography to analyse local radial compression. Data analysis focussed on the differences between mechanical properties of earlywood and latewood. Measurements were conducted at both room temperature and 135 C. The effect of prefatigue treatment was also studied. A simple material model was defined linearly in parts and fitted to the measurement data to quantify the differences. New results were found on the differences in inelastic behaviour of earlywood and latewood at large deformations. In addition, other results were in line with previously published results.

Keywords
Norway spruce, Radial compression, Split-Hopkinson pressure bar, High-speed photography, Local strain
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-26437 (URN)10.1007/s10570-015-0826-5 (DOI)000368802700061 ()2-s2.0-84955692300 (Scopus ID)
Note

Publ online 26 Nov 2015

Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2017-12-01Bibliographically approved
Nelsson, E., Sandberg, C., Svensson-Rundlöf, E., Paulsson, M., Granfeldt, T., Engberg, B. & Engstrand, P. (2016). Mill scale production of TMP with double disk refining-The effects of a mild sulfonation, atmospheric preheating and refining temperatures. In: International Mechanical Pulping Conference 2016, IMPC 2016: . Paper presented at International Mechanical Pulping Conference 2016, IMPC 2016; Jacksonville; United States; 26 September 2016 through 28 September 2016 (pp. 249-259). TAPPI Press
Open this publication in new window or tab >>Mill scale production of TMP with double disk refining-The effects of a mild sulfonation, atmospheric preheating and refining temperatures
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2016 (English)In: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, p. 249-259Conference paper, Published paper (Refereed)
Abstract [en]

The aim of this work was to study the effects of a mild dosage of sodium sulfite in chip impregnation at diffen temperatures during atmospheric preheating and during refining for production of TMP for printing papers usi high intensity double disk refining. Two trials were performed in the 800 bdt/day double disc line at I Braviken paper mill (Holmen Paper AB, Sweden) using Norway spruce chips. During the trials, chips w( impregnated in an Impressafiner where chips were preheated at 1.8 bar(g) for a few seconds and th compressed before impregnation. During impregnation, sodium sulfite was added to chips at pH 9 in dosages 0.6 or 1.2%. Reference pulps without addition of sulfite were also produced. In the first trial, the effect different temperatures and retention times (80°C for 6 minutes vs. 96°C for 9 minutes) in the atmosphe preheating bin following impregnation was evaluated both with and without the addition of 1.2% sodium sulf In the second trial, the effect of different refining temperatures (refiner house pressures of 4.6 or 6.4 bar(g), 1 or 167°C) was evaluated with different additions of sodium sulfite (0.0, 0.6 or 1,2%) during impregnation. The results from the two trials showed that the increase in refiner house pressure increased the tensile index pulps both with and without addition of sodium sulfite, when compared at certain SEC. However, the increase preheater bin temperature and retention time did not increase the tensile index of pulps but rather led to a sm reduction in tensile index when combined with an addition of 1.2% sodium sulfite. The two different methc used to increase the temperature in the system led to different effects in the disc gap at certain SEC. The disc j temperature was increased by both methods but disc gap was only reduced at certain SEC when the refini temperature was increased by increasing the refiner housing pressure. The difference in the effect on the disc j may hold the answer to the different effects seen in tensile index.

Place, publisher, year, edition, pages
TAPPI Press, 2016
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-29835 (URN)2-s2.0-85006384917 (Scopus ID)978-151083073-8 (ISBN)
Conference
International Mechanical Pulping Conference 2016, IMPC 2016; Jacksonville; United States; 26 September 2016 through 28 September 2016
Note

Conference Paper

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2017-02-07Bibliographically approved
Moilanen, C., Biörkgvist, T., Ovaska, M., Koivisto, J., Miksic, A., Engberg, B., . . . Alava, M. (2016). Modelling and simulation of radial spruce compression to optimize energy efficiency in mechanical pulping. In: International Mechanical Pulping Conference 2016, IMPC 2016: . Paper presented at International Mechanical Pulping Conference 2016, IMPC 2016; Jacksonville; United States; 26 September 2016 through 28 September 2016 (pp. 18-35). TAPPI Press
Open this publication in new window or tab >>Modelling and simulation of radial spruce compression to optimize energy efficiency in mechanical pulping
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2016 (English)In: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, p. 18-35Conference paper, Published paper (Refereed)
Abstract [en]

Energy efficiency of mechanical pulping is rather low. One possibility to facilitate design of more energy efficient defibration is to model and simulate wood compression. This paper presents an effort to model the behavior of Norwegian spruce in radial compression at defibration circumstances. To identify strain rate dependent properties, compression tests were conducted at both quasi-static conditions and at high strain rate. All tests were done at relevant moisture content and up to defibration zone temperatures and strain rates. Additionally the tests were performed both on native wood and on pre-fatigued wood to include behavior dependency of fatigue. The compression tests were monitored on fiber level to separately model behavior of early- and latewood. The chosen continuum model structure for earlywood and latewood was Voight-Kelvin to enable explicit viscous behavior conditioned by strain rate in parallel to the elastic behavior. The presented model is the first wood compression behavior model individually for earlywood and latewood that is based on wood experiments at industrial defibration circumstances. The influences of temperature and pre-fatigue rise are both softening as expected, The utilization of the compression model was demonstrated in an initial multilayered wood compression simulation.

Place, publisher, year, edition, pages
TAPPI Press, 2016
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-29839 (URN)2-s2.0-85006380887 (Scopus ID)978-151083073-8 (ISBN)
Conference
International Mechanical Pulping Conference 2016, IMPC 2016; Jacksonville; United States; 26 September 2016 through 28 September 2016
Note

Funding details: 251748, Academy of Finland through its Centres of Excellence Programme

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2017-01-09Bibliographically approved
Moilanen, C. S., Saarenrinne, P., Engberg, B. A. & Björkqvist, T. (2015). Image-based stress and strain measurement of wood in the split-Hopkinson pressure bar. Measurement science and technology, 26(8), Article ID 085206.
Open this publication in new window or tab >>Image-based stress and strain measurement of wood in the split-Hopkinson pressure bar
2015 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 26, no 8, article id 085206Article in journal (Refereed) Published
Abstract [en]

The properties of wood must be considered when designing mechanical pulping machinery. The composition of wood within the annual ring is important. This paper proposes a novel image-based method to measure stress and planar strain distribution in soft, heterogeneous materials. The main advantage of this method in comparison to traditional methods that are based on strain gauges is that it captures local strain gradients and not only average strains. Wood samples were subjected to compression at strain rates of 1000-2500 s-1 in an encapsulated split-Hopkinson device. High-speed photography captured images at 50 000-100 000 Hz and different magnifications to achieve spatial resolutions of 2.9 to 9.7 μm pixels-1. The image-based analysis utilized an image correlation technique with a method that was developed for particle image velocimetry. The image analysis gave local strain distribution and average stress as a function of time. Two stress approximations, using the material properties of the split-Hopkinson bars and the displacement of the transmitter bar/sample interface, are presented. Strain gauges on the bars of the split-Hopkinson device give the reference average stress and strain. The most accurate image-based stress approximation differed from the strain gauge result by 5%. © 2015 IOP Publishing Ltd.

Keywords
digital image correlation, local strain, split-Hopkinson pressure bar, stress approximation, wood
National Category
Materials Engineering Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-25894 (URN)10.1088/0957-0233/26/8/085206 (DOI)000362220900042 ()2-s2.0-84940398942 (Scopus ID)
Note

CODEN: MSTCE

Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2017-12-01Bibliographically approved
Berg, J.-E., Sandberg, C., Engberg, B. A. & Engstrand, P. (2015). Low-consistency refining of mechanical pulp in the light of forces on fibres. Nordic Pulp & Paper Research Journal, 30(2), 225-229
Open this publication in new window or tab >>Low-consistency refining of mechanical pulp in the light of forces on fibres
2015 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 225-229Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Low consistency, Two-zoned refiners, Fibre length, Refining intensity, Disc gap, Specific edge load, Forces on fibres, Thermomechanical pulping
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-25656 (URN)10.3183/NPPRJ-2015-30-02-p225-229 (DOI)000354806700006 ()2-s2.0-84951952932 (Scopus ID)
Available from: 2015-08-28 Created: 2015-08-18 Last updated: 2017-08-10Bibliographically approved
Engstrand, P. O. & Engberg, B. A. (2014). Filling the Gap - Final Report. Sundsvall
Open this publication in new window or tab >>Filling the Gap - Final Report
2014 (English)Report (Other academic)
Abstract [en]

Executive Summary

As energy prices continue to rise long-term it is very important to come up with suggestions toefficiency-improving solutions based on modifications of the existing refining technology withoutlarge investments. There are several suggestions to relatively large modifications of processsolutions, in design of refiner plate patterns, chip pre-treatment and chip feed strategies to existingrefiners, but these suggestions are often expensive and difficult to implement as the knowledge ofthe mechanisms prevalent in the refiner gap is still insufficient.

To help solving this problem FSCN and CIT initiated the research project “Filling the Gap” togetherwith the companies Dametric, Holmen, Metso Paper, Norske Skog, Pöyry, SCA and Stora Enso cofinancedby the Swedish authorities Vinnova and the Swedish Energy Agency. The research projectwas designed with the intension to show how to improve the electric energy efficiency of chiprefining by means of utilizing fundamental knowledge of wood material properties relevant for chiprefining in relation to refining hypotheses and in combination with output variables from new andimproved refining zone measurement methods as; exact gap distance, temperature-, force- and fibrematerial radial distributions combined with the traditional out/in-put variables normally used. Thepotential of the above mentioned ideas as well as the specific goal of this project was to show how toreach 25% efficiency improvement in existing refiners and at the same time reduce refiner causedstops by >50% and plate wear also by >50%.

The data produced within the project was utilized in two ways:

1. To optimize refining conditions in a static way, i.e. optimization of conditions to maximizeenergy efficiency to reach the functional fibre properties aimed for.

2. To maximize process stability and minimize quality variations at the functional fibreproperties aimed for.

The general conclusion from the project is that we can show that there are great opportunities toimprove electric energy efficiency in refining according to the goal by means of using the abovementioned measurement techniques. More specifically the full-scale trials performed during theperiod 2010 – beginning of 2013 showed the possibility to improve the electric energy efficiency by25% at similar functional properties of the pulp, i.e. a reduction in electricity consumption by 20%. Inorder to implement similar strategies in other TMP or CTMP lines it will just as in this case benecessary to use the same measurement system and evaluation techniques together with verythorough and statistically well controlled pulp/fibre evaluation techniques. It would of course beinteresting to implement the same techniques on as many other production lines as possible withinthe participating companies, but it must be emphasized that the procedure is very demanding. Eachproduction line needs to perform a corresponding detailed process analysis as the one performed inthe mill case study of this research project. Furthermore it would also be necessary to utilize therefiner gap measurement techniques, especially the combination of temperature profile and gapdistance measurements, in a modern but still simple process control system making it easier for theoperator to continuously run the process in a more energy efficient mode. Implementation of thetechniques evaluated in pilot scale within this research project, i.e. fibre distribution and force3distribution measurements, would of course have potential to further improve the process efficiencyas well as improve the fibre property level.

Place, publisher, year, edition, pages
Sundsvall: , 2014. p. 337
Series
Rapportserie FSCN, ISSN 1650-5387 ; 2014:57
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-27662 (URN)
Projects
Fillling the Gap - Förbättrad energieffektivitet och kvalitetsstablilitet vid tillverkning av mekanisk massa
Funder
VINNOVA, Project No.33397-1Swedish Energy Agency, Project no. 31676-1
Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-09-26Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3381-5516

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