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Sandberg, Christer
Publications (10 of 20) Show all publications
Sandberg, C., Berg, J.-E. & Engstrand, P. (2019). Low Consistency Refining Combined with Screen Fractionation: Reduction of Mechanical Pulping Process Complexity. BioResources, 14(1), 882-894
Open this publication in new window or tab >>Low Consistency Refining Combined with Screen Fractionation: Reduction of Mechanical Pulping Process Complexity
2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 1, p. 882-894Article in journal (Refereed) Published
Abstract [en]

Process intensification is a process development methodology aimed at a considerable reduction in the energy consumption and process complexity. The approach has been applied to mechanical pulping process design. A process denoted as HC-LC-S consisting of single stage high consistency (HC) refining, followed by low consistency (LC) refining and screening was evaluated in mill trials at the Holmen Paper Braviken Mill in Sweden. After LC refining, the pulp was screened, and the reject fraction was fed back to LC refining. Two HC primary refiner types were evaluated, namely single disc (SD) and double disc (DD). Double disc chip refining was more suitable than SD refining for the HC-LC-S process because of the higher light scattering and lower shives content of the final pulp. The tensile index and shives content of the pulp produced with the DD-LC-S process was similar to that of the reference process, consisting of single stage DD refining and HC reject refining, but the fibre length and light scattering were somewhat lower. The specific refining energy was approximately 200 kWh/adt lower for the DD-LC-S process compared with the reference. Additionally, the auxiliary specific energy was 100 kWh/adt lower for the HC-LC-S processes, since a number of equipment units were omitted.

Keywords
mechanical pulping, TMP, low consistency refining, screening, fractionation, process intensification
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-35393 (URN)000459494400063 ()2-s2.0-85061297839 (Scopus ID)
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-08-07Bibliographically approved
Sandberg, C., Berg, J.-E. & Engstrand, P. (2018). LC refining combined with screen fractionation – Reduction of system complexity for mechanical pulping. 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 >>LC refining combined with screen fractionation – Reduction of system complexity for mechanical pulping
2018 (English)In: IMPC 2018, Trondheim, Norway, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Process intensification - a process development method used in the chemical process industry has been appliedto mechanical pulping process design. Process intensification is characterized by significant reduction of energyconsumption and process complexity.A process with single stage high consistency (HC) refining followed by low consistency (LC) refining andscreening was evaluated in mill trials at the Holmen Paper Braviken mill, Sweden. After LC refining, pulp wasscreened and the reject was fed back to LC refining. The process is called HC-LC-S. Two different HC primaryrefiner types were evaluated – single disc (SD) and double disc (DD).High intensity DD chip refining was more suitable than single disc refining for the process due to higher lightscattering and lower shives content of the final pulp. It was also easier to reach high enough tensile index beforeLC refining with the DD refining. The DD-LC-S process required 1940 kWh/adt total specific energy for newsgrade TMP, which was 300 kWh/adt lower than the reference TMP line; DD chip refining and HC rejectrefining. The auxiliary specific energy was reduced with 100 kWh/adt.Six unit operations and three chests with agitators and pumps were omitted compared to a conventional TMPline.

Place, publisher, year, edition, pages
Trondheim, Norway: , 2018
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34674 (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
Rubiano Berna, J. E., Sandberg, C., Martinez, D. M. & Olson, J. A. (2018). Theoretical Study of Systems Composed of Low Consistency Refining and Pressure Screening. 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 >>Theoretical Study of Systems Composed of Low Consistency Refining and Pressure Screening
2018 (English)In: IMPC 2018, Trondheim, Norway, 2018Conference paper, Published paper (Refereed)
Abstract [en]

The main objective of this work is to study the LC rening of mechanical pulps from system-design point of view. Mathematical models that describe bre length distribution changes were used to develop aframework capable of simulating LC rening { pressure screening systems. Specically, pressure screening models and comminution models for LC rening that are available in literature together with heuristic and a developed correlation to predict rening power were implemented in MATLAB Simulink toolbox.Later on, this same environment was used to simulate three basic rening systems found in TMP mills. In this study, each considered system was composed of a single rener and single pressure screen arranged in dierent congurations. Performance curves of length-weighed mean bre length were generated from simulation results andused to assess each system behaviour in terms of rener gap, reject ratio and rener power. The impact of some design aspects such as rener size, recirculation and reject ratio were also described. Furthermore,comparisons between systems and some basic recommendations and suggested applications are made. This theoretical framework was compared to industrial-scale data from a TMP mill sub-system. Simulation results showed good agreement with real data, where relative errors between 6-18% on the predicted variables were observed.

Place, publisher, year, edition, pages
Trondheim, Norway: , 2018
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34681 (URN)
Conference
International Mechanical Pulping Conference (IMPC) 2018, May 27-30, 2018, Trondheim, Norway
Available from: 2018-10-08 Created: 2018-10-08 Last updated: 2018-10-08Bibliographically approved
Sandberg, C., Ferritsius, O. & Ferritsius, R. (2017). Energy efficiency in mechanical pulping. In: : . Paper presented at 10th Fundamental Mechanical Pulping Research Seminar, Jyväskylä, Finland, 13–14 of June, 2017.
Open this publication in new window or tab >>Energy efficiency in mechanical pulping
2017 (English)Conference paper, Published paper (Refereed)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34661 (URN)
Conference
10th Fundamental Mechanical Pulping Research Seminar, Jyväskylä, Finland, 13–14 of June, 2017
Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-10-09Bibliographically approved
Sandberg, C., Berg, J.-E. & Engstrand, P. (2017). Low consistency refining of mechanical pulp - system design. TAPPI Journal, 16(7), 419-429
Open this publication in new window or tab >>Low consistency refining of mechanical pulp - system design
2017 (English)In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 7, p. 419-429Article in journal (Refereed) Published
Abstract [en]

Many mechanical pulping mills use low consistency (LC) refining for energy efficient fiber development. In this study, energy efficiency and pulp quality were evaluated for six processes, of which four included LC refining. We studied two different types of chip refiners - single disc (SD) and double disc (DD) - with LC refining in the main and reject lines. All process combinations have been used in the Holmen Paper Braviken mill, Sweden, to make thermomechanical pulp for printing papers. LC refining was more energy efficient than high consistency (HC) refining at certain tensile index increases in all evaluated combinations. LC refining in the main line had somewhat higher energy efficiency than did LC refining in the reject line. The type of chip refiner (DD or SD) did not affect the efficiency or pulp property development in LC refining. The process with a combination of DD chip refining and LC refining had the highest energy efficiency (tensile index at certain specific energy consumption). All processes with LC refining produced pulp with somewhat lower light scattering and fiber length than did the corresponding system with only HC refining. Thus, for printing papers, the best combination was LC refining with DD chip refining. LC refiners seem to have a narrow range in specific energy for maximum energy efficiency and a good balance between tensile index increase and fiber length reduction. Much higher specific energy was applied on reject pulp. However, the reject share was only around 30%. The LC refining specific energy, based on main line production, was around 80 kWh/air-dried metric ton (a.d. metric ton), whereas up to 180 kWh/a.d. metric ton was applied in main line.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-31894 (URN)000411860500005 ()2-s2.0-85026809547 (Scopus ID)
Available from: 2017-10-18 Created: 2017-10-18 Last updated: 2017-11-29Bibliographically approved
Nelsson, E., Paulsson, M., Sandberg, C., Svensson-Rundlöf, E. & Engstrand, P. (2017). Low dosage sulfite pretreatment at different refining temperatures in mill scale TMP production. Nordic Pulp & Paper Research Journal, 32(1), 59-69
Open this publication in new window or tab >>Low dosage sulfite pretreatment at different refining temperatures in mill scale TMP production
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2017 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 1, p. 59-69Article in journal (Refereed) Published
Abstract [en]

The effects of low dosage sodium sulfite ( Na2SO3) pretreatment (0, 0.6 and 1.2% on bone dry wood, pH 9) at two different refining temperatures (4.6 and 6.4 bar(g) refiner housing pressure) were evaluated for production of thermomechanical pulp with a double disc refiner in mill scale using Norway spruce wood at Braviken paper mill (Holmen Paper AB, Sweden). The sulfonate content of the pulps was not affected by the different refining temperatures and was 0.29% (as Na2SO3 equivalents) for the highest sulfite addition.

Tensile index at constant SEC was increased by 3.2 Nm/g when the refining temperature was increased, and by 8.6 Nm/g when 1.2% sodium sulfite was added. The effects were additive and led to an increase in tensile index of similar to 12 Nm/g at constant SEC when combined and would enable a reduction in SEC of 380 kWh/bdt (similar to 20%) to similar tensile index. The degree of delamination and internal fibrillation of the fibers was increased by both increased refining temperature and sulfite addition.

Pulp brightness was slightly reduced (<= 0.4% ISO) by increased refining temperature and increased (2-3% ISO), when sodium sulfite was added. Spectra of reflectance factors (360-740 nm) were used to study the optical properties of produced pulps.

Keywords
Double disc refining, Energy reduction, Mill scale, Norway spruce, Pulp properties, Refining temperature, Sulfite pretreatment, TMP
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-27332 (URN)10.3183/NPPRJ-2017-32-01-p059-069 (DOI)000398384400008 ()2-s2.0-85016434323 (Scopus ID)
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2017-12-18Bibliographically approved
Sandberg, C., Berg, J.-E. & Engstrand, P. (2017). Process intensification in mechanical pulping. Nordic Pulp & Paper Research Journal, 32(4), 615-622
Open this publication in new window or tab >>Process intensification in mechanical pulping
2017 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 4, p. 615-622Article in journal (Refereed) Published
Abstract [en]

Process intensification is a term used in the chemical process industry for major improvements in the process design leading to radical changes in process complexity, equipment size and efficiency. We suggest that a similar approach is applied in the pulp and paper industry. We have focused on the production of mechanical pulp, but a similar approach can be applied to other areas within the pulp and paper industry. Inspired by process intensification methodology, we suggest five principles for development of the mechanical pulping process. Three fundamental principles; 1. Break up the wood and fibre wall structure in the right positions. 2. Give each fibre, of certain morphology, the same processing experience. 3. Optimize the applied mechanical forces and the physiochemical state of the wood and fibre material.  and two system oriented principles; 1. Select wood raw material based on final product specifications. 2. Design the process to facilitate observability, controllability and maintenance. Implications of these principles on process design and future challenges for mechanical pulping are discussed.

Keywords
Energy efficiency, High intensity, Low consistency refining, Mechanical pulping, Process control, Process intensification, Softening, TMP
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-32571 (URN)10.3183/NPPRJ-2017-32-04-p615-622 (DOI)000418122100012 ()2-s2.0-85052688960 (Scopus ID)
Projects
e2mp, energy efficient mechanical pulping
Funder
Knowledge Foundation, 20100281Swedish Energy Agency, 32326-1
Available from: 2017-12-21 Created: 2017-12-21 Last updated: 2018-10-03Bibliographically approved
Ferritsius, R., Sandberg, C., Ferritsius, O., Rundlöf, M., Daniel, G., Mörseburg, K. & Fernando, D. (2016). Development of Fiber Properties in Full Scale HC and LC Refining. In: TAPPI conference proceedings: . Paper presented at 2016 International Mechanical Pulping (IMPC) Conference. TAPPI Press
Open this publication in new window or tab >>Development of Fiber Properties in Full Scale HC and LC Refining
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2016 (English)In: TAPPI conference proceedings, TAPPI Press, 2016Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
TAPPI Press, 2016
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-34668 (URN)
Conference
2016 International Mechanical Pulping (IMPC) Conference
Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-10-09Bibliographically approved
Sandberg, C., Engstrand, P. & Berg, J.-E. (2016). System Aspects on Low Consistency Refining of Mechanical Pulp. In: TAPPI 2016 International Mechanical Pulping Conference (IMPC): . Paper presented at 2016 International Mechanical Pulping Conference (IMPC), September 26 -28, 2016, Jacksonville, US (pp. 485-495). TAPPI Press, 1
Open this publication in new window or tab >>System Aspects on Low Consistency Refining of Mechanical Pulp
2016 (English)In: TAPPI 2016 International Mechanical Pulping Conference (IMPC), TAPPI Press, 2016, Vol. 1, p. 485-495Conference paper, Published paper (Refereed)
Abstract [en]

Several combinations of high consistency (HC) and low consistency (LC) refiners were evaluated both in main line and reject line for production of pulp for printing papers. HC-LC processes were compared with processes with only HC refining. Processes with two different types of chip refiners were studied – single disc (SD) and double disc (DD). All process combinations were evaluated during continuous production in the Holmen Paper Braviken mill, Sweden. The purpose of this work was to evaluate energy efficiency and pulp quality for the processes.

LC refining was more energy efficient than HC refining for certain tensile index increase in all evaluated combinations. The highest energy efficiency was attained when LC refining was utilized in main line, but the difference was small compared to application on reject. Much higher specific energy was applied on reject pulp, but since the reject share was only around 30%, the LC refining specific energy, based on main line production, was around 80 kWh/air dry ton (adt) whereas up to 180 kWh/adt was applied in main line.

The combination of DD chip refining and LC refining had the highest energy efficiency (tensile index at certain specific energy consumption) and produced pulp with somewhat lower fibre length but higher light scattering and lower shives content compared to a line with only SD HC refining. Thus, for printing papers it seems beneficial to combine LC refining with high intensity HC chip refining. All processes with LC refining had lower light scattering and fibre length compared to the corresponding system with only HC refining.

Place, publisher, year, edition, pages
TAPPI Press, 2016
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-29540 (URN)2-s2.0-85006494192 (Scopus ID)978-151083073-8 (ISBN)
Conference
2016 International Mechanical Pulping Conference (IMPC), September 26 -28, 2016, Jacksonville, US
Projects
e2mp
Funder
Swedish Energy Agency, 32326-1Knowledge Foundation, 20100281
Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2017-01-09Bibliographically approved
Sandberg, C. & Berg, J.-E. (2015). Effect of flow recirculation on pulp quality and energy efficiency in low consistency refining of mechanical pulp. Nordic Pulp & Paper Research Journal, 30(2), 230-233
Open this publication in new window or tab >>Effect of flow recirculation on pulp quality and energy efficiency in low consistency refining of mechanical pulp
2015 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 230-233Article in journal (Refereed) Published
Abstract [en]

The effect of pulp flow recirculation on energy efficiency and pulp properties development in low consistency refining of TMP has been studied. Trials were made with TwinFlo 58 refiners in two mills in Sweden. The refiners were operated at constant specific refining energy but different flow conditions. No effect of recirculation was seen on refining energy efficiency, pulp quality or fibre wall delamination/internal fibrillation. At high degree of recirculation though, a somewhat larger fibre length reduction was seen. This means that a large degree of recirculation can be used to attain a high specific energy in one stage low consistency refining, without significant negative effects on fibre properties. If a high specific energy input is desirable, it is more cost effective to install one large refiner with recirculation compared to several small without recirculation in series. When recirculation was increased by means of increased flow through the refiner, the outlet pressure dropped. The lower pressure drop over the refiner probably decreased the internal recirculation between rotor and stator, which could explain the observation that there was little effect on fibre development by recirculation. This means that at certain conditions the distribution in fibre treatment might not increase so much when the outer recirculation is increased, since the internal recirculation might be reduced simultaneously.

Keywords
Low consistency refining, Flow recirculation, Fibre properties, Energy efficiency, Mechanical pulping, TMP
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-25691 (URN)000354806700007 ()2-s2.0-84951927913 (Scopus ID)
Available from: 2015-08-24 Created: 2015-08-18 Last updated: 2017-08-10Bibliographically approved
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