| 1. |
- Björkqvist, T., et al.
(författare)
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Towards optimal defibration : Energy reduction by fatiguing pre-treatment
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 168-172
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Tidskriftsartikel (refereegranskat)abstract
- A motive for fatiguing wood prior to defibration would be to reduce the energy consumption needed in mechanical pulping processes. Therefore, the effects of fatiguing pre-treatment were here studied on wood samples, on defibration and also on produced paper. The results indicate that pre-fatiguing changes the mechanic response of wood to be more favorable for harsh defibration which in turn is positive for the process efficiency.
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| 2. |
- Engstrand, Per O., 1955-, et al.
(författare)
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Filling the Gap - Final Report
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Executive SummaryAs 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.
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| 3. |
- Logenius, Louise, 1975-, et al.
(författare)
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Mechanical Properties of Sulphonated Spruce Wood
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The chip-refining stage in the production of high yield pulps as TMP and CTMP determines a large part of the optical and mechanical characteristics of the pulp. Softening of the raw material influences where the fiber walls fracture sites will be located.In the thermomechanical pulping (TMP) processes, refining is performed at temperatures close to the lignin softening temperature, which normally leads to fractures located in the in the primary wall and outer parts of the secondary wall. When wood material is chemically treated before chip-refining the position of the fracture is altered due to that the softening and swelling properties of the fiber walls are changed. In the chemi-thermomechanical (CTMP) process most of the fractures are, therefore, located in the middle lamella or in the primary wall due to introduction of charged groups in the lignin which facilitates the fiber separation. At alkaline pH phenolic lignin structures are sulphonated, at lower pH non-phenolic structures in the lignin are also sulphonated. In the mechanical pulping processes the wood material is subjected to both low strain rates (e.g. plug screw treatment) and high strain rates (refining). Since wood is a viscoelastic material it behaves differently at different strain rates.In this study, sulphonation has been carried out using different sulphite concentrations and pH-levels and we have thereby influenced the sulphonation degree as well as where in the lignin the sulphonation takes place.We used a hydraulic testing machine for low strain-rate testing and a Split-Hopkinson pressure bar device for high strain-rate testing to categorize pretreatments according to their material softening effect and the energy needed for fiber separation. This gives us increased fundamental knowledge of how the mechanical properties of wood are affected by the sulphonation in order to develop new/improved pretreatments.
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| 4. |
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| 5. |
- Moilanen, C., et al.
(författare)
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Local compression behaviour of pre-fatigured and chemically pre-treated wood at high strain rate and high temperature
- 2014
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Konferensbidrag (refereegranskat)abstract
- Radial compression behaviour of spruce wood was here studied in a steam environment at high strain rate and elevated temperatures. The difference in compression characteristics between earlywood and latewood was the main focus of the study. Effects of mechanical and chemical pre-treatments were also investigated. Mechanical pre-treatment affected the E- modulus of the samples more than the chemical pre- treatments. Also elevated temperature softened the wood. No significant compression of latewood could be registered with the methods tested.
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| 6. |
- Nelsson, Erik, 1983-, et al.
(författare)
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Improved energy efficiency in thermomechanical pulping through co-optimixation of intensity by segment design and wood softening by sulfonation
- 2014
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Ingår i: International mechanical pulping conference IMPC 2014. - : PI.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A mill scale trial was performed where chips were mechanically pretreated and impregnated with sodium sulfite (<7.2 g/kg). Pretreated chips were refined in two parallel double disc refiners (RGP68DD) using two different conditions: Turbine™ segment at higher production rate (higher intensity) and Low Shive™ segment at normal production rate (lower intensity). By combining the Turbine segments with chip pretreatment using a sodium sulphite charge of 3.6 g/kg it was possible to reduce the specific energy consumption by 15%, while maintaining pulp properties, compared with the lower intensity refining without pretreatment.
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| 7. |
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| 8. |
- Salmi, Ari, et al.
(författare)
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Repetitive impact loading causes local plastic deformation in wood
- 2012
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 111:2, s. Art. no. 024901-
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between the impactor velocity and the amount of strain localization in a single impact compression of cellular solids is known. However, few studies report on the effects of repeated high frequency compression. We therefore studied the mechanical behavior of Norway spruce, a cellular viscoelastic material, before, during, and after cyclic high frequency, high strain rate, compression. A custom made device applied 5000-20 000 unipolar (constrained compression and free relaxation) fatigue cycles with a 0.75 mm peak-to-peak amplitude at 500 Hz frequency. The consequences of this treatment were quantified by pitch-catch ultrasonic measurements and by dynamic material testing using an encapsulated Split-Hopkinson device that incorporated a high-speed camera. The ultrasonic measurements quantified a stiffness modulus drop and revealed the presence of a fatigued low modulus layer near the impacting surface. Such a localized plastic deformation is not predicted by classical mechanics. We introduce a simple model that explains several changes in the mechanical properties caused by fatiguing. The high speed images indicated pronounced strain localization in the weakest (thinnest walls) parts of the earlywood layers, and revealed strain propagation as a function of time. We present a hypothesis explaining why there is a fatigued layer formed in a piece of wood that has sustained cyclic compression and free relaxation. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3676206]
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| 9. |
- Salminen, Lauri, et al.
(författare)
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Cyclic loading and fatigue of wood
- 2011
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Ingår i: Progress in Paper Physics Seminar2011. - 9783851251630 ; , s. 243-245
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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