| 1. |
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| 2. |
- Bengtsson, Fredrik, 1989, et al.
(author)
-
Modeling of tensile index using uncertain data sets
- 2020
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 35:2, s. 231-242
-
Journal article (peer-reviewed)abstract
- The objective of this investigation is to analyze and model tensile index. Two approaches are used, one based on training and validation data, while the other novel approach tests models using all possible combinations of data points. This approach is focused on small data sets which have here been obtained from nineteen pulp samples at different refining conditions in a full-scale TMP production line with a CD-76 refiner as a primary stage. From each pulp sample twenty handsheet strips for tensile index measurements were performed. Initially, specific energy and the external variables (dilution water feed rates and plate gaps) are used as predictors in a modeling approach based on an adjusted R 2 {R^{2}} approach. Thereafter, the resulting models are compared with a combination of specific energy and internal variables (primarily consistencies) obtained from temperature measurements inside the refining zones using a soft sensor concept. It is found that specific energy and internal variables as predictors outperform the external variables when estimating tensile index.
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| 3. |
- Bengtsson, Fredrik, 1989, et al.
(author)
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On the modeling of pulp properties in CTMP processes
- 2021
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 36:2, s. 234-248
-
Journal article (peer-reviewed)abstract
- The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.
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| 4. |
- Bengtsson, Fredrik, 1989, et al.
(author)
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Raw data for Tensile index estimations from a CD72-refiner
- 2019
-
Reports (other academic/artistic)abstract
- This report presents measurement from a CD72-refiner taken under a five day period. Moreover the data processing steps taken are discussed. The data sets contain measurements of tensile index, specific energy, maximum temperature, dilution water feed rates and plate gaps taken on 19 different occasions. Separate measurements are available from the flat and conical zones. Moreover the data sets included also contains estimated variables, namely consistencies and residence times in the different zones.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Bernhardsson, Anders, et al.
(author)
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Direct self-consistent reaction field with Pauli repulsion : Solvation effects on methylene peroxide
- 1996
-
In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 251:3-4, s. 141-149
-
Journal article (peer-reviewed)abstract
- The properties of methylene peroxide in the gas phase and water have been examined. The solution effects have been modeled with a cavity. To make it possible to optimize the geometry of the cavity, we have added an approximate description of the Pauli repulsion between the solvent and the solute. An efficient direct implementation of the calculation of multicenter multipole operators is also described. We have applied the method to calculate the electric properties of methylene peroxide, a system that is characterized by its near degeneracy between a biradical and a zwitterionic state. As expected, it is shown that solvent effects will stabilize the ionic configuration, resulting in a considerably weakened OO bond and an increased double bond character in the CO bond. The theoretical study has been performed using the multiconfigurational (CAS) SCF method and second-order perturbation theory (CASPT2).
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| 10. |
- Burgdorf, Klaas, 1966, et al.
(author)
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Using multi-rate filter banks to detect internal combustion engine knock
- 1997
-
In: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; , s. 971670-
-
Journal article (peer-reviewed)abstract
- The wavelet transform is used in the analysis of the cylinder pressure trace and the ionic current trace of a knocking, single-cylinder, spark ignition engine. Using the wavelet transform offers a significant reduction of mathematical operations when compared with traditional filtering techniques based on the Fourier transform. It is shown that conventional knock analysis in terms of average energy in the time domain (AETD), corresponding to the signal's energy content, and maximum amplitude in the time domain (MATD), corresponding to the maximum amplitude of the bandpass filtered signal, can be applied to both the reconstructed filtered cylinder pressure and the wavelet coefficients. The use of the filter coefficients makes possible a significant additional reduction in calculation effort in comparison with filters based on the windowed Fourier transform. A knock classification system based on the duration of the knocking process, defined as the time during which the signal exceeds an energy threshold, is presented using different scales. An advantage of this method is that the relation of the duration between different frequency bands can be used to draw conclusions about the presence of multiple knock.
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| 11. |
- Engkvist, Ola, et al.
(author)
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On the relation between retention indexes and the interaction between the solute and the column in gas-liquid chromatography
- 1996
-
In: Journal of chemical information and computer sciences. - : American Chemical Society (ACS). - 0095-2338 .- 1520-5142. ; 36:6, s. 1153-1161
-
Journal article (peer-reviewed)abstract
- Gas-liquid chromatography retention indexes for organic molecules are determined by the interaction between the molecule and the column liquid phase. In this article, a model for calculating the interaction energy between a molecule and a dielectric wall is developed. The model is at least to our knowledge the first attempt to predict retention indexes from the interaction between the molecules and the column. This approach to predict retention indexes is radically different from methods proposed before. Earlier predictions of the retention indexes have been done by a large number of descriptors, which were Linearly correlated to the retention indexes. The developed model has been tested for polycyclic aromatic hydrocarbons mainly with a molecular weight of 302. For the molecules with MW 302 the obtained correlation coefficient is 0.92. A somewhat simpler model is used to fit PAH with different MWs. A correlation coefficient of 0.998 is obtained if the retention indexes were fitted to the logarithm of the interaction energies between the PAHs and the column.
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| 12. |
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| 13. |
- Engstrand, Per, et al.
(author)
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The impact of chemical addition on refining parameters
- 1995
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In: International Mechanical Pulping Conference 1995, Ottawa/St Paul, Canada. - Ottawa, : Ontario Technical Section, CPPA. - 1895288843 ; , s. 281-286
-
Conference paper (other academic/artistic)
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| 14. |
- Eriksson, Karin, 1976, et al.
(author)
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A note on decoupling
- 2009
-
In: Proceedings 15th Nordic Process Control Workshop. ; , s. 36-37
-
Conference paper (other academic/artistic)
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| 15. |
- Eriksson, Karin, 1976, et al.
(author)
-
Internal interconnections impact on control performance in a thermomechanical pulping process
- 2014
-
In: 2009 10th European Control Conference, ECC 2009; Budapest; Hungary; 23 August 2009 through 26 August 2009. - : IEEE. ; , s. 3486-3491
-
Conference paper (peer-reviewed)abstract
- Process integration may indeed be advantageous, particularly in a plant-wide economical sense, but there is also a potential risk that unnecessary difficulties are introduced when it comes to process control. This work identified several internal interconnections in a thermomechanical pulp refiner line as a result of an integration approach adopted during the process design. Firstly, a disturbance sensitivity analysis for the overall production process is carried out. Secondly, a simulation model is constructed and using real process data it is found to successfully reflect the complex dynamic behavior observed at the actual plant. The simulation model can provide indications on how the process performance can be improved by process design modifications. The results suggest that the presence of internal interconnections increases the demands on the control system and also set limits for its performance. If control aspects had been considered at the earliest stages of process development, the possibility to achieve satisfactory process performance could have been significantly improved.
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| 16. |
- Eriksson, Karin, 1976, et al.
(author)
-
Internal interconnections impact on process operability
- 2005
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In: Proceedings of the International Mechanical Pulping Conference, 7-9 June 2005, Oslo, Norway. ; , s. 284-289
-
Conference paper (peer-reviewed)abstract
- A model structure for a TMP production line, including allthe internal interconnections, has been derived. Simulationresults show that the model structure reflects thecharacteristics of the interconnected process and that thenature of the disturbance pattern arises from the fact that so many internal interconnections are present. The model candeliver insight into how modifications of the plant designwould affect the production performance. Besidesperformance, the internal interconnections also influence the process operability, which demonstrates the importance of considering control aspects at the process design stage.
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| 17. |
- Eriksson, Karin, 1976, et al.
(author)
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Modeling approaches for critical process limitations in the operation of thermomechanical pulp refiners
- 2009
-
In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 24:2, s. 231-238
-
Journal article (peer-reviewed)abstract
- Two independent models for describing critical limitations in the operation of wood-chip disc refiners are presentedand compared. One model has been derived using forcedistributions of the axial thrust and the steam pressure inside the refining zone. The other model is based on an extended entropy model, where physical variables like dynamic viscosity and fiber concentration along the radius in the refiner are central. The results suggest that both models are suitable for implementation in process computers for on-line limit protection. Both models predict non-linear dynamic process behavior in operating regions with impending risk of plate clash.
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| 18. |
- Eriksson, K., et al.
(author)
-
On techniques for measuring fiber distribution in refining zones
- 2014
-
In: International Mechanical Pulping Conference, IMPC 2014; Helsinki; Finland; 2 June 2014 through 5 June 2014.
-
Conference paper (peer-reviewed)abstract
- The objective of this research project was to develop measurement techniques to strengthen the knowledge about fiber distribution inside refining zones. A method where light extinction, dynamic pressure and temperature are simultaneously measured at high sampling rates were developed and evaluated on a pilot refiner. The characteristics of the sampled signals were clearly affected by the changes process conditions like changes in production rate, changes in dilution water feed rate and changes in plate gap. It was verified that measurement techniques like this can be used for qualitative studies on fiber distribution inside the refining zones and the results obtained strengthen several earlier hypotheses in the area.
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| 19. |
- Eriksson, Karin, 1976, et al.
(author)
-
Pre-study on the establishment of a research collaboration between industrial energy systems and process control at Chalmers
- 2013
-
Reports (other academic/artistic)abstract
- The aim of the project described in this report has been to create a platform for collaboration between the research areas of industrial energy systems and process control at Chalmers. The authors of this report, belonging to the division of Heat and Power Technology, the Automatic control group and to CIT Industriell Energi, are convinced that a close collaboration between these areas could generate benefits for the process industry including •Improved efficiency with respect to energy•Improved opportunities to ensure satisfying operability•Improved process stability and product uniformity•Intensified utilization of available process equipment•Increased profitabilityIn accordance with the project scope, an inventory of relevant academic literature and of past and ongoing activities within the relevant research community has been conducted. Firstly, this inventory recognizes that researchers at Lehigh University (US), NTNU (Norway) and Carnegie Mellon University (US) have been strongly involved in the establishment of a research field commonly referred to as Integrated design and control. It is found that the research questions that are in the interest of the project partners largely can be attributed to this field. Other related labels used, and investigated as part of the project, are plant-wide control and heat exchanger network control. In a specific section of the report, definitions of important terms like operability, controllability and flexibility are given and commented on. Secondly, international research groups of special interest that has been identified are presented. In this category, I2C2 at University of Auckland and CAPEC at Technical University of Denmark can be mentioned. Relevant publications of the above mentioned research groups and their associates have been studied and are commented on in the report. Special emphasize has been put on review papers and on recent publications. Furthermore, the project has mapped the competences, experience and interest of the project partners. On this basis, the following keywords were identified:•Retrofit•Bio-based processes•Pulp and paper industry•Real life case studies•Industrial co-operation•Economic evaluation•Simulation•Scale up challengesThis list was used during discussions on research questions and project ideas for future collaboration. This project has provided the partners an opportunity to obtain deeper insight into each other’s knowledge and experiences, and, moreover, research areas of common interest have been recognized. To further develop the collaboration, the next step seems to imply joint participation in specific research projects. Research questions of interest and ideas for future projects are presented in the full report. This relates to the prevailing possibilities to apply for research grant - an issue that is addressed lastly in this report. In relation to this it should be noted that there is a program on Industrial Process Automation, supported by Vinnova, the Swedish Energy Agency and Formas, that is soon to be launched. A strategy for monitoring calls from this program as well as other relevant programs was formulated. As a result of the work in this project, it has also been possible to formulate proposals for two specific PhD-student projects within the Preem-Chalmers cooperation. These proposals take the outcome of this project into account and include opportunities to further develop the collaboration between industrial energy systems and process control at Chalmers.
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| 20. |
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| 21. |
- Eriksson, Karin, 1976, et al.
(author)
-
Refining zone temperature control: a good choice for pulp quality control?
- 2009
-
In: 2009 International Mechanical Pulping Conference, IMPC 2009; Sundsvall; Sweden; 31 May 2009 through 4 June 2009. ; , s. 67-74
-
Conference paper (peer-reviewed)abstract
- The results presented in this work show that it is not motivated to use the specific energy for controlling pulp quality in terms of CSF and MFL. This statement is based on the fact that it gives limited dynamic information of the refining process besides what already is given by the three traditional process variables, i.e. production rate, dilution water flow, and hydraulic pressure when predicting CSF and MFL by using ARMAX modeling procedures. Whereas, using the refining zone temperature measurements as inputs to the ARMAX models results in a significant improvement of the ability to predict these pulp quality variables. From a control perspective, this implies that refining zone temperature control is preferable to any concepts based on specific energy when it comes to minimization of pulp quality variations.
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| 22. |
- Eriksson, Karin, 1976, et al.
(author)
-
Refining zone temperature control: a good choice for pulp quality control?
- 2008
-
Reports (other academic/artistic)abstract
- In control strategies for thermomechanical pulp refiners, the relation between energy consumption and production rate,often called specific energy, has been used as a key variable for decades. The importance of controlling the specific energy and thereby indirectly the pulp quality, has been an indisputable axiom for most engineers engaged in the pulp and paper industry. Recently, another competing concept based on refining zone temperature measurements has been presented as an alternative for improved pulp quality control, but so far no comparison between these two concepts has been made.In this study, the two concepts are compared based on a system identification procedure using “Auto Regressive Moving Average eXogenous” (ARMAX) models. The identification procedure adopted creates dynamic models that can provide predictions of the commonly used pulp quality variables Canadian Standard Freeness (CSF) and Mean Fiber Length (MFL). These predictions are all based on thetraditional process variables, i.e. production rate, dilution water flow, and hydraulic pressure, in combination with information of either the specific energy and or the temperature profile.The results show that it is not motivated to use the specific energy for predictions of CSF and MFL, as it giveslimited dynamic information of the refining process besides what already is given by the three traditional process variables. Whereas, using the refining zone temperature measurements as inputs to the ARMAX models results in a significant improvement of the ability to predict the pulp quality variables. From a control perspective, this implies that refining zone temperature control is preferable to any concepts based on specific energy when it comes to minimization of pulp quality variations.
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| 23. |
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| 24. |
- Ferritsius, Olof, et al.
(author)
-
Process considerations and its demands on TMP property measurements - A study on tensile index
- 2017
-
In: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:1, s. 45-53
-
Journal article (peer-reviewed)abstract
- As a vital component in the strive towards improved energy efficiency in the operation of TMP refining processes, this work highlights the importance of well- designed procedures when collecting and analysing pulp properties with respect to process conditions. Process data and pulp from a CD82 chip refiner have been used to show that tensile index has strong covariance with fibre residence time calculated by the extended entropy model. A combination of theoretical and practical analysis methods has shown that, in order to assure representative, reliable results, pulp sampling procedures should comprise composite pulp samples collected during a sampling period of about three minutes. In addition, at least four subsequently collected composite pulp samples should be included in the analysis to effectively dampen effects from fast process variations as well as from slow process drift. An in-depth study on tensile index measurements clarifies that 40-60 strips should be used in the case we studied regardless if machine made paper or handsheets are considered.
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| 25. |
- Ferritsius, Rita, et al.
(author)
-
On energy efficiency in chip refining
- 2014
-
In: International Mechanical Pulping Conference, IMPC 2014. - : Paper Engineers' Association (PI). - 9780000000002
-
Conference paper (peer-reviewed)abstract
- The quality of TMP has been investigated for a CD82 chip refiner both with respect to normal variations and as a result of step changes of production rate, dilution water feed rates and plate gaps. A given level of tensile index was reached over a wide range in specific energy input. The energy efficiency with respect to tensile index decreased if the pulp consistency in the blow line exceeded 55 %. The extended entropy model applied on the refiner showed that the calculated pulp consistency after the flat zone could be extremely high, leading to lower energy efficiency. This was not possible to detect by the measured values for the pulp consistency in the blow line. The short time variations in tensile index correlated more strongly with the model based total residence time in the two refining zones than with the motor load.
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| 26. |
- Ferritsius, Rita, et al.
(author)
-
TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II: Comparison of the five tests
- 2018
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 82-94
-
Journal article (peer-reviewed)abstract
- This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.
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| 27. |
- Ferritsius, Rita, et al.
(author)
-
TMP properties and refining conditions in a CD82 chip refiner. Part I: Step changes of process variables, description of the tests
- 2018
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 69-81
-
Journal article (peer-reviewed)abstract
- The study explores how changes in process variables, residence time and pulp consistency in refining influence the pulp properties. The equipment utilized in this study was a conical disc chip refiner (RGP82CD) producing thermomechanical pulp (TMP). The focus was on the ratio between tensile index and specific energy consumption. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. This showed that the CD-refiner, with the flat and conical refining zone, has a process performance similar to that of a two-stage refiner set-up, and that the consistency in both refining zones is of high importance. Comparing different periods revealed that even if the values of measured blow line consistency are similar, significant differences in the estimated consistency in the flat zone can prevail. Therefore, only monitoring blow line consistency is not enough. Specifically, it was found that the pulp consistency after the flat zone could be very high, considerably higher than in the blow line, and this could have negative effects on tensile index and fibre length.
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| 28. |
- Franzén, Stig, 1943, et al.
(author)
-
EUkraft - En samlad västsvensk EU-satsning
- 2006
-
Reports (other academic/artistic)abstract
- Rapporten behandlar åtgärder för att öka västsvensk närvaro inom olika internationella och europeiska FUD-program med fokus på västsvenska lärosäten. I korthet är slutsatseerna att; 1) olika strategiskt viktiga europeiska aktörer måste identifieras och värderas; 2) proaktivt agerande krävs för att a) skapa allianser med redan framgångsrika aktörer, b) synliggöra västsvenska unika kompetenser, c) etablera västsvenska aktörer i strategiska positioner för utformning av EUs olika program, t ex ramprogram för FUD. Dessutom redovisas en lång lista på nödvändiga specificerade operativa insatser, t ex coaching av nya aktörer, specifika tjänster inom juridik mm utökas, konkreta förberedelser ges monetärt stöd och att systematiskt "intelligence work" genomförs. Samordning av EUkraft bör ske genom en flexibel och virtuell organisation
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| 29. |
- Gjirja, Savo, 1945, et al.
(author)
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Considerations on Engine Design and Fuelling Technique Effects on Qualitative Combustion in Alcohol Diesel Engines.
- 1998
-
In: SAE, Society of Automotive Engineers, Inc. 400 Commonwealth Drive Warrendale, PA 15096-0001 USA, October 1998. - 0768003059 ; :982530, s. 175-187
-
Conference paper (peer-reviewed)abstract
- The paper depicts the main topics of the experimental investigation on alcohol engine development field, aiming at the engineering targets for the emission levels. The first part of this study was focused on engine design optimization for running on ethanol mexed with poly-ethylene glycol (PEG) as ignition improver. It was shown that some design changes in compression ratio, turbine casing, injector nozzle configuration and exhaust pressure governor (EPG) activation, lead to a better engine thermodynamics and thermochemistry. The second objective of this study was the investigation of engine performance and enmission levels, when the ignition improver diethyl ether (DEE) would be generated on board via catalyticallly dehydration of ethanol, and used directly as soluble mixture or separately fumigated. Both alternatives: ether fumigation technique and dissolved ether in alcohol fuel application were conceptually analyzed, and a stand up system based on DEE fumigation was used to determine the optimum DEE-ethanol ratio at any engine operating range. The heat release investigation, when the engine was run on neat ethanol and optimum fumigated DEE, has been indicated earlier combustion, and very short ignition delay. Verified possibilities for using DEE as ignition improver, would lead to a proper version of the on board ether reactor design, which would bring to another solution for ethanol fuelled engines.
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| 30. |
- Gjirja, Savo, 1945, et al.
(author)
-
Ether Fumigation, a New Alternative for the Neat Ethanol Diesel Engine
- 1998
-
In: 31st ISATA, International Symposium on Automotive Technology and Automation, 2nd-5th June 1998 Duseldorf, Germany. ; 31:98EL008, s. 301-309
-
Journal article (peer-reviewed)abstract
- The main purpose of this study has been to investigate the possibilities off using diethylether (DEE) as ignition improver in an ethanol (EtOH) fuelled Volvo AH10A245 diesel engine, previously optimized to run on ethanol with a polyethylene-glycol ignition improver of trade mark "Beraid".Comparisons between DEE and Beraid is included in the study and it is shown that DEE can be used as excellent cetane enhancer due to the low autoignition temperature.A special fuel system based on DEE-EtOH-H2O fumigation, i.e. a small amount of DEE,EtOH and water fed directly into the inlet air duct, has been designed in order to overcome the problems associated with longer ignition delay when running the engine on DEE-EtOH mixture.The optimum enhancer content during the fumigation tests has been determined according to the engine economy and emission levels. The heat release investigation has indicated earlier combustion, and very short ignition delay. The engine runs smoothely and the peak of the heat release is lower than that obtained when the EtOH-Beraid mixture is used. Extensive increase of the negative work during compression stroke, has been avoided by the fumigation technique. Since the NOx formation rate depends strongly on combustion temperature, the DEE-EtOH mixture has been optimized in respect to low NOx level. It has been observed that HC and CO increase with the fumigation flow and engine load due to overlapping time. It is shown that a reduction of the overlapping time by optimizing the camshaft configuration improve the emissions levels and fuel consumption considerably.
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| 31. |
- Gjirja, Savo, 1945, et al.
(author)
-
Investigation on Methanol Engine with DME Fumigation
- 1999
-
In: 32nd ISATA International Symposium on Automotive Technology and Automation, 14th-18th June 1999 - Vienna-Austria. ; 32:99CPE029, s. 83-91
-
Journal article (peer-reviewed)abstract
- Being a non-soot and low NOx emission level fuel, methanol (MeOH) might be considered as an attractive candidate for use in diesel engine. However, having low cetane number and high heat of vaporization, it is not possible to use in diesel engines without engine modifications. In order to take advantages of the alcohol fuels and to avoid engine complexities, which might come along with such modifications, the use of ignition improver additives dissolved in the base fuel is a normal practice. Another promising solution for qualitative combustion in methanol diesel engines is to design an onboard methanol dehydration reactor which can generate dimethyl ether (DME), for use as ignition improver. As a dissolved mixture MeOH-DME requires a special fuel system, the main emphasis was put on the fumigation technique, where a small quantity of DME has been injected into the inlet duct of the engine and the base fuel (MeOH) is conventionally injected through the common rail pump. A research program was set up for evaluating the effectiveness of DME as ignition improver and to compare results with the conventional additive poly-ethylene-glycol (PEG). The heat release analysis has shown that, the fumigated DME undergoes sufficient combustion during compression stroke. Consequently, the temperature and pressure of the gases in the cylinder increase to the point, where the ignition delay of the base fuel (MeOH) is very short. Such precombustion affects the engine performance and emission output, especially NOx and HC levels. It was generally observed that, the regulated emissions were lower and the engine efficiency slightly higher when compared with those obtained when ethanol (EtOH) mixed with PEG or EtOH with fumigated DEE were used. However, the fumigation tests have shown that running on MeOH fuel, the maximum torque and maximum power could not be reached, as it was expected, due to the limited delivery of flow from the fuel pump.Nevertheless, verified possibilities for using DME as ignition improver in a methanol diesel engine, leads to a proper version of the on-board DME reactor design, which would bring to another solution for methanol fuelled engines.
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| 32. |
- Horch, Alexander, et al.
(author)
-
Dynamic simulation of a thermomechanical pulp refiner
- 1997
-
In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 12:4, s. 270-275
-
Journal article (peer-reviewed)abstract
- The aim of this paper is to describe a model for dynamic simulation of a TMP refiner. The temperature profile along the radius of the refiner, outlet consistency and motor load are considered as outputs of the simulation, whereas the chip screw speed and dilution water flow setpoints are the inputs. The dynamic model of the refiner, as such, has been derived from first principles. The motor load and input dynamics, however, are based on black-box identifications. The model has been implemented in MATLAB/SIMULINK. Simulations are compared to corresponding data from experiments with the refiner.
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| 33. |
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| 34. |
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| 35. |
- Karlström, Anders, 1958, et al.
(author)
-
Can we increase the proportion of electrical energy into fibre development in existing HC-refiners?
- 2014
-
In: International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference. - : Paper Engineers' Association (PI).
-
Conference paper (peer-reviewed)abstract
- Currently some 5 % of the electrical energy input in high consistency refining can be attributed to fibre development work. The rest is related to thermo- dynatnical steam generation. Can this unfavourable relation between fibre development and heat generation eventually be improved? A pre-requisite to consistent improvement is a stable process, controlled to targets deduced from profound process evaluations. This statement is elaborated based on two case studies and extensive refiner modelling. It is indicated that a well designed process including its basic process control can with proper refiner control reach energy reductions in excess of 20 %. Proper selections of process targets aligned with choice of segments can further increase the energy reduction in existing lines. These drastic energy reductions will demand concurrent observations and process modelling based on spatial measurements in the refining zone rather than slow, inadequate feedback control from pulp property measurements downstream. This will furthermore stress the need for more advanced control schemes if the full potential is to be captured. Additionally this approach will be a key element in the development of novel process approaches with even larger potential of energy reduction.
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| 36. |
- Karlström, Anders, 1958, et al.
(author)
-
Control strategies for refiners Part I: Soft sensors for CD-refiner control
- 2018
-
In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 28-43
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Journal article (peer-reviewed)abstract
- Internal variables in (C)TMP-refining processes (e. g. temperature, consistency, fiber residence time, backward flowing steam and forces acting upon the chips and pulp) are defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e. g. dilution water feed rate and specific energy) which are not obtained from measurements or physical models of the process in the refining zone. The internal variables are the backbone of physical models and are used in this paper as soft sensors for advanced process control. Besides the shape of the temperature profile, the position of the maximum temperature and the shape of the consistency profiles inside the refining zones are important to control as they are directly linked to the development of different pulp and handsheet properties. To illustrate the capability when using combined modeling and control strategies, the concept is applied on a full scale CD82 refiner. This means both temperature and consistency control in the flat zone and the conical zone, together with an overall estimator for fiber development. Finally, in this paper it is shown that the production can be increased significantly without changing the refiner motor load nor violating the pulp property specification.
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| 37. |
- Karlström, Anders, 1958, et al.
(author)
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Control strategies for refiners Part II: Consistency control in twin-disc refining zones using temperature profile information
- 2018
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 44-57
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Journal article (peer-reviewed)abstract
- Consistency profiles in the refining zones of twin-disc refiners have always been cumbersome to estimate with good accuracy. To overcome such challenges, this paper shows that it is vital to measure temperature profiles between the refining discs to estimate uneven chip/pulp feed distribution. It is also shown that the plate clearance, measured by plate gap measurement devices, is changed dramatically when changing the amount of dilution water to the refining zones asymmetrically. At the same time, the inlet temperature will change as well while the maximum temperature is rather stable. This makes the maximum temperature a good candidate for use when estimating the split of the pulp mass flow rates to the refining zones. This also opens for a new consistency control concept for each refining zone. The findings in this paper have been validated in a commercial TMP production line with two serially linked twin-disc refiners, and it is shown that the pulp and handsheet property variations, in terms of mean fiber length and tensile index, between the refining zones can be reduced considerably when running the refiners with similar consistency in each refining zone.
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| 38. |
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| 39. |
- Karlström, Anders, 1958, et al.
(author)
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CTMP process optimization Part I: Internal and external variables impact on refiner conditions
- 2017
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In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 32:1, s. 35-44
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Journal article (peer-reviewed)abstract
- In this paper, internal variables (e. g. temperature, consistency and fiber residence time) are introduced and defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e. g. dilution water feed rate and specific energy), which are not available as distributed variables from refining zone measurements. The internal variables can be seen as the backbone of physical models and we illustrate that based on a model for a CD-82 refiner in a CTMP production line. Such a model can be used for on-line implementation of soft sensors for advanced process control and it is shown that the refining segment pattern affects the temperature profile. It is particularly interesting to study how the segment parameters in terms of the distributed width of the bars and grooves together with the segment taper affect the back-flowing steam, the cross-sectional area and thereby the fiber residence time. To illustrate the capability to use a modeling strategy it is shown how to reach a 40% reduction in specific energy without violating the required pulp properties.
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| 40. |
- Karlström, Anders, 1958, et al.
(author)
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CTMP Process Optimization Part II: Reliability in Pulp and Handsheet Measurements
- 2017
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 32:2, s. 253-265
-
Journal article (peer-reviewed)abstract
- The objective of this investigation is to analyze and model pulp and handsheet properties using two different approaches based on a reduced set of binomial coefficients for small data sets and constrained linear functions for larger data sets.The properties are linked to process data from the daily CTMP operation in a CD-82 refiner. From a laboratory test program perspective, the test series was extensive and covered 80 pulp samples at different process conditions.In this paper, external variables (dilution water feed rate, specific energy and plate clearance) are compared with internal variables (consistency and fiber residence time) as predictors.It is shown that internal variables as predictors seem to outperform the external variables when estimating CSF Freeness, sheet density, tensile strength, tensile index, elongation to rupture, tensile energy absorption, tensile energy absorption index, tensile stiffness, tensile stiffness index, tear strength, tear index, short-span compressive test index, ISO brightness, Scott-Bond, Z-strength, shives(>= 0.3mm), long fibers and fines.It is important to cover all important dynamics to select the best possible models. Here, the absolute differences between the measured and estimated pulp and handsheet properties are ranked in ascending order, followed by a selection procedure before the polynomial fitting. Moreover, three different sets of chip mixtures were analyzed, and the results shown in this paper indicate that only one model is required for each pulp and handsheet property when using internal variables as predictors.Finally, at a given threshold of shives, it is shown that both Scott-Bond and sheet density can be optimized by changing the consistency and fiber residence time in the refining zones individually. This opens for implementation of new control strategies based on soft sensors.
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| 41. |
- Karlström, Anders, 1958, et al.
(author)
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CTMP Process Optimization Part III: On the Predicition of Scott-Bond, Z-strength and Tensile index
- 2017
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 32:2, s. 266-279
-
Journal article (peer-reviewed)abstract
- Here, the objective is to analyze estimates of the handsheet properties Scott-Bond, Z-strength and tensile index. It is shown that temperature profile measurements from the refining zones make it is possible to derive hidden physical phenomena that are impossible to measure inside the refining zones. Such measures are typical internal variables (consistency and fiber residence time) which can be used as predictors in multilinear models. The analysis is based on process data comprises three different chip mixtures. It is shown that the selected internal variables as predictors outperform the external variables (such as dilution water and plate clearance) in the polynomial fit. This is even more pronounced when validating the models using a holdout set. The methodology outlined in this paper makes it possible to model Scott-Bond, Z-strength and tensile index independently of the type of chip mixture when internal variables are used. It is also shown that the use of mean values of the handsheet properties can deteriorate the final model prediction considerably. Only about 60 % of all handsheet property samples were acceptable for modeling purposes. However, due to the extended laboratory test procedures a ranked and assured database as well as on-line models where possible to derive.
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| 42. |
- Karlström, Anders, 1958, et al.
(author)
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Data-Driven Soft Sensors in Pulp Refining Processes Using Artificial Neural Networks
- 2024
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In: BioResources. - 1930-2126 .- 1930-2126. ; 19:1, s. 1030-1057
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Journal article (peer-reviewed)abstract
- Pulp refining processes are most often complicated to describe using linear methodologies, and sometimes an artificial neural network (ANN) is a preferable alternative when assimilating non-linear operating data. In this study, an ANN is used to predict pulp properties, such as shives (wide), fiber length, and freeness. Both traditional process variables (external variables) and refining zone variables (internal variables) are necessary to include as model inputs. The estimation of shives (wide) results achieved an R2 (coefficient of determination) of 0.9 (0.7) for the training and (validation) sets. Corresponding measures for fiber length and freeness can be questioned using this methodology. It is shown that the maximum temperature in the flat zone can be modeled using the external variables motor load and production instead of the specific energy. This resulted in an R2 of approximately 0.9 for the training sets, while the R2 for the validation set did not reach an acceptable level – most likely due to inherent non-linearities in the process. Additional results showed that the consistency profile is difficult to estimate properly using an ANN. Instead, a model-driven sensor is preferred to be used. The main results from this study indicate that shives (wide) should be the prime candidate when introducing advanced pulp property control concepts.
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| 43. |
- Karlström, Anders, 1958, et al.
(author)
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Data-Driven Soft Sensors in Refining Processes – Pulp Property Estimation Using ARX-Models
- 2023
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In: BioResources. - 1930-2126 .- 1930-2126. ; 18:4, s. 8163-8186
-
Journal article (peer-reviewed)abstract
- This paper focuses on estimation of shives(wide) and fiber length in RGP82CD-refiners using an AutoRegressive eXogenous (ARX) structure in a data-driven soft sensor concept. Both external and internal variables are considered as model inputs. The pulp properties were sampled every 15 min from an on-line device positioned after the latency chest, whereas other process data were sampled every 6 seconds. Notably, despite the high data sampling rate, the development of robust models necessitated a dataset spanning over two months of process information. The external variables studied in this paper were specific energy, the sawmill chip content, plate gaps, and dilution water feed rates to each refining zone. Additional internal variables, such as the inlet flat zone temperature, the maximum temperature, and the periphery temperature in the conical zone, were also used as model inputs. It was concluded that both shives(wide) and fiber length can be estimated with relatively good accuracy although large uncertainties exist in the measured properties. Finally, it was shown that fast pulp property dynamics in the blow-line can be followed, which outperforms current practices of using pulp measurement devices positioned after the latency chest. This offers implementation of more advanced future pulp property control concepts.
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| 44. |
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| 45. |
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| 46. |
- Karlström, Anders, 1958, et al.
(author)
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Fiber energy efficiency Part I: Extended entropy model
- 2014
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In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 29:2, s. 322-331
-
Journal article (peer-reviewed)abstract
- This is the first in a series of papers presenting the development of a comprehensive multiscale model with focus on fiber energy efficiency in thermo mechanical pulp processes. The fiber energy efficiency is related to the defibration and fibrillation work obtained when fibers and fiber bundles interact with the refining bars. The fiber energy efficiency differs from the total refining energy efficiency which includes the thermodynamical work as well. Extracting defibration and fibrillation work along the radius in the refining zone gives information valuable for fiber development studies. Models for this process must handle physical variables as well as machine specific parameters at different scales. To span the material and energy balances, spatial measurements from the refining zone must be available. In this paper, measurements of temperature profile and plate gaps from a full-scale CD-refiner are considered as model inputs together with a number of process variables. This enables the distributed consistency in the refining zone as well as the split of the total work between the flat zone and the CD-zone to be derived. As the temperature profile and the plate gap are available in the flat zone and the CD-zone at different process conditions it is also shown that the distributed pulp dynamic viscosity can be obtained. This is normally unknown in refining processes but certainly useful for all fluid dynamic models describing the bar-to-fiber interactions. Finally, it is shown that the inclusion of the machine parameters will be vital to get good estimates of the refining conditions and especially the split between the thermodynamical work and the defibration/fibrillation work.
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| 47. |
- Karlström, Anders, 1958, et al.
(author)
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Fiber energy efficiency Part II: Forces acting on the refiner bars
- 2014
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 29:2, s. 332-343
-
Journal article (peer-reviewed)abstract
- In this paper it is shown that the defibration and fibrillation work in thermo mechanical pulp refiners can differ significantly dependent on the process conditions. This has a direct impact on the distributed force in the refining zones obtained when the bars hit the fibers or fiber bundles. The distributed force, which is defined as a vector along the surface of the refining segments, is estimated using a model where the total work can be split into reversible and irreversible work. Besides traditional refiner variables such as motor load, dilution water added and inlet-and casing pressures, measurements of temperature profiles in the refining zone and plate gaps from a fullscale CD-refiner are available as inputs. Three data sets are analyzed and it is shown that the shape of the temperature profile and the force distribution vary significantly. This means that the fiber distribution in the refining zone varies as well which affects the final development of the pulp properties. The refining segment pattern and taper play an important role when estimating the force distribution and it is stated that the force distribution close to the contraction part of the flat zone as well as the outer part of the conical section are larger than in other positions. Therefore, specific energy which can be seen as the integral of the total energy distribution along the refining segments cannot be
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| 48. |
- Karlström, Anders, 1958, et al.
(author)
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Fiber energy efficiency Part III: Modeling of bar-to-fiber interaction
- 2014
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 29:3, s. 401-408
-
Journal article (peer-reviewed)abstract
- This paper presents a model for fluid dynamic studies describing the bar-to-fiber interaction in refining processes. The approach is to introduce and validate assumptions for a deeper understanding of physical phenomena between refining bars in a micro-scale perspective. The model is based on Navier-Stokes equations in 2D and special emphasize is put on the pressure dynamics occurring when changing the plate gap, i.e. the distance between refining segments. It is shown that the model can reproduce pressure fluctuations like those obtained in experimentally validated measurements. It is also shown that the pressure varies considerably dependent on the plate gap as well as the position studied along the bar in tangential direction. This is a consequence of varying shear forces between the bars. Moreover, it is stated that the fiber network density variations will be important to describe in more details. Finally, it is shown that the model for the bar-to-fiber interaction can handle different aspects regarding plate pattern design which have significant impact on the fluid dynamics and thereby the final pulp properties in full-scale refiners.
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| 49. |
- Karlström, Anders, 1958, et al.
(author)
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Fiber energy efficiency Part IV: Multi-scale modeling of refining processes
- 2014
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 29:3, s. 409-417
-
Journal article (peer-reviewed)abstract
- Models of thermomechanical pulp processes must handle a large number of physical variables and machine specific parameters at different scales. Some variables, measured in the refining zone, will be invaluable when spanning the material and energy balances and thereby they provide essential information to the models. In this paper, measurements of temperature profile and plate gaps from a full-scale CD-refiner are used as model inputs together with process variables such as motor load, production, dilution water, inlet pressure and casing pressure. Two independent models, a micro-model describing fluid mechanics between the refining bars and an extended entropy model (macro-model) describing the material and energy balances for a complete refiner are used to get a realistic estimate of the pulp dynamic viscosity inside the refining zone. The models comprise a multi-scale concept and it is shown that the variability in the estimated pulp dynamic viscosity is directly related to the fiber energy efficiency in a micro-as well as in a macro perspective. To produce homogeneous pulp quality at energy efficient process conditions, it is concluded that large variations in the pressure pulses must be reduced. This can be performed by optimizing refining segments as well as stabilizing conditions by improved control strategies.
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| 50. |
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