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  • 1.
    Berghel, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Renström, Roger
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Particle mixing and residence time when drying sawdust in a continuous spouted bed2008In: Chemical Engineering and Processing, ISSN 0255-2701, E-ISSN 1873-3204, Vol. 47, no 8, p. 1252-1257Article in journal (Refereed)
  • 2.
    Ekbåge, Daniel
    et al.
    Store Enso Pulp & Paper Asia AB, Karlstad Res Ctr, POB 9090, SE-65009 Karlstad, Sweden..
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Potential energy improvements in a multiple-effect evaporation system: Case studies of heat recovery2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 4, p. 583-591Article in journal (Refereed)
    Abstract [en]

    The primary objective of this study was to quantify the amount of excess energy that is present in the evaporation system of an integrated pulp and paper-board mill and to analyze a number of energy recovery cases. These focus on improving the energy efficiency in the evaporation plant and are mainly based on the process data of performance tests from the full-scale production site. A computer script was developed in order to analyze the process streams and can be used to construct the Grand Composite Curve (GCC) of the evaporation system. In addition, the study identified seasonal variations in the potential excess of energy (higher in warmer weather and lower, or even non-existent, in colder) and suggestions are made as to how this energy may be used in a thermodynamically optimal way. In the case studies, the thermodynamically optimal method of recovering heat involved a combination of sensible heat and flash evaporation, indicating the maximum reduction in steam consumption. For the case of only utilizing sensible heat outside the evaporator system to pre-heat one of the liquor flows, the results indicated a lower reduction in steam but also a lower capital cost.

  • 3.
    Ekbåge, Daniel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Håkansson, Helena
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Time series analysis of refining conditions and estimated pulp properties in a chemi-thermomechanical pulp process2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 3, p. 5451-5466Article in journal (Refereed)
    Abstract [en]

    Frequently sampled process data from a conical disc refiner and infrequently sampled pulp data from a full scale chemi-thermomechanical pulp (CTMP) mill were evaluated to study autocovariance with aspects of potential dynamic modelling applicability. Two trial measurements with an online pulp analyzer at decreased sampling intervals were performed. For variability analysis, time-series containing up to one day of operational data were used. At the chip refiner, the clearest significant autocovariance was identified for the specific electricity consumption, based on the longer sequences. Most of the estimated pulp properties indicated low or non-significant autocovariance, limiting applicability of a specific dynamic model. A mill trial was conducted to investigate the impact from an increase in the conical disc gap on the specific electricity consumption and the resulting freeness. The response time from the gap change in the refiner to measured change in freeness was estimated at 19 min, which was approximately the hydraulic residence time in the latency chest. The relevance of this study lies in applicability of mill-data-driven modelling to capture the dynamics of a specific refining process. Through mill trials the sampling speed of pulp properties was more than doubled to gain insights into short term systematic variations by applying time-series-analysis.

  • 4.
    Ekbåge, Daniel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Håkansson, Helena
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Trial measurements in a CTMP-process to perform time-series analysis of refining conditions and estimated pulp properties2017Conference paper (Other academic)
  • 5. Granevald, Rickard
    et al.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Stenström, Stig
    Evaluation of different forming fabric parameters during vacuum dewatering2004In: Nordic Pulp and Paper Research Journal, 19(4):481-486Article in journal (Refereed)
  • 6.
    Gustavsson, Christer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Addition/Correction: Co-production of pyrolysis oil in district heating plants: Systems analysis of dual fluidized-bed pyrolysis with sequential vapor condensation (Energy and Fuels (2013) 27:9 (5313?5319) DOI: 10.1021/ef401143v)2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6333-6333Article in journal (Refereed)
  • 7.
    Gustavsson, Christer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Co-production of pyrolysis oil in district heating plants: Systems analysis of dual fluidized-bed pyrolysis with sequential vapor condensation2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 9, p. 5313-5319Article in journal (Refereed)
    Abstract [en]

    Flash pyrolysis of biomass yields a liquid applicable as a fuel oil substitute and as a basis for production of chemicals and fuels. Biomass, being a renewable resource, is foreseen to be in increasing demand. An increased usage may lead to scarcity of biomass and emphasizes the need for high-efficiency conversion processes. In this study, the efficiency and capacity aspects of an integration of pyrolysis oil production with a district heating plant by means of dual fluidized-bed technology has been modeled. Further, fractional condensation of the pyrolysis vapors has been applied, enabling part of the condensation energy to be recovered. The concept shows potential for significant pyrolysis oil production while keeping the delivered power and heat constant. The use of excess heat from the pyrolysis production in the district heating net results in a 10% higher overall efficiency than production without heat supply to the district heating net.

  • 8.
    Gustavsson, Christer
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Renström, Roger
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Syngas as an Additional Energy Carrier in the Pulp and Paper Industry: A Mill-Wide System Analysis of a Combined Drying Concept, Utilizing On-Site Generated Gas and Steam2014In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, no 9, p. 5841-5848Article in journal (Refereed)
    Abstract [en]

    Large amounts of thermal energy are required for different unit operations in the pulp and paper industry. Typically, this energy is distributed by means of steam. In this study, introduction of in-situ-generated syngas as an energy carrier in parallel to the predominant steam has been investigated. The examined systems use dual fluidized-bed gasification integrated with a solid fuel boiler of a paper mill together with impingement drying in combination with cylinder drying, a concept enabling higher specific drying rates. The studied systems exhibit reduced overall energy use when compared to the present situation with conventional steam-heated cylinder drying. Cold tar cleaning by condensation/absorption and firing of the syngas in a gas turbine followed by utilization of the exhaust gases for drying are interesting options because this results in reduced biomass consumption with maintained power production.

  • 9.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013), Paper Surface Centre.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Abaca as a reinforcement fibre for softwood pulp2007In: TAPPI Journal, ISSN 0734-1415, Vol. 6, no 10, p. 25-32Article in journal (Refereed)
  • 10.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Handsheet former for the production of stratified sheets2009In: Appita journal, ISSN 1038-6807, Vol. 62, no 4, p. 272-278Article in journal (Refereed)
  • 11.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science.
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Paper strength of both stratified and homogeneous sheets with selected fibres: Part II: Effect of refining.2010Manuscript (preprint) (Other academic)
    Abstract [en]

    The effect on the tensile strength and tearing resistance of refining one of the pulps in mixed and stratified sheets composed of two pulps was examined. The aim was to see whether the stratification has a positive effect on the tensile-tear relationship, or whether the same effect can be reached by adjusting the degree of refining of the pulps. Moderately refined, fractionated abaca (Musa textilis) pulp with a high tearing resistance potential was added to a Swedish softwood sulfate pulp. The softwood pulp was refined to three different dewatering resistances. It was shown that by stratifying the sheets consisting of 50wt% abaca and 50wt% softwood, the tensile index can be increased by refining the softwood pulp while the tearing resistance is retained. The effect of stratification on the tensile-tear relationship thus differs from the effect of refining. However, for sheets composed of 17wt% abaca and 83wt% softwood, no effect of the stratification was observed. The effect of stratification with different amounts of abaca was also examined. In general, the tensile and tear indices of mixed as well as stratified sheets were close to the results predicted by linear mass fraction additivity. However the stratified sheets showed a slightly lower tensile index than predicted and the mixed sheets a slightly higher tensile index.

  • 12.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Paper strength of both stratified and homogeneous sheets with selected fibres: Part I: Effect of fibre properties.2010Manuscript (preprint) (Other academic)
    Abstract [en]

    The effect on paper strength of placing different types of fibres in separate layers instead of homogeneously mixing the fibres was examined. The aim was to displace the tensile‑tear relationship towards higher strength values. Two‑layer laboratory sheets were made in a multilayer handsheet former and compared to single‑layer sheets made from a homogeneous mixture of the two pulps. Fibres with high coarseness (southern pine) and fibres with a high fibre length (abaca, Musa textilis) were added to a Swedish softwood sulfate pulp. Placing the different fibres in separate layers was shown to give a higher tearing resistance but a lower tensile strength than mixing the fibres. The sheets containing southern pine showed results as expected, based on linear mass fraction additivity and the differences in density between the sheets, whereas the sheets containing abaca indicated a synergism for tensile strength in the mixed sheets. The results are discussed with respect to differences in load distribution in the sheets during the tensile and tear tests. It is suggested that the high tear index of the stratified sheets is because the degree of bonding is at a low level in the southern pine and abaca layers, while the high tensile index of the stratified sheets is a result of an increased activation of the additive fibres in the network together with the more flexible softwood fibres. Fibre length seems to be more important than fibre coarseness for achieving a positive effect on paper strength of stratification.

  • 13.
    Karlsson, Hanna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Stolpe, Lennart
    Karlstad University, Faculty of Technology and Science.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    The effect on paper strength of man-made fibres added to a softwood kraft pulpManuscript (preprint) (Other academic)
  • 14.
    Kullander, Johan
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Barbier, Christophe
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Evaluation of furnishes for tissue manufacturing; additivesArticle in journal (Refereed)
    Abstract [en]

    Additives are widely used in the tissue manufacturing process to facilitate the operation of the tissue machine and to improve tissue paper properties like wet strength, softness and water absorbency. Chemical retention and drainage programs are created to enhance the runnability of the tissue machine. A raise in dryness in the wet end of the tissue machine can lead to huge savings during the manufacturing process.

    In this work, the effect of 4 different additives on vacuum dewatering, wet pressing and paper properties was evaluated. Conditions representative for tissue machines regarding vacuum levels and dwell times were chosen. Paper properties relevant for tissue, like wet strength and absorption were measured on non-creped papers. Water retention and thermoporometry were used to determine the pore structure of the fibres.

    The solids content after vacuum dewatering and wet pressing is shown to be unaffected by addition of any of the four additives used in this study. The dryness after wet pressing is however increased by addition of a PAE-resin to the stock which probably is due to crosslinking in the fibre wall. Thermoporometry shows that the PAE-resin reduces the volume of both micro- and macropores which will leave less water deposited in the fibre wall. Tensile index is increased with the PAE-resin and further increased by addition of a flocculant and a micropolymer to the stock. Wet strength is increased while absorption capacity is decreased with the PAE-resin. No further effect on the two properties can be seen with additional chemicals in the furnish.

  • 15.
    Kullander, Johan
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Barbier, Christophe
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Evaluation of furnishes for tissue manufacturing; suction box dewatering and paper testing2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 1, p. 143-150Article in journal (Refereed)
    Abstract [en]

    Water removal on a tissue machine becomes progressively more difficult and expensive in each successive zone. A good way to reduce cost can therefore be to improve the dewatering prior to evaporative drying. This can be done by selecting proper raw materials and optimizing the treatment of the fibres in the furnish.

    In this work, four pulps beaten to different levels were studied in vacuum dewatering trials. Mixing of the pulps, common in tissue manufacturing, was also performed. To simulate the suction boxes on a tissue machine, bench-scale laboratory equipment was used. Conditions typically used on a tissue machine regarding dwell times and vacuum levels were chosen. Paper properties relevant for tissue, like wet strength and absorption were measured on non-creped papers. To obtain information about the fibre properties, fibre characterization and microscope studies were also conducted.

    Vacuum dewatering in tissue manufacturing is shown to be affected by the choice of pulp which can be explained by structural differences in the networks caused by variations in fibre properties. Beating has a strong negative impact on the solids contents reached, which is believed to be an effect of both internal and external fibrillation. These results, together with additional data from mixing and paper testing, give a better understanding of how the furnish should be prepared to reduce energy use in the process and still fulfil consumer requirements on properties.

  • 16.
    Kullander, Johan
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Barbier, Christophe
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Evaluation of furnishes for tissue manufacturing: wet pressing2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 5, p. 947-951Article in journal (Refereed)
    Abstract [en]

    Wet pressing is the last operation on the tissue machine in which water can be removed prior to the expensive evaporative drying of the web. An increase in dryness at this stage can lead to major savings during the manufacturing process. A higher solids content can be achieved by suitable selection of raw materials and by optimizing the treatment of the fibres in the furnish. In this work, wet pressing was evaluated with four pulps beaten to different levels in a PFI mill. Wet pressing was done in a dynamic press simulator and conditions representative of tissue machines with regard to nip pressures and dwell times were chosen. Water retention and thermoporometry were used to determine the pore structure of the fibres. Thickness measurements were made to determine the permanent deformation of the sheets after the pressure pulse.

    Wet pressing in tissue manufacturing is shown to be affected by the choice of pulp, which can be explained by differences in pore structure of the fibres and consequently differences in ability to retain water. More water available before pressing leads to more water that can be removed. Beating has a negative impact on the solids contents reached after pressing, which is believed to be an effect of both internal and external fibrillation. These effects of beating seem mainly to affect the dryness after vacuum dewatering, which is also reflected after pressing. Beating delaminates macropores in the fibre wall but has a minor effect on micropores. Both water between the fibres and water in macropores are removed during pressing. These results give knowledge of how the furnish should be prepared in order to reduce energy consumption in the process.

  • 17.
    Lin, Wamei
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Malutta, Raffaelle
    Waste heat recovery by organic rankine cycle (ORC) for moist exhaust gases from paper industry2017In: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), American Society of Mechanical Engineers (ASME) , 2017, Vol. 6Conference paper (Refereed)
    Abstract [en]

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

  • 18.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Air Flow and Compression Work in Vacuum Dewatering of Paper2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 1, p. 39-46Article in journal (Refereed)
    Abstract [en]

    Dewatering on the paper machine takes place by gravity, suction, pressing, and evaporation. Optimizing the operation of the vacuum system is important, since the electricity consumption of the vacuum pumps might be one-fifth of the total electricity consumption of the paper machine. Vacuum dewatering involves large volumes of air penetrating the web. The present study presents four sets of measured air flow rates useful for designing industrial equipment. The mass flux of air increases with increasing applied vacuum and decreases with increasing basis weight. Paper technological parameters, such as fiber size and fiber flexibility, also influence the mass flux. © 2014 Copyright Taylor and Francis Group, LLC.

  • 19.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Air flow through paper during suction box dewatering2012In: IDS 2012: Conference Proceedings / [ed] Chen, X.D., 2012Conference paper (Refereed)
  • 20.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Heat and mass transfer in multicylinder drying: Part I:Analysis of machine data2004In: Chemical Engineering and Processing, 43:1547-1553Article in journal (Refereed)
  • 21.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Heat and mass transfer in multicylinder drying: Part II: Analysis of internal and external transport resistances2004In: Chemical Engineering and Processing, 43:1555-1560, 2004Article in journal (Refereed)
  • 22.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Mathematical models for compressible flow in porous media2014In: Proceedings of the 19th International Drying Symposium / [ed] Julien Andrieu, Roman Peczalski, Séverine Vessot, 2014Conference paper (Refereed)
    Abstract [en]

    Mechanical dewateringcan be accomplished by applying vacuum on one side of the material. In suchapplications, the air flow accompanying dewatering can be substantial and energy-efficient operation requires accurate design and control of the vacuum system. The present study analyses one-dimensional, compressible flow through porous media.Three types of flow are investigated: isothermal, isentropic and adiabatic. The results are presented in terms of relations between dimensionless numbers. The main result is that the difference between assumptions of adiabatic andisothermal flow will be quite small for the majority of foreseeable process conditions.

  • 23.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 13, p. 1587-1597Article in journal (Refereed)
  • 24.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The small-scale production of hydrogen, with the co-production of electricity and district heat, by means of the gasification of municipal solid waste2016In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 106, p. 174-179Article in journal (Refereed)
    Abstract [en]

    Reducing the use of fossil fuels and increasing the recycling of waste are two important challenges for a sustainable society. Fossil fuels contribute to global warming whilst waste causes the pollution of land, water and air. Alternative fuels and innovative waste management systems are needed to address these issues. In this study a gasification process, fuelled with municipal solid waste, was assumed to be integrated into a heat plant to produce hydrogen, electricity and district heat. A whole system, which includes a gasification reactor, heat plant, steam cycle, pressure swing adsorption, gas turbine and compressors was modelled in Microsoft Excel and an energy balance of the system was solved. Data from the scientific literature were used when setting up the heat and mass balances of the gasification process as well as for assessment of the composition of the syngas. The allocation of energy of the products obtained in the process is 29% hydrogen, 26% electricity and 45% district heat. A significant result of the study is the high energy efficiency (88%) during the cold period of the year when the produced heat in the system is utilized for district heat. The system also shows a competitive energy efficiency (56.5%) all year round.

  • 25.
    Nilsson, Lars
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Hauri, Nils
    Gustavsson, Christer
    Renström, Roger
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Consequences of a dew point increase in tissue drying2006Conference paper (Refereed)
  • 26.
    Nilsson, Lars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Karlsson, Victor
    Co-production of pyrolysis oil and district cooling in biomass-based CHP plants: Utilizing sequential vapour condensation heat as driving force in an absorption cooling machine2015In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 79, p. 9-16Article in journal (Refereed)
    Abstract [en]

    The ever-increasing demand for cooling requires new and sustainable ways of producing it. Absorption cooling is one such well-known technique that can be employed, the driving force in which is heat. When a flash pyrolysis process, with sequential vapour condensation, is integrated into a biomass-based combined heat and power plant (CHP plant), excess heat may arise in the condensers. This study demonstrates the utilization of this excess heat in an absorption cooling machine for producing district cooling. The maximum boiler load in the used CHP plant was 80 MW: the excess condenser heat created during the period June–August was 6.4 MW, which resulted in the production of 5 MW district cooling. The production of electrical power increased by 8.6% on a yearly basis, with a base load production during June–August of 2.8 MW. Using an absorption cooling machine increases the energy conversion efficiency of the CHP plant with an integrated pyrolysis process by 1.3% on a yearly basis; the energy efficiency of the pyrolysis process alone increases by 6%. An increased utilization of the condenser heat for district cooling is possible at an almost constant overall energy conversion efficiency and is demonstrated with two additional cases.

  • 27.
    Nilsson, Lars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Stenström, Stig
    Lunds universitet.
    Predicting water removal during vacuum dewatering from fundamental fibre property data2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 265-271Article in journal (Refereed)
    Abstract [en]

    Control of the solids content after vacuum dewatering is vital for efficient control and energy use of the paper machine. Dewatering is a complex function of many parameters such as fibre and pulp properties as well as settings on the paper machine and a predictive model for dewatering will require extensive and detailed studies of the occurring physical phenomena. The hypothesis investigated in the present study is that fibre width and fibre length density measured for fibres suspended in water can be used for estimating the achievable dryness in vacuum dewatering. The hypothesis was tested by comparing model predictions to experimental data for 11 different pulps. The results show that the dryness after vacuum dewatering can be estimated from the fibre length density and the fibre width for the fresh pulps using an elliptical fibre cross-section model with a ratio of 0.48 between the short and long axes. For the dried pulps a lower value was needed to reach a good agreement.

  • 28.
    Nilsson, Lars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Tysén, Aron
    Innventia AB.
    Vomhoff, Hannes
    Innventia AB.
    The influence of grammage and pulp type on through air drying2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 4, p. 651-659Article in journal (Refereed)
    Abstract [en]

    The influence of grammage and pulp type on through air drying was studied. The temperature of a sample was measured during the drying process and the observed temperature changes were used to evaluate the drying process. Laboratory sheets with grammages 15- 60 g/m², from two softwood and two hardwood bleached chemical pulps were used. All samples were analysed with respect to formation, flow resistance, modified permeability, mean drying time, non-uniformity of drying time, and area- and mass-specific drying rate. The pulps had different modified permeabilities but showed similar behaviour when analysed as a function of grammage. A constant value was found for higher grammages, while an increase in modified permeability was found at decreasingly low grammages. Almost all pulp and grammage combinations had similar area-specific drying rates, but the mass-specific drying rates decreased with grammage. However, the samples with lower grammages had mass specific drying rates independent of modified permeability, where samples with increasing grammage showed an increasing dependency. This implies that the drying efficiency at low grammages was not controlled by the volume flow of the drying air. A good correlation was found between energy needed to evaporate water and energy supplied by the drying air as estimated from the surface temperature and air flow measurement. The surface temperature can therefore be used to quantify the drying process.

  • 29.
    Ottosson, Anders
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Berghel, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A mathematical model of heat and mass transfer in Yankee drying of tissue2017In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 35, no 3, p. 323-334Article in journal (Refereed)
    Abstract [en]

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

  • 30. Ottosson, Anders
    et al.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Berghel, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Analogies between heat and mass transfer for estimation of air humidity2013In: Sixth Nordic Drying Conference NDC 2013, Copenhagen, Denmark, 2013Conference paper (Refereed)
  • 31.
    Renström, Roger
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Berghel, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Frodeson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Granström, Karin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Lestelius, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Stawreberg, Lena
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    The drying process from a product perspective2013Conference paper (Refereed)
  • 32.
    Rezk, Kamal
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Forsberg, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Berghel, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Characterizing flow resistance in 3-dimensional disordered fibrous structures based on Forchheimer coefficients for a wide range of Reynolds numbers2016In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 40, no 21-22, p. 8898-8911Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 33.
    Rezk, Kamal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Forsberg, Jan
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Berghel, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Using a Level-Set Model to Estimate Dwell Time in a Vacuum Dewatering Process for Paper,2012Conference paper (Refereed)
  • 34.
    Rezk, Kamal
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Forsberg, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Berghel, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Modelling of water removal during a paper vacuum dewatering process using a Level-Set method2013In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 101, p. 543-553Article in journal (Refereed)
    Abstract [en]

    Water removal in paper manufacturing is an energy-intensive process. The dewatering process generally consists of four stages of which the first three stages include mechanical water removal through gravity filtration, vacuum dewatering and wet pressing. In the fourth stage, water is removed thermally, which is the most expensive stage in terms of energy use.

    In order to analyse water removal during a vacuum dewatering process, a numerical model was created by using a Level-Set method. Various different 2D structures of the paper model were created in MATLAB code with randomly positioned circular fibres with identical orientation. The model considers the influence of the forming fabric which supports the paper sheet during the dewatering process, by using volume forces to represent flow resistance in the momentum equation.

    The models were used to estimate the dry content of the porous structure for various dwell times. The relation between dry content and dwell time was compared to laboratory data for paper sheets with basis weights of 20 and 50 g/m2 exposed to vacuum levels between 20 kPa and 60 kPa. The comparison showed reasonable results for dewatering and air flow rates. The random positioning of the fibres influences the dewatering rate slightly. In order to achieve more accurate comparisons, the random orientation of the fibres needs to be considered, as well as the deformation and displacement of the fibres during the dewatering process.

  • 35.
    Rezk, Kamal
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Forsberg, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Berghel, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Simulation of water removal in paper based on a 2D Level-Set model coupled with volume forces representing fluid resistance in 3D fiber distribution2015In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 33, no 5, p. 605-615Article in journal (Refereed)
    Abstract [en]

    A numerical model of a vacuum dewatering process was established with a Level-Set method to simulate two-phase flow in a 2-dimensional paper sheet model with constructed volume forces representing flow resistance in a 3-dimensional environment. Nine cases of various volume force representations were compared to numerical and experimental data. Based on the dry content and dwell time relation, the case with the influence of the paper/wire interface showed the most pleasing result compared to experimental data. Compared to the other numerical cases, considering the blockage of the pore space at the top layer of the forming fabric plays an essential role in determining the flow resistance during the vacuum process. Also, the dynamics of the dewatering rate is captured well with the influence of the blockage of fibers on the top layer of the forming fabric. The peak of the dewatering rate could be investigated further with a higher frequency of sample points on new experimental data.

    The computational time for the two-phase flow models in this study is extensively reduced due to the removal of the internal structure. This distinction enables time efficient simulations of vacuum dewatering process in which several dewatering parameters such as level of vacuum, influence of moving vacuum pulse and higher basis weights could be investigated.

  • 36.
    Sjöstrand, Björn
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Barbier, Christophe
    R&D Gruvön, BillerudKorsnäs AB.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Influence on sheet dewatering by structural differences in forming fabrics2016In: Paper Conference and Trade Show (PaperCon 2016); Vol. 2: Proceedings of a meeting held 15-18 May 2016, Cincinnati, Ohio, USA., Peachtree Corners, Georgia: TAPPI Press, 2016, p. 767-776Conference paper (Refereed)
    Abstract [en]

    Forming fabrics for paper manufacturing are designed with great care to enhance both process and products and are accountable for a lot of the performance of paper machines in the forming section, both with regards to energy and quality aspects. Different approaches to the design of the weave pattern and the choice of yarn materials and diameters have given the market different fabric structures. Fabric parameters that have been shown to cause differences in dewatering are caliper, void volume and permeability. To understand how the structure of the forming fabrics affects sheet dewatering selected fabrics have been tested experimentally, with dewatering equipment that simulates vacuum dewatering.

    Dryness of the paper sheet was determined after dewatering and the air volume sucked through sheet and fabric was calculated. The fabrics that were chosen had similar values for all the known parameters previously shown to affect dewatering but had different structures that are defined by the open area (%) in the paper side and the wear side. Tests were performed with three fabric structures and 80 g/m2 softwood sheets. The sheets were made of both unbeaten and highly beaten pulp, and two vacuum levels were used during trials.

    The results show that the fabric structure influences the sheet dewatering rate even if the caliper, void volume and permeability are the same. The air volume sucked through the structure of sheet and wire during the dewatering increased linearly with dwell time indicating that a constant air volume was reached. No significant differences were observed between the different fabrics in terms of the air volume at steady state. The conclusions are that the structure of forming fabrics affects the dewatering rate at certain conditions even with constant air volume and outgoing dryness. This is believed to be connected to (i) the fibers’ penetration of the fabric’s surface during the dewatering process or to (ii) the different resistances to in-plane and thickness- direction flow of the fabrics or to a combination of (i) and (ii). Studies of surface topography are used to explain the phenomenon and numerical simulations will be made in a later study to further evaluate this. 

  • 37.
    Sjöstrand, Björn
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Barbier, Christophe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Rewetting after high vacuum suction boxes in a pilot paper machine2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 4, p. 667-672Article in journal (Refereed)
    Abstract [en]

    Increased energy efficiency is a major concern for all companies today. Not only does the cost efficiency follow energy efficiency but also environmental and sustainability aspects motivate more energy efficient production lines. A study has been made on a pilot paper machine with the purpose to show the magnitude and time of rewetting after high vacuum suction box dewatering. The grammages used in this study were 20 and 100 g/m2 to cover both tissue and printing paper grades. Machine speed was varied from 400 to 1600 m/min and the maximum pressure drop in the suction box was 32 kPa. The pulp used was unbeaten, chemical, fully bleached softwood from Sweden. Rewetting is observed when the dewatering in the suction box is sufficiently high. No rewetting takes place when the dewatering in the suction box is limited due to insufficient pressure drop and dwell time. The time for the rewetting is in the range of 10-50 ms and in this study the maximum rewetting observed is 180 g/m2, or 6.1% decrease in dryness. The mechanisms behind the phenomenon are believed to be capillary forces caused by sufficiently low sheet moisture and expansion of the network. This study shows that rewetting is so fast that it would be difficult to prevent it without changing major machine parameters.

  • 38.
    Sjöstrand, Björn
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Barbier, Christophe
    BillerudKorsnäs AB, R&D Gruvön, Solna, Sweden.
    Ullsten, Henrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Dewatering of Softwood Kraft Pulp with Additives of Microfibrillated Cellulose and Dialcohol Cellulose2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 3, p. 6370-6383Article in journal (Refereed)
    Abstract [en]

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

  • 39.
    Sjöstrand, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Barbier, Christophe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Modeling of forming fabric structure influence on vacuum box dewatering2017In: TAPPI Journal, ISSN 0734-1415, no 8, p. 477-Article in journal (Refereed)
  • 40.
    Stawreberg, Lena
    et al.
    Karlstad University, Faculty of Technology and Science.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Modelling of Specific Moisture Extraction Rate and Leakage Ratio in a Condensing Tumble Dryer2010In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, p. 2173-2179Article in journal (Refereed)
  • 41.
    Stawreberg, Lena
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Nilsson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Potential Energy Savings Made by Using a Specific Control Strategy when Tumble Drying Small Loads2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 102, p. 484-491Article in journal (Refereed)
    Abstract [en]

    Tumble dryers manufactured today are optimised for their maximum capacity, i.e., 6–8 kg of dry load. An average washing load in ordinary households lands at between 2 and 3.5 kg dry load, which implies that the drying load is even smaller. The energy efficiency decreases with reduced drying load. The aim of this study is to establish a mathematical model for studying alternative control strategies for the venting tumble dryer in order to increase the energy efficiency of drying small loads. Two series of test runs were performed: the first series with three different drying loads was used as reference tests for validation of the mathematical model, and the second series was performed with airflow reduction. The model shows good agreement with the test runs. Two control strategies were tested using the model on the smallest drying load. By lowering the heat supply to the heater and by reducing the airflow, the energy efficiency increases by 6% in a small load drying cycle. It was not possible, however, for the investigated dryer, to reach the same energy efficiency for small loads as for the maximum drying load by using a control strategy.

  • 42.
    Tysén, Aron
    et al.
    RISE.
    Vomhoff, Hannes
    Holmen AB.
    Nilsson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Through air drying assisted by infrared radiation: The influence of radiator power on drying rates and temperature2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 4, p. 581-591Article in journal (Refereed)
    Abstract [en]

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

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