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  • 1. Abel, S
    et al.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Arpagaus, C
    Mazzotti, M
    Stadler, J
    Two-fraction and three-fraction continuous simulated moving bed separation of nucleosides2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1043, no 2, 201-210 p.Article in journal (Refereed)
    Abstract [en]

     A new experimental set-up and a new simulated moving bed (SMB) operation are presented in this work. A desktop SMB unit developed as a modification of the commercial AKTA(TM) explorer working platform has been utilized for the separation of different mixtures of nucleosides. Both two fraction and three fraction SMB separations have been carried out, the latter made possible by the adoption of a new SMB configuration and operating mode (three fraction SMB, 3F-SMB, operation). Experiments demonstrate the feasibility of the 3F-SMB operation, and confirm the trends predicted based on considerations about retention of the components to be separated along the unit. 

  • 2.
    Agthe, Michael
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Wetterskog, Erik
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Salazar-Alvarez, German
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Bergström, Lennart Magnus
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Dynamic growth modes of ordered arrays and mesocrystals during drop-casting of iron oxide nanocubes2014In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, no 8, 1443-1450 p.Article in journal (Refereed)
    Abstract [en]

    The growth modes of self-assembled mesocrystals and ordered arrays from dispersions of iron oxide nanocubes with a mean edge length of 9.6 nm during controlled solvent removal have been investigated with a combination of visible light video microscopy, atomic force microscopy and scanning electron microscopy. Mesocrystals with translational and orientational order of sizes up to 10 μm are formed spontaneously during the final, diffusion-controlled, drop-casting stage when the liquid film is very thin and the particle concentration is high. Convection-driven deposition of ordered nanocube arrays at the edge of the drying droplet is a manifestation of the so called coffee-ring effect. Dendritic growth or fingering of rapidly growing arrays of ordered nanocubes could also be observed in a transition regime as the growth front moves from the initial three-phase contact line towards the centre of the original droplet.

  • 3.
    Aguilar, Wilson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    ZSM-5 is an aluminosilicate with high silica ratio with suitable properties for catalysis, ion exchange, adsorption and membrane applications. ZSM-5 is usually produced industrially from concentrated systems in which there is formation of an amorphous gel phase. Typical syntheses of ZSM-5 require sources of silicon and aluminium, a mineralizer and an organic molecule as so-called templating agent. The silicon and aluminum sources widely used for the synthesis are pure reagent chemicals and in particular quaternary ammonium compounds like tetrapropyl ammonium hydroxides (TPA-OH), are employed as templating agents. Unfortunately, these compounds are rather expensive. Demand for inexpensive sources of aluminosilicates for the synthesis of ZSM-5 has increased during the last two decades. Natural raw materials such as kaolin clay and diatomaceous earth (diatomite) are two potential inexpensive sources of silica and alumina. Moreover, the molecule n-butylamine (NBA) has been reported as a low-cost templating agent to replace the quaternary ammonium compounds. The aim of this work was to show for the first time that leached metakaolinite or diatomite in combination with sodium hydroxide and n-butylamine could be used as inexpensive raw materials for the synthesis of ZSM-5 without using an additional source of silica. After synthesis optimization, both sources of aluminosilicate were found to behave differently during the course of synthesis and led to slightly different products. The chemical composition of the raw materials and the products were determined using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). Crystallinity was examined by X-ray diffractometry (XRD), the morphology was studied by extreme-high-resolution scanning electron microscopy (XHR-SEM) and the specific surface area was estimated from nitrogen adsorption data by the BET method. The chemical composition of individual crystals was determined by energy dispersive spectrometry (EDS). Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and reduced the amount of impurities. The final ZSM-5 products had a SiO2/Al2O3 ratio in the range 20 – 40. The use of leached diatomite allowed reaching higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of mordenite were formed, which was related to the high calcium content of diatomite. Another considerable advantage of diatomite over kaolin is that diatomite does not require heat treatment at high temperature to convert the kaolin to reactive metakaolin. Further characterization of the system by XHR-SEM and EDS at low voltage was carried out in order to understand the nucleation and early growth of the ZSM-5 zeolite crystals. The observations with unprecedented detail strongly suggest that nucleation and the succeeding growth occurs on the gel surface. The growth rates in the various crystallographic directions already at an early stage are such that the shape of the growing crystals resembles that of the final crystals. However, as the early growth is interface mediated, the growth rate along the gel particles is high and the gel particles will become partially embedded inside the growing crystals at an early stage. The Si and Al nutrients are probably transported along the solid/liquid interface and possibly through the liquid in the form of nanoparticles detaching from the gel. The organic template was initially contained in the liquid. However, it remains unclear at which stage the template becomes incorporated in the solid material. EDS at low voltage was also used to gain compositional information about the sodium/calcium ion exchanged products and extraneous phases when kaolin and Bolivian montmorillonite clay were used for the synthesis of zeolite A by alkali fusion. In order to evaluate the cation exchange capacity (CEC) of the synthesized zeolite, ICP-SFMS and EDS were compared. The EDS method used in this work resulted in (Na,Ca)/Al ratios in equivalent moles very close to 1.0 as expected and was therefore found more reliable than ICP-SFMS to measure cation exchange capacity for zeolite A. To summarize, the present work shows that it was possible to synthesize well-crystallized ZSM-5 zeolite from inexpensive raw materials such as leached metakaolin or leached diatomite, sodium hydroxide and n-butyl amine. Furthermore, the crystallization mechanism evidenced in this system might be more general and also apply for other concentrated systems, e.g. those using TPA as structure-directing. Finally, this work displays that EDS at low voltage can provide valuable local compositional information in the field of zeolite synthesis.

  • 4.
    Aguilar, Wilson
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Garcia, Gustavo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-52014In: SpringerPlus, E-ISSN 2193-1801, Vol. 3, no 1Article in journal (Refereed)
    Abstract [en]

    Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO2/Al2O3 molar ratios in the range 20 - 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n-butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.

  • 5.
    Ahlawat, Paramvir
    KTH, School of Chemical Science and Engineering (CHE).
    Modellering och implementering av simultan dubbel gradient kromatografi2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Polypeptides are becoming an important component of the antibiotic therapeutics. The production demand of therapeutic polypeptides is increasing and there is a significant interest in developing more efficient production processes. In pharmaceutical industries, polypeptides are produced as a crude mixture. Reverse phase high performance liquid chromatography (RP HPLC) is used as a typical separation technique to purify the target polypeptide from other impurities. Currently organic modifier gradients are used to elute product peptides separately from impurities. In this work, we add a second, simultaneous counter-ion gradient, in the hope of increasing separation performance and call it double gradient reverse phase chromatography. A general procedure of the model-based optimization of a polypeptide crude mixture purification process was followed to evaluate the effects of the double gradients on industrial chromatographic process. The target polypeptide elution profile was modeled with a bi-Langmuir adsorption equilibrium isotherm. The isotherm parameters of the target polypeptide were estimated by the inverse method. The model parameters of the impurities were regressed from experimental data. The variations of the isotherm parameters with the modifier concentration and counter-ion concentration were taken into account of the adsorption model. After model calibration and validation by comparison with suitable experimental data, Pareto optimization of the process were carried out to analyze the differences between single gradient chromatography and double gradient chromatography. It was observed that the additional linear gradient of counter-ion concentration did not improve the separation process. Conclusively we were able to demonstrate the concept of double gradient reverse phase chromatography within limited time and possible least experimental efforts.

  • 6.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sjöberg, Erik
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, 206–211- p.Article in journal (Refereed)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 7.
    Aldaeus, F.
    et al.
    RISE, Innventia.
    Schweinebarth, H.
    RISE, Innventia.
    Törngren, P.
    RISE, Innventia.
    Jacobs, A.
    RISE, Innventia.
    Simplified determination of total lignin content in kraft lignin samples and black liquors2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, no 4, 601-604 p.Article in journal (Refereed)
  • 8.
    Alevanau, Aliaksandr
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Study of pyrolysis and gasification of biomass from the self-organization perspective2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on the analysis of kinetics of i) low-temperature pyrolysis of gaseous hydrocarbons, ii) high-temperature steam gasification of char of wood pellets (>700oC), iii) high temperature pyrolysis of straw pellets in an atmosphere of argon and steam, and iv) high temperature pyrolysis of slices of transversally cut wooden sticks. The results of the kinetic measurements in the high-temperature cases are approximated using a least-square based optimization software, which was specially developed to analyse kinetics prone for deviation from the Arrhenius law.In the thesis a general analysis of the researched materials and kinetics of their pyrolysis and gasification is presented from the self-organization perspective. The energy transfer phenomena in both the pyrolysis and gasification processes of biomass are discussed with an emphasis on an analysis of basic phenomena involving the self-organized dynamics on fractal structures in the chosen biomass samples.

  • 9.
    Alvfors, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Arnell, Jenny
    IVL.
    Berglin, Niklas
    Innventia.
    Björnsson, Lovisa
    LU.
    Börjesson, Pål
    LU.
    Grahn, Maria
    Chalmers/SP.
    Harvey, Simon
    Chalmers.
    Hoffstedt, Christian
    Innventia.
    Holmgren, Kristina
    IVL.
    Jelse, Kristian
    IVL.
    Klintbom, Patrik
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lidén, Gunnar
    LU.
    Magnusson, Mimmi
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Pettersson, Karin
    Chalmers.
    Rydberg, Tomas
    IVL.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Stålbrand, Henrik
    LU.
    Wallberg, Ola
    LU.
    Wetterlund, Elisabeth
    LiU.
    Zacchi, Guido
    LU.
    Öhrman, Olof
    ETC Piteå.
    Research and development challenges for Swedish biofuel actors – three illustrative examples: Improvement potential discussed in the context of Well-to-Tank analyses2010Report (Other academic)
    Abstract [en]

    Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.

  • 10.
    Andersson, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Semi-deterministic chemo-mechanical model of boundary lubrication2012In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 156, 343-360 p.Article in journal (Refereed)
    Abstract [en]

    A model for tribofilm growth is developed. The model is used in combination with numerical contact mechanics tools to enable evaluation of the combined effects of chemistry and contact mechanics. The model is tuned with experimental data and is thereafter applied to rough surfaces. The growth of the tribofilm is evaluated for 3 different contact cases and short-term tribofilm growth behaviour is analyzed. The results show how tribofilms grow in patches. The model is expected to be used as a tool for analysis of the interaction between rough surfaces.

  • 11.
    Anugwom, Ikenna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku FI-20500, Finland.
    Rujana, L.
    Wärnå, J.
    Hedenström, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku FI-20500, Finland.
    In quest for the optimal delignification of lignocellulosic biomass using hydrated, SO2 switched DBU MEASIL switchable ionic liquid2016In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 297, 256-264 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, various process parameters aiming at optimal short-time-high-temperature (STHT) process were studied upon fractionation of Nordic woody biomass into its primary constituents. Highly diluted, aqueous 'SO2-switched' switchable ionic liquid (SIL) based on an alkanol amine (monoethanol amine, MEA) and an organic superbase (1,8-diazabicyclo-[5.4.0]-undec-7-ene, DBU) was applied. The ultimate goal was to develop a more sustainable, environmentally friendly and cost efficient systems for efficient separation of the lignocellulosic fractions. One of the main products from the SIL fractionation is cellulose-rich pulp with very low lignin content, complemented with hemicelluloses. The NMR results reveal that substantial removal of lignin occurs even when relatively low amount of SIL was used. Further, a simple mathematical model describing the dissolution of the lignocellulose components (hemicellulose and lignin) and weight loss of wood as a function of time is described. Moreover, the most efficient process involved the use of SpinChem (R) rotating bed reactor while upon use of a flow through (loop) reactor, promising results were obtained at a treatment time of 4 h. Still, all the reactor systems studied gave rise to a rather low removal of hemicelluloses which mean that the solvent system is primary selective towards lignin dissolution.

  • 12.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Idiyatullin, Zhamil Sh
    Kazan National Research Technological University.
    Potapova, Elisaveta
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 20, 5480-5487 p.Article in journal (Refereed)
    Abstract [en]

    We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols - C9H19C6H 4O(C2H4O)nH, where n = 6, 8, 9, 10, or 12 - in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols

  • 13.
    Arkhipov, Victor
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Potapova, Elisaveta
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Micelle structure and molecular self-diffusion in isononylphenol ethoxylate–water systems2013In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, no 7, 424-430 p.Article in journal (Refereed)
    Abstract [en]

    The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated

  • 14.
    Arman, S.Y.
    et al.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Omidvar, H.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Tabaian, S.H.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Sajjadnejad, M.
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Fouladvand, Shahpar
    Department of Mining and Metallurgical Engineering, Amirkabir University of Technology.
    Afshar, Sh.
    Department of Chemistry, Iran University of Science and Technology.
    Evaluation of nanostructured S-doped TiO2 thin films and their photoelectrochemical application as photoanode for corrosion protection of 304 stainless steel2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Article in journal (Refereed)
    Abstract [en]

    Undoped and S-doped TiO2 thin films were prepared on titanium substrate through a sol–gel method. The photoelectrochemical behavior of S-doped TiO2 thin film (as photoanode) was studied. The effect of Sulfur doping on structural, optical and morphological properties of TiO2 was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR, UV–ViS and FE-SEM. Superiority of the S-doped TiO2 film was shown through taking advantage of linear sweep voltametry measurement, open-circuit potential of 304 stainless steel as well as potetiodynamic polarization technique. Results showed that S-doped TiO2 thin film is an efficient photoanode with long term stability (several hours).

  • 15.
    Asfaw, Habtom Desta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Tai, Cheuk-Wai
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Emulsion-templated graphitic carbon foams with optimum porosity for 3D Li-ion microbatteriesManuscript (preprint) (Other academic)
  • 16.
    Asfaw, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Tai, Cheuk-Wai
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Surface-oxidized NbO2 nanoparticles for high performance lithium microbatteriesManuscript (preprint) (Other academic)
  • 17.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    González, N.
    Lualdi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    The effect of catalyst pellet size on nickel carbonyl-induced particle sintering under low temperature CO methanation2016In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 514, 91-102 p.Article in journal (Refereed)
    Abstract [en]

    Abstract The present work aims to evaluate the effect of catalyst pellet size on deactivation due to nickel carbonyl-induced particle sintering. For that purpose, a γ-Al2O3-supported nickel catalyst was prepared and tested under low temperature and high CO partial pressure. A total of four different pellet sizes were employed in the present study. It was found that the deactivation rate decreases with increasing pellet size. A very severe deactivation was observed when using small pellets. Large pellets exhibited instead a more stable performance. This difference in catalyst stability was explained by X-ray diffraction analyses which revealed that the growth of the nickel particles was very severe when using small pellets. An evaluation of heat and mass transfer phenomena in these four pellets was also conducted. It was found that, under the present low temperature reaction conditions, the temperature at the catalyst external surface can greatly differ from that in the bulk gas when using sufficiently large pellets. It was also shown that, for large pellets, the major part of the interior of the catalyst is exposed to negligible CO partial pressures and high temperatures, fact that can reduce the potential for nickel carbonyl formation.

  • 18.
    Barrientos, Javier
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Montes, V.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Further insights into the effect of sulfur on the activity and selectivity of cobalt-based Fischer–Tropsch catalysts2016In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 275, 119-126 p.Article in journal (Refereed)
    Abstract [en]

     A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.

  • 19.
    Becker, Sebastian
    KTH, School of Chemical Science and Engineering (CHE).
    Inverkan av olika joner och jonconcentrationer på porstorleksfördelningen i trämassa-fibrer2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The basic ingredient of paper is the individual wood fibers. The property of the fibers depends on a variety of factors e.g., method of pulp production and processing. The final sheet quality depends in part on how the fibers interface between each other and therefore factors that affect the fiber size are of interest.

    The flexibility of the fibers depends in part on the pore water i.e., the fiber swelling. The sheet becomes less flexible at low water content which gives a loss in strength. Thus it becomes desirable to increase the water uptake.

    The experimental investigation described in this report consists of exposing the wood fibers to different ions and ionic strength and then measure the pore size by thermoporosimetry where a DSC (Differential Scanning Calorimeter) is used. DSC measures the freezing point of water in the pores of the wood fibers. As the freezing point varies with the pore size the size distribution can be determined.

    The results show that there are complications with thermoporosimetry measurements at different ion concentrations. The strength of the ionic solutions will contribute to a fictitious pore volume, which makes analysis difficult to interpret.

  • 20.
    Bertini, Lorenzo
    KTH, School of Chemical Science and Engineering (CHE).
    Modeling and Optimization of a Fuel Cell Hybrid System2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project was the modeling, optimization and prediction of a hybrid system composed of a fuel cell, a dc-dc converter and a supercapacitor in series. Lab tests were performed for each device to understand their behavior, and then each one was modeled using software (Simulink). The validation of the model was done by comparing its results with measured data; finally the model was used for the optimization and the prediction of the hybrid system

  • 21.
    BHANDARI, SHASHANK
    KTH, School of Chemical Science and Engineering (CHE).
    Design of a solvent recovery system in a pharmaceutical manufacturing plant2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Solvents play a crucial role in the Active Pharmaceutical Ingredient (API) manufacturing and are used in large quantities. Most of the industries incinerate the waste solvents or send it to waste management companies for destruction to avoid waste handling and cross-contamination. It is not a cost effective method and also hazardous to the environment. This study has been performed at AstraZeneca’s API manufacturing plant at Sodertalje, Sweden. In order to find a solution, a solvent recovery system is modeled and simulated using ASPEN plus and ASPEN batch modeler. The waste streams were selected based on the quantity and cost of the solvents present in them. The solvent mixture in the first waste stream was toluene-methanol in which toluene was the key-solvent whereas in the second waste stream, isooctane-ethyl acetate was the solvent mixture in which isooctane was the key-solvent. The solvents in the waste stream were making an azeotrope and hence it was difficult to separate them using conventional distillation techniques. Liquid-Liquid Extraction with water as a solvent followed by batch distillation was used for the first waste stream and Pressure Swing Distillation was used for the second waste stream. The design was optimized based on cost analysis and was successful to deliver 96.1% toluene recovery with 99.5% purity and 83.6% isooctane recovery with 99% purity. The purity of the solvents was decided based on the quality conventions used at AstraZeneca so that it can be recovered and recycled in the same system. The results were favorable with a benefit of €335,000 per year and preventing nearly one ton per year carbon dioxide emissions to the environment. A theoretical study for the recovery system of toluene-methanol mixture was performed. The proposed design was an integration of pervaporation to the batch distillation. A blend of polyurethane / poly(dimethylsiloxane) (PU / PDMS) membrane was selected for the separation of methanol and toluene mixture. The results of preliminary calculations show 91.4% toluene recovery and 72% methanol recovery with desired purity.

  • 22.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Microstructural characterization of iron ore green pellets2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis work was to develop new methodologies to characterize iron ore green pellets, in wet and dry state. The new characterization methods applied and developed in this work were mainly based on scanning electron microscopy (SEM) to gather both qualitative and quantitative data on different components of the pellets, i.e. mineral particles, water, bentonite and entrapped bubbles.In a first attempt to preserve the structure of wet iron ore green pellets by freezing before investigation by cryogenic SEM, wet pellets were frozen in liquid nitrogen by direct plunging or a new method developed in the present work denoted unidirectional freezing. The former method was found useful to study the degree of water filling at the outer surface of the pellet but led to artifacts in the interior of the pellet. The latter method was developed to confirm that the spherical cavities observed in dry pellets were related to entrapped bubbles in wet pellets. Capillaries were observed at the outer surface of the pellets and fine particles were lacking within a layer of approximately 100 µm from the outer surface and also in the direct vicinity of the air bubbles in the interior of the pellets.More advanced freezing methods were subsequently employed to reveal the artifact free microstructure of bentonite in wet pellets. In order to verify the observations made on a slice of a wet pellet frozen by plunging in liquid ethane, SEM investigations were also carried out on a bentonite suspension and a bentonite-iron ore slurry, which could be cryo-fixed by the most reliable freezing method, i.e. high pressure freezing. All microstructures were comparable and consisted in a voluminous network of well-dispersed clay platelets. This network was found to collapse upon drying. Bentonite was drawn to the contact points between the particles and formed what appeared as bridges, which may impart strength to the dry pellets. A combination of energy dispersive spectroscopy (EDS) and imaging by low-loss backscattered electrons at low voltage evidenced the presence of very finely divided silicate species on the magnetite particles. In order to visualize the three dimensional structure of dispersed bentonite clay with unprecedented resolution, a method based on SEM imaging with a monochromatic and decelerated beam was used for the first time. The recorded images showed very well-dispersed clay platelets forming a fine network of Y shaped contacts, which is quite different from earlier reports of much coarser structures formed as a result of poor sample preparation. Finally, in order to gain quantitative data about the porosity due to bubble entrapment in dry pellets, the entire cross-section of dry epoxy embedded and polished pellets were recorded by SEM. The three-dimensional bubble size distribution was unfolded from 2D SEM data using image processing, image analysis and stereological principles. The same type of pellets was also investigated by X-ray micro-tomography (XMT). The resulting three-dimensional dataset allowed the validation of the unfolding procedure based on stereology. However, the lack of resolution obtained by XMT was shown to lead to slight discrepancies with the SEM data for small bubble sizes. Entrapped air bubbles due to the addition of extra flotation reagent in pellets were shown to be responsible for additional porosity observed by mercury intrusion porosimetry (MIP). In summary, useful characterization methods for iron ore pellets based on SEM have been developed in this work, which opens up new possibilities to for instance study agglomeration processes in more detail.

  • 23.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, 312–318- p.Article in journal (Refereed)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 24.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Schröppel, Birgit
    Natural and Medical Sciences Institute (NMI), University of Tübingen.
    Kaech, Andres
    Center for Microscopy and Image Analysis, University of Zurich.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forsmo, Seija P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Microstructure of Bentonite in Iron Ore Green Pellets2014In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 20, no 1, 33-41 p.Article in journal (Refereed)
    Abstract [en]

    Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

  • 25.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Huang, Shan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. Linnaus University, Sweden.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Isolation of exceedingly low oxygen consuming fungal strains able to utilize lignin as carbon sourceIn: Cellulose Chemistry and Technology, ISSN 0576-9787Article in journal (Refereed)
  • 26.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Spadiut, Oliver
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Isolation and identification of microorganisms from soil able to live on lignin as acarbon source and to produce enzymes which cleave the β-o-4 bond in a lignin model compound2012In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, no 3-4, 227-242 p.Article in journal (Refereed)
    Abstract [en]

    Several strains of fungi were isolated and identified from Scandinavian soil using agar plates with lignin as a carbon source. The strains grew significantly faster on this medium than on control plates without lignin. Different types of technical lignins were used, some of which contained trace amounts of sugars, even if the increased growth rate seemed not related to the sugar content. Some strains were cultivated in shaking flask cultures with lignin as a carbon source, with lignin apparently consumed by microbes - while accumulation of the microorganism biomass occurred. The cell-free filtrates of these cultures could reduce the apparent molecular weights of lignosulphonates, while the culture filtrate of one strain could cleave the beta-O-4 bond in a lignin model compound.

  • 27.
    BIN HANNAN, KHALID
    KTH, School of Chemical Science and Engineering (CHE).
    Organiska kväveföreningars påverkan på vätebehandlingsanläggningens prestanda2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Various distillates are treated with hydrogen gas during hydrotreatment in the presence of catalyst in order to reduce the sulfur and aromatic content of the product. Optimal hydrotreater performance is essential for producing Nynas specialty oils, in order to fulfill the planned production volume and to meet the product specification. Loss of catalyst activity is inevitable during the production. To adjust for the impact of catalyst deactivation, different process variables are manipulated. Different distillates affect the catalyst in different ways due to the variation in distillate composition. Distillates with higher organic nitrogen content and running at a lower temperature tend to deactivate the catalyst more due to the adsorption of nitrogen compounds on the active sites of the catalyst and their slow nature of desorption.

    In this master thesis, different catalyst deactivation mechanisms with a focus on nitrogen deactivation have been studied. Since nitrogen is not normally measured at Nynas, nitrogen content of different distillates and products and how these values change during operation was not known. Different distillates, blend of distillates and different products were measured to estimate roughly the typical nitrogen value of the distillates and products. The temperature data inside the reactors were analyzed to calculate and plot WABT (weighted average bed temperature) during different product runs and to see whether there is a correlation between the nitrogen content of the feed and operation severity (increase in WABT). Historical process data from hydrotreater unit 2 (mostly from 2013-2014) were analyzed with a view to finding out signs of catalyst deactivation. Similar product runs were also analyzed and compared to see how the catalysts performed at different periods of time. A kinetic model, based on HDS kinetics, has been used for following up two product runs. To do so, sulfur content of the feed and product were measured. Aromatic content of the product was also measured to see whether the product was on specification.

    .From the calculation and plotting of WABTs, it could be seen that there is an increase in WABT during the product runs operating at lower temperatures and with higher nitrogen content. From the comparison of two P3 product runs at two different time periods, it could be seen that ∆T development over one bed (amount of reaction over the bed) was much lower at one time. This can possibly be a sign of catalyst deactivation since it contributed to lesser amount of reaction over the bed.

    From the calculations by using the kinetic model, it could be seen that the actual temperatures were higher than the predicted temperatures. The increase in WABTs could also be noticed. These observations can possibly be coupled with nitrogen deactivation of the catalysts.  However, more tests are required to verify whether the temperature differences were significant or not. Other parameters which are also important from product selling point of view such as viscosity, color, flash point, acid number etc. and have not been covered in this degree project need to be taken into consideration before making further conclusions.

  • 28.
    Biswas, Amit Kumar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Thermochemical behavior of pretreated biomass2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mankind has to provide a sustainable alternative to its energy related problems. Bioenergy is considered as one of the potential renewable energy resources and as a result bioenergy market is also expected to grow dramatically in future. However, logistic issues are of serious concern while considering biomass as an alternative to fossil fuel. It can be improved by introducing pretreated wood pellet.

    The main objective of this thesis is to address thermochemical behaviour of steam exploded pretreated biomass. Additionally, process aspects of torrefaction were also considered in this thesis. Steam explosion (SE) was performed in a laboratory scale reactor using Salix wood chips. Afterwards, fuel and thermochemical aspects of SE residue were investigated. It was found that Steam explosion pretreatment improved both fuel and pellet quality. Pyrolysis of SE residue reveals that alerted biomass composition significantly affects its pyrolysis behaviour. Contribution from depolymerized components (hemicellulose, cellulose and lignin) of biomass was observed explicitly during pyrolysis. When devolatilization experiment was performed on pellet produced from SE residue, effect of those altered components was observed. In summary, pretreated biomass fuel characteristics is significantly different in comparison with untreated biomass. On the other hand, Process efficiency of torrefaction was found to be governed by the choice of appropriate operating conditions and the type of biomass.

  • 29.
    Biswas, Amit Kumar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Steam pretreatment of Salix to upgrade biomass fuel for wood pellet production2011In: Fuel processing technology, ISSN 0378-3820, Vol. 92, no 9, 1711-1717 p.Article in journal (Refereed)
    Abstract [en]

    Steam explosion (SE) pretreatment is served to separate the main components of woody biomass. In general there is a noticeable gap in literature in terms of application of steam explosion process to upgrade biomass fuel for wood pellet production. In order to study the influence of steam explosion pretreatment on biomass fuel, Salix wood chips was used as raw material. Four different SE experiments were performed by varying two key process factors; time and temperature. Elementary quality and ash properties of the pretreated residue were investigated. Moreover, physical and thermochemical properties of the pellet, produced from the residue, were also investigated. Reduction in ash content especially in alkali metals was observed in steam treated residue. Pretreatment of biomass also enhanced carbon content and reduced oxygen amount in the fuel which enhanced the heating value of the fuel. Moreover, pretreatment enhanced pellet density, impact resistance, and abrasive resistance of pellet. However, small degradation in ash fusion characteristics and char reactivity was also observed as the severity of the process increased.

  • 30.
    Biswas, Amit Kumar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Devolatilization characteristics of steam explosion pretreated wood pelletIn: Fuel processing technology, ISSN 0378-3820Article in journal (Other academic)
  • 31.
    Bleken, Bjørn Tore L.
    et al.
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Wragg, David Stephen
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Arstad, Bjørnar
    SINTEF Materials and Chemistry, Blindern.
    Gunnæs, Anette Eleonora
    Department of Physics, University of Oslo FERMiO.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Helveg, Stig
    Haldor Topsøe A/S.
    Lundegaard, Lars Fahl
    Haldor Topsøe A/S.
    Beato, Pablo
    Haldor Topsøe A/S.
    Bordiga, Silvia
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Olsbye, Unni
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Svelle, Stian
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Lillerud, Karl Petter
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Unit cell thick nanosheets of zeolite H-ZSM-5: Structure and activity2013In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, 558-566 p.Article in journal (Refereed)
    Abstract [en]

    nosheets of zeolite H-ZSM-5 were synthesized and characterized by X-ray diffraction, transmission electron microscopy (TEM), N2- physisorption, FT-IR spectroscopy, 27Al and 29Si MAS NMR spectroscopy in addition to catalytic testing in conversion of methanol to hydrocarbons (MTH). It was found that Rietveld analysis, involving anisotropic broadening parameters, gave average crystallite dimensions in good agreement with TEM images. The selectivities in MTH is intact in the mesoporous nanosheet H-ZSM-5 with the largest difference being a higher C3/C2 ratio compared to regular H-ZSM-5.

  • 32.
    Brandin, Jan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bio-Propane from glycerol for biogas addition2008Report (Other academic)
    Abstract [en]

    In this report, the technical and economical feasibility to produce higher alkanes from bioglycerol has been investigated. The main purpose of producing this kind of chemicals would be to replace the fossil LPG used in upgraded biogas production. When producing biogas and exporting it to the natural gas grid, the Wobbe index and heating value does not match the existing natural gas. Therefore, the upgraded biogas that is put into the natural gas grid in Sweden today contains 8-10 vol-% of LPG. The experimental work performed in association to this report has shown that it is possible to produce propane from glycerol. However, the production of ethane from glycerol may be even more advantageous. The experimental work has included developing and testing catalysts for several intermediate reactions. The work was performed using different micro-scale reactors with a liquid feed rate of 18 g/h. The first reaction, independent on if propane or ethane is to be produced, is dehydration of glycerol to acrolein. This was showed during 60 h on an acidic catalyst with a yield of 90%. The production of propanol, the second intermediate to producing propane, was shown as well. Propanol was produced both using acrolein as the starting material as well as glycerol (combining the first and second step) with yields of 70-80% in the first case and 65-70% in the second case. The propanol produced was investigated for its dehydration to propene, witha yield of 70-75%. By using a proprietary, purposely developed catalyst the propene was hydrogenated to propane, with a yield of 85% from propanol. The formation of propane from glycerol was finally investigated, with an overall yield of 55%.

    The second part of the experimental work performed investigated the possibilities of decarbonylating acrolein to form ethane. This was made possible by the development of a proprietary catalyst which combines decarbonylation and water-gas shift functionality. By combining these two functionalities, no hydrogen have to be externally produced which is the case of the propane produced. The production of ethane from acrolein was shown with a yield of 75%, while starting from glycerol yielded 65-70% ethane using the purposely developed catalyst. However, in light of this there are still work to be performed with optimizing catalyst compositions and process conditions to further improve the process yield. The economic feasibility and the glycerol supply side of the proposed process have been investigated as well within the scope of the report. After an initial overview of the glycerol supply, it is apparent that at least the addition of alkanes to biogas can be saturated by glycerol for the Swedish market situation at the moment and for a foreseeable future. The current domestic glycerol production would sustain the upgraded biogas industry for quite some time, if necessary. However, from a cost standpoint a lower grade glycerol should perhaps be considered.

  • 33.
    Brandin, Jan
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Usage of Biofuels in Sweden2013In: CSR-2 Catalyst for renewable sources: Fuel, Energy, Chemicals Book of Abstracts / [ed] Vadim Yakovlev, Boreskov Institute of Catalysis, Novosibrisk, Russia: Boreskov Institute of Catalysis , 2013, 5-7 p.Conference paper (Refereed)
    Abstract [en]

    In Sweden, biofuels have come into substantial use, in an extent that are claimed to be bigger than use of fossil oil. One driving force for this have been the CO2-tax that was introduced in 1991 (1). According to SVEBIO:s calculations (2) based on the Swedish Energy Agency´s prognosis, the total energy consumption in Sweden 2012 was 404 TWh. If the figure is broken down on the different energy sources (figure 1) one can see that the consumption roughly distribute in three different, equally sized, blocks, Biofuels, fossil fuels and water & nuclear power. The major use of the fossil fuels is for transport and the water & nuclear power is used as electric power. The main use of the biofuels is for heating in the industrial sector and as district heating. In 2009 the consumption from those two segments was 85 TWh, and 10 TWh of bio power was co-produced giving an average biomass to electricity efficiency of 12%. This indicates a substantial conversion potential from hot water production to combined heat and power (CHP) production. in Sweden 2013 broken down on the different energy sources. In 2006 the pulp, paper and sawmill industry accounted for 95% of the bio energy consumption in the industrial sector, and the major biofuel consumed was black liquor (5). However, the pulp and paper industries also produced the black liquor in their own processes. The major energy source (58%) for district heating during 2006 was woody biomass (chips, pellets etc.) followed by waste (24%), peat (6%) and others (12%) (5). The use of peat has probably decreased since 2006 since peat is no longer regarded as a renewable energy source. While the use of biofuel for heating purpose is well developed and the bio-power is expected to grow, the use in the transport sector is small, 9 TWh or 7% in 2011. The main consumption there is due to the mandatory addition (5%) of ethanol to gasoline and FAME to diesel (6). The Swedish authorities have announced plans to increase the renewable content to 7.5 % in 2015 on the way to fulfill the EU’s goal of 10 % renewable transportation fuels in 2020. However the new proposed fuel directive in EU says that a maximum of 5% renewable fuel may be produced from food sources like sugars and vegetable oils. Another bothersome fact is that, in principle, all rape seed oil produced in Sweden is consumed (95-97%) in the food sector, and consequently all FAME used (in principle) in Sweden is imported as FAME, rape seed oil or seed (6). In Sweden a new source of biodiesel have emerged, tall oil diesel. Tall oil is extracted from black liquor and refined into a diesel fraction (not FAME) and can be mixed into fossil diesel, i.e. Preem Evolution diesel. The SUNPINE plant in Piteå have a capacity of 100 000 metric tons of tall oil diesel per annum, while the total potential in all of Sweden is claimed to be 200 000 tons (7). 100 000 tons of tall oil corresponds to 1% of the total diesel consumption in Sweden. in Sweden for 2010 and a prognosis for 2014. (6). Accordingly, the profoundest task is to decrease the fossil fuel dependency in the transport sector, and clearly, the first generation biofuels can´t do this on its own. Biogas is a fuel gas with high methane content that can be used in a similar way to natural gas; for instance for cooking, heating and as transportation fuel. Today biogas is produced by fermentation of waste (municipal waste, sludge, manure), but can be produced by gasification of biomass, for instance from forest residues such as branches and rots (GROT in Swedish). To get high efficiency in the production, the lower hydrocarbons, mainly methane, in the producer gas, should not be converted into synthesis gas. Instead a synthesis gas with high methane content is sought. This limits the drainage of chemically bonded energy, due to the exothermic reaction in the synthesis step (so called methanisation). In 2011 0.7 TWh of biogas was produced in Sweden by fermentation of waste (6) and there were no production by gasification, at least not of economic importance. The potential seems to be large, though. In 2008 the total potential for biogas production, in Sweden, from waste by fermentation and gasification was estimated to 70 TWh (10 TWh fermentation and 60 TWh gasification) (8). This figure includes only different types of waste and no dedicated agricultural crops or dedicated forest harvest. Activities in the biogas sector, by gasification, in Sweden are the Göteborgs energi´s Gobigas project in Gothenburg and Eon´s Bio2G-project, now pending, in south of Sweden. If the producer gas is cleaned and upgraded into synthesis gas also other fuels could be produced. In Sweden methanol and DME productions are planned for in the Värmlands metanol-project and at Chemrecs DME production plant in Piteå.

  • 34.
    Brandin, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Hulteberg, Christian
    Biofuel-Solution AB, Limhamn .
    Multi-function catalysts for glycerol upgrading2010Conference paper (Other academic)
    Abstract [en]

    During the last three years Biofuel-Solution, a privately held Swedish entity, has developed an IP-portfolio around gas-phase glycerol conversion into medium-value chemicals. The targeted chemicals have large to very large markets, to allow for use by more than a fraction of the glycerol available today without impacting the cost of the product. The reason behind is that glycerol is a by-product from the biofuel industry, including biodiesel and bioethanol. This indicates large production volumes, even though the glycerol is a fraction of the fuel produced. A by-product from any fuel process will be vast and therefore any chemical produced from this side-product will have to have a large market to offset it to. In order to avoid changing the fundamental market behavior, similar to what the biodiesel industry has done to the glycerol market.

    In the course of this work, several end-products have been targeted. These include plastic monomers, mono-alcohols and energy gases; using acrolein as a common starting point. To produce chemicals with high purity and efficiency, selective and active catalysts are required. For instance, a process for producing propionaldehyde and n-propanol has been developed to the point of demonstration and commercialization building on the gas-phase platform.

    By developing multi-function catalysts which perform more than one task simultaneously, synergies can be reached that cannot be achieved with traditional catalysts. For instance, by combining catalyst functionalities, reactions that are both endothermic and exothermic can be performed simultaneously.

    This mean lower inlet reactor temperatures (in this particular case) and a more even temperature distribution. By performing the dehydration of glycerol to acrolein in combination with another, exothermal reaction by-products can be suppressed and yields increased.

    It also means that new reaction pathways can be achieved, allowing for new ways to produce chemicals and fuels from glycerol. As in the case of ethane production from acrolein, where a catalyst surface has been devised where acrolein is first adsorbed. The actual mechanism is unknown but in speculation, the adsorbed acrolein is decarbonyled into ethylene and carbon monoxide on a first reaction site. The formed carbon monoxide diffuses to another active site, where it reacts with water through the so called water-gas shift reaction to carbon dioxide and hydrogen. Said carbon dioxide leaves as an end-product, and the hydrogen diffuses to another active site where it reacts with ethylene to form ethane. This gives a way of producing energy gases from glycerol in a very compact reactor set-up, effectively reducing footprint and capital cost and increasing productivity of an installation.

  • 35.
    Brandin, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Hulteberg, Christian
    Lund University.
    Odenbrand, Ingemar
    Lund University.
    High-temperature and high concentration SCR of NO with NH3: application in a CCS process for removal of carbon dioxide2012In: Chemical Engineering Journal, ISSN 1385-8947, Vol. 191, 218-227 p.Article in journal (Refereed)
    Abstract [en]

    This study investigates several commercial selective catalytic reduction (SCR) catalysts (A–E) for application in a high-temperature (approximately 525 °C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NOx seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by measurement in a fixed-bed reactor at 300–525 °C. All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amount of catalyst needed varied considerably and was much higher for the zeolithic materials. The formation of N2O increased with temperature for almost all materials except the zeolithic ones. The selectivity to N2 production at 525 °C was 98.6% for the best material and 95.7% for the worst with 1000 ppm NOx in the inlet; at 5000 ppm NOx, the values were much better, i.e., 98.3 and 99.9%, respectively.

  • 36.
    Brandin, Jan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Tunér, Martin
    Lunds Tekniska Högskola.
    Odenbrand, Ingemar
    Lunds Tekniska Högskola.
    Small Scale Gasifiction: Gas Engine CHP for Biofuels2011Report (Other academic)
    Abstract [en]

    In a joint project, Linnaeus University in Växjö (LNU) and the Faculty of Engineering at Lund University (LTH) were commissioned by the Swedish Energy Agency to make an inventory of the techniques and systems for small scale gasifier-gas engine combined heat and power (CHP) production and to evaluate the technology. Small scale is defined here as plants up to 10 MWth, and the fuel used in the gasifier is some kind of biofuel, usually woody biofuel in the form of chips, pellets, or sawdust. The study is presented in this report.

    The report has been compiled by searching the literature, participating in seminars, visiting plants, interviewing contact people, and following up contacts by e-mail and phone.

    The first, descriptive part of the report, examines the state-of-the-art technology for gasification, gas cleaning, and gas engines. The second part presents case studies of the selected plants:

    • Meva Innovation’s VIPP-VORTEX CHP plant
    • DTU’s VIKING CHP plant
    • Güssing bio-power station
    • Harboøre CHP plant
    • Skive CHP plant

    The case studies examine the features of the plants and the included unit operations, the kinds of fuels used and the net electricity and overall efficiencies obtained. The investment and operating costs are presented when available as are figures on plant availability. In addition we survey the international situation, mainly covering developing countries.

    Generally, the technology is sufficiently mature for commercialization, though some unit operations, for example catalytic tar reforming, still needs further development. Further development and optimization will probably streamline the performance of the various plants so that their biofuel-to-electricity efficiency reaches 30-40 % and overall performance efficiency in the range of 90 %.

    The Harboøre, Skive, and Güssing plant types are considered appropriate for municipal CHP systems, while the Viking and VIPP-VORTEX plants are smaller and considered appropriate for replacing hot water plants in district heating network. The Danish Technical University (DTU) Biomass Gasification Group and Meva International have identified a potentially large market in the developing countries of Asia.

    Areas for suggested further research and development include:

    • Gas      cleaning/upgrading
    • Utilization      of produced heat
    • System      integration/optimization
    • Small scale      oxygen production
    • Gas engine      developments
  • 37.
    Brusved Andersson, Linnea
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Future Strategy for Wastewater Treatment at Skärblacka Mill2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To replace nonrenewable materials, glass, plastics and metals, at the market the production of the environmental friendly material paper needs to increase numerously. An increased paper production leads to an enlarged wastewater flow at the paper mill and thereby higher surface load in the biologicalwastewater plant. Higher surface load in turn, leads to lower efficiency and higher emissions. To be able to increase the capacity of the paper production, the wastewater flow to the biological wastewater treatment needs to be decreased.

    In this thesis, the wastewater at Skärblacka mill has been studied to identify how to increase the production without increasing the flow of wastewater to the biological wastewater treatment. Different wastewater has been studied to identify sufficient clean wastewater flows that today are directed to the biological wastewater treatment.

    The outcome of this thesis is that up to 600 m3/h wastewater could be removed from the biological wastewater treatment due to sufficiently high purity. This outcome is primarily based on measurements of the emission parameters, Total Organic Carbon, Suspended Solids, Total Phosphorus and Total Nitrogen and the calculation of PEC/PNEC, environmental assessment, for the chemicals in the wastewater.

    The unload of up to 600 m3/h will contribute to an increased efficiency in the biological wastewater treatment and thereby lower emissions. Increased efficiency and lower levels of emissions will in turn contribute to a possibility to increase the paper production at Skärblacka mill without interfering withenvironmental demands.

  • 38.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hansson, Anders
    Energy policy on shaky ground?: A study of CCS-scenarios2009In: Energy Procedia, ISSN 1876-6102, no 1, 4673-4680 p.Article in journal (Refereed)
    Abstract [en]

    Scenarios play an important role for the societal acceptance of CCS. This paper looks into influential reports containing CCS scenarios and analyses results, key assumptions and drivers for CCS' deployment. Significant uncertainties regarding CCS' development were in several cases excluded or marginalized. Despite these shortcomings, scenarios support a massive deployment of CCS and reflect an undivided optimism. If CCS would fail to meet the high expectations a backlash could follow. Indications were found that new scenarios including uncertainties are needed to balance this over-optimism. So-called unpleasant scenarios are often valuable in helping decision makers develop flexible strategies and policies.

  • 39.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lindfeldt, Erik G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Heller, Jan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture2009In: International journal of greenhouse gas control, ISSN 1750-5836, Vol. 3, no 3, 255-262 p.Article in journal (Refereed)
    Abstract [en]

    This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.

  • 40.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Feasibility study of CO2 removal from pressurized flue gas in a fully fired combined cycle: the Sargas project2005In: Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS, 2005, 703-710 p.Conference paper (Refereed)
    Abstract [en]

    In this article a novel concept for CO2 removal from power plants is discussed from a systems perspective. The main advantage of the process is that the investment cost and the power penalty for CO2 removal can be substantially reduced compared to conventional combined cycles. The proposed technical solution comprises fully fired combined cycle, which minimizes the amount of flue gas. Furthermore, the CO2 absorption is performed at pressurized conditions prior to the expansion, which further enhances the CO2 removal. The modification of the power cycle and integration of absorption stages makes CO2 removal equipment much more compact and allows the use Of CO2 absorbents with lower heat demand for the regeneration. The partial pressure of CO2 is above atmospheric pressure and removal efficiencies above 95% can be obtained with potassium carbonate absorption (the Benfield process). The treated flue gas is then reheated and re-humidified before the expansion in the gas turbine.

    A Norwegian consortium has developed the concept and feasibility studies have been performed for 100 MW and 400 MW power plants based on natural gas in Norway. The produced carbon dioxide is intended for storage in the Norwegian oil and gas fields in order to enhance the oil recovery. The suggested localizations of the power plants have been chosen accordingly. The design study is based on the same gas turbine and steam cycle as used in the commercial Pressurized Fluidized Bed Combustion (PFBC) cycle. PFBC plants are presently fired with coal but the fluid bed combustor for coal will be replaced by a gas combustor if natural gas is used. A key advantage is that the process can be built solely from commercially available components.

    This report is an assessment of the features, capabilities, advantages and future possibilities of the suggested power cycle with integrated CO2 removal. A power plant for 100 MW power output and based on natural gas is considered suitable as a first demonstration plant to be built in Hammerfest, Norway. A permit application has been turned in. For such a demonstration plant the process simulations have indicated that an efficiency of about 40% can be obtained, including the penalties from CO2 capture and compression. Further improvements, e.g. supercritical steam cycle or more advanced gas turbine increases the efficiency and for a 400 MW power cycle a net efficiency of about 44-48% has been simulated (including CO2 capture and compression). The cycle may also be suitable for CO2 removal from coal-fired plants.

  • 41.
    Bryngelsson, Mårten
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Westermark, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    CO2 capture pilot test at a pressurized coal fired CHP plant2009In: Energy Procedia, ISSN 1876-6102, Vol. 1, no 1, 1403-1410 p.Article in journal (Refereed)
    Abstract [en]

    CO2 capture from pressurized flue gas using a variation of the hot potassium carbonate process has been demonstrated at a pilot plant with authentic flue gas from the Vartan combined heat and power plant in Stockholm. The plant has served as a proof of concept installation, and has confirmed that: i) the pre-treatment of the flue gas is adequate for protecting the absorbent from degradation, ii) the CO2 capture efficiency is high (> 98 %), iii) no harmful components are fed to the gas turbine, and iv) absorbent degradation is low (0.85 mole percent/month).

  • 42.
    Brännvall, Elisabet
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Jansson, Zheng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Characterisation of dissolved spruce xylan in kraft cooking2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 26, no 4, 380-385 p.Article in journal (Refereed)
    Abstract [en]

    Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been demonstrated to affect paper strength properties. Earlier studies have demonstrated that it is the xylan characteristics, rather than simply the amount of xylan, that influence the strength-enhancing effect of xylan. To use xylan optimally, it is useful to understand xylan’s beneficial characteristics and how cooking conditions affect them.

    In this study, spruce chips were kraft cooked under various cooking conditions and the xylan in the black liquor was characterized. We found that dissolved spruce xylan had a much higher amount of bound lignin than found in previous studies of xylan dissolved from hardwoods. The ionic strength of the cooking liquor affected the amount of dissolved xylan as well as the uronic acid content of the xylan.

  • 43.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    A collision efficiency model for flow-induced coagulation of fractal aggregates2008In: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 54, no 7, 1748-1760 p.Article in journal (Refereed)
    Abstract [en]

    A model for flow-induced collisions of fractal aggregates is developed. The model is based on the analysis of the relative trajectories between a pair of aggregates that takes into account their hydrodynamic and their colloidal interactions. Regarding the former, the aggregates are modeled as permeable spheres where the Brinkman equation is used to describe the flow inside the aggregates. Interparticle forces are incorporated by considering the forces between the primary particles in the two aggregates that are the nearest. The model results in a collision efficiency that depends on the masses of the colliding aggregates, the fractal dimension, and a nondimensional Hamaker constant characterizing the interparticle forces. The collision efficiency model is used to investigate the dynamics of a suspension undergoing coagulation. Significant deviations with respect to existing collision efficiency models are evidenced. 

  • 44.
    Bäbler, Matthäus
    ETH Zurich.
    Modelling of aggregation and breakage of colloidal aggregates in turbulent flows: Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 17139, 20072007Doctoral thesis, monograph (Other academic)
  • 45.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Mazzotti, Marco
    Soos, Miroslav
    Morbidelli, Massimo
    Breakup and aggregation in turbulently stirred vessels2009In: 13th European Conference on Mixing, 2009Conference paper (Refereed)
    Abstract [en]

    The breakup and aggregation of small solid particle aggregates in hetero-geneous °ows is modeled through a multizonal population balance model. Breakupand aggregation are described through comprehensive rate expressions that takeinto account the local properties of the turbulent °ow. Two approaches are pursuedto de¯ne the zones: in the ¯rst approach the zones are prede¯ned and computational°uid dynamics is used to compute the zone properties. In the second approach thezone properties are directly ¯tted to experimental data. Model results compare wellwith experiments for the aggregation of a polystyrene latex in a stirred tank evenwhen only two zones are used.

  • 46.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Analysis of the aggregation-fragmentation population balance equation with application to coagulation2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, no 2, 428-441 p.Article in journal (Refereed)
    Abstract [en]

    Coagulation of small particles in agitated suspensions is governed by aggregation and breakage. These two processes control the time evolution of the cluster mass distribution (CMD) which is described through a population balance equation (PBE). In this work, a PBE model that includes an aggregation rate function, which is a superposition of Brownian and flow induced aggregation, and a power law breakage rate function is investigated. Both rate functions are formulated assuming the clusters are fractals. Further, two modes of breakage are considered: in the fragmentation mode a particles splits into w ≥ 2 fragments of equal size, and in the erosion mode a particle splits into two fragments of different size. The scaling theory of the aggregation-breakage PBE is revised which leads to the result that under the negligence of Brownian aggregation the steady state CMD is self-similar with respect to a non-dimensional breakage coefficient θ. The self-similarity is confirmed by solving the PBE numerically. The self-similar CMD is found to deviate significantly from a log-normal distribution, and in the case of erosion it exhibits traces of multimodality. The model is compared to experimental data for the coagulationof a polystyrene latex. It is revealed that the model is not flexible enough to describecoagulation over an extended range of operation conditions with a unique set of parameters. In particular, it cannot predict the correct behavior for both a variation in the solid volume fraction of the suspension and in the agitation rate (shear rate).

  • 47.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Baldyga, Jerzy
    Modelling the breakup of solid aggregates in turbulent flows2008In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 612, 261-289 p.Article in journal (Refereed)
    Abstract [en]

    The breakup of solid aggregates suspended in a turbulent flow is considered. The aggregates are assumed to be small with respect to the Kolmogorov length scale and the flow is assumed to be homogeneous. Further, it is assumed that breakup is caused by hydrodynamic stresses acting on the aggregates, and breakup is therefore assumed to follow a first-order kinetic where K-B(x) is the breakup rate function and x is the aggregate mass. To model K-B(x), it is assumed that an aggregate breaks instantaneously when the surrounding flow is violent enough to create a hydrodynamic stress that exceeds a critical value required to break the aggregate. For aggregates smaller than the Kolmogorov length scale the hydrodynamic stress is determined by the viscosity and local energy dissipation rate whose fluctuations are highly intermittent. Hence, the first-order breakup kinetics are governed by the frequency with which the local energy dissipation rate exceeds a critical value (that corresponds to the critical stress). A multifractal model is adopted to describe the statistical properties of the local energy dissipation rate, and a power-law relation is used to relate the critical energy dissipation rate above which breakup occurs to the aggregate mass. The model leads to an expression for K-B(x) that is zero below a limiting aggregate mass, and diverges for x -> infinity. When simulating the breakup process, the former leads to an asymptotic mean aggregate size whose scaling with the mean energy dissipation rate differs by one third from the scaling expected in a non-fluctuating flow.

  • 48.
    Bäbler, Matthäus
    et al.
    Swiss Fed Inst Technol, Inst Proc Engn.
    Moussa, Amgad S.
    Soos, Miroslav
    Morbidelli, Massimo
    Structure and Kinetics of Shear Aggregation in Turbulent Flows: I. Early Stage of Aggregation2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 16, 13142-13152 p.Article in journal (Refereed)
    Abstract [en]

    Aggregation of rigid colloidal particles leads to fractal-like structures that are characterized by a fractal dimension d(f) which is a key parameter for describing aggregation processes. This is particularly true in shear aggregation where d(f) strongly influences aggregation kinetics. Direct measurement of d(f) in the early stages of shear aggregation is however difficult, as the aggregates are small and few in number. An alternative method for determining d(f) is to use an aggregation model that when fitted to the time evolution of the cluster mass distribution allows for estimating d(f). Here, we explore three such models, two of which are based on an effective collision sphere and one which directly incorporates the permeable structure of the aggregates, and we apply them for interpreting the initial aggregate growth measured experimentally in a turbulent stirred tank reactor. For the latter, three polystyrene latexes were used that differed only in the size of the primary particles (d(p) = 420, 600, and 810 nm). It was found that all three models describe initial aggregation kinetics reasonably well using, however, substantially different values for 4 To discriminate among the models, we therefore also studied the regrowth of preformed aggregates where d(f) was experimentally accessible. It was found that only the model that directly incorporates the permeable structure of the aggregates is able to predict correctly this second type of experiments. Applying this model to the initial aggregation kinetics, we conclude that the actual initial fractal dimension is d(f) = 2.07 +/- 0.04 as found from this model.

  • 49.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Sefcik, J
    Morbidelli, M
    Baldyga, J
    Hydrodynamic interactions and orthokinetic collisions of porous aggregates in the Stokes regime2006In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 18, no 1, 013302- p.Article in journal (Refereed)
    Abstract [en]

    The hydrodynamic interaction of two neutrally buoyant porous aggregates is investigated under creeping flow conditions for the case where the undisturbed velocity of the surrounding flow field is a linear function of position. In this framework, the relative velocity between two aggregates is given by the deformation of the undisturbed flow expressed through the rate of strain and the angular velocity of the flow field, and by two flow-independent hydrodynamic functions, typically referred to as A and B, which account for the disturbance of the flow field due to the presence of the particles [G. K. Batchelor and J. T. Green, J. Fluid Mech. 56, 375 (1972)]. In the present paper, the analysis of thehydrodynamic interaction that is known for the case of two impermeable, solid particles is extended to the case of porous aggregates by applying Brinkman's equation to describe the flow within the aggregates. A reflection scheme is applied to calculate A and B and the obtained expressions are applied to interpret the orthokinetic aggregation ofaggregates in diluted suspensions, where the collision frequency is computed using the method of relative trajectories of a pair of aggregates.

  • 50.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Computational Studies of Metal Clusters and Carbon Nanotubes2008Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Carbon nanotubes constitute a promising candidate material in the realisation of nanoscaled electronics. This requires the ability for systematic production of carbon nanotubes with certain properties. This is called selective carbon nanotube growth. Two important aspects related to carbon nanotube growth are investigated in order to shed some light on this issue. First the melting behaviour of nanometer sized iron particles is investigated using molec- ular dynamics simulations. The iron nanoparticles studied are mounted on a porous Al2 O3 substrate in order to mimic the experimental situation during nanotube growth with the chemical vapour deposition method. This showed that the melting temperature of a cluster on a porous substrate may be lower than the melting temperature of a cluster on a flat sub- strate. This means that the catalyst particles used for nanotube growth may be liquid. In association with these studies the role of surface curvature to melting behaviour is explored further. The second presented study concerns the docking of nickel clusters to open single wall carbon nanotube ends. The motivation for this study was the possibility to continue growth of a carbon nanotube by docking of catalyst particles to its end. This work may also be of importance for the creation of electric junctions between carbon nanotubes and metal elec- trodes. This study showed that independent of whether the metal was gently put on the nanotube end or brutally forced to the end, it is the metal that adapts to the nanotube and not vice versa. For forced docking it was seen that carbon might dissolve in to the metal. This was not seen for the gently docked clusters. Carbon dissolution might affect the electronic properties of the metal (carbide) and nanotube-metal junction.

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