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  • 101.
    Skoglund, Nils
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kuba, Matthias
    BioEnergy2020+.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Effects of Bed Material Type and Fuel Ash Composition on Layer Formation and Bed Agglomeration in Thermo-chemical Conversion of Biomass and Waste Streams in Fluidized Beds2018In: 23rd International Conference on Fluidized Bed Conversion, 13-17 May 2018, Seoul, Korea, 2018Conference paper (Refereed)
    Abstract [en]

    The role of fluidized beds is increasingly important for challenging and ash-rich fuels, such as fast-growing biomass and waste streams. From a biomass perspective, the relatively homogeneous woody-type fuels are most commonly used in fluidized beds today whereas the fuel feedstock for waste streams is more heterogeneous. A key issue in enabling a broader fuel feedstock for existing and planned fluidized beds is how the fuel ash interacts with bed materials of different types during combustion or gasification. The resulting bed particle coating, layers, and cracks formed in bed grains are responsible for bed agglomeration and bed material deposition mechanisms, but studies have suggested that there is a possibility to affect melting temperatures of bed ash and reduce interaction between fuel ash and bed material through additives or by fuel blend design. Furthermore, it is of interest to extend the life-time of bed materials in the reactor to reduce the amount of material that is generated as waste streams, as well as increase the timespan between bed replacements.The aim of this review is therefore to summarize some of our previous research in this topic, to discuss current knowledge concerning layer formation and bed agglomeration mechanisms, address the benefit for different bed materials, and discuss how fuel ash composition can be used to reduce bed agglomeration issues. This is achieved by comparing studies from different combustion and gasification facilities using different biomasses as well as agricultural residues and waste streams. In particular, the possibility of using fuel blend design to reduce interaction of fuel ash with bed material will be highlighted. Using such approaches, coupled with a fundamental understanding of how differences between bed materials affect layer formation mechanisms, has the potential to reduce operational issues caused by interactions between fuel ash and bed materials as well as increase the potential fuel feedstock.

  • 102.
    Skoglund, Nils
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ash transformation reactions for phosphorus-rich biomass and waste streams2017In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 254Article in journal (Other academic)
  • 103. Sterchele, Stefano
    et al.
    Bortolus, Marco
    Biasi, Pierdomenico
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemical Engineering, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Åbo-Turku, Finland.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemical Engineering, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Åbo-Turku, Finland.
    Salmi, Tapio
    Is selective hydrogenation of molecular oxygen to H2O2 affected by strong metal–support interactions on Pd/TiO2 catalysts?: A case study using commercially available TiO22016In: Comptes rendus. Chimie, ISSN 1631-0748, E-ISSN 1878-1543, Vol. 19, no 8, p. 1011-1020Article in journal (Refereed)
    Abstract [en]

    In this study, titania-supported Pd catalysts were prepared and their performance evaluated upon H2O2 direct synthesis. Typically, the materials contained different ratios of anatase and rutile phases, which gave rise to different surface properties of the supports, e.g., surface area, number of Lewis acidic and basic sites as well as different compositions of the phases, i.e. the amount of anatase phase and crystallite size. Two materials, Pd-A98 and Pd-A05 samples, respectively, apparently hint the existence of the so-called SMSI (strong metal–support interaction) phenomenon giving rise to 1080 and 683 molH2O2·molPd−1·h−1 of H2O2 productivity and 22 and 14% of H2O2 selectivity, respectively. However, the best material, Pd-A82, gave rise to 949 molH2O2·molPd−1·h−1 of H2O2 productivity and 26% of H2O2 selectivity.

  • 104. Stjernberg, Jesper
    et al.
    Jonsson, Carrie Y. C.
    Wiinikka, Henrik
    Lindblom, Bo
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Energy Technology and Thermal Process Chemistry (ETPC).
    Ohman, Marcus
    Deposit Formation in a Grate-Kiln Plant for Iron-Ore Pellet Production. Part 2: Characterization of Deposits2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 10, p. 6171-6184Article in journal (Refereed)
    Abstract [en]

    Buildup of deposit material in chunks on refractory linings caused by combustion of various fuels is a well-known problem. This study characterizes the short-term deposits on refractory material in a grate kiln process, carried out through in situ measurements using a water-cooled probe with a part of a refractory brick mounted in its end. Sampling was carried out during combustion of both oil and coal. A significant difference in deposition rates was observed; deposition during oil firing was negligible compared to coal firing. The deposits are mainly hematite particles embedded in bonding phase, mainly comprising Si, Al, Fe, Ca, and O. Moreover, it was found that the prevailing flue-gas direction determines the formation of the deposits on the probe and that inertial impaction controls the deposition rate. However, this rate can also be affected by the amount of air-borne particles present in the kiln.

  • 105.
    Sundberg, Peter
    et al.
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Fagerström, Jonathan
    Åbo Akademi University, Faculty of Science and Engineering, Energy and Environmental Engineering.
    Rebbling, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hermansson, Sven
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Tullin, Claes
    Research Institutes of Sweden, RISE Bioeconomy/Biorefinery and Energy.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Engineering.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Biomass and peat co-combustion in full scale grate boilers - a primary measure for reduction of fine particle emissions2017Conference paper (Refereed)
  • 106.
    Velaga, Sitaram P.
    et al.
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Vangala, Venu R.
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Basavoju, Srinivas
    Department of Health Sciences, Luleå University of Technology, Luleå S-971 87, Sweden.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Polymorphism in acesulfame sweetener: structure-property and stability relationships of bending and brittle crystals2010In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, no 20, p. 3562-3564Article in journal (Refereed)
    Abstract [en]

    Acesulfame is found to exist in two crystalline forms of which Form I (needles) shows bending upon mechanical stress. Crystal structures explain their mechanical response. This is the first case of aliphatic organic compounds featuring a bending phenomenon. Form I is physically more stable than Form II in ambient conditions.

  • 107. Velaga, Sitaram P
    et al.
    Vangala, Venu R
    Basavoju, Srinivas
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Polymorphism in acesulfame sweetener: structure–property and stability relationships of bending and brittle crystals2010In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, no 20, p. 3562-3564Article in journal (Refereed)
  • 108.
    Viggh, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wilhelmsson, Bodil
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Raw meal and slag reactions during cement clinker formation2019Conference paper (Refereed)
    Abstract [en]

    Natural limestones as raw material for OPC clinker manufacturing contribute to emissions of CO2gases during the production of clinker. In addition, the mining of limestone can regionally be controlledby restrictions due to environmental concerns. Slags from the steel industry can replace limestone tominimize the use of the mineral deposits. Both materials have similar chemistry and are compatible asraw materials.Utilizing slags raises questions about how slag particles will react with other raw meal components asthe temperature in the kiln increases during clinker formation. This study establishes the chemical andmineralogical aspects of replacing a portion of the limestone with slags. Of interest is how the materialsreact during the formation of the liquid phase and the formation of phases containing MgO.Three different slags were examined, a basic oxygen furnace slag BOF, a crystalline blast-furnace slagand a granulated blast-furnace slag. In the study, the microstructural causes of reactivity, as well asmineral formation in the transition zone between raw meal components, developing liquid phase andslag particles were studied. Heated raw meals were studied using HT-QXRD, QXRD, SEM andthermodynamic modeling to describe the reactions of particles at higher temperatures. The resultsshow that the formation of clinker minerals is strongly influenced by the type and amount of slag. Thus,a careful selection must be done of both composition and quantity of metallurgical slags for naturallimestone replacement in order to maintain clinker quality.

  • 109.
    Wallner, Fredrik K
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Spjut, Sara
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis and evaluation of 2-(2-fluoro-4-hydroxymethyl-5-methoxy-phenoxy)acetic acid as a linker in solid-phase synthesis monitored by gel-phase 19F NMR spectroscopy2007In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 5, p. 2464-2471Article in journal (Refereed)
    Abstract [en]

    Gel-phase 19F NMR spectroscopy is a useful monitoring technique for solid-phase organic chemistry due to the high information content it delivers and swift acquisition times, using standard NMR spectrometers. This paper describes the synthesis of the novel linker 2-(2-fluoro-4-hydroxymethyl-5-methoxy-phenoxy)acetic acid in 29% yield over seven steps, using nucleophilic aromatic substitutions on 2,4,5-trifluorobenzonitrile as key steps. Following standard solid-phase synthesis a peptide could be cleaved from the linker using 20% TFA in CH2Cl2 in 30 minutes, in contrast to a previously described monoalkoxy linker that requires 90% TFA in water at elevated temperature. A resin-bound peptide could be successfully glycosylated using only two equivalents of a thioglycoside donor, activated with N-iodosuccinimide and trifluoromethanesulfonic acid, and subsequent cleavage and deprotection gave the target glycopeptide. Direct glycosylation of the linker itself followed by mild acidic cleavage gave a fully protected hemiacetal for further chemical manipulation.

  • 110. Wei, Maogui
    et al.
    Andersson, Roger
    Xie, Guanghui
    Salehi, Shahrbanoo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Xiong, Shaojun
    Properties of Cassava Stem Starch Being a New Starch Resource2018In: Starke (Weinheim), ISSN 0038-9056, E-ISSN 1521-379X, Vol. 70, no 5–6, article id 1700125Article in journal (Refereed)
    Abstract [en]

    This study aims to understand the starch properties of cassava stems, currently a discarded crop residue, which contain up to 40% starch by dry mass. Granule sizes and size distribution of cassava stem starch, and their variations with genotype, growing location, and position along the stem are investigated using scanning electron microscopy (SEM) images. Amylose contents, crystallinity, and pasting characteristics of stem and root starch are also compared. The mean of granule sizes range from 5.65 to 7.64 µm, depending on the environment and position along stems, but not on genotype. Stem starch has a similar granule shape, X-ray diffraction pattern, and amylose content (20.8% of starch basis) to root starch, but a significantly smaller granule size with narrower distribution range and higher pasting temperature (72.1 degrees C). Cassava stem has a woody nature; a development of an efficient starch isolation method shall be included in future studies.

  • 111. Werkelin, Johan
    et al.
    Lindberg, Daniel
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Skrifvars, Bengt-Johan
    Hupa, Mikko
    Ash-forming elements in four Scandinavian wood species part 3: Combustion of five spruce samples2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 1, p. 725-733Article in journal (Refereed)
    Abstract [en]

    Forest residue is the remaining fraction after the outtake of timber, which comprises the tree tops and branches. It may as fuel cause damage to the combustion device through ash slagging and fouling. The objective of this work was to model the ash composition from well-specified samples of a spruce tree: wood, bark, twigs, needles, and shoots. Their ash at 1000 °C was modelled using global chemical equilibrium calculations, and laboratory-made ash of the five samples was analyzed by XRD and SEM-EDXA. According to the results, the risk of slagging arises from the spruce foliage: molten alkali silicates from spruce needles and probably molten alkali phosphates from spruce shoots may cause problems in the furnace. Fouling caused by condensing alkali vapours can be produced by all five samples. The amount of alkali vapours in the flue gas was in the same order of magnitude for all five samples, in spite of large differences in their original alkali contents.

  • 112.
    Widman, Susanne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Öhman, Marcus
    Luleå Tekniska Universitet.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Early release of NH3 from nitrogen rich fuels - a TG-FTIR study2013In: European Biomass Conference and Exhibition Proceedings: 21st European Biomass Conference and Exhibition, ETA-Florence Renewable Energies , 2013, p. 974-976Conference paper (Other academic)
    Abstract [en]

    Release and transformation mechanisms of nitrogen during thermal fuel conversion are important for environmental reasons. Release of NH3, HCN and HNCO from three different fuel samples (dried digested domestic sewage sludge, wheat distillers dried grain with solubles mixed with wheet straw, and rapeseed cake mixed with bark) with high nitrogen contents were investigated in this study. Samples were heated in a nitrogen flow in a thermobalance coupled to a Fourier transform infrared spectrometer (FTIR). Thereby time and temperature resolved release profiles for the nitrogen compounds were collected. By comparing FTIR signals (compound specific peaks) with weight loss rates it was possible to determine if the release patterns and mechanisms were different depending on raw material. The nitrogen was found to be released mainly in the form of NH3 for all three samples. Sewage sludge showed a somewhat different release profile where NH3 constituted a larger part of the weight loss at lower temperatures. For the biomass samples the NH3 release correlated well to the overall mass loss, indicating it was more evenly distributed in the gas evolving during conversion. The results are of importance for the research on nitrogen release and transformations and for the efforts on finding possible measures to reduce problems related to NOx formation.

  • 113.
    Wiinika, Henrik
    et al.
    Energy Technology Centre, Box 726, S-941 28, Piteå, Sweden.
    Gebart, Rikard
    Energy Technology Centre, Box 726, S-941 28, Piteå, Sweden.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Influence of fuel ash composition on high temperature aerosol formation in fixed bed combustion of woody biomass pellets2007In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 86, no 1-2, p. 181-193Article in journal (Refereed)
    Abstract [en]

    In this work, the influence of fuel ash composition on high temperature aerosol formation during fixed bed combustion of woody biomass (two wood pellets and one bark pellets) were investigated experimentally in a laboratory reactor and theoretically through chemical equilibrium model calculations. For all fuels, the particle mass size distribution in the PM2.5 region was bimodal, with one fine mode and one coarse mode. Early in the flame, the fine mode was dominated by particles from incomplete combustion and these particles were rapidly oxidised in the post flame zone. After the hot flame, the fine mode concentration and the particle diameter increases gradually when the temperature decreases due to condensation of vaporised inorganic matter, K, Na, S, Cl, and Zn. For two of the fuels also P could be found in the fine particles. The coarse mode consisted of carbon, refractory metals and considerable amount of alkali. Further, the initial fuel alkali concentration and the alkali to silicon ratio (K + Na)/Si influenced the amount of vaporised aerosol forming alkali matter. Finally, the present study shows that, combustion temperature and fuel ash composition is of major importance for the formation of high temperature aerosols in fixed bed combustion of woody biomass pellets.

  • 114.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Box 726, S-941 28 Piteå, Sweden.
    Gebart, Rikard
    Energy Technology Centre, Box 726, S-941 28 Piteå, Sweden.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    High-temperature aerosol formation in wood pellets flames: Spatially resolved measurements2006In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 147, no 4, p. 278-293Article in journal (Refereed)
    Abstract [en]

    The formation and evolution of high-temperature aerosols during fixed bed combustion of wood pellets in a realistic combustion environment were investigated through spatially resolved experiments. The purpose of this work was to investigate the various stages of aerosol formation from the hot flame zone to the flue gas channel. The investigation is important both for elucidation of the formation mechanisms and as a basis for development and validation of particle formation models that can be used for design optimization. Experiments were conducted in an 8-kW-updraft fired-wood-pellets combustor. Particle samples were withdrawn from the centerline of the combustor through 10 sampling ports by a rapid dilution sampling probe. The corresponding temperatures at the sampling positions were in the range 200-1450 degrees C. The particle sample was size-segregated in a low-pressure impactor, allowing physical and chemical resolution of the fine particles. The chemical composition of the particles was investigated by SEM/EDS and XRD analysis. Furthermore, the experimental results were compared to theoretical models for aerosol formation processes. The experimental data show that the particle size distribution has two peaks, both of which are below an aerodynamic diameter of 2.5 mu m (PM2.5). The mode diameters of the fine and coarse modes in the PM2.5 region were similar to 0.1 and similar to 0.8 mu m, respectively. The shape of the particle size distribution function continuously changes with position in the reactor due to several mechanisms. Early, in the flame zone, both the fine mode and the coarse mode in the PM2.5 region were dominated by particles from incomplete combustion, indicated by a significant amount of carbon in the particles. The particle concentrations of both the fine and the coarse mode decrease rapidly in the hot oxygen-rich flame due to oxidation of the carbon-rich particles. After the hot flame, the fine mode concentration and particle diameter increase gradually when the temperature of the flue gas drops. The main contribution to this comes from condensation on preexisting particles in the gas of alkali sulfates, alkali chlorides, and Zn species formed from constituents vaporized in the fuel bed. The alkali sulfates were found to condense at a temperature of similar to 950 degrees C and alkali chlorides condensed later at similar to 600 degrees C. This agrees well with results of chemical equilibrium calculation of the gas-to-particle conversion temperature. After the hot flame the coarse mode concentration decreased very little when the flue gas was cooled. In addition to carbon, the coarse mode consists of refractory metals and also considerable amounts of alkali. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  • 115.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Piteå, Sweden.
    Grönberg, Carola
    Energy Technology Centre, Piteå, Sweden.
    Öhrman, Olov
    Energy Technology Centre, Piteå, Sweden.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Influence of TiO2 additive on vaporisation of potassium during straw combustion2009In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, no 11, p. 5367-5374Article in journal (Refereed)
    Abstract [en]

    In this work, the influence of TiO2 on the vaporization of K during combustion of straw under fixed bed condition was investigated experimentally. Controlled combustion experiments with a varied amount of TiO2 in straw pellets were performed in an 8 kW pellet burner together with sampling of particles (impactor and absolute filter), analysis of the flue gas composition (Fourier transform infrared, FTIR), and chemical analyses of the collected particles and bottom ash (inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and X-ray diffraction (XRD)). The experimental results showed that the vaporization of K from the fuel bed was significantly reduced when TiO2 was used as an additive. The vaporization of K was reduced by ~40−50% for an optimal amount of TiO2 additive. The optimal added TiO2 for the straw used in this work corresponds to a Ti/K (wt) ratio between ~0.6−1.0. If more TiO2 was added to the fuel, the release of K to the gas phase was not further reduced and unreacted TiO2 was found in the bottom ash.

  • 116.
    Wiinikka, Henrik
    et al.
    Energy Technology Centre, Box 726, SE-941 28, Piteå, Sweden.
    Grönberg, Carola
    Energy Technology Centre, Box 726, SE-941 28, Piteå, Sweden.
    Öhrman, Olov
    Energy Technology Centre, Box 726, SE-941 28, Piteå, Sweden.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Influence of TiO2 Additive on Vaporization of Potassium during Straw Combustion2009In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, p. 5367-5374Article in journal (Refereed)
    Abstract [en]

    In this work, the influence of TiO2 oil the vaporization of K during combustion of straw under fixed bed condition was investigated experimentally. Controlled combustion experiments with a varied amount of TiO2 in straw pellets were performed in an 8 kW pellet burner together with sampling of particles (impactor and absolute filter), analysis of the flue gas composition (Fourier transform infrared, FTIR), and chemical analyses of the collected particles and bottom ash (inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and X-ray diffraction (XRD)). The experimental results showed that the vaporization of K from the fuel bed was significantly reduced when TiO2 was used as an additive. The vaporization of K was reduced by similar to 40-50% for an optimal amount of TiO2 additive. The optimal added TiO2 for the straw used in this work corresponds to a Ti/K (wt) ratio between similar to 0.6-1.0. If more TiO2 was added to the fuel, the release of K to the gas phase was not further reduced and unreacted TiO2 was found in the bottom ash.

  • 117. Yin, YG
    et al.
    Forsling, W
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Antzutkin, O
    Lindberg, M
    Ivanov, A
    Polymeric structure and solid NMR spectra of cadmuim(II) dialkyldithiophosphates (alkyl = propyl, butyl, isopropyl and isobutyl)2003In: Chinese Journal of Chemistry, Vol. 21, no 3, p. 291-5Article in journal (Refereed)
    Abstract [en]

    By dropwise adding thio ligands to concentrated aqueous solutions of Cd(ClO4)(2).6H(2)O, Polymeric complexes, Cd(II) O, O'-dipropyl- dithiophosphate (1), O, O'-dibutyl-dithiophosphate (2), O, O'- diisopropyl-dithiophosphate (3) and O, O'-diisobutyl-dithiophosphate (4) were obtained. The structure of 4 was determined by Xray diffraction analysis, showing that the metal ion sits in distorted tetrahedral sulphur coordination sphere and that the eight-membered bimetallic rings take the twist chair and boat conformations, alternately. Based on facts that the S(1)-Cd bond length [0.25099(12) ran] is shorter than the other S-Cd bond length [0.25399(12)-0.25701(18) nm] and that the S(1)-involving angles [113.45(4)degrees-118.43(5)degrees] are systematically larger than the normal angles of a tetrahedron, the ligands are hypothesized to be erratically functionalized to Cd(H). To certify the steric nonequivalence of ligands, the compounds were investigated by solid C-13, P-31 and Cd-113 NMR spectroscopy.

  • 118. Yin, YG
    et al.
    Forsling, W
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Antzutkin, O
    Lindberg, M
    Ivanov, A
    Polymeric structure and solid P-31, Cd-113 NMR spectra of cadmium(11) dialkyldithiophosphate (alkyl = n-butyl and i-butyl)2003In: Chinese Chemical Letters, ISSN 1001-8417, E-ISSN 1878-5964, Vol. 14, no 2, p. 188-190Article in journal (Refereed)
    Abstract [en]

    Two polymeric complexes, [Cd(BTP)(2)](n) and [Cd(i-BTP)(2)](n) 2, were prepared and investigated by solid P-31 and Cd-113 NMR spectroscopies. The crystal structure of 2 was determined by X-ray diffraction.

  • 119. Zhu, Youjian
    et al.
    Piotrowska, Patrycja
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    van Eyk, Philip J.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kwong, Chi Wai
    Wang, Dingbiao
    Cole, Andrew J.
    de Nys, Rocky
    Gentili, Francesco G.
    Ashman, Peter J.
    Cogasification of Australian Brown Coal with Algae in a Fluidized Bed Reactor2015In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 29, no 3, p. 1686-1700Article in journal (Refereed)
    Abstract [en]

    Recently, the use of algae for CO2 abatement, wastewater treatment, and energy production has increasingly gained attention worldwide. In order to explore the potential of using algae as an alternative fuel as well as the possible challenges related to the algae gasification process, two species of macroalgae, Derbesia tenuissima and Oedogonium sp., and one type of microalgae, Scenedesmus sp. were studied in this research. In this work, Oedogonium sp. was cultivated with two protocols: producing biomass with both high and low levels of nitrogen content. Cogasification of 10 wt % algae with an Australian brown coal was performed in a fluidized bed reactor, and the effects of algae addition on syngas yield, ash composition, and bed agglomeration were investigated. It was found that CO and H-2 yield increased and CO2 yield decreased after adding three types of macroalgae in the coal, with a slight increase of carbon conversion rate, compared to the coal alone experiment. In the case of coal/Scenedesmus sp, the carbon conversion rate decreased with lower CO/CO2/H-2 yield as compared to coal alone. Samples of fly ash, bed ash, and bed material agglomerates were analyzed using scanning electron microscopy combined with an energy dispersive X-ray detector (SEM-EDX) and X-ray diffraction (XRD). It was observed that both the fly ash and bed ash samples from all coal/macroalgae tests contained more Na and K as compared to the coal test. High Ca and Fe contents were also found in the fly ash and bed ash from the coal/Scenedesmus sp. test. Significant differences in the characteristics and compositions of the ash layer on the bed particles were observed from the different tests. Agglomerates were found in the bed material samples after the cogasification tests of coal/Oedogonium N+ and coal/Oedogonium N. The formation of liquid alkalisilicates on the sand particles was considered to be the main reason for agglomeration for the coal/Oedogonium N+ and coal/Oedogonium N tests. Agglomerates of fused ash and tiny silica sand particles were also found in the coal/Scenedesmus sp. test. In this case, however, the formation of a Fe-Al silicate eutectic mixture was proposed to be the main reason for agglomeration. Debersia was suggested to be a potential alternative fuel, which can be cogasified with brown coal without any significant operating problems under the current experimental conditions. However, for the other algae types, appropriate countermeasures are needed to avoid agglomeration and defluidization in the cogasification process.

  • 120.
    Zhu, Youjian
    et al.
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Piotrowska, Patrycja
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    van Eyk, Philip Joseph
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wu, Xuehong
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Zhang, Jun
    School of Energy and Power Engineering, Zhengzhou University of Light Industry, Zhengzhou, Henan 450002, People’s Republic of China.
    Kwong, Chi Wai
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Wang, Dingbiao
    School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, Henan 450001, People’s Republic of China.
    Cole, Andrew J
    MACRO, the Centre for Macroalgal Resources and Biotechnology, James Cook University, Townsville, Queensland 4811, Australia.
    de Nys, Rocky
    MACRO, the Centre for Macroalgal Resources and Biotechnology, James Cook University, Townsville, Queensland 4811, Australia.
    Gentili, Francesco G.
    Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences (SLU), 901 83 Umeå, Sweden.
    Ashman, Peter J.
    School of Chemical Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
    Fluidized bed co-gasification of algae and wood pellets: gas yields and bed agglomeration analysis2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, p. 1800-1809Article in journal (Refereed)
    Abstract [en]

    Algae utilization in energy production has gained increasing attention as a result of its characteristics, such as high productivity, rapid growth rate, and flexible cultivation environment. In this paper, three species of algae, including a fresh water macroalgae, Oedogonium sp., a saltwater macroalgae, Derbersia tenuissima, and a microalgae species, Scenedesmus sp., were studied to explore the potential of using smaller amounts of algae fuels in blends with traditional woody biomasses in the gasification processes. Co-gasification of 10 wt % algae and 90 wt % Swedish wood pellets was performed in a fluidized bed reactor. The effects of algae addition on the syngas yield and carbon conversion rate were investigated. The addition of 10 wt % algae in wood increased the CO, H2, and CH4 yields by 3–20, 6–31, and 9–20%, respectively. At the same time, it decreased the CO2 yield by 3–18%. The carbon conversion rates were slightly increased with the addition of 10 wt % macroalgae in wood, but the microalgae addition resulted in a decrease of the carbon conversion rate by 8%. Meanwhile, the collected fly ash and bed material samples were analyzed using scanning electron microscopy combined with an energy-dispersive X-ray detector (SEM–EDX) and X-ray diffraction (XRD) technique. The fly ashes of wood/marcoalgae tests showed a higher Na content with lower Si and Ca contents compared to the wood test. The gasification tests were scheduled to last 4 h; however, only wood and wood/Derbersia gasification experiments were carried out without significant operational problems. The gasification of 10 wt % Oedogonium N+ and Oedogonium N– led to defluidization of the bed in less than 1 h, and the wood/Scenedesmus (WD/SA) test was stopped after 1.8 h as a result of severe agglomeration. It was found that the algae addition had a remarkable influence on the characteristics and compositions of the coating layer. The coating layer formation and bed agglomeration mechanism of wood/macroalgae was initiated by the reaction of alkali compounds with the bed particles to form low-temperature melting silicates (inner layer). For the WD/SA test, the agglomeration was influenced by both the composition of the original algae fuel as well as the external mineral contaminations. In summary, the operational problems experienced during the co-gasification tests of different algae–wood mixtures were assigned to the specific ash compositions of the different fuel mixtures. This showed the need for countermeasures, specifically to balance the high alkali content, to reach stable operation in a fluidized bed gasifier.

  • 121. Zhu, Youjian
    et al.
    van Eyk, Philip J.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kirtania, Kawnish
    Piotrowska, Patrycja
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    de Nys, Rocky
    Bhattacharya, Sankar
    Gentili, Francesco G.
    Ashman, Peter J.
    Preliminary understanding on the ash behavior of algae during co-gasification in an entrained flow reactor2018In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 175, p. 26-34Article in journal (Refereed)
    Abstract [en]

    Algae are considered as a promising alternative fuel to produce energy due to its advantages such as high production yield, short growth cycle and flexible growing environment. Unfortunately, ash-related issues restrict its thermochemical utilization due to the high ash content and especially the high alkali metal concentration. In this paper, the gasification performance and ash behavior were experimentally analysed for three macro- and micro-algal species. Clear differences in the proximate and ultimate compositions were found between the cultivated algae used in this study and macroalgae (seaweed) harvested from the marine environments. Algal biomass generally contained higher Na and P contents than lignocellulosic biomass. Microalgae also had a relatively high mineral content due to the impurities in the harvesting process which included centrifugal pumping followed by sedimentation. Co-gasification of 20 wt% algae with softwood was investigated using an entrained flow reactor. The addition of both macroalgal species Derbersia tenuissima and Oedogonium to softwood had a limited influence on the gas yields and carbon conversion. On the other hand, the addition of the microalgal species Scenedesmus significantly decreased the main gas yields and carbon conversion. Moreover, the addition of algae clearly changed the residual ash composition of the base fuel. Finally, a preliminary understanding of the ash behavior of the tested algae blends was obtained through the analysis of the fuel ashes and the collected residual ashes. Fouling and corrosion were presumably occurred during the co-gasification of wood/macroalgae blends in view of the high alkali metal content. Microalga Scenedesmus had a high mineral content which could potentially capture the alkali metal in the ash and mitigate fouling when gasified with softwood. The growing environment and harvesting method were found to be significantly affecting the ash behavior implying the need for careful consideration regarding co-gasification process.

  • 122.
    Åberg, Veronica
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boström, Dan
    Fischer, A
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis and absolute configuration of methyl (-)-(3R)-8-(4-bromophenyl)-7-(naphthalen-1-ylmethyl)-5-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyridine-3-carboxylate2002In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 58, no 8, p. 812-814Article in journal (Refereed)
    Abstract [en]

    The title molecule, C26H20BrNO3S, contains a ring-fused 2-pyridinone framework substituted with a 4-bromo-phenyl-, a naphthalen-1-ylmethyl and a methoxycarbonyl substituent. The main goal of this work was to confirm the stereochemistry for the methoxycarbonyl substituent, which proved to be 3R. Moreover, the 4-bromophenyl substituent was shown to be rotated out of the plane of the 2-pyridinone ring, with a torsion angle of 61.2 (5)°. To allow the best packing arrangement, the naphthalen-1-ylmethyl substituent is positioned to mediate an intermolecular - interaction.

  • 123.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hedman, Henry
    Energy Technology Centre, Piteå, Sweden.
    Effect of kaolin and limestone addition on slag formation during combustion of wood fuels2004In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, no 5, p. 1370-1376Article in journal (Refereed)
    Abstract [en]

    Ash-related problems have more than occasionally been observed in wood-fuel-fired boilers and also recently in wood-pellet burners. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were, therefore, to determine the effects of kaolin and limestone addition on the slagging propensities of problematic and problem-free wood fuels during combustion in residential pellet appliances (burners), thus contributing to the understanding of the role of kaolin and limestone in preventing slagging on furnace grates. Pellets with additive-to-fuel ratios between 0 and 0.7 wt %d.s. were combusted in three different types of burner constructions (10 kW): over-, horizontal-, and under-feeding of the fuel. The collected slag deposits from the under-fed burner as well as the corresponding deposited fly ash in the boiler were characterized with X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The initial sintering temperatures of the formed slags were also determined. By adding limestone with an additive-to-fuel ratio of 0.5 wt %d.s. to the problematic stemwood raw material (Si-enriched probably because of contamination of sand/soil), the severe slagging of the fuel could totally be eliminated. Adding kaolin to the problematic raw material gave a minor decrease in slagging tendency of the problematic raw material and a major increase in slagging tendency of the problem-free stemwood raw material. When adding limestone to the problematic raw material, the composition of the formed slag was changed from relatively low temperature melting silicates to high temperature melting silicates and oxides. On the other hand, kaolin addition to the problematic raw material changed the content of the slag from mainly Ca-Mg silicates to be dominated by K-Al silicates which have relatively low melting points. When introducing kaolin to the problem-free raw material, the high temperature melting Ca-Mg oxides react to form lower temperature melting Ca-Al-K silicates. Chemical equilibrium model calculations were used to interpret the experimental findings, and generally good qualitative agreements between modeling and experimental results were obtained.

  • 124. Öhman, Marcus
    et al.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Kofod-Hansen, Marie
    Minskade askrelaterade driftsproblem genom inblandning av torv i åkerbränslen2010Report (Other academic)
    Abstract [sv]

    Resultaten visar att inblandning av typisk starrbaserad bränntorv i salix och rörflen med låg askhalt ger positiva effekter vad avser bäddagglomerering och beläggningsbildning/(korrosion) i pannors konvektionsdelar redan vid relativt låga inblandningsgrader (15 vikts-% på TS basis). En starrbaserad bränntorv med relativt högt Ca/Si förhållande bör väljas för sameldning med salix i rosteranläggningar för att inte öka slaggningsrisken. Samma torvtyp kan också i rosteranläggningar nyttjas i sameldning med rörflen med låg askhalt (relativt låga inblandningsgrader räcker) och vetehalm (höga inblandningsgrader krävs) för att reducera slaggningsrisken. Vid val av torvslag för att maximera de ovanstående positiva effekterna vid förbränning kan därför en allmän rekommendation göras att torvar med hög askhalt (starrinnehållande torv), och gärna med högt inslag av svavel, ger de bästa sameldningsegenskaperna med det tilläget att vid rostereldning bör en torv med relativt högt Ca/Si förhållande väljas (gärna upp mot 1 på vikts-% basis).

  • 125.
    Öhman, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lundholm, Karin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hedman, Hedman
    Energy Technology Centre, Piteå.
    Lundberg, Margareta
    Kvaerner Pulping AB, Power Division, Göteborg.
    Ash Transformations during Combustion of Meat-, Bonemeal, and RDF in a (bench-scale) Fluidized Bed Combustor2003In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 17, no 5, p. 1153-1159Article in journal (Refereed)
    Abstract [en]

    Following the recent Bovine spongiform encephalopathy (BSE) experiences, thermal treatment of meat- and bonemeal (MBM) in existing fluidized bed combustion (FBC) plants for refuse-derived fuels (RDFs) has evolved as an interesting disposal and disintegration method. However, only a limited number of studies have previously been performed for combustion of MBM in fluidized beds. The objectives of the present work were, therefore, to determine the bed agglomeration tendencies of these materials during combustion in fluidized beds and to evaluate the effects of dolomite and kaolin addition to the fuel mix, as well as to elucidate the overall ash transformation mechanisms governing the potential bed agglomeration and fouling processes. By controlled agglomeration experiments in a 5 kW bench-scale fluidized bed reactor, the fuel-specific critical agglomeration temperatures in normal quartz bed material were determined for the different fuel/additive mixtures. All collected samples of bed materials, final bed agglomerates, and cyclone ashes were analyzed using SEM/EDS and XRD. The results indicated that the MBM fuels could be expected to be problematic concerning bed agglomeration in normal quartz beds, while kaolin and possibly dolomite addition could be used to reduce this risk to moderate levels. A significant elemental fractionation between the bed material and the cyclone ash was obtained. Apatite (Ca5(PO4)3(OH) or potentially some other calcium phosphates are elutriated from the bed and enriched in the fly ash, while sodium and potassium are enriched in the bed material. The characteristics and the corresponding melting behavior estimations of the necks formed between agglomerated bed particles suggest that silicate melts are responsible for the bed agglomeration. Results from XRD analysis of the fly ash formed from the fuels used in the present study indicated that the risk for melt-related fly ash problems seem relatively small.

  • 126.
    Örberg, Håkan
    et al.
    Sveriges Lantbruksuniversitet, Enheten för Biomassateknologi och Kemi.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Öhman, Marcus
    Teknikutveckling för ökad etablering och nyttjande av rörflen: Demonstrationsförsök i fullskala2010Report (Other academic)
    Abstract [sv]

    Resultaten visar att energigräset rörflen kan utgöra ett kompletterande bränsle till det skogsbränsle och den torv som idag används i svenska värme- och kraftvärmeanläggningar. En inblandning av rörflen med ca 10 % på energibasis i en bränslemix som för övrigt består av 10-20 % carextorv och 70-80 % träbränsle har i demonstrationsförsök visat goda resultat. Denna bränslemix har vid fullskaliga förbränningsförsök i fluidiserande bädd (Hedensbyn,CFB 98 MW) under sammanlagt 4 dygn inte gett upphov till störningar eller negativa effekter på utrustning eller ökade utsläpp i rökgaserna i form av partiklar eller gasformiga emissioner. Vid simulerade påverkan på överhettare i form av kylda sonder har även konstaterats att beläggningstillväxten varit oförändrad och ej givit upphov till ökad korrosion.

    Inblandning i bränslemixen har skett med hackad rörflen (40-50 mm) i torvdelen för att en jämn inblandning kunde åstadkommas. Rörflensmaterialet har levererats i samband med skörden så att det hackats direkt på fältet med exakthack kopplad till vagn eller med containerhantering. Vid leverans under vår och försommar har rörflenen hållit mycket låg fukthalt med ett medel på 11,3 % fukt. Jämförande studier har gjorts med system där rörflen vid skörden under vår pressats till storbalar för vidare transport till terminal eller gårdscentrum. Detta system har visat sig mindre effektivt jämfört med direkthackning på fältet och transport av hackat material till värmeverk. En fördel med storbalssystemet är dock att det möjliggör mer kostnadseffektiv lagring utan att t.ex. fukthalten höjs under lagringstiden. Även vägtransport från terminal eller gårdscentrum till värmeverk har visat sig mer effektivt med storbalar jämfört med hackat material. Vid lastning av stora fyrkantsbalar (90x120x220 cm) på lastbil med släp uppnåddes i stort sett dubbla lastvikten jämfört med hackad rörflen (20,9 ton jmf. m. 11,0 ton).

    För de något mindre anläggningarna av typen rosterpannor som provats (0,6 och 4 MW) har den briketterade formen av rörflen använts för att uppnå en jämn och koncentrerad bränslematning. Även här har en blandning av rörflen och torv visat sig användbar och speciellt för rörflen med låg askhalt har torvinblandning på 15 vikts-% av gett minskad tendens till sintring av askan. Rörflen med hög askhalt (utan torvinblandning) har kunnat sameldas med träbränsle utan risk för sintrad aska i dessa anläggningar. Tillverkningen av briketter för försöken, sammanlagt ca 35 ton, varav hälften med inblandning av torv har genomförts utan störningar och med bra kvalité på briketterna.

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