umu.sePublikasjoner
Endre søk
Begrens søket
123 1 - 50 of 114
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ajaikumar, Samikannu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ahlkvist, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Kordas, K
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Highly active and selective bimetallic catalysts supported on transition metal oxides for the oxidation of α-pinene using molecular oxygen2010Konferansepaper (Annet vitenskapelig)
  • 2. Alhalaweh, Amjad
    et al.
    George, Sumod
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Velaga, Sitaram P.
    1:1 and 2:1 urea-Succinic acid cocrystals: structural diversity, solution chemistry, and thermodynamic stability2010Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, nr 11, 4847-4855 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to study the crystal structures of 1:1 and 2:1 urea-succinic acid (U-SA) cocrystals and to investigate the role of solution chemistry in the formation and stability of different stoichiometric cocrystals. The structural diversity of other urea-dicarboxylic acid cocrystals is also discussed. The 1:1 U-SA cocrystal was stabilized by an acid-amide heterosynthon while acid-amide heterosynthons and amide amide homosynthons stabilized the 2:1 cocrystals. The hydrogen bonding motifs 1:1 and 2:1 U-SA cocrystals were consistent with other urea-dicarboxylic acid systems with similar stoichiometrics. The 1:1 cocrystals were transformed to 2:1 cocrystals upon slurrying in various solvents at 25 degrees C. The phase solubility diagram was used to define the stability regions of different solid phases in 2-propanol at 25 degrees C. While no phase stability region for 1:1 cocrystal could be found, the stable regions for the 2:1 cocrystals and their pure components were defined he eutectic points. The solubility of the 2:1 cocrystals was dependent on the concentration of the ligand in the solution and explained by the solubility product and 1:1 solution complexation. The mathematical models predicting the solubility of the 2:1 cocrystals were evaluated and found to fit the experimental data.

  • 3.
    Barath, Stefan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Mills, Nicholas L
    Lundbäck, Magnus
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Törnqvist, Håkan
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Lucking, Andrew J
    Langrish, Jeremy P
    Söderberg, Stefan
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Westerholm, Roger
    Löndahl, Jakob
    Donaldson, Ken
    Mudway, Ian S
    Sandström, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Newby, David E
    Blomberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Impaired vascular function after exposure to diesel exhaust generated at urban transient running conditions2010Inngår i: Particle and fibre toxicology, ISSN 1743-8977, Vol. 7, nr 1, 19- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND: Traffic emissions including diesel engine exhaust are associated with increased respiratory and cardiovascular morbidity and mortality. Controlled human exposure studies have demonstrated impaired vascular function after inhalation of exhaust generated by a diesel engine under idling conditions.

    OBJECTIVES: To assess the vascular and fibrinolytic effects of exposure to diesel exhaust generated during urban-cycle running conditions that mimic ambient 'real-world' exposures.

    METHODS: In a randomised double-blind crossover study, eighteen healthy male volunteers were exposed to diesel exhaust (approximately 250 mug/m3) or filtered air for one hour during intermittent exercise. Diesel exhaust was generated during the urban part of the standardized European Transient Cycle. Six hours post-exposure, vascular vasomotor and fibrinolytic function was assessed during venous occlusion plethysmography with intra-arterial agonist infusions.

    MEASUREMENTS AND MAIN RESULTS: Forearm blood flow increased in a dose-dependent manner with both endothelial-dependent (acetylcholine and bradykinin) and endothelial-independent (sodium nitroprusside and verapamil) vasodilators. Diesel exhaust exposure attenuated the vasodilatation to acetylcholine (P < 0.001), bradykinin (P < 0.05), sodium nitroprusside (P < 0.05) and verapamil (P < 0.001). In addition, the net release of tissue plasminogen activator during bradykinin infusion was impaired following diesel exhaust exposure (P < 0.05).

    CONCLUSION: Exposure to diesel exhaust generated under transient running conditions, as a relevant model of urban air pollution, impairs vasomotor function and endogenous fibrinolysis in a similar way as exposure to diesel exhaust generated at idling. This indicates that adverse vascular effects of diesel exhaust inhalation occur over different running conditions with varying exhaust composition and concentrations as well as physicochemical particle properties. Importantly, exposure to diesel exhaust under ETC conditions was also associated with a novel finding of impaired of calcium channel-dependent vasomotor function. This implies that certain cardiovascular endpoints seem to be related to general diesel exhaust properties, whereas the novel calcium flux-related effect may be associated with exhaust properties more specific for the ETC condition, for example a higher content of diesel soot particles along with their adsorbed organic compounds.

  • 4. Basavoju, Srinivas
    et al.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Velaga, Sitaram P.
    Indomethacin-saccharin cocrystal: design, synthesis and preliminary pharmaceutical characterization2008Inngår i: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 25, nr 3, 530-541 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose. To design and prepare cocrystals of indomethacin using crystal engineering approaches, with the ultimate objective of improving the physical properties of indomethacin, especially solubility and dissolution rate. Materials and Methods. Various cocrystal formers, including saccharin, were used in endeavours to obtain indomethacin cocrystals by slow evaporation from a series of solvents. The melting point of crystalline phases was determined. The potential cocrystalline phase was characterized by DSC, IR, Raman and PXRD techniques. The indomethacin-saccharin cocrystal (hereafter IND-SAC cocrystal) structure was determined from single crystal X-ray diffraction data. Pharmaceutically relevant properties such as the dissolution rate and dynamic vapour sorption (DVS) of the IND-SAC cocrystal were evaluated. Solid state and liquid-assisted (solvent-drop) cogrinding methods were also applied to indomethacin and saccharin. Results. The IND-SAC cocrystals were obtained from ethyl acetate. Physical characterization showed that the IND-SAC cocrystal is unique vis-a-vis thermal, spectroscopic and X-ray diffraction properties. The cocrystals were obtained in a 1:1 ratio with a carboxylic acid and imide dimer synthons. The dissolution rate of IND-SAC cocrystal system was considerably faster than that of the stable indomethacin gamma-form. DVS studies indicated that the cocrystals gained less than 0.05% in weight at 98%RH. IND-SAC cocrystal was also obtained by solid state and liquid-assisted cogrinding methods. Conclusions. The IND-SAC cocrystal was formed with a unique and interesting carboxylic acid and imide dimer synthons interconnected by weak N-H center dot center dot center dot O hydrogen bonds. The cocrystals were non-hygroscopic and were associated with a significantly faster dissolution rate than indomethacin (gamma-form).

  • 5. Basavoju, Srinivas
    et al.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Velaga, Sitaram P.
    Pharmaceutical cocrystal and salts of norfloxacin2006Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, nr 12, 2699-2708 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to investigate the structural and pharmaceutical properties of norfloxacin ( a poorly soluble antibacterial drug), its cocrystal, and salts. Norfloxacin in the anhydrous form ( form A, 1) was crystallized. It was cocrystallized with isonicotinamide ( 2), and organic salts were prepared with succinic acid, malonic acid, and maleic acid (3-5, respectively). These phases were characterized by differential scanning calorimetry (DSC), infrared (IR) and Raman spectroscopy, and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction data were obtained, and crystal structures were solved. The apparent solubility of these phases was determined. Robust O-H center dot center dot center dot O, O-H center dot center dot center dot O-, O-H center dot center dot center dot N, N-H center dot center dot center dot O, N+- H center dot center dot center dot O-, and N-H center dot center dot center dot N interactions were present in all these structures. Quinolone moieties in these structures stack with pi...pi interactions and form channels to include CHCl3 or H2O. Herein we report a new cocrystal and salts of norfloxacin with improved aqueous solubility.

  • 6. Basavoju, Srinivas
    et al.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Velaga, Sitaram P
    Pharmaceutical salts of fluoroquinolone antibacterial drugs with acesulfame sweetener2012Inngår i: Molecular Crystals and Liquid Crystals, ISSN 1542-1406, Vol. 562, nr 1, 254-264 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel organic salts of norfloxacin and ciprofloxacin with artificial sweeteners such as saccharin and acesulfame were prepared. The two salts 1 and 2 were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Finally, the crystal structures were solved by single crystal X-ray diffraction data and the structures were analyzed in terms of supramolecular synthons. In norfloxacin acesulfamate 1, two norfloxacin cations and two acesulfame anions form an eight membered cyclic tetramer supramolecular synthon. The salt, ciprofloxacin acesulfamate 2, has a similar structure as salt 1. This study contributes the importance of crystal engineering and supramolecular chemistry to the pharmaceutical applications in terms of interactions and structural correlations in the design of new solid phases. Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.

  • 7.
    Behndig, Annelie
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Mudway, IS
    Brown, JL
    Stenfors, Nikolai
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Helleday, Ragnberth
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Duggan, ST
    Wilson, SJ
    Boman, C
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Cassee, FR
    Frew, AJ
    Kelly, FJ
    Sandström, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Blomberg, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Lungmedicin.
    Airway antioxidant and inflammatory responses to diesel exhaust exposure in healthy humans.2006Inngår i: European Respiratory Journal, ISSN 0903-1936, E-ISSN 1399-3003, Vol. 27, nr 2, 359-365 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [sv]

    Pulmonary cells exposed to diesel exhaust (DE) particles in vitro respond in a hierarchical fashion with protective antioxidant responses predominating at low doses and inflammation and injury only occurring at higher concentrations. In the present study, the authors examined whether similar responses occurred in vivo, specifically whether antioxidants were upregulated following a low-dose DE challenge and investigated how these responses related to the development of airway inflammation at different levels of the respiratory tract where particle dose varies markedly. A total of 15 volunteers were exposed to DE (100 microg x m(-3) airborne particulate matter with a diameter of <10 microm for 2 h) and air in a double-blinded, randomised fashion. At 18 h post-exposure, bronchoscopy was performed with lavage and mucosal biopsies taken to assess airway redox and inflammatory status. Following DE exposure, the current authors observed an increase in bronchial mucosa neutrophil and mast cell numbers, as well as increased neutrophil numbers, interleukin-8 and myeloperoxidase concentrations in bronchial lavage. No inflammatory responses were seen in the alveolar compartment, but both reduced glutathione and urate concentrations were increased following diesel exposure. In conclusion, the lung inflammatory response to diesel exhaust is compartmentalised, related to differing antioxidant responses in the conducting airway and alveolar regions.

  • 8. Bergström, Dan
    et al.
    Israelsson, Samuel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Dahlqvist, Sten-Axel
    Gref, Rolf
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Wästerlund, Iwan
    Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets2008Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 89, nr 12, 1324-1329 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (similar to 300 kg h(-1)). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant. The results are of practical importance suggesting that grinding of saw dust particle sizes below 8 mm is probably needless when producing softwood pellets. Thus it seem that less energy could be used if only over sized particles are grinded before pelletizing.

  • 9. Bolling, Anette Kocbach
    et al.
    Pagels, Joakim
    Yttri, Karl Espen
    Barregard, Lars
    Sallsten, Gerd
    Schwarze, Per E
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Health effects of residential wood smoke particles: the importance of combustion conditions and physicochemical particle properties2009Inngår i: Particle and Fibre Toxicology, ISSN 1743-8977, E-ISSN 1743-8977, Vol. 6, 29Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Background: Residential wood combustion is now recognized as a major particle source in many developed countries, and the number of studies investigating the negative health effects associated with wood smoke exposure is currently increasing. The combustion appliances in use today provide highly variable combustion conditions resulting in large variations in the physicochemical characteristics of the emitted particles. These differences in physicochemical properties are likely to influence the biological effects induced by the wood smoke particles.

    Outline: The focus of this review is to discuss the present knowledge on physicochemical properties of wood smoke particles from different combustion conditions in relation to wood smoke-induced health effects. In addition, the human wood smoke exposure in developed countries is explored in order to identify the particle characteristics that are relevant for experimental studies of wood smoke-induced health effects. Finally, recent experimental studies regarding wood smoke exposure are discussed with respect to the applied combustion conditions and particle properties.

    Conclusion: Overall, the reviewed literature regarding the physicochemical properties of wood smoke particles provides a relatively clear picture of how these properties vary with the combustion conditions, whereas particle emissions from specific classes of combustion appliances are less well characterised. The major gaps in knowledge concern; (i) characterisation of the atmospheric transformations of wood smoke particles, (ii) characterisation of the physicochemical properties of wood smoke particles in ambient and indoor environments, and (iii) identification of the physicochemical properties that influence the biological effects of wood smoke particles.

  • 10.
    Boman, B Christoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Forsberg, A Bertil
    Järvholm, Bengt G
    Adverse health effects from ambient air pollution in relation to residential wood combustion2003Inngår i: Scandinavian Journal of Work, Environment and Health, Vol. 29, nr 4, 251-260 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 11.
    Boman, Christoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Characterization of inorganic particulate matter from residential combustion of pelletized biomass fuels2004Inngår i: Energy and Fuels, ISSN 0887-0624, Vol. 18, nr 2, 338-348 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The increased focus on potential adverse health effects associated with exposure to ambient particulate matter (PM) motivates a careful characterization of particle emissions from different sources. Combustion is a major anthropogenic source of fine PM, and, in urban areas, traditional residential wood combustion can be a major contributor. New and upgraded biomass fuels have become more common, and fuel pellets are especially well-suited for the residential market. The objective of the present work was to determine the mass size distributions, elemental distributions, and inorganic-phase distributions of PM from different residential combustion appliances and pelletized biomass fuels. In addition, chemical equilibrium model calculations of the combustion process were used to interpret the experimental findings. Six different typical pellet fuels were combusted in three different commercial pellet burners (10−15 kW). The experiments were performed in a newly designed experimental setup that enables constant-volume sampling. Total-PM mass concentrations were measured using conventional filters, and the fractions of products of incomplete combustion and inorganic material were thermally determined. Particle mass size distributions were determined using a 13-step low-pressure cascade impactor with a precyclone. The PM was analyzed for morphology (using environmental scanning electron microscopy, ESEM), elemental composition (using energy-dispersive spectroscopy, EDS), and crystalline phases (using X-ray diffractometry, XRD). For complementary chemical structural characterization, time-of-flight secondary ion mass spectrometry (TOF−SIMS), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy were also used. The emitted particles were mainly found in the fine (<1 μm) mode with mass median aerodynamic diameters of 0.20−0.39 μm and an average PM1 of 89.5% ± 7.4% of total PM. Minor coarse-mode fractions (>1 μm) were present primarily in the experiments with bark and logging residues. Relatively large and varying amounts (28%−92%) were determined to be products of incomplete combustion. The inorganic elemental compositions of the fine particles were dominated by potassium, chlorine, and sulfur, with minor amounts of sodium and zinc. The dominating alkali phase was KCl, with minor but varying amounts of K3Na(SO4)2 and, in some cases, also K2SO4. The results showed that zinc is almost fully volatilized, subsequently and presumably forming a more complex solid phase than that previously suggested (ZnO). However, the formation mechanism and exact phase identification remain to be elucidated. With some constrains, the results also showed that the amounts and speciation of the inorganic PM seemed to be quite similar to that predicted by chemical equilibrium calculations.

  • 12.
    Boman, Christoffer
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Westerholm, Roger
    Pettersson, Esbjörn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Evaluation of a constant volume sampling set-up for residential biomass fired appliances: influence of dilution conditions on particulate and PAH emissions2005Inngår i: Biomass and Bioenergy, ISSN 0961-9534, Vol. 29, nr 4, 258-268 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increased concerns about particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH) emissions from residentialbiomass combustion and their potential health effects, motivates detailed emission measurements under controlled conditions. Traditional sampling in raw flue gases can suffer from drawbacks mainly related to transient flows and the condensable nature of organic compounds. Whole flow dilution with constantvolumesampling (CVS) is an alternative method but different samplingconditions may, however, influence the emission characteristics. The objective was to design a CVS system for emission measurements in residentialbiomassfiredappliances and determine the influence of dilutionsamplingconditions on the characteristics and distributions of PM and PAH. Softwood pellets were combusted in a pellet stove with variations in; dilution ratio (3–7x), sampling temperature (45–75 °C), dilution tunnel residence time (2–4 s) and fuel load (2.3 and 4.8 kW) according to a statistical experimental design. The samplingconditions did not influence either the emission concentrations of PM, CO and NO or the particle size distribution. Variations in residence time had no significant effect on any studied emission parameter. However, increased concentrations of organic gaseous carbon (OGC) and PAH were observed with increased dilution ratio. The distribution between particulate and semivolatile phase was influenced for 12 of the 37 analyzed PAH compounds, mainly by increased fractions of semivolatile material at higher sampling temperature. No influence of sampling temperature was observed for the concentrations of PAHtot or the dominating PAH compounds, i.e. phenanthrene, fluoranthene and pyrene. The results together with practical considerations also suggest sampling at 50±5 °C and 3–4 times dilution as robust and applicable conditions in the presently designed setup.

  • 13.
    Boström, Dan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Gunnar
    Division of Energy Engineering, Department of Applied Physics and Mechanical Engineering, Luleå Technical University.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Division of Energy Engineering, Department of Applied Physics and Mechanical Engineering, Luleå Technical University.
    Ash transformations in fluidized-bed combustion of rapeseed meal2009Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, nr 5, 2700-2706 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The global production of rapeoil is increasing. A byproduct is rapeseed meal that is a result of the oil extraction process. Presently the rapeseed meal mainly is utilized as animal feed. An interesting alternative use is, however, energy conversion by combustion. This study was undertaken to determine the combustion properties of rapeseed meal and bark mixtures in a bubbling fluidized bed, with emphasis on gas emissions, ash formation, -fractionation and -interaction with the bed material. Due to the high content of phosphorus in rapeseed meal the fuel ash is dominated by phosphates, in contrast to most woody biomass where the ash is dominated by silicates. From a fluidized bed combustion (FBC) point of view, rapeseed meal could be a suitable fuel. Considering FBC agglomeration effects, pure rapeseed meal is in level with the most suitable fuels, as earlier tested by the methods utilized in the present investigation. The SO2 emission, however, is higher than most woody biomass fuels as a direct consequence of the high levels of sulfur in the fuel. Also the particulate matter emission, both submicron and coarser particles, is higher. Again this can be attributed the high ash content of rapeseed meal. The high abundance of SO2 is apparently effective for sulfatization of KCl in the flue gas. Practically no KCl was observed in the particulate matter of the flue gas. A striking difference in the mechanisms of bed agglomeration for rapeseed meal compared to woody biomass fuels was also observed. The ubiquitous continuous layers on the bed grains found in FBC combustion of woody biomass fuels was not observed in the present investigation. Instead very thin and discontinuous layers were observed together with isolated partly melted bed ash particles. The latter could occasionally be seen as adhered to the quartz bed grains. Apparently the bed agglomeration mechanism, that obviously demanded rather high temperatures, involved more of adhesion by partly melted ash derived potassium -calcium phosphate bed ash particles/droplets than direct attack of gaseous alkali on the quartz bed grains forming potassium -calcium silicate rich bed grain layers. Am explanation could be found in the considerable higher affinity for base cations of phosphorus than silicon. This will to a great extent withdraw the present basic oxides from attacking the quartz bed grains with agglomeration at low temperatures as a result.

  • 14.
    Boström, Dan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Grimm, Alejandro
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Björnbom, Emilia
    Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Öhman, Marcus
    Division of Energy Engineering, Luleå University of Technology, SE- 971 87 Luleå, Sweden.
    Influence of kaolin and calcite additives on ash transformations in small-scale combustion of oat2009Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, nr 10, 5184-5190 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A growing interest has been observed for the use of cereal grains in small- and medium-scale heating. Previous studies have been performed to determine the fuel quality of various cereal grains for combustion purposes. The present investigation was undertaken in order to elucidate the potential abatement of low-temperature corrosion and deposits formation by using fuel additives (calcite and kaolin) during combustion of oat. Special emphasis was put on understanding the role of slag and bottom ash composition on the volatilization of species responsible for fouling and emission of fine particles and acid gases. The ash fractions were analyzed with scanning electron micro scopy/energy dispersive spectroscopy (SEM/EDS), for elemental composition, and with X-ray diffraction (XRD) for identification of crystalline phases. The previously reported K and Si capturing effects of kaolin additive were observed also in the present study using P-rich biomass fuels. That is, the prerequisites for the formation of low melting K-rich silicates were reduced. The result of using kaolin additive on the bottom ash was that no slag was formed. The effect of the kaolin additive on the formation of submicrometer flue gas particles was an increased share of condensed K-phosphates at the expense of K-sulfate and KCl. The latter phase was almost completely absent in the particulate matter. Consequently, the levels of HCl and SO2 in the flue gases increased somewhat. The addition of both calcite assortments increased the amount of farmed slag, although to a considerably higher extent for the precipitated calcite. P was captured to a higher degree in the bottom ash, compared to the combustion of pure oat. The effect of the calcite additives on the fine particle emissions in the flue gases was that the share of K-phosphate decreased considerably, while the content of K-sulfate and KCl increased. Consequently, also the flue-gas levels of acidic HCl and SO2 decreased. This implies that the low-temperature corrosion observed in small-scale combustion of oat possibly can be abated by employing calcite additives. Alternatively, if problems with slagging and deposition of corrosive matter at heat convection surfaces are to be avoided, kaolin additive can be utilized, on the condition that the higher concentrations of acidic gases can be tolerated.

  • 15.
    Brostrom, Markus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Pommer, Linda
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Branca, C.
    Di Blasi, C.
    Influence of torrefaction on the devolatilization and oxidation kinetics of wood2012Inngår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 96, 100-109 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Devolatilization and oxidation kinetics of torrefied wood have been studied by evaluating thermogravimetric curves measured in nitrogen and air at various heating rates. Samples consist of Norway spruce wood chips torrefied at several process temperatures and residence times. Data about untreated wood have also been obtained for comparison. Measured curves are well predicted by means of a five-reaction mechanism, consisting of three devolatilization reactions for the pseudo-components hemicellulose. cellulose and lignin and, in air, of two additional reactions for char devolatilization and combustion. The torrefaction pre-treatment only requires model modifications in the amounts of volatiles generated from the decomposition of pseudo-components, indicating that only their relative percentages and not their reactivities are modified. On the other hand, a slightly different thermal stability is found for the char generated from torrefied wood, which results in higher activation energy and lower reaction order for the oxidation step. Hence torrefaction conditions can affect the subsequent conversion characteristics of the char product. (C) 2012 Elsevier B.V. All rights reserved.

  • 16.
    Broström, Marcus
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Utveckling och utvärdering av mätteknik och additiv för alkalikomponenter i termiska energiomvandlingsprocesser2006Rapport (Annet (populærvitenskap, debatt, mm))
  • 17.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Aspects of alkali chloride chemistry on deposit formation and high temperature corrosion in biomass and waste fired boilers2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Combustion of biomass and waste has several environmental, economical and political advantages over the use of fossil fuels for the generation of heat and electricity. However, these fuels often have a significantly different composition and the combustion is therefore associated with additional operational problems. A high content of chlorine and alkali metals (potassium and sodium) often causes problems with deposit formation and high temperature corrosion. Some different aspects of these issues are addressed in this thesis.

    The overall objective of this thesis was to study and highlight different means by which operational problems related to alkali chlorides can be overcome, reduced or prevented.

    The most important results of this thesis are: (1) A full description of the in-situ alkali chloride monitor, its operational principles, the calibration procedure, and an example of a full-scale application was made public in a scientific publication. (2) Efficient sulfation of gaseous alkali chlorides in a full-scale boiler was achieved by injecting ammonium sulfate in a water solution into the hot flue gas. (3) Reduced deposit growth and corrosion rates were achieved by lowering the alkali chloride concentration in the flue gas by sulfation. (4) Evidence of decreased deposit growth and chlorine content in deposits during peat co-combustion. (5) Results are presented from high temperature corrosion tests with different superheater steels in two different combustion environments. (6) Controlled KCl and NaCl condensation under simulated combustion conditions resulted in deposits which consisted of mostly pure phases, in contrast to the solid solution that would be expected under the prevailing conditions at chemical equilibrium.

  • 18.
    Broström, Markus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Enestam, Sonja
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mäkelä, Kari
    Condensation in the KCl-NaCl system2013Inngår i: Fuel processing technology, ISSN 0378-3820, Vol. 105, 142-148 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Condensation of gaseous KCl and NaCl is known to participate in deposit formation and high temperature corrosion processes in heat and power plants. Little is known about interaction between the two salts, which is of interest for the overall understanding of deposit and corrosion problems. Within this study, condensation at different material surface temperatures and salt mixtures was investigated.

    Salt vapors were prepared by temperature controlled evaporation. A cooled condensation probe with a temperature gradient was inserted in the hot gas. After exposure, the probe surface was visually inspected and analyzed with SEM/EDS and XRD for elemental and phase composition. TGA/DTA was used to provide complementary information on vaporization and sintering.

    The results indicated that a mixture of KCl and NaCl probably condenses as separate phases at concentrations and temperatures below the melting points of the salts. Condensation was possibly followed by a secondary sintering process. It was verified by TGA/DTA that a mixture of solid KCl and NaCl particles sinters and melts rapidly at temperatures above the melting temperature of a corresponding solution. It was also seen that sintering took place at lower temperatures with slow solid-gas interactions, possibly with the formation of solid solutions.

  • 19.
    Broström, Markus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Kassman, Håkan
    Vattenfall Power Consultant AB, Box 1046, SE-611 29 Nyköping, Sweden.
    Helgesson, Anna
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Berg, Magnus
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Andersson, Christer
    Vattenfall Research and Development AB, SE-814 26 Älvkarleby, Sweden.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Sulfation of corrosive alkali chlorides by ammonium sulfate in a biomass fired CFB boiler2007Inngår i: Fuel processing technology, ISSN 0378-3820, Vol. 88, nr 11-12, 1171-1177 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomass and waste derived fuels contain relatively high amounts of alkali and chlorine, but contain very little sulfur. Combustion of such fuels can result in increased deposit formation and superheater corrosion. These problems can be reduced by using a sulfur containing additive, such as ammonium sulfate, which reacts with the alkali chlorides and forms less corrosive sulfates. Ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) is patented and known as "ChlorOut". IACM measures the concentrations of alkali chlorides (mainly KCl in biomass combustion) at superheater temperatures. Tests with and without spraying ammonium sulfate into the flue gases have been performed in a 96MW(th)/25MW(e) circulating fluidized bed (CFB) boiler. The boiler was fired mainly with bark and a chlorine containing waste. KCl concentration was reduced from more than 15 ppm to approximately 2 ppm. during injection of ammonium sulfate. Corrosion probe measurements indicated that both deposit formation and material loss due to corrosion were decreased using the additive. Analysis of the deposits showed significantly higher concentration of sulfur and almost no chlorine in the case with ammonium sulfate. Results from impactor measurements supported that KCl was sulfated to potassium sulfate by the additive. (C) 2007 Elsevier B.V. All rights reserved.

  • 20.
    Brus, Elisabet
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Umeå universitet.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mechanisms of bed agglomeration during fluidized-bed combustion of biomass fuels2005Inngår i: Energy & Fuels, ISSN 0887-0624, Vol. 19, nr 3, 825-832 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The major ash-related problem encountered in fluidized beds is bed agglomeration, which, in the worst case, may result in total defluidization of the bed and unscheduled downtime. Because of the special ash-forming constituents of biomass fuels, several of these fuels have been shown to be especially problematic. Despite the frequent reporting, a precise and quantitative knowledge of the bed agglomeration process during fluidized bed combustion of biomass fuels has not yet been presented. Bed sampling versus operation time was performed in four different biomass-fired full-scale fluidized beds, as well as during controlled fluidized bed agglomeration tests in bench-scale testing of five representative biomass fuels. The bed materials and agglomerates were further analyzed using scanning electron microscopy, coupled with energy-dispersive spectroscopy SEM/EDS, to determine the characteristics of the formed bed particle layers. For typical wood fuels, coating-induced agglomeration with subsequent attack reaction and diffusion by calcium into the quartz was identified to be the dominating bed agglomeration mechanism. Low-melting calcium-based silicates (including minor amounts of, for example, potassium) were formed with subsequent viscous-flow sintering and agglomeration. For high-alkali-containing biomass fuels, direct attack of the quartz bed particle by potassium compounds in a gas or aerosol phase formed a layer of low-melting potassium silicate. Thus, formation and subsequent viscous-flow sintering and agglomeration seemed to be the dominating agglomeration mechanism for these fuels.

  • 21.
    Brus, Elisabet
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Hedman, Henry
    Energy Technology Centre, Piteå, Sweden.
    Eklund, Anders
    Bed agglomeration characteristics of biomass fuels using blast-furnace slag as bed material2004Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, nr 4, 1187-1193 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Agglomeration of bed material may cause severe operating problems during fluidized bed combustion. The attack or coating layers that are formed on the bed particles during combustion play an important role in the agglomeration process. To reduce bed agglomeration tendencies, alternative bed materials may be used. In this paper, bed agglomeration characteristics during the combustion of biomass fuels using a relatively new bed material (iron blast-furnace slag) as well as ordinary quartz sand were determined. Controlled agglomeration tests lasting 40 h, using five representative biomass fuels (bark, olive residue, peat, straw, and reed canary grass) were conducted in a bench-scale fluidized bed. The bed materials and agglomerates were analyzed using SEM/EDS and X-ray diffraction. Chemical equilibrium calculations were performed to interpret the experimental findings. The results showed that blast-furnace slag had a lower tendency to agglomerate than quartz sand for most of the fuels. The quartz particles showed an inner attack layer more often than did the blast-furnace slag. The blast-furnace slag had a lower tendency to react with elements from the fuel. The outer coating layer had similar characteristics and thickness for both bed materials when the same fuel was combusted. However, the inner attack layer thickness was larger for quartz particles. SEM/EDS analyses of the agglomerates showed that the inner Ca-K-silicate-rich attack layer was responsible for the agglomeration of quartz sand. The composition of blast-furnace slag agglomerate was similar to the outer coating layer. Chemical equilibrium calculations showed that the original composition of the blast-furnace slag was close to the equilibrium composition, and hence there was no major driving force for reactions between that bed material and K and Ca from the fuel. The homogeneous silica-rich attack layer (with a low melting temperature) was not formed to the same extent for blast-furnace slag, thus explaining the lower bed agglomeration tendency.

  • 22. Capablo, Joaquin
    et al.
    Arendt Jensen, Peter
    Hougaard Pedersen, Kim
    Hjuler, Klaus
    Nikolaisen, Lars
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Frandsen, Flemming
    Ash properties of alternative biomass2009Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, 1965-1976 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ash behavior during suspension firing of 12 alternative solid biofuels, such as pectin waste, mash from a beer brewery, or waste from cigarette production have been studied and compared to wood and straw ash behavior. Laboratory suspension firing tests were performed on an entrained flow reactor and a swirl burner test rig, with special emphasis on the formation of fly ash and ash deposit. Thermodynamic equilibrium calculations were performed to support the interpretation of the experiments. To generalize the results of the combustion tests, the fuels are classified according to fuel ash analysis into three main groups depending upon their ash content of silica, alkali metal, and calcium and magnesium. To further detail the biomass classification, the relative molar ratio of Cl, S, and P to alkali were included. The study has led to knowledge on biomass fuel ash composition influence on ash transformation, ash deposit flux, and deposit chlorine content when biomass fuels are applied for suspension combustion.

  • 23.
    de Geyter, Sigrid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Morgan
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Effects of non-quartz minerals in natural bed sand on agglomeration characteristics during fluidized bed combustion of biomass fuels2007Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 21, nr 5, 2663-2668 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most of the previous literature on fluidized bed agglomeration during biomass combustion is based on quartz as a bed material. Full-scale installations however often use natural sand, which apart from quartz may contain a high fraction of non-quartz minerals such as potassium feldspar and plagioclase. The objective of the present study was therefore to elucidate the effects of non-quartz minerals occurring in natural sand on the agglomeration behavior during fluidized bed combustion of biomass fuels. Three fuels typical for previously determined agglomeration mechanisms were chosen as model fuels: calcium-rich bark, potassium-rich olive residues, and silica- and potassium-rich wheat straw. Two different feldspar minerals were used: a potassium feldspar and a plagioclase, labradorite, which both occur in many commercial bed materials. Furthermore, olivine was used as a bed material as this mineral represents another type of bed material used in some fullscale installations. Quartz was used as a reference bed material. The effects of non-quartz minerals in natural sand on initial defluidization temperature were assessed during carefully controlled, bench-scale fluidized bed agglomeration experiments. Bed material samples and agglomerates were analyzed using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) in order to explore the occurrence and chemical composition of coating and attack layers on the bed particles and necks between agglomerated particles. Significant differences in agglomeration characteristics were found for the different minerals when bark and olive residue were combusted. Potassium-feldspar was shown to lower the initial defluidization temperature for combustion of bark and olive residues. Plagioclase and olivine on the other hand were found to increase the initial defluidization temperature as compared to quartz for the combustion of olive residue, but for bark combustion, they did not differ significantly from quartz. During combustion of wheat straw, all bed materials agglomerated shortly after the startup of the experiment. For bark and olive residue samples, attack layers were found on all bed materials and the composition of the inner attack layer and agglomerate necks differed significantly with the fuel/bed material combination. For wheat straw however, no continuous attack layers were found, and the bed material composition was concluded not to influence the agglomeration characteristics for this biomass. The results were used to suggest possible mechanisms involved in layer formation for the different minerals.

  • 24.
    Dopson, Mark
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Halinen, Anna-Kaisa
    Rahrmen, Nelli
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Sundkvist, Jan-Eric
    Riekkola-Vanhanen, Marja
    Kaksonen, Anna H.
    Puhakka, Jaakko A.
    Silicate mineral dissolution during heap bioleaching2008Inngår i: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 99, nr 4, 811-820 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicate minerals are present in association with metal sulfides in ores and their dissolution occurs when the sulfide minerals are bioleached in heaps for metal recovery. It has previously been suggested that silicate mineral dissolution can affect mineral bioleaching by acid consumption, release of trace elements, and increasing the viscosity of the teach solution. In this study, the effect of silicates present in three separate samples in conjunction with chalcopyrite and a complex multi-metal sulfide ore on heap bioleaching was evaluated in column bioreactors. Fe2+ oxidation was inhibited in columns containing chalcopyrite samples A and C that leached 1.79 and 1.11 mM fluoride, respectively but not in sample B that contained 0.14 mM fluoride. Microbial Fe2+ oxidation inhibition experiments containing elevated fluoride concentrations and measurements of fluoride release from the chalcopyrite ores supported that inhibition of Fe2+ oxidation during column leaching of two of the chalcopyrite ores was due to fluoride toxicity. Column bioleaching of the complex sulfide ore was carried out at various temperatures (7-50 degrees C) and pH values (1.5-3.0). Column leaching at pH 1.5 and 2.0 resulted in increased acid consumption rates and silicate dissolution such that it became difficult to filter the leach solutions and for the leach liquor to percolate through the column. However, column temperature (at pH 2.5) only had a minor effect on the acid consumption and silicate dissolution rates. This study demonstrates the potential negative impact of silicate mineral dissolution on heap bioleaching by microbial inhibition and liquid flow.

  • 25.
    Dopson, Mark
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Lövgren, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Silicate mineral dissolution in the presence of acidophilic microorganisms: implications for heap bioleaching2009Inngår i: Hydrometallurgy, ISSN 0304-386X, Vol. 96, nr 4, 288-293 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicate minerals are found with sulfide minerals and therefore, can be present during heap bioleaching for metal extraction. The weathering of silicate minerals by chemical and biological means is variable depending on the conditions and microorganisms tested. In low pH metal rich environments their dissolution can influence the solution chemistry by increasing pH, releasing toxic trace elements, and thickening of the leach liquor. The amenity of five silicate minerals to chemical and biological dissolution was tested in the presence of either ‘Ferroplasma acidarmanus’ Fer1 or Acidithiobacillus ferrooxidans with olivine and hornblende being the most and least amenable, respectively. A number of the silicates caused the pH of the leach liquor to increase including augite, biotite, hornblende, and olivine. For the silicate mineral olivine, the factors affecting magnesium dissolution included addition of microorganisms and Fe2+. XRD analysis identified secondary minerals in several of the experiments including jarosite from augite and hornblende when the medium contained Fe2+. Despite acidophiles preferentially attaching to sulfide minerals, the increase in iron coupled with very low Fe2+ concentrations present at the end of leaching during dissolution of biotite, olivine, hornblende, and microcline suggested that these minerals supported growth. Weathering of the tested silicates would affect heap bioleaching by increasing the pH with olivine, fluoride release from biotite, and production of jarosite during augite and hornblende dissolution that may have caused passivation. These data have increased knowledge of silicate weathering under bioleaching conditions and provided insights into the effects on solution chemistry during heap bioleaching.

  • 26.
    Enestam, Sonja
    et al.
    Åbo Akademi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Niemi, Jere
    Metso Power.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mäkele, Kari
    Metso Power.
    Hupa, Mikko
    Åbo Akademi.
    Occurrence of zinc and lead in aerosols and deposits in the fluidized bed combustion of recovered waste wood:  Part 1: Samples from boilers2011Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 4, 1396-1404 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combustion of recovered waste wood (RWW) has led to increased fouling and corrosion of furnace walls, superheaters, and economizers. These problems have been associated mainly with chlorine, zinc, and lead in the deposits but also with sodium and titanium. The presence of lead and zinc compounds, especially lead and zinc chlorides, has been shown to increase the corrosivity of the deposits even at relatively low metal temperatures (230−450 °C). The present work determined experimentally the distribution and speciation of zinc and lead compounds in aerosol particles and deposits in the fluidized-bed combustion of RWW. Measurements were conducted in both a full-scale (20 MWth) plant with as-received RWW and in a pilot-scale (2 MWth) setup with as-received RWW and RWW doped with zinc and lead. The results show that the amount and speciation of zinc and lead in the deposits vary depending upon the fuel composition, flue gas temperature, and metal temperature. Both lead and zinc chlorides are found in temperature ranges typical for the primary superheater area. A caracolite-type compound [Na3Pb2(SO4)3Cl] was identified in deposits from the economizer area and K2ZnCl4 in the sub-micrometer aerosol particle fraction.

  • 27. Enestam, Sonja
    et al.
    Mäkelä, Kari
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Hupa, Miko
    Occurrence of Zinc and Lead in Aerosols and Deposits in the Fluidized-Bed Combustion of Recovered Waste Wood. Part 2: Thermodynamic Considerations2011Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 4, 1970-1977 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, which is the second part in a series of two, multi-phase, multi-component equilibrium calculations were used to study the chemistry and deposition behavior of lead and zinc in the combustion of recovered waste wood (RWW). Particular attention was paid to the deposition behavior in different parts of the boiler under varying flue gas and material temperature conditions. In addition, the influence of fuel composition was considered by studying three different fuel compositions. The results from the calculations were compared to experimental results from two measurement campaigns, whose goal was to experimentally determine the distribution and speciation of zinc and lead compounds in aerosol particles and deposits in the fluidized-bed combustion of RWW. The results from the experimental work are presented in part 1 (10.1021/ef101478n) of this work.

  • 28.
    Eriksson, Gunnar
    et al.
    Forest Resource Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Bergsten, Urban
    Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Bergström, Dan
    Forest Planning and Operations Management, Forest Resource Management, Swedish University of Agricultural Science, Umeå, Sweden.
    Fuel characterization of pellet chips2011Inngår i: Forest products journal, ISSN 0015-7473, Vol. 61, nr 2, 143-148 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Small hardwood chips, known as pellet chips, were characterized and combusted in two different pellet burners, installed in a residential boiler specially designed for pellet combustion. The average particle mass was about 10 percent of the mass of an 8-mm pellet, with a similar surface-to-volume ratio. The bulk density of pellet chips was 160 to 170 kg m<sup>-3</sup> at 10 percent moisture content (about 25% to 35% of 8-mm pellet bulk densities). The combustion performance was good, with average O<sub>2</sub> and CO values (by volume) at 17.6 percent (SD, 0.6%) and 200 ppm (SD, 210 ppm), respectively, for the bottom-fed burner and 14.2 percent (SD, 1.1%) and 330 ppm (SD, 93 ppm), respectively, for the top-fed burner. Thus the study indicates that pellet chips produced with commercially available equipment can be used in ordinary pellet combustors, provided that the fuel feeding rates are increased and the moisture content well below 20 percent. More accurate market assessments will require the investigation of the performance of different types of combustion equipment with fuels of different qualities.

  • 29.
    Eriksson, Gunnar
    et al.
    Swedish Univ Agr Sci, Dept Forest Resource Management, S-90183 Umea, Sweden.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications2012Inngår i: Fuel, ISSN 0016-2361, Vol. 102, 208-220 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present transition to a sustainable global energy system requires that biomass is increasingly combusted for heat and power production. Agricultural fuels considered include alkali-rich fuels with high phosphorus content. One such fuel is wheat distiller’s dried grain with solubles (wheat DDGS) from wheat-based ethanol production. Further increases in ethanol production may saturate the current market for wheat DDGS as livestock feed, and fuel uses are therefore considered. Fuel properties of wheat DDGS have been determined. The ash content (5.4 ± 1.6 %wt d.s.) is similar to many agricultural fuels. In comparison to most other biomass fuels the sulphur content is high (0.538 ± 0.232 %wt d.s.), and so are the contents of nitrogen (5.1 ± 0.6 %wt d.s.), phosphorus (0.960. ± 0.073 %wt d.s.) and potassium (1.30 ± 0.35 %wt d.s.). To determine fuel-specific combustion properties, wheat DDGS and mixes between wheat DDGS and logging residues (LR 60 %wt d.s. and DDGS 40 %wt d.s.), and wheat straw (wheat straw 50 %wt d.s., DDGS 50 %wt d.s.) were pelletized and combusted in a bubbling fluidised bed combustor (5 kW) and in a pellets burner combustor (20 kW). Pure wheat DDGS powder was also combusted in a powder burner (150 kW). Wheat DDGS had a high bed agglomeration and slagging tendency compared to other biomass fuels, although these tendencies were significantly lower for the mixture with the Ca-rich LR, probably reflecting the higher first melting temperatures of K–Ca/Mg-phosphates compared to K-phosphates. Combustion and co-combustion of wheat DDGS resulted in relatively large emissions of fine particles (<1 μm) for all combustion appliances. For powder combustion PMtot was sixteen times higher than from softwood stem wood. While the Cl concentrations of the fine particles from the the mixture of LR and wheat DDGS in fluidised bed combustion were lower than from combustion of pure LR, the Cl- and P-concentrations were considerably higher from the wheat DDGS mixtures combusted in the other appliances at higher fuel particle temperature. The particles from powder combustion of wheat DDGS contained mainly K, P, Cl, Na and S, and as KPO3 (i.e. the main phase identified with XRD) is known to have a low melting temperature, this suggests that powder combustion of wheat DDGS should be used with caution. The high slagging and bed agglomeration tendency of wheat DDGS, and the high emissions of fine particles rich in K, P and Cl from combustion at high temperature, mean that it is best used mixed with other fuels, preferably with high Ca and Mg contents, and in equipment where fuel particle temperatures during combustion are moderate, i.e. fluidised beds and possibly grate combustors rather than powder combustors.

  • 30.
    Eriksson, Gunnar
    et al.
    Division of Energy Engineering, Department of Applied Physics and Mechanical Engineering, Luleå University of Technology.
    Hedman, Henry
    Energy Technology Centre, Piteå, Sweden.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Pettersson, Esbjörn
    Division of Energy Engineering, Department of Applied Physics and Mechanical Engineering, Luleå University of Technology.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Öhman, Marcus
    Division of Energy Engineering, Department of Applied Physics and Mechanical Engineering, Luleå University of Technology.
    Combustion characterization of rapeseed meal and possible combustion applications2009Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 23, nr 8, 3930-3939 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A future shortage of biomass fuel can be foreseen. The production of rapeseed oil for a number of purposes is increasing, among others, for biodiesel production. A byproduct from the oil extraction process is rapeseed meal (RM), presently used as animal feed. Further increases in supply will make fuel use an option. Several energy companies have shown interest but have been Cautious because of the scarcity of data on fuel properties, which led to the present study. Combustion-relevant properties of RM from several producers have been determined. The volatile fraction (74 +/- 0.06%(wt ds)) is comparable to wood; the moisture content (6.2-11.8%(wt)) is lows and the ash content (7.41 +/- 0.286%(wt) (ds)) is high compared to most other biomass fuels. The lower heating value is 18.2 +/- 0.3 MJ/kg (dry basis). In comparison to other biomass fuels, the chlorine content is low (0.02-0.05%(wt ds)) and the sulfur content is high (0.67-0.74%(wt ds)). RM has high contents of nitrogen (5.0-6.4%(wt) (ds)) phosphorus (1.12-1.23%(wt) (ds)) and potassium (1.2-1.4%(wt) (ds)). Fuel-specific combustion properties of typical RM were determined through combustion tests. with an emphasis oil gas emissions, ash formation, and potential ash-related operational problems. Softwood bark was chosen as a suitable and representative co-combustion (woody) fuel. RM was added to the bark at two levels: 10 and 30%(wt) (ds). These mixtures were pelletized, and so was RM without bark (for durability mixed With cutter shavings, contributing 1%(wt) of the ash). Each of these fuels was combusted in a 5 kW fluidized bed and an underfed pellet burner (to simulate grate combustion). Pure RM was combusted in a powder burner. Emissions of NO and SO, were high for all combustion tests, requiring applications with flue gas cleaning, economically viable only at large scale. Emissions of HCl were relatively low, Temperatures for initial bed agglomeration in the fluidized-bed tests were high for RM compared to many other agricultural fuels, thereby indicating that RM could be an attractive fuel from a bed agglomeration point of view. The results of grate combustion Suggest that slagging is not likely to be severe for RM, pure or mixed with other fuels. Fine-mode particles from fluidized-bed combustion and grate combustion mainly contained sulfates of potassium, suggesting that the risk of problems caused by deposit formation should be moderate. The chlorine concentration of the particles was reduced when RM was added to bark, potentially lowering the risk of high-temperature corrosion. Particle emissions from powder combustion of RM were 17 times higher than for wood powder, and the fine-mode fraction contained mainly K-phosphates known to cause deposits, suggesting that powder combustion of RM should be used With Caution. A possible use of RM is as a sulfur-containing additive to biomass fuels rich in Cl and K for avoiding ash-related operational problems in fluidized beds and grate combustors originated from high KCl concentrations in the fuel gases.

  • 31.
    Fick, Jerker
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Pommer, Linda
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Andersson, Barbro
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nilsson, Calle
    Unit for Biomass Technology and Chemistry, Swedish University of Agricultural Sciences, Umeå.
    A study of the gas-phase ozonolysis of terpenes: the impact of radicals formed during the reaction2002Inngår i: Atmospheric Environment, ISSN 1352-2310, Vol. 36, nr 20, 3299-3308 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The gas-phase ozonolysis of α-pinene, Δ3-carene and limonene was investigated at ppb levels and the impact of the ozone, relative air humidity (RH), and time was studied using experimental design. The amounts of terpene reacted varied in the different settings and were as high as 8.1% for α-pinene, 10.9% forΔ3-carene and 23.4% for limonene. The designs were able to describe almost all the variation in the experimental data and were also successful in predicting omitted values. The results described the effects of time and ozone and also showed that RH did not have a statistically significant effect on the ozonolysis. The results also showed that all three terpenes were affected by an additional oxidation of OH radicals and/or other reactive species. The results from the designs states that this additional oxidation was responsible for 40% of the total amount of α-pinene reacted, 33% of the total amount of Δ3-carene reacted and 41% of the total amount of limonene reacted at the settings 20 ppb terpene, 75 ppb ozone, 20% RH and a reaction time of 213 s. Additional experiments with 2-butanol as OH radical scavenger showed that the reaction with OH radicals was responsible for 37% of the total α-pinene reacted and 39% of the total Δ3-carene reacted at the same settings. The scavenger experiments also showed that there were no significant amounts of OH radicals formed during the ozonolysis of limonene. The results from the designs were also compared to a mathematical model in order to evaluate further the data.

  • 32.
    Forsberg, Christer
    et al.
    Vattenfall AB Nordic Heat, S-162 87 Stockholm, Sweden .
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Edvardsson, Elin
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Badiei, Shahriar
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Berg, Magnus
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Kassman, Håkan
    Vattenfall Power Consultant AB, Box 1046, S-611 29 Nyköping, Sweden.
    Principle, calibration, and application of the in situ alkali chloride monitor2009Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 80, nr 2, 023104-1-023104-4 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The In-Situ Alkali Chloride Monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (>650 oC). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO2 concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations, and 4-750 ppm for SO2. This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.

  • 33. Gilbe, Carl
    et al.
    Lindström, Erica
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Samuelsson, Robert
    Burvall, Jan
    Ohman, Marcus
    Predicting slagging tendencies for biomass pellets fired in residential appliances: a comparison of different prediction methods2008Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 22, nr 6, 3680-3686 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a comparison between four different types (both empirical and theoretical) of techniques to predict the slagging tendencies in residential pellet combustion appliances was performed. The four techniques used were the standard ash fusion test (SS ISO-540) used in the Swedish pellet standard (SS 18 7120), thermal analysis (TGA/DTA), thermochemical model calculations, and a laboratory-scale sintering test. The tests were performed with 12 pelletized biomass raw materials, and the results were compared with measured slagging tendencies in controlled combustion experiments in a commercial under-fed pellet burner (20 kW) installed in a reference boiler. The results showed significant differences in the prediction of slagging tendencies between different predicting techniques and fuels. The method based on thermal analysis (TGA/DTA) of produced slags must be further developed before useful information could be provided of the slagging behavior of different fuels. The used sintering method must also be further improved before the slagging tendency of fuels forming slags extremely rich in silicon (e.g., some grasses) can be predicted. Relatively good agreement was obtained between results from chemical equilibrium calculations and the actual slagging tendencies from the combustion tests. However, the model calculations must be further improved before quantitative results can be used. The results from the standard ash fusion test (SS ISO 540) showed, in general, relatively high deformation temperatures, therefore predicting a less problematic behavior of the fuels in comparison to the actual slagging tendencies obtained from controlled combustion experiments in commercial pellet burner equipment. Nevertheless, the method predicted, in most cases, the same fuel-specific slagging (qualitatively) trends as the corresponding combustion behavior.

  • 34. Gilbe, Carl
    et al.
    Öhman, Marcus
    Lindström, Erica
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Samuelsson, Robert
    Burvalll, Jan
    Slagging characteristics during residential combustion of biomass pellets2008Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 22, nr 5, 3536-3543 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Limited availability of sawdust and planer shavings and an increasing demand for biomass pellets in Europe are pushing the market toward other, more problematic raw materials with broader variation in total fuel ash content and composition of the ash forming elements as well as in their slagging tendencies. The main objective in the present work was therefore to determine the influence of fuel-ash composition on residual ash and slag behavior. Twelve different biomass pellets were used: reed canary grass (two different samples), hemp (two different samples), wheat straw. salix, logging residues (two different samples), stern wood (sawdust) as well as spruce, pine, and birch bark. The different pellet qualities were combusted in a commercial under fed pellet burner (20 kW) installed in a reference boiler. Continuous measurements of O-2, CO, CO2, HCl, SO2, and total particle matter mass concentrations were determined in the exhaust gas directly after the boiler. The collected slag deposits, the corresponding deposited bottom ash in the boiler and the collected particle matter were Characterized with X-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive X-ray analysis (SEM/EDS). For biomass fuel pellets rich in silicon (either inherent or contaminated with sand) and low content of alkaline earth metals the main part of the potassium reacted with the silicon rich ash-residual. forming sticky alkali-silicate particles, which were not entrained front the burner and thereby giving rise to/initiating slag formation. Silicon rich fuels, i.e. fuels were the ash characteristics were dominated by silicate-alkali chemistry, therefore generally showed relatively high slagging tendencies. Straw fuels have typically this ash composition but exceptions to these general trends exists (e.g., one of the hemp fuels used in this work). Wood derived fuels with a relatively low inherent silicon content therefore showed low or relatively moderate slagging tendencies. However, contamination of sand material to these fuels may greatly enhance the slagging tendencies.

  • 35.
    Golriz, Mohammad R
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Eriksson, Morgan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Öhman, Marcus
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Rainer, Backman
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Influence of Fluidization Velocity on Bed Defluidization in fluidized bed combustors2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Effects of superficial gas velocity and bed particle size on bed defluidization during biomass combustion were investigated. Sampled bed particles from four different large-scale circulating- and bubbling fluidized bed combustors, using biomass as fuel, were collected and analyzed. The bed particles from each fluidized bed unit were divided into small and large particle size fractions. The results indicate no significant difference in elemental compositions between small and large coated bed particles but the ratio of coating thickness to the mean particle diameter was higher for the small particles compared to the large ones. Controlled fluidized bed agglomeration tests revealed strong influence from fluidization velocity on initial defluidization temperatures at lower velocities, but little effect at higher velocities. Influence of bed particle size on initial defluidization temperature varied depending on operating conditions. Finally, a model based on viscous flow sintering is proposed for the relation between agglomeration temperature and superficial gas velocity. The model predictions are in good agreement with experimental data.

  • 36. Grimm, Alejandro
    et al.
    Ohrnan, Marcus
    Lindberg, Therese
    Fredriksson, Andreas
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Bed Agglomeration Characteristics in Fluidized-Bed Combustion of Biomass Fuels Using Olivine as Bed Material2012Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, nr 7, 4550-4559 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The bed agglomeration characteristics during combustion of typical biomass fuels were determined in a bench-scale bubbling fluidized-bed reactor (5 kW) using olivine and quartz sand as bed material. The fuels studied include willow, logging residues, wheat straw, and wheat distiller's dried grain with solubles (wheat DDGS). Bed material samples and agglomerates were analyzed by means of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), for morphology and elemental composition. Furthermore, bed ash particles were separated by sieving from the bed material samples and analyzed for elemental composition by SEM-EDS and for determination of crystalline phases by powder X-ray diffraction (XRD). Chemical equilibrium calculations were performed to interpret the experimental findings of layer formation and reaction tendencies in both bed materials. Significant difference in the agglomeration tendency between olivine and quartz was found during combustion of willow and logging residues. These fuels resulted in inner layers that were more dependent on the bed material composition, and outer layers that have a composition similar to the fuel ash characteristics. The elemental composition of the inner layer formed on the quartz bed particles was dominated by Si, K, and Ca. In the olivine bed, the inner layer consisted mainly of Mg, Si, and Ca. Chemical equilibrium calculations made for both bed materials showed a low chemical driving force for K to react and be retained by the olivine bed particles, which is in accordance to the experimental findings. For the quartz case, the inner layer was found responsible for the initiation of the agglomeration process. The composition of the fewer and more porous agglomerates found after the experiments in the olivine bed showed neck composition and characteristics similar to the individual bed ash particles found in the bed or outer bed particle coating composition. For DDGS (rich in S, P, K, and Mg) and wheat straw (rich in Si and K), no significant differences in the bed agglomeration tendency between olivine and quartz bed materials were found. The results show that the bed particle layer formation and bed agglomeration process were associated to direct adhesion of bed particles by partly molten fuel ash derived K Mg phosphates for DDGS and K-silicates for wheat straw.

  • 37.
    Grimm, Alejandro
    et al.
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden.
    Influence of phosphorus on alkali distribution during combustion of logging residues and wheat straw in a bench-scale fluidized bed2012Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, nr 5, 3012-3023 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of phosphorus on the alkali distribution in fluidized (quartz) bed combustion using two different typical biomasses (logging residues and wheat straw) was studied. Phosphoric acid (H3PO4) was used as an additive. The produced ash fractions were analyzed for morphology and elemental composition by scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and crystalline phases by powder X-ray diffraction (P-XRD). For both fuel assortments tested, a reduction of volatilized deposit and fine particle-forming matter, containing mainly KCl, was achieved by adding phosphorus. For the wheat straw, this effect was considerable at medium and high phosphorus addition. As a consequence, an increased amount of potassium was found in the coarse ash particle fractions, principally as CaKPO4, KMgPO4, and CaK2P2O7, at the same time that the levels of HCl and SO2 in the flue gases increased. Generally, the addition of phosphorus to the studied biomasses changed the alkali distribution from being dominated by amorphous K-silicate coarse ash fractions and fine particulate KCl, to a system dominated by crystalline coarse ash of K-Ca/Mg-phosphates and fine particulate K2SO4. This implies that the fouling and high-temperature corrosion observed in industrial-scale combustion of problematic biofuels can possibly be reduced by employing additives rich in reactive phosphorus, on the condition that the higher concentrations of acidic gases can be tolerated. In order to achieve these effects, the relationship between alkali and alkaline-earth metals (i.e., (K + Na)/(Ca + Mg)) in the overall fuel ash must be considered. With respect to this, the formation of low-temperature-melting alkali-rich phosphates should not be promoted, to avoid potential increases in bed agglomeration tendencies and phosphorus release from the bed.

  • 38.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bed agglomeration characteristics in fluidized quartz bed combustion of phosphorus-rich biomass fuels2011Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 3, 937-947 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The bed agglomeration characteristics during combustion of phosphorus-rich biomass fuels and fuel mixtures were determined in a fluidized (quartz) bed reactor (5 kW). The fuels studied (separately and in mixtures) included logging residues, bark, willow, wheat straw, and phosphorus-rich fuels, like rapeseed meal (RM) and wheat distillers dried grain with solubles (DDGS). Phosphoric acid was used as a fuel additive. Bed material samples and agglomerates were studied by means of scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX), in order to analyze the morphological and compositional changes of coating/reaction layers and necks between agglomerated bed particles. Furthermore, bed ash particles were separated by sieving from the bed material samples and analyzed with SEM/EDS and powder X-ray diffraction (XRD). For logging residues, bark, and willow, with fuel ash rich in Ca and K but with low contents of P and organically bound Si, the bed layer formation is initiated by reactions of gaseous or liquid K compounds with the surface of the bed material grains, resulting in the formation of a potassium silicate melt. The last process is accompanied by the diffusion/dissolving of Ca into the melt and consequent viscous flow sintering and agglomeration. The addition of high enough phosphorus content to convert the available fuel ash basic oxides into phosphates reduced the amount of K available for the reaction with the quartz bed material grains, thus preventing the formation of an inner bed particle layer in the combustion of logging residues, bark, and willow. Some of the phosphate-rich ash particles, formed during the fuel conversion, adhered and reacted with the bed material grains to form noncontinuous phosphate−silicate coating layers, which were found responsible for the agglomeration process. Adding phosphorus-rich fuels/additives to fuels rich in K and Si (e.g., wheat straw) leads to the formation of alkali-rich phosphate−silicate ash particles that also adhered to the bed particles and caused agglomeration. The melting behavior of the bed particle layers/coatings formed during combustion of phosphorus-rich fuels and fuel mixtures is an important controlling factor behind the agglomeration tendency of the fuel and is heavily dependent on the content of alkaline earth metals in the fuel. A general observation is that phosphorus is the controlling element in ash transformation reactions during biomass combustion in fluidized quartz beds because of the high stability of phosphate compounds.

  • 39.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Diaz, Maryori
    Eriksson, Gunnar
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Effects of phosphorus addition by additives or co-firing on the ash transformation processes such as bed agglomerations and deposit formation during combustion of ash-rich biomass fuels2009Inngår i: 17th European Biomass Conference & Exhibition - Proceedings: From Research to Industry and Markets, 2009Konferansepaper (Fagfellevurdert)
  • 40.
    Grimm, Alejandro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Gunnar
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boman, Christoffer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Effekter av fosfortillsats vid förbränning av biomassa2010Rapport (Annet vitenskapelig)
    Abstract [sv]

    Resultaten från försöken visar att fosforrika additiv kan vara intressanta för att reducera beläggningsbildning och högtemperaturkorrosion utan att i någon större omfattning öka slaggnings- och bäddagglomereringstendensen hos typiska biobränslen. För att erhålla en märkbar positiv effekt av kaliumbindning till fosfater krävs att mängden kalcium och magnesium i den slutgiltiga bränslemixen inte är alltför hög relativt mängden fosfor, då framför allt Ca men till viss del även Mg reagerar med P innan K binds in effektivt. Generellt behövs troligen inblandningsgrader motsvarande en molkvot P/(K+Na+2/3Mg+2/3Ca) i bränslemixen som närmar sig 1. För att erhålla en molkvot på 1 i ett typiskt halm-, salix- eller grotbränsle innebär det i praktiken en fosfortillsats motsvarande 12, 4.7 respektive 3.7 gram rent P per kg torrt bränsle.

  • 41. Kassman, Håkan
    et al.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Berg, Magnus
    Åmand, Lars-Erik
    Measures to reduce chlorine in deposits: Application in a large-scale circulating fluidised bed boiler firing biomass2011Inngår i: Fuel, ISSN 0016-2361, Vol. 90, nr 4, 1325-1334 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combustion of biomass with a high content of alkali (mainly potassium, K) and chlorine (Cl) can result in operational problems including deposit formation and superheater corrosion. Among the measures applied to decrease such problems are co-combustion and the use of additives. The positive effects of these measures are to a large extent either sulphation of the alkali chlorides (KCl) to less corrosive alkali sulphates or capture of alkali from KCl during release of HCl. A test campaign was carried out in a large-scale circulating fluidised boiler fired with biomass where the measures applied were sulphation by ammonium sulphate and co-combustion with peat. Their performance was evaluated by means of several advanced measurement tools including: IACM (on-line measurements of gaseous KCl); a low-pressure impactor (size distribution and chemical composition of extracted fly ash particles) and deposit measurements (chemical composition in collected deposits). The overall performance was better for ammonium sulphate, which significantly lowered KCl in the flue gas. Meanwhile no chlorine was found in the deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion with peat although the chlorinecontent in the deposits was greatly reduced. These findings were supported by the results from the impactor measurements.

  • 42. Kirilin, A
    et al.
    Mäki-Arvela, P
    Kordas, K
    Leino, A-R
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kustov, L M
    Salmi, T O
    Murzin, D Yu
    Chemo-bio catalyzed synthesis of R-1-phenylethyl acetateover bimetallic PdZn catalysts, lipase and Ru/Al2o3. Part I2011Inngår i: Kinetics and catalysis, ISSN 0023-1584, E-ISSN 1608-3210, Vol. 52, nr 1, 72-76 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of calcination and reduction temperature on the physical properties of PdZn/Al2O3 catalysts, prepared by coprecipitation deposition technique and characterized by XPS, XRD and TEM methods are reported. The temperatures were varied in a range of 300–500°C. The catalyst calcined at 300°C and reducedat 400°C exhibited the metal particle size of 2–6 nm and contained the highest surface concentrations of Pd and Zn according to XPS measurements. The size and the fraction of large particles (above 10 nm) increased with increasing the calcinations and reduction temperatures.

  • 43. Kirilin, A
    et al.
    Mäki-Arvela, P
    Kordas, K
    Leino, A-R
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kustov, L M
    Salmi, T O
    Murzin, D Yu
    Chemo-bio catalyzed synthesis of R-1-phenylethyl acetateover bimetallic PdZn catalysts, lipase and Ru/Al2o3: part II2011Inngår i: Kinetika i kataliz, ISSN 0453-8811, Vol. 52, nr 1, 78-82 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Onepot synthesis of R1phenyethylacetate at 70°C was investigated using three different catalysts simultaneously, namely a bimetallic PdZn/Al2O3 as a hydrogenation catalyst, an immobilized lipase as an acylation catalyst and Ru/Al2O3 as a racemization catalyst. The most active bimetallic catalyst was PdZn/Al2O3 calcined at 300°C and reduced at 400°C, whereas the most selective although less active catalyst was the one being calcined and reduced at 500°C. The highest selectivity to R1phenylethyl acetate over this catalyst was 32% at 48% conversion. Ru/Al2O3 was confirmed to have a positive effect on the formation of the desired product, although it was not very active in the racemization during onepot synthesis.

  • 44. Larsson, Anders
    et al.
    Lindberg, Gustav
    Råberg, Mathias
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Nordin, Anders
    Warnqvist, Björn
    Rosén, Erik
    Boström, Dan
    Sodium and sulfur process chemistry in black liquor gasification and combustion: review of basic thermochemical dataManuskript (Annet vitenskapelig)
  • 45.
    Larsson, Anders
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Warnqvist, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Gunnar
    Influence of black liquor variability, combustion, and gasification process variables and inaccuracies in thermochemical data on equilibrium modeling results2006Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, nr 1, 359-363 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work is a systematic sensitivity study of how inaccuracies in thermochemical data influence important parameters resulting from chemical equilibrium modeling of black liquor combustion and gasification processes. These effects have also been compared with those originating from normal variations in process variables and black liquor composition. Determination of the effects was achieved by performing a large number of equilibrium calculations structured according to statistical designs. Evaluation of the chemical equilibrium model calculations was facilitated by regression analysis. From the results, it can be concluded that uncertainties in thermochemical data of several key components have significant effects on important chemical and physical modeling responses in black liquor combustion and gasification. These effects are in many cases comparable to, or larger than, the effects from variation in fuel and process variables. Experimental redetermination of thermochemical data for Na2S, K2S, and gaseous NaOH is suggested.

  • 46.
    Larsson, Sylvia H.
    et al.
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Rudolfsson, Magnus
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Nordwaeger, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Olofsson, Ingemar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Samuelsson, Robert
    Swedish University of Agricultural Sciences, Unit of Biomass Technology and Chemistry.
    Effects of moisture content, torrefaction temperature, and die temperature in pilot scale pelletizing of torrefied Norway spruce2013Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 102, 827-832 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pilot scale pelletizing of torrefied Norway spruce was performed in a factorial design with controlled factors at two levels: material moisture content (11% and 15%) and torrefaction temperature (270 and 300 °C), and die temperature as an uncontrolled factor (60–105 °C). Compared to commercial wood pellets, produced pellets had comparable bulk densities (630–710 kg/m3) but lower pellet durability (80–90%). Energy consumption for pelletizing of torrefied materials was approximately 100% higher than for softwood pelletizing, despite using a much shorter die channel length (35 vs. 55 mm:s), and the amounts of fines were high (10–30%). Die temperature showed a strong positive correlation with pellet production rate. Material moisture content had little influence on pellet quality and production rate, but addition of water created handling problems due to bad flow behavior.

  • 47.
    Lind, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Carlsson, Marcus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Eriksson, Anders
    Glimsdal, Eirik
    Lindgren, Mikael
    Eliasson, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Structural, photophysical, and nonlinear absorption properties of trans-di-arylalkynyl Platinum(II) Complexes with Phenyl and Thiophenyl Groups2007Inngår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, nr 9, 1598-1609 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optical power limiting and luminescence properties of two Pt(II) complexes with thiophenyl and phenyl groups in the ligands, trans-Pt(P(n-Bu)3)2(C[triple bond]C-Ar)2, where Ar = -C4H2S-C[triple bond]C-p-C6H4-n-C5H11 (1) and -p-C6H4-C[triple bond]C-C4H3S (2), have been investigated. The fluorescence lifetimes were found to be on the sub-nanosecond time scale, and the quantum yields were low, in accord with fast intersystem crossing from the excited singlet to triplet manifold. The phosphorescence lifetimes of 1 and 2 were shorter than that of a Pt(II) complex having two phenyl groups in the ligands. In order to elucidate the C-Pt bonding nature in the ground state, the 13C NMR chemical shift of the carbon directly bonded to Pt, the coupling constants 1JPtC, 2JPtC, and 1JPtP, and IR νC[triple bond]C wavenumbers were obtained for 1, 2, and three other trans-diarylalkynyl Pt(II) complexes. X-ray diffraction data of 1 and 2 and density functional theory calculated geometries of models of 1, 2, and trans-Pt(P(n-Bu)3)2(C[triple bond]C-p-C6H4-C[triple bond]C-C6H5)2 (3) show that 1 preferably exists in a different conformation from that of 2 and 3. The variations in photophysical, NMR, and IR data can be rationalized by differences in geometry and pi-backbonding from Pt to the alkynyl ligand.

  • 48. Lindberg, D
    et al.
    Perander, L
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Hupa, M
    Kochesfahani, S
    Rickards, H
    Borate autocausticizing equilibria in recovery boiler smelt2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 2, 232-236 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of the potassium and boron concentration in an alkali carbonate/borate mixture and the effect of CO, concentration in the gas were studied with thermogravimetry and thermal analysis up to 900 degrees C. Results show that the auto-causticizing reaction is readily reversible with 1 % CO2 or higher in the gas if the mixtures contain only sodium compounds. Both a higher CO, concentration and a higher potassium concentration lead to lower autocausticizing. In systems that contain only potassium compounds, the autocausticizing is low and no recarbonation is observed. In potassium-rich systems, volatilization of alkali- and/or boron-components becomes more prominent than in sodium systems.

  • 49. Lindberg, Daniel
    et al.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Chartrand, Patrice
    Thermodynamic evaluation and optimization of the (Na2CO3+Na2SO4+Na2S+K2CO3+K2SO4+K2S) system2007Inngår i: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 39, nr 6, 942-960 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A critical evaluation of all phase diagram and thermodynamic data were performed for the solid and liquid phases of the (Na2CO3 + Na2SO4 + Na2S + K2CO3 + K2SO4 + K2S) system and optimized model parameters were obtained. The Modified Quasichemical Model in the Quadruplet Approximation was used for modelling the liquid phase. The model evaluates first- and second-nearest-neighbour short-range ordering, where the cations (Na+ and K+) are assumed to mix on a cationic sublattice, while anions are (CO32- ,SO42-, and S2-) are assumed to mix on an anionic sublattice. The Compound Energy Formalism was used for modelling the solid solutions of (Na, K)(2)(CO3, SO4, S). The models can be used to predict the thermodynamic properties and phase equilibria in multicomponent heterogeneous systems. The experimental data from the literature were reproduced within experimental error limits.

  • 50. Lindberg, Daniel
    et al.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi. Åbo Akademi Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FI-20500 Turku, Finland.
    Chartrand, Patrice
    Thermodynamic evaluation and optimization of the (Na2SO4+K2SO4+Na2S2O7+K2S2O7) system2006Inngår i: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 38, nr 12, 1568-1583 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A complete, critical evaluation of all phase diagram and thermodynamic data was performed for all phases of the (Na2SO4 + K2SO4 + Na2S2O7 + K2S2O7) system and optimized model parameters were obtained. The Modified Quasichemical Model in the Quadruplet Approximation was used for modelling the liquid phase. The model evaluates first- and second-nearest-neighbour short-range ordering, where the cations (Na+ and K+) are assumed to mix on a cationic sublattice. The Compound Energy Formalism was used for modelling the solid Solutions of (Na,K)(2)SO4 and (Na,K)(2)S2O7. The models can be used to predict the thermodynamic properties and phase equilibria in multicomponent heterogeneous systems. The experimental data from the literature were reproduced within experimental error limits.

123 1 - 50 of 114
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf