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| 2. |
- Boman, Christoffer, et al.
(författare)
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Characterization of inorganic particulate matter from residential combustion of pelletized biomass fuels
- 2004
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:2, s. 338-348
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Tidskriftsartikel (refereegranskat)abstract
- 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 ( less than or equal 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.
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| 4. |
- Boström, Dan, et al.
(författare)
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Hexakis(dimethyl sulfoxide-kappa O)aluminium(III) trichloride
- 2003
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Ingår i: Acta Crystallographica Section E. - 1600-5368. ; 59, s. M934-M935
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, [Al{(CH3)(2)SO}(6)]Cl-3, crystallizes in the trigonal space group R(3) over bar. In this structure, the O atoms of six dimethyl sulfoxide (DMSO) molecules are bonded to the Al3+ ion in the form of a trigonally distorted octahedron. The Al3+ ion is situated at special site 3b (symmetry (3) over bar), while the Cl- ions are situated at special sites 3a and 6c (symmetries (3) over bar and 3). Considering only the Al3+ ions separately, they are arranged in a slightly distorted cubic close-packed arrangement. In this crystal structure, the Cl- ions occupy both the tetrahedral sites and the octahedral sites, giving a Cl-:Al3+ ratio of 3:1. This geometric condition results in a distorted rhombododecahedral arrangement of Cl- ions around the Al3+ ions.
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| 5. |
- Boström, Dan, et al.
(författare)
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Hexakis(dimethyl sulfoxide-KO)aluminium(III) trichloride
- 2003
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Ingår i: Acta Crystallographica Section E. - : International Union of Crystallography. - 1600-5368. ; 59:10, s. m934-m935
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, [Al{(CH3)2SO}6]Cl3, crystallizes in the trigonal space group R. In this structure, the O atoms of six dimethyl sulfoxide (DMSO) molecules are bonded to the Al3+ ion in the form of a trigonally distorted octahedron. The Al3+ ion is situated at special site 3b (symmetry ), while the Cl- ions are situated at special sites 3a and 6c (symmetries and 3). Considering only the Al3+ ions separately, they are arranged in a slightly distorted cubic close-packed arrangement. In this crystal structure, the Cl- ions occupy both the tetrahedral sites and the octahedral sites, giving a Cl-:Al3+ ratio of 3:1. This geometric condition results in a distorted rhombododecahedral arrangement of Cl- ions around the Al3+ ions.
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| 6. |
- Boström, Dan, et al.
(författare)
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Sodium trirubidium metavanadate monohydrate
- 2003
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Ingår i: Acta Crystallographica Section E. - : International Union of Crystallography. - 1600-5368. ; E59:11, s. i151-i153
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, sodium trirubidium metavanadate monohydrate, NaRb3(VO3)4(H2O), crystallizes in the orthorhombic space group Pnma. The structure, which represents a rare type of catena-vanadate, is built up of strongly folded chains of corner-sharing [VO4] tetrahedra, running in the [010] direction with a periodicity of four. A three-dimensional framework is obtained by sodium ions linking adjacent chains in the [001] direction and by rubidium ions linking adjacent chains in the [100] direction. The single water molecule binds to the sodium ion and to two rubidium ions.
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| 7. |
- Brus, Elisabet, et al.
(författare)
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Bed agglomeration characteristics of biomass fuels using blast-furnace slag as bed material
- 2004
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Ingår i: Energy & Fuels. - Washington, D.C. : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:4, s. 1187-1193
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Ramstedt, Madeleine, et al.
(författare)
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Thermodynamic and spectroscopic studies of cadmium(II)–N-(phosphonomethyl)glycine (PMG) complexes
- 2004
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Ingår i: Inorganica Chimica Acta. - : Elsevier. - 0020-1693 .- 1873-3255. ; 357:4, s. 1185-1192
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Tidskriftsartikel (refereegranskat)abstract
- Speciation and equilibria in the H+–Cd2+–N-(phosphonomethyl)glycine (PMG, H3L) system have been studied in 0.1 M Na(Cl) medium at 25.0 °C. Formation constants for a series of mononuclear complexes, CdHL, CdL−, CdL2 4− and CdL(OH)2− were determined from potentiometric titrations. The structures of the predominating species CdL−, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. In the 1:1 complex bonds are formed between the Cd(II) ion and all three donor groups (amino, carboxylate, phosphonate) of the PMG molecule resulting in two 5-membered chelate rings. At the remaining three of the corners of the distorted Cd(II) octahedra oxygens were found which are replaced by donor groups of a second PMG molecule in the 1:2 complex. Furthermore, a solid phase consisting of Cd9(PMG)6(H2O)12 · 6H2O crystals was synthesized and the crystal structure was determined. The structure consists of six CdL− octahedra connected through a seventh Cd–O octahedron in the centre of the entity, with two additional Cd–O octahedra located at the apices of the unit formed. Speciation and equilibria in the H+–Cd2+–N-(phosphonomethyl)glycine (PMG, H3L) system have been studied using potentiometry, and formation constants for CdHL, CdL−, CdL2 4− and CdL(OH)2− were determined. The structures of CdL−, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. The results indicated chelating PMG molecules forming two 5-membered chelate rings.
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| 10. |
- Råberg, Mathias, et al.
(författare)
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Improvement of the binary phase diagram Na2CO3 -Na2S
- 2003
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Ingår i: Energy & Fuels. - : American Chemistry Society. - 0887-0624 .- 1520-5029. ; 17:6, s. 1591-1594
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Tidskriftsartikel (refereegranskat)abstract
- Gasification of black liquor is an attractive alternative to the traditional recovery boiler. However, in process modeling of gasification, thermodynamic data for the key components are quite uncertain, which will reduce the reliability of the modeling of the chemical processes in a gasifier. The objective of this work was to experimentally re-determine and improve data on the binary phase diagram Na2CO3−Na2S, especially on the Na2CO3 side of the system, which is the region of interest concerning black liquor combustion and gasification, and also the region with the most significant uncertainties. Measurements were carried out in a dry inert atmosphere at temperatures from 25 to 1200 °C, using high-temperature microscopy (HTM) and high-temperature X-ray powder diffraction (HT-XRD). To examine the influence of pure CO2 atmosphere on the melting behavior, HTM experiments in the same temperature interval were made. This paper presents new data complementary to earlier published data on the binary phase diagram Na2CO3−Na2S. These include re-determination of liquidus curves, in the Na2CO3-rich area, melting points of the pure components, as well as determination of the extent of the solid solution, Na2CO3(ss), area.
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