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| 2. |
- Boström, Dan, 1954-, et al.
(författare)
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Ash transformations in fluidized-bed combustion of rapeseed meal
- 2009
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 23:5, s. 2700-2706
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Tidskriftsartikel (refereegranskat)abstract
- 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. An 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.
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| 3. |
- Gemo, Nicola, et al.
(författare)
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TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis : the influence of N and Au doping
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 6:105, s. 103311-103319
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Tidskriftsartikel (refereegranskat)abstract
- The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product.
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| 4. |
- Boman, Christoffer, et al.
(författare)
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Stove performance and emission characteristics in residential wood log and pellet combustion : Part 1: Pellet stoves
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 25:1, s. 307-314
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Tidskriftsartikel (refereegranskat)abstract
- Stove performance, characteristics and quantities of gaseous and particulate emissions were determined for two different pellet stoves, varying fuel load, pellet diameter and chimney draught. This approach aimed at covering variations in emissions from stoves in use today. The extensive measurement campaign included CO, NOx, organic gaseous carbon, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), total particulate matter (PMtot) as well as particle mass and number concentrations, size distributions and inorganic composition. At high load, most emissions were similar. For stove B, operating at high residual oxygen and solely with primary air, the emissions of PMtot and particle numbers were higher while the particles were smaller. Lowering the fuel load, the emissions of CO and hydrocarbons increased dramatically for stove A, which operated continuously also at lower fuel loads. On the other hand for stove B, which had intermittent operation at lower fuel loads, the emissions of hydrocarbons increased only slightly lowering the fuel load, while CO emissions increased sharply, due to high emissions at the end of the combustion cycle. Beside methane, dominating VOCs were ethene, acetylene and benzene and the emissions of VOC varied in the range 1.1-47 mg/MJfuel. PAH emissions (2-340 µg/MJfuel) were generally dominated by phenantrene, fluoranthene and pyrene. PMtot (15-45 mg/MJfuel) were in all cases dominated by fine particles with mass median diameters in the range 100-200 nm, peak mobility diameters of 50-85 nm and number concentrations in the range 4×1013- 3×1014 particles/MJfuel. During high load conditions the particulate matter was totally dominated by inorganic particles at 15-25 mg/MJfuel consisting of potassium, sodium, sulfur and chlorine, in the form of K2SO4, K3Na(SO4)2 and KCl. The study shows that differences in operation and modulation principles for the tested pellet stoves, relevant for appliances in use today, will affect the performance and emissions significantly, although with lower scattering in the present study compared to compiled literature data.
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| 5. |
- Sterchele, Stefano, et al.
(författare)
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Is selective hydrogenation of molecular oxygen to H2O2 affected by strong metal–support interactions on Pd/TiO2 catalysts? : A case study using commercially available TiO2
- 2016
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Ingår i: Comptes rendus. Chimie. - : Elsevier. - 1631-0748 .- 1878-1543. ; 19:8, s. 1011-1020
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Tidskriftsartikel (refereegranskat)abstract
- In this study, titania-supported Pd catalysts were prepared and their performance evaluated upon H2O2 direct synthesis. Typically, the materials contained different ratios of anatase and rutile phases, which gave rise to different surface properties of the supports, e.g., surface area, number of Lewis acidic and basic sites as well as different compositions of the phases, i.e. the amount of anatase phase and crystallite size. Two materials, Pd-A98 and Pd-A05 samples, respectively, apparently hint the existence of the so-called SMSI (strong metal–support interaction) phenomenon giving rise to 1080 and 683 molH2O2·molPd−1·h−1 of H2O2 productivity and 22 and 14% of H2O2 selectivity, respectively. However, the best material, Pd-A82, gave rise to 949 molH2O2·molPd−1·h−1 of H2O2 productivity and 26% of H2O2 selectivity.
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| 6. |
- Kuba, Matthias, et al.
(författare)
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Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:9, s. 7410-7418
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Tidskriftsartikel (refereegranskat)abstract
- Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid-solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles
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| 8. |
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| 9. |
- Boström, Dan, et al.
(författare)
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CIS-Trans Influences on Square-Planar Platinum(II) Complexes : Structure of CIS-BIS (Dimethyl Sulfoxide) Dinitratoplatinum (II)
- 1991
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Ingår i: Acta Crystallographica Section C. - Copenhagen, Denmark : Munksgaard International Publishers. - 0108-2701 .- 1600-5759. ; 47, s. 2101-2104
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Tidskriftsartikel (refereegranskat)abstract
- cis-[Pt{(CH3)2SO}2(NO3)2], M(r) = 475.36, monoclinic, P2(1)/c, a = 9.006 (1), b = 14.209 (2), c = 10.908 (2) angstrom, beta = 117.88 (1)-degrees, V = 1233.9 (2) angstrom 3, Z = 4, D(x) = 2.559 Mg m-3, lambda(Mo K-alpha)BAR = 0.7107 angstrom, mu = 11.84 mm-1, F(000) = 896, T = 293 K, R = 0.033 for 1763 unique reflections [I > 3-sigma(I)]. The Pt atom coordinates two S atoms from two dimethyl sulfoxide ligands and two O atoms from different nitrate ions in a slightly distorted square-planar geometry (maximal deviation 0.10 angstrom) in a cis arrangement. The compound consists of van der Waals packed molecules appearing in pairs with a Pt-Pt distance of 4.008 (1) angstrom. The acceptor-donor distances observed are: Pt-S = 2.214 (3), 2.220 (3) and Pt-O = 2.040 (9), 2.059 (9) angstrom. These are almost the same as the corresponding ones previously found in tetrakis(dimethyl sulfoxide)platinum(II) bis(trifluoromethanesulfonate) where two dimethyl sulfoxide ligands bond to Pt via their O atoms, also in a cis position. A literature survey of platinum dimethyl sulfoxide compounds shows that the Pt-S distance is significantly affected by both cis and trans influences.
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| 10. |
- 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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