| 1. |
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| 2. |
- Bauhn, Lovisa, 1981, et al.
(författare)
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The fate of hydroxyl radicals produced during H2O2 decomposition on a SIMFUEL surface in the presence of dissolved hydrogen
- 2018
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 507, s. 38-43
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Tidskriftsartikel (refereegranskat)abstract
- Over geologic timescales hydrogen peroxide will be one of the most important radiolytic oxidants challenging the spent fuel integrity in a deep repository. Consequently, the reaction between hydrogen peroxide and different kinds of UO 2 based materials has been the subject of several studies over recent decades. Parts of these studies have investigated the effect of dissolved hydrogen on this reaction, as large amounts of hydrogen are expected to be produced by anoxic corrosion of iron in the deep repositories. In some of the studies hydrogen has been shown to offset the radiolysis-driven oxidative dissolution of the fuel despite the expected inertia of hydrogen at repository temperatures. However, the underlying mechanism is primarily based on the effect of the metallic particles contained in the spent fuel. One clue to the mechanistic understanding is whether or not a reaction takes place between dissolved hydrogen and hydroxyl radicals adsorbed to a fuel surface resulting from the decomposition of H 2 O 2 . In the study presented here this reaction could be confirmed in an autoclave system with SIMFUEL, a hydrogen peroxide spiked solution, and deuterium gas. The results show that the studied reaction does not only occur, but accounts for a substantial part of the hydrogen peroxide consumption in the system. Only a very minor part, 0.02%, of the total consumed hydrogen peroxide caused oxidative dissolution of the SIMFUEL. The conclusion is supported by quantitative measurements of HDO, dissolved U in solution and O 2 in the gas phase.
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| 3. |
- Corcoran, Angelica, 1988, et al.
(författare)
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Comparing the structural development of sand and rock ilmenite during long-term exposure in a biomass fired 12 MWth CFB-boiler
- 2018
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 171, s. 39-44
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen Carrier Aided Combustion (OCAC) is a novel combustion concept with the purpose to increase the overall efficiency in conventional circulating fluidized bed (CFB) boilers. By replacing the commonly used bed material with an oxygen carrier (OC), the conceptual idea is to utilize the fluid dynamics in a CFB and the inherent oxygen transport supported by the OC to increase the oxygen distribution within the furnace in time and space. The OCAC concept has been successfully validated and further reached long-term demonstration in full scale operation (75-MW th ). This work presents a first evaluation of how ilmenite particles are affected in regard to mechanical resistance during long-term exposure to OCAC conditions in Chalmers 12-MW th CFB-boiler. A sand and a rock ilmenite are evaluated with regard to their mechanical stability. For evaluation, samples of the fresh materials and samples collected during operation in the Chalmers boiler are investigated. The study shows that the two materials differ in how the mechanical degradation occurs with exposure time. The sand ilmenite form cavities which are held together by an ash layer before they are shattered into numerous pieces, whereas the rock ilmenite develops distinct cracks that cause splitting of the particles.
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| 4. |
- Maric, Jelena, 1983, et al.
(författare)
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Valorization of Automobile Shredder Residue Using Indirect Gasification
- 2018
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 32:12, s. 12795-12804
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Tidskriftsartikel (refereegranskat)abstract
- Dual fluidized bed (DFB) gasification offers the possibility to convert solid fuels into a valuable gas, comprised of syngas, and hydrocarbons that can be readily handled in petrochemical units. DFB gasifiers are especially suitable for nonhomogeneous fuels, such as waste fractions. In this work, the possibility to use DFB gasification as a recycling/valorization method of automobile shredder residue is investigated. The gasification tests were carried out in the Chalmers 2–4 MWth gasifier over 4 days. The effects of ash on the gas and tar compositions, as well as on the activity of the bed inventory, were evaluated. The results show that 60% of the total carbon in the fuel can be recovered in the form of a permanent gas, whereby the produced gas contains 12%mol of C2–3 hydrocarbons. The tar levels measured in the produced gas were high, although it was clear that decomposition into monomer-like compounds occurred in the reactor, which resulted in the production of valuable petrochemical compounds, corresponding to 8–9% of the carbon in the feed. Using a higher operating temperature was found to be beneficial in terms of obtaining a higher gas yield, regardless of the level of ash enrichment in the system. The high ash levels in the fuel feed did not negatively affect the technical operation of the fluidized bed. Possible routes of carbon recovery are discussed.
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| 5. |
- Brandin, Jan, 1958-, et al.
(författare)
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Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications
- 2018
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Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 148:1, s. 312-327
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Tidskriftsartikel (refereegranskat)abstract
- Catalysts used for selective catalytic reduction were deactivated for various times in a slipstream from a municipal solid waste incineration plant and then characterized. The activity for NO reduction with NH3 was measured. The Brunauer–Emmett–Teller surface areas were determined by N2 adsorption from which the pore size distributions in the mesopore region were obtained. Micropore areas and volumes were also obtained. The composition of fresh and deactivated catalysts as well as fly ash was determined by atomic absorption spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. The changes in surface area (8% decrease in BET surface area over 2311 h) and pore structure were small, while the change in activity was considerable. The apparent pre-exponential factor was 1.63 × 105 (1/min) in the most deactivated catalyst, compared to 2.65 × 106 (1/min) in the fresh catalyst, i.e. a reduction of 94%. The apparent activation energy for the fresh catalyst was 40 kJ/mol, decreasing to 27 kJ/mol with increasing deactivation. Characterization showed that catalytic poisoning is mainly due to decreased acidity of the catalyst caused due to increasing amounts of Na and K.
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| 6. |
- Canton, S. E., et al.
(författare)
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Watching the dynamics of electrons and atoms at work in solar energy conversion
- 2015
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Ingår i: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498. ; 185, s. 51-68
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Tidskriftsartikel (refereegranskat)abstract
- The photochemical reactions performed by transition metal complexes have been proposed as viable routes towards solar energy conversion and storage into other forms that can be conveniently used in our everyday applications. In order to develop efficient materials, it is necessary to identify, characterize and optimize the elementary steps of the entire process on the atomic scale. To this end, we have studied the photoinduced electronic and structural dynamics in two heterobimetallic ruthenium-cobalt dyads, which belong to the large family of donor-bridge-acceptor systems. Using a combination of ultrafast optical and X-ray absorption spectroscopies, we can clock the light-driven electron transfer processes with element and spin sensitivity. In addition, the changes in local structure around the two metal centers are monitored. These experiments show that the nature of the connecting bridge is decisive for controlling the forward and the backward electron transfer rates, a result supported by quantum chemistry calculations. More generally, this work illustrates how ultrafast optical and X-ray
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| 7. |
- Eivazihollagh, Alireza, et al.
(författare)
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On chelating surfactants : Molecular perspectives and application prospects
- 2019
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Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322 .- 1873-3166. ; 278, s. 688-705
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Tidskriftsartikel (refereegranskat)abstract
- Chelating agents, molecules that very strongly coordinates certain metal ions, are used industrially as well as in consumer products to minimize disturbances and increase performance of reactions and applications. The widely used sequestering agents, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) belong to this branch of readily water-soluble compounds. When these chemical structures also have hydrophobic parts, they are prone to adsorb at air-water interfaces and to self-assemble. Such bifunctional molecules can be called chelating surfactants and will have more extended utilization prospects than common chelating agents or ordinary ionic surfactants. The present review attempts to highlight the fundamental behavior of chelating surfactants in solution and at interfaces, and their very specific interactions with metal ions. Methods to recover chelating surfactants from metal chelates are also described. Moreover, utilization of chelating surfactants in applications for metal removal in environmental engineering and mineral processing, as well as for metal control in the fields of biology, chemistry and physics, is exemplified and discussed.
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| 8. |
- Ferritsius, Rita, et al.
(författare)
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TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II: Comparison of the five tests
- 2018
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 82-94
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Tidskriftsartikel (refereegranskat)abstract
- This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.
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| 9. |
- Ferritsius, Rita, et al.
(författare)
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TMP properties and refining conditions in a CD82 chip refiner. Part I: Step changes of process variables, description of the tests
- 2018
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- The study explores how changes in process variables, residence time and pulp consistency in refining influence the pulp properties. The equipment utilized in this study was a conical disc chip refiner (RGP82CD) producing thermomechanical pulp (TMP). The focus was on the ratio between tensile index and specific energy consumption. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. This showed that the CD-refiner, with the flat and conical refining zone, has a process performance similar to that of a two-stage refiner set-up, and that the consistency in both refining zones is of high importance. Comparing different periods revealed that even if the values of measured blow line consistency are similar, significant differences in the estimated consistency in the flat zone can prevail. Therefore, only monitoring blow line consistency is not enough. Specifically, it was found that the pulp consistency after the flat zone could be very high, considerably higher than in the blow line, and this could have negative effects on tensile index and fibre length.
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| 10. |
- Forero Saboya, Juan, 1992, et al.
(författare)
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Water-in-Bisalt Electrolyte with Record Salt Concentration and Widened Electrochemical Stability Window
- 2019
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 10:17, s. 4942-4946
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Tidskriftsartikel (refereegranskat)abstract
- Water-in-salt and water-in-bisalt electrolytes have recently attracted much attention due to their expanded electrochemical stability windows. The concentration limit of such electrolytes is constrained by the solubility of the lithium salts employed, ca. 21 m (mol kg−1) for LiTFSI (lithium bis(trifluoromethanesulfonyl)imide). By adding a second lithium salt, the total salt concentration can be increased, but the hydrogen evolution keeps limiting the application of such systems in batteries with low potential anodes. Herein we report a water-in-bisalt electrolyte with a record salt concentration (31.4 m LiTFSI + 7.9 m Li[N(CH3)2((CH2)3SO3)((CH2)4SO3)]) in which the bulky anion completely prevents the crystallization, even at such low water contents. Although the hydrogen evolution reaction is not completely suppressed, the expanded electrochemical stability window allows for low potential reactions such as aluminum−lithium alloying. The high salt concentration favors the formation of a suitable passivation layer that can be further engineered by modifying the anion structure
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