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| 2. |
- Jansson, Stina, et al.
(författare)
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Effect of injection of di- and tricyclic aromatic compounds on post-combustion formation of polychlorinated dibenzo-p-dioxins and dibenzofurans
- 2011
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Ingår i: Science of the Total Environment. - Amsterdam : Elsevier. - 0048-9697 .- 1879-1026. ; 409:18, s. 3386-3393
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Tidskriftsartikel (refereegranskat)abstract
- The formation of mono- to octachlorinated dibenzo-p-dioxins (PC(1-8)DD) and dibenzofurans (PC(1-8)DF) was studied using a model waste in a laboratory-scale combustion reactor with simultaneous collection of flue gas at three different temperatures (450°C, 300°C, and 200°C) in the post-combustion zone. To investigate the influence of chlorination reactions and the effects of carbon backbone-containing compounds present in the flue gases, five aromatic compounds were injected into the flue gas, namely dibenzofuran (DF), biphenyl (BP), naphthalene, phenanthrene and fluorene. The injection of DF induced a reduction in the concentration of PC(3-5)DD, but did not significantly influence the concentration of PCDF. A reduction in the concentration of PC(3-5)DD was also observed during the injection of fluorene, which is structurally very similar to DF. The injection of biphenyl, naphthalene and phenanthrene had less pronounced effects on the formation of PCDD and PCDF. A possible explanation of the observed changes during injection of DF and fluorene, based on homologue profiles and affected congeners, involves formation of radical species from fluorene and/or dibenzofuran. The fluorene radical is stabilized by the delocalization of electrons across the aromatic ring structure and has the propensity to react with highly abundant hydrogen chloride, whereas the molecular species would require reaction with Cl(2) or chlorine radicals.
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| 3. |
- Jansson, Stina, et al.
(författare)
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Multivariate Relationships between Molecular Descriptors and Isomer Distribution Patterns of PCDD/Fs Formed during MSW Combustion
- 2009
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Ingår i: Environmental Science & Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 43:18, s. 7032-8
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Tidskriftsartikel (refereegranskat)abstract
- The isomer distribution patterns of mono- to hepta-chlorinated dibenzo-p-dioxins (PC1−7DD) and dibenzofurans (PC1−7DF) in postcombustion zone flue gas during incineration of an artificial municipal solid waste in a laboratory-scale fluidized-bed reactor were evaluated. Bidirectional orthogonal projections to latent structures (O2PLS) was used to correlate a set of physicochemical properties and chlorine substitution descriptors with the objective to identify parameters correlated with postcombustion zone PCDD and PCDF formation. The most influential variable for the distribution of PCDD congeners was chlorine substitution in positions 1 and 3 (Cl1 + 3), and overall the chlorine substitution descriptors exerted a larger impact on PCDDs than on PCDFs. For the PCDF, chlorination of the 9-position was the most influential X-variable. Distinct clustering was observed and was most pronounced for PCDFs, dividing most of the homologues into two or three subgroups of congeners. These subgroups seemed to correspond to the probability of formation by chlorophenol condensation. The sterically crowded dibenzofuran bay-sites (1- and 9-positions) were found to negatively influence PCDF formation, with chlorination of the 9-position having the greatest impact. Since PCDD/F toxicity is related to the lateral positions, elucidating the factors governing chlorination may be of great importance for detoxification of incineration byproducts.
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| 4. |
- Jansson, Stina, et al.
(författare)
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Post-combustion formation of PCDD, PCDF, PCBz, and PCPh in a laboratory-scale reactor : Influence of dibenzo-p-dioxin injection
- 2009
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 76:6, s. 818-25
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Tidskriftsartikel (refereegranskat)abstract
- Formation of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), benzenes (PCBz), and phenols (PCPh) was studied during combustion of an artificial municipal solid waste (MSW) in a laboratory-scale fluidized-bed reactor with simultaneous collection of flue gas samples at three different temperatures in the post-combustion zone (450 degrees C, 300 degrees C, and 200 degrees C). PCDF, PCBz, and PCPh were predominantly formed at or above the first sampling point (450 degrees C) with a dominance of the lower chlorinated homologues. PCDDs, on the other hand, were dominated by the intermediately chlorinated homologues with concentrations peaking at 300 degrees C. The dominating PCPh congeners clearly displayed the ortho-para directionality, which is indicative of electrophilic aromatic substitution, as did the PCBz isomer distribution patterns to some extent. Comparison of the observed PCBz isomer distribution patterns to prior work may indicate coupling of aliphatic species in chlorobenzene formation. The PCDDs seemed to be largely influenced by chlorophenol condensation reactions and to some extent chlorination reactions, while the PCDFs displayed a chlorination-oriented pattern for the mono- to tri-chlorinated homologues and a PCPh condensation pattern for the higher chlorinated homologues. Injection of non-chlorinated dibenzo-p-dioxin at 650 degrees C resulted in increased formation of Tri-HxCDD and a decrease in the dibenzofuran levels. The affected PCDD and PCDF congeners were not products expected to form from chlorine substitution, but instead are well known chlorophenol condensation products.
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| 5. |
- Jansson, Stina, 1975-
(författare)
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Thermal formation and chlorination of dioxins and dioxin-like compounds
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contributes to an increased understanding of the formation of dioxins and dioxin-like compounds in combustion processes. Although emissions to air from waste incineration facilities have been greatly reduced by the use of efficient air pollution control measures, the resulting residues (ashes and filters) are highly toxic and are classified as hazardous waste. The main objective of the work underlying this thesis was to elucidate the formation and chlorination pathways of dioxins and dioxin-like compounds in waste combustion flue gases in the temperature range 640-200°C in a representative, well-controlled laboratory-scale reactor using artificial municipal solid waste. This could contribute to the reduction of harmful emissions to air and also reduce the toxicity of waste incineration residues, thus reducing or even eliminating the need for costly and potentially hazardous after-treatment. A comparison of four different quenching profiles showed that the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was rapid and mainly occurred in the 640-400°C temperature region, with high dependency on sufficient residence time within a specific temperature region. Prolonged residence time at high temperatures (450/460°C) reduced the PCDD yields, even at lower temperatures along the post-combustion zone. PCDD, PCDF and PCN (polychlorinated naphthalene) isomer distribution patterns indicated contributions from chlorophenol condensation as well as chlorination reactions for all three classes of compounds. The formation of PCDDs was largely influenced by chlorophenol condensation and to some extent by chlorination reactions. For the PCDFs, chlorine substitution adjacent to the oxygen bridges was unfavoured, as demonstrated by the notably lower abundance of 1,9-substituted congeners. This was supported by bidirectional orthogonal partial least squares (O2PLS) modelling. The variable with the greatest influence on the distribution of PCDD congeners was the relative free energy (RΔGf). The O2PLS models displayed distinct clusters, dividing most of the homologues into two or three sub-groups of congeners which seemed to correspond to the probability of origination from chlorophenol condensation. The effects of injection of aromatic structures into the flue gas differed for each class of compounds. Injection of naphthalene increased the formation of monochlorinated naphthalene but the remaining homologues appeared to be unaffected. This was probably due to insufficient residence time at temperatures necessary for further chlorination. Injected dibenzo-p-dioxin was decomposed, chlorinated and re-condensated into PCDDs and PCDFs, whereas injection of dibenzofuran and fluorene reduced the PCDD levels in the flue gas.
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| 6. |
- Røyne, Frida, 1985-
(författare)
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Exploring the relevance of uncertainty in the life cycle assessment of forest products
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The role of forest biomass as a replacement for fossil fuels and products is becoming increasingly prominent as a means to mitigate climate change. To guide a sustainable transition towards a forest-based bio-economy, it is important that advantages and disadvantages of forest products are assessed, to ensure that the products deliver environmental impact reduction. Life Cycle Assessment (LCA) has become heavily relied upon for assessing the environmental impact of bio-based products. However, LCAs of similar product systems can lead to results that differ considerably, and the method is, thus, associated with uncertainties. It is, therefore, necessary to explore the relevance of uncertainties, to build knowledge about enablers and challenges in using LCA for assessing forest products.Three important challenges in the context of uncertainty in LCA are the focus of this thesis: 1) system boundaries, 2) climate impact assessment practice, and 3) allocation. More specifically, the relevance of a) including and excluding life cycle phases, b) potentially important climate aspects, and c) applying different allocation methods, was assessed. Case studies involved a chemical industry cluster, a biorefinery, and single product value chains for a plastic box, a fuel, and a building.In summary, the thesis demonstrates that:A major share of the environmental impact related to the production of an industry cluster can occur outside the cluster gates, so when strategies involving a transition to forest biomass feedstock are developed and evaluated, a life cycle perspective reveals the full environmental impact reduction potential.For bio-based products differing in functional properties from the fossil products they are meant to replace, material deterioration in the use phase can contribute substantially to overall environmental performance. This is acknowledged if all life cycle phases are regarded.As climate aspects commonly not assessed in forest product LCAs could influence results greatly, and even affect the outcome of comparisons between forest and non-forest products, the climate impact of forest products is uncertain. It is, therefore, important that this uncertainty is acknowledged and communicated, and that appropriate methods and guidelines are developed.The choice of allocation method in the LCA of biorefinery products can have a major influence on results, especially for physically non-dominant products and in consequential studies. In these cases, scenario analysis is especially valuable to show the possible range of results.LCA provides useful guidance for forest product development and production as the life cycle approach reveals causes of environmental impact throughout the product value chain. Proper identification, estimation, and management of uncertainties strengthen the provision of reliable decision support.
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| 7. |
- Shanmugam, Kavitha, et al.
(författare)
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Ecoefficiency of Thermal Insulation Sandwich Panels Based On Fly Ash Modified with Colloidal Mesoporous Silica
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:24, s. 20000-20012
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Tidskriftsartikel (refereegranskat)abstract
- The current practice of landfilling fly ash generated by waste incineration is nonsustainable, so alternative ways of using this material are needed. Silanization effectively immobilizes the heavy metal contaminants in the incineration fly ash and enables its circular utilization because silanized fly ash (SFA) has market value as a low-cost filler for polymer composites. This study examines the ecoefficiency of a thermal insulation panel that consists of a polyurethane (PU) foam core sandwiched between two epoxy composite skins prepared by reinforcing glass fibers (GF) and SFA in epoxy resin. The ecoefficiency of such panels was evaluated by comparing their life cycle environmental externality costs (LCEE) to their life cycle costs (LCC). The LCEE was calculated by monetizing the panels’ environmental impacts, which were quantified by performing a life cycle assessment (LCA). The results revealed that the ecoefficiency of the composite panels is positive (47%) and superior to that of market incumbent alternatives with PU foam or rockwool cores and steel skins. The two market incumbents have negative ecoefficiencies, primarily due to their high LCEE. The environmental performance of the panel with SFA–GF epoxy composite skins can be further improved by using lignin-based epoxy resin or thermoplastic polypropylene as the polymer matrix of composite skins. Overall, application as a filler in fabricating polymer composite skins of sandwich panels is an upcycling pathway of SFA that combines circular economy prospects with sustainability benefits.
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