| 1. |
- Berg, Magnus, et al.
(author)
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Förbränning av utsorterade avfallsfraktioner
- 2005
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Reports (other academic/artistic)abstract
- Projektet har visat på möjligheter och problem vid förbränning av utsorterade avfallsfraktioner bestående av papper, trä och plast i fluidbädd. Denna typ av bränslen kan antingen samförbrännas eller användas som enda bränsle i en avfallspanna. I båda fallen bör gällande gränsvärden för emissioner till luft kunna klaras men man får däremot räkna med ökade drift- och underhållskostnader, främst beroende på ökade problem med påslag och korrosion. Dessa problem är starkt kopplade till bränslets innehåll av oönskade ämnen såsom klor, alkali och vissa andra metaller. Innehållet av dessa ämnen varierar kraftigt mellan olika bränslefraktioner och därmed blir omfattningen av problemen beroende både av inblandningsgrad och av bränslets ursprung. Projektet har även visat att mängden påslag kan minskas genom tillsats av svaveladditiv samtidigt som den kemiska samansättningen i påslagen förändras på ett sådant sätt att även risken för korrosion bör minska.
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| 2. |
- De Geyter, Sigrid, et al.
(author)
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Effects of non-quartz minerals in natural bed sand on agglomeration characteristics during fluidized bed combustion of biomass fuels
- 2007
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 21:5, s. 2663-2668
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Journal article (peer-reviewed)abstract
- 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 full-scale 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.
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| 3. |
- De Geyter, Sigrid, et al.
(author)
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Skillnader i bäddagglomereringstendens mellan alternativa bäddmaterial och olika mineraler i natursand
- 2005
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Reports (other academic/artistic)abstract
- Projektets resultat visar på skillnaderna i bäddagglomereringstendens mellan olika mineraler i natursand och ett antal alternativa bäddmaterial, t.ex. olivinsand, gjuterisand och hyttsand. Vid förbränning av ett bränsle med hög andel kalium, olivkross, visar försöken att K-fältspater har en högre benägenhet till bäddagglomerering. Detta kan även förklara skillnaden mellan ren kvartssand och Rådasand vilket innehåller en förhållandevis hög andel fältspater.
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| 4. |
- Erhardsson, Thomas, et al.
(author)
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Bäddagglomereringsrisk vid förbränning av odlade bränslen (hampa, rörflen, halm) i kommersiella bäddmaterial
- 2006
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Reports (other academic/artistic)abstract
- The market of forest products is expanding and thus resulting in more expensive biomass fuels. Therefore research within the combustion industry for alternative fuels is needed, for example cultivated fuels. Combustion and gasification research on these cultivated fuels are limited. The objectives of this work was to increase the general knowledge of silicon rich cultivated fuels by study the agglomeration characteristics for wheat straw, reed canary grass and industrial hemp in combination with commercial bed materials.Controlled fluidized bed agglomeration tests was conducted in a 5 kW, bench-scale, bubbling fluidized bed reactor. The tendencies of agglomeration were determined with the three cultivated fuels in combination with various minerals present in natural sand (quarts, plagioclase and potassium feldspar) and an alternative bed material (olivine). During the experiments bed samples and formed agglomerates were collected for further analyses with a scanning electron microscope (SEM) and with X-ray microanalysis (EDS).Wheat straw had the highest agglomeration tendency of the studied fuels followed by reed canary grass and industrial hemp. No significant layer formation was found around the different bed particles. Instead, the ash forming matter were found as individual ash sticky (partial melted) particles in the bed. The bed material mineralogical composition had no influence of the agglomeration process because of the non layer formation propensities of the used silicon rich fuels.
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