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Bed material deposition in cyclones of wood fuel fired circulating fluidized beds (CFBs)
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
2007 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 21, no 1, 104-109 p.Article in journal (Refereed) PublishedText
Abstract [en]

Bed material samples were collected at different times from a full-scale combustion boiler, and bed material deposits were taken from the cyclone and the riser at two different occasions from a wood-fired circulating fluidized bed boiler (104 MWth). The bed materials and the bed material deposits were analyzed with environmental scanning electron microscopy/energy-dispersive X-ray spectroscopy (ESEM/EDXS) to determine the characteristics of the formed bed particle layers and bed material deposits. On the basis of their elemental composition, the corresponding melting behavior was estimated, using data extracted from phase diagrams. The bed material was also fractionated by sieving, and the alkali metal concentration dependence on the particle size was determined. The bed material deposits found in the cyclone and the riser consisted of bed particles embedded in a low-temperature melting (sticky) alkali metal silicate (K and Na) that resemble the composition of the layer found around the cracks in older quartz bed particles. The alkali silicate formation, which is in progress in the vicinity of the formed cracks of older quartz bed particles, significantly transforms a large part of the bed particle and makes it less resistant against fragmentation. The results therefore suggest that elutriated alkali silicate-rich fragments from old quartz bed particles are responsible for bed material depositions in cyclones of wood-fired circulating fluidized beds (CFBs).

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 2007. Vol. 21, no 1, 104-109 p.
Keyword [en]
biomass fuels, agglomeration characteristics, combustion, gasification, straw, mechanisms, boilers, sand
National Category
Chemical Engineering Bioenergy
Identifiers
URN: urn:nbn:se:umu:diva-118229DOI: 10.1021/ef060175fISI: 000243503600013OAI: oai:DiVA.org:umu-118229DiVA: diva2:913491
Available from: 2016-03-21 Created: 2016-03-14 Last updated: 2016-03-21Bibliographically approved

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Öhman, Marcus
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