Mechanisms Behind the Positive Effects on Bed Agglomeration and Deposit Formation Combusting Forest Residue with Peat Additives in Fluidized Beds

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• 作者：Linda Pommer ; Marcus hman ; Dan Bostrm ; Jan Burvall ; Rainer Backman ; Ingemar Olofsson ; Anders Nordin
• 刊名：Energy & Fuels
• 出版年：2009
• 出版时间：September 17, 2009
• 年：2009
• 卷：23
• 期：9
• 页码：4245-4253
• 全文大小：1006K
• 年卷期：v.23,no.9(September 17, 2009)
• ISSN：1520-5029

文摘

A compilation was made of the composition of peat from different areas in Sweden, of which a selected set was characterized and co-combusted with forest residue in controlled fluidized-bed agglomeration tests with extensive particle sampling. The variation in ash-forming elements in the different peat samples was large; thus, eight peat samples were selected from the compilation to represent the variation in peat composition in Sweden. These samples were characterized in terms of botanical composition, analyzed for ash-forming elements, and oxidized using a low-temperature ashing procedure, followed by characterization using scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The selected peat samples had in common the presence of a small fraction of crystalline phases, such as quartz, microcline, albite, and calcium sulfate. The controlled fluidized-bed agglomeration tests that co-combusted forest residue with peat resulted in a significant increase in agglomeration temperatures compared to combusting forest residue alone. Plausible explanations for this were an increase of calcium, iron, or aluminum in the bed particle layers and/or the reaction of potassium with clay minerals, which prevented the formation of low-melting bed particle layers. The effects on particle and deposit formation during co-combustion were reduced amounts of fine particles and an increased number of coarse particles. The mechanisms for the positive effects were a transfer and/or removal of potassium in the gas phase to a less reactive particular form via sorption and/or a reaction with the reactive peat ash (SiO₂ and CaO), which in most cases formed larger particles (>1 μm) containing calcium silicon and potassium.