A field study on ash behavior during circulating fluidized-bed combustion of biomass: 1. Ash formation

Tuomas Valmari, Terttaliisa Lind, George Sfiris, Kristina Nilsson, Willy Maenhaut, E.I. Kauppinen (Corresponding Author)

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Ash formation was studied experimentally during combustion of forest residue and willow in a 35 MW circulating fluidized-bed co-generation plant. Ash particles and vapors were sampled downstream of the process cyclone at flue gas temperatures of 810−850 °C. Inorganic vapors and fly ash particles were collected separately on filters. Size-classified fly ash particle samples were collected with an impactor. Elemental analysis methods and electron microscopy were used for ash characterization. During combustion of forest residue, about 30−40% of the total ash and a similar percentage of Ca and P was attached on the bed-material particles and were eventually removed from the bed along with bottom ash. K was retained with a higher efficiency (about 50%). S and Cl were volatilized in the furnace and were not retained in the bed. During combustion of forest residue, 80% of S had already reacted with species present in supermicrometer ash particles when detected after the process cyclone at 810−850 °C. When willow was combusted, about one-half of the sulfur remained as SO2. More than one-half of the particle-phase S was present as alkali sulfate fine particles that were almost nonexistent during forest residue combustion. Cl was present as gaseous species (KCl and presumably HCl) at 810−850 °C with both fuels.
Original languageEnglish
Pages (from-to)379-389
JournalEnergy & Fuels
Issue number2
Publication statusPublished - 1999
MoE publication typeA1 Journal article-refereed


  • fluidized beds


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