Ultrafine ash particle formation during waste sludge incineration in fluidized bed reactors

Jouko Latva-Somppi, Esko Kauppinen, Juha Kurkela, Unto Tapper, Marcus Öhman, Anders Nordin, Bo Johanson

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    Abstract

    Ash formation during the bubbling fluidized bed (BFB) combustion of bark and pulp mill sludge has been studied on an industrial and bench scale. During co-firing in an industrial BFB a submicron fly ash mode was formed via condensation of volatilized K, Na, Sand Cl species at 0.05–0.3 μm.
    The submicron mass mode below 0.3 μm made up 2.2–5.0% of the fly ash, while the share of the supermicron mass fraction was 93.6–97.2%. Elements depleted in the ultra fine ash were Ca, Si, Al, Mg, Fe, Mn, P and Ti. The bench-scale test showed that the ultrafine particle concentration was increased by a higher bed temperature and decreased due to sludge moisture. As, Cd, Pb and Rb were enriched in the ultrafine ash on a bench scale, while Ba, Co, Sr and V were depleted.
    Cu and Zn were enriched in the ultrafine ash during the combustion of dried sludge, but not when wet sludge was fired. Micron-size ash particles composed of non-volatile species, Ca, Si, Mg, Al, P and Mn, adhered to the bed sand, presumably by surface forces, and sintering densified the ash layer.
    Original languageEnglish
    Pages (from-to)433-455
    JournalCombustion Science and Technology
    Volume134
    Issue number1-6
    DOIs
    Publication statusPublished - 1998
    MoE publication typeA1 Journal article-refereed

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    Keywords

    • fluidized beds

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