Fate of biosludge nitrogen in black liquor evaporation and combustion

Niklas Vähä-Savo, Nikolai De Martini, Mikko Hupa

    Forskningsoutput: TidskriftsbidragArtikelVetenskapligPeer review

    3 Citeringar (Scopus)

    Sammanfattning

    At many mills, biosludge, which has a high nitrogen content, is added to black liquor and burned in kraft recovery boilers. The aim of this work was to determine the fate of biosludge nitrogen in the high solids black liquor concentrators and in the recovery boiler. Specifically, does biosludge addition result in higher nitric oxide (NO) and cyanate formation during black liquor combustion? To obtain this information, samples were collected from the chemical recovery cycle of a Finnish kraft pulp mill along with relevant process data. Laboratory combustion experiments clearly showed an increase in NO formation for the mill black liquor with biosludge, but no clear increase in nitrogen oxide emissions was detected in the recovery boiler after biosludge addition. Analysis of the green liquor samples from the dissolving tank showed a significant increase in nitrogen exiting the recovery boiler as cyanate. This finding was supported by laboratory tests studying cyanate formation. The increased cyanate results in increased ammonia formation in the recausticizing cycle, which can lead to higher NO emissions, as seen in the non-condensible gas incinerator at the mill.
    OriginalspråkOdefinierat/okänt
    Sidor (från-till)53–59
    Antal sidor7
    TidskriftTappi Journal
    Volym11
    Nummer9
    StatusPublicerad - 2012
    MoE-publikationstypA1 Tidskriftsartikel-refererad

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