Ultrafine ash emission control of pulverized coal-fired boilers with electrostatic precipitators

Juha Mustonen, Juha Pohjola, Kjell Porle, Christer Mauritzson, Srivats Srinivasachar, Esko Kauppinen, Terttaliisa Lind, Bertram Schleicher, Juha Kurkela, Jorma Joutsensaari, Tuomas Valmari, Unto Tapper, Sampo Ylätalo

    Research output: Chapter in Book/Report/Conference proceedingChapter or book articleProfessional

    Abstract

    We have studied ash formation during the pulverized combustion of coal both at laboratory and field scale combustion systems, with special emphasis on the formation of ultrafine ash particles below 0.5 µm in diameter. In addition, we have determined ash penetration through the electrostatic precipitator (ESP) as the function of particle diameter at various ESP operation conditions, both at field scale and at pilot-scale ESP. Volatilized ash species, mainly oxides of Al and Si, form agglomerated ultrafine ash particles during char combustion. The fraction of ash volatilized and accordingly the average particle size increases as the function of char surface temperature, i.e. when increasing the oxygen partial pressure surrounding the burning char particle. In addition, the ultrafine particle size decreases when increasing the distance between the burning char particles. The size distribution of ultrafine ash formed at given combustion conditions varied from one coal to another. The maximum penetration value from 3 to 10 % was measured for particles from 0.1 to 0.5 µm in diameter at full scale industrial ESP's. Pilot-scale studies showed that ultrafine ash particle collection efficiency can be significantly improved by reducing the ion concentration within the ESP via pulsed mode operation, by increasing the gas humidity and by reducing the gas temperature within the ESP.
    Original languageEnglish
    Title of host publicationSIHTI 2: Energia- ja ympäristöteknologia. Tutkimusohjelman vuosikirja 1998
    Subtitle of host publicationProjektiesittelyt
    EditorsRabbe Thun, Maija Korhonen
    Place of PublicationEspoo
    PublisherVTT Technical Research Centre of Finland
    Pages289-312
    ISBN (Electronic)951–38–5266–0
    ISBN (Print)951–38–5265–2
    Publication statusPublished - 1999
    MoE publication typeD2 Article in professional manuals or guides or professional information systems or text book material

    Publication series

    SeriesVTT Symposium
    Number191
    ISSN0357-9387

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