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Forum » EMEP-EEA Guidebook discussions » HCB from wood in small combustion plant

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Author Topic: HCB from wood in small combustion plant 2783 Views
  • Carlo
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    HCB from wood in small combustion plant Link to this post

    I report a question related to HCB and residential wood combustion we received from Peter Meulepas from the Implementation Committee (see below in italics) through Kristina Saarinen.

    Here is what Peter asked:

    Current default emission factors for HCB for residential combustion: In the information we received from you on 11 May you refer to the large uncertainties associated with the default emission factors for the residential combustion. For example the default emission factor (tier 1 and 2) for HCB for residential wood combustion is 6 ug/GJ with a 95% confidence interval of 3 to 9 ug/GJ. Several Parties however in their response to the Committee refer to the fact that the default emission factors themselves are obsolete, not taking into account the technological improvements taken place since 1990 and not taken into account implemented abatement measures for inter alia PM, DIOX and PAH, having simultaneous impact on HCB. What is your assessment of this claim that some of the default emission factors for HCB are obsolete and in need for an update? Do you have any comments to make on the fact that the tier 2 default emission factor for HCB for residential wood combustion is the same for all technologies (6 ug/GJ). Are HCB emissions not dependent at all on the type of technologies used? Do you have any recent information on this issue? Are there any plans to provide more detailed emission factors for this pollutant?

    and Kristina Saarinen comment:

    It seems that little information is out there about real emission measurements according to the attached earlier Guidebook chapter on HCB sources, as well as according to other litterature. However, some countries are also using other EFs in their inventories (see www.apef-library.fi. According to some sources it also seems that HCB maybe connected more to fuel (e.g. Cl containing waste) than the combustion technique. In case you have better information, could you kindly inform us asap, as the meeting of the IC is already next week? Otherwise we maybe just state the facts that we do not actually know other than what the earlier GB chapter already states that information is a bit unsure....

    I agree that EFs for HCB (but also for dioxins and PCB) can be improved. Don't seems to me that in APEF there are other wood EFs (some more higher values for Austria and other for Polland but in g/Gg and without heat content). So it's very difficult to update this information. A lot of new information I have found in:

    Emission of PCDD/F, PCB, and HCB from Combustion of Firewood and Pellets in Residential Stoves and Boilers
    jorn Hedman,* Morgan Naslund, and Stellan Marklund
    Unit of Biomass Technology and Chemistry, Swedish University of Agricultural Sciences, P.O. Box 4097, SE-904 03 Umea, Sweden, and Chemistry Department, Environmental Chemistry, Umea University, SE-901 87 Umea, Sweden
    Environ. Sci. Technol., 2006, 40 (16), pp 4968-4975

    Abstract
    To assess potential emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) from residential combustion of biofuels, experiments were performed in which various types of pellets and firewood were combusted in four types of stoves and boilers, with both full and reduced rates of air supply. Intermittent combustion of wood pellets resulted in emissions of 11 ng(WHO-TEQ)/kg combusted fuel (dry weight). A modern, environmentally certified boiler yielded somewhat lower emissions of PCCD/F and PCB than a wood stove. Both gave <0.1 ng(WHO-TEQ)/m3n(1.3?6.5 ng(WHO-TEQ)/kg) and considerably lower emissions than an old boiler (7.0?13 ng(WHO-TEQ)/kg). No positive effect on emissions could be observed in full air combustion (simulating the use of a heat storage tank) compared to combustion with reduced air. Two of the wood combustion experiments included paper and plastic waste fuels. Chlorine-containing plastic waste gave rise to high emissions: ca. 310 ng(WHO-TEQ)/kg over the whole combustion cycle. The homologue profiles of PCDD/Fs show characteristic differences between ashes and flue gas from combustions with different levels of air supply. These differences do not, however, seem to have any correlation to the relative amount of toxic congeners

    But I have only abstract and I wait for the paper.

    There are someone with more information.

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