Effect of temperature on coal mercury release

    Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

    Abstract

    Coals contain small quantities of mercury which have the potential to be emitted to the atmosphere during thermal processing. There is widespread acceptance that all the mercury originally present in the coal matrix is converted to the very volatile form, elemental mercury, Hg(0), which is insoluble in water and difficult to capture. In this form very high levels of emissions to atmosphere are possible, approaching 100% of the mercury in the coal. During coal combustion, the oxidation process of mercury is a complex function of coal properties and plant conditions. Initially it was believed that gas phase reactions of Hg(0) with chlorine species were largely responsible for the extent of oxidation. Under equilibrium calculations, chlorination of mercury Hg occurs with atomic chlorine Cl commencing at 700oC and is entirely completed at about 450oC during cooling of the flue gas. Besides electricity generation, significant mercury emissions from coal occur during metal production. Emission estimates from these sources are not well understood, and it is clear that current knowledge of emissions may significantly underestimate emissions from metal smelting sources. While significant research effort has been devoted to improving knowledge of emissions from direct combustion of coal in power stations to produce electricity, much less effort has been devoted to emissions from smelting and metal processing. This paper discusses laboratory investigations of mercury release with temperature. Two coals, one from Australian and one from USA origin were subjected to thermal treatment to temperatures ranging between 300 and 800oC. The level of mercury was monitored using cold-vapour atomic fluorescence spectrometry. The largest fraction of mercury was released at temperatures between 300 to 500oC, however some amount of strongly bonded mercury was retained in coal samples even at temperatures of 600oC. The paper evaluates mercury emission results against coal use in ironmaking processes.

    Original languageEnglish
    Title of host publication24th Annual International Pittsburgh Coal Conference 2007, PCC 2007
    Place of PublicationNew York
    PublisherCurran Associates
    Pages1168-1174
    Number of pages7
    Volume2
    ISBN (Print)9781604238617
    Publication statusPublished - 2007
    Event24th Annual International Pittsburgh Coal Conference 2007, PCC 2007 - Johannesburg, South Africa
    Duration: 10 Sep 200714 Sep 2007

    Other

    Other24th Annual International Pittsburgh Coal Conference 2007, PCC 2007
    CountrySouth Africa
    CityJohannesburg
    Period10/09/0714/09/07

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