Absorption of HCl by limestone in hot flue gases. Part II: importance of calcium hydroxychloride

J Partanen, Peter Backman, R Backman, Mikko Hupa

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    Abstract

    In the present study, the potential for products other than CaCl2 to be formed during HCl absorption was studied to shed light on the mechanisms of limestone chlorination. Experiments of different durations were made with a thermogravimetric apparatus, and the crystalline reaction products were identified by X-ray diffractometry (XRD). In the experiments, absorption products with Cl/Ca molar ratios of less than two were found to be formed in the early stages of absorbent chlorination. Calcium hydroxychloride, CaClOH, was found to be a particularly important chloride product; the XRD analyses of the chlorinated samples indicated that CaClOH is the first product to form when HCl is absorbed by limestone. The end product of chlorination, however, was found to be CaCl2. This result was true for the reactions of both calcined and uncalcined limestone at two temperature levels, 650 and 850 degrees C. The thermodynamic equilibrium calculations performed suggested that the CaClOH would not be thermodynamically stable above 700 degrees C for gas concentrations that are encountered in combustion installations.
    Original languageUndefined/Unknown
    Pages (from-to)1674–1684
    Number of pages11
    JournalFuel
    Volume84
    Issue number12-13
    DOIs
    Publication statusPublished - 2005
    MoE publication typeA1 Journal article-refereed

    Keywords

    • absorption
    • CaClOH
    • FBC
    • HCl
    • limestone
    • mechanism

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