Abstract
Vaporization behavior (1163–1463 K) of lead in the slag system of FeO-CaO-SiO 2-Al 2O 3 with CaCl 2 was examined. A thermodynamic estimation with the principle of Gibbs free energy minimization showed that the major vapor species from the sample of the FeO-CaO-SiO 2-Al 2O 3 system+PbO+CaCl 2 were metallic Pb, PbCl, PbCl 2, and FeCl 2, at the experimental temperature range. The experimental results show that the mole ratio of vaporized Cl in lead chlorides to vaporized Pb, simply expressed as Cl/Pb, decreases with increasing temperature. The larger Cl/Pb means a larger ratio of gaseous PbCl 2, since metallic Pb and PbCl vapors are formed in a similar reduction atmosphere. The evaporation is initially rapid and becomes steady after holding for 10 min. Gaseous PbCl 2 is mainly formed during the heating period, and at the holding stage, it reacts with FeO to produce gaseous FeCl 2. With regard to slag composition, FeO content and basicity significantly affect the evaporation of lead. High FeO content and high basicity promotes the formation of metallic Pb and PbCl, whereas, it prohibits PbCl 2 evaporation.
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