Chlorine Addition to Existing Zinc Fuming Processes: A Thermodynamic Study

Abstract

Zinc fuming processes are used to volatilize heavy metals from slags and produce a clean slag. Since alternative fuel sources containing plastics are explored, the effect of chlorides becomes relevant. In this paper, the influence of Cl additions to a zinc fuming process on the Zn volatilization is investigated. Thermodynamic calculations were carried out on available industrial data from three different installations. The effects on the fuming performance of the α-value (mol O2/ mol C, in a range of 0.5 to 0.75), chloride source (Cl2, KCl, NaCl, MgCl2, and CaCl2), and added chloride amounts (50, 150, and 500 ppm Cl/min) were investigated. Although the α-value is still the most influential parameter for the overall zinc fuming rate, chloride additions can have positive effects as well. They make ZnCl2 volatilization possible, which supplements the Zn volatilization. Large additions of CaCl2 and MgCl2 improve the fuming rate the most since they cause the largest formation of the volatile ZnCl2 and they do not negatively influence Zn volatilization.