2010 Volume 50 Issue 8 Pages 1084-1088
The chlorination and evaporation behaviors of Zn in the ZnO–Fe2O3–CaCl2 system was studied by gravimetry from 1173 to 1323 K and the effects of carrier gas flow rate, temperature and the initial Zn content of specimen on the chlorination rate were investigated. Moreover, thermodynamic calculation was carried out. Fe and Zn were separated because Zn was selectively chlorinated by CaCl2 from ZnO–Fe2O3 system and volatilized as ZnCl2 while Fe remained as oxide in chlorinated residue. From the chemical analyses, it was clarified that the volatilization of ZnCl2 mainly cause the weight loss of specimen. Based on these results, the chlorination mechanism and kinetic model were discussed. The weight change of specimen was expressed as a function of reaction time reasonably well by assuming the first order reaction with respect to presumed ZnCl2. Apparent activation energy of chlorination reaction, calculated from obtained reaction rate constants for various initial Zn contents, was in the range between 107 and 172 kJ/mol. It is considered the rate determining step of chlorination is chemical reaction, such as the reaction between ZnO and CaCl2, or the interfacial evaporation of ZnCl2 from the specimen.