Evaporation Kinetics of the Molten PbCl₂–ZnCl₂ System from 973 to 1073 K

Abstract

The clarification of chlorides evaporation behavior from chloride or oxychloride melts is quite important for the treatment and recycling of fly ash generated from incineration processes of municipal solid waste. In the present study, the evaporation rate of the molten PbCl₂–ZnCl₂ binary chloride system was measured at 973, 1023 and 1073 K. The effects of temperature, composition of the melt and the oxygen partial pressure of atmosphere on the evaporation rate of molten chloride were investigated. The ZnCl₂ in chloride melt evaporated preferentially, but the evaporated amount of PbCl₂ was negligibly small. Calculated activation energy of ZnCl₂ evaporation was 194±4 kJ/mol and that evaporation rate was smaller than that estimated from ZnCl₂ activity for the PbCl₂–ZnCl₂ system. Therefore, the evaporation is considered to be controlled by the slower chemical reaction step than the interfacial evaporation reaction. The evaporation rate increased with increasing oxygen partial pressure in the atmosphere, which might be due to the effect of oxychloride formation.