Chloride removal from zinc ash

Zinc ash generated during the galvanizing of steel and iron contains appreciable amount of zinc in the form of metallic zinc, zinc oxide, zinc chloride and zinc oxy-chloride. The chloride removal from zinc ash is very important for producing zinc metal or zinc oxide. In this study, 3 different types of ash containing varying levels of chloride have been subjected, to 3 types of treatments. Various parameters, such as roasting temperature and time, alkali washing temperature and time, solid/liquid ratio and alkali addition, have been studied. Based on the laboratory-scale experiments, large-scale operations have been carried out for chloride removal from the zinc ash. The results indicate that pyrometallurgical roasting followed by alkali wash treatment with sodium carbonate of the ash will be useful in the removal of chloride from zinc ash.