EXPERIMENTAL INVESTIGATION OF SELECTIVE CHLORIDIZING ROASTING FOR THE FEMOVAL OF IMPURITIES FROM EAF DUST AND OTHER ZINC FEED-STOCKS PRIOR TO THERMAL REDUCTION

摘要

An experimental study was undertaken to evaluatethe feasibility of a selective chloridizing roasting pre-treatmentprocess for the elimination of impurities from zinc feed-stocksprior to recovering zinc by conventional unit operations. In thisinvestigation, a number of chemistries that might serve as abasis for such a pretreatment process were examined. A varietyof chloridizing agents were admixed with EAF dust to promotethe selective removal of lead and cadmium by the formation ofvolatile metal chlorides.The results of the experimentation firmly establish that selectivechloridizing roasting is a technically feasible means ofeliminating lead and cadmium from EAF dust. Excellentextraction efficiencies were accomplished with a number ofchloride additives; as high as 98 percent lead extraction and 88percent cadmium extraction were attained with minimal zinclosses. Continuous pilot-scale tests reinforced the trendsestablished by laboratory-scale experimentation. Attempts ofchlorine elimination using pyrohydrolysis were less successful.The extent of chlorine elimination was found to be highlydependent upon EAF dust sample type and treatment temperature.