New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace(EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite(Zn Fe2O4), which accounts for more than half of total zinc in the EAF dust, into Zn O and Ca2Fe2O5 by Ca O addition. The EAF dust was mixed with Ca O powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All Zn Fe2O4 was transformed into Zn O and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient Ca O to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess Ca O beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than Zn Fe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when Ca O was added.