The Effect of Temperature and Roasting Time on the Conversion of Zinc Ferrite to Zinc Oxide in the Electric Arc Furnace Dust

Abstract

The dust of electric arc furnaces (EAF-dust) contains significant amounts of zinc in the form of various chemical compounds. Therefore, dust can be used as a raw material for zinc extraction. EAF-dust containing 20 wt.% Zn has been studied. The effect of dust roasting with Ca O and Na2CO3 additives on the degree of conversion of ZnFe2O4 to Zn O was studied experimentally. The effect of the roasting temperature of 700, 850 and 1000 °C and the roasting duration of 1, 2 and 3 hours were established. Ca O and Na2CO3 additives in dust contribute to the destruction of ZnFe2O4 due to the formation of Ca2Fe2O5 and NaFeO2. After treatment, zinc is presented in the form of acid soluble zinc oxide. The content of acid-soluble zinc increases from 25% in the initial dust to 97 – 98% in the roasting product (“cinder”) under optimal roasting conditions.

Thermodynamic analysis of zinc ferrite (ZnFe2O4) formation inside the HIsarna off-gas system

“…As will be discussed in coming sections, the off-gas system provides the most favourable environment for the ZnFe 2 O 4 formation. This is due to a high concentration of molten pre-reduced iron oxide particles (Fe 3 O 4 ), low temperature and high partial pressure of oxygen (or equivalently low partial pressure of carbon monoxide) [10][11][12][13][14][15][16][17].…”