Thermodynamic analysis of the carbothermic reduction of electric arc furnace dust in the presence of ferrosilicon

Thermodynamic analysis of zinc recovery from electric arc furnace (EAF) dust by carbon in the presence of ferrosilicon was studied. A preheating process was performed to remove volatile compounds from dust to avoid impurities in the final zinc product. The main process includes reduction of zinc oxide and gasification and condensation of zinc vapor. Equilibrium condition was computed using FactSage program for the processes of reduction and gasification. The effect of ferrosilicon addition on the recovery of zinc was investigated for the temperature range of 950-1050 °C at the constant pressure of one atmosphere. It is shown that ferrosilicon provides a better kinetic condition for zinc recovery by facilitating slag formation. The preferred condition for formation of liquid slag was predicted based on thermodynamic calculations and verified by performing some experiments. The experimental results show that good agreement between calculations and experiments can be obtained with higher amounts of silicon contents and at higher temperatures where liquid slag is presented. A mixture of the dust with 10% C and 7% FeSi(75%) can be used to achieve over 97% zinc recovery.