Kinetic Analysis of Recovering Zinc from Electric Arc Furnace Dust by Vacuum Carbothermic Reduction at 20 Pa

Abstract

Electric arc furnace dust (EAFD) presents a contamination hazard due to its heavy metal leachability. The traditional disposal methods of landfill or stacking not only pose a threat to the environment but also waste metal resources. This paper adopted vacuum carbothermic reduction to dispose of EAFD and the zinc metal could be obtained as a product. The reduction ratios of the EAFD were carried out under various reaction temperatures and times at 20 Pa. Furthermore, the kinetics of the reduction process was also studied. The reduction ratio of the reaction process can be facilitated through increasing the temperature or lengthening the time and can reach up to 99.6% under the condition of 1373 K with 60 min. The zinc ferrite and zinc oxide were reduced first and then iron oxide reduction occurred. The reduction process could be divided into three stages: Stage 1 involved the direct reduction of zinc ferrite and zinc oxide, and the control step was the phase boundary reaction with the apparent activation energy of 48.54 kJ/mol; Stage 2 involved the reduction of zinc oxide and iron oxide, and the control step was also the phase boundary reaction with the apparent activation energy of 56.27 kJ/mol; Stage 3 involved the escape of gas phase products and the control step was diffusion with the apparent activation energy of 105.3 kJ/mol.