Synthetic zinc ferrite reduction by means of mixtures containing hydrogen and carbon monoxide

Solid waste generation is one of the main problems in the steelmaking process. One of the most problematic waste products is the electric arc furnace dust, which is a by-product rich in iron and zinc and is present as zincite (zinc oxide) or franklinite (zinc ferrite). This work focuses on the reduction kinetics of synthetic zinc ferrite by gases containing hydrogen and carbon monoxide. This process was examined via forced stepwise isothermal analysis. The test was conducted at temperatures ranging from 500 to 950 °C. Reduction of zinc was accomplished using a mixture of hydrogen and carbon monoxide in order to simulate reformed natural gas. The results indicated that reduction of zinc ferrite occurred in two stages (550–750 °C and 800–900 °C). The first stage was characterized by iron oxide reduction, where a mix control between nucleation and diffusion was determined. The apparent activation energy obtained was 71.5 kJ mol−1. The second stage was characterized by zinc oxide reduction, where the controlling mechanism was identified as a mixed control between diffusion and phase boundary reaction. The apparent activation energy was 135.5 kJ mol−1. The formation of a dense layer of metallic iron around the unreacted core may have caused the apparent activation energy to increase.