The isothermal kinetics of zinc ferrite reduction with carbon monoxide

The reduction kinetics of zinc ferrite in CO was investigated under isothermal conditions at different CO concentration and roasting temperature with the help of the thermogravimetric analysis (TGA). The reduction of zinc ferrite was a step-wise mechanism. As the model fitting results suggest, the first stage was controlled by the rate of first-order (when CO = 4%) or the second-order (when CO = 6%, 8%) reaction, with the E-a in 4%, 6%, and 8% of CO being 91.45 kJ mol(-1), 73.08 kJ mol(-1), and 73.49 kJ mol(-1), correspondingly. Also, the diffusion of reactant proves to constitute the rate-determining step in the second stage, and the reaction model is R2 (contracting cylinder), wherein the E-a in 4%, 6%, and 8% of CO is 80.81 kJ mol(-1), 59.11 kJ mol(-1), and 59.19 kJ mol(-1), correspondingly. The generation of magnetite and zinc oxide is the chemical reaction control, and the generation of ferrous oxide, metal iron was the diffusion control. The increase in the CO concentration from 4% to 6% or 8% could decrease the E-a and increase the reaction order, consequently, the reductive roasting was accelerated.

Automated summary

The reduction kinetics of zinc ferrite in CO atmosphere follows a step-wise mechanism influenced by reaction rate and diffusion, with higher CO concentrations accelerating the reduction process. The reduction is controlled by the rate of the first or second order in different CO conditions, with diffusion being the rate-determining step in the second stage.