Comparison of reduction kinetics of Fe2O3, ZnOFe2O3 and ZnO with hydrogen (H2) and carbon monoxide (CO).

Electric arc furnace dust (EAFD) recycling is based on the reduction of oxides containing iron and zinc. With regard to the sustainability of industrial processes, hydrogen reduction processes could be the key technology to replace current recycling technologies based on carbothermal reduction. In this context, hydrogen is often claimed to provide better reduction kinetics, but it is mostly unclear how much faster it is. The present work gives a comprehensive comparison of the reduction kinetics of the major zinc- and iron-containing oxides in EAFD (Fe 2 O 3 , ZnOFe 2 O 3 , and ZnO) using hydrogen and carbon monoxide under various process parameters. The influence of specimen size, reduction gas flow rate, and temperature were evaluated. The kinetic advantage of hydrogen compared to carbon monoxide was confirmed, enabling the reduction of direct CO 2 -emission. Hydrogen results in a 2.5 times faster reduction of Fe 2 O 3 and a doubling of the reduction rate for ZnOFe 2 O 3. ZnO reduction was determined to be 1.5 faster. Furthermore, ZnO was found to be the rate-limiting substance in the recycling of EAFD, regardless of the reducing agent. • The kinetical advantage of H 2 compared to CO is the most pronounced for Fe 2 O 3 and decreases for ZnOFe 2 O 3 and ZnO. • The temperature dependency for both reducing agent is only visible for ZnO. for the entire experiment. • Within the applied temperature (800–900 °C) both reducing agents only show a marginal temperature dependency for Fe 2 O 3. • Fe 2 O 3 reduction was found to be controlled by diffusion and ZnO reduction was found to be controlled by chemical reaction. • Doubling of gas flow leads to a doubled reduction rate. Quadrupling of the gas flow results in a tripled reduction rate. [ABSTRACT FROM AUTHOR]