Evolution of deposited carbon during multi-stage fluidized-bed reduction of iron ore fines

Abstract The influence of reduction conditions on carbon deposition during fluidized-bed pre-reduction of iron ore fines was investigated experimentally. The results showed that reduction temperature and the composition of reducing gases had a significant effect on the rate of carbon deposition and the type of carbon deposits (graphite and Fe 3 C). Low reduction temperature, high CO content, and addition of H 2 favored the deposition of carbon, especially graphite. The reduction conditions also significantly affected the surface morphology of the as-reduced iron ore fines. As the amount of deposited graphite increased, the formation of fibrous iron disappeared and graphite filaments were observed. The pre-reduced iron ore fines were further fluidized in pure CO at 850 °C for final reduction. The results showed that graphite could suppress the formation of fibrous iron and decrease the surface viscosity, thereby inhibiting agglomeration during the final high-temperature reduction stage. Reactions that consume the deposited carbon during the final high-temperature reduction were identified and graphite was shown to be more reactive than Fe 3 C. To enhance the application of fluidization technology in producing sponge iron, a novel solid-state high-temperature reduction method via deposited carbon was proposed and demonstrated to be feasible.