Enhancement of wüstite reducibility in blast furnace: reaction kinetics and morphological changes

Abstract

Two wüstite samples were prepared from reagent grade haematite and Baharia iron ore sinter by gaseous reduction with 50CO–CO₂ gas mixture at 1273 K. Using a thermogravimetric technique, the samples were isothermally reduced at 1173–1373 K by different ratios of H₂/CO/N₂ to simulate the composition of reducing gas in the case of high natural gas injection with high oxygen enrichment in the blast furnace. The influences of temperature and gas composition on the reduction behaviour and morphology were investigated. As reduction proceeds, the effect of temperature in increasing reduction becomes clearer. The effect of various gas compositions on the reaction rate was not so clear due to the fast reduction process. The apparent activation energy values were calculated and correlated with the gas–solid reaction formulations to elucidate the corresponding mechanism at both early and final reduction stages. The reduction rates of pure samples and wüstite from iron ore sinter at both initial and final stages are most likely controlled by the interfacial chemical reaction mechanism.