Rate of reduction of FeO in slag by Fe-C drops

Abstract

The rate of reduction of FeO in slags by Fe-C drops plays an important role in several metallurgical processes, including iron bath smelting. In this study, the rate of this reaction was determined by measuring the volume of CO generated as a function of time, and the reaction was observed by X-ray fluoroscopy. The drops entered the slag in a nearly spherical shape, remained as single particles, and for the major portion of the reaction remained suspended in the slag surrounded by a gas halo. The rate was found to decrease with carbon content for alloys with low sulfur contents. The rate decreased significantly with increasing the sulfur content. Based on the results and a comparison of the calculated rates, for the possible rate-controlling mechanisms, a kinetic model was developed. The model is a mixed control model including mass transfer in the slag, mass transfer in the gas halo, and chemical kinetics at the metal interface. At high sulfur contents (>0.01 pct), the rate is primarily controlled by the dissociation of CO₂ on the surface of the iron drop. At very low sulfur, the rate is controlled by the two mass-transfer steps and increases as the gas evolution from the particle increases.