Reaction rates and swelling phenomenon of Fe-C droplets in FeO bearing slag

Abstract

The reduction of FeO in slag by an iron droplet, decarburisation of the droplet and the droplet swelling phenomenon during slag-metal droplet reaction were analyzed by a kinetic model. Diffusions in the slag phase, diffusions throughout the droplet, interfacial reactions, equilibrium relations and homogeneous nucleation of gas bubbles within the droplet were incorporated in the model. During an Fe-C droplet reaction with FeO bearing slag, decarburisation rate increases with increasing FeO in slag, carbon in the droplet and the droplet size, but the rate decreases with increasing silicon in metal and ambient pressure. The decarburisation rate in unit surface area of the droplet increases with increasing the droplet size. Slow decarburisation during the initial stage of the reaction was suggested by the model, and the desiliconisation and oxygen absorption of the droplet were found to be responsible for this initial slow decarburisation. The initial slow decarburisation is pronounced when the droplet contains higher carbon and silicon, or when the reaction occurs under higher pressure and with the slag containing lower FeO. CO bubble generation within the droplet was suggested to cause the swelling of the droplet. The occurrence of swelling is promoted when the droplet contains higher carbon and lower silicon, slag contains higher FeO, or when the droplet is small, and the reaction occurs under lower pressure. © 2006 ISIJ.