Decarburization of Bloated Droplets: An Experimental Study to Understand the Kinetics of Decarburization of Metallic Iron Droplets in FeO Containing CaO-SiO2 Slags

Bloating of metal droplets in the BOF is important in developing fundamental models of the process. Bloating is controlled by the decarburization behavior of individual metal droplets in oxidizing slag. In this paper, a detailed investigation has been performed to elucidate the mechanism and rate controlling steps for decarburization of droplets over a range of droplet carbon concentration, droplet mass, slag basicity and slag FeO concentration. Four different carbon levels and three droplet masses were tested. Droplets typically exhibited three stages of decarburization: incubation period, where decarburization was mostly on the outer surface of the droplet, followed by a steady state reaction period where most decarburization was internal, and finally the end decarburization period. The rate of decarburization was found to be a mixed controlled process; the contributions of resistance from slag transport, interfacial chemical reaction, internal nucleation and growth of bubbels varied based on slag and metal chemistry. A mixed controlled kinetic model has been developed for steady state decarburization period and a partial validation of the mixed controlled kinetic model has been presented here. By varying slag FeO concentration and basicity for droplets containing 2.5 wt pct C, mixed controlled kinetics of decarburization reaction were explored.