Kinetics of gas oxidation of liquid Fe-C-S alloys and carbon boil phenomenon

Abstract

The decarburization and oxygen absorption rates in liquid iron droplets by an oxidizing gas were investigated at 1 723-1 843 K. More rapid carbon oxidation was observed at lower sulfur concentration or at higher temperature. The rate of oxygen absorption by liquid iron droplets was found to be suppressed by the interfacial carbon oxidation initially, and then increased rapidly even when there was still a high content of carbon left behind in the liquid. Sulfur content of the liquid was essentially unchanged during the oxidation. These observed results are well explained by a kinetic model assuming that either the transport in gas and liquid, or the interfacial reaction are jointly controlling the process of the oxidation. A model describing gas bubble nucleation from the liquid is also proposed in the present work. The profiles of liquid composition, pressure of CO in equilibrium with the liquid, interfacial specific energy and the critical radius for gas nucleation from the liquid in the droplet were predicted with these models. These predicted results were found applicable to the interpretation of the carbon boil phenomenon during gaseous oxidation.