Analysis of Droplet Generation in Oxygen Steelmaking

Knowledge of droplet generation during oxygen blowing, which can be characterized by a blowing number (N-B), is crucial for better understanding of the fundamentals of the kinetics of oxygen steelmaking. A mathematical model has been developed considering the influence of surface tension on the blowing number (N-B) using plant data from the study of Holappa and Jalkanen. The model predicts the droplet formation as a function of carbon, sulphur and oxygen contents in the metal, the temperature profile of the metal bath and lance height. This study includes a sensitivity analysis to investigate the effect of the changes in the oxygen concentration throughout the process. It has been found that the rate of droplet generation increases with increasing jet momentum onto the metal bath and with decreasing surface tension of the liquid metal. The model also suggests that generally the variation in oxygen and sulphur contents in liquid bath has relatively little influence on droplet generation compared to the effect of blowing parameters. However, in the case of low carbon steels (<0.05 mass% C), the blowing number increases by more than 50% at the end of the blow due to lowering of surface tension.