A Dynamic Flux Dissolution Model for Oxygen Steelmaking
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IN oxygen steelmaking, flux is added in a solid form to the process to form a basic slag that will limit the degradation of the refractory lining and will remove oxidation products such as phosphorus and silicon. The progress of flux dissolution determines the efficiency of fluxing of impurities and prolongs contact time with refractory lining. Since top blowing process takes only 15 to 20 minutes to refine impurities from the steel, full utilization of flux added requires rapid flux dissolution in the slag. Therefore, the degree of flux dissolution is of crucial interest for understanding the progress of slag–metal reactions in the oxygen steelmaking system. There have been several experimental studies[1–12] on the mechanism and kinetics of flux dissolution into stirred and stagnant slag baths at high temperatures. However, these are generally limited studies with experimental conditions, such as the stirring intensity, composition, and temperature of molten slag system, which can be practically studied at laboratory scale. Although these studies provide qualitative information on flux dissolution, it is difficult to apply the findings to predict the kinetics of flux dissolution under full-scale operating
AMEYA KADROLKAR, Ph.D. Student, and NESLIHAN DOGAN, Assistant Professor, are with the Department of Materials Science & Engineering, McMaster University, Hamilton, ON, Canada. Contact e-mail: [email protected] NILS A˚.I. ANDERSSON, Postdoctoral Researcher, formerly with the Department of Materials Science & Engineering, McMaster University, is now with the Royal Institute of Technology (KTH), Stockholm, Sweden. Manuscript submitted January 20, 2016. Article published online August 18, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
conditions. In order to close this knowledge gap, there have been few modeling attempts[13–16] made. Asai et al.,[13] Graveland-Gisolf et al.,[15] Dogan et al.,[14] and Lytvynyuk et al.[16] developed a process model for oxygen steelmaking process and they incorporated a flux dissolution submodel as a part of their process model. In all models, rate of lime dissolution is assumed to be controlled by CaO diffusion through boundary layer and is a function of difference between the CaO content in slag phase and saturation concentration. Asai et al.[13] expressed the saturation concentration of CaO in slag as a polynomial expression (derived from a simplified ternary phase diagram of FeO-SiO2-CaO system) of slag and bath temperature. They were able to predict the amount of lime dissolved as a function of lime addition and blow time; however, the validation of this model against industrial operations was not provided in their study. Graveland-Gisolf et al.[15] took into account the silicate layer formation around the lime particles. However, detailed description of the model is not available in open literature. Dogan et al.[14] calculated the saturation limit of CaO in slag using the ternary phase diagram FeO-SiO2-CaO, considering intersections between the liquidus line with a straight line connect
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