The Decarburization Kinetics of Metal Droplets in Emulsion Zone
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INTRODUCTION
IN oxygen steelmaking, large number of metal droplets are generated and ejected into the slag due to the high speed oxygen jet impingement on the metal bath.[1,2] This leads to the formation of a large interfacial area between the metal droplets and the slag and enhances the kinetics of the refining reactions during oxygen blow. Few studies[1–6] investigated the contribution of refining reactions in the emulsion zone by sampling metal droplets from pilot plant trials. Meyer et al.[1] quantified the number of droplets generated in the emulsion zone and predicted the residence time of these droplets in order to investigate the refining rates in the emulsion zone. It was found that instantaneous carbon content of droplets in the emulsion were lower than that of bath[1] thus establishing the emulsion zone as a significant contributor to the decarburization reaction. Similar findings were reported by other researchers.[3,6] These industrial findings motivated several researchers[7–14] to study the behavior of a single metal droplet in a slag for a more fundamental understanding of reaction kinetics between metal and
AMEYA KADROLKAR and NESLIHAN DOGAN are with the McMaster Steel Research Centre, McMaster University, JHE 357, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada. Contact e-mail: [email protected] Manuscript submitted March 26, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
slag. Mulholland et al.[7] pioneered the use of X-ray fluoroscopy to study the effect of metal droplet size, metal and slag compositions, and temperature on the decarburization behavior of droplets. The study provided valuable qualitative insight about formation of gas halo surrounding the metal droplet. Gaye and Riboud[9] firstly measured the reaction rate through measurement of flow rate of gas formed inside the chamber and came to be known as Constant Volume Pressure Increase (CVPI) technique. The combination of X-ray fluroscopy and CVPI technique aided the in situ observation and quantitative measurement of decarburization reaction.[10–12,14–16] This combination was firstly employed by Min and Fruehan[10] for studying the decarburization rate of a metal droplet reacting with slags containing less than 10 wt pct FeO and suggested a ‘mixed control model’ for emulsion zone decarburization. Later, using similar set-up, Molloseau and Fruehan[11] observed that the decarburization rate of droplets ([C] = 2.9 wt pct) in contact with slags with (FeO) > 10 wt pct ‘emulsified’. The CO evolution from the metal droplets (with similar carbon content) was found to be dependent on the FeO content in slag. Similar technique was used for Coley and his coworkers[12,14,17] to further study the decarburization kinetics under various conditions relevant to steelmaking operations. Chen and Coley[12] focussed on the effect of droplet size, FeO content in the slag and temperature on internal CO gas generation rates and bloating behavior. They proposed a model to predict the rate of internal CO gas generation. Homogeneous nucleation of CO gas
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