Water model experiment on the liquid flow behavior in a bottom blown bath with top layer
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INTRODUCTION
PREVENTION of top slag entrainment into molten steel in a ladle agitated by bottom gas injection is of essential importance for producing clean steel. The critical condition for the initiation of the entrainment of the top slag into molten steel therefore has attracted the interest of many researchers for a long time.it-9] An empirical correlation of the critical condition for a water model using silicone oil, liquid paraffin, or normal pentane as a model of the top slag was derived by the present authors as a function of gas flow rate, the size and shape of the vessel, and the physical properties of slag and metal.[~o] This empirical correlation was found to be valid for some hot models under certain blowing conditions, t~~ At the present stage, however, its applicability to the practical steelmaking processes has not been confirmed. While the mechanism of initiation of slag entrainment is well known, studies on the effects of top slag on the liquid flow dynamics in a bath agitated by bottom gas injection are rather limited, t".~2.~31 Nakajima eta/. [11] measured the axial and radial mean velocity components and the root-mean-square (rms) values of the axial and radial turbulence components only in the recirculation region using a laser Doppler velocimeter. They found that at any gas flow rate, the mean speed of
MANABU IGUCHI, Associate Professor, is with the Department of Materials Science and Processing, Faculty of Engineering, Osaka University, Osaka, 565 Japan. OLUSEGUN J. ILEGBUSI, Associate Professor, is with the Department of Mechanical Engineering, Northeastern University, Boston, MA 02115. HIROSHI UEDA, formerly Graduate Student, Department of Materials Science and Processing, Osaka University, is with Ishikawajirna-Harirna Heavy Industries Ltd.. Yokohama, TOMOAKI KURANAGA, formerly Undergraduate Student, Department of Materials Science and Processing, Osaka University, is Graduate Student, University of Tokyo, Tokyo 106, Japan. ZEN-ICHIRO MORITA, Advisor Emeritus Professor, Department of Materials Science and Processing, Osaka University, is with Surnitomo Metal Industries Ltd., Hyogo, 660 Japan. Manuscript submitted August 3, 1994. METALLURGICALAND MATERIALSTRANSACTIONS B
bath circulation and mean fluctuation velocity in the bath are considerably reduced in the presence of top slag. Furthermore, Nakajima and GuthrieU21 measured the population of slag droplets entrained in the bath and compared the data with their numerical calculation. Lin and GuthrieU3J studied, among other things, the effect of density difference between the top and lower layers on the emulsification process. They found that at a high density difference (as in a real steel/slag system), the emulsification is dominated by the entrainment of the droplets of the lower (denser) layer into the upper layer. At low density ratios, on the other hand, an inverse emulsion of top layer droplets in the lower layer occurs. Measurements of mean velocities and turbulence components in the bubbling jet region have not been made by
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