Modeling of slag eye area in argon stirred ladles

Abstract

Slag eye area in an axi-symmetrical water model of an argon stirred ladle has been measured through video photography as a function of gas flow rates, liquid depth, slag layer thickness and different types of upper phase liquid. It is shown that in addition to the principal operating parameters (i.e., gas flow rate, liquid depth and amount of slag), physical properties of the overlying liquid, particularly kinematic viscosity and density exert considerable influence on slag eye formation. Based on our experimental observation, it is shown that existing correlations do not constitute a sufficiently reliable basis for prediction of slag eye area in steelmaking ladles. Accordingly, a new correlation for slag eye area has been formulated through dimensional analysis embodying a large set of experimental data, derived from different combinations of bulk and upper phase liquids. Polynomial regression indicates that dimensionless slag eye area can be expressed in terms of Froude number, (Up 2/gH), density ratio, [RL/Δρ), and Reynolds number, (HUp/vs), via: (Aes/hH)=3.25(U P2/gH)1.28(ρL/Δρ) 055(νs/HUP)-005 in which, A es is the eye area, H is the slag layer thickness, h is the bulk liquid depth and UP is the average plume rise velocity. Experimental data reported by many investigators on aqueous as well as industrial scale ladle gas stirred ladles systems were subsequently applied to demonstrate the adequacy and appropriateness of the proposed correlation. Possible extrapolation of the correlation to eccentric gas injection and melt covered with a thick slag layer, which are more typical of ladle metallurgy steelmaking, is also examined. © 2010 ISIJ.