Physical Modeling of Gas Jet-Liquid Free Surface in Steelmaking Processes.
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Mater. Res. Soc. Symp. Proc. Vol. 1243 © 2010 Materials Research Society
Physical Modeling of Gas Jet-Liquid Free Surface in Steelmaking Processes. J. Solórzano-López1, R. Zenit2, C. González-Rivera1 and M. A. Ramírez-Argáez1. 1 Facultad de Química, UNAM, Av. Universidad 3000, Coyoacán, 04510, México, D.F. 2 Instituto de Investigaciones en Materiales, UNAM, Av. Universidad 3000, Coyoacán, 04510, México, D.F. ABSTRACT Gas jets play a key role in several steelmaking processes as in the Basic Oxygen Furnace (BOF) or in the Electric Arc Furnace (EAF). They improve heat, mass and momentum transfer in the liquid bath, improve mixing of chemical species and govern the formation of foaming slag in EAF. In this work experimental measurements are performed to determine the dimensions of the cavity formed at the liquid free surface when a gas jet impinges on it as well as liquid velocity vector maps measured in the zone affected by the gas jet. Cavities are measured using a high speed camera while the vector maps are determined using a Particle Image Velocimetry (PIV) technique. Both velocities and cavities are determined as a function of the main process variables: gas flow rate, distance from the nozzle to the free surface and lance angle. Cavity dimensions (depth and diameter) are statistically treated as a function of the process variables and also as a function of the adequate dimensionless numbers that govern these phenomena. It is found that Froude number and Weber number control the depression geometry. INTRODUCTION Oxygen jets are widely used in steelmaking processes. These jets play important roles in controlling chemical reaction kinetics, forming foaming slags, bath mixing and splashing phenomena since they exchange momentum, heat and mass with the steel bath [1,2]. It is difficult to measure these parameters in actual process conditions [3]. However, water physical modeling is a useful tool to perform studies in a laboratory scale at very low cost and safe working conditions[3-7]. The mathematical models are also useful [8-10] for process simulation at low cost. In this work, experimental measurements of the geometry of the cavity formed by the impingement of a gas jet on a water free surface are reported together with velocity profiles of the liquid bath driven by the momentum transfer of the gas jet. EXPERIMENT A cylindrical (height=0.3 m, internal diameter=0.2 m) water model is constructed using transparent acrylic. The model is enclosed in a rectangular tank to reduce image distortion. A cylindrical lance of 0.012 m internal diameter is made of copper and coupled to a cylindrical nozzle. An air compressor and a flow meter are used to regulate the gas flow rate. Measurements of the dimensions of the cavity are made using a high speed camera (HSC) at 500 frames per second with an exposure time of 1/500 s during 2 s. Photographs included a length scale to allow measurement of width and depth of the cavity. These measurements are processed statistically by applying multivariable linear regressions. A PIV system
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