Mathematical and Physical Modeling of Three-Phase Gas-Stirred Ladles
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Mathematical and Physical Modeling of Three-Phase Gas-Stirred Ladles Juan A. López, Marco A. Ramírez-Argáez, Adrián M. Amaro-Villeda and Carlos González National Autonomous University of Mexico, School of Chemistry, Building D, Circuito de los Institutos s/n, Cd. Universitaria, Del. Coyoacán, C.P. 04510, México D.F., México ABSTRACT A very realistic 1:17 scale physical model of a 140-ton gas-stirred industrial steel ladle was used to evaluate flow patterns measured by Particle Image Velocimetry (PIV), considering a three-phase system (air-water-oil) to simulate the argon-steel-slag system and to quantify the effect of the slag layer on the flow patterns. The flow patterns were evaluated for a single injector located at the center of the ladle bottom with a gas flow rate of 2.85 l/min, with the presence of a slag phase with a thickness of 0.0066 m. The experimental results obtained in this work are in excellent agreement with the trends reported in the literature for these gas-stirred ladles. Additionally, a mathematical model was developed in a 2D gas-stirred ladle considering the three-phase system built in the physical model. The model was based on the Eulerian approach in which the continuity and the Navier Stokes equations are solved for each phase. Therefore, there were three continuity and six Navier-Stokes equations in the system. Additionally, turbulence in the ladle was computed by using the standard k-epsilon turbulent model. The agreement between numerical simulations and experiments was excellent with respect to velocity fields and turbulent structure, which sets the basis for future works on process analysis with the developed mathematical model, since there are only a few three-phase models reported so far in the literature to predict fluid dynamics in gas-stirred steel ladles. INTRODUCTION Independently of the steelmaking route, the most important step defining the quality of the steel is the secondary refining in the Ladle Furnace (LF). In the LF, under reducing conditions, important refining operations such as deoxidation, desulphurization, chemical composition adjustment, homogenization of composition and temperature, and elimination or modification of non-metallic inclusions, are performed. These operations are responsible for the quality of the steel and, therefore, it is important to understand, to control, to optimize and to improve the process. In the LF not only the liquid steel is present; there is also a basic slag layer that protects the steel from the environment, avoiding its re-oxidation as well as heat losses through radiation. The slag also absorbs the oxides and sulfides coming from the deoxidation and desulphurization processes of the steel, among other metal-slag exchanges that take place. In order to accelerate the refining processes, the steel bath is stirred by injecting argon gas through a porous plug located at the bottom of the ladle. Thus, the LF is a very complex three-phase fluid flow system involving momentum, and heat and mass transport phenomena. To study the LF under t
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