Numerical Study of a Three-Phase System: A Metallurgical Ladle

Abstract

From an industrial point of view, knowledge of flow conditions in a metallurgi-cal ladle is of fundamental importance for optimization of refining process. Three differentphases coexist in the ladle: two liquid phases, the molten metal and the slag, and a gaseousphase, the argon injected through a nozzle located at the bottom of the ladle. The dispersedgas phase induces a recirculating flow in the metal and generates turbulence in the plumeregion. As a consequence of buoyancy, the slag has a tendency to stratify above the metal,but there is also entrainment caused by the metal flow. Understanding flow conditionsin the slag region will help in the comprehension of various phenomena such as mixing,slag emulsification, and chemical reactions between phases. To avoid difficulties due tooperating conditions, a water-air scaled physical model is frequently used to simulate theargon and the metal (water and molten steel have similar kinematic viscosity), and theslag is modelled using oil or kerosene. Since there are much more experimental data forwater-air models, we start simulating numerically this class of systems. In particular,we analyzed the experimental data obtained by Castillejos and Brimacombe*. Numericalcalculations were made using the commercial code CFX. This program can predict the flowin a turbulent multiphase system and allows us to establish which are the most importantphysical phenomena that determine the behavior of the main variables in a metallurgicalladle. We analyze which are the governing equations that properly describe the system andpresent a detailed study of the water-air system. In addition, we show how the principalcharacteristics of the flow are modified when the free surface and the slag are incorporatedinto the model. The results obtained compare very well with experimental measurementsand this suggests that the effects included in the model are the most relevant in order tosuitably represent the ladle for technological purpose.* A. H. Castillejos and J. K. Brimacombe, Metall. Trans., 18B, 659 (1987).