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

CARLOS MENDEZ; NORBERTO NIGRO; ALBERTO CARDONA

Applications of Computational Mechanics in Structures and Fluids

CIMNE

Lugar: Barcelona; Año: 2005; p. 237 - 253

From an industrial point of view, knowledge of flow conditions in a metallurgical ladle is of fundamental importance for optimization of refining process. Three different phases coexist in the ladle: two liquid phases, the molten metal and the slag, and a gaseous phase, the argon injected through a nozzle located at the bottom of the ladle. The dispersed gas phase induces a recirculating flow in the metal and generates turbulence in the plume region. 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 conditions in 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 to operating conditions, a water-air scaled physical model is frequently used to simulate the argon and the metal (water and molten steel have similar kinematic viscosity), and the slag is modelled using oil or kerosene. Since there are much more experimental data for water-air models, we start simulating numerically this class of systems. Numerical calculations were made using the commercial code CFX. This program can predict the flow in a turbulent multiphase system and allows us to establish which are the most important physical phenomena that determine the behavior of the main variables in a metallurgical ladle. We analyze which are the governing equations that properly describe the system and present a detailed study of the water-air system. In addition, we simulate the injection of a salt solution, used to determine mixing times, and also show how the principal characteristics of the flow are modified when the free surface and the slag are incorporated into the model. The results obtained compare very well with experimental measurements and this suggests that the effects included in the model are the most relevant in order to suitably represent the ladle for technological purpose.