Development of advanced methods for the control of ladle stirring process

Abstract

The theoretical and industrial aspects of gas stirring of steel in ladles have been considered over the last two decades. Numerical modeling (CFD simulation) and small-scale experiments have been used as tools for studying the process. Physical modeling (water as well as system with Wood metal) has been carried out to investigate the gas-stirred ladle system. Three different groups of modeling studies are reported in the literature: Quasi single-phase, Lagrangian and Eulerian simulation. Simulation involving three phases or gas/steel/slag, has been applied for analyzing the fluid flow, heat transfer, mass transfer and associated phenomena such as chemical reaction and inclusion removal. Development of transient mathematical models, which could simulate the vibrations or periodic oscillations in the ladle, is necessary. Recently, some effort on the dynamic simulation in other metallurgical reactors has been published, such as LES (Large Eddy Simulation) simulation of flows in moulds. Hallberg et al. has described the profile of the free steel surface in the ladle. In this work, a method involving adaptive grid was used to describe the steady profile. Other methods such as scalar methods can also be used for simulations of steel/slag interface. However, simulations of a time dependent transient free surface including slag have not been found. Minion et al. described the first application of measurements of vibrations applied on an electric arc ladle furnace. Two characteristic frequencies were found. Vibrations around 60 Hz were an indication of the stirring intensities while 120 Hz were found to be generated when arc heating was active. Vibrations as an indicator of the onset of ladle slag carry-away into the ladle shroud have also been reported and used. Laser system has an advantage over the accelerometers since it could work without contact.