Effect of vacuum on mixing behavior in a ladle - a watermodel study

Abstract

Rising inert gas bubbles in a vacuum ladle experience phenomenal expansion in the top portion of the bath due to the steep variation of absolute pressure. This makes the top layers of the melt substantially more agitated than the bottom regions. The present study is an attempt to characterize the mixing process in such a vacuum ladle by a watermodel, simulating the effect of extra stirring in the top layers of the bath. The simulation is done through a two-level blowing, in which an additional gas stream is injected into the main bubble plume at 75% of the bath height. It was found that mixing under such a simulated condition is worse than that in a bottom purged ladle, for identical total energy inputs to the bath. The study reveals that the energy imparted in the top layers of the liquid in the vacuum ladle is less effective in promoting mixing. The pattern of stirring energy input distribution along the height of the bath is an important parameter in determining the mixing behavior in a ladle, apart from the total energy input.