Modelling Study of Inclusions Removal by Bubble Flotation in the Tundish

Abstract

Non‐metallic inclusion removal from liquid steel in a tundish is studied using two‐phase flow modelling by Particle Image Velocimetry (PIV) techniques and mathematical simulation. The removal efficiency is studied as a function of Flow Control Devices (FCD) arrangements inside the tundish, gas bubbling and mass flow rate. The mathematical two‐phase model includes an Eulerian‐Eulerian approach for the gas‐liquid system and a Lagrange approach for the solid particles trajectories. The validation of this model was acceptably proved through PIV measurements and colour tracer experiments in a two‐phase water model. The removal efficiency of the tundish in the cases of gas bubbling becomes independent of particle size and FCD arrangements. An increase of mass flow rate decreases the particle mean residence time in the tundish and therefore the removal efficiency. Under the same conditions coupling‐uncoupling phenomena of solid particles from the liquid flow depends strongly on their response time. Where this phenomena occurs, it is determined that the particle response time in the model goes from 10−5 to 10−3 seconds for particle size ranging from 20 to 160 μm, respectively; this transition is dependent on particles size and mass flow rate.