Experimental Study of Mass Transfer Mechanisms for Solute Mixing in a Gas-Stirred Ladle Using the Particle Image Velocimetry and Planar Laser-Induced Fluorescence Techniques

Particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) are synergically used to study from first principles the relative importance of the mass transport mechanisms governing the mixing of tracers in a physical model of a gas-stirred ladle. A scaled 1/17th physical model of a 200 ton prototype is used to obtain flow patterns and turbulent kinetic energy maps by PIV, while PLIF provides instantaneous measured concentration fields on a complete plane. Results of both techniques allow computing the convection and the turbulent diffusion instantaneous mass transport fluxes from measured data to analyze comprehensively the ladle mixing. Two single injection modes, i.e., centric and eccentric midradius position, are analyzed and compared; eccentric injection is found to promote better mixing. Convective fluxes are bigger than turbulent diffusion fluxes in both injection modes during mixing. Both mechanisms act cooperatively to promote mixing and turbulent diffusion is key on mixing, although it has a smaller effect than convection. The single loop flow pattern and the bigger and better distributed turbulence result in mass transfer combined fluxes (convective plus turbulent diffusion) twice as optimal in the eccentric injection as in the centric injection, which explains why mixing is faster in eccentric than in centric mode.