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

Abstract

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.

Volumetric Flow Field inside a Gas Stirred Cylindrical Water Tank

“…Conversely, for a single injection at 0.1 LPM, a distant area of turbulence is evident, presenting a notable contrast. Observable in both single and double injections, an increase in the gas rate corresponds to a considerable escalation in turbulence, primarily concentrated within the uppermost portion of the flow domain, which is consistent with other studies on the gas-stirred steel-refining ladle [16,23,24]. However, in the case of double injection, the turbulence exhibits greater turbulence strength and is more consistently concentrated throughout as more momentum is added to the flow, compared to single gas injection.…”

Optimizing the Performance of a Dual‐Injection Gas‐Stirred Ladle Using Physical Modeling

“…The reason that mixing is faster in the case of Figure 7 versus Figure 6, which differ only by the gas flow rate values, is that the increase in the flow rate duplicates convection and turbulent dispersion mass transfer mechanisms, allowing for a fast mixing with a high flow rate as demonstrated by Jardon et al [21] The results displayed in Figure 6 and 7 that the availability of instantaneous concentration measured with the PLIF technique together with fluid dynamics obtained with PIV is valuable to better understand the mixing kinetics. In addition, the use of these tools allows both analyzing the performance of physical models of steel ladles in greater depth and identifying any improvements in their operation.…”

“…The reason that mixing is faster in the case of Figure 7 versus Figure 6, which differ only by the gas flow rate values, is that the increase in the flow rate duplicates convection and turbulent dispersion mass transfer mechanisms, allowing for a fast mixing with a high flow rate as demonstrated by Jardon et al [ 21 ]…”

Fluid Flow, Dissolution, and Mixing Phenomena in a Multibottom Tuyere‐Stirred Gas‐Oxygen Refining Furnace

“…Convection was responsible for the dragging of the solute along the flow pattern, while the turbulent diffusion was responsible for the lateral dispersion of tracers, enabling the tracer mixing throughout the entire molten pool. [ 59 ] Therefore, the mixing time was in a negative correlation with the turbulent dissipation rate. The greater the dissipation rate of turbulent kinetic energy, the shorter the mixing time.…”