Abstract

In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial process than the typically used water/glycerol–air/helium systems. The experimental activity was carried out in a quasi-2D vessel (144times 144times 12,{hbox {mm}}^{3}) filled with GaInSn, a metal alloy with eutectic at room temperature. Ar was used as the inert gas. The structure and behavior of the gas phase were visualized and quantitatively analyzed by X-ray radiography and high-speed imaging. Computational Fluid Dynamics (CFD) was applied to simulate the multiphase flow in the vessel and the Volume Of Fluid (VOF) model chosen to track the interface using a geometric reconstruction of the interface. Three different vertical lance positions were investigated, applying a gas flow rate of Q_{text {gas}}=6850,{hbox {cm}}^{3}/{hbox {min}}. The CFD model is able to predict the bubble detachment frequency, the average void fraction distributions, and the bubble size and hydrodynamic behavior, demonstrating its applicability to simulate such complex multiphase systems. The use of numerical models also provides a deep insight into fluid dynamics to study particular phenomena such as bubble break-up and free surface oscillations.

Highlights

  • THE downward injection of process gas through a top lance is the main feature of the Top-Submerged-Lance (TSL) smelting reactor

  • A complementary approach is the usage of Computational Fluid Dynamics (CFD), which allows multiphase flows to be studied under conditions where detailed experimental measurements are difficult, if not impossible

  • To simulate the multiphase flow, CFD is used with the Volume Of Fluid (VOF) method to track the interface between Ar and the liquid metal alloy

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Summary

INTRODUCTION

THE downward injection of process gas through a top lance is the main feature of the Top-Submerged-Lance (TSL) smelting reactor. The authors of the present study performed previous numerical investigations on TSL gas injection for non-ferrous applications with the aim of evaluating the effect of viscous and interfacial forces on the multiphase flow.[15] The results showed that important phenomena of the smelting process, such as the gas–liquid interface area, liquid mixing and splashing, strongly depend on the properties of the liquid This means that the usage of lab vessels which are scaled down based on Froude number similarity may not be appropriate for studying TSL flows in non-ferrous systems, because such scaling does not consider the effect of viscosity and surface tension. A CFD model based on the VOF approach is employed and compared with the experimental data, proving the reliability of the numerical approach when dealing with highly turbulent liquid metal bubbly flows and providing a valuable insight into multiphase interaction

THE EXPERIMENTAL SETUP
The VOF Model
Post-processing the Data
Grid Convergence Study
Qualitative Comparison of Bubble Shape and Ascent Behavior
Average Distribution of Void Fraction
Bubble Frequency
Bubble Size Distributions
VBi : p
Velocity Field
Bubble Break-up
Analysis of the Free Surface Motion
SUMMARY AND CONCLUSIONS
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