Effect of Froude Number on Submerged Gas Blowing Characteristics.

Jonas Svantesson,Mikael Ersson,Pär Jönsson

doi:10.3390/ma14030627

Abstract

The flow behavior of gas in compressible and incompressible systems was investigated at an ambient temperature in an air–water system and at an operating process temperature in the IronArc system, using computational fluid dynamics. The simulation results were verified by experiments in the air–water system and established empirical equations to enable reliable predictions of the penetration length. The simulations in the air–water system were found to replicate the experimental behavior using both the incompressible and compressible models, with only small deviations of 7–8%. A lower requirement for the modified Froude number of the gas blowing to produce a jetting behavior was also found. For gas blowing below the required modified Froude number, the results illustrate that the gas will form large pulsating bubbles instead of a steady jet, which causes the empirical equation calculations to severely underpredict the penetration length. The lower modified Froude number limit was also found to be system dependent and to have an approximate value of 300 for the studied IronArc system. For submerged blowing applications, it was found that it is important to ensure sufficiently high modified Froude numbers of the gas blowing. Then, the gas penetration length will remain stable as a jet and it will be possible to predict the values using empirical equations.

Highlights

In metallurgical processes, such as the argon-oxygen decarburization (AOD) converter and ladle furnace, the use of submerged gas nozzles and tuyeres is a major part of the process design
The accuracy of the established empirical equation for gas penetration presented in Equation (7) was studied to see how well it predicts the flows in the IronArc process at high temperature and density ratios, as the empirical equation was not designed for such systems
This study aimed to investigate the gas blowing behavior from a plasma generator in the IronArc process to determine the penetration length of the gas jet and study how it could be simulated using incompressible and compressible simulations in OpenFOAM

Summary

Introduction

In metallurgical processes, such as the argon-oxygen decarburization (AOD) converter and ladle furnace, the use of submerged gas nozzles and tuyeres is a major part of the process design. Nozzles or tuyeres are used to inject gas below the surface of the molten metal to cause reactions and stirring. In other metallurgical processes, such as the electric arc furnace (EAF) and blast furnace, submerged oxy-fuel burners are used with combustible gas to provide heat in local regions. Due to the extreme conditions in the melt, a mechanical stirring by impeller is hard to achieve, as the impeller will quickly wear down from the heat and reactions with the steel. By injecting gas into the melt, the bubbles which form will provide stirring by the drag they produce when rising to the surface [1]

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