Effect of Differentiated Injection Ratio, Gas Flow Rate, and Slag Thickness on Mixing Time and Open Eye Area in Gas-Stirred Ladle Assisted by Physical Modeling

Luis E Jardón-Pérez,Marco A Ramírez-Argáez,Daniel R González-Morales,Gerardo Trápaga,Carlos González-Rivera

doi:10.3390/met9050555

Abstract

In this work, the effects of equal (50%/50%) or differentiated (75%/25%) gas flow ratio, gas flow rate, and slag thickness on mixing time and open eye area were studied in a physical model of a gas stirred ladle with dual plugs separated by an angle of 180°. The effect of the variables under study was determined using a two-level factorial design. Particle image velocimetry (PIV) was used to establish, through the analysis of the flow patterns and turbulence kinetic energy contours, the effect of the studied variables on the hydrodynamics of the system. Results revealed that differentiated injection ratio significantly changes the flow structure and greatly influences the behavior of the system regarding mixing time and open eye area. The Pareto front of the optimized results on both mixing time and open eye area was obtained through a multi-objective optimization using a genetic algorithm (NSGA-II). The results are conclusive in that the ladle must be operated using differentiated flow ratio for optimal performance.

Highlights

The ladle furnace plays a key role in the production of high-quality steel, because in this reactor several processes are carried out, such as desulfurization, deoxidation, chemical and temperature control, and elimination or modification of inclusions [1]
The prototype, an industrial ladle furnace operating at Qfs gas flow rate, was scaled through Equation (1) proposed by Mazumdar et al [22] to the gas flow rate in a physical model (Qmod ) with a geometric scale factor λ = 1/17 to meet the dynamic similarity in a gas stirred ladle where agitation is dominated by the modified Froude number
The gas flow rates for the physical model were between 1.54 and 2.22 L/min and in practice these were set with a couple of Cole Palmer flow meters

Summary

Introduction

The ladle furnace plays a key role in the production of high-quality steel, because in this reactor several processes are carried out, such as desulfurization, deoxidation, chemical and temperature control, and elimination or modification of inclusions [1]. Most of the ladle objectives can be improved by achieving an efficient mixing of the liquid, and mixing time has been used extensively as an efficiency criterion of the process. There has been a great interest to understand the effect of different process parameters on the mixing time in ladles, [2,3,4] including the gas flow rate, the number of plugs, the radial and angular position of the plugs in systems with multiple gas injection points, the presence or absence of slag, the thickness of the slag layer, and the diameter of the plugs, among other variables. The gas flow rate is by far the variable affecting the most the mixing time and it is well known that the larger the gas flow rate the shorter is the mixing time obtained in ladles. Regarding the number of plugs and their positions, Conejo et al [5] reported the best mixing conditions with one plug located at 2/3 R, whereas González-Bernal et al [6] reported the best injection point with one nozzle located at 3/4 R.

Methods

Results

Conclusion