The modeling of gas-bubble driven circulations systems.

Ilegbusi, Olusegun J.; Szekely, J.

doi:10.2355/isijinternational.30.731

Cited by 47 publications

(31 citation statements)

References 2 publications

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“…1) Mixing is essentially a "convectionϩdiffusion phenomenon" and therefore, elaborate flow calculation is a prerequisite to the modeling of mixing. To this end, a wide variety of computational procedures have so far been applied and these have accordingly resulted in to: quasi single phase, 2,3) Eulerian two phase 4,5) and Eulerian-Lagrangian two phase 6,7) (also known as the discrete phase modeling approach) models respectively. Multiphase flow modeling embodying the VOF (Volume of Fluid) technique has also been applied recently 8) to model flow and mixing in a slag covered ladle.…”

Section: Introductionmentioning

confidence: 99%

“…Multiphase flow modeling embodying the VOF (Volume of Fluid) technique has also been applied recently 8) to model flow and mixing in a slag covered ladle. These [2][3][4][5][6][7][8] as well as a vast majority of the model studies reported in the literature, 1) as one would note here, were primarily restricted to axisymmetrical and/or asymmetrical gas injection configuration in which, a single nozzle/plug located at the base of the vessel was used to supply the gas. As such, not much information on fluid flow and mixing on dual plug/nozzle stirred ladles is available in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of Mixing in Ladles Fitted with Dual Plugs

2005

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A physical and mathematical modeling study has been carried out to investigate mixing in a gas stirred ladle fitted with dual plugs, located diametrically opposite at Ϯ1/2 R positions. While conductivity measurement technique was applied to record 95 % mixing times, mathematical modeling was carried out via the commercial CFD package FLUENT ® wherein, a two phase flow calculation procedure based on discrete phase approach was adapted. It was demonstrated that numerically predicted flow and mixing times in general agree reasonably well with the corresponding experimental measurements.In addition to the above, a relatively simple, quasi single phase flow calculation procedure, developed inhouse, was also applied to predict mixing times and thereby, assess an earlier work. It is shown that the quasi single phase model, despite its simplicity, is reasonably effective in simulating mixing phenomena in such system. A comparison between different modeling approaches vis a vis experimental measurements is also illustrated in the text.KEY WORDS: dual plug stirred ladles; flow; mixing; discrete phase modeling; quasi single phase modeling; experimental measurements; comparison.ladle are reported in the subsequent sections. Present WorkIn the present study, mathematical modeling was carried out adopting two conceptually different approaches namely, the discrete phase and the quasi single phase procedures; the former via the commercial CFD package FLUENT ® and the later via a three dimensional, turbulent flow calculation procedure developed in house. Parallel to these, experiments were carried out on a 0.20 scale water model of a 210 T industrial lade and 95 % mixing times were measured over a wide range of operating conditions (viz., liquid depth, gas flow rate etc.). In this section, a summary of the computational and experimental procedures is presented. ExperimentalMixing times were measured in a cylindrical vessels (I.D.ϭ0.60 m) in which, water was agitated by injecting air or N 2 , in 1 : 1 proportion, through a pair of nozzles located at the bottom of the vessel at the mid bath radius position. Prior to monitoring mixing, air/N 2 was bubbled into the water bath at the desired flow rate for a few minutes to ensure the stability of the flow in the vessel as well as to remove any inhomogeneities present in the bath. The gas flow rates were so chosen to ensure gentle stirring condition as are typically encountered in actual ladle metallurgy steelmaking operations 1) (viz., ϳ0.001 to 0.015 Nm 3 /t · min). While lower end flow rates are typically used for bath homogenization (i.e., of thermal and/or material), relatively large gas flow rates are used to achieve enhanced slag-metal reactions. However, as the primary objective of this study was to ascertain the general adequacy of mixing models, consequently it was deliberately decided to employ only a small fraction of the above mentioned range of gas flow rates, such that some meaningful experimental data, required for validation of the mathematical models can be derived.A ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling of Mixing in Ladles Fitted with Dual Plugs

2005

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“…Therefore, fundamental models are very useful for analyzing the mixing behavior of alloys added to the steel in ladles. [30][31][32][33][34][35][36][37][38][39] The possibilities for studying different ways to add the alloy are virtually unlimited and there are also few limitations in expressing and presenting predicted mixing results. In a recent investigation Jauhiainen et al studied the way in which different porous plug arrangements influence fluid flow and the mixing of alloys into steel in a 110 ton gasstirred production ladle ( Table 2).…”

Section: Alloyingmentioning

confidence: 99%

The Use of Fundamental Process Models in Studying Ladle Refining Operations.

Jönsson

Jonsson

2001

ISIJ International

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Existing fundamental models of ladle refining operations have been reviewed. No fundamental model that takes all the individual parts of ladle refining into account has been found in the open literature. Nor does a model exist which considers all refining in only one part of a refining step such as vacuum treatment. However, separate fundamental models for prediction regarding alloying, temperature, hydrogen, sulfur, reoxidation, and inclusion growth and removal do exist. In one case, a reoxidation model has also been combined with a sulfur-refining model. Predicted values from the separate models for alloying, temperature, sulfur and hydrogen have been found to agree well with corresponding measured data. The verification of the models for reoxidation and the growth and removal of inclusions is currently lacking and separate models for refining operations such as nitrogen or carbon removal need to be developed. Also, more complex models of parts of ladle refining such as vacuum treatment need to be developed, incorporating the sulfur, hydrogen, reoxidation and inclusion growth and removal models. The ultimate goal is, of course, one overall model that can predict desired parameter values for all steps of ladle refining. Even though such a model does not exist today, the usefulness of existing fundamental models is exemplified. This is to illustrate the potential of more complex and more realistic ladle models in process optimization.KEY WORDS: secondary refining; ladle; modeling; fundamental; steel; slag and gas.tration gradient of the element exists at the interface between two phases. This can, for example, be in the steel phase, if the diffusion of the solutes to be removed or added in steel is the rate controling step. Furthermore, it is assumed that the phases on each side of the concentration boundary layer, the steel phase and the refining phase (gas for hydrogen removal and slag for sulfur removal), are steadily and completely mixed. Therefore, the removal rate of an impurity elements from steel can, for example, be described as follows: 5) ................. (1) where x is the element to be refined (i.e. S or H), k is the total mass-transfer coefficient, r is the steel density, M is the steel mass, and [%x] is the actual concentration of the element to be refined. The parameter [%x] e is the hypothetical concentration of the refined element in the steel phase in equilibrium with the actual concentration in the refining phase. "A" is the interfacial area between the steel and the phase to which the element is refined. In the cases of hydrogen refining and sulfur refining, this is the gas phase and slag phase, respectively.One disadvantage with this traditional approach is that due to the assumptions mentioned, more often than not the coefficients in Eq. (1) can only be valid for one specific case at a time. Therefore, this equation tends to be of limited usefulness in prediction for refining processes in general. For example, the interfacial area A, to be used in prediction of desulfurization during gas...

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“…The two standard k-ε turbulence models, employing the concept of isotropic turbulent viscosity, performs well for a wide variety of flows, but for strong swirl flows, the RNG k-ε improves the prediction of turbulence. To simplify the analysis and get a viable solution, early work has focused on the flow patterns induced by injecting gas bubbles [4,5]. Johansen [6] and Hop [7] modeled flow patterns induced by the rotor by means of transport equations for one phase, assuming that purge gas bubbles are introduced into the computational domain as a disperse phase, and monitoring their trajectory using a Lagrange reference frame.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Impeller Design on Degasification Kinetics Using the Impeller Injector Technique Assisted by Mathematical Modeling

Abreú-López

Amaro-Villeda

Acosta-González

et al. 2017

Metals

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A mathematical model was developed to describe the hydrodynamics of a batch reactor for aluminum degassing utilizing the rotor-injector technique. The mathematical model uses the Eulerian algorithm to represent the two-phase system including the simulation of vortex formation at the free surface, and the use of the RNG k-ε model to account for the turbulence in the system. The model was employed to test the performances of three different impeller designs, two of which are available commercially, while the third one is a new design proposed in previous work. The model simulates the hydrodynamics and consequently helps to explain and connect the performances in terms of degassing kinetics and gas consumption found in physical modeling previously reported. Therefore, the model simulates a water physical model. The model reveals that the new impeller design distributes the bubbles more uniformly throughout the ladle, and exhibits a better-agitated bath, since the transfer of momentum to the fluids is better. Gas is evenly distributed with this design because both phases, gas and liquid, are dragged to the bottom of the ladle as a result of the higher pumping effect in comparison to the commercial designs.

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The modeling of gas-bubble driven circulations systems.

Cited by 47 publications

References 2 publications

Modeling of Mixing in Ladles Fitted with Dual Plugs

Modeling of Mixing in Ladles Fitted with Dual Plugs

The Use of Fundamental Process Models in Studying Ladle Refining Operations.

Effect of the Impeller Design on Degasification Kinetics Using the Impeller Injector Technique Assisted by Mathematical Modeling

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