Gas-stirred Ladle Research Articles

Mathematical Modeling of the Fluid Hydrodynamics and Refining Effects in a Gas-Stirred Ladle with Pulsed Bottom Blowing

Mathematical Modeling of the Fluid Hydrodynamics and Refining Effects in a Gas-Stirred Ladle with Pulsed Bottom Blowing

Assessment of Measured Mixing Time in a Water Model of Eccentric Gas-Stirred Ladle with a Low Gas Flow Rate: Tendency of Salt Solution Tracer Dispersions

The measurement of mixing time in a water model of soft-stirring steelmaking ladles is practically facing a problem of bad repeatability. This uncertainty severely affects both the understandings of transport phenomenon in ladles and the measurement accuracy. Scaled down by a ratio of 1:4, a water model based on an industrial 260-ton ladle is used. This paper studies the transport process paths and mixing time of salt solution tracers in the water model of eccentric gas-stirred ladles with a low gas flow rate. After a large number of repeated experiments, the different transport paths of the tracer and the error of the mixing time in each transport path are discussed and compared with the numerical simulation results. The results of a large number of repeated experiments on the water model show that there are five transport paths for the tracer in the ladle. The tracer of the first path is mainly transported by the left-side main circulation flow, which is identical to the numerical simulation results. The tracer of the second and third paths are also mainly transported by the left-side circulation flow, but bifurcations occur when the tracer in the middle area is transported downward. In the third path, the portion and intensity of the tracer transferring to the right side from the central region is higher than in the second path. The fourth path is that the tracer is transported downward from the left, middle, and right sides with a similar intensity at the same time. While the tracer in the fifth path is mainly transported on the right side, and the tracer forms a clockwise circulation flow on the right side. The mixing times from the first transport path to the fifth transport path are 158.3 s, 149.7 s, 171.7 s, 134 s and 95.7 s, respectively, among which the third transport path and the fifth transport path are the maximum and minimum values among all transport paths. The error between the mixing time and the averaged mixing time at each monitoring point in the five transport paths of the tracer is between −34.7% and 40.9%. Furthermore, the error of the averaged mixing time of each path and the path-based average value is between 5.5% and 32.6%.

Effect of Salt Solution Tracer Dosage on the Transport and Mixing of Tracer in a Water Model of Asymmetrical Gas-Stirred Ladle with a Moderate Gas Flowrate

In previous research simulating steelmaking ladles using cold water models, the dosage/volume of the salt tracer solution is one of the factors that has been overlooked by researchers to a certain extent. Previous studies have demonstrated that salt tracers may influence the flow and measured mixing time of fluids in water models. Based on a water model scaled down from an industrial 130-ton ladle by a ratio of 1:3, this study investigates the impact of salt tracer dosage on the transport and mixing of tracers in the water model of gas-stirred ladle with a moderate gas flow rate. A preliminary uncertainty analysis of the experimental mixing time is performed, and the standard deviations were found to be less than 15%. It was observed in the experiments that the transport paths of tracers in the ladle can be classified into two trends. A common trend is that the injected salt solution tracer is asymmetrically transported towards the left sidewall of the ladle by the main circulation. In another trend, the injected salt solution tracer is transported both by the main circulation to the left side wall and by downward flow towards the gas column. The downward flow may be accelerated and become a major flow pattern when the tracer volume increases. For the dimensionless concentration curve, the sinusoidal type, which represents a rapid mixing, is observed at the top surface monitoring points, while the parabolic type is observed at the bottom monitoring points. An exception is the monitoring point at the right-side bottom (close to the asymmetric gas nozzle area), where both sinusoidal-type and parabolic-type curves are observed. Regarding the effect of tracer volume on the curve and mixing time, the curves at the top surface monitoring points are less influenced but curves at the bottom monitoring points are noticeably influenced by the tracer volume. A trend of decreasing and then increasing as the tracer volume increases was found at the top surface monitoring points, while the mixing times at the bottom monitoring points decrease with the increase in the tracer volume.

Effect of the injection position on mixing time in a centric gas-stirred ladle water model assisted by a systematic CFD study

Effect of the injection position on mixing time in a centric gas-stirred ladle water model assisted by a systematic CFD study

Investigating Chemical Heterogeneity in Inclusion Populations: A Multivariate Population Balance Model Study in Gas-Stirred Ladles

Investigating Chemical Heterogeneity in Inclusion Populations: A Multivariate Population Balance Model Study in Gas-Stirred Ladles

Numerical Simulation of Bubble Breakup and Coalescence Behavior in Gas-stirred Ladle

Numerical Simulation of Bubble Breakup and Coalescence Behavior in Gas-stirred Ladle

Effects of Entrained Slag Droplets on Slag-Metal Interface in A Gas-Stirred Ladle

This study explores the underlying mechanism between secondary refining efficiency, gas flow rate, and slag properties. The secondary refining efficiency is directly affected by the slag-metal interface area. Traditionally, the slag-metal interface has been limited to the liquid-liquid interface of the ladle cross-section and does not include the interface area between the entrained slag droplets and metal. To investigate the interface area with different slags and metals under various bottom blow rates, a physical model of a single-nozzle gas-stirred ladle was established using oil to simulate slag and water to simulate metal. The roles of relevant variables that affect the volume of entrained oil, the diameter of entrained droplets, and interface area were studied, as well as oil viscosity, interfacial tension, and oil thickness. Experimental data were collected using colorants and image processing techniques. Based on these findings, the increase in gas flow rate and oil layer thickness increased the volume of entrained oil and interface area, while the increase in oil viscosity and interfacial tension decreased these parameters. When the gas flow rate increased, the mean diameter of droplets first increased and then decreased. However, the specific surface area of droplets revealed the opposite trend. Furthermore, the mean diameter and specific surface area increased and decreased with increasing oil-layer thickness.

Two-Way PBM-Euler Model for Gas and Liquid Flow in the Ladle.

Ladle metallurgy is an important steelmaking technology in high-quality steel production. The blowing of argon at the ladle bottom has been applied in ladle metallurgy for several decades. Until now, the issue of breakage and coalescence among bubbles was still far from being solved. In order to have a deep insight into the complex process of fluid flow in the gas-stirred ladle, the Euler-Euler model and population balance model (PBM) are coupled to investigate the complex fluid flow in the gas-stirred ladle. Here, the Euler-Euler model is applied to predict the two-phase flow, and PBM is applied to predict the bubble and size distribution. The coalescence model, which considers turbulent eddy and bubble wake entrainment, is taken into account to determine the evolution of the bubble size. The numerical results show that if the mathematical model ignores the breakage of bubbles, the mathematical model gives the wrong bubble distribution. For bubble coalescence in the ladle, turbulent eddy coalescence is the main mode, and wake entrainment coalescence is the minor mode. Additionally, the number of the bubble-size group is a key parameter for describing the bubble behavior. The size group number 10 is recommended to predict the bubble-size distribution.

CFD modelling of steel desulfurisation in a gas-stirred ladle

ABSTRACT Low sulfur content is crucial in secondary steelmaking to enhance steel quality. The desulfurization rate is influenced by slag-steel interactions, including slag eye size and interfacial mass transfer coefficient. Gas-stirred ladles can impact the interaction through stirring conditions such as argon flow rate and dual plug separation angle. Using a 3D CFD simulation model, the effects of different stirring conditions on the desulfurization rates, molten steel flow, and slag-steel interfacial behaviors were investigated. Results showed that 180° separation angle leads to higher desulfurization efficiency than 90°. A higher argon gas flow rate increases desulfurization rate, and using 20 SCFM (8.92×10-3 Nm3/s) argon flow rate for both plugs resulted in higher desulfurization rate than using 5 SCFM (2.23×10-3 Nm3/s) for one plug and 20 SCFM for the other. The smallest desulfurization efficiency was observed when using 5 SCFM for both plugs.

Investigation of gas purging configuration in an industrial ladle by computational fluid dynamics

A three-dimensional model was developed to investigate the effects of gas nozzle configuration in an industrial gas-stirred ladle on flow pattern, mixing time, heat transfer, inclusion removal, and shear stress on the wall. Population balance model coupled with computational fluid dynamics was chosen to evaluate the inclusion removal. The properties of phases and the size distribution of inclusion were in agreement with literature data. Gas nozzle locations were investigated in terms of radius and angle. It was found that an increase in angle and decrease in radius of gas nozzle location decreased shear stress on the wall. Also, as gas nozzle locations got closer to each other, bubble plumes overlapped, and turbulent kinetics was affected. This in turn affected temperature, mixing time, and inclusion removal. Therefore, by changing angle and radius, these parameters did not have similar trends. From the performed investigations, it was found that the best gas injection location was angle of 140° and radius of 0.65R. Shear stress, mixing time and inclusion removal at ladle with the plug radius of 0.65R were improved by 38.7%, 1.3%, and 0.87%, respectively. In addition, at ladle with the plug angle of 140°, shear stress, mixing time, and inclusion removal were increased by 6%, −6.57%, and 8%, respectively. By choosing this gas injection location, ladle performance was optimum in all parameters.

Large Bubble-Resolved Direct Numerical Simulation for Multiphase Flow Applied to Gas-Stirred Ladles: Grid Resolution and Plug Eccentricity Effects

Large Bubble-Resolved Direct Numerical Simulation for Multiphase Flow Applied to Gas-Stirred Ladles: Grid Resolution and Plug Eccentricity Effects

Fluid Flow and Mixing Phenomena in Mechanically Agitated and Gas Stirred Ladle Systems and Their Comparisons

Fluid Flow and Mixing Phenomena in Mechanically Agitated and Gas Stirred Ladle Systems and Their Comparisons

Computational Fluid Dynamics Study of Gas Stirred Ladle Used in the Secondary Metallurgy

The computational fluid dynamics study was developed for simulate the behavior of gas stirred ladle. In this paper, the injection of air in water was simulated, in a scale model of 1/7 of an industrial 35 ton steel ladle with a porous plug located eccentric 2/3 of the radius in order to increase the mixing process and eliminating the dead zones. For the analysis the model the multiphase Eulerian three-dimensional was used. The numerical models has been applied and compared with experiments to investigate their differences and theirs potentials of predicting the flow in gas stirred ladle 3D, transient with turbulence using standard k-epsilon in the finite volume method of the commercial program FLUENT™ 6.3.

Effect of Build-ups on Ladle Wall on Acoustic Signals in Gas-Stirred Ladles

Effect of Build-ups on Ladle Wall on Acoustic Signals in Gas-Stirred Ladles

3D numerical investigation of effects of density and surface tension on mixing time in bottom-blown gas-stirred ladles

In molten phase metallurgical processes, mixing via gas injection has a vital role in obtaining a homogeneous product. The efficiency of mixing depends on operational variables such as gas flow rate and slag height as well as physical properties of the molten phases. A numerical simulation is conducted to study the above parameters in the flow behavior of a bottom-blown bath. The molten metal and the slag are modeled by water and oil, respectively. The numerical results, particularly the mixing time, are validated against experimental data. The results show that mixing time increases as the slag height increases and decreases as the density of the slag material increases. The mixing time decreases with an increase in the density of the primary phase; however, it increases as the surface tension between air and water increases. A case with properties close to a real molten metal is also modeled. The performance of the system is influenced by the momentum rather than the dissipative forces. Thus, the effect of the density of the molten phase on the mixing process is more pronounced compared to the effect of the surface tension between the air and the molten phase.

Computational Investigation of Inclusion Removal in the Steel-Refining Ladle Process

In a steel-refining ladle, the properties of manufactured steel can be notably degraded due to the presence of excessive inclusions. Stirring via gas injection through a porous plug is often used as part of the steel-refining process to reduce these inclusions. In this paper, 3D computational fluid dynamics (CFD) modeling is used to analyze transient multiphase flow and inclusion removal in a gas-stirred ladle. The effects of gas stirring with bubble-inclusion interaction are analyzed using the Euler–Euler approach for multiphase flow modeling, while the effects of inclusions aggregation and removal are modeled via a population balance model (PBM).

Influence of Argon Gas Flow Parameters in the Slot Plug on the Flow Behavior of Molten Steel in a Gas-Stirred Ladle

Influence of Argon Gas Flow Parameters in the Slot Plug on the Flow Behavior of Molten Steel in a Gas-Stirred Ladle

Interface-Resolved Simulation of Bubbles–Metal–Slag Multiphase System in a Gas-Stirred Ladle

A grid-filtered scale interface-resolved volume of fluid (VoF) model coupling a sub-grid scale large eddy simulation (LES) was used to directly simulate bubble behavior and the evolution of multiphase interfaces and free surfaces in a bubble–metal–slag multiphase system. The model has been applied to an industrial 150-ton gas-stirred ladle. The results show transient behavior of the slag eye, with large variations over time of the eye size. Bubble detachment frequency and rise characteristics (including coalescence and breakup) directly affect the size, position and variation of the slag eye. The effects of the argon flow rate, slag thickness, slag viscosity, and slag–steel interfacial energy were investigated; the latter two have little effect. The calculated average slag eye size agrees with previously reported results for industrial ladles. A new correlation for the time-averaged slag eye area, based on the modified Froude number, is proposed for industrial ladles.

Effect of Side Blowing on Fluid Flow and Mixing Phenomenon in Gas-Stirred Ladle

To investigate the gas agitation characteristics of side blowing, the fluid flow and mixing phenomenon in a 1:3 scale model ladle of a 150 t industrial gas-stirred ladle with bottom and side plugs were studied by using physical and numerical modelings together. Side blowing enhanced the horizontal flow of water in the model ladle. Compared with bottom blowing, side blowing that is close to the ladle bottom with more than two plugs increases the average velocity of water, which represents the agitation power, improves the uniformity of water velocity distribution, reduces the stagnant region rate, and shortens the mixing time. The mixing time of dual bottom plugs is almost 1.5 times of that of four side plugs at 116 mm under the same flow rate. The mixing time is not only influenced by the agitation power but also by the uniformity of water velocity distribution. Although the agitation power of four side plugs at 450 mm under the flow rate of 1.8 m3/h is about 1.5 times of that at 116 mm with 0.6 m3/h. The mixing time of the 1.8 m3/h flow rate is about 1.2 times of that of the 0.6 m3/h because of the different water velocity distributions.

On the turbulence modelling of bubble plumes

Proper turbulence modelling of bubble plumes is critical for accurate simulation of liquid phase and bubble dynamics. The k-epsilon turbulence model is widely used. However, the model is unsatisfactory due to not accounting for the following physics: (1) turbulence damping in the vicinity of a free surface; (2) turbulence modifications created by non-uniform distribution of the bubbles; (3) extra turbulence agitation by bubble wakes. In order to remedy these deficiencies, an enhanced turbulence model has been developed, followed with application to a literature experiment of a gas-stirred ladle. The model framework is an Eulerian-Lagrangian large scale interface-capturing computational fluid dynamics (CFD) approach, coupling a volume-of-fluid model with discrete phase model. The implications of each physical process in turbulence modelling are investigated. The detailed model-experiment comparisons indicate that the enhanced turbulence model allows improved representation of the physics of bubble plumes, as well as the transport phenomena at, and close to, the free surface.