Dual Plugs Research Articles

Optimizing the Performance of a Dual‐Injection Gas‐Stirred Ladle Using Physical Modeling

Herein, the effects of the angle between nozzles, oil thickness, gas flow ratio, and gas flow rate on mixing time and open eye area in a physical model of a gas‐stirred ladle with dual plugs are studied. The effect of the variables under study is determined using a two‐level factorial design. Particle image velocimetry (PIV) is used to establish, through the analysis of flow patterns, the effect of the studied variables on the hydrodynamics of the system. Results suggest that operating conditions significantly change the flow structure and greatly influence the system's mixing time and open eye area behavior. The Pareto front of the optimized results on mixing time and open eye area is obtained through a multiobjective optimization using a genetic algorithm (NSGA‐II). The results are conclusive in that, for optimal performance, the ladle must be operated using an angle slightly higher than 90° between plugs, a differentiated flow ratio, high oil thickness, and a gas flow rate adjusted according to whether the preference is given to the protection of the bath or to the mixing process.

Inclusion Removements in a Bottom-Stirring Ladle with Novel Slot-Porous Matched Dual Plugs

The cleanness of steel has always been a big problem for secondary refining. In this work, a new method, which is coupled with slot and porous plugs, is proposed to improve the cleanness in steel. Water experiments and numerical simulations were performed to study this effect. Results revealed that when using slot-porous plugs, the flow field was obviously asymmetrical, and the circulation flow was pushed towards the porous side. Then, the removement of inclusions was increased to about 22.7% percent, comparing with traditional two-slot bottom stirring and reducing the dead zone area near the bottom of the ladle; however, the mixing time delay was 16%, comparing with traditional plugs. Then, in order to explain the reason for these phenomena, we established a mathematical model through large eddy simulation and discrete particle modeling (DPM). Results shows that the asymmetry flow field awoke the recirculation flow downwards after using slot-porous plugs, which would homogenize the flow at the bottom, promoting floating in steel. What is more, the velocity near the free surface was lowered; therefore, it could also stabilize the surface velocity as well, which is also beneficial for removing inclusions as well.

Physical and Numerical Modelling on the Mixing Condition in a 50 t Ladle

The bubbly flow and mixing conditions for gas stirring in a 50t ladle were investigated by using physical modelling and mathematical modelling. In the physical modelling, the effect of the porous plugs’ configurations on the tracer homogenization was studied by using a saturated NaCl solution to predict the mixing time and a color dye to show the mixing pattern. In the mathematical modelling, the Euler–Lagrange model and species transport model were used to predict the flow pattern and tracer homogenization, respectively. The results show that, for a ±5% homogenization degree, the mixing time with dual plugs using a radial angle of 180° is shortest. In addition, the mixing time using a radial angle of 135° decreases the most with an increased flow rate. The flow pattern and mixing conditions predicted by mathematical modelling agree well with the result of the physical modelling. For a ±1% homogenization degree, the influence of the tracer’s natural convection on its homogenization pattern cannot be neglected. This is especially true for a ‘soft bubbling’ case using a low gas flow rate. Overall, it is recommended that large radial angles in the range of 135°~180° are chosen for gas stirring in the present study when using dual porous plugs.

Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open‐Eye in Gas‐Stirred Ladles With Single and Dual‐Plugs

In secondary steelmaking, the optimal size and position of open‐eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open‐eye in a gas stirred ladle was investigated. A one‐fifth scale water model of 150‐ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open‐eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5 cm using a gas flow rate of 7.5 NL min−1. The effect of the number of plugs on the open‐eye area for the same range of top layer thickness mentioned above was also studied. The relative open‐eye area generated due to the gas injection through the dual plugs decreased from 49.9 to 5.8%. To study the effect of top layer properties, rapeseed oil, castor oil and paraffin oil were employed for studying the effect of density and dynamic viscosity on the open‐eye formation. The results revealed that a larger open‐eye is formed when the density is increased. Furthermore, it was found out that the density of the upper phase dominates the open‐eye formation while dynamic viscosity has only minor effect. The results obtained from numerical simulations and physical modeling were found to be in good agreement.

Numerical Investigations on the Effect of Gas Flow Rate in the Gas Stirred Ladle with Dual Plugs

Ladle or secondary steelmaking is an essential metallurgy process in which the steel is adjusted to the chemical compositions required in the final product. The objective of this study was to predict 95% mixing time curve using CFD simulation in order to investigate the possibility to optimize the gas flow rate in gas stirred ladle systems. The commercial software, Flow-3D, was used in this study. This study was divided into three parts. The first two parts of the study was the investigation of the effects of bubble sizes and diffusion coefficient on the mixing time by setting constant-volume gas flow rate. The last part was the study of the effect of gas flow rate on the mixing time. The ladle geometry and operation condition from the example steel plant, Millcon Steel PLC were used in this study. The simulation results indicated that different sizes of bubble have minor effects on the mixing time. The investigation of the effect on the mixing time with and without diffusion coefficient showed that the diffusion coefficient has no significant influence on the mixing time but has significant effects on the characteristics of the plume regions and the velocity flow field. Finally, it was found that gas flow rate has significant effects on turbulent kinetic energy, the mixing time and the steel cleanliness. The results can support the example steel plant to optimize the mixing process concerning productivity and cleanliness quality of the liquid steel.

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

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.

Effects of Nozzle Radial Position, Separation Angle, and Gas Flow Partitioning on the Mixing, Eye Area, and Wall Shear Stress in Ladles Fitted with Dual Plugs

Mixing time, slag eye area, and wall shear stress in a ladle fitted with dual plugs have been studied as a function of operating variables, namely, gas flow rate, radial nozzle position, separation angle between nozzles and flow rate partitioning. While the mixing time and slag eye area have been experimentally investigated in a scaled water model (with and without a top slag layer), the shear stress on the vessel wall has been studied computationally via a RANS-based turbulent, three-dimensional coupled Eulerian–Lagrangian (VOF-DPM), multiphase flow model. Experimental and computational results have indicated that the mixing, eye area, and wall shear stress depend on the gas flow rate, i.e., while mixing efficiency increases with the increasing gas flow rate, the slag eye area, and wall shear stress, in contrast, become more pronounced with the increasing gas flow, leading to an undesirable operating regime. The radial nozzle position, separation angle between the nozzles and flow rate partitioning at any given flow rate also influence the ladle process performance, influencing the mixing, eye area, and wall shear stress, albeit to a varied degree. Within the range of operating conditions studied, an expected inverse correspondence between mixing time and shear behavior was observed. Experimental and computational results in conjunction have indicated that the best arrangement of porous plugs or gas injection nozzles for superior ladle process performance is dependent on the gas flow rate and is specific to the desired objective (i.e., decreasing the mixing time, or slag eye area and wall shear stress). Hence, a unique gas injection practice cannot and should not be suggested as the optimum for ladle metallurgy in steelmaking. Nevertheless, if the mixing time is the parameter of primary interest, a nozzle configuration with equal flow partitioning (1:1) between the nozzles and identical nozzle radial positions (0.7R/0.7R, 45 deg) should suffice for both low and high gas flow rates. In contrast, a nonidentical nozzle radial position (0.7R/0.5R, 90 deg) and an unequal gas flow rate per nozzle (1:3) appear preferable if both ladle eye and shear stresses, rather than mixing, are the issues of concern.

A novel dual plugs gas blowing mode for efficient ladle metallurgy

ABSTRACTA novel gas blowing mode with different flowrates for two plugs of metallurgical ladle is explored and studied through a sophisticated water model. The results show that this mode can efficiently decrease the mixing time and the total area of the slag eye for most cases, as compared with the conventional mode with same flowrates for two plugs. Generally, a relatively close angle between the porous plugs and a small radial position are beneficial to a decrease in the mixing time of bath, while a relatively far plug radial position leads to a smaller slag eye. In addition, tracers fed from the middle of the dual plugs are proven to be very beneficial to the mixing of the ladle. The slag layer will prolong the mixing time due to its consumption on the stirring energy compared with the situation without slag.

Modeling of the Effect of the Gas Flow Rate on the Fluid Flow and Open‐Eye Formation in a Water Model of a Steelmaking Ladle

In ladle metallurgy of steelmaking, the role of gas injection into the metal bath is been studied to a great extent as it improves the quality of steel. The size of the open‐eye is associated with higher emulsification of top slag, which intensifies metal–slag reactions, and information about the position and size of the open‐eye is important for effective alloying practice. Moreover, the open‐eye has an effect on the energy balance since it increases heat losses. In this work, experimental measurements and numerical simulations are performed to study the effect gas flow rate on the formation of the open‐eye in a steelmaking ladle. A one‐fifth scale water model is constructed for studying gas injection with single and dual plug configurations. For the numerical modeling, the Multiphase Volume of Fluid (VOF) model is used for simulating the system including the behavior of the slag layer. The physical modeling results show that the open‐eye area changes from 9.22 to 198.34 cm2 when the gas flow rate varies from 0.75 to 15 SLM using a single plug. The effect of the number of plugs on the open‐eye area for the same range of flow rates mentioned above is also studied. The two open‐eye areas generated due to the gas injected through the dual plugs change from 37.59 to 231.1 cm2 when the gas flow rate is increased from 0.75 to 7.5 SLM for each plug in the physical modeling. The numerical simulation results of the open‐eye area are found to be in good agreement with the experimental data obtained from the water model. During the gas stirring process, the slag layer is deformed such that the thickness of the slag becomes thick near to the wall and thin near the slag eye at high gas flow rates. In dual plug system, the two open‐eyes tends to merge and form a huge open‐eye at high flow rates that suits for better alloying purposes. The high‐flow velocity near the surface, which could damage the ladle refractory, tends to be reduced in dual plug system when compared to single plug system.

Parametric study on some combustion characteristics in a natural gas fueled dual plug SI engine

A parametric study on some combustion characteristics was carried out in a natural gas fueled dual plugs SI engine. Mass fraction burned, cylinder pressure histories and combustion durations of the engine were investigated by three equivalence ratio and spark advance for three spark plug configurations. It was found that equivalence ratio and spark plug configurations were more effective parameters on the total combustion duration than spark timing and was concluded that centrally located single plug configuration for equivalence ratio of 1.0 gives best combustion characteristics in compared to the other conditions. In addition, presented study showed that dual plugs serve an alternative for fast combustion in case of geometric constraints to use central location of the plug.

Effect of Gas Blown Modes on Mixing Phenomena in a Bottom Stirring Ladle with Dual Plugs

Effect of Gas Blown Modes on Mixing Phenomena in a Bottom Stirring Ladle with Dual Plugs

Numerical Simulation of Fluid Flow and Interfacial Behavior in Three‐phase Argon‐Stirred Ladles with One Plug and Dual Plugs

AbstractA numerical investigation is performed to describe the quasi‐steady fluid flow and interfacial behavior in a three‐phase argon gas‐stirred ladle with off‐centered bottom Ar injection through a plug and two plugs placed in 180° and 90°configurations, respectively. The flow of the fluid phase is solved in an Eulerian frame of reference together with the motion of every individually injected Ar bubble, tracked in its own Lagrangian frame. Volume of fluid (VOF) model is used to track any interface between two or more immiscible phases, which include slag/metal, slag/gas and metal/gas. The characteristics of fluid flow in a gas‐stirred ladle with one plug or two plugs configuration are described when the slag layer and the top gas are presented. The slag layer deformation and slag open‐eye formation at different Ar gas flow rates for three types of plug arrangements are given. The comparison of the mixing time, the deformation of slag layer and the behavior of slag/steel interface between one‐plug and two‐plug system is made. Several implications for ladle operational issues during a gas‐stirred ladle refining cycle are discussed. It is found that the proper selection of Ar gas flow rate and plug arrangements during a ladle refining cycle is required for different refining purposes considering the mixing and metallurgical reaction in a three‐phase ladle system.

Optimization of mixing time in a ladle with dual plugs

Based on the two-phase fluid (Eulerian-Eulerian) model, a mathematical model about the gas-liquid flow and mixing behavior was developed to investigate the effect of the offset of dual plugs, the included angle of dual plugs with a center point, and gas flow rate on the mixing time in a ladle with dual plugs. Numerical results indicate that two types of recirculation zones exist in the ladle. One is the middle recirculation between gas and liquid plumes, and the other is the sidewall recirculation between plumes and the ladle sidewall. The correction shows that the mixing time is in proportion to −0.2676 power of gas flow rate. There is a unique optimum offset of dual plugs with a particular included angle, in turn, a unique optimum included angle of dual plugs exits with a particular offset.

Improvement in LF Process Through Optimization of Dual Porous Plugs Location in Gas Stirred Ladles

Mathematical and physical simulation of fluid flow had been carried out for a scaled down model of a gas stirred 300 T ladle of Bokaro Steel Plant, Steel Authority of India Ltd. The existing ladle is equipped with two porous plugs located in adjacent quadrant at the bottom of ladle. Comparison of fluid flow and mixing efficiency of the existing arrangement is made with a modified arrangement of porous plugs located diagonally across to each other. Simulation study reveal that the modified arrangement of porous plug leads to improved mixing efficiency in the ladle. Based on the results from the simulations, the operating parameters like argon pressure and flow rate were modified. Plant trials with optimized ladle furnace (LF) operating parameters were carried out in a modified ladle having porous plugs located diagonally across. While the desulphurization efficiency improved, aluminium loss from the melt was reduced by 8.2%. Redistribution of the gas plumes from adjacent quadrant to diagonal quadrant led to uniform wear of refractory walls of the ladle, which led to increase in the lining life of the ladle. Improved mixing of the melt at lower argon pressure and flow rate also led to reduction in hood jamming of the LF.

Modeling of Mixing in Ladles Fitted with Dual Plugs

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 ±1/2R 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 in-house, 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 visa vis experimental measurements is also illustrated in the text.