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Numerical simulations are performed to explore the basic blowing characteristics of a dynamic free lance converter applied to hot metal dephosphorization technology, in which the sliding mesh model (SMM) is used to regulate the rotation motion of the top lance and the volume of fluid (VOF) model is inducted to simulate flows of gaseous oxygen, liquid slag and metal. The fundamental phenomena such as the motion of phase interfaces, slag–metal emulsion and mixing, and shape and magnitude of the velocity field inside the slag–metal bath are predicted reasonably well, and effects of lance designs including the lance twist angle and rotation speed on the blowing characteristics are evaluated. The results show that the rotation motion of the lance improves the flows inside the molten bath and induces remarkable circumferential and swirl flows around the hot spot. Such flows change the splashing mode and accelerate the dispersion of the splashed metal inside the slag layer, consequently producing a quite uniform distribution of metal phase in emulsion and promoting slag–metal emulsion and mixing. The slag–metal emulsion is strengthened when increasing the lance twist angle, but achieves its minimum at the lance rotation speed of 1.0472 rad/s. The effects of the lance twist angle and rotation speed on flow fields inside the molten bath vary with the bath depth.

The impinging of multiple jets onto the molten bath in the BOF steelmaking process plays a crucial role in reactor performance but is not clearly understood. This paper presents a numerical study of the interaction between the multiple jets and slag–metal bath in a BOF by means of the three-phase volume of fluid model. The validity of the model is first examined by comparing the numerical results with experimental measurement of time-averaged cavity dimensions through a scaled-down water model. The calculated results are in reasonably good agreement with the experimental data. The mathematical model is then used to investigate the primary transport phenomena of the jets-bath interaction inside a 150-ton commercial BOF under steelmaking conditions. The numerical results show that the cavity profile and interface of slag/metal/gas remain unstable as a result of the propagation of surface waves, which, likely as a major factor, governs the generation of metal droplets and their initial spatiotemporal distribution. The total momentum transferred from the jets into the bath is consumed about a half to drive the movement of slag, rather than fully converted as the stirring power for the metal bath. Finally, the effects of operational conditions and fluid properties are quantified. It is shown that compared to viscosity and surface tension of the melts, operating pressure and lance height have a much more significant impact on the slag–metal interface behavior and cavity shape as well as the fluid dynamics in the molten bath.

There are four types of bubble ascent paths: rectilinear, zigzag, spiral, and chaotic, but fewer quantitative studies on the dynamics of bubble spiral motion. In this paper, the spiral path dynamics of a single bubble with an initial diameter of 1.75–3.86 mm in still water is investigated. The bubble position on the spiral trajectory was quantitatively characterized as a function of time using the three-dimensional shadow imaging technique combined with image digitization processing. The additional forces that induce spiral motion were derived using Newton’s second law and subsequently integrated into the Lagrangian framework through Fluent User-Defined Functions (UDFs) to reproduce the spiral trajectory of the single bubble. The simulation results for bubble velocity and trajectory closely matched the experimental data. The forces, accelerations, velocities, trajectories, and swept volumes of the bubbles are discussed. Compared to the rectilinear motion, the swept volumes of the bubbles obtained after considering the spiral paths were increased by 29.5%, 34.4%, 38.2%, 40.6%, and 37.1% for 1.75, 1.83, 1.93, 2.05, and 3.86 mm, respectively. These results will contribute to a better understanding of the dynamic behavior of the bubble spiral motion.

The breakthrough route involving a reduction shaft furnace operated with pure hydrogen gas (here called H2-SF) and the electric arc furnace is widely accepted as one of the most viable future alternatives for industrial-scale production of primary steel with minor CO2 emissions. It has been clarified that the largest portion of the total energy for the entire route is consumed by the H2-SF operation, but this unit has not yet received much attention and should therefore be explored. For this, a mathematical model of a reduction shaft furnace is presented in this paper, where a set of simulations were also performed to shed more light on the operation of the H2-SF equipped with a top gas recycling system. The results show that a high gas feed rate is required for guaranteeing a smooth H2-SF operation due to the strong heat demand. An increase in the feed temperature of the gas or in furnace height can reduce the required gas feed. However, an excessive length may conversely result in an increase in the total energy consumption. The model and its results are expected to be helpful for gaining a better understanding of the complex processes in and constraints of the H2-SF.

This study employs a numerical simulation approach to investigate argon bubble flow behavior within a steel continuous casting mold, with a focus on the impact of bubble swarm correction models. Three scenarios are compared: one without any correction and two incorporating drag coefficient corrections, specifically designed for bubble swarm effects. The results demonstrate that incorporating these correction models significantly improves the predictive accuracy of simulations. In particular, the inclusion of a bubble swarm correction model reduces the error in predicted bubble trajectories by 51.7% and 23.0%, respectively, when measured by Hausdorff distances against experimental trajectory data, compared to the scenario without corrections. These findings underline the importance of selecting an appropriate drag correction model for accurate simulations of bubble dynamics and their interaction with the liquid steel in continuous casting molds. This study highlights that drag correction models tailored to the specific conditions of the continuous casting process are essential for achieving realistic predictions.

The article addresses the particle-induced effect on gas flow by a developed mathematical model simulating the supersonic oxygen–limestone powder mixture jet from a newly designed, freely swinging oxygen lance for dephosphorization in a converter. The model was validated first and then employed to analyze the gas flow dynamics with respect to the jet structure, pressure wave sequence and velocity distribution, and particle motion behaviors over a range of powder particle sizes and mass flowrates. Numerical results reveal that the powder causes significant changes of the oxygen jet structure and weakens the pressure wave sequence outside the nozzle despite the higher gas flow static pressure of the powder-laden oxygen jet than that of the single-phase oxygen jet there. Furthermore, the powder creates nonuniform radial distribution of the gas velocity as an “M-type” curve and greatly restricts the gas jet flowing along the nozzle axis, which results in the smaller gas flow velocity but slower velocity attenuation. These phenomena become increasingly remarkable as the powder particle size is decreased or the powder mass flowrate is increased. The particles are accelerated but the acceleration declines gradually along the nozzle axis. The greater powder mass flowrate or particle size induces the lower particle velocity.

Oxygen-powder injection from a BOF lance has received much attention in attempts to improve refining efficiency, but knowledge of particle-induced erosion to the lance nozzle, as one of the foreseeable concerns in such a process, is still limited. Thus, numerical studies on gas-particle flow through a Laval nozzle were performed to clarify what the nozzle erosion distribution is and how it is influenced by particle motion. The results show that the most serious erosion occurs in the nozzle convergent section, where nozzle erosion can be further intensified by increasing the powder feeding rate or particle size. The powder blowing parameters have a significant influence on the erosion rate and distribution. Increasing the powder feeding rate or decreasing the particle size worsens erosion downstream of the nozzle divergent section. Therefore, in order to reduce erosion, the powder feeding rate and particle size should be smaller than 2.0 kg/s and larger than 10 μm, respectively.

Numerical simulations of a gas-particle jet through a Laval nozzle are performed using a modified point-particle Euler–Lagrange approach. By excluding the particle-occupied fluid fraction when solving the fluid phase equations and accounting for gas-particle and inter-particle interactions in the mathematical framework, the particle motion behaviors in gas stream and their impact on gas stream structure are studied, and the nonequilibrium dynamics of the two-phase flow are revealed by depicting the particle velocity and temperature evolution in gas stream. The results indicate that the preferential concentration of particles occurs in gas stream, resulting in nonuniform jet structure. The preferential concentration mainly occurs in nozzle divergent section and makes the local flows there lie in dense regime even if a dilute two-phase flow is predetermined. The level of the preferential concentration increases when the powder feeding rate or the particle size increases. Thus, it is necessary to consider the volumetric displacement effect of dispersed phase when modelling such a gas-particle jet system. Based on the impact of powder blowing parameters on particles motion and distribution and oxygen jet structure, the powder feeding rate no more than 2.0 kg/s and the particle size of 50 to 100 µm are suggested for real industrial operations.

This paper presents an experimental and theoretical study on the cavity profile induced by the impingement of top-blown multiple gas jets onto a water or oil/water bath. The depth and diameter of the cavity were measured with respect to the lance height, gas flow rate, jets inclination angle, and oil volume. The experimental results show that the cavity depth increases with the increase of gas flow rate or oil thickness but the decrease of lance height or jets inclination angle. The cavity diameter is much less affected by gas flow rate compared to other variables. Then, the importance of the surface tension in the modeling of the cavity was theoretically identified. It was found that in the cratering process, the effect of the liquid surface tension on the cavity depth could be remarkably significant for a basic oxygen furnace (BOF) cold model but negligible for a real BOF steelmaking system. An improved theoretical model was hence proposed and validated using the experimental data obtained from both the single- or two-layer liquid baths. The new model includes not only the explicit consideration of the liquid surface tension but also that of the energy utilization efficiency of the jets impinging kinetic energy contributed to the cratering process.

Gas was injected into the upper part of a water model ladle shroud, producing micro-bubbles by the shearing action of the high-speed entry flow of water, combined with subsequent bubble breaking actions of turbulence. An impact pad was used in favor of a standard turbulence inhibitor, to maintain the integrity of the micro-bubbles, and assure their wide distribution within the tundish. The effects of these two systems on removing small inclusions were investigated, and a numerical model was developed to simulate the motion behaviors of bubbles in the tundish, considering bubble coalescence. Both the turbulence inhibitor and the impact pad performed similar on flow improvement, but the impact pad effectively restrained coalescence between bubbles, leading to a 55.3 pct drop in the average bubble size within the tundish, and generating a 53.9 pct reduction in the residual numbers of inclusions below 51 μm diameter, by contrast with the turbulence inhibitor data. The impact pad fits well with gas bubbling for deep cleaning the liquid steel in tundish.