Top Lance Research Articles

Evaluating the Efficiency of Using Coherent-Type Nozzles for the Conditions of Additional Postcombustion of CO to CO2 in the Wor king Space of the Oxygen Converter

Introduction. The requirements for the working conditions of metallurgical industry have been becoming stricter, both in terms of increasing the process indicators and in terms of environmental friendliness of processes.Problem Statement. The main controlling factor of the oxygen-converter process is the oxygen jet supplied through the nozzles of the top lance. The main task of the process is the active mixing for refi ning and the provision of conditions for the postcombustion of CO to СО2 in off -gases to additionally increase the heat content of the bath in order to enable increasing scrap processing, which improves the environmental friendliness of the process. In electrometallurgy, to solve the problem of deep mixing, it has been proposed to use nozzles of the coherent type (like a cylinder in a cylinder, through which oxidizing and protective gases are supplied).Purpose. To study and to establish the features of using nozzles of the coherent type for the conditions of top oxygen purging in the converter.Materials and Methods. Samples of laboratory nozzles of the coherent type, which diff er in the ratio of the central and peripheral parts (75, 50, 25%) with respect to the force of the jet, have been studied with the use of a modifi ed liquid manometer; by two-phase cold modeling; by evaluating the degree of afterburning of CO-containing gases in comparison with the performance parameters of an equivalent cylindrical nozzle.Results. It has been established that the force with which the jet fl owing out of the nozzle acts on the liquid is signifi cantly less when that in the case of coherent type nozzles and decreases as the share of the peripheral part of the nozzle increases. According to the results of two-phase cold modeling, it has been noted that the use of coherent type nozzles contributes to the active formation of a foamed emulsion and increases the activity of mixing two-phase liquids during top blowing. The use of the coherent-type nozzles with a peripheral part of 75% increases the postcombustion of CO-containing gases by 42.36%.Conclusions. According to the obtained results, it is possible to recommend the use of nozzles of the coherent type to replace the cylindrical nozzles of oxygen lances, which perform the function of additional sources of infl uence on the bath and for the oxidation of CO in the waste gases.

Numerical Analysis of Postcombustion Effects on the Supersonic Jet Behavior

During the top blowing process of the basic oxygen furnace, the oxygen jet may react with CO before it reaches the surface of the molten bath. This combustion reaction affects the dynamic characteristics of the jet, which, in turn, affects its interaction with the bath. In this study, a numerical model is developed to investigate the transient and steady combustion characteristics of the supersonic jet emitted from the top lance. The transient combustion simulation shows that the CO ratio gradually decreases while the CO2 mole fraction increases at the interaction boundary region between jet and ambient due to the chemical reactions. In addition, the jet profile is changed when the postcombustion is introduced. Due to the flame formation and turbulence change at the jet combustion interface, the axial velocity at height of 2 m (x = 73 re) is 89% higher than that of the noncombustion reaction jet flow. In the results, it is demonstrated that the combustion interface is favorable to reduce the jet decay, resulting a higher dynamic pressure before the jet reaches the bath surface. Furthermore, a higher core temperature and lower density are obtained for the combustion jet compared to that of without combustion reaction.

Effect of the Jet from Top Lance on Slag Foaming Behavior in Basic Oxygen Furnace process

Effect of the Jet from Top Lance on Slag Foaming Behavior in Basic Oxygen Furnace process

Numerical study of post-combustion characteristic in a smelting reduction furnace

Abstract For a smelting reduction furnace, the main role of the post-combustion operation in the upper space is to supply the energy required by the endothermic reduction reaction of iron oxide occurring in the melt bath, and thus the post-combustion behavior is important in the respect of reducing the coal consumption. In this paper, based on a developed 3D model composed of the Realizable k–ε model and DO radiation model, the post-combustion characteristics in a smelting reduction furnace was studied by numerical simulation, and the effects of top lance height, top-blown hot air flowrate and nozzle inclination angle of top lance on the flow and temperature fields, CO content distribution in the upper space were investigated. The results show that with the increase of top lance height, the length and temperature of combustion flame in the upper space increase, which is beneficial to expanding the post-combustion zone and improving the post-combustion of CO gas. And as the top-blown hot air flowrate increases, the position of the maximum temperature in the upper space gradually moves down and the CO content in gas mixtures decreases, which is conducive to the heat transport back to the melt bath. In addition, a proper velocity and temperature distribution in the upper space and distribution of CO content is obtained under the nozzle inclination angle range from 10° to 15°, but a larger nozzle inclination angle reduces the velocity and temperature in the central zone.

Antimony recovery from antimony-rich slag by top blowing nitrogen into the molten slag bath

We study the evaporation of antimony trioxide from an antimony-rich slag by bubbling nitrogen gas through a submerged top lance at 1000–1300 °C. Experiments are carried out with 300 g slag at gas flow rates of 20–60 l/h with the lance height of 1.5 and 10 mm. Slag samples are taken and analyzed to identify changes in the antimony trioxide content during the evaporation. By fitting the antimony trioxide content evolution of the slag to the calculation according to the integrated rate law, the antimony trioxide evaporation under the present conditions is found to be a second-order reaction. The evaporation rate constants and Sb recovery are enhanced with increasing temperature and gas flow rate and decreasing lance height. The deposited antimony trioxide product is characterized to determine its impurity level and microstructure. The rate-limiting step of the antimony trioxide evaporation is discussed, and the residual slag is analyzed to understand the antimony trioxide evaporation limits.

Information-modeling forecasting system for thermal mode of top converter lance

On basis of mathematical modeling and object-oriented programming, a computer information-modeling forecasting system (IMFS) for thermal mode of top lance barrel (TLB) of oxygen converter was developed in order to fulfill the urgent and economically feasible task of determining the compliance of input technological parameters with certain safety criteria for conducting converter melting.The program was created in the form of a Windows-oriented application by refining the previously developed mathematical model of the temperature mode of the top converter lance barrel using the object-oriented programming language C# in Microsoft Visual Studio 2019 IDE. The mathematical model provides the solution of differential heat conduction equation in cylindrical coordinates (two-dimensional formulation) with assignment of the initial (temperature distribution in the computational domain) and boundary conditions of the II and III kind (respectively, on the outer and inner surfaces of the TLB). The finite-difference approximation of the heat conduction equation and boundary conditions was obtained by the integro-interpolation method (balance method). A numerical sweep method (modified Gauss method) and an unconditionally stable implicit scheme were used to calculate the temperature field. Thermophysical values were obtained by approximating the corresponding tabular values. The application does not put forward special requirements for the computer infrastructure, operates locally (without the need for access to Internet), does not require special skills to work with it, having an intuitive user interface: the working area of the program consists of three windows (sections), in which the results of calculating the thermal mode of the TLB are displayed. The developed IMFS allows evaluating the design and technological parameters of the top blowing device as a criterion for its safe operation. Its application in the “advisor” mode ensures the optimal design of the top oxygen lances with a rational water cooling system in order to ensure the proper thermal mode of the TLB throughout the entire operation period, as well as trouble-free operation of the blowing device, which is especially important for the conditions of converter shops in Ukraine equipped with outdated designs of top lances with low service life.

Аналітичне дослідження характеристик струменів, що витікають із сопел складеного типу

The urgent task for oxygen converter process is the improvement of environmental indicators due to the reduction of emissions of carbon oxides into the atmosphere. It is possible due to the reduction of iron consumption and the increase of the possibility of processing scrap metal. For this, it is necessary to increase the heat content of the bath that is possible due to the use of top lances equipped with special nozzles. The article presents the results of research and analysis of the use of composite nozzles of the coherent type for this purpose. Such nozzles are the nozzles for supplying oxygen, consisting of a central nozzle and an annular peripheral nozzle surrounding it. Conducted physical and analytical studies of the features of the outflow of gas jets from compound nozzles of a coherent type of different designs (with the size of the peripheral part from 0.07 to 0.47 calibers of the central nozzle) under the conditions of 2M blowing made it possible to establish that the compound design under certain conditions can add additional obstacles and limitations of the development of the central jet (with a width of the peripheral part of 0.07 - 0.17 calibers), or to provide additional impulse with a larger width of the peripheral part. This is connected with the peculiarities of the formation of the jet in the initial area of development. Therefore, it is necessary to take into account the geometric arrangement of the central and peripheral parts relative to each other to obtain the required result of forming a complex jet with specified properties. According to the results of an analytical study of the dependence of the weight of the jet flowing out of composite nozzles of the coherent type, a mathematical expression was established for calculating the energy consumption coefficient of the jet when passing through the nozzle and an expression for calculating the weight of the jet as a necessary indicator of the momentum responsible for its power and penetrating properties. Use of established expressions make it is possible to predict the characteristics of the studied composite nozzle of the coherent type based on its geometric design and pressure indicators.

CFD Investigations of Bath Dynamics in a Pilot-Scale TSL Furnace

The hydrodynamics of a Top Submerged Lance (TSL) slag bath are investigated here by means of Computational Fluid Dynamics (CFD) simulation. The object of the study is the pilot-scale furnace located at TU Bergakademie Freiberg, where air is injected beneath the slag bath with a top lance. The fluid dynamics system is evaluated at operating conditions, with experimentally measured slag physical properties and real flow rates. The numerical approach is based on the Volume Of Fluid (VOF) model, a front-tracking method that allows the interface to be geometrically reconstructed. Using a fine computational grid, the multiphase interactions are calculated with a high level of detail, revealing the mechanisms of bubble formation and bath dynamics. Two lance configurations are compared, with and without a swirler, and the effect on the hydrodynamics is discussed with regards to key features of the process, such as bubble dynamics, slag splashing, the interface area, rotational sloshing, and bath mixing. The model predicts bubble frequencies in the range of 2.5 to 3 Hz and captures rotational sloshing waves with half the frequencies of the bubble detachment. These results agree with real furnace data from the literature, proving the reliability of the computing model and adding value to the empirical understanding of the process, thanks to the direct observation of the resolved multiphase flow features. The comparative study indicates that the air swirler has an overall positive effect in addition to the proposed enhancement of lance cooling, with an increase in the bath mixing and a reduction in the splashing.

A Numerical Study on Blowing Characteristics of a Dynamic Free Oxygen Lance Converter for Hot Metal Dephosphorization Technology Using a Coupled VOF-SMM Method

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.

Visualization of Intermittent Splash with Gas Blowing from a Top Lance – Breakup of Cavity Surface Causing Intermittent Splash –

Visualization of Intermittent Splash with Gas Blowing from a Top Lance – Breakup of Cavity Surface Causing Intermittent Splash –

Toward the Bath Flow Interaction of a 250 t Combined Top and Bottom Blowing Converter Based on a Mathematical Modeling

Herein, the fluid mechanical aspects involving flow interactions between flows formed by the top impinging jet and bottom blowing bubbles in a combined blowing converter bath are focused on. The effects of different operation conditions on the flow field and the kinetic energy of the bath are investigated to examine different roles of the blowing operations with the help of numerical model. It is found that the stirring intensity in the region near the bath wall is decreased even though the flow is more active in the vicinity of the impact cavity when the top lance declines. For the combined blowing converter, the bottom blowing plumes normally dominate the bath flow. However, the bath stirring intensity is increased slightly when the bottom blowing flowrate is higher than a critical value (0.08 Nm3 min−1 t−1). In addition, the results of energy dissipation demonstrate that higher flowrate of bottom blowing causes more intensive interaction between flows formed by the top and the bottom blowing, which, in turn, causes more energy dissipation.

Prediction of Plunging Depth Induced by Top Lance Gas Blowing onto a Low-melting-point Metal Bath

Prediction of Plunging Depth Induced by Top Lance Gas Blowing onto a Low-melting-point Metal Bath

Prediction of Plunging Depth Induced by Top Lance Gas Blowing onto a Low-melting-point Metal Bath

Prediction of Plunging Depth Induced by Top Lance Gas Blowing onto a Low-melting-point Metal Bath

A Mathematical Model for Reactions During Top-Blowing in the AOD Process: Validation and Results

In earlier work, a fundamental mathematical model was proposed for side-blowing operation in the argon oxygen decarburization (AOD) process. In the preceding part “Derivation of the Model,” a new mathematical model was proposed for reactions during top-blowing in the AOD process. In this model it was assumed that reactions occur simultaneously at the surface of the cavity caused by the gas jet and at the surface of the metal droplets ejected from the metal bath. This paper presents validation and preliminary results with twelve industrial heats. In the studied heats, the last combined-blowing stage was altered so that oxygen was introduced from the top lance only. Four heats were conducted using an oxygen–nitrogen mixture (1:1), while eight heats were conducted with pure oxygen. Simultaneously, nitrogen or argon gas was blown via tuyeres in order to provide mixing that is comparable to regular practice. The measured carbon content varied from 0.4 to 0.5 wt pct before the studied stage to 0.1 to 0.2 wt pct after the studied stage. The results suggest that the model is capable of predicting changes in metal bath composition and temperature with a reasonably high degree of accuracy. The calculations indicate that the top slag may supply oxygen for decarburization during top-blowing. Furthermore, it is postulated that the metal droplets generated by the shear stress of top-blowing create a large mass exchange area, which plays an important role in enabling the high decarburization rates observed during top-blowing in the AOD process. The overall rate of decarburization attributable to top-blowing in the last combined-blowing stage was found to be limited by the mass transfer of dissolved carbon.

Physical simulation of converter steelmaking with powder injection

A water model of top and bottom blown converter with top lance powder injection and bottom tuyere powder injection was established to investigate the powder injection. The results show that the powder penetration ratio under the condition of top lance injection is greater than that under the condition of bottom tuyere powder injection. In both cases, the powder penetration ratio increases with the increase of solid/gas ratio and powder particle size. Powder uniform dispersion time with top lance powder injection is longer than that with bottom tuyere powder injection. Top lance powder injection, lance height of 258 mm, bottom blowing rate of 1·96 Nm3 h−1 and powder particle size of 0·212–0·380 mm are suggested as the optimum powder injection operation under the experimental condition. The corresponding optimum operation for prototype is top lance powder injection with lance height of 1550 mm, powder size of 1–5 mm and bottom blowing rate of 450 Nm3 h−1.

Numerical Simulations of the Kinetic Energy Transfer in the Bath of a BOF Converter

The paper focuses on the fundamental aspects of the kinetic energy transfer from a top and bottom gas injection to the bath of the basic oxygen furnace (BOF) by applying a mathematical model. The analyses revealed that the energy transfer is less efficient when top lance height is lowered or the flowrate is increased in the top blowing operations. However, an inverse trend was found that the kinetic energy transfer is increased when the bottom flowrate is increased for the current bottom blowing operation conditions. The kinetic energy transfer index results indicated that the energy transfer for the bottom blowing is much more efficient than that of the top blowing operations. To understand the effects of the upper buoyant phase on the energy dissipation of the bulk liquid in the bath, different mass and physical properties of slag and foam were considered in the bottom blowing simulations. The slag on top of the bath is found to dissipate by 6.6, 9.4, and 11.2 pct for slag mass values of 5, 9, and 15 t compared to the case without slag atop the surface of the bath, respectively. The results showed that the kinetic energy transfer is not largely influenced by the viscosity of the upper slag or the foaming phases.

CFD Modeling of a Supersonic Top Blown Lance in a CAS-OB Process: Development of Gas Heat and Mass Transfer Correlation

While many metallurgical processes involve the use of top lances, little is known about the heat and mass transfer coefficients of such instruments due to difficulties in measurement procedures. This paper presents a new gas heat and mass transfer coefficient model which can be implemented as part of a CAS-OB process model. We begin by testing several turbulence models against the data provided in the literature, in order to identify a model suitable for the supersonic jet CFD model. We then further test the resulting modeling setup using jet impingement measurement data. Following the successful validation of this CFD setup, we use the setup to simulate several cases of real lance conditions under a CAS-OB bell refractory. Based on these simulations, we calculate the overall heat and mass transfer coefficients and develop heat and mass transfer correlations for a CAS-OB lance.

Comparative Studies of Silicon Dissolution in Molten Aluminum Under Different Flow Conditions, Part I: Single-Phase Flow

Following on a study of Si dissolution in molten Al, the effect of gas agitation is examined. The effects of gas flow rate, liquid bulk velocity, the position of a top injection lance, and bath temperature on the dissolution rate are quantified. A higher gas flow rate produced larger bubbles while bubble frequency remained relatively unchanged. This resulted in larger bubble-induced fluctuating velocities which in turn increased the dissolution rate. At lower bulk velocities, the effect of gas agitation is localized around the lance. By increasing the velocity, the effect of gas agitation is transported further into the bath. The dissolution rate enhancement varies with increasing bulk velocity, and explanations are provided. When combined with a bulk flow, gas agitation increases the dissolution rate regardless of lance position. Also, the enhancement of dissolution rate due to gas injection decreases at higher superheats, as the higher bath temperature increases the mass boundary thickness. In addition, the dissolution rate without gas agitation (single-phase flow) and with gas agitation (two-phase flow) is compared in terms of mean mass transfer coefficients. It was found that for the same liquid bulk velocities, the mean mass transfer coefficients are higher in two-phase flow than in single-phase flow. Finally, an increment to the single-phase flow bulk velocity that would be required to gain parity with the two-phase flow dissolution rate rise is demonstrated.

Improvement of the decarburization rate in austenitic stainless steelmaking

In order to enhance the decarburization rate at low carbon content region during the decarburization of molten stainless steel in argan oxygen decarburization, inert gas was blown into top slag and molten steel through a top lance. The carbon content at the end point of the decarburization process was found to reach lower values than conventional levels without the inert gas top blowing. The decarburization rate might be improved, probably due to the disturbance of the slag/metal interface and the dilution of CO gas. The influence of slag in decarburization step on the decarburization and the reduction reactions of chrome oxides in the slag were also experimentally and theoretically investigated by establishing a kinetic model of the decarburization of molten stainless steel under the existence of slag containing chrome oxide. The liquid fraction of the slag appears to be essential for a more effective decarburization reaction. Countermeasures were also proposed to prevent carbon pickup from burnt lime for better slag control.

Simulation and Application of Top Lance with Various Tilt Angles in Dephosphorization Ladle Furnace

Simulation and Application of Top Lance with Various Tilt Angles in Dephosphorization Ladle Furnace