Oxygen Lance Research Articles

Flow Field of Supersonic Oxygen Jet Generated by Various Wear Lengths at the Laval Nozzle Exit

As a main apparatus, the oxygen lance is used to deliver the oxygen element and transfer kinetic energy into the molten bath in the steelmaking process. However, the Laval nozzle exit would be gradually worn out during the service life, which suppresses the performance of the oxygen lance. This paper investigated three different wear length (Lw) conditions at the exit of the Laval nozzle through numerical simulations and high-temperature experiments with various oxygen flow rates. The result showed that the entrainment of the ambient gas was the key factor of the wear phenomenon for the Laval nozzle exit. The maximum total temperature of the gas phase at the Laval nozzle exit formed by the Lw of 0 mm, 2 mm, and 4 mm were 300 K, 959 K, and 1700 K, respectively. Thus, by increasing the Lw value, the total temperature of the gas phase was rapidly improved at the exit of the Laval nozzle, which further accelerated the wear phenomenon at the exit of the Laval nozzle. Besides, axial velocities at the end of the potential core formed by the Lw of 0 mm, 2 mm, and 4 mm were 483.7 m/s, 480.0 m/s, and 478.7 m/s, respectively. As a result, the wear phenomenon reduced the impaction ability of the oxygen jet, which suppressed the impaction depth and radius, resulting in a smaller droplet generation rate.

Continuous [C] Content Prediction Model in Molten Steel of the All-Scrap Electric Arc Furnace

The continuous [C] content prediction model in molten steel of the all-scrap electric arc furnace was established through the explicit finite difference method combined with numerical simulation based on the thermodynamics and kinetics of the decarburization reaction. Initially, a method to figure out the average [C] content of mixed input scrap was proposed, which provided a basis for subsequent calculations. Furthermore, scrap melting rate, mixing side-blowing / bottom stirring, and oxygen blowing intensity adjustment of oxygen lance had been considered as the three key elements. Decreasing scrap melting time was beneficial to improving the EAF efficiency because it accounts for 80% of the total operation time. The research found that the scrap melting rate was mainly affected by the solid-liquid phase heat transfer and [C] content transfer, and the heat transfer played a dominant role. Applying mixing side blowing / bottom stirring could lead to an improvement in the mass transfer coefficient of the decarburization reaction, and the value was increased from the range of 0.0059 s-1-0.021 s-1 by using single side-blowing to the range of 0.0079 s-1-0.023 s-1. The mass transfer coefficient could be enhanced by the oxygen intensity adjustment of oxygen lances when mixing side blowing / bottom stirring was used. This was a benefit of deeper jet impact zones on the molten steel surface caused by high oxygen flow. After the model was applied to an industrial site, the prediction accuracy of the endpoint [C] content within the error range of ±0.02% and ±0.01% reached 91.2% and 85.7%, respectively.

Numerical Study on Droplet Splashing Behavior of Slag‐Splashing for Converter Protection Using Volume of Fluid‐Discrete Phase Model Two‐Way Conversion Model

Limited quantitative research exists on the complex phenomenon of slag splashing in converters. A comprehensive modeling framework is developed to fill this gap, integrating a 3D two‐phase flow model with a volume of fluid‐discrete phase model two‐way conversion model. This framework explores droplet behavior during splashing for converter protection, encompassing the mutual conversion between slag and discrete droplets induced by top‐blowing oxygen. It also tracks the trajectories of all droplets, enabling a detailed quantitative analysis of the splashing process. The Eulerian wall film model is used to simulate liquid film formation on the converter wall. Model predictions are validated against 1:10 scale experimental data from a 50 t converter. This assessment covers splashing rates, droplet locations, and size distribution under various operating conditions. Parametric studies identified an optimal top‐blowing flow rate of 8.80 Nm3 h−1 and an oxygen lance height of 233.2 mm, balancing splashing effectiveness with production cost and safety.

Mathematical Modeling on the Multiphase Flow during Top–Bottom Combined Blowing Basic Oxygen Furnace Steelmaking Process

A 3D mathematical model on the multiphase flow and splashing phenomenon in a 210 t Basic oxygen furnace converter is established. The turbulent multiphase flow of the molten steel, slag, and oxygen is simulated by the combined realizable k−ε model and volume of fluid model. The trajectory of argon bubbles and the interaction between the molten steel and argon is simulated by the two‐way coupled Lagrangian discrete phase model. Effects of the lance height and bottom‐blowing gas flow rate on the multiphase flow and splashing phenomenon are investigated. The results indicated that the cavity depth is decreased from 0.45 to 0.36 m when the lance height increases from 1700 to 2300 mm. The cavity depth is not significantly affected by the bottom‐blowing argon flow rate with the 44 000 m3 h−1 top‐blowing oxygen flow rate and 1700 mm lance height. The increased lance height resulted in a decrease in splashing. When the oxygen lance height increases from 1700 to 2300 mm, the amount of the splashed molten steel decreases from 3774.3 to 1953.0 kg.

Influence of operating parameters on the flow of the molten bath during the swirl-type oxygen lance blowing process

ABSTRACT In top-blowing steelmaking, the flow behaviour of molten steel during supersonic jet impact into the molten bath is crucial for the refining process. In this study, the effects of lance height and operation pressure on velocity distribution and the flow characteristics of the molten bath during the swirl-type oxygen lance blowing process in a 260t converter were explored. The results demonstrate that compared to the traditional oxygen lance, the stirring efficiency of a molten bath with the swirl-type oxygen lance is improved due to the tangential momentum of the jet and the increase in cavity diameter. As the lance height increases, the flow is improved at the bottom and surroundings of the molten bath, and the dead zone volume of the molten bath decreases first and then increases. The best stirring efficiency is achieved at H = 40de. As the operation pressure increases, the impact strength of the jet increases, the flow at the upper zone of the bath is significantly improved, and the dead zone volume decreases.

Variation in Flow Characteristics of Molten Baths at Different Blowing Stages in the Converter

The metallurgical tasks at different stages of converter blowing are different. The process operation and physical properties of molten baths are also different. It is very important to determine the flow characteristics of molten baths at different blowing stages for optimizing process operation. In this paper, a three-dimensional, full-scale model of a 120 t top–bottom combined blowing converter is established. Based on the parameters of oxygen lance position, bath temperature, bottom blowing intensity, and bath physical properties at different blowing stages, the changes in bath flow field, turbulent kinetic energy, impact depth, impact area, and wall shear force with blowing process are studied. The results show that at the initial stage of blowing, the lance position is high, the impact depth of the molten bath is 0.23 m, the impact area is 5.06 m2, the dead zone area of the longitudinal section is 0.40 m2, and the high-speed zone area is 2.73 m2. As the blowing time increases, the lance position decreases, the impact depth of the molten bath increases, the impact area decreases, and the internal velocity of the molten bath increases. In the later stage of tuyere blowing, the lance level decreases to its lowest, the impact depth increases to 0.42 m, the impact area decreases to 2.83 m2, the dead zone area of longitudinal section decreases to 0.18 m2, and the high-speed area increases to 3.34 m2. The area with the highest wall shear stress is situated within the gas–slag–metal three-phase region, where the lining experiences the most significant erosion. The fluctuation in the slag–metal interface is small, and the wall shear force is 2.80 Pa at the initial stage of blowing. From the early to late stages of blowing, the lance position decreases, the fluctuation range of the slag–metal interface increases, and the erosion of the furnace lining increases. In the later stage of blowing, the maximum wall shear force is 3.81 Pa.

Combustion Behavior of Supersonic Jet for Single‐Flow Postcombustion Oxygen Lance with Various Secondary Nozzle Parameters

A 3D model is established to discuss the influence of combustion reaction on jet characteristics. Based on this, combustion behaviors of supersonic jet for single‐flow postcombustion oxygen lance with various secondary nozzle parameters (diameter, inclination angle, and number) are analyzed. The results indicate that after activating combustion reaction, the jet velocity, dynamic pressure, density, and temperature of primary jet at H = 1.45 m are 1.27, 1.15, 0.56, and 1.97 times than those of without considering the combustion, respectively. Enlarging secondary nozzle diameter is helpful to extend the flame core lengths of primary and secondary jets (the axial distance from lance tip to isotherm of 1773 K) as well as the combustion region. With the increase of secondary nozzle angle, the two flame core lengths both decrease, while the combustion zone increases. Increasing the number of secondary nozzles, the flame core length of primary jet increases while that of the secondary jet decreases, and the combustion region first increases and then decreases. As for the influences of the above parameters on flame core lengths of primary and secondary jets as well as the combustion region, the number is the greatest, followed by the inner diameter, and the inclination angle is the smallest.

Numerical analysis and industrial practice of single-flow post-combustion oxygen lance with high oxygen supply intensity

The oxygen supply process is a vital operation in converter steelmaking, which is to inject oxygen and kinetic energy into the liquid bath with an oxygen lance. Herein, a single-flow post-combustion oxygen lance (SF-PCL) with four primary holes and six secondary holes was designed to increase the oxygen supply intensity of a 60-ton converter in a steel plant. The attenuation and coalescence behaviors of supersonic jets for the conventional four-hole oxygen lance (COL) and the newly designed SF-PCL were studied by numerical simulation. And then, their metallurgical effects were verified by industrial practice. The simulation results indicated that the SF-PCL effectively suppresses the attenuation and coalescence of supersonic jets as well as simultaneously increases both the impact area and penetration depth. In industrial practice, compared with the COL, the newly designed SF-PCL increases the oxygen supply intensity from the original 4.89 m3 (t·min)−1 to 5.43 m3 (t·min)−1, rises the dephosphorization rate by 1.4%, shortens the blowing time by 34 s, reduces the ferrous charges consumption by 7 kg t−1 and decreases the total iron content in final slag by 0.85%.

Effect of cavity shape caused by jet impact of swirl-type oxygen lance on molten bath mixing efficiency

Effect of cavity shape caused by jet impact of swirl-type oxygen lance on molten bath mixing efficiency

Simulating and Evaluating the Multiphase Jet Flow Characteristics of a Five‐Hole Oxygen Lance under Nonisothermal Conditions

The oxygen lance jet plays a crucial role in the steelmaking process in a converter. The quantitative relationship between the operating parameters of the oxygen lance and the volume of the impact cavity is established for the first time, and the leading factors affecting the volume of the impact cavity are identified through correlation analysis. This article examines the influence of operating pressure and lance position on the impact cavity of a 170 t converter in a nonisothermal environment through numerical analysis. The results show that the ambient temperature in the converter presents a layered phenomenon. The temperature near the free surface ranges from 1550 to 1600 K and then gradually decreases to 900 K at the oxygen lance outlet. When the ratio of the operating pressure to the design working pressure is less than 1.0 or greater than 1.3, the cavity volume is significantly affected by the operating pressure but has less of an impact when the ratio is between 1.0 and 1.3. The cavity volume shows a linear relationship with the oxygen lance position. Moreover, the oxygen lance position has a greater influence on the cavity volume and velocity distribution than do the operating pressure.

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.

Effect of Swirl Angle on Interaction between Swirl Oxygen Lance Jet and Melt Pool

In order to clarify the action law of the swirl oxygen lance jet on the melt pool of the converter and to determine the optimal swirl angle of the swirl oxygen lance for the 120t converter, this study establishes the gas-liquid two-phase flow model of the oxygen lance with different swirl angles based on the realizable k-ε model and the VOF multiphase flow model. The gas-liquid interface behavior during the interaction between the jet and the molten pool was analyzed, and the flow pattern of molten steel in the molten pool was mainly investigated. The results show that compared with traditional oxygen lance, the rotating oxygen lance jet enhances the stirring of the melt pool and intensifies the fluctuation of the melt pool liquid level. The depth of the impact cavity decreases with the increase of the swirl angle, but the diameter of the impact cavity increases with the increase of the swirl angle. When the jet with a swirl angle of 10 ° impacts the surface of the melt pool, the turbulence energy obtained by the molten steel is the highest, the average flow velocity inside the melt pool is the highest, and the molten steel is stirred more thoroughly, achieving better melting effects.

Flow Field Characteristic of Postcombustion Oxygen Lance Formed by Various Secondary Nozzle Arrangements

Flow Field Characteristic of Postcombustion Oxygen Lance Formed by Various Secondary Nozzle Arrangements

Numerical Simulation of Heat Transfer Behavior in Hot Spot Zone of Converter Molten Bath

The multiphase fluid flow and heat transfer behavior in the steelmaking converter are essential for efficient and stable smelting. Herein, a mathematical model of heat transfer for the hot spot zone of the converter is established. The temperature distribution of the molten bath is clarified, and the effects of operating parameters and the exothermic rate of hot spot zone on the heat transfer behavior of the molten bath are investigated. The results show that the temperature gradient between the hot spot zone and the liquid steel as well as the circulation of liquid steel will lead to the nonuniform distribution of temperature. Both the direction of flow field and the mixing characteristics of molten bath influence the heating rate of molten bath, whereas the direction of the flow field plays a dominant role. In addition, the oxygen lance height has a significant influence on the heat transfer behavior; as the lance height increases from 1.35 to 1.65 m, the heating rate increases by 68.32%. The increase of exothermic rate will remarkably increase the temperature gradient and the heating rate increases by 65.84% and 114.28% when the exothermic rate increases by 1.5 and 2 times, respectively.

Analysis of Melt Flow Characteristics in Large Bottom-Blowing Furnace Strengthened by Oxygen Lance Jet at Different Positions

Analysis of Melt Flow Characteristics in Large Bottom-Blowing Furnace Strengthened by Oxygen Lance Jet at Different Positions

Simulation of gas dynamics of oxygen flow and hydrodynamics of cooling water flow in tuyere tips with tangential optimized nozzles and results of their pilot tests.

The blowing mode largely determines the technical and economic indicators of BOF smelting, which was confirmed during the technological audit of the BOF shop of Azovstal Iron and Steel Works, carried out in 2021. It was found that the blowing mode of the process using an oxygen lance of the basic design was noticeably shifted from the optimal one in the direction of “hard” blowing. In a significant number of melts this led to an increase in the specific consumption of metal sheets, deterioration of lime assimilation by slag, dephosphorization and desulphurization of the metal. Taking into account that adjustment of the blowing mode by changing the working height of blowing and oxygen consumption did not provide a stable positive result, changes were made in the design of the tuyere tip. The design of the head with tangential arrangement of nozzles is proposed to “soften” the blowing of melts. The advantages and dis-advantages of oxygen lances of this type are considered. Numerical modeling of the gas dynamics of the oxygen flow and the hydrodynamics of the flow of cooling water in a tip with a tangential arrangement of nozzles has been per-formed. On the basis of simulation results, two variants of an improved design of the tips of 350-t LD converters with five (variant 1) and four (variant 2) main peripheral tangentially oriented nozzles and a central nozzle of lower throughput were developed to use them mainly in the second and first periods of the campaign according to the lining of the converters, respectively. It is shown that the design parameters of the nozzle blocks provide an oxygen jet outflow regime close to the design one in the main range of oxygen operating flow rates and a “non-separated” outflow regime with a decrease in the off-design ratio down to 0.8. The design parameters of the cooling system provide both an acceptable loss of water pressure in the head (0.9 MPa), the absence of local low-speed vortex zones of water, and a fairly high average coolant flow rate along the most heat-stressed (the lower) surface of the tip (about 4.5 m/s). As a result of industrial testing of a pilot batch of experimental heads with five main peripheral tangentially oriented nozzles, manufactured at the plant’s own repair and mechanical base, an increase in the resistance of copper tips was found to be 1.2 times, the resistance of lances to removal for cleaning from accretion was found to be 6.8 times, reduction in the specific consumption of metal charge by 0.9–5.6 kg/t, an increase in the dephosphorization and desulfurization coefficients of metal in the converter by 0.7–1.5 and 1.3–3.2%, respectively.

STUDYING THE POSSIBILITY OF USING COHERENT TYPE NOZZLES FOR BOF BLOWING AT THE GAS DYNAMIC SIMULATION STAND

Introduction. The BOF technology is the leading one in the production of structural steel due to its undeniable advantages.Problem Statement. In the conditions of most Ukrainian converter shops, when the blowing parameters change significantly during the campaign (temperature of the lining, dimensions of the workspace, quality of scrap metal, temperature and composition of iron), and the bath is blown at a constant flow rate with conventional Laval nozzles, sometimes it is impossible to ensure a stable purging process with high rate of post-combustion of CO up to CO2. Therefore, one of the main problems of oxygen conversion is the improvement of the designs of blowing devices, in particular, the nozzles.Purpose. The purpose of this research is to study the possibility of using nozzles of the coherent type for the top oxygen blowing of the converter.Material and Methods. In the research, we have used samples of coherent-design laboratory nozzles having different central part-to-periphery ratio under fixed equal general conditions of jet output (percentage of the annular gap to the total area of the nozzle, %: 75, 65, 50, 45, 35, 25). They have been studied by calculating the jet momentum, through weighing and taking shadow shots when the gas flow velocity reaches 2 M. The results have been compared with those for the cylindrical nozzle.Results. When the gas is supplied at 2 M, the coherent-type nozzles with a fraction of the outer part of 65—75% contribute to the formation of 1.5—1.6 times wider jets as compared with the cylindrical nozzle, with a multinode structure. It helps to increase the jet momentum by 45—55%.Conclusions. The design of a coherent type nozzle with an outer part share of 75% can be recommended to be used as the second tier or the second level nozzles of the top oxygen lance for post-combustion in an oxygen converter due to an increase in the surface area of the jet contact. The efficiency of post-combustion of CO from waste converter gases is expected to increase due to the increasing reaction surface area of additional oxygen jets.

Effect of oxygen lance seat arrangement on flow characteristics of large-scale copper smelting bottom-blown furnace

Effect of oxygen lance seat arrangement on flow characteristics of large-scale copper smelting bottom-blown furnace

Numerical Simulation of CO2 Used for Slag Splashing Process in Converter

Utilizing CO2 for the slag splashing process presents a novel approach that enhances CO2 utilization in the steel industry and promotes efficient slag splashing. Herein, numerical simulation is employed to investigate the kinetic feasibility of this technique on a 100 t converter. The volume of fluid (VOF) model is utilized to trace the gas–slag interface, while the standard k–ε model is selected to describe the turbulent flow of each phase. Initially, the model is validated via isentropic theory and experimental data. Subsequently, the effects of gas and oxygen lance replacement are evaluated. The results indicate that employing CO2 solely instead of N2 leads to a reduction in jet velocity and slag mass flow rates at different positions. However, the utilization of the innovative oxygen lance slows down the jet decay and increases the slag mass flow rate at various heights and sidewalls, except for the lower cone, resulting in a satisfactory slag splashing performance. The present study verifies the feasibility of this new technology and its potential to contribute to CO2 reduction in the industry positively.

Numerical Simulation and Application of an Oxygen-Enriched Side-Blown Smelting Furnace for the Treatment of Electroplating Sludge

In the oxygen-enriched side-blown smelting furnace for the treatment of electroplating sludge, fluent was used to simulate the gas–liquid two-phase flow process. The relationship between the lance diameter, lance inclination, bath depth, and the bath evaluation indicators were studied, and the oxygen lance spacing was optimized. The results show that the high velocity and high gas rate areas were near the oxygen lance, while the stirring dead zones with low velocity appeared in the central and bottom areas of the molten pool. The key parameters were optimized using single-factor analysis and multifactor comprehensive optimization. The results showed that the bath evaluation indicators were all at good levels under the optimal parameter conditions. These were comprehensively obtained as the following: the lance diameter was 25 mm, the lance inclination was 15°, the lance spacing was 1050 mm, and the bath depth was 1500 mm. The industrial test carried out in an environmental protection enterprise in Guangdong achieved satisfactory results. The test shows that the electroplating sludge containing 7.24% Cu can be melted at 1300~1400 °C to obtain matte. Compared with industrial copper slag, the smelting slag has a higher CaO and a lower Fe content.