BOF Steelmaking Research Articles

Energy balance between multiple supersonic jets and molten bath in BOF steelmaking

ABSTRACT A multi-fluid volume of fluid (VOF) model for compressible oxygen flow in a 260t top blown converter was established. The energy transfer efficiency of the top blown gas to the molten pool was analyzed. A user-defined function was used to calculate splash energy consumption. The energy conservation equation of ‘jet attenuation – cavity formation – bath stirring – molten steel splashing’ was established. The results show that more than 75% of the total energy is wasted in jet attenuation. The energy used stirring bath and used for molten steel splashing are less than 1.5% and 3% of the total energy, respectively. Approximately 15%–20% of the energy is used to form cavity and maintain its shape. As the lance position decreases from 2.2 to 1.8 m, the energy used for stirring molten pool increases by 13.3%, while the energy used for splashing and cavity formation decreases by 7.7% and 5.22%, respectively.

Behavior of Top-Blown Jet under a New Cyclone Oxygen Lance during BOF Steelmaking Process

An oxygen lance is the operation unit that generates supersonic oxygen jets, controls their behavior, and acts as a vital role in the steelmaking process. It is thought that airflow similar to a tornado may suppress upward splashing because of part of the jet pressure shifting from the axis of the oxygen lance to the tangential direction. Therefore, a new oxygen lance is designed to form a tornado jet, and the numerical simulation consequences are verified by the physical model. The structure of the new oxygen lance is optimized by numerical simulation results, and the comparison of simulation results before and after optimization is analyzed. On this basis, the effect of the cyclone oxygen lance on the upward splashing behavior, penetrating depth, turbulent kinetic energy, turbulent dissipation rate, and rotation of molten bath is investigated. The conclusions present that, compared with the conventional oxygen lance, the upward splashing with the cyclone oxygen lance decreases, and the penetrating depth and reaction area increase. In other words, for obtaining the same penetrating depth, the cyclone lance height can be higher than that of a conventional oxygen lance, which leads to a better protective effect on the refractories of the oxygen lance. Moreover, the average value of the turbulent kinetic energy of the cyclone nozzle is larger than that of the traditional Laval nozzle at the interface between oxygen and slag, which improves the effect of steelmaking.

Simulation study on multiphase behavior of gas-metal-slag in the 260t converter

Taking the 260t BOF steelmaking process as the research object, it is of great significance to study the Gas-metal-slag interaction with oxygen lance. In this paper, a 3D mathematical model is established by using fluent. Through changing some physical parameters of lance height and slag, the impact depth, impact cavity area and energy transfer and flow are analyzed. The numerical results show that with the increase of lance height, the diameter of impact cavity in molten steel becomes larger, but the impact depth decreases. When the lance height is 32de, the area of high speed zone in the molten steel pool is the largest, the energy in oxygen jet is mostly dissipated in the process of reaching the slag level, and the kinetic energy obtained by the slag is only about 14% of the kinetic energy of molten steel. With the increase of slag thickness, the depth and area of the cavity decrease, and the flow of molten steel is restrained. The change of slag viscosity and slag density has little effect on the flow velocity. This study can provide reference and guidance for the regulation and control of the process parameters of converter refining.

Feature selection of BOF steelmaking process data by using an improved grey wolf optimizer

Feature selection of BOF steelmaking process data by using an improved grey wolf optimizer

Value in use of lime in BOF steelmaking process

ABSTRACT In the BOF steelmaking process, lime quality and quantity directly affect slag quality, affecting metallurgical results, liquid metal yield, productivity, and therefore the total cost and environmental impact of the steel production. In this paper, a value in use model based on mass balance and heat balance was developed and used to evaluate the impact of lime quality on the BOF process. The model has been successfully validated using the data of the Steel Plant. Then three types of lime with different qualities were used to elaborate on the impact of lime characteristics in optimizing the steelmaking process, metallurgical benefits, overall cost impact, potential savings, and environmental benefits. The calculation results show that good-quality lime could increase the scrap ratio, reduce the lime consumption, and reduce iron loss, accordingly, improve the steel quality, increase steel yield, reduce the smelting costs, stabilize smelting operations, and reduce CO2 emissions.

Jet characteristics of a double-structure oxygen lance and its interaction with the molten pool in BOF steelmaking

An oxygen lance represents a commonly used piece of equipment in converter steelmaking. Its jet characteristics and the interaction of these jets with the molten pool will directly affect the smelting effect and blowing time. This work investigates the oxygen lance of a 260 t converter in a steel plant. Through numerical simulations and physical experiments, the influence of the operating pressure, ambient temperature, top-blowing flow, lance position, and other operating parameters on the jet flow characteristics of the oxygen lance is studied. Furthermore, the oxygen lance interaction with the molten pool is analyzed. The results show that the operating pressure has little effect on the fusion distance of the jet; however, its size determines the impact force of the jet on the molten pool. In addition, the high-temperature environment causes the density of the jet fluid to decrease, the jet attenuation speed to decrease, the jet fusion speed to increase, and the degree of fusion to attenuate. Furthermore, the spray volume of the furnace mouth continues to increase upon increasing the top-blowing flow; by contrast, the spray volume first increases and then decreases as the gun position increases. The maximum spray volume of the furnace mouth occurs at the 35-de gun position; the diameter of the impact pit varies with the gun position. As the top-blowing flow increases, the depth of the impact pit increases with the decrease in the gun position and the increase in the top-blowing flow. The mixing time gradually reduces with the increase in the top-blowing flow and the decrease in the gun position.

Effect of blowing parameters on bath mixing efficiency during basic oxygen furnace steelmaking process

AbstractBasic Oxygen Furnace (BOF) steelmaking is the main method for steelmaking production, mixing efficiency of BOF vessel would greatly affect the uniformity of chemical composition and temperature in molten steel. Therefore, this paper conducted the effect of blowing parameters on bath mixing efficiency during BOF steelmaking process. Through measuring the mixing time of steel bath in BOF vessel, the effect of different blowing parameters was studied. Based on analysis of variance for the experimental results, the influence degree on mixing efficiency by different blowing parameters was acquired, and the optimized combination of blowing parameters was obtained. Moreover, the mixing index which indicated the mixing degree of steel bath in BOF vessel was proposed in this study, and an apparent nonlinear relation was acquired after determining relationship between the mixing index and blowing parameters. The optimal blowing parameters were applied to an 80 t industrial BOF vessel in a special steel plant, the end point carbon and oxygen equilibrium was decreased from 0.0032 to 0.0026, end point phosphorus and total Fe content in slag were reduced by 0.0012% and 2.21%, respectively. The mixing index and results presented in this work could be helpful to improve mixing efficiency in commercial BOF vessels.

Behaviors of supersonic double-parameter jets and their impingement onto molten bath in BOF steelmaking

The dynamic characteristics of supersonic double-parameter jets and their interaction with the molten pool were experimentally studied. The effects of jet inclination angles and gas flow ratios on gas intensity, coalescence characteristics, and dynamic parameter distributions were discussed. The characteristics of the cavity formed by the interaction of the jet and molten pool were revealed. The results show that the jet inclination angle has more influence on the jet coalescence compared with the gas flow rate. However, the gas flow ratio plays a decisive role in the velocity distribution along the jet centerline compared with the jet inclination angle. The velocity peaks of the double-parameter jets were obviously different at fixed axial distances. Compared with other variables, the small-nozzle inclination has a greater impact on the cavity diameter, while the large-nozzle flow ratio has a greater impact on the cavity depth. The depth and width of the cavity formed by the double-parameter jets are more advantageous than that formed by the single-parameter jets. Furthermore, the double-parameter jets were applied to the actual smelting of a 260t converter.

Metallurgical performance of innovative double-parameter oxygen lance in BOF steelmaking

ABSTRACT The metallurgical performance of a double-parameter oxygen lance was characterized using the prototype of a 260 t converter. The influences of nozzle arrangement on the cavity size, mixing ability and splashing capacity were discussed. The results demonstrated that the small-nozzle inclination has a greater impact on the cavity diameter, while the large-nozzle flow ratio has a greater impact on the cavity depth. The influence of the large-nozzle gas flow rate on the stirring strength is greater than that of the nozzle inclination. The maximum splash flux is located at the outer edge of the large nozzle farthest from the axis of the lance. The large-nozzle flow of the double-parameter lance shall be limited to less than 65% of the total flow to prevent the molten steel from splashing out of the converter. Many metallurgical indexes were improved by the application of the double-parameter lance under commercial production conditions.

Application of Combined Developments in Processes and Models to the Determination of Hot Metal Temperature in BOF Steelmaking

Nowadays, the steel industry is seeking to reduce its carbon footprint without affecting productivity or profitability. This challenge needs to be supported by continuous improvements in equipment, methods, sensors and models. The present work exposes how the combined development of processes and models (CDPM) has been applied to the improvement of hot metal temperature determination. The synergies that arise when both sides of this research are simultaneously approached are evidenced. A workflow that takes into account the CDPM approach is proposed. First, a thermal model of the process is developed, making it possible to identify that hot metal temperature is a key lever for carbon footprint reduction. Then, three main alternatives for hot metal temperature determination are compared: infrared thermometry, time-series forecasting and machine learning prediction. Despite considering only few process variables, machine learning techniques succeed in extracting relevant information from process databases. An accuracy close to infrared thermometry is obtained, with a much higher applicability. This research shows that process-model alternatives are complementary when judiciously nested in the process computer routines. Combining measurement and modelling techniques, 100% applicability is achieved with an error reduction of 7 °C.

Numerical investigation on behaviors of interlaced jets and their interaction with bath in BOF steelmaking

The jet behavior of interlaced multiple nozzles and the impingement of multiple jets onto the surface of the molten metal bath in a steelmaking converter are numerically studied. The interlaced jet hydrodynamic behaviors such as jet profile, coalescence characteristics, and dynamic parameter distributions penetration depth and impact area, as well as time-dependent evolution of liquid bath are discussed. The results are compared with traditional nozzles. It is found that the single nozzle characteristics of staggered jet are similar to those of traditional jet. However, two sets of staggered nozzles with different flow rate and inclination angle having a less disturbance flows, cause weaker coalescence of the jets and larger area surrounded by isovelocity in the molten pool. In the initial stage of the interaction between the interlaced nozzles and the molten pool, the “low stirring zone” is more likely to concentrate in the outer side near the furnace wall than in the center of the molten pool. Two cavities, one deep and one shallow, are formed on the bath surface. The average depth of the two cavities is similar to traditional nozzles, and the diameter of the cavity is increased by about 11% compared to traditional nozzles.

Thermodynamics-Based Modeling of Iron- and Steelmaking Processes Using Flow Sheet-Based Approach Employing METSIM

Iron- and steelmaking processes consume an enormous amount of materials in a large-scale production unit. The overall process consists of the flow of material as well as heat across large number of interconnected unit process reactors. Almost all reactors have deviations from thermodynamic equilibrium in overall sense, but they can be classified as large number of interconnected localized equilibrium reactors with restricted interactions among them. Therefore, the role of thermodynamic package like FactSage [1] and sequential modular-based package like METSIM [2] becomes very important for process design and control as well as for studying the parameters to achieve minimum cost and CO2 emissions. In the paper flow sheet, modeling-based approach with coupled application of METSIM is demonstrated for modeling of blast furnace ironmaking, BOF steelmaking and ladle furnace processes. These processes are demonstrated using the capabilities of METSIM for effective process control.

SURFACE PHENOMENA PECULIARITIES IN THE BOF STEELMAKING BATH

BOF steelmaking technology is largely determined with processes taking place in the LD-converter reaction zone, which consists of “primary” and “secondary” sub-zones. The “primary” zone is a crater formed as result of supersonic gas stream impact on metal melt sur- face, fulfilled with metal droplets of 0.1 – 2 mm in diameter. Surrounding in the “secondary” zone consists of the large amount of gas bubbles of 0.2 – 4 mm in diameter. The total surface area of droplets and bubbles is by four orders of magnitude larger as compared with the stable metal surface of magnitude larger as compared with the stable metal surface place. This suggests important role of interface phenomena at steel refining processes. The reaction zone structure and its temperature distribution were studied with “hot” modeling method, where molten cast iron was blown with oxygen in transparent quartz crucible. Each blow was accomplished with photo- and cinema filming through crucible wall. Besides temperature distribution obtained material also allowed study of metal bath hydrodinamics directly in blowing zone. The most unexpected result here was the motion trajectory of bubbles in the “secondary” zone. They moved normally to the crater surface, i.e. almost in a horizontal direction instead of vertical float as it was noticed at “cold” modeling with water. This very important phenomenon is caused by surface tension in homogeneity, due to which the bubbles are moved at higher temperatures direction. Surface tension forces in front of and behind gas bubble in liquid with temperature gradient are different. Because contact forces behind bubble are larger as compared that in front, it is pushed out in direction of surface tension decrease. Surface tension inhomogeneity is generated with temperature (up to 1200 °C) and oxygen concentration gradients in the “secondary” reaction zone. Iron-carbon surface tension changes with temperature rise inconsistently. Surface tension increases with temperature rise up to 1550 °C. At reaching 1550 – 1600 °C there is a bend, which after surface tension begin to decrease. This bend point is as higher as lower carbon concentration in alloy gas bubbles and heterogeneous phase’s motion in surface decrease direction starts from 1550 °C isotherm. So it is outward border of “secondary” reaction zone, which separates it from main metal bath. Inside it resulting surface tension forces push gas bubbles and slag particles into accelerating motion with mass of metal melt in horizontal direction to the crater. This phenomenon determines whole steelmaking bath hydrodynamics with oxygen redistribution between molten metal components and hence the steel refining process in general.

Prediction model of end-point phosphorus content in BOF steelmaking process based on PCA and BP neural network

A prediction model based on the principal component analysis (PCA) and back propagation (BP) neural network is proposed for BOF end-point phosphorus content, based on the characters of BOF metallurgical process and production data. PCA is used to reduce dimensionality of the factors influencing end-point phosphorus content, and eliminate the correlations among the factors, and then the obtained principal components are used as BP neural network input vectors. The combined PCA-BP neural network model is trained and tested by history data, and is further compared with multiple linear regression (MLR) model and BP neural network model. The results of the comparison show that the PCA-BP neural network model has the highest prediction accuracy and PCA improved the generalization capability. Finally, online prediction system of BOF end-point phosphorus content based on PCA and BP neural network is developed and applied in actual productive process. Field application results indicate that the hit rate of end-point phosphorus content is 96.67%, 93.33% and 86.67% respectively when prediction errors are within ±0.007%, ±0.005% and ±0.004%. The combined PCA-BP neural network model has achieved the effective prediction for end-point phosphorus content, and provided a good reference for end-point control and judgment of quick direct tapping of BOF.

50 tons of steel mill BOF steelmaking dynamic control system and the application of variable-frequency emergency power supply-gun incident oxygen converter steel to enhance the development of power

Abstract: This article emphatically about laigangsteel mills bof dynamic steelmaking control system.Detailed introduces the characteristics of the dynamic steelmaking converter characteristics and its key of technology is described.

Study on Slopping Prevention in the BOF Steelmaking Process

A new method of preventing slopping is proposed in this paper, by simply blowing gas at the top of the foam surface. The physical experiment results show that the foam height can be effectively dec ...

Interaction behaviour between top blown jet and molten steel during BOF steelmaking process

During oxygen steelmaking process, a systematical description of the interaction behaviour between top blown jet and molten steel is extremely important. In the present study, a cold model experiment and the corresponding numerical simulation were carried out to illustrate the highly complex interaction process inside an 80-t converter. First, the interaction process was presented in a numerical way. On this basis, the quantitative effect of pertinent operational parameters on the interaction process was investigated. To clearly describe the cavity appearance, the cavity shape index () was put forward, which is a dimensionless factor to demonstrate the cavity shape related to cavity depth and cavity width. In addition, a functional relationship correlating cavity shape index and blowing number was proposed. It can be concluded that higher blowing number (NB) results in deeper cavity depth and smaller cavity width. Moreover, the effect of cavity shape on the stirring characteristics and the mixing effect in the converter were investigated. The results show that lower and higher cavity shape index may lead to longer mixing time in smelting process. For 80-t converter, the penetration depth and impact width should be controlled approximately equal ( fluctuates around 1) to obtain better mixing effect.

Making BOF Steelmaking More Efficient Based on the Experience of the Cherepovets Metallurgical Combine

Results are reported from a study of BOF steelmaking at the Cherepovets Metallurgical Combine (CherMK), and the main measures that can make the BOF shop more efficient are described. The measures include improving the logistics of transport operations, the installation of new production equipment, or upgrade of the existing equipment. It is shown that the technical-economic indices of the shop can be improved in a short period of time at minimal cost by adopting a comprehensive approach to modernization of the present facilities.

A Kinetic Model for Limestone Decomposition under BOF Steelmaking Condition

A Kinetic Model for Limestone Decomposition under BOF Steelmaking Condition

Dependence of Temperature and Slag Composition on Dephosphorization at the First Deslagging in BOF Steelmaking Process

AbstractEffects of temperature and slag composition on dephosphorization in a 120 ton top-bottom combined blown converter steelmaking process by double slag method were studied. The slag properties were determined by scanning electron microscope- energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD). The results show that the transition oxidation temperature between dephosphorization and decarbonization Tf is not the favorable temperature for the first deslagging. The optimum first deslagging temperature is confirmed to be approximately 1,673 K which is about 70 K higher than Tf. High melting temperatures phases (such as 3CaO·SiO2) in the slag with high basicity and MgO content are unfavorable to the dephosphorization. The optimum process condition for dephosphorization at the first deslagging in present work is approximately 1,673 K in temperature, 2.0 in slag basicity, 6 and 17 mass% in MgO and T.Fe content, 6 mass% ≤ MnO content.