BOF Shop Research Articles

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.

SIMULATION MODELING OF IRONMAKING AND STEELMAKING PROCESSES AT CHEREPOVETS STEEL MILL OF PAO SEVERSTAL

This paper presents the results of running the model of ironmaking and steelmaking processes at Cherepovets steel mill of PAO Severstal. The model was developed using Anylogic software. The main goals of the work were: modeling of changes in the quantities of raw materials/ finished products; determining optimal productivity values for the equipment units involved in the process chain; identification of the process stages which may be overloaded in the process of modeling with further debottlenecking; conducting experiments on increasing throughput of the process stages (by increasing productivity or accumulation of accepted raw materials at the warehouses); checking achievability of the business plan targets for production of hot metal and steel. The main results of the work done are as follows: it is possible to get a 50% increase in the quantity of pellets transported by conveyors from tilting cars to blast furnaces considering the conveyor repairs; the system of conveyors would allow transportation of materials (sinter and concentrate) in case of increase in the blast furnaces productivity by 7.8% versus the current level; it has been established that the BOF shop productivity is influenced by geometry of slabs produced, line speed of the slab casting and tap-to-tap time; minimum tap-to-tap time at which the BOF shop productivity would be at maximum level is 36 minutes. Further reduction of tapto-tap time may be advised only if the casting machines are upgraded.

Static-dynamic model for endpoint control used in Smederevo's BOF shop

This paper describes the computer model for BOF control that was in use at Smederevo, Serbia, during the period 1994-2006. The model was developed at the Institute of Metallurgy of the Smederevo Steelwork in mid-1994 and was motivated by the fact that the plant in Smederevo, by that time, had many years of experience in endpoint control using Intermediate Stop Practice (ISP). The vision for the model was to continuously improve and adapt to the working conditions of production through self-learning and adjustments. The model belongs to the well-known family of Static-Dynamic models (SDMs). It is aimed to reduce the "oxygen off-to-start tap" time and thus increase productivity and reduce production costs. The paper briefly describes the metallurgical software, operator operations and provides some information on the model's effectiveness.

Direct microalloying of structural steels by boron from oxide system CaO–SiO<sub>2</sub>–B<sub>2</sub>O<sub>3</sub>–Al<sub>2</sub>O<sub>3</sub>–MgO

The results of fundamental studies of the physicochemical properties of slags of the CaO–SiO2–B2O3–Al2O3–MgO system were used as the basis for the development of the technology for the formation of boron-containing slags in ladle-furnace units (LFU). The recommended composition of ladle slags (1–4% B2O3, 15% Al2O3 and 8% MgO) ensures the development of direct microalloying processes of steel with boron, low viscosity, not exceeding 0.32 Pa∙s, and preservation of sufficiently high refining properties. Colemanite (Turkey) was used as boron-containing raw material, having, %: 39–41 B2O3, 26–28 CaO, no more than 5% of SiO2 and 3% of MgO. The implementation of the developed technology of direct microalloying of structural steels of a wide grade composition by boron in the BOF shop of ArcelorMittal Temirtau JSC provided the boron content at the level of 0.001–0.008%, a decrease in the consumption of manganese-based ferroalloys from 0.3 kg/t of 08кп steel to 0.8 kg/t of steel 17Г1С-У, exclusion of additives into the ladle of ferroboron and fluorspar. The proposed mode of formation of slags of the recommended composition in the melt of LFU provided a sufficiently high degree of metal desulfurization in comparison with the existing production routes. For example, with pipe steel 17Г1С-У, despite a decrease in lime consumption by 500 kg per a heat and a decrease of the steel processing time at the LFU by 40 minutes, a high degree of desulfurization, reaching 66.7%, provided a sulfur content of 0.004% in the metal. Microalloying of structural steels by boron results in their high strength properties with invariance of plasticity apart from sufficiently high refining effect.

Strategy of automation of electric arc heating of steel melt in ladle-furnaceStrategy of automation of electric arc heating of steel melt in ladle-furnaceStrategy of automation of electric arc heating of steel melt in ladle-furnace

Prices hike for consumable materials and energy carriers, increase of requirements to steel quality stipulate the items of intensification of ladle treatment processes and decrease of their energy- and material capacity. Analysis of energy losses in ladlefurnace accomplished, as well as basic factors effecting the energy costs during treatment analyzed. A methodology elaborated for making thermal balance of ladle-furnace: it was proposed to present the melt treatment process in ladle-furnace as a series of separate operations, each having specific features of the process (heating, desulphurization, alloying) and their combination. Based on analysis of 20 thousand heats passports at ladle-furnace of MMK BOF shop, a mathematical model of energy supply system of ladle-furnace was elaborated. Based on the analysis made, a strategy of heating automation was proposed. In particular, electric losses were emphasized, t. e. total losses of electric arc energy, in which provisionally losses at arc open part radiation were included. Control of those flows creates conditions for heating efficiency increase. Conclusions were made that decrease of electric losses is observed at prolonged (about 8−12 min) heating periods and sufficient amount of slag, as well as at injection of additives after heating. Such a mode provides decrease of thermal losses by 4−5%. A new technology of steel melt treatment in ladle-furnace was proposed, characterized by decreased consumption of electric energy.

Domestic developments of equipment and technologies of steel in-linne degassing in the process of continuous casting

Apart from traditional methods of steel ladle treatment, degassing in the process of continuous casting (in-line degassing) is a perspective one. In the world a line of process flowsheets have been elaborated, but in practice the only one process has been implemented, which was developed by Professor G.A. Sokolov based on theoretical elaborations. The experience of its application in the BOF shop No. 2 of NLMK confirmed the efficiency of degassing in the process of continuous casting and expediency of further work on perfection of the technology and facilities structure for in-line degassing. Accounting the experience gained at AKHK “VNIIMETMASH”, a modified variant of in-line degassing facility was elaborated based on technological specifications of CNIIchermet. It was noted, that thanks to additional bunker-accumulator, fixed at the vacuum chamber, a possibility appeared to change steel ladles without disruption of continuous casting series. It enables to increase the share of degassed steel. At the designing of BOF shop of “Zaporozhstal” steel-works, planned for construction, specialists of AKHK “VNIIMETMASH”, CNIIchermet and YUMZ elaborated a design of two-position facility of increased efficiency for steel in-line degassing. Detailed description of the facility design presented as well as description of its basic units, elaborated at the level in invention. Taking into account that the facility height with the accumulator will make it difficult to place it in the existing shops, a modified in-line degassed elaborated without accumulator, which makes it possible continuous degassing of several heats. Such a degasser can be applied at both continuous casting of steel and casting of large ingots from several heats. The backlog, created by domestic scientists and specialists enables to solve technical problems, arising at elaboration and running of modern facilities of in-line degassing.

Features of ladle desulfuration of pipe steel with low sulfur content

At the present time the sulfur content in pipe steel is strictly regulated. Under conditions of PJSC “Magnitogorsk Iron and Steel Works” the metal is smelted in BOF shop with preliminary desulfurization of molten iron, treatment of tapping steel by a solid slag-forming mixture and final desulfurization in the “Ladle-Furnace” unit (LP-unit). In order to increase the efficiency of the sulfur removal process, the influence of the covering slag composition on metal desulfurization is considered. Statistical processing of production data array consisting of 14 melts of steel grade 10Г2ФБЮ with K60 strength class was performed. The dependences of the sulfur content in the metal after desulfurization in the LP-unit on the oxidizing ability, covering slag basicity and the content of magnesium oxide was established: it is shown that the amount of sulfur removed during the ladle treatment process increases with the increase of the covering slag basicity and with the decrease of the magnesium oxide content in slag. For describing this dependence, a new parameter was proposed – the ratio of slag basicity to MgO content in it, %–1. A high content of magnesium oxide in the “white” slag was revealed. This fact indicates a significant amount of converter slag getting into the ladle due to its poor cut-off in the process of metal tapping from the unit. The study of the influence of the coating “white” slag composition on the metal desulfurization process in the LP-unit showed, that for the effective sulfur removal, it is necessary to provide not only welldeoxidized slag with a total content of iron and manganese oxides of less than 1%, but also to ensure the ratio of its basicity to the magnesium content in this slag not less than 0.60–0.65%–1.

Experience of graphite-containing dust of metallurgical plants processing

Graphite is a component of graphite-containing dust – one of wastes, formed at metallurgical plants. From the other side, it is a scare resource for the Russian industry. Involvement of graphite-containing wastes into processing can contribute to solving actual problems of resource, economic and ecological significance. Study of the graphite wastes utilization possibility showed an absence of constant practice of their processing at domestic metallurgical plants. The work of graphite department of Magnitogorsk steel-works (MMK) can be one of not numerous examples of the graphite dust processing at the same plant. At the department the processing of graphite-containing dust of accomplished, the dust being collected from 90 kg/h productivity gas cleaning systems of BOF shop. As a result of processing graphite concentrate obtained after flotation and iron powder – after magnetic separation. At the Department “Minerals enrichment” of the Magnitogorsk State Technical University after G.I. Nosov, the theory of graphite flotation is being elaborated under the direction of Professor V.B. Chizhevsky for many years. Besides study of graphite ores washability, which are difficult to be enriched is also carried out. Based on the gained extensive experience on perfection of reagent flotation modes for the graphite ores, it was recommended to use first VKP reagent at the MMK graphite department, and next – RAS foam formation agent, which is a refined sodium alkylartile-sulfonate. At the industrial tests, the RAS foam formation agent consumption was two times as lower comparing with industrial reagent mode, resulting in obtaining higher technological flotation indices. The experience of metallurgical plant graphite-containing dust processing can be used at both the MMK graphite department re-operation and at other plants of the industry for obtaining marketable products of high quality, that can meet requirements not only metallurgical plants, but also used for production of state-of-the-art carbon materials.

Exergy analysis of silicon content in hot metal and its temperature influence on energy efficiency of “BF shop – BOF shop” complex operation

Application of pulverized-coal fuel in BF production results in changes of blast furnace heat operation, in particular, in hot metal temperature and silicon content in it changes, that effects the energy efficiency of “BF shop – BOF shop” complex operation. Isolated consideration of energy utilization by facilities (blast furnace, basic oxygen furnace) without taking into account their energy-technological ties does not provide steel smelting rational solutions obtaining. An exergy analysis of silicon content in hot metal and its temperature influence on energy efficiency of “BF shop – BOF shop” complex operation accomplished by application of the elaborated method of calculation of complete energy balance of “BF shop – BOF shop” system under existing conditions of pulverized-coal fuel application in Ukraine. It was shown, that silicon content decreasing down to level, which does not allow malfunctions of BF heat operation is strategically important for improving of energy efficiency of “BF shop – BOF shop” complex operation under conditions of pulverized-coal fuel application in BF production. It was determined, that under conditions of pulverized-coal fuel application in “BF shop – BOF shop” system, silicon content in hot metal decrease by 0.1% results in decreasing of exergy losses by 18–180 MJ/ton of steel, which is equivalent to standard fuel consumption decrease by 0.5–6.0 kg/ton of steel, increase of hot metal production by ~0.3–1.2 %. Hot metal temperature in blast furnace increase by 50 °С results in exergy losses decrease by 26–29 MJ/ton of steel, which is equivalent to standard fuel decrease by 0.9–1.0 kg/ton of steel.

Efficient Configuration for the Vent System of a 250-Ton Steel-Pouring Ladle

This article describes the main principles behind a method developed at the Institute of Ferrous Metallurgy of the Ukrainian Academy of Sciences (IChM NANU) to validate an efficient configuration that was found for the vent system of a 250-ton steel-pouring ladle in the BOF shop at the Dneprovskiy Metallurgical Combine (DMKD). Statistical analysis of production data over a three-year period of use of ladles with such an injection system showed that the campaign of the linings had increased by amounts ranging from 10.7 to 18.8%.

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.

Minimizing the Loss of Pig Iron During Its Treatment on Pig-Iron Desulfurization Units in BOF Shop No. 1

This article examines the issue of reducing the amount of pig iron that is lost when the slag is pumped off during the iron’s desulfurization in BOF shop No. 1 at the Novolipetskii Metallurgical Combine, Tests were conducted of an alternative technology which employs a new desulfurizing agent to treat iron on the desulfurization unit. Results from the use of the new material are reported.

Alleviating Slag Encrustation of the Submersible Nozzles on the Continuous Caster in BOF Shop No. 1

Results are presented from work that was done to increase the service life of the submersible nozzles on a continuous caster at the Novolipetskii Metallurgical Combine and stabilize the steel-casting operation.

Principles of the Development and Introduction of an Automated Process Control System for Blast-Furnace Smelting at the Magnitogorsk Metallurgical Combine

The principles of construction and the architecture of an automated system for controlling blast-furnace smelting are examined. A block diagram of a hardware-software complex developed for a blast furnace is presented along with scheme for integrating the furnace control system into the corporate control system at the factory. The system that has been developed creates a single informational-technological and control space that is closely linked to other information systems at the factory – especially the systems of the subdivisions whose performance has the greatest impact on the quality of the pig iron: the shop that prepares the sintering-machine charges, the sinter shop, the coke and coal chemicals plant, the BOF shop, the rail transport facility, the oxygen-plant/compressor station, and others. The main functional capabilities of the software are realized in the form of a model system that supports decision-making. This system is based on a group of mathematical models that solve various problems related to blast-furnace smelting. Users of the system can obtain missing information which is needed to make a decision by engaging in a dialog with the mathematical model. The results that have been obtained from using the informational-modeling system have improved response time and performance in the analysis, prediction, and planning of production situations, which in turn has improved decision-making by engineers and technicians when there are fl uctuations in the composition and quality of the iron-ore-bearing materials being smelted in the furnaces and changes in the market conditions.

Development of Steelmaking

BOF shop No. 2 at the EVRAZ ZSMK combine is working on increasing its capacity to improve productivity, changing over completely to continuous casting, improving the quality of the steel, and expanding the ranges of grades and product sizes. The combine's equipment as a whole is also undergoing an extensive upgrade, with this change including the black-plate production unit and the steelmaking and rolling divisions. The ultimate result will be a more diversified product mix.

Improving the Design of the Oxygen Lance and the Blowing Regime for BOF Steelmaking in the BOF Shop at the Azovstal Metallurgical Combine

Newly designed tips for oxygen lances and new blowing regimes for BOF steelmaking have been developed, tested, and introduced in the BOF shop at the Azovstal Metallurgical Combine (part of the Metinvest Holding Company, Ltd.). The new tips and regimes improve the performance indices for steel production under different charging and operating conditions in the shop.

Upgrading of a teeming crane in the BOF shop at the Chelyabinsk metallurgical combine

This article discusses a project being carried out in the BOF shop at the Chelyabinsk Metallurgical Combine to describe the experience of upgrading teeming cranes and increasing their load-carrying capacity. The cost of the upgrades was minimized by maximizing the use of the existing equipment and minimizing expenditures on equipment disassembly and assembly, commissioning, and startup.

排ガス情報を利用した転炉吹錬の計算機制御技術の開発

Mass spectrometer for analyzing the exhaust gas was mounted at No. 2 BOF shop in NKK Fukuyama Works, and the level-up of refining under the computer control system using the exhaust gas information has been achieved. As the result, the continuous estimations of bath temperature, [O] and [C] etc. have been enabled, and the accuracy of end point control has been much improved. Moreover, rationalizing such as reductions of flux and steel making time has been achieved. Especially the productivity has been remarkably improved and the production amount has reached to 330 000 t month under one vessel operation with two vessels.

Analysis of Converter Process Variables from Exhaust Gas

A new mathematical model of which the dynamic equations of material and heat balance are combined with the exhaust gas information obtained by mass-spectrometer has been established for the improvement of the end point control of BOF.The outline of the model calculation is as follows:(1) From the amounts of oxygen and submaterials charged into BOF and the composition and flow rate of the gas exhausted from BOF, the amounts of oxygen consumed on the surface of cavity of molten steel and of oxygen consumed by decarburization can be determined.(2) The transition of composition and temperature of steel bath can be estimated from the amount of oxygen calculated by the above way on the basis of model of reaction theory.At No. 1 BOF shop in Wakayama Steel Works, the model is now being used as the guide of the operation and contributes to the reduction of reblow ratio.

Mathematical Model of End Point Control for the Top and Bottom Blowing Process in BOF

For the endpoint control of the top and bottom blowing process in BOF, a simplified mathematical model which is suitable for the online application has been established by the following procedure.(1)The basic equations for the rates of oxygen consumption and temperature increase, which have the comprehensive characteristics in both the ranges of low and carbon high carbon contents, have been derived in the current work.(2) On the basis of the basic equations, the fundamental curves of oxygen consumption and temperature increase, which show the progress of blowing, have been determined by the analysis of the actual operational data. The fundamental curve of dephosphorization has also been determined in the same way.(3) A control model for the endpoint carbon content and the endpoint temperature of metal has been established by the use of the fundamental curves.At No. 2 BOF shop in Kashima Steel Works, Sumitomo Metal Industries, Ltd., the model is now being used for the automatic blowing and contributes to the reduction of reblow ratio and furnace refractories.