Heat power analysis of performance indicators blast furnace No. 3 PJSC «AZOVSTAL IRON & STEEL WORKS» with natural gas and pulverized coal after oven overhaul of blast furnace

In 2019, according to the technological assignment of the Iron and Steel Institute (ISI), the reconstruction of the blast furnace (BF) No. 3 of PJSC «AZOVSTAL IRON & STEEL WORKS» was carried out for the long-term energy-efficient production of pig iron with using pulverized coal (PCI) up to 180 kg/t with a change in the profile according to the technological task of ISI. The design of the BF No. 3 profile corresponds to the best world solutions for furnaces efficiently working with pulverized coal, and the furnace was equipped with five mathematical models of ISI («Horn», «Mine», «Heat losses», «Loading», «Slag»). Specialists of ISI developed recommendations and carried out technological support for the operation of BF No.3, which made it possible to increase the removal of pig iron from the design 2.1 t/m3 to 2.27 t/m3 and achieved the best indicators in the blast furnace workshop in terms of coke and equivalent fuel consumption by increasing the productivity of the burden system, using a rational burden loading matrix, using a rational pressure drop in the furnace, which allows the maximum use of the power of the blower machine, forcing the furnace with technical oxygen and other measures. Using the heat power model of I.D. Semikin was made a comparative analysis of the best for six months indicators of thermal performance and technical and economic indicators of BF №3 of PJSC «AZOVSTAL IRON & STEEL WORKS», with a volume of 1800 m3 before (work with natural gas) and after major repairs (work with pulverized coal and with natural gas). Using the exergy method of analysis based on the results of calculating heat and power balances, a comparative analysis of changes in the energy efficiency and environmental indicators of BF No. 3 before and after its major repairs was carried out. It shown the expediency of integrated mastering of operating modes and modernization of the blast furnace for long-term and energy-efficient operation with pulverized coal. It disclosed the mechanism for improving the technical and economic indicators of work after major repairs by changing the heat and power conditions of the blast furnace. Its shown Improvement of exergy efficiency factor and environmental performance of BF No. 3 after major repairs.

Features of technological schemes and equipment for the production of thin strips on hot strip mill

The purpose of the work is to determine rational schemes for their production by analyzing the technological and design parameters of a number of broadband mills that roll hot-rolled strips less than 2,0 mm thick. It is shown that at present there is a constant increase in the production of extremely thin hot-rolled strips (0,8-1,5 mm thick), which can be used instead of more expensive (by $ 20-30 per ton) cold-rolled strips. The development of the production of hot-rolled strips of such a thickness is limited by a number of problems, in particular, the low temperature of the end of rolling (760-820 °C), which leads to a significant decrease in the ductility of the rolled stock; limiting the rolling filling speed, which does not allow increasing the temperature of the end of rolling the complexity of controlling the cross-sectional profile and flatness of the strips. Using mathematical modeling, it was found that the strip thickness and rolling speed have the greatest influence on the temperature of the end of rolling. The thickness and temperature of the rolls at the entrance to the finishing group of stands have a lesser effect. A decrease in the number of stands in the finishing group increases the temperature of the end of rolling at a constant thickness of the rolls, but when the thickness of the rolls changes in accordance with the number of stands, the effect is significantly reduced. The most favorable technological parameters for the production of extra-thin hot-rolled strips are provided by casting and rolling units, which are characterized, in comparison with broad-strip mills, as a rule, by a greater thickness and temperature of the rolls (or continuously cast slabs) and a smaller number of stands. An increase in the thickness of billets (slabs) requires an increase in the permissible values of the energy-power parameters of rolling, as well as the use of special solutions that will ensure minimal heat loss by the rolls before entering the finishing group of stands. Calculations show that, based on the reliable maximum refueling speed of hotrolled strips (10-11.5 m / s) achieved in the industry, the minimum thickness of strips with high plastic characteristics is: for broad-strip mills - 1.9-2.0 mm; for casting and rolling units, depending on their type - 1.3-1.6 mm.

Study of the conditions of mixing and thermal state of the melt during degassing of steel on a chamber (VD) type equipment

Increasing requirements for the quality of metal products are regulated by international, state standards and other documents, in particular, on the content of gases and non-metallic inclusions in metal. In some cases, normative documents stipulate the need for degassing of steel with high quality requirements, including flock-sensitive grades. For this purpose, equipment for chamber (VD, VOD-types) degassing is used at metallurgical and machine-building enterprises of Ukraine. Due to insufficient knowledge of the process of degassing, real numerical studies have been carried out. As the object of study, we determined the installation for the degassing of the Mannesmann Demag company of the above type with a 60t bucket with reinforcement of the lining in impact zone of the PJSC «DSS» enterprise. Based on the initial data of the degassing process, a mathematical model was developed by DSTU to consider heat and mass transfer processes in a liquid metal bath during its degassing. Specialized software has been created that allows you to take into account the changing technological parameters during metal processing in vacuum, the configuration and capacity of the bucket bath. Employees of the ISI of NASU using the database on out-of-furnace processing of electric steel at PJSC «DSS» for the previous period determined that the values of the mass of the heats were in the range from 54t to 66t. Given the previously established that the intensity of argon purging through the bottom (s) tuyeres (s) and different masses of metal in a ladle of the same capacity from smelting to smelting create different hydrodynamic and thermal conditions for metal processing processes in the bucket, and the above information required an additional evaluation of the process degassing. At the first stage of numerical studies, the hydrodynamic conditions of degassing in a metal bath were studied taking into account the listed influence factors. Contour diagrams of the vertical component of the velocity of metal flows in different vertical axial sections of the bath were constructed at 20 minutes of degassing (at a pressure of 1 mm Hg). In the given vertical sections, the descending metal flows are concentrated in the upper half of the bath, and the ascending flows in its lower half. It was noted that with an increase in the flow rate of argon for mixing with the same mass of smelting, the absolute values of the vertical component of the metal velocity increase, and with the same consumption of argon, it decreases with an increase in the mass of smelting, which is similar to processing conditions at normal atmospheric pressure. At the second stage of research, thermal conditions were studied during the degassing of steel at a similar reduced pressure. Contour diagrams with isotherms (average metal temperature in the ladle) are constructed depending on the duration of the degassing process and argon consumption. A comparative assessment of the thermal conditions during degassing on chamber-type equipment and on LF (at normal pressure) with operating conditions at a similar initial temperature and the corresponding argon flow rate was made. An increase in heat loss by metal was found with an increase in argon consumption and with a decrease in smelting mass. Thus, it has been established that the mixing features of the metal bath create different hydrodynamic conditions for the degassing process on the chamber-type equipment, affect its thermal state, which probably can affect the efficiency of gas removal.

Information and mathematical support of cast iron desulfurization technology

The concept of the expert decision-making system for technological process management, created earlier at the Iron and Steel Institute of the National Academy of Sciences of Ukraine, provides for the choice of a rational technology for out-of-furnace desulfurization of cast iron. The purpose of this work is the further development of information and mathematical support of the expert system module for out-of-furnace processing of cast iron by co-injection of magnesium and lime in the framework of the target project to create end-to-end technology for high quality metal products. An integrated database of cast iron desulfurization process of a number of metallurgical enterprises of the People's Republic of China and the domestic DMK plant is presented. Based on the analysis of technological data, empirical equations were obtained to determine the final sulfur content in the cast iron melt, as well as the expression for estimating the specific consumption of metallic magnesium in the reagent. The developed models for calculating the specific consumption of reagents are the basis of the algorithm for calculating the indicators of the process of desulfurization of cast iron with co-injection of magnesium and lime. The input parameters are: temperature of cast iron, mass of cast iron, chemical composition of cast iron and slag, sulfur content initial and final, the proportion of magnesium in the reagent. Replenishment of the database with information on the technology of desulfurization of cast iron with a mixture of magnesium and lime allowed to clarify the existing and obtain descriptive models for these reagents. The developed information and mathematical support of the subsystem of out-of-furnace processing of pig-iron takes into account material and energy costs for redistribution, providing resource savings and the required quality of metal products.

TECHNOLOGICAL DEVELOPMENT OF FERROUS METALLURGY OF UKRAINE IN THE MEDIUM-TERM AND LONG-TERM PERSPECTIVE

The purpose of the study is to identify current trends in metallurgical technologies, taking into account environmental problems. The world is undergoing major changes in environmental policy, which has become an integral part of industrial policy and international trade. The analysis shows a certain connection between the increase in Earth's temperature and the growth of steel production in the world. Therefore, the Paris Climate Agreement, which was supported by most industrialized countries, is based on the idea of limiting and reducing greenhouse gas emissions by industrial enterprises. On the one hand, industrial emissions undoubtedly affect the ecological state of the environment. On the other hand, a sharp reduction in production emissions significantly increases financial costs. In the world, environmental requirements for metallurgical processes are gaining such a level that threatens the prospects for the development of metallurgy. It is shown that the choice of the optimal path of ecological development requires the search for new solutions to increase the level of implementation of ecological innovations by Ukrainian enterprises. To identify the impact of production technologies of different types of metallurgical products, the method of expert-mathematical evaluation using the Harrington desirability function was used. It is shown that for rolled products the rating means «satisfactory» or «good». The situation with the production of iron ore, pig iron and steel is worse - here a comprehensive assessment shows the value of «unsatisfactory» and «satisfactory». This thesis is confirmed by the fact that investments of ecological orientation of the Ukrainian metallurgical enterprises are now directed on improvement of ecological indicators in the specified directions. Prospects for the development of metallurgy in Ukraine should be associated with the implementation of new technical solutions, in particular those developments that are in the stage of exploratory research and experimental samples. Scientific developments of the Iron and Steel Institute of the National Academy of Sciences of Ukraine, aimed at reducing energy consumption and improving the environmental performance of metallurgical production

Analysis of the amount of retained austenite in the structure of steel rolls for sheet rolling

The amount of residual austenite in martensitic roll steels is an important technological parameter of heat treatment, which affects the performance properties of the rolls. But determining its amount in roll steels is a complex and not fully solved scientific and technical problem. The aim of the work was to comparatively analyze the amount of residual austenite in the structure of alloy steel rolls by X-ray diffraction, ultrasonic methods and metallography analysis. However, the qualitative difference of microstructures in the content of the light phase - austenite, confirms the results of X-ray diffraction analysis. No correlation was found between the austenite content in the samples and their hardness. It was found that the X-ray method, based on the comparison of the intensities of the α- and γ-phase lines of iron, overestimates the value of the amount of residual austenite in some samples of roll steels. The results of the analysis of residual austenite by ultrasound rate showed better convergence. The amounts of residual austenite, calculated on the sample of stainless steel (100% γ-Fe), had reduced values (2.6-4.5%). The most accurate results on the amount of residual austenite gave the use of the established regression dependence with the selected standard (2.7-7.8%). This dependence is obtained at the speed of sound in austenite ~ 4000 m / s. It is determined that the application of the ultrasonic method allows to determine the content of residual austenite in the samples of roll steels quite quickly and accurately.

Development of the model complex of the expert system of control and management of the slag mode in modern mixed blast furnace conditions

The aim of the work is to develop physicochemical bases for predicting the technological properties of finite blast furnace slags, algorithmic and software for the subsystem for diagnosing the slag regime of blast furnace smelting. Based on experimental data on the properties of natural finite blast furnace slags, predictive models for calculating the viscosity of the final slag at a temperature of 1400-1550 °C were improved by including in the model structure an integrated slag melt index of the parameter Δe, which reflects the individual effect. Using the integral parameters of the slag melt characterizing the charge state of the system Δe and the structure of the slag ρ, an equation was developed to determine the viscosity of the slag at any temperature corresponding to the slag temperature at the cast iron outlet. As a result of analytical research, a predictive model for determining the enthalpy of slag depending on the integral parameters Δe and ρ and the temperature of the melt has been developed. It is shown that the viscosity characterizes the fluidity of the slag and provides desulfurizing and drainage properties. The calculation of the viscosity for the specified production of pig iron by the chemical composition of the slag is carried out according to the basic model of slag in a conditionally "homogeneous" state and taking into account its heterogeneity. This takes into account the presence of macroheterogeneous inclusions formed when using coke with low strength characteristics and due to incomplete combustion of pulverized coal fuel in the blast furnace. The improved models for evaluating the viscosity and enthalpy of the final slag are software implemented in the new version of the «Slag» system for operational control of the slag mode of blast furnaces in Ukraine. Rapid assessment of the slag mode using the «Slag» system as part of the DCS allows you to effectively and at a modern level solve the problems of optimizing the slag mode and the quality of pig iron in modern conditions of blast furnace smelting.

Physicochemical prerequisites for the development of complex relationships between the properties of metallurgical melts in order to predict the regularities of the distribution of elements during the finishing of steel on a ladle furnace

The aim of the work is to create a base of physical and chemical knowledge with blocks of operational analytical expressions that predict the complex properties of metal, slag melts and additives. The base is designed for a scientifically sound product of control actions for the purpose of directed formation of high-quality metal when bringing steel to the UCP. As a basis for describing the processes of interaction of phases in the work used the original method of physico-chemical modeling of the composition and properties of metallurgical melts, as well as experience in creating information and analytical systems for forecasting and controlling the smelting process. Models for forecasting the properties of steels and alloys for special purposes (chromium-nickel, iron-carbon steels of a wide range, aluminum, magnesium, heat-resistant nickel alloys) and ferroalloys of domestic production have been developed. High accuracy of forecast and stability of analytical expressions is obtained, which is confirmed by comparison with calculations on a software computer complex. The possibility of using interatomic interaction parameters to determine the activities of components in binary and multicomponent metal systems is shown. On the example of steel 09G2C, the structure of models for the distribution coefficients of elements, in particular Si and Mn, between the products of smelting during ladle processing was generated. The structural similarity of the models for determining the distribution coefficients of these elements is revealed, which is due to their proximity to the structure of clusters of one-component melts. The results of the work should be recommended for integration in ASNI and ASUTP of steel production in order to form a competitive end product.

Research on the physical model of features of the behavior of a two-phase bath at top blowing through a tip with folded nozzles

At the previous stage of research using a physical model of an oxygen converter, the results of studying the features of purging a single-phase liquid through a single composite nozzle were obtained. The aim of this work was to study the behavior of a two-phase bath using a multi-nozzle lance with folded nozzles. At this stage of the study, silicone oil was used to simulate the slag phase of a two-phase bath. The peculiarities of the influence of experimental nozzles on the processes of mixing and foaming of two phases were studied. Three variants of the experimental nozzle design were investigated: a combination of a conventional and a slit nozzle with a ratio of their areas of 1: 1, 1: 2 and 2: 1. It is established that the use of a tip with four nozzles during purging from above promotes the active formation of a two-layer foamed emulsion on the surface of the bath. Comparison of the operation of the tip with folded nozzles with a tip with a cylindrical indicates more active mixing of the two liquids and the formation of a more stable and much higher layer of foamed emulsion. The most favorable conditions for the organization of full mixing of the two phases in the converter bath are formed when using folded nozzles with a slit size of about 35% and a ratio of slot and nozzle area of 1: 2. To intensify the mixing processes in the upper zone of the unit, it is most expedient to use folded nozzles with a larger fraction of the slit (up to 65%) and the ratio of the areas of the components of the nozzle 2: 1. The use of nozzles with equal areas of components in the studied conditions does not have a positive effect on metabolic processes in the converter bath.

Comparative study on a physical model of specific features of top blowing through the tip with folded nozzles when blowing single-phase liquids

The aim of the work was to study the nature and peculiarities of the interaction of the lance of the converter lance flowing from the folded nozzles with a liquid bath of single-phase liquid. The study was conducted on the basis of a physical model of the converter with top purge. The design of a folded nozzle consisting of a central cylindrical nozzle and a slit annular nozzle located around it is investigated. A visual and video recording comparative study in comparable operating conditions of the folded nozzle with different design features, in particular, with an additionally deepened central nozzle in the folded nozzle and a protruding central nozzle; with operation of one cylindrical nozzle, four nozzles of identical section and an annular slot nozzle. It is established that the jet flowing from the folded nozzle differs in the possibility of more active interaction with the liquid bath than one cylindrical nozzle and four nozzles of equivalent plane. The depth of penetration of the jet into the bath liquid, the parameters of the formed hole of the jet penetration, the oscillations of the bath were studied. It is established that the peculiarities of crater formation in the liquid, characteristic when using a folded nozzle, are due to the use of a slotted annular part of the nozzle. The wider crater is due to the use of a slotted annular part of the nozzle. It is shown that the structural variants of the folded nozzle with a recessed or protruding central nozzle do not increase either the depth or the width of the formed crater. It is also established that the peculiarities of crater formation in the liquid when using a folded nozzle are due to the use of a slotted annular part of the nozzle. To form the best purge conditions, the slice of the slotted annular part should be flush with the slice of the central nozzle. With this design, the jet pulse is maintained for a longer period compared to the use of only one central nozzle, probably due to the protection of the central jet, and due to its deep penetration properties.