Browsing by Author "Mihailov E."
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Item Agglomeration process productivity increasing by a sinter mix preheating(2019-01-01) Shapovalov A.; Dema R.; Kalugina O.; Kharchenko M.; Nefedyev S.; Koldin A.; Mihailov E.To increase the productivity of the agglomeration process, preheating of the charge is proposed. A series of industrial experiments was carried out on the sinter machine No. 1 of the sinter department of JSC ``Ural Steel``. The dynamics of the sinter mix temperature during the technological stages of its preparation from pelleting to loading on pallets was studied, depending on a water temperature change during pelletizing. It was defined that for the winter working of the sinter department of JSC ``Ural Steel`` the water temperature increase which supplied of the pelletizer to moistening, for every 10°C, facilitates an increase in the temperature of the sinter mix on the pallets by 1.5-2.0°C. Therefore, for stable sinter mix production with a temperature higher than 55°C, it is necessary to supply a pelletizer with water, which temperature is at least 85°C. To implement the proposed technology, it is necessary to equip the sinter machines with water-heating recuperative heater, installed above the sintering machine behind the ignition hood and using heat, radiated from the surface of the sinter.Item An effect of heat insulation parameters on thermal losses of water-cooled roofs for secondary steelmaking electric arc furnaces(2016-06-01) Mihailov E.; Popgeorgiev P.; Ivanova M.The aim of this work is research in the insulation parameters effect on the thermal losses of watercooled roofs for secondary steelmaking electric arc furnaces. An analytical method has been used for the investigation in heat transfer conditions in the working area. The results of the research can be used to choose optimal cooling parameters and select a suitable kind of insulation for water-cooled surfaces.Item An information-analytical system of ranging analysis of cast iron grades(2015-01-01) Galkin A.; Mihailov E.; Shipelnikov A.; Blyumin S.In this article the information system is presented consisting of a database containing information about cast iron grades and a client application permitting adding, editing, deleting information from the database, as well as searching for cast iron grades by different parameters. The database along with the client application are an automated help system, which contains a chemical composition, mechanical properties, application and possible problems grades of cast iron. The client application allows analysis through cluster analysis of grades of cast iron on the chemical composition, mechanical properties, or both on the chemical composition and mechanical properties. This analysis identifies a close group of grades. In addition classification analysis to determine the expected properties of newly developed grades of cast iron. At realization cluster analysis were used to calculate the distance interval analysis techniques, for several grades of cast iron parameters specified intervals.Item CONDITION BASED ASSESSMENT FOR PREDICTIVE MAINTENANCE OF METALLURGICAL EQUIPMENT(2024-01-01) Mihailov E.; Petrova I.; Asenova M.The continuous nature of metallurgical technologies and the intensification of production increase the risk of damage to high-temperature equipment during the technological process. The destruction of the structural integrity of the refractory insulation of this equipment leads to the forced interruption of production and significant costs of emergency response and require measures to be taken to reduce the risk of such situations. An opportunity to solve these problems in the metallurgical industry is the introduction into the production process of sustainable systems for making informed decisions and predictive maintenance of equipment, based on continuous or periodic monitoring of the condition of refractory insulation of high-temperature furnaces and auxiliary equipment. Predictive maintenance of technological equipment and aggregates, based on an assessment of their current condition, extends their life, reduces downtime, maintains the optimal level of production, and guarantees compliance with the exact delivery time of production (raw materials, materials, energy). A procedure is presented for assessing the real condition of steel ladles based on periodic monitoring results as part of a decision-making system for predictive and safe use of their maximum resource.Item Decision support system for condition based maintance of steel casting ladles(2019-01-01) Petrova I.; Mihailov E.; Boshnakov K.In these paper are represented the results from the capability evaluation for establishing small size defects with crack shape in the area of the joints between the refractory bricks. For the investigation methods for complex approach are developed and embedded upon diagnostic and evaluation of the equipment condition, based on the use of the results from the thermographic measurements in combination with those from mathematical simulation of the transient heat transfer (describing the heat exchange processes and temperature fields depending on the insulation thickness, type of refractory materials and conditions of operation) and visual expertise. A multi-model approach has been suggested for evaluation of the defect criticality with the purpose of diagnostic of the condition and taking a decision on the maintenance and operation of the steel cast ladle. A Decision Support System for operation and maintenance of the steel casting ladles with the purpose of the safe utilization of their maximal resource is presented.Item DETERMINATION OF DEFECTS PARAMETERS IN INFRARED DIAGNOSIS OF STEEL LADLE WALL(2020-01-01) Petrova I.; Mihailov E.This publication presents the results from the capability evaluation for establishing the geometrical dimensions of the local defects in the wall of steel casting ladles during infrared diagnostic procedure. A 3D mathematical model of the ladle wall is used in this study. The analysis of the results demonstrates that the coordinates of the minimal and maximal value of the derivative of the temperature contrast in the fault area can be used as diagnostic indica-tors. Regression relations have been produced enabling the evaluation of the fault extend. This can be applied in diagnostic procedures for taking decisions during predictive maintenance of the equipment.Item Diagnosis of metallurgical ladle refractory lining based on non-stationary on-line data processing(2013-08-29) Petkov V.; Hadjiski M.; Boshnakov K.; Mihailov E.A new method for diagnosis of the remaining thickness of metallurgical ladle refractory lining working in a batch mode is proposed, where directly measured by a thermovision camera data about the amplitude and phase delay of the maximum surface temperature is used. Regression equations are obtained to determine the remaining thickness of the ladle refractory lining depending on the parameters of steady auto oscillations of the maximum surface temperature. It is shown that the data from nonstationary auto oscillations could be used for adaptation of the regression equations, predicting the remaining thickness of the ladle refractory lining in case of a local damage.Item Image processing for technological diagnostics of metallurgical facilities(2012-01-01) Doukovska L.; Petkov V.; Mihailov E.; Vassileva S.The paper presents an overview of the image-processing techniques. The set of basic theoretical instruments includes methods of mathematical analysis, linear algebra, probability theory and mathematical statistics, theory of digital processing of one-dimensional and multidimensional signals, wavelet-transforms and theory of information. This paper describes a methodology that aims to detect and diagnose faults, using thermographs approaches for the digital image processing technique.Item INFLUENCE OF Fe-Si-Mg-REM-INOCULANTS ON THE MICROSTRUCTURE OF IRON CASTINGS WITH VERMICULAR GRAPHITE(2022-01-01) Boldyrev D.; Nefedyef S.; Dema R.; Kharchenko M.; Chernyi S.; Suvorova E.; Mihailov E.; Latypov O.; Yordanova R.Complex additives, inherently, are not only inoculants, but also complex alloyed products having their own specific structure, whose influence on the crystallization processes of an alloy is actually not taken into account or studied. The work investigates inoculants made by two technologies. According to the first technology, an inoculant is made in the form of an ingot by crystallizing melt in a mold, according to the second technology, an inoculant is made in the form of an extra-thin ingot (0.5 - 3 mm thick plates) by continuous casting and freezing on water-cooled molds (drums). A phase electron and X-ray spectral analysis of the inoculants’ structure are carried out to produce vermicular graphite iron. Thus, the paper presents a research on the microstructure of CGI castings “Countershaft” molded in a ladle with the use of inoculants and describes specific features of their influenceItem Modeling of biomass gasification(2014-02-25) Petkov V.; Mihailov E.; Kazakova N.Optimal conversion of chemical energy of the biomass or other solid fuel into the desired gas depends on proper configuration, sizing, and choice of gasifier operating conditions. Optimum operating conditions are often derived through trials on the unit or by experiments on pilot plants. Simulation, or mathematical modeling, allows the designer or plant engineer to reasonably optimize the operation or design of the plant. The good mathematical model can: find optimum operating conditions or a design for the gasifier, provide information on extreme operating conditions (high temperature, high pressure) where experiments are difficult to perform, provide information over a much wider range of conditions than those obtained experimentally, better interpret experimental results and analyze abnormal behavior of a gasifier, if that occurs. The equilibrium model is independent of the gasifier design which can make them more suitable for a system study of the most important process parameters. The use of an equilibrium model assumes that the residence time of the reactants in the gasifier is high enough to reach chemical equilibrium. For established biomass ultimate analysis, temperature of gasification air and temperature of produced gas, combining the mass balance equations with the equations for the equilibrium constants and equation of energy balance, the equivalence ratio (ER) and composition of produced gas can be obtained. A mathematical model for investigation of the influence of temperature of the produced gas and temperature of gasification air on the process parameters was developed. It can be used for estimation and design of gasification equipment.Item Modeling of the thermal state of a hot rolled strip in an accelerated cooling process Part 2: A calculation of the thermal field of the strip. Results and conclusions(2020-01-01) Koldin A.; Dema R.; Nalimova M.; Shapovalov A.; Mihailov E.The physical and mathematical model of cooling a moving steel strip by a water jet system is described in Part 1 of this paper. The temperature distribution along the steel strip motion direction and at its cross section is obtained. Two main variants of the relative position of the upper and the lower jets are considered. An analysis of the jets pattern effect on the steel strip temperature field is performed. The validity of the heat transfer mathematical model and the program for calculating the temperature field is verified by comparing the results of the functioning Hot Rolling Mill 2000 of the Public Joint-Stock Company «Magnitogorsk Iron and Steel Works» with the calculated data referring to a specific steel grade. The transverse temperature distributions for different layouts of the jets as well as the longitudinal distributions of the maximum temperature differences of the steel strip sections are obtained. Results referring to the steel strip temperature field calculation in view of the temperature dependence of the thermo-physical properties of low-carbon steel are presented in this communication. Conclusions on the need of considering the temperature dependence of the steel thermo-physical properties when predicting the final temperature are drawn based on these calculations.Item Modeling of the thermal state of the hot rolled strip in the accelerated cooling process part I: Heat transfer model(2019-01-01) Koldin A.; Dema R.; Nalimova M.; Mihailov E.; Shapovalov A.; Kharchenko M.This article presents a solution to the problem of determining the local heat flux density during cooling of a high temperature surface with a water jet. The solution takes into account the flow rate of the water jet and the diameter in the conditions of a transient boiling fluid. A local physic-mathematical model of moving strip's laminar cooling on a discharge roller table was compiled. Regions of jet impingement, film boiling, convective and radiative cooling in air are considered in this model.Item Modelling of biomass pyrolysis(2015-01-01) Kazakova N.; Petkov V.; Mihailov E.Pyrolysis is an essential preliminary step in a gasifier. The first step in modelling the pyrolysis process of biomass is creating a model for the chemical processes taking place. This model should describe the used fuel, the reactions taking place and the products created in the process. The numerous different polymers present in the organic fraction of the fuel are generally divided in three main groups. So, the multistep kinetic model of biomass pyrolysis is based on conventional multistep devolatilization models of the three main biomass components - cellulose, hemicelluloses, and lignin. Numerical simulations have been conducted in order to estimate the influence of the heating rate and the temperature of pyrolysis on the content of the virgin biomass, active biomass, liquid, solid and gaseous phases at any moment.Item Numerical investigation of thermal and fluid dynamic behavior of solar chimney building systems(2014-02-25) Manca O.; Nardini S.; Romano P.; Mihailov E.In this paper a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The analysis is carried out on a three-dimensional model in air flow and the governing equations are given in terms of k-ε turbulence model. Two geometrical configurations are investigated: 1) a channel with principal walls one vertical and the other inclined and 2) a channel with vertical parallel walls. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0,20 m for the vertical parallel walls configuration and at the inlet 0,34 m and at the outlet 0,20 m for the inclined ones. The problem is solved by means of the commercial code Ansys-Fluent and the results are performed for an uniform wall heat flux on the vertical wall equal to 300 and 600 W.m-2. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles in order to evaluate the differences between the two base configurations and thermal and fluid dynamic behaviors. Further, the ground effect on thermal performances is examined and discussed.Item Possibilities for saving energy in ferrous metallurgy: Integration of technological processes(2016-01-01) Mihailov E.; Petkov V.; Ivanova M.; Stoyanova B.One of the main factors having a significant effect on fuel and energy saving in the production of rolled ferrous metals is matching the operation of the continuous casting machines with that of the re-heating furnaces so called continuous technologies in the form of direct rolling or hot charging. In order to investigate the heat exchange processes, the opportunities for enhancing the energy efficiency and determining the optimal parameters of the flat product production process in ferrous metallurgy, some mathematical models of metal solidification and cooling in a continuous steel casting machine were determined as well as a mathematical model of metal heating in the re-heating furnaces. For efficient implementation of such technologies one common algorithm was built on the basis of the individual mathematical models, representing the continuous casting - rolling mill complex control technology, dynamically matching the operation of the individual units to the actual production conditions in on-line mode. The developed algorithm can be used as part of a system for analyzing the thermal condition of the blocks at any single moment for the purpose of optimization of the units' operation within the whole technological process. As a conclusion, considering the original developed algorithm, a 21-51% energy saving was noticed.