Tuyere Zone Research Articles

Assessment of the effectiveness of technological measures to extend the campaign of blast furnace No. 5 of PJSC Severstal (2006 – 2024) based on an examination of its working space during a first-category overhaul

The paper presents the findings from the study of the working space of blast furnace No. 5 of PJSC Severstal during its first-category overhaul in 2024 lasting 17.46 years, which significantly exceeded the standard service life. The effectiveness of technological measures taken to extend the furnace’s campaign from 2006 to 2024, aimed at protecting the refractory lining in critical areas such as the hearth, lower shaft, and the upper bosh, was evaluated. The residual thickness of the refractory lining in the shaft, hearth, and metal receiver is analyzed, and maps showing the actual thickness of the lining across different sections are generated. The measured maximum wear of the shaft refractory lining is 344 mm (37.4 % of the original value); the measured maximum wear of carbon blocks in the area of cesspool openings – 313 mm (23.4 % of the original block size). In the upper part of the hearth, the minimum residual thickness of refractories with an Al2O3 content of 43 % is 220 mm or 31.9 % of the initial value. The paper also discusses safe remote measurement methods, including 3D laser scanning of the furnace shaft during the removal of residual charge materials. It highlights the advantages of ground-based laser scanners in capturing dense, high-quality 3D geometric data. Additionally, the paper describes the experience of remotely measuring the residual thickness of carbon blocks around the raking openings. Comparisons are made between the actual residual thickness of the refractory lining in the hearth, bottom carbon blocks, and high-alumina refractories of the tuyere zone, and the results obtained using ultrasonic echo-sounding technology (AU-E) during the furnace’s operation. The paper also includes a description of the stress wave propagation technology, which utilizes data analysis in the time and frequency domains to determine lining thickness and detect anomalies. The results of the current and previous blast furnace campaigns are compared in terms of pig iron production, the number of cooling system failures, and refractory wear across the entire working space of the furnace. The total production of pig iron in the 2006 – 2024 campaign, related to the furnace area, amounted to 420.0 thousand tons/m2 and exceeded the figure for the previous campaign by 1.90 times.

Analytical assessment of the behavior of biochar, as an additionally injected fuel, under conditions of blast-furnace smelting

The relevance of the issue of using carbon-neutral types of raw materials in metallurgical production is considered. One of the promising directions is the use of biomass pyrolysis product - biochar, which has a high carbon content and, as a result, a calorific value relative to biomass. A comparative analysis of the main characteristics of biochar and pulverized coal injected fuel (PCI) produced from "T" and "G" coal grades was carried out. Biochar contains less carbon and ash with a higher content of volatile substances compared to PCI. To study the combustion process of biochar in the blast furnace tuyere zone, a study of the kinetics of its combustion in a laboratory installation for the solid fuel combustion was carried out. In order to adapt the obtained biochar combustion kinetics to the conditions of the blast furnace tuyere zone, a similar study was carried out for the considered types of pulverized coal. The results of the experimental study of the combustion kinetics of the studied types of fuel are presented, according to which the fuel combustion process in front of the tuyeres consists of two phases: the first one is accompanied by a high oxygen consumption for the combustion of volatile substances; the second one is characterized by slow afterburning of the carbon residue. The longest burning time of 0.6 g fuel at a temperature of 1200 °C is 762 s for T-grade PCI. Pulverized coal grade “G” and biochar have the similar combustion kinetics, but the latter burns faster: grade “G” pulverized coal burns in 369 s, and biochar in 162 s. The conclusion is made about a higher degree of biochar afterburning in the conditions of the blast furnace tuyere zone in comparison with pulverized coal fuel.

Investigation of factors affecting the safety of a blast furnace operation

Blast furnace air tuyeres are one of the most important elements of the blast furnace design, determining the efficiency of its operation. Formation of “dead man” on the hearth bottom, or in other words, ore-coke sinter is considered as an unfavorable factor affecting the safety of large-volume blast furnaces. The main factors influencing the formation of "dead man" are violation of normal gas distribution and "cooling" of the blast furnace. This work is devoted to determination of the effluence procedure of the gas-coal flow using the Glinkov criterion. It is shown that a bubble effluent flow prevails in large-volume blast furnaces, i.e. a stable gas zone does not form in front of the tuyere tip. The bubble effluence mode of the gas-coal flow contributes to the growth of "dead man", which, as a result, can lead to an emergence situation. Prerequisites for burnout of the walls of the tuyeres are created in these conditions, while frequent terminations of the blast furnace operation to replace the tuyeres disorganize the melting technology. The maximal temperature in the tuyere zone has been calculated in this work. It exceeds the theoretical combustion temperature in the blast furnace hearth, what can adversely affect its operation, because the likelihood of an explosion of the blown natural gas will increase. The resulting heat flow on the tuyere tip was calculated in the work, taking into account the "dead man" formation. This flow exceeds the allowable one, what provokes a massive burnout of the tuyeres and the tuyere cooler.

On-line detecting the tuyere coke size and temperature distribution of raceway zone in a working blast furnace

Developing the new injection energy including full oxygen, hydrogen and natural gas injection in raceway zone of blast furnace is one of the effective and feasible measures to reducing the carbon emission and satisfying the carbon neutral plan. While the tuyere combustion condition under all-coke smelting model of blast furnace could supplying a direct manner to observing how the new energy affecting the coke combustion and temperature variety process during raceway process. In this paper, the tuyere coke particle sizes and raceway temperature distribution, as the representative parameters of raceway combustion, are online detected at the same time in a working 2500 m3 blast furnace under the all-coke smelting model by machine vision, Fully Convolutional Networks (FCN), and colorimetric thermometry method (CTM). The results showed the same ranges compared to research of coke sampling and average temperature in tuyere zone. And the calculation of coke belt length (CBL) in raceway zone by empirical model were modified to evaluate the coke combustion and size decaying under all-coke smelting model. Which could not only benefit to study the coke cracking and formation mechanism in the raceway zone in a blast furnace after the new energy injection, but also provide a new method to online detect particle size and temperature distribution at the same time in complex environment by deep learning and machine vision methods.

Experimental Studies of Structural and Technological Parameters of a Downdraft Gasifier Based on Plant Biomass

The relevance of the study is conditioned upon the need to develop and implement structural and technological solutions to improve the efficiency of the chemical and thermal conversion of biomass into combustible gas. Within the framework of the above, the authors of this paper have designed a downdraft gasifier running on plant biomass. The presented research links the heat quantity received from the utilisation of syngas produced during the gasifier operation cycle with the parameters of the gas blow regime and the physico-chemical properties of biomass. For an in-depth study of the influence of the gas blow regime on the yield and calorific value of syngas produced from biomass, the authors introduce the concept of the blow coverage quality coefficient. This coefficient describes the quality of the cross-section coverage of the gasification chamber neck with gas currents of the tuyere zone. The purpose of this study is to establish the influence of the blow coverage quality coefficient, the volume of blow gases and the void ratio of the bulk biomass layer on the heat quantity received from syngas produced during the gasifier operation cycle. A multi-factor experiment was planned and performed, which relates the dependent factor to variables, and the corresponding response surfaces were constructed. The research findings are that the maximum value of the heat quantity received from the utilisation of syngas produced during the one-hour gasifier operation cycle was 519 MJ. This value is achieved with 0.8 blow coverage quality coefficient and a blow gas volume of 47.4 m3/h and 46.75% void ratio of the bulk biomass layer. The measurement results are highly consistent with the calculated data. The coefficient of determination was R2=0.983. The practical value of this study is to substantiate the rational design and technological parameters of the downdraft biomass gasifier operation, which will increase the efficiency of biomass energy production. The findings presented in this study can be used both to design new gasifiers and to improve the efficiency of the available ones

The influence of ash-content pulverized coal particles on their burning characteristics in tuyere hearth

Effect of ash content in coal dust on the burning characteristics in tuyere zone of blast furnace is studied. The ash is considered as an individual fraction in addition to two fractions of coal dust. It is shown, that the variation of pulverized coal fractional composition allows increase of carbon monoxide yield and fuel particles burnout. The presence of ash results in oxygen zone extension and increase of coke residue burnout. At the same time the total coal dust burnout is lower than that of low-ash coal. Fine pulverized coal combustion is characterized by increased production of carbon monoxide and reduction of carbon dioxide percentage.

Effects of single lance configuration on coal combustion process in tuyere from viewpoint of coal plume

Pulverized coal utilization in the blast furnace is decided by the particle flow and combustion behaviors in the raceway. Under a specific operating condition, these behaviors are directly related to the lance configuration in the upstream tuyere zone. Focusing on single straight lance, six types of single lance configurations were designed by assembling four parameters in different ways. These four parameters are the lance diameter, lance insertion angle, and the horizontal and vertical distances from the lance tip to the tuyere tip. With different lance configuration schemes applied, the pulverized coal combustion process in the lance–blowpipe–tuyere zone was simulated. The simulation results regarding particle diffusion and combustion behaviors were characterized by three indicators from the viewpoint of a coal plume. They are the plume diffusion angle, diffusion uniformity, and the average plume temperature at the tuyere outlet. To promote coal utilization, the values of these indicators under different configurations were analyzed, yielding two optimal configurations. The first one is to reduce the lance length immersed in the blowpipe–tuyere by 100 mm. The other is to increase the horizontal distance from the lance tip to the tuyere outlet by 50 mm, and the insertion angle to 11° with the lance tip located at the tuyere centerline. The findings can enhance the understanding of the influence mechanism of lance configuration on the coal utilization and provide guidelines for the design of new lance configurations.

Reducing the carbonitride formation risk with increasing titanium dioxide content in the blast furnaces charge of JSC EVRAZ NTMK

Analyse of the blast furnace charge chemical content changing with the JSC EVRAZ NTMK raw materials base alteration was carried out. That expected change would result in TiO2 content increasing in the blast furnace slags. That increasing would lead to carbonitride formation in the upper levels of the blast furnace, which reduce technical parameters of the blast furnace operation by reducing effective volume of the furnace and derange regular charge moving. Possible ways of that problem solving was shown. It was proposed the complex technology, that affect 3 technological stages: agglomeration, blast furnace process and out-of-furnace treatment of steel. Converting of TiO2 into CaO·TiO2 allows to delay carbonitride formation due to increasing required temperature for that process. In that case, carbonitride formation would move to the tuyere zone of blast furnace, where it increase lining durability. The proposed technology was industrially tested, and the main idea was proved. Few problems were found during industrial tests, but theoretical solving of them was proposed.

From Henry Bessemer’s invention to comprehensive converter process optimization

The Bessemer process enabling to produce high-quality steels was implemented at steel mills of the Urals region more than 200 years ago. At the beginning of the 20th century, the process was modified by scientists from the Mining Institute and was then adopted by copper and nickel alloy producers. The converter process became one of the key processing stages with Russian copper and nickel smelters. This paper examines certain ways to improve the tuyere air flow in a horizontal converter. The authors came up with a generic equation for calculating specific blast air pressure and discuss the use of hydrothermal and aerodynamic techniques for tuyere purging. The blast air limit was determined for a horizontal converter that is characterized with massive melt ejections. The authors demonstrate that, in spite of all the process and design improvements, the modern converter process still has three major drawbacks. They include process cycling, the gas ductwork not being completely tight, unbalanced thermal and chemical status of the vessel leading to excessive thermal and chemical loads on the tuyere zone and incomplete slag formation in zones that are farther from the tuyeres. Research work is ongoing on a novel continuous converter design which involves the use of special-design unsubmerged tuyeres. Such tuyeres produce spatially oriented high-pressure blasts which enable consistent rotation of the molten matte in a tight cylindrical vessel.

Еfficiency increase of powdered coal application at hot metal production and limestone calcination under unstable technology conditions

Operation of Ukraine ferrous metallurgy under conditions of dependence on import and instability of energy carriers supply, shortage of investments in modernization of production equipment, make the matter of cooperation between steel-works and research organization particularly actual. Basic results of cooperation between Z.I. Nekrasov Institute of Ferrous metallurgy, NAN of Ukraine and Dnepr steel-works in 2017–2019 on blast sfurnace operation pefection and technology of powdered coal injection into rotating limestone calcination furnaces. Results of the finding of the powdered coal optimal consumption shown, which ensure a high efficiency of the coke substitution, reaching of maximum possible blast furnace productivity as well as satisfactory utilization degree of the reducing gas ability. Results of implementation of a complex of measures presented, which ensure a rational distribution of the powdered coal by BF air tuyeres for making the heat conditions of the tuyere zone even by the blast furnace circle. Efficiency of application of technology of joint injection the powdered coal and natural gas was shown, which is achieved by improving the powdered coal combustion conditions in case of increase their mixing degree. Recommendations quoted for blast furnaces starting-up after their idling for a period exceeding the permissible one, without tapping the plug hot metal. The recommendations ensure an accident-free putting a blast furnace into operation followed by reaching planned parameters. Results of usage sensors information, measuring temperature of gas flow above the charge surface presented. The results allow to prove the correction of blast furnace charging mode by an expert module, generating correction impact to support control actions by technological personal. A complex of measures formed to prevent a disturbance of a blast furnace running in case of powdered coal injection in an amount exceeding 140 kg/t of hot metal and without application of special washover materials. The results of efficiency of the mastered technology, envisaging application manganese-bearing materials at a constant base, were shown. Results of diagnostics of workability of the facility for powdered coal injection into rotating limestone calcinating furnace presented, followed by elaboration recommendation on correction parameters of injection facility operation.

Elaboration and realization of new approaches to diagnostic and control of blast furnace heat

Under conditions of unstable supply of quality charge materials and technological fuel, the elaboration of new effective means of blast furnace heat control becomes actual for reaching acceptable technical and economic indices of its operation. Results of the studies carried out at the BF No. 3 of Enakievo steel-works (EMZ, Ukraine) during the period from October 2011 until December 2016 presented. During the period, various fuel additives to the blast were used within a wide range of their variation, and composition of charge materials was characterized by numerous components and variable quality. In the charge content, various additives were used: iron ore, limestone, BOF slag, briquettes of pellets siftings, manganese-containing additives. The new approach to the selection of rational charging programs was justified, providing stable economic BF running under variation of heat technological conditions. For the first time the temperature indices of estimation of gas stream distribution along the furnace radius were elaborated, the rational ranges of their variation at the operation under various gas-dynamic and fuel conditions determined, requirements to the gas stream temperature distribution along the furnace radius formulated. Based on analysis of information about lining temperature along the furnace height over the five year of EMZ BF No. 3 running, its values were ascertained, showing the partial or complete lining wear in the middle and upper part of the shaft. For the lining of the furnace bottom and other parts the temperature was ascertained, showing the formation in the lower zone unstable protective scull, as well the temperature characterizing its complete absence. The influence of blast mode during addition into it an increased volume of steam, natural gas and pulverized coal on variation of distribution of peripheral gas stream temperature along the furnace height from the tuyere zone to the top studied. It became a reason for an elaboration a method of the identification of the viscous-plastic state zone border in the peripheral zone of the furnace. Regulations of the blowing-in of blast furnaces after a long time stoppage without tapping the emergency hot metal elaborated. The technology of usage manganese-containing materials in the BF charge adjusted, which demonstrated the most effective washing out of the hearth under conditions of low and unstable charge materials quality and pulverized coal injection.

Method for determining blast furnace tuyere zone blackness degree on pulverized coal fuel injection

Pulverized coal fuel (PCF) supply is one of the modern methods of improving the cast iron production technology in blast furnaces (BF). It has a significant effect on the heat exchange in the tuyere zone (TZ). The known method of radiant heat transfer calculation in TZ accounts only for the ash particle effect on the TZ blackness degree. The aim of this work is to develop a method for determining TZ blackness degree and to investigate the effect of different factors on this value. The work was based on the elements of the proven method of calculating heat exchange in boiler furnaces. Parametric sensitivity was investigated by alternately simulating an error in each of the input values and determining its effect on the sought value. By analysing the processes, the authors have derived dependences for obtaining the concentration of ash particles and triatomic gases and determined the degrees of TZ blackness by Bouguer’s law simultaneously taking into account the radiation of the burning coke and ash particles, and triatomic gases. It has been established that an increase in the PCF consumption from 0 to 250 kg/t of pig iron changes the TZ blackness degree from 0,067 to 0,243; and a 1 % increase in the pressure, concentration of triatomic gases, ray effective length, TZ temperature and ash particle size changes the TZ blackness by 0,714 %, 0,151 %, 0,72 %, –1,557 % and –0,176 %, respectively. The calculations have shown that the effects of coke particles, triatomic gases and ash particles on the sought value are approximately equal. In contrast, when the conventional method is applied, it results in an approximately 2-time underestimation of the values, while even for evaluation calculations, the maximum permissible error is 10–15 %. The developed method accounting for all factors has the maximum error of 5 %. It is important for designing tuyeres and TZ refrigerators.

Existence state and structures of extracted coke and accompanied samples from tuyere zone of a large-scale blast furnace

An in-depth understanding about the existence state and structure of materials in the high-temperature zone of a blast furnace is critical to optimize both the ironmaking blast furnace and many other metallurgical processes based on carbothermic reduction. In the present study, coke as well as other accompanied samples (slag, metal and fines) were extracted from an industrial large-scale blast furnace (BF) tuyere zone and were comprehensively characterized to evaluate their existence state and structure. It was found that the weight percentage of slag and metal in the total extracted samples increases first and then keeps at a relative stable level, while the average coke particle size decreases firstly and then keeps at a relatively small size when the position is closer to the blast furnace center. This indicates that smelting and separation of slag and iron as well as the main coke degradation process occur mainly in the center part of BF, and the state in the region (deadman) is relatively stable with similar permeability. Tuyere cokes with various sizes are all extensively reacted with highly developed pores. Due to the improvement of coke pore size, blast furnace melts (bosh slag or molten coke/coal ash) can migrate into the coke matrix through those connected open pores. Coke carrying slag in its inner pores may enter the iron bath of the BF hearth, which might affect coke dissolution into hot metal and degrade the refractory of the hearth bottom. Alkalis content increase significantly when the distance to the tuyere entrance increases, indicating the alkali vapors are mainly recycled and enriched in the center part of blast furnace. The graphitization of coke in the high temperature zone start from the coke surface and the graphitization process may lead to the formation of coke fines.

Creation of High-Efficiency Promising Refractory Materials and Constructions for the Lining of Metallurgical Units

The causes of the low level of stability of the tuyere zone of converters and the reaction zone of rotating furnaces are studied and methods of impregnating standard refractories with different binding agents and effective refractory bodies, glues, gunning bodies, and constructions of linings are developed. A construction of a plant for the fabrication of gunning bodies is proposed. On the basis of tests and the introduction of these measures, the stability of the lining of converters and rotating furnaces can be increased 1.5 – 2-fold at nonferrous metallurgical enterprises and the number of repairs and volume of losses of nonferrous metals reduced.

Reactions in the Tuyere Zone of Ironmaking Blast Furnace

A series of slags can be formed in the lower part of the ironmaking blast furnace that play important roles in smooth furnace operation, and in determining iron quality and productivity. The final slag tapped from the BF has been investigated extensively as it can be collected directly. Unfortunately, difficulties in accessing the interiors of the blast furnace limit the full understanding of other slags such as primary and bosh slags. In this study, different types of samples directly obtained from the tuyere zone of the blast furnace have been systematically analyzed and characterized using scanning electron microscopy (SEM), electron probe X-ray microanalysis (EPMA), and X-ray fluorescence (XRF), with focus on the characteristics of slags formed in the tuyere level. The samples were identified into three groups according to their morphological, mineralogical, and chemical properties: (1) tuyere slags originating from the reactions between ash and dripping slags; (2) bosh slags in the CaO-SiO2-Al2O3-MgO-FeO system, with a CaO/SiO2 weight ratio of around 1.50, and Al2O3 and MgO concentrations close to those of final slags; and (3) coke ash that did not react with bosh slags. These findings will provide useful information on the evaluation of slags inside the blast furnace and the reactions in the tuyere zone.

Study of the combustion behaviour and temperature of pulverised coal in a tuyere zone of blast furnace

ABSTRACTThe combustion behaviour and temperature of pulverised coal in a tuyere zone of the blast furnace could benefit to adjust the operation parameters, assure the stable state as well as maintaining high quality of hot metal of the blast furnace. However, there have been rare studies about this subject. In this paper, the digital imaging system based on the colour charge coupled device within gas-cooling and dustproof functions was established to capture the combustion radiation in the tuyere zone. For instance, images of tuyere zones of 2000 and 2500 m3 blast furnaces were detected through a peephole in front of the blowpipe by the application of digital imaging and image processing techniques, and the temperature distributions were also calculated. Some measurements were used to improve the accuracy of the results, and the combustion behaviour was also analysed.

Structure of the Tuyere Zone of A Tank Furnace with A Bubbling Layer and Gas Delivery Through A Tuyere Located on the Side Wall Below the Level of the Molten Glass

Possible regimes of gas efflux into a layer of molten glass through a horizontal tuyere as well as the structure of the blowing zone formed in the process are investigated using a physical model of a glass furnace with a bubbling layer. The initial data required for uniqueness are obtained in a mathematical model of mixing of molten glass in a tank furnace.

Fused Refractory Oxides Increasing Nonferrous Metallurgy Unit Lining Life

Technology is developed for preparing periclase-chromite composition refractories based on fused grains of increased thermal-shock resistance. Technology is created for preparing periclase composition refractories based on fused grains exhibiting a high service temperature (up to 1900°C) and improved thermal shock resistance. Refractory material SHS-technology is developed on whose basis fused refractory objects, brickwork mortars, and torcrete mixes for hot torcreting are created. Refractory materials are turned out on an industrial scale in OAO Kombinat Magnezit. They are used for the most worn parts of linings such as the tuyere zone in horizontal converters, the slag belt of ore-roasting furnaces (ORF), in the reaction zone of a Waelz kiln, ORF outlet assemblies, Kivcet unit arches, and Vanyukov furnaces. Lining life is increased by a factor of 1.5 – 2.5.

Gazification of coal dust particles in the blast furnace tuyere apparatus

The mathematical statement of the problem on gasification of coal dust particles in the blast-furnace tuyere apparatus is given, which includes the motion equation of a variable mass particle, heat equation of a particle and the heat-balance equation of the blast flow. The results of calculations are obtained by using mathematical software packages (Mathcad, Maple). Relatively weak effect of the volatiles combustion process on the thermal state of the tuyere zone is shown.

Regulation of high-temperature blast-furnace processes by adjusting the fuel-additive supply

A method is developed for analysis of the processes in the tuyere zone. Analysis permits calculation of the change in the yield, composition, and temperature of the intermediate gas at the axis of the tuyere zone and determination of the final composition of the hot reducing gases at the output from this zone. The quantitative ratios of the residual oxygen ΔO2 and the oxidized gases CO2 and H2O along the axis of the tuyere zone in the combustion of fuel additives are established. It is possible to regulate the proportions (by volume) of the gases ΔO2, CO2, and H2O in coke consumption so as to ensure heat transfer from the wall to the center of the furnace. If the fuel-additive consumption is regulated according to specific technological protocols, the additives may not only be regarded as a replacement for coke but will also provide information regarding the blast-furnace process. A formula for the degree of direct reduction of the metals is derived. Continuous determination of the direct reduction will also provide valuable information regarding the process.