Blast Furnace Performance Research Articles

Influence of Coating Granulation Process on Iron Ore Sinter Quality and Productivity

AbstractFor better blast furnace performance, there has always been a need for better quality raw materials like sinter, lump ore, and pellets. Among these raw materials the usage of sinter in blast furnace is at higher side compared to other iron bearing materials. As the quality of sinter product improves, its usage in blast furnaces also increases. Iron ore fines are the main source for sinter making. To improve the sinter properties it is necessary to provide good quality of iron ore fines. Due to depletion of high grade iron ore resources, goethite and limonitic ore content in iron ore fines is expected to increase gradually. Usually limonitic and goethite ore are associated with higher alumina and LOI. The conventional sintering process is one of the well established processes for high quality hematite ore. It does not fully respond to the low grade iron ore associated with goethite and limonite. This has led to deterioration in sinter properties and productivity. In recent years the improvement in the quasi‐particle structure with the granulation process is an effective method for improving sinter quality and productivity. To improve the sinter quality and productivity for low grade iron ore fines, different granulation processes like the conventional one, and other two advanced granulation processes like coke breeze, and flux & coke breeze coating granulation were studied in detail by conducting laboratory pot grate sintering experiments. From the test results it was found that sinter productivity, physical and metallurgical properties of the sinter improved with flux & coke breeze coating granulation process compared to conventional and coke breeze coating granulation process.Proper selection of the granulation time is very important to achieve the desired sinter properties. In the present work detailed laboratory experiments have been carried out by varying the coating time from 30s to 110s to study the influence of flux & coke breeze coating granulation time on mineralogy, productivity, physical, and metallurgical properties of sinter. With a coating granulation time of 50s, higher productivity, higher yield, and stronger sinter (higher T.I) with lower RDI and ‐5mm size sinter were achieved.

Effect of the quality of the iron-ore-bearing raw materials and coke on the performance indices of blast furnaces at the Novolipetsk metallurgical combine

Results are presented from an evaluation of the effect of the quality of the iron-ore-bearing raw materials and coke on the performance of blast furnaces at the Novolipetsk Metallurgical Combine. It is shown that the technical-economic indices of the smelting operation are improved by increasing the pellet content of the charge, the basicity of the sinter, and the sinter’s content of the ‐5 mm fraction. An analysis of the performance of the blast furnaces on coke with a hot-strength index CSR = 40‐60% confirmed the qualitative and quantitative effect of this index on furnace productivity and coke consumption. The analysis also showed that the magnitude of this effect depends on smelting rate and the basicity of the furnace slag.

Influence of Alumina on Iron Ore Sinter Properties and Productivity in the Conventional and Selective Granulation Sintering Process

Iron ore sinter constitutes a major proportion of blast furnace burden. Hence, its quality and consistency have a significant impact on blast furnace performance. Iron ore fines are the main source for sinter, and the chemical composition of the iron ore fines, together with the thermal conditions that blends are subjected to, plays an important role in forming the primary melt during the sintering process and accordingly determines the sinter structure and quality. Therefore, considerable importance has been placed on the chemical composition and consistency of iron ore fines, particularly in terms of alumina content. Due to depletion of high grade iron ore resources, alumina content in the iron ore fines is expected to increase gradually. Ore with higher alumina content is usually expected to be detrimental in forming the sinter matrix, if sintered alone, due to the low reactivity of alumina bearing minerals and the high viscosity of primary melts. The selective granulation process is a new sintering process for high alumina iron ore fines, and can eliminate the adverse effects of ‘hard to sinter’ or ‘unsuitable – for ironmaking’ ores. In the present work laboratory sintering experiments have been carried out with iron ore fines of different alumina level (2.00 to 5.46 mass-%) to know the influence of alumina on mineralogy, productivity, physical and metallurgical properties of sinter prepared by the conventional and the selective granulation process. With increasing alumina content in sinter of both the conventional and selective granulation process, the fractions of hematite and of silico-ferrites of calcium and alumina (SFCA) as well as the pore phase increased whereas the magnetite and silicate phases decreased. With increase in alumina content sinter productivity and tumbler index (T.I.) decreased, and metallurgical properties like sinter RDI and reducibility improved. However, sinter of the selective granulation process showed better results compared to the conventional process.

Discrete Element Method-Computational Fluid Dynamic Simulation of the Materials Flow in an Iron-making Blast Furnace

The cohesive zone, where the ore fed into the blast furnace softens and melts, is critical to the blast furnace performance and stability due to its influence on the gas and solid flow. Here we describe a project for the development of a process model to predict the cohesive zone properties and results of an important part of the work; the solid and gas flow models. The process model will be developed to describe a realistic solid burden flow and the formation of the cohesive zone, its shape, location, structure and permeability. This will be achieved using various simulation and computing tools: a combination of the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD), the coupled DEM-CFD approach, together with models for the thermodynamics and reaction kinetics. The key benefits of the coupled approach lie in the coupling of the continuous phase and the discrete particles, and the possibility of introducing thermodynamics and reaction kinetics into the system in a more realistic manner. DEM and coupled DEM-CFD simulations in several geometries are presented for reduced scale blast furnace investigation on the influence of non-spherical particles and gas flow on the solid flow. A large influence of the geometry shape and boundary conditions on the solid flow was also found.

Purification of blast-furnace gas and energy conservation

499 Given the rising prices of natural gas and electric power, Ukrainian metallurgical enterprises need to introduce energy-saving technologies. To reduce energy costs, and hence produce more competitive metal products, the manufacturing technology may be improved, and energy use at the enterprise may be rationalized, with the utilization of waste gases. It is expedient to make full use of the blast-furnace gas produced at the plant. The compressorless waste-gas turbine is intended to generate electrical energy on the basis of the excess pressure of the blast-furnace gas. The turbine power developed depends on the blast-furnace operating conditions and the flow rate and pressure of the gas passing through the turbine. Only the energy of the compressed gas is used; its heat of combustion remains. Radial and axial turbines are made in Russia and Japan and are going into production in Ukraine. They are easily adapted to the technological cycles of new or existing blast-furnace equipment. Such turbines operate effectively at metallurgical enterprises in Europe and Japan and are under design in Russia. In Ukraine, blast-furnace production accounts for most (60%) of the energy consumption in metal production. Currently, Ukraine operates more than 30 blast furnaces of volume 1386 m 3 or more, which may be equipped with waste-gas turbines for power generation. No turbines operate in Ukraine today, although four operated up to 1990. At the Institute of Ferrous Metallurgy (IFM), Ukrainian Academy of Sciences, efforts to improve blast-furnace smelting began in 1953, under the direction of Z. I. Nekrasov; one of the goals was to reduce energy consumption in hot-metal production. On an industrial scale, research focused on the operation of furnaces with an elevated gas pressure at the charge hole, the use of natural gas and complex injection, and the use of higher-grade raw materials. The construction of larger blast furnaces equipped with redesigned (nonconical) charging units was shown to be expedient. These measures proved effective in improving blast-furnace performance and reducing energy consumption. At present, small blast furnaces with outdated equipment, characterized by elevated energy and resource consumption, are being withdrawn from service in Ukraine and Russia, and around the world. The first level of the furnaces is undergoing major overhaul, including modernization of the systems for the preparation and use of blast-furnace gas, with the installation of compressorless waste-gas turbines. Efforts to reduce energy consumption and environmental impact must address blast-furnace technology. Effective operation of waste-gas turbines is hindered by the low quality of the iron ore, by design faults of the conical charging devices, and by furnace operation with a low excess gas pressure at the charge hole (less than 1.5 MPa). The operation of waste-gas turbines is improved by using nonconical charging units capable of stably maintaining an excess gas pressure of 2 MPa at the charge hole. We know that the furnace process is faster when the gas pressure at the charge hole is higher. Experience shows that each 10-kPa increase in gas pressure raises furnace productivity (hot-metal output) by 1.0‐2.0% and reduces coke consumption by 0.1‐0.5%. When furnaces operate at higher gas pressure, charge-hole dust releases are reduced by 35‐50%. The compressorless waste-gas turbine provides an effective means of reducing the energy consumption in hot-metal product and hence the price of the final metal product [1, 2]. Operational experience with such waste-gas turbines within the Commonwealth of Independent States

Influence of pellet consumption on blast-furnace performance at OAO NLMK

201 In the special literature, there are conflicting opinions on the benefits of metallic pellets in blast-furnace batch. Thus, according to [1], saturation of the slag with alumina and decrease in the magnesia–alumina modulus will result from increase in the content of low-basicity iron-ore pellets in the batch; such pellets are also associated with increase in the consumption of raw limestone and overconsumption of coke.

Effect of coke quality on blast-furnace performance indices

The quality of coke has a strong effect on the performance indices of a blast furnace. For a furnace to operate with high productivity and a low coke rate, it is necessary to use coke with high strength characteristics. The Novolipetsk Metallurgical Combine has conducted studies of the effect of coke quality on the operation of blast furnaces of different sizes. The quality of the coke was evaluated on the basis of the following indices: CSR, CRL, the cold-strength indices M10 and M25, and the integral coke-quality index Ig.c used by the Sidmar company. Furnace productivity, coke rate, and the totterman index (DMI) were also used for the sake of comparison.

Blast-furnace performance with coal-dust injection

Blast-furnace performance with coal-dust injection

Development of New Coal Blend Preparation Methodologies for Improvement in Coke Quality

Coal preparation has become a very important technique for preparation of high-quality metallurgical coke, the quality characteristics of which play a major role in the performance and economics of blast furnaces. Since availability of good quality metallurgical coals are meager in India, coal charge blends for carbonization in slot-type coke ovens are prepared from blending of various indigenous and imported sources of diverse characteristics. Preparation of coal blends for carbonization assumes paramount importance in terms of cost, quality, and resource utilization. Judicious coal-blending techniques based on intrinsic quality parameters coupled with various precarbonization steps to maintain blend homogeneity, granulometry, caking and coking properties of the blend are practiced under Indian conditions. The quality of metallurgical coke depends on type of coal, its physico-chemical properties including its granulometry, and its thermochemical behavior. Quality parameters of coke produced from a particular coal blend can be significantly influenced by the coal preparation technique adopted particularly when the blend comprises several sources of diverse quality parameters. Groupwise crushing of coal was developed with the aim to reduce the heterogeneity of different size fractions in terms of distribution of inerts and reactive contents. The groupings were based on their grindability indices, caking/coking properties, and dilation properties of individual size fractions. This article discusses in detail new coal preparation methodologies for improvement in coal charge blend granulometry and flowability, reduction in microfines content, and improvement in blast furnace coke quality.

The relation between coke quality and blast-furnace performance

The relation between coke quality and blast-furnace performance

Performances of pulverized coal injection in blowpipe and tuyere at various operational conditions

Combustion efficiencies of pulverized coal in blowpipes and tuyeres under various operational conditions are numerically predicted to recognize the performance of pulverized coal injection in a blast furnace. A variety of parameters including the injection pattern of the pulverized coal, oxygen content in the hot blast, inlet temperature of the hot blast and mass flow rate of coal carrier gas are taken into consideration. The effect of installing a ceramic sleeve around the tuyere on pulverized coal combustion is also evaluated. The predictions indicate that pulverized coal combustion is highly related to the injection pattern, hot blast temperature, mass flow rate of the carrier gas and installation of the ceramic sleeve, whereas it is insensitive to the oxygen concentration. The present study is conducted based on the practical operational conditions of the blast furnace at the China Steel Corporation. Consequently, the obtained results have provided a useful insight into the operation of pulverized coal injection, and they enable us to further improve the blast furnace performance in the future.

Numerical Analysis of Blast Furnace Performance Under Charging Iron-Bearing Burdens With High Reducibility

The reducibility of iron-bearing burdens was emphasized for improving the operation efficiency of blast furnace. The blast furnace operation of charging the burdens with high reducibility has been numerically evaluated using a multi-fluid blast furnace model. The effects of reaction rate constants and diffusion coefficients were investigated separately or simultaneously for clarifying the variations of furnace state. According to the model simulation results, in the upper zone, the indirect reduction of the burdens proceeds at a faster rate and the shaft efficiency is enhanced with the improvement under the conditions of interface reaction and intra-particle diffusion. In the lower zone, direct reduction in molten slag is restrained. As a consequence, CO utilization of top gas is enhanced and the ratio of direct reduction is decreased. It is possible to achieve higher energy efficiency of the blast furnace, and this is represented by the improvement in productivity and the decrease in consumption of reducing agent. The use of high-reducibility burdens contributes to a better performance of blast furnace. More efforts are necessary to develop and apply high-reducibility sinter and carbon composite agglomerates for practical application at a blast furnace.

Application of nontraditional reducing agents in the production of metallized briquettes

The growing deficiency and increasing cost in highquality low-sulfur reducing agents (coke and natural gas) result in the necessity of focusing on improving the quality of raw material preparation, using alternative methods of direct iron reduction, including those that feature obtaining of a metallized semiproduct of a particular degree of reduction and subsequent processing in a blast furnace. Thus, in the application of partially metallized pellets with a degree of metallization of 47‐ 53%, blast furnace performance increases by 8‐13% and coke consumption is reduced by 25‐26% [1]. Under conditions when there is deficiency of highquality scrap metal and one is forced to use light and oxidated scrap metal, this material can serve as a good substitute in steelmaking.

Numerical Evaluation on Lower Temperature Operation of Blast Furnaces by Charging Carbon Composite Agglomerates

This paper places emphasis on evaluating ironmaking operation at lower temperature. Blast furnace operation with carbon composite agglomerates (CCB) charging and/or lower operation temperature has been numerically examined using a modified multi‐fluid blast furnace model under constant thermal conditions of the raceway. The numerical calculation shows that a lower in‐furnace temperature level is achieved under the operation with the CCB charging. With CCB charging, the location of the cohesive zone shifts downward and the temperature of the thermal reserve zone decreases. The decrease in heat requirements for solution loss, sinter reduction and silicon transfer reactions compensates the increase in heat demands for CCB reduction and direct reduction, and rather improves the efficiency of blast furnaces. Consequently, the productivity improves, the coke rate shows a notable decrease and the total reducing agent rate also tends to decline compared with conventional operation without CCB charging. Therefore, charging carbon composite agglomerates contributes to the enhancement of blast furnace performance. Furthermore, the model predicts that higher operation efficiency is achieved if the melting and/or tapping temperature could be dropped. The innovative technology of lower temperature ironmaking is expected to be applied in industrial blast furnaces after resolving the problems in engineering and economic evaluations.

Current strategies and future challenges on exploration, beneficiation and value addition of iron ore resources with special emphasis on iron ores from Eastern India

Eighty per cent of the world's steelmaking is through the blast furnace route and hence the role of iron ore as a raw material and its quality become very critical to achieve steel with the best quality from hot metal. The world's iron ore resource base has been estimated at 180 000 million tonnes (MT), while the reserves are 79 000 MT. India ranks the sixth among producers of iron ore, with a 6200 MT reserve base. The majority of Indian iron ore deposits occur in the eastern, central and southern parts of India in the regions of Jharkhand, Orissa, Karnataka, Chhattisgarh and Goa. Among these provinces, the iron ores of Eastern India are of high quality and present in large quantities. Indian iron ore resources consist of both hematitic (10 052 MT) and magnetite (3408 MT) varieties. Major ore types are hard, flaky/friable, lateritic and blue dust or powdery ores. The ratio of lumps and fines in the deposits is 50 : 50, but the high grade lumpy variety is rare and constitutes <10% of the total reserves. India's iron ore production has just doubled in the last 5 years, achieving a total of 154 MT in 2005–06 compared with 86 MT in 2001–02. The Indian iron ores in general and Eastern Indian iron ores in particular consist of various impurities in the forms of Al, P and Si, and this poses major beneficiation problems especially in fines processing. The presence of these elements along with sulphur adversely affects the quality of iron ores and has a great bearing on performance of blast furnaces. Reduction of the alumina content in iron ore by 1% improves blast furnace performance by 3%, reduces reduction degradation index (RDI) by 6 points, lowers the coke rate by 14 kg per tonne of hot metal and increases sinter productivity by 10–15%. The presence of phosphorus and sulphur increases surface cracking during steel processing. High alkali contents lead to a lowering of the mechanical strength of coke and sinter, imbalances in the furnace operation and a reduction in furnace productivity. The Indian iron ore industry is going to face major challenges in the near future, as the production trend of iron ore worldwide is swinging up every year owing to the iron ore boom in recent years. It calls for mineral conservation and prevention of mineral losses in terms of wastes/slimes. This needs to be achieved through detailed exploration work, mine planning techniques, scientific exploitation and mineral beneficiation processes. For optimum utilisation of mineral resources, total beneficiation of iron ores, mineral rejects and wastes need to be augmented. In addition, alternative processes for ironmaking, such as COREX, ROMELT and HISMELT, need to be introduced by the major producers. This paper addresses the importance of quality raw materials in achieving benchmark iron- and steelmaking while maintaining the cost effectiveness. Emphasis has been given on the value addition of the subgrade and marginal-grade ores for mineral conservation and prevention of losses.

Java-Based Integrated Non-Stationary Blast Furnace Simulator

In the field of pig ironmaking process, operation malfunction is caused by both enlarging a blast furnace and increasing use of low quality ore. Thus, operation support systems predicting a blast furnace performance are demanded. On the other hand, the method of integrating many partial simulators for a complicated system in the consideration of interaction has been proposed. This paper presents Java-based integrated non-stationary blast furnace simulator that is constructed by applying the method to the partial simulators of the blast furnace. To construct the simulator, a partial non-stationary model is developed by using a stationary model as fundamental model. Moreover, the dynamic temperature in the blast furnace is calculated adequately by the simulator.

Modelling and analysis of blast furnace performance for efficient utilization of energy

A simple model is presented to assess thermal performance of blast furnace (BF) for efficient utilization of energy with an integrated view to improving the productivity of the plant. The model is developed using the mass, energy and availability balance equations and is applied to an existing Iron and Steel industry in India. A comparison of the actual operation of the BF is made with that of the model prediction. The model provides a reasonable agreement with the real time (on-site) data of the BF operation. The predicted values of BF coke rate and blast rate are 8.6% and 5.11% higher than that of the actual values, respectively. The First and Second law efficiencies of the BF operating system were found to be 77.3% and 39.13%, respectively. Irreversibility of the actual operation of BF was found to be 18.9%, which included the irreversibility due to the transformation of chemical energy and promotion of reduction reactions. The main cause of the irreversibility in the process was the conversion of chemical energy of the fuel (coke) to thermal energy. The effect of the changing operating parameters on the plant productivity is also investigated. This study suggests that the plant productivity can be improved by increasing the hot air blast temperature, reducing hot metal silicon level, reducing coke ash level and increasing sinter volume in the charge.

Numerical Simulation of Innovative Operation of Blast Furnace Based on Multi-Fluid Model

A multi-fluid blast furnace model was simply introduced and was used to simulate several innovative iron-making operations. The simulation results show that injecting hydrogen bearing materials, especially injecting natural gas and plastics, the hydrogen reduction is enhanced, and the furnace performance is improved simultaneously. Total heat input shows obvious decrease due to the decrease of heat consumption in direct reduction, solution loss and silicon transfer reactions. If carbon composite agglomerates are charged into the furnace, the temperature of thermal reserve zone will obviously decrease, and the reduction of iron-bearing burden materials will be retarded. However, the efficiency of blast furnace is improved just due to the decrease in heat requirements for solution loss, sinter reduction, and silicon transfer reactions, and less heat loss through top gas and furnace wall. Finally, the model is used to investigate the performance of blast furnace under the condition of top gas recycling together with plastics injection, cold oxygen blasting and carbon composite agglomerate charging. The lower furnace temperature, extremely accelerated reduction rate, drastically decreased CO2 emission and remarkably enhanced heat efficiency were obtained by using the innovative operations, and the blast furnace operation with superhigh efficiency can be realized.

Numerical analysis on blast furnace performance with novel feed material by multi-dimensional simulator based on multi-fluid theory

Multi-dimensional blast furnace operation simulator based on multi-fluid theory and reaction kinetics is applied to the novel operations of blast furnace. The effective use of carbon composite agglomerates (CCB) in blast furnace is expected to have several advantages to improve furnace efficiency. In this study, mathematical expression of reduction behavior of CCB was introduced into the blast furnace simulator and the effect of charging CCB to blast furnace and accompanying temperature lowering were numerically examined. The calculation results showed the increase in productivity and decrease in reducing agent rate with CCB charging while reduction of iron-bearing materials was retarded due to temperature decrease in stack region. Thermal analysis revealed that this improvement of heat efficiency is caused by the decrease in heat requirements for solution loss, sinter reduction and silicon transfer reactions, heat outflow by top gas and wall heat transfer.

Coke fitness for high BF performance at high coal injection rate

The Arcelor plant in Dunkerque depends on external coke for one third of its total coke consumption. A global approach has been carried out: To assess the effect of coke properties on the blast furnace performance. To specify the requested coke properties. Appropriate coke characteristics have been defined, aiming at high blast furnace productivity (63t/m2/d), at high PCI rate (210kg/thm for all three blast furnaces) and at low consumption of large coke (230kg/thm).