Blast Furnace Performance Research Articles

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).

高炉羽口から入射したマイクロ波反射強度によるレースウェイ形成挙動の解析

The blast furnace raceway formation under the intensive coal injection by measurement of micro wave reflection gunned through a tuyere is discussed. As the flow rate of coke as the momentum of coke into raceway decreases by combustion of coal injected into tuyeres, the depth of raceway defined as the maximum position of micro wave reflection is easy to contract. It is expected that this new technology could detect the raceway collapse phenomena in short time and that the stability of raceway in coal injection is different from that in all coke operation. Finally the paper ends by summarizing the effect of raceway formation on unsteady phenomena forcing functional disorder on blast furnace performance of burden distribution for high productivity performance.

Numerical prediction and practical improvement of pulverized coal combustion in blast furnace

The burning characteristics of pulverized coal in blowpipe and tuyere at two different injection patterns are simulated numerically, to aid improving the practical performance of blast furnace. With the condition of the same fuel and oxidant mass flow rates, the predictions indicate that the combustion efficiency of pulverized coal using double-lance can be substantially enhanced compared with that using single lance. Accordingly, the pulverized coal injection in a practical blast furnace was modified from single lance to double-lance. As a result, the practical injection rate of the pulverized coal in the blast furnace was increased from 110 to 153 kg/tHM, revealing that a profound decrease in operating cost of the blast furnace has been implemented.

Analyses on Blast Furnace Raceway Formation by Micro Wave Reflection Gunned through Tuyere

The blast furnace raceway formation under the intensive coal injection by measurement of micro wave reflection gunned through a tuyere is discussed. As the flow rate of coke as the momentum of coke into raceway decreases by combustion of coal injected into tuyeres, the depth of raceway defined as the maximum position of micro wave reflection is easy to contract. It is expected that this new technology could detect the raceway collapse phenomena in short time and that the stability of raceway in coal injection is different from that in all coke operation. Finally the paper ends by summarizing the effect of raceway formation on unsteady phenomena forcing functional disorder on blast furnace performance of burden distribution for high productivity performance.

The Use of Neural-Network-Based Technologies to Analyze the Effect of a Combination Blast on Blast-Furnace Performance Indices

Methods of mathematical modeling ‐ not only classical methods [1, 2], but also those based on the use of artificial intelligence [3, 4] ‐ are widely used to analyze and control blast-furnace smelting. It is interesting to examine the feasibili ty of using neural networks to calculate the effect of the parameters of a combination blast (the consumption of natural gas and the oxygen content of the blast) on smelting indices ‐ furnace productivity and coke rate. We used instructional neural networks to calculate the process parameters in question. In this case, the calculation models not the smelting operation itself, but the actions that might be taken by an experienced melter foreman, metallurgical engineer, or other technologist. The aim of the modeling is to determine the control actions that should be taken and to develop recommendations. This involves also using classical mathematical models of blast-furnace smelting. The neural network, instructed by the collective experience of above-mentioned technologists, functions as a tool for controllling the blast furnace with the use of a computer. Such a network has been developed and incorporated into a program created by UGTU‐UPI: “Neuro-Robot ‐ the Melter Foreman’s Partner.” So that the program has the desired effect, it is augmented by use of the technique of calculating response functions (objective functions) and a method developed to determine the degree of competency of robots based on neural network technology (neuro-robots). The use of these additional tools significantly enhances the reliability of the results that are obtained. The program includes a file of Excel tables and files with designs of neural networks. To generate and instruct the neuro-robot, we are also using a standard software item for working with neural networks in Excel ‐ the application package Excel Neural Package developed by the company Neurok. This software includes the component Winnet 3.0 and is designed to find and model relationships hidden in large files of numerical information ‐ relationships that cannot be expressed by any known explicit analytical expression. Figure 1 shows the algorithm used to design the operation of the Neuro-Robot program. We used typical information on the current operation of a 2700-m 3 blast furnace (Table 1) to formulate the instructional data sample, which incorporates the technologists’ expert opinions on the most representative and characteristic operating situations (OSs) encountered with blast furnaces. The quantitative (number of (OSs) and temporal (the duration of the “time window”) dimensions of the sample are determined in relation to a number of factors (furnace productivity, coke rate, blast temperature, the silicon content of the pig iron, etc.), and the ultimate goal of the program’s use includes real-time control of the smelting regime, prediction of the outcomes, analysis of trial heats, and other objectives. As an example, we chose 12 weeks as the size of the time window and one week as the interval for averaging the data (see Table 1). The program was used to calculate recommendations on the optimum values for the consumption of natural gas and the oxygen content of the blast in order to be able to incorporate these two parameters into the monthly operat

Modelos de previsão da qualidade metalúrgica do coque a partir da qualidade dos carvões individuais e do coque obtido no forno-piloto de coqueificação

É bem conhecido o alto peso que o coque representa no custo final dos produtos, além do que as suas propriedades estão intimamente ligadas à performance dos altos-fornos. Portanto buscar uma qualidade do coque compatível com as necessidades do alto-forno e com o menor custo possível se transforma em uma tarefa difícil se não se dispuser de ferramentas que permitam uma correta seleção de carvões. O objetivo principal desse trabalho é desenvolver modelo de previsão para o DI - resistência mecânica do coque, através de análises estatísticas de dados industriais e coqueificação em escala-piloto. O modelo de previsão do DI representa 75,8% dos dados industriais, obtendo-se um aumento de precisão de 8,07 pontos percentuais em comparação com o modelo atual. Portanto o novo modelo desenvolvido mostrou-se adequado e pode ser usado como ferramenta para auxiliar a compra de carvões.

Numerical Analysis on Charging Carbon Composite Agglomerates into Blast Furnace

The carbon composite agglomerates have been numerically examined. The previously presented multi-fluid blast furnace model is modified to simulate blast furnace operation with carbon composite agglomerates charging. The model considers the behavior of carbon composite agglomerates, namely, conservation equations of chemical species contained in this material including chemical reactions and phase transformations are newly added. A series of simulating calculations are performed to examine the effect of charging carbon composite agglomerates. The result reveals that with increase in carbon composite agglomerates charging ratio in-furnace temperature level tends to decrease, the location of cohesive zone shifts downward, and the reductions of carbon composite agglomerates and sinter are delayed. On the other hand, the productivity tends to increase while coke rate and total reducing agent rate show decrease. The energy consumption for unit production of hot metal is lowered. The performance of blast furnace is improved in the tested range mainly due to the decrease in heat requirements for solution loss, sinter reduction and silicon transfer reactions, heat outflow by top gas and wall heat loss.

Numerical Analysis on Blast Furnace Performance under Operation with Top Gas Recycling and Carbon Composite Agglomerates Charging

The blast furnace operations with top gas recycling, carbon composite agglomerates (CCB) charging, cold oxygen blast and waste plastics injection are numerically evaluated by means of multi-fluid blast furnace model on the premise of constant raceway conditions and hot metal temperature. These evaluations are in comparison with conventional operation. Simulation results reveal that CCB charging and/or cold oxygen blast lead to low temperature level in the shaft region, which retards the reduction of CCB. On the other hand, injection of waste plastics enriches hydrogen gas in the furnace. And top gas (after CO2 removal) recycling tremendously enhances the concentrations of H2 and CO in the whole furnace, which greatly promote the indirect reduction of sinter in shaft despite lower temperature. Under the innovative operations, the efficiency of blast furnace shows evident improvement, especially in the case with simultaneous injections of treated top gas through shaft and tuyere. The model computations predicted that total heat input decreases while the productivity increases under the operation with top gas recycling. Additionally, top gas recycling and waste plastics injection also contribute to considerably reduce carbon dioxide emission. It is expectable to develop high efficiency blast furnace with improved productivity and lowered environment load through exploiting the processes presented in this study. If scrubbing and fixing of CO2 and manufacturing of process oxygen are commercially available, these innovative processes will possess broad applying potential.

Non-spherical Carbon Composite Agglomerates: Lab-scale Manufacture and Quality Assessment

For recycling steel work dust and improving blast furnace (BF) performance, a few types of non-spherical carbon-iron oxide agglomerates were manufactured in laboratory scale and their strength and reducibility were evaluated using a shatter and a tumbler tester, a simulator for lumpy zone in BF and a softening/melting tester. The flat or ragged shape was expected to enhance reducibility and to prevent the agglomerate from unwilling rolling down to the center of BF. Agglomerate in the shape of column with concave triangle cross-section (Tetra) showed the highest yield during extruding and almost same strength compared with a commercial spherical cold-bond pellet. In reducibility Tetra excelled sinter but spherical carbon composite pellet, which denied shape effect. Reduction disintegration of Tetra initiated at 600°C and reached to the maximum of 60% at 860°C, the entrance of thermal reserve zone, meaning the issue of cement bonding on disintegration remained unsolved. In case of single use, Tetra did not melt down up to the upper limit temperature of the softening/melting tester, causing S-value enlarged. Using Tetra mixed with sinter was recommended as a trial of admixing 50% Tetra to sinter accelerate reduction rate of sinter, improving BF efficiency by 45 kg/t decreases in RAR; moreover, the mixture remarkably reduced the pressure loss of cohesive zone.

Modeling Portland Blast-Furnace Slag Cement High-Performance Concrete

This work focused on portland blast-furnace slag cement high performance concrete (HPC), with specified 28-day compressive strengths of 60-110 MPa. Compressive and flexural strength, elastic modulus, abrasion resistance, and shrinkage properties were studied. Lab test results showed it is possible to develop a general compressive strength model combining a hyperbolic equation for strength evolution and an exponential equation for mixture design parameters. It was also concluded that the measured moduli of elasticity are lower than the ACI predicted values, and that the square root of the compressive strength was not a good predictor of the flexural strength for the materials used. Also, it was concluded that the ASTM C 944-99 abrasion test is not an effective way to measure abrasion resistance of HPC. Autogenous shrinkage was shown to be a significant part of total shrinkage. An updated FIB 2000 model to local conditions was successfully developed to predict shrinkage of HPC.

Melt Down Behaviour of a Fused Layer in the Blast Furnace Cohesive Zone.

The cohesive, or softening-melting zone plays a critical role in determining blast furnace performance and stability. The effect of changes in the permeability of softening-melting ore and the subsequent distribution of gases and liquids around the anisotropic packing structure of coke and ore layers in this region must be understood before the blast furnace can be adequately modelled. This study aimed to address issues related to cohesive zone formation through low-temperature experimentation. Two investigations of meltdown behaviour were performed, classified according to geometrical characteristics. The first ‘flat layer meltdown’ investigation examined the softening-melting of flat cohesive layers extending across the furnace diameter. This configuration matched that used in high-temperature softening-melting tests. The second ‘single layer meltdown’ investigation concentrated on a single cohesive layer embedded in a permeable packing. This configuration can be likened to a single cohesive layer in a permeable cohesive zone, where gas is able to bypass ore through intermediate coke slits as permeability is lost. The meltdown of flat cohesive zones was characterised by variability and gas channelling, promoting furnace instability and preventing accurate modelling. The meltdown of single layers demonstrated the possibility of structural variation between the surface and core, and the change in contribution of convection and conduction to heating.

Reduction Behavior of Carbon Composite Iron Ore Hot Briquette in Shaft Furnace and Scope on Blast Furnace Performance Reinforcement

The reduction and melting behavior of carbon composite iron ore hot briquette in shaft furnace are discussed. As these agglomerates are made by the use of thermal plasticity of coal, the reduction rate by chain reactions in interface between ore and coal could be increased. The carbon composite iron ore hot briquettes achieve 95 % reduction degree in about 10-min descent time to the 1 100°C heat reserve zone bottom end and the drop of molten iron temperature is kept to 20°C. As a result, it is expected that these new agglomerates could decrease the fuel rate and discharging amount of CO 2 as well as have a possibility of extension of furnace life. Finally the paper ends by shaping the future of blast furnace on environmental phases for the new century. Especially, it is expected that carbon composite iron ore hot briquette lowers temperature of heat reserve zone and shortens the length, suggesting the possibility of shortening of the reserve zone (inactivity zone), that is, shortening of the blast furnace height.

Heat (mass) transfer in serpentine flow passage with rectangular cross-section

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.

Predicting the Quality of Coke Based on Expert Evaluation of Blast-Furnace Performance

Predicting the Quality of Coke Based on Expert Evaluation of Blast-Furnace Performance

00/02843 Blast furnace performance as influenced by coke quality

00/02843 Blast furnace performance as influenced by coke quality

99/02699 Measurement of radial gas flow in upper shaft and its influence on blast furnace performance

Fluidized bed coal combustors emit much higher concentrations of nitrous oxide (N2O) than do most other combustion systems. This is of concern because N2O is highly stable in the atmosphere, and may contribute to both the greenhouse effect and to stratospheric ozone depletion. In this article laboratory results are presented on N2O removal by the reburning (i.e., afterburning) method. The destruction of N2O is observed during contact between hot flue gases containing N2O and various reburning fuels. A laboratory combustion reactor is used to sequentially generate the hot combustion gas, and to put this gas in contact with N2O and reburning fuel under well-characterized conditions. The initial N2O in the primary combustion products is between 200 and 350 ppmv (dry). The temperature of the primary combustion products is varied between 1080 and 1370 K, and the oxygen level of these gases is varied between 3.3 and 4.8% (dry). Five reburning fuels are tested. The rank order of reburning effectiveness (based on equal heat input by the reburning fuels) is H2 > CH4 > C2H4 and C2H6 > CO. Experiments are also performed with the primary combustor operated fuel rich. Without any reburning fuel added, removal of large amounts of N2O are obtained when the fuel-air equivalence ratio of the primary combustion is about 1.1. The experimental results are presented, discussed, and compared to chemical kinetic modeling. Also, some discussion of the practical implications is presented.

Blast furnace performance as influenced by burden distribution

Burden distribution is one of the key operating parameters influencing blast furnace performance, particularly the productivity and the coke rate. The proper distribution of burden materials improves bed permeability, wind acceptance, and efficiency of gas utilisation. In furnaces operating with high coal injection rates, the distribution resulting in predominant central working (steep cohesive zone profile) was found to be beneficial. Since a high coal injection rate increases the peripheral working (wall heat flux), an attempt should be made to minimise the wall heat flux by striking a proper balance between peripheral and central working. In a typical Indian blast furnace equipped with a bell-less (Paul Wurth) distribution system, the decrease in coke rate that is due exclusively to burden distribution was found to be 10–12 kg/thm.

98/04111 Smelting process with direct reduction of iron ore for manufacture of cast iron melt in two-chamber vertical furnace

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.

98/03251 Effect of injected coal properties on performance of the blast furnace

98/03251 Effect of injected coal properties on performance of the blast furnace

Prediction of Blast Furnace Performance with Top Gas Recycling.

Top gas recycling has been suggested as a method for reducing blast furnace fuel rates and thus reducing carbon emissions from the ironmaking process. Three methods of top gas recycling are numerically investigated using a mathematical model to predict the furnace performance at fixed blast volume and constant coke, ore and pulverised coal compositions with varying recycle volumes. For each recycling method, a first calculation sequence is performed varying recycle volume at fixed ore : fuel ratio, and also a second sequence at fixed average liquid metal outflow temperature. Simple replacement of normal blast gases with recycled top gas is predicted to cause the production rate to decrease and the fuel rate to increase. Likewise, oxygen enriched blast replacement has similar effects, although the severity is less as the blast oxygen rate is maintained in this case. Both of these methods reduce furnace efficiency. Hot reducing gas (HRG) replacement, where CO2 is stripped from the recycled gas, leads to an increase in production of up to 25 % with a simultaneous decrease in fuel rate of 20 % at fixed metal temperature. These calculations show that top gas recycling could be used to increasing furnace efficiency while decreasing carbon emissions thus making a positive contribution to efforts to prevent global warming.