Blast Furnace Tuyere Research Articles

Simulation of Pulverized Coal Combustion in Blast Furnace Tuyere

Coal injection is an important way to reduce the coke ratio in the blast furnace. The combustion of pulverized coal in tuyere and raceway directly affects the production efficiency of smelting. Based on the design and production data of a 2000 m3 blast furnace, a three‐dimensional mathematical model of pulverized coal combustion in tuyere and raceway is established. The lower part of the blast furnace consisting of blowpipe‐coal lance‐tuyere‐raceway and coke bed is numerically simulated to study the influence of blast rate and oxygen on pulverized coal combustion under a certain coal injection ratio and a certain coal particle size distribution. The simulation results show that the pulverized coal burnout decreases from 69.2% to 67.4% when the blast velocity is increased by 20 m s−1, and the oxygen content increases from 23% to 27%, which can improve the pulverized coal burnout and increase the temperature in the raceway. A new direction is proposed to increase the pulverized coal burnout by optimizing the particle size selection and increasing the injection ratio of small particle size below 50 μm. The research provides theoretical and data support for increasing pulverized coal burnout.

High-temperature wear resistance, oxidation resistance and melting loss resistance of plasma cladded Co06–Ni60A composite coating for coppery blast furnace tuyere

High-temperature wear resistance, oxidation resistance and melting loss resistance of plasma cladded Co06–Ni60A composite coating for coppery blast furnace tuyere

Research on the failure mechanism of blast furnace tuyere based on experiment and numerical simulation results

The tuyere, an integral component of a blast furnace, plays a vital role in conveying energy and ensuring stable furnace operation. Given the tuyere’s exposure to a complex working environment within the blast furnace, it is prone to breakage and failure. Thus, investigating the causes of tuyere failure is crucial. This study employs computational fluid dynamics alongside experimental characterization to conduct a numerical simulation of the blast furnace tuyere. The research focuses on comparing the velocity and temperature fields of the tuyere under various cooling conditions to analyze the reasons behind its breakage. The findings reveal that the accumulation of alkali metal elements such as Zn, K, and Na on the tuyere’s surface significantly hampers its longevity. Moreover, the cooling water’s flow rate, inlet temperature, and scale thickness emerge as critical factors influencing the tuyere’s cooling efficiency. Notably, each increase of 30 L/min in the inlet flow rate results in a decrease of approximately 3–5 K in the tuyere’s maximum temperature. For every 2 K rise in the inlet water temperature, the tuyere’s maximum temperature increases by 2–3 K. Furthermore, an exponential increase in the tuyere’s maximum temperature is observed with each 0.1 mm increment in scale thickness. When the scale thickness reaches 0.4 mm, the tuyere’s maximum temperature rises to 545.07 K, an increase of 18.49 %. Thus, this study offers novel insights into the causative factors of tuyere failure, contributing significantly to the efficient utilization of energy within the blast furnace and the optimization of the production process.

Numerical simulation of the effect of coaxial and cross-axis injection modes on pulverized coal combustion in the raceway of blast furnace tuyere

The aim of this study is to investigate the influence of the angle of the pulverized coal (PC) injection lance on the combustion characteristics of fuel in the raceway of blast furnace tuyeres. Using FLUENT software, a Euler-Lagrange three-dimensional numerical model was constructed to analyze the influence of different positions of blast furnace tuyere coal powder injection lance (coaxial and cross-axis) on key parameters such as temperature distribution, gas flow, and combustion efficiency. The results demonstrate that adjusting the angle of the injection lance significantly modifies the average and peak temperatures in the raceway, while the composition of gas components remains relatively stable. When the injection lance angle is 10°, the average temperature and peak temperature in the raceway are 2294 K and 2747 K, respectively. When the injection lance angle is 12°, the combustion efficiency of the PC reaches 80.8%. This study reveals the significant impact of the injection lance angle on the combustion process. Especially at an angle of 12°, the combustion efficiency of the blast furnace significantly improves. With coaxial injection, the combustion rate increases as the distance between the injection lance tip and the tuyere increases. This paper is instructive for the optimization of the blast furnace combustion system, which improve fuel utilization efficiency and reduce environmental emissions. This paper provides practical recommendations for adjusting blast furnace operational parameters, offering insights for achieving more efficient and environmentally friendly industrial production.

A Method for Image-Based Interpretation of the Pulverized Coal Cloud in the Blast Furnace Tuyeres

The conditions in the combustion zones, i.e., the raceways, are crucial for the operation of the blast furnace. In recent years, advancements in tuyere cameras and image processing and interpretation techniques have provided a better means by which to obtain information from this region of the furnace. In this study, a comprehensive approach is proposed to visually monitor the status of the pulverized coal cloud at the tuyeres based on a carefully designed processing strategy. Firstly, tuyere images are preprocessed to remove noise and enhance image quality, applying the adaptive Otsu algorithm to detect the edges of the coal cloud, enabling precise delineation of the pulverized coal region. Next, a Swin–Unet model, which combines the strengths of Swin Transformer and U-Net architecture, is employed for accurate segmentation of the coal cloud area. The extracted pulverized coal cloud features are analyzed using RGB super-pixel weighting, which takes into account the variations in color within the cloud region. It is demonstrated that the pulverized coal injection rate shows a correlation with the state of the cloud detected based on the images. The effectiveness of this visual monitoring method is validated using real-world data obtained from a blast furnace of SSAB Europe. The experimental results align with earlier research findings and practical operational experience.

Combustion behavior of co-injecting flux, pulverized coal, and natural gas in blast furnace and its influence on blast furnace smelting

The integration of advanced high-ratio pellet ore smelting technology with flux injection at the blast furnace tuyere offers significant carbon emission and air pollution reductions for iron and steel manufacturers. This study presents a comprehensive thermogravimetric analysis and burnout rate assessment of Russian Bituminous Coal (RB) and flux mixtures across varying mass ratios, alongside a detailed exploration of the catalytic mechanisms of three distinct fluxes on RB combustion. The findings reveal that lime, when added to the coal-flux blend, markedly enhances the overall combustion characteristic index and catalytic impact, more so than limestone or dolomite. The optimal lime admixture of 5 % resulted in a peak S value of 6.30 and a burnout rate of 70.63 %, constituting an increase of 7.64 % over the base case without flux. Lime's superior catalytic performance is attributed to its higher content of calcium-containing compounds, which amplify catalytic activity through increased Ca2+ ion exchange with carboxyl groups. Mathematical model calculations considering the combustion rate of the pulverized coal show that: after the addition of 5 % lime, there is a 133.43 t/d increase in iron production, compared to the 11,323.98 t/d without the addition of flux. When the lime addition amount is 7 %, the proportion of sintered ore in the blast furnace decreases by 6.53 %, and the coke saving is 2.8 kg/t. This research is expected to enhance the understanding of pulverized coal combustion when amalgamated with basic fluxes and serve as a theoretical foundation for optimizing industrial applications.

Injection of hydrogenous gases into the blast furnace tuyeres for reducing CO<sub>2</sub> emissions: a review

Injection of hydrogenous gases into the blast furnace tuyeres for reducing CO<sub>2</sub> emissions: a review

Numerical study of the feasibility of injecting CO2-containing off-gas in an ironmaking blast furnace

The injection of CO2-containing blast furnace top gas (BFTG) to replace reducing gas partially in an ironmaking blast furnace (BF) is a promising approach to achieve carbon neutralisation while potentially maintaining or improving BF performance. However, the feasible injection operating strategy for using CO2-containing BFTG and its effects on in-furnace phenomena are not well understood. In this study, a multi-fluid industrial-scale BF model with a tuyere injection submodel is developed to investigate the impacts of injecting CO2-containing BFTG at the BF tuyere on the in-furnace phenomena in terms of gas flow, temperature field, iron oxides distribution, and BF performance. The results show that: the maximum reducing gas replacement ratio by BFTG is ∼ 15 %, and a further increase leads to an unacceptable flame temperature. As more reducing gas is replaced by the BFTG, the start temperature of the intensified reduction for hematite and magnetite increases while those for wustite and iron decreases; the indirect reduction of iron oxides is improved in 1073–1273 K. The coke rate is increased by around 0.87 kg-coke/tHM with every 1 % reducing gas replaced by the BFTG. The top CO2 emission rate is decreased. This work provides a cost-effective tool to understand the flow-thermal-chemical behaviours inside a BF when CO2-containing gases are recycled in the BF ironmaking process.

Evolution and modification of physicochemical properties of coal-coke-slag powder within the tuyere bird's nest area of a blast furnace

Understanding the occurrence of phases and the evolution of physicochemical properties in coal-coke-slag powder within the blast furnace tuyere's bird's nest area is crucial for reducing carbon emissions and energy consumption in the blast furnace. By dissecting a 2200 m3 blast furnace in China, the temperature field and high-temperature physicochemical properties of coal-coke-slag powder in the tuyere bird's nest area along the radial direction were determined. Firstly, the temperature range in the tuyere bird's nest area spanned from 1523 °C to 1709 °C, with the maximum temperature near the end of the bird's nest area. Secondly, the mass proportions of coal, coke and slag in coal-coke-slag powder were 42.16 %, 25.90 % and 31.94 %, respectively. Along the radial direction of the blast furnace, the degree of graphitization of carbon components of coal-coke-slag increased gradually, and the melting temperature and viscosity of the slag phase also exhibited a gradual increase. Finally, the modification suggestions of the physicochemical properties of coal-coke-slag were put forward, with a focus on three factors: fuel, slag, and temperature. By employing tuyere injection operations with Ca-Fe flux, and using fuel with low ash content, larger particle size, fewer harmful elements, and excellent combustion performance, more heat input was provided to the front of the bird's nest area, which contributed to improved furnace efficiency and performance.

A Study on the Potential of Carbon Dioxide Utilization Through its Co‐Injection with Hydrogen into the Blast Furnace Tuyeres

The potential of CO2 utilization through its injection into blast furnace (BF) tuyeres is studied using the 1D steady‐state zonal model. Scenarios with the injection of CO2, hydrogen, and their co‐injection at various H2/CO2 mass ratios are analyzed. The impacts on factors affecting vertical temperature patterns and the position of the cohesive zone in the BF are identified. A life cycle assessment for several scenarios with various carbon emissions intensities of hydrogen production, carbon capture, and grid electricity generation is performed. Injection of CO2 without the addition of hydrogen increases the coke rate, reduces productivity, and increases direct CO2 emissions; however, thanks to producing top gas with higher calorific value, injection of CO2 may reduce the global warming potential (GWP) if the electric grid carbon intensity is above 654 kg‐CO2 kWh−1, while carbon capture is powered by green electricity. Although the injection of hydrogen alone would result in a more substantial reduction of GWP from the baseline than the injection of H2/CO2 mix at any mass ratio, considering the identified impacts on heat exchange and the position of the cohesive zone in the BF, co‐injection might be an enabling solution for the adoption of hydrogen injection.

Abnormality Detection of Blast Furnace Tuyere Based on Knowledge Distillation and a Vision Transformer

The blast furnace tuyere is a key position in hot metal production and is primarily observed to assess the internal state of the furnace. However, detecting abnormal tuyere conditions has relied heavily on manual judgment, leading to certain limitations. We proposed a tuyere abnormality detection model based on knowledge distillation and a vision transformer (ViT) to address this issue. In this approach, ResNet50 is employed as the Teacher model to distill knowledge into the Student model, ViT. Firstly, we introduced spatial attention modules to enhance the model’s perception and feature-extraction capabilities for different image regions. Furthermore, we simplified the depth of the ViT and improved its self-attention mechanism to alleviate training losses. In addition, we employed the knowledge distillation strategy to achieve model lightweighting and enhance the model’s generalization capability. Finally, we evaluate the model’s performance in tuyere abnormality detection and compare it with other classification methods such as VGG-19, ResNet-101, and ResNet-50. Experimental results showed that our model achieved a classification accuracy of 97.86% on a tuyere image dataset from a company, surpassing the original ViT model by 1.12% and the improved ViT model without knowledge distillation by 0.34%. Meanwhile, the model achieved a competitive classification accuracy of 90.31% and 77.65% on the classical fine-grained image datasets, Stanford Dogs and CUB-200-2011, respectively, comparable to other classification models.

Analysis of Erosion Mechanism of Wear‐Resistant Layer in Large Blast Furnace Tuyere

The blast furnace tuyere is a crucial component for blast furnace production. The frequent damage of the copper tuyere impedes the smooth operation of the blast furnace. Welding a wear‐resistant layer on the tuyere can extend its service life, but it still falls short of the expectation in a large blast furnace. In this article, it is aimed to elucidate the erosion mechanism of the wear‐resistant layer. A scanning electron microscope, an energy dispersive spectrometer, and an optical microscope are employed to examine the morphology, composition, and metallographic structure of the samples obtained from a 5800 m3 blast furnace tuyere in China, as well as to calculate the frequency of daily slag crust shedding from cooling staves. The results indicate that the main cause of the erosion of the wear‐resistant layer is the shedding of slag crust due to the temperature fluctuation of the cooling staves. Finally, the erosion mechanism of the wear‐resistant layer is proposed. It is suggested that the formation and propagation of cracks caused by erosion of slag and hot metal are the primary failure mode of the wear‐resistant layer.

Effect of ring groove in a heat-insulating insert on efficiency of its work in blast channel of blast furnace tuyere

One of the main disadvantages when supplying natural gas to the air tuyere of a blast furnace is low intensity of its combustion inside the tuyere blast channel. Ring groove on the surface of blast channel improves the mixing of natural gas with blast and increases completeness of gas combustion in it, but reduces the tuyere durability. One of the ways to simultaneously solve these problems is to install a heat-insulating ceramic insert in the tuyere blast channel. The insert significantly reduces heat losses through the tuyere surface, improves natural gas combustion in the blast channel due to its contact with hot walls of the insert instead of cold copper walls in its absence. This increases the temperature of the hot blast at the tuyere outlet. In addition, the insert affects the tuyere durability by reducing the heat flow acting on the tuyere. In this work, we studied influence of the ring groove and its parts in the insert on efficiency of its work. In the Ansys 21.1 software, the processes occurring in the blast channel of a blast furnace tuyere with a ceramic insert installed in it, having a groove of a quadrangular section in the form of a ring or its part in the circumferential direction, were simulated. It was established that improvement of natural gas combustion in the tuyere blast channel is achieved using a ring groove or part of it from the side of gas supply.

Analysis of the failure mechanism of a blast furnace tuyere sleeve with protective coating

The tuyere sleeve plays a crucial role in blast furnaces, enduring a harsh working environment that frequently leads to substantial damage. One approach to extend the service life of tuyere sleeve is to prepare a Ni-based alloy protective layer on its surface. However, there is a lack of experimental information concerning the failure of these protective coatings after real-world use. Therefore, in this study, the failure of a blast furnace tuyere sleeve with protective layer was investigated. Characterizations were performed on both the “original” and failed protective layers, as well as the scale layer. The “original” protective layer exhibits two main issues: excessive copper dilution (＞40%) and significant Ni-Cr enrichment at the interface, which may be attributed to inadequate preparation techniques. The failed protective layer surface is covered with molten slag and iron, and there is a crack running almost completely through the coating. Both oxidation reaction and sulfur corrosion are important factors contributing to the accelerated failure of the coating. Moreover, it is suggested that the compositional inhomogeneity of the protective layer of the tuyere sleeve leads to local stress concentration within the coating, which is an internal cause for thermal fatigue crack formation. Additionally, it can be inferred that the molten slag and iron falling onto the protective layer surface under abnormal furnace conditions not only accelerates crack initiation and propagation but also directly melts the coating material or causes interface reactions, leading to the failure of the protective layer.

Effect of the Surface Relief of the Heat-Insulating Insert in the Blast Channel of Blast-Furnace Tuyere on Its Efficiency

Effect of the Surface Relief of the Heat-Insulating Insert in the Blast Channel of Blast-Furnace Tuyere on Its Efficiency

Optimization Study of Annular Wear-Resistant Layer Structure for Blast Furnace Tuyere

A new tuyere small sleeve coating structure that balances the high thermal conductivity of the copper substrate with the high wear resistance of the protective layer was developed in this paper. This structure can achieve a low-carbon blast furnace by reducing the heat loss from the tuyere. The 3D model was established via Solidworks for modeling and Ansys for numerical simulation, the temperature field of the annular wear-resistant layer structure tuyere small sleeve with different widths of the wear-resistant layer was analyzed and compared with the temperature and stress field of traditional tuyere small sleeve. The results show that the design of the annular wear-resistant layer structure of the tuyere small sleeve is more effective. The new annular wear-resistant layer structure for the tuyere small sleeve results in a decrease of 24 K in the average temperature of the wear-resistant coating. The comparison of this structure with tuyere sleeves without wear-resistant coatings shows a 16.7% reduction in heat loss, improves the wear resistance of the tuyere, providing new technological ideas for low-carbon blast furnace production. Compared with the tuyere sleeve completely covered with a wear-resistant coating, the maximum thermal stress of this structure decreased from 624.98 Mpa to 427.99 Mpa, resulting in a reduction of 31.5%, which is beneficial for the service life of the tuyere sleeve. The copper surface temperature of the new tuyere small sleeve is in a safe range when the temperature is below 2273 K.

A high temperature wear-resistant Ni-based alloy coating for coppery blast furnace tuyere application

With the aim to improve the high temperature wear resistance of copper, a Ni-based coating was fabricated on its surface by plasma cladding. The coating has no crack defects and forms a metallurgical bonding with copper substrate (dilution rate 13.3 %). The γ-(Cu, Fe, Ni), Cr23C6, CrB, Fe3Ni and Ni3Si phases make the coating have strong bearing and plastic shear resistance, resulting in significantly higher wear resistance than the copper substrate. As the temperature increases, the wear resistance of the coating shows a trend of increasing first (about 400 °C and 500 °C) and then decreasing (above 600 °C). NiO oxide layer on the coating surface plays an important role in the transformation of wear resistance and wear mechanism. Heat transfer characteristics analysis results (based on the service conditions of blast furnace tuyere) show that manufacturing the coating on the inner wall of tuyere has no obvious effect on the overall temperature field distribution. The maximum temperature of the coating surface is only about 191.06 °C, which is far below its allowable temperature (600 °C). Therefore, the Ni-based coating can be applied to the surface strengthening for the inner wall of blast furnace tuyere.

Research on Blast Furnace Tuyere Image Anomaly Detection, Based on the Local Channel Attention Residual Mechanism

The channel attention mechanism is widely used in deep learning. However, the existing channel attention mechanism directly performs the global average pooling and then full connection for all channels, which causes the local information to be ignored and the feature information cannot be reasonably assigned with the proper weights. This paper proposed a local channel attention module, based on the channel attention. This module focuses on the local information of the feature image, obtains the weight of each regional channel through convolution, and then integrates the information, so that the regional information can be fully utilized. Moreover, the local channel attention module is combined with the residual module, and the local channel attention residual network LSERNet is constructed to detect the abnormal state of the blast furnace tuyere image. With sufficient experiments on the collected datasets of the blast furnace tuyere, the results show that the proposed method can efficiently extract the feature information, and the recognition accuracy of the LSERNet model reached 98.59%. Further, our model achieved the highest accuracy, compared with SE-ResNet50, ResNet50, LSE-ResNeXt, SE-ResNeXt, and ResNeXt models.

Effect of natural gas flow rate and temperature on the processes occurring in a blast furnace tuyere with heat-insulating insert in blast channel

The purpose of this work was to analyze the effect of a heat-insulating insert, as well as the flow rate and temperature of natural gas on the processes occurring in blast channel of an air tuyere. The paper analyzes the results of industrial and numerical experiments obtained by different researchers on the use of various methods for increasing the completeness of combustion reaction within the air tuyere of natural gas (NG) fed into it: increase of NG flow rate; increase of NG temperature; the use of heat-insulating inserts installed in the inner glass of the air tuyere. Using the Ansys Fluent software complex, the effect of a heat-insulating insert and increase in NG flow rate on the temperature and composition of gases leaving the tuyere of blast furnace no. 5 of PJSC Severstal was studied. It was found that with an increase in NG flow rate from 0.283 to 0.328 kg/s, the temperature of the gas medium at the tuyere outlet decreases by 6 °С for the variant without an insert and increases by 3 °С for the variant with it. When studying the effect of a heat-insulating insert and increase in NG temperature (in different combinations) on the processes occurring in a tuyere, it was found that temperature of the gaseous medium at the tuyere outlet in case of using a heat-insulating insert without NG heating is slightly higher than when NG is heated to 200 °С without inserts. However, the effect of NG heating in the presence of an insert is significantly higher than without it – there is mutual amplification of two factors influencing the completeness of NG combustion within the tuyere, accompanied by protection of the tuyere inner nozzle from burnout.

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.