Blast Furnace Hearth Research Articles

Analysis of existence state and deterioration mechanism of coke in a blast furnace hearth

Analysis of existence state and deterioration mechanism of coke in a blast furnace hearth

Experience of co-injection of pulverized coal and natural gas into blast furnace hearth under the conditions of PJSC "KAMET-STEEL"

The article provides an analysis of the practical and analytical results of the methods of co-injection of pulverized coal and natural gas into the hearth of blast furnaces by American researchers and practitioners. The analysis shows the advantage of supplying natural gas, as well as pulverized coal, through the lance into the blow channel of the tuyere device. Practical results obtained for the first time in Ukraine of co-injection of pulverized coal and natural gas into the hearth of a blast furnace in unstable charge and fuel conditions of PJSC "KAMET-STEEL" are presented. Practical experiments have proven the efficiency of such injection when fuel additives are injected onto separate lances into the blow channel of the tuyere device, and the natural gas lance is withdrawn so that its combustion occurs before the injection of pulverized coal into the blow channel. The effectiveness of the practical application of the method of co-injecting pulverized coal and natural gas into the hearth of a blast furnace is expressed in a reduction in the specific coke consumption by 10.3 kg/ton of cast iron (or 2.85 %) at a consumption of pulverized coal — 153.4 kg/ton of cast iron and natural gas — 24.5 m3/ton of cast iron. The results obtained allow us to recommend this method of injecting fuel additives under acceptable price conditions, as well as at other metallurgical plants, especially those operating with better conditions for ensuring high temperatures of hot blast — more than 1050 °C. As a result of the analytical studies performed, it was established that: nozzles with two inlets for natural gas and pulverized coal, ensuring the introduction of natural gas into the blast channel before pulverized coal, contribute to the maximum burnout rate of the latter in the blast flow; with this injection method, more methane natural gas is burned, more heat is released due to the combustion reaction, which leads to an increase in the blast temperature at the outlet of the tuyere.

Узагальнення методичних підходів до розрахунку енергетичних параметрів газового потоку в горні доменних печей при вдуванні комбінованого дуття

Узагальнення методичних підходів до розрахунку енергетичних параметрів газового потоку в горні доменних печей при вдуванні комбінованого дуття

Dissolution characteristics of TiC0.3N0.7 in low-carbon and safe blast furnace hearth

Investigating the presence of a Ti(C,N) protective layer in molten iron is of great significance for achieving low carbon and safe production in blast furnaces. This study focuses on analyzing the high temperature dissolution experiment of TiC0.3N0.7 in molten iron to elucidate the kinetics and mechanisms involved, as well as strategies for regulating its dissolution. The results reveal that the dissolution reaction of TiC0.3N0.7 is predominantly influenced by the temperature and flow speed of the molten iron. The dissolution process can be categorized into two stages: dissolution reaction and physical penetration. Diffusion mass transfer is the dominant factor controlling the dissolution of TiC0.3N0.7, with an apparent activation energy of 60.15 kJ/mol. Upon contact with molten iron, dendritic penetration of TiC0.3N0.7 particles occurs, starting from the edges. To enhance the stable presence of TiC0.3N0.7, recommendations include reinforcing furnace cylinder cooling, reducing the heat transfer coefficient of the blast furnace hearth's resistant material, increasing the carbon content of the molten iron, and decreasing the sulfur content of the molten iron.

Evaluation, Prediction, and Feedback of Blast Furnace Hearth Activity Based on Data‐Driven Analysis and Process Metallurgy

For complex, difficult‐to‐control, and hour‐delay blast furnace (BF) systems, the quantitative characterization, prediction, and adjustment of the BF hearth activity are significant in improving the furnace status. In this study, data including raw fuel, process operation, smelting state, and slag and iron discharge during the entire BF process are analyzed, with a total of 171 variables and 5033 groups of data. Based on the knowledge of BF technology, a comprehensive index of hearth activity is then proposed to quantitatively characterize and grade the activity level of the BF hearth; the rationality of this method is verified from the two aspects of furnace heat level and furnace status coincidence. Compared with the traditional single‐machine learning algorithm, the performance of the proposed method that combines genetic algorithm and stacking exhibits significant improvement. The hit rates for 10% and 5% errors in the prediction and estimation of hearth activity are 94.64% and 80.36%, respectively. To enhance the BF hearth activity, quantized and dynamic actions and suggestions are also simultaneously pushed. The model of BF hearth activity is successfully applied in practical online production. During the application period, the average furnace hearth activity increases by 10% compared to the historical value.

Regulation of Ti(C,N) deposition on hot surface of refractory in blast furnace hearth

Regulation of Ti(C,N) deposition on hot surface of refractory in blast furnace hearth

Research on Weighing System and Debugging Technology for Batching Under Blast Furnace Ore Tank

The article introduces the composition and working principle of the batching and weighing system underneath the blast furnace hearth. Besides, the shortcomings of the batching and weighing system during installation, debugging, and calibration, as well as the dynamic errors in the batching process are also analyzed. Corresponding solutions are then provided.

Phase and formation mechanism of the brittle layer of ASC castable in blast furnace hearth

An Al2O3-SiC C castable BF was dissected and investigated in the present work. The phase composition and microstructure of the brittle layer of castable and the original castable after service were analyzed by XRD, chemical analysis, and SEM-EDS. The results show that a brittle layer of castable with a thickness of about 50–300 mm is found at the bonding surface between the carbon brick and castable on the sidewall of the hearth. Zn enrichment was found in the brittle layer of castable. In the high-temperature environment of the furnace sidewall, the evaporation of water and formation of mullite phase in the process of phase transformation at high-temperature lead to the formation of pores and microcracks in the castable. Stress concentration in the joint area of the castable and carbon brick was produced due to their different expansion coefficient, and the microcracks in the castable gradually develop and expand under the action of thermal stress. In addition, the diffusion of CO, alkali metal steam, and Zinc vapor in the blast furnace hearth and the expansion caused by the reaction product with the original phase of castable accelerated the propagation of microcracks in castable and finally formed the macro-brittle layer.

Erosion Mechanism of Carbon Brick in Hearth of 4000 m3 Industrial Blast Furnace

After dissection of a large blast furnace, the erosion mechanism of carbon bricks after service in a blast furnace (BF) hearth was studied. Obvious “elephant foot” erosion characteristics emerged in the height direction of the BF. The existing forms of carbon bricks after service were characterized by X-ray diffraction (XRD), scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS), and chemical analysis. The results showed that Zn and iron erosion above and below the taphole was observed in the BF, while iron and Zn erosion acted only as a key factor of carbon brick erosion. The convective heat transfer coefficient in the lower part of the hearth of the BF was large, which increased the temperature of the hearth sidewall, resulting in the increase in the carbon-unsaturation of the molten iron at the sidewall, and intensified erosion to the hearth sidewall. The average pore size (1.083 μm) of the carbon bricks on the hot-face of the hearth sidewall was smaller than the critical size (2.12 μm) of the molten iron that penetrated the pores of the carbon bricks, which was not conducive to the penetration of molten iron.

Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

The brittle layer of carbon brick in a Chinese 4000 m3 blast furnace hearth is investigated in detail, and its formation mechanism is proposed correspondingly. The occurrence form of the brittle layer in carbon brick is characterized by chemical analysis, X‐ray diffraction, and scanning electron microscopy–energy dispersive spectroscopy. The results show that obvious harmful element (K, Na, and Zn) erosion on the sidewall of the blast furnace hearth is observed, in which Zn erosion is dominant. The K2O, Na2O, and KCl produced in the carbon brick by K and Na are the inducement of the brittle layer formation, and the ZnO formed by Zn is the main reason for the brittle layer formation. The thermal stress caused by temperature gradients in carbon brick is greater than its bending strength, which will increase the microcracks in carbon brick. The brittle layer has a lower thermal conductivity due to higher porosity, resulting in a large temperature difference. The resulting thermal stress will aggravate the embrittlement degree.

Material composition and microstructure of ceramic glass й hearth of blast furnace No. 6 of JSC EVRAZ NTMK after service. Refractory microstructure after service

The results of a comprehensive study of the material microstructure of refractory samples after service in the furnace of a blast furnace with a useful volume of 2200 m3 for 14 years are presented. Structural and genetic analysis established a characteristic sequence of processes of degeneration and wear of the ceramic furnace stack, including 6 stages: the formation of micro-and macro-cracks; condensation of vaporous zinc; zinc oxidation with the formation of fire-resistant ZnO zincite and the deposition of carbon black by the; chemical interaction of zinkite with mullite and corundum to form ZnAl2O4 ganite and 2ZnO·SiO2 willemite; partial oxidation of silicon carbide with the release of silica glass SiO2, eutectic melt of complex composition, and wellimite. Due to intensive accumulation of capillary pores, infiltration of the slag melt in the volume of refractories does not occur. Wear of refractories in the furnace has a complex, mainly thermochemical mechanism and a low speed due to the formation of a garnish containing refractory compounds. Ill. 5. Ref. 14.

State of Deadman in Blast Furnace Hearth and Its Internal Phase Distribution Characteristics

State of Deadman in Blast Furnace Hearth and Its Internal Phase Distribution Characteristics

Mathematical Model of the Movement of Charge Layers and Melt Accumulation in a Blast Furnace Hearth

Mathematical Model of the Movement of Charge Layers and Melt Accumulation in a Blast Furnace Hearth

Effect of water vapour on the interface reaction between carbon brick and molten iron in blast furnace hearth

ABSTRACT In the production process of blast furnace, the damage of cooler and tuyere sleeve and some operation problems often lead to ponding in the hearth. Steam will not only oxidize carbon bricks, but also lead to the falling off of solidification layer, which poses a great threat to the longevity of the hearth. By studying the influence of water vapour content change, the influence mechanism of water vapour on the interface between carbon brick and molten iron in blast furnace hearth is revealed. The results show that the entry of water vapour will isolate the molten iron and carbon brick, and oxidize in contact with the carbon brick, increase the ceramic phase, dissolve into the molten iron, destroy the carbon brick structure at the iron carbon interface, produce spalling, accelerate the destruction and falling off of the solidification layer, so as to reduce the service life of the blast furnace.

Analysis of the impact of carbon dissolution and energy transport on the flow in the hearth of an ironmaking blast furnace by transient CFD simulations

In the ironmaking blast furnace, layers of coke, ferrous burden (sinter, pellets, lump ore) and additions are heated by an uprising gas flow. While the layers are descending, the iron ore is reduced and begins to melt. The liquid products slag and hot metal trickle downwards into the hearth, where they prevail as two immiscible phases filling the voids within the coke bed and with the slag floating on top of the hot metal. As the hearth is lined with carbon blocks, which are eroded by the passing hot metal flow, this region has a major impact on the campaign length of the blast furnace. The blast furnace hearth is drained intermittently by opening the taphole and closing it to end the tap. Hence, the fluid phases in the hearth are in a transient state with the liquid levels constantly varying and the flow conditions being determined by the tapping/non-tapping state. In addition, dissolution of carbon into the hot metal and cooling applied to the refractory affect the local hot metal flow. This work presents a CFD-model, which is capable to calculate the multiphase flow in a 3-dimensional hearth at an industrial scale. The tool allows for modelling of the transient transport processes, including multiple tapping cycles by utilizing new approaches for the transition between tapping/non-tapping and the inflow of liquids into the hearth. Furthermore, the dissolution of carbon, energy transport in the liquids and the locally varying density of hot metal depending on temperature and carbon content are included. With this approach, thermal stratification and circulation effects induced by buoyancy can be described over a period of nearly 8 h, thus covering 4 tapping cycles. In addition to an analysis of energy, carbon content and velocity fields, the transient evolution of tapped hot metal properties (temperature, carbon) are obtained and compared to available plant data.

Thermal Stress Analysis of Blast Furnace Hearth with Typical Erosion Based on Thermal Fluid-Solid Coupling

The life of the hearth is the main limiting link of the campaign of a blast furnace. As the equipment for holding molten iron in the furnace, the high-temperature molten iron is in direct contact with the refractory, which makes the refractory have a larger temperature increase. If the temperature gradient inside the refractory is large, it generates large thermal stress and causes the refractory to crack. Blast furnace gas and molten iron intrude into the gap, which directly causes melting erosion and other chemical erosion with carbon bricks. It aggravates the erosion degree of the furnace and seriously affects the production life of the furnace. Therefore, the furnace often occurs with different types of severe depression erosion in the late service of the blast furnace. In this study, the calculation model of the thermal fluid-solid coupling considering the molten iron flow and the solidification of molten iron was established. This calculation model was applied to study thermal stresses in the furnace with severe erosion. Based on the calculation model, the effect of blast furnace production parameters and deadman condition on thermal stresses in the furnace with severe depression erosion were analyzed, including tapping productivity, tapping temperature, cooling intensity, and deadman geometry. The research results are of great significance for prolonging the safe production life of blast furnaces.

Consideration of long campaign based on analysis of 4038 m3 blast-furnace hearth core investigation

In order to explore the erosion reason of the hearth sidewall built with high thermal conductivity and small hot-pressed graphite carbon bricks, the carbon brick samples were obtained by boring in different parts of the hearth sidewall. By the research on microcosmic structure, thermal conductivity, chemical composition of the carbon bricks, it was concluded that the high portion of large size pore leaded to poor properties of resistance to Zn permeation. And due to the formation of the weakened layer, the transfer system of lining was destroyed, which result in poor effect of titanium protecting and resistance to hot metal erosion. For the purpose of prolonging the campaign of BF hearth, the properties of resistance to hot metal erosion and the thermal conductivity of carbon brick should be matched well.

Finite element based Model Order Reduction for parametrized one-way coupled steady state linear thermo-mechanical problems

This contribution focuses on the development of Model Order Reduction (MOR) for one-way coupled steady state linear thermo-mechanical problems in a finite element setting. We apply Proper Orthogonal Decomposition (POD) for the computation of reduced basis space. On the other hand, for the evaluation of the modal coefficients, we use two different methodologies: the one based on the Galerkin projection (G) and the other one based on Artificial Neural Network (ANN). We aim to compare POD-G and POD-ANN in terms of relevant features including errors and computational efficiency. In this context, both physical and geometrical parametrization are considered. We also carry out a validation of the Full Order Model (FOM) based on customized benchmarks in order to provide a complete computational pipeline. The framework proposed is applied to a relevant industrial problem related to the investigation of thermo-mechanical phenomena arising in blast furnace hearth walls. • Computational pipeline for fast and accurate thermo-mechanical FEM simulations. • Comparison between POD-Galerkin and POD-ANN model order reduction. • Parametric setting involving both physical properties and geometrical features. • Assessment of MOR approach with an industrial problem related to ironmaking process.

Influence of blast volume on hot blast distribution rule around the hearth circumferentially

Abstract Based on Ansteel’s new No. 5 blast furnace (BF), the distribution rule of hot blast on the circumference of blast furnace hearth under different blast volume was studied. The results show that, the blast volume distribution rule is similar under different blast volumes, that is, there are four regions with large blast volumes at the 0°, 90°, 180° and 270° positions of the bustle pipe. Under different blast volumes, the difference of blast volume near 90° and 270° is close to 0, which has a minor effect on the uneven distribution of gas flow and circumferential asymmetry of packed bed in BF. However, the blast volume of the tuyere near the 180° is always larger than that of the tuyere near 0°, and with the increase of blast volume from 4600 to 5000 nm3/min, this difference keeps increasing, 0.69 to 0.95 nm3/min. This phenomenon will lead to an increase in the coke consumption on the 180° side, and cause a higher descending velocity of coke than that on the 0° side, this difference increases from 0.39 to 0.54 m, which could further result in the unevenness of blast volume distribution and the circumferential asymmetry of packed bed in BF. Comparing with the actual production in Ansteel, the results obtained in this work are in good agreement with the phenomenon in practical production.

Migration Behavior of K, Na, S, Ti in Hearth of a Commercial Blast Furnace

Migration Behavior of K, Na, S, Ti in Hearth of a Commercial Blast Furnace