Hearth Erosion Research Articles

Erosion Behavior and Longevity Technologies of Refractory Linings in Blast Furnaces for Ironmaking: A Review

Erosion of the refractory materials in blast furnaces (BFs) greatly limits their campaign life, which seriously reduces the economic benefits of iron and steel plants and endangers workers. Therefore, it is important to detect and monitor the erosion process of refractory materials in the BF hearth. In this review, the mechanisms of physical damage, chemical corrosion, and mechanical erosion of BF hearths during BF operation are analyzed and summarized. In addition, the effects of hearth structure, refractory type, and protective layer on hearth erosion behavior and hearth life are analyzed and discussed. Some longevity technologies of BF hearths are analyzed and compared, such as reasonable hearth structure design, refractory selection, and technologies to form protective layers. Finally, some suggestions and prospects for the future development of long campaign life BF hearths are discussed.

Estimation of the Blast Furnace Hearth State Using an Inverse-Problem-Based Wear Model

An undisturbed and well-controlled hearth state is an essential prerequisite for achieving a long campaign life and low production costs in an ironmaking blast furnace, because hearth wear and hot metal and slag drainage are crucial factors in its operation. With the objective to estimate the hearth state of the refractory of a three-taphole blast furnace, a wear model of the hearth erosion and skull formation was developed. The model is based on thermocouple readings in the hearth lining and solves an inverse heat conduction problem for a series of co-axial vertical slices, where the erosion and skull lines are optimized simultaneously. The model is optimized for fast computation by adopting a novel procedure featuring fixed mesh during the looping calculation. The results revealed that the hearth refractory showed an elephant-foot-shaped profile with excessive erosion in the hearth periphery, indicating that liquid flows are suppressed in the hearth bottom and that the permeability of the core of the deadman is low. These findings were further elaborated and confirmed by a comparison between the estimated hearth state and other key operation variables, including the coke rate, blast kinetic energy, and residual carbon appetite of the hot metal.

Investigation of the Hearth Erosion of WISCO No. 1 Blast Furnace Based on the Numerical Analysis of Iron Flow and Heat Transfer in the Hearth

The campaign life of a blast furnace is largely limited by the erosion state of its hearth section. Therefore, the study of hearth erosion is important for blast furnace ironmaking. In this study, the hearth erosion of the WISCO No. 1 blast furnace was investigated in combination with the numerical analysis of the iron flow and heat transfer in the hearth. The distributions of the wall shear stress and the temperature in the hearth were simulated and the hearth sections with high erosion risk were discussed. The hearth lining with higher shear stress is generally located near the taphole region and the 1423 K isotherm is totally located inside the hearth lining structure, with a deeper position in the central part of the hearth bottom. Based on the measurement data from the hearth damage investigation, the erosion state of the hearth bottom and the lower part of the hearth sidewall is more serious. The erosion line at the hearth bottom showed a typical “pot-bottom” shaped contour and for the hearth corner section, the average erosion depth was about 1/3 of the total wall thickness. The empirical expressions between the hearth erosion depth and the wall shear stress and the temperature were established. Moreover, the effects of key iron tapping factors on the wall shear stress and the effect of the hearth’s refractory structure on the heat transfer in the hearth are respectively discussed, aiming to provide more suggestions for hearth protection.

Hot metal flow characteristics and its contribution to hearth erosion in the early stage of blast furnace campaign

Hot metal circulation is one of the most important factors for hearth erosion. In this article, both the production conditions reflected by production parameters and the actual erosion state are considered. A series of cases are set up to analyze the hot metal flow characteristics and its contribution to hearth erosion. The main results are as follow: (1) There are two asymmetric high-speed bands existed on both side of the taphole, which is caused by the inner shape of blast furnace hearth and will cause the erosion of blast furnace hearth. (2) The velocity inside the deadman has an obvious decrease from top to middle part and then keeps almost stable, especially at the edge of deadman. It is caused by the inhibition effect of molten iron flow around deadman, and may result in a slower update rate of deadman in the lower part as well as an increase of carbon unsaturation in the molten iron. (3) The velocity of line 4–5# around the bottom increases with the increasing of daily output, and decreases with the increasing of the depth of salamander. Therefore, in the early stage of the blast furnace campaign, a production process with high utilization factor will increase hearth erosion. (4) The inner shape of hearth and the distance between sidewall and deadman are the main factors affecting the flow rate of molten iron.

Effect of titanium on the skull formation of the blast furnace hearth

The erosion of the blast furnace hearth has become one of the key factors affecting the life of the blast furnace, because of the limited on-line monitoring and control means in the blast furnace hearth area, the burn-through accidents of the blast furnace hearth and bottom occur occasionally. In this work, based on the self-built platform of heat flow regulation, the control mechanism of the high melting phases of TiC is studied. The on-line control mechanism of the hearth erosion by adding titanium-containing materials was discussed. There are three steps for the on-line control of iromaking using titanium-containing materials in blast furnace. Firstly, Ti(C, N) precipitated from the molten iron due to the decrease of temperature in the erosion zone of the hearth. Secondly, the viscosity of the molten iron increased with the precipitation of Ti(C, N) in the erosional cryogenic zone and temperature further decreasing. Finally, the protective layer, included pig iron matrix and Ti(C, N) solid fulcrum, formed because of the solidification of the molten iron. The protective layer can replace the corroded lining of the blast furnace to prevent its hearth from being eroded.

Investigation of water distribution features among pipes in BF hearth

The cooling system is important for the safety of blast furnace production. Measurements for over six months on a 1350 m3 blast furnace have shown that water volume distribution among the pipes in hearth is not uniform. The nature of the water volume distribution curve remains constant while furnace operation is normal, but is influenced by features of heat flux and hydrodynamic to the bustle pipe, which result in a 40–60% difference between maximum and minimum flow rates through individual pipe assemblies. A change in water volume is generally taken up by pipes that are working well. The water volume varies by 20–40% between pipes. That the problem about water non-uniform distribution of water-supplying system in cooling system is caused by the hydrodynamic pulsations existed between the parallel pipes and individual pipe. The cooling water temperature difference and water volume shows negative relationship. There may be some false positives of hearth erosion trends when the state of erosion is determined by water temperature difference for the non-uniform distribution of water volume. The inhomogeneity of the cooling intensity among the pipes merits attention.

Fuzzy grey relational analysis for influencing factors of heat transfer in a blast furnace hearth

ABSTRACTFor a blast furnace, the hearth erosion profile is mainly determined by the temperature distribution in the refractory. Numerical simulation was conducted to simulate the heat transfer and flow in a blast furnace hearth. Based on the simulation results, a fuzzy grey relation analysis method combining the grey entropy analysis and Euclidean grey relation analysis was put forward for evaluating the effects of various factors on the temperature distribution of sample areas at the bottom and sidewall refractory. Impacts of four typical factors (porosity of deadzone, floating height of deadman, radius of deadzone and temperature of cooling water) were evaluated by grey entropy analysis and Euclidean grey relational analysis, respectively. Lastly, a fuzzy grey relational analysis was employed to make a comprehensive evaluation of the four factors. Results have shown that the floating height of deadman is the dominant factor affecting the temperature distribution both on the bottom and sidewall.

Analysis of the Relationship between Productivity and Hearth Wall Temperature of a Commercial Blast Furnace and Model Prediction

High smelting intensity and long campaign life are highly desired for blast furnace ironmaking. However, high smelting intensity or productivity has an adverse effect on the campaign life. An analysis of the relationship between productivity and the temperature of a side wall of a hearth based on the data from a commercial blast furnace is first presented in this work. Then, to predict the temperature, a mathematical model is established with an iron flow estimation model. Based on the model, an outline of measures to extend the campaign life of a BF is discussed. Finally, a better initial profile for a BF hearth is proposed. The prediction shows that the convective heat transfer coefficient increases with the increase of molten iron circulation. The hearth erosion at 1.5 m below the taphole centerline is more severe than other locations because the corner of the deadman is located at this level and the distance between the deadman surface to the side wall reaches the minimum point. The sidewall of hearth might be constructed with a slope so that the distance between the sidewall of hearth and the deadman surface can be large at the deadman corner, reducing the circulation of the molten iron.

Critical Heat Flux of Blast Furnace Hearth in China

The critical heat flux surveys of thirteen Chinese blast furnaces were carried out. The mathematical model of hearth bottom was established and the temperature field was simulated by utilizing the method of inverse problem based on the collected parameters and temperature data. The critical heat flux and dangerous critical heat flux of hearth were defined and analyzed as well as the initial and investigative critical heat flux of hearth, and the influences of thermal conductivity and residual thickness of carbon bricks on critical heat flux were discussed. The relationships between critical heat flux of stave and hearth bricks were also compared. It is found that the dangerous critical heat flux of these blast furnaces ranged from 9.38 to 57 kW/m2. Therefore, there was no uniform critical heat flux of hearth due to the structure design, refractory materials selection, construction quality of hearth and other factors. The heat flux should be lower than the critical heat flux with corresponding thickness of carbon bricks to control the erosion of hearth. The critical heat flux of stave would be much lower than that of hearth bricks with the air gap. However, the critical heat flux of stave should be higher than that of hearth bricks when gas existed between furnace shell and staves.

Sensitive Influence of Floating State of Blast Furnace Deadman on Molten Iron Flow and Hearth Erosion

Sensitive Influence of Floating State of Blast Furnace Deadman on Molten Iron Flow and Hearth Erosion

Influence of Different Porosity of Dead-Man to Flow of Hot Metal in the Hearth of Blast Furnace

Circuiting flow of hot metal is one of reasons for erosion in hearth, which is brought mainly by dead-man in hearth. Studies the influence of different porosity of dead-man to flow of hot metal in the hearth of blast furnace .The results show that:When the porosity of dead-man is reduced,the hot metal on the bottom and the wall of furnace erosion increase.

Influence of Hot Metal Flow State to the Hearth Flow Field during Blast Furnace Tapping

Blast furnace tapping is one of the most important aspects of BF iron-making, a process during which the ideal state is for the molten iron to remain the invariant and the level of liquid to remain stable. However, due to the viscosity of molten iron, the liquid level will tilt to one side near the tap-hole, causing the iron flow field during blast furnace tapping to change with time. This research simulated two cases of horizontal and inclined molten iron liquid levels in the process of blast furnace tapping. This study also discusses different hearth erosion situations and explains the rationality of blast furnace large-scale trends from the perspective of molten iron liquid level stability.

Monitoring of Blast Furnace Hearth Erosion

The distribution function of temperature in blast furnace satisfies a series of equations. The location and shape of hearth erosion line of blast furnace can be calculated by the data from thermocouple. We use the method of perturbation solution to solve the inverse problem and estimated the error by using related mathematical theories.

Monitoring System of Firebrick Lining Erosion of Blast Furnace Hearth

It is possible to increase the efficiency of the computer-based system of diagnostics of the elements state of the firebrick lining by means of use in their structure of the module, in real time revealing the structural changes of non-stationary controlled signals. These changes as a rule testify the occurred deviations in the technical condition of the controlled object. The received information about the revealed structural features in analyzed signals it is expedient to use for forecasting of further dynamics of controlled parameters. The mathematical description and the computer program “Hearth Erosion” of calculation the two-dimensional temperature fields in any vertical and horizontal section of the blast furnace hearth are developed. Calculation is carry out the decision of the equations of heat conductivity with use of indications of the big number of sensing transducers of temperature (to 1000), built in the furnaces firebrick lining between the firebrick blocks. The continuous control of the temperature change in each point allows to define the remained thickness the firebrick lining and to warn, in case of need, the furnace personnel about the beginning of the firebrick lining erosion. The continuous control of change of temperature in the firebrick lining is made on the basis of mathematical model. The system of collecting, processing and transfer information from sensing transducers of temperature or thermal streams in a program database “Hearth Erosion” is used. Programs are installed on blast furnaces of Chinese National Republic: Jinan, Jiyuan and Liuzhou Iron and Steel Works together with Russian-Chinese company SKKONT.

Numerical Prediction of Iron Flow and Bottom Erosion in the Blast Furnace Hearth

AbstractThe blast furnace (BF) campaign life, which is limited by the hearth erosion, will be decisive for the process to maintain its dominance in ore‐based iron production, so timely prediction of the hearth erosion and proper measures to protect the hearth are important issues. The erosion at the hearth bottom has not received much attention, even though the region is believed to be the most vulnerable part of the hearth. A computational fluid dynamic (CFD) model has been developed to deepen the understanding of iron flow and refractory erosion at the bottom of the hearth. Key boundary and internal conditions, such as slag–iron interface and dead man state, are provided by a BF drainage model which reproduces the tapping process. Simulations with the CFD model illustrate how different factors affect the flow pattern, hearth erosion profile, and bottom breakage ratio. It is shown that the dead man state plays an important role for the flow behavior and erosion conditions in the hearth. The model is demonstrated to predict two erosion types that are commonly encountered in practice.

The Numerical Prediction of the Titanium Carbide Distribution in the Blast Furnace During Tapping Process: A Preliminary Study

To prolong the campaign life of the furnace hearth for high demand in the steel market, the theme of preventing the hearth wall from erosion phenomenon is worthily studied for steel industry. The titanium carbide (TiC) concentration distributions in the blast furnace hearth can be used to suppress the erosion phenomenon of the hearth wall. In this work, we solve the momentum and the thermal-energy-balance equations, as well as the mass transfer equation with chemical reaction effects to investigate the TiC concentration profiles in the hearth of Port Kembla no. 5 blast furnace (PKBF5) by means of a computational fluid dynamics (CFD) package, Fluent (version 6.2). As shown in the results, the elephant foot erosion and pot-like erosion in the hearth may be restrained based on the calculated TiC concentration distributions. Additionally, this work illustrates that deadman type may be inferred based on the calculated TiC concentration profiles when the blast furnace is revamped.

Monitoring erosion and skull profile in blast furnace hearth

In the blast furnace process, the hearth is subject to chemical and physical erosion. A mathematical model for the prediction of the refractory material thickness in the wall and bottom area of the hearth (MUSA) is presented. By combining online reading of temperatures and historical data, the erosion profile in the hearth lining and the thickness of any skull can be calculated by the model. For the prediction of erosion and skull profile, a heat conduction problem was considered: numerical results are presented and discussed.

Model for Fast Computation of Blast Furnace Hearth Erosion and Buildup Profiles

A model for estimation of the profiles of erosion and buildup material in the hearth of an ironmaking blast furnace has been developed. The model is based on thermocouple readings in the hearth wall and bottom and solves an inverse heat transfer problem for two-dimensional slices of the hearth geometry to estimate the inner profile. Special attention has been paid to the mathematical formulation of the problem at hand, yielding a general model optimized for fast computation. This includes a flexible formulation of the boundary conditions, a generic setup of the lining materials applied in the hearth refractory, and a sophisticated iterative procedure in the estimation of the location of the internal profile. These steps have led to a model that facilitates process analysis with estimation and reestimation of the furnace hearth conditions over whole campaigns using different parameter settings. The model has been applied to study the evolution of the hearth erosion and buildup formation processes in severa...

CFD Modelling of Liquid Metal Flow and Heat Transfer in Blast Furnace Hearth

An in-depth understanding of the liquid metal flow and heat transfer is essential in order to identify the key mechanisms for the hearth erosion of a blast furnace. In this study, a comprehensive computational fluid dynamics model is described which predicts the flow and temperature distributions of liquid iron in blast furnace hearth, and the temperature distribution in the refractories. The new model addresses conjugate heat transfer, natural convection and turbulent flow through porous media, with its main features including improved transport equations (a modified k–ε turbulence model and thermal dispersion term) and a three-dimensional, high-resolution grid. The new turbulence model and terms take account of the effect of microscopic flows around coke particles and allow unified treatment of coke bed and coke-free layer. The predicted results show a well-organized flow pattern: two large-scale recirculation zones are separated vertically at the taphole level. This flow pattern controls the temperature distribution in the liquid phase, so that the temperature remains nearly uniform in the upper zone, but changes mainly across the lower zone. The effects of several factors were examined, such as cases comparing fluid buoyancy with constant fluid density as well as the shape and position of the coke free zone (i.e. based on reported dissection studies). Natural convection is found to be most important for the liquid metal flow patterns observed. Comparison with the plant data shows that the refractory pad temperature is under-predicted when assuming intact hearth lining. The pad temperature is very sensitive to the erosion of protection layer in the hearth lining.

A Methodology for Blast Furnace Hearth Inner Profile Analysis

The wear of a blast furnace hearth and the hearth inner profile are highly dependent on the liquid iron flow pattern, refractory temperatures, and temperature distributions at the hot face. In this paper, the detailed methodology is presented along with the examples of hearth inner profile predictions. A new methodology along with new algorithms is proposed to calculate the hearth erosion and its inner profile. The methodology is to estimate the hearth primary inner profile based on 1D heat transfer and to compute the hot-face temperature using the 3D CFD hearth model according to the 1D preestimated and reestimated profiles. After the hot-face temperatures are converged, the hot-face positions are refined by a new algorithm, which is based on the difference between the calculated and measured results, for the 3D computational fluid dynamics (CFD) hearth model further computations, until the calculated temperatures well agree with those measured by the thermocouples.