Hearth Wall Research Articles

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.

STUDY OF COMPOSITION AND STRUCTURE OF NLMK BF No. 6 HEARTH SCULL. Report 2

Resistance of hearth walls lining and their joint with hearth plug considerably governs a blast furnace (BF) campaign duration. Development of hearth design of modern BFs provides a high effective heat sink by copper cooling plates and application for the lining carbonaceous blocks having high heat conductivity, which causes stable scull formation. Study of the composition and the structure of the scull is an important and actual task to provide the highest technical and economical indices of blast furnace production, increasing of the furnaces campaign duration. It was shown that the scull in the hearth zone has a laminated structure. It was established that content of titanium compounds (oxide, carbides and nitrides) in the scull is low. Zinc buildups were not found on the carbonaceous refractories of the hearth walls lower the tap hole. Considerable content of zinc compounds was revealed in the scull of brickwork of the hearth top, in the area of tap holes and hole channels, on the hearth refractories. It was found that basic components of the scull were represented by carbon in the form of graphite, metal (mainly in the form of α-Fe) and slag, amount of which was nincreasing from the lower part of the hearth to the upper one while the content of metal and graphite in it was decreasing.

The end of the era of the working carbon lining of the blast furnace metal receiver?

This рaper describes «pumped hearth» product technology, lining configuration considerations and the value/benefits derived from the application of sol-gel bonded, Metpump brand pumpables as compared to conventional carbonaceous linings, which as «pumped hearth» utilization success experience continues to grow, could ultimately portend the end of carbonaceous hearth wall working linings and the CO 2 that’s generated during their manufacture.

Prognostics of fractional degradation processes with state-dependent delay

In modern industrial processes, the remaining useful life (RUL) of core manufacturing equipments is regarded as an important indicator for assessing the continuous serving ability by considering safety and reliability. Accurate RUL predictions contribute to saving maintenance costs, and can be applied to the life extension technologies. Being subjected to complicated noise environments, the fractional characteristic usually exists in the stochastic heterogeneous diffusions. Traditional methods mostly utilize the fractional Brownian motion (FBM) to describe a simple class of memory effect in the time domain, but lose sight of potential time-varying state-dependencies from historical information. In view of uncertain lagging levels, the state-dependent delay (SDD) is introduced to construct a novel nonlinear fractional degradation model in this paper. Based on a specific discretization scheme, the unknown parameters are estimated by optimizing an approximate log-likelihood function. The RUL distribution is then derived under a Markovian statistical transformation. Finally, a case study on certain hearth wall degradation processes is provided to validate the proposed prognostic method in production practice.

Dissection study of the deadman in a commercial blast furnace hearth

The slag, iron and coke in the deadman are extremely difficult to obtain in regular production. In this study, a commercial blast furnace was shut down and the samples were adopted systematically through a dissection study. The image processing method was also involved to clarify the macroscopic morphology of the deadman coke and the coke size distribution as well as the variation of the deadman voidage. It was found that the average size of coke was distributed in “M-shape” and voidage of deadman decreased with the increase of distance to the hearth wall in the horizontal direction. The voidage in the middle and lower of the vertical deadman was the largest and the average size of coke decreased with the increase of the distance to the taphole centerline in the height direction. In addition, the formation mechanism was analyzed, including carburization with hot metal, coke graphitization, the erosion of slag, hot metal, gas flow, etc., which provided an important reference for the high efficiency and low carbon smelting of the blast furnace.

An Integrated Mathematical Model for Ironmaking Blast Furnace

This paper presents an integrated model by combining the raceway combustion model, the process model, and the hearth flow and heat transfer model for simulating an entire ironmaking blast furnace (BF). This integration eliminates major assumptions at the boundaries shared by these sub-models and enables linking the model with operating parameters at the BF top and bottom directly. The applicability of this integration is first examined through various applications. On this base, the usefulness of the integrated model is demonstrated by studying the effect of burden distribution on the in-furnace states of a 5000 m3 industrial BF. The simulation results with and without the integration are compared. Also, via the integrated model, the effect of the ore-to-coke (O/C) radial profile at the burden surface is evaluated in terms of internal flow and thermochemical behaviors as well as overall process performance. It is shown that for given BF conditions except for the O/C radial profile, the indirect reduction in the upper furnace increases with the improvement of uniformity in the radial profile, leading to higher top gas utilization and lower productivity. Meanwhile, the hearth center tends to develop lower temperatures and stronger natural convection that reduces the heat loss through hearth walls. This integrated model would open up a cost-effective method to examine the effect of top and bottom factors on BF performance under different conditions in a comprehensive matter.

Study of composition and structure of NLMK BF No. 6 hearth scull (Report 1)

Analysis of blast furnaces running experience in Japan, Europe and North America shows, that duration of their operating period determines to a great extent by hearth and bottom lining endurance. Study of structure change of scull and hearth walls and bottom lining at different burden compositions and BF heat conditions will enable to elaborate organization and technical solutions for BF efficiency increasing. Study of hearth scull composition at the level of iron notch and lower at PAO NLMK BF No. 6 after 2nd category overhaul stoppage from 26.08.2016 through 29.09.2016. Lump samples of mass from 10 up to 70 kg were taken with careful visual inspection to exclude oxidized and hydrated pieces. Based on visual inspection of samples as well as petrographic, chemical, X-ray structural and microprobe analysis it was determined, that the scull base comprises products formed during crystallization of heat products. They included a metal, in which a magnetic part (α-iron) is prevailed with iron carbide and graphite inclusions, graphite as a separate phase, slag components with a base of melilite at the level of iron notch and silicates (X-ray amorphous) of variable content of СaO–K2O–Na2O–SiO2–Al2O3system. The quantity of metal and graphite in the hearth walls scull increases from iron notch to the bottom and reaches a value >85 % at the level 300 mm lower than iron notch. Content of titanium compounds in oxide form in all the samples as well as nitrides, carbo-nitrides totally does not exceeds 1–2%.

Study of scull and lining in the hearth of blast furnace No. 2 of JSC EVRAZ ZSMK (Report 1)

Results of study of lining and scull of the hearth of blast furnace No. 2 of JSC EVEAZ ZSMK presented, done after BF stop for major overhaul. It was determined, that the scull has a zonal structure, due to different conditions of the forming of it during the furnace running and blowing-down. The scull consists of isolations of graphite, metal and slag inclusions having distinctly lamellar structure. Number of slag inclusions in the scull of the hearth walls lower the hot metal tap hole is not big and sharply arises in samples at levels above the tap hole. In metal structure within the scull ferrite (a-Fe) prevails, also there are some lamellar graphite isolations and perlite. Quantity and thickness of metal isolations in the samples increases from the scull periphery to the center of blast furnace (from 20–30% and tens of microns to 70–90% (mass) and 30–50 microns correspondently) and decreases from the lower part of the hearth wall to the upper one. Titanium nitride (osbornite) TiN and titanium oxide (rutile) TiO2, sulfides of calcium, iron, manganese, silicon carbide SiC present in the scull in a small quantity (less 2%). In samples taken higher the hot metal tap hole, in the scull slag isolations there are a considerable amount of alkali metals oxides and sulfides, and phosphide and iron sulfides were exhibited in the metal phase. It speaks about considerable evaporation/sublimation of compositions of potassium, sodium, Sulphur and phosphorus in the blast furnace hearth following by their condensation/crystallization at the cooled lining of hearth walls.

Studies to overcome the manufacturing problems in blast furnace tap hole clay of Integrated Steel Plants: Experimental approach

Integrated Steel Plants commonly uses Blast Furnace route for iron production which accounts for over 60 % of the world iron output. Blast Furnace runs for ten to twenty years without repairing hearth walls and Tap Hole (TH). Tap hole is an outlet for hot metal produced in a Blast Furnace and run from the shell of the furnace into the interior allowing access to the molten material. Tapping is the term used for drilling a hole through the tap hole which allows the molten iron and slag to flow out. In Iron making process, removal of liquid iron from furnace and sending it for steel making is known as cast house practice. For tapping liquid iron and operating the tap hole requires a special type of clay. Tap hole clay (THC) used to stop the flow of liquid iron and slag from the blast furnace. Present work deals with the study on manufacturing of THC at Visakhapatnam Steel Plant and problems related to manufacturing. Experiments were conducted to solve the identified problems and results are furnished in detail. The findings can improve the manufacturing process and improve the productivity of tap hole clay.

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.

Model of Draining of the Blast Furnace Hearth with an Impermeable Zone

Due to demands of lower costs and higher productivity in the steel industry, the volume of operating blast furnaces has grown during the last decades. As the height is limited by the allowable pressure drop, the hearth diameter has grown considerably and, along with this, also draining-related problems. In this paper a mathematical model is developed for simulating the drainage in the case where an impermeable region exists in the blast furnace hearth. The model describes the quasi-stationary drainage process of a hearth with two operating tapholes, where the communication between the two pools of molten slag and iron can be controlled by parameterized expressions. The model also considers the case where the buoyancy of the liquids is sufficient for lifting the coke bed. The implications of different size of the liquid pools, communication between the pools, bed porosity, etc. are studied by simulation, and conclusions concerning their effect on the drainage behavior and evolution of the liquid levels in the hearth are drawn. The simulated liquid levels are finally demonstrated to give rise to a pressure profile acting on the hearth which agrees qualitatively with signals from strain gauges mounted in the hearth wall of an industrial ironmaking process.

Evaluation of Refractory Lining of the Blast Furnace Hearth and Bottom in Five Years of its Operation on the Basis of the Isotherms Shapes

Based on archival temperature measurement data regarding a blast furnace (capacity of 3200 m3) hearth and bottom refractory lining, empirical isotherms T = 300°C, for various periods of the first five years of the furnace campaign were determined. This resulted in an attempt to assess the hearth and bottom refractory lining in the third month and subsequently, in the next years of the blast furnace operation. The empirical isotherms, determined after the first three months, were compared to the isotherms determined using the method of mathematical modelling. These empirical isotherms were compared to each other, respectively in one-year intervals. The most distinctive changes of the hearth and bottom refractory lining were observed during the first three months of the furnace campaign. In the further period of five years, the changes were insignificant. During the early stage of furnace operation, observed deterioration of the refractory lining was associated with partial damage of the bottom ceramic layer and elephants foot-shaped defects of the refractory lining in the lower, thickened parts of the hearth walls. Early, elephants foot-shaped wear of the refractory lining is related to the mechanism of its wash-out by liquid products of the process during tapping, which results from certain maladjustment of the hearth and bottom inner geometry in modern furnaces to the hydrodynamic conditions of metal and slag flow.

Monitoring and control of hearth refractory wear to improve blast furnace operation

Refractory wear and skull growth on the hearth walls and the bottom of the blast furnace have been researched. A series of thermocouples were installed in the hearth, and the temperature measurements were recorded in a structured query language every minute. A heat transfer model was used to study the temperature evolution and hearth wear profile using a commercial software package (MATLAB version 5.0) based on computational fluid dynamics. The location of the 1150°C isotherm in the hearth lining has been calculated. An online monitoring tool was used to analyse the temperature distribution in the hearth and offers, to the plant operators, periodic information on the refractory state. Electromotive force (EMF) probes were installed in the hearth to estimate the variations in the liquid level in the hearth and to determine the thermal state (TS) evolution. Good correlation is seen between EMF and TS, and the EMF amplitudes in the different tapholes follow and even precede the local TS.

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.

Experimentally determined temperatures in blast furnace hearth

In this study temperature measurements have been carried out at blast furnace no. 2 at SSAB Oxelösund. The temperature was measured in the hearth lining and at the outer surfaces of the hearth wall and bottom. The lining temperature was measured using permanently installed thermocouples and surface temperatures were measured using a hand held thermocouple. The aims of the study were to find a correlation between lining and surface temperatures as well as to find a method to determine the surface temperature based on readings from lining thermocouples. The overall conclusion is that the bottom and wall surface temperatures can be determined based on lining temperatures.

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...

Emergency repair of the hearth wall of BF A at Aceralia

Emergency repair of the hearth wall of BF A at Aceralia

Emergency repair of the hearth wall of BF A at Aceralia

Aceralia blast furnace A suffered a 28-days emergency repair in September 2004, due to accelerated wear of the hearth walls and severe damage of the cast iron staves at the bosh area. Considering the shortage of supplies, Aceralia resorted to non conventional repair methods in order to prolong the campaign by one year, until full relining: small format carbon bricks and carbon ramming mass for the hearth and tapholes and steel staves at the bosh.

Three dimensional iron flow and heat transfer in the hearth of a blast furnace during tapping process

The aim of this research is to numerically simulate iron flow and heat transfer in the hearth of a blast furnace by solving the three-dimensional turbulent Navier–Stokes equation coupled with the transport equation of energy at steady state. Under the effects of conjugate heat transfer and natural convection, a computational fluid dynamic calculation was performed to generate flow field in the hearth and the temperature distribution in the refractories during the tapping process. The accuracy and computation of the model is validated using operation data from BHP Steel's No. 5 blast furnace. The shear stress and heat flux on the wall were then predicted for the different vertical movements, shapes of the coke zone (dead-man), and the lengths of the tap-hole. As shown in the results, it is worth noticing that an increase in the tap-hole length causes the peak values of shear stress to shift in the increasing azimuthal direction at a particular plane, and the location of the peak value of shear stress coincides with the location of higher temperature actually measured on the hearth wall, signifying enhanced heat transfer to the wall at location of peak stress.

Effect of FeO in Dripping Slag on Drainage Ability of Slag

Japanese iron and steelmaking industry has to reduce CO2 emission by 11.5% in 2010 relative to the level of emissions in 1990. Stable blast furnace operation is required to reduce energy consumption and CO2 emission in iron and steelmaking industry. For the stable blast furnace operation, precise controlled drainage is one of the important factors. However, there are many unrevealed phenomena in the hearth to perform the stable operation. Therefore, in this work, the effect of iron and slag dripping pattern, FeO concentration in the dripping slag on the iron and slag surfaces, thermal properties of refractory and brick on drainage temperature, temperature distribution in the hearth, temporal variation of iron and slag drainage rates and interfaces shapes were investigated by using tree-dimensional mathematical model.The results indicate that more than 2 mass% FeO in dripping slag will cause deterioration of slag drainage ability due to high slag viscosity around tapholes. Continuous monitoring of FeO concentration in the tapping slag is effective to prevent deterioration of slag drainage ability. The trends of the other side of tapping taphole temperature were varied dramatically according with FeO concentration in the dripping slag. Even in the case of 0 mass% FeO in the dripping slag, there is a solidified slag near the hearth wall except around the tapholes. A peripheral distribution pattern will result in a stable drainage. Slag, which dripped on near the other side of the tapping taphole, stays around the taphole, and does not drain from the tapping taphole located opposite side.