Improved CFD Model to Predict Flow and Temperature Distributions in a Blast Furnace Hearth

The campaign life of a blast furnace is limited by the erosion of hearth refractories. Flow and temperature distributions of the liquid iron have a significant influence on the erosion mechanism. In this work, an improved three-dimensional computational fluid dynamics model is developed to simulate the flow and heat transfer phenomena in the hearth of BlueScope’s Port Kembla No. 5 Blast Furnace. Model improvements feature more justified input parameters in turbulence modeling, buoyancy modeling, wall boundary conditions, material properties, and modeling of the solidification of iron. The model is validated by comparing the calculated temperatures with the thermocouple data available, where agreements are established within ±3 pct. The flow distribution in the hearth is discussed for intact and eroded hearth profiles, for sitting and floating coke bed states. It is shown that natural convection affects the flow in several ways: for example, the formation of (a) stagnant zones preventing hearth bottom from eroding or (b) the downward jetting of molten liquid promoting side wall erosion, or (c) at times, a vortex-like peripheral flow, promoting the “elephant foot” type erosion. A significant influence of coke bed permeability on the macroscopic flow pattern and the refractory temperature is observed.     

CFD Modeling and Analysis of The Flow,Heat Transfer and Mass Transfer in a Blast Furnace Hearth

Understanding the complex phenomena in the BF hearth is essential to increasing furnace productivity and to extending furnace campaign. Numerical modeling provides a cost‐effective tool to obtain such knowledge. We have developed several continuum‐based mathematical/numerical models to simulate the flow, heat transfer and mass transfer in the lower part of BF and in the hearth. These models have generated an improved insight into the mechanisms for liquid drainage efficiency, lining erosion and wall protection in BF hearth under operational conditions. The current paper provides an overview of these studies, as well as dealing with three specific aspects: (a) Gas flow and pressure on the liquid surface, and its effect on the drainage characteristics; (b) Flow and temperature distributions of liquid iron in the hearth, and the temperature distribution in the refractories; and (c), Titania injection to form Ti(C,N)‐rich scaffolds on the hearth refractory surface, to protect the hearth from erosion.     

A Model to Simulate Titanium Behavior in the Iron Blast Furnace Hearth

The erosion of hearth refractory is a major limitation to the campaign life of a blast furnace. Titanium from titania addition in the burden or tuyere injection can react with carbon and nitrogen in molten pig iron to form titanium carbonitride, giving the so-called titanium-rich scaffold or buildup on the hearth surface, to protect the hearth from subsequent erosion. In the current article, a mathematical model based on computational fluid dynamics is proposed to simulate the behavior of solid particles in the liquid iron. The model considers the fluid/solid particle flow through a packed bed, conjugated heat transfer, species transport, and thermodynamic of key chemical reactions. A region of high solid concentration is predicted at the hearth bottom surface. Regions of solid formation and dissolution can be identified, which depend on the local temperature and chemical equilibrium. The sensitivity to the key model parameters for the solid phase is analyzed. The model provides an insight into the fundamental mechanism of solid particle formation, and it may form a basic model for subsequent development to study the formation of titanium scaffold in the blast furnace hearth.     

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

The 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.     

高炉炉缸铁水流场数值模拟

铁水环流是造成炉缸＂蒜头状＂侵蚀的主要原因,而导致铁水环流行程主要是由于炉缸内的死料柱引起的。为此,以流体力学有关理论为基础,建立了炉缸炉底三维流体数学模型,应用FLUENT软件,研究了高炉炉缸中不同死料柱位置、状态及出铁口尺寸对炉缸内铁水流动的影响。结果表明：死料柱有较小的浮起时造成炉底铁水流量较大对炉底产生较强的侵蚀。当中心死料柱尺寸大时自由铁水区的铁水流速较快,反之较慢。当出铁口直径增大时,铁水的质量流量增大,炉缸底部的铁水环流明显增大。     

Heat flow in blast furnace hearths

Abstract

Heat flow and temperature distribution in iron blast furnace hearths has been investigated using a digital computer implemented simulation. Furnace hearths, with and without underhearth cooling, have been simulated to provide dynamic thermal response characteristics and to explore refractory material requirements for improved hearth design.

A digital computer program utilizing numerical approximations to the heat flow equations in three dimensions (two dimensions with radial symmetry in the third) was used to calculate unsteady state heat transfer characteristics. Stave cooling, carbon and ceramic refractories, refractory thermal property variations, salamander formation, underhearth cooling systems, and other design and operating parameters were considered in evaluating the steady and unsteady state temperature distributions in blast furnace hearths.

Résumé

On fait l' étude du flux de chaleur et de la distribution de température dans le creuset d'un haut fourneau par une simulation à l'aide d'un ordinateur. Nous considérons le creuset sans ou avec refroidissemen t afin d'obtenir l' évolution des proprietes thermiques et de sonder les besoins en matériaux réfractaire pour ameliorer le design du creuset.

Un programme d'ordinateur basé sur la méthode d'approximations numeriques aux équations tridimentionnelles de transfert de chaleur (deux dimensions rectilignes avec symétrie radiale dans la troisième direction) a été employé dans le calcul du comportement de transfert de chaleur en régime transitoire. Nous avons considéré le refroidissement des douves, l'u tilisation des réfractaires à carbone et à ceramique, la variation des propriétés thermiques des réfractaires, la formation d'un loup ferreux, d'autres designs et les paramètres d' opération dans cette évaluation des distributions des températures en régime transitoire et en régime permanent des creusets des hauts-fourneaux.     

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.     

提高大型高炉炉缸寿命的探讨

结合宝钢高炉生产实践,重点探讨了大型高炉炉缸长寿的措施.以传热分析为基础,探讨了炉缸耐材的侵蚀机理及影响因素,认为炉缸耐材及冷却系统的合理选择是提高炉缸寿命的关键,并提出了高炉大型化后减缓炉缸侵蚀的措施.     

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

Abstract

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.     

太钢高炉炉底炉缸长寿探讨

通过分析计算确定了太钢3号高炉侵蚀预测数学模型。为了保障高炉生产的安全,根据太钢3号高炉热电偶历史最高数据预测了炉缸炉底侵蚀状况。同时应用该软件分析铁水流动、耐材导热系数、死铁层深度和高炉异常对炉缸炉底的侵蚀影响,并得出炉缸炉底长寿的若干推论,对评价目前侵蚀状况和护炉及未来太钢长寿高效高炉的建设提出若干参考意见。     

Numerical Simulation of Fluid Flow in Blast Furnace Hearth

SymbolList C———Coefficient,1inthepackedbedand0inother place; C1,C2,Cμ,σκ,σε———Empiricalconstant; d———Diameterofcokeparticle; H———Heightofpackedbed,m; P———Pressure,Pa; ui,uj———Velocityalongdirectioni,jrespectively,m·s-1; vA———Vel     

高炉炉缸长寿智能管理系统的开发与应用

针对当前高炉长寿管理滞后和针对性差的现状,将高炉炉缸工艺设计、传热学理论与高炉操作工艺相结合,开发了一套炉缸长寿智能管理系统。除传统炉缸侵蚀模型的炭砖侵蚀曲线计算功能以外,还具有凝铁层在线监控、炉缸气隙判断、凝铁层减薄原因诊断和给出针对性改善建议4项核心功能。该系统全部模块均进行在线监测、计算、诊断和建议,其关键目的不是计算侵蚀曲线,而是防止炉缸侵蚀的发生,可为做好高炉的长寿管理、延长高炉寿命起到重要作用。     

关于高炉炉缸长寿的关键问题解析

 高炉长寿化是大型高炉发展的必然趋势,实现高炉长寿的关键在于弄清高炉侵蚀的根本原因。从高炉炉缸侵蚀机理、高炉炉缸象脚型侵蚀原因、高炉炉缸圆周方向侵蚀不均匀性、高炉冷却强度与冷却效率以及高炉炉缸维护技术等5个方面探讨了高炉长寿存在的共性问题,指出高炉炉缸炭砖损毁的本质是碳不饱和铁水对炭砖的溶蚀。具体结果表明,首先,高炉炉缸象脚型侵蚀最严重部位位于高炉炉缸死料柱的根部位置;其次,阐明了直接导致高炉存在不均匀侵蚀的主要原因在于冷却系统的冷却水量和送风系统的风量在高炉周向方向分配不均匀;然后,阐明了冷却系统的作用本质是降低耐火材料热面温度,并提出了高炉冷却强度指数及高炉冷却效率指数;最后,分析了采用无钛矿护炉和钛矿护炉两种模式的高炉炉缸维护技术。     

高炉耐火炉衬设计原则及“陶瓷杯”的应用

随着新型耐火材料的发展，“耐火材料法”在高炉内衬的设计中也得到了越来越广泛的应用，采用该法的主要好处是热损失小、炉缸状况稳定。以“耐火材料法“为基础，将导热性不同的材料进行合理安排后设计出了用于高炉炉缸的“陶瓷杯”。从１９８４年到１９９３年已有２３套“陶瓷杯”得到了安装或订购。     

沙钢3号高炉炉缸安全评估分析

为探究沙钢3号高炉炉缸侧壁温度升高原因,对沙钢3号高炉开炉以来的热电偶温度数据及热流强度变化趋势进行统计,并计算了炭砖的残余厚度.结合3号高炉的死铁层深度及冷却系统设计等参数,对炉缸侧壁温度升高的原因进行了解析.结果表明,沙钢3号高炉炭砖侵蚀薄弱区域处于铁口下方1?2 m,最薄位置处于西铁口,炭砖残余厚度约为517 m...     

Flow induced stress distribution on wall of blast furnace hearth

Abstract

The flow induced shear stress on the wall of a blast furnace hearth has been computed by solving the Navier–Stokes and Darcy flow equations in the hearth numerically. The Navier–Stokes equations are utilised to compute the flow field in the coke free zone while the Darcy flow equations are utilised for the flow of liquid metal in the coke packed porous zone, known as the deadman. The shape of the deadman was taken to be hemispherical and it was simulated to be porous in nature. The taphole was placed through a block of refractory material through which the metal was allowed to flow out of the hearth. From the resulting flow field the shear stresses on the side wall of the hearth were computed as a function of the length and size of the taphole when the hearth was filled with liquid metal. It has been found that the peak stress value at the bottom plane, midplane (halfway between the bottom and the taphole exit plane), and at the plane of the taphole reduces significantly compared with the case of having no taphole block at all. However, the effect of the size of the taphole on the wall shear stress was not found to be very significant. It was also found that the peak stress decreases with an increase in the taphole length and the location of the peak stress shifts slightly in the increasing direction of θ. Such an arrangement of placement of the block does not produce any more peak stress anywhere in the azimuthal direction at a particular plane; rather, it helps to smooth out the peaks in the stresses arising due to fluid flow. The reasons for mechanical erosion inside the hearth are complicated. However, flow induced shear stresses play a very important role in initiating and aggravating the amount of erosion along with other factors. This has provided the main motivation to compute the flow induced shear stress on the inside wall of the hearth and study the effect of various parameters on it in the present work.     

Estimation model of the hearth refractory thickness and its application to the operation

A numerical model considering heat flow path and heat flux area was developed to estimate residual refractory thickness of blast furnace hearth. The predictions indicated that the wear profile of Kwangyang No. 1 BF was elephant foot type, deeply eroded around the tap‐hole and the corner of the hearth. The high heat load at the hearth sidewall was caused mainly by the carbon brick with low thermal conductivity, and it resulted in a severe erosion of hearth refractory. In the early stage of the furnace campaign, the wear rate of hearth refractory turned out to be higher than that of the following 7 years. Additionally, a thermal analysis of the hearth shell was carried out by means of an infrared camera, which is effective for simultaneous observation of a large area. A locally hot spotted region was not detected and the measured results showed a good agreement with the temperature trends measured by thermocouple.     

长寿高炉炉缸保护层综合调控技术

 在高炉炉缸砖衬热面形成的稳定的保护层,将铁水与砖衬隔离开,避免直接接触,这是保证高炉炉缸长寿、延缓砖衬侵蚀的必要条件。为了研究高炉炉缸长寿的本质,首先通过高炉破损调查和解剖调研,分析了炉缸保护层的物相组成和显微结构,建立了高炉炉缸保护层类别体系。从保护层形成机制的角度将保护层分为富铁层、富渣层、富石墨碳层和富钛层。制定了高炉炉缸保护层综合调控技术路线,提出高炉炉缸保护层能否形成的关键在于合理控制炉缸耐火材料热面温度和铁水成分。最后明确,在高炉正常生产过程中,应从设计、铁水质量、生产操作等3个方面采取措施以促进保护层的有效形成。     

大型高炉合理炉缸冷却制度

合理的炉缸冷却制度是保证大型高炉长寿的基础,不同冷却制度对高炉炉缸的温度分布和侵蚀状况具有直接影响.结合某4000 m³级高炉,根据传热学理论建立了高炉炉缸、炉底温度场物理模型和数学模型,通过数值模拟对\