COREX熔化气化炉物料运动和气流分布

摘要：基于离散元数值计算方法(DEM),建立了熔化气化炉模型的离散元数学模型。应用此模型从颗粒尺度对气化炉3种软熔区域形状下的物料质量、运动速度、法向力、空隙度分布进行了研究。利用DEM计算空隙度数值,再结合计算流体力学软件对气化炉气流分布进行了计算。结果表明：软熔区域形状对气化炉料面形状和炉内下部法向力的分布影响很小,炉中心下部区域的物料所受的法向力较大;得到了3种软熔区域形状下,气化炉内空隙度分布平均数值;倒“V”型软熔区域结构可使气流分布均匀、稳定,利于气化炉生产实践。     

COREX熔化气化炉物料运动行为

基于离散元方法,建立了二维扁平熔化气化炉的离散元模型,应用此模型从颗粒尺度对物料运动流型、速度场以及空隙度分布进行了研究。结果表明:采用加入示踪颗粒的方法,对颗粒运动流型进行分析,示踪颗粒层逐渐由直线型变为两侧向下弯曲型;从物料速度场分布可以看出,炉内存在死料柱区、活塞流区以及管道流区等运动区域。回旋区对炉内竖直方向速度分布的影响限于距炉缸底部上方0.18m处,回旋区半径的减小导致炉内颗粒活跃区域缩小,死料柱区高度增加;炉内物料运动存在一定的偏析现象,该现象也可从空隙度分布看出。炉内死料柱区空隙度为0.37左右,回旋区处为0.65左右,位于自由空间下方和死料柱区以及回旋区之间的活塞流区空隙度在0.37~0.65之间。     

喷煤对COREX熔化气化炉炉况影响的物理模拟

通过COREX喷煤整体和区域模型整体和区域模型计算分析,研究了喷煤对块煤用量、理论燃烧温度、风口煤气量等重要参数的影响。计算结果表明：随着喷煤量的增加,风口煤气量增大,块煤用量和理论燃烧温度均降低。最后,本文建立了二维COREX熔化气化炉热态模型,利用石蜡模拟矿石,玉米粒子模拟焦炭。在热态物理模拟实验中,考察了矿/(块煤+焦)体积比、风温和风量等操作参数对COREX熔化气化炉炉况的影响。     

COREX气化炉炉缸侵蚀模型的预测与实践

COREX炉缸与全氧高炉类似,面临着炉缸侵蚀加剧的问题,甚至发生了炉缸烧穿事故,炉缸寿命已成为安全高效生产的限制性环节。根据数值分析、有限元法、传热学等理论,建立了COREX气化炉炉缸二维稳态传热模型。在此基础上,利用BP神经网络开发了COREX气化炉炉缸侵蚀预测模型。应用该炉缸侵蚀模型对炉缸侵蚀曲线进行计算,计算出的炉缸侵蚀曲线与实际情况基本相符。模型应用表明,该侵蚀预测模型具有可靠性,能为COREX炉缸安全生产提供技术依据。     

炉缸侵蚀模型的应用

介绍了炉缸侵蚀模型的计算原理,结合国内某高炉炉役末期的热电偶温度和耐材配置开发了炉缸侵蚀模型,应用该模型计算出此高炉的炉缸侵蚀曲线,利用该高炉的大修解剖调查结果对炉缸侵蚀模型的理论计算进行了验证,并对结果进行了分析.     

喷煤对COREX熔融气化炉风口前理论燃烧温度的影响

 风口前理论燃烧温度是衡量熔融气化炉风口前热平衡和预测炉缸热状态的重?问弧Ｒ谰菘悸荢iO2还原的理论燃烧温度计算公式,分析了在熔融气化炉喷煤对风口前理论燃烧温度的影响。计算了不同喷煤条件下,熔融气化炉风口前的理论燃烧温度。在此基础上讨论了喷煤比、挥发分及焦炭(半焦)进入燃烧区域的温度等参数的影响,为选择适合COREX熔融气化炉喷吹煤提供了必要的依据。     

炉缸侵蚀模型的开发

根据高炉炉缸传热、侵蚀的特点,应用有限元和设计优化技术相结合的方法,并依据炉缸侵蚀模型的计算流程、基本概念,应用APDL开发了高炉炉缸侵蚀模型计算软件,并对该模型调试过程中的关键问题进行了讨论。应用该炉缸侵蚀模型对国内某高炉的炉缸侵蚀曲线进行计算,计算出的炉缸侵蚀曲线与实际情况基本相符。     

昆钢新区2500m~3高炉炉缸炉底侵蚀模型

为了分析投产初期高炉炉缸炉底的温度分布情况,以经典传热模型为基础,采用有限元计算技术,建立了昆钢新区2 500 m~3高炉炉缸炉底侵蚀模型。本模型以高炉开炉初期温度为基础,绘制出炉缸炉底温度场分布曲线,模型计算值与热电偶实测值相比,误差在-6.52%~+7.69%的范围内,表明模型计算较为准确。根据模型计算结果,提出了加长风口小套长度、提高鼓风动能和加大死铁层厚度等工作建议,为制定高炉合理的操作维护方针和完善高炉长寿设计提供重要参考。     

基于有限元法的高炉炉缸炉底侵蚀模型的研究及应用

采用有限元法求解高炉炉缸炉底侵蚀模型,利用边界单元变形方式模拟侵蚀边界,采用最小二乘法将参考点温度计算值与实际测量值的离差平方和最小值作为优化判据,修正侵蚀边界的方向及幅度,从而快速逼近实际侵蚀线位置。该模型用于推定高炉炉缸炉底1 150℃等温线的位置和形状,以便了解和分析高炉炉缸炉底侵蚀情况。模型应用结果表明,采用有限元法计算高炉炉缸炉底温度场分布,具有计算速度快、计算结果精确可靠等优点。     

高炉寿命与利用系数之间的关系

研究了高炉利用系数对炉缸侵蚀以及高炉寿命的影响.首先,利用模型实验和预测模型研究了炉缸内铁水的流动.其次,利用传热模型,计算了炉缸侧壁的温度分布,估测了炉缸侧壁的侵蚀程度和凝固层形状.该模型给出了一种已经被实践所证实的高炉一代炉役期间炉缸侵蚀图形的估测方法.     

Mathematical model of COREX melter gasifier: Part I. Steady-state model

The COREX melter gasifier is a countercurrent reactor to produce liquid iron. Directly reduced iron (DRI), noncoking coal, and other additives are charged to the melter gasifier at their respective temperatures, and O₂ is blown through the tuyeres. Functionally, a melter gasifier is divided into three zones: a moving bed, fluidized bed, and free board. A model has been developed for the moving bed, where the tuyere region is two-dimensional (2-D) and the rest is one-dimensional (1-D). It is based on multiphase conservation of mass, momentum, and heat. The fluidized bed has been treated as 1-D. Partial equilibrium is calculated for the free board. The calculated temperature of the hot metal, the top gas, and the chemistry of the top gas agree with the reported plant data. The model has been used to study the effects of bed height, injection of impure O₂, coal chemistry, and reactivity on the process performance.     

加焦方式对气化炉炉料结构和气流分布的影响

装料模式决定了料床的孔隙度结构,进而决定了煤气流的分布信息。建立了气化炉炉料结构的离散单元模型和煤气流动的多孔介质模型,以自编程和软件Fluent为载体,结合两个模型共同描述了不同加焦方式对气化炉的炉料结构和煤气流动带来的变化,获得了炉内炉料结构的孔隙度分布信息和煤气的速度场、流线和质量通量。结果表明：首先,由离散单元模型获得的炉料结构信息可作为气流分布模型的边界条件输入;其次,煤气流模型的模拟结果表明焦柱的加入会在加焦位置处形成煤气发展通路,进而改善气化炉透气性,但应控制焦炭加入量,避免气流过度发展,进而影响煤气利用率。通过模拟计算获得的非均匀床层气体流动规律的认识对气化炉加焦工艺有借鉴意义。     

Blast furnace circumferential process symmetry: effect of flow distribution in hot blast systems

Abstract

Solid particle flow patterns in the moving bed zone of a melter/gasifier were studied using discrete element method (DEM). Interparticle forces were calculated using the Hertz–Mindlin no slip contact model. The simulation results of the solid particle flow patterns agree well with the experimental results exhibited by tracer particles. The solid particle flow pattern and descending velocity were studied, as well as the effect of the discharge rate of solid particles in the raceway on solid particle flow pattern in the moving bed.

Results show that the moving bed could be divided into four subdomains based on the velocity of solid particles. A stagnation zone with semielliptic geometry is formed at the central bottom of the moving bed during drainage of solid particles. Furthermore, the simulated results of compressive force among solid particles in the moving bed zone indicate that the deadman zone undergoes a high degree of compressive force, especially at the centre of the gasifier. This finding implies that more compressive force resistant solid material should be placed at the centre zone by manipulating solid particles fed into the melter/gasifier.     

熔融气化炉风口回旋区冶炼特征的数值模拟研究

相比于高炉风口喷吹富氧热风,熔融气化炉风口采用常温纯氧,使得炉内质量、动量、热量的传输以及煤气流分布等冶炼特征与高炉存在较大差异.通过建立熔融气化炉风口回旋区二维数学模型,系统考察熔融气化炉风口回旋区内速度分布、温度分布及气体组分分布的冶炼特征.结果表明:在气固相热交换及焦炭 (或块煤形成的半焦) 燃烧反应的综合作用下,熔融气化炉风口回旋区内气体温度迅速升高至3 500 K以上;此外,风口前端存在小规模的气体循环流动现象,故风口前端扩孔破损现象严重,进而导致非计划休风率较高;为减少此类休风现象,可适当额外喷吹富氢燃料性气体 (天然气、焦炉煤气),不仅能降低风口回旋区内气体温度,更可替代部分固体燃料,并充分发挥其中H₂的高温还原优势,提升熔融气化炉冶炼效率.      

COREX熔化气化炉软熔区域的实验研究

为了模拟COREX熔融气化炉软熔区域,本研究建立了COREX熔融气化炉热态模型,利用石蜡模拟矿石,玉米粒子模拟焦炭和块煤。在热态物理模拟试验中,考察了实际生产过程中熔炼率、矿/(块煤+焦)体积比、风口回旋区煤气温度和风口回旋区煤气量等操作参数对软熔区域高度和厚度的影响。试验获得不同操作参数下软熔区域高度和厚度的变化趋势。     

Mathematical Simulation of Burden Distribution in COREX Melter Gasifier by Discrete Element Method

 COREX process is one of the earliest industrialized smelting reduction ironmaking technology. A numerical simulation model based on discrete element method (DEM) has been developed to analyze the burden distribution in the melter gasifier of COREX process. The DEM considering the collisions between particles can directly reproduce the charging process. The burden trajectory, the location and the burden surface profile are analyzed in melter gasifier with a mixing charging of coal and direct reduction iron (DRI) at the same time. Considering the porosity of packed bed has an important effect on the gas flow distribution of melter gasifier, a method to calculate porosity has been proposed. The distribution of DRI and coal and the porosity in the radial direction are given under different charging patterns, which is necessary to judge the gas flow distribution and provide base data for further researching the melter gasifier for the next work in the future. The research results can be used to guide the operation of adjusting charging and provide important basis for optimizing the charging patterns in order to obtain the reasonable gas distribution.     

COREX熔融气化炉Rist操作线的建立和应用

考虑了块煤在熔融气化炉上部挥发分的析出和采用部分氧气燃烧析出挥发分中的焦油和碳氢化合物这一特点,利用改进的Rist操作线原理,建立了熔融气化炉操作线图,直观地体现了不同因素对炼铁过程能耗的影响.讨论了COREX熔融气化炉内上部吹氧燃烧焦油和碳氢化合物后操作线的变化,对比了加入不同块煤和半焦对上部吹氧量、能耗的影响,分析了将块煤中挥发分脱除后以半焦的形式加入炉内,熔融气化炉上部煤气氧化度、温度和煤气量的变化,以及对能耗的影响.      

Influence of Cohesive Zone Shape on Solid Flow in COREX Melter Gasifier by Discrete Element Method

Based on the principle of discrete element method(DEM),a 2Dslot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow,including mass distribution,velocity distribution,normal force distribution and porosity distribution at a microscopic level.The results show that the cohesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape.The particles in the lower central bottom experience large normal force to support the particles above them,while particles around the raceway and in the fast flow zone exhibit weak force network.The porosity distribution was also examined under three kinds of cohesive zones.Like the velocity distribution,the whole packed bed can be divided into four main regions.With the increase of cohesive zone position,the low porosity region located in the root of cohesive zone increases.And the porosity distribution becomes asymmetric in the case of biased cohesive zone.     

The Burden Structure and Its Consumption in the Melter Gasifier of the Corex Process

A major advancement in the Corex ironmaking process is the usage of lump coal considering the shortage of coking coal resources worldwide. However, the burden similar to that of the blast furnace is still essential for the enlarged melter gasifier. The notable difference is that the burden of the melter gasifier is composed of char formed from lump coal with a small amount of coke. The burden structure of the melter gasifier was investigated by the tuyere probing while the plant was shut down at different operating conditions. The specimens representing the different positions of lump zone, cohesive zone, and dripping zone were analyzed by means of coke/char size distribution and X-ray diffraction (XRD) for the degree of graphitization of coke. A chemical analysis of metal composition has also been performed to get a better understanding of the final reduction in the melter gasifier. The burden structure is supposed to be divided into three zones: active zone, outer of deadman, and deadman core, where coke/char was consumed differently. Based on these analyses, some technical advice to improve the Corex operation is given.