弓形浸渍管RH钢液流动行为的物理模拟

为了提高RH真空精炼系统的效率,设计了一种弓形浸渍管结构的RH真空槽。通过水模型试验对弓形和传统圆形浸渍管的RH设备进行了循环流量和均混时间的测定。试验发现:在实际生产条件下,弓形浸渍管RH比传统圆形浸渍管RH循环流量增加100%～180%;均混时间比传统RH减少35%左右。当提升气体流量超过饱和值时,弓形浸渍管RH的循环流量随着提升气体流量的增大而更加明显。弓形浸渍管RH可显著提高精炼效率,具有重要的应用前景。     

单嘴浸渍管RH和弓形浸渍管RH的应用效果

敬业钢铁有限公司现场试验了单嘴浸渍管结构RH炉和弓形浸渍管结构RH炉真空精炼超低碳钢的应用效果,记录两种RH炉提升气体流量和真空度的变化,多次取样检测钢液中w([C])和w([Mn]),分析对比两种RH炉的脱碳效果和混匀时间。结果显示,在真空处理6 min内,两种RH炉的真空度都可降至100 Pa以下,10 min后稳定在50 Pa左右;在真空处理20 min内,前者钢中w([C])基本脱至0.001 0%~0.001 5%,而后者钢中w([C])可以脱至0.000 5%左右,后者的脱碳速率也明显快于前者;前者和后者的混匀时间分别在3和1 min左右。结果表明,后者的冶炼效果明显优于前者,弓形浸渍管比单嘴浸渍管更适用于小吨位RH真空精炼炉。     

REDA与RH精炼过程钢液流动规律比较

以300 t REDA和RH精炼装置为研究对象,借助计算流体力学软件模拟REDA与RH两种精炼工艺下钢液流动行为,从精炼过程流场形态、循环流量、氩气行程及熔池表面湍动能等方面进行分析,研究结果表明:RH对钢包底部熔池的搅拌作用强于REDA,REDA的单浸渍管结构有利于延长浸渍管寿命及提高钢液循环流量,REDA只需RH提升气体流量的30%便能达到相同的循环流量。     

攀钢RH浸渍管粘渣原因分析与对策

针对攀钢现行工艺下发生的RH浸渍管粘渣的问题,通过实验及理论计算研究了RH浸渍管的粘渣原因及其对策。对RH浸渍管粘渣物的物相分析结果表明,RH精炼过程中高熔点的镁铝尖晶石相在熔渣中析出是导致RH浸渍管粘渣的根本原因;精炼渣组成对浸渍管粘渣影响的研究表明,提高精炼渣的碱度、增大渣中CaO/Al2O3含量比、降低渣中MgO含量,可以降低渣中高熔点相的作用浓度,改善了熔渣粘度和熔点,有利于减轻RH浸渍管的粘渣。     

RH真空处理装置浸渍管优化及应用

针对小钢包使用RH精炼设备进行真空处理过程中存在钢包空间有限、浸渍管内径小、钢水循环量低等问题,阐述了一种经过优化的真空槽浸渍管结构,并同过计算和流体仿真对比了新型浸渍管和传统浸渍管钢水循环量的差异,通过实际工程项目验证了新型浸渍管的实用性。     

RH真空精炼过程循环流量的水模型研究

建立了钢厂250 t RH真空精炼装置1/4的水模型,研究浸渍管内径(520～750 mm)、驱动气体流量(1 000～3 000 L/min)、浸渍管浸入深度(525～800 mm)和真空室压力(0～25 kPa)等参数对RH循环流量的影响。结果表明,随驱动气体流量、浸渍管浸入深度增加、浸渍管内径增大以及真空室压力减少,RH钢水循环流量增加;为获得较大流量,浸渍管浸入深度应≥560 mm,真空室液面高度应≥200 mm。得出循环流量的回归方程,通过对钢厂250 t RH设备工艺参数作相应调整后,RH装置的生产效率明显提高。     

优化工艺提高RH浸渍管寿命

分析了RH浸渍管寿命较低的原因,采取了优化环砖砌筑、改善浸渍管焊接质量、完善热喷补工艺、优化钢种冶炼工艺等措施,使RH浸渍管的平均寿命大幅提高,由41.3炉次提高到91.6炉次,最高达到122炉次。     

RH炉浸渍管使用寿命分析及改进

分析中厚板卷厂RH炉浸渍管使用寿命低的原因,通过优化RH炉浸渍管耐材的理化指标、浸渍管喷补料及喷补工艺,改进顶渣设备及优化烘烤制度等措施的实施,浸渍管平均使用寿命由2007年投产初期的32炉提高到2009年的72炉,RH炉真空钢月生产量由2万吨提高到8.3万吨。     

RH浸渍管镁铬砖侵蚀分析

分析了影响RH浸渍管镁铬砖侵蚀速率的因素,采取了控制驱动气体流量、制定烘烤火焰标准、改变合金加入方式和提高浸渍管利用率等,使RH浸渍管正常情况下的使用炉次由78炉增加到了86炉,增加了10.25%,有效地降低了炼钢成本。     

单管RH精炼过程钢液流场的水模型实验

采用物理模拟方法对单管 RH 真空精炼过程流场的循环流动、混合特性等进行了研究,建立与 RH 真空精炼装置原型相似比为1∶5的水模型,研究了不同工艺参数对单管 RH 装置内钢液循环流动的影响。对比实验测量数据发现,增大吹氩量和浸渍管插入深度以及浸渍管有效横截面有利于提高循环流量,减小均混时间;在相同的实验条件下,椭圆形浸渍管 RH 比传统浸渍管 RH 的循环流量要大15％以上,单管 RH 的均混时间比传统RH 可以缩短20％;单管 RH 钢包底部吹氩位置位于距钢包中心0.4R(R 是钢包半径)处时,均混时间最短。     

Effect of snorkel shape on the fluid flow during RH degassing process: mathematical modelling

A mathematical model was developed to investigate the effect of snorkel shape on the recirculation rate and the erosion of the lining refractory during RH degassing process. A particle image velocimetry technique was used to measure the velocity distribution in a water modelling experiment. The calculated results were well validated with the measured ones. In the mathematical model, the interfaces between the molten steel and the gas phase, and the motion of argon bubbles were simulated and tracked using VOF?+?DPM model by which the argon bubbles were treated as the discrete phase in the molten steel and the top gas phase, and the top gas phase was treated as a second continuous phase. It was found that the recirculation rate of the molten steel with oval snorkels was significantly larger than that with round snorkels. For round snorkels, the optimum gas flow rate was 1800?L?min^?1 and it was 2800?L?min^?1 for oval snorkels. Furthermore, the volume distribution of the argon in the radial direction of the up-snorkel with oval snorkels was much more homogeneous than that with round snorkels. Meanwhile, the predicted maximum wall shear stress showed that the bottom and the sidewall of the ladle with round snorkels were more seriously eroded than that with oval snorkels. Therefore, the oval snorkel was beneficial to improve the service life of the RH degasser.     

马钢RH KTB流场的数值模拟

利用CFX数值计算软件建立的数值耦合模型对马钢RH KTB的流场进行了分析,得出了包括钢包、真空室、上升管、下降管的RH全系统的流场状态及其在精炼过程中的变化规律。在RH吹氩气液两相区的处理上,应用了非均相多相流模型。模拟结果表明RH真空室内流场中存在小环流现象。     

RH炉浸渍管非对称腐蚀的数值模拟和应用

某钢厂 100 t RH炉存在上升管与下降管非对称腐蚀的问题,下部槽在上升管侧入口处的侵蚀远大于下降管侧出口处的侵蚀,无法满足设计的下部槽与浸渍管更换频率为1∶3的要求。通过数值模拟,对RH 炉吹气进行了流场模拟,得出了上升管和下降管的速度场分布,确定了该问题存在的原因是上升管与下降管内钢液的流速差异大,采取浸渍管对调等优化措施后,下部槽和浸渍管寿命分别达到 333和111炉,第3次浸渍管能与下部槽同步下线,降低了耐材成本。     

马钢RH KTB流场的数值模拟

利用CFX数值计算软件建立的数值耦合模型对马钢RH KTB的流场进行了分析，得出了包括钢包、真空室、上升管、下降管的RH全系统的流场状态及其在精炼过程中的变化规律。在RH吹氩气液两相区的处理上，应用了非均相多相流模型。模拟结果表明RH真空室内流场中存在小环流现象。     

Mathematical Modelling of Molten Steel Flow Process in a Whole RH Degasser during the Vacuum Circulation Refining Process: Application of the Model and Results

A three‐dimensional mathematical model for the molten steel flow during the RH refining process has been applied to the circulatory flow processes in both a practical RH degasser and its water model unit. The model was presented earlier [1] and one of its characteristics is that ladle, snorkels and vacuum vessel are regarded as a whole. Using this model, the fluid flow field and the gas holdups of liquid phases and others have been computed respectively for a 90 t RH degasser and its water model unit with a 1/5 linear scale. The results show that the mathematical model can properly describe the flow pattern of molten steel during the refining process in an RH degasser. Except in the area close to the liquid's free surface and in the zone between the two snorkels in the ladle, a strong mixing of the molten steel occurs, especially in the vacuum vessel. However, there is a boundary layer between the descending liquid stream from the down‐snorkel and its surrounding liquid, which is a typical liquid‐liquid two‐phase flow, and the molten steel in the ladle is not in a perfect mixing state. The lifting gas blown is ascending mostly near the up‐snorkel wall, which is more obvious under the conditions of a practical RH degasser, and the flow pattern of the bubbles and molten steel in the up‐snorkel is closer to an annular flow. The calculated circulation rates for the water model unit at different lifting gas rates are in good agreement with experimentally determined values.     

Mathematical modelling of molten steel flow in a whole degasser during RH refining process

Abstract

A three-dimensional mathematical model for molten steel flow in a whole degasser during the RH (Ruhrstahl–Heraeus) refining process is proposed. The model has been developed considering the physical characteristics of the process, particularly the behaviour of gas–liquid two phase flow in the up snorkel and the momentum exchange between the two phases. The fluid flow fields and gas holdups of liquid phases, among other parameters, in a 90 t RH degasser and a water model unit of one-fifth linear scale have been computed using this mathematical model. The results show that the flow pattern of molten steel in a whole RH degasser can be well represented by the mathematical model. Apart from the area close to the free surface and the zone between the two snorkels in the ladle, the molten steel in an RH degasser, especially in the vacuum vessel, is reasonably fully mixed during the refining process. However, there is a boundary layer between the descending liquid stream from the down snorkel and the surrounding liquid, which is typical liquid–liquid two phase flow, and the molten steel in the ladle is not perfectly mixed. The blown lifting gas ascends mostly near the up snorkel wall, which is more obvious under the conditions of an actual RH degasser, and the flow pattern of bubbles and molten steel in the up snorkel is closer to annular flow. Calculated circulation rates for the water model unit at various lifting gas rates are in good agreement with values determined by means of water modelling experiments.     

RH装置内夹杂物聚合与去除的三维数值模拟

 摘 要：基于RH精炼装置内流场,建立了一个研究夹杂物聚合与去除行为的三维数学模型。数值结果表明,夹杂物在钢包内上升管左侧存在一个侧“V”分布,上升管下方及下降管右侧均存在大的环状分布;夹杂物浓度和数量密度具有相似的空间分布;钢包内夹杂物的平均数量密度及浓度大于真空室内的平均值;夹杂物在气液两相区浓度较低;整个过程前400秒夹杂物去除最快,900秒后可去除大部分夹杂物,在处理后期,夹杂物平均特征尺寸有减小的趋势。