REDA精炼过程钢液流场及循环流量的数值模拟

基于欧拉多相流模型建立REDA精炼过程钢液流动行为的数学模型,并借助计算流体力学软件PHOE- NICS对钢液流动过程进行仿真模拟,重点分析了底吹喷嘴位置、吹氩流量、浸渍管插入深度及浸渍管内径等工艺 参数对REDA精炼过程流场及循环流量的影响。数值模拟结果表明:对于300 t REDA精炼装置底吹喷嘴位置取 1/2 R处为宜,浸渍管插入深度对循环流量影响不显著,扩大浸渍管内径可显著提高钢水循环流量,吹氩流量为1 200 L/min时,钢液循环流量约可达到210 t/min     

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。     

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 Elliptical Snorkel on the Decarburization Rate in Single Snorkel Refining Furnace

In the present work, physical model experiments were performed to investigate the effect of elliptical snorkel on the decarburization in single snorkel refining furnace. A round snorkel with the same cross‐section area as the elliptical snorkel was also made for comparison. Bubble behavior was recorded by a high speed video camera in this study. A volumetric mass transfer coefficient kA/V was used to evaluate the decarburization rate. Measurement of the volumetric mass transfer coefficient kA/V was made by means of the carbon dioxide desorption from a NaOH solution. It is found when the plug location is close to the center of the ladle bottom, almost all the bubbles get into the snorkels. However, when the plug location is too far away from the center of ladle bottom, bubbles will escape from the outside of the snorkel. kA/V generally rises with increasing gas flow rate. Moreover, kA/V is increased when the plug is moved from the center to the half radius of the ladle bottom. However, kA/V is decreased when the plug is moved from the half radius of ladle bottom to the ladle sidewall. It is indicated that kA/V for the elliptical snorkel is larger than that for the round one when the plug is located between the center and half radius of ladle bottom. Nevertheless, when the plug is located between the half radius and the ladle sidewall, the kA/V for the elliptical snorkel is smaller than that for the round one.     

RH熔池内弱搅拌区特性的模拟研究

以某钢铁厂170 tRH精炼装置为原型,运用数值模拟的方法对其在不同吹气量、浸渍管内径、插入深度和真空度下的流场进行了模拟,并对熔池内弱搅拌区的分布和变化进行了分析。研究表明:大包熔池上部存在3个弱搅拌区。随着吹气量的增大,1区、3区区域迅速减小;2区先增大后减小,在100 m3/h时达到最大。增大浸渍管内径,1区、2区、3区区域减小,2区在两浸渍管中下方出现了一狭长的弱搅拌区。增大浸渍管插入深度,3个弱搅拌区增大,熔池液面处速度降低,趋于平稳。增大真空度,3个弱搅拌区略有减小。在降低弱搅拌区的几个因素中,吹气量影响最大,浸渍管内径次之,真空度最小。     

单嘴精炼炉合金料加入方式及混匀特性水模型研究

根据相似理论,以80 t单嘴精炼炉1:4的水模型模拟,研究了单嘴精炼炉加合金料位置、吹气流量(2～10 L/min)、单嘴内液面高度(18.5～67.0 cm)、浸入深度(75～150 mm)、吹气位置等对混匀时间的影响。结果表明,在单嘴气体上升区对面加料混匀时间较短;吹气流量为6 L/min、浸入深度100～125 mm、单嘴内液面高度≥52 cm、在钢包底r/R=0.5位置吹气有利于混匀时间的缩短。     

RH真空精炼过程的动态模拟

建立了描述RH真空精炼装置内钢液动态脱碳（脱气）模型。对RH真空精炼时的脱碳、脱氧、脱氮和脱氢过程进行了动态模拟研究，考察了浸渍管直径、循环流量、吹氩量、氧含量和真空度对脱碳和脱气过程的影响。动态脱碳（脱气）模型考虑了反应机理，认为脱碳是通过上升管中Ar气泡表面、真空室中钢液的自由表面和真空室钢液内部脱碳反应生成的CO气泡表面进行的，并且考虑了精炼处理时的抽真空制度。该模型能全面描述RH精炼过程中不同时刻钢液中碳、氧、氮和氢的含量，能较好预测实际过程，可用于RH真空精炼过程的优化和新工艺开发。     

单嘴精炼炉技术的开发与应用

单嘴精炼炉是由我国提出的一种新型真空钢水精炼设备。它具有结构简单、精炼效率高、真空冶炼喷溅少、生产成本低等优点,已经为越来越多的冶金工作者所认识。通过在工业性生产中冶炼轴承钢、超低碳钢和无取向硅钢等品种的实践表明：该炉型在深脱碳、脱硫、脱氧和夹杂物去除等方面表现出了很好的冶金特性,并取得了较为满意的精炼效果。采用物理模拟和数学模型相结合的办法,对单嘴精炼炉的主要操作参数：如吹气流量、吹气位置、浸渍管内径、浸渍管插入深度等工艺参数和流动特性均进行了详细和深入的摸索,所得出的研究结果对实际生产起到了重要的参考和指导作用。随着单嘴精炼炉技术研究的不断深入和完善,这种新型炉外精炼设备必将发挥其自身特点,逐步得到应用和推广。本文也介绍了由日本新日铁提出的REDA精炼炉,它的装备和原理与单嘴精炼炉有一定的相似性,已经被成功应用于超低碳钢及不锈钢的生产。     

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.     

100 t单咀真空精炼炉底吹位置的优化

结合钢厂100 t单咀真空精炼炉相关参数,运用数值模拟的方法对脱气时单咀炉内的钢液流场进行了仿真计算,分析单咀炉内钢液流动的基本特征,研究了距底部圆心0.1～0.424 m吹气位置对钢液流场、钢液循环流量和混匀时间的影响。结果表明,原吹氩位置(距底部中心0.424 m),大部分氩气没有进入浸渍管,为避免氩气逸出,吹气孔距圆心应≤0.3 m;随吹气位置至圆心距离增大,钢水混匀时间减小,综合考虑钢液脱气效果和浸渍管寿命,最佳吹气位置应为距底部中心0.25～0.3 m处。     

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。     

210t RH浸渍管内钢液流动机理的水模型实验研究

采用1:4的比例建立水力学模型模拟210 t多功能RH浸渍管内钢液流动装置,对钢液流态进行分析,并考察吹氩量、浸渍管插入深度及吹氩孔个数对钢液流场和混匀时间的影响.结果表明:钢包内存在一主回流和大量小回流,并且来自下降管的下降液流和其周围液体形成了液-液两相流,这种流动状态对钢包内的混合及传质起着决定性的作用;本文得到的关于RH钢包内液体的这种流动状态,否定了RH过程的早期研究中关于下降管和上升管间存在\     

底吹钢包内流动及混合的两相流数值模拟

应用欧拉-欧拉模型建立了钢包内钢液流动及混合过程的数学模型,考察了吹气量对中心底吹及偏心底吹钢包内流场及均混时间的影响。计算结果表明,钢包底部四周为流动缓慢区域;吹气量越大,一方面可以降低均混时间,另一方面会导致钢包自由液面的钢液流速增大,从而容易造成卷渣;从缩短混合时间,提高生产效率考虑,偏心底吹更为有利。     

Mathematical Modelling of Non‐equilibrium Decarburization Process during Vacuum Circulation Refining of Molten Steel: Application of the Model and Results (I) ‐ Decarburization Process and Influences of Some Technological Factors

A novel three‐dimensional mathematical model proposed and developed for the non‐equilibrium decarburization process during the vacuum circulation (RH) refining of molten steel has been applied to the refining process of molten steel in a 90‐t multifunction RH degasser. The decarburization processes of molten steel in the degasser under the conditions of RH and RH‐KTB operations have been modelled and analysed, respectively, using the model. The results demonstrate that the changes in the carbon and oxygen contents of liquid steel with the treatment time during the RH and RH‐KTB refining processes can be precisely modelled and predicted by use of the model. The distribution patterns of the carbon and oxygen concentrations in the steel are governed by the flow characteristics of molten steel in the whole degasser. When the initial carbon concentration in the steel is higher than 400 · 10⁻⁴ mass%, the top oxygen blowing (KTB) operation can supply the oxygen lacking for the decarburization process, and accelerate the carbon removal, thus reaching a specified carbon level in a shorter time. Moreover, a lower oxygen content is attained at the decarburization endpoint. The average contributions at the up‐snorkel zone, the bath bulk and the free surface with the droplets in the vacuum vessel in the refining process are about 11, 46 and 42% of the overall amount of decarburization, respectively. The decarburization roles at the gas bubble‐molten steel interface in the up‐snorkel and the droplets in the vacuum vessel should not be ignored for the RH and RH‐KTB refining processes. For the refining process in the 90‐t RH degasser, a better efficiency of decarburization can be obtained using an argon blow rate of 417 I(STP)/min, and a further increase in the argon blowing rate cannot obviously improve the effectiveness in the RH refining process of molten steel under the conditions of the present work.     

RH精炼过程钢液流动数值模拟和应用

结合某钢厂RH精炼装置,运用数值模拟的方法对脱气时的流场进行了计算,得出了该型号RH装置在该厂操作条件下的流场,并成功解释了操作中遇到的一些现象.利用实践生产中的经验公式与数据对模拟结果进行了验证,结果表明模拟结果可靠.最后利用该模型计算了RH内钢液的湍动能耗散情况以及钢液循环流量与吹Ar量的关系,并给出了最佳吹Ar量的控制范围.     

透气砖在炉底位置与钢液吹氩行为的数值模拟

以精炼钢包为研究对象,在不同的透气砖位置的条件下,采用多相流模型计算了吹氩后钢包内钢液的流场,通过对流场数值的多元回归,计算了透气砖在钢包底部的最佳位置.结果表明:随着透气砖在钢包底部位置的变化,吹氩对钢液的搅拌效果也有很大的影响,当透气砖位置在钢包底部距中心位置为0.44R₀~0.48R₀之间时,底吹氩对钢液搅拌得更均匀.     

Simulation on flow field and mixing phenomenon in RH degasser with ladle bottom blowing

Abstract

A numerical method has been employed to investigate the flow field and mixing characteristic in the Rheinsahl–Heraeus (RH) degasser with side–bottom blowing. The numerical results showed that stream flows in the up snorkel, the vacuum chamber, the down snorkel and the ladle form a large rectangular circulation zone in the RH degasser with side–bottom blowing, which can enhance the circulation flow rate effectively. For an RH with side–bottom blowing, when the included angle of the line between bottom blowing location and ladle centre and the line between two snorkels is zero, the circulation flow rate increases initially with increasing dimensionless distance between the bottom blowing location and the ladle centre and then decreases, while the mixing time increases with increasing dimensionless distance. On the other hand, when the dimensionless distance is 0·2, both the circulation flow rate and the mixing time decrease with the increasing included angle initially, reach their minimum value and then increase. The optimum values for the dimensionless distance and the included angle to achieve large circulation flow rate and small mixing time are 0·2 and π/4 in the present work.     

LF精炼炉盖内惰性气氛的流动模拟

采用耦合数值求解的方法,计算并分析了LF精炼炉盖内气体流动的速度分布状态以及液面附近惰性气体氩(Ar)的流动行为和分布.结果表明:露弧加热期和埋弧加热期炉盖的合理抽气压力分别为-200~-250 Pa和-120 Pa;底吹氩气量过小不能在液面上部弥散,而增大到20~50 m³·h^-1,在液面附近弥散且流动分布状态相似,有利于液面附近惰性气氛的保持;液面距钢包上边缘的距离增大,氩气在液面上部回旋的区域扩大,可防止钢液增[N]或[O].     

RH喷吹参数对循环流量和均混时间影响的物理模拟

以某厂300tRH真空精炼装置为研究原型,建立1∶6.5的水力模型对RH喷吹精炼工艺进行物理模拟。研究了喷吹位置、喷吹气量及驱动气体流量对循环流量和均混时间的影响。结果表明:不同喷吹气量、驱动气体流量条件下,获得大循环流量和短均混时间的最优喷吹位置不同。较小的喷吹气量(2.98~3.53m3/h)或者较小的驱动气体流量(0.93~1.02m3/h)时,宜采用低顶枪枪位(153.8mm)喷吹;喷吹气量大于3.91m3/h或者驱动气体流量大于1.12m3/h时,宜采用真空槽底部喷吹角度120°的侧喷嘴喷吹。顶枪与侧喷嘴复合喷吹有利于提高RH喷吹工艺的适应性及循环效率。     

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。