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1.
Based on the mass and momentum balances in the system, a new mathematical model for decarburisation and degassing in the vacuum circulation refining process of molten steel has been proposed and developed. The refining roles of the three reaction sites, i.e. the upsnorkel zone, the droplet group and steel bath in the vacuum vessel, have been considered in the model. It was assumed that the mass transfer of reactive components in the molten steel is the rate control step of the refining reactions. And the friction losses and drags of flows in the snorkels and vacuum vessel were all counted. For the refining process of molten steel in a 90 t multifunction RH degasser, the parameters of the model have been discussed and more reasonably determined. 相似文献
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《钢铁冶炼》2013,40(5):427-434
AbstractA 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. 相似文献
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基于相似的动力学机理,利用水溶液中溶解氧的去除过程模拟了钢液的真空脱气行为. 在负压25 kPa条件下发现,容器壁面或测氧探头表面会析出大量细小气泡,这一现象与以往脱气数学模型假设的内部脱气反应非常类似;为了验证内部脱气位点的存在,通过引入机械搅拌,对溶池表面和内部脱气速率进行了分析计算. 实验结果表明,在整个脱气过程中溶池表面脱气速率很低,内部脱气位点析出的气泡会极大地提高溶解氧的去除速率,尤其当真空压力为25 kPa时,其脱气速率约为自由表面的脱气速率的10倍,但内部反应仅局限于脱气的初始阶段,即高溶解氧浓度范围内. 另外,水溶液中溶解氧的去除为一级反应过程,其体积传质系数(k · A · V?1)为常数,因此可以利用溶解氧在水溶液中的去除过程模拟钢液的真空脱气行为. 为了描述真空压力和吹氩流量对k · A · V?1的影响,引入搅拌动能密度(ε)的概念,通过线性回归得到了lg (k · A · V?1)与lg ε之间的函数关系,并与以往的模拟研究进行了对比. 相似文献
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The decarburisation process is studied with the help of mathematical modelling of RH degasser with reaction interface area approach, considering multi-component mixed phase mass transport theory. An algorithm is developed by considering Ar gas, bath surface and CO gas bubbles as the reaction sites for decarburisation process. On the basis of this, the model is developed using MATLAB. The model is tested with five sets of data which are obtained from JSW Steel Plant Ltd. The results obtained from the model have been compared with the industrial data as well as the data obtained from literature survey. It is shown that the nitrogen and hydrogen removal are triggered more for higher CO evolution rate. The relations between carbon removal and factors like area of interface, time and vacuum pressure are proposed. 相似文献
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Mathematical modeling of the argon-oxygen decarburization refining process of stainless steel: Part I. Mathematical model of the process 总被引:2,自引:0,他引:2
Some available mathematical models for the argon-oxygen decarburization (AOD) stainless steelmaking process have been reviewed.
The actual situations of the AOD process, including the competitive oxidation of the elements dissolved in the molten steel
and the changes in the bath composition, as well as the nonisothermal nature of the process, have been analyzed. A new mathematical
model for the AOD refining process of stainless steel has been proposed and developed. The model is based on the assumption
that the blown oxygen oxidizes C, Cr, Si, and Mn in the steel and Fe as a matrix, but the FeO formed is also an oxidant of
C, Cr, Si, and Mn in the steel. All the possible oxidation-reduction reactions take place simultaneously and reach a combined
equilibrium in competition at the liquid/bubble interfaces. It is also assumed that at high carbon levels, the oxidation rates
of elements are primarily related to the supplied oxygen rate, and at low carbon levels, the rate of decarburization is mainly
determined by the mass transfer of carbon from the molten steel bulk to the reaction interfaces. It is further assumed that
the nonreacting oxygen blown into the bath does not accumulate in the liquid steel and will escape from the bath into the
exhaust gas. The model performs the rate calculations of the refining process and the mass and heat balances of the system.
Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the
nonisothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors have all been
taken into account.
[]—metal phase; ()—slag phase; {}—gaseous phase; and 〈〉—solid phase 相似文献
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RH-MFB真空精炼过程中循环流量的物理模拟研究 总被引:2,自引:0,他引:2
在120 t RH-MFB多功能真空精炼装置1∶5.45比例的水模型上,采用毕托管测定下降管内钢水流速,从而测定循环流量的方法,研究了真空循环精炼过程中钢液的环流特性.考察了该冶金反应器主要结构参数和工艺操作因素,包括插入管内径、驱动气体流量、驱动气体用喷嘴个数及其布置、驱动气体引入位置(气泡行程)、插入管浸入深度、钢水处理容量等对循环流量的影响关系.结果表明,循环流量随插入管内径、驱动气体流量、驱动气体用喷嘴个数、气泡行程、插入管浸入深度的增加而加大. 相似文献
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RH真空循环脱气装置水模型循环流量的实验分析 总被引:3,自引:1,他引:2
循环流量是判断RH真空脱气装置冶炼效率的最重要的指标之一。本文中采取了两种方法--超声波流量计法和粒子示踪法对RH真空脱气装置的水模型的循环流量进行测量分析,同时也研究了新型的多管RH装置的循环流动,比较新型装置同传统装置的循环流动的差别。结果表明:利用超声波流量计和粒子示踪法两种方法测量的结果都显示新型多管RH真空脱气装置循环流量大于传统的两管RH装置循环流量,并且,随着喷入气体量的增加,新装置循环流量的增加幅度也大于传统装置的增加幅度。 相似文献
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大尺寸非金属夹杂物是引起超低碳钢冷轧钢板表面线状缺陷的重要原因。以IF钢为例,铸坯中大尺寸夹杂物主要有3类,即结晶器保护渣卷入后被凝固坯壳捕获;连铸过程中钢水二次氧化产生且未上浮去除的;钢液中未充分去除的夹杂物在浸入式水口处粘连、堵塞,后续堵塞物脱落被凝固坯壳捕获。钢液一次脱氧生成的夹杂物中,不低于100 μm的夹杂物在RH处理过程中较容易去除,100 μm以下的夹杂物受钢液的流动影响较大,特别是不超过20 μm的夹杂物由于其上浮时间长、钢液流动的跟随性好,去除难度较大。RH是超低碳钢最重要的精炼设备,也是夹杂物去除的关键环节,研究RH去除20 μm夹杂物的新技术具有重要的意义。研究了RH脱碳结束加铝后真空度对夹杂物去除的影响,创新性提出了低真空度去除不超过20 μm夹杂物的新技术。研究结果表明,与高真空度处理工艺(常规工艺)相比,低真空度(压力5 kPa)处理的钢液中夹杂物数量降低更显著,中间包钢液总氧质量分数平均降低0.000 2%,钢液增氮水平相当。冷轧钢板因炼钢原因导致的线状缺陷降级率比常规工艺降低了29%。夹杂物在钢液中的跟随性理论分析表明,低真空度处理工艺下RH内钢液循环流量和钢液流速减小,降低了RH处理过程中夹杂物随钢液的跟随性,提高了不超过20 μm夹杂物的去除效率,有效改善了水口堵塞程度、提高了轧板表面质量。 相似文献
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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。 相似文献
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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. 相似文献
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为了优化RH处理工艺、提高RH精炼后的IF钢水洁净度,通过分析T[O]含量的变化研究了RH纯循环时间、镇静时间、钢包顶渣氧化性对IF钢洁净度的影响.实验结果表明:适当延长纯循环时间有利于钢液洁净度的提高,加TiFe后保证纯循环时间6~8min以上可使RH真空处理结束后钢液T[O]降至30×10-6以下;随着RH真空处理结束后镇静时间的延长,中间包钢水T[O]含量总体呈下降趋势,镇静时间大于30 min的炉次,T[O]可控制在35×10-6以下;RH结束后渣中T.Fe每提高1%,平均Al、Ti总损失会增加1.05×10-6 min-1,其中Al损失率0.40×10-6 min-1,Ti损失率0.65×10-6 min-1. 相似文献
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The mathematical model proposed and presented in Part I of the present work has been used to deal with and analyze the austenitic
stainless steel making (including ultralow-carbon steel) and has been tested on data of 32 heats obtained in producing 18Cr9Ni-grade
steel in an 18-t argon-oxygen decarburization (AOD) vessel. The results indicated that the carbon concentrations and bath
temperatures at the endpoints of blowing periods, calculated by the model, are in excellent agreement with the determined
data, and the Cr content after the predeoxidization, obtained from the model predictions, also agrees very well with the observed
value. The Gibbs free energies of the oxidation reactions of elements can be used to characterize fully the competitive oxidation
among the elements during the refining process and to determine reasonably the corresponding distribution ratios of oxygen.
The critical carbon concentration of decarburization (after which the decarburization changes to become controlled by the
mass transfer of carbon in molten steel) for the AOD refining process of austenitic stainless steel in an 18-t AOD vessel
is in the range of 0.25 to 0.40 mass pct. The model can provide some very useful information and a reliable basis for optimization
of the technology of the AOD refining process of stainless steel and control of the process in real time and online. 相似文献
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If greater use is to be made of vacuum technologies in out-of-furnace treatments of steel within Russia, more stringent requirements
will have to be met in regard to the reliability, productivity, and efficiency of the pieces of equipment used to create the
vacuum-the vacuum pumps. Unfortunately, Russian-made vacuum pumps do not presently meet these requirements.
The equipment traditionally used to create a vacuum in units designed to treat steel outside the steelmaking furnace is based
on steam-jet ejectors. This article compares the operating costs of a vacuum-degassing unit for 90-ton heats when the unit
is equipped with mechanical pumps and when it has a steam-jet-ejector station. In the latter case, liquid-ejector pumps are
used as the starting stage. It was found that the costs of the material resources and maintenance of the auxiliary equipment
of a vacuum-degassing unit with mechanical pumps are roughly 10 times less than the analogous costs of a vacuum system with
steam-jet ejectors. Another important advantage of vacuum-degassing units with mechanical pumps is that they are environmentally
safe.
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Translated from Metallurg, No. 4, pp. 58–61, April, 2007. 相似文献