RH真空精炼炉脱气工艺分析

结合生产实际数据,分析了RH真空脱气工艺过程。如要求[H]≤1.8×10-6,需真空处理9min;当要求[H]≤1.5×10-6时,冬、春季节RH处理时间为≥11min,夏季则为≥12min,秋季应为≥13min;RH脱氮率约为23%,且在脱气超过8min时RH脱氮出现拐点,延长真空处理时间对脱氮影响不大。     

炼钢真空脱气系统泄漏的控制

阐述了炼钢真空脱气系统由于联接环节多,工作环境恶劣等种种原因导致泄漏激境,并指出应从设计、制造、安装调试和投产使用各个环节控制和减少泄漏的产生。     

不同搅拌桨形式对稀土萃取槽内搅拌效果的影响模拟分析

搅拌桨是稀土萃取搅拌反应器最重要的辅助设备之一,不同搅拌桨类型对搅拌效果有不同影响.利用计算流体力学模拟软件--MIXSIM,对圆盘式四直叶涡轮搅拌桨及开式45 ℃折叶涡轮搅拌桨的搅拌情况进行模拟分析,得出了2种搅拌桨的搅拌混合特点及应用范围.     

不同搅拌参数的双层浆搅拌槽三维流场数值模拟

运用Fluent软件,采取多重参考系法(MRF)和标准k-ε紊流模型对搅拌槽在水中产生的流场进行数值模拟,分析了桨叶高度和转速对三维流场的影响,并对其宏观流动特性和时均速度分布进行详细对比分析。结果表明,当上桨叶高度为1 200mm、转速为1 909r/min(200rad/s)时,搅拌效果最佳。     

An Analysis of Recirculatory Flow in Gas‐Stirred Ladles

The paper is concerned with the fluid mechanics characterizing the bulk flow region in a gas‐stirred ladle. A theoretical framework, previously derived for the analysis of the gas‐liquid plume region, is extended to include the bulk flow phenomena. In this study, the liquid recirculation and mixing have been quantified in terms of simple dimensionless parameters related to the ladle geometry and gas flow rate. A new correlation for mixing time, consistent with the proper form of the Froude similitude criterion, is presented. The work has implications for the fundamental as well as applied aspects of ladle processing.     

含钒页岩浸出槽搅拌速度优化的数值模拟

含钒页岩浸出槽是钒页岩湿法提钒浸出段的主要操作单元,存在固相分布不均、槽底矿物易沉积等问题。通过数值模拟研究来对比分析搅拌桨叶双层同速以及异速方案下对搅拌浸出槽内固液两相流搅拌功率和效率的影响。结果表明,当搅拌桨叶双层同速由1.3 r/s改变至1.7 r/s时,死区由5.02 m³减少至2.03 m³,混匀时间由1 501 s降低至1 116 s,近自由液面平均速度也由0.32 m/s增大至0.56 m/s,因此搅拌桨转速选择1.7 r/s更为合适;搅拌桨叶双层异速可以得到与双层同速情况下基本一致的搅拌效果,当上层桨叶转速由1.5 r/s改变至1.7 r/s时,死区由2.95 m³减少至2.33 m³,混匀时间由1 261 s降低至1 146 s,近自由液面平均速度也由0.44 m/s增大至0.54 m/s。因此搅拌桨转速选择上层1.7 r/s、下层1.5 r/s能在保持较低的搅拌功率同时能得到较好的搅拌效率。     

氟钽酸钾钠还原搅拌釜中的搅拌流场数值模拟

采用标准k-ε湍流模型、Eluer-Eluer双流体模型,结合滑移网格法,对氟钽酸钾钠还原搅拌釜中搅拌流场进行数值模拟,研究不同转速、搅拌桨叶类型对液钠-熔盐分散特性、流场的影响。结果表明,在两种桨叶模型下,液钠仅局部分布在混合熔盐表面;平直叶桨、折叶桨搅拌均在搅拌釜内形成四个循环流区域,且在搅拌轴附近区域存在搅拌死区;液钠在液面的分散面积均随着转速的增加而减小,沿搅拌轴进入熔盐的深度随转速的增加而增大;在折叶桨模型下,随着搅拌转速的增加,近液面处流场速度增大,速度沿X轴方向呈对称分布。     

Inclusion Growth and Removal in Gas‐Stirred Ladles

A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas‐stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical‐cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical‐cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical‐cap bubbles (assuming plane contact between the inclusion and the bubble).     

Effect of Gas Forming Compounds on the Vibration of a Submerged Lance in Hot Metal Desulfurization

Hot metal desulfurization is the main process step for removing sulfur in blast furnace-based steelmaking. A desulfurization reagent is pneumatically injected into the hot metal through a submerged lance causing it to vibrate. The aim of this study is to develop a mechanical vibration measurement-based method that can detect changes in the gas-forming properties of the reagent. The detection is performed using Elastic Net regression and eXtreme Gradient Boosting-based classification models the classification performance of which is compared. The lance aging causes changes in its dynamic characteristics, and the disturbing effect of this is removed from the measured data of the lance vibration prior to classification by means of a developed cleaning algorithm. The best classification performance in detecting changes in the gas-forming properties, with an area under the receiver operating characteristic curve of 0.916 and Matthews correlation coefficient of 0.699, is achieved using an Elastic Net regression-based classification model. The results of this work serve as a basis for developing industrial applications in which the effective utilization of the excitation, such as vibrations generated by the gas formation can be utilized for process monitoring and as a soft sensor for predicting the reagent-induced process variance.     

Mathematical Model for Growth and Removal of Inclusions in Molten Steel under Gas‐stirring Conditions

A three‐dimensional mathematical model has been developed to predict growth and removal of inclusions during gas stirring through eccentric tuyeres in a ladle. In the model, the efficiency of inclusion removal is investigated under three different collision mechanisms: Brownian, turbulent and Stokes collision. The Importance of the three approaches of wall adhesion, Stokes flotation and bubble adhesion on inclusion removal is analysed and the efficiency of inclusion removal through three types of tuyeres in central, eccentric and multi‐tuyere form is studied. The results indicate that inclusion growth resulting from turbulent collision is most important and the effect of Stokes collision is remarkable with increased inclusion size, while inclusion growth resulting from Brownian collision is negligible. Removal by Stokes flotation is the main mechanism for large inclusions, while inclusion removal by wall adhesion is negligible. The smaller the bubbles are, the higher the efficiency of inclusion removal is. The type of tuyere arrangement has a great effect on inclusion removal. Inclusion removal in a 135t ladle with one eccentric tuyere is more efficient than in a ladle with central tuyere or multi‐tuyere design.     

Modelling of Gas‐Powder Flow in a Blast Furnace

This paper presents a study of the gas‐powder flow in a slot type packed bed in order to investigate the distribution of powder flow and accumulation in an ironmaking blast furnace. The effects of operational parameters such as gas flow rate, and cohesive zone shape are examined. It is shown that a distinct and stable accumulation region can be formed in the low gas‐powder velocity zone in a bed with a lateral gas inlet. Also, the existence of a cohesive zone changes the powder accumulation pattern significantly. The inverse‐V cohesive zone leads to low accumulation in the bed compared to other cohesive zone shapes. A mathematical model is developed to describe the gas‐powder flow and powder accumulation. Its validity is verified by comparing the predicted and measured distributions of powder accumulation under various flow conditions.     

Numerical Simulation of Nonmetallic Inclusions Behaviour in Gas‐Stirred Ladles

The secondary refining of molten steel in gas‐stirred ladle has played a more and more important role in the production of high quality steel. In the present work, a mathematical model of the fluid flow and inclusions behaviour in a 150t gas‐stirred ladle was presented, and the variations in concentration, size and density for non‐metallic inclusions in the ladle during the refining process were predicted. The results show that during the refining process, the variations in the number density of the inclusions differed depending on size. The inclusions with a diameter less than 25 μm decrease during the whole period, while inclusions with diameter larger than 25 μm increase in the first stage of the treatment and gradually decrease during the later stage. After 15 minutes, all inclusions show a tendency to decrease, but the removal rate for inclusions of smaller size becomes slower. After treatment in the ladle, inclusions with a diameter larger than 50 μm were removed, the number of inclusions with a size between 30‐40 μm was not high, while inclusions that were smaller than 25 μm still remained in the molten steel. Two‐jet bubbling demonstrated an advantage over one‐jet for inclusion removal. The practice of bubbling argon with a higher gas flowrate initially, followed by a lower flowrate in the ladle was found to be beneficial for inclusions removal.     

基于CFD建模的生物氧化槽空气分散器结构优化研究

针对生物氧化槽充气效率低,能耗高的问题,利用CFD软件对氧化提金的生物氧化预处理过程进行数值模拟,分析了氧化槽内气体分布情况以及空气分散器的结构半径对氧化槽中气体浓度的影响。结果表明,氧化槽内气体在越接近空气分散器位置时气体浓度越高,距离空气分散器越远时气体浓度越低;空气分散器结构直径在2～5m时,随着空气分散器直径的增大,在氧化槽高度9m处的气体浓度增大。当直径大于5m时,气体浓度达到1.225 8kg/m~3后不变。     

Investigation of the Gas‐Liquid Flow in a Stopper‐Rod Controlled SEN

The behaviour of two‐phase gas‐liquid flows in a stopper‐rod controlled submerged entry nozzle (SEN) is investigated in water model experiments. The observed two‐phase flow patterns can be classified into either bubble coring or bubbly slug. The scaling of the two‐phase flows by means of similarity parameters is discussed. In the experiments, it is found that the liquid flow rates depend strongly on the two‐phase flow patterns. Additionally, the influence of swirl on the flow patterns is investigated in detail. It is shown that swirl has a marked impact on the transition from bubble coring to bubbly slug. Finally, an estimation of the two‐phase argon‐steel flow patterns in industrialscale SEN flows is given.