钢液RH精炼非平衡脱碳过程数学模拟：过程数学模型

考虑和分析了钢液RH非平衡脱碳过程的特征,基于冶金反应工程学和非平衡态热力学及气-液两相流的双流体模型和修正的紊流k-ε模型,引入熵衡算和非线性耗散因子,对该过程提出了一个新的三维数学模型,给出了该模型的具体细节,包括控制方程的建立、修正的k-ε双方程模型、相应的源项和边界条件的确定等;对90 t装置内的RH和RH-KTB精炼过程,讨论和确定了该模型各有关参数.     

真空循环精炼过程中钢液流动的数学模拟:流动的数学模型

考虑到RH过程的物理特性,特别是上升管内气液两相流的行为和两相间的动量传输,建立了该精炼过程中整个装置内钢液流动的三维数学模型.在该模型中,将钢包,插入管和真空室视为一个整体,基于双流体模型处理和描述了气液两相流,并采用了特殊修正的k-ε双方程模型.给出了该模型的有关细节.     

真空循环精炼过程中钢液流动的数学模拟:模型的应用及结果

应用提出的RH真空循环精炼过程中钢液流动的三维数学模型,分别计算了90 t RH装置及线尺寸为其1/5的水模型装置内流体的流场和上升管内液相的含气率等.结果表明,该模型能相当精确地模拟整个RH装置内钢液的流场.除靠近钢包内钢液表面和两插入管间的区域外,精炼过程中液体混合相当充分,但在下降液流与其周围液体间存在一典型的液-液两相流界面层,钢包内的钢液并不处于完全混合状态.吹入的提升气体主要在上升管壁附近上升,在实际RH装置的条件下更为显著,相应的流态接近于环状流;计算得的模型装置环流量与实测结果很吻.     

钢液RH精炼非平衡脱碳过程数学模拟:模型的应用及结果(Ⅰ)——脱碳过程及某些工艺因素的影响

应用基于冶金反应工程学和非平衡态热力学对钢液RH精炼脱碳过程提出的新三维数学模型于90 t RH装置内的精炼,处理了RH和RH-KTB条件下铜液的脱碳.结果表明,该模型可相当精确地估计RH和RH-KTB精炼中碳和氧浓度的变化;碳和氧浓度分布为钢液流动所左右;钢中碳高于4×10-4(ω)时,KTB操作既可补充脱碳所短缺的氧,使脱碳加速,在更短的时间内达到规定的碳含量水平,也可达到较低的脱碳终点氧含量;对RH和RH-KTB脱碳,都不应忽略上升管内气泡-钢液界面和真空室内液滴群的作用.本工作条件下,对该90 t RH装置,以417 L/min的吹Ar量即可获得相当好的脱碳效果,进一步增大Ar流量并不能显著改善RH精炼过程的脱碳效果.     

钢液RH精炼非平衡脱碳过程数学模拟:模型的应用及结果(Ⅱ)——非平衡因素及其对脱碳过程的影响

应用提出的新三维数学模型于90t RH装置内RH和RH-KTB精炼中钢液的脱碳,结果表明,本工作条件下,整个精炼中由气泡穿过液相时所作曳力功、流动和扩散及化学反应等非平衡过程引起的体系内耗散函数Κ2的值不大,体系整个流场内非线性耗散因子qe(Κ)≈1;体系内熵产生和能量耗散随精炼的进行很快减小:与气泡穿过液相时所作曳力功、粘性和紊流耗散及扩散相比,C-O反应对体系内熵产生和能量耗散起主导作用,低碳和超低碳钢的RH精炼似乎接近非平衡态的线性区;粘性和紊流耗散及扩散对非平衡活度系数的影响可忽略,除发生化学反应的部位(上升管区段和真空室熔池)外,RH装置中其他部位钢液内碳和氧非平衡活度系数的非平衡分量都趋于1;非平衡效应(主要是碳氧反应)对RH精炼中钢液的脱碳有抑制作用.与不考虑非平衡效应的情况相比,该模型能更合理和精确地模拟RH精炼中钢液的脱碳.     

RH真空处理装置的应用

从工艺装备,控制系统组成以及真空处理的效果等方面,介绍了安钢第二炼轧厂170tRH真空处理装置的应用。     

液滴行为与液-液混合设备

总结了液-液非均相混合过程中的液滴运动速率计算模型,分析了液滴破碎及合并的机理。在结合各种工业应用的基础上,总结了搅拌釜、射流混合器、静态混合器、撞击流混合器及纤维液膜混合器等五种混合设备的混合原理及研究现状。展望了液-液混合设备的研究前景。     

内构件存在时提升管内流动及颗粒混合行为研究

he hydrodynamics and solids mixing behavior in a riser with blunt internals are studied. A uniform radial distribution for solids fraction and particle velocity achieves near the internals. The turbulent velocity of particles near the wall increases with the addition of the internals, with the lateral solids mixing enhanced significantly. Probability density distribution of particle velocity is bimodal in the riser with internals, which is similar to that in the conventional riser, indicating that no significant difference in the micro flow structure exists between the riser with internals and the conventional riser. At the same time, the axial solids mixing behavior changes insignificantly with the addition of internals. These results indicate that the micro flow structure in the riser is very stable, which changes insignificantly with the change of the bed structure.     

Numerical Investigation of Degassing Behavior of Highly Viscous Non-Newtonian Fluids under Stirring

A method for accelerating bubble removal in non-Newtonian liquids by forced stirring is proposed. Numerical simulations based on an Eulerian-Eulerian multiphase model are performed to test its feasibility for various liquids including shear-thickening, shear-thinning, and Newtonian ones. Effects of the rotating speed of the stirrer and rheological properties of liquids on the degassing efficiency are evaluated, and the influencing mechanisms are analyzed in detail. The feasible regions of degassing in shear-thinning liquids covering a certain range of viscosities are determined, from which one can easily decide the optimal rotating speed given the viscosity of liquids. The results provide a new idea of efficient degassing in shear-thinning liquids for researchers and engineers.     

含油污泥-石英砂颗粒混合物的混合分离特性

在内径60 mm、高1000 mm的冷态气固流化床实验装置上,研究了含油污泥-石英砂混合颗粒的流化特性.实验结果表明,对于含油污泥含量较高的混合颗粒,随着气速由高到低,含油污泥颗粒与石英砂的流化行为可以分为四个阶段,双组分完全流化、石英砂流化-油泥趋于静止、石英砂趋于静止和固定床阶段;通过两组份分层填装流化实验,发现仅...     

RH精炼装置流场对混合、脱碳、夹杂物行为的影响

基于计算流体力学、反应热力学及动力学,对RH气液流场、脱碳及夹杂物碰撞长大进行了数值模拟. 结果表明,在提升气量为400 NL/min条件下,气泡在上升管存在贴壁效应;1000 NL/min下,侧吹气体可形成吹透现象;RH脱碳处理中,0~3 s的脱碳速率为45~70 mol/s,3~500 s时降低到5 mol/s,500 s后脱碳速率进一步降低;经过14 min处理后夹杂物质量浓度可降低到5′10-5以下;数值模拟结果与实验测量结果符合良好,说明数值模拟方法可完全用于RH真空精炼过程中关键工艺参数的预测.     

Mixing Agglomeration in a High‐Shear Mixer with a Stirred Mixing Vessel

This paper deals with the agglomeration process in a high‐shear mixer. High‐shear mixers rotate with a very high mixing tool speed such that not only a mixing effect, but also a grinding effect is achieved. The parameter study reported here was carried out to determine the parameters influencing mixing agglomeration. The results will help the user to decide which parameters have to be considered for an optimum mixing agglomeration. This article will highlight some of the findings obtained from the comprehensive parameter study.     

Viscosity of Bone Cement Influences Effectiveness of Vacuum Mixing

Four commercially available Polymethylmethacrylate (PMMA)-based bone cements of differing viscosities were tested after open bowl and vacuum mixing techniques. Their properties were evaluated using scanning electron microscopy, density measurements, and mechanical testing. High viscosity cements had greater density, implying reduced porosity, when mixed under vacuum conditions. The decrease was related to the timing of the waiting phase of mixing. However, the decrease in porosity was not associated with an increase in the compressive strength. High viscosity cements, particularly those with a late completion of the waiting phase, may be more suitable to vacuum mixing techniques.     

RH真空精炼过程数值模拟的研究现状及展望

近年来,RH真空精炼已成为重要的二次精炼工艺之一,相应的数值模拟工作受到许多研究者的关注.目前涉及到RH精炼过程的数值模拟研究主要集中于以下几个方面:RH精炼装置内气液两相流动行为的数值模拟,脱碳和脱气过程的数值模拟以及夹杂物碰撞长大行为的数值模拟.本文综述了RH精炼过程数值模拟的研究现状,并提出了应重点解决的问题.     

显示剂实验橡胶在密炼机内的混炼性能

本文在密炼机内 ,用顺丁橡胶加入聚四氟乙烯显示剂 ,研究转子的螺旋角 (从 5°～15°)变化对胶料分散性能的影响 ,证明了螺旋角越大混炼效果越好的结论。     

真空绝热容器外壳腐蚀裕量的分析

通过对国内外压力容器技术标准的研究,结合低温真空绝热容器外壳的选材、表面防腐处理工艺,综合考虑经济效益,论证了该类产品的外壳腐蚀裕量取0的可行性.在确保真空绝热容器安全、正常运行的前提下,使设备总成本尽可能降低.同时,该方法为真空绝热容器轻量化的研究提供了依据.     

混沌混合中流体指数拉伸与混合效率的数值研究

The stretching and folding of fluid element during chaotic mixing field is studied using numerical method. The chaotic mixing process is caused by periodic secondary flow in a twisted curved pipe. Using the nonlinear discrete velocity field as the dynamical system, the present study connects the fluid particle‘s stretching along its trajectory in one period to a linearized time-varying variational equation. After numerical approximation of the variational equation, fluid stretching is calculated on the whole cross section. The stretching distribution shows an exponential fluid stretching and folding, which indicates an excellent mixing performance.