钢铁综合企业的水流模型及吨钢综合水耗分析

 钢铁在工业领域里是耗水和排污大户,钢铁企业的节水减排势在必行。运用物质流分析跟踪观察模型构建钢铁企业的水流模型,依此分析吨钢综合水耗的构成;借鉴系统节能理论,建立钢铁企业吨钢综合水耗的[w-p]模型,在此基础上提出钢铁工业综合水耗的[w-p]分析方法。以中国某大型钢铁综合企业为例,分析工序水耗变化和钢比系数变化对综合水耗的影响,结果表明,降低各工序的工序水耗是降低吨钢水耗的主要影响因素,并指出随着钢铁企业结构的调整和技术水平的进步,降低工序水耗是钢铁企业节水减排的主要研究趋势。通过模型分析及案例研究得到降低吨钢综合水耗的方向及措施。     

绅士在传统乡村社会自治中的作用

在阐述绅士的含义及来源的基础上,剖析了绅士在乡村社会自治中的作用,探讨了绅士自治在我国传统社会管理中的重要意义,以期为相关研究提供借鉴.     

Bi-Pb合金熔体作用浓度计算模型

根据含化合物金属熔体共存理论,结合相图和有关的实验结果,确定Bi-Pb合金熔体的结构单元为Bi原子、Pb原子以及PbBi分子,从而推导了该熔体的作用浓度计算模型。模型计算的N_(Bi)和N_(Pb)与实测的活度值完全符合。同时求得了生成PbBi化合物的lgK～T和相应的△G°～T的关系式为:lgK_(PbBi)=451.098/T_(K)-0.5853△G°_(PbBi)=8642.610-11.2138T_(K)J/mol}(700～1223K)     

Fe-C-O三元金属熔体作用浓度计算模型

根据含化合物的金属熔体结构的共存理论,推导了Fe-C-O金属熔体作用浓度计算模型。计算的N_o'与相应的实测α_o相符合,从而证明所得模型可以反映Fe-C-O金属熔体的结构本质。     

多元体系作用浓度通用计算模型研究

根据冶金中广泛使用的共存理论作用浓度模型基本原理,结合Newton-Raphson算法建立了通用作用浓度计算数学模型.与传统针对具体体系建立专用作用浓度模型相比,该模型具有适用范围广、构建速度快、易于编程的特点.通过比较4元渣系、5元渣系和8元渣系作用浓度模型发现,该通用模型可在较少的步数下快速收敛.     

Fe—N熔体作用浓度计算模型

根据含化合物金属熔体的共存理论、相图以及前人的研究成果,推导了Fe—N熔体作用浓度计算模型,并求得了符合实际的结果。同时进一步确定氮的分配比与温度的关系式为:lgL_N=-1679.75/T_(K)+4.155(660～810℃);其相应的析出自由能的关系式为:△G_析~0=32182.42—79.605T_(K)J/mol(660～810℃)。     

Fe-Al系金属熔体作用浓度的计算模型

根据含化合物金属熔体的共存理论和Fe-Al系相图,用回归分析法确定了Fe-Al系金属熔体在1315℃和1600℃时的结构单元,进而推导了各组元的作用浓度模型。将计算的N_Fe,N_Al和实测的活度值α_Fe,α_Al相比较,得到了比较满意的结果。     

Al-Si-Fe合金熔体质量作用浓度的热力学模型

基于原子分子共存理论(AMCT)建立了计算Al-Si二元熔体及Al-Si-Fe三元熔体结构单元质量作用浓度的热力学模型.针对Al-Si二元系熔体,根据FactSage热力学软件计算的活度得到生成复杂分子Al2Si和AlSi的反应的标准摩尔吉布斯自由能的表达式,进而获得了 Al-Si二元熔体中标准摩尔溶解吉布斯能变的表达...     

超声波作用下锑盐净化除钴试验研究

在试验确定常规锑盐净化优化工艺条件的基础上,探索研究了超声波对锑盐净化除钴速率及深度的影响.试验结果表明,超声波对提高锌粉置换除钴速率具有一定的作用;在80～200 W的试验范围内,改变超声波功率对置换除钴影响较小;高频率(如100 kHz)超声波对净化除钴有利,若超声波净化时间超过60 min,低频率(如45 kHz...     

MgO—SiO2熔渣作用浓度计算模型

本文根据炉渣结构的共存理论，结合相图，推导了ＭｇＯ—ＳｉＯ＿２渣系作用浓度计算模型。在进一步分析和处理了出现饱和相作用浓度的基础上，使得模型计算结果和实测的活度值完全符合。从而证明了此模型的正确性。     

板坯连铸结晶器钢液行为的水模拟试验

以某钢厂250mm×2 100mm断面板坯连铸结晶器为研究对象,采用水力模拟的方法研究了拉速在0.88m/min条件下不同水口结构参数对钢液行为的影响。研究表明:1号水口(原方案)在浸入深度为57mm时,液面波峰谷差值达到3.67mm,卷渣严重,冲击深度为205mm;优化设计的5号水口在浸入深度为57mm时,液面波峰谷差值减小为2.74mm,卷渣现象基本消失,冲击深度为177mm。确定5号水口为最优水口结构参数,浸入深度以57~67mm为宜。     

Computational and experimental study of turbulent flow in a 0.4-scale water model of a continuous steel caster

Single-phase turbulent flow in a 0.4-scale water model of a continuous steel caster is investigated using large eddy simulations (LES) and particle image velocimetry (PIV). The computational domain includes the entire submerged entry nozzle (SEN) starting from the tundish exit and the complete mold region. The results show a large, elongated recirculation zone in the SEN below the slide gate. The simulation also shows that the flow exiting the nozzle ports has a complex time-evolving pattern with strong cross-stream velocities, which is also seen in the experiments. With a few exceptions, which are probably due to uncertainties in the measurements, the computed flow field agrees with the measurements. The instantaneous jet is seen to have two typical patterns: a wobbling “stair-step” downward jet and a jet that bends upward midway between the SEN and the narrow face. A 51-second time average suppressed the asymmetries between the two halves of the upper mold region. However, the instantaneous velocity fields can be very different in the two halves. Long-term flow asymmetry is observed in the lower region. Interactions between the two halves cause large velocity fluctuations near the top surface. The effects of simplifying the computational domain and approximating the inlet conditions are presented.     

An experimental study of process behavior in planar flow melt spinning

A parametric study concerning the process behavior in planar flow melt spinning (PEMS) of Pb−Sn alloy ribbons is presented in this article. Experiments were conducted to develop correlations between the produced ribbon thickness and process variables, including wheel speed, crucible pressure, nozzle-wheel gap, and melt superheat. The ribbon thickness was found to vary with the wheel speed to the power of −2/3 and the crucible pressure to the power of 1/3. Puddle lengths were found to increase linearly with crucible pressure. The ribbon thickness behaved in a two-term exponential manner in relation to the melt superheat. A processing window for the production of high-quality ribbons was determined using dimensionless parameters. Five distinct ribbon patterns were identified, and their respective surface roughnesses were measured and reported.     

Water model simulation of tundish flow under varying conditions

Water model studies have been conducted to characterise the flow conditions in continuous casting tundishes under conditions of open and submerged nozzles. In this investigation simulations of practical problems of flow interruptions from the ladle, thermal inversions due to uninsulated ladle, and pneumatic agitation near the tundish end wall were conducted. The studies showed that incorporation of suitable flow control devices brings about homogenisation of temperature and composition between strands in the above cases. This study also showed that agitation of the liquid at the end wall reduces the extent of stagnant zone in the tundish.     

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\     

高应力下顶板充填体破断机理与试验研究

下向分层进路尾砂胶结充填采矿法顶板为胶结充填体,深部高应力下回采,顶板的稳定性直接关系到整个回采过程的安全.判别顶板的稳定性是安全回采的前提条件.通过理论分析并结合数值模拟、相似模拟等试验手段判别了顶板充填体的破坏机理,提出了充填体破坏形式及预防顶板破坏的合理布筋方式,确保了回采过程的安全.     

Right ventricular blood flow during left ventricular support in an experimental porcine model

BACKGROUND: Right ventricular blood flow may be adversely affected during left ventricular assist device (LVAD) use leading to right ventricular (RV) ischemia and RV dysfunction. This study characterized normal RV blood flow responses to LVAD operation. METHODS: Seven Yorkshire pigs weighing 74.4 +/- 3.4 kg underwent right coronary artery blood flow measurements with an ultrasonic flow probe and injection of radiolabeled microspheres. A Thoratec LVAD was used in either synchronous or asynchronous modes and RV loading was increased using a pulmonary artery snare. RESULTS: The RV blood flow was compared between three regions that differed in proximity to the right coronary artery: proximal segment, mid-RV, and distal. The right ventricular distal flow was 0.93 +/- 0.07 mL x min-1 x g-1 compared with 0.74 +/- 0.06 mL x min-1 x g-1 at right ventricular proximal flow during control measurements (p = 0.0001). This difference was maintained during LVAD operation in either synchronous or asynchronous modes and also during pulmonary artery constriction. CONCLUSIONS: Global RV flow is not adversely affected by LVAD use. A flow gradient occurs along the right coronary artery with the distal vascular bed having relatively less reserve, which may be more susceptible to ischemia in patients with preexisting coronary disease or RV distention during LVAD use.     

The action of anabolic steroids on bone in experimental animals

Anabolic steroids are currently used in the treatment of established osteoporosis. It has been demonstrated that, at least partly, anabolic steroids increase bone density by stimulating bone formation. Very little is known about how anabolic steroids affect bone in experimental animals. Because bone studies in animals have been performed only with the anabolic steroid nandrolone, or its long-acting ester nandrolone decanoate (ND), we present a general overview in this paper of the effect of these anabolic agents in various steroid-affected animal models for osteoporosis, viz. gonadectomized rats, heparin-treated mice and intact or ovariectomized dogs. In rats and mice these agents increase longitudinal and periosteal bone growth and bone mass, thus demonstrating their anabolic action. They also decrease trabecular bone resorption in ovariectomized and orchidectomized rats, which indicates that they have anti-catabolic effects. In ovariectomized rats, ND was found to increase the mechanical strength of cortical bone, which is an important property in a drug that is intended to be used in treating established osteoporosis. In elderly dogs, ND was found to stimulate endosteal bone formation. These findings indicate that nandrolone and ND have beneficial effects on bone in both oestrogen and androgen-deficient animals.     

Modelling criteria for flow simulation in gas stirred ladles: experimental study

Abstract

Criteria for modelling isothermal flows encountered in typical gas stirred ladles have been investigated both theoretically and experimentally. To this end, the phenomena of fluid mixing in ladles have been investigated in order to deduce the relationship between model and full scale gas flowrates, needed for maintaining dynamic similarity between the two. Starting with the governing equation for material transport, mixing times in geometrically and dynamically similar gas stirred systems were first correlated theoretically. On the basis of this, it is shown that, in the Froude dominated flow regime (typical of industrial ladle refining operations), the ratio of mixing times in geometrically and dynamically similar gas stirred systems can be represented in terms of the geometrical scale factor λ(=L _mod /L _fs ) according to τ_m,mod /τ_{m,fs = λ}^1/2. To assess the adequacy and appropriateness of various scaling equations reported in the literature (namely Q_{mod /Q fs} =λⁿ, proposed values of nbeing 1·5, 2·5, and 2·75, respectively), extensive experimental measurements of mixing times were carried out in three differently sized water model ladles. To measure mixing times, the conventional conductivity measurement technique was adopted. Comparisons of experimental ratios of mixing times with the corresponding theoretical ratio (=λ^1/2 ) confirm that, in the Froude dominated flow regime, the most appropriate criterion for dynamic similarity between model and full scale ladles is Q _mod /Q _fs = λ^2·5. Such findings were also corroborated through consideration of empirical mixing time correlations reported for Froude dominated ladle flows.