不锈钢冶炼底吹CO2对熔池动力学条件影响

 近年来,CO₂在钢铁行业的资源化利用技术被广为开发,研究表明CO₂在不锈钢冶炼中的应用颇具潜力。通过建立底吹CO₂气泡反应动力学模型并结合水力学模拟试验研究,量化研究不锈钢冶炼条件下底吹CO₂对熔池动力学条件的影响。由于CO₂脱碳导致气体体积增加会造成气泡膨胀或分裂的情况不明确,假设两种极端条件,即条件a,CO₂反应气泡体积增大后只膨胀不分裂;条件b,CO₂反应气泡体积增大后只分裂不膨胀,并取某厂70 t不锈钢炉冶炼中期工艺参数对两种条件下CO₂气泡反应动力学进行计算。结果表明在本研究条件下,不锈钢冶炼底吹CO₂反应后气体增加无论是导致气泡膨胀或者分裂,反应平衡时气泡最终体积约为初始体积的1.3倍,并且气泡体积随反应时间的变化呈线性关系。水力学模拟研究发现,相对于对照组试验,条件a和条件b下熔池的混匀时间分别缩短16.5 s和8.4 s,因此得出实际底吹CO₂在反应后会使熔池混匀时间缩短8.4~16.5 s,使熔池的动力学条件得到显著改善。此外,通过墨水示踪剂观察底吹CO₂对熔池流场变化的影响,发现底吹CO₂反应后导致气泡膨胀会促进熔池的溶质向横向扩散,相对抑制溶质在纵向的扩散速度;相反地,CO₂反应后导致气泡分裂会促进熔池的溶质向纵向扩散,相对抑制溶质在横向的扩散速度。     

贫化电炉气液混合顶吹的气泡群形态及搅拌效果

针对贫化电炉还原油枪中气、油混合顶吹对渣层搅拌效果的研究,等比例制作贫化电炉水模型,进行气液混合喷吹实验。实验结果表明：顶吹气液两相混合射流在熔池中形成大小不一的气泡或气泡群,气泡本身的形变、破裂以及气泡间的团聚运动决定了油枪对熔池的搅拌效果。通过测量不同流量下气泡群尺寸的变化,分析气液流量混合比对熔池搅拌效果的影响。     

板坯结晶器水模型内气泡运动行为的数学模拟

建立了吹氩板坯结晶器水模型内气泡运动行为的数学模型.以水模型实验获得的整个结晶器内各气泡尺寸和数量浓度为气泡的初始条件,对不同尺寸气泡的运动行为进行数值模拟.结果表明:当水流量为2.54 m3/h,气流量为0.037m3/h,水口浸入深度为78 mm时,气泡都分布在上回流区,没有卷入下回流区.较大的气泡在水口附近上浮,较小的气泡在距离水口较远的区域上浮.这和实验结果相吻合.     

底吹转炉熔池内气泡特性的连续测定

底吹转炉熔池内气泡特性的连续测定［日］井口学等１前言近年来，钢铁冶炼不但积极地采用了气体喷吹技术，而且利用在较低温度下易处理的水、水银及伍德易熔合金等对熔池内气泡特性、流动特性以及均匀混合时间等进行了基础研究。有关吹入气体产生的气泡行为的冷模实验结果...     

双流体模型在AOD熔池流场数学模拟中的应用

基于气液双流体模型和湍流的修正k-ε模型,考虑了多股气流侧吹操作对熔池流场的影响,以及AOD熔池内气液两相流的行为和两相间的动量传输,建立了AOD多股气流侧吹精炼过程中熔池内流体流动的数学模型,并对宝钢股份不锈钢事业部120 tAOD原型和线尺寸为其1/4的水模型熔池内流体的流动作了模拟,结果表明,确实可以采用双流体模型来模拟AOD精炼过程中熔池内流体的流动;用该模型计算的结果表明,整个熔池流体处于活泼的搅拌和循环运动状态。     

机械搅拌反应器内气体分布的数值模拟

机械搅拌反应器内通常包含气、液、固等多相体系,利用计算流体力学方法针对其内部复杂物料运动的模拟近年来取得了很大进展。欧拉双流体模型被用来模拟一种装配Rushton型叶轮机械搅拌反应器内包含气泡的气液两相流,并通过不同的相间力模型及自定义湍流子模型描述槽内气泡复杂运动。分析了不同曳力、气泡诱导湍流、升力、湍流分散力等模型在模拟气泡分布时的效果,并将模拟结果与Barigou和Greaves的试验结果进行比较。结果表明,提出的模拟方法在机械搅拌反应器模拟中能够得到准确的气体分布结果。     

喷嘴结构对铁水脱硫气泡微细化的影响

针对铁水预处理镁蒸气脱硫的气泡微细化问题,本文通过水模型实验,研究了喷嘴结构对气泡在熔池中的分散、CO_2吸收速率和利用率以及均混时间的影响规律.结果表明:使用SSB-D桨,搅拌转速200 r/min,通气流量为1.0 m~3/h,偏心度0.4,浸入深度250 mm时,透气砖结构的喷嘴可以使熔池内的气泡分布"死区"减小,同时缩短了均混时间,提高了镁蒸气的容积传质系数和利用率.     

氧气转炉熔池流体力学模拟方法的探讨

从氧流与熔池作用流体力学过程的实际情况出发,用因次分析的方法导出两个无因次数作为相似准则。在此基础上研究了以水模拟钢液,以压缩空气模拟氧气的普通冷模型中有关参数的确定方法,并在实验室内对15吨氧气顶吹转炉和10吨氧气底吹转炉中氧流对熔池的穿透情况、熔池的可吹性进行了模拟测定,结果证明此种模拟方法与实际情况比较接近。     

铜底吹熔池熔炼炉多相流数值模拟

在铜的富氧底吹熔池熔炼过程中,熔池内的多相流动决定了颗粒下料、传热传质及化学反应速率。本文建立了包含气泡、铜锍、渣的三相数学模型,并通过水力学模型实验对数学模型进行了验证。对不同气流速度、铜锍深度、渣层厚度进行了数值模拟,研究炉内渣眼尺寸、旋流强度及漩涡位置等情况。结果表明,随着气流速度增大,气泡流对熔池的搅拌程度逐渐强烈,气泡弥散程度降低,但气流速度过大容易造成熔体喷溅。铜锍深度越大,旋涡搅拌面积越大,旋流强度越大,渣层变短变厚,有利于排渣,但熔池深度增大到一定程度时渣眼直径急剧减小,并且铜锍卷渣程度增大。随着渣层厚度增加,铜锍层内气泡尺寸增大,渣眼尺寸急剧减小,甚至消失,漩涡同时出现在铜锍和渣层内,导致卷渣严重。     

钢包内气泡的形成与运动过程的数值模拟

 以钢包精炼底吹氩气过程中氩气泡为研究对象,运用VOF模型追踪氩气与钢液的界面,在层流条件下三维数值模拟了氩气泡的生成和运动过程。采用Tecplot进行模拟结果的后处理,研究了不同气体流量条件对气泡脱离直径的影响以及气泡的运动特性。模拟结果显示,氩气泡的形成历经膨胀、脱离两个阶段,气泡脱离直径随着气体流量的增加而增加,针对2 mm直径的孔口,其鼓泡流量上限为1.325 L/min。气泡从孔口脱离后历经近似球形、扁平的椭球形、规则的椭球形和不规则的球帽形的形状变化;气体流量越大,气泡的变形程度越剧烈,气泡位于钢包高度中上部位置时,全部呈现近似规则的球形,不随流量的改变而改变。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.