Study on the Kinetics of Aluminum Removal from Liquid Silicon to Slag with Mechanical Stirring

Metallurgical and Materials Transactions B - The kinetics of aluminum removal from silicon melt to CaO-SiO2-Al2O3 slag was studied. A recently designed experimental setup using mechanical stirring...     

Mass Transfer of Phosphorus in Silicon Melts Under Vacuum Induction Refining

An experimental investigation into the mass transfer of phosphorus in molten silicon under vacuum induction refining has been carried out. In a pilot-scale experiment, in the temperature range 1773 K (1500 °C) to 1873 K (1600 °C) and a vacuum of 0.1 to 0.035 Pa smelting for 7200 seconds (2 hours), phosphorus is decreased from 15 ppmw to 0.08 ppmw, which achieved the target for solar-grade silicon of less than 0.1 ppmw. Lab-scale experiments are used to determine the effects of vacuum, refining time, and temperature on the rate of mass transfer of phosphorus during vacuum refining. Hardly any phosphorus was removed when the vacuum pressure is greater than 100 Pa. Mass-transfer coefficients are nearly independent of pressure at 1783 K (1510 °C) when pressures are below 0.1 Pa and are highly correlated with vacuum pressures above 0.1 Pa. A model of vacuum refining of inductively stirred silicon melts is discussed to explain the transfer path of phosphorus out of the melt.     

Development of Slag Recycling Process in Hot Metal Desulfurization with Mechanical Stirring

In order to develop an environment‐friendly steelmaking process, a slag recycling process for hot metal desulfurization by mechanical stirring was designed. The process was developed with 70 kg‐scale hot metal experiments and actual plant tests. The recycled slag has a 70% desulfurization ability compared with that of virgin flux (CaO‐5%CaF₂). The lower efficiency of the recycled slag was caused by SiO₂ contamination carried over from the previous process. There is no particular size requirement for the recycled slag, as the effect of the recycled slag size on the desulfurization ability is small. The ratio of CaO in the recycled slag to total CaO should be less than 60% in order to prevent an increase in the amount of slag. Slag recycling operation can be repeated more than twice when the optimum conditions are applied. The slag recycling process was established in an industrial operation, and consumption of desulfurization flux decreased by 40% with the process compared with that without slag recycling. Slag hot recycling was adopted at another plant where consumption of desulfurization flux decreased by 50% compared to operation without slag recycling. The positive effect of hot slag recycling is estimated to be a result of the temperature of the recycled slag.     

Improvement of Impeller Blade Structure for Gas Injection Refining under Mechanical Stirring简

Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central part of the impeller is disk- or plate-shaped, and the blades are fitted to the side of the disk or plate. In addition, a disk is put on the top side of the impeller blades. The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller. These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller. In addition, the sloped swept-back impeller requires less power consumption. The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidi- rectional impeller rotation and without installing baffles. The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath. Highly efficient gas injection refining can be established under the conditions of proper impeller size, larger nozzle immersion depth, larger eccen- tricity and rotation speed of the impeller. The sloped swept back blade impeller can decrease the power consumption and vet improve the bubble disintegration and wide dist~ersion in the bath.     

Rate of Transfer of Manganese Across Metal-Slag Interface and Interfacial Phenomena

Abstract

The rate of oxidation of manganese in liquid iron by oxidizing slag and rate of reduction of manganese oxide in liquid slag by liquid iron were measured at 1873 K. At the same time the liquid iron-slag interface was observed by an X-ray TV and the shape of iron drops was photographed on a film to determine the interfacial tension. From the results of the rate measurements it was found that the reaction proceeded rapidly over the initial period in the case of oxidation, but not in the case of reduction. The rate of reaction was analysed on the assumption that the reaction was controlled by simultaneous transport of manganese and oxygen. The change of interfacial tension during a run was small in spite of the transfer of surface active oxygen.

Résumé

Les vitesses d'oxydation et de réduction du manganèse ont été mesurées à l'interface métal-scorie d'un bain de fonte liquide à 1873 K. Simultanément, l'interface fonte-scorie a été observée à l'aide d'une caméra de télévision R-X et les goutelettes de fonte photographiées afin de déterminer la tension interfaciale. A partir des résultats des vitesse de réaction, il s'est avéré que la réaction s'effectue rapidement lors de la période initiale d'oxydation, mais non lors de la réduction. La vitesse de la réaction a été analysée en supposant qu'elle était contrôlée par le transport simultané du manganèse et de l'oxygène. Le changement de tension interfaciale lors d'un essai étai faible malgré le transfert d'oxygène actif en surface.     

Boron Removal From Metallurgical Grade Silicon by Molten Slag Refining in Induction Furnace

The impurities Al,Ca,Ti,B,P etc in metallurgical grade silicon（MG-Si）can be effectively removed by refining using molten slag based CaO-SiO₂,and it is especially effective for boron removal.The experiments of boron removal were studied using CaO-SiO₂ binary slag in induction furnace.The results showed that the distribution coefficient of boron（L_B）between slag and silicon increased with more proportion of CaO/SiO₂（mass%）.It was advantaged to boron removal for higher basicity of slag,so the boron in MG-Si was reduced from 18ppmw to 1.4ppmw with the addition of Li₂O and K₂O to Ca0-SiO₂ slag.The proportion of SiO₂ in slag affected the oxidizing capacity of slag,which reduced the efficiency of boron removal.     

一种薄带连铸工艺中瞬态界面传热模拟测量方法

研究和开发了一种可以测量钢水在铜辊表面凝固过程中瞬态界面传热的模拟装置及相应的界面热流计算方法.结果显示,钢水和铜基体接触的瞬间,热流达到最大值9 MW/m2左右,随后很快降低至4 MW/m2,然后维持在2～5 MW/m2之间.对比前人的研究结果,该模拟装置可以有效地用于研究薄带连铸中的界面传热现象.     

X射线荧光光谱法测定精炼合成渣中的CaO、Al_2O_3、MgO和SiO_2

采用铂金坩埚电热熔融的方法制取玻璃片试样,应用X荧光光谱仪测定精炼合成渣中的CaO、Al2O3、MgO和SiO2,分析方法快速、准确,与传统的化学分析方法相比,精确度与准确度都能满足要求.     

Study on Absorption Rate by Eccentric Mechanical Stirring in Gas Injection Refining for Iron and Steel Making

In gas injection refining processes, a great amount of gas is injected into molten metal in short time, so that very large bubbles are inevitably formed. Wide dispersion of small bubbles in the bath is indispensable for high refining efficiency. Eccentric mechanical stirring with unidirectional impeller rotation was tested using a water model for pursuing better bubble disintegration and dispersion. Absorption rate are used to research on the influence law of the bubble dispersion and disintegration and gas-liquid absorption by the influence of, rotation mode, rotation speed and gas flow rate. Compared to the experimental results of absorption rate under eccentric stirring and centric stirring ,provide the scientific experimental and theoretical guidance for high-temperature experiment of hot metal desulfurization .According to experimental and theoretical analysis, this paper has studied various factors effecting on gas absorption process and volumetric mass transfer coefficient using the system of CO2-NaOH-H2O.The results show that:the volumetric mass transfer coefficient and absorption efficiency of CO2 can be increased under eccentric stirring mode, Because bubble disperse quickly with eccentric mechanical stirring, which results in promoting complete reaction between CO2 and NaOH, and improving the mass transfer coefficient and absorption. Volumetric mass transfer coefficient and efficiency of CO2 increase with the increasing rotation speed under the condition of eccentric stirring .But volumetric mass transfer coefficient and efficiency of CO2 decrease with the increasing rotation speed under the condition of centric stirring.     

X射线荧光光谱法测定精炼合成渣中的CaO、A12O3、MgO和SiO2

采用铂金坩埚电热熔融的方法制取玻璃片试样,应用X荧光光谱仪测定精炼合成渣中的CaO、Al2O3、MgO和SiO2,分析方法快速、准确,与传统的化学分析方法相比,精确度与准确度都能满足要求。     

铝液搅拌车扒渣板的改进

简要介绍搅拌车的结构及其在混合炉、熔炼炉铝液处理过程中的作用,分析搅拌车扒渣板使用中出现的问题,提出改进措施并实施,取得良好效果.     

Mathematical Simulation of Flow Phenomena in CAS-OB Refining Ladle

SymbolList　　Ag———Projectareaofgasbubble ,m2 ;　　C1 ,C2 ,Cμ———Empiricalturbulentconstants;　　Cd———Dragcoefficient;　　Cf———Frictioncoefficient;　　db———Diameterofbubble ,m ;　　dmax———Maximumdiameterofbubble ,m ;　　dp———Diameterofporousplug ,mm ;　　ds———Innerdiameterofsnorkel,mm ;　　dt———Topdiameterofladle ,mm ;　　du———Bottomdiameterofladle ,mm ;　　F———Interphasefrictionforce ;　　Fi———Additionalforce ;　　g———Gravityaccelerationconstant,…     

高碱度渣精炼的轴承钢中夹杂物研究

对国内三个主要特殊钢厂和日本山阳特钢生产的轴承钢中夹杂物进行了研究。结果表明,在炉渣碱度较高(CaO／Sio2=3～4．5)的精炼条件下,低氧含量的轴承钢中夹杂物主要有：含Cr、Fe的复合MnS夹杂、TiN型夹杂、具有不同MgO含量的镁铝尖晶石夹杂;未发现单独存在的铝酸钙型球状夹杂物。随渣碱度提高和钢中氧含量降低,镁铝尖晶石夹杂物中的MgO含量增加。当渣中CaO／SiO2达4．5时,镁铝尖晶石夹杂物中含有CaO。     

还原精炼条件下炉渣的泡沫化

针对电弧炉还原期和ＬＦ炉精炼过程中造泡沫渣的工艺特点，向精炼渣中加入发泡剂使炉渣的泡沫化，通过在实验室内对各种碳酸盐，氯化盐发泡材料的发泡性能研究，得出几点结论：（１）碳酸盐和氯化盐中，ＣａＣＯ３，ＣａＣｌ２的发泡性能较好；（２）向ＣａＣＯ３中加入Ｎａ２ＣＯ３会使ＣａＣＯ３的发泡效果明显降低；（３）当起泡时间相差较大的几种发泡剂混合后，发泡过程中起泡高度会出现多个峰值；（４）采用以ＣａＣＯ３为主要     

临钢炉外精炼用合成渣的实践

临钢炼钢厂结合生产实际开发出脱硫、脱氧合成精炼渣,并能快速实现LF埋弧精炼。采用改进配比的精炼渣,能实现w(S)小于100×10-6、全氧质量分数小于20×10-6的钢种,为以后品种钢的开发积累了经验。     

150tRH-IJ精炼条件下钢液—颗粒间的传质特性

采用线性尺寸为150tRH装置1/4的水模型研究了RH-PB(IJ)过程中钢液和粉剂颗粒间的传质特性,测定了液体侧的传质系数,考察提升气体流量,上升管、下降管内径和颗粒粉剂对传质系数的影响。结果表明,在上升管径和下降管径相同的情况下,增大气体流量可增大钢液与喷吹粉剂颗粒钢液侧的传质系数,但不宜增大到使环流量达到饱和。在现有工作条件下,传质系数为3.392×10-5～2.661×10-4m/s。在给定的增大气体流量和下降管径下,钢液与粉剂颗粒间钢液侧的传质系数随上升管径的增大而增加。当气体流量增大和上升管径给定时,钢液与粉剂颗粒间钢液侧的传质系数随下降管径的增大而减小。钢液与粉剂颗粒间钢液侧的传质系数随环流量的增大而增大。其他参数相同时,在现有工作所取范围内,粉剂颗粒的粒径越大,其与钢液间钢液侧的传质系数越大;为增大传质速率,粉剂不宜过细。     

复吹转炉钢-渣间容量传质系数的水-油模型

在熔池直径880mm、深258mm的冷态模型中，利用水模拟钢水、机油模拟渣、苯甲酸模拟钢-渣间传输物质来研究熔池直径5285mm、深1545mm的复吹转炉吹炼工艺参数对钢-渣间容量传质系数的影响。结果表明，枪位350mm，顶吹流量117m^3/h，底吹流量1．68m^3/h至2．36m^3/h时，传输物质苯甲酸的容量传质系数变化最显著，在采用枪位350mm，顶吹流量140m^3/h，底吹流量1．68m^3/h，底枪布置方式为8孔对称布置在0．66直径的圆上时，传输物质的容量传质系数最大。