Vacuum distillation refining of metallurgical grade silicon （Ⅰ） ——-Thermodynamics on removal of phosphorus from metallurgical grade silicon

The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10^-7 P, and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.     

Application of vacuum distillation in refining crude indium

Vacuum distillation is a technique suitable for low boiling and melting point materials,to remove the heavy and low vapor pressure impurities at low level.As indium has low melting point and high boiling point,it is suitable for refining by vacuum distillation.First,saturation vapor pressure for major elements in crude indium was calculated by the Clausius–Clay Prang equation,which could approximately predict the temperature and pressure during vacuum distillation process.Second,the activity coefficients for In–Cd,In–Zn,In–Pb,In–Tl at 1373 K,and In–Sn at 1573 K were acquired by means of molecular interaction on volume model.Vapor–liquid equilibrium composition diagrams of those above systems in crude indium were drawn based on activity coefficients.These diagrams could estimate the compositions of products in each process during the refinement of crude indium.Finally,1.2–1.6 ton crude indium was used per day when vacuum distillation experiments were carried out,and experimental results are in good agreement with the predicted values of the vapor–liquid equilibrium composition diagrams.     

Study of ultrahigh-purity copper billets refined by vacuum melting and directional solidification

The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation (VMDS). The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer (GDMS). The re-sults demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%-66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu > 1.5, and they can be removed effectively under the vacuum condition of 1650-1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segrega-tion effect in directional solidification can be remarkable when the equilibrium distribution coefficient (k0) value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.     

真空熔炼直接定向凝固制备99.999%高纯铜大铸锭

对真空熔炼直接定向凝固制备99.999%高纯铜大尺寸铸锭进行了研究,探索了制备99.999%高纯铜时真空精炼温度、时间和蒸气压对去除杂质的影响,及温度梯度对大尺寸铸锭定向凝固的影响和杂质分布规律,采用GDMS(辉光放电质谱仪)对杂质元素进行了检测。结果表明:真空熔炼直接定向凝固能够将原料为99.9988711%的电解阴极铜,制备成99.9996219%~99.9995833%的高纯铜Φ67mm大尺寸铸锭;真空熔炼可以使蒸气压比Cu高的杂质元素有效去除;通过定向凝固的提纯,杂质去除效果较好,说明定向凝固有利于99.999%高纯铜大尺寸铸锭的提纯制备。     

Preparation of high-purity bismuth by sulphur deleadization in vacuum distillation

The feasibility of separation of impurities in refined bismuth and sulphur deleadization with vacuum distillation was studied theoretically. Experimental studies on sulphur deleadization were carried out under vacuum. The influences of amount of sulphur, distillation temperature, vacuum degree and distillation time on deleadization were investigated and an optimal technical condition was achieved. The content of lead in refined bismuth can be decreased from 30μg/g to 0.21 μg/g, which has reached the level of“5N” high-purity bismuth. Other impurities in refined bismuth can be also removed effectively under certain conditions.     

THE SEPARATION CRITERION OF IMPURITIES IN CRUDE METALS BY VACUUM DISTILLATION

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铅锡合金的真空蒸馏深度脱铅(英文)

采用分子相互作用体积模型计算在777℃时不同Pb含量铅锡合金的活度系数,结果与实验值符合较好。对800～1300℃全成分范围内铅锡合金的活度系数进行预测,为铅锡金真空蒸馏分离提供必要的热力学参数。对两种不同铅含量的铅锡合金进行小型和工业实验,将锡中的铅含量降至0.01%以下。设计全成分范围的铅锡合金真空蒸馏处理流程,对铅含量10%～90%的铅锡合金经真空蒸馏处理后可得到纯度为99.5%的粗铅和铅含量在0.01%以下的精锡。     

粗颗粒碳化钨粉制取过程中的质量控制

对粗颗粒碳化钨粉制取过程中杂质含量和碳化质量的控制问题进行了探讨。指出 ,为了降低 W粉中的杂质含量 ,操作者在倒料之前一定要认真清除 W粉表面异物 ,不允许把 W粉筛上物强行擦碎过筛 ,并选用在 960℃的还原温度下性能较 Cr2 5Ni2 0更稳定的舟皿材质 ,以减少舟皿给 W粉带来的污染。此外 ,对生产场地的文明卫生也应引起足够的重视。为了提高粗颗粒碳化钨粉质量 ,宜采用加 Co、通 H2 碳化 ,且碳化温度不宜太高 ,不要超过 1 890℃。实验结果表明 ,如果氧化钨原料中存在含量偏高的、但在碳化温度下能大量挥发的某些杂质元素 ,通过工艺过程的严格控制 ,仍可生产出综合性能较好的合金。     

Preparation of high-purity tantalum ethoxide by vacuum distillation

Effects of reflux ratio, water addition and content of water in ethanol on the purity and yield of tantalum ethoxide during vacuum distillation were investigated under the operational conditions of pressure of 1kPa, oil bath temperature of 210-230 ℃, and outlet temperature of 190℃. The condensate sample was characterized by FTIR, 1↑H-NMR spectroscopy and Raman spectra, respectively. The contents of tantalum, carbon and hydrogen in the sample were also determined with elemental analysis instrument. The obtained results consistently demonstrate that the condensate is tantalum ethoxide. The content of impurity, such as Al, As, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sn, Ti, V and Zn, in tantalum ethoxide is less than 0.000 05%, while Nb content is less than 0.000 5%. The content of impurities in tantalum ethoxide sample excels that of Epichem Group＇s requirement for Ta（OC2H5）5 of 99.999%.     

Lifshitz topological impurity transitions in bismuth wires doped with acceptor and donor impurities

This paper reports the results of an experimental study of electronic topological transitions in bismuth glass-covered wires doped with acceptor (Sn) and donor (Te) impurities. The temperature dependences of the thermoelectric power and resistance are measured within the temperature range from 1.5 to 300 K and magnetic fields up to 14T. The position of the Fermi level ε_F and the concentration of charge carriers at doping are estimated from the Shubnikov de Haas (SdH) oscillations which are clearly visible from both L electrons and L and T holes in all crystallographic directions. We demonstrate anomalies in the temperature dependences of the thermopower in Bi wires doped with acceptor (Sn) and donor (Te) impurities in the form of a triple (doping by Sn) and double (doping by Te) change in the sign of the thermopower. The effect is interpreted with relation to the manifestation of impurity Lifshitz topological transitions. The SdH oscillation method was used to determine the energy position of the Σ band by doping Bi wires with the acceptor impurity Sn and the T band conduction by doping with Te. It is shown that the appearance of the Σ and T bands in Bi wires doped with the acceptor and donor impurities is responsible for the anomalies in the diffusive thermoelectric power, which gives a good conform with to the theoretical models and predictions.     

Impurity control and removal in copper tankhouse operations

During copper smelting, most of the undesirable impurities such as Pb, Sb, Bi, and As are only partially removed by oxidation. When white metal and blister copper are in equilibrium, these impurities are distributed mainly into the copper phase, from which their removal is difficult. When copper dissolves during electrorefining in a copper tankhouse, these impurities are continuously released from the anodes either as insoluble phases (slimes), which fall to the bottom of the cell, or as dissolved species in the electrolyte, the transfer of which to the cathode must be inhibited. This article presents impurity control methods in copper tankhouse operations with traditional and newly developed processes. It also summarizes the technologies demonstrated for removal of impurities from electrolyte that prevent them from being recycled in the copper smelting and refining circuit. For more information, contact Shijie Wang, Phelps Dodge Refining Corporation, 850 Hawkins Blvd., El Paso, TX 79915; (915) 775-8836; fax(915) 775-8352; e-mail swang@phelpsdodge.com.     

高纯金属镝的制备

为制备高纯度稀土金属Dy以适应高科技发展的需求,在钙热一次还原法生产的Dy-4,Dy-8的基础上,用中频感应炉进行二次精炼和真空蒸馏,并对工艺进行优化选择得出,二次精炼温度为1450℃,保温40min最适宜;真空蒸馏1500℃～1530℃,保温8h最佳。用此工艺所制备的金属Dy的纯度超过国标高纯度Dy-1和Dy-2的要求,接近国外高纯Dy的先进技术指标。     

Impurity distribution in distillate of terbium metal during vacuum distillation purification

The distribution rules of impurities in distilled terbium metal were investigated by vacuum distillation purification experiment and theoretical analysis. It is found that Ti impurity in distilled terbium is 220 mg/kg in the initial stage of the distillation purification, increases slowly in the middle stage, and increases rapidly in the last stage, reaching 2260 mg/kg, and the modified separation coefficient of Ti is 1/19.02. The diffusion of the impurity Ti in liquid metal can reach a quasi-equilibrium state in the initial stage of distillation purification and the calculated results agree well with experimental results; the distribution profile of impurity Cu is opposite to Ti, being 380 mg/kg in the initial stage, decreasing linearly to 290 mg/kg in the last stage, and the modified separation coefficient is 17.99, and the theoretical calculated results are inconsistent with the experimental result.     

Separation of cadmium and nickel from waste Ni—Cd batteries

To separate the cadmium and nickel resources in waste Ni-Cd batteries,a self-designed vacuum distillation recycling system was studied under laboratory conditions.The effects of system temperature,operating pressure,and time on the separation of Ni and Cd were studied respectively.The mechanism of vacuum thermal recycling was also discussed.Results show that vacuum distillation is a very effective separation method for waste Ni-Cd batteries.At a Constant pressure,the increase of temperature can improve the separating efficiency of Cd.When the temperature is 1173K,Cadmium can evaporate completely from the samples during 3h at 10Pa,The reduction of pressure in a certain range is effective to the separating of Cd from Ni-Cd batteries by vacuum distillation.     

稀土金属提纯方法与研究进展

对各种提纯稀土金属方法的机理进行了阐述,包括真空熔炼、电解精炼、真空蒸馏/升华、熔盐萃取、区域熔炼、固态电迁移、电化学脱氧、外吸气剂法、等离子体熔炼(通氢气或通氩气)等。对研究现状和提纯效果进行了总结。杂质去除需采用多种手段结合,同时提升装备水平,以达到提高提纯效果、降低成本、缩短生产周期的目的。     

5A90铝锂合金真空熔炼工艺研究

采用真空精炼技术对自备的5A90铝锂合金进行处理,研究了不同真空度和熔炼时间对于合金中氢等杂质的去除效果,得出合理的真空熔炼参数。结果表明真空熔炼5A90铝锂合金的真空度在1000Pa,真空精炼时间为5min时．能够很好地保留合金元素并去除其中的氢和碱金属杂质。     

Bi2S3-ZnO-Na2CO3体系热力学分析及应用

对Bi2S3-ZnO-Na2CO3低温熔盐体系进行热力学分析,计算了在700～1 500 K温度下体系中各反应的标准吉布斯自由能变化值(ΔG TΘ),并绘制了相应的ΔG TΘ—T图。热力学分析结果表明,在700～1 100 K温度范围内,Bi2S3中的Bi会被C还原成金属Bi进入金属相中,S将以ZnS形式进入固体物渣中。根据分析结果,在700～1 100 K温度下,以Na2CO3等钠盐为熔剂、ZnO为固硫剂、粉煤为还原剂,开展了验证试验。试验得到了直收率达98%的粗铋,S几乎100%以ZnS的形式固定在渣中,与热力学分析结果一致。     

银精炼技术的改进

采用传统的电解精练工艺,粗银所含杂质直接或间接地影响纯银产品的质量。作者提出了一种改进传统银电解工艺的方法—阴离子隔膜电解法,将银电解槽分为阳极区和阴极区,阻挡杂质元素从阳极区进入阴极区,使多杂粗银经1次电解得到纯度>99.99%的纯银产品。     

一种新的精炼太阳能级多晶硅工艺的热力学分析(英文)

提出了一种新的硅精炼工艺生产太阳能级多晶硅,即Si-Al熔体低温凝固精炼硅技术。通过杂质在固相硅和Si-Al熔体中的分离热力学分析研究了采用Si-Al熔体分区凝固精炼硅的可行性。用温度梯度区域熔炼法来测定磷和硼的分离比,采用热力学计算金属杂质的分离比。新工艺具有很小的杂质低温分离比,表明其有很好的精炼能力。采用感应加热分区凝固实验进行验证;对Si-Al合金定向凝固中硅晶体生长进行了研究,结果表明,硅晶体的生长过程是受扩散控制的。     

含铅锌难选铁矿石的矿物学及铅锌杂质产出特征

以新疆某含铁(FeT)47.04%、含Pb 0.39%、含Zn 0.30%的难选铁矿石为试样,采用化学分析、显微镜观察鉴定、EPMA和EDS等手段,考察其化学成分、铁铅锌的物相组成及铅锌杂质矿物的产出特征,探讨影响选矿工艺的矿物学因素与选矿前景。结果表明:含铁矿物中主要组合为赤褐铁矿、高达91.35%,少量磁性铁和硅酸铁;含铅杂质主要为氧化铅和铅铁矾中的铅,分别占49.0%和41.3%(质量分数);而氧化锌中的锌为主要含锌杂质,占比90.6%。试样中可见少量闪锌矿、方铅矿及黄铁矿等杂质矿物,而未发现含铅锌的氧化状态晶质矿物产出。EPMA和EDS分析表明:氧化状态的铅锌杂质呈单独或共同产出形式,且锌的产出更为普遍和广泛;铅含量多为2.89%~3.89%(质量分数)不等,而锌含量多处于0.67%~1.17%(质量分数)之间。预计强常规磁选与浮选工艺均难于取得有效排除铅锌杂质的效果,建议采用高温还原焙烧预处理工艺。