Production of High Purity Rare Earth Metals by the Continuous Processing Composed of Calciothermic Reduction and Vacuum Melting.

采用热还原和真空熔炼连续工艺生产高纯稀土金属。

• 批准号: 07455299
• 负责人: YAMAUCHI Chikabumi
• 金额: $ 4.99万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455299/
• 关键词: reduction; vacuum melting; rare earth metals; neodymium; neodymium fluoride; calcium; oxygen; oxygen analysis

1. Preliminary ExperimentsDTA revealed calciothermic reduction of NdF_3 starts at 1093 K.The phase diagram of the NdF_3-CaF_2 system was estimated by thermal analysis. The analytical procedures of oxygen content in neodymium using the device in our laboratory were also studied as a function of flux and temperature.2. Optimization of Calciothermic Reduction of NdF_3Calciothermic reduction of NdF_3 were studied for various temperatures, reaction periods, and quantities of calcium addition. Optimum conditions for obtaining a lump of neodymium were considered not only based on purity and reduction ratio but also separation between slag and metal, and that between slag and crucible.3. Optimization of Vacuum MeltingUsing commercially produced neodymium and calcium, model experiments of vacuum melting were conducted for various temperatures, reaction periods, initial impurity contents, and stirring condition. Optimum conditions were discussed not only for the removal of volatile impurities but also precipitation of crucible material dissolved during the calciothermic reduction and the vacuum melting.4. Optimization of the Continuous ProcessingOn the basis of the previous experimental results, optimum conditions for the continuous processing were determined as follows : calciothermic reduction is carried out for 0.9 ks at 1750 K by the addition of calcium 1.2 times as much as the stoichiometric moles : and vacuum melting is carried out at first for 1.2 ks at 1500 K with stirring, then, by decreasing temperature down to just above the melting point of neodymium, for 3.6ks.

1. 初步实验显示NdF_3的钙热还原始于1093 K。通过热分析估算了NdF_3-CaF_2体系的相图。本文还研究了用该装置分析钕中氧含量随通量和温度的变化规律。研究了不同温度、不同反应周期、不同钙加入量对NdF_3钙热还原反应的影响。从纯度、还原比、炉渣与金属、炉渣与坩埚的分离等方面考虑了获得一块钕的最佳条件。以市产钕和钙为原料，在不同温度、反应周期、初始杂质含量和搅拌条件下进行了真空熔融模型实验。讨论了去除挥发性杂质的最佳条件，以及钙热还原和真空熔融过程中坩埚中溶解物质的析出。连续工艺的优化在以往实验结果的基础上，确定了连续工艺的最佳条件如下：钙热还原在1750 K下进行0.9 ks，加入量为化学量摩尔的1.2倍的钙；真空熔化在1500 K下搅拌1.2 ks，然后将温度降低到刚好高于钕的熔点，进行3.6ks。