Production Of Rare Earth Metals Research Articles

希土類金属の製造とそのリサイクル

希土類金属の製造とそのリサイクル

Neodymium Production Processes

This overview describes the major processes for rare earth metals production, including chloride electrolysis for producing cerium, lanthanum and misch metal; oxide electrolysis for producing neodymium metal and its alloys; calciothermic reduction for producing neodymium commercially; a reduction-diffusion process for making powders of SmCO5; and a co-reduction process for producing powders of rare earth metal alloys. A new molten salt extraction process, “NE0CHEM,” has been developed by which neodymium metal or its alloys can be produced by the reduction of Nd203, with sodium in the presence of CaCl2 by the reaction Nd2O3 + 3 CaCl2 + 6 Na → 2 Nd + 3 CaO + 6 NaCl. In comparison to existing processes, the proposed process holds great promise toward lowering the cost of neodymium.

Recent production of rare earth metals as hydriding materials

Recent production of rare earth metals as hydriding materials

Commercial production of rare earth metals by fused salt electrolysis

The commercial production of rare earth metals by fused salt electrolytic methods is described. These methods are used to make mischmetal, cerium, lanthanum, and didymium (Nd + Pr). The feed materials consist essentially of anhydrous chlorides of the metal to be produced, augmented by additions of nonrare earth salts to yield an electrolyte with satisfactory properties for reduction. The rare earths are derived either from monazite or from bastnasite ores. The anhydrous chlorides are manufactured from the hydrated chlorides by methods which minimize oxidation or hydrolysis. Alternatively, anhydrous chlorides may be used which result from the direct chlorination of rare earth ores by the Gold-schmidt process. These are particularly suitable for electrolysis due to their very low oxychloride content. Fluorides and oxides of the rare earths are produced by wet chemical methods to provide the relatively small quantities of these compounds now used for commercial fused salt electrolysis. Reduction cells in use today are constructed mainly from a) ceramics, b) graphite, or c) iron. The advantages and disadvantages of these types of cells are described together with the typical products which result from their use. Primary attention is given to production of mischmetal (mixed rare earth metal), which is the rare earth metal produced on the largest scale today. Brief reference is made also to production of cerium, lanthanum, and didymium (Nd + Pr) metal. Finally, a resume of the current uses of these metals is presented with reference to recent trends in the industrial applications of the rare earth metals.

A process for direct chlorination of rare earth ores at high temperatures on a production scale

A process for direct chlorination of rare earth ores without the necessary preparation of carbides or other intermediate compounds is described. Complete chlorination of all non-volatile components of the ores is obtained in a special, electrically heated furnace at temperatures between 1000 and 1200°C. The construction of the furnace permits quick replacement of some important components while the furnace is still hot. This reduces the unavoidable corrosion problem. The flowsheet of the process is presented. The process permits a high productive capacity with a small space, low investment, and low labor input. It is possible to process the most varied ores, such as Bastnasite, Monazite, Allanite, Cerite, Xenotime, Euxenite, Fergusonite, Gadolinite, etc., in the same installation. Reference is made to the treatment of off-gases. Fused anhydrous rare earth chlorides, without contaminants, are obtained as the final product, which is very suitable for the production of rare earth metals. This process can also be used to convert pure rare earth oxides to anhydrous chlorides.