Liquid-liquid extraction unit, multistage liquid-liquid extraction apparatus using the unit, and multistage continuous extraction system for rare earth elements

Abstract

A liquid-liquid extraction unit includes an extraction/separation tank (10) into which an aqueous phase in bubble form is admitted from an upper inlet (20) in one sidewall and an organic phase in bubble form is admitted from a lower inlet (30) in the one sidewall. The upward moving organic phase is contacted with the downward moving aqueous phase. After contact, the organic phase is discharged through an upper outlet (40) in an opposite sidewall and the aqueous phase is discharged through a lower outlet (50) in the opposite sidewall.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2012-005224 filed in Japan on Jan. 13, 2012, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD[0002]This invention relates to a liquid-liquid extraction unit adapted to contact an aqueous phase with an organic phase, separate them, and recover the desired extract from the thus separated aqueous phase and / or organic phase, more particularly, to a liquid-liquid extraction unit suitable for the extraction and separation of rare earth elements, especially rare earth elements including yttrium and light rare earth elements (La, Ce, Pr, Nd, Sm, and Eu); a multistage liquid-liquid extraction apparatus and a multistage continuous extraction system using the unit.BACKGROUND ART[0003]Nowadays, rare earth magnets as typified by Nd magnets are widely used in motors, sensors and other parts built in hard disk drives, air co...

AI Technical Summary

Benefits of technology

[0041]The liquid-liquid extraction unit of the invention is of small size and maintains a sufficient extraction efficiency. When a multistage extraction apparatus comprising a plurality of units connected for fluid communication and a multistage continuous extraction system in which a plurality of sections each comprising the multistage extraction apparatus and assigned to different steps are connected for fluid communication are constructed, the footprint can be significantly reduced, and the volume of liquid necessary for extraction can be significantly reduced. These contribute to a substantial reduction of cost required for extraction and separation of rare earth elements.

Problems solved by technology

However, in the prior art method wherein aqueous and organic phases are contacted and separated solely via vertical upward and downward movements using a well-known spray column or a vertical cylindrical tank used in an extraction unit based on emulsion flow as described in Patent Document 4, reaction cannot catch up at a high flow rate equivalent to the flow rate available in the above-mentioned mixer-settler.

Thus reaction must be carried out at a low flow rate in order to maintain an acceptable efficiency, resulting in a loss of processing efficiency.

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