JP2018012861A - Device for conducting molten salt electrolysis and molten salt electrolysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for conducting molten salt electrolysis capable of increasing deposition rate of a deposition metal for example, by dramatically increasing a surface area of an anode compared to the case using an anode of solid body such as columnar or bow shaped, and a molten salt electrolysis method conducted by using the device.SOLUTION: A device has at least an electrolysis tank for holding molten salts, a cathode part and a casing with opening through which molten salt can be distributed for constituting an anode part together with filled anode material pieces by filling the anode material pieces, which are arranged inside of the electrolysis tank.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus used for molten salt electrolysis performed to recover a rare earth metal by reducing rare earth element oxides, and a molten salt electrolysis method performed using the apparatus.

  As is well known, R-Fe-B permanent magnets (R is a rare earth element) are used in various fields today because of their high magnetic properties. Against this backdrop, R-Fe-B permanent magnet production plants produce a large amount of magnets every day, but due to the increase in production of magnets, processing defects etc. during the manufacturing process. As a result, the amount of magnet scrap discharged as magnets and magnet processed scraps discharged as cutting scraps, grinding scraps, and the like is also increasing. In particular, since the magnets used there are also miniaturized due to the weight reduction and miniaturization of information equipment, the machining allowance ratio tends to increase. Therefore, it will be an important technical issue in the future how to recover and reuse the metal elements, especially rare earth elements, without discarding the magnet scraps and magnet processing scraps discharged during the manufacturing process. Yes. The same applies to how rare earth elements are recovered and reused as recycled resources from electrical appliances using R-Fe-B permanent magnets. Therefore, as a method for recovering rare earth elements from a processing object containing a rare earth element and an iron group element, such as an R—Fe—B permanent magnet, after oxidizing the processing object, the processing environment is changed to carbon. Patent Document 1 proposes a method in which a rare earth element is separated from an iron group element as an oxide and recovered by being transferred to the presence and heat-treated at a temperature of 1150 ° C. or higher.

  An oxide of a rare earth element separated from an iron group element by the method described in Patent Document 1 can be converted into a rare earth metal by reduction, for example, by a molten salt electrolysis method. The molten salt electrolysis method is a well-known method that can reduce an oxide of a base metal having a redox potential such as a rare earth metal. As a molten salt electrolysis device, a cylindrical cathode made of tungsten, molybdenum, iron or the like, and a plurality of graphite cathodes arranged opposite to the cathode inside an electrolytic cell for holding molten salt Devices having a cylindrical shape, a plurality of arcuate anodes, and a cylindrical anode surrounding the cathode are known, and rare earth metals deposited on the cathode surface and alloys of rare earth metals and iron are liquid. Then, it flows down through the cathode, drops down from the lower end, and is collected and collected in a tray placed below the cathode (see, for example, Patent Document 2).

International Publication No. 2013/018710 JP-A-62-222095

  However, in a molten salt electrolyzer having a solid structure such as a columnar or arcuate anode, even if an attempt is made to increase the surface area of the anode in order to increase the deposition rate of the deposited metal, the number or the number of the anodes can be increased. Since there is no choice but to increase the shape of this, there is a limit to how much it can be made.

  Therefore, the present invention can increase the electrodeposition rate of the deposited metal, for example, by increasing the surface area of the anode dramatically, compared with the case of using a solid anode such as a columnar or arcuate shape. It is an object of the present invention to provide an apparatus for performing the above and a molten salt electrolysis method performed using the apparatus.

An apparatus for performing molten salt electrolysis of the present invention made in view of the above points, as described in claim 1, an electrolytic cell for holding molten salt, a cathode portion disposed therein, It is characterized by comprising at least a casing having an opening through which molten salt can circulate for constituting the anode part together with the anode material piece filled by filling the anode material piece.
The apparatus for performing molten salt electrolysis according to claim 2 is the apparatus for performing molten salt electrolysis according to claim 1, characterized in that the casing has a supply port for replenishing anode material pieces. To do.
Moreover, the molten salt electrolysis method of the processing object of this invention is characterized by filling the casing of the apparatus for performing molten salt electrolysis of Claim 1 with an anode material piece as described in Claim 3. To do.

  According to the apparatus for performing molten salt electrolysis and the molten salt electrolysis method of the present invention, the anode part is composed of a casing having an opening through which the molten salt can flow and an anode material piece filled therein. Thus, the surface area of the anode can be dramatically increased as compared with the case where a solid anode such as a columnar shape or an arc shape is used, so that molten salt electrolysis of the object to be treated can be performed efficiently.

It is typical sectional drawing of the internal structure of an example of the molten salt electrolysis apparatus using the apparatus for performing molten salt electrolysis of this invention.

  Hereinafter, an apparatus and a molten salt electrolysis method for performing molten salt electrolysis according to the present invention will be described with reference to the drawings. However, an apparatus and a molten salt electrolysis method for performing molten salt electrolysis according to the present invention are limited to the following descriptions. Are not to be interpreted.

  The apparatus for performing molten salt electrolysis of the present invention is characterized by comprising a casing having an opening through which molten salt can flow for filling an anode material piece, and the casing is filled with the anode material piece. Thus, the casing filled with the anode material piece functions as an anode part in the molten salt electrolysis apparatus. FIG. 1 is a schematic cross-sectional view of an internal structure of an example of a molten salt electrolysis apparatus using an apparatus for performing molten salt electrolysis according to the present invention. The molten salt electrolysis apparatus 1 includes a columnar cathode part 3 and two columnar anode parts 4 arranged opposite to the cathode part 3 in an electrolytic cell 2 for holding a molten salt. Have

The molten salt held inside the electrolytic cell 2 is filled in the electrolytic cell 2 in a molten state or melted inside the electrolytic cell 2, and is appropriately selected according to the object to be treated. Is done. When the object to be treated is an oxide of a rare earth element, the molten salt may be, for example, LiF—NdF ₃ or LiF—NdF ₃ —PrF ₃ —DyF ₃ depending on the type of rare earth element contained in the object to be treated. BaF ₂ or the like is added as necessary. The columnar cathode portion 3 is made of tungsten, molybdenum, iron, or the like. The shape of the cathode portion 3 is appropriately determined according to the device design and the like, and may be a prismatic shape or the like.

  The columnar anode portion 4 disposed opposite the cathode portion 3 is configured by filling a hollow columnar casing 6 having an opening 5 through which molten salt can flow on a side surface with an anode material piece 7. Yes. The number (number) of the anode portions 4 is appropriately determined according to the device design and the like, and is not limited to two. In this molten salt electrolysis apparatus 1, the surface area of the anode that contributes to the molten salt electrolysis treatment is not the surface area of the casing 6, but the approximate sum of the surface areas of the individual anode material pieces 7 filled in the casing 6. Therefore, compared with the solid anode having the same surface area as that of the casing 6, the surface area of the anode is very large, so that the molten salt electrolysis can be performed efficiently.

  The casing 6 can be filled with the anode material piece 7 and has a structure in which the original anode material piece 7 accommodated therein does not spill out of the casing 6 from the opening 5 through which the molten salt can flow. . The installation location of the opening 5 is not limited to the side surface of the casing 6, and may be the bottom surface of the casing 6. The shape of the casing 6 is appropriately determined according to the device design or the like, and may be a prismatic shape or the like. The casing 6 is difficult to be consumed or dissolved by the molten salt electrolysis treatment, for example, nitride ceramics such as silicon nitride, boron nitride, and aluminum nitride, and oxide ceramics such as alumina, magnesia, zirconia, and calcia. It is desirable to be made of an insulating material. The anode material piece 7 accommodated inside the casing 6 is consumed and gradually becomes smaller when the molten salt electrolysis treatment is performed. When the anode material piece 7 becomes smaller than the size of the opening 5, the anode material piece 7 spills out of the casing 6. There is. When the consumable piece of the anode material piece 7 spills out of the casing 6 from the opening 5, it floats and stays on the liquid surface of the molten salt. When the casing 6 is made of a conductive material such as metal and the upper end portion thereof is at a position higher than the liquid surface of the molten salt, the consumable pieces of the anode material piece 7 that floats and stays on the liquid surface of the molten salt. There is a risk of causing a short circuit between the cathode 3 and the anode 4. Making the casing 6 made of an insulating material has an advantage that such a problem can be avoided.

  The anode material piece 7 is made of graphite or the like. Examples of the individual shapes include a cubic shape, a plate shape, a rod shape, and a spherical shape having a size (maximum diameter) when filled in the casing 6 of about 5 to 50 mm. In this case, the size (maximum diameter) of the opening 5 through which the molten salt of the casing 6 can flow is preferably about 2 to 10 mm (however, it is smaller than the individual size of the anode material piece 7 when the casing 6 is filled). As a condition). If the size of the opening 5 is large, the consumed anode material piece 7 spills out of the casing 6 at an early stage, resulting in a decrease in usage rate. The shape of the opening 5 includes a polygonal shape such as a triangle or a quadrangle, and a circular shape such as a regular circle or an ellipse.

  When the molten salt electrolysis treatment is performed, an electrolyte is deposited on the surface of the cylindrical cathode portion 3, and the deposited electrolyte flows in a liquid state along the cathode portion 3 and drops from the lower end. When the object to be treated is an oxide of a rare earth element, the molten salt electrolytic treatment is performed at a treatment temperature of, for example, 800 to 1200 ° C., and the obtained electrolyte is a rare earth metal or an alloy of a rare earth metal and iron. Electrolyte dripped from the lower end of the cathode part 3 is collected and collected in a tray 8 installed below the cathode part 3.

  The casing 6 is preferably provided with a supply port 9 for replenishing the anode material piece 7 from the outside. By replenishing the anode material piece 7 from the supply port 9 according to the degree of consumption of the anode material piece 7 filled in the casing 6, stable molten salt electrolysis can be continuously performed over a long period of time (consumption). No interruption of the process to replace the treated anode). As shown in FIG. 1, the supply port 9 may be provided via a supply pipe 10 (which may be fixed to the main body of the casing 6 or may be detachable) connected to the main body of the casing 6. However, it may be provided directly on the main body of the casing 6, but is preferably provided at a position higher than the liquid level of the molten salt. The supply port 9 may be provided with a lid mechanism that can be opened and closed. The degree (number) of filling of the anode material piece 7 into the casing 6 and the timing of replenishment of the anode material piece 7 may be appropriately determined according to the processing conditions.

  Note that all or most of the anode material pieces 7 filled in the casing 6 can be energized between the individual pieces by being filled in the casing 6, but in order to make the energization more reliable, the casing 6 A graphite energizing core made of graphite may be inserted into the inside.

  Further, the molten salt is stirred by a molten salt stirring device such as a molten salt stirring propeller in a place where it does not hinder the molten salt electrolysis treatment by the cathode part 3 and the anode part 4 and the recovery of the electrolyte collected in the receiving tray 8. Thus, the deposition of the electrolyte on the surface of the cathode portion 3 may be promoted.

  Also, a device for peeling and removing gas (carbon monoxide, oxygen, etc.) generated on the surface of each anode material piece 7 by performing molten salt electrolysis treatment (rotating the casing 6 with a motor or vibrating it) Or the like that is vibrated by a child).

  Moreover, the combination of a cathode part and an anode part may be a combination of a cylindrical or inverted frustoconical cathode part and a columnar anode part arranged at the center of the inside thereof. When the cathode part has an inverted truncated cone shape, there is an advantage that the deposited electrolyte can be collected and collected.

  As mentioned above, although the apparatus for performing molten salt electrolysis of this invention and the molten salt electrolysis method were demonstrated taking the case where the process target was an oxide of rare earth elements as an example, the apparatus for performing molten salt electrolysis of this invention The molten salt electrolysis method can be used for any object to be processed that can be subjected to molten salt electrolysis. The processing conditions according to each processing object, for example, the molten salt to be used and the processing temperature may be known per se.

  In the present invention, by using a solid anode such as a columnar or arcuate shape, the surface area of the anode can be dramatically increased. The present invention has industrial applicability in that it can provide an apparatus for performing the method and a molten salt electrolysis method performed using the apparatus.

DESCRIPTION OF SYMBOLS 1 Molten salt electrolysis apparatus 2 Electrolysis tank 3 Cathode part 4 Anode part 5 Opening 6 Casing 7 Anode material piece 8 Sauce 9 Anode material piece supply port 10 Anode material piece supply pipe

Claims (3)

  An electrolytic cell for holding a molten salt, a cathode portion disposed therein, and a molten salt for constituting the anode portion together with the anode material piece filled by filling the anode material piece are distributed. An apparatus for performing molten salt electrolysis, comprising at least a casing having a possible opening.   2. The apparatus for performing molten salt electrolysis according to claim 1, wherein the casing has a supply port for replenishing the anode material piece.   A molten salt electrolysis method for an object to be treated, which is performed by filling a casing of an apparatus for performing molten salt electrolysis according to claim 1 with an anode material piece.

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