JP2019059987A - Detecting method of leakage of contents from electrolytic bath of molten salt electrolytic apparatus and molten salt electrolytic apparatus - Google Patents

Abstract

To provide: a method that can detect, with a simple configuration in high reliability, the leakage of contents from an electrolytic bath of a molten salt electrolytic apparatus used for collecting a rare-earth metal by reducing, for example, an oxide of a rare-earth element; and the molten salt electrolytic apparatus that can carry out the method.SOLUTION: A concave part is arranged on the lower-part outer periphery of the side face of an electrolytic bath along the outer periphery. Gas is supplied from a gas supply port situated inside the concave part. The change of an amount of gas supply from the gas supply port is detected, which is caused by the leak, from the electrolytic bath, of the contents inflowing into the concave part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of detecting leakage of contents from an electrolytic cell in a molten salt electrolytic device used to recover, for example, a rare earth metal by reducing an oxide of a rare earth element, and a melting method capable of performing this method. It relates to a salt electrolytic device.

  As R-Fe-B based permanent magnets (R is a rare earth element) have high magnetic properties, it is well known that they are used in various fields today. Under these circumstances, a large number of magnets are produced daily at R-Fe-B permanent magnet production factories, but with the increase in the amount of magnets produced, processing defects etc. during the manufacturing process As a result, the amount of magnet scrap discharged and the amount of magnet processing scrap discharged as cutting scraps and grinding scraps are also increasing. In particular, since the magnets used therein are also miniaturized due to the reduction in weight and size of information devices, the processing cost ratio tends to increase. Therefore, it will become an important technical issue in the future how to recover and reuse the metal elements, especially the rare earth elements contained therein, without discarding the magnet scraps and magnet processing scraps discharged during the manufacturing process. There is. Moreover, it is the same also about how to collect | recover and recycle a rare earth element as circulation resources from the electrical appliances etc. which used R-Fe-B type | system | group permanent magnet. Therefore, as a method of recovering a rare earth element from an object to be treated containing a rare earth element and an iron group element such as R-Fe-B permanent magnet, the object to be treated is oxidized and then the treatment environment is carbon. Patent Document 1 proposes a method of separating a rare earth element as an oxide from an iron group element and recovering it by transferring it to the presence and performing heat treatment at a temperature of 1150 ° C. or higher.

The oxide of the rare earth element separated from the iron group element by the method described in Patent Document 1 can be converted to a rare earth metal by reduction using, for example, molten salt electrolysis. Molten salt electrolysis is a method well known as a method capable of reducing an oxide of a base metal having a redox potential such as a rare earth metal. As the molten salt electrolytic device, a cylindrical negative electrode made of tungsten, molybdenum, iron or the like and a negative electrode made of graphite or the like are disposed in the inside of an electrolytic cell made of graphite or the like for holding the molten salt. Devices having a plurality of cylindrical or plural arcuate anodes, a cylindrical anode surrounding the cathode, etc. are known, and rare earth metals and rare earth metals which are electrolytes deposited on the surface of the cathode. The alloy with iron flows in a liquid state, flows down the cathode, drips down from the lower end, is collected in a receptacle installed below the cathode, and is recovered from the electrolytic cell (for example, patent documents) 2)). For the molten salt, for example, LiF-NdF ₃ or LiF-NdF ₃ -PrF ₃ -DyF ₃ may be used depending on the type of the rare earth element contained in the oxide of the rare earth element to be treated. BaF ₂ etc. are added. Molten salt electrolytic treatment is usually carried out under an inert gas atmosphere such as nitrogen or argon or under reduced pressure (including vacuum) so that the electrolyte recovered from the electrolytic cell is not oxidized in a temperature range of 800 to 1200 ° C. ) It takes place in the atmosphere.

  Although the electrolytic cell made of graphite is stable against chemical attack by the molten salt as described above, the high temperature content is still around the periphery of the electrolytic cell while the molten salt electrolytic treatment is still performed due to deterioration with time. Or leach out from the outer periphery of the electrolytic cell. In such a case, if not promptly dealt with, it may lead to damage of the entire device. Therefore, it is important to quickly detect the leakage (leaching or outflow) of the hot contents from the electrolytic cell. As a method of detecting the leak of the high temperature contents from the electrolytic cell, for example, a method of detecting the temperature change in the processing chamber by the leak of the high temperature contents from the electrolytic cell by a thermocouple, the leached contents There is a method of detecting a change in current caused by sticking to the current circuit, but a method that can be detected with high reliability while having a simple configuration is desired.

International Publication No. 2013/018710 Japanese Patent Application Laid-Open No. 62-222095

  Therefore, the present invention, for example, leaks the contents from the electrolytic cell in the molten salt electrolytic apparatus used to reduce the oxides of the rare earth elements and recover the rare earth metals, while having a simple structure and high reliability. It is an object of the present invention to provide a method that can be detected originally, and a molten salt electrolysis apparatus that can perform this method.

Contents from the electrolytic cell in the molten salt electrolytic apparatus, in which the cathode and the anode for electrolytically treating the object to be treated of the present invention, which are made in view of the above points, are arranged and the molten salt is held. According to a first aspect of the present invention, there is provided a method of detecting a leak of the second aspect, wherein a recess is provided along the outer periphery below the outer periphery of the side surface of the electrolytic cell and a gas supply port is positioned inside the recess to supply gas. By detecting a change in the gas supply amount from the gas supply port caused by the content leaked from the electrolytic cell entering the recess.
The method for detecting leakage of contents from the electrolytic cell in the molten salt electrolytic device according to claim 2 is a method for detecting leakage of contents from the electrolytic cell in the molten salt electrolytic device according to claim 1 In the above, the recessed portion has a circumferential shape along the side surface of the electrolytic cell, and the gas supply port is positioned inside at least n points thereof to supply a gas (n is an integer of 2 or more).
In the method for detecting leakage of contents from the electrolytic cell in the molten salt electrolytic device according to claim 3, a method for detecting leakage of contents from the electrolytic cell in the molten salt electrolytic device according to claim 2 Wherein the electrolytic cell has a circular cross-sectional outer periphery, the recess has a circumferential shape along the outer periphery of the side surface of the electrolytic cell, and the circumference of the recess is equally divided n The gas supply port is positioned inside the portion to supply gas (n is an integer of 2 or more).
Further, according to the molten salt electrolyzing device of the present invention, as described in claim 4, an electrolytic cell in which a cathode and an anode for subjecting a processing object to molten salt electrolysis are disposed, and the electrolytic salt in which molten salt is held; A recess provided along the outer periphery below the outer periphery of the side surface of the tank, a gas supply passage for supplying gas to the inside of the recess, wherein a gas supply port is located inside the recess, the gas supply port And at least a detector for detecting a change in gas supply amount from
The molten salt electrolyzing apparatus according to claim 5 is the molten salt electrolyzing apparatus according to claim 4, wherein the recess has a circumferential shape along the side surface of the electrolytic cell, and Position the gas supply port (n is an integer of 2 or more).
The molten salt electrolytic apparatus according to claim 6 is the molten salt electrolytic apparatus according to claim 5, wherein the electrolytic cell has a circular cross-sectional outer periphery, and the concave portion is a side surface of the electrolytic cell. It has a circumferential shape along the outer periphery, and the gas supply port is positioned inside n places obtained by equally dividing the circumference of the recess by n (n is an integer of 2 or more).

  According to the method for detecting the leakage of the contents from the electrolytic cell in the molten salt electrolytic device of the present invention, the leakage of the contents from the electrolytic cell can be made with high reliability while having a simple configuration. It can be detected.

It is a typical front sectional view and a top view of an internal structure of an example of a molten salt electrolysis device which can perform a method of detecting a leak of contents from an electrolytic cell in a molten salt electrolysis device of the present invention. FIG. 6 is a schematic plan view of another molten salt electrolysis apparatus of the present invention.

  Hereinafter, the method for detecting leakage of contents from the electrolytic cell in the molten salt electrolyzing device of the present invention and the molten salt electrolytic device will be described based on the drawings, but the contents from the electrolytic cell in the molten salt electrolyzing device of the present invention The method for detecting the leak of material and the molten salt electrolysis apparatus are not construed as being limited to the following description.

  FIG. 1 is a schematic front cross-sectional view and a plan view of an internal structure of an example of a molten salt electrolytic device capable of detecting a leak of contents from an electrolytic cell in the molten salt electrolytic device of the present invention. is there. A molten salt electrolyzer 1 shown in FIG. 1 includes a cylindrical cathode 3 and a cylindrical anode 4 surrounding the cathode 3 inside an electrolytic cell 2 having a circular cross-sectional outer periphery for holding molten salt. And are arranged. When the molten salt electrolytic treatment is performed, the electrolyte is deposited on the surface of the cylindrical cathode 3 and the deposited electrolyte is liquefied and flows down the cathode 3 and drips down from the lower end and is below the cathode 3. It is collected in the installed tray 5 and collected from the electrolytic cell 2. In the plan view of FIG. 1, the cathode 3, the anode 4, and the tray 5 are not shown.

  The electrolytic cell 2 is supported on an electrolytic cell table 7 fixed to a hot water receptacle 6 made of a material such as alumina, for example. The hot water receiver 6 is provided with a recess 8 having a circumferential shape along the outer periphery of the side surface of the electrolytic cell 2, and high temperature contents from the outer periphery of the side surface of the electrolytic cell 3 during molten salt electrolytic treatment When it leaks out, the leaked content flows down along the side of the electrolytic cell 3 and drips from the lower end to enter the recess 8. A constant amount of gas is always supplied to the recess 8 from the gas supply port 9 positioned inside two places where the circumference is divided into two equal parts. If the content leaked from the electrolytic cell 2 enters the recess 8 and interferes with the supply of gas from the gas supply port 9, when the amount of gas supply from the gas supply port 9 changes, the change is a detector Is detected by the pressure sensor 10 (detection of pressure rise). It is desirable to use an inert gas such as nitrogen or argon which does not oxidize the electrolyte recovered from the electrolytic cell 2 as the gas supplied to the recess 8 provided in the hot water receptacle 6. The material of the gas supply port 9 which is the tip of the gas supply path is, for example, stainless steel which is excellent in corrosion resistance and heat resistance. A change in gas supply amount from the gas supply port 9 may be detected by a flow rate sensor (detection of flow rate decrease).

  As described above, in the molten salt electrolytic apparatus 1 shown in FIG. 1, the gas supply ports 9 are positioned in two places obtained by dividing the circumference of the recess 8 into two equal parts, and the contents of the outer periphery of the side surface of the electrolytic cell 2 Leaks from the lower end depending on the location where the oil leaked out, and the contents in the recess 8 flow to reach one of the two gas supply ports 9 earlier, so that the contents leak from the electrolytic cell 2 Ejection can be detected earlier (that is, detection is possible at a stage where the amount of content leakage is small). That the hot water receptacle 6 and the electrolytic bath stand 7 are made of a material such as alumina is that they are heated during the treatment because they have heat resistance and heat retention to the temperature rise of the electrolytic bath 2 during molten salt electrolytic treatment, The heat content of the content in the recess 8 is maintained to contribute to the maintenance of the fluidity. The bottom of the recess 8 is inclined downward from the two farthest locations from the two locations where the gas supply openings 9 are positioned inside the circumferential recess 8 to the respective locations where the gas supply openings 9 are positioned, 2 By positioning any one of the two gas supply ports 9 inside the lowest position of the bottom surface of the recess 8, the flow of contents leaked from the electrolytic cell 2 in the recess 8 to the gas supply port 9 is promoted. It is also good.

  FIG. 2 is a schematic plan view of another molten salt electrolysis apparatus of the present invention. The molten salt electrolyzer 21 shown in FIG. 2 is obtained by equally dividing the circumference of the circumferential recess 28 along the outer periphery of the side surface of the electrolytic cell 22 having a circular cross-sectional outer periphery into four parts. The gas supply port 29 is positioned in the inside of the portion, and the contents on the outer periphery of the side surface of the electrolytic cell 22 drip from the lower end depending on the location where the contents leaked out, and the contents in the recess 28 flow 4 The melting shown in FIG. 1 except that the pressure sensor 30 can detect the leakage of the contents from the electrolytic cell 22 more quickly by reaching the gas supply port 29 earlier. The configuration is the same as that of the salt electrolysis apparatus 1 (in FIG. 2, the cathode, the anode, and the pan are not shown). The molten salt electrolyzer 21 shown in FIG. 2 can be detected at a stage where the amount of leaked contents is smaller than the molten salt electrolyzer 1 shown in FIG. 1 as the number of gas supply ports is large.

  In addition, although the recessed part provided in the hot water receptacle does not necessarily need to be circumferential shape, although circumferential shape may be divided and you may form the division which consists of a peripheral shape, at least 1 gas supply port is formed in each division. Need to be located internally (otherwise leakage of contents from the electrolytic cell can not be detected based on the contents that leaked from the electrolytic cell that entered the compartment).

  Moreover, the cross-sectional outer periphery of an electrolytic cell may be polygonal shape, and the recessed part provided in the hot water receptacle may be a peripheral shape where polygonal peripheral shape and polygonal peripheral shape were divided.

  The above description is for detecting the leakage of the contents from the outer periphery of the side surface of the electrolytic cell, but the leaked contents also when the leakage of the contents from the electrolytic cell occurs from the bottom surface By entering the recess, it is possible to detect the leakage of the contents from the electrolytic cell. A downward slope may be provided from the center of the hot water receiver toward the outer periphery to promote the flow of the contents leaked from the bottom of the electrolytic cell to the recess.

  The present invention is a method capable of detecting leakage of contents from an electrolytic cell in a molten salt electrolytic device with high reliability while having a simple configuration, and a melting method capable of performing this method. It has industrial applicability in that it can provide a salt electrolytic device.

1, 21 molten salt electrolyzer 2, 22 electrolyzer 3 cathode 4 anode 5 saucer 6, 26 hot water receptacle 7 electrolyzer stand 8, 28 recessed portion 9, 29 gas supply port 10, 30 detector (pressure sensor)

Claims (6)

  A method for detecting leakage of contents from an electrolytic cell in a molten salt electrolyzer, in which a cathode and an anode for electrolyzing molten salt of an object to be treated are disposed and the molten salt is held, A recess is provided along the outer periphery below the outer periphery of the side surface of the tank, the gas supply port is positioned inside the recess to supply gas, and the content leaked from the electrolytic cell enters the recess A method for detecting leakage of contents from an electrolytic cell in a molten salt electrolytic device by detecting a change in gas supply amount from the gas supply port caused.   The concave portion has a circumferential shape along the side surface of the electrolytic cell, and the gas supply port is positioned at the inside of at least n points to supply the gas (n is an integer of 2 or more), A method of detecting leakage of contents from an electrolytic cell in a molten salt electrolytic device.   The electrolytic cell has a circular cross-sectional outer periphery, and the concave portion has a circumferential shape along the outer periphery of the side surface of the electrolytic cell, and n portions of the concave portion divided equally by n The method for detecting the leak of the contents from the electrolytic cell in the molten salt electrolytic device according to claim 2, wherein the gas supply port is positioned inside to supply the gas (n is an integer of 2 or more). An electrolytic cell in which a cathode and an anode for electrolyzing molten salt of an object to be treated are disposed, and the molten salt is held,
A recess provided along the outer periphery below the outer periphery of the side surface of the electrolytic cell;
A gas supply passage for supplying a gas to the inside of the recess, wherein a gas supply port is located inside the recess;
A detector for detecting a change in gas supply amount from the gas supply port;
A molten salt electrolyzer comprising at least:   The molten salt according to claim 4, wherein the recessed portion has a circumferential shape along the side surface of the electrolytic cell, and the gas supply port is positioned inside at least n points thereof (n is an integer of 2 or more). Electrolyzer.   The electrolytic cell has a circular cross-sectional outer periphery, and the recess is a circumferential shape along the outer periphery of the side surface of the electrolytic cell, and n places equally dividing the periphery of the recess by n The molten salt electrolysis apparatus according to claim 5, wherein the gas supply port is positioned inside (n is an integer of 2 or more).

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