JP2022051429A - Passage partition structure of melt feed pipe and manufacturing method of metallic magnesium - Google Patents

Abstract

To provide a passage partition structure of a melt feed pipe capable of satisfactorily suppressing damage to an anode due to inflow of outside air into a molten salt electrolytic cell during supply of magnesium chloride and recovery of metallic magnesium, and a manufacturing method of the metallic magnesium.SOLUTION: A passage partition structure 11 of the present invention that is provided in a molten salt electrolytic cell 1 for partitioning a passage 12 of a melt feed pipe 51 inserted from outside into an inside the molten salt electrolytic cell 1, includes a tubular main body portion 13 in which the passage 12 is partitioned inside, an opening/closing end portion 14 located at one end, which corresponds to the aforementioned outside, in an axial direction of the main body portion 13, an opening end portion 15 located at the other end in the axial direction of the main body portion 13, and immersed in a molten salt bath located in the aforementioned inside, a connecting portion 16 that connects the main body portion 13 to the molten salt electrolytic cell 1, and ventilation holes 17a and 17b provided in the main body portion 13.SELECTED DRAWING: Figure 3

Description

The present invention relates to a passage partition structure of a melt feed pipe used in molten salt electrolysis using a molten salt electrolytic cell, and a method for producing metallic magnesium.

In the production of metallic titanium by the Kroll process, molten metallic magnesium is brought into contact with titanium tetrachloride, and titanium tetrachloride is reduced with metallic magnesium to form a sponge titanium lump. Titanium sponge lumps are crushed to form granular sponge titanium, which is then used for casting titanium ingots and the like.

The metallic magnesium used for the reduction of titanium tetrachloride can be obtained, for example, by molten salt electrolysis using magnesium chloride secondarily produced by the reduction of titanium tetrachloride as a raw material. In molten salt electrolysis, a molten salt containing magnesium chloride is stored in a molten salt electrolysis tank to form a molten bath, and magnesium chloride in the molten bath is decomposed into metallic magnesium and chlorine by an electrode including an anode and a cathode. The metallic magnesium produced thereby is recovered after floating on the bath surface side of the molten bath due to the density difference with the molten salt.

This metallic magnesium easily reacts with oxygen and nitrogen in the atmosphere, especially in the molten state. Oxides and nitrides produced by the reaction with oxygen and nitrogen may be transferred to titanium sponge when the metallic magnesium is used for reduction of titanium tetrachloride, and further to the titanium ingot obtained after that. When mixed, it deteriorates its mechanical properties. Therefore, it is required to suppress the oxidation and nitriding of metallic magnesium as much as possible.

In relation to this, Patent Document 1 states, "While transferring molten metal magnesium or molten magnesium chloride produced in a molten salt electrolytic tank to the next step, contact with the atmosphere is avoided as much as possible, and as a result, oxides are formed. Providing a method capable of producing high-purity metallic magnesium free of magnesium and nitrides, an apparatus for extracting molten magnesium suitable for carrying out the method, and magnesium chloride as a raw material for producing the molten metallic magnesium. It is an object of the present invention to provide an extraction device and a method capable of effectively suppressing a decrease in purity during transfer from a reduction step to an electrolysis step. " Further, in Patent Document 1, "a solution extraction device that seals a connection portion between a solution extraction nozzle for extracting a solution from a molten salt electrolytic tank or a solution receiving container and a solution transfer container that receives the solution from the extraction nozzle. A connection flange and a connection pipe are connected to the tip of the solution extraction nozzle, and the lower end of the connection pipe is configured to be fitted and connected to the solution receiving nozzle provided in the solution transfer container. A solution extraction device, characterized in that a seal cover is disposed so as to cover the fitting portion, has been proposed.

Japanese Unexamined Patent Publication No. 2009-30161

By the way, although the inside of the molten salt electrolytic cell is usually sealed with a lid, a melt feed pipe is inserted when supplying magnesium chloride to the molten bath or when recovering metallic magnesium produced by electrolysis. Therefore, the lid may be temporarily and partially opened. At this time, there is a problem that the atmosphere (outside air) containing oxygen flows into the molten salt electrolytic cell, which causes damage to the graphite anode. That is, the inflow of the atmosphere (outside air) into the molten salt electrolytic cell may cause not only the formation of oxides and nitrides of metallic magnesium but also the problem of damaging the graphite anode.

The "solution extraction device" described in Patent Document 1 is useful because it can suppress the mixing of oxides and nitrides in the metallic magnesium during the recovery and subsequent storage of the metallic magnesium. However, when setting the melt feed pipe, the inside of the molten salt electrolytic cell, which often exerts a negative pressure on the external environment, is opened, so that the outside air flows into the molten salt electrolytic cell from the open portion, which is the cause. Can damage the anode. The technique described in Patent Document 1 has room for further improvement in this respect.

An object of the present invention is to satisfactorily suppress damage to the anode due to the inflow of outside air into the molten salt electrolytic cell during the supply of magnesium chloride and the recovery of metallic magnesium. It is an object of the present invention to provide a structure and a method for producing metallic magnesium.

As a result of diligent studies, the inventor has devised a passage partition structure for passing a melt feed pipe in the molten salt electrolytic cell. In this passage partition structure, the inside can be sealed between the opening / closing end portion on one end side and the opening end portion on the other end side immersed in the melting bath, and the atmosphere inside the inside can be adjusted. This makes it possible to insert the melt feed pipe into the inside of the molten salt electrolytic cell to supply magnesium chloride and recover metallic magnesium while suppressing the inflow of outside air into the molten salt electrolytic cell.

The passage partition structure of the present invention is a passage partition structure provided in the molten salt electrolytic cell and partitions the passage of the melt feed pipe inserted from the outside inside the molten salt electrolytic cell, and the passage is inside. Is immersed in the melting bath inside the main body, the open / close end located on the outside on one end side in the axial direction of the main body, and the other end side in the axial direction of the main body. It is provided with an open end portion, a connecting portion for connecting the main body portion to the molten salt electrolytic cell, and a vent provided in the main body portion.

The passage partition structure of the present invention further includes a gas supply pipe connected to each of the vents and connected to an inert gas supply source, and a communication pipe that communicates the inside of the main body with the outside air to supply the gas. It is preferable that each of the pipe and the communication pipe includes a valve.

Further, in the passage partition structure of the present invention, it is preferable to further include a cover portion attached to the opening / closing end portion and capable of opening and closing the opening / closing end portion.

In the passage partition structure of the present invention, the connecting portion may have a flange shape extending from the outer peripheral surface of the main body portion to the outer peripheral side at least a part in the circumferential direction of the outer peripheral surface. In this case, it is preferable that the main body portion is arranged through a through hole provided in the lid of the molten salt electrolytic cell, and the flange-shaped connecting portion is connected to the peripheral edge portion around the through hole. Is.

The method for producing metallic magnesium of the present invention is a method in which magnesium chloride is electrolyzed in a molten bath of a molten salt containing magnesium chloride, and the metallic magnesium is produced by the electrolysis, wherein any of the above passage compartment structures is formed. A provided molten salt electrolysis tank is used.

The method for producing metallic magnesium of the present invention is an inert gas filling step in which the inside of the main body is filled with an inert gas in a state where the opening / closing end is closed when the passage partition structure is not used. Is preferably included.

Further, in the method for producing metallic magnesium of the present invention, magnesium chloride of a melt is sent through a melt feed pipe inserted into the inside of the molten salt electrolytic tank from the inside of the main body portion, and magnesium chloride is passed through the molten bath. In the magnesium chloride supply step of supplying , It is preferable to include a metal magnesium recovery step of recovering metallic magnesium.

More specifically, in the magnesium chloride supply step and / or the metallic magnesium recovery step, the inside of the main body portion is communicated with the outside air through the vent, the opening / closing end portion is opened, and the inside of the main body portion is opened. This includes inserting a melt feed pipe, passing the melt through the melt feed pipe, and taking out the melt feed pipe from the inside of the main body to close the opening / closing end portion. Is even more preferable.

Further, here, the magnesium chloride supply step and / or the metallic magnesium recovery step is performed after the melt is passed through the melt feed pipe and before the opening / closing end is closed, or the opening / closing end is closed. After that, it is preferable to further include supplying an inert gas to the inside of the main body portion.

Further, in the magnesium chloride supply step and / or the metallic magnesium recovery step, it is preferable to immerse the tip end portion of the melt feed pipe to a position deeper in the melt bath than the open end portion.

According to the passage partition structure of the melt feed pipe of the present invention and the method for producing metallic magnesium, the anode is damaged due to the inflow of outside air into the molten salt electrolytic cell during the supply of magnesium chloride and the recovery of metallic magnesium. Can be satisfactorily suppressed.

It is sectional drawing along the depth direction of the molten bath which shows an example of the molten salt electrolytic cell which comprises the passage partition structure of one Embodiment of this invention. It is sectional drawing which follows the II-II line of FIG. FIG. 3 is an enlarged cross-sectional view showing the passage section structure of the molten salt electrolytic cell of FIG. 1. It is sectional drawing which shows the passage section structure of another embodiment. It is sectional drawing which shows the state which inserted the molten metal feed pipe into the inside of the molten salt electrolytic cell from the inside of the main body part of the passage partition structure of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The molten salt electrolytic cell 1 exemplified in FIG. 1 is provided with the passage partition structure 11 according to the embodiment of the present invention. The passage partition structure 11 partitions the passage 12 of the melt feed pipe, which will be described later, to be inserted from the outside inside the molten salt electrolytic cell 1. More specifically, the passage partition structure 11 has a tubular main body 13 in which the passage 12 is partitioned inside and one end side (upper side in FIG. 1) of the main body 13 in the axial direction (vertical direction in FIG. 1). An opening / closing end portion 14 located outside the molten salt electrolytic cell 1 and an opening immersed in the molten bath inside the molten salt electrolytic cell 1 at the other end side (lower side in FIG. 1) in the axial direction of the main body portion 13. It is provided with an end portion 15, a connecting portion 16 for connecting the main body portion 13 to the molten salt electrolytic cell 1, and vents 17a and 17b provided in the main body portion 13.

(Melted salt electrolysis)
The molten salt electrolytic tank 1 shown in FIG. 1 has a container shape mainly made of fire-resistant bricks such as Al ₂ O ₃ and other suitable materials, and is composed of a molten salt containing magnesium chloride stored therein. In the molten bath, the magnesium chloride in the molten salt is electrolyzed.

In the molten salt electrolysis performed using the molten salt electrolytic cell 1, as shown in FIG. 1, metallic magnesium (Mg) is generated as a molten metal and chlorine (Cl ₂ ) is produced as a gas by electrolysis of magnesium chloride. Occur. The metallic magnesium produced by molten salt electrolysis can be used for the reduction of titanium tetrachloride in the Kroll process for producing metallic titanium, and the chlorine gas can be used for the chloride of titanium ore. As the magnesium chloride used as a raw material for this electrolysis, those produced as a by-product by the Kroll process can be used.

The molten salt in the molten bath may contain supporting salts in addition to the above-mentioned magnesium chloride (MgCl ₂ ). This supporting salt means an electrolyte that lowers the crystallization temperature and lowers the viscosity when mixed with magnesium chloride. The supporting salt is specifically selected from the group consisting of sodium chloride (NaCl), calcium chloride (CaCl ₂ ), potassium chloride (KCl), magnesium fluoride (MgF ₂ ) and calcium fluoride (CaF ₂ ). It can be a kind. The crystallization temperature refers to the temperature at which a phenomenon of crystallization in which one type of electrolyte component begins to precipitate as a solid occurs when the temperature of a molten salt composed of two or more types of electrolytes is lowered from the liquid state. When there is only one type of molten salt, the crystallization temperature corresponds to the freezing point, that is, the melting point, because the whole becomes solid at the freezing point when the temperature is lowered from the liquid state. Since magnesium chloride is preferentially decomposed by electrolysis, it is common to use an electrolyte having a higher decomposition voltage than magnesium chloride as the supporting salt.

The illustrated molten salt electrolytic cell 1 is arranged substantially along the depth direction (vertical direction in FIG. 1), and is provided in a partition wall 3 for partitioning the inside into an electrolytic cell 2a and a recovery chamber 2b, and an electrolytic cell 2a. It is provided with an electrode 4 including an anode 4a and a cathode 4b having portions arranged in parallel with the depth direction of the molten bath, and a lid 5 for covering the opening on the upper side of the molten salt electrolytic cell 1. Is. Although not shown, the molten salt electrolytic cell 1 may be further arranged in a recovery chamber 2b or the like and provided with a temperature adjusting tube or the like as a heat exchanger for adjusting the temperature of the molten bath.

Here, the inside of the molten salt electrolytic cell 1 is obtained by electrolysis in the electrolytic cell 2a located on the right side of FIG. 1 where the electrode 4 is arranged and the electrolytic cell 2a located on the left side by the partition wall 3. It is partitioned into a recovery chamber 2b where the metallic magnesium flows into the metal magnesium and the metallic magnesium accumulates on the upper side due to the density difference with the molten salt. Specifically, the partition wall 3 is arranged close to the lid 5 for covering the upper opening of the molten salt electrolytic cell 1. As a result, a molten salt circulation path 3a that enables the movement of the molten salt bath from the recovery chamber 2b to the electrolytic cell 2a is formed between the molten salt electrolytic cell 1 and the lower bottom portion. Further, the molten metal flow path 3b provided on the upper side of the partition wall 3 enables the inflow of metallic magnesium from the electrolytic chamber 2a to the recovery chamber 2b.

Further, here, the electrode 4 arranged in the electrolytic chamber 2a has at least an anode 4a and a cathode 4b connected to a power source or the like (not shown). Based on the reaction of MgCl ₂ → Mg + Cl ₂ , these anodes 4a and 4b generate chlorine gas by an oxidation reaction on the surface of the anode 4a and metallic magnesium by a reduction reaction on the surface of the cathode 4b.

If the electrode 4 has at least an anode 4a and a cathode 4b, magnesium chloride in the molten salt can be electrolyzed. On the other hand, from the viewpoint of improving the generation efficiency of electrolysis, as can be seen from the point shown in FIG. 2, the voltage between the anode 4a and the cathode 4b is not connected to the power source and is connected between the anode 4a and the cathode 4b. It is preferable to further have one or more, for example, two bipolar electrodes 4c that are polarized by the application of the above. However, such a bipolar electrode 4c is not always necessary. If necessary, insulating members such as refractory bricks can be provided below the anode 4a and the cathode 4b.

In the molten salt electrolysis when the illustrated molten salt electrolysis tank 1 was used, as shown in FIG. 1, the molten salt electrolysis flowed from the recovery chamber 2b to the electrolytic chamber 2a via the molten salt circulation path 3a on the bottom side due to the convection of the molten bath. Magnesium chloride in the molten salt is electrolyzed. As a result, metallic magnesium is produced in the molten state in the electrolytic chamber 2a. Then, this metallic magnesium flows into the recovery chamber 2b through the molten metal flow path 3b on the bath surface Sb side of the partition wall 3. After that, the metallic magnesium having a small specific gravity with respect to the molten salt floats in a shallow part of the recovery chamber 2b and accumulates there. The metallic magnesium surfaced in the recovery chamber 2b can be recovered by a pump or the like (not shown). In this case, the melt feed pipe 51, which will be described later, can be used. Therefore, according to this, metallic magnesium can be produced from a molten salt containing magnesium chloride. At the same time, chlorine gas is obtained.

(Aisle section structure)
In the molten salt electrolysis tank 1 described above, the inside is generally sealed with a lid 5 while the molten salt electrolysis is being performed. Therefore, normally, outside air hardly flows into the inside of the molten salt electrolytic cell 1. In addition, leakage of chlorine gas generated by electrolysis of magnesium chloride is prevented.
However, during the molten salt electrolysis, when replenishing magnesium chloride in the molten bath that is consumed as the electrolysis progresses, or when the metal generated by the electrolysis and accumulated on the bath surface Sb side of the recovery chamber 2b When recovering magnesium, it is necessary to insert a melt feed pipe used for supplying magnesium chloride and recovering metallic magnesium from the outside to the inside of the molten salt electrolytic tank 1. In many cases, the inside of the molten salt electrolytic cell 1 has a slightly depressurized atmosphere for the purpose of preventing the chlorine gas generated by electrolysis from leaking to the outside, so that it is opened when the melt feed pipe is inserted. Therefore, the outside air is easily drawn into the molten salt electrolytic cell 1. Conventionally, the wall thickness of the immersed portion of the anode 4a of the molten salt electrolytic cell 1 may be reduced. Oxygen enters the molten salt electrolytic cell from the outside by opening when the melt feed pipe is inserted, and magnesium oxide generated by this oxygen, chlorine gas, and graphite constituting the anode 4a immersed in the melting bath ( It is considered that the graphite reacts with C) to become carbon monoxide to reduce the thickness of the immersed portion of the anode, and further, it is considered that the electric resistance increases and the power loss increases due to the thinning.

In order to deal with this problem, in this embodiment, as shown in FIGS. 1 and 3, the molten salt electrolytic cell 1 is provided with a passage partition structure 11 for partitioning the passage 12 of the melt feed pipe inside the molten salt electrolytic cell 1. As shown in FIG. 1, it is desirable that the passage partition structure 11 is provided on the lid 5 in the molten salt electrolytic cell 1 because it is easy to install and is excellent in convenience.

The passage partition structure 11 will be described in detail later, but in addition to partitioning the passage 12 for the melt feed pipe, the passage partition structure 11 is one end side (vertical direction in FIGS. 1 and 3) of the main body 13 (in FIGS. 1 and 3). The open / closed end 14 on the upper end side) can be closed, and the open end 15 on the other end side (lower end side in FIGS. 1 and 3) can be sealed with the bath surface Sb of the melting bath. When the inside of the main body 13 is filled with an inert gas such as argon gas, the bath surface Sb of the melting bath is deeply located at the portion where the main body 13 is immersed. Further, in the passage section structure 11, the atmosphere inside the main body 13 can be adjusted by the vents 17a and 17b provided in the main body 13.
By inserting the melt feed pipe using such a passage partition structure 11, oxidation and nitriding of metallic magnesium in the melt bath at that time can be satisfactorily suppressed.

The passage partition structure 11 is a tubular body that extends substantially parallel to the depth direction of the molten bath from inside and outside the molten salt electrolytic cell 1 through a through hole 5a provided in the lid 5 on the recovery chamber 2b. A unit 13 is provided. Inside the main body 13, a passage 12 through which the melt feed pipe is inserted into the molten salt electrolytic cell 1 is defined. In this embodiment, the main body 13 has a single-layered tubular shape, but it is also possible to adopt a tubular shape having a multi-layered structure partially or entirely.

An opening / closing end portion 14 that is located outside the molten salt electrolytic cell 1 and can be opened / closed is provided on one end side of the main body portion 13 in the axial direction, and is located on the other end side by being immersed in a melting bath. An open end portion 15 is provided.

Here, although not shown, the opening / closing end portion 14 can be closed by, for example, placing and arranging a plate-shaped member that is not included in the passage partition structure 11. On the other hand, in the illustrated embodiment, a plate-shaped cover portion 18 capable of opening and closing the opening / closing end portion 14 is attached to the opening / closing end portion 14, and the passage section structure 11 includes the cover portion 18. .. It is preferable to provide a seal member (not shown) between the cover portion 18 and the opening / closing end portion 14 for suppressing the flow of gas from the gap between them when the cover portion 18 is closed.

Further, here, it is assumed that the open end portion 15 is arranged at a position deeper than the bath surface Sb of the molten bath when the molten bath is formed inside the molten salt electrolytic cell 1. As a result, the passage 12 inside the main body 13 is blocked from the space 1a inside the molten salt electrolytic cell 1. The molten salt electrolytic cell 1 is provided with a chlorine gas recovery port (not shown), and the space 1a inside the molten salt electrolytic cell 1 is constantly under negative pressure with respect to the external environment. Since the opening end portion 15 is arranged at a position deeper than the bath surface Sb of the melting bath, the inside of the passage 12 is partitioned from the internal space 1a, and the passage 12 is filled with an inert gas such as argon gas. Is possible. For example, in the depth direction of the molten bath, the distance De from the lower surface of the lid 5 to the end surface of the opening end 15 is the distance from the lower surface of the lid 5 to the bottom surface 2c of the recovery chamber 2b of the molten salt electrolytic tank 1. If it is 10% or more, it is recognized that the opening / closing end portion 14 is sufficiently immersed in the molten bath when the molten bath is formed inside the molten salt electrolysis tank 1 by general molten bath electrolysis. It may be preferable to position the end portion 15 in the storage region of metallic magnesium in the vicinity of the bath surface Sb of the melting bath.

The specific shape and structure of the connecting portion 16 is not particularly limited as long as the main body portion 13 can be attached to the lid 5 of the molten salt electrolytic cell 1 or the surrounding wall portion or the like. In the illustrated embodiment, the main body 13 is provided with a flange-shaped connecting portion 16 extending from the outer peripheral surface to the outer peripheral side. The main body 13 is provided with a plan view provided in the lid 5 through a through hole 5a having a circular shape or the like, and the connecting portion 16 is provided on a peripheral portion such as an annular shape around the through hole 5a. It can be abutted and attached to it by any fastening means such as a screw. Here, the flange-shaped connecting portion 16 penetrates on the outer peripheral side of the main body portion 13 in order to suppress the passage of gas between the inside and the outside of the molten salt electrolytic cell 1 at the connecting portion of the passage partition structure 11. It is preferably arranged on the lid 5 so as to cover the hole 5a.

The connecting portion 16 can connect the main body portion 13 to the molten salt electrolytic cell 1 as long as it is at least a part of the peripheral surface of the main body portion 13 in the circumferential direction and extends from the outer peripheral surface to the lid 5. If the connecting portion 16 is an annular shape or other annular shape formed over the entire circumference of the outer peripheral surface, the connecting portion 16 may seal the gap between the lid 5 and the main body portion 13. can. Alternatively, when the connecting portion 16 is formed in a rod shape or the like provided at a plurality of locations in the circumferential direction of the outer peripheral surface of the main body portion 13, for example, a hood or the like for sealing the gap between the lid body 5 and the main body portion 13. A seal member or the like can be provided separately.

The connecting portion 16 may connect the main body portion 13 so as to be removable from the molten salt electrolytic cell 1, but from the viewpoint of further suppressing the inflow of outside air from the connecting portion 16 into the molten salt electrolytic cell 1, the main body is used. It is preferable that the portion 13 is firmly connected so that it cannot be removed from the molten salt electrolytic cell 1.

Further, the main body 13 of the passage partition structure 11 is provided with vents 17a and 17b for passing an inert gas or other gas as needed. The vents 17a and 17b can be used to adjust the atmosphere inside the main body 13. In the illustrated embodiment, the two vents 17a and 17b are connected to a gas supply pipe 19a connected to an inert gas supply source (not shown) and a communication pipe 19b that communicates the inside of the main body 13 with the outside air, respectively. ing. In the middle of each of the gas supply pipe 19a and the communication pipe 19b made of carbon steel or stainless steel, valves 20a and 20b for controlling the flow rate of the gas flowing therein are provided. However, although not shown, the number of vents may be one or three or more, and in the case of one vent, the gas should pass through the same vent by using a pipe that branches in the middle. You can also. Even in this case, if at least one of the branched pipes is used as a gas supply pipe and an inert gas supply source is connected, the inert gas can be supplied to the inside of the main body 13 from the vent. Further, at least one of the branching pipes may be a communication pipe that communicates the inside of the main body 13 with the outside air.

By the way, the main body of the passage partition structure can be made movable with respect to the connecting portion with the molten salt electrolytic cell. As an example, the passage partition structure 31 of another embodiment shown in FIG. 4 has a main body portion 33 having a passage 32, an opening / closing end portion 34, a cover portion 38, and an opening end portion, which are substantially the same as the passage partition structure 11 described above. The 35 and the vents 37a and 37b are provided, but the main body 33 can be moved in the depth direction of the melting bath by changing the connecting portion 36.

More specifically, in the passage partition structure 31 of FIG. 4, the connecting portion 36 is located adjacent to the outer peripheral surface of the main body portion 33, and has an outer tubular body 36a having a shorter axial length than the main body portion 33. It includes a connecting member 36b that connects the outer cylinder 36a to the lid 5 of the molten salt electrolytic cell 1. The main body 33 is configured to be slidable in the axial direction with respect to the outer cylinder 36a. This makes it possible to change the position of the open end portion 35 of the main body 33 in the depth direction to a position corresponding to each of the steps in, for example, the magnesium chloride supply step and the metallic magnesium recovery step described later. Become.

(Manufacturing method of metallic magnesium)
In order to produce metallic magnesium, as described above, magnesium chloride is electrolyzed with a molten salt containing magnesium chloride in the molten salt electrolytic tank 1 as shown in FIG. 1, thereby producing metallic magnesium. .. Here, the passage partition structure 11 as described above can be used when supplying magnesium chloride to the melting bath for replenishment or when recovering the metallic magnesium produced by electrolysis. In addition to the through hole 5a in which the passage partition structure 11 is installed, the molten salt electrolytic cell 1 as shown in FIG. 1 further has an openable and closable through hole in the lid 5 on the recovery chamber 2b side, which is not shown. It may be a thing. In the case of such a structure, for example, one of the operations of supplying magnesium chloride to the molten bath and recovering the metallic magnesium contained in the molten bath is performed by using the passage partition structure 11, and the other operation is performed by the passage partition structure 11. It can be carried out in the through hole where is not installed. Since the work of supplying magnesium chloride may be carried out more frequently than the work of recovering the metallic magnesium, at least the work of supplying magnesium chloride may be carried out using the passage partition structure 11. ..

When the passage partition structure 11 is not used, for example, with the opening / closing end 14 closed as shown in FIG. 3, the valve 20a of the gas supply pipe 19a is opened and the inert gas is introduced through the vent 17a. It is supplied in advance to the inside of the main body 13. As a result, the inside of the main body 13 can be filled with the inert gas as the inert gas filling step for at least a predetermined period when the passage partition structure 11 is not used. At this time, it is desirable to close the valve 20b of the communication pipe 19b in order to prevent the outflow of the inert gas from the inside of the main body 13. During the inert gas filling step, the electrolysis of magnesium chloride may continue.
The inside of the main body 13 may contain metallic magnesium on the bath surface Sb side of the melting bath, but by filling it with an inert gas, the entry of metallic magnesium and the solidification of metallic magnesium there can be suppressed. Can be done. As shown in FIG. 3, the internal pressure of the main body 13 rises due to the inert gas filled in the main body 13, so that the position of the bath surface Sb in the arranged portion of the main body 13 is the end surface of the open end portion 15. It is down to the position. In this case, it is possible to prevent the metallic magnesium in the vicinity of the bath surface Sb from entering the main body portion 13 and solidifying.

Then, when the electrolysis progresses and the magnesium chloride in the molten bath is consumed, it may be necessary to supply magnesium chloride to the molten bath to replenish it. In such a case, the magnesium chloride supply step can be performed.
Further, when the metallic magnesium generated by electrolysis accumulates on the bath surface Sb side of the melting bath in the recovery chamber 2b, the metallic magnesium recovery step can be performed to recover the metallic magnesium.

In such a magnesium chloride supply step and a metallic magnesium recovery step, when the melt feed pipe 51 as shown in FIG. 5 is used for supply and recovery, the melt feed pipe 51 is placed inside the molten salt electrolytic tank 1. When inserting, as shown in the figure, it is inserted from the inside of the main body 13 of the passage partition structure 11. Then, in that state, in the magnesium chloride supply step, magnesium chloride as a melt is sent into the melt feed pipe 51 from a magnesium chloride supply source (not shown), and magnesium chloride is supplied to the melt bath. Further, in the metal magnesium recovery step, the metal magnesium as a melt contained in the melt bath is sucked and passed through the melt feed pipe 51 to recover the metal magnesium. An example of a specific usage mode of the passage partition structure 11 in the magnesium chloride supply step and the metallic magnesium recovery step is as described below.

In the magnesium chloride supply step and / or the metallic magnesium recovery step, first, the valve 20b of the communication pipe 19b is opened, and the inside of the main body 13 is communicated with the outside air through the ventilation port 17b. As a result, for example, when the inside of the main body 13 is filled with the inert gas in the above-mentioned inert gas filling step, the inert gas is released from the inside of the main body 13 to the outside via the communication pipe 19b. It is discharged and the internal pressure of the main body 13 can be reduced. As a result, when the opening / closing end portion 14 is opened next time, the high-temperature inert gas does not suddenly eject from the inside of the main body portion 13, so that the opening / closing end portion 14 can be safely opened.

Next, the opening / closing end portion 14 is opened by opening the cover portion 18 or the like, and the melt feed pipe 51 is inserted inside the main body portion 13 as shown in FIG. At this time, as shown in FIG. 5, it is preferable to immerse the tip of the melt feeding pipe 51 to a position deeper in the melting bath than the opening end 15. In this case, even if the metallic magnesium on the bath surface Sb side of the melting bath enters the inside of the main body 13 and solidifies, when the melt feeding pipe 51 is inserted, the operator is based on the insertion failure, and that is the case. It is possible to notice. As a result, when the melt is passed through the melt feed pipe 51 as described later, the risk of backflow of the melt such as magnesium chloride due to the solidification of the metallic magnesium inside the main body 13 can be removed.

The metallic magnesium produced by electrolysis is accumulated in a layer having a certain thickness near the bath surface Sb of the melting bath in the recovery chamber 2b. When recovering this metallic magnesium, it is better not to immerse the melt feed pipe 51 so deeply. However, also when recovering the metallic magnesium, it is preferable to immerse the tip of the melt feed pipe 51 to a position deeper in the melt bath than the open end 15. In this case, even if the metallic magnesium on the bath surface Sb side of the melting bath enters the inside of the main body 13 and solidifies, when the melt feeding pipe 51 is inserted, the operator is based on the insertion failure, and that is the case. It is possible to notice. As a result, it is possible to prevent the atmosphere containing nitrogen and oxygen from being mixed into the metallic magnesium recovery container (not shown) connected to the melt feed pipe 51. That is, it is possible to suppress the oxidation and nitriding of the metallic magnesium that is subsequently recovered, or the oxidation and nitriding of the metallic magnesium that is already stored inside the recovery container.
On the other hand, when supplying magnesium chloride, it is desirable to immerse the melt feed pipe 51 to a position deeper than the storage region of metallic magnesium in the vicinity of the bath surface Sb of the melt bath. In this case, the metallic magnesium near the bath surface Sb of the melting bath is less likely to be caught in the magnesium chloride supplied by the melt feeding pipe 51, so that a decrease in current efficiency can be suppressed.

Although not shown, a flange-shaped seal portion such as a disk-shaped seal portion extending toward the outer peripheral side can be provided on the outer surface of the melt feed pipe 51 in the middle of the longitudinal direction. In this case, when the melt feed pipe 51 is inserted inside the main body 13, the flange-shaped seal portion is brought into contact with the opening / closing end portion 14, so that the flange-shaped seal portion and the bath surface Sb of the melting bath are brought into contact with each other. The inside of the main body 13 can be sealed between the two.

After that, a melt of magnesium chloride or metallic magnesium is passed through a melt feed pipe 51 to supply magnesium chloride or recover the metallic magnesium.
Further, after that, the melt feeding pipe 51 is taken out from the inside of the main body portion 13, the cover portion 18 is closed, and the opening / closing end portion 14 is closed.

Here, after the magnesium chloride is supplied or the metallic magnesium is recovered by passing the melt through the melt feed pipe 51, the valve is before the opening / closing end portion 14 is closed or after the opening / closing end portion 14 is closed. The inert gas can be supplied to the inside of the main body 13 by opening 20a. In this case, the outside air that may flow into the main body 13 when the magnesium chloride is supplied or the metallic magnesium is recovered is before the vent 17b on the communication pipe 19b side where the valve 20b is open or the vent is blocked. If there is, the outside air discharged from the opening / closing end portion 14 and entering the inside of the main body portion 13 is replaced with the inert gas. Following this, the above-mentioned inert gas filling step is executed.

Next, the passage section structure of the present invention was prototyped and its effect was confirmed, which will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

(Example)
The passage partition structure 11 shown in FIG. 3 was produced, molten salt electrolysis was performed using the molten salt electrolytic cell 1 (see FIGS. 1 and 2) provided with the passage partition structure 11, and metallic magnesium was produced by electrolysis of magnesium chloride. During the molten salt electrolysis, when magnesium chloride is supplied to the molten bath in the molten salt electrolysis tank 1, as shown in FIG. 5, the melt feed pipe 51 is connected to the molten salt electrolysis tank from the inside of the passage partition structure 11. Magnesium chloride was supplied while being inserted inside 1.

In the supply of magnesium chloride, more specifically, first, the inside of the main body 13 was communicated with the outside air through the vent 17b of the passage partition structure 11. Next, the opening / closing end portion 14 was opened, the melt feed pipe 51 was inserted inside the main body portion 13, and then magnesium chloride was passed through the melt feed pipe 51. After that, the melt feed pipe 51 was taken out from the inside of the main body 13, and the opening / closing end 14 was closed. After supplying magnesium chloride from the melt feed pipe 51, the inert gas was supplied to the inside of the main body 13. As described above, during almost all the periods when the passage partition structure 11 was not used, the inside of the main body 13 was filled with the inert gas in a state where the opening / closing end 14 was closed.

The conditions for molten salt electrolysis are as follows. As the molten salt electrolytic cell 1, the one having an inner wall made of refractory bricks, an electrolytic cell 2a of 2 m ³ and a recovery chamber 2 b of 1 m ³ was used. A graphite anode 4a and a carbon steel cathode 4b were installed in the electrolytic chamber 2a, and two bipolar electrodes 4c were arranged between the anode 4a and the cathode 4b. Regarding the bath composition of the molten bath, MgCl ₂ , CaCl ₂ , NaCl, and MgF ₂ were made into molten salts having a mass ratio of 20%, 30%, 49%, and 1%, respectively, and operated for one year.

After the molten salt electrolysis was completed, the molten salt electrolytic cell 1 was disassembled and the anode 4a was taken out, and the amount of decrease in the thickness of the anode 4a with respect to the molten bath immersion portion of the anode 4a was evaluated. As a result, it was confirmed that the thickness of the anode 4a was reduced by 10 μm / day at the portion where the thickness was most reduced in the portion immersed in the melting bath.

(Comparative example)
The molten salt electrolysis was performed in substantially the same manner as in the examples, except that the molten salt electrolysis tank not provided with the passage partition structure 11 was used. Magnesium chloride was supplied to the molten bath by opening the lid on the recovery chamber of the molten salt electrolytic cell and inserting a melt feed pipe from there.

After the completion of the molten salt electrolysis, the thickness reduction amount of the portion where the thickness was most reduced in the portion immersed in the melting bath of the anode was 15 μm / day. It is considered that this is because oxygen flowed into the molten salt electrolytic cell from the outside due to the opening of the lid when the magnesium chloride was supplied, and the thickness of the anode was reduced.

From the above, it was found that according to the present invention, damage to the anode due to the inflow of outside air during the supply of magnesium chloride and the recovery of metallic magnesium in the molten salt electrolytic cell can be satisfactorily suppressed.

1 Molten salt electrolysis tank 1a Internal space 2a Electrolysis chamber 2b Recovery chamber 2c Bottom of recovery chamber 3 Partition 4 Electrode 4a Anode 4b Cathode 4c Bipolar electrode 5 Lid 11 Passage section structure 12 Passage for melt feed pipe 13 Main body 14 Opening and closing end 15 Opening end 16 Connecting part 17a, 17b Vent 18 Cover part 19a Gas supply pipe 19b Communication pipe 20a, 20b Valve 51 Melt feed pipe De Distance from the lower surface of the lid to the end face of the opening end Sb Melting Bath surface

Claims (10)

It is a passage partition structure provided in the molten salt electrolytic cell and partitioning the passage of the melt feed pipe inserted from the outside inside the molten salt electrolytic cell.
A tubular main body in which the passage is partitioned, an opening / closing end located on the outer side on one end side in the axial direction of the main body, and melting of the inside on the other end side in the axial direction of the main body. A passage partition structure including an opening end portion immersed in a bath, a connecting portion connecting the main body portion to the molten salt electrolytic cell, and a vent provided in the main body portion. Further, a gas supply pipe connected to the vent and connected to the inert gas supply source, and a communication pipe for communicating the inside of the main body with the outside air are further provided.
The passage partition structure according to claim 1, wherein each of the gas supply pipe and the communication pipe includes a valve. The passage partition structure according to claim 1 or 2, further comprising a cover portion attached to the opening / closing end portion and capable of opening and closing the opening / closing end portion. The connecting portion has a flange shape extending from the outer peripheral surface of the main body portion to the outer peripheral side at least a part in the circumferential direction of the outer peripheral surface.
3. The passage section structure according to any one item. In a molten salt electrolysis tank, magnesium chloride is electrolyzed in a molten salt bath containing magnesium chloride, and metallic magnesium is produced by the electrolysis.
A method for producing metallic magnesium using a molten salt electrolytic cell having the passage partition structure according to any one of claims 1 to 4. The metal according to claim 5, further comprising an inert gas filling step in which the inside of the main body is filled with the inert gas in a state where the opening / closing end is closed when the passage partition structure is not used. How to make magnesium. A magnesium chloride supply step of feeding magnesium chloride of the melt into a melt feed pipe inserted from the inside of the main body into the inside of the molten salt electrolytic cell to supply magnesium chloride to the melt bath, and / or.
The metal magnesium recovery step of recovering the metallic magnesium by sucking and passing the metallic magnesium of the melt contained in the molten bath through the molten metal feed pipe inserted from the inside of the main body to the inside of the molten salt electrolytic tank is included. , The method for producing metallic magnesium according to claim 5 or 6. Magnesium chloride supply process and / or metallic magnesium recovery process
Communicating the inside of the main body with the outside air through the vent.
Opening the opening / closing end and inserting the melt feed pipe inside the main body,
Passing the melt through the melt feed pipe and
The method for producing metallic magnesium according to claim 7, wherein the melt feed pipe is taken out from the inside of the main body portion and the opening / closing end portion is closed in this order. Magnesium chloride supply process and / or metallic magnesium recovery process
After passing the melt through the melt feed pipe and before closing the opening / closing end, or after closing the opening / closing end, the inert gas is supplied to the inside of the main body. The method for producing metallic magnesium according to claim 8, further comprising. 6. Manufacturing method of metallic magnesium.

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