JP6945398B2 - Molten salt electrolytic cell - Google Patents

Description

The present invention relates to a molten salt electrolytic cell used in a molten salt electrolysis method for obtaining metallic magnesium by electrolyzing a molten salt containing magnesium chloride.

Titanium metal is industrially produced based on titanium sponge produced by the Kroll process. The titanium sponge titanium manufacturing process by this Kroll process is roughly divided into four steps: a chloride distillation step, a reduction separation step, a crushing step, and an electrolysis step.

In the electrolysis step, which is one of these steps, magnesium chloride, which is a by-product of the reduction step of reducing titanium tetrachloride with metallic magnesium to produce sponge titanium, is electrolyzed by molten salt to regenerate metallic magnesium. It is a process to do.

Examples of the molten salt electrolytic cell used in the electrolysis step include, in Patent Document 1, a cathode having a prismatic space inside, a prismatic anode arranged inside the cathode, and the cathode and the anode. An electrolytic cell in which one or more bipolar poles arranged between the two poles are installed and the molten salt is electrolyzed, and a magnesium holding portion in which metallic magnesium generated by the electrolysis of the molten salt is held in the upper part. A molten salt electrolytic cell including a metal recovery chamber having a metal recovery chamber is disclosed.

Further, Patent Document 2 describes a cathode having a columnar space inside, a columnar anode arranged inside the cathode, and one or more duplexes arranged between the cathode and the anode. A molten salt electrolytic cell comprising an electrolysis chamber in which a Is disclosed.

In Patent Document 3, a flat cathode, a flat anode installed in parallel with the cathode, and one or more multiple poles arranged between the cathode and the anode are installed, and the molten salt is electrolyzed. A molten salt electrolytic cell comprising an electrolysis chamber to be decomposed and a metal recovery chamber having a magnesium holding portion for holding metallic magnesium generated by electrolysis of the molten salt is disclosed.

WO2017018441 WO 1996/033297 JP 2001-35589

However, in the production of titanium sponge, impurities in the metallic magnesium may be trapped in the titanium sponge during the reduction of titanium tetrachloride, so in the electrolysis process, simply reusing the metallic magnesium is possible. Not only is it required to produce high-purity metallic magnesium.

However, in the molten salt electrolytic cell disclosed in Patent Documents 1 to 3, there is a problem that impurities derived from the bricks constituting the electrolytic cell are mixed in the generated metallic magnesium.

Therefore, an object of the present invention is to provide a molten salt electrolytic cell capable of producing high-purity metallic magnesium.

The above problem is solved by the present invention shown below.
That is, the present invention (1) is constructed of refractory bricks, has one or more pairs of electrodes installed, an electrolysis chamber in which the molten salt is electrolyzed, and a metal generated by electrolysis of the molten salt in the upper part. A molten salt electrolyzer consisting of a metal recovery chamber having a magnesium holding portion for holding magnesium and a molten salt electrolyzer.
The upper part of the electrolysis chamber and the metal recovery chamber is separated by a partition wall.
At the lower part of the boundary between the electrolysis chamber and the metal recovery chamber, a molten salt inflow path for the molten salt to flow from the metal recovery chamber into the electrolysis chamber is formed, and the electrolysis chamber and the molten salt inflow path are formed. Above the molten salt inflow path at the boundary of the metal recovery chamber, a metal magnesium inflow path through which the metal magnesium and the molten salt produced in the electrolysis chamber flow into the metal recovery chamber is formed.
A shielding member made of carbon, silicon nitride, or silicon carbide is installed on a part or all of the wall surface of the magnesium holding portion that comes into contact with metallic magnesium.
The present invention provides a molten salt electrolytic cell characterized by the above.

Further, the present invention (2) comprises the molten salt electrolytic cell of (1), wherein the shielding member is installed on all the wall surfaces of the magnesium holding portion that come into contact with metallic magnesium. It is to provide.

Further, the present invention (3) is characterized in that a shielding member made of carbon, silicon nitride or silicon carbide is installed on a part or all of the wall surface forming the metallic magnesium inflow path (1) or. It provides the molten salt electrolytic cell of (2).

Further, the present invention (4) is characterized in that the material of the refractory brick is _{any one or more of Al 2} O ₃ , SiO ₂ , and Mg O (1) to (3). ) One of the molten salt electrolytic cells is provided.

According to the present invention, it is possible to provide a molten salt electrolytic cell capable of producing high-purity metallic magnesium.

It is a schematic perspective view which shows the morphological example of the molten salt electrolytic cell of this invention. FIG. 1 is a diagram showing a molten salt inflow path and a metallic magnesium inflow path of a molten salt electrolytic cell. It is an end view which cut the molten salt electrolytic cell in FIG. 1 by a vertical plane. It is an end view which cut the molten salt electrolytic cell in FIG. 1 by the vertical plane different from FIG. It is an end view which shows the form example of the installation method of a shielding member. It is a schematic end view of the form example of the molten salt electrolytic cell of this invention.

The molten salt electrolytic cell of the present invention is constructed of refractory bricks, has one or more pairs of electrodes installed, an electrolysis chamber in which the molten salt is electrolyzed, and a metal generated by electrolysis of the molten salt in the upper part. A molten salt electrolyzer consisting of a metal recovery chamber having a magnesium holding portion for holding magnesium and a molten salt electrolytic cell.
The upper part of the electrolysis chamber and the metal recovery chamber is separated by a partition wall.
At the lower part of the boundary between the electrolysis chamber and the metal recovery chamber, a molten salt inflow path for the molten salt to flow from the metal recovery chamber into the electrolysis chamber is formed, and the electrolysis chamber and the molten salt inflow path are formed. Above the molten salt inflow path at the boundary of the metal recovery chamber, a metal magnesium inflow path through which the metal magnesium and the molten salt produced in the electrolysis chamber flow into the metal recovery chamber is formed.
A shielding member made of carbon, silicon nitride, or silicon carbide is installed on a part or all of the wall surface of the magnesium holding portion that comes into contact with metallic magnesium.
It is a molten salt electrolytic cell characterized by.

The molten salt electrolytic cell of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic perspective view showing a morphological example of the molten salt electrolytic cell of the present invention, and is a molten salt electrolytic cell for producing metallic magnesium. FIG. 2 is a diagram showing a molten salt inflow path and a magnesium inflow path of the molten salt electrolytic cell in FIG. FIG. 3 is an end view of the molten salt electrolytic cell in FIG. 1 cut along a vertical plane, and is a diagram showing a state in which the molten salt electrolysis is performed in the molten salt electrolytic cell. FIG. 4 is an end view of the molten salt electrolytic cell in FIG. 1 cut by a vertical plane different from that in FIG. In FIG. 1, for convenience of explanation, only the outlines of the side wall 2 and the lid 4 are shown by dotted lines. Further, in FIG. 2, for convenience of explanation, the cathode on the magnesium inflow path side is described as the cathode.

As shown in FIGS. 1 to 3, the outside of the molten salt electrolytic cell 1 is composed of a side wall 2, a hearth 3, and a lid 4. The side wall 2 and the hearth 3 are constructed of refractory bricks, and the lid 4 is constructed of castable refractory. Further, although not shown, the lid 4 on the upper portion of the metal recovery chamber 22 has a magnesium recovery port and a molten metal for recovering the metallic magnesium stored in the magnesium holding portion 14 continuously, at regular intervals, or irregularly. When the amount of salt consumed by electrolysis is reduced, a molten salt replenishment port for replenishing the molten salt is formed in the molten salt electrolytic cell 1, and chlorine is formed on the lid 4 of the upper portion of the electrolysis chamber 21. A gas recovery port is formed, and a chlorine gas discharge pipe for discharging chlorine gas to the outside is attached.

The upper part inside the molten salt electrolytic cell 1 is separated into an electrolysis chamber 21 and a metal recovery chamber 22 by a partition wall 5. At the lower part of the boundary between the electrolysis chamber 21 and the metal recovery chamber 22, a molten salt inflow route 8 which is an inflow route for the molten salt to flow from the metal recovery chamber 22 into the electrolysis chamber 21 is formed. The portion above the molten salt inflow path 8 at the boundary between the electrolysis chamber 21 and the metal recovery chamber 22 is a path for the metallic magnesium and the molten salt produced in the electrolysis chamber 21 to flow into the metal recovery chamber. A metallic magnesium inflow path 7 is formed. The lower part of the electrolysis chamber 21 and the metal recovery chamber 22 refers to a portion below each partition wall 5. Further, the boundary between the electrolysis chamber 21 and the metal recovery chamber 22 is a position where the cathode 25 on the metal recovery chamber 22 side is installed from the vicinity of the position where the partition wall 5 is installed when viewed in the lateral direction. Refers to the range up to the vicinity.

On the upper side of the electrolysis chamber 21, one or more pairs of cathode 25 and anode 23, and one or more double poles 24 charged between the cathode 25 and the anode 23 are installed. The cathode 25, the anode 23, and the double electrode 24 are provided at the lower part of the electrode support portion 151 provided on the lower side of the side wall 2 side of the electrolysis chamber 21, and the lower part of the boundary portion between the electrolysis chamber 21 and the metal recovery chamber 22. By being installed on the electrode support portion 152, it is installed on the upper side of the electrolysis chamber 21. Therefore, the electrolysis chamber 21 has a molten salt holding portion 26 on the lower side.

On the upper side of the metal recovery chamber 22, a magnesium holding portion 14 for holding metallic magnesium is provided. Further, a molten salt holding portion 27 is provided below the metal recovery chamber 22. Then, in the magnesium holding portion 14, the metallic magnesium flowing in from the electrolysis chamber 21 is held in a state of floating on the magnesium chloride of the molten salt holding portion 27 of the metal recovery chamber 22, so that the side wall 2 is held. Metallic magnesium comes into contact with the portion surrounding the magnesium holding portion 14 and the partition wall 5. Therefore, carbon shielding members 6a, 6c, and 6d are installed on the wall surface of the side wall 2 surrounding the magnesium holding portion 14, and the wall surface of the partition wall 5 surrounding the magnesium holding portion 14 is made of carbon. Shielding member 6b is installed.

As shown in FIG. 4, when molten salt electrolysis is being performed, the molten salt 11 containing magnesium chloride is used in the cathode 25, the anode 23, and the multi-pole 24 on the upper side of the electrolysis chamber 21 of the molten salt electrolytic cell 1. Is electrolyzed. Therefore, in the molten salt electrolytic tank 1, the molten salt 11 is electrolyzed in the vicinity of the cathode 25, the anode 23, and the compound pole 24 on the upper side of the electrolysis chamber 21 to generate molten magnesium and chlorine gas, both of which are molten salts. Since the specific gravity is smaller, a flow of molten salt that moves upward is generated, the molten salt 11 on the lower side of the electrolysis chamber 21 moves upward, and the movement of the molten salt causes the molten salt to move to the lower side of the metal recovery chamber 22. A flow 111 of molten salt is generated in which a certain molten salt 11 moves to the lower side of the electrolysis chamber 21 through the molten salt inflow path 8. Then, a flow 101 of metallic magnesium in which the metallic magnesium 10 and the molten salt generated by electrolysis on the upper side of the electrolysis chamber 21 move to the upper side of the metal recovery chamber 22 through the metallic magnesium inflow path 7 is generated. The metallic magnesium 10 that has moved to the upper side of the metal recovery chamber 22 is held by the magnesium holding portion 14 at the upper part of the metal recovery chamber 22. Further, since the chlorine gas 12 is also generated together with the metallic magnesium 10 by the electrolysis of the molten salt 11, the generated chlorine gas 12 is discharged to the outside by the chlorine gas recovery port and the chlorine gas discharge pipe formed on the lid 4 (not shown). It is discharged.

At this time, the metallic magnesium 10 held by the magnesium holding portion 14 holds the shielding members 6a, 6c, 6d and the magnesium holding portion 14 of the partition wall 5 installed on the wall surface of the portion surrounding the magnesium holding portion 14 of the side wall 2. It is in contact with the shielding member 6b installed on the wall surface of the surrounding portion. Since the shielding members 6a, 6b, 6c, and 6d have lower reactivity with metallic magnesium than the fire-resistant bricks for which the side wall 2 and the partition wall 5 are constructed, the molten salt electrolytic tank 1 is fire-resistant for constructing the side wall and the partition wall. When the brick reacts with the metallic magnesium, it is possible to prevent the problem that impurities derived from the refractory brick are eluted in the metallic magnesium.

The molten salt electrolytic cell of the present invention is constructed of refractory bricks, has one or more pairs of electrodes installed, an electrolysis chamber in which the molten salt is electrolyzed, and a metal generated by electrolysis of the molten salt in the upper part. A molten salt electrolyzer consisting of a metal recovery chamber having a magnesium holding portion for holding magnesium and a molten salt electrolytic cell.
The upper part of the electrolysis chamber and the metal recovery chamber is separated by a partition wall.
At the lower part of the boundary between the electrolysis chamber and the metal recovery chamber, a molten salt inflow path for the molten salt to flow from the metal recovery chamber into the electrolysis chamber is formed, and the electrolysis chamber and the molten salt inflow path are formed. Above the molten salt inflow path at the boundary of the metal recovery chamber, a metal magnesium inflow path through which the metal magnesium and the molten salt produced in the electrolysis chamber flow into the metal recovery chamber is formed.
A shielding member made of carbon, silicon nitride, or silicon carbide is installed on a part or all of the wall surface of the magnesium holding portion that comes into contact with metallic magnesium.
It is a molten salt electrolytic cell characterized by.

The molten salt electrolytic cell of the present invention is constructed of refractory bricks. For example, the side wall of the molten salt electrolytic cell of the present invention, the hearth, the partition wall between the electrolysis chamber and the metal recovery chamber, the support member for the electrode, and the like are made of refractory brick. The refractory brick may be any one having heat resistance to a temperature of 650 to 800 ° C. and corrosion resistance to molten salt and magnesium produced metal, and the material of the refractory brick is usually a molten salt electrolytic tank. The material of the refractory brick is not particularly limited as long as it is used as the construction material of the _{above, and examples thereof include Al 2} O ₃ brick, SiO ₂ brick, Mg O brick, and a combination of two or more of these. Be done.

The side wall and hearth of the molten salt electrolytic cell of the present invention may have a double structure in which the inside is constructed of refractory bricks and the outside is constructed of heat insulating bricks. The material of the heat insulating brick is not particularly limited as long as it is usually used as a material for constructing a molten salt electrolytic cell, for example, Al ₂ O ₃ brick, SiO ₂ brick, Mg O brick, and 2 of these. Combinations of more than seeds can be mentioned.

The lid is constructed of castable refractory. A chlorine gas recovery port is formed in the portion of the lid that closes the top of the electrolysis chamber, and a chlorine gas recovery pipe is attached. Further, a magnesium recovery port and a molten salt supply port are formed in a portion of the lid that closes the top of the metal recovery chamber.

The inside of the molten salt electrolytic cell of the present invention is separated into an electrolysis chamber and a metal recovery chamber by a partition wall.

A pair or more of cathodes and anodes are installed above the electrolysis chamber. The electrode may be a horizontal type, a cylindrical type, or a square pillar type. The shape of the electrode is preferably a shape having a large area in contact with the molten salt in that the amount of energization can be increased. Further, one or more double poles are charged and installed between the cathode and the anode. The material of the cathode and the material of the anode are not particularly limited as long as they have excellent electrical conductivity and chemical durability against chlorine gas and high-temperature molten salt, and the combination of the material of the cathode and the material of the anode is particularly limited. Not limited. Examples of the material of the cathode include iron, graphite and the like. Further, as the material of the anode, for example, graphite and the like can be mentioned. The material of the multi-pole is not particularly limited as long as it has excellent electrical conductivity and chemical durability against chlorine gas and high-temperature molten salt, and examples thereof include graphite.

The cathode, anode and duplex are supported above the electrolysis chamber by suitable supports such as support members and supports formed on side walls or bulkheads. Therefore, the electrolysis chamber has a molten salt holding portion on the lower side.

The metal recovery chamber has a magnesium holding portion at the upper part, which holds a metal produced by electrolysis of the molten salt. The magnesium holding portion is formed in the metal recovery chamber above the position of the outlet of the metallic magnesium inflow path. Further, the metal recovery chamber has a molten salt holding portion on the lower side.

Of the wall surface of the magnesium holding portion, a shielding member is installed on a part or all of the wall surface that comes into contact with metallic magnesium. The content of impurities derived from refractory bricks in the metallic magnesium generated by molten salt electrolysis because the shielding member is installed on a part or all of the wall surface of the magnesium holding portion that comes into contact with the metallic magnesium. Can be reduced. If the shielding member is installed on a part of the wall surface of the magnesium holding portion that comes into contact with metallic magnesium, the content of impurities derived from the refractory brick in the metallic magnesium generated by molten salt electrolysis is reduced. However, when the shielding member is installed on a part of the wall surface of the magnesium holding portion that comes into contact with the metallic magnesium, the outlet of the metallic magnesium inflow path is formed in the wall surface of the magnesium holding portion. It is preferable that the shielding member is installed on the wall surface on the side facing the wall surface. Then, the fact that the shielding member is installed on all the wall surfaces of the magnesium holding portion in which the metallic magnesium comes into contact determines the content of impurities derived from the refractory brick in the metallic magnesium generated by the molten salt electrolysis. It is particularly preferable in that the effect of being able to reduce the amount is increased.

The shielding member needs to have resistance to the generated metallic magnesium and the molten salt, and also have heat resistance to the temperature of the molten salt at the time of molten salt electrolysis. The material of the shielding member is carbon, silicon nitride or silicon carbide. As the material of the shielding member, carbon is preferable because it can be easily formed into a large shape. The shielding member may have a porous structure, but the pore size and porosity may be such that the produced metallic magnesium does not permeate. The porosity of the shielding member is preferably 40% or less. When the shielding member is a sintered body of particles made of the material of the shielding member, the structure is porous, and the porosity of the shielding member in that case is preferably 5 to 40%, particularly preferably 5 to 25. %.

The shape and thickness of the shielding member are appropriately selected depending on the structure of the magnesium holding portion and the like. For example, a plate shape, a cylindrical shape, and a square tubular shape can be mentioned.

The shielding member may be further installed on the wall surface forming the metallic magnesium inflow path. Further, by installing the shielding member on the wall surface forming the metal magnesium inflow path, there is an effect that the content of impurities derived from the refractory brick in the metal magnesium generated by molten salt electrolysis can be reduced. It gets higher.

The method of installing the shielding member on the refractory brick for constructing the molten salt electrolytic cell is not particularly limited, and the method of fixing the shielding member to the wall surface of the refractory brick with bolts, the refractory brick at the installation site of the shielding member is hollowed out, and the hollowed out portion is used. Examples thereof include a method of fitting a shielding member, a method of providing a supporting portion of the shielding member on a refractory brick, and a method of placing the shielding member on the supporting portion. For example, when the shielding member has a square cylinder shape, a support portion for placing the shielding member on the four wall surfaces surrounding the magnesium holding portion is provided, and the square cylinder-shaped shielding member is placed on the support portion. There is a way to put it.

In the embodiment shown in FIGS. 1 to 4, the shielding member 6b is installed in contact with the partition wall 5, but the present invention is not limited to this. For example, as in the embodiment shown in FIG. 5, if the lower end of the shielding member 6b is in contact with the partition wall 5 and the generated metal does not flow between the shielding member 6b and the partition wall 5, the shielding member 6b There may be a gap 20 between the partition wall 5 and the partition wall 5. That is, in the present invention, there may be no gap between the shielding member and the wall surface of the molten salt electrolytic cell in the portion where the shielding member is installed, or the portion where the shielding member and the shielding member are installed. As long as the generated metallic magnesium does not flow into the wall surface of the molten salt electrolytic cell, there may be a gap between the shielding member and the wall surface of the molten salt electrolytic cell where the shielding member is installed. The gap between the shielding member and the wall surface of the molten salt electrolytic cell where the shielding member is installed serves as a buffering gap when the wall surface of the molten salt electrolytic cell thermally expands.

A molten salt inflow path, which is an inflow path for molten salt to flow from the metal recovery chamber to the electrolysis chamber, is formed in the lower part of the boundary between the electrolysis chamber and the metal recovery chamber. Above the molten salt inflow path at the boundary between the electrolysis chamber and the metal recovery chamber, a metal magnesium inflow path is formed, which is a route for the metal magnesium and molten salt generated in the electrolysis chamber to flow into the metal recovery chamber. Has been done.

The structure of the partition wall, the molten salt inflow path, and the metal magnesium inflow path is not particularly limited, and the partition wall separates the electrolysis chamber and the metal recovery chamber, and a magnesium holding portion is formed in the upper part of the metal recovery chamber. The molten salt in the molten salt holding section on the lower side of the metal recovery chamber moves to the molten salt holding section on the lower side of the electrolysis chamber through the molten salt inflow path, and passes through the metal magnesium inflow path to the electrolytic decomposition chamber. The structure may be such that the metallic magnesium and the molten salt produced in the above can be moved to the metal recovery chamber.

For example, in the embodiment shown in FIG. 6, the partition wall 5 is provided and the metal magnesium inflow path 71 is formed. In the embodiment shown in FIG. 6, the metal recovery chamber 22 has a magnesium holding portion 14 at the upper portion, and shielding members 6a and 6b are installed on the wall surface of the portion of the magnesium holding portion 14 where the metal magnesium contacts. ing. Further, a molten salt inflow path 81 is formed.

In the molten salt electrolysis tank of the present invention, since a shielding member having low reactivity with the generated metallic magnesium is installed on a part or all of the wall surface of the magnesium holding portion, the produced metallic magnesium reacts with the refractory brick. Since the impurities generated by the above can be prevented from being eluted into the produced metallic magnesium, the molten salt electrolyzer of the present invention can produce high-purity metallic magnesium.

The molten salt that undergoes molten salt electrolysis in the molten salt electrolysis tank of the present invention may be a molten salt that is electrolyzed by applying a voltage to produce metallic magnesium, and is a molten salt containing magnesium chloride. That is, the molten salt electrolysis tank of the present invention is a molten salt electrolysis tank for producing metallic magnesium that electrolyzes a molten salt containing magnesium chloride to produce metallic magnesium.

The molten salt containing magnesium chloride is known to contain one or more of potassium chloride, calcium chloride and sodium chloride for adjusting the electrical conductivity, the specific gravity, the melting point, and the like. In addition to magnesium chloride, potassium chloride, calcium chloride and sodium chloride, molten salts containing magnesium chloride include magnesium fluorides, hydroxides, magnesium salts such as carbonates and nitrates, magnesium oxide, and metallic magnesium. It may be included.

Molten salts containing magnesium chloride include 10 to 30% by mass of magnesium chloride, 20 to 40% by mass of calcium chloride, and 40 to 60% by mass in terms of electrical conductivity, specific gravity, melting point, vapor pressure, and viscosity. Molten salt containing% sodium chloride is preferred, with 20 ± 5% by weight magnesium chloride, 30 ± 5% by weight calcium chloride, 49 ± 5% by weight sodium chloride, and 1 ± 1% by weight. A molten salt containing magnesium chloride and is particularly preferable.

Hereinafter, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention.

(Preparation of molten salt electrolytic cell)
The molten salt electrolytic cell having the structure shown in FIGS. 1 to 4 was prepared, and the molten salt electrolytic cell having the detailed shape shown below was produced.
<Structure of molten salt electrolytic cell>
-Refractory bricks: HIGH ROZX-98, Al ₂ O ₃ manufactured by Rosai Kogyo Co., Ltd. 98.0% by mass, SiO ₂ 0.5% by mass
-Mortar: HR95 mortar manufactured by Rosai Kogyo Co., Ltd., Al ₂ O ₃ by 95.0 mass, SiO ₂ by 3 mass%
・ Electrolysis room: 2m ³
・ Metal collection room: 1m ³
-Material of shielding member: carbon (porosity 25%), silicon nitride (porosity 10%) or silicon carbide (porosity 5%)
-Dimensions of the shielding member: height 0.4 m, thickness 10 mm
-Installation position of the shielding member: All four surfaces surrounding the magnesium holding portion (described as four surfaces in Table 1), or the wall surface of the magnesium holding portion facing the wall surface on which the outlet of the metallic magnesium inflow path is formed. One of only one wall surface on the side to be used (described as one surface in Table 1).
-Number of unit electrolysis cells: 2
-Anode material: Graphite-Cathode material: Iron-Double pole material: Graphite-Number of double poles between cathode and anode: 2

(Examples 1 to 4, Comparative Example 1)
To the molten salt electrolytic cell produced as described above, 2900 kg of a molten salt having a composition of 20% by mass of _{MgCl 2 , 30% by mass of CaCl 2} , 49% by mass of NaCl, and _{1% by mass of MgF 2 was charged.}
Then, the molten salt was electrolyzed for 6 months under the conditions shown below. While the electrolysis of the molten salt is being continued, in order to replenish magnesium chloride corresponding to the amount of metallic magnesium produced, magnesium chloride, which is a by-product of the chlor method, is supplied to the electrolytic tank as a replenished molten salt. The content of magnesium chloride in the molten salt was adjusted to be 15 to 25% by mass.
Mg samples were taken 5 days and 6 months after the start of electrolysis of the molten salt, and the contents of Al and Si in Mg were measured. In addition, the amount of thinning of the refractory brick in the magnesium holding portion and the amount of thinning of the shielding member were measured 6 months after the start of electrolysis of the molten salt. The results are shown in Table 1.
In Table 1, in Comparative Example 1, the shielding member was not installed.

<Melted salt electrolysis conditions>
-Molten salt temperature: 660 ° C on average
・ Applied voltage: 10V
-Current density: 0.48 A / cm ²
-Theoretical Mg production: 21.8 kg / hour-Supply molten salt: Magnesium chloride produced by the Kroll process,

＊）耐火レンガの減肉量は、遮蔽部材を設置していない面の耐火レンガの減肉量

*) The amount of thinning of refractory bricks is the amount of thinning of refractory bricks on the surface where no shielding member is installed.

1 Molten salt electrolytic tank 2 Side wall 3 Hearth 4 Lid 5 Partition 6a, 6b, 6c, 6d Shielding members 7, 71 Metal magnesium inflow path 8, 81 Molten salt inflow path 10 Metal magnesium 11 Molten salt 12 Chlorine gas 14 Magnesium holding part 20 Gap 21 Electrolysis chamber 22 Metal recovery chamber 23 Anode 24 Double pole 25 Cathode 26, 27 Molten salt holding part 101 Molten salt flow 111 Molten salt flow 151, 152 Electrode support part

Claims (7)

It is constructed of refractory bricks, has one or more pairs of electrodes installed, an electrolysis chamber in which the molten salt is electrolyzed, and a magnesium holding part in the upper part where the metallic magnesium generated by the electrolysis of the molten salt is held. A molten salt electrolyzer consisting of a metal recovery chamber and a molten salt electrolyzer.
The upper part of the electrolysis chamber and the metal recovery chamber is separated by a partition wall.
At the lower part of the boundary between the electrolysis chamber and the metal recovery chamber, a molten salt inflow path for the molten salt to flow from the metal recovery chamber into the electrolysis chamber is formed, and the electrolysis chamber and the molten salt inflow path are formed. Above the molten salt inflow path at the boundary of the metal recovery chamber, a metal magnesium inflow path through which the metal magnesium and the molten salt produced in the electrolysis chamber flow into the metal recovery chamber is formed.
Of a wall surface of the magnesium holder, a part or the whole of the wall surface which metallic magnesium is contacted, the carbon emissions or the shielding member made of silicon carbide is provided,
A molten salt electrolytic cell characterized by. The molten salt electrolytic cell according to claim 1, wherein the shielding member is installed on all the wall surfaces of the magnesium holding portion that come into contact with metallic magnesium. Some or all of the wall surface forming the metallic magnesium inflow path, carbon emissions or molten salt electrolysis according to claim 1 or 2 any one of claims, characterized in that the shielding member made of silicon carbide is provided Tank. The molten salt electrolytic cell according to any one of claims 1 to ₃ , wherein the material of the refractory brick is _{any one or more of Al 2} O 3, SiO _{2 and Mg O.} The molten salt electrolytic cell according to any one of claims 1 to 4, wherein the shielding member is a sintered body, and the porosity of the shielding member is 5 to 25%. The molten salt electrolytic cell according to any one of claims 1 to 5, wherein the shielding member has a thickness of 10 mm or more. The molten salt electrolytic cell according to any one of claims 1 to 6, wherein there is a gap between the shielding member and the wall surface of the molten salt electrolytic cell in which the shielding member is installed.

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