JP2024094070A - Molten salt electrolysis apparatus and method for producing titanium-based electrodeposits - Google Patents

Abstract

The present invention provides a molten salt electrolysis apparatus capable of efficiently producing a titanium-based electrodeposit through electrolytic refining of a crude titanium-based material containing Ti, Al, and O, and a method for producing a titanium-based electrodeposit.
[Solution] The molten salt electrolysis device 1 is equipped with an electrolytic cell that performs electrolytic refining by using electrodes 61 including an anode 61a and a cathode 61b to dissolve Ti from a crude titanium-based material in the anode in a molten salt bath and deposit a refined titanium-based material on the cathode, wherein the crude titanium-based material contains Ti, Al, and O and is conductive, the electrodes include a portion in which electrode plates 62 that function as either an anode or a cathode are arranged alternately, the electrolytic cell has two or more openings 3a, 3b that can be opened and closed connecting the inside and outside, and the two or more openings include at least a first opening 3a used for discharging gas, and a second opening 3b that is located deeper in the depth direction of the electrolytic cell than the first opening and is used for discharging at least molten salt.
[Selected Figure] Figure 1

Description

This invention relates to a molten salt electrolysis device equipped with an electrolytic cell that performs electrolytic refining by dissolving Ti from a crude titanium-based material in an anode in a molten salt bath and depositing a refined titanium-based material on a cathode, and a method for producing a titanium-based electrodeposit using the same.

Titanium metal and titanium alloys are generally manufactured by a method based on the Kroll process, which is suitable for mass production. However, this method requires the chlorination of titanium ore, the subsequent purification of titanium tetrachloride, and the reduction of titanium tetrachloride with metallic magnesium. It also requires the crushing of titanium sponge lumps and the electrolysis of the magnesium chloride produced by the reduction, and involves many batch steps, so it is difficult to say that titanium metal can be manufactured efficiently and at low cost.

In contrast, electrolytic refining using a molten salt bath may make it easier to produce titanium metal with fewer impurities than the Kroll process.

As an example of this type of technology, Patent Document 1 describes a method for extracting a titanium product from titanium ore, the method comprising the steps of: mixing a chemical blend containing titanium ore and a reducing agent, the ratio of the titanium ore to the reducing agent being 0.9 to 2.4, the mass ratio of the titanium oxide component in the titanium ore to the reducing agent being equivalent to 0.9 to 2.4; heating the chemical blend to start an extraction reaction, the chemical blend being heated at a heating rate of 1° C. to 50° C./min; heating the chemical blend at a reaction temperature of 1500 to 1800° C. for a time between 5 and 30 minutes; maintaining the chemical blend at a temperature below 1670°C; cooling the chemical blend to a temperature below 1670°C; and separating the titanium product from the residual slag," the document states, "including the steps of placing the titanium product in a reaction vessel having an anode, a cathode and an electrolyte; heating the reaction vessel to a temperature of between 600°C and 900°C to produce a molten mixture and applying an electrical differential between the anode and cathode to deposit titanium ions on the cathode; and terminating the electrical differential and cooling the molten mixture to produce a refined titanium product; wherein the refined titanium product has a surface area of at least 0.1 ^m2 /g."

JP 2015-507696 A

In electrolytic refining using a molten salt bath, a crude titanium-based material containing Ti, Al, and O and having electrical conductivity is used as the anode in the molten salt bath in an electrolytic cell, and a voltage is applied between the anode and cathode. This causes mainly Ti to dissolve from the crude titanium-based material in the anode, while a refined titanium-based material with a higher purity than the crude titanium-based material is precipitated on the cathode, producing a titanium-based electrolytic deposit.

Here, in order to industrially mass-produce titanium-based electrodeposits, it is preferable to arrange electrode plates, each functioning as either an anode or a cathode, in an alternating array. If the electrodes are in such a plate shape (i.e., electrode plates), it is possible to ensure a wide electrodeposition surface of the cathode facing the anode on which the refined titanium-based material is deposited. Furthermore, it is possible to arrange a relatively large number of electrode plates in an electrolytic cell of a given volume. As a result, the use of electrode plates makes it possible to increase the total area of the electrodeposition surface of the cathode in the electrolytic cell, facilitating mass production of refined titanium-based materials.

When electrolytic refining is continued, the refined titanium-based material that precipitates on the cathode gradually grows. In particular, when the anode and cathode are arranged so that the distance between the electrodes is short in order to reduce the effect of electrical resistance in the molten salt bath and increase productivity, the distance over which the current flows through the molten salt bath is shortened, and power loss due to the resistance of the molten salt bath can be reduced. However, there is a risk that a short circuit will occur within a relatively short period of time due to contact between the refined titanium-based material growing on the cathode and the anode, making it impossible to continue electrolytic refining. For this reason, the duration of electrolytic refining cannot be extended very long.

Therefore, in order to mass-produce titanium-based electrodeposits, it is desirable to continue electrolytic refining for a certain period of time, then replace the electrode plates that function as anodes and cathodes, and continue to produce titanium-based electrodeposits by repeating this replacement.

However, after electrolytic refining, it is necessary to remove the electrode plate from the molten salt bath and remove the molten salt residue adhering to the refined titanium-based material on the cathode. At this time, it is desirable to prevent the high-temperature cathode and the refined titanium-based material deposited there from coming into contact with the atmosphere as much as possible in order to suppress an increase in the O content due to oxidation. Such removal of the electrode plate and removal of the residue are one of the factors that reduce the efficiency of mass production of titanium-based electrodeposits.

The object of this invention is to provide a molten salt electrolysis apparatus capable of efficiently producing titanium-based electrodeposits through electrolytic refining of crude titanium-based material containing Ti, Al, and O, and a method for producing titanium-based electrodeposits.

The molten salt electrolysis device of the present invention is equipped with an electrolytic cell that performs electrolytic refining by using electrodes including an anode and a cathode to dissolve Ti from a crude titanium-based material of the anode in a molten salt bath and deposit a refined titanium-based material on the cathode, the crude titanium-based material containing Ti, Al, and O and having electrical conductivity, the electrodes including a portion in which electrode plates functioning as either the anode or the cathode are arranged alternately, the electrolytic cell has two or more openings that can be opened and closed to connect the inside and the outside, the two or more openings including at least a first opening used to discharge gas, and a second opening located deeper in the depth direction of the electrolytic cell than the first opening and used to discharge at least the molten salt.

It is preferable that the molten salt electrolysis device has a plurality of the electrolytic cells, and that one of the plurality of electrolytic cells can be connected to the other electrolytic cells through the first communication port.

In this case, it is preferable that a pressure reducing device can be connected to at least one of the communication ports of the other electrolytic cell, and the other electrolytic cell is used as a molten salt condenser.

The communication port of the other electrolytic cell includes at least a third communication port used for reducing pressure, and a pressure reducing device can be connected to the third communication port.

It is preferable that the above-mentioned molten salt electrolysis device is equipped with a pressure reducing device that can be connected to at least one of the communication ports.

The molten salt electrolysis device preferably includes a temperature regulator disposed inside the electrolytic cell to adjust at least the temperature of the cathode.

The temperature regulator is a heat exchanger, and is preferably installed at the bottom of the electrolytic cell, at least directly below the cathode.

It is preferable that the above-mentioned molten salt electrolysis device is provided with an electrode holding mechanism that holds the electrode plate and is capable of moving the electrode plate between the inside and outside of the electrolytic cell.

The electrode holding mechanism preferably has a holding rod provided for each electrode plate, extending in the vertical direction to suspend and hold each electrode plate, and a lifting plate located above the holding rod and outside the electrolytic cell, to which each of the holding rods is attached.

The molten salt electrolysis apparatus preferably includes an electrical connection mechanism that electrically connects a power source and the electrode plate, and the electrical connection mechanism preferably includes a conductor that is located outside the electrolytic cell and connected to the power source, and an electrically conductive member that extends vertically in parallel with the holding rod and connects the electrode plate to the conductor.

It is preferable that 2 to 100 of the electrode plates can be arranged inside the electrolytic cell.

The method for producing a titanium-based electrodeposit of the present invention is a method for producing a titanium-based electrodeposit by electrolytic refining using any of the above-mentioned molten salt electrolysis devices, and includes an electrolysis step in which, inside the electrolysis cell, Ti is dissolved from the crude titanium-based material of the anode in a molten salt bath and a refined titanium-based material is precipitated on the cathode, a molten salt discharge step in which, after the electrolysis step, the molten salt inside the electrolysis cell is discharged to the outside through the second communication port, and, after the molten salt discharge step, the gas inside the electrolysis cell is discharged through the first communication port while the refined titanium-based material on the cathode is heated, and a residue separation step in which the residue of the molten salt is separated from the refined titanium-based material.

In the above-mentioned method for producing titanium-based electrolytic deposits, it is preferable that, prior to carrying out the residue separation step, one electrolytic cell used in the electrolysis step and the molten salt discharge step is connected to another electrolytic cell used as a molten salt condenser through the first communication port, and the communication port of the other electrolytic cell is connected to a pressure reducing device, and in the residue separation step, the pressure reducing device creates a reduced pressure atmosphere inside the one electrolytic cell through the inside of the other electrolytic cell, and the molten salt residue is cooled and recovered inside the other electrolytic cell.

In this case, after the residue separation process, the electrolysis process can be carried out using the other electrolytic cell.

According to this invention, it is possible to efficiently produce titanium-based electrodeposits by electrolytic refining of crude titanium-based material containing Ti, Al, and O.

1 is a cross-sectional view taken along the depth direction of an electrolytic cell, showing a molten salt electrolysis apparatus according to an embodiment of the present invention together with electrodes. FIG. 2 is a cross-sectional view taken along the depth direction of the electrolytic cell, showing the molten salt electrolysis apparatus of FIG. 1 in a state after electrolytic refining. 3 is a cross-sectional view taken along the depth direction of the electrolytic cell, showing a state in which the electrolytic cell of the molten salt electrolysis apparatus of FIG. 2 is connected to another electrolytic cell after the molten salt is discharged. FIG. FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. 4 is a cross-sectional view taken along the depth direction of the electrolytic cell, showing a state in which an electrode plate is removed from the electrolytic cell of the molten salt electrolysis apparatus of FIG. 3. [0023] FIG.

The following describes in detail an embodiment of the present invention with reference to the drawings. Note that the drawings are schematic illustrations of an example of an embodiment for ease of understanding, and the dimensions and shapes of each part in the drawings, the number of components such as electrodes, and other aspects may be modified as appropriate.

(Molten salt electrolysis equipment)
The molten salt electrolysis apparatus 1 illustrated in Fig. 1 includes an electrolytic cell 2. In the electrolytic cell 2, using electrodes 61 including an anode 61a and a cathode 61b, electrolytic refining is performed in which Ti is eluted from the crude titanium-based material of the anode 61a in a molten salt bath Bm and a refined titanium-based material is deposited on the cathode 61b.

This electrolytic refining is performed for the purpose of obtaining a refined titanium-based material having a higher purity than the crude titanium-based material from the crude titanium-based material. The crude titanium-based material contains elements such as Ti (titanium), Al (aluminum), and O (oxygen), as well as elements generally contained in ores such as Fe (iron) and Si (silicon), and is conductive, and is included in the anode 61a as a part or all of the anode 61a. As shown in FIG. 1, when a voltage is applied between the anode 61a and the cathode 61b with at least a part of each of the anode 61a and the cathode 61b immersed in a molten salt bath Bm, mainly Ti is dissolved from the crude titanium-based material of the anode 61a, and the refined titanium-based material is precipitated on the cathode 61b, and at least a part of Al, O, etc. is removed. This allows the production of a titanium-based electrolytic product such as metallic titanium or a titanium alloy as a refined titanium-based material. In the production of titanium using this type of electrolytic refining, the amount of carbon used and the associated carbon dioxide emissions can be reduced compared to the production of titanium using a method based on the Kroll process, in which titanium ore is salified, and this can greatly contribute to the realization of a carbon-neutral, and ultimately decarbonized, society. Details of the production methods for titanium-based electrodeposits, including electrolytic refining, will be described later.

The electrolytic cell 2 shown in the figure, which performs electrolytic refining, is composed of a cell body 2b with an opening 2a on the upper side, and a cover 2c that is detachable from the opening 2a of the cell body 2b and covers the opening 2a when attached to the opening 2a of the cell body 2b. The cell body 2b is, for example, a container made of steel, Ni, brick, or the like, with the lower side of the cylindrical peripheral wall portion 2d, such as an elliptical or rectangular tube, sealed with the bottom portion 2e, and molten salt is stored inside to form the molten salt bath Bm. Specific examples of the material of the steel electrolytic cell 2 include carbon steel, stainless steel (JIS standard SUS, etc.), heat-resistant steel (JIS standard SUH, etc.), etc. For example, the inner surface of the brick electrolytic cell 2 may be lined with steel, Ni, etc.

In addition, during electrolytic refining, the electrode 61, which is immersed in the molten salt bath Bm inside the electrolytic cell 2, includes a portion in which electrode plates 62, each functioning as either an anode 61a or a cathode 61b, are arranged alternately.

By arranging such plate-shaped electrode plates 62 so that their main surfaces face each other, a large number of them can be arranged per given volume inside the electrolytic cell 2, and furthermore, electrolytic refining can be efficiently performed while maintaining a relatively short distance between the electrodes on the wide surfaces. For example, although not shown, when multiple cylindrical cathodes are arranged in a circumferential direction inside a cylindrical anode, or when one cylindrical or cylindrical cathode is arranged concentrically with the anode, there are the following problems and it is inefficient. That is, in the former case, the refined titanium-based material deposited on the cathode is concentrated on the cathode at the part of the opposing surface where the given distance between the electrodes is short, and in the latter case, the initial distance between the electrodes is long, and the power consumed by the electrical resistance of the electrolytic bath is large, and as the refined titanium-based material grows, the distance between the electrodes becomes shorter, but the surface area increases, so the amount of current increases and the power consumption increases, and it is generally inefficient. The electrode plate 62 preferably has a rectangular or square shape or a polygonal shape when viewed from the front of the main surface. The electrode plate 62 is not limited to the flat plate shown in the figure, and may be a plate with at least a bent and/or curved portion, or may have a thickness that varies at least in part. The term "plate-like" refers to a shape in which the dimensions (length and width, etc.) of the main surface are longer than the thickness, and includes rectangular parallelepiped and disk-like shapes. In addition, in the case of an electrode plate 62 having corners on the periphery or four corners of a rectangular parallelepiped or other shape, chamfering such as rounding the corners to eliminate the corners or processing such as changing the thickness at the periphery and center are also included in the plate-like shape.

When the electrode plates 62, which provide either the anode 61a or the cathode 61b with a polarity, are arranged alternately as shown in the figure and electrolytic refining is performed, the refined titanium-based material 63 is deposited on each surface (electrodeposition surface) of the cathode 61b that faces the anode 61a, as shown in FIG. 2. Although such an alternating arrangement of many electrode plates 62 does not allow a thick deposition of refined titanium-based material 63 on each cathode 61b because the distance between the electrodes is short, it is possible to obtain a relatively large amount of refined titanium-based material 63 in one electrolytic refining run in a relatively short time, making it suitable for mass production. The electrode plates 62 may be arranged in a number of rows, for example, 2 to 100, 5 to 100, or 10 to 100, or in some cases even more.

After electrolytic refining, in order to obtain a titanium-based electrodeposit from the refined titanium-based material 63 deposited on the cathode 61b, it is necessary to separate the electrode plate 62 including the cathode 61b from the molten salt bath Bm and remove the molten salt residue adhering to the refined titanium-based material 63 on the cathode 61b. When the lid 2c of the electrolytic cell 2 is opened and the electrode plate 62 immersed in the molten salt bath Bm is pulled out of the molten salt bath Bm and removed from the electrolytic cell 2, the refined titanium-based material 63 on the cathode 61b is oxidized due to contact with the air at a high temperature, and its O content increases. In addition, if the refined titanium-based material 63 has molten salt residue adhering thereto, the molten salt may absorb moisture and even decompose, which may result in deterioration of the refined titanium-based material 63.

In contrast, in this embodiment, the electrolytic cell 2 is provided with two or more, for example three, communication ports 3a-3c that can be opened and closed to connect the inside and outside of the electrolytic cell 2. The two or more communication ports 3a-3b include a first communication port 3a and a second communication port 3b. The first communication port 3a located on the upper side in Figures 1 and 2 is mainly used to discharge gas from inside the electrolytic cell 2. The second communication port 3b located on the lower side, deeper in the depth direction of the electrolytic cell 2 (vertical direction in Figures 1 and 2) than the first communication port 3a, is mainly used to discharge molten salt from inside the electrolytic cell 2.

Thereby, for example, after electrolytic refining, the lid 2c of the electrolytic cell 2 is kept closed, the molten salt of the molten salt bath Bm in the electrolytic cell 2 is discharged through the second communication port 3b, and then the inside of the electrolytic cell 2 is heated while creating a reduced pressure atmosphere with a pressure reducing device, so that the molten salt residue can be separated and removed from the first communication port 3a. In this way, the first communication port 3a and the second communication port 3b are preferably configured to be connectable to a discharge destination of the molten salt (such as another electrolytic cell 12 described below) or a pressure reducing device such as a vacuum pump.

The discharge of the molten salt and separation of the residue described above can be performed inside the sealed electrolytic cell 2, so that the refined titanium-based material 63 on the cathode 61b can be prevented from coming into contact with the atmosphere, and the resulting oxidation, increase in O content, and moisture absorption of bath components can be suppressed. In this case, the lifting of the electrode plate 62 from the molten salt bath Bm and the separation of the residue outside the electrolytic cell 2 can be simplified, and since it is no longer necessary to separately ensure a state in which the refined titanium-based material 63 is prevented from coming into contact with the atmosphere, titanium-based electrodeposits can be produced efficiently.

The electrolytic cell 2 may have at least two communication ports 3a and 3b, and may have three or more communication ports. For example, the illustrated electrolytic cell 2 has three communication ports 3a, 3b, and 3c. As described below, the third communication port 3c is used at least for reducing the pressure, and may be connected to a pressure reducing device 21 at that time. Although not shown, the number of communication ports may be four or more. Of the multiple communication ports 3a, 3b, and 3c, the second communication port 3b located relatively deep in the depth direction of the electrolytic cell is used at least for discharging the molten salt, and the first communication port 3a located on the opposite side is used at least for discharging the gas. However, each of the communication ports 3a, 3b, and 3c may be used for other purposes, including the following examples.

In addition to the above uses, the communication ports 3a, 3b, and 3c may be used to supply molten salt or the like to the inside of the electrolytic cell 2, or to supply an inert gas such as argon gas or helium gas. Supplying an inert gas to the inside of the electrolytic cell 2 from the first communication port 3a makes it possible to increase the internal pressure of the electrolytic cell 2 and suppress the intrusion of outside air, and to prevent melting or deterioration due to heating of the current-carrying members 5c and 5d and sealing members described below.

In the illustrated example, of the at least two communication ports 3a and 3b provided in the electrolytic cell 2, the first communication port 3a located above the bath surface of the molten salt bath Bm is used to supply molten salt to the inside of the electrolytic cell 2 and to exhaust gas from the inside of the electrolytic cell 2. This first communication port 3a can be connected to an inert gas supply source and may also be used to supply gas such as an inert gas to the inside of the electrolytic cell 2. In addition, the second communication port 3b located below the bath surface of the molten salt bath Bm and closer to the bottom 2e of the electrolytic cell 2 is used to exhaust molten salt from the inside of the electrolytic cell 2. However, when multiple communication ports 3a and 3b are provided, the role of each communication port 3a and 3b is not limited to this.

From the viewpoint of enabling most of the molten salt constituting the molten salt bath Bm to be discharged by its own weight, the second communication port 3b used to discharge the molten salt is preferably provided in a position near the bottom 2e of the electrolytic cell 2. On the other hand, although not shown, it is also possible to discharge the molten salt using, for example, a suction pipe and a pump inserted into the second communication port 3b, in which case the position of the second communication port 3b does not have to be near the bottom 2e. Note that although the communication ports 3a to 3c are provided in the peripheral wall portion 2d of the cell body 2b of the electrolytic cell 2, it is also conceivable to provide at least one of them in the bottom 2e or the lid 2c.

The dimensions of each communication port 3a, 3b, and 3c can be determined appropriately as long as the molten salt and gas can flow through them and they can perform their role. In addition, each communication port 3a, 3b, and 3c is provided with a valve (not shown) that can be opened and closed, and the valve can be closed when not in use, such as during electrolytic refining.

The molten salt of the molten salt bath Bm can be discharged from inside the electrolytic cell 2, for example, by connecting the second communication port 3b to a molten salt storage container (not shown) and opening the valve to transfer the molten salt from inside the electrolytic cell 2 to inside the molten salt storage container. At this time, a pump may be used if necessary. Also, at this time, if necessary, an inert gas may be supplied from the first communication port 3a to pressurize the inside of the electrolytic cell 2 and promote the discharge of the molten salt.

In the subsequent separation of the molten salt residue from the refined titanium-based material 63, it is preferable to use the other electrolytic cell 12, as shown in FIG. 3. More specifically, the first electrolytic cell 2 from which the molten salt has been discharged after electrolytic refining is connected to the other electrolytic cell 12 not containing the molten salt, via the first communication ports 3a and 13a. The other electrolytic cell 12 is also connected to a pressure reducing device 21. The connection point of the pressure reducing device 21 to the other electrolytic cell 12 is arbitrary, but in this example, it is the third communication port 13c of the other electrolytic cell 12. In this state, when the first electrolytic cell 2 is heated and sucked by the pressure reducing device 21, the inside of the first electrolytic cell 2 becomes a reduced pressure atmosphere, and at least a part of the molten salt residue attached to the refined titanium-based material 63 evaporates and is sent to the inside of the other electrolytic cell 12 via the first communication ports 3a and 13a. The residue is cooled and condensed in the other electrolytic cell 12, where it is collected. Here, the other electrolytic cell 12 functions as a molten salt condenser (a so-called condenser), and the third communication port 13c is used for reducing pressure. The molten salt recovered inside the other electrolytic cell 12 can be used as part of the molten salt bath in subsequent electrolytic refining using the other electrolytic cell 12.

To achieve the recovery and reuse of the residue as described above, the molten salt electrolysis device 1 is provided with multiple electrolytic cells 2, 12, and it is preferable that the first electrolytic cell 2 and the other electrolytic cell 12 can be connected to each other via their respective first communication ports 3a, 13a. It is also preferable here to make it possible to connect a pressure reducing device to the third communication port 13c of the other electrolytic cell 12, and to use the other electrolytic cell 12 as a molten salt condenser. The other electrolytic cell 12 can be configured substantially the same as the first electrolytic cell 2.

When the discharge of the molten salt and the separation of the residue are completed, the electrode plate 62 and the refined titanium-based material 63 electrolytically deposited thereon are naturally or forcibly cooled, and then removed from inside the electrolytic cell 2 with the lid 2c open. Here, in the illustrated embodiment, the electrode plate 62 is held by the electrode holding mechanism 4, and by using this electrode holding mechanism 4, the electrode plate 62 can be easily removed from inside the electrolytic cell 2, as shown in FIG. 5.

The electrode holding mechanism 4 holds the electrode plate 62 and can move the electrode plate 62 between the inside and outside of the electrolytic cell 2. In the illustrated example, the electrode holding mechanism 4 has a holding rod 4a made of stainless steel or heat-resistant steel, etc., which is provided for each electrode plate 62 and extends in the vertical direction to suspend and hold each electrode plate 62, and a lifting plate 4b located above the holding rod 4a and outside the electrolytic cell 2, with each holding rod 4a attached at its upper end.

Of these, the holding rod 4a is connected to the electrode plate 62 at its lower end. In order to stably hold the electrode plate 62, two holding rods 4a may be attached to each electrode plate 62, one on each side of the upper surface of the electrode plate 62 in the width direction (vertical direction in FIG. 4), as shown in FIG. 4. One or three or more holding rods 4a may be provided for each electrode plate 62. Each holding rod 4a extends through the lid 2c of the electrolytic cell 2. It is preferable that the lid 2c is attached to the holding rod 4a so that it moves together with the holding rod 4a, and a sealing member such as an O-ring can be provided at the place where the holding rod 4a passes through the lid 2c. The lifting plate 4b is provided above the lid 2c of the electrolytic cell 2, and is driven by a driving source (not shown) to move up and down in the vertical direction.

The molten salt electrolysis device 1 is provided with an electrical connection mechanism 5 that electrically connects the power source and the electrode plate 62. Specifically, the electrical connection mechanism 5 may be composed of conductors 5a, 5b (so-called bus bars, etc.) made of copper or aluminum in a plate shape or other shape that are located, for example, above the lift plate 4b and connected to the power source outside the electrolytic cell 2, and conductors 5c, 5d made of copper, nickel, carbon steel, iron, etc. that extend in the vertical direction parallel to the holding rod 4a and connect the electrode plate 62 to the conductors 5a, 5b. By providing the conductors 5a, 5b, the number of connection points to the power source can be reduced even when a large number of electrode plates 62 are provided. Two types of conductors 5a, 5b and electrical conductive members 5c, 5d are provided, one connected to the positive pole of the power source and one connected to the negative pole. Of the electrode plates 62 arranged in a direction perpendicular to the depth direction of the molten salt bath Bm, every other electrode plate 62 that is given the polarity of the anode 61a is connected to the conductor 5a and the current-carrying member 5c, and every other electrode plate 62 that is given the polarity of the cathode 61b is connected to the conductor 5b and the current-carrying member 5d.

As shown in FIG. 4, for example, the current-carrying members 5c, 5d are connected to the upper surface of the electrode plate 62 at a position between the two holding rods 4a in the width direction, and two current-carrying members 5c, 5d may be connected to one electrode plate 62. One or three or more current-carrying members 5c, 5d may be connected to one electrode plate 62. As shown in FIGS. 1 to 3 and 5, the current-carrying members 5c, 5d each extend vertically beyond the holding rod 4a in front of the paper, or on the back side of the paper, and penetrate the lid 2c of the electrolytic cell 2 to be connected to the conductor 5a or 5b.

In order to prevent the holding rod 4a and the current-carrying members 5c and 5d from becoming extremely hot due to the heat of the molten salt bath Bm, it is preferable to place the electrode plate 62 in the molten salt bath Bm so that its upper portion is exposed above the bath surface of the molten salt bath Bm, as shown in Figures 1 and 2. It is also preferable to provide a heat insulating material on the lid 2c. This is to prevent deterioration of the external conductors 5a, 5b, and other members due to the heat inside the electrolytic cell 2 during electrolytic refining or residue separation. The installation of a heat insulating material is also effective in increasing the safety of workers working around the electrolytic cell 2 and reducing the burden on the workers. From the viewpoint of suppressing the temperature rise of the members near the lid 2c, a heat exchanger that flows a coolant such as water may be provided on the lid 2c.

In the drawings, to make it easier to understand the structure, the holding rod 4a and the current-carrying members 5c and 5d are shown at positions offset from the center line in the thickness direction on the upper surface of the electrode plate 62, but they can also be placed on the center line in the thickness direction. From the viewpoint of ensuring uniformity of the load and current/voltage applied, it is preferable to place the holding rod 4a and the current-carrying members 5c and 5d at positions on the center line in the thickness direction of the electrode plate 62, which is a symmetrical position.

The molten salt electrolysis apparatus 1 can be provided with a temperature regulator 6 for adjusting the temperature of at least the cathode 61b inside the electrolytic cell 2. In the illustrated embodiment, the temperature regulator 6 is a heat exchanger including a pipe for flowing a heat medium, which is installed inside the electrolytic cell 2 on the bottom 2e side (lower or lower side) of the electrode 61, at least directly below the cathode 61b. If the vertically downward projection area of the cathode 61b and the area where the heat exchanger pipes are installed overlap at least partially, the heat exchanger is deemed to be installed at a position directly below the cathode 61b. However, it is preferable not to install the temperature regulator 6 directly below the anode 61a.

The temperature regulator 6 can be used during electrolytic refining and when discharging the molten salt thereafter, but by placing it at least directly below the cathode 61b, it can be particularly useful when separating the molten salt residue adhering to the purified titanium-based material 63 from the purified titanium-based material 63. At this time, in order to vaporize or liquefy the residue adhering to the purified titanium-based material 63 and separate it from the purified titanium-based material 63, it is necessary to heat the cathode 61b on which the purified titanium-based material 63 is electrodeposited to a relatively high temperature that exceeds at least the melting point of the bath components.

On the other hand, as described below, heating by the temperature regulator 6 may cause an alloying reaction between the residue of the crude titanium-based material remaining on the anode 61a and Ni. To prevent this, it is desirable to place the temperature regulator 6 so that the majority of it is located directly below the cathode 61b and so as not to overheat the anode 61a. More preferably, the piping of the heat exchanger serving as the temperature regulator 6 has at least a portion directly below the cathode 61b that extends parallel to the width direction of the cathode 61b (the depth direction of the paper in Figures 1 to 3 and 5).

(Method for producing titanium-based electrodeposits)
To produce a titanium-based electrodeposit, a crude titanium-based material is prepared in advance prior to the electrolysis step of electrolytic refining using the electrolytic cell 2 of the above-mentioned molten salt electrolysis apparatus 1. The crude titanium-based material can be obtained by an extraction step.

In the extraction process, a mixture of a titanium raw material such as titanium ore containing titanium oxide such as titanium oxide (TiO ₂ ) and a reducing agent containing aluminum (Al) is heated. At this time, a separating agent may be mixed. The reaction at this time is complex, but generally, for example, a reaction such as 3TiO ₂ + 4Al → 3Ti + 2Al ₂ O ₃ is considered to occur. Here, Ti on the right side is a solid solution of a certain amount of Al and O, which corresponds to the crude titanium-based material. This crude titanium-based material may contain small amounts of Fe, Si, V, Cr, Ni, Mn, etc., which are impurities in the ore. The heating temperature may be, for example, 1500°C to 1800°C. After the mixture is heated to a molten state, the crude titanium-based material (liquid or solid) and slag are separated due to the density difference, so that the crude titanium-based material (Ti in the above reaction formula) can be extracted. Since such an extraction step does not include carbon in the reaction system, the titanium-based electrodeposit produced by electrolytic refining in the subsequent electrolysis step is one that has been refined without using carbon.

The titanium raw material used in the extraction step may be any material containing titanium oxide, such as titanium ore, titanium ore that has been subjected to upgrading treatment such as leaching or other treatment as necessary, and titanium slag (UGS) obtained by separating iron oxide from ilmenite (iron ore). The content of TiO ₂ in the titanium ore used as the titanium raw material may be, for example, 50 mass% or more, typically 80 mass% or more, and particularly 90 mass% or more. The separating agent is used to facilitate the generation of slag after heating and to facilitate separation. Specifically, the separating agent is preferably one or more selected from calcium fluoride, aluminum fluoride, potassium fluoride, magnesium fluoride, calcium chloride, calcium oxide, and sodium fluoride. Among them, calcium fluoride (CaF ₂ ) is particularly suitable because it provides excellent separation of the crude titanium-based material from the mixture and has little effect on anything other than the separation. The reducing agent may be one that substantially contains Al alone, or may further contain Ca, Na, Mg, Cu, Si, Fe, etc. For example, a mixture may be prepared with a molar ratio of TiO ₂ :Al:CaF ₂ adjusted to 3:1-8:2-6.

The crude titanium-based material obtained in the extraction process contains Ti, Al, and O, and may have, for example, a Ti content of 50% to 80% by mass, an Al content of 1% to 30% by mass, and an O content of 5% to 20% by mass. Typically, the Ti content of the crude titanium-based material may be 60% by mass or more, an Al content of 20% by mass or less, and an O content of 20% by mass or less. However, in the crude titanium-based material, the Al and O content in Ti may be less than the above-mentioned contents, and may be contained at a level that may correspond to unavoidable impurities. The crude titanium-based material may contain very small amounts of Al and O. It may also contain small amounts of unavoidable impurities such as impurities derived from ores.

Such a crude titanium-based material has electrical conductivity and can be impregnated into the anode 61a in the electrolysis step described below and subjected to electrolytic refining. The resistivity of the crude titanium-based material measured at room temperature is, for example, 1×10 ^-8 Ω·m to 1×10 ^-4 Ω·m, typically 1×10 ^-7 Ω·m to 5×10 ^-5 Ω·m.

In the electrolysis process, the molten salt electrolysis device 1 described above is used to perform electrolytic refining in which Ti is dissolved from the crude titanium-based material on the anode 61a in the molten salt bath Bm inside the electrolytic cell 2, and refined titanium-based material 63 is precipitated on the cathode 61b.

Here, the anode 61a contains the crude titanium-based material obtained in the extraction process described above. As an example, the anode 61a has a plate-shaped outer shape and a cage-shaped container with many through holes made of Ni, Ni-based alloy, Hastelloy, or steel coated with Ni or Ni-based alloy, and in this case, the crude titanium-based material in the form of particles or powder can be placed in the cage-shaped container. When the anode 61a has a cage-shaped container, the current-carrying members 5c and 5d can be connected to the cage-shaped container. However, the shape of the anode 61a is not limited to this, and it may be, for example, a plate-shaped (rectangular parallelepiped) one made of the crude titanium-based material by melting and casting. The cathode 61b can be a plate-shaped one with at least its surface made of Ti, and can be, for example, a titanium plate made entirely of Ti. It is possible to arrange a bipolar electrode between the anode 61a and the cathode 61b, but the bipolar electrode is not necessary.

The molten salt bath Bm may be a chloride bath mainly containing metal chlorides, for example, containing alkali metal chlorides and/or alkaline earth metal chlorides, for example, at 70 mol% or more, further 90 mol% or more, and further 95 mol% or more. Such a chloride bath is preferable because it is less corrosive, has a low environmental impact, and is less expensive than a fluoride bath, a bromide bath, or an iodide bath. In particular, when a chloride bath containing magnesium chloride (MgCl ₂ ) is used, a purified titanium-based material 63 in which not only the O content but also the Al content is sufficiently reduced can be obtained. The MgCl ₂ content in the chloride bath is preferably 30 mol% or more, further 50 mol% or more, further 80 mol% or more, further 85 mol% or more, and particularly 95 mol% or more. The chloride bath may contain one or more metal chlorides selected from lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), beryllium chloride ( _BeCl2 ), calcium chloride ( _CaCl2 ), strontium chloride ( _SrCl2 ), and barium chloride ( _BaCl2 ), for example, at 70 mol% or less, further 50 mol% or less, further 20 mol% or less, further 10 mol% or less, and further 5 mol% or less.

In addition, the molten salt bath Bm may contain lower titanium chlorides having a lower Ti valence than titanium tetrachloride, specifically titanium dichloride (TiCl ₂ ) or titanium trichloride (TiCl ₃ ), if necessary. The content of titanium ions in the molten salt bath Bm is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 6 mol% or more, and may be 10 mol% or more, and is preferably 20 mol% or less. The content of metal chlorides and metal ions in the molten salt bath Bm can be measured by ICP emission spectrometry or atomic absorption spectrometry. The content of titanium ions is determined as a percentage of the total content of metal ions in the molten salt bath Bm.

The above-mentioned molten salt bath Bm can be provided inside the electrolytic cell 2 by placing a specific salt in granular or lump form inside the electrolytic cell 2 and heating it to form a molten salt. Alternatively, if the molten salt has already been obtained, the molten salt may be injected into the electrolytic cell 2 through the first communication port 3a or the like. In this case, the first communication port 3a is formed above the final bath surface height of the molten salt bath Bm inside the electrolytic cell 2, so that the molten salt flows into the electrolytic cell 2 under its own weight and accumulates there.

In the subsequent electrolysis process, electricity is passed from the power source to the anode 61a and cathode 61b of the electrodes 61 via the current-carrying members 5c and 5d, and a voltage is applied between the electrodes 61. This causes titanium ions to dissolve from the crude titanium-based material contained in the anode 61a into the molten salt bath Bm, and the titanium ions precipitate as titanium atoms on the cathode 61b, forming a refined titanium-based material 63 as shown in FIG. 2. The refined titanium-based material 63 precipitated on the cathode 61b may correspond to a titanium-based electrolytic deposit.

The conditions for the electrolysis step may include, for example, a temperature of the molten salt bath Bm of 450°C to 900°C and a current density at the cathode 61b of 0.01 A/ ^cm2 to 3 A/ ^cm2 . The current density may be calculated by the formula: current density (A/ ^cm2 ) = current (A) ÷ electrodeposition area ( ^cm2 ). A current may be continuously passed through the electrode 61, or a pulse current may be passed through the electrode 61 in which a current-passing period and a current-passing period are alternately repeated, with a current-passing period being set to zero. The maximum voltage between the electrodes 61 may be, for example, 0.2 V to 3.5 V. During the electrolysis step, the inside of the electrolytic cell 2 is preferably maintained in an inert atmosphere such as argon.

After the electrolysis process is completed, the molten salt discharge process can be performed. In the molten salt discharge process, the molten salt inside the electrolytic cell 2 is discharged to the outside through the second communication port 3b. More specifically, although not shown, a molten salt storage container that has room for molten salt because no molten salt is stored at all is connected to the second communication port 3b, and a valve (not shown) of the second communication port 3b is opened. Here, since the second communication port 3b is provided on the bottom 2e side below the bath surface height of the molten salt bath Bm, the molten salt flows out of the inside of the electrolytic cell 2 into the inside of the molten salt storage container by its own weight when the valve of the second communication port 3b is opened. At this time, if necessary, an inert gas may be supplied from the first communication port 3a to pressurize the inside of the electrolytic cell 2 and promote the discharge of the molten salt. As a result, the molten salt inside the electrolytic cell 2 is discharged, and the refined titanium-based material 63 can be exposed from the molten salt bath Bm. In the molten salt discharge process, it is sufficient that almost the entire purified titanium-based material 63 is exposed from the molten salt bath Bm, but the molten salt may be discharged until substantially no molten salt bath Bm is present inside the electrolytic cell 2.

After the molten salt discharge process, a residue separation process is carried out to separate the molten salt residue adhering to the purified titanium-based material 63 from the purified titanium-based material 63. In the residue separation process, the temperature regulator 6 is used to heat the purified titanium-based material 63 mainly on the cathode 61b. By heating with the temperature regulator 6, at least a portion of the molten salt residue adhering to the purified titanium-based material 63 evaporates into gas, or in some cases, a portion melts into liquid, and is separated from the purified titanium-based material 63. Taking into account the effect on other components such as the anode 61a, it is preferable to adjust the heating temperature by the temperature regulator 6 to cause the vaporization or liquefaction separation described above.

In either case of vaporization or liquefaction, at least a portion of the molten salt residue is evaporated into gas by heating in the temperature regulator 6 and discharged from inside the electrolytic cell 2. In order to recover and reuse this, in the residue separation process, as shown in FIG. 3, it is preferable to use another electrolytic cell 12, different from the one electrolytic cell 2 used in the electrolysis process and the molten salt discharge process, as a molten salt condenser.

When the other electrolytic cell 12 is used in the residue separation process, the first electrolytic cell 2 and the other electrolytic cell 12 are connected to each of the first communication ports 3a and 13a beforehand, and the third communication port 13c of the other electrolytic cell 12 is connected to the pressure reducing device 21 beforehand. At this time, the second communication port 3b and the third communication port 3c of the first electrolytic cell 2 and the second communication port 13b of the other electrolytic cell 12 are all closed. In this state, the purified titanium-based material 63 on the cathode 61b is heated inside the first electrolytic cell 2 in the residue separation process, and the pressure reducing device 21 creates a reduced pressure atmosphere inside the first electrolytic cell 2 through the inside of the other electrolytic cell 12. Then, in the first electrolytic cell 2, gas generated by evaporation of at least a part of the molten salt residue is sent from the inside of the first electrolytic cell 2 to the inside of the other electrolytic cell 12. The other electrolytic cell 12 is at a lower temperature than the first electrolytic cell 2 being heated, and the gas is cooled and condensed inside the other electrolytic cell 12. This allows the molten salt residue to be collected inside the other electrolytic cell 12.

The heating temperature inside one electrolytic cell 2 in the residue separation step may be, for example, 500° C. to 1000° C., 750° C. to 1000° C., or 850° C. to 1000° C. When heating at 850° C. to 1000° C., the viscosity of the bath components is reduced due to the high temperature, making it easier to remove the bath components from the purified titanium-based material 63. It is desirable to set this heating temperature to an appropriate temperature in consideration of the materials of the components of the anode 61a and other conditions.
For example, in the case of the anode 61a having a cage-shaped container with a surface made of Ni or Ni-based alloy, there is a risk that the Ni of the cage-shaped container and the Ti of the residue of the crude titanium-based material remaining inside the cage will be alloyed when heated at a high temperature. In this case, the cage-shaped container of the anode 61a will require maintenance for use in the next electrolysis step, and if the alloy cannot be completely removed during maintenance, there is a risk that the refined titanium-based material will be contaminated by the elution of the alloy into the molten salt bath Bm. To prevent this, the heating temperature can be lowered to a certain extent. If the heating temperature is low, in the residue separation step, the residue adhering to the refined titanium-based material 63 will mainly become liquid and drip and be separated, but some of it may be vaporized and sent to another electrolytic cell 12.
Alternatively, when the anode 61a does not have a cage-shaped container with a surface made of Ni or Ni-based alloy, it is preferable to set the heating temperature relatively high, vaporize most of the residue, and send it to another electrolytic cell 12. In this way, the molten salt residue is sufficiently removed, making it possible to omit subsequent cleaning such as pickling and water washing, thereby suppressing an increase in the content of impurities such as oxygen in the titanium-based electrodeposit.

After the residue separation process, it is preferable to use another electrolytic cell 12 into which the molten salt residue has been transferred, add molten salt therein as necessary to form a molten salt bath Bm, and perform the above-mentioned electrolysis process. The electrolysis process using the other electrolytic cell 12 can be performed in the same manner as the above-mentioned electrolysis process using one electrolytic cell 2, so a repeated explanation will be omitted.

It is preferable that the residue separation step is performed with an electrode plate disposed inside the other electrolytic cell 12. If the residue separation step is performed without disposing an electrode plate inside the other electrolytic cell 12, it is necessary to dispose an electrode plate inside the other electrolytic cell 12 prior to the subsequent electrolysis step using the other electrolytic cell 12. At that time, the molten salt residue recovered inside the other electrolytic cell 12 in the residue separation step may come into contact with the atmosphere. In particular, when the molten salt contains magnesium chloride, magnesium chloride is highly hygroscopic, so the moisture content increases when it comes into contact with the atmosphere, and if it is exposed to high temperatures in the electrolysis step in a hygroscopic state, magnesium chloride decomposes to produce magnesium oxide and hydrochloric acid, which may reduce the quality and electrodeposition efficiency of the refined titanium-based material. For this reason, it is preferable to dispose an electrode plate inside the other electrolytic cell 12 before performing the residue separation step and recover the molten salt residue inside the other electrolytic cell 12.

After the residue separation process, in one electrolytic cell 2, the electrode holding mechanism 4 is operated to raise the electrode plate 62 together with the lid 2c as shown in FIG. 5. This opens the lid 2c and allows the electrode plate 62 to be removed from inside the electrolytic cell 2. The refined titanium-based material 63 removed from inside the electrolytic cell 2 may still contain molten salt residue, in which case it can be washed with water, pickled, or otherwise cleaned.

The electrolysis process can be repeated multiple times to further refine the refined titanium-based material 63 obtained thereby. When the electrolysis process is performed multiple times, the refined titanium-based material 63 deposited on the cathode 61b in the previous electrolysis process is used as the crude titanium-based material in the next electrolysis process. That is, in the next electrolysis process, the refined titanium-based material 63 deposited on the cathode 61b in the previous electrolysis process is used as the crude titanium-based material and is used for the anode 61a containing the crude titanium-based material. Furthermore, the anode 61a used in the previous electrolysis process is replaced with the cathode 61b to perform the next electrolysis process. As a result, in the next electrolysis process, the refined titanium-based material 63 from which impurities have been further removed from the crude titanium-based material is deposited on the newly installed cathode 61b. By performing multiple electrolysis processes, it is also possible to produce an electrodeposit as metallic titanium that contains almost no impurities. The cage-shaped container and cathode 61b used for the anode 61a can be reused by performing appropriate maintenance such as washing with water after recovery. For example, the anode 61a can be reused by removing the residue from the cage-shaped container and filling the cage-shaped container with crude titanium-based material. The cathode 61b can also be reused after the refined titanium-based material is recovered.

The titanium-based electrodeposit as the purified titanium-based material 63 obtained by one or more electrolysis steps has a total content of elements other than Ti of, for example, 40,000 ppm by mass or less, preferably 5,000 ppm by mass or less, more preferably 2,000 ppm by mass or less, even more preferably 1,000 ppm by mass or less, and particularly preferably 200 ppm by mass or less.

The titanium-based electrodeposit may be metallic titanium, and may have, for example, an Al content of 5 ppm to 20,000 ppm by mass, an O content of 50 ppm to 20,000 ppm by mass, with the remainder consisting of Ti and unavoidable impurities. Alternatively, the titanium-based electrodeposit may have an Al content of 5 ppm to 1,000 ppm by mass, an O content of 50 ppm to 1,000 ppm by mass, with the remainder consisting of Ti and unavoidable impurities. It may also be possible to produce titanium-based electrodeposits made of metallic titanium with a purity of 4N5 or higher, or even 5N or higher, or even 5N5 or higher.

The inevitable impurities in titanium-based electrodeposits include those derived from the ore, the chloride bath, the reducing agent, the separating agent, those derived from the components constituting the molten salt electrolysis device such as the electrolytic cell, and those generated when in contact with the air. Specifically, the inevitable impurities in titanium-based electrodeposits may be N (nitrogen) content of 0.03 mass% or less, C (carbon) content of 0.01 mass% or less, Fe content of 0.050 mass% or less, Mg content of 0.02 mass% or less, Ni content of 0.03 mass% or less, Cr content of 0.03 mass% or less, Si content of 0.001 mass% or less, Mn content of 0.05 mass% or less, and Sn content of 0.01 mass% or less.

REFERENCE SIGNS LIST 1 Molten salt electrolysis device 2, 12 Electrolytic cell 2a Opening 2b Cell body 2c Lid 2d Peripheral wall 2e Bottom 3a, 13a First communication port 3b, 13b Second communication port 3c, 13c Third communication port 4, 14 Electrode holding mechanism 4a Holding rod 4b Lifting plate 5, 15 Electrical connection mechanism 5a, 5b Conductor 5c, 5d Current-carrying member 6 Temperature regulator 21 Pressure reducing device 61 Electrode 61a Anode 61b Cathode 62 Electrode plate 63 Refined titanium-based material Bm Molten salt bath

Claims (14)

A molten salt electrolysis apparatus including an electrolytic cell for performing electrolytic refining by using electrodes including an anode and a cathode to dissolve Ti from a crude titanium-based material of the anode in a molten salt bath and deposit a refined titanium-based material on the cathode,
The crude titanium-based material contains Ti, Al, and O and is conductive, and the electrode includes a portion in which electrode plates each functioning as either the anode or the cathode are arranged alternately,
The molten salt electrolysis apparatus includes an electrolytic cell having two or more communication ports that can be opened and closed to connect the inside and the outside, the two or more communication ports including a first communication port used for discharging at least a gas, and a second communication port that is located deeper in the depth direction of the electrolytic cell than the first communication port and is used for discharging at least a molten salt. A plurality of the electrolytic cells is provided,
2. The molten salt electrolysis apparatus according to claim 1, wherein one electrolytic cell and another electrolytic cell among the plurality of electrolytic cells are connectable to each other through the first communication ports. The molten salt electrolysis apparatus according to claim 2, wherein a pressure reducing device can be connected to at least one of the communication ports of the other electrolysis cell, and the other electrolysis cell is used as a molten salt condenser. The molten salt electrolysis apparatus according to claim 3, wherein the communication port of the other electrolytic cell includes at least a third communication port used for reducing pressure, and a pressure reducing device can be connected to the third communication port. The molten salt electrolysis apparatus according to claim 1, further comprising a pressure reducing device that can be connected to at least one of the communication ports. The molten salt electrolysis apparatus according to claim 1, further comprising a temperature regulator disposed inside the electrolytic cell and regulating at least the temperature of the cathode. The molten salt electrolysis apparatus according to claim 6, wherein the temperature regulator is a heat exchanger and is installed at the bottom side of the electrolytic cell at a position at least directly below the cathode. The molten salt electrolysis apparatus according to claim 1, further comprising an electrode holding mechanism capable of holding the electrode plate and moving the electrode plate between the inside and outside of the electrolytic cell. The molten salt electrolysis apparatus according to claim 8, wherein the electrode holding mechanism includes a holding rod provided for each of the electrode plates, extending in the vertical direction to suspend and hold each of the electrode plates, and a lifting plate located above the holding rods and outside the electrolytic cell, to which each of the holding rods is attached. The molten salt electrolysis apparatus includes an electrical connection mechanism that electrically connects a power source and the electrode plate,
10. The molten salt electrolysis apparatus according to claim 9, wherein the electrical connection mechanism comprises a conductor located outside the electrolytic cell and connected to the power source, and a current-carrying member extending in the vertical direction parallel to the holding rod and connecting the electrode plate to the conductor. The molten salt electrolysis device according to claim 1, in which 2 to 100 of the electrode plates can be arranged inside the electrolytic cell. A method for producing a titanium-based electrodeposit by electrolytic refining using the molten salt electrolysis apparatus according to any one of claims 1 to 11, comprising:
an electrolysis step in which, in the electrolytic cell, Ti is dissolved from the crude titanium-based material of the anode in a molten salt bath and a refined titanium-based material is deposited on the cathode;
a molten salt discharging step of discharging the molten salt inside the electrolytic cell to the outside through the second communication port after the electrolysis step;
and a residue separation step of discharging gas from within the electrolytic cell through the first communication port while heating the purified titanium-based material on the cathode after the molten salt discharge step, and separating a residue of the molten salt from the purified titanium-based material. Prior to carrying out the residue separation step, one electrolytic cell used in the electrolysis step and the molten salt discharge step is connected to another electrolytic cell used as a molten salt condenser via the first communication port, and the communication port of the other electrolytic cell is connected to a pressure reducing device;
13. The method for producing a titanium-based electrodeposit according to claim 12, wherein in the residue separating step, the inside of the one electrolytic cell is made into a reduced pressure atmosphere via the inside of the other electrolytic cell by the pressure reducing device, and the residue of the molten salt is cooled and recovered inside the other electrolytic cell. The method for producing a titanium-based electrodeposit according to claim 13, wherein the electrolysis step is carried out using the other electrolytic cell after the residue separation step.