KR102123841B1 - Electrolytic reduction apparatus - Google Patents

Abstract

An electrolytic reduction apparatus for metal oxide according to an exemplary embodiment of the present invention includes a reactor including a LiCl molten salt; A carrier gas supply pipe supplying carrier gas into the reactor; An anode immersed in the molten salt; And a cathode disposed under the anode and connected to the carrier gas supply pipe, and spraying the carrier gas supplied through the carrier gas supply pipe upward. The metal oxide mixed with the molten salt between the cathode and the anode may flow with the molten salt by the carrier gas injected from the cathode.

Description

Electrolytic reduction device for metal oxides {ELECTROLYTIC REDUCTION APPARATUS}

The present invention relates to a metal oxide electrolytic reduction device.

The electrolytic reduction process is an essential technology for pyroprocessing, which is a recycling process of spent nuclear fuel, and converts the spent fuel in the form of oxide into a metal form and supplies it to the subsequent electrolytic refining process. The electrolytic reduction process is carried out using a metal anode basket and anode containing LiCl molten salt, oxide (used nuclear fuel) containing a small amount of Li ₂ O (typically around 1.0 wt%), which is an electrolyte. When a voltage is applied between both electrodes, Li metal is generated at the cathode, and after using the lithium metal contained in the basket, the spent fuel is converted into a metal form, and at the same time, Li ₂ O is generated to generate gas such as oxygen at the anode. It replenishes Li ₂ O consumed by. Therefore, the Li ₂ O concentration is kept constant during the reaction and electrolysis can proceed stably.

In order for the Li metal generated in the cathode basket through electrolysis to effectively participate in the reaction, continuous mixing and contact with the oxide fixed to the cathode basket is required. Conventionally, the resulting Li metal is suspended in the upper portion of the LiCl molten salt due to the difference in density from the LiCl molten salt, and is contained in the cathode basket, making it impossible to contact with the fixed oxide. . In particular, as the capacity of the electrolytic reduction process increases, there is a problem in that the proportion of the excess Li metal that does not participate in the reaction increases compared to the Li metal produced in the process. This lowers the efficiency of the electrolytic reduction process and lowers productivity.

In addition, a method of increasing the size of the basket (or the cathode itself) used as the cathode may be used for capacity increase, but the size of the process equipment including a reaction vessel that accommodates the basket therein in response to the increase in the size of the basket may also be used. There is a limit to capacity increase because it needs to be increased.

In addition, an anode generating gas exhaust system is provided to remove gases, such as oxygen generated from the anode, in the reaction vessel during the operation of the electrolytic reduction process, and thus, volatilization of the LiCl molten salt used as the electrolyte is very active. Volatilization of these electrolytes not only requires replenishment due to the loss of electrolyte, but also causes a problem of diffusion of LiCl and other volatile substances in a hot cell in which a process apparatus is installed.

Japanese Patent Publication No. 2000-131489

An object of the present invention is to provide a metal oxide electrolytic reduction device capable of solving the existing problems in a metal oxide electrolytic reduction process using a hot molten salt.

However, the object of the present invention is not limited to this, and even if not explicitly stated, the object or effect that can be grasped from the solving means or embodiments of the subject described below will be included in this.

An electrolytic reduction apparatus for metal oxide according to an exemplary embodiment of the present invention includes a reactor including a LiCl molten salt; A carrier gas supply pipe supplying carrier gas into the reactor; An anode immersed in the molten salt; And a negative electrode disposed under the positive electrode and connected to the carrier gas supply pipe, and the negative electrode spraying the carrier gas supplied through the carrier gas supply pipe upwards, wherein the molten salt is mixed with the negative electrode between the negative electrode and the positive electrode. The metal oxide may flow with the molten salt by the carrier gas injected from the cathode.

According to one embodiment of the present invention, lithium metal is effectively used in a reduction reaction to reduce the proportion of excess Li metal, and an electrolytic reduction device for metal oxides capable of solving the limitations of capacity increase in process equipment and problems caused by electrolyte volatilization Can be provided.

Various and beneficial advantages and effects of the present invention are not limited to the above, and will be more readily understood in the course of describing the specific embodiments of the present invention.

1 is a block diagram schematically showing an electrolytic reduction device of a metal oxide according to an exemplary embodiment of the present invention.
2 is a perspective view schematically showing a cathode in an electrolytic reduction device of a metal oxide.
Figure 3 is a cross-sectional view schematically showing the cathode of Figure 2;
4A and 4B are cross-sectional views schematically showing the rotational driving of the cathode.

Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains can easily implement the present invention. However, in the detailed description of a preferred embodiment of the present invention, when it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, the same reference numerals are used throughout the drawings for parts having similar functions and functions.

In addition, throughout the specification, when a part is said to be'connected' to another part, it is not only'directly connected', but also'indirectly connected' with another element in between. Includes. In addition, "including" a component means that other components may be further included instead of excluding other components, unless otherwise stated.

An electrolytic reduction device of a metal oxide according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 4.

1 is a configuration diagram schematically showing an electrolytic reduction device of a metal oxide according to an exemplary embodiment of the present invention, Figure 2 is a perspective view schematically showing a cathode in the electrolytic reduction device of a metal oxide, Figure 3 is a 4A and 4B are schematic cross-sectional views showing the negative electrode, and FIGS. 4A and 4B are schematic cross-sectional views showing the rotational driving of the negative electrode.

1 to 4, the electrolytic reduction device 1 of a metal oxide according to an exemplary embodiment of the present invention may include a reactor 10.

The reactor 10 may accommodate the molten salt L in a liquid state therein. The reactor 10 may have, for example, a cylindrical structure having a circular cross section. However, the structure of the reactor 10 is not limited thereto. The molten salt (L) may include a LiCl molten salt, and in addition, Li ₂ O may be added to promote the reaction.

The reactor 10 may be made of a material having mechanical stability while being corrosion resistant in the molten salt L at a high temperature. For example, the reactor 10 may be made of nickel-based superalloy such as inconel, stainless steel, tantalum metal, or ceramic, but the material of the reactor 10 is not limited thereto.

A condensation unit 11 may be provided on the upper portion of the reactor 10. The condensation unit 11 may correspond to a space located above the molten salt L upper layer in the reactor 10. The vaporized molten salt may be condensed in the condensation unit 11 and converted into a solid powder form.

A product recovery unit 12 may be provided below the reactor 10. The product recovery part 12 may correspond to a space located below the cathode 40 inside the reactor 10. The product RO in which the electrolytic reduction process is completed may be moved to the product recovery unit 12 and discharged to the outside. In this case, a continuous process system can be constructed by directly connecting the product recovery unit 12 to a subsequent process, such as a residual salt removal process device or an electrorefining process device.

A heating unit (not shown) may be provided outside the reactor 10 to maintain the molten salt L inside the reactor 10 at a constant temperature. For example, the molten salt (L) can be heated and maintained at a temperature of approximately 650°C.

Referring to the drawings, the metal oxide electrolytic reduction apparatus 1 according to an exemplary embodiment of the present invention may include a carrier gas supply pipe 20.

The carrier gas supply pipe 20 may supply the carrier gas G into the reactor 10. Here, argon gas may be used as the carrier gas G. The carrier gas supply pipe 20 may be connected to the cathode 40 provided inside the reactor 10. This will be described later.

Referring to the drawings, the metal oxide electrolytic reduction apparatus 1 according to an exemplary embodiment of the present invention may include an anode 30 and a cathode 40. The positive electrode 30 and the negative electrode 40 are immersed in molten salt L in the reactor 10 and may be connected to a power supply 2 provided outside the reactor 10.

The positive electrode 30 may be applied with a positive voltage to oxidize oxygen ions to form an oxygen gas. As the anode 30, a non-consumable electrode such as platinum as a metal electrode and SrRuO ₃ as a ceramic electrode, or a consumable electrode such as carbon may be used. The material of the anode 30 is not limited thereto, and a material used as an existing electrode material may be used. In the case of using a non-consumable electrode, oxygen ions are formed as oxygen gas and discharged to the outside. When using a consumable electrode, oxygen ions may be discharged to the outside in the form of oxygen, carbon dioxide, or carbon monoxide.

The cathode 40 is spaced apart from the anode 30 and is disposed under the anode 30, and a negative voltage may be applied. As described above, the carbon particles generated in the anode 30 floating in the upper portion of the molten salt (L) by the cathode 40 being disposed under the anode 30 (if the anode is a consumable electrode) flow into the cathode 40 Can be prevented.

The cathode 40 may have a structure corresponding to the cross-sectional shape of the reactor 10 as a whole. For example, it may have a circular plate structure. In this case, the cathode 40 may have a diameter of a size corresponding to the cross-sectional diameter of the reactor 10. However, in order to prevent electrical insulation with the reactor 10 and contact with the inner surface of the reactor 10, an insulating material 41 may be provided on the edge of the cathode 40.

A metal oxide (MO) to be subjected to electrolytic reduction may be disposed on the cathode 40. The metal oxide (MO) may be provided on the upper surface of the cathode 40 and diffused as wide as the area corresponding to the cross-sectional size of the reactor 10. Therefore, the existing metal oxide (MO) is accommodated in a basket of a limited size and can perform an electrolytic reduction process with a larger capacity than that provided in the reactor. For example, in order to increase the capacity, the size of the basket needs to be increased, but the size of the reactor needs to be considered. That is, since the size of the basket must be smaller than the reactor, there is a limit to increase the size of the basket, and there is a problem that the size of the reactor must be increased by the increased size of the basket.

In the present invention, without using a conventional basket, the cathode 40 corresponding to the cross-sectional size of the reactor 10 performs a basket function to support the metal oxide (MO), so that the metal oxide (MO) is the size of the reactor 10. ) Has the advantage of being easy to increase capacity.

The metal oxide (MO) may include UO ₂ used in pyroprocessing, but is not limited thereto, and may include various types of oxide or spent fuel such as Ta ₂ O ₅ , TiO ₂ , and U ₃ O ₈ . The metal oxide (MO) may be provided in various forms such as powder, granules, crushed pellets, porous pellets, and high-density pellets, and micropores generated when the metal oxide (MO) is reduced to metal (U, etc.) by an electrolytic reduction process. The molten salt penetrates into the metal oxide (MO), and an interface with the molten salt (L) is formed, thereby causing an electrolytic reduction reaction. Therefore, in the case of a metal oxide (MO) lump having a dense internal structure such as a high-density pellet, when the length of the cross section is 1 cm or less, the efficiency of electrolytic reduction reaction is improved, and the size of the metal oxide raw material is cross-section considering ease of handling The length of may be 0.5cm, but is not limited thereto.

In one embodiment, the cathode 40 may be connected to the carrier gas supply pipe 20 to spray the carrier gas (G) supplied to the upper portion. Therefore, the metal oxide (MO) placed on the cathode 40 is mixed with the molten salt (L) and the cathode 40 together with the molten salt (L) by the carrier gas (G) injected from the cathode (40) It can flow between the anode (30).

The cathode 40 includes a body 42 having an upper surface on which a metal oxide (MO) is placed, and a flow path 43 through which the carrier gas G provided in the body 42 and supplied from the carrier gas supply pipe 20 flows , It may include a plurality of nozzles 44 for connecting the flow path 43 and the upper surface to spray the carrier gas (G) over the upper surface.

The body 42 has a substantially circular plate structure corresponding to the cross-sectional shape of the reactor 10, and may be made of a material having mechanical stability while being corrosion resistant in the hot molten salt (L). For example, it may be made of a nickel-based superalloy, stainless steel or tantalum metal, but is not limited thereto.

In one embodiment, the plurality of nozzles 44 includes a first nozzle group 44a arranged in a central area of the upper surface of the body 42 and a second nozzle group 44b arranged in an edge area around the central area. can do. In this case, the first nozzle group 44a and the second nozzle group 44b may inject the carrier gas G at different injection pressures.

In one embodiment, the flow path 43 may include a first flow path 43a connected to the first nozzle group 44a and a second flow path 43b connected to the second nozzle group 44b. In this case, the first flow path 43a and the second flow path 43b may flow the carrier gas G at different pressures from each other.

Thus, the metal oxide (MO) is placed on the cathode 40 and does not maintain a fixed state, and has a flow state with the molten salt L by the carrier gas G injected to the upper surface of the body 42. . And, the metal oxide (MO) may be repeatedly dispersed and stirred in the molten salt (L) by repeatedly ascending and descending by the carrier gas (G) injected at different pressures depending on the region.

When the metal oxide (MO) together with the molten salt (L) is placed in a flow state, an electrolytic reduction process is performed by applying a voltage to the anode 30 and the cathode 40 through the power supply 2. Therefore, the efficiency of the electrolytic reduction process can be improved by effectively mixing Li metal and metal oxide (MO) produced through electrolysis, and when the metal oxide accommodated in the basket is subjected to an electrolytic reduction process in a fixed state as in the prior art. Since it does not participate effectively in the reduction reaction, the problem that the ratio occupied by the surplus Li metal increases due to the presence of surplus Li metal can be solved.

In one embodiment, the cathode 40 may be rotatably provided within the reactor 10. The rotating shaft 45 provided on the body 42 of the cathode 40 may be connected to a driving unit 46 disposed outside the reactor 10. The driving unit 46 may rotate the cathode 40 disposed in a horizontal state along the rotation axis 45 to be inclined at a predetermined slope.

As the cathode 40 is disposed in an inclined state, the product (RO) having the electrolytic reduction process placed on the cathode 40 is completed, for example, the reduced metal is a product recovery unit 12 under the reactor 10 in the cathode 40 Can be moved to. When the movement of the product RO is completed, the driving unit 46 may rotate the cathode 40 again to be placed in an original horizontal state.

The product RO transferred to the product recovery unit 12 may be transferred to a device for subsequent processing.

Referring to the drawings, the metal oxide electrolytic reduction apparatus 1 according to an exemplary embodiment of the present invention may include a filtration membrane 50.

The filtration membrane 50 is disposed between the anode 30 and the cathode 40 so that the liquid containing molten salt L passes through the anode 30 and passes through the reduced metal of metal oxide (MO) and metal oxide (MO) ( U, etc.) may block the passage. Therefore, it is possible to prevent the metal oxide (MO) in the fluidized state and the reduced metal from contacting the anode 30.

The filtration membrane 50 may be formed of a mesh or a porous membrane through which liquid and gaseous substances can pass and block solid substances, and is detachably mounted inside the reactor 10 in a structure that crosses the cross section of the reactor 10. Can be.

The molten salt (L) that has passed through the filtration membrane 50 may volatilize and reach the condensation unit 11 provided on the upper part of the reactor 10 together with the carrier gas G. Then, the vaporized molten salt may be condensed in the condensation unit 11 to be converted into a solid powder form.

Referring to the drawings, the metal oxide electrolytic reduction apparatus 1 according to an exemplary embodiment of the present invention may include a cyclone 60. The cyclone 60 may be provided on one side of the reactor 10 to be connected to the reactor 10.

In one embodiment, the cyclone 60 is connected to the condensation unit 11 of the reactor 10, the first connecting pipe 61 for introducing the solid powder (L') and the carrier gas (G) into the cyclone (60) ), the second connecting pipe 62 connected to the reactor 10 to introduce the solid powder (L') separated from the carrier gas (G) into the molten salt (L) in the reactor 10, and the solid powder ( L′) may include a gas outlet 63 for discharging the separated carrier gas G from the cyclone 60.

The solid powder (L') and the carrier gas (G) introduced into the cyclone (60) through the first connecting pipe (61) may be separated inside the cyclone (60).

The gas outlet 63 may discharge the carrier gas G separated from the solid powder L'to the outside of the cyclone 60. In one embodiment, the gas outlet 63 may be installed with a mixed gas separation device (not shown), it is possible to reuse the argon gas used as the carrier gas (G). In this case, argon gas may be supplied into the reactor 10 through the carrier gas supply pipe 20, and may be reused as the carrier gas (G).

The second connection pipe 62 may be connected to the reactor 10 at the bottom of the cyclone 60, and the solid powder (L') separated from the carrier gas (G) to the molten salt (L) in the reactor 10 Can be introduced. Therefore, the conventional problem that requires replenishment due to the loss due to volatilization of the molten salt can be solved by reusing the molten salt to be circulated and reused. In addition, it is possible to solve the problem of volatilization of molten salt and diffusion of volatile substances in the hot cell.

The second connection pipe 62 may be connected to a reactant inlet 64 for introducing the metal oxide (MO) into the reactor 10. The connector 62a of the second connector 62 connected to the reactor 10 so that the metal oxide (MO) injected through the reactant inlet 64 is placed on the cathode 40 in the reactor 10 is a cathode ( 40). When the reactor 10 is initially operated or when the molten salt is replenished, a metal oxide (MO) or a salt may be injected into the reactor 10 through the reactant inlet 64. At this time, the injected salt may be in a solid state rather than a molten salt state.

In one embodiment, the second connecting pipe 62 may further include a gas inlet 65 connected to the gas outlet 63, and the argon gas supplied from the gas outlet 63 to the carrier gas (G) By doing so, the solid powder (L') and the metal oxide (MO) can be introduced into the reactor 10.

As described above, by implementing a circulation structure such that the vaporized molten salt and the carrier gas discharged from the reactor 10 are supplied to the reactor 10 again through the cyclone 60, a supplementary problem due to loss and a problem caused by the diffusion of volatile substances Can solve it. In addition, it can be expected to reduce the cost through reuse.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may realize that the present invention can be implemented in other specific forms without changing its technical spirit or essential features. You will understand. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

1... Electrolytic reduction device of metal oxide
10... reactor
11... Condensation
12... Product recovery unit
20... Carrier gas supply pipe
30... anode
40... cathode
41... insulation
42... body
43... Euro
43a... 1st Euro, 43b... 2nd Euro
44... Nozzle
44a... first nozzle group, 44b... second nozzle group
45... rotating shaft
46... Drive
50...filtration membrane
60... cyclone
61... 1st connector
62... second connector
63... Gas outlet
64... reactant inlet
65... gas inlet
L... molten salt, L'... solid powder
G... carrier gas
MO... metal oxide, RO... product

Claims (9)

A reactor comprising a LiCl molten salt;
A carrier gas supply pipe supplying carrier gas into the reactor;
An anode immersed in the molten salt;
A negative electrode disposed under the anode and connected to the carrier gas supply pipe, and spraying the carrier gas supplied through the carrier gas supply pipe upward; And
A cyclone for separating the solid powder and the carrier gas from a condensation unit in which the molten salt vaporized at the top of the reactor condenses and is converted into a solid powder form;
It includes,
The cyclone is connected to the condensation part, the first connection tube for introducing the solid powder and the carrier gas into the cyclone, and the solid powder separated from the carrier gas as the reactor is used as the molten salt in the reactor. A second connecting pipe for introducing, a gas outlet for discharging the carrier gas from which the solid powder is separated from the cyclone,
A metal oxide electrolytic reduction device characterized in that the metal oxide mixed with the molten salt between the cathode and the anode flows together with the molten salt by the carrier gas injected from the cathode.
According to claim 1,
The cathode includes a body, a flow path through which the carrier gas supplied from the carrier gas supply pipe flows, and a plurality of nozzles connected to the flow path and spraying the carrier gas onto the upper surface of the body. Metal oxide electrolytic reduction device.
According to claim 2,
The plurality of nozzles includes a first nozzle group arranged in a central area of the body and a second nozzle group arranged in an edge area around the central area, wherein the first nozzle group and the second nozzle group are different from each other. Electrolytic reduction device of a metal oxide, characterized in that for spraying the carrier gas at a pressure.
According to claim 3,
The flow path includes a first flow path connected to the first nozzle group, and a second flow path connected to the second nozzle group, wherein the first flow path and the second flow path flow the carrier gas at different pressures. Metal oxide electrolytic reduction device.
According to claim 1,
Metal oxide, which is disposed between the anode and the cathode further comprises a filter membrane to pass the liquid containing the molten salt to the anode side and to block the metal oxide and the solid containing the reduced metal of the metal oxide. Electrolytic reduction device.
delete According to claim 1,
The second connection pipe is connected to a reactant inlet for introducing the metal oxide into the reactor,
Electrolytic reduction device for a metal oxide, characterized in that the connector of the second connector connected to the reactor is located above the cathode so that the metal oxide injected through the reactant injection port is placed on the cathode in the reactor. .
According to claim 1,
The gas outlet is connected to the carrier gas supply pipe or the second connection pipe, the metal oxide electrolytic reduction device, characterized in that for introducing the carrier gas into the reactor.
According to claim 1,
The cathode is rotatably provided in the reactor, and is connected to a rotating shaft of the cathode, further comprising a driving unit for driving the cathode to rotate.

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