JP5787580B2 - Electrolytic reduction device - Google Patents

Description

  The present invention relates to an electrolytic reduction apparatus for performing metal recovery using an electrolytic reduction method.

As a means for recovering rare earth metals from general waste or as a means for recovering metals such as U, Zr, and Re from spent fuel, a recovery method by electrolytic reduction is known.
In this recovery method, as shown in FIG. 7, the metal oxide 8 to be recovered is housed in a gasket-like cathode 4 disposed in a high-temperature molten salt 2 in the electrolytic vessel 1, and then made of platinum or carbon. A voltage is applied to the anode 5 and the cathode basket 4 by a power source 6 to recover the metal by reducing the metal oxide 8 in the cathode 4 (Patent Document 1). At that time, oxygen ions and electrons are combined at the anode 5 to generate oxygen gas.

JP 2009-288178 A

  In the conventional electrolytic reduction method described above, the anode requires a material with high conductivity and high corrosion resistance at high temperatures, and it is necessary to select a metal having a high redox potential in order to suppress dissolution of the anode. It was. Therefore, platinum or sintered solid carbon is used as the anode. However, noble metal materials such as platinum are expensive, and carbon is a sintered product due to the reaction with oxygen as the electrolysis progresses. There was a possibility that it would collapse and contaminate the molten salt or cause a short circuit between the electrodes.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly efficient electrolytic reduction apparatus that can prevent corrosion and contamination of the electrolytic reduction apparatus and has a high reduction treatment speed.

In order to solve the above problems, an electrolytic reduction apparatus according to the present invention includes an electrolytic container in which a molten salt is accommodated, a basket-like cathode that is disposed in the electrolytic container and in which a metal compound to be collected is accommodated, And an anode made of a fibrous carbon bundle disposed in the electrolytic vessel, wherein the fibrous carbon bundle is housed in a ceramic tube, and the fibrous carbon bundle is taken from a lower end portion of the ceramic tube. It is characterized by protruding a predetermined length .

  According to the present invention, it is not necessary to use an expensive noble metal by using a fibrous carbon bundle as the anode, and since the fibrous carbon bundle can form a large anode area, oxygen and carbon generated at the anode can be formed. The carbon dioxide gas can be efficiently reacted to prevent contamination of the molten salt by carbon, and the reduction treatment speed can be greatly improved.

(A) is a schematic longitudinal cross-sectional view which shows the electrolytic reduction apparatus which concerns on 1st Embodiment, (b) is a side view which shows the anode structure. The schematic longitudinal cross-sectional view which shows the anode structure which concerns on 2nd Embodiment. The schematic longitudinal cross-sectional view which shows the anode structure which concerns on 3rd Embodiment. The schematic longitudinal cross-sectional view which shows the anode structure which concerns on 4th Embodiment. (A), (b) is a schematic longitudinal cross-sectional view which shows the anode structure which concerns on 5th Embodiment, respectively. (A) is a top view of the electrolytic reduction apparatus which concerns on 6th Embodiment, (b) is the longitudinal cross-sectional view. The longitudinal cross-sectional view which shows the outline | summary of the conventional electrolytic reduction apparatus.

Hereinafter, embodiments of an electrolytic reduction apparatus according to the present invention will be described with reference to the drawings.
[First Embodiment]
The electrolytic reduction apparatus according to the first embodiment will be described with reference to FIGS.
(Constitution)
As shown in FIG. 1A, the electrolytic reduction device of the present embodiment controls the heating of the electrolytic vessel 1, the molten salt 2 accommodated in the electrolytic vessel 1, and the surroundings of the electrolytic vessel 1. The heating device 3 includes a basket-like cathode 4, an anode 5, and a power source 6 in which a metal oxide 8 to be collected is accommodated.
As the anode 5, a fibrous carbon bundle 7 is used as shown in FIG.

(Function)
In the electrolytic reduction apparatus configured as described above, in the basket-like cathode 4, the metal oxide 8 generates oxygen ions and metal by a reduction reaction, and the metal is deposited on the cathode 4 and collected. In the anode 5 made of a fibrous carbon bundle, oxygen ions are combined with electrons to generate oxygen gas. At that time, since the anode 5 made of the fibrous carbon bundle 7 has a large contact area with the molten salt 2, the oxygen generated at the anode 5 efficiently combines with the carbon of the fibrous carbon bundle 7 to generate carbon dioxide gas. To do.

(effect)
As described above, the conventional anode structure uses noble metal or the like to prevent the anode from being consumed and suppress the corrosion, whereas in the anode structure according to the present embodiment, the anode functions as a sacrificial anode. That is, the anode is made into a fibrous carbon bundle, and the reaction between carbon and oxygen is actively promoted to generate CO ₂ , thereby preventing diffusion of unreacted carbon powder from the anode into the molten salt. And contamination of the molten salt can be prevented.
In addition, by using fibrous carbon as the anode, it is possible to increase the anode surface area per unit volume, thereby greatly improving the reduction treatment speed.

  As described above, according to the first embodiment, it is not necessary to use an expensive noble metal by using an anode made of a fibrous carbon bundle, and the fibrous carbon bundle obtains a large anode area. Therefore, contamination of the molten salt can be prevented by efficiently reacting oxygen generated at the anode with carbon to produce carbon dioxide gas, and the reduction processing rate can be greatly improved.

[Second Embodiment]
An electrolytic reduction apparatus according to the second embodiment will be described with reference to FIG.
The anode 5 of the electrolytic reduction apparatus according to this embodiment houses the fibrous carbon bundle 7 in the ceramic tube 9 and connects the upper part of the ceramic tube 9 to the exhaust device 10. The fibrous carbon bundle 7 protrudes from the lower end portion of the ceramic tube 9 so as to form a protruding portion 13, and the length of the protruding portion 13 is such that only oxygen and carbon in the molten salt are excessive. It is adjusted so that it can react without lack. Thereby, it is possible to prevent carbon as the anode material from being diffused and contaminated into the electrolytic reduction system.

  Furthermore, by using the ceramic tube 9, the fibrous carbon of a flexible material is held as a rod, and carbon dioxide is discharged out of the system by the exhaust device 10 provided on the upper portion of the ceramic tube 9 to reduce the pressure inside the ceramic tube 9. .

  According to the second embodiment, the tip end portion of the fibrous carbon bundle is housed in the ceramic tube 9 in a state of projecting into the molten salt 2, and a necessary electrolytic reaction can be caused only by the projecting portion. As a result, it is possible to prevent diffusion contamination of carbon as an anode material into the electrolytic reduction system, and to discharge the carbon dioxide gas generated by the electrolytic reaction outside the system without diffusing into the electrolytic cell.

[Third Embodiment]
An electrolytic reduction apparatus according to a third embodiment will be described with reference to FIG.
In the present embodiment, the heating device 11 is arranged around the tip of the ceramic tube 9 that accommodates and holds the fibrous carbon bundle constituting the anode 5.

  As a result, even when a molten salt such as LiCl—KCl that melts at a low temperature is used, the heating device 11 maintains the anode 5 at a high temperature to promote the reaction between oxygen and carbon, and oxygen into the electrolytic reduction system. Diffusion contamination can be suppressed.

[Fourth Embodiment]
An electrolytic reduction apparatus according to a fourth embodiment will be described with reference to FIG.
The protruding portion 13 of the fibrous carbon bundle 7 constituting the anode 5 is gasified and consumed as the electrolytic reaction proceeds. Therefore, in the fourth embodiment, as shown in FIG. 4, for example, a long fibrous carbon bundle 7 wound around a delivery member 12 made of a take-up member is delivered to the ceramic tube 9, and as the electrolytic reduction proceeds. The fibrous carbon bundle 7 is gradually sent to the ceramic tube 9.

By sending out the fibrous carbon bundle 7 as the protruding portion 13 of the fibrous carbon bundle 7 is consumed by the delivery member 12, the metal can be stably and continuously recovered without stagnation of the electrolytic reaction. .
The delivery member is not limited to a winding delivery member, and a linear delivery member may be used.

[Fifth Embodiment]
An electrolytic reduction apparatus according to the fifth embodiment will be described with reference to FIGS.
In the present embodiment, the tip 14 of the ceramic tube 9 that houses the fibrous carbon bundle 7 is arranged so as to face the cathode 4 as illustrated in FIGS. 5 (a) and 5 (b).
Thereby, the flow of the electrolysis current becomes efficient and the inter-liquid resistance between the cathode 4 and the anode 5 can be reduced, so that the electrolysis reaction efficiency can be improved.

[Sixth Embodiment]
The electrolytic reduction apparatus according to the sixth embodiment will be described with reference to FIG.
In the present embodiment, a plurality of anodes 5 are provided with respect to the cathode 4.
In the example shown in FIG. 6, a plurality of anodes 5 are arranged around the cathode 4.
As a result, the anode area can be further increased, the electrolytic reduction rate can be improved, and the generation of carbon dioxide per unit area can be promoted by suppressing the amount of oxygen generated per electrode, so Oxygen diffusion contamination can be prevented.

  In the above embodiment, the method for recovering the metal oxide in the molten salt has been described. However, the anode structure composed of the fibrous carbon bundle according to the present embodiment has a metal compound other than the metal oxide, such as a normal compound. It can be applied to electrolytic reduction in alkali metals and alkaline earth metal chlorides used for electrolytic reduction, and it can be used as an electrolytic reduction electrode in fluoride-based molten salt if similar oxides are added to the electrolytic solution. Is possible.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, combinations, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Electrolytic container, 2 ... Molten salt, 3 ... Heating device, 4 ... Anode, 5 ... Cathode, 6 ... Power supply, 7 ... Fibrous carbon bundle, 8 ... Reducing material amount, 9 ... Ceramic tube, 10 ... Exhaust device, DESCRIPTION OF SYMBOLS 11 ... Heating device, 12 ... Delivery member, 13 ... Projection part, 14 ... Tip part.

Claims (6)

An electrolytic container containing a molten salt, a basket-like cathode arranged in the electrolytic container and containing a metal compound to be collected, an anode made of a fibrous carbon bundle arranged in the electrolytic container, In an electrolytic reduction apparatus having
An electrolytic reduction apparatus characterized in that the fibrous carbon bundle is housed in a ceramic tube, and the fibrous carbon bundle is protruded from a lower end portion of the ceramic tube by a predetermined length . Electrolytic reduction apparatus according to claim 1, wherein the connecting the exhaust system to the top of the ceramic tube. Electrolytic reduction apparatus according to claim 1 or 2, characterized in that a heating device to a lower end periphery of the ceramic tube. The electrolytic reduction apparatus according to any one of claims 1 to 3 , wherein a delivery member capable of delivering the fibrous carbon bundle to the ceramic tube is provided on an upper portion of the ceramic tube. Electrolytic reduction apparatus according to any one of claims 1 to 4, characterized in that the front end portion of the ceramic tube was opposed to the cathode. Electrolytic reduction apparatus according to any one of claims 1 to 5, characterized in that arranging a plurality of the anode around the cathode.

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