CO2 ELECTROLYSIS DEVICE

Description

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on Japanese Patent Application No. 2024-046463, filed Mar. 22, 2024, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a CO₂ electrolysis device.

Description of Related Art

Efforts aimed at mitigating or reducing the impact of climate change have been ongoing in the related art, and research and development into reducing CO₂ emissions is being carried out to achieve this goal.

The technology of recovering CO₂ from exhaust gas or the atmosphere and obtaining valuable products through electrochemical reduction is a promising technology with the potential to achieve carbon neutrality, but the biggest challenge is economic efficiency. In order to improve the economic efficiency, it is important to increase the energy efficiency and reduce the loss of CO₂ in the recovery and reduction of CO₂ .

As the technique of recovering CO₂, for example, Japanese Unexamined Patent Application, First Publication No. 2022-151866 discloses that, by making the pH of a cathode-side electrolyte used in an electrochemical reactor higher than that of the anode-side electrolyte and suppressing hydrogen generation at the cathode, compared to the case where CO₂ is adsorbed onto an adsorbent and then desorbed and reduced by heating, the energy required to desorb CO₂ can be reduced, energy efficiency can be improved, and CO₂ loss can also be reduced.

SUMMARY OF THE INVENTION

Incidentally, in order to reduce CO₂ emissions, it is necessary to further increase the size of CO₂ recovery devices in order to further increase the recovery efficiency of CO₂ .

As shown in FIG. 3A and FIG. 3B, an electrochemical reactor (a CO₂ electrolytic laminate 11) disclosed in Japanese Unexamined Patent Application, First Publication No. 2022-151866 includes end plates 20 provided on both ends in a lamination direction, bolts 3 inserted through a plurality of bolt holes 20a, and nuts 4, constituting a CO₂ electrolysis device 100. By fastening the bolts 3 and the nuts 4, the end plates 20 come into contact with the CO₂ electrolytic laminate 11, and a pressure is applied to the CO₂ electrolytic laminate 11.

When the pressure is applied to the CO₂ electrolytic laminate 11, current flows in a CO₂ electrolysis cell 1, and a chemical reaction can be promoted. However, when the CO₂ electrolysis device 100 is increased in size, since only end portions of the end plates 20 are fastened by the bolts 3 and the nuts 4, as emphasized by the two-dot chain line in FIG. 3B, central portions of the end plates 20 may bend outward in a lamination direction, making it impossible to apply sufficient pressure to the CO₂ electrolytic laminate 11. When there are any parts of the CO₂ electrolytic laminate 11 that do not receive sufficient pressure, sufficient current may not flow through those parts, and reaction efficiency in the CO₂ electrolysis cell 1 may decrease.

One way to solve this problem is to use thicker end plates 20 to increase rigidity and reduce deflection in the central portion. However, this will result in problems such as increased costs due to the increased amount of material used for the end plates 20 and an increase in the weight of the CO₂ electrolysis device 100, including the CO₂ electrolytic laminate 11.

An aspect of the present invention is directed to providing a CO₂ electrolysis device with improved recovery efficiency of CO₂. The aspect of the present invention contributes to mitigating or reducing the impact of climate change.

The summary of the present invention is as follows.

• • [1] A CO₂ electrolysis device including:
  • a CO₂ electrolytic laminate constituted by a plurality of CO₂ electrolysis cells, which are laminated;
  • end plates provided on both ends of the CO₂ electrolytic laminate in a lamination direction; and
  • collars that are provided on both ends of the CO₂ electrolytic laminate in a first direction perpendicular to the lamination direction and that are disposed between the end plates,
  • wherein the collars are longer than the CO₂ electrolytic laminate in the lamination direction, and
  • the end plates have a shape bent inward in the lamination direction at a central portion of the CO₂ electrolytic laminate in the first direction.
  • [2] The CO₂ electrolysis device according to the above-mentioned [1], wherein the end plates include a plurality of bolt holes, and
  • the end plates are bent inward in the lamination direction by fastening bolts inserted through the bolt holes to nuts.
  • [3] The CO₂ electrolysis device according to the above-mentioned [1] or [2], wherein an electrolyte inlet of the CO₂ electrolytic laminate is disposed closer to a center in a second direction, which is perpendicular to the lamination direction and the first direction, than an electrolyte outlet.

According to the aspect of the present invention, it is possible to provide a CO₂ electrolysis device with improved recovery efficiency of CO₂ .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram showing an example of a CO₂ electrolysis device according to the present invention.

FIG. 1B is a schematic diagram showing the example of the CO₂ electrolysis device according to the present invention.

FIG. 2 is a schematic diagram showing another example of the CO₂ electrolysis device according to the present invention.

FIG. 3A is a schematic diagram showing an example of a CO₂ electrolysis device according to the related art.

FIG. 3B is a schematic diagram showing the example of the CO₂ electrolysis device according to the related art.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Further, dimensions of the drawings illustrated in the following description are merely examples, and the present invention is not necessarily limited to them, and can be modified as appropriate within the scope that does not change the scope of the invention.

As shown in FIG. 1A and FIG. 1B, a CO₂ electrolysis device 10 according to the embodiment includes a CO₂ electrolytic laminate 11 constituted by a plurality of CO₂ electrolysis cells 1, which are laminated, end plates 2 provided on both ends of the CO₂ electrolytic laminate 11 in a lamination direction, and collars 5 provided on both ends in a first direction perpendicular to the lamination direction of the CO₂ electrolytic laminate 11 and disposed between the end plates 2.

Here, the lamination direction in the embodiment is a direction perpendicular to the paper surface in FIG. 1A and FIG. 2, and an upward/downward direction parallel to the paper surface in FIG. 1B. In addition, the first direction perpendicular to the lamination direction is a leftward/rightward direction parallel to the paper sheet of FIG. 1A and FIG. 2. In an example shown in FIG. 1A to FIG. 2, the first direction coincides with a longitudinal direction of the CO₂ electrolytic laminate 11.

The collars 5 are longer in the lamination direction than the CO₂ electrolytic laminate 11. For this reason, for example, when bolts 3 and nuts 4 are fastened in sequence as shown in FIG. 1A, the end plates 2 are bent inward in the lamination direction at the central portion in the first direction of the CO₂ electrolytic laminate 11, as emphasized by the two-dot chain line in FIG. 1B. Accordingly, a pressure stronger than that applied to both end portions of the CO₂ electrolytic laminate 11 in the first direction can be applied to the CO₂ electrolytic laminate 11. Here, it is preferable to use the end plates 2 with low rigidity so that the central portion of the CO₂ electrolytic laminate 11 in the first direction can bend inward in the lamination direction.

With the configuration described above, in the CO₂ electrolysis device 10 according to this embodiment, even if the device is enlarged, the central portions of the end plates 2 are prevented from bending outward in the lamination direction, and a sufficient pressure can be applied to the CO₂ electrolytic laminate 11. For this reason, it is possible to prevent a decrease in reaction efficiency in the CO₂ electrolysis cells 1.

In addition, since it is not necessary to use thick end plates 2 to increase rigidity, an increase in the amount of material required for the end plates 2 can be prevented. Further, when the end plates 2 with lower rigidity are used, the material amount and weight of the end plates 2 can be reduced.

Further, the collars 5 are preferably several um units longer than the CO₂ electrolytic laminate 11 so that a sufficient pressure is applied to both end portions of the CO₂ electrolytic laminate 11 in the first direction. By making the length of the collars 5 not too long, but by making them longer by a few um units, it is possible to prevent the pressure from being applied to the CO₂ electrolytic laminate 11 at both end portions in the first direction.

As shown in FIG. 1A and FIG. 1B, the CO₂ electrolysis device 10 may be a rectangular parallelepiped with a longitudinal direction or may be a cube. When the CO₂ electrolysis device 10 is a rectangular parallelepiped, for example, the dimensions may be approximately 300 mm in the longitudinal direction and 100 mm in the lateral direction.

In the CO₂ electrolysis device 10 according to the embodiment, as shown in FIG. 1A and FIG. 1B, the end plates 2 may have a plurality of bolt holes 2a, and when the bolts 3 inserted into the bolt holes 2a are fastened to the nuts 4, the end plates 2 may have a shape that is bent inward in the lamination direction.

As described above, by tightening the bolts 3 and the nuts 4 in the order shown in FIG. 1A, the end plates 2 can be preferably bent inward in the lamination direction.

Further, in FIG. 1A, a distinction is shown between bolt holes 2b, which do not have the collars 5 disposed between them, and bolt holes 2a, which have the collars 5 disposed between them. In addition, in FIG. 1B, only some of the bolts 3 and the nuts 4 are shown.

In addition, in the CO₂ electrolysis device 10 according to the embodiment, as shown in FIG. 2, it is preferable that an electrolyte inlet 6 of the CO₂ electrolytic laminate 11 is positioned closer to the center in the lamination direction and in the second direction perpendicular to the first direction than an electrolyte outlet 7.

Further, in the embodiment, the lamination direction and the second direction perpendicular to the first direction are an upward/downward direction parallel to the paper sheet of FIG. 2. In FIG. 2, the second direction coincides with a short direction of the CO₂ electrolytic laminate 11.

In the CO₂ electrolytic laminate 11, in general, raw materials for at least one of the cathode and the anode are solutions, and products are gases. For this reason, in the CO₂ electrolytic laminate 11, from the viewpoint of product discharge, and with the aim of utilizing gas buoyancy, the entrance for the raw materials is located below the lamination direction, and the outlet is located above the lamination direction. In addition, in the CO₂ electrolytic laminate 11, chemical reactions are more likely to occur near the electrolyte inlet 6 (a cathode inlet 6a, an anode inlet 6b) where the raw materials concentration is high, and hydrogen as a by-product is more likely to be produced near the electrolyte outlet 7 (a cathode outlet 7a, an anode outlet 7b) where the raw materials concentration is low.

In the CO₂ electrolysis device 10 according to the embodiment, the highest pressure is applied to an area indicated by the two-dot chain line in FIG. 2. Here, as shown in FIG. 2, by disposing the electrolyte inlet 6 of the CO₂ electrolytic laminate 11 near the center in the second direction (short direction), a higher pressure can be applied to the vicinity of the electrolyte inlet 6. Accordingly, a current can preferably flow near the electrolyte inlet 6, and the chemical reaction can be further promoted. In addition, since the pressure is lower near the electrolyte outlet 7 than near the electrolyte inlet 6, the current flow is inhibited, which suppresses the generation of hydrogen that is a by-product. These effects can further increase the CO₂ recovery efficiency of the CO₂ electrolysis device 10.

In addition, as shown in FIG. 2, the CO₂ electrolytic laminate 11 is preferably disposed such that a distance of a flow path 8 (a cathode flow path 8a, an anode flow path 8b) is shortened. Accordingly, for example, in comparison with the case in which the CO₂ electrolytic laminate 11 is disposed such that the flow path 8 is disposed in the leftward/rightward direction (the longitudinal direction of the CO₂ electrolytic laminate 11) parallel to the drawing of FIG. 2, pressure loss in the end portions in the longitudinal direction can be suppressed, and CO₂ recovery efficiency can be further improved.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.