DIRECT AIR CAPTURE DEVICE AND CARBON DIOXIDE CAPTURE METHOD

A direct air capture device according to one aspect of the present disclosure includes a carrier with a carbon dioxide adsorbent supported thereon. The direct air capture device electrically heats the carrier when desorbing the carbon dioxide adsorbed by the carbon dioxide adsorbent. Since the direct air capture device according to one aspect of the present disclosure electrically heats the carrier without using a heat medium, heat is not lost from the heat medium to a pipe or the like, and the heating efficiency is excellent.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2023-003128 filed on Jan. 12, 2023, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to direct air capture devices and carbon dioxide capture methods.

2. Description of Related Art

Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2014-516771 (JP 2014-516771 A) discloses a direct air capture (DAC) device having a reaction channel and a heat exchange channel. The reaction channel contains a carbon dioxide adsorbent in its wall. A heat medium for heating or cooling the reaction channel flows through the heat exchange channel.

SUMMARY

The inventors found the following problem with the DAC device disclosed in JP 2014-516771 A. In the DAC device disclosed in JP 2014-516771 A, the reaction channel is heated by causing the heat medium to flow through the heat exchange channel. Therefore, heat is inevitably lost to a pipe through which the heat medium flows, which results in poor heating efficiency.

The present disclosure was made in view of such circumstances, and provides a direct air capture device and a carbon dioxide capture method that are excellent in heating efficiency.

A direct air capture device according to an aspect of the present disclosure includes a carrier with a carbon dioxide adsorbent supported on the carrier. The direct air capture device is configured to electrically heat the carrier when desorbing carbon dioxide adsorbed by the carbon dioxide adsorbent.

A carbon dioxide capture method according to an aspect of the present disclosure includes the steps of: passing air through a carrier with a carbon dioxide adsorbent supported on the carrier to cause the carbon dioxide adsorbent to adsorb carbon dioxide; and heating the carrier to desorb and capture the carbon dioxide adsorbed by the carbon dioxide adsorbent. The carrier is electrically heated in the step of desorbing the carbon dioxide.

In the above aspect of the present disclosure, the carrier is electrically heated when desorbing the carbon dioxide adsorbed by the carbon dioxide adsorbent. That is, since the carrier is electrically heated without using any heat medium, heat is not lost from the heat medium to a pipe etc. Therefore, excellent heating efficiency is provided.

The carrier may be made of metal or may be made of an electrically conductive ceramic material. With such a configuration, the carrier can be easily electrically heated.

The carrier may be porous. With such a configuration, carbon dioxide can be adsorbed with high efficiency.

The present disclosure can provide a direct air capture device and a carbon dioxide capture method that are excellent in heating efficiency.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are simplified as appropriate.

First, a direct air capture device according to a first embodiment will be described with reference toFIGS.1to4.FIG.1is a perspective view of a direct air capture device according to the first embodiment.FIG.2is a plan view seen from directly above the surface electrode20(minus side in the x-axis direction) inFIG.1.FIG.3is a cross-sectional view of the direct air capture device taken along line III-III inFIG.2.FIG.3shows the adsorption process in a non-energized state.FIG.4is a cross-sectional view of the direct air capture device taken along line III-III inFIG.2.FIG.4shows the desorption process in the energized state.

It should be noted that, of course, the right-handed xyz coordinates shown in the drawings are for convenience in describing the positional relationship of the constituent elements. The xyz coordinates in each drawing are common. The y-axis direction is the axial direction of the carrier10.

A direct air capture device100is a device that passes air through a carrier10with a carbon dioxide adsorbent supported thereon and capture carbon dioxide in the air by allowing the carbon dioxide adsorbent to adsorb the carbon dioxide. The direct air capture device100can be electrically heated. Therefore, as shown inFIG.1, the direct air capture device100includes surface electrodes20, wiring members30and fixing layers40on the outer peripheral surface of the carrier10. Note that the surface electrode20, the wiring member30, and the fixing layer40are merely an embodiment for enabling the carrier10to be electrically heated, and are not limited in any way.

Note thatFIG.2shows the positional relationship of one surface electrode20with the carrier10, the wiring member30, and the fixing layer40. The same applies to the other surface electrode20. Specifically, as shown inFIGS.1and3, the two surface electrodes20are in a positional relationship of mirror symmetry with respect to a plane of symmetry parallel to the yz plane.

The carrier10is, for example, a porous member and carries a carbon dioxide adsorbent thereon. Carrier10need not be porous. However, when the carrier10is porous, the surface area in contact with air is increased, and carbon dioxide can be adsorbed with high efficiency. Further, since the carrier10itself is electrically heated, the carrier10is made of an electrically conductive ceramic material such as SiC (silicon carbide). The carrier10maybe made of metal such as nichrome or stainless steel. Examples of the carbon dioxide adsorbent include polyethyleneimine, primary amines, secondary amines, and secondary alkanolamines.

As shown inFIG.1, the carrier10has, for example, a substantially cylindrical outer shape. The inside of the carrier10has a honeycomb structure composed of a plurality of channels extending in the y-axis direction. Air passes through the inside of the carrier10in the axial direction (y-axis direction), as indicated by the hollow arrow.

The surface electrodes20are a pair of electrodes formed on the outer peripheral surface of the carrier10and arranged to face each other with the carrier10interposed therebetween, as shown inFIG.1. The surface electrode20is in physical contact with and electrically connected to the carrier10. Moreover, as shown inFIG.2, each surface electrode20has, for example, a rectangular planar shape. Each surface electrode20extends, for example, in the carrier axis direction (y-axis direction).

Furthermore, as shown inFIGS.3and4, the surface electrode20is electrically connected to the battery BT via the wiring member30, the external electrode81, and the external wiring82. With such a configuration, current is supplied to the entire carrier10. Thereby, the carrier10is uniformly electrically heated. One of the pair of surface electrodes20is a plus pole and the other is a minus pole. Any surface electrode20maybe a positive electrode or a negative electrode. In other words, the direction of current flowing through the carrier10is not limited.

The surface electrode20is, for example, a thermal spray coating formed by plasma thermal spraying. The thickness of the surface electrode20is, for example, approximately 50 to 200 μm. The surface electrode20is energized in the same manner as the wiring member30. Therefore, this thermal spray coating must be metal-based. Examples of the metal that constitutes the matrix of the thermal spray coating include copper, aluminum, and alloys thereof having high electrical conductivity.

The wiring members30are arranged on the respective surface electrodes20, as shown inFIGS.1and2. As shown inFIG.2, the wiring member30includes a comb-like wiring31, a root portion32and a lead portion33. Details of each will be described later. The entire wiring member30is, for example, a thin metal plate having a thickness of about 0.1 mm. Also, the wiring member30is made of copper, aluminum, an alloy thereof, or the like having high conductivity.

As shown inFIG.2, the plurality of comb-like wirings31extend in the circumferential direction of the carrier over substantially the entire region where the surface electrode20is formed. A plurality of comb-tooth-shaped wirings31are arranged side by side at approximately equal intervals along the carrier axis direction (y-axis direction). Furthermore, all of the comb-like wirings31are connected to the root portion32on the positive side in the z-axis direction of the surface electrode20formation region. All of the comb-like wirings31are fixed to the surface electrode20by the fixing layer40. All of the comb-like wirings31are electrically connected to the surface electrodes20. As a matter of course, the width and the number of the comb-shaped wirings31are appropriately determined.

As shown inFIG.2, the root portion32is a portion extending along the surface electrode20in the carrier axial direction (y-axis direction). All of the comb-like wirings31are extended from the root portion32in the circumferential direction of the carrier. The root portion32is not fixed to the carrier10and the surface electrode20. The lead-out portion33is provided on the side opposite to the comb-like wiring31in the central portion of the root portion32in the carrier axial direction (y-axis direction). The lead portion33is also not fixed to the carrier10and the surface electrode20.

The fixing layer40is a button-shaped thermal spray coating formed on the comb-like wiring31. A wiring member30is arranged on the surface electrode20. The fixing layer40can be formed by arranging a masking jig thereon and performing plasma spraying. The material forming the fixing layer40is the same as that of the surface electrode20described above. By sandwiching the comb-like wiring31between the fixing layer40and the surface electrode20, the comb-like wiring31is fixed and electrically connected to the surface electrode20.

In the example ofFIG.2, each comb-like wiring31is fixed to the surface electrode20by one fixing layer40. In other words, the comb-like wiring31is not fixed to the surface electrode20at the portion where the fixing layer40is not formed. With such a configuration, thermal strain (thermal stress) due to the difference in linear expansion coefficient between the wiring member30made of the thin metal plate and the carrier10made of ceramics can be relaxed. In other words, the thermal strain (thermal stress) can be alleviated by forming the individual fixing layers40as small as possible and by interspersing them. The number and spacing of the fixing layers40to be arranged may be determined as appropriate.

As shown inFIGS.3and4, the wiring member30(lead portion33) is electrically connected to the battery BT via the external electrode81and the external wiring82. With such a configuration, an electric current is supplied to the carrier10, and the carrier10is electrically heated. Here, the battery BT is connected in series with the switch SW. A control unit83controls on/off of the switch SW by a control signal cnt. That is, the control unit83controls energization and non-energization of the carrier10.

FIG.3shows the carbon dioxide adsorption process when the switch SW is off, that is, in a non-energized state (non-heating state). On the other hand,FIG.4shows the desorption process of the adsorbed carbon dioxide when the switch SW is on, that is, in an energized state (heating state). The heating temperature of the carrier10in the desorption step is, for example, about 100° C.

In the carbon dioxide capture method using the direct air capture device100, the adsorption step shown inFIG.3and the desorption step shown inFIG.4are repeated. When shifting from the desorption step to the adsorption step, air is introduced into the inside of the carrier10to cool the carrier10as in the adsorption step. Thereby, it is possible to quickly shift to the adsorption step.

As described above, in the direct air capture device100according to the present embodiment, the carrier10is electrically heated when the carbon dioxide adsorbed by the carbon dioxide adsorbent is desorbed. That is, the carrier10is electrically heated without using a heat medium. Therefore, heat is not lost from the heat medium to a pipe etc., and the heating efficiency is excellent.

It should be noted that the present disclosure is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit of the present disclosure. Also, the present disclosure contributes to carbon neutrality, decarbonization, and Sustainable Development Goals (SDGs).