Honeycomb structure and direct air recovery device

Abstract

To provide a honeycomb structure that is a structure used in direct air capture (DAC), which has a structure suitable for heating from the surface of an outer peripheral wall.SOLUTION: A honeycomb structure includes a partition wall for partitioning and forming a plurality of through holes as flow channels of air containing CO2, an outer peripheral wall provided on the outer periphery, and a CO2 adsorbent carried on the surface of the partition wall, wherein the partition wall and the outer peripheral wall are composed of silicon carbide and have opening ratios of 65 to 86%, the surface area of the partition wall is 20 to 36 cm2 per 1 cm3 of the honeycomb structure, and the honeycomb structure is used for direct air capture (DAC) application of desorbing CO2 adsorbed to the CO2 adsorbent by heating from the surface of the outer peripheral wall, and capturing CO2 in the air.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure and a direct air recovery device. [Background technology]

[0002] It is widely known that carbon dioxide (CO2) concentrations show a strong correlation with global warming, which leads to rising atmospheric temperatures and an increased chance of natural disasters such as typhoons and floods.

[0003] Patent Document 1 describes a method for removing CO2 from air using direct air capture (DAC). In DAC, when CO2 is adsorbed and desorbed onto an adsorbent such as an amine, it is desirable to increase the number of adsorption and desorption cycles and efficiently remove CO2 from air per volume.

[0004] In Patent Document 1, CO2 is desorbed by heating the adsorbent mainly using low-pressure steam. Furthermore, Patent Document 2 describes a CO2 capture device that is designed to capture CO2 generated from power generators, plants, etc., rather than capturing CO2 using DAC, in which a reaction layer and a heating layer are stacked, and steam is introduced into the heating layer to heat the reaction layer and desorb CO2. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2023-520609 [Patent Document 2] Japanese Patent Publication No. 2022-067481 Summary of the Invention [Problem to be solved by the invention]

[0006] When capturing CO2, such as when capturing CO2 from exhaust gases from power generators or plants, as in the technology of Patent Document 2, there is a heat medium (exhaust heat) nearby, so steam can be used to desorb the CO2. On the other hand, when removing CO2 from the atmosphere, as in DAC, there is no heat medium nearby, making it difficult to use steam for heating. Furthermore, the technology described in Patent Document 1 involves directly introducing steam into the carbon dioxide capture structure, which can result in the steam being mixed into the captured gas, lowering the CO2 concentration in the captured gas. In this case, a separate device is required to remove the steam from the captured gas.

[0007] In light of this background, the inventors investigated the possibility of preventing steam from being mixed into the recovered gas by heating the surface of the outer wall of the structure, rather than flowing steam into the structure. In the process, we discovered that the structure needed to be designed to be suitable for heating from the surface of the outer wall.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a honeycomb structure to be used in a DAC, which has a structure suitable for heating from the surface of the outer wall. [Means for solving the problem]

[0009] The honeycomb structure of the present invention is A partition wall that defines a plurality of through holes that serve as flow paths for air containing CO2; An outer periphery wall provided on the outer periphery; A honeycomb structure comprising: a CO adsorbent supported on a surface of the partition wall; the partition wall and the outer peripheral wall are made of silicon carbide, The aperture ratio is 65 to 86%. The surface area of ​​the partition wall is 1 cm 3 20-36cm per 2 and This honeycomb structure is used for direct air capture (DAC) applications in which CO2 adsorbed in the CO2 adsorbent is desorbed by heating the surface of the outer wall, thereby capturing CO2 in the air.

[0010] The honeycomb structures of the present invention are used in direct air capture (DAC) applications. When the partition walls and outer wall of the honeycomb structure are made of silicon carbide, the time required for the temperature to rise to the center of the honeycomb structure when heated from the surface of the outer wall can be shortened compared to other ceramic honeycomb structures that can also be used for DAC applications, because silicon carbide has high thermal conductivity. A short heating time means that the number of CO2 adsorption and desorption cycles can be increased for the same amount of CO2 adsorbed, resulting in a honeycomb structure that can efficiently capture CO2 when used for DAC applications.

[0011] Furthermore, the opening ratio of the honeycomb structure and the surface area of ​​the partition walls are set within appropriate ranges, and with these specifications, the heat capacity of the honeycomb structure falls within an appropriate range, shortening the temperature drop time, and therefore increasing the number of CO2 adsorption and desorption cycles for the same adsorption amount. Furthermore, the large surface area of ​​the partition walls allows a large amount of CO2 adsorbent to be supported. From this viewpoint, the honeycomb structure of the present invention is a honeycomb structure for DAC that is suitable for heating from the surface of the outer peripheral wall.

[0012] In the honeycomb structure of the present invention, it is preferable that the heating from the surface of the outer peripheral wall is performed by an electric heater. By heating with an electric heater, the honeycomb structure can be heated from the surface of the outer wall even if there is no heat medium nearby.

[0013] In the honeycomb structure of the present invention, it is preferable that the area to be heated on the surface of the outer peripheral wall is 50% or more. When the range of the heated region is as wide as 50% or more, the temperature of the entire honeycomb structure can be raised more quickly, and the time for one cycle can be shortened.

[0014] In the honeycomb structure of the present invention, the CO2 adsorbent is preferably at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks). These CO2 adsorbents can be suitably used for CO2 adsorption and desorption.

[0015] The cross-sectional area of ​​the honeycomb structure of the present invention is 100 to 400 cm2 in a cross section perpendicular to the longitudinal direction, which is the direction in which the through holes extend. 2 It is preferable that: Furthermore, the honeycomb structure of the present invention preferably has a length in the longitudinal direction, which is the direction in which the through holes extend, of 100 to 500 mm. Cross-sectional area is 100cm 2 If the cross-sectional area is smaller than 400 cm, the volume of the honeycomb structure per DAC device will be smaller, which may result in a smaller CO2 absorption capacity. 2 If the temperature exceeds this value, the central part of the honeycomb structure may become difficult to heat, and the overall temperature rise time may become longer. If the length is less than 100 mm, the amount of CO2 adsorption may be small, and if the length exceeds 500 mm, the pressure loss when air flows through the through-holes may be large. The preferred dimensions of the honeycomb structure are as described above, and the honeycomb structure having the above dimensions can be suitably used for DAC applications.

[0016] The direct air recovery (DAC) device of the present invention comprises the honeycomb structure of the present invention and a heater provided on the surface of the outer wall of the honeycomb structure; and a container for storing CO2 desorbed from the honeycomb structure. The DAC device of the present invention can desorb CO2 by heating the surface of the outer wall of the honeycomb structure with a heater, even if there is no heat medium nearby.Since the honeycomb structure has a material and structure that are suitable for heating from the surface of the outer wall, CO2 can be efficiently captured by DAC. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a honeycomb structure. [Figure 2] FIG. 2 is a perspective view schematically showing a state in which an electric heater is provided on the surface of the outer wall of a honeycomb structure. [Figure 3] FIG. 3 is a front view of a honeycomb structure for explaining the range of the region to be heated on the surface of the outer wall of the honeycomb structure. [Figure 4] FIG. 4 is a perspective view schematically showing a state in which a plurality of honeycomb structures are combined and arranged in a casing. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of a DAC device.

[0018] (Detailed Description of the Invention) The honeycomb structure of the present invention will be described below. The honeycomb structure of the present invention is A partition wall that defines a plurality of through holes that serve as flow paths for air containing CO2; An outer periphery wall provided on the outer periphery; A honeycomb structure comprising: a CO adsorbent supported on a surface of the partition wall; the partition wall and the outer peripheral wall are made of silicon carbide, The aperture ratio is 65 to 86%. The surface area of ​​the partition wall is 1 cm 3 20-36cm per 2 and This honeycomb structure is used for direct air capture (DAC) applications in which CO2 adsorbed in the CO2 adsorbent is desorbed by heating the surface of the outer wall, thereby capturing CO2 in the air.

[0019] The honeycomb structures of the present invention are used in direct air capture (DAC) applications. DAC is a technology that captures CO2 from the atmosphere (air), unlike technology that captures CO2 from gases with high CO2 concentrations, such as exhaust gas from factories. The CO2 concentration in the atmosphere is said to be around 0.04% (400 ppm), and DAC can be said to be a technology that captures CO2 from the atmosphere where the CO2 concentration is between 0.01% and 0.1%.

[0020] In DAC, CO2 in the air is adsorbed onto a CO2 adsorbent. The CO2 adsorbent may be at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks). These CO2 adsorbents have the ability to adsorb CO2 and have the property of releasing the adsorbed CO2 when heated.

[0021] Examples of amines include polyethyleneimine, monoethanolamine, diethanolamine, triethanolamine, tetraethyleneaminepentamine, methyldiethanolamine, dibutylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexaethylenediamine, benzylamine, metaxylenediamine, polyethyleneimine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

[0022] Zeolites include LTA type, FAU type, CHA type, DDR type, and AFI type. Examples of MOFs (metal organic frameworks) include Co-substituted MOFs and Zn-substituted MOFs.

[0023] The honeycomb structure of the present invention comprises partition walls that define a plurality of through holes that serve as flow paths for CO2-containing air, an outer peripheral wall provided on the outer periphery, and a CO2 adsorbent supported on the surface of the partition walls. FIG. 1 is a perspective view schematically showing an example of a honeycomb structure. 1 has a shape in which a plurality of through holes 21 are arranged side by side in the longitudinal direction (the direction indicated by the double-headed arrow f in FIG. 1) with partition walls 22 between them, and an outer peripheral wall 23 is provided on the periphery. The through holes 21 serve as flow paths for air containing CO2. A CO2 adsorbent is supported on the surface of the partition wall 22. The above-mentioned materials can be used as the CO2 adsorbent.

[0024] During CO2 adsorption, CO2 in the air that flows into the through-holes 21 from the gas inlet end portions 21a of the through-holes 21 is adsorbed by the CO2 adsorbent supported on the surfaces of the partition walls 22. The air, whose CO2 concentration has been reduced compared to before it flowed into the honeycomb structure 20, flows out from the gas outlet end portions 21b of the through-holes 21.

[0025] During CO2 capture, the honeycomb structure 20 is heated from the surface of the outer wall 23, whereby the CO2 adsorbed in the CO2 adsorbent is desorbed and the CO2 is captured. The desorbed gas containing a high concentration of CO2 is made to flow out from the gas outlet end 21b of the through-hole 21 and stored in a container such as a CO2 cylinder, which will be described later, for recovery.

[0026] The partition walls and outer peripheral wall of the honeycomb structure are made of silicon carbide. Silicon carbide has a high thermal conductivity of 190 W / mK, which means that compared to other ceramic honeycomb structures that can be used for DAC, it takes less time for the temperature to rise from the surface of the outer wall to the center of the honeycomb structure. A short heating time means that the number of CO2 adsorption and desorption cycles can be increased for the same amount of CO2 adsorbed, resulting in a honeycomb structure that can efficiently capture CO2 when used for DAC applications. Incidentally, the phrase "the partition walls and the outer peripheral wall are made of silicon carbide" means that the main component of the partition walls and the outer peripheral wall is silicon carbide, and does not mean that the partition walls and the outer peripheral wall are made only of silicon carbide. For example, it includes a composite of silicon carbide and metal silicon, silicon-containing silicon carbide, and silicon carbide bonded with metal silicon.

[0027] In addition, in order to obtain a honeycomb structure that can efficiently capture CO2 when used for DAC applications, the opening ratio of the honeycomb structure and the surface area of ​​the partition walls are set to appropriate ranges. The honeycomb structure has an opening ratio of 65 to 86%, and preferably 68 to 80%. The surface area of ​​the partition wall is 1cm for a honeycomb structure 3 20-36cm per 2 Also, 23 to 30 cm 2 It is preferable that: The opening ratio and surface area of ​​the partition walls can be calculated from the cell structure (thickness of the partition walls, cell density) of the honeycomb structure. When the opening ratio and the surface area of ​​the partition walls of the honeycomb structure are set within these ranges, the heat capacity of the honeycomb structure falls within an appropriate range, shortening the temperature-lowering time, and therefore increasing the number of CO2 adsorption and desorption cycles for the same adsorption amount. In addition, the large surface area of ​​the partition walls allows a large amount of CO2 adsorbent to be supported.

[0028] The partition walls and the outer peripheral wall are preferably porous, and the porosity thereof is preferably 30 to 70%, and more preferably 35 to 50%. By setting the porosity of the partition walls and the outer peripheral wall within the above range, the time required for heating and cooling the honeycomb structure can be shortened while maintaining the strength of the honeycomb structure. The porosity of the partition walls and the outer peripheral wall can be measured by mercury porosimetry under conditions of a contact angle of 130° and a surface tension of 485 mN / m.

[0029] The specific heat of the partition walls and outer peripheral wall as porous ceramic is preferably 0.5 to 0.8 J / gK, and more preferably 0.6 to 0.7 J / gK. The specific heat of the partition walls and the outer peripheral wall can be measured by cutting out a portion of the partition walls or the outer peripheral wall and subjecting it to DSC (differential scanning calorimetry) using a PerkinElmer DSC8000 at a measurement temperature of 25°C, a heating rate of 20°C / m, and a nitrogen atmosphere using sapphire as a reference sample.

[0030] The density of the partition walls and outer peripheral wall as porous ceramic is preferably 1.7 to 2.0 g / cc, and more preferably 1.8 to 1.9 g / cc. The density of the partition walls and the outer peripheral wall can be measured by cutting out a portion of the partition walls or the outer peripheral wall and using the Archimedes method.

[0031] The thermal conductivity of the partition walls and outer peripheral wall as porous ceramic is preferably 10 to 50 W / mK, and more preferably 15 to 40 W / mK. The thermal conductivity of the partition walls and the outer peripheral wall can be calculated by the formula: thermal conductivity=specific heat×density×thermal diffusivity. Thermal diffusivity can be measured using a NETZSCH LFA467 by the flash method at room temperature in a nitrogen atmosphere, and can be calculated by analysis including pulse width correction and heat loss correction.

[0032] The cross-sectional area of ​​the honeycomb structure perpendicular to the longitudinal direction, which is the direction in which the through holes extend, is 100 to 400 cm 2 The cross-sectional area is the sum of the area of ​​the partition wall, the area of ​​the outer peripheral wall, and the area of ​​the through-holes in the cross section. Furthermore, it is preferable that the length of the honeycomb structure in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm. Cross-sectional area is 100cm 2 If the cross-sectional area is smaller than 400 cm, the volume of the honeycomb structure per DAC device will be smaller, which may result in a smaller CO2 absorption capacity. 2 If the temperature exceeds this value, the central part of the honeycomb structure may become difficult to heat, and the overall temperature rise time may become longer. If the length is less than 100 mm, the amount of CO2 adsorption may be small, and if the length exceeds 500 mm, the pressure loss when air flows through the through-holes may be large.

[0033] It is desirable that the thickness of the partition walls of the honeycomb structure is uniform. The thickness of the partition walls of the honeycomb structure is preferably 0.1 to 1.0 mm, and more preferably 0.15 to 0.5 mm. The thickness of the peripheral wall of the honeycomb structure may be the same as the thickness of the partition walls, or may be thicker than the thickness of the partition walls.

[0034] The through-hole density in the cross section perpendicular to the longitudinal direction of the honeycomb structure is 31 to 155 pcs / cm 2 (200~1000 pieces / inch 2 ) is preferably 46.5 to 124 particles / cm 2 (300~800 pieces / inch 2 ) is more preferred.

[0035] The honeycomb structure of the present invention is used for DAC by being heated from the surface of the outer wall, that is, the heating method of the honeycomb structure is not a method of circulating high-temperature steam through the through holes to heat the partition walls. When the honeycomb structure is heated from the surface of the outer wall, if the temperature rise time from the surface of the outer wall to the center of the honeycomb structure during CO2 capture is short and the cooling time of the entire honeycomb structure after CO2 capture is short, this means that the number of CO2 adsorption and desorption cycles can be increased, resulting in a honeycomb structure that can efficiently capture CO2 when used for DAC applications.

[0036] The heating from the surface of the outer peripheral wall is preferably performed by a heater, and more preferably by an electric heater. The electric heater is an electric heating wire provided on the surface of the outer wall of the honeycomb structure. FIG. 2 is a perspective view schematically showing a state in which an electric heater is provided on the surface of the outer wall of a honeycomb structure. FIG. 2 shows a state in which an electric heater 30 is provided on the surface of the outer wall 23 of the honeycomb structure 20 shown in FIG. The electric heater 30 comprises an electric heating wire 31 and electrodes 32 attached to both ends of the wire.

[0037] Of the surfaces of the honeycomb structure, the two surfaces where the through holes are exposed are called end surfaces, and the other four surfaces are called side surfaces. An electric heater is provided on the side surface of the honeycomb structure. Fig. 2 shows that electric heaters 30 are provided on all four side surfaces of the honeycomb structure 20. In Fig. 2, the dotted lines indicate that electric heaters 30 are also provided on side surfaces that are located on the back side and cannot be seen directly.

[0038] In addition, an electric heater may be provided on some of the side surfaces of the honeycomb structure. When a plurality of honeycomb structures are used in combination as described below, if one electric heater is provided between two adjacent honeycomb structures, the two adjacent honeycomb structures can be heated by one electric heater. Therefore, when viewed as a single honeycomb structure, there may be a side surface on which an electric heater is not provided. Nichrome wire or the like can be used as the heating wire. In addition, examples of heaters other than electric heaters include far-infrared heaters and oil heaters.

[0039] It is also preferable that the area to be heated on the surface of the outer wall of the honeycomb structure is 50% or more. FIG. 3 is a front view of a honeycomb structure for explaining the range of the region to be heated on the surface of the outer wall of the honeycomb structure. In Fig. 3, the region S1 where the electric heater is provided is hatched, while the region S2 (two locations) where the electric heater is not provided is not hatched. The area S1 where the electric heater is provided is defined as a rectangular area that includes all the parts heated by the electric heating wire.

[0040] The area of ​​the surface of the outer wall of the honeycomb structure (side surface of the honeycomb structure) is the sum of the areas of region S1 and region S2 (two locations), and the ratio (%) of the area of ​​region S1 to the area of ​​the surface of the outer wall of the honeycomb structure is defined as the range of the heated area of ​​the surface of the outer wall of the honeycomb structure. This range is preferably 50% or more. When the range of the heated region is as wide as 50% or more, the temperature of the entire honeycomb structure can be raised more quickly, and the time for one cycle can be shortened.

[0041] The direct air capture (DAC) device of the present invention comprises the honeycomb structure of the present invention, a heater provided on the surface of the outer wall of the honeycomb structure, and a container for storing CO2 desorbed from the honeycomb structure.

[0042] A plurality of honeycomb structures can be combined and used in a DAC device. FIG. 4 is a perspective view schematically showing a state in which a plurality of honeycomb structures are combined and arranged in a casing. FIG. 4 shows a state in which nine honeycomb structures 20 in total are arranged in a casing 40, with three arranged vertically and three arranged horizontally. An electric heater is provided between the side surfaces of adjacent honeycomb structures. As described above, when a plurality of honeycomb structures are used in combination, it is sufficient to provide one electric heater between two adjacent honeycomb structures. The side surfaces of adjacent honeycomb structures may or may not be bonded together with an adhesive or the like.

[0043] The casing 40 may be a metal casing, such as a stainless steel casing. The number of honeycomb structures disposed in one casing is not limited, and may be 9 to 400.

[0044] FIG. 5 is a schematic diagram showing the configuration of a DAC device. In the DAC device 100 shown in Fig. 5, an inlet pipe 51 for letting in atmospheric air and an outlet pipe 52 for letting gas out into the atmosphere are connected to a casing 40 in which a honeycomb structure 20 is disposed. A valve 61 is provided in the inlet pipe 51, and a valve 62 is provided in the outlet pipe 52. By opening and closing the valves 61 and 62, it is possible to control the inflow of atmospheric air into the honeycomb structure 20 and the outflow of gas from the honeycomb structure 20. In addition, a fan 72 provided in the outlet pipe 52 may be driven to facilitate the flow of gas from the inlet pipe 51 through the honeycomb structure 20 to the outlet pipe 52.

[0045] A CO2 storage container 70 that stores CO2 desorbed from the honeycomb structure 20 is connected to the casing 40 via a CO2 storage pipe 53. The CO2 storage container 70 may be a CO2 cylinder. A valve 63 is provided on the CO2 storage pipe 53, and a vacuum pump 64 is provided between the CO2 storage pipe 53 and the CO2 storage container 70. By opening and closing the valve 63 and turning the vacuum pump 64 on and off, the outflow of gas containing CO2 from the honeycomb structure 20 to the CO2 storage pipe 53 can be controlled. It should be noted that the direct use of captured CO2 is also included in this case, since the location of use serves the same role as the storage vessel 70. For example, the captured CO2 may be introduced into a greenhouse to grow crops at higher concentrations than usual, thereby increasing crop yields, or the captured CO2 may be reacted with hydrogen in a synthesis vessel to synthesize methane.

[0046] The procedure for direct air recovery in the DAC device 100 will now be described. First, valves 61 and 62 are opened, and with valve 63 closed, atmospheric air is allowed to flow from the inlet pipe 51 into the through holes of the honeycomb structure 20, and CO2 in the atmospheric air is adsorbed by the CO2 adsorbent supported on the partition walls of the honeycomb structure 20. The gas having a lower CO2 concentration than the air flowing into the honeycomb structure 20 flows out from the through-holes of the honeycomb structure 20 to the outflow pipe 52 and is released into the air.

[0047] Once sufficient CO2 has been adsorbed into the CO2 adsorbent, valves 61 and 62 are closed, valve 63 is opened, vacuum pump 64 is started, the heater provided on the surface of the outer wall of honeycomb structure 20 is driven, and honeycomb structure 20 is heated from the surface of the outer wall, causing CO2 to be desorbed from the CO2 adsorbent. 5 shows only one electrode 32 of the electric heater and one power supply 33 connected to the electrode. As described above, an electric heater may be provided on each surface of the outer wall of the honeycomb structure. The CO2 desorbed from the CO2 adsorbent is stored in the CO2 storage container 70 via the CO2 storage pipe 53. In this way, CO2 in the atmosphere is collected.

[0048] Heating with a heater is preferably performed by controlling the heater output so that the temperature of the CO2 adsorbent is high enough to desorb CO2 but not so high that the CO2 adsorbent is deactivated. The appropriate heating temperature varies depending on the type of CO2 adsorbent, but a temperature of, for example, about 70 to 120°C is preferable.

[0049] Once desorption of CO2 from the CO2 adsorbent has progressed, heating by the heater is stopped. When CO2 has been sufficiently desorbed from the CO2 adsorbent, valves 61 and 62 are opened, valve 63 is closed, and the process of adsorbing CO2 in the atmosphere onto the CO2 adsorbent supported on the partition walls of honeycomb structure 20 is carried out again. By repeating the above steps, direct air recovery in the DAC device 100 can be performed.

[0050] An example of a method for manufacturing a honeycomb structure of the present invention will be described.

[0051] A molding step is carried out in which a wet mixture containing silicon carbide powder and a binder is extrusion-molded to produce a honeycomb molded body. Specifically, first, silicon carbide powders having different average particle sizes, an organic binder, a liquid plasticizer, a lubricant, and water are mixed together to prepare a wet mixture for manufacturing a honeycomb molded body.

[0052] If necessary, a pore-forming agent such as balloons, which are minute hollow spheres made of oxide ceramic, spherical acrylic particles, graphite, etc. may be added to the above-mentioned wet mixture. The balloons are not particularly limited, and examples thereof include alumina balloons, glass microballoons, shirasu balloons, fly ash balloons (FA balloons), mullite balloons, etc. Among these, alumina balloons are preferred.

[0053] Subsequently, the wet mixture is put into an extrusion molding machine and extrusion-molded to produce a honeycomb molded body of a predetermined shape. At this time, a mold capable of producing a cross-sectional shape having the through-hole structure (shape and arrangement of the through-holes) shown in FIG. 1 is used to produce a honeycomb formed body.

[0054] The honeycomb molded body is cut to a predetermined length and dried using a microwave dryer, hot air dryer, dielectric dryer, reduced pressure dryer, vacuum dryer, freeze dryer or the like.

[0055] The honeycomb formed body is heated to 300 to 650°C in a degreasing furnace to perform a degreasing process to remove organic matter from the honeycomb formed body, and then the degreasing honeycomb formed body is transported to a firing furnace and subjected to a firing process in which it is heated to 2000 to 2200°C to obtain a honeycomb structure.

[0056] Next, the CO2 adsorbent is supported on the partition walls of the honeycomb structure. The CO2 adsorbent can be supported by immersing the honeycomb structure in a solution containing the CO2 adsorbent. Alternatively, the CO2 adsorbent may be attached to a support material with a large specific surface area, such as silica, and then the support material with the CO2 adsorbent attached may be supported on the honeycomb structure. Examples of support materials include silica and alumina.

[0057] When a heater is provided on the surface of the outer wall of the honeycomb structure, a method of printing a conductive paste on the surface of the outer wall of the honeycomb structure so as to form a pattern of heating wires can be used. Alternatively, a method of attaching a metal wire, which has been previously prepared to form a predetermined pattern, to the surface of the outer wall of the honeycomb structure with a heat-resistant adhesive can also be used.

[0058] The present specification discloses the following:

[0059] The present disclosure (1) provides a gas-permeable device comprising: a partition wall that defines a plurality of through-holes that serve as a flow path for air containing CO2; An outer periphery wall provided on the outer periphery; A honeycomb structure comprising: a CO adsorbent supported on a surface of the partition wall; the partition wall and the outer peripheral wall are made of silicon carbide, The aperture ratio is 65 to 86%. The surface area of ​​the partition wall is 1 cm 3 20-36cm per 2 and This honeycomb structure is used for direct air capture (DAC) applications in which CO2 adsorbed in the CO2 adsorbent is desorbed by heating the surface of the outer wall, thereby capturing CO2 in the air.

[0060] The present disclosure (2) is the honeycomb structure according to the present disclosure (1), wherein the heating from the surface of the outer peripheral wall is performed by an electric heater.

[0061] The present disclosure (3) is the honeycomb structure according to the present disclosure (1) or (2), wherein the range of the heated region on the surface of the outer peripheral wall is 50% or more.

[0062] The present disclosure (4) is a honeycomb structure according to any one of the present disclosures (1) to (3), wherein the CO2 adsorbent is at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks).

[0063] The present disclosure (5) is a method for manufacturing a honeycomb structure having a cross-sectional area of ​​100 to 400 cm in a cross section perpendicular to the longitudinal direction, which is the direction in which the through holes extend. 2 The honeycomb structure according to any one of the present disclosures (1) to (4) is as follows.

[0064] The present disclosure (6) is the honeycomb structure according to any one of the present disclosures (1) to (5), wherein the length of the honeycomb structure in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm.

[0065] The present disclosure (7) is a direct air recovery (DAC) device comprising a honeycomb structure according to any one of the present disclosures (1) to (6), a heater provided on the surface of the outer wall of the honeycomb structure, and a container for storing CO2 desorbed from the honeycomb structure.

[0066] (Example) EXAMPLES Hereinafter, examples will be given that more specifically disclose embodiments of the present invention, but the present invention is not limited to these examples.

[0067] (Thermal cycle simulation) For a honeycomb structure having a predetermined structure and material, the time required for heating to a predetermined temperature and for cooling to the predetermined temperature was determined by simulation.

[0068] The fixed conditions for the simulation are as follows: Honeycomb structure size: (end face □ 150mm x 150mm) x longitudinal length 150mm Heating temperature of outer wall surface: 100℃ Cooling gas flow rate and temperature: SV=36000 / h, 25℃

[0069] The physical properties of the material are as shown in Table 1 below. [Table 1]

[0070] Regarding heating, assuming that there is no heat radiation from the end faces of the honeycomb structure and no heat transfer in the longitudinal direction, the heat transfer from the outer wall to the center of the honeycomb structure was modeled in two dimensions, and the heating temperature on the surface of the outer wall was set to 100°C (heater temperature), the heating start temperature was set to 22°C, and the heating time until the central temperature reached 100°C was defined as the temperature rise time (sec).

[0071] For cooling, cooling gas was circulated through the through-holes, assuming no heat radiation from the outer peripheral wall. The temperature of the cell partition walls at the start of cooling was set to 100°C, and the time required for the temperature of the cell partition walls to reach 25°C was defined as the cooling time (sec).

[0072] [Table 2]

[0073] The silicon carbide honeycomb structures of Examples 1 to 3 had a short heat cycle time and were suitable for DAC applications using heating from the surface of the outer wall. The cordierite honeycomb structure of Comparative Example 1 required a long temperature rise time and is therefore considered to be unsuitable for DAC applications using heating from the surface of the outer wall. [Explanation of symbols]

[0074] 20 Honeycomb structure 21 Through hole 21a Gas inlet end of through hole 21b Gas outlet end of through hole 22 Bulkhead 23 Outer wall 30 Electric heater 31 Heating wire 32 electrodes 33 Power supply 40 Casing 51 Inlet piping 52 Outlet piping 53 CO2 storage piping 61, 62, 63 valves 64 Vacuum Pump 70 CO2 storage container 72 fans 100 DAC devices

Claims

1. CO ２ a partition wall that defines a plurality of through holes that serve as flow paths for air containing the An outer periphery wall provided on the outer periphery; CO supported on the surface of the partition wall ２ A honeycomb structure comprising an adsorbent, the partition wall and the outer peripheral wall are made of silicon carbide, The aperture ratio is 65 to 86%, The surface area of ​​the partition wall is 1 cm of the honeycomb structure. ３ 20-36cm per ２ and By heating from the surface of the outer peripheral wall, ２ CO adsorbed on the adsorbent ２ CO in the air is desorbed ２ A honeycomb structure for use in direct air capture (DAC) applications.

2. 2. The honeycomb structure according to claim 1, wherein the heating from the surface of the outer peripheral wall is performed by an electric heater.

3. 2. The honeycomb structure according to claim 1, wherein the heated area of ​​the surface of the outer wall is 50% or more.

4. The CO ２ 2. The honeycomb structure according to claim 1, wherein the adsorbent is at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks).

5. The cross-sectional area of ​​the honeycomb structure perpendicular to the longitudinal direction, which is the direction in which the through holes extend, is 100 to 400 cm ２ The honeycomb structure according to claim 1, wherein

6. 2. The honeycomb structure according to claim 1, wherein the length of the honeycomb structure in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm.

7. The honeycomb structure according to any one of claims 1 to 6, a heater provided on the surface of the outer wall of the honeycomb structure; CO desorbed from the honeycomb structure ２ and a container for containing the air.

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