Honeycomb structure

Abstract

To provide a honeycomb structure that can realize an economical filter with catalytic function. [Solution] The honeycomb structure has multiple channels through which a fluid passes, and comprises a base material and a catalyst. The base material is provided with a first channel whose fluid outlet end face is sealed and a second channel whose fluid inlet end face is sealed. The catalyst is packed into at least one of the first and second channels.

Description

Technical Field

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[0001] This specification discloses technologies related to honeycomb structures.

Background Art

[0002] Patent Document 1 discloses a filter cloth having a catalytic function. The filter cloth of Patent Document 1 includes a bag-shaped filter cloth body and a catalyst layer supported inside the filter cloth body. This filter cloth is used as a filter (bag filter) for exhaust gas purification. Specifically, the exhaust gas is passed from the outside to the inside of the filter cloth, and the exhaust gas is decomposed by the catalyst supported inside the fiber, and the harmless gas is released from the inside of the filter cloth. Also, particles and the like contained in the exhaust gas are captured by the outer surface of the filter cloth. ​​​​​​​​​​​​​​​​​​​​​​​​​​​​The first technology disclosed herein is a honeycomb structure having a plurality of fluid channels through which a fluid passes, comprising a substrate and a catalyst. The substrate may be provided with a first channel whose fluid outlet end face is sealed and a second channel whose fluid inlet end face is sealed. The catalyst may be filled in at least one of the first channel and the second channel.

[0006] The second technology disclosed herein is a honeycomb structure of the first technology described above, wherein the catalyst may be spherical or cylindrical.

[0007] The third technology disclosed herein is a honeycomb structure of the second technology described above, wherein the diameter of the catalyst may be 1 mm or more and 6 mm or less.

[0008] The fourth technology disclosed herein is a honeycomb structure of any of the first to third technologies described above, wherein the first channel and the second channel may be adjacent to each other.

[0009] The fifth technology disclosed herein is a honeycomb structure of any of the first to fourth technologies described above, wherein the catalyst may be removable from the substrate. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram of the honeycomb structure is shown. [Figure 2] Figure 1 shows a cross-section along line II-II. [Figure 3] A magnified section is shown to illustrate the details of the honeycomb structure. [Figure 4] A diagram illustrating the advantages of the honeycomb structure is shown. [Figure 5] The results of the experimental example are shown below. [Modes for carrying out the invention]

[0011] The honeycomb structure disclosed herein can be used as a filter for purifying particles and harmful gases contained in exhaust gas, etc. The honeycomb structure comprises a ceramic substrate and a catalyst filled within the substrate. The substrate has a plurality of channels through which a fluid (exhaust gas, etc.) passes. The channels extend in one direction and include a first channel whose fluid outlet end face is sealed and a second channel whose fluid inlet end face is sealed. The first channel and the second channel are separated by a partition wall.

[0012] The honeycomb structure is placed on the fluid flow path. Specifically, the inlet end face of the honeycomb structure is positioned upstream of the flow path, and the outlet end face is positioned downstream of the flow path. In this case, when the fluid passes through the honeycomb structure, it flows into the honeycomb structure from the first flow path, moves through the partition wall to the second flow path, and flows out of the honeycomb structure from the second flow path. When the fluid passes through the partition wall, particles and other substances contained in the fluid are trapped by the partition wall and removed from the fluid. The cross-sectional shapes of the first and second flow paths are arbitrary and may be, for example, triangular, square, hexagonal, circular, etc. In other words, in a narrow sense, a structure having multiple hexagonal openings (flow paths) is called a "honeycomb structure". However, in this specification, a structure (base material) having multiple openings of the same shape is called a "honeycomb structure".

[0013] As described above, when the fluid moves from the first channel to the second channel, particles and other contaminants contained in the fluid are removed. Therefore, it is desirable that the first and second channels be arranged alternately. In other words, it is preferable that the first and second channels be adjacent to each other. This allows for efficient removal of particles and other contaminants contained in the fluid.

[0014] The honeycomb structure disclosed herein has a catalyst packed in the first channel of the substrate and / or the second channel of the substrate. The term "catalyst" as used herein may be formed solely from a material having catalytic function, or it may be a material having catalytic function (such as a precious metal) supported on a carrier. The form of the catalyst is arbitrary and may be rod-shaped, pellet-shaped (spherical, cylindrical, prismatic, etc.). From the viewpoint of improving contact efficiency with the fluid, the form of the catalyst is particularly preferably spherical or cylindrical. Ceramics such as alumina, silica, and zeolite can be used as the carrier.

[0015] The diameter of the catalyst should be such that it can be accommodated in the flow channels (first flow channel, second flow channel) of the substrate. Considering the gas flow resistance when detoxifying harmful gases contained in exhaust gas, etc., the flow channel size of the substrate is preferably a 6mm x 6mm rectangle. In this case, the diameter of the catalyst is preferably less than 6mm. Specifically, if the shape of the catalyst is spherical or cylindrical, the diameter of the catalyst may be between 1mm and 6mm. If the diameter of the catalyst is 1mm or more, it is possible to suppress the scattering of the catalyst when filling the flow channel or when flowing the fluid (the gas to be treated, etc.) through the honeycomb structure. It is also possible to suppress an increase in the fluid flow resistance. The particle size of the catalyst may be 2mm or more, 3mm or more, 4mm or more, or 5mm or more. Furthermore, if the diameter of the catalyst is 6mm or less, a sufficient surface area of ​​the catalyst is secured, and the fluid treatment efficiency (decomposition efficiency) is improved. The diameter of the catalyst may be 5 mm or less, 4 mm or less, 3 mm or less, or 2 mm or less. If the catalyst is cylindrical, the diameter of the catalyst refers to the diameter of the surface where the "circle" is exposed.

[0016] As described above, the catalyst may be filled in the first channel, the second channel, or both the first and second channels. However, it is more preferable that the catalyst be filled in the second channel. The fluid from which impurities (particles, etc.) have been removed by the partition wall is introduced into the second channel. Therefore, if the catalyst is filled in the second channel, the adhesion of impurities contained in the fluid to the catalyst is suppressed, and a decrease in catalytic function can be suppressed.

[0017] The catalyst filling the channels (first channel, second channel) can be removed from the substrate. In other words, the catalyst is not fixed to the substrate. Therefore, when maintaining or replacing the honeycomb structure, the catalyst can be removed from the substrate. This allows for separate maintenance of the substrate and the catalyst. For example, if the partitions of the substrate become clogged, the substrate may be heated to a high temperature to regenerate it (clear the blockage). Since the catalyst can be removed from the substrate and heated, the catalyst is not exposed to high temperatures, and catalyst degradation can be suppressed.

[0018] Furthermore, if the substrate is difficult to regenerate, the catalyst can be removed from the substrate and loaded into a new substrate. Alternatively, if the catalytic function deteriorates and regeneration becomes difficult, the catalyst can be removed from the substrate and loaded into the substrate with a new catalyst. In other words, when the function of the honeycomb structure deteriorates, it is only necessary to replace a part of the honeycomb structure (substrate or catalyst) without replacing the entire honeycomb structure. The honeycomb structure disclosed herein can reduce costs and is economical.

[0019] Furthermore, when regenerating the substrate, the fluid may be flowed in the reverse direction, that is, from the outlet side to the inlet side of the honeycomb structure, to remove particles and other debris clogging the substrate. In this case as well, since the substrate can be regenerated with the catalyst removed, the fluid flow resistance is reduced, and the regeneration efficiency can be improved. Moreover, since the catalyst can be removed from the substrate, the type of catalyst can be changed depending on the type of fluid being treated. In other words, different types of fluids can be treated using a common substrate.

[0020] In addition, since the honeycomb structure disclosed in the present specification has a ceramic base material, it can process fluids at high temperatures (e.g., 900 °C or higher). For example, in the case of a filter with a catalyst supported on a filter cloth, since the heat resistance of the filter cloth is low, a process for cooling the fluid to be treated is required. Since the honeycomb structure disclosed in the present specification can process high-temperature fluids, the cooling process can be omitted, and the process of the entire treatment system can be simplified.

Example

[0021] Referring to FIGS. 1 to 3, the honeycomb structure 10 will be described. FIG. 1 shows a view of the honeycomb structure 10 observed from the fluid outflow side surface. The honeycomb structure 10 can be used as a filter for exhaust gas purification. As shown in FIG. 1, the outer shape of the honeycomb structure 10 is rectangular, and a plurality of first flow paths 2 and second flow paths 12 are provided in the base material 8. The base material 8 is made of ceramics. In actuality, the first flow path 2 is sealed by the sealing material 6, and no flow path (opening) appears on the outflow side surface. Also, although not shown, on the inflow side surface of the honeycomb structure 10, since the second flow path 12 is sealed by the sealing material 6, no flow path (opening) of the second flow path 12 appears on the inflow side surface.

[0022] As is clear from FIG. 1, in the honeycomb structure 10, the first flow paths 2 and the second flow paths 12 are provided alternately. That is, a second flow path 12 is provided next to the first flow path 2, and a first flow path 2 is provided next to the second flow path 12. In actuality, the honeycomb structure 10 is formed by providing a plurality of through holes in the base material 8 and forming the sealing material 6 every other one at the ends of the through holes.

[0023] Figure 2 shows a cross-sectional view of the honeycomb structure 10. Note that the catalyst 20, which will be described later, is not shown in Figure 2. As shown in Figure 2, the base material 8 has a plurality of first channels 2 and a plurality of second channels 12 formed therein. The first channels 2 and the second channels 12 are separated by a partition wall 4. The partition wall 8 is the remaining part of the base material 8 after through holes (channels 2 and 12) have been formed. The first channels 2 are provided with a sealing material 6 on the fluid outlet side (upper part of Figure 2). The second channels 12 are also provided with a sealing material 6 on the fluid inflow side (lower part of Figure 2).

[0024] Figure 3 shows an enlarged cross-sectional view of the honeycomb structure 10. Note that the vertical scale in Figure 3 has been changed from Figure 2 to illustrate the characteristics of the honeycomb structure 10. As shown in Figure 3, the second channel 12 is filled with a spherical catalyst 20. The catalyst 20 consists of a spherical alumina carrier on which a catalytic metal (e.g., platinum) is supported. A mesh-like cover 40 is provided at the opening (upper end face) of the second channel 12. The cover 40 prevents the catalyst 20 from spilling out of the second channel 12. The cover 40 is made of metal.

[0025] When treating exhaust gas with the honeycomb structure 10, the opening of the first passage 2 is positioned upstream of the gas flow path, and the opening of the second passage 12 is positioned downstream of the gas flow path. As a result, the exhaust gas flows into the first passage 2 as shown by arrow 30. The exhaust gas that has flowed into the first passage 2 moves to the second passage 12 through the partition wall 4 as shown by arrow 32. When moving from the first passage 2 to the second passage 12, impurities (particles, etc.) contained in the exhaust gas are removed by the partition wall 4. Therefore, the exhaust gas from which impurities have been removed flows into the second passage 12.

[0026] The exhaust gas flowing into the second flow path 12 is decomposed (detoxified) by the catalyst 20. The decomposed exhaust gas flows out of the honeycomb structure 10, as shown by arrow 34. The size of the catalyst 20 in the honeycomb structure 10 is adjusted so as not to increase the resistance to exhaust gas passage within the second flow path 12.

[0027] Figure 4 shows the manufacturing method and maintenance method for the honeycomb structure 10. First, a substrate 8 is prepared with sealing material 6 provided in the first channel 2 and the second channel 12, and the catalyst 20 is introduced into the second channel 12 (a). Next, after filling the second channel 12 with the catalyst 20, a lid 40 is attached to the opening of the second channel 12 (b). This completes the production of the honeycomb structure 10. The honeycomb structure 10 can be manufactured simply by introducing the catalyst 20 into the substrate 8, eliminating the need for a process such as supporting the catalyst 20 on the substrate 8.

[0028] When performing maintenance on the honeycomb structure 10, the lid 40 is removed and the catalyst 20 is taken out from the second channel 12 (c). The base material 8 is then regenerated by heat treatment or by flowing fluid from the second channel 12 to the first channel 2 (i.e., flowing fluid in the opposite direction to that used during operation). The catalyst 20 is also regenerated by heat treatment or washing. In the honeycomb structure 10, the base material 8 and the catalyst 20 can be regenerated separately, so for example, they can be treated at a heating temperature suitable for the regeneration of each.

[0029] (Example of experiment) A sample (honeycomb structure 10) was prepared by filling a substrate 8, which was 150 mm long, 150 mm wide, and 515 mm in length, with each channel measuring 9 mm x 9 mm, with catalysts 20 of different shapes and sizes. The fluid flow resistance and the ease of extracting the catalysts 20 were evaluated. The shapes and sizes of the catalysts 20 were as follows. Sample 1: Spherical catalyst with a diameter of 0.5 mm Sample 2: Spherical catalyst with a diameter of 1 mm Sample 3: Spherical catalyst with a diameter of 2 mm Sample 4: Spherical catalyst with a diameter of 3 mm Sample 5: Spherical catalyst with a diameter of 4 mm Sample 6: Spherical catalyst with a diameter of 5.5 mm Sample 7: Cylindrical catalyst with a diameter of 3 mm and a height of 3 mm.

[0030] The fluid flow resistance was evaluated by measuring the differential pressure between the pressure required to circulate a certain amount of fluid through a sample filled with catalyst 20 (honeycomb structure 10) and the pressure required to circulate a certain amount of fluid through a sample not filled with catalyst 20 (substrate 8). Samples with a differential pressure below the allowable value were rated "A," and samples with a differential pressure exceeding the allowable value were rated "B." Samples through which fluid could not be circulated were rated "C." The results are shown in Figure 5.

[0031] The ease of extracting catalyst 20 was evaluated as follows: Samples in which all of the catalyst 20 could be extracted from the second channel 12 when the lid 40 was removed and the second channel 12 was positioned downwards were rated "A". Samples in which all of the catalyst 20 could be extracted from the second channel 12 when vibration was applied with the lid 40 removed and the second channel 12 positioned downwards were rated "B". Samples in which the catalyst 20 could not be extracted even when vibration was applied with the lid 40 removed and the second channel 12 positioned downwards, but the catalyst 20 could be extracted by inserting a jig (rod) into the second channel 12 were rated "C". The results are shown in Figure 5.

[0032] As shown in Figure 5, sample 1, with a diameter of 0.5 mm (less than 1 mm), could not allow the fluid to pass through. Furthermore, a portion of the catalyst 20 in sample 1 was fixed within the second channel 12 and could not be removed. Samples with a diameter of 1-2 mm (samples 2 and 3) had a B rating for passage resistance, but an A rating for removal. It was confirmed that adjusting the diameter of the catalyst 20 to 1-2 mm could realize a honeycomb structure 10 with excellent maintenance performance. Additionally, samples with a diameter of 3-5.5 mm (samples 4-6) showed low passage resistance and yielded good results (A rating). In particular, the spherical samples with diameters of 4 mm and 5.5 mm (samples 5 and 6), and the cylindrical sample with a diameter of 3 mm, also showed good removal performance (A or B rating). Therefore, it was confirmed that a catalyst diameter of 1 mm to 6 mm is preferable. It was confirmed that using these catalysts can realize a honeycomb structure 10 with excellent maintenance characteristics and low fluid movement resistance.

[0033] In the above embodiment, a honeycomb structure 10 with a rectangular outer shape on the base material 8 was described. However, the outer shape of the honeycomb structure (base material) is not limited to a rectangle; for example, it may be circular.

[0034] In the above embodiment, a honeycomb structure 10 in which the second channel 12 is filled with catalyst 20 was described. However, the technology disclosed herein can also be applied to a configuration in which the first channel 2 is filled with catalyst 20, or to a configuration in which both the first channel 2 and the second channel 12 are filled with catalyst 20. The important point is that the catalyst 20 is not fixed to the substrate 8, but rather filled into the channels 2 and 20.

[0035] Furthermore, in the above embodiment, an example was described in which a lid 40 is provided at the opening of the catalyst-filled channel (second channel 12). However, the lid may be provided so as to cover the entire surface where the opening of the catalyst-filled channel exists. For example, in the honeycomb structure 10, the entire outlet end face may be covered with a mesh-like lid. Alternatively, the entire surface of the honeycomb structure may be covered with a mesh-like lid.

[0036] Furthermore, in the above embodiment, a catalyst 20 was described in which a metal having catalytic function is supported on a spherical carrier. However, the shape of the carrier is not limited to spherical, and may be, for example, rod-shaped, cylindrical, etc. If the shape of the carrier (catalyst) is rod-shaped, the process of filling the flow path with catalyst can be simplified. Also, if the shape of the carrier (catalyst) is cylindrical, it becomes easier to secure gaps between catalysts, and the resistance to fluid passage can be reduced.

[0037] Furthermore, the above embodiment described an example in which the honeycomb structure 10 is used as a filter for purifying harmful gases such as exhaust gas. However, the honeycomb structure 10 can be used for any purpose as long as it decomposes organic components, flammable gases, etc. For example, it can be used to decompose organic components contained in gas and recover useful gases such as hydrogen. Alternatively, it can be used to decompose or react polymer compounds to produce raw materials for plastics. Because the base material 8 of the honeycomb structure 10 is made of ceramics, it can be used particularly suitably in applications where it is necessary to decompose and react fluids at high temperatures.

[0038] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. Furthermore, the technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0039] 2: First channel 8: Base material 10: Honeycomb structure 12: Second channel 20: Catalyst

Claims

1. A honeycomb structure having multiple channels through which a fluid passes, A substrate is provided with a first flow path whose fluid outlet end face is sealed and a second flow path whose fluid inlet end face is sealed, A honeycomb structure comprising a catalyst filled in at least one of the first and second channels.

2. The honeycomb structure according to claim 1, wherein the catalyst is spherical or cylindrical.

3. The honeycomb structure according to claim 2, wherein the diameter of the catalyst is 1 mm or more and 6 mm or less.

4. The honeycomb structure according to claim 1, wherein the first channel and the second channel are adjacent to each other.

5. A honeycomb structure according to any one of claims 1 to 4, wherein the catalyst can be removed from the substrate.

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