JP5195416B2 - Ceramic honeycomb filter and exhaust gas purification device - Google Patents

Description

  The present invention relates to a ceramic honeycomb filter and an exhaust gas purification device suitable for purifying particulate matter contained in exhaust gas of a diesel engine or the like.

  In order to preserve the environment, a honeycomb filter that removes fine particles mainly composed of carbon from exhaust gas of a diesel engine is used. In the honeycomb filter, both end surfaces of the exhaust gas inflow side and the outflow side are alternately plugged. An example of a conventional ceramic honeycomb filter having such a structure is shown in FIGS. 6 (a) and 6 (b). The ceramic honeycomb filter 50 includes a porous ceramic honeycomb structure 11 including a porous partition wall 2 forming a plurality of flow paths 3a and 3b, and an outer peripheral portion 1 surrounding the porous partition wall 2, and a porous ceramic honeycomb structure. As a result of sealing the flow path 3b at one end of the body 11, the result of sealing the flow path 3a at the other end of the porous ceramic honeycomb structure 11 and the plugged portions 5 arranged in a checkered pattern The plugging portions 6 are arranged in a checkered pattern that does not overlap the plugging portions 5. The exhaust gas containing fine particles flows into the flow path 3a from the inflow side opening end 12, passes through the partition wall 2, and then is discharged from the outflow side end face 13 through the adjacent flow path 3b. At this time, the fine particles contained in the exhaust gas are collected in pores (not shown) formed in the partition wall 2. If fine particles continue to be collected in the ceramic honeycomb filter 50, clogging occurs in the pores of the partition walls 2 to greatly reduce the collection function, and the pressure loss increases to reduce the engine output. The deposited fine particles (PM) are burned by an electric heater, a burner, a microwave, or the like, and the ceramic honeycomb filter 50 is regenerated. In addition, the oxidation of fine particles deposited by the catalyst supported on the ceramic honeycomb filter 50 is promoted to regenerate the ceramic honeycomb filter 50. However, depending on the operating state, a large amount of fine particles accumulate, the regeneration is not performed sufficiently, the engine output decreases, and in the worst case, the filter is damaged.

  In order to solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 2002-371826 discloses a ceramic honeycomb filter for exhaust gas purification in which a part of a sealing portion is omitted to be in a flow-through state, and a pressure loss in a filter unit cross section is reduced. Yes. In this ceramic honeycomb filter, a small number of open flow paths having no sealing portion on either the exhaust gas inflow side or the exhaust gas outflow side are provided at arbitrary positions. However, in this ceramic honeycomb filter, when the open channels provided arbitrarily are adjacent to each other through the partition walls, the exhaust gas flows in a concentrated manner in the adjacent open channels having a small ventilation resistance. Is likely to flow out and the collection rate becomes worse.

  Japanese Patent Application Laid-Open No. 2004-251137 seals the ends of the channels in a checkered pattern only on one end face of the ceramic honeycomb structure having a large number of channels that penetrate in the axial direction partitioned by porous partition walls. A honeycomb filter is disclosed. In this ceramic honeycomb filter, since no sealing portion is provided on the other end surface, substantially no sealing portion is present in almost half of all the flow paths. Accordingly, a low pressure loss can be obtained, but there is a problem that the particulate collection performance is not sufficient because there are too many open flow paths without sealing portions.

  Japanese Unexamined Patent Publication No. 57-201518 discloses a ceramic honeycomb filter provided with an open flow path through which 5 to 20% of exhaust gas passes. In this ceramic honeycomb filter, an open flow path is formed without providing a sealing part in a flow path (a sealing part is not provided on the four sides) where the sealing part should be originally provided on the opening end side. The proportion of open channels is about 5% of the total channels. However, the ratio of the open flow path is too small, and the effect of reducing the pressure loss is not sufficient. Furthermore, all of the periphery of the open flow path is a flow path in which one side is sealed, and the open flow paths are not adjacent to each other in the diagonal direction. Therefore, there is a problem that the exhaust gas flow is concentrated in the open flow path having a small ventilation resistance, and the collection rate of the fine particles is deteriorated.

  Japanese Patent Application Laid-Open No. 60-3420 is a ceramic honeycomb filter having a large number of cells in which an inlet end and an outlet end are alternately plugged, and is sealed at a ratio of 1 to 15% of the entire flow path near the outer peripheral wall. A ceramic honeycomb filter provided with an open channel without a stop is disclosed. However, since the central part of the ceramic honeycomb filter is easier to pass exhaust gas and fine particles are more likely to accumulate in the central part, the effect of reducing the pressure loss is not sufficient only with such an outer flow path.

  Japanese Patent Publication No. 1-27767 discloses a ceramic honeycomb filter that suppresses an increase in pressure loss during exhaust gas passage by providing a blowout hole with a diameter larger than that of the partition wall in a part of the exhaust gas flow path. doing. Furthermore, it is also disclosed that an open flow path that does not seal both end faces is provided in the ceramic honeycomb filter at a ratio of 0.5 to 10% of the total flow path. However, the effect of reducing the pressure loss is not sufficient with an open channel of about 0.5 to 10% of the total channel.

  In the above prior art, the arrangement of the open channel is not studied. As a result of intensive research, if there is an adjacent open channel, there is no differential pressure between the two through the partition wall, so the exhaust gas flows without passing through the partition wall, and as a result, the exhaust gas flow is adjacent to the open channel. It was found that the collection rate of fine particles deteriorated overall.

  Accordingly, an object of the present invention is to provide a ceramic honeycomb filter in which pressure loss is reduced without impairing particulate collection performance, and an exhaust gas purification apparatus having such a ceramic honeycomb filter.

  As a result of diligent research in view of the above object, the present inventors have found that when an open channel having no sealing portion on both sides is formed so as to be adjacent in the diagonal direction, pressure loss is not impaired without impairing the collection performance of the fine particles. The present inventors have found that it has been reduced, and have arrived at the present invention.

That is, the ceramic honeycomb filter of the present invention includes a ceramic honeycomb structure having a large number of flow paths partitioned by porous partition walls, and a sealing provided on an exhaust gas inflow side or an exhaust gas outflow side of a predetermined flow path. in the ceramic honeycomb filter to have a the parts, a flow path having a sealing portion on the exhaust gas inlet side, a flow passage provided by arranging a seal on Hitotsumatsu pattern on the exhaust gas outlet side, exhaust gas inflow And an open flow path that does not have a sealing portion on either the exhaust side or the exhaust gas outflow side, and the open flow path is more than 15% and 40% or less of the number of all flow paths, The arrangement is a diagonal direction.

It is preferable that the number of open channels diagonally adjacent to the sealing channel having the sealing portion on the exhaust gas inflow side or the exhaust gas outflow side is 10 to 90% of the number of all open channels.

  The exhaust gas purifying apparatus of the present invention comprises the above ceramic honeycomb filter.

  The ceramic honeycomb filter of the present invention having the above structure is suitable for efficiently removing particulate matter contained in exhaust gas of a diesel engine or the like because the pressure loss is reduced without impairing the collection performance of fine particles. .

It is a front view which shows the end surface of an example of the ceramic honeycomb filter of this invention. It is a fragmentary sectional view showing an example of the ceramic honeycomb filter of the present invention. It is a rear view which shows the other end surface of an example of the ceramic honeycomb filter of this invention. It is the schematic which shows an example of the manufacturing process of the ceramic honeycomb filter of this invention. It is the schematic which shows the process of sticking a tape on the film which has a through-hole so that an open flow path may be formed. It is a front view which shows the end surface of the other example of the ceramic honeycomb filter of this invention. It is a fragmentary sectional view showing other examples of the ceramic honeycomb filter of the present invention. It is a rear view which shows the other end surface of the other example of the ceramic honeycomb filter of this invention. It is a schematic diagram which shows the apparatus which inject | pours a plugging material. It is a front view which shows the end surface of the conventional ceramic honeycomb filter. It is a fragmentary sectional view which shows the conventional ceramic honeycomb filter.

  As shown in FIGS. 1 (a) to 1 (c), the ceramic honeycomb filter 10 of the present invention has the number of open channels 30 adjacent in the diagonal direction exceeding 15% and 40% or less of the total number of channels. Therefore, it has the following effects. Exhaust gas flowing into the flow path 3a from the exhaust gas inflow side end face 12 of the ceramic honeycomb filter 10 passes through the partition wall 2 and flows out from the adjacent flow path 3b, but is sealed to the exhaust gas inflow side and the exhaust gas outflow side. Since the exhaust gas that has flowed into the open flow path 30 that does not have the parts 5 and 6 flows out without passing through the partition wall 2, it is possible to suppress an increase in pressure loss. In addition, when there is an open flow channel adjacent through the partition wall surface, the open flow channel surrounded by the open flow channel has low ventilation resistance, and the exhaust gas flow is concentrated there. Are arranged so as to be adjacent to each other in the diagonal direction, so that the open flow paths 30 are not adjacent to each other through the partition wall, and the exhaust gas flow does not concentrate. As a result, the exhaust gas flow is dispersed in the open flow paths 30 adjacent in the diagonal direction, and the outflow of fine particles in the exhaust gas can be suppressed while reducing the pressure loss.

  When the number of open channels 30 is 15% or less of the total number of channels, the effect of reducing pressure loss is small. When the number of open channels 30 exceeds 40%, the amount of fine particles flowing out increases, and the collection rate decreases. Preferably, the number of open channels 30 is 20 to 35% of the number of all channels. Each open channel 30 is adjacent to four channels in the diagonal direction, and at least one of the channels may be an open channel.

  The number of open channels adjacent to the sealed channels in the diagonal direction is preferably 10 to 90% of the number of all open channels. As a result, the exhaust gas flow is dispersed by the open flow path 30 having a small ventilation resistance, and the outflow of fine particles in the exhaust gas is reduced. If it is less than 10% or more than 90%, the effect of reducing pressure loss is small, and the ability to collect fine particles is low. Preferably, the diagonally adjacent sealed channels are 20-60% of the number of all open channels 30.

  Since the partition walls and the sealing portion of the ceramic honeycomb structure mainly function as a filter for removing fine particles in the exhaust gas of the diesel engine, it is preferable that the ceramic honeycomb structure is made of a material having excellent heat resistance. Specifically, a ceramic material having a main crystal of at least one selected from the group consisting of cordierite, alumina, mullite, silicon nitride, silicon carbide, LAS, aluminum titanate, titania, zirconia, and aluminum nitride is used. Is preferred. Among them, a ceramic honeycomb filter having cordierite as a main crystal is most preferable because it is inexpensive, excellent in heat resistance and corrosion resistance, and has low thermal expansion.

  The porosity of the partition walls of the ceramic honeycomb structure is preferably 45 to 80%. Most of the fine particles in the exhaust gas flowing into the open flow path pass through the flow path as it is, but if the porosity of the partition walls is 45 to 80%, some of the fine particles are formed in the partition walls. Since it is collected in the pores, the collection rate does not decrease so much. When the porosity is less than 45%, the pressure loss of the honeycomb filter increases, leading to a decrease in engine output. When the porosity exceeds 80%, the strength of the partition walls decreases, and it is easily damaged by thermal shock or vibration. . Further, the porosity of the plugging material of the honeycomb structure may be either lower, lower, or higher than the partition wall porosity, but if it is higher than the partition wall porosity, the exhaust gas Can pass through the inside of the pores in the plugging material, which is preferable because the accumulation of fine particles on the exhaust gas inflow side end face 51 of the exhaust gas inflow side plugging portion hardly occurs.

  The partition wall thickness of the ceramic honeycomb structure is preferably 0.1 to 0.5 mm, and the partition wall pitch is preferably 1.2 mm or more. When the partition wall thickness is less than 0.1 mm, the strength of the ceramic honeycomb structure is reduced. When the partition wall thickness exceeds 0.5 mm, the ventilation resistance of the partition wall against exhaust gas increases, and the pressure loss of the filter increases. A more preferable partition wall thickness is 0.2 to 0.4 mm. If the partition wall pitch is less than 1.3 mm, the opening area on the exhaust gas inflow side of the honeycomb structure becomes small, and the pressure loss at the filter inlet increases.

  The apparatus for purifying exhaust gas of the present invention comprising a ceramic honeycomb filter having 20 to 40% of the total number of open channels has a low pressure loss while maintaining a good particulate collection rate. By disposing such a ceramic honeycomb filter in the subsequent stage of the SCR catalyst, fine particles and NOx can be efficiently removed with low pressure loss.

  FIG. 2 shows a manufacturing process of the ceramic honeycomb filter of the present invention. The ceramic honeycomb structure 11 having a large number of flow paths surrounded by the partition walls is obtained by kneading a kneaded material of ceramic raw material powder, extrusion molding, and firing the obtained honeycomb structure molded body. Affixing a resin film 7 to the end face 12 of the ceramic honeycomb structure 11 [step (a)], the sealing flow paths are arranged in a checkered pattern, and the open flow paths 30 are arranged in a diagonal direction on the film 7 The through hole 8 is opened by laser processing or the like [step (b)]. Instead of opening the through holes 8 so as to form the open flow paths 30, as shown in FIG. 3, after opening the through holes 8 so that the sealing flow paths are arranged in a checkered pattern, tape is applied on the film 7. 9a may be attached to close the through-hole 8 at a position corresponding to the open flow path 30. Depending on the arrangement of the open channel 30, a tape 9b may be further applied.

  The end face 12 of the ceramic honeycomb structure 11 is immersed in a sealing slurry 21 in the container 20 [step (c)], and the other end face 13 of the ceramic honeycomb structure 11 is pushed by the pressurizing means 22 and sealed from the through hole 8. A stopping material slurry is introduced into the end of the flow path [step (d)]. The sealing portion 5 is provided on the end face 12 of the honeycomb structure 11 by removing the film 7 and drying [step (e)]. Similarly, the film 7 is attached to the other end surface 13, and a through hole 8 'is opened in a checkered pattern in the flow path where the sealing portion 5 is not provided on the end surface 12 side by laser processing or the like. Introducing into the end of the channel on the 13th side [step (f)]. After the film 7 is removed, the molded body having the sealing portions 5 and 6 on the end faces 12 and 13 side is obtained by drying. By firing this, the ceramic honeycomb filter 10 in which the sealing portions 5 and 6 are integrated with the partition walls 2 is obtained [step (g)].

  Alternatively, the sealing material slurry may be directly introduced by inserting the nozzle 32 of the sealing material injection device 31 shown in FIG. When the sealing material injection device 31 is used, the sealing portion 5 can be formed inside the flow path as shown in FIG.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1
A kaolin powder, a talc powder, a silica powder, an aluminum hydroxide powder and an alumina powder are composed of 47 to 53% by mass of SiO ₂ , 32 to 38% by mass of Al ₂ O ₃ , and 21 to 16% by mass of MgO. , Na ₂ O, K ₂ O, TiO ₂ , Fe ₂ O ₃ , PbO, P ₂ O _{5 and} other inevitable impurities are blended so that the total composition is 2.5% or less. Produced. This cordierite-forming raw material powder was sufficiently mixed with water, a forming aid and a pore former to prepare a ceramic clay which can be extruded into a honeycomb structure. This ceramic clay was extruded to produce a honeycomb structure molded body with a peripheral wall and a square-shaped channel surrounded by partition walls inside the outer wall, dried and fired, diameter 267 mm, full length A honeycomb structure having a partition structure of L300 mm, partition wall pitch 1.5 mm, partition wall thickness 0.3 mm, and partition wall porosity of 65% was manufactured.

  A ceramic honeycomb filter of the present invention was produced according to the procedure shown in FIG. A resin film 7 is attached to the end face 12 of the ceramic honeycomb structure [step (a)], and a through-hole 8 is opened in the film 7 by a laser so that an open channel having the arrangement shown in Table 1 is formed [step (b)]. The end face 12 of the ceramic honeycomb structure 11 was immersed in the sealing slurry 21 in the container 20 [step (c)], and the sealing material slurry was introduced into the end of the flow path [step (d)]. After removing the film, the sealing part 5 was dried [step (e)]. Similarly, the film 7 is affixed to the other end face 13, and a through-hole 8 ′ is opened in a checkered pattern on the film 7 by a laser so that only one end is sealed in the sealing flow path. Similarly, the sealing material slurry was introduced into the end of the flow path [step (f)]. After removing the film 7, the sealing part 6 was dried, and both the sealing parts 5 and 6 were fired to obtain a ceramic honeycomb filter in which the both sealing parts 5 and 6 were integrated with the partition wall [step (g )]. The ceramic honeycomb filter had sealing flow channels arranged in a checkered pattern and open flow channels arranged in a diagonal direction.

Examples 2-6 and Comparative Examples 1-3
Except for changing the method of opening the through holes 8 of the resin film 7 attached to the end face 12 of the ceramic honeycomb structure so as to form an open channel having the arrangement shown in Table 1, the same manner as in Example 1 was performed. Thus, a ceramic honeycomb filter was produced. The ceramic honeycomb filter of Comparative Example 3 was not provided with an open channel.

Examples 7-9 and Comparative Examples 4-5
Using the sealing material injection device 31 shown in FIG. 5, the nozzle 32 is inserted into the flow path forming the sealing portion so that the open flow path having the arrangement shown in Table 1 is formed, The slurry was introduced at the position to form the sealing portion 5 on the end face 12 of the ceramic honeycomb structure. A ceramic honeycomb filter was manufactured in the same manner as in Example 1 except for the above. The ceramic honeycomb filter of Comparative Example 6 was not provided with an open channel.

With respect to the ceramic honeycomb filters of Examples 1 to 9 and Comparative Examples 1 to 6, the pressure loss and the particulate matter collection rate were measured. The pressure loss is obtained from the differential pressure between the inlet side and the outlet side of the ceramic honeycomb filter at an air flow rate of 15 Nm ³ / min using a pressure loss test stand, and the measurement result of Example 1 is shown as a relative value. The fine particle collection rate was 10 Nm ³ / min with an air flow rate, carbon powder with an average particle size of 0.042 μm was charged into the ceramic honeycomb filter at a rate of 3 g / h for 2 hours, and the weight of the collected carbon powder was measured. , (Weight of collected carbon powder / weight of input carbon powder) × 100 (%). These results are shown in Table 1.

注：(1) 全流路数に対する開放流路数の割合。
(2) 全開放流路のうち、対角線方向に封止流路が隣接するものの数の割合。
(3) 「端面」は図1(a)〜図1(c)に示すように封止部が流路の端面に接して設けられている場合であり、「内側」は図4(a)〜図4(c)に示すように封止部が流路端面より内側に設けられている場合である。

Note: (1) Ratio of the number of open channels to the total number of channels.
(2) Percentage of the number of all the open channels that are adjacent to the sealed channel in the diagonal direction.
(3) `` End face '' is the case where the sealing part is provided in contact with the end face of the flow path as shown in FIGS. 1 (a) to 1 (c), and `` inner side '' is shown in FIG. 4 (a) FIG. 4 (c) shows a case where the sealing portion is provided on the inner side of the flow path end face.

  From Table 1, in the ceramic honeycomb filters of Examples 1 to 9, in which the open channels are adjacent in the diagonal direction and the number thereof is more than 15% and not more than 40% of the number of all channels, the particulate collection performance is not impaired. It can be seen that the pressure loss is reduced. In particular, when the proportion of the open channel was 20 to 35%, the balance between the collection performance of the fine particles and the pressure loss was good. On the other hand, the ceramic honeycomb filters of Comparative Examples 1 and 4 in which the number of open channels was 15% or less of the total number of channels were large in pressure loss. The ceramic honeycomb filters of Comparative Examples 2 and 5 in which the number of open channels exceeded 45% of the total number of channels were small in pressure loss but low in the collection rate, and did not reach a practical level. In Comparative Examples 3 and 6 having no open channel, the collection rate was good, but the pressure loss was high.

  Although the present invention has been described in detail with reference to the accompanying drawings, the present invention is not limited to them, and various modifications can be made within the scope of the technical idea of the present invention.

Claims (3)

In the ceramic honeycomb filter having a ceramic honeycomb structure having a large number of flow paths partitioned by porous partition walls, and a sealing portion provided in the exhaust gas inlet side or exhaust gas outlet side of the predetermined flow path, the exhaust Sealed on both the exhaust gas inflow side and the exhaust gas outflow side, the flow path in which the sealing part is provided on the gas inflow side, the flow path in which the sealing parts are arranged in a pine pattern on the exhaust gas outflow side, and An open channel without a stop , wherein the open channel is more than 15% and 40% or less of the total number of channels, and the arrangement of adjacent open channels is diagonal. Ceramic honeycomb filter. 2. The ceramic honeycomb filter according to claim 1, wherein an open channel diagonally adjacent to a sealing channel having a sealing portion on an exhaust gas inflow side or an exhaust gas outflow side is 10 to 90% of the total open channel. A ceramic honeycomb filter characterized by that. An exhaust gas purification apparatus comprising the ceramic honeycomb filter according to claim 1.

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