JP4302419B2 - Catalytic converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalytic converter.
[0002]
[Prior art]
Conventionally, a catalytic converter in which two honeycomb-type catalyst carriers are accommodated in one casing has been proposed (see, for example, Patent Document 1). In this catalytic converter, the upstream catalyst carrier and the downstream catalyst carrier are housed in one casing via individual ceramic fiber holding seal members, and the upstream catalyst carrier is the downstream catalyst carrier. It is formed so that the amount of catalyst supported is larger than that of the carrier. As a result, a good low temperature rise characteristic is obtained with a small amount of catalyst supported compared to a catalytic converter in which one catalyst carrier is arranged.
[0003]
[Patent Document 1]
JP-A-64-7935 (FIG. 1)
[0004]
[Problems to be solved by the invention]
However, in the above-described catalytic converter, since the holding seal member does not exist between the upstream catalyst carrier and the downstream catalyst carrier, the gas passing therethrough directly contacts the casing. As a result, when the temperature of the casing is low, the gas loses heat to the casing, so that the catalyst carrier heated by the gas may not easily reach the catalyst activation temperature. Further, when the gas temperature is high, the casing may be deformed due to heat damage.
[0005]
This invention is made | formed in view of such a subject, and makes it one of the objectives to provide what can improve heat insulation compared with the former in the catalytic converter provided with a some catalyst support | carrier. Another object of the present invention is to provide a catalytic converter including a plurality of catalyst carriers that can suppress deformation of the casing due to heat damage as compared with the conventional converter.
[0006]
[Means for solving the problems and their functions and effects]
The present invention adopts the following means in order to achieve at least one of the above objects.
[0007]
The catalytic converter of the present invention is
A hollow cylindrical casing;
A plurality of catalyst carriers arranged at intervals along the axial direction of the casing;
One holding sealing member made of a heat-resistant fiber is provided so as to cover the outer periphery of the plurality of catalyst carriers and filled between the plurality of catalyst carriers and the casing.
[0008]
In this catalytic converter, since one holding seal member is wound so as to cover the outer circumferences of a plurality of catalyst carriers arranged at intervals along the axial direction of the casing, the catalyst converter is not provided between the catalyst carrier and the catalyst carrier. There is no portion where the holding seal member does not exist. As a result, when the gas passes through the plurality of catalyst carriers, the gas does not directly contact the casing, and the heat insulation of the gas passage is improved as compared with the conventional case. Thereby, even when the temperature of the casing is low, the gas is not deprived of heat by the casing, and the catalyst carrier heated by the gas can quickly reach the catalyst activation temperature. Further, even if the temperature of the gas is high, there is no possibility that the casing is deformed due to heat damage caused by the gas.
[0009]
The catalytic converter of the present invention may be provided with a protective portion having higher wind erosion resistance than the holding seal member in a portion of the inner peripheral surface of the holding seal member where the plurality of catalyst carriers are spaced apart. The gas passing through the catalyst carrier directly hits the portion of the inner peripheral surface of the holding seal member where the spaces between the catalyst carriers are spaced apart. It is possible to prevent the deterioration of this portion due to the gas to be discharged.
[0010]
In the catalytic converter of the present invention adopting this aspect, the protective portion is provided on the catalyst carrier side adjacent to the portion of the inner circumferential surface of the holding seal member, in addition to the portion where the plurality of catalyst carriers are spaced apart from each other. You may form so that it may enter. In this way, it is possible to prevent deterioration of the inner peripheral surface of the holding seal member and the surrounding area where the plurality of catalyst carriers are spaced apart from each other due to the gas. At this time, it is preferable that the portion entering the catalyst carrier side is within 20 mm in the axial direction of the casing so that the holding seal member does not reduce the holding force for holding the catalyst carrier.
[0011]
Such a protection part may be formed by processing the holding seal member with an inorganic binder. If it carries out like this, the inner surface of a holding sealing member will be hardened by an inorganic binder, and wind erosion resistance will increase. This protective part may be formed by treating not the entire thickness direction of the holding seal member but only the inner surface side with an inorganic binder. By so doing, the contact pressure required when the holding seal member holds the plurality of catalyst carriers in the casing is not greatly impaired. In the case where the holding seal member is a non-woven fabric made of heat-resistant short fibers, it is preferable to form a protective part by treating with an inorganic binder in this way.
[0012]
Alternatively, the protective part may be a metal ring or a heat resistant cloth that is separate from the holding seal member. By doing so, the inner surface of the holding seal member is protected by the metal ring or the heat-resistant cloth, so that the wind erosion resistance is enhanced.
[0013]
In the catalytic converter of the present invention, the plurality of catalyst carriers may be arranged via a spacer so that a predetermined interval is provided along the axial direction of the casing. In this case, when a plurality of catalyst carriers are wound around one holding seal member and then press-fitted into the casing to produce a catalytic converter, the plurality of catalyst carriers are press-fitted into the casing while maintaining a predetermined interval. This spacer is preferably formed so as not to prevent the gas from flowing through the plurality of catalyst carriers. For example, the ring may be a ring along the periphery of the gas passage surface of the catalyst carrier, or the ring may be divided into a plurality of parts and several of the divided bodies may be arranged along the periphery of the gas passage surface of the catalyst carrier. May be.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a configuration of a catalytic converter 10 according to an embodiment of the present invention, FIG. 2 is a perspective view showing a positional relationship between both catalyst carriers 18 and 20 and a spacer 30, and FIG. 3 is a catalytic converter. 10 is a perspective view illustrating a state in which 10 is assembled.
[0015]
As shown in FIG. 1, the catalytic converter 10 of the present embodiment is disposed between an exhaust manifold connected to an engine in a vehicle exhaust system and a muffler that reduces exhaust gas noise, and is included in the exhaust gas. It is a device for detoxifying harmful components before they are released into the atmosphere. The catalytic converter 10 has a hollow cylindrical casing 12 formed of a metal material having high heat resistance typified by SUS409 and the like, and the diameter thereof is reduced in order to be connected to the upstream end of the casing 12 and connected to the exhaust manifold. A substantially truncated cone-shaped upstream cone 14, a substantially truncated cone-shaped downstream cone 16 that is joined to the downstream end of the casing 12 and has a reduced diameter for connection to the exhaust pipe, and the casing 12 accommodates the exhaust gas upstream. The first catalyst carrier 18, the second catalyst carrier 20 accommodated in the casing 12 on the downstream side of the exhaust gas, the catalyst carriers 18, 20 are held in the casing 12, and the casing 12 and the catalyst carriers 18, 20 And one holding seal member 24 for preventing the exhaust gas from flowing through the gap. Below, among these structures, the 1st catalyst carrier 18, the 2nd catalyst carrier 20, and the holding seal member 24 are further demonstrated.
[0016]
The first catalyst carrier 18 is formed by forming a highly heat-resistant ceramic material typified by cordierite, alumina, mullite, spinel or the like into a cylindrical honeycomb, and oxidizes HC and CO in exhaust gas and reduces NOx. Are carried out simultaneously to carry a three-way catalyst for conversion to H ₂ O, CO ₂ and N ₂ . The first catalyst carrier 18 has an overall length that is substantially half of the entire length of the catalyst carrier accommodated in the casing, and has a large number of through holes 19 in the axial direction. The first catalyst carrier 18 is disposed on the exhaust gas upstream side in the casing 12.
[0017]
The second catalyst carrier 20 is formed by forming a highly heat-resistant ceramic material typified by cordierite, alumina, mullite, spinel or the like into a cylindrical honeycomb, and oxidizes HC and CO in an oxygen-rich region. A NOx occlusion reduction catalyst that occludes NOx and reduces NOx released from the stoichiometric air-fuel ratio region in a fuel-rich region is supported. The entire length of the second catalyst carrier 20 is substantially half of the entire length of the catalyst carrier accommodated in the casing, and has a large number of through holes 21 in the axial direction. The second catalyst carrier 20 is arranged at a predetermined interval along the axial direction with the first catalyst carrier 18 on the exhaust gas downstream side in the casing 12. As a result, a space S is formed between the catalyst carriers 18 and 19 in the casing 12. A spacer 30 is disposed in the space S. The spacer 30 is formed of a material having high heat resistance and rigidity typified by stainless steel and ceramic in an arc shape along the peripheral edges of the gas passage surfaces of the catalyst carriers 18 and 20 as shown in FIG. Three are arranged along the outer periphery.
[0018]
The holding seal member 24 is a belt-like member obtained by forming a heat-resistant inorganic short fiber typified by ceramic fiber (alumina fiber, alumina silica fiber, silica fiber, etc.), rock wool, glass fiber or the like into a nonwoven fabric. The holding seal member 24 is wound around the outer circumferences of the catalyst carriers 18 and 20 and press-fitted into the casing 12, thereby filling between the catalyst carriers 18 and 20 and the casing 12. Further, as shown in FIG. 3, when the holding seal member 24 is wound around the outer circumferences of the catalyst carriers 18 and 20, a gap along the circumferential direction is formed between the one end 25 and the other end 26 that face each other. The convex portions 25a, 25b provided at the one end 25 and the concave portions 26a, 26b provided at the other end 26 fit closely together without causing a gap in the axial direction (direction orthogonal to the circumferential direction).
[0019]
In the inner surface of the holding seal member 24, a portion of the first catalyst carrier 18 and the second catalyst carrier 20 that are spaced apart and spaced apart (surface of the gap) A0 is filled with inorganic binder slurry on the holding seal member 24. The protective part 27 is formed by applying and drying. The protection part 27 protects the gap surface A0 by hardening the inorganic short fibers of the holding seal member 24 with an inorganic binder. Here, any inorganic binder may be used as long as the surface of the holding seal member 24 can be hardened. For example, silica sol or a viscous mineral (montmorillonite, etc.) may be used. Moreover, you may sinter as needed. In the present embodiment, the protective portion 27 is provided in the axial direction of the casing 12 on the first catalyst carrier side and the second catalyst carrier side adjacent to the gap surface A0 in the holding seal member 24 in addition to the gap surface A0. It is formed so as to enter within a range of 20 mm or less.
[0020]
Next, the procedure for assembling the catalytic converter 10 will be described with reference to FIGS. First, as shown in FIG. 2, three spacers 30 are arranged at substantially equal intervals along the periphery of the gas passage surface of the second catalyst carrier 20, and the first catalyst carrier 18 and the second catalyst carrier 20 perform these spacers. The spacer 30 is sandwiched. Subsequently, as shown in FIG. 3, the holding seal member 24 is wound around the outer circumferences of the two catalyst carriers 18 and 20 with the spacer 30 interposed therebetween, and the convex portions 25 a and 25 b at one end 25 are formed on the concave portions 26 a and 26 b at the other end 26. Fit. Then, although the convex part 25a, 25b of the one end 25 and the recessed part 26a, 26b of the other end 26 have a gap along the circumferential direction, there is no gap in the axial direction and they are in close contact. At this time, the convex portion 25 a and the concave portion 26 a are located on the outer periphery of the first catalyst carrier 18, and the convex portion 25 b and the concave portion 26 b are located on the outer periphery of the second catalyst carrier 20. In this state, the one end 25 and the other end 26 are fastened with one or several places with tape, and then press-fitted into the casing 12. At this time, since the spacer 30 is interposed between the catalyst carriers 18 and 20, the catalyst carriers 18 and 20 are press-fitted into the casing while maintaining a predetermined interval (an interval corresponding to the thickness of the spacer 30). . The holding seal member 24 is compressed in the radial direction and is press-fitted into the casing 12. Therefore, after the press-fitting is completed, the gap between the catalyst carriers 18 and 20 and the casing 12 is tightly filled with the holding seal member 24, and the convex portion 25a and the concave portion 26a of the holding seal member 24 have a gap in the axial direction. Contact closely without generating. As a result, the catalyst carriers 18 and 20 are securely held in the casing 12 by the holding seal member 24, and the gap between the catalyst carriers 18 and 20 and the casing 12 is sealed to prevent the gas from flowing. Further, the distance between the catalyst carriers 18 and 20 is ensured by the thickness of the spacer 30 as before the press-fitting. Thereafter, the upstream cone 14 is joined to the upstream end of the casing 12, and the downstream cone 16 is joined to the downstream end of the casing 12, thereby completing the catalytic converter 10.
[0021]
Next, the operation of the catalytic converter 10 of this embodiment will be described. As shown in FIG. 1, the exhaust gas from the engine flows into the catalytic converter 10 after passing through the exhaust manifold. The exhaust gas flowing into the catalytic converter 10 first passes through the through hole 19 of the first catalyst carrier 18. At this time, the exhaust gas is purified by converting CO, HC, NOx in the exhaust gas into CO ₂ , H ₂ O, N ₂ by the oxidation action and reduction action of the three-way catalyst. Subsequently, the gas that has passed through the first catalyst carrier 18 passes through the space S formed between the catalyst carriers 18 and 20. Since the periphery of the space S is also covered with the holding seal member 24, the heat insulation of the gas passage is enhanced as compared with the case where the periphery of the space S is exposed. For this reason, the exhaust gas passes through the space S with almost no change in temperature. Thereafter, the exhaust gas passes through the through hole 21 of the second catalyst carrier 20. At this time, HC and CO are oxidized and NOx is occluded in the oxygen-rich region by the action of the NOx occlusion reduction catalyst. Further, in the fuel rich region from the stoichiometric air fuel ratio region, the NOx storage reduction catalyst releases NOx to reduce.
[0022]
According to the catalytic converter 10 described in detail above, the exhaust gas does not directly contact the casing 12 when the exhaust gas passes through the catalyst carriers 18 and 20, and the heat insulation of the gas passage is improved as compared with the conventional case. Thereby, even when the temperature of the casing 12 and the exhaust gas is low, such as when the engine is started, the exhaust gas is not deprived of heat by the casing 12, and both the catalyst carriers 18 and 20 heated by the exhaust gas can be quickly The catalyst activation temperature can be reached. On the other hand, even when the temperature of the exhaust gas is high, the casing 12 is not likely to be deformed due to heat damage caused by the exhaust gas.
[0023]
Moreover, since the protection part 27 with high wind erosion resistance is formed on the gap surface A0 in the inner peripheral surface of the holding seal member 24, even if the exhaust gas passing through the space S directly hits the protection part 27 Thus, the void surface A0 is not deteriorated. In particular, since the protective portion 27 is formed not only on the gap surface A0 but also on the first catalyst carrier side and the second catalyst carrier side adjacent to the gap surface A0, the gap surface A0 of the holding seal member 24 is formed. In addition, it is possible to prevent the surroundings from being deteriorated by the exhaust gas. Since the portion entering the catalyst carrier side is within 20 mm in the axial direction of the casing 12, the holding seal member 24 does not greatly impair the surface pressure by the protective portion 27 and holds both the catalyst carriers 18 and 20 well. be able to. Further, since the protective portion 27 is formed by applying the inorganic binder only to the surface rather than impregnating the entire thickness direction of the holding seal member 24 with the inorganic binder, the holding seal member 24 also has a large loss in surface pressure. Therefore, both catalyst carriers 18 and 20 can be held well.
[0024]
Further, when the outer circumferences of the catalyst carriers 18 and 20 are wound around the holding seal member 24 and then press-fitted into the casing 12, a spacer 30 is interposed between the catalyst carriers 18 and 20; 20 is press-fitted into the casing while maintaining a predetermined interval. Since the spacer 30 is formed in an arc shape along the outer edges of the catalyst carriers 18 and 20, the spacer 30 does not prevent the exhaust gas from flowing through the catalyst carriers 18 and 20.
[0025]
Needless to say, the present invention is not limited to the above-described embodiments, and can be implemented in various forms.
[0026]
For example, in the above-described embodiment, the protective portion 27 is formed by applying an inorganic binder slurry to the gap surface A0 of the holding seal member 24 and drying it. However, as shown in FIG. A ring made of a separate heat-resistant metal material may be disposed as the protective portion 28 so as to cover the void surface A0. As this type of ring, any ring having heat resistance that can withstand the operating temperature of the catalytic converter 10 may be used. For example, a ring made of stainless steel or the like may be used. Or you may arrange | position so that the space | gap part surface A0 may be covered by using the heat resistant cloth wound in the ring shape as the protection part 28. FIG. Any heat resistant cloth may be used as long as it has heat resistance capable of withstanding the operating temperature of the catalytic converter 10. For example, ceramic fiber (alumina fiber, alumina silica fiber, silica fiber, etc.), rock wool, etc. And a woven fabric produced by weaving long fibers of heat-resistant inorganic fibers typified by glass fibers. In any case, since the air gap surface A0 of the holding seal member 24 is protected by the protection portion 2, the wind erosion resistance is improved, and the same effect as that of the above-described embodiment can be obtained.
[0027]
In the above-described embodiment, the catalyst supported on the first catalyst carrier 18 and the catalyst supported on the second catalyst carrier 20 are different from each other. However, both catalysts may be the same. Supported catalysts include the above-described three-way catalyst and NOx storage reduction catalyst, an oxidation catalyst that oxidizes HC and CO in the exhaust gas and converts them into H ₂ O and CO ₂ , and ammonia that purifies NOx with ammonia. You may select suitably from adsorption denitration catalysts etc.
[0028]
Furthermore, in the above-described embodiment, one of the first catalyst carrier 18 and the second catalyst carrier 20 may be a harmful component adsorbent that adsorbs harmful components at low temperatures and desorbs them at high temperatures. As this kind of harmful component adsorbent, for example, an HC adsorbent such as zeolite arranged upstream of a three-way catalyst or an oxidation catalyst is known. This HC adsorbent adsorbs HC when the exhaust gas is at a low temperature, desorbs after the exhaust gas is heated, and leads it to a downstream three-way catalyst or oxidation catalyst.
[0029]
Furthermore, in the embodiment described above, the number of catalyst carriers accommodated in the casing 12 is two, but may be three or more. Since the catalyst supported on the catalyst carrier has already been exemplified, the description thereof is omitted here. What kind of catalyst is supported on which catalyst carrier is combined may be appropriately determined according to the engine used, the air-fuel ratio control method, and the like.
[0030]
In the above-described embodiment, the example in which the present invention is applied to the catalytic converter 10 for purifying exhaust gas has been described. However, the present invention may be applied to a catalytic converter used in a reformer for a fuel cell. In a fuel cell system equipped with a fuel cell that generates electricity through an electrochemical reaction between hydrogen (fuel gas) and oxygen (oxidizing gas), hydrocarbon fuels such as methanol, gasoline, and city gas react with water vapor and oxygen. In some cases, a reforming apparatus that takes out hydrogen by reforming and takes it out and supplies it to the fuel cell may be used. Then, when reforming the hydrocarbon fuel with this reformer, a catalytic converter is prepared that houses a honeycomb catalyst carrier on which a catalyst suitable for the reforming is supported, and the vaporized hydrocarbon fuel and steam or oxygen are prepared. May pass through the catalytic converter. The present invention can also be applied to this type of catalytic converter. That is, the catalytic converter according to one embodiment of the present invention is formed by winding one holding seal member so as to cover the outer periphery of a plurality of honeycomb catalyst carriers arranged at intervals along the axial direction of the casing. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of a catalytic converter 10. FIG.
FIG. 2 is a perspective view showing a positional relationship between both catalyst carriers 18 and 20 and a spacer 30. FIG.
FIG. 3 is a perspective view showing how the catalytic converter 10 is assembled.
FIG. 4 is a cross-sectional view schematically showing the configuration of another catalytic converter.
[Explanation of symbols]
10 catalytic converter, 12 casing, 14 upstream cone, 16 downstream cone, 18 first catalyst carrier, 19 through hole, 20 second catalyst carrier, 21 through hole, 24 holding seal member, 25 one end, 25a convex portion, 26 The other end, 26a concave portion, 27 protective part, 28 protective part, 30 spacer, A0 gap surface, S space.

Claims (6)

A hollow cylindrical casing;
A plurality of catalyst carriers arranged at intervals along the axial direction of the casing;
One holding seal member made of heat-resistant fiber wound around the outer periphery of the plurality of catalyst carriers and filled between the plurality of catalyst carriers and the casing ;
A protective portion that is formed in a portion of the inner peripheral surface of the holding seal member that is spaced from the plurality of catalyst carriers and has higher erosion resistance than the holding seal member;
With catalytic converter. The protection unit according to claim 1, which is formed so as to enter the other catalyst carrier side which is adjacent to that portion of the interval empty portion among the plurality of catalyst support of the inner circumferential surface of the holding seal member Catalytic converter. The protection unit, the catalytic converter according to claim 1 or 2 is formed by treating the holding seal member in the inorganic binder. 4. The catalytic converter according to claim 3 , wherein the protection part is formed by treating not the entire thickness direction of the holding seal member but only the inner surface side with an inorganic binder. 5. The protection unit, the catalytic converter according to claim 1 or 2, wherein the holding seal member is a separate metal ring or refractory cloth. The catalytic converter according to any one of claims 1 to 5 , wherein the plurality of catalyst carriers are arranged via a spacer so as to have a predetermined interval along the axial direction of the casing.

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