JP2022119538A - Heat exchange device and reformer - Google Patents

Abstract

To provide a heat exchange device in which breakage or positional deviation is hard to occur, and a reformer equipped with the heat exchange device.SOLUTION: A heat exchange device is composed of a heat exchanger in which a first circulation path and a second circulation path that are honeycomb structures are assembled so as to intersect each other, a metal casing that stores the heat exchanger, and a holding mat that is arranged between the heat exchanger and the metal casing. The heat exchanger has a substantially columnar shape in which the first circulation path opens on both end surfaces and the second circulation path opens on an outer peripheral surface. The holding mat is arranged along the outer peripheral surface of the heat exchanger so as not to cover a part of the second circulation path opening on the outer peripheral surface. A surface of the second honeycomb structure of the outer peripheral surface of the heat exchanger has an opening area where the second circulation path is not covered by the holding mat and opens on the outer peripheral surface of the heat exchanger, and sealing areas which are respectively provided on both end surface side of the head exchanger with respect to the opening area and where the second circulation path is covered by the holding mat.SELECTED DRAWING: Figure 5

Description

The present invention relates to a heat exchange device and a reformer.

As a technique for improving fuel efficiency by reforming fuel of an internal combustion engine, Patent Document 1 discloses the following technique. That is, part of the exhaust gas from the exhaust passage of the internal combustion engine is recirculated to the intake passage as EGR (exhaust gas recirculation) gas. and a fuel reforming catalyst for reforming the reforming fuel. Then, the reforming fuel injected by the reforming fuel injection valve and the moisture (water vapor) in the EGR gas are reformed by the fuel reforming catalyst to produce hydrogen (H ₂ ) and carbon monoxide (CO). By generating it, the reforming fuel is reformed to generate reformed gas with high combustibility, and the reformed gas is supplied to the intake passage of the internal combustion engine. In addition, deterioration of the fuel reforming catalyst is suppressed by controlling the injection amount of the reforming fuel so that it falls within a control range set based on the temperature of the fuel reforming catalyst and the amount of reformed gas. We are trying to improve the reforming performance.

In the above fuel reforming catalyst, when steam and hydrocarbons react in the reformer, heat is taken from the exhaust gas, so the fuel reforming catalyst is configured to exchange heat with the exhaust gas flowing through the exhaust pipe, Heat is supplied from the exhaust gas to promote the reforming reaction.

Although Patent Document 1 does not describe specific materials or configurations of the fuel reforming catalyst, a temperature of 600° C. or higher is required to promote the reaction in the reformer. A reforming catalyst that can withstand a temperature of 600° C. or more and has a heat exchange function is required as a material constituting the reforming catalyst.

Patent Literature 2 discloses a heat exchanger having a monolithic ceramic structure in which a first layer having flow channels and a second layer are stacked in directions crossing each other and fired.

JP 2015-166591 A JP-A-7-151478

In the reforming method described in Patent Document 1, since the pressure received from the exhaust gas environment is high, it was necessary to maintain the heat exchanger at a high canning pressure. When adopting the heat exchanger described in Cited Document 2 in the method described in Cited Document 1, a columnar heat exchanger is required instead of a prismatic shape due to the relationship between the installation location and piping layout. something happened. However, if the heat exchanger described in Cited Document 2 is deformed into a cylindrical shape and adopted in the method described in Cited Document 1, there is a problem that the heat exchanger is damaged by high canning pressure, and the heat exchanger When the canning pressure is set so as not to damage the heat exchanger, there arises a problem that the position of the heat exchanger is shifted due to the pressure of the exhaust gas.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat exchanger that is less likely to be damaged or misaligned, and a reformer that includes the heat exchanger.

The heat exchange device of the present invention comprises a first honeycomb structure in which a large number of cells serving as first flow passages for fluid are arranged in parallel in the longitudinal direction with partition walls interposed therebetween, and a large number of cells serving as second flow passages for fluid. a second honeycomb structure arranged in parallel with partition walls in the longitudinal direction, a heat exchanger in which the first flow passage and the second flow passage intersect; and the heat exchange and a holding mat disposed between the heat exchanger and the metal casing, wherein the heat exchanger has the first flow path on both end faces. The holding mat has a substantially cylindrical shape in which the passage is open and the second flow path is open on the outer peripheral surface, and the holding mat is arranged along the outer peripheral surface of the heat exchanger so that the second flow path is open on the outer peripheral surface. The entire surface of the first honeycomb structure of the outer peripheral surface of the heat exchanger is covered with a coat layer, and the heat exchanger Of the outer peripheral surface of the above, the surface of the second honeycomb structure has an opening region in which the second flow path is not covered with the holding mat and is open to the outer peripheral surface of the heat exchanger; A sealing region provided on each of the end faces of the heat exchanger with respect to the opening region, the second flow path being covered with the holding mat, and a total area of the opening region and the sealing region The ratio of the area occupied by the opening region is 72 to 93%.

According to the heat exchange device of the present invention, since the heat exchanger is combined so that the first flow path and the second flow path intersect, the heat exchange performance is improved and the heat is exchanged. Two types of fluids can be smoothly circulated from different directions.

Further, in the heat exchange device of the present invention, the entire surface of the first honeycomb structure among the outer peripheral surfaces of the heat exchanger is covered with the coating layer, and one of the surfaces of the second honeycomb structure is covered with the coat layer. The part is a sealing area where the second flow path is covered with the retaining mat.
The portion covered with the coat layer has higher mechanical strength than the portion not covered with the coat layer. The portions covered with a coating layer having high mechanical strength and the plugging regions provided on both end sides of the second honeycomb structure are used as portions to which canning pressure is applied.
Therefore, even when the canning pressure is increased, the heat exchanger is less likely to be damaged, and displacement can be prevented.

Furthermore, in the heat exchange device of the present invention, part of the second flow path is covered with the retaining mat. Since the circulation of the fluid is blocked in the second circulation passage covered with the holding mat, the temperature change caused by the circulation of the fluid becomes slow and functions as a mass (heat capacity) for storing heat. Therefore, even when the temperature of the exhaust gas flowing into the second honeycomb structure is lowered, the high temperature can be maintained, and the reforming property at the inlet portion can be enhanced.

In the heat exchange device of the present invention, the ratio of the area of the opening region to the total area of the opening region and the sealing region is 72 to 93%. Therefore, the proportion of the second flow passages (opening area) used for heat exchange with the first honeycomb structure in normal times and the ratio of the second flow passages (sealing area) functioning as a heat capacity when the temperature of the exhaust gas decreases. The balance of the ratio is good, and it is possible to improve the reforming property at the inlet when the temperature of the exhaust gas is lowered while sufficiently securing the heat exchange efficiency in normal times.

In the heat exchange device of the present invention, it is desirable that the holding mat has a thickness of 3 to 5 mm.

In the heat exchange device of the present invention, when the thickness of the holding mat is 3 to 5 mm, the heat exchanger can be stably held without increasing the volume of the heat exchange device so much.
If the thickness of the holding mat is less than 3 mm, the heat exchanger cannot be stably held, and the holding mat may be damaged. On the other hand, if the thickness of the holding mat exceeds 5 mm, the volume of the heat exchange device may become too large.

In the heat exchange device of the present invention, it is desirable that the second honeycomb structure is arranged on both sides of the first honeycomb structure.

In the heat exchange device of the present invention, when the second honeycomb structures are arranged on both sides of the first honeycomb structure, heat can be propagated from the second honeycomb structures on both sides. Heat can be well supplied to the first honeycomb structure.

In the heat exchange device of the present invention, it is desirable that the partition walls of the cells constituting the first honeycomb structure carry a catalyst.

In the heat exchange device of the present invention, when the partition walls of the cells constituting the first honeycomb structure are loaded with a catalyst, the reforming reaction can be carried out inside the first honeycomb structure. By receiving the supply of heat from the exhaust gas that has flowed into the second honeycomb structure, the function as a reforming catalyst can be sufficiently exhibited.

In the heat exchange device of the present invention, the ratio of the total opening area of the second flow path to the total opening area of the first flow path (total opening area of the second flow path/opening area of the first flow path ) is desirably 1.25-2.

In the heat exchange device of the present invention, the ratio of the total opening area of the second flow path to the total opening area of the first flow path (total opening area of the second flow path/opening area of the first flow path ) is 1.25 to 2, the reforming reaction occurring inside the first honeycomb structure and the amount of heat propagated from the second honeycomb structure to the first honeycomb structure are well balanced. becomes.
When the ratio is less than 1.25, the amount of heat transferred from the second honeycomb structure to the first honeycomb structure is relatively reduced, and the reforming reaction may be difficult to occur. On the other hand, when the ratio exceeds 2, it means that the opening area of the second flow path is large, and the sealing area is relatively small. As a result, sufficient Canning pressure cannot be applied, and the heat exchanger may shift during use.

In the heat exchange device of the present invention, both the first honeycomb structure and the second honeycomb structure are preferably made of silicon carbide and silicon.

In the heat exchange device of the present invention, when both the first honeycomb structure and the second honeycomb structure are made of silicon carbide and silicon, they are excellent in thermal conductivity and heat resistance, and therefore good heat exchange. Even if it has a function and a large temperature difference occurs, it is more difficult to break. Furthermore, it is less corrosive to hydrogen contained in the reformed gas.

In the heat exchange device of the present invention, it is preferable that each of the first honeycomb structure and the second honeycomb structure is formed by bonding a plurality of ceramic honeycomb segments via an adhesive layer.

In the heat exchange device of the present invention, when each of the first honeycomb structure and the second honeycomb structure has a structure in which a plurality of ceramic honeycomb segments are bonded via an adhesive layer, one honeycomb Since the size of the segment can be reduced and the adhesive layer serves as a cushioning material, even if a large temperature difference occurs in the entire heat exchanger, damage or the like is less likely to occur.

In the heat exchange device of the present invention, the adhesive layer is preferably made of silicon carbide and silicon.

In the heat exchange device of the present invention, when the adhesive layer is made of silicon carbide and silicon, the heat conductivity is excellent, and the heat exchange performance between the first honeycomb structure and the second honeycomb structure is further improved. can be done.

In the heat exchange device of the present invention, the heat exchanger preferably has a volume of 1.2 to 3.2 liters.

In the heat exchange device of the present invention, when the volume of the heat exchanger is 1.2 to 3.2 liters, the heat exchanger has an appropriate volume, so that it is easy to mount on a vehicle or the like, and heat is generated. The effect as an exchange device can be sufficiently exhibited.
If the volume of the heat exchanger is less than 1.2 liters, the volume of the heat exchanger is too small and it becomes difficult to support a sufficient amount of catalyst. If it exceeds 2 liters, the capacity of the heat exchange device becomes large, making it difficult to mount it on a vehicle.

In the heat exchange device of the present invention, the heat exchanger is formed by alternately arranging the first honeycomb structure and the second honeycomb structure. and the second honeycomb structure having four layers.

In the heat exchange device of the present invention, the heat exchanger is formed by alternately arranging the first honeycomb structures and the second honeycomb structures. When the second honeycomb structure is included, the contact area between the second honeycomb structure and the first honeycomb structure is large, and heat can be efficiently exchanged.

The reformer of the present invention is a reformer equipped with the heat exchange device configured as described above, and the exhaust gas discharged from the internal combustion engine and flowing through the main exhaust pipe passes through the second honeycomb structure. In the first honeycomb structure, a catalyst for reforming is carried on partition walls, and the exhaust gas flowing into the exhaust gas recirculation pipe branched from the main exhaust pipe passes through the first honeycomb structure. It is characterized by

When the reformer of the present invention is configured as described above, the heat of the exhaust gas can be well supplied from the second honeycomb structure to the first honeycomb structure, and the fuel of the internal combustion engine can be reformed. performance as a reformer that improves fuel efficiency.
Further, in the reformer of the present invention, since the retaining mat is arranged between the heat exchanger and the metal casing, the coating layer is less likely to be damaged even when the heat exchanger reaches a high temperature.

FIG. 1 is a perspective view schematically showing a heat exchanger that constitutes a heat exchange device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the heat exchanger shown in FIG. 1 taken along the line II-II. FIG. 3 is a perspective view schematically showing a holding mat used when housing the heat exchanger shown in FIG. 1 in a metal casing. FIG. 4 is an explanatory diagram schematically showing a winding method for winding the holding mat shown in FIG. 3 around the heat exchanger shown in FIG. FIG. 5 is a perspective view schematically showing an example of the heat exchange device according to the first embodiment of the invention. 6 is a perspective view schematically showing an example of a honeycomb assembly for manufacturing the heat exchanger shown in FIG. 1. FIG. FIG. 7 is a perspective view schematically showing a heat exchanger that constitutes a heat exchange device according to a second embodiment of the present invention. 8 is a cross-sectional view of the heat exchanger shown in FIG. 7 taken along line VIII-VIII. FIG. 9 is an explanatory view schematically showing a fuel reforming gasoline engine system equipped with the reformer of the present invention.

(Detailed description of the invention)
A heat exchange device of the present invention will be described.
The heat exchange device of the present invention comprises a first honeycomb structure in which a large number of cells serving as first flow passages for fluid are arranged in parallel in the longitudinal direction with partition walls interposed therebetween, and a large number of cells serving as second flow passages for fluid. a second honeycomb structure arranged in parallel with partition walls in the longitudinal direction, a heat exchanger in which the first flow passage and the second flow passage intersect; and the heat exchange and a holding mat disposed between the heat exchanger and the metal casing, wherein the heat exchanger has the first flow path on both end faces. The holding mat has a substantially cylindrical shape in which the passage is open and the second flow path is open on the outer peripheral surface, and the holding mat is arranged along the outer peripheral surface of the heat exchanger so that the second flow path is open on the outer peripheral surface. The entire surface of the first honeycomb structure of the outer peripheral surface of the heat exchanger is covered with a coat layer, and the heat exchanger Of the outer peripheral surface of the above, the surface of the second honeycomb structure has an opening region in which the second flow path is not covered with the holding mat and is open to the outer peripheral surface of the heat exchanger; A sealing region provided on each of the end faces of the heat exchanger with respect to the opening region, the second flow path being covered with the holding mat, and a total area of the opening region and the sealing region The ratio of the area occupied by the opening region is 72 to 93%.

FIG. 1 is a perspective view schematically showing a heat exchanger constituting a heat exchange device according to a first embodiment of the present invention, and FIG. 2 is a line II-II of the heat exchanger shown in FIG. It is a sectional view.
As shown in FIGS. 1 and 2, the heat exchanger 100 is a first honeycomb in which a large number of first cells 13 serving as first flow paths for fluid are arranged in the longitudinal direction with first partition walls 12 interposed therebetween. A first flow passage ( The heat exchanger 100 is a substantially cylindrical heat exchanger 100 in which a first cell 13) and a second flow path (second cell 23) are combined so as to intersect each other.
In addition, when the first honeycomb structure and the second honeycomb structure are not particularly distinguished, they may simply be referred to as a honeycomb structure. As with the honeycomb structure, the first cells and the second cells, and the first partition walls and the second partition walls are also simply referred to as cells and partition walls when they are not distinguished from each other.

1 and 2, the extending direction of the first cells 13 constituting the first honeycomb structure 10 is the vertical direction (direction indicated by arrow z in FIGS. 1 and 2). The extending direction of the second cells 23 constituting the second honeycomb structure 20 is the horizontal direction (direction indicated by arrow y in FIG. 1). In the first honeycomb structure 10 and the second honeycomb structure 20, since the flow paths intersect with each other, two kinds of fluids (especially gas) can be easily circulated, and heat exchange can be efficiently performed. can.

In the heat exchanger 100 shown in FIGS. 1 and 2, the first honeycomb structures 10 and the second honeycomb structures 20 are alternately arranged with the adhesive layers 19 interposed therebetween. and a second honeycomb structure 20 of four layers. In the heat exchanger 100 shown in FIGS. 1 and 2, one first honeycomb segment 11 constitutes one layer of the first honeycomb structure 10, but two or more first honeycomb segments The first honeycomb structure 10 of one layer may be configured by bonding the segments 11 via an adhesive layer. Therefore, in the present invention, an assembly of one or more first honeycomb segments 11 sandwiched between second honeycomb structures 20 is counted as one layer of first honeycomb structure 10 . The first honeycomb segment is a member having the same structure as the first honeycomb structure.

In the heat exchange device of the present invention, the fluid to be subjected to heat exchange may be water, an organic solvent such as ethylene glycol, a liquid such as liquefied gas, or a gas (gas), but gas is preferable. , the exhaust gas is more desirable.
In this specification, when the term "heat exchange device of the present invention" is used, it means the heat exchange device according to the first embodiment described above and the heat exchange device according to the second embodiment described later. etc., the characteristics, conditions, etc. common to the members constituting the heat exchange device according to all the embodiments of the present invention, the members related to the above heat exchange device, and the like are described.

In the heat exchanger 100 shown in FIGS. 1 and 2, one layer of the second honeycomb structure 20 is configured by bonding two second honeycomb segments 21 via an adhesive layer 18. .
The method of counting the second honeycomb structures 20 is the same as the method of counting the first honeycomb structures 10, and one or two or more second honeycomb segments sandwiched between the first honeycomb structures 10 are counted. The assembly of 21 is called a second honeycomb structure 20 of one layer. However, the second honeycomb structure 20 may be positioned on the outermost side, and in that case, the assembly of one or more second honeycomb segments 21 on the outermost side is also one layer of the second honeycomb segment 21. It is a honeycomb structure 20 .
When the first honeycomb segment and the second honeycomb segment are not particularly distinguished, they are simply referred to as honeycomb segments.

Each of the first honeycomb structure and the second honeycomb structure constituting the heat exchange device of the present invention may be composed of one ceramic honeycomb segment, or may be composed of a plurality of ceramic honeycomb segments. Individuals may be bonded via an adhesive layer.

The number of honeycomb segments forming the first honeycomb structure and the second honeycomb structure may be the same or different.

In the heat exchange device of the present invention, it is desirable that the second honeycomb structure is arranged on both sides of the first honeycomb structure.
When the second honeycomb structures are arranged on both sides of the first honeycomb structure, heat can be propagated from the second honeycomb structures on both sides, and heat can be efficiently transferred to the first honeycomb structures. can supply.

In a first embodiment of the heat exchange device of the present invention, the heat exchanger is formed by alternately arranging the first honeycomb structures and the second honeycomb structures, and the three-layer first honeycomb structure It is desirable to include a body and a four-layer second honeycomb structure.
The heat exchanger has first honeycomb structures and second honeycomb structures alternately arranged, and includes three layers of the first honeycomb structures and four layers of the second honeycomb structures. , the contact area between the second honeycomb structure and the first honeycomb structure is large, and heat can be efficiently exchanged.

In the substantially cylindrical heat exchanger 100 shown in FIGS. 1 and 2, the first cells 13 serving as the first flow passages of the first honeycomb structure 10 are opened on both end surfaces, and the second honeycomb structure is formed on the outer peripheral surface. A second cell 23 serving as a second flow path of the structure 20 is open.
A part of the outer peripheral surface is covered with the coat layer 32 . The coat layers 32 consist of a coat layer 32a covering the entire surface of the first honeycomb structure 10 forming the outer peripheral surface and a coat layer 32b covering a part of the surface of the second honeycomb structure 20 forming the outer peripheral surface. and have
The portion covered with the coat layer 32 has higher mechanical strength than the portion not covered with the coat layer. Therefore, the portion covered with the coat layer 32 can be used as a portion to which canning pressure is applied.

In addition, since the entire surface of the first honeycomb structure 10 constituting the outer peripheral surface is covered with the coat layer 32a, the fluid flowing through the first cells 13 serving as the first flow paths and the second flow paths It is possible to prevent mixing with the fluid flowing through the second cell 23 that becomes .
The surface of the second honeycomb structure 20 forming the outer peripheral surface may or may not be partially covered with the coat layer 32 .

Since the entire surface of the first honeycomb structure 10 constituting the outer peripheral surface is covered with the coating layer 32a, the fluid flowing through the first cells 13, which are the first flow passages, and the second cell, which is the second flow passage, 2 can be prevented from being mixed with the fluid flowing through the cells 23 .

Although the thickness of the coat layer is not particularly limited, it is preferably 0.1 to 0.5 mm.
If the thickness of the coating layer is less than 0.1 mm, the coating layer is too thin and may be damaged by the pressure during canning. On the other hand, when the thickness of the coat layer exceeds 0.5 mm, the coat layer is too thick, and breakage may occur due to the temperature difference between the outermost surface of the coat layer and the portion in contact with the honeycomb structure.

In the heat exchange device of the present invention, the material of the honeycomb structure or the honeycomb segment, which is a constituent member thereof, is not particularly limited. , carbide-based ceramics such as zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide; nitride-based ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride; and composite materials of these ceramics and metals. be done. Among these, a composite material of silicon carbide is desirable, and a composite material composed of silicon and silicon carbide is particularly desirable.

Although the specific configuration of the composite material composed of silicon and silicon carbide is not particularly limited, it is an embodiment in which silicon enters the gaps between silicon carbide particles and independent silicon carbide particles are bonded by the surrounding silicon. A composite of silicon and silicon carbide is preferred.
Such a composite material composed of silicon and silicon carbide can be produced by bringing molten silicon into contact with the degreased body of the honeycomb formed body, as will be described later.
Silicon may be filled in the open pores of a porous silicon carbide sintered body having open pores.

When the molten silicon and silicon carbide are brought into contact with each other, the degreased bodies of the plurality of honeycomb formed bodies are brought into contact with the molten silicon in a state in which they are in close contact with each other via a layer that serves as an adhesive layer containing silicon carbide. An adhesive layer made of silicon and silicon is also formed, and a heat exchanger in which a plurality of honeycomb structures (or honeycomb segments) are bonded with an adhesive layer made of silicon carbide and silicon can be obtained.

The material of the adhesive layer that bonds the honeycomb structures (or honeycomb segments) together is not particularly limited, but as with the honeycomb structure (or honeycomb segments), silicon is in the state of entering the gaps between silicon carbide particles. Composite materials are preferred. As will be described later, such a composite material is obtained by applying a raw material paste containing silicon carbide to the sidewalls for bonding the honeycomb formed bodies together, drying the honeycomb formed bodies after bonding them together, and putting them in a molten state. can be made by contacting the silicon of

The thickness of the adhesive layer that bonds the honeycomb structures (or honeycomb segments) together is not particularly limited, but is preferably 0.5 to 2.0 mm.

The material of the coat layer is not particularly limited, but a composite material in which silicon is interspersed between silicon carbide particles is desirable, like the honeycomb structure (or honeycomb segment) and the adhesive layer.
As will be described later, such a composite material is prepared by applying a raw material paste containing silicon carbide to a portion of the outer peripheral surface of the cylindrical dried honeycomb body, which will become the first honeycomb structure, followed by drying, followed by melting. It can be made by contacting the silicon of the state.

In the heat exchange device of the present invention, it is desirable that the partition walls of the first honeycomb structure and the second honeycomb structure have a uniform thickness. Specifically, the thickness of the partition walls of the first honeycomb structure supporting the catalyst is desirably 0.08 to 0.30 mm, and more desirably 0.10 to 0.20 mm. Since the thickness of the partition walls of the first honeycomb structure is thin, the surface area is large and a larger amount of catalyst can be supported.

The partition walls of the second honeycomb structure preferably have a thickness of 0.10 to 0.40 mm, more preferably 0.15 to 0.30 mm. Since the thickness of the partition walls of the second honeycomb structure is large, the heat capacity is large, and a large amount of heat can be supplied to the first honeycomb structure.

When the thicknesses of the partition walls of the first honeycomb structure and the second honeycomb structure are set as described above, a larger amount of the catalyst can be supported, the reforming efficiency is increased, and the second honeycomb structure is improved. Since a larger amount of heat can be supplied from the structure to the first honeycomb structure, the activity of the catalyst can be increased.

In the heat exchange device of the present invention, the shape of the cells constituting the honeycomb structure is preferably, for example, a rectangular end surface and a quadrangular pillar shape as a whole, but may be a triangular pillar shape or a hexagonal pillar shape. .
Although the cells may have different shapes, it is desirable that they all have the same shape. That is, it is desirable that the cells surrounded by the partition walls have the same size in the cross section perpendicular to the longitudinal direction of the honeycomb structure. This is because it can be easily manufactured.

In the heat exchange device of the present invention, the cell density (first cell density) in the cross section perpendicular to the longitudinal direction of the cells of the first honeycomb structure is 46 to 124 cells/cm ² (300 to 800 cells/inch ² ). ), more preferably 62 to 93/cm ² (400 to 600/inch ² ). This is because when the first cell density is within the above range, the surface area of the first honeycomb structure is increased, and a large amount of catalyst can be supported.
In addition, the cell density (second cell density) in the cross section perpendicular to the longitudinal direction of the cells of the second honeycomb structure is desirably 16 to 78 cells/cm ² (100 to 500 cells/inch ² ). , 31 to 62/cm ² (200 to 400/inch ² ). When the second cell density is within the above range, the heat capacity of the second honeycomb structure increases, and a large amount of heat can be supplied to the first honeycomb structure.

In the heat exchange device of the present invention, the ratio of the total opening area of the second flow path to the total opening area of the first flow path (total opening area of the second flow path / total opening area of the first flow path ) is preferably between 1.25 and 2.
The ratio of the total opening area of the second flow passages to the total opening area of the first flow passages (total opening area of the second flow passages/total opening area of the first flow passages) is 1.25 to 2. Then, the reforming reaction occurring inside the first honeycomb structure and the amount of heat propagated from the second honeycomb structure to the first honeycomb structure are well balanced.
When the ratio is less than 1.25, the amount of heat transferred from the second honeycomb structure to the first honeycomb structure is relatively reduced, and the reforming reaction may be difficult to occur. On the other hand, when the ratio exceeds 2, it means that the opening area of the second flow path is large, and the sealing area is relatively small. As a result, sufficient Canning pressure cannot be applied, and the heat exchanger may shift during use.

In the heat exchange device of the present invention, the first cells constituting the first honeycomb structure preferably support a catalyst, and more preferably support a fuel reforming catalyst.
Preferred catalysts are Co, Ni, Rh, Pt and Pd, with Rh being more preferred.
The catalyst may be supported on the carrier and supported on the first cells constituting the first honeycomb structure. Rh/ZrO ₂ and Rh/CoO ₂ are desirable as the catalyst supported on the carrier. The support may also be other ceramics such as silica, alumina and the like.

In the heat exchange device according to the first embodiment of the present invention, the heat exchanger preferably has a volume of 1.2 to 3.2 liters.
When the volume of the heat exchanger is 1.2 to 3.2 liters, the heat exchanger has an appropriate volume, so it can be easily mounted on a vehicle or the like, and the effect as a heat exchange device is sufficiently exhibited. can do.
If the volume of the heat exchanger is less than 1.2 liters, the volume of the heat exchanger is too small and it becomes difficult to support a sufficient amount of catalyst, while the volume of the heat exchanger is 3.2 liters. If it exceeds liters, the capacity of the heat exchange device becomes large, making it difficult to mount it on a vehicle.

Next, the metal casing that constitutes the heat exchange device of the present invention will be described.
A metal casing is a metal container for housing a heat exchanger, and its shape can be appropriately selected according to the shape of the heat exchanger.
The casing is made of metal such as SUS.

The shape of the metal casing is not particularly limited, but it is desirable that the opening be provided so as not to cover the opening area of the outer peripheral surface of the heat exchanger.

Next, the holding mat that constitutes the heat exchange device of the present invention will be described.
A retaining mat is made of ceramic fibers and is disposed between the heat exchanger and the metal casing.

As the holding mat, a needle-punched needle mat, a mat obtained by a wet papermaking method, or the like can be used.

The ceramic fibers constituting the holding mat preferably have an average fiber diameter of 3 to 50 μm, and more preferably an average fiber length of 100 to 100000 μm.
In addition, it is desirable that the ceramic fibers constituting the holding mat include at least one selected from alumina fibers, silica fibers, alumina-silica fibers, mullite fibers, glass fibers and biosoluble fibers.
When the ceramic fibers constituting the retaining mat have the above-described shape and material, the surface pressure of the retaining mat can be sufficiently improved, and the heat exchanger can be stably retained in the reformer.

Also, the holding mat may contain an organic binder or an inorganic binder.
Examples of organic binders include rubber-based resins, styrene-based resins, silicone-based resins, acrylic-based resins, polyester-based resins, and polyurethane resins.
Inorganic binders include alumina sol, silica sol, aerogel, fumed silica, titanium particles and the like.

The thickness of the retaining mat is desirably 3 to 5 mm.
When the thickness of the holding mat is 3 to 5 mm, the heat exchanger can be stably held without increasing the volume of the heat exchange device.
If the thickness of the holding mat is less than 3 mm, the heat exchanger cannot be stably held, and the holding mat may be damaged. On the other hand, if the thickness of the holding mat exceeds 5 mm, the volume of the heat exchange device may become too large.

3 is a perspective view schematically showing a holding mat used when housing the heat exchanger shown in FIG. 1 in a metal casing, and FIG. 4 shows the holding mat shown in FIG. It is explanatory drawing which shows typically the winding method which winds around a heat exchanger, and FIG. 5 is a perspective view which shows typically an example of the heat-exchange apparatus which concerns on the 1st Embodiment of this invention.

As shown in FIG. 3, the holding mat 50 has protrusions 51a and recesses 51b at both ends of the mat 51, and when wound around the heat exchanger 100, the second cells 23, which are the fluid inlet and the fluid outlet, are formed. Mat openings 51c, 51d, 51e, 51f, 51g, and 51h are formed to be exposed.
As shown in FIG. 4, when the holding mat 50 is wrapped around the heat exchanger 100, the second cells 23, which are the fluid inlet and the fluid outlet, are exposed through the mat openings 51c, 51d, 51e, 51f, 51g, and 51h. do.

As shown in FIG. 4 , the holding mat 50 covers the entire surface of the first honeycomb structure 10 in the outer peripheral surface of the heat exchanger 100 . On the other hand, the surface of the second honeycomb structure 20 constituting the outer peripheral surface of the heat exchanger 100 is open to the outer peripheral surface of the heat exchanger 100 without the second flow passages being covered with the holding mat 50 . An opening area A1 (an area indicated by a dashed line in FIG. 4), and a sealing area A2 provided on both end surface sides of the heat exchanger 100 with respect to the opening area A1, and in which the second flow path is covered with the holding mat 50. , A3 (the area indicated by the dashed line in FIG. 4).
4, the opening area A1 and the sealing areas A2 and A3 are shown on the surface of the retaining mat 50. However, when the retaining mat 50 is wound around the heat exchanger 100, the opening area A1 and the sealing areas A3 are formed. , sealing regions A2 and A3, and the actual opening region A1 and sealing regions A2 and A3 are present on the outer peripheral surface of the heat exchanger 100.

When the retaining mat 50 is wrapped around the heat exchanger 100 and accommodated in the metal casing 60 as shown in FIG. 4, the heat exchange device 70 shown in FIG. 5 is obtained.
The heat exchange device 70 shown in FIG. Become.
Openings 60c, 60d, 60e, 60f, 60g, and 60h corresponding to the openings 51c, 51d, 51e, 51f, 51g, and 51h of the holding mat 50 are formed on the surface of the metal casing 60 (however, The openings 60d and 60e are not shown).
Therefore, also in the heat exchange device 70, the opening area A1 is not covered with the metal casing 60 and is exposed. Therefore, the areas of the opening region A1 and the sealing regions A2 and A3 described with reference to FIG. 4 are maintained in the heat exchange device 70 as well.

In the heat exchange device of the present invention, the ratio of the area of the opening area A1 to the total area of the opening area A1 and the sealing areas A2 and A3 is 72 to 93%, preferably 72 to 83%.
When the above ratio is 72 to 93%, it functions as a ratio of the second flow passage (opening area) used for heat exchange with the first honeycomb structure in normal times and as a heat capacity when the temperature of the exhaust gas is lowered. The ratio of the second flow path (sealing area) is well balanced, and the reforming property at the inlet when the temperature of the exhaust gas is lowered can be improved while sufficiently ensuring the heat exchange efficiency in normal times. .
When the above ratio is 72 to 83%, it functions as a ratio of the second flow passage (opening area) used for heat exchange with the first honeycomb structure in normal times and as a heat capacity when the temperature of the exhaust gas is lowered. The ratio of the second flow path (sealing area) is particularly well balanced, and the reforming property at the inlet part when the temperature of the exhaust gas is lowered can be further improved while further ensuring the heat exchange efficiency in normal times. can.

If the above ratio is less than 72%, the ratio of the second flow passages (opening regions) used for heat exchange with the first honeycomb structure in normal times is too small, and the heat exchange efficiency in normal times decreases. put away. On the other hand, if the above ratio exceeds 93%, the ratio of the second flow path (sealing region) that functions as a heat capacity when the temperature of the exhaust gas decreases is too small, and when the temperature of the exhaust gas decreases Reformability is lowered. Furthermore, the area for holding the second honeycomb structure during canning may be too narrow, resulting in breakage of the heat exchanger.
In addition, the sealing area is an area provided on both end surface sides of the heat exchanger with respect to the opening area. Therefore, in the heat exchanger 100 shown in FIG. 1, the area where the coat layer 32b is formed is covered with the holding mat 50 as shown in FIG. This area is not included in the area of the sealing area because it is not located on the side.

The ratio of the area of the open area to the sum of the area of the open area and the area of the sealing area is determined by the shape of the retaining mat disposed between the heat exchanger and the metal casing. Therefore, by adjusting the shape of the retaining mat (especially the shape and position of the openings), the ratio can be adjusted.

[Method for manufacturing heat exchanger]
Next, a method for manufacturing the heat exchange device of the present invention will be described.
When manufacturing the heat exchange device of the present invention, first, a heat exchanger including a first honeycomb structure and a second honeycomb structure is manufactured through the following steps. Subsequently, the manufactured heat exchanger is wound with a holding mat and housed in a metal casing to form a heat exchange device.
A case where silicon carbide and silicon are used as the materials constituting the honeycomb structure will be described below, but the materials constituting the honeycomb structure are not limited to the above materials.

The heat exchanger is produced by forming a raw material paste containing, for example, silicon carbide powder, an organic binder, etc. to form a honeycomb formed body in which a plurality of cells are arranged in parallel in the longitudinal direction with partition walls interposed therebetween; A drying step of drying the honeycomb formed body formed in the forming step, and bonding the honeycomb formed body to be the first honeycomb structure and the honeycomb formed body to be the second honeycomb structure dried in the drying step. A honeycomb aggregate producing step of producing an aggregate of honeycomb formed bodies (honeycomb aggregate) by bonding through an adhesive layer paste that serves as a layer, and a columnar body producing step of processing the honeycomb aggregate into a substantially cylindrical shape. , a coat layer paste application step of applying a coat layer paste to a part of the outer peripheral portion of the columnar body processed into a substantially cylindrical shape to form a coat layer paste layer; The coated columnar body is degreased, heated to a high temperature, and impregnated with molten silicon to form a honeycomb structure composed of a composite material of silicon carbide and silicon, an adhesive layer, and a coating layer. It can be manufactured by performing the degreasing, impregnation, and bonding processes for manufacturing the heat exchanger.

(Molding process)
In the molding step, first, silicon carbide powder, an organic binder, and the like are mixed to prepare a raw material paste.
The raw material paste may further contain a pore-forming agent, a molding aid, a dispersion medium such as water, and the like.

Examples of organic binders include, but are not limited to, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethylene glycol, phenolic resins, epoxy resins, and the like, and two or more of them may be used in combination.

Examples of the pore-forming agent include, but are not particularly limited to, acrylic resin, coke, starch, and the like. A pore-forming agent is used to introduce pores into the inside of a honeycomb structure (or honeycomb segment) when manufacturing the honeycomb structure (or honeycomb segment).

Examples of molding aids include, but are not limited to, ethylene glycol, dextrin, fatty acids, fatty acid soaps, polyalcohols, and the like, and two or more of them may be used in combination.

Examples of the dispersion medium include, but are not limited to, water, organic solvents such as benzene, and alcohols such as methanol, and two or more of them may be used in combination.

When preparing the raw material paste, it is desirable to mix and knead, and the mixture may be mixed using a mixer, an attritor or the like, or may be kneaded using a kneader or the like.

In the forming step, the raw material paste is extruded to obtain a formed honeycomb body in which a plurality of cells are arranged in parallel in the longitudinal direction with partition walls interposed therebetween.
The shape of the formed honeycomb body is not particularly limited, but a prismatic shape is desirable, and a quadrangular prismatic shape is more desirable. Moreover, the honeycomb formed body that serves as the first honeycomb structure (or the first honeycomb segments) and the honeycomb formed body that serves as the second honeycomb structure (or the second honeycomb segments) have different partition wall thicknesses and cell densities. Therefore, it is necessary to manufacture each honeycomb formed body having a shape that matches it.

When the honeycomb formed body has a rectangular end face, the length of the longer side is preferably 20 to 120 mm.

(Drying process)
Subsequently, a drying step of drying the formed honeycomb body to obtain a dried honeycomb body is performed.
In the drying step, the formed honeycomb body is dried using a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a reduced pressure dryer, a vacuum dryer, or a freeze dryer to produce a dried honeycomb body.
Through this step, a dried honeycomb body for a first honeycomb structure (or first honeycomb segment) and a dried honeycomb body for a second honeycomb structure (or second honeycomb segment) are produced.

(Honeycomb aggregate manufacturing process)
In this step, an adhesive layer paste having substantially the same composition as the raw material paste is used, and the dried honeycomb bodies are adhered via the adhesive layer paste to fabricate an aggregated body of dried honeycomb bodies (honeycomb aggregated body).
At this time, through the degreasing, impregnation, and bonding steps, two types of honeycomb dried bodies having different shapes, that is, the first honeycomb structure (or the second The dried honeycomb body for the first honeycomb segment) and the dried honeycomb body for the second honeycomb structure (or the second honeycomb segment) are combined and bonded together.

6 is a perspective view schematically showing an example of a honeycomb assembly for manufacturing the heat exchanger shown in FIG. 1. FIG.
An aggregate 90 of dried honeycomb bodies shown in FIG. 6 has a prismatic shape, in which first honeycomb structures 10 and second honeycomb structures 20 are alternately laminated and bonded via an adhesive layer 19. It is a honeycomb aggregate 90 . The honeycomb aggregate 90 has three layers of first honeycomb structures 10 and four layers of second honeycomb structures 20 . One layer of the first honeycomb structure 10 is composed of one first honeycomb segment 11 . A one-layer second honeycomb structure 20 is formed by bonding two second honeycomb segments 21 via an adhesive layer 18 .

(Column-shaped body manufacturing process)
In this step, the prismatic honeycomb aggregated body is cut using a cutting tool such as a diamond cutter, and processed into a cylindrical shape in which the second flow passages of the second honeycomb structure are opened on the outer peripheral surface. do.

(Coating layer paste application step)
A layer to be a coat layer can be formed by applying a coat layer paste to the entire surface of the first honeycomb structure constituting the outer peripheral surface of the columnar body, and drying and solidifying the paste.
As the coating layer paste, one having almost the same composition as the raw material paste can be used.
After the degreasing/impregnation/adhesion process described later, the coat layer paste application process may be performed, and the coat layer may be formed by drying and heating and solidifying the coat layer paste.

(degreasing, impregnation, adhesion process)
In this step, the honeycomb aggregated body that has been processed into a cylindrical shape and formed with a layer to be the coat layer is subjected to a degreasing step, and then to an impregnation and bonding step.
Therefore, in this step, silicon (metallic silicon) is placed on the bottom of a ceramic container with an open top, and the honeycomb assembly is placed inside the container via a support made of porous ceramic. After performing the degreasing process, the impregnation/adhesion process is performed.

In the degreasing step, the aggregate of the dried honeycomb bodies dried in the drying step is heated at a temperature of 400 to 1400° C. to burn off the organic matter contained in the dried honeycomb bodies. A degreasing temperature of 400 to 600° C. is more desirable. The atmosphere is desirably an atmosphere containing oxygen.

Subsequently, an impregnation/adhesion process is performed. That is, the degreased body that has completed the degreasing process is heated at a temperature of 1420 to 2000° C. to form a composite material of silicon carbide and silicon. A heating temperature of 1420 to 1600° C. is more desirable. The atmosphere is desirably an inert gas atmosphere.
Silicon (metallic silicon) melted by heating at the above temperature enters the gaps between the silicon carbide particles forming the partition walls of the degreased body through the porous support by capillary action, and the gaps are impregnated with silicon.

The melted silicon also enters between the degreased body of the adhesive layer paste and the degreased body of the coat layer paste, forming a composite material with silicon carbide contained in the degreased body. The degreased body of the adhesive layer paste serves as an adhesive layer to firmly bond the honeycomb structures (or honeycomb segments) together. The degreased body of the coat layer paste becomes a coat layer covering the outer peripheral portion.

When the temperature of the impregnation/adhesion step is within the above temperature range, most of the silicon carbide constituting the heat exchanger is not sintered, and the silicon carbide particles and silicon exist independently. An unsintered honeycomb structure is obtained. That is, the partition walls constituting the honeycomb structure (or honeycomb segment) are composed of a composite material of silicon and silicon carbide in a state in which independent silicon carbide particles are adhered by the silicon surrounding them. This unsintered honeycomb structure has a high Young's modulus and is resistant to deformation, and is useful as a heat exchanger.

Further, through the above steps, a first honeycomb structure in which a large number of cells serving as first flow passages for fluid are arranged in parallel in the longitudinal direction with partition walls interposed therebetween, and a large number of cells serving as second flow passages for fluid are formed. A heat exchanger can be produced by combining a second honeycomb structure in which cells are arranged side by side in the longitudinal direction with partition walls interposed therebetween so that the first flow passages and the second flow passages intersect. .

In the method for manufacturing a heat exchange device of the present invention, after performing a degreasing step of degreasing each dried honeycomb body, a normal firing process is performed to manufacture a honeycomb fired body composed of a porous sintered body of silicon carbide. After that, a bonding step of bonding the honeycomb fired bodies together, a processing step of processing into a circular shape, an impregnation/bonding step of impregnating with silicon, a step of forming a coat layer, a step of forming a sealing region, etc. may be performed. .

(Catalyst supporting step)
The heat exchanger of the present invention can be used as a fuel reforming catalyst by carrying a catalyst such as a fuel reforming catalyst on the heat exchanger.
As a method of supporting a catalyst such as a fuel reforming catalyst made of a noble metal such as rhodium on the heat exchanger, for example, a method of immersing a honeycomb structure in a solution containing noble metal particles or a complex, then pulling it out and heating it, and the like. mentioned.

The resulting heat exchanger is then wrapped with a retaining mat and housed in a metal casing.
At this time, in the outer peripheral surface of the heat exchanger, on the surface of the second honeycomb structure, the second flow path is not covered with the holding mat and is open to the outer peripheral surface of the heat exchanger; A sealing region provided on each end face side of the heat exchanger with respect to the opening region, the second flow path being covered with a retaining mat, and a total area of the opening region and the sealing region The shape of the retaining mat is selected so that the proportion of the
When winding the holding mat around the heat exchanger, the position where the second flow path of the heat exchanger opens to the outer peripheral surface of the heat exchanger is aligned with the position of the mat opening of the holding mat to prepare a wound body. The reformer is obtained by pressing the wound body into the metal casing and fixing it.

An example of a heat exchanger that constitutes a heat exchange device according to a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG.
FIG. 7 is a perspective view schematically showing a heat exchanger that constitutes a heat exchange device according to a second embodiment of the present invention, and FIG. 8 shows the line VIII-VIII of the heat exchanger shown in FIG. It is a sectional view.

As shown in FIGS. 7 and 8, a heat exchanger 200 constituting a heat exchange device according to a second embodiment of the present invention has a large number of first cells 113 serving as first flow paths for fluid. A first ceramic honeycomb structure 110 arranged in parallel in the longitudinal direction with partition walls 112 interposed therebetween, and a large number of second cells 123 serving as second flow paths for fluid are arranged longitudinally with the second partition walls 122 interposed in between. The second honeycomb structures 120 made of ceramic and arranged in parallel in the direction are combined so that the first flow passages (first cells 113) and the second flow passages (second cells 123) intersect. It is a columnar heat exchanger 200 consisting of.

7 and 8, the extending direction of the first cells 113 constituting the first honeycomb structure 110 is the vertical direction (direction indicated by arrow z in FIGS. 7 and 8). The extending direction of the second cells 123 forming the second honeycomb structure 120 is the horizontal direction (direction indicated by arrow y in FIG. 7). In the first honeycomb structure 110 and the second honeycomb structure 120, since the flow paths intersect with each other, two kinds of fluids (particularly gas) can be easily circulated, and heat exchange can be efficiently performed. can.

In the heat exchanger 200 constituting the heat exchange device according to the second embodiment of the present invention, the second honeycomb structure 120 is arranged on both sides of the first honeycomb structure 110 with the adhesive layer 119 interposed therebetween. .
As in the case of the heat exchangers constituting the heat exchange device according to the second embodiment of the present invention, the one-layer first honeycomb structure 110 and the one-layer second honeycomb structure 120 are each: It may be configured by bonding two or more honeycomb segments via an adhesive layer.

In the heat exchanger 200 shown in FIGS. 7 and 8, the first cells 113 serving as the first flow paths of the first honeycomb structure 110 are opened on both end surfaces, and the second honeycomb structure 120 is formed on the outer peripheral surface. A second cell 123 serving as a second flow path is open.
The outer peripheral surface is covered with a coat layer 132 . The coat layer 132 has a coat layer 132a that covers the entire surface of the first honeycomb structure 10 that constitutes the outer peripheral surface.
The portion covered with the coat layer 132 has higher mechanical strength than the portion not covered with the coat layer. Therefore, the portion covered with the coat layer 132 can be used as a portion to which canning pressure is applied.

In addition, since the entire surface of the first honeycomb structure 110 constituting the outer peripheral surface is covered with the coat layer 132, the fluid flowing through the first cells 113 serving as the first flow paths and the second flow paths It is possible to prevent mixing with the fluid flowing through the second cell 123 that becomes .

It is desirable that the volume of the heat exchanger constituting the heat exchange device according to the second embodiment of the present invention is 1.2 to 3.2 liters.
When the volume of the heat exchanger constituting the heat exchange device according to the second embodiment of the present invention is 1.2 to 3.2 liters, the heat exchanger has an appropriate volume, so the vehicle It can be easily mounted on a vehicle, etc., and can sufficiently exhibit its effect as a heat exchange device.
If the volume of the heat exchanger constituting the heat exchange device according to the second embodiment of the present invention is less than 1.2 liters, the volume of the heat exchanger is too small to support a sufficient amount of catalyst. On the other hand, if the volume of the heat exchanger that constitutes the heat exchange device according to the second embodiment of the present invention exceeds 3.2 liters, the capacity of the heat exchange device becomes large. becomes difficult to do.

The material of the honeycomb structure constituting the heat exchanger constituting the heat exchange device according to the second embodiment of the present invention, the type of the supported catalyst, and other configurations of the heat exchanger are the same as those of the first embodiment. The configuration of the honeycomb structure is the same as that of the honeycomb structure that constitutes the heat exchanger that constitutes the heat exchange device according to the above. Also, since the method for manufacturing the heat exchange device according to the second embodiment of the present invention is also the same as the method for manufacturing the heat exchange device according to the first embodiment of the present invention, the description thereof will be omitted. .

Further, in the heat exchanger constituting the heat exchange device according to the first embodiment of the present invention, the three layers of the first honeycomb structure and the four layers of the second honeycomb structure are alternately arranged. In the heat exchanger constituting the heat exchange device according to the second embodiment of the present invention, the second honeycomb structure is arranged on both sides of the first honeycomb structure, but the present invention The heat exchanger constituting the heat exchange device of is not limited to these embodiments, and a first first in which a large number of cells serving as first flow paths for fluid are arranged in parallel in the longitudinal direction with partition walls interposed. A honeycomb structure and a second honeycomb structure in which a large number of cells serving as second flow paths for the fluid are arranged side by side in the longitudinal direction with partition walls interposed therebetween are arranged so that the direction in which the first flow paths extend and the second flow path are aligned. The number of combinations is not limited as long as the paths intersect with the direction in which the paths extend, but it is desirable that the first honeycomb structures and the second honeycomb structures are alternately arranged.

The reformer of the present invention is a reformer equipped with the heat exchange device of the present invention, and the exhaust gas discharged from the internal combustion engine and flowing through the main exhaust pipe passes through the second honeycomb structure. In the first honeycomb structure, a catalyst for reforming is carried on partition walls, and the exhaust gas flowing into the exhaust gas recirculation pipe branched from the main exhaust pipe passes through the first honeycomb structure. It is characterized by

When the reformer of the present invention is configured as described above, the heat of the exhaust gas can be well supplied from the second honeycomb structure to the first honeycomb structure, and the fuel of the internal combustion engine can be reformed. performance as a reformer that improves fuel efficiency.

FIG. 9 is an explanatory view schematically showing a fuel reforming gasoline engine system equipped with the reformer of the present invention.
In this fuel-reforming gasoline engine system 300, an exhaust pipe 42 through which exhaust gas emitted from a gasoline engine 41 passes is connected to a main exhaust pipe 43 and an exhaust gas recirculation pipe 44 (hereinafter referred to as an EGR pipe). A reformer 80 containing a heat exchanger 70 functioning as a fuel reforming catalyst is arranged in the middle of the EGR pipe 44 . As shown in FIG. 9 , the main exhaust pipe 43 is also connected to the reformer 80 , and the gas flowing through the main exhaust pipe 43 flows through mat openings 51 c , 51 d , 51 e , 51 f , 51 g of the retention mat 50 . , 51h and the mat openings, which are the fluid inlet and fluid outlet of the heat exchanger 100, are introduced into and discharged from the cells of the second honeycomb structure, while the gas flowing through the EGR tube 44 passes through the heat exchanger 100. Heat is exchanged through the cells of the first honeycomb structure. In the figure, 45 is an automatic valve, which opens and closes appropriately according to the situation.

A reforming fuel injection device 46 is arranged at the entrance of the reformer 80 in the EGR pipe 44 , and the reforming fuel is injected from this reforming fuel injection device 46 . On the other hand, a port-type fuel injection device 48 is arranged in an intake pipe 49 of the gasoline engine 41, and fuel for the engine is injected during intake.

In the reformer 80, the fuel injected from the reforming fuel injection device 46 is activated by the fuel reforming catalyst supported on the heat exchanger 100 by the steam in the exhaust gas and the hydrocarbons that are the main components of the gasoline fuel. reacts to form hydrogen, carbon monoxide and methane. The hydrogen-containing gas having such a composition mixes with the intake air of the engine and also with the fuel injected from the port-type fuel injection device 48 to form an air-fuel mixture, which enters the gasoline engine 41 and enters the gasoline engine 41. Burned inside. Hydrogen mixed in the air-fuel mixture can increase the combustion speed and improve the combustion efficiency of the gasoline engine 41 .

In the first honeycomb structure in the reformer 80, heat is taken away by the endothermic reaction in the presence of the above-described fuel reforming catalyst. The heat of the exhaust gas can be well supplied to the honeycomb structure of 1, the temperature drop is suppressed, and the performance as a reforming catalyst that reforms the fuel of the internal combustion engine (gasoline engine) to improve fuel efficiency is improved. can be demonstrated. Furthermore, when the heat exchanger is made of silicon carbide and silicon, it is less corroded by hydrogen contained in the reformed gas.

(Example)
Examples that more specifically disclose embodiments of the present invention are shown below. In addition, the present invention is not limited only to these examples.

(Example 1)
56.3% by weight of coarse silicon carbide powder having an average particle size of 22 μm and 24.1% by weight of fine silicon carbide powder having an average particle size of 0.5 μm are mixed, and an organic binder is added to the resulting mixture. (Methylcellulose) 4.4% by weight, lubricant (Unilube manufactured by NOF Corporation) 0.8% by weight, glycerin 0.8% by weight, oleic acid 2.2% by weight, and water 11.4% by weight A raw material paste was obtained by kneading.

After that, using a mold for manufacturing the honeycomb segments constituting the first honeycomb structure and a mold for manufacturing the honeycomb molded body constituting the second honeycomb structure, the raw material paste is extruded. Molding was carried out to produce a honeycomb molded body.

The formed honeycomb body for the honeycomb segment constituting the first honeycomb structure produced by the above steps had a rectangular end face shape of 14.6 mm×105.4 mm, a length of 140 mm, and a cell density of , 47 pieces/cm ² (300 pieces/inch ² ), and the partition wall thickness was 0.25 mm. Further, the formed honeycomb body for the honeycomb segments constituting the second honeycomb structure manufactured by the above steps had a rectangular end face shape of 14.6×70 mm, a length of 105 mm, and a cell density of , 47 pieces/cm ³ (300 pieces/inch ³ ), and the partition wall thickness was 0.25 mm.

Next, the raw honeycomb formed body was dried using a microwave dryer to prepare a dried honeycomb formed body.

Using the obtained dried honeycomb body for the honeycomb segment constituting the first honeycomb structure and the obtained dried honeycomb body for the honeycomb segment constituting the second honeycomb structure, and using the raw material paste as an adhesive, the manufacturing process is carried out. The dried honeycomb bodies were combined so that the finished assembly of the dried honeycomb bodies (honeycomb aggregated body) had the configuration shown in FIG. The thickness of each adhesive layer was set to 1 mm. The first honeycomb structure was composed of one first honeycomb segment, and the second honeycomb structure was composed of two second honeycomb segments.
As for the dimensions of the dried honeycomb body, the shape of the surface of the second honeycomb structure where the second flow passages were exposed was approximately rectangular parallelepiped with a width of 108.2 mm, a length of 140 mm, and a depth of 105 mm.

The obtained assembly of the dried honeycomb bodies was externally processed into a columnar shape having a diameter of 105 mm and a length of 140 mm so that both end faces thereof corresponded to the end faces of the first honeycomb structure. Furthermore, a coat layer paste is applied to the entire surface of the first honeycomb structure and part of the surface of the second honeycomb structure, which constitutes the outer peripheral surface of the columnar honeycomb aggregate, and dried and solidified. let me

An assembly of dried honeycomb bodies having a coat layer formed thereon was placed via a support in a ceramic container having metal silicon (silicon) placed on the bottom, and then carried into a heating furnace. After performing a degreasing step of degreasing at 0° C., the inside of the heating furnace was replaced with argon gas, and an impregnation bonding step was performed under heating conditions of 1450° C. for 1 hour to obtain a heat exchanger having the configuration shown in FIG.

In the obtained heat exchanger having the configuration shown in FIG. 1, the outer shape was 105 mm in diameter and 140 mm in length, and the cell densities of the honeycomb segments constituting the first and second honeycomb structures were both 47 cells/cm. ² (300 pieces/inch ² ), and the thickness of the partition wall is 0.25 mm.
The first honeycomb structure is composed of one first honeycomb segment, and the second honeycomb structure is composed of two second honeycomb segments bonded with an adhesive layer via end faces. It had been. In addition, the first honeycomb segment channel (the cell serving as the first flow channel) that constitutes the first honeycomb structure and the second honeycomb segment channel (the second flow channel) that constitutes the second honeycomb structure cells) were arranged to intersect with each other.

The mat was cut into a shape having concave portions, convex portions and openings as shown in FIG. 3 to prepare a holding mat.
A cylindrical metal casing having an opening similar to that of the retaining mat and having an inner diameter slightly larger than the diameter of the heat exchanger, with the resulting retaining mat wrapped around the heat exchanger configured as shown in FIG. to obtain a heat exchange device according to Example 1. The thickness of the mat after accommodation was 4 mm. In addition, in the heat exchange device according to Example 1, the ratio of the opening area to the total area of the opening area and the sealing area was 90%.

(Example 2, Comparative Examples 1 and 2)
The same as Example 1 except that the ratio of the area of the opening region to the total area of the opening region and the sealing region was changed to the numerical value shown in Table 1 by changing the shape of the opening formed in the holding mat. The heat exchange devices according to Example 2 and Comparative Examples 1 and 2 were manufactured according to the procedure of .

(evaluation)
[Evaluation of canning property]
When the heat exchanger was wrapped with the holding mat and accommodated in the metal casing, the heat exchanger was checked for damage and evaluated according to the following criteria. Table 1 shows the results.
However, the thickness and basis weight of the holding mats were all the same.
[evaluation]
Good: No damage such as cracks occurred in the heat exchanger after canning.
x: Damage such as cracks occurred in the heat exchanger after canning.

[Heat Exchange Test and Measurement of Holding Stability]
A gas at 800° C. is passed through the cells forming the second honeycomb structure at a flow rate of 50 g/sec, and a gas at 500° C. is passed through the cells forming the first honeycomb structure at a flow rate of 15 g/sec for 10 minutes. After 10 minutes, the temperature of the gas flowing out from the first honeycomb structure was measured and evaluated according to the following criteria. Table 1 shows the results.
Also, before and after this operation, it was confirmed whether the holding mat and/or the heat exchanger were misaligned. Table 1 shows the results.
[Evaluation of heat exchange efficiency]
◯: The temperature of the gas flowing out from the first honeycomb structure is 600° C. or higher.
x: The temperature of the gas flowing out from the first honeycomb structure is less than 600°C.
[Evaluation of retention stability]
◯: No positional deviation is observed between the holding mat and the heat exchanger.
x: Positional deviation is observed in the holding mat and/or the heat exchanger.

As shown in Table 1, in the heat exchange devices according to Examples 1 and 2, even when the temperature of the gas flowing into the cells constituting the second honeycomb structure was lowered, the first honeycomb structure The temperature of the gas flowing out of the structure could be maintained above 600°C.
The heat exchange device according to Comparative Example 1 was damaged during canning. This is probably because the area where the second honeycomb structure is in contact with the holding mat (sealing area) is narrower than in Examples 1 and 2, and excessive pressure is applied to the sealing area, leading to breakage. When the basis weight of the holding mat was adjusted so that the heat exchanger according to Comparative Example 1 was not damaged during canning, the position of the heat exchanger was shifted in the heat exchange test, and the holding stability was not sufficient. It turns out not.
In the heat exchange device according to Comparative Example 2, the temperature of the gas flowing out from the first honeycomb structure was less than 600° C. during normal heat exchange. It is considered that this is because the ratio of the sealing region is too large, so that the heat exchange efficiency during normal operation is lowered.

10, 110 First honeycomb structures 11, 111 First honeycomb segments 12, 112 First partition walls 13, 113 First cells (first flow passages)
18, 19, 119 adhesive layers 20, 120 second honeycomb structures 21, 121 second honeycomb segments 22, 122 second partition walls 23, 123 second cells (second flow passages)
32, 32a, 32b, 132, 132a, 132b Coat layer 41 Gasoline engine 42 Exhaust pipe 43 Main exhaust pipe 44 Exhaust gas recirculation pipe (EGR pipe)
45 automatic valve 46 reforming fuel injection device 48 port type fuel injection device 49 suction pipe 50 holding mat 51 mat 51a convex portion 51b concave portion 51c, 51d, 51e, 51f, 51g, 51h opening portion 60 metal casing 60c, 60d, 60e, 60f, 60g, 60h Opening 70 Heat exchange device 80 Reformer 90 Aggregate of dried honeycomb bodies 100, 200 Heat exchanger 300 Gasoline engine system A1 Opening areas A2, A3 Sealing area

Claims (11)

A first honeycomb structure in which a large number of cells serving as first flow passages for fluid are arranged in parallel in the longitudinal direction across partition walls, and a large number of cells serving as second flow passages for fluid are arranged in the longitudinal direction across the partition walls. a heat exchanger in which second honeycomb structures arranged in parallel are combined so that the first flow passage and the second flow passage intersect;
a metal casing housing the heat exchanger;
A heat exchange device comprising a retaining mat disposed between the heat exchanger and the metal casing,
The heat exchanger has a substantially cylindrical shape in which the first flow passage opens on both end surfaces and the second flow passage opens on the outer peripheral surface,
The holding mat is arranged along the outer peripheral surface of the heat exchanger so as not to cover a part of the second flow path that opens to the outer peripheral surface,
The entire surface of the first honeycomb structure of the outer peripheral surface of the heat exchanger is covered with a coat layer,
Of the outer peripheral surface of the heat exchanger, the surface of the second honeycomb structure is open to the outer peripheral surface of the heat exchanger without the second flow passage being covered with the holding mat. and an opening area, and a sealing area provided on each of the two end surface sides of the heat exchanger with respect to the opening area, wherein the second flow path is covered with the holding mat,
A heat exchanger according to claim 1, wherein the ratio of the area of the opening region to the total area of the opening region and the sealing region is 72 to 93%. 2. The heat exchange device according to claim 1, wherein the retaining mat has a thickness of 3 to 5 mm. 3. The heat exchange device according to claim 1, wherein the second honeycomb structure is arranged on both sides of the first honeycomb structure. The heat exchange device according to any one of claims 1 to 3, wherein a catalyst is supported on the partition walls of the cells forming the first honeycomb structure. The ratio of the total opening area of the second flow passages to the total opening area of the first flow passages (total opening area of the second flow passages/total opening area of the first flow passages) is 1.25. The heat exchange device according to any one of claims 1 to 4, wherein the heat exchange device is ∼2. The heat exchange device according to any one of claims 1 to 5, wherein both the first honeycomb structure and the second honeycomb structure are made of silicon carbide and silicon. 7. The first honeycomb structure and the second honeycomb structure according to any one of claims 1 to 6, wherein a plurality of ceramic honeycomb segments are bonded via an adhesive layer. heat exchange device. 8. The heat exchange device of claim 7, wherein said adhesion layer comprises silicon carbide and silicon. The heat exchange device according to any one of claims 1 to 8, wherein the heat exchanger has a volume of 1.2 to 3.2 liters. In the heat exchanger, the first honeycomb structures and the second honeycomb structures are alternately arranged, and the three layers of the first honeycomb structures and the four layers of the second honeycomb structures are arranged alternately. The heat exchange device according to any one of claims 1 to 9, comprising a honeycomb structure of A reformer comprising the heat exchange device according to any one of claims 1 to 10,
The second honeycomb structure is configured so that the exhaust gas discharged from the internal combustion engine and flowing through the main exhaust pipe passes through the second honeycomb structure, and the partition walls of the first honeycomb structure support a reforming catalyst. and is constructed so that the exhaust gas flowing into the exhaust gas recirculation pipe branched from the main exhaust pipe passes through.

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