JP2016200117A - Exhaust system component and exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system component that can prevent deposition of urea at the surface thereof when the component is provided in a part coming into contact with an exhaust gas containing nitrogen oxide in an urea SCR system.SOLUTION: The exhaust system component provided in a part coming into contact with an exhaust gas containing nitrogen oxide includes a substrate constituted of a metal; and a ceramic coat layer formed on a surface on a side coming into contact with the exhaust gas at the surface of the substrate. The ceramic coat layer contains urea decomposition catalyst. The urea decomposition catalyst is exposed at the surface of the ceramic coat layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust system component and an exhaust gas purification device.

NOx (nitrogen oxide) is contained in exhaust gas discharged from internal combustion engines such as diesel engines used in transportation equipment such as automobiles and ships, and exhaust gas discharged from cement plants.
In recent years, a technique called a urea SCR (Selective Catalytic Reaction) system has been studied as a method for purifying nitrogen oxides in exhaust gas.
In the urea SCR system, urea water is sprayed into an exhaust passage through which exhaust gas containing nitrogen oxide flows in an exhaust gas purification device, ammonia is generated by thermal decomposition of urea, and nitrogen oxide reduction reaction is performed by ammonia. .

A urea injection device for injecting urea water is provided in the exhaust passage of the exhaust gas purification device, and a catalyst carrier is provided on the downstream side of the urea injection device (for example, Patent Document 1).
The catalyst carrier has a catalytic action that promotes a reduction reaction of nitrogen oxides, and a honeycomb shape having a large number of through holes for exhaust gas to flow is often adopted.

In addition, an exhaust gas purification device in which a NOx occlusion reduction catalyst is provided in the middle of an exhaust pipe in order to purify NOx in exhaust gas is also known (Patent Document 2).
In Patent Document 2, in order to prevent fuel (light oil) injected as a reducing agent from adhering to the exhaust pipe and getting wet only when the exhaust pipe is wet, it is downstream from the nozzle tip of the fuel injector. It is described that a ceramic coating as a heat insulating structure is applied to a predetermined range of the exhaust pipe.

Further, Patent Document 3 discloses that a mixer or swirler is provided in the exhaust passage so as to generate a swirling flow in the exhaust gas in order to sufficiently mix ammonia as a reducing agent and exhaust gas in the urea SCR system. Yes.

Special table 2011-523585 gazette JP-A-2005-76460 JP 2008-280882 PR

In the exhaust gas purifying apparatus in which the catalyst carrier is provided on the downstream side of the urea injection device as described in Patent Document 1, when urea water is injected into the exhaust passage, the urea water attached to the surface of the exhaust passage is cooled. In some cases, urea was deposited and deposited on the surface of the exhaust passage.
If urea is deposited on the surface of the exhaust passage, the flow of exhaust gas is hindered and pressure loss increases, and the purification efficiency of nitrogen oxides may decrease. Further, when the temperature of the exhaust gas is lowered, urea may be deposited at the inlet of the through hole of the catalyst carrier and the through hole of the catalyst carrier may be clogged.
In addition, the precipitation of urea means that the injected urea is not converted to ammonia, so that the amount of ammonia contributing to the reduction of nitrogen oxides is insufficient, and also from this point, the purification efficiency of nitrogen oxides may be reduced. . If the nitrogen oxide purification efficiency is low, the sensor that monitors the nitrogen oxide concentration at the catalyst carrier outlet performs feedback control to further increase the injection amount of urea water. The amount of precipitation increases, and as a result, the flow of exhaust gas may be further inhibited and the purification rate of nitrogen oxides may be reduced.

The ceramic coating technique described in Patent Document 2 is not a technique intended for use in a urea SCR system, but heat insulation for maintaining the temperature of the exhaust pipe surface at 180 to 350 ° C. or higher, which is the boiling point of light oil. It is a coating technology. With this technique, the assumed temperature for maintaining the temperature of the exhaust pipe surface is considerably higher than 133 to 135 ° C., which is the melting point of urea, and the purpose of the heat insulating coating is different. Further, Patent Document 2 does not disclose what kind of coating is specifically applied in order to maintain the temperature of the exhaust pipe surface at such a high assumed temperature.

The mixer and swirler described in Patent Document 3 are members that generate a swirling flow in the exhaust gas by partially inhibiting the flow of the exhaust gas, and the exhaust gas flow path is narrow. Therefore, when urea is deposited on the surfaces of these members, the exhaust gas flow path is further narrowed, which may lead to an increase in pressure loss and clogging of the exhaust gas. Moreover, if urea is deposited on the surfaces of these members, the purification efficiency of nitrogen oxides may be reduced.

The present invention has been made in view of the above-described problems, and prevents urea from precipitating on the surface of the urea SCR system when it is provided at a site in contact with exhaust gas containing nitrogen oxides. It is an object of the present invention to provide an exhaust system component that can be used, and an exhaust gas purification device that includes the exhaust system component.

In order to achieve the above object, the exhaust system component of the present invention is
An exhaust system component provided at a site that comes into contact with exhaust gas containing nitrogen oxides,
A base material made of metal;
It consists of a ceramic coat layer formed on the surface of the base material on the side in contact with the exhaust gas,
The ceramic coat layer contains a urea decomposition catalyst, and the urea decomposition catalyst is exposed on the surface of the ceramic coat layer.

In the exhaust system component of the present invention, the ceramic coat layer is formed on the surface of the base material made of metal and in contact with the exhaust gas, and the urea decomposition catalyst is exposed on the surface of the ceramic coat layer. .
When the exhaust gas containing vaporized urea comes into contact with such exhaust system components, the vaporized urea and the urea decomposition catalyst can come into contact with each other. Then, urea that has contacted the urea decomposition catalyst and moisture (water vapor) contained in the exhaust gas can react with the following chemical formula (1) to form ammonia and carbon dioxide, and can flow to the catalyst carrier side.
(NH ₂ ) CO + H ₂ O → 2NH ₃ + CO ₂ Chemical formula (1)
Urea that has come into contact with the ceramic coat layer is decomposed by the above reaction, so that urea is prevented from being deposited on the ceramic coat layer.
In the exhaust system component of the present invention, since the urea decomposition catalyst is present on the surface of the ceramic coat layer, the effect of coexistence of the urea decomposition catalyst and the ceramic coat layer is also exhibited. That is, since the ceramic coat layer has a heat insulating performance, the time during which the urea decomposition catalyst is maintained at the catalyst activation temperature or longer is prolonged, and the catalytic effect can be sustained for a long time. Furthermore, since the specific surface area is increased by the ceramic coat layer, the urea decomposition catalyst can be highly dispersed, and even when the exhaust system parts are used for a long time, the urea decomposition catalyst does not aggregate and the catalytic effect can be maintained for a long time. it can.

In the exhaust system component of the present invention, the urea decomposition catalyst is preferably at least one selected from the group consisting of a tungsten compound, a vanadium compound, and a molybdenum compound.
In the exhaust system component of the present invention, the urea decomposition catalyst is preferably at least one selected from the group consisting of tungsten oxide, vanadium oxide, and molybdenum oxide.
These catalysts are suitable as urea decomposition catalysts.

In the exhaust system component of the present invention, the ceramic coat layer preferably contains an amorphous inorganic material and a crystalline inorganic material.
The ceramic coating layer containing an amorphous inorganic material and a crystalline inorganic material provides a preferable heat insulation coating by being provided on a base material made of metal. Is more effectively prevented.

In the exhaust system component of the present invention, the amorphous inorganic material is preferably a low-melting glass having a softening point of 300 to 1000 ° C.
When the amorphous inorganic material is the low-melting glass, the amorphous inorganic material is softened and melted by heating at a temperature exceeding the softening point and spreads on the surface of the base material to form a ceramic coat layer.

In the exhaust system component of the present invention, it is preferable that pores are formed in the ceramic coat layer.
If pores are formed in the ceramic coat layer, the heat insulating performance of the ceramic coat layer is further increased, and therefore the temperature of the exhaust system component surface is further less likely to be lowered, and urea precipitation is further effectively prevented.

The exhaust system component of the present invention is preferably a cylindrical member used as an exhaust passage through which exhaust gas containing nitrogen oxides flows.
When the exhaust system component of the present invention is used as an exhaust passage, urea is prevented from being deposited and deposited on the surface of the exhaust passage.

In addition, the exhaust system component of the present invention is preferably a diffusion member that is installed inside an exhaust passage through which exhaust gas containing nitrogen oxides flows and partially blocks the flow of exhaust gas flowing from the upstream of the exhaust passage.
When the exhaust system component of the present invention is used as a diffusion member, urea is prevented from being deposited and deposited on the surface of the diffusion member.

The exhaust gas purification apparatus of the present invention is
An exhaust passage through which exhaust gas containing nitrogen oxides flows;
A urea injection device that is provided upstream of the exhaust passage and injects urea into the exhaust passage;
An exhaust gas purification apparatus comprising a catalyst carrier provided on the downstream side of the exhaust passage,
The exhaust system component of the present invention is used in a portion where the exhaust gas contacts with the downstream side of the urea injection device and the upstream side of the catalyst carrier.

In the exhaust gas purification apparatus having the above configuration, the urea injection device is provided upstream of the exhaust passage, and the exhaust gas purification device is provided downstream of the exhaust passage.
The exhaust system component of the present invention is used at a site where exhaust gas contacts with the downstream side of the urea injection device and the upstream side of the catalyst carrier.
With such a configuration, even if the exhaust gas containing urea injected and vaporized from the urea injection device into the exhaust passage comes into contact with the exhaust system component in the region between the urea injection device and the catalyst carrier, The contacted urea is decomposed by the action of the urea decomposition catalyst exposed on the surface of the ceramic coat layer. Therefore, it is possible to prevent urea from being deposited on the surface of the exhaust system part located between the urea injection device and the catalyst carrier.

In the exhaust gas purification apparatus of the present invention, it is preferable to use the exhaust system parts of the present invention as the exhaust passage.
When the exhaust passage is composed of the exhaust system parts of the present invention, even if the exhaust gas containing urea contacts the surface of the exhaust passage, the urea contacting the surface of the exhaust passage is caused by the action of the urea decomposition catalyst exposed on the surface of the ceramic coat layer. Disassembled. Therefore, it is possible to prevent urea from being deposited on the surface of the exhaust passage located between the urea injection device and the catalyst carrier.

In the exhaust gas purification apparatus of the present invention, it is preferable that the exhaust system component of the present invention is used also as an exhaust passage upstream of the urea injection apparatus.
Since the exhaust system component of the present invention has a ceramic coat layer, and the ceramic coat layer can function as a heat insulation coating, the exhaust gas temperature is prevented from lowering upstream of the urea injector, and the urea injector Precipitation of urea on the downstream side is more effectively prevented.

In the exhaust gas purification apparatus of the present invention, it is preferable that the exhaust system component of the present invention is used as a diffusion member that is installed inside the exhaust passage and partially blocks the flow of exhaust gas flowing from the upstream of the exhaust passage.
When the diffusion member is composed of the exhaust system part of the present invention, even if the exhaust gas containing urea contacts the surface of the diffusion member, the urea that contacts the surface of the diffusion member is caused by the action of the urea decomposition catalyst exposed on the surface of the ceramic coat layer. Disassembled. Therefore, it is possible to prevent urea from being deposited and deposited on the surface of the diffusion member positioned between the urea injection device and the catalyst carrier.

FIG. 1 is a cross-sectional view schematically showing an exhaust system component of the present invention. FIG. 2 is a perspective view schematically showing an example of an exhaust pipe which is an embodiment of the exhaust system component of the present invention. FIG. 3 is a perspective view schematically showing another example of an exhaust pipe which is an embodiment of the exhaust system component of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus provided with an exhaust pipe as an exhaust system component of the present invention. FIG. 5 is a perspective view schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention. FIG. 6 is a perspective view schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention. FIG. 7 is a perspective view schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention. FIG. 8 is a perspective view schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention. FIG. 9 is a perspective view schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention. FIG. 10 is a perspective view schematically showing an example of a diffusion member that is an embodiment of the exhaust system component of the present invention. FIG. 11 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus provided with both a diffusion member and an exhaust pipe as an exhaust system component of the present invention. FIG. 12A is a perspective view schematically showing an example of a flue that is an embodiment of the exhaust system component of the present invention, and FIG. 12B is a cross-sectional view taken along line AA in FIG. FIG.

(Detailed description of the invention)
Hereinafter, the exhaust system parts and the exhaust gas purification apparatus of the present invention will be described in detail. However, the present invention is not limited to the following configurations, and can be applied with appropriate modifications without departing from the scope of the present invention. Note that the present invention also includes a combination of two or more desirable configurations of the present invention described below.

First, the exhaust system parts of the present invention will be described.
The exhaust system parts of the present invention are:
An exhaust system component provided at a site that comes into contact with exhaust gas containing nitrogen oxides,
A base material made of metal;
It consists of a ceramic coat layer formed on the surface of the base material on the side in contact with the exhaust gas,
The ceramic coat layer contains a urea decomposition catalyst, and the urea decomposition catalyst is exposed on the surface of the ceramic coat layer.

The exhaust system component of the present invention is a component provided at a site that comes into contact with exhaust gas containing nitrogen oxides.
Sources of exhaust gas containing nitrogen oxides are not particularly limited, but examples of sources of exhaust gas containing nitrogen oxides include diesel engines and gasoline engines used in vehicles, ships, construction machinery, etc. Examples include factories such as internal combustion engines, cement plants, and power plants.

Even if the generation source of the exhaust gas is different, the configuration of the exhaust system component of the present invention is common in that it includes a base material and a ceramic coat layer. The urea decomposition catalyst contained in the material, the ceramic coat layer and the ceramic coat layer will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an exhaust system component of the present invention.
An exhaust system component 10 shown in FIG. 1 includes a base material 11 made of metal and a single ceramic coat layer 12 formed on the surface of the base material 11.

In the exhaust system component 10 shown in FIG. 1, the ceramic coat layer 12 formed on the surface of the substrate 11 includes an amorphous inorganic material 13 and a crystalline inorganic material 14.
Further, the ceramic coating layer 12 includes a urea decomposition catalyst 15, and the urea decomposition catalyst is exposed on the surface of the ceramic coating layer 12.
Further, pores 16 are formed in the ceramic coat layer 12.

Examples of the material of the base material 11 constituting the exhaust system component 10 include metals such as stainless steel, steel, iron, and copper, or nickel alloys such as Inconel, Hastelloy, and Invar.
As will be described later, the base material made of these metal materials brings the ceramic coating layer 12 and the base material 11 made of metal into close contact with each other by bringing the thermal expansion coefficient closer to the amorphous inorganic material 13 constituting the ceramic coating layer 12. The power can be improved.
Further, in order to improve the adhesion with the ceramic coat layer, a roughening treatment such as sandblasting or chemicals may be applied to the surface of the substrate.

Surface roughness _{Rz JIS} of the surface of the substrate formed by the above roughening treatment, 1.5～20Myuemu is desirable. The surface roughness Rz _JIS of the roughened surface described above is a ten-point average roughness defined by JIS B 0601 (2001).
When the surface roughness Rz _{JIS of the} roughened surface of the exhaust system parts is less than 1.5 μm, the surface area of the base material becomes small, and it is difficult to obtain sufficient adhesion between the base material and the ceramic coat layer. Become. On the other hand, when the surface roughness Rz _{JIS of the} roughened surface of the base material of the exhaust system component exceeds 20 μm, there is a problem that the base material is deformed. In particular, the deformation of the base material increases as the roughened area increases.
In addition, the surface roughness Rz _JIS of the roughened surface of the base material of the exhaust system component can be measured according to JIS B 0601 (2001) using Handy Surf E-35B manufactured by Tokyo Seimitsu Co., Ltd. . The measuring distance is 4 mm.

The shape of the base material is not particularly limited, and the shape of the outer edge of the cross section other than a flat plate, a semi-cylinder, and a cylindrical shape can be any shape such as an ellipse or a polygon.
When used as an exhaust passage to be described later, a tubular shape is preferable.
When the base material of the exhaust system part is cylindrical, the diameter of the base material may not be constant along the longitudinal direction, and the cross-sectional shape perpendicular to the length direction may not be constant along the longitudinal direction. Also good.
Moreover, when using as a diffusion member, it is preferable that it is a shape which can inhibit the flow of exhaust gas partially.

In the exhaust system part of the present invention, the desirable lower limit of the thickness of the substrate is 0.2 mm, the more desirable lower limit is 0.4 mm, the desirable upper limit is 10 mm, and the more desirable upper limit is 4 mm.
When the thickness of the base material of the exhaust system component is less than 0.2 mm, the strength of the exhaust system component is insufficient. In addition, if the thickness of the base material of the exhaust system component exceeds 10 mm, the weight of the exhaust system component increases, and it becomes difficult to mount the exhaust system component on a vehicle such as an automobile, for example.
However, in the case of an exhaust system part used in a flue of a factory such as a cement plant, the base material may be thicker.

The ceramic coat layer 12 constituting the exhaust system component 10 is formed on the surface that comes into contact with the exhaust gas. The surface on the side in contact with the exhaust gas is determined by the portion where the exhaust system parts are arranged, but usually is naturally determined from the shape of the exhaust system parts.
When the exhaust system component is a cylindrical member used as an exhaust passage, the inner peripheral surface through which the exhaust gas flows is the surface on the side in contact with the exhaust gas.
When the exhaust system component is used as a diffusion member, the surface corresponding to the portion where the exhaust gas collides and contacts is the surface on the side in contact with the exhaust gas.

The ceramic coat layer 12 illustrated in FIG. 1 includes an amorphous inorganic material 13 and a crystalline inorganic material 14, and pores 16 are formed in the ceramic coat layer 12. However, since the ceramic coat layer formed on the exhaust system component of the present invention is not limited to the above-described configuration, a preferred form of the ceramic coat layer formed on the exhaust system component of the present invention will be described below.

The ceramic coat layer formed on the exhaust system component of the present invention preferably contains an amorphous inorganic material, more preferably contains an amorphous inorganic material and a crystalline inorganic material, and is a layer of an amorphous inorganic material. And more preferably, particles of crystalline inorganic material dispersed in the amorphous inorganic material layer.

Moreover, it is preferable that pores are formed in the ceramic coat layer.
When pores are formed in the ceramic coat layer, the pores hinder internal heat conduction, and thus excellent heat insulating properties can be obtained.

The porosity can adjust the porosity and the average pore diameter by a pore former described later, and the porosity of the ceramic coat layer is preferably 20 to 80%.
When the porosity of the ceramic coat layer is 20 to 80% and these pores are well dispersed, the heat transfer in the ceramic coat layer can be effectively blocked by the pores, and good heat insulation is achieved. Can be maintained.
The porosity of the ceramic coat layer is calculated by calculating the bulk density from the thickness of the ceramic coat layer and the thickness of the ceramic coat layer measured with a film thickness meter (dual scope), and calculating the ratio of the true density calculated by the pycnometer. Then, the value obtained by subtracting the value from 1 can be calculated as the porosity.

When the porosity of the ceramic coat layer is less than 20%, the heat insulating property may be deteriorated because the ratio of the pores is too small. On the other hand, when the porosity of the ceramic coat layer exceeds 80%, the ratio of the pores is excessively increased, so that the mechanical strength is lowered and the heat insulation performance is lowered due to coalescence of the pores.

The average pore diameter of the pores in the ceramic coat layer is preferably 0.1 to 150 μm, and more preferably 0.1 to 50 μm. When the average pore diameter of the pores in the ceramic coat layer is 0.1 to 150 μm, heat transfer in the ceramic coat layer can be effectively blocked by the pores, and the high thermal insulation of the ceramic coat layer can be maintained. it can. As the average pore diameter of the pores in the ceramic coat layer is smaller, heat transfer due to radiant heat transfer and convective heat transfer in the pores can be reduced, and the closer to 1 μm, the more preferable. ˜50 μm is more preferable, and 1 to 5 μm is more preferable. When the average pore diameter is in the range of 1 to 5 μm, the heat transfer in the pores can be reduced most.
When the thickness of the ceramic coat layer is thin, the upper limit of the average pore diameter is preferably the thickness of the ceramic coat layer. This means that the pores do not jump out of the ceramic coat layer and become blind pores, and it is preferable that the pores exist as independent pores in the ceramic coat layer.

If the average pore diameter of the pores is less than 0.1 μm, it is technically difficult to form pores of such a size, and a very small pore former is used to form such pores. It is necessary to use a special material such as, which is not preferable because the material cost increases rapidly.
On the other hand, when the pore diameter exceeds 150 μm, the pores are often already joined by movement. As described above, when pores having a large pore diameter are formed in the ceramic coat layer, the mechanical properties of the ceramic coat layer are deteriorated because the solid portion of the ceramic coat layer is small. In addition, pores having a diameter exceeding 150 μm have a reduced heat insulation property because the heat dissipation effect is promoted by convective heat transfer and radiative heat transfer within the pores.

The average pore diameter of the pores can be measured by cutting the exhaust system parts and observing the cross section with a digital microscope or SEM.
Specifically, a digital microscope image or SEM image is taken so that the whole area of the ceramic coat layer in the thickness direction is included, the pore diameters of all the pores are measured, and the average pore diameter is obtained by obtaining an average value. Is obtained. When the shape of the pores is not substantially spherical, the diameter of the pores is the diameter corresponding to the projected area circle (Haywood diameter).
The measurement magnification is 2000 times when the thickness of the ceramic coat layer is less than 5 to 50 μm, 1000 times when it is less than 50 to 100 μm, 500 times when it is less than 100 to 300 μm, and 200 times when it is less than 300 to 500 μm. In the case of 500 to less than 1000 μm, the magnification is 150 times, and in the case of 1000 to 2000 μm, the magnification is 100 times. When the magnification is 100 times, it is preferable to measure with a digital microscope (VHX5000 manufactured by Keyence Corporation), and when using other magnifications, it is preferable to observe using SEM.

Below, the amorphous inorganic material which comprises a ceramic coat layer is demonstrated.

The amorphous inorganic material is preferably an amorphous inorganic material containing silica, more preferably contains 20% by weight or more of silica, and is a low melting glass having a softening point of 300 to 1000 ° C. More preferably.
The kind of the low melting point glass is not particularly limited, but soda lime glass, alkali-free glass, borosilicate glass, potash glass, crystal glass, titanium crystal glass, barium glass, strontium glass, alumina silicate glass, soda zinc glass And soda barium glass.
These glasses may be used alone or in combination of two or more.

When the softening point of the amorphous inorganic material is in the range of 300 to 1000 ° C., the low melting point glass is melted and coated (coated) on the surface of the base material (metal material), and then heated and fired. It is possible to easily form a ceramic coat layer on the surface of a substrate made of metal and to form a ceramic coat layer excellent in adhesion to the substrate.

When the softening point of the amorphous inorganic material is less than 300 ° C., the temperature of the softening point is too low, so that during the heat treatment, the layer that becomes the ceramic coat layer easily flows due to melting or the like, and has a uniform thickness. It becomes difficult to form a layer. On the other hand, when the softening point of the amorphous inorganic material exceeds 1000 ° C., on the contrary, it is necessary to set the temperature of the heat treatment to be extremely high, so that the mechanical properties of the substrate may be deteriorated by heating.
The softening point can be measured using a glass automatic softening point / strain point measuring device (SSPM-31) manufactured by Opt Corporation, for example, based on the method defined in JIS R 3103-1: 2001. it can.

Kind of the borosilicate glass is not particularly _limited, SiO ₂ -B ₂ O 3 -ZnO type _{glass, SiO 2 -B 2 O 3 -Bi} 2 O 3 system glass. The crystal glass is a glass containing PbO, and the type thereof is not particularly limited, but SiO ₂ —PbO glass, SiO ₂ —PbO—B ₂ O ₃ glass, SiO ₂ —B ₂ O ₃ —PbO glass. Etc. Kind of the barium glass is not particularly limited, include BaO-SiO ₂ based glass or the like.
Further, the amorphous inorganic material may be composed of only one kind of the above-described low-melting glass, or may be composed of a plurality of kinds of low-melting glass.

Subsequently, the crystalline inorganic material will be described.

When the crystalline inorganic material is present in the ceramic coat layer, when the ceramic coat layer becomes high temperature, the crystalline inorganic material particles obstruct the movement of the pores and prevent the movement of the pores. It can prevent that heat insulation performance falls by coalescence of a pore.

The crystalline inorganic material preferably contains zirconia, more preferably contains 20% by weight or more of zirconia, and more preferably contains 50% by weight or more of zirconia.
Specific examples of the crystalline inorganic material containing zirconia include CaO-stabilized zirconia (5 wt% CaO—ZrO ₂ , 8 wt% CaO—ZrO ₂ , 31 wt% CaO—ZrO ₂ ), MgO stabilized zirconia (20 wt%). MgO—ZrO ₂ , 24 wt% MgO—ZrO ₂ ), Y ₂ O ₃ stabilized zirconia (6 wt% Y ₂ O ₃ —ZrO ₂ , 7 wt% Y ₂ O ₃ —ZrO ₂ , 8 wt% Y ₂ O ₃ —ZrO _{2 , 10wt% Y 2 O 3 -ZrO} 2, 12wt% Y 2 O 3 -ZrO 2, 20wt% Y 2 O 3 -ZrO 2), zircon _{(ZrO 2 -33wt% SiO 2)} , include CeO stabilized zirconia It is done.
Among these, zirconia, Y ₂ O ₃ -stabilized zirconia, CaO-stabilized zirconia, and MgO-stabilized zirconia having excellent heat resistance and corrosion resistance and a thermal conductivity at 25 ° C. of 4 W / mK or less are preferable.

In addition, the crystalline inorganic material particles mechanically strengthen the ceramic coat layer and have excellent heat resistance, so the ceramic coat layer has excellent heat resistance, and cracks and the like are generated due to deterioration of mechanical strength. Can be prevented.

The thickness of the ceramic coat layer is preferably 5 to 2000 μm, and more preferably 50 to 2000 μm.
When the thickness of the ceramic coat layer is less than 5 μm, the thickness of the ceramic coat layer is too thin, so that sufficient heat insulation performance cannot be exhibited when used as an exhaust system component. On the other hand, if the thickness of the ceramic coat layer exceeds 2000 μm, the ceramic coat layer is too thick, so that when subjected to thermal shock, the bonding surface with the base material of the ceramic coat layer and the surface exposed to the atmosphere The temperature difference is likely to be large, and the ceramic coat layer is easily broken.

The maximum thickness of the ceramic coat layer is preferably 1.2 to 20 times the minimum thickness of the ceramic coat layer.
When the maximum thickness of the ceramic coat layer exceeds 20 times the minimum thickness, there are portions where the thickness of the ceramic coat layer is too thick, and the ceramic coat layer may be destroyed by thermal shock, or In other words, there are portions where the thickness of the ceramic coat layer is too thin, and the improvement of heat insulation by the ceramic coat layer may not be sufficiently measured.

The thermal conductivity of the ceramic coat layer at 25 ° C. is preferably 0.05 to 2 W / mK.
When the thermal conductivity of the ceramic coat layer at 25 ° C. is 0.05 to 2 W / mK, the exhaust system parts of the present invention have excellent heat insulation properties, and the thermal conductivity is difficult to increase even at high temperatures. It is possible to prevent the temperature of gas or the like from decreasing.
Realizing a ceramic coat layer having a thermal conductivity at 25 ° C. of less than 0.05 W / mK of the ceramic coat layer is not easy considering the balance between both technical and economic viewpoints. On the other hand, if the thermal conductivity at 25 ° C. of the ceramic coat layer exceeds 2 W / mK, the heat retention in the low temperature region becomes insufficient, and for example, when used in a urea SCR system, the temperature of the exhaust gas decreases. The reduction of NOx may not proceed sufficiently.
The thermal conductivity of the ceramic coat layer at 25 ° C. can be measured by a laser flash method.

The thermal conductivity of the ceramic coat layer is measured by the laser flash method by measuring the thermal diffusion coefficient (α). The thermal conductivity (k) is a value calculated from the measured thermal diffusion coefficient (α), specific heat capacity (Cp), and density (ρ).
The thermal diffusion coefficient can be measured under the following conditions.
Measuring device: LFA467 made by NETZSCH
Surface treatment: Graphite spray Measurement temperature: 25 ° C
Measurement atmosphere: N ₂
Sample size: φ10mm, thickness = 2mm
When measuring the thermal diffusion coefficient of the ceramic coat layer, it is measured in a state integrated with the substrate, and the thermal diffusion coefficient of only the ceramic coat layer is calculated by multilayer analysis. Further, when measuring the thermal diffusion coefficient of the ceramic coat layer, the sample is set so that the laser is irradiated perpendicularly to the ceramic coat layer.

The thermal conductivity is calculated from the following formula.
k = ρ · Cp · α [W / mK]
<Measurement of bulk density (ρ)>
When determining the bulk density of the ceramic coat layer, first measure the weight of the substrate, then form a ceramic coat layer on the substrate and then subtract the ceramic coat layer from the measurement of the weight of the substrate with the ceramic coat layer. The weight of (= A) is measured. Thereafter, the volume (= B) of the ceramic coat layer is calculated from the film thickness of the ceramic coat layer, and A / B is defined as the bulk density.
<Measurement of specific heat capacity (Cp)>
The specific heat capacity can be measured under the following conditions.
Measuring device: Seiko Denshi Kogyo DSC210 type Measuring temperature: 25 ° C
Measurement method: DSC method Measurement atmosphere: Ar
When measuring the specific heat capacity of the ceramic coat layer, the ceramic coat layer can be formed into a bulk body having a diameter of 4 mm and a thickness of 1 mm.

In the exhaust system component 10 shown in FIG. 1, the ceramic coating layer 12 includes a urea decomposition catalyst 15, and the urea decomposition catalyst 15 is exposed on the surface of the ceramic coating layer 12.
That the urea decomposition catalyst is exposed on the surface of the ceramic coat layer means that at least a part of the particles of the urea decomposition catalyst is exposed from the surface of the ceramic coat layer. And what is necessary is just to come to contact with a urea decomposition catalyst, when waste gas contacts a ceramic coat layer.
Also, if the urea decomposition catalyst particles are only placed on the ceramic coat layer, the urea decomposition catalyst may be scattered by the flow of exhaust gas, so the urea decomposition catalyst particles are buried in the ceramic coat layer. It is preferable that the urea decomposition catalyst particles are adhered to the ceramic coat layer.

The urea decomposition catalyst is preferably at least one selected from the group consisting of a tungsten compound, a vanadium compound, and a molybdenum compound.
In particular, at least one selected from the group consisting of tungsten oxide, vanadium oxide, and molybdenum oxide is preferable.
Specifically, tungsten trioxide (WO ₃ ), divanadium pentoxide (V ₂ O ₅ ), molybdenum trioxide (MoO ₃ ), and the like can be given.
These compounds are preferable because they are suitable as a catalyst for promoting the reaction of ammonia and carbon dioxide by reacting vaporized urea with water (water vapor) contained in the exhaust gas.
In addition, since these compounds are excellent in heat resistance, even if they come into contact with high-temperature exhaust gas, they are hardly deteriorated and can exhibit a catalytic action over a long period of time.

The average particle size of the urea decomposition catalyst particles is preferably 0.5 to 100 μm.
The weight of the urea decomposition catalyst is 0.5 to 50% by weight with respect to the total weight of the ceramic coat layer (the total weight of the amorphous inorganic material and the crystalline inorganic material, excluding the weight of the urea decomposition catalyst). It is preferable.

Examples of exhaust system parts of the present invention include an exhaust passage through which exhaust gas containing nitrogen oxides flows. Specific examples of the exhaust passage include diesel engines, gasoline engines, etc. used in vehicles, ships, construction machinery, etc. An example of an exhaust pipe through which exhaust gas discharged from the internal combustion engine flows and an exhaust gas purification apparatus including the exhaust pipe will be described.

FIG. 2 is a perspective view schematically showing an example of an exhaust pipe which is an embodiment of the exhaust system component of the present invention.
The exhaust pipe 50 shown in FIG. 2 is a cylindrical tubular member. Since the ceramic coat layer 12 is formed on the inner peripheral surface of the cylindrical base material 11, the ceramic coat layer 12 is on the side where the exhaust gas flows. It can be said that it is formed on the surface.
Since the urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12, when the exhaust gas containing nitrogen oxides flows along with the vaporized urea in the exhaust pipe 50, urea decomposes into ammonia and carbon dioxide. Is done.

FIG. 3 is a perspective view schematically showing another example of an exhaust pipe which is an embodiment of the exhaust system component of the present invention.
The exhaust pipe 60 shown in FIG. 3 is a cone-shaped cylindrical member, and is the same as the exhaust pipe 50 shown in FIG. 2 except that its diameter decreases from the first end face 61 toward the other end face 62. It is a cylindrical member.
Also in this exhaust pipe 60, since the ceramic coat layer 12 is formed on the inner peripheral surface of the base material 11, it can be said that the ceramic coat layer 12 is formed on the surface on the side where the exhaust gas flows.
Since the urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12, when the exhaust gas containing nitrogen oxides flows along with the vaporized urea in the exhaust pipe 60, urea is mixed with ammonia and carbon dioxide. Is broken down into

Subsequently, an exhaust gas purification apparatus of the present invention using an exhaust pipe as an embodiment of the exhaust system component of the present invention as an exhaust passage will be described.
FIG. 4 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus provided with an exhaust pipe as an exhaust system component of the present invention.
In the exhaust gas purification apparatus 100, a holding sealing material 300 is wound around the catalyst carrier 400 and disposed in the exhaust pipe.
The exhaust pipe has a cross-sectional shape as shown in FIG. 4 by combining a cylindrical exhaust pipe 50a, a cone-shaped exhaust pipe 60, and a cylindrical exhaust pipe 50b. The inner diameter of the exhaust pipe 50b is that of the exhaust pipe 50a. It is larger than the inner diameter.

In FIG. 4, the flow of exhaust gas is indicated by an arrow G, and in FIG. 4, the left side corresponds to the upstream side of the exhaust pipe, and the right side corresponds to the downstream side.
A urea injection device 500 is provided on the upstream side of the exhaust pipe, and the exhaust pipe located downstream of the urea injection device 500 and upstream of the catalyst carrier 400 is an exhaust system component of the present invention. It is an exhaust pipe. That is, in the exhaust pipe 50a, the exhaust pipe 60, and the exhaust pipe 50b that are located downstream of the urea injection device 500 and upstream of the catalyst carrier 400, the ceramic coat layer 12 is provided at a site where exhaust gas contacts. The urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12.

The urea water injected from the urea injection device 500 is vaporized by the heat of the exhaust gas G and becomes exhaust gas containing urea and flows in the exhaust pipes (50a, 60, 50b). The exhaust gas containing urea contacts the ceramic coat layer 12 formed in the exhaust pipe (50a, 60, 50b) in the region between the urea injection device 500 and the catalyst carrier 400. At this time, urea contained in the exhaust gas is decomposed by the action of the urea decomposition catalyst 15 exposed on the surface of the ceramic coat layer 12. Therefore, urea is prevented from depositing and depositing on the surfaces of the exhaust pipe 50a, the exhaust pipe 60, and the exhaust pipe 50b located between the urea injection device 500 and the catalyst carrier 400.
Urea is prevented from depositing and accumulating on the surfaces of the exhaust pipes (50a, 60, 50b) in the region between the urea injection device 500 and the catalyst carrier 400. The waste gas is introduced into the inside of the catalyst carrier 400 from the exhaust gas inflow side end face 400a without waste, and the nitrogen oxides are reduced and decomposed.
In addition, as a catalyst carrier used for the exhaust gas purification apparatus, a catalyst carrier conventionally used in this field such as a ceramic honeycomb catalyst can be used.

Further, an exhaust pipe that is an exhaust system component of the present invention may be used as an exhaust pipe that is an exhaust passage upstream of the urea injection device.
FIG. 4 also shows a state in which an exhaust pipe 50c, which is an exhaust system component of the present invention, is provided upstream of the urea injector 500.
In this case, the exhaust pipe 50c is also provided with the ceramic coat layer 12, and the ceramic coat layer 12 can function as a heat insulating coating, so that the exhaust gas temperature is prevented from lowering upstream of the urea injection device 500. Further, precipitation of urea on the downstream side of the urea injection device is more effectively prevented.
Although the exhaust pipe 50c and the exhaust pipe 50a are illustrated as continuous members in FIG. 4, the upstream side of the urea injection device 500 is distinguished as the exhaust pipe 50c, and the downstream side is distinguished as the exhaust pipe 50a.
The exhaust pipe 50c and the exhaust pipe 50a may be continuous members, or originally separate members that are integrated by welding or the like.

As an example of the exhaust system component of the present invention, there is a diffusion member that is installed inside an exhaust passage through which exhaust gas containing nitrogen oxides flows and partially obstructs the flow of exhaust gas flowing from the upstream of the exhaust passage.
Hereinafter, specific examples of the diffusing member will be described.
5, FIG. 6, FIG. 7, FIG. 8, FIG. 9 and FIG. 10 are perspective views schematically showing an example of a diffusion member which is an embodiment of the exhaust system component of the present invention.

The shape of the diffusing member is not particularly limited as long as it is disposed inside the exhaust passage and can partially block the flow of the exhaust gas flowing in from the upstream of the exhaust passage. For example, the shape shown in FIG.
FIG. 5 is a perspective view schematically showing an example of the diffusing member.
A diffusing member 110 shown in FIG. 5 includes a cylindrical outer edge portion 111 and a plurality of blades 112 extending radially from the substantially center of the outer edge portion 111, and the blades 112 are inclined at a predetermined angle with respect to the passage direction of the exhaust gas. Yes.
Therefore, the exhaust gas flowing into the diffusing member 110 flows into the diffusing member 110 from the exhaust gas inflow side end surface 110a, a part of the flow path is blocked by the blades 112, force is applied in the swirl direction, and the exhaust gas outflow side end surface It flows out from 110b. Therefore, on the exhaust gas outflow side of the diffusing member 110, a flow in the swirl direction is generated in the exhaust gas, and the deviation of components contained in the exhaust gas can be reduced.

The diffusion member 110 is provided with a ceramic coat layer 12 at a site where exhaust gas comes into contact. Since the urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12, nitrogen oxide is applied to the diffusion member 110. When the exhaust gas that is contained flows with the vaporized urea, urea is decomposed into ammonia and carbon dioxide.

FIG. 6 is a perspective view schematically showing another example of the diffusing member of the present invention, and FIGS. 7, 8 and 10 are perspective views schematically showing still another example of the diffusing member of the present invention. FIG. 9 is a perspective view of still another example of the diffusing member of the present invention as viewed from the exhaust gas outflow side end surface.
Also in these diffusing members, the ceramic coat layer 12 is provided at the site where the exhaust gas comes into contact. Since the urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12, nitrogen oxide is applied to the diffusing member. When the exhaust gas that is contained flows with the vaporized urea, urea is decomposed into ammonia and carbon dioxide. Since this action is the same for any diffusing member, its description is omitted, and only the shape of the diffusing member will be described.

The diffusing member 120 shown in FIG. 6 includes a cylindrical outer edge portion 121 and a plurality of blades 122 that spirally extend from substantially the center of the outer edge portion 121, and the blades 122 are inclined at a predetermined angle with respect to the passage direction of the exhaust gas. ing.
Like the diffusion member 110 shown in FIG. 5, the diffusion member 120 applies rotation in the swirl direction to the exhaust gas that has passed through the diffusion member, so that the exhaust gas is mixed and the deviation of components contained in the exhaust gas is reduced. Can do.

The diffusing member 130 shown in FIG. 7 includes a cylindrical outer edge portion 131 and a plurality of blades 132 protruding from the inner surface of the outer edge portion 131 toward the substantially center of the outer edge portion. It is inclined at a predetermined angle.
Although the wing 132 is not disposed at the center of the outer edge 131 of the diffusing member 130, it is not essential to block all the flow paths of the exhaust gas passing through the diffusing member 130. Even if it exists, waste gas can fully be mixed and the bias | inclination of the component contained in waste gas can be reduced.

In the diffusing member 140 shown in FIG. 8, a plurality of holes 141 penetrating the front and back are formed on the surface of a disk-shaped base material.
Since the exhaust gas passing through the diffusion member 140 inevitably passes through the hole 141, the flow of the exhaust gas is disturbed when passing through the hole 141, and the exhaust gas is mixed. Can be reduced.

The diffusion member 150 shown in FIG. 9 has a projection 152 for changing the moving direction to a predetermined direction when exhaust gas collides inside the cylindrical outer edge portion 151, and the movement direction of the exhaust gas in a direction different from the projection 152. And a protrusion 153 for changing the shape.
The exhaust gas passing through the diffusion member 150 flows into the diffusion member 150 from the exhaust gas inflow side end surface 150a and flows out from the exhaust gas outflow side end surface 150b. At this time, the exhaust gas collides with the protrusion 152 or the protrusion 153, but the direction in which the exhaust gas colliding with the protrusion 152 moves is different from the direction in which the exhaust gas that has collided with the protrusion 153 moves. The bias of the contained components can be reduced.

10 has a cylindrical outer edge 161, a donut-shaped plate 163 having a hole 164, and a spiral shape extending from the inner surface of the plate 163 toward the approximate center of the plate 163. It consists of a plurality of blades 162, and the blades 162 are inclined at a predetermined angle with respect to the exhaust gas passage direction.
Since the diffusing member 160 has the wings 162, similarly to the diffusing member 110 shown in FIG. 5, the swirl direction rotation is applied to the exhaust gas that has passed through the diffusing member. Furthermore, when the exhaust gas passes through the holes 164 formed in the plate portion 163, the flow of the exhaust gas is disturbed similarly to the diffusion member 140 shown in FIG. 8, the exhaust gas is mixed, and the components contained in the exhaust gas are mixed. The bias can be reduced.

The shape of the diffusing member is not limited to that described above. For example, the holes shown in FIG. 8 may have different sizes and shapes, and are not necessarily arranged at equal intervals. The shapes of the wings, holes, and protrusions described in FIGS. 5, 6, 7, 8, 9, and 10 can be arbitrarily combined.
Further, the diffusion member basically has no movable part, but may have a valve or the like for opening the exhaust gas when the pressure of the exhaust gas increases and forming a new exhaust gas flow path.

FIG. 11 is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus provided with both a diffusion member and an exhaust pipe as an exhaust system component of the present invention.
The configuration of the exhaust gas purification apparatus 200 shown in FIG. 11 is substantially the same as that of the exhaust gas purification apparatus 100 shown in FIG. 4, but a diffusion member 110 is provided in the exhaust pipe.
The diffusion member 110 is arranged on the downstream side of the urea injection device 500 and on the upstream side of the catalyst carrier 400.
When the exhaust gas containing urea injected from the urea injection device passes through the diffusion member 110, a part of the flow is obstructed and rotates in the swirl direction (the exhaust gas flow is schematically shown by an arrow G). .
Therefore, since the exhaust gas that has passed through the diffusion member 110 circulates in the exhaust pipe while swirling, when the exhaust gas reaches the exhaust gas inflow end surface 400a of the catalyst carrier 400, the component bias in the exhaust gas and / or the temperature distribution. Will be reduced.
Since the urea water injected from the urea injection device 500 reaches the catalyst carrier 400 in a sufficiently dispersed state in the exhaust gas, the urea SCR system can be sufficiently operated.
In addition, since the ceramic coat layer is formed on the diffusing member 110, it has excellent heat insulation performance, can suppress a decrease in exhaust gas temperature, and urea exists due to the presence of the urea decomposition catalyst exposed on the surface of the ceramic coat layer. Is prevented from being deposited and deposited on the surface of the diffusion member.
Further, since the exhaust gas purification apparatus 200 is also provided with exhaust pipes (50a, 60, 50b) made of the exhaust system parts of the present invention, it is possible to prevent urea from being deposited on the surface of the exhaust pipe.

An example of the exhaust system part of the present invention is an exhaust passage through which exhaust gas containing nitrogen oxides flows. As a specific example of the exhaust passage, the exhaust passage is discharged from a factory such as a cement plant instead of the exhaust pipe described above. An example of a flue through which smoke passes will be described below.

FIG. 12A is a perspective view schematically showing an example of a flue that is an embodiment of the exhaust system component of the present invention, and FIG. 12B is a cross-sectional view taken along line AA in FIG. FIG.
In FIG. 12A, exhaust gas G containing nitrogen oxides discharged from a factory such as a cement plant flows toward the catalyst carrier 400 in the direction of the arrows (solid line and dotted line).
A tubular member having a rectangular tube shape, which is an exhaust passage through which the exhaust gas G flows, is the flue 70, and a urea injection device 500 that injects urea water into the flue 70 is provided on the upstream side of the exhaust passage.

The exhaust system component of the present invention is provided on the downstream side of the urea injection device 500, and is a flue 70 in which the ceramic coat layer 12 is formed on the inner peripheral surface of the base material 11 which is a rectangular tubular member. is there.
Since the urea decomposition catalyst 15 is exposed on the surface of the ceramic coat layer 12, when the exhaust gas containing nitrogen oxides flows along with the vaporized urea in the flue 70, the urea is decomposed into ammonia and carbon dioxide. Is done.
That is, similar to the case of the exhaust pipe as an exhaust passage, the effect of the present invention is exhibited even when the exhaust system component of the present invention is used as a flue through which exhaust gas from a factory or the like flows. be able to.

Moreover, you may arrange | position the diffusion member as an exhaust-system component of this invention in the flue as an exhaust passage.
Furthermore, a flue in which a ceramic coat layer is formed and a urea decomposition catalyst is exposed on the surface of the ceramic coat layer may be used as an exhaust passage disposed upstream of the urea injection device.
In addition, as a catalyst support | carrier arrange | positioned in a flue, the catalyst support | carrier conventionally used in this field | area, such as a ceramic honeycomb catalyst, can be used.

Next, an example of a method for manufacturing an exhaust system component of the present invention will be described.
First, a base material is prepared.
Since the material which comprises a base material was demonstrated in description of the diffusion member of this invention, it abbreviate | omits.
A substrate is prepared by processing the substrate into a shape of an exhaust passage such as a cylinder or a rectangular tube, or the shape of a diffusion member shown in FIG.
Subsequently, if necessary, a cleaning process may be performed to remove impurities on the surface of the substrate. The cleaning process is not particularly limited, and a conventionally known cleaning process can be used. Specifically, for example, a method of performing ultrasonic cleaning in an alcohol solvent can be used.

In addition, after the cleaning treatment, as necessary, the surface of the base material is subjected to a roughening treatment in order to increase the specific surface area of the base material or adjust the surface roughness of the base material. May be. Specifically, for example, a roughening process such as a sandblast process, an etching process, or a high temperature oxidation process may be performed. These may be used alone or in combination of two or more.
You may perform a washing process after this roughening process.

Then, the raw material composition for forming a ceramic coat layer is prepared.
The raw material composition used for forming the ceramic coat layer preferably contains an amorphous inorganic material, and more preferably contains a crystalline inorganic material and / or a pore former.

Since the kind, material, material, and other characteristics of the amorphous inorganic material have already been described, a description thereof will be omitted.
When preparing the raw material composition used for the formation of the ceramic coat layer, each raw material is prepared and then wet pulverization is performed. The amorphous inorganic material powder is first adjusted to an appropriate particle size. After preparing the raw material, it is preferable to obtain a product having a target particle size by wet pulverization.
Amorphous inorganic material is applied to the surface of the substrate, fired, and then melted to form a coating film (a layer of amorphous inorganic material), so there is no need to strictly control the particle size of the amorphous inorganic material. However, it is preferable that the amorphous inorganic particles are uniformly dispersed in the raw material composition.
In this respect, the final average particle size after wet pulverization of the amorphous inorganic material is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm. In the range of 1 to 20 μm, it is presumed that the influence of electricity charged on the particle surface is small, but the particles are easily dispersed uniformly.

As for the crystalline inorganic material, its type, material, material, its characteristics and the like have already been described, and therefore will be omitted. When preparing the raw material composition used for forming the ceramic coat layer, wet pulverization is performed after each raw material is prepared, but in the case of a crystalline inorganic material, the first adjusted to an appropriate particle size is used. It is preferable to obtain the desired particle size by wet pulverization after preparation of the raw materials.

The weight of the particles of the crystalline inorganic material is 5 to 60 parts by weight with respect to 100 parts by weight of the entire ceramic coat layer (the total weight of the amorphous inorganic material and the crystalline inorganic material, excluding the weight of the urea decomposition catalyst). Preferably there is.
By using the particles of the crystalline inorganic material in such a weight ratio with respect to the total weight of the ceramic coat layer, the crystalline inorganic material is contained in the amorphous inorganic material layer constituting the manufactured exhaust system part. The particles can be dispersed at an appropriate ratio to ensure the heat resistance and heat insulation of the ceramic coat layer. It is more preferable that the weight of the crystalline inorganic material particles is set to 10 to 40 parts by weight with respect to 100 parts by weight of the entire ceramic coat layer.

When the weight of the crystalline inorganic material particles relative to 100 parts by weight of the entire ceramic coat layer is less than 5 parts by weight, the amount of the crystalline inorganic material particles dispersed in the amorphous inorganic material layer is small. The pores dispersed inside are easily moved in the high temperature range, and the heat insulating property is lowered.
On the other hand, when the weight of the crystalline inorganic material particles exceeds 60 parts by weight with respect to 100 parts by weight of the entire ceramic coat layer, the amount of the amorphous inorganic material is relatively reduced. Layer formation) becomes difficult, and peeling from the base material is likely to occur.

Next, the pore former will be described.
The pore former is used to form pores in the ceramic coat layer when a coating film is formed on the surface of the substrate using the raw material composition and then the ceramic coat layer is formed by heating and firing.

As the pore former, for example, balloons that are fine hollow spheres composed of oxide ceramics, spherical acrylic particles, carbon such as graphite, carbonates, foaming agents, and the like can be used. The formed ceramic coat layer preferably has a high heat insulating performance. For that purpose, it is preferable that pores having a diameter as small as possible are uniformly dispersed.

From such a viewpoint, the pore former is preferably carbon, carbonate or foaming agent.
Examples of the carbonate and the foaming agent include CaCO ₃ , BaCO ₃ , NaHCO ₃ , Na ₂ CO ₃ , (NH ₄ ) ₂ CO _{3 and the} like.
Further, among these pore formers, carbon such as graphite is preferable. This is because carbon can be dispersed as fine particles in the raw material composition by a treatment such as pulverization, and can be decomposed by heating and firing to form pores having a suitable pore size.

From the above viewpoint, the average particle diameter of the pore former particles is preferably 0.1 to 25 μm.
When the average particle diameter of the pore former particles is 0.1 to 25 μm, the pore diameter in the formed ceramic coat layer can be easily adjusted to 0.1 to 150 μm. The average particle size of the pore former is more preferably 0.5 to 10 μm.

When the average particle diameter of the pore former particles is less than 0.1 μm, it becomes difficult to disperse the pore former in the raw material composition, and as a result, the pores in the formed ceramic coat layer are dispersed. When the degree decreases and the temperature becomes high, the pores are easily united. On the other hand, when the average particle diameter of the pore-forming material particles exceeds 25 μm, the diameter of pores formed in the ceramic coat layer becomes too large, and the heat insulating property of the ceramic coat layer tends to be lowered.

The weight of the pore former particles is preferably 0.001 to 1 part by weight based on 100 parts by weight of the total amount of the paint (raw material composition). When the weight of the pore former relative to 100 parts by weight of the total amount of the paint (raw material composition) is set to 0.001 to 1 part by weight, the pore former is well dispersed in the raw material composition, and the base material When a coating film is formed on the surface and a ceramic coating layer is formed by heating and baking, a ceramic coating layer in which pores are well dispersed can be formed. The weight of the pore former particles with respect to 100 parts by weight of the total amount of the paint (raw material composition) is preferably set to 0.005 to 0.5 parts by weight.

If the weight of the pore-forming material particles is less than 0.001 part by weight with respect to 100 parts by weight of the total amount of the paint (raw material composition), the ceramic coating layer has a good heat insulating property because the proportion of pores in the ceramic coating layer is too small. May not be able to demonstrate. On the other hand, if the weight of the pore-forming material particles exceeds 1 part by weight with respect to 100 parts by weight of the total amount of the paint (raw material composition), the proportion of the pore-forming material is too large, so that the pores are improved in the formed ceramic coat layer It becomes difficult to disperse, large pores are easily formed, and the ceramic coat layer may not be able to exhibit good heat insulating properties.

In addition to the amorphous inorganic material, the crystalline inorganic material, and the pore former, a dispersion medium, an organic binder, and the like may be added to the raw material composition.
Examples of the dispersion medium include water and organic solvents such as methanol, ethanol, and acetone. The blending ratio of the mixed powder or the amorphous inorganic material powder and the dispersion medium contained in the raw material composition is not particularly limited, but for example, dispersed with respect to 100 parts by weight of the amorphous inorganic material powder. The medium is preferably 50 to 150 parts by weight. It is because it becomes a viscosity suitable for apply | coating to a base material.
As an organic binder which can be mix | blended with a raw material composition, polyvinyl alcohol, methylcellulose, ethylcellulose, carboxymethylcellulose etc. can be mentioned, for example. These may be used alone or in combination of two or more.
Moreover, you may use a dispersion medium and an organic binder together.

Furthermore, a slurry containing a urea decomposition catalyst is prepared separately from the raw material composition.
Since the type, material, material and other characteristics of the urea decomposition catalyst have already been described, the description thereof will be omitted.
The slurry containing the urea decomposition catalyst is prepared by dispersing the particles of the urea decomposition catalyst in a dispersion medium.
Examples of the dispersion medium include water and organic solvents such as methanol, ethanol, and acetone, as in the case of the dispersion medium used for the raw material composition. Similarly to the raw material composition, for example, polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, or the like may be mixed as the organic binder.

An exhaust system part is manufactured as follows using the above-described base material, raw material composition, and slurry containing a urea decomposition catalyst.

(1) Process of coating the raw material composition on the surface of the substrate As a method of coating the raw material composition on the surface of the substrate, for example, spray coating, electrostatic coating, inkjet, transfer using a stamp or roller, Methods such as brush coating or electrodeposition coating can be used. Moreover, you may coat the said raw material composition by immersing a base material in a raw material composition.
If necessary, the substrate coated with the raw material composition may be dried.
The drying conditions are preferably 50 to 150 ° C. and about 10 to 180 minutes.

(2) Process for coating slurry containing urea decomposition catalyst The slurry containing the urea decomposition catalyst is coated on the raw material composition coated on the base material.
By doing so, the urea decomposition catalyst is distributed on the surface of the raw material composition.
As a method for coating the slurry containing the urea decomposition catalyst, a method similar to the method exemplified as the method for coating the raw material composition can be used.
If necessary, the substrate coated with the slurry containing the urea decomposition catalyst may be dried.
The drying conditions are preferably 50 to 150 ° C. and about 10 to 180 minutes.

(3) Step of performing firing treatment Specifically, a ceramic coat layer is formed by heating and firing a base material coated with a slurry containing a raw material composition and a urea decomposition catalyst.
The firing temperature is preferably equal to or higher than the softening point of the amorphous inorganic material, and is preferably 700 ° C. to 1100 ° C., although it depends on the type of the blended amorphous inorganic material and the type of pore former. By setting the firing temperature to a temperature equal to or higher than the softening point of the amorphous inorganic material, the substrate and the amorphous inorganic material can be firmly adhered to each other, and a ceramic coat layer that is firmly adhered to the substrate is formed. Because you can.
By the firing treatment, the urea decomposition catalyst distributed on the surface of the raw material composition is exposed on the surface of the ceramic coat layer and is contained in the ceramic coat layer.

Further, as a method for manufacturing an exhaust system component of the present invention, instead of using a slurry containing a urea decomposition catalyst, the urea decomposition catalyst may be supplied so as to be exposed from the surface of the ceramic coat layer by the following method. Good.

For example, the ceramic coating layer is formed on the base material by the above-described step (1) step of coating the raw material composition on the surface of the base material and (3) the step of performing a baking treatment, and then the urea decomposition catalyst powder. You may make it sprinkle. In this case, in order to fix the urea decomposition catalyst on the ceramic coat layer, an inorganic binder or an organic binder layer is provided on the ceramic coat layer, and the urea decomposition catalyst powder is sprinkled and dried or fired. By performing, the urea decomposition catalyst can be fixed on the ceramic coat layer via an inorganic binder or an organic binder.

The following may also be used.
First, after performing the above-mentioned step (1) coating the raw material composition on the surface of the substrate, the powder of the urea decomposition catalyst is sprinkled before or after drying, and the raw material composition in an unsolidified state is applied. The powder of the urea decomposition catalyst is fixed on. Subsequently, by performing the step of performing the above-described (3) firing treatment, the urea decomposition catalyst can be included in the ceramic coat layer in a state of being exposed on the surface of the ceramic coat layer.

The effects of the exhaust system parts and the exhaust gas purification apparatus of the present invention will be listed below.
(1) In the exhaust system component of the present invention, a ceramic coat layer is formed on the surface of the base material made of metal and in contact with the exhaust gas, and the urea decomposition catalyst is exposed on the surface of the ceramic coat layer. doing.
When the exhaust gas containing vaporized urea comes into contact with such exhaust system components, the vaporized urea and the urea decomposition catalyst can come into contact with each other. Then, urea that has contacted the urea decomposition catalyst and moisture (water vapor) contained in the exhaust gas can react with the following chemical formula (1) to form ammonia and carbon dioxide, and can flow to the catalyst carrier side.
(NH ₂ ) CO + H ₂ O → 2NH ₃ + CO ₂ Chemical formula (1)
Urea that has come into contact with the ceramic coat layer is decomposed by the above reaction, so that urea is prevented from being deposited on the ceramic coat layer.

(2) The exhaust system component of the present invention can be a cylindrical member used as an exhaust passage through which exhaust gas containing nitrogen oxides flows. When the exhaust system component is used as an exhaust passage, urea is formed on the surface of the exhaust passage. Is prevented from depositing and depositing.

(3) The exhaust system component of the present invention can be a diffusion member that is installed inside an exhaust passage through which exhaust gas containing nitrogen oxides flows, and that partially inhibits the flow of exhaust gas flowing from the upstream of the exhaust passage. When the exhaust system component is used as the diffusion member, urea is prevented from being deposited and deposited on the surface of the diffusion member.

(4) In the exhaust gas purification apparatus of the present invention, the urea injection device is provided upstream of the exhaust passage, and the exhaust gas purification device is provided downstream of the exhaust passage.
The exhaust system component of the present invention is used at a site where exhaust gas contacts with the downstream side of the urea injection device and the upstream side of the catalyst carrier.
With such a configuration, even if the exhaust gas containing urea injected and vaporized from the urea injection device into the exhaust passage comes into contact with the exhaust system component in the region between the urea injection device and the catalyst carrier, The contacted urea is decomposed by the action of the urea decomposition catalyst exposed on the surface of the ceramic coat layer. Therefore, it is possible to prevent urea from being deposited on the surface of the exhaust system part located between the urea injection device and the catalyst carrier.

(Example)
Examples that specifically disclose one embodiment of the present invention will be described below. In addition, this invention is not limited only to these Examples.

Example 1
(1) Preparation of base material As a base material, a 40 mm × 40 mm × 1.5 mmt stainless steel base material (manufactured by SUS430) is prepared, subjected to ultrasonic cleaning in an alcohol solvent, and subsequently subjected to a sand blast treatment. The surface (both sides) of was roughened. The sandblast treatment was performed for 10 minutes using # 100 Al ₂ O ₃ abrasive grains.
When the surface roughness of the substrate was measured using a surface roughness measuring machine (Handy Surf E-35B, manufactured by Tokyo Seimitsu Co., Ltd.), the surface roughness of the substrate was Rz _JIS = 8.8 μm. .
The base material was prepared by the said process.

(2) Preparation of raw material composition Barium silicate glass (softening point 600 ° C) was prepared as a powder of an amorphous inorganic material. The amorphous inorganic material powder had an average particle size of 15 μm and contained 20% by weight of silica.
In addition to 35 parts by weight of the amorphous inorganic material powder, 15 parts by weight of crystalline inorganic material (zirconia), 0.012 parts by weight of carbon as a pore former, 0.5 parts by weight of organic binder (methylcellulose), And water was added and mixed so that a total weight might be 100 weight part.

(3) Application of raw material composition and the raw material composition was applied to the entire surface of the dried substrate by a spray coating method and dried in a dryer at 70 ° C. for 20 minutes.

(4) Application of Urea Decomposition Catalyst A powder of urea decomposition catalyst is sprinkled on a dry, unsolidified raw material composition layer and powdered with vanadium pentoxide (V ₂ O ₅ ). Was allowed to settle on the layer.

(5) Formation of ceramic coating layer by firing treatment Subsequently, a ceramic coating layer having a thickness of 100 μm is formed by heating and firing treatment in air at 650 ° C. for 90 minutes, and the evaluation sample according to Example 1 is formed. Obtained.
Urea decomposition catalyst particles were exposed on the surface of the formed ceramic coat layer.

(Measurement of weight of urea decomposition catalyst)
In the production process of Example 1, the weight of the urea decomposition catalyst relative to the weight of the ceramic coat layer was measured by the following equation.
A: Weight of substrate (weight after step (1))
B: Weight after drying of raw material composition (weight after step (3))
C: Weight after application of urea decomposition catalyst (weight after step (4))
Weight of urea decomposition catalyst with respect to weight of ceramic coat layer (%)
= [(C−B) / (B−A)] × 100
The weight (%) of the urea decomposition catalyst determined by the above formula is the weight of the urea decomposition catalyst relative to the weight of the raw material composition before the calcination treatment. Since the ratio of the organic binder is very small, it is calculated assuming that it is zero.
In Example 1, the weight of the urea decomposition catalyst with respect to the weight of the ceramic coat layer was 6%.

(Examples 2 and 3)
As the urea decomposition catalyst powder, instead of the powder of divanadium pentoxide (V ₂ O ₅ ) of Example 1, a powder of molybdenum trioxide (MoO ₃ ) is used in Example 2, and tungsten trioxide (WO ₃ ) is used in Example _3. Samples for evaluation according to Example 2 and Example 3 were obtained in the same manner as in Example 1 except that each of the above powders was used.
The weight of the urea decomposition catalyst with respect to the weight of the ceramic coat layer was 15% and 36%, respectively.

(Comparative Example 1)
In Example 1, an evaluation sample in which only a ceramic coat layer made of a raw material composition was formed on a base material without applying a urea decomposition catalyst was obtained.

(Comparative Example 2)
In Example 1, without forming a ceramic coat layer, the substrate prepared in (1) Preparation of substrate was used as an evaluation sample as it was.

(Comparative Example 3)
In Example 1, without forming the ceramic coat layer, (1) powder of vanadium pentoxide (V ₂ O ₅ ) was sprinkled on the surface of the base material prepared in the preparation of the base material, and (5) An evaluation sample was obtained by firing under the same conditions.
Note that the powder of vanadium pentoxide (V ₂ O ₅ ) was sprinkled so that the absolute amount (weight) to which the powder of vanadium pentoxide (V ₂ O ₅ ) adhered was the same as in Example 1.

(Urea adhesion evaluation)
One drop of urea water (32.5% urea water for SCR system: AdBlue (registered trademark)) was dropped on the surface of the evaluation sample prepared in each example and comparative example, which was provided with a urea decomposition catalyst. The weight of the sample for evaluation before and after the dropping was measured.
In Comparative Example 1, urea water was dropped on the surface on which the ceramic coat layer was formed, and in Comparative Example 2, urea water was dropped on the surface of the base material.
Each sample for evaluation was heated on a hot plate set at an iron plate temperature of 200 ° C. for 1.5 hours, and the weight of the sample for evaluation was measured after completion of heating.
From the result of the above weight measurement, the residual ratio (%) of urea solid content was calculated by the following formula.
D: Weight before dropping urea solution E: Weight after dropping urea solution F: Weight after heating on hot plate Residual rate of urea solids (%)
= [(FD) / ((ED) × 0.325)] × 100
The evaluation results are summarized in Table 1.

From this, when the urea decomposition catalyst is exposed on the surface of the ceramic coat layer as in the evaluation samples according to Examples 1 to 3, it is possible to reduce the adhesion amount of urea derived from urea water. I understood.

DESCRIPTION OF SYMBOLS 10 Exhaust system component 11 Base material 12 Ceramic coat layer 13 Amorphous inorganic material 14 Crystalline inorganic material 15 Urea decomposition catalyst 16 Pore 50, 50a, 50b, 50c, 60 Exhaust pipe 70 Flue 100, 200 Exhaust gas purification device 110, 120, 130, 140, 150, 160 Diffusion member 400 Catalyst carrier 500 Urea injection device G Exhaust gas

Claims (12)

An exhaust system component provided at a site that comes into contact with exhaust gas containing nitrogen oxides,
A base material made of metal;
A ceramic coat layer formed on the surface of the base material on the side in contact with the exhaust gas,
The exhaust system component according to claim 1, wherein the ceramic coat layer contains a urea decomposition catalyst, and the urea decomposition catalyst is exposed on a surface of the ceramic coat layer. The exhaust system component according to claim 1, wherein the urea decomposition catalyst is at least one selected from the group consisting of a tungsten compound, a vanadium compound, and a molybdenum compound. The exhaust system component according to claim 2, wherein the urea decomposition catalyst is at least one selected from the group consisting of tungsten oxide, vanadium oxide, and molybdenum oxide. The exhaust system part according to any one of claims 1 to 3, wherein the ceramic coat layer includes an amorphous inorganic material and a crystalline inorganic material. The exhaust system component according to claim 4, wherein the amorphous inorganic material is a low-melting glass having a softening point of 300 to 1000 ° C. The exhaust system component according to claim 1, wherein pores are formed in the ceramic coat layer. The exhaust system component according to any one of claims 1 to 6, which is a cylindrical member used as an exhaust passage through which exhaust gas containing nitrogen oxides flows. The exhaust system component according to any one of claims 1 to 6, wherein the exhaust system component is a diffusion member that is installed inside an exhaust passage through which exhaust gas containing nitrogen oxides flows and partially inhibits the flow of exhaust gas flowing from upstream of the exhaust passage. . An exhaust passage through which exhaust gas containing nitrogen oxides flows;
A urea injection device that is provided upstream of the exhaust passage and injects urea into the exhaust passage;
An exhaust gas purification apparatus comprising a catalyst carrier provided downstream of the exhaust passage,
The exhaust system component according to any one of claims 1 to 6, wherein the exhaust system component according to any one of claims 1 to 6 is used at a portion where the exhaust gas contacts downstream of the urea injection device and upstream of the catalyst carrier. Purification equipment. The exhaust gas purification apparatus according to claim 9, wherein the exhaust system part according to any one of claims 1 to 6 is used as the exhaust passage. The exhaust gas purification apparatus according to claim 9, wherein the exhaust system part according to any one of claims 1 to 6 is used as an exhaust passage upstream of the urea injection apparatus. The exhaust system component according to any one of claims 1 to 6, wherein the exhaust system component according to any one of claims 1 to 6 is used as a diffusion member that is installed inside the exhaust passage and partially inhibits a flow of exhaust gas flowing from upstream of the exhaust passage. The exhaust gas purification apparatus according to any one of the above.

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