Exhaust gas treatment system

Abstract

To provide an exhaust gas treatment system capable of decomposing nitrous oxide in exhaust gas with high efficiency.SOLUTION: An exhaust gas treatment system 1 comprises an exhaust passage 10, a first catalyst device 11, a second catalyst device 21, and a third catalyst device 31. The first catalyst device 11 is arranged upstream of the second catalyst device 21. The first catalyst device 11 also has a first catalyst 12 that decomposes ammonia, and a dummy catalyst 13 that does not decompose ammonia. The first catalyst 12 includes a first active metal that decomposes ammonia, and a first carrier that carries the first active metal. The dummy catalyst 13 includes a dummy carrier that does not carry the first active metal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas treatment system. More specifically, the present invention relates to a system for treating ammonia (NH), nitrous oxide (N2O), and nitrogen oxides (NO X ) and relates to an exhaust gas treatment system including the same. [Background technology]

[0002] BACKGROUND ART Conventionally, in order to treat exhaust gas, a technique is known in which an exhaust gas treatment catalyst is disposed in an exhaust passage through which the exhaust gas flows, and harmful substances in the exhaust gas are decomposed.

[0003] For example, as a method for treating nitrogen oxides and nitrous oxides contained in exhaust gas, a technology has been proposed in which a denitration catalyst and a nitrous oxide decomposition catalyst are arranged in sequence to decompose nitrogen oxides and nitrous oxides (see, for example, Patent Document 1).

[0004] The exhaust gas treatment method of Patent Document 1 adds ammonia and / or urea as a reducing agent to the exhaust gas, and then introduces the exhaust gas into a denitration catalyst and a nitrous oxide decomposition catalyst, thereby enabling the efficient decomposition of nitrogen oxides and nitrous oxide in the exhaust gas. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-71071 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the exhaust gas treatment method of Patent Document 1 has a drawback in that the nitrous oxide decomposition catalyst does not function sufficiently when the temperature of the exhaust gas is low, resulting in a low efficiency in decomposing nitrous oxide.

[0007] The present invention provides an exhaust gas treatment system that can decompose nitrous oxide in exhaust gas with high efficiency. [Means for solving the problem]

[0008] The present invention [1] provides an exhaust gas treatment system for treating exhaust gas containing ammonia, nitrous oxide, and nitrogen oxides, the exhaust gas treatment system comprising: an exhaust passage through which the exhaust gas flows; a first catalyst device interposed in the exhaust passage and having a first catalyst that decomposes ammonia and a dummy catalyst that does not decompose ammonia; a second catalyst device interposed in the exhaust passage and having a second catalyst that decomposes nitrous oxide; and a third catalyst device interposed in the exhaust passage and having a third catalyst that reduces nitrogen oxides, the first catalyst device being disposed upstream of the second catalyst device; the first catalyst comprising a first active metal that decomposes ammonia and a first support supporting the first active metal; and the dummy catalyst comprising a dummy support that does not support the first active metal.

[0009] The present invention [2] includes the exhaust gas treatment system described in [1], wherein the first catalyst and the dummy catalyst are arranged in a direction perpendicular to the flow direction of the exhaust gas, and each of the first catalyst and the dummy catalyst is arranged along the flow direction of the exhaust gas.

[0010] The present invention [3] includes the exhaust gas treatment system described in [1], wherein the first catalyst device is provided with a mixing unit in which the first catalyst and the dummy catalyst are alternately packed in a direction perpendicular to the flow direction of the exhaust gas, and the mixing unit is arranged in plurality in the direction perpendicular to the flow direction of the exhaust gas.

[0011] The present invention [4] includes the exhaust gas treatment system described in [1], wherein the first catalytic device comprises a first unit filled with only the first catalyst and a dummy unit filled with only the dummy catalyst, and the first units and dummy units are arranged in multiple units in a direction perpendicular to the flow direction of the exhaust gas.

[0012] The present invention [5] includes an exhaust gas treatment system according to any one of [1] to [4], wherein the first catalyst and the dummy catalyst each have a flat and / or corrugated shape extending along the flow direction of the exhaust gas.

[0013] The present invention [6] includes the exhaust gas treatment system according to [5], wherein each of the first support and the dummy support is flat glass paper and / or corrugated glass paper aligned in the flow direction of the exhaust gas.

[0014] The present invention [7] includes the exhaust gas treatment system according to any one of [1] to [4], wherein the third catalytic device is disposed downstream of the second catalytic device.

[0015] The present invention [8] includes the exhaust gas treatment system according to any one of [1] to [4], wherein the third catalytic device is disposed upstream of the first catalytic device.

[0016] The present invention [9] includes the exhaust gas treatment system according to any one of [1] to [4], wherein the third catalytic device is disposed between the first catalytic device and the second catalytic device. [Effects of the Invention]

[0017] In the exhaust gas treatment system of the present invention, the first catalytic device is disposed upstream of the second catalytic device, so that exhaust gas passes through the first catalytic device before being introduced into the second catalytic device. Therefore, even if the temperature of the exhaust gas is low, the heat generated when ammonia is decomposed (oxidized) in the first catalytic device raises the temperature of the exhaust gas, allowing nitrous oxide to be decomposed highly efficiently in the second catalytic device.

[0018] In addition, in the exhaust gas treatment system of the present invention, the first catalytic device includes a first catalyst and a dummy catalyst. This allows a portion of the ammonia in the exhaust gas to be decomposed, and the remaining ammonia in the exhaust gas to be introduced into the second catalytic device without being decomposed. This makes it possible to maintain a constant ratio of the remaining ammonia even if the composition and / or flow rate of the exhaust gas fluctuates. Therefore, in the second catalytic device, ammonia can be used as a reducing agent when decomposing nitrous oxide, allowing for highly efficient decomposition of nitrous oxide.

[0019] Furthermore, in the exhaust gas treatment system of the present invention, the first catalytic device includes the first catalyst and a dummy catalyst, so that a constant proportion of ammonia can be introduced into the second catalytic device 21 without being decomposed, without providing a bypass in the exhaust passage, thereby simplifying the device configuration and saving space. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic configuration diagram showing an exhaust gas treatment system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a first catalyst device having a mixing unit in which a first catalyst and a dummy catalyst are alternately packed in a direction perpendicular to the flow direction of exhaust gas. [Figure 3] FIG. 3 is a perspective view showing a first catalyst device including a first unit filled with only the first catalyst and a dummy unit filled with only the dummy catalyst. [Figure 4] FIG. 4 is a schematic configuration diagram showing an exhaust gas treatment system according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a schematic configuration diagram showing an exhaust gas treatment system according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1. First embodiment A first embodiment of an exhaust gas treatment system 1 will be described with reference to FIG.

[0022] The exhaust gas treatment system 1 is a system for treating exhaust gas discharged from, for example, a combustion device.

[0023] The exhaust gas is an exhaust gas containing ammonia, nitrous oxide, and nitrogen oxides, and examples thereof include exhaust gas emitted from combustion devices that use ammonia fuel or a fuel obtained by mixing ammonia fuel with fossil fuel (e.g., gasoline or heavy oil), and exhaust gas emitted from chemical plants, power plants, etc. Examples of such combustion devices include internal combustion engines such as land engines and marine engines.

[0024] The composition of the exhaust gas (concentrations of oxygen, ammonia, nitrous oxide, and nitrogen oxides contained in the exhaust gas) is not particularly limited. As will be described later, for example, the oxygen concentration and ammonia concentration in the exhaust gas can vary depending on the combustion conditions of the combustion device, and there may be cases where the oxygen concentration in the exhaust gas is insufficient or where a sufficient amount of ammonia is not supplied. In such cases, the oxygen concentration and ammonia concentration in the exhaust gas can be appropriately changed by changing the combustion conditions of the combustion device or by supplying a reducing agent to the exhaust passage 10 using a reducing agent supply device, which will be described later.

[0025] The flow rate of the exhaust gas is not particularly limited. For example, the flow rate of the exhaust gas is 50,000 Nm 3 / h.

[0026] The temperature of the exhaust gas is not particularly limited. The inlet temperature of the exhaust gas is, for example, 300°C or higher, preferably 350°C or higher, and for example, 450°C or lower, preferably 400°C or lower.

[0027] In the following description, the upstream side and downstream side refer to the upstream side and downstream side in the flow direction of exhaust gas.

[0028] The exhaust gas treatment system 1 of the first embodiment includes an exhaust passage 10, a first catalytic device 11, a second catalytic device 21, and a third catalytic device 31. Specifically, the exhaust passage 10, the first catalytic device 11 disposed in the exhaust passage 10 and having a first catalyst 12 that decomposes ammonia and a dummy catalyst 13 that does not decompose ammonia, the second catalytic device 21 disposed in the exhaust passage 10 and having a second catalyst that decomposes nitrous oxide, and the third catalytic device 31 disposed in the exhaust passage 10 and having a third catalyst that reduces nitrogen oxides. The exhaust gas treatment system 1 according to the first embodiment includes the first catalytic device 11, the second catalytic device 21, and the third catalytic device 31, arranged in this order from upstream to downstream.

[0029] 1.1.Exhaust passage The upstream end (inlet) of the exhaust passage 10 is connected to an exhaust port for exhaust gas discharged from the combustion device. The exhaust gas discharged from the combustion device flows through the exhaust passage 10. The downstream end of the exhaust passage 10 is open to the outside air or is connected to a known aftertreatment device.

[0030] 1.2.First catalyst device The first catalytic device 11 is disposed in the exhaust passage 10 and includes a first catalyst 12 that decomposes (oxidizes) ammonia and a dummy catalyst 13 that does not decompose ammonia. When exhaust gas passes through the first catalytic device 11, a portion of the ammonia in the exhaust gas is decomposed, while the remaining portion of the ammonia in the exhaust gas is not decomposed. The first catalytic device 11 is disposed upstream of the second catalytic device 21.

[0031] <One embodiment of the first catalytic device> Referring to FIG. 2, an embodiment of the first catalytic device 11 will be described.

[0032] 2, the first catalyst device 11 includes, for example, a mixing unit 14. The mixing unit 14 includes a casing 41, and a first catalyst 12 and a dummy catalyst 13 packed in the casing 41.

[0033] The first catalytic device 11 includes a plurality of mixing units 14. The number of mixing units 14 in the first catalytic device 11 is not particularly limited as long as it is two or more, and is adjusted appropriately depending on the installation space of the exhaust gas treatment system 1, etc. The arrangement of the mixing units 14 is also not particularly limited as long as a plurality of mixing units 14 are arranged in a direction perpendicular to the flow direction of the exhaust gas. In one embodiment of the first catalytic device 11 shown in FIG. 2, the plurality of mixing units 14 are aligned in a first direction (e.g., width direction) perpendicular to the flow direction of the exhaust gas, and in a second direction (e.g., height direction) perpendicular to the flow direction of the exhaust gas and the first direction.

[0034] The shape of the casing 41 is not particularly limited, and examples thereof include a rectangular tube shape and a cylindrical shape extending in the exhaust gas flow direction. A rectangular tube shape extending in the exhaust gas flow direction is preferred. Specifically, the casing 41 may be one consisting of a casing main body that is generally U-shaped in cross section and a flat lid that covers the opening of the casing main body, one consisting of only a casing main body that is generally square-shaped in cross section, or one consisting of a casing main body that is generally L-shaped in cross section and a lid that fits into the casing and has a generally inverted L-shaped in cross section.

[0035] The dimensions of the casing 41 are adjusted appropriately depending on the application. Specifically, the widthwise length of the casing 41 is not particularly limited as long as it can accommodate the first catalyst 12 and / or the dummy catalyst 13. Furthermore, the heightwise length of the casing 41 is not particularly limited as long as it can ensure an appropriate number of stacked first catalysts 12 and / or dummy catalysts 13.

[0036] An inorganic fiber blanket 42 may be laid on the entire inner circumferential surface of the casing 41. By laying the inorganic fiber blanket 42 on the inner surface of the casing 41, vibrations can be suppressed.

[0037] Examples of inorganic fibers of the inorganic fiber blanket 42 include ceramic fibers, glass fibers, silica sol fibers, alumina fibers, and rock wool. Ceramic fibers are preferred.

[0038] In the mixing unit 14, the first catalysts 12 and the dummy catalysts 13 are alternately packed in a direction perpendicular to the flow direction of the exhaust gas (the height direction in FIG. 2 ) within the casing 41. Specifically, in the mixing unit 14, the first catalyst regions 15 and the dummy catalyst regions 16 are alternately stacked in the second direction (the height direction) within the casing 41.

[0039] The number of stacked first catalyst regions 15 and dummy catalyst regions 16 in the mixing unit 14 is not particularly limited, and may be the same or different.

[0040] In the first catalyst region 15, flat plate-shaped first catalysts 12 and corrugated plate-shaped first catalysts 12 are alternately stacked without being bonded, and in the dummy catalyst region 16, flat plate-shaped dummy catalysts 13 and corrugated plate-shaped dummy catalysts 13 are alternately stacked without being bonded. By being stacked in this manner, the first catalysts 12 and dummy catalysts 13 form a cross-sectional mesh structure (honeycomb structure).

[0041] There is no particular limitation on the number of stacked flat plate-shaped first catalysts 12 and corrugated plate-shaped first catalysts 12 in the first catalyst region 15. Specifically, there may be one set or multiple sets of flat plate-shaped first catalysts 12 and corrugated plate-shaped first catalysts 12.

[0042] There is no particular limitation on the number of stacked flat dummy catalysts 13 and corrugated dummy catalysts 13 in the dummy catalyst region 16. Specifically, there may be one set of flat dummy catalysts 13 and corrugated dummy catalysts 13, or multiple sets.

[0043] In the mixing unit 14, the ratio of the volume of the first catalyst 12 to the total volume of the first catalyst 12 and the dummy catalyst 13 is, for example, 60% or more, preferably 70% or more, and for example, 95% or less, preferably 85% or less.

[0044] In the mixing unit 14, the ratio of the volume of the dummy catalyst 13 to the total volume of the first catalyst 12 and the dummy catalyst 13 is, for example, 5% or more, preferably 15% or more, and for example, 40% or less, preferably 30% or less.

[0045] [First catalyst] As described above, the first catalyst 12 is arranged in a direction perpendicular to the flow direction of the exhaust gas and is disposed along the flow direction of the exhaust gas. The first catalyst 12 is in the form of a flat plate and / or a corrugated plate that is aligned along the flow direction of the exhaust gas.

[0046] The first catalyst 12 includes a first active metal that decomposes ammonia and a first support that supports the first active metal. When the exhaust gas comes into contact with the first catalyst 12, the ammonia in the exhaust gas can be decomposed.

[0047] The first active metal is not particularly limited as long as it can decompose (oxidize) ammonia into nitrogen and water. Examples of the first active metal include transition metals and non-transition metals, and preferably transition metals. Examples of transition metals include molybdenum, vanadium, tungsten, platinum, palladium, rhodium, ruthenium, iridium, manganese, copper, silver, cobalt, iron, and nickel. Preferably, platinum is used. The first active metal can be used alone or in combination of two or more types.

[0048] The first support may be, for example, an inorganic fiber sheet. Examples of the inorganic fiber sheet include glass paper and ceramic paper. Preferably, glass paper is used.

[0049] Commercially available glass paper containing organic binders can also be used, such as acrylic resin, polyvinyl alcohol (PVA)-polyvinyl acetate copolymer, unsaturated polyester resin, and epoxy resin.

[0050] The shape of the first support is, for example, a flat plate and / or a corrugated plate along the flow direction of the exhaust gas. In other words, the shape of the first support forms the shape of the first catalyst 12. The first support is preferably flat glass paper and / or corrugated glass paper along the flow direction of the exhaust gas. More preferably, it is flat glass paper along the flow direction of the exhaust gas and / or corrugated glass paper along the flow direction of the exhaust gas.

[0051] If the first catalyst 12 has a flat and / or corrugated shape aligned with the flow direction of the exhaust gas, the first active metal can be efficiently supported on the first support, and a sufficient contact area with the exhaust gas can be secured, thereby enabling efficient decomposition of ammonia.

[0052] The dimensions of the first support are adjusted appropriately depending on the application. Specifically, the length of the first support in the exhaust gas flow direction and the width direction are not particularly limited. The length of the first support in the exhaust gas flow direction is, for example, 100 mm to 2000 mm. The length of the first support in the width direction is, for example, 100 mm to 2000 mm.

[0053] The thickness of the first support is, for example, 0.1 mm to 1.0 mm.

[0054] The amount of the first active metal supported per unit volume of the first catalyst is, for example, 0.1 g / L or more, preferably 1 g / L or more, and for example, 10 g / L or less, preferably 5 g / L or less.

[0055] [Method for producing the first catalyst] The first catalyst 12 is formed, for example, by applying a slurry containing the first active metal to a first support and then firing the coating. Specifically, a sol (inorganic binder sol) in which an inorganic binder is dispersed in a dispersion medium is prepared. The first active metal is added to the inorganic binder sol to prepare a slurry containing the first active metal and the inorganic binder. The slurry containing the first active metal and the inorganic binder is applied to the first support, and is dried and fired as necessary, thereby obtaining the first catalyst 12 in which the first active metal is supported on the first support.

[0056] The inorganic binder increases the strength of the first support. Examples of inorganic binders include inorganic oxides. Examples of inorganic oxides include zeolite, titania, alumina, zirconia, and silica. Silica is preferred. The inorganic binders can be used alone or in combination of two or more types.

[0057] The dispersion medium is not particularly limited, and examples thereof include water and organic solvents.

[0058] The first catalyst 12 may contain additives other than the inorganic binder, if necessary.

[0059] Examples of methods for applying the slurry containing the first active metal to the first support include the so-called dipping method, brush coating method, spray coating method, and drop coating method. The brush coating method is preferred.

[0060] [Dummy catalyst] As described above, the dummy catalysts 13 are arranged in a direction perpendicular to the flow direction of the exhaust gas and are arranged along the flow direction of the exhaust gas. The dummy catalysts 13 are in the form of flat plates and / or corrugated plates that are aligned along the flow direction of the exhaust gas.

[0061] The dummy catalyst 13 includes a dummy carrier that does not support the first active metal that decomposes ammonia. That is, even if the exhaust gas comes into contact with the dummy catalyst 13, the ammonia in the exhaust gas is not decomposed.

[0062] Examples of the dummy carrier include the same first carriers as those described above for the first catalyst 12. Preferably, glass paper is used. The commercially available glass paper described above for the first catalyst 12 can be used as the glass paper.

[0063] The shape of the dummy support is, for example, a flat plate and / or a corrugated plate along the flow direction of the exhaust gas. In other words, the shape of the dummy support forms the shape of the dummy catalyst. The dummy support is preferably flat glass paper and / or corrugated glass paper along the flow direction of the exhaust gas. More preferably, it is flat glass paper along the flow direction of the exhaust gas and corrugated glass paper along the flow direction of the exhaust gas.

[0064] [Manufacturing method of dummy catalyst] The dummy catalyst 13 is formed, for example, by applying a slurry that does not contain the first active metal to a dummy carrier and then firing the slurry. Specifically, a sol (inorganic binder sol) in which an inorganic binder is dispersed in a dispersion medium is prepared. This inorganic binder sol is applied to a dummy carrier, and the dummy catalyst 13 can be obtained by drying and firing the dummy carrier as necessary.

[0065] The inorganic binder increases the strength of the dummy carrier. Examples of the inorganic binder include the same inorganic binders as those described above for the first catalyst 12. The inorganic binders can be used alone or in combination of two or more types.

[0066] Examples of the dispersion medium include the same dispersion medium as described above for the first catalyst 12.

[0067] The dummy catalyst 13 may contain additives other than the inorganic binder, if necessary.

[0068] The method for applying the slurry to the dummy carrier may be the same as the application method described for the first catalyst 12 above.

[0069] [Mixing unit manufacturing method] The flat first catalysts 12 manufactured as described above that are aligned with the flow direction of the exhaust gas and the corrugated first catalysts 12 that are aligned with the flow direction of the exhaust gas are alternately stacked in the height direction to form a first catalyst region 15. Similarly, the flat dummy catalysts 13 that are aligned with the flow direction of the exhaust gas and the corrugated dummy catalysts 13 that are aligned with the flow direction of the exhaust gas are alternately stacked in the height direction to form a dummy catalyst region 16.

[0070] The mixing unit 14 can be manufactured by alternately arranging the first catalyst regions 15 and the dummy catalyst regions 16 inside a casing 41 having an inorganic fiber blanket 42 laid over the entire inner circumferential surface thereof.

[0071] <Another embodiment of the first catalytic device> Another embodiment of the first catalytic device 11 will be described with reference to Fig. 3. Note that detailed description of the same configuration as the first catalytic device 11 of the above embodiment will be omitted.

[0072] 3, the first catalytic device 11 includes, for example, a first unit 17 and a dummy unit 18. The first unit 17 includes a casing 41 and a first catalyst 12 packed in the casing 41. The dummy unit 18 includes a casing 41 and a dummy catalyst 13 packed in the casing 41.

[0073] The first catalytic device 11 includes a plurality of first units 17 and a plurality of dummy units 18. In the first catalytic device 11, the number of each of the first units 17 and dummy units 18 is not particularly limited as long as it is one or more, and is adjusted appropriately depending on the installation space of the exhaust gas treatment system 1, etc. The arrangement of the first units 17 and dummy units 18 is also not particularly limited as long as they are arranged in a direction perpendicular to the flow direction of the exhaust gas. In another embodiment of the first catalytic device 11 shown in FIG. 3, the plurality of first units 17 and the plurality of dummy units 18 are arranged alternately in the width direction and the height direction.

[0074] When the first catalytic device 11 is equipped with a first unit 17 and a dummy unit 18, the ratio of the volume of the first unit 17 to the total volume of the first unit 17 and the dummy unit 18 in the first catalytic device 11 is, for example, 60% or more, preferably 70% or more, and, for example, 95% or less, preferably 85% or less.

[0075] When the first catalytic device 11 is equipped with a first unit 17 and a dummy unit 18, the ratio of the volume of the dummy unit 18 to the total volume of the first unit 17 and the dummy unit 18 in the first catalytic device 11 is, for example, 5% or more, preferably 15% or more, and, for example, 40% or less, preferably 30% or less.

[0076] The casing 41 may be the same as that described in the embodiment of the first catalytic device 11 above, for example.

[0077] In the first unit 17, the first catalyst 12 is packed in a direction perpendicular to the flow direction of exhaust gas within the casing 41. Specifically, the first unit 17 has only a first catalyst region 15 in which flat plate-shaped first catalysts 12 and corrugated plate-shaped first catalysts 12 are alternately stacked without being bonded within the casing 41. By stacking in this manner, the first catalyst 12 forms a cross-sectional network structure (honeycomb structure).

[0078] In the dummy unit 18, the dummy catalysts 13 are packed in a direction perpendicular to the flow direction of the exhaust gas within the casing 41. Specifically, the dummy unit 18 has only a dummy catalyst region 16 in the direction perpendicular to the flow direction of the exhaust gas within the casing 41, where flat dummy catalysts 13 and corrugated dummy catalysts 13 are alternately stacked without being bonded together. By stacking in this manner, the dummy catalysts 13 form a cross-sectional network structure (honeycomb structure).

[0079] In the first unit 17, the flat first catalysts 12 that are produced as described above and the corrugated first catalysts 12 that are produced as described above and that are also produced as corrugated first catalysts 12 that are produced as described above are alternately stacked in the height direction to form the first catalyst region 15. Then, the first unit 17 can be produced by disposing only the first catalyst region 15 inside a casing 41 whose entire inner circumferential surface is covered with an inorganic fiber blanket 42.

[0080] Similarly, in the dummy unit 18, flat dummy catalysts 13 aligned with the exhaust gas flow direction and corrugated dummy catalysts 13 aligned with the exhaust gas flow direction are alternately stacked in the height direction to form the dummy catalyst region 16. Then, the dummy unit 18 can be manufactured by placing only the dummy catalyst region 16 inside a casing 41 whose entire inner circumferential surface is covered with an inorganic fiber blanket 42.

[0081] 1.3.Second catalyst device The second catalytic device 21 is disposed in the exhaust passage 10 and has a second catalyst that decomposes nitrous oxide. The nitrous oxide in the exhaust gas is decomposed by the exhaust gas passing through the second catalytic device 21. The second catalytic device 21 is disposed downstream of the first catalytic device 11 and upstream of the third catalytic device 31.

[0082] The second catalytic converter 21 includes, for example, a second unit. The second unit includes a casing and a second catalyst packed in the casing.

[0083] The second catalytic device 21 includes a plurality of second units. The number of second units in the second catalytic device 21 is not particularly limited as long as it is two or more, and is adjusted appropriately depending on the installation space of the exhaust gas treatment system 1, etc. The arrangement of the second units is also not particularly limited as long as multiple second units are arranged in a direction perpendicular to the flow direction of the exhaust gas. The second units are preferably arranged in alignment in the width direction and height direction.

[0084] The casing 41 may be the same as that described in the embodiment of the first catalytic device 11 above, for example.

[0085] In the second unit, the second catalyst is packed in the casing in a direction perpendicular to the flow direction of the exhaust gas. Specifically, the second unit has only a second catalyst region in which flat second catalysts and corrugated second catalysts are alternately stacked without being bonded together. By stacking them in this manner, the second catalyst forms a cross-sectional mesh structure (honeycomb structure).

[0086] The number of stacked flat plate-shaped second catalysts and corrugated plate-shaped second catalysts in the second catalyst region is not particularly limited.

[0087] [Second catalyst] The second catalyst is arranged in a direction perpendicular to the flow direction of the exhaust gas and is disposed along the flow direction of the exhaust gas, and is in the form of a flat plate and / or a corrugated plate along the flow direction of the exhaust gas.

[0088] The second catalyst comprises a second active metal that decomposes nitrous oxide. When the exhaust gas comes into contact with the second catalyst, the nitrous oxide in the exhaust gas can be decomposed. Preferably, the second catalyst further comprises a second support that supports the second active metal.

[0089] The second active metal is not particularly limited as long as it can decompose nitrous oxide. Examples of the second active metal include transition metals and non-transition metals, and preferably transition metals. Examples of the transition metal include cobalt, nickel, and iron, and more preferably cobalt and iron. The second active metal can be used alone or in combination of two or more types.

[0090] The second catalyst may also contain a promoter component in addition to the second active metal.

[0091] Examples of the promoter component include alkali metals and alkaline earth metals, and preferably alkali metals.

[0092] Examples of the second support include the same first support as described above for the first catalyst 12. Preferably, glass paper is used. The commercially available glass paper described above for the first catalyst 12 can be used as the glass paper.

[0093] The shape of the second support may be, for example, the same as the shape of the first support described above for the first catalyst 12. In other words, the second support has the same shape as the second catalyst. The second support is preferably flat glass paper and / or corrugated glass paper aligned with the exhaust gas flow direction. More preferably, the second support is flat glass paper aligned with the exhaust gas flow direction and / or corrugated glass paper aligned with the exhaust gas flow direction.

[0094] If the second catalyst has a flat and / or corrugated shape aligned with the flow direction of the exhaust gas, the second active metal can be efficiently supported on the second support, and a sufficient contact area with the exhaust gas can be secured, thereby enabling efficient decomposition of nitrous oxide.

[0095] The dimensions of the second support are adjusted appropriately depending on the application. Specifically, the dimensions of the second support may be the same as those of the first support described above for the first catalyst 12.

[0096] The amount of the second active metal supported per unit volume of the second catalyst is, for example, 0.1 g / L or more, preferably 1 g / L or more, and for example, 10 g / L or less, preferably 5 g / L or less.

[0097] [Method for producing the second catalyst] The second catalyst is formed, for example, by applying a slurry containing the second active metal to a second support and then firing the coating. Specifically, a sol (inorganic binder sol) is prepared in which an inorganic binder is dispersed in a dispersion medium. The second active metal and a promoter component are added to the inorganic binder sol to prepare a slurry containing the second active metal, the promoter component, and the inorganic binder. The slurry containing the second active metal, the promoter component, and the inorganic binder is applied to a second support, and is dried and fired as necessary, thereby supporting the second active metal on the second support and obtaining the second catalyst.

[0098] The inorganic binder increases the strength of the first support, and examples of the inorganic binder include the same inorganic binders as those described for the first catalyst 12 above.

[0099] The dispersion medium is not particularly limited, and examples thereof include the same dispersion medium as described above for the first catalyst 12.

[0100] The second catalyst may contain additives other than the promoter component and the inorganic binder, if necessary.

[0101] The method for applying the slurry containing the second active metal to the second support may be, for example, the same application method as described above for the first catalyst.

[0102] [Manufacturing method of the second unit] In the second unit, the flat second catalysts manufactured as described above that are aligned with the flow direction of the exhaust gas and the corrugated second catalysts that are aligned with the flow direction of the exhaust gas are alternately stacked in the height direction to form a second catalyst region.The second unit can then be manufactured by placing only the second catalyst region inside a casing whose entire inner surface is covered with an inorganic fiber blanket.

[0103] 1.4.Third catalyst device The third catalytic device 31 is disposed in the exhaust passage 10 and has a third catalyst that decomposes nitrogen oxides. The nitrogen oxides in the exhaust gas can be decomposed by the exhaust gas passing through the third catalytic device 31. The third catalytic device 31 is disposed downstream of the second catalytic device 21.

[0104] The third catalytic converter 31 includes, for example, a third unit. The third unit includes a casing 41 and a third catalyst packed in the casing 41.

[0105] The third catalytic device 31 includes a plurality of third units. The number of third units in the third catalytic device 31 is not particularly limited as long as it is two or more, and is adjusted appropriately depending on the installation space of the exhaust gas treatment system 1, etc. The arrangement of the third units is also not particularly limited as long as multiple third units are arranged in a direction perpendicular to the flow direction of the exhaust gas. The third units are preferably arranged in alignment in the width direction and height direction.

[0106] The casing 41 may be the same as that described in the embodiment of the first catalytic device 11 above, for example.

[0107] In the third unit, the third catalyst is packed in the casing in a direction perpendicular to the flow direction of the exhaust gas. Specifically, the third unit has only a third catalyst region in which flat and corrugated third catalysts are alternately stacked without being bonded together. Packed in this manner, the third catalyst forms a cross-sectional mesh structure (honeycomb structure).

[0108] The number of stacked flat plate-shaped third catalysts and corrugated plate-shaped third catalysts in the third catalyst region is not particularly limited.

[0109] [Third catalyst] The third catalyst is arranged in a direction perpendicular to the flow direction of the exhaust gas and is disposed along the flow direction of the exhaust gas, and is in the form of a flat plate and / or a corrugated plate along the flow direction of the exhaust gas.

[0110] The third catalyst comprises a third active metal that decomposes nitrogen oxides. When exhaust gas comes into contact with the third catalyst, the nitrogen oxides in the exhaust gas can be decomposed. Preferably, the third catalyst further comprises a third support that supports the third active metal.

[0111] The third active metal is not particularly limited as long as it can decompose nitrogen oxides. Examples of the third active metal include transition metals and non-transition metals, and preferably transition metals. Examples of the transition metal include molybdenum, vanadium, tungsten, nickel, cobalt, and iron. The third active metal can be used alone or in combination of two or more types.

[0112] Examples of the third support include the same first support as described above for the first catalyst 12. Preferably, glass paper is used. The commercially available glass paper described above for the first catalyst 12 can be used as the glass paper.

[0113] The shape of the third support may be, for example, the same as the shape of the first support described above for the first catalyst 12. In other words, the shape of the third support defines the shape of the third catalyst. The third support is preferably flat glass paper and / or corrugated glass paper aligned with the exhaust gas flow direction. More preferably, the third support is flat glass paper aligned with the exhaust gas flow direction and / or corrugated glass paper aligned with the exhaust gas flow direction.

[0114] If the third catalyst has a flat and / or corrugated shape aligned with the flow direction of exhaust gas, the third active metal can be efficiently supported on the third support, and a sufficient contact area with the exhaust gas can be secured, thereby enabling efficient decomposition of nitrogen oxides.

[0115] The dimensions of the third support are adjusted appropriately depending on the application. Specifically, the dimensions of the third support may be the same as those of the first support described above for the first catalyst 12.

[0116] The amount of the third active metal supported per unit volume of the third catalyst is, for example, 0.1 g / L or more, preferably 1 g / L or more, and for example, 10 g / L or less, preferably 5 g / L or less.

[0117] [Method for producing the third catalyst] The third catalyst is formed, for example, by applying a slurry containing a third active metal to a third support and then firing the slurry. Specifically, a sol (inorganic binder sol) in which an inorganic binder is dispersed in a dispersion medium is prepared. The third active metal is added to the inorganic binder sol to prepare a slurry containing the third active metal and the inorganic binder. The slurry containing the third active metal and the inorganic binder is applied to a third support, and is dried and fired as necessary, thereby supporting the third active metal on the third support and obtaining the third catalyst.

[0118] The inorganic binder increases the strength of the third support, and examples of the inorganic binder include the same inorganic binders as those described for the first catalyst 12 above.

[0119] The dispersion medium is not particularly limited, and examples thereof include the same dispersion medium as described above for the first catalyst 12.

[0120] The third catalyst may contain additives other than the inorganic binder, if necessary.

[0121] The method for applying the slurry containing the third active metal to the third support may be, for example, the same application method as described above for the first catalyst 12.

[0122] [Manufacturing method of the third unit] In the third unit, the flat third catalysts manufactured as described above that are aligned with the exhaust gas flow direction and the corrugated third catalysts that are aligned with the exhaust gas flow direction are alternately stacked in the height direction to form a third catalyst region.The third unit can then be manufactured by placing only the third catalyst region inside a casing whose entire inner surface is covered with an inorganic fiber blanket.

[0123] 1.5.Other Configurations Although not shown, the exhaust gas treatment system 1 may further include a concentration sensor, a reducing agent supply device, and a control unit.

[0124] [Concentration sensor] An example of a concentration sensor is a non-contact gas concentration meter that detects the oxygen concentration or ammonia concentration in exhaust gas.

[0125] The location of the concentration sensor is not particularly limited. The concentration sensor is disposed in the exhaust passage 10 upstream of at least one of the first catalytic converter 11, the second catalytic converter 21, and the third catalytic converter. The concentration sensor is electrically connected to a control unit, which will be described later.

[0126] The concentration sensor detects the oxygen concentration in the exhaust gas, and the control unit can change the combustion conditions of the combustion device.

[0127] The concentration sensor detects the ammonia concentration in the exhaust gas, and the control unit controls the reducing agent supply device (described later) to supply an appropriate amount of reducing agent.

[0128] [Reducing agent supply device] The arrangement of the reducing agent supply device as the reducing agent supply unit is not particularly limited. The reducing agent supply device is connected to the exhaust passage 10 downstream of the concentration sensor and upstream of at least one of the first catalytic device 11, the second catalytic device 21, and the third catalytic device. The reducing agent supply device is also electrically connected to a control unit, which will be described later.

[0129] Although not shown, the reducing agent supply device may be configured to supply a reducing agent to the exhaust passage 10, and may include, for example, a tank for storing the reducing agent, a metering pump for supplying the reducing agent to the exhaust passage 10, and a valve. The reducing agent supply device supplies the reducing agent to the exhaust passage 10 by, for example, adjusting the flow rate of the metering pump and the opening degree of the valve according to the supply amount.

[0130] Examples of the reducing agent supplied from the reducing agent supply device include ammonia gas, ammonia water, and urea water.

[0131] [Control unit] The control unit is a unit that performs electrical control in the exhaust gas treatment system 1. The control unit is composed of a microcomputer that includes a central processing unit (CPU), a memory unit, etc. The control unit controls the exhaust gas treatment system 1 based on a control program stored in the memory unit.

[0132] Furthermore, the control unit is electrically connected to the concentration sensor and the reducing agent supply device as described above.

[0133] The control unit adjusts the supply amount of the reducing agent supplied from the reducing agent supply device based on the concentration of ammonia detected by the concentration sensor.

[0134] 1.5.Effects In the first embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the second catalytic device 21 and includes a first catalytic region 15. As a result, when exhaust gas passes through the first catalytic device 11, a portion of the ammonia in the exhaust gas is decomposed by the first catalyst 12. Therefore, compared to conventional exhaust gas treatment systems, even if the temperature of the exhaust gas is low, the heat generated when the ammonia is decomposed (oxidized) in the first catalytic device increases the temperature of the exhaust gas, allowing nitrous oxide to be decomposed highly efficiently in the second catalytic device 21. Furthermore, the ammonia concentration in the exhaust gas introduced into the second catalytic device 21 and the third catalytic device 31 is prevented from becoming excessively high, allowing nitrous oxide and nitrogen oxide to be decomposed highly efficiently.

[0135] In the first embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the second catalytic device 21 and the third catalytic device 31 and includes a dummy catalytic region 16. Therefore, even when exhaust gas passes through the first catalytic device 11, the remaining ammonia in the exhaust gas is not decomposed by the dummy catalyst 13. This allows the second catalytic device 21 and the third catalytic device 31 to use ammonia as a reducing agent when decomposing nitrous oxide and reducing nitrogen oxide, thereby enabling highly efficient decomposition of nitrous oxide and nitrogen oxide. Furthermore, even if the composition and / or flow rate of the exhaust gas fluctuates, the first catalytic device 11 allows a constant proportion of ammonia to be introduced into the second catalytic device 21 and the third catalytic device 31 without being decomposed, enabling highly efficient decomposition of nitrous oxide and nitrogen oxide.

[0136] In the first embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 includes a first catalyst 12 and a dummy catalyst 13. Therefore, a constant proportion of ammonia can be introduced into the second catalytic device 21 and the third catalytic device 31 without being decomposed, without providing a bypass in the exhaust passage 10, thereby simplifying the device configuration and saving space.

[0137] In the first embodiment of the exhaust gas treatment system of the present invention, the first catalyst device 11 includes a first catalyst 12 and a dummy catalyst 13, which are aligned in a direction perpendicular to the flow direction of the exhaust gas, and which are arranged so that the first catalyst 12 and the dummy catalyst 13 are aligned along the flow direction of the exhaust gas. As a result, all of the exhaust gas passages in the first catalyst device 11 are parallel, which makes it possible to equalize the pressure loss in each of the passages, and allows the ratio of the dummy catalyst 13 to the first catalyst 12 to be designed easily and accurately.

[0138] In the first embodiment of the exhaust gas treatment system of the present invention, if the first catalytic device 11 is equipped with only the mixing unit 14, the concentration distribution of ammonia that passes through the first catalytic device 11 without being decomposed in the exhaust gas is narrow. Therefore, it is possible to shorten the distance between the first catalytic device 11 and the second catalytic device 21 arranged downstream of the first catalytic device 11 (the length of the exhaust passage 10 between the first catalytic device 11 and the second catalytic device 21 arranged downstream of the first catalytic device). Consequently, it is possible to save space in the exhaust gas treatment system 1.

[0139] 2. Second embodiment A second embodiment of the exhaust gas treatment system 1 will be described with reference to Fig. 4. Note that detailed descriptions of the same configurations as those of the first embodiment of the exhaust gas treatment system 1 will be omitted.

[0140] The exhaust gas treatment system 1 of the second embodiment is provided with, in order from the upstream side to the downstream side, a third catalytic device 31, a first catalytic device 11, and a second catalytic device 21. In other words, the first catalytic device 11 is disposed downstream of the third catalytic device 31, and the second catalytic device 21 is disposed downstream of the first catalytic device 11.

[0141] 2.1.Effects In the second embodiment of the exhaust gas treatment system of the present invention, the third catalytic device 31 is disposed upstream of the first catalytic device 11. That is, the exhaust gas is introduced into the third catalytic device 31 before passing through the first catalytic device 11. Therefore, the third catalytic device 31 can use ammonia in the exhaust gas as a reducing agent, and can decompose nitrogen oxides with high efficiency. Furthermore, depending on the temperature of the exhaust gas, nitrogen oxides can be decomposed with even higher efficiency.

[0142] In the second embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the second catalytic device 21 and includes a first catalytic region 15. As a result, when exhaust gas passes through the first catalytic device 11, a portion of the ammonia in the exhaust gas is decomposed by the first catalyst 12. Therefore, compared to conventional exhaust gas treatment systems, even if the temperature of the exhaust gas is low, the heat generated when the ammonia is decomposed (oxidized) in the first catalytic device increases the temperature of the exhaust gas, allowing nitrous oxide to be decomposed highly efficiently in the second catalytic device 21. Furthermore, the ammonia concentration in the exhaust gas introduced into the second catalytic device 21 is prevented from becoming excessively high, allowing nitrous oxide to be decomposed highly efficiently.

[0143] In the second embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the second catalytic device 21 and includes a dummy catalytic region 16. Therefore, even when exhaust gas passes through the first catalytic device 11, the remaining ammonia in the exhaust gas is not decomposed by the dummy catalyst 13. This allows the second catalytic device 21 to use ammonia as a reducing agent when decomposing nitrous oxide, thereby enabling highly efficient decomposition of nitrous oxide. Furthermore, even if the composition and / or flow rate of the exhaust gas fluctuates, the first catalytic device 11 allows a constant proportion of ammonia to be introduced into the second catalytic device 21 without being decomposed, enabling highly efficient decomposition of nitrous oxide.

[0144] In the second embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 includes a first catalyst 12 and a dummy catalyst 13. Therefore, a constant proportion of ammonia can be introduced into the second catalytic device 21 without being decomposed, without providing a bypass in the exhaust passage 10, thereby simplifying the device configuration and saving space.

[0145] In a second embodiment of the exhaust gas treatment system of the present invention, the first catalyst device 11 includes a first catalyst 12 and a dummy catalyst 13, which are aligned in a direction perpendicular to the flow direction of the exhaust gas, and which are respectively arranged along the flow direction of the exhaust gas. As a result, all of the exhaust gas passages in the first catalyst device 11 are parallel, making it possible to equalize pressure loss in all of the passages, and enabling the ratio of the dummy catalyst 13 to the first catalyst 12 to be designed easily and accurately.

[0146] In the second embodiment of the exhaust gas treatment system of the present invention, if the first catalytic device 11 is equipped with only the mixing unit 14, the concentration distribution of ammonia that passes through the first catalytic device 11 without being decomposed in the exhaust gas is narrow. This makes it possible to shorten the distance between the first catalytic device 11 and the second catalytic device 21 located downstream of the first catalytic device 11 (the length of the exhaust passage 10 between the first catalytic device 11 and the second catalytic device 21 located downstream of the first catalytic device). This in turn makes it possible to save space in the exhaust gas treatment system 1.

[0147] 3. Third embodiment A third embodiment of the exhaust gas treatment system 1 will be described with reference to Fig. 5. Note that detailed descriptions of the same configurations as those of the first embodiment of the exhaust gas treatment system 1 will be omitted.

[0148] The exhaust gas treatment system 1 of the third embodiment is provided with, in order from the upstream side to the downstream side, a first catalytic device 11, a third catalytic device 31, and a second catalytic device 21. In other words, the third catalytic device 31 is disposed downstream of the first catalytic device 11, and the second catalytic device 21 is disposed downstream of the third catalytic device 31.

[0149] 3.1.Effects In the third embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the second catalytic device 21 and includes a first catalytic region 15. As a result, when exhaust gas passes through the first catalytic device 11, a portion of the ammonia in the exhaust gas is decomposed by the first catalyst 12. Therefore, compared to conventional exhaust gas treatment systems, even if the temperature of the exhaust gas is low, the heat generated when the ammonia is decomposed (oxidized) in the first catalytic device increases the temperature of the exhaust gas, allowing nitrous oxide to be decomposed highly efficiently in the second catalytic device 21. Furthermore, the ammonia concentration in the exhaust gas introduced into the third catalytic device 31 and the second catalytic device 21 is prevented from becoming excessively high, and nitrogen oxides and nitrous oxides can be decomposed highly efficiently.

[0150] In a third embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 is disposed upstream of the third catalytic device 31 and the second catalytic device 21 and includes a dummy catalytic region 16. Therefore, even when exhaust gas passes through the first catalytic device 11, the remaining ammonia in the exhaust gas is not decomposed by the dummy catalyst 13. This allows the third catalytic device 31 and the second catalytic device 21 to use ammonia as a reducing agent for reducing nitrogen oxides and decomposing nitrous oxide, thereby enabling highly efficient decomposition of nitrogen oxides and nitrous oxide. Furthermore, even if the composition and / or flow rate of the exhaust gas fluctuates, the first catalytic device 11 allows a constant proportion of ammonia to be introduced into the third catalytic device 31 and the second catalytic device 21 without being decomposed, enabling highly efficient decomposition of nitrogen oxides and nitrous oxide.

[0151] In the third embodiment of the exhaust gas treatment system of the present invention, the first catalytic device 11 includes a first catalyst 12 and a dummy catalyst 13. Therefore, a constant proportion of ammonia can be introduced into the third catalytic device 31 and the second catalytic device 21 without being decomposed, without providing a bypass in the exhaust passage 10, thereby simplifying the device configuration and saving space.

[0152] In a third embodiment of the exhaust gas treatment system of the present invention, the first catalyst device 11 includes a first catalyst 12 and a dummy catalyst 13, which are aligned in a direction perpendicular to the flow direction of the exhaust gas, and which are arranged so that the first catalyst 12 and the dummy catalyst 13 are aligned along the flow direction of the exhaust gas. As a result, all of the exhaust gas passages in the first catalyst device 11 are parallel, which makes it possible to equalize the pressure loss in each of the passages, and allows the ratio of the dummy catalyst 13 to the first catalyst 12 to be designed easily and accurately.

[0153] In the third embodiment of the exhaust gas treatment system of the present invention, if the first catalytic device 11 is equipped with only the mixing unit 14, the concentration distribution of ammonia that passes through the first catalytic device 11 without being decomposed in the exhaust gas is narrow. Therefore, it is possible to shorten the distance between the first catalytic device 11 and the third catalytic device 31 located downstream of the first catalytic device 11 (the length of the exhaust passage 10 between the first catalytic device 11 and the third catalytic device 31 located downstream of the first catalytic device). Consequently, it is possible to save space in the exhaust gas treatment system 1.

[0154] 4. Variations In the modified example, the same components and steps as those of the first embodiment of the exhaust gas treatment system are denoted by the same reference numerals, and detailed description thereof will be omitted. Furthermore, the modified example can achieve the same effects as the first embodiment of the exhaust gas treatment system, unless otherwise specified. Furthermore, the first to third embodiments of the exhaust gas treatment system and the modified example can be combined as appropriate.

[0155] [Variation 1] In the first embodiment of the exhaust gas treatment system described above, an inorganic fiber sheet is used as the first support for supporting the first active metal in the first catalyst 12, but this is not limiting. Specifically, an inorganic oxide may also be used as the first support for supporting the first active metal. In this case, an inorganic binder is not used.

[0156] Inorganic oxides include zeolites, titania, alumina, zirconia, and silica.

[0157] Methods for supporting the first active metal on an inorganic oxide include, for example, an impregnation method, a co-precipitation method, a kneading method, and an alkoxide method.

[0158] The first catalyst 12 may optionally include an additive.

[0159] The first catalyst 12 is obtained by supporting the first active metal on an inorganic oxide using the method described above, and then molding the composition containing the first active metal and the inorganic oxide supporting the first active metal into a pellet shape, a honeycomb structure, or the like by extrusion molding or the like.

[0160] The dummy catalyst 13, the second catalyst, and the third catalyst can be obtained in the same manner. The dummy catalyst 13 is obtained by molding a composition containing an inorganic oxide that does not support the first active metal into a pellet shape, a honeycomb structure, or the like by extrusion molding or the like.

[0161] The first catalyst 12 and dummy catalyst 13 manufactured as described above make it difficult to pack the first catalyst region 15 and the dummy catalyst region 16 separately within a single casing. In other words, the first catalyst 12 and dummy catalyst 13 manufactured as described above cannot form a mixing unit 14. Therefore, when the first catalyst 12 and dummy catalyst 13 manufactured as described above are used, the first catalyst device 11 includes a first unit 17 and a dummy unit 18, as shown in FIG. 3 .

[0162] [Variation 2] In the first embodiment of the exhaust gas treatment system described above, the first catalytic device 11 may, for example, include only the mixing unit 14 as shown in Fig. 2, or include the first unit 17 and the dummy unit 18 as shown in Fig. 3, but is not limited to this. Specifically, the first catalytic device 11 may include the mixing unit 14 and the first unit 17, the mixing unit 14 and the dummy unit 18, or the mixing unit 14, the first unit 17, and the dummy unit 18.

[0163] [Variation 3] In the first embodiment of the exhaust gas treatment system described above, in other embodiments of the first catalytic device 11, the first units 17 and the dummy units 18 are arranged alternately in the width direction and the height direction as shown in Fig. 3, but this is not limited to this. Specifically, only the first units 17 or only the dummy units 18 may be provided in the width direction, only the first units 17 or only the dummy units 18 may be provided in the height direction, or the first units 17 or the dummy units 18 may be provided so as to be partially continuous in the width direction and / or the height direction. [Explanation of symbols]

[0164] 1. Exhaust gas treatment system 11 First catalyst device 12 First catalyst 13 Dummy catalyst 21 Second catalyst device 31 Third catalyst device

Claims

1. An exhaust gas treatment system for treating exhaust gas containing ammonia, nitrous oxide, and nitrogen oxides, comprising: an exhaust passage through which the exhaust gas flows; a first catalyst device interposed in the exhaust passage and having a first catalyst that decomposes ammonia and a dummy catalyst that does not decompose ammonia; a second catalyst device disposed in the exhaust passage and having a second catalyst for decomposing nitrous oxide; a third catalyst device disposed in the exhaust passage and having a third catalyst for reducing nitrogen oxides; Equipped with the first catalytic converter is disposed upstream of the second catalytic converter; the first catalyst comprises a first active metal that decomposes ammonia and a first support that supports the first active metal; The dummy catalyst includes a dummy carrier that does not support the first active metal.

2. the first catalyst and the dummy catalyst are aligned in a direction perpendicular to the flow direction of the exhaust gas, The exhaust gas treatment system according to claim 1 , wherein the first catalyst and the dummy catalyst are each disposed along a flow direction of the exhaust gas.

3. the first catalyst device includes a mixing unit in which the first catalyst and the dummy catalyst are alternately filled in a direction perpendicular to a flow direction of the exhaust gas, The exhaust gas treatment system according to claim 1 , wherein a plurality of the mixing units are arranged in a direction perpendicular to the flow direction of the exhaust gas.

4. the first catalyst device includes a first unit filled with only the first catalyst and a dummy unit filled with only the dummy catalyst, The exhaust gas treatment system according to claim 1 , wherein a plurality of the first units and a plurality of the dummy units are arranged in a direction perpendicular to the flow direction of the exhaust gas.

5. 5. The exhaust gas treatment system according to claim 1, wherein the first catalyst and the dummy catalyst each have a flat plate shape and / or a corrugated plate shape extending along the flow direction of the exhaust gas.

6. 6. The exhaust gas treatment system according to claim 5, wherein each of the first support and the dummy support is a flat glass paper and / or a corrugated glass paper extending along the flow direction of the exhaust gas.

7. 5. The exhaust gas treatment system according to claim 1, wherein the third catalytic converter is disposed downstream of the second catalytic converter.

8. 5. The exhaust gas treatment system according to claim 1, wherein the third catalytic device is disposed upstream of the first catalytic device.

9. 5. The exhaust gas treatment system according to claim 1, wherein the third catalytic converter is disposed between the first catalytic converter and the second catalytic converter.

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