Title of invention: Denitration device
Technical field
[0001]
　The present invention relates to a denitration device for purifying exhaust gas from a boiler.
Background technology
[0002]
　In a thermal power plant that burns fuel with a boiler to generate electricity, the exhaust gas from the boiler is purified by a flue gas treatment system and then discharged into the atmosphere. The flue gas treatment system includes a denitration device that reduces and removes nitrogen oxides (NOx) in the exhaust gas, an air preheater that heats the combustion air by exchanging heat with the exhaust gas, and soot dust (combustion ash) in the exhaust gas. An electrostatic precipitator for collecting and removing is installed.
[0003]
　Patent Document 1 describes that nitrogen oxides are used as a reducing agent in the first or second stage of a NOx purification catalyst that reduces and purifies nitrogen oxides in exhaust gas using carbon monoxide or hydrocarbons in exhaust gas, using ammonia (NH 3 ) as a reducing agent. An exhaust gas purification device is disclosed in which a reducing catalyst (ammonia denitration catalyst) is installed and ammonia is blown into the exhaust gas before the ammonia denitration catalyst.
Prior art literature
Patent documents
[0004]
Patent Document 1: Japanese Unexamined Patent Publication No. 2008-238069
Outline of the invention
Problems to be solved by the invention
[0005]
　In the case of a denitration device using a catalyst that uses ammonia as a reducing agent, if the temperature of the exhaust gas flowing into the denitration device is low, acidic ammonium sulfate (ammonium hydrogensulfate: NH 4 HSO 4 ) is generated and the device on the downstream side of the denitration device. It may adhere to and accumulate on (for example, an air preheater), causing deterioration or malfunction of the device (for example, blockage of the air preheater). Further, if the mixture of fuel and combustion air is poor, the concentration of carbon monoxide in the exhaust gas becomes high, so that it is necessary to reduce carbon monoxide.
[0006]
　On the other hand, in a denitration device using a denitration catalyst using ammonia as a reducing agent (ammonia denitration catalyst) and a denitration catalyst using carbon monoxide as a reducing agent (carbon monoxide denitration catalyst) as in Patent Document 1, ammonia is used. The amount of ammonia injected into the exhaust gas can be reduced as compared with the case where only the denitration catalyst is used. Therefore, it becomes difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acidic ammonium sulfate on the equipment on the downstream side of the denitration apparatus. Further, since the carbon monoxide denitration catalyst using carbon monoxide as a reducing agent is provided, carbon monoxide in the exhaust gas can be reduced.
[0007]
　However, the carbon monoxide concentration of the exhaust gas flowing through the denitration device is not uniform in the cross section of the flow path, and there are low and high concentrations, and in the low carbon monoxide concentration, nitrogen produced by the carbon monoxide denitration catalyst is used. The reduction and removal of oxides are not effectively performed, and the effect of the carbon monoxide denitration catalyst cannot be obtained. That is, arranging the carbon monoxide denitration catalyst over the entire cross section of the flow path raises the cost more than necessary.
[0008]
　Therefore, the present invention provides a denitration device capable of suppressing the adhesion and deposition of acidic ammonium sulfate on the equipment on the downstream side of the denitration device and reducing carbon monoxide in the exhaust gas, while suppressing the increase in cost. The purpose.
Means to solve problems
[0009]
　In order to achieve the above object, the denitration device according to the first aspect of the present invention includes a gas flow passage, a first catalyst layer, a second catalyst layer, and a reducing agent injection means.
[0010]
　The gas flow passage has a rectangular cross section, and the exhaust gas discharged from the boiler flows through the gas flow passage. The first catalyst layer is arranged in the gas flow passage and carries a first catalyst that reduces and removes nitrogen oxides in the exhaust gas using ammonia as a reducing agent. The second catalyst layer is arranged in at least one gas flow passage on the upstream side or the downstream side of the first catalyst layer, and carries a second catalyst that reduces and removes nitrogen oxides in the exhaust gas using carbon monoxide as a reducing agent. .. The reducing agent injection means injects ammonia into the exhaust gas flowing through the gas flow passage on the upstream side of the first catalyst layer.
[0011]
　The second catalyst layer is arranged at at least four corners of the flow path cross section of the gas flow path to support the second catalyst, and is arranged at the center of the flow path cross section of the gas flow path. It has two catalyst-non-catalyst-supported regions, and is configured so that the pressure loss of the flowing exhaust gas is equivalent over the entire area of ​​the flow path cross section including the catalyst-supported region and the catalyst-non-supported region.
[0012]
　In the above configuration, the nitrogen oxide in the exhaust gas is reduced and removed by using a first catalyst using ammonia as a reducing agent (ammonia denitration catalyst) and a second catalyst using carbon monoxide as a reducing agent (carbon monoxide denitration catalyst). Therefore, the amount of ammonia injected into the exhaust gas from the reducing agent injection means can be reduced as compared with the case where only the ammonia denitration catalyst is used. Therefore, it is difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acidic ammonium sulfate on a device (for example, an air preheater) on the downstream side of the denitration device.
[0013]
　Since the cross section of the gas flow path is rectangular, the carbon monoxide concentration of the exhaust gas flowing into the second catalyst layer tends to be high at the four corners and low at the center, and this tendency is taken into consideration. The corner portion where the carbon monoxide concentration is high is the catalyst-supporting region, and the central portion where the carbon monoxide concentration is low is the catalyst-non-supporting region. In this way, the second catalyst is placed in the corner where the reduction and removal of nitrogen oxides by the second catalyst (carbon monoxide denitration catalyst) can be expected, and the second catalyst is in the central part where the reduction and removal of nitrogen oxides cannot be expected. Since no catalyst is arranged, it is possible to suppress an increase in cost due to the material cost of the second catalyst.
[0014]
　Further, since the second catalyst layer is configured so that the pressure loss of the flowing exhaust gas is the same in the entire flow path cross section including the catalyst-supported region and the catalyst-non-supported region, the second catalyst layer is formed at the inlet of the second catalyst layer. The flow direction of exhaust gas does not fluctuate significantly. Therefore, the exhaust gas having a high carbon monoxide concentration can be distributed to the catalyst-supporting region, and the exhaust gas having a low carbon monoxide concentration can be distributed to the catalyst-non-supporting region.
[0015]
　A second aspect of the present invention is the denitration device of the first aspect, wherein the catalyst-supporting region of the second catalyst layer is an annular shape along the outer peripheral edge of the flow path cross section of the gas flow passage, and is a catalyst-non-supporting region. Is an inner region surrounded by an annular catalyst-supporting region.
[0016]
　In the above configuration, since the flow path cross section of the gas flow path is rectangular, the carbon monoxide concentration of the exhaust gas flowing into the second catalyst layer is determined by the annular outer peripheral edge portion (four points) along the outer peripheral edge of the flow path cross section. (Including corners) is high, and the inner region (central portion) surrounded by the outer peripheral edge tends to be lower. In consideration of this tendency, the outer peripheral edge having a high carbon monoxide concentration is used as the catalyst-supporting region. The inner region where the carbon monoxide concentration is low is defined as the catalyst non-supporting region. Therefore, the reduction and removal of nitrogen oxides can be performed in a wider range than in the case where the second catalyst is arranged only in the four corners.
[0017]
　A third aspect of the present invention is the denitration device of the first or second aspect, which includes an exhaust gas cooling means for cooling the exhaust gas. The second catalyst layer is arranged in the gas flow passage on the downstream side of the first catalyst layer, and the exhaust gas cooling means is the exhaust gas flowing through the gas flow passage on the downstream side of the first catalyst layer and on the upstream side of the second catalyst layer. To cool.
[0018]
　In the above configuration, even when the temperature of the exhaust gas flowing on the upstream side of the second catalyst layer is higher than the activation temperature of the second catalyst, the exhaust gas flowing through the second catalyst layer is subjected to the second catalyst by the exhaust gas cooling means. The temperature can be lowered to the activation temperature of the above, and the reduction and removal of nitrogen oxides using a second catalyst can be preferably performed.
[0019]
　Further, since the temperature of the exhaust gas is lowered on the downstream side of the first catalyst layer, the reduction of nitrogen oxides using the first catalyst when the activation temperature of the first catalyst is higher than the activation temperature of the second catalyst. Both removal and reduction and removal of nitrogen oxides using a second catalyst can be preferably performed.
Effect of the invention
[0020]
　According to the present invention, it is possible to suppress the adhesion and deposition of acidic ammonium sulfate on the equipment on the downstream side of the denitration device and reduce the amount of carbon monoxide in the exhaust gas while suppressing the increase in cost.
A brief description of the drawing
[0021]
FIG. 1 is a schematic diagram of a flue gas treatment system including a denitration device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a schematic configuration of the denitration device of FIG.
3A and 3B are cross-sectional views taken along the flow path cross section of the second catalyst layer of FIG. 2, where FIG. 3A is a case where a rectangular annular outer peripheral edge portion is used as a catalyst-supporting region, and FIG. The case where only the part is used as the catalyst supporting region is shown.
4A and 4B are enlarged perspective views of part IV of FIG. 3A, in which FIG. 4A is an example in which a second catalyst layer is composed of a porous structure, and FIG. 3B is a plate-shaped catalyst unit in which the second catalyst layer is formed. An example configured by is shown below.
5A and 5B are perspective views of a structure constituting the second catalyst layer, FIG. 5A is a porous body constituting the porous structure of FIG. 4A, and FIG. 5B is a plate of FIG. 4B. The state catalyst units are shown respectively.
6A and 6B are enlarged cross-sectional views of the second catalyst layer of FIG. 5A, in which FIG. 6A shows a catalyst-supporting region and FIG.
FIG. 7 is a cross-sectional view of a modified example of the denitration device.
Mode for carrying out the invention
[0022]
　The denitration device according to the embodiment of the present invention will be described with reference to the drawings. The arrow Df in the figure indicates the flow direction of the exhaust gas.
[0023]
　As shown in FIG. 1, the flue gas treatment system that purifies the exhaust gas from the boiler (coal-cooked boiler) 1 and discharges it into the atmosphere includes a denitration device 2, an air preheater (AH: air heater) 3, and an electrostatic precipitator 4. And an attracting blower 5 is provided. The boiler 1 may be a boiler other than coal-cooking.
[0024]
　The denitration device 2 is arranged downstream of the boiler 1 and reduces and removes nitrogen oxides (NOx) in the exhaust gas. The air preheater 3 is arranged downstream of the denitration device 2 and heats the combustion air by heat exchange with the exhaust gas. The electrostatic precipitator 4 is arranged downstream of the air preheater 3 and collects and removes soot dust (combustion ash) in the exhaust gas. The attraction ventilator 5 is arranged downstream of the electrostatic precipitator 4 and attracts exhaust gas to guide it to the chimney 6.
[0025]
　The gas flow passage from the inside of the boiler 1 to the air preheater 3 communicates between the boiler 1 and the denitration device 2 and between the denitration device 2 and the air preheater 3 via exhaust ducts 8 and 9, respectively. The cross section of the flow path (the cross section substantially orthogonal to the flow direction Df of the exhaust gas) is formed in a substantially rectangular shape.
[0026]
　The combustion air is introduced into the air preheater 3 by the forced ventilator 7, is preheated by the heat of the exhaust gas, and is supplied to the boiler 1.
[0027]
　As shown in FIG. 2, the denitration device 2 includes a denitration reactor 10, a first catalyst layer 11, a second catalyst layer 12, a plurality of reducing agent injection nozzles (reducing agent injection means) 13, and a cooling pipe (exhaust gas cooling means). ) 14. Inside the denitration reactor 10, a gas flow passage 15 having a rectangular cross section is partitioned. The first catalyst layer 11, the second catalyst layer 12, and the reducing agent injection nozzle 13 are arranged in the gas flow passage 15 and fixed to the denitration reactor 10.
[0028]
　The first catalyst layer 11 is composed of a first catalyst (ammonia denitration catalyst) that reduces and removes nitrogen oxides in exhaust gas using ammonia as a reducing agent, and a first carrier that carries the first catalyst. The second catalyst layer 12 is composed of a second catalyst (carbon monoxide denitration catalyst) that reduces and removes nitrogen oxides in the exhaust gas using carbon monoxide as a reducing agent, and a second carrier that supports the second catalyst. It is arranged on the downstream side of the first catalyst layer.
[0029]
　The first catalyst layer 11 and the second catalyst layer 12 may be one layer (one stage) or a plurality of layers (multiple stages). Known catalysts and carriers are used as the first catalyst, the first carrier, the second catalyst, and the second carrier.
[0030]
　The reducing agent injection nozzle 13 is arranged in the gas flow passage 15 on the upstream side of the first catalyst layer 11, and injects ammonia into the exhaust gas flowing through the gas flow passage 15. The reducing agent injection nozzle 13 may be arranged in the gas flow passage in the exhaust duct 8 (see FIG. 1) connecting the boiler 1 and the denitration device 2.
[0031]
　The cooling pipe 14 is arranged in the gas flow passage 15 between the first catalyst layer 11 and the second catalyst layer 12. Cooling water flows through the inside of the cooling pipe 14, and the exhaust gas is cooled by heat exchange with the cooling water. In addition to or in addition to the cooling pipe 14, another exhaust gas cooling means (for example, a cooling water injection nozzle for injecting cooling water into the gas flow passage 15 in the form of mist) may be provided.
[0032]
　As shown in FIGS. 2 and 3A, the second catalyst layer 12 has a catalyst-supporting region (hatched region) 21 that supports the second catalyst and a catalyst-non-supporting region (hatched region) that does not support the second catalyst. It has a non-shaded region) 22 in the figure. In the present embodiment, the rectangular annular outer peripheral edge portion along the outer peripheral edge of the flow path cross section of the gas flow passage 15 is defined as the catalyst-supporting region 21, and the inner region (central portion of the flow path cross section) surrounded by the catalyst-supporting region 21 is defined as the catalyst-supporting region 21. The catalyst non-supporting region 22 is used.
[0033]
　In this way, the catalyst-supporting region 21 is arranged on the outer peripheral edge portion, because the carbon monoxide concentration of the exhaust gas flowing through the rectangular gas flow passage 15 and flowing into the second catalyst layer 12 is the cross section of the flow path. This is because the annular outer peripheral edge portion (including the four corners) along the outer peripheral edge portion tends to be high, and the inner region (central portion) surrounded by the outer peripheral edge portion tends to be low.
[0034]
　Further, when the carbon monoxide concentration in the outer peripheral edge of the ring is compared, the carbon monoxide concentration tends to increase at the four corners. In particular, in the case of a combustion type boiler (tangential-fired boiler) in which burners are placed on each of the four walls of the combustion furnace (fireplace) to generate a swirling flame in the furnace, the carbon monoxide concentration at the four corners. Is significantly higher.
[0035]
　From the tendency of the concentration distribution of carbon monoxide, the catalyst-supporting region 21 may be arranged at at least four corners (corners) of the cross section of the gas flow passage 15, for example, FIG. 3 (b). As shown in the above, four corners of the flow path cross section of the gas flow passage 15 may be designated as the catalyst-supporting region 21, and the other regions may be designated as the catalyst-non-supporting region 22.
[0036]
　As shown in FIG. 4A, in the second catalyst layer 12 of the present embodiment, a large number of porous structures 24 and 25 are arranged adjacent to each other in the cross section of the flow path (arranged in a plurality of rows and columns and spread over). ) Consists of. The second catalyst layer 12 is provided with partition walls 29 for arranging a predetermined number of porous structures 24 and 25 (in this embodiment, three rows in each of the vertical and horizontal directions).
[0037]
　As shown in FIG. 5A, the porous structures 24 and 25 are composed of a rectangular parallelepiped porous body 23 in which a large number of ventilation holes (cells) 28 penetrate between both end faces, and both end faces thereof are exhaust gas. It is arranged so as to be located on the upstream side and the downstream side of the distribution direction Df. The porous body 23 may have a honeycomb structure or another structure.
[0038]
　The porous structure (second catalyst structure) 24 arranged in the catalyst-supporting region 21 is a structure in which the porous body 23 supports the second catalyst, and the porous body 23 of the second catalyst structure 24 is the second. It is a second carrier that carries a catalyst. On the other hand, the porous structure (dummy structure) 25 arranged in the catalyst non-supporting region 22 is a structure in which the porous body 23 does not support the second catalyst.
[0039]
　Further, instead of the porous structures 24 and 25, as shown in FIG. 4B, plate-shaped catalyst units 31 and 32 in which a plurality of plate-shaped catalyst carriers 30 are laminated may be arranged. In the example of FIG. 4 (b), one plate-shaped catalyst unit 31 and 32 are arranged in the space partitioned by the partition wall 29, but as shown in FIG. 5 (b), the space is partitioned by the partition wall 29. A plurality of plate-shaped catalyst units 31 and 32 (multiple rows and columns) may be spread over, or the partition wall 29 may be omitted.
[0040]
　As shown in FIG. 5B, the plate-shaped catalyst units 31 and 32 are composed of units in which a plurality of plate-shaped catalyst carriers 30 are laminated in a rectangular tubular metal frame 33 so as to be separated from each other. The ventilation space 34 through which the exhaust gas flows is between the two adjacent catalyst carriers 30 and between the outermost catalyst carrier 30 and the metal frame 33, and both end surfaces of the ventilation space 34 are the exhaust gas flow direction Df. It is arranged so as to be located on the upstream side and the downstream side of. The ventilation space 34 formed between the two adjacent catalyst carriers 30 or between the outermost catalyst carrier 30 and the metal frame 33 is a wavy bent portion partially formed in each catalyst carrier 30. The protruding tip of the 35 is held in a desired size (width) by abutting on the adjacent catalyst carrier 30 or the metal frame 33. The catalyst carrier 30 may be formed in a flat plate shape, and a separate spacer may be used to secure the ventilation space 34.
[0041]
　The plate-shaped catalyst unit (second catalyst structure) 31 arranged in the catalyst-supporting region 21 is a structure in which the plate-shaped catalyst carrier 30 supports the second catalyst, and the plate-shaped catalyst carrier 30 has the second catalyst. Is applied. That is, the plate-shaped catalyst carrier 30 of the second catalyst structure 31 is a second carrier that supports the second catalyst. On the other hand, the plate-shaped catalyst unit (dummy structure) 32 arranged in the catalyst non-supporting region 22 is a structure in which the plate-shaped catalyst carrier 30 does not support the second catalyst.
[0042]
　Although not particularly shown, the first catalyst layer 11 is also configured by arranging a large number of porous structures or plate-shaped catalyst units adjacent to each other in the cross section of the flow path, similarly to the second catalyst layer 12. To. The porous structure or plate-shaped catalyst unit arranged in the first catalyst layer 11 is a structure in which the porous or plate-shaped catalyst carrier (first carrier) carries the first catalyst.
[0043]
　The second catalyst layer 12 is configured so that the pressure loss of the flowing exhaust gas is the same over the entire cross section of the flow path including the catalyst-supporting region 21 and the catalyst-non-supporting region 22.
[0044]
　In the present embodiment, as shown in FIG. 6, a porous body 23 having the same shape is used in the second catalyst structure 24 and the dummy structure 25. In the second catalyst structure 24, the thin layer 26 of the second catalyst is fixedly formed on the inner peripheral surface of the ventilation holes 28 of the porous body 23, and the ventilation holes 28 are reduced by the amount of the thin layer 26 (FIG. 6 (a). )reference). Therefore, in the dummy structure 25, the dummy structure does not have the active component of the second catalyst so as to have the same thickness as the thin layer 26 of the second catalyst on the inner peripheral surface of the ventilation holes 28 of the porous body 23. The layer 27 is fixedly formed. As a result, the second catalyst structure 24 and the dummy structure 25 can have the same shape, and the densities of the ventilation holes of both (the number of holes per unit area and the size of the effective inner diameter of each hole) can be made equal. can do. As a result, the pressure loss of the exhaust gas flowing through the second catalyst structure 24 and the pressure loss of the exhaust gas flowing through the dummy structure 25 can be equally configured.
[0045]
　When the plate-shaped catalyst units 31 and 32 are arranged in place of the porous structures 24 and 25, the second catalyst structure 31 and the dummy structure 32 have the same shape as in the case of the porous structures 24 and 25 (as in the case of the porous structures 24 and 25). The number and size of the ventilation spaces 34 are the same), and the pressure loss of the exhaust gas flowing over the entire flow path cross section of the second catalyst layer 12 is the same.
[0046]
　The configuration in which the entire area of ​​the flow path cross section including the catalyst-supported region 21 and the catalyst-non-supported region 22 has the same pressure loss is not limited to the above, and other configurations (for example, the inner diameter of the ventilation hole of the dummy structure) A porous body having a smaller inner diameter of the vent hole than the porous body of the second catalyst structure may be used as the dummy structure so as to be equal to the inner diameter of the vent hole of the second catalyst structure).
[0047]
　According to the present embodiment, the exhaust gas passes through both the first catalyst layer 11 and the second catalyst layer 12, and the first catalyst (ammonia denitration catalyst) using ammonia as a reducing agent and carbon monoxide as the reducing agent are used. Since nitrogen oxides in the exhaust gas are reduced and removed using the two catalysts (carbon monoxide denitration catalyst), the amount of ammonia injected into the exhaust gas from the reducing agent injection nozzle 13 is determined when only the ammonia denitration catalyst is used. It can be reduced in comparison. Therefore, it is difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acidic ammonium sulfate on the equipment (for example, the air preheater 3) on the downstream side of the denitration device.
[0048]
　In addition, a second catalyst is placed in a region (outer peripheral edge including four corners) where reduction and removal of nitrogen oxides by the second catalyst (carbon monoxide denitration catalyst) can be expected, and reduction and removal of nitrogen oxides is performed. Since the second catalyst is not arranged in the central portion where it cannot be expected, it is possible to suppress an increase in cost due to the material cost of the second catalyst.
[0049]
　Further, since the second catalyst is arranged on the outer peripheral edge portion, the reduction and removal of nitrogen oxides can be performed in a wider range than in the case where the second catalyst is arranged only at the four corners.
[0050]
　Further, since the second catalyst layer 12 is configured so that the pressure loss of the flowing exhaust gas is the same over the entire area of ​​the flow path cross section including the catalyst-supporting region 21 and the catalyst-non-supporting region 22, the second catalyst layer is formed. The flow direction of the exhaust gas does not fluctuate significantly at the 12 inlets. Therefore, the exhaust gas having a high carbon monoxide concentration can be circulated to the catalyst-supporting region 21, and the exhaust gas having a low carbon monoxide concentration can be circulated to the catalyst-non-supporting region 22.
[0051]
　Further, even when the temperature of the exhaust gas flowing on the upstream side of the second catalyst layer 12 is higher than the activation temperature of the second catalyst, the exhaust gas flowing through the second catalyst layer 12 is subjected to the second catalyst by the cooling pipe 14. The temperature can be lowered to the activation temperature of the above, and the reduction and removal of nitrogen oxides using a second catalyst can be preferably performed.
[0052]
　Further, since the temperature of the exhaust gas is lowered on the downstream side of the first catalyst layer 11, when the activation temperature of the first catalyst is higher than the activation temperature of the second catalyst, the nitrogen oxides using the first catalyst Both reduction removal and reduction removal of nitrogen oxides using a second catalyst can be preferably performed.
[0053]
　The present invention is not limited to the above-described embodiment and modification described as an example, and is not limited to the above-described embodiment and the like as long as it does not deviate from the technical idea of ​​the present invention. , Various changes are possible depending on the design and the like.
[0054]
　For example, as shown in FIG. 7, the first catalyst layer 11 is arranged on the downstream side of the second catalyst layer 12, and the reducing agent injection nozzle 13 is arranged between the second catalyst layer 12 and the first catalyst layer 11. You may.
Code description
[0055]
1: Boiler
2: Denitration device
3: Air preheater
4: Electroelectric dust collector
5: Induction ventilator
6: Chimney
7: Push-in ventilator
8, 9: Exhaust duct
10: Denitration reactor
11: First catalyst layer
12: Second Catalyst layer
13: Reducing agent injection nozzle (reducing agent injecting means)
14: Cooling pipe (exhaust gas cooling means)
15: Gas flow passage
21: Catalyst supporting region
22: Catalyst non-supporting region
23: Porous body
24: Porous structure (No. 1) 2 catalyst structure)
25: Porous structure (dummy structure)
26, 27: Thin layer
28: Vent hole (cell)
29: Partition
30: Plate-shaped catalyst carrier
31: Plate-shaped catalyst unit (second catalyst structure) )
32: plate-shaped catalyst unit
(dummies) 33: metal frame
34: ventilation space
35: bent portion
The scope of the claims
[Claim 1]
　A
　first catalyst having a rectangular flow path cross section and arranged in a gas flow path through which exhaust gas discharged from a boiler flows and a first catalyst that reduces and removes nitrogen oxides in the exhaust gas using ammonia as a reducing agent. Is
　arranged in at least one of the gas flow passages on the upstream side or the downstream side of the first catalyst layer and the first catalyst layer, and carbon monoxide is used as a reducing agent to reduce and remove nitrogen oxides in the exhaust gas. The second catalyst layer
　comprises a second catalyst layer carrying the two catalysts and a reducing agent injection means for injecting ammonia into the exhaust gas flowing through the gas flow passage on the upstream side of the first catalyst layer
　. A catalyst-supporting region arranged at at least four corners of the flow path cross section of the gas flow passage to support the second catalyst, and a second catalyst arranged at the center of the flow path cross section of the gas flow passage. and a supported non-catalyst carrying area, in the entire region of the flow path section including the said catalyst supporting area the catalyst-unloaded region, the pressure loss of the exhaust gas flows is configured to be equal
　to that A featured denitration device.
[Claim 2]
　The denitration device according to claim 1,
　wherein the catalyst-supporting region is an annular shape along the outer peripheral edge of the flow path cross section of the gas flow passage, and the
　catalyst non-supporting region is surrounded by the annular catalyst-supporting region.
　A denitration device characterized by being an inner region .
[Claim 3]
　The denitration device according to claim 1 or 2
　, further
　comprising an exhaust gas cooling means for cooling the exhaust gas, the second catalyst layer is arranged in the gas flow passage on the downstream side of the first catalyst layer.
　The exhaust gas cooling means is
　a denitration device that cools the exhaust gas flowing through the gas flow passage on the downstream side of the first catalyst layer and on the upstream side of the second catalyst layer .