JP2020044461A - Denitrification device - Google Patents

Abstract

To suppress adhesion and accumulation of acidic ammonium sulfate to a device on the downstream side of a denitrification device and to reduce carbon monoxide in exhaust gas, while suppressing an increase in cost.MEANS FOR SOLVING THE PROBLEM: A first catalyst layer 11 is arranged on a gas flow passage 15, and carries a first catalyst for reducing and removing a nitride oxide in exhaust gas by using ammonia as a reducing agent. A second catalyst layer 12 is arranged on one gas flow passage 15 of at least one of the upstream or downstream of the first catalyst layer 11, and reduces and removes the nitride oxide in the exhaust gas by using carbon monoxide as a reducing agent. The second catalyst layer 12 has a catalyst-carrying region 21 which is arranged in at least four corner parts of a flow channel cross section of the gas flow passage 15 and carries a second catalyst, and a catalyst non-carrying region 22 which is arranged in the center part of the flow channel cross section of the gas flow passage 15 and does not carry the second catalyst, and a pressure loss of the flowing exhaust gas is equal to each other in the whole region of the flow channel cross section including the catalyst-carrying region 21 and the catalyst non-carrying region 22.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a denitration apparatus for purifying exhaust gas from a boiler.

  In a thermal power plant that generates power by burning fuel in a boiler, exhaust gas from the boiler is purified by a flue gas treatment system and then discharged to 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 combustion air by heat exchange with the exhaust gas, and dust (combustion ash) in the exhaust gas. An electric precipitator for collecting and removing is provided.

Patent Literature 1 discloses that a nitrogen oxide using ammonia (NH ₃ ) as a reducing agent is provided before or after a NOx purification catalyst that reduces and purifies nitrogen oxides in exhaust gas using carbon monoxide or hydrocarbons in exhaust gas. There is disclosed an exhaust gas purifying apparatus in which a reducing catalyst (ammonia denitration catalyst) is installed and ammonia is blown into exhaust gas at a stage preceding the ammonia denitration catalyst.

JP 2008-238069 A

In the case of a denitration apparatus using a catalyst using ammonia as a reducing agent, when the temperature of the exhaust gas flowing into the denitration apparatus is low, acidic ammonium sulfate (ammonium hydrogen sulfate: NH ₄ HSO ₄ ) is generated, and equipment downstream of the denitration apparatus is used. (For example, an air preheater), which may cause deterioration or malfunction of the device (for example, blockage of the air preheater). In addition, if the fuel and the combustion air are mixed poorly, the concentration of carbon monoxide in the exhaust gas increases, so that it is necessary to reduce carbon monoxide.

  On the other hand, in a denitration apparatus 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 disclosed in Patent Document 1, ammonia The amount of ammonia injected into the exhaust gas can be reduced as compared with the case where only the denitration catalyst is used. For this reason, it becomes difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acidic ammonium sulfate on equipment downstream of the denitration apparatus. Further, since a carbon monoxide denitration catalyst using carbon monoxide as a reducing agent is provided, carbon monoxide in exhaust gas can be reduced.

  However, the concentration of carbon monoxide in the exhaust gas flowing through the denitration device is not uniform in the cross section of the flow channel, and there are low and high concentrations of the carbon monoxide. The reduction and removal of oxides are not effectively performed, and the effect of the carbon monoxide denitration catalyst cannot be obtained. In other words, arranging the carbon monoxide denitration catalyst over the entire cross section of the flow path unnecessarily increases the cost.

  Thus, the present invention provides a denitration apparatus capable of suppressing the adhesion and deposition of acidic ammonium sulfate to equipment downstream of the denitration apparatus and reducing carbon monoxide in exhaust gas while suppressing an increase in cost. Aim.

  In order to achieve the above object, a denitration apparatus according to a first aspect of the present invention includes a gas flow passage, a first catalyst layer, a second catalyst layer, and a reducing agent injection unit.

  The gas flow path has a rectangular flow path cross section, and exhaust gas discharged from the boiler flows. The first catalyst layer is disposed in the gas flow passage, and carries a first catalyst for reducing and removing nitrogen oxides in exhaust gas using ammonia as a reducing agent. The second catalyst layer is disposed in at least one of the gas flow passages on the upstream side or the downstream side of the first catalyst layer, and carries a second catalyst for reducing and removing nitrogen oxides in 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.

  The second catalyst layer is disposed at at least four corners of the cross section of the gas flow passage and supports the second catalyst. The second catalyst layer is disposed at the center of the cross section of the flow passage of the gas flow passage. It has a catalyst non-supporting region that does not support two catalysts, and is configured such that the pressure loss of flowing exhaust gas is equal in the entire region of the flow path cross section including the catalyst supporting region and the catalyst non-supporting region.

  In the above configuration, nitrogen oxides in exhaust gas are reduced and removed using the first catalyst (ammonia denitration catalyst) using ammonia as a reducing agent and the second catalyst (carbon monoxide denitration catalyst) using carbon monoxide as a reducing agent. 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. For this reason, it is difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acid ammonium sulfate on equipment downstream of the denitration apparatus (for example, an air preheater).

  Since the cross section of the gas flow passage is rectangular, the carbon monoxide concentration of the exhaust gas flowing into the second catalyst layer tends to be higher at four corners and lower at the center. Thus, the corners where the concentration of carbon monoxide is high are defined as catalyst-supporting regions, and the central portions where the concentration of carbon monoxide is low are defined as regions where catalyst is not supported. As described above, the second catalyst is disposed at a corner where reduction and removal of nitrogen oxides by the second catalyst (carbon monoxide denitration catalyst) can be expected, and the second catalyst is disposed at a center where reduction and removal of nitrogen oxides cannot be expected. Since no catalyst is provided, an increase in cost due to the material cost of the second catalyst can be suppressed.

  In addition, since the second catalyst layer is configured so that the pressure loss of the flowing exhaust gas is equal in the entire area of the flow path cross section including the catalyst supporting area and the catalyst non-supporting area, the second catalyst layer is formed at the entrance of the second catalyst layer. The flow direction of the exhaust gas does not greatly change. For this reason, exhaust gas with a high concentration of carbon monoxide can flow through the catalyst-carrying region, and exhaust gas with a low concentration of carbon monoxide can flow through the catalyst-non-carrying region.

  A second aspect of the present invention is the denitration apparatus according to the first aspect, wherein the catalyst supporting region of the second catalyst layer is annular along the outer peripheral edge of the gas flow passage cross section, and the catalyst non-supporting region Is an inner region surrounded by an annular catalyst carrying region.

  In the above configuration, since the cross section of the gas flow passage is rectangular, the concentration of carbon monoxide in the exhaust gas flowing into the second catalyst layer is determined by an annular outer peripheral portion along the outer periphery of the cross section of the flow passage (at four locations). (Including corners) is high, and the inner region (central portion) surrounded by the outer peripheral edge tends to be lower. In consideration of such a tendency, the outer peripheral edge having a high carbon monoxide concentration is defined as a catalyst supporting region, The inner region where the concentration of carbon monoxide is low is defined as a 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 at four corners.

  A third aspect of the present invention is the denitration apparatus according to the first or second aspect, further comprising an exhaust gas cooling means for cooling exhaust gas. The second catalyst layer is disposed in a gas flow passage downstream of the first catalyst layer, and the exhaust gas cooling unit is configured to control the exhaust gas flowing through the gas flow passage downstream of the first catalyst layer and upstream of the second catalyst layer. To cool.

  In the above configuration, even if 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 on the second catalyst layer is cooled by the second catalyst layer by the second catalyst. , And the reduction and removal of nitrogen oxides using the second catalyst can be suitably performed.

  In addition, since the temperature of the exhaust gas is reduced on the downstream side of the first catalyst layer, when the activation temperature of the first catalyst is higher than the activation temperature of the second catalyst, reduction of the nitrogen oxide using the first catalyst is performed. Both removal and reduction removal of nitrogen oxides using the second catalyst can be suitably performed.

  ADVANTAGE OF THE INVENTION According to this invention, while suppressing the increase in cost, it can aim at suppression of the adhesion accumulation of the acidic ammonium sulfate to the downstream equipment of a denitration apparatus, and reduction of carbon monoxide in exhaust gas.

It is a schematic diagram of a flue gas treatment system including a denitration device according to an embodiment of the present invention. It is sectional drawing which shows schematic structure of the denitration apparatus of FIG. 3A and 3B are cross-sectional views of a second catalyst layer along a flow path cross section of FIG. 2, wherein FIG. 2A shows a case where a rectangular annular outer peripheral edge is used as a catalyst supporting region, and FIG. Each case is shown as a supporting area. 4A is an enlarged perspective view of a portion IV in FIG. 3A, wherein FIG. 3A illustrates an example in which a second catalyst layer is configured by a porous structure, and FIG. 3B illustrates an example in which the second catalyst layer is configured by a plate-shaped catalyst unit. Are respectively shown. It is a perspective view of the structure which comprises a 2nd catalyst layer, (a) is the porous body which comprises the porous structure of FIG.4 (a), (b) is the plate-shaped catalyst unit of FIG.4 (b). Shown respectively. It is an expanded sectional view of the 2nd catalyst layer of Drawing 5 (a), (a) shows a catalyst loading field, and (b) shows a catalyst non-loading field, respectively. It is sectional drawing of the modification of a denitration apparatus.

  A denitration apparatus according to one embodiment of the present invention will be described with reference to the drawings. Note that the arrow Df in the figure indicates the flow direction of the exhaust gas.

  As shown in FIG. 1, a flue gas treatment system for purifying exhaust gas from a boiler (coal-fired boiler) 1 and discharging the exhaust gas to the atmosphere includes a denitration device 2, an air preheater (AH: air heater) 3, and an electric dust collector 4. And an induction draft fan 5 are provided. In addition, the boiler 1 may be a boiler other than coal-fired.

  The denitration device 2 is disposed downstream of the boiler 1, and reduces and removes nitrogen oxides (NOx) in exhaust gas. The air preheater 3 is arranged downstream of the denitration device 2 and heats combustion air by heat exchange with exhaust gas. The electric dust collector 4 is disposed downstream of the air preheater 3 and collects and removes dust (combustion ash) in exhaust gas. The induction ventilator 5 is arranged downstream of the electric precipitator 4, and attracts and guides the exhaust gas to the chimney 6.

  The boiler 1 and the denitration device 2 and the denitration device 2 and the air preheater 3 communicate with each other via exhaust ducts 8 and 9, respectively, and serve as gas flow passages from inside the boiler 1 to the air preheater 3. A cross section of the flow path (a cross section substantially orthogonal to the exhaust gas flow direction Df) is formed in a substantially rectangular shape.

  The combustion air is introduced into the air preheater 3 by the forced draft fan 7, preheated by the heat of the exhaust gas, and supplied to the boiler 1.

  As shown in FIG. 2, the denitration apparatus 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 is provided. Inside the denitration reactor 10, a gas flow passage 15 having a rectangular cross section is defined. 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.

  The first catalyst layer 11 includes 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 supports the first catalyst. The second catalyst layer 12 includes a second catalyst (carbon monoxide denitration catalyst) that reduces and removes nitrogen oxides in exhaust gas using carbon monoxide as a reducing agent, and a second carrier that supports the second catalyst. It is arranged downstream of the first catalyst layer.

  The first catalyst layer 11 and the second catalyst layer 12 may be a single layer (one step) or a plurality of layers (a plurality of steps). Known catalysts and carriers are used for the first catalyst, the first carrier, the second catalyst, and the second carrier.

  The reducing agent injection nozzle 13 is disposed in the gas flow passage 15 on the upstream side of the first catalyst layer 11 and injects ammonia into exhaust gas flowing through the gas flow passage 15. Note that the reducing agent injection nozzle 13 may be disposed in a gas flow passage in the exhaust duct 8 (see FIG. 1) connecting the boiler 1 and the denitration device 2.

  The cooling pipe 14 is disposed 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 cools the exhaust gas by heat exchange with the cooling water. In addition, instead of or in addition to the cooling pipe 14, another exhaust gas cooling means (for example, a cooling water injection nozzle that sprays cooling water into the gas flow passage 15 in a mist state) may be provided.

  As shown in FIGS. 2 and 3A, the second catalyst layer 12 includes a catalyst-carrying region (a hatched region in the drawing) 21 for carrying the second catalyst and a catalyst-non-carrying region (not shown) for supporting the second catalyst. (A non-hatched area in the drawing) 22. In the present embodiment, a rectangular annular outer peripheral edge along the outer peripheral edge of the flow path cross section of the gas flow passage 15 is defined as the catalyst supporting area 21, and an inner area (central portion of the flow path cross section) surrounded by the catalyst supporting area 21 is defined. This is the catalyst non-supporting region 22.

  As described above, the catalyst supporting region 21 is arranged at the outer peripheral edge because the concentration of carbon monoxide in the exhaust gas flowing through the rectangular gas flow passage 15 and flowing into the second catalyst layer 12 is determined by the cross section of the flow passage. This is because the annular outer peripheral portion (including the four corners) along the outer peripheral edge of tends to be high, and the inner region (central portion) surrounded by the outer peripheral edge tends to be low.

  Further, when the carbon monoxide concentration in the annular outer peripheral portion is compared, the carbon monoxide concentration tends to increase at four corners. In particular, in the case of a combustion type boiler (tangential combustion boiler) in which burners are arranged on four wall surfaces of a combustion furnace (furnace) and generate a swirling flame in the furnace, the carbon monoxide concentration at four corners Is significantly higher.

  From the tendency of the carbon monoxide concentration distribution, 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, as shown in FIG. As shown in (4), the four corners of the gas flow passage 15 in the cross section may be the catalyst supporting region 21, and the other regions may be the catalyst non-supporting regions 22.

  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 a flow path cross section (they are arranged in a plurality of rows and columns and are laid down). ). The second catalyst layer 12 is provided with a partition wall 29 for arranging a predetermined number of porous structures 24 and 25 (in this embodiment, three rows vertically and horizontally).

  As shown in FIG. 5 (a), the porous structures 24 and 25 are each formed by a rectangular parallelepiped porous body 23 in which a large number of ventilation holes (cells) 28 penetrate between both end faces. It is arranged so as to be located on the upstream side and the downstream side in the flow direction Df. The porous body 23 may have a honeycomb structure or another structure.

  The porous structure (second catalyst structure) 24 disposed in the catalyst support 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 This is a second support for supporting 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.

  Further, instead of the porous structures 24 and 25, plate catalyst units 31 and 32 in which a plurality of plate catalyst carriers 30 are stacked may be arranged as shown in FIG. In the example of FIG. 4B, one plate-shaped catalyst unit 31, 32 is arranged in the space defined by the partition 29, but as shown in FIG. A plurality (plurality of rows and columns) of plate-like catalyst units 31 and 32 may be spread, and the partition wall 29 may be omitted.

  As shown in FIG. 5B, the plate-shaped catalyst units 31 and 32 are configured by a unit in which a plurality of plate-shaped catalyst carriers 30 are stacked in a rectangular cylindrical metal frame 33 while being separated from each other. Between the two adjacent catalyst carriers 30 and between the outermost catalyst carrier 30 and the metal frame 33 are ventilation spaces 34 through which the exhaust gas flows, and both end surfaces of the ventilation space 34 have exhaust gas flow directions Df. Are arranged so as to be located on the upstream side and the downstream side. The ventilation space 34 formed between the two adjacent catalyst carriers 30 or between the outermost catalyst carrier 30 and the metal frame 33 has a wavy bent portion partially formed in each catalyst carrier 30. The projecting tip 35 is held at a desired size (width) by contacting the adjacent catalyst carrier 30 or metal frame 33. The catalyst carrier 30 may be formed in a flat plate shape, and the ventilation space 34 may be secured by a separate spacer.

  The plate-shaped catalyst unit (second catalyst structure) 31 arranged in the catalyst support region 21 is a structure in which the plate-shaped catalyst carrier 30 supports the second catalyst. Is applied. That is, the plate-shaped catalyst carrier 30 of the second catalyst structure 31 is a second carrier that carries 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.

  Although not specifically shown, the first catalyst layer 11 is also formed by arranging a number of porous structures or plate-like catalyst units adjacent to each other in the flow channel cross section, similarly to the second catalyst layer 12. You. Each of the porous structure or the plate-shaped catalyst unit arranged in the first catalyst layer 11 is a structure in which a porous or plate-shaped catalyst carrier (first carrier) supports the first catalyst.

  The second catalyst layer 12 is configured such that the pressure loss of flowing exhaust gas is equal over the entire area of the flow path cross section including the catalyst supporting region 21 and the catalyst non-supporting region 22.

  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 vent 28 of the porous body 23, and the vent 28 is reduced by the thickness of the thin layer 26 (FIG. 6 (a)). )reference). For this reason, in the dummy structure 25, a dummy thin film having no active component of the second catalyst is formed on the inner peripheral surface of the vent hole 28 of the porous body 23 so as to have the same thickness as the thin layer 26 of the second catalyst. The layer 27 is fixedly formed. Thereby, the second catalyst structure 24 and the dummy structure 25 can be made to have the same shape, and the density of the ventilation holes (the number of holes per unit area and the size of the effective inner diameter of each hole) can be made equal to each other. 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 made equal.

  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 (the same as the case of the porous structures 24 and 25). The number and the size of the ventilation spaces 34 are equal), and the pressure loss of the exhaust gas flowing in the entire area of the cross section of the second catalyst layer 12 is equalized.

  The configuration in which the entire area of the cross section of the flow path including the catalyst supporting region 21 and the catalyst non-supporting region 22 has the same pressure loss is not limited to the above, and other configurations (for example, when the inner diameter of the ventilation hole of the dummy structure is A porous body having a smaller inner diameter of the ventilation 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 ventilation hole of the second catalyst structure.

  According to this 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 the second catalyst using carbon monoxide as a reducing agent. Since the 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 reduced when only the ammonia denitration catalyst is used. It can be reduced in comparison. For this reason, it is difficult to generate acidic ammonium sulfate, and it is possible to suppress the adhesion and deposition of acid ammonium sulfate on equipment downstream of the denitration device (for example, the air preheater 3).

  Further, the second catalyst is disposed in a region where the reduction and removal of nitrogen oxides by the second catalyst (carbon monoxide denitration catalyst) can be expected (the outer peripheral edge including four corners), and the reduction and removal of nitrogen oxides Since the second catalyst is not disposed in the central portion where is not expected, an increase in cost due to the material cost of the second catalyst can be suppressed.

  Further, since the second catalyst is arranged at the outer peripheral edge, the reduction and removal of nitrogen oxides can be performed in a wider range than when the second catalyst is arranged only at four corners.

  Further, since the second catalyst layer 12 is configured such that the pressure loss of the exhaust gas flowing therethrough is equal in 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 The flow direction of the exhaust gas does not fluctuate greatly at the inlet of the nozzle 12. Therefore, the exhaust gas with a high concentration of carbon monoxide can flow through the catalyst-supporting region 21 and the exhaust gas with a low concentration of carbon monoxide can flow through the non-catalyst-supporting region 22.

  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 on the second catalyst layer 12 is cooled by the cooling pipe 14 to the second catalyst. , And the reduction and removal of nitrogen oxides using the second catalyst can be suitably performed.

  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 are reduced. Both reduction and removal of nitrogen oxides using the second catalyst can be suitably performed.

  Note that the present invention is not limited to the above-described embodiment and the modified example described as an example, and other than the above-described embodiment and the like, as long as the technical idea according to the present invention is not deviated. Various changes are possible according to the design and the like.

  For example, as shown in FIG. 7, the first catalyst layer 11 is disposed downstream of the second catalyst layer 12, and the reducing agent injection nozzle 13 is disposed between the second catalyst layer 12 and the first catalyst layer 11. You may.

1: Boiler 2: Denitration device 3: Air preheater 4: Electric precipitator 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 injection means)
14: Cooling pipe (exhaust gas cooling means)
15: gas flow path 21: catalyst supporting region 22: catalyst non-supporting region 23: porous body 24: porous structure (second catalyst structure)
25: Porous structure (dummy structure)
26, 27: thin layer 28: vent (cell)
29: Partition wall 30: Plate-shaped catalyst carrier 31: Plate-shaped catalyst unit (second catalyst structure)
32: Plate-shaped catalyst unit (dummy structure)
33: metal frame 34: ventilation space 35: bent portion

Claims (3)

A gas flow passage having a rectangular flow path cross section, through which exhaust gas discharged from the boiler flows,
A first catalyst layer disposed in the gas flow passage and carrying a first catalyst for reducing and removing nitrogen oxides in exhaust gas using ammonia as a reducing agent;
A second catalyst layer disposed in at least one of the gas flow passages on the upstream side or the downstream side of the first catalyst layer and carrying a second catalyst for reducing and removing nitrogen oxides in exhaust gas using carbon monoxide as a reducing agent; When,
Reducing agent injection means for injecting ammonia into exhaust gas flowing through the gas flow passage on the upstream side of the first catalyst layer,
The second catalyst layer is disposed at at least four corners of a cross section of the gas flow passage and supports a catalyst carrying the second catalyst, and a central portion of the cross section of the flow passage of the gas flow passage. A catalyst non-supporting region that is disposed and does not support the second catalyst, and the pressure loss of flowing exhaust gas is equal in the entire region of the flow path cross section including the catalyst supporting region and the catalyst non-supporting region. A denitration apparatus characterized by comprising: The denitration apparatus according to claim 1,
The catalyst-carrying region has an annular shape along an outer peripheral edge of a cross section of the gas flow passage,
The denitration apparatus, wherein the non-catalyst carrying region is an inner region surrounded by the annular catalyst carrying region. The denitration device according to claim 1 or claim 2,
Equipped with exhaust gas cooling means for cooling exhaust gas,
The second catalyst layer is disposed in the gas flow passage downstream of the first catalyst layer,
The denitrification apparatus, wherein the exhaust gas cooling means cools exhaust gas flowing through the gas flow passage downstream of the first catalyst layer and upstream of the second catalyst layer.

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