Denitration apparatus

Abstract

To provide a denitration apparatus where denitration efficiency can be increased.SOLUTION: A denitration apparatus 10 comprises: an ammonia injection part 11 being installed in a duct 3 in which an exhaust gas flows and injecting ammonia into the exhaust gas flowing in the duct 3; an NOx removal catalyst 13 installed at the downstream side of the ammonia injection part 11 in the duct 3; and a rectification part 20 being installed so as to be apart a prescribed distance from the ammonia injection part 11 at the upstream side of the ammonia injection part 11 in the duct 3 and rectifying the exhaust gas flowing in the duct 3.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a denitration device. [Background technology]

[0002] In a heat recovery steam generator (HRSG), exhaust gas discharged from a gas turbine or the like passes through a duct, and heat is exchanged between the exhaust gas and water or steam in a heat transfer tube, generating steam. Inside the duct of the heat recovery steam generator, multiple heat exchangers with numerous heat transfer tubes through which water or steam flows, as well as a denitrification device that removes (denitrifies) nitrogen oxides (NOx) from the exhaust gas, are installed.

[0003] A denitration device, for example, injects a reducing agent (e.g., ammonia or urea water) that has the effect of reducing nitrogen oxides from an injection nozzle into exhaust gas flowing through a duct, and the exhaust gas into which the reducing agent has been injected passes through a reaction device (e.g., a denitration catalyst), thereby removing nitrogen oxides from the exhaust gas. For example, a denitration device described in Patent Document 1 is known as such a denitration device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-75673 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to increase the efficiency of removing nitrogen oxides (hereinafter referred to as "denitrification efficiency") in a reaction device, it is effective to make the molar ratio of nitrogen oxides to reducing agent uniform over the cross section of the flow path of the duct. On the other hand, in a denitration device, due to various factors, the flow rate of exhaust gas may vary over the entire cross section of the duct. If a reducing agent is injected into the exhaust gas in this state, the concentration of the reducing agent varies over the entire cross section of the flow path. If exhaust gas flows into the reactor in a state in which the reducing agent concentration varies, the amount of reducing agent flowing in will vary depending on the position of the reactor. If the amount of reducing agent flowing into the reactor varies, there is a possibility that the denitration efficiency of the reactor will decrease.

[0006] In order to mix the exhaust gas and the reducing agent and to homogenize the concentration of the reducing agent in the exhaust gas in the cross section of the flow path, a mixer for mixing the exhaust gas and the reducing agent may be installed downstream of the injection nozzle and upstream of the reactor. However, the mixer is generally configured by combining a plurality of cells for mixing the exhaust gas. Therefore, when the variation in the flow rate of the exhaust gas extends over the entire cross section of the flow path of the duct, the variation in the concentration of the reducing agent exceeds the range that one cell can mix, so that the mixer may not be able to homogenize the concentration of the reducing agent appropriately. Therefore, even in a configuration with a mixer, the denitrification efficiency of the reactor may be reduced.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a denitration device capable of improving denitration efficiency. [Means for solving the problem]

[0008] In order to solve the above problems, the denitration device of the present disclosure employs the following measures. A denitration device according to one embodiment of the present disclosure includes an injection section provided in a duct through which exhaust gas flows, which injects a reducing agent into the exhaust gas flowing through the duct, a denitration catalyst provided in the duct downstream of the injection section, and a straightening section provided in the duct upstream of the injection section a predetermined distance away from the injection section, which straightens the exhaust gas flowing through the duct. Effect of the Invention

[0009] According to the present disclosure, it is possible to improve denitration efficiency. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram showing a heat recovery steam generator according to an embodiment of the present disclosure. [Diagram 2] 1 is a schematic configuration diagram showing a denitration device according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a schematic side view showing a porous plate according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a schematic side view illustrating a mixer according to an embodiment of the present disclosure. [Diagram 5] FIG. 2 is a schematic perspective view illustrating a cell of a mixer according to an embodiment of the present disclosure. [Figure 6] 4 is a graph showing the relationship between the variation in flow velocity of exhaust gas and the distance D1 in a denitration device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A denitration device according to an embodiment of the present disclosure will be described below with reference to Figures 1 to 6. In the following description and drawings, the vertical direction is referred to as the Z-axis direction, the horizontal direction in which exhaust gas flows is referred to as the X-axis direction, and the direction perpendicular to the X-axis direction and the Z-axis direction is referred to as the Y-axis direction. The flow direction of exhaust gas is indicated by arrow E in Figures 2 and 5.

[0012] First, with reference to FIG. 1, a heat recovery steam generator 2 according to this embodiment will be described. The heat recovery steam generator 2 according to this embodiment is a horizontal type heat recovery steam generator in which exhaust gas flows in the X-axis direction (predetermined direction) as shown in Fig. 1. In this embodiment, the X-axis direction, which is the direction in which the exhaust gas flows, is set to the horizontal direction. In the present embodiment, an example in which the denitration device is provided in a horizontal duct through which exhaust gas flows horizontally will be described, but the present disclosure is not limited thereto. For example, the denitration device may be provided in a vertical duct through which exhaust gas flows vertically.

[0013] The heat recovery boiler 2 according to this embodiment includes a duct 3 extending in the X-axis direction through which exhaust gas flows, a denitrification device 10 provided inside the duct 3 for removing nitrogen oxides (NOx) contained in the exhaust gas, and a first heat exchange section (resistance section) 4 and a second heat exchange section 5 provided inside the duct 3.

[0014] The first heat exchange section 4 has a plurality of heat transfer tubes 4a (see FIG. 2) extending in the vertical direction (Z-axis direction) so as to intersect with the exhaust gas flow direction. The length (height H) of the heat transfer tubes 4a in the Z-axis direction is 5 m or more and 30 m or less (see FIG. 2). The first heat exchange section 4 recovers heat from the exhaust gas by heat exchange between the exhaust gas and a heat medium (e.g., water or steam) flowing inside the heat transfer tubes 4a. The first heat exchange section 4 is provided upstream of the denitration device 10. The first heat exchange section 4 may be, for example, a superheater that superheats the heat medium flowing inside the heat transfer tubes 4a.

[0015] The second heat exchange unit 5 has a plurality of heat transfer tubes (not shown) extending in a vertical direction (Z-axis direction) so as to intersect with the exhaust gas flow direction. The second heat exchange unit 5 recovers heat from the exhaust gas by heat exchange between the exhaust gas and a heat medium (e.g., water or steam) flowing inside the heat transfer tubes. The second heat exchange unit 5 is provided downstream of the denitration device 10. The second heat exchange unit 5 may be, for example, an evaporator that evaporates the heat medium flowing inside the heat transfer tubes.

[0016] High-temperature combustion exhaust gas (exhaust gas) discharged from the combustion engine 1 is introduced into the duct 3 from the inlet of the duct 3, passes through the first heat exchange section 4, the denitrification device 10 and the second heat exchange section 5 in sequence, and is then discharged from the chimney 7 via the outlet of the duct 3.

[0017] Next, the denitration device 10 will be described in detail with reference to FIGS. The denitration device 10 supplies a reducing agent having the ability to reduce nitrogen oxides, such as ammonia or urea water, to the exhaust gas flowing through the duct 3, and promotes a reaction between the nitrogen oxides (NOx) in the exhaust gas to which the reducing agent has been supplied and the reducing agent through the catalytic action of the denitration catalyst 13, thereby removing and reducing the nitrogen oxides in the exhaust gas. In the following description, an example in which ammonia gas is used as the reducing agent will be described. Note that the reducing agent according to the present disclosure is not limited to ammonia gas. For example, it may be liquid ammonia, or may be something other than ammonia.

[0018] As shown in Figures 1 and 2, the denitration device 10 includes a flow straightening section 20, an ammonia injection section (injection section) 11, a mixer 12, a denitration catalyst 13, and an ammonia decomposition catalyst 14, which are arranged in this order from the upstream side of the exhaust gas flow in a duct 3.

[0019] The flow straightening section 20 has a flow straightening grid (not shown) and a porous plate 21 (not shown in FIG. 3). The flow straightening grid is disposed upstream of the porous plate 21. The flow straightening grid is a lattice-shaped member disposed so as to cover substantially the entire area of ​​the flow path cross section of the duct 3.

[0020] The perforated plate 21 is attached to the downstream portion of the straightening grid. As shown in Fig. 3, the perforated plate 21 is arranged so as to cover substantially the entire cross section of the flow passage of the duct 3. The perforated plate 21 is a metal plate-shaped member. As shown in Fig. 3, the perforated plate 21 has a plurality of through holes 21a penetrating in the X-axis direction. The plurality of through holes 21a are arranged at predetermined intervals along the Z-axis direction and the Y-axis direction. The diameter d of the through holes 21a is set to a length capable of straightening the exhaust gas.

[0021] 2, the ammonia injection unit 11 has an ammonia pipe 11a extending in the Z-axis direction and a plurality of injection nozzles (not shown) provided on the side surface of the ammonia pipe 11a. The ammonia injection unit 11 injects ammonia gas from the plurality of injection nozzles into the duct 3 along the X-axis direction, thereby injecting ammonia into the exhaust gas flowing through the duct 3. The ammonia pipe 11a is a cylindrical member through which ammonia flows. The multiple injection nozzles are arranged side by side at a predetermined interval along the extension direction of the ammonia pipe 11a (i.e., the Z-axis direction). Ammonia gas is injected from each injection nozzle at a predetermined injection pressure. Each injection nozzle injects ammonia gas in a cone shape.

[0022] The denitration catalyst 13 is disposed so as to cover substantially the entire cross section of the flow passage of the duct 3. The denitration catalyst 13 has, for example, a rectangular cylindrical frame portion (not shown) and a plurality of catalysts (not shown) provided inside the rectangular frame portion. Examples of the shape of the catalyst include, but are not limited to, a honeycomb shape or a corrugated plate shape through which exhaust gas can pass in the X-axis direction. The catalyst promotes a reduction reaction of NOx (nitrogen oxides) contained in the exhaust gas (combustion gas) passing through the inside, and removes at least a portion of the NOx. The catalyst component is, for example, based on titanium oxide.

[0023] The ammonia decomposition catalyst 14 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. The ammonia decomposition catalyst 14 removes ammonia from the exhaust gas by decomposing the ammonia contained in the exhaust gas. In this embodiment, the ammonia decomposition catalyst 14 is provided downstream of the denitration catalyst 13, so that ammonia in the exhaust gas that has not been completely reacted by the denitration catalyst 13 can be decomposed by the ammonia decomposition catalyst 14.

[0024] The mixer 12 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. As shown in Fig. 4, the mixer 12 includes a plurality of mixing sections 12A that form a swirling flow S swirling around a central axis extending in the X-axis direction. The mixing section 12A also has a plurality of cells 12a (four in this embodiment, for example). That is, the mixing section 12A forms one swirling flow (vortex) S by combining the plurality of cells 12a. The swirling flow S is formed substantially at the center of the mixing section 12A. The exhaust gas (more specifically, the exhaust gas into which ammonia has been injected) that has passed through the mixer 12 becomes a plurality of swirling flows S and flows in the space downstream of the mixer 12. In this manner, the mixer 12 forms the swirling flows S to mix the exhaust gas and ammonia flowing through the duct.

[0025] 4, the mixing sections 12A are arranged in a row in the Z-axis direction (two in this embodiment, as an example), and in a row in the Y-axis direction (two in this embodiment, as an example). Note that the number of mixing sections 12A is just an example, and is not limited to the number in this embodiment.

[0026] The mixer 12A has a plurality of cells 12a (two in this embodiment as an example) arranged in the Z-axis direction and the Y-axis direction. The cells 12a have a regular shape. The cells 12a adjacent to each other in the Z-axis direction and the Y-axis direction are arranged so that their orientations are rotated 90 degrees around a central axis extending in the X-axis direction.

[0027] 5, the cell 12a has four triangular plate-like plate portions 18. The four plate portions 18 have the same shape. The four plate portions 18 have two upstream plate portions 18a arranged upstream of the center point of the cell 12a in the X-axis direction, and two downstream plate portions 18b arranged downstream of the center point.

[0028] The two upstream plate portions 18a are arranged to form two opposing faces of an imaginary quadrangular pyramid whose apex is located on the downstream side. The two upstream plate portions 18a are arranged such that their downstream-most apexes are in contact with each other. The two downstream plate portions 18b are arranged so as to form two opposing faces of an imaginary quadrangular pyramid whose apex is located on the upstream side. The two downstream plate portions 18b are arranged so that their upstream-most apexes come into contact with each other.

[0029] The most downstream vertex of the upstream plate portion 18a and the most upstream vertex of the downstream plate portion 18b are in contact with each other. The upstream plate portion 18a and the downstream plate portion 18b are arranged so that their orientations are rotated 90 degrees around a central axis extending in the X-axis direction.

[0030] The structure of the mixer 12 is not limited to the above-described structure. The mixer 12 may have a structure in which regular shapes that generate a swirling flow by combining a plurality of flat or curved surfaces are arranged side by side.

[0031] Next, the arrangement of each device in the denitration device 10 will be described. 2, the distance D1 from the downstream end of the first heat exchange section 4 to the upstream end of the flow straightening section 20 is set to 140 mm or more. Preferably, the distance D1 from the first heat exchange section 4 to the flow straightening section 20 is set to 530 mm or more.

[0032] Further, a distance D2 from the downstream end of the flow straightening section 20 to the upstream end of the ammonia injection section 11 is set to be 11 times or more the diameter d of the through-hole 21a formed in the porous plate 21 of the flow straightening section 20. That is, the following formula (1) is established.

[0033] D2 ≥ 11d (1)

[0034] According to this embodiment, the following advantageous effects are obtained. In this embodiment, the rectifying unit 20 is provided upstream of the ammonia injection unit 11 at a predetermined distance from the ammonia injection unit 11. As a result, the exhaust gas is rectified by the rectifying unit 20 upstream of the ammonia injection unit 11, so that the flow velocity distribution of the exhaust gas in the flow path cross section of the duct 3 can be made uniform. Therefore, the ammonia injection unit 11 injects ammonia into the exhaust gas whose flow velocity has been made uniform. Therefore, it is possible to suppress the variation in ammonia concentration caused by the variation in flow velocity at each position in the flow path cross section. Therefore, the exhaust gas flows into the denitration catalyst 13 in a state in which the variation in ammonia concentration is suppressed, and the denitration reaction occurs favorably in the denitration catalyst 13, so that the denitration efficiency can be improved.

[0035] Generally, the flow straightening section 20 (e.g., a grid or a porous plate 21) acts to equalize the flow velocity of gas upstream of the flow straightening section 20 so that the pressure loss in the flow path cross section of the gas passing through the flow straightening section 20 is uniform. In this case, if the first heat exchange section 4 is provided in the gas flow upstream of the flow straightening section 20, the first heat exchange section 4 may hinder the equalization of the flow velocity of the exhaust gas. In particular, if the heat transfer tube 4a of the first heat exchange section 4 extends in the Z-axis direction, there is a tendency for the variation in flow velocity in the Z-axis direction to become large.

[0036] On the other hand, in this embodiment, the flow straightening section 20 is provided at a position separated by a predetermined distance (specifically, 140 mm or more) from the first heat exchange section 4. This allows a sufficient distance D1 between the flow straightening section 20 and the first heat exchange section 4, thereby reducing the influence of the first heat exchange section 4 on the flow straightening action of the exhaust gas in the flow straightening section 20 (uniformization of the flow velocity in the exhaust gas flow direction in the flow path cross section). Therefore, in the flow straightening section 20, the flow velocity distribution of the exhaust gas in the flow path cross section of the duct 3 can be uniformized. This allows the denitrification efficiency to be improved. In particular, when the longitudinal length H of the heat transfer tube 4a of the first heat exchange section 4 is 5 m or more and 30 m or less, the flow velocity distribution of the exhaust gas in the flow path cross section of the duct 3 can be more suitably uniformed in the flow straightening section 20.

[0037] The effect of improving the denitration efficiency will be described in detail with reference to the graph in Fig. 6. The vertical axis of Fig. 6 indicates the variation in the flow velocity of the exhaust gas in the ammonia injection section 11 (AIG) (specifically, the RMS: root mean square), and the horizontal axis indicates the value of the distance D1 from the first heat exchange section 4 to the straightening section 20.

[0038] In Figure 6, the greater the distance D1, the smaller the variation in the flow velocity of the exhaust gas. In particular, it can be seen that when the distance D1 is 140 mm or more, the variation in the flow velocity of the exhaust gas is sufficiently small. Therefore, from the graph in Figure 6, it can be seen that the variation in the flow velocity of the exhaust gas can be suppressed by setting the distance D1 to a length of 140 mm or more. 6, when the distance D1 is 530 mm or less, the slope is larger than when the distance D1 is greater than 530 mm. Therefore, it can be seen that the variation can be more effectively suppressed when the distance D1 is up to 530 mm. Therefore, it can be seen that the variation in the flow velocity of the exhaust gas can be more effectively suppressed by setting the distance D1 to a length of 530 mm or more. 6, when the distance D1 is 0, this indicates the case where the flow straightening unit 20 is not provided. In this case, the variation in the flow rate is the largest. Therefore, it can be seen that the flow straightening unit 20 has a variation suppressing effect.

[0039] In this embodiment, the flow straightening section 20 has a lattice section. This allows the exhaust gas passing through the lattice section to be straightened. Therefore, the flow velocity distribution of the exhaust gas in the flow passage cross section of the duct 3 can be made uniform in the lattice section. This improves the denitrification efficiency.

[0040] In this embodiment, the flow straightening unit 20 has a perforated plate 21. This allows the exhaust gas passing through the perforated plate 21 to be straightened. Therefore, the perforated plate 21 can uniformize the flow velocity distribution of the exhaust gas in the flow passage cross section of the duct 3. This allows the denitration efficiency to be improved.

[0041] In addition, in this embodiment, the distance D2 from the porous plate 21 to the ammonia injection section 11 is longer than 11 times the length of the diameter d of the through hole 21a. A jet is generated in the exhaust gas by passing through the through hole 21a of the porous plate 21, but in this embodiment, the distance D2 from the porous plate 21 to the ammonia injection section 11 can be made longer, so that the exhaust gas in a state where the jet is sufficiently attenuated reaches the ammonia injection section 11. That is, the exhaust gas in a state where the variation in the flow rate at each position of the flow path cross section is suppressed reaches the ammonia injection section 11. As a result, ammonia can be injected into the exhaust gas in a state where the variation is suppressed. Therefore, the variation in the ammonia concentration caused by the variation in the flow rate at each position of the flow path cross section can be suppressed. Therefore, the exhaust gas flows into the denitration catalyst 13 in a state where the variation in the ammonia concentration is suppressed, and the denitration reaction occurs suitably in the denitration catalyst 13, so that the denitration efficiency can be improved.

[0042] The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure. For example, in the above embodiment, an example was described in which the distance from the first heat exchange section 4 to the porous plate 21 was 140 mm or more (more preferably 530 mm or more), but the present disclosure is not limited thereto. The distance from a structure (hereinafter referred to as an "upstream structure") that is provided upstream of the porous plate 21 and affects the flow of exhaust gas in the duct 3 to the porous plate 21 may be 140 mm or more (more preferably 530 mm or more). The upstream structure is, for example, a structure having a long member extending in the Y-axis direction or the Z-axis direction, and an example thereof is a reinforcing member (such as a strut or a brace) that reinforces the duct 3 from the inside. When there are a plurality of upstream structures, the distance from the upstream structure closest to the porous plate 21 to the porous plate 21 may be set to 140 mm or more (more preferably 530 mm or more).

[0043] The denitration device according to the above-described embodiment can be understood, for example, as follows. The denitration device according to the first aspect of the present disclosure includes an injection section (11) provided in a duct (3) through which exhaust gas flows, which injects a reducing agent into the exhaust gas flowing through the duct, a denitration catalyst (13) provided in the duct downstream of the injection section, and a straightening section (20) provided in the duct upstream of the injection section at a predetermined distance from the injection section, which straightens the exhaust gas flowing through the duct.

[0044] In the above configuration, a straightening section is provided upstream of the injection section at a predetermined distance from the injection section. As a result, the exhaust gas is straightened by the straightening section upstream of the injection section, so that the flow velocity distribution of the exhaust gas in the flow path cross section of the duct can be made uniform. Therefore, the injection section injects the reducing agent into the exhaust gas whose flow velocity has been made uniform. Therefore, it is possible to suppress the variation in the reducing agent concentration caused by the variation in the flow velocity at each position in the flow path cross section. Therefore, the exhaust gas flows into the denitration catalyst in a state in which the variation in the reducing agent concentration is suppressed, and the denitration reaction occurs favorably in the denitration catalyst, so that the denitration efficiency can be improved.

[0045] In addition, the denitration device according to a second aspect of the present disclosure is the above-mentioned first aspect, further comprising a resistance section (4) provided within the duct and upstream of the straightening section for providing resistance to the flow of exhaust gas, the straightening section being provided at a position 140 mm or more away from the resistance section.

[0046] Generally, a flow straightening section (e.g., a grid or a porous plate) acts to equalize the flow velocity of gas upstream of the flow straightening section so that the pressure loss in the flow passage cross section of the gas passing through the flow straightening section is uniform. In this case, if a resistance section to the gas flow is provided upstream of the flow straightening section, the resistance section may hinder the uniformization of the flow velocity of the exhaust gas. In the above configuration, the flow straightening section is provided at a position 140 mm or more away from the resistance section. This allows a sufficient distance to be provided between the flow straightening section and the resistance section, thereby reducing the effect of the resistance section on the flow straightening of the exhaust gas (uniformization of the flow velocity in the exhaust gas flow direction in the flow path cross section). Therefore, the flow straightening section can uniformize the flow velocity distribution of the exhaust gas in the flow path cross section of the duct. This can improve the denitrification efficiency. It is more preferable that the rectifying portion is provided at a position 530 mm or more away from the resistor portion.

[0047] Further, in the denitration device according to a third aspect of the present disclosure, in the first or second aspect, the flow straightening section has a lattice section in a lattice shape.

[0048] In the above-mentioned configuration, the exhaust gas passing through the lattice portion can be rectified. This makes it possible to equalize the flow velocity distribution of the exhaust gas in the cross section of the duct in the lattice portion, thereby improving the denitration efficiency.

[0049] Further, in the denitration device according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the flow straightening portion includes a porous plate (21) having a plurality of through-holes (21a).

[0050] In the above-mentioned configuration, the flow of the exhaust gas passing through the perforated plate can be rectified. This makes it possible to uniformize the flow velocity distribution of the exhaust gas in the cross section of the flow passage of the duct at the perforated plate, thereby improving the denitration efficiency.

[0051] Further, in the denitration device according to a fifth aspect of the present disclosure, in the above-mentioned fourth aspect, a distance from the porous plate to the injection part is longer than 11 times a diameter of the through-hole.

[0052] In the above configuration, the distance from the perforated plate to the injection part is longer than 11 times the diameter of the through hole. A jet is generated in the exhaust gas by passing through the through hole of the perforated plate, but in the above configuration, the distance from the perforated plate to the injection part can be made longer, so that the exhaust gas reaches the injection part in a state where the jet is sufficiently attenuated. That is, the exhaust gas reaches the injection part in a state where the variation in the flow rate at each position of the flow path cross section is suppressed. As a result, the reducing agent can be injected into the exhaust gas in a state where the variation is suppressed. Therefore, the variation in the reducing agent concentration caused by the variation in the flow rate at each position of the flow path cross section can be suppressed. Therefore, the exhaust gas flows into the denitration catalyst in a state where the variation in the reducing agent concentration is suppressed, and the denitration reaction occurs suitably in the denitration catalyst, so that the denitration efficiency can be improved. [Explanation of symbols]

[0053] 1: Combustion engine 2: Waste heat recovery boiler 3: Duct 4: 1st heat exchange section (resistance section) 4a: Heat transfer tube 5:Second heat exchange section 7: Chimney 10: Denitration equipment 11: Ammonia injection section (injection section) 11a: Ammonia piping 12: Mixer 12A: Mixing section 12a: Cell 13:Denitrification catalyst 14: Ammonia decomposition catalyst 18: Board part 18a:Upstream side plate part 18b: Downstream side plate part 20: Rectifier 21: Perforated plate 21a: Through hole

Claims

1. An injection unit is provided within a duct through which exhaust gas flows, which extends horizontally or vertically, and which injects a reducing agent into the exhaust gas flowing through the duct. A denitrification catalyst is provided in the duct downstream of the injection section, A denitrification apparatus comprising: a flow straightening section provided within the duct, upstream of the injection section and at a predetermined distance from the injection section, for straightening the exhaust gas flowing through the duct.

2. The duct is provided on the upstream side of the rectifier and includes a resistance section that provides resistance to the flow of exhaust gas, The denitrification apparatus according to claim 1, wherein the rectifier is provided at a position at least 140 mm away from the resistance section.

3. The denitrification apparatus according to claim 1, wherein the rectifying section has a grid-like grid section.

4. The denitrification apparatus according to claim 1, wherein the rectifier section has a porous plate having a plurality of through holes.

5. The denitrification apparatus according to claim 4, wherein the distance from the perforated plate to the injection section is longer than 11 times the diameter of the through hole.

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