Reductant injection device

Abstract

To equalize a concentration of reductant to a gas circulating in a duct.SOLUTION: An ammonia injection part 20 injects a reductant, which has an action for reducing nitrogen oxide containing in an exhaust gas circulating in a duct 3, to the exhaust gas. The ammonia injection part 20 comprises: a plurality of injection nozzles 21 which inject ammonia gas to the exhaust gas circulating in the duct 3; a plurality of main pipes 22 which are provided with the plurality of injection nozzles 21, and in which ammonia gas circulates; and a header 23 which is provided in the duct 3 and on a downstream side of gas flow in the main pipe 22, and supplies the reductant to the plurality of main pipes 22. A distance D from the main pipe 22 to the header 23 is longer than three times of an outer diameter d of the main pipe 22.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a reductant injection 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 (flue) and exchanges heat 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] For example, a denitration device injects a reducing agent (e.g., ammonia or urea water) that has the effect of reducing nitrogen oxides from multiple injection nozzles into the exhaust gas flowing through a duct.The denitration device then removes the nitrogen oxides in the exhaust gas by passing the exhaust gas into which the reducing agent has been injected through a reaction device (e.g., a denitration catalyst). A plurality of injection nozzles for injecting a reducing agent are attached at a predetermined interval to a mother pipe provided in a flue through which exhaust gas flows. A supply pipe is connected to the mother pipe via a header or the like, and the reducing agent is supplied to the mother pipe via the header and the supply pipe. In order to equalize the injection amount of each injection nozzle, it is desirable that the temperature of the reducing agent does not change in the mother pipe. For this reason, a header and a supply pipe are provided in the flue, and the reducing agent to be supplied to the mother pipe is sometimes sufficiently heated in the supply pipe (for example, Patent Document 1). Patent Document 1 describes an apparatus for supplying an ammonia diluted gas to a nozzle mother pipe that injects an ammonia diluted gas into exhaust gas via an ammonia supply pipe provided in an exhaust gas duct. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-134259 Summary of the Invention [Problem to be solved by the invention]

[0005] When an ammonia supply pipe or a header is installed in the flue, the flow velocity of part of the exhaust gas flowing through the flue is slowed down by the influence of the ammonia supply pipe. As a result, an area (wake) where the flow velocity is slower than other areas is generated downstream of the ammonia supply pipe. Therefore, when an ammonia supply pipe or the like is installed upstream of a mother pipe as in Patent Document 1, a part of the ammonia injected from an injection nozzle provided on the mother pipe is injected into the wake. This may cause variation in the concentration of ammonia in the exhaust gas flowing through the duct. If variation occurs in the injected ammonia concentration, the ammonia may not reach the reactor provided downstream of the mother pipe uniformly, and the nitrogen oxides in the exhaust gas may not be removed suitably in the reactor.

[0006] In the flue, downstream of the mother pipe, a Karman vortex occurs which has the effect of diffusing the ammonia injected from the injection nozzle. However, when an ammonia supply pipe or the like is provided downstream of the mother pipe and in the vicinity of the mother pipe, the development of the Karman vortex is hindered by the ammonia supply pipe or the like. For this reason, it becomes difficult for the Karman vortex to develop downstream of the mother pipe, and there is a possibility that the diffusion of ammonia is suppressed. The suppression of the diffusion of ammonia may cause variation in the concentration of ammonia in the exhaust gas flowing through the duct. Therefore, there is a possibility that the ammonia does not reach the reactor uniformly, and the nitrogen oxides in the exhaust gas cannot be suitably removed in the reactor.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a reducing agent injection device that can homogenize the concentration of a reducing agent in gas flowing through a duct. [Means for solving the problem]

[0008] In order to solve the above problems, the reducing agent injection device of the present disclosure employs the following measures. A reducing agent injection device according to one embodiment of the present disclosure is a reducing agent injection device that injects a reducing agent having an effect of reducing nitrogen oxides contained in a gas flowing through a duct, and includes a plurality of injection sections that inject a reducing agent into the gas flowing through the duct, a plurality of mother pipes in which a plurality of the injection sections are provided and through which the reducing agent flows, and a supply section that is provided within the duct downstream of the gas flow of the mother pipe and supplies the reducing agent to the plurality of mother pipes, and the distance from the mother pipe to the supply section is longer than three times the outer diameter of the mother pipe. Effect of the Invention

[0009] According to the present disclosure, the concentration of the reducing agent in the gas flowing through the duct can be made uniform. [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 horizontal cross-sectional view showing an ammonia injection section according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Diagram 5] FIG. 2 illustrates the distribution of ammonia at an ammonia injector according to an embodiment of the present disclosure. [Figure 6] FIG. 13 is a diagram showing the distribution of ammonia in an ammonia injection section according to a comparative example 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 to 6.

[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 an 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.

[0013] The heat recovery boiler 2 in this embodiment includes a duct 3 extending in the X-axis direction and 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 4 and a second heat exchange section 5 provided inside the duct 3.

[0014] The first heat exchange section 4 and the second heat exchange section 5 have a plurality of heat transfer tubes (not shown) extending so as to intersect with the exhaust gas flow direction. The first heat exchange section 4 and the second heat exchange section 5 recover 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 first heat exchange unit 4 is provided upstream of the denitration device 10. The first heat exchange unit 4 may be, for example, a superheater that superheats the heat medium flowing inside the heat transfer tube. 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 tube.

[0015] 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.

[0016] Next, the denitration device 10 will be described in detail with reference to FIGS. The denitration device 10 supplies a reducing agent (ammonia, urea water, etc.) having the effect of reducing nitrogen oxides 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 by the catalytic action of the denitration catalyst 40, thereby removing and reducing the nitrogen oxides in the exhaust gas. In the following explanation, an example in which ammonia gas is used as the reducing agent will be explained. 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.

[0017] As shown in Figures 1 and 2, the denitration device 10 includes an ammonia injection section (reducing agent injection device) 20, a mixer 30, a denitration catalyst 40, and an ammonia decomposition catalyst 50, which are arranged in this order from the upstream side of the exhaust gas flow in a duct 3.

[0018] The ammonia injection unit 20 injects ammonia gas from a plurality of injection nozzles 21 into the duct 3 along the X-axis direction, thereby injecting the ammonia gas into the exhaust gas flowing through the duct 3. The ammonia injection unit 20 will be described in detail later.

[0019] The mixer 30 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. Ammonia gas injected from the ammonia injection section 20 and exhaust gas flow into the mixer 30. The mixer 30 forms a swirling flow that swirls around a central axis extending in the X-axis direction. The exhaust gas (more specifically, the exhaust gas into which ammonia has been injected) that has passed through the mixer 30 becomes one or more swirling flows in the space downstream of the mixer 30 and circulates. In this way, the mixer 30 mixes the exhaust gas and ammonia flowing through the duct 3 by forming a swirling flow.

[0020] The denitration catalyst 40 is disposed so as to cover substantially the entire cross section of the flow passage of the duct 3. The denitration catalyst 40 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 exhaust gas) passing through the inside, and removes at least a portion of the NOx. The catalyst component is, for example, based on titanium oxide.

[0021] The ammonia decomposition catalyst 50 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. The ammonia decomposition catalyst 50 removes ammonia from the exhaust gas by decomposing the ammonia contained in the exhaust gas. In this embodiment, the ammonia decomposition catalyst 50 is provided downstream of the denitration catalyst 40, so that ammonia in the exhaust gas that has not been completely reacted by the denitration catalyst 40 can be decomposed by the ammonia decomposition catalyst 50.

[0022] Next, details of the ammonia injection section 20 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a top view of the ammonia injection section 20. Fig. 4 is a vertical cross-sectional view of the ammonia injection section 20. In detail, Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3.

[0023] As shown in Figures 3 and 4, the ammonia injection section 20 has a plurality of injection nozzles (injection section) 21 that inject ammonia gas, a plurality of mother pipes 22 on which the injection nozzles 21 are provided and which extend in the Y-axis direction, and a supply section 27 that supplies ammonia gas to the mother pipes 22.

[0024] The multiple injection nozzles 21 are arranged side by side at a predetermined interval along the extending direction of the mother pipe 22 (i.e., the Y-axis direction). The injection nozzle 21 is provided on the downstream surface of the mother pipe 22 in the exhaust gas flow. The injection nozzle 21 may be a hole formed on the side surface of the mother pipe 22. The injection nozzle 21 injects ammonia gas at a predetermined injection pressure. In detail, the injection nozzle 21 injects ammonia gas toward the downstream side in the exhaust gas flow. The diameter of the injection hole of the injection nozzle 21 is, for example, 3 mm to 6 mm. The injection nozzle 21 injects ammonia gas in a cone shape. Note that the diameter of the injection hole of the injection nozzle 21 and the injection mode described above are merely examples and are not limited thereto.

[0025] The main pipe 22 extends along the Y-axis direction. Ammonia gas flows through the main pipe 22. The main pipe 22 has a circular tubular shape. The main pipe 22 has an outer diameter d of a predetermined length. In addition, a connection pipe 24 is connected to the main pipe 22. There are provided a plurality of main pipes 22. As shown in Fig. 4, the main pipes 22 are arranged side by side at predetermined intervals along the Z-axis direction.

[0026] 3 and 4, the supply unit 27 is provided in the duct 3 on the downstream side of the gas flow of the header pipe 22, and supplies the reducing agent to the multiple header pipes 22. The supply unit 27 has a header 23 connected to the multiple header pipes 22, a connection pipe 24 connecting the header pipe 22 and the header 23, and a supply pipe 25 that supplies ammonia gas to the header 23 from the outside.

[0027] The header 23 is provided on the downstream side of the exhaust gas flow of the mother pipe 22. As shown in Fig. 4, the header 23 extends along the Z-axis direction. A connecting pipe 24 is connected to the header 23. A plurality of mother pipes 22 are connected to the header 23 via the connecting pipe 24. A plurality of headers 23 are provided. The plurality of headers 23 are arranged side by side at predetermined intervals along the Y-axis direction. For convenience of illustration, only one header 23 is shown in Fig. 3 and Fig. 4. Each header 23 is connected to one supply pipe 25.

[0028] The distance D from the main pipe 22 to the header 23 is set to be longer than three times the outer diameter d of the main pipe 22. That is, the following formula (1) is established. Note that the distance D may be the shortest distance from the downstream end of the main pipe 22 to the central axis of the header 23.

[0029] D>3d···(1)

[0030] The connecting pipe 24 is provided on the downstream side of the exhaust gas flow of the main pipe 22. The connecting pipe 24 extends along the X-axis direction. The connecting pipe 24 connects the main pipe 22 and the header 23. There are provided a plurality of connection pipes 24. The plurality of connection pipes 24 are arranged side by side at predetermined intervals along the Z-axis direction.

[0031] The supply pipe 25 is provided downstream of the header 23. Ammonia gas flows inside the supply pipe 25. The supply pipe 25 guides ammonia gas supplied from an ammonia gas supply unit (not shown) provided outside the duct 3 to the header 23. The upstream end of the supply pipe 25 is connected to the ammonia gas supply unit. The downstream end of the supply pipe 25 is connected to the downstream surface of the header 23. The downstream end of the supply pipe 25 is connected to approximately the center of the header 23 in the Z-axis direction. The overall length of each supply pipe 25 is set so that the ammonia gas flowing inside the supply pipe 25 exchanges heat with the exhaust gas flowing outside the supply pipe 25, thereby raising the temperature to approximately the same as the temperature of the exhaust gas.

[0032] A plurality of supply pipes 25 are provided. For ease of illustration, only one supply pipe 25 is shown in Fig. 3 and Fig. 4. The entire length of each supply pipe 25 is approximately the same. Each of the plurality of supply pipes 25 is connected to a header 23. There is a one-to-one correspondence between the supply pipes 25 and the headers 23.

[0033] Next, the flow of ammonia gas in the ammonia injector 20 according to this embodiment will be described. An ammonia gas supply unit provided outside the duct 3 introduces ammonia gas into the supply pipe 25. The ammonia gas introduced into the supply pipe 25 flows inside the supply pipe 25. At this time, the ammonia gas exchanges heat with the exhaust gas flowing outside the supply pipe 25, and the temperature of the ammonia gas is raised to approximately the same temperature as the temperature of the exhaust gas. The ammonia gas that has flowed inside the supply pipe 25 is introduced into the header 23. The ammonia gas introduced into the header 23 flows inside the header 23 and is distributed to each mother pipe 22 via the connection pipe 24. The ammonia gas introduced into the mother pipe 22 flows inside the mother pipe 22 and is injected into the duct 3 from each injection nozzle. Note that the temperature of the ammonia gas is sufficiently raised inside the supply pipe 25 and the header 23, so there is almost no temperature change when the ammonia gas flows inside the mother pipe 22.

[0034] According to this embodiment, the following advantageous effects are obtained. In this embodiment, the header 23 and the supply pipe 25 are provided downstream of the mother pipe 22. That is, the mother pipe 22 is provided upstream of the header 23 and the supply pipe 25. This makes it possible to prevent the ammonia gas injected into the duct 3 from the injection nozzle 21 provided on the mother pipe 22 from being affected by the wake (low flow velocity region) occurring downstream of the header 23. Therefore, the flow velocity of the injected ammonia gas is made uniform, so that the concentration of ammonia gas in the exhaust gas flowing through the duct 3 can be made uniform. Therefore, the ammonia gas reaching the mixing section provided downstream of the ammonia injection section 20 and the denitrification catalyst 40 can be made uniform. Therefore, the nitrogen oxides in the exhaust gas can be suitably removed in the denitrification catalyst 40.

[0035] In the duct 3, Karman vortices are generated downstream of the mother pipe 22 by the exhaust gas that has passed near the mother pipe 22. The Karman vortices have the effect of diffusing ammonia gas injected from the mother pipe 22 into the exhaust gas flowing through the duct 3. On the other hand, when the distance between the mother pipe 22 and the header 23 is 3d or less, the development of the Karman vortex is inhibited by the header 23, and the Karman vortex is not formed stably. As a result, there is a possibility that the Karman vortex is not formed stably in the downstream region of the location where the header 23 is provided. On the other hand, stable Karman vortex streets (linked vortex shedding) are formed in a region that is separated from the main pipe 22 by a distance longer than three times the length of the outer diameter of the main pipe 22. The formation of the Karman vortexes promotes the diffusion of ammonia. In this embodiment, the distance from the mother pipe 22 to the header 23 is longer than three times the outer diameter of the mother pipe 22. That is, the distance between the mother pipe 22 and the header 23 is longer than three times. This suppresses the inhibition of the Karman vortex by the header, making it easier for the Karman vortex to be formed. Therefore, it is possible to diffuse the ammonia gas injected from the mother pipe 22 into the exhaust gas flowing through the duct 3. Therefore, it is possible to uniformize the concentration of ammonia gas in the exhaust gas flowing through the duct 3. Therefore, it is possible to suitably remove nitrogen oxides in the exhaust gas in the denitrification catalyst 40.

[0036] The effect of the Karman vortex in homogenizing the concentration of ammonia gas will be described in detail with reference to Figures 5 and 6. In Figures 5 and 6, the points where the ammonia concentration is the same are connected by lines. Also, the darker the black line, the higher the ammonia concentration.

[0037] Fig. 5 shows a state in which the main pipe 22 and the header 23 are arranged at a distance 12 times the outer diameter d of the main pipe 22. That is, in Fig. 5, the header 23 and the main pipe 22 are arranged so that the following formula (2) is established.

[0038] D = 12d (2)

[0039] 5, when the mother pipe 22 and the header 23 are spaced apart by a sufficient distance, Karman vortices are generated over approximately the entire area in the extension direction (Y-axis direction) of the mother pipe 22 on the downstream side of the mother pipe 22. Therefore, the exhaust gas and ammonia gas are mixed by the Karman vortices over approximately the entire area in the Y-axis direction, and the ammonia concentration in the exhaust gas is suitably uniformed as shown in FIG.

[0040] 5, the generated Karman vortexes decay approximately uniformly in the Y-axis direction, which suppresses variation in the concentration of ammonia gas in the exhaust gas in the Y-axis direction of the mother pipe 22. In addition, since the exhaust gas and the ammonia gas pass near the header 23 in a state of being mixed to a certain extent, variations in the concentration of ammonia gas in the exhaust gas caused by the header 23 are suppressed.

[0041] In this way, when the mother pipe 22 and the header 23 are spaced apart by a sufficient distance, it is possible to uniform the concentration of ammonia gas in the exhaust gas flowing through the duct 3. Therefore, it is possible to suitably remove nitrogen oxides in the exhaust gas in the denitration catalyst 40. In other words, it is possible to improve the denitration efficiency in the denitration catalyst 40.

[0042] 6, the distance between the main pipe 22 and the header 23 is set to 3d or less. That is, the header 23 and the main pipe 22 are arranged so that the following formula (3) is satisfied.

[0043] D≦3d (3)

[0044] As shown in FIG. 6, when the mother pipe 22 and the header 23 are not spaced apart by a sufficient distance, a flow of ammonia gas expands in the Y-axis direction around the header 23, and the ammonia gas injected from the injection nozzle 21 is divided by the header 23 before it is sufficiently mixed with the exhaust gas.

[0045] In addition, the header 23 inhibits the generation of Karman vortexes. Therefore, the Karman vortexes are unlikely to be generated downstream of the header 23, and the diffusion of ammonia is suppressed. Therefore, as shown in FIG. 6, in the region where the Karman vortexes are not generated, the exhaust gas and the ammonia gas are not mixed appropriately. Therefore, the ammonia concentration varies.

[0046] In this way, when the mother pipe 22 and the header 23 are not spaced apart by a sufficient distance, there occurs variation in the concentration of ammonia gas in the exhaust gas flowing through the duct 3. Therefore, there is a possibility that the denitration efficiency of the denitration catalyst 40 will decrease.

[0047] In addition, in this embodiment, the supply pipe 25 is provided downstream of the header 23. That is, the distance from the mother pipe 22 to the supply pipe 25 is also longer than three times the outer diameter d of the mother pipe 22. As a result, the supply pipe 25 does not hinder the generation of Karman vortices. Therefore, by providing both the header 23 and the supply pipe 25 at a position farther away from the mother pipe 22 than 3d, it is possible to more suitably generate Karman vortices. Therefore, it is possible to more suitably diffuse the ammonia gas injected from the mother pipe 22 into the exhaust gas flowing through the duct 3. Therefore, it is possible to more suitably uniformize the concentration of ammonia gas in the exhaust gas flowing through the duct 3.

[0048] 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 in which the denitration device is provided in a horizontal duct through which exhaust gas flows horizontally has been 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.

[0049] 5, an example has been described in which the mother pipe 22 and the header 23 are arranged at a distance 12 times the outer diameter d of the mother pipe 22, but the present disclosure is not limited to this. The mother pipe 22 and the header 23 may be arranged at a distance at which the Karman vortex naturally disappears (a distance longer than three times the outer diameter of the mother pipe 22).

[0050] The reducing agent injection device according to the embodiment described above can be understood, for example, as follows. A reducing agent injection device according to a first aspect of the present disclosure is a reducing agent injection device (20) that injects a reducing agent having an effect of reducing nitrogen oxides contained in a gas flowing through a duct (3), and includes a plurality of injection sections (21) that inject a reducing agent into the gas flowing through the duct, a plurality of mother pipes (22) in which the plurality of injection sections are provided and through which the reducing agent flows, and a supply section (27) that is provided within the duct downstream of the gas flow of the mother pipe and supplies the reducing agent to the plurality of mother pipes, and a distance from the mother pipe to the supply section is longer than three times the outer diameter of the mother pipe.

[0051] In the above configuration, the supply unit is provided downstream of the mother pipe. In other words, the mother pipe is provided upstream of the supply unit. This makes it possible to prevent the reducing agent injected from the injection unit provided in the mother pipe from being affected by the wake (low flow velocity region) occurring downstream of the supply unit. Therefore, the concentration of the reducing agent in the gas flowing through the duct can be made uniform.

[0052] In the duct, Karman vortices are generated downstream of the mother pipe by the gas that has passed near the mother pipe. The Karman vortices have the effect of diffusing the reducing agent injected from the mother pipe into the gas flowing in the duct. On the other hand, when the distance between the mother pipe and the supply part is 3d or less, the development of the Karman vortex is inhibited by the supply part, and the Karman vortex is not formed stably. As a result, the Karman vortex may not be formed stably in the downstream region of the supply part. On the other hand, in the region away from the main pipe by a distance longer than three times the outer diameter of the main pipe, stable Karman vortex streets (connected vortex shedding) are formed. The formation of Karman vortices promotes the diffusion of the reducing agent.

[0053] In the above configuration, the distance from the mother pipe to the supply part is longer than three times the outer diameter of the mother pipe. In other words, the distance between the mother pipe and the supply part is longer than three times. This suppresses the inhibition of the Karman vortex by the header, making it easier for the Karman vortex to be formed. Therefore, the reducing agent injected from the mother pipe can be diffused in the gas flowing through the duct. Therefore, the concentration of the reducing agent in the gas flowing through the duct can be made uniform.

[0054] A reducing agent injection device according to a second aspect of the present disclosure is such that, in the first aspect described above, the supply section includes a header to which a plurality of mother pipes are connected and which supplies reducing agent to the plurality of mother pipes, and a supply pipe which guides reducing agent from outside the duct to the header, and the distance from the mother pipe to the header and the supply pipe is longer than three times the outer diameter of the mother pipe.

[0055] In the above configuration, the distance from the mother pipe to the header and the supply pipe is longer than three times the outer diameter of the mother pipe. In this way, by locating both the header and the supply pipe at a position that is longer than three times the outer diameter of the mother pipe from the mother pipe, it is possible to more suitably generate and maintain the Karman vortex. Therefore, it is possible to more suitably diffuse the reducing agent injected from the mother pipe into the gas flowing through the duct. Therefore, it is possible to more suitably uniformize the concentration of the reducing agent in the gas flowing through the duct. [Explanation of symbols]

[0056] 1: Combustion engine 2: Waste heat recovery boiler 3: Duct 4: 1st heat exchange section 5:Second heat exchange section 7: Chimney 10: Denitration equipment 20: Ammonia injection section (reducing agent injection device) 21: Injection nozzle (injection part) 22: Main pipe 23: Header 24: Connecting pipe 25: Supply pipe 27: Supply Department 30 :Mixer 40: Denitrification Catalyst 50: Aminamine decomposition catalyst

Claims

1. A reducing agent injection device that injects a reducing agent having an effect of reducing nitrogen oxides contained in gas flowing through a duct, a plurality of injection units configured to inject a reducing agent into the gas flowing through the duct; a plurality of mother pipes each having a plurality of the injection portions and through which the reducing agent flows; a supply unit that is provided in the duct downstream of the mother pipe in the gas flow, and that supplies a reducing agent to the plurality of mother pipes, the supply unit includes a header connected to the plurality of header pipes and supplying the reducing agent to the plurality of header pipes, and a supply pipe introducing the reducing agent from outside the duct to the header, A reducing agent injection device, wherein the distance from the main pipe to the header and the supply section is longer than three times the outer diameter of the main pipe.

2. 2. The reducing agent injection device according to claim 1, wherein the supply unit is provided downstream of the main pipe in the gas flow, and includes a connecting pipe that connects the main pipe and the header and supplies the reducing agent from the header to the main pipe.

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