Denitration device

Abstract

The purpose of the present invention is to improve denitration efficiency. A denitration device (10) comprises: an ammonia injection device (11) that is provided in a duct (3) in which an exhaust gas flow path (9) through which exhaust gas flows is formed, and has a plurality of injection nozzles (11b) for injecting ammonia gas into exhaust gas flowing through the exhaust gas flow path (9); a denitration catalyst (13) that is provided in the duct (3) downstream from the ammonia injection device (11); and partition plates (16) that are provided between the ammonia injection device (11) and the denitration catalyst (13) and partition the exhaust gas flow path (9) into a plurality of divided flow paths (9a). In the divided flow paths (9a), the injection nozzles (11b) are arranged at a density of at least 8 nozzles / m2 in a cross-section orthogonal to the direction in which the exhaust gas flows.

Description

Denitration equipment

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

[0002] In a heat recovery steam generator (HRSG), exhaust gas discharged from a gas turbine or the like passes through a duct, and heat exchange occurs between the exhaust gas and water or steam in heat transfer tubes, generating steam. Inside the duct of the heat recovery steam generator, multiple heat exchangers having multiple heat transfer tubes through which water or steam flows, and a denitration device that removes (denitrifies) nitrogen oxides (NOx) from the exhaust gas are installed.

[0003] In a denitration device, for example, a reducing agent (e.g., ammonia or urea water) that has the effect of reducing nitrogen oxides is injected from an injection device 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.

[0004] Patent Document 1 discloses an apparatus in which exhaust gas generated by combustion in a boiler passes through an exhaust gas duct and is sent to a denitration device equipped with a catalyst layer, where nitrogen oxides are treated and then released into the atmosphere. In this apparatus, an ammonia injection nozzle for injecting ammonia is provided in the exhaust gas duct that guides the exhaust gas to the denitration device. Furthermore, the exhaust gas duct is formed with divided flow paths that guide the exhaust gas into multiple sections.

[0005] Patent No. 3554997

[0006] In order to improve the efficiency of nitrogen oxide removal (hereinafter referred to as "denitrification efficiency") in a reactor, it is effective to make the molar ratio of nitrogen oxides to reducing agent uniform across the cross section of the duct. However, due to various factors, variations in the flow rate of exhaust gas may occur across the entire cross section of the duct in a denitrification device. When a reducing agent is injected into exhaust gas with varying flow rates at the position where the injection device is installed, variations in the concentration of the reducing agent occur across the entire cross section of the flow path. When exhaust gas flows into the reactor with variations in the concentration of the reducing agent, variations occur in the amount of reducing agent flowing in depending on the position of the reactor. Variations in the amount of reducing agent flowing into the reactor could reduce the denitrification efficiency of the reactor.

[0007] Furthermore, when forming multiple divided flow paths in a duct as in Patent Document 1, if the density of ammonia injection nozzles corresponding to each divided flow path is not appropriately set, regions (low concentration regions) in the exhaust gas where the reducing agent does not sufficiently diffuse will occur. If a region (low concentration region) in the exhaust gas where the reducing agent does not sufficiently diffuse will occur, the amount of reducing agent flowing in will vary depending on the position in the reactor, which may reduce the denitration efficiency of the reactor. However, the device described in Patent Document 1 does not take into consideration the density of ammonia injection nozzles provided in each divided flow path. Therefore, there is a possibility that the denitration efficiency of the reactor will be reduced.

[0008] The present disclosure has been made in view of the above circumstances, and has an object to provide a denitration device that can improve denitration efficiency.

[0009] In order to solve the above problems, the denitration device of the present disclosure employs the following means: The denitration device according to one aspect of the present disclosure includes an injection device that is provided in a duct that defines an exhaust gas flow path through which exhaust gas flows, and that has a plurality of injection parts that inject a reducing agent into exhaust gas flowing through the exhaust gas flow path, a denitration catalyst that is provided in the duct and downstream of the injection device, and a partition plate that is provided between the injection device and the denitration catalyst and that divides the exhaust gas flow path into a plurality of divided flow paths, and each of the divided flow paths has 8 injection parts per meter in a cross section perpendicular to the flow direction of the exhaust gas. ２ The above arrangement is made.

[0010] According to the present disclosure, denitration efficiency can be improved.

[0011] Fig. 1 is a schematic configuration diagram showing a heat recovery boiler according to a first embodiment of the present disclosure; Fig. 2 is a front view showing a denitration device according to a first embodiment of the present disclosure; Fig. 3 is a graph showing the relationship between the number of nozzles per square meter and the ammonia concentration; Fig. 4 is a front view showing a denitration device according to a second embodiment of the present disclosure; Fig. 5 is a schematic side view showing a perforated plate according to a second embodiment of the present disclosure; Fig. 6 is a front view showing a denitration device according to a third embodiment of the present disclosure;

[0012] Embodiments of a denitration device according to the present disclosure will be described below with reference to the drawings. [First Embodiment] A denitration device according to a first embodiment of the present disclosure will be described below with reference to Figures 1 to 3. In the following description and drawings, the vertical direction will be referred to as the Z-axis direction, the horizontal direction in which exhaust gas flows will be referred to as the X-axis direction, and the direction perpendicular to the X-axis direction and the Z-axis direction will be referred to as the Y-axis direction. In Figure 2, the flow direction of exhaust gas is indicated by arrow E.

[0013] First, with reference to FIG. 1 , a heat recovery steam generator 2 according to this embodiment will be described. As shown in FIG. 1 , the heat recovery steam generator 2 according to this embodiment is a horizontal heat recovery steam generator in which exhaust gas flows in an X-axis direction (a predetermined direction). In this embodiment, the X-axis direction, which is the direction in which exhaust gas flows, is set to the horizontal direction. Note that, although this embodiment describes an example in which a denitration device is provided in a horizontal duct in which exhaust gas flows horizontally, the present disclosure is not limited thereto. For example, the denitration device may be provided in a vertical duct in which exhaust gas flows vertically.

[0014] The heat recovery boiler 2 according to this embodiment includes a duct 3 extending in the X-axis direction and through which exhaust gas flows, a denitration device 10 provided inside the duct 3 and configured to remove nitrogen oxides (NOx) contained in the exhaust gas, and a first heat exchanger 4 and a second heat exchanger 5 provided inside the duct 3. An exhaust gas flow path 9 through which exhaust gas flows is formed inside the duct 3.

[0015] The first heat exchange unit 4 has a plurality of heat transfer tubes (not shown) extending in the vertical direction (Z-axis direction) so as to intersect with the flow direction of the exhaust gas. The length (height H) of the heat transfer tubes in the Z-axis direction is 5 m or more and 30 m or less (see FIG. 2 ). The first heat exchange unit 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. 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 tubes.

[0016] 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 flow direction of the exhaust gas. 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.

[0017] The high-temperature combustion exhaust gas (exhaust gas) discharged from the combustion engine 1 is introduced into the duct 3 from the inlet thereof, passes through the first heat exchange section 4, the denitration 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.

[0018] Next, the denitration device 10 will be described in detail with reference to Figures 1 and 2. The denitration device 10 supplies a reducing agent, such as ammonia or urea water, which has the ability to reduce nitrogen oxides, to the exhaust gas flowing through the duct 3, and promotes the 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 will be described in which ammonia gas is used as the reducing agent. Note that the reducing agent according to the present disclosure is not limited to ammonia gas. For example, the reducing agent may be liquid ammonia or a substance other than ammonia.

[0019] 1 and 2 , the denitration device 10 is provided downstream of the first heat exchange section 4. The denitration device 10 includes an ammonia injector (injector) 11 and a denitration catalyst 13, which are arranged in this order from the upstream side of the exhaust gas flow in the duct 3.

[0020] 2 , the ammonia injector 11 has a plurality of ammonia pipes 11a extending in the Z-axis direction and a plurality of injection nozzles (injection portions) 11b provided on the side of each ammonia pipe 11a. The ammonia injector 11 injects ammonia gas from the plurality of injection nozzles 11b toward the downstream side along the X-axis direction into the duct 3, thereby injecting ammonia into the exhaust gas flowing through the duct 3. Note that the direction in which the injection nozzles 11b inject the ammonia gas is not limited to the above-mentioned direction. For example, the injection nozzles 11b may inject the ammonia gas toward the upstream side along the X-axis direction, or may inject the ammonia gas in a direction different from the X-axis direction.

[0021] The ammonia pipe 11a is a cylindrical member. Ammonia flows through the ammonia pipe 11a. The multiple ammonia pipes 11a are arranged side by side at predetermined intervals (e.g., equal intervals) in the Y-axis direction (the depth direction of the paper in FIG. 2 ). The multiple ammonia pipes 11a are provided over substantially the entire area in the Y-axis direction.

[0022] The multiple injection nozzles 11b are arranged side by side at predetermined intervals (for example, equal intervals) along the extension direction of the ammonia pipe 11a (i.e., the Z-axis direction). Ammonia gas is injected from each injection nozzle 11b at a predetermined injection pressure. Each injection nozzle 11b injects ammonia gas in a conical shape. Each injection nozzle 11b injects ammonia gas downstream.

[0023] The denitration catalyst 13 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. The denitration catalyst 13 has, for example, a rectangular cylindrical frame (not shown) and a plurality of catalysts (not shown) provided inside the rectangular frame. Examples of the catalyst shape include, but are not limited to, a honeycomb shape or a corrugated plate shape that allows exhaust gas to 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 catalyst, thereby removing at least a portion of the NOx. The catalyst component is, for example, based on titanium oxide.

[0024] The denitration device 10 is also provided with a plurality of partition plates 16 that are provided between the ammonia injector 11 and the denitration catalyst 13 and that divide the exhaust gas flow path 9 into a plurality of divided flow paths 9a. The partition plates 16 are arranged side by side at predetermined intervals (e.g., equal intervals) in the Z-axis direction. The partition plates 16 are arranged over substantially the entire area in the Z-axis direction.

[0025] The partition plate 16 is a plate-shaped member and is provided so that its plate surface is horizontal. The partition plate 16 extends over substantially the entire area in the Y-axis direction. The partition plate 16 integrally includes a base 16a provided between the ammonia injector 11 and the denitration catalyst 13 and a protruding portion 16b protruding from the upstream end of the base 16a toward the upstream side of the ammonia injector 11. The partition plate 16 connects the ammonia injector 11 and the denitration catalyst 13. The downstream end of the partition plate 16 is connected to the upstream end of the denitration catalyst 13. The upstream end of the partition plate 16 (more specifically, the upstream end of the base 16a) is connected to the ammonia injector 11 (more specifically, the ammonia piping 11a). The protruding portion 16b is located upstream of the ammonia injector 11. That is, the upstream end of the partition plate 16 is located upstream of the ammonia injector 11 (more specifically, the ammonia piping 11a).

[0026] The partition plates 16 form divided flow paths 9a between themselves and adjacent partition plates 16 in the Z-axis direction. The partition plate 16 provided at the top stage forms a divided flow path 9a between itself and the ceiling part of the duct 3. The partition plate 16 provided at the bottom stage forms a divided flow path 9a between itself and the bottom part of the duct 3. The flow path area of ​​each divided flow path 9a may be constant. Each divided flow path 9a guides the exhaust gas flowing in from the inlet and the ammonia gas injected from the ammonia injector 11 to the DeNOx catalyst 13.

[0027] Each divided flow path 9a has 8 injection nozzles 11b per m in a cross section (flow path cross section) perpendicular to the flow direction of the exhaust gas (X-axis direction). ２ In other words, in each divided flow path 9a, the injection nozzles 11b are arranged at a density of 8 nozzles / m when viewed from the flow direction of the exhaust gas (X-axis direction). ２ They are arranged so that the density is equal to or greater than this.

[0028] This embodiment provides the following advantageous effects. The present embodiment includes a partition plate 16 disposed between the ammonia injector 11 and the denitration catalyst 13, which divides the exhaust gas flow path 9 into multiple sections. The partition plate 16 divides the exhaust gas flow path 9 into multiple sections in the region between the injection nozzle 11b and the denitration catalyst 13. A large pressure loss (flow resistance) occurs in the exhaust gas passing through the denitration catalyst 13. Therefore, the resistance of the denitration catalyst 13 acts on the exhaust gas flowing through each divided flow path 9a separated by the partition plate 16. This makes it difficult for the exhaust gas to flow through the divided flow paths 9a, thereby uniforming the amount of exhaust gas flowing into each divided flow path 9a (see the black arrows in FIG. 2 ). Therefore, the flow velocity of the exhaust gas is uniformed at the upstream end of the partition plate 16 (i.e., the end on the ammonia injector 11 side). Since the flow velocity of the exhaust gas can be uniformed at a position close to the ammonia injector 11, variations in the ammonia gas concentration at each position in the flow path cross section can be suppressed. Therefore, the exhaust gas flows into the denitration catalyst 13 with the variation in ammonia gas concentration suppressed, and the denitration reaction occurs favorably in the denitration catalyst 13, thereby improving the denitration efficiency.

[0029] In this embodiment, each divided flow path 9a has 8 injection nozzles 11b per meter in a cross section perpendicular to the flow direction of the exhaust gas. ２ The injection nozzles 11b are arranged so as to have a density of at least 1 / 2 or more. In this way, by setting the number of injection nozzles 11b corresponding to each divided flow path 9a to a certain number or more, an appropriate amount of ammonia gas can be injected into the exhaust gas in each divided flow path 9a. This makes it difficult for a region (low concentration region) in which ammonia gas does not sufficiently diffuse in the exhaust gas to occur. Therefore, the ammonia gas concentration at the inlet of the denitration catalyst 13 can be made more uniform. Therefore, the denitration reaction occurs suitably in the denitration catalyst 13, and the denitration efficiency can be improved.

[0030] The effect of equalizing the ammonia gas concentration at the inlet of the denitration catalyst 13 will be explained using the graph in Fig. 3. Fig. 3 is a graph showing the relationship between the number of nozzles (horizontal axis) and the ammonia gas concentration deviation (vertical axis). The values ​​on the horizontal axis indicate the number of nozzles installed per square meter. The values ​​on the vertical axis indicate the ammonia gas concentration deviation in percentage. The concentration deviation is calculated by dividing the standard deviation by the average.

[0031] The concentration deviation shown on the horizontal axis may be the concentration deviation at a point 100D downstream from the ammonia pipe 11a when the diameter of the ammonia pipe 11a is D (for example, 30 mm or more and 100 mm or less). The graph in FIG. 3 may also be a graph showing the relationship between the number of nozzles (horizontal axis) and the ammonia gas concentration deviation (vertical axis) under the conditions of an exhaust gas temperature of 150°C or more and 450°C or less, an exhaust gas flow velocity of 2 m / s or more and 10 m / s or less, and an exhaust gas pressure of -10 KPa or more and 10 KPa or less. The nozzle may have a structure in which a hole is provided in the ammonia pipe or a structure in which a cylindrical nozzle protrudes from the pipe. The nozzle injection direction may be the same direction, the opposite direction, or perpendicular to the exhaust gas flow, and the nozzle injection speed may be 2 m / s or more and 50 m / s or less. When these nozzle structures or the like are applied, there is no change in the tendency of ammonia diffusion (spreading), and the same concentration distribution is obtained. For this reason, as will be described later, the nozzles are set to 8 pieces / m. ２ Under the above conditions, the adoption of these nozzle structures is particularly useful for forming a uniform distribution with a density deviation of 10% or less.

[0032] As shown in FIG. 3, the number (density) of nozzles is 8 / m. ２ The ammonia gas concentration deviation significantly decreases with the boundary of 8 nozzles / m. ２ This makes it possible to suitably reduce the ammonia gas concentration deviation, i.e., to make the ammonia gas concentration at the inlet of the denitration catalyst 13 more uniform.

[0033] Another possible method for suppressing variations in ammonia gas concentration is to provide a mixer between the ammonia injector 11 and the denitration catalyst 13. However, providing a mixer requires providing an area for mixing the exhaust gas and ammonia gas stirred by the mixer, which requires ensuring a long distance between the mixer and the denitration catalyst 13. Furthermore, it is also necessary to ensure space for installing the mixer, which may result in a long distance between the ammonia injector 11 and the denitration catalyst 13. On the other hand, in this embodiment, the partition plate 16 is used to suppress variations in ammonia gas concentration. Therefore, for example, compared to providing a mixer between the ammonia injector 11 and the denitration catalyst 13, the distance between the ammonia injector 11 and the denitration catalyst 13 can be shortened. This allows the denitration device 10 to be made smaller.

[0034] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Figures 4 and 5. This embodiment differs from the first embodiment in that a perforated plate 21 is provided upstream of the ammonia injector 11. Since the other points are the same as those in the first embodiment, the same components are denoted by the same reference numerals and their description will be omitted.

[0035] As shown in FIG. 4, a denitration device 10A according to this embodiment is provided upstream of the ammonia injector 11 and includes a perforated plate 21 for rectifying the flow of exhaust gas flowing through the duct 3.

[0036] The perforated plate 21 is disposed so as to cover substantially the entire cross section of the flow path of the duct 3. The perforated plate 21 is connected to the upstream ends of all the partition plates 16. More specifically, the perforated plate 21 is connected to the upstream ends of the protruding portions 16b of all the partition plates 16. The perforated plate 21 is a metal plate-shaped member. As shown in FIG. 5 , 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 side by side 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 that allows the exhaust gas to be rectified.

[0037] Furthermore, a distance d2 from the downstream end of the perforated plate 21 to the upstream end of the ammonia injector 11 is set to be 11 times or more the diameter d1 of the through-hole 21a formed in the perforated plate 21. That is, the following formula (1) is established.

[0038] d2 ≧ 11d1 (1)

[0039] According to this embodiment, the following advantageous effects are achieved. In this embodiment, a perforated plate 21 is provided upstream of the ammonia injector 11. As a result, the perforated plate 21 rectifies the exhaust gas upstream of the injection nozzle 11b, making it possible to uniform the flow velocity distribution of the exhaust gas in the cross section of the duct 3. Therefore, the injection nozzle 11b injects ammonia gas into the exhaust gas whose flow velocity has been uniformed. This makes it possible to suppress variations in ammonia gas concentration caused by variations in flow velocity at various positions in the cross section of the flow path. Therefore, the exhaust gas flows into the denitration catalyst 13 in a state in which variations in ammonia gas concentration are suppressed, and the denitration reaction occurs favorably in the denitration catalyst 13, thereby improving denitration efficiency.

[0040] Furthermore, in this embodiment, the distance from the perforated plate 21 to the ammonia injector 11 is longer than 11 times the diameter of the through-hole 21a. A jet flows in the exhaust gas as it passes through the perforated plate 21a. However, in this embodiment, the distance from the perforated plate 21 to the ammonia injector 11 can be increased, allowing the exhaust gas to reach the injection nozzle 11b with the jet flow sufficiently attenuated. That is, the exhaust gas reaches the ammonia injector 11 with the flow velocity variation suppressed at each position on the flow path cross section. This allows ammonia gas to be injected into the exhaust gas with the variation suppressed. Therefore, the variation in ammonia gas concentration caused by the variation in flow velocity at each position on the flow path cross section can be suppressed. Therefore, the exhaust gas flows into the denitration catalyst 13 with the variation in ammonia gas concentration suppressed, and the denitration reaction occurs favorably in the denitration catalyst 13, thereby improving the denitration efficiency.

[0041] Third Embodiment Next, a third embodiment of the present disclosure will be described with reference to Fig. 6. This embodiment differs from the first embodiment in that a mixer 30 is provided between the ammonia injector 11 and the denitration catalyst 13. Since the other points are the same as those in the first embodiment, the same components are denoted by the same reference numerals and their description will be omitted.

[0042] As shown in Fig. 6, the denitration device 10B according to this embodiment includes a mixer 30 that is provided between the ammonia injector 11 and the denitration catalyst 13 and mixes the exhaust gas with a reducing agent. The mixer 30 is provided at a midpoint in the divided flow path 9a. The position (position in the X-axis direction) at which the mixer 30 is provided may be determined based on the temperature, flow rate, etc. of the exhaust gas. For example, the mixer 30 may be provided at a position closer to the ammonia injector 11 than the denitration catalyst 13.

[0043] The mixer 30 is arranged so as to cover substantially the entire cross section of the flow path of the duct 3. The mixer 30 has a structure in which, for example, a plurality of flat or curved surfaces are combined to form a regular shape that generates a swirling flow and are arranged side by side.

[0044] According to this embodiment, the following advantageous effects are achieved. In this embodiment, a mixer 30 is provided between the ammonia injector 11 and the denitration catalyst 13, and mixes the exhaust gas with ammonia gas. This facilitates the diffusion of the injected ammonia gas, thereby suppressing variations in the ammonia gas concentration. Therefore, the exhaust gas flows into the denitration catalyst 13 with the variations in the ammonia gas concentration suppressed, and the denitration reaction occurs favorably in the denitration catalyst 13, thereby improving the denitration efficiency.

[0045] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0046] The denitration device according to the above-described embodiment can be understood as follows, for example. A denitration device according to a first aspect of the present disclosure includes: an injection device (11) provided in a duct (3) that defines an exhaust gas flow path (9) through which exhaust gas flows, the injection device having a plurality of injection parts (11b) that inject a reducing agent into exhaust gas flowing through the exhaust gas flow path (9); a denitration catalyst (13) provided in the duct (3) downstream of the injection device (11); and a partition plate (16) provided between the injection device (11) and the denitration catalyst (13) that divides the exhaust gas flow path (9) into a plurality of divided flow paths (9a), and each of the divided flow paths (9a) has 8 injection parts (11b) per meter in a cross section perpendicular to the flow direction of the exhaust gas. ２ The above arrangement is made.

[0047] The above configuration includes a partition plate disposed between the injection device and the denitration catalyst, which divides the exhaust gas flow path into multiple sections. The partition plate thereby divides the exhaust gas flow path into multiple sections in the region between the injection device and the denitration catalyst. A large pressure loss (flow resistance) occurs in the exhaust gas passing through the denitration catalyst. Therefore, the resistance of the denitration catalyst acts on the exhaust gas flowing through each divided flow path separated by the partition plate. This makes it difficult for the exhaust gas to flow through the divided flow paths, thereby uniforming the amount of exhaust gas flowing into each divided flow path. Therefore, the flow velocity of the exhaust gas is uniformed at the upstream end (i.e., the end on the injection device side) of the partition plate. Since the flow velocity of the exhaust gas can be uniformed at a position close to the injection device, variations in the reducing agent concentration at each position on the flow path cross section can be suppressed. Therefore, the exhaust gas flows into the denitration catalyst with reduced variations in the reducing agent concentration, and the denitration reaction occurs favorably in the denitration catalyst, thereby improving the denitration efficiency.

[0048] In the above configuration, each divided flow path has 8 injection parts per meter in a cross section perpendicular to the flow direction of the exhaust gas. ２The reducing agent is arranged so as to have a density of at least 1 / 2 or more. In this way, by setting the number of injection parts corresponding to each divided flow path to a certain number or more, an appropriate amount of reducing agent can be injected into the exhaust gas in each divided flow path. This makes it difficult for regions (low concentration regions) in which the reducing agent does not sufficiently diffuse in the exhaust gas to occur. Therefore, the reducing agent concentration at the inlet of the denitration catalyst can be made more uniform. Therefore, the denitration reaction occurs suitably in the denitration catalyst, and the denitration efficiency can be improved.

[0049] Another possible method for suppressing variations in reducing agent concentration is to provide a mixer between the injection device and the denitration catalyst. However, providing a mixer requires providing an area for mixing the exhaust gas stirred by the mixer and the reducing agent, which requires a long distance between the mixer and the denitration catalyst. Furthermore, space for installing the mixer must also be secured, potentially increasing the distance from the injection device to the denitration catalyst. On the other hand, the above configuration uses a partition plate to suppress variations in reducing agent concentration. Therefore, for example, compared to providing a mixer between the injection device and the denitration catalyst, the distance between the injection device and the denitration catalyst can be shortened. This allows the denitration device to be made smaller.

[0050] In the denitration device according to the second aspect of the present disclosure, in the above-described first aspect, the partition plate (16) has a base (16a) provided between the injection device (11) and the denitration catalyst (13) and a protrusion (16b) protruding from the upstream end of the base (16a) toward the upstream side of the injection device (11), and is equipped with a rectifier provided on the protrusion (16a) for rectifying the exhaust gas flowing through the duct (3).

[0051] In the above configuration, a rectifying unit is provided upstream of the injection device. This rectifies the exhaust gas upstream of the injection unit, making it possible to uniformize the flow velocity distribution of the exhaust gas across the cross section of the duct. Therefore, the injection unit injects the reducing agent into the exhaust gas with a uniform flow velocity. This makes it possible to suppress variations in the reducing agent concentration due to variations in the flow velocity at various positions across the cross section of the flow path. Therefore, the exhaust gas flows into the denitration catalyst with suppressed variations in the reducing agent concentration, and the denitration reaction occurs favorably in the denitration catalyst, thereby improving the denitration efficiency.

[0052] In a denitration device according to a third aspect of the present disclosure, in the second aspect, the straightening device has a porous plate (21) having a plurality of through holes, and the distance from the porous plate (21) to the injection device (11) is longer than 11 times the diameter of the through holes.

[0053] In the above configuration, the flow of the exhaust gas passing through the perforated plate can be rectified, thereby making the flow velocity distribution of the exhaust gas uniform in the cross section of the flow path of the duct at the perforated plate, thereby improving the denitration efficiency.

[0054] A denitration device according to a fourth aspect of the present disclosure is the denitration device of any of the first to third aspects, further comprising a mixer (30) provided between the injection device (11) and the denitration catalyst (13) and configured to mix exhaust gas with a reducing agent.

[0055] The above configuration includes a mixer disposed between the injection device and the denitration catalyst, which mixes the exhaust gas with the reducing agent. This facilitates the diffusion of the injected reducing agent, thereby suppressing variations in the reducing agent concentration. Therefore, the exhaust gas flows into the denitration catalyst with reduced variations in the reducing agent concentration, which allows the denitration reaction to occur favorably in the denitration catalyst, thereby improving denitration efficiency.

[0056] REFERENCE SIGNS LIST 1: Combustion engine 2: Exhaust heat recovery boiler 3: Duct 4: First heat exchange section 5: Second heat exchange section 7: Chimney 9: Exhaust gas flow path 9a: Divided flow path 10: Denitration device 10A: Denitration device 10B: Denitration device 11: Ammonia injection device (injection device) 11a: Ammonia piping 11b: Injection nozzle (injection section) 13: Denitration catalyst 16: Partition plate 16a: Base 16b: Protrusion 21: Perforated plate (flow straightener) 21a: Through-hole 30: Mixer

Claims

1. A system comprising: an injection device provided in a duct that forms an exhaust gas flow path through which exhaust gas flows, the injection device having a plurality of injection parts for injecting a reducing agent into exhaust gas flowing through the exhaust gas flow path; a denitration catalyst provided in the duct downstream of the injection device; and a partition plate provided between the injection device and the denitration catalyst and dividing the exhaust gas flow path into a plurality of divided flow paths, each of the divided flow paths having 8 injection parts per meter in a cross section perpendicular to the flow direction of the exhaust gas. ２ The denitration device is arranged so that the above conditions are satisfied.

2. The denitration device according to claim 1, wherein the partition plate has a base provided between the injection device and the denitration catalyst, and a protrusion protruding from the upstream end of the base toward the upstream side of the injection device, and further comprises a rectifying device provided on the protrusion for rectifying the flow of exhaust gas flowing through the duct.

3. A denitration device according to claim 2, wherein the flow straightening device has a perforated plate with a plurality of through holes, and the distance from the perforated plate to the injection device is longer than 11 times the diameter of the perforations.

4. A denitration device according to any one of claims 1 to 3, further comprising a mixer disposed between the injection device and the denitration catalyst for mixing exhaust gas with a reducing agent.

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