Denitration device

Abstract

A denitration device (10) is provided with: an ammonia injection unit (11) that injects ammonia into exhaust gas flowing through a duct (3); a mixer (12) that is provided on the downstream side of the ammonia injection unit (11) and mixes the exhaust gas with ammonia; and a denitration catalyst (13) that is provided downstream of the mixer (12), that imparts resistance to the flow of a mixed fluid in which the exhaust gas and ammonia are mixed, and that is provided over the entire flow path cross-section of the duct (3). The ammonia injection unit (11) has an ammonia pipe (11a) and a spray nozzle (11b) provided in the ammonia pipe (11a) and spraying ammonia into the pipe (3). The distance (A) from the ammonia injection unit (11) to the mixer (12) is 10-30 times the outer diameter (d) of the ammonia pipe (11a). The distance (B) from the mixer (12) to the denitration catalyst (13) is longer than the distance (A) from the ammonia injection unit (11) to the mixer (12).

Description

Technical Field

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

[0002] In a heat recovery steam generator (HRSG), exhaust gas from a gas turbine or the like passes through a pipe, and the exhaust gas exchanges heat with water or steam in a heat transfer pipe, thereby generating steam. Inside the pipe of the heat recovery steam generator, there are multiple heat exchangers with multiple heat transfer pipes for water and steam flow, and a denitration device for removing nitrogen oxides (NOx) from the exhaust gas (denitrification).

[0003] The denitration device, for example, injects a reducing agent (e.g., ammonia, urea water) having the function of reducing nitrogen oxides into the exhaust gas flowing in the pipe from an injection nozzle, and the exhaust gas injected with the reducing agent passes through a reaction device (e.g., a denitration catalyst), thereby removing nitrogen oxides from the exhaust gas. In such a denitration device, in order to mix the exhaust gas with the reducing agent and make the concentration of the reducing agent in the exhaust gas uniform, a mixing device for mixing the exhaust gas with the reducing agent is sometimes provided on the downstream side of the injection nozzle and the upstream side of the reaction device (e.g., Patent Document 1). Patent Document 1 describes a denitration device in which a mixing device having a plurality of triangular plates is provided on the upstream side of the reaction device.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Utility Model Application Laid-Open No. 6-31826 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the denitration device described in Patent Document 1, exhaust gas injected with a reducing agent passes through a mixing device, thereby generating a gas vortex on the downstream side of the mixing device, and the exhaust gas and the reducing agent are mixed by the vortex. The fluid mixed with the exhaust gas and the reducing agent passes through a reaction device arranged on the downstream side of the mixing device to be denitrated.

[0009] When the vortex of the gas generated in the mixing device is not sufficiently attenuated, the mixed fluid of the exhaust gas and the reducing agent flowing through the mixing device in the pipe has a flow velocity deviation at each position of the flow path cross section. If the mixed fluid of the exhaust gas and the reducing agent flows into the reaction device in this state, the amount of the mixed fluid flowing in will deviate according to each position of the reaction device. If the amount of the mixed fluid flowing into the reaction device deviates, the denitration efficiency of the reaction device may be reduced.

[0010] In addition, when the exhaust gas injected with the reducing agent flows into the mixing device, if the concentration of the reducing agent is not uniform, the exhaust gas and the reducing agent may not be properly mixed in the mixing device. If the exhaust gas and the reducing agent are not properly mixed, the denitration efficiency of the reaction value increase may be reduced.

[0011] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a denitration device capable of improving denitration efficiency.

[0012] Means for solving problems

[0013] In order to solve the above-mentioned problems, the denitration device of the present disclosure adopts the following means.

[0014] A denitration device according to one embodiment of the present disclosure is a denitration device arranged in a pipe through which exhaust gas flows in a predetermined direction, and the denitration device comprises: an injection portion, which injects a reducing agent into the exhaust gas flowing in the pipe, and the reducing agent has a function of reducing nitrogen oxides contained in the exhaust gas; a mixing portion, which is arranged on the downstream side of the injection portion, and mixes the exhaust gas flowing in the pipe with the reducing agent by forming a vortex centered on a central axis extending in the predetermined direction; and a resistance portion, which is arranged on the downstream side of the mixing portion, and mixes the exhaust gas mixed with the reducing agent. The invention relates to a method for applying resistance to the flow of a mixed fluid of the reducing agent and the reducing agent, wherein the resistance portion is arranged in the entire area of ​​the flow path cross section of the pipeline, the injection portion has a reducing agent piping extending in a direction intersecting with the specified direction, i.e., the intersecting direction, and inside which the reducing agent flows, and a nozzle arranged on the side of the reducing agent piping and spraying the reducing agent into the pipeline, the distance from the injection portion to the mixing portion is not less than 10 times and not more than 30 times the outer diameter of the reducing agent piping, and the distance from the mixing portion to the resistance portion is longer than the distance from the injection portion to the mixing portion.

[0015] Effects of the Invention

[0016] According to the present disclosure, the denitration efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic configuration diagram showing a waste heat recovery boiler according to an embodiment of the present disclosure.

[0018] Figure 2 It is a schematic structural diagram showing a denitration device according to an embodiment of the present disclosure.

[0019] Figure 3 It is a schematic perspective view showing a unit of a mixer according to an embodiment of the present disclosure.

[0020] Figure 4 : is a schematic side view showing a mixer according to an embodiment of the present disclosure.

[0021] Figure 5 It is a schematic front view showing a mixer according to an embodiment of the present disclosure.

[0022] Figure 6 This is a graph showing the relationship between the ammonia concentration and the distance from the ammonia injection unit to the mixer.

[0023] Figure 7 This is a graph showing the relationship between the standard deviation of the flow rate of the mixed fluid and the distance from the mixer to the denitration catalyst.

[0024] Figure 8 It is a schematic configuration diagram of a denitration device showing a modified example of the embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] Below, use Figures 1 to 8 The denitration device of the embodiment of the present disclosure is described. In the following description and drawings, the up-down direction is referred to as the Z-axis direction, the direction of exhaust gas flow in the horizontal direction is referred to as the X-axis direction, and the direction orthogonal to the X-axis direction and the Z-axis direction is referred to as the Y-axis direction. Figure 2 , Figure 3 , Figure 5 and Figure 8 In FIG. 1 , arrow E indicates the flow direction of the exhaust gas.

[0026] First, refer to Figure 1 The waste heat recovery boiler 2 according to the present embodiment will be described.

[0027] like Figure 1 As shown, the waste heat recovery boiler 2 of this embodiment is a horizontal waste heat recovery boiler in which the exhaust gas flows in the X-axis direction (predetermined direction). In this embodiment, the X-axis direction, which is the direction in which the exhaust gas flows, is the horizontal direction.

[0028] The waste heat recovery boiler 2 of this embodiment includes: a pipe 3, which is extended in the X-axis direction and allows exhaust gas to flow inside; a denitrification device 10, which is arranged inside the pipe 3 to remove nitrogen oxides (NOx) contained in the exhaust gas; and a first heat exchange part 4 and a second heat exchange part 5, which are arranged inside the pipe 3.

[0029] The first heat exchanger 4 and the second heat exchanger 5 have a plurality of heat transfer pipes (not shown) extending in a vertical direction (Z-axis direction) in a manner intersecting the flow direction of the exhaust gas. The first heat exchanger 4 and the second heat exchanger 5 recover the heat of the exhaust gas by heat exchange between the heat medium (such as water or steam) flowing inside the heat transfer pipes and the exhaust gas.

[0030] The first heat exchanger 4 is provided at a position upstream of the denitration device 10. The first heat exchanger 4 may be, for example, a superheater that superheats the heat medium flowing inside the heat transfer tube. The second heat exchanger 5 is provided at a position downstream of the denitration device 10. The second heat exchanger 5 may be, for example, an evaporator that evaporates the heat medium flowing inside the heat transfer tube.

[0031] The high-temperature combustion exhaust gas (exhaust gas) discharged from the combustion engine 1 is introduced into the pipe 3 from the inlet of the pipe 3, passes through the first heat exchange unit 4, the denitrification device 10 and the second heat exchange unit 5 in sequence, and is discharged from the chimney 7 through the outlet of the pipe 3.

[0032] Next, use Figures 1 to 5 The denitration device 10 will be described in detail.

[0033] The denitration device 10 supplies a reducing agent having the function of reducing nitrogen oxides such as ammonia and urea water to the exhaust gas flowing in the pipe 3, and promotes the reaction between nitrogen oxides (NOx) in the exhaust gas supplied with the reducing agent and the reducing agent through the catalytic action of the denitration catalyst 13, thereby removing and reducing nitrogen oxides in the exhaust gas. In the following description, an example of using ammonia as a reducing agent is described. It should be noted that the reducing agent disclosed in the present invention is not limited to ammonia. For example, it can be liquid ammonia, and it can also be a substance other than ammonia.

[0034] like Figure 1 and Figure 2 As shown, the denitration device 10 includes an ammonia injection unit (injection unit) 11 , a mixer 12 , a denitration catalyst (resistance unit) 13 , and an ammonia decomposition catalyst 14 , which are arranged in order from the upstream side of the exhaust gas flow in the duct 3 .

[0035] The ammonia injection unit 11 includes an ammonia pipe (reducing agent pipe) 11a extending in the Z-axis direction and a plurality of injection nozzles (nozzles) 11b provided on the side of the ammonia pipe 11a. The ammonia injection unit 11 injects ammonia into the exhaust gas flowing in the pipe 3 by injecting ammonia gas from the plurality of injection nozzles 11b into the pipe 3 in the X-axis direction.

[0036] The ammonia pipe 11a is in a circular tube shape. Ammonia flows in the ammonia pipe 11a. The outer diameter d of the ammonia pipe 11a is a predetermined length.

[0037] A plurality of injection nozzles 11b are arranged at predetermined intervals along the extension direction (i.e., the Z-axis direction) of the ammonia pipe 11a. The injection nozzle 11b may be a circular hole formed on the side of the ammonia pipe 11a. Ammonia gas is injected from the injection nozzle 11b at a predetermined injection pressure. In addition, the diameter of the injection hole of the injection nozzle 11b is, for example, 3 mm to 6 mm. The injection nozzle 11b injects ammonia gas in a conical shape. It should be noted that the diameter of the injection hole and the injection method of the above-mentioned injection nozzle 11b are examples and are not limited thereto.

[0038] The denitration catalyst 13 is arranged in a manner covering substantially the entire area of ​​the flow path cross section of the pipe 3. The denitration catalyst 13 has, for example, a rectangular frame portion (not shown) in the shape of a rectangular cylinder and a plurality of catalysts (not shown) arranged inside the rectangular frame portion. As the shape of the catalyst, a honeycomb-shaped or corrugated plate-shaped catalyst through which the exhaust gas can pass along the X-axis direction is exemplified, but it is not limited thereto. The catalyst promotes the 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 components of the catalyst are based on, for example, titanium oxide.

[0039] The ammonia decomposition catalyst 14 is arranged so as to cover substantially the entire area of ​​the flow path cross section of the duct 3. The ammonia decomposition catalyst 14 removes ammonia from the exhaust gas by decomposing ammonia contained in the exhaust gas. In the present embodiment, since the ammonia decomposition catalyst 14 is provided on the downstream side of the denitration catalyst 13, the ammonia in the exhaust gas that is not fully reacted in the denitration catalyst 13 can be decomposed by the ammonia decomposition catalyst 14.

[0040] The mixer 12 is arranged so as to cover substantially the entire area of ​​the flow path cross section of the pipe 3. Figure 3 and Figure 4 As shown, the mixer 12 has a plurality of mixing sections 12A, and the mixing section 12A forms a swirling flow S that swirls around a central axis extending in the X-axis direction. In addition, the mixing section 12A has a plurality of (four as an example in this embodiment) units 12a. That is, the mixing section 12A forms a swirling flow (eddy flow) S by combining a plurality of units 12a. The swirling flow S is formed approximately at the center of the mixing section 12A.

[0041] The exhaust gas (more specifically, the exhaust gas injected with ammonia) having passed through the mixer 12 flows as a plurality of swirl flows S in the space on the downstream side of the mixer 12. The mixer 12 forms the swirl flows S in this way to mix the exhaust gas and ammonia flowing in the duct.

[0042] like Figure 4 As shown, a plurality of mixing sections 12A are arranged in a plurality (two in this embodiment as an example) in the Z-axis direction, and a plurality (two in this embodiment as an example) in the Y-axis direction. Figure 5 As shown, a plurality of mixing sections 12A are also arranged in the X-axis direction (two as an example in this embodiment). That is, the mixing section 12A is arranged in a manner of forming two layers in the X-axis direction. It should be noted that the number of mixing sections 12A is an example and is not limited to the number of this embodiment.

[0043] The mixing section 12A includes a plurality of (two as an example in the present embodiment) cells 12 a arranged in the Z-axis direction (first intersecting direction) and the Y-axis direction (second intersecting direction). The cells 12 a have a regular shape.

[0044] In addition, if Figure 4 As shown, a plurality of units 12a are arranged in the Z-axis direction (two in this embodiment as an example) and in the Y-axis direction relative to one mixing section 12A. The units 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 the central axis extending in the X-axis direction. Figure 2 As shown, the length of the unit 12a in the Z-axis direction is length D. In addition, the length of the unit 12a in the X-axis direction is length L. The size of the unit 12a affects the size of the vortex formed on the downstream side of the mixer 12. That is, the unit 12a determines the size of the vortex formed.

[0045] like Figure 3 As shown, the unit 12a has four triangular plate-shaped plates 18. The four plates 18 have the same shape. The four plates 18 include two upstream plates 18a arranged on the upstream side of the center point of the unit 12a in the X-axis direction and two downstream plates 18b arranged on the downstream side of the center point.

[0046] The two upstream plate portions 18a are disposed so as to form two opposing surfaces of a virtual quadrangular pyramid whose apex is disposed on the downstream side. The two upstream plate portions 18a are disposed so that the apex disposed on the most downstream side contacts each other.

[0047] The two downstream plate portions 18b are disposed so as to form two opposing surfaces of a virtual quadrangular pyramid whose apex is disposed on the upstream side. The two downstream plate portions 18b are disposed so that the apex disposed on the most upstream side contacts each other.

[0048] The apex of the upstream plate portion 18a disposed on the most downstream side contacts the apex of the downstream plate portion 18b disposed on the most upstream side. In addition, the upstream plate portion 18a and the downstream plate portion 18b are disposed so that their orientations are rotated 90 degrees around the central axis extending in the X-axis direction.

[0049] It should be noted that the structure of the mixer 12 is not limited to the structure described above. The mixer 12 may be a structure in which a combination of a plurality of flat surfaces or curved surfaces is arranged in a regular shape to generate a swirling flow.

[0050] In addition, the shape of the plate portion 18 is not limited to a triangular shape, and may be, for example, a trapezoid. In the case of a trapezoid, the upstream plate portion 18a is configured so that the short side (the short side of a pair of parallel sides) is located on the downstream side, and the downstream plate portion 18b is configured so that the short side is located on the upstream side. In addition, the short sides (the short sides of a pair of parallel sides) of the two upstream plate portions 18a and the short sides of the two downstream plate portions 18b are connected to each other in a square manner. That is, there is a square plate portion that connects all the short sides of the four plate portions 18.

[0051] Next, the arrangement of each part of the denitration device 10 will be described.

[0052] like Figure 2 As shown, the distance B from the mixer 12 to the denitration catalyst 13 is longer than the distance A from the ammonia injection unit 11 to the mixer 12. The distance B is the distance from the downstream end of the mixer 12 to the upstream end of the denitration catalyst 13. In addition, the distance A is the distance from the downstream end of the ammonia injection unit 11 to the upstream end of the mixer 12.

[0053] The distance A from the ammonia injection unit 11 (specifically, the downstream end of the ammonia pipe 11 a ) to the mixer 12 is 10 to 30 times the outer diameter d of the ammonia pipe 11 a . That is, the following formula (1) holds.

[0054] 10d≤A≤30d・・・(1)

[0055] In addition, the distance B from the mixer 12 to the denitration catalyst 13 is longer than 5 times the length D of the unit 12a in the Z-axis direction. That is, the following formula (2) holds. It should be noted that in this embodiment, since the length of the unit 12a in the Y-axis direction is the same as the length of the unit 12a in the Z-axis direction, the length of the unit 12a in the Y-axis direction can also be set to the length D.

[0056] B / D>5・・・(2)

[0057] According to this embodiment, the following effects are achieved.

[0058] The fluid (mixed fluid formed by mixing exhaust gas and ammonia) that has passed through the mixer 12 forms a swirling flow in the space on the downstream side of the mixer 12. Therefore, in the space from the mixer 12 to the denitration catalyst 13 where the swirling flow is formed, the exhaust gas and the reducing agent are further mixed compared to the space from the ammonia injection section 11 to the mixer 12. In the present embodiment, the distance B from the mixer 12 to the denitration catalyst 13 is longer than the distance A from the ammonia injection section 11 to the mixer 12. Thus, the length of the space from the mixer 12 to the denitration catalyst 13 can be extended, so that the exhaust gas and ammonia can be properly mixed. Therefore, the denitration reaction occurs appropriately in the denitration catalyst 13, thereby improving the denitration efficiency.

[0059] use Figure 6 The graph below explains the effect of improving the denitrification efficiency in detail. Figure 6 The vertical axis represents the standard deviation of the ammonia concentration at a position separated by 60 d (60 times the length d of the outer diameter of the ammonia pipe 11 a ) from the ammonia injection unit 11 . Figure 6 The horizontal axis of represents the distance A from the ammonia injection unit 11 to the mixer 12 as the length based on the outer diameter d of the ammonia pipe 11a. Figure 6 The case where the distance B from the mixer 12 to the denitration catalyst 13 is 30 d is shown.

[0060] exist Figure 6 In the case where the distance A is less than 30d, the smaller the value of the distance A is, the smaller the standard deviation of the ammonia concentration is. That is, the smaller the value of the distance A is, the smaller the deviation of the ammonia concentration is, and the mixing is performed. In particular, in the range of the distance A from 30d to 20d, it can be judged that the standard deviation is rapidly reduced.

[0061] Thus, according to Figure 6 As can be understood from the graph of , by making the distance B from the mixer 12 to the denitration catalyst 13 longer than the distance A from the ammonia injection unit 11 to the mixer 12 , the exhaust gas and ammonia can be appropriately mixed.

[0062] When the swirling flow is generated, the flow velocity varies at each position of the flow path cross section in the duct. Therefore, when the mixed fluid flows into the denitration catalyst 13 without the swirling flow being sufficiently attenuated, the denitration efficiency may be reduced.

[0063] On the other hand, in the present embodiment, the distance B from the mixer 12 to the denitration catalyst 13 is longer than 5 times the length D of the unit 12a in the Z-axis direction. Thus, the distance B from the mixer 12 to the denitration catalyst 13 can be extended, so that the mixed fluid in the state where the swirl flow is sufficiently attenuated (the state where the swirl force is sufficiently weakened) reaches the denitration catalyst 13. Therefore, the mixed fluid can flow into the denitration catalyst 13 in a state where the deviation of the flow velocity at each position of the flow path cross section of the pipe 3 is suppressed. Therefore, the mixed fluid in a homogenized state can be supplied to the denitration catalyst 13. Therefore, the denitration reaction occurs appropriately in the denitration catalyst 13, thereby improving the denitration efficiency.

[0064] use Figure 7 The graph below explains the effect of improving the denitrification efficiency in detail. Figure 7 The vertical axis represents the standard deviation of the flow rate of the mixed fluid. Figure 7 The horizontal axis represents the value of B / D.

[0065] exist Figure 7 In the case where B / D is less than 5, the smaller the value of B / D, the larger the standard deviation of the flow velocity of the mixed fluid. On the other hand, when B / D is greater than 5, the standard deviation of the flow velocity of the mixed fluid is the same as that in the case where there is no mixer 12. Thus, when B / D is greater than 5, it can be determined that the swirling flow formed by the mixer 12 is attenuated to the same extent as that in the case where there is no mixer 12.

[0066] Thus, according to Figure 7 As can be understood from the graph of , by making the distance B longer than five times the length D of the cell 12 a , the swirling flow can be sufficiently attenuated, and a mixed fluid in a uniform state can be supplied to the denitration catalyst 13 .

[0067] In addition, in the present embodiment, the distance A from the ammonia injection section 11 to the mixer 12 is more than 10 times the outer diameter d of the ammonia pipe 11a. Thus, the ammonia injected from the injection nozzle 11b flows into the mixer 12 in a properly diffused state, so that the exhaust gas and the ammonia can be properly mixed in the mixer 12. Therefore, the denitration efficiency can be improved. In addition, in the present embodiment, the distance A from the ammonia injection section 11 to the mixer 12 is less than 30 times the outer diameter d of the ammonia pipe 11a. Thus, the total length of the pipeline 3 can be shortened. Therefore, the denitration device 10 can be miniaturized. In this way, in the present embodiment, the mixing performance in the mixer 12 can be improved, and the denitration device 10 can be miniaturized.

[0068] [Modification 1]

[0069] Next, use Figure 8 Modifications of this embodiment will be described.

[0070] In the above embodiment, an example in which no large resistance body is provided between the mixer 12 and the denitration catalyst 13 is described, but the present disclosure is not limited thereto. Figure 8 As shown, a high-pressure heat exchange portion (heat exchanger) 21 as a resistance body may be provided between the mixer 12 and the denitration catalyst 13 . In this modification, the denitration catalyst 13 is provided downstream of the high-pressure heat exchange portion 21 .

[0071] The high-pressure heat exchange section 21 has a heat transfer pipe (not shown) inside which a heat medium flows, similarly to the first heat exchange section 4 and the second heat exchange section 5, so that the heat medium flowing in the heat transfer pipe and the exhaust gas flowing outside the heat transfer pipe perform heat exchange. In such a structure, the distance between the mixer 12 and the high-pressure heat exchange section 21 is a length B. That is, the distance (distance B) from the mixer 12 to the high-pressure heat exchange section 21 is set to be longer than 5 times the length D of the unit 12a of the mixer 12 in the Z-axis direction.

[0072] Thus, the distance B in the present embodiment only needs to be the distance between the mixer 12 and the resistance body (for example, the denitration catalyst 13, the high-pressure heat exchange unit 21) arranged on the downstream side of the mixer 12 and arranged at the most upstream side. The resistance body refers to an object that is arranged in a manner covering substantially the entire area of ​​the flow path area of ​​the pipe 3 and applies resistance to the exhaust gas (in detail, the exhaust gas injected with ammonia) flowing in the pipe 3. Specifically, the resistance body is an object that greatly attenuates the swirling flow generated by the mixer 12. For example, in addition to the denitration catalyst 13 and the high-pressure heat exchange unit 21 described in the above embodiment, the resistance body may also be an ammonia decomposition catalyst that decomposes ammonia and a CO decomposition catalyst that decomposes carbon monoxide.

[0073] According to this modification, the following effects are achieved.

[0074] In the present embodiment, the mixed fluid flows into the high-pressure heat exchange section 21 in a state where the deviation is suppressed, so the deviation of the flow velocity of the mixed fluid can be sufficiently suppressed also on the downstream side of the high-pressure heat exchange section 21. Therefore, the mixed fluid in a uniform state can also flow into the denitration catalyst 13 disposed on the downstream side of the high-pressure heat exchange section 21. Therefore, the denitration reaction occurs appropriately in the denitration catalyst 13, thereby improving the denitration efficiency.

[0075] It should be noted that the present disclosure is not limited to the above-described embodiments, and can be modified appropriately without departing from the gist of the present disclosure.

[0076] For example, in the above embodiment, an example in which two (2 layers) of mixing sections 12A (units 12a) are provided in the X-axis direction is described, but the present disclosure is not limited thereto. For example, three (3 layers) or more mixing sections 12A (units 12a) may be provided in the X-axis direction, or only one (1 layer) of mixing sections 12A (units 12a) may be provided in the X-axis direction.

[0077] In the above embodiment, an example of installing a denitration device in a horizontal duct where exhaust gas flows horizontally is described, but the present disclosure is not limited thereto. For example, the denitration device may be installed in a vertical duct where exhaust gas flows vertically.

[0078] The denitration device described in the above-described embodiment can be understood, for example, as follows.

[0079] The first mode of the present disclosure is a denitration device (10) arranged in a pipe (3) for exhaust gas to flow in a predetermined direction (X-axis direction), the denitration device comprising: an injection section (11) for injecting a reducing agent into the exhaust gas flowing in the pipe, the reducing agent having a function of reducing nitrogen oxides contained in the exhaust gas; a mixing section (12) arranged on the downstream side of the injection section, for mixing the exhaust gas flowing in the pipe with the reducing agent by forming a vortex centered on a central axis extending in the predetermined direction; and a resistance section (13, 21) arranged on the downstream side of the mixing section. , a resistance is applied to the flow of a mixed fluid mixed with the exhaust gas and the reducing agent, the resistance portion is arranged in the entire area of ​​the flow path cross section of the pipe, the injection portion has a reducing agent piping extending in a direction intersecting with the specified direction, that is, a cross direction and allowing the reducing agent to flow inside, and a nozzle arranged on the side of the reducing agent piping and spraying the reducing agent into the pipe, the distance (A) from the injection portion to the mixing portion is not less than 10 times and not more than 30 times the outer diameter (d) of the reducing agent piping, and the distance (B) from the mixing portion to the resistance portion is longer than the distance (A) from the injection portion to the mixing portion.

[0080] The fluid that has passed through the mixing section forms a vortex in the space on the downstream side of the mixing section. Therefore, the exhaust gas and the reducing agent are further mixed in the space from the mixing section to the resistance section where the vortex is formed, compared with the space from the injection section to the mixing section. In the above structure, the distance from the mixing section to the resistance section is longer than the distance from the injection section to the mixing section. Thus, the distance from the mixing section to the resistance section can be extended, so that the exhaust gas and the reducing agent can be properly mixed. Therefore, the denitration reaction occurs properly in the denitration catalyst, thereby improving the denitration efficiency.

[0081] In addition, since the gas flows into the resistance part in a state where the deviation is suppressed, the deviation of the flow velocity of the mixed fluid can be fully suppressed on the downstream side of the resistance part. Therefore, for example, even if the resistance part is a heat exchanger and a denitration catalyst is provided on the downstream side of the heat exchanger, the deviation of the flow velocity of the mixed fluid is fully suppressed on the downstream side of the heat exchanger, so the mixed fluid in a uniform state flows into the denitration catalyst. Therefore, the denitration reaction occurs appropriately in the denitration catalyst, thereby improving the denitration efficiency.

[0082] In addition, in the above structure, the distance from the injection section to the mixing section is more than 10 times the outer diameter of the reducing agent piping. Thus, the reducing agent injected from the nozzle flows into the mixing section in a properly diffused state, so the exhaust gas and the reducing agent can be properly mixed in the mixer. Therefore, the denitration efficiency can be improved. In addition, in the above structure, the distance from the injection section to the mixing section is less than 30 times the outer diameter of the reducing agent piping. Thus, the total length of the pipeline can be shortened. Therefore, the denitration device can be miniaturized. In this way, in the above structure, the mixing performance in the mixing section can be improved, and the denitration device can be miniaturized.

[0083] In addition, in the second mode of the denitrification device disclosed in the present invention, based on the above-mentioned first mode, the mixing section has a plurality of units (12a) that determine the size of the vortex formed, and the distance (B) from the mixing section to the resistance section is longer than 5 times the length (D) of the unit in a direction intersecting the specified direction, i.e., the intersecting direction.

[0084] In the above structure, the distance from the mixing section to the resistance section is greater than 5 times the length of the unit in the cross direction. Thus, the distance from the mixing section to the resistance section can be extended, so that the mixed fluid in a state where the vortex formed in the mixing section is fully attenuated reaches the resistance section. Therefore, the mixed fluid can flow into the resistance section while suppressing the deviation of the flow velocity at each position of the flow path cross section. Therefore, for example, in the case where the resistance section is a denitration catalyst, the mixed fluid in a homogenized state flows into the denitration catalyst, and a denitration reaction occurs appropriately in the denitration catalyst, thereby improving the denitration efficiency.

[0085] In addition, in a third aspect of the present disclosure, in addition to the first aspect or the second aspect, the resistance portion includes a denitration catalyst (13) that removes nitrogen oxides contained in the exhaust gas by allowing the mixed fluid to pass therethrough.

[0086] In the above structure, the mixed fluid can flow into the denitration catalyst while suppressing the deviation of the flow velocity at each position of the flow path cross section. Therefore, the mixed fluid in a uniform state flows into the denitration catalyst, and the denitration reaction occurs appropriately in the denitration catalyst, thereby improving the denitration efficiency.

[0087] In addition, the fourth mode of the denitration device of the present disclosure is provided with a denitration catalyst (13) based on the above-mentioned first mode or second mode. The denitration catalyst (13) is arranged on the downstream side of the resistance part, and the nitrogen oxides contained in the exhaust gas are removed by passing the mixed fluid. The resistance part has a heat exchanger (21), and the heat exchanger (21) has a heat pipe for circulating water or steam inside, and the water or steam circulating in the heat pipe is heat-exchanged with the exhaust gas circulating in the pipe.

[0088] In the above structure, the flow velocity of the mixed fluid can be sufficiently suppressed on the downstream side of the resistance part (heat exchanger), so that the mixed fluid in a uniform state can flow into the denitration catalyst. Therefore, the denitration reaction occurs appropriately in the denitration catalyst, thereby improving the denitration efficiency.

[0089] Description of reference numerals:

[0090] 1: Combustion Engine

[0091] 2: Waste heat recovery boiler

[0092] 3: Pipeline

[0093] 4: The first heat exchange part

[0094] 5: Second heat exchange part

[0095] 7: Chimney

[0096] 10: Denitrification device

[0097] 11: Ammonia injection section

[0098] 11a: Ammonia piping

[0099] 11b: Spray nozzle

[0100] 12: Mixer

[0101] 12A: Mixing section

[0102] 12a: Unit

[0103] 13: Denitrification catalyst

[0104] 14: Ammonia decomposition catalyst

[0105] 18: Board

[0106] 18a: Upstream side plate

[0107] 18b: Downstream side plate

[0108] 21: High pressure heat exchange section.

Claims

1. A denitration device, which is a denitration device arranged in a pipe for exhaust gas to flow in a predetermined direction, wherein: The denitration device comprises: an injection unit for injecting a reducing agent into the exhaust gas flowing through the pipe, wherein the reducing agent has a function of reducing nitrogen oxides contained in the exhaust gas; a mixing portion provided on a downstream side of the injection portion, and mixing the exhaust gas flowing in the duct with the reducing agent by forming a vortex flow centered on a central axis extending in the predetermined direction; and a resistance portion, which is provided on the downstream side of the mixing portion and applies resistance to the flow of the mixed fluid in which the exhaust gas and the reducing agent are mixed, and the resistance portion is provided over the entire area of ​​the flow path cross section of the pipe, The injection portion includes a reducing agent pipe and a nozzle, wherein the reducing agent pipe extends in a direction intersecting the predetermined direction, that is, an intersecting direction, and allows the reducing agent to flow therein, and the nozzle is disposed on a side of the reducing agent pipe and injects the reducing agent into the pipe. The distance from the injection portion to the mixing portion is not less than 10 times and not more than 30 times the outer diameter of the reducing agent pipe. A distance from the mixing portion to the resistance portion is longer than a distance from the injection portion to the mixing portion.

2. The denitration device according to claim 1, wherein: The mixing section has a plurality of units that determine the size of the vortex formed. The distance from the mixing portion to the resistance portion is longer than five times the length of the unit in a direction intersecting the predetermined direction, that is, in a direction intersecting the predetermined direction.

3. The denitration device according to claim 1 or 2, wherein: The resistance portion includes a denitration catalyst configured to remove nitrogen oxides contained in the exhaust gas by allowing the mixed fluid to pass therethrough.

4. The denitration device according to claim 1 or 2, wherein: The denitration device includes a denitration catalyst, which is disposed on the downstream side of the resistance portion and removes nitrogen oxides contained in the exhaust gas by allowing the mixed fluid to pass therethrough. The resistance portion includes a heat exchanger having a heat transfer pipe inside which water or steam flows, and the heat exchanger performs heat exchange between the water or steam flowing in the heat transfer pipe and the exhaust gas flowing in the pipe.

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