SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices

Abstract

This utility model discloses an SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices. The flue includes an SCR denitrification flue where exhaust gas enters from the top inlet and flows along the flue to exit from the bottom outlet. A first denitrification spray gun system is located at the top of the flue, and a first nitrogen oxide and oxygen detection device is located at the bottom bend. A second denitrification spray gun system is located in the upward flow section of the flue, and a second nitrogen oxide and oxygen detection device is also located at the bottom outlet. As can be seen from the above structure, this SCR denitrification flue with nitrogen oxide and oxygen concentration detection devices allows the first and second denitrification spray gun systems to adjust the ammonia injection rate based on feedback from the first and second detection devices, ensuring that the nitrogen oxide content in the exhaust gas meets emission requirements and also enabling more precise ammonia usage.

Description

Technical Field

[0001] This utility model relates to the technical field of SCR denitrification flue, specifically to an SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices. Background Technology

[0002] The principle of SCR denitrification is to inject ammonia into the exhaust gas duct through an ammonia injection system. The ammonia reacts with nitrogen oxides in a high-temperature environment to produce water and nitrogen, thereby removing nitrogen oxides from the exhaust gas.

[0003] However, since the nitrogen oxide content in the exhaust gas is not constant, the traditional exhaust gas denitrification process can only inject excessive ammonia through an ammonia injection system to ensure that all nitrogen oxides in the exhaust gas are treated. However, injecting excessive ammonia not only increases the cost of ammonia use, but also requires additional treatment afterward, thus increasing the process cost and equipment investment cost.

[0004] For those skilled in the art, the best approach is undoubtedly to monitor the nitrogen oxide (NOx) content in the exhaust gas after injecting ammonia through the ammonia injection system, and then adjust the amount of ammonia injected to ensure that the ammonia reacts precisely with the NOx. Therefore, some companies have begun using online NOx detection equipment to monitor the NOx and oxygen content in the exhaust gas pipeline, thus determining whether the amount of ammonia injected is too high or too low relative to the NOx content in the exhaust gas. However, based on experience, it has been found that even after adjusting the ammonia injection volume according to the detection equipment, it is still impossible to achieve precise ammonia injection to correspond with the NOx content. In the exhaust gas after SCR denitrification, the relative NOx content and ammonia content can never be perfectly aligned.

[0005] The inventors of this application discovered that the problem lies in the fact that the detected nitrogen oxide content in the exhaust gas is not accurate relative to the actual nitrogen oxide content inside the SCR denitrification pipeline. This is because the detection device is located at different positions relative to the SCR denitrification pipeline, resulting in different detection results; the airflow velocity inside the SCR denitrification pipeline is also different, resulting in different detection results; in addition, long-term contact with airflow at a certain velocity can also cause structural damage to the sampling port, resulting in different sampling amounts and different detection results. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices. This allows the first and second denitrification spray gun systems to adjust the ammonia injection volume based on feedback from the first and second detection devices, ensuring that the nitrogen oxide content in the exhaust gas meets emission requirements and also making the ammonia usage more precise.

[0007] The technical solution adopted by this utility model is: The SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices includes an SCR denitrification flue with a "∽" shaped structure. The exhaust gas enters from the top inlet end of the SCR denitrification flue and flows along the SCR denitrification flue to exit from the bottom outlet end of the SCR denitrification flue. The top of the SCR denitrification flue is equipped with a first denitrification spray gun system, the bottom bend of the SCR denitrification flue is equipped with a first nitrogen oxide and oxygen detection device, the upward flow section of the exhaust gas in the SCR denitrification flue is equipped with a second denitrification spray gun system, and the bottom outlet end of the SCR denitrification flue is also equipped with a second nitrogen oxide and oxygen detection device.

[0008] A further improvement of this utility model is that the first detection device for nitrogen oxides and oxygen includes multiple sampling inlets A fixed inside the SCR denitrification flue. Each sampling inlet A is connected to a first detector for nitrogen oxides and oxygen fixed outside the SCR denitrification flue via a sampling main pipe A equipped with a jet switching device A. The sampling inlets A are evenly distributed in the same cross section at corresponding positions inside the SCR denitrification flue. The exhaust gas after being detected by the first detector for nitrogen oxides and oxygen is connected to the area at the bottom bend of the SCR denitrification flue, located between the first detector for nitrogen oxides and oxygen and the second denitrification spray gun system, through a connecting pipe A. The first detector for nitrogen oxides and oxygen also includes an inlet pipe A fixed to the SCR denitrification flue. The inlet pipe A extends into the SCR denitrification flue and is connected to the jet switching device A.

[0009] A further improvement of this utility model is that each of the sampling inlet A is connected to a corresponding sampling branch pipe, and the sampling branch pipe is connected to the sampling main pipe A through a sampling branch pipe.

[0010] A further improvement of this utility model is that the sampling main tube A is connected to the nitrogen oxide detection device A and the oxygen detection device A in the first nitrogen oxide and oxygen detector respectively through two detection branch tubes.

[0011] A further improvement of this utility model is that a heating device A is also connected to the air intake pipe A.

[0012] A further improvement of this utility model is that the first detection device for nitrogen oxides and oxygen further includes a horizontal angle steel arranged perpendicularly to the exhaust gas flow direction at the bottom bend of the SCR denitrification flue. The bend of the horizontal angle steel is located at the top of the bottom bend in the SCR denitrification flue. The edges of the two side plates of the horizontal angle steel are located at the bottom of the bottom bend in the SCR denitrification flue. The air inlet sampling port A is uniformly fixed to the inner end face of the side plate on the side of the horizontal angle steel away from the top air inlet end.

[0013] A further improvement of this utility model is that the second detection device for nitrogen oxides and oxygen includes multiple sampling inlets B fixed inside the SCR denitrification flue. Each sampling inlet B is connected to a nitrogen oxide and oxygen second detector or an ammonia detector fixed outside the SCR denitrification flue via a sampling main pipe B equipped with a jet switching device B. The sampling inlets B are evenly distributed in the middle of the same cross section within the corresponding position inside the SCR denitrification flue. The exhaust gas after being detected by the nitrogen oxide and oxygen second detector and the ammonia detector is connected to the bottom outlet of the SCR denitrification flue, located below the sampling inlets B, via a connecting pipe B. The second detection device for nitrogen oxides and oxygen also includes an inlet pipe B fixed to the SCR denitrification flue. The inlet pipe B extends into the SCR denitrification flue and is connected to the jet switching device B.

[0014] A further improvement of this utility model is that the sampling air inlets B are located in the same horizontal plane and are set downwards. A horizontal baffle is fixedly provided above each sampling air inlet B, and the horizontal baffles are respectively located in the same horizontal plane at corresponding positions in the SCR denitrification flue.

[0015] A further improvement of this utility model is that the inner wall cross-sectional dimensions of the flue section directly connected to the top air inlet or the bottom air outlet of the SCR denitrification flue are larger than the inner wall cross-sectional dimensions of the bottom bend section and the upward flow section of the exhaust gas of the SCR denitrification flue, respectively, and the inner wall cross-sectional dimensions of the bottom air outlet of the SCR denitrification flue gradually decrease from top to bottom to form a constricted structure.

[0016] A further improvement of this utility model is that the first denitrification spray gun system includes multiple denitrification spray guns, and the second denitrification spray gun system includes multiple spray nozzles connected in parallel. The spray nozzles are evenly distributed in the same horizontal plane of the upward flow section of the SCR denitrification flue gas, and the spray direction of the spray nozzles is set downward.

[0017] The beneficial effects of this utility model are as follows: First, the SCR denitrification flue of this utility model, equipped with nitrogen oxide and oxygen concentration detection devices, enables the first and second denitrification spray gun systems to adjust the ammonia injection volume based on feedback from the first and second detection devices, ensuring that the nitrogen oxide content in the exhaust gas meets emission requirements, and also making the ammonia usage more precise.

[0018] Secondly, the SCR denitrification flue of this utility model, equipped with nitrogen oxide and oxygen concentration detection devices, ensures that the first detection device can detect more comprehensive exhaust gas samples through the distribution of the sampling inlet A, thus guaranteeing the accuracy of the detection results of the first detection device.

[0019] Third, the SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices of this utility model, through the set angle steel structure, eliminates as much as possible the influence of the exhaust gas flow in the SCR denitrification flue on the sampling quality of the sampling inlet A, and further ensures the accuracy of the detection results of the first detection device.

[0020] Fourth, the SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices of this utility model can also form turbulent airflow in the exhaust gas flow area of ​​the SCR denitrification flue through the set angle steel structure, so as to make the exhaust gas in the area more fully mixed, thereby making the nitrogen oxides in the exhaust gas and the ammonia gas sprayed by the first denitrification spray gun system more fully contact and react in the area, thus improving the removal effect of nitrogen oxides in the exhaust gas.

[0021] Fifth, the SCR denitrification flue of this utility model, equipped with nitrogen oxide and oxygen concentration detection devices, uses the sampling inlet B of the second detection device to correspond to the horizontal baffles. This not only reduces the impact of the exhaust gas flow in the SCR denitrification flue on the sampling quality of the sampling inlet B, but also creates turbulence in the exhaust gas flow in this area of ​​the SCR denitrification flue. This allows the exhaust gas in this area to mix more thoroughly, thereby enabling the nitrogen oxides in the exhaust gas to come into more complete contact and reaction with the ammonia gas sprayed by the second denitrification spray gun system in this area. This improves the removal efficiency of nitrogen oxides in the exhaust gas and ensures the accuracy of the detection results of the second detection device.

[0022] Sixth, the SCR denitrification flue of this utility model, equipped with nitrogen oxide and oxygen concentration detection devices, forms a constricted structure by gradually decreasing the cross-sectional size of the inner wall of the bottom outlet end of the SCR denitrification flue from top to bottom. Furthermore, the sampling inlet B is evenly distributed in the middle of the same cross-section within the corresponding position of the SCR denitrification flue. Thus, the constricted structure blocks the airflow, and combined with the dual effect of the horizontal baffle, the thorough mixing effect of the exhaust gas in the corresponding position area is further improved, thereby further improving the accuracy of the detection results of the second detection device.

[0023] Seventh, the SCR denitrification flue of this utility model, equipped with nitrogen oxide and oxygen concentration detection devices, can allow the exhaust gas in the SCR denitrification flue to flow under negative pressure to the corresponding detection device for detection through the action of jet switching device A and jet switching device B. Moreover, it can also backflush the detection pipeline after closing to avoid blockage in the detection pipeline. Attached Figure Description

[0024] Figure 1 This is a side sectional view of the SCR denitrification flue structure of this application.

[0025] Figure 2This is a magnified front view of the full-section nitrogen oxide and oxygen concentration detection device of this application, with the front side panel hidden.

[0026] Among them: 1-SCR denitrification flue, 2-first denitrification spray gun system, 3-sampling inlet A, 4-second denitrification spray gun system, 5-sampling inlet B, 6-sampling main pipe A, 7-sampling main pipe B, 8-horizontal angle steel, 9-horizontal baffle, 10-jet switching device A, 11-first detector for nitrogen oxides and oxygen, 12-detection branch pipe, 13-sampling branch pipe, 14-sampling branch pipe, 15-inlet pipe A, 16-heating device A. Detailed Implementation

[0027] Combination Figures 1-2 It is known that the SCR denitrification flue equipped with nitrogen oxide and oxygen concentration detection devices includes an SCR denitrification flue 1 with a "∽" shaped structure. After the exhaust gas enters from the top inlet end of the SCR denitrification flue 1, it flows along the SCR denitrification flue 1 and exits from the bottom outlet end of the SCR denitrification flue 1. The top of the SCR denitrification flue 1 is equipped with a first denitrification spray gun system 2. The bottom bend of the SCR denitrification flue 1 is equipped with a first detection device for nitrogen oxides and oxygen. The upward flow section of the exhaust gas in the SCR denitrification flue 1 is equipped with a second denitrification spray gun system 4. The bottom outlet end of the SCR denitrification flue 1 is also equipped with a second detection device for nitrogen oxides and oxygen.

[0028] A further improvement of this utility model is that the first detection device for nitrogen oxides and oxygen includes multiple sampling inlets A3 fixed inside the SCR denitrification flue 1. The sampling inlets A3 are respectively connected to the first nitrogen oxide and oxygen detector 11 fixed outside the SCR denitrification flue 1 via a sampling main pipe A6 equipped with a jet switching device A10. The sampling inlets A3 are evenly distributed in the same cross section at corresponding positions inside the SCR denitrification flue 1. The exhaust gas after being detected by the first nitrogen oxide and oxygen detector 11 is connected to the area at the bottom bend of the SCR denitrification flue 1, located between the first nitrogen oxide and oxygen detection device and the second denitrification spray gun system 4, through a connecting pipe A. The first nitrogen oxide and oxygen detection device also includes an inlet pipe A15 fixed to the SCR denitrification flue 1. The inlet pipe A15 extends into the SCR denitrification flue 1 and is connected to the jet switching device A10.

[0029] The sampling inlet A3 is connected to a corresponding sampling branch pipe 14, and the sampling branch pipe 14 is connected to the sampling main pipe A6 through the sampling branch pipe 13.

[0030] The sampling main tube A6 is connected to the nitrogen oxide detection device A and the oxygen detection device A in the first nitrogen oxide and oxygen detector 11 through two detection branch tubes 12.

[0031] A heating device A16 is also connected to the air intake pipe A15.

[0032] The first detection device for nitrogen oxides and oxygen also includes a horizontal angle steel 8 whose length direction is perpendicular to the exhaust gas flow direction at the bottom bend of the SCR denitrification flue 1. The bend of the horizontal angle steel 8 is located at the top of the bottom bend inside the SCR denitrification flue 1. The edges of the two side plates of the horizontal angle steel 8 are located at the bottom of the bottom bend inside the SCR denitrification flue 1. The air inlet sampling port A3 is uniformly fixed to the inner end face of the side plate on the side of the horizontal angle steel 8 away from the top air inlet end.

[0033] The second detection device for nitrogen oxides and oxygen includes multiple sampling inlets B5 fixed inside the SCR denitrification flue 1. Each sampling inlet B5 is connected to a nitrogen oxide and oxygen second detector and an ammonia detector fixed outside the SCR denitrification flue 1 via a sampling main pipe B7 equipped with a jet switching device B (not shown in the attached figure). The sampling inlets B5 are evenly distributed in the middle of the same cross section within the corresponding position inside the SCR denitrification flue 1. The exhaust gas after being detected by the nitrogen oxide and oxygen second detector or the ammonia detector is connected to the bottom outlet of the SCR denitrification flue 1 below the sampling inlets B5 via a connecting pipe B. The second detection device for nitrogen oxides and oxygen also includes an inlet pipe B (not shown in the attached figure) fixed to the SCR denitrification flue 1. The inlet pipe B extends into the SCR denitrification flue 1 and is connected to the jet switching device B.

[0034] The sampling air inlets B5 are located in the same horizontal plane and are set downwards. A horizontal baffle 9 is fixed above each sampling air inlet B5. The horizontal baffle 9 are located in the same horizontal plane at corresponding positions in the SCR denitrification flue 1.

[0035] A heating device B (not shown in the attached drawing) is also connected to the air intake pipe B.

[0036] The inner wall cross-sectional dimensions of the flue section directly connected to the top air inlet or bottom air outlet of the SCR denitrification flue 1 are larger than the inner wall cross-sectional dimensions of the bottom bend section and the upward flow section of the exhaust gas of the SCR denitrification flue 1, respectively. Furthermore, the inner wall cross-sectional dimension of the bottom air outlet of the SCR denitrification flue 1 gradually decreases from top to bottom, forming a constricted structure.

[0037] The first denitrification spray gun system 2 includes multiple denitrification spray guns, and the second denitrification spray gun system 4 includes multiple spray nozzles connected in parallel. The spray nozzles are evenly distributed in the same horizontal plane of the upward flow section of the SCR denitrification flue 1, and the spray direction of the spray nozzles is downward.

[0038] During normal use, ammonia is injected into the exhaust gas entering from the top inlet of the SCR denitrification flue 1 through the first denitrification spray gun system 2. Then, as the exhaust gas passes through the first detection device, the clean air in the inlet pipe A15 is heated by the heating device A16 and the heat from the flue gas in the SCR denitrification flue 1. The jet switching device A10 then generates a jet negative pressure, which causes the negative pressure at the sampling inlet A3 to draw the exhaust gas from the SCR denitrification flue 1 into the sample. The sample then passes through the sampling main pipe A6 into the first nitrogen oxide and oxygen detector 11 to detect the nitrogen oxide and oxygen concentrations of the exhaust gas. After being detected by the first nitrogen oxide and oxygen detector 11, the exhaust gas returns through the connecting pipe A to the area between the first nitrogen oxide and oxygen detector and the second denitrification spray gun system 4 at the bottom bend of the SCR denitrification flue 1, preventing exhaust gas leakage and environmental pollution. Next, based on the detection results of the first nitrogen oxide and oxygen detector 11, the corresponding amount of ammonia is sprayed through the second denitrification spray gun system 4. Finally, when passing through the second detection device, the clean air in the inlet pipe B is heated by the heating device B and the flue gas in the SCR denitrification flue 1, and then generates a jet negative pressure through the jet switching device B. This causes the negative pressure of the sampling inlet B5 to draw the exhaust gas in the SCR denitrification flue 1 into the sample. After sampling, the exhaust gas enters the second nitrogen oxide and oxygen detector and the ammonia detector through the sampling main pipe B7 to detect the nitrogen oxide concentration, oxygen concentration and ammonia concentration of the exhaust gas respectively. After being detected by the second nitrogen oxide and oxygen detector and the ammonia detector, the exhaust gas returns to the area below the second nitrogen oxide and oxygen detector at the bottom outlet of the SCR denitrification flue 1 through the connecting pipe B, to avoid exhaust gas leakage and environmental pollution.

[0039] Based on the detection results of the first nitrogen oxide and oxygen detectors, the ammonia injection rate of the first ammonia injection system is adjusted to match the nitrogen oxide content in the exhaust gas as closely as possible. Furthermore, the ammonia injection rate of the second ammonia injection system is adjusted to match the remaining nitrogen oxides detected by the first nitrogen oxide and oxygen detectors, ensuring that the nitrogen oxides in the SCR pipeline are essentially or even completely reacted. Based on the detection results of the second nitrogen oxide and oxygen detectors, the ammonia injection rate of the second ammonia injection system is adjusted to match the residual nitrogen oxides in the exhaust gas detected by the first nitrogen oxide and oxygen detectors as closely as possible, or even just barely reacted.

[0040] When reverse air blowing is required in this application, jet switching devices A10 and B are closed respectively. Clean air in inlet pipe A15 is heated by heating device A16 and the flue gas in SCR denitrification flue duct 1 before entering sampling main pipe A6 for hot air backflushing. Clean air in inlet pipe B is heated by heating device B and the flue gas in SCR denitrification flue duct 1 before entering sampling main pipe B7 for hot air backflushing. By setting timers for jet switching devices A10 and B, they are ensured to perform backflushing after a period of normal use. Furthermore, when the unit is in start-up / shutdown or other abnormal operating conditions, jet switching devices A10 and B perform backflushing to prevent flue gas from entering the sampling pipeline or related detectors, condensing into droplets and causing pipeline blockage.

Claims

1. SCR denitration flue provided with nitrogen oxide and oxygen concentration detection device, its characterized in being: The system includes an SCR denitrification flue (1) with a "∽" shaped structure. The exhaust gas enters from the top inlet of the SCR denitrification flue (1) and flows along the SCR denitrification flue (1) to exit from the bottom outlet of the SCR denitrification flue (1). The top of the SCR denitrification flue (1) is equipped with a first denitrification spray gun system (2). The bottom bend of the SCR denitrification flue (1) is equipped with a first detection device for nitrogen oxides and oxygen. The upward flow section of the exhaust gas in the SCR denitrification flue (1) is equipped with a second denitrification spray gun system (4). The bottom outlet of the SCR denitrification flue (1) is also equipped with a second detection device for nitrogen oxides and oxygen.

2. The SCR denitration flue provided with the nitrogen oxide and oxygen concentration detection device according to claim 1, characterized in that: The first detection device for nitrogen oxides and oxygen includes multiple sampling inlets A (3) fixed inside the SCR denitrification flue (1). The sampling inlets A (3) are connected to the first nitrogen oxide and oxygen detector (11) fixed outside the SCR denitrification flue (1) via a sampling main pipe A (6) connected to a jet switching device A (10). The sampling inlets A (3) are evenly distributed in the same cross section at corresponding positions inside the SCR denitrification flue (1). The exhaust gas after being detected by the first nitrogen oxide and oxygen detector (11) is connected to the area between the first nitrogen oxide and oxygen detection device and the second denitrification spray gun system (4) at the bottom bend of the SCR denitrification flue (1) via a connecting pipe A. The first nitrogen oxide and oxygen detection device also includes an inlet pipe A (15) fixed to the SCR denitrification flue (1). The inlet pipe A (15) extends into the SCR denitrification flue (1) and is connected to the jet switching device A (10).

3. The SCR denitrification flue gas duct equipped with nitrogen oxide and oxygen concentration detection devices as described in claim 2, characterized in that: The sampling inlet A (3) is connected to a sampling branch pipe (14), and the sampling branch pipe (14) is connected to the sampling main pipe A (6) through the sampling branch pipe (13).

4. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 2, characterized in that: The sampling main tube A (6) is connected to the nitrogen oxide detection device A and the oxygen detection device A in the first nitrogen oxide and oxygen detector (11) through two detection sub-tubes (12).

5. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in any one of claims 2 to 4, characterized in that: A heating device A (16) is also connected to the air intake pipe A (15).

6. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 2, characterized in that: The first detection device for nitrogen oxides and oxygen also includes a horizontal angle steel (8) whose length direction is perpendicular to the exhaust gas flow direction at the bottom bend of the SCR denitrification flue (1). The bend of the horizontal angle steel (8) is located at the top of the bottom bend in the SCR denitrification flue (1). The edges of the two side plates of the horizontal angle steel (8) are located at the bottom of the bottom bend in the SCR denitrification flue (1). The sampling inlet A (3) is uniformly fixed to the inner end face of the side plate on the side away from the top inlet end of the horizontal angle steel (8).

7. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 1, characterized in that: The second detection device for nitrogen oxides and oxygen includes multiple sampling inlets B (5) fixed inside the SCR denitrification flue (1). The sampling inlets B (5) are respectively connected to the nitrogen oxide and oxygen second detector and the ammonia detector fixed outside the SCR denitrification flue (1) through the sampling main pipe B (7) which is equipped with the jet switching device B. The sampling inlets B (5) are evenly distributed in the middle of the same cross section in the corresponding position inside the SCR denitrification flue (1). The exhaust gas after being detected by the nitrogen oxide and oxygen second detector or the ammonia detector is connected to the bottom outlet of the SCR denitrification flue (1) located below the sampling inlets B (5) through the connecting pipe B. The second detection device for nitrogen oxides and oxygen also includes an inlet pipe B fixed to the SCR denitrification flue (1). The inlet pipe B extends into the SCR denitrification flue (1) and is connected to the jet switching device B.

8. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 7, characterized in that: The sampling inlet B (5) is located in the same horizontal plane and is set downward. A horizontal baffle (9) is fixed above each sampling inlet B (5). The horizontal baffle (9) is located in the same horizontal plane at the corresponding position in the SCR denitrification flue (1).

9. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 1, characterized in that: The inner wall cross-sectional dimensions of the flue section directly connected to the top air inlet or bottom air outlet of the SCR denitrification flue (1) are larger than the inner wall cross-sectional dimensions of the bottom bend section and the upward flow section of the exhaust gas of the SCR denitrification flue (1). Furthermore, the inner wall cross-sectional dimensions of the bottom air outlet of the SCR denitrification flue (1) gradually decrease from top to bottom to form a constricted structure.

10. The SCR denitrification flue gas duct equipped with a nitrogen oxide and oxygen concentration detection device as described in claim 1, characterized in that: The first denitrification spray gun system (2) includes multiple denitrification spray guns, and the second denitrification spray gun system (4) includes multiple spray nozzles connected in parallel. The spray nozzles are evenly distributed in the same horizontal plane of the upward flow section of the SCR denitrification flue (1), and the spray direction of the spray nozzles is set downward.

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