Accurate ammonia spraying system for SCR (Selective Catalytic Reduction) denitration

Abstract

The utility model discloses an accurate ammonia spraying system for SCR (Selective Catalytic Reduction) denitration. The accurate ammonia spraying system comprises a urea hydrolysis reactor, a pressure stabilizing unit, a concentration stabilizing unit, a flow regulating unit, a flue, an ammonia gas mixture pipeline and an ammonia spraying device, the pressure stabilizing unit comprises a pressure gauge, an inverter compressor, a pressure stabilizing regulating valve and a pressure stabilizing tank; the surge tank is connected with the variable-frequency compressor through a first pipeline, the variable-frequency compressor is connected and communicated with the ammonia gas mixture pipeline through a second pipeline, the discharge end of the surge tank is connected and communicated with the ammonia gas mixture pipeline through a third pipeline, and the third pipeline is provided with a surge regulating valve; the concentration stabilizing unit comprises a concentration regulating valve A, a concentration regulating valve B, an ammonia gas storage tank, a compressed air buffer tank and an ammonia concentration analyzer; the urea hydrolysis reactor is connected with an ammonia spraying device in a flue through an ammonia gas mixed gas pipeline; and a pressure gauge and an ammonia concentration analyzer are arranged on the ammonia gas mixture pipeline. The ammonia spraying amount can be reasonably matched with the required ammonia spraying amount, and the ammonia spraying flow can be accurately controlled.

Description

Technical Field

[0001] The utility model relates to the technical field of nitrogen oxide purification in coal-fired power plants, in particular to an SCR denitration precision ammonia injection system. Background Art

[0002] Nitrogen oxides (NOx) are a major component of flue gas emissions from coal-fired power plants and are considered a significant pollutant. Therefore, effective removal is essential. In China, selective catalytic reduction (SCR) technology is primarily used to reduce NOx emissions from coal-fired power plants. This technology operates by injecting ammonia into the flue gas. With the help of a catalyst, a chemical reaction occurs with NOx in the flue gas (primarily nitric oxide, NO). This reaction produces harmless nitrogen and water vapor, effectively reducing NOx emissions.

[0003] An ammonia injection system is a system that injects ammonia gas or a mixture containing ammonia into the flue for denitrification. It usually includes a gas source, pipelines, an ammonia injection grid in the flue, and an ammonia flow control unit.

[0004] Storing large amounts of ammonia in high-pressure tanks poses certain safety risks. To ensure inherent safety in the future, more and more coal-fired power plants are adopting urea hydrolysis to produce ammonia. The chemical equation is: (NH₂)₂CO + 2H₂O → 2NH₃ + CO₂. The gas produced by urea hydrolysis is a mixture of ammonia, carbon dioxide, and water vapor, with an ammonia concentration of approximately 5% by volume.

[0005] In traditional ammonia injection systems, a closed loop consisting of a flow control valve and a flow meter ensures precise control of the ammonia flow rate. However, in actual operation, various system disturbances, such as temperature fluctuations in the urea hydrolysis reactor, feed fluctuations, and changes in pipeline pressure due to changes in ammonia demand, can lead to a mismatch between the actual and required ammonia injection rates. In particular, large fluctuations in the urea hydrolyzer load can lead to significant changes in the gaseous product composition, particularly in ammonia concentration.

[0006] In short, the fluctuations and changes in pipeline pressure and ammonia concentration in the ammonia injection system will cause a deviation between the actual injected ammonia and the ammonia required for denitrification, reducing the operating efficiency of the denitrification system. Utility Model Content

[0007] The utility model provides an SCR denitrification precision ammonia injection system, which solves the problem that in traditional ammonia injection systems, fluctuations and changes in pipeline pressure and ammonia concentration may cause deviations between the actually injected ammonia and the ammonia required for denitrification, thereby reducing the operating efficiency of the denitrification system.

[0008] The utility model provides an SCR denitration precision ammonia injection system, comprising a urea hydrolysis reactor, a pressure stabilizing unit, a concentration stabilizing unit, a flow regulating unit, a flue, an ammonia mixed gas pipeline, and an ammonia injection device; the pressure stabilizing unit comprises a pressure gauge, a variable frequency compressor, a pressure stabilizing regulating valve, and a pressure stabilizing tank; the feed end of the pressure stabilizing tank is connected to the discharge end of the variable frequency compressor through a first pipeline, the feed end of the variable frequency compressor is connected to the ammonia mixed gas pipeline through a second pipeline, the discharge end of the pressure stabilizing tank is connected to the ammonia mixed gas pipeline through a third pipeline, and the pressure stabilizing regulating valve is provided on the third pipeline; the concentration stabilizing unit comprises a concentration regulating valve A , concentration regulating valve B, ammonia storage tank, compressed air buffer tank, ammonia concentration analyzer; the ammonia storage tank is connected to the ammonia mixed gas pipeline through a fourth pipeline, the compressed air buffer tank is connected to the ammonia mixed gas pipeline through a fifth pipeline, a concentration regulating valve A is provided on the fourth pipeline, and a concentration regulating valve B is provided on the fifth pipeline; the flow regulating unit includes a flow meter and a flow regulating valve, and the flow meter and the flow regulating valve are both provided on the ammonia mixed gas pipeline; wherein, the urea hydrolysis reactor is connected to the ammonia injection device in the flue through the ammonia mixed gas pipeline; a pressure gauge and an ammonia concentration analyzer are provided on the ammonia mixed gas pipeline.

[0009] Furthermore, the pressure gauge is electrically connected to the variable frequency compressor and the pressure stabilizing regulating valve respectively.

[0010] Furthermore, the ammonia concentration analyzer is electrically connected to the concentration regulating valve A and the concentration regulating valve B respectively.

[0011] Furthermore, the flow meter is electrically connected to the flow regulating valve.

[0012] Furthermore, the pressure gauge, variable frequency compressor, pressure stabilizing regulating valve, ammonia concentration analyzer, concentration regulating valve A, concentration regulating valve B, flow meter, and flow regulating valve are controlled by a control system.

[0013] Furthermore, the pressure gauge, ammonia concentration analyzer, and flow meter are all located at the end of the ammonia mixed gas pipeline.

[0014] It can be seen from the above technical solutions that the utility model provides an SCR denitrification precision ammonia injection system.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. By controlling the pressure-stabilizing regulating valve and variable-frequency compressor, the pressure in the pipeline is always maintained within a small range near the set pressure, keeping it generally stable. This avoids the impact of system disturbances on the pressure, provides conditions for precise control of the ammonia injection flow rate, and improves the operating efficiency of the denitrification system.

[0017] 2. An ammonia concentration analyzer measures the ammonia concentration in the pipeline in real time. By controlling the opening and closing of concentration control valves A and B, the compressed air in the compressed air buffer tank is regulated to ensure that the ammonia concentration in the pipeline is always maintained within a small range near the set concentration, maintaining overall stability. This avoids the impact of system disturbances on ammonia concentration and provides conditions for precise control of ammonia injection flow.

[0018] 3. The denitrification system calculates the required ammonia injection amount based on data such as unit load and nitrogen oxide concentration, and transmits this data to the flow regulation unit. Since the influence of pressure and ammonia concentration fluctuations is eliminated, the flow regulation unit can achieve high-quality and precise ammonia injection flow regulation, thereby achieving efficient denitrification ammonia injection control. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for implementation. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 This is a schematic diagram of the overall structure of an SCR denitrification precision ammonia injection system proposed in this utility model;

[0021] Figure 2 This is a schematic diagram of the overall structure of an SCR denitrification precision ammonia injection system proposed in the utility model.

[0022] In the picture:

[0023] 1-urea hydrolysis reactor;

[0024] 2-pressure stabilizing unit; 21-pressure gauge; 22-frequency conversion compressor; 23-pressure stabilizing regulating valve; 24-pressure stabilizing tank;

[0025] 3-concentration stabilization unit; 31-concentration regulating valve A; 32-concentration regulating valve B; 33-ammonia storage tank; 34-compressed air buffer tank; 35-ammonia concentration analyzer;

[0026] 4-flow regulating unit; 41-flow meter; 42-flow regulating valve;

[0027] 5- Flue;

[0028] 6- ammonia mixed gas pipeline;

[0029] 7- ammonia injection device;

[0030] 101 - first pipeline; 102 - second pipeline; 103 - third pipeline; 104 - fourth pipeline; 105 - fifth pipeline. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0032] Example 1:

[0033] See also Figure 1-2 , an SCR denitrification precise ammonia injection system, comprising a urea hydrolysis reactor 1, a pressure stabilizing unit 2, a concentration stabilizing unit 3, a flow regulating unit 4, a flue 5, an ammonia mixed gas pipeline 6, and an ammonia injection device 7; the pressure stabilizing unit 2 comprises a pressure gauge 21, a variable frequency compressor 22, a pressure stabilizing regulating valve 23, and a pressure stabilizing tank 24; the feed end of the pressure stabilizing tank 24 is connected to the discharge end of the variable frequency compressor 22 through a first pipeline 101, the feed end of the variable frequency compressor 22 is connected to the ammonia mixed gas pipeline 6 through a second pipeline 102, the discharge end of the pressure stabilizing tank 24 is connected to the ammonia mixed gas pipeline 6 through a third pipeline 103, and the pressure stabilizing regulating valve 23 is provided on the third pipeline 103; the concentration stabilizing unit 3 comprises a concentration regulating valve A31, a concentration regulating valve B32, an ammonia storage tank 33, a compressed air buffer tank 34, and an ammonia concentration analyzer 35; the ammonia storage The tank 33 is connected to the ammonia mixture pipeline 6 through the fourth pipeline 104, and the compressed air buffer tank 34 is connected to the ammonia mixture pipeline 6 through the fifth pipeline 105. A concentration regulating valve A31 is provided on the fourth pipeline, and a concentration regulating valve B32 is provided on the fifth pipeline 105; the flow regulating unit 4 includes a flow meter 41 and a flow regulating valve 42, and the flow meter 41 and the flow regulating valve 42 are both provided on the ammonia mixture pipeline 6; the urea hydrolysis reactor 1 is connected to the ammonia injection device 7 in the flue 5 through the ammonia mixture pipeline 6; a pressure gauge 21 and an ammonia concentration analyzer 35 are provided on the ammonia mixture pipeline 6. By controlling the pressure stabilizing regulating valve and the variable frequency compressor, the pressure in the pipeline is always maintained within a small range near the set pressure, and the overall pressure remains stable, thereby avoiding the influence of system disturbances on the pressure and providing conditions for precise control of the ammonia injection flow rate. An ammonia concentration analyzer measures the ammonia concentration in the pipeline in real time. By controlling the opening and closing of concentration control valves A and B, the compressed air in the compressed air buffer tank is regulated to enter the pipeline, ensuring that the ammonia concentration in the pipeline is always maintained within a small range near the set concentration, maintaining overall stability. This avoids the impact of system disturbances on ammonia concentration, providing conditions for precise control of ammonia injection flow. The denitrification system calculates the required ammonia injection volume based on data such as unit load and nitrogen oxide concentration, and transmits this data to the flow control unit. Because the effects of pressure and ammonia concentration fluctuations are eliminated, the flow control unit can achieve high-quality and precise ammonia injection flow regulation, thereby achieving efficient denitrification ammonia injection control.

[0034] In this embodiment, see Figure 1The pressure gauge 21 is electrically connected to the variable frequency compressor 22 and the pressure regulating valve 23 respectively.

[0035] In this embodiment, see Figure 1 The ammonia concentration analyzer 35 is electrically connected to the concentration regulating valve A31 and the concentration regulating valve B32 respectively.

[0036] In this embodiment, see Figure 1 , the flow meter 41 is electrically connected to the flow regulating valve 42 .

[0037] In this embodiment, the pressure gauge 21, the variable frequency compressor 22, the pressure regulating valve 23, the ammonia concentration analyzer 35, the concentration regulating valve A31, the concentration regulating valve B32, the flow meter 41, and the flow regulating valve 42 are controlled by the control system.

[0038] The ammonia injection device 7 is a prior art device, which consists of an ammonia injection pipe and a nozzle arranged on the ammonia injection pipe. Ammonia is supplied to the ammonia injection pipe through the ammonia injection main pipe, and then evenly sprayed from the nozzle in the flue 5 for delayed full contact denitrification.

[0039] In this embodiment, the pressure gauge 21 , the ammonia concentration analyzer 35 , and the flow meter 41 are located at the end of the ammonia mixed gas pipeline 6 .

[0040] In this embodiment, when the pressure is higher than the set pressure, the pressure-stabilizing regulating valve 23 is closed and the variable-frequency compressor 22 is turned on. The material in the pipeline is stored in the pressure-surge tank 24 through the variable-frequency compressor 22, thereby reducing the pressure. When the pressure is lower than the set pressure, the pressure-stabilizing regulating valve 23 is opened and the variable-frequency compressor 22 is turned off. The gas in the pressure-surge tank 24 then enters the pipeline, increasing the pressure. This method maintains the pressure in the pipeline within a small range near the set pressure, maintaining overall stability. This prevents the impact of system disturbances on pressure and provides conditions for precise control of the ammonia injection flow rate.

[0041] The ammonia concentration analyzer 35 measures the ammonia concentration in the pipeline in real time. When the ammonia concentration is higher than the set concentration, the concentration regulating valve A31 is closed and the concentration regulating valve B32 is opened. At this time, the compressed air in the compressed air buffer tank 34 enters the pipeline, thereby reducing the ammonia concentration in the pipeline; conversely, when the ammonia concentration is lower than the set concentration, the concentration regulating valve B32 is closed and the concentration regulating valve A31 is opened. The pure ammonia in the ammonia storage tank 33 enters the pipeline, thereby increasing the ammonia concentration in the pipeline. In this way, the ammonia concentration in the pipeline is always maintained within a small range near the set concentration and remains stable overall. The influence of system disturbances on the ammonia concentration is avoided, providing conditions for precise control of the ammonia injection flow rate.

[0042] The denitrification system calculates the required ammonia injection amount through PID according to data such as unit load and nitrogen oxide concentration, and transmits this data to the flow control unit 4. Since the influence of pressure and ammonia concentration fluctuations is eliminated, the flow control unit 4 can achieve high-quality and precise ammonia injection flow regulation, thereby achieving efficient denitrification ammonia injection control. The specific regulation block diagram is shown in the figure. Figure 2 shown.

[0043] Those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered merely as exemplary; the true scope of the invention is indicated by the claims.

[0044] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The above-described embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention.

Claims

1. An SCR denitrification precision ammonia injection system, characterized by: It comprises a urea hydrolysis reactor (1), a pressure stabilizing unit (2), a concentration stabilizing unit (3), a flow regulating unit (4), a flue (5), an ammonia mixed gas pipeline (6), and an ammonia spraying device (7); The pressure stabilizing unit (2) comprises a pressure gauge (21), a variable frequency compressor (22), a pressure stabilizing regulating valve (23), and a pressure stabilizing tank (24); the feed end of the pressure stabilizing tank (24) is connected to the discharge end of the variable frequency compressor (22) via a first pipeline (101), the feed end of the variable frequency compressor (22) is connected to the ammonia mixed gas pipeline (6) via a second pipeline (102), the discharge end of the pressure stabilizing tank (24) is connected to the ammonia mixed gas pipeline (6) via a third pipeline (103), and the pressure stabilizing regulating valve (23) is provided on the third pipeline (103); The concentration stabilization unit (3) comprises a concentration regulating valve A (31), a concentration regulating valve B (32), an ammonia storage tank (33), a compressed air buffer tank (34), and an ammonia concentration analyzer (35); the ammonia storage tank (33) is connected to the ammonia mixed gas pipeline (6) via a fourth pipeline (104), the compressed air buffer tank (34) is connected to the ammonia mixed gas pipeline (6) via a fifth pipeline (105), the fourth pipeline is provided with a concentration regulating valve A (31), and the fifth pipeline (105) is provided with a concentration regulating valve B (32); The flow regulating unit (4) comprises a flow meter (41) and a flow regulating valve (42), and the flow meter (41) and the flow regulating valve (42) are both arranged on the ammonia mixed gas pipeline (6); The urea hydrolysis reactor (1) is connected to an ammonia injection device (7) in a flue (5) via an ammonia mixed gas pipeline (6); a pressure gauge (21) and an ammonia concentration analyzer (35) are provided on the ammonia mixed gas pipeline (6).

2. The SCR denitrification precision ammonia injection system according to claim 1, characterized in that: The pressure gauge (21) is electrically connected to the variable frequency compressor (22) and the pressure regulating valve (23) respectively.

3. The SCR denitrification precise ammonia injection system according to claim 1, characterized in that: The ammonia concentration analyzer (35) is electrically connected to the concentration regulating valve A (31) and the concentration regulating valve B (32), respectively.

4. The SCR denitrification precise ammonia injection system according to claim 1, characterized in that: The flow meter (41) is electrically connected to the flow regulating valve (42).

5. The SCR denitrification precise ammonia injection system according to claim 1, characterized in that: The pressure gauge (21), the variable frequency compressor (22), the pressure regulating valve (23), the ammonia concentration analyzer (35), the concentration regulating valve A (31), the concentration regulating valve B (32), the flow meter (41), and the flow regulating valve (42) are controlled by a control system.

6. The SCR denitrification precision ammonia injection system according to claim 1, characterized in that: The pressure gauge (21), the ammonia concentration analyzer (35), and the flow meter (41) are located at the end of the ammonia mixed gas pipeline (6).

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