SCR (Selective Catalytic Reduction) precise ammonia spraying system in partition arrangement in shape of Chinese character

Abstract

The utility model relates to an SCR (Selective Catalytic Reduction) precise ammonia spraying system in partition arrangement in the shape of a Chinese character'tian ', which aims to solve the technical problem that the sampling in the linear arrangement of the traditional SCR system is not representative, and adopts the technical scheme that an ammonia spraying grid in the shape of a Chinese character'tian' is arranged in an uptake flue of the partition ammonia spraying system, and an ammonia large header is arranged at the upstream of the ammonia spraying grid; a plurality of small ammonia headers are connected with the large ammonia header through ammonia spraying branch pipes, the top surfaces of the small ammonia headers are vertically arranged to spray pipes and extend into each ammonia spraying partition, each ammonia spraying branch pipe is provided with a regulating valve and a flow meter, an ammonia supply system is connected with one end of the large ammonia header, a sampling grid is arranged in an outlet flue, a flue gas sampling rod extends into a sampling partition, and an analysis probe analyzes flue gas data. The partition balance control system is in a main control and auxiliary control mode, the partition ammonia injection grid and the partition sampling grid are arranged in a shape like a Chinese character'tian ', and the problem that sampling is not representative due to the fact that the section of a flue below a denitration outlet catalyst is wide and linear arrangement is adopted is solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of environmental protection denitration equipment, and particularly relates to an SCR precise ammonia injection system with a cross-shaped partition layout. Background Art

[0002] Many major power generation groups across the country have actively promoted the deep peak shaving operation of coal-fired units, giving full play to the flexibility of thermal power units in frequency modulation and peak shaving and their basic supporting role for the power grid.

[0003] When the unit is deeply peak-shaved to 30% THA load and flexibly operates under low load conditions for a long time, the flue gas temperature at the denitration inlet decreases, the flue gas flow rate decreases, and the non-uniformity of the flue gas flow field increases. The layout of the traditional SCR denitration system's NOx / O2 sampling probes is unreasonable, resulting in unrepresentative sampling. Moreover, with the extraction measurement method, there is a large lag in measurement. The SCR denitration system cannot accurately control the ammonia injection amount, leading to problems such as local NOx emission exceeding the standard, high ammonia slip, and air preheater blockage. Therefore, it is urgent to reform the traditional SCR ammonia injection system to achieve precise ammonia injection, improve the denitration efficiency, reduce the consumption of reducing agents, reduce ammonia slip, and ensure that the NOx emission concentration in the flue gas after denitration meets the environmental protection standards. Summary of the Invention

[0004] The purpose of the utility model is to solve the above problems and provide an SCR precise ammonia injection system with a cross-shaped partition layout.

[0005] To solve the above technical problems, the technical solution adopted by the utility model is:

[0006] An SCR precise ammonia injection system with a cross-shaped partition layout includes an ammonia supply system, a partition ammonia injection system, a partition sampling system, and a partition balance control system;

[0007] The partition ammonia injection system includes a large ammonia header, several ammonia injection branch pipes, several small ammonia headers, several regulating valves, several flow meters, and an ammonia injection grid. The ammonia injection grid is formed by connecting several nozzles in parallel and is arranged in the rising flue at the SCR inlet. There are several guide plates upstream of the nozzles. The cross-section of the rising flue is evenly divided into several cross-shaped ammonia injection zones by the guide plates. The large ammonia header is horizontally arranged on the steel structure platform below the ammonia injection grid. The several ammonia injection branch pipes are vertically and evenly distributed, with the lower ends connected to the large ammonia header and the upper ends respectively connected to the middle of several horizontally arranged small ammonia headers. The two ends of the small ammonia headers are blocked, and several spray pipes are vertically and evenly connected to the top surface. The upper ends of the spray pipes on each small ammonia header extend towards the ammonia injection grid and are connected to the nozzles corresponding to the ammonia injection zones. The regulating valve and the flow meter are respectively arranged on each ammonia injection branch pipe, and the regulating valve is located upstream of the flow meter;

[0008] The ammonia supply system includes an ammonia supply main pipe, a main pipe regulating valve, a dilution air pipe, and an ammonia-air mixer. One end of the ammonia gas header is blocked, and the other end is connected to the outlet end of the ammonia-air mixer. The inlet end of the ammonia-air mixer is connected to the dilution air pipe, and the other inlet end is connected to the ammonia supply main pipe. The main pipe regulating valve is arranged on the ammonia supply main pipe;

[0009] The partition sampling system includes several flue gas sampling rods, several analysis probes, and a sampling partition matrix. The sampling partition matrix is arranged in the outlet flue below the bottom layer catalyst of the SCR. The cross-section of the outlet flue is evenly divided into several "field" - shaped sampling partitions by flow guiding plates. The front ends of the several flue gas sampling rods extend into the middle of each sampling partition, and the rear ends are connected to the analysis probes;

[0010] The tails of the several analysis probes are connected to the total gas source in the control cabinet through a drainage / purging gas source pipe. The analysis probes, regulating valves, and flow meters are respectively electrically connected to the connectors in the control cabinet through hard wiring. The control cabinet is electrically connected to the distributed control system through hard wiring;

[0011] Further, the number of ammonia injection zones of the ammonia injection grid is determined by the sampling partitions of the sampling partition matrix, and the number of ammonia injection branch pipes, ammonia gas small headers, analysis probes is the same as the number of ammonia injection zones and sampling partitions.

[0012] Further, the length of the ammonia injection branch pipe upstream of the flow meter is ≥ 5 times the pipe diameter, and the length of the ammonia injection branch pipe downstream of the flow meter is ≥ 3 times the pipe diameter.

[0013] Further, the materials of the regulating valve, flow meter, main pipe regulating valve, flue gas sampling rod, and analysis probe are all stainless steel, and the flue gas sampling adopts the compressed air drainage method.

[0014] Compared with the prior art, the beneficial effects of the present utility model are:

[0015] 1. Both the partition ammonia injection grid and the partition sampling matrix of the present utility model adopt a "field" - shaped layout, effectively avoiding the problem that due to the relatively wide cross-section of the flue below the denitration outlet catalyst and the relatively short length of the flue gas sampling rod, the sampling is not representative when using a linear layout;

[0016] 2. The analysis probe of the present utility model adopts in-situ NOx rapid measurement, which can measure and upload the nitrogen oxide data at the inlet of the denitration device in real time, providing accurate and real-time data for denitration control;

[0017] 3. After adopting the SCR precise ammonia injection system of the present utility model, the denitration reducing agent is reduced, the ammonia slip is reduced, the frequency of air preheater flushing is reduced, the power consumption of the induced draft fan is reduced, and the denitration system realizes automatic control, improving the safety and stability of unit operation. Description of the Drawings

[0018] Fig. 1 Schematic diagram of the ammonia injection grid and pipeline zoning of the present utility model;

[0019] Fig. 2 Schematic diagram of the sampling grid of the present utility model;

[0020] Fig. 3 Schematic diagram of the installation position structure of the ammonia injection grid and sampling grid of the present utility model;

[0021] In the figure: 1. Ammonia large header; 2. Ammonia injection branch pipe; 3. Ammonia small header; 4. Control valve; 5. Flowmeter; 6. Ammonia injection grid; 7. Ammonia supply main pipe; 8. Main pipe control valve; 9. Dilution air pipe; 10. Ammonia-air mixer; 11. Flue gas sampling rod; 12. Analysis probe; 13. Drainage / purging gas source pipe; 14. Hard wiring; 15. Control cabinet; 16. Distributed control system; 17. Sampling partition matrix; 18. Upward flue; 19. Outlet flue; 20. Bottom layer catalyst. Detailed implementation manners

[0022] The present utility model will be further described below in conjunction with the drawings and embodiments.

[0023] [[ID= twenty - one]]As Figs. 1-3 shown, a precise ammonia injection system for SCR with a "field" - shaped partition layout includes an ammonia supply system, a partition ammonia injection system, a partition sampling system, and a partition balance control system;

[0024] The partition ammonia injection system includes an ammonia large header 1, six ammonia injection branch pipes 2, six ammonia small headers 3, six control valves 4, six flowmeters 5, and an ammonia injection grid 6. The ammonia injection grid 6 is formed by connecting a number of nozzles and is arranged in the upward flue 18 at the SCR inlet. The cross - sectional size of the upward flue 18 is 12.3m×3.3m, and the cross - section of the upward flue 18 is evenly divided into six "field" - shaped ammonia injection zones by a deflector. The ammonia large header 1 is horizontally arranged on the steel structure platform below the ammonia injection grid 6. The six ammonia injection branch pipes 2 are vertically and evenly distributed, with the lower ends connected to the ammonia large header 1 and the upper ends respectively connected to the middle of six horizontally arranged ammonia small headers 3. The two ends of the ammonia small header 3 are blocked, and a number of spray pipes are vertically and evenly connected to the top surface. The spray pipes on each ammonia small header 3 extend into the ammonia injection grid 6 evenly. The control valve 4 and the flowmeter 5 are respectively arranged on each ammonia injection branch pipe 2, and the control valve 4 is located upstream of the flowmeter 5. The length of the ammonia injection branch pipe 2 upstream of the flowmeter 5 is ≥5 times the pipe diameter, and the length of the ammonia injection branch pipe 2 downstream of the flowmeter 5 is ≥3 times the pipe diameter. The main function of the control valve 4 is to adjust the ammonia flow rate of the partition, and the main function of the flowmeter 5 is to measure the ammonia flow rate of the partition.

[0025] The described sectional ammonia injection system includes an ammonia header 1, six ammonia injection branch pipes 2, six ammonia small headers 3, six regulating valves 4, six flow meters 5, and an ammonia injection grid 6. The ammonia injection grid 6 is formed by connecting a number of nozzles in parallel and is arranged in the rising flue 18 at the SCR inlet. The cross-sectional dimension of the rising flue 18 is 12.3m × 3.3m. There are a number of flow guiding plates upstream of the nozzles. The cross-section of the rising flue 18 is evenly divided into six "field"-shaped ammonia injection zones by the flow guiding plates. The ammonia header 1 is horizontally arranged on the steel structure platform below the ammonia injection grid 6. The several ammonia injection branch pipes 2 are vertically and evenly distributed, with the lower ends connected to the ammonia header 1 and the upper ends respectively connected to the middle of six horizontally arranged ammonia small headers 3. The two ends of the ammonia small headers 3 are blocked, and a number of spray pipes are vertically and evenly connected to the top surface. The upper ends of the spray pipes on each ammonia small header 3 extend towards the ammonia injection grid 6 and are connected to the nozzles corresponding to the ammonia injection zones. The regulating valves 4 and the flow meters 5 are respectively arranged on each ammonia injection branch pipe 2, and the regulating valve 4 is located upstream of the flow meter 5. The length of the ammonia injection branch pipe 2 upstream of the flow meter 5 is ≥ 5 times the pipe diameter, and the length of the ammonia injection branch pipe 2 downstream of the flow meter 5 is ≥ 3 times the pipe diameter. The main function of the regulating valve 4 is to adjust the ammonia flow rate in the zone, and the main function of the flow meter 5 is to measure the ammonia flow rate in the zone;

[0026] The ammonia supply system includes an ammonia supply main pipe 7, a main pipe regulating valve 8, a dilution air pipe 9, and an ammonia-air mixer 10. One end of the ammonia header 1 is blocked, and the other end is connected to the outlet end of the ammonia-air mixer 10. The inlet end of the ammonia-air mixer 10 is connected to the dilution air pipe 9, and the other inlet end is connected to the ammonia supply main pipe 7. The main pipe regulating valve 8 is arranged on the ammonia supply main pipe 7. The main pipe regulating valve 8 adopts total quantity control, with the SCR outlet NOx concentration as the controlled object and the goal of ensuring that the hourly average value of the NOx emission concentration at the chimney inlet does not exceed the standard. By introducing the average SCR outlet NOx concentration, the average O₂ concentration, the flue gas volume, etc., the overall operating conditions of the SCR area are predicted and feedback is provided to ensure the safe, stable and economic operation of the denitration system and provide stable operating conditions for sectional balanced control. After the main pipe regulating valve 8 adjusts the ammonia flow rate, the ammonia is mixed and diluted with the dilution air in the dilution air pipe 9 in the ammonia-air mixer 10, and then enters the ammonia header 1. To prevent reaching the ammonia explosion limit, the ammonia-air volume ratio is controlled below 20% during operation.

[0027] Taking a 660MW pulverized coal boiler as an example, each boiler is equipped with 2 SCR reactors, which are arranged between the outlet of the economizer of the boiler and the inlet of the air preheater flue gas. Each SCR reactor is designed with three layers of catalysts. The denitration reducing agent uses ammonia produced by urea hydrolysis to meet the emission standard that the NOx at the denitration outlet is not higher than 50mg / m3. The ammonia injection grid 6 of the single-sided SCR reactor is divided into 6 ammonia injection zones in the cross-sectional direction, and correspondingly 6 regulating valves 4 and flow meters 5 are added. On both sides of the SCR outlet, two new in-situ rapid analysis probes 12 for NOx are added, which are arranged in the outlet flue 19 below the bottom layer catalyst 20 of the SCR. Three analyzers are arranged along the length direction on each side, and two groups are arranged along the width direction, with a total of 6 analyzers, providing feedback signals for the ammonia injection regulation of the zones.

[0028] The partition sampling system includes 6 flue gas sampling rods 11, 6 analysis probes 12 and a sampling partition matrix 17. The sampling matrix 17 is arranged in the outlet flue 19 at a position 1.5m below the bottom layer catalyst 20 of the SCR. The cross-sectional size of the outlet flue 19 is 13.9m×10.2m. The cross-section of the outlet flue 19 is evenly divided into 6 "field"-shaped sampling partition matrices 17 by baffle plates. The number of ammonia injection zones is determined by the sampling zones, and the number of ammonia injection branches 2, ammonia small headers 3, analysis probes 12 is the same as the number of ammonia injection zones and sampling zones. The front ends of the 6 flue gas sampling rods 11 extend into the middle of each sampling partition matrix 17, and the rear ends are connected to the analysis probes 12. The analysis probe 12 is an in-situ NOx / O2 rapid measuring instrument. The instrument adopts advanced sensor and sampling technologies, can measure and upload nitrogen oxide data in real time, and provides accurate and real-time data for denitration control. The "field"-shaped arrangement of the sampling partition matrix 17 effectively avoids the problem that due to the relatively wide cross-section of the flue below the denitration outlet catalyst and the relatively short length of the flue gas sampling rod, the one-dimensional arrangement causes unrepresentative sampling.

[0029] The analysis probe 12 is connected to the total gas source in the control cabinet 15 through a drainage / purging gas source pipe 13, and the analysis probe 12 is electrically connected to the connector of the control cabinet 15 through a hard wire 14. The regulating valve 4, the flow meter 5, and the connector of the control cabinet 15 are respectively electrically connected to the distributed control system 16 through hard wires 14;

[0030] The partition balancing control system adopts a combination of main control and sub-control. Under the condition that the catalyst performance is normal, the NOx concentration distribution at the SCR outlet is used as the data basis for partition balancing control, and at the same time, the NH3 concentration at the SCR outlet is combined. On the premise of ensuring that the NOx emission concentration at the chimney inlet does not exceed the standard, the control is carried out with the goal of minimizing the ammonia slip concentration at a relatively low level. The display and control use an embedded controller, and data acquisition is completed with the supporting relevant hardware.

[0031] The regulating valve 4, flow meter 5, main pipe regulating valve 8, flue gas sampling rod 11, and analysis probe 12 are all made of stainless steel. Flue gas sampling adopts compressed air diversion and is equipped with an automatic temperature control module, which will not cause blockage of the sampling device due to the precipitation of moisture in the flue gas. Data acquisition adopts NOx sensor, which measures total nitrogen based on the dual-chamber zirconium oxide measurement principle.

[0032] After the device was put into use, the consumption of denitrification reducing agent was reduced by about 10%, the relative standard deviation of NOx concentration at the outlet of the denitrification reactor was <10%, and the average ammonia slip at the reactor outlet was less than 3 ppm, which met the environmental protection operation requirements.

[0033] The working process of this utility model:

[0034] In use, air is introduced into the dilution duct 9, and ammonia is introduced into the ammonia supply main duct 7. The ammonia flow rate is adjusted in real time by regulating the main duct regulating valve 8. Then, the ammonia and dilution air are mixed and diluted in the ammonia-air mixer 10. After dilution, the ammonia enters the ammonia main header 1 and flows upward from each ammonia injection branch pipe 2 into the ammonia sub-header 3. The ammonia flow rate in the corresponding ammonia injection branch pipe 2 is adjusted by the regulating valve 4 on each ammonia injection branch pipe 2. The corresponding ammonia flow rate is measured by the corresponding flow meter 5 and fed back to the distribution system in real time. In the control system 16, the ammonia gas in each ammonia manifold 3 enters the ammonia injection zone of the corresponding ammonia injection grid 6 through the corresponding nozzle. The ammonia gas in the injection zone continues to rise along the rising flue 18. After passing through three layers of catalyst, the flue gas descends along the outlet flue 19 and enters the sampling zone matrix 17. Each flue gas sampling rod 11 collects the flue gas sample in the corresponding zone. The analysis probe 12 analyzes the nitrogen oxide data of the flue gas in real time and uploads the data to the distributed control system 16 in real time, providing accurate and real-time data for denitrification control.

[0035] Under normal catalyst performance, the NOx concentration distribution at the SCR outlet is used as the data basis for zoned balanced control. At the same time, the NH3 concentration at the SCR outlet is combined with the NOx emission concentration at the chimney inlet. The goal is to control the ammonia slip concentration at a low level while ensuring that the NOx emission concentration at the chimney inlet does not exceed the standard.

[0036] Both the zoned ammonia injection grid and the zoned sampling matrix adopt a grid-like arrangement, which effectively avoids the problem of unrepresentative sampling caused by a straight-line arrangement due to the wide cross-section of the flue below the catalyst at the denitrification outlet and the short length of the flue gas sampling rod.

[0037] The analytical probe uses in-situ rapid NOx measurement, which can measure and upload nitrogen oxide data at the inlet of the denitrification unit in real time, providing accurate and real-time data for denitrification control;

[0038] After adopting the SCR precision ammonia injection system, the amount of denitrification reducing agent is reduced, ammonia slippage is reduced, the air preheater flushing frequency is reduced, the induced draft fan power consumption is reduced, and the denitrification system is automatically controlled, thus improving the safety and stability of the unit operation.

Claims

1. A field-divisional arrangement of SCR precise ammonia injection system, characterized in that, It includes an ammonia supply system, a sectional ammonia injection system, a sectional sampling system and a sectional balancing control system; The sectional ammonia injection system includes an ammonia header (1), a number of ammonia injection branch pipes (2), a number of ammonia small headers (3), a number of regulating valves (4), a number of flow meters (5) and an ammonia injection grid (6). The ammonia injection grid (6) is formed by connecting a number of nozzles in parallel, and is arranged in the rising flue (18) at the SCR inlet. There are a number of flow guiding plates upstream of the nozzles. The cross-section of the rising flue (18) is evenly divided into a number of "field"-shaped ammonia injection zones by the flow guiding plates. The ammonia header (1) is horizontally arranged on the steel structure platform below the ammonia injection grid (6). The number of ammonia injection branch pipes (2) is vertically and evenly distributed, with the lower ends connected to the ammonia header (1), and the upper ends respectively connected to the middle of a number of horizontally arranged ammonia small headers (3). The two ends of the ammonia small header (3) are blocked, and a number of spray pipes are vertically and evenly connected to the top surface. The upper ends of the spray pipes on each ammonia small header (3) extend towards the ammonia injection grid (6) and are connected to the nozzles corresponding to the ammonia injection zones. The regulating valve (4) and the flow meter (5) are respectively arranged on each ammonia injection branch pipe (2), and the regulating valve (4) is located upstream of the flow meter (5); The ammonia supply system includes an ammonia supply main pipe (7), a main pipe regulating valve (8), a dilution air pipe (9) and an ammonia-air mixer (10). One end of the ammonia header (1) is blocked, and the other end is connected to the outlet end of the ammonia-air mixer (10). The inlet end of the ammonia-air mixer (10) is connected to the dilution air pipe (9), and the other inlet end is connected to the ammonia supply main pipe (7). The main pipe regulating valve (8) is arranged on the ammonia supply main pipe (7); The sectional sampling system includes a number of flue gas sampling rods (11), a number of analysis probes (12) and a sampling zone matrix (17). The sampling zone matrix (17) is arranged in the outlet flue (19) below the SCR bottom catalyst (20). The cross-section of the outlet flue (19) is evenly divided into a number of "field"-shaped sampling zones by the flow guiding plates. The front ends of the number of flue gas sampling rods (11) extend into the middle of each sampling zone, and the rear ends are connected to the analysis probes (12); The tails of the number of analysis probes (12) are connected to the total gas source in the control cabinet (15) through a drainage / purging gas source pipe (13). The analysis probes (12), regulating valves (4), and flow meters (5) are respectively electrically connected to the connectors in the control cabinet (15) through hard wires (14). The control cabinet (15) is electrically connected to the distributed control system (16) through hard wires (14).

2. The cross-shaped zoned arrangement of SCR precise ammonia injection system according to claim 1, characterized in that, The number of ammonia injection zones of the ammonia injection grid (6) is determined by the sampling zones of the sampling zone matrix (17), and the number of ammonia injection branch pipes (2), ammonia small headers (3), analysis probes (12) is the same as the number of ammonia injection zones and sampling zones.

3. The cross-shaped zoned arrangement of SCR precise ammonia injection system as claimed in claim 1, wherein, The length of the ammonia injection branch pipe (2) upstream of the flow meter (5) is ≥5 times the pipe diameter, and the length of the ammonia injection branch pipe (2) downstream of the flow meter (5) is ≥3 times the pipe diameter.

4. The cross-shaped zoned arrangement of SCR precise ammonia injection system according to claim 1, characterized in that, The adjusting valve (4), the flow meter (5), the main pipe adjusting valve (8), the flue gas sampling rod (11) and the analysis probe (12) are made of stainless steel, and the flue gas sampling adopts compressed air drainage mode.

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