A zoned ammonia injection control device

Abstract

This utility model relates to the field of environmental protection technology. Its purpose is to provide a zoned ammonia injection control device, comprising multiple control branches corresponding to the number of reaction zones. One end of each control branch is connected to an ammonia source. Each control branch includes, along the airflow direction, a sequentially connected ammonia flow control section, an ammonia-air mixing section, and an ammonia-air flow control section. The end of the ammonia-air flow control section is connected to an ammonia injection grid within the reaction zone. This utility model enables independent and precise ammonia injection control for each reaction zone within the reaction flue through multiple control branches, effectively ensuring the accuracy of ammonia injection; it prevents interference between reaction zones, improving the accuracy, timeliness, and stability of ammonia injection, and providing a guarantee for the refined management of the denitrification system.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection technology, specifically to a zoned ammonia injection control device. Background Technology

[0002] In recent years, with increasingly stringent environmental protection requirements, the limits for nitrogen oxide emissions have been continuously lowered. For example, according to ultra-low emission standards, NO... x Emission concentration must be strictly controlled at 50 mg / Nm³ 3 (6% O2) and below. Coal-fired power plants, as major emitters of nitrogen oxides, must take effective measures to reduce emissions to meet environmental protection requirements. Selective catalytic reduction (SCR) denitrification technology is widely used in flue gas pollution control in large-scale coal-fired power plants both domestically and internationally, possessing advantages such as high denitrification efficiency, mature technology, and reliable operation. However, this technology also has some shortcomings in practical applications, leading to a series of challenges. For example:

[0003] 1. Insufficient uniformity of flue gas flow: The large geometric space of the denitrification system and the presence of bends and gradual size changes in the flue gas flow affect the uniformity of the system's flow field and ammonia nitrogen concentration field, leading to increased NO at the outlet. x Uneven distribution and localized ammonia escape are problems. Furthermore, traditional SCR denitrification processes cannot precisely control the ammonia injection rate. Although the unit meets the requirements for ultra-low nitrogen oxide emission control and operation, the large flue gas volume, wide flow range, significant time delay, and high inertia of the SCR denitrification system cause uneven spatial distribution and temporal lag in ammonia injection, resulting in slow response and ultimately leading to a deviation between the denitrification efficiency and the expected target.

[0004] II. Poor Matching of Unit Operation with Actual Operating Conditions: Under the influence of deep peak shaving in thermal power plants, unit load fluctuates greatly, and the existing SCR ammonia injection regulation system can no longer meet the needs of flexible unit operation. Most units, in order to ensure the outlet NO x To meet emission standards, excessive ammonia injection is necessary. While this ensures the denitrification rate, unreacted NH3 will escape and react with H2O and SO3 to form highly viscous NH4HSO4, which adheres to the catalyst or air preheater. This not only increases system resistance and affects the efficient operation of the system, but also corrodes the air preheater, seriously affecting the safety and economy of the unit operation.

[0005] Third, insufficient level of refined ammonia injection management: The existing denitrification system lacks refined management of ammonia injection. This crude ammonia injection method makes it impossible to adjust the management based on the NO levels in each zone. x Reasonable scheduling of ammonia injection rates in each zone, along with other gas concentrations, has drawbacks such as low denitrification efficiency, large ammonia escape, and high operating costs, and also significantly impacts equipment lifespan.

[0006] To this end, the applicant proposed a precise zoned ammonia injection denitrification system based on SCR. How to achieve zoned control of ammonia injection under this system is an important part of realizing the system's functions. Summary of the Invention

[0007] The purpose of this invention is to provide a zoned ammonia injection control device that can achieve precise control of ammonia injection and improve the stability of ammonia injection.

[0008] To achieve the above-mentioned objectives, the technical solution adopted by this utility model is: a zoned ammonia injection control device, comprising multiple control branches arranged according to the number of reaction zones, one end of each control branch being connected to an ammonia source; each control branch includes, along the airflow direction, a sequentially connected ammonia flow control section, an ammonia-air mixing section, and an ammonia-air flow control section; the end of the ammonia-air flow control section is connected to an ammonia injection grid within the reaction zone;

[0009] The ammonia flow control section is provided with an ammonia switch valve, an ammonia flow meter and an ammonia regulating valve in sequence along the airflow direction.

[0010] The ammonia-air mixing section is equipped with an ammonia-air mixer. The two inlets of the ammonia-air mixer are connected to the ammonia flow control section and the hot air inlet pipeline, respectively, and the outlet is connected to the ammonia flow control section. A hot air regulating valve is installed on the hot air inlet pipeline.

[0011] The ammonia air flow control section is equipped with a mixed gas regulating valve and a mixed gas flow meter arranged sequentially along the airflow direction.

[0012] Preferably, the control branch is located outside the reaction flue.

[0013] Preferably, the ammonia-air mixer is a passive mixer.

[0014] Preferably, the ammonia switch valve, ammonia regulating valve, hot air regulating valve, and mixed gas regulating valve are all solenoid valves with manual operation function and are electrically connected to the control device.

[0015] Both the ammonia flow meter and the mixed gas flow meter are electronic flow meters and are electrically connected to the control device.

[0016] Preferably, the ammonia-air mixer includes a hollow cylindrical body, one end of which is an ammonia inlet connected to an ammonia flow control section, and the other end is a mixed gas outlet connected to the ammonia-air flow control section; an annular air inlet cavity is provided on the side of the body near the ammonia inlet, a hot air inlet connected to a hot air inlet pipe is provided on the outer wall of the air inlet cavity, and a plurality of side air holes connecting the air inlet cavity and the inner cavity of the body are provided on the inner wall of the air inlet cavity;

[0017] Two perforated plates are provided at both ends of the main body inner cavity corresponding to the inlet cavity, and the two perforated plates form a preliminary mixing zone.

[0018] Two perforated plates are also provided in the main body behind the airflow direction of the initial mixing zone, and the two perforated plates form a fine mixing zone. The fine mixing zone is provided with a mixing labyrinth formed by bending several sheets.

[0019] The beneficial effects of this invention are mainly reflected in the following aspects: by using multiple control branches to independently and precisely control the ammonia injection of each reaction zone in the reaction flue, the accuracy of ammonia injection can be effectively guaranteed; the reaction zones do not interfere with each other, improving the accuracy, timeliness and stability of ammonia injection, and providing a guarantee for the refined management of the denitrification system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of this utility model;

[0021] Figure 2 for Figure 1 The structure shown is viewed from direction AA.

[0022] Figure 3 This is a schematic diagram of the sampler in the partitioned sampling device of this utility model;

[0023] Figure 4 This is a top view of the sampler;

[0024] Figure 5 This is a schematic diagram of the internal structure of the flow distribution module.

[0025] Figure 6 This is a top view of the flow distribution module;

[0026] Figure 7 This is a schematic diagram of the flow guide baffle.

[0027] Figure 8 This is a top view of the catalytic module;

[0028] Figure 9 Top view of the four catalytic modules assembled together;

[0029] Figure 10 This is a three-dimensional structural diagram of the connecting components;

[0030] Figure 11 This is a top view of an SCR catalytic converter in a preferred embodiment;

[0031] Figure 12 This is a schematic diagram of the ammonia injection grid structure;

[0032] Figure 13 This is a bottom view of the ammonia injection grille;

[0033] Figure 14 This is a top view of the distribution plate structure.

[0034] Figure 15 This is a system diagram of a zoned ammonia injection control device;

[0035] Figure 16 This is a schematic diagram of the structure of an ammonia-air mixer in a preferred embodiment. Detailed Implementation

[0036] like Figure 1 As shown, this utility model is a precision zoned ammonia injection denitrification system based on SCR, mainly used for denitrification treatment of flue gas in coal-fired power plants. It mainly includes a reactor 1, which includes a reaction flue 2, and an inlet flue 3 and an outlet flue 4 connected to the reaction flue 2. The outlet flue 4 is connected to an economizer, and the inlet flue 3 is connected to a flue gas source. Generally, the inlet flue 3 is located on one side of the upper part of the reaction flue 2, and the outlet flue 4 is located at the bottom of the reaction flue 2. The top plate of the reactor 1 adopts an inclined plate structure to facilitate the introduction of flue gas.

[0037] like Figure 1 As shown, multiple sets of SCR catalytic converters 5 are arranged along the airflow direction within the reaction flue 2. Three sets of SCR catalytic converters 5 are shown in the figure; however, in direct application, each unit can select more or fewer SCR catalytic converters 5 according to actual conditions. The reaction flue 2 above and below the SCR catalytic converters 5 of this invention is equipped with zoned flow guiding and equalization devices 6. (See figure...) Figure 1 As shown, with three sets of SCR catalytic converters 5, four sets of zoned flow distribution devices 6 should be installed to meet usage requirements. A rectifier grid 7 and an ammonia injection device 8 are also installed from top to bottom in the upper end of the reaction flue 2. A zoned sampling device 9 is installed in the lower end of the reaction flue 2. After entering from the inlet flue 3, the flue gas first passes through the rectifier grid 7, and then mixes with the ammonia gas injected by the ammonia injection device 8 in the ammonia injection zone below the rectifier grid 7. After the treated flue gas flows through the lowermost zoned flow distribution device 6, the zoned flow distribution device 6 is used to collect and detect the treated sample gas.

[0038] To address the problems of large size of the reaction flue 2 in traditional SCR ammonia injection denitrification systems, uneven gas flow distribution within the cross-section of the reaction flue 2, and uneven ammonia injection, the partitioned flow distribution device 6 of this invention includes several longitudinal baffles 10 for dividing the reaction flue 2 into multiple flow channels, and flow distribution modules 11 arranged within each flow channel. The vertically corresponding flow channels and the SCR catalytic devices 5 between the flow channels together constitute a reaction zone. In other words, the reaction flue 2 of this invention has several reaction zones, the number of which is mainly determined by the number and arrangement of the baffles 10. It can be like... Figure 1 As shown, the reaction zones are divided into four longitudinally extending reaction zones arranged in a row by three sets of partitions 10 on multiple flow distribution modules 11. Alternatively, the partitions 10 can be arranged in a crisscross pattern in a top view, dividing the reaction zones into more longitudinally extending reaction zones arranged in a matrix.

[0039] The ammonia injection device 8 of this invention includes multiple ammonia injection grids 12 arranged according to the number of reaction zones. Each ammonia injection grid 12 typically corresponds to one reaction zone, but in cases where the reaction zones are large, two ammonia injection grids 12 can be arranged within one reaction zone. The ammonia injection grid 12 adopts a grid-like structure and is connected to the ammonia source 14 through a zoned ammonia injection control device 13. It is used to inject ammonia gas into the ammonia injection zone, thereby initially mixing it with the flue gas. The flue gas, after initial mixing, flows downward along the guide distribution module 11, where it is further mixed, and the reaction is completed within the SCR catalytic device 5.

[0040] This utility model also includes a control device 0 for controlling electrical components. The control device 0 is used to receive feedback signals from the partition sampling device 9 and send control commands to the partition ammonia injection control device 13 so as to control the ammonia injection device 8 to perform ammonia injection operation using the partition ammonia injection control device 13.

[0041] The overall workflow of this utility model is as follows: The reaction flue 2 is divided into multiple independent reaction zones by the partition 10 of the SCR catalytic device 5 and the zoned flow distribution device 6. After the flue gas enters from the inlet flue 3, it is rectified by the rectifier grid 7. The ammonia injection device 8 injects ammonia gas to mix thoroughly with the flue gas. The mixed gas enters the flow distribution module 11 of each zoned flow distribution device 6. After being evenly distributed and mixed by the flow distribution module 11, it enters the corresponding area of ​​the SCR catalytic device 5 in the corresponding reaction zone. During this process, the gas undergoes multiple flow distributions and catalytic reactions by the SCR catalytic device 5, resulting in a high degree of reaction. Finally, the flue gas is discharged from the bottom exhaust flue 4. Before the gas enters the exhaust flue 4, the zoned sampling device 9 can collect and detect the gas in real time, accurately grasp the gas state, and feed the signal back to the control device 0. The control device 0 controls the operation of the ammonia injection device 8 through the zoned ammonia injection regulation device 13, thereby accurately injecting ammonia according to the detected gas state, which can ensure the precise matching of ammonia usage with flue gas composition and prevent excessive or insufficient ammonia injection.

[0042] The specific structure and working mode of each functional device of this utility model are as follows:

[0043] I. Zonal Sampling Device 9

[0044] like Figure 1As shown, the zone sampling device 9 includes multiple samplers 15 corresponding to the reaction zones. Generally, one sampler 15 can be set for one reaction zone. When the size of the reaction zone is large, multiple samplers can also be set, generally corresponding to the number of ammonia injection grids 12. Each sampler 15 is connected to the gas path of the detection instrument 17 through a gas intake pipe 16. The detection instrument 17 is electrically connected to the control device 0 and feeds back signals to the control device 0.

[0045] Combination Figure 2-4 As shown, the sampler 15 includes a vertical mixing tube 18 and multiple sampling tubes 19 disposed around the mixing tube 18 and communicating with the mixing tube 18, such as... Figure 4 As shown, each sampler 15 has four sampling tubes 19 arranged in an X-shape. In some embodiments, the number of sampling tubes 19 may be more or less, and the number is usually determined based on the cross-sectional area of ​​the reaction zone. To ensure smooth entry of the sample gas, the sampling tubes 19 typically extend obliquely upwards from the inner end to the outer end, with an inclination angle usually set to 15-20° to ensure coverage area. The outer end of the sampling tube 19 is provided with an upwardly bent vertical sampling port 21. The upwardly bent vertical sampling port 21 at the outer end (i.e., the upper end) of the sampling tube 19 has a certain guiding effect when the sample gas enters, preventing the sample gas from directly entering the inclined sampling tube 19 and causing flow obstruction.

[0046] One side of the lower section of the mixing tube 18 is connected to one end of the gas sampling tube 16, and the other end of the gas sampling tube 16 extends to the outside of the reaction flue 2 and is connected to the detection instrument 17 to ensure that the detection instrument 17 is not affected by flue gas. The lower end of the mixing tube 18 forms a chute 20 for the discharge of excess flue gas. The gas sampling tube 16 delivers the required amount of sample to the detection instrument 17, while excess gas is discharged directly through the chute 20 at the lower end of the mixing tube 18.

[0047] This partitioned sampling device 9 ensures the stability of sampling in each partition, providing a reliable sample gas source for subsequent detection and improving the stability and accuracy of the detection. Its specific working process is as follows: the gas after the reaction is completed enters the sampling tube 19 through the sampling port 21, and then enters the mixing tube 18 along the sampling tube 19. In the mixing tube 18, the multi-point sample gas is mixed. Part of the sample gas is discharged to the detection instrument 17 through the gas sampling tube 16, while the rest of the sample gas continues to be discharged directly through the chute 20. To improve the mixing effect of the sample gas from multiple sampling tubes 19 in the mixing tube 18, such as... Figure 3 As shown, a spiral mixing air passage 22 is provided in a section of the sampling tube 19 located above the gas sampling tube 16.

[0048] II. Zonal diversion and distribution device 6

[0049] The zoned flow distribution device 6 includes a flow distribution module 11 and a baffle 10. Through a special design of the flow distribution module 11, it possesses both zoned flow distribution and gas mixing functions. Figure 5 As shown, the flow distribution module 11 includes a porous top plate 23, a porous bottom plate 24, and several vertically arranged flow-guiding baffles 25 disposed side by side between the porous top plate 23 and the porous bottom plate 24. The porous top plate 23 and the porous bottom plate 24 are made of corrosion-resistant metal plates, such as... Figure 6 As shown, the porous top plate 23 has a plurality of flow holes 27 arranged in a rectangular shape, and the flow holes 27 on the porous bottom plate 24 are designed in the same way as those on the porous top plate 23.

[0050] The flow guide baffle 25 is Z-shaped and has an overall wavy shape. The Z-shaped bending angle of the flow guide baffle 25 is generally 45° to ensure relatively balanced flow deflection in each bending segment. The flow guide baffle 25 is generally made of steel plate with a thickness of at least 6mm to ensure its strength. Its specific dimensions are designed according to the reaction zone and the flow distribution module 11. The width of each flow guide baffle 25 is generally 300-600mm to reduce the risk of deformation caused by large spans.

[0051] The two adjacent guide baffles 25 form a guide mixing zone 26, where flue gas and ammonia gas can be mixed multiple times and conveyed downwards along the guide mixing zone 26. In terms of installation, the porous top plate 23 and porous bottom plate 24 are provided with first reserved connectors for welding to the SCR catalytic converter 5. These can be assembled on-site. The specific form of the first reserved connector can vary; for example, it can be a connecting post 28 located at the corners and edges of the porous top plate 23 and porous bottom plate 24. In addition to the porous top plate 23 and porous bottom plate 24 at the guide distribution module 11, it may also include side plates on both sides, with second reserved connectors provided on the side plates for welding to the reaction flue 2 and the partition plate 10. On the one hand, the side plate can serve as the side enclosure structure of the flow distribution module 11 to improve the strength of the module unit. On the other hand, it can also be assembled with the partition 10 through the second reserved connector. There are many specific structural forms of the second reserved connector, and the structure is relatively simple, so it will not be described in detail in this utility model.

[0052] The flow-guiding and distribution module 11 of this invention can effectively guide the airflow in each reaction zone, avoiding interference between reaction zones caused by lateral flow, while also having a highly efficient gas mixing function. During use, ammonia and flue gas enter the module through the flow holes 27 on the porous top plate 23. As they pass through the flow-guiding and mixing zone 26, they are deflected by the bending sections of the flow-guiding baffles 25, thus achieving efficient mixing. Finally, the gas exits through the flow holes 27 on the porous bottom plate 24 and continues to move downwards.

[0053] Regarding the specific connection method between the porous top plate 23 and the porous bottom plate 24 and the flow guide baffle 25, it can be achieved by welding or by combining. Figure 5 and 7 As shown, the porous top plate 23 and porous bottom plate 24 have connecting grooves 29 on the side facing the flow guide baffle 25 for the upper and lower edges of the flow guide baffle 25 to be inserted. The top and bottom of the flow guide baffle 25 are provided with vertical sections 30 that cooperate with the connecting grooves 29. The vertical section 30 is provided with a connecting hole 31. The vertical section 30 of the flow guide baffle 25 is inserted into the connecting groove 29 and is detachably connected to the connecting groove 29 by connecting bolts 32.

[0054] In addition, to further improve the gas mixing performance of the flow distribution module 11, such as... Figure 7 As shown, the bends of the flow guide baffle 25 are provided with flow diversion holes 33, and the flow diversion holes 33 on adjacent bends are staggered. This structure allows for a certain degree of gas exchange between the two flow guide baffles 25, thereby improving the mixing effect.

[0055] III. SCR Catalytic Unit 5

[0056] The SCR catalytic device 5 of this invention includes multiple module groups that correspond to the number of reaction zones within the reaction flue 2 and are adapted to the reaction zones; that is, each layer of the SCR catalytic device 5 includes multiple module groups, and the SCR catalytic device 5 is formed by splicing multiple module groups together. Each module group consists of multiple catalytic modules 34 arranged in a matrix and spliced ​​together.

[0057] like Figure 9 As shown, a module group can consist of four catalytic modules 34, or multiple catalytic modules 34; the specific number and size are designed according to the reaction partition. Figure 11 As shown, in some embodiments, multiple partitions 10 divide the reaction flue 2 into four rectangularly arranged reaction zones. The size of each reaction zone is the same as the size of a module group consisting of four catalytic modules 34. Thus, four module groups can constitute an SCR catalytic device 5. Of course, in other embodiments, more or fewer catalytic modules 34 can form module groups, and more or fewer module groups can constitute the SCR catalytic device 5. The catalytic modules 34 can be arranged in a rectangular arrangement.

[0058] From the perspective of a single catalytic module 34, the catalytic module 34 includes a mold shell 35 and a honeycomb-shaped catalytic core 36 disposed within the mold shell 35. Adjacent catalytic modules 34 can be connected either by welding rods, splicing strips, etc., on the sidewall of the mold shell 35, or as shown in the diagram. Figure 9-11As shown, the corners of the mold shell 35 are arc-shaped, and the mold shells 35 of four adjacent catalyst modules 34 form a connection channel 37. The four adjacent catalyst modules 34 are connected by a connection component disposed in the connection channel 37.

[0059] Multiple catalytic modules 34 in this structural form constitute the SCR catalytic device 5, enabling modular assembly and facilitating on-site installation. The number of catalytic modules 34 can be flexibly adjusted according to site conditions, making installation more flexible. Furthermore, the catalytic modules 34 are assembled using connecting components positioned between them, without occupying additional space, thus facilitating the installation and arrangement of other devices. In practical use, this SCR catalytic device 5 allows for on-site assembly of each catalytic module 34 according to the site conditions of the reaction flue 2 and the reaction zone. The sides of the catalytic module 34 housings 35 located at the edges of the SCR catalytic device 5 can be directly welded or bolted to the sidewalls of the reaction flue 2. Meanwhile, the sides of the housings 35 of the catalytic modules 34 located in the middle are connected using traditional bolting or welding methods, and also reinforced with connecting components, balancing overall stability and installation flexibility.

[0060] The specific structure of the connection component is as follows: Figure 10 As shown, the connecting assembly includes a connecting rod 38 passing through the connecting channel 37. End plates 39 are provided at both ends of the connecting rod 38, and each end plate 39 has at least four first splicing holes 40. A triangular connecting block 41 is provided at the corner of the mold shell 35. Each connecting block 41 has a second splicing hole 42 corresponding to the position of the first splicing hole 40. The end plates 39 and the connecting blocks 41 are detachably connected by splicing bolts passing through the first and second splicing holes 40 and 42. In this configuration, multiple catalyst modules 34 are connected and restrained by the connecting rod 38 and the end plates 39, greatly improving stability and ensuring ease of assembly and disassembly. The connection between the end plates 39 and the connecting rod 38 can be either welding or threaded. Welding is more suitable for larger catalyst modules 34, providing higher connection strength and allowing for on-site fabrication; while threaded connections offer greater flexibility and are suitable for small and medium-sized catalyst modules 34. In order to achieve a fast and stable connection between the catalytic module 34 and the flow distribution module 11, the mold shell 35 of the catalytic module 34 is also provided with a welding component for welding with the flow distribution module 11 and the partition plate 10. The welding component has many specific forms, such as a welding component made of channel steel, steel bar, etc. The welding component is designed in pairs with the welding component on the flow distribution module 11.

[0061] In addition, to further enhance the overall structural strength of the SCR catalytic converter 5, this invention also includes a reinforcing rod 44, which is used to connect various connecting components. It can adopt an X-shaped, square-shaped, or rectangular layout, etc., without limitation, and can be selected according to the site conditions. The specific connection method of the reinforcing rod 44 to the connecting components is as follows: a short stud 43 is provided on the side of the end plate 39 away from the connecting rod 38. Both ends of the reinforcing rod 44 are sleeved on the threaded studs and locked to the end plate 39 by tightening nuts.

[0062] IV. Ammonia Injection Device 8

[0063] The ammonia injection device 8 of this utility model includes multiple ammonia injection grids 12 arranged according to the number of reaction zones. The specific structural form of the ammonia injection grid 12 is as follows:

[0064] like Figure 12-13 As shown, each of the ammonia injection grids 12 includes a main ammonia injection pipe 45, one end of which is connected to the zoned ammonia injection control device 13, and the other end is a blind end. It also includes several ammonia injection branch pipes 46 arranged side-by-side below the main ammonia injection pipe 45. The number of rows of ammonia injection branch pipes 46 is designed according to the size of the reaction zone, but generally the gap between each row does not exceed 20 cm. The main ammonia injection pipe 45 and the ammonia injection branch pipes 46 are connected by a short pipe 47. Both ends of the ammonia injection branch pipes 46 are blind ends, and several nozzles 48 are evenly arranged at the bottom of the ammonia injection branch pipes 46. The nozzles 48 are arranged in a matrix, and the spacing between the nozzles 48 on the ammonia injection branch pipes 46 generally does not exceed 20 cm. This matrix arrangement effectively ensures overall coverage and reduces the occurrence of blind spots.

[0065] However, for the longer ammonia injection main pipe 45, its length is closer to the head end (i.e. Figure 12 The position of the right end (in the middle) is relative to the tail end (that is...) Figure 12 Regarding the left end of the ammonia injection grid, the internal gas pressure is higher, which can lead to uneven ammonia injection to some extent. Therefore, a particularly unique feature of this invention is that each ammonia injection grid 12 is also equipped with a pressure balancing component to balance the pressure difference between the head and tail ends of the ammonia injection main pipe 45. The pressure balancing component reduces the pressure difference between the head and tail ends, making the overall ammonia injection action of the ammonia injection grid 12 more stable and preventing uneven ammonia injection within the reaction zone.

[0066] There are various specific structural forms of the pressure balancing assembly. For example, the pressure balancing assembly consists of multiple rubber expansion zones arranged on the side wall of the ammonia injection main pipe 45 along its length. The size of the rubber expansion zones gradually decreases from the head end to the tail end of the ammonia injection main pipe 45. In this structure, through the expansion of the rubber expansion zones, the larger rubber expansion zone at the head end can provide greater buffering of the head end pressure, while the smaller rubber expansion zone at the tail end buffers less pressure, thus making the pressure at both ends more balanced. In addition, the pressure balancing assembly can also be as follows... Figure 12 As shown, a U-shaped balance pipe 49 is installed at the top of the ammonia injection main pipe 45, with its two ends connected to positions near the head and tail of the main pipe 45, respectively. A balance piston 50 is installed inside the balance pipe 49, forming a sliding fit with the middle section of the balance pipe 49. In use, the automatic sliding of the balance piston 50 within the balance pipe 49 effectively balances the pressure at both ends of the ammonia injection main pipe 45.

[0067] Regarding the connection between the ammonia injection main pipe 45 and the ammonia injection control device 13, the specific details are as follows: the head end of the ammonia injection main pipe 45 is connected to one end of the ammonia inlet pipe 52 through a bend 51, and the other end of the ammonia inlet pipe 52 extends to the outside of the reaction flue 2 and is connected to the zoned ammonia injection control device 13. This lead-out structure of the ammonia inlet pipe 52 allows the zoned ammonia injection control device 13 to be located outside the reaction flue 2, avoiding interference from flue gas.

[0068] In addition, to further improve the uniformity of ammonia injection in the ammonia injection grid 12 of this utility model, a nozzle such as a... can be provided below each of the nozzles 48. Figure 14 The distribution disk 53 shown is mounted below the nozzle 48 via support arms. Multiple support arms are typically provided, with their upper ends fixed to the sidewall of the nozzle 48 and their lower ends fixed to the edge of the distribution disk 53. The distribution disk 53 consists of a central area and several radially extending cutting arms 54 arranged around the periphery of the central area.

[0069] After the ammonia-air mixed gas is ejected from the nozzle 48, the sputtering in the central region and the redispersion by the cutting arm 54 ensure that the jet of gas ejected from the nozzle 48 forms a larger dispersion zone, thus facilitating mixing with the flue gas. Furthermore, a flow-dividing cone 55 can be provided in the central region, with the apex of the flow-dividing cone 55 opposite to the center of the nozzle 48. The flow-dividing cone 55 further enhances the dispersion effect. Additionally, serrated edges on both sides of the cutting arm 54 can further strengthen the dispersion effect.

[0070] V. Zoned Ammonia Injection Control Device 13

[0071] The ammonia injection control device 13 of this utility model includes multiple control branches set according to the number of reaction zones. The control branches can correspond one-to-one with the aforementioned ammonia injection grids 12. When there are two ammonia injection grids 12 in a reaction zone, one control branch can also connect to two ammonia injection grids 12 at the same time to control the two ammonia injection grids 12 simultaneously.

[0072] like Figure 15 As shown in the figure, four control branches are illustrated, one end of which is connected to ammonia source 14 (liquid ammonia or hydrolysis product gas). Each control branch includes, along the airflow direction, a sequentially connected ammonia flow control section, an ammonia-air mixing section, and an ammonia-air flow control section. The end of the ammonia-air flow control section is connected to the ammonia injection grid 12 within the reaction zone of the reaction flue 2.

[0073] The ammonia flow control section is provided with an ammonia switch valve 56, an ammonia flow meter 57, and an ammonia regulating valve 58 arranged sequentially along the airflow direction.

[0074] The ammonia-air mixing section is equipped with an ammonia-air mixer 59. The two inlets of the ammonia-air mixer 59 are connected to the ammonia flow control section and the hot air inlet pipe 60, respectively, and the outlet is connected to the ammonia-air flow control section. A hot air regulating valve 61 is installed on the hot air inlet pipe 60.

[0075] The ammonia air flow control section is provided with a mixed gas regulating valve 62 and a mixed gas flow meter 63 arranged sequentially along the airflow direction.

[0076] This utility model's zoned ammonia injection control device 13 independently and precisely controls ammonia injection into each reaction zone within the reaction flue 2 through multiple control branches, effectively ensuring the accuracy of ammonia injection; it prevents interference between reaction zones, improves the accuracy, timeliness, and stability of ammonia injection, and provides a guarantee for the refined management of the denitrification system.

[0077] All the aforementioned control branches are located outside the reaction flue 2 to prevent their electrical control components from being exposed to flue gas for extended periods, thus reducing their lifespan and ensuring the reliability of long-term automated control. The ammonia switch valve 56, ammonia regulating valve 58, hot air regulating valve 61, and mixed gas regulating valve 62 are all solenoid valves with manual operation functions and are electrically connected to the control device 0, offering both manual and automatic modes. The ammonia flow meter 57 and mixed gas flow meter 63 are both electronic flow meters and are electrically connected to the control device 0, enabling them to control ammonia flow rate and provide real-time feedback to the control device 0, achieving precise automated control.

[0078] The ammonia-air mixer 59 described in this utility model can be either an active mixer or a passive mixer. An active mixer usually has a mixing component (such as a mixing shaft) that can rotate actively, while a passive mixer does not have a rotating component and the ammonia and hot air are automatically mixed after being introduced.

[0079] like Figure 16 As shown, in some embodiments, an ammonia-air mixer 59 can be used, which has the characteristics of good mixing effect and high mixing efficiency. As shown in the figure, the ammonia-air mixer 59 includes a hollow cylindrical body 64. One end of the body 64 is an ammonia inlet 65 connected to the ammonia flow control section, and the other end is a mixing outlet 66 connected to the ammonia flow control section. An annular air inlet cavity 67 is provided on the side of the body 64 near the ammonia inlet 65. A hot air inlet 68 connected to the hot air inlet pipe 60 is provided on the outer wall of the air inlet cavity 67. A plurality of side air holes 69 connecting the air inlet cavity 67 and the inner cavity of the body 64 are provided on the inner wall of the air inlet cavity 67. Two perforated plates 70 are provided at both ends of the inner cavity of the body 64 corresponding to the air inlet cavity 67, and the two perforated plates 70 form a primary mixing zone 71. Two perforated plates 70 are also provided in the main body 64 behind the airflow direction of the initial mixing zone 71, and the two perforated plates 70 form a fine mixing zone 72. The fine mixing zone 72 is provided with a mixing labyrinth formed by bending several sheets.

[0080] During operation, ammonia gas enters through ammonia inlet 65, and hot air enters through hot air inlet 68. The annular inlet cavity 67 allows the hot air to enter the initial mixing zone 71 evenly through the side air holes 69, mixing with the ammonia gas dispersed by the first perforated plate 70. After initial mixing, the gas undergoes secondary mixing as it passes through the second perforated plate 70, achieving initial mixing overall. The mixed gas then passes through the third perforated plate 70 into the fine mixing zone 72. In the fine mixing zone 72, the gas is continuously cut and collided within a mixing labyrinth formed by bending sheets, resulting in radial fine mixing, and finally discharged through the mixed gas outlet 66.

Claims

1. A zonal ammonia injection control device, characterized by: The system includes multiple control branches set according to the number of reaction zones, one end of which is connected to the ammonia source (14); each control branch includes an ammonia flow control section, an ammonia-air mixing section and an ammonia-air flow control section connected in sequence along the airflow direction; the end of the ammonia-air flow control section is connected to the ammonia injection grid (12) in the reaction zone; The ammonia flow control section is provided with an ammonia switch valve (56), an ammonia flow meter (57), and an ammonia regulating valve (58) in sequence along the airflow direction; The ammonia-air mixing section is equipped with an ammonia-air mixer (59). The two inlets of the ammonia-air mixer (59) are connected to the ammonia flow control section and the hot air inlet pipe (60) respectively, and the outlet is connected to the ammonia flow control section. A hot air regulating valve (61) is installed on the hot air inlet pipe (60). The ammonia air flow control section is provided with a mixed gas regulating valve (62) and a mixed gas flow meter (63) arranged sequentially along the airflow direction.

2. The zoned ammonia injection control device of claim 1, wherein: The control branch is located outside the reaction flue (2).

3. The zoned ammonia injection control device of claim 2, wherein: The ammonia-air mixer (59) is a passive mixer.

4. The zoned ammonia injection control device of claim 3, wherein: The ammonia switch valve (56), ammonia regulating valve (58), hot air regulating valve (61), and mixed gas regulating valve (62) are all solenoid valves with manual operation function and are electrically connected to the control device (0). The ammonia flow meter (57) and the mixed gas flow meter (63) are both electronic flow meters and are electrically connected to the control device (0).

5. The zoned ammonia injection control device of claim 4, wherein: The ammonia-air mixer (59) includes a hollow cylindrical body (64), one end of which is an ammonia inlet (65) connected to the ammonia flow control section, and the other end is a mixed gas outlet (66) connected to the ammonia-air flow control section; an annular air inlet cavity (67) is provided on the side of the body (64) near the ammonia inlet (65), a hot air inlet (68) connected to the hot air inlet pipe (60) is provided on the outer wall of the air inlet cavity (67), and a plurality of side air holes (69) connecting the air inlet cavity (67) and the inner cavity of the body (64) are provided on the inner wall of the air inlet cavity (67); Two perforated plates (70) are provided at both ends of the inner cavity of the main body (64) corresponding to the cavity (67), and the two perforated plates (70) form a preliminary mixing zone (71). Two perforated plates (70) are also provided in the main body (64) behind the airflow direction of the initial mixing zone (71), and the two perforated plates (70) form a fine mixing zone (72), which is provided with a mixing labyrinth formed by bending several sheets.

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