Ammonia spraying and mixing device for SCR (Selective Catalytic Reduction) denitration

Abstract

The invention discloses an ammonia spraying and mixing device for SCR denitration, and belongs to the technical field of flue gas environment-friendly denitration devices. The two-stage mixer structure is arranged in the ammonia spraying mixing device for SCR denitration, that is, the ammonia spraying grating module and the air cap type nozzle which are matched form a first-stage mixing structure, and the mixer module forms a second-stage mixing structure, so that the mixing distance of mixed gas of flue gas and ammonia gas is short, and the mixing efficiency is high. And the whole device adopts a modular design, through the hierarchical corresponding relationship between the ammonia injection grid module and the mixer module, the precise ammonia gas distribution and mixing effect is realized, and the device can be suitable for flue ammonia injection denitration transformation projects under different working conditions. In practical application, the SCR denitration system can adopt the modular design and is arranged in a partitioned mode in the depth direction of the flue, and the number of the modules can be flexibly adjusted so as to adapt to the change requirements of the flue gas amount of different units.

Description

Technical Field

[0001] This application relates to the technical field of flue gas environmental protection denitrification devices, and in particular to an ammonia injection mixing device for SCR denitrification. Background Technology

[0002] Selective catalytic reduction (SCR) denitrification technology is a mainstream technology in the field of industrial flue gas treatment. Its core advantages lie in its high denitrification performance and reliable operational stability. Currently, more than 80% of the global flue gas denitrification market uses SCR technology. Especially under the driving force of my country's "ultra-low emission" policy, this technology has formed a large-scale application system in industries such as power, steel, and cement. The SCR denitrification process involves injecting ammonia or ammonia water into the flue gas containing nitrogen oxides. Through the catalytic action of a catalyst, ammonia reacts with nitrogen oxides in a redox reaction, ultimately converting them into harmless nitrogen and water.

[0003] In SCR denitrification systems, key factors affecting nitrogen oxide removal efficiency include the degree of diffusion and mixing of ammonia and flue gas, the ammonia-to-nitrogen molar ratio, catalyst activity, and reaction residence time. Among these, the uniformity of ammonia-to-flue gas mixing is the core limiting factor. When uneven local concentration field distribution occurs, it will lead to incomplete reaction, thereby significantly weakening the denitrification efficiency of the system. Summary of the Invention

[0004] This application provides an ammonia injection mixing device for SCR denitrification. It solves the problem of poor ammonia-flue gas mixing in the prior art. The technical solution is as follows: On the one hand, an ammonia injection mixing device for SCR denitrification is provided, the ammonia injection mixing device for SCR denitrification includes: at least one ammonia injection grid module, at least one mixer module and multiple wind cap type nozzles; Each of the ammonia injection modules has multiple arrayed ammonia injection zones, each ammonia injection zone has multiple ammonia injection ports, and the number of ammonia injection ports in each ammonia injection zone is the same; the multiple ammonia injection ports in each ammonia injection zone are connected one-to-one with multiple wind cap type nozzles, and the wind cap type nozzles are used to spray out ammonia gas mixture. The at least one mixer module corresponds one-to-one with the at least one ammonia injection grid module. Each mixer module has a mixing unit that corresponds one-to-one with multiple ammonia injection zones. Each mixing unit is located downstream of multiple wind cap nozzles set in the corresponding ammonia injection zone. As the flue gas flows sequentially through the ammonia injection grid module, the wind cap nozzle, and the mixer module, it undergoes primary mixing with the ammonia gas mixture sprayed from the wind cap nozzle and secondary mixing at the mixer module.

[0005] Optionally, the wind-cap type nozzle includes: a conical component and a nozzle component arranged opposite each other in a vertical direction, and a plurality of supporting connecting plates distributed between the conical component and the nozzle component. The nozzle component has a hollow channel, one end of which is connected to the ammonia injection port, and the other end of which faces the bottom surface of the conical component. The plurality of supporting connecting plates are arranged in a ring array around the axis of the hollow channel. The two ends of each supporting connecting plate are respectively connected to the bottom edge of the conical component and the circumferential side surface of the nozzle component, and there is an airflow channel between every two adjacent supporting connecting plates.

[0006] Optionally, the nozzle component includes: a frustum and a nozzle tube, the frustum being fitted onto the circumferential side of the nozzle tube, one end of the nozzle tube extending out of the frustum and engaging with the ammonia injection port, and the other end of the nozzle tube being flush with the top surface of the frustum; wherein, the bottom diameter of the frustum is larger than the top diameter, and the bottom diameter of the conical component is larger than the bottom diameter of the frustum; one end of the supporting connecting plate is connected to the bottom edge of the frustum.

[0007] Optionally, the inner diameter of the nozzle tube is D1, the bottom diameter of the frustum is D2, the bottom diameter of the conical part is D3, the height of the conical part is H1, and the height difference between the bottom of the conical part and the bottom of the frustum is H2; wherein, D2=(2~6)D1, D3=(8~15)D1, H1=(6~10)D1, and H2=(3~5)D1.

[0008] Optionally, multiple supporting connecting plates are distributed at equal intervals in a ring around the central axis of the hollow channel.

[0009] Optionally, each of the mixing units includes: four semi-circular blades, the straight edges of which intersect at a focal point on a virtual axis, the arrangement direction of two semi-circular blades in one group of semi-circular blades being perpendicular to the arrangement direction of two semi-circular blades in another group of semi-circular blades, the two semi-circular blades in each group of semi-circular blades being symmetrical about the focal point, and the virtual axis being parallel to the flue gas flow direction.

[0010] Optionally, the four semi-circular blades have the same diameter.

[0011] Optionally, the angle between each of the semicircular blades and the virtual axis ranges from 30 degrees to 60 degrees.

[0012] Optionally, the ammonia injection grid module includes: an ammonia injection main pipe, and a first ammonia injection branch pipe, an ammonia injection bend pipe, and a second ammonia injection branch pipe disposed in each ammonia injection zone. Both ends of the ammonia injection main pipe are connected to the inner wall of the flue. One end of the first ammonia injection branch pipe is connected to the ammonia injection main pipe. One end of the ammonia injection bend pipe is connected to the first ammonia injection branch pipe, and the other end of the ammonia injection bend pipe is bent upwards. One end of the second ammonia injection branch pipe is connected to the ammonia injection bend pipe. The inner diameter of the ammonia injection main pipe is larger than the inner diameter of the first ammonia injection branch pipe, the inner diameter of the first ammonia injection branch pipe is larger than the inner diameter of the ammonia injection bend pipe, the inner diameter of the ammonia injection bend pipe is larger than the inner diameter of the second ammonia injection branch pipe, and the other end of the second ammonia injection branch pipe is connected to the nozzle component. Multiple ammonia injection zones are evenly distributed on both sides of the ammonia injection main pipe, and multiple nozzles in the ammonia injection zones on both sides are arranged in multiple rows and columns.

[0013] Optionally, the outer diameter D of the main ammonia injection pipe, the diameter D4 of the first ammonia injection branch pipe is (0.75~0.85)D, the outer diameter D5 of the ammonia injection bend pipe is (0.5~0.75)D, and the outer diameter D6 of the second ammonia injection branch pipe is (0.15~0.20)D.

[0014] Optionally, the distance between every two columns of nozzles is L1, and the distance between every two rows of nozzles is L2, where L2 = (0.85~1.15)L1.

[0015] Optionally, the diameter D7 of the semi-circular blade is (1.4~2.6)L1.

[0016] Optionally, in the case where the ammonia injection mixing device for SCR denitrification includes multiple ammonia injection modules, the other ends of the first ammonia injection branch pipes in two adjacent ammonia injection modules are separated by a spacer plate, which is used to connect the two adjacent ammonia injection modules.

[0017] The beneficial effects of the technical solutions provided in this application include at least the following: By incorporating a two-stage mixer structure in the ammonia injection mixing unit used for SCR denitrification—namely, the complementary ammonia injection grid module and wind cap nozzle, along with the two-stage mixing structure of the mixer module—the mixing distance between flue gas and ammonia is shortened, resulting in high mixing efficiency. Furthermore, the overall modular design, through the hierarchical correspondence between the ammonia injection grid module and the mixer module, achieves precise ammonia distribution and mixing, effectively ensuring the system's denitrification performance and making it suitable for flue gas ammonia injection denitrification retrofit projects under various operating conditions. In practical applications, the SCR denitrification system can adopt the above modular design, arranged in sections along the depth of the flue gas duct, allowing for flexible adjustment of the number of modules to adapt to changes in flue gas volume requirements of different units. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an ammonia injection mixing device for SCR denitrification provided in an embodiment of this application; Figure 2 yes Figure 1 A front view of the ammonia mixing device is shown. Figure 3 This is a schematic diagram of the structure of a wind-cap type nozzle provided in an embodiment of this application; Figure 4 This is a bottom view of a wind-cap type nozzle provided in an embodiment of this application; Figure 5 This is a front view of a wind-cap type nozzle provided in an embodiment of this application; Figure 6 This is a schematic diagram of the structure of a mixer module provided in an embodiment of this application; Figure 7 This is a front view of another ammonia mixing device provided in the embodiments of this application; Figure 8 yes Figure 6 The diagram shows the structure of the mixer module; Figure 9 This is a schematic diagram of a vortex effect generated at a mixer module according to an embodiment of this application; Figure 10 This is a schematic diagram of the structure of an ammonia injection grid module provided in an embodiment of this application; Figure 11 This is a schematic diagram showing the connection of two ammonia injection grid modules provided in an embodiment of this application; Figure 12 This is a schematic diagram of the ammonia mixing device provided in this application embodiment, which is installed in flue Y. Figure 13 A schematic diagram of the flow field distribution of the ammonia injection mixing device proposed in this application is provided, which relates to the technology. Figure 14 This is a graph showing the variation of the Cv value of the NH3 / NOx molar ratio distribution uniformity with mixing distance, provided in the embodiments of this application.

[0020] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0023] Please refer to Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of an ammonia injection mixing device for SCR denitrification provided in an embodiment of this application. Figure 2 yes Figure 1 The diagram shows a front view of the ammonia injection mixing device. This ammonia injection mixing device for SCR denitrification can be installed in a vertical flue Y and may include: at least one ammonia injection grid module 100, at least one mixer module 200, and multiple hood-type nozzles 300.

[0024] Each ammonia injection module 100 may have multiple arrayed ammonia injection zones q, each ammonia injection zone q may have multiple ammonia injection ports q1, and the number of ammonia injection ports q1 in each ammonia injection zone q is the same. The multiple ammonia injection ports q1 in each ammonia injection zone q may be connected one-to-one with multiple wind cap type nozzles 300, which can be used to spray ammonia gas mixture.

[0025] At least one mixer module 200 can correspond one-to-one with at least one ammonia injection grid module 100. Each mixer module 200 can have mixing units 201 corresponding one-to-one with multiple ammonia injection zones q. Each mixing unit 201 can be located downstream of multiple hood-type nozzles 300 arranged in the corresponding ammonia injection zone q. As the flue gas flows sequentially through the ammonia injection grid module 100, the hood-type nozzles 300, and the mixer module 200, it undergoes primary mixing with the ammonia gas mixture ejected from the hood-type nozzles 300, and secondary mixing at the mixer module 200. Here, both the ammonia injection grid module 100 and the mixer module 200 can be fixed inside the flue.

[0026] In this embodiment, a two-stage mixer structure is incorporated into the ammonia injection mixing device for SCR denitrification. This structure comprises a two-stage mixing structure: the ammonia injection grid module 100 and the wind-cap type nozzle 300, along with the mixer module 200. This results in a short mixing distance between the flue gas and ammonia mixture and high mixing efficiency. Furthermore, the system employs a modular design. The hierarchical correspondence between the ammonia injection grid module 100 and the mixer module 200 ensures precise ammonia distribution and mixing, effectively guaranteeing the system's denitrification performance. This design is suitable for flue gas ammonia injection denitrification retrofit projects under various operating conditions. In practical applications, the SCR denitrification system can utilize this modular design, with modules arranged along the flue gas depth, and the number of modules can be flexibly adjusted to accommodate varying flue gas volume requirements of different units.

[0027] In summary, this application provides an ammonia injection mixing device for SCR denitrification, which may include at least one ammonia injection grid module, at least one mixer module, and a hood-type nozzle. By setting a two-stage mixer structure in the ammonia injection mixing device for SCR denitrification, namely the matching ammonia injection grid module and hood-type nozzle, and the two-stage mixing structure of the mixer module, the mixing distance of the flue gas and ammonia gas mixture is short, and the mixing efficiency is high. Furthermore, the overall modular design, through the hierarchical correspondence between the ammonia injection grid module and the mixer module, achieves precise ammonia distribution and mixing effect, effectively ensuring the denitrification effect of the system, and is suitable for flue gas ammonia injection denitrification retrofit projects under different operating conditions. In practical applications, the SCR denitrification system can adopt the above modular design, arranged in sections along the depth direction of the flue gas duct, and the number of modules can be flexibly adjusted to adapt to the flue gas volume changes of different units.

[0028] Optional, please refer to Figure 3 , Figure 4 and Figure 5 , Figure 3 This is a schematic diagram of the structure of a wind-cap type nozzle provided in an embodiment of this application. Figure 4 This is a bottom view of a wind-cap type nozzle provided in an embodiment of this application. Figure 5This is a front view of a wind-cap type nozzle provided in an embodiment of this application. Each wind-cap type nozzle 300 may include: a conical member 301 and a nozzle member 302 arranged opposite each other in a vertical direction, and a plurality of supporting connecting plates 303 distributed between the conical member 301 and the nozzle member 302. The nozzle member 302 may have a hollow channel k, one end of which can be connected to an ammonia injection port q1, and the other end of the hollow channel k faces the bottom surface of the conical member 301. The plurality of supporting connecting plates 303 are arranged in a ring array around the axis of the hollow channel k, and the two ends of each supporting connecting plate 303 are respectively fastened to the bottom edge of the conical member 301 and the circumferential side surface of the nozzle member 302, and there is an airflow channel k1 between every two adjacent supporting connecting plates 303. In this way, the wind-cap type nozzle 300 is a nozzle structure formed by connecting the conical member 301 and the nozzle member 302 through a plurality of supporting connecting plates 303, which has a simple structure and is convenient for on-site installation. Furthermore, ammonia gas is ejected from the nozzle 302 and diffuses outwards through the airflow channel formed by multiple supporting connecting plates 303, increasing the mixing stroke and facilitating the achievement of uniform mixing within a shorter distance. The outer surface of the conical component 301 is conical, making it less prone to dust accumulation. It should be noted that the vertical direction here refers to the flow direction of the flue gas, and the multiple supporting connecting plates 303 are evenly distributed in a ring around the axis of the hollow channel; the number of supporting connecting plates can be four. The conical component 301 can be a cylindrical cone.

[0029] Here, as Figure 5 As shown, the nozzle component 302 may include a frustum 302a and a nozzle tube 302b. The frustum 302a can be fitted onto the circumferential side of the nozzle tube 302b. One end of the nozzle tube 302b extends out of the frustum 302a and connects with the ammonia injection port q1. The other end of the nozzle tube 302b is flush with the top surface of the frustum 302a. The bottom diameter of the frustum 302a can be larger than its top diameter. The top surface of the frustum 302a is closer to the bottom surface of the conical component 301 than its bottom surface. The bottom diameter of the conical component 301 can be larger than the bottom diameter of the frustum 302a. One end of the supporting connecting plate 303 is connected to the bottom edge of the frustum 302a. Thus, the combined structure of the cone and frustum, with its pointed top and flared bottom, utilizes the inclined surface to guide ash flow and prevent nozzle clogging. The ammonia spraying grid and the wind-cap type nozzle adopt a pre-assembled integrated design in the workshop, which can effectively reduce the amount of on-site installation work. For example, the structure of the support connecting plate 303 is a plurality of evenly distributed fan-shaped plate structures, that is, the orthographic projection of the support connecting plate on the plane containing the bottom surface of the frustum part is in the shape of a fan ring. The central angle β of the fan-shaped support connecting plate is generally taken as 20°~40°. In other possible implementations, the support connecting plate can also be replaced by angle steel or round steel. The inclination angle α of the frustum side of the frustum part 302a relative to the horizontal plane is not less than 40 degrees.

[0030] Optional, such as Figure 5 As shown, the inner diameter of the nozzle tube 302b can be D1, the bottom diameter of the frustum 302a can be D2, the bottom diameter of the conical part 301 can be D3, the height of the conical part 301 can be H1, and the height difference between the bottom surface of the conical part 301 and the bottom surface of the frustum 302a is H2. Where D2 = (2~6)D1, D3 = (8~15)D1, H1 = (6~10)D1, and H2 = (3~5)D1. Thus, when the inner diameter of the nozzle tube 302b, the bottom diameter of the frustum 302a, the bottom diameter of the conical part 301, the height of the conical part 301, and the height difference between the bottom surface of the conical part 301 and the bottom surface of the frustum 302a satisfy the above relationships, the outward spraying effect of the wind-cap nozzle on the ammonia mixture and the uniform mixing effect with the flue gas can be effectively guaranteed.

[0031] In the embodiments of this application, please refer to Figure 6 , Figure 7 and Figure 8 , Figure 6 This is a schematic diagram of the structure of a mixer module provided in an embodiment of this application. Figure 7 This is a front view of another ammonia mixing device provided in the embodiments of this application. Figure 8 yes Figure 6 The diagram shows the structure of the mixer module. Each mixing unit 201 may include four semi-circular blades 201a, the straight edges of which intersect at a focal point on the virtual axis z. The arrangement direction of two semi-circular blades 201a in one group is perpendicular to the arrangement direction of two semi-circular blades 201a in another group. The two semi-circular blades 201a in each group are symmetrical about the focal point. The virtual axis z is parallel to the flue gas flow direction. Furthermore, the sides containing the diameters of the two semi-circular blades 201a in each group are perpendicular to each other. Here, each semi-circular blade 201a has the same deflection angle relative to the virtual axis z, and the four semi-circular blades 201a have the same diameter. The diameter D7 of the semi-circular blade 201a is (1.4~2.6)L1, where L1 will be further explained later. For example, the angle γ between the semi-circular blade 201a and the virtual axis z is generally taken as 30°~60°.

[0032] In this case, please refer to Figure 9 , Figure 9This is a schematic diagram illustrating the vortex effect generated at the mixer module according to an embodiment of this application. The semi-circular blades 201a continuously cut and block the flowing flue gas and ammonia, creating a velocity difference between the gas at the edge and the back, thereby forming a vortex on the leeward side of the blades. The vortex entrains the surrounding fluid, enhancing turbulence. As the flue gas and ammonia flow through the mixing unit, the inclined blades deflect each stream of air, forming spiral vortices downstream of each mixing unit. The vortices generated by adjacent mixing units interact and entrain the surrounding flue gas, forming a large-scale circulating vortex within the entire module to further enhance mixing. In addition, the inclined arrangement of the semi-circular blades makes it less prone to dust accumulation.

[0033] Optional, please refer to Figure 10 and Figure 11 , Figure 10 This is a structural schematic diagram of an ammonia injection grid module provided in an embodiment of this application. Figure 11 This is a schematic diagram showing the connection of two ammonia injection grid modules provided in this application embodiment. Each ammonia injection grid module 100 may include: an ammonia injection main pipe 101, and a first ammonia injection branch pipe 102, an ammonia injection bend pipe 103, and a second ammonia injection branch pipe 104 disposed in each ammonia injection zone q. Both ends of the ammonia injection main pipe 101 are connected to the inner wall of the flue Y. One end of the first ammonia injection branch pipe 102 can be connected to the ammonia injection main pipe 101. One end of the ammonia injection bend pipe 103 is connected to the first ammonia injection branch pipe 102, and the other end of the ammonia injection bend pipe 103 is bent upwards. One end of the second ammonia injection branch pipe 104 is connected to the ammonia injection bend pipe 103. The inner diameter of the ammonia injection main pipe 101 is larger than the inner diameter of the first ammonia injection branch pipe 102, the inner diameter of the first ammonia injection branch pipe 102 is larger than the inner diameter of the ammonia injection bend pipe 103, the inner diameter of the ammonia injection bend pipe 103 is larger than the inner diameter of the second ammonia injection branch pipe 104, and the other end of the second ammonia injection branch pipe 104 is connected to the nozzle component 302. Multiple ammonia injection zones q are evenly distributed on both sides of the ammonia injection main pipe 101, and the multiple nozzles in the ammonia injection zones on both sides can be arranged in multiple rows and columns. In this application, as... Figure 11 As shown, the distance between every two rows of nozzles is L1, and the value of L1 can range from 400 mm to 1000 mm. The distance between every two rows of nozzles is L2, where L2 = (0.85~1.15)L1. In this way, the nozzles of the ammonia injection grid adopt a matrix design, making the nozzles roughly square. The larger nozzle spacing can reduce the number of grid sections and help to finely control the ammonia injection.

[0034] For example, each ammonia injection zone is provided with at least one set of ammonia injection bends 103 and at least one set of second ammonia injection branch pipes 104. The at least one set of ammonia injection bends 103 includes two ammonia injection bends 103 symmetrically arranged relative to the first ammonia injection branch pipe 102. One end of each ammonia injection bend 103 is connected to the first ammonia injection branch pipe 102, and the other end of the ammonia injection bend 103 is bent upwards. The at least one set of second ammonia injection branch pipes 104 includes two second ammonia injection branch pipes 104 that are connected one-to-one with the at least one set of ammonia injection bends 103. Here, the two first ammonia injection branch pipes 102 located in every two ammonia injection zones q on both sides of the main ammonia injection pipe 101 are symmetrically distributed relative to the main ammonia injection pipe 101, that is, these two first ammonia injection branch pipes 102 symmetrically distributed relative to the main ammonia injection pipe 101 are coaxially arranged. Here, the ammonia injection grid structure using the above-described structure is simple, easy to install, and can use fewer ammonia injection zones, making it more suitable for precision ammonia injection denitrification retrofit projects. In addition, the symmetrical arrangement of the first ammonia injection branch pipe 102 and the ammonia injection bend pipe 103 allows the ammonia gas mixture flowing out of the main ammonia injection pipe 101 to be distributed relatively evenly to the first ammonia injection branch pipe 102 and the ammonia injection bend pipe 103 on both sides of the flow channel.

[0035] In this application, the first ammonia injection branch pipe 102 in the ammonia injection zone q located on the same side as the ammonia injection main pipe 101 is arranged in parallel; when the ammonia injection grid module 100 includes multiple sets of ammonia injection bend pipes 103, the multiple sets of ammonia injection bend pipes are arranged along the length direction of the first ammonia injection branch pipe 102.

[0036] For example, the outer diameter D of the main ammonia injection pipe 101 is generally no greater than 150 mm to avoid dust accumulation at the top of the pipe, and the flow velocity is generally no greater than 12 m / s to avoid excessive resistance. The pipe diameter D4 of the first ammonia injection branch pipe 102 is generally (0.75~0.85) D, the outer diameter D5 of the ammonia injection bend pipe 103 is generally (0.5~0.75) D, and the outer diameter D6 of the second ammonia injection branch pipe 104 is generally (0.15~0.20) D, with a flow velocity generally between 15 and 30 m / s. In this way, by controlling the flow velocity of the ammonia injection grid to a low range, the flow resistance of the pipeline can be reduced, thereby reducing the system energy consumption.

[0037] Here, as Figure 11As shown, in the case where the ammonia injection mixing device for SCR denitrification includes multiple ammonia injection modules 100, the other ends of the first ammonia injection branch pipes 102 in two adjacent ammonia injection modules 100 are separated by a spacer plate B, which connects the two adjacent ammonia injection modules 100. It should be noted that, for the two outermost ammonia injection modules 100, the other ends of the first ammonia injection branch pipes 102 are connected to the inner wall of the flue Y. It should also be noted that, in the case where the ammonia injection mixing device for SCR denitrification includes one ammonia injection module 100, the other end of the first ammonia injection branch pipe 102 is connected to the inner wall of the flue. For example, each ammonia injection module 100 may have four ammonia injection zones q, two of which are located on one side of the main ammonia injection pipe 101, and the other two are located on the other side of the main ammonia injection pipe 101. Each ammonia injection zone q contains two sets of ammonia injection bends 103 and two sets of second ammonia injection branches 104 arranged along the extension direction of the first ammonia injection branch 102.

[0038] This section provides an illustrative explanation of the mixing method for flue gas and ammonia gas: Ammonia gas is injected through the ammonia injection grid module pipeline to the wind-cap type nozzle. It diffuses outwards through the gaps in the supporting connecting plates, creating a "one-to-many" diffusion effect and increasing the ammonia diffusion range. The incoming flue gas generates turbulence on the windward side of the truncated cone base plate, completing a small-scale preliminary mixing of ammonia and flue gas in the area surrounding the supporting connecting plates and the side walls of the truncated cone component; this is the first stage of mixing. The wind-cap type nozzle design increases the mixing and diffusion rate of ammonia and flue gas, which is beneficial for achieving the required mixing uniformity over a shorter distance. After the first stage of mixing, the ammonia and flue gas flow through the mixing units of the downstream mixer module. The mixed gas is continuously cut and blocked by the inclined semi-circular blades, forming multiple airflows. Each airflow forms a vortex on the leeward side of the blades, and each airflow is deflected, thus forming a spiral vortex downstream of each mixing unit. The swirling flows generated by adjacent mixing units interact and entangle the surrounding flue gas, forming a large-scale circulating vortex throughout the module, further enhancing the mixing; this is the second stage of mixing. Two-stage mixing refines the fluid contact process, achieving the required mixing uniformity within a shorter mixing distance, thus improving mixing efficiency and uniformity.

[0039] The present invention will be further illustrated below with numerical simulation results of specific embodiments: Please refer to the model for specific embodiments. Figure 12 , Figure 12 This is a schematic diagram of the ammonia mixing device provided in this application embodiment, installed in flue Y. The main design parameters are as follows: flue gas volume is 486,000 m³ / h. 3The flue gas temperature is 350℃. An ammonia injection grid, a nozzle hood, and a semi-circular mixer are sequentially installed along the airflow direction within the vertical flue. This example includes one ammonia injection grid module, one mixer module, and 16 nozzle hoods. One ammonia injection grid module contains one main ammonia injection pipe and several branch pipes, which can be divided into four ammonia injection zones. Each zone contains four ammonia injection ports, each corresponding to a nozzle hood. The ammonia injection grid and nozzle hoods are pre-assembled as a single unit in the workshop. One mixing module contains four mixing units, each containing four semi-circular blades. These mixing units work in conjunction with the ammonia injection zones.

[0040] Ammonia gas is injected through the ammonia injection grid distribution pipeline to the wind-cap nozzle. It diffuses outwards through the gaps in the supporting connectors, creating a "one-to-four" diffusion effect and increasing the diffusion range. The incoming flue gas generates turbulence on the windward side of the truncated cone base plate, achieving a small-scale initial mixing of ammonia and flue gas in the area surrounding the supporting connectors and the sidewalls of the truncated cone. After this initial mixing, the ammonia and flue gas flow through the mixing units of the downstream mixing module. The inclined blades continuously cut and block the mixed gas, forming multiple airflows. Each airflow forms a vortex on the leeward side of the blades, and each airflow is deflected, creating spiral vortices downstream of each mixing unit. The swirling flows generated by adjacent mixing units interact and entrain the surrounding flue gas, forming a large-scale circulating vortex throughout the module, further enhancing mixing. This two-stage mixing process refines the fluid contact process, achieving the required mixing uniformity within a shorter mixing distance, thus improving mixing efficiency and uniformity. Please refer to [reference needed]. Figure 14 , Figure 14 This is a graph showing the variation of the Cv value of the NH3 / NOx molar ratio distribution uniformity with mixing distance, provided in the embodiments of this application. Using the device of this application, the Cv value of the NH3 / NOx molar ratio distribution uniformity at a mixing distance of 10m is 3.81%, at 15m it is 2.27%, and at 20m it is 1.35%, which is far superior to the technical requirement of less than 5% for the NH3 / NOx molar ratio distribution uniformity in the national standard GB / T 21509-2008. Statistical analysis shows that the resistance generated by the ammonia injection grid, the wind-cap type nozzle, and the semi-circular mixer is 140Pa, which is not high overall and is within the acceptable range for the denitrification system.

[0041] In this embodiment, please refer to Figure 13 , Figure 13 A schematic diagram of the flow field distribution of the ammonia injection mixing device of the related technology and the present application is provided. The ammonia injection mixing device of the present application has turbulent streamlines, with small individual vortices and a large number of them. The ammonia injection mixing device of the related technology has a large vortex range, and the vortex distribution is sparse in the middle and dense around the perimeter.

[0042] Large-scale eddies primarily lead to macroscopic mixing, while small-scale eddies are more conducive to microscopic homogeneity and a more uniform concentration distribution. Figure 14 The uniformity of the NH3 / NOx molar ratio distribution in existing technologies can also be derived from this. V The values ​​are all greater than those of the ammonia injection mixing device proposed in this application. The ammonia injection mixing device proposed in this application has met the technical requirement of less than 5% uniformity of NH3 / NOx molar ratio distribution in the national standard GB / T 21509-2008 at a mixing distance of 8m, while the existing technology requires a mixing distance of 12m to meet the technical requirement, which verifies the technical advantages of the ammonia injection mixing device proposed in this application in terms of short mixing distance and high mixing efficiency.

[0043] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0044] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An ammonia injection mixing device for SCR denitrification, characterized in that, include: At least one ammonia injection grid module, at least one mixer module, and multiple wind-cap type nozzles; Each of the ammonia injection modules has multiple arrayed ammonia injection zones, each ammonia injection zone has multiple ammonia injection ports, and the number of ammonia injection ports in each ammonia injection zone is the same; the multiple ammonia injection ports in each ammonia injection zone are connected one-to-one with multiple wind cap type nozzles, and the wind cap type nozzles are used to spray out ammonia gas mixture. The at least one mixer module corresponds one-to-one with the at least one ammonia injection grid module. Each mixer module has a mixing unit that corresponds one-to-one with multiple ammonia injection zones. Each mixing unit is located downstream of multiple wind cap nozzles set in the corresponding ammonia injection zone. As the flue gas flows sequentially through the ammonia injection grid module, the wind cap nozzle, and the mixer module, it undergoes primary mixing with the ammonia gas mixture sprayed from the wind cap nozzle and secondary mixing at the mixer module.

2. The ammonia injection mixing device for SCR denitrification according to claim 1, characterized in that, Each of the mixing units includes: four semi-circular blades, the straight edges of which intersect at a focal point on a virtual axis, the arrangement direction of two semi-circular blades in one group of semi-circular blades is perpendicular to the arrangement direction of two semi-circular blades in another group of semi-circular blades, the two semi-circular blades in each group of semi-circular blades are symmetrical about the focal point, and the virtual axis is parallel to the flue gas flow direction.

3. The ammonia injection mixing device for SCR denitrification according to claim 2, characterized in that, The four semi-circular blades have the same diameter.

4. The ammonia injection mixing device for SCR denitrification according to claim 2, characterized in that, The angle between each of the semicircular blades and the virtual axis ranges from 30 degrees to 60 degrees.

5. The ammonia injection mixing device for SCR denitrification according to any one of claims 2-4, characterized in that, The wind-cap type nozzle includes: a conical component and a nozzle component arranged opposite each other in a vertical direction, and a plurality of supporting connecting plates distributed between the conical component and the nozzle component. The nozzle component has a hollow channel, one end of which is connected to the ammonia injection port, and the other end of which faces the bottom surface of the conical component. The plurality of supporting connecting plates are arranged in a ring array around the axis of the hollow channel. The two ends of each supporting connecting plate are respectively connected to the bottom edge of the conical component and the circumferential side surface of the nozzle component, and there is an airflow channel between every two adjacent supporting connecting plates.

6. The ammonia injection mixing device for SCR denitrification according to claim 5, characterized in that, The nozzle component includes a frustum and a nozzle tube. The frustum is fitted onto the circumferential side of the nozzle tube. One end of the nozzle tube extends out of the frustum and connects with the ammonia injection port. The other end of the nozzle tube is flush with the top surface of the frustum. The bottom diameter of the frustum is larger than the top diameter, and the bottom diameter of the conical component is larger than the bottom diameter of the frustum. One end of the support connecting plate is connected to the bottom edge of the frustum.

7. The ammonia injection mixing device for SCR denitrification according to claim 6, characterized in that, The inner diameter of the nozzle tube is D1, the bottom diameter of the frustum is D2, the bottom diameter of the cone is D3, the height of the cone is H1, and the height difference between the bottom of the cone and the bottom of the frustum is H2; wherein, D2=(2~6)D1, D3=(8~15)D1, H1=(6~10)D1, and H2=(3~5)D1.

8. The ammonia injection mixing device for SCR denitrification according to claim 5, characterized in that, Multiple supporting connecting plates are distributed at equal intervals in a ring around the central axis of the hollow channel.

9. The ammonia injection mixing device for SCR denitrification according to claim 5, characterized in that, The ammonia injection grid module includes: an ammonia injection main pipe, and a first ammonia injection branch pipe, an ammonia injection bend pipe, and a second ammonia injection branch pipe disposed in each ammonia injection zone. Both ends of the ammonia injection main pipe are connected to the inner wall of the flue. One end of the first ammonia injection branch pipe is connected to the ammonia injection main pipe. One end of the ammonia injection bend pipe is connected to the first ammonia injection branch pipe, and the other end of the ammonia injection bend pipe is bent upwards. One end of the second ammonia injection branch pipe is connected to the ammonia injection bend pipe. The inner diameter of the ammonia injection main pipe is larger than the inner diameter of the first ammonia injection branch pipe, the inner diameter of the first ammonia injection branch pipe is larger than the inner diameter of the ammonia injection bend pipe, the inner diameter of the ammonia injection bend pipe is larger than the inner diameter of the second ammonia injection branch pipe, and the other end of the second ammonia injection branch pipe is connected to the nozzle component. Multiple ammonia injection zones are evenly distributed on both sides of the ammonia injection main pipe, and multiple nozzles in the ammonia injection zones on both sides are arranged in multiple rows and columns.

10. The ammonia injection mixing device for SCR denitrification according to claim 9, characterized in that, The outer diameter D of the main ammonia injection pipe, the diameter D4 of the first ammonia injection branch pipe = (0.75~0.85)D, the outer diameter D5 of the ammonia injection bend pipe = (0.5~0.75)D, and the outer diameter D6 of the second ammonia injection branch pipe = (0.15~0.20)D.

11. The ammonia injection mixing device for SCR denitrification according to claim 9, characterized in that, The distance between every two columns of nozzles is L1, with a value ranging from 400mm to 1000mm. The distance between every two rows of nozzles is L2, where L2 = (0.85~1.15)L1.

12. The ammonia injection mixing device for SCR denitrification according to claim 11, characterized in that, The diameter of the semi-circular blade is D7 = (1.4~2.6)L1.

13. The ammonia injection mixing device for SCR denitrification according to claim 9, characterized in that, In the case of an ammonia injection mixing device for SCR denitrification containing multiple ammonia injection modules, the other ends of the first ammonia injection branch pipes in two adjacent ammonia injection modules are separated by a partition plate, which is used to connect the two adjacent ammonia injection modules.

Images