Ammonia injection grid with injection and mixing functions

Abstract

The present invention relates to an ammonia injection grid with injection and mixing functions, which is installed in a flue. The ammonia injection grid is composed of a plurality of partitions arranged at equal intervals along the cross section of the flue, and a plurality of injection units arranged at equal intervals along the cross section of the flue are provided between adjacent partitions. A venturi channel is formed between adjacent injection units, and the venturi channel has a convergent section, a throat, and a divergent section. Each injection unit includes an upper cone section and a lower cone section that are relatively arranged, and the upper cone section and the lower cone section are connected by a straight section located at the throat of the venturi channel, and an ammonia injection port is provided on the straight section. The ammonia injection grid with injection and mixing functions provided in this embodiment realizes the integration of ammonia injection and mixing by constructing a venturi channel between adjacent injection units and providing a straight section and an ammonia injection port at the throat, which greatly shortens the mixing distance, saves equipment space, and reduces system costs.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitration, in particular to an ammonia injection grid with injection and mixing functions. Background Art

[0002] With growing global environmental awareness, emission controls on nitrogen oxides (NOx) are becoming increasingly stringent. Flue gas from industrial enterprises such as coal-fired power plants, cement plants, and steel mills contains significant amounts of NOx, a major cause of air pollution. Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are currently the most widely used flue gas denitrification technologies. These technologies typically involve injecting a reducing agent (such as ammonia) into the flue gas, where it reacts with the NOx in the flue gas, reducing it to harmless nitrogen and water.

[0003] In the flue gas denitrification system, the ammonia injection grid is one of the key devices. Its main function is to evenly inject ammonia and other reducing agents into the flue and fully mix them with the flue gas, thereby improving the denitrification efficiency. Traditional ammonia injection grids usually use porous tubes or nozzles installed in the flue to inject ammonia. However, this method has some problems:

[0004] Low mixing efficiency: The ammonia injected from traditional ammonia injection grids has a limited diffusion range, and mixing with flue gas relies mainly on the turbulence of the flue gas, resulting in low mixing efficiency. A long mixing distance is required to achieve a good mixing effect. This leads to incomplete denitrification reaction and limited denitrification efficiency.

[0005] Uneven ammonia distribution: Due to factors such as uneven flue gas velocity distribution in the flue and differences in injection pressure from the nozzles of the ammonia grid, ammonia distribution is uneven across the flue cross section, resulting in localized excessively high or low ammonia concentrations. This not only reduces denitrification efficiency but can also lead to ammonia escape and secondary pollution.

[0006] Large equipment size: To improve mixing efficiency, traditional ammonia injection grids usually require increasing the flue length or installing additional static mixers, which results in a large denitrification system, increased floor space, and higher construction costs.

[0007] To solve the above problems, some improvement solutions have been proposed in the prior art, such as adopting multi-stage injection, optimizing nozzle arrangement, etc. However, these improvement solutions still have certain limitations and it is difficult to achieve efficient mixing, uniform distribution and miniaturization at the same time. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides an ammonia injection grid with injection and mixing functions, which achieves efficient mixing, uniform distribution, space saving and cost reduction.

[0009] In order to achieve the above-mentioned purpose, the present invention is designed to provide an ammonia injection grid with injection and mixing functions, which is installed in a flue, and the ammonia injection grid is composed of a plurality of partitions arranged at equal intervals along the transverse cross-section of the flue, and a plurality of injection units arranged at equal intervals along the longitudinal cross-section of the flue are provided between adjacent partitions; a Venturi channel is formed between adjacent injection units, and the Venturi channel has a convergent section, a throat and a divergent section; each of the injection units includes an upper cone section and a lower cone section arranged opposite to each other, and the upper cone section and the lower cone section are connected by a straight section located at the throat of the Venturi channel, and an ammonia injection port is provided on the straight section; wherein the cross-sectional area of ​​the convergent section gradually decreases along the direction of flue gas flow, and the cross-sectional area of ​​the divergent section gradually increases along the direction of flue gas flow; the angle α between the side wall of the convergent section and the central axis of the throat is 17°-21°, and the angle β between the side wall of the divergent section and the central axis of the throat is 22°-26°.

[0010] Preferably, the ammonia injection port is an oblong hole extending longitudinally along the flue cross section, and the aperture of the oblong hole increases from its air inlet end to the injection end toward the location of the throat.

[0011] Preferably, the cross-sections of the upper cone section and the lower cone section parallel to the flue gas flow direction are isosceles triangles.

[0012] Preferably, a mixing space is formed between any two adjacent partitions, and the injection units in the mixing spaces adjacent to each other in the longitudinal direction of the flue cross section are staggered, and the staggered distance is equal to the width of the throat.

[0013] Preferably, some of the partitions are provided with an ammonia main pipe connected to an external ammonia source, and each of the straight sections is provided with an intake branch pipe connected to an ammonia injection port, and each of the intake branch pipes is connected to the ammonia main pipe in the corresponding partition; wherein, among the partitions, a partition with the ammonia main pipe is provided for every other partition without the ammonia main pipe.

[0014] Preferably, tenons are provided on the connecting surfaces of the upper cone section, the lower cone section and the straight section, and mortises matching the tenons are provided on the straight section; screw holes penetrating to the lower cone section are provided on the cone surface of the upper cone section, and the upper cone section, the straight section and the lower cone section are fixedly connected as a whole through the screw holes and bolts.

[0015] Preferably, positioning countersunk holes adapted to the upper conical section, the straight section and the lower conical section of the injection unit are provided on the plate surface of the partition, and the straight section is connected to the partition by bolts.

[0016] Preferably, the partition, upper cone section, straight section and lower cone section are all made of high temperature resistant and corrosion resistant alloy material.

[0017] Preferably, the ammonia injection grid further includes a fixed frame, and the partitions are fixedly connected via the fixed frame.

[0018] The ammonia injection grid designed by the present invention, which has injection and mixing functions, realizes the integration of ammonia injection and mixing by constructing a Venturi channel between adjacent injection units and setting a straight section and an ammonia injection port at the throat, which greatly shortens the mixing distance, saves equipment space, and reduces system costs; at the same time, the special structure of the Venturi channel significantly improves the mixing efficiency, reduces or even eliminates the dependence on the static mixer, further simplifies the system structure, and reduces operating costs. In addition, the uniform distribution of multiple injection units and the design of the ammonia injection port at the throat of each Venturi channel achieve uniform distribution of ammonia, overcome the problem of uneven ammonia distribution in traditional technologies, thereby improving denitrification efficiency, reducing ammonia waste, and further optimizing the injection effect. Finally, it is worth mentioning that it is not only suitable for flue gas denitrification in coal-fired power plants, but also suitable for flue gas denitrification scenarios in other industrial fields, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the ammonia injection grid structure provided in an embodiment of the present application.

[0020] Figure 2 This is a schematic diagram of the installation structure of a single injection unit provided in an embodiment of the present application.

[0021] Figure 3 yes Figure 2 3D exploded view of .

[0022] Figure 4 yes Figure 2 Top view of .

[0023] Figure 5 yes Figure 4 Cross-sectional view at AA in the middle.

[0024] Figure 6 yes Figure 4 Cross-sectional view at the middle BB.

[0025] Figure 7 This is a partial cross-sectional schematic diagram of the ammonia injection grid provided in an embodiment of the present application installed in a flue.

[0026] Among them: partition 10, ammonia main pipe 11, positioning countersunk hole 12, injection unit 20, upper cone section 21, lower cone section 22, straight section 23, mortise 24, screw hole 25, Venturi channel 30, convergent section 31, throat 32, divergent section 33, ammonia injection port 40, and intake branch pipe 41. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] The ammonia injection grid with injection and mixing functions provided in the embodiment of the present application is mainly used in the flue gas denitrification system of industrial enterprises such as coal-fired power plants to improve the mixing efficiency of ammonia and flue gas, thereby improving the denitrification effect.

[0029] like Figures 1 to 7 As shown, the ammonia injection grid with injection and mixing functions described in this embodiment is installed in the flue, and the ammonia injection grid is composed of a plurality of partitions 10 arranged at equal intervals along the transverse cross-section of the flue, and a plurality of injection units 20 arranged at equal intervals along the longitudinal cross-section of the flue are provided between adjacent partitions 10; a Venturi channel 30 is formed between adjacent injection units 20, and the Venturi channel 30 has a convergent section 31, a throat 32 and a divergent section 33; each of the injection units 20 includes an upper cone section 21 and a lower cone section 22 arranged opposite to each other, and the upper cone section 21 and the lower cone section 22 are connected by a straight section 23 located at the throat 32 of the Venturi channel 30, and an ammonia injection port 40 is provided on the straight section 23; wherein, the cross-sectional area of ​​the convergent section 31 gradually decreases along the flue gas flow direction, and the cross-sectional area of ​​the divergent section 33 gradually increases along the flue gas flow direction.

[0030] When doing specific work, such as Figure 7 As shown, an ammonia injection grid is installed in the flue. Flue gas flows into the converging section 31 of the Venturi channel 30. As the cross-sectional area of ​​the converging section 31 gradually decreases, the flue gas flow rate accelerates and reaches its maximum value at the throat 32. Simultaneously, ammonia is injected into the throat 32 of the Venturi channel 30 through the ammonia injection port 40 provided on the straight section 23, thereby rapidly mixing with the high-speed flue gas. Finally, the ammonia-flue gas mixture enters the subsequent flue through the diverging section 33. In the diverging section 33, the flue gas flow rate slows down due to the gradual increase in cross-sectional area, and further mixing occurs. In this structure, the Venturi channel 30, through the rational design of the converging section 31, throat 32, and diverging section 33, not only ensures that the flue gas flows through the throat 32 at a relatively high flow rate, but also forms a negative pressure zone at the throat 32, which is conducive to the thorough mixing of ammonia and flue gas. In addition, the uniform distribution of the injection units 20 ensures the uniform distribution of the injected ammonia gas across the entire flue cross-section, effectively improving the mixing efficiency of the ammonia and flue gas.

[0031] In this embodiment, the angle α between the sidewall of the converging section 31 and the central axis of the throat 32 is 17°-21°, and the angle β between the sidewall of the diverging section 33 and the central axis of the throat 32 is 22°-26°. This angle design ensures sufficient mixing of ammonia and flue gas in the throat without generating excessive flow resistance. In a specific embodiment, the angle α is 19° and the angle β is 24°. This angle combination ensures good mixing without generating excessive flow resistance.

[0032] In this embodiment, the partition 10, the upper conical section 21, the straight section 23 and the lower conical section 22 are all made of a high temperature resistant and corrosion resistant alloy material. In some embodiments, stainless steel, nickel-based alloys, high temperature alloys and the like can be used.

[0033] In some embodiments, as Figure 2 、 Figure 6 As shown, the ammonia injection port 40 is an oblong hole extending longitudinally along the flue cross-section. The diameter of the oblong hole increases gradually from the air inlet end to the injection end toward the location of the throat 32. Specifically, on the straight section 23, the ammonia injection port 40 is shaped like an elongated ellipse. Its diameter is smaller near the connection with the ammonia pipeline (i.e., the air inlet end). As it approaches the throat 32 along the injection direction, the diameter gradually increases. This design increases the coverage of ammonia on the flue cross-section. In other words, traditional point-like or columnar injection often concentrates ammonia into a small area. In contrast, this oblong hole injection method allows ammonia to be ejected in a thin layer, greatly increasing the contact area between ammonia and flue gas. This more efficiently utilizes the accelerated mixing effect of the Venturi channel 30, thereby greatly avoiding uneven mixing of ammonia and significantly reducing the possibility of ammonia escape.

[0034] In some embodiments, the cross-section of the upper conical section 21 and the lower conical section 22 parallel to the direction of flue gas flow in the flue is an isosceles triangle. Utilizing this structural design, two adjacent baffles 10 can be tightly connected to the two opposite sides of the upper conical section 21 and the lower conical section 22, respectively, thereby more effectively enclosing the convergent section 31 and the divergent section 33, ensuring the structural integrity and airtightness of the Venturi channel 30. At the same time, the isosceles triangle cross-section structure is relatively simple and easy to process and manufacture, which can effectively reduce production costs; ensuring the long-term stable and reliable operation of the injection unit 20 in harsh working environments such as high temperature and high pressure, thereby reducing maintenance requirements and downtime caused by component damage.

[0035] In some embodiments, as Figure 7 As shown, a mixing space is formed between any two adjacent partitions 10 , and the injection units 20 in the mixing spaces adjacent to each other in the longitudinal direction of the flue cross section are staggered, and the staggered distance is equal to the width of the throat 32 .

[0036] When implementing it specifically, Figure 2 As shown, the plate surface of the partition 10 is provided with positioning countersunk holes 12 adapted to the upper conical section 21, the straight section 23 and the lower conical section 22 of the injection unit 20, and the straight section 23 is connected to the partition 10 by bolts.

[0037] In this way, the straight sections 23 located on both sides of the same partition 10 are designed to be fixed at different positions in the longitudinal direction of the partition 10, thereby effectively avoiding structural weaknesses caused by excessive concentration of fixing points, ensuring the overall stability and reliability of the ammonia injection grid. At the same time, the staggered arrangement makes the distribution of ammonia more uniform on the flue cross section, avoiding the concentration or lack of ammonia in certain areas, and further improving the mixing uniformity.

[0038] In some embodiments, as Figure 5 、 Figure 6 、 Figure 7 As shown, some of the partitions 10 are provided with an ammonia main pipe 11 connected to an external ammonia source, and each of the straight sections 23 is provided with an intake branch pipe 41 connected to an ammonia injection port 40, and each of the intake branch pipes 41 is connected to the ammonia main pipe 11 in the corresponding partition 10; wherein, among the partitions 10, a partition 10 with the ammonia main pipe 11 is provided for every other partition 10 without the ammonia main pipe 11.

[0039] During operation, ammonia flows into the ammonia main pipe 11 from an external ammonia source and is then transported through the air intake branch pipe 41 to the ammonia injection ports 40 on each straight section 23 for injection and mixing. Since the ammonia injection ports 40 correspond one-to-one with the straight sections 23, and the straight sections 23 correspond one-to-one with the injection units 20, this method enables independent ammonia supply to each injection unit 20. Furthermore, since a partition 10 with an ammonia main pipe 11 is provided for every other partition 10 without an ammonia main pipe 11, the injection units 20 on both sides of the partition 10 with an ammonia main pipe 11 can be supplied with gas through the same ammonia main pipe 11. This structural layout not only ensures uniform ammonia injection across the entire flue cross-section, but also greatly simplifies the overall structure, reduces the number of unnecessary pipes, and significantly reduces the difficulty of installation and maintenance, while also lowering manufacturing costs.

[0040] In some embodiments, as Figure 3As shown, the upper and lower conical sections 21, 22, and the straight section 23 are each provided with a tenon on their connecting surfaces. The straight section 23 is provided with a mortise 24 that mates with the tenon. Screw holes 25 are provided on the conical surface of the upper conical section 21 and extend through the lower conical section 22. The upper, straight, and lower conical sections 21, 23, and 22 are fastened together via screw holes and bolts. During assembly, the tenons on the upper and lower conical sections 21, 22, are first aligned with the mortise 24 on the straight section 23. The upper, straight, and lower conical sections 21, 23, and 22 are then assembled together. The coordination of the tenons and mortise 24 allows for quick and accurate positioning of the three components. Then, the bolts are passed through the screw holes 25 on the conical surface of the upper conical section 21 and extended to the lower conical section 22, thereby firmly connecting the upper conical section 21, the straight section 23 and the lower conical section 22 into a whole. This connection method is not only convenient for assembly, but also has high connection strength and good reliability.

[0041] In some embodiments, the ammonia injection grid (IAG) further includes a fixed frame (not shown), through which the baffles 10 are fixedly connected. Specifically, the fixed frame typically consists of multiple interconnected beams or plates, and can be made of steel, stainless steel, or other materials with sufficient strength and rigidity. The baffles 10 can be securely fastened to the fixed frame via bolts, welding, or other connection methods, forming a single, integrated structure. This structural design eliminates the need for multiple independent baffles and instead creates a single, high-strength structure that effectively resists the impact and vibration caused by flue gas flow. In addition, the fixed frame not only provides overall support, but also serves as a reference for installation, making the installation of the ammonia spray grid in the flue more convenient and quick, that is, the installer only needs to fix the fixed frame at a predetermined position in the flue, and then fix each partition 10 on the fixed frame, without the need to measure and position each partition 10 separately. This installation method not only reduces errors in the installation process, but also reduces the requirements for the skill level of the installer, thereby saving installation time and cost; at the same time, the fixed frame can also ensure the accurate position of each partition 10 in the flue, thereby ensuring the dimensional consistency of the Venturi channel, and can effectively avoid installation deviations, making the operation of the ammonia spray grid more stable and reliable.

[0042] The ammonia injection grid with injection and mixing functions provided in this embodiment realizes the integration of ammonia injection and mixing by constructing a Venturi channel between adjacent injection units and setting a straight section and an ammonia injection port at the throat, which greatly shortens the mixing distance, saves equipment space, and reduces system costs; at the same time, the special structure of the Venturi channel significantly improves the mixing efficiency, reduces or even eliminates the dependence on the static mixer, further simplifies the system structure, and reduces operating costs. In addition, the uniform distribution of multiple injection units and the design of the ammonia injection port at the throat of each Venturi channel achieve uniform distribution of ammonia, overcome the problem of uneven ammonia distribution in traditional technologies, thereby improving denitrification efficiency, reducing ammonia waste, and further optimizing the injection effect. Finally, it is worth mentioning that it is not only suitable for flue gas denitrification in coal-fired power plants, but also suitable for flue gas denitrification scenarios in other industrial fields, and has broad application prospects.

[0043] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0044] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0045] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An ammonia injection grid with injection and mixing functions, installed in the flue, characterized in that: The ammonia injection grid is composed of a plurality of partitions arranged at equal intervals along the transverse cross-section of the flue, and a plurality of injection units arranged at equal intervals along the longitudinal cross-section of the flue are provided between adjacent partitions; a Venturi channel is formed between adjacent injection units, and the Venturi channel has a convergent section, a throat section, and a divergent section; each injection unit includes an upper cone section and a lower cone section arranged opposite to each other, and the upper cone section and the lower cone section are connected by a straight section located at the throat of the Venturi channel, and an ammonia injection port is provided on the straight section; wherein the cross-sectional area of ​​the convergent section gradually decreases along the direction of flue gas flow, and the cross-sectional area of ​​the divergent section gradually increases along the direction of flue gas flow; the angle α between the side wall of the convergent section and the central axis of the throat section is 17°-21°, and the angle β between the side wall of the divergent section and the central axis of the throat section is 22°-26°; An ammonia main pipe connected to an external ammonia source is provided in some of the partitions, and an air intake branch pipe connected to an ammonia injection port is provided in each of the straight sections, and each of the air intake branch pipes is connected to the ammonia main pipe in the corresponding partition; wherein, among the partitions, a partition with the ammonia main pipe is provided for every other partition without the ammonia main pipe.

2. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The ammonia injection port is an oblong hole extending longitudinally along the cross section of the flue, and the aperture of the oblong hole increases from the air inlet end to the injection end toward the position of the throat.

3. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The cross sections of the upper cone section and the lower cone section parallel to the flue gas flow direction are isosceles triangles.

4. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: A mixing space is formed between any two adjacent partitions, and the injection units in the mixing spaces adjacent to each other in the longitudinal direction of the flue cross section are staggered, and the staggered distance is equal to the width of the throat.

5. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The upper and lower cone sections are connected to the straight section on surfaces with tenons, and the straight section is provided with mortises that match the tenons. The upper cone section is provided with screw holes that penetrate through to the lower cone section on the cone surface, and the upper cone section, the straight section and the lower cone section are fixedly connected as a whole through the screw holes and bolts.

6. The ammonia injection grid with injection and mixing functions according to claim 1 or 5, characterized in that: Positioning countersunk holes matching the upper conical section, the straight section and the lower conical section of the injection unit are provided on the plate surface of the partition, and the straight section is connected to the partition by bolts.

7. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The partition, the upper cone section, the straight section and the lower cone section are all made of high-temperature resistant and corrosion-resistant alloy materials.

8. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The ammonia injection grid further includes a fixed frame, and the partitions are fixedly connected via the fixed frame.

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