Ammonia spraying grid with spraying and mixing functions

Abstract

The invention relates to an ammonia spraying grid with spraying and mixing functions, which is mounted in a flue and consists of a plurality of partition plates which are transversely arranged at equal intervals along the section of the flue, and a plurality of spraying units which are longitudinally arranged at equal intervals along the section of the flue are arranged between the adjacent partition plates; venturi channels are formed between the adjacent spraying units, and each Venturi channel is provided with a convergent section, a throat part and a divergent section; each spraying unit comprises an upper conical section and a lower conical section which are oppositely arranged, the upper conical section and the lower conical section are connected through a straight section located at the throat part of the Venturi channel, and an ammonia spraying opening is formed in the straight section. According to the ammonia spraying grating with the spraying and mixing functions, the venturi channels are constructed between the adjacent spraying units, and the straight sections and the ammonia spraying openings are arranged at the throat parts, so that integration of ammonia spraying and mixing is realized, the mixing distance is greatly shortened, the equipment space is saved, and the system cost is reduced.

Description

Technical Field

[0001] The 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] As global environmental awareness continues to increase, the emission control of nitrogen oxides (NOx) is becoming increasingly stringent. The flue gas produced by industrial enterprises such as coal-fired power plants, cement plants, and steel plants contains a large amount of nitrogen oxides, which is one of the main causes 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 usually require the injection of a reducing agent (such as ammonia) into the flue to react with the nitrogen oxides in the flue gas and reduce them to harmless nitrogen and water.

[0003] In the flue gas denitrification system, the ammonia injection grid is one of the key equipment. Its main function is to spray ammonia and other reducing agents evenly 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 in the flue to spray ammonia. However, this method has some problems: Low mixing efficiency: The diffusion range of ammonia injected by traditional ammonia injection grid is limited, and the mixing with flue gas mainly depends on the turbulence of flue gas, with low mixing efficiency. A longer mixing distance is required to achieve a better mixing effect. This leads to inadequate denitrification reaction and limited denitrification efficiency.

[0004] Uneven distribution of ammonia: Due to the uneven distribution of flue gas velocity in the flue and the difference in injection pressure of each nozzle of the ammonia grid, the distribution of ammonia in the flue cross section will be uneven, resulting in excessive or low local ammonia concentration. This not only reduces the denitrification efficiency, but may also cause ammonia to escape and cause secondary pollution.

[0005] Large equipment size: In order to improve the mixing efficiency, traditional ammonia injection grids usually need to increase the flue length or install additional static mixers, which will cause the denitrification system to be bulky, increase the floor space, and increase the construction cost.

[0006] In order to solve the above problems, some improvement schemes have been proposed in the prior art, such as adopting multi-stage injection, optimizing nozzle arrangement, etc. However, these improvement schemes still have certain limitations and it is difficult to achieve efficient mixing, uniform distribution and miniaturization at the same time. Summary of the invention

[0007] 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.

[0008] In order to achieve the above-mentioned purpose, the ammonia injection grid with injection and mixing functions designed in the present invention is installed in the 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 arranged 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, 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 arranged on the straight section; wherein the cross-sectional area of ​​the convergent section gradually decreases along the flow direction of the flue gas, and the cross-sectional area of ​​the divergent section gradually increases along the flow direction of the flue gas; 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°.

[0009] Preferably, the ammonia injection port is an oblong hole extending longitudinally along the flue cross section, and the aperture of the oblong hole increases gradually from the air inlet end to the injection end toward the throat.

[0010] Preferably, the cross-sections of the upper cone section and the lower cone section parallel to the flue gas flow direction are isosceles triangles.

[0011] 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.

[0012] 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.

[0013] Preferably, the connecting surfaces of the upper cone section, the lower cone section and the straight section are all provided with tenons, and the straight section is provided with mortises matched with the tenons; the cone surface of the upper cone section is provided with screw holes penetrating to the lower 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.

[0014] Preferably, positioning countersunk holes matching the upper cone section, the straight section and the lower cone 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.

[0015] Preferably, 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.

[0016] Preferably, the ammonia injection grid further comprises a fixed frame, and the partitions are fixedly connected via the fixed frame.

[0017] The ammonia spray grid with injection and mixing functions designed by the present invention realizes the integration of ammonia spray and mixing by constructing a Venturi channel between adjacent injection units and setting a straight section and an ammonia spray 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 the operating cost. In addition, the uniform distribution of multiple injection units and the design of the ammonia spray port at the throat of each Venturi channel realize the uniform distribution of ammonia, overcome the problem of uneven ammonia distribution in traditional technology, thereby improving the 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

[0018] Figure 1 It is a schematic diagram of the ammonia injection grid structure provided in an embodiment of the present application.

[0019] Figure 2 It is a schematic diagram of the installation structure of a single injection unit provided in an embodiment of the present application.

[0020] Figure 3 yes Figure 2 Exploded three-dimensional diagram.

[0021] Figure 4 yes Figure 2 Top view of the .

[0022] Figure 5 yes Figure 4 Section view at AA in the middle.

[0023] Figure 6 yes Figure 4 Cross-sectional view at BB in the middle.

[0024] Figure 7 It is a partial cross-sectional schematic diagram of an ammonia injection grid provided in an embodiment of the present application installed in a flue.

[0025] 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, intake branch pipe 41. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below in conjunction with 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.

[0027] 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.

[0028] 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 cross section of the flue in the transverse direction, and a plurality of injection units 20 arranged at equal intervals along the cross section of the flue in the longitudinal direction are arranged 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 arranged 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.

[0029] When doing specific work, such as Figure 7 As shown, the ammonia spray grid is installed in the flue, and the flue gas flows in from the convergent section 31 of the Venturi channel 30. As the cross-sectional area of ​​the convergent section 31 gradually decreases, the flue gas velocity accelerates and reaches the maximum value at the throat 32. At the same time, ammonia is sprayed to the throat 32 of the Venturi channel 30 through the ammonia spray port 40 arranged on the straight section 23, so as to quickly mix with the high-speed flowing flue gas; finally, the mixture of ammonia and flue gas enters the subsequent flue through the divergent section 33. In the divergent section 33, due to the gradual increase in the cross-sectional area, the flue gas velocity slows down and further mixes. In this structure, the Venturi channel 30 can not only ensure that the flue gas passes through the throat 32 at a faster flow rate through the reasonable design of the convergent section 31, the throat 32 and the divergent section 33, but also form a negative pressure area at the throat 32, which is conducive to the full mixing of ammonia and flue gas. In addition, the uniform distribution of the spray unit 20 ensures the uniformity of the distribution of the sprayed ammonia gas on the entire flue cross section, and effectively improves the mixing efficiency of ammonia and flue gas.

[0030] In this embodiment, the angle α between the side wall of the convergent section 31 and the central axis of the throat 32 is 17°-21°, and the angle β between the side wall of the divergent section 33 and the central axis of the throat 32 is 22°-26°. Such an angle design allows ammonia and flue gas to be fully mixed in the throat without causing excessive flow resistance. In a specific embodiment, the angle α is 19° and the angle β is 24°. Under this angle combination, a good mixing effect can be ensured without causing excessive flow resistance.

[0031] In this embodiment, the partition 10, the upper cone section 21, the straight section 23 and the lower cone section 22 are all made of high temperature resistant and corrosion resistant alloy materials. In some embodiments, stainless steel, nickel-based alloys, high temperature alloys and other materials can be used.

[0032] In some embodiments, Figure 2 , Figure 6 As shown, the ammonia injection port 40 is an oblong hole extending longitudinally along the flue cross section, and the aperture of the oblong hole increases from the air inlet end to the injection end toward the position of the throat 32. Specifically, on the straight section 23, the shape of the ammonia injection port 40 is similar to an elongated ellipse, and its aperture is smaller near the ammonia pipeline connection (i.e., the air inlet end), and the aperture gradually increases as it gradually approaches the throat 32 along the injection direction. Such a design increases the coverage of ammonia on the flue cross section, that is, the traditional point or column injection often concentrates the ammonia injection into a small area, and this oblong hole injection method allows the ammonia to be sprayed in the form of a thin layer, greatly increasing the contact area between the ammonia and the flue gas, thereby more efficiently utilizing the accelerated mixing effect of the Venturi channel 30, thereby greatly avoiding the uneven phenomenon of ammonia in the mixing process, and greatly reducing the possibility of ammonia escape.

[0033] In some embodiments, the cross-section of the upper cone section 21 and the lower cone section 22 parallel to the flue gas flow direction is an isosceles triangle. With this structural design, the two adjacent partitions 10 can be tightly connected to the two opposite sides of the upper cone section 21 and the lower cone section 22, respectively, so as to more effectively enclose the convergence section 31 and the divergence section 33, ensuring the integrity and airtightness of the Venturi channel 30 structure. At the same time, the isosceles triangle cross-section structure is relatively simple, easy to process and manufacture, and 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.

[0034] In some embodiments, 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 .

[0035] When implementing it, Figure 2 As shown, the plate surface of the partition 10 is provided with positioning countersunk holes 12 which are matched with the upper cone section 21, the straight section 23 and the lower cone section 22 of the injection unit 20, and the straight section 23 is connected to the partition 10 by bolts.

[0036] 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 weak points 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 in the flue cross section more uniform, avoiding the concentration or lack of ammonia in certain areas, and further improving the mixing uniformity.

[0037] In some embodiments, 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 having the ammonia main pipe 11 is provided for every other partition 10 not having the ammonia main pipe 11.

[0038] During specific operation, ammonia flows into the ammonia main pipe 11 through an external ammonia source, and then is transported to the ammonia injection ports 40 on each straight section 23 through the air intake branch pipe 41 for injection and mixing. Since the ammonia injection ports 40 correspond to the straight sections 23 one by one, and the straight sections 23 correspond to the injection units 20 one by one, in this way, independent ammonia supply is achieved for each injection unit 20. In addition, since a design of providing a partition 10 with an ammonia main pipe 11 for every partition 10 without an ammonia main pipe 11 is adopted, the injection units 20 on both sides of the partition 10 with the ammonia main pipe 11 can be supplied with gas through the same ammonia main pipe 11. This structural layout can not only ensure that ammonia is evenly injected into the entire flue cross section, but also greatly simplify the overall structure, reduce the number of unnecessary pipelines, thereby significantly reducing the difficulty of installation and maintenance, and also reducing the manufacturing cost.

[0039] In some embodiments, Figure 3As shown, the upper cone section 21 and the lower cone section 22 are both provided with tenons on the connection surfaces with the straight section 23, and the straight section 23 is provided with a mortise 24 adapted to the tenon; the cone surface of the upper cone section 21 is provided with a screw hole 25 penetrating to the lower cone section 22, and the upper cone section 21, the straight section 23 and the lower cone section 22 are fixedly connected as a whole through the screw hole and bolt locking. In the actual assembly process, the tenons on the upper cone section 21 and the lower cone section 22 are first aligned with the mortise 24 on the straight section 23, and then the upper cone section 21, the straight section 23 and the lower cone section 22 are assembled together. At this time, the cooperation of the tenon and the mortise 24 enables the three components to be positioned quickly and accurately. 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, so that the upper conical section 21, the straight section 23 and the lower conical section 22 are firmly connected into a whole. This connection method is not only convenient for assembly, but also has high connection strength and good reliability.

[0040] In some embodiments, the ammonia injection grid further includes a fixed frame (not shown), and each of the partitions 10 is fixedly connected by the fixed frame. Specifically, the fixed frame is usually composed of a plurality of interconnected beams or plates, which can be made of steel, stainless steel or other materials with sufficient strength and rigidity, and the partition 10 can be firmly fixed to the fixed frame by bolts, welding or other connection methods, thereby forming an integral structure. This structural design makes the ammonia injection grid no longer a plurality of independent partitions, but an integral structure with high strength, which can effectively resist the impact and vibration caused by the flow of flue gas. In addition, the fixed frame can not only provide overall support, but also serve 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.

[0041] The ammonia spray grid with injection and mixing functions provided in this embodiment realizes the integration of ammonia spray and mixing by constructing a Venturi channel between adjacent injection units and setting a straight section and an ammonia spray 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 static mixers, further simplifies the system structure, and reduces operating costs. In addition, the uniform distribution of multiple injection units and the design of the ammonia spray 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.

[0042] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0043] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is 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 can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ammonia spray grid with spraying 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 cross section of the flue, and a plurality of injection units arranged at equal intervals along the cross section of the flue are arranged 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 arranged on the straight section; wherein the cross-sectional area of ​​the convergent section gradually decreases along the flow direction of the flue gas, and the cross-sectional area of ​​the divergent section gradually increases along the flow direction of the flue gas; 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°.

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 flue cross section, and the aperture of the oblong hole increases gradually from the air inlet end to the injection end toward 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 arranged in a staggered manner, 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 or 4, characterized in that: An ammonia main pipe connected to an external ammonia source is provided in some of the partitions, and an intake branch pipe connected to an ammonia injection port is provided in each of the straight sections, 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.

6. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The connecting surfaces of the upper cone section and the lower cone section with the straight section are all provided with tenons, and the straight section is provided with mortises matched with the tenons; the cone surface of the upper cone section is provided with screw holes penetrating to the lower 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.

7. The ammonia injection grid with injection and mixing functions according to claim 1 or 6, characterized in that: Positioning countersunk holes matching the upper cone section, the straight section and the lower cone 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.

8. 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.

9. The ammonia injection grid with injection and mixing functions according to claim 1, characterized in that: The ammonia injection grid also includes a fixed frame, and each of the partitions is fixedly connected via the fixed frame.

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