The application discloses an ammonia injection nozzle for an SCR ammonia injection grid and an SCR ammonia injection grid.

Abstract

The application discloses a kind of anti-abrasion and anti-blocking nozzle of SCR ammonia injection grid and SCR ammonia injection grid.The nozzle is arranged on the branch pipe of SCR ammonia injection grid, including nozzle body, leeward shroud, main nozzle hole, annular gas protection hole, blowback micro hole, blockage detection pressure tapping hole, differential pressure detection unit, blowback gas source and ammonia-air mixture inlet.Leeward shroud is located on the dust side of nozzle, and forms anti-abrasion shielding area in the upstream of main nozzle hole;Annular gas protection hole forms gas film around main nozzle hole;Blockage detection pressure tapping hole detects nozzle differential pressure, when differential pressure meets the trigger condition of blockage, blowback gas source blows back and clears blockage through blowback micro hole to main nozzle hole and annular gas protection hole.The application also discloses a kind of SCR ammonia injection grid comprising the above-mentioned nozzle.The application can consider the uniformity of ammonia injection, anti-abrasion and on-line blockage removal ability under the condition of high-ash coal, high fly ash hardness and easy blockage of ammonia injection grid.

Description

Technical Field

[0001] This application belongs to the field of flue gas denitrification technology for coal-fired power units, and specifically relates to an anti-wear and anti-clogging nozzle for an SCR ammonia injection grid and an SCR ammonia injection grid. Background Technology

[0002] In coal-fired power plant SCR denitrification systems, the ammonia injection grid is typically positioned in the high-dust section between the economizer outlet and the SCR reactor inlet, with the nozzles directly exposed to flue gas carrying a large amount of fly ash particles. When the boiler burns high-ash coal or blends in low-quality coal, the ash concentration in the flue gas increases significantly, and the proportion of hard mineral particles (such as quartz and mullite) increases. The windward side of the nozzle and the edge of the nozzle orifice are continuously eroded by high-speed ash particles. After long-term operation, problems such as increased nozzle wear, jet direction deflection, and changes in flow characteristics will occur, directly leading to a decrease in ammonia injection uniformity and an increase in local ammonia escape.

[0003] On the other hand, as deep peak shaving and low-load operation of coal-fired units become increasingly common, the flue gas temperature at the SCR inlet decreases, and the flue gas velocity drops. This makes it easier for ammonium salt deposits, unburned carbon ash, and adhesive ash to accumulate in the nozzle cavity and at the nozzle orifice edges. After nozzle blockage, the ammonia injection rate of different nozzles within the same zone shifts, leading to an imbalance in the ammonia-nitrogen molar ratio in some areas, resulting in localized NOx emissions exceeding standards or ammonia escape becoming more severe. Current operation and maintenance methods largely rely on periodic manual cleaning, making it difficult to detect early blockages in a timely manner, and shutdowns for treatment affect unit availability.

[0004] To address the aforementioned issues, some technologies have attempted to add simple protective covers to the ammonia injection nozzles to reduce wear on the windward side, or to indirectly determine blockages through changes in total flow rate. However, these covers only provide shielding and cannot protect the nozzle edges from localized high-speed dust particle erosion. Furthermore, single-channel flow rate monitoring is insufficient to pinpoint specific nozzles or zones, making early-stage blockages difficult to detect. In addition, conventional purging methods often employ continuous high-flow-rate purging, which lacks targeted blockage removal and significantly disrupts the uniformity of ammonia injection. Summary of the Invention

[0005] The purpose of this application is to provide an anti-wear and anti-clogging nozzle for an SCR ammonia injection grid and an SCR ammonia injection grid itself. This addresses the problems mentioned in the background art regarding the ease of wear and clogging of existing nozzles under high-ash coal conditions, as well as the lack of online detection and directional unclogging capabilities.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, a wear-resistant and anti-clogging nozzle for an SCR ammonia injection grid is provided, which is installed on a branch pipe of the SCR ammonia injection grid. The nozzle includes a nozzle body, a windproof shield, a main injection orifice, an annular protective air hole, a backflush micro-orifice, a clogging detection pressure tap, a differential pressure detection unit, a backflush gas source, and an ammonia-air mixture inlet. The windproof shield is located on the dust-facing side of the nozzle body, forming a wear-resistant shielding area upstream of the main injection orifice. The main injection orifice is connected to the ammonia-air mixture inlet and is used to inject ammonia-air mixture into the flue gas. The annular protective air hole surrounds the main injection orifice. The system is configured to form a protective gas film at the edge of the main nozzle outlet; the backflush micro-orifice is connected to the backflush air source, and the outlet of the backflush micro-orifice faces the outlet area of ​​the main nozzle and the annular protective air hole; the blockage detection pressure tap is connected to the differential pressure detection unit, and is used to detect the pressure difference inside and outside the nozzle or the pressure difference before and after the nozzle; when the pressure difference detected by the differential pressure detection unit meets the blockage triggering condition, the backflush air source outputs backflush clearing airflow to the outlet area of ​​the main nozzle and the annular protective air hole through the backflush micro-orifice.

[0007] In one possible implementation, the leeward shield is an arc-shaped structure, a folded plate structure, or a streamlined shield structure. The dust-facing surface of the leeward shield is provided with a ceramic wear-resistant layer, a welded wear-resistant layer, a sprayed wear-resistant layer, or a replaceable wear-resistant lining. Furthermore, the leading edge of the leeward shield extends forward relative to the outlet of the main nozzle.

[0008] In one possible implementation, the angle between the axis of the main nozzle and the mainstream direction of the flue gas is 30° to 90°, and a replaceable wear-resistant nozzle ring is provided at the outlet of the main nozzle. The replaceable wear-resistant nozzle ring is detachably connected to the nozzle body by means of threaded connection, snap ring connection or pressure cap connection.

[0009] In one possible implementation, the annular air shield includes 4 to 16 small holes arranged circumferentially along the main nozzle, the total flow area of ​​the annular air shield is 5% to 30% of the flow area of ​​the main nozzle, and the ejection direction of the annular air shield is deflected outward by 5° to 45° relative to the axis of the main nozzle.

[0010] In one possible implementation, the backflush micro-orifice includes 2 to 8 micro-orifices communicating with the backflush chamber inside the nozzle body, the pulse width of the backflush clearing airflow is 0.1s to 1s, and the backflush interval is adaptively adjusted according to the pressure difference deviation value, the ammonia injection flow rate deviation value, or the deviation value of adjacent nozzles.

[0011] In one possible implementation, the blockage detection pressure tap includes a pressure tap located on the inlet side of the nozzle body and a pressure tap located on the outlet side of the nozzle body. The differential pressure detection unit determines the degree of blockage based on the differential pressure change between the inlet-side pressure tap and the outlet-side pressure tap, the rate of differential pressure change, or the differential pressure deviation between different nozzles in the same zone.

[0012] In one possible implementation, a swirling guide core is also provided in the nozzle body. The swirling guide core is located in the flow channel between the ammonia-air mixture inlet and the main nozzle, and is used to generate swirling flow in the ammonia-air mixture to improve the diffusion angle of the ammonia jet and reduce the fall of ash retained during backflushing.

[0013] In one possible implementation, the nozzle body is connected to the SCR ammonia injection grid branch pipe via a flange connection, a threaded short section connection, or a quick-connect coupling, and is provided with a positioning structure for defining the orientation of the leeward shield.

[0014] In one possible implementation, the differential pressure detection unit establishes a differential pressure reference value for each nozzle in the unit load stable range. When the current differential pressure exceeds a preset proportional threshold of the differential pressure reference value, is lower than a preset proportional threshold of the differential pressure reference value, or the differential pressure deviation with other nozzles in the same zone exceeds a set deviation threshold, the backflush air source is triggered to perform single-nozzle backflush or zone rotation backflush.

[0015] Secondly, this application also provides an SCR ammonia injection grid, including a plurality of anti-wear and anti-clogging nozzles as described in any of the preceding claims. The plurality of nozzles are arranged in sections according to the flue cross section. Each section determines the backflushing sequence and backflushing duration based on the nozzle differential pressure detection value, the ammonia injection flow rate deviation value, and the SCR outlet NOx concentration distribution deviation value.

[0016] Compared with the prior art, this application has the following beneficial effects: This application provides an SCR ammonia injection grid anti-wear and anti-clogging nozzle, which integrates a backwind shield, main nozzle, annular air protection hole, backflush micro-hole, and clogging detection pressure tap into one unit. Under conditions of high ash, high hard mineral particles, and long-term low load and easy ash accumulation, it can still maintain a relatively stable ammonia injection flow area and jet direction. It has multiple functions such as anti-wear shielding, nozzle edge air film protection, local pressure difference detection, and online directional backflush clogging removal, effectively solving the common problems of existing nozzles having single protective functions and difficulty in timely locating and cleaning clogging.

[0017] In one possible implementation, by setting the leeward shield as an arc-shaped, folded, or streamlined shield structure, and having its leading edge extend forward relative to the main nozzle outlet, it can guide and deflect the dust-laden airflow upstream of the nozzle in advance, significantly reducing the probability of high-hardness fly ash particles directly impacting the nozzle edge. Combined with the ceramic wear-resistant layer, welded wear-resistant layer, sprayed wear-resistant layer, or replaceable wear-resistant lining on the ash-facing surface, the service life of the shield itself is further extended, making it particularly suitable for working conditions where high-ash, high-quartz-content coal is burned.

[0018] In one possible implementation, by setting the angle between the main nozzle axis and the mainstream flue gas direction to 30° to 90°, the jet direction can be flexibly adjusted according to the flue section position and injection coverage requirements to ensure uniform ammonia-nitrogen mixing. The replaceable wear-resistant nozzle ring at the main nozzle outlet is made of wear-resistant materials such as ceramic, silicon carbide, or weld overlay alloy, and is detachably connected by threads, snap rings, or pressure caps. When the nozzle ring wears out, there is no need to replace the entire nozzle, which significantly reduces maintenance costs and downtime.

[0019] In one possible implementation, by arranging 4 to 16 annular protective air holes at circumferential intervals around the main nozzle, and making their total flow area 5% to 30% of the main nozzle and deflecting the ejection direction outward by 5° to 45°, a small amount of protective gas can be used to form an outwardly expanding air curtain-like protective air film at the nozzle edge, effectively preventing fly ash particles from directly adhering to and scouring the sharp edge of the nozzle; at the same time, this air film forms a continuous positive pressure protection for the nozzle area, further reducing the risk of adhesive ash depositing at the nozzle edge, and achieving a dual anti-wear effect in conjunction with the leeward shield.

[0020] In one possible implementation, by setting 2 to 8 backflush micro-holes and connecting them to the backflush chamber inside the nozzle, and using a pulsed backflush airflow of 0.1s to 1s to clear blockages, it is possible to precisely remove deposits in the main nozzle and annular protective air outlet areas with a small amount of air consumption. The backflush interval is adaptively adjusted according to the pressure difference deviation, ammonia injection flow rate deviation, or adjacent nozzle deviation, which ensures the timeliness of clearing blockages and avoids the disturbance of ammonia injection uniformity caused by frequent backflush.

[0021] In one possible implementation, by setting pressure taps on the inlet and outlet sides of the nozzle body, the differential pressure detection unit can simultaneously acquire multi-dimensional information such as differential pressure change, differential pressure change rate, and differential pressure deviation between different nozzles in the same zone. Compared with the single main pipe flow monitoring method, it can detect the local blockage trend of a single nozzle earlier and accurately locate the blocked nozzle, effectively avoiding ammonia injection deviation and increased ammonia escape caused by misjudgment or omission of blockage.

[0022] In one possible implementation, a swirling guide core is installed in the flow channel between the ammonia-air mixture inlet and the main nozzle within the nozzle body. This causes the ammonia-air mixture to swirl moderately before injection. On the one hand, this increases the diffusion angle of the ammonia jet in the flue gas, improving the uniformity of ammonia-nitrogen mixing. On the other hand, the swirling effect increases the airflow velocity near the inner wall of the nozzle, reducing the retention and deposition of ash on the inner wall of the nozzle. At the same time, the swirling guide core can also guide the flow during backflushing, reducing the probability that the ash stripped off during backflushing will fall back into the nozzle.

[0023] In one possible implementation, by using flange connections, threaded short section connections, or quick-connect couplings and setting up a positioning structure, the installation, disassembly, and maintenance of the nozzle body are facilitated, and the back wind shield can be accurately oriented to the direction of flue gas flow after installation. This avoids the reduction in anti-wear effect caused by the orientation deviation of the shield, and is especially suitable for the rapid installation and positioning of multiple nozzles in flues with limited space.

[0024] In one possible implementation, by establishing a pressure difference benchmark value for each nozzle within the stable load range of the unit, and employing a multi-condition joint judgment strategy that considers factors such as the current pressure difference exceeding or falling below a preset proportional threshold of the benchmark value, and the pressure difference deviation between nozzles in the same zone exceeding a set deviation threshold, the interference of unit load fluctuations and ammonia injection total volume adjustments on pressure difference detection is effectively eliminated, thereby improving the accuracy and reliability of blockage detection. When backflushing is triggered, single-nozzle backflushing or zone-based alternating backflushing is supported, which saves backflushing gas consumption and minimizes instantaneous disturbances to ammonia injection uniformity.

[0025] This application also provides an SCR ammonia injection grid, which arranges multiple nozzles according to the flue section. Each section determines the backflushing sequence and backflushing duration based on the nozzle differential pressure detection value, ammonia injection flow deviation value, and SCR outlet NOx concentration distribution deviation value. This achieves hierarchical intelligent backflushing management from individual nozzles to sections, ensuring denitrification efficiency while minimizing the disturbance of backflushing to system operation. It is suitable for large coal-fired units with high ash coal, wide load operation, and long-term exposure of the ammonia injection grid to high dust flue gas. Attached Figure Description

[0026] Figure 1 This application provides a schematic diagram of the installation structure of an anti-wear and anti-clogging nozzle for an SCR ammonia injection grid on a branch pipe of the SCR ammonia injection grid. Figure 2 This application provides a partial cross-sectional view of an SCR ammonia injection grid anti-wear and anti-clogging nozzle, as well as schematic diagrams of normal ammonia injection protection state and backflushing and clogging removal state.

[0027] The attached diagram is labeled as follows: 10, SCR ammonia injection grid branch pipe; 101, nozzle body; 102, windproof shield; 103, main nozzle; 104, annular protective air hole; 105, backflush micro-hole; 106, blockage detection pressure tap; 107, differential pressure detection unit; 108, backflush air source; 109, ammonia-air mixture inlet; 110, replaceable wear-resistant nozzle ring; 111, swirl guide core; 112, protective air film; 113, backflush clearing airflow. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly defined. The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] like Figure 1 and Figure 2 As shown, this application discloses an anti-wear and anti-clogging nozzle for an SCR ammonia injection grid, which is installed on the branch pipe 10 of the SCR ammonia injection grid. Multiple nozzle bodies 101 are installed on the branch pipe 10 of the SCR ammonia injection grid and arranged in sections according to the flue cross-section. The nozzle body 101 receives ammonia-air mixture from the upstream ammonia supply pipeline through the ammonia-air mixture inlet 109 and sprays it into the flue gas through the main nozzle 103.

[0035] In this embodiment, the nozzle body 101 is a tubular or shell-shaped structure, with an internal channel for the flow of the ammonia-air mixture. The nozzle body 101 can be made of stainless steel or alloy steel to withstand corrosion and erosion conditions in high-ash flue gas environments. The ammonia-air mixture inlet 109 is located at the root or side of the nozzle body 101 and is connected to the air supply port of the SCR ammonia injection grid branch pipe 10.

[0036] In one possible embodiment, the nozzle body 101 is connected to the SCR ammonia injection grid branch pipe 10 via a flange connection, a threaded short section connection, or a quick-connect coupling, and is provided with a positioning structure for defining the orientation of the leeward shield 102. This positioning structure can be a positioning pin and positioning hole mating structure on the flange surface, or a threaded short section mating structure with a non-circular cross-section, to ensure that the leeward shield 102 accurately faces the flue gas flow direction after installation.

[0037] like Figure 1As shown, the fly ash inflow (i.e., the mainstream direction of the dust-laden flue gas, indicated by arrows in the figure) first acts on the dust-facing side of the nozzle. The leeward shield 102 is located on the dust-facing side of the nozzle body 101, forming an anti-wear shielding zone upstream of the main nozzle 103. The function of the leeward shield 102 is to shield the area around the main nozzle 103, reducing the direct impact of dust particles on the nozzle edge, thereby reducing the wear rate at the nozzle.

[0038] In this embodiment, the leeward shield 102 has an arc-shaped structure, a folded plate structure, or a streamlined shield structure. The dust-facing surface of the leeward shield 102 (i.e., the surface facing the flue gas flow) is provided with a ceramic wear-resistant layer, a welded wear-resistant layer, a sprayed wear-resistant layer, or a replaceable wear-resistant lining to enhance its erosion resistance. Furthermore, the leading edge of the leeward shield 102 extends forward relative to the outlet of the main nozzle 103, that is, the leeward shield 102 extends beyond the outlet plane of the main nozzle 103 on the upstream side in the flue gas flow direction, thereby forming an effective shielding shadow area in front of the nozzle.

[0039] In this embodiment, the angle between the axis of the main nozzle 103 and the mainstream direction of the flue gas is 30° to 90°. Preferably, this angle can be adjusted according to the flue section position and injection coverage requirements, so that the ammonia-air mixture is injected into the flue gas at an appropriate angle to ensure uniform ammonia-nitrogen mixing. A replaceable wear-resistant nozzle ring 110 is provided at the outlet of the main nozzle 103. The replaceable wear-resistant nozzle ring 110 is made of ceramic, silicon carbide, weld overlay alloy, or other wear-resistant materials, and is detachably connected to the nozzle body 101 by threaded connection, snap ring connection, or pressure cap connection. When the wear-resistant nozzle ring wears out, it can be replaced separately without replacing the entire nozzle, reducing maintenance costs.

[0040] like Figure 2 As shown, annular protective air holes 104 are arranged around the main nozzle 103 to form a protective gas film 112 at the outlet edge of the main nozzle 103. In this embodiment, the annular protective air holes 104 include 4 to 16 small holes spaced apart circumferentially along the main nozzle 103. The total flow area of ​​the annular protective air holes 104 is 5% to 30% of the flow area of ​​the main nozzle 103, to ensure that an appropriate amount of ammonia-air mixture is ejected from the annular protective air holes 104 to form a protective gas film, while not excessively diverting the amount of ammonia injected from the main nozzle. The ejection direction of the annular protective air holes 104 is deflected outward by 5° to 45° relative to the axis of the main nozzle 103, so that the protective gas film 112 forms an outwardly expanding air curtain effect, pushing fly ash particles away from the nozzle edge.

[0041] Under normal ammonia injection protective gas conditions, the ammonia-air mixture is ejected from the main nozzle 103 to form the main jet, and from the annular protective gas hole 104 to form a protective gas film 112. The protective gas film 112 is close to the nozzle edge, making it difficult for fly ash particles to directly adhere to the sharp edge of the nozzle, thus reducing the erosion and adhesion deposition of fly ash particles on the nozzle edge.

[0042] In this embodiment, a swirling guide core 111 is also provided inside the nozzle body 101. The swirling guide core 111 is located within the flow channel between the ammonia-air mixture inlet 109 and the main nozzle 103, and is used to generate a moderate swirling flow in the ammonia-air mixture to improve the diffusion angle of the ammonia jet and reduce the fall of retained ash during backflushing. The swirling guide core 111 can be a helical blade structure fixed within the flow channel, or a columnar structure with helical grooves. Through the swirling effect generated by the swirling guide core 111, the ammonia-air mixture acquires a tangential velocity component before entering the main nozzle 103, which facilitates faster diffusion in the flue gas after injection, while also reducing localized ash retention on the inner wall of the nozzle.

[0043] like Figure 2 As shown, the backflush micro-orifice 105 is connected to the backflush air source 108, and the outlet of the backflush micro-orifice 105 faces the outlet area of ​​the main nozzle 103 and the annular protective air hole 104. In this embodiment, the backflush micro-orifice 105 includes 2 to 8 micro-orifices connected to the backflush chamber inside the nozzle body 101. The backflush air source 108 is an independent compressed air source or nitrogen source, connected to the backflush micro-orifice 105 of each nozzle through an independent branch. The pulse width of the backflush clearing airflow 113 is 0.1s to 1s, and the backflush interval is adaptively adjusted according to the pressure difference deviation value, ammonia injection flow rate deviation value, or adjacent nozzle deviation value. By adopting pulsed short-time backflush, a targeted clearing effect can be obtained under conditions of small air consumption, while reducing continuous disturbance to the main ammonia injection airflow.

[0044] The blockage detection pressure tap 106 is connected to the differential pressure detection unit 107 and is used to detect the pressure difference inside and outside the nozzle or the pressure difference before and after the nozzle orifice. In this embodiment, the blockage detection pressure tap 106 includes a pressure tap on the inlet side of the nozzle body 101 and a pressure tap on the outlet side of the nozzle body 101. The inlet-side pressure tap can be located near the ammonia-air mixture inlet 109 or inside the nozzle body 101 near the inlet, and the outlet-side pressure tap can be located near the outlet of the main nozzle orifice 103 or outside the nozzle body 101 near the outlet. The differential pressure detection unit 107 determines the degree of blockage based on the amount of pressure difference change between the inlet-side pressure tap and the outlet-side pressure tap, the rate of pressure difference change, or the pressure difference deviation between different nozzles in the same zone.

[0045] In this embodiment, the differential pressure detection unit 107 establishes a differential pressure reference value for each nozzle within the stable load range of the unit. When the current differential pressure exceeds a preset proportional threshold of the differential pressure reference value (e.g., differential pressure increase exceeding 150% of the reference value), falls below a preset proportional threshold of the differential pressure reference value (e.g., differential pressure decrease falling below 50% of the reference value), or the differential pressure deviation from other nozzles in the same zone exceeds a set deviation threshold, the backflushing air source 108 is triggered to perform single-nozzle backflushing or zone-by-zone alternating backflushing. Employing dual-condition or triple-condition judgment logic can reduce misjudgments caused by relying solely on the total ammonia injection flow rate and avoid misinterpreting normal flow rate changes as blockages.

[0046] When the differential pressure detection unit 107 determines that the nozzle differential pressure is abnormally high (indicating a tendency for blockage in the nozzle orifice or air vent), it controls the backflushing air source 108 to be turned on briefly. The backflushing clearing airflow 113 enters the vicinity of the main nozzle 103 and the annular air vent 104 outlet through the backflushing micro-hole 105, performing reverse impact stripping on the blockage. Backflushing can be performed by sequentially backflushing individual nozzles or by rotating backflushing according to the flue section sequence to reduce instantaneous disturbance to the ammonia-nitrogen molar ratio distribution at the SCR inlet.

[0047] In one possible implementation, when the differential pressure detection unit 107 determines that the differential pressure of a certain nozzle is continuously increasing while the differential pressure of other nozzles in the same zone is normal, it determines that the nozzle is partially blocked, and the control system only performs a backflushing operation on that nozzle. After the backflushing is completed, the differential pressure detection unit 107 continues to record the differential pressure recovery range. If the differential pressure still does not recover to near the reference value after two consecutive backflushings, a maintenance prompt is output to notify the maintenance personnel to manually inspect or replace the nozzle.

[0048] In one possible implementation, multiple nozzles are arranged in zones according to the flue cross-section. The backflushing sequence and duration for each zone are determined based on the nozzle differential pressure detection value, ammonia injection flow rate deviation value, and SCR outlet NOx concentration distribution deviation value. For example, during periods of stable load, the system can prioritize backflushing the zone with the largest differential pressure deviation, with each backflushing lasting several seconds and the backflushing interval ranging from several minutes to tens of minutes. The specific parameters can be adaptively adjusted according to the actual operating conditions.

[0049] This application also provides an SCR ammonia injection grid, comprising multiple anti-wear and anti-clogging nozzles as described in any of the above embodiments. The multiple nozzles are arranged in sections according to the flue cross-section. The backflushing sequence and duration for each section are determined based on the nozzle differential pressure detection value, the ammonia injection flow rate deviation value, and the SCR outlet NOx concentration distribution deviation value. This SCR ammonia injection grid can maintain a relatively stable ammonia injection flow area and jet direction under conditions of high ash, high hard mineral particles, and long-term low load with easy ash accumulation. It also possesses online clogging identification and directional backflushing capabilities, significantly improving the operational reliability of the denitrification system.

[0050] The backflush trigger threshold is preferably determined by both the percentage and absolute differential pressure of the reference pressure difference. When the unit load changes rapidly or the total ammonia injection is significantly adjusted, the system delays the backflush judgment or uses the relative deviation of the nozzles in the same group to avoid misjudging normal flow changes as blockages. After the backflush is completed, the differential pressure detection unit 107 continues to record the differential pressure recovery range. If the differential pressure still does not recover after two consecutive backflushes, a maintenance prompt is output.

[0051] In summary, this application integrates the leeward shield 102, main nozzle 103, annular air vent 104, backflush micro-hole 105, and blockage detection pressure tap 106 into a single unit. This allows the nozzle to maintain a relatively stable ammonia injection flow area and jet direction even under conditions of high ash, high-hardness mineral particles, and long-term low-load ash accumulation. It also possesses online blockage identification and directional backflush capabilities. This nozzle is suitable for high-ash coal, wide-load operation, and situations where the ammonia injection grid is exposed to dusty flue gas for extended periods. It can effectively improve the operational stability of the ammonia injection grid and reduce the impact of nozzle wear and blockage on denitrification performance.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A wear-resistant and anti-clogging nozzle for an SCR ammonia injection grid, disposed on a branch pipe (10) of the SCR ammonia injection grid, characterized in that, It includes a nozzle body (101), a windproof shield (102), a main nozzle (103), an annular air protection hole (104), a backflush micro-hole (105), a blockage detection pressure tap (106), a differential pressure detection unit (107), a backflush air source (108), and an ammonia-air mixture inlet (109). The windproof shield (102) is disposed on the dust-facing side of the nozzle body (101) and forms an anti-wear shielding area upstream of the main nozzle (103); The main nozzle (103) is connected to the ammonia-air mixture inlet (109) and is used to inject ammonia-air mixture into the flue gas; The annular protective air hole (104) is arranged around the main nozzle (103) to form a protective air film (112) at the outlet edge of the main nozzle (103). The backflush micro-hole (105) is connected to the backflush air source (108), and the outlet of the backflush micro-hole (105) faces the outlet area of ​​the main spray hole (103) and the annular protective air hole (104). The blockage detection pressure tap (106) is connected to the differential pressure detection unit (107) and is used to detect the pressure difference inside and outside the nozzle or the pressure difference before and after the nozzle. When the differential pressure detected by the differential pressure detection unit (107) meets the blockage triggering condition, the backflush gas source (108) outputs backflush clearing airflow (113) to the outlet area of ​​the main nozzle (103) and the annular protective air hole (104) through the backflush microhole (105).

2. The SCR ammonia injection grid anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The leeward shield (102) is an arc-shaped structure, a folded plate structure or a streamlined shield structure. The dust-facing surface of the leeward shield (102) is provided with a ceramic wear-resistant layer, a welded wear-resistant layer, a sprayed wear-resistant layer or a replaceable wear-resistant lining. The leading edge of the leeward shield (102) extends forward relative to the outlet of the main nozzle (103).

3. The SCR ammonia injection grille anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The angle between the axis of the main nozzle (103) and the mainstream direction of the flue gas is 30° to 90°. A replaceable wear-resistant nozzle ring (110) is provided at the outlet of the main nozzle (103). The replaceable wear-resistant nozzle ring (110) is detachably connected to the nozzle body (101) by means of threaded connection, snap ring connection or pressure cap connection.

4. The SCR ammonia injection grid anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The annular air-protecting hole (104) includes 4 to 16 small holes arranged circumferentially along the main nozzle (103). The total flow area of ​​the annular air-protecting hole (104) is 5% to 30% of the flow area of ​​the main nozzle (103). The ejection direction of the annular air-protecting hole (104) is deflected outward by 5° to 45° relative to the axis of the main nozzle (103).

5. The SCR ammonia injection grille anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The backflush micro-hole (105) includes 2 to 8 micro-holes that communicate with the backflush chamber inside the nozzle body (101). The pulse width of the backflush clearing airflow (113) is 0.1s to 1s. The backflush interval is adaptively adjusted according to the pressure difference deviation value, the ammonia injection flow rate deviation value, or the adjacent nozzle deviation value.

6. The SCR ammonia injection grid anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The blockage detection pressure tap (106) includes a pressure tap on the inlet side of the nozzle body (101) and a pressure tap on the outlet side of the nozzle body (101). The differential pressure detection unit (107) determines the degree of blockage based on the differential pressure change between the inlet side pressure tap and the outlet side pressure tap, the differential pressure change rate, or the differential pressure deviation between different nozzles in the same zone.

7. The SCR ammonia injection grid anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The nozzle body (101) is also provided with a swirling guide core (111). The swirling guide core (111) is located in the flow channel between the ammonia-air mixture inlet (109) and the main nozzle (103). It is used to generate swirling flow in the ammonia-air mixture to improve the diffusion angle of the ammonia jet and reduce the fall of ash during backflushing.

8. The SCR ammonia injection grille anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The nozzle body (101) is connected to the SCR ammonia injection grid branch pipe (10) by a flange connection, a threaded short section connection or a quick-connect coupling, and is provided with a positioning structure for limiting the orientation of the leeward shield (102).

9. The SCR ammonia injection grid anti-wear and anti-clogging nozzle according to claim 1, characterized in that, The differential pressure detection unit (107) establishes a differential pressure reference value for each nozzle in the unit load stable range. When the current differential pressure exceeds the preset proportional threshold of the differential pressure reference value, is lower than the preset proportional threshold of the differential pressure reference value, or the differential pressure deviation with other nozzles in the same zone exceeds the set deviation threshold, the backflush air source (108) is triggered to perform single nozzle backflush or zone rotation backflush.

10. An SCR ammonia injection grid, characterized in that, It includes multiple anti-wear and anti-clogging nozzles for SCR ammonia injection grid as described in any one of claims 1 to 9. The multiple nozzles are arranged in sections according to the flue section. The backflushing sequence and backflushing duration are determined for each section based on the nozzle differential pressure detection value, the ammonia injection flow rate deviation value, and the SCR outlet NOx concentration distribution deviation value.

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