Flue gas denitration ammonia injection mixing system, static mixing assembly thereof and ammonia injection control method

Abstract

The application discloses a static mixing assembly arranged in a flue, comprising: a plurality of mixing units uniformly distributed in the flue, each mixing unit comprising: a reduced-diameter pipe extending along the axial direction of the flue, the wide end of the reduced-diameter pipe facing downward; a spoiler arranged above the reduced-diameter pipe; and a float accommodated in the reduced-diameter pipe, the float moving up and down along the axis of the reduced-diameter pipe, thereby changing the flow area between the edge of the float and the reduced-diameter pipe. The application also discloses a flue gas denitration ammonia injection mixing system and an ammonia injection control method. The static mixing assembly of the application can automatically adjust the flow area according to the flow fluctuation of the flue gas by the cooperation of the reduced-diameter pipe and the float, thereby significantly improving the uniformity of the flue gas flow rate distribution in the cross section of the flue.

Description

Technical Field

[0001] This invention relates to the field of flue gas denitrification technology, and in particular to a flue gas denitrification ammonia injection mixing system, its static mixing components, and an ammonia injection control method. Background Technology

[0002] For selective catalytic reduction (SCR) denitrification technology, flue gas denitrification efficiency and NH3 slip rate are two core performance indicators. Studies have shown that the uniformity of the mixed gas flow field across the cross-section of the SCR reactor is a key factor in ensuring complete SCR denitrification, improving denitrification efficiency and ammonia utilization, and controlling a low ammonia slip rate. The uniformity of the mixed gas flow field mainly includes uniform gas velocity distribution and the ammonia-to-nitrogen molar ratio (NH3 / NO3). x The paper addresses two aspects: uniformity of distribution. According to relevant industry standards, at 500mm before the catalyst inlet of the first layer in the SCR reactor, the velocity deviation at various points within a 100% flue gas cross-section should be -15% to 15%, and the NH3 / NO3 ratio at various points within a 100% flue gas cross-section should be... x The deviation of the molar ratio should be -10% to 10%.

[0003] Flue gas ducts are generally rectangular or circular, with most coal-fired boilers using rectangular ducts. The flue gas velocity within the same cross-section of the duct is typically uneven, especially near bends and diameter changes, where the velocity distribution can vary significantly, sometimes by as much as double. In an SCR reactor, the catalyst is uniformly distributed. If there is a large deviation in the flue gas velocity passing through the catalyst bed, the residence time of the flue gas through the catalyst bed will be relatively short in areas with higher velocities, resulting in relatively lower denitrification efficiency. The NO content in the flue gas after passing through the denitrification catalyst will be higher. x The content is difficult to meet environmental protection requirements, and the flue gas contains a lot of dust. In areas with higher gas velocities, the catalyst is more worn, and the catalyst's service life is reduced in these areas; in areas with lower gas velocities, the flue gas stays in the catalyst bed for a relatively longer time, and the denitrification efficiency is relatively high, but the catalyst utilization rate is insufficient in these areas.

[0004] The deviation in flue gas velocity within a rectangular flue is difficult to further reduce using conventional methods, hence the widespread application of zoned ammonia injection. However, zoned ammonia injection divides the cross-section of the ammonia injection inlet flue into numerous regions, each corresponding to a flow meter and regulating valve, significantly increasing the initial investment. Adjustment of the ammonia-nitrogen molar ratio uniformity is generally performed during plant startup, based on on-site measurements of NO levels at the SCR reactor inlet or outlet flue. x The concentration distribution was adjusted one by one using the manual ammonia injection control valve. xIn areas with high concentrations, the corresponding manual ammonia injection valve is opened more, and vice versa. This repeated adjustment ensures the uniformity of the ammonia-nitrogen molar ratio, aiming to make the ratio consistent across different areas. This results in a lengthy adjustment period for the uniformity of the ammonia-nitrogen molar ratio each time the system is started. Once adjusted, the opening of the manual ammonia injection valve is no longer adjusted. Additionally, the existing SCR inlet and outlet NO... x Concentration detection typically uses single-point measurement, with the monitoring point usually set at the center of the flue. However, NO concentrations across the same cross-section of the flue can vary. x The concentration differences are quite large, and the representativeness of single-point detection is poor, making it difficult to accurately reflect NO levels. x The average concentration is a concern. Even within the same area, flue gas velocity can vary, and the velocity measured at a flue gas measuring point may not accurately reflect the true velocity in that area. Therefore, the ammonia injection rate will still deviate from the actual velocity. The flue gas flows from the ammonia injection inlet duct through bends and diameter change sections before entering the SCR reactor. The flow distance is long and the flow conditions are complex. The NO concentration after the SCR reactor... x The distribution of NO₂ in the flue gas flow field at the cross-section of the ammonia injection inlet duct is not one-to-one with the actual ammonia injection inlet duct. Some valves, even when fully opened, cannot guarantee sufficient ammonia injection, while others, even slightly opened, result in excessive ammonia injection. This often makes it difficult to balance the flow or adapt to multiple loads in actual operation. When the flue gas NO₂… x The emission standard is 100 mg / m³ 3 This problem is not very noticeable at present; however, when flue gas is subject to ultra-low emission standards (NOx)... x ≤50mg / m 3 When exporting NO, in order to ensure x To meet the standards, the NO in the exhaust gas is generally... x Content controlled at 35mg / m 3 The following points highlight this problem.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] One of the objectives of this invention is to provide a flue gas denitrification ammonia injection mixing system, its static mixing components, and an ammonia injection control method, thereby improving the problem of poor flow field uniformity of the mixed gas.

[0007] Another objective of this invention is to provide a flue gas denitrification ammonia injection mixing system, its static mixing components, and an ammonia injection control method, thereby improving denitrification efficiency and ammonia utilization.

[0008] Another objective of this invention is to provide a flue gas denitrification ammonia injection mixing system, its static mixing components, and an ammonia injection control method, thereby extending the service life of flue gas denitrification equipment.

[0009] Another objective of this invention is to provide a flue gas denitrification ammonia injection mixing system, its static mixing components, and an ammonia injection control method, thereby meeting higher environmental protection requirements for flue gas emissions.

[0010] To achieve the above objectives, according to a first aspect of the present invention, a static mixing assembly is provided, disposed in a flue. The static mixing assembly includes: a plurality of mixing units uniformly distributed in the flue, each mixing unit including: a reduced-diameter tube extending axially along the flue, the wide end of the reduced-diameter tube facing downward; a flow-disrupting element disposed above the reduced-diameter tube; and a floating element housed within the reduced-diameter tube, the floating element moving up and down along the axis of the reduced-diameter tube to change the flow area between the edge of the floating element and the reduced-diameter tube.

[0011] Furthermore, in the above technical solution, the narrow end of the reduced-diameter pipe extends upwards with a guide section.

[0012] Furthermore, in the above technical solution, the static mixing component also includes: an elastic element, one end of which is connected to the floating element, and the other end of which is connected to the turbulence element or the reduced diameter tube.

[0013] Furthermore, in the above technical solution, the elastic element is a spring, and a limiting rod is inserted through the middle of the spring, with the lower end of the limiting rod being lower than the upper end face of the reduced diameter tube.

[0014] Furthermore, in the above technical solution, the center of the spoiler is connected to the guide rod, the lower part of the guide rod is provided with a limiting part, and the floating part passes through the guide rod and floats up and down between the limiting parts along the guide rod.

[0015] Furthermore, in the above technical solution, the agitator is mounted above the reduced-diameter pipe by a fixing component; the horizontal projected area of ​​the agitator is larger than the port area of ​​the narrow end of the reduced-diameter pipe.

[0016] Furthermore, in the above technical solution, the upper end face of the reduced diameter tube is circular or polygonal, and the lower end face is square or rectangular; the floating component is a circular plate, a polygonal plate, or a cone; the turbulence-disrupting component is one or more layers of turbulence-disrupting plates.

[0017] Furthermore, in the above technical solution, the baffle plate is provided with sieve holes, and the opening rate of the baffle plate is 2%~20%.

[0018] According to a second aspect of the present invention, the present invention provides a flue gas denitrification ammonia injection mixing system, which includes, in sequence along the flue gas flow direction: a plurality of ammonia nozzles; and one or more static mixing components as described in any of the above technical solutions, wherein the mixing unit of the lowest layer static mixing component is arranged corresponding to the ammonia nozzle.

[0019] Furthermore, in the above technical solution, each mixing unit of the lowest layer static mixing component corresponds to the same number of ammonia nozzles.

[0020] Furthermore, in the above technical solution, each mixing unit corresponds to 1 to 9 ammonia nozzles.

[0021] Furthermore, in the above technical solution, the flue upstream of the static mixing component is divided into multiple first ammonia injection zones, each first ammonia injection zone corresponding to one or more mixing units. The ammonia nozzle in each first ammonia injection zone is connected to the ammonia injection header, and the ammonia injection headers of the multiple first ammonia injection zones are connected to the ammonia injection main pipe. The ammonia injection header is equipped with a first flow regulating valve, and the ammonia injection main pipe is equipped with a second flow regulating valve. The flue downstream of the static mixing component is divided into multiple second ammonia injection zones, each second ammonia injection zone corresponding to one or more first ammonia injection zones. Each second ammonia injection zone is equipped with a flue gas detection unit.

[0022] Furthermore, in the above technical solution, the flue gas detection unit includes one or more flue gas detectors, which monitor the NO in the second ammonia injection zone in real time. x Concentration and ammonia concentration.

[0023] Furthermore, in the above technical solution, an ammonia-air mixer is installed on the ammonia injection main pipe, and the ammonia-air mixer is connected to the dilution air duct.

[0024] Furthermore, in the above technical solution, when the static mixing component is multi-layered, the area of ​​the lower end face of the mixing unit of the upper static mixing component is 2 to 16 times the area of ​​the lower end face of the mixing unit of the lower static mixing component, and the distance between two adjacent static mixing components is 0.2 to 5m.

[0025] Furthermore, in the above technical solution, the flue gas denitrification ammonia injection mixing system also includes: a denitrification unit, which is located downstream of the static mixing component, the denitrification unit includes at least one layer of denitrification catalyst, and a rectifier grid is provided on the upper part of the denitrification unit; and a flow guiding component, which is located between the static mixing component and the denitrification unit, the flow guiding component turns the upward flue gas into the downward flow into the denitrification unit.

[0026] According to a third aspect of the present invention, the present invention provides an ammonia injection control method for a flue gas denitrification ammonia injection mixing system as described above, the ammonia injection control method comprising the following steps:

[0027] The flue upstream of the static mixing component is divided into multiple first ammonia injection zones, each corresponding to a mixing unit of the static mixing component. The flue downstream of the static mixing component is divided into multiple second ammonia injection zones, each corresponding to one or more first ammonia injection zones. The ammonia-to-nitrogen molar ratio of each second ammonia injection zone and the NO content of the multiple second ammonia injection zones are obtained.x Average concentration, average ammonia-nitrogen molar ratio; based on NO x Calculate the required total ammonia injection flow rate based on the average concentration and flue gas flow rate; adjust the actual total ammonia injection flow rate to the required total ammonia injection flow rate; and adjust the ammonia injection flow rate of each first ammonia injection zone so that the ammonia-nitrogen molar ratio of each second ammonia injection zone is equal to the average ammonia-nitrogen molar ratio.

[0028] Compared with the prior art, the present invention has one or more of the following beneficial effects:

[0029] 1. The static mixing component of this invention, through the cooperation of a reduced-diameter tube and a floating element, can automatically adjust the flow area according to the fluctuation of flue gas flow rate, thereby significantly improving the uniformity of flue gas velocity distribution. In areas of high flow velocity in the flue, the dynamic pressure generated by the flue gas is greater, the floating distance of the mixing unit is relatively larger, and the flow area between the floating element and the reduced-diameter tube is reduced, thus reducing the flue gas flow rate through this mixing unit. Under the action of the floating element, the flow area of ​​the area with high flow velocity is reduced, so some of the flue gas in this area will flow through other mixing units with larger flow areas. Under the action of the static mixing component of this invention, a portion of the flue gas in the area with relatively high flow rate (higher flow velocity) will be diverted to the area with lower flow velocity, thereby effectively regulating the flue gas velocity at the same cross-section of the flue, and the deviation of flue gas velocity distribution after passing through the static mixing component will be greatly reduced.

[0030] 2. The flue gas flows upward through the static mixing assembly of this invention. When passing the floating member, the flue gas changes from vertical upward flow to upward flow along the gap between the floating member and the narrowing pipe, forming a vortex on the back of the floating member, which forces the ammonia and flue gas to mix. The turbulence member above the narrowing pipe diverts the collected mixed gas, and the mixed gas forms a vortex on the back of the turbulence member, forcing the ammonia and flue gas to mix under the action of the vortex. When the flue gas flows through the static mixing assembly of this invention, vortices are formed twice, which greatly enhances the mixing effect, improves the mixing uniformity of ammonia and flue gas, and effectively shortens the distance required for uniform mixing.

[0031] 3. The static mixing components can be configured in multiple layers, and the mixing units of each layer of static mixing components can have different sizes, thereby achieving the mixing of ammonia and flue gas in different areas, improving the mixing uniformity of ammonia and flue gas, reducing the deviation of gas velocity distribution and ammonia concentration distribution on the same cross-section of the flue, improving the denitrification rate of flue gas and the utilization rate of catalyst, and reducing ammonia escape.

[0032] 4. The static mixing assembly is equipped with a baffle. On the one hand, it can generate eddies in the mixed gas to promote mixing. On the other hand, when large pieces of ash fall from the flue support and bends above the static mixing assembly due to the impact or disturbance of the flowing flue gas, the baffle can prevent the ammonia nozzles below the mixing unit from being blocked by large pieces of ash, thus ensuring the uniformity of ammonia spray from the ammonia nozzles and effectively extending the maintenance cycle of the unit.

[0033] 5. After passing through the static mixing component, the flue gas flow field deviation and concentration deviation are significantly reduced, basically achieving uniform mixing and approximately equal flow velocities of the flue gas within the same ammonia injection zone. Then, the horizontal cross-section of the flue downstream of the static mixing component is divided into multiple second ammonia injection zones. The NO from these second ammonia injection zones is then used... x The average concentration is used as the basis for adjusting the total ammonia flow rate. This is different from using single-point measurement of NO in flue gas. x Compared to the concentration, NO concentration is significantly lower after using the ammonia injection control method of this invention. x The concentration measurement is more accurate, and therefore the total flow rate of the injected ammonia is also more precise.

[0034] 6. The average ammonia-nitrogen molar ratio of the second ammonia injection zone is used as the basis for adjusting the ammonia flow rate of the first ammonia injection zone. This two-stage adjustment is more conducive to precise control of the ammonia flow rate, improving the uniformity of ammonia-nitrogen distribution on the same cross-section of the flue gas duct downstream of the static mixing component, thereby increasing ammonia utilization and reducing ammonia escape. This avoids excessive ammonia injection that could lead to corrosion, leakage, or severe blockage in downstream air preheaters or economizers, as well as excessive ammonia-nitrogen content in the desulfurization wastewater from subsequent wet desulfurization units.

[0035] 7. The static hybrid components on the same layer can have the same structure, which enables modular mass production of static hybrid components, reducing production and installation costs and improving product competitiveness.

[0036] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0037] Figure 1 This is a cross-sectional schematic diagram of a mixing unit according to an embodiment of the present invention.

[0038] Figure 2 yes Figure 1 The diagram shows a top view of the hybrid unit.

[0039] Figure 3 This is a cross-sectional schematic diagram of a hybrid unit according to another embodiment of the present invention.

[0040] Figure 4 yes Figure 3 The diagram shows a top view of the hybrid unit.

[0041] Figure 5 A partial cross-sectional schematic diagram of a flue gas denitrification ammonia injection mixing system according to an embodiment of the present invention, wherein the static mixing component is a single layer.

[0042] Figure 6 yes Figure 5 A schematic diagram of the first ammonia injection zone.

[0043] Figure 7 yes Figure 5 A schematic diagram of the second ammonia injection zone.

[0044] Figure 8 yes Figure 5 A top view of the static hybrid component.

[0045] Figure 9 This is a partial cross-sectional schematic diagram of a flue gas denitrification ammonia injection mixing system according to an embodiment of the present invention, wherein the static mixing component consists of two layers.

[0046] Figure 10 yes Figure 9 A schematic diagram of the first ammonia injection zone.

[0047] Figure 11 yes Figure 9 A schematic diagram of the second ammonia injection zone.

[0048] Figure 12 yes Figure 9 A top view of the upper-middle static hybrid components.

[0049] Figure 13 This is a cross-sectional schematic diagram of a flue gas denitrification ammonia injection mixing system according to an embodiment of the present invention.

[0050] Explanation of key figure labels:

[0051] 10-Flue duct, 100-Static mixing assembly, 110-Mixing unit, 111-Reduced diameter pipe, 112-Break current device, 1121-Square sieve hole, 113-Floating component, 114-Guide section, 115-Fixed component, 116-Spring, 117-Limiting rod, 300-Ammonia nozzle, 301-Ammonia injection main pipe, 3011-First flow regulating valve, 3012-First flow meter, 302-Ammonia injection main pipe, 3021-Second flow regulating valve, 3022-Second flow meter, 311-First ammonia injection zone, 312-Second ammonia injection zone, 360-Flue gas detection unit, 370-Dilution air duct, 371-Ammonia-air mixer;

[0052] 20-Flue duct, 200-Static mixing assembly, 210-Mixing unit, 211-Reduced diameter pipe, 212-Break current device, 2121-Circular sieve hole, 213-Floating component, 215-Fixing component, 216-Guide rod, 217-Limiting part, 500-Ammonia nozzle, 501-Ammonia injection main pipe, 5011-First flow regulating valve, 5012-First flow meter, 502-Ammonia injection main pipe, 5021-Second flow regulating valve, 511-First ammonia injection zone, 512-Second ammonia injection zone, 560-Flue gas detection unit, 570-Dilution air duct, 571-Ammonia-air mixer;

[0053] 60-Flue duct, 610-Ammonia nozzle, 620-Static mixing assembly, 630-Detection unit, 641-Guide plate, 642-Baffle plate, 650-Rectifying grid, 660-Denitrification unit, 661-Denitrification catalyst. Detailed Implementation

[0054] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0055] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0056] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” other elements or features will be oriented “above” the element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. Objects may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0057] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0058] like Figure 1 , Figure 2 and Figure 5As shown, a static mixing assembly 100 according to a specific embodiment of the present invention is disposed in a flue 10. The static mixing assembly 100 includes a plurality of mixing units 110 uniformly distributed in the flue 10. Each mixing unit 110 includes a narrow-diameter pipe 111 extending axially along the flue 10. The narrow-diameter pipe 111 is a tubular structure that is wider at the bottom and narrower at the top, with its wide end facing downwards. The narrow-diameter pipe 111 increases the flow velocity of the mixed gas and accelerates mixing. A flow-deflecting element 112 is provided above the narrow-diameter pipe 111. A gap is left between the flow-deflecting element 112 and the narrow end of the narrow-diameter pipe 111. When the gas flows through this gap, it can form a vortex on the back side of the flow-deflecting element 112, accelerating gas mixing. Exemplarily, the flow-deflecting element 112 can be mounted above the narrow-diameter pipe 111 by a fixing element 115. The fixing element 115 can be a hollow bracket or a support rod structure, and the present invention is not limited thereto. The floating element 113 is housed within the narrowed-diameter pipe 111. The floating element 113 can move up and down along the axis of the narrowed-diameter pipe 111, thereby changing the flow area between the edge of the floating element 113 and the narrowed-diameter pipe 111. Flue gas flows upward through the static mixing assembly 100 of this invention. The flow of flue gas impacts the floating element 113, causing it to float up and down under the influence of the flue gas. When the flue gas velocity (flow rate) is sufficiently high, the resulting force causes the floating element 113 to float upward. At this time, the gap between the floating element 113 and the narrowed-diameter pipe 111 decreases, the flue gas velocity (flow rate) decreases, the upward force decreases, and the floating element 113 descends, thus achieving dynamic equilibrium. Under the action of the floating element 113, the flow area of ​​the region with higher flow velocity decreases, so some of the flue gas in that region will flow through other mixing units with larger flow areas. Under the action of the static mixing component of the present invention, a portion of the flue gas in the area with a relatively large flue gas flow rate (faster flow velocity) will be diverted to the area with a lower flow velocity, thereby effectively regulating the flue gas flow velocity on the same cross-section. In addition, the gas can form a vortex on the back side of the floating member 113, accelerating gas mixing.

[0059] Furthermore, in one or more exemplary embodiments of the present invention, the narrow end of the reduced diameter pipe 111 extends upward to a guide section 114, which is a tubular structure used to rectify the mixed gas and guide the mixed gas passing through the reduced diameter pipe 111 to the turbulence member 112.

[0060] Furthermore, in one or more exemplary embodiments of the present invention, the floating member 113 can be connected to the baffle member 112 or the reduced-diameter tube 111 via an elastic member. Exemplarily, in... Figure 1In the illustrated embodiment, the elastic element is a spring 116, and the floating element 113 is connected to the center of the turbulence-disrupting element 112 via the spring 116. The spring 116 can limit the floating element 113, preventing it from completely blocking the reduced-diameter tube 111 or leaving the reduced-diameter tube 111. Further, in one or more exemplary embodiments of the present invention, a limiting rod 117 is provided through the middle of the spring 116. The limiting rod 117 limits the spring 116 on one hand and the floating element 113 on the other hand, with the lower end of the limiting rod 117 lower than the upper end face of the reduced-diameter tube 111.

[0061] Furthermore, in one or more exemplary embodiments of the present invention, the cross-section of the reduced-diameter tube 111 is square. It should be understood that the present invention is not limited thereto, and the cross-section of the reduced-diameter tube can also be circular, elliptical, semi-circular, heart-shaped, plum blossom-shaped, polygonal, etc., and the shapes of the upper and lower end faces of the reduced-diameter tube can be the same or different. The three-dimensional structure of the reduced-diameter tube can be a trapezoidal body, a square frustum, a pentagonal frustum, a hexagonal frustum, a truncated cone, a hyperboloid, and a geometric body with a circle on top and a square bottom, etc.

[0062] Furthermore, in one or more exemplary embodiments of the present invention, the floating element 113 may be a circular piece, a polygonal piece, or a cone. Preferably, but not limitingly, the shape of the bottom surface of the floating element 113 is the same as the shape of the lower end surface of the reduced-diameter tube 111.

[0063] Furthermore, in one or more exemplary embodiments of the present invention, the baffle 112 may be one or more baffles. The baffles may be provided with sieve holes, and the opening ratio of the baffles may be 2% to 20%. Figure 2 The central turbulence element 112 is a square piece with square sieve holes 1121, but the present invention is not limited thereto.

[0064] Furthermore, in one or more exemplary embodiments of the present invention, the horizontal projected area of ​​the baffle 112 is larger than the port area of ​​the narrow end of the reduced diameter pipe 111. The baffle 112 can shield the reduced diameter pipe 111, thereby preventing large pieces of dust falling from above from entering the reduced diameter pipe 111 and its upstream.

[0065] Combination Figures 5-8 As shown, the flue gas denitrification ammonia mixing system according to one or more exemplary embodiments of the present invention includes, in sequence along the flue gas flow direction: a plurality of ammonia nozzles 300 and a layer of static mixing assembly 100, wherein the mixing unit 110 of the static mixing assembly 100 is arranged corresponding to the ammonia nozzles 300.

[0066] For example, each mixing unit 110 of the static mixing assembly 100 corresponds to the same number of ammonia nozzles 300, for example, each mixing unit 110 corresponds to two ammonia nozzles 300, but the present invention is not limited thereto.

[0067] Further, in one or more exemplary embodiments of the present invention, the flue 10 upstream of the static mixing component 100 is divided into a plurality of first ammonia injection zones 311, each first ammonia injection zone 311 corresponding to one or more mixing units 110. The ammonia nozzles 300 within each first ammonia injection zone 311 are connected to an ammonia injection header 301. The ammonia injection headers 301 of the plurality of first ammonia injection zones 311 are connected to an ammonia injection main pipe 302. The ammonia injection header 301 is equipped with a first flow regulating valve 3011 and a first flow meter 3012, and the ammonia injection main pipe 302 is equipped with a second flow regulating valve 3021 and a second flow meter 3022. The flue downstream of the static mixing component 100 is divided into a plurality of second ammonia injection zones 312, each second ammonia injection zone 312 corresponding to one or more first ammonia injection zones 311. Each second ammonia injection zone 312 is equipped with a flue gas detection unit 360. Exemplarily, the flue gas detection unit 360 includes one or more flue gas detectors, which monitor the NO levels in the second ammonia injection zone 312 in real time. x Parameters such as concentration and ammonia concentration.

[0068] Furthermore, in one or more exemplary embodiments of the present invention, an ammonia air mixer 371 is provided on the ammonia injection main pipe 301. The ammonia air mixer 371 is connected to the dilution air duct 370, thereby reducing the ammonia gas to below its explosion limit before it is injected into the flue 10 by the ammonia gas nozzle 300.

[0069] Combination Figures 5-7 As shown, the ammonia injection control method according to a specific embodiment of the present invention is used in the flue gas denitrification ammonia injection mixing system as described above. The ammonia injection control method includes the following steps: dividing the flue duct 10 upstream of the static mixing component 100 into multiple first ammonia injection zones 311, each first ammonia injection zone 311 corresponding to a mixing unit 110 of the static mixing component 100; dividing the flue duct 10 downstream of the static mixing component 100 into multiple second ammonia injection zones 312, each second ammonia injection zone 312 corresponding to one or more first ammonia injection zones 311; obtaining the ammonia-nitrogen molar ratio of each second ammonia injection zone 312, and the NO content of the multiple second ammonia injection zones 312. x Average concentration, average ammonia-nitrogen molar ratio; based on NO x Calculate the required total ammonia injection flow rate based on the average concentration and flue gas flow rate; adjust the actual total ammonia injection flow rate to the required total ammonia injection flow rate; and adjust the ammonia injection flow rate of each first ammonia injection zone 311 so that the ammonia-nitrogen molar ratio of each second ammonia injection zone 312 is equal to the average ammonia-nitrogen molar ratio.

[0070] like Figure 3 , Figure 4 and Figure 9As shown, a static mixing assembly 200 according to a specific embodiment of the present invention is disposed in a flue 20. The static mixing assembly 200 includes a plurality of mixing units 210 uniformly distributed in the flue 20. Each mixing unit 210 includes a narrow-diameter pipe 211 extending axially along the flue 20. The narrow-diameter pipe 211 is a tubular structure that is wider at the bottom and narrower at the top, with its wide end facing downwards. The narrow-diameter pipe 211 increases the flow velocity of the mixed gas and accelerates mixing. A flow-deflecting element 212 is provided above the narrow-diameter pipe 211. A gap is left between the flow-deflecting element 212 and the narrow end of the narrow-diameter pipe 211. When the gas flows through this gap, it can form a vortex on the back side of the flow-deflecting element 212, accelerating gas mixing. Exemplarily, the flow-deflecting element 212 can be mounted above the narrow-diameter pipe 211 by a fixing element 215. The fixing element 215 can be a hollow bracket or a support rod structure, and the present invention is not limited thereto. The floating element 213 is housed within the narrowed-diameter pipe 211. The floating element 213 can move up and down along the axis of the narrowed-diameter pipe 211, thereby changing the flow area between the edge of the floating element 213 and the narrowed-diameter pipe 211. Flue gas flows upward through the static mixing assembly 200 of this invention. The flow of flue gas impacts the floating element 213, causing it to float up and down under the influence of the flue gas. When the flue gas velocity (flow rate) is sufficiently high, the resulting force causes the floating element 213 to float upward. At this time, the gap between the floating element 213 and the narrowed-diameter pipe 211 decreases, the flue gas velocity (flow rate) decreases, the upward force decreases, and the floating element 213 descends, thus achieving dynamic equilibrium. Under the action of the floating element 213, the flow area of ​​the region with higher flow velocity decreases, so some of the flue gas in that region will flow through other mixing units with larger flow areas. Under the action of the static mixing component of the present invention, a portion of the flue gas in the area with a relatively large flue gas flow rate (faster flow velocity) will be diverted to the area with a lower flow velocity, thereby effectively regulating the flue gas flow velocity on the same cross-section. In addition, the gas can form a vortex on the back side of the floating member 213, accelerating gas mixing.

[0071] Furthermore, in one or more exemplary embodiments of the present invention, the center of the baffle 212 is connected to the guide rod 216, and the lower part of the guide rod 216 is provided with two limiting portions 217. The floating member 213 passes through the guide rod 216 and floats up and down between the limiting portions 217 along the guide rod 216. The limiting portions 217 can prevent the floating member 213 from completely blocking the reduced diameter pipe 211 when sliding upward, thus preventing the flue gas from passing through, or from falling off the guide rod 216 when sliding downward.

[0072] Furthermore, in one or more exemplary embodiments of the present invention, the cross-section of the reduced-diameter tube 211 is square. It should be understood that the present invention is not limited thereto, and the cross-section of the reduced-diameter tube can also be circular, elliptical, semi-circular, heart-shaped, plum blossom-shaped, polygonal, etc., and the shapes of the upper and lower end faces of the reduced-diameter tube can be the same or different. The three-dimensional structure of the reduced-diameter tube can be a trapezoidal body, a square frustum, a pentagonal frustum, a hexagonal frustum, a truncated cone, a hyperboloid, and a geometric body with a circle on top and a square bottom, etc.

[0073] Furthermore, in one or more exemplary embodiments of the present invention, the floating element 213 may be a circular piece, a polygonal piece, or a cone.

[0074] Furthermore, in one or more exemplary embodiments of the present invention, the baffle 212 may be one or more baffles. The baffles may be provided with sieve holes, and the opening ratio of the baffles may be 0% to 50%, preferably 2% to 20%. Figure 4 The intermediate turbulence element 212 is a circular piece with circular sieve holes 2121, but the present invention is not limited thereto.

[0075] Combination Figures 9-12 As shown, in a flue gas denitrification ammonia mixing system according to one or more exemplary embodiments of the present invention, the system sequentially includes, along the flue gas flow direction: a plurality of ammonia nozzles 500 and two layers of static mixing components. Exemplarily, the lower layer employs... Figure 5 The static mixing assembly 100 shown above uses a static mixing assembly 200 as its upper layer. The exemplary structure can be understood in conjunction with the description in the corresponding drawings, and will not be repeated here. It should be understood that the number of layers of the static mixing assembly can be set according to the structure of the flue and actual needs, for example, 1 to 5 layers, but this invention is not limited thereto. The mixing unit 110 of the lower static mixing assembly 100 is correspondingly arranged with the ammonia nozzle 500.

[0076] Furthermore, in one or more exemplary embodiments of the present invention, the area of ​​the lower end face of the mixing unit 210 of the upper static mixing component 200 is 2 to 16 times the area of ​​the lower end face of the mixing unit 110 of the lower static mixing component 100, and the distance between two adjacent static mixing components is 0.2 to 5 m.

[0077] For example, each mixing unit 110 of the static mixing assembly 100 corresponds to the same number of ammonia nozzles 500, for example, each mixing unit 110 corresponds to one ammonia nozzle 500, but the present invention is not limited thereto.

[0078] Further, in one or more exemplary embodiments of the present invention, the flue 20 upstream of the static mixing component 100 is divided into a plurality of first ammonia injection zones 511, each first ammonia injection zone 511 corresponding to one or more mixing units 110. The ammonia nozzles 500 within each first ammonia injection zone 511 are connected to an ammonia injection header 501. The ammonia injection headers 501 of the plurality of first ammonia injection zones 511 are connected to an ammonia injection main pipe 502. The ammonia injection header 501 is equipped with a first flow regulating valve 5011 and a first flow meter 5012, and the ammonia injection main pipe 502 is equipped with a second flow regulating valve 5021 and a second flow meter 5022. The flue downstream of the static mixing component 200 is divided into a plurality of second ammonia injection zones 512, each second ammonia injection zone 512 corresponding to one or more first ammonia injection zones 511. Each second ammonia injection zone 512 is equipped with a flue gas detection unit 560. Exemplarily, the flue gas detection unit 560 includes one or more flue gas detectors, which monitor the NO levels in the second ammonia injection zone 512 in real time. x Parameters such as concentration and ammonia concentration.

[0079] Furthermore, in one or more exemplary embodiments of the present invention, an ammonia air mixer 571 is provided on the ammonia injection main pipe 501. The ammonia air mixer 571 is connected to the dilution air duct 570, thereby reducing the ammonia gas to below its explosion limit before it is injected into the flue 20 by the ammonia gas nozzle 500.

[0080] Combination Figures 9-12 As shown, the ammonia injection control method according to a specific embodiment of the present invention is used in a flue gas denitrification ammonia injection mixing system as described above. The ammonia injection control method includes the following steps: dividing the flue duct 20 upstream of the lower static mixing component 100 into multiple first ammonia injection zones 511, each first ammonia injection zone 511 corresponding to a mixing unit 110 of the static mixing component 100; dividing the flue duct 20 downstream of the upper static mixing component 200 into multiple second ammonia injection zones 512, each second ammonia injection zone 512 corresponding to one or more first ammonia injection zones 511; obtaining the ammonia-nitrogen molar ratio of each second ammonia injection zone 512, and the NO content of the multiple second ammonia injection zones 512. x Average concentration, average ammonia-nitrogen molar ratio; based on NO x Calculate the required total ammonia injection flow rate based on the average concentration and flue gas flow rate; adjust the actual total ammonia injection flow rate to the required total ammonia injection flow rate; and adjust the ammonia injection flow rate of each first ammonia injection zone 511 so that the ammonia-nitrogen molar ratio of each second ammonia injection zone 512 is equal to the average ammonia-nitrogen molar ratio.

[0081] Combination Figure 13As shown, a flue gas denitrification ammonia mixing system according to one or more exemplary embodiments of the present invention is used in a flue duct 60, and sequentially includes, along the flue gas flow direction: a plurality of ammonia nozzles 610, a static mixing assembly 620, a detection unit 630, a flow guiding assembly, a flow rectifier 650, and a denitrification unit 660. The mixing unit 621 of the static mixing assembly 620 is correspondingly arranged with respect to the ammonia nozzles 610. The denitrification unit 660 includes a three-layer denitrification catalyst 661. The flow guiding assembly directs the upward flue gas downwards into the denitrification unit 660; exemplaryly, the flow guiding assembly may include a flow guide plate 641 and a baffle plate 642. It should be understood that the flow guiding assembly, the flow rectifier 650, and the denitrification unit 660 can all employ existing technology, and the present invention is not limited thereto.

[0082] The present invention will now be described in more detail by way of specific embodiments. It should be understood that the present invention is not limited thereto.

[0083] Example 1

[0084] In this embodiment, the flue gas denitrification ammonia mixing system includes, in sequence along the flue gas flow direction: multiple ammonia nozzles, a single layer of static mixing components, a detection unit, a flow guiding component, a rectifier grid, and a denitrification unit.

[0085] refer to Figure 1 , 2 As shown in Figures 5 and 8, the static mixing assembly 100 of this embodiment includes 40 mixing units 110, each mixing unit 110 corresponding to two ammonia nozzles 300. The upstream flue 10 of the static mixing assembly 100 is divided into 10 first ammonia injection zones 311, each first ammonia injection zone 311 corresponding to four mixing units 110. The ammonia nozzles 300 in each first ammonia injection zone 311 are connected to the ammonia injection header 301, and all ammonia injection headers 301 are connected to the ammonia injection main pipe 302. The downstream flue 10 of the static mixing assembly 100 is divided into 10 second ammonia injection zones 312, each second ammonia injection zone 312 corresponding to one first ammonia injection zone 311. Each second ammonia injection zone 312 is equipped with a flue gas detection unit 360, which is a flue gas detector used to monitor the NO in the second ammonia injection zone 312 in real time. x Concentration and ammonia concentration.

[0086] Hybrid Unit 110 Structural Reference Figure 1 and Figure 2 As shown, the floating component 113 is a square plate, fixed to the center of the turbulence-inducing component 112 by a spring 116. The reduced-diameter tube 111 has a truncated quadrangular structure, with both the upper and lower end faces being square. The turbulence-inducing component 112 is a single-layer square turbulence-inducing plate with square sieve holes 1121, having an opening ratio of 5.2%.

[0087] After adopting the flue gas denitrification ammonia injection mixing system of this embodiment in the boiler flue gas denitrification unit of a certain refining and chemical enterprise, the deviation of the flow velocity at various points within 100% of the flue gas cross-section 500mm before the inlet of the first layer catalyst of the boiler SCR reactor decreased from ±26.6% to ±4.5%; the NH3 / NO ratio at various points in the flue gas within 100% of the flue gas cross-section also decreased. x The deviation of the molar ratio was reduced from ±21.7% to ±3.5%, which is better than the relevant industry requirements.

[0088] Example 2

[0089] In this embodiment, the flue gas denitrification ammonia injection mixing system includes, in sequence along the flue gas flow direction: multiple ammonia nozzles, two layers of static mixing components, a detection unit, a flow guiding component, a rectifier grid, and a denitrification unit.

[0090] refer to Figure 1 , 2 As shown in Figures 3, 4, 9, and 12, the lower static mixing assembly 100 of this embodiment includes 40 mixing units 110, and the upper static mixing assembly 200 includes 10 mixing units 210. Each mixing unit 110 corresponds to one ammonia nozzle 500. The flue duct 20 upstream of the static mixing assembly 100 is divided into 10 first ammonia injection zones 311, and each first ammonia injection zone 311 corresponds to four mixing units 110. The ammonia nozzles 500 in each first ammonia injection zone 311 are connected to the ammonia injection header 501, and all ammonia injection headers 501 are connected to the ammonia injection main pipe 502. The downstream flue duct 20 of the static mixing assembly 200 is divided into 5 second ammonia injection zones 512, and each second ammonia injection zone 512 corresponds to two first ammonia injection zones 511. Each second ammonia injection zone 512 is equipped with a flue gas detection unit 560, which is a flue gas detector used to monitor the NO in the second ammonia injection zone 512 in real time. x Concentration and ammonia concentration.

[0091] The structure of hybrid unit 110 is as described in Embodiment 1. Hybrid unit 210 is as described in Embodiment 1. Figure 3 and Figure 4 As shown, the center of the baffle 212 is connected to the guide rod 216, and the floating part 213 is a circular plate that passes between the two limiting parts 217 of the guide rod 216. The reduced diameter tube 211 has a truncated quadrangular structure with square upper and lower end faces. The baffle 212 is a single-layer circular baffle with circular sieve holes 2121, and the opening ratio is 9%.

[0092] After adopting the flue gas denitrification ammonia injection mixing system of this embodiment in the flue gas denitrification device of a coal-fired boiler in a power plant, the deviation of the flow velocity at various points within 100% of the flue gas cross-section 500mm before the inlet of the first catalyst layer of the boiler SCR reactor decreased from ±35% to ±2.5%; the NH3 / NO ratio at various points in the flue gas within 100% of the flue gas cross-section also decreased. xThe deviation of the molar ratio was reduced from ±21% to ±1.4%, which is better than the relevant industry requirements.

[0093] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. An ammonia injection control method characterized by, For a flue gas denitrification ammonia injection mixing system, the system sequentially includes, along the flue gas flow direction: multiple ammonia nozzles; and one or more layers of static mixing components, with the mixing units of the lowest layer of the static mixing component corresponding to the ammonia nozzles; the static mixing component includes: multiple mixing units uniformly distributed in the flue, each mixing unit including: a reducing pipe extending axially along the flue, with the wide end of the reducing pipe facing downwards; a flow-turbating element disposed above the reducing pipe; and a floating element housed within the reducing pipe, the floating element moving up and down along the axis of the reducing pipe to change the flow area between the edge of the floating element and the reducing pipe; the ammonia injection control method includes the following steps: The flue upstream of the static mixing component is divided into multiple first ammonia injection zones, and the first ammonia injection zones are set corresponding to the mixing units of the static mixing component. The flue downstream of the static mixing component is divided into multiple second ammonia injection zones, each of which corresponds to one or more first ammonia injection zones; obtaining the ammonia nitrogen molar ratio of each of the second ammonia injection sub-zones, and the NO x average value of the concentration, average value of the ammonia nitrogen molar ratio; According to the NO x The total flow of ammonia required is calculated from the average concentration and the flow of flue gas. Adjust the actual total ammonia injection flow rate to the required total ammonia injection flow rate; and Adjust the ammonia injection flow rate of each of the first ammonia injection zones so that the ammonia-nitrogen molar ratio of each of the second ammonia injection zones is equal to the average ammonia-nitrogen molar ratio.

2. The ammonia injection control method according to claim 1, characterized by, The narrow end of the reduced-diameter pipe extends upwards to form a flow guide section.

3. The ammonia injection control method according to claim 1, characterized by, The static mixing component also includes: An elastic element, one end of which is connected to the floating element, and the other end of which is connected to the turbulence element or the reduced diameter tube.

4. The ammonia injection control method according to claim 3, characterized by, The elastic element is a spring, and a limiting rod is inserted through the middle of the spring. The lower end of the limiting rod is lower than the upper end face of the reduced diameter tube.

5. The ammonia injection control method of claim 1, wherein The center of the spoiler is connected to a guide rod, and the lower part of the guide rod is provided with a limiting part. The floating part passes through the guide rod and floats up and down along the guide rod between the limiting parts.

6. The ammonia injection control method of claim 1, wherein The agitator is mounted above the reduced-diameter pipe by a fixing member; the horizontal projected area of ​​the agitator is larger than the port area of ​​the narrow end of the reduced-diameter pipe.

7. The ammonia injection control method of claim 1, wherein The upper end face of the reduced diameter tube is circular or polygonal, and the lower end face is square or rectangular; the floating component is a circular plate, a polygonal plate, or a cone; the turbulence-disrupting component is one or more layers of turbulence-disrupting plates.

8. The ammonia injection control method of claim 7 wherein, The baffle plate is provided with sieve holes, and the opening rate of the baffle plate is 2%~20%.

9. The ammonia injection control method of claim 1 wherein, Each mixing unit of the lowest layer of the static mixing assembly corresponds to the same number of ammonia nozzles.

10. The ammonia injection control method of claim 1 wherein, Each of the mixing units corresponds to 1 to 9 of the ammonia nozzles.

11. The ammonia injection control method according to claim 1, characterized in that, The ammonia nozzles in each of the first ammonia injection zones are connected to the ammonia injection header, and the ammonia injection headers of multiple first ammonia injection zones are connected to the ammonia injection main pipe. The ammonia injection header is equipped with a first flow regulating valve, and the ammonia injection main pipe is equipped with a second flow regulating valve. Each of the second ammonia injection zones is equipped with a flue gas detection unit.

12. The ammonia injection control method according to claim 11, characterized in that, The flue gas detection unit comprises one or more flue gas detectors that monitor the NOx concentration and ammonia concentration of the second ammonia injection zone in real time x concentration and ammonia concentration.

13. The ammonia injection control method according to claim 11, characterized in that, An ammonia-air mixer is installed on the ammonia injection main pipe, and the ammonia-air mixer is connected to the dilution air duct.

14. The ammonia injection control method according to claim 1, characterized in that, When the static mixing component is multi-layered, the area of ​​the lower end face of the mixing unit of the upper static mixing component is 2 to 16 times the area of ​​the lower end face of the mixing unit of the lower static mixing component, and the distance between two adjacent static mixing components is 0.2 to 5m.

15. The ammonia injection control method according to claim 1, characterized in that, The flue gas denitrification ammonia injection mixing system also includes: A denitrification unit is disposed downstream of the static mixing assembly. The denitrification unit includes at least one layer of denitrification catalyst, and a rectifier grid is provided on the upper part of the denitrification unit. A flow guiding component is disposed between the static mixing component and the denitrification unit, which deflects the upward flue gas into the downward flow of the denitrification unit.

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