A precision ammonia injection system and method

Abstract

The application relates to the field of environmental protection technologies of coal-fired power plants, in particular to a precise ammonia injection system and method. The system is suitable for a denitration system, the denitration system comprises an inlet flue and an outlet flue, and the system comprises: an ammonia injection device and an inlet flow velocity measuring device arranged in the inlet flue, the ammonia injection device comprises a plurality of ammonia injection nozzles, any ammonia injection nozzle is provided with an ammonia injection valve which can be used for controlling the size of the ammonia injection amount; a flue gas concentration detection device and an outlet flow velocity measuring device arranged in the outlet flue; and a control device, the control device is used for acquiring inlet flow velocity information fed back by the inlet flow velocity measuring device, acquiring flue gas concentration information fed back by the flue gas concentration detection device and outlet flow velocity information fed back by the outlet flow velocity measuring device, and determining the ammonia injection valve which needs to be adjusted and the size of the opening degree of the ammonia injection valve based on the flue gas concentration information and the outlet flow velocity information. The system can realize precise ammonia injection and rapid response.

Description

Technical Field

[0001] This application relates to the field of environmental protection technology for coal-fired power plants, specifically to a precision ammonia injection system and a precision ammonia injection method. Background Technology

[0002] Selective catalytic reduction (SCR) has become the most widely used flue gas denitrification technology in domestic coal-fired power plants due to its high denitrification efficiency and mature technology. This technology reduces NOx through a V2O5 catalyst, but it also reduces SO2 to SO3, thereby promoting the formation of ammonium bisulfate (ABS), a denitrification byproduct.

[0003] In some regions, coal-fired power units have been operating under prolonged deep peak-shaving conditions, resulting in persistently low cold-end temperatures in the air preheaters. This further promotes ABS liquefaction, severely impacting the safe operation of units, especially those burning coal with high sulfur content. Frequent changes in load and coal type have led to increased NO₂ at the SCR inlet. x The concentration and flow field distribution fluctuate greatly; the uneven inlet flow field causes poor ammonia injection effect in some areas, resulting in NO at the SCR outlet. x Uneven distribution; large flue cross-sectional area, making it difficult for simple single-point and multi-point monitoring to reflect the internal conditions of the flue; traditional flue gas extraction methods are seriously lagging behind, resulting in the inability to accurately inject ammonia in a timely manner.

[0004] In summary, how to solve the serious lag in the response of the precision ammonia injection system in coal-fired power plants, and the poor ammonia injection effect due to large fluctuations in the flow field distribution, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a precision ammonia injection system and a precision ammonia injection method.

[0006] To achieve the above objectives, the first aspect of this application provides a precision ammonia injection system suitable for denitrification systems. The denitrification system includes an inlet flue and an outlet flue. The precision ammonia injection system includes: an ammonia injection device and an inlet flow rate measuring device disposed within the inlet flue; the ammonia injection device includes multiple ammonia injection nozzles, each nozzle being equipped with an ammonia injection valve for controlling the amount of ammonia injected; the ammonia injection range of the ammonia injection device can cover the radial section of a specific area of ​​the inlet flue; a flue gas concentration detection device and an outlet flow rate measuring device disposed within the outlet flue; and a control device. The inlet velocity measuring device, flue gas concentration detection device, outlet velocity measuring device, and ammonia injection valve are electrically connected to the control equipment. The control equipment is used to acquire the inlet velocity information fed back by the inlet velocity measuring device and determine whether the opening of the ammonia injection valve needs to be adjusted based on the inlet velocity information. When the opening of the ammonia injection valve needs to be adjusted, the control equipment is used to acquire the flue gas concentration information fed back by the flue gas concentration detection device and the outlet velocity information fed back by the outlet velocity measuring device, and determine the ammonia injection valve to be adjusted and its opening size based on the flue gas concentration information and the outlet velocity information.

[0007] Based on the first aspect, in some embodiments of the present invention, multiple ammonia injection nozzles are mapped onto the radial cross-section of the inlet flue in a grid-like distribution.

[0008] Based on the first aspect, in some embodiments of the present invention, the precision ammonia injection system includes multiple inlet flow rate measuring devices, which are evenly distributed on the inlet flue detection surface.

[0009] Based on the first aspect, in some embodiments of the present invention, the flue gas concentration detection device includes multiple flue gas concentration sensors, and each flue gas concentration sensor is connected to a corresponding sampling branch pipe with a valve at its sampling end. The valves of the flue gas concentration sensor and the sampling branch pipe are electrically connected to the control equipment respectively. Multiple sampling branches are evenly distributed on the sampling surface of the outlet flue.

[0010] Based on the first aspect, in some embodiments of the present invention, each ammonia spray nozzle is connected to a rotating component that can drive the ammonia spray nozzle to rotate, and the rotating component is electrically connected to the control device.

[0011] Secondly, the present invention provides a precise ammonia injection method applicable to a denitrification system. The denitrification system includes an inlet flue and an outlet flue. The inlet flue is equipped with an ammonia injection device and an inlet flow rate measuring device, and the outlet flue is equipped with a flue gas concentration detection device and an outlet flow rate measuring device. The ammonia injection device includes multiple ammonia injection nozzles, each of which is equipped with an ammonia injection valve for controlling the amount of ammonia injected. The method includes: acquiring inlet flow rate information using the inlet flow rate measuring device; determining whether the opening of the ammonia injection valve needs to be adjusted based on the inlet flow rate information; if the opening of the ammonia injection valve needs to be adjusted, further acquiring flue gas concentration information using the flue gas concentration detection device and acquiring outlet flow rate information using the outlet flow rate measuring device; and determining the ammonia injection valve to be adjusted and its opening size based on the flue gas concentration information and the outlet flow rate information.

[0012] Based on the second aspect, in some embodiments of the present invention, a first detection surface is provided radially inside the inlet flue, and multiple inlet velocity measuring devices are evenly distributed on each first detection point of the first detection surface. The inlet velocity information includes the flue gas velocity at each first detection point. The step of determining whether the opening of the ammonia injection valve needs to be adjusted based on the inlet velocity information includes: determining whether the flue gas field inside the inlet flue is uniform based on the flue gas velocity at each point on the detection surface; if it is not uniform, then it is determined that the opening of the ammonia injection valve needs to be adjusted.

[0013] Based on the second aspect, in some embodiments of the present invention, an execution surface is provided radially inside the inlet flue, and multiple ammonia injection nozzles are evenly distributed in a grid pattern at each execution point of the execution surface; a second detection surface and a third detection surface are provided radially inside the outlet flue, close to each other, and multiple outlet flow rate measuring devices are evenly distributed at each second detection point of the second detection surface; the flue gas concentration detection device includes multiple flue gas concentration sensors, and the acquisition end of each flue gas concentration sensor is connected to a corresponding acquisition branch pipe with a valve, and multiple acquisition branch pipes are evenly distributed at each third detection point of the third detection surface; the arrangement of each second detection point is consistent with the arrangement of each execution point, and the arrangement of each third detection point is consistent with the arrangement of each execution point; the outlet flow rate information includes the flue gas velocity at each second detection point. The flue gas concentration information includes the flue gas concentration at each third detection point; determining the ammonia injection valve to be adjusted and its opening degree based on the flue gas concentration information and outlet flow rate information includes: determining the ammonia injection nozzle whose valve needs adjustment based on the flue gas concentration at each third detection point, thus obtaining the ammonia injection nozzle to be adjusted; obtaining the flue gas velocity at the second detection point corresponding to the location of the ammonia injection nozzle to be adjusted, thus obtaining the flue gas velocity at the location to be adjusted; obtaining the flue gas concentration at the third detection point corresponding to the location of the ammonia injection nozzle to be adjusted, thus obtaining the flue gas concentration at the location to be adjusted; calculating the mass of flue gas flowing at the location to be adjusted per unit time based on the flue gas velocity and the flue gas concentration at the location to be adjusted; determining the ammonia injection amount of the ammonia injection nozzle to be adjusted based on the flue gas mass; and determining the opening degree of the ammonia injection valve corresponding to the ammonia injection nozzle to be adjusted based on the ammonia injection amount.

[0014] Based on the second aspect, in some embodiments of the present invention, there are N third detection points on the third detection surface, the flue gas concentration detection device includes N collection branches with valves, and the ammonia injection device includes N ammonia injection nozzles; determining the ammonia injection nozzle whose ammonia injection valve needs to be adjusted based on the flue gas concentration at each third detection point includes: calculating the average flue gas concentration value on the third detection surface. Close the valve of the i-th sampling branch pipe and calculate the average flue gas concentration value of the remaining third detection points. The i-th sampling branch pipe is used to collect the flue gas at the i-th third detection point; the average flue gas concentration value of the remaining third detection points is determined. The average flue gas concentration value on the third detection surface If the difference between them exceeds the threshold range, then the i-th ammonia injection head is determined to be an adjustment head, where the ammonia injected by the i-th ammonia injection head is used to change the flue gas concentration at the location of the i-th third detection point and its vicinity.

[0015] Based on the second aspect, in some embodiments of the present invention, each ammonia injection nozzle is connected to a rotating component that can drive the ammonia injection nozzle to rotate, and the precise ammonia injection method further includes: determining the direction of rotation and rotation angle of the rotating component based on the inlet flow velocity information.

[0016] The precision ammonia injection system provided by this invention achieves closed-loop precision control of the ammonia injection valve of the ammonia injection head in the inlet channel by using information fed back from the flue gas concentration detection device and the outlet flow rate measurement device installed in the outlet channel. Under the premise of meeting the flue gas concentration requirements, it reduces ammonia waste and avoids ammonia escape.

[0017] The precise ammonia injection method provided by this invention can quickly adjust the flue gas concentration at various points in the outlet channel to near the average value through uniform distribution, which can avoid the situation where the outlet flue gas concentration cannot meet the standard due to local areas exceeding the adjustment range of the ammonia injection nozzle.

[0018] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings:

[0020] Figure 1 This diagram illustrates the location and installation of each device in the precision ammonia injection system.

[0021] Figure 2 A schematic diagram of the precision ammonia injection system is shown.

[0022] Explanation of reference numerals in the attached figures

[0023] 1-Ammonia injection nozzle; 2-Inlet flow rate measuring device; 3-Flue gas concentration detection device; 31-Collection branch pipe; 32-Flue gas concentration sensor; 33-Flue gas measuring device; 4-Outlet flow rate measuring device; 5-Control equipment; 100-Inlet flue; 200-Outlet flue. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0025] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0026] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0027] Example 1

[0028] This embodiment provides a precision ammonia injection system suitable for denitrification systems. The denitrification system includes an inlet flue 100 and an outlet flue 200. The precision ammonia injection system includes:

[0029] like Figure 1 As shown, an ammonia injection device and an inlet flow rate measuring device are installed in the inlet flue 100. The ammonia injection device includes multiple ammonia injection nozzles. Each ammonia injection nozzle is equipped with an ammonia injection valve that can be used to control the amount of ammonia injected. The ammonia injection range of the ammonia injection device can cover the radial section (i.e., cross section) of a specific area of ​​the inlet flue 100.

[0030] Preferably, the multiple ammonia injection nozzles are evenly distributed on the same plane, and when all ammonia injection nozzles are open, their ammonia injection range can cover the entire cross-section within a specific area, ensuring that the incoming flue gas can fully contact the ammonia and avoid excessively high nitrogen oxide (NOx) emission concentrations. For example, the multiple ammonia injection nozzles are distributed in a grid pattern on the radial cross-section of the inlet flue 100.

[0031] Preferably, there are multiple inlet velocity measuring devices, and they are located closer to the inlet of the flue duct 100 than the ammonia injection nozzles. This allows the distribution of flue gas volume to be known in advance before the flue gas reaches the ammonia injection range of the ammonia injection nozzles, enabling timely adjustment of the ammonia injection valve opening. Furthermore, the number and distribution of the inlet velocity measuring devices can be consistent with the ammonia injection nozzles. For example, the inlet velocity measuring device can be a pressure sensor, calculating the wind speed (flue gas velocity) based on the detected wind pressure. Since the flue gas concentration at the inlet is usually relatively uniform, a higher wind speed means a greater amount of flue gas passing through that location per unit time. Correspondingly, the ammonia injection nozzle at that location needs to increase the amount of ammonia injected to ensure that the flue gas concentration (NOx concentration) at that location is controlled below a specified value. Furthermore, to ensure that the ammonia injected by a single ammonia injection nozzle can cover a larger area, a rotating component can be configured for each ammonia injection nozzle. This rotating component drives the ammonia injection nozzle to adjust the ammonia injection direction, for example, directing the ammonia injection nozzle towards areas with higher flue gas concentrations.

[0032] The precision ammonia injection system also includes: a flue gas concentration detection device 3 and an outlet flow rate measurement device 4 installed in the outlet flue 200;

[0033] Specifically, in this embodiment, the flue gas concentration detection device 3 is NO. x Concentration detection device, flue gas concentration mainly refers to NO x Concentration. The flue gas concentration detection device 3 includes multiple flue gas concentration sensors 32, and the acquisition end of each flue gas concentration sensor 32 is connected to a corresponding acquisition branch pipe 31 with a valve (e.g., Figure 2 As shown in the diagram, all flue gas concentration sensors 32 are connected to the flue gas measuring device 33, and the flue gas concentration in each sampling branch pipe 31 can be read through the flue gas measuring device 33 during use. The valves of the flue gas measuring device 33, the flue gas concentration sensors 32 and the sampling branch pipes are electrically connected to the control device 5; multiple sampling branch pipes 31 are evenly distributed on the sampling surface of the outlet flue duct 200.

[0034] Specifically, there are multiple outlet flow velocity measuring devices 4, and pressure sensors can also be used to calculate the outlet wind speed (flue gas velocity) based on the detected wind pressure.

[0035] The arrangement of the collection branch pipe 31 and the outlet flow rate measuring device 4 can refer to that of the ammonia spray nozzle and the outlet flow rate measuring device 4, using the same quantity and grid arrangement method.

[0036] The precision ammonia injection system further includes: a control device 5; the inlet flow rate measuring device, the flue gas concentration detection device 3, the outlet flow rate measuring device 4, and the ammonia injection valve are electrically connected to the control device 5; the control device 5 is used to acquire the inlet flow rate information fed back by the inlet flow rate measuring device, and to determine whether the opening of the ammonia injection valve needs to be adjusted based on the inlet flow rate information; and, when the opening of the ammonia injection valve needs to be adjusted, it is used to acquire the flue gas concentration information fed back by the flue gas concentration detection device 3 and the outlet flow rate information fed back by the outlet flow rate measuring device 4, and to determine the ammonia injection valve to be adjusted and its opening size based on the flue gas concentration information and the outlet flow rate information.

[0037] Example 2

[0038] Based on some of the structures in the precision ammonia injection system in Example 1, this example provides a precision ammonia injection method. In the method provided in this example, the data processing part can be completed by the control device 5 in Example 1.

[0039] Specifically, this embodiment provides a precise ammonia injection method, the method comprising:

[0040] S1. Obtain inlet flow velocity information using inlet flow velocity measuring device 2;

[0041] In practical applications, the inlet channel of the denitrification system has a relatively large diameter, thus requiring multiple inlet velocity measuring devices 2. Specifically, a first detection surface is radially arranged within the inlet flue 100, and multiple inlet velocity measuring devices 2 are evenly distributed at each first detection point on the first detection surface. Simultaneously, an execution surface is radially arranged within the inlet flue 100, and multiple ammonia injection nozzles 1 are evenly distributed in a grid pattern at each execution point on the execution surface. The arrangement of the first detection points is consistent with the arrangement of the execution points. That is, spatially, the ammonia injection nozzles 1 and the inlet velocity measuring devices 2 can correspond one-to-one, with each pair of ammonia injection nozzles 1 and inlet velocity measuring devices 2 responsible for the flue gas (NO) in the corresponding area. X Concentration adjustment and flow rate detection.

[0042] Due to factors such as the surrounding environment and airflow, the velocity of the flue gas entering the inlet passage may not be uniform throughout, but the NO contained in the flue gas... X The concentrations should be basically the same, therefore only an inlet flow velocity measuring device 2 needs to be installed at the inlet. The flow velocity at each first detection point reflects the NO passing through each first detection point. X The quantity. The first detection points can be distributed in a grid pattern. The value measured by the inlet velocity measuring device 2 set at the first detection point represents the flue gas velocity at the first detection point (and its vicinity). That is, each inlet velocity measuring device 2 is only responsible for detecting the flue gas velocity at its location and a small area nearby.

[0043] Specifically, the inlet flow velocity information includes the flue gas velocity at each first detection point (and its vicinity).

[0044] S2. Determine whether the opening of the ammonia injection valve needs to be adjusted based on the inlet flow rate information; specifically,

[0045] S201. Determine whether the flue gas flow field in the inlet flue 100 is uniform based on the flue gas flow velocity at various points on the detection surface.

[0046] S202. If the ammonia injection valve is not uniform, it is determined that the opening of the ammonia injection valve needs to be adjusted.

[0047] Under normal operation of a coal-fired power plant (with minimal load changes and consistent coal type), the opening degree of each ammonia injection valve is initially set based on the incoming flue gas concentration to ensure stable NOx emission compliance. However, when the load of the coal-fired power plant changes significantly or the type of coal is changed, the inlet NOx concentration and flow field distribution will fluctuate considerably. Uneven inlet flow field can lead to poor ammonia injection in some areas, resulting in uneven NOx concentration distribution at the SCR outlet. If the opening degree of each ammonia injection valve is not adjusted, it is impossible to guarantee that the emitted NOx meets the standards. If all ammonia injection valves are kept at their maximum opening to ensure NOx compliance, it is easy to waste ammonia, and excessive ammonia injection can cause ammonia escape. Excess ammonia will generate a large amount of ammonium bisulfate in the desulfurization system, causing blockage of downstream equipment, affecting stable equipment operation, and posing a safety hazard to the power plant. Therefore, this embodiment proposes a method for precise control of the ammonia injection quantity of ammonia injection head 1.

[0048] The system uses inlet flow velocity information (flue gas velocity at each first detection point (and its vicinity)) to determine whether the opening of the ammonia injection valve needs to be adjusted. If a large difference in flow velocity is detected at each first detection point, it means that the flue gas flow field within the inlet flue 100 is extremely uneven. In this case, it means that the opening of the corresponding ammonia injection valve needs to be adjusted to control the amount of ammonia injected. More ammonia needs to be injected at locations with higher flow velocities, and less ammonia needs to be injected at locations with lower flow velocities. For locations where the flow velocity change (compared to the initial state) is not significant, no adjustment is needed and the original state can be maintained.

[0049] S3. If it is necessary to adjust the opening of the ammonia injection valve, the flue gas concentration detection device 3 is used to obtain flue gas concentration information, and the outlet flow rate measurement device 4 is used to obtain outlet flow rate information.

[0050] Specifically, the outlet flue 200 has a second detection surface and a third detection surface that are close to each other along the radial direction. Multiple outlet flow velocity measuring devices 4 are evenly distributed on each second detection point of the second detection surface. The flue gas concentration detection device 3 includes multiple flue gas concentration sensors 32. The acquisition end of each flue gas concentration sensor 32 is connected to a corresponding acquisition branch pipe 31 with a valve. Multiple acquisition branch pipes 31 are evenly distributed on each third detection point of the third detection surface. The arrangement of each second detection point is consistent with the arrangement of each execution point, and the arrangement of each third detection point is consistent with the arrangement of each execution point.

[0051] S4. Determine the ammonia injection valve that needs to be adjusted and its opening degree based on the flue gas concentration information and the outlet flow rate information.

[0052] In step S2, the inlet flow rate information is used to determine whether the opening of the ammonia injection valve needs to be adjusted, or the ammonia injection valve is roughly adjusted based on its original state according to the inlet flow rate information. In this step, the ammonia injection valve is precisely controlled based on the flue gas concentration information and the outlet flow rate information.

[0053] The outlet flow rate information includes the flue gas flow rate at each second detection point, and the flue gas concentration information includes the flue gas concentration at each third detection point.

[0054] The specific implementation steps are as follows:

[0055] S401. Based on the flue gas concentration at each third detection point, determine the ammonia injection nozzle 1 that needs to be adjusted, and obtain the ammonia injection nozzle 1 to be adjusted.

[0056] S402. Obtain the flue gas velocity at the second detection point corresponding to the location of the ammonia injection nozzle 1 to be adjusted, and obtain the flue gas velocity at the location to be adjusted.

[0057] S403. Obtain the flue gas concentration at the third detection point corresponding to the location of the ammonia injection nozzle 1 to be adjusted, and obtain the flue gas concentration at the location to be adjusted.

[0058] S404. Based on the flue gas velocity and flue gas concentration at the location to be adjusted, calculate the mass of flue gas flowing at the location to be adjusted per unit time.

[0059] S405. Determine the amount of ammonia to be injected from the ammonia injection nozzle 1 based on the flue gas quality.

[0060] S406. Determine the opening degree of the ammonia injection valve corresponding to the ammonia injection nozzle 1 to be adjusted based on the ammonia injection quantity.

[0061] This step mainly includes two parts: first, identifying the ammonia injection nozzle 1 whose ammonia injection valve opening needs adjustment; and second, determining the opening of the ammonia injection valve. Regarding the second point, as explained in the previous step, it involves calculating the flue gas mass passing through each execution point (second detection point / third detection point) per unit time at the location to be adjusted (corresponding to each execution point position in the inlet channel) based on the flue gas mass. Then, based on the flue gas mass, the ammonia injection quantity (per unit time) of the ammonia injection nozzle 1 to be adjusted is determined. Finally, based on the ammonia injection quantity, the opening of the ammonia injection valve corresponding to the ammonia injection nozzle 1 to be adjusted is precisely controlled to achieve precise ammonia injection.

[0062] Example 3

[0063] This embodiment provides a detailed description of step S401 in Embodiment 2.

[0064] S401. Based on the flue gas concentration at each third detection point, determine the ammonia injection nozzle 1 that needs to be adjusted, and obtain the ammonia injection nozzle 1 to be adjusted.

[0065] For example, there are N third detection points on the third detection surface, the flue gas concentration detection device 3 includes N collection branch pipes 31, and the ammonia injection device includes N ammonia injection nozzles 1; then the steps for determining whether the i-th ammonia injection nozzle 1 belongs to the ammonia injection nozzle 1 to be adjusted are as follows:

[0066] A1. Calculate the average flue gas concentration value on the third detection surface.

[0067] A2. Obtain the flue gas concentration value R in the i-th sampling branch pipe 31. i

[0068] A3. Determine the flue gas concentration value R in the i-th sampling branch pipe 31. i The average flue gas concentration value on the third detection surface Does the difference between them exceed the threshold range?

[0069] A4. If it exceeds the limit, the i-th ammonia injection nozzle 1 is determined to be an adjustment nozzle, wherein the ammonia injected by the i-th ammonia injection nozzle 1 is used to change the flue gas concentration at the location of the i-th third detection point and its vicinity.

[0070] Furthermore, the flue gas concentration value R in the i-th sampling branch pipe 31 can also be used as a reference. i The average flue gas concentration value on the third detection surface The sign of the difference determines whether the ammonia injection valve of the i-th ammonia injection head 1 should be adjusted larger or smaller. Specifically, if the flue gas concentration (NOx) value R in the i-th sampling branch pipe 31... i Subtract the average flue gas concentration value on the third detection surface If the difference is positive, it means that the opening of the ammonia injection valve of the i-th ammonia injection head 1 needs to be increased; if the difference is negative, it means that the opening of the ammonia injection valve of the i-th ammonia injection head 1 needs to be decreased. The specific amount to be increased / decreased can be solved using the method provided in step S4.

[0071] Example 4

[0072] In addition to the method for obtaining the ammonia injection nozzle 1 to be adjusted provided in Example 3, this example provides another method for obtaining the ammonia injection nozzle 1 to be adjusted and a method for determining whether the opening of the ammonia injection valve needs to be increased or decreased.

[0073] S401. Based on the flue gas concentration at each third detection point, determine the ammonia injection nozzle 1 that needs to be adjusted, and obtain the ammonia injection nozzle 1 to be adjusted.

[0074] For example, there are N third detection points on the third detection surface, the flue gas concentration detection device 3 includes N collection branch pipes 31 with valves, and the ammonia injection device includes N ammonia injection nozzles 1; then the steps for determining whether the i-th ammonia injection nozzle 1 belongs to the ammonia injection nozzle 1 to be adjusted are as follows:

[0075] B1. Calculate the average flue gas concentration value on the third detection surface.

[0076] B2. Close the valve of the i-th sampling branch pipe 31, and calculate the average flue gas concentration value of the remaining third detection points. The i-th collection branch pipe 31 is used to collect the flue gas at the i-th third detection point;

[0077] B3. Determine the average flue gas concentration values ​​at the remaining third detection points. The average flue gas concentration value on the third detection surface Does the difference between them exceed the threshold range?

[0078] B4. If it exceeds the limit, the i-th ammonia injection nozzle 1 is determined to be an adjustment nozzle, wherein the ammonia injected by the i-th ammonia injection nozzle 1 is used to change the flue gas concentration at the location of the i-th third detection point and its vicinity.

[0079] Furthermore, the average flue gas concentration values ​​at the remaining third detection points can also be used as a basis. The average flue gas concentration value on the third detection surface The sign of the difference determines whether the ammonia injection valve of the i-th ammonia injection head 1 should be adjusted larger or smaller. Specifically, if the average flue gas (NOx) concentration value at all third detection points except the i-th third detection point is... Subtract the average flue gas concentration value on the third detection surface If the difference is positive, it means that the opening of the ammonia injection valve of the i-th ammonia injection head 1 needs to be reduced; if the difference is negative, it means that the opening of the ammonia injection valve of the i-th ammonia injection head 1 needs to be increased (the control logic is the opposite of that in Example 3). The specific amount to be reduced / increased can be determined using the method provided in step S4.

[0080] The advantage of this embodiment compared to the method provided in Embodiment 3 is that it is easier for the intelligent control system to adjust. In the case of extremely unbalanced flue gas concentration in the outlet channel, each ammonia injection valve can also respond quickly so that the detection value of each third detection point can approach the average value more quickly, that is, the flue gas concentration in each part of the outlet channel can reach a uniform state more quickly.

[0081] The specific principle is illustrated through the following example:

[0082] As shown in Table 1 below, there are a total of 8 third detection points on the third detection surface, and the measured concentration values ​​are as follows:

[0083] Table 1 Concentration Distribution of the Third Detection Surface

[0084]

[0085] In the table above, the third row of data ( The row represents the average value of all other measuring points besides the corresponding measuring point. For example, the value 97.2 in the second column of the third row is the average value of measuring points 2 to 8.

[0086] As shown in the table above, if the ammonia injection valve opening is controlled based on the method in Example 3, it may be impossible to achieve the desired target (average value) for the flue gas concentration at each measuring point in a short time. Since the value at measuring point 6 is much higher than the average value of 96.1125, this means that the opening of the ammonia injection valve of the 6th ammonia injection nozzle 1 corresponding to measuring point 6 needs to be increased to increase the ammonia injection rate. However, the opening of the ammonia injection valve is finite and cannot be increased or decreased indefinitely. Therefore, even if the opening is maximized, it is impossible to reduce the flue gas (NOx) concentration near this measuring point to near the average value in a short time. Similarly, for measuring point 8, the opening of the ammonia injection valve of the 8th ammonia injection nozzle 1 corresponding to measuring point 8 needs to be reduced. However, the flue gas concentration near measuring point 8 is also significantly different from the average value. Even if the ammonia injection valve of the 8th ammonia injection nozzle 1 is directly closed, it is impossible to adjust the flue gas (NOx) concentration near measuring point 8 to near the average value in a short time. Furthermore, in this embodiment, ammonia reacts with NOx to reduce the flue gas concentration in the outlet flue 200. This control process itself has a large delay. If the opening of the ammonia injection valve is adjusted significantly, it will be detrimental to the stability and balance of the control system.

[0087] Compared to Example 3, if the ammonia injection valve opening is controlled using the method provided in this example, the aforementioned situation of exceeding the adjustment range of a single ammonia injection nozzle 1 does not occur. As shown in Table 1 above, The values ​​are not significantly different from the average value, and are all within the adjustable range of each ammonia injection head 1. Essentially, this distributes the pressure for adjusting the flue gas concentration across all ammonia injection valves, rather than adjusting the flue gas concentration in a specific area by significantly increasing or decreasing the opening of a particular ammonia injection valve. By controlling the opening of each ammonia injection valve within its adjustable range, and simultaneously adjusting all ammonia injection valves whose differences exceed the threshold range, the flue gas concentration at each detection point can quickly reach the desired value, achieving rapid and precise control.

[0088] In addition, in practical applications, the NOx concentration released into the air needs to be below 50 mg / m³. 3 The above data are for illustrative purposes only. Preferably, the NOx concentration emitted into the air is 45 mg / m³. 3 At this point, the emission requirements are met, and there will be no ammonia escape due to excessive ammonia injection.

[0089] Example 5

[0090] As described in Example 4, for local areas, the flue gas concentration may exceed the adjustment range of a single ammonia injection nozzle 1. Therefore, in this example, a rotating component can be configured for any ammonia injection nozzle 1 to drive the ammonia injection nozzle 1 to rotate, i.e., change the ammonia injection direction of the ammonia injection nozzle 1. The precise ammonia injection method further includes: determining the direction of rotation and rotation angle of the rotating component based on the flue gas concentration information. For example, when the flue gas concentration is high at a certain location, exceeding the adjustment range of the ammonia injection nozzle 1 at that location, the ammonia injection direction of other ammonia injection nozzles 1 nearby can be changed to increase the injection volume directed to that location, thereby increasing the upper limit of the concentration adjustment range.

[0091] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0092] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A precision ammonia injection system, suitable for a denitrification system, said denitrification system comprising an inlet flue (100) and an outlet flue (200), characterized in that, The precision ammonia injection system includes: An ammonia injection device and an inlet flow rate measuring device (2) are installed in the inlet flue (100). The ammonia injection device includes multiple ammonia injection nozzles (1). Each ammonia injection nozzle (1) is equipped with an ammonia injection valve that can be used to control the amount of ammonia injected. The ammonia injection range of the ammonia injection device can cover the radial section of a specific area of ​​the inlet flue (100). The flue gas concentration detection device (3) and the outlet flow rate measurement device (4) are installed in the outlet flue (200). The control device (5) is electrically connected to the inlet velocity measuring device (2), the flue gas concentration measuring device (3), the outlet velocity measuring device (4), and the ammonia injection valve, respectively. The control device (5) is used to obtain the inlet velocity information fed back by the inlet velocity measuring device (2) and to determine whether the opening of the ammonia injection valve needs to be adjusted based on the inlet velocity information. When the opening of the ammonia injection valve needs to be adjusted, the control device (5) is used to obtain the flue gas concentration information fed back by the flue gas concentration measuring device (3) and the outlet velocity information fed back by the outlet velocity measuring device (4), and to determine the ammonia injection valve to be adjusted and its opening size based on the flue gas concentration information and the outlet velocity information. Each of the ammonia spray nozzles (1) is connected to a rotating component that can drive the ammonia spray nozzle (1) to rotate, and the rotating component is electrically connected to the control device (5). The control device (5) determines the direction and rotation angle of the rotating part based on the flue gas concentration information. When the flue gas concentration is high at a certain place and exceeds the adjustment range of the ammonia injection nozzle (1) at that place, the ammonia injection direction of other ammonia injection nozzles (1) in the vicinity can be changed to increase the amount of ammonia injected to that place.

2. The precision ammonia injection system according to claim 1, characterized in that, Multiple ammonia injection nozzles (1) are mapped onto the radial cross-section of the inlet flue (100) in a grid pattern.

3. The precision ammonia injection system according to claim 1, characterized in that, The precision ammonia injection system includes multiple inlet velocity measuring devices (2), which are evenly distributed on the detection surface of the inlet flue (100).

4. The precision ammonia injection system according to claim 1, characterized in that, The flue gas concentration detection device (3) includes multiple flue gas concentration sensors (32). Each flue gas concentration sensor (32) has a corresponding collection branch pipe (31) with a valve connected to its collection end. The valves of the flue gas concentration sensor (32) and the collection branch pipe (31) are electrically connected to the control device (5). Multiple collection branch pipes (31) are evenly distributed on the collection surface of the outlet flue (200).

5. A precise ammonia injection method, applicable to a denitrification system, said denitrification system comprising an inlet flue (100) and an outlet flue (200), characterized in that, The inlet flue (100) is equipped with an ammonia injection device and an inlet flow rate measuring device (2), and the outlet flue (200) is equipped with a flue gas concentration measuring device (3) and an outlet flow rate measuring device (4). The ammonia injection device includes multiple ammonia injection nozzles (1). Each ammonia injection nozzle (1) is equipped with an ammonia injection valve that can control the amount of ammonia injected. Each ammonia injection nozzle (1) is connected to a rotating component that can drive the ammonia injection nozzle (1) to rotate. The method includes: Inlet velocity information is obtained using an inlet velocity measuring device (2); Determine whether the opening of the ammonia injection valve needs to be adjusted based on the inlet flow rate information; If it is necessary to adjust the opening of the ammonia injection valve, the flue gas concentration detection device (3) is used to obtain flue gas concentration information, and the outlet flow rate measurement device (4) is used to obtain outlet flow rate information. The ammonia injection valve that needs to be adjusted and its opening degree are determined based on the flue gas concentration information and the outlet flow rate information. Based on the flue gas concentration information, the direction and rotation angle of the rotating parts are determined. When the flue gas concentration is high at a certain place and exceeds the adjustment range of the ammonia injection nozzle (1) at that place, the ammonia injection direction of other ammonia injection nozzles (1) in the vicinity can be changed to increase the amount of ammonia injected to that place.

6. The precise ammonia injection method according to claim 5, characterized in that, The inlet flue (100) is provided with a first detection surface along the radial direction, and multiple inlet flow velocity measuring devices (2) are evenly distributed on each first detection point of the first detection surface. The inlet flow velocity information includes the flue gas velocity at each first detection point. The method of determining whether to adjust the opening of the ammonia injection valve based on the inlet flow rate information includes: The uniformity of the flue gas field in the inlet flue (100) is determined based on the flue gas velocity at various points on the detection surface. If the ammonia injection is uneven, it is determined that the opening of the ammonia injection valve needs to be adjusted.

7. The precise ammonia injection method according to claim 5, characterized in that, The inlet flue (100) has an execution surface arranged radially, and multiple ammonia injection nozzles (1) are evenly distributed in a grid pattern at each execution point of the execution surface; the outlet flue (200) has a second detection surface and a third detection surface arranged radially close to each other, and multiple outlet flow rate measuring devices (4) are evenly distributed at each second detection point of the second detection surface; the flue gas concentration detection device (3) includes multiple flue gas concentration sensors (32), and each flue gas concentration sensor (32) has a corresponding sampling branch pipe (31) with a valve connected to its sampling end, and multiple sampling branch pipes (31) are evenly distributed at each third detection point of the third detection surface; the arrangement of each second detection point is consistent with the arrangement of each execution point, and the arrangement of each third detection point is consistent with the arrangement of each execution point; The outlet flow rate information includes the flue gas flow rate at each second detection point, and the flue gas concentration information includes the flue gas concentration at each third detection point; Based on flue gas concentration and outlet flow rate information, determine the ammonia injection valves that need adjustment and their opening degree, including: Based on the flue gas concentration at each third detection point, the ammonia injection nozzle (1) that needs to be adjusted is determined, and the ammonia injection nozzle (1) to be adjusted is obtained. Obtain the flue gas velocity at the second detection point corresponding to the location of the ammonia injection nozzle (1) to be adjusted, and obtain the flue gas velocity at the location to be adjusted; Obtain the flue gas concentration at the third detection point corresponding to the location of the ammonia injection nozzle (1) to be adjusted, and obtain the flue gas concentration at the location to be adjusted; Based on the flue gas velocity and flue gas concentration at the location to be adjusted, calculate the mass of flue gas flowing at the location to be adjusted per unit time. The amount of ammonia to be injected by the ammonia injection nozzle (1) to be adjusted is determined based on the flue gas quality. The opening degree of the ammonia injection valve corresponding to the ammonia injection nozzle (1) to be adjusted is determined based on the ammonia injection quantity.

8. The precise ammonia injection method according to claim 7, characterized in that, There are N third detection points on the third detection surface. The flue gas concentration detection device (3) includes N collection branch pipes (31) with valves. The ammonia injection device includes N ammonia injection nozzles (1). Based on the flue gas concentration at each third detection point, the ammonia injection nozzles (1) that require adjustment of the ammonia injection valve are determined, including: Calculate the average flue gas concentration value on the third detection surface. ; Close the valve of the i-th sampling branch pipe (31) and calculate the average flue gas concentration value of the remaining third detection points. , where the i-th collection branch pipe (31) is used to collect the flue gas at the i-th third detection point; Determine the average flue gas concentration values ​​at the remaining third detection points. The average flue gas concentration value on the third detection surface Does the difference between them exceed the threshold range? If the value exceeds the limit, the i-th ammonia injection nozzle (1) is determined to be an adjustment nozzle, wherein the ammonia injected by the i-th ammonia injection nozzle (1) is used to change the flue gas concentration at the location of the i-th third detection point and its vicinity.

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