External boiler denitrification ammonia injection control system and control method

Abstract

This invention discloses an external boiler denitrification ammonia injection control system and method. The system includes a feedforward compensation module, a fluctuation optimization module, a phase compensation module, an ammonia injection prediction module, a control optimization module, and a command generation module. Based on acquired denitrification unit operating data, including total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration, the control system uses each module to calculate feedforward compensation values, phase compensation values, fluctuation optimization values, and ammonia injection prediction values, further generating ammonia injection flow commands. This system fully considers multiple factors affecting the accuracy of ammonia injection flow, effectively improving the control precision of ammonia injection flow.

Description

Technical Field

[0001] This invention belongs to the field of denitrification technology in thermal power generation, specifically, it relates to an external boiler denitrification ammonia injection control system and control method. Background Technology

[0002] Environmental protection has become one of the most pressing issues of national and societal concern. With the increasing stringency of national environmental emission standards for nitrogen oxides (NOx) concentrations from thermal power units, denitrification systems have been successively constructed and put into operation in domestic thermal power units. These systems often employ selective catalytic reduction (SCR) denitrification devices, using ammonia as a reducing agent for ammonia injection control. The ammonia injection control system typically involves conventional logic configuration based on the existing DCS control system to control NOx concentration.

[0003] For example, thermal power units often use MACSV distributed control systems for automatic denitrification control. The controller employs cascade PID regulation, with the primary controller using outlet NOx as the controlled variable and the secondary controller using the product of the primary controller's output * (inlet NOx - setpoint) * load as the ammonia flow rate setpoint. In actual operation, these conventional configurations and model controls, while having simple algorithms, often fail to achieve ideal control results. In some cases, ammonia escape at the SCR outlet exceeds the limit, especially causing frequent sulfate scaling and blockage in the air preheater due to ammonia escape. This leads to increased differential pressure at the air preheater inlet and outlet, increased induced draft fan energy consumption, and even damage to some power plants due to excessive negative pressure in the flue. If ammonia injection consistently exceeds the limit, it further affects filter bag clogging, reducing filter bag life and severely impacting the normal operation of the denitrification system and downstream equipment. Excessive ammonia injection in the denitrification system leading to excessive ammonia residue in ash can cause serious environmental incidents, resulting in huge economic losses, environmental damage, and safety risks for power generation companies.

[0004] Therefore, how to accurately control the ammonia injection flow rate and avoid excessive ammonia injection is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The technical problem solved by this invention is: how to accurately control the ammonia injection process.

[0006] This application discloses an external boiler denitrification ammonia injection control system, which includes:

[0007] The feedforward compensation module is used to calculate the feedforward compensation value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0008] The fluctuation optimization module is used to calculate the fluctuation optimization value based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0009] The phase compensation module is used to calculate the phase compensation value based on the total coal feed, total air volume, chimney inlet concentration and the actual ammonia injection flow rate at the previous moment.

[0010] The ammonia injection prediction module is used to calculate the predicted ammonia injection value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0011] The control optimization module is used to calculate the control optimization value at the current moment based on the nitrogen oxide concentration setpoint, the fluctuation optimization value, the phase compensation value, and the ammonia injection prediction value.

[0012] The instruction generation module is used to generate the ammonia injection flow instruction at the current moment based on the control optimization value and the feedforward compensation value.

[0013] Preferably, the phase compensation module includes:

[0014] The adaptive submodule is used to calculate the state change value based on the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment.

[0015] The phase compensation submodule is used to calculate the phase compensation value based on the state change value and the chimney inlet concentration.

[0016] Preferably, the external boiler denitrification ammonia injection control system further includes:

[0017] The state variable control compensation module is used to calculate the state correction value based on the nitrogen oxide inlet concentration, the nitrogen oxide outlet concentration, the phase compensation value, the state change value, and the ammonia injection flow command at the previous moment.

[0018] The concentration setting module is used to calculate the nitrogen oxide concentration setting value based on the set control value and the state correction value.

[0019] Preferably, the external boiler denitrification ammonia injection control system further includes:

[0020] A communication module is used to send ammonia injection flow commands to the DCS control system.

[0021] Preferably, the communication module is also used to acquire the total coal feed, total air volume, nitrogen oxide inlet concentration, nitrogen oxide outlet concentration, load, load command, chimney inlet concentration, and actual ammonia injection flow rate at the previous moment collected by the DCS control system.

[0022] Preferably, the nitrogen oxide outlet concentration is obtained by measuring and analyzing from different regions using a multi-point sampling and analysis device.

[0023] This application also discloses a method for controlling ammonia injection for denitrification in an external boiler, the method comprising:

[0024] The feedforward compensation value and ammonia injection prediction value are calculated based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0025] The fluctuation optimization value is calculated based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0026] The phase compensation value is calculated based on the total coal feed, total air volume, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment.

[0027] The control optimization value at the current moment is calculated based on the nitrogen oxide concentration setpoint, the fluctuation optimization value, the phase compensation value, and the ammonia injection prediction value.

[0028] The ammonia injection flow command for the current moment is generated based on the control optimization value and the feedforward compensation value.

[0029] Preferably, the external boiler denitrification ammonia injection control method further includes:

[0030] The state change value is calculated based on the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment.

[0031] The phase compensation value is calculated based on the state change value and the concentration at the chimney inlet.

[0032] Preferably, the external boiler denitrification ammonia injection control method further includes:

[0033] The state correction value is calculated based on the nitrogen oxide inlet concentration, the nitrogen oxide outlet concentration, the phase compensation value, the state change value, and the ammonia injection flow command at the previous moment.

[0034] The nitrogen oxide concentration setpoint is calculated based on the set control value and the state correction value.

[0035] The present invention discloses an external boiler denitrification ammonia injection control system and control method, which has the following technical effects:

[0036] Based on the acquired operating data of the denitrification unit, including the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration, the control system calculates feedforward compensation value, phase compensation value, fluctuation optimization value, and ammonia injection prediction value, and further generates ammonia injection flow command. The system fully considers multiple factors affecting the accuracy of ammonia injection flow and can effectively improve the control accuracy of ammonia injection flow. Attached Figure Description

[0037] Figure 1 This is a logic block diagram of the external boiler denitrification and ammonia injection control system according to Embodiment 1 of the present invention.

[0038] Figure 2 This is a flowchart of the external boiler denitrification and ammonia injection control method according to Embodiment 2 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Before describing the various embodiments of this application in detail, the technical concept of this application is first briefly described: Existing technologies rely on distributed control systems to adjust ammonia injection flow, which cannot accurately control the ammonia injection flow and easily damages the denitrification device. Therefore, this application provides an external boiler denitrification ammonia injection control system. Based on the acquired operating data of the denitrification device, including total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration, each module of the system calculates feedforward compensation values, phase compensation values, fluctuation optimization values, and ammonia injection prediction values, further generating ammonia injection flow commands. This system fully considers multiple factors affecting the accuracy of ammonia injection flow, effectively improving the control precision of ammonia injection flow.

[0041] Specifically, such as Figure 1 As shown, the external boiler denitrification ammonia injection control system of this embodiment includes a feedforward compensation module 10, a fluctuation optimization module 20, a phase compensation module, an ammonia injection prediction module 40, a control optimization module 50, and an instruction generation module 60. The feedforward compensation module 10 is used to calculate the feedforward compensation value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The fluctuation optimization module 20 is used to calculate the fluctuation optimization value based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The phase compensation module is used to calculate the phase compensation value based on the total coal feed, total air volume, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment. The ammonia injection prediction module 40 is used to calculate the ammonia injection prediction value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The control optimization module 50 is used to calculate the control optimization value at the current moment based on the nitrogen oxide concentration setpoint, fluctuation optimization value, phase compensation value, and ammonia injection prediction value. The instruction generation module 60 is used to generate the ammonia injection flow rate instruction at the current moment based on the control optimization value and the feedforward compensation value.

[0042] Specifically, in the feedforward compensation module 10, the input parameter signal first needs to be processed. Specifically, a signal function generator is used to convert the input signal into the required functional relationship, which is then unified into a percentage. The conversion formula is as follows:

[0043]

[0044] Where X represents the current input value, X n This represents the nearest X-axis specification point to the right of the current input value, X. n-1 This represents the nearest X-axis specification point to the left of the current input value, and the Y-axis specification point. n Indicates corresponding to X n The value of the Y-axis, Y n-1 Indicates corresponding to X n-1 The value of the Y-axis, This represents the slope of the line segment corresponding to the current input, and the unit of output change for a given unit input change. X-X n-1 This indicates that the input value is higher than the value of the nearest specification on the left. a1, a2, a3, and a4 represent the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration input to the feedforward compensation module, respectively. This step involves signal conversion processing.

[0045] Furthermore, the changes in the input parameter signal are processed in advance, as follows:

[0046]

[0047] in, <s1>This represents the current input value. <S1 L > represents the input value of the operation cycle, S3 represents the value of the lead time constant T1 (seconds), S4 represents the value of the lag time constant T2 (seconds), and Y represents the current output value. L This indicates the output value of the previous operation cycle, and dt represents the module cycle time (seconds). Specification S2 is a parameter that determines whether this function is enabled. <s2>If it is logic 0, the output value will always track the input value. <s2>If the logic is 1, then the lead or lag function will be executed. This step involves calculating the change in the signal for each scan cycle and transmitting the change based on the original signal in sequence or according to its strength.

[0048] Finally, the feedforward compensation module outputs the feedforward compensation value A. O :

[0049] A O =<a5>×K1+<a6>×K2+<a7>×K3+<a8>×K4+<a9>×K5

[0050] Where K1, K2, K3, K4, and K5 represent the gain coefficients of the signal input.

[0051] Specifically, the phase compensation module includes an adaptive submodule 31 and a phase compensation submodule 32. The adaptive submodule 31 is used to calculate the state change value based on the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment; the phase compensation submodule 32 is used to calculate the phase compensation value based on the state change value and the chimney inlet concentration.

[0052] The adaptive submodule 31 integrates self-learning and adaptive intelligent control technology algorithms. First, it needs to process the input parameter signal. Specifically, it uses a signal function generator to convert the input signal into the required functional relationship, unifying it into a percentage. The conversion formula is as follows:

[0053]

[0054] Where X represents the current input value, X n This represents the nearest X-axis specification point to the right of the current input value, X. n-1 This represents the nearest X-axis specification point to the left of the current input value, and the Y-axis specification point. n Indicates corresponding to X n The value of the Y-axis, Y n-1 Indicates corresponding to X n-1 The value of the Y-axis, This represents the slope of the line segment corresponding to the current input, and the unit of output change for a given unit input change. X-X n-1 This indicates that the input value is higher than the value of the nearest specification on the left. d1, d2, d3, and d4 represent the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment, which are input to the adaptive submodule 31.

[0055] The state change value output by the adaptive submodule 31 is D0 = T(D1; D2; D3; D4), where

[0056] D1 = k 11 'f(d1,θ1)+k 12 f(d1, θ2)...

[0057] D2=k 21 'f(d1,θ1)+k 22 f(d1, θ2)...

[0058] D3=k 31 'f(d1,θ1)+k 32 f(d1, θ2)...

[0059] D4 = k 41 'f(d1,θ1)+k 42 f(d1, θ2)...

[0060] Where, k 11 ' represents the effect intensity gain coefficient in the first time period of the first input parameter, k 12 "This represents the gain coefficient of the effect intensity of the second time period of the first input parameter, and so on. The ellipsis represents the cumulative record of the first input parameter over a certain period of time (e.g., an 8-hour shift or a day). k 21 ' represents the effect intensity gain coefficient during the first time period of the second input parameter, k 22 "This represents the gain coefficient of the second time period of the second input parameter, and so on. The ellipsis represents the cumulative record of the second input parameter over a certain period of time (e.g., an 8-hour shift or 1 day). And so on, k" 31 ' represents the effect intensity gain coefficient in the first time period of the third input parameter, k 41 'Indicates the effect intensity gain coefficient in the first time period of the fourth input parameter.

[0061] Furthermore, the phase compensation submodule 32 first performs integration processing on the input data:

[0062]

[0063] The output phase compensation value is When |D1(ω π )∣e jπ When ≤1, b3=D1(ω π )+D2(ω π ).

[0064] Furthermore, the external boiler denitrification ammonia injection control system also includes a state variable control compensation module 70 and a concentration setting module 80. The state variable control compensation module 70 is used to calculate the state correction value based on the nitrogen oxide inlet concentration, nitrogen oxide outlet concentration, phase compensation value, state change value, and the ammonia injection flow command at the previous moment; the concentration setting module 80 is used to calculate the nitrogen oxide concentration setting value based on the set control value and the state correction value.

[0065] In the state variable control compensation module 70, the input parameter signal is first processed to calculate the integral cumulative change of each signal over a certain period of time.

[0066] A3=∫0 t f(a3); A4=∫0 t f(a4); B1=∫0 t f(b1); B2=∫0 t f(b2); B3=∫0 t f(b3)

[0067] Where A = A3 + A4 + B1 + B2 + B3, and t represents the time interval. Further analysis of state variable changes is then performed:

[0068] A3 1 =K2 / K3*A4;

[0069] A4 1 = -1 / T4*A4 + K2 / T2*B1;

[0070] B1 1 =-1 / T3*B1-K1*K4 / T1*A3+K3 / T3*B2;

[0071] B2 1 =-1 / T2*B2-K1*K4 / T1*B1-K4*K5 / T4*B2+K4 / T4*B3;

[0072] B3 1 =-1 / T1*B3-K1*K5 / T1*A3-K2*K5 / T2*A4 1 -K3*K5 / T3*B1+K1 / T1*A

[0073] The output state correction value is B O =f(A3) 1 A4 1 B1 1 B2 1 B3 1 ), where T1-T5 are the time constants of each input signal; K1-K5 are the gain coefficients of each function.

[0074] The nitrogen oxide concentration setting value output by the concentration setting module 80 is C0 = C1 + B. O

[0075] C1 represents the set control value.

[0076] Specifically, in the fluctuation optimization module 20, the input parameter signal first needs to be processed. This is done by using a signal function generator to convert the input signal into the required functional relationship, which is then standardized as a percentage. The conversion formula is as follows:

[0077]

[0078] Where X represents the current input value, X n This represents the nearest X-axis specification point to the right of the current input value, X. n-1 This represents the nearest X-axis specification point to the left of the current input value, and the Y-axis specification point. n Indicates corresponding to X n The value of the Y-axis, Y n-1 Indicates corresponding to X n-1 The value of the Y-axis, This represents the slope of the line segment corresponding to the current input, and the unit of output change for a given unit input change. X-X n-1 This indicates that the input value is higher than the nearest specification number on the left. e1, e2, e3, and e4 represent the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration input to the fluctuation optimization module 20.

[0079] Further optimization is needed:

[0080] E 11 =k 11 f(e1, e2) + k 12 f(e2, e3) + k 13 f(e3, e4) + k 14 f(e4, e1) + k 15 f(e1, e3) + k 16 f(e2, e4)

[0081] E 21 =k 21 f(e1, e2) + k 22 f(e2, e3) + k 23 f(e3, e4) + k 24 f(e4, e1) + k 25 f(e1, e3) + k 26 f(e2, e4)

[0082] E 31 =k 31 f(e1, e2) + k 32 f(e2, e3) + k 33 f(e3, e4) + k 34 f(e4, e1) + k 35 f(e1, e3) + k 36 f(e2, e4)

[0083] E 41 =k 41 f(e1, e2) + k 42 f(e2, e3) + k 43 f(e3, e4) + k 44 f(e4, e1) + k 45 f(e1, e3) + k 46 f(e2, e4)

[0084] The fluctuation optimization value output by fluctuation optimization module 20 is: E0 = Min(E 11 E 21 E 31 E 41 ).

[0085] By setting up the fluctuation optimization module 20, the fluctuation of nitrogen oxide concentration is predicted in real time according to the change pattern of the unit's AGC command. The control algorithm is adjusted to always keep it in the opposite phase with the change of AGC command, reducing unnecessary control adjustments and significantly reducing ammonia consumption.

[0086] Specifically, in the ammonia injection prediction module 20, the input parameter signal first needs to be processed. This is done by using a signal function generator to convert the input signal into the required functional relationship, which is then standardized as a percentage. The conversion formula is as follows:

[0087]

[0088] Where X represents the current input value, X n This represents the nearest X-axis specification point to the right of the current input value, X. n-1 This represents the nearest X-axis specification point to the left of the current input value, and the Y-axis specification point. n Indicates corresponding to X n The value of the Y-axis, Y n-1 Indicates corresponding to X n-1 The value of the Y-axis, This represents the slope of the line segment corresponding to the current input, and the unit of output change for a given unit input change. X-X n-1 This indicates that the input value is higher than the value of the nearest specification on the left. e3, e4, g1, and g2 represent the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration input into the ammonia injection prediction module 20.

[0089] The time-varying function of the prediction model in ammonia injection prediction module 20 is:

[0090] G 11 =f(g1, θ1)+f(g1, θ2)...f(g1, θ t )

[0091] G 21 =f(g2, θ1)+f(g2, θ2)...f(g2, θ t )

[0092] E 31 =f(e3, θ1)+f(e3, θ2)...f(e3, θ t )

[0093] E 41 =f(e4, θ1)+f(e4, θ2)...f(e4, θ t )

[0094] The calculation process for the relationship between the time-varying function and the input vector is as follows:

[0095] G1=k1f(G 11 g1)

[0096] G2=k2f(G 21 g2)

[0097] E3=k3f(E 31 e3)

[0098] E4=k4f(E 41 e4)

[0099] The predicted values ​​of the prediction model are:

[0100] Next, the ammonia injection prediction module 20 outputs the ammonia injection prediction value as follows:

[0101]

[0102] Where m is the number of samples, Y i These are actual measured values.

[0103] The current control optimization value output by control optimization module 50 is:

[0104] I0 = K i (K1B3, K2C0, K3E0, K4G0)

[0105] Wherein, B3, C0, E0, and G0 represent the phase compensation value, nitrogen oxide concentration setpoint, fluctuation optimization value, and ammonia injection prediction value, respectively.

[0106] Finally, the instruction generation module 50 determines the control optimization value I0 and the feedforward compensation value A based on the current control optimization value I0 and the feedforward compensation value A. O Generate the ammonia injection flow rate command for the current moment.

[0107] The adjustment target of the ammonia injection flow command in this embodiment is the measured value of nitrogen oxide concentration at the chimney inlet, which can solve the problem of large pure delay in inertial system control of ammonia injection control system.

[0108] Furthermore, the external boiler denitrification ammonia injection control system in this embodiment also includes a communication module. This module sends ammonia injection flow commands to the DCS control system. The communication module also acquires operating parameters collected by the DCS control system, including total coal feed, total air volume, nitrogen oxide inlet concentration, nitrogen oxide outlet concentration, load, load command, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment. These operating parameters are then transmitted to the corresponding modules. This allows for on-site control using existing equipment, enabling control based on future changes in the controlled quantity, effectively adjusting the process in advance, and significantly improving the closed-loop stability and anti-disturbance capability of the denitrification system.

[0109] For example, in this embodiment one, the nitrogen oxide outlet concentration is obtained by measuring and analyzing from different areas using a multi-point sampling and analysis device, which can improve the measurement accuracy of the data.

[0110] The external boiler denitrification ammonia injection control system disclosed in Embodiment 1, through optimized ammonia injection control, minimizes NH3 escape and reduces or eliminates air preheater scaling and blockage while ensuring that nitrogen oxide emission concentrations do not exceed standards. This reduces the ammonia injection amount per unit of power generation, decreasing ammonia consumption per unit of power generation by 10-25%, saving on environmentally friendly power generation costs and avoiding environmental pollution. Actual measurements show that the average deviation between the actual and expected steady-state nitrogen oxide concentration at the denitrification SCR outlet is less than 10 mg / Nm3. Under the dynamic indicators meeting the Ministry of Environmental Protection's assessment standards, the setpoint for operating nitrogen oxide concentration can be increased by 20-30 mg / Nm3. 3 This reduces or eliminates ammonia escape caused by the automatic ammonia injection adjustment system.

[0111] This second embodiment also discloses a method for controlling ammonia injection for denitrification in an external boiler, which includes the following steps:

[0112] Step S10: Calculate the feedforward compensation value and ammonia injection prediction value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration.

[0113] Step S20: Calculate the fluctuation optimization value based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration;

[0114] Step S30: Calculate the phase compensation value based on the total coal feed, total air volume, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment;

[0115] Step S40: Calculate the control optimization value at the current moment based on the nitrogen oxide concentration setpoint, fluctuation optimization value, phase compensation value, and ammonia injection prediction value;

[0116] Step S50: Generate the ammonia injection flow command for the current moment based on the control optimization value and the feedforward compensation value.

[0117] The detailed calculation process of each step S50 above can be found in the relevant description of Embodiment 1, and will not be repeated here.

[0118] The specific embodiments of the present invention have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that modifications and improvements can be made to these embodiments without departing from the principles and spirit of the present invention as defined by the claims and their equivalents, and such modifications and improvements should also be within the protection scope of the present invention.

Claims

1. An external boiler denitrification ammonia injection control system, characterized in that, The external boiler denitrification ammonia injection control system includes: The feedforward compensation module is used to calculate the feedforward compensation value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The fluctuation optimization module is used to calculate the fluctuation optimization value based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The phase compensation module is used to calculate the phase compensation value based on the total coal feed, total air volume, chimney inlet concentration and the actual ammonia injection flow rate at the previous moment. The ammonia injection prediction module is used to calculate the predicted ammonia injection value based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The control optimization module is used to calculate the control optimization value at the current moment based on the nitrogen oxide concentration setpoint, the fluctuation optimization value, the phase compensation value, and the ammonia injection prediction value. The instruction generation module is used to generate the ammonia injection flow instruction at the current moment based on the control optimization value and the feedforward compensation value.

2. The external boiler denitrification ammonia injection control system according to claim 1, characterized in that, The phase compensation module includes: The adaptive submodule is used to calculate the state change value based on the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment. The phase compensation submodule is used to calculate the phase compensation value based on the state change value and the chimney inlet concentration.

3. The external boiler denitrification ammonia injection control system according to claim 2, characterized in that, The external boiler denitrification ammonia injection control system also includes: The state variable control compensation module is used to calculate the state correction value based on the nitrogen oxide inlet concentration, the nitrogen oxide outlet concentration, the phase compensation value, the state change value, and the ammonia injection flow command at the previous moment. The concentration setting module is used to calculate the nitrogen oxide concentration setting value based on the set control value and the state correction value.

4. The external boiler denitrification ammonia injection control system according to claim 1, characterized in that, The external boiler denitrification ammonia injection control system also includes: A communication module is used to send ammonia injection flow commands to the DCS control system.

5. The external boiler denitrification ammonia injection control system according to claim 4, characterized in that, The communication module is also used to acquire the total coal feed, total air volume, nitrogen oxide inlet concentration, nitrogen oxide outlet concentration, load, load command, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment from the DCS control system.

6. The external boiler denitrification ammonia injection control system according to claim 1, characterized in that, The nitrogen oxide outlet concentration was obtained by measuring and analyzing it from different areas using a multi-point sampling and analysis device.

7. A method for controlling ammonia injection in an external boiler denitrification system, characterized in that, The external boiler denitrification ammonia injection control method includes: The feedforward compensation value and ammonia injection prediction value are calculated based on the total coal feed, total air volume, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The fluctuation optimization value is calculated based on the load, load command, nitrogen oxide inlet concentration, and nitrogen oxide outlet concentration. The phase compensation value is calculated based on the total coal feed, total air volume, chimney inlet concentration, and the actual ammonia injection flow rate at the previous moment. The control optimization value at the current moment is calculated based on the nitrogen oxide concentration setpoint, the fluctuation optimization value, the phase compensation value, and the ammonia injection prediction value. The ammonia injection flow command for the current moment is generated based on the control optimization value and the feedforward compensation value.

8. The method for controlling ammonia injection for denitrification in an external boiler according to claim 7, characterized in that, The external boiler denitrification ammonia injection control method also includes: The state change value is calculated based on the total coal feed, total air volume, chimney inlet concentration, and ammonia injection flow rate at the previous moment. The phase compensation value is calculated based on the state change value and the concentration at the chimney inlet.

9. The method for controlling ammonia injection for denitrification in an external boiler according to claim 8, characterized in that, The external boiler denitrification ammonia injection control method also includes: The state correction value is calculated based on the nitrogen oxide inlet concentration, the nitrogen oxide outlet concentration, the phase compensation value, the state change value, and the ammonia injection flow command at the previous moment. The nitrogen oxide concentration setpoint is calculated based on the set control value and the state correction value.

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