Ammonia injection control method and device for boiler SCR denitration system
By combining error correction and a preset NOx concentration prediction model with a PID controller, the ammonia-nitrogen ratio and ammonia injection rate are calculated, solving the emission problem caused by NOx concentration fluctuations in the SCR denitrification system, achieving precise control of ammonia injection rate, and avoiding excessive emissions and ammonia escape.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG ELECTRIC POWER SCI RES INST ENERGY TECH CO LTD
- Filing Date
- 2023-09-12
- Publication Date
- 2026-05-19
AI Technical Summary
In existing SCR denitrification systems, the NOx concentration at the denitrification outlet is unstable over time, resulting in poor ammonia injection control and a tendency for emissions to exceed standards or for ammonia to escape significantly, making it difficult to achieve the desired control effect.
By employing a prediction model based on error correction and preset NOx concentration, combined with a PID controller, the ammonia-nitrogen ratio and ammonia injection rate are calculated through multiple regression analysis to generate accurate ammonia injection valve control commands and precisely control the ammonia injection rate.
It achieves precise control of ammonia injection, avoids excessive emissions and ammonia escape, and significantly improves the control effect of the SCR denitrification system.
Smart Images
Figure CN117101404B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of coal-fired boiler technology, and in particular to a method and apparatus for controlling ammonia injection in a boiler SCR denitrification system. Background Technology
[0002] Currently, coal-fired boilers or gas-fired waste heat boilers primarily employ Selective Catalytic Reduction (SCR) denitrification systems for NOx removal and control. The reducing agent is either liquid ammonia or urea, with urea requiring pyrolysis to generate ammonia. SCR denitrification systems typically have two main ammonia injection valves, one on each side, to control NOx emission concentrations at the system outlet and chimney. In recent years, some SCR denitrification systems have installed online adjustable ammonia injection branch valves and outlet NOx monitoring systems to control the NOx concentration distribution at the outlet, ensuring uniform NOx concentration distribution after the reaction and preventing excessive ammonia escape from certain areas. The effectiveness of the ammonia injection branch valves in adjusting the spatial uniformity of NOx through the outlet NOx monitoring system depends on the temporal uniformity of the NOx concentration at the outlet. That is, only when the NOx concentration at the outlet is stable over time can spatial uniformity adjustment be achieved through cyclic monitoring of the NOx concentration. Figure 3 As shown.
[0003] The unstable variation of the average NOx concentration at the denitrification outlet over time leads to incorrect adjustments of the ammonia injection branch valves during routine monitoring. Furthermore, with the increasing operating time of the SCR denitrification system, many boilers experience severe ammonia escape, causing problems such as air preheater blockage and fan blade jamming. This is directly related to poor control of the ammonia injection main valve and large fluctuations in the average NOx concentration at the denitrification outlet. Existing SCR denitrification systems generally have poor ammonia injection control performance, frequently exhibiting instantaneous values of excessively high or low NOx concentrations in the clean flue gas. High concentrations result in emissions exceeding standards, while low concentrations cause ammonia escape. Some SCR denitrification systems employ a portion of predictive control combined with feedback control of clean flue gas NOx concentration, but due to a lack of understanding of the key factors in denitrification control, they also struggle to achieve ideal results. Summary of the Invention
[0004] This application provides a method and device for controlling ammonia injection in a boiler SCR denitrification system, which solves the technical problem that the average NOx concentration at the denitrification outlet of the existing SCR denitrification system is unstable over time, which either leads to excessive emissions or large ammonia escape, making it difficult to achieve ideal control results.
[0005] In view of this, the first aspect of this application provides a method for controlling ammonia injection in a boiler SCR denitrification system, comprising:
[0006] The predicted NOx concentration at the inlet of the boiler SCR denitrification system is determined based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction.
[0007] A multiple regression analysis was performed based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, the flue gas volume flow rate, the flue gas temperature, and the unit load, and the ammonia-to-nitrogen ratio was calculated.
[0008] The ammonia injection amount is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction factor.
[0009] A PID controller is used to generate ammonia injection valve control commands based on the ammonia injection quantity, and ammonia injection control is implemented based on the ammonia injection valve control commands.
[0010] Preferably, the predicted NOx concentration at the inlet of the boiler SCR denitrification system is determined based on the correction error and a preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction, and includes:
[0011] The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained.
[0012] The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the boiler SCR denitrification system inlet monitoring system.
[0013] Based on the correction error, the initial NOx concentration prediction value is corrected to obtain the NOx concentration prediction value.
[0014] Preferably, the step of performing a multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, flue gas volumetric flow rate, flue gas temperature, and unit load, and calculating the ammonia-to-nitrogen ratio, includes:
[0015] The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load.
[0016] After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function.
[0017] The ammonia nitrogen ratio at different times is calculated based on the multivariate linear function and the preset ammonia nitrogen ratio function.
[0018] Preferably, the step of calculating the ammonia injection amount based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient includes:
[0019] The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the amount of coal fed into the boiler.
[0020] The initial ammonia injection rate is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, the flue gas volumetric flow rate, and the net flue gas volume.
[0021] The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount.
[0022] Preferably, the step of calculating the ammonia injection amount based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient further includes:
[0023] Determine the measured value and set value of NOx concentration at the outlet of the boiler SCR denitrification system, respectively;
[0024] A PID controller is used to generate an ammonia injection correction coefficient based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration.
[0025] The second aspect of this application provides an ammonia injection control device for a boiler SCR denitrification system, comprising:
[0026] The concentration prediction unit is used to determine the predicted NOx concentration at the inlet of the boiler SCR denitrification system based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction.
[0027] The first calculation unit is used to perform multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, the flue gas volume flow rate, the flue gas temperature and the unit load, and to calculate the ammonia-nitrogen ratio.
[0028] The second calculation unit is used to calculate the amount of ammonia to be injected based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient.
[0029] The ammonia injection control unit is used to generate ammonia injection valve control commands based on the ammonia injection quantity using a PID controller, and to implement ammonia injection control based on the ammonia injection valve control commands.
[0030] Preferably, the concentration prediction unit is specifically used for:
[0031] The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained.
[0032] The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the boiler SCR denitrification system inlet monitoring system.
[0033] Based on the correction error, the initial NOx concentration prediction value is corrected to obtain the NOx concentration prediction value.
[0034] Preferably, the first computing unit is specifically used for:
[0035] The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load.
[0036] After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function.
[0037] The ammonia nitrogen ratio at different times is calculated based on the multivariate linear function and the preset ammonia nitrogen ratio function.
[0038] Preferably, the second computing unit is specifically used for:
[0039] The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the amount of coal fed into the boiler.
[0040] The initial ammonia injection rate is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, the flue gas volumetric flow rate, and the net flue gas volume.
[0041] The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount.
[0042] Preferably, it also includes:
[0043] The parameter determination unit is used to determine the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration of the boiler SCR denitrification system, respectively.
[0044] The correction calculation unit is used to generate an ammonia injection correction coefficient using a PID controller based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration.
[0045] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:
[0046] This application provides a method for controlling ammonia injection in a boiler SCR denitrification system, comprising: determining the predicted NOx concentration at the inlet of the boiler SCR denitrification system based on a correction error and a preset NOx concentration prediction model, wherein the correction error is calculated based on the lag time between measurement and prediction; performing a multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, flue gas volume flow rate, flue gas temperature, and unit load, and calculating the ammonia-to-nitrogen ratio; calculating the ammonia injection quantity based on the predicted NOx concentration, the ammonia-to-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient; and using a PID controller to generate ammonia injection valve control commands based on the ammonia injection quantity, and implementing ammonia injection control based on the ammonia injection valve control commands.
[0047] This application provides an ammonia injection control method for a boiler SCR denitrification system. It fully considers the measurement delay of NOx concentration at the boiler SCR denitrification system inlet. By combining the predicted NOx concentration value and the calculated ammonia-to-nitrogen ratio with the target NOx concentration value, the ammonia injection quantity is accurately calculated, and based on this, accurate and reliable ammonia injection valve control commands are generated. This process analyzes the key factors in the ammonia injection valve control process, ensuring the accuracy of the ammonia injection control commands and thus avoiding excessive emissions or large ammonia escape. Therefore, this application can solve the technical problem of large fluctuations in the average NOx concentration at the denitrification outlet of existing SCR denitrification systems over time, leading to either excessive emissions or large ammonia escape, making it difficult to achieve ideal control results. Attached Figure Description
[0048] Figure 1 A schematic flowchart illustrating an ammonia injection control method for a boiler SCR denitrification system provided in this application embodiment;
[0049] Figure 2 A schematic diagram of the structure of an ammonia injection control device for a boiler SCR denitrification system provided in this application embodiment;
[0050] Figure 3 Example diagram of NOx concentration distribution at different times at the outlet of an existing SCR denitrification system, provided as background for this application. Detailed Implementation
[0051] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.
[0052] For easier understanding, please refer to Figure 1Embodiment 1 of an ammonia injection control method for a boiler SCR denitrification system provided in this application includes:
[0053] Step 101: Determine the predicted NOx concentration at the inlet of the boiler SCR denitrification system based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction.
[0054] Further, step 101 includes:
[0055] The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained.
[0056] The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the inlet monitoring system of the boiler SCR denitrification system;
[0057] The initial NOx concentration prediction value is corrected based on the correction error to obtain the NOx concentration prediction value.
[0058] A pre-set NOx concentration prediction model can be used to predict the NOx concentration at the inlet of the boiler SCR denitrification system in real time; if it is at time j, then the initial predicted NOx concentration value at time j, NOx1,yc(j), can be obtained. The measured NOx concentration value detected by the boiler SCR denitrification system inlet monitoring system can be expressed as NOx1. Based on NOx1,yc(j) and the lag time D between the measurement and prediction of the boiler SCR denitrification system inlet expressed by NOx1,yc(j), and NOx1, the following can be defined. j1 The correction error DNOx can be calculated. 1j :
[0059] DNOx 1j =NOx1(j)-NOx1,yc(jD) j1 )
[0060] NOx1(j) is the measured NOx concentration at time j. It is understandable that the calculated correction error DNOx... 1j A moving average process is required over a certain period of time, which is then used to correct the initial NOx concentration prediction value, resulting in the corrected NOx concentration prediction value. The specific correction process is expressed as follows:
[0061]
[0062] Where m is the moving average time in seconds; NOx1,j,xz is the predicted NOx concentration at time j.
[0063] Lag time D j1This can be directly determined through experimentation. The specific procedure is as follows: First, disconnect the exhaust port of the continuous emission monitoring system to draw in atmospheric gas; at this point, the instrument reading will be 0. Then, introduce a certain concentration of NOx standard gas into the exhaust port and start timing. Next, as the instrument reading rises from 0 to 90% of the standard gas concentration, stop timing. Record the time as D. j1 .
[0064] Step 102: Perform a multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, the flue gas volume flow rate, the flue gas temperature, and the unit load, and calculate the ammonia-nitrogen ratio.
[0065] Further, step 102 includes:
[0066] The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load.
[0067] After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function.
[0068] The ammonia nitrogen ratio at different times is calculated based on a multivariate linear function and a preset ammonia nitrogen ratio function.
[0069] It should be noted that this embodiment involves various calculations of the boiler SCR denitrification system, so it is necessary to obtain various relevant data in the system in advance, including but not limited to the unit load Pi, coal feed rate GMi, total air volume GAI, NOx concentration measurement value NOx1i of the i-th data set, oxygen content O2,1i at the inlet of the denitrification system, NOx concentration NOx2i measured in the clean flue gas, oxygen content O2,2i measured in the clean flue gas, current ammonia injection rate GNH3i, and flue gas temperature T1i at the inlet of the denitrification system, etc. These data can be divided into data sets in 1-second intervals and used in subsequent calculations.
[0070] The average values of NOx concentration at the inlet of the boiler SCR denitrification system, flue gas volume flow rate, flue gas temperature, and unit load can all be calculated. Taking the average unit load as an example...
[0071]
[0072] Where n represents the number of generating units; other parameters can be averaged using this method to obtain the average NOx concentration measurement. Average flue gas volume flow rate Average flue gas temperature Such data can be combined into a set of data, and multiple sets of data can be obtained using this method, enabling multiple sets of data to cover different unit loads.
[0073] Obtain the average value of multiple NOx concentration measurements Average flue gas volume flow rate Average flue gas temperature and unit load average Then, multiple regression analysis was performed to obtain the multiple linear function:
[0074]
[0075] The preset ammonia-nitrogen ratio function is expressed as:
[0076]
[0077] Where Qy1i is the inlet flue gas volumetric flow rate of the denitrification system, NOx1i is the measured NOx concentration in the i-th data set, Qy2i is the net flue gas volume at the chimney inlet, η is the ammonia consumption correction coefficient considering ammonia slip within the calculation time, and n is the calculation time in seconds, which is also the number of data sets since one set of data is acquired per second. The calculation method for Qy1i is as follows:
[0078] Qy1i=Gy1i÷ρ y
[0079] Where, ρ y The standard density of flue gas can be taken as 1.36 kg / m³. 3 Gy1i is the inlet flue gas volume of the denitrification system, and the calculation process is as follows:
[0080] Gy1i=GMi*ki+GAi
[0081] Where ki is the correction factor for the moisture content Mti and ash content Aari of the coal fed into the furnace.
[0082] The calculation method for Qy2i is as follows:
[0083]
[0084] The method for calculating η is as follows:
[0085] η = f1(x)
[0086]
[0087] Where f1(x) is a piecewise function, x is the standard deviation of a set of NOx2i. If x is greater than 20, then η = 0.96; if x is between 10 and 20, then η = 0.98; if x is less than 10, then η = 1.0.
[0088] K is calculated over 24 hours using a time-sliding method based on a preset ammonia-nitrogen ratio function. NH3NOx(24) Substituting multiple sets of data from 24 hours—namely, multiple NOx concentration measurements (NOx1), flue gas volumetric flow rate (Qy1), average flue gas temperature (T), and average unit load (P)—into a multivariate linear function, the linear regression ammonia-to-nitrogen ratio (K) is calculated. NH3NOx(回归) Therefore, the ammonia-nitrogen ratio at any time j can be expressed as:
[0089]
[0090] Where Pj is the unit load at time j, and the other parameters are deduced similarly.
[0091] Step 103: Calculate the ammonia injection amount based on the predicted NOx concentration, ammonia-nitrogen ratio, target NOx concentration, and ammonia injection correction factor.
[0092] Further, step 103 includes:
[0093] The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the amount of coal fed into the boiler.
[0094] The initial ammonia injection rate is calculated based on the predicted NOx concentration, ammonia-nitrogen ratio, target NOx concentration, flue gas volumetric flow rate, and net flue gas volume.
[0095] The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount.
[0096] Qy1i represents the inlet flue gas volumetric flow rate of the denitrification system, and Qy2i represents the net flue gas volumetric flow rate at the chimney inlet. Both parameters have been calculated, and the current flue gas volumetric flow rate and net flue gas volumetric flow rate can be calculated in real time. The process of calculating the initial ammonia injection rate based on the predicted NOx concentration, ammonia-nitrogen ratio, target NOx concentration, flue gas volumetric flow rate, and net flue gas volumetric flow rate is expressed as follows:
[0097] G0 SP,NH3 =Kj×(Qy1j×NOx1,xz-Qy2j×NOx2sp)
[0098] Wherein, NOx1,xz represents the predicted NOx concentration, Kj represents the ammonia-nitrogen ratio, and NOx2,sp represents the target NOx concentration; G0 SP,NH3 This is the initial ammonia injection rate.
[0099] In this embodiment, the ammonia injection correction factor is expressed as K1. NH3 The ammonia injection correction factor K1 is used. NH3 Correction calculations are performed on the initial ammonia injection rate:
[0100] G SP,NH3 =G0 SP,NH3 ×K1 NH3
[0101] Among them, G SP,NH3 This is the amount of paint sprayed after correction.
[0102] Furthermore, step 103, preceding the following, also includes:
[0103] Determine the measured value and set value of NOx concentration at the outlet of the boiler SCR denitrification system, respectively;
[0104] A PID controller is used to generate an ammonia injection correction coefficient based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration.
[0105] Determining the measured NOx concentration (NOxpv) and setpoint (NOxsp) at the outlet of the boiler's SCR denitrification system refers to establishing the temporal and quantitative correspondence between these parameter values. This embodiment first requires obtaining the temporal and quantitative correspondence between the measured NOx concentration (NOx2) in the clean flue gas and the measured NOx concentration (NOxpv) at the outlet of the boiler's SCR denitrification system.
[0106] NOxpv(jD j2 )=f3(NOx2j)
[0107] Where j represents the current time, and D j2 The time difference between the measured NOx concentration (NOxpv) at the outlet of the denitrification system and the measured NOx concentration (NOx2) in the clean flue gas can be obtained using the experimental method described above. The f3 function is obtained through correlation analysis of a set of NOxpv and NOx2 values, and its functional relationship is specifically expressed as follows:
[0108] NOxpv=K1*NOx2+K2
[0109] Where K1 and K2 are coefficients.
[0110] Based on the above formula, the NOx concentration setpoint at the outlet of the denitrification system corresponding to the NOx2sp setpoint in the clean flue gas NOx concentration can be calculated:
[0111] NOxsp = f3(NOx2sp)
[0112] A PID controller is used to generate an ammonia injection correction coefficient K1 based on the measured and setpoint values of the outlet NOx concentration. NH3 The process can be expressed as:
[0113] K1 NH3 =PID(NOxsp,NOxpv)
[0114] Step 104: Use a PID controller to generate ammonia injection valve control commands based on the ammonia injection quantity, and implement ammonia injection control based on the ammonia injection valve control commands.
[0115] The process of generating control commands for the ammonia injection valve is expressed as follows:
[0116] V NH3 =PID(G SP,NH3 G PV,NH3 )
[0117] Among them, G PV,NH3 This refers to the actual amount of paint sprayed in real time.
[0118] This application provides an ammonia injection control method for a boiler SCR denitrification system. It fully considers the measurement delay of NOx concentration at the boiler SCR denitrification system inlet. By combining the predicted NOx concentration value and the calculated ammonia-to-nitrogen ratio with the target NOx concentration value, the ammonia injection quantity is accurately calculated, and an accurate and reliable ammonia injection valve control command is generated based on this. This process analyzes the key factors in the ammonia injection valve control process, ensuring the accuracy of the ammonia injection control command and thus avoiding excessive emissions or large ammonia escape. Therefore, this application can solve the technical problem of large fluctuations in the average NOx concentration at the denitrification outlet of existing SCR denitrification systems over time, leading to either excessive emissions or large ammonia escape, making it difficult to achieve ideal control results.
[0119] For easier understanding, please refer to Figure 2 This application provides an embodiment of an ammonia injection control device for a boiler SCR denitrification system, comprising:
[0120] The concentration prediction unit 201 is used to determine the predicted value of NOx concentration at the inlet of the boiler SCR denitrification system based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction.
[0121] The first calculation unit 202 is used to perform multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, the flue gas volume flow rate, the flue gas temperature and the unit load, and to calculate the ammonia-nitrogen ratio.
[0122] The second calculation unit 203 is used to calculate the amount of ammonia to be injected based on the predicted value of NOx concentration, the ammonia-nitrogen ratio, the target value of NOx concentration and the ammonia injection correction coefficient.
[0123] The ammonia injection control unit 204 is used to generate ammonia injection valve control commands based on the ammonia injection quantity using a PID controller, and to implement ammonia injection control based on the ammonia injection valve control commands.
[0124] Furthermore, the concentration prediction unit 201 is specifically used for:
[0125] The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained.
[0126] The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the inlet monitoring system of the boiler SCR denitrification system;
[0127] The initial NOx concentration prediction value is corrected based on the correction error to obtain the NOx concentration prediction value.
[0128] Furthermore, the first computing unit 202 is specifically used for:
[0129] The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load.
[0130] After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function.
[0131] The ammonia nitrogen ratio at different times is calculated based on a multivariate linear function and a preset ammonia nitrogen ratio function.
[0132] Furthermore, the second computing unit 203 is specifically used for:
[0133] The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the boiler coal feed rate.
[0134] The initial ammonia injection rate is calculated based on the predicted NOx concentration, ammonia-nitrogen ratio, target NOx concentration, flue gas volumetric flow rate, and net flue gas volume.
[0135] The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount.
[0136] Furthermore, it also includes:
[0137] The parameter determination unit 205 is used to determine the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration of the boiler SCR denitrification system, respectively.
[0138] The correction calculation unit 206 is used to generate an ammonia injection correction coefficient based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration using a PID controller.
[0139] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.
[0140] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.
[0141] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0142] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for executing all or part of the steps of the methods described in the various embodiments of this application through a computer device (which may be a personal computer, server, or network device, etc.). The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.
[0143] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A method for controlling ammonia injection in a boiler SCR denitrification system, characterized in that, include: The predicted NOx concentration at the inlet of the boiler SCR denitrification system is determined based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction. Based on the measured NOx concentration at the boiler SCR denitrification system inlet, flue gas volumetric flow rate, flue gas temperature, and unit load, a multiple regression analysis was performed to calculate the ammonia-to-nitrogen ratio. The specific process is as follows: The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load. After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function. The ammonia nitrogen ratio at different times is calculated based on the multivariate linear function and the preset ammonia nitrogen ratio function; Determine the measured value and set value of NOx concentration at the outlet of the boiler SCR denitrification system, respectively; A PID controller is used to generate an ammonia injection correction coefficient based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration; The ammonia injection rate is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient. The specific process is as follows: The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the amount of coal fed into the boiler. The initial ammonia injection rate is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, the flue gas volumetric flow rate, and the net flue gas volume. The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount; A PID controller is used to generate ammonia injection valve control commands based on the ammonia injection quantity, and ammonia injection control is implemented based on the ammonia injection valve control commands.
2. The ammonia injection control method for a boiler SCR denitrification system according to claim 1, characterized in that, The predicted NOx concentration at the inlet of the boiler SCR denitrification system is determined based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction, and includes: The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained. The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the boiler SCR denitrification system inlet monitoring system. Based on the correction error, the initial NOx concentration prediction value is corrected to obtain the NOx concentration prediction value.
3. An ammonia injection control device for a boiler SCR denitrification system, characterized in that, include: The concentration prediction unit is used to determine the predicted NOx concentration at the inlet of the boiler SCR denitrification system based on the correction error and the preset NOx concentration prediction model. The correction error is calculated based on the lag time between measurement and prediction. The first calculation unit is used to perform multiple regression analysis based on the measured NOx concentration at the inlet of the boiler SCR denitrification system, flue gas volume flow rate, flue gas temperature, and unit load, and to calculate the ammonia-to-nitrogen ratio. Specifically, the first calculation unit is used for: The average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load at the inlet of the boiler SCR denitrification system were calculated respectively to obtain the average values of NOx concentration, flue gas volume flow rate, flue gas temperature and unit load. After obtaining the average values of multiple sets of NOx concentration measurements, average flue gas volume flow rate, average flue gas temperature, and average unit load, a multiple regression analysis was performed to obtain a multiple linear function. The ammonia nitrogen ratio at different times is calculated based on the multivariate linear function and the preset ammonia nitrogen ratio function; The parameter determination unit is used to determine the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration of the boiler SCR denitrification system, respectively. The correction calculation unit is used to generate an ammonia injection correction coefficient based on the measured value of the outlet NOx concentration and the set value of the outlet NOx concentration using a PID controller; The second calculation unit is used to calculate the ammonia injection amount based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, and the ammonia injection correction coefficient. Specifically, the second calculation unit is used for: The flue gas volumetric flow rate and net flue gas volume at the inlet of the SCR denitrification system are calculated based on the amount of coal fed into the boiler. The initial ammonia injection rate is calculated based on the predicted NOx concentration, the ammonia-nitrogen ratio, the target NOx concentration, the flue gas volumetric flow rate, and the net flue gas volume. The initial ammonia injection amount is corrected and calculated based on the ammonia injection correction coefficient to obtain the ammonia injection amount; The ammonia injection control unit is used to generate ammonia injection valve control commands based on the ammonia injection quantity using a PID controller, and to implement ammonia injection control based on the ammonia injection valve control commands.
4. The ammonia injection control device for the boiler SCR denitrification system according to claim 3, characterized in that, The concentration prediction unit is specifically used for: The initial NOx concentration at the inlet of the boiler SCR denitrification system was predicted using a pre-set NOx concentration prediction model, and the initial NOx concentration prediction value was obtained. The correction error is calculated based on the lag time between the initial predicted NOx concentration and the measured NOx concentration detected by the boiler SCR denitrification system inlet monitoring system. Based on the correction error, the initial NOx concentration prediction value is corrected to obtain the NOx concentration prediction value.