Reverse blowing compensation control method and system based on denitration oxynitride signal

Abstract

The invention relates to a back flushing compensation control method and system based on a denitration oxynitride signal, and belongs to the field of environmental engineering and automation control, and the method comprises the following steps: (1) a data collection step; (2) calculating a mean value and a deviation; (3) a compensation correction function application step; (4) a signal superposition step; and (5) a delay control step. The system has the advantages that automatic control is achieved, human intervention is reduced, and the intelligent level of the system is improved. The change trend of NOx can be predicted more accurately by collecting data before back flushing of the CEMS instrument; by adjusting an ammonia injection control valve instruction in real time, the system can quickly adapt to working condition changes, and the denitration efficiency is improved.

Description

Technical Field

[0001] The invention relates to a denitration nitrogen oxide signal backflush compensation control method, belonging to the field of environmental engineering and automatic control. Background Art

[0002] Denitrification treatment in thermal power plants is an important part of modern environmental protection requirements. CEMS is a key device for monitoring NOx emissions, and its accuracy and reliability are crucial to the efficiency of the entire denitrification system. However, although the purging process of CEMS is necessary, it inevitably leads to the temporary loss of monitoring data, which to some extent affects the continuity and stability of denitrification control.

[0003] During the CEMS purge, due to the lack of real-time data, it is difficult for traditional feedforward control systems to make accurate adjustments. In this case, if the operating conditions of the thermal power plant change, such as changes in combustion efficiency, fuel type or combustion temperature, it may cause fluctuations in the generation of NOx. Once the CEMS purge is completed, these changes will suddenly be reflected in the monitoring data, forming a sudden signal change, which will bring difficulties to the placement of denitrification agents and the control of NOx.

[0004] Combined with the existing technology, it mainly has the following disadvantages:

[0005] (1) Data acquisition interruption: During the hourly purge process, the CEMS system temporarily interrupts the monitoring of NOx emissions, resulting in the inability to obtain real-time emission data during this period of approximately eight minutes. This lack of data makes it impossible for the control system to accurately assess the current emission situation.

[0006] (2) Response delay: Due to the sudden change of the CEMS signal after purge, the traditional feedforward control system often takes a certain amount of time to recognize and respond to this change. This delay may cause NOx emissions to exceed environmental protection standards in a short period of time.

[0007] (3) Inaccurate predictions: Feedforward control systems are usually adjusted based on historical data or preset parameters, but these data may not accurately reflect current operating conditions, resulting in inaccurate amounts of denitrifiers and inability to effectively control NOx emissions.

[0008] (4) Lack of adaptability: Existing technologies often lack the ability to adapt to changes in operating conditions and are unable to adjust control strategies based on real-time operating conditions. This can seriously affect denitrification efficiency when the operating conditions of thermal power plants change frequently. Summary of the invention

[0009] In order to overcome the defects of the prior art, the present invention provides a denitration nitrogen oxide signal backflush compensation control method and system thereof. The technical solution of the present invention is:

[0010] A denitration nitrogen oxide signal backflush compensation control method comprises the following steps:

[0011] (1) Data collection steps: Collect the ammonia injection control command and outlet NOx value 5-10 minutes before the CEMS instrument backflush, and use this value to predict and compensate for the change of nitrogen oxides;

[0012] (2) Mean and deviation calculation steps: Calculate the deviation between the mean of the 5-10 minutes before the blowback signal and the current instruction;

[0013] (3) Compensation correction function application steps: using the compensation correction function to correct the deviation and obtain a blowback compensation feedforward signal;

[0014] (4) Signal superposition step: directly superimposing the blowback compensation feedforward signal onto the ammonia injection control valve command. This step ensures that the ammonia injection control valve command can be adjusted in real time during the blowback of the CEMS instrument to adapt to the changes in nitrogen oxides;

[0015] (5) Delay control step: After the backflush of the CEMS instrument is completed, delay for 5-10 minutes and set the compensation feedforward signal to zero.

[0016] The step (1) is specifically as follows:

[0017] 1.1 Determine the frequency of collecting the ammonia injection control command and the outlet nitrogen oxide value, and record the data point once a minute to obtain the data set;

[0018] 1.2 Record the command value of the ammonia injection valve and the outlet nitrogen oxide concentration value measured by the CEMS instrument;

[0019] 1.3 Store the collected data in a database;

[0020] 1.4 Data Verification: Perform quality checks on the collected data to ensure the accuracy and completeness of the data and exclude outliers or erroneous data.

[0021] The step (2) is specifically as follows:

[0022] 2.1 Determine the time window for data calculation, that is, the data 5-10 minutes before the backflush signal will be used to calculate the mean;

[0023] 2.2 Filter out all ammonia injection valve adjustment commands and outlet NOx values ​​within the time window from the data set obtained in the data collection step;

[0024] 2.3 Average the ammonia injection valve control commands and outlet NOx values ​​collected within the time window to obtain the mean value within this period;

[0025] For the ammonia injection valve adjustment command:

[0026] For outlet NOx values: Where n is the total number of data points in the time window; i represents the index in the data set. When performing mean calculation or deviation analysis, i is used to traverse the data points in the time window, from the first data point to the nth data point; 2.4 Immediately before the backflush signal, obtain the current command value of the ammonia injection valve and the real-time value of the outlet NOx;

[0027] 2.5 Calculate the deviation between the current instruction value and the mean value in the time window:

[0028] For the ammonia injection valve control command deviation: Deviation 调门 = Current valve command - average value 调门 ;

[0029] For the outlet NOx value deviation: Deviation NOx = Current NOx value - average value NOx ;

[0030] 2.6 Deviation analysis: Analyze the positive and negative and size of the deviation to determine the trend of NOx emissions; 2.7 Data recording: Record the calculated mean and deviation in the system for use in subsequent steps;

[0031] 2.8 The calculated mean and deviation are passed as input to the compensation correction function to provide a basis for the next step of signal correction.

[0032] The step (3) is specifically as follows:

[0033] 3.1 The ammonia injection valve control command deviation and the outlet NOx value deviation calculated in step (2) are used as inputs to the compensation correction function;

[0034] 3.2 According to the predefined compensation correction function relationship, apply the corresponding correction coefficient to each deviation value and use linearity to determine the correction value;

[0035] 3.3 Perform correction calculation on each deviation value to obtain the corrected compensation value;

[0036] 3.4 Convert the corrected compensation value into a backflush compensation feedforward signal, which will be superimposed on the current ammonia injection valve adjustment instruction.

[0037] 3.6 According to the value of the compensation feedforward signal, adjust the opening of the ammonia injection valve to achieve a smooth transition of NOx emissions during the CEMS backflush.

[0038] The correction function is:

[0039] X1=-100, Y1=20; X2=-50, Y2=20; X3=-30, Y3=15;

[0040] X4=20, Y4=10; X5=0, Y5=0; X6=-20, Y6=-10;

[0041] X7=30, Y7=-15; X8=50, Y8=-20; X9=100, Y9=-20.

[0042] A system for realizing a denitration-based nitrogen oxide signal backflush compensation control method, comprising:

[0043] The data collection module is used to collect the ammonia injection adjustment instructions and outlet NOx values ​​5-10 minutes before the CEMS instrument backflush, and use these values ​​to predict and compensate for the changes in nitrogen oxides;

[0044] Mean and deviation calculation module, used to calculate the deviation between the mean of the 5-10 minutes before the blowback signal and the current instruction;

[0045] A compensation correction function application module is used to correct the deviation using the compensation correction function to obtain a backflush compensation feedforward signal;

[0046] The signal superposition module directly superimposes the blowback compensation feedforward signal onto the ammonia injection control valve instruction. This step ensures that the ammonia injection control valve instruction can be adjusted in real time during the blowback of the CEMS instrument to adapt to the changes in nitrogen oxides.

[0047] The delay control module is used to delay for 5-10 minutes after the backflush of the CEMS instrument is completed and set the compensation feedforward signal to zero.

[0048] The advantages of the present invention are: it realizes automatic control, reduces human intervention, and improves the intelligence level of the system. By collecting data before the backflush of the CEMS instrument, the change trend of NOx can be predicted more accurately; by adjusting the ammonia injection control command in real time, the system can quickly adapt to changes in operating conditions and improve denitrification efficiency; the application of the compensation correction function makes the control strategy more flexible and can be dynamically adjusted according to the actual deviation; the signal superposition step ensures the stability of NOx emissions during the backflush of the CEMS instrument and reduces emission fluctuations caused by monitoring interruptions; by timely adjusting the amount of ammonia injection, the risk of excessive NOx emissions caused by backflush operations is effectively avoided; protect equipment and extend service life: the delay control step avoids equipment wear caused by rapid adjustment, which helps to extend the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the main structure of the system of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0051] See also Figure 1 The present invention relates to a denitration nitrogen oxide signal backflush compensation control method, comprising the following steps:

[0052] (1) Data collection steps: Collect the ammonia injection control command and outlet NOx value 5-10 minutes before the CEMS instrument backflush, and use this value to predict and compensate for the change of nitrogen oxides;

[0053] (2) Mean and deviation calculation steps: Calculate the deviation between the mean of the 5-10 minutes before the blowback signal and the current instruction;

[0054] (3) Compensation correction function application steps: using the compensation correction function to correct the deviation and obtain a blowback compensation feedforward signal;

[0055] (4) Signal superposition step: directly superimposing the blowback compensation feedforward signal onto the ammonia injection control valve command. This step ensures that the ammonia injection control valve command can be adjusted in real time during the blowback of the CEMS instrument to adapt to the changes in nitrogen oxides;

[0056] (5) Delay control step: After the backflush of the CEMS instrument is completed, delay for 5-10 minutes and set the compensation feedforward signal to zero.

[0057] The step (1) is specifically as follows:

[0058] 1.1 Determine the frequency of collecting the ammonia injection control command and the outlet nitrogen oxide value, and record the data point once a minute to obtain the data set;

[0059] 1.2 Record the command value of the ammonia injection valve and the outlet nitrogen oxide concentration value measured by the CEMS instrument;

[0060] 1.3 Store the collected data in a database;

[0061] 1.4 Data Verification: Perform quality checks on the collected data to ensure the accuracy and completeness of the data and exclude outliers or erroneous data.

[0062] In the step (1), the collection frequency is determined to be once per minute, which means that the system will record the command value of the ammonia injection valve and the outlet NOx concentration value once every 60 seconds.

[0063] If data collection begins at 9:00 AM, the first data point will be recorded at 9:00 AM, the next data point will be recorded at 9:01 AM, and so on.

[0064] The system will record the command value of the ammonia injection valve as 45%, indicating the degree of opening of the valve.

[0065] At the same time, the CEMS instrument will provide the real-time concentration value of outlet NOx at 100mg / m 3 .

[0066] The collected data will be stored in a structured database, and each data point will have three fields: timestamp, throttle command value, and NOx concentration value.

[0067] Perform a quality check on the data in the database to check if the data points have logical errors or outliers that do not fit within the expected range.

[0068] For example, if the throttle command value is recorded as 110%, this is clearly outside the range of 0-100% and needs to be flagged as an outlier and further investigated.

[0069] Similarly, if the NOx concentration suddenly increases from 100 mg / m 3 Jumped to 1000mg / m 3 Without any reasonable explanation, this may indicate measurement error or equipment failure and requires further verification.

[0070] The step (2) is specifically as follows:

[0071] 2.1 Determine the time window for data calculation, that is, the data 5-10 minutes before the backflush signal will be used to calculate the mean;

[0072] 2.2 Filter out all ammonia injection valve adjustment commands and outlet NOx values ​​within the time window from the data set obtained in the data collection step;

[0073] 2.3 Average the ammonia injection valve control commands and outlet NOx values ​​collected within the time window to obtain the mean value within this period;

[0074] For the ammonia injection valve adjustment command:

[0075] For outlet NOx values: Where n is the total number of data points in the time window; i represents the index in the data set. When performing mean calculation or deviation analysis, i is used to traverse the data points in the time window, from the first data point to the nth data point; 2.4 Immediately before the backflush signal, obtain the current command value of the ammonia injection valve and the real-time value of the outlet NOx;

[0076] 2.5 Calculate the deviation between the current instruction value and the mean value in the time window:

[0077] For the ammonia injection valve control command deviation: Deviation 调门 = Current valve command - average value 调门 ;

[0078] For the outlet NOx value deviation: Deviation NOx = Current NOx value - average value NOx ;

[0079] 2.6 Deviation analysis: Analyze the positive and negative and size of the deviation to determine the trend of NOx emissions; 2.7 Data recording: Record the calculated mean and deviation in the system for use in subsequent steps;

[0080] 2.8 The calculated mean and deviation are passed as input to the compensation correction function to provide a basis for the next step of signal correction.

[0081] In the step (2), the specific values ​​and operations are as follows:

[0082] Assume that 10 minutes is selected as the time window, that is, data collection starts 10 minutes before the backflush signal.

[0083] Filter the data points from the last 10 minutes from the data set collected in step (1). If it is recorded once every minute, we will get 10 data points.

[0084] For the mean calculation of the ammonia injection control command, assume that we have 10 data points, namely A1, A2, ..., A10:

[0085] For the mean calculation of the outlet NOx value, assume that the 10 data points are B1, B2, ..., ppm:

[0086] Get the current command and value: the current ammonia injection control command value obtained immediately before the backflush signal is C (45%), and the real-time value of outlet NOx is D (150ppm).

[0087] Calculate the ammonia injection valve command deviation: deviation valve = C-mean valve;

[0088] Calculate the outlet NOx value deviation: Deviation NOx = D-mean NOx;

[0089] Deviation Analysis:

[0090] Analyze the positive and negative values ​​and magnitude of the deviation valve and deviation NOx. For example, if the deviation valve is positive, it means that the current valve instruction is higher than the average value, and the amount of ammonia injection may need to be reduced; if the deviation NOx is negative, it means that the current NOx concentration is lower than the average value, and adjustments may be required to ensure emission compliance.

[0091] The calculated mean tuning, mean NOx, deviation tuning and deviation NOx are recorded in the system. For example: mean tuning = 47%, mean NOx = 0.06ppm, mean tuning = 47%, mean NOx = 0.06ppm, deviation tuning = 48%-47% = 1%, deviation tuning = 48%-47% = 1%, deviation NOx = 0.07ppm-0.06ppm = 0.01ppm, deviation NOx = 0.07ppm-0.06ppm = 0.01ppm.

[0092] The calculated mean and deviation are passed as input to the compensation correction function.

[0093] The step (3) is specifically as follows:

[0094] 3.1 The ammonia injection valve control command deviation and the outlet NOx value deviation calculated in step (2) are used as inputs to the compensation correction function;

[0095] 3.2 According to the predefined compensation correction function relationship, apply the corresponding correction coefficient to each deviation value and use linearity to determine the correction value;

[0096] 3.3 Perform correction calculation on each deviation value to obtain the corrected compensation value;

[0097] 3.4 Convert the corrected compensation value into a backflush compensation feedforward signal, which will be superimposed on the current ammonia injection valve adjustment instruction.

[0098] 3.6 According to the value of the compensation feedforward signal, adjust the opening of the ammonia injection valve to achieve a smooth transition of NOx emissions during the CEMS backflush.

[0099] The correction function is:

[0100] X1=-100, Y1=20; X2=-50, Y2=20; X3=-30, Y3=15;

[0101] X4=20, Y4=10; X5=0, Y5=0; X6=-20, Y6=-10;

[0102] X7=30, Y7=-15; X8=50, Y8=-20; X9=100, Y9=-20;

[0103] Where X represents the deviation value and Y represents the correction factor.

[0104] If the deviation valve = -40, the X value closest to -40 in the table is -50, and the corresponding Y value is 20, so the correction coefficient is 20, then the compensation value = -40×20 = -800. This compensation value will be converted into a feedforward signal and superimposed on the current ammonia injection valve command to adjust the valve opening.

[0105] The present invention also relates to a system for realizing a denitration nitrogen oxide signal backflush compensation control method, comprising:

[0106] Data collection module 1 is used to collect the ammonia injection valve adjustment instructions and outlet NOx values ​​5-10 minutes before the backflush of the CEMS instrument, and use these values ​​to predict and compensate for the changes in nitrogen oxides; mean and deviation calculation module 2 is used to calculate the deviation between the mean value 5-10 minutes before the backflush signal and the current instruction;

[0107] The compensation correction function application module 3 is used to correct the deviation using the compensation correction function to obtain a backflush compensation feedforward signal;

[0108] The signal superposition module 4 directly superimposes the blowback compensation feedforward signal onto the ammonia injection valve control command. This step ensures that during the blowback of the CEMS instrument, the ammonia injection valve control command can be adjusted in real time to adapt to the changes in nitrogen oxides.

[0109] The delay control module 5 is used to delay for 5-10 minutes after the backflush of the CEMS instrument is completed and set the compensation feedforward signal to zero.

[0110] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A denitrification nitrogen oxide signal backflush compensation control method, characterized in that: The following steps are involved: (1) Data collection steps: Collect the ammonia injection control command and outlet NOx value 5-10 minutes before the CEMS instrument backflush, and use this value to predict and compensate for the change of nitrogen oxides; (2) Mean and deviation calculation steps: Calculate the deviation between the mean of the 5-10 minutes before the blowback signal and the current instruction; (3) Compensation correction function application steps: using the compensation correction function to correct the deviation and obtain a blowback compensation feedforward signal; (4) Signal superposition step: directly superimpose the blowback compensation feedforward signal onto the ammonia injection control valve command. This step ensures that the ammonia injection control valve command can be adjusted in real time during the blowback of the CEMS instrument to adapt to the changes in nitrogen oxides; (5) Delay control step: After the backflush of the CEMS instrument is completed, delay for 5-10 minutes and set the compensation feedforward signal to zero.

2. The denitration nitrogen oxide signal backflush compensation control method according to claim 1 is characterized in that: The step (1) is specifically as follows: 1.1 Determine the frequency of collecting the ammonia injection control command and the outlet nitrogen oxide value, and record the data point once a minute to obtain the data set; 1.2 Record the command value of the ammonia injection valve and the outlet nitrogen oxide concentration value measured by the CEMS instrument; 1.3 Store the collected data in a database; 1.4 Data Verification: Perform quality checks on the collected data to ensure the accuracy and completeness of the data and exclude outliers or erroneous data.

3. The denitration nitrogen oxide signal backflush compensation control method according to claim 1 or 2, characterized in that: The step (2) is specifically as follows: 2.1 Determine the time window for data calculation, that is, the data 5-10 minutes before the backflush signal will be used to calculate the mean; 2.2 Filter out all ammonia injection valve adjustment commands and outlet NOx values ​​within the time window from the data set obtained in the data collection step; 2.3 Average the ammonia injection valve control commands and outlet NOx values ​​collected within the time window to obtain the mean value within this period; For the ammonia injection valve adjustment command: For outlet NOx values: Where n is the total number of data points in the time window; i represents the index in the data set. When performing mean calculation or deviation analysis, i is used to traverse the data points in the time window, from the first data point to the nth data point; 2.4 Immediately obtain the current command value of the ammonia injection valve and the real-time value of outlet NOx before the backflush signal; 2.5 Calculate the deviation between the current instruction value and the mean value in the time window: For the ammonia injection valve control command deviation: Deviation 调门 = Current valve command - average value 调门 ; For the outlet NOx value deviation: Deviation NOx = Current NOx value - average value NOx ; 2.6 Deviation analysis: Analyze the positive and negative and size of the deviation to determine the changing trend of NOx emissions; 2.7 Data recording: The calculated mean and deviation are recorded in the system for use in subsequent steps; 2.8 The calculated mean and deviation are passed as input to the compensation correction function to provide a basis for the next step of signal correction.

4. The denitration nitrogen oxide signal backflush compensation control method according to claim 3 is characterized in that: The step (3) is specifically as follows: 3.1 The ammonia injection valve control command deviation and the outlet NOx value deviation calculated in step (2) are used as inputs to the compensation correction function; 3.2 According to the predefined compensation correction function relationship, apply the corresponding correction coefficient to each deviation value and use linearity to determine the correction value; 3.3 Perform correction calculation on each deviation value to obtain the corrected compensation value; 3.4 Convert the corrected compensation value into a backflush compensation feedforward signal, which will be superimposed on the current ammonia injection valve adjustment instruction. 3.6 According to the value of the compensation feedforward signal, adjust the opening of the ammonia injection valve to achieve a smooth transition of NOx emissions during the CEMS backflush.

5. The denitration nitrogen oxide signal backflush compensation control method according to claim 4 is characterized in that: The correction function is: X1=-100, Y1=20; X2=-50, Y2=20; X3=-30, Y3=15; X4=20, Y4=10; X5=0, Y5=0; X6=-20, Y6=-10; X7=30, Y7=-15; X8=50, Y8=-20; X9=100, Y9=-20.

6. A system for implementing any one of claims 1 to 5 based on the denitration nitrogen oxide signal backflush compensation control method, characterized in that: include: The data collection module is used to collect the ammonia injection adjustment instructions and outlet NOx values ​​5-10 minutes before the CEMS instrument backflush, and use these values ​​to predict and compensate for the changes in nitrogen oxides; Mean and deviation calculation module, used to calculate the deviation between the mean of the 5-10 minutes before the blowback signal and the current instruction; A compensation correction function application module is used to correct the deviation using the compensation correction function to obtain a backflush compensation feedforward signal; The signal superposition module directly superimposes the blowback compensation feedforward signal onto the ammonia injection control valve command. This step ensures that the ammonia injection control valve command can be adjusted in real time during the blowback of the CEMS instrument to adapt to the changes in nitrogen oxides. The delay control module is used to delay for 5-10 minutes after the backflush of the CEMS instrument is completed and set the compensation feedforward signal to zero.

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