A method and device for correcting the calorific value of a coal-fired boiler under weak steady state

Abstract

The application discloses a kind of weak steady-state energy conservation's coal-fired boiler calorific value correction method and device, the method includes the following steps: extracting weak steady-state parameter main parameter from the real-time data of unit operation, each main parameter is filtered in time detection window and weak steady-state condition is judged, when all main parameters meet weak steady-state judgment condition during detection, the mean value of energy conservation parameter under the corresponding detection number is output;Using the mean value of energy conservation parameter carries out boiler heat balance calculation, obtains the actual fuel heat value corresponding to current unit load;Actual fuel heat value Q net.ar The ratio COR of the original design fuel heat value Q design Of unit is used as coal-fired boiler calorific value correction amount, and the fuel quantity of unit is adjusted by coal-fired boiler calorific value correction amount;The application has the advantages that: avoid system repeated oscillation, improve calorific value correction precision.

Description

Technical Field

[0001] This invention relates to the field of calorific value detection and control technology for coal-fired boilers, and more specifically to a method and apparatus for correcting the calorific value of a coal-fired boiler under weak steady-state conditions with energy conservation. Background Technology

[0002] Because the coal used in boiler combustion is highly time-varying, its calorific value varies greatly at different times. This increases the instability factors in boiler combustion, causing fluctuations in important unit parameters. In particular, for the coordinated control system, the phenomenon of calorific value changes leading to coordinated control imbalances and decreased control quality is becoming increasingly serious. Therefore, calorific value correction is a difficult and painful point for adaptive control of thermal power unit coordinated control systems.

[0003] The coordinated control system of a thermal power unit comprises boiler main control and turbine main control. Taking the boiler and turbine as the controlled objects, it overcomes the different characteristics of the boiler and turbine through coordinated control command loop design, static feedforward loop design, and dynamic feedforward loop design. This enables the system to quickly and stably transition from one equilibrium state to another, ensuring the safe, efficient, and stable operation of the unit. The coordinated control system loop mainly includes the load command loop, turbine main control loop, and boiler main control loop. To adapt to the requirements of power system units such as AGC and primary frequency regulation, the coordinated control system of a thermal power unit typically employs necessary adjustment methods, such as calorific value correction and adaptive parameters, to cope with disturbances to the coordinated control system caused by different coal qualities under complex operating conditions. Among these, calorific value correction technology is widely used.

[0004] One of the main disturbances in a coordinated control system comes from changes in fuel calorific value. In recent years, most coal-fired boilers have reduced coal costs through technologies such as fuel coupling and blending. However, the resulting variations in calorific value due to different coal qualities cause significant disturbances to the coordinated control system. These disturbances are characterized by variability and unpredictability. Therefore, for a coordinated control system, correcting calorific value deviations by changing the fuel quantity suppresses system disturbances, enabling the coal-fired boiler to quickly and stably adjust the relationship between unit load and actual coal quantity, achieving unit heat balance and preventing overshooting of main steam pressure, intermediate point temperature, unit load, and main steam temperature. The main idea of ​​calorific value correction technology is to adjust the calorific value deviation between the designed coal type and the actual coal type. Based on the numerical relationship between unit load and actual required heat, the unit fuel quantity is changed to compensate for the calorific value deviation, thereby reducing fluctuations in main steam pressure and unit load overshooting.

[0005] Currently, most existing calorific value correction technologies employ indirect methods to obtain unit calorific value information. Indirect methods mainly include process control and numerical modeling. The process control method uses the deviation between the design fuel quantity corresponding to the current load and the actual fuel quantity output by the boiler's main control as the input to the PID corrector. Through closed-loop regulation of the PID, the amount of fuel fed into the furnace is continuously adjusted to achieve a new equilibrium. For example, the distributed control system implementation method for the self-balancing control loop of coal-fired power generation in a supercritical boiler, disclosed in Chinese Patent Publication No. CN104238520A, also uses this process control method. The main disadvantage of this method is that, for the boiler, the overall process is long and the control process is slow. When the fuel calorific value changes, it takes a considerable amount of time for this to be reflected in the main steam pressure, main steam temperature, and other key control parameters. If the PID corrector parameters are mismatched, it can easily cause repeated system oscillations, resulting in low calorific value correction accuracy. Secondly, under load or fuel variation conditions, the calorific value correction PID controller struggles to accurately grasp the unit's current calorific value information. Therefore, its output not only has no effect but may also exacerbate the drastic fluctuations in the coordinated control parameters. Numerical modeling uses real-time operating data of the unit. By filtering the data and extracting features, it establishes a precise relationship between the unit load and the amount of fuel required by the unit. Then, it calculates the deviation between the current calorific value and the original design calorific value, which is used to correct the static feedforward control quantity of the coordinated control system. This method has good applicability, but it has high requirements for the data filtering method and relies on high-precision modeling data. If the accuracy of the modeling data is not high, it will directly affect the accuracy of calorific value correction. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing coal-fired boiler calorific value correction method has a slow control process, which easily causes repeated system oscillations and low calorific value correction accuracy.

[0007] This invention solves the above-mentioned technical problems through the following technical means: a method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation, the method comprising the following steps:

[0008] Step 1: Extract the main parameters of the weak steady-state parameters from the real-time data of the unit operation, filter each main parameter and judge the weak steady-state conditions in the time detection window, and output the average value of the energy conservation parameters for the corresponding number of detections after all main parameters meet the weak steady-state judgment conditions during the detection period.

[0009] Step 2: Calculate the boiler heat balance using the average value of the energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load;

[0010] Step 3: Actual fuel calorific value Q net.ar Compared with the original design fuel calorific value Q of the unit designThe ratio COR is used as a correction factor for the calorific value of coal-fired boilers, and the fuel quantity of the unit is adjusted based on the calorific value correction factor of the coal-fired boilers.

[0011] This invention employs a direct modeling method to propose a calorific value correction method for coal-fired boilers under weak steady-state conditions. By judging the weak steady-state conditions of the unit data, weak steady-state data screening is achieved, providing relatively steady-state data for boiler heat balance calculation, reducing data disturbances, avoiding repeated system oscillations, and improving the accuracy of calorific value correction. Using the boiler heat balance method, the current calorific value information of the unit can be calculated quickly, directly, and accurately. Furthermore, the functional relationship between the unit load and the actual fuel quantity is derived and used as the calorific value correction amount for the unit at future times. The obtained information is the true boiler fuel calorific value information, which can more accurately reflect the current calorific value change of the unit and further improve the accuracy of calorific value correction.

[0012] Further, step one includes:

[0013] Step 101: Determine the start conditions for calorific value correction. If the start conditions for calorific value correction are met, proceed to step 102.

[0014] Step 102: Within the limited time detection window, use dynamic mean filtering to filter the main parameters in the unit's original data; the filtered main parameters include unit load, main steam pressure, and actual coal quantity.

[0015] Step 103: Real-time iteration of the main parameters after filtering and detection, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n The deviation value is checked to see if it meets the weak steady-state condition. If it does not, the process returns to step 101. If it does, the process continues to the next detection until the Nth detection is completed. Then, the average value of the energy conservation parameters of the Nth detection is output.

[0016] Furthermore, the energy conservation parameters include total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, blast cylinder exhaust enthalpy, total air volume, reference temperature, and flue gas temperature.

[0017] Furthermore, step 101 includes:

[0018] Record real-time data of the generator unit. When the main parameters of the generator unit simultaneously meet the following startup conditions...

[0019] |P t -P t-1 |<E P ,|Yt -Y t-1 |<E Y |B t -B t-1 |<E B 、|P t -Q t |<E P If the condition is met, proceed to step 102; otherwise, continue to determine the start-up conditions. Here, P is the unit load, Y is the main steam pressure, B is the actual coal quantity, Q is the unit load command, t is the current time, and E is the start-up condition. P E Y E B These are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively.

[0020] Furthermore, step 102 includes:

[0021] Through formula Design a time detection window for detecting the main parameters of the unit, where T is the detection period, L is the length of the time window, and N is the total number of detections in the window;

[0022] Within the time detection window, dynamic mean filtering is used to filter the main parameters in the unit's raw data. The filtered main parameters are as follows:

[0023]

[0024] In the nth detection, n∈{1,2,…,N}, P Ln For the filtered unit load, Y Ln BL represents the filtered main steam pressure. n The actual amount of coal after filtering is given, and avg() is the mean function.

[0025] Furthermore, step 103 includes:

[0026] a) If n = 1, where n represents the nth detection, the initial weakly steady-state state variable F = false, and the maximum and minimum values ​​of each principal parameter are set as follows:

[0027]

[0028] At this point, the mean value of each energy conservation parameter is denoted as...

[0029]

[0030] in, This represents the mean value of the i-th energy conservation parameter during the first detection. This represents the value of the i-th energy conservation parameter during the first detection;

[0031] If n > 1, the maximum and minimum values ​​of each main parameter are respectively

[0032]

[0033] At this point, the mean values ​​of all energy conservation parameters are

[0034]

[0035] in, Let represent the mean value of the i-th energy conservation parameter during the n-th detection. Let represent the mean value of the i-th energy conservation parameter during the (n-1)-th detection. This represents the value of the i-th energy conservation parameter during the n-th detection;

[0036] b) During each test, determine the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n Does the deviation value satisfy the following weak steady-state conditions?

[0037]

[0038] If the condition is not met, return to step 101; if the condition is met, return to step a) to perform the next test, until the Nth test is completed, then execute step c).

[0039] c) Set the weakly steady-state state variable F = true, and output the mean value of the energy conservation parameter of the Nth test.

[0040] Furthermore, step two includes:

[0041] Through formula Perform boiler heat balance calculations to obtain the fuel calorific value, where Q net.ar Q represents the calorific value of the fuel. b Where η is the total calorific value of the fuel, η is the efficiency correlation coefficient, and B is the total amount of coal entering the furnace.

[0042] The total heat capacity of the boiler is expressed by the formula calculate,

[0043] Where, q 34 Loss due to incomplete combustion; q 56 For ash residue, heat dissipation, and manufacturing losses;

[0044] Q1 is the effective heat absorption of the boiler and Q1 = D. gr i gr -D gs i gs -D jws i jws +Dzr (i zr -i gp );D gr Main steam flow rate; i gr Main vapor enthalpy; i gs For water enthalpy; D gs D is the water supply flow rate; jws To reduce the flow rate of the heated water; jws To reduce the enthalpy of water; D zr i is the reheat steam flow rate; zr For reheat steam enthalpy; i gp For high cylinder exhaust enthalpy;

[0045] Q2 is the total heat of the flue gas and Q2 = 1.071(1.3593 + 0.000188t1)(t1 - t0)Q a Q a t0 represents the total air volume; t0 represents the reference temperature; and t1 represents the exhaust gas temperature.

[0046] Furthermore, step three includes:

[0047] Using the formula COR = Q net.ar / Q design Obtain the actual fuel calorific value Q net.ar Compared with the original design fuel calorific value Q of the unit design The ratio of the actual fuel calorific value to the design calorific value is as follows: when the actual fuel calorific value is lower than the original design fuel calorific value of the unit, the calculated correction amount COR is less than 1, and the fuel master control PID increases the fuel amount to compensate for the total heat of the system; when the actual calorific value is higher than the design calorific value, the calculated correction amount COR is greater than 1, and the fuel master control PID decreases the fuel amount to reduce the total heat of the system.

[0048] The present invention also provides a calorific value correction device for a coal-fired boiler with energy conservation under weak steady-state conditions, the device comprising:

[0049] The energy conservation parameter acquisition module is used to extract the main parameters of the weak steady-state parameters from the real-time data of the unit operation. It filters each main parameter and judges the weak steady-state conditions in the time detection window. When all main parameters meet the weak steady-state judgment conditions during the detection period, it outputs the average value of the energy conservation parameters under the corresponding number of detections.

[0050] The boiler heat balance calculation module is used to perform boiler heat balance calculations using the average value of energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load.

[0051] The calibration module is used to verify the actual fuel calorific value Q. net.ar Compared with the original design fuel calorific value Q of the unit design The ratio COR is used as a correction factor for the calorific value of coal-fired boilers, and the fuel quantity of the unit is adjusted based on the calorific value correction factor of the coal-fired boilers.

[0052] Furthermore, the energy conservation parameter acquisition module is also used for:

[0053] Step 101: Determine the start conditions for calorific value correction. If the start conditions for calorific value correction are met, proceed to step 102.

[0054] Step 102: Within the limited time detection window, use dynamic mean filtering to filter the main parameters in the unit's original data; the filtered main parameters include unit load, main steam pressure, and actual coal quantity.

[0055] Step 103: Real-time iteration of the main parameters after filtering and detection, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n The deviation value is checked to see if it meets the weak steady-state condition. If it does not, the process returns to step 101. If it does, the process continues to the next detection until the Nth detection is completed. Then, the average value of the energy conservation parameters of the Nth detection is output.

[0056] Furthermore, the energy conservation parameters include total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, blast cylinder exhaust enthalpy, total air volume, reference temperature, and flue gas temperature.

[0057] Furthermore, step 101 includes:

[0058] Record real-time data of the generator unit. When the main parameters of the generator unit simultaneously meet the following startup conditions...

[0059] |P t -P t-1 |<E P ,|Y t -Y t-1 |<E Y |B t -B t -1|<E B 、|P t -Q t |<E P If the condition is met, proceed to step 102; otherwise, continue to determine the start-up conditions. Here, P is the unit load, Y is the main steam pressure, B is the actual coal quantity, Q is the unit load command, t is the current time, and E is the start-up condition. P E Y E B These are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively.

[0060] Furthermore, step 102 includes:

[0061] Through formula Design a time detection window for detecting the main parameters of the unit, where T is the detection period, L is the length of the time window, and N is the total number of detections in the window;

[0062] Within the time detection window, dynamic mean filtering is used to filter the main parameters in the unit's raw data. The filtered main parameters are as follows:

[0063]

[0064] In the nth detection, n∈{1,2,…,N}, PL n For the filtered unit load, YL n BL represents the filtered main steam pressure. n The actual amount of coal after filtering is given, and avg() is the mean function.

[0065] Furthermore, step 103 includes:

[0066] a) If n = 1, where n represents the nth detection, the initial weakly steady-state state variable F = false, and the maximum and minimum values ​​of each principal parameter are set as follows:

[0067]

[0068] At this point, the mean value of each energy conservation parameter is denoted as...

[0069]

[0070] in, This represents the mean value of the i-th energy conservation parameter during the first detection. This represents the value of the i-th energy conservation parameter during the first detection;

[0071] If n > 1, the maximum and minimum values ​​of each main parameter are respectively

[0072]

[0073] At this point, the mean values ​​of all energy conservation parameters are

[0074]

[0075] in, Let represent the mean value of the i-th energy conservation parameter during the n-th detection. Let represent the mean value of the i-th energy conservation parameter during the (n-1)-th detection. This represents the value of the i-th energy conservation parameter during the n-th detection;

[0076] b) During each test, determine the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n Does the deviation value satisfy the following weak steady-state conditions?

[0077]

[0078] If the condition is not met, return to step 101; if the condition is met, return to step a) to perform the next test, until the Nth test is completed, then execute step c).

[0079] c) Set the weakly steady-state state variable F = true, and output the mean value of the energy conservation parameter of the Nth test.

[0080] Furthermore, the boiler heat balance calculation module is also used for:

[0081] Through formula Perform boiler heat balance calculations to obtain the fuel calorific value, where Q net.ar Q represents the calorific value of the fuel. b Where η is the total calorific value of the fuel, η is the efficiency correlation coefficient, and B is the total amount of coal entering the furnace.

[0082] The total heat capacity of the boiler is expressed by the formula calculate,

[0083] Where, q 34 Loss due to incomplete combustion; q 56 For ash residue, heat dissipation, and manufacturing losses;

[0084] Q1 is the effective heat absorption of the boiler and Q1 = D. gr i gr -D gs i gs -D jws i jws +D zr (i zr -i gp );D gr Main steam flow rate; i gr Main vapor enthalpy; i gs For water enthalpy; D gs D is the water supply flow rate; jws To reduce the flow rate of the heated water; jws To reduce the enthalpy of water; D zr i is the reheat steam flow rate; zr For reheat steam enthalpy; i gp For high cylinder exhaust enthalpy;

[0085] Q2 is the total heat of the flue gas and Q2 = 1.071(1.3593 + 0.000188t1)(t1 - t0)Q a Q a t0 represents the total air volume; t0 represents the reference temperature; and t1 represents the exhaust gas temperature.

[0086] Furthermore, the correction module is also used for:

[0087] Using the formula COR = Q net.ar / Q design Obtain the actual fuel calorific value Q net.ar Compared with the original design fuel calorific value Q of the unit design The ratio of the actual fuel calorific value to the design calorific value is as follows: when the actual fuel calorific value is lower than the original design fuel calorific value of the unit, the calculated correction amount COR is less than 1, and the fuel master control PID increases the fuel amount to compensate for the total heat of the system; when the actual calorific value is higher than the design calorific value, the calculated correction amount COR is greater than 1, and the fuel master control PID decreases the fuel amount to reduce the total heat of the system.

[0088] The advantages of this invention are:

[0089] (1) This invention adopts the direct modeling method and proposes a method for correcting the calorific value of a coal-fired boiler under weak steady-state conditions. By judging the weak steady-state conditions of the unit data, the weak steady-state data is filtered, providing relatively steady-state data for boiler heat balance calculation, reducing data disturbance, avoiding repeated system oscillations, and improving the accuracy of calorific value correction. The boiler heat balance method can quickly, directly and accurately calculate the current calorific value information of the unit, and further derive the functional relationship between the unit load and the actual fuel quantity, which is used as the calorific value correction amount of the unit at future times. What is obtained is the real boiler fuel calorific value information, which can more accurately reflect the current calorific value change of the unit and further improve the accuracy of calorific value correction.

[0090] (2) The present invention uses the mean filtering method, which can retain the original information while reducing the interference of noise on weak steady-state detection.

[0091] (3) The present invention uses boiler heat balance calculation to accurately obtain the current fuel calorific value, and uses the ratio between the actual calorific value and the design calorific value to correct the fuel main control, and can adjust the fuel quantity in a timely manner according to the change of calorific value.

[0092] (4) The present invention adopts the boiler heat balance calculation method to realize online fuel calorific value calculation and real-time detection of unit fuel calorific value data, providing accurate and timely information for unit calorific value correction. Attached Figure Description

[0093] Figure 1 This is a flowchart of a method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation, as provided in Embodiment 1 of the present invention.

[0094] Figure 2 This is a schematic diagram of the calorific value correction principle in a coal-fired boiler calorific value correction method with energy conservation under weak steady state provided in Embodiment 1 of the present invention. Detailed Implementation

[0095] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0096] Example 1

[0097] like Figure 1 As shown, this invention proposes a method for correcting the calorific value of a coal-fired boiler under weak steady-state conditions based on energy conservation. Under steady-state conditions, the main parameters of a coal-fired unit fluctuate within a small range, and most of the main boiler parameters do not change significantly. Therefore, under steady-state conditions, boiler combustion is in a process of energy conservation. In this energy-conserving state, the boiler's input heat and output heat are balanced, and the fuel calorific value can be calculated from the output heat (output power). Therefore, based on the calorific value information calculated according to energy conservation, the correspondence between the unit load and the required fuel quantity under the current calorific value can be accurately reflected. In the next dynamic operating condition, this correspondence can be used to correct the calorific value of the original coordinated control system, enabling rapid and stable control of various main parameters when the unit changes from one load condition to another, reducing system overshoot.

[0098] In new power systems, most coal-fired units operate under dynamic load regulation conditions, with few steady-state conditions. Data available for boiler energy conservation calculations is even scarcer, making the acquisition of effective information from steady-state parameters a significant challenge in this field. This invention is based on a weak steady-state method. Through dynamic mean filtering and data screening, it extracts a large amount of effective weak steady-state data from real-time data, providing accurate modeling data for energy conservation calorific value calculation. Based on the real-time calculated calorific value data, a compensation relationship between the unit load and actual fuel demand under the current calorific value is designed and applied to the static feedforward loop of the unit's coordinated control system, thereby achieving stable adjustment of various key parameters under changing operating conditions. This method is used to correct calorific value during dynamic processes and to calculate calorific value information in real-time during weak steady-state processes to monitor changes in coal type and promptly correct the unit's calorific value, achieving true adaptive calorific value control.

[0099] like Figure 1As shown, the weak steady-state judgment parameters detected by this invention are: unit load, main steam pressure, actual coal quantity, and unit load command. During the time detection window, each key parameter is filtered and over-limit judgment is performed. When all parameters meet the weak steady-state judgment conditions during the detection period, the system selects the weak steady-state parameters and provides a weak steady-state signal. According to the boiler energy conservation method, the fuel calorific value under the current coal type is calculated, and the correspondence between unit load and calorific value is calculated to correct for unit load fluctuations and improve the control quality of the unit coordinated control system. The following details the method steps of this invention, which include the following steps:

[0100] S1: Extract the main parameters of the weak steady-state parameters from the real-time data of the unit operation. Filter each main parameter and determine the weak steady-state conditions within the time detection window. When all main parameters meet the weak steady-state judgment conditions during the detection period, output the average value of the energy conservation parameters for the corresponding number of detections. The specific process is as follows:

[0101] Step 101: Record real-time data of the unit. When the main parameters of the unit simultaneously meet the following start-up conditions...

[0102] |P t -P t-1 |<E P ,|Y t -Y t-1 |<E Y |B t -B t-1 |<E B 、|P t -Q t |<E P If the condition is met, proceed to step 102; otherwise, continue to determine the start-up conditions. Here, P is the unit load, Y is the main steam pressure, B is the actual coal quantity, Q is the unit load command, t is the current time, and E is the start-up condition. P E Y E B These are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively.

[0103] Step 102: After the startup conditions are met, a weak steady-state judgment is performed within a limited time window. To eliminate the influence of noise on the weak steady-state judgment, the sampled mean filtering method is used to process the real-time data. After the weak steady-state judgment is completed within the limited time window, the energy conservation calculation parameter X for that period is output. i Where i = 1, 2…I, and I is the total number of energy conservation calculation parameters, including total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, blast furnace exhaust enthalpy, total air volume, reference temperature, and exhaust gas temperature. The system simultaneously outputs the state quantity F indicating that the system is in a weak steady state. The specific process is as follows:

[0104] Through formula Design a time detection window for detecting the main parameters of the unit, where T is the detection period, L is the length of the time window, and N is the total number of detections in the window.

[0105] Noise signals can severely affect the judgment of weak steady-state conditions, making it difficult to achieve weak steady-state operating conditions in practical applications. Therefore, filtering the raw data is essential. Considering that mean filtering, compared with other filtering methods, can better preserve the information in the raw data, dynamic mean filtering is used to filter the raw data in real time, reducing the impact of noise on weak steady-state judgment. During the nth detection, within the time detection window, dynamic mean filtering is used to filter the main parameters in the unit's raw data. The filtered main parameters are...

[0106]

[0107] In the nth detection, n∈{1,2,…,N}, PL n For the filtered unit load, YL n BL represents the filtered main steam pressure. n Let be the actual amount of coal after filtering. avg() is the mean function. Assuming the function input is x1, x2, x3, then the expression for avg(·) is avg(x1, x2, x3) = (x1 + x2 + x3) / 3.

[0108] Step 103: Real-time iteration of the main parameters after filtering and detection, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n The deviation value is checked against the weak steady-state condition. If not, the process returns to step 101. If it is satisfied, the next detection continues until the Nth detection is completed. Finally, the mean value of the energy conservation parameters from the Nth detection is output. The specific process is as follows:

[0109] a) If n = 1, where n represents the nth detection, the initial weakly steady-state state variable F = false, and the maximum and minimum values ​​of each principal parameter are set as follows:

[0110]

[0111] At this point, the mean value of each energy conservation parameter is denoted as...

[0112]

[0113] in, This represents the mean value of the i-th energy conservation parameter during the first detection. This represents the value of the i-th energy conservation parameter during the first detection. The above formula shows that during the first detection, the mean of each energy conservation parameter is its initial value, which is also the value during the first detection.

[0114] If n > 1, the maximum and minimum values ​​of each main parameter are respectively

[0115]

[0116] At this point, the mean values ​​of all energy conservation parameters are

[0117]

[0118] In the above formula Let represent the mean value of the i-th energy conservation parameter during the n-th detection. Let represent the mean value of the i-th energy conservation parameter during the (n-1)-th detection. This represents the value of the i-th energy conservation parameter during the n-th detection.

[0119] b) Within the defined time window, at each test, determine the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n Does the deviation value satisfy the following weak steady-state conditions?

[0120]

[0121] If the condition is not met, return to step 101; if the condition is met, return to step a) to perform the next test, until the Nth test is completed, then execute step c).

[0122] c) Set the weak steady-state state variable F = true, output the average value of the energy conservation parameters of the Nth test, and proceed to the next step.

[0123] S2: Calculate the boiler heat balance using the average value of energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load; the specific process is as follows:

[0124] a) Boiler heat balance calculation

[0125]

[0126] In the formula: Q net.ar Q represents the calorific value of the fuel. b Let represent the total calorific value of the fuel, in MJ. η is the efficiency correlation coefficient, η = 1. B is the total amount of coal entering the furnace, in kg / s.

[0127] b) Method for calculating total boiler heat capacity:

[0128]

[0129] Where: Q1 is the effective heat absorption of the boiler, MW; Q2 is the total heat of flue gas, MW; q 34 Loss due to incomplete combustion, %; q 56 For ash residue, heat dissipation, and manufacturing losses, %.

[0130] Q1 = D gr i gr -D gs i gs -D jws i jws +D zr (i zr -i gp )

[0131] In the formula: D gr Main steam flow rate, kg / s; i gr Main vapor enthalpy, MJ / kg; i gs For feedwater enthalpy, MJ / kg; D gs The water supply flow rate is expressed in kg / s; D jws To reduce the flow rate of the heated water, kg / s; i jws For the enthalpy of water under cooling, MJ / kg; D zr The reheat steam flow rate is kg / s; i zr The reheat steam enthalpy is expressed in MJ / kg; gp The enthalpy of high-pressure cylinder exhaust is MJ / kg.

[0132] Q2=1.071(1.3593+0.000188t1)(t1-t0)Q a

[0133] In the formula: Q a t0 represents the total air volume (kg / s); t0 represents the reference temperature (°C); and t1 represents the exhaust gas temperature (°C).

[0134] After obtaining the energy conservation parameters under the weak steady-state condition, the calorific value Q of the fuel is calculated using the law of conservation of energy. net.ar .

[0135] S3: Using the formula COR = Q net.ar / Q design Obtain the actual fuel calorific value Q net.ar Compared with the original design fuel calorific value Q of the unit design The ratio COR is used as a correction factor for the calorific value of coal-fired boilers, and is used to correct the actual fuel quantity in the fuel master control of the coordinated control system. See Figure 2When the actual fuel calorific value is lower than the unit's original design fuel calorific value, the calculated correction value (COR) is less than 1. Multiplying this by the actual fuel quantity yields the corrected fuel quantity. At this point, the deviation from the fuel setting is less than 0. This deviation value is input to the main control PID controller. The fuel main control PID controller automatically corrects based on the deviation, gradually increasing the output to make the corrected fuel quantity equal to the fuel setting, thereby compensating for the system's total heat. When the actual fuel calorific value is higher than the unit's original design fuel calorific value, the calculated correction value (COR) is greater than 1. Multiplying this by the actual fuel quantity yields the corrected fuel quantity. At this point, the deviation from the fuel setting is greater than 0. This deviation value is input to the main control PID controller. The fuel main control PID controller automatically corrects based on the deviation, gradually decreasing the output to make the corrected fuel quantity equal to the fuel setting, thereby preventing system over-adjustment. It should be noted that PID control is a mature existing technology. This invention simply provides the deviation, fuel quantity, and fuel quantity setting to the PID controller, which automatically adjusts. The internal adjustment process of the PID controller is a conventional existing technology and will not be elaborated upon here.

[0136] Through the above technical solutions, this invention proposes a method for correcting the calorific value of a coal-fired boiler under weak steady-state conditions by adopting a direct modeling method. By judging the weak steady-state conditions of the unit data, weak steady-state data screening is achieved, providing relatively steady-state data for boiler heat balance calculation, reducing data disturbance, and improving the accuracy of calorific value correction. Using the boiler heat balance method, the current calorific value information of the unit can be calculated directly and accurately, and the functional relationship between the unit load and the actual fuel quantity can be further derived and used as the calorific value correction amount of the unit at future times. What is obtained is the true boiler fuel calorific value information, which can more accurately reflect the current calorific value change of the unit and further improve the accuracy of calorific value correction.

[0137] Example 2

[0138] Based on Embodiment 1, Embodiment 2 of the present invention also provides a coal-fired boiler calorific value correction device with energy conservation under weak steady-state conditions, the device comprising:

[0139] The energy conservation parameter acquisition module is used to extract the main parameters of the weak steady-state parameters from the real-time data of the unit operation. It filters each main parameter and judges the weak steady-state conditions in the time detection window. When all main parameters meet the weak steady-state judgment conditions during the detection period, it outputs the average value of the energy conservation parameters under the corresponding number of detections.

[0140] The boiler heat balance calculation module is used to perform boiler heat balance calculations using the average value of energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load.

[0141] The calibration module is used to verify the actual fuel calorific value Q. net.ar Compared with the original design fuel calorific value Q of the unit designThe ratio COR is used as a correction factor for the calorific value of coal-fired boilers, and the fuel quantity of the unit is adjusted based on the calorific value correction factor of the coal-fired boilers.

[0142] Specifically, the energy conservation parameter acquisition module is also used for:

[0143] Step 101: Determine the start conditions for calorific value correction. If the start conditions for calorific value correction are met, proceed to step 102.

[0144] Step 102: Within the limited time detection window, use dynamic mean filtering to filter the main parameters in the unit's original data; the filtered main parameters include unit load, main steam pressure, and actual coal quantity.

[0145] Step 103: Real-time iteration of the main parameters after filtering and detection, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n The deviation value is checked to see if it meets the weak steady-state condition. If it does not, the process returns to step 101. If it does, the process continues to the next detection until the Nth detection is completed. Then, the average value of the energy conservation parameters of the Nth detection is output.

[0146] More specifically, the energy conservation parameters include total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, blast cylinder exhaust enthalpy, total air volume, reference temperature, and exhaust gas temperature.

[0147] More specifically, step 101 includes:

[0148] Record real-time data of the generator unit. When the main parameters of the generator unit simultaneously meet the following startup conditions...

[0149] |P t -P t-1 |<E P ,|Y t -Y t-1 |<E Y |B t -B t-1 |<E B 、|P t -Q t |<E P If the condition is met, proceed to step 102; otherwise, continue to determine the start-up conditions. Here, P is the unit load, Y is the main steam pressure, B is the actual coal quantity, Q is the unit load command, t is the current time, and E is the start-up condition. P E Y E BThese are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively.

[0150] More specifically, step 102 includes:

[0151] Through formula Design a time detection window for detecting the main parameters of the unit, where T is the detection period, L is the length of the time window, and N is the total number of detections in the window;

[0152] Within the time detection window, dynamic mean filtering is used to filter the main parameters in the unit's raw data. The filtered main parameters are as follows:

[0153]

[0154] In the nth detection, n∈{1,2,…,N}, PL n For the filtered unit load, YL n BL represents the filtered main steam pressure. n The actual amount of coal after filtering is given, and avg() is the mean function.

[0155] More specifically, step 103 includes:

[0156] a) If n = 1, where n represents the nth detection, the initial weakly steady-state state variable F = false, and the maximum and minimum values ​​of each principal parameter are set as follows:

[0157]

[0158] At this point, the mean value of each energy conservation parameter is denoted as...

[0159]

[0160] in, This represents the mean value of the i-th energy conservation parameter during the first detection. This represents the value of the i-th energy conservation parameter during the first detection;

[0161] If n > 1, the maximum and minimum values ​​of each main parameter are respectively

[0162]

[0163] At this point, the mean values ​​of all energy conservation parameters are

[0164]

[0165] In the above formula Let represent the mean value of the i-th energy conservation parameter during the n-th detection. Let represent the mean value of the i-th energy conservation parameter during the (n-1)-th detection. This represents the value of the i-th energy conservation parameter during the n-th detection.

[0166] b) During each test, determine the deviation between the maximum and minimum values ​​of each main parameter and the unit load command Q. n Compared with the actual load P n Does the deviation value satisfy the following weak steady-state conditions?

[0167]

[0168] If the condition is not met, return to step 101; if the condition is met, return to step a) to perform the next test, until the Nth test is completed, then execute step c).

[0169] c) Set the weakly steady-state state variable F = true, and output the mean value of the energy conservation parameter of the Nth test.

[0170] More specifically, the boiler heat balance calculation module is also used for:

[0171] Through formula Perform boiler heat balance calculations to obtain the fuel calorific value, where Q net.ar Q represents the calorific value of the fuel. b Where η is the total calorific value of the fuel, η is the efficiency correlation coefficient, and B is the total amount of coal entering the furnace.

[0172] The total heat capacity of the boiler is expressed by the formula calculate,

[0173] Where, q 34 Loss due to incomplete combustion; q 56 For ash residue, heat dissipation, and manufacturing losses;

[0174] Q1 is the effective heat absorption of the boiler and Q1 = D. gr i gr -D gs i gs -D jws i jws +D zr (i zr -i gp );D gr Main steam flow rate; i gr Main vapor enthalpy; i gs For water enthalpy; D gs D is the water supply flow rate; jws To reduce the flow rate of the heated water; jws To reduce the enthalpy of water; D zr i is the reheat steam flow rate; zr For reheat steam enthalpy; i gp For high cylinder exhaust enthalpy;

[0175] Q2 is the total heat of the flue gas and Q2 = 1.071(1.3593 + 0.000188t1)(t1 - t0)Q a Q a t0 represents the total air volume; t0 represents the reference temperature; and t1 represents the exhaust gas temperature.

[0176] More specifically, the correction module is also used for:

[0177] Using the formula COR = Q net.ar / Q design Obtain the actual fuel calorific value Q net.ar Compared with the original design fuel calorific value Q of the unit design The ratio of the actual fuel calorific value to the actual fuel quantity is calculated as follows: When the actual fuel calorific value is lower than the original design fuel calorific value of the unit, the calculated correction amount COR is less than 1. Multiplying this by the actual fuel quantity yields the corrected fuel quantity. At this point, the deviation from the fuel setting is less than 0. This deviation value is input to the main control PID controller. The main fuel control PID controller automatically corrects based on the deviation, gradually increasing the output to make the corrected fuel quantity equal to the fuel setting, thereby compensating for the total system heat. When the actual fuel calorific value is higher than the original design fuel calorific value of the unit, the calculated correction amount COR is greater than 1. Multiplying this by the actual fuel quantity yields the corrected fuel quantity. At this point, the deviation from the fuel setting is greater than 0. This deviation value is input to the main control PID controller. The main fuel control PID controller automatically corrects based on the deviation, gradually decreasing the output to make the corrected fuel quantity equal to the fuel setting, thereby preventing system over-adjustment. It should be noted that PID control is a mature existing technology. This invention simply provides the deviation amount, fuel quantity, and fuel quantity setting to the PID controller, which automatically adjusts. The internal adjustment process of the PID controller is a relatively conventional existing technology and will not be elaborated upon here.

[0178] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 the present invention.

Claims

1. A method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation, characterized in that, The method includes the following steps: Step 1: Extract the main parameters of the weak steady-state parameters from the real-time data of the unit operation. Filter each main parameter and determine the weak steady-state condition within a time detection window. When all main parameters meet the weak steady-state judgment condition during the detection period, output the average value of the energy conservation parameter for the corresponding number of detections. The filtered main parameters include the unit load, main steam pressure, and actual coal quantity. The output value is calculated based on the deviation between the maximum and minimum values ​​of each main parameter and the unit load command. Compared with actual load When all deviation values ​​are less than the corresponding preset deviation values, the weak steady-state condition is met; otherwise, the weak steady-state condition is not met. Step one includes: Step 101: Determine the start-up conditions for calorific value correction. If the start-up conditions for calorific value correction are met, proceed to step 102. Step 101 includes: Record real-time data of the generator unit. When the main parameters of the generator unit simultaneously meet the following startup conditions... , , , If the condition is met, proceed to step 102; otherwise, continue to evaluate the startup conditions. For unit load, Main steam pressure This represents the actual amount of coal. For unit load command, For the current moment, , , These are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively. Step 102: Within the limited time detection window, use dynamic mean filtering to filter the main parameters in the unit's raw data; Step 103: Real-time traversal of the main parameters after filtering, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command. Compared with actual load Check if the deviation value meets the weak steady-state condition. If not, return to step 101; if it does, continue to the next test until the [number missing]. After the first test, the output will be... The average value of the energy conservation parameters detected in each test; the energy conservation parameters include total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, high-pressure cylinder exhaust enthalpy, total air volume, reference temperature, and exhaust gas temperature; Step 2: Calculate the boiler heat balance using the average value of the energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load; Step 3: Actual fuel calorific value Fuel calorific value compared with the original design of the unit ratio As a calorific value correction value for coal-fired boilers, the fuel quantity of the unit is adjusted using the calorific value correction value for coal-fired boilers.

2. The method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation as described in claim 1, characterized in that, Step 102 includes: Through formula Design a time-based detection window for detecting the main parameters of the generator unit, where... For the testing cycle, The time window length, This represents the total number of window checks. Within the time detection window, dynamic mean filtering is used to filter the main parameters in the unit's raw data. The filtered main parameters are as follows: Among them, the During the second test , The filtered unit load, This is the filtered main steam pressure. This is the actual coal quantity after filtering. This is a mean function.

3. The method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation as described in claim 2, characterized in that, Step 103 includes: a) If , Indicates the first The state variables of the initial weakly steady state during the second detection. The maximum and minimum values ​​of each main parameter are set to At this point, the mean value of each energy conservation parameter is denoted as... in, Indicates the first test The mean of the energy conservation parameters, Indicates the first The values ​​of the energy conservation parameters during the first detection; like The maximum and minimum values ​​of each main parameter are respectively At this point, the mean values ​​of all energy conservation parameters are in, Indicates the first The first test The mean of the energy conservation parameters, Indicates the first The first test The mean of the energy conservation parameters, Indicates the first The first test The values ​​of the energy conservation parameters; b) During each test, determine the deviation between the maximum and minimum values ​​of each main parameter and the unit load command. Compared with actual load Does the deviation value satisfy the following weak steady-state conditions? If the condition is not met, return to step 101; if the condition is met, return to step a) to perform the next check, until the [number]th [step / step / etc.]. After the second test is completed, proceed to step c). c) The state variables of the weakly steady state Output the first The mean of the energy conservation parameters of each test.

4. The method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation as described in claim 3, characterized in that, Step two includes: Through formula Perform boiler heat balance calculations to obtain the fuel calorific value, among which, The calorific value of the fuel. Total heat of fuel For efficiency correlation coefficient, This refers to the total amount of coal entering the furnace. The total heat capacity of the boiler is expressed by the formula calculate, in, Losses due to incomplete combustion; For ash residue, heat dissipation, and manufacturing losses; For the boiler to effectively absorb heat and ; Main steam flow rate; Main vapor enthalpy; For water enthalpy; For water supply flow rate; To reduce the flow rate of the heated water; To reduce the enthalpy of water; This refers to the reheat steam flow rate; It is the enthalpy of reheated steam; For high cylinder exhaust enthalpy; For the total heat of exhaust smoke and ; Total air volume; Reference temperature; This refers to the exhaust gas temperature.

5. The method for correcting the calorific value of a coal-fired boiler under weak steady-state energy conservation as described in claim 4, characterized in that, Step three includes: Through formula Obtain the actual fuel calorific value Fuel calorific value compared with the original design of the unit The ratio, when the actual fuel calorific value is lower than the original design fuel calorific value of the unit, is the calculated correction amount. When the value is less than 1, the fuel master PID control increases the fuel quantity to compensate for the total heat of the system; when the actual calorific value is higher than the design calorific value, the calculated correction amount... If the value is greater than 1, the fuel master PID control reduces the amount of fuel and the total heat of the system.

6. A calorific value correction device for a coal-fired boiler under weak steady-state energy conservation, characterized in that, The device includes: The energy conservation parameter acquisition module extracts the main parameters of weak steady-state parameters from real-time data of unit operation. It filters each main parameter and judges weak steady-state conditions within a time detection window. When all main parameters meet the weak steady-state judgment conditions during the detection period, it outputs the average value of the energy conservation parameters for the corresponding number of detections. The filtered main parameters include unit load, main steam pressure, and actual coal quantity. The module also calculates the average value of the energy conservation parameters based on the deviation between the maximum and minimum values ​​of each main parameter and the unit load command. Compared with actual load When all deviation values ​​are less than the corresponding preset deviation values, the weak steady-state condition is met; otherwise, the weak steady-state condition is not met. The energy conservation parameter acquisition module is also used for: Step 101: Determine the start-up conditions for calorific value correction. If the start-up conditions for calorific value correction are met, proceed to step 102. Step 101 includes: Record real-time data of the generator unit. When the main parameters of the generator unit simultaneously meet the following startup conditions... , , , If the condition is met, proceed to step 102; otherwise, continue to evaluate the startup conditions. For unit load, Main steam pressure This represents the actual amount of coal. For unit load command, For the current moment, , , These are the preset deviation values ​​for unit load, main steam pressure, and actual coal quantity, respectively. Step 102: Within the limited time detection window, use dynamic mean filtering to filter the main parameters in the unit's raw data; Step 103: Real-time traversal of the main parameters after filtering, calculation of the maximum and minimum values ​​of each main parameter under the current number of detections, and the mean value of the energy conservation parameter under the corresponding number of detections, and determination of the deviation between the maximum and minimum values ​​of each main parameter and the unit load command. Compared with actual load Check if the deviation value meets the weak steady-state condition. If not, return to step 101; if it does, continue to the next test until the [number missing]. After the first test, the output will be... The average value of the energy conservation parameters detected in each test; the energy conservation parameters include total fuel heat, total coal quantity, main steam flow rate, main steam enthalpy, feedwater enthalpy, feedwater flow rate, desuperheating water flow rate, desuperheating water enthalpy, reheat steam flow rate, reheat steam enthalpy, high-pressure cylinder exhaust enthalpy, total air volume, reference temperature, and exhaust gas temperature; The boiler heat balance calculation module is used to perform boiler heat balance calculations using the average value of energy conservation parameters to obtain the actual fuel calorific value corresponding to the current unit load. Calibration module for actual fuel calorific value Fuel calorific value compared with the original design of the unit ratio As a calorific value correction value for coal-fired boilers, the fuel quantity of the unit is adjusted using the calorific value correction value for coal-fired boilers.

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