Method for determining low-load stable combustion capacity of thermal power generating unit boiler

Abstract

The invention provides a method for determining the low-load stable combustion capacity of a thermal power generating unit boiler, and belongs to the field of power grids. The method comprises the following steps: taking a designed minimum load as an initial value of a minimum operation load; determining deviation of each technical parameter of the boiler according to the minimum operation load, and determining whether a test suspension condition is triggered or not according to the deviation of each technical parameter of the boiler; if the test suspension condition is not triggered, reducing the minimum operation load according to a first preset step length, and skipping to determine the deviation of each technical parameter of the boiler according to the minimum operation load, and determining whether the step of triggering the test suspension condition or not according to the deviation of each technical parameter of the boiler continues to be executed; if the test suspension condition is triggered, increasing the minimum operation load according to a second preset step length, and taking the increased minimum operation load as a target load; according to the method, the minimum operation load is gradually reduced through the test, the target load is obtained, and the low-load stable combustion capacity of the boiler can be effectively identified.

Description

Technical Field

[0001] The invention relates to the technical field of power grids, and in particular to a method for determining the low-load stable combustion capability of a boiler of a thermal power unit. Background Art

[0002] With the addition of new energy sources such as photovoltaics and wind power to the power grid, thermal power units that provide basic power supply have begun to frequently participate in deep peak regulation, making the load of thermal power units lower and lower.

[0003] On the one hand, the minimum load stable combustion capability of thermal power unit boilers determines the lower limit of the peak load regulation capability of thermal power units. Reducing the minimum load of the unit will bring rich peak load regulation benefits to thermal power companies. On the other hand, when participating in the deep peak regulation of the power grid, the poor low-load stable combustion capability of thermal power boilers will cause the unit to disconnect from the grid, which will bring major hidden dangers to the safety of the local power grid. Therefore, the minimum load stable combustion capability of thermal power unit boilers is increasingly valued by thermal power companies and local power grids, so it is necessary to carry out the identification of the low-load stable combustion capability of thermal power unit boilers.

[0004] In the existing technology, usually only the combustion fluctuation and duration, negative pressure fluctuation and duration, and over-temperature and deviation of the heating surface involved in the low-load stable combustion capability are required; and when the unit participates in heating or blends non-coal fuels, the low-load stable combustion capability is difficult to determine, which makes unqualified thermal power boiler units participate in the deep peak regulation of the power grid, reducing the peak regulation benefits of thermal power units and bringing huge safety risks to the power grid. Summary of the invention

[0005] The embodiment of the present invention provides a method for determining the low-load stable combustion capability of a thermal power unit boiler, so as to solve the problem that there is a lack of an effective evaluation method for the low-load stable combustion capability of a power unit boiler in the prior art, which affects the peak-shaving benefits of the thermal power unit and brings safety risks to the power grid.

[0006] In a first aspect, an embodiment of the present invention provides a method for determining the low-load stable combustion capability of a boiler of a thermal power unit, comprising:

[0007] The design minimum load is used as the initial value of the minimum operating load;

[0008] Determine the deviation of various technical parameters of the boiler according to the minimum operating load, and determine whether to trigger the test termination condition according to the deviation of various technical parameters of the boiler;

[0009] If the test termination condition is not triggered, the minimum operating load is reduced according to the first preset step length, and the process jumps to the step of determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether the test termination condition is triggered according to the deviation of various technical parameters of the boiler to continue execution;

[0010] If the test termination condition is triggered, the minimum operating load is increased according to the second preset step length, and the increased minimum operating load is used as the target load;

[0011] The absolute value of the second preset step length is greater than the absolute value of the first preset step length.

[0012] The embodiment of the present invention provides a method for determining the low-load stable combustion capability of a boiler of a thermal power unit, the method comprising: taking the designed minimum load as the initial value of the minimum operating load; determining the deviation of each technical parameter of the boiler according to the minimum operating load, and determining whether to trigger a test termination condition according to the deviation of each technical parameter of the boiler; if the test termination condition is not triggered, reducing the minimum operating load according to a first preset step length, and jumping to the step of determining the deviation of each technical parameter of the boiler according to the minimum operating load, and determining whether to trigger the test termination condition according to the deviation of each technical parameter of the boiler to continue to execute; if the test termination condition is triggered, increasing the minimum operating load according to a second preset step length, and taking the increased minimum operating load as the target load; in the embodiment of the present invention, the minimum operating load is gradually reduced through experiments, and the operation of the boiler is monitored through the deviation of the technical parameters. When the deviation of each technical parameter is too large, it means that the current minimum operating load has reached the minimum and cannot be further reduced, thereby obtaining the target load, that is, the actual minimum load at which the boiler can operate normally. This can effectively identify the boiler's low-load stable combustion capability, thereby preventing unqualified thermal power boiler units from participating in the deep peak regulation of the power grid, increasing the peak regulation benefits of thermal power units and reducing the risk of power grid failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 This is a flow chart of a method for determining the low-load stable combustion capability of a boiler of a thermal power unit provided by an embodiment of the present invention;

[0015] Figure 2 It is a structural schematic diagram of a device for determining the low-load stable combustion capability of a boiler of a thermal power unit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0018] Figure 1 A flowchart of a method for determining the low-load stable combustion capability of a boiler of a thermal power unit is provided in accordance with an embodiment of the present invention. Figure 1 The method for determining the low-load stable combustion capability of the above-mentioned thermal power unit boiler includes:

[0019] S101: taking the designed minimum load as the initial value of the minimum operating load;

[0020] S102: determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether to trigger the test termination condition according to the deviation of various technical parameters of the boiler;

[0021] S103: If the test termination condition is not triggered, the minimum operating load is reduced according to the first preset step length, and the process jumps to the step of determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether the test termination condition is triggered according to the deviation of various technical parameters of the boiler to continue execution;

[0022] When the load of the boiler is too low, the boiler will run abnormally and the technical parameters will deviate. For example, the technical parameters include the rated values, minimum load design values, alarm high and low values, and shutdown values ​​of parameters such as main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, and reheat tube wall temperature.

[0023] Based on this, in the embodiment of the present invention, the designed minimum load can be used as the initial value of the minimum operating load, and then the designed minimum load can be gradually reduced until the test termination condition is triggered.

[0024] S104: If the test termination condition is triggered, the minimum operating load is increased according to the second preset step length, and the increased minimum operating load is used as the target load;

[0025] The absolute value of the second preset step length is greater than the absolute value of the first preset step length.

[0026] Triggering the test termination condition indicates that the minimum operating load is too low at this time. Therefore, the minimum operating load can be increased according to the second preset step to avoid triggering the test termination condition. Since the absolute value of the second preset step is greater than the absolute value of the first preset step, the increased minimum operating load usually does not trigger the test termination condition. It can be used as the target load, that is, the minimum load for the low-load stable combustion of the boiler, to achieve effective identification of the low-load stable combustion capability of the thermal power unit boiler.

[0027] Based on the above, the embodiment of the present invention gradually reduces the minimum operating load through experiments, monitors the boiler operation through the deviation of technical parameters, and when the deviation of each technical parameter is too large, it means that the current minimum operating load has reached the minimum and cannot be further reduced. The target load is obtained, that is, the actual minimum load at which the boiler can burn stably, which can effectively identify the low-load stable combustion capacity of the boiler, thereby avoiding unqualified thermal power boiler units from participating in the deep peak regulation of the power grid, improving the peak regulation benefits of thermal power units, and reducing the risk of power grid failure.

[0028] It should be noted that after increasing the minimum operating load according to the second preset step size, it is necessary to confirm that the operation is maintained for 2 hours after the triggering test termination condition disappears, and confirm that it can operate stably before the adjusted minimum operating load can be used as the target load.

[0029] At the same time, in order to improve the accuracy of determining the target load, in a possible implementation manner, the above method may further include:

[0030] S108: Repeat steps S101 to S104 until the deviation of the target load determined twice in succession is less than 5%;

[0031] S109: The average of the target loads determined twice in succession with deviations less than 5% is taken as the final target load.

[0032] The result of the target load determination may not be accurate enough. In the embodiment of the present invention, the grinding group can be adjusted to above the designed minimum load, and the steps S101 to S104 are repeated to determine the target load for the second time. If the deviation of the target loads before and after is less than 5%, the average of the two target loads is taken as the final target load; if the deviation of the target loads before and after is not less than 5%, the test needs to be repeated until the deviation of the target loads in the two adjacent tests is within 5%, thereby improving the accuracy of the low-load stable combustion capability identification.

[0033] In a possible implementation, S102 may include:

[0034] S1021: For any technical parameter, if the deviation of the technical parameter is greater than the preset deviation, the test termination condition is triggered.

[0035] The preset deviation can be 30%. When the deviation of any technical parameter is greater than 30%, the test should be terminated immediately, and the low-load identification conditions are not met. At the same time, two judgment criteria of 5% and 10% can also be set. When any technical parameter exceeds 10%, it should be determined as a key monitoring technical parameter. Measures should be taken before the test, and the technical parameter should be monitored before the minimum load stable combustion test. When the technical parameter exceeds the reasonable operating range, the test should be stopped; when any technical parameter exceeds 5%, the technical parameter should be monitored, and the change curve during the test should be listed to calculate the average value, maximum value and minimum value, and recorded for subsequent analysis.

[0036] It should be noted that before S101, it is necessary to determine whether the test can be carried out. Only when the conditions for carrying out the test are met can the steps S101 to S104 be executed, and the output of the target load is accurate; if the conditions for carrying out the test are not met, it means that it is not appropriate to carry out the test at present, and even if it is carried out forcibly, the output target load is inaccurate.

[0037] Specifically, the process of determining whether the test can be carried out includes:

[0038] S105: Data collection of thermal power units and investigation of coal quality entering the furnace;

[0039] Specifically, it includes statistics on the types of coal entering the furnace and the blending methods. The types of coal entering the furnace are distinguished based on the volatile matter, moisture and low calorific value in the industrial analysis results. When the relative deviation of the volatile matter, moisture and low calorific value of two coals exceeds 5%, they are identified as two types of coal. The blending methods need to be distinguished into two types: blending before the coal mill and blending after the coal mill.

[0040] S106: Determine whether the test can be carried out;

[0041] Specifically, it includes the following aspects:

[0042] 1. Check whether the operating parameters such as pressure, temperature, water level, etc. of the operating units are within the design technical parameter range. When the parameters exceed the alarm high or low values, it is judged that the low-load operation identification conditions are not met;

[0043] 2. According to the coal quality survey results, when there are more than two types of coal quality entering the furnace, it is necessary to select the coal with higher calorific value and store the coal that can meet the low-load stable combustion test for more than 8 hours, otherwise it will be judged as not meeting the low-load identification conditions;

[0044] 3. Observe for 2 hours under the designed minimum load. If any of the operating burners show missing fire detection signals, over-temperature of the heating surface, excessive negative pressure fluctuations, mill vibration, large deviation in furnace outlet flue gas temperature, large deviation in water levels on both sides of the drum, turbine vibration, and other signals that affect combustion, it should be determined that the low load identification conditions are not met.

[0045] When the low load identification conditions are met, the above steps S101 to S104 are executed.

[0046] At the same time, it is also possible to set up the inspection of the fire detection signal before the low-load stable combustion test and the judgment of the qualified conditions of the grinding group change or load change during the low-load stable combustion test.

[0047] The inspection of the fire detection signal before the low-load stable combustion test includes: a customized inspection of the fire detection signal within 2 hours before the test, the condition is that all fire detection signals are not missing, and the next test can only be carried out after this condition is met.

[0048] The qualified conditions for grinding group changes or load changes during the low-load stable combustion test include: 1. The fire detection switch value of any burner is 0 due to no combustion fluctuation, or the fire detection simulation value of any burner is less than 50% and lasts for more than 5s, or the negative pressure fluctuation amplitude of the furnace is greater than 300Pa and lasts for more than 5s; 2. The hot surface overtemperature and negative pressure fluctuation amplitude are lower than the set value; 3. Pollutant emissions meet the environmental protection requirements of the local government;

[0049] In one possible implementation, S102 may include:

[0050] S1021: Obtaining actual values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load;

[0051] S1022: According to the actual values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load, predict the predicted values ​​of various technical parameters of the boiler when it is actually running at the minimum operating load;

[0052] S1023: Obtaining design values ​​of various technical parameters of the boiler at a first preset load, a second preset load, and a design minimum load;

[0053] S1024: predicting the predicted values ​​of the technical parameters of the boiler under the design conditions at the minimum operating load according to the design values ​​of the technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load;

[0054] S1025: Determine the deviation of each technical parameter according to the predicted value of each technical parameter under design conditions when the boiler is at the lowest operating load and the predicted value of each technical parameter during actual operation when the boiler is at the lowest operating load.

[0055] The deviation in the embodiment of the present invention is the deviation between the actual value and the design value. When the deviation of each technical parameter is too large, it means that the current minimum operating load has reached the minimum. Therefore, the embodiment of the present invention predicts each technical parameter at the current minimum operating load based on the known first preset load, second preset load and the design value and actual value of the technical parameter at the design minimum load, including the predicted value under the design conditions and the predicted value during actual operation, so as to obtain the deviation of each technical parameter.

[0056] In a possible implementation, S1025 may include:

[0057] 1. Determine the deviation of each technical parameter according to the predicted value of each technical parameter under design conditions when the boiler is at the lowest operating load and the predicted value of each technical parameter when the boiler is at the lowest operating load during actual operation, and determine the deviation of each technical parameter in combination with the first formula;

[0058] The first formula may include:

[0059]

[0060] Among them, N i is the deviation of the i-th technical parameter; is the predicted value of the ith technical parameter of the boiler under design conditions when the boiler is at the lowest operating load, is the predicted value of the ith technical parameter of the boiler during actual operation when the boiler is at the lowest operating load, are the design values ​​of the i-th technical parameter at the first preset load, the second preset load and the design minimum load respectively; are the actual values ​​of the i-th technical parameter at the first preset load, the second preset load and the designed minimum load respectively; f i () is the prediction function, P b The minimum operating load.

[0061] In a possible implementation, S1022 may include:

[0062] 1. According to the actual values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load, the predicted values ​​of various technical parameters of the boiler at the minimum operating load during actual operation are obtained by fitting.

[0063] In the embodiment of the present invention, fitting can be performed based on the known first preset load, second preset load and various technical parameters at the designed minimum load to obtain a fitting curve, and then the predicted values ​​of various technical parameters at the minimum operating load during actual operation can be predicted.

[0064] The specific fitting method is a conventional technical means in this field and will not be described in detail here.

[0065] Similarly, in S1024, a fitting method may be used to predict the predicted values ​​of various technical parameters of the boiler under design conditions when the boiler is at the lowest operating load.

[0066] In a possible implementation manner, the first preset load may be 70% of the rated output, and the second preset load may be 50% of the rated output.

[0067] In a possible implementation manner, the above method may further include:

[0068] S107: Determine the ratio of the plasma combustion-supporting equipment to the target load when the boiler is at the target load;

[0069] S108: According to the ratio of the plasma combustion-supporting equipment to the target load, determine the influence of the plasma combustion-stabilizing equipment on the combustion state of the boiler when the boiler is at the target load.

[0070] Furthermore, the target load can be evaluated by determining the effect of the plasma combustion stabilization equipment on the combustion state.

[0071] In a possible implementation, S107 may include:

[0072] S1071: Obtain the current, voltage and power factor of each plasma device, and determine the power of each plasma device;

[0073] S1072: Calculate the power of each burner according to the target load and the number of burners to be put into use;

[0074] S1073: Determine the ratio of the plasma combustion-supporting equipment and the target load when the boiler is at the target load.

[0075] In a possible implementation, S1073 may include:

[0076] 1. Combined with the second formula, determine the ratio of plasma combustion-supporting equipment and target load when the boiler is at target load;

[0077] The second formula may include:

[0078]

[0079] Among them, P i l is the power of a single plasma combustion-supporting device, W; is the voltage of a single plasma combustion-supporting device, V; is the current of a single plasma combustion-supporting device, A; is the phase of a single plasma combustion-supporting device; U l is the voltage of the plasma system, V; I l is the current of the plasma system, A; φl is the phase of the plasma system; n l is the number of plasma combustion-supporting equipment to be invested; P i r is the power of a single burner, W, P b is the target load, n r is the number of burners put into use under the target load; r l is the ratio of the power of the plasma combustion-supporting equipment to the burner, P i l is the power of single plasma combustion equipment, W; P i r is the burner power, W; r l,P It is the ratio of plasma combustion equipment to target load.

[0080] The smaller the ratio of the plasma combustion-supporting equipment to the target load, the better. Therefore, the target load can be evaluated based on the ratio of the plasma combustion-supporting equipment to the target load.

[0081] Specifically, different numerical ranges can be defined, corresponding to different levels. The specific evaluation levels can be:

[0082] 1. Excellent, no oil injection or plasma maintenance of stable combustion, no missing fire detection signal, and the fluctuations of steam temperature and pressure are within the set range;

[0083] 2. Good, no oil injection or other combustion-supporting equipment such as plasma is used to maintain stable combustion, there is no combustion fluctuation that causes the fire detection switch value of any burner to be 0, or the fire detection analog value of any burner is less than 50% and lasts for more than 5s, or the fluctuation amplitude of the furnace negative pressure is greater than 300Pa and lasts for more than 5s, and the steam temperature and steam pressure fluctuations are within the set range;

[0084] 3. After maintaining stable combustion through other combustion-supporting equipment such as oil injection or plasma, there is no combustion fluctuation causing the fire detection switch value of any burner to be 0, or the fire detection analog value of any burner is less than 50% and lasts for more than 5s, or the fluctuation amplitude of the furnace negative pressure is greater than 300Pa and lasts for more than 5s, and the steam temperature and steam pressure fluctuations are within the set range;

[0085] 4. After maintaining stable combustion through other combustion-supporting equipment such as oil injection or plasma, if any of the following is met, the conditions are deemed to be unsatisfied: fire detection is greater than 3 times, steam temperature and steam pressure fluctuations exceed the range, heating surface overtemperature, negative pressure fluctuations exceed the range, and pollutant emissions exceed the standard.

[0086] Furthermore, the steam flow rate at the boiler outlet can be recorded, and the minimum load stable combustion output of the boiler can be determined by the evaporation index; the power generation of the unit can also be recorded, and the minimum load stable combustion output of the unit can be determined by the power generation index.

[0087] In another possible implementation, the above method may further include:

[0088] According to the target load, the coal storage quantity is determined in combination with the third formula;

[0089]

[0090] Wherein, B is the amount of coal used, t / h; is the average density of the coal to be used, kg / m3; V M is the volume of the coal mill, m 3 ; V P is the volume of the powder bin, m 3 ;P b is the target load, MW; is the minimum load actually operated before the test, MW; It is the coal feed rate under the minimum load in actual operation before the test, MW.

[0091] In the embodiment of the present invention, the coal storage amount calculated based on the static volume of the coal mill and the powder silo can be sufficient to maintain the operation of all burners for 5 hours under the target load, and the minimum coal consumption during the low-load stable combustion test of the thermal power unit boiler can be estimated.

[0092] The above method is described in detail below with reference to specific embodiments.

[0093] Embodiment 1

[0094] 1. Data collection of thermal power units and investigation of coal quality entering the furnace.

[0095] The technical parameters include: rated values, minimum load design values, high and low alarm values, and shutdown values ​​of parameters such as main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, and reheat tube wall temperature.

[0096] Because the unit provides heating, the minimum output is determined according to the boiler evaporation index. The first preset load is 70% of the rated output (717.5t / h), the second preset load is 50% of the rated output (512.5t / h) and the designed minimum load (410t / h);

[0097] There are only two types of coal quality entering the furnace, which are pre-mill blending. The low calorific value deviation is 6%, which exceeds 5%. The coal type A with high calorific value is selected as the test coal type;

[0098] The coal storage amount calculated based on the static volume of the coal mill and powder silo is sufficient to maintain the operation of all burners for 5 hours under the target load.

[0099] 2. Analysis of the status of boilers in operation.

[0100] Obtain technical parameters under three working conditions: 70% rated output, 50% rated output and designed minimum load, including: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, reheat tube wall temperature and other technical parameters;

[0101] 3. Determine whether the conditions for conducting the test can be met.

[0102] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the operating units such as pressure, temperature, water level, etc. are within the design technical parameter range, and the parameters are within the alarm high and low ranges; the power plant has reserved coal with higher calorific value and stored coal to meet the low-load stable combustion test for more than 8 hours; under the minimum load of the three units, no signals affecting combustion such as missing fire detection signals, overheating of the heating surface, excessive negative pressure fluctuations, vibration of the pulverizer, large deviation of the flue gas temperature at the furnace outlet, large deviation of the water level on both sides of the drum, vibration of the steam turbine, etc., were observed for 2 hours. It is determined that the low-load identification conditions are met and the next test can be carried out;

[0103] 4. Predict the deviation of various technical parameters.

[0104] After calculation, it was found that the exhaust temperature deviation exceeded 5%, while the other parameters did not exceed 5%. The exhaust temperature was listed as a key monitoring technical parameter, and the average, maximum and minimum values ​​of the change curve during the test were listed and written into the report. When anticipating measures, it was found that the exhaust temperature could be further reduced by lowering the burner and reducing the air volume to reduce the deviation. The low-load certification conditions were met and the next test was carried out;

[0105] 5. Verify the impact of plasma and other combustion stabilization measures on the combustion state.

[0106] Obtain the current, voltage and power factor of each plasma device according to the design data, and calculate the power of each plasma device; calculate the power of each burner according to the target load and the number of burners to be put into use; compare the power of each plasma device with the power of the burner;

[0107] Calculation found r l ≥0.6 and r l,P ≥0.1, it is judged that the plasma combustion stabilization equipment has a great influence on the combustion state.

[0108] 6. Gradually reduce the minimum operating load.

[0109] The minimum stable combustion output target for this oil cut-off is 307.5t / h of main steam evaporation. During the test, the boiler uses existing coal and remains stable. During the test, the burner should keep at least two adjacent layers in operation. Starting from 60% of the rated electrical load of the unit, the boiler load is reduced at a rate of 9MW / minute. During the load reduction process, the oxygen content at the furnace outlet is guaranteed to be within the appropriate range. Every time the evaporation volume is reduced by 9t / h, observe for 10-20 minutes until the main steam evaporation volume reaches 307.5t / h. You can also quickly reduce the load to the target evaporation volume according to the operating habits of the operating personnel while ensuring the safety of the boiler. During the test, the operating personnel monitor the main operating parameters of the boiler to ensure that the furnace pressure is normal, the combustion is stable, the flame detection is normal, the oxygen content at the furnace outlet is normal, and the parameters on the steam-water side are stable and normal. If it is found that the boiler combustion is unstable, the negative pressure swings greatly and there is a tendency to extinguish the fire, or there are two fire detection flashes on a certain layer, oil should be added in time to assist combustion and stop the test.

[0110] 7. After the test termination conditions are triggered, the rated load will increase by 3%.

[0111] At 298t / h, the fire detection signal of the lower burner was lower than 50%, triggering the test termination condition. The unit load returned to around 307t / h. After observation, it was found that the burner fire detection signal was restored and other parameters were within the normal range.

[0112] 8. After confirming that the conditions that trigger the test termination disappear, maintain operation for 2 hours.

[0113] Finally, the unit stabilized at around 309t / h and remained stable for 2 hours. Continuous observation revealed that all technical parameters were within the normal range.

[0114] 9. Confirm that the first target load is 309t / h.

[0115] 10. Adjust the mill group to restore the design minimum load. At 415t / h, the 8 burners of the AB mill were changed to 8 burners of the AC mill. During this period, all technical parameters were within the normal range and were rated as excellent.

[0116] 11. Repeat steps 6 to 9.

[0117] Confirm that the second target load is 310t / h.

[0118] 12. Compare the two target loads and determine the final target load.

[0119] The deviation of the two target loads was less than 5%, and the average value was taken to confirm that the final target load was 309.5t / h.

[0120] 13. The test ends when the load is restored to above the designed minimum load of 410t / h.

[0121] Embodiment 2

[0122] 1. Data collection of thermal power units and investigation of coal quality entering the furnace.

[0123] The technical parameters include: rated values, minimum load design values, high and low alarm values, and shutdown values ​​of parameters such as main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, and reheat tube wall temperature.

[0124] Since the unit is used for heating, the minimum output is determined according to the boiler evaporation index. The loads involved include 70% rated output (717.5t / h), 50% rated output (512.5t / h) and the designed minimum output (410t / h);

[0125] There are only two types of coal quality entering the furnace, which are pre-mill blending. The low calorific value deviation is 6%, which exceeds 5%. The coal type A with high calorific value is selected as the test coal type;

[0126] 2. Analysis of the status of boilers in operation.

[0127] Obtain technical parameters under three working conditions: 70% rated output, 50% rated output and designed minimum load, including: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, reheat tube wall temperature and other technical parameters;

[0128] 3. Determine whether the conditions for conducting the test can be met.

[0129] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the operating units, such as pressure, temperature, and water level, are within the design technical parameter range, and the parameters are within the alarm high and low ranges; the power plant has reserved coal with higher calorific value and stored coal that meets the low-load stable combustion test for more than 8 hours; under the lowest load of the three units, no signals affecting combustion, such as missing fire detection signals, overheating of the heating surface, over-limit of negative pressure fluctuation, vibration of the pulverizer, large deviation of flue gas temperature at the furnace outlet, large deviation of water level on both sides of the drum, vibration of the steam turbine, etc., were observed for 2 hours. Inspection found that the heating surface of the boiler superheater had overheating at around 410t / h, and the overheating tended to expand as the load decreased. It was determined that the boiler did not meet the low-load identification conditions, and it was recommended to use the maintenance period to check and replace the heating surface and then reapply for the test.

[0130] Embodiment 3

[0131] 1. Data collection of thermal power units and investigation of coal quality entering the furnace.

[0132] The technical parameters include: rated values, minimum load design values, high and low alarm values, and shutdown values ​​of parameters such as main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, and reheat tube wall temperature.

[0133] Since the unit is used for heating, the minimum output is determined according to the boiler evaporation index. The loads involved include 70% rated output (717.5t / h), 50% rated output (512.5t / h) and the designed minimum output (410t / h);

[0134] There are only two types of coal quality entering the furnace, which are pre-mill blending. The low calorific value deviation is 6%, which exceeds 5%. The coal type A with high calorific value is selected as the test coal type;

[0135] The coal storage amount calculated based on the static volume of the coal mill and powder silo is sufficient to maintain the operation of all burners for 5 hours under the target load.

[0136] 2. Analysis of the status of boilers in operation.

[0137] Obtain technical parameters under three working conditions: 70% rated output, 50% rated output and designed minimum load, including main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, exhaust gas temperature, oxygen content, furnace negative pressure, fire detection wind pressure, fuel oil pressure, first-pass tube wall temperature, screen-pass tube wall temperature, second-pass inlet wall temperature, second-pass outlet wall temperature, reheat tube wall temperature and other technical parameters;

[0138] 3. Determine whether the conditions for conducting the test can be met.

[0139] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the operating units such as pressure, temperature, water level, etc. are within the design technical parameter range, and the technical parameters are within the alarm high and low ranges; the power plant has reserved coal with higher calorific value and stored coal to meet the low-load stable combustion test for more than 8 hours; under the minimum load of the three units, no signals affecting combustion such as missing fire detection signals, overheating of the heating surface, excessive negative pressure fluctuations, vibration of the pulverizer, large deviation of the flue gas temperature at the furnace outlet, large deviation of the water level on both sides of the drum, vibration of the steam turbine, etc., were observed for 2 hours. It is determined that the low-load identification conditions are met and the next test can be carried out;

[0140] 4. Predict the deviation of various technical parameters.

[0141] After calculation, it was found that the exhaust temperature deviation exceeded 5%, while the other parameters did not exceed 5%. The exhaust temperature was listed as a key monitoring technical parameter, and the average, maximum and minimum values ​​of the change curve during the test were listed and written into the report. When anticipating measures, it was found that the exhaust temperature could be further reduced by lowering the burner and reducing the air volume to reduce the deviation. The low-load certification conditions were met and the next test was carried out;

[0142] 5. Verify the impact of plasma and other combustion stabilization measures on the combustion state.

[0143] Obtain the current, voltage and power factor of each plasma device according to the design data, and calculate the power of each plasma device; calculate the power of each burner according to the target load and the number of burners to be put into use; compare the power of each plasma device with the power of the burner;

[0144] Calculation found r l ≥0.6 and r l,P ≥0.1, it is judged that the plasma combustion stabilization equipment has a great influence on the combustion state.

[0145] 6. Gradually reduce the minimum operating load.

[0146] The minimum stable combustion output target for this oil cut-off is 307.5t / h of main steam evaporation. During the test, the boiler uses existing coal and remains stable. During the test, the burner should keep at least two adjacent layers in operation. Starting from 60% of the rated electrical load of the unit, the boiler load is reduced at a rate of 9MW / minute. During the load reduction process, the oxygen content at the furnace outlet is guaranteed to be within the appropriate range. Every time the evaporation volume is reduced by 9t / h, observe for 10-20 minutes until the main steam evaporation volume reaches 307.5t / h. You can also quickly reduce the load to the target evaporation volume according to the operating habits of the operating personnel while ensuring the safety of the boiler. During the test, the operating personnel monitor the main operating parameters of the boiler to ensure that the furnace pressure is normal, the combustion is stable, the flame detection is normal, the oxygen content at the furnace outlet is normal, and the parameters on the steam-water side are stable and normal. If it is found that the boiler combustion is unstable, the negative pressure swings greatly and there is a tendency to extinguish the fire, or there are two fire detection flashes on a certain layer, oil should be added in time to assist combustion and stop the test.

[0147] 7. After the test termination conditions are triggered, the rated load will increase by 3%.

[0148] At 298t / h, the fire detection signal of the lower burner was lower than 50%, triggering the test termination condition. The unit load returned to around 307t / h. After observation, it was found that the burner fire detection signal was restored and other technical parameters were within the normal range.

[0149] 8. After confirming that the conditions that trigger the test termination disappear, maintain operation for 2 hours.

[0150] Finally, the unit stabilized at around 309t / h and remained stable for 2 hours. Continuous observation revealed that all technical parameters were within the normal range.

[0151] 9. Confirm that the first target load is 309t / h.

[0152] 10. Adjust the grinding group to restore the load above the designed minimum load.

[0153] At 415t / h, the 8 burners of AB coal mill were changed to 8 burners of AC coal mill. During this period, all technical parameters were within the normal range and were rated as excellent.

[0154] 11. Repeat steps 6 to 9.

[0155] Confirm that the second target load is 325t / h.

[0156] 12. Compare the two target loads and determine the final target load.

[0157] When the deviation of the two target loads is higher than 5%, it is necessary to increase the load to about 415t / h and then switch the AB grinding group again and reduce the load.

[0158] 13. Repeat steps 6 to 9.

[0159] The third target load was confirmed to be 316t / h.

[0160] 14. Compare the target loads of the second and third times, the deviation is less than 5%, take the average value of 320.5t / h, and confirm that the final target load is 320.5t / h.

[0161] 15. The test ends when the load is restored to above the designed minimum load of 410t / h.

[0162] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0163] The following is an embodiment of the device of the present invention. For details not described in detail, reference may be made to the corresponding method embodiments described above.

[0164] Figure 2 The structure diagram of the device for determining the low-load stable combustion capability of a thermal power unit boiler provided by an embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0165] like Figure 2 As shown, the device for determining the low-load stable combustion capability of the boiler of a thermal power unit includes:

[0166] An initialization module 21, used for taking the designed minimum load as the initial value of the minimum operating load;

[0167] The test termination condition judgment module 22 is used to determine the deviation of various technical parameters of the boiler according to the minimum operating load, and determine whether to trigger the test termination condition according to the deviation of various technical parameters of the boiler;

[0168] A loop module 23, for if the test termination condition is not triggered, reducing the minimum operating load according to a first preset step length, and jumping to the step of determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether the test termination condition is triggered according to the deviation of various technical parameters of the boiler to continue execution;

[0169] A first target load output module 24 is used to increase the minimum operating load according to a second preset step length if the test termination condition is triggered, and use the increased minimum operating load as the target load;

[0170] The absolute value of the second preset step length is greater than the absolute value of the first preset step length.

[0171] In a possible implementation, the test termination condition determination module 22 may include:

[0172] A first parameter acquisition unit is used to acquire actual values ​​of various technical parameters of the boiler at a first preset load, a second preset load and a designed minimum load;

[0173] The first prediction unit is used to predict the predicted values ​​of the various technical parameters of the boiler when it is actually running at the minimum operating load according to the actual values ​​of the various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load;

[0174] The second parameter acquisition unit is used to obtain the design values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load;

[0175] The second prediction unit is used to predict the predicted values ​​of various technical parameters of the boiler under the design conditions at the minimum operating load according to the design values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load;

[0176] The deviation calculation unit is used to determine the deviation of each technical parameter according to the predicted value of each technical parameter under design conditions when the boiler is at the lowest operating load and the predicted value of each technical parameter when the boiler is actually operating at the lowest operating load.

[0177] In a possible implementation, the deviation calculation unit may be specifically used to: determine the deviation of each technical parameter according to the predicted value of each technical parameter under design conditions when the boiler is at the lowest operating load and the predicted value of each technical parameter when the boiler is at the lowest operating load during actual operation, and determine the deviation of each technical parameter in combination with the first formula;

[0178] The first formula may include:

[0179]

[0180] Among them, N i is the deviation of the i-th technical parameter; is the predicted value of the ith technical parameter of the boiler under design conditions when the boiler is at the lowest operating load, is the predicted value of the ith technical parameter of the boiler during actual operation when the boiler is at the lowest operating load, are the design values ​​of the i-th technical parameter at the first preset load, the second preset load and the design minimum load respectively; are the actual values ​​of the i-th technical parameter at the first preset load, the second preset load and the designed minimum load respectively; f i () is the prediction function, P b The minimum operating load.

[0181] In a possible implementation, the first prediction unit can be specifically used to fit the predicted values ​​of various technical parameters of the boiler during actual operation at the minimum operating load based on the actual values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load.

[0182] In a possible implementation manner, the first preset load may be 70% of the rated output, and the second preset load may be 50% of the rated output.

[0183] In a possible implementation manner, the above device may further include:

[0184] A ratio determination module is used to determine the ratio of the plasma combustion-supporting equipment to the target load when the boiler is at the target load;

[0185] The impact assessment module is used to determine the impact of the plasma combustion stabilization equipment on the combustion state of the boiler at the target load based on the ratio of the plasma combustion-supporting equipment to the target load.

[0186] In a possible implementation, the ratio determination module may include:

[0187] The third parameter acquisition unit is used to acquire the current, voltage and power factor of each plasma device and determine the power of each plasma device;

[0188] The power calculation unit is used to calculate the power of each burner according to the target load and the number of burners to be put into use;

[0189] The ratio output unit is used to determine the ratio of the plasma combustion-supporting equipment and the target load when the boiler is at the target load.

[0190] In a possible implementation, the ratio output unit may be specifically used to: determine the ratio of the plasma combustion-supporting device and the target load of the boiler at the target load in combination with the second formula;

[0191] The second formula may include:

[0192]

[0193] Among them, P i l is the power of a single plasma combustion-supporting device, W; is the voltage of a single plasma combustion-supporting device, V; is the current of a single plasma combustion-supporting device, A; is the phase of a single plasma combustion-supporting device; U l is the voltage of the plasma system, V; I l is the current of the plasma system, A; φ l is the phase of the plasma system; n l is the number of plasma combustion-supporting equipment to be invested; P i r is the power of a single burner, W, P b is the target load, n r is the number of burners put into use under the target load; r l is the ratio of the power of the plasma combustion-supporting equipment to the burner, P i l is the power of single plasma combustion equipment, W; P i r is the burner power, W; r l,P It is the ratio of plasma combustion equipment to target load.

[0194] In a possible implementation manner, the above device may further include:

[0195] A verification module, for repeatedly executing the steps of taking the designed minimum load as the initial value of the minimum operating load, and if the test termination condition is triggered, increasing the minimum operating load according to a second preset step length, and taking the increased minimum operating load as the target load, until the deviation of the target load determined twice in succession is less than 5%;

[0196] The second target load output module is used to take the average of two consecutive determined target loads with a deviation less than 5% as the final target load.

[0197] In a possible implementation manner, the above device may further include:

[0198] A coal storage estimation module is used to determine the coal storage according to the target load and in combination with the third formula;

[0199] The third formula may include:

[0200]

[0201] Wherein, B is the amount of coal used, t / h; is the average density of the coal to be used, kg / m3; V M is the volume of the coal mill, m 3 ; V P is the volume of the powder bin, m 3 ;P b is the target load, MW; is the minimum load actually operated before the test, MW; It is the coal feed rate under the minimum load in actual operation before the test, MW.

[0202] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0203] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0204] If the module / unit is implemented in the form of 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 present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned method for determining the low-load stable combustion capacity of the boiler of each thermal power unit can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. Computer-readable media may include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0205] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for determining the low-load stable combustion capability of a thermal power unit boiler, characterized in that: include: The design minimum load is used as the initial value of the minimum operating load; Determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether to trigger the test termination condition according to the deviation of various technical parameters of the boiler; If the test termination condition is not triggered, the minimum operating load is reduced according to a first preset step length, and the process jumps to the step of determining the deviation of various technical parameters of the boiler according to the minimum operating load, and determining whether the test termination condition is triggered according to the deviation of various technical parameters of the boiler to continue execution; If the test termination condition is triggered, the minimum operating load is increased according to a second preset step length, and the increased minimum operating load is used as the target load; The absolute value of the second preset step length is greater than the absolute value of the first preset step length.

2. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 1, characterized in that: Determining the deviation of various technical parameters of the boiler according to the minimum operating load includes: Obtaining actual values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load; According to the actual values ​​of the technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load, the predicted values ​​of the technical parameters of the boiler when actually operating at the minimum operating load are predicted; Obtaining design values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load; According to the design values ​​of various technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load, predict the predicted values ​​of various technical parameters of the boiler under the design conditions at the minimum operating load; The deviation of each technical parameter is determined according to the predicted value of each technical parameter of the boiler under design conditions at the minimum operating load and the predicted value of each technical parameter of the boiler during actual operation at the minimum operating load.

3. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 2, characterized in that: Determining the deviation of each technical parameter according to the predicted value of each technical parameter of the boiler under design conditions at the lowest operating load and the predicted value of each technical parameter of the boiler during actual operation at the lowest operating load includes: Determine the deviation of each technical parameter according to the predicted value of each technical parameter of the boiler under the design conditions at the minimum operating load and the predicted value of each technical parameter of the boiler during actual operation at the minimum operating load, and determine the deviation of each technical parameter in combination with the first formula; The first formula includes: Among them, N i is the deviation of the i-th technical parameter; is the predicted value of the ith technical parameter of the boiler under the design conditions at the minimum operating load, is the predicted value of the ith technical parameter of the boiler during actual operation at the minimum operating load, are respectively the design values ​​of the i-th technical parameter at the first preset load, the second preset load and the designed minimum load; are the actual values ​​of the i-th technical parameter at the first preset load, the second preset load and the designed minimum load respectively; i () is the prediction function, P b is the minimum operating load.

4. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 3, characterized in that: The method of predicting the predicted values ​​of the technical parameters of the boiler during actual operation at the minimum operating load according to the actual values ​​of the technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load includes: According to the actual values ​​of the technical parameters of the boiler at the first preset load, the second preset load and the designed minimum load, the predicted values ​​of the technical parameters of the boiler during actual operation at the minimum operating load are fitted.

5. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 3, characterized in that: The first preset load is 70% of the rated output, and the second preset load is 50% of the rated output.

6. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to any one of claims 1 to 5, characterized in that: The method further comprises: Determining the ratio of the plasma combustion-supporting equipment to the target load when the boiler is at the target load; According to the ratio of the plasma combustion-supporting equipment and the target load, the influence of the plasma combustion-stabilizing equipment on the combustion state of the boiler at the target load is determined.

7. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 6, characterized in that: The step of determining the ratio of the plasma combustion-supporting equipment to the target load when the boiler is at the target load includes: Obtain the current, voltage and power factor of each plasma device, and determine the power of each plasma device; Calculate the power of each burner according to the target load and the number of burners to be put into use; The ratio of the plasma combustion-supporting equipment to the target load is determined when the boiler is at the target load.

8. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to claim 7, characterized in that: The determining of the ratio of the plasma combustion-supporting equipment of the boiler to the target load at the target load includes: In combination with the second formula, determining the ratio of the plasma combustion-supporting device to the target load when the boiler is at the target load; The second formula includes: Among them, P i l is the power of a single plasma combustion-supporting device, W; is the voltage of a single plasma combustion-supporting device, V; is the current of a single plasma combustion-supporting device, A; is the phase of a single plasma combustion-supporting device; U l is the voltage of the plasma system, V; I l is the current of the plasma system, A; φ l is the phase of the plasma system; n l is the number of plasma combustion-supporting equipment to be invested; P i r is the power of a single burner, W, P b is the target load, n r is the number of burners put into use under the target load; r l is the ratio of the power of the plasma combustion-supporting equipment to the burner, P i l is the power of single plasma combustion equipment, W; P i r is the burner power, W; r l,P It is the ratio of the plasma combustion-supporting equipment to the target load.

9. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to any one of claims 1 to 5, characterized in that: The method further comprises: Repeat the step of using the designed minimum load as the initial value of the minimum operating load, until the step of increasing the minimum operating load according to a second preset step length if the test termination condition is triggered, and using the increased minimum operating load as the target load, until the deviation of the target load determined twice in succession is less than 5%; The average of two consecutive determinations with a deviation of less than 5% of the target load was taken as the final target load.

10. The method for determining the low-load stable combustion capability of a thermal power unit boiler according to any one of claims 1 to 5, characterized in that: The method further comprises: According to the target load, the coal storage quantity is determined in combination with the third formula; The third formula includes: Wherein, B is the amount of coal used, t / h; is the average density of the coal to be used, kg / m3; V M is the volume of the coal mill, m 3 ; V P is the volume of the powder bin, m 3 ;P b is the target load, MW; P s min is the minimum load actually operated before the test, MW; It is the coal feed rate under the minimum load in actual operation before the test, MW.

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