Method for determining low load combustion stability of boiler of thermal power unit

Abstract

The present application provides a kind of determination method for low load combustion stability of thermal power generating unit boiler, belong to power grid field.The method includes: the design minimum load is as the initial value of minimum operating load;According to the minimum operating load, the deviation of each technical parameter of boiler is determined, and whether the test abort condition is triggered according to the deviation of each technical parameter of boiler is determined;If the test abort condition is not triggered, then the minimum operating load is reduced according to the first preset step size, and jump to the step of determining the deviation of each technical parameter of boiler according to the minimum operating load, and whether the test abort condition is triggered according to the deviation of each technical parameter of boiler is determined to continue to execute;If the test abort condition is triggered, then the minimum operating load is increased according to the second preset step size, and the increased minimum operating load is used as target load;The present application gradually reduces the minimum operating load by test, obtains target load, and can effectively identify the low load combustion stability of boiler.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power grid, and particularly relates to a method for determining low-load stable combustion capability of a thermal power unit boiler. BACKGROUND

[0002] With the addition of new energy such as photovoltaic and wind power to the power grid, the thermal power unit which bears the basic power source begins to participate in deep peak regulation frequently, so that the load of the thermal power unit is getting lower and lower.

[0003] On the one hand, the minimum load stable combustion capability of the thermal power unit boiler determines the lower limit of the peak regulation capability of the thermal power unit, and reducing the minimum load of the unit will bring substantial peak regulation benefits to the thermal power enterprise; on the other hand, when participating in deep peak regulation of the power grid, the poor low-load stable combustion capability of the thermal power boiler will cause the unit to be disconnected from the grid, which will bring a major hidden danger to the safety of the local power grid. Therefore, the minimum load stable combustion capability of the thermal power unit boiler is paid more and more attention by the thermal power enterprise and the local power grid, and therefore it is necessary to carry out the identification of the low-load stable combustion capability of the thermal power unit boiler.

[0004] In the prior art, only the combustion fluctuation and duration, negative pressure fluctuation and duration, and over-temperature and deviation of the heating surface are required for the low-load stable combustion capability; and when the unit participates in heat supply or mixed combustion of non-coal fuel, the low-load stable combustion capability is difficult to identify, so that the unqualified thermal power boiler unit participates in deep peak regulation of the power grid, reduces the peak regulation benefits of the thermal power unit, and brings a huge safety risk to the power grid. SUMMARY

[0005] The embodiment of the present application 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 no effective evaluation method for the low-load stable combustion capability of the unit boiler in the prior art, which affects the peak regulation benefits of the thermal power unit and brings a safety risk to the power grid.

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

[0007] taking the designed minimum load as an initial value of the minimum operating load;

[0008] determining the deviation of each technical parameter of the boiler according to the minimum operating load, and determining whether a test termination condition is triggered according to the deviation of each technical parameter of the boiler;

[0009] if the test termination condition is not triggered, reducing the minimum operating load by a first preset step, 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 the test termination condition is triggered according to the deviation of each technical parameter of the boiler, and continuing to execute;

[0010] If the test termination condition is triggered, the minimum operating load is increased by a second preset step size, and the increased minimum operating load is taken as the target load.

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

[0012] The embodiment of the present application provides a method for determining the low-load stable combustion capability of a boiler of a thermal power unit, which comprises the following steps: taking a design minimum load as an initial value of a minimum operating load; determining the deviation of each technical parameter of the boiler according to the minimum operating load, and determining whether a test termination condition is triggered according to the deviation of each technical parameter of the boiler; if the test termination condition is not triggered, reducing the minimum operating load by a first preset step size, 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 the test termination condition is triggered according to the deviation of each technical parameter of the boiler; if the test termination condition is triggered, increasing the minimum operating load by a second preset step size, and taking the increased minimum operating load as a target load; in the embodiment of the present application, the minimum operating load is gradually reduced through a test, the operation of the boiler is monitored through the deviation of the technical parameters, and when the deviation of each technical parameter is too large, it is indicated that the current minimum operating load has reached the minimum and cannot be reduced any more, so that the target load, i.e., the actual minimum load at which the boiler can normally operate, is obtained. Therefore, the low-load stable combustion capability of the boiler can be effectively determined, so that unqualified thermal power boiler units are prevented from participating in deep peak regulation of a power grid, the peak regulation income of the thermal power unit is improved, and the risk of power grid failure is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0014] Figure 1 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 the embodiment of the present application;

[0015] Figure 2 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 by the embodiment of the present application. DETAILED DESCRIPTION

[0016] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, technologies, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0017] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be described by specific embodiments in conjunction with the accompanying drawings.

[0018] Figure 1 A flow chart of a method for determining the low-load stable combustion capability of a boiler of a thermal power generating unit is provided for the embodiments of the present application. Referring to Figure 1 The method for determining the low-load stable combustion capability of a boiler of a thermal power generating unit, comprises:

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

[0020] S102: 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;

[0021] S103: if the test termination condition is not triggered, reducing the minimum operating load by a first preset step size, 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, and continuing to execute;

[0022] When the load of the boiler is too low, the boiler operation is abnormal, and the technical parameters deviate. For example, the technical parameters include the rated values of the main steam pressure, the main steam temperature, the reheat steam pressure, the reheat steam temperature, the steam drum water level, the exhaust gas temperature, the oxygen content, the furnace negative pressure, the fire detection air pressure, the fuel oil pressure, the one-pass tube wall temperature, the screen-pass tube wall temperature, the two-pass inlet wall temperature, the two-pass outlet wall temperature, the reheat tube wall temperature, the minimum load design value, the alarm high value and low value, and the shutdown value.

[0023] Based on this, in the embodiments of the present application, the design minimum load can be taken as the initial value of the minimum operating load, and then the design minimum load is gradually reduced until the test termination condition is triggered.

[0024] S104: if the test termination condition is triggered, increasing the minimum operating load by a second preset step size, and taking the increased minimum operating load as the target load;

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

[0026] The triggering of the test termination condition indicates that the minimum operating load at this time is too low, and therefore, the minimum operating load can be increased by a second preset step size to avoid triggering the test termination condition. Since the absolute value of the second preset step size is greater than the absolute value of the first preset step size, the increased minimum operating load generally does not trigger the test termination condition, and can be used as the target load, that is, the minimum load at which the boiler can stably burn, thereby effectively identifying the low-load stable combustion capability of the thermal power generating unit boiler.

[0027] Based on the above, the embodiments of the present application gradually reduce the minimum operating load through tests, monitor the boiler operation through the deviation of the technical parameters, and when the deviation of each technical parameter is too large, it indicates that the current minimum operating load has reached the minimum and cannot be further reduced. The target load, that is, the actual minimum load at which the boiler can stably burn, is obtained, thereby effectively identifying the low-load stable combustion capability of the boiler, thereby avoiding unqualified thermal power boiler units from participating in deep peak regulation of the power grid, improving the peak regulation income of the thermal power generating unit, and reducing the risk of power grid failure.

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

[0029] Meanwhile, to improve the accuracy of the determination of the target load, in one possible implementation, the above method can further include:

[0030] S108: The steps of S101 to S104 are repeatedly performed until the deviation of the target loads determined continuously for two times is less than 5%;

[0031] S109: The average of the target loads determined continuously for two times with a deviation less than 5% is used as the final target load.

[0032] The determination result of the target load may not be accurate enough, and in the embodiments of the present application, the design minimum load and above can be adjusted to repeat the steps of S101 to S104 to determine the target load twice. If the deviation of the target loads determined for two times 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 determined for two times is not less than 5%, the test needs to be performed again until the deviation of the target loads in adjacent two tests is within 5%, thereby improving the accuracy of the identification of the low-load stable combustion capability.

[0033] In one possible implementation, S102 can include:

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

[0035] The preset deviation can be 30%, when the deviation of any one technical parameter is greater than 30%, the test should be immediately suspended, and the low load identification condition is not met. Meanwhile, two determination standards of 5% and 10% can also be set. When any one technical parameter exceeds 10%, it should be determined as a key monitoring technical parameter, measures should be taken before the test to predict, 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 one technical parameter exceeds 5%, the technical parameter should be monitored, and the average value, maximum value and minimum value of the change curve during the test period are listed and recorded for subsequent analysis.

[0036] It should be noted that before S101, it is also necessary to determine whether the test can be carried out. Only when the test conditions are met, the steps of S101-S104 can be executed, and the output of the target load is accurate; if the test conditions are not met, it means that the current test is not suitable, and even if it is forced to carry out, the output of the target load is not accurate.

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

[0038] S105: Collecting data of thermal power generating units and investigating coal quality entering the furnace;

[0039] Specifically, it includes counting the types and blending combustion methods of all coal entering the furnace. The types of coal entering the furnace are distinguished according to the volatile matter, moisture and low calorific value in the industrial analysis results. When the relative deviation of one value of volatile matter, moisture and low calorific value of two kinds of coal exceeds 5%, it is determined that the two kinds of coal are different. The blending combustion method needs to be distinguished into two kinds of pre-mill blending combustion and post-mill blending combustion.

[0040] S106: Condition determination of 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 and water level of the running unit are within the design technical parameter range. When the parameters exceed the high or low alarm value, it is determined that the low load operation identification condition is not met;

[0043] 2. According to the results of coal quality investigation, when there are more than two kinds of coal entering the furnace, the coal with higher calorific value should be selected and stored for more than 8h to meet the low load stable combustion test, otherwise it is determined that the low load identification condition is not met;

[0044] 3. Observe for 2h at the designed minimum load, when any one of the following signals affecting combustion appears, such as the absence of fire detection signal of any one running burner, the overheating of heating surface, the fluctuation of negative pressure exceeding the limit, the vibration of coal mill, the large deviation of flue gas temperature at the furnace outlet, the large deviation of water level on both sides of the steam drum, the vibration of steam turbine, etc., it should be determined that the low load identification condition is not met.

[0045] When the low load determination condition is met, the steps S101-S104 are performed.

[0046] Meanwhile, the checking of the fire detection signal before the low load stable combustion test and the determination of the qualified condition of the change of the mill group or the change of the load during the low load stable combustion test can also be set.

[0047] The checking of the fire detection signal before the low load stable combustion test includes: the checking of the fire detection signal is performed within 2 hours before the test, and the condition is that all the fire detection signals have no missing phenomenon, and the next test can be performed after the condition is met.

[0048] The determination of the qualified condition of the change of the mill group or the change of the load during the low load stable combustion test includes: 1. any one of the combustion burner fire detection switch value is 0 caused by the combustion fluctuation, or the analog value of any one of the combustion burner fire detection is lower than 50% and the duration is more than 5s, or the fluctuation amplitude of the furnace negative pressure is greater than 300Pa and the duration is more than 5s; 2. the over-temperature of the heating surface, the fluctuation amplitude of the negative pressure is lower than the set value; 3. the pollutant emission meets the local government environmental protection requirement;

[0049] In one possible implementation manner, S102 can include:

[0050] S1021: acquiring actual values of the respective technical parameters of the boiler at the first preset load, the second preset load and the design minimum load;

[0051] S1022: according to the actual values of the respective technical parameters of the boiler at the first preset load, the second preset load and the design minimum load, predicted values of the respective technical parameters of the boiler at the minimum operating load in actual operation are obtained;

[0052] S1023: acquiring design values of the respective technical parameters of the boiler at the first preset load, the second preset load and the design minimum load;

[0053] S1024: according to the design values of the respective technical parameters of the boiler at the first preset load, the second preset load and the design minimum load, predicted values of the respective technical parameters of the boiler at the minimum operating load under the design condition are obtained;

[0054] S1025: according to the predicted values of the respective technical parameters of the boiler at the minimum operating load under the design condition and the predicted values of the respective technical parameters of the boiler at the minimum operating load in actual operation, the deviation of the respective technical parameters is determined.

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

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

[0057] 1. Determine the deviation of each technical parameter according to the predicted value of each technical parameter of the boiler at the minimum operating load under the design condition and the predicted value of each technical parameter of the boiler at the minimum operating load during actual operation, and determine the deviation of each technical parameter by combining the first formula.

[0058] The first formula can include:

[0059]

[0060] Wherein, N i is the deviation of the i th technical parameter; is the predicted value of the i th technical parameter of the boiler at the minimum operating load under the design condition, is the predicted value of the i th technical parameter of the boiler at the minimum operating load during actual operation, are respectively the design value of the i th technical parameter at the first preset load, the second preset load and the design minimum load; are respectively the actual value of the i th technical parameter at the first preset load, the second preset load and the design minimum load;f i is a prediction function, P b is the minimum operating load.

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

[0062] 1. According to the actual value of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load, the predicted value of each technical parameter of the boiler at the minimum operating load during actual operation is fitted.

[0063] In the embodiment of the present application, each technical parameter at the first preset load, the second preset load and the design minimum load can be fitted based on the known technical parameters to obtain a fitting curve, and then the predicted value of each technical parameter at the minimum operating load during actual operation is predicted.

[0064] Wherein, the specific fitting method is a conventional technical means in the art, which will not be described here.

[0065] Similarly, in S1024, the predicted values of the technical parameters of the boiler at the lowest operating load under the design condition can also be obtained by fitting.

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

[0067] In a possible implementation, the method can further include:

[0068] S107: determining the ratio of the plasma combustion-supporting device to the target load of the boiler at the target load;

[0069] S108: determining the influence of the plasma combustion-supporting device on the combustion state of the boiler at the target load according to the ratio of the plasma combustion-supporting device to the target load.

[0070] Further, the target load can be evaluated by determining the influence of the plasma combustion-supporting device on the combustion state.

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

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

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

[0074] S1073: determining the ratio of the plasma combustion-supporting device to the target load of the boiler at the target load.

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

[0076] 1. determining the ratio of the plasma combustion-supporting device to the target load of the boiler at the target load in combination with the second formula;

[0077] The second formula can include:

[0078]

[0079] wherein 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 devices to be put into operation; P i r is the power of a single burner, W, P b is the target load, n r is the number of burners to be put into operation under the target load; r l is the ratio of the plasma combustion-supporting device to the burner power, P i l is the power of a single plasma combustion-supporting device, W; P i r is the power of a single burner, W; r l,P is the ratio of the plasma combustion-supporting device to the target load.

[0080] The smaller the ratio of the plasma combustion-supporting device to the target load is, the better, and thus the target load can be evaluated based on the ratio of the plasma combustion-supporting device to the target load.

[0081] Specifically, different numerical ranges can be drawn to correspond to different levels, and the specific evaluation levels can be:

[0082] 1. Excellent, no oil is put into operation or the plasma maintains stable combustion, no loss of fire detection signal, and the steam temperature and pressure fluctuate within the set range.

[0083] 2. Good, no oil is put into operation or the plasma or other combustion-supporting devices maintain stable combustion, no combustion fluctuation causes any one burner fire detection switch to be 0, or any one burner fire detection analog quantity to be less than 50% and the duration to be more than 5s, or the furnace negative pressure fluctuation amplitude to be greater than 300Pa and the duration to be more than 5s, and the steam temperature and pressure fluctuate within the set range.

[0084] 3. After putting oil or plasma or other combustion-supporting devices into operation to maintain stable combustion, no combustion fluctuation causes any one burner fire detection switch to be 0, or any one burner fire detection analog quantity to be less than 50% and the duration to be more than 5s, or the furnace negative pressure fluctuation amplitude to be greater than 300Pa and the duration to be more than 5s, and the steam temperature and pressure fluctuate within the set range.

[0085] 4. After putting oil or plasma or other combustion-supporting devices into operation to maintain stable combustion, any of the following is achieved, i.e., it is determined that the conditions are not met: the fire detection is greater than 3 times, the steam temperature and pressure fluctuate out of range, the heating surface over-temperature, the negative pressure fluctuation out of range, and the pollutant emission exceeds the standard.

[0086] Further, the boiler outlet steam flow can be recorded to judge the minimum load stable combustion output of the boiler with the evaporation amount index; and the power generation of the unit can be recorded to judge the minimum load stable combustion output of the unit with the power generation index.

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

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

[0089]

[0090] Wherein, B is the coal consumption, 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 coal mill, m 3 ; P b is the target load, MW; is the minimum load actually operated before the test, MW; is the coal feeding amount under the minimum load actually operated before the test, MW.

[0091] In the embodiment of the application, the coal storage amount calculated according to the static volumes of the coal mill and the coal bunker can meet the requirement that all burners maintain operation for 5 hours under the target load, so as to estimate the minimum coal consumption during the low load stable combustion test of the thermal power unit boiler.

[0092] The above method will be described in detail in combination with specific embodiments.

[0093] Embodiment one

[0094] 1. Collection of thermal power unit data and investigation of coal quality fed into the furnace.

[0095] The technical parameters include the rated values, minimum load design values, alarm high and low values, and shutdown values of the following parameters: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace negative pressure, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, and reheat tube wall temperature.

[0096] Since the unit is with heat supply, the minimum output is determined according to the boiler evaporation capacity index. The first preset load is 70% of the rated output (717.5 t / h), the second preset load is 50% of the rated output (512.5 t / h), and the design minimum load is 410 t / h.

[0097] There are only two kinds of coal fed into the furnace, which are mixed and burned before grinding. The low calorific value deviation is 6%, which exceeds 5%, so the coal with high calorific value, i.e., coal A, is selected as the test coal.

[0098] The coal storage amount calculated according to the static volumes of the coal mill and the coal bunker can meet the requirement that all burners maintain operation for 5 hours under the target load.

[0099] 2. Analysis of the state of the running boiler.

[0100] Obtain the technical parameters under three conditions of 70% rated output, 50% rated output and design minimum load, including: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace negative pressure, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, reheat tube wall temperature and other technical parameters;

[0101] 3. Condition judgment for whether to carry out the test.

[0102] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the unit, such as pressure, temperature and water level, are within the range of the design technical parameters, and the parameters are within the range of the high and low alarm values. The power plant has stored coal with high calorific value and has stored coal amount sufficient for low load stable combustion test for more than 8 hours. Under the minimum load of the three-unit group, no signal affecting combustion, such as absence of fire detection signal of any operating burner, overheating of heating surface, negative pressure fluctuation exceeding the limit, vibration of coal mill, large deviation of flue gas temperature at the furnace outlet, large deviation of water level at both sides of the drum, vibration of the steam turbine, etc., occurred within 2 hours of observation. It is judged that the low load recognition condition is met, and the next test can be carried out;

[0103] 4. Prediction of deviation of each technical parameter.

[0104] It is found through calculation that the deviation of flue gas temperature exceeds 5%, and the deviations of the remaining parameters do not exceed 5%. The flue gas temperature is listed as the key monitoring technical parameter, and the change curve during the test is listed, the average value, maximum value and minimum value are calculated, and they are written in the report. When taking measures, it is found that the burner can be lowered and the air volume can be reduced to further reduce the flue gas temperature and reduce the deviation. The low load recognition condition is met, and the next test is carried out;

[0105] 5. Verification of the influence of plasma and other stable combustion measures on the combustion state.

[0106] According to the design data, the current, voltage and power factor of each plasma device are obtained, and the power of each plasma device is calculated. According to the target load and the number of burners to be put into operation, the power of each burner is calculated. The power of each plasma device is compared with the power of each burner.

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

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

[0109] The minimum stable combustion power target of this oil cut is 307.5t / h of main steam evaporation. During the test, the boiler burns the existing coal and remains stable. During the test, the burner should at least maintain the adjacent two layers in operation. From 60% of the rated electric load of the unit, the boiler load is reduced at a rate of 9MW / min. During the load reduction process, the oxygen content at the furnace outlet is ensured to be within a suitable range. Every 9t / h of evaporation is reduced, and 10-20 minutes are observed until the main steam evaporation reaches 307.5t / h. According to the operation habit of the operator, the boiler can be quickly reduced to the target evaporation under the condition of ensuring the safety of the boiler. During the test, the operator monitors 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, the steam-water side parameters are stable and normal. If the boiler combustion is unstable, the negative pressure swings greatly, there is a tendency to extinguish the fire, or there are two flame detection flickers in a layer, the oil combustion should be stopped immediately.

[0110] 7. After triggering the test termination condition, the load is increased by 3% of the rated load.

[0111] At 298t / h, the lower 1 burner flame detection signal is below 50%, triggering the test termination condition, and the unit load is increased to about 307t / h. After observation, it is found that the burner flame detection signal is restored, and other parameters are within the normal range.

[0112] 8. After confirming that the test termination condition disappears, maintain operation for 2h.

[0113] Finally, the unit is stabilized at about 309t / h, and after 2h of stabilization, it is found that all technical parameters are within the normal range.

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

[0115] 10. Restore the design minimum load above to adjust the mill group. At 415t / h, 8 burners of AB mill are changed to 8 burners of AC mill. During this period, all technical parameters are within the normal range, and the evaluation is excellent.

[0116] 11. Repeat steps 6-9.

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

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

[0119] The deviation of the two target loads is less than 5%, and the average value is confirmed as the final target load of 309.5t / h.

[0120] 13. Restore to the design minimum load of 410t / h or above, and the test is completed.

[0121] Example Two

[0122] 1. Collecting data of thermal power unit and investigating coal quality for entering the furnace.

[0123] Technical parameters include: rated value, minimum load design value, alarm high value and low value, shutdown value of main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace negative pressure, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, reheat tube wall temperature, etc.

[0124] Due to the unit with heat supply, the minimum output is determined according to the boiler evaporation capacity index. The involved loads include 70% rated output (717.5 t / h), 50% rated output (512.5 t / h) and design minimum output (410 t / h);

[0125] There are only two kinds of coal quality for entering the furnace, which belongs to pre-milling blending combustion. The low calorific value deviation is 6%, which exceeds 5%. The coal with high calorific value, i.e. coal A, is selected as the test coal.

[0126] 2. Analysis of the state of the in-service boiler.

[0127] Technical parameters under three conditions of 70% rated output, 50% rated output and design minimum load are obtained, including: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace negative pressure, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, reheat tube wall temperature, etc.

[0128] 3. Condition judgment for whether the test can be carried out.

[0129] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the in-service unit, such as pressure, temperature and water level, are within the range of the design technical parameters. The parameters are within the range of alarm high value and low value. The power plant has reserved coal with high calorific value and stored coal amount satisfying the low load stable combustion test for more than 8 h. Under the minimum load of the three-unit, no signal affecting combustion, such as absence of fire detection signal of any in-service burner, over-temperature of heating surface, negative pressure fluctuation out of limit, vibration of coal mill, large deviation of flue gas temperature at the furnace outlet, large deviation of water level at both sides of the drum, vibration of the steam turbine, etc. occurs for 2 h. It is found that there are 3 over-temperature of heating surface of the superheater of the boiler at about 410 t / h. The over-temperature has a tendency to expand with the decrease of load. It is determined that the boiler does not have the low load recognition condition. It is suggested to replace the heating surface during the maintenance period and then apply for the test again.

[0130] Example Three

[0131] 1. Collecting data of thermal power unit and investigating coal quality for entering the furnace.

[0132] Technical parameters include: main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace draft, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, reheat tube wall temperature, etc.

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

[0134] There are only two kinds of coal into the furnace, which belongs to pre-milling blending, and the low calorific value deviation is 6%, which exceeds 5%, so the coal with high calorific value is selected as the test coal;

[0135] The coal storage calculated according to the static volume of the coal mill and the powder bin meets the requirement of maintaining the operation of all burners for 5 hours under the target load.

[0136] 2. Analysis of the operating boiler state.

[0137] Obtain technical parameters under three conditions of 70% rated output, 50% rated output and design minimum load, including main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, drum water level, flue gas temperature, oxygen content, furnace draft, fire detection air pressure, fuel oil pressure, one-pass tube wall temperature, screen-pass tube wall temperature, two-pass inlet wall temperature, two-pass outlet wall temperature, reheat tube wall temperature, etc.

[0138] 3. Condition judgment for whether the test can be carried out.

[0139] According to the design data, technical parameters and coal quality, under the three loads investigated, the operating parameters of the unit, such as pressure, temperature and water level, are within the range of the design technical parameters, and the technical parameters are within the range of the high and low alarm values. The power plant has stored coal with high calorific value and has stored coal quantity sufficient for stable combustion test under low load for more than 8 hours. Under the minimum load of the 3-unit, no signal affecting combustion, such as absence of fire detection signal of any operating burner, overheating of heating surface, draft fluctuation exceeding the limit, coal mill vibration, large deviation of flue gas temperature at the furnace outlet, large deviation of water level at both sides of the drum, turbine vibration, etc. is observed for 2 hours. It is determined that the low load recognition conditions are met, and the next test can be carried out;

[0140] 4. Prediction of the deviation of each technical parameter.

[0141] It is found that the deviation of flue gas temperature exceeds 5%, and the rest of the parameters do not exceed 5%. The flue gas temperature is listed as the key monitoring technical parameter, and the change curve during the test is listed, the average value, maximum value and minimum value are calculated, and written in the report. When taking measures, it is found that the burner can be lowered and the air volume can be reduced to further reduce the flue gas temperature and reduce the deviation. With the low load identification condition, the next test is carried out;

[0142] 5. Verify the influence of plasma and other stable combustion measures on the combustion state.

[0143] According to the design data, the current, voltage and power factor of each plasma device are obtained, and the power of each plasma device is calculated; according to the target load and the number of burners to be put into operation, the power of each burner is calculated; compare the power of each plasma device and the power of each burner;

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

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

[0146] The target of this oil cut minimum stable combustion output is 307.5t / h of main steam evaporation capacity. During the test, the boiler burns the existing coal and keeps stable. During the test, at least two adjacent layers of burners should be kept in operation. From 60% rated electric load of the unit, reduce the boiler load at a rate of 9MW / min. During the load reduction process, ensure that the oxygen content at the furnace outlet is within a reasonable range. Observe for 10-20 minutes every 9t / h of evaporation capacity reduction until the main steam evaporation capacity reaches 307.5t / h. According to the operation habit of the operator, the boiler can be quickly reduced to the target evaporation capacity under the condition of ensuring the safety of the boiler. During the test, the operator monitors 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, the steam-water side parameters are stable and normal. If the boiler combustion is unstable, the negative pressure swings greatly and has a tendency to extinguish the fire, or two fire detectors in a layer flicker, the oil combustion should be added in time and the test should be stopped.

[0147] 7. After triggering the test termination condition, increase the load by 3% of the rated load.

[0148] When the load is 298t / h, the lower 1 burner fire detection signal is lower than 50%, which triggers the test termination condition. The unit load is increased to about 307t / h, and it is found that the burner fire detection signal is restored and other technical parameters are within the normal range.

[0149] 8. After confirming that the test termination condition disappears, maintain operation for 2 hours.

[0150] Finally, the unit is stabilized at about 309t / h, and after 2h, it is found that all the technical parameters are within the normal range.

[0151] 9. The first target load is confirmed to be 309t / h.

[0152] 10. The mill group is adjusted above the designed minimum load.

[0153] At 415t / h, the 8 burners of the AB mill are changed to the 8 burners of the AC mill, and during the period, all the technical parameters are within the normal range, and it is evaluated as excellent.

[0154] 11. Steps 6-9 are repeated.

[0155] The second target load is confirmed to be 325t / h.

[0156] 12. The two target loads are compared and the final target load is determined.

[0157] The deviation of the two target loads is higher than 5%, and it is required to be raised to about 415t / h again to switch the AB mill group and reduce the load.

[0158] 13. Steps 6-9 are repeated.

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

[0160] 14. The second and second target loads are compared, the deviation is lower than 5%, the average value is 320.5t / h, and the final target load is confirmed to be 320.5t / h.

[0161] 15. It is restored to the designed minimum load of 410t / h or above, and the test is ended.

[0162] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0163] The following is a device embodiment of the present application, and for details not described in detail, reference can be made to the corresponding method embodiments described above.

[0164] Figure 2 The structure schematic diagram of the device for determining the low load stable combustion capability of the thermal power unit boiler provided by the embodiment of the present application is shown, only the parts related to the embodiment of the present application are shown for the convenience of description, and the details are as follows:

[0165] As shown in Figure 2 , the device for determining the low load stable combustion capability of the thermal power unit boiler comprises:

[0166] The initialization module 21 is configured to set the design minimum load as an initial value of the minimum operation load.

[0167] The test termination condition judgment module 22 is configured to determine the deviation of each technical parameter of the boiler according to the minimum operation load, and determine whether a test termination condition is triggered according to the deviation of each technical parameter of the boiler.

[0168] The loop module 23 is configured to, if the test termination condition is not triggered, decrease the minimum operation load by a first preset step, and continue to execute the step of determining the deviation of each technical parameter of the boiler according to the minimum operation load, and determining whether the test termination condition is triggered according to the deviation of each technical parameter of the boiler.

[0169] The first target load output module 24 is configured to, if the test termination condition is triggered, increase the minimum operation load by a second preset step, and output the increased minimum operation load as the target load.

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

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

[0172] The first parameter acquisition unit is configured to acquire actual values of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

[0173] The first prediction unit is configured to predict the predicted values of each technical parameter of the boiler at the minimum operation load in actual operation according to the actual values of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

[0174] The second parameter acquisition unit is configured to acquire design values of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

[0175] The second prediction unit is configured to predict the predicted values of each technical parameter of the boiler at the minimum operation load in design conditions according to the design values of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

[0176] The deviation calculation unit is configured to determine the deviation of each technical parameter according to the predicted values of each technical parameter of the boiler at the minimum operation load in design conditions and the predicted values of each technical parameter of the boiler at the minimum operation load in actual operation.

[0177] In a possible implementation, the deviation calculation unit can be specifically configured to: determine the deviation of each technical parameter according to the predicted value of each technical parameter of the boiler at the minimum operating load under the design condition and the predicted value of each technical parameter of the boiler at the minimum operating load in actual operation, and determine the deviation of each technical parameter in combination with the first formula.

[0178] The first formula can include:

[0179]

[0180] wherein N i is the deviation of the i th technical parameter; is the predicted value of the i th technical parameter of the boiler at the minimum operating load under the design condition, is the predicted value of the i th technical parameter of the boiler at the minimum operating load in actual operation, are respectively the design values of the i th technical parameter at the first preset load, the second preset load and the design minimum load; are respectively the actual values of the i th technical parameter at the first preset load, the second preset load and the design minimum load;f i is a prediction function, P b is the minimum operating load.

[0181] In a possible implementation, the first prediction unit can be specifically configured to: fit to obtain the predicted value of each technical parameter of the boiler at the minimum operating load in actual operation according to the actual values of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

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

[0183] In a possible implementation, the apparatus can further include:

[0184] The ratio determination module is configured to determine the ratio of the plasma combustion-supporting device to the target load of the boiler at the target load;

[0185] The influence evaluation module is configured to determine the influence of the plasma combustion-supporting device on the combustion state of the boiler at the target load according to the ratio of the plasma combustion-supporting device to the target load.

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

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

[0188] a power calculation unit configured to calculate the power of each burner according to the target load and the number of burners to be put into operation;

[0189] a ratio output unit configured to determine the ratio of the plasma combustion-supporting device to the target load when the boiler is at the target load.

[0190] In a possible implementation, the ratio output unit can be specifically configured to determine the ratio of the plasma combustion-supporting device to the target load when the boiler is at the target load in combination with a second formula.

[0191] The second formula can include:

[0192]

[0193] wherein 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 devices to be put into operation; P i r is the power of a single burner, W, P b is the target load, n r is the number of burners to be put into operation at the target load; r l is the ratio of the plasma combustion-supporting device to the burner power, P i l is the power of a single plasma combustion-supporting device, W; P i r is the power of a single burner, W; r l,P is the ratio of the plasma combustion-supporting device to the target load.

[0194] In a possible implementation, the device described above can further include:

[0195] a verification module configured to repeatedly perform the steps of taking the design minimum load as the initial value of the minimum operating load, if the test termination condition is triggered, increasing the minimum operating load by a second preset step size, and taking the increased minimum operating load as the target load, until the deviation of the target load determined for two consecutive times is less than 5%;

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

[0197] In a possible implementation, the device can further include:

[0198] a coal storage amount estimation module configured to determine the coal storage amount according to the target load in combination with a third formula;

[0199] The third formula can include:

[0200]

[0201] wherein B is the coal consumption, 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 coal bunker, m 3 ; P b is the target load, MW; is the minimum load actually operated before the test, MW; is the coal supply amount under the minimum load actually operated before the test, MW.

[0202] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0203] Those skilled in the art can realize that the templates, units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software manner depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0204] The modules / units, if implemented in the form of software functional units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiments of the method of the present application can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned various embodiments of the method for determining the low load combustion stability of a thermal power generating unit boiler can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0205] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for determining the low load combustion stability capability of a thermal power unit boiler, characterized in that, The method comprises: taking the design minimum load as an initial value of the minimum operation load; determining the deviation of each technical parameter of the boiler according to the minimum operation load, and determining whether to trigger a test abort condition according to the deviation of each technical parameter of the boiler; if the test abort condition is not triggered, reducing the minimum operation load by a first preset step, and continuing to execute the step of determining the deviation of each technical parameter of the boiler according to the minimum operation load and determining whether to trigger the test abort condition according to the deviation of each technical parameter of the boiler; if the test abort condition is triggered, increasing the minimum operation load by a second preset step, and taking the increased minimum operation load as a target load; wherein the absolute value of the second preset step is greater than the absolute value of the first preset step; determining the ratio of the plasma combustion-supporting equipment power to the target load when the boiler is at the target load; determining the influence of the plasma combustion-supporting equipment on the combustion state when the boiler is at the target load according to the ratio of the plasma combustion-supporting equipment power to the target load; the determination of the ratio of the plasma combustion-supporting equipment power to the target load when the boiler is at the target load comprises: obtaining the current, voltage and power factor of each plasma equipment, and determining the power of each plasma equipment; calculating the power of each burner according to the target load and the number of burners to be put into operation; determining the ratio of the plasma combustion-supporting equipment power to the target load when the boiler is at the target load; the determination of the ratio of the plasma combustion-supporting equipment power to the target load when the boiler is at the target load comprises: determining the ratio of the plasma combustion-supporting equipment power to the target load when the boiler is at the target load in combination with a second formula; the second formula comprises: wherein, P is the power of a single plasma-assisted combustion device, W; V is the voltage of a single plasma-assisted combustion device, V; I is the current of a single plasma-assisted combustion device, A; Φ is the phase of a single plasma-assisted combustion device; Vp is the voltage of the plasma system, V; Ip is the current of the plasma system, A; Φp is the phase of the plasma system; N is the number of plasma-assisted combustion devices to be put into operation; Pb is the power of a single burner, W, P is the target load, N is the number of burners to be put into operation at the target load; Pp is the ratio of the power of the plasma-assisted combustion device to the power of the burner, P is the power of a single plasma-assisted combustion device, W; Pb is the power of a single burner, W; Pp is the ratio of the power of the plasma-assisted combustion device to the target load.

2. The method for determining the low load combustion stability capability of a thermal power unit boiler according to claim 1, characterized in that, the determination of the deviation of each technical parameter of the boiler according to the minimum operation load comprises: obtaining the actual values of each technical parameter of the boiler at a first preset load, a second preset load and a design minimum load; obtaining the actual values of each technical parameter of the boiler at a first preset load, a second preset load and a design minimum load; obtaining the actual values of each technical parameter of the boiler at a first preset load, a second preset load and a design minimum load; obtaining the actual values of each technical parameter of the boiler at a first preset load, a second preset load and a design minimum load; determining the deviation of each technical parameter according to the predicted values of each technical parameter of the boiler at the design condition when the boiler is at the minimum operation load and the predicted values of each technical parameter of the boiler at the actual operation when the boiler is at the minimum operation load.

3. The method for determining the low load combustion stability capability of a thermal power unit boiler according to claim 2, characterized in that, the determination of the deviation of each technical parameter according to the predicted values of each technical parameter of the boiler at the design condition when the boiler is at the minimum operation load and the predicted values of each technical parameter of the boiler at the actual operation when the boiler is at the minimum operation load comprises: According to the predicted value of each technical parameter of the boiler at the minimum operating load under the design condition and the predicted value of each technical parameter of the boiler at the minimum operating load in actual operation, the deviation of each technical parameter is determined, and the deviation of each technical parameter is determined in combination with a first formula; The first formula comprises: wherein, is the deviation of the first technical parameter; is the predicted value of the first technical parameter of the boiler at the design condition at the minimum operating load, is the predicted value of the first technical parameter at actual operation of the boiler at the minimum operating load, are the design values of the first technical parameter at the first predetermined load, the second predetermined load and the design minimum load, respectively; are the actual values of the first technical parameter at the first predetermined load, the second predetermined load and the design minimum load, respectively; is a prediction function, is the minimum operating load.​​​​​ 4. The method for determining the low load anti-explosion capability of a boiler of a thermal power unit according to claim 3, characterized in that, The predicted value of each technical parameter of the boiler at the minimum operating load in actual operation is obtained according to the actual value of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load, and comprises: The predicted value of each technical parameter of the boiler at the minimum operating load in actual operation is obtained by fitting according to the actual value of each technical parameter of the boiler at the first preset load, the second preset load and the design minimum load.

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

6. The method for determining the low load anti-explosion capability of a thermal power unit boiler according to any one of claims 1 to 5, characterized in that, The method further comprises: The step of taking the design minimum load as the initial value of the minimum operating load is repeatedly executed until the deviation of the target load determined for two consecutive times is less than 5% if the test termination condition is triggered, and the minimum operating load is increased by a second preset step size, and the increased minimum operating load is taken as the target load; The mean value of the target load with a deviation of less than 5% determined for two consecutive times is taken as the final target load.

7. The method for determining the low load anti-explosion 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 amount is determined in combination with a third formula; The third formula comprises: wherein, is the amount of coal to be used, t / h; is the average density of the coal to be used, kg / m3; is the volume of the coal mill, m 3 ; is the volume of the coal silo, m 3 ; is the target load, MW; is the minimum load actually operated before the test, MW; is the amount of coal to be used at the minimum load actually operated before the test, MW.

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