A combustion control method for a gas-fired boiler

Abstract

This invention discloses a combustion control method for a gas-fired boiler. The method includes: installing M pressure fluctuation measuring devices in the boiler furnace, where M is an integer greater than or equal to 6; controlling the boiler to operate under boiler design parameters; acquiring corresponding furnace pressure fluctuation measurement data through the M pressure fluctuation measuring devices for multiple different discrete load points; calculating pressure fluctuation warning limits, pressure fluctuation lockout load limits, and pressure fluctuation trip limits for each load point based on the furnace pressure fluctuation measurement data; and inputting the pressure fluctuation warning limits, pressure fluctuation lockout load limits, and pressure fluctuation trip limits into the boiler control system to perform combustion control on the gas-fired boiler in conjunction with the boiler design parameters. The combustion control method for a gas-fired boiler disclosed in this invention can monitor and control the combustion stability of the gas-fired boiler in real time based on the measured pressure fluctuation values ​​in the boiler furnace.

Description

Technical Field

[0001] This invention belongs to the field of gas-fired boiler technology, and particularly relates to a combustion control method for gas-fired boilers. Background Technology

[0002] As coal-fired boilers are gradually being replaced by gas-fired boilers, and natural gas consumption is increasing, national and local emission standards for nitrogen oxides are also gradually being tightened. More and more gas-fired boilers are adopting low-NOx combustion technologies to control NOx emissions in new or retrofitted projects, with flue gas recirculation (FGR) being a commonly used technology. Due to variations in load, ambient temperature, and gas composition, the efficiency or output / fuel ratio of gas-fired boilers is not constant but fluctuates within a range. FGR effectively reduces the combustion temperature and high-temperature zone distribution within the boiler furnace, dilutes the concentration of oxygen and nitrogen in the gas mixture, and thus effectively inhibits the formation of nitrogen oxides during combustion, resulting in excellent low-NOx performance. However, an increased FGR rate can affect boiler efficiency; when the FGR rate exceeds a certain level, combustion becomes difficult to control and may even lead to flameout.

[0003] Existing technologies consider comprehensive optimization control of boiler efficiency and environmental indicators in aspects such as gas regulation, combustion air regulation, and flue gas recirculation rate regulation. However, they lack real-time monitoring and control of boiler combustion stability and do not consider the impact of factors such as changes in gas composition, temperature and pressure differences between combustion air and recirculated flue gas, and changes in actuator characteristics on the combustion stability boundary. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a combustion control method for gas-fired boilers to solve the problem that existing gas-fired boilers lack real-time monitoring and control of combustion stability during operation.

[0005] To address the above problems, the present invention provides a combustion control method for a gas-fired boiler, the combustion control method comprising:

[0006] S10. Install M pressure fluctuation measuring devices in the furnace of the gas-fired boiler, where M is an integer greater than or equal to 6.

[0007] S20. Control the gas-fired boiler to operate under the boiler design parameters. For multiple different discrete load points, obtain the corresponding furnace pressure fluctuation measurement data through M pressure fluctuation measurement devices. Based on the furnace pressure fluctuation measurement data, calculate and obtain the pressure fluctuation warning limit, pressure fluctuation lockout load limit and pressure fluctuation trip limit for each load point.

[0008] S30. Input the pressure fluctuation warning limit, pressure fluctuation lockout load limit and pressure fluctuation trip limit to the boiler control system, and perform combustion control on the gas boiler in combination with the boiler design parameters.

[0009] Preferably, the M pressure fluctuation measuring devices include at least three pressure fluctuation measuring devices with low-frequency band measurement performance and at least three pressure fluctuation measuring devices with high-frequency band measurement performance.

[0010] Preferably, the pressure fluctuation measuring device with low-frequency measurement performance refers to the pressure fluctuation measuring device with a measurement operating frequency of 0 to 50 Hz; the pressure fluctuation measuring device with high-frequency measurement performance refers to the pressure fluctuation measuring device with a measurement operating frequency of 50 Hz or higher.

[0011] Preferably, in step S20, N different discrete load points LD(1) to LD(N) are selected, where N is an integer greater than or equal to 5; the discrete load points LD(1) to LD(N) include the minimum load and 100% load, as well as at least three load points located between the minimum load and 100% load.

[0012] Preferably, step S20 includes:

[0013] S21. For any discrete load point LD(k), control the gas boiler to operate stably I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain the dataset V1nm(i)(m); I is an integer greater than or equal to 3, i = 1 to I, m = 1 to M.

[0014] S22. Take the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)] for each stable operation, calculate the average value of the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)], and obtain the pressure fluctuation reference value Vnm(k) corresponding to the load point LD(k);

[0015] S23. Repeat steps S21 to S22 above to calculate the pressure fluctuation reference values ​​Vnm(1) to Vnm(N) corresponding to the discrete load points LD(1) to LD(N); perform linear interpolation on the data LD(1) to LD(N) and Vnm(1) to Vnm(N) to obtain the correspondence between the load and the pressure fluctuation reference value Vnm.

[0016] S24. For any discrete load point LD(k), control the gas boiler to operate unstablely I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain a dataset V2nm(i)(m); i = 1 to I, m = 1 to M.

[0017] S25. Take the minimum pressure fluctuation data mix[V2nm(i)(m)] from the dataset V2nm(i)(m) to obtain the pressure fluctuation trip limit Vtp(k) corresponding to the load point LD(k);

[0018] S26. Repeat steps S24 to S25 above to calculate the pressure fluctuation trip limit values ​​Vtp(1) to Vtp(N) corresponding to the discrete load points LD(1) to LD(N); perform linear interpolation on the data LD(1) to LD(N) and Vtp(1) to Vtp(N) to obtain the correspondence between the load and the pressure fluctuation trip limit value Vtp.

[0019] S27. Calculate the pressure fluctuation warning limit Vwp and the pressure fluctuation blocking load limit Vlp based on the pressure fluctuation reference value Vnm and the pressure fluctuation trip limit Vtp; where Vwp = Vnm + (Vtp - Vnm) × Th1, Vlp = Vnm + (Vtp - Vnm) × Th2, Th is 10% to 33%, and Th2 is 33% to 67%; thereby obtaining the correspondence between load and pressure fluctuation warning limit Vwp and the correspondence between load and pressure fluctuation blocking load limit Vlp.

[0020] Preferably, during the combustion control process in step S30, for the control parameters of the pressure fluctuation warning limit Vwp and the pressure fluctuation lockout load limit Vlp, if the boiler control system receives a missed alarm signal, the value of Th1 or Th2 is reduced accordingly; if the boiler control system receives a false alarm signal, the value of Th1 or Th2 is increased accordingly.

[0021] Preferably, during the combustion control process in step S30:

[0022] When the pressure fluctuation measurement value of one of the pressure fluctuation measuring devices reaches or exceeds the pressure fluctuation warning limit or the pressure fluctuation lockout load limit, the gas boiler control system issues a prompt message.

[0023] When the pressure fluctuation measurement values ​​of two of the pressure fluctuation measuring devices reach or exceed the pressure fluctuation lockout load limit, the gas boiler control system executes an instruction to increase the lockout gas boiler load and an instruction to increase the lockout flue gas recirculation regulating valve.

[0024] When the pressure fluctuation measurement values ​​of two of the pressure fluctuation measuring devices reach or exceed the pressure fluctuation trip limit, the gas boiler control system executes a gas boiler shutdown command.

[0025] Preferably, when the gas boiler control system executes the command to add a lock-up flue gas recirculation regulating valve, a negative bias is superimposed on the added lock-up flue gas recirculation regulating valve command every time interval T.

[0026] Preferably, the time T is 60s to 180s, and the value of the negative bias is positively correlated with the maximum pressure fluctuation measurement value measured in real time by the M pressure fluctuation measuring devices.

[0027] The present invention provides a combustion control method for gas-fired boilers, which monitors the combustion stability of the gas-fired boiler in real time based on pressure fluctuations. Compared with the existing gas-fired boiler combustion method using flue gas recirculation for low-NOx combustion, this method has the following advantages:

[0028] (1) Based on the monitoring data of combustion pressure fluctuations in gas-fired boilers, the combustion stability can be determined, and corresponding measures can be taken to limit the issuance of operation commands that aggravate combustion instability based on the deterioration of combustion stability.

[0029] (2) It can monitor the combustion pressure fluctuation of the gas boiler in real time, making the judgment of combustion stability more direct and accurate; and it can identify the unstable boundary conditions of combustion based on the measured pressure fluctuation value, and determine whether it is necessary to perform operations such as load limiting and reducing flue gas recirculation rate to improve combustion stability.

[0030] (3) Since it is based on the combustion pressure fluctuation of the gas boiler, it can take into account the influence of factors such as changes in gas composition, temperature and pressure differences between combustion air and recirculated flue gas, and changes in actuator characteristics on the combustion stability boundary, thereby optimizing the combustion control of the gas boiler with low nitrogen combustion mode of flue gas recirculation. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a gas-fired boiler provided in an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of a combustion control method for a gas-fired boiler provided in an embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0034] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0035] Figure 1 This is a schematic diagram of the structure of a gas-fired boiler provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the gas-fired boiler includes a burner 1 and a furnace 11. The furnace 11 (combustion chamber) is where fuel combustion takes place. The burner 1 contains burners and is connected to a blower, which has its own damper. A gas pipeline 2 connects to the burner 1, supplying gas to it. A gas regulating valve 3 is installed on the gas pipeline 2 to control the flow rate of gas entering the burner 1. A mixer 4 is connected to the air inlet of the burner 1. A flue gas recirculation pipeline 5 and a combustion air pipeline 6 are connected to the two air inlets of the mixer 4. The flue gas recirculation pipeline 5 is connected to the flue gas duct 7 of the gas-fired boiler. The flue gas discharged from the gas-fired boiler can be reintroduced into the burner 1 and furnace 11 for re-combustion through the flue gas recirculation pipeline 5. A flue gas recirculation regulating valve 8 is installed on the flue gas recirculation pipeline 5 to regulate the flow rate of the returning flue gas. A combustion air regulating valve 9 is installed on the combustion air pipeline 6, which can regulate the flow rate of the combustion air. The combustion air and the returned flue gas are mixed in the mixer 4 and then enter the blower of the burner 1, and then continue to enter the burner 1 for combustion under the action of the blower. The gas boiler is equipped with a flue gas online monitoring system 10, which can monitor the composition of the flue gas in the flue 7, such as the content of oxygen, carbon monoxide, and nitrogen oxides.

[0036] Figure 2 A schematic diagram of the combustion control method for a gas-fired boiler provided in this embodiment of the invention is shown below. Figure 1 and Figure 2 Based on the gas-fired boiler and the combustion control method of the gas-fired boiler provided by the present invention, multiple pressure fluctuation measuring devices are set in the furnace 11 of the gas-fired boiler to monitor the combustion pressure fluctuation of the gas-fired boiler in real time.

[0037] The combustion control method for a gas-fired boiler in this embodiment includes the following steps:

[0038] S10. Install M pressure fluctuation measuring devices in the furnace of the gas-fired boiler, where M is an integer greater than or equal to 6.

[0039] Specifically, such as Figure 1 As shown, a pressure fluctuation measurement point is set in the furnace 11 of the gas boiler, and a pressure fluctuation measurement device is set at the location of the pressure fluctuation measurement point to measure and obtain furnace pressure fluctuation measurement data.

[0040] The M pressure fluctuation measurement devices include at least three pressure fluctuation measurement devices with low-frequency measurement performance and at least three pressure fluctuation measurement devices with high-frequency measurement performance. Specifically, the pressure fluctuation measurement device with low-frequency measurement performance refers to the pressure fluctuation measurement device whose measurement operating frequency is 0-50Hz; the pressure fluctuation measurement device with high-frequency measurement performance refers to the pressure fluctuation measurement device whose measurement operating frequency is above 50Hz.

[0041] S20. Control the gas-fired boiler to operate under the boiler design parameters. For multiple different discrete load points, obtain the corresponding furnace pressure fluctuation measurement data through M pressure fluctuation measurement devices. Based on the furnace pressure fluctuation measurement data, calculate and obtain the pressure fluctuation warning limit, pressure fluctuation lockout load limit and pressure fluctuation trip limit for each load point.

[0042] Specifically, the boiler design parameters mainly include the following parameters:

[0043] (1) Gas boiler load command.

[0044] (2) Control commands and status feedback for gas boiler gas regulating valve, combustion air regulating actuator (combustion air regulating valve or blower motor frequency converter), and flue gas recirculation regulating valve.

[0045] (3) Measurement parameters of flue gas components such as oxygen, carbon monoxide, and nitrogen oxides in the flue gas online monitoring system.

[0046] Specifically, in step S20, N different discrete load points LD(1) to LD(N) are selected, where N is an integer greater than or equal to 5; the discrete load points LD(1) to LD(N) include the minimum load and 100% load, as well as at least three load points located between the minimum load and 100% load.

[0047] In one specific implementation, step S20 includes the following sub-steps:

[0048] S21. For any discrete load point LD(k), control the gas boiler to operate stably I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain the dataset V1nm(i)(m); I is an integer greater than or equal to 3, i = 1 to I, m = 1 to M.

[0049] For example, in this embodiment, five different discrete load points LD(1), LD(2), LD(3), LD(4), and LD(5) are selected. The load of discrete load point LD(1) is 0%, and the load of discrete load point LD(5) is 100%.

[0050] For load point LD(1), the gas-fired boiler is controlled to operate stably three times under the boiler design parameters. Each operation acquires six furnace pressure fluctuation measurement data points from the six pressure fluctuation measurement devices, thus obtaining the pressure fluctuation measurement dataset for the discrete load point LD(1).

[0051] S22. Take the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)] for each stable operation, calculate the average value of the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)], and obtain the pressure fluctuation reference value Vnm(k) corresponding to the load point LD(k).

[0052] For example, in this embodiment, the gas boiler was run 3 times for load point LD(1), and three pressure fluctuation data were generated in the low frequency band and the high frequency band each time. The maximum value was selected from the pressure fluctuation data measured in each run, and a total of three maximum values ​​were selected. The average value of the three selected maximum values ​​was calculated as the pressure fluctuation reference value Vnm(1) corresponding to the discrete load point LD(1).

[0053] S23. Repeat steps S21 to S22 above to calculate the pressure fluctuation reference values ​​Vnm(1) to Vnm(N) corresponding to the discrete load points LD(1) to LD(N); perform linear interpolation on the data LD(1) to LD(N) and Vnm(1) to Vnm(N) to obtain the correspondence between the load and the pressure fluctuation reference value Vnm.

[0054] For example, in this embodiment, for discrete load points LD(1) to LD(5), the steps described above are repeated to obtain the pressure fluctuation reference values ​​Vnm(1), Vnm(2), Vnm(3), Vnm(4), and Vnm(5) corresponding to the discrete load points LD(1), LD(2), LD(3), LD(4), and LD(5). The data LD(1) to LD(5) and Vnm(1) to Vnm(5) are linearly interpolated to obtain the correspondence between the load and the pressure fluctuation reference value Vnm.

[0055] S24. For any discrete load point LD(k), control the gas boiler to operate unstablely I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain the dataset V2nm(i)(m); i = 1 to I, m = 1 to M.

[0056] For example, in this embodiment, the gas boiler is controlled to operate unstablely three times under the boiler design parameters. During each operation, six furnace pressure fluctuation measurement data are obtained by six pressure fluctuation measurement devices.

[0057] S25. Take the minimum pressure fluctuation data mix[V2nm(i)(m)] from the dataset V2nm(i)(m) to obtain the pressure fluctuation trip limit value Vtp(k) corresponding to the load point LD(k).

[0058] For example, in this embodiment, for load point LD(1), the gas boiler is controlled to operate unstablely 3 times under the boiler design parameters. Each time, 6 pressure fluctuation measurement devices acquire 6 furnace pressure fluctuation measurement data. Each time, 3 pressure fluctuation data are generated in the low frequency band and 3 in the high frequency band, so as to obtain the pressure fluctuation data of the gas boiler operating unstablely 3 times at load point LD(1). The minimum value is selected from these pressure fluctuation data as the pressure fluctuation trip limit value Vtp(1) corresponding to load point LD(1).

[0059] S26. Repeat steps S24 to S25 above to calculate the pressure fluctuation trip limit Vtp(1) to Vtp(N) corresponding to the discrete load points LD(1) to LD(N); perform linear interpolation on the data LD(1) to LD(N) and Vtp(1) to Vtp(N) to obtain the correspondence between the load and the pressure fluctuation trip limit Vtp.

[0060] For example, in this embodiment, for discrete load points LD(1) to LD(5), the above steps are repeated to calculate the pressure fluctuation trip limit Vtp(1) to Vtp(5) corresponding to the discrete load points LD(1) to LD(5). The data LD(1) to LD(5) and Vtp(1) to Vtp(5) are linearly interpolated to obtain the correspondence between the load and the pressure fluctuation trip limit Vtp.

[0061] S27. Calculate the pressure fluctuation warning limit Vwp and the pressure fluctuation blocking load limit Vlp based on the pressure fluctuation reference value Vnm and the pressure fluctuation trip limit Vtp; where Vwp = Vnm + (Vtp - Vnm) × Th1, Vlp = Vnm + (Vtp - Vnm) × Th2, Th is 10% to 33%, and Th2 is 33% to 67%; thereby obtaining the correspondence between load and pressure fluctuation warning limit Vwp and the correspondence between load and pressure fluctuation blocking load limit Vlp.

[0062] In the specific scheme, for the control parameters of pressure fluctuation early warning limit Vwp and pressure fluctuation lockout load limit Vlp, if the boiler control system has a missed alarm signal, the value of Th1 or Th2 will be reduced accordingly; if the boiler control system has a false alarm signal, the value of Th1 or Th2 will be increased accordingly.

[0063] S30. Input the pressure fluctuation warning limit, pressure fluctuation lockout load limit and pressure fluctuation trip limit to the boiler control system, and perform combustion control on the gas boiler in combination with the boiler design parameters.

[0064] In the specific scheme, during the combustion control process of step S30: when the pressure fluctuation measurement value of one of the pressure fluctuation measuring devices reaches or exceeds the pressure fluctuation warning limit or the pressure fluctuation lockout load limit, the gas boiler control system issues a prompt message.

[0065] For example, in this embodiment, more than six pressure fluctuation measurement points are set in the furnace 11 of the gas-fired boiler, and each pressure fluctuation measurement point is equipped with a pressure fluctuation measuring device to measure the pressure fluctuation value of the furnace 11. After the obtained pressure fluctuation warning limit, pressure fluctuation lockout load limit, and pressure fluctuation trip limit are input to the boiler control system, when the gas-fired boiler is controlled for combustion, if the pressure fluctuation measurement value of one of these pressure fluctuation measuring devices reaches or exceeds the pressure fluctuation warning limit or the pressure fluctuation lockout load limit, the gas-fired boiler control system issues a prompt message.

[0066] In the specific scheme, during the combustion control process of step S30: when the pressure fluctuation measurement values ​​of two pressure fluctuation measuring devices reach or exceed the pressure fluctuation lock-up load limit, the gas boiler control system executes an instruction to increase the lock-up of the gas boiler load and an instruction to increase the lock-up of the flue gas recirculation regulating valve.

[0067] For example, in this embodiment, more than six pressure fluctuation measuring devices are installed in the furnace 11 of the gas-fired boiler. The obtained pressure fluctuation early warning limit, pressure fluctuation lockout load limit, and pressure fluctuation trip limit are input to the boiler control system. When the gas-fired boiler is controlled for combustion, if the pressure fluctuation measurement values ​​of two of these pressure fluctuation measuring devices reach or exceed the pressure fluctuation lockout load limit, the gas-fired boiler control system executes an instruction to increase the load of the gas-fired boiler and an instruction to increase the load of the flue gas recirculation regulating valve.

[0068] When the gas boiler control system executes the command to add a lock-up flue gas recirculation regulating valve, a negative bias is superimposed on the added lock-up flue gas recirculation regulating valve command every time interval T.

[0069] The time T is 60s to 180s, and the value of the negative bias is positively correlated with the maximum pressure fluctuation measured in real time by the M pressure fluctuation measuring devices.

[0070] In the specific scheme, during the combustion control process of step S30: when the pressure fluctuation measurement values ​​of two pressure fluctuation measuring devices reach or exceed the pressure fluctuation trip limit, the gas boiler control system executes the gas boiler shutdown command.

[0071] For example, in this embodiment, more than six pressure fluctuation measuring devices are installed in the furnace 11 of the gas-fired boiler. The obtained pressure fluctuation early warning limit, pressure fluctuation lockout load limit, and pressure fluctuation trip limit are input to the boiler control system. When the gas-fired boiler is controlled for combustion, if the pressure fluctuation measurement value of two of these pressure fluctuation measuring devices reaches or exceeds the pressure fluctuation trip limit, the gas-fired boiler control system executes a gas-fired boiler shutdown command.

[0072] It should be noted that the combustion control method for gas-fired boilers provided by this invention is implemented on the existing gas-fired boiler control system. The existing control system comprehensively optimizes boiler efficiency and environmental indicators in aspects such as gas regulation, combustion air regulation, and flue gas recirculation rate regulation. The combustion control method provided by this invention adds combustion stability control functionality to the existing control system, enabling the gas-fired boiler to not only consider comprehensive optimization control of boiler efficiency and environmental indicators during operation but also monitor combustion stability. After combustion stability control is implemented, if the measured value of furnace pressure fluctuation exceeds the normal operating range, operations such as issuing warning messages, locking the gas-fired boiler load increase, reducing the flue gas recirculation regulating valve command, and shutting down the gas-fired boiler are executed based on the measured value of furnace pressure fluctuation.

[0073] Specifically, such as Figure 1 As shown, in the combustion control method provided by this invention, combustion instability boundary conditions are identified based on the measured pressure fluctuation values ​​of the furnace 11, determining whether operations such as load limiting and reducing the flue gas recirculation rate need to be performed. During operation, the operation of the gas regulating valve 3, the combustion air pipeline 6, and the flue gas recirculation regulating valve 8 are controlled by relevant commands. For example, adding a command to lock the flue gas recirculation regulating valve will control the operation of the flue gas recirculation regulating valve 8, thereby improving combustion stability.

[0074] Specifically, such as Figure 1 As shown, since the boiler combustion stability is monitored based on the pressure fluctuation of the furnace 11, and the pressure fluctuation takes into account the influence of factors such as changes in gas composition, temperature and pressure differences between combustion air and recirculated flue gas, and changes in actuator characteristics on the combustion stability boundary, the combustion control of gas boilers with low-NOx combustion mode of flue gas recirculation can be optimized.

[0075] Specifically, such as Figure 1As shown, the measured pressure fluctuation of the furnace 11 and the flue gas composition monitored by the flue gas online monitoring system 10 are monitored simultaneously, which can monitor the combustion conditions to reach the expected values ​​and thus maintain stable combustion.

[0076] Specifically, such as Figure 1 As shown, by monitoring the combustion pressure fluctuation data in the furnace 11, the situation of combustion stability deterioration can be determined, thereby enabling corresponding measures to limit the issuance of operation commands that exacerbate combustion instability.

[0077] In summary, the embodiments of the present invention provide a combustion control method for a gas-fired boiler, which can monitor and control the combustion stability of the gas-fired boiler in real time based on the measured pressure fluctuation value of the boiler furnace, thus solving the problem of lack of real-time monitoring and control of combustion stability in gas-fired boilers.

[0078] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A combustion control method for a gas-fired boiler, characterized in that, include: S10. Install M pressure fluctuation measuring devices in the furnace of the gas-fired boiler, where M is an integer greater than or equal to 6; S20. Control the gas boiler to operate under the boiler design parameters, and obtain the corresponding furnace pressure fluctuation measurement data through M pressure fluctuation measurement devices for multiple different discrete load points. Based on the furnace pressure fluctuation measurement data, the pressure fluctuation early warning limit, pressure fluctuation lockout load limit, and pressure fluctuation trip limit for each load point are calculated and obtained. S30. Input the pressure fluctuation warning limit, pressure fluctuation lockout load limit and pressure fluctuation trip limit to the boiler control system, and perform combustion control of the gas boiler in combination with the boiler design parameters. Step S20 includes: S21. For any discrete load point LD(k), control the gas boiler to operate stably I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain the dataset V1nm(i)(m); I is an integer greater than or equal to 3, i=1~I, m=1~M. S22. Take the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)] for each stable operation, calculate the average value of the maximum pressure fluctuation data max[V1nm(1)(m)]~max[V1nm(I)(m)], and obtain the pressure fluctuation reference value Vnm(k) corresponding to the load point LD(k); S23. Repeat steps S21~S22 above to calculate the pressure fluctuation reference values ​​Vnm(1)~Vnm(N) corresponding to the discrete load points LD(1)~LD(N); perform linear interpolation on the data LD(1)~LD(N) and Vnm(1)~Vnm(N) to obtain the correspondence between the load and the pressure fluctuation reference value Vnm. S24. For any discrete load point LD(k), control the gas boiler to operate unstablely I times under the boiler design parameters. Each time, M furnace pressure fluctuation measurement data are obtained by M pressure fluctuation measurement devices to obtain the dataset V2nm(i)(m); i=1~I, m=1~M. S25. Take the minimum pressure fluctuation data mix[V2nm(i)(m)] from the dataset V2nm(i)(m) to obtain the pressure fluctuation trip limit Vtp(k) corresponding to the load point LD(k); S26. Repeat steps S24~S25 above to calculate the pressure fluctuation trip limit Vtp(1)~Vtp(N) corresponding to the discrete load points LD(1)~LD(N); perform linear interpolation on the data LD(1)~LD(N) and Vtp(1)~Vtp(N) to obtain the correspondence between the load and the pressure fluctuation trip limit Vtp. S27. Calculate the pressure fluctuation warning limit Vwp and the pressure fluctuation blocking load limit Vlp based on the pressure fluctuation reference value Vnm and the pressure fluctuation trip limit Vtp; where Vwp=Vnm+(Vtp-Vnm)×Th1, Vlp=Vnm+(Vtp-Vnm)×Th2, Th is 10%~33%, and Th2 is 33%~67%; thereby obtaining the correspondence between load and pressure fluctuation warning limit Vwp and the correspondence between load and pressure fluctuation blocking load limit Vlp.

2. The combustion control method according to claim 1, characterized in that, The M pressure fluctuation measurement devices include at least three pressure fluctuation measurement devices with low-frequency band measurement performance and at least three pressure fluctuation measurement devices with high-frequency band measurement performance.

3. The combustion control method according to claim 2, characterized in that, The pressure fluctuation measuring device with low-frequency measurement performance refers to the pressure fluctuation measuring device with a measurement operating frequency of 0~50Hz; the pressure fluctuation measuring device with high-frequency measurement performance refers to the pressure fluctuation measuring device with a measurement operating frequency of 50Hz or higher.

4. The combustion control method according to claim 1, characterized in that, In step S20, N different discrete load points LD(1)~LD(N) are selected, where N is an integer greater than or equal to 5; the discrete load points LD(1)~LD(N) include the minimum load and 100% load, as well as at least three load points located between the minimum load and 100% load.

5. The combustion control method according to claim 1, characterized in that, During the combustion control process in step S30, for the control parameters of the pressure fluctuation warning limit Vwp and the pressure fluctuation lockout load limit Vlp, if the boiler control system has a missed alarm signal, the value of Th1 or Th2 will be reduced accordingly; if the boiler control system has a false alarm signal, the value of Th1 or Th2 will be increased accordingly.

6. The combustion control method according to claim 1, characterized in that, During the combustion control process in step S30: When the pressure fluctuation measurement value of one of the pressure fluctuation measuring devices reaches or exceeds the pressure fluctuation warning limit or the pressure fluctuation lockout load limit, the gas boiler control system issues a prompt message. When the pressure fluctuation measurement values ​​of two of the pressure fluctuation measuring devices reach or exceed the pressure fluctuation lockout load limit, the gas boiler control system executes an instruction to increase the lockout gas boiler load and an instruction to increase the lockout flue gas recirculation regulating valve. When the pressure fluctuation measurement values ​​of two of the pressure fluctuation measuring devices reach or exceed the pressure fluctuation trip limit, the gas boiler control system executes a gas boiler shutdown command.

7. The combustion control method according to claim 6, characterized in that, When the gas boiler control system executes the command to add a lock-up flue gas recirculation regulating valve, a negative bias is superimposed on the added lock-up flue gas recirculation regulating valve command every time interval T.

8. The combustion control method according to claim 7, characterized in that, The time T is 60s~180s, and the value of the negative bias is positively correlated with the maximum pressure fluctuation measurement value measured in real time by the M pressure fluctuation measuring devices.

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