Low-pressure heater condensate pump outlet control valve control method, system, and storage medium

Abstract

This invention relates to a method, system, and storage medium for controlling the outlet valve of a low-pressure heater condensate pump. The method includes the following steps: Step S1, sending an increase opening command to the outlet valve of the low-pressure heater condensate pump; Step S2, in response to the completion of the increase opening command, acquiring the liquid level height inside the low-pressure heater; if the current liquid level height is lower than the previously acquired liquid level height, proceeding to Step S3; if the current liquid level height is higher than the previously acquired liquid level height, proceeding to Step S4; Step S3, sending a decrease operating frequency command to the low-pressure heater condensate pump; in response to the completion of the decrease operating frequency command, acquiring the liquid level height inside the low-pressure heater; if the current liquid level height reaches a preset value, proceeding to Step S1; otherwise, proceeding to Step S5. Compared with the prior art, this invention has advantages such as reducing throttling losses, improving economic efficiency, and enhancing environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of water supply regeneration technology, and in particular to a method, system, and storage medium for controlling the outlet regulating valve of a low-pressure heater condensate pump. Background Technology

[0002] The feedwater regeneration system is the core of the power plant's thermal system. Its operation and regulation play a crucial role in the unit's thermal economy and are an important part of the thermal cycle. It uses extracted steam from the high- and low-pressure cylinders of the turbine to heat the feedwater, thereby reducing exhaust steam losses and increasing the feedwater temperature entering the boiler, thus improving the power plant's thermal cycle efficiency. The steam after heating the feedwater forms condensate, which accumulates in the heater. Since the condensate has a certain temperature, directly discharging it into the condenser would cause some heat loss. Therefore, a low-pressure heated condensate pump is usually used to pump it to the condensate side outlet of the low-pressure heater to recover the heat from the condensate.

[0003] In actual operation, it was found that the low-pressure heating condensate pump operates at a frequency close to the power frequency under high load, while the opening of the condensate regulating valve is less than 50%, resulting in a large throttling loss. In addition, the output of the frequency converter increases and the coil heats up severely.

[0004] In summary, there is currently a lack of a control method for the outlet regulating valve of the low-pressure heater condensate pump to solve or resolve the aforementioned problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a method, system, and storage medium for controlling the outlet regulating valve of a low-pressure heater condensate pump, so as to solve or partially solve the problem of large throttling losses in power plant feedwater regeneration systems.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One aspect of the present invention provides a method for controlling the outlet regulating valve of a low-pressure heater condensate pump, comprising the following steps:

[0008] Step S1: Send an instruction to increase the opening degree to the regulating valve at the outlet of the low-pressure heater drain pump;

[0009] Step S2: In response to the completion of the increased opening command, obtain the liquid level height in the low-pressure heater. If the current liquid level height is lower than the previously obtained liquid level height, proceed to step S3. If the current liquid level height is higher than the previously obtained liquid level height, proceed to step S4.

[0010] Step S3: Send a command to reduce the operating frequency to the low-pressure heater drain pump. In response to the completion of the command to reduce the operating frequency, obtain the liquid level height in the low-pressure heater. If the current liquid level height reaches the preset value, execute step S1; otherwise, execute step S3.

[0011] Step S4: Send a command to reduce the opening degree of the regulating valve at the outlet of the low-pressure heater drain pump.

[0012] As a preferred technical solution, it is applied to generator sets under medium and / or high load conditions.

[0013] As a preferred technical solution, the control method further includes the following steps:

[0014] Step S5: In response to reaching the preset stable condition, save the current low-pressure heater drain pump outlet valve opening value and complete the valve opening test under the current load condition.

[0015] As a preferred technical solution, the stability condition is that the fluctuation degree of the heater drain pump outlet valve opening and / or the fluctuation degree of the liquid level height in the low-pressure heater are less than a preset threshold.

[0016] As a preferred technical solution, step S2 further includes:

[0017] If the current liquid level is equal to the previously obtained liquid level, then proceed to step S1.

[0018] Another aspect of the present invention provides a power plant feedwater regeneration system, comprising a condenser and at least one low-pressure heater module connected to the condenser, the low-pressure heater module comprising:

[0019] Low-pressure heater;

[0020] A variable frequency condensate pump is connected to the low-pressure heater;

[0021] A drain regulating valve is connected to the variable frequency drain pump. The drain regulating valve and the variable frequency drain pump are used to implement the aforementioned low-pressure heater drain pump outlet regulating valve control method.

[0022] As a preferred technical solution, the low-pressure heater module further includes:

[0023] Emergency drain valves are connected to the low-pressure heater and the condenser, respectively.

[0024] As a preferred technical solution, the condenser is connected to the low-pressure heater module via a condensate pump and a cooler.

[0025] In another aspect, an electronic device is provided, comprising: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the aforementioned low-pressure heater drain pump outlet valve control method.

[0026] In another aspect, the present invention provides a computer-readable storage medium comprising one or more programs executable by one or more processors of an electronic device, said one or more programs including instructions for performing the aforementioned low-pressure heater drain pump outlet valve control method.

[0027] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0028] (1) Reduce throttling losses: In view of the problem that the frequency of the condensate pump and the opening of the condensate regulating valve cannot be well matched, resulting in large throttling losses, this invention provides a control method for the outlet regulating valve of the condensate pump of the low-pressure heater, so as to realize the outlet regulating valve of the condensate pump as fully as possible under the condition of unit operation and without the addition of measuring points, thereby reducing throttling losses.

[0029] (2) Improve economic and environmental benefits: By controlling the outlet valve of the low-pressure heater condensate pump, the working frequency of the condensate pump is reduced by increasing the valve opening under the premise of ensuring the water level in the low-pressure heater is stable. This effectively reduces the power consumption of the pump and reduces carbon emissions while having good economic benefits.

[0030] (3) Wide range of applications: By conducting experiments on the valve opening under load conditions and recording the opening size under different load conditions, a mapping between the conditions and the valve opening can be further established. The valve opening can be determined directly based on the mapping during control, thereby further reducing energy consumption. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the power plant feedwater regeneration system in the embodiment.

[0032] Among them, 1. Condenser, 2. Low-pressure heater, 3. Variable frequency condensate pump, 4. Condensate regulating valve, 5. Emergency condensate valve, 6. Condensate pump, 7. Cooler, 8. Pressure measuring point, 9. Condensate pump inlet valve, 10. Condensate pump outlet valve. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] Example 1

[0036] In this embodiment, in the power plant feedwater regeneration system, the condensate from the low-pressure heater is discharged by gravity in stages and finally pumped to the condensate outlet of a certain low-pressure heater (assumed to be heater 8) by a low-pressure heater condensate pump to recover the heat from the condensate. The low-pressure heater condensate pump (i.e., variable frequency condensate pump 3) operates in variable frequency mode, and the water level of low-pressure heater 8 is controlled by the spontaneous change of frequency. The condensate pressure is automatically controlled by the condensate regulating valve to ensure that the condensate pressure is always greater than the condensate pressure so that the condensate can be recovered to the condensate.

[0037] During unit operation, for safety reasons, it is not possible to install pressure measuring points at the outlet of the condensate pump on side 8, but only at the inlet pressure of the cooler (i.e., Figure 1 Pressure measuring point 8) is added. However, the pressure measuring point is located at 0 meters in the turbine hall. After that, the condensate passes through the condensate cooler and the low-pressure heater in sequence. The heater has many bends and long flow, and the heater is located at 6 meters or even higher in the turbine hall. Therefore, the pressure on the condensate side of the heater outlet must be lower than the pressure at the inlet of the condensate cooler. So it is unreasonable to set the condensate pressure setting value higher than the pressure at the inlet of the condensate cooler. In order to maintain high pressure, the outlet regulating valve of the condensate pump is closed, resulting in throttling loss. At the same time, in order to maintain the water level of the heater, the output of the frequency converter is increased, and the coil heats up severely.

[0038] To address the aforementioned issues, this embodiment provides a method for controlling the outlet regulating valve of a low-pressure heater condensate pump. This method is applied to the condensate regulating valve 4 and the variable frequency condensate pump 3 in a power plant feedwater reheat system. The method uses a safe experimental approach to fully open the condensate regulating valve, thereby reducing throttling losses and lowering the heating of the condensate pump coil.

[0039] See Figure 1 The power plant feedwater regeneration system includes a condenser 1 and multiple low-pressure heater modules connected to the condenser 1 (corresponding to...). Figure 1(8, 9, and 10 in the model), condenser 1 is connected to the low-pressure heater module via condensate pump 6 and cooler 7. The low-pressure heater module includes a low-pressure heater 2, a variable frequency drain pump 3, and a drain regulating valve 4 connected in sequence. In addition, the low-pressure heater module also includes an emergency drain valve 5 connected to the low-pressure heater 2 and condenser 1 respectively.

[0040] The system works as follows: Condensate in condenser 1 enters a multi-stage low-pressure heater module through condensate pump inlet valve 9, condensate pump 6, condensate pump outlet valve 10, and condensate cooler 7. In each module, condensate enters low-pressure heater 2 through inlet valve. The heated condensate enters the next stage low-pressure heater module through variable frequency condensate pump 3 and condensate regulating valve 4. Multi-stage energy recovery further reduces heat loss. In case of emergency, condensate in low-pressure heater 2 is discharged into condenser 1 through emergency condensate drain valve 5.

[0041] The control method for the outlet regulating valve of the low-pressure heater condensate pump includes the following steps:

[0042] Step S0: Confirm that the emergency drain valves of each heater can operate normally and that the heater water level protection is activated to ensure that the protection operates reliably in the event of an abnormal situation, preventing water from entering the turbine and ensuring that condensate is not interrupted.

[0043] Step S1: Increase the opening of the regulating valve at the outlet of the low-pressure heater drain pump.

[0044] Step S2: Collect the liquid level height inside the low-pressure heater through the sensor. If the current liquid level height is lower than the previously acquired liquid level height, proceed to step S3. If the current liquid level height is higher than the previously acquired liquid level height, proceed to step S4. If the current liquid level height is equal to the previously acquired liquid level height, proceed to step S1.

[0045] Step S3: Reduce the operating frequency of the low-pressure heater drain pump and collect the liquid level height in the low-pressure heater again. If the current liquid level height reaches the preset value, execute step S1; otherwise, execute step S3.

[0046] Step S4: Send a command to reduce the opening degree of the regulating valve at the outlet of the low-pressure heater drain pump.

[0047] It should be noted that increasing the frequency of the condensate pump cannot be used to increase the condensate pressure and flow rate. This is not energy-efficient, and more importantly, it will cause the condensate flow rate to exceed the steam extraction rate, ultimately causing the water level to drop and the condensate pump to trip.

[0048] Step S5: When the fluctuation of the valve opening at the outlet of the heater condensate pump and / or the fluctuation of the liquid level height in the low-pressure heater are less than the preset threshold, save the current valve opening value at the outlet of the low-pressure heater condensate pump and complete the valve opening experiment under the current load conditions.

[0049] It should be noted that, considering the large steam extraction volume, high steam inlet pressure, and large condensate volume at high loads, the condensate pump is less prone to cavitation, and the water level control of Unit 8 is relatively stable, the experiment was conducted from high load to medium load. That is, after the regulating valve was successfully fully opened at high load, the original state was restored, the unit load was reduced, and the regulating valve was opened fully again to ensure the accuracy of the experimental results and the safety of the experiment.

[0050] Considering that the pipeline resistance loss is small when the regulating valve is fully open at low load, the pump's operating point is in the high flow and low head region, the steam extraction volume is small, the condensate volume is small, and the high flow rate cannot be met, resulting in unstable pump operation, a self-controlled mode is adopted under low load conditions to avoid the fluctuation of the water level at 8 units affecting the safe operation of the unit.

[0051] In summary, this method involves slowly opening the drain regulating valve to reduce pressure. If the water level at the No. 8 heater drops, the frequency automatically decreases to raise the water level back to normal. The valve is then opened again until it is fully open. If the water level at the No. 8 heater rises instead of opening fully, it indicates that the drain pressure is lower than the condensate outlet pressure at the No. 8 low-pressure heater, preventing drainage. In this case, the drain regulating valve should be closed slightly to maintain the drain pressure. This method allows for full opening of the drain pump outlet regulating valve, reducing throttling losses and coil heating, even during unit operation and without additional measuring points. Furthermore, this method identifies the minimum load threshold corresponding to full valve opening. Below the threshold, the original control method is used; above the threshold, the valve automatically opens fully.

[0052] Taking a 650MW double reheat unit in a power plant as an example, after adopting this method, the drain valves were fully open during high load conditions, the No. 8 heater water level remained stable, and the drain pump frequency decreased by 3-5Hz and the current decreased by 26-72A under the same load conditions, resulting in significant energy savings. Nearly a month after modifying the control logic on April 14, 2024 (automatically fully opening the valves during high load (450MW-650MW), the low-pressure heater drain pumps have been operating stably without fluctuations in the No. 8 heater water level or flow rate. The drain pump frequency and current during high load conditions have significantly decreased compared to before the modification. Based on an average current reduction of 47A, the plant's electricity consumption can be saved by 1.732*380*47*0.8 = 24.75 kWh per hour during high load conditions. Simultaneously, the temporary cooling fan for the drain pump motor has been removed, and no high-temperature alarms have occurred with the drain pump coil, indirectly reducing energy consumption.

[0053] Example 2

[0054] This embodiment provides an electronic device, including: one or more processors and a memory, wherein the memory stores one or more programs, the one or more programs including instructions for executing the low-pressure heater drain pump outlet regulating valve control method as described in Embodiment 1.

[0055] Example 3

[0056] This embodiment provides a computer-readable storage medium including one or more programs executable by one or more processors of an electronic device, the one or more programs including instructions for performing the low-pressure heater drain pump outlet regulating valve control method as described in Embodiment 1.

[0057] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the outlet regulating valve of a low-pressure heater condensate pump, characterized in that, Includes the following steps: Step S1: Send an instruction to increase the opening degree to the regulating valve at the outlet of the low-pressure heater drain pump; Step S2: In response to the completion of the increased opening command, obtain the liquid level height in the low-pressure heater. If the current liquid level height is lower than the previously obtained liquid level height, proceed to step S3. If the current liquid level height is higher than the previously obtained liquid level height, proceed to step S4. Step S3: Send a command to reduce the operating frequency to the low-pressure heater drain pump. In response to the completion of the command to reduce the operating frequency, obtain the liquid level height in the low-pressure heater. If the current liquid level height reaches the preset value, execute step S1; otherwise, execute step S3. Step S4: Send a command to reduce the opening degree of the regulating valve at the outlet of the low-pressure heater drain pump; Step S5: In response to reaching the preset stability condition, save the current low-pressure heater drain pump outlet valve opening value and complete the valve opening experiment under the current load condition. The stability condition is that the fluctuation degree of the heater drain pump outlet valve opening and / or the fluctuation degree of the liquid level height in the low-pressure heater is less than the preset threshold.

2. The method for controlling the outlet regulating valve of a low-pressure heater condensate pump according to claim 1, characterized in that, Generator sets used in medium and / or high load conditions.

3. The method for controlling the outlet regulating valve of a low-pressure heater condensate pump according to claim 1, characterized in that, Step S2 further includes: If the current liquid level is equal to the previously obtained liquid level, then proceed to step S1.

4. A power plant feedwater regeneration system, characterized in that, The system includes a condenser (1) and at least one low-pressure heater module connected to the condenser (1), the low-pressure heater module comprising: Low-pressure heater (2); A variable frequency condensate pump (3) is connected to the low-pressure heater (2); A drain regulating valve (4) is connected to the variable frequency drain pump (3). The drain regulating valve (4) and the variable frequency drain pump (3) are used to implement the low-pressure heater drain pump outlet regulating valve control method as described in any one of claims 1-3.

5. A power plant feedwater regeneration system according to claim 4, characterized in that, The low-pressure heater module also includes: Emergency drain valve (5) is connected to the low-pressure heater (2) and the condenser (1), respectively.

6. A power plant feedwater regeneration system according to claim 4, characterized in that, The condenser (1) is connected to the low-pressure heater module via a condensate pump (6) and a cooler (7).

7. An electronic device, characterized in that, include: One or more processors and a memory, the memory storing one or more programs, the one or more programs including instructions for executing the low-pressure heater drain pump outlet regulating valve control method as described in any one of claims 1-3.

8. A computer-readable storage medium, characterized in that, It includes one or more programs that are executed by one or more processors of an electronic device, the one or more programs including instructions for performing the low-pressure heater drain pump outlet regulating valve control method as described in any one of claims 1-3.

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