A vibration-resistant condensate recirculation system and method for thermal power units

Abstract

This invention discloses a vibration-resistant condensate recirculation system and method for thermal power units. The system includes a condenser and a deaerator. The condenser is connected to the deaerator via a condensate pump set. A recirculation pipeline returning water to the condenser is also provided on the pipeline between the condensate pump set and the deaerator. A first pressure-reducing device and a second pressure-reducing device are connected in series on the recirculation pipeline to form a two-stage pressure reduction. The first or second pressure-reducing device is positioned close to the condenser so that the medium in the recirculation pipeline enters the condenser directly after pressure reduction. The pressure difference between the first and second pressure-reducing devices is matched to the outlet pressure of the condensate pump set. This invention can avoid pipeline vibration caused by two-phase flow in the recirculation system, ensuring the safe operation of the recirculation system.

Description

Technical Field

[0001] This invention belongs to the technical field of thermal power units, and particularly relates to a vibration-resistant condensate recirculation system and method for thermal power units. Background Technology

[0002] Condensate recirculation is usually connected to the condensate system shaft heater outlet pipeline, returning water to the condenser hot well. Its purpose is to save water resources, ensure the minimum flow of the condensate pump, ensure that the condensate pump does not cavitation, and provide cooling water for the shaft heater during the low condensate flow stage such as unit start-up and shutdown, ensuring that the shaft heater forms a micro vacuum, and ensuring smooth steam return to the turbine shaft seal. Condensate recirculation is usually turned on when the pump starts, at low flow, and before the pump stops, and when the deaerator stops supplying water and the flow rate is lower than the set value. That is, condensate recirculation system is widely used in thermal power units.

[0003] The condensate pump is connected to the deaerator. When the unit capacity is large, that is, when the condensate pump head is high, the inventor found that the recirculation pipeline vibrates violently, causing the pipeline supports to break and posing a serious safety threat to the unit operation. After research and analysis, it was found that the pressure of the condenser hot well is close to vacuum. After the pressure is reduced by the pressure reducing device, the two-phase flow in the recirculation pipeline causes violent vibration in this part of the pipeline. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a vibration-resistant condensate recirculation system for thermal power units. This system employs a two-stage pressure reduction mechanism. The second-stage pressure reduction device acts as a barrier between the condenser and the first-stage pressure reduction device, preventing vibration of the pipeline caused by the two-phase flow in the pipeline connected to the pressure reduction device (which operates at near-vacuum pressure) when the condensate pump head is high. Specifically, the pressure of the medium in the pipeline is adjusted to be higher than the saturated water pressure after adjusting the first-stage pressure reduction device, thus avoiding pipeline vibration caused by the two-phase flow. Simultaneously, the second-stage pressure reduction device is positioned close to the condenser hot well, allowing the two-phase flow passing through it to immediately and rapidly enter the condenser hot well, further preventing pipeline vibration and ensuring the safe operation of the recirculation system.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A vibration-resistant condensate recirculation system for thermal power units includes a condenser and a deaerator. The condenser is connected to the deaerator via a condensate pump set. A recirculation pipeline for returning water to the condenser is also provided on the pipeline between the condensate pump set and the deaerator. A first pressure reducing device and a second pressure reducing device are connected in series on the recirculation pipeline to form a two-stage pressure reducing system.

[0007] The first or second pressure reducing device is located near the condenser so that the medium in the recirculation pipeline can directly enter the condenser after pressure reduction. The pressure difference of the first pressure reducing device and the pressure difference of the second pressure reducing device are matched with the outlet pressure of the condensate pump set.

[0008] In one embodiment, the first pressure reducing device is a regulating valve, and the second pressure reducing device is a throttling plate, which is located close to the condenser.

[0009] In one embodiment, the pressure difference between the first pressure reducing device and the second pressure reducing device is equal, and the sum of the two matches the outlet pressure of the condensate pump set under power frequency conditions. Through this embodiment, considering the outlet pressure of the condensate pump set under power frequency conditions, the pressure is evenly distributed to the first pressure reducing device and the second pressure reducing device, which can ensure that the medium pressure after the first pressure reducing device is higher than the saturated water pressure, and avoid vibration of the recirculation pipeline caused by two-phase flow.

[0010] In one embodiment, the pressure difference of the first or second pressure reducing device located near the condenser is designed to be the pressure difference between the lowest outlet pressure of the condensate pump set under variable frequency operation and the condenser. In this embodiment, for economic reasons, the condensate pump often operates under variable frequency operation, and the difference between the lowest outlet pressure and the highest outlet pressure under variable frequency operation is large. That is, the pressure difference of the second-stage pressure reducing device is set to the lowest outlet pressure of the condensate pump set under variable frequency operation. Furthermore, the pressure difference of the first-stage pressure reducing device is set to the highest outlet pressure minus the pressure of the second-stage pressure reducing device. That is, when the condensate pump set is running under a lower outlet pressure condition, the circulating water can flow normally into the hot well, avoiding the situation of small water flow.

[0011] In one embodiment, the condensate pump group includes a first condensate pump and a second condensate pump connected in parallel.

[0012] In one embodiment, the thermal power unit has a capacity exceeding 300MW.

[0013] The present invention also provides a vibration-resistant condensate recirculation method for thermal power units, comprising:

[0014] A two-stage pressure reduction system is installed on the condensate recirculation pipeline;

[0015] The secondary pressure reduction system includes a first pressure reduction device and a second pressure reduction device connected in series. One of the pressure reduction devices in the secondary pressure reduction system is located in the middle of the condensate recirculation pipeline, and the other pressure reduction device is located near the condenser so that the medium can directly enter the condenser after secondary pressure reduction. The pressure difference of the first pressure reduction device and the pressure difference of the second pressure reduction device are matched with the outlet pressure of the condensate pump set.

[0016] In one embodiment, the pressure difference between the first pressure reducing device and the second pressure reducing device is equal, and the sum of the two matches the outlet pressure of the condensate pump set under power frequency conditions.

[0017] In one embodiment, the pressure difference of the first pressure reducing device or the second pressure reducing device located near the condenser is designed to be the pressure difference between the lowest outlet pressure of the condensate pump set under variable frequency operation and the condenser.

[0018] The beneficial effects of this invention are as follows:

[0019] Applicable to thermal power units of 300MW and above, this invention solves the technical problem of vibration in the recirculation pipeline between the condenser hot well and the deaerator when the condensate pump head is high and the pressure is close to vacuum. It implements a two-stage pressure reduction system for the condensate recirculation system. The second-stage pressure reduction device acts as a barrier between the condenser and the first-stage pressure reduction device, preventing vibration of the pipeline caused by two-phase flow in the pipeline connected to the pressure reduction device (which is close to vacuum pressure) when the condensate pump head is high. Specifically, after adjusting the pressure of the medium in the pipeline to be higher than the saturated water pressure after the first-stage pressure reduction device is applied, pipeline vibration caused by two-phase flow is avoided. Simultaneously, the second-stage pressure reduction device is positioned close to the condenser hot well, allowing the two-phase flow passing through it to immediately and quickly enter the condenser hot well, further preventing pipeline vibration and ensuring the safe operation of the recirculation system. Attached Figure Description

[0020] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0021] Figure 1 A schematic diagram of the structure of the present invention is shown;

[0022] In the accompanying drawings, the same parts use the same reference numerals. The drawings are not to scale.

[0023] Figure label:

[0024] 1-Condenser, 2-Condensate pump set, 3-Regulating valve, 4-Throttle plate, 201-First condensate pump, 202-Second condensate pump. Detailed Implementation

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] This invention provides a vibration-resistant condensate recirculation system for thermal power units, such as... Figure 1As shown, it includes a condenser 1 and a deaerator. The condenser 1 is connected to the deaerator through a condensate pump set 2. A recirculation pipeline for returning water to the condenser 1 is also provided on the pipeline between the condensate pump set 2 and the deaerator. A first pressure reducing device and a second pressure reducing device connected in series are provided on the recirculation pipeline to form a two-stage pressure reducing system.

[0027] The first or second pressure reducing device is located near the condenser 1 so that the medium in the recirculation pipeline can directly enter the condenser 1 after pressure reduction. The pressure difference of the first pressure reducing device and the pressure difference of the second pressure reducing device are matched with the outlet pressure of the condensate pump group 2.

[0028] Specifically, the first pressure reducing device is a regulating valve 3, the second pressure reducing device is a throttling plate 4, the throttling plate 4 is set close to the condenser 1, and the condensate pump group 2 includes a first condensate pump 201 and a second condensate pump 202 connected in parallel.

[0029] It should be noted that in thermal power units of 300MW and above, and in thermal power units constructed by one or more units in succession, when the condensate pump head is high, such as around 4MPa, the pressure of the condenser 1 hot well is close to vacuum. A regulating valve 3 and a throttling plate 4 are used to perform two-stage pressure reduction on the condensate recirculation system. The throttling plate 4 acts as a barrier between the condenser 1 and the regulating valve 3, preventing the two-phase flow in the pipeline connected to the regulating valve 3 (which has a near-vacuum pressure) from causing vibration in the pipeline when the condensate pump head is high. In this embodiment, the pressure of the medium in the pipeline after the regulating valve 3 is higher than the saturated water pressure, avoiding pipeline vibration caused by the two-phase flow. At the same time, the throttling plate 4 is positioned close to the condenser 1 hot well, allowing the medium after the plate to immediately and quickly enter the condenser 1 hot well, further preventing pipeline vibration and ensuring the safe operation of the recirculation system.

[0030] In one embodiment, the pressure difference between the first pressure reducing device and the second pressure reducing device is equal, and the sum of the two matches the outlet pressure of the condensate pump group 2 under power frequency conditions. For example, taking the condensate pump head of about 4MPa as an example, the pressure difference between the regulating valve 3 and the throttle plate 4 is designed to be 2MPa, so that the outlet pressure of the condensate pump group 2 under power frequency conditions is evenly distributed to the two-stage pressure reducing devices, ensuring that the medium pressure after the first-stage pressure reducing device is higher than the saturated water pressure, and avoiding vibration of the recirculation pipeline caused by two-phase flow.

[0031] In one embodiment, the pressure difference of the first pressure reducing device or the second pressure reducing device located near the condenser 1 is designed to be the pressure difference between the lowest outlet pressure of the condensate pump group 2 under variable frequency operation and the condenser 1.

[0032] It should be noted that, for economic reasons, condensate pumps often operate in variable frequency mode. The difference between the minimum and maximum outlet pressures under variable frequency operation is significant. Therefore, the pressure difference of the second-stage pressure reducing device is set to the minimum outlet pressure of the condensate pump group 2 under variable frequency operation. Furthermore, the pressure difference of the first-stage pressure reducing device is set to the maximum outlet pressure minus the pressure difference of the second-stage device. This ensures that when the condensate pump group 2 operates at a lower outlet pressure, circulating water can flow normally into the hot well, avoiding situations where the water flow is too small. For example, taking a condensate pump head of approximately 4 MPa as an example, its minimum outlet pressure under variable frequency operation is 1.5 MPa. This means the pressure difference of the throttling plate 4 is designed to be 1.5 MPa, while the design pressure difference of the regulating valve 3 is the maximum outlet pressure difference of the pump group minus the pressure difference of the throttling plate 4. This ensures that the medium pressure between the regulating valve 3 and the throttling plate 4 is higher than the saturated water pressure, preventing severe vibration in this section of the circulating pipeline. It also prevents circulating water from failing to flow into the hot well when the condensate pump group 2 operates at a lower outlet pressure, which would not only affect water flow but also increase energy consumption.

[0033] In one embodiment, the present invention also provides a vibration-resistant condensate recirculation method for thermal power units, comprising:

[0034] A two-stage pressure reduction system is installed on the condensate recirculation pipeline;

[0035] The secondary pressure reduction system includes a first pressure reduction device and a second pressure reduction device connected in series. One of the pressure reduction devices in the secondary pressure reduction system is located in the middle of the condensate recirculation pipeline, and the other pressure reduction device is located near the condenser so that the medium can directly enter the condenser after secondary pressure reduction. The pressure difference of the first pressure reduction device and the pressure difference of the second pressure reduction device are matched with the outlet pressure of the condensate pump set.

[0036] It should be noted that by setting up a two-stage pressure reduction system in the condensate recirculation pipeline and designing the position and layout of the two pressure reducing devices connected in series in the two-stage pressure reduction system, on the one hand, the medium pressure in the first pressure reducing device and the second pressure reducing device is higher than the saturated water pressure, avoiding pipeline vibration caused by two-phase flow. On the other hand, the medium that has been depressurized by the second pressure reducing device quickly enters the condenser. In other words, by setting up a two-stage pressure reduction system and the layout of the pressure reducing devices, a dual vibration prevention effect is achieved. Compared with conventional condensate recirculation pipelines, the vibration is greatly reduced, ensuring its safe operation and avoiding accidents.

[0037] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. 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.

[0038] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A vibration-resistant condensate recirculation system for thermal power units, characterized in that, It includes a condenser and a deaerator. The condenser is connected to the deaerator through a condensate pump set. A recirculation pipeline for returning water to the condenser is also provided on the pipeline between the condensate pump set and the deaerator. A first pressure reducing device and a second pressure reducing device connected in series are provided on the recirculation pipeline to form a two-stage pressure reducing system. The first or second pressure reducing device is located near the condenser so that the medium in the recirculation pipeline can directly enter the condenser after pressure reduction. The pressure difference of the first pressure reducing device and the pressure difference of the second pressure reducing device are matched with the outlet pressure of the condensate pump set.

2. The vibration-resistant condensate recirculation system for thermal power units according to claim 1, characterized in that, The first pressure reducing device is a regulating valve, and the second pressure reducing device is a throttling plate, which is located close to the condenser.

3. The vibration-resistant condensate recirculation system for thermal power units according to claim 1, characterized in that, The pressure difference between the first pressure reducing device and the second pressure reducing device is equal, and the sum of the two matches the outlet pressure of the condensate pump set under power frequency conditions.

4. The vibration-resistant condensate recirculation system for thermal power units according to claim 1, characterized in that, The pressure difference of the first pressure reducing device or the second pressure reducing device located near the condenser is designed to be the pressure difference between the lowest outlet pressure of the condensate pump set under variable frequency operation and the condenser.

5. The vibration-resistant condensate recirculation system for thermal power units according to claim 1, characterized in that, The condensate pump set includes a first condensate pump and a second condensate pump connected in parallel.

6. The vibration-resistant condensate recirculation system for thermal power units according to claim 1, characterized in that, The thermal power units have a capacity of over 300MW.

7. A vibration-resistant condensate recirculation method for thermal power units, characterized in that, The system includes a condenser and a deaerator, wherein the condenser is connected to the deaerator via a condensate pump set, and further includes: A two-stage pressure reduction system is installed on the condensate recirculation pipeline; The secondary pressure reduction system includes a first pressure reduction device and a second pressure reduction device connected in series. One of the pressure reduction devices in the secondary pressure reduction system is located in the middle of the condensate recirculation pipeline, and the other pressure reduction device is located near the condenser so that the medium can directly enter the condenser after secondary pressure reduction. The pressure difference of the first pressure reduction device and the pressure difference of the second pressure reduction device are matched with the outlet pressure of the condensate pump set.

8. A method for recirculating condensate in a vibration-resistant thermal power unit according to claim 7, characterized in that, The pressure difference between the first pressure reducing device and the second pressure reducing device is equal, and the sum of the two matches the outlet pressure of the condensate pump set under power frequency conditions.

9. A method for recirculating condensate in a vibration-resistant thermal power unit according to claim 7, characterized in that, The pressure difference of the first pressure reducing device or the second pressure reducing device located near the condenser is designed to be the pressure difference between the lowest outlet pressure of the condensate pump set under variable frequency operation and the condenser.

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