A peak regulation system and method for thermal power unit boiler in wet operation mode

Abstract

The present invention discloses a peak-shaving system and method for a thermal power unit boiler in a wet-state operation mode, comprising a steam generator, an extraction steam heater, a superheater, a turbine high-pressure cylinder, a turbine intermediate-pressure cylinder, and a reheater. The steam output end of the steam generator is connected to the cold-end inlet of the extraction steam heater, the cold-end outlet of the extraction steam heater is connected to the input end of the superheater, the output end of the superheater is connected to the input end of the turbine high-pressure cylinder, the exhaust end of the turbine high-pressure cylinder is connected to the input end of the reheater, and the output end of the reheater is connected to the input end of the turbine intermediate-pressure cylinder; the hot-end inlet of the extraction steam heater is connected to the first-stage extraction port of the turbine high-pressure cylinder and / or the first-stage extraction port of the turbine intermediate-pressure cylinder. The present invention can effectively prevent overheating of the superheater system, reduce the injection of coal or plasma into the boiler furnace, save costs, increase the temperature and pressure of the main steam entering the turbine, and ensure safe and reliable operation of the turbine.

Description

Technical Field

[0001] The present invention belongs to the technical field of wet-state operation peak regulation of supercritical thermal power units, and in particular relates to a peak regulation system and method under wet-state operation of a thermal power unit boiler. Background Art

[0002] To meet rapidly growing electricity demand while ensuring sustainable development, large-capacity, high-parameter supercritical and ultra-supercritical once-through boilers are increasingly being adopted. At the same time, new energy sources are being vigorously developed. However, integrating new energy sources into the grid presents certain challenges. For example, wind power, solar power, and biomass power generation lack peak-shaving capabilities. Therefore, developing deep peak-shaving capabilities for traditional thermal power units has become an effective means of addressing these issues.

[0003] When supercritical thermal power units participate in wide-load, deep peak regulation, they often operate at low loads (20%-30%) and experience large load fluctuations. Low-load operation presents the following challenges: First, supercritical units operate in a wet state, or the steam generator outlet steam superheat is low. This is because the coal-to-water ratio is low during wet operation, resulting in low heat absorption by the water-cooled walls. This requires a higher heat absorption rate in the superheater system, potentially causing overheating. Second, wet operation can lead to unstable combustion within the furnace, requiring the addition of oil or plasma to stabilize combustion, which increases costs. Third, if the steam temperature at the steam generator outlet is too low, the main steam temperature and pressure entering the turbine may be too low. This low main steam temperature will increase the steam humidity of the turbine's last-stage blades, increasing moisture loss and aggravating water droplet erosion of the last-stage moving blades, shortening their service life. It will also increase the reaction of each stage, significantly increasing the rotor's axial thrust and raising the temperature of the thrust pads. If the load is reduced too quickly, the main steam temperature will drop rapidly, causing the inner wall temperature of high-temperature components such as the regulating stage and cylinder to drop sharply, generating significant thermal stress and thermal deformation. In severe cases, this can cause cracks in metal components or wear accidents in the moving and static parts of the turbine, reducing the safety and reliability of the unit's operation. Currently, there are few countermeasures to the above-mentioned problems, resulting in their continued negative effects and no solution. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a peak-shaving system and method for the wet operation mode of a thermal power unit boiler, which can effectively prevent overheating of the superheater system, reduce the addition of coal or plasma into the boiler furnace, save costs, increase the temperature and pressure of the main steam entering the turbine, and ensure the safe and reliable operation of the turbine.

[0005] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0006] A peak-shaving system for a thermal power unit boiler in a wet operation mode comprises a steam generator, an extraction steam heater, a superheater, a turbine high-pressure cylinder, a turbine intermediate-pressure cylinder and a reheater, wherein the steam output end of the steam generator is connected to the cold end inlet of the extraction steam heater, the cold end outlet of the extraction steam heater is connected to the input end of the superheater, the output end of the superheater is connected to the input end of the turbine high-pressure cylinder, the exhaust end of the turbine high-pressure cylinder is connected to the input end of the reheater, and the output end of the reheater is connected to the input end of the turbine intermediate-pressure cylinder; the hot end inlet of the extraction steam heater is connected to the first-stage extraction port of the turbine high-pressure cylinder and / or the first-stage extraction port of the turbine intermediate-pressure cylinder.

[0007] Furthermore, the hot end inlet of the extraction steam heater is connected to a hot steam extraction pipeline, the first stage extraction port of the high pressure cylinder of the steam turbine is connected to the first stage extraction main pipe of the high pressure cylinder, and the first stage extraction port of the intermediate pressure cylinder of the steam turbine is connected to the first stage extraction main pipe of the intermediate pressure cylinder;

[0008] When the hot end inlet of the extraction steam heater is connected to the first stage extraction port of the high pressure cylinder of the steam turbine, the hot steam extraction pipeline is connected to the first stage extraction main pipe of the high pressure cylinder;

[0009] When the hot end inlet of the extraction steam heater is connected to the first stage extraction port of the intermediate pressure cylinder of the steam turbine, the hot steam extraction pipeline is connected to the first stage extraction main pipe of the intermediate pressure cylinder;

[0010] When the hot end inlets of the extraction steam heater are connected to the first-stage extraction port of the high-pressure cylinder of the turbine and the first-stage extraction port of the intermediate-pressure cylinder of the turbine, the hot steam extraction pipelines are connected to the first-stage extraction main pipe of the high-pressure cylinder and the first-stage extraction main pipe of the intermediate-pressure cylinder.

[0011] Furthermore, a high-pressure cylinder steam extraction regulating valve is provided on the high-pressure cylinder first-stage steam extraction main pipe.

[0012] Furthermore, a high-pressure cylinder first-stage steam extraction shut-off valve is provided on the high-pressure cylinder first-stage steam extraction main pipe, and the high-pressure cylinder steam extraction shut-off valve is located between the high-pressure cylinder steam extraction regulating valve and the first-stage steam extraction port of the high-pressure cylinder of the steam turbine.

[0013] Furthermore, an intermediate pressure cylinder steam extraction regulating valve is provided on the intermediate pressure cylinder first-stage steam extraction main pipe.

[0014] Furthermore, an intermediate pressure cylinder steam extraction stop valve is provided on the intermediate pressure cylinder first stage steam extraction main pipe, and the intermediate pressure cylinder steam extraction stop valve is located between the intermediate pressure cylinder steam extraction regulating valve and the first stage steam extraction port of the turbine intermediate pressure cylinder.

[0015] Furthermore, the hot end outlet of the extraction steam heater is connected to an extraction steam recycling pipeline, and the extraction steam recycling pipeline is used to connect to heat-using equipment.

[0016] Furthermore, a steam extraction recycling stop valve is provided on the steam extraction recycling pipeline.

[0017] Furthermore, a boiler is included, and the output end of the furnace water-cooled wall is connected to the input end of the steam generator.

[0018] A peak-shaving method for a thermal power unit boiler in a wet operation mode, using the aforementioned peak-shaving system, comprises:

[0019] When the temperature of the steam output end of the steam generator is lower than the set temperature, steam is extracted from the first-stage extraction port of the intermediate pressure cylinder of the steam turbine and input into the extraction steam heater, or steam is extracted from the first-stage extraction port of the intermediate pressure cylinder of the steam turbine and input into the extraction steam heater, or steam is extracted from the first-stage extraction port of the high pressure cylinder of the steam turbine and the first-stage extraction port of the intermediate pressure cylinder of the steam turbine and input into the extraction steam heater; the steam input from the hot end inlet of the extraction steam heater is heat exchanged with the unsuperheated steam input from the cold end inlet, and after the heat exchange, the unsuperheated steam is output from the cold end outlet of the extraction steam heater and enters the superheater for further heating, and the heated steam is input into the high pressure cylinder of the steam turbine to perform work, and the steam after doing work enters the reheater for heating and is then input into the intermediate pressure cylinder of the steam turbine to perform work.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] The present invention provides a peak-shaving system for a thermal power unit boiler operating in a wet-state mode. When the unit is operating in a wet-state mode, steam is extracted from the first-stage steam extraction port of the high-pressure cylinder of the steam turbine and / or the first-stage steam extraction port of the intermediate-pressure cylinder of the steam turbine and input into the extraction steam heater. That is, the high-temperature steam obtained from the first-stage steam extraction port of the high-pressure cylinder of the steam turbine and / or the first-stage steam extraction port of the intermediate-pressure cylinder of the steam turbine is used to heat the unsuperheated steam entering the extraction steam heater from the steam generator. Due to the extraction steam heating, a higher coal-to-water ratio can be used than under the original operating conditions, which is conducive to stable combustion at low loads, reduces the amount of coal and plasma added to the furnace, and saves costs. At the same time, the higher coal-to-water ratio increases the heat absorption of the water-cooled wall, reduces the heat absorption of the superheater system, and avoids overload operation of the superheater system. In addition, the steam temperature at the steam generator outlet is increased, which increases the temperature and pressure of the main steam entering the steam turbine, ensuring safe and reliable operation of the turbine. In summary, the present invention increases the steam temperature by connecting the first-stage extraction steam of the high-pressure cylinder of the turbine or the first-stage extraction steam of the intermediate-pressure cylinder to the extraction steam heater behind the steam generator, which can increase the coal-water ratio of the unit, is beneficial to the stability of the boiler at low load, reduces the addition of oil and plasma auxiliary combustion, reduces costs, ensures that the superheater will not be overloaded due to the low steam temperature at the steam generator outlet, and also ensures the increase of the main steam temperature under low load, avoids turbine accidents caused by the reduction of main steam temperature, and improves the safety and reliability of turbine operation.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 The present invention is a schematic diagram of a peak regulation system for a thermal power unit boiler in wet operation mode.

[0025] In the figure: 1-steam generator; 2-extraction steam heater; 3-superheater; 4-turbine high-pressure cylinder; 5-turbine intermediate-pressure cylinder; 6-reheater; 7-hot steam extraction pipeline; 8-high-pressure cylinder first-stage extraction main pipe; 9-intermediate-pressure cylinder first-stage extraction main pipe; 10-high-pressure cylinder extraction regulating valve; 11-intermediate-pressure cylinder extraction regulating valve; 12-high-pressure cylinder extraction stop valve; 13-intermediate-pressure cylinder extraction stop valve; 14-extraction steam recycling pipeline; 15-extraction steam recycling stop valve; 16-furnace water-cooled wall. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] As a specific embodiment of the present invention, Figure 1 As shown, a peak-shaving system for a thermal power unit boiler in wet operation mode includes a steam generator 1, an extraction steam heater 2, a superheater 3, a turbine high-pressure cylinder 4, a turbine intermediate-pressure cylinder 5 and a reheater 6. The steam output end of the steam generator 1 is connected to the cold end inlet of the extraction steam heater 2, the cold end outlet of the extraction steam heater 2 is connected to the input end of the superheater 3, the output end of the superheater 3 is connected to the input end of the turbine high-pressure cylinder 4, the exhaust end of the turbine high-pressure cylinder 4 is connected to the input end of the reheater 6, and the output end of the reheater 6 is connected to the input end of the turbine intermediate-pressure cylinder 5. The hot end inlet of the extraction steam heater 2 is connected to the first-stage extraction port of the turbine high-pressure cylinder 4; or, the hot end inlet of the extraction steam heater 2 is connected to the first-stage extraction port of the turbine intermediate-pressure cylinder 5; or, the hot end inlets of the extraction steam heater 2 are both connected to the first-stage extraction port of the turbine high-pressure cylinder 4 and the first-stage extraction port of the turbine intermediate-pressure cylinder 5. As shown Figure 1 As shown, specifically, the hot end inlet of the extraction steam heater 2 is connected to a hot steam extraction pipe 7, the first-stage extraction port of the high-pressure cylinder 4 of the steam turbine is connected to the first-stage extraction main pipe 8 of the high-pressure cylinder, and the first-stage extraction port of the intermediate-pressure cylinder 5 of the steam turbine is connected to the first-stage extraction main pipe 9 of the intermediate-pressure cylinder. When the hot end inlet of the extraction steam heater 2 is connected to the first-stage extraction port of the high-pressure cylinder 4 of the steam turbine, the hot steam extraction pipe 7 is in communication with the first-stage extraction main pipe 8 of the high-pressure cylinder; when the hot end inlet of the extraction steam heater 2 is connected to the first-stage extraction port of the intermediate-pressure cylinder 5 of the steam turbine, the hot steam extraction pipe 7 is in communication with the first-stage extraction main pipe 9 of the intermediate-pressure cylinder; when the hot end inlet of the extraction steam heater 2 is connected to both the first-stage extraction port of the high-pressure cylinder 4 of the steam turbine and the first-stage extraction port of the intermediate-pressure cylinder 5 of the steam turbine, the hot steam extraction pipe 7 is in communication with both the first-stage extraction main pipe 8 of the high-pressure cylinder and the first-stage extraction main pipe 9 of the intermediate-pressure cylinder.

[0028] The method for peak shaving by using the peak shaving system of the present invention in the wet operation mode of the thermal power unit boiler is as follows: when the thermal power unit boiler is in wet operation, when the temperature of the steam output end of the steam generator 1 is lower than the set temperature, that is, when the steam temperature at the outlet of the steam generator 1 is too low, steam is extracted from the first-stage extraction port of the steam turbine intermediate pressure cylinder 5 and input into the extraction steam heater 2, or steam is extracted from the first-stage extraction port of the steam turbine intermediate pressure cylinder 5 and input into the extraction steam heater 2, or steam is extracted from the first-stage extraction port of the steam turbine high pressure cylinder 4 and the first-stage extraction port of the steam turbine intermediate pressure cylinder 5 and input into the extraction steam heater 2; the steam input from the hot end inlet of the extraction steam heater 2 is heat exchanged with the unsuperheated steam input from the cold end inlet, and after the heat exchange, the unsuperheated steam is output from the cold end outlet of the extraction steam heater 2 and enters the superheater 3 for further heating, and the heated steam is input into the steam turbine high pressure cylinder 4 to perform work, and the steam after doing work enters the reheater 6 for heating and then is input into the steam turbine intermediate pressure cylinder 5 to perform work.

[0029] That is, the present invention utilizes high-temperature steam obtained from the first-stage extraction port of the steam turbine high-pressure cylinder 4 and / or the first-stage extraction port of the steam turbine intermediate-pressure cylinder 5 to heat the non-superheated steam entering the extraction steam heater 2 from the steam generator 1, thereby increasing the steam temperature by 20°C to 30°C.

[0030] like Figure 1 As shown, the hot end outlet of the extraction steam heater 2 is connected to an extraction steam recycling pipeline 14. Extraction steam recycling pipeline 14 is used to connect to heat-consuming equipment. After the extracted steam heats the unsuperheated steam, it still has a certain amount of heat. Therefore, it is input into the heat-consuming equipment through extraction steam recycling pipeline 14 for heat recycling. In this embodiment, the heat-consuming equipment includes a deaerator, a No. 2 high-pressure heater, or a heating pipeline. After heat exchange, the extraction steam can be passed into the deaerator or No. 2 high-pressure heater under appropriate conditions. Otherwise, it can be mixed into the heating pipeline for energy recycling. Preferably, a steam extraction reuse stop valve 15 is provided on the steam extraction reuse pipe 14, and the steam extraction after heat exchange is passed through the steam extraction reuse pipe 14 to the deaerator or the No. 2 high-pressure heater to realize energy reuse or is connected to the heating pipe to realize energy cascade utilization, and the feed water is heated to further achieve the effect of increasing the outlet temperature of the steam generator. When the unit is operating normally, the steam extraction reuse stop valve 15 on the steam extraction reuse pipe 14 is closed, and the steam extraction after heat exchange is passed through the steam extraction reuse pipe 14 to the deaerator or the No. 2 high-pressure heater to realize energy reuse or is connected to the heating pipe to realize energy cascade utilization, and the feed water is heated to further achieve the effect of increasing the outlet temperature of the steam generator. When the unit is operating normally, the steam extraction reuse stop valve 15 on the steam extraction reuse pipe 14 is closed to isolate the system.

[0031] Based on the above embodiment, as a more preferred embodiment, a high-pressure cylinder extraction steam regulating valve 10 is installed on the high-pressure cylinder first-stage extraction steam main pipe 8, and an intermediate-pressure cylinder extraction steam regulating valve 11 is installed on the intermediate-pressure cylinder first-stage extraction steam main pipe 9. By adjusting the openings of the high-pressure cylinder extraction steam regulating valve 10 and the intermediate-pressure cylinder extraction steam regulating valve 11, the extraction steam flow rate is controlled, and thus the increase in the steam temperature at the steam output end of the steam generator 1 is controlled.

[0032] Based on the above embodiment, as a more preferred embodiment, a high-pressure cylinder first-stage steam extraction shutoff valve 12 is provided on the high-pressure cylinder first-stage steam extraction main pipe 8. The high-pressure cylinder steam extraction shutoff valve 12 is located between the high-pressure cylinder steam extraction regulating valve 10 and the first-stage steam extraction port of the steam turbine high-pressure cylinder 4. An intermediate-pressure cylinder steam extraction shutoff valve 13 is provided on the intermediate-pressure cylinder first-stage steam extraction main pipe 9. The intermediate-pressure cylinder steam extraction shutoff valve 13 is located between the intermediate-pressure cylinder steam extraction regulating valve 11 and the first-stage steam extraction port of the steam turbine intermediate-pressure cylinder 5. The high-pressure cylinder steam extraction shutoff valve 12 and the intermediate-pressure cylinder steam extraction shutoff valve 13 can control the source of steam extraction. When the high-pressure cylinder steam extraction shutoff valve 12 and the intermediate-pressure cylinder steam extraction shutoff valve 13 are closed simultaneously, the entire system is shut off.

[0033] As a preferred embodiment of the present invention, the extraction steam heater 2 adopts a plate heat exchanger, which has the advantages of high heat transfer coefficient, relatively small resistance, compact structure, low metal consumption, high flexibility in use, and easy disassembly and cleaning.

[0034] As a preferred embodiment of the present invention, pressure sensors and temperature sensors are installed on the hot end inlet, hot end outlet, cold end inlet, and cold end outlet pipes of the extraction steam heater 2. The pressure sensors and temperature sensors are used to monitor the steam changes at each port of the extraction steam heater 2 in real time.

[0035] Of course, the peak load regulation system of the thermal power unit boiler in the wet operation mode further includes a furnace water-cooled wall 16 , and the output end of the furnace water-cooled wall 16 is connected to the input end of the steam generator 1 .

[0036] Specifically, the peak-shaving system under the wet operation mode of the thermal power unit boiler described in the present invention, during specific operation, when the thermal power unit boiler is in wet operation and the temperature of the steam generator outlet 1 is too low, part of the steam is extracted from the high-pressure cylinder first-stage extraction main pipe 8 and / or the medium-pressure cylinder first-stage extraction main pipe 9 through the hot steam extraction pipe 7 and sent to the extraction steam heater 2, and the extraction steam is heat-exchanged with the steam with too low temperature from the outlet pipe of the steam generator 1, so that the steam temperature from the steam generator 1 is increased, and the steam temperature entering the superheater 3 is higher, which effectively avoids the overload of the superheater 3 and increases the main steam temperature entering the turbine, ensuring the safe and efficient operation of the turbine; after the extraction temperature is reduced, if the conditions are met, it can enter the deaerator or the No. 2 high-pressure heater to ensure full utilization of energy. If the conditions are not met, it is discharged through the extraction reuse pipe and connected to the heating pipe system to achieve cascade utilization of energy.

[0037] The working process of the peak regulation system of the thermal power unit boiler in the wet operation mode of the present invention is described in detail as follows:

[0038] When the unit operates normally, the high-pressure cylinder steam extraction stop valve 12 and the medium-pressure cylinder steam extraction stop valve 13 are closed, and the peak-shaving system is not connected to the unit.

[0039] When the unit load is reduced, steam is extracted from the first-stage extraction port of the high-pressure cylinder 4 and / or the first-stage extraction port of the intermediate-pressure cylinder 5. Under low-load operation, the extraction pressure of the first-stage extraction port of the high-pressure cylinder 4 is generally 7.5±0.5 MPa, and the extraction pressure of the first-stage extraction port of the intermediate-pressure cylinder 5 is generally 2.5±0.5 MPa, with the steam temperature ranging from 400°C to 450°C. When the unit load is too low (20% to 25% of rated load), steam from the first-stage extraction port of the intermediate-pressure cylinder 5 is used as the hot steam source. When the unit load is slightly higher (25% to 30% of rated load), steam from the first-stage extraction port of the high-pressure cylinder 4 is used as the steam source. This is because the first-stage extraction steam of the intermediate-pressure cylinder 5 is hotter than that of the high-pressure cylinder 4, and the steam extraction cut-in can be controlled by the high-pressure cylinder extraction stop valve 12 and the intermediate-pressure cylinder extraction stop valve 13.

[0040] The extracted steam passes through extraction steam heater 2 (a plate heat exchanger) to heat the steam from steam generator 1, raising its temperature by 20°C to 30°C. Extraction steam heater 2 is a steam-to-steam heat exchanger. Considering that both the heat-releasing and heat-absorbing sides are gas, plate heat exchangers are used, offering advantages such as high heat transfer coefficients and a compact structure. The degree of temperature increase of the steam from steam generator 1 can be controlled by the extraction rate, which is adjusted by controlling the openings of the high-pressure cylinder extraction steam regulating valve 10 and the intermediate-pressure cylinder extraction steam regulating valve 11.

[0041] After heat exchange, the extraction steam is routed through extraction steam recycling pipe 14 to the deaerator or No. 2 high-pressure heater for energy reuse, or connected to the heating pipe for cascade energy utilization, heating the feedwater and further raising the outlet temperature of steam generator 1. When the unit is operating normally, the extraction steam recycling stop valve 15 on extraction steam recycling pipe 14 is closed to isolate the system.

[0042] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A peak-shaving system for a thermal power unit boiler in wet operation mode, characterized in that: The invention comprises a steam generator (1), an extraction steam heater (2), a superheater (3), a high-pressure cylinder of a steam turbine (4), an intermediate-pressure cylinder of a steam turbine (5) and a reheater (6), wherein the steam output end of the steam generator (1) is connected to the cold-end inlet of the extraction steam heater (2), the cold-end outlet of the extraction steam heater (2) is connected to the input end of the superheater (3), the output end of the superheater (3) is connected to the input end of the high-pressure cylinder of the steam turbine (4), the exhaust end of the high-pressure cylinder of the steam turbine (4) is connected to the input end of the reheater (6), and the output end of the reheater (6) is connected to the input end of the intermediate-pressure cylinder of the steam turbine (5); and the hot-end inlet of the extraction steam heater (2) is in communication with the first-stage extraction port of the high-pressure cylinder of the steam turbine (4) and / or the first-stage extraction port of the intermediate-pressure cylinder of the steam turbine (5).

2. A peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 1, characterized in that: The hot end inlet of the extraction steam heater (2) is connected to a hot steam extraction pipe (7), the first stage extraction port of the high-pressure cylinder (4) of the steam turbine is connected to a first stage extraction main pipe (8) of the high-pressure cylinder, and the first stage extraction port of the intermediate-pressure cylinder (5) of the steam turbine is connected to a first stage extraction main pipe (9) of the intermediate-pressure cylinder; When the hot end inlet of the extraction steam heater (2) is connected to the first stage extraction port of the high-pressure cylinder (4) of the steam turbine, the hot steam extraction pipe (7) is communicated with the first stage extraction main pipe (8) of the high-pressure cylinder; When the hot end inlet of the extraction steam heater (2) is connected to the first stage extraction port of the intermediate pressure cylinder (5) of the steam turbine, the hot steam extraction pipe (7) is connected to the first stage extraction main pipe (9) of the intermediate pressure cylinder; When the hot end inlets of the extraction steam heater (2) are connected to the first-stage extraction port of the high-pressure cylinder (4) of the steam turbine and the first-stage extraction port of the intermediate-pressure cylinder (5) of the steam turbine, the hot steam extraction pipeline (7) is connected to the first-stage extraction main pipe (8) of the high-pressure cylinder and the first-stage extraction main pipe (9) of the intermediate-pressure cylinder.

3. A peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 2, characterized in that: A high-pressure cylinder steam extraction regulating valve (10) is provided on the high-pressure cylinder first-stage steam extraction main pipe (8).

4. A peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 3, characterized in that: A high-pressure cylinder first-stage steam extraction main pipe (8) is provided with a high-pressure cylinder steam extraction stop valve (12), and the high-pressure cylinder steam extraction stop valve (12) is located between the high-pressure cylinder steam extraction regulating valve (10) and the first-stage steam extraction port of the high-pressure cylinder (4) of the steam turbine.

5. The peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 2, characterized in that: The intermediate pressure cylinder first stage steam extraction main pipe (9) is provided with an intermediate pressure cylinder steam extraction regulating valve (11).

6. A peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 5, characterized in that: An intermediate pressure cylinder steam extraction stop valve (13) is provided on the intermediate pressure cylinder first-stage steam extraction main pipe (9), and the intermediate pressure cylinder steam extraction stop valve (13) is located between the intermediate pressure cylinder steam extraction regulating valve (11) and the first-stage steam extraction port of the turbine intermediate pressure cylinder (5).

7. The peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 1, characterized in that: The hot end outlet of the extraction steam heater (2) is connected to an extraction steam recycling pipeline (14), and the extraction steam recycling pipeline (14) is used to connect to heat-using equipment.

8. A peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 7, characterized in that: The extracted steam recycling pipeline (14) is provided with an extracted steam recycling stop valve (15).

9. The peak-shaving system for a thermal power unit boiler in wet operation mode according to claim 1, characterized in that: It also includes a furnace water-cooled wall (16), the output end of the furnace water-cooled wall (16) being connected to the input end of the steam generator (1).

10. A peak load regulation method for a thermal power unit boiler in wet operation mode, characterized in that: The peak shaving system according to any one of claims 1 to 9 comprises: When the temperature of the steam output end of the steam generator (1) is lower than the set temperature, steam is extracted from the first-stage extraction port of the steam turbine intermediate-pressure cylinder (5) and input into the extraction steam heater (2), or steam is extracted from the first-stage extraction port of the steam turbine intermediate-pressure cylinder (5) and input into the extraction steam heater (2), or steam is extracted from the first-stage extraction port of the steam turbine high-pressure cylinder (4) and the first-stage extraction port of the steam turbine intermediate-pressure cylinder (5) and input into the extraction steam heater (2); the steam input from the hot end inlet of the extraction steam heater (2) is heat-exchanged with the unsuperheated steam input from the cold end inlet, and after the heat exchange, the unsuperheated steam is output from the cold end outlet of the extraction steam heater (2) and enters the superheater (3) for further heating, and the heated steam is input into the steam turbine high-pressure cylinder (4) to perform work, and the steam that has performed work enters the reheater (6) and is heated, and then input into the steam turbine intermediate-pressure cylinder (5) to perform work.

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