A condensate drainage system and method for the first-stage high-pressure heater of a steam turbine.

Abstract

This invention discloses a condensate drainage system and method for a first-stage high-pressure heater of a steam turbine. The system includes a deaerator, a steam-driven feedwater pump, a feedwater pump turbine, a condensate pump, a No. 3 high-pressure heater, and a condensate drainage pipeline for the No. 3 high-pressure heater. The deaerator is equipped with a turbine extraction steam inlet, a condensate inlet, and a condensate inlet. The deaerator outlet is connected to the inlet of the steam-driven feedwater pump, and the outlet of the steam-driven feedwater pump is connected to the inlet of the No. 3 high-pressure heater. The condensate drainage outlet of the No. 3 high-pressure heater is connected to the inlet of the condensate pump via a condensate drainage pipeline for the No. 3 high-pressure heater. The outlet of the condensate pump is connected to the condensate drainage inlet of the deaerator. The steam-driven feedwater pump is coaxially connected to the condensate pump via the feedwater pump turbine. The method involves using the steam-driven feedwater pump to drive the condensate pump through the feedwater pump turbine, causing the condensate from the No. 3 high-pressure heater to enter the condensate drainage pipeline for the No. 3 high-pressure heater. The system structure involved in this invention is simple, requires fewer additional equipment and pipelines, and has low investment costs.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation, specifically relating to a condensate drainage system and method for a first-stage high-pressure heater of a steam turbine. Background Technology

[0002] The high-pressure heater is an important auxiliary device in a steam turbine system. It recovers some of the residual energy of the steam that has already performed work by heating the extracted steam from the high and intermediate pressure cylinders. This residual energy is then used to heat the feedwater in stages, thereby reducing exhaust losses from the turbine and improving system cycle efficiency. During this heat exchange process, the extracted steam condenses into a liquid state and is discharged through the condensate drain system.

[0003] In actual production, some power plants experience problems with poor drainage of high-pressure heaters. This primarily manifests as the inability to promptly discharge condensate from the first-stage high-pressure heater to the deaerator, causing the heater's water level to rise continuously. This poses a safety hazard to pipelines and cylinders, impacting unit safety; furthermore, it leads to a continuous deterioration of the heater's heat exchange capacity, affecting power generation efficiency. To address this issue, power plants typically keep the emergency drain open for extended periods, continuously discharging high-pressure heater condensate to the condenser. However, this approach results in a significant waste of condensate energy, greatly reducing the unit's economic efficiency.

[0004] A utility model patent with authorization announcement number CN 203395907 U discloses a flow-through high-pressure heater condensate drainage system with a condensate pump. The core of this invention involves adding a condensate pump to the condensate drainage pipe of the first-stage high-pressure heater to increase the condensate drainage pressure, and connecting the condensate drainage outlet pipe to the feedwater pre-pump outlet pipe instead of the deaerator inlet pipe. The main drawbacks of this design are: First, after the modification, the condensate enters the feedwater directly without passing through the deaerator, failing to effectively remove dissolved oxygen and other impurities, thus compromising feedwater quality. Second, the feedwater pre-pump is designed for the total feedwater flow rate, at which it achieves maximum efficiency. The modification, by bypassing the pre-pump, causes it to operate in a lower efficiency range, reducing economic efficiency. Third, the patent claims that reducing the feedwater flow rate entering the pre-pump reduces its power consumption, thus achieving energy savings. However, the newly added condensate pump also requires energy, and the overall energy-saving effect needs further consideration.

[0005] In summary, there is currently a lack of a solution to the problem of poor drainage in the first-stage high-pressure heater of a steam turbine that can both ensure feedwater quality and minimize system energy consumption while guaranteeing the economic efficiency of unit operation. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems in the prior art by providing a condensate drainage system and method for the first-stage high-pressure heater of a steam turbine.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A condensate drain system for a first-stage high-pressure heater of a steam turbine includes a deaerator, a steam-driven feedwater pump, a feedwater pump turbine, a condensate pump, a No. 3 high-pressure heater, and a condensate drain pipe for the No. 3 high-pressure heater.

[0009] The deaerator is equipped with a turbine extraction steam inlet, a condensate inlet, and a condensate drain inlet. The deaerator outlet is connected to the inlet of the steam-driven feedwater pump, the steam-driven feedwater pump outlet is connected to the inlet of the No. 3 high-pressure heater, the condensate drain outlet of the No. 3 high-pressure heater is connected to the inlet of the condensate drain pump through the No. 3 high-pressure heater condensate drain pipe, and the condensate drain pump outlet is connected to the condensate drain inlet of the deaerator. The steam-driven feedwater pump is coaxially connected to the condensate drain pump through the feedwater pump turbine.

[0010] A further improvement of the present invention is that a bypass pipe for the condensate pump is provided between the inlet and outlet of the condensate pump.

[0011] A further improvement of the present invention is that it also includes a coupling, through which the condensate pump is coaxially connected to the steam-driven feedwater pump and the feedwater pump turbine.

[0012] A further improvement of the present invention is that the condensate pump is equipped with a gearbox.

[0013] A further improvement of the present invention is that the inlet of the No. 3 high-pressure heater is connected to the boiler in sequence through the No. 2 high-pressure heater and the No. 1 high-pressure heater.

[0014] A further improvement of the present invention is that a drainage pipe for the No. 1 high-pressure heater is provided between the No. 2 high-pressure heater and the No. 1 high-pressure heater.

[0015] A further improvement of the present invention is that a drainage pipe for the No. 2 high-pressure heater is provided between the No. 3 high-pressure heater and the No. 2 high-pressure heater.

[0016] A method for draining water from a first-stage high-pressure heater of a steam turbine, the method being based on a draining system for the first-stage high-pressure heater of a steam turbine, comprising:

[0017] The steam-driven feedwater pump is used to drive the condensate pump through the feedwater pump turbine, so that the condensate from the No. 3 high-pressure heater enters the condensate pipe of the No. 3 high-pressure heater.

[0018] A further improvement of the present invention is that it also includes: providing a bypass pipe for the condensate pump between the inlet and outlet of the condensate pump;

[0019] When the condensate from the No. 3 high-pressure heater can flow smoothly into the deaerator, open the bypass pipe of the condensate pump to stop the condensate pump from working, and all the condensate will flow directly into the deaerator from the bypass pipe of the condensate pump.

[0020] When the condensate from the No. 3 high-pressure heater has difficulty flowing by itself or the condensate is not flowing smoothly, open the bypass pipe of the condensate pump and start the condensate pump at the same time. Part of the condensate flows directly into the deaerator from the bypass pipe of the condensate pump; the other part of the condensate flows into the deaerator after being pressurized by the condensate pump.

[0021] When the condensate from the No. 3 high-pressure heater is completely unable to flow to the deaerator by its own power, close the bypass pipe of the condensate pump to put the condensate pump into operation. The condensate will then flow into the deaerator after being pressurized by the condensate pump.

[0022] A further improvement of the present invention is that it also includes: the condensate pump is equipped with a gearbox, and when the condensate pump is put into operation, the speed of the condensate pump is reduced by means of the gearbox, while ensuring that the condensate flow capacity of the No. 3 high-pressure heater is normal.

[0023] The present invention has at least the following beneficial technical effects:

[0024] This invention provides a condensate drainage system and method for the first-stage high-pressure heater of a steam turbine. By transferring the mechanical energy of the steam-driven feedwater pump to the condensate pump, the pump is driven to operate and pressurize the condensate drained from the high-pressure heater. After being pressurized, the condensate drains from the high-pressure heater, creating a significant pressure difference with the deaerator. The condensate can then flow by gravity into the deaerator along the outlet pipe of the condensate pump, thus solving the problem of poor condensate drainage from the high-pressure heater.

[0025] Furthermore, this invention incorporates a gearbox, which can adjust the condensate pump speed based on the pressure difference between the condensate drain and the deaerator, thereby minimizing the condensate pump shaft power and reducing energy consumption. Additionally, a bypass pipeline for the No. 3 high-pressure heater condensate drain is added.

[0026] Furthermore, when the condensate from the No. 3 high-pressure heater can flow smoothly into the deaerator, the bypass pipe of the condensate pump is opened, the coupling is disconnected to stop the condensate pump from working, and all the condensate flows directly into the deaerator from the bypass pipe of the condensate pump.

[0027] When the condensate from the No. 3 high-pressure heater experiences difficulties in self-flowing or becomes obstructed, the bypass pipe of the condensate pump is opened, and the condensate pump is simultaneously put into operation via the coupling. Part of the condensate flows directly into the deaerator from the bypass pipe; the other part flows into the deaerator after being pressurized by the condensate pump. By adjusting the opening of the bypass valve, the ratio of the two condensate flows can be flexibly allocated, ideally ensuring normal condensate flow while keeping the pump shaft power relatively low.

[0028] When the condensate from the No. 3 high-pressure heater can no longer flow to the deaerator by its own power, the bypass pipe of the condensate pump is closed, and the condensate pump is put into operation through the coupling. All the condensate from the high-pressure heater flows into the deaerator after being pressurized by the condensate pump.

[0029] In summary, this invention is relatively simple, requires fewer new devices and pipelines, and has low investment costs. It allows for flexible switching between three condensate flow schemes based on the pressure difference between the high-pressure heater's condensate drain and the deaerator. The mechanical energy of the steam-driven feedwater pump directly drives the condensate pump, avoiding the secondary energy conversion required by electric pumps, resulting in high system efficiency. Furthermore, the speed of the condensate pump is adjusted in real-time by a transmission, further reducing energy consumption. Based on conventional high-pressure heaters and feedwater system piping, this invention specifically addresses the problem of poor condensate drainage in the first-stage high-pressure heater. This method has broad applicability and can be widely adopted. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the condensate drainage system of the first-stage high-pressure heater of a steam turbine according to the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Deaerator; 2. Steam-driven feedwater pump; 3. Feedwater pump turbine; 4. Coupling; 5. Drain pump; 6. No. 3 high-pressure heater; 7. No. 2 high-pressure heater; 8. No. 1 high-pressure heater; 9. Drain pipe of No. 1 high-pressure heater; 10. Drain pipe of No. 2 high-pressure heater; 11. Drain pipe of No. 3 high-pressure heater; 12. Drain pump outlet pipe; 13. Deaerator outlet pipe; 14. Feedwater pipe; 15. Gearbox; 16. Drain pump bypass pipe; 17. Drain pump outlet main pipe. Detailed Implementation

[0033] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0037] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0038] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0039] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] Example 1

[0042] like Figure 1As shown, this embodiment provides a condensate drain system for the first-stage high-pressure heater of a steam turbine, including a deaerator 1, a steam-driven feedwater pump 2, a feedwater pump turbine 3, a condensate pump 5, a No. 3 high-pressure heater 6, and a No. 3 high-pressure heater condensate drain pipe 11. The deaerator 1 is provided with a turbine extraction steam inlet, a condensate inlet, and a condensate drain inlet. The outlet of the deaerator 1 is connected to the inlet of the steam-driven feedwater pump 2, and the outlet of the steam-driven feedwater pump 2 is connected to the inlet of the No. 3 high-pressure heater 6. The condensate drain outlet of the No. 3 high-pressure heater 6 is connected to the inlet of the condensate pump 5 through the No. 3 high-pressure heater condensate drain pipe 11. The outlet of the condensate pump 5 is connected to the condensate drain inlet of the deaerator 1. The steam-driven feedwater pump 2 is coaxially connected to the condensate pump 5 through the feedwater pump turbine 3.

[0043] In this embodiment, a bypass pipe 16 is provided between the inlet and outlet of the condensate pump 5. When the bypass pipe 16 is opened, condensate can flow directly into the deaerator 1 from the bypass pipe 16.

[0044] In this embodiment, the condensate pump 5 is coaxially connected to the steam-driven feedwater pump 2 and the feedwater pump turbine 3 via the coupling 4, and the condensate pump 5 can be put into operation via the coupling 4.

[0045] In this embodiment, the condensate pump 5 is equipped with a gearbox 15, which reduces the rotational speed of the condensate pump 5.

[0046] In this embodiment, the inlet of high-pressure heater 6 (No. 3) is connected to the boiler in sequence through high-pressure heater 7 (No. 2) and high-pressure heater 8 (No. 1).

[0047] In this embodiment, a drain pipe 9 for high-pressure heater 1 is provided between high-pressure heater 2 7 and high-pressure heater 1 8. A drain pipe 10 for high-pressure heater 2 is provided between high-pressure heater 3 6 and high-pressure heater 2 7.

[0048] In this embodiment, the system is relatively simple, with fewer new devices and pipelines, resulting in lower investment costs. It can flexibly switch between three condensate flow schemes based on the pressure difference between the high-pressure heater's condensate and the deaerator. The mechanical energy of the steam-driven feedwater pump directly drives the condensate pump, avoiding the secondary energy conversion required by electric pumps, thus achieving high system efficiency. The speed of the condensate pump is adjusted in real time by the gearbox, further reducing energy consumption.

[0049] Example 2

[0050] like Figure 1As shown in the figure, the condensate drainage system of the first-stage high-pressure heater of a steam turbine provided in this embodiment includes a deaerator 1, a steam-driven feedwater pump 2, a feedwater pump turbine 3, a coupling 4, a condensate drainage pump 5, a No. 3 high-pressure heater 6, a No. 2 high-pressure heater 7, a No. 1 high-pressure heater 8, a condensate drainage pipe for the No. 1 high-pressure heater 9, a condensate drainage pipe for the No. 2 high-pressure heater 10, a condensate drainage pipe for the No. 3 high-pressure heater 11, a condensate drainage pump outlet pipe 12, a deaerator outlet pipe 13, a feedwater pipe 14, a gearbox 15, a condensate drainage pump bypass pipe 16, and a condensate drainage pump outlet main pipe 17.

[0051] In this embodiment, one end of the deaerator outlet water pipe 13 is connected to the deaerator 1, and the other end is connected to the steam-driven feedwater pump 2. Steam extracted from the turbine, condensate, and high-pressure heater condensate flow into the deaerator 1, where oxygen and other impurities are removed and the water is heated. After being pressurized by the steam-driven feedwater pump 2, the water flows into the feedwater pipe 14.

[0052] In this embodiment, the water supply pipe 14 is sequentially connected to high-pressure heater 6 (No. 3), high-pressure heater 7 (No. 2), and high-pressure heater 8 (No. 1). High-pressure water flows along the water supply pipe 14, passes through the three high-pressure heaters in sequence, and finally enters the boiler.

[0053] In this embodiment, the condensate from the three high-pressure heaters flows by gravity through the condensate pipes, and then enters the condensate pump 5 through the condensate pipe 11 of the No. 3 high-pressure heater. After being pressurized by the condensate pump, it finally flows into the deaerator 1.

[0054] In this embodiment, the drain pump 5, the steam-driven feedwater pump 2, and the feedwater pump turbine 3 are coaxially connected via coupling 4, and the mechanical energy of the steam-driven feedwater pump 2 drives the drain pump 5 to rotate. Compared with using an electric pump, this avoids secondary energy conversion and improves energy utilization efficiency.

[0055] In this embodiment, the drain pump 5 is equipped with a gearbox 15. The purpose is to reduce the speed of the drain pump 5 by appropriately reducing the speed of the drain pump 5 while ensuring the normal drain flow capacity of the No. 3 high-pressure heater. This can effectively reduce the shaft power of the drain pump and reduce the system energy consumption.

[0056] In this embodiment, the inlet of the condensate pump 5 is connected to the condensate drain pipe 11 of the No. 3 high-pressure heater, and the outlet is connected to the outlet pipe 12 of the condensate pump. The condensate from the three high-pressure heaters flows by gravity along the drain pipes in stages. After being mixed in the No. 3 high-pressure heater, it enters the condensate pump 5 through the No. 3 high-pressure heater condensate drain pipe 11. After being pressurized by the condensate pump, it flows out from the outlet pipe 12 of the condensate pump and finally flows into the deaerator 1 through the main outlet pipe 17 of the condensate pump.

[0057] In this embodiment, the system also includes a bypass pipe 16 for the condensate pump. One end of this pipe is connected to the condensate pipe 11 of the No. 3 high-pressure heater, and the other end merges with the condensate pump outlet pipe and then connects to the main outlet pipe of the condensate pump, thus serving as a bypass for the condensate pump. The purpose is to switch between different solutions based on the actual condensate flow conditions.

[0058] In this embodiment, various types of valves should be installed on each pipeline according to actual needs.

[0059] In this embodiment, the system is designed according to common unit types, where the No. 3 high-pressure heater represents the first-stage high-pressure heater. Other models can also be adjusted accordingly, making it widely applicable.

[0060] Example 3

[0061] like Figure 1 As shown, this embodiment provides a condensate drainage method for the first-stage high-pressure heater of a steam turbine. This method is based on a condensate drainage system for the first-stage high-pressure heater of a steam turbine, including a deaerator 1, a steam-driven feedwater pump 2, a feedwater pump turbine 3, a condensate pump 5, a third high-pressure heater 6, and a condensate drainage pipe 11 for the third high-pressure heater. The deaerator 1 is equipped with a turbine extraction steam inlet, a condensate inlet, and a condensate drainage inlet. The outlet of the deaerator 1 is connected to the inlet of the steam-driven feedwater pump 2, and the outlet of the steam-driven feedwater pump 2 is connected to the inlet of the third high-pressure heater 6. The condensate drainage outlet of the third high-pressure heater 6 is connected to the inlet of the condensate pump 5 through the condensate drainage pipe 11 for the third high-pressure heater. The outlet of the condensate pump 5 is connected to the condensate drainage inlet of the deaerator 1. The steam-driven feedwater pump 2 is coaxially connected to the condensate pump 5 through the feedwater pump turbine 3. The method includes:

[0062] Since the condensate pump 5, the steam-driven feedwater pump 2, and the feedwater pump turbine 3 are coaxially connected, the mechanical energy of the steam-driven feedwater pump 2 is used to drive the condensate pump 5 to rotate and work; the condensate from the three high-pressure heaters flows by gravity in stages, and after being mixed in the No. 3 high-pressure heater, it enters the condensate pipe of the No. 3 high-pressure heater.

[0063] In this embodiment, when the condensate from the No. 3 high-pressure heater can flow smoothly into the deaerator 1, the bypass pipe 16 of the condensate pump is opened, the coupling 4 is disconnected to stop the condensate pump 5 from working, and all the condensate flows directly into the deaerator 1 from the bypass pipe 16 of the condensate pump.

[0064] In this embodiment, when the condensate from the No. 3 high-pressure heater experiences difficulties in self-flowing or poor drainage, the bypass pipe 16 of the condensate pump is opened, and the condensate pump 5 is simultaneously put into operation via the coupling 4. A portion of the condensate flows directly into the deaerator 1 from the bypass pipe 16; the other portion flows into the deaerator 1 after being pressurized by the condensate pump 5. By adjusting the opening of the bypass valve, the ratio of the two condensate flows can be flexibly allocated, ideally ensuring normal condensate flow while keeping the shaft power of the condensate pump 1 low.

[0065] In this embodiment, when the condensate from the No. 3 high-pressure heater is completely unable to flow to the deaerator 1 by its own power, the bypass pipe 16 of the condensate pump is closed, and the condensate pump 5 is put into operation through the coupling 4. All the condensate from the high-pressure heater flows into the deaerator 1 after being pressurized by the condensate pump 5.

[0066] When the condensate pump 5 is put into operation, under the premise of ensuring the normal condensate flow capacity of the No. 3 high-pressure heater, the speed of the condensate pump 5 can be appropriately reduced by the speed reducer 15, which can effectively reduce the shaft power of the condensate pump 5 and reduce the system energy consumption.

[0067] In summary, this invention solves the problem of poor drainage in the first-stage high-pressure heater, has wide applicability, and can be widely promoted and used.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0069] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A drain system for a first stage high pressure heater of a steam turbine, characterized by, The system comprises a deaerator (1), a steam-driven feed water pump (2), a feed water pump turbine (3), a drain pump (5), a No. 3 high-pressure heater (6) and a No. 3 high-pressure heater drain pipeline (11). The deaerator (1) is provided with a turbine steam inlet, a condensate water inlet and a drain inlet, the outlet of the deaerator (1) is connected to the inlet of the steam-driven feed water pump (2), the outlet of the steam-driven feed water pump (2) is connected to the inlet of the No. 3 high-pressure heater (6), the drain outlet of the No. 3 high-pressure heater (6) is connected to the inlet of the drain pump (5) through the No. 3 high-pressure heater drain pipeline (11), the outlet of the drain pump (5) is connected to the drain inlet of the deaerator (1), the steam-driven feed water pump (2) is coaxially connected to the drain pump (5) through the feed water pump turbine (3), and the drain pump bypass pipeline (16) is arranged between the inlet and the outlet of the drain pump (5).

2. A drain system for a first stage high pressure heater of a steam turbine as claimed in claim 1, wherein, The system further comprises a coupling (4) for coaxially connecting the drain pump (5) to the steam-driven feed water pump (2) and the feed water pump turbine (3).

3. A drain system for a first stage high pressure heater of a steam turbine as claimed in claim 2, wherein, The drain pump (5) is provided with a speed variator (15).

4. A drain system for a first stage high pressure heater of a steam turbine as recited in claim 1, wherein, The inlet of the No. 3 high-pressure heater (6) is connected to a boiler in sequence through a No. 2 high-pressure heater (7) and a No. 1 high-pressure heater (8).

5. A drain system for a first stage high pressure heater of a steam turbine as claimed in claim 4 wherein, A No. 1 high-pressure heater drain pipeline (9) is arranged between the No. 2 high-pressure heater (7) and the No. 1 high-pressure heater (8).

6. A drain system for a first stage high pressure heater of a steam turbine as claimed in claim 4 wherein, A No. 2 high-pressure heater drain pipeline (10) is arranged between the No. 3 high-pressure heater (6) and the No. 2 high-pressure heater (7).

7. A method of draining a first stage high pressure heater of a steam turbine, characterized by, The method is based on the drain system of the first-stage high-pressure heater of the steam turbine according to claim 1, and comprises the following steps: The steam-driven feed water pump (2) drives the drain pump (5) to rotate and work through the feed water pump turbine (3), so that the drain of the No. 3 high-pressure heater (6) enters the No. 3 high-pressure heater drain pipeline (11).

8. A drain method for a first stage high pressure heater of a steam turbine as claimed in claim 7, wherein, When the drain of the No. 3 high-pressure heater (6) can flow smoothly into the deaerator (1) by itself, the drain pump bypass pipeline (16) is opened, the drain pump (5) is stopped, and all the drain directly flows into the deaerator (1) through the drain pump bypass pipeline (16); When the drain of the No. 3 high-pressure heater (6) cannot flow by itself, the drain pump bypass pipeline (16) is opened, the drain pump (5) is put into work, a part of the drain directly flows into the deaerator (1) through the drain pump bypass pipeline (16), and another part of the drain flows into the deaerator (1) after being pressurized by the drain pump (5); When the drain of the No. 3 high-pressure heater (6) cannot flow into the deaerator (1) by itself, the drain pump bypass pipeline (16) is closed, the drain pump (5) is put into work, and the drain flows into the deaerator (1) after being pressurized by the drain pump (5).

9. A method of draining a first stage high pressure heater of a steam turbine as claimed in claim 7, wherein, The system further comprises: The drain pump (5) is provided with a speed variator (15), when the drain pump (5) is put into work, the speed of the drain pump (5) is reduced through the speed variator (15) under the premise that the flow capacity of the drain of the No. 3 high-pressure heater (6) is normal.

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