A thermal power unit starting system and method without external steam source

Abstract

This invention discloses a start-up system and method for thermal power units without external steam source. The start-up system includes a steam turbine, a main steam pipeline, a high-pressure bypass pipeline, an auxiliary steam header pipeline, and a start-up steam pipeline. The main steam pipeline connects the high-pressure cylinder of the steam turbine and the high-pressure bypass pipeline. The start-up steam pipeline connects the high-pressure bypass pipeline and the auxiliary steam header pipeline. The start-up steam pipeline is equipped with a first valve group and a first desuperheater and pressure reducer. The start-up system for thermal power units without external steam source provided by this invention can achieve start-up without relying on external steam from other units or start-up boilers, and is simple to operate and stable and reliable.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, and in particular to a thermal power unit starting system without an external steam source. This invention also relates to a method for starting a thermal power unit without an external steam source. Background Technology

[0002] When a power plant is built and put into operation, it is equipped with a start-up boiler to provide auxiliary steam for the unit to start up, so as to ensure the safe start-up of the unit.

[0003] During cold startup of a power plant, the primary function of the start-up boiler is to connect to the auxiliary steam system and provide steam for shaft seals, deaerators, coal mills, feedwater pumps, and air preheater soot blowing. As the power plant is successfully commissioned and multiple units operate simultaneously, these units can serve as backup steam sources for each other during startup. Start-up boilers will be used less frequently, and routine maintenance of them incurs significant manpower and material costs, increasing production costs. Therefore, some power plants choose to shut down their start-up boilers. Furthermore, due to changes in environmental policies, many start-up boilers have been forced to shut down because they do not meet environmental requirements. After a start-up boiler is shut down, if a plant-wide shutdown and subsequent restart or a single unit trips and is then restarted, there will be no start-up steam source, making it impossible to provide external auxiliary steam for the normal startup of the thermal power unit system.

[0004] The main current starting methods for thermal power units without an external steam source are:

[0005] During cold startup of the unit, the turbine first establishes a partial vacuum. After boiler ignition and steam production, cold reheat steam is introduced into the auxiliary steam header as the auxiliary steam source during startup by opening the high-pressure bypass valve and closing the low-pressure bypass valve. When the high-pressure bypass steam temperature is too high, the high-pressure bypass valve closes, causing the high-pressure bypass to lock up. When the high-pressure bypass steam temperature is too low, the parameters of the cold reheat steam need to be coordinated and controlled by simultaneously adjusting the bypass valves of both the high-pressure and low-pressure bypasses to ensure that the cold reheat steam meets the requirements of the auxiliary header.

[0006] When the unit starts up in a hot or extremely hot state, there is excess steam in the superheater and main steam pipeline of the boiler. By controlling the opening of the high-pressure and low-pressure bypass, this excess steam is used as the auxiliary steam source during startup and fed into the auxiliary steam header. In addition to paying attention to the adjustment speed of the high-pressure and low-pressure bypass valves, attention should also be paid to the boiler's heat preservation and pressure maintenance to avoid the boiler's heat storage being consumed too quickly and causing the auxiliary steam source to be interrupted.

[0007] Both of the above-mentioned startup processes require the bypass valves of the high-pressure and low-pressure bypasses to coordinate and control the cold reheat steam parameters as the steam source for the auxiliary steam header. The operation is complex, the control is difficult, and there are certain risks. Furthermore, some power plants only have a single-stage startup bypass, and cannot use the high-pressure and low-pressure bypass valves to control the cold reheat steam to be introduced into the auxiliary steam header as the auxiliary steam source during startup.

[0008] Therefore, how to ensure stable startup of the unit without an external steam source has become a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a thermal power unit startup system without an external steam source. This system enables startup without relying on external steam from other units or starting boilers, and is simple to operate and stable and reliable. Another purpose of this invention is to provide a method for starting a thermal power unit without an external steam source.

[0010] To achieve the above objectives, the present invention provides a thermal power unit starting system without external steam source, including a steam turbine, a main steam pipeline, a high-pressure bypass pipeline, an auxiliary steam header pipeline, and a starting steam pipeline. The main steam pipeline is connected to the high-pressure cylinder of the steam turbine and the high-pressure bypass pipeline. The starting steam pipeline is connected to the high-pressure bypass pipeline and the auxiliary steam header pipeline. The starting steam pipeline is equipped with a first valve group and a first desuperheater and pressure reducer.

[0011] Optionally, the exhaust port of the high-pressure cylinder is provided with a cold reheat steam pipeline, the cold reheat steam pipeline is provided with a shut-off valve, and the auxiliary steam header pipeline is connected to the shut-off valve of the cold reheat steam pipeline.

[0012] Optionally, the high-pressure bypass pipeline is equipped with a high-pressure bypass valve and a second desuperheating and pressure reducing device, and the starting steam pipeline is connected before the second desuperheating and pressure reducing device.

[0013] Optionally, the high-pressure bypass pipeline is equipped with a high-pressure bypass valve and a second desuperheating and pressure reducing device, and the starting steam pipeline is connected after the second desuperheating and pressure reducing device.

[0014] Optionally, a first pressure detection mechanism and a first temperature detection mechanism are provided in the start-up steam pipeline before the first desuperheater.

[0015] Optionally, a second pressure detection mechanism and a second temperature detection mechanism are provided in the start-up steam pipeline after the first desuperheater.

[0016] Optionally, it also includes a hot reheat steam pipeline and a low-pressure bypass pipeline connected to the hot reheat steam pipeline, the hot reheat steam pipeline being connected to the steam inlet of the intermediate-pressure cylinder of the turbine.

[0017] Optionally, the low-pressure bypass pipeline is equipped with a low-pressure bypass valve and a third desuperheater and pressure reducer, and the low-pressure bypass pipeline is connected to the condenser.

[0018] This invention also provides a method for starting a thermal power unit without an external steam source, applied to the aforementioned thermal power unit starting system without an external steam source, comprising:

[0019] The high-pressure bypass pipeline of the steam turbine is connected to the auxiliary steam header pipeline through a start-up steam pipeline, wherein the start-up steam pipeline is equipped with a first valve group and a first desuperheater and pressure reducer.

[0020] Open the first valve group and start the first desuperheater and pressure reducer to adjust the steam inlet parameters of the auxiliary steam header pipeline;

[0021] Once the parameters of the cold reheat steam discharged from the high-pressure cylinder stabilize, the first valve group is closed and the shut-off valve of the cold reheat steam pipeline located at the exhaust port of the high-pressure cylinder is opened.

[0022] Compared to the aforementioned background technology, the thermal power unit start-up system without external steam source provided by this invention, during the unit start-up process, before the main steam reaches the turbine start-up parameters, cools and depressurizes the main steam through a high-pressure bypass pipeline before discharging it to the condenser. Since the turbine requires vacuuming and shaft sealing using steam before startup, the start-up system provided by this invention uses a start-up steam pipeline to supply main steam from the main steam pipeline to the bypass pipeline that does not meet the start-up parameters as steam for the auxiliary steam header. The first valve group and the first desuperheater and pressure reducer of the start-up steam pipeline are used to adjust the main steam parameters to meet the steam requirements for shaft sealing and purging, and the steam is then transported to the auxiliary steam header via the auxiliary steam header pipeline. Once the unit has completed start-up and is operating stably, the start-up steam pipeline and the high-pressure bypass pipeline can be disabled, and the exhaust steam from the turbine's high-pressure or intermediate-pressure cylinder can be used as the steam source for the auxiliary steam header.

[0023] The aforementioned thermal power unit start-up system and method without external steam source solves the problem that systems with only a single-stage bypass cannot achieve start-up without an external steam source. After modification, the start-up steam pipeline has an independent first desuperheater and pressure reducer and a first valve group, which makes it easier to control the parameters of the auxiliary steam, and the modification investment is relatively small. After the two-stage bypass system is modified, the start-up steam pipeline has an independent first desuperheater and pressure reducer and a first valve group, which facilitates the control of auxiliary steam parameters and reduces the control difficulty. The modified system can start feedwater heating in advance, reduce the temperature rise rate and the thermal stress on the boiler heating surface, and can effectively inhibit the shedding of oxide scale from the boiler heating surface. The auxiliary steam in the start-up steam pipeline can also increase the feedwater temperature, shorten the start-up time, reduce fuel consumption during start-up, and has good economic benefits. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1A schematic diagram of the thermal power unit starting system with a primary bypass without external steam source provided by the present invention;

[0026] Figure 2 A schematic diagram of the starting system for a thermal power unit with a two-stage bypass without an external steam source provided by the present invention;

[0027] Figure 3 The flowchart illustrates the method for starting a thermal power unit without an external steam source, as provided by this invention.

[0028] in:

[0029] 1-Main steam pipeline, 2-High-pressure cylinder, 3-High-pressure bypass pipeline, 4-Start-up steam pipeline, 5-Cold reheat steam pipeline, 6-Auxiliary steam header pipeline, 7-Intermediate-pressure cylinder, 8-Low-pressure cylinder, 9-Hot reheat steam pipeline, 10-Low-pressure bypass pipeline;

[0030] 11-Main steam valve, 12-Regulating steam valve, 31-High pressure bypass valve, 32-Second desuperheater and pressure reducer, 41-First valve group, 42-First desuperheater and pressure reducer, 51-Stop valve, 61-Auxiliary steam regulating valve group, 101-Low pressure bypass valve, 102-Third desuperheater and pressure reducer. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Please refer to Figures 1 to 3 , Figure 1 This is a schematic diagram of the thermal power unit start-up system with a primary bypass and no external steam source provided by the present invention. Figure 2 This is a schematic diagram of the starting system for a thermal power unit with a two-stage bypass that does not require an external steam source, provided by the present invention. Figure 3 The flowchart illustrates the method for starting a thermal power unit without an external steam source, as provided by this invention.

[0034] The thermal power unit start-up system without external power source provided by this invention includes a steam turbine, a main steam pipeline 1, a high-pressure bypass pipeline 3, an auxiliary steam header pipeline 6, and a start-up steam pipeline 4. The start-up steam pipeline 4 connects the high-pressure bypass pipeline 3 and the auxiliary steam header pipeline 6, and is equipped with a first valve group 41 and a first desuperheater / pressure reducer 42. The main steam generated by the boiler is heated by the heat exchanger and then transported to the steam turbine through the main steam pipeline 1 as the steam source for turbine start-up and operation. Before the main steam reaches the turbine's start-up parameters, the high-pressure bypass pipeline 3 cools and depressurizes the main steam before discharging it to the condenser or reheater. Before startup, the turbine requires vacuuming and steam for shaft sealing. The startup system provided by this invention uses the startup steam pipeline 4 to supply steam from the main steam pipeline 1 (which does not meet the start-up parameters) to the bypass pipeline as steam for the auxiliary steam header. The first valve group 41 and the first desuperheater / pressure reducer 42 of the startup steam pipeline 4 are used to adjust the main steam parameters to meet the steam requirements for shaft sealing and purging. The steam is then transported to the auxiliary steam header via the auxiliary steam header pipeline 6. Once the unit has completed its start-up and is operating stably, the startup steam pipeline 4 and the high-pressure bypass pipeline 3 can be disabled, and the exhaust steam from the turbine's high-pressure cylinder 2 or intermediate-pressure cylinder 7 can be used as the steam source for the auxiliary steam header.

[0035] During the above startup process, it is only necessary to adjust the opening / closing of the first valve group 41 and the first desuperheating and pressurizing device to desuperheat and reduce the pressure of the main steam supplied to the high-pressure bypass pipeline 3 to meet the parameter requirements of the auxiliary steam header. The adjustment is convenient, stable and reliable, and there is no need to rely on the startup boiler for steam supply or other units for steam supply.

[0036] In the optional embodiments provided by the present invention, the working principle is explained using a unit start-up system including a primary bypass as an example, as detailed below. Figure 1 As shown. The main steam pipeline 1 is connected to the steam inlet of the high-pressure cylinder 2, and a main steam valve 11 and a regulating steam valve 12 are installed at the steam inlet to regulate the steam intake of the high-pressure cylinder 2. The high-pressure bypass pipeline 3 is connected before the main steam valve 11 of the main steam pipeline 1. When the main steam parameters do not meet the turbine start-up parameters, the main steam valve 11 and the regulating steam valve 12 are closed, and the main steam does not enter the high-pressure cylinder 2 but is directly discharged into the condenser after being cooled and depressurized through the high-pressure bypass pipeline 3. This application extends a start-up steam pipeline 4 from the high-pressure bypass pipeline 3 and connects the start-up steam pipeline 4 to the auxiliary steam header pipeline 6. At the same time, a first valve group 41 and a first desuperheater and pressure reducer 42 are installed on the start-up steam pipeline 4 so that the main steam that does not meet the start-up parameters is cooled and depressurized and then transported to the auxiliary steam header through the auxiliary steam header pipeline 6 as the steam source for auxiliary steam used for shaft seal and purging before start-up.

[0037] The exhaust port of high-pressure cylinder 2 is connected to cold reheat steam pipeline 5. Cold reheat steam pipeline 5 is used to transport the exhaust steam from high-pressure cylinder 2 to the boiler reheater for heating. The other steam inlet of auxiliary steam header pipeline 6 is connected after the shut-off valve 51 of cold reheat steam pipeline 5. Auxiliary steam header pipeline 6 is equipped with auxiliary steam regulating valve group 61 to regulate the steam supply from cold reheat steam pipeline 5 to auxiliary steam header pipeline 6. After the steam turbine completes its initial start-up and stabilizes under load and grid connection, the steam parameters of cold reheat steam pipeline 5 stabilize. The start-up steam pipeline 4 and high-pressure bypass pipeline 3 can be bypassed, and auxiliary steam regulating valve group 61 can be opened to supply steam to auxiliary steam header pipeline 6 using a portion of the steam from cold reheat steam pipeline 5.

[0038] The high-pressure bypass pipeline 3 is equipped with a high-pressure bypass valve 31 and a second desuperheater and pressure reducer 32 to cool and depressurize the main steam before sending it to the condenser for condensation. The cooling water for the first desuperheater and pressure reducer 42 and the second desuperheater and pressure reducer 32 both come from the condensate drain of the condenser.

[0039] Alternatively, the start-up steam pipe 4 can be connected before the high-pressure bypass valve 31 and the second desuperheater 32 of the high-pressure bypass pipe 3, or it can be connected after the high-pressure bypass valve 31 and the second desuperheater 32 of the high-pressure bypass pipe 3.

[0040] In another embodiment provided by the present invention, the working principle is explained using a unit start-up system including a two-stage bypass as an example, as detailed below. Figure 2 As shown. The main steam pipeline 1 is connected to the steam inlet of the high-pressure cylinder 2, and a main steam valve 11 and a regulating steam valve 12 are installed at the steam inlet. The high-pressure bypass pipeline 3 is connected before the main steam valve 11 of the main steam pipeline 1. A starting steam pipeline 4 is led out from the high-pressure bypass pipeline 3 and connected to the auxiliary steam header pipeline 6. At the same time, a first valve group 41 and a first desuperheater and pressure reducer 42 are installed on the starting steam pipeline 4.

[0041] The exhaust port of high-pressure cylinder 2 is connected to cold reheat steam pipeline 5, which transports the exhaust steam from high-pressure cylinder 2 to the boiler reheater for heating. The boiler reheater outlet is connected to hot reheat steam pipeline 9, which transports steam to the inlet of intermediate-pressure cylinder 7. The exhaust steam from intermediate-pressure cylinder 7 enters the inlet of low-pressure cylinder 8. Hot reheat steam pipeline 9 is also connected to low-pressure bypass pipeline 10. When the hot reheat steam parameters do not meet the inlet steam requirements of intermediate-pressure cylinder 7 or the hot reheat steam flow rate is greater than the inlet steam requirements of intermediate-pressure cylinder 7, the excess hot reheat steam is transported to the condenser for condensation via low-pressure bypass valve 101 and the third desuperheater 102. Another steam inlet of auxiliary steam header pipeline 6 is connected after the shut-off valve 51 of cold reheat steam pipeline 5. Auxiliary steam header pipeline 6 is equipped with auxiliary steam regulating valve group 61 to regulate the steam supply from cold reheat steam pipeline 5 to auxiliary steam header pipeline 6. When the steam parameters of the cold reheat steam pipeline 5 are stable, the start-up steam pipeline 4 and the high-pressure bypass pipeline 3 can be shielded, the auxiliary steam regulating valve group 61 can be opened, and part of the steam from the cold reheat steam pipeline 5 can be used to supply steam to the auxiliary steam header pipeline 6.

[0042] The high-pressure bypass pipeline 3 is equipped with a high-pressure bypass valve 31 and a second desuperheater and pressure reducer 32 to cool and depressurize the main steam before sending it to the condenser for condensation. The cooling water for the first desuperheater and pressure reducer 42 and the third desuperheater and pressure reducer 102 can come from the condensate drain of the condenser, and the cooling water for the second desuperheater and pressure reducer 32 can come from the main feedwater.

[0043] To optimize the above embodiments, this application further provides a first temperature detection mechanism and a first pressure detection mechanism at the steam inlet of the first desuperheater 42, so as to adjust the opening degree of the corresponding valves of the first desuperheater 42 and the first valve group 41 according to the steam inlet pressure detected by the first temperature mechanism, and to adjust the condensate flow rate according to the steam inlet temperature detected by the first temperature detection mechanism.

[0044] Furthermore, the steam outlet of the first desuperheater 42 is also equipped with a second temperature detection mechanism and a second pressure detection mechanism, so as to provide feedback adjustment on the valve opening and condensate flow of the first desuperheater 42 and the first valve group 41 according to the exhaust steam temperature and exhaust steam pressure of the first desuperheater 42, so as to ensure that the steam parameters entering the auxiliary steam header pipeline 6 meet the auxiliary steam demand.

[0045] This invention also provides a method for starting a thermal power unit without an external steam source, the specific steps of which are as follows: Figure 3 As shown, it includes:

[0046] Step S10: Connect the high-pressure bypass pipeline 3 of the steam turbine to the auxiliary steam header pipeline 6 through the start-up steam pipeline 4, wherein the start-up steam pipeline 4 is equipped with a first valve group 41 and a first desuperheater and pressure reducer 42;

[0047] Step S20: Open the first valve group 41 and start the first desuperheater and pressure reducer 42 to adjust the steam inlet parameters of the auxiliary steam header pipeline;

[0048] Step S30: After the parameters of the cold reheat steam discharged from the high-pressure cylinder 2 stabilize, close the first valve group 41 and open the shut-off valve 51 of the cold reheat steam pipeline 5 located at the exhaust port of the high-pressure cylinder 2.

[0049] The core of this startup method lies in connecting the high-pressure bypass pipeline 3 to the auxiliary steam header pipeline 6 via the startup steam pipeline 4. This allows the main steam discharged into the high-pressure bypass pipeline 3 to be used to cool and depressurize the main steam through the first valve group 41 and the first desuperheater 42 during the initial startup phase of the unit, before the high-pressure cylinder 2 has no exhaust steam (i.e., cold reheat steam) before the cylinder warm-up. This meets the auxiliary steam requirements for shaft seals and other applications. Once the main steam valve 11 and regulating valve 12 of the high-pressure cylinder 2 are opened, and the turbine has completed its start-up and is running stably, the exhaust parameters of the high-pressure cylinder 2 are stable. At this point, the high-pressure bypass pipeline 3 and the startup steam pipeline 4 can be disabled, and the cold reheat steam pipeline 5 can be connected to the auxiliary header pipeline to provide auxiliary steam. At this time, the unit's cold reheat steam parameters are stable, making it easy to adjust the steam parameters and stably supply steam to the auxiliary steam header pipeline 6.

[0050] Preferably, when cooling and depressurizing the main steam entering the start-up steam pipe 4, the inlet steam temperature and inlet steam pressure of the first desuperheater and pressure reducer 42 can be detected, so as to adjust the valve opening of the first desuperheater and pressure reducer 42 and the first valve group 41 according to the inlet steam pressure, and adjust the condensate flow rate according to the inlet steam pressure of the first desuperheater and pressure reducer 42.

[0051] Furthermore, it also includes detecting the exhaust temperature and exhaust pressure of the first desuperheater and pressure reducer 42, comparing them with the set steam parameters required to enter the auxiliary steam header, and performing negative feedback adjustment on the valve opening and condensate flow of the first desuperheater and pressure reducer 42 and the first valve group 41 based on the deviation values ​​of temperature and pressure.

[0052] The thermal power unit startup system and method without external steam source provided by the present invention, by setting up a startup steam pipeline 4 and installing a first pressure reducing and desuperheating device and a first valve group 41, can cool and depressurize the main steam entering the high-pressure bypass pipeline 3 to meet the temperature, pressure and flow requirements of the auxiliary steam in the initial stage of startup; the startup steam pipeline 4 is connected to the original cold reheat steam pipeline 5 to the auxiliary steam header pipeline 6 of the system, so that the steam can enter the auxiliary steam header and then supply the startup steam for the shaft sealing system, denitrification system, air preheater soot blowing system, feedwater pump turbine and deaerator and other systems during the startup of the unit.

[0053] Depending on the different bypass systems or the required start-up steam volume, the connection position between the start-up steam pipe 4 and the unit's original bypass will vary. Furthermore, depending on the actual start-up steam volume requirements, the start-up steam pipe 4 can be selected with different pipe diameters to achieve a balance between economy and practicality.

[0054] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0055] The above provides a detailed description of the thermal power unit start-up system and method without external steam source provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for starting a thermal power unit without an external steam source, characterized in that, The method is based on a thermal power unit starting system without external steam source. The system includes a steam turbine, a main steam pipeline, a high-pressure bypass pipeline, an auxiliary steam header pipeline, and a starting steam pipeline. The main steam pipeline is connected to the high-pressure cylinder of the steam turbine and the high-pressure bypass pipeline. The starting steam pipeline is connected to the high-pressure bypass pipeline and the auxiliary steam header pipeline. The starting steam pipeline is equipped with a first valve group and a first desuperheater and pressure reducer. The exhaust port of the high-pressure cylinder is equipped with a cold reheat steam pipeline, the cold reheat steam pipeline is equipped with a shut-off valve, and the auxiliary steam header pipeline is connected to the shut-off valve of the cold reheat steam pipeline. A first pressure detection mechanism and a first temperature detection mechanism are provided in the starting steam pipeline before the first desuperheating and pressure reducing device; A second pressure detection mechanism and a second temperature detection mechanism are provided in the starting steam pipeline after the first desuperheater and pressure reducer. The high-pressure bypass pipeline is equipped with a high-pressure bypass valve and a second desuperheating and pressure reducing device, and the start-up steam pipeline is connected before the second desuperheating and pressure reducing device; It also includes a hot reheat steam pipeline and a low-pressure bypass pipeline connected to the hot reheat steam pipeline, the hot reheat steam pipeline being connected to the steam inlet of the intermediate pressure cylinder of the steam turbine; The low-pressure bypass pipeline is equipped with a low-pressure bypass valve and a third desuperheater and pressure reducer, and the low-pressure bypass pipeline is connected to the condenser. The method includes: The high-pressure bypass pipeline of the steam turbine is connected to the auxiliary steam header pipeline through a start-up steam pipeline, wherein the start-up steam pipeline is equipped with a first valve group and a first desuperheater and pressure reducer. Open the first valve group and start the first desuperheater and pressure reducer to adjust the steam inlet parameters of the auxiliary steam header pipeline; Once the parameters of the cold reheat steam discharged from the high-pressure cylinder stabilize, the first valve group is closed and the shut-off valve of the cold reheat steam pipeline located at the exhaust port of the high-pressure cylinder is opened.

2. The method for starting a thermal power unit without an external steam source according to claim 1, characterized in that, The steps of opening the first valve group and starting the first desuperheater and pressure reducer to adjust the steam inlet parameters of the auxiliary steam header pipeline include: Obtain the inlet steam temperature and inlet steam pressure of the first desuperheater and pressure reducer, adjust the opening of the first valve group according to the inlet steam pressure, and adjust the cooling water flow rate of the first desuperheater and pressure reducer according to the inlet steam temperature and inlet steam pressure. And / or, obtain the exhaust temperature and exhaust pressure of the first desuperheater and pressure reducer, correct the opening of the first valve group according to the exhaust pressure, and adjust the cooling water flow rate of the first desuperheater and pressure reducer according to the exhaust temperature and the exhaust pressure.

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