Ultra-supercritical steam turbine shaft seal steam supply system and steam supply method

Abstract

The present invention discloses a steam supply system and a steam supply method for an ultra-supercritical steam turbine shaft seal. The steam supply system includes a high-pressure cylinder front shaft seal, a high-pressure cylinder rear shaft seal, a medium-pressure cylinder front shaft seal, a medium-pressure cylinder rear shaft seal and a low-pressure cylinder shaft seal, and also includes a high-pressure rear shaft seal leakage steam pipe, a medium-pressure rear shaft seal leakage steam pipe, a low-pressure shaft seal steam inlet pipe, a high-pressure front shaft seal leakage steam pipe, and a medium-pressure front shaft seal leakage steam pipe. The steam supply end is respectively connected to the high-pressure rear shaft seal leakage steam pipe, the medium-pressure rear shaft seal leakage steam pipe, the low-pressure shaft seal steam inlet pipe, the high-pressure front shaft seal leakage steam pipe and the medium-pressure front shaft seal leakage steam pipe to realize steam supply. The steam supply method adopts the above-mentioned steam supply system, and uses the steam supply end to supply steam to each pipeline and / or recycle excess steam. The present invention can not only isolate the high and low temperature parts of the shaft seal system and provide three different temperatures, but also improve the system operation status, the system is more stable, the structure is simple, the construction is convenient, the cost is low, and the stability and safety of the unit operation are improved.

Description

Technical Field

[0001] The invention belongs to the field of steam turbine shaft seal steam supply systems for thermal power generation, and in particular relates to an ultra-supercritical steam turbine shaft seal steam supply system and a steam supply method. Background Art

[0002] According to Article 5.2.12 of DL / T 863-2004 "Guidelines for Steam Turbine Start-up and Commissioning", "The steam source for the shaft seal should ensure that the temperature difference between the shaft seal steam and the rotor metal is less than 110°C."

[0003] In ultra-supercritical units, especially medium-pressure cylinder single-divided units, the operating temperature of the high-pressure front shaft seal and the medium-pressure front shaft seal is very high, reaching above 500°C, and even up to 570°C; the temperature of the high-pressure cylinder rear shaft seal and the medium-pressure rear shaft seal is relatively low at around 300°C, while the required temperature of the low-pressure shaft seal is about 150°C. The conventional shaft seal system uses a mother pipe to transfer the steam leakage from the high-pressure and medium-pressure cylinder shaft seals to the mother pipe, and then supplies steam to the low-pressure shaft seal after cooling. There are the following problems:

[0004] 1. Conventional shaft seal systems cannot provide three different temperature matches according to system requirements during hot or extremely hot startup, resulting in large rotor thermal stress. Although the current system with shaft seal electric heaters can provide three temperatures, on the one hand, the shaft seal electric heater takes a long time to heat up from startup to temperature stabilization, and there is a short period of cold steam inflow, which also has a great impact on the rotor thermal stress; on the other hand, it is necessary to convert high-quality electricity into low-quality thermal energy, which is not conducive to energy saving and consumption reduction. In addition, the system has high requirements for the stability of the electrical system, and the equipment needs to be in standby for a long time, with a high probability of failure and difficult maintenance.

[0005] 2. With the massive development of new energy, deep peak-shaving operation of coal-fired units is becoming more and more frequent, and the thermal stress of the rotor at the medium-pressure rear shaft seal is large. The steam flow state at the medium-pressure rear shaft seal during deep peak-shaving operation will change frequently, switching back and forth from the steam leakage state to the steam supply state; when the steam is leaking, the temperature is around 300°C, and when the steam is supplied, the steam is provided by the main pipe of the shaft seal system, and the temperature reaches more than 500°C. The frequent changes in steam supply and leakage cause frequent changes in the rotor temperature at the medium-pressure rear shaft seal, which seriously affects the rotor life.

[0006] 3. The low-pressure shaft seal has poor temperature reduction stability. The steam supply for the low-pressure shaft seal is provided by the shaft seal mother pipe. During the startup phase, the mother pipe is supplied by auxiliary steam with a temperature of about 300°C. During the operation phase, the mother pipe leaks steam from the high-pressure and medium-pressure cylinder shaft seals with a temperature above 500°C. During hot or extremely hot operation, the main steam is used to supply steam with a temperature close to 600°C. The steam temperature before the low-pressure shaft seal desuperheater varies from 300°C to 600°C, making it very difficult to select the nozzle for the low-pressure shaft seal water spray desuperheater. The nozzle has a large working range and poor atomization. Although various measures are taken, such as double nozzles, the temperature still fluctuates greatly after desuperheating in actual use, causing the low-pressure cylinder shaft vibration to increase, seriously affecting operational safety.

[0007] 4. The high-temperature steam from the shaft seal mother pipe directly overflows to the low-pressure heater, where it is mixed with the low-temperature extraction steam for condensation and heat exchange. This not only causes large thermal stress at the connection point, which has an adverse effect on the safe operation of the pressure vessel, but also the heat in the high-temperature section is not utilized in a quality manner, which is not conducive to energy saving and consumption reduction. Summary of the invention

[0008] The purpose of the present invention is to provide a steam supply system and a steam supply method for an ultra-supercritical steam turbine shaft seal, which solves the problem that the existing shaft seal steam supply system is not suitable for current needs. The present invention can not only isolate the high and low temperature parts of the shaft seal system and provide three different temperatures, but also improve the operating conditions of the system, making the system more stable, simple in structure, convenient in construction, low in cost, and improving the stability and safety of the unit operation.

[0009] The object of the present invention is achieved through the following technical solutions:

[0010] A steam supply system for shaft seals of an ultra-supercritical steam turbine comprises a high-pressure cylinder front shaft seal and a high-pressure cylinder rear shaft seal of a high-pressure cylinder, an intermediate-pressure cylinder front shaft seal and an intermediate-pressure cylinder rear shaft seal of an intermediate-pressure cylinder, and a low-pressure cylinder shaft seal of a low-pressure cylinder, wherein the high-pressure cylinder rear shaft seal is connected to a high-pressure rear shaft seal leakage steam pipe, the intermediate-pressure cylinder rear shaft seal is connected to a intermediate-pressure rear shaft seal leakage steam pipe, the low-pressure cylinder shaft seal is connected to a low-pressure shaft seal steam inlet pipe, the high-pressure cylinder front shaft seal is connected to a high-pressure front shaft seal leakage steam pipe, the intermediate-pressure cylinder front shaft seal is connected to a intermediate-pressure front shaft seal leakage steam pipe, a steam supply end is respectively connected to the high-pressure rear shaft seal leakage steam pipe, the intermediate-pressure rear shaft seal leakage steam pipe, the low-pressure shaft seal steam inlet pipe, the high-pressure front shaft seal leakage steam pipe, and the intermediate-pressure front shaft seal leakage steam pipe, and the steam supply end is used to supply steam to each pipeline and / or recycle excess steam.

[0011] Furthermore, the steam supply end includes a high-temperature pipeline subsystem and a low-temperature pipeline subsystem. The low-temperature pipeline subsystem is respectively connected to the high-pressure rear shaft seal steam leakage pipe, the medium-pressure rear shaft seal steam leakage pipe, and the low-pressure shaft seal steam inlet pipe. The high-temperature pipeline subsystem is respectively connected to the high-pressure front shaft seal steam leakage pipe and the medium-pressure front shaft seal steam leakage pipe. A series pipeline is connected between the high-temperature pipeline subsystem and the low-temperature pipeline subsystem, and a check valve for one-way flow from low temperature to high temperature is provided on the series pipeline.

[0012] Furthermore, the low-temperature pipeline subsystem includes auxiliary steam, which is connected to the auxiliary steam supply pipe. The auxiliary steam supply pipe is respectively connected to the low-temperature mother pipe, the low-pressure shaft seal steam inlet pipe, and the series pipeline. The low-temperature mother pipe is respectively connected to the high-pressure rear shaft seal leakage pipe and the medium-pressure rear shaft seal leakage pipe.

[0013] Furthermore, the auxiliary steam supply pipe is provided with an auxiliary steam regulating valve and an auxiliary steam rear pressure measuring point, the auxiliary steam 5 regulating valve is interlocked with the auxiliary steam rear pressure measuring point, the low-pressure shaft seal steam inlet pipe is provided with a low-temperature water spray desuperheater and a low-pressure shaft seal temperature measuring point, the condensate is connected with the low-temperature water spray desuperheater through the low-temperature water spray regulating valve, and the low-pressure shaft seal temperature measuring point is interlocked with the low-temperature water spray regulating valve.

[0014] Furthermore, the high temperature pipeline subsystem includes main steam, which is connected to the main steam supply pipe.

[0015] The main steam supply pipe is connected with the high-temperature mother pipe and the series pipeline respectively, and the high-temperature mother pipe is connected with the high-pressure front shaft seal leakage steam 0 pipe and the medium-pressure front shaft seal leakage steam pipe respectively.

[0016] Furthermore, the main steam supply pipe is provided with a main steam regulating valve and a main steam rear pressure measuring point, and the main steam regulating valve is interlocked with the main steam rear pressure measuring point.

[0017] Furthermore, the main steam supply pipe is also connected to the overflow pipe, and subsequent steam recovery and utilization is achieved through the overflow pipe.

[0018] 5 Further, the overflow pipe is connected with the heater, the heater is a heater with a superheated steam cooling section, the overflow pipe is provided with a high-temperature water spray desuperheater, an overflow temperature measuring point and an overflow regulating valve, the condensate is connected with the high-temperature water spray desuperheater through the high-temperature water spray regulating valve, the high-temperature water spray regulating valve is interlocked with the overflow temperature measuring point and the overflow regulating valve, and the overflow regulating valve is interlocked with the main steam rear pressure measuring point on the main steam supply pipe.

[0019] A method for supplying steam to the shaft seal of an ultra-supercritical steam turbine adopts the above-mentioned ultra-supercritical steam turbine shaft seal steam supply system, and in the cold and warm start-up stages of the unit, as well as in the tripping, hot and extremely hot start-up stages of the unit,

[0020] Steam is supplied from the steam supply end, and steam is supplied to the high-pressure cylinder rear shaft seal through the high-pressure rear shaft seal leakage pipe, steam is supplied to the intermediate-pressure cylinder rear shaft seal through the medium-pressure rear shaft seal leakage pipe, steam is supplied to the low-pressure cylinder shaft seal through the low-pressure shaft seal steam inlet pipe, steam is supplied to the high-pressure cylinder front shaft seal through the high-pressure front shaft seal leakage pipe, and steam is supplied to the intermediate-pressure cylinder front shaft seal through the medium-pressure front shaft seal leakage pipe.

[0021] 5 Furthermore, during the cold and warm start-up phases of the unit, the main steam of the high-temperature pipeline subsystem is shut down.

[0022] Steam is supplied by auxiliary steam from the low-temperature piping subsystem. One path of steam supplies steam to the high-pressure rear shaft seal steam leakage pipe, the medium-pressure rear shaft seal steam leakage pipe, and the low-pressure shaft seal steam inlet pipe, and the other path of steam supplies steam to the high-pressure front shaft seal steam leakage pipe and the medium-pressure front shaft seal steam leakage pipe after passing through the check valve on the series pipeline. During the unit tripping, hot and extremely hot start-up stages, the auxiliary steam from the low-temperature piping subsystem supplies steam to the high-pressure rear shaft seal steam leakage pipe, the medium-pressure rear shaft seal steam leakage pipe, and the low-pressure shaft seal steam inlet pipe, and the main steam from the high-temperature piping subsystem supplies steam to the high-pressure front shaft seal steam leakage pipe and the medium-pressure front shaft seal steam leakage pipe. The check valve on the series pipeline is closed, and the high-temperature piping subsystem and the low-temperature piping subsystem are effectively isolated.

[0023] Furthermore, during the self-sealing stage of the unit, the main steam of the high-temperature piping subsystem and the auxiliary steam of the low-temperature piping subsystem are closed, and the excess steam of the low-temperature piping subsystem enters the high-temperature piping subsystem through the check valve on the series pipe, and enters the overflow pipe together with the overflow steam of the high-temperature piping subsystem for subsequent steam recovery and utilization; during the deep peak regulation stage of the unit, the leakage steam of the high-pressure cylinder rear shaft seal passes through the high-pressure rear shaft seal leakage pipe and the low-temperature main pipe, and then supplies steam to the medium-pressure cylinder rear shaft seal through the medium-pressure rear shaft seal leakage pipe.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention provides three types of shaft seal temperatures that are independently matched with the rotor temperature. The steam source is the common steam source (auxiliary steam, main steam) of the power plant. When the unit is started in a hot state or an extremely hot state, steam can be quickly added to match the rotor temperature.

[0026] 2 The present invention isolates the high temperature part (high pressure front shaft seal and medium pressure front shaft seal) and the low temperature part (high pressure rear shaft seal and medium pressure rear shaft seal, low pressure shaft seal) of the shaft seal system, eliminating the disadvantages of a single mother pipe control. Not only is the system operation more stable, but it is also beneficial to pipeline layout, material selection and cost savings.

[0027] 3. The present invention mixes the leakage steam of the high-pressure rear shaft seal and the medium-pressure rear shaft seal to form a low-temperature mother pipe, making full use of the unit characteristic that the leakage steam temperature of the high-pressure rear shaft seal is equivalent to the leakage steam temperature of the medium-pressure rear shaft seal, eliminating the problem of rotor thermal stress at the medium-pressure rear shaft seal when the unit is in deep peak regulation.

[0028] 4. The low-temperature mother pipe of the present invention supplies steam to the low-pressure shaft seal after cooling, making full use of the unit characteristic that the mixed temperature of the leakage steam of the high-pressure rear shaft seal and the leakage steam of the medium-pressure rear shaft seal is equivalent to the auxiliary steam temperature. The steam before the desuperheater is maintained at about 300°C in various working conditions. The desuperheating nozzle only needs to operate in a very small range. The nozzle selection is simple and the operating conditions are stable, which can ensure both the atomization effect of the nozzle and the stability of the steam supply temperature of the low-pressure shaft seal.

[0029] 5. The high-temperature mother pipe of the present invention heats the condensate after cooling. The desuperheater is arranged in front of the overflow valve. Compared with cooling after the overflow valve, the steam pressure in the pipe is higher, the specific volume is smaller, and the flow rate in the pipe is lower, which enhances the residence time of the spray water in the desuperheater pipe and is more conducive to heat exchange. At the same time, an overflow check valve is arranged on the pipeline to avoid the problem of cooling water or cold steam flowing back into the shaft seal after the machine is tripped. The overflow steam temperature is reduced to 300°C and then discharged to the heater with a superheated steam cooling section, which not only meets the allowable temperature of the carbon steel material of the heater and saves the heater cost to the maximum extent, but also can utilize the steam superheat to achieve the zero end difference or negative end difference of the heater.

[0030] 6. The system of the present invention is simple, low in cost, and the control is basically consistent with the existing control strategy, which is very convenient for the design of new units and the transformation of old units.

[0031] The aforementioned main scheme of the present invention and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and claimed for protection by the present invention; and in the present invention, (non-conflicting options) options and other options can also be freely combined. After understanding the scheme of the present invention, those skilled in the art can understand that there are many combinations based on the prior art and common knowledge, all of which are technical schemes to be protected by the present invention, and they are not exhaustively listed here. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the present invention.

[0033] In the figure: 1-high pressure cylinder, 2-medium pressure cylinder, 3-low pressure cylinder, 4-high pressure cylinder front shaft seal, 5-medium pressure cylinder front shaft seal, 6-high pressure cylinder rear shaft seal, 7-medium pressure cylinder rear shaft seal, 8-low pressure cylinder shaft seal, 9-low temperature spray water desuperheater, 10-overflow regulating valve, 11-auxiliary steam regulating valve, 12-check valve, 13-main steam regulating valve, 14-auxiliary steam, 15-main steam, 16-heater, 17-auxiliary steam rear pressure measuring point, 18-main steam rear pressure measuring point, 19-overflow temperature measuring point, 20- Low-temperature mother pipe, 21-high-pressure rear shaft seal leakage pipe, 22-medium-pressure rear shaft seal leakage pipe, 23-low-pressure shaft seal steam inlet pipe, 24-auxiliary steam supply pipe, 25-series pipeline, 26-high-temperature mother pipe, 27-high-pressure front shaft seal leakage pipe, 28-medium-pressure front shaft seal leakage pipe, 29-overflow pipe, 30-low-pressure shaft seal temperature measuring point, 31-low-temperature water spray regulating valve, 32-condensate, 33-high-temperature water spray desuperheater, 34-high-temperature water spray regulating valve, 35-overflow check valve, 36-main steam supply pipe. DETAILED DESCRIPTION

[0034] The following non-limiting examples serve to illustrate the invention.

[0035] Embodiment 1:

[0036] refer to Figure 1 As shown, an ultra-supercritical steam turbine shaft seal steam supply system includes a high-pressure cylinder front shaft seal 4 and a high-pressure cylinder rear shaft seal 6 of a high-pressure cylinder 1, an intermediate-pressure cylinder front shaft seal 5 and an intermediate-pressure cylinder rear shaft seal 7 of an intermediate-pressure cylinder 2, and a low-pressure cylinder shaft seal 8 of a low-pressure cylinder 3.

[0037] The high-pressure cylinder rear shaft seal 6 is connected to the high-pressure rear shaft seal steam leakage pipe 21, the medium-pressure cylinder rear shaft seal 7 is connected to the medium-pressure rear shaft seal steam leakage pipe 22, the low-pressure cylinder shaft seal 8 is connected to the low-pressure shaft seal steam inlet pipe 23, the high-pressure cylinder front shaft seal 4 is connected to the high-pressure front shaft seal steam leakage pipe 27, and the medium-pressure cylinder front shaft seal 5 is connected to the medium-pressure front shaft seal steam leakage pipe 28.

[0038] The steam supply end is respectively connected to the high-pressure rear shaft seal steam leakage pipe 21, the medium-pressure rear shaft seal steam leakage pipe 22, the low-pressure shaft seal steam inlet pipe 23, the high-pressure front shaft seal steam leakage pipe 27 and the medium-pressure front shaft seal steam leakage pipe 28, and the steam supply end is used to supply steam to each pipeline and / or recycle excess steam.

[0039] The steam supply end includes a high-temperature piping subsystem and a low-temperature piping subsystem.

[0040] The low-temperature piping subsystem includes the high-pressure cylinder rear shaft seal 6, the medium-pressure cylinder rear shaft seal 7, the low-pressure cylinder shaft seal 8, the low-temperature water spray cooler 9, the auxiliary steam regulating valve 11, the auxiliary steam 14, the auxiliary steam rear pressure measuring point 17, the low-temperature main pipe 20, the high-pressure rear shaft seal steam leakage pipe 21, the medium-pressure rear shaft seal steam leakage pipe 22, the low-pressure shaft seal steam inlet pipe 23, the auxiliary steam supply pipe 24, the low-pressure shaft seal temperature measuring point 30, the low-temperature water spray regulating valve 31, and the condensate 32.

[0041] The high-temperature pipeline subsystem includes the high-pressure cylinder front shaft seal 4, the medium-pressure cylinder front shaft seal 5, the overflow regulating valve 10, the main steam regulating valve 13, the main steam 15, the heater 16, the main steam rear pressure measuring point 18, the overflow temperature measuring point 19, the high-temperature mother pipe 26, the high-pressure front shaft seal steam leakage pipe 27, the medium-pressure front shaft seal steam leakage pipe 28, the overflow pipe 29, the condensate 32, the high-temperature water spray desuperheater 33, the high-temperature water spray regulating valve 34, the overflow check valve 35, and the main steam supply pipe 36.

[0042] A series pipe 25 is connected between the auxiliary steam supply pipe 24 and the main steam supply pipe 36. A check valve 12 for one-way flow from low temperature to high temperature is provided on the series pipe 25. The check valve 12 allows flow from the low-temperature pipe part to the high-temperature pipe part and blocks flow in the reverse direction.

[0043] The auxiliary steam 14 is connected to the auxiliary steam supply pipe 24, on which the auxiliary steam regulating valve 11 and the auxiliary steam after-pressure measuring point 17 are provided. The auxiliary steam regulating valve 11 is interlocked with the auxiliary steam after-pressure measuring point 17, and the pressure setting value is 24KPa.

[0044] The auxiliary steam supply pipe 24 is respectively connected with the low temperature main pipe 20, the low pressure shaft seal steam inlet pipe 23 and the series pipe 25, and the low temperature main pipe 20 is respectively connected with the high pressure rear shaft seal steam leakage pipe 21 and the medium pressure rear shaft seal steam leakage pipe 22. The steam in the high pressure rear shaft seal steam leakage pipe 21, the medium pressure rear shaft seal steam leakage pipe 22 and the low pressure shaft seal steam inlet pipe 23 is realized.

[0045] A low-pressure shaft seal steam inlet pipe 23 is provided with a low-temperature water spray cooler 9 and a low-pressure shaft seal temperature measuring point 30. The condensate 32 is connected to the low-temperature water spray cooler 9 through a low-temperature water spray regulating valve 31. The low-pressure shaft seal temperature measuring point 30 is interlocked with the low-temperature water spray regulating valve 31, and the temperature setting value is 150°C.

[0046] The main steam 15 is connected to the main steam supply pipe 36, on which the main steam regulating valve 13 and the main steam after-pressure measuring point 18 are provided. The main steam regulating valve 13 is interlocked with the main steam after-pressure measuring point 18, and the pressure setting value is 27KPa. In the cold state or warm state, the main steam regulating valve 13 is closed and interlocked with the pressure measuring point 18 of the main steam after-pressure measuring point 18, and is in the closed state; in the hot state or extremely hot state, the main steam regulating valve 13 is opened and interlocked with the pressure measuring point 18 of the main steam after-pressure measuring point 18.

[0047] The main steam supply pipe 36 is respectively connected with the high temperature mother pipe 26 and the series pipe 25, and the high temperature mother pipe 26 is respectively connected with the high pressure front shaft seal leakage steam pipe 27, the medium pressure front shaft seal leakage steam pipe 28, and the overflow pipe 29. The steam in the high pressure front shaft seal leakage steam pipe 27 and the medium pressure front shaft seal leakage steam pipe 28 is circulated, and the subsequent steam recovery is realized through the overflow pipe 29.

[0048] The overflow pipe 29 is connected to the heater 16. The heater 16 is a shell and tube heater with a superheated steam cooling section and a condensing section, and the interior is condensed water of the heat recovery system. The overflow pipe 29 is provided with an overflow check valve 35, a high-temperature spray water desuperheater 33, an overflow temperature measuring point 19 and an overflow regulating valve 10. The overflow check valve 35 allows the flow to flow from the high-temperature main pipe 26 to the high-temperature spray water desuperheater 33, and prevents the flow in the reverse direction.

[0049] The condensed water 32 is connected to the high-temperature water spray desuperheater 33 through the high-temperature water spray regulating valve 34. The high-temperature water spray regulating valve 34 is interlocked with the overflow regulating valve 10. When the overflow regulating valve 10 is opened, the high-temperature water spray regulating valve 34 is put into operation. The high-temperature water spray regulating valve 34 is interlocked with the overflow temperature measuring point 19, and the temperature setting value is 300°C. At the same time, the overflow regulating valve 10 is interlocked with the main steam rear pressure measuring point 18 on the main steam supply pipe 36, and the pressure setting value is 30KPa.

[0050] Embodiment 2:

[0051] refer to Figure 1 As shown, a method for supplying steam to a shaft seal of an ultra-supercritical steam turbine adopts the ultra-supercritical steam turbine shaft seal steam supply system described in Example 1.

[0052] During the cold and warm start-up phase of the unit, the main steam regulating valve 13 is interlocked and closed, the main steam 15 of the high-temperature pipeline subsystem is closed, and the auxiliary steam 14 of the low-temperature pipeline subsystem is used to supply steam. After the pressure is adjusted by the auxiliary steam regulating valve 11, one path of steam passes through the auxiliary steam supply pipe 24, and supplies steam to the high-pressure rear shaft seal leakage pipe 21 and the medium-pressure rear shaft seal leakage pipe 22 through the low-temperature mother pipe 20, supplies steam to the high-pressure cylinder rear shaft seal 6 through the high-pressure rear shaft seal leakage pipe 21, and supplies steam to the medium-pressure cylinder rear shaft seal 7 through the medium-pressure rear shaft seal leakage pipe 22; and supplies steam to the low-pressure shaft seal steam inlet pipe 23 after being cooled by the auxiliary steam supply pipe 24 and the low-temperature spray water desuperheater 9, and supplies steam to the low-pressure cylinder shaft seal 8 through the low-pressure shaft seal steam inlet pipe 23.

[0053] After passing through the check valve 12 on the series pipe 25, the other steam is supplied to the high-pressure front shaft seal leakage pipe 27 and the medium-pressure front shaft seal leakage pipe 28 through the main steam supply pipe 36 and the high-temperature mother pipe 26, and then to the high-pressure cylinder front shaft seal 4 through the high-pressure front shaft seal leakage pipe 27, and to the medium-pressure cylinder front shaft seal 5 through the medium-pressure front shaft seal leakage pipe 28. The system pressure is controlled to 24KPa by interlocking the auxiliary steam regulating valve 11 through the auxiliary steam rear pressure measuring point 17. At this time, the overflow regulating valve 10 does not meet the opening condition of 30KPa and is in a closed state. The high-temperature water spray regulating valve 34 is interlocked with the overflow regulating valve 10 and is also in a closed state.

[0054] During the self-sealing stage of the unit, the main steam rear pressure measuring point 18 interlocks the overflow regulating valve 10 to control the system pressure at 30KPa. The pressure is higher than the opening value of the auxiliary steam regulating valve 11 and the main steam regulating valve 13. The auxiliary steam regulating valve 11 and the main steam regulating valve 13 are in a closed state. The excess steam from the low-temperature mother pipe 20 enters the high-temperature mother pipe 26 through the check valve 12, and together with the overflow steam from the high-temperature mother pipe 26, passes through the overflow check valve 35 and the high-temperature water spray desuperheater 33. The overflow temperature measuring point 19 is interlocked with the high-temperature water spray regulating valve 34. After the temperature is controlled at 300°C, it is discharged to the heater 16 with a superheated steam cooling section after passing through the overflow regulating valve 10, realizing the zero end difference or negative end difference of the heater, and recovering the working fluid and utilizing the heat quality in stages.

[0055] During the deep peak regulation stage of the unit, the steam leakage from the high-pressure cylinder rear shaft seal 6 passes through the high-pressure rear shaft seal leakage pipe 21 and the low-temperature mother pipe 20, and then supplies steam to the intermediate-pressure cylinder rear shaft seal 7 through the intermediate-pressure rear shaft seal leakage pipe 22. The supply and leakage steam temperatures are similar, which effectively avoids the rotor thermal stress caused by the large temperature difference. The rest of the parts are the same as the self-sealing stage.

[0056] During the unit trip, hot state and extremely hot state start-up phase, the low temperature part is supplied by auxiliary steam 14, and the auxiliary steam rear pressure measuring point 17 interlocks the auxiliary steam regulating valve 11 to control the pressure of the low temperature main pipe 20 to 24KPa. The high temperature part is supplied by main steam 15, and the main steam rear pressure measuring point 18 interlocks the main steam regulating valve 13 to control the pressure of the high temperature main pipe 26 to 27KPa. The pressure on the outlet side of the check valve 12 is higher than the pressure on the inlet side, the check valve 12 is closed, and the low temperature main pipe 20 and the high temperature main pipe 26 are effectively isolated, eliminating the high temperature steam entering the low temperature main pipe 20. The high pressure cylinder rear shaft seal 6 and the medium pressure cylinder rear shaft seal 7 cause the rotor thermal stress, and the low pressure cylinder shaft seal 8 caused by the large increase in the temperature before the low temperature spray water desuperheater 9 is unstable.

[0057] The above basic examples of the present invention and their further optional examples can be freely combined to form multiple embodiments, all of which are embodiments that can be adopted and claimed for protection by the present invention. In the scheme of the present invention, each optional example can be arbitrarily combined with any other basic examples and optional examples.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-supercritical steam turbine shaft seal steam supply system, comprising a high-pressure cylinder front shaft seal (4) and a high-pressure cylinder rear shaft seal (6) of a high-pressure cylinder (1), an intermediate-pressure cylinder front shaft seal (5) and an intermediate-pressure cylinder rear shaft seal (7) of an intermediate-pressure cylinder (2), and a low-pressure cylinder shaft seal (8) of a low-pressure cylinder (3), characterized in that: The high-pressure cylinder rear shaft seal (6) is connected to the high-pressure rear shaft seal steam leakage pipe (21), the medium-pressure cylinder rear shaft seal (7) is connected to the medium-pressure rear shaft seal steam leakage pipe (22), the low-pressure cylinder shaft seal (8) is connected to the low-pressure shaft seal steam inlet pipe (23), the high-pressure cylinder front shaft seal (4) is connected to the high-pressure front shaft seal steam leakage pipe (27), the medium-pressure cylinder front shaft seal (5) is connected to the medium-pressure front shaft seal steam leakage pipe (28), and the steam supply end is respectively connected to the high-pressure rear shaft seal steam leakage pipe (21), the medium-pressure rear shaft seal steam leakage pipe (22), the low-pressure shaft seal steam inlet pipe (23), the high-pressure front shaft seal steam leakage pipe (27) and the medium-pressure front shaft seal steam leakage pipe (28); The steam supply end comprises a high-temperature pipeline subsystem and a low-temperature pipeline subsystem. The low-temperature pipeline subsystem is respectively connected to a high-pressure rear shaft seal steam leakage pipe (21), a medium-pressure rear shaft seal steam leakage pipe (22), and a low-pressure shaft seal steam inlet pipe (23). The high-temperature pipeline subsystem is respectively connected to a high-pressure front shaft seal steam leakage pipe (27) and a medium-pressure front shaft seal steam leakage pipe (28). A series pipeline (25) is connected between the high-temperature pipeline subsystem and the low-temperature pipeline subsystem. A check valve (12) for one-way flow from low temperature to high temperature is provided on the series pipeline (25). The low-temperature pipeline subsystem comprises auxiliary steam (14), the auxiliary steam (14) is connected to the auxiliary steam supply pipe (24), the auxiliary steam supply pipe (24) is respectively connected to the low-temperature mother pipe (20), the low-pressure shaft seal steam inlet pipe (23), and the series pipe (25), and the low-temperature mother pipe (20) is respectively connected to the high-pressure rear shaft seal leakage steam pipe (21) and the medium-pressure rear shaft seal leakage steam pipe (22); The auxiliary steam supply pipe (24) is provided with an auxiliary steam regulating valve (11) and an auxiliary steam rear pressure measuring point (17), the auxiliary steam regulating valve (11) is interlocked with the auxiliary steam rear pressure measuring point (17), the low-pressure shaft seal steam inlet pipe (23) is provided with a low-temperature water spray desuperheater (9) and a low-pressure shaft seal temperature measuring point (30), the condensate (32) is connected to the low-temperature water spray desuperheater (9) through the low-temperature water spray regulating valve (31), and the low-pressure shaft seal temperature measuring point (30) is interlocked with the low-temperature water spray regulating valve (31); The high-temperature pipeline subsystem comprises main steam (15), the main steam (15) is connected to a main steam supply pipe (36), the main steam supply pipe (36) is respectively connected to a high-temperature mother pipe (26) and a series pipe (25), and the high-temperature mother pipe (26) is respectively connected to a high-pressure front shaft seal leakage steam pipe (27) and a medium-pressure front shaft seal leakage steam pipe (28); The main steam supply pipe (36) is also connected to the overflow pipe (29), and subsequent steam recovery and utilization is achieved through the overflow pipe (29); The overflow pipe (29) is connected to the heater (16), and the heater (16) is a heater provided with a superheated steam cooling section. The overflow pipe (29) is provided with a high-temperature water spray desuperheater (33), an overflow temperature measuring point (19) and an overflow regulating valve (10). The condensate (32) is connected to the high-temperature water spray desuperheater (33) through the high-temperature water spray regulating valve (34). The high-temperature water spray regulating valve (34) is interlocked with the overflow temperature measuring point (19) and the overflow regulating valve (10). The overflow regulating valve (10) is interlocked with the main steam rear pressure measuring point (18) on the main steam supply pipe (36).

2. A method for supplying steam to a shaft seal of an ultra-supercritical steam turbine, using the ultra-supercritical steam turbine shaft seal steam supply system according to claim 1, characterized in that: During the cold and warm start-up phases of the unit, as well as during the unit trip, hot and extremely hot start-up phases, steam is supplied from the steam supply end to the high-pressure cylinder rear shaft seal (6) through the high-pressure rear shaft seal leakage pipe (21), to the intermediate-pressure cylinder rear shaft seal (7) through the intermediate-pressure rear shaft seal leakage pipe (22), to the low-pressure cylinder shaft seal (8) through the low-pressure shaft seal steam inlet pipe (23), to the high-pressure cylinder front shaft seal (4) through the high-pressure front shaft seal leakage pipe (27), and to the intermediate-pressure cylinder front shaft seal (5) through the intermediate-pressure front shaft seal leakage pipe (28).

3. The method for supplying steam to the shaft seal of an ultra-supercritical steam turbine according to claim 2, characterized in that: During the cold and warm start-up phases of the unit, the main steam (15) of the high-temperature pipeline subsystem is shut down, and the auxiliary steam (14) of the low-temperature pipeline subsystem is used to supply steam. One steam path supplies steam to the high-pressure rear shaft seal steam leakage pipe (21), the medium-pressure rear shaft seal steam leakage pipe (22), and the low-pressure shaft seal steam inlet pipe (23), and the other steam path passes through the check valve (12) on the series pipe (25) and supplies steam to the high-pressure front shaft seal steam leakage pipe (27) and the medium-pressure front shaft seal steam leakage pipe (28); During the unit trip, hot state and extremely hot state start-up phases, the auxiliary steam (14) of the low-temperature piping subsystem supplies steam to the high-pressure rear shaft seal steam leakage pipe (21), the medium-pressure rear shaft seal steam leakage pipe (22) and the low-pressure shaft seal steam inlet pipe (23), and the main steam (15) of the high-temperature piping subsystem supplies steam to the high-pressure front shaft seal steam leakage pipe (27) and the medium-pressure front shaft seal steam leakage pipe (28). The check valve (12) on the series pipe (25) is closed, and the high-temperature piping subsystem and the low-temperature piping subsystem are effectively isolated.

4. The method for supplying steam to the shaft seal of an ultra-supercritical steam turbine according to claim 2 or 3, characterized in that: During the self-sealing stage of the unit, the main steam (15) of the high-temperature pipeline subsystem and the auxiliary steam (14) of the low-temperature pipeline subsystem are closed, and the excess steam of the low-temperature pipeline subsystem enters the high-temperature pipeline subsystem through the check valve (12) on the series pipeline (25), and enters the overflow pipe (29) together with the overflow steam of the high-temperature pipeline subsystem for subsequent steam recovery and utilization; During the deep peak regulation stage of the unit, the steam leakage from the high-pressure cylinder rear shaft seal (6) passes through the high-pressure rear shaft seal leakage pipe (21), the low-temperature mother pipe (20), and then supplies steam to the intermediate-pressure cylinder rear shaft seal (7) through the intermediate-pressure rear shaft seal leakage pipe (22).

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