Main steam drainage device of steam turbine and starting system of steam turbine

Abstract

The utility model relates to a main steam drainage device of a steam turbine and a starting system of the steam turbine. The main steam drainage device comprises a body drainage pipeline (101), a body drainage flash tank (103), a drainage pipeline (102) for starting and a periodic drainage flash tank (104). And a steam output end (200a) of the boiler superheater (200) is communicated with the body drain flash tank through a body drain pipeline and is communicated with the periodic blowdown flash tank through a drain pipeline for starting. The drainage pipeline for starting is used for transmitting main steam drainage output by the boiler superheater to the periodic blowdown flash tank when the steam turbine is started and before shaft seal steam supply and vacuumizing are carried out; the body drain pipeline is used for conveying main steam drain output by the boiler superheater to the body drain flash tank after shaft seal steam supply and vacuumizing are carried out when the steam turbine is started. By means of the main steam drainage device of the steam turbine, it can be ensured that a unit is smoothly and safely started under the condition that the steam turbine is in the temperature state and has no auxiliary steam source.

Description

Technical Field

[0001] The present disclosure relates to the technical field of starting a steam turbine unit in a thermal power plant, and in particular to a main steam drain device of a steam turbine and a starting system of the steam turbine. Background Art

[0002] In the relevant technologies in the field of starting steam turbine units in thermal power plants, after both units are shut down, the boiler is started to provide auxiliary steam to the power plant, supplying steam to the turbine start-up seal system and deaerator heating, etc., and performing the unit vacuum operation. In the case that the starting boiler is unable to be put into operation to provide auxiliary steam, steam cannot be supplied to the shaft seal. If vacuum is performed without supplying air to the shaft seal, it is easy for cold air to enter the turbine, causing the temperature of the turbine rotor and cylinder to drop sharply, resulting in deformation. Therefore, if there is no auxiliary steam to supply steam to the shaft seal, the unit vacuum operation cannot be performed first. In the case that there is no vacuum in the low-pressure cylinder exhaust device and the main steam trap expansion tank, the steam pipe trap cannot be directly and continuously opened to enter the exhaust device and the main steam trap expansion tank during the process of heating and pressurizing the main steam and reheated steam, which can easily cause the exhaust device to form a positive pressure and rupture the explosion-proof membrane, damaging the equipment. Utility Model Content

[0003] The present invention aims to provide a main steam drain device for a steam turbine and a starting system for the steam turbine, which can safely start the steam turbine when the starting boiler cannot be put into operation.

[0004] To achieve the above-mentioned objectives, the present disclosure provides a main steam drain device for a steam turbine. The main steam drain device comprises a main steam drain pipe, a main steam drain expansion tank, a startup drain pipe, and a fixed-discharge expansion tank;

[0005] The steam output end of the boiler superheater is connected to the main body drain expansion tank through the main body drain pipe, and is connected to the fixed-discharge expansion tank through the startup drain pipe;

[0006] The startup drain pipe is used to transfer the main steam drain output from the boiler superheater to the fixed-discharge expansion tank before the shaft seal steam supply and vacuum pumping when the steam turbine is started;

[0007] The body drain pipe is used to transmit the main steam drain output from the boiler superheater to the body drain expansion tank after the shaft seal steam supply and vacuum pumping when the steam turbine is started.

[0008] Optionally, a first valve is provided in the main body drain pipe, and a second valve is provided in the startup drain pipe.

[0009] Optionally, the first valve is a pneumatic valve and the second valve is an electric valve.

[0010] Optionally, the fixed-row expander is a boiler fixed-row expander.

[0011] Optionally, the main body drain pipe includes three parallel pipes, and the startup drain pipe includes three parallel pipes.

[0012] Optionally, the three-way pipeline of the startup drain pipeline is connected to the fixed-row expansion tank via a common pipeline.

[0013] Optionally, an electric valve is provided in the common pipeline.

[0014] The present disclosure provides a steam turbine starting system, wherein the steam turbine starting system includes the main steam drain device provided by the present disclosure.

[0015] Optionally, the startup system further includes a boiler superheater, a boiler reheater and a high-pressure bypass pipeline;

[0016] The steam output end of the boiler superheater is communicated with the steam input end of the boiler reheater through the high-pressure bypass pipeline, and the steam output end of the boiler reheater is communicated with the main body hydrophobic expansion tank.

[0017] Optionally, the starting system further includes a low-pressure bypass line and an exhaust device;

[0018] The steam output end of the boiler reheater is also connected to the exhaust device through the low-pressure bypass pipeline.

[0019] Through the above technical solution, a startup drain pipe and a fixed-discharge expansion tank are added to the main steam drain device in the related art, which includes a main steam drain pipe and a main steam drain expansion tank. In this way, when the turbine cylinder temperature has not completely dropped to the ambient temperature, the turbine boiler can be ignited first. In the initial stage of main steam heating and warming up, before the shaft seal steam supply and vacuum pumping are performed, the main steam drain output from the boiler superheater is transferred to the fixed-discharge expansion tank via the startup drain pipe without entering the exhaust device and the main steam drain expansion tank. After the high-pressure bypass line is put into operation, the shaft seal steam supply and vacuum pumping are performed, and the main steam drain output from the boiler superheater is transferred to the main steam drain expansion tank via the main steam drain pipe. In this way, in the initial stage of main steam heating and warming up, the main steam drain is discharged to the fixed-discharge expansion tank through the newly added startup drain pipe, preventing the positive pressure from entering the un-vacuumed main steam drain expansion tank and causing equipment damage. The main steam drain device of the steam turbine provided by this solution can ensure the smooth and safe startup of the unit when the turbine is warm and there is no auxiliary steam source.

[0020] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0022] Figure 1 It is a schematic structural diagram of a main steam drain device of a steam turbine provided by an exemplary embodiment.

[0023] Figure 2 1 is a schematic structural diagram of a main steam drain device of a steam turbine provided by another exemplary embodiment.

[0024] Figure 3 It is a structural schematic diagram of a steam turbine starting system provided by an exemplary embodiment.

[0025] Description of Reference Numerals

[0026] DETAILED DESCRIPTION

[0027] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0028] Figure 1 FIG. 1 is a schematic structural diagram of a main steam drain device for a steam turbine provided by an exemplary embodiment. Figure 1 As shown, the main steam drain device 100 of the steam turbine includes a main steam drain pipe 101 , a main steam drain expansion tank 103 , a startup drain pipe 102 and a fixed-discharge expansion tank 104 .

[0029] The steam output end 200 a of the boiler superheater 200 is connected to the main body drain expansion tank 103 through the main body drain pipe 101 , and is connected to the fixed discharge expansion tank 104 through the startup drain pipe 102 .

[0030] The startup drain pipe 102 is used to transfer the main steam drain output from the boiler superheater 200 to the fixed-discharge expansion tank 104 before the shaft seal steam supply and vacuum pumping are carried out when the steam turbine is started; the main body drain pipe 101 is used to transfer the main steam drain output from the boiler superheater 200 to the main body drain expansion tank 103 after the shaft seal steam supply and vacuum pumping are carried out when the steam turbine is started.

[0031] The main steam drain device for a steam turbine disclosed herein can be used in situations where it is not possible to first supply steam to the shaft seal and perform vacuum pumping. For example, if both units are shut down, but one unit has been out of service for a short time and has a high cylinder temperature (not yet cooled to ambient temperature), it is necessary to start the steam turbine unit. The unit startup may include the following steps:

[0032] 1) Ignite the steam turbine boiler. During the initial stage of main steam heating and piping, the main steam drain is discharged through the newly added startup drain pipe 102 to the fixed-discharge expansion tank 104, bypassing the exhaust system and the main steam drain expansion tank 103. Once pressure is established on the boiler side, the high-pressure bypass line is commissioned, while the low-pressure bypass line is not commissioned yet. The exhaust steam is heated and pressurized via the high-pressure bypass line and reheater. The turbine-side reheat steam drain is manually controlled and routed to the exhaust system.

[0033] 2) Use the high-pressure bypass pipeline to control the pressure of the reheated steam, and put the cold resupply auxiliary steam system into use to increase the auxiliary steam pressure.

[0034] 3) Auxiliary steam is supplied to the shaft seal to quickly create a vacuum. The main steam drain is transferred from the fixed-discharge expansion vessel 104 to the main steam drain expansion vessel 103. The startup drain pipe 102 is closed.

[0035] 4) Warm up the main steam and cold resupply shaft seal pipes, and put the steam source into standby use in time.

[0036] 5) After the auxiliary steam system is normal, start heating the deaerator while ensuring the steam supply to the shaft seal.

[0037] Through the above technical solution, a startup drain pipe and a fixed-discharge expansion tank are added to the main steam drain device in the related art, which includes a main steam drain pipe and a main steam drain expansion tank. In this way, when the turbine cylinder temperature has not completely dropped to the ambient temperature, the turbine boiler can be ignited first. In the initial stage of main steam heating and warming up, before the shaft seal steam supply and vacuum pumping are performed, the main steam drain output from the boiler superheater is transferred to the fixed-discharge expansion tank via the startup drain pipe without entering the exhaust device and the main steam drain expansion tank. After the high-pressure bypass line is put into operation, the shaft seal steam supply and vacuum pumping are performed, and the main steam drain output from the boiler superheater is transferred to the main steam drain expansion tank via the main steam drain pipe. In this way, in the initial stage of main steam heating and warming up, the main steam drain is discharged to the fixed-discharge expansion tank through the newly added startup drain pipe, preventing the positive pressure from entering the un-vacuumed main steam drain expansion tank and causing equipment damage. The main steam drain device of the steam turbine provided by this solution can ensure the smooth and safe startup of the unit when the turbine is warm and there is no auxiliary steam source.

[0038] Figure 2 FIG. 1 is a schematic structural diagram of a main steam drain device for a steam turbine provided by another exemplary embodiment. Figure 2 As shown, a first valve 105 is provided in the main body drain pipe 101, and a second valve 106 is provided in the startup drain pipe 102. Valves are provided in the main body drain pipe 101 and the startup drain pipe 102, respectively, to control the flow direction of drain water as needed, avoiding unsafe factors during draining.

[0039] The second valve 106 may be configured as an electric valve, so that the opening and closing of the second valve 106 can be controlled by an electric signal when needed according to a control strategy to control whether drain water enters the fixed-discharge expansion vessel 104 .

[0040] The first valve 105 is a pneumatic valve that can automatically open when the main steam reaches a predetermined pressure to control the drain to enter the main drain expansion tank 103.

[0041] The flow expansion vessel 104 can be a dedicated flow expansion vessel or a boiler flow expansion vessel. A boiler flow expansion vessel is a flow expansion vessel installed in the unit's boiler. When used as a boiler flow expansion vessel, flow expansion vessel 104 can be reused, saving space and operating costs.

[0042] exist Figure 2 In the embodiment, the main body drain pipe 101 comprises three parallel pipes, and the startup drain pipe 102 comprises three parallel pipes. The three pipes of the startup drain pipe 102 are connected to the fixed-discharge expansion tank 104 via a common pipe 107. An electric valve 108 is provided in the common pipe 107.

[0043] The common pipeline 107 can be set to simultaneously control the on-off of the three-way starting drain pipeline 102 by opening and closing the electric valve 108, thereby achieving good control effect.

[0044] The present disclosure also provides a steam turbine starting system. Figure 3 FIG. 1 is a schematic diagram of a steam turbine startup system according to an exemplary embodiment. Figure 3 As shown, the steam turbine startup system 10 includes the main steam trap 100 provided by the present disclosure.

[0045] like Figure 3 As shown, the startup system 10 further includes a boiler superheater 200 , a boiler reheater 300 and a high-pressure bypass line 400 .

[0046] The steam output end 200 a of the boiler superheater 200 is communicated with the steam input end 300 a of the boiler reheater 300 through the high-pressure bypass line 400 , and the steam output end 300 b of the boiler reheater 300 is communicated with the main body drain expansion tank 103 .

[0047] The startup system 10 further includes a low-pressure bypass line 500 and an exhaust device 600. The steam output end 300b of the boiler reheater 300 is also connected to the exhaust device 600 through the low-pressure bypass line 500.

[0048] Using the above-mentioned starting system 10 provided by the present disclosure, the preparations before starting the unit without auxiliary steam are as follows:

[0049] 1) Check that the preparatory work before starting the unit's vacuum system is complete: vacuum pump water injection, vacuum pump cooling water system input, vacuum pump inlet manual door open, vacuum pump inlet pneumatic door transmission is normal, air cooling island valve transmission is normal and all open.

[0050] 2) Check that the turbine cranking device and lubricating oil system are operating normally. Contact the thermal engineer to verify the logic for forcing the high bypass valve to open.

[0051] 3) Pre-condition the shaft seal system for startup. This includes: 1. Start the condensate system before starting the boiler fan and complete the injection of water into the multi-stage shaft seal. 2. Open the auxiliary steam supply shaft seal system's pressure-free drain valve and the central auxiliary supply shaft seal main valve. As the auxiliary steam system warms up, warm up the pipes in front of the auxiliary steam supply shaft seal's electric valve. 3. Verify that the shaft seal fan is ready for startup.

[0052] 4) Restore the auxiliary steam system in advance and meet operational requirements: 1. Open the drain system, primarily opening the drain in front of the cold resupply high auxiliary electric door and the drain behind the manual door, opening the drain behind the high auxiliary to medium auxiliary electric door, opening the drain in the medium auxiliary header, opening the drain in the high auxiliary header, and opening the drain from the boiler start to the high auxiliary check valve. 2. Close the auxiliary steam system to all user manual doors. 3. Close the steam inlet electric door from the medium auxiliary main pipe to the unit's medium auxiliary header and open the drain in front of the electric door. 4. Close the high auxiliary header's liaison electric door. 5. Open the manual steam supply door from the high auxiliary to medium auxiliary. 6. Ensure that all valves in the auxiliary steam system are fully actuated and functioning normally.

[0053] 5) The original main steam drain pipe was modified in advance to add three startup drain pipes 102 to the boiler expansion vessel 104, which were then connected to a main pipe (common pipe 107) and then to the boiler expansion vessel 104. Three corresponding drain electric valves (second valve 106) were also added to isolate the system after startup.

[0054] 6) Open the manual drain door of the main reheat steam pipe on the machine side, open the pneumatic drain door of the main reheat steam pipe on the machine side, open the electric primary and secondary doors of the reheat steam exhaust air on the furnace side, modify the high and low bypass logic relationship, and do not open the low bypass valve temporarily.

[0055] 7) Clean the oil gun under the steam turbine grate, make sure it passes the atomization test, and check that the fire detection signal device of the oil gun under the boiler grate is normal.

[0056] 8) Prepare sufficient diesel (for example, no less than 60 tons). To ensure stable main steam pressure and temperature, delay the removal of the oil nozzles during boiler startup. The initial plan is to gradually remove the oil nozzles during initial grid-connected load warm-up (the specific amount will be determined based on actual parameters).

[0057] Using the above-mentioned starting system 10 provided by the present disclosure, an embodiment of the unit starting process without auxiliary steam is as follows:

[0058] 1) Steam turbine boiler ignition. During the initial main steam heating phase, the main steam drain is discharged through the newly added startup drain pipe 102 to the fixed-discharge expansion vessel 104. The three main steam drain pneumatic valves (first valve 105) are kept fully closed to prevent the main steam drain expansion vessel 101 from forming a positive pressure and potentially damaging the equipment.

[0059] 2) As the main steam pressure and temperature gradually increase, slowly open the valves in the high-pressure bypass pipeline, keeping the drain pneumatic valves behind the high-pressure bypass valves fully open to warm up the pipes. At this point, when the temperature behind the high-pressure bypass valves gradually rises above the saturation temperature, the drains cannot be opened continuously. Multiple, staged, alternating drains to the exhaust device are required to warm up the pipes and commission the high-pressure bypass system.

[0060] 3) During the high bypass process, the reheat steam pipe drain is kept fully open until the reheat steam temperature reaches 115℃. After that, the reheat steam pipe drain is warmed up by multiple stages of rotation draining to the exhaust device, and the reheat steam is continuously opened when exhausting to the air. During the temperature and pressure increase and pipe warming period, keep the warm water in the main body drain expansion tank continuously added, and the vacuum breaking door is in the fully open state. When heating the pipe, pay attention to the exhaust device vacuum not exceeding 1kpa and the exhaust cylinder temperature not exceeding 80℃. Strictly follow the cold start curve for temperature and pressure increase, and ensure that the bed temperature rise rate is less than 100℃ / h, the main steam temperature rise rate is less than 1.5℃ / min, and the steam pressure is 0.03MPa / min by controlling the output of each oil gun and the number of oil guns put into use.

[0061] 4) As the unit heats up and the pressure increases, when the reheat steam pressure reaches 0.2MPa and the reheat steam temperature is greater than 170℃, open the cold reheat to auxiliary steam main pipe electric door, the electric door throttle 5% and the manual door to warm up the auxiliary steam pipeline and the auxiliary steam header. When the temperature of the auxiliary steam pipeline and the auxiliary steam header reaches above 170℃, the pipe warming is completed and the auxiliary steam system is fully put into use. Use the high bypass valve to adjust the reheat steam pressure to increase the reheat steam pressure to greater than 0.5MPa and the auxiliary steam pressure to greater than 0.45MPa as soon as possible.

[0062] 5) During the auxiliary steam header pipe warming process, simultaneously open the 12.6-meter medium-pressure auxiliary steam header to the shaft seal regulating station steam supply manual main door, and open the auxiliary steam supply shaft seal electric door pipeline drain valve to fully drain the warm pipe.

[0063] 6) When the auxiliary steam manifold pressure is greater than 0.5MPa and the temperature of the pipeline in front of the auxiliary steam supply shaft seal electric door reaches above 150℃, start the auxiliary steam supply shaft seal steam source and adjust the shaft seal pressure to 21~27KPa. If necessary, use the auxiliary steam supply shaft seal bypass door to participate in the adjustment, and start the three vacuum pumps at the same time to quickly establish vacuum.

[0064] 7) Start the shaft seal fan, adjust the negative pressure of the shaft seal cooler to 500Pa, and engage the interlock. Note that the shaft liquid level must not exceed 200mm.

[0065] 8) When the vacuum reaches -60KPa, gradually open the low-pressure bypass valve to perform pipe warming operations, and use the high and low bypass valves to adjust the main reheat steam pressure. The reheat steam pressure should be maintained at 0.5~0.8MPa and should not fluctuate significantly.

[0066] 9) While evacuating the steam supply, quickly fully open the manual valves and pneumatic valves for draining the main reheat steam pipe to the main steam expansion vessel. Close the electric valves for draining the main steam pipe to the fixed-discharge expansion vessel, returning the steam supply to normal. Fully open the electric valves for draining the main steam and cold resupply shaft seals. When the drain pipe temperature reaches above 150°C, start the main steam and cold resupply shaft seal steam supply as standby.

[0067] 10) As the boiler temperature and pressure increase, if the steam volume can meet the main steam and cold resupply shaft seal requirements (determined by the shaft seal steam supply valve opening and shaft seal pressure), gradually start auxiliary steam source heating of the deaerator.

[0068] 11) When the main steam pressure is greater than 4MPa, as the cylinder temperature gradually increases, part of the main steam is put into supplying the shaft seal, and the shaft seal system is supplied with steam from two steam sources at the same time.

[0069] 12) When the turbine start-up conditions are met, start the run-up. For warm start, the turbine start-up conditions should be as follows:

[0070] 1. Joint start-up of high and medium pressure cylinders: main steam pressure: 3.0-3.2 MPa; reheat steam pressure: 0.8 MPa; main and reheat steam temperatures: 320-360°C.

[0071] 2. The temperature deviation between main steam and reheat steam is less than 10℃.

[0072] 3. The exhaust pressure of the exhaust device is 20~25KPa.

[0073] 4. The axial displacement and expansion difference are within the normal range.

[0074] 5. The temperature difference between the upper and lower parts of the high and medium pressure inner cylinder is less than 42℃.

[0075] 6. Rotor eccentricity <0.076mm.

[0076] 7. The cranking machine runs continuously for 4 hours, the cranking current is normal, and there is no abnormal sound.

[0077] 8. Lubricating oil pressure: 0.12~0.15MPa, lubricating oil temperature: 38~45℃.

[0078] 9. EH oil pressure: 14.00MPa; EH oil temperature: 40~50℃.

[0079] 10. The oil pressure and bearing oil flow are normal.

[0080] 11. All turbine valves are in normal position; high and low bypass and rear steam temperatures and pressures are normal. Check that the low-pressure cylinder spray valve is in "auto" mode and that the condensate pressure is normal.

[0081] 12. All drain valves on the cylinder body and pipelines have been opened to confirm that the main and reheat steam pipelines have been drained.

[0082] 13. The superheat of main steam and reheated steam is greater than 56°C; the oil pressure difference of the sealing oil system is 0.084MPa.

[0083] 14. The hydrogen pressure inside the machine is 0.3MPa and the hydrogen purity is not less than 98%.

[0084] 15. The generator stator cooling water system is normal, the water inlet flow rate is greater than 50t / h, and the stator coil water inlet pressure is at least 0.035MPa lower than the hydrogen pressure.

[0085] 16. Check that the pneumatic control air source pressure is normal.

[0086] 17. The quality of soda meets the requirements.

[0087] 18. All protection functions of the unit are normal.

[0088] Dangerous points and control measures for starting a unit without auxiliary steam may include:

[0089] Risk 1: Main reheat steam pipe vibration.

[0090] During the process of heating and heating the pipes, since the exhaust device is not vacuumed, the drain valve cannot be fully opened and can only drain in turns. Therefore, the rotation drain operation may cause sudden temperature rise and fall, which may cause pipeline shock.

[0091] Control Measures: 1) During the entire warm-up process of the main reheat steam, shaft seal steam supply, and auxiliary steam systems, strict compliance with regulations must be followed to control the temperature and pressure rise rates. The main steam temperature rise rate should be 1.5°C / min to 2.5°C / min, the reheat steam temperature rise rate should be 2°C / min to 3°C / min, and the cylinder wall temperature rise rate should be 2°C / min to 2.5°C / min. 2) The main steam temperature on the boiler side must be maintained at a sufficient superheat level, and the main steam pressure should not rise too quickly, which could cause water carryover. 3) The main reheat steam desuperheating water level should be adjusted in small, repeated adjustments to prevent large temperature fluctuations that could cause water carryover when supplying the shaft seals. 4) During the initial stage of boiler ignition and temperature rise, the main steam pressure on the turbine side should be less than 0.06 MPa. Before the temperature reaches 116°C, the main reheat steam piping pneumatic valves on the turbine side should remain fully open. Ensure that the exhaust pressure does not exceed 1 kPa during this period. If the main steam pressure and temperature continue to rise, multiple, staged, and alternating drains to the exhaust system should be performed to warm up the piping.

[0092] Risk 2: Water accumulates in front of the high bypass valve, causing steam leakage at the high bypass valve stem.

[0093] If the water in front of the high bypass valve is not drained in time and the temperature is low, water may accumulate in front of the high bypass valve, causing steam leakage at the high bypass valve stem.

[0094] Control measures: During the initial stage of boiler ignition and temperature increase, when the main steam pressure on the unit side is less than 0.06 MPa and the temperature reaches 116°C, keep the pneumatic drain valves of the main reheat steam pipe on the unit side fully open. Ensure that the pressure of the exhaust device does not exceed 1 kPa. When the main steam pressure and temperature rise further, close the pneumatic drain valves on the left and right sides of the main steam pipe, keep the pneumatic drain valve on the main steam main pipe fully open, keep the pneumatic drain valve behind the high bypass valve fully open, and open the high bypass valve to warm the pipes.

[0095] Risk 3: The exhaust device creates positive pressure, causing the explosion-proof membrane of the low-pressure cylinder to rupture.

[0096] Since the cylinder temperature is relatively high, vacuum cannot be drawn in advance. Increasing the temperature and pressure before vacuum is established may cause positive pressure to form in the exhaust device.

[0097] Control measures: 1) Keep the vacuum breaker valve fully open. 2) Closely monitor the exhaust pressure. If it exceeds 1 kPa, promptly activate a vacuum pump to create a slight negative pressure. During this time, the turbine's high and medium pressure cylinders must be kept in a blocked state to ensure there is no negative pressure inside. If the negative pressure exceeds 1 kPa, throttle the manual valve at the vacuum pump inlet to maintain a negative pressure of approximately 0.5 kPa.

[0098] Risk 4: The temperature and pressure of the steam supply to the shaft seal fluctuate greatly, and the shaft seal may lose pressure.

[0099] When adjusting the high and low bypasses, it is easy for the main and reheat steam pressures to fluctuate, causing fluctuations in the auxiliary steam header pressure, shaft seal steam supply pressure and temperature.

[0100] Control measures: 1) The shaft seal temperature must match the turbine high and low pressure cylinder end wall temperature; the steam superheat of the shaft seal steam supply main must be greater than 50 degrees Celsius; the difference between the shaft seal steam supply temperature and the rotor metal temperature in the steam seal area (the rotor metal temperature in the steam seal area is based on the high and low pressure cylinder end wall temperature) must be controlled within 111 degrees Celsius. 2) After the auxiliary steam header is commissioned, dedicated personnel will monitor and adjust the reheat steam pressure to maintain stability. The cold reheat to high pressure auxiliary regulating valve will be automatically activated in a timely manner, with the set pressure not exceeding 0.4-0.6 MPa and a maximum of 0.8 MPa. During startup, all auxiliary steam users will be temporarily deactivated. 3) Both the main steam and cold reheat steam supply sources for the shaft seals will be promptly activated as standby to accommodate fluctuations in shaft seal pressure and temperature. 4) The shaft seal steam source must be switched slowly to prevent large fluctuations in shaft seal pressure and temperature during the switching process, which could cause abnormal parameters such as turbine cylinder temperature difference and eccentricity.

[0101] Risk 5: The turbine cylinder temperature changes suddenly, or the main steam valve is not closed tightly, causing steam to enter the turbine.

[0102] Due to the high cylinder temperature, vacuum cannot be drawn in advance. Increasing the temperature and pressure before vacuum is established may cause the hydrophobic steam to flow back to the high and medium pressure cylinders, causing a sudden change in cylinder temperature.

[0103] Control measures: 1) Keep the high and medium pressure cylinders of the turbine in a stuffy state before vacuum is established. 2) Pay attention to monitor the temperature changes of each drain and drain manifold. If the pneumatic door is not closed tightly, close the corresponding manual door in time. 3) Keep the vacuum breaking door fully open and closely monitor the exhaust pressure. When it is greater than 1KPa, start a vacuum pump in time to form a slight negative pressure. If the negative pressure is greater than 1KPa, throttle the manual door at the inlet of the vacuum pump to maintain the negative pressure at around 0.5KPa. 4) Open the drain in front of the medium pressure main steam valve and close the drain behind the door. 5) Open the door rod to leak steam to the fourth extraction manual door, and close it to the third extraction manual door. 6) Control the main steam pressure not to exceed 5MPa before starting. 7) After the turbine is started, if the shaft seal pressure and temperature fluctuate greatly, causing abnormal parameters such as turbine expansion, expansion difference, cylinder temperature difference, eccentricity, etc., as long as any parameter exceeds the limit, break the vacuum and open the valve in time to prevent the accident from expanding.

[0104] Risk 6: Boiler failure, MFT or BT. The shaft seal steam supply pressure decreases and cannot meet the shaft seal steam supply source pressure.

[0105] Control measures: After the boiler MFT and BT, when the main steam pressure drops and the normal shaft seal steam supply pressure cannot be guaranteed, the vacuum must be destroyed immediately, and the main and reheat steam pipeline drain pneumatic doors and manual doors must be closed in time, and the shaft seal steam supply pipeline drain to the exhaust device manual door must be closed. After the vacuum reaches zero, the shaft seal steam supply regulating valve, electric door and manual door must be closed in time.

[0106] Risk 7: Turbine eccentricity increases and reaches the alarm value. The eccentricity increases due to insufficient superheat of the steam supplied to the shaft seal or water in the steam supply.

[0107] Control Measures: 1) High- and low-pressure bypass operations must be monitored by dedicated personnel, especially the control of the desuperheating water after the high-pressure bypass. The steam temperature after the high-pressure bypass must be maintained between 280°C and 350°C to prevent large temperature fluctuations. This could cause water to enter the reheat cold-section steam supply to the shaft seals, potentially leading to turbine water hammer. 2) During startup, pay attention to cylinder temperature fluctuations. The cylinder temperature difference must not exceed 42°C. If the cylinder temperature difference rises abnormally and exceeds 56°C, immediately break the vacuum. Once the vacuum reaches zero, stop supplying steam to the shaft seals and implement cylinder standby measures until the cylinder temperature difference drops below 30°C before restarting.

[0108] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0109] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0110] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A main steam drain device (100) of a steam turbine, characterized in that: The main steam drain device comprises a main body drain pipe (101), a main body drain expansion tank (103), a startup drain pipe (102) and a fixed-discharge expansion tank (104); The steam output end (200a) of the boiler superheater (200) is in communication with the main body drain expansion tank (103) through the main body drain pipe (101), and is in communication with the fixed-discharge expansion tank (104) through the startup drain pipe (102); The startup drain pipe (102) is used to transmit the main steam drain output from the boiler superheater (200) to the fixed-discharge expansion tank (104) before the shaft seal steam supply and vacuum pumping when the steam turbine is started; The main body drain pipe (101) is used to transmit the main steam drain output from the boiler superheater (200) to the main body drain expansion tank (103) after the shaft seal steam supply and vacuum extraction when the steam turbine is started.

2. The main steam trap (100) according to claim 1, characterized in that: A first valve (105) is provided in the main body drain pipe (101), and a second valve (106) is provided in the startup drain pipe (102).

3. The main steam trap (100) according to claim 2, characterized in that: The first valve (105) is a pneumatic valve, and the second valve (106) is an electric valve.

4. The main steam trap (100) according to claim 1, characterized in that: The fixed-discharge expansion tank (104) is a boiler fixed-discharge expansion tank.

5. The main steam trap (100) according to claim 1, characterized in that: The main body drain pipe (101) includes three parallel pipes, and the startup drain pipe (102) includes three parallel pipes.

6. The main steam trap (100) according to claim 5, characterized in that: The three-way pipeline of the startup drain pipeline (102) is connected to the fixed-discharge expansion container (104) via a common pipeline (107).

7. The main steam trap (100) according to claim 6, characterized in that: An electric valve (108) is provided in the common pipeline (107).

8. A steam turbine starting system, characterized in that: The steam turbine startup system (10) comprises the main steam drain device (100) according to any one of claims 1 to 7.

9. The starting system (10) according to claim 8, characterized in that The startup system (10) further includes a boiler superheater (200), a boiler reheater (300), and a high-pressure bypass pipeline (400); The steam output end (200a) of the boiler superheater (200) is communicated with the steam input end (300a) of the boiler reheater (300) via the high-pressure bypass pipe (400), and the steam output end (300b) of the boiler reheater (300) is communicated with the main body hydrophobic expansion tank (103).

10. The starting system (10) according to claim 9, characterized in that The starting system (10) further includes a low-pressure bypass pipeline (500) and an exhaust device (600); The steam output end (300b) of the boiler reheater (300) is also connected to the exhaust device (600) via the low-pressure bypass pipeline (500).

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