A multi-steam source shaft seal steam / gas supply system for a power station unit and its control method

Abstract

A multi-steam-source shaft seal steam / gas supply system for a power station unit and its control method, comprising a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a shaft seal cooler, a drain-air heat exchanger, a desuperheater, a desuperheater, and a rotor connected to the cylinder accessories; the steam inlet sides of the high-pressure cylinder and the intermediate-pressure cylinder share the first branch shaft seal supply steam, and the remaining steam after sealing in the shaft seal chamber enters the shaft seal return steam main pipe through the manual valve of the return steam pipeline; the exhaust sides of the high-pressure cylinder and the intermediate-pressure cylinder share the second branch shaft seal supply steam, a desuperheater is installed on the second branch supply pipeline, and a measuring point for measuring the steam temperature is installed before entering the shaft seal body after the desuperheater; all the shaft seal return steam of the high-pressure cylinder, the intermediate-pressure cylinder and the low-pressure cylinder is collected and then enters the shaft seal cooler. The invention has the advantages of diversified steam supply, parameter matching, flexible control mode, reliable protection logic, and automatic tracking under accident conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbine shaft seal system transformation, and particularly relates to a multi-steam-source shaft seal steam / gas supply system for power station units and a control method thereof. Background Art

[0002] The steam turbine shaft seal system is an important part of the steam turbine. At the part where the steam turbine passes through the outer cylinder, some measures must be taken to prevent external air from leaking in or steam from leaking out of the cylinder. In the high-pressure section of the steam turbine, the function of the shaft seal system is to prevent steam from leaking outwards to ensure high efficiency of the steam turbine. In the low-pressure area of the steam turbine, the function of the shaft seal system is to prevent external air from entering the steam turbine to ensure the highest possible vacuum degree and high efficiency of the steam turbine. The shaft seal system mainly consists of sealing devices, shaft seal steam headers, shaft seal heaters and other equipment, as well as corresponding valves and pipeline systems.

[0003] Taking a typical Harbin Steam Turbine Supercritical C350 new unit as an example, the shaft seal system has been greatly transformed. Especially for new units with a split design of the high and intermediate cylinders, the shaft seal temperatures required for the high and intermediate pressure cylinder chambers are different during high-load stages. In addition, during the coast-down process of the new unit after a (very) hot state trip, once the shaft seal temperature is not properly controlled, the vibration of the unit is obvious, and even the vibration value reaches the full scale (500 μm) near the critical region. Over time, it will cause great damage to the shafting. Therefore, proposing an effective and reliable multi-steam-source shaft seal steam supply system is crucial for ensuring the safety and reliability of the steam turbine unit during the entire operation stage.

[0004] To ensure reliable and effective shaft seal steam supply, in addition to retaining the auxiliary steam and main steam as shaft seal steam sources in conventional thermal power units, a new steam source of directly supplying shaft seal with cold reheat steam is added, and at the same time, a route of compressed air is introduced as an emergency air source. It is found that when the rotor of the steam turbine coasts down to near the critical speed after a trip, improper control of the shaft seal steam supply temperature will exacerbate the vibration of the entire shafting, and even further cause the risk of large shaft seizure. Therefore, once a (very) hot state trip occurs, quickly inputting matching shaft seal steam supply parameters becomes a key factor. Summary of the Invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide a multi-steam-source shaft seal steam / gas supply system for power station units and a control method thereof. The system has the advantages of diversified steam supply, parameter matching, flexible control mode, reliable protection logic, and automatic tracking under accident conditions, and has been well verified in actual field applications.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention and the beneficial effects of the present invention are:

[0007] A multi-steam-source shaft seal steam / gas supply system for a power station unit, comprising a high-pressure cylinder I, an intermediate-pressure cylinder II, a low-pressure cylinder III, a shaft seal cooler IV, a drain-air heat exchanger V, a desuperheater A, a desuperheater B, and a rotor connected to the cylinder body accessories;

[0008] On the steam inlet side of the high-pressure cylinder I, there is a rotor temperature T calculated using the cylinder body metal temperature;

[0009] The steam inlet sides of the high-pressure cylinder I and the intermediate-pressure cylinder II share the first branch shaft seal supply steam. After the steam remaining after sealing in the shaft seal chamber passes through the manual valve of the return steam pipeline, it enters the shaft seal return steam main pipe;

[0010] The exhaust sides of the high-pressure cylinder I and the intermediate-pressure cylinder II share the second branch shaft seal supply steam. A desuperheater A is installed on the second branch supply steam pipeline, and a measuring point T for steam temperature is installed before entering the shaft seal body after the desuperheater A; 1 ;

[0011] All the shaft seal return steam of the high-pressure cylinder I, the intermediate-pressure cylinder II, and the low-pressure cylinder III converges and then enters the shaft seal cooler IV.

[0012] The desuperheating water in the desuperheater A comes from condensate. A regulating valve 28 is provided on the pipeline between the desuperheater A and the condensate. A front manual valve 27 and a rear manual valve 29 are respectively provided at the front and rear ends of the regulating valve 28, and a bypass manual valve 30 is connected in parallel on the pipeline.

[0013] The overflow steam from the shaft seal chamber of the high-pressure cylinder I is introduced into the four-stage extraction pipeline.

[0014] The shaft seal supply steam of the low-pressure cylinder III comes from the shaft seal supply steam main pipe. A desuperheater B is installed before entering the low-pressure shaft seal, and a measuring point T for steam temperature is installed before entering the shaft seal body after the desuperheater B; 2 。

[0015] The desuperheating water of the desuperheater B comes from condensate. A regulating valve 32 is provided on the pipeline between the desuperheater B and the condensate. A front manual valve 31 and a rear manual valve 33 are respectively provided before and after the regulating valve 32, and a bypass manual valve 34 is connected in parallel on the pipeline.

[0016] The steam sources include an auxiliary steam supply for shaft seal, a main steam supply for shaft seal, a reheated cold section steam supply for shaft seal, an emergency standby gas source, and shaft seal overflow, which are connected in parallel.

[0017] The auxiliary steam supply for shaft seal includes a check valve 1 at the inlet, an electric valve 2, and a shaft seal supply regulating valve 4 connected in sequence through a pipeline, and a bypass electric valve 3 is provided on the parallel pipeline.

[0018] The described main steam supply for shaft sealing steam source includes a check valve II 5, an electric valve 6, and a shaft sealing steam regulating valve 7 connected in sequence through pipelines. A bypass electric valve 8 is provided on the parallel - arranged pipeline, and a drain pneumatic valve 9 is connected to the pipeline of the bypass electric valve 8.

[0019] The described reheated cold - section steam supply for shaft sealing steam source includes a check valve III 10, an electric valve 11, and a shaft sealing steam regulating valve 12 connected in sequence through pipelines. A bypass electric valve 13 is provided on the parallel - arranged pipeline.

[0020] The described accident standby gas source comes from the compressed - air main pipe. The normal - temperature air in the compressed - air main pipe passes through a check valve IV 19 and a pneumatic valve 20 and enters the drain - air heat exchanger V. The heated air passes through a check valve V 21, an electric valve 22, and a regulating valve 23 and is supplied to the shaft - sealing steam main pipe.

[0021] The high - temperature heat source of the described drain - air heat exchanger V comes from the main - steam supply for shaft - sealing drain. It enters the heat exchanger through the drain pneumatic valve 9. After releasing heat, the drain is discharged to the condenser through the pneumatic valve 26. The drain - air heat exchanger V is equipped with a bypass regulating valve 35. A branch is led out from the outlet pipeline of the drain - air heat exchanger V and is discharged to the atmosphere through the pneumatic valve 24 and the orifice plate 25. A temperature measuring point T is installed on a branch led out from the outlet pipeline of the drain - air heat exchanger V. 2 。

[0022] The described shaft - sealing overflow includes an overflow regulating valve 15 and an electric valve 14 connected in sequence through pipelines, forming a first branch. At the same time, an overflow bypass electric valve 16 is provided on the parallel - arranged pipeline, forming a second branch. The first branch passes through the electric valve 17 to the No. 7 low - pressure heater, and the second branch passes through the electric valve 18 to the condenser.

[0023] A control method for a multi - steam - source shaft - sealing steam / gas supply system of a power - station unit includes the following steps;

[0024] a. During the unit startup stage, the cylinder is in a cold state. At this time, auxiliary steam is used to supply shaft sealing steam. Before steam supply, the drains of the auxiliary - steam pipeline are fully opened to ensure that the auxiliary steam has a superheat of not less than 20 °C. The shaft - sealing pressure is controlled by the auxiliary - steam - supply - for - shaft - sealing regulating valve 4, and the pressure set value is P 0 ,P 0 Generally, it is subject to the manufacturer's instruction manual. The shaft - sealing steam temperature T 0 depends on the auxiliary - steam temperature. In principle, it is required that |T - T 0 | < 110 °C, where T is the rotor metal temperature calculated using the cylinder temperature. When it is monitored that the shaft - sealing steam temperature T 1 at the exhaust end of the high - and medium - pressure cylinders far exceeds the rotor metal temperature T, the cooling - water regulating valve 28 is opened for temperature control. Similarly, for the low - pressure shaft - sealing steam temperature T 2When the limit value required by the equipment manufacturer is exceeded, the cooling water regulating valve 32 is opened for temperature control. At this stage, the cold reheat steam supply gland steam regulating valve 12, the main steam supply gland steam regulating valve 7, the emergency standby air regulating valve 23, and the gland steam overflow regulating valve 15 are all in the closed state.

[0025] b. During the stage when the unit is synchronized and loaded with no more than 25% Pe (Pe is the rated load), the cylinder temperature gradually rises, the bypass system is fully closed, and the cold reheat pressure and temperature gradually increase. Since the cold reheat steam comes from the extraction steam of the first stage of the high-pressure cylinder and can better match the metal temperature of the cylinder body, the gland steam supply is gradually switched from auxiliary steam to cold reheat steam during this stage. The gland steam header pressure P 0 is jointly determined by the overflow steam from the high-pressure cylinder gland steam chamber and the externally supplied cold reheat steam. The cold reheat steam supply gland steam pressure regulating valve 12 is used to control the pressure P 0 , the auxiliary steam supply gland steam regulating valve 4 exits the automatic mode and is gradually manually closed to an opening of 3%. The minimum valve limit (i.e., 3%) of the auxiliary steam supply gland steam regulating valve 4 is defined in the logic to ensure that this pipeline is in a hot state throughout the full load range. At this stage, the main steam supply gland steam regulating valve 7, the emergency standby air regulating valve 23, and the gland steam overflow regulating valve 15 are all in the closed state. The gland steam supply temperature T 0 depends on the cold reheat steam temperature, and the adjustment strategy is the same as in step a;

[0026] c. When the unit load is higher than 25% Pe, the gland steam system gradually turns into a self-sealing state. The cold reheat to gland steam supply regulating valve 12 gradually closes as the load increases and exits the automatic mode after being fully closed. At this time, it is necessary to manually open the gland steam overflow regulating valve 15 and the gland steam overflow to No. 7 low-pressure heater motorized valve 17, and set the pressure set value of the gland steam overflow regulating valve to 1.25P 0 . When the No. 7 low-pressure heater malfunctions during operation, the gland steam overflow steam is switched to the condenser. At the stage when the gland steam pressure reaches the self-sealing state, the high and middle pressure cylinder gland steam temperature T 1 is not adjusted, and the low-pressure gland steam temperature T 2 is supplied by the overflow steam from the high and middle pressure cylinder gland chambers. At this time, it is necessary to put into operation the low-pressure gland steam desuperheating water regulating valve 32 and set the valve temperature to the given value by the manufacturer, generally 121 - 177 °C. After the cold reheat steam supply gland steam regulating valve 12 is closed and exits the automatic mode, the main steam supply gland steam regulating valve 7 is put into the automatic mode, and the pressure set value is 0.85P 0 , the auxiliary steam supply gland steam regulating valve 4 is manually maintained at an opening of 3%, the emergency standby air regulating valve 23 is closed, and the gland steam overflow regulating valve 15 is used to maintain the stability of the gland steam header pressure P 0 , and in addition, keep the drain valve 9 in front of the main steam supply gland steam regulating valve fully open;

[0027] d. When abnormal conditions such as turbine trip or load rejection occur in the (extremely) hot state of the steam turbine unit, the gland steam system instantaneously changes from the self-sealing state to the chamber vacuum state, and the gland steam header pressure P 0Quickly drops to a negative pressure, and the main steam supply shaft seal pressure regulating valve 7 automatically tracks the steam supply pressure. The initial pressure setting value is 0.85P 0 , when the main steam tracking is normal, gradually increase the set value manually to P 0 , at this time, manually control the auxiliary steam supply shaft seal regulating valve 4 and manually adjust the shaft seal steam supply temperature T 0 , the shaft seal temperature control targets the temperature before the unit trips. At the same time, the shaft seal overflow regulating valve 12 overrides and closes completely. When the command of the overflow regulating valve 12 < 3%, it triggers the interlock closing of the shaft seal overflow electric valve 11 and the bypass electric valve 13. At the same time, ensure that the compressed air emergency standby steam supply regulating valve 23 and the cold reheat to shaft seal steam supply regulating valve 12 are in the manually fully closed state, and the drain pneumatic valve 9 in front of the main steam supply shaft seal regulating valve is in the fully open state;

[0028] e. For the extremely hot start-up condition, in principle, maintain the main steam supply shaft seal regulating valve 7 automatic to control the shaft seal steam supply pressure, and the target pressure setting value is P 0 , the auxiliary steam supply shaft seal regulating valve 4 is manual to control the shaft seal steam supply temperature (T 0 ), and the temperature range is controlled between 320 and 450 °C. The specific temperature setting value is based on the principle of matching the cylinder temperature, and it is required that |T - T 0 | < 110 °C, where T 0 is the temperature of the shaft seal steam supply header, and T is the rotor metal temperature calculated using the cylinder temperature;

[0029] f. In the case of a complete cut-off of the unit's shaft seal steam source, manually put into the standby compressed air source, and control the shaft seal steam supply pressure through the compressed air emergency standby gas supply regulating valve 23. The pressure setting value is set to P 0 , use the drain-air heat exchanger V to control the compressed air temperature. The compressed air supply shaft seal temperature control targets the temperature value before the unit trips, and the range is between 320 and 450 °C;

[0030] The drain-air heat exchanger uses the high-temperature steam from the main steam pipeline drain to complete the surface heat exchange with the compressed air. The drained water after heat release is discharged to the condenser through the pneumatic valve 26. In order to ensure that the air at the outlet of the drain-air heat exchanger V always maintains the required high temperature (320 - 450 °C), a bypass regulating valve 35 of the drain-air heat exchanger is introduced for adjustment. This regulating valve always tracks the temperature T after the accident discharge valve in the standby state 3 , when the emergency standby gas supply regulating valve 23 is closed, the emergency standby gas discharge valve 24 interlocks and opens, and the emergency standby gas is discharged to the atmosphere through an orifice plate with a diameter of Ф5. When the compressed air emergency standby gas supply regulating valve 23 is opened, the emergency standby gas discharge valve 24 interlocks and closes.

[0031] Advantages of the present invention:

[0032] (1) The steam sources for shaft seal steam supply are diversified. In addition to retaining the conventional auxiliary steam and main steam, cold reheat steam is introduced, and in particular, a novel approach is to introduce a stream of compressed air as an emergency standby gas source.

[0033] (2) It not only considers the control strategy for the shaft seal during the normal operation of the unit from normal startup to full load operation, but also provides the control strategy for the shaft seal under accident conditions such as (ultra) hot state turbine trip, (ultra) hot state startup, and total loss of steam sources for the entire plant.

[0034] (3) The control method is flexible, simple, easy to operate, and highly automated. The shaft seal steam supply pressure is under automatic control throughout the entire stage, especially being able to intervene in operation immediately under accident conditions.

[0035] (4) The supplied steam parameters better match the cylinder temperature of the steam turbine. The shaft seal steam supply temperature takes into account the different control requirements under accident conditions in cold state, warm state, and (ultra) hot state, avoiding the risk of increased rotor vibration caused by mismatched shaft seal temperatures.

[0036] (5) Utilizing the characteristics of the high-temperature drain of the main steam to exchange heat with the emergency standby gas source not only solves the problem of temperature matching of the accident gas source, but also reduces the temperature of the drain returning to the condenser, being more energy-efficient.

[0037] (6) This control strategy greatly improves the safety and reliability of the operation of the shaft seal system of the steam turbine unit and has been fully verified during (ultra) hot state turbine trip and startup stages, with good effects. Brief Description of the Drawings

[0038] Figure 1 It is a schematic flow diagram of the present invention.

[0039] Among them, I is the high-pressure cylinder, II is the intermediate-pressure cylinder, III is the low-pressure cylinder, IV is the gland steam cooler, V is the drain-air heat exchanger, A is the desuperheater for the gland steam supply between the high-pressure and intermediate-pressure cylinders, B is the desuperheater for the gland steam supply of the low-pressure cylinder, 1, 5, 10, 19, and 21 are all check valves, 27, 29, 30, 31, 33, and 34 are all manual valves, 2 is the motorized valve for the auxiliary steam to supply the gland steam inlet, 3 is the motorized valve for the bypass of the auxiliary steam to supply the gland steam, 4 is the regulating valve for the auxiliary steam to supply the gland steam, 6 is the motorized valve for the main steam to supply the gland steam inlet, 7 is the regulating valve for the main steam to supply the gland steam, 8 is the motorized valve for the bypass of the main steam to supply the gland steam, 9 is the pneumatic drain valve for the main steam to supply the gland steam pipeline, 11 is the motorized valve for the reheated cold section steam to supply the gland steam inlet, 12 is the regulating valve for the reheated cold section steam to supply the gland steam, 13 is the motorized valve for the bypass of the reheated cold section steam to supply the gland steam, 14 is the motorized valve for the gland steam overflow, 15 is the regulating valve for the gland steam overflow, 16 is the motorized valve for the bypass of the gland steam overflow, 17 is the motorized valve for the gland steam overflow to the No. 7 low-pressure heater, 18 is the motorized valve for the gland steam overflow to the condenser, 20 is the pneumatic valve for the compressed air to enter the drain-air heat exchanger, 22 is the motorized valve for the emergency standby air source of the compressed air to supply the gland steam, 23 is the regulating valve for the emergency standby air source of the compressed air to supply the gland steam, 24 is the pneumatic valve for the emergency standby air source of the compressed air to discharge to the atmosphere, 25 is the throttle orifice plate with a diameter of Ф5, 26 is the pneumatic valve for the drain of the drain-air heat exchanger to the condenser, 28 is the regulating valve for the condensate water to reduce the temperature of the gland steam between the high-pressure and intermediate-pressure cylinders, 32 is the regulating valve for the condensate water to reduce the temperature of the gland steam of the low-pressure cylinder, and 35 is the regulating valve for the bypass of the drain of the drain-air heat exchanger.

[0040] In addition, measuring points P 0 and T 0 for measuring the pressure and temperature of the main pipe are arranged on the gland steam supply main pipe, and measuring point T 1 for measuring the gland steam temperature supplied to the high-pressure and intermediate-pressure cylinders is arranged behind the desuperheater nozzle (A), and measuring point T 2 for measuring the gland steam temperature supplied to the low-pressure cylinder is arranged behind the desuperheater nozzle (B), and measuring point T 3 is arranged behind the accident discharge valve at the air side outlet of the drain-air heat exchanger. At the same time, measuring point T representing the rotor metal temperature in the turbine supervisory system (TSI) is cited.

[0041] ① represents from the auxiliary steam, ② represents from the main steam, ③ represents from the reheated cold section steam, ④ represents to the condenser, ⑤ represents to the No. 7 low-pressure heater, ⑥ represents from the condensate water, ⑦ represents to the extraction pipeline of the fourth stage, and ⑧ represents from the compressed air main pipe. Specific implementation mode

[0042] The present invention will be further described in detail below with reference to the accompanying drawings.

[0043] As Figure 1As shown in the figure, a conventional thermal power unit includes a high-pressure cylinder I, an intermediate-pressure cylinder II, and a low-pressure cylinder III. During the operation of the unit, it is necessary to seal the parts where the rotor passes through the cylinder. The present invention has a total of three external steam supply sources. The first route comes from auxiliary steam, passes through check valve 1, motorized valve 2, and regulating valve 4, and enters the shaft seal steam supply main pipe. To ensure the reliability of the system, a parallel bypass motorized valve 3 is configured in this pipeline; the second route comes from main steam, passes through check valve 5, motorized valve 6, and regulating valve 7, and enters the shaft seal steam supply main pipe. To ensure the reliability of the system, a parallel bypass motorized valve 8 is configured in this pipeline; the third route comes from the cold section of the reheated steam, passes through check valve 10, motorized valve 11, and regulating valve 12, and enters the shaft seal steam supply main pipe. To ensure the reliability of the system, a parallel bypass motorized valve 13 is configured in this pipeline. In addition to the above three normal steam sources, the present invention also particularly adds a route of compressed air as an emergency standby gas source. The gas coming from the compressed air main pipe passes through check valve 19 and intake pneumatic valve 20 and enters the drain-air heat exchanger V. The heated air passes through check valve 21, motorized valve 22, and regulating valve 23 and enters the shaft seal steam supply main pipe. To ensure that the compressed air in the drain-air heat exchanger V is always in a hot flow state, an external discharge pipeline is led out before the main check valve for the heated compressed air. The hot air in this pipeline passes through pneumatic valve 24 and a throttle orifice plate 25 with a diameter of Ф5 and is discharged into the atmosphere. The heat source in the drain-air heat exchanger V is led from the drain of the main steam supply shaft seal pipeline, enters the heat exchanger from the upper part through drain valve 9, and is led out from the lower part and discharged into the condenser through drain valve 26.

[0044] The first branch of the steam (gas) entering the shaft seal main pipe is directly supplied to the steam inlet ends of the high-pressure cylinder I and the intermediate-pressure cylinder II. The second branch is supplied to the steam exhaust ends of the high-pressure cylinder I and the intermediate-pressure cylinder II through desuperheater A. The third branch is supplied to the two-side steam exhaust ends of the low-pressure cylinder III through desuperheater B. The shaft seal return steam finally enters the shaft seal cooler IV through the return steam main pipe. Among them, the steam leakage from the high-pressure side shaft seal of the high-pressure cylinder I enters the four-stage extraction pipeline. The desuperheating water for the high- and intermediate-pressure cylinder shaft seal desuperheater A comes from condensate, passes through the desuperheating water regulating valve 28, the front manual valve 27, and the rear manual valve 29, and enters the desuperheater A nozzle. A parallel bypass manual valve 30 is configured in this pipeline; the desuperheating water for the low-pressure cylinder shaft seal desuperheater B also comes from condensate, passes through the desuperheating water regulating valve 32, the front manual valve 4 31, and the rear manual valve 5 33, and enters the desuperheater B nozzle. A parallel bypass manual valve 6 34 is configured in this pipeline.

[0045] In addition to retaining the conventional auxiliary steam and main steam as the main steam sources for the shaft seal, the present invention adds a new steam source of cold reheat steam directly supplying the shaft seal, and innovatively introduces a path of compressed air as an accident standby gas source. In order to better match the accident standby gas source with the metal temperature of the shaft seal chamber, a drain-air heat exchanger is provided, and the drain of the main steam supply shaft seal pipeline is specially modified to heat the compressed air with the high-temperature drain to achieve a suitable supply air temperature. This system meets the requirements of safe, reliable, and energy-efficient operation during all operating stages such as unit startup, grid connection with low load, high load shaft seal self-sealing, load rejection or (extremely) hot state accident trip, and shaft seal losing all steam source accident states. This system has the advantages of diversified steam supply, parameter matching, flexible control mode, reliable protection logic, and automatic tracking under accident conditions, and has been well verified in on-site practical applications.

[0046] a. In one embodiment, taking the new C350 unit of Harbin Steam Turbine as an example, during the unit startup stage, auxiliary steam is used to supply the shaft seal, and the shaft seal header pressure P is set by using the auxiliary steam supply shaft seal regulating valve 4. 0 Automatically, in accordance with the manufacturer's requirements, P 0 is 24.1 kPa. The shaft seal supply steam temperature T 0 depends on the auxiliary steam temperature. The low-pressure cylinder shaft seal desuperheating water is put into automatic control to control the shaft seal supply steam temperature T 2 between 121 and 177 °C, and the shaft seal temperatures of the high- and medium-pressure cylinders are not adjusted. During this stage, the cold reheat supply shaft seal regulating valve 12, the main steam supply shaft seal regulating valve 7, the accident standby gas regulating valve 23, and the shaft seal overflow regulating valve 15 are all in the closed state.

[0047] b. In one embodiment, during the stage when the unit is connected to the grid with a load not higher than 25% Pe (Pe is the rated load), the shaft seal steam supply is gradually switched from auxiliary steam to cold reheat steam. The pressure value of the cold reheat supply shaft seal regulating valve 12 is set to 1.15P 0 , that is, (27.7 kPa), and it is put into automatic. The auxiliary steam supply shaft seal regulating valve 4 exits automatic control and is gradually manually closed to 3% opening to ensure that this pipeline is in a hot state throughout the full load section. During this stage, the main steam supply shaft seal regulating valve 7, the accident standby gas regulating valve 23, and the shaft seal overflow regulating valve 15 are all in the closed state. The shaft seal supply steam temperature T 0 depends on the cold reheat steam temperature, and the adjustment strategy is the same as in step a.

[0048] c. In one embodiment, when the unit load is higher than 25% Pe, the shaft seal system gradually turns into a self-sealing state. After the cold reheat to shaft seal supply regulating valve 12 is gradually closed and exits automatic control, the shaft seal overflow regulating valve 15 and the shaft seal overflow to No. 7 low-pressure heater motorized valve 17 are opened. The pressure setting value of the shaft seal overflow regulating valve is set to 1.25P 0(i.e., 30.1 kPa), when the No. 7 low-pressure heater malfunctions during operation, the gland steam overflow is switched to the condenser. When the gland reaches the self-sealing stage, the gland temperatures of the high- and intermediate-pressure cylinders T 1 are not adjusted, and for the gland temperature of the low-pressure cylinder T 2 desuperheating water needs to be introduced to control the temperature at 121 - 177 °C. When the cold reheat steam supply gland regulating valve 12 is fully closed and taken out of automatic control, the main steam supply gland regulating valve 7 is put into automatic control, and the pressure setpoint is 0.85P 0 (i.e., 20.5 kPa), the auxiliary steam supply gland regulating valve 3 is kept at 3% opening in manual mode, the emergency standby air regulating valve 23 is closed, and the gland steam overflow regulating valve 15 is used to maintain the pressure P 0 of the gland steam header stable, and the drain valve 9 in front of the main steam supply gland regulating valve is kept fully open.

[0049] d. In one embodiment, when the steam turbine unit trips in a (very) hot state, the gland seal system instantaneously changes from the self-sealing state to the chamber vacuum state. At this time, the gland steam overflow regulating valve 15 is overridden and fully closed, and the overflow regulating valve command < 3% triggers the interlock closing of the gland steam overflow electric valve 14 and the bypass electric valve 16. The main steam supply gland regulating valve 7 automatically tracks the supply steam pressure, and the pressure setpoint is 0.85P 0 (i.e., 20.5 kPa). After the main steam tracking is normal, the setpoint is gradually increased manually to P 0 (i.e., 24.1 kPa). Manually control the auxiliary steam supply gland regulating valve 4 to adjust the gland steam supply temperature T 0 , T 0 with the temperature before the unit trips as the target. At the same time, ensure that the standby emergency air regulating valve 23 and the cold reheat to gland steam supply regulating valve 12 are in the fully closed manual state, and the drain pneumatic valve 9 in front of the main steam supply gland regulating valve is in the fully open state.

[0050] e. In one embodiment, for the very hot state startup condition, the drain pneumatic valve 9 in front of the main steam supply gland regulating valve is kept fully open, the main steam supply gland regulating valve 7 is maintained in automatic control, and the target pressure setpoint is set to P 0 (i.e., 24.1 kPa). The auxiliary steam supply gland regulating valve 4 is in manual mode to adjust the gland steam supply temperature T 0 , and the temperature range is controlled at 320 - 450 °C. The specific temperature setpoint is based on the principle of matching the cylinder temperature. Ensure that |T - T 0 | < 110 °C, where T 0 is the temperature of the gland steam supply header, and T is the rotor metal temperature calculated using the cylinder temperature.

[0051] f. In one embodiment, when the gland steam source of the unit is completely cut off, manually open the standby emergency air regulating valve 23, and the pressure setpoint is set to P 0(i.e., 24.1 kPa), after the accident standby gas regulating valve 23 is fully opened, the accident standby gas discharge valve 24 is interlocked and closed. The temperature of the accident standby gas is controlled by the drain-air heat exchanger V and the bypass regulating valve 35. The temperature control of the shaft seal supplied with compressed air targets the temperature value before the unit trips, with a range between 320 and 450 °C.

Claims

1. A multi-steam source shaft seal steam / gas supply system for power station units, characterized in that, it includes a high-pressure cylinder (I), an intermediate-pressure cylinder (II), a low-pressure cylinder (III), a shaft seal cooler (IV), a drain-air heat exchanger (V), a first desuperheater (A), a second desuperheater (B), and a rotor connected to the cylinder body accessories; on the steam inlet side of the high-pressure cylinder (I), there is a rotor temperature (T) calculated using the cylinder body metal temperature; the steam inlet sides of the high-pressure cylinder (I) and the intermediate-pressure cylinder (II) share the first branch shaft seal supply steam, and the remaining steam after sealing in the shaft seal chamber enters the shaft seal return steam main pipe through the manual valve of the return steam pipe; The exhaust sides of the high-pressure cylinder (I) and the intermediate-pressure cylinder (II) share the steam supply for the second branch shaft seal. A first desuperheater (A) is installed on the second branch steam supply pipeline. A measuring point (T 1 ) for the steam temperature is installed before entering the shaft seal body after the first desuperheater (A); all the shaft seal return steam of the high-pressure cylinder (I), the intermediate-pressure cylinder (II) and the low-pressure cylinder (III) converges and then enters the shaft seal cooler (IV); the desuperheating water in the first desuperheater (A) comes from condensate, and a regulating valve two (28) is arranged on the pipe between the first desuperheater (A) and the condensate. A first manual valve one (27) and a second manual valve two (29) are respectively arranged at the front and rear ends of the regulating valve two (28), and a bypass manual valve three (30) is arranged in parallel on the pipe; the overflow steam of the shaft seal chamber of the high-pressure cylinder (I) is introduced into the extraction four pipeline; The gland steam supply of the said low-pressure cylinder (III) comes from the gland steam supply header. A second desuperheater (B) is installed before the low-pressure gland seal. A measuring point (T 2 ) for the steam temperature is installed before entering the gland seal body after the second desuperheater (B); the desuperheating water of the second desuperheater (B) comes from condensate, and a regulating valve three (32) is arranged on the pipe between the second desuperheater (B) and the condensate. A fourth manual valve one (31) and a fifth manual valve five (33) are respectively arranged before and after the regulating valve three (32), and a bypass manual valve six (34) is arranged in parallel on the pipe; the steam sources include an auxiliary steam supply for shaft seal, a main steam supply for shaft seal, a reheated cold section steam supply for shaft seal, an accident standby gas source and shaft seal overflow arranged in parallel; the auxiliary steam supply for shaft seal includes a check valve one (1), an electric valve one (2) and a shaft seal supply regulating valve one (4) connected in sequence through a pipe, and a bypass electric valve one (3) is arranged on the parallel pipe; the main steam supply for shaft seal includes a check valve two (5), an electric valve two (6) and a shaft seal supply regulating valve two (7) connected in sequence through a pipe, and a bypass electric valve (8) is arranged on the parallel pipe. A drain pneumatic valve (9) is connected to the pipe of the bypass electric valve (8); the reheated cold section steam supply for shaft seal includes a check valve three (10), an electric valve three (11) and a shaft seal supply regulating valve three (12) connected in sequence through a pipe, and a bypass electric valve two (13) is arranged on the parallel pipe; the accident standby gas source comes from the compressed air main pipe. The normal temperature air of the compressed air main pipe passes through a check valve four (19) and a pneumatic valve one (20) and enters the drain-air heat exchanger (V). The heated air passes through a check valve five (21), an electric valve seven (22) and a regulating valve one (23) and is supplied to the shaft seal supply main pipe; The high-temperature heat source of the hydrophobic-air heat exchanger (V) comes from the main steam supply for gland steam drainage, enters the heat exchanger through the hydrophobic pneumatic valve (9), and the hydrophobic water after heat release is discharged to the condenser through the third pneumatic valve (26); the hydrophobic-air heat exchanger (V) is equipped with a bypass regulating valve (35); a branch is led out from the outlet pipeline of the hydrophobic-air heat exchanger (V) and discharged to the atmosphere through the second pneumatic valve (24) and the orifice plate (25); a temperature measuring point (T 3 ) is installed on a branch led out from the outlet pipeline of the hydrophobic-air heat exchanger (V). the shaft seal overflow includes an overflow regulating valve (15) and an electric valve four (14) connected in sequence through a pipe to form a first branch, and an overflow bypass electric valve (16) is arranged on the parallel pipe to form a second branch.

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