1. A low-pressure shaft seal temperature reducing system of a steam turbine is characterized by comprising a shaft seal main pipe, a water spraying temperature reducing system, a steam-water separation system, a pipeline drainage system, a water spraying preposed heating system connected with the water spraying temperature reducing system and a low-pressure shaft seal; the main shaft seal pipe, the water spraying and temperature reducing system, the steam-water separation system and the low-pressure shaft seal system are sequentially connected, and the pipeline drainage system is located between the steam-water separation system and the low-pressure shaft seal and is respectively connected with the steam-water separation system and the low-pressure shaft seal system.

2. The steam turbine low pressure shaft seal desuperheating system of claim 1, wherein a water spray regulating valve is disposed between said water spray preheating system and said water spray desuperheating system;

a low-pressure shaft seal steam supply pipeline is arranged between the steam-water separation system and the low-pressure shaft seal; the pipeline drainage system is connected with the low-pressure shaft seal steam supply pipeline;

and a thermocouple is arranged on the low-pressure shaft seal steam supply pipeline and is connected with the water spray regulating valve through a power plant control system.

3. The steam turbine low pressure shaft seal desuperheating system of claim 2, wherein the water spray desuperheating system comprises a water spray desuperheater connected to the shaft seal main pipe, a water spray pipe connected to the output end of the water spray regulating valve, and a nozzle installed at the output end of the water spray pipe and located in the water spray desuperheater; and the input end of the water spray regulating valve is connected with the water spray preheating system.

4. The steam turbine low-pressure shaft seal temperature reducing system according to claim 3, wherein the water spray preheating system comprises a temperature reducing water spray pipeline connected with a water spray regulating valve, a water drainage heat exchanger, a condensate pump temperature reducing water main pipe, a shaft seal heater and a water drainage flash tank; the condensate pump temperature-reducing water main pipe, the shaft seal heater and the drainage flash tank are respectively connected with the drainage heat exchanger; the hydrophobic heat exchanger is connected with a desuperheating water spraying pipeline.

5. The steam turbine low-pressure shaft seal temperature reducing system according to claim 3, wherein the steam-water separation system comprises a steam-water separator connected with the output end of the water spray temperature reducer, a separator drain pipeline arranged at the bottom of the steam-water separator, and a throttle orifice plate front stop valve and a throttle orifice plate which are sequentially arranged on the separator drain pipeline; the throttle orifice front stop valve is arranged between the throttle orifice and the steam-water separator; the throttling orifice plate is connected with the drainage flash tank through a discharge pipeline.

6. The steam turbine low pressure shaft seal desuperheating system of claim 5, wherein said steam-water separation system further comprises a bypass line having both ends connected to the separator drain line and the discharge line, respectively, a trap front stop valve installed on the bypass line, and a separator trap installed on the bypass line and located between the trap front stop valve and the drain flash tank; one end of the bypass pipeline is arranged between the front stop valves of the throttling orifice plate, and the other end of the bypass pipeline is arranged between the throttling orifice plate and the drainage flash tank.

7. The steam turbine low pressure shaft seal desuperheating system of claim 5, wherein a desuperheater rear pipeline is arranged between the water spray desuperheater and the steam-water separator, and the water spray desuperheater is obliquely arranged towards one side of the steam-water separator, and the inclination angle is not less than 1 degree.

8. The steam turbine low pressure shaft seal desuperheating system of claim 7, wherein said desuperheater rear duct includes an inclined straight section connected at one end to a water spray desuperheater, an inclined section connected to another end of the inclined straight section; the length of the inclined straight section is not less than 5 m.

9. The turbine low-pressure shaft seal temperature reduction system according to claim 2, wherein the pipeline drainage system comprises a drainage bag, a drainage pipeline, a drainage device and a drainage discharge pipeline which are sequentially connected with the low-pressure shaft seal steam supply pipeline; the drain bag is connected with the low-pressure shaft seal; and the drainage discharge pipeline is connected with the drainage flash tank.

Background

According to the 5.2.12 requirement of DL/T863-2004 'turbine start-up debugging guide rule', the shaft seal steam source should pay attention to ensure that the temperature difference between the shaft seal steam and the rotor metal is less than 110 ℃, and the low-pressure shaft seal steam supply temperature is usually required to be controlled within the range of 120-180 ℃.

The steam supply temperature of the low-pressure shaft seal directly relates to the stability and safety of a unit, and if the steam supply temperature is too high, the shaft seal gap is too large, so that the sealing performance of a condenser is influenced, the vacuum tightness of the condenser is reduced, the running backpressure of the unit is higher, and the economical efficiency of a power plant is influenced; in order to ensure the vacuum tightness of the condenser, the steam supply pressure of the shaft seal main pipe has to be increased, and although the requirement of vacuum tightness can be met, the steam can be emitted from the shaft end, so that the lubricating oil carries water, and the safety risk is brought to the operation of a unit. The steam supply temperature is too low, which may cause water inflow of the low-pressure shaft seal, shaft vibration exceeding standard, great influence on safe and stable operation of the unit, and even serious accident of unit trip.

Because the steam supply temperature of the low-pressure shaft seal is influenced by a plurality of factors, the conventional shaft seal system has a plurality of defects, so that the water spraying atomization heat exchange is insufficient, the water drainage quantity is large, and the temperature cannot be stably controlled; from the operation condition of the existing power plant shaft seal system, the unstable phenomenon of the steam supply temperature of the low-pressure shaft seal generally exists, and the failure rate is high; the stability of the steam supply temperature of the low-pressure shaft seal becomes a problem which is urgently needed to be solved by a power plant.

Disclosure of Invention

The invention aims to solve the technical problem of providing a low-pressure shaft seal temperature reduction system of a steam turbine, which effectively realizes stable steam supply temperature, thereby improving the stability and safety of unit operation.

The technical problem to be solved by the invention is as follows:

a low-pressure shaft seal temperature reducing system of a steam turbine comprises a shaft seal main pipe, a water spraying temperature reducing system, a steam-water separation system, a pipeline drainage system, a water spraying preposed heating system connected with the water spraying temperature reducing system and a low-pressure shaft seal; the main shaft seal pipe, the water spraying and temperature reducing system, the steam-water separation system and the low-pressure shaft seal system are sequentially connected, and the pipeline drainage system is located between the steam-water separation system and the low-pressure shaft seal and is respectively connected with the steam-water separation system and the low-pressure shaft seal system.

In some possible embodiments, a water spray regulating valve is arranged between the water spray preheating system and the water spray temperature reduction system;

a low-pressure shaft seal steam supply pipeline is arranged between the steam-water separation system and the low-pressure shaft seal;

and a thermocouple is arranged on the low-pressure shaft seal steam supply pipeline and is connected with the water spray regulating valve through a power plant control system.

In some possible embodiments, the water spray desuperheater system comprises a water spray desuperheater connected with the shaft seal main pipe, a water spray pipeline connected with the output end of the water spray regulating valve, and a nozzle installed at the output end of the water spray pipeline and located in the water spray desuperheater; and the input end of the water spray regulating valve is connected with the water spray preheating system.

In some possible embodiments, the water spray preheating system comprises a reduced-temperature water spray pipeline connected with a water spray regulating valve, a water drainage heat exchanger, a condensate pump reduced-temperature water main pipe, a shaft seal heater and a water drainage flash tank; the condensate pump temperature-reducing water main pipe, the shaft seal heater and the drainage flash tank are respectively connected with the drainage heat exchanger; the hydrophobic heat exchanger is connected with a desuperheating water spraying pipeline.

In some possible embodiments, the steam-water separation system comprises a steam-water separator connected with the output end of the water spray desuperheater, a separator drain pipeline installed at the bottom of the steam-water separator, and a throttle orifice plate front stop valve and a throttle orifice plate which are sequentially installed on the separator drain pipeline; the throttle orifice front stop valve is arranged between the throttle orifice and the steam-water separator; the throttling orifice plate is connected with the drainage flash tank through a discharge pipeline.

In some possible embodiments, the steam-water separation system further comprises a bypass pipeline with two ends respectively connected with the trap drain pipeline and the discharge pipeline, a trap front stop valve installed on the bypass pipeline, and a trap installed on the bypass pipeline and located between the trap front stop valve and the trap flash tank; one end of the bypass pipeline is arranged between the front stop valves of the throttling orifice plate, and the other end of the bypass pipeline is arranged between the throttling orifice plate and the drainage flash tank.

In some possible embodiments, a desuperheater rear pipeline is arranged between the water spray desuperheater and the steam-water separator, and the water spray desuperheater is inclined towards one side of the steam-water separator, and the inclination angle is not less than 1 °.

In some possible embodiments, the post-desuperheater pipeline comprises an inclined straight section with one end connected with the water spray desuperheater, and an inclined section connected with the other end of the inclined straight section; the length of the inclined straight section is not less than 5 m.

In some possible embodiments, the pipeline drainage system comprises a drainage bag, a drainage pipeline, a drainage device and a drainage discharge pipeline which are sequentially connected with the low-pressure shaft seal steam supply pipeline; the drain bag is connected with the low-pressure shaft seal; and the drainage discharge pipeline is connected with the drainage flash tank.

In some possible embodiments, the thermocouple is interlocked with the water spray regulating valve opening by the power plant control system.

Compared with the prior art, the invention has the beneficial effects that:

the invention fully recycles the waste heat of drainage of the shaft seal heater, correspondingly reduces the low-pressure steam extraction amount and the heat load of the cold end of the steam turbine, reduces the running back pressure of the unit and improves the economy of the unit;

according to the invention, by arranging the water spraying temperature reduction system, the temperature of the temperature-reduced water spraying is increased to be close to a saturated state (relative to the steam supply pressure of the shaft seal) from the mechanism of water spraying temperature reduction, so that the heat exchange time with steam is reduced, and the shortage of residence heat exchange time caused by too short heat exchange straight section is compensated; the thermodynamic property of the temperature-reducing water can be improved, the surface tension of the cooling water is reduced, and the atomization of the nozzle is facilitated;

the inclined straight section of the pipeline behind the desuperheater is set to be not less than 5 m; the heat exchange residence time is ensured, and the heat exchange problems that water is wrapped in steam due to overhigh flow velocity in the pipe and water drops cannot be supported due to overlow flow velocity and meet the wall to converge are also prevented;

the invention is provided with the steam-water separator and the drain bag, realizes secondary dehydration treatment, and effectively prevents the phenomenon that water is carried in steam supplied by the low-pressure shaft seal; the steam trap of the water separator of the steam-water separator is provided with a bypass, so that the water drainage amount and the steam flow after temperature reduction can be slightly adjusted, the water drainage amount is matched with the operation working condition, and the temperature reduction nozzle can be in the optimal working state;

the invention thoroughly solves the problem of unstable steam supply temperature of the low-pressure shaft seal, improves the sealing performance of the low-pressure shaft seal, reduces the running back pressure of the unit, and improves the running stability, safety and economy of the unit;

the system is simple, the cost is lower, the effect is obvious, the control is completely consistent with the existing control strategy, and the system is very convenient for the design of a new unit and the reconstruction of an old unit.

Drawings

FIG. 1 is a schematic diagram of the connection relationship of the present invention;

wherein: 1. shaft sealing the main pipe; 2. a shaft seal heater; 3. a desuperheating water spray line; 4. a water spray regulating valve; 5. a hydrophobic flash tank; 6. a nozzle; 7. a water spray desuperheater; 8. a desuperheater rear pipeline; 9. a steam-water separator; 10. a steam trap front stop valve; 11. a water separator steam trap; 12. a separator drain line; 13. a throttle orifice front stop valve; 14. a low-pressure shaft seal steam supply pipeline; 15. a thermocouple; 16. a drain bag; 17. a drain pipe; 18. a steam trap; 19. a hydrophobic heat exchanger; 20. a restriction orifice plate; 21. a low pressure shaft seal; 22. the condensate pump desuperheating water main pipe.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail and completely with reference to the accompanying drawings. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention.

In the description of the present invention, it is to be understood that the terms indicating an orientation or positional relationship are based on the orientation or positional relationship shown in the drawings only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the drawings of the present invention, it should be understood that different technical features which are not mutually substituted are shown in the same drawing only for the convenience of simplifying the drawing description and reducing the number of drawings, and the embodiment described with reference to the drawings does not indicate or imply that all the technical features in the drawings are included, and thus the present invention is not to be construed as being limited thereto.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; either directly or indirectly through intervening media, either internally or in any other relationship. Reference herein to "first," "second," and similar words, does not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. In the implementation of the present application, "and/or" describes an association relationship of associated objects, which means that there may be three relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In the description of the embodiments of the present application, the meaning of "a plurality" means two or more unless otherwise specified. For example, the plurality of positioning posts refers to two or more positioning posts. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The present invention will be described in detail below.

As shown in fig. 1:

a low-pressure shaft seal temperature reducing system of a steam turbine comprises a shaft seal main pipe 1, a water spraying temperature reducing system, a steam-water separation system, a pipeline drainage system, a water spraying preposed heating system connected with the water spraying temperature reducing system and a low-pressure shaft seal 21; the main shaft seal pipe 1, the water spraying and temperature reducing system, the steam-water separation system and the low-pressure shaft seal 21 system are sequentially connected, and the pipeline drainage system is located between the steam-water separation system and the low-pressure shaft seal 21 and is respectively connected with the steam-water separation system and the low-pressure shaft seal system.

In some possible embodiments, a water spray regulating valve 4 is arranged between the water spray preheating system and the water spray temperature reduction system;

a low-pressure shaft seal steam supply pipeline 14 is arranged between the steam-water separation system and the low-pressure shaft seal 21;

a thermocouple 15 is arranged on the low-pressure shaft seal steam supply pipeline 14, and the thermocouple 15 is connected with the water spray regulating valve 4 through a power plant control system.

Preferably, a thermocouple 15 is located between the trap heat exchanger 9 and the pipe trap system.

The thermocouple 15 transmits data to a power plant control system, and the water spray regulating valve 4 is controlled by the power plant control system

In some possible embodiments, the water spray desuperheater system comprises a water spray desuperheater 7 connected with the shaft seal main pipe 1, a water spray pipeline connected with the output end of the water spray regulating valve 4, and a nozzle 6 which is arranged at the output end of the water spray pipeline and is positioned in the water spray desuperheater 7; and the input end of the water spray regulating valve 4 is connected with a water spray preheating system.

Preferably, the nozzles 6 are directed in the direction of steam flow, which is described herein as the direction of flow from the steam spray desuperheater 7 to the steam separation system.

In some possible embodiments, the water spray preheating system comprises a reduced temperature water spray line 3 connected with a water spray regulating valve 4, a water drainage heat exchanger 19, a condensate pump reduced temperature water header 22, a shaft seal heater 2, and a water drainage flash tank 5; the condensate pump temperature-reducing water main pipe 22, the shaft seal heater 2 and the drainage flash tank 5 are respectively connected with the drainage heat exchanger 19; the heat exchanger 19 is connected to the desuperheating water spray line 3.

In some possible embodiments, the steam-water separation system comprises a steam-water separator 9 connected with the output end of the water spray desuperheater 7, a separator drain pipeline 12 installed at the bottom of the steam-water separator 9, and a throttle orifice front stop valve 13 and a throttle orifice 20 which are sequentially installed on the separator drain pipeline 12; the throttle orifice front stop valve 13 is arranged between the throttle orifice 20 and the steam-water separator 9; the orifice 20 is connected to the trap 5 via a drain line.

In some possible embodiments, the steam-water separation system further includes a bypass line connected at both ends to the separator drain line 12 and the drain line, respectively, a trap front stop valve 10 installed on the bypass line, and a separator trap 11 installed on the bypass line and located between the trap front stop valve 10 and the drain flash tank 5; one end of the bypass line is disposed between the orifice plate front stop valves 13, and the other end is disposed between the orifice plate 20 and the drain flash tank 5.

In some possible embodiments, a desuperheater rear pipeline 8 is arranged between the water spray desuperheater 7 and the steam-water separator 9, and the water spray desuperheater 7 is arranged in an inclined mode towards the steam-water separator 9, and the inclined angle is not less than 1 degree.

The inclined arrangement described here means in particular that the outlet of the spray desuperheater 7 is at a high point and the inlet of the steam separator 9 is at a low point, thus forming an incline.

In some possible embodiments, the post-desuperheater pipeline 8 comprises an inclined straight section connected at one end to the water spray desuperheater 7, an inclined section connected at the other end of the inclined straight section; the length of the inclined straight section is not less than 5 m.

The flow rate of the steam is controlled within a certain range of 20-30m/s through the limitation of the inclined angle and the length of the inclined straight section.

By adopting the inclined mode and the length, the heat exchange residence time is ensured, and the heat exchange problems that water is wrapped in steam due to overhigh flow velocity in the pipe and water drops cannot be supported and meet the wall to converge due to overlow flow velocity are also prevented;

in some possible embodiments, the pipeline drainage system comprises a drainage bag 16, a drainage pipe 17, a steam trap 18 and a drainage discharge pipe which are sequentially connected with the low-pressure shaft seal steam supply pipe 14; the drain bag 16 is connected with a low-pressure shaft seal 21; the drain discharge pipe is connected with a drain flash tank 5.

In some possible embodiments, the hydrophobic bag 16 is disposed at a low point of the low-pressure shaft seal steam supply pipe 14; the bottom of the drain bag 16 is connected with a drain 18 through a drain pipe 17 to drain the drain into the drain flash tank 5.

The low pressure shaft seal steam supply pipe 14 is arranged with a relief, and preferably, the drain bag 16 is installed at a low point of the low pressure shaft seal steam supply pipe 14.

The pipeline drainage systems are in multiple groups and are all arranged on the low-pressure shaft seal steam supply pipeline 14.

In some possible embodiments, the thermocouple 15 is located between the steam-water separator 9 and the hydrophobic pocket 16; the thermocouple 15 is interlocked with the opening degree of the water spray regulating valve 4 through a power plant control system.

(1) In the starting stage of the unit, auxiliary steam is supplied to the shaft seal steam, and steam is supplied to the low-pressure shaft seal 21 from the shaft seal main pipe 1 through the water spray desuperheater 7.

The desuperheating water is from a desuperheating water pump desuperheating water main pipe 22, heat exchange is carried out with the drainage of a shaft seal heater 2 in a drainage heat exchanger 19, the temperature is increased, the pressure is adjusted through a water spray adjusting valve 4, the desuperheating water is sprayed out from a nozzle 6, heat exchange is carried out with steam in a pipeline 8 behind the desuperheater, the steam (containing a small amount of water drops which do not fully exchange heat) enters a steam-water separator 9 after heat exchange, most of water in the steam is separated and collected to the bottom by the steam-water separator 9, the steam is discharged into a drainage flash tank 5 through a separator steam trap 11 under pressure difference, the steam separated from the water enters a low-pressure shaft seal steam supply pipeline 14, a drainage bag 16 is arranged at the low position of the pipeline, the steam is subjected to secondary dehydration by the drainage bag 16 and then is supplied to a low-pressure shaft seal 21, and the drainage collected by the drainage bag 16 is discharged into the drainage flash tank 5 through the steam trap 18 and the pipeline. The steam temperature is interlocked with the opening degree of the water spray regulating valve 4 through the thermocouple 15, and the water spray quantity is regulated to ensure that the steam supply temperature of the shaft seal after water spray reaches a preset value.

(2) In the self-sealing stage of the unit, steam leaks from the high-medium pressure shaft seal to the main shaft seal pipe 11, then the steam is supplied to the low-pressure shaft seal 21 through the water spray desuperheater 7, and the rest is consistent with the starting stage.

(3) If the unit operation condition deviates from the design condition, the drainage quantity is increased or the opening of the water spray regulating valve 4 is smaller, the regulating performance is not good, the opening of the stop valve 13 in front of the orifice plate is regulated, so that the drainage through-flow capacity is increased or the steam leakage quantity is increased to enable the regulating valve and the nozzle 6 to work in the best state, the front-back pressure difference of the stop valve 13 in front of the orifice plate is reduced by the orifice plate 20, the flow rate is accurately regulated, and the regulation and control capacity and the adaptability of the system are enhanced.

According to the invention, by arranging the water spraying temperature reduction system, the pressure of the shaft seal heater 2 is about 95kPa.a and the corresponding hydrophobic temperature is about 98 ℃ from the water spraying temperature reduction mechanism, the water spraying temperature after the condensation pump can be fully raised to be close to the saturated state (relative to the shaft seal steam supply pressure: 130kPa.a), the heat exchange time with steam is reduced, the influence of the arrangement space on the normal heat exchange straight section is compensated, and the insufficient residence heat exchange time caused by too short time is compensated; the thermodynamic property of the temperature-reducing water can be improved, the surface tension of the cooling water is reduced, and the atomization of the nozzle 6 is facilitated;

the inclined straight section of the rear pipeline 8 of the desuperheater is set to be not less than 5m, and the inclined angle is limited; the heat exchange residence time is effectively ensured for the steam flow rate control, and the heat exchange problems that water is wrapped in steam due to overhigh flow rate in the pipe and water drops cannot be supported due to overlow flow rate and meet the wall for converging are also prevented;

the invention inclines the pipeline slope of the pipeline 8 behind the desuperheater towards the direction of the steam-water separator 9 (the direction far away from the main shaft seal pipe 1), changes the direction of supplying steam source to the main shaft seal pipe 1 by the conventional drainage slope, prevents drainage from flowing back to the high-temperature shaft seal pipeline of the high and medium pressure cylinder to leak steam, and avoids the safety problems of metal material fatigue, pipeline bulging, welding seam cracking and the like caused by overlarge thermal stress of the pipeline and periodic alternating stress.

The steam-water separator 9 and the drain bag 16 are arranged, so that secondary dehydration is realized, and the phenomenon that water is carried in steam supplied by the low-pressure shaft seal 21 is effectively prevented; the bypass pipeline, the steam trap front stop valve 10 and the separator steam trap 11 which are arranged on the bypass pipeline are matched with each other to perform micro-adjustment on the drainage quantity and the steam flow after temperature reduction, so that the drainage quantity is matched with the operation working condition, and the temperature reduction nozzle 6 can be in the optimal working state.

The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.