CN214577220U - Multi-steam-source shaft seal steam/gas supply system of power station unit - Google Patents
Multi-steam-source shaft seal steam/gas supply system of power station unit Download PDFInfo
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- CN214577220U CN214577220U CN202023273062.XU CN202023273062U CN214577220U CN 214577220 U CN214577220 U CN 214577220U CN 202023273062 U CN202023273062 U CN 202023273062U CN 214577220 U CN214577220 U CN 214577220U
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Abstract
一种电站机组多汽源轴封供汽/气系统，包括高压缸、中压缸、低压缸、轴封冷却器，疏水‑空气换热器、减温器、减温器，以及与缸体附属相连接的转子；所述的高压缸和中压缸进汽侧共用第一分支轴封供汽蒸汽，在轴封腔室完成密封后剩余的蒸汽经回汽管道手动阀进入轴封回汽母管；所述的高压缸和中压缸排汽侧共用第二分支轴封供汽蒸汽，在第二分支供汽管道上装设有减温器，减温器后进轴封体前安装有测量蒸汽温度的测点；所述的高压缸、中压缸及低压缸的所有轴封回汽汇集后进入轴封冷却器。本实用新型具有供汽多源化、参数匹配化、控制方式灵活、保护逻辑可靠、事故工况下自动跟踪的优点。
A multi-steam source shaft seal steam/gas supply system for a power station unit, comprising a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a shaft seal cooler, a drain-air heat exchanger, a desuperheater, a desuperheater, and a cylinder block Auxiliary connected rotors; the steam inlet side of the high-pressure cylinder and the medium-pressure cylinder share the first branch shaft seal for steam supply, and after the shaft seal chamber is sealed, the remaining steam enters the shaft seal return steam through the manual valve of the steam return pipeline Main pipe; the exhaust side of the high-pressure cylinder and the medium-pressure cylinder share the second branch shaft seal for steam supply, a desuperheater is installed on the second branch steam supply pipeline, and a measuring device is installed after the desuperheater enters the shaft seal body. The measuring point of steam temperature; all the shaft seal return steam of the high pressure cylinder, medium pressure cylinder and low pressure cylinder are collected and then enter the shaft seal cooler. The utility model has the advantages of multi-source steam supply, parameter matching, flexible control mode, reliable protection logic, and automatic tracking under accident conditions.
Description
Technical Field
The utility model relates to a steam turbine bearing seal system reforms transform technical field, in particular to many vapour sources bearing seal of power station unit supplies vapour/gas system.
Background
The turbine gland seal system is an important component of a steam turbine, and measures must be taken to prevent leakage of outside air or leakage of steam from the cylinder at the point where the turbine passes through the outer casing. In the high pressure section of the steam turbine, the function of the gland seal system is to prevent steam from leaking outwardly to ensure a higher efficiency of the steam turbine. In the low pressure area of the steam turbine, the function of the shaft seal system is to prevent outside air from entering the interior of the steam turbine, and to ensure that the steam turbine has as high a vacuum degree as possible and high efficiency of the steam turbine. The shaft seal system mainly comprises a sealing device, a shaft seal steam main pipe, a shaft seal heater and other equipment, and a corresponding valve and a pipeline system.
Taking a typical novel Ha steam supercritical C350 unit as an example, a shaft seal system is greatly improved, particularly for the novel unit with a high-medium cylinder and a separate cylinder design, the shaft seal temperatures of chambers of the high-medium cylinder and the medium-medium cylinder which need to be matched at a high load stage are different; in addition, in the process that the novel unit designed by the cylinders runs down after the unit is switched off in an extremely hot state, once the temperature of the shaft seal is improperly controlled, the unit vibrates obviously, even when the vibration value is close to a critical area, the vibration value reaches a full range (500 mu m), and great damage is caused to a shaft system in a long time. Therefore, an effective and reliable multi-steam-source shaft seal steam supply system is provided, and is of great importance for realizing the safety and reliability of the steam turbine set in the whole operation stage.
In order to ensure reliable and effective shaft seal steam supply, except that auxiliary steam and main steam adopted in a conventional thermal power generating unit are kept as shaft seal steam sources, a cold steam source for directly supplying the shaft seal is additionally arranged, and one path of compressed air is introduced to serve as an accident air source. Researches find that when a rotor idles to a position near a critical rotating speed after the turbine trips, the vibration of the whole shafting is aggravated by improper control of the steam supply temperature of the shaft seal, and even further the risk of locking the large shaft is caused. Therefore, once (extreme) hot trip occurs, rapid input of matched shaft seal steam supply parameters becomes a key factor.
Disclosure of Invention
In order to overcome the technical problem above, an object of the utility model is to provide a many vapour sources of power station unit bearing seal supplies vapour/gas system, this system have supply vapour many humanizations, parameter matching ization, control mode are nimble, protection logic is reliable, automatic tracking's under the accident operating mode advantage to obtain fine verification at on-the-spot practical application.
In order to achieve the above object, the utility model discloses a technical scheme with the beneficial effect of the utility model is:
a multi-steam-source shaft seal steam/gas supply system of a power station unit comprises a high-pressure cylinder I, an intermediate-pressure cylinder II, a low-pressure cylinder III, a shaft seal cooler IV, a hydrophobic-air heat exchanger V, a desuperheater A, a desuperheater B and a rotor which is connected with a cylinder body accessory;
the steam inlet side of the high-pressure cylinder I is provided with a rotor temperature T calculated by using the metal temperature of a cylinder body;
the steam inlet sides of the high-pressure cylinder I and the medium-pressure cylinder II share the first branch shaft seal for supplying steam, and the residual steam after the sealing of the shaft seal cavity is finished enters the shaft seal steam return main pipe through a manual valve of a steam return pipeline;
the high-pressure cylinder I and the medium-pressure cylinder II are arrangedThe steam side shares the second branch shaft seal steam supply, a desuperheater A is arranged on the second branch steam supply pipeline, a measuring point T for measuring the steam temperature is arranged behind the desuperheater A and in front of the shaft seal body1；
And all shaft seal return steam of the high-pressure cylinder I, the intermediate-pressure cylinder II and the low-pressure cylinder III is collected and then enters a shaft seal cooler IV.
The desuperheater A is characterized in that the desuperheater A is made of condensed water, a regulating valve 28 is arranged on a pipeline between the desuperheater A and the condensed water, a front manual valve I27 and a rear manual valve II 29 are respectively arranged at the front end and the rear end of the regulating valve 28, and a bypass manual valve III 30 is connected on the pipeline in parallel.
And the overflow steam of the shaft seal chamber of the high-pressure cylinder I is introduced into a four-pumping pipeline.
The shaft seal steam supply of the low-pressure cylinder III is from a shaft seal steam supply main pipe, a desuperheater B is installed before entering the low-pressure shaft seal, and a measuring point T for measuring the steam temperature is installed before a rear shaft seal body of the desuperheater B2。
The desuperheater B is characterized in that desuperheating water of the desuperheater B comes from condensed water, an adjusting valve 32 is arranged on a pipeline between the desuperheater B and the condensed water, a front manual valve IV 31 and a rear manual valve V33 are respectively arranged at the front and the rear of the adjusting valve 32, and a bypass manual valve VI 34 is arranged in parallel on the pipeline.
The steam source comprises an auxiliary steam supply shaft seal steam source, a main steam supply shaft seal steam source, a reheating cold section steam supply shaft seal steam source, an accident standby air source and shaft seal overflow which are arranged in parallel.
The auxiliary steam supply shaft seal steam source comprises a first inlet check valve 1, an electric valve 2 and a shaft seal steam supply regulating valve 4 which are sequentially connected through a pipeline, and a bypass electric valve 3 is arranged on the pipeline which is connected in parallel.
The main steam supply shaft seal steam source comprises a second inlet check valve 5, an electric valve 6 and a shaft seal steam supply regulating valve 7 which are sequentially connected through pipelines, meanwhile, a bypass electric valve 8 is arranged on the pipeline which is arranged in parallel, and a drain pneumatic valve 9 is connected on the pipeline of the bypass electric valve 8.
The reheating cold section steam supply shaft seal steam source comprises an inlet check valve III 10, an electric valve 11 and a shaft seal steam supply regulating valve 12 which are sequentially connected through a pipeline, and a bypass electric valve 13 is arranged on the pipeline which is arranged in parallel.
The emergency air source is from a compressed air main pipe, normal-temperature air in the compressed air main pipe enters the hydrophobic-air heat exchanger V through a check valve IV 19 and a pneumatic valve 20, and heated air is supplied to the shaft seal steam supply main pipe through a check valve V21, an electric valve 22 and an adjusting valve 23.
The high-temperature heat source of the hydrophobic-air heat exchanger V is from main steam for shaft seal drainage, the main steam enters the heat exchanger through a hydrophobic pneumatic valve 9, and the drained water after heat release is discharged to a condenser through a pneumatic valve 26; the hydrophobic-air heat exchanger V is provided with a bypass regulating valve 35; a branch is led out from the outlet pipeline of the hydrophobic-air heat exchanger V and is exhausted to the atmosphere through a pneumatic valve 24 and a throttling orifice plate 25; a branch led out from a V-shaped outlet pipeline of the hydrophobic-air heat exchanger is provided with a temperature measuring point T2。
The shaft seal overflow comprises an overflow regulating valve 15 and an electric valve 14 which are sequentially connected through a pipeline to form a first branch, and an overflow bypass electric valve 16 is arranged on the pipeline which is arranged in parallel to form a second branch; the first branch passes through an electric valve 17 to No. 7 low pressure heater, and the second branch passes through an electric valve 18 to a condenser.
A control method of a multi-steam-source shaft seal steam/gas supply system of a power station unit comprises the following steps;
a. in the starting stage of the unit, the cylinder is in a cold state, and auxiliary steam is adopted for shaft sealing; before supplying steam, the auxiliary steam pipeline is fully opened by draining water, the auxiliary steam is guaranteed to have superheat degree not less than 20 ℃, the shaft seal pressure is controlled by an auxiliary steam supply shaft seal adjusting valve 4, and the pressure set value is P0，P0The steam supply temperature T of the shaft seal is generally based on the specification of a manufacturer0Depending on the auxiliary steam temperature, | T-T is required in principle0The temperature is less than 110 ℃, wherein T is the metal temperature of the rotor calculated by using the cylinder temperature, and when the temperature T of the shaft seal steam at the steam exhaust end of the high and medium pressure cylinder is monitored1When the temperature of the rotor metal is far higher than T, the cooling water regulating valve 28 is opened to control the temperature; in the same way, the steam supply temperature T of the low-pressure shaft seal2When the temperature exceeds the required limit value of the equipment manufacturer, the cooling water adjusting valve 32 is opened to control the temperature, and the shaft seal adjusting valve 12 and the main shaft are supplied with cold again at the stageThe steam supply shaft seal adjusting valve 7, the emergency air adjusting valve 23 and the shaft seal overflow adjusting valve 15 are all in a closed state.
b. In the stage that the unit mesh belt is not higher than 25% of Pe (Pe is rated load), the temperature of the cylinder is gradually increased, the bypass system is completely closed, the cold pressure and the temperature are gradually increased, and because the cold steam comes from the steam exhaust of the high-pressure cylinder I, the metal temperature of the cylinder body can be better matched, the shaft seal steam supply is gradually switched from the auxiliary steam to the cold steam supply in the stage, and the pressure P of the main pipe of the shaft seal is higher than the pressure P of the main pipe of the shaft seal0The pressure P is controlled by the cold re-supply shaft seal pressure adjusting valve 12 determined by the overflow steam and the cold re-supply steam of the high pressure cylinder shaft seal chamber0The auxiliary steam supply shaft seal adjusting valve 4 is automatically withdrawn, manually and gradually closed to 3% of opening degree, the minimum valve limit (namely 3%) of the auxiliary steam supply shaft seal adjusting valve 4 is limited in logic, the full load section of the pipeline is ensured to be in a hot state, the main steam supply shaft seal adjusting valve 7, the emergency air adjusting valve 23 and the shaft seal overflow adjusting valve 15 are all in a closed state in the stage, and the shaft seal steam supply temperature T is higher than the normal temperature T0Depending on the cold re-steam temperature, the strategy is adjusted as in step a;
c. when the load of the unit is higher than 25% Pe, the shaft seal system gradually turns into a self-sealing state, the shaft seal steam supply regulating valve 12 is cooled and then gradually closed along with the rise of the load, the automatic closing is stopped after the full closing, at the moment, the shaft seal overflow regulating valve 15 and the shaft seal overflow to the No. 7 low-voltage electric valve 17 need to be manually opened, and the pressure setting value of the shaft seal overflow regulating valve is set to be 1.25P0When the No. 7 low pressure addition is abnormal in the operation process, the shaft seal overflow steam is switched to the condenser, and when the shaft seal pressure reaches the self-sealing stage, the shaft seal temperature T of the high-medium pressure cylinder is higher than the shaft seal temperature T of the medium-pressure cylinder1Without adjustment, the low-pressure shaft seal temperature T2The steam is supplied by the overflow steam of the high and medium pressure shaft seal chamber, at the moment, the low pressure shaft seal temperature-reducing water regulating valve 32 is required to be put in, the temperature of the regulating valve is set to be a given value of a manufacturer, generally 121-177 ℃, the main steam shaft seal regulating valve 7 is put in automatically after the cold re-supply shaft seal regulating valve 12 is closed, and the pressure set value is 0.85P0The auxiliary steam supply shaft seal adjusting valve 4 is manually kept at 3 percent of opening, the emergency air adjusting valve 23 is closed, and the shaft seal overflow adjusting valve 15 is utilized to maintain the pressure P of the shaft seal main pipe0The main steam is kept to be fully opened for the drain valve 9 before the shaft seal is adjusted;
d. when the steam turbine set is in abnormal working conditions such as (extreme) hot trip or load shedding, the shaft seal system is instantaneously changed from a self-sealing state to a cavity vacuum state, and the pressure P of a main pipe of the shaft seal0The pressure of the main steam supply shaft seal pressure adjusting valve 7 automatically tracks the steam supply pressure after the pressure is rapidly reduced to negative pressure, and the pressure is set to be 0.85P0Gradually and manually increasing the set value to P after the main steam tracking is normal0At this time, the auxiliary steam supply shaft seal adjusting valve 4 is manually controlled, and the shaft seal steam supply temperature T is manually adjusted0The shaft seal temperature control aims at the temperature before the tripping of the unit, meanwhile, the shaft seal overflow regulating valve 12 is completely closed in an overriding way, when the instruction of the overflow regulating valve 12 is less than 3 percent, the shaft seal overflow electric valve 11 and the bypass electric valve 13 are triggered to be closed in a linkage way, meanwhile, the standby steam supply regulating valve 23 for compressed air accidents is ensured to be in a manual completely closed state, the shaft seal steam supply regulating valve 12 is cooled again, and the front drainage pneumatic valve 9 of the main steam supply shaft seal regulating valve is in a fully opened state;
e. for the extreme hot starting working condition, the main steam supply shaft seal adjusting valve 7 is maintained to be automatic in principle, the shaft seal steam supply pressure is controlled, and the target pressure fixed value P0The auxiliary steam supply shaft seal adjusting valve 4 is manual to control the shaft seal steam supply temperature (T)0) The temperature range is controlled to be 320-450 ℃, the specific temperature constant value is based on the principle of matching the cylinder temperature, and the absolute value of T-T is required0< 110 ℃ where T0Supplying the temperature of a main pipe of the shaft seal with steam, wherein T is the metal temperature of the rotor calculated by using the cylinder temperature;
f. under the condition that the steam source of the shaft seal of the unit is completely supplied in an off-line manner, a standby compressed air source is manually put in, the steam supply pressure of the shaft seal is controlled by a compressed air accident standby air supply regulating valve 23, and the fixed pressure value is set as P0Controlling the temperature of compressed air by using a hydrophobic-air heat exchanger V, wherein the temperature of the compressed air for shaft seal control is targeted at a temperature value before tripping of the unit and ranges from 320 ℃ to 450 ℃;
the drain-air heat exchanger completes surface heat exchange by utilizing high-temperature steam drained by a main steam pipeline and compressed air, drained drain after heat release is discharged to a condenser through a pneumatic valve 26, and a bypass adjusting valve 3 of the drain-air heat exchanger is introduced to ensure that air at a V outlet of the drain-air heat exchanger is always kept at a required high temperature (320-450 ℃), so that5, which in the standby state always tracks the post-emergency exhaust valve temperature T3When the air supply and adjustment valve 23 for spare air for accident is closed, the discharge valve 24 for spare air for accident is opened in an interlocking manner, the spare air for accident is discharged to the atmosphere through the throttle orifice with the diameter phi 5, and when the air supply and adjustment valve 23 for compressed air spare air for accident is opened, the discharge valve 24 for spare air for accident is closed in an interlocking manner.
The utility model has the advantages that:
1) the shaft seal supplies diversified steam sources, and except the conventional auxiliary steam and main steam, cold re-steam is also introduced, in particular one path of compressed air is introduced innovatively as an accident standby air source.
2) By utilizing the high-temperature hydrophobic characteristic of the main steam and exchanging heat with the emergency air source, the problem of temperature matching of the emergency air source is solved, the temperature of the hydrophobic condenser is reduced, and the energy is saved.
3) In order to facilitate the control of the temperature of the accident air source, a bypass regulating valve of a hydrophobic-air heat exchanger is added, and a temperature measuring point T is added to an accident exhaust gas pipeline3。
4) The accident discharge gas pipeline is additionally provided with a throttle orifice plate with the diameter of 5mm, so that the compressed air after heat exchange is ensured to be in a flowing state, and the hot air is prevented from carrying water; and the discharge amount of the spare gas for accidents is reduced to the maximum extent.
5) The system can meet the steam supply requirement of the shaft seal in the normal operation of the unit from the normal start to the full-load operation stage, and increases the steam supply of the shaft seal under the accident working conditions of unit (pole) hot trip, (pole) hot start and full loss of a steam source of a whole plant.
6) The system is simple, easy to operate and high in automation degree. The steam supply pressure of the shaft seal is automatically controlled in all stages, and particularly can be intervened to operate in the first time under the accident condition.
7) Steam supply parameters are better matched with the temperature of a steam turbine cylinder. The shaft seal steam supply temperature considers different control requirements of cold state, temperature state and (extreme) hot state under the accident state, and the risk of aggravation of rotor vibration caused by mismatching of the shaft seal temperature is avoided.
Drawings
Fig. 1 is a schematic flow chart of the present invention.
Wherein, I is a high pressure cylinder, II is an intermediate pressure cylinder, III is a low pressure cylinder, IV is a shaft seal cooler, V is a hydrophobic-air heat exchanger, A is a high and intermediate pressure shaft seal steam supply desuperheater, B is a low pressure shaft seal steam supply desuperheater, 1, 5, 10, 19 and 21 are check valves, 27, 29, 30, 31, 33 and 34 are hand valves, 2 is an auxiliary steam supply shaft seal steam inlet electric valve, 3 is an auxiliary steam supply shaft seal bypass electric valve, 4 is an auxiliary steam supply shaft seal regulating valve, 6 is a main steam supply shaft seal steam inlet electric valve, 7 is a main steam supply shaft seal regulating valve, 8 is a main steam supply shaft seal bypass electric valve, 9 is a main steam supply shaft seal pipeline pneumatic hydrophobic valve, 11 is a reheat cold section steam supply shaft seal inlet electric valve, 12 is a reheat cold section steam supply shaft seal regulating valve, 13 is a reheat cold section steam supply shaft seal bypass electric valve, 14 is a shaft seal overflow electric valve, 15 is an overflow regulating valve, 16 is a shaft seal overflow bypass electric valve, 17 is a shaft seal overflow to No. 7 low-voltage electric valve, 18 is a shaft seal overflow to condenser electric valve, 20 is a compressed air to hydrophobic-air heat exchanger air inlet pneumatic valve, 22 is a compressed air accident standby air source supply shaft seal electric valve, 23 is a compressed air accident standby air source supply shaft seal adjusting valve, 24 is a compressed air accident standby air source air exhaust pneumatic valve, 25 is a throttle orifice plate of phi 5, 26 is a hydrophobic-air heat exchanger hydrophobic to condenser electric valve, 28 is a condensed water to high and medium pressure shaft seal temperature reduction water adjusting valve, 32 is a condensed water to low pressure shaft seal temperature reduction water adjusting valve, and 35 is a hydrophobic-air heat exchanger hydrophobic bypass adjusting valve.
In addition, a measuring point P for measuring the pressure and the temperature of the main pipe is arranged on the main pipe of the shaft seal steam supply pipe0、T0A measuring point T for measuring the shaft seal temperature of the high and medium pressure cylinders is arranged behind the desuperheater nozzle (A)1A measuring point T for measuring the shaft seal temperature of the low pressure cylinder is arranged behind the desuperheater nozzle (B)2A temperature measuring point T is arranged behind an air side outlet accident discharge valve of the hydrophobic-air heat exchanger3And simultaneously, a measuring point T for representing the metal temperature of the rotor in a turbine monitoring system (TSI) is quoted.
The method comprises the following steps of firstly, indicating auxiliary steam, secondly, indicating main steam, thirdly, indicating steam from a reheating and cooling section, fourthly, indicating steam to a condenser, fifthly, indicating steam to a position of 7, sixthly, indicating steam from condensed water, seventhly, indicating a four-pumping pipeline and eighthly, indicating steam from a compressed air main pipe.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, a conventional thermal power generating unit includes high pressure cylinder I, intermediate pressure cylinder II and low pressure cylinder III, and the position that the rotor passed the cylinder in the unit operation process forms sealedly, the utility model discloses set up three routes external steam supply altogether, first way is from supplementary steam to come vapour through check valve 1, motorised valve 2, governing valve 4 and get into the shaft seal and supply the main pipe of vapour, and for the guarantee system is reliable, this pipeline configuration parallelly connected bypass motorised valve 3; the second path of main steam enters a shaft seal steam supply main pipe through a second check valve 5, an electric valve 6 and a regulating valve 7, and the pipeline is provided with a parallel bypass electric valve 8 for ensuring the reliability of the system; and a third path of self-reheating steam cold section enters a shaft seal steam supply main pipe through a check valve III 10, an electric valve 11 and a regulating valve 12, and the pipeline is provided with a parallel bypass electric valve 13 for ensuring the reliability of the system. Except the normal vapour source of above-mentioned three routes, the utility model discloses still very much increase compressed air all the way as the reserve air supply of accident. The air from the compressed air main pipe enters the hydrophobic-air heat exchanger V through the check valve IV 19 and the air inlet pneumatic valve 20, and the air after heat exchange enters the shaft seal steam supply main pipe through the check valve V21, the electric valve 22 and the regulating valve 23. In order to ensure that the compressed air in the hydrophobic-air heat exchanger V is always in a heat flowing state, an external discharge pipeline is led out of the heated compressed air in front of the check valve of the main intake pipeline, and the hot air in the pipeline is discharged into the atmosphere through a pneumatic valve 24 and a throttling orifice plate 25 with the diameter phi 5. A heat source in the drainage-air heat exchanger V leads main steam to supply a shaft seal pipeline for drainage, the main steam enters the heat exchanger from the upper part through a drain valve 9, and the main steam is led out from the lower part and is discharged into a condenser through a drain valve 26.
The steam (gas) entering the shaft seal main pipe is directly fed into the steam inlet ends of the high-pressure cylinder I and the medium-pressure cylinder II through the first branch, the second branch is fed into the steam exhaust ends of the high-pressure cylinder I and the medium-pressure cylinder II through the desuperheater A, and the third branch is fed into the steam exhaust ends of the two sides of the low-pressure cylinder III through the desuperheater B. And the shaft seal return steam finally enters a shaft seal cooler IV through a return steam main pipe, wherein the high-pressure side shaft of the high-pressure cylinder I is sealed and leaks steam to enter a four-pump pipeline. The desuperheating water of the high and medium pressure cylinder shaft seal desuperheater A comes from condensed water and enters a nozzle of the desuperheater A through a desuperheating water adjusting valve 28, a first front manual valve 27 and a second rear manual valve 29, and a third bypass manual valve 30 is arranged on the pipeline; the desuperheater water of the low-pressure cylinder shaft seal desuperheater B also comes from condensed water and enters a nozzle of the desuperheater B through a desuperheater water adjusting valve 32, a front manual valve four 31 and a rear manual valve five 33, and a pipeline is provided with a bypass manual valve six 34.
The utility model discloses keep conventional supplementary steam and main steam outside as the main vapour source of bearing seal, newly increased the vapour source that cold steam directly supplied the bearing seal again, the introduction of novelty is compressed air all the way as the reserve air supply of accident simultaneously. In order to better realize the matching of the emergency standby air source and the metal temperature of the shaft seal cavity, a drainage-air heat exchanger is arranged, a main steam supply shaft seal pipeline is specially modified for drainage, and high-temperature drainage is utilized to heat compressed air so as to achieve the proper air supply temperature. The system meets the requirements of safe, reliable and efficient energy-saving operation in the full operation stages of starting the unit, grid-connected self-sealing of the shaft seal with low load and high load, load shedding or (extreme) thermal accident tripping, accident state of losing all steam sources of the shaft seal and the like. The system has the advantages of multiple steam supply, parameter matching, flexible control mode, reliable protection logic, automatic tracking under accident conditions and the like, and is well verified in field practical application.
a. In one embodiment, taking the novel Ha steam C350 unit as an example, in the starting stage of the unit, auxiliary steam is adopted for shaft sealing, and the pressure P of a shaft sealing main pipe is set by using an auxiliary steam supply shaft sealing adjusting valve 40Automatic, according to manufacturer's requirements, P024.1 kPa. Shaft seal steam supply temperature T0Depending on the temperature of the auxiliary steam, the temperature T of the steam supply of the shaft seal of the low-pressure cylinder is controlled by automatically putting the shaft seal desuperheating water of the low-pressure cylinder into the low-pressure cylinder2The temperature of the shaft seal of the high and medium pressure cylinders is not adjusted between 121 ℃ and 177 ℃. In the stage, the shaft seal adjusting valve 12 for cold re-supply, the shaft seal adjusting valve 7 for main steam supply, the emergency air adjusting valve 23 and the shaft seal overflow adjusting valve 15 are all in a closed state.
b. In one implementation, the unit does not have more than 25% Pe (Pe is the amount of net)Constant load) stage, the shaft seal steam supply is gradually switched from auxiliary steam to cold steam supply. The pressure value of the cold re-supply shaft seal adjusting valve 12 is set to be 1.15P0I.e. (27.7kPa), and put into automation. The auxiliary steam supply shaft seal adjusting valve 4 automatically exits, and is manually and gradually closed to 3% of opening, so that the full-load section of the pipeline is ensured to be in a hot state. In this stage, the main steam supply shaft seal adjusting valve 7, the emergency air adjusting valve 23 and the shaft seal overflow adjusting valve 15 are all in a closed state. Shaft seal steam supply temperature T0The strategy is adjusted to step a depending on the cold re-steam temperature.
c. In one embodiment, the shaft seal system is progressively transitioned to a self-sealing condition when the unit load is greater than 25% Pe. When the shaft seal steam supply adjusting valve 12 is cooled again and is gradually closed, the shaft seal automatic flow adjusting valve is automatically withdrawn, the shaft seal overflow flow adjusting valve 15 is opened, and the shaft seal overflows to the No. 7 low-voltage electric valve 17. The pressure setting value of the shaft seal overflow regulating valve is set to be 1.25P0(30.1 kPa), and when the No. 7 low pressure addition is abnormal in the operation process, the shaft seal overflow steam is switched to a condenser. When the shaft seal reaches the self-sealing stage, the shaft seal temperature T of the high and medium pressure cylinders1Without adjustment, the low-pressure shaft seal temperature T2And adding temperature-reducing water, and controlling the temperature to be 121-177 ℃. When the cold re-supply shaft seal adjusting valve 12 is completely closed and automatically quits, the main steam supply shaft seal adjusting valve 7 is automatically put into operation, and the pressure set value is 0.85P0(20.5 kPa), the auxiliary steam is supplied to the shaft seal adjusting valve 3 to keep the manual position with 3 percent of opening degree, the emergency air adjusting valve 23 is closed, and the shaft seal overflow adjusting valve 15 is used for maintaining the pressure P of the shaft seal main pipe0And (4) stabilizing and keeping the drain valve 9 fully opened before main steam is supplied to the shaft seal adjusting valve.
d. In one implementation, when the steam turbine set trips in the (extreme) hot state, the shaft seal system is instantaneously changed from the self-sealing state to the cavity vacuum state, the shaft seal overflow regulating valve 15 is completely closed in an overriding mode, and the overflow regulating valve instruction is less than 3% to trigger the shaft seal overflow electric valve 14 and the bypass electric valve 16 to be closed in an interlocking mode. The main steam supply shaft seal adjusting valve 7 automatically tracks the steam supply pressure, and the pressure set value is 0.85P0(i.e., 20.5kPa), gradually increasing the set point manually to P after the main steam tracking is normal0(i.e., 24.1 kPa). Manually controlling the auxiliary steam supply shaft seal adjusting valve 4 to adjust the shaft seal steam supply temperature T0，T0The temperature before tripping of the unit is targeted. Andmeanwhile, the standby accident air adjusting valve 23, the shaft seal air supply adjusting valve 12 after cooling are in a manual full-closed state, and the main steam air supply shaft seal adjusting valve front drainage pneumatic valve 9 is in a full-open state.
e. In one implementation, for an extreme hot starting working condition, the front hydrophobic pneumatic valve 9 of the main steam supply shaft seal regulating valve is kept fully opened, the main steam supply shaft seal regulating valve 7 is maintained to be switched automatically, and the target pressure setting value is set to be P0(24.1 kPa), the auxiliary steam supply shaft seal adjusting valve 4 is manually operated to adjust the shaft seal steam supply temperature T0The temperature range is controlled to be 320-450 ℃, and the specific temperature fixed value is based on the principle of matching the cylinder temperature. Satisfy | T-T0< 110 ℃ where T0And supplying the temperature of a main pipe of the shaft seal with steam, wherein T is the metal temperature of the rotor calculated by using the cylinder temperature.
f. In one embodiment, in the case of full-off supply of the shaft seal steam source of the unit, the emergency air regulating valve 23 is manually opened, and the pressure setting value is set to be P0(i.e., 24.1kPa), the emergency backup air release valve 24 is interlocked and closed after the emergency backup air adjustment valve 23 is fully opened. The temperature of the emergency backup air is controlled by the aid of the drain-air heat exchanger V and the bypass adjusting valve 35, and the temperature of the compressed air for shaft seal temperature control is controlled by taking the temperature value before tripping of the unit as a target, and ranges from 320 ℃ to 450 ℃.
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