JPS5867909A - Warming-up device for steam turbine - Google Patents

Abstract

PURPOSE:To prevent liquefaction of residual steam by furnishing a residual steam exhaust pipeline, which is to exhaust the steam remaining in the turbine casing, between the steam room and the condenser. CONSTITUTION:A hole d is bored in the high-pressure external casing 24 forming part of steam room 27, and a exhaust pipe 30 for the warming-up steam is connected to this hole d. This exhaust pipe 30 is connected to the condenser 8 through a exhaust valve 31. According to this arrangement, opening the exhaust valve 31 immediately after completion of warming-up will permit the steam to go out to the condenser 8 from the steam room 27. Accordingly, there is no risk of causing condensation of the steam remaining in the steam room 27 after completion of warming-up, contributing to prevention of deformation of a casing due to flush of the residual steam.

Description

[Detailed description of the invention] The present invention relates to a warm-up device for a steam turbine.

In large-capacity steam turbines, high-temperature steam of 500° C. or higher is widely used as main steam. When such high-temperature steam is used, there is a large difference between the temperature of the metal parts of the turbine and the steam temperature during cold startup, so
There is a risk of generating excessive thermal stress and damaging the equipment.

Particularly in the high-pressure turbine located in the main steam introduction section, the above-mentioned temperature difference is large, and the rotor of the high-pressure turbine is subjected to centrifugal stress and thermal stress, which may cause cracks to occur on the rotor surface.

To prevent damage caused by thermal stress as described above,
When starting the cold machine, it is warmed up in advance.

This is an operation in which heating steam is sent from the auxiliary steam system to the high-pressure turbine while turning the rotor before startup, and the rotor of the high-pressure turbine is heated to a specified temperature.

FIG. 1 is a system diagram of a reheat steam turbine plant equipped with a high-pressure turbine warm-up mechanism, and FIG. 2 is a longitudinal sectional view of the high-pressure turbine.

(See Figure 1) During normal operation, main steam generated in the boiler 5 passes through the main steam stop valve 3, the main steam system 15, and the control valve 4, flows into the high-pressure turbine 1, performs work, and then It flows into the reheater 6 via the high-pressure exhaust port 13 and the low-temperature reheat system 16. The steam heated in the reheater 6 is supplied to an intermediate pressure turbine (not shown) to perform work through a high temperature reheat system 17 and a reheat steam stop valve 12, and then flows into the low pressure turbine 2 to perform work. and is collected in the condenser 8.

On the other hand, in order to warm up the high-pressure turbine 1 before starting the cold engine, the condenser 8 is operated to vacuum the inside of the turbine.
The warm-up valve 9 provided in the warm-up air system 11 rotates the rotor at a low speed by turning, and the steam control valve 4 is opened.
is opened, and warm-up steam 29 is sent from the auxiliary steam header 7 to the high-pressure exhaust port 13 of the high-pressure turbine 1 via the low-temperature reheat system 16.

The warm-up steam 29 that has flowed into the high-pressure exhaust port 13 flows through the high-pressure turbine 1 and heats the high-pressure turbine. That is, (see Fig. 2), the warm-up steam 29 heats the high-pressure rotor 20 while flowing from the high-pressure exhaust port 13 through the high-pressure exhaust chamber 28 and along the high-pressure rotor 20 in the direction of the arrow. 4
flows out from (See FIG. 1) The warm-up steam flowing out of the control valve 4 flows into the condenser 8 via the main steam system 15, the main steam drain valve 10, and the main steam drain pipe 18.

(See Figure 2) A part of the warm steam 29 that has passed through the rotor 20 of the high-pressure turbine passes through the gap between the first-stage blades 21 and the first-stage nozzle 22, and is transferred to the high-pressure rotor 20 and the high-pressure inner casing 23. It flows into the steam chamber 27 through the gap between the gland packing 26 and the rotor. This steam chamber 27 is a space surrounded by a high-pressure inner compartment 23, a high-pressure outer compartment 24, and a partition wall 25.

Gap e between the high-pressure inner casing 23 and the high-pressure outer casing 24
Generally, the steam chamber 27 is designed to be as narrow as possible within the scope of its construction, so that the steam that has flowed into the steam chamber 27 remains stagnant within the same chamber.

゛ The steam used for warming up is usually supplied from other units operating within the same power plant, and is temporarily stored in the auxiliary steam header 7 (Figure 1) for use, and its optimal steam conditions are enthalpy 705 Kcal 7Kg It is said to be before and after. and warm-up valve 9 and main steam drain valve 10.10
The inside of the high pressure turbine 1 is approximately 5Kg/cm2 by adjusting the opening degree.
It is adjusted so that it is pressurized around g and is sent to the high-pressure turbine 1.

The progress of warm-up is monitored by a thermometer (not shown) provided after the high-pressure first stage, and normally, when this temperature reaches 150° C. or higher, warm-up valve 9 is closed to stop the supply of warm steam.

After the warm-up is completed as described above, the steam in the high-pressure turbine 1 is discharged to the condenser 8 via the control valve 4, the main steam drain valve 10, and the main steam drain pipe 18. Further, residual steam in the low-temperature reheat system 16 and the high-temperature reheat system 17 is discharged to the condenser 8 via the reheat drain valve 14 and the reheat drain pipe 19.

In the warm-up according to the conventional technology described above (see FIG. 2), after the warm-up is completed, the warm steam stagnant in the steam chamber 27 flows backward through the inflow path and passes through the gap e, and the warm steam stagnates in the steam chamber 27.
6 and the rotor 20, and between the first-stage blade 21 and the first-stage nozzle 22, and the discharge from the control valve 4 follows the route. The gap between this and the opposing rotor is 0.
Since it takes about 4 hours, the discharge of warm residual steam does not proceed quickly.

Due to the structure of the turbine, the volumes of the high-pressure inner casing 23 and the high-pressure outer casing 24 are significantly larger than that of the high-pressure rotor 20, so that the rate of temperature rise during warm-up is slow.

Therefore, when the warm-up operation is completed, the high-pressure interior and the exterior compartment 23.
24 hasn't warmed up completely yet. For this reason, steam room 2
There is a possibility that the warm steam remaining in the tank 7 will be cooled down by losing heat in the high-pressure interior and the outer compartment 23, 24, and some of it will turn into water droplets.

Also, as mentioned above, warm steam has an enthalpy of 705Kc.
Superheated steam around al/Kg is said to be desirable, but
Since warm steam is supplied from another unit, it is not always possible to obtain superheated steam under optimal conditions, and saturated steam may be supplied.

In such a case, some of the stagnant steam in the steam chamber 27 liquefies and accumulates in the steam chamber 27 even during warm-up operation.

If liquid water accumulates in the steam chambers 2 and 7 during warm-up due to the above-mentioned circumstances, it will flash when the steam is discharged from the control valve 4 upon completion of warm-up, and the latent heat of vaporization will be taken away. Cools the rotor to reduce the warming effect.

In addition, even if liquid water does not accumulate in the steam chamber 27 during warm-up operation, if residual steam in the steam chamber 27 liquefies after warm-up due to the above-mentioned circumstances, it will flash when the turbine is started, resulting in high pressure. The portions of the inner and outer compartments 23, 24 that are in contact with the steam chamber 27 are locally cooled, causing adverse effects such as deformation of the compartment.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and (a) prevent warm steam from remaining in the steam chamber to prevent the residual steam from liquefying, and φ) use saturated steam. It is desirable to provide a steam turbine warm-up device that can provide a sufficient warm-up effect even when warmed up.

In order to achieve the above object, the present invention provides a space between a steam chamber formed between an internal casing and an external casing of a steam turbine, and a condenser after the steam turbine is warmed up. The vehicle is characterized by being provided with a residual steam discharge pipe for discharging residual steam in the vehicle interior.

Next, an embodiment of the present invention will be described with reference to FIGS. 3 and 4.

FIG. 3 is a system diagram of a reheat steam turbine plant equipped with a high-pressure turbine warm-up mechanism according to the present invention, and corresponds to FIG. 1 in the conventional technology. FIG. 4 is also a longitudinal cross-sectional view of the high-pressure turbine, and corresponds to FIG. 2 in the prior art.

In FIGS. 3 and 4, the same drawing reference numbers as in FIGS. 1 and 2 indicate the same or similar components as in the conventional device.

In this embodiment, as shown in FIG.
Connect the warm-up steam exhaust pipe 3o to.

This warm-up steam exhaust pipe 3o is connected to the condenser 8 via a warm-up steam exhaust valve 31, as shown in FIG.

Since the present embodiment is configured as described above, when the warm-up steam discharge valve 31 is fully opened immediately after the warm-up is completed, the steam chamber 2
Residual steam in 7 is discharged to condenser 8. Therefore, there is no risk that the residual steam in the steam chamber 27 will liquefy after completion of warm-up, and deformation of the cabin due to flash of liquefied residual steam can be prevented.

In addition, if the warm-up steam has a low enthalpy and is saturated steam or steam in a state close to saturation, if the warm-up steam discharge valve 31 is opened during warm-up operation, the water liquefied in the steam chamber 27 will be discharged. Since the water is discharged to the condenser 8 and does not accumulate in the steam chamber 27, there is no possibility that the water in the steam chamber 27 will flash at the time of startup and reduce the warming effect.

In addition, when starting warm-up, the warm-up steam exhaust valve 31
By keeping the control valve 4 open, warm-up steam can be circulated into the high-pressure turbine 1 even when the control valve 4 is closed, and the pressurized state inside the high-pressure turbine 1 can be maintained by adjusting the opening of the warm-up steam discharge valve 31. It can be adjusted. Therefore, it is possible to omit the opening/closing operation of the control valve 4 and the opening/closing operation of the main steam drain valve 1o during warm-up operation, and it is also possible to simplify the operating operation.

As explained above, the present invention provides a residual steam exhaust pipe that connects a steam chamber formed between an internal casing and an external casing of a steam turbine, and a condenser. After the warm-up is completed, the residual steam in the cabin of the steam turbine can be promptly discharged, so that the warm-up effect can be maintained.

[Brief explanation of drawings]

Figure 1 is a warm-up system diagram of a high-pressure turbine in the conventional technology.
Fig. 2 is a vertical cross-sectional view of a conventional high-pressure turbine; Fig. 83 is a diagram of a high-pressure turbine warm-up system equipped with a steam turbine warm-up device according to an embodiment of the present invention; and Fig. 4 is a diagram of a high-pressure turbine warm-up system according to an embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view of such a high-pressure turbine.

Claims (1)

[Claims] 1. After the steam turbine has been warmed up, the steam turbine A steam turbine warm-up device characterized by being provided with a residual steam exhaust pipe for discharging residual steam in a vehicle compartment.