JPH05125908A - Water induction protector for steam turbine - Google Patents

Abstract

PURPOSE:To provide a protector capable of completely preventing water induction caused by a feed water heater. CONSTITUTION:Temperature detectors 11, 12 are disposed in the vicinity of an extraction steam inlet of a feed water heater 4 for heating water by turbine extraction steam and in the vicinity of an extraction steam outlet of an extraction steam pipe, respectively. Extraction steam valve controllers 13, 14 are provided for fully closing an extraction steam valve when a difference between temperatures in both the vicinities exceeds a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for avoiding water induction in which water flows backward from a feed water heater into a steam turbine in a steam turbine plant.

[0002]

2. Description of the Related Art Generally, in a steam turbine plant, a steam turbine drives a generator to generate electric power, and steam working in the steam turbine is condensed by a condenser to be supplied by a feed water heater. It is heated and supplied to the boiler.

That is, FIG. 7 is a system diagram of the feed water heater system, in which a steam turbine 1 is connected to a generator 3 by a shaft coupling 2, and the steam turbine 1 drives the generator 3 to rotate. Electric power is generated. On the other hand, the steam extracted from the middle stage of the steam turbine 1 is supplied to the feed water heater 4 as heating steam through the extraction pipe 5, and heat is exchanged with the feed water supplied through the water supply pipe 6 to heat the feed water. Done.

By the way, a surface contact type heat exchanger is usually used as the feed water heater, and a large number of heating thin tubes are arranged inside the main body, and the feed water passing through the thin tubes is outside the thin tubes. It is heated by extraction steam from. However, since the pressure of the feed water flowing in the thin tube is a high pressure of 200 to 300 kg / cm ² because it is necessary to send it against the steam pressure generated in the boiler, if the heating thin tube is damaged, The water supply spouts and leaks into the water supply heater from the damaged part with a tremendous force, and the water supply heater is filled with water and goes back to the bleed pipe 5 that guides the bleed air for heating, and then flows into the turbine to cause water induction. Can cause a great deal of damage to.

Further, due to damage to the partition plate between the desuper heater zone and the drain cooling zone of the feed water heater, the drain may flow into the desuper heater zone side and the drain may flow back into the turbine extraction side.

Therefore, the feed water heater 4 is provided with a drain level detector 7 for detecting the water level in the feed water heater, and provided in the bleed pipe 5 when the water level in the feed water heater exceeds a certain level. The extracted bleed valve 8 and the bleed check valve 9 are forcibly closed to prevent the feed water from flowing into the turbine,
Alternatively, measures such as constantly monitoring the temperature difference between the upper and lower turbine compartments are taken.

[0007]

However, in the case of monitoring the presence or absence of leakage of the supply water by the rise of the water level in the supply water heater, since the water level in the supply device itself is unstable, an erroneous signal is likely to occur and the supply of water is properly performed. If there is a problem such as not being able to monitor the leakage of the water, and if the drain level detector fails, the drain level adjusting valve malfunctions, and an excessive leak of the feed water heating pipe occurs at the same time, the backup is the turbine upper and lower casing temperature. Since only the difference is monitored, there is a risk of treatment delay, and there are problems such as insufficient plant reliability.

In view of the above points, the present invention has an object to obtain a water induction protection device for a steam turbine which can completely prevent water induction caused by the feed water heater.

[0009]

According to the present invention, temperature detectors are provided in the vicinity of the extraction inlet of a surface contact type feed water heater for heating the supply water by turbine extraction and in the vicinity of the extraction outlet of the extraction pipe. At the same time, a bleed valve control device is provided to fully close the bleed valve when the temperature difference between both parts exceeds a predetermined value. The second invention provides a level detector in the desuperheater zone of the vertical feedwater heater that heats the feedwater by turbine bleed air, and when the water level in the desuperheater zone exceeds a predetermined level A bleed valve control device is provided, which is operated by a signal from a detector and fully closes the bleed valve.

[0010]

When the feed water leaks into the feed water heater due to damage to the heating thin tube or the like, the temperature in the vicinity of the extraction inlet of the feed water heater decreases and the temperature difference from the extraction temperature in the vicinity of the extraction outlet increases. Therefore, when the temperature difference becomes equal to or higher than a predetermined temperature, the bleeding valve is fully closed to prevent the feed water from flowing back to the steam turbine. Further, when the water level in the desuperheater zone becomes higher than a predetermined level due to the leakage of the water supply, the water level is detected by the level detector, and the bleed valve is fully closed by the detection signal to prevent water induction.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. In the figure, the same parts as those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the feed water heater 4 is provided with a first temperature detector 11 for detecting the temperature inside the feed water heater 4 at its bleed inlet, and the bleed pipe 5 is equipped with a steam turbine 1 A second temperature detector 12 for detecting the extraction temperature is provided near the extraction port.

The temperature signals from both temperature detectors 11 and 12 are input to a temperature difference calculator 13 via signal cables 11a and 12a, respectively, and the difference between the two temperatures is calculated there. When this temperature difference becomes equal to or higher than the set temperature (40 ° C.), a control signal is input to the control device 14 so that the bleed valve 8 and the bleed check valve 9 are fully closed by the control device 14. There is.

However, during normal operation, the temperature of the extraction inlet of the feed water heater is substantially equal to the extraction temperature, and
There is almost no difference between the temperature detector 11 and the temperature detected by the second temperature detector 12, and the full closing signal of the extraction valve 8 is not output to the control device 14, and the extraction valve 8 normally operates. Control operation is performed.

Therefore, when the feed water leaks into the feed water heater due to damage to the heating thin tube or the like and the reverse flow of the feed water to the extraction pipe 5 starts, the temperature of the extraction inlet of the feed water heater 4 decreases, and the temperature thereof decreases. It is detected by the first temperature detector 11. Then, in the temperature difference calculator 13, a temperature difference of 150 to 200 ° C.
Is calculated, the bleed valve 8 and the bleed check valve 9 are fully closed via the control device 14.

That is, as shown in FIG. 2, when the bleed valve is not fully closed and the difference between the bleed air temperature and the temperature inside the feed water heater exceeds the set temperature during turbine reset, the bleed valve and the bleed check valve. Is fully closed, and the reverse flow of feed water to the steam turbine is reliably prevented. Moreover, by directly monitoring the flow of the feed water with the temperature, the delay of the detection time can be shortened, and the malfunction of the bleeding valve due to the erroneous signal can be prevented.

3 and 4 are views showing another embodiment of the present invention, in which the desuper heater zone 15 of the feed water heater is shown.
The temperature of is detected. That is, in the feed water heater 4, especially in the vertical feed water heater, the lower part thereof is the partition plate 1
It is divided into a drain cooling zone 17 and a desuperheater zone 15 by 6, and the temperature of the desuperheater zone 15 has a certain temperature difference from the heating steam temperature, that is, the extraction temperature in the extraction operation state from the turbine. Transition to.

Therefore, the above desuperheater zone 1
5, the temperature detector 18 is provided, and the temperature detected by the temperature detector 18 and the bleed air temperature detected by the temperature detector 12 provided in the bleed pipe 5 are calculated by the addition / subtraction calculator 19;
When the difference exceeds the set temperature set in the temperature setter 20, the relay 21 operates, and the bleed valve 8 and the bleed check valve 9 are automatically and forcibly closed by the relay 21. In the figure, reference numeral 22 is a level controller, and 23.
Is a level switch, 24 is a drain level adjusting valve, and 25 is a drain pipe.

However, when the heating thin tube or partition plate of the feed water heater is damaged and the feed water or the drain flows into the de super heater zone 15 side, the temperature of the de super heater zone 15 is lowered and the heating steam is heated. The temperature difference from the temperature increases. Then, when this temperature difference becomes equal to or larger than the set value of the normal temperature difference + α of the feed water heater, the relay 21 is activated because water has flowed into the desuperheater zone 15, and the bleed valve 8 and the bleed check valve are operated. 9 is forcibly closed, preventing the occurrence of water induction.

That is, as shown in FIG. 4, when the bleed valve is open, and the temperature difference between the bleed temperature and the temperature inside the desuperheater zone of the feedwater heater is equal to or higher than the set temperature during turbine reset, The extraction valve and the extraction check valve are closed.

FIGS. 5 and 6 are views showing still another embodiment of the present invention, in which a water level gauge 26 and a level switch 27 are provided in the desuper heater zone 15 of the feed water heater 4.

However, if the water level in the desuperheater zone 15 becomes higher than a predetermined level, that is, a certain level below the inlet of the heated steam, due to some accident, the level switch 27 is activated and the relay 21 is activated. Two
By the operation of 1, the bleed valve 8 and the bleed check valve 9 are forcedly closed.

Desuper heater zone 1 of feed water heater
In No. 5, during normal operation, since the relevant part is in a heated state and water is not evaporated, the rise in the water level at that part indicates that damage to the heating thin tube, partition plate, etc. has occurred. Conceivable.

In this embodiment, therefore, the rise of the water level in the desuperheater zone 15 is directly detected to detect the damage of the heating thin tube and the partition plate, and the bleeding valve and the like are fully closed. Therefore, it is possible to completely prevent the water induction that occurs due to the side of the feed water heater.

[0025]

As described above, according to the present invention, by detecting the difference between the extraction temperature and the temperature in the vicinity of the extraction inlet in the feed water heater, or the water level in the desuper heater zone, the feed water heater side Since it is designed to detect the occurrence of an abnormality, the time when the feed water actually starts to flow backward in the bleed pipe or the state immediately before that can be detected immediately by temperature change or water level change, and the water induction of the steam turbine can be reliably prevented. be able to. Moreover, unlike the control based on the drain water level, the extraction valve does not malfunction, and the steam turbine can be operated stably.

[Brief description of drawings]

FIG. 1 is a system diagram showing a schematic configuration of a water induction protection device of the present invention.

FIG. 2 is an operation block diagram of the apparatus shown in FIG.

FIG. 3 is a schematic configuration diagram of another embodiment of the present invention.

4 is an operation block diagram of the apparatus shown in FIG.

FIG. 5 is a schematic configuration diagram of still another embodiment of the present invention.

6 is an operation block diagram of the apparatus shown in FIG.

FIG. 7 is a system diagram of a conventional feed water heater unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam turbine 3 Generator 4 Feed water heater 5 Extraction pipe 8 Extraction valve 9 Extraction check valve 11 Temperature detector 12 Temperature detector 18 Temperature detector 13 Temperature difference calculator 14 Controller 15 Desuperheater zone 16 Partition plate 17 Drain cooling zone 19 Adjusting calculator 21 Relay

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Matsuura 1-1-1 Shibaura, Minato-ku, Tokyo Inside Toshiba Head Office

Claims (2)

[Claims] 1. A temperature detector is provided in the vicinity of the extraction inlet of a surface contact type feed water heater that heats the supply water by turbine extraction, and in the vicinity of the extraction outlet of the extraction pipe. A bleed valve control device that fully closes the bleed valve when a predetermined value or more is provided,
Water induction protection device for steam turbines. 2. A level detector is provided in a desuperheater zone of a vertical feedwater heater for heating feedwater by turbine extraction, and the level detector is provided when the water level in the desuperheater zone exceeds a predetermined level. A water-induction protection device for a steam turbine, which is provided with a bleed valve control device that is actuated by a signal from the exhaust gas control device to fully close the bleed valve.