JPS63223403A - Feedwater-heater drain tank pressure controler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to a so-called feed water system which is configured to recover heat by guiding steam drain generated in a feed water heater to condensation and a water supply system. The present invention relates to a feedwater heater drain tank pressure control device attached to a turbine plant using a heater drain pump-up method.

(Prior art) In the regenerative cycle type nuclear turbine Plan I, a feed water heater, which is a type of heat exchanger, is used to heat the condensate or feed water flowing in the condensate system or feed water system with steam extracted from the steam turbine. or used. In this feedwater heater, steam drain produced by condensing the bleed air of the steam turbine described above or steam drain led from the upper stage feedwater heater is collected and used for heat exchange with condensed water or feedwater there. These steam drains (hereinafter referred to as feed water heater drains) are roughly divided into high-pressure systems where the pressure temperature is relatively high depending on the extracted steam pressure, and low-pressure systems where the pressure temperature is at a lower level. It was common for the feed water heater drain of the system to be disposed of in a condenser or the like after heat exchange was completed at the last feed water heater in the system. However, in recent years, a so-called feedwater heater drain pump-up method has been proposed and is attracting attention, in which heat is recovered from the feedwater heater drain at a location other than the feedwater heater after the heat has been recovered.

An example of this method will be described below with reference to FIG. That is, the steam extracted from the high pressure turbine 1 is passed through the extraction pipe 2.
The feed water is sent to the high pressure feed water heater 3 through the feed water pump 4 and heated and condensed. This feed water heater drain is led to the feed water heater drain tank 5 via a drain pipe 6 and stored there. A pressure equalizing pipe 7 is provided between the feed water heater drain tank 5 and the high pressure feed water heater 3 to balance the internal pressures of both so that the feed water heater drain flows smoothly into the feed water heater drain tank 5. I have to. The feedwater heater drain stored in the feedwater heater drain tank 5 is extracted via a drain downpipe 10 and a drain pump 11 while the water level is regulated by a control valve 9 controlled by a controller 8, and then transferred to a drain injection pipe. 12 into the condensate flowing through the condensate pipe 13. After this, the feedwater heater drain mixes with the condensate and increases its temperature,
The pressure is increased by the feedwater pump 4 to become feedwater, which is heated through the high-pressure feedwater heater 3 and then sent to the reactor 15 via the water supply pipe 14.
sent to. In addition to the above, the turbine plant includes a low-pressure turbine 16 that obtains power by further expanding the exhaust gas of the high-pressure turbine 1, and a low-pressure feed water heater 1 that heats condensate with steam extracted from the low-pressure turbine 16 through a bleed pipe 17.
8, a condenser for condensing turbine exhaust gas, and a condensate pump 20 for extracting condensate from the condenser and feeding it to the low-pressure system. In addition, the code 21
Reference numeral 22 indicates a steam control valve, reference numeral 22 indicates an intermediate steam stop valve, and reference numeral 23 indicates a generator.

(Problems to be Solved by the Invention) As described above, the feed water heater drain tank 5, which stores the feed water heater drain, is connected to the high pressure feed water heater 3 via the pressure equalizing pipe 7, so that the water pressure of the water heater is reduced to a high pressure. I am trying to balance it with the feed water heater 3. In this state, if Plan 1~ is affected by sudden plant transient changes such as load shedding,
As the internal pressure of the high-pressure feedwater heater 3 decreases, the internal pressure of the feedwater heater drain tank 3 rapidly decreases through the pressure equalization pipe 7 and the drain pipe 6. This slant leads to the feedwater heater drain in the feedwater heater drain tank 5, and further to the drain downpipe 1 from the feedwater heater drain tank 5 to the drain pump 11.
There is a risk that the feed water heater drain in the path 0 will begin to evaporate, and the pushing pressure of the drain pump 11 that was maintained until then will drop, leading to cavitation. In addition, since the feedwater heater drain flow rate injected into the condensate pipe 13 by the drain pump 11 accounts for approximately 30% of the total feedwater flow rate, when the operation of the drain pump 11 is stopped due to load cutoff, 3.
The water supply corresponding to 0″X cannot be supplied.

In a nuclear turbine plant, the water level control of the nuclear reactor 15 and the flow rate control of the water supply system are closely related, and a sudden decrease in the water supply flow rate becomes a major obstacle in maintaining stable operation of the plant.

Therefore, the purpose of the present invention is to suppress the occurrence of cavitation in the drain pump to prevent damage to vanes, etc., and to maintain stable plant operation by eliminating sudden drops in the water supply flow rate in the water supply system. An object of the present invention is to provide a feed water heater drain tank pressure control device that is capable of controlling the pressure of a feed water heater and a drain tank.

[Structure of the Invention] (Means for Solving the Problems) The feed water heater drain tank pressure control device according to the present invention connects the feed water heater drain tank and the high pressure feed water heater to balance the internal pressures of both. A condensate supply pipe that connects the feedwater heater drain tank and the condensate pipe on the discharge side of the condensate pump and guides condensate from the condensate pipe to the feedwater heater drain tank as necessary, while providing a pressure equalization pipe via a closing means. is provided via a switching means, and further provided with a control means for detecting a plant transient change, comparing the output signal with a set value to close the closing means, and outputting a control signal for opening the switching means, respectively. It is characterized by:

(Function) During normal operation, the closing means in the path of the pressure equalization pipe is fully opened, and the feed water heater drain tank is in communication with the high pressure feed water heater via the pressure equalization pipe. As a result, the internal pressures of both vessels are in an equilibrium state, and the feedwater heater drain can be smoothly recovered to the feedwater heater drain tank. Further, at this time, the switching means for the condensate supply pipe is fully closed.

On the other hand, when sudden plan l transient changes occur, such as during load shedding, the high-pressure feedwater heater connected to the high-pressure turbine suffers a pressure drop; however, at this time, the internal pressure of the feedwater heater drain tank While closing the closing means to cut off communication through the pressure equalization pipe, the switching means is fully opened to guide condensate from the condensate pipe to the feedwater heater drain tank, so that the drop in internal pressure in the feedwater heater drain tank will be gradual. apply control means.

(Example) An embodiment of the present invention will be described below with reference to FIG.

Note that among the configurations shown in FIG. 1, the same components as those shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

In FIG. 1, a gate valve 24 is provided in the path of a pressure equalizing pipe 7 that connects the high-pressure feed water heater 3 and the feed water heater drain tank 5. Further, a condensate supply pipe 25 is provided which is branched from the condensate pipe 13 on the discharge side of the condensate pump 20 and whose other end is connected to the feed water heater drain tank 5. A condensate supply valve 26 is interposed.

Furthermore, the following control circuit for opening and closing the gate valve 24 and the condensate replenishment valve 26 is connected. That is, the control circuit includes an electric output detector 27 that detects the electric output of the generator 23,
It is comprised of a controller 28 that compares the output signal from the electrical output detector 27 with a set value and outputs a control signal to the gate valve 24 and the condensate supply valve 26. Note that two reference numerals in the figure indicate check valves.

In the above configuration, when a plant transient change such as loss of load on the generator 23 occurs, the steam sent to the high-pressure turbine 1 is transferred to the steam control valve 21 installed on the inlet side.
As a result, the pressure of the high-pressure turbine 1 drops rapidly. With this pressure drop in the high-pressure turbine 1, the internal pressure of the high-pressure feedwater heater 3 decreases, and the internal pressure of the feedwater heater drain tank 5, which is connected to this via the pressure equalization pipe 7, also rapidly decreases. However, in the present invention, the plan I transient change is detected by the electrical output detector 27 that detects the electrical output of the power generator 'a23, and the gate valve 24 is fully closed based on the output signal. The communication between the high pressure feed water heater 3 and the feed water heater drain tank 5 via the pressure equalization pipe 7 is cut off. In addition, since two check valves are provided in the path of the drain pipe 6,
The internal pressure of the feed water heater drain tank 5 is prevented from dropping rapidly through the drain pipe 6.

Furthermore, while the drain pump 11 continues to operate, if the feed water heater drain in the feed water heater drain tank 5 is not replenished with the same amount of water as the discharge bone, the feed water heater drain tank 5 will end up being drained. The pressure inside the vessel will drop.

In order to prevent this, the condensate replenishment valve 26 is fully opened by the output signal from the electric output detector 27, and the condensate is guided to the feed water heater drain tank 5. Thereby, the feed water heater drain tank 5 and the path of the drain downcomer pipe 10 are prevented from having their internal pressure drop rapidly.

On the other hand, when the plant transient changes are completed and normal operation is resumed, this control device also needs to be returned to the state before operation. In this procedure, the gate valve 24 is opened smoothly to equalize the internal pressures of the feed water heater drain tank 5 and the high pressure feed water heater 3. Even if the pressure is gradually lowered, if the pushing pressure of the drain pump 11 is maintained, cavitation etc. will not occur and stable operation will continue. That is, while the drain pump 11 continues to operate, the gate valve 24 is opened so that the effective pushing pressure is ensured.

Then, when the gate valve 24 opens, the condensate supply valve 26 is fully closed. However, since the meteor ratio of the feed water heater drain is 30% of the total water supply amount, if the plant output drops to 70% or less, the flow rate of the condensate and water supply system alone will be sufficient without operating the drain pump 11. The required water supply amount is reduced. therefore,
At this time, it is possible to stop the operation of the drain pump 11, and while the gate valve 24 is immediately fully opened, the condensate supply valve 26 may be fully closed.

Note that in the above embodiment, plant transient changes are detected by the electrical output detector 27, and the gate valve 24 and the condensate replenishment valve 2
For example, the valve opening of the steam control valve 21, the steam pressure after the first stage of the high-pressure turbine 1, the exhaust steam pressure of the high-pressure turbine 1, and the high-pressure feedwater heater Transient plant changes can also be detected in the method of detecting the internal pressure in No. 3, and both are embodiments of the present invention.

[Effects of the Invention] As explained above, the present invention provides a pressure equalizing pipe that connects the feedwater heater drain tank and the high-pressure feedwater heater to balance the internal pressures of the two via a closing means, and also A condensate supply pipe connecting the drain tank and the condensate pipe on the discharge side of the condensate pump and guiding condensate from the condensate pipe to the feed water heater drain tank as necessary is provided via a switching means, and these closing means and switching means are provided. Since the system detects transient plant changes and opens and closes based on the output signal, it is possible to prevent a sudden drop in internal pressure in the feedwater heater drain tank, which may occur due to lack of pumping pressure in the drain pump. This has the excellent effect of preventing the occurrence of cavitation, and also eliminating a sudden drop in the flow rate of water supply, thereby maintaining stable plant operation.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the feedwater heater drain tank pressure control device according to the present invention, and Fig. 2 is a system-12 showing an example of a turbine plant adopting the feedwater heater drain pump-up system according to the prior art. = It is a systematic diagram. 3... High pressure water heater 4... Water pump 5... Water heater drain tank 7...
...... Pressure equalization pipe 11 ...... Drain tank 13 ...... Condensate pipe 14 ...... Water supply pipe 20 ... ...Condensate pump 24...Gate valve 25...Condensate supply pipe 26...Condensate supply valve 27... ......Electric output detector 28...
...Controller 29...Check valve applicant Toshiba Corporation Representative Patent attorney Satoshi Suyama - Figure 1

Claims (4)

[Claims] (1) A pressure equalizing pipe that connects the feedwater heater drain tank and the high-pressure feedwater heater to balance the internal pressures of both is provided via a closing means, and a pressure equalization pipe is provided between the feedwater heater drain tank and the condensate pump discharge side. A condensate supply pipe is connected to the condensate pipe and leads the condensate from the condensate pipe to the feedwater heater drain tank as necessary via a switching means, and further detects plant transient changes and based on the output signal. 2. A feed water heater drain tank pressure control device, comprising control means for outputting a control signal for closing the closing means and opening the switching means by comparing the pressure with a set value. (2) The feed water heater drain tank pressure control device according to claim 1, wherein the closing means is a gate valve. (3) The feed water heater drain tank pressure control device according to claim 1, wherein the switching means is a condensate replenishment valve. (4) The feed water heater drain tank pressure control device according to claim 1, wherein the means for detecting plant transient changes is an electric output detector that detects the electric output of a generator.