JPS6235592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a condensate system minimum flow control device for circulating part or all of the condensate in a condensate piping system of a thermal power and nuclear steam plant to a condenser.

Figure 1 shows the condensate piping system of a nuclear power plant, Figure 2 shows the relationship between the condensate flow rate, low-pressure condensate pump outlet pressure, ReNPSH and inlet pressure of the high-pressure condensate pump, and Figure 3 A conventional condensate system minimum flow control device is shown.

The condensate piping system of a nuclear power plant shown in FIG.
through, air extractor 3, ground capacitor 4,
Water is sent to a high-pressure condensate pump 6 through a condensate desalination device 5, and after being pressurized by the high-pressure condensate pump 6, it is sent to a reactor feed water pump 8 through a low-pressure feed water heater 7.

The reactor feed water pump 8 further pressurizes the water, passes it through the water supply pipe 13, passes through the high pressure feed water heater 9, and supplies it to the reactor 1.
Supply water to 0.

The feed water sent to the nuclear reactor 10 is heated and turned into steam, which passes through the main steam pipe 14 to the turbine 11.
The steam is introduced into a turbine 11, performs work in a turbine 11, and the steam that has done the work is discharged to a condenser 1, where it is cooled and becomes condensed water, which is pumped up again by a low-pressure condensate pump 2. .

The condensate and water supply have a characteristic that the flow rate increases when the plant output increases, and the flow rate decreases when the plant output decreases. In order to operate 4 and 4 normally, it is necessary to always secure condensate at a flow rate higher than the specified flow rate, so a condensate recirculation pipe is installed to return condensate from the outlet of the condensate desalination device 5 to the condenser 1. A system is established.

This condensate recirculation piping system includes a condensate flow rate transmitter 21 provided at the outlet of the condensate desalination device 5,
Condensate piping 12 on the upstream side of high pressure condensate pump 6
It is equipped with a condensate recirculation pipe 16 branched from the condensate recirculation pipe 16 and a condensate minimum flow control valve 23 provided therein, and the condensate flow rate transmitter 21 and the condensate minimum flow control valve 23 are connected to Connected via a flow control device.

The conventional condensate system minimum flow control device has a condenser minimum flow controller 25, as shown in FIG.

Further, an air source 41 is connected to the condensate flow rate transmitter 21, the condenser minimum flow controller 25, and the condensate minimum flow control valve 23, respectively.

Then, the condensate flow rate is measured by the condensate flow rate transmitter 21, and the signal 26 thereof is inputted to the condensate minimum flow controller 25.
The deviation between the signal 26 from
to control the condensate minimum flow control valve 23,
The system is designed to ensure the minimum flow of the condensate system.

In addition, even if the air source 24 or power supply for operating the condensate minimum flow control valve 23, condensate minimum flow controller 25, and condensate flow rate transmitter 21 is lost, the minimum flow of the condensate system is ensured. Generally, when the control signal increases, the condensate minimum flow control valve 23 is closed, and when the control signal decreases, the condensate minimum flow control valve 23 is opened, that is, a fail-open characteristic.

During high-load operation, the condensate flow rate is higher than the set flow rate, so the condensate minimum flow controller 25
The output is a control signal 27 that fully closes the condensate minimum flow control valve 23.

In this case, if any of the positions of the condensate flow rate transmitter 21, the condensate minimum flow controller 25, or the condensate minimum flow control valve 23 fails, or if the operating air source 24 or power supply is lost, the control signal Because 27 will not come out,
The condensate minimum flow control valve 23 is fully opened, and condensate is circulated from the condensate recirculation piping system to the condenser 1, so the condensate flow rate increases, and as shown in Figure 2, the high pressure condensate pump inlet The pressure may drop and cavitation may occur in the high pressure condensate pump 6.

Therefore, when the high pressure condensate pump inlet pressure falls below the specified pressure, in order to protect the high pressure condensate pump 6, the high pressure condensate pump inlet pressure switch detects the pressure and turns on the high pressure condensate pump. It often causes tripping.

In the BWR type nuclear power plants that are currently in practical use, the low-pressure condensate pump 2, high-pressure condensate pump 6, and reactor feed water pump 8 are connected in series on the condensate and water supply piping system, so the high-pressure condensate When the pump 6 trips, the reactor feed water pump 8 also trips, resulting in a loss of reactor feed water, resulting in a reactor scram, which causes the nuclear power plant to be shut down.

Furthermore, although the above description has been made regarding a nuclear power plant, the same applies to thermal power plants as well, as tripping of the high-pressure condensate pump makes it difficult to continue the plant operation.

The purpose of the present invention is to prevent the condensate minimum flow rate control valve from failing when the air source or power supply for operating the condensate flow rate control system fails during high-load operation, which is most often used in nuclear power plants or thermal power plants. To provide a safe condensate system minimum flow control device capable of preventing opening defects.

The present invention is characterized by having a condensate flow rate transmitter, a condensate minimum flow controller, and a condensate minimum flow control valve that are branched from the condensate pipe, and the condensate flow rate is constantly measured by the condensate flow rate transmitter. Then, the condensate minimum flow controller performs proportional + integral calculations between the condensate flow rate and the specified flow rate, and when the plant is operating at low load, the condensate minimum flow control valve is opened to recirculate the condensate to the condenser. In a steam plant equipped with a condensate recirculation system that fully closes the condensate minimum flow control valve during high-load operation,
Separately from the condensate flow rate transmitter and the condensate minimum flow controller, the condensate minimum flow control valve is configured to control the feed water flow rate, which has a functional relationship with the condensate flow rate, the turbine extraction pressure, the output of the generator, etc., and the steam turbine. A transmitter that measures at least one of the pressures after the first stage, and a signal from the transmitter that is constantly monitored and compared with the specified flow rate of the condensate minimum flow controller, and the set value that exceeds the specified flow rate or more. a control valve that forcibly fully closes the condensate minimum flow control valve by excluding the signal from the condensate minimum flow controller based on the signal from the monitor switch; With this configuration, the above object can be reliably achieved.

Hereinafter, the present invention will be explained based on the drawings.

4 and 5 show a first embodiment of the present invention, in which a condensate minimum flow controller 25 connected to a condensate flow rate transmitter 21 and controlling a condensate minimum flow control valve 23 is shown. Separately, a feed water flow rate monitor switch 29 connected to the feed water flow rate transmitter 22 and a condensate minimum flow control valve 2 connected to the feed water flow rate monitor switch 29 and
A solenoid valve 30 for controlling the

The condensate minimum flow control valve 23 includes a valve body 23a, a positioner 23b, and an actuator 2.
3c.

The condensate flow rate transmitter 21, the condensate minimum flow controller 25, the condensate minimum flow control valve 23, the water supply flow rate transmitter 22, and the solenoid valve 30
are each connected to an air source 24. on the other hand,
The water supply flow rate monitor switch 29 is connected to a power source 28.

The condensate flow rate transmitter 21 is
The condensate flow rate at the outlet of the condensate desalination device 5 is measured and a signal 26 is sent to the condensate minimum flow controller 25.

The condensate minimum flow controller 25 receives a signal 26 sent from the condensate flow rate transmitter 21.
The deviation between the set flow rate and the set flow rate is calculated proportionally and integrally, and if the measured flow rate is lower than the set flow rate, a control signal 27 is issued to open the condensate minimum flow control valve 23,
Conversely, if the measured flow rate is higher than the set flow rate, the control signal 7 closes the condensate minimum flow control valve 23.
7, controls the condensate minimum flow control valve 23, and returns the necessary flow rate of condensate to the condenser 1 through the condensate recirculation piping 16, so that the condensate flow rate does not always fall below the minimum flow rate of the condensate system. to control.

As the output of the generator 15 increases and the water supply flow rate increases, the condensate flow rate increases, and when the condensate flow rate eventually exceeds the set flow rate of the condensate minimum flow controller 25, the condensate minimum flow is reached as described above. The control signal 27 from the controller 25 causes the condensate minimum flow control valve 23 to be fully closed. As the output of the generator 15 further increases, the flow rate of water supply and the flow rate of condensate increase, so if each meter and control valve are normal, the condensate minimum flow control valve 23 will not open.

The water supply flow rate transmitter 22 is connected to the water supply pipe 1.
3 to the reactor 10, and sends a signal 31 to the feed water flow rate monitor switch 29.

The water supply flow rate monitor switch 29 constantly monitors the signal 31 sent from the water supply flow rate transmitter 22, and outputs a signal to determine whether the signal 31 is greater than or equal to a set value. The set value is the condensate minimum flow controller 2.
The value is set to the specified flow rate of 5 plus approximately 10% margin. Then, the water supply flow rate monitor switch 29
sends a control signal 32 to the solenoid valve 30 when the water supply flow rate exceeds the set value.

The solenoid valve 30 is connected to the water supply flow rate monitor switch 2.
9, the air 33 is excited by the control signal 32 from the condensate minimum flow control valve 23, and the air 33 is sent to the actuator 23c of the condensate minimum flow control valve 23.
The operation of the control signal 27 from 5 is excluded, and the condensate minimum flow control valve 23 is fully closed.

Therefore, during high load operation of the plant, due to the coordinated operation of the feed water flow rate transmitter 22, the feed water monitor switch 29, and the solenoid valve 30,
The condensate minimum flow control valve 23 is forced to be fully closed, and as a result, either the condensate flow rate transmitter 21, the condensate minimum flow control meter 25, or the positioner 23b of the condensate minimum flow control valve 23 malfunctions. Alternatively, even if the air source 24 is lost, the condensate minimum flow control valve 23 is fully closed, and no condensate flows into the condensate recirculation system.

Note that the configurations and actions of other members and parts are as described in the first section.
This is the same as described for the figure.

Next, FIGS. 6 and 7 show a second embodiment of the present invention, in which the condensate pipe 12
A condensate flow rate transmitter 21 and a monitoring condensate flow rate transmitter 34 are provided across an orifice (not shown), and a condensate flow rate monitor switch 35 is connected to the monitor condensate flow rate transmitter 34. The condensate flow rate monitor switch 35 compares the condensate flow rate signal 36 from the monitoring condensate flow rate transmitter 34 with the set value, and if the signal 36 > the set value, sends a control signal 37 to the solenoid valve 30 to energize it. The second embodiment is the same as the first embodiment except that it is set to .

Next, FIGS. 8 and 9 show a third embodiment of the present invention, in which the generator 15 is provided with a generator output transmitter 38, to which a generator output monitor switch 39 is connected, The generator output monitor switch 39 compares the generated output signal 40 from the generator output transmitter 38 with the set value, and if the signal 40 > the set value, a control signal 41 is sent to the solenoid valve 30.
It is the same as the first embodiment except that it is configured to send and excite.

Further, FIGS. 10 and 11 show a fourth embodiment of the present invention, in which a turbine bleed pressure transmitter 43 is provided in the turbine bleed pipe 42, and a turbine bleed pressure monitor switch 4 is provided in the turbine bleed pipe 42.
4, and the turbine bleed pressure monitor switch 44 connects the turbine bleed pressure transmitter 43.
The measured pressure signal 45 is compared with the set value, and the signal
45> This is the same as the first embodiment except that the control signal 46 is sent to the solenoid valve 30 at the set value to energize it.

Further, in the present invention, the pressure after the first stage of the turbine, which has a functional relationship with the condensate flow rate, may be measured, and the condensate minimum flow control valve 23 may be controlled based on this.

Furthermore, the operation of each instrument and control valve is controlled by an air source,
In addition to the power source, other operating sources can also be used.

Further, although the drawings have been described with reference to a nuclear power plant, it goes without saying that the present invention can also be applied to thermal power plants and the like.

Note that in FIGS. 1 to 11, the same members are designated by the same reference numerals.

The present invention has the configuration and operation described above,
According to the present invention, during high-load operation when there is no need for recirculation to the condenser, the control signal from the condensate minimum flow controller to the condensate minimum flow control valve is excluded, and the condensate flow rate transmitter and condensate Through the coordinated operation of the transmitter, monitor switch, and control valve, which are installed separately from the minimum flow controller,
Force the condensate minimum flow control valve to fully close,
Since malfunction of the condensate minimum flow control valve due to failure of each meter or control valve can be prevented, the safety of the plant can be significantly improved.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a nuclear reactor power plant, and Figure 2 is a characteristic diagram showing the relationship between the condensate flow rate of the plant shown in Figure 1, the outlet pressure of the low pressure condensate pump, and the ReNSH and inlet pressure of the high pressure condensate pump. , FIG. 3 is a condensate minimum flow control system diagram showing the prior art. 4 and 5 show a first embodiment of the present invention, FIG. 4 is a system diagram of a plant to which the first embodiment is applied, and FIG. 5 is a system diagram showing details of main parts. . 6 and 7 show the second embodiment, FIG. 6 is a system diagram of a plant to which the second embodiment is applied, and FIG. 7 is a system diagram showing details of the main parts.
FIG. 8 and FIG. 9 show the third embodiment.
The figure is a system diagram of a plant to which this third embodiment is applied, and FIG. 9 is a system diagram showing details of the main parts. Furthermore, FIGS. 10 and 11 show the fourth embodiment, FIG. 10 is a system diagram of a plant to which the fourth embodiment is applied, and FIG. 11 is a diagram showing details of the main parts thereof. 1... Condenser, 10... Nuclear reactor, 11... Steam turbine, 12... Condensing pipe, 13... Water supply pipe, 1
4... Steam pipe, 15... Generator, 16... Condensate recirculation piping, 21... Condensate flow rate transmitter, 2
3... Condensate minimum flow control valve, 25... Condensate minimum flow controller, 26... Signal of measured flow rate of condensate, 27... Control signal of condensate minimum flow control valve, 22, 34, 38, 43... Transmitter for measuring flow rate and pressure having a functional relationship with condensate flow rate, 29, 35, 39, 44... Monitor switch, 30... Solenoid valve as condensate minimum flow control valve, 31, 36, 40, 45...signals that are the outputs of the transmitters, 32, 37, 41, 46...
...Control output signal which is the determination result of the monitor switch, 42...Turbine bleed pipe.

Claims (1)

[Claims] 1. A system that supplies condensate from the condenser to the steam generation source, a main system that supplies steam from the steam generation source to the steam turbine, a system that returns the steam that has done work in the steam turbine to the condenser, and It is branched from the piping and has a condensate flow transmitter, a condensate minimum flow controller, and a condensate minimum flow control valve, the condensate flow transmitter constantly measures the condensate flow rate, and the minimum condensate flow controller measures the condensate flow rate at all times. The deviation between the condensate flow rate and the set flow rate is calculated proportionally and integrally, and the condensate minimum flow control valve is opened during low load operation of the plant to recirculate the condensate to the condenser, and during high load operation the condensate minimum flow control valve is opened. In a steam plant equipped with a condensate recirculation system that completely closes a flow control valve, the condensate minimum flow control valve is provided with a condensate flow rate transmitter and a condensate minimum flow controller separately. Feedwater flow rate, turbine extraction pressure, output of generator, etc., which are in a functional relationship, steam turbine No. 1
A transmitter that measures at least one of the post-stage pressures, and a signal from the transmitter that is constantly monitored and set to a flow rate higher than the set flow rate of the condensate minimum flow controller, and generates a signal when the flow rate exceeds the set value. and a control valve that excludes the operation of the condensate minimum flow controller and forcibly fully closes the condensate minimum flow control valve based on the signal from the monitor switch. Features a condensate system minimum flow control device.