JPH076607B2 - Water heater Drain pump up system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedwater heater drain pump up system for a power plant, and more particularly to a feedwater heater drain pump up system suitable for controlling the feedwater heater drain flow rate.

[Background of the Invention]

As a system configuration for pumping up the conventional feedwater heater drain to the condensate feedwater system, Mitsubishi Heavy Industries Technical Report Val.17, No.2 (198
0-3), but this is in a PWR plant,
In a BWR plant that supplies condensate from a turbine plant directly to a nuclear reactor, it is necessary to secure water quality with a purification device.
Further, this document also showed a plant control method at the time of drain pump trip.

In order to adopt the feedwater heater drain pump up system in the BWR plant, it is possible to continue the operation stably after ensuring the reactor feedwater purification method at the time of drain pump trip and securing the reactor feedwater flow rate. It was necessary to develop a new control device.

Conventionally, the feed water heater drain pump was equipped with three pumps with a capacity of 50%, and a standby machine was thrown in when a failure occurred. If the equipment cost is reduced by removing the spare unit, the quality of the water supply to the reactor will be reduced, and the reactor water supply capacity will be reduced, leading to a plant scrum.

[Object of the Invention]

The present invention has been made in view of the above points, and an object thereof is to stabilize a power generation plant without using a standby unit of the feed water heater drain pump even when the feed water heater drain pump fails. The purpose is to provide a highly reliable feed water heater drain pump up system that can continue operation.

[Outline of Invention]

In order to achieve the above object, the present invention, a feed water heater that heats the condensate sent through a condensate pump, a drain tank that stores the drain discharged from the water feed heater,
In a feedwater heater drain pump up system having a plurality of drain pumps for supplying the condensate of the drain tank to a pipe for guiding the condensate to the feedwater heater, in the condensate pump from the inlet side of the plurality of drain pumps. A first conduit connected to the inlet side and having a first flow rate adjusting valve, and a second conduit having a second flow rate adjusting valve connected from the outlet side of the condensate pump to the outlet sides of the plurality of drain pumps. Of the drain pump, a trip detection device that detects a trip of the plurality of drain pumps, and a trip flow detection of the drain pump, and the flow rate of the first conduit and the drain amount that the tripped drain pump is delivering water. Compare
The first control means for controlling the first flow rate adjusting valve on the basis of the comparison result and the drain pump which is operated by trip detection of the drain pump, and the drain pump which has tripped with the flow rate flowing through the second conduit are supplying water. And a second control means for controlling the second flow rate adjusting valve based on the comparison result.

As a result, when the drain pump trips, it is possible to secure the flow rate of the water supply to the reactor without degrading the water quality of the water supply.
Stable operation can be continued without lowering the output of the power plant, and it is not necessary to provide a spare drain pump.

Further, the present invention provides a switching device for switching the first flow rate adjusting valve as a water level control valve of the drain tank.

This eliminates the need to operate the drain pump when the water supply to the nuclear reactor is low at the time of starting and stopping the plant, so that the head of the drain pump can be lowered and the outlet of the drive motor can be reduced.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. The steam generated by the nuclear reactor 1 drives the steam turbine 2 to generate electric power. Exhaust steam from the steam turbine 2 is condensed in the condenser 3, boosted by the low-pressure condensate pump 4, purified by the condensate purifier 5 and the condensate demineralizer 7, and boosted by the high-pressure condensate pump 9. The low pressure feed water heater 10 heats the extracted steam of the steam turbine 2 and sends it to the feed water pump 11. The pressure is further increased by the water supply pump 11, and the extracted steam of the steam turbine 2 is supplied by the high-pressure water supply heater 12 to
It is further heated and sent to the reactor 1. The extracted steam that has heated the high-pressure feed water heater 12 condenses into drain and is sent to the low-pressure feed water heater 10. Extracted steam that has heated the low-pressure feed water heater 10 is also condensed to form drain. Low pressure water heater 10
The drain inside is sent to the drain tank 13. The drain in the drain tank 13 is pressurized by the drain pump 14 and is sent to the drain passing device 16 where it is purified to improve the water quality and is injected into the inlet or outlet of the high pressure condensate pump 9 which is the condensate system.

The flow rate of water supplied to the reactor 1 is controlled by a drive water supply pump 11 (not shown) by a reactor water level detection device (not shown).

The water level is detected by the water level detection device 19 provided in the drain tank 13, the water level of the drain tank 13 is kept constant by the water level control valve, and the drain pump 14 is stably operated.
The drain in the drain tank 13 is injected into the condensate system, and the water level is controlled so that the supply flow rate of water to the reactor 1 does not become insufficient.

Three 50% capacity low-pressure condensate pumps 4, three 50% capacity high-pressure condensate pumps 9, 50% capacity water supply pump 11, a spare water supply pump not shown, and a 50% capacity drain pump 14
Two units will be provided.

Condensate purification equipment is approximately 60% of the supply flow rate to the reactor 1.
A condensate-separating device 5 capable of processing a% flow rate, a condensate-desalting device 7 and a draining device 16 capable of processing a flow rate of about 40% are provided.

This system is generally called the low pressure heater drain pump up system, and the drain of the feed water heaters 10 and 12 is connected to the condenser 3
Since it is injected into the condensate system at a high temperature without being cascade-cooled to the plant, the plant thermal efficiency is improved, the plant output is increased, and the capacity of the condensate demineralizer 7 can be reduced. The equipment cost will decrease due to the decrease of the building and the volume of the building.

In the present invention, the drain pump at the outlet of the drain tank 13
A conduit 20 connecting from the inlet of 14 to the condenser 3, and a conduit 20
Has a flow rate control valve 17 and a flow rate detecting device 21, which are connected to the inlet of the drainage device 16 from the outlet of the low pressure condensate pump 4, and the flow rate control valve 18 provided in the water guide pipe 22.
And a flow rate detector 18 are provided.

The problems with this system are shown below.

Since two 50% capacity low-pressure drain pumps 14 are installed, the ability to inject the drain in the drain tank 13 into the condensate system is reduced if one of them trips due to a failure.
Therefore, the water level of the drain tank 13 rises, and by extension, the water level of the low-pressure feed water heater 10 also rises and the feed water heating capacity decreases,
The plant output also drops. Furthermore, since the amount of condensate injected into the condensate system also decreases, the flow rate of water supplied to the reactor 1 also decreases, and the water level in the reactor 1 decreases, leading to a plant scrum. Therefore, it is necessary to reduce the plant output. As described above, the failure of the drain pump 14 may lead to a plant scrum, and in order to avoid this, it is necessary to reduce the plant output by some means to forcibly reduce the required water supply amount of the reactor 1. .

As a measure against this, in the present invention, the trip of the drain pump 14 is detected by the trip detection device 26, and the flow rate setting device is detected.
Activate 24 and 25. The flow rate setting device 24 sets a drain amount equivalent to the amount of water drained by the drain pump 14 that has tripped, compares the flow rate detected by the flow rate detection device 21, and controls the flow control valve 17 to control the water conduit 20. A predetermined drain is cascaded to the condenser 3 via the condenser. As a result, the water level of the drain tank 13 can be kept constant by treating the drain water flowing into the drain tank 13 by the water supply by the drain pump 14 that has not tripped and the cascade to the condenser 3.

On the other hand, the flow rate setting device 25 is set to the same flow rate as the flow rate setting device 24, operates by a signal from the trip detection device 26, compares the flow rate detected by the flow rate detection device 23, and sets the flow control valve 18 The amount of drain that is controlled and cascaded to the condenser 3 by the water conduit 20 is injected from the outlet of the low pressure condensate pump 4 to the upstream of the drainage device 16 by the water conduit 22 for purification treatment, and the high pressure condensate pump 9 The required amount of water supply to the reactor 1 can be secured by injecting it into the inlet side of the reactor.

As a result, the amount of drain cascaded to the condenser 3 does not have to be passed to the condensate purifier 5 and the condensate demineralizer 7. Therefore, deterioration of water quality due to excessive flow of water, damage to the device, and high-pressure condensate It is possible to prevent a decrease in the inlet pressure of the pump 9,
Further, since water is injected into the high-pressure condensate pump 9 after passing through the drainage device, it is possible to prevent deterioration of water quality and to secure a required amount of water supply to the reactor 1. Therefore, the drain pump
At the time of the trip of 14, the feed water flow rate to the reactor 1 can be secured without deteriorating the feed water quality, so that stable operation can be continued without reducing the plant output.

Next, changes in the flow rate of the drain pump 14 after the trip will be described with reference to FIGS. 2 and 3.

FIG. 2 shows changes in the flow rate around the drain pump 14. Due to the trip of the drain pump 14, the flow rate of the tripped drain pump 14 decreases and
The total flow rate of the drain pump 14 is reduced although the flow rate of the drain pump 14 is increased to a value that can be processed.

By cascading the reduced flow rate to the condenser 3 by the water conduit 20, the amount of inflow to the drain tank 13 can be processed, so that the water level in the drain tank 13 can be kept constant. On the other hand, the water flow rate of the drainage device 16 is
Although the amount of water sent from 14 decreases by the amount passing through the water conduit 20, it can be kept the same as before the trip of the drain pump 14 by the amount sent from the water conduit 22 as shown in FIG.

FIG. 3 shows changes in the flow rate around the low-pressure condensate pump 4, but the trip of the drain pump 14 causes
Low pressure condensate pump 4 by the flow rate from the water conduit 20 shown in the figure.
The amount of water passing through will increase. As the water flow rate of the water conduit 22 increases, water flows to the drainage device 16, so that the water flow rates of the condensate water passage device 5 and the condensate water desalination device 7 can be kept the same as before the trip of the drain pump 14. .

Here, after the drain pump 14 trips, the flow rates of the sound drain pump 14 and the low-pressure condensate pump 4 increase, but it is easy to design in advance to operate at this flow rate. If this is not possible, a sound drain pump
The flow rate of 14 is not increased, the flow rate of the feed water passing through the water conduit 20 is increased, and the flow rate of the low pressure condensate pump 4 is not increased.
This can be dealt with by turning on the spare low-pressure condensate pump 4.

As shown in FIGS. 2 and 3, even if a trip of the drain pump 14 occurs, the water supply to the reactor 1 is controlled by the condensing device 5.
Can be operated through the condensate desalination unit 7 and the drainage unit,
Furthermore, the flow rate does not decrease.

Therefore, it becomes possible to secure the water quality and the water supply flow rate,
There is no need to reduce the plant output and stable operation can be continued.

Another problem in this system is shown below.

In the required lift of the low-pressure drain pump 14, it is necessary to make the pressure equal to or higher than the pressure obtained by adding the system pressure loss of the drainage device 16 to the inlet pressure of the high-pressure condensate pump 9. Here, the inlet pressure of the high-pressure condensate pump 9 is the pressure obtained by subtracting the system pressure loss of the condensate permeation device 5, the condensate demineralization device 7, etc. from the head of the low-pressure condensate pump 4, but it is low when the plant starts During the output operation, the flow rate of the water supplied to the reactor 1 is small, so that the characteristics of the low-pressure condensate pump 4 are that the discharge pressure increases and the system pressure loss also decreases. Due to this addition effect, the inlet pressure of the high-pressure condensate pump 9 becomes extremely high. Therefore, heater drain pump
The required lifting height of 14 will also be high, resulting in excessive equipment specifications.

As a measure against this, in the present invention, when the amount of water supplied to the reactor 1 at the time of plant startup is small, the total amount of drain flowing into the drain tank 13 is cascaded to the condenser 3 through the water conduit 20 by the flow control valve 17. At this time, the control signal of the flow rate control valve 17 is switched by the switching device 27 from the signal from the flow rate setting device 24 to the signal of the water level detection device 19, so that the water level in the drain tank 13 can be kept constant.

On the other hand, the drain cascaded to the condenser 3 is purified by the low-pressure condensate pump 4 by the condensate purifier 5 and the condensate demineralizer 7, and is supplied to the reactor 1. Here, since the amount of water supply at the time of starting the plant is low, the water supply capacity of the condensate pump 4, the condensate purifying apparatus 5 and the condensing water desalination apparatus 7 are sufficiently satisfied.

In this way, it is possible to avoid raising the drain pump 14 to a high head, and a rational facility design is possible.

According to the present embodiment, (1) the drain water heater drain can be properly treated even when the drain pump 14 fails, so that the water level in the drain tank can be kept constant, and the total amount of water supplied to the reactor 1 Since water can be passed through the condensate filter 5, the condensate demineralizer 7, and the drainer 16 in an appropriate amount and purified, the water quality can be secured and the reactor 1
Since it is possible to secure the required feed water flow rate, it is not necessary to reduce the plant output, and stable operation can be continued. As a result, it is not necessary to install a spare machine for the drain pump 14.

(2) When the amount of water supplied to the reactor 1 at the time of starting and stopping the plant is low, it is not necessary to operate the drain pump 14, so that the head of the drain pump 14 can be lowered and the drive motor output can be reduced.

FIG. 4 shows another embodiment of the present invention.

The feature of this embodiment is that an overflow pipe 41 is provided in the drain tank 13 and a U-seal is attached to secure a differential pressure between the drain tank 13 and the condenser 3 and the overflow pipe 41 is connected to the water pipe 20.
Is connected to.

According to the present embodiment, in addition to the effects of the embodiment of FIG. 1, the flow control valve 17, the flow rate detection device 21, the flow rate setting device 24, and the switching device 27 provided in the water conduit 20 are unnecessary, and the control device Can be simplified as

In the overflow pipe 41, the water supply capacity of the drain pump 14 is lowered, such as when the drain pump 14 trips or when the inlet pressure of the high-pressure condensate pump 9 at the time of plant startup is high, and the water level in the drain tank 13 rises. Occasionally, an overflow pipe is introduced through a U-seal to prevent water level rise.
Water is sent to 20 and the condenser 3 is cascaded.

〔The invention's effect〕

According to the present invention, even when the feedwater heater drain pump fails, a highly reliable feedwater heater drain pump up system capable of stably continuing the operation of the power plant without using the standby unit of the feedwater heater drain pump. Can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIGS. 2 and 3 are characteristic diagrams of flow rate and time, and FIG. 4 is a system diagram of another embodiment of the present invention. 4 …… Low pressure condensate pump, 9 …… High pressure condensate pump, 10 ……
Low-pressure water heater, 12 …… High-pressure water heater, 13 …… Drain tank, 14 …… Drain pump, 20 …… Water pipe, 22 ……
Water pipe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiki Kobayashi 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi, Ltd. (72) Toyohiko Masuda 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. Within

Claims (2)

[Claims] 1. A feed water heater for heating condensate sent through a condensate pump, a drain tank for storing drainage discharged from the feed water heater, and a drain of the drain tank for the condensate. A feed water heater drain pump up system having a plurality of drain pumps for supplying to a pipe leading to a feed water heater, wherein a first flow rate adjustment is connected from an inlet side of the plurality of drain pumps to an inlet side of the condensate pump. A first conduit having a valve, a second conduit connected from an outlet side of the condensate pump to an outlet side of the plurality of drain pumps and having a second flow rate adjusting valve, and a trip of the plurality of drain pumps And a drain detection device that operates by the trip detection of the drain pump and detects the flow rate through the first conduit and the drain amount that the drain pump was sending. And a first control means for controlling the first flow rate adjusting valve based on the comparison result, and a drain pump which operates by trip detection of the drain pump and trips with the flow rate flowing through the second conduit. And a second control means for controlling the second flow rate adjusting valve based on a result of the comparison, the feed water heater drain pump up system. 2. The feed water heater drain pump up system according to claim 1, further comprising a switching device for switching the first flow rate adjusting valve as a water level control valve of the drain tank.