JPH05256405A - Drain pumping-up in feed water heater - Google Patents

Abstract

PURPOSE:To prevent drain having quality lower than a prescribed level from entering into condensation stream. CONSTITUTION:Drain condensated by feed water heaters 9 and 10 is collected in a drain tank 12, then led through a drain tank downpipe 13 into a drain pump 14, and finally poured into condensation stream which flows through a condensation pipe 7 after its pressure is increased by the drain pump 14. In an emergency. the drain is led into a condenser 2 through an emergency drain pipe 21. The drain is sampled at a sample take-out point 24 provided in the drain tank pipe 13 or in the emergency drain pipe 21 to determine the quality of the sampled drain. The drain in the drain tank 12 is poured into the condensation stream flowing through the condensation pipe 7, at least after it satisfies predetermined conditions of the drain quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pumping up a feed water heater drain, in which the drain condensed by a feed water heater of a nuclear power plant is pressurized by a drain pump and sent to a condensate pipe.

[0002]

2. Description of the Related Art Generally, in a nuclear power plant, condensed water or feed water is fed to a steam generator after being heated by turbine bleed air in a feed water heater. Then, the turbine bleed air condensed by this feed water heater becomes a drain and is cascaded to the feed water heater on the low pressure side, and finally collected in the condenser.

Recently, as a means for further improving the thermal efficiency of a nuclear power plant, rather than cascading the drain of a feed water heater and collecting it in a condenser, a drain pump is used to feed a condensate to a condensate pipe. A system for supplying water by a water supply system, that is, a feed water heater drain pump up system has been adopted. In this feedwater heater drain pump up system, the drain condensed in the feedwater heater is directly mixed with the condensate, which greatly contributes to the increase of the condensate temperature and the feedwater temperature, and the efficiency of the power plant is about 0.5%.
The degree can be improved. Therefore, in the latest nuclear power plants, the feedwater heater drain pump up system tends to be adopted.

An example of such a feed water heater drain pump up system is shown in FIG.

Exhaust gas from the turbine 1 is condensed in a condenser 2 and temporarily condensed as condensate. After that, the pressure is raised by a condensate pump 3, and after passing through a condensate purification device 4, a low pressure feed water heater 5, It is heated in 6 and is led to the feed water pump 8 through the condensate pipe 7. This condensate water is further pressurized as water supply by the water supply pump 8, further heated by the high-pressure water supply heaters 9 and 10, and then fed to the steam generator (not shown) through the water supply pipe 11.

On the other hand, the low-pressure feed water heaters 5, 6 and the high-pressure feed water heaters 9, 10 are supplied with bleed air from the turbine 1 through an bleed pipe (not shown), and the respective feed water heaters 5, 5 are supplied.
Heat is exchanged and condensed at 6, 9 and 10 to produce drain. The drain of the low-pressure feed water heater 5 is cascaded and sent to the low-pressure feed water heater 6 and finally collected in the condenser 6.
On the other hand, the drain of the high-pressure feed water heater 10 is cooled by the built-in drain cooler and then sent to the drain tank 12 through the drain pipe. The drain of the high-pressure feed water heater 9 is directly sent to the drain tank 12 through the drain pipe.

The high-pressure feed water heater drain thus collected is temporarily stored in the drain tank 12 and is sent to the drain pump 14 through the drain tank downcomer 13.
The drain whose pressure has been increased by the drain pump 14 passes through the water level control valve 16 and the drain pump discharge valve 17 installed in the drain pump discharge pipe 15, and is further injected into the condensate pipe 7 through the drain injection pipe 18 and mixed with the condensate. It is supposed to be done.

On the other hand, the water level of the drain tank 12 is detected by a drain tank water level gauge 19 attached thereto, and this detection signal is converted into a water level control signal by the drain tank water level control device 20 and sent to the water level control valve 16. Has been. Further, an emergency water level control valve 22 is installed in the emergency drain pipe 21 that branches from the drain tank downcomer 13 to the condenser 2, and the water level control signal from the drain water level control device 20 is an emergency water level. It is also sent to the control valve 22. The water level in the drain tank 12 is normally controlled by the water level control valve 16 while the drain pump 14 is in operation. When the drain pump 14 stops and the water level in the drain tank 12 rises, the emergency water level control valve 22 operates. It is configured to open and drain the drain to the condenser 2.

As described above, the feed water heater drain pump-up system described above directly mixes the drains of the high-pressure feed water heaters 9 and 10 with the condensate to raise the condensate temperature and the feed water temperature to improve the efficiency of the power plant. I am trying.

[0010]

However, the above-described pump-up system for the feed water heater drain has a drawback in that the water quality of the drain cannot be determined prior to the operation of the drain pump 14 or the injection of the drain into the condensate. There was

In a nuclear power plant equipped with a feedwater heater drain pump-up system, the drain pump 14 is normally started after the turbine 1 reaches a certain load. One of the reasons for this is that the pressure in the high-pressure feed water heaters 9 and 10 does not reach a sufficient value when the turbine load is low,
Therefore, the suction pressure of the drain pump 14 is also low,
On the contrary, the condensate pressure in the condensate pipe 7 is high because the discharge flow rate of the condensate pump 3 is small. That is, because the total head of the drain pump 14 is limited, a sufficient discharge pressure that overcomes the internal pressure of the condensate pipe 7 cannot be obtained when the turbine load is low.

However, another important reason is that the drain of the feed water heater does not satisfy the water quality requirement standard at the time of low load during the starting process of the turbine 1. This is because in the process of starting the turbine 1 and increasing the load, the dirt such as the school adhered to the turbine, the extraction pipe or the feed water heater is released and brought into the drain of the feed water heater.

Therefore, when the turbine load is low, the drain pump 14 is stopped, and the drain of the drain tank 12 is discharged to the condenser 2 through the emergency water level control valve 22. The drain discharged to the condenser 2 becomes condensate together with the condensed water of the exhaust steam of the turbine 1 and the low-pressure feed water heater drain, and after being pressurized by the condensate pump 3, it is purified by the condensate purifier 4. Delivered to the steam generator. Then, when the load on the normal turbine 1 reaches about 50%, the drain pump 14 is normally started to inject the drain into the condensate pipe 7, that is, to start pumping up the drain.

However, conventionally, it was not possible to judge the water quality of the feed water heater drain in the operating state in which the drain is discharged to the condenser 2 through the emergency water level control valve 22. In many feed water heater drain pump up systems, as shown in FIG. 7, a sampling point 23 is installed in the drain injection pipe 18 from the drain pump discharge valve 17 to the condensate pipe 7, and the drain is collected. .. However, when the drain pump 14 is operated at the sampling point 23 and the drain is flowing through the drain injection pipe 18, the drain is collected,
Although the water quality can be determined, the drain water quality cannot be determined when the drain pump 14 is stopped because there is no drain flow.

For this reason, conventionally, the drain pump 14 was started and the drain was injected into the condensate pipe 7 without determining the water quality of the drain. Therefore, the water quality of the injected drain is often insufficient, and In many cases, the harmful impurities of the above were sent to the steam generator through the water supply pipe 11. This has been a cause of polluting the steam generator, reducing its reliability, increasing radiation exposure, and preventing safe operation of a nuclear power plant.

The present invention provides a pump-up method for a feed water heater drain, which can determine the drain water quality prior to the injection of the feed water heater drain into the condensate and inject the drain satisfying the water quality requirement into the condensate pipe. The purpose is to do.

[0017]

A pump-up method for a feed water heater drain according to the present invention collects the drain condensed in the feed water heater into a drain tank, and then drains the feed water heater drain through a drain tank downcomer. It is led to a pump, pressurized by a drain pump and injected into the condensate flowing in the condensate pipe, and in an emergency, it goes through the emergency drain pipe to reach the condenser. Drain is collected from the sampling point provided on the drain pipe for use to determine the drain water quality, and after the drain water quality meets the specified conditions, the drain of the drain tank is injected into the condensate flowing in the condensate pipe. Is.

[0018]

As a result, the drain pump can be started after the water quality required for the drain is satisfied, and the drain injection into the condensate flowing through the condensate pipe can be started. Therefore, drainage that does not meet the water quality requirements will not be sent to the condensate.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIG.

In FIG. 1, a sampling point 24 is provided on an emergency drain pipe 21 branched from the drain tank downcomer 13, and the emergency drain pipe 21 is connected from the drain tank 12 through the drain tank downcomer 13 to the emergency drain pipe 21. It is configured to collect the drainage that passes through.

In the first embodiment of the present invention, the drain tank 12 is used when the turbine 1 is started and the load is still low.
Drained through the emergency drain pipe 21 and discharged to the condenser 2. The drain discharged to the condenser 2 becomes condensate together with the condensed water of the exhaust steam of the turbine 1 and the drain of the low-pressure feed water heater, and after being pressurized by the condensate pump 3, the condensate purification device 4
Is purified by. The purified condensate is a low-pressure feed water heater 5,6
It is heated by and is guided to the water supply pump 8 through the condensate pipe 7. This condensate is further boosted by the feed water pump 8 as feed water, further heated by the high-pressure feed water heaters 9 and 10, and then sent to the steam generator through the feed pipe 11. Since the drain pump 14 is stopped when the turbine load is low, the drain is not injected through the drain injection pipe 18.

In the first embodiment, when the load of the turbine 1 rises and reaches about 50%, the drain is sampled from the sampling point 24 provided in the emergency drain pipe 21. The collected drain is analyzed and organic matter in the drain,
It is judged whether the concentration of impurities such as iron and nickel meets the water quality requirement. If the result of the judgment is that the drain water quality does not meet the required standard, the drain pump 14
Is stopped and drain is not injected into the condensate pipe 7.

The drain of the drain tank 12 is discharged to the condenser 2 through the emergency drain pipe 21 and the emergency water level control valve 22, and is further recovered as condensed water together with the condensed water of the turbine exhaust steam and the low pressure feed water heater drain. The water is sent to the water purification device 4, and the purification operation is continued until the drain water quality satisfies the required standard. Then, after it is determined that the drain collected from the sampling point 24 satisfies the water quality requirement standard, the drain pump 14 is activated for the first time and the drain of the drain tank 12 is passed through the drain injection pipe 18 to the condensate pipe 7. Start drain injection.

As described above, according to the first embodiment, the drain pump 1 is used after the drain is sampled from the sampling point 24 provided on the emergency drain pipe 21 and the drain water quality is determined.
4 is started, and the drain of the drain tank 12 is injected into the condensate pipe 7. Therefore, the drain that does not satisfy the water quality requirement standard is not injected into the condensate and sent to the steam generator as feed water. It is possible to prevent the generator from being contaminated.

Next, FIG. 2 shows a second embodiment in which a sampling point 24 is provided on the drain downcomer 13 upstream of the branch point of the emergency drain 21. While the drain pump 14 is stopped, the drain of the drain tank 12 passes through the drain tank downcomer 13 and is led to the emergency drain 21 through the branch point of the emergency drain 21. Therefore, since there is also a drain flow in the drain downcomer 13 upstream of the branch point of the emergency drain pipe 21, it is possible to collect the drain from the sampling point 24 in FIG. After determining the water quality of the drainage, the drain pump 14 is activated and the drain tank 1
The drain of 2 can be injected into the condensate flowing in the condensate pipe 7.

FIG. 3 shows a third embodiment in the case where the emergency drain pipe 21 is directly taken out from the drain tank 12. In the third embodiment, while the drain pump 14 is stopped, the drain of the drain tank 12 is guided to the condenser through the emergency drain pipe 21 from the drain tank 12 to the condenser 2. Therefore, the drain is collected from the sampling point 24 provided on the emergency drain pipe 21, and after the drain water quality is judged, the drain pump 14 is activated to drain the drain tank 1.
The drain 2 may be injected into the condensate flowing in the condensate pipe 7.

In the fourth embodiment shown in FIG. 4, a minimum flow pipe 25 for preventing the drain pump 14 from overheating.
An example in which a sampling point 24 is provided is shown in FIG. In the fourth embodiment, when the load on the turbine 1 reaches about 50%, the minimum flow valve 26 is opened to activate the drain pump 14. However, since the drain pump discharge valve 17 is fully closed, the drain of the drain tank 12 is drained by the drain injection pipe 18
Through the minimum flow pipe 25 and the minimum flow valve 26, and returns to the drain tank 12 to form a recirculation flow. Here, the drain water quality can be determined by collecting the drain from the sampling point 24. If the drain pump discharge valve 17 is opened and the drain of the drain tank 12 is injected into the condensate pipe 7 after it is determined that the drain water quality satisfies the required standard, the same effect as the above-described embodiment can be obtained. Can be done.

The sampling point 24 may be provided in the drain pump discharge pipe 15 upstream of the branch point of the minimum flow pipe 25 as shown in the fifth embodiment of FIG. Also in this case, the minimum flow valve 26 is opened, and the drain pump discharge valve 1
When the drain pump 14 is operated with 7 being fully closed,
A recirculation flow is formed from the drain pump 14 back to the drain tank 12. For this reason, a drain flow occurs in the drain pump discharge pipe 15 upstream of the branch point of the minimum flow pipe 25, so that the drain water quality can be determined by collecting the drain from the sampling point 24.

FIG. 6 shows a sixth embodiment applied to a structure in which a plurality of drain pumps 14 are installed and a plurality of drain tank downcomer pipes and emergency drain pipes are also provided. As shown in FIG. 6, three drain tank downcomers 13a, 13b, 13c are provided from the drain tank 12, and are connected to three drain tanks 14a, 14b, 14c, respectively. The drain pressure-increased by the drain pump passes through the water level control valves 16a, 16b, 16c and the drain pump discharge valves 17a, 17b, 17c installed in the three drain pump discharge pipes 15a, 15b, 15c, and then merges to form a drain. It is guided to the condensate pipe 7 through the injection pipe 18. Also, the drain tank downcomers 13a, 13b, 13c
From each of the three emergency drain pipes 21a, 21b,
21c is branched, and drain pumps 14a, 14b,
While 14c is stopped, the drain of the drain tank 12 is discharged to the condenser 2 through the emergency drain pipes 21a, 21b, 21c and the emergency water level control valves 22a, 22b, 22c.

In this embodiment, the drain pump 14
While a, 14b and 14c are stopped, the drain is collected from the sampling point 24 provided on one emergency drain pipe, for example, the emergency drain pipe 21a, and after the drain water quality is judged, the drain pump is started. The drain of the drain tank 12 may be injected into the condensate pipe 7.

In this embodiment, the sampling points 24
Is not necessarily three emergency drain pipes 21a, 21b, 21
It is not necessary to provide it in c, and it is sufficient to provide it in one emergency drain pipe, for example, the emergency drain pipe 21a. this is,
While the drain pumps 14a, 14b, 14c are stopped, the water level control signal from the drain tank water level control device 20 is usually 3
It is sent in parallel to the emergency water level control valves 22a, 22b, 22c of the table, and the emergency water level control valves 22a, 22b, 2
Since 2c controls the water level of the drain tank 12 in the open state, the three emergency drain pipes 21a, 21
This is because there is a drain flow in both 1b and 21c and drain can be collected.

In the above-described embodiment, the example in which the present invention is applied to the system in which the drain from the high pressure feed water heater is pressurized by the drain pump and injected into the condensate pipe is described. Needless to say, the same can be applied to the pump system of. That is, the drain condensed by the low-pressure feed water heater was collected in the drain tank, and the drain of the low-pressure feed water heater was led to the drain pump through the drain tank downcomer, and was pressurized by the drain pump to be injected into the condensate. In the system as well, a sampling point may be similarly provided, and after the drain is sampled from the sampling point to determine the drain water quality, the drain of the drain tank may be injected into the condensate flowing in the condensate pipe.

[0033]

As described above, according to the pump-up method for the feed water heater drain of the present invention, the water quality requirement standard is determined after the drain water quality is determined prior to the injection of the feed water heater drain into the condensate. Since it is possible to inject a drain that satisfies the above conditions into the condensate pipe, prevent the harmful impurities in the drain from being sent to the steam generator and contaminating the steam generator to improve the reliability and safety of the nuclear power plant. Can be done.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Turbine 2 Condenser 3 Condensate Pump 4 Condensate Purifier 5 Low Pressure Water Heater 6 Low Pressure Water Heater 7 Condensate Pipe 8 Water Pump 9 High Pressure Water Heater 10 High Pressure Water Heater 11 Water Supply Pipe 12 Drain Tank 13 Drain Tank Precipitation pipe 14 Drain pump 15 Drain pump discharge pipe 16 Water level control valve 17 Drain pump discharge valve 18 Drain injection pipe 19 Drain tank water level gauge 20 Drain tank water level control device 21 Emergency drain pipe 22 Emergency water level control valve 23 Sampling point 24 Sampling point 25 Minimum flow tube 26 Minimum flow valve

Claims (5)

[Claims] 1. A condensate flowing through a condensate pipe is recovered by collecting drainage condensed by a feedwater heater into a drain tank, guiding the drainage of the feedwater heater through a drain tank downcomer pipe to a drain pump, and increasing the pressure by the drain pump. In the method of pumping up the feed water heater drain, which was injected and, at the time of an emergency, reached the condenser through the emergency drain pipe branched from the drain pipe, provided a sampling point on the emergency drain pipe. The drain water quality is determined by collecting the drain from this sampling point, and after the drain water quality satisfies the specified condition, the drain of the drain tank is injected into the condensate flowing in the condensate pipe. How to pump up the feed water heater drain. 2. The condensate which is condensed by the feed water heater is collected in a drain tank, and the drain of the feed water heater is led to a drain pump through a drain tank downcomer pipe to raise the pressure by the drain pump to condense water flowing in the condensate pipe. In the method of pumping up the feed water heater drain, which is injected and, at the time of emergency, reaches the condenser through the emergency drain pipe branched from the drain pipe, the drain upstream of the emergency drain pipe. A sampling point is provided on the tank downcomer,
The drain water quality is determined by collecting the drain from this sampling point, and after the drain water quality satisfies the specified condition, the drain of the drain tank is injected into the condensate flowing in the condensate pipe. How to pump up the feed water heater drain. 3. The condensate collected in the feed water heater is collected in a drain tank, and the drain of the feed water heater is introduced into a drain pump through a drain tank downcomer pipe and is pressurized by the drain pump to condense water flowing in the condensate pipe. In the pump-up method of the feed water heater drain, which was introduced and was connected to the condenser from the drain tank through the emergency drain pipe in an emergency, the emergency drain pipe was provided with a sampling point, and the sampling was performed. Drain water from a point is collected to determine the drain water quality, and after the drain water quality satisfies specified conditions, the drain of the drain tank is injected into the condensate flowing in the condensate pipe. Pump up method for drainage. 4. The condensate collected in the feed water heater is collected in a drain tank, and the drain of the feed water heater is led to a drain pump through a drain tank downcomer pipe to increase the pressure by the drain pump into condensed water flowing in the condensate pipe. In the method of pumping up the feed water heater drain, in which the water is injected and, in an emergency, it is led to the condenser through the emergency drain pipe branched from the drain tank downcomer pipe, branched from the drain pump discharge pipe at the drain pump outlet. Then, a minimum flow pipe of the drain pump leading to the drain tank is provided, a sampling point is provided on the minimum flow pipe of the drain pump, and the drain water quality is determined by collecting the drain from the sampling point,
A pump-up method for a feed water heater drain, characterized in that the drain of the drain tank is injected into the condensate flowing in the condensate pipe after the drain water quality satisfies a specified condition. 5. The condensate condensed in the feed water heater is collected in a drain tank, and the drain of the feed water heater is led to a drain pump through a drain tank downcomer pipe to increase the pressure in the drain pump to condense water flowing in the condensate pipe. In the method of pumping up the feed water heater drain, in which the water is injected and, in an emergency, it is led to the condenser through the emergency drain pipe branched from the drain tank downcomer pipe, branched from the drain pump discharge pipe at the drain pump outlet. Then, the minimum flow pipe of the drain pump leading to the drain tank is provided, and a sampling point is provided on the drain pump discharge pipe upstream of the branch point of the minimum flow pipe of the drain pump, and the drain from this sampling point is provided. After draining, the drain water quality is judged, and after the drain water quality meets the specified conditions, the drain of the drain tank flows through the condensate pipe. The method for pumping up the drain of the feed water heater is characterized in that the water is injected into the condensate.