JPH04327787A - Circulating water pipe device - Google Patents

Abstract

PURPOSE:To reduce the power of a circulation pump and prevent generation of water bubbles in a circulating water pipe device wherein a great amount of water such as sea water is used as cooling water for a condenser. CONSTITUTION:In a circulating water pipe device, wherein water such as sea water sucked up by a circulating water pump is used to cool a condenser and the water after heat exchange is discharged through a forebay 8 and a flood- way 9 and a submerged dam 16 is provided in said forebay 8 or flood-way 9, a sluice gate 17 is installed on the downstream side of the dam 16 and also at least a water level detector 19 for detecting the water level on the upstream side of the dam 16 and a sluice gate control device 26 for controlling the opening of the gate 17 in response to the water level signals from the detector 19 are provided.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to circulating water system equipment for a steam turbine power plant in which a surface contact type condenser for condensing exhaust steam of a steam turbine power plant is cooled with seawater.

0003

2. Description of the Related Art Seawater is generally used as cooling water for a condenser that condenses exhaust steam from a steam turbine in a steam turbine power plant.

As shown in FIG. 2, seawater 1 passes through an intake channel 2, is pumped up from a water intake by a circulating water pump 3, and is led to a condenser 5 through an intake pipe 4. After exchanging heat with the exhaust steam of the steam turbine through the heat transfer tube 6, the water discharge pipe 7
The water is discharged into a water discharge garden 8 and returned to the sea via a discharge channel 9.

[0005] The condenser 5 is installed inside the turbine building 10, and in general, in steam turbine power plants, from the economic point of view of reducing the amount of excavation under the turbine building 10 due to civil engineering work, The installation level of the condenser 5 is normally higher than the ground level 11. Further, as the capacity of power generation plants increases, the amount of seawater used increases, and the power of the circulating water pump 3 tends to increase.

In order to reduce the power of this circulating water pump 3, a siphon is provided in the circulating water system to supply seawater to the condenser 5, which is installed at a high level, and the water level 12 of the water discharge garden 8 is kept as low as possible at the interface. The motive power of the circulating water pump 3 is reduced so as not to become higher than the above.

[0007] The height limit of the siphon is theoretically atmospheric pressure 10 mAq, but in practice it is about 8 m (7 to 9 m).
). That is, in order to have a siphon, it is necessary to suppress the difference between the water level 12 of the water discharge garden 8 and the highest seawater level in the system between the outlet of the circulating water pump 3 and the water discharge garden 8 to within about 8 m.

Generally, the highest seawater level is at the condenser 5.
Often. Therefore, if the difference S between the water level 12 in the water garden 8 and the level 13 at the top of the tube bundle of the condenser 5 is made equal to or higher than the siphon height limit (S > 8 m), the heat exchanger tubes 6 at the top of the tube bundle of the condenser 5 A vacuum is created, creating a part where seawater no longer flows. This results in a substantial reduction in the heat transfer area, and if the pressure in the vacuum section increases due to some reason, it may disappear and cause water hammer in the heat transfer tubes 6 at the top of the tube bundle of the condenser 5. Therefore, it is necessary to design the system equipment to stay within the siphon limit.

[0009] Furthermore, by increasing the capacity of a power generation plant or reducing the number of condensers by reducing the number of turbine casings even in plants with the same output, the condenser 1
The size of the base is becoming larger and larger, and along with this, the water level 12 of the water garden 8 and the pipe bundle head level 13 of the condenser 5 are increasing.
There is a tendency for the difference S to become larger and larger.

Therefore, if the difference S between the water level 12 in the waterway 8 and the pipe bundle head level 13 of the condenser 5 does not satisfy the siphon restriction, the submerged weir 16 is placed in the waterway 8 or the waterway 9. (See Figure 1) to install water level 12 in water garden 8.
Measures have been taken to increase the

[0011]

[Problem to be Solved by the Invention] However, when the submerged weir 16 is installed in this way, a difference in water level occurs before and after the submerged weir 16, and the head of the seawater caused by this water level difference causes bubbles to form. The problem arises that this occurs. The seawater discharged from the water pipe 7 to the water garden 8 causes a water level difference F (see Fig. 1) before and after the submerged weir 16, and the water level value F is approximately 40
cm or more (F>40 cm), the turbulence of the seawater flow after the submerged weir 16 and the entrainment of seawater will cause small air bubbles to be drawn into the seawater flow.

[0012] In the case of seawater, once bubbles are generated, they generally do not disappear easily, and when these bubbles are released into the sea, they can cause problems such as contamination of fishing nets due to foam adhesion and salt damage due to flying bubbles. It will cause it.

Conventionally, there is no effective means for solving these problems, or even if there is, it is not suitable for application to circulating water system equipment that processes large volumes of seawater. The reality is that maintenance and inspection are difficult. In order to remove air bubbles once trapped in seawater, for example, the speed of the flow should be reduced by approximately 0.2 between the submerged weir 16 and the sea.
A fairly large water tank is required to allow time for small air bubbles to rise to the seawater surface at a speed of less than m/s.

[0014] Recently, a movable vane type circulating water pump that can change the flow rate of seawater according to the output of a turbine has been adopted as the circulating water pump 3. This circulating water pump can change the amount of seawater supplied to the condenser 5 according to the output of the turbine, and can reduce the power of the circulating water pump 3. Therefore, when the submerged weir 16 is installed, the water level difference F before and after the submerged weir 16 changes according to changes in seawater flow rate.

[0015] Furthermore, the waterway resistance of the waterway 9 differs between the new year and the old time due to the adhesion of algae, etc. in the waterway 9, and the water surface level also changes depending on the tide level. At present, there has been no circulating water system equipment that takes these water level change conditions into consideration, reduces the power of the circulating water pump, and prevents the generation of bubbles.

[0016] As the capacity of power generation plants increases, the seawater used in the condenser increases to 1100M.
This is approximately 85m3/s for a W-class nuclear power plant and approximately 60m3/s for an 800MW-class nuclear power plant, so if a water tank that meets the above conditions is installed, it will be extremely large (400 to 600m2) and require a large installation space. In addition, the cost of civil engineering work increases and is not economical.

The present invention has been made in consideration of the above-mentioned circumstances, and is intended for use in circulating water system equipment of large-capacity steam turbine power generation plants that use large amounts of water such as seawater as cooling water for condensers. It is an object of the present invention to provide circulating water system equipment that can reduce the power of a pump and prevent the generation of seawater foam. [Structure of the invention]

[0018]

[Means for Solving the Problems] In order to achieve the above object, the circulating water system equipment according to the present invention cools a condenser with water such as seawater pumped up by a circulating water pump, and discharges the water after heat exchange. In a circulating water system facility in which water is discharged through a garden and a waterway, and a submerged weir is installed in the waterway or waterway, a water gate is installed downstream of the submerged weir, and at least This system includes a water level detector that detects the water level on the upstream side of the submerged weir, and a water gate control device that controls the opening degree of the water gate based on the water level signal from the water level detector.

[0019]

[Operation] According to the present invention configured as described above, the water level on the upstream side of the submerged weir is detected by the water level detector, and the opening degree of the water gate installed on the downstream side of this submerged weir is controlled by the water gate control device. By doing so, the difference in seawater level before and after the submerged weir can be set to about 40 cm or less, which does not generate bubbles.

[0020]

Embodiment An embodiment of the present invention will be described below with reference to FIG. Note that the same members as those in the conventional circulating water system shown in FIG. 2 are given the same reference numerals, and the explanation thereof will be omitted.

A submerged weir 16 is erected inside the water discharge garden 8 to raise the water level here, and on the downstream side of this submerged weir 16, there is a submerged weir 16 at the entrance of the water discharge channel 9. A water gate 17 is installed at this location. The opening degree 18 of this water gate 17 can be determined by water level detectors 19 installed before and after the submerged weir 16.
20, the water level difference F between the front water level 21 and the rear water level 22 of the submerged weir 16 is controlled to be approximately 40 cm or less. This prevents flow turbulence and air bubble entrainment.

The water gate 17 is equipped with a water gate driving device 23 and a water gate opening gauge 24, and this water gate driving device 23 is connected to a water gate control device 26 via a cable 25 together with the water level detectors 19 and 20. This water gate control device 26 is
It is connected to a power source 27 and a display panel 28 via a cable 22. The water gate control device 26 compares the target water level difference with the water level difference F before and after the submerged weir 16 measured by the water level detectors 19 and 20, and if it deviates from the control target range, the water gate 17 is moved to the water gate drive device 23. The opening degree 18 of the water gate 17 is changed by moving the water gate 17 through the water gate 17.

[0023] In other words, when the flow rate of seawater is constant,
When the water level difference F becomes approximately 40 cm or more, the water level 22 after the submerged weir 16 is raised by reducing the opening degree 18 of the water gate 17. In this case, the water level 21 before the submerged weir 16 will also rise slightly, but it is clear from the fluid relations of the submerged weir 16 that the increase will be less than the increase in the water level 22 after the submerged weir 16.

Further, when the opening degree 18 of the water gate 17 is constant and the seawater flow rate increases, the rear water level 22 of the submerged weir 16 becomes high, and the front water level 21 also becomes high. In this case, as the flow rate of seawater increases, the water level difference F approaches zero, and the front water level 21 becomes higher, so the power of the circulating water pump 3 increases. Therefore, in order to suppress the power of the circulating water pump 3, the opening degree 18 of the water gate 17 is increased until the water level difference F reaches about 40 cm, which is close to the limit value at which bubbles do not occur after the submerged weir 16. By doing so, the water level 2 in front of the submerged weir 16
1 can be kept low.

Here, since the spillway 9 communicates with the sea, the water level 29 behind the water gate 17 is influenced by changes in the tide level and rises and falls. Further, the level of the water level 29 after the water gate 17 differs between when the spillway 9 is in the new year and when it is old. In other words, when the open ocean is at high tide and the spillway 9 is old, the water level 29 after the water gate 17 is the highest. However, the flow rate shall be the maximum flow rate. Conversely, the water level 29 after the water gate 17 becomes small at low spring tide, when the system flow rate is at its minimum.

As described above, the water level 29 after the water gate 17 changes depending on various conditions. As a result, the front water level 21 and rear water level 22 of the submerged weir 16 are greatly affected by the flow and go up and down, but by changing the opening degree 18 of the water gate 17 to keep the water level difference within the level that does not generate bubbles, Generation of bubbles can be prevented. In addition, since the water level 21 in front of the submerged weir 16 can be kept as low as possible by adjusting the opening degree 18 of the water gate 17, it is also possible to suppress an increase in the power of the circulating water pump 3 as much as possible.

[0027] Above, the water level difference F is the bubble generation limit of about 40c.
This is a case where the opening degree 18 of the water gate 17 is controlled to be within m, but in actual control, a control range of approximately ±10 to 20 cm is provided for this target water level difference of 40 cm.

Further, the maximum opening degree 30 of the water gate is determined to be such that the maximum system flow rate can flow at the time of high tide when the water level difference before and after the water gate 17 is the minimum.

The above embodiment is an example in which the water level before and after the submerged weir 16 is measured and this water level difference F is kept within the target value. The generation of bubbles can be prevented by controlling it within a certain range.

In other words, in order to set the water level difference F before and after the submerged weir 16 at the maximum system flow rate to a level difference that does not generate bubbles,
Both the front water level 21 and the rear water level 22 can be uniquely determined from the water level relationship.

The water level 29 after the water gate 17 is determined by the system flow rate, the tide level, and the resistance of the spillway 9. For this reason, water gate 17
The opening degree 18 of the water gate 17 is determined by the water level 22 after the submerged weir 16 based on the conditions for creating a water level difference F that does not generate bubbles, and the water level 22 after the submerged weir 16 and the water level 29 after the water gate 17 and the system flow rate. The opening degree 18 is determined.

Based on this relationship, the water level at the front water level 21 of the submerged weir 16 is determined at the time of maximum flow rate, and when the flow rate changes,
The water level 21 in front of the submerged weir 16 is measured by the water level detector 19, and the opening degree of the water gate 17 is set to 1 so that the water level is equal to or higher than the maximum flow rate.
8, that is, by comparing the front water level 21 of the submerged weir 16 with the target value and adjusting the opening degree 18 of the flood gate 17 via the flood gate driving device 23, the water level difference F before and after the submerged weir 16 can be changed. The water level difference can be kept below the level where bubbles do not occur. Of course,
In this case, the opening degree 18 of the water gate 17 also changes as the tide level changes.

Controlling the water level 21 in front of the submerged weir 16 to be above a certain water level by the water gate 17 as described above is as follows:
Although the power of the recirculation pump 3 is slightly inferior, the water level detector only needs to measure the water level 21 in front of the submerged weir 16, and the water level is controlled instead of controlling the water level difference. Therefore, control is easier to perform than water level difference control, and control is more reliable.

[0034] In this case as well, it goes without saying that the controlled water level actually has a certain control range, similar to the water level difference control described above. In this case, considering the fluctuation of the water level and the accuracy of the water level detector, the actual difference is approximately ±20 cm. This is -0
~+40cm may also be used. In the case of ±20 cm, bubbles are not generated even when the control target value is -20 cm. Since this value is preferably as small as possible, it does not define a small control width.

Although the number of water gates is not shown in this embodiment, considering the case where one gate fails, it is recommended to install a plurality of water gates in parallel from the viewpoint of securing seawater flow rate in the circulating water system. preferable. Further, although an example is shown in which the submerged weir 16 is provided in the water discharge garden 8, the present invention can also be applied to a structure in which the submerged weir is provided in the water discharge channel 9.

[0036]

As described above, according to the present invention, the generation of bubbles in circulating water system equipment can be easily and reliably prevented by controlling the opening degree of the water gate, and the power of the circulating water pump can be easily and reliably prevented. increase can be suppressed as much as possible. Furthermore, sluice gates are more economical than other forms of foam prevention;
This also has the effect of making maintenance and inspection easier.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing essential parts of an embodiment of circulating water system equipment according to the present invention.

FIG. 2 is a schematic cross-sectional diagram showing circulating water system equipment of a steam turbine power generation plant.

[Explanation of symbols]

3 Circulating water pump 5 Condenser 8 Water garden 9　Discharge channel 16 Submerged weir 17 Floodgate 18 Floodgate opening degree 19,20 Water level detector 21 Water level in front of submerged weir 22 Water level after submerged weir 23 Flood gate drive device 26 Floodgate control device F Water level difference

Claims (1)

[Claims] Claim 1: A condenser is cooled with water such as seawater pumped up by a circulating water pump, and the water after heat exchange is discharged through a waterway and a waterway, and the water is provided in the waterway or waterway. In a circulating water system facility in which a submerged weir is installed, a water gate is installed on the downstream side of the submerged weir, and a water level detector that detects at least the water level on the upstream side of the submerged weir;
A circulating water system facility comprising: a water gate control device that controls the opening degree of the water gate based on a water level signal from the water level detector.