JP2001003345A - Structure of tail water pit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure capable of reducing the generation of foam by providing a bypass of which the intake level coincides with the height of the weir of a water tank, and charging a part of the discharging volume to reduce the cascading volume falling from the weir. SOLUTION: A bypass 4 to be installed in a water tank 2 is constituted of an intake 4a and a pressure water way 4b. A spirally inclined plates are provided at the inner peripheral face of the intake 4a and the installation height is set to coincide with the top of the weir 3. The weir 3 of a partition wall is formed at the downstream end of the water tank 2 and the pressure water way 4b is arranged horizontally toward the weir 3. Water W in the water tank 2 overflows from the weir 3 and discharged outside the water tank 2 as a dropping water stream and also discharged through the bypass 4 outside the water tank 2. The discharging water W flowing out outside the water tank 2 through the bypass 4 flows in the pressure water way 4b in a spiral flow without generation of foam 5 and thereafter, it is discharged outside the water tank 2. In this way, generation of foam can be reduced and the water tank can be made compact and hence, the construction cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the structure of a water discharge pit.

[0002]

2. Description of the Related Art In a thermal power plant and a nuclear power plant, foams generated in a spillway system may be discharged into the sea area to damage the landscape.
If foaming occurs after the start of operation of the power plant, a large amount of cost is required for countermeasures. Therefore, it is desired to design a water discharge channel without foaming. The basic measure for preventing foaming of bubbles generated by air entrainment is a method that does not create a water flow that falls by overflowing a weir, which is a typical foaming cause, that is, a so-called waterfall drop. However, when the damping method is unavoidable, the following method is used as a foam prevention measure.

<A> Prevention of air entrainment In order to operate the water level of the water discharge tank within a certain range, a valve adjustment discharge type in which the valve opening is adjusted by the flow rate. A saophone discharge type in which the on / off of one of the valve adjustment discharges is replaced by a saophone. A water flow cover that covers the waterfall drop area with a strong sheet or steel floating body to prevent air entrainment.

<B> Bubble treatment A pipe discharge type with an air pipe that floats bubbles in a pressure channel and exhausts the air from an air pipe. Curtain wall and shower type that prevent foam from flowing out at the end of the waterway or the curtain wall at the front and defoam in the shower. Dispersion falling bottom layer discharge type, in which falling water veins are dispersed by a grid etc. to reduce the depth of penetration of bubbles into the water tank and discharge from the bottom layer without bubbles. Suction hot air treatment type that sucks floating bubbles and separates air.

However, among the above-mentioned various methods, the valve adjustment discharge type requires consideration of the mechanical system such as the valve type, design, and maintenance, and the siphon discharge type requires a temporary start and stop time for the siphon. Inevitable foaming,
In setting the initial conditions, valve adjustment is required, and there is a problem that a mechanical system needs to be examined similarly to the valve adjustment discharge type.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure of a water discharge pit in which the flow rate of a waterfall is reduced and the amount of generated bubbles is small in order to solve the above problems.

[0007]

A first aspect of the present invention is a water discharge pit for reducing bubbles generated by air entrainment, in which a bypass is provided in a water tank, and a part of a drainage amount in the water tank is borne by the bypass. The structure of the water discharge pit is characterized in that the flow rate of the waterfall falling from the weir is reduced. The second invention is a structure of the water discharge pit according to the first invention, wherein the height of the bypass suction port is made to match the height of the weir of the water tank. According to a third invention, in the structure of the water discharge pit according to any one of the first invention and the second invention, an inner peripheral surface of the bypass suction port is formed in a spiral shape, and a water force of drainage flowing down to the bypass suction port is reduced. The structure of the water discharge pit.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

<A> Overall Configuration FIG. 1 is a side sectional view showing the structure of a water discharge pit according to the present invention, and FIG. 2 is a plan view thereof. Wastewater W discharged from the thermal and nuclear power plants into the sea area is discharged from the discharge pipe 1 to the water tank 2.
And is discharged from the weir 3 by overflowing the weir 3 to form a falling water vein and being discharged out of the water tank 2, and a part of the drainage amount in the water tank 2 is borne by the bypass 4 installed in the water tank 2, thereby falling from the weir 3. The generation amount of the bubbles 5 is reduced by reducing the flow rate of the falling waterfall.

<B> Bypass The bypass 4 installed in the water tank 2 is composed of a suction port 4a and a pressure water channel 4b. The installation height of the suction port 4 a is set to be the same as the top end of the weir 3. (FIG. 1) Generally, cooling water of a power plant is flowed by a pump. In order to further reduce the load on the pump, the flow is carried out using the action of a siphon. The weir 3 is installed to make use of the action of the siphon, and if there is no weir 3, the water level of the water tank 2 drops and a phenomenon that the siphon does not work (siphon break) occurs.
Therefore, the installation height of the suction port 4a needs to match the top end height of the weir 3.

<C> Suction Port FIG. 3 is a plan view of the suction port 4a. By providing the inclined plate 6 in a spiral shape on the inner peripheral surface of the suction port 4a, the drainage W is formed into a spiral shape (arrow) and can flow into the pressure water channel 4b. If the inclined plate 6 is not provided, a waterfall occurs at the suction port 4a depending on hydraulic conditions, and air bubbles are generated at the suction port 4a. By installing the inclined plate 6, the suction port 4
The water flowing down to a can be reduced.

<D> Pressure channel A pressure channel 4b is provided continuously below the suction port 4a.
It is arranged horizontally toward the weir 3 of the partition wall. Pressure channel 4
b is formed of, for example, a circular pipe.

<E> Weir A partition wall weir 3 is provided at the downstream end of the water tank 2. A pressure water channel 4b penetrates through the center of the weir 3 of the partition wall, and discharge water W inside the pressure water channel 4b is discharged from the water tank 2 to the outside. Since the drainage W discharged from the inside of the pressure water channel 4b to the outside of the water tank 2 does not come into contact with air, there is no concern about air entrainment,
Therefore, no bubbles 5 are generated. Further, the outlet of the pressure water channel 4b may be arranged downward. With this downward arrangement, the flow discharged from the pressure water channel 4b is applied to the bottom plate 2 of the water tank 2.
The water can be weakened by hitting a.

[0014]

The operation of the present invention will be described below.

<B> Drainage into the water tank Drainage W discharged into the sea from thermal power and nuclear power plants
Is discharged from the discharge pipe 1 into the water tank 2.

<B> Discharge to the outside of the water tank The waste water W discharged into the water tank 2 overflows the weir 3 to form a falling water vein and is discharged outside the water tank 2.
A part of the drainage amount in the water tank 2 is borne by the bypass 4 installed in the inside. Therefore, the water tank 2 can be made compact and the construction cost can be reduced. In addition, the amount of drainage that overflows the weir 3 and becomes a falling water vein decreases, the downward flow velocity of the wedge-shaped water vein (nap) decreases, and the generation of bubbles 5 can be reduced.

On the other hand, the waste water W discharged to the outside of the water tank 2 by the bypass 4 installed below the water surface in the water tank 2 does not come into contact with the air, so that there is no fear of entrainment of the air, and the water W is swirled without generating bubbles 5. (Arrow), after flowing into the pressure channel 4b, it can be discharged out of the water tank 2. Since the outlet of the pressure water channel 4b is arranged downward, the flow discharged from the pressure water channel 4b can be applied to the bottom plate 2a of the water tank 2 to reduce the water force.

[0018]

Since the present invention has been described above,
The following effects can be obtained. <B> Since the water is also discharged from the bypass to the outside of the water tank, the waterfall drop flow rate is reduced, and the amount of generated bubbles can be reduced. <B> For the same reason, the water tank can be made compact, and the construction cost can be reduced. <C> Compared to the method in which all the waterfalls are discharged through a pressure channel, the present invention uses a partially open channel, so that the water level fluctuation on the downstream side such as ocean waves has less influence on the water tank.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing the structure of a water discharge pit according to the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a plan view of a bypass suction port.

Claims (3)

[Claims] Claims: 1. A water discharge pit for reducing bubbles generated by air entrainment, wherein a bypass is installed in a water tank, a part of the drainage amount in the water tank is borne by the bypass, and a waterfall falling from the weir is reduced. The structure of the water discharge pit. 2. The structure of the water discharge pit according to claim 1, wherein the height of the bypass suction port is made equal to the height of the weir of the water tank. 3. The structure of the water discharge pit according to claim 1, wherein the inner peripheral surface of the bypass suction port is formed in a spiral shape so as to reduce the water force of the drainage flowing down to the bypass suction port. Characterized by the structure of the water discharge pit.