JP2001004786A - Drain tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise solved oxygen removing effect in a drain tank in a thermal/ nuclear power plants. SOLUTION: In the upper part of a drain tank body shell 1, drain inlets 2 and 3 and a generated steam outlet 4 are provided and inside the drain tank body shell 1, a water scattering tray 8 are placed below the drain inlets 2 and 3. A partition wall 8a for cutting the connection between the drain inlet 3 and the generated steam outlet 4 adjacent to each other is stood from at least one end of the water scattering tray 8. Only on the opposite side of the generated steam outlet 4, an opening 9 connecting the upper space of the scattering tray with the drain tank body shell inside is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a drain tank in a thermal / nuclear power plant.

[0002]

2. Description of the Related Art Generally, a thermal / nuclear power plant is provided with a drain tank for collecting drain generated by a feed water heater or a moisture separator and separating high enthalpidrain into steam and drain. FIG. 5 is a cross-sectional view showing a schematic configuration of a conventional drain tank. A plurality of pairs of low enthalpidrain inlets 2 and high enthalpidrain inlets 3 are provided at the top of a main body 1 of the drain tank.
A generated steam outlet 4 is provided in the vicinity of both ends of the top of the main body 1. A drain outlet 5 is provided at the bottom of the main body 1.

On the other hand, inside the main body 1, a hole is provided at the bottom below the low enthalpidrain inlet 2 and the high enthalpidrain inlet 3 and above the water storage surface 6, and the drain is formed into a liquid column or a droplet. A watering tray 7 is provided.

Thus, a low enthalpy drain supplied from a feed water heater or a moisture separator (not shown) is guided from the low enthalpy drain inlet 2 into the drain tank main body 1, and similarly a feed water heater is provided. And a high enthalpy drain supplied from a moisture separator is introduced into the main body 1 through the high enthalpy drain inlet 3.

[0005] Therefore, a part of the high enthalpidrain introduced into the main body 1 from the high enthalpidrain inlet 3 is flushed on the way from the high enthalpidrain inlet 3 to the watering tray 7 and separated into drain and steam. . And
The drain which did not become steam reaches the watering tray 7, where it mixes with the low enthalpidren introduced into the main body 1 from the low enthalpidrain inlet 2 and forms a liquid column or droplet from the watering tray 7, It is discharged below the watering tray 7. The drain discharged below the watering tray 7 generates steam until it becomes saturated water while falling to the water storage surface 6, is separated into steam and drain, and the drain is stored in the main body 1. . On the other hand, non-condensable gas such as steam and air separated from the drain as described above is discharged from the generated steam outlet 4.

[0006]

In recent power generation plants, the concentration of dissolved oxygen contained in feed water has become a problem, and it has been known that stress corrosion cracking occurs in equipment due to the high concentration of dissolved oxygen. I have.

By the way, since the drain generated in the drain tank is recovered in the feed water, it is possible to reduce the dissolved oxygen concentration in the feed water by reducing the dissolved oxygen concentration in the drain of the drain tank.

[0008] However, in the above-mentioned conventional drain tank, the purpose of flushing high enthalpidrain and separating steam and drain has been achieved, but there is a problem that dissolved oxygen in low enthalpidrain is not sufficiently degassed.

In view of the above, an object of the present invention is to provide a drain tank having a high dissolved oxygen removing effect.

[0010]

According to a first aspect of the present invention, a drain inlet and a generated steam outlet are provided at an upper portion of a drain tank main body, and water is sprinkled inside the drain tank main body below the drain inlet. In a drain tank provided with a tray, a partition wall for cutting off communication between a drain inlet and a generated steam outlet adjacent to each other from at least one edge of the water spray tray is provided, and water is sprayed only on a side opposite to the generated steam outlet. An opening communicating the upper space of the tray with the inside of the drain tank body is formed.

According to a second aspect of the present invention, in the first aspect of the invention, the watering tray has a side wall constituting a partition wall,
It is a box-shaped body having an opening only in the side wall part opposite to the generated steam outlet.

The invention according to claim 3 is the invention according to claim 1, wherein the amount of dissolved oxygen in the drain introduced into the drain tank and the amount of steam generated from the drain are equalized for each watering tray. It is characterized in that the introduced steam is appropriately combined for each inlet.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a perforated plate is provided above the water storage surface in the drain tank body.

A fifth aspect of the present invention is characterized in that, in any one of the first to third aspects of the present invention, a perforated plate is provided in the water storage in the body of the drain tank main body.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the figure, the same parts as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a view showing a first embodiment of the present invention. A watering tray 8 provided below a low enthalpidrain inlet 2 and a high enthalpidrain inlet 3 has:
A partition wall 8a reaching the upper inner wall surface of the drain tank main body 1 is integrally provided upright at one end edge thereof. The communication between the high enthalpidrain inlet 3 and the generated steam outlet 4 adjacent to each other is cut off by the partition wall 8a. On the other hand, an opening 9 that communicates the upper space of the watering tray 8 with the inside of the drain tank main body 1 is formed only on the side opposite to the generated steam outlet 4.

However, a part of the drain introduced from the high enthalpidrain inlet 3 is separated from the drain by the time it falls to the sprinkling tray 8 and becomes steam. The generated steam flows from the opening 9 formed only on the side opposite to the generated steam outlet to the lower part of the watering tray 8 and further flows to the generated steam outlet 4 through the lower part of the watering tray 8 as shown by the solid arrow. . On the other hand, high enthalpidren, which did not become steam,
It can be received on the watering tray 8.

The low enthalpidren introduced from the low enthalpidren inlet 2 is heated and degassed by steam generated by the high enthalpidren while falling into the sprinkling tray 8, then received by the sprinkling tray 8, and Mix with the drain that did not become steam. And
The mixed drain falls from the perforations of the watering tray 8 and, before reaching the water storage surface, is further heated and degassed by the steam generated from the high enthalpidrain passing through the lower part of the watering tray 8 as described above.

Accordingly, the steam generated in the watering tray always passes through the lower part of the watering tray 8 and is heated by contact with the drain having dissolved oxygen, thereby effectively removing the dissolved oxygen in the drain. That is, the solubility of oxygen in the drain is proportional to the oxygen gas partial pressure according to Henry's law, and the Henry's constant, which is a proportionality constant, becomes smaller as the temperature of the drain becomes higher at a drain temperature of about 100 ° C. or higher. Becomes difficult to dissolve in the drain. Therefore, the drain can be effectively degassed by heating the drain and increasing the temperature of the drain.

In the above-described embodiment, the partition wall 8a is provided at one side edge of the watering tray 8, but the watering tray is formed as a box and each side wall forms a partition wall. The opening 9 may be formed on the side opposite to the generated steam outlet.

If the amount of dissolved oxygen in the drain and the amount of steam flushed from the drain are not uniform for each watering tray, sufficient steam is supplied to one of the watering trays, and the drain is sufficiently heated and degassed. However, in the other watering tray, sufficient steam is not supplied to deaerate the dissolved oxygen of the drain, so that the heating of the drain becomes insufficient and the dissolved oxygen in the drain may not be sufficiently degassed.

FIG. 2 is a view showing a second embodiment of the present invention in which dissolved oxygen in the drain can be evenly degassed. Are disposed so that the amount of dissolved oxygen and the amount of generated steam are equal.

That is, each of the steams introduced into the drain inlets 10a and 10b and the drain inlets 10c and 10d has a rate of generation in consideration of the dissolved oxygen amount in the steam and the generated steam amount calculated in advance in the design stage. They are almost identical. For example, when the amount of steam generated at the drain inlet 10a is 1 and the amount of dissolved oxygen is 2, the amount of steam generated at the drain inlet 10b is 2 and the amount of dissolved oxygen is 1 Accordingly, when the respective steams are mixed in the watering tray 8, the generated steam amount becomes 3 and the dissolved oxygen amount becomes 3, and both become equal. Drain inlet 10c,
In the case of 10d as well, a combination is made in the same manner in consideration of the amount of steam to be introduced and the amount of dissolved oxygen.

Thus, by supplying the steam necessary for degassing the dissolved oxygen in the drain evenly to each of the watering trays 8, the dissolved oxygen in the drain can be degassed effectively.

FIG. 3 is a view showing a third embodiment of the present invention, in which a perforated plate,
A perforated plate 11 such as a net-like flat plate or a grid-like plate is provided. Other points are the same as the embodiment shown in FIG.

In this embodiment, however, the drain that has fallen from the watering tray 8 is once received by the perforated plate 11 above the water storage surface 6 and does not directly fall on the water storage surface. Therefore, entrapment of air bubbles on the water storage surface is reduced, and oxygen contained in the air bubbles is prevented from dissolving into the water storage.

When bubbles are trapped in the drain on the water storage surface, the pressure in the bubbles increases due to the water pressure due to the depth from the water storage surface, and the partial pressure of oxygen in the bubbles increases. As a result, the solubility of oxygen in the drain increases according to Henry's law, and the concentration of dissolved oxygen in the storage drain increases. Also,
As the entrainment of the air bubbles increases, the pressure inside the air bubbles increases, so that the vapor inside the air bubbles condenses and the air bubbles become smaller. As the bubbles become smaller, their surface tension further increases the pressure within the bubbles, causing more oxygen to dissolve in the reservoir drain.

However, in this embodiment, since the perforated plate 11 is provided as described above, entrapment of air bubbles into the drain on the water storage surface is reduced, and dissolution of oxygen into the water storage drain is prevented. It is possible to prevent the degassed oxygen from being dissolved into the water again.

FIG. 4 is a view showing a fourth embodiment of the present invention, in which a perforated plate 11 is provided in a reservoir. In this case as well, the drain that has fallen directly from the water spray tray 8 into the water storage reduces the entrapment of air bubbles by the perforated plate 11 provided in the water storage, and oxygen contained in the air bubbles may dissolve into the water storage. Is prevented.

[0030]

The present invention is constructed as described above.
The generated steam always comes into contact with the drain falling from the watering tray without the steam separated from the drain in the watering tray portion being directly discharged from the generated steam outlet, so that the drain can be effectively degassed. Further, in the case where the drain inlet is arranged such that the amount of dissolved oxygen and the amount of generated steam are equalized for each watering tray, the dissolved oxygen in the drain can be more effectively degassed. Furthermore, in the case where the obstruction plate is provided on or in the water storage surface, the entrapment of air bubbles is reduced, and the degassed oxygen is prevented from being dissolved into the water storage again.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a drain tank according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a drain tank according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a schematic configuration of a drain tank according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a schematic configuration of a drain tank according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing a schematic configuration of a conventional drain tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Low enthalpidrain inlet 3 High enthalpidrain inlet 4 Generated steam outlet 5 Drain outlet 6 Water storage surface 7,8 Watering tray 8a Partition wall 9 Opening 10,10a, 10b, 10c, 10d Drain inlet 11 Perforated plate

Claims (5)

[Claims] 1. A drain tank having a drain inlet and a generated steam outlet at an upper portion of a drain tank main body, and a sprinkler tray provided below the drain inlet in the drain tank main body. A partition wall that cuts off communication between the drain inlet and the generated steam outlet adjacent to each other from one end edge is provided, and the upper space of the watering tray and the inside of the drain tank body are connected only to the side opposite to the generated steam outlet. A drain tank having an opening formed therein. 2. The drain according to claim 1, wherein the watering tray has a side wall constituting a partition wall, and is a box-shaped body having an opening only in a side wall opposite to the generated steam outlet. tank. 3. The system according to claim 2, wherein the amount of dissolved oxygen in the drain introduced into the drain tank and the amount of steam generated from the drain are appropriately combined at each drain inlet so that the amount of steam generated from the drain becomes uniform for each watering tray. The drain tank according to claim 1 or 2. 4. The drain tank according to claim 1, wherein a perforated plate is disposed above a water storage surface in the body of the drain tank body. 5. The drain tank according to claim 1, wherein a perforated plate is disposed in the water stored in the body of the drain tank body.