JP3345509B2 - Drain discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drain pipe such as a drain tank for accommodating a drain flowing from a moisture separator or the like in a nuclear power plant. The present invention relates to a drain discharge device suitable for preventing the generation.

[0002]

2. Description of the Related Art A drain tank for storing a drain at a saturation temperature is, for example, a drain tank for a moisture separation heater of a nuclear power plant. This drain tank is provided to collect saturated drain discharged from the moisture separator and supply it to downstream equipment or a water supply system.

FIG. 9 shows an example of a general nuclear power plant having a conventional moisture separator and a high pressure feed water heater drain system. The steam generated by the steam generator 1 is sent to the high-pressure turbine 2 and the low-pressure turbine 4 to perform work, and an electric output is obtained by a generator 5 directly connected to the turbine shaft. Moisture separator 3
Is provided in a path between the high-pressure turbine 2 and the low-pressure turbine 4, where moisture contained in the steam is removed. Since the moisture separated by the moisture separator 3, that is, the drain, has a high temperature, it is recovered in its entirety for the purpose of improving the thermal efficiency of the plant, and is used for heating the water supply to the steam generator 1.

For this reason, a drain tank 6 is attached to the moisture separator 3, and the drain is collected by a drain pipe 7, and is guided to a low-pressure water heater 9 by a drain pipe 8.

[0005] Usually, adjustment is performed by water level meters 10a and 10b so that the drain water level in the drain tank 6 is kept constant. When the amount of drain collected is stable, the water level gauge 10a reads the water level control valve 11a to maintain a constant water level.
And the drain is supplied to the low-pressure feed water heater 9. On the other hand, when the collected drain fluctuates greatly due to a sudden change in the plant load or the like, the water level gauge 10b operates to open the water level control valve 11b and discharge the large amount of drain to the condenser 12b.
To prevent the water level in the drain tank 6 from rising. Reference numeral 13 indicates a high-pressure water heater.

Incidentally, the drain pipe 8 connected to the drain tank 6 is generally constituted by a pipe element as shown in FIG. That is, the short pipe 14 having a short length is connected almost perpendicularly to the bottom of the drain tank 6,
A straight pipe 16 oriented in the horizontal direction is connected to the short pipe 14 via an elbow 15 to form a drain pipe 8. When the elbow 15 is not interposed before the straight pipe 16, a T joint 17 is interposed as shown in FIG. The T joint 17 is used when connecting the straight pipe 16 in two directions. Also,
A check valve 18 is interposed in each straight pipe 16 of the drain pipe 8.

[0007]

In the above-described nuclear power plant, when the flow rate of the drain flowing out of the drain tank 6 changes or the water level changes in the drain tank 6, the flow of the drain becomes unstable. .
That is, when the drain flows out through the opening O connected to the short pipe 14 of the drain tank 6 shown in FIG. 10, the inside of the system is under the pushing pressure by the water level H held in the drain tank 6, The pressure drops near the opening O due to an increase in pressure loss due to the rapid narrowing of the flow path and a drop in static pressure. If the pressure drop at this time falls below the saturation pressure of the drain, the drain self-evaporates in the system. I do.

This will be described in detail with reference to FIG. When the drain flow rate is stable, the drain tank 6
The pressure in the system under the water level H maintained in the pressure curve at all points is as shown by a curve a at a pressure higher than the saturation pressure b of the drain. On the other hand, when the operation state of the plant changes and the change in the flow rate of the drain becomes remarkable, the increase in the pressure loss and the decrease in the static pressure in the opening O are larger than those in the other regions, so that the curve c shows this. As described above, the pressure becomes lower than the saturation pressure b of the drain, and a part of the drain self-evaporates to generate a large amount of bubbles in the system. The inclusion of such bubbles in the system may cause the flow of the drain to be unstable, or may cause damage to the equipment due to the water hammer.

The drain pipe 8 shown in FIGS. 10 and 11 is provided with an elbow 15 or a T-joint 17 immediately after the short pipe 14, but if the length Lt of the short pipe 14 is short, the shape immediately after the short pipe 14 is changed. In addition to the effect of streamline turbulence at the rapidly changing joint, more bubbles are generated in the system.

For example, as shown in FIG. 13, the drain maintaining the streamline 1 in the drain tank 6 is throttled by the opening O, the flow velocity increases in the short pipe 14, and the static pressure drops. Immediately after this, the pressure loss increases due to the presence of the joint that suddenly changes the flow path that disturbs the streamline l, and further, the inside of the system experiences a pressure drop. When the joint portion is constituted by the T joint 17, the turbulence of the streamline 1 is further increased, and the pressure loss is further increased.

Accordingly, an object of the present invention is to provide a drain discharge device capable of minimizing the influence of bubbles even when drain self-evaporates due to a drop in system pressure at a joint portion such as an elbow constituting a drain pipe. It is in.

[0012]

In order to achieve the above object, the present invention provides a container containing a drain at a saturation temperature ,
A first pipe vertically connected to a bottom surface of the container,
A second pipe horizontally arranged below the first pipe,
Connection pipe for connecting the first pipe and the second pipe
Alternatively, in a drain discharge device formed by connecting a drain pipe having a connection joint , the pipe is configured to maintain the following relationship.

L / D = 2 to 10 where L = from the first pipe inlet to the center of the second pipe
Vertical length D = internal diameter of the first pipe.

[0014]

The principle of the present invention will be described with reference to the characteristic diagram shown in FIG.

The characteristic diagram shows the ratio of the length L in the vertical direction from the inlet of the drain pipe starting from the opening in the drain tank to the center of the drain pipe connected horizontally to the inner diameter D of the pipe to the ratio of the bubble generation length to the inner diameter D of the pipe. The transition is represented by a curve K, and the transition of the amount of steam generated by self-evaporation is represented by a curve W. The curve K is a high value while the length L in the vertical direction / the inner diameter D of the pipe is small in the figure, which means that a large amount of bubbles are generated. As the length L in the vertical direction / the inner diameter D of the pipe increases, the generation of bubbles decreases, and when the ratio of both exceeds 2, it is almost constant. This value does not change even if the water level in the drain tank 6 is changed. That is, it can be seen from the characteristic diagram that the generation of bubbles is suppressed by extending the vertical length L to some extent regardless of whether the water level is high or low.

On the other hand, the internal pressure of the drain tank fluctuates due to various plant operating conditions, and the internal pressure of the drain pipe communicating therewith also fluctuates under the influence. When experiencing a sharp pressure drop, the drain at the saturation temperature will self-evaporate. The amount of generated steam at this time is determined by the amount of drain at the saturation point, and the shorter the drain pipe constituting the system, the smaller the amount of generated steam. Conversely, if it is long, the amount of generated steam will greatly increase.

The curve W shows the transition of the amount of generated steam, and the amount of generated steam is small while the length L in the vertical direction / the inner diameter D of the pipe is small. This amount increases as the length L in the vertical direction / the inner diameter D of the pipe increases, and when the ratio of both exceeds 10, the steam amount sharply increases. That is, in order to suppress the generation of steam due to the self-evaporation of the saturated drain, it is understood that the vertical length L / the pipe inner diameter D needs to be within 10 or less.

Thus, the drain pipe connected to the drain tank has a vertical length determined by the pressure loss, and has a vertical length determined by the amount of steam generated by self-evaporation which must be considered separately, and both of them are satisfied. The length is preferably in the range of 2 to 10D, and the present invention determines the drain pipe length based on this value.

[0019]

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

In FIG. 1, a drain pipe 8 connected to the drain tank 6 has a short pipe 14 extending substantially perpendicularly to the bottom surface of the drain tank 6 to a distal elbow 15 over a predetermined length, and a tip of the short pipe 14. And a straight pipe 16 which is connected to the outlet of the elbow 15 in a substantially horizontal direction. Also,
A check valve 18 is interposed on each of the straight pipes 16. The opening O, that is, the length in the vertical direction from the entrance of the short pipe 14 to the center of the straight pipe 16 is indicated by reference numeral L in the figure. In this embodiment, when the inside diameter D of the short pipe is set to L, L is 5D. Having. Of course, L is not limited to this, and the length can be appropriately changed according to the present invention.

The operation of this embodiment will be described with reference to FIG. The drain flows from the drain tank 6 through the opening O into the drain pipe 8 in which the elbow 15 is interposed between the short pipe 14 and the straight pipe 16. At this time, the drain streamline 1 becomes a curve as shown in the figure. In this embodiment, the length L from the inlet of the short pipe 14 to the center of the straight pipe 16 is sufficiently long. The pressure drop caused by the large pressure loss in the vicinity can be reduced. This can prevent the pressure in the system from dropping below the saturation pressure of the drain, reduce the self-evaporation of the drain in the system, and keep the flow of the drain stable.

Another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the elbow 15 of the above embodiment is constituted by a T-joint 17. In this embodiment, similarly to the above-described embodiment, it is possible to prevent a pressure drop due to a pressure loss caused by a streamline being disturbed near the opening O.

Next, another embodiment will be described. In FIG. 4, the present embodiment is configured such that, instead of extending the short tube 14, the short tube 14 is bent immediately from the tip thereof, and the bent tube 19 having a large radius R is extended. This bent tube 1
9, the bending radius R is determined so that the length L from the opening O to the center of the straight pipe 16 has a predetermined dimension, for example, L = 5D .

The drain stream 1 of the present embodiment has a smooth curve as shown in FIG. That is, the elbow 1
5 does not cause streamline turbulence, and a smooth streamline 1 is maintained, so that an increase in pressure loss near the opening O can be prevented.

In this embodiment, a certain amount of space is required below the drain tank 6 for the bent pipe 19, but a pressure drop due to pressure loss can be suppressed more reliably than in the above two embodiments. It is possible to reduce self-evaporation of the drain.

In FIG. 6, this embodiment is a further improvement of the arrangement of the embodiment shown in FIG. 3, and the drain pipe is composed of, for example, two systems. Drain piping 8a, 8b
Short pipe 14a of the same size, 14b, T fitting 1 7 a, 1
7 b and the straight pipe 16a, composed 16b. Also,
A check valve 18 is interposed in each of the straight pipes 16a and 16b.

The streamline 1 of the present embodiment is a curve as shown in FIG. In this embodiment, a straight pipe 1
The vertical length L to the center of 6a, 16b is sufficiently long,
Even if disturbance of the streamline l arises T joint 1 7 a, 1 7 b is interposed, is away from the opening O, reducing the pressure drop caused by the pressure loss is large near the opening O Can be.

In this embodiment, in addition to this, the flow rate and the flow rate of the drain at the opening O are suppressed to be low by the two drain pipes 8, and for example, the increase of the dynamic pressure is about half of that of the one system. Thus, the static pressure can be prevented from dropping, and the pressure drop near the opening O can be reduced. Therefore, the pressure in the system can be more reliably prevented from lowering than the saturation pressure of the drain, and the self-evaporation of the drain is suppressed. As a result, the flow of the drain is kept stable, and a problem such as an extreme water hammer is caused. Can be prevented from occurring. In this embodiment, two systems are used, but three systems may be used.

Although the above embodiments are all examples of application to a drain tank used in a nuclear power plant, the present invention is not limited to this, and the present invention is not limited to this case. It is equally applicable to drain pipes that are used.

This includes, for example, a container for storing drain collected from a feed water heater of a thermal power plant, a water storage tank for receiving condensate from a deaeration chamber provided in a deaerator, and the like.

[0031]

As described above, according to the present invention, the drain pipe connected to the bottom surface of the container containing the drain at the saturation temperature is provided.
When the length L in the vertical direction from the first pipe inlet to the center of the second pipe and the inner diameter D of the first pipe are defined as L / D = 2 to 10, the elbow , T-joint
Even when the pressure in the system drops due to pressure loss or the like at a connection pipe or connection joint such as a hand, and the drain self-evaporates, the effect can be reduced.

Therefore, according to the present invention, it is possible to prevent a large amount of air bubbles from being generated in the drain pipe and to prevent a water hammer from being retained in the system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a drain discharge device according to the present invention.

FIG. 2 is a diagram for explaining the behavior of a fluid in the device shown in FIG.

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

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

FIG. 5 is a view for explaining the behavior of the drain in the apparatus shown in FIG. 4;

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

FIG. 7 is a view for explaining the behavior of the fluid in the device shown in FIG. 6;

FIG. 8 is a characteristic diagram for explaining the operation of the present invention.

FIG. 9 is a system diagram showing a main configuration of a conventional nuclear power plant.

FIG. 10 is a configuration diagram showing an example of a conventional drain pipe.

FIG. 11 is a configuration diagram showing another example of a conventional pipe.

FIG. 12 is a characteristic diagram for explaining the operation of a conventional drain pipe.

FIG. 13 is a view for explaining the behavior of a fluid in a conventional drain pipe.

[Explanation of symbols]

6 Drain tank 8 Drain piping 14, 14a, 14b Short pipe 15 Elbow 16, 16a, 16b Straight pipe 17 , 17a, 17b T-joint 18 Check valve 19 ...... Bent tube

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-124503 (JP, A) JP-A-59-151698 (JP, A) JP-A-2-118303 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G21D 1/00 F16T 1/38 F22D 11/00

Claims (2)

(57) [Claims] 1. A container for storing a drain at a saturation temperature.
And a first pipe connected vertically downward to the bottom surface of the container
And a second pipe horizontally arranged below the first pipe
Connecting the first pipe and the second pipe
A drain discharge device comprising a drain pipe connected to a pipe or a connection joint , wherein the pipe is configured to maintain the following relationship. L / D = 2 to 10, where L = from the first pipe inlet to the center of the second pipe
Vertical length D = internal diameter of the first pipe 2. A drainage device according to claim 1, characterized in that the drain pipe is provided with a plurality.