JPH0512597B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drain tank used by being incorporated into a feedwater heater drain system of a power generation plant, for example.

[Technical background of the invention] Figure 1 shows a feed water heater drain system.
Turbine exhaust discharged from the steam turbine 1 is cooled by cooling water such as seawater in the condenser 2, and becomes condensate into a hot well 3 formed in the condenser 2.
stored in The condensate stored in the hot well 3 is extracted by the condensate pump 4, passes through the condensate pipe 5, flows into the low-pressure feed water heater 6, and is then sequentially passed through the low-pressure feed water heater 7 and a multi-stage low-pressure feed water heater (not shown). The water then flows into a steam generator (not shown), where it becomes steam and is supplied to the steam turbine 1 again.

On the other hand, heating steam to the low-pressure feed water heaters 6 and 7 is supplied through bleed air extracted from the middle stage of the steam turbine 1 through bleed air pipes 8 and 9, respectively, where the condensate is heated and then condensed. It becomes drain and is temporarily stored there.

Further, the drain from the multi-stage low-pressure feed water heater (not shown) flows into the low-pressure feed water heater 7 through a drain pipe 10, and further includes a drain pipe equipped with a control valve 11 together with the drain generated from the multi-stage low-pressure feed water heater. 12 and is collected in the drain tank 13.

On the other hand, the drain from the low-pressure feed water heater 6 is introduced below the drain tank 13 through the drain pipe 14.
It is mixed with the drain from the low-pressure feedwater heater 7 and led into the condenser 2 through a drain pipe 16 equipped with a regulating valve 15 .

The drain tank 13 and the low-pressure feed water heater 6 are connected by a drain pipe 14 and a balance pipe 17, and the drain from the low-pressure feed water heater 7 is connected to the control valve 1.
When the drain flows into the drain tank 13 through the drain tank 13, a part of the drain flashes and becomes a gas-liquid two-phase flow. ,
It is led to a low pressure feed water heater 6.

Further, the drain water level in the drain tank 13 is controlled by the control valve 15 according to the level signal from the level switch 18.
is maintained within a certain level range by controlling.

FIGS. 2 and 3 show details of the vertical cylindrical drain tank 13 shown in FIG.
A flash drain inlet pipe 20 connected to the drain pipe 12 is provided on the upper side of the drain tank body 19.
is open. A flash steam outlet pipe 21 connected to the balance pipe 17 is opened at the upper end of the drain tank body 19, and a drain exit pipe 22 connected to the drain pipe 16 is opened at the end. A drain pipe 14 is installed on the lower side of the drain tank body 19.
The drain inlet pipe 23 connected to is open.
Additionally, a liquid level gauge 2 is provided on the side of the drain tank body 19 to measure the liquid level inside the drain tank body 19.
4 are arranged.

In the drain tank 13 configured in this way,
The gas-liquid two-phase flow flowing in from the flush drain inlet pipe 20 flows downward while swirling along the wall surface of the drain tank body 19, as shown by the arrow in FIG.
By utilizing the difference in specific gravity of the gas-liquid two-phase flow, the flash vapor flowing in from the flash drain inlet pipe 20 is separated into a gas component and a liquid component.

[Problems with the Background Art] However, in the above-mentioned drain tank 13, the water surface 25 of the drain liquid stored at the bottom of the drain tank body 19 is affected by the swirling of the liquid components, and the liquid level decreases in the center and increases toward the inner wall. It presents an unstable liquid level condition where the liquid level rises. For this reason, it becomes difficult to accurately detect the liquid level in the drain tank 13 using the liquid level gauge 24.

Furthermore, in this drain tank 13, if the swirling effect of the liquid component is large, the drop in the liquid level at the center described above will be very large, and there is a possibility that air bubbles will be drawn into the drain flowing into the drain outlet pipe 22. be.

In this case, the pressure loss within the drain pipe 16 and at the control valve 15 shown in FIG. If the liquid level rises, it becomes necessary to discharge the condensate to the condenser 2 using an emergency relief valve (not shown).

Furthermore, if the liquid level of the drain exceeds the highest set level, there is a risk that the drain in the drain tank 13 will flow back into the low-pressure feed water heater 6 and the bleed pipe 8, causing so-called water induction. The plant is forced to shut down.

Therefore, in order to prevent the condensate stored in the drain tank body 19 from being adversely affected by the swirling motion of the gas-liquid two-phase flow flowing in from the flush drain inlet pipe 20, the length of the drain tank body 19 is increased. Measures may be taken to

Furthermore, in order to prevent this phenomenon, as shown in FIG. 4 and FIG.
A method is used to prevent the liquid level 25 from falling by forcibly stopping the swirling movement of the gas-liquid two-phase flow flowing in from the flash drain inlet pipe 20.

However, even in a drain tank equipped with such a rotation prevention plate 26, as shown in FIGS. 6 and 7, the gas-liquid two-phase flow A flowing into the drain tank body 19 from the flash drain inlet pipe 20 is Due to centrifugal force, the drain with a high specific gravity is biased toward the wall surface, and most of the drain B is concentrated at a position approximately 180 degrees away from the flush drain inlet pipe 20, and after this, the drain flowing downward no longer flows uniformly.
Since the flow is concentrated in a part of the rotation prevention plate 26, the air bubbles C existing in the space inside the drain tank main body 19 are violently entrained, and the air bubbles C are carried to the drain outlet pipe 22, so that the flow can be kept stable. It disappears.

[Object of the Invention] Therefore, the object of the present invention is to provide a drain tank that can significantly reduce air bubbles drawn in from the drain outlet pipe by the liquid component of the gas-liquid two-phase flow flowing from the flush drain inlet pipe. It is about providing.

[Summary of the Invention] In order to achieve the above object, the present invention includes a vertical cylindrical drain tank body having a flash steam outlet pipe at the upper end and a drain outlet pipe at the lower end,
In a drain tank in which a flash drain inlet pipe is connected to the upper side of the drain tank body so that the gas-liquid two-phase flow sent from the outside is guided into the vessel from a direction substantially perpendicular to the axis of the drain tank body and from a tangential direction. A separation device is installed to form a vertically separated two-phase gas-liquid flow from the opening of the flush drain inlet pipe into the vessel, and a separation device is maintained in the axial direction from the drain outlet pipe to prevent swirling. It is characterized by the provision of a plate.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

8 and 9 show a drain tank according to an embodiment of the present invention, in which one end is placed at the opening of a flush drain inlet pipe 20 which is connected horizontally along the tangential direction of the drain tank body 19. A separation plate 27 is arranged which extends horizontally along the circumference of the drain tank main body 19 and has its other end placed approximately halfway around the circumference. As shown in FIG. 9, this separation plate 27 has one end that maintains the same width as the diameter of the opening of the flash drain inlet pipe 20, and the width gradually decreases from the middle, and the width at the other end remains the same. The dimensions are formed to be zero.

Furthermore, a rotation prevention plate 28 is provided at the lower end of the drain tank main body 19 with a distance maintained in the axial direction from the drain outlet pipe 22, and this rotation prevention plate 28 is constructed by combining plate materials in a lattice shape. be done. It should be noted that, except for the above-mentioned parts, it has the same structure as the drain tank shown in FIGS. 2 and 3.
Identical parts are given the same reference numerals and explanations will be omitted.

In the drain tank configured as described above, as shown in FIGS. 11 and 12, the gas-liquid two-phase flow A flowing into the flash drain inlet pipe 20 is
are vertically separated by a separating plate 27. Drain B separated on the lower side is connected to the flash drain inlet pipe 2.
The drain D, which is separated on the upper side, flows approximately once around while flowing along the upper surface of the separation plate 27 due to centrifugal force. After flowing to a certain point, it flows downward. In other words, the drain flowing above the separation plate 27 is subjected to the action of gravity after passing through the separation plate 27, which is halfway around the inner wall, and reaches a place further away than the drain separated below. be able to. Thereby, the concentrated flow of drain can be effectively dispersed in the circumferential direction, and it is possible to keep the deviation of the drain flowing into the rotation prevention plate 28 to a minimum. By reducing this deviation, the non-uniformity of the inflow velocity will be reduced,
It is possible to reduce the entrainment depth of the bubbles C.

Further, since the rotation prevention plate 28 is provided at the lower part of the drain tank body 19, the flow state of the drain is rectified, and it is possible to more effectively suppress the entrainment of air bubbles into the drain reservoir due to drift.

Furthermore, since the liquid level 25 of the drain stored in the drain tank body 19 does not exhibit an unstable state as shown in FIG. 2, an accurate liquid level can be given to the liquid level gauge 24. .

In addition, in the embodiment described above, an example was explained in which one separation plate 27 was arranged at the opening of the flush drain inlet pipe 20, but the present invention is not limited to such an embodiment. For example, two separation plates may be arranged, and the dispersion effect can be further enhanced than in the above embodiment.

[Effects of the Invention] As explained above, in the present invention, the flow of a gas-liquid two-phase flow separated into upper and lower parts from the opening of the flush drain inlet pipe facing the interior of the drain tank body toward the interior of the vessel is realized. In addition to arranging the separation device for forming the water heater, a rotation prevention plate is provided at a distance from the drain outlet pipe in the axial direction, so that it is possible to significantly reduce air bubbles caught in the drain outlet pipe. This has the excellent effect of maintaining stable operation by avoiding plant shutdowns due to system abnormalities.

[Brief explanation of the drawing]

Fig. 1 is a piping system diagram showing an example of a feed water heater drain system, Fig. 2 is a longitudinal sectional view showing an example of a conventional drain tank, and Fig. 3 is a sectional view taken along the - line in Fig. 2. Fig. 4 is a vertical sectional view showing another embodiment of the conventional drain tank, and Fig. 5 is a - of Fig. 4.
6 and 7 are explanatory diagrams showing the drain flow of the drain tank shown in FIGS. 4 and 5, and FIG. 8 shows an embodiment of the drain tank according to the present invention. A vertical sectional view, FIG. 9 is a sectional view taken along the - line in FIG. 8, and FIG. 10 is a sectional view taken along the - line in FIG. 8.
11 and 12 are explanatory diagrams for explaining the flow of drain in the drain tank shown in FIG. 8. 19...Drain tank body, 22...Flush drain inlet pipe, 21...Flush steam outlet pipe, 22
...Drain outlet pipe, 23...Drain inlet pipe, 27...Separation plate, 28...Swivel prevention plate.

Claims (1)

[Claims] 1 Equipped with a vertical cylindrical drain tank body having a flash vapor outlet pipe at the upper end and a drain outlet pipe at the lower end, the gas-liquid two-phase flow sent from the outside is directed almost perpendicularly to the axis of the drain tank body, and A drain tank in which a flash drain inlet pipe is connected to an upper side surface of the drain tank body so as to lead into the vessel from a tangential direction of the drain tank body,
A separation device is arranged to form a vertically separated gas-liquid two-phase flow toward the inside of the vessel from the opening of the flash drain inlet pipe, and is rotated while keeping a distance from the drain outlet pipe in the axial direction. A drain tank characterized by being equipped with a prevention plate.