JPH10122504A - Drain discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to prevent an unstable fluid state of drain in a drain pipe. SOLUTION: This drain discharge device is designed to connect the first equipment which stores drain to the second equipment on a low pressure side by way of a drain pipe 8 and conduct the drain in the aforesaid first equipment to the second equipment and provide a control valve 7 in the drain pipe 8 so as to control the flow rate of the drain which flows out from the first equipment. In this case, a vent pipe 20 is branched from the drain pipe 8 on the upstream side of the control valve 7 so that the gas in the drain pipe 8 may be released by way of the vent pipe 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drain discharge device in a feed water heater or the like used in a thermal or nuclear power plant.

[0002]

2. Description of the Related Art Generally, in a thermal or nuclear power plant, a plurality of feed water heaters are installed in order to increase the thermal efficiency of the plant, and the feed water sent to a boiler or a nuclear reactor is heated by extraction from a turbine. .

FIG. 9 is a diagram showing an example of the configuration of a feed water heater section in the above-mentioned thermal power plant or the like. The feed water supplied from the condenser 1 passes through a feed pipe 2 and the internal pressure thereof is sequentially increased. The water is sequentially fed to a plurality of raised feedwater heaters 3, 4, and 5, where it is heated through a heating pipe and then sent to a boiler or a nuclear reactor (not shown).

On the other hand, the feed water heaters 3, 4 and 5 are supplied with extracted steam extracted from the turbine, respectively, by means of extraction tubes 6a and 6a.
b, 6c, where it exchanges heat with the feedwater to form a drain. Each of the feed water heaters 3, 4, and 5 is connected to the next-stage feed water heater on the low pressure side by a drain pipe 8 having a control valve 7, and the drain condensed by heat exchange with the feed water is drained as a heat source medium. It is sent to the next-stage feedwater heater on the low-pressure side through the pipe 8 and serves as a part of a heating source of the feedwater. The non-condensable gas remaining when the steam in the feed water heater becomes drained is discharged from each of the feed water heaters 3, 4, and 5 to the condenser 1 via the orifice 10 through the vent pipe 9 respectively. .

The feed water heater generally employs a multi-tube heat exchanger because the feed water has a high pressure. The feed water flowing in the heater is heated by the extracted steam flowing outside the pipe and its drain. . Therefore, since the drain stays in the feed water heater body, a water level control device for appropriately controlling the drain water level and efficiently performing heat exchange is provided.

That is, the drain pipe 8 is provided with a control valve 7, and each of the feed water heaters 3, 4, and 5 directly drains the drain when the drain water level becomes abnormally high. A drain pipe 11 is provided to escape the air, and the drain pipe 11 is provided with a control valve 12.

Each of the feed water heaters 3, 4, and 5 is provided with a reference water level detector 13 and a high water level detector 14, respectively.
, Where it is compared with a standard water level setting signal, and the deviation signal controls the opening of the control valve 7, and the detection signal from the high water level detector 14 is input to the controller 16,
Then, it is compared with the high water level setting signal, and the opening degree of the control valve 12 is controlled by the deviation signal.

[0008]

Generally, the control valve 7 described above is used.
The fluid at the valve inlet flows in as a single-phase drain liquid, but the gas phase entrained by the drain increases, and a gas exists inside the drain pipe 8 to form a two-phase flow of the drain and the gas and the inflow. Therefore, the valve opening increases as much as the gas passes through the valve. Therefore, when the gas flow rate increases,
Even if the control valve 7 is fully opened, the drain cannot be completely discharged, and the water level of the feed water heater rises. Further, when the water level of the feed water heater rises, the control valve 12 is opened by a signal from the high water level detector 14, and the drain as the heat source medium is discharged to the condenser 1.

Further, taking the flow of drain from the feed water heater 4 to the feed water heater 3 as an example, the presence of gas inside the drain pipe 8 makes the drain flow unstable, unlike a stable single-phase flow. Because of the two-phase flow, the amount of drain passing through the control valve 7 fluctuates, and in conjunction with the fluctuation of the drain water level of the feed water heater 3, the opening degree of the control valve 7 is changed, and the controllability of the control valve 7 deteriorates. . On the other hand, even if the opening degree of the control valve 7 changes, if gas exists inside the drain pipe 8, the change in the drain flow rate passing through the control valve 7 is replaced as a change in the volume of gas inside the drain pipe 8, The change in the water level of the heater 3 is delayed. As a result, there is a problem that the change in the drain water level of the feed water heater 3 cannot follow the change in the opening degree of the control valve 7 and the controllability of the control valve 7 is impaired.

FIG. 10 is a view showing an example of a drain flow in the above-mentioned conventional drain discharge device.
Drain flow in the pipe shows extremely various situations, depending on the type of drain and gas in the pipe, as well as pipe conditions and flow rates.
Generates unstable flow. This unstable flow causes the controllability of the control valve 7 to deteriorate. In an experiment in which the amounts of water and air were changed by simulating the configuration example shown in FIG. 10, the relationships shown in FIGS. 11 and 12 were obtained. In FIG. 11, Q ₁
The water flow rate, Q ₂ represents the flow rate of air, P is indicative of the pressure fluctuations in the pipe. FIG. 11 shows that as the amount of water increases and the proportion of air increases, pressure fluctuations increase. In FIG. 12, Q
_1, Q ₂ is similar to FIG. 11, water, indicates the amount of air, H is shows the fluctuation range of the water level in the tank simulating the feedwater heater. FIG. 12 shows that the fluctuation of the water level increases as the amount of water increases and the proportion of air increases.

In the vertical portion of the drain pipe 8 shown in FIG. 10, if gas is present in the pipe, the drain falls like a waterfall. For this reason, in the downstream piping, the pushing pressure due to the hydrostatic head of the drain in the vertical portion of the piping cannot be expected, and it is also expected that a flush will occur below the saturation pressure of the drain due to the piping pressure loss and flow turbulence.

Therefore, as a method for preventing gas from flowing into the drain pipe, when the extracted steam is drained inside the feed water heaters 3, 4, and 5, the remaining non-condensable gas is removed from the feed water heaters 3, 4, and 5.
A vent pipe 9 is provided in the main body 4, 5 and discharged to the condenser 1 through an orifice 10. However, the original purpose of discharging the non-condensable gas by the vent pipe 9 is to prevent the non-condensable gas in the feed water heater from interfering with heat exchange.
The controllability of the control valve 7 cannot be sufficiently ensured.

That is, the above-mentioned feed water heaters 3, 4, 5
In the method of discharging the non-condensable gas from the main body to the condenser 1 through the vent pipe 9, the non-condensable gas of about 1% of the amount of the extracted steam at the time of the rated operation can be discharged in consideration of the thermal efficiency of the plant. In this manner, the specification of the orifice 10 installed in the vent pipe 9 is selected. However, the total amount of the non-condensable gas and the non-condensable gas remaining when the extracted steam is drained from the upper feed water heater through the drain pipe 8 may be reduced through the vent pipe 9 depending on the operation state of the plant. Is expected to exceed the amount that can be discharged to Further, since the feedwater heaters 3, 4, and 5 are much larger than the vent pipe 9, it is structurally impossible to discharge all the non-condensable gas in the feedwater heater to the condenser 1 through the vent pipe 9. It is possible, and the remaining non-condensable gas is mixed with the drain and flows into the drain pipe 8, which may cause the above-described problem.

The drain from the feed water heaters 3, 4, and 5 falls below the saturated steam pressure in the drain pipe 8 due to pressure loss in the pipe and pressure fluctuations in the pipe, and flashes to form a vapor phase. In order to prevent this, it has been proposed to provide a drain cooling device inside the feed water heaters 3, 4, and 5 to cool the drain to a temperature lower than the saturation temperature by heat exchange with the feed water.

However, in the method of providing a drain cooling device inside the feed water heater in order to prevent the drain from being flushed inside the drain pipe 8, in order to lower the drain temperature, it is necessary to increase the cooling area accordingly. Accordingly, the fluid resistance increases and the drain pressure decreases. In consideration of these facts, the drain temperature is actually set to a saturation temperature of about -5 ° C to -10 ° C. Therefore, in the drain pipe 8, it is predicted that the pipe pressure partially falls below the saturation pressure of the drain due to the pressure fluctuation due to the pipe pressure loss and the turbulence of the drain flow. In addition, it is predicted that the pre-valve pressure decreases due to a sudden change in the opening degree of the control valve 7 and the drain partially falls below the saturation pressure. As described above, when the internal drain of the drain pipe 8 falls below the saturation pressure, the drain flashes to generate steam, the volume increases rapidly, and an unstable gas-liquid two-phase flow with the drain is formed. become. on the other hand. When the saturated drain is cooled by the cooling device, it is expected that the gas dissolved inside the drain is separated and flows into the drain pipe 8 together with the drain.

In view of the foregoing, it is an object of the present invention to provide a drain discharge device capable of preventing unstable flow of drain in a drain pipe.

[0017]

According to a first aspect of the present invention, a first device for storing a drain is connected to a second device on a low pressure side by a drain pipe, and a drain in the first device is connected to a second device on a low pressure side. In a drain discharge device provided with a control valve for adjusting the flow rate of drain flowing out of the first device to the drain pipe, a vent pipe is branched from the drain pipe on the upstream side of the control valve, and the drain pipe is connected to the drain pipe. It is characterized in that the gas in the pipe is released to another device through the vent pipe.

According to a second aspect of the present invention, a first device for storing a drain is connected to a second device on a low pressure side by a drain pipe, and the drain in the first device is led out to a second device. In a drain discharge device provided with a control valve for controlling a flow rate of drain flowing out of the first device in the drain pipe,
The drain pipe at the outlet from the first device has a falling portion.

According to a third aspect of the present invention, there is provided a drain pipe as described above, wherein a horizontal straight pipe section having a diameter of at least five times the inner diameter of the drain pipe is provided immediately upstream of the control valve.

In a fourth aspect of the present invention, in the apparatus provided with the drain pipe, a gas-liquid mixture for mixing a gas flowing in the drain pipe and the drain into the drain pipe between the first device and the control valve. A device is provided.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawing, the same parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Each of the feed water heaters 3, 4, and 5 is connected to a feed water heater at the next stage on the low pressure side, and the feed water heaters 3, 4, and 5 are connected.
Vent pipes 20 are respectively branched and led upstream of the control valve 7 from each drain pipe 8 for sequentially feeding the drain in 5 to the low-pressure side feed water heater. Each vent pipe 20
Are connected to feed water heaters at the next stage on the low pressure side, bypassing the control valve 7 of the drain pipe 8, and a vent valve 21 is provided in the middle of each vent pipe 20.

FIG. 2 shows the drain pipe 8 and the vent pipe 2.
FIG. 5 is an enlarged view of part 0, in which the drain from the feed water heater 4 is sent to the next-stage feed water heater 3 on the low-pressure side through the drain pipe 8, and a control valve provided in the drain pipe 8 during that time. The flow rate flowing through the drain pipe 8 is adjusted by the control of 7, and the water level of the feed water heater 4 is controlled.

In the case where the drain from the feed water heater 4 is a gas-liquid two-phase mixed flow containing gas, as shown in FIG. 2, at the horizontal portion of the drain pipe 8 at the outlet of the feed water heater 4, Most of the gas rises to the upper part of the pipe due to buoyancy.
Thus, by connecting the vent pipe 20 to the horizontal portion of the drain pipe 8, the gas in the drain pipe 8 can be effectively discharged.

In the case where the drain pipe 8 is constituted by a falling vertical pipe following the horizontal pipe at the outlet of the feed water heater 4,
By connecting the vent pipe 20 to the horizontal portion immediately before the falling pipe, which is one of the places where the drain water level is the lowest, gas can be discharged through the vent pipe 20 more effectively. Further, when the horizontal part of the drain pipe 8 at the outlet of the feed water heater is long, it is effective to connect a plurality of vent pipes to the horizontal part.

By connecting the vent pipe 20 to the drain pipe 8 as described above, the gas in the drain pipe 8 is released from the vent pipe 2.
0, the amount of gas in the drain pipe can be reduced, and unstable flow of the drain in the drain pipe can be prevented.

When the gas remaining in the drain pipe 8 is discharged and the gas does not substantially flow from the feed water heater, the vent valve 21 can be shut off.
The drain can be prevented from being discharged through the vent valve 21, and when there is a constant flow of gas from the feed water heater, the vent valve 21 can be continuously adjusted while controlling the opening degree as an adjustable valve. Gas can be exhausted.

FIG. 3 is a view showing an embodiment of the present invention. In this embodiment, the vent pipe 20 is installed not in the feed water heater of the next stage but in a container or other facility on the low pressure side of the feed water heater 4. Connected. Therefore, the gas contained in the drain flowing out of the feed water heater 4 is discharged to the low pressure side container or other facilities through the vent pipe 20.

The vent pipe 20 may be provided with an orifice 22 in addition to the vent valve 21 according to the pressure at the connection destination.

FIG. 4 is a view showing still another embodiment, in which a drain pipe 20 is provided with a void meter 23.
The void meter 23 measures the volume ratio between the drain and the gas in the drain pipe, and the measured volume ratio is compared with the reference void ratio by the calculator 24. The deviation signal controls the opening of the vent valve 21. is there.

When the amount of gas flowing into the drain tube 8 changes, the void meter 23 controls the drain tube 8.
The amount of gas inside is measured, and the vent valve 21
Is controlled, and the amount of gas discharged through the vent pipe 9 is controlled. Therefore, the amount of gas in the drain pipe 8 can be controlled, and the flow of the drain in the drain pipe 8 can be stabilized.

FIG. 5 is a view showing still another embodiment of the present invention, in which the vertical pipe portion between the upper and lower positions of the falling vertical pipe portion of the drain pipe 8 at the outlet of the feed water heater 4 is connected. A differential pressure gauge 25 for detecting a differential pressure between pipes before and after sandwiching is provided in the drain pipe 8. Then, the differential pressure signal detected by the differential pressure gauge 25 is compared with a reference differential pressure by a calculator 26, and the opening degree of the vent valve 21 is controlled by the deviation signal.

That is, if there is no gas in the drain pipe 8, the drain pipe 8 becomes a full flow, and the difference in the drain hydrostatic head due to the installation level difference of the pressure guiding pipe is detected as a differential pressure. However, when gas is present in the drain pipe 8 and the drain flow falls like a waterfall in the vertical pipe part, the difference in hydrostatic head of the drain becomes small. It is very different from the time of full flow. Generally, since the change in the differential pressure due to the difference in the drain hydrostatic head is larger than the pressure loss due to the frictional resistance of the pipe due to the change in the pipe flow, the amount of gas in the vertical pipe section is detected by detecting the differential pressure. Can be predicted.

However, also in this case, when it is determined that the amount of gas in the drain pipe is large, the gas is discharged through the vent valve 21, the amount of gas flowing in the drain pipe 8 is controlled, and the drain is controlled. The flow of the drain in the pipe is stabilized.

FIG. 6 is a view showing still another embodiment, in which a falling portion 8a is provided in the drain pipe 8 immediately after exiting the feed water heater 4. As shown in FIG.

However, a pushing pressure is applied to the drain pipe 8 downstream of the falling part 8a by the drain hydrostatic head of the vertical pipe, and pressure fluctuation due to pressure loss in the drain pipe 8 and turbulence of flow at the joint and the like. Can prevent flash caused by
It is possible to prevent gas from being generated in the drain pipe upstream of the control valve 7.

FIG. 7 is a view showing still another embodiment of the present invention, in which a drain pipe 8 immediately before a control valve 7 is provided with a horizontal straight pipe portion 8b having a length of at least five times the inner diameter of the pipe. ing.

However, even if the drain is flushed in the drain pipe 8 due to the pressure loss and the pressure fluctuation in the pipe, the flow of the drain is rectified in the horizontal straight pipe portion 8b, and the pressure fluctuation is reduced. Therefore, the steam generated in the drain pipe is condensed, and a stable flow is obtained at the inlet of the control valve 7. Also, in the case of a two-phase flow of drain and gas inside the drain pipe 8, the flow is rectified by the horizontal straight pipe portion 8b, and the controllability of the control valve 7 is improved.

FIG. 8 is a view showing another embodiment of the present invention, in which a reducer 2 is provided in the middle of a drain tube 8 as a mixer.
7 are provided. Thus, the gas remaining inside the drain pipe 8 is mixed with the drain due to the stirring effect of the flow generated by the reducer 27. Then, the gas mixed with the drain flows out together with the drain through the control valve 7, the gas remaining in the drain pipe 8 is discharged, and the flow in the drain pipe is stabilized. In addition, as the mixer, a stirring effect can be obtained by using a three-dimensionally bent pipe for the drain pipe 8 in addition to the reducer.

[0040]

As described above, in the first invention, the vent pipe is branched from the drain pipe connecting the first equipment for storing the drain and the second equipment on the low pressure side, so that it flows into the drain pipe. Alternatively, the gas generated and retained can be discharged through the vent pipe, the flow of the drain in the drain pipe can be stabilized, and the controllability of the control valve provided in the drain pipe can be maintained. Further, in the case where the falling portion is provided in the drain pipe immediately after the outlet from the first device, it is possible to prevent the flush of the drain, to stabilize the flow of the drain in the drain pipe, and to further control the inlet of the control valve. In the part provided with a horizontal straight pipe part, the flow of the drain can be rectified, and in the one provided with a mixer in the middle of the drain pipe, the gas in the drain pipe is effectively discharged together with the drain The flow of the drain in the drain pipe can be made to be a stable flow, and the controllability of the control valve can be maintained well.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing a main part of the present invention.

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 configuration diagram showing another embodiment of the present invention.

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

FIG. 7 is a configuration diagram showing another embodiment of the present invention.

FIG. 8 is a configuration diagram showing another embodiment of the present invention.

FIG. 9 is a system diagram showing an example of a conventional drain discharge device.

FIG. 10 is a partially enlarged explanatory view of a conventional drain discharge device.

FIG. 11 is a diagram for explaining pressure fluctuation due to a gas ratio in a drain pipe.

FIG. 12 is a diagram for explaining a fluctuation in a container water level due to a gas ratio in a drain pipe.

[Explanation of symbols]

 2 Water supply pipe 3,4,5 Feed water heater 6a, 6b, 6c Bleed pipe 7 Control valve 8 Drain pipe 20 Vent pipe 21 Vent valve 10,22 Orifice 23 Void meter 24,26 Operation unit 25 Differential pressure gauge 27 Reducer 27

Claims (8)

[Claims] A first device for storing a drain is connected to a second device on a low pressure side by a drain tube, and the drain in the first device is led out to a second device, and the drain is connected to the drain device. In a drain discharge device provided with a control valve for adjusting a flow rate of drain flowing out of the first device, a vent pipe is branched from a drain pipe on an upstream side of the control valve, and gas in the drain pipe is passed through the vent pipe. A drain discharge device characterized by being made to escape to other devices. 2. The drain discharge device according to claim 1, wherein the vent pipe is provided with a valve device that can be shut off. 3. The drain discharge device according to claim 1, wherein the vent pipe is provided with a valve device capable of adjusting a flow rate of gas released from the drain pipe to another device. 4. The drain discharge device according to claim 3, wherein a void meter is provided in the drain pipe, and the valve device is controlled based on an amount of bubbles detected by the void meter. 5. The drain discharge device according to claim 3, wherein a differential pressure gauge is provided in a vertical portion of the drain pipe, and the valve device is controlled by a differential pressure detected by the differential pressure gauge. 6. A first device for storing drain is connected to a second device on the low pressure side by a drain tube, and the drain in the first device is led out to a second device, and the drain is connected to the drain tube. A drain discharge device provided with a control valve for adjusting a flow rate of drain flowing out of the first device, wherein a fall portion is provided in a drain pipe at an outlet from the first device. . 7. A first device for storing a drain is connected to a second device on a low pressure side by a drain tube, and the drain in the first device is led out to a second device, and the drain tube is connected to the second device. In a drain discharge device provided with a control valve for adjusting a flow rate of drain flowing out of the first device, a horizontal straight pipe portion having a diameter of at least 5 times the inner diameter of the drain pipe is provided immediately upstream of the control valve. To drain drain. 8. A first device for storing drain is connected to a second device on the low pressure side by a drain tube, and the drain in the first device is led out to the second device, and the drain tube is connected to the second device. In a drain discharge device provided with a control valve for adjusting a flow rate of drain flowing out of a first device, a gas and a drain flowing in the drain tube are mixed in a drain tube between the first device and the control valve. A drain discharge device comprising a gas-liquid mixing device.