JPH044481B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a feed water heater drain system that recovers drain from a water supply system in a power generation plant, etc., and particularly relates to an increase in plant output by recovering the entire amount of heat held in the feed water drain. The present invention relates to a feed water heater drain system that can provide a stable supply of water even during sudden load changes, pump trips, etc.

[Background of the invention]

In water supply systems such as power plants, condensate generated in feedwater heaters is recovered after heat exchange with condensate. Fig. 11 shows the general recovery system. Drain from the low-pressure feed water heaters 6 and 7 is sent to the drain cooler 5 via the drain tank 8, where the heat is recovered into condensate water, and then The water is collected in a water container (not shown).

However, with this method, not all of the heat held by the drain is recovered into condensate, which has been a factor that hinders improvements in the thermal efficiency of power plants.

That is, FIG. 11 shows a low-pressure feed water heater system and its drain recovery system. After condensate in a condenser (not shown) is pressurized by a low-pressure condensate pump 1,
Impurities are removed through a filter demineralizer 2 and a deep bed demineralizer 3, which are condensate filtration devices. The removed condensate is pressurized by a high-pressure condensate pump 4, passes through a drain cooler 5, low-pressure feedwater heaters 6 and 7, and is then sent to a high-pressure feedwater heater system (not shown).
sent to.

Drain generated in the low-pressure feed water heaters 6 and 7 is collected in a drain tank 8, then sent to a drain cooler 5, and after exchanging heat with condensate, is collected in a condenser.

In the above system, all the feedwater heater drains are collected in the drain cooler 5, so the volume of the drain cooler 5 becomes very large. Furthermore, it is difficult for the drain cooler 5 to recover all of the heat held by the drain. However, since the amount of drain water accounts for approximately 43% of the total amount of water supplied, not being able to recover all of this heat becomes a factor that hinders the improvement of thermal efficiency of power plants. Furthermore, since the drain collected in the condenser passes through the filter demineralizer 2 and the deep bed demineralizer 3 again, the capacity of these must also be large. In view of the above, there has been a demand for a drain system that can eliminate the drain cooler 5 and recover the entire amount of heat held by the drain.

FIG. 12 shows a conventional high-pressure feed water heater system and its drain recovery system.

In the figure, condensate that has passed through low-pressure feedwater heaters 9 and 10 is pressurized by a feedwater pump 11, passes through a drain cooler 12 and high-pressure feedwater heaters 13 and 14, and is sent to a steam generator such as a nuclear reactor. After the drain from the high-pressure feed water heater 14 recovers part of the retained heat in the high-pressure feed water heater 13, it is mixed with the drain from the high-pressure feed water heater 13 and sent to a drain cooler, where a part of the retained heat is recovered. is given to the feed water, and then the entire amount is sent to the low pressure feed water heater 10 side.

In this case, as in the case of low pressure, it is not possible to recover all of the heat held by the high-pressure feed water heater drain into the system, which becomes a factor that inhibits improvement in thermal efficiency. Further, as mentioned above, since the entire amount of the high pressure feed water heater drain flows into the low pressure feed water heater side, there arises a drawback that the capacity of each of the feed water heaters 9, 10, etc. of the low pressure feed water heater system must be increased. Therefore, in this case as well, there is a need for a drain system that can directly recover the entire amount of heat held in the water supply without recovering the high-pressure feedwater heater drain to the low-pressure feedwater heater side.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to reduce equipment costs by reducing the capacity of filters and feed water heaters, etc. in water supply systems of power generation plants, etc., and eliminating drain coolers.
It is designed to reduce the equipment installation space, recover all of the heat held in the drain to the water supply, improve the thermal efficiency of the power plant, ensure a stable supply of water, and control the amount of dissolved oxygen to prevent corrosion. The purpose of the present invention is to provide a feed water heater drain system that can be used.

[Summary of the invention]

In order to achieve the above-mentioned objects, in the first to fourth inventions, the drain is returned to the water supply system of the feed water heater instead of being returned to the condenser, thereby improving thermal efficiency and reducing the capacity of component equipment. On the other hand, in order to ensure a stable supply of water and prevent corrosion, the following configurations are provided.

In the first invention (the invention described in claim 1), drain from the feed water heater is stored in a drain tank, and the drain in the drain tank is transferred to the water supply system of the feed water heater through a drain pump up circuit system. In the drain system in which the drain tank and the feed water heater are connected by a vent steam pipe, the drain system is characterized in that a control means is provided in the vent steam pipe and the control means is controlled according to the load. According to the first aspect of the invention, when the load suddenly decreases, the vent steam piping is shut off, drain flush inside the drain tank and drain pump up circuit system is avoided, and a stable supply of water is achieved.

In the second invention (the invention set forth in claim 7), the drain from the feed water heater is collected into a drain tank, and the drain in the drain tank is transferred to the water supply system of the feed water heater through a drain pump up circuit system. The drain system is characterized in that the drain tank and the condenser are connected to each other by a vent gas pipe, and the vent gas pipe is provided with a vent gas valve to control the opening and closing of the vent gas valve. According to the second invention, for example, when the oxygen concentration exceeds a specified range, the vent gas valve is opened to promote flushing of drain flowing into the drain tank from the feed water heater, thereby reducing the oxygen concentration.

In the third invention (the invention described in claim 9), the drain from the feed water heater is stored in a drain tank, and the drain in the drain tank is transferred to the water supply system of the feed water heater through a drain pump up circuit system. In the drain system to be returned, a bypass line is provided to connect the water supply system to the upstream side of a filter provided in a part of the drain pump up circuit system connected to the water supply system, so that the pump of the drain pump up circuit system is tripped. The bypass system is characterized in that the bypass path is opened at the time. According to this third invention, since the increase in water supply during the pump trip is absorbed by the bypass system, the burden on the water supply route is reduced.
Water supply can be stabilized.

In the fourth invention (the invention described in claim 10), the drain from the feed water heater is stored in a drain tank, and the drain in the drain tank is transferred to the water supply system of the feed water heater through a drain pump up circuit system. The present invention is characterized in that the returning drain system is configured to detect the dissolved oxygen concentration in the drain and supply oxygen to the drain in the drain pump up circuit system in accordance with the detected value. According to the fourth invention, the oxygen concentration can be maintained within a specified range, and the occurrence of corrosion within the system can be reduced.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

First, an outline of this embodiment will be explained. In FIGS. 1 and 2, the same reference numerals as in FIGS. 11 and 12 indicate the same parts and the same functions.

As shown in FIG. 1, feed water heater drain pipes 31 and 32 are connected between the low pressure feed water heaters 6 and 7 and a drain tank 8 that stores drain from the feed water heater. In addition, a low pressure drain pump recovery system 20 is provided between the drain tank 8 and the high pressure condensate pump 4 on the upstream side.
A low pressure drain pump 21 and a filter demineralizer 22 are interposed in the low pressure drain pump up recovery system 20. Also drain tank 8
A vent steam pipe 35 is connected between the low pressure feed water heater 6 and the low pressure feed water heater 6 . Note that the drain cooler 5 shown in FIG. 11 is removed.

With the above configuration, the drain in the drain tank 8 is directly sent to the water supply system on the suction side of the high-pressure condensate pump 4, and the entire amount is sucked into the high-pressure condensate pump 4 side, and all the retained heat is recovered. As mentioned above, the amount of drain generated in the low pressure feed water heaters 6 and 7 is 43% of the total water supply amount.
Therefore, the amount of water supplied through the filter demineralizer 2 etc. is 57% of the total amount of water supplied, which is significantly reduced compared to the conventional technology. As a result, filter demineralizer 2, deep bed filter demineralizer 3
It is possible to significantly reduce the capacity of

FIG. 2 shows this embodiment applied to a high-pressure feed water heater and a high-pressure feed water heater drain pump up circuit system, between the drain tank 23 that stores drain from the high-pressure feed water heater 13 and the upstream side of the water pump 11. A high-pressure drain pump-up recovery system 26 is connected to the high-pressure drain pump-up recovery system 26, and a high-pressure drain pump 24 and a high-temperature filter 25 are interposed in the high-pressure drain pump-up recovery system 26. Further, a vent steam pipe 35a is connected between the drain tank 23 and the high pressure feed water heater 13. Note that the drain cooler 12 shown in FIG. 12 is removed.

With the above configuration, the entire amount of heat held in the drain can be directly recovered to the water supply system, and the low pressure water heater 1
Since no drain is collected on the zero side, the capacity of the low pressure feed water heaters 9, 10, etc. can be reduced. In addition, since the amount of condensate is about 70% of the total amount of condensate, the capacities of the low pressure condensate pump 1, filter demineralizer 2, deep bed filter demineralizer 3, high pressure condensate pump 4, etc. shown in Figure 1 are reduced. Ru.

FIG. 8 shows an embodiment of the combined invention in which a water supply system bypass piping 50 is provided as will be described in detail later.

Further, FIG. 10 shows an embodiment of the combined invention provided with a vent gas pipe 60, an oxygen concentration meter 62, and an oxygen supply device 63, as will be described in detail later.

Examples of the present invention will be described in more detail below.

As shown in FIG. 3, one end side of the feed water heater drain pipes 31, 32 is connected to the low pressure feed water heaters 6, 7 disposed in the condenser 30, and the other end side is connected to a drain header 33. There is. Drain header 33
is connected below the drain liquid level of the drain tank 8. A water level control valve 34 is interposed in the feed water heater drain pipe 32, and the water level control valve 34 is opened and closed by a control signal from a water level controller 38 provided in the low pressure feed water heater 7.

Drain is stored in the drain tank 8, and vent vapor is present above the liquid level. One end side of the vent steam piping 35 is connected to the portion of the drain tank 8 where the vent steam exists, and the other end side is connected to the low pressure feed water heater 6.

One end of a low-pressure drain pump-up recovery system 20 is connected to the portion below the drain liquid level of the drain tank 8, and the other end is connected to the upstream side of the high-pressure condensate pump 4 of the water supply system, as shown in FIG. As described above, the low pressure drain pump 21, filter demineralizer 22 and water level control valve 36 are interposed in the low pressure drain pump up recovery system 20. This water level regulating valve 36 is opened and closed by a control signal from a water level regulator 41 installed in the drain tank 8. Further, one end of a minimum flow pipe 40 is connected to the downstream side of the low pressure drain pump 21 of the low pressure drain pump up recovery system 20, and the other end of the minimum flow pipe 40 is connected to the drain tank 8.
Note that a flow rate control valve 39 is interposed within the minimum flow piping 40. Furthermore, a drain overflow pipe 37 is installed between a portion of the drain tank 8 below the liquid level and a position of the condenser 30 higher than the drain tank 8 .

In the above configuration, the vent steam pipe 35 serves to keep the pressure in the drain tank 8 and the pressure in the low pressure feed water heater 6 almost equal, and the drain in the low pressure feed water heaters 6 and 7 is caused by the difference in hydrostatic head. The drain tank 8 is configured such that only the water that flows into the drain tank 8 flows into the drain tank 8.

With the above configuration, the drain generated in the low-pressure feed water heater 7 is sent below the liquid level of the drain tank 8 while the water level is controlled, and the pressure of the drain is increased by the low-pressure drain pump 21 while the water level is also controlled.
The water is passed through the filter demineralizer 22 and sent to the upstream side of the high pressure condensate pump 4 in its entirety. Also, the abnormal water level is sent to the condenser 30 through the drain overflow pipe 37.

Since the drain from the low-pressure feed water heaters 6 and 7 is sent to the drain tank 8 due to the difference in hydrostatic head as described above, flashing of the drain is suppressed. Since this flashing is suppressed, the pipe diameter of the vent steam pipe 35 can be reduced. By making the pipe diameter small, the flashing of the drain in the drain tank 8 and the low-pressure drain pump up recovery system 20 during the pressure reduction process when the load suddenly decreases is suppressed, and the flashing of the drain on the suction side of the drain pump 21 can be prevented. Cavitation of the drain pump 21 is prevented. This allows the low-pressure drain pump 21 to operate stably even when the load suddenly decreases, thereby making it possible to stably supply water. Moreover, when the flushing of the drain in the drain tank 8 is suppressed, the water level regulator 41 in the drain tank 8 can operate stably, and stable and accurate water level adjustment can be performed.

In FIGS. 4, 5, and 7, the same reference numerals as in FIG. 3 indicate the same components or components having the same function.

A quick-closing valve 43, which is one of the above-mentioned control means, is interposed in the middle of the vent steam pipe 35.
A valve quick-closing device 42 is engaged with the valve. The quick-closing valve 43 is configured to be closed by a command from the valve quick-closing device 42 when there is a sudden load reduction such as a runback of a rapid reactor load or an intermittent load. As a result, flashing of the drain in the drain tank 8 and the low-pressure drain pump recovery system 20 when the load suddenly decreases is completely prevented, cavitation of the low-pressure drain pump 21 is completely prevented, and water is stably supplied.

In FIG. 5, an autonomous check valve 44 is provided as a control means in place of the quick-closing valve 43 shown in FIG. As shown in FIG. 6, this autonomous check valve 44 is formed so that it opens slightly when the differential pressure across the autonomous check valve 44 is small, and closes when it is large.
As in the embodiment shown in FIG. 4, this completely prevents the drain in the drain tank 8 and the low-pressure drain pump-up recovery system 20 from flashing, thereby ensuring a safe supply of water.

In FIG. 7, check valves 45 and 46 are provided in the feed water heater drain pipes 31 and 32 to stop the flow of drain from the low pressure feed water heaters 6 and 7 side to the drain tank 8 side.

When the load decreases rapidly, the check valves 45, 46
By closing the feed water heater drain pipe 3
It is possible to completely prevent flashing of the drains in the drains 1 and 32, and prevent turbine overspeed due to backflow of flash steam to the turbine, thereby improving the reliability of the turbine plant.

FIG. 8 shows an embodiment of a merged invention related to the above-mentioned specific invention. In the figures, the same reference numerals as in FIG. 11 indicate the same parts or the same functions.

As shown in the figure, a water supply system bypass pipe 50 is provided between the discharge side of the low pressure condensate pump 1 on the upstream side of the high pressure condensate pump 4 and the upstream side of the filter demineralizer 22 of the low pressure drain pump up recovery system 20. A bypass valve 51 is provided in the water supply system bypass piping. Further, the bypass valve 51 is connected to a water supply overpass bypass control device 55 . The water supply over-bypass control device 55 is operated by a detection signal from a pump trip detector 54 that engages the low pressure drain pump 21.

The preliminary low-pressure condensate pump 53 is installed together with the low-pressure condensate pump 1, and is engaged with the water supply over-bypass control device 55. The preliminary low pressure condensate pump 53 is configured to start when the low pressure drain pump 21 trips.

With the above configuration, when the low-pressure drain pump 21 trips, if the water supply system bypass piping 50 is not installed, water is also sent from the preliminary low-pressure condensate pump 53, and a larger amount of water is supplied than during normal operation. The amount passes through a filter demineralizer 23 and a deep bed filter demineralizer 3.
As a result, an excessive pressure loss occurs, and the suction pressure of the high-pressure condensate pump 4 on the downstream side decreases, resulting in loss of cavitation supply water, causing problems such as plant shutdown and damage to the filter demineralizer 2, etc. A problem occurs. However, according to the configuration of this embodiment, when the low pressure drain pump 21 trips, a signal from the pump trip detector 54 is input to the water supply over-bypass control device 55, thereby opening the bypass valve 51. Therefore, even if the preliminary low-pressure condensate pump 53 is activated, a portion of the supplied water flows to the water supply system bypass piping 50 side, passes through the filter demineralizer 22, and is then passed to the suction side of the high-pressure condensate pump 4. , where it joins the water supply that has passed through the deep bed filter demineralizer 3. Therefore, it is possible to stably supply water without increasing the pressure loss of the filter demineralizer 2 or the like and without damaging them.

FIG. 9 shows time on the horizontal axis and the flow rate of water supply on the vertical axis, showing the state of decrease in flow rate due to tripping of the low pressure drain pump 21 and the preliminary low pressure condensate pump 5.
3 shows the bypass amount of water supplied due to activation of step 3, and it can be seen that the bypass amount to compensate for the decrease in drain amount due to the trip is supplied to the high pressure condensate pump 4 side after a slight delay.

FIG. 10 shows an embodiment of a combined invention related to the above-mentioned specific invention, and the same reference numerals as in FIG. 3 etc. indicate the same items or items with the same function.

As shown in the figure, the feed water heater drain piping 32 that sends the drain of the low pressure feed water heater 7 to the drain tank 8 side is connected to the vent vapor layer above the drain liquid level of the drain tank 8. Further, the vent gas pipe 60 branches from the vent steam pipe 35 and is connected to the condenser 30. A vent gas valve 61 is provided in the vent steam pipe 60.
is intervened.

On the other hand, an oxygen concentration meter 62 is connected to the low pressure drain pump recovery system 20, and an oxygen supply pipe 65 for supplying oxygen from an oxygen supply device 63 via an oxygen supply valve 64 is connected.

Generally, it is necessary to maintain the dissolved oxygen concentration of the feed water supplied to the steam generator of a power plant within a specified range in order to reduce the occurrence of corrosion within the system. However, since the dissolved oxygen concentration in the drain of the feedwater heater changes depending on the operating conditions, it is necessary to detect this and control the oxygen concentration.

With the above configuration, a portion of the drain of the low pressure feed water heater 7 is flushed downstream of the water level control valve 34. However, since the drain is subcooled by a drain cooler (not shown) of the low-pressure feed water heater 7, oxygen dissolved in the drain is removed by the flush, and the oxygen concentration decreases. During normal operation, the removed oxygen is sent to the low pressure feed water heater 6 via the vent steam line 35 and returned through a non-condensable gas extraction pipe (not shown) installed in the low pressure feed water heater 6. The water is sent to the water dispenser 30 side.

Furthermore, if the oxygen concentration meter 62 installed in the low-pressure drain pump-up recovery system 20 detects that the oxygen concentration has exceeded the specified range, the vent gas valve 61 of the vent gas pipe 60 is opened to remove the water from the low-pressure water heater 7. Dissolved oxygen can be removed by further promoting flashing downstream of the drain water level control valve 34.

On the other hand, if the oxygen concentration is lower than the specified range,
The oxygen supply valve 64 is opened to increase the oxygen concentration in the low pressure drain pump up recovery system 20. As a result of the above, drain having an oxygen concentration within the specified range is stably sent to the water supply system.

Although the above embodiment has been mainly described with reference to the low-pressure feed water heaters 6 and 7, the same applies to the high-pressure feed water heaters 13 and 14 shown in FIG. 2, and stable water supply is achieved.

In the case of the example shown in Figure 1, the thermal efficiency can be improved by about 0.1%, and in the case of the example shown in Figure 2, it is approximately 0.1%.
It has been demonstrated that thermal efficiency can be improved by 0.4%.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the capacity of filters, feed water heaters, etc. in the water supply system is reduced, the drain cooler is eliminated, equipment costs are reduced, equipment piping space is reduced, and the drain The total amount of heat retained in the water is recovered to the feed water, improving the thermal efficiency of the plant, and furthermore, the stable supply of the feed water is achieved, and the concentration of oxygen dissolved in the drain is controlled within a specified range, thereby achieving the effect of preventing corrosion.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the low-pressure feed water heater system and drain pump-up recovery system of the present invention, and Fig. 2 is a configuration diagram of an embodiment of the high-pressure feed water heater system and drain pump-up recovery system of the present invention. Fig. 3 is a configuration diagram of an embodiment of the drain pump up recovery system of the present invention, and Figs. FIG. 6 is a line diagram for explaining the operation of the check valve shown in FIG. 7. FIG. 8 is a diagram showing the configuration of an embodiment of the related invention. is a diagram for explaining the operation of FIG. 8, FIG. 10 is a configuration diagram of an embodiment of yet another related invention, and FIG. 11 is a configuration diagram showing a conventional low-pressure feed water heater system and drain recovery system. , FIG. 12 is a block diagram showing a conventional high-pressure feed water heater system and drain recovery system. 1...Low pressure condensate pump, 2...Filter demineralizer, 3...Deep bed filter demineralizer, 4...High pressure condensate pump, 5...Drain cooler, 6...Low pressure feed water heater, 7... Low pressure feed water heater, 8...Drain tank, 9...Low pressure feed water heater, 10...Low pressure feed water heater, 11...Water pump, 12...Drain cooler, 13...High pressure feed water heater, 14...High pressure Feed water heater, 20...Low pressure drain pump up recovery system, 21...Low pressure drain pump, 22...Filter demineralizer, 23...
...Drain tank, 24...High pressure drain pump, 2
5... High temperature filter, 26... High pressure drain pump up recovery system, 30... Condenser, 31... Feed water heater drain piping, 32... Feed water heater drain piping, 33... Drain header, 34... Water level Control valve, 35...Bend steam piping, 35a...Bent steam piping, 36...Water level control valve, 37...Drain overflow pipe, 38...Water level controller, 39...
Flow rate control valve, 40... Minimum flow piping, 41
...Water level controller, 42...Valve quick closing device, 43...
Quick closing valve, 44...Autonomous check valve, 45...Check valve, 46...Check valve, 50...Water supply system bypass piping, 51...Bypass valve, 52...Check valve,
53... Reserve low pressure condensate pump, 54... Pump trip detector, 60... Vent gas piping, 61...
...Vent gas valve, 62...Oxygen concentration meter, 63...
Oxygen supply device, 64...Oxygen supply valve, 65...Oxygen supply piping.

Claims (1)

[Claims] 1. Condensate supplied by a pump is heated with a feed water heater and sent to the steam generator side, and the drain from the feed water heater is collected into a drain tank, and the drain in the drain tank is drained. In a feed water heater drain system in which the drain tank is returned to the upstream side of the pump and the feed water heater is connected by a vent steam pipe, a control means is provided in the middle of the vent steam pipe to open and close in response to sudden changes in load. A water supply heater drain system characterized by being provided with. 2. The feed water heater drain system according to claim 1, wherein the control means is a quick-closing valve that suddenly closes in response to a closing command when the load suddenly decreases. 3. The feed water heater drain system according to claim 1, wherein the control means is a self-supporting check valve that opens and closes depending on the magnitude of the pressure difference before and after the valve. 4. The feed water heater drain system according to claim 1, characterized in that a check valve is provided in the middle of a path for collecting drain from the feed water heater to the drain tank. 5. The feed water heater drain system according to claim 1, characterized in that a demineralizer is provided downstream of the drain pump in the middle of a path for returning drain to the upstream side of the pump. 6. The feed water heater drain system according to claim 1, characterized in that piping of a drain system for collecting drain from the feed water heater into the drain tank is connected below the drain liquid surface of the drain tank. . 7 Condensate supplied from the condenser by a pump is heated with a feed water heater and sent to the steam generator side, and the drain from the feed water heater is collected into a drain tank, and the drain in the drain tank is pumped into the drain pump. A feed water heater drain system in which the drain tank returned to the upstream side of the pump and the condenser are connected by a vent gas pipe, the feed water heater being characterized in that a vent gas valve is provided in the middle of the vent gas pipe. Drain system. 8. The feed water heater drain system according to claim 7, wherein the vent gas valve is controlled to open and close depending on the dissolved oxygen concentration in the drain. 9 Condensate is sent to a feed water heater via a pump, the condensate is heated by the feed water heater and sent to the steam generator side, and the drain generated in the feed water heater is recovered as heat to the condensate. In the feed water heater drain system to be formed, a drain tank that stores the drain of the feed water heater, a drain pump up circuit system that connects the drain tank and the upstream side of the pump, and a drain pump up circuit system that is interposed within the circuit system. A drain pump and a filter are provided, and a water supply system bypass piping is provided that connects the upstream side of the pump and the upstream side of the filter, and a bypass valve that is opened and closed by a pump trip of the drain pump is provided in the piping system. A feed water heater drain system characterized by: 10 A drain system comprising a system that uses a pump to send condensate to a feed water heater, heats the condensate with the feed water heater, sends it to the steam generator side, and collects the drain from the feed water heater into a drain tank. , in the feed water heater drain system comprising a drain pump up circuit system for returning the drain in the drain tank to the upstream side of the pump by a drain pump, a pipe for collecting the drain of the feed water heater into the drain tank is connected to the drain. Connected above the drain liquid level of the tank,
A feed water heater drain characterized by being provided with an oxygen concentration meter that detects the dissolved oxygen concentration in the drain, and an oxygen supply device that supplies oxygen to the drain pump up circuit system based on the detection signal of the oxygen concentration meter. system.