JPH08177408A - Drain tank controller for steam turbine plant - Google Patents

Abstract

(57) [Summary] [Purpose] To stabilize the drain flow rate sent from the drain tank to the condensate / water supply system, and to prevent the drain flow rate fluctuation due to the tank water level fluctuation in the drain tank. . [Constitution] Water supply heater 5a provided in the condensate / water supply system,
Of the steam turbine plant equipped with a feed water heater drain pump up system that stores the drain condensed in 5b, ... 7a, 7b in the drain tank 11 and then feeds it to the condensate / water supply system via the drain pump 12. In the drain tank control device, a correction signal corresponding to the water level in the drain tank is added to the flow rate control signal for controlling the flow rate of the drain sent from the drain tank 11 to the condensate / water supply system. And

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drain tank control device in a steam turbine plant having a feed water heater drain pump up system for a nuclear power plant or the like.

[0002]

2. Description of the Related Art Generally, in a nuclear power plant, a reactor water condensate / water supply system from a condenser to a reactor is provided with a feed water heater. The condensate or the supply water is heated. Then, the condensate water or the feed water heated by the feed water heater is fed to the reactor as a steam generator.

On the other hand, the condensate or the turbine bleed air obtained by heating the feedwater is condensed by each feedwater heater, becomes a drain, and is sequentially sent to the feedwater heater on the low pressure side in a cascade form, and finally to the condenser. Be recovered.

By the way, recently, as a means for further improving the plant efficiency of a nuclear power plant, rather than guiding the drain of the feed water heater in a cascade form and collecting it in the condenser, the drain is pumped to the condensate pipe. A feed water heater drain pump up system has come into use.

In this feedwater heater drain pump-up system, the saturated drain condensed in the feedwater heater is directly mixed with the condensate water from the condenser, so that it greatly contributes to the increase of the condensate temperature and hence the feedwater temperature. The efficiency of the power plant can be improved by about 0.5%. For this reason,
In state-of-the-art nuclear power plants, the adoption of feedwater heater drain pump up system technology is being attempted.

In the meantime, the feed water heater drain pump up system is roughly classified into a low pressure feed water heater drain pump up system for pumping up the drain generated in the low pressure feed water heater and sending it to the condensate pipe, and a drain of the high pressure feed water heater. There are two types, a high-pressure feed water heater drain pump-up system for pumping up the water and sending it to the condensate pipe, and each drain popup system is used alone or in combination.

FIG. 6 is a system diagram exemplifying a reactor condensate / water supply system of a nuclear power plant equipped with a high pressure and low pressure feed water heater drain pump up system.

That is, the steam expanded by performing work in the steam turbine 1 is introduced into the condenser 2 where it is condensed and condensed. This condensate is temporarily accumulated in the condenser 2 and then boosted in pressure by the condensate pump 3, and the condensate purification device 4
Is filtered and desalted. The filtered desalted condensate is successively heated by the low-pressure feed water heaters 5a, 5b, 5c, and 5d, pressurized by the feed water pump 6, and then supplied to the high-pressure feed water heaters 7a and 7b as feed water. It is heated and supplied to the reactor 9 through the water supply pipe 8.

On the other hand, turbine bleed air is supplied to the low-pressure feed water heaters 5a, 5b ... And the high-pressure feed water heaters 7a, 7b by bleed pipes (not shown), respectively.
Heat is exchanged with a, 5b ... 7a, 7b to heat condensed water or feed water. By this heat exchange, it is condensed and becomes a drain, which is sequentially sent to the feed water heater on the low pressure side and collected in the drain tank.

That is, the drain generated in the high-pressure feed water heaters 7a, 7b is collected in the drain tank 11 via the drain pipes 10a, 10b, temporarily stored, and then pressurized by the drain pump 12 and fed through the drain recovery line 13. It is mixed with water supply on the suction side of the pump 6. Further, the drain generated in the low pressure feed water heater 5d is fed to the low pressure side low pressure feed water heater 5c via the drain pipe 14a, and the drain generated in the low pressure feed water heater 5c is drain pipe 14b.
Is supplied to the low-pressure feed water heater 5d via. Then, the drains generated in the low-pressure feed water heaters 5b and 5a are collected in the drain tank 15 via the drain pipes 14c and 14d, respectively, and then boosted in pressure by the drain pump 16, and the suction side of the condensate pump 3 via the drain recovery line 17. Is mixed with condensate.

The water level of the drain tank 11 is detected by a water level meter 18, the detected water level signals are compared with the water level set values by drain tank water level controllers 19 and 20, respectively, and a deviation signal thereof is provided in a drain recovery line 13. The water level control valve 21 and the water level control valve 23 provided on the drain line 22 are provided to both the water level control valves 21 and 23.
The opening is adjusted to maintain the water level in the drain tank 11 constant (FIG. 7). In the drain tank 15 as well, the water level is similarly kept constant.

As described above, in the feedwater heater drain pump up system, the feedwater heaters 5a, 5b ... 7a,
Since the drain generated in 7b is directly mixed with the condensate or the feed water, the condensate temperature and thus the feed water temperature can be raised, and the plant efficiency can be improved.

[0013]

The control of water supply to the reactor 9 in a nuclear power plant employing the water supply heater drain pump up system as described above is performed by rotating the water supply pump according to the water level, the water supply flow rate, and the main steam flow rate of the reactor. The reactor water level of the reactor 9 is kept constant by changing the number.

On the other hand, the water level of, for example, the drain tank 11 of the feed water heater dress pump up system is kept constant by adjusting the opening degree of the water level control valves 21 and 23. When the opening degree of the water level control valve 21 changes, the drain flow rate supplied to the water supply pipe 8 changes, so that the feed water flow rate sent to the reactor 9 changes.

As a result of this, the adverse effect that the reactor water level fluctuates occurs. In particular, when the drain flow rate supplied to the water supply pipe 8 suddenly increases, such as when the drain pump 12 is started, this will appear as a change in the feed water flow rate to the reactor, causing an abnormal reactor water level. High and, in extreme cases, can cause reactor scrum.

In view of the above points, the present invention stabilizes the drain flow rate sent from the drain tank to the condensate / water supply system, and ensures the fluctuation of the drain flow rate due to the fluctuation of the tank water level in the drain tank. It is an object of the present invention to obtain a drain tank control device that can prevent water leakage and can perform stable water supply control.

[0017]

According to the present invention, after the drain condensed by the feed water heater provided in the condensate / water supply system is stored in a drain tank, the condensate / water supply system is connected to the condensate / water supply system via a drain pump. In the drain tank control device of the steam turbine plant equipped with the feed water heater drain pump up system for sending, in the drain tank, the flow control signal for controlling the flow rate of the drain sent from the drain tank to the condensate / water supply system It is characterized in that a correction signal corresponding to the water level is added.

The second aspect of the invention is to provide a deviation signal between the actual drain flow rate signal and the setting signal of the drain sent from the drain tank to the condensate / water supply system, and a flow rate correction signal corresponding to the water level in the drain tank. Is output as a drain flow rate control signal.

[0019]

Since the present invention is configured as described above, it is possible to send a stable drain flow rate of a required amount to the condensate / water supply system in a form in which there is no change in the drain flow rate due to the change in the water level in the drain tank, It is possible to reliably prevent the drain flow rate from becoming a condensate and a disturbance of the water supply flow rate of the water supply system, and it is possible to perform stable water supply control. Moreover, the water level in the drain tank can be maintained at the required level.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure, the same parts as those in FIGS. 6 and 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, high-pressure feed water heaters 7a, 7b
The drain generated in 1) is temporarily stored in the drain tank 11 and then mixed by the drain pump 12 into the water supply system through the drain recovery line 13.

Similarly, the low-pressure feed water heaters 5a, 5b, 5
The drains generated in c and 5d are also temporarily stored in the drain tank 15 and then the drain recovery line 17 is provided by the drain pump 16.
And then mixed into the condensate of the condensate system. In this case, from the drain tank 11, for example, about 30% of the total feed water flow is mixed in the feed water, and from the drain tank 15, for example, about 15% of the total feed water flow is mixed in the condensate water.

Since the drain processing principle in the high-pressure and low-pressure feed water heater drain pump-up system does not differ between the two, FIG. 2 will be described by taking the high-pressure feed water heater drain pump-up system as an example.

A drain pump 12 is provided in the drain recovery line 13 for supplying the drain from the drain tank 11 to the water supply system.
Further, a drain flow meter 31 such as an orifice is sequentially provided while the drain control valve 30 is provided, and the actual drain flow rate sent to the water supply system is detected by the drain flow meter 31. Then, the actual drain flow rate signal detected by the drain flow rate meter 31 is input to the flow rate control unit 32,
Then, it is compared with the drain flow rate setting signal, and the deviation signal is input to the adder 33 as a flow rate control signal.

On the other hand, the water level in the drain tank 11 is 1
8 is detected, and is input to the actual tank water level control unit 34 detected by the water level meter 18, where the water level setting signal is compared and calculated, and the deviation signal is input to the adder 33 via the gain setting unit 35. To be done. Then, the adder 33 adds the output signal from the flow rate control unit 32, the added signal is added to the drain control valve 30, and the opening degree of the drain control valve 30 is adjusted.

The output signal from the water level control unit 34 is a correction control function and the main control function is an output signal from the flow rate control unit 32. Therefore, for example, when the water level suddenly rises due to a sudden load change, A drain line 22 for guiding the drain in the drain tank 11 to the condenser is provided, and the water level is controlled to a predetermined level by controlling the opening degree of a water level control valve 23 provided in the drain line 22. That is,
The water level control valve 23 has its valve opening adjusted and controlled by a control signal output when the water level controller 20 reaches a water level setting position equal to or higher than the water level setting value of the water level controller 34.

Therefore, when the drain from the drain tanks 11 and 15 is supplied to the condensate / water supply system, the actual drain flow rate signal detected by the drain flow meter 31 is compared with the setting signal, and the deviation signal is used. Drain control valve 3
0 is controlled, and the drain supply amount to the condensate / water supply system is maintained at a predetermined value. On the other hand, if there is a deviation signal in the drain water level control section 34 at this time, the deviation signal from the drain water level control section, that is, the correction signal corresponding to the water level in the drain tank is added to the drain flow rate deviation signal, that is, the drain flow rate control signal. Is added to the drain control valve 30 to prevent a change in the drain flow rate due to the fluctuation of the water level in the drain tanks 11 and 15, so that a predetermined drain flow rate is stably supplied.
Disturbances due to changes in condensate flow rate, and consequently changes in feedwater flow rate, are eliminated.

FIG. 3 is a diagram showing another embodiment of the present invention, in which each output signal from the flow rate control unit 32 and the drain water level control unit 34 is inputted to the high value priority device, and the high value signal is supplied to the drain control valve. To the control signal. Therefore, the larger deviation in the flow rate control unit 32 and the drain water level control unit 34 is preferentially controlled.

Further, the flow rate set value in the flow rate control unit 32 does not necessarily have to be a constant value, and the flow rate setter 37 connected to the flow rate control unit 32 receives, for example, a load signal of the turbine generator, As shown in FIG. 4, the drain flow rate setting signal may be changed according to the load signal.

Further, in the apparatus shown in FIG. 3, an overflow prevention setting device 38 for preventing a pump trip due to an overflow of the drain pump 12 is provided. That is, the setting signal from the overflow prevention setting device 38 is input to the low value priority device 39, and the high value priority device 36 that gives priority to the high value signal among the output signals from the drain flow rate control unit 32 and the drain water level control unit 34 there. Compared to the output signal from
The low value signal is applied to the drain control valve 30 as a control signal. Therefore, the actual drain flow rate is always limited so as not to exceed the set flow rate of the overflow prevention setting device 38,
The opening degree of the drain control valve 30 is controlled so that the pump overflow does not always occur.

In this case, the overflow drain set value is not necessarily a constant value and corresponds to, for example, the load signal of the turbine / generator, and the overflow drain set value is changed as shown in FIG. I am doing it.

Further, the water level in the drain tank 11 is lowered, and the minimum pump head (NPS) required for the drain pump 12 is increased.
If it is less than H), the operation will be in a state where bubbles are entrained in the pump, and the blades of the pump may be damaged by cavitation. Therefore, an NPSH setting device 40 is provided in order to secure the required minimum push head. Then, the set signal of the NPSH setter 40 and the actual water level from the drain water level gauge 18 are compared, and the deviation signal thereof is input to the multiplier 42 via the gain setter 41, and the high-priority value is prioritized by the multiplier 42. Is calculated with the output signal from the device 36,
A control signal is applied to the drain control valve 30 so that the actual water level of the drain tank 11 does not fall below the set value of the NPSH setter 40.

In this case, the drain water level is NPSH setting device 4
When the water level set value of 0 is reached, the deviation signal between the set water level of the NPSH setter 40 and the actual water level is passed through the gain setter 41 to increase the responsiveness corresponding to the deviation signal and control so as to suppress the water level drop. The signal is output. This allows
The drain control valve 30 is regulated and controlled so as to restore the water level, so that the minimum pushing head of the pump can be secured.

[0034]

As described above, according to the present invention, the correction signal corresponding to the water level in the drain tank is added to the flow control signal for controlling the flow rate of the drain sent from the drain tank to the condensate / water supply system. Alternatively, the high value signal of the deviation signal between the actual drain flow rate signal and the setting signal and the correction signal corresponding to the water level in the drain tank is output as the drain flow rate control signal, so that the condensate is returned from the drain tank. -The amount of drain sent to the water supply system can be stabilized, the drain flow rate fluctuation due to the tank water level fluctuation in the drain tank can be prevented in advance, and the disturbance of the water supply flow rate can be eliminated. The feed water flow rate control can be stably performed, and the tank water level in the drain tank can be maintained at a predetermined level.

[Brief description of drawings]

FIG. 1 is a system diagram of a condensate / water supply system of a steam turbine plant to which a drain tank control device of the present invention is applied.

FIG. 2 is a diagram showing an embodiment of a drain tank control device of the present invention.

FIG. 3 is a diagram showing another embodiment of the drain tank control device of the present invention.

FIG. 4 is a change diagram of a flow rate setting value with respect to a load.

FIG. 5 is a change diagram of an overflow drain set value with respect to a load.

FIG. 6 is a system diagram of a condensate / water supply system of a conventional nuclear power plant.

FIG. 7 is a diagram showing a conventional drain tank control device.

[Explanation of symbols]

 5a, 5b, 5c, 5d Low-pressure feed water heater 7a, 7b High-pressure feed water heater 11,15 Drain tank 12 Drain pump 18 Water level meter 23 Water level control valve 30 Drain control valve 31 Flow meter 32 Flow control unit 33 Adder 34 Water level control Part 36 High value priority device 37 Flow rate setting device 38 Flow prevention setting device 39 Low value priority device 40 NPSH setting device 42 Multiplier

Claims (6)

[Claims] 1. A feed water heater drain pump for storing drainage condensed by a feed water heater provided in a condensate / feed water system in a drain tank and then feeding the drain water to the condensate / feed water system via a drain pump. In a drain tank control device of a steam turbine plant equipped with an up system, a correction signal corresponding to the water level in the drain tank is added to the flow rate control signal that controls the flow rate of the drain sent from the drain tank to the condensate / water supply system. A drain tank control device for a steam turbine plant, characterized in that addition is performed. 2. A feed water heater drain pump that stores the drain condensed by a feed water heater provided in the condensate / feed water system in a drain tank and then feeds it to the steam condensate / feed water system via a drain pump. In a drain tank control device of a steam turbine plant equipped with an up system, it corresponds to the deviation signal of the actual drain flow rate signal and setting signal of the drain sent from the drain tank to the condensate / water supply system, and the water level in the drain tank. A drain tank control device for a steam turbine plant, wherein a high value signal with a flow rate correction signal is output as a drain flow rate control signal. 3. A drain tank controller for a steam turbine plant according to claim 1, wherein the flow rate setting signal for controlling the flow rate of the drain is corrected based on the load signal of the generator. . 4. The drain tank control of a steam turbine plant according to claim 1, wherein the drain flow rate control signal is limited by a setting signal from a drain pump overflow prevention setting device. apparatus. 5. The drain tank control device for a steam turbine plant according to claim 4, wherein the setting signal of the drain pump overflow prevention setting device is corrected based on the load signal of the generator. 6. A minimum push head setting device for ensuring the minimum push head of the drain pump is provided, and a control signal is given to the drain control valve so that the actual water level does not fall below the set value of the minimum push head setting device. The drain tank control device for a steam turbine plant according to claim 1 or 2, characterized in that.