JPH02241994A - Anti-flashing equipment - Google Patents

Abstract

PURPOSE:To prevent flash symptom for enabling stable plant operation by draining water to a condensor by temperature control valves and limiting the quantity of water to be drained utilizing temperature difference, when the temperatures of the feed water in a deaerator storage tank 2 is reversed to that at the entrance of feed booster pumps. CONSTITUTION:In unloaded or stopped condition of a plant, when water feed booster pumps 3A to 3C are stopped and the temperature of the feed water in a deaerator storage tank 2 is reversed to that at the entrance of the water feed booster pumps 3A to 3C and a temperature difference is produced, respective temperature control valves 10 to 10C are opened to control the plant continuously. Namely, water is drained from the deaerator storage tank 2 through downcomers 5A to 5C and drain pipes 9A to 9C and into a condensor 8, and a quantity of water to be drained is controlled by the temperature control valves 10A to 10C utilizing temperature difference so that the temperature of the feed water in the deaerator storage tank 2 may not be reversed to that at the entrance of the water feed booster pumps 3A to 3C, so as to prevent flash.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to water supply equipment for thermal power plants, nuclear power plants, etc. The present invention relates to a flash prevention device that prevents a flash phenomenon at a pump inlet.

(Prior Art) In thermal or nuclear power plants, flash may occur at the inlet of the water booster pump during a sudden load drop or during shutdown of the plant.

Such a flash phenomenon will be explained with reference to FIG. 5, which shows a part of a conventional water supply system.

As shown in the figure, in the conventional water supply equipment, a deaerator 1 and a deaerator water storage tank 2 are used as water booster pumps to ensure the suction pressure of water booster pumps 3 A, 3 B, and 3 C during load interruption, etc. 3 A, 3 B, 3
It is located higher than downcomer pipes 5 A and 5.
B, Water supply booster pump 3 through 5C A, 3
B, 3 Connected to C. Water booster pump 3
A, 3 B, 3 C are main water pumps 4 A, 4
It is installed to pressurize the main water pumps 4A, 4B, and 4C, and ensures the suction pressure of the main water supply pumps 4A, 4B, and 4C.

As mentioned above, normally three systems of water supply booster pumps and main water supply pumps are provided, but in the following explanation, only one system will be explained as a representative.

By the way, water that has been heated and degassed in the deaerator 1 is used as the water supply, and the temperature is normally set to be equal to the saturation temperature of the pressure inside the deaerators during load operation of the plant.

This water supply is stored in a deaerator water storage tank 2, and is sent to a water supply booster pump 3 via a downcomer pipe 5 while controlling the water level at a constant level.

Therefore, during normal operation, the temperature of the feed water in the deaerator water storage tank 2 and the temperature of the feed water at the inlet of the feed water booster pump 3 are equal, and no flash occurs.

(Problem to be Solved by the Invention) However, if the heated steam to the deaerator 1 is cut off, for example at the time of load interruption, the deaerator pressure will drop rapidly and the deaerator water storage tank A temperature difference (reversal) occurs between the temperature of the water supply in the pump 2 and the temperature of the water supply at the inlet of the water booster pump 3, and a flash occurs. Also, during the plant shutdown process, as in the case of load shedding, there is a temperature difference ( (reversal) and a flash occurs. In this way, when a flush occurs at the inlet of the water booster pump 3,
There has been a problem in that troubles may occur due to vibrations caused by the cavity in the downcomer pipe 5, water hammer, or penetration into other water supply pumps.

The present invention was made to solve the above problem, and its purpose is to detect the temperatures of the feed water in the deaerator water storage tank and the feed water temperature at the water booster pump inlet so that they do not reverse. Therefore, it is an object of the present invention to provide a flash prevention device that controls the discharge amount based on the temperature difference and prevents flash from occurring.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides water supply equipment that supplies water from a deaerator water storage tank to a water supply booster pump and a main water supply pump via a downpipe. A discharge pipe is provided from upstream of the water supply booster pump to the condenser, and the discharge pipe is provided with a temperature at which the discharge amount is controlled by the temperature difference between the temperature of the water supply in the deaerator water storage tank and the temperature of the water supply at the inlet of the water supply booster pump. It is characterized by being equipped with a control valve.

(Function) According to the flash prevention device of the present invention, when the temperature of the water supply in the deaerator water storage tank and the temperature of the water supply at the inlet of the water supply booster pump are reversed and a temperature difference occurs during load shedding or plant shutdown process. Since the temperature control valve is continuously controlled until this temperature difference disappears, flushing at the inlet of the water supply booster pump can be prevented.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram of an embodiment of the present invention. In the figure, a deaerator 1 and a deaerator water storage tank 2 are used as a water supply booster pump 3A during load cutoff, etc.

In order to ensure the suction pressure of 3B and 3C, the water supply booster pump is placed at a higher position than 3A and 38. Connected to 3A, 3B, and 3C. Water supply booster pump 3A, 3B,
3C is installed to pressurize the main water supply pumps 4A, 4B, and 4C, and is the main water supply pump 4A.

This is to ensure the suction pressure of 4B and 4C.

On the other hand, the feed water that has been heated and deaerated by the deaerator 1 is stored in the deaerator water storage tank 2, and is transferred to the downcomer pipe 5A while controlling the water level at a constant level.
Water supply booster pump 3A via 5B and 5C,
3B, 3C, main water pump 4A,
Water is sent to 4B and 4C.

The above-mentioned configuration is the same as the conventional example, but in the present invention, the water supply booster pumps 3A, 3 are connected from the deaerator water storage tank 2.
Downcomer pipes 5 A, 5 B, 5 C leading to B, 3 G
Discharge pipes 9A, 9B, which reach the condenser 8 from the middle of the
9C is provided. In addition, these discharge pipes 9 A, 9
Temperature control valves 10A and 10B are installed in B and 9C, respectively.
, an IOC has been established. Furthermore, a temperature detector 6 that detects the temperature of the water supply in the water storage tank 2 and temperature detectors 7A, 7B, and 7C that detect the temperature of the water supply at the inlet of each water supply booster pump are provided.

Therefore, when the water supply booster pumps 3 A, 3 B, and 3 C are stopped during load shedding or during a plant shutdown process, the water supply temperature in the deaerator water storage tank 2 and the water supply booster pumps 3 A, 38.3 C are different. When the inlet water supply temperature reverses and a temperature difference occurs, the respective temperature control valves 10A, 10B, and IOC are opened to perform continuous control. That is, from the deaerator water storage tank 2 to the downcomer pipe 5
A, 58.5C and discharge pipe 9 A, 9 B, 9
The temperature of the water supply in the deaerator water storage tank 2 and the water supply booster pump 3 are
Temperature control valves 10A, 10B, and IOC are used to control the amount of water discharged based on the temperature difference so that the inlet water temperatures at A, 3B, and 3C do not reverse, thereby preventing flash.

Next, the feed water temperature control circuit of this embodiment will be explained with reference to FIG.

In the figure, a subtracter 11 calculates a deaerator water storage tank temperature signal S1 of a temperature detector 6 and a water booster pump inlet feed water temperature signal S2 of a temperature detector 7, and the feed water temperature difference signal S3 is calculated by a function generator. Enter 12. When this feed water temperature difference signal S3 has a positive value, that is, the feed water booster pump inlet feed water temperature signal S2 is larger than the deaerator water storage tank temperature signal @S1, a temperature control valve opening command signal S4 is generated and the switching device 1
Output to 3.

As shown in Fig. 4, this opening command signal S4 outputs the valve 0% opening (valve closed) when the supply water temperature difference is 0°C, and outputs the valve from 0% opening to 100% opening when the temperature difference becomes large. It has the characteristic of occurring. For example, in the A system, when the opening command signal S4 output from the function generator 12 is input to the switch 13,
The switching arm 14 of the switching device 13 is switched to the EHA side of the switching device 13 when the booster pump 3A is stopped, and the function generator 1
The temperature control valve 10A is controlled by the opening command signal @S4 from 2 as shown in FIG. Further, while the booster pump is in operation, the switching arm 14 of the switching device 13 is switched to the lower side, outputs the 0% opening command signal, and performs forced operation of the temperature control valve 10A as shown in FIG. A control block diagram similar to that of the A system as shown in FIG. 3 is also configured for the 8 system and the C system.

Therefore, according to this embodiment, when the temperature of the water supplied to the deaerator water storage tank and the temperature of the water supplied to the water supply booster pump inlet are reversed and a temperature difference occurs, the temperature control valve controls the amount of water discharged in proportion to the temperature difference. As a result, it is possible to prevent a flash phenomenon at the inlet of the water supply booster pump, thereby preventing serious accidents such as trips due to low water supply flow rate due to flushing, as well as failures of the water supply pump, and enabling stable plant operation.

[Effects of the Invention] As explained above, according to the present invention, when the water supply temperature in the deaerator water storage tank and the water supply temperature at the water supply booster pump inlet are reversed, the temperature control valve drains the water to the condenser, and the temperature By controlling the amount of water discharged based on the difference, flash phenomena can be prevented, thereby preventing serious accidents such as trips due to low water supply flow rate due to flushing, and failures of water supply pumps, making it possible to operate the plant stably.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention, FIG. 2 is a feed water temperature control circuit diagram according to the present invention, FIG. 3 is a control block diagram according to the present invention, and FIG. 4 is a function diagram of FIG. 2. Characteristic diagram of the generator,
FIG. 5 is a system diagram of the deaerator and water pump of a conventional thermal power plant. 1... Deaerator 2... Deaerator water storage tank 3.
3A, 38.3C... Water booster pump 4.4A,
48.4C...Main water pump 5.5A, 58.5C.
... Downpipe 6.7, 7A, 78.7C ... Temperature detector 8 ... Condenser 9.9A, 98.9C ... Discharge pipe 10, IOA, 10B, 10C ... Temperature control valve 11
...Subtractor 12...Function generator 13...
Switching device 14... Switching arm of the switching device (87
33) Agent Patent attorney Yoshiaki Inomata (1 idiot)

Claims (1)

[Claims] In a water supply system in which water is supplied from a deaerator water storage tank to a water supply booster pump and a main water supply pump via a downcomer pipe, a discharge pipe is provided from upstream of the water supply booster pump to the condenser, and the deaerator is connected to the discharge pipe. 1. A flash prevention device comprising a temperature control valve that controls a discharge amount based on a temperature difference between a water supply temperature of a water supply tank and a water supply temperature at an inlet of the water supply booster pump.