JPH03251603A - Downcomer of deaerator - Google Patents

Abstract

PURPOSE:To prevent the flushing in a downcomer during the shut-out of load to a turbine with a simple piping in the subject downcomer in a thermal power plant by connecting the downcomers that are connected to respective pumps mutually by a communication pipe near the suction port of a boiler supply water pump. CONSTITUTION:Dueing the shut-off of load to a turbine the extraction steam from a steam turbine 3 is shut off, and the auxiliary steam is supplied to a deaerator 10 from an auxiliary steam pipe 29 and the temperature in the deaerator 10 drops and the temperature of the hot water becomes low. This low temperature hot water is supplied to, for instance, two boiler supply water pumps 17, 18 which are in operation from down comers 13 - 15 through a communication pipe 38. Accordingly in the downcomer 13 that is connected to a pump 16 that is not in operation the hot water of temperature same as that of the hot water in the downcomers 14 and 15 flows. It is, therefore, possible to prevent the flushing in the downcomers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a deaerator downcomer pipe connected to a plurality of boiler feed pumps arranged in parallel in a thermal power plant.

[Conventional technology]

Condensate generated in a condenser, etc. using extracted steam from a steam turbine is heated and degassed in a deaerator, and this hot water is supplied to the boiler using a boiler feed pump to produce steam.

The system shown in FIG. 2 is known as a system of a thermal power plant that supplies this steam to a steam turbine. In FIG. 2, steam from a boiler 1 flows into a steam turbine 3 through a main steam pipe 2, expands in the blade stages, does work, and generates electric power in a generator 4 connected to the steam turbine 3. .

Work is done on the blade stage of the steam turbine 3.
The steam discharged from the is cooled and condensed in a condenser 5 to become condensate, and this condensate is pressurized by a condensate pump 6 and passes through a condensate pipe 8 equipped with a low-pressure water supply heater 7 to a deaerator 10. is supplied to The condensate supplied to the deaerator 10 is passed through the steam turbine 3
The water is heated and degassed by the bleed steam that passes through the bleed pipe 11 and is stored in the deaerator 10. The hot water stored in the deaerator 10 is transferred to a downcomer pipe ν extending downward from the deaerator 10, and a downcomer pipe 13 that branches from this downcomer pipe and connects to each suction port of the boiler feed pumps 16, 17, and 18. The water is supplied to the boiler feed water pumps 16, 17, and 18 via the boiler feed water pumps 14 and 15, and the pressure is increased by these boiler feed water pumps, and the water is supplied to the boiler 1 through the water feed pipe 19, where it is heated and turned into steam.

In addition, 21.22 is an inlet stop valve, 24.25 is an outlet stop valve, and 26, 27.28 are reverse valves.

Further, auxiliary steam is supplied to the deaerator 10 from the load cutoff FI# auxiliary steam pipe 4 of the turbine.

In addition, the downcomer pipes 13, 14, and 15 are equipped with remotely controllable on-off valves 31, 32, and 33, which communicate with each other and are connected to the condensate pipe 8, and are provided with communication/supply pipes equipped with circulation pumps to open and close them. When a specific on-off valve among the valves 31, 32, and 33 is opened, the hot water in the downcomer pipe connected to this on-off valve is returned to the deaerator by driving a circulation pump.

In this way, when the thermal power plant is in normal operation, the internal pressure of the deaerator is kept high by allowing extracted steam to flow into the deaerator lO from the steam turbine 3, so that the boiler feed water pumps 16, 17, 18 Inhalation NPS required for
Sufficient H is ensured.

However, when the turbine load is cut off, the steam extracted from the turbine is cut off, so the pressure and temperature inside the deaerator decrease. In order to prevent this, auxiliary steam is supplied into the deaerator 10 through the auxiliary steam pipe 29, but since the amount of this auxiliary steam is small compared to the amount of extracted steam from the turbine,
The pressure inside the deaerator drops rapidly, and the hot water inside the deaerator
The degree also decreases. For this reason, the suction NPSH required for the boiler feed pump decreases, but if the level of the base neck of the deaerator 10 is maintained by a certain amount of light, there will be no problem with the boiler feed pump during operation.

By the way, in thermal power plants, usually in consideration of the soundness of the plant's operation, at least one of the three boiler feed pumps is stopped, and at least the other boiler feed pumps are operated. Therefore, if boiler feed pumps 17 and 18 of boiler feed pumps 16 and 17 and 18 are operated and boiler feed pump 16 is stopped, boiler feed pumps that are stopped with the inlet stop valve closed The hot water in the downcomer pipe 13 connected to I6 is not sent out by the boiler feed water pump but is swung into the downcomer pipe.

- When all of the hot water in the downcomer pipes 14 and Is connected to the operating boiler feed pumps 17 and 18 is discharged by the pump, the low-temperature hot water in the deaerator caused by load shedding is sucked in. Boiler feed pump 1 on the operation side
A flash phenomenon occurred in the piping from the vicinity of the junction of the downcomer pipes 14 and 15 connected to the boiler water pumps 14 and 15 connected to the boiler water pumps 7 and 18 and the downcomer pipes 13 holding high temperature hot water connected to the boiler feed pump 16 on the stop side to the boiler water pump on the stop side. occurs. Due to this flash phenomenon, the required N of the boiler feed water pump during operation is reduced.
Cavitation occurs in the boiler feed pump due to a decrease in FSH and the suction of air bubbles, and in the worst case, the pump may be damaged.

The above problem has conventionally been solved by the following method. When the turbine load is cut off, it is detected that the turbine is in the load cutoff state, and the #2 ring pump control is driven, and the boiler feedwater pump when the stoppage occurs, for example, only the opening/closing of the downcomer pipe connected to the boiler 3 feedwater pump 16 (9P31) is opened in response to a load shedding detection signal, the hot water in the downcomer pipe 13 is discharged into the forced zone, passed through the connecting supply pipe, and returned to the deaerator 101, and then flushed in the downcomer pipe 1:3. is prevented from occurring.

Another method is to detect that the turbine is in a load shedding state at the time of turbine load shedding, and inject water while it is stopped, for example, by connecting it to the downcomer pipe 13 connected to the boiler feed water pump 16 and having an on-off valve (not shown). Install piping and open/close this 9
9 for F? When opened by the iFJ cutoff detection signal, cooling water such as condensate or make-up water is supplied from the outside to each downcomer pipe 13, and the hot water in the downdown pipe 13 is sent out to the outside of the system or to a deaerator, etc. [Problem to be solved by the invention] Connecting to the stopped boiler feed pump when the load of the turbine is interrupted In order to prevent the hot water in the downcomer pipes from flashing, there is a conventional method of returning the hot water in the downcomer pipes to the deaerator using a circulation pump or replacing it with cooling water using water injection piping. Since piping and a control device including a pump and an on-off valve operated by a load cutoff detection signal are required, the control becomes complicated and the equipment cost increases.

The purpose of the present invention is to provide a boiler feed pump that is stopped even when the load of the turbine is cut off with a simple piping configuration! i! ! 5! [Means for solving the problem] In order to solve the above problem, according to the present invention, the steam inside the deaerator is provided. A plurality of boiler feed water pumps connected in parallel to the bottom of the deaerator and each suction port of a plurality of boiler feed water pumps arranged below the deaerator supply hot water that has been heated and degassed by extracted steam from the turbine to the boiler. In a deaerator downcomer pipe consisting of the same number of downcomer pipes as the boiler feed pump, a communication pipe through which these downcomer pipes communicate with each other shall be connected to a downcomer pipe near the suction port of the boiler feed pump.

[Effect]

The degassed hot water from the deaerator is sent to the boiler feed pump, which operates even if one of the multiple boiler feed pumps is stopped. 1fl
The hot water from the deaerator is also supplied through a connecting pipe that communicates with the downcomer pipe that is in use, so that hot water from the deaerator is constantly flowing even into the downcomer pipe that is connected to the boiler feed water pump that is stopped.

Therefore, even if the steam extracted from the turbine is cut off and the temperature inside the deaerator drops when the turbine load is cut off, low-temperature hot water will still be in contact with the operating and stopped boiler feed pumps.
Since hot water with a high degree of temperature does not exist in the downcomer pipes connected to the stopped boiler feed water pump as in the conventional case, flash does not occur.

〔Example〕

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

FIG. 1 is a system diagram of a thermal power plant with offset deaerator downcomers according to an embodiment of the invention.

2. In FIG. 1, parts that are the same as those in the conventional example shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. What is different from the conventional example in FIG. 1 is that the circulation pump shown in FIG. A connecting pipe 13 is provided to communicate with each other, and this connecting pipe 13 is connected to
Stop valves 39, 40, and 41 are provided to stop the flow of hot water from each downcomer pipe No. 14 and 15 to the other downcomer pipes.

With such a configuration, during normal operation, the stop valve 39,
40 and 41 are opened to keep the downcomers 13, 14, and 15 in communication. In this state, for example, in an operation pattern in which the boiler feed pumps 17 and 18 are operated and the boiler feed pump LTL is stopped (the large mouth valve is closed), the deaerator 1
The degassed hot water from the
゜After passing through 14 and 15, two boiler water pumps 17,
The water is supplied to the boiler 1 by driving 18.

By the way, when the load of the turbine is cut off, even if the extracted steam from the steam turbine 3 is cut off and the auxiliary steam from the auxiliary steam pipe 4 is supplied to the deaerator 10, the tAK in the deaerator is
decreases, and the hot water becomes colder.

This low-temperature hot water is passed from the downcomer pipes 13, 14, and 15 to the two boiler feed pumps 17 in operation via the connecting pipes.
18. Therefore, hot water of the same temperature as the other downcomers 17 and 18 flows through the downcomer pipe 13 connected to the stopped boiler feed pump lb even during load cutoff.
There is no flash like before.

In addition, when the boiler feed pumps 16, 17, and 18 are driven separately, the stop boxes 39, 40, and 41 may be closed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the connecting pipes connecting the same number of downcomer pipes connected to the boiler feed pumps arranged in parallel from the deaerator to the boiler water feed pumps are connected to the boiler water feed pumps. Even if one of the boiler feed pumps is stopped, the operating boiler feed pump will be connected to the downcomer pipe connected to the stopped and running boiler feed pump. Hot water is supplied from the deaerator to the boiler feed pump, so even if the hot water in the deaerator becomes cold due to turbine load interruption, the downcomer pipe connected to the stopped boiler feed pump will still be in operation. Because the same low-temperature hot water flows through the downcomer pipes that come into contact with the boiler feed pump, flash does not occur in the downcomer pipes that are connected to the boiler water pipes that are stopped. The advantage of C is that it eliminates the need for conventional equipment such as a circulation pump, an on-off valve that opens in response to a load cutoff detection signal, and a control IIL device, resulting in lower equipment costs.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a steam turbine installation equipped with a deaerator downcomer pipe according to an embodiment of the present invention, and FIG. 2 is a system diagram of a steam turbine installation equipped with a conventional deaerator downcomer pipe.

Claims (1)

[Claims] 1) The deaerator and each suction port of the boiler feed water pump, which is installed in parallel below the deaerator, supplies hot water that has been heated and deaerated by steam extracted from the steam turbine in the deaerator to the boiler. In the deaerator downcomer pipe, which is composed of the same number of downcomer pipes as the boiler feed pump and is connected to the bottom of the boiler feed pump, a communication pipe through which these downcomer pipes communicate with each other is connected to a downcomer pipe near the suction port of the boiler feed pump. A deaerator downcomer pipe is provided.