JP2006220393A - Water hammering prevention method for deaerator, and boiler feed water device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent water hammering of a deaerator in time of rapid reduction or the like of a plant load without providing a deaerator circulation pump. <P>SOLUTION: When boiler feed water pumps 10-13 feeding condensed water deaerated by the deaerator 4 to a boiler are stopped when a pressure regulating valve 7 for auxiliary steam is opened, an automatic opening/closing valve 14 of a condensed water return pipe 15 is opened to return the condensed water inside the deaerator to a condenser 1 to supply the low-temperature condensed water to the deaerator 4 through a deaerator water level adjustment valve 2, heat exchange with superheated steam filling inside the deaerator is made to be performed, and pressure inside the deaerator is stabilized to prevent generation of the water hammering. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a boiler water supply apparatus, and more specifically, to a technique for preventing a water hammer of a deaerator.

  After the steam generated in the boiler is driven to the steam turbine and the generator is driven, the steam power plant is configured to guide the steam turbine exhaust to the condenser and condense it, and supply the condensed water to the boiler again. Yes. In general, a boiler water supply device heats the condensate condensed in a condenser with low-pressure extraction steam in a low-pressure feed water heater with a condensate pump, and then guides it to a deaerator to further heat and deaerate it. The steamed condensate is boosted by a feed water pump, further heated by a high pressure bleed steam by a high pressure feed water heater, and supplied to the boiler.

  The deaerator is usually configured to deaerate the condensate by heating with the extracted steam of the steam turbine, and store the degassed condensate in a water storage unit such as a bottom in the deaerator. Condensate in the reservoir is led to the boiler feed pump through the downpipe. Since the deaerator is saturated during normal operation, the deaerator is placed at a higher position (for example, about 15 to 25 m) than the boiler feed pump in order to secure the effective pushing pressure at the inlet of the boiler feed pump with the hydrostatic head. It is installed. Further, in order to prevent the extraction steam of the steam turbine from being obtained at the time of starting and stopping the plant, the auxiliary steam can be introduced from an auxiliary steam system provided separately.

  In such a boiler water supply apparatus, when the plant load is suddenly reduced, the main steam entering the steam turbine is suddenly reduced, and the extracted steam introduced into the deaerator is also sharply reduced accordingly. At this time, since the temperature of the condensate flowing into the deaerator from the low pressure feed water heater also decreases, the pressure in the deaerator rapidly decreases unless a sufficient amount of auxiliary steam is introduced from the auxiliary steam system. become. As a result, the pressure in the downcomer from the deaerator to the boiler feed pump also drops sharply. However, since the temperature of the condensate in the downcomer does not drop sharply, a saturated state breaks down and a flash occurs where the condensate in the downcomer evaporates. As a result, the boiler feed pump may cause cavitation or a water hammer in the downpipe.

  In order to solve such problems, the boiler water supply apparatus described in Patent Document 1 is provided with a cold water injection pipe that bypasses the deaerator and injects low-temperature condensate upstream of the low-pressure feed water heater into the downpipe. When a sudden decrease in plant load occurs, flush water is injected into the downcomer pipe in accordance with the plant load so that the saturation pressure of the feed water at the boiler feed pump inlet does not exceed the pressure in the deaerator. It has been proposed to prevent.

  On the other hand, as described in Patent Document 2, in the case of a boiler water supply apparatus equipped with a deaerator circulation pump that circulates water from the downcomer to the deaerator, the deaerator circulation pump is operated to By constantly replacing the water supply, the temperature of the water supply in the downcomer can be prevented from exceeding the saturation temperature of the pressure in the deaerator. Therefore, even when the plant load is suddenly reduced, cavitation in the boiler feed pump and water hammer in the downpipe can be prevented.

JP 2003-21305 A JP-A-8-170805

  However, in the boiler water supply apparatus described in Patent Document 1, when the auxiliary steam pressure control valve for supplying auxiliary steam to the deaerator is open and the boiler water pump is stopped, a water hammer is generated in the deaerator. There is no consideration for what happens.

  That is, when the boiler feed pump stops, the flow of feed water from the deaerator to the downcomer and the boiler stops. Further, the flow of condensate from the condenser to the deaerator is also stopped by the water level adjustment control of the deaerator. At this time, if the auxiliary steam pressure control valve is open, the superheated steam is continuously supplied into the deaerator where the flow is stopped. To charge. When the boiler feed pump is activated in this state, a minimum flow of the boiler feed pump or a low-temperature condensate from the condenser is rapidly introduced into the deaerator filled with superheated steam. As a result, rapid thermal condensation occurs inside the deaerator, and there is a risk of generating a water hammer due to a sudden change in pressure.

  Such a problem occurs when a deaerator circulation pump is installed as in Patent Document 2, even if the auxiliary steam pressure control valve of the deaerator is open and the boiler feed pump is stopped. By replacing the feed water in the downcomer and the deaerator by operating the air circulation pump, heat can be exchanged between the superheated steam in the deaerator and the circulating water.

  However, in the case where the deaerator circulation pump described in Patent Document 2 is provided, the increase in the effective pushing pressure at the boiler feed pump inlet due to the cold water injection cannot be obtained as in Patent Document 1, so that the cold water injection pipe is provided. The deaerator must be installed at a higher position than that, which is not desirable from the viewpoint of reducing the height of the plant building, reducing the amount of piping, and reducing the plant construction cost.

  This invention makes it a subject to prevent the water hammer of a deaerator at the time of sudden reduction of a plant load, etc., without providing a deaerator circulation pump.

  In order to solve the above-mentioned problems, the present invention provides a dehumidifier water hammer that heats and degass condensate supplied from a condenser with auxiliary steam supplied from another system in addition to the extracted steam of its own system. In the prevention method, when the pressure control valve for the auxiliary steam is open, when the boiler feed pump that supplies the boiler with the condensate deaerated by the deaerator is stopped, the condensate in the deaerator is reduced. It is characterized by being returned to a condenser. In this case, it is preferable to throttle the auxiliary steam pressure control valve.

  Thus, according to the present invention, when the boiler feed water pump is stopped while the auxiliary steam pressure control valve is open, the condensate of the deaerator is returned to the condenser. As a result, the deaerator water level control valve operates and condensate is supplied to the deaerator, so that the water supply in the deaerator is replaced and the superheated steam filling the deaerator is replaced. Heat exchange takes place. As a result, the generation of water hammer can be prevented because the occurrence of rapid thermal condensation inside the deaerator is suppressed and the sudden change in pressure is suppressed. Here, as a pipe for returning the condensate of the deaerator to the condenser, a clean-up pipe generally used for purifying the water supply when the deaerator is activated can be applied.

  A boiler water supply apparatus for carrying out the water hammer prevention method for a deaerator according to the present invention includes a deaerator that heats the condensate supplied from the condenser with extracted steam to deaerate, and another system for the deaerator. An auxiliary steam supply pipe for supplying the auxiliary steam generated in the above, a boiler feed pump connected to the bottom of the deaerator via a precipitation pipe to supply degassed condensate to the boiler, and the condenser Boiler feed water provided with a deaerator water level control valve for controlling the flow rate of condensate supplied to the deaerator according to the water level of the deaerator, and an auxiliary steam pressure control valve for controlling the flow rate of the auxiliary steam A condensate return pipe for returning the condensate from either the deaerator or the downcomer to the condenser, an automatic on-off valve provided in the condensate return pipe, and the auxiliary When the steam pressure control valve is open and the boiler feed pump is stopped, Characterized in that a control device to open the water return automatic opening and closing valve installed in the pipe.

  With this configuration, when the boiler feed pump stops, the automatic open / close valve of the condensate return pipe that returns the condensate from either the deaerator or the precipitation pipe to the condenser is opened. A channel is provided to return the condenser or the condensate of the downcomer to the condenser. As a result, the deaerator water level control valve is actuated and condensate is supplied to the deaerator, so that the water supply in the deaerator is replaced and the heat from the superheated steam filling the deaerator. Exchange is performed. As a result, the generation of water hammer can be prevented because the occurrence of rapid thermal condensation inside the deaerator is suppressed and the sudden change in pressure is suppressed.

  In addition, the condensate return pipe can be a pipe that is normally used during a clean-up operation of a system from the condenser to the deaerator, or a blow of feed water in the deaerator.

  In addition to the above control or alone, the auxiliary steam pressure control valve may be throttled or closed to prevent the auxiliary steam from filling up in the deaerator, which is the original cause of water hammer. It is preferable to limit the inflow.

  ADVANTAGE OF THE INVENTION According to this invention, the water hammer of a deaerator can be prevented at the time of sudden reduction of a plant load, etc., without providing a deaerator circulation pump.

Hereinafter, the present invention will be described based on embodiments.
(Embodiment 1)
FIG. 1 shows a system configuration diagram of a boiler water supply apparatus according to an embodiment to which the dehumidifier water hammer prevention method of the present invention is applied. As shown in the figure, in the boiler water supply apparatus of the present embodiment, the condensate supplied from the condenser 1 is led to a low-pressure feed water heater 3 that is heated by low-pressure extraction steam through a deaerator water level control valve 2. The condensate that has been subjected to constant heating is supplied to the deaerator 4. Extracted steam is introduced into the deaerator 4 from a steam turbine (not shown) through an extracted steam supply pipe 5. In addition, auxiliary steam generated in another system is introduced into the deaerator 4 through the auxiliary steam supply pipe 6 in order to perform deaeration when the extracted steam is not obtained, such as when the plant is started or stopped. It has come to be. The amount of the auxiliary steam is controlled by the auxiliary steam pressure control valve 7. Therefore, the deaerator 4 heats the condensate with extracted steam and auxiliary steam to deaerate it. Further, the water level of the deaerator 4 is controlled to be constant by controlling the deaerator water level control valve 2 by a control system (not shown).

  In the case of this embodiment, three downcomers 9 are connected to the bottom of the deaerator 4. The two downcomer pipes 9 are connected to two boiler feed booster pumps 10 and a boiler feed pump 11 respectively driven by turbine bleed air, and the condensate deaerated by the deaerator 4 is shown as boiler feed water. There is no supply to the boiler. Moreover, the boiler feed water booster pump 12 and the boiler feed water pump 13 are driven by an electric motor at a low load when the turbine bleed air decreases.

  Further, a condensate return pipe 15 provided with an automatic open / close valve 14 is connected to the liquid phase part of the deaerator 4, and the condensate return pipe 15 is connected to the condenser 1. The auxiliary steam pressure control valve 7 and the automatic opening / closing valve 14 are controlled to be opened / closed by a control device 16.

  Operation | movement of the boiler water supply apparatus comprised in this way is demonstrated. Condensate supplied from a condensate pump (not shown) of the condenser 1 is heated by the low-pressure feed water heater 3 and then led to the deaerator 4, where it is usually heated by the extraction steam and deaerated. The Adjustment of the condensate flow rate to the deaerator 4 is performed by a deaerator water level adjustment valve 2 that keeps the water level of the deaerator 4 constant. The water stored in the deaerator 4 is guided by the downcomer 9 and is boosted by the boiler feed booster pump 10 and the boiler feed pump 11 to be supplied to the boiler. Further, when the plant is started, the condensate that has flowed into the deaerator 4 is returned to the condenser 1 via a condensate return pipe 15 having an automatic on-off valve 14, and the quality of the feed water is supplied to the boiler. It is circulated and purified until the conditions are met. This condensate return pipe 15 is also called a low-pressure cleanup pipe.

  Next, the control device 16 of the characteristic part of the present embodiment will be described with reference to the functional block diagram of FIG. Now, it is assumed that all the boiler feed pumps 10, 11, 12, 13 including the booster pump are stopped in a state where the auxiliary steam pressure control valve 7 is opened. At this time, an open signal of the auxiliary steam pressure control valve 7, that is, a fully closed NOT signal is input to the control device 16. In addition, stop signals for all boiler feed pumps 10, 11, 12, 13 are also input to the control device 16. When all these conditions are satisfied, the controller 16 outputs an opening command signal for opening the automatic opening / closing valve 14 and a closing command signal for closing the auxiliary steam pressure control valve 7.

  Thus, when the automatic opening / closing valve 14 is opened, a flow path from the deaerator 4 to the condenser 1 is secured via the condensate return pipe 15, and the hydrostatic head between the deaerator 4 and the condenser 1 is secured. Due to the difference, the condensate in the deaerator 4 is returned to the condenser 1. On the other hand, when the water level of the deaerator 4 is lowered, the deaerator water level control valve 2 is opened, and low-temperature condensate is supplied from the condenser 1 to the deaerator 4. Thereby, since the inside of the deaerator 4 is replaced with a low-temperature condensate, heat exchange with the superheated steam filled in the deaerator 4 is performed, and a water hammer is generated inside the deaerator 4. Can be prevented.

  Further, when a closing command signal is output from the control device 16 to the auxiliary steam pressure regulating valve 7, the auxiliary steam pressure regulating valve 7 is closed, whereby the flow of superheated steam into the deaerator 4 is stopped, and water hammer is generated. Can be prevented promptly. At this time, the auxiliary steam pressure control valve 7 does not necessarily need to be fully closed, and may be a small opening degree that limits the inflow amount of the auxiliary steam to the deaerator 4.

  The phenomenon of water hammer generation in the deaerator 4 and the like will be described with reference to FIG. In FIG. 3, the horizontal axis indicates time, the vertical axis in (a) is the plant load control command value, the vertical axis in (b) is the pressure in the deaerator, and the vertical axis in (c) is in the deaerator. Shows the water supply temperature. In FIG. 1A, the solid line indicates the load control command value, and the two-dot chain line indicates the actual load. Moreover, in the figure (b), the continuous line has shown the pressure in a deaerator, and the dashed-two dotted line has shown the saturation pressure in the feed water temperature in a deaerator.

  Now, when a load drop needs to occur and a load control command value as shown in (a) is issued, the actual load drops slightly later as shown in the figure because of the responsiveness. At this time, if the turbine bleed air and the auxiliary steam are not introduced into the deaerator 4, there is no heat source for heating the feed water in the deaerator 4, so that low-temperature condensate flows into the deaerator 4 from the condenser 1. As a result, the pressure in the deaerator 4 decreases as shown in FIG. However, since the heat retention amount of the water supply stored in the deaerator 4 is large, as shown in (c), the rate of decrease in the water supply temperature becomes gradual, and the inside of the deaerator 4 shown in (b) The rate of pressure drop is greater. Therefore, the saturation pressure at the feed water temperature in the deaerator 4 (the two-dot chain line of (b)) exceeds the pressure in the deaerator 4 (solid line of (b)). The water supply is flushed only in the shaded area b). As a result, the pump effective pushing pressure is not secured by the transient flush at the inlets of the boiler feed pumps 10, 11, 12, and 13, and pump cavitation may occur or water hammer may occur in the downcomer 9. . Such pump cavitation and water hammer in the downcomer can be avoided by the technique of Patent Document 1.

  However, there is a problem when the auxiliary steam pressure control valve 7 for supplying auxiliary steam to the deaerator 4 is open. That is, when the boiler feed pumps 10, 11, 12, and 13 are stopped, the flow of feed water from the deaerator 4 to the downcomer 9 and the boiler is stopped, and the deaerator water level control valve 2 is closed to return the condenser. The flow of condensate from 1 to the deaerator 4 is also stopped. At this time, if the auxiliary steam pressure control valve 7 is open, the superheated steam is continuously supplied into the deaerator 4 where the flow is stopped. Fill with superheated steam. When the boiler feed pumps 10, 11, 12, and 13 are started again in this state, the boiler feed pump minimum flow or the low-temperature condensate from the condenser 1 is added to the deaerator 4 filled with superheated steam. Will be introduced rapidly. As a result, rapid heat condensation occurs inside the deaerator 4, and there is a risk of generating a water hammer due to a sudden change in pressure.

  In contrast, according to the present embodiment, as described with reference to FIG. 2, when all the boiler feed pumps 10, 11, 12, and 13 are stopped with the auxiliary steam pressure control valve 7 being opened, the control device 16. To output an opening command signal for opening the automatic opening / closing valve 14 and a closing command signal for closing the auxiliary steam pressure control valve 7. As a result, the condensate in the deaerator 4 is returned to the condenser 1 via the condensate return pipe 15, and the deaerator water level control valve 2 is opened to lower the temperature from the condenser 1 to the deaerator 4. Condensate is supplied. As a result, heat exchange with the superheated steam filled in the deaerator 4 is performed, and the pressure in the deaerator 4 is stabilized, so that generation of a water hammer can be prevented.

  Further, if a closing command signal is output from the control device 16 to the auxiliary steam pressure control valve 7, the inflow of superheated steam to the deaerator 4 is stopped, and the generation of water hammer can be prevented promptly. At this time, the auxiliary steam pressure control valve 7 does not necessarily need to be fully closed, and may be a small opening degree that limits the inflow amount of the auxiliary steam to the deaerator 4.

In this embodiment, the condensate return pipe 15 is connected to the liquid phase part of the deaerator 4. However, the present invention is not limited to this, and the condensate is returned to the condenser 1 by connecting to the downcomer 9. Can be.
(Embodiment 2)
In FIG. 4, the system | strain block diagram of the boiler water supply apparatus of other embodiment of this invention is shown. This embodiment differs from the embodiment of FIG. 1 in that a cold water injection pipe 20 branched from the condensate pipe on the inlet side of the deaerator water level control valve 2 and connected to the downcomer pipe 9, and the downcomer pipe 9 is provided with a cold water injection amount adjusting valve 21 for adjusting the flow rate of the cold water injected into 9. Since others have the same configuration as that of FIG. 1, the same reference numerals are given and description thereof is omitted.

  According to the present embodiment, as described in FIG. 3, when the auxiliary steam pressure control valve 7 is closed and the load control command value is drastically reduced, as in the technique described in Patent Document 1, Cavitation of the generated boiler feed pumps 10, 11, 12, 13 and water hammer in the downcomer 9 can be prevented.

It is a system configuration | structure figure of the boiler water supply apparatus of one Embodiment of this invention. It is a figure which shows the functional block of the characteristic part of the control apparatus of FIG. 1 embodiment. It is a figure explaining the phenomenon of water hammer generation in a deaerator. It is a system configuration | structure figure of the boiler water supply apparatus of other embodiment of this invention.

Explanation of symbols

1 Condenser 2 Deaerator Water Level Control Valve 3 Low Pressure Water Heater 4 Deaerator 5 Extraction Steam Supply Pipe 6 Auxiliary Steam Supply Pipe 7 Auxiliary Steam Pressure Control Valve 9 Precipitation Pipe 10, 12 Boiler Feed Booster Pump 11, 13 Boiler Water supply pump 14 Automatic open / close valve 15 Condensate return pipe 16 Controller 20 Cold water injection pipe 21 Cold water injection amount adjustment valve

Claims (5)

In the dehumidifier water hammer prevention method of heating and degassing the condensate supplied from the condenser with auxiliary steam supplied from another system in addition to the extraction steam of the own system,
When the auxiliary steam pressure control valve is open, when the boiler feed pump that supplies the boiler with the condensate deaerated by the deaerator is stopped, the condensate in the deaerator is supplied to the condenser. A method for preventing a water hammer of a deaerator, wherein the deaerator is returned.   The method of preventing water hammer of a deaerator according to claim 1, wherein the pressure control valve for the auxiliary steam is throttled. A deaerator that degass the condensate supplied from the condenser by heating with extracted steam, an auxiliary steam supply pipe that supplies the deaerator with auxiliary steam generated in another system, and the deaerator A boiler feed pump for supplying degassed condensate connected to the bottom of the boiler to the boiler, and condensate supplied from the condenser to the deaerator according to the water level of the deaerator In a boiler water supply apparatus comprising a deaerator water level control valve for controlling the flow rate and an auxiliary steam pressure control valve for controlling the flow rate of the auxiliary steam,
A condensate return pipe for returning the condensate from one of the deaerator and the downcomer to the condenser, an automatic on-off valve provided in the condensate return pipe, and the auxiliary steam pressure control valve; A boiler water supply device comprising: a control device that opens and opens the automatic opening / closing valve of the condensate return pipe when the boiler water supply pump is stopped.   The boiler water supply device according to claim 3, wherein the control device throttles the auxiliary steam pressure control valve when the auxiliary steam pressure control valve is open and the boiler water supply pump is stopped. A deaerator that degass the condensate supplied from the condenser by heating with extracted steam, an auxiliary steam supply pipe that supplies the deaerator with auxiliary steam generated in another system, and the deaerator A boiler feed pump for supplying degassed condensate connected to the bottom of the boiler to the boiler, and condensate supplied from the condenser to the deaerator according to the water level of the deaerator In a boiler water supply apparatus comprising a deaerator water level control valve for controlling the flow rate and an auxiliary steam pressure control valve for controlling the flow rate of the auxiliary steam,
A boiler water supply apparatus comprising: a control device that throttles or closes the auxiliary steam pressure control valve when the auxiliary steam pressure control valve is open and the boiler water supply pump is stopped.

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