JP3537219B2 - Water hammer prevention device for water supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water hammer prevention apparatus incorporated in a boiler water supply system of a power generation turbine plant.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a conventional boiler water supply system used in a power generation turbine plant. In the figure, condensate from a low pressure feed water heater (not shown) is supplied to a deaerator 1
Inside, it is heated and degassed by the bleed steam from the bleed pipe 3 and flows into the lower water storage tank 2. Then, it is sent to the high-pressure water heater through the deaerator downcomer 4a, the shutoff valve 5a, the water supply booster pump 6a, the connecting pipe 7a, and the water supply pump 8a.
Water is supplied to a boiler (not shown).

[0003] At the start-up of the plant, a deaerator downcomer 4a is used to remove a large amount of air dissolved in the boiler feedwater.
Deaerator circulation pump using a deaerator circulation pipe 9 branched from
By operating 10, the boiler feedwater circulates in the deaerator 1 to remove air.

[0004] Generally, a plurality of feed water pumps are divided into a series, and in addition to a feed water pump 8a system, a deaerator downcomer 4a, a shutoff valve 5b, a feed water booster pump 6b, a connecting pipe 7b, a feed water pump 8b, and the like. Is installed. These pumps are driven by steam turbines, electric motors, etc.
Generally, the steam turbine drive is used for normal use, and the motor drive is used for emergency use.

[0005]

When the load on the steam turbine is reduced during the operation of the plant, the pressure in the deaerator 1 is reduced almost in proportion to this load, and the water supply in the water storage tank 2 is also reduced to the internal pressure. Follow the saturation temperature. However, when the load suddenly decreases due to load shedding, station-only operation, or the like, the supply of turbine extracted steam to the deaerator 1 also decreases rapidly, so that the internal pressure also decreases sharply. And the water supply in the deaerator downcomer 4 will be left at the temperature before the load change, and will remain at the saturation temperature of the internal pressure. For this reason, the water supply in the water storage tank 2 and the deaerator downcomer 4 self-evaporates,
In some cases, the water supply containing the air bubbles reaches the water supply booster pump 6a. In the feed water pump system 8a during operation, this feed water flows continuously as it is, and is sucked into the feed water booster pump 6a, so that no abnormality occurs. (Referred to as a hammer), and the vibration may damage the piping system or disable the stopped water supply booster pump 6b or the water supply pump 8b. Further, water containing bubbles in the water storage tank 2 may make level control of the water storage tank 2 unstable.

For this reason, in the conventional water supply pump, the deaerator circulation pump 10 is operated in order to replace the water supply in the deaerator downcomer pipe 4 in a specific load range, or the pressure drop in the deaerator 1 is reduced. Auxiliary steam is supplied from the auxiliary steam pipe 11 to reduce the rate as much as possible, thereby preventing troubles in the feedwater pump 8b system.

However, when such a conventional method of preventing water hammer in a water supply system is used,
The capacity of the deaerator circulation pump 10, which is originally installed for the purpose of venting air at the time of startup, is insufficient, and the intended effect cannot be obtained. In addition, since there is a restriction on the amount of auxiliary steam, it is not possible to completely prevent trouble caused by water containing air bubbles, and a water hammer is generated in the piping of the feed water pump 8b as a standby unit, In some cases, the water supply booster pump 6b and the water supply pump 8b cannot be started.

Accordingly, an object of the present invention is to provide a water hammer prevention device for a water supply system which surely prevents self-evaporation of water supply in a deaerator downcomer and a water storage tank when a load rejection, an in-house operation, or the like occurs. Is to provide.

[0009]

Means for Solving the Problems According to claim 1 of the present invention,
A water tank connected to a deaerator, and a deaerator downcomer for guiding water in the water tank to a water supply pump, comprising a gas injection control valve for injecting non-condensable gas into the deaerator. A non-condensable gas injection pipe is provided to open the gas injection control valve and inject non-condensable gas into the deaerator during load shedding and single-site operation.

[0010] The invention according to claim 2 is characterized in that the gas injection control valve is provided with control means for controlling the injection of the non-condensable gas in accordance with the rate of decrease in the pressure in the deaerator during normal stop.

Further, the invention according to claim 3 is characterized in that the gas injection control valve is provided with control means for controlling the injection of the non-condensable gas in accordance with the pressure difference between the pressure inside the deaerator and the pressure at the inlet of the feed water pump. I do.

Further, the invention according to claim 4 is characterized in that the gas injection control valve is provided with control means for controlling the injection of the non-condensable gas by an opening signal of the bleed check valve. Further, the invention according to claim 5 is characterized in that an initial gas injection control valve is provided in the path of the non-condensable gas injection pipe in parallel with the gas injection control valve.

[0013]

The gas injection control valve of the non-condensable gas injection pipe connected to the deaerator is fully opened, for example, when a load is cut off or a station alone operation signal is given. For this reason, the non-condensable gas flows into the deaerator through the non-condensable gas injection pipe, and rises before the pressure in the chamber drops significantly. By avoiding this pressure drop, the feedwater can be prevented from self-evaporating in the degassing downcomer and the water storage tank.

The gas injection control valve is controlled in accordance with the pressure drop rate of the deaerator at the time of a normal stop or in accordance with the differential pressure between the pressure in the deaerator and the inlet pressure of the feed water pump. Alternatively, the control may be performed by an opening signal of the bleed check valve. This can increase the internal pressure with a minimum time delay.

Further, the initial gas injection control valve is a control valve having a high opening / closing speed, and is opened, for example, at an initial stage when load interruption occurs. Next, when the internal pressure becomes stable, the gas injection control valve may be opened. By doing so, the non-condensable gas can be introduced into the deaerator without delay.

[0016]

FIG. 1 is a diagram showing a boiler water supply system showing an embodiment of the present invention. In FIG. 1, a non-condensable gas injection pipe 12 for injecting non-condensable gas into a deaerator 1 is a gas injection control valve.
13 and a pressure transmitter 14 for detecting the pressure in the deaerator 1 is provided. This pressure transmitter
The pressure signal of 14 is input to the controller 15, the pressure drop rate in the deaerator 1 of the actual machine at a specified time is calculated, and the pressure drop rate is abnormally reduced in comparison with a preset maximum pressure drop rate at normal stop. When the rate is high, the gas injection control valve 13 is opened to control the pressure drop rate in the deaerator 1 to a specified rate.

FIG. 2 is a control explanatory diagram of the gas injection control valve 13 in FIG. The gas injection control valve 13 controls the pressure drop in the deaerator 1 of the actual machine taken into the controller 15 and a preset maximum pressure drop rate in the deaerator at a normal stop, that is, a maximum load drop rate at a normal stop. The pressure reduction rate in the deaerator 1 is compared with the pressure drop rate in the deaerator, and the pressure control in the deaerator 1 is started at a time when the rate of the pressure drop becomes inconceivable at the time of the normal stop. Prevents self-evaporation in the tank 2 and reliably prevents water hammer.
Water level control is maintained well.

FIG. 3 is a view showing a boiler water supply system according to another embodiment of the present invention. In FIG. 3, a non-condensable gas injection pipe 12 for injecting a non-condensable gas is connected to the deaerator 1 via a gas injection control valve 13. Also deaerator 1
And pressure feeders 14, 16a, 16b are installed at the inlets of the feed water booster pumps 6a, 6b via pipes, respectively.
The pressure inside the deaerator 1 and the lower part of the deaerator downcomer 4, that is, the pressure at the inlet of the feedwater booster pump 6 is detected. When these detection signals enter the controller 15 and the calculated differential pressure value becomes equal to or less than a specified value, the controller 15 sends the gas injection control valve 13
Control signal is sent to the deaerator 1 so that the differential pressure value becomes constant.
The pressure in the chamber is controlled. This makes it possible to keep the internal pressure of the deaerator 1 higher than the pressure at the lower part of the deaerator downcomer 4, that is, at the inlet of the water supply booster pump 6 by a certain value or more. To prevent self-evaporation, reliably prevent water hammer, and maintain good water level control of the water storage tank 2.

Next, another embodiment of the present invention will be described.
In FIG. 4, the control start timing of the gas injection control valve is set to the pressure drop rate in the deaerator in the above embodiment (FIG. 1), and the pressure in the deaerator and the deaerator in another embodiment (FIG. 3). Instead of starting with the differential pressure signal at the lower part of the downcomer, it is performed with the opening signal of the bleed check valve. In each of the above embodiments, the control start timing is captured by the pressure signal. However, in the case of the pressure signal, the detection delay is caused, so that when the amount of the heating steam supplied to the deaerator 1 decreases, the bleed check valve operates immediately. The initial injection of the non-condensable gas can be performed by the opening degree signal.

Further, an embodiment different from the above will be described. In FIG. 5, a non-condensable gas injection pipe 12 for injecting a non-condensable gas is connected to the deaerator 1. The non-condensable gas injection pipe 12 has a gas injection control valve 13 and an initial gas injection control valve 16. Are installed in parallel. Since the initial gas injection control valve 17 is installed to assist the delay of the opening operation time of the gas injection control valve 13, the valve is opened for a certain time in response to the signal of the controller 15, and the injection of the non-condensable gas is performed without time delay. To make it possible. As a result, it is possible to prevent a flash from being generated in the deaerator downcomer 4 and the water storage tank 2.

Further, in each of the above embodiments, the connection port of the non-condensable gas injection pipe 12 to the deaerator 1 is constituted by a single port. The pressure distribution in the deaerator 1 at the time of injection can be kept uniform.

Further, by switching between the injection of the non-condensable gas and the injection of the auxiliary steam in a specified time, the pressure deviation between the deaerator 1 and the deaerator downcomer 4 becomes very small, and when the stable state is reached. Then, the operation shifts to the original heating degassing operation, and the non-condensable gas can be smoothly discharged out of the system.

[0023]

As is clear from the above description, the present invention can prevent the self-evaporation of the water supply in the deaerator downcomer and the water storage tank, can reliably prevent water hammer, and control the water level of the water storage tank. Can be kept good.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a water hammer prevention device according to the present invention.

FIG. 2 is an explanatory diagram showing a control method of the gas injection control valve in FIG.

FIG. 3 is a system diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a control circuit of the present invention.

FIG. 5 is a system diagram showing another embodiment of the present invention.

FIG. 6 is a system diagram showing a conventional boiler water supply system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Deaerator 2 Water storage tank 3 Turbine extraction pipe 4 Deaerator downcomer 5 Shut-off valve 6 Water supply booster pump 7 Communication pipe 8 Water supply pump 9 Deaerator circulation pipe 10 Deaerator circulation pump 11 Deaerator auxiliary steam pipe 12 Non-condensable gas injection pipe 13 Gas injection control valve 14 Pressure transmitter 15 Controller 16 Pressure transmitter 17 Gas injection initial control valve

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F22D 1/28

Claims (5)

(57) [Claims] 1. A dewatering device comprising: a water storage tank communicating with a deaerator; and a deaerator downcomer for guiding water supplied from the water storage tank to a water supply pump, wherein non-condensable gas is injected into the deaerator. Providing a non-condensing gas injection pipe with a gas injection control valve,
A water hammer prevention device for a water supply system, wherein the gas injection control valve is opened to inject non-condensable gas into the deaerator during load shedding and in-house independent operation. 2. The water supply system according to claim 1, wherein said gas injection control valve includes a control means for controlling the injection of the non-condensable gas in accordance with a rate of decrease in the pressure in the deaerator when the injection is normally stopped. Water hammer prevention device. 3. The gas injection control valve according to claim 1, further comprising control means for controlling the injection of the non-condensable gas in accordance with a pressure difference between the pressure inside the deaerator and the pressure at the inlet of the feed water pump. Water hammer prevention equipment for water supply system. 4. The water hammer prevention device for a water supply system according to claim 1, wherein said gas injection control valve includes control means for controlling injection of non-condensable gas by an opening signal of a bleed check valve. 5. The water hammer prevention device for a water supply system according to claim 1, wherein an initial gas injection control valve is provided in parallel with the gas injection control valve in a path of the non-condensable gas injection pipe.