JPH0223929Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a drain system for a feed water heater, and in particular, a feed water heater drain that prevents the generation of a gas phase in the drain pipe when drain is led to a deaerator. This invention relates to a pipe water hammer prevention device.

[Conventional technology]

Generally, steam turbine plants employ a regeneration cycle in which water that has lost thermal energy due to work in the turbine is heated in a feed water heater and then circulated to a steam generator such as a boiler. In this case, the feedwater heater takes in the steam extracted from the turbine as a heat source, and the condensate generated after the aforementioned heat exchange with the feedwater is further used as a heat source for other feedwater heaters or deaerators from the standpoint of heat recovery. It's being used.

[Problem that the invention attempts to solve]

By the way, when sending the condensate generated by the feed water heater to the deaerator, there is a considerable difference in water head between the deaerator and the feed water heater based on the height of the installation location. During high-load operation, condensate flows to the deaerator, but when the load decreases, the turbine bleed pressure decreases, resulting in a phenomenon in which condensate no longer flows to the deaerator due to the water head difference.

For this reason, when the load becomes low, a gas phase is generated inside the drain pipe that sends condensate from the feedwater heater to the deaerator, and as a result, when the plant returns to a high load state, the condensate flows through the drain pipe. There is a problem in that water hammer occurs because the gas phase remains when the water flows from the water to the deaerator.

The object of the present invention is to provide a water hammer prevention device for a feed water heater drain pipe that prevents water hammer from occurring when the operation shifts from low load to high load.

[Means for solving problems]

The present invention includes a drain pipe that guides the drain generated in the feed water heater to a deaerator, a regulating valve that is inserted into the drain pipe and is opened and closed according to the drain water level in the feed water heater, and the water supply water heater. A drain line that discharges the drain generated in the heater to another system, a flow control valve that is inserted in this drain line and opens and closes depending on the drain water level in the feed water heater, and the regulating valve when the load decreases. In the water hammer prevention device for a feed water heater drain pipe, which includes a control means for closing and maintaining the drain pipe to a certain opening degree, when the load decreases, pressurized water from the booster pump is taken out and sent to the drain pipe, and from the feed water heater. This is a water hammer prevention device for a drain pipe of a feed water heater, which is equipped with a water pipe that compensates for the lack of pressure in the drain sent to the deaerator.

[Effect]

Two pipes, a drain pipe and a drain line, are connected to the feed water heater to discharge drain, and a regulating valve and a flow rate control valve are inserted in each pipe. These valves are controlled to open and close so that the drain water level in the feed water heater remains constant.

However, when the load decreases, the internal pressure of the feed water heater decreases, making it difficult to guide condensate to the deaerator through a drain pipe with a large water head difference.
Therefore, at this time, drain is exclusively discharged from the drain line to other systems. Further, at the same time as the load decreases, the water supply valve of the water pipe that leads water to the drain pipe is opened, and on the other hand, the opening degree of the regulating valve of the drain pipe is closed to a certain minimum opening degree. Therefore, due to the load reduction, almost no drain from the feedwater heater flows into the drain pipe, but high-pressure water is supplied via the water pipe.

Therefore, as the load decreases, the drain pipe will be filled with water supply, and as a result, no gas phase will remain in the drain pipe, so even if the load subsequently increases and drain from the feedwater heater flows in, the water will not flow. There is no risk of hammer occurring. Moreover, when the load decreases, the opening degree of the regulating valve is reduced to the minimum, so the gas phase is completely eliminated, and at this time, the amount of water supplied to the deaerator via the drain pipe is kept to a minimum while warming the drain pipe. be able to.

〔Example〕

The attached drawing shows an embodiment of the present invention, in which feed water is fed from the condenser side (not shown) and is led to a deaerator 2 via a feed water heater 1, where it is degassed. After that, the pressure is increased by a booster pump 3 and a feed water pump 4, and the water is finally led to a boiler (not shown) through a feed water heater 5. Turbine extraction air 6 is introduced into the feed water heater 5 as a heat source for heating, and the drain generated in the vessel as a result of heat exchange is passed from the drain line 7 to the feed water heater 1 in the previous stage.
It is also supplied from the drain pipe 8 to the deaerator 2 as a heat source. Further, a water supply pipe 9 is connected to the drain pipe 8 to introduce water from the downstream side of the booster pump 3.

On the other hand, the feed water heater 5 is equipped with a pressure switch 10 that is activated by detecting the internal pressure, and the solenoid valve 11, which is excited by a signal from the pressure switch 10, has two setting devices 12a, 12b is connected, and one of the setting devices is selected depending on the pressure inside the feed water heater 5. That is, when the internal pressure of the feed water heater 5 is lower than a certain reference pressure, the setter 12a is selected, and when it is higher than this, the setter 12b is selected. Each of these setters includes a setter 12a that sets the set water level.
The water level is set in advance so that L ₁ and the setting device 12b reach the set water level L ₃ (L ₁ >L ₃ ). Thus, the signal from the setting device selected by the solenoid valve 11 is input to the controller 13, and the water level signal 1 indicating the drain water level in the feed water heater 5 is input to the controller 13.
Adjustment valve 15 calculated as 4 and inserted into drain pipe 8
The opening degree is controlled. The opening degree of the regulating valve 15 is controlled to reduce the deviation between the water level signal 14 and the set water level selected by the solenoid valve 11, but when the setting device 12a (set water level L ₁ ) is selected. In this case, as long as the water level signal 14 indicates a water level lower than the set water level _L1 , the regulating valve 15 is kept closed to the minimum opening degree.

On the other hand, the water level signal 14 is the set water level L ₂ (L ₁ >L ₂
> L ₃ ) is also input to the controller 17 connected to the setting device 16, and the controller 17 calculates the set water level L ₂ so that the flow rate control valve 18 inserted in the drain line 7 is opened/closed. It's getting old.
Further, the water supply valve 19 inserted in the water pipe 9 is opened and closed based on a signal from the pressure switch 10 via a delay circuit 20 that prevents instantaneous pressure fluctuations. This delay circuit 20 is activated when the signal from the pressure switch 10 indicates that the pressure is lower than a certain reference pressure mentioned above, and opens the water supply valve 19 after a certain period of time.

The solenoid valve 11 and the delay circuit 20 are activated depending on whether the internal pressure of the feed water heater 5 detected by the pressure switch 10 is higher or lower than a certain reference pressure, and this reference pressure is determined by the drain as described later. This corresponds to the internal pressure of the feed water heater when the water is no longer discharged from the drain pipe 8 to the deaerator 2.

In the above configuration, during normal operation, the internal pressure of the feed water heater 5 is maintained at a high pressure according to the turbine bleed air, so the solenoid valve 11 is set to the setting device 12b (set water level L ₃ ) by the signal from the pressure switch 10. is selected. This set water level _L3 is compared with the water level signal 14 of the feed water heater 5 in the controller 13,
Based on the deviation, the controller 13 opens and closes the regulating valve 15 so that the water level in the vessel matches the set water level _L3 . At this time, since the internal pressure of the feed water heater 5 is high, the drain reaches the deaerator 2 through the drain pipe 8 and is discharged, and the water level in the container is maintained at the set water level _L3 by the regulating valve 15. It will be done. On the other hand, when the water level in the vessel is maintained at L ₃ in this way, the flow rate control valve 18 of the drain line 7 is set to the setting device 16.
Since the set water level L ₂ is greater than L ₃ , the controller 17
It is held fully closed by.

Next, if the load decreases while driving in this condition,
The pressure of the turbine bleed air 6 decreases and the internal pressure of the feed water heater 5 decreases, but the pressure switch 10 detects this pressure change, operates the solenoid valve 11, and sets the setting device 12.
The setting device 12a (set water level L ₁ ) is selected instead of the setting device b, and the delay circuit 20 is activated to open the water supply valve 19 after a certain period of time. On the other hand, as the internal pressure of the feed water heater 5 decreases, the drain generated inside the vessel flows through the drain pipe 8 due to the water head difference with the deaerator 2.
The water will no longer be discharged, and the drain water level in the vessel will exceed the previously set water level _L3 . When the water level in the vessel increases further and exceeds the set water level _L2 of the setting device 16, the controller 17 opens the flow rate control valve 18 based on the water level signal, and the drain is drained from the drain line 7 to the water supplied to the previous stage. The water is discharged to the heater 1, and the drain water level in the feed water heater 5 is the set water level.
It will now be held at L ₂ .

On the other hand, at this time, the setting device 12a is selected by the solenoid valve 11 as described above, and the set water level _L1 is input to the controller 13, and at the same time, the water level signal 14 input to the controller 13 is as described above. Since it indicates approximately L ₂ , L ₁ >L ₂ and the controller 13 becomes the regulating valve 15.
The opening will be kept closed to the minimum opening. Further, as described above, when the delay circuit 20 is activated and the water supply valve 19 is opened, the high pressure water on the downstream side of the booster pump 3 is fed to the drain pipe 8, and as a result, the internal pressure of the water heater 5 is Even if the water level decreases, the drain pipe 8 will still be filled with water. Therefore, even if the load decreases and condensate stops flowing into the drain pipe 8 due to the difference in water head with the deaerator 2, water is supplied to the drain pipe 8 instead of condensate, so that there is no water inside the pipe. The generation of gas phase is effectively prevented. Furthermore, even if a gas phase occurs before water is supplied from the water pipe 9, the regulating valve 15 is closed to the minimum opening as described above, so water cannot be supplied to the drain pipe 8 later. As a result, the drain pipe 8 can be filled with water without leaving much of the gas phase inside.

However, when the load increases again and the pressure of the turbine bleed air 6 rises, causing the internal pressure of the feedwater heater 5 to rise, the feedwater supply valve 19 is activated via the delay circuit 20 based on the signal from the pressure switch 10. When it is closed, the solenoid valve 11 is operated and the setting device 12b (set water level L ₃ ) is selected instead of the setting device 12a. At this time, _the drain water level of the feed water heater 5 is maintained at L2 by the controller 17 and the flow control valve 18 based on the set water level _L2 of the setting device 16, and _L2 >
Since the relationship is _L3 , the controller 13 opens the regulating valve 15 so that the drain water level becomes the newly selected water level _L3 set by the setting device 12b. Since the internal pressure of the feed water heater 5 has already increased, the drain inside the vessel is discharged from the drain pipe 8 to the deaerator 2 when the regulating valve 15 is opened.
At this time, no gas phase remains in the drain pipe 8, so water hammer does not occur, and the drain pipe 8 is warmed by the water that has been supplied so far, so the temperature of the drain that has flowed in is low. It does not suddenly change and cause unstable flow. On the other hand, when the drain comes to be discharged from the drain pipe 8, the drain water level reaches the set water level of the setting device 16.
_As a result, the flow control valve 18 is closed, and the drain water level of the feed water heater 5 is maintained at the set water level L ₃ by the regulating valve 15.

In addition, in cases where it is difficult to close the regulating valve 15 to the minimum opening degree as described above, a small diameter bypass line that bypasses the regulating valve 15 is connected to the drain pipe 8, and the bypass valve is connected to this bypass line. Needless to say, the same effect as above can be obtained even if the regulator 13 is used to fully close the regulating valve 15 and open the bypass valve when the internal pressure of the feed water heater 5 decreases. Nor.

Furthermore, in this embodiment, a decrease in load on the turbine is detected by detecting the internal pressure of the feed water heater using a pressure switch, but instead of this, a decrease in load may be detected based on, for example, the generator output. You can do it like this.

[Effect of idea]

As described above, according to the present invention, even if the load decreases, no gas phase remains in the drain pipe, and therefore, even if the load continues to increase, the inconvenience of water hammer is eliminated. In addition, by keeping the drain pipe at its minimum opening and guiding water to it when the load decreases, the drain pipe can be warmed up, and even if the load increases and the feed water heater drain starts flowing in, the drain suddenly cools down. This has the advantage of not causing unstable flow.

[Brief explanation of the drawing]

The drawing is a system diagram showing a water hammer prevention device for a drain pipe of a feed water heater according to an embodiment of the present invention. 2... Deaerator, 5... Water heater, 7... Drain line, 8... Drain pipe, 9... Water pipe, 15
...Adjustment valve, 18...Flow rate control valve, 19...Water supply valve.

Claims (1)

[Scope of utility model registration request] a drain pipe that guides drain generated in the feed water heater to a deaerator; a regulating valve inserted in the drain pipe that opens and closes according to the drain water level in the feed water heater; A drain line that discharges the generated drain to another system, a flow control valve that is inserted into this drain line and opens and closes according to the drain water level in the feed water heater, and a flow rate control valve that opens and closes the control valve at a constant opening when the load decreases. In the water hammer prevention device for a feed water heater drain pipe, the apparatus includes a water hammer prevention device for a drain pipe of a feed water heater, which takes out pressurized water from the booster pump when the load decreases and sends it to the drain pipe, and from the water heater to the deaerator. A water hammer prevention device for a drain pipe of a feed water heater, characterized in that it is equipped with a water pipe that compensates for the lack of pressure in the drain that is being sent to the drain pipe.