JPH044482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and device for interlocking a bleed check valve in a steam power generation plant, and in particular to a method and device for interlocking a bleed check valve in a steam power generation plant, and particularly for interlocking a steam turbine using flash steam when the amount of power generation is rapidly reduced. The present invention relates to a method and apparatus for interlocking a bleed check valve in a steam power generation plant suitable for preventing damage.

[Background of the invention]

As a prior art for a forced closing device for a bleed check valve installed in a bleed air pipe connecting a feed water heater and a steam turbine, Japanese Patent Publication No. 1888/1988 states that the water level of the condensate drain in the feed water heater is higher than the water level of normal operation. A device is disclosed that forcibly closes the bleed check valve when the air pressure rises. However, in this prior art, when the water level is normal, the steam turbine undergoes a rapid load drop, the pressure in the steam turbine decreases, the feedwater heater drain flashes, and the steam may flow back into the steam turbine. Even under these circumstances, if the water level in the feedwater heater was normal, the bleed check valve would not be forcibly closed, and there was a risk that flash steam would flow back into the steam turbine.

Further, as another prior art, there is known an interlock means that forcibly closes a bleed check valve in response to an activation signal of a relay dump valve that generates hydraulic pressure to close a main check valve when a steam turbine stops.
However, this interlock method is not suitable for FCB (first cutback) operation, where the load rapidly drops from a high load to an on-site load due to a transmission line accident, or from a high load to a medium load due to a failure of a large auxiliary machine, etc. In the case of a load runback that rapidly drops the load, the relay dump valve does not operate because the main check valve remains open, and as a result, the bleed check valve is not forcibly closed. Ta.

The interlock device for the bleed check valve in the prior art and the problems encountered during load runback operation and FCB operation will be described below with reference to the drawings.

FIG. 1 shows an overview of a steam turbine plant as a steam power turbine plant.

In the steam turbine plant shown in Fig. 1,
The steam generated from the steam generator 1 is transferred to the main steam pipe 6,
It passes through the main stop valve 100 and the control valve 101, flows into the steam turbine 2, and does work. The steam that has completed its work is reduced to water in the condenser 3, and is then sent to the water supply pump 4.
The steam is fed under pressure, passes through the water supply pipe 7 and the water supply heater 5, and returns to the steam generator 1. Meanwhile, steam extracted from the steam turbine 2 flows into the feed water heater 5 through the bleed pipe 8 and the bleed check valve 9, and heats the feed water.

Next, FIGS. 2 and 3 show a prior art interlock device for forcibly closing a bleed check valve.

In the interlock device shown in these figures, when the water level of the feed water heater 5 is detected by the feed water heater water level monitoring device 56, the bleed air check valve 9 receives a signal from the bleed air check valve control device 65, and from there the bleed air is controlled. A forced closing signal is sent to the check valve 9. In addition, among the opening and closing signals of the main blocking valve 100 installed at the inlet of the steam turbine 2, the main blocking valve fully closed signal 59, or the steam turbine when the steam turbine 2 is stopped due to some circumstances. A stop signal 60 enters the relay dump valve controller 63 which operates the relay dump valve 11 and sends a forced close signal to the bleed check valve 9.

Supplementing these operations with FIG. 3, when the steam turbine plant is operating normally, air flows to the actuator section of the bleed check valve 9 through the air pipe 12, relay dump valve 11, and solenoid valve 10. has been introduced, and the bleed air check valve 9 is in an open state. Therefore, the air flow direction of the relay dump valve 11 is from a to b, and the direction c is in a closed state. Further, in the solenoid valve 10, the air flow is from d to e, and the direction f is closed.

Here, the direction of air flow is determined by at least one of the main stop valve fully closed signal 59 and the steam turbine stop signal 60 that have entered the relay dump valve control device 63 that operates the relay dump valve 11 described above. It switches from to c and blocks the direction a. As a result, the air supply to the bleed air check valve 9 is cut off, and the air that had been introduced into the actuator section of the bleed air check valve 9 flows backward through the air pipe 12 and the solenoid valve 10, causing the relay dump valve 11 to move from b to c. The air flows to and is exhausted, and the bleed air check valve 9 becomes closed.

On the other hand, the bleed air check valve control device 65 receives the feedwater heater water level high signal 13 sent from the feedwater heater water level monitoring device 56, or the arbitrary P.
When at least one of the B (push button) signals 14 enters the OR circuit 15, the solenoid valve 10 is actuated by the signal, the air flow direction is switched from e to f, and the d direction is cut off. As a result, similar to the operation of the relay dump valve 11, the bleed check valve 9
The air that had been introduced into the actuator of the bleed check valve 9 flows backward through the air pipe 12, flows through the solenoid valve 10 from e to f, and is exhausted, and the bleed check valve 9 closes. state.

The above is an overview of the interlock device for the bleed check valve 9 in the prior art. In this technology, the condensate accumulated inside the feed water heater 5 that is generated when the steam turbine 2 performs a rapid load drop operation is removed. Even in a situation where there is a risk of flashing and backflow to the steam turbine 2, if the water level in the feed water heater 5 is normal, the bleed check valve 9 will not be forcibly closed. This problematic backflow phenomenon will be explained in more detail with reference to the drawings.

One of the typical examples of rapid load operation of the steam turbine 2 is load runback operation, which is performed when the auxiliary machines that make up the steam turbine plant, especially large auxiliary machines, stop for some reason. Figure 4 shows the dynamic characteristics of the extraction system during runback operation. In FIG. 4, the horizontal axis represents time T, and the vertical axis represents turbine load L, bleed air flow rate F, bleed air pressure P ₁ , and feedwater heater pressure P ₂ .

In FIG. 4, when the steam turbine plant continues normal operation, it is assumed that load runback operation starts at time T ₀ and ends at time T ₂ , then the turbine load L is equal to the line L ₀ Transition as follows. At this time, the extraction pressure P ₁ is as shown by the line P ₁ ,
Also, the feed water heater pressure P ₂ shifts as shown by the line P ₂ . As can be seen from FIG. 4, at time t ₁ between time T ₁ and time T ₃ after the start of load runback operation,
The feedwater heater pressure _P2 is higher than the bleed pressure _P1 .
At this time, if the bleed air check valve 9 is normal, the bleed air flow rate F ₀ will be 0 as shown in the figure, but in the unlikely event that the bleed air check valve 9 does not fully close on its own due to an abnormality such as a stay, Drain accumulated inside the feedwater heater 5 flashes, causing low-temperature steam to flow back into the steam turbine 2.

Further, FIG. 5 shows the dynamic characteristics during FCB operation, which is another typical example of rapid load drop operation.

Also in FIG. 5, during the time t ₂ from the FCB occurrence time T ₀ to the subsequent time T ₄ , the bleed pressure P ₁
When the feedwater heater pressure _P2 reverses and the bleed check valve 9 is abnormal as described above, low-temperature steam flows into the steam turbine 2.
A phenomenon of backflow occurs.

Furthermore, in the current operation of thermal power steam turbine plants, DSS (Daily Startup and Shutdown) operations are becoming more common, and rapid load drop operations are becoming more frequent, which increases the frequency with which the steam backflow phenomenon described above occurs. Become.

As described above, in the prior art of the interlock device for a steam turbine plant as a steam power generation plant, when considering the current operation of a steam turbine plant, the bleed check valve 9 does not close even in a situation where it should be closed. I was afraid.

In conventional steam turbine plants, the bleed check valve is forcibly closed when a turbine trip occurs, so once the bleed check valve is forcibly closed,
All signals will have to be reset and the steam turbine will have to be restarted. Therefore, if you blindly increase the conditions for forced closure or relax the conditions to forcibly close the bleed check valve, forced closure will occur more frequently, and you will have to restart the steam turbine each time. It will stop happening.
This is undesirable because it impedes the smooth operation of the steam turbine plant.

[Purpose of the invention]

It is an object of the present invention to eliminate the drawbacks of the prior art and to prevent flash steam in the feedwater heater from flowing back into the steam turbine when the power generation is rapidly reduced and the steam turbine load is rapidly reduced. Another object of the present invention is to provide a method for interlocking a bleed check valve that can more reliably prevent flash steam in a feedwater heater from flowing back into a steam turbine. Another object of the present invention is to provide an interlock device for a bleed check valve that can reliably carry out the method of the present invention.

[Summary of the invention]

The first invention of the present invention is as claimed in claim 1.
As described in section 1, the bleed check valve is forcibly closed by at least one of a signal that rapidly decreases the amount of power generation and a change in the state value that occurs due to the rapid decrease in the amount of power generation, and then, The feature is that the forced closure is released after a set time, and even if the power generation amount is rapidly reduced by this method and the steam turbine load is rapidly reduced, the steam turbine of the flash steam in the feedwater heater can be It is possible to prevent backflow to.

Further, the second aspect of the present invention is, as described in claim 4, a signal that rapidly decreases the amount of power generation, a change in state value that occurs due to the rapid decrease in the amount of power generation, The bleed check valve is forcibly closed by at least one of the small differential pressure signals between the upstream pressure of the bleed check valve and the feed water heater pressure, and then the small differential pressure signal is resolved. This method is characterized in that the forced closure is released when this happens, and by this method it is possible to more reliably prevent flash steam in the feedwater heater from flowing back into the steam turbine.

Furthermore, the third aspect of the present invention is to provide a control device for the bleed check valve with a signal that rapidly reduces the amount of power generation, and a signal that causes the amount of power generation to rapidly decrease. This device is characterized in that it has a function to forcibly close the bleed check valve due to at least one of the changes in the state value that occurs, and to release this forced closure after a set time elapses. The method of the first invention can be carried out reliably.

Next, the fourth aspect of the present invention is to provide a control device for a bleed check valve with a signal that rapidly reduces the amount of power generation, and a signal that causes the amount of power generation to rapidly decrease, as described in claim 11. The bleed check valve is forcibly closed by at least one of a change in the state value caused by the change in the state value and a small differential pressure signal between the pressure on the upstream side of the bleed check valve and the pressure of the feed water heater, and then This device is characterized in that it has a function of releasing the forced closure when the signal of a small differential pressure disappears, and with this device, the method of the second aspect of the invention can be carried out reliably.

[Embodiments of the invention]

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

FIG. 1 shows an outline of a steam turbine plant as an example of a steam power generation plant to which the present invention is applied.

As mentioned above, the steam turbine plant shown in FIG. 1 includes a steam generator 1 and a steam turbine 2.
, a generator (not shown) connected thereto, a condenser 3 , and a feed water heater 5 . The steam generator 1 and the steam turbine 2 have a main steam pipe 6
This main steam pipe 6 is connected to a main stop valve 1.
00 and a heating valve 101 are provided. The condenser 3 and the feed water heater 5 are connected by a water supply pipe 7, and the water supply pipe 7 is provided with a water supply pump 4. The feed water heater 5 and the steam generator 1 are connected by a water feed pipe 7. The steam turbine 2 and the feed water heater 5 are connected through a bleed pipe 8, and the bleed pipe 8 is provided with a bleed check valve 9. The bleed air check valve 9 is provided with an actuator section, to which an air pipe is connected, and this air pipe is provided with a relay dump valve and a solenoid valve. Air piping, relay dump valves, and solenoid valves are omitted.
The solenoid valve is incorporated into a bleed check valve control device, which will be described later.

Next, FIG. 6 shows an example of an apparatus for carrying out the method of the present invention.

The embodiment shown in FIG. 6 includes a load runback control device 51 having a steam turbine load control device 62, a feed water heater water level monitoring device 56,
FCB control device 52 having an OR circuit 66, relay dump valve control device 63, bleed check valve differential pressure monitoring device 61, and state value change detector 7 due to sudden load reduction
0, a bleed check valve control device 65, etc.

The steam turbine load control device 62 of the load runback control device 51 receives a power supply command signal 53 corresponding to the power demand, a steam turbine output signal 54 sent from a device that monitors the current plant operating load, and a plant configuration. An auxiliary equipment stop signal 55 or the like transmitted from a device that monitors the operation of auxiliary equipment is input. And steam turbine load control device 62
Next, determine whether it is possible to continue operation with the current plant load. As a result of the determination, if the operation can be continued, the load reduction signal 80 is not transmitted, and if the operation cannot be continued, a plant load that can continue the operation is selected, and the load is lowered to the target load 64 at a certain load rate. At the same time, a load runback signal 80 is sent from the steam turbine load control device 62 of the load runback control device 51 to the extraction check valve control device 65.
The bleed check valve controller 65 sends a forced close signal 91 to the bleed check valve 9 to forcibly close the bleed check valve 9.

When the feed water heater water level monitoring device 56 detects the high water level of the feed water heater 5, it sends a detection signal to the bleed air check valve control device 65, and the bleed air check valve control device 65 forces the bleed air check valve 9. A close signal 91 is sent to forcibly close this.

The FCB control device 52 generates a circuit breaker open signal 57 which is generated when a circuit breaker installed inside or in the middle of electrical wiring connecting a generator, transformer, power transmission line, etc. to an OR circuit 66 is opened. When the control valve 101 installed at the inlet of the steam turbine 2 is fully closed or slightly opened (hereinafter referred to as fully closed), at least one of the control valve fully closed signals 58, etc., emitted when the control valve 101 installed at the inlet of the steam turbine 2 is fully closed or slightly opened (hereinafter referred to as fully closed) is input. , determines FCB operation. Then, the OR circuit 66 of the FCB control device 52
The FCB signal 81 is transmitted from the plant to rapidly reduce the plant load to the target load 64. At the same time, from the OR circuit 66 to the bleed check valve control device 6.
5, and the bleed check valve control device 65 sends a forced close signal 91 to the bleed check valve 9 to forcibly close it.

On the other hand, in the bleed check valve differential pressure monitoring device 61,
When the differential pressure between the upstream pressure of the bleed check valve 9 and the pressure of the feed water heater 5 becomes less than a specified value, a signal 82 indicating a small differential pressure is transmitted, and this signal 82 is transmitted to the bleed check valve control device 65. The bleed check valve control device 65 gives a forced close signal 91 to the bleed check valve 9 to forcibly close the bleed check valve 9. Thereby, it is possible to prevent backflow of steam from the feed water heater 5 to the steam turbine 2 and protect the steam turbine 2 in any operation mode without selecting the operation mode of the steam turbine plant. That is, the bleed air pressure of the steam turbine 2 begins to drop due to some phenomenon, the differential pressure with the feed water heater 5 becomes minute, and before the pressure difference reverses, the bleed air check valve 9 is forcibly closed. If a pressure reversal phenomenon occurs during subsequent operation, the steam turbine 2
Prevent steam from flowing back into the tank.

The state value change detector 70 due to the sudden load decrease,
For example, a situation in which the differential pressure across the bleed air check valve 9 suddenly decreases, a situation in which the bleed air pressure rapidly decreases, a situation in which the bleed air amount rapidly decreases, a condition in which the water supply amount suddenly decreases, When detecting at least one of the following conditions, such as a condition in which the condenser is suddenly reduced, a signal 82 indicating the change in the condition value is transmitted, and the signal 82 is transmitted to the bleed check valve control device 65.
The bleed check valve control device 65 sends a forced close signal 91 to the bleed check valve 9 to forcibly close the bleed check valve 9.

Therefore, in the embodiment shown in FIG. 6, the load runback signal 80 or FCB signal 81 as a signal that rapidly reduces the amount of power generation, the pressure on the upstream side of the bleed check valve 9 and the feed water heater 5 are combined. At least one of the signal 82 of a small differential pressure and the signal 83 of a change in state value due to a sudden load decrease, which is a change in state value caused by a rapid decrease in the amount of power generation, is transmitted. Based on the signal, the bleed check valve control device 65 sends a forced close signal 91 to the bleed check valve 9 to forcibly close it.

Furthermore, in the embodiment shown in FIG. 6, the relay dump valve control device 63 receives a signal 59 for closing the main stop valve
When either the signal 60 or the steam turbine stop signal 60 is input, the relay dump valve control device 63 operates the relay dump valve 11, and the relay dump valve 11 is activated.
A forced closing signal is sent to the bleed air check valve 9 to forcibly close the bleed air check valve 9.

Next, various other embodiments of the present invention will be described.

In the following explanation, the aforementioned load runback signal 8
0, FCB signal 81 and other conditions during steam turbine load drop operation are collectively referred to as a sudden load drop signal. Further, the signal 82 indicating a small differential pressure between the pressure on the upstream side of the bleed check valve 9 and the pressure of the feed water heater 5 is referred to as a small check valve differential pressure signal.

FIG. 7 shows the logic of one embodiment of a bleed check valve control system.

In this embodiment, the operations of the feed water heater water level high signal 13, the P/B signal 14 determined by the operator, and the solenoid valve 10 are the same as those described above (in the Background of the Invention section), and therefore their explanation will be omitted.

In this embodiment, the bleed check valve control device 65
The OR circuit 18 inside is always held by a hold signal 19. Here, when the sudden load reduction signal 16 is input to the bleed check valve control device 65, this sudden load reduction signal 16 is input to the OR circuit 18, and then
It is led to the solenoid valve 10 via the OR circuit 15, operates the solenoid valve 10, and forcibly closes the bleed check valve 9. At the same time, the load sudden decrease signal 16 is activated by timer 1.
7, the timer 17 operates, and when the time set by the timer 17 has elapsed, the hold signal 19 is cut off.

As a result, the sudden load reduction signal 16 that operated the electromagnetic valve 10 is automatically canceled, and the closure of the bleed check valve 9 can be canceled so that the bleed check valve 9 is opened by the pressure on the steam turbine 2 side. .

Next, FIG. 8 shows another embodiment of the bleed check valve control device.

The bleed check valve control device 65 shown in FIG.
The sudden load reduction signal 16 is configured to be released by at least one of a release signal from a timer 17 and a release signal determined by an operator.

That is, the OR circuit 28 is configured to receive the release signal from the timer 17 and the P/B signal 20 transmitted when the operator presses P/B. When at least one of the release signal from the timer 17 and the P/B signal 20 determined by the operator is input to the OR circuit 28, the OR circuit 28 causes the load operating the solenoid valve 10 to suddenly decrease. The signal 16 is automatically canceled to release the bleed check valve 9 from closing.

Therefore, the bleed check valve 9 can be unblocked at the operator's discretion before the time set in the timer 17 has elapsed, and even if the timer 17 does not operate due to some abnormality, the operator can The bleed check valve 9 can be unblocked as desired.

The other structure and operation of the embodiment shown in FIG. 8 are the same as those shown in FIG. 7 above.

Further, in the embodiment shown in FIG. 8, the timer 17 and the OR circuit 28 are omitted, and the OR circuit 18 is omitted.
P・ as a release signal at the discretion of the operator.
A B signal 20 may also be input.

FIG. 9 shows an embodiment of a bleed check valve differential pressure monitoring device.

The bleed check valve differential pressure monitoring device 61 of this embodiment is as follows:
It includes a first pressure gauge 21 provided in the bleed pipe 8 on the outlet side of the steam turbine 2, a second pressure gauge 22 provided in the feed water heater 5, and a differential pressure calculator 23. The first pressure gauge 21 detects the pressure upstream of the bleed check valve 9 and sends the pressure signal to the differential pressure calculator 23, and the second pressure gauge 22 detects the pressure of the feed water heater 5. Then, the pressure signal is sent to the differential pressure calculator 2.
Send to 3. The differential pressure calculator 23 calculates the differential pressure from the pressure signals sent from the first and second pressure gauges 21 and 22, and when the differential pressure is less than a specified value, a check valve differential pressure small signal is generated. 24. This check valve differential pressure small signal 24 is input to the OR circuit 15, and the solenoid valve 1
0 to forcefully close the bleed check valve 9.

In the embodiment shown in FIG. 9, when the differential pressure between the pressure on the upstream side of the bleed check valve 9 and the pressure in the feed water heater 5 recovers to a specified value or more, a non-return valve operates the solenoid valve 10. Automatically cancels the valve differential pressure small signal 24,
It may be configured to release the bleed check valve 9 from closing.

Next, FIG. 10 shows another embodiment of the bleed check valve differential pressure monitoring device.

The bleed check valve differential pressure monitoring device 61 of this embodiment is as follows:
Bleed pipe 8 and feed water heater 5 on the outlet side of the steam turbine 2
A differential pressure gauge 25 is provided between the differential pressure gauge 2
5, the differential pressure between the pressure on the upstream side of the bleed air check valve 9 and the pressure of the feed water heater 5 is detected.
Bleed check valve differential pressure monitoring device 61 shown in FIG.
The other structures and functions are the same as those shown in FIG. 9 above.

According to the embodiment of the present invention described above, when the steam turbine 2 continues to operate and the water level of the feedwater heater 5 is maintained at a normal level, the load is suddenly reduced. steam turbine 2
This can prevent steam from flowing backwards.

Next, various embodiments will be described in which the various embodiments of the present invention described above are combined with the technology shown in Japanese Patent Publication No. 53-1888 as the prior art.

FIG. 11 shows the first embodiment, in which a sudden load decrease signal 1 is sent to the bleed check valve control device 65.
6, the check valve differential pressure small signal 24, the feed water heater water level high signal 13, and the P/B signal 14 determined by the operator, the solenoid valve 10 is operated. and bleed check valve 9.
Forced to close. Further, the bleed check valve differential pressure monitoring device 61 includes first and second pressure gauges 21 and 22, and a differential pressure calculator 23. Further, after the set time set in the timer 17 has elapsed, the sudden load reduction signal 16 that operates the solenoid valve 10 is automatically canceled, and the bleed check valve 9 is released from closing.

FIG. 12 shows a second embodiment,
When at least one of the release signal from the timer 17 and the P/B signal 20 determined by the operator is input to the OR circuit 28, the sudden load reduction signal 16 that operates the solenoid valve 10 is automatically released.
This embodiment is the same as the first embodiment except that the bleed check valve 9 is configured to release the closure.

FIG. 13 shows a third embodiment, in which a bleed check valve differential pressure monitoring device 61 measures the differential pressure between the pressure on the upstream side of the bleed check valve 9 and the pressure of the feed water heater 5 using a differential pressure gauge 25. is configured to detect by
This is the same as the first embodiment.

FIG. 14 shows a fourth embodiment, which is the same as the second embodiment except that the bleed check valve differential pressure monitoring device 61 is constituted by a differential pressure gauge 25.

FIG. 15 shows a fifth embodiment, in which both the check valve differential pressure small signal 24 and the sudden load reduction signal 16 sent via the OR circuit 26 are ANDed as the forced closing condition for the bleed check valve 9. The output signal 90 is output only when input to the circuit 27, the feed water heater water level high signal 13, and the P.
At least one of the B signals 14
The configuration is similar to the first embodiment except that the solenoid valve 10 is operated when the signal is input to the OR circuit 15.

FIG. 16 shows the sixth embodiment,
When at least one of the release signal from the timer 17 and the P/B signal 20 determined by the operator is input to the OR circuit 28, the sudden load reduction signal 16 that operates the solenoid valve 10 is automatically released. This embodiment is the same as the fifth embodiment except that the bleed check valve 9 is configured to release the closure.

FIG. 17 shows a seventh embodiment, which is the same as the fifth embodiment except that the bleed check valve differential pressure monitoring device 61 is constituted by a differential pressure gauge 25.

FIG. 18 shows an eighth embodiment, which is the same as the sixth embodiment except that the bleed check valve differential pressure monitoring device 61 is constituted by a differential pressure gauge 25.

Next, the case where the present invention is applied during load operation and FCB operation as an example of sudden load reduction operation,
The dynamic characteristics when this is not applied will be explained according to the drawings.

FIG. 19 shows the dynamic characteristics when the present invention is not applied during load runback operation and the seventh embodiment of the present invention.
8 shows dynamic characteristics when the embodiment shown in FIG. 8 is applied.

In FIG. 19, the bleed check valve 9 is forcibly closed at the load runback operation start time _T0 . Then, after time T ₃ when the pressure reversal phenomenon between the bleed pressure P ₁ and the feed water heater pressure P ₂ has occurred, the bleed check valve 9 is closed.
Release the closure. When this release is automatically performed by the timer 17, if a time _t3 is set in the timer 17 so that the release occurs after time _T3 , the bleed check valve 9 opens at time _T5 . As a result, the bleed air flow rate F changes as shown in _F1 , and the bleed steam always flows from the steam turbine 2 to the feed water heater 5. Also, depending on the operator's judgment,
By releasing the closure of the bleed check valve 9 at time _T5 , the same dynamic characteristics as automatic release by the timer 17 are obtained.

FIG. 20 shows the dynamic characteristics when the present invention is not applied and the dynamic characteristics when the present invention is applied during FCB operation.

In this Fig. 20, FCB operation start time T ₀
The bleed check valve 9 is forcibly closed. Here, if a time t4 is set in the timer ₁₇ such that the pressure reversal phenomenon between the bleed air pressure _P1 and the feed water heater pressure _P2 is released after the time _T4 , the bleed air check valve 9 opens at time _T6 . As a result, the bleed air flow rate F changes to _F2 , and the bleed steam always flows from the steam turbine 2 to the feed water heater 5. Furthermore, when the operator decides to release the bleed check valve 9 from closing at time _T6 , the same dynamic characteristics will be obtained, and will be almost the same as the dynamic characteristics during load runback operation.

FIG. 21 shows the dynamic characteristics when the present invention is not applied during load runback operation and the ninth embodiment of the present invention.
The figure shows the dynamic characteristics when the embodiment shown in FIG. 12 is applied.

This is _almost the same as _the dynamic characteristic explained in FIG. As in the embodiments shown in FIGS. 9, 10, 15 to 18, when the condition of the check valve differential pressure small signal 24 is met, the time T when the bleed pressure _P1 starts the load runback operation. Starts to fall from ₀ , time
At _T1 , the pressure is reversed to the feedwater heater pressure _P2 , but when this pressure difference becomes small and reaches the pressure difference ΔP set in the check valve differential pressure monitoring device 61, the bleed check valve 9 is forcibly closed. . In addition, the bleed air check valve 9 is connected to the differential pressure ΔP.
will be automatically canceled at time T ₈ when it is recovered.
During time t ₅ between time T ₇ and time T ₈ , the bleed air check valve 9 is forcibly closed, and the bleed air flow rate F changes as shown in F ₃ . Further, in the case of the embodiment shown in FIGS. 11 to 14, the bleed air check valve 9 is forcibly closed at time t ₇ between time T ₀ and time T ₈ , and the bleed air flow rate F is as shown in F ₅ . Transition.

FIG. 22 shows the dynamic characteristics in the embodiment under the conditions explained in FIG. 21, ie, when the check valve differential pressure small signal 24 is input during FCB operation.

In this Fig. 22, FCB operation start time T ₀
At time t ₆ until the time T ₉ when the differential pressure ΔP which was later set in the check valve differential pressure monitoring device 61 is restored, the bleed air check valve 9 is forcibly closed, and the bleed air flow rate F shifts as shown in F ₄ do.

As can be seen from the above description, according to the embodiments of the present invention, the problems in the prior art can be solved.

Also, as mentioned above, the combination of the present invention and the prior art makes it easy to protect steam turbines from water induction and steam injection under all operating conditions.

〔Effect of the invention〕

According to the first invention of the present invention explained above,
The bleed check valve is forcibly closed by at least one of a signal that rapidly reduces the amount of power generated and a change in state value that occurs due to the rapid decrease in the amount of power generated. Even when the steam turbine load is rapidly reduced, there is an effect of preventing flash steam in the feedwater heater from flowing back into the steam turbine.

Further, according to the second aspect of the present invention, a signal that rapidly decreases the amount of power generation, a change in state value that occurs due to the rapid decrease in the amount of power generation, and a pressure on the upstream side of the bleed check valve. Since the bleed check valve is forcibly closed by at least one of the small differential pressure signals with respect to the pressure of the feedwater heater, backflow of flash steam in the feedwater heater to the steam turbine is prevented. This has the effect of making prevention even more reliable.

Furthermore, according to the third aspect of the present invention, the bleed check valve control device receives at least one of a signal that rapidly reduces the amount of power generation and a change in state value that occurs due to the rapid decrease in the amount of power generation. Since the function of forcibly closing the bleed check valve is provided by either one, there is an effect that the method according to the first aspect of the present invention can be carried out reliably.

According to the fourth invention of the present invention, the bleed check valve control device is provided with a signal that rapidly reduces the amount of power generation, a change in state value that occurs due to the rapid decrease in the amount of power generation, and a bleed check valve control device that controls the bleed Since the bleed check valve is provided with a function of forcibly closing the bleed air check valve by at least one of the small differential pressure signals between the pressure on the upstream side of the stop valve and the pressure of the feed water heater, the second aspect of the present invention is provided.
This has the effect that the method of the second invention can be carried out reliably.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a steam turbine plant as a steam power generation plant to which the present invention is applied, Fig. 2 is a block diagram showing an interlock device of a bleed check valve in the prior art, and Fig. 3 is a diagram showing an interlock device in the prior art. A diagram showing the bleed check valve control device, Figure 4 is a dynamic characteristic diagram during load runback operation, Figure 5 is a dynamic characteristic diagram during FCB operation, and Figure 6 is a bleed check valve control device for carrying out the method of the present invention. A block diagram showing one embodiment of a valve interlock device; FIGS. 7 to 10 are diagrams showing the logic of various embodiments of the bleed check valve control device constituting the interlock device of the present invention, respectively;
Figures 11 to 18 are diagrams showing the first to eighth embodiments of the device combining the present invention and the prior art, respectively, and Figures 19 to 22 are diagrams showing the case where the present invention is applied and the case where the present invention is applied, respectively. FIG. 3 is a diagram showing the dynamic characteristics of turbine load, bleed air flow rate, bleed air pressure, and feed water heater pressure when there is no air flow. 1...Steam generator, 2...Steam turbine, 3
... Condenser, 4 ... Water supply pump, 5 ... Water supply heater, 6 ... Main steam pipe, 7 ... Water supply pipe, 8 ... Air bleed pipe, 9 ... Air bleed check valve, 13 ... Water supply Heater water level high signal, 14... P/B signal, 16... Load sudden decrease signal, 17... Timer, 20... P/B signal to automatically release the closure of the bleed air check valve, 21, 22... Air bleed First and second pressure gauges of the check valve differential pressure monitoring device, 2
3...Differential pressure calculator, 24...Check valve differential pressure small signal, 25...Differential pressure gauge, 51...Load runback control device, 52...FCB control device, 61...Bleed check valve Differential pressure monitoring device, 64...Target load, 65
...Bleed air check valve control device, 70... State change detector due to sudden load reduction, 80... Load runback signal, 81... FCB signal, 82... Pressure on the upstream side of the bleed air check valve and feed water heater pressure and differential pressure small signal,
83...Signal of state change due to sudden load reduction, 91...
...Forced closing signal, L ₀ ...Turbine load, F ₀ ~ _{F 5}
...Bleed air flow rate, P ₁ ...Bleed air pressure, P ₂ ...Feed water heater pressure, ΔP...Differential pressure between the pressure on the upstream side of the bleed air check valve and the feed water heater pressure, T ₀ to T ₅ ... …time,
t ₁ - _{t 2} ... Check time for the bleed air pressure and feed water heater pressure, t ₃ - _{t 7} ... Forced closing time of the bleed air check valve.

Claims (1)

[Claims] 1. Bleed air is sent from the steam turbine to the feedwater heater through a bleed air pipe having a bleed air check valve that can be forcibly closed, and the feed water to be supplied from the condenser to the steam generator is sent to the feed water heater. In a steam power generation plant that heats by bleed air, the bleed air check valve is forcibly closed by at least one of a signal that rapidly reduces the amount of power generation and a change in state value that occurs due to the rapid decrease in the amount of power generated. A method for interlocking a bleed check valve, characterized in that the closed state of the bleed check valve is automatically canceled by a release signal transmitted after a set time has elapsed since the forced closure. 2. The method for interlocking a bleed check valve according to claim 1, characterized in that the closed state of the bleed check valve is also released by the operator's judgment. 3 Steam power generation in which bleed air is sent from a steam turbine to a feed water heater through an bleed pipe having a bleed air check valve that can be forcibly closed, and the feed water to be supplied from a condenser to a steam generator is heated by the bleed air in the feed water heater. In a plant, a signal that rapidly reduces the amount of power generated, a change in state value that occurs due to a rapid decrease in the amount of power generated, and a small differential pressure between the pressure upstream of the bleed check valve and the pressure of the feed water heater. The bleed check valve is forcibly closed by at least one of the signals, and then the closed state of the bleed check valve is automatically canceled by a release signal sent when the small differential pressure is eliminated. A method for interlocking a bleed check valve. 4. The bleed check valve according to claim 3, wherein the closed state of the bleed check valve is also automatically released by a release signal transmitted after a set time has elapsed since the forced closure. Interlock method. 5. The method for interlocking a bleed check valve according to claim 3 or 4, characterized in that the closed state of the bleed check valve is also released by an operator's judgment. 6 A steam generator, a steam turbine, a condenser, a feedwater heater that heats the feedwater to be supplied from the condenser to the steam generator, and a bleed air from the steam turbine to the feedwater heater through a bleed air check valve. In a steam power generation plant equipped with an air bleed pipe that sends air and an air bleed check valve control device, the air bleed check valve control device includes:
After the bleed check valve is forcibly closed by at least one of a signal that rapidly reduces the amount of power generation and a change in state value that occurs due to the rapid decrease in the amount of power generated, the bleed check valve is closed. An interlock device for a bleed check valve, characterized in that it is provided with means for automatically releasing the closed state after a set time. 7 Claim 6 is characterized in that, in addition to the means for releasing the closed state of the bleed check valve, a means for releasing the closed state of the bleed check valve is provided according to the operator's judgment. Bleed check valve interlock device. 8 A steam generator, a steam turbine, a condenser, a feedwater heater that heats the feedwater to be supplied from the condenser to the steam generator, and a bleed air from the steam turbine to the feedwater heater through a bleed air check valve. In a steam power generation plant equipped with an air bleed pipe that sends air and an air bleed check valve control device, the air bleed check valve control device includes:
A signal that rapidly decreases the amount of power generated, a change in state value that occurs due to the rapid decrease in the amount of power generated,
The bleed check valve is forcibly closed by at least one of the small differential pressure signals between the upstream pressure of the bleed check valve and the pressure of the feed water heater, and then the small differential pressure signal is resolved. An interlock device for a bleed check valve, comprising means for automatically releasing the closed state of the bleed check valve by issuing a release signal when the check valve is closed. 9 In claim 8, the bleed check valve control device includes, in addition to the automatic release means, means for releasing the closed state of the bleed check valve after a set time has elapsed from the forced closing of the bleed check valve. An interlock device for a bleed check valve, characterized by comprising: 10 The bleed check valve according to claim 8 or 9, characterized in that the bleed check valve control device also includes means for releasing the closed state of the bleed check valve according to an operator's judgment. interlock device.