JP3116815B2 - Control method of combined cycle plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a combined plant provided with a gas turbine for controlling the number of fuel nozzles for supplying fuel in accordance with a load. It relates to a control method.

[0002]

2. Description of the Related Art As a combustor capable of reducing nitrogen oxides discharged from a gas turbine, a combustion method in which combustion is switched from one stage to one stage plus two stages in a partial load zone is sometimes adopted. In particular, it is widely used in a combined cycle plant formed by combining a gas turbine and a steam turbine.

[0003] Japanese Patent Application Laid-Open No. 64-19126 discloses a gas turbine provided with a diffusion combustor and a premixed combustor, which suppresses load fluctuation when switching from operation by a diffusion combustor to operation by a premixed combustor. For this reason, an operation in which the switching point is corrected in consideration of the atmospheric temperature and the like is described.

Japanese Patent Application Laid-Open No. 7-4265 discloses that when operation is performed at a combustion switching point, a logic for judging combustion switching and prohibiting increase / decrease of a combustion command signal for load control for a certain period of time is provided. However, it is described that the combustion switching is not frequently performed, but as a result, the cycle of the combustion switching is lengthened and the repetition of the combustion switching is not fundamentally avoided.

[0005]

In a combustor provided with a plurality of combustion sections, combustion operation may be frequently switched when operated in a combustion switching region. Frequent combustion switching causes load fluctuations and the like. Also, JP-A-7-426
In JP-A-5, the combustion switching cycle becomes longer as a result, but it has not yet been possible to avoid repeated combustion switching.

[0006] The present invention relates to a gas turbine that operates in a combustion switching zone, including when the load is reduced due to a shift in system independent operation of a combined cycle plant comprising a gas turbine and a steam turbine. An object of the present invention is to provide a combined cycle in which combustion switching is not continued and stable operation can be continued.

[0007]

A first feature of the present invention is as follows.
It has a gas turbine and an exhaust heat recovery boiler that generates steam by gas turbine exhaust gas, and a steam turbine driven by steam from the exhaust heat recovery boiler, wherein the gas turbine is compressed by the compressor and the compressor. A plurality of combustors for burning air and fuel, a turbine driven by exhaust gas from the combustor, the combustor has first and second combustors, and the first combustor burns the fuel and the fuel. In the operating method of a combined cycle plant, in which the second combustor is switched to burn or extinguish in accordance with an increase or decrease in the flow command value, the fuel flow command value may be close to switching the combustion or extinguishing of the second combustor. The output of the steam turbine is reduced and the fuel flow rate
Combustion switch in which the limit burns or extinguishes the second combustor
The output of the gas turbine is increased so as to be larger than the band, and even if the fuel flow rate command value falls below the switching value, the combustion switching is limited to maintain the combustion of the second combustor. And

When the fuel flow rate command value is in the vicinity of switching between combustion and extinguishing of the second combustor, the output of the steam turbine is reduced and the output of the gas turbine is increased. The combustion in the second combustor is maintained by limiting the decrease beyond the switching value.

A second feature is that the gas turbine includes a gas turbine, an exhaust heat recovery boiler for generating steam from gas turbine exhaust gas, and a steam turbine driven by steam from the exhaust heat recovery boiler. , A compressor, a plurality of combustors for burning air and fuel compressed by the compressor, and a turbine driven by exhaust gas from the combustor, wherein the combustor has first and second combustors A first fuel flow rate adjusting means for adjusting the fuel supplied to the first combustor, and a second fuel flow rate adjusting means for adjusting the fuel supplied to the second combustor; When the fuel flow rate command signal for controlling the supply amount is lower than a predetermined value, the first fuel flow rate adjusting means supplies fuel to the first combustor and does not supply the fuel to the second fuel flow rate adjusting means. Command signal is higher than specified value In a combined cycle plant provided with a control device for performing switching control to supply fuel to the second combustor by the second fuel flow rate adjusting means, the fuel flow rate command signal sends the fuel to the second fuel flow rate adjusting means. If it is detected that it is in the vicinity of switching whether to supply or not, even if the fuel flow rate command signal drops beyond the predetermined value, the supply of fuel to the second combustor is maintained, While reducing the output of the steam turbine ,
The fuel flow command signal burns or extinguishes the second combustor.
Control means for issuing a command to increase the output of the gas turbine so as to make it larger than the combustion switching zone to be made.

When it is detected that the fuel flow rate command signal is in the vicinity of switching whether or not to supply fuel to the second fuel flow rate adjusting means, the fuel flow rate command signal exceeds the predetermined value. Limit the lowering, the second
Control means for maintaining the supply of fuel to the combustor and reducing the output of the steam turbine and increasing the output of the gas turbine.

When the operation shifts to the system independent operation, the power transmission to the power supply destination is cut off, so that the power supply from the power plant becomes excessive and the system frequency increases. For this reason, the gas turbine narrows down the fuel to reduce the gas turbine load. However, in a gas turbine having a combustion switching type combustor, the required load at this time may be near the combustion switching point. Even if the steam control valve that is fully open during normal operation is closed or the steam control valve is closed so that the load on the gas turbine is increased so as not to operate near the combustion switching point of the combined cycle plant, the power is Depending on the consumption on the consuming side, the operation may be in the vicinity of the combustion switching point. Combustion switching is repeated by providing a lower limiter so that the fuel command signal does not fluctuate more than necessary, especially if the fuel command signal once rises and then tries to descend, so that it does not drop and shift to F1 operation. Can not be.

[0012] Even if the operation is performed in the vicinity of combustion switching during normal operation due to the required load, stable combustion can be ensured while suppressing repetition of switching.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the load is sharply reduced due to the shift of the combined cycle plant to the system independent operation, the load control can reduce the fast following gas turbine load by adjusting the fuel flow rate. This fuel flow adjustment is achieved by operating a fuel valve by a fuel command signal.However, in a combined cycle plant, the steam generated from the exhaust heat recovery boiler is guided to the steam turbine, so that the load of the steam turbine is reduced. In this case, it is preferable to adjust the load so that only the gas turbine balances the power consumption side, because the change is slow to follow. Immediately after system independent operation, if the load of the gas turbine is greatly reduced including the slow load following of the steam turbine, the gas turbine having a combustor that performs combustion switching leads to low-load operation of only one stage of combustion. Sometimes.
Thereafter, the load on the gas turbine is reduced, so that the steam generated from the exhaust heat recovery boiler decreases, and the load on the steam turbine falls gradually with a delay, and the load is reduced more than necessary. Sometimes. Next, the gas turbine load is gradually increased to maintain the balance with the power consumption side. In this process, when the fuel enters the combustion switching zone, the combustion state is switched from 1st stage to 1st stage + 2nd stage. When trying to maintain balance, if the balance load required at this time is too high, the stage is switched again from 1st stage + 2nd stage to 1st stage. And the operation is continuously repeated. According to the present invention, the combustion switching from one stage to one stage plus two stages is one.
After performing this operation, a lower limiter of the fuel command signal is provided so as not to shift to combustion switching from 1st stage + 2nd stage to 1st stage,
Even if the required balance load is too high, keep the gas turbine load from lowering, close the steam control valve to reduce the steam turbine output, and increase the gas turbine load to maintain the load balance with the power consuming side. be able to. This makes it possible to smoothly shift to system independent operation and perform stable operation that does not enter the combustion switching zone of the gas turbine.

An embodiment of the present invention will be described below.

FIG. 1 shows a typical configuration of a combined cycle plant. The components include a gas turbine 3, a generator 5, a steam turbine 6, a condenser 7, a condensate pump 8, an exhaust heat recovery boiler 9, a fuel flow control valve 10, a combustor 11, a steam control valve 12, a low-pressure steam. There is a control valve 13 and a main steam bypass valve 14. In the gas turbine 3, the air compressed by the compressor 1 is guided to a combustor 11, where the air is mixed with fuel whose flow rate has been adjusted by a fuel flow control valve 10, burns, and flows into a turbine 2 as a combustion gas. I do. Here, the power is generated by rotating the turbine 2, the work is performed by rotating the generator 5, and the subsequent combustion gas is referred to as exhaust gas 4 and is guided to the exhaust heat recovery boiler 9 downstream thereof, and the chimney 1
It is released into the atmosphere via 5. In the waste heat recovery boiler 9, heat is recovered from the exhaust gas 4 and steam is generated by water supplied from the condensate pump 8. High-pressure steam passes through the steam control valve 12, and low-pressure steam passes through the low-pressure steam control valve 13. Then, the power is guided to the steam turbine 6 to generate power, and the generator 5 is rotated to generate power. The steam that has worked in the steam turbine 6 is cooled by a condenser 7 downstream of the steam turbine 6 so as to be condensed, and is again circulated to a waste heat recovery boiler by a condensate pump 8. Further, a main steam bypass valve 14 for guiding steam from the exhaust heat recovery boiler 9 to the condenser 7 by bypassing the steam turbine 6 as necessary is provided. Can work by linking. This figure shows the case of a single-shaft combined cycle plant in which a gas turbine and a steam turbine are directly connected to one generator, but a multi-shaft combined cycle in which the gas turbine and the steam turbine have respective generators. The present invention can be applied to a cycle plant. In normal operation, the steam generated in the exhaust heat recovery boiler 9 by the exhaust gas 4 from the gas turbine 3 is guided to the entire steam turbine 6, and the steam control valve 12 and the low-pressure steam control valve 13 for adjusting the steam amount are fully opened. In this state, the main steam bypass valve 14 that bypasses the steam turbine 6 and guides steam to the condenser 7 is fully closed. In this state, the load is controlled mainly by adjusting the amount of fuel supplied to the gas turbine 3 by the fuel flow control valve 10. Fuel flow control valve 10
Operate according to a fuel command signal corresponding to a deviation from the output from the generator 5 in response to a load request.

A combustor 11 having first and second combustors
Although not shown, a control device for switching combustion by a fuel flow rate command signal is arranged.

For example, a first fuel flow regulating valve for regulating fuel supplied to the first combustor and a second fuel flow regulating valve for regulating fuel supplied to the second combustor are provided. When the fuel flow command signal for controlling the amount of combustion supplied to the combustor is lower than a predetermined value, the first fuel flow control valve is opened to supply fuel to the first combustor and the second fuel flow control valve Is closed to supply no fuel, and when the fuel flow rate command signal is higher than a predetermined value, switching control is performed so as to open the second fuel flow rate adjusting valve and supply fuel to the second combustor. is there.

When the load changes, the gas turbine load immediately responds to the change in the fuel amount, while the steam turbine output delays the generation of steam from the exhaust heat recovery boiler 9 and the main steam control valve 12, the low pressure steam control. Since the valve 13 remains fully open, the response becomes very slow. Therefore, the output responsiveness to the required output as a plant in which the outputs of the gas turbine and the steam turbine are summed is as shown in FIG. The load control can be performed in such a pattern that the gas turbine precedes and the steam turbine lags behind as shown in FIG.

The gas turbine employs a low NOx combustor capable of reducing nitrogen oxides in the exhaust gas. This combustor is used at a partial load in order to achieve a low NOx in a wide load range. It employs a two-stage combustion system in which combustion is switched. The first-stage combustion section is composed of an F1 combustion nozzle, and employs a combustion method in which stable combustion with respect to changes in the amount of fuel and the amount of air from startup to the rated load is sustainable. The two-stage combustion unit is provided with an F2 combustion nozzle and employs a premixed combustion system in which fuel and air that can achieve low NOx in a high load zone are mixed and then burned. FIG. 3 shows a fuel system diagram. The fuel supply system to the F1 and F2 combustion nozzles has F1 and F2 for adjusting the fuel flow rate, respectively.
Two fuel flow control valves are provided. The load of the gas turbine is controlled by a fuel command signal, and the signal is used to control the opening of the fuel flow control valve to adjust the fuel amount, thereby performing load control. In the adoption of this combustor, in the partial load operation, from one stage to one stage + two stages or one stage +
The operation is such that the combustion is switched from two stages to one stage. FIG. 4 shows a method of operating the fuel flow control valve at this time. At the time of ignition of the second stage combustion part, the F1 fuel flow control valve is gradually closed, and the amount of reduced fuel is injected by opening the F2 fuel flow control valve, and the fuel amount is adjusted before and after switching of combustion. Thus, the load does not fluctuate, but the load fluctuates as shown in the figure. Specifically, initially, the load decreases due to the narrowing of the F1 fuel flow control valve, and then the ratio of the fuel amount and the air amount of the F2 combustion nozzle portion approaches the ignition condition and combustion starts suddenly. The movement is settling. On the other hand, when the combustion of the F2 combustion nozzle is extinguished, the operation is the reverse of that at the time of ignition. Therefore, a load change similarly occurs.

FIG. 6 shows switching points between the operation of the first-stage combustion section and the operation of using the two-stage combustion section.

The switching is performed when a fuel flow rate command signal for controlling the fuel flow rate control valve reaches a predetermined value. For example, when the fuel flow command signal is in the increasing state,
When the fuel flow command signal is in the decreasing state when the switching point B is reached, the switching is performed at the switching point A lower than the point B. Here, the area between the point A and the point B is called a combustion switching zone. In normal operation, the logic is such as to avoid continuous operation in the combustion switching zone, and there are few problems.However, in the case of system independent operation, the balance load between the power supply side and the consumption side is in the combustion switching zone. There is a possibility that a predetermined balance load cannot be settled due to a load change due to the combustion switching, and the combustion switching may continue forever. Here, if a grid accident occurs on the power transmission side during power supply, power transmission to the power supply destination is cut off, resulting in excessive power supply. The operation shifts to an operation in which the load on the power supply decreases and the power supply is suppressed to maintain a balance between supply and consumption. This is called system independent operation, and attempts to maintain power supply within the transmittable range. In order to avoid the above continuation, an attempt is made to cope with the logic according to the flow shown in FIG. First, when the system shifts to system independent operation, the gas turbine load with a fast response is rapidly reduced. It is determined whether or not the vehicle has entered the fire extinguishing area (F1 operation) of the F2 combustion section. When the gas enters the fire extinguishing area, the load of the slow-responding steam turbine is reduced to half the opening of the main steam control valve so that the load can be adjusted on the gas turbine side, and unnecessary steam is bypassed by the main steam bypass valve 14. So that the gas turbine has a large load. In this state, the load on the gas turbine side is increased. It is determined whether the gas turbine has entered the F2 ignition range. If F2 ignition occurs, if the balance load is in the vicinity of this combustion switching zone, F2 will be extinguished again due to the load fluctuation at the time of combustion switching. Therefore, a lower limiter is provided in the fuel command signal and F2 extinguishes. To prevent Since the fuel flow rate command value fluctuates with the load fluctuation, it is possible to prevent the combustion switching from occurring due to the temporary combustion switching point. When the fuel command signal is F2
A control circuit may be provided for controlling the F2 so as not to extinguish the fire even at the switching point for extinguishing the fire. Further, a limiting circuit for removing a signal such that the fuel command signal becomes equal to or less than the switching point may be arranged in the fuel command signal system.

When the balance load is larger than the fuel switching zone, the operation is maintained, and when the cause of the transition to the single operation is released, the limiter is released and the main steam control valve 12 is released.
And normal operation can be performed by obtaining a gas turbine output corresponding to the load request and the steam turbine output.

In the switching, a switching point may be selected based on a fuel flow command signal, a fuel flow control valve opening, and a combustion load. For example, the fuel flow control valve opening is 40% of full open.
The switching may be performed when the load becomes approximately intermediate. On the other hand, when the fuel command signal is applied to the lower limiter (for example, when applied to the fuel switching zone) in the operation with the balanced load, the main steam control valve of the steam turbine is fully installed to further load the gas turbine. Close. In the two-stage combustion state, stable operation continuation that does not involve the combustion switching zone is possible. If the balance load is not applied to the lower limiter, stable operation can be performed as it is. On the other hand, when the main steam control valve is half-opened,
When the operation state of the gas turbine is only the first stage and the fuel command signal is operating with the minimum fuel amount (about several percent of the fully opened state) set for ensuring combustion stability, the steam turbine load is Is too high, the main steam control valve is fully closed.

When the balance load is larger than the fuel switching zone, the operation is maintained, and when the cause of the transition to the single operation is eliminated, the limiter is released (reset) and the main steam control valve 12 of the steam turbine is opened. Then, it is possible to shift to the normal operation so as to obtain the gas turbine output corresponding to the load request and the steam turbine output.

For example, a case can be considered where the difference between the required frequency and the frequency of electricity obtained by the combined cycle plant falls within a predetermined control range. For example,
It can be within 50 or 60 ± 0.2 or 0.3 Hz.

Even if the main steam control valve is fully closed, if the fuel command signal reaches the lower limiter (for example, the combustion switching zone), the lower limiter of the fuel command signal is reset. The load is adjusted by the gas turbine. If necessary, the operation shifts to a predetermined operation such as an operation in the one-stage combustion section.

The degree of increasing the gas turbine load is 5 to 10% from the combustion switching zone in consideration of combustion stability.
It is practical that the degree of opening of the valve is as large as possible.

Specifically, the required load is appropriately adjusted so that the remaining required load obtained from the steam turbine output obtained by the predetermined opening degree of the control valve of the steam turbine as described above is carried by the gas turbine output. . By closing the control valve, it can be determined in relation to the required load.

In the above description, the opening and closing of the control valve of the steam turbine was made to be fully closed at 1/2. However, the present invention is not limited to this, and the steam turbine may be further divided into multiple stages. Alternatively, the opening may be continuously adjusted.

By controlling the valve opening degree of the steam turbine having a gradual response in a predetermined value step-like manner and adjusting the gas turbine load with a high response in relation to the required load, system independent operation or the like can be performed. This is practical because a more rapid response can be taken even when the load suddenly changes.

Further, by making the change stepwise, it is possible to cope with a rapid load sudden change and to adjust the correspondence with the required load in each step, so that more stable operation can be performed.

According to the present embodiment, it is possible to suppress the gas turbine from being subjected to a short heat cycle due to the short-time repetition of ignition and extinguishing of the two-stage load combustion section, and to prolong the life of the equipment. be able to.

It is possible to prevent the control from becoming difficult due to the short-time repetition of the ignition and the fire extinguishing, and it is possible to stably supply the electric power. In a premixed combustor that requires management of the ratio of fuel to air, switching can be controlled to improve the stability of the premixed combustion section.

Whether or not to start the control of the present invention may be determined by starting the present control when it is detected that the frequency fluctuates abruptly, for example, when shifting to an isolated operation. Once the output drops until the two-stage combustion unit extinguishes, within a few seconds (for example, it may be set to a few seconds)
This control may be started when the output increases until the two-stage combustion unit is ignited.

In that case, a lower limiter is provided for the fuel flow rate command signal. Still, when the fuel flow rate command signal reaches the lower limiter, the main steam control valve is set to 開. When the balance load is larger than the fuel switching zone, the operation is maintained, and when the cause of the transition to the single operation is released, the limiter is released, the main steam control valve 12 of the steam turbine is opened, and the load request is satisfied. The operation can be shifted to the normal operation so as to obtain the gas turbine output corresponding to the steam turbine output.

Further, when the fuel flow rate command signal reaches the lower limiter, the main steam control valve is fully closed. Even so, when the fuel flow rate command signal reaches the lower limiter, the limiter is reset and the load is adjusted by the gas turbine.

Further, the two-stage combustion section of the combustor has a plurality of fuel systems, the number of fuel supply systems increases with an increase in combustion load, and the number of fuel supply systems decreases with a decrease in combustion load. The present invention can be applied to a combined cycle plant in which a gas turbine having a combustor is operated and which is operated by increasing or decreasing the number of systems supplying fuel in a two-stage combustion section.

For example, four fuel systems (2
-1, 2-2, 2-3, 2-4), for example, in accordance with an increase in load, the fuel is supplied to 2-1 of the two-stage combustion unit from the combustion by the first-stage combustion unit to perform premix combustion None, if the load further rises, fuel can be supplied to the 2-2 system for combustion, and 2-3 and 2-4 can be sequentially ignited and burned as the load increases.

The required load is the combustion switching zone between the first-stage combustion unit and the second-stage combustion unit, or 2-1 to 2-2, 2-
In the case of any one of the combustion switching zones of the systems 3 and 2-4, for example, a transition from the 2-4 combustion state (all system combustion state) to the 2-4 fire extinguishing state is taken as an example. When the extinguishing of the combustor of the 2-4 system is detected, the opening of the main steam control valve 12 is reduced to a predetermined opening (an appropriate opening can be set according to the specifications of each plant. For example, about 3/4 opening) ), Increase to gas turbine load. After confirming reignition of the 2-4 system, an adjustment limiter is provided for the fuel command signal to suppress the 2-4 system from extinguishing.

Still, if the balance load is in a state in which the fuel command signal is applied to the lower limiter, the opening of the main steam control valve 12 is further reduced to a predetermined opening smaller than the above (appropriate depending on the specifications of each plant, etc.). (For example, about 1/2 opening). In this way, the operation can be sequentially shifted to the operation in the system.

When the balance load is larger than each of the fuel switching zones, the operation is maintained, and when the cause of the shift to the single operation is eliminated, the limiter is released and the opening of the main steam control valve 12 is increased. The operation can be shifted to the normal operation so as to obtain the gas turbine output corresponding to the load request and the steam turbine output.

By developing the logic according to the above flow, it is possible to operate the system solely while avoiding operation in the combustion switching zone.

In the above-described embodiment, the operation at the time of the transition to the isolated operation has been described. However, the present invention is not limited to this.
Even when it reaches the combustion switching zone of the gas turbine,
As shown in FIG. 5, by increasing the gas turbine load and decreasing the steam turbine load, it is possible to suppress continuous combustion switching or the like and maintain stable operation.

Further, the two-stage combustion section of the combustor has a plurality of fuel systems, the number of fuel supply systems increases as the combustion load increases, and the number of fuel supply systems decreases as the combustion load decreases. In a combined cycle plant in which a gas turbine provided with a combustor is operated, the operation can be performed as described above even at the time of switching between increasing and decreasing the number of systems for supplying fuel in the two-stage combustion section.

FIG. 7 shows a schematic diagram of another embodiment.

The same configuration as that of the above-described embodiment can be used for the control device and the detector of the combustor. A configuration not shown in FIG. 1 will be described.

Reference numeral 17 denotes a compressed air extraction valve. The valve only needs to be able to extract air to be supplied to the combustor, and may be at an appropriate position such as a compressor or a path through which the compressed air flows to the combustor. Further, a path is provided in which the bleed air that has passed through the bleed valve merges with the gas discharged from the gas turbine.

During system independent operation or when the second combustor extinguishes due to a decrease in required load and reignites under the predetermined conditions as described above, the fuel flow rate command signal does not fall below the switching point. Set a lower limiter to limit,
Ensure that the second combustor does not extinguish. Alternatively, the second combustor is maintained even if the fuel flow rate command signal falls below the above-described combustion switching point, so that the second combustor is not extinguished.

If the limiter has been applied, the compressed air bleed valve 17 is opened to reduce the amount of air supplied to the combustor 11 and reduce the amount of combustion gas. As a result, the amount of work in the turbine 2 is reduced, and the operation is performed with the output suppressed even if the fuel flow rate command signal is the same. As described above, while adjusting the gas turbine load, the second combustor can be prevented from operating in the combustion switching zone, and stable combustion of the gas turbine can be ensured.

In particular, it is possible to cope with a sudden change in load, such as in a system independent operation.

When the cause of the single operation shift is eliminated or when the normal load shifts due to an increase in the required load, the limiter is released, the compressed air bleed valve 17 is closed, and the gas turbine is operated in response to the load request. The operation can be shifted to the normal operation so as to obtain the output.

Also, as in the above-described embodiment, depending on the situation, when it is determined that the second combustor has extinguished, the compressed air bleed valve 17 is opened and the ignition of the second combustor is confirmed. The system is operated with the limiter.

Further, when the fuel flow rate command signal reaches the lower limiter, the opening degree of the compressed air bleed valve 17 is increased and the same operation is performed. Alternatively, when a plurality of compressed air bleeding valves 17 are provided, the number of valves that open the valves is further increased.

If the fuel flow rate command signal reaches the lower limiter even when the valve 17 is fully opened, the limiter is reset and the second combustor is ignited or extinguished according to the fuel flow rate command signal. Adjust the load with the gas turbine.

The first combustor and the second combustor may be a diffusion combustor and a premix combustor, but may be a combustor related to one fuel system of the premix combustor and a combustor related to another fuel system. It may be a combustor.

[0056]

According to the present invention, it is possible to provide a combined cycle plant or a gas turbine combustor operating method capable of maintaining stable operation while suppressing continuous combustion switching, and suppressing load fluctuation. Can drive.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a combined cycle plant according to one embodiment.

FIG. 2 is an output control characteristic diagram of a combined cycle plant.

FIG. 3 is a fuel system diagram of a gas turbine.

FIG. 4 is a combustion switching characteristic diagram of a gas turbine.

FIG. 5 is a flowchart of a system independent operation transition.

FIG. 6 is an outline of a combustion switching point.

FIG. 7 is a configuration diagram of a gas turbine according to one embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Turbine, 3 ... Gas turbine, 4 ... Exhaust gas, 5 ... Generator, 6 ... Steam turbine, 7 ... Condenser, 8
... condensing pump, 9 ... waste heat recovery boiler, 10 ... fuel flow control valve, 11 ... combustor, 12 ... steam control valve, 13 ... low pressure steam control valve, 14 ... main steam bypass valve, 15 ... chimney.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-101502 (JP, A) JP-A-7-4265 (JP, A) JP-A-61-142335 (JP, A) JP-A-4-104 124521 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) F01K 23/10 F02C 6/18 F02C 9/34

Claims (5)

(57) [Claims] 1. A gas turbine comprising: a gas turbine; an exhaust heat recovery boiler for generating steam from gas turbine exhaust gas; and a steam turbine driven by steam from the exhaust heat recovery boiler; A plurality of combustors for burning air and fuel compressed by the machine, and a turbine driven by exhaust gas from the combustor, wherein the combustor is a first combustor.
And a second combustor, wherein the first combustor burns, and the second combustor is switched to burn or extinguish according to an increase or decrease in the fuel flow command value. in the method, the fuel flow rate command value is in the vicinity of switching the combustion or extinguishing of the second combustor, while decreasing the output of the steam turbine, the fuel flow rate
The command value is the combustion cutoff for burning or extinguishing the second combustor.
The output of the gas turbine is increased so as to be larger than the replacement zone, and even if the fuel flow rate command value falls below the switching value, the combustion switching is limited to maintain the combustion of the second combustor. The operating method of the combined plant. 2. A gas turbine comprising: a gas turbine; an exhaust heat recovery boiler for generating steam from gas turbine exhaust gas; and a steam turbine driven by steam from the exhaust heat recovery boiler; A plurality of combustors for burning air and fuel compressed by the machine, and a turbine driven by exhaust gas from the combustor, wherein the combustor is a first combustor.
And a second combustor, wherein the first combustor burns, and the second combustor is switched to burn or extinguish according to an increase or decrease in the fuel flow command value. in the method, the fuel flow rate command value is in the vicinity of switching the combustion or extinguishing of the second combustor, while decreasing the output of the steam turbine, the fuel flow rate
The command value is the combustion cutoff for burning or extinguishing the second combustor.
Increasing the output of the gas turbine so as to be larger than the replacement zone , restricting the fuel flow rate command value from exceeding the switching value, and maintaining the combustion of the second combustor. How to operate the plant. 3. The control method for a combined plant according to claim 1, wherein the decrease in the output of the steam turbine includes reducing an opening of a steam control valve for controlling a flow rate of steam supplied to the steam turbine to a predetermined value. Characteristic method of operating a combined plant. 4. A gas turbine comprising: a gas turbine; an exhaust heat recovery boiler for generating steam from gas turbine exhaust gas; and a steam turbine driven by steam from the exhaust heat recovery boiler; A plurality of combustors for burning air and fuel compressed by the machine, and a turbine driven by exhaust gas from the combustors, wherein the combustors have first and second combustors; First fuel flow rate adjusting means for adjusting fuel to be supplied to the second combustor;
A fuel flow rate control signal for controlling the amount of combustion supplied to the combustor is lower than a predetermined value, the first fuel flow rate adjusting means supplies fuel to the first combustor. If the fuel flow rate command signal is higher than a predetermined value without supplying fuel to the second fuel flow rate adjusting means, a control device for switching control to supply fuel to the second combustor by the second fuel flow rate adjusting means is provided. In the combined cycle plant provided, when detecting that the fuel flow rate command signal is in the vicinity of switching whether or not to supply the fuel to the second fuel flow rate adjusting means, the fuel flow rate command signal changes the predetermined value. The fuel flow to the second combustor is reduced, the output of the steam turbine is reduced , and the fuel flow rate is reduced.
The command signal is used to burn or extinguish the second combustor.
A combined cycle plant comprising control means for issuing a command to increase the output of a gas turbine so as to make it larger than a replacement zone . 5. A gas turbine, comprising: an exhaust heat recovery boiler for generating steam from gas turbine exhaust gas; and a steam turbine driven by steam from the exhaust heat recovery boiler, wherein the gas turbine includes a compressor; A plurality of combustors for burning air and fuel compressed by the machine, and a turbine driven by exhaust gas from the combustors, wherein the combustors have first and second combustors; First fuel flow rate adjusting means for adjusting fuel to be supplied to the second combustor;
A fuel flow rate control signal for controlling the amount of combustion supplied to the combustor is lower than a predetermined value, the first fuel flow rate adjusting means supplies fuel to the first combustor. If the fuel flow rate command signal is higher than a predetermined value without supplying fuel to the second fuel flow rate adjusting means, a control device for switching control to supply fuel to the second combustor by the second fuel flow rate adjusting means is provided. Equipped,
In the combined cycle plant, when it is detected that the fuel flow rate command signal is in the vicinity of switching whether or not to supply fuel to the second fuel flow rate adjusting means, the fuel flow rate command signal exceeds the predetermined value. Limiting the fuel flow to the second combustor, reducing the output of the steam turbine and reducing the fuel flow rate.
The command signal is used to burn or extinguish the second combustor.
A combined cycle plant comprising control means for issuing a command to increase the output of a gas turbine so as to make it larger than a replacement zone .