JP2000045791A - Gas turbine intake controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the elevation of the exhaust gas temperature in the stopping of a gas turbine and to prevent each equipment of an exhaust system from receiving the excess heat hysteresis. SOLUTION: An intake controller comprises a first exhaust gas temperature set value computing unit 22 for calculating a set value for the starting and the ordinary operation of a gas turbine and a second exhaust gas temperature set value computing unit 28 for calculating a set value for the stopping. A compressor discharge pressure signal (a) is inputted to both of the set value computing units 22, 28, and the exhaust gas temperature set values are respectively determined on the basis of the included functions. The exhaust gas temperature set value signals (b, g) are inputted to a switching unit 29. The switching unit 29 outputs the exhaust gas temperature set value signal (b) when a gas turbine stop signal (h) is not inputted, and outputs the exhaust gas temperature set value signal (g) for the stopping, when the gas turbine stop signal (h) is given.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine intake control device suitable for suppressing a rise in the temperature of exhaust gas from a gas turbine to a temperature that is not desirable for maintaining the life of the equipment when the gas turbine is stopped.

[0002]

2. Description of the Related Art As shown in FIG. 5, a single-shaft combined cycle power plant comprises a gas turbine unit 1, an exhaust heat recovery boiler 2, a steam turbine 3 and a generator 4 as main components. It is driven by both the turbine unit 1 and the steam turbine 3. More specifically, air sucked from the atmosphere is compressed in the compressor 5, and the fuel control valve 7 in the combustor 6.
Is mixed with the fuel flowing from the fuel cell to generate hot combustion gas. This combustion gas expands in the gas turbine 8 to generate power. The generator 4 is driven by a part of this power,
Electric output occurs. The remaining power of the gas turbine 8 is used to drive the compressor 5.

[0003] The exhaust gas from the gas turbine 8 is guided to the exhaust heat recovery boiler 2 and is used for heating the supply water and generating steam, which will be described later. The exhaust gas whose temperature has dropped in the exhaust heat recovery boiler 2 is discharged into the atmosphere through a chimney 9.

On the other hand, the feed water pressurized by the feed water pump 11 from the condenser 10 is led to the economizer 12 of the exhaust heat recovery boiler 2 and is heated by the exhaust gas. The supply water whose temperature has risen flows into the steam drum 13 and is further circulated through the evaporator 14 while being heated by the exhaust gas to generate steam. The generated steam becomes superheated steam through the superheater 15, flows into the steam turbine 3, and expands. Power is generated by this expansion, and the generator 4 is driven to generate an electric output. The exhaust gas of the steam turbine 3 is guided to a condenser 10 and is cooled and condensed by cooling water sent through a circulating water system (not shown) to be condensed.

[0005] The temperature of the exhaust gas of the gas turbine 8 is maintained at a high temperature (for example, 550 ° C to 650 ° C) in order to generate steam in the exhaust heat recovery boiler 2.
In order to appropriately maintain the exhaust gas temperature, the following turbine intake control device is used. As shown in FIG. 6, the compressor discharge pressure signal a given from the compressor discharge pressure sensor 21 is input to the exhaust gas temperature set value calculator 22 and the exhaust gas temperature set value signal b obtained in the compressor 5 The air amount is adjusted by changing the opening degree of the compressor inlet guide vane 23 provided in the above.

The output of the exhaust gas temperature set value calculator 22 must be determined so that the gas temperature at the gas turbine inlet is maintained in a temperature range that is allowable so as not to deteriorate the material strength. Based on the exhaust gas temperature signal c, it is determined taking into account the gas temperature at the gas turbine inlet.

An exhaust gas temperature set value signal b and a gas turbine exhaust gas temperature signal c provided from a gas turbine exhaust gas temperature sensor 24 are compared in a subtractor 25 to determine a deviation. The obtained deviation signal d is the PI controller 26
Is input to the controller, a proportional operation and an integral operation are performed, and further amplified to generate a flow rate request.

The flow request signal e is input to the valve controller 27, which outputs an opening command f, and the opening of the compressor inlet guide vane 23 changes accordingly. For example, when the opening degree of the compressor inlet guide vane 23 increases, the intake air amount increases, and at this time, the exhaust gas temperature decreases.
On the other hand, when the opening degree of the compressor inlet guide vanes 23 becomes smaller, the intake air amount decreases, and at this time, the exhaust gas temperature rises.

FIG. 7 shows changes in the exhaust gas temperature of the gas turbine and the gas temperature at the gas turbine inlet in the gas turbine intake control. An exhaust gas temperature set value curve C41 shown in (a) is a curve for giving an exhaust gas temperature set value signal b corresponding to the compressor discharge pressure signal a obtained from a function built in the exhaust gas temperature set value calculator 22. When the gas turbine 8 starts and the gas turbine output and fuel increase, the compressor discharge pressure increases, and the exhaust gas temperature gradually increases as shown in (b). When the exhaust gas temperature reaches the value given by the exhaust gas temperature set value curve C41 shown by the broken line, the opening of the compressor inlet guide vane 23 opens as shown in (c), and finally opens fully (84 in the example of the figure).
Degree).

An exhaust gas temperature set value curve C4 shown in FIG.
When the compressor discharge pressure becomes a constant value, the curve 1 is a curve which is lowered to the right. This is because the exhaust gas temperature is a value proportional to the n-th power of the reciprocal of the compressor discharge pressure in order to maintain the gas temperature at the gas turbine inlet at a constant value. That is,
When the output of the gas turbine 8 rises and reaches the downward slope of the exhaust gas temperature set value curve C41, the gas temperature at the gas turbine inlet reaches the maximum allowable value, and when the output of the gas turbine 8 further rises, Compressor inlet guide vane 23
At this time, the exhaust gas temperature starts to decrease, and at the same time, the gas temperature at the gas turbine inlet is maintained at a constant value while maintaining the allowable maximum temperature as shown in (d).

It is to be noted that starting the compressor with the opening degree of the compressor inlet guide vanes 23 kept at the minimum opening degree first raises the temperature of the exhaust gas of the gas turbine 8 from the earliest possible stage and increases the temperature of the steam in the exhaust heat recovery boiler 2. Is intended to hasten the occurrence of this, whereby it becomes possible to establish the conditions for ventilation to the steam turbine 3 at an early stage.

On the other hand, when the gas turbine 8 is stopped, the operation is the reverse of the operation at the time of starting. That is, as the output and fuel of the gas turbine 8 decrease and the compressor discharge pressure decreases,
The compressor inlet guide vanes 23 start to close, and only the exhaust gas temperature rises as shown in FIG. 3B while the gas turbine inlet gas temperature is kept at a constant value. Thereafter, after the compressor inlet guide vane 23 reaches the minimum opening (57 degrees in the example in the figure), the gas temperature at the gas turbine inlet and the exhaust gas temperature gradually decrease as the fuel flow rate decreases.

[0013]

The above-described gas turbine intake control is a method that is almost free of dissatisfaction at the time of start-up and during normal operation with careful consideration. It is inevitable that the temperature rises and falls, resulting in an adverse effect. For example, in a combined cycle power plant, the gas turbine 8 is frequently started and stopped, and each equipment of the exhaust system inevitably receives an excessive heat history due to repeated rise and fall of the exhaust gas temperature. Each device may consume its life due to the thermal stress of.

In the case where the superheater 15 of the exhaust heat recovery boiler 2 is provided with a desuperheater, the steam temperature becomes too high when the temperature of the exhaust gas rises. Spray water needs to be blown out, which greatly increases spray water consumption and affects operating costs.

Further, in a plant where the superheater 15 does not have a desuperheater, the components of the steam turbine 3 have an excessive heat history due to the repeated rise and fall of the steam temperature, and the thermal stress at that time causes the steam turbine 3 Components may consume their lifetime.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas turbine intake control device which suppresses an increase in exhaust gas temperature when the gas turbine is stopped so as to prevent each component of the exhaust system from receiving an excessive heat history. To provide.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is to calculate a set value which defines an exhaust gas temperature during startup and normal operation of a gas turbine as a function of a compressor discharge pressure. Exhaust gas temperature set value calculator,
A subtractor for calculating a deviation between the set value signal from the first exhaust gas temperature set value calculator and the detected gas turbine exhaust gas temperature signal; and an air amount flowing into the compressor based on the obtained deviation signal. And a control means for generating an opening command for changing the opening of the compressor inlet guide vane for adjusting the exhaust gas temperature. A set value changing means for setting a different set value from that during the operation is provided, and the exhaust gas temperature when the gas turbine is stopped is kept lower than that during the normal operation.

In the gas turbine intake control device having the above configuration, when the gas turbine is stopped, the set value that regulates the exhaust gas temperature is changed to a lower set value that is different from that during normal operation, and is output. The temperature is kept lower than during normal operation, and it is possible to reliably prevent the temperature from rising to a temperature range not originally required. As a result, it is possible to prevent each device in the exhaust system from receiving an excessive heat history due to repeated rise and fall of the exhaust gas temperature, and it is possible to prevent the life from being consumed due to thermal stress.

Further, the invention according to claim 2 is characterized in that the set value changing means calculates a set value defining the exhaust gas temperature when the gas turbine is stopped as a function of the compressor discharge pressure; A switching unit for switching and outputting an output signal from the first and second exhaust gas temperature set value calculators, wherein when the gas turbine is stopped, the set value from the first exhaust gas temperature set value calculator is changed to the second exhaust gas temperature set value. The present invention is characterized in that the temperature is switched to a set value from a temperature set value calculator and output.

In the gas turbine intake control device having the above configuration, the set value for defining the exhaust gas temperature when the gas turbine is stopped is obtained from a function provided from the second exhaust gas temperature set value calculator, which is different from that during normal operation. Since the output is switched, the exhaust gas temperature of the gas turbine can be reliably prevented from rising beyond a temperature according to a predetermined function. As a result, it is possible to prevent each device in the exhaust system from receiving an excessive heat history due to repeated rise and fall of the exhaust gas temperature, and it is possible to prevent the life from being consumed due to thermal stress.

According to a third aspect of the present invention, the set value changing means stores the exhaust gas temperature lower than the exhaust gas temperature at the start of the gas turbine stop operation, and the set value from the exhaust gas temperature set value calculator. And a low value selection circuit for selecting any low value of the exhaust gas temperature signal from the storage circuit.When the gas turbine is stopped, the exhaust gas temperature signal from the storage circuit has priority over the set value from the exhaust gas temperature set value calculator. And output as a set value.

In the gas turbine intake control device having the above-described structure, the set value which is given from the storage circuit when the gas turbine is stopped and does not exceed the exhaust gas temperature at the start of the stop operation is output. It is possible to reliably prevent the temperature from becoming higher than the temperature at the time. As a result, it is possible to prevent each device in the exhaust system from receiving an excessive heat history due to repeated rise and fall of the exhaust gas temperature, and it is possible to prevent the life from being consumed due to thermal stress.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a gas turbine intake control device calculates a first exhaust gas temperature set value calculator 2 for calculating set values for starting and normal operation of a gas turbine 8.
2 and a second exhaust gas temperature set value calculator 28 for calculating a set value for stopping. The first and second exhaust gas temperature set value calculators 22 and 28 are each supplied with a compressor discharge pressure signal a, and the exhaust gas temperature set value is obtained from a built-in function. The exhaust gas temperature set value signals b and g are input to the switch 29, respectively.

The switch 29 is a contact signal.
A gas turbine stop signal h is provided. Switch 29
Outputs an exhaust gas temperature set value signal b when the gas turbine stop signal h is not input, and outputs an exhaust gas temperature set value signal g for stop when the gas turbine stop signal h is given.

The present embodiment has the above-described structure. During normal operation, the exhaust gas temperature set value signal b from the first exhaust gas temperature set value calculator 22 and the gas turbine exhaust gas temperature sensor 24
Is compared with the gas turbine exhaust gas temperature signal c provided by the subtractor 25 to determine a deviation. The obtained deviation signal d is input to the PI controller 26, where a proportional operation and an integral operation are performed and further amplified to generate a flow rate request. The flow rate request signal e is input to the valve controller 27, from which an opening command f is output, and the opening of the compressor inlet guide vane 23 changes accordingly. That is, the control at the time of startup and during normal operation is the same as that of the conventional control.

On the other hand, when the engine is stopped, the exhaust gas temperature is controlled so as not to exceed a temperature according to a predetermined function according to an exhaust gas temperature set value curve C51 shown by a solid line in FIG.
In the illustrated example, the stop operation starts at an exhaust gas temperature of 520 ° C. When the gas turbine stop signal h is given, the exhaust gas temperature set value curve C41 during normal operation indicated by the broken line is switched to the exhaust gas temperature set value curve C51. As the compressor discharge pressure decreases due to the output of the gas turbine 8,
As shown in (c), the compressor inlet guide vanes 23 begin to close, and the exhaust gas temperature gradually decreases as shown by the solid line in (b). At this time, the gas temperature at the gas turbine inlet is also (d)
As shown in (1), it starts to decrease at the same time as the start of the stop operation, and gradually decreases.

Thus, by switching the exhaust gas temperature set value curve from the exhaust gas temperature set value curve C41 used during the normal operation to the exhaust gas temperature set value curve C51 for stopping, the exhaust gas temperature rises above the temperature according to a predetermined function. Can be reliably suppressed.

As described above, according to the present embodiment, it is possible to prevent the exhaust gas temperature from rising above a temperature according to a predetermined function, and it is possible for each device in the exhaust system to raise and lower the exhaust gas temperature. It is possible to avoid receiving an excessive heat history due to the repetition of the above, and it is possible to prevent each device from consuming its life due to thermal stress.

Next, another embodiment of the present invention will be described. In FIG. 3, the gas turbine intake control device includes a storage circuit 30 for storing an exhaust gas temperature lower than the exhaust gas temperature at the start of the stop operation of the gas turbine 8. Further, a low value selection circuit 31 connected to the output terminal of the exhaust gas temperature set value calculator 22 is provided. The low value selection circuit 31 receives an exhaust gas temperature set value signal b obtained by inputting the compressor discharge pressure signal a to the exhaust gas temperature set value calculator 22 and the storage circuit 3
Any low value of the gas turbine exhaust gas temperature signal c from 0 is selected, and a stop exhaust gas temperature set value signal i is output.

In this embodiment, the exhaust gas temperature set value signal b from the exhaust gas temperature set value calculator 22 and the gas turbine exhaust gas temperature signal c given from the gas turbine exhaust gas temperature sensor 24 during normal operation. Subtractor 25
And the deviation is determined. The obtained deviation signal d is input to the PI controller 26, where a proportional operation and an integral operation are performed and further amplified to generate a flow rate request. This flow request signal e is transmitted to the valve controller 27.
The opening degree command f is output from this, and the opening degree of the compressor inlet guide vane 23 changes accordingly. That is, the control at the time of startup and during normal operation is the same as that of the conventional control.

On the other hand, when the engine is stopped, the exhaust gas temperature is controlled based on an exhaust gas temperature curve C61 shown by a solid line in FIG. In the illustrated example, the stop operation starts at an exhaust gas temperature of 520 ° C. lower than the exhaust gas temperature at the start of the stop operation.
When the gas turbine stop signal h is given, the low value selection circuit 31 selects the exhaust gas temperature curve C61 based on the gas turbine exhaust gas temperature signal c given from the storage circuit 30 in preference to the exhaust gas temperature curve C41.

For this reason, as the compressor discharge pressure decreases due to the decrease in the output of the gas turbine 8, the compressor inlet guide vane 23 will maintain the exhaust gas temperature at a constant value (520 ° C.) as shown in FIG. , And eventually reaches the minimum opening degree (57 degrees in the illustrated example). From this, the exhaust gas temperature gradually decreases as shown by the solid line in FIG.
As shown in (d), the gas temperature at the inlet of the gas turbine also starts to decrease simultaneously with the start of the stop operation, and gradually decreases.

Thus, in the present embodiment, it is possible to reliably prevent the exhaust gas temperature from becoming higher than the temperature at the start of the stop operation.

As described above, according to the present embodiment, it is possible to prevent the exhaust gas temperature from rising beyond the temperature at the start of the stop operation. It is possible to avoid receiving an excessive heat history due to the repetition of the descent, and it is possible to prevent each device from consuming its life due to thermal stress.

Needless to say, the gas turbine intake control apparatus according to each of the above-described embodiments can be applied to single-shaft and multi-shaft combined cycle power plants. In this case, in the case where the superheater 15 of the exhaust heat recovery boiler 2 is provided with a desuperheater, the rise in the exhaust gas temperature of the gas turbine 8 is suppressed, so that the amount of spray water blown out from the desuperheater can be greatly reduced. .

Further, in a plant having no superheater 15 in which the superheater 15 has a desuperheater, an increase in the exhaust gas temperature is suppressed, so that an excessive heat history is caused in the components of the steam turbine 3 due to the repeated increase and decrease of the steam temperature. Therefore, it is possible to suppress the consumption of the life of each component.

[0037]

As described above, according to the present invention, when the gas turbine is stopped, the set value that regulates the exhaust gas temperature is changed to a lower set value that is different from that during normal operation, and the output is changed. The temperature is kept lower than the temperature during operation, and it is possible to reliably suppress the temperature from rising to a temperature range that is not originally required. Thus, according to the present invention,
It is possible to prevent each device of the exhaust system from receiving an excessive heat history, and it is possible to prevent the life from being consumed due to thermal stress.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a gas turbine intake control device according to the present invention.

FIG. 2 is a graph showing changes in gas turbine exhaust gas temperature, compressor inlet guide vane opening, and gas turbine inlet gas temperature in the control of the present invention.

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

FIG. 4 is a graph showing changes in gas turbine exhaust gas temperature, compressor inlet guide vane opening, and gas turbine inlet gas temperature according to another embodiment.

FIG. 5 is a system diagram showing an example of a conventional combined cycle power plant.

FIG. 6 is a block diagram showing a conventional gas turbine intake control device.

FIG. 7 shows a gas turbine exhaust gas temperature in a conventional control,
4 is a graph showing changes in the opening degree of a compressor inlet guide blade and a gas temperature at a gas turbine inlet.

[Explanation of symbols]

 5 Compressor 22 First exhaust gas temperature set value calculator 23 Compressor inlet guide blade 25 Subtractor 26 PI controller 28 Second exhaust gas temperature set value calculator 29 Switching device 30 Storage circuit 31 Low value selection circuit

Claims (3)

[Claims] 1. A first exhaust gas temperature set value calculator for calculating a set value defining an exhaust gas temperature during startup and normal operation of a gas turbine as a function of a compressor discharge pressure;
A subtractor for calculating a deviation between the set value signal from the exhaust gas temperature set value calculator and the detected gas turbine exhaust gas temperature signal, and adjusting the amount of air flowing into the compressor based on the obtained deviation signal. In a gas turbine intake control device comprising an adjusting means for creating an opening command for changing the opening of the compressor inlet guide vane, a set value that defines the exhaust gas temperature when the gas turbine is stopped is set at startup and during normal operation. A gas turbine intake control device comprising a set value changing means for setting different set values, wherein an exhaust gas temperature when the gas turbine is stopped is kept lower than during normal operation. 2. A second exhaust gas temperature set value calculator, wherein the set value changing means calculates a set value defining an exhaust gas temperature when the gas turbine is stopped as a function of a compressor discharge pressure, and the first and second exhaust gas temperature calculators. A switching unit for switching and outputting an output signal from the exhaust gas temperature set value computing unit, wherein the set value from the first exhaust gas temperature set value computing unit is changed to the second exhaust gas temperature set value when the gas turbine is stopped. 2. The gas turbine intake control device according to claim 1, wherein the output is switched to a set value from an arithmetic unit. 3. A storage circuit in which the set value changing means stores an exhaust gas temperature lower than the exhaust gas temperature at the start of the gas turbine stop operation, and a set value from the exhaust gas temperature set value calculator and the storage circuit. A low value selection circuit that selects any low value of the exhaust gas temperature signal of the exhaust gas temperature signal from the storage circuit when the gas turbine is stopped in preference to the set value from the exhaust gas temperature set value calculator. 2. The gas turbine intake control device according to claim 1, wherein the output is set as a set value.