JPH06101502A - Gas turbine system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a gas turbine system that can respond to rapid load changes without the temperature change of the gas turbine exhaust heat recovery system and the gas turbine exhaust gas temperature being constant even during partial load operation of the gas turbine. To provide. [Configuration] Low-pressure compressor 25 at the inlet of the gas turbine compressor 1
Is provided and high-pressure air is supplied to the inlet of the compressor 1 at the rated point, and the supply air pressure by the low-pressure compressor 25 is reduced in accordance with the decrease in the load to reduce the compressor flow rate and the combustor 2 Depending on the amount of fuel supplied to the gas turbine 3
It is designed to control the exhaust gas temperature. [Effect] Since the exhaust gas temperature of the gas turbine 3 can be kept constant during the partial load operation of the gas turbine,
It is possible to easily provide a gas turbine system that can respond to a rapid change in partial load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine system suitable for partial load operation, and more particularly to a gas turbine system suitable for a combined cycle system that utilizes exhaust gas from a gas turbine.

[0002]

2. Description of the Related Art A gas turbine has a high exhaust gas temperature. Therefore, if this exhaust gas is discarded as it is, it is a waste of energy. Therefore, a system for recovering the energy of exhaust gas by generating steam from this exhaust gas and supplying it to a steam turbine to generate power or by utilizing it in a chemical process has been put into practical use. The system is called a combined cycle system.

By the way, in a gas turbine for power generation, the number of revolutions at the time of power generation is fixed by the rated frequency of the AC generator to be driven thereby. On the other hand, in a gas turbine, an axial compressor is mainly used, and the corrected flow rates of the axial compressor and the turbine are calculated by the following equations,
It is expressed by a formula and is almost constant if the rotation speed does not change.

(Gc × √Tc) / Pc = constant Gc: Corrected flow rate of the compressor expressed by weight flow rate Tc: Compressor inlet air temperature Pc: Compressor inlet air pressure (Gt × √Tt) / Pt = constant Gt : Corrected flow rate of turbine expressed by weight flow rate Tt: Turbine inlet air temperature Pt: Turbine inlet air pressure As described above, the flow rate characteristic of the compressor at a constant rotation speed is:
If the temperature and pressure conditions of the inlet air do not change, the weight flow rate will be almost constant.Therefore, in order to change the load of the gas turbine without changing the rotation speed, it has been conventionally supplied to the combustor of the gas turbine. This is achieved by controlling the fuel flow rate that is present and changing the inlet air temperature of the gas turbine.
However, in this case, the turbine inlet air temperature Tt
Even if is changed, the weight flow rate Gc of the compressor is constant,
The weight flow rate Gt of the turbine is also substantially constant (only the fuel flow rate increases) and hardly changes.

On the other hand, therefore, as is clear from the equation representing the turbine corrected flow rate, even if the turbine inlet air temperature Tt changes, the turbine inlet air pressure Pt changes in proportion to the 1/2 power of the turbine inlet temperature. Therefore, the temperature of the air at the turbine outlet, that is, the temperature of the exhaust gas, fluctuates greatly due to the change in the load.

As a result, in a combined cycle system or the like, when a steam generator using exhaust gas is installed, the fuel flow rate is reduced to reduce the load on the gas turbine and the inlet air temperature of the gas turbine is decreased. If this is done, the gas turbine exhaust gas temperature will decrease, and the heat recovery efficiency will decrease due to the decrease in the exhaust gas temperature. Further, when the steam turbine is driven by this steam, the decrease in the steam temperature results in a decrease in the efficiency of the steam turbine cycle.

Further, it is important that the gas turbine has a small heat capacity in a high temperature portion and can cope with a rapid heat change and can easily follow a sudden change in load, but the steam generator and the steam turbine have a large heat capacity, Since it is necessary to suppress the generation of thermal stress due to the change, even if the exhaust gas temperature changes, this change speed limit limits the followability to load changes.

[0008] Therefore, for example, Transactions of the AS
ME), Vol.105, January 1983 (PP72-79), "Gas Turbine Airflow" for Gas Turbine Airflow Control for Optimum Heat Recovery.
Control for Optimum Heat Recovery), an inlet guide vane is installed in the gas turbine compressor, and at the time of partial load, the inlet guide vane is controlled to reduce the compressor flow rate, thereby reducing the gas turbine inlet pressure and reducing the turbine exhaust gas. The prior art is disclosed in which the temperature is prevented from decreasing even under partial load.

[0009]

The above-mentioned prior art has a problem in that the temperature of the exhaust gas of the turbine is not sufficiently taken into consideration due to the load control, and the load control is restricted in a wide range. That is, in the prior art, as shown in the above document, the flow rate control range by the compressor inlet guide vanes is about 80% of the design point load, and the load below this causes the turbine outlet temperature to drop. There is.

An object of the present invention is to provide a gas turbine system capable of keeping the temperature of a gas turbine exhaust gas constant during a partial load operation of a gas turbine, thereby sufficiently responding to a rapid partial load change. Especially.

[0011]

The above-mentioned object is to provide an air supply means, which is independent of the gas turbine and capable of pressure control, on the inlet side of the gas turbine compressor, and the air supply means is operated during rated load operation. To supply high-pressure air to the compressor to reduce the supply air pressure as the load decreases, and at the same time reduce the fuel supply amount to the gas turbine combustor.

[0012]

Operation: Under the rated output, the air pre-pressurized by the separate air supply means is supplied to the gas turbine compressor inlet, and the air pressure by this air supply means is reduced as the load decreases. If it is decreased, the weight flow rate of air passing through the compressor can be changed without changing the corrected flow rate of the compressor.

On the other hand, the turbine also has a characteristic that the corrected flow rate is constant, but it corresponds to a change in the combustor outlet temperature (= turbine inlet temperature) due to a decrease in the combustor fuel supply amount, by changing the turbine inlet pressure. . That is, turbine corrected flow rate (Gt × √Tt) / Pt = constant turbine outlet temperature Te = Tt × (Pe / Pt) ^ α α = ηt × (κ−1) / κ Pe: turbine outlet pressure ηt: turbine polytropic efficiency κ: Specific heat ratio Here, “^ α” represents “α power”.

Therefore, from these relational expressions, Gt × [Te / (Pe / Pt) ^ α] ^ 0.5 / Pt = constant, and even if the turbine outlet temperature Te is assumed to be constant, G
Once t is determined, Pt can be changed to satisfy the turbine characteristics, and the purpose can be achieved.

Here, "^ 0.5" is "0.5".
Power, that is, the square root.

The shift to the partial load according to the present invention is specifically performed as follows.

The pressure of the air supply means is reduced.

Since the gas turbine compressor has a constant rotation speed, the air weight flow rate decreases in proportion to the decrease in the inlet pressure.

When the combustor fuel amount is reduced, the turbine inlet (air) temperature, the turbine inlet pressure, and the turbine outlet temperature are changed so as to satisfy the above formula, and at the same time, the load is reduced.

If the turbine outlet temperature drops when the partial load is transferred, the air flow rate is reduced by lowering the pressure of the air supply means, and if the outlet temperature rises, the fuel amount is reduced. Reach the partial load.

According to the present invention, by thus controlling the pressure of the air supply means and the amount of fuel supplied to the combustor,
Partial load can be achieved while controlling the exhaust gas temperature.

[0022]

The gas turbine system according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. Figure 1
In one embodiment of the present invention, the present invention is applied to a gas turbine / steam turbine combined power generation plant. In the figure, a gas turbine system includes a high pressure air compressor 1, a combustor 2 and a gas turbine. 3, the steam turbine system includes a high-pressure steam turbine 19, a reheat steam turbine 20, a low-pressure turbine 21, a condenser 23, and a feed water pump 2.
4 and the generator 4 is driven by these.

In the figure, 25 is a separately installed low pressure compressor,
The compressed air output of the low-pressure compressor 25 is the intercooler 26.
And an air supply pipe 34 to the air inlet of the high-pressure compressor 1. The low pressure compressor 25 is driven by a low pressure compressor driving electric motor 27.

The output air of the high-pressure air compressor 1 is supplied to the combustor 2, and the high-temperature high-pressure gas output from the combustor 2 is supplied to the gas turbine 3 and converted into rotational energy. Therefore, the fuel supply pipe 35 is connected to the combustor 2, and the fuel is supplied through the fuel control valve 28.

The exhaust gas discharged from the gas turbine 3 is
Gas turbine exhaust duct 2 because the temperature is still quite high
It is supplied to the exhaust heat recovery boiler 5 via 2 and the exhaust heat is recovered. The exhaust heat recovery boiler 5 includes a low pressure economizer 9, a low pressure drum 6, a low pressure evaporator 10, a medium pressure economizer-11, a medium pressure drum 7, a medium pressure evaporator 12, a high pressure economizer 13, a high pressure drum 8, and a high pressure. Evaporator 1
4, a superheater 15, a reheater 16, a medium-pressure pressurizing pump 17, and a high-pressure pressurizing pump 18 are installed.

A main steam pipe 150 is connected to the superheater 15 in the exhaust heat recovery boiler 5, and steam from the superheater 15 is supplied to the high-pressure steam turbine 19. Then, from the outlet of the high-pressure steam turbine 19, the reheater 1 in the exhaust heat recovery boiler 5
The reheat steam return pipe 190 is connected to the No. 6 pipe. The pipe from the medium-pressure drum 7 is also connected to the pipe 190.

A reheat steam pipe 160 reaching the reheat steam turbine 20 is connected from the outlet of the reheater 16, and a pipe line reaching the low pressure turbine 21 is connected from the outlet of the reheat steam turbine 20. . Further, a pipe from the low pressure drum 6 is also connected to the low pressure steam turbine 21. A pipe line reaching the condenser 23 is connected to the outlet of the low-pressure steam turbine 21.

Condensed water in the condenser 23 is supplied to the low pressure economizer 9 in the exhaust heat recovery boiler 5 by the water supply pump 24. The outlet of the low pressure economizer 9 is connected to the low pressure drum 6, and the medium pressure pressurizing pump 17
And a high-pressure pressurizing pump 18. Therefore, the outlet pipe of the intermediate pressure pressurizing pump 17 is connected to the intermediate pressure drum 7 via the intermediate pressure economizer-11, while the high pressure pressurizing pump 1 is connected.
The pipe of the outlet of 8 is connected to the high-pressure drum 8 via the high-pressure economizer 13.

The gas turbine exhaust duct 22 is provided with an exhaust temperature detector 31, and a signal from this is input to the load control device 33. The generator 4 is provided with a load detector 32, and a signal from the load detector 32 is also input to the load control device 33. Further, the low-pressure compressor 25 is provided with a rotation speed detector 36, and a signal from this detector 36 is also supplied to the load control device 33. The signal output from the load control device 33 is supplied to the fuel drive valve control device 29 provided in the fuel control valve 28 and the rotation speed converter 3 provided in the low pressure compressor driving electric motor 27.
Input to 0.

Next, the operation of this embodiment will be described. The low-pressure compressor 25 is driven by a low-pressure compressor driving electric motor 27 and sucks and pressurizes the atmosphere. Since the temperature of the pressurized air rises, it is introduced into the intercooler 26, where it is cooled by cooling water and introduced into the high-pressure compressor 1 through the air supply pipe 34. The installation of the intercooler 26 cools the air that has been compressed by the low-pressure compressor 25 and the temperature of which has risen, so that the compression power in the high-pressure compressor 1 can be reduced and the temperature of the inlet of the high-pressure compressor 1 can be reduced. Is kept constant so that the inlet pressure and the flow rate of the high-pressure compressor 1 are kept in a proportional relationship.

The air supplied to the high-pressure compressor 1 is boosted in pressure and becomes high-pressure air, which is supplied to the combustor 2.
In the combustor 2, the fuel supplied from the fuel control valve 28 through the fuel supply pipe 35 is burnt and becomes high-temperature combustion gas, which is supplied to the gas turbine 3 and is expanded there to generate power. .

The combustion gas discharged from the gas turbine 3 is supplied to the exhaust heat recovery boiler 5 through the gas turbine exhaust duct 22. In the exhaust heat recovery boiler 5, the water supply from the condenser 23 is boosted by the water supply pump 24 and the water supply pipe 2
5 is supplied to the low-pressure economizer 9 and the feed water at the outlet of the low-pressure economizer 9 is sent to the low-pressure drum 6, while the intermediate-pressure pressurizing pump 17 pressurizes the low-pressure economizer.
9 or recirculate it to the medium pressure drum 7 through the medium pressure economizer-11. Further, the feed water at the outlet of the low pressure economizer-9 is pressurized by the high pressure pressurizing pump 18 and sent to the high pressure drum 8 through the high pressure economizer-13.

The high-pressure drum 8 is provided with a high-pressure evaporator 14. The vapor evaporated here is superheated by the superheater 15 and is supplied to the high-pressure steam turbine 19 through the main steam pipe 26. After being converted into power by the high pressure steam turbine 19, the reheater 1 is passed through the reheated steam return pipe 150.
Return to 6. At the inlet of the reheater 16, the vapor evaporated in the medium pressure evaporator 12 provided in the medium pressure drum 7 is mixed. Then, the steam reheated by the reheater 16 is supplied to the reheat steam turbine 20 through the reheat steam pipe 160.

The steam generated by the reheat steam turbine 20 is supplied to the low pressure steam turbine 21. Low pressure drum 6
The vapor evaporated by the low-pressure evaporator 10 provided at is also supplied to the low-pressure steam turbine 21. Then, the steam generated by the low-pressure steam turbine 21 is condensed in the condenser 23. Therefore, the high-pressure compressor 1 and the generator 4 are driven by the power generated in the steam turbines 20 and 21 and the gas turbine 3, and the generator 4 generates electric power.

The load detector 32 installed in the generator 4 detects the load generated in the generator 4 and inputs it to the load controller 33, and the exhaust temperature detector 31 installed in the gas turbine exhaust duct 22 uses the gas turbine exhaust gas. The temperature is detected and input to the load control device 33. Therefore, the load control device 33 calculates the required fuel supply amount and air amount from the deviation between the requested load and the load detected by the load detector 32, and signals the fuel drive valve control device 29 and the rotation speed converter 30 to the signals. The fuel flow rate is changed by the fuel control valve 28 and the rotation speed of the low pressure compressor driving electric motor 27 is changed by the rotation speed converter 30, and the low pressure compressor 25 outlet pressure (= high pressure compressor 1 inlet pressure).
To control.

Next, an example of performance calculation examination when the load is changed while the turbine exhaust gas temperature is kept constant by this embodiment will be shown. When the inlet pressure of the high-pressure compressor 1 is changed by the low-pressure compressor 25 during partial load, the compressor weight flow rate change and the high-pressure compressor inlet and outlet pressure changes are:
As shown in FIG. At this time, if the fuel flow rate is controlled so that the outlet temperature of the combustor 2 becomes as shown in FIG. 6 with respect to the plant load, the outlet temperature of the turbine 3 can be kept constant regardless of the plant load.

In practice, as described above, the low pressure compressor 25
And the outlet pressure of the low-pressure compressor 25 is changed. Then, according to the change of the outlet pressure of the low pressure compressor 25, the characteristics of the high pressure compressor 1 will cause
The weight flow rate of V varies proportionally. Since the turbine exhaust gas temperature changes with the change of the compressor flow rate, the fuel supply amount to the combustor 2 is controlled so as to be constant. In addition, in FIG. 6, for comparison, the partial load characteristics of the conventional combined plant (without control of the inlet guide valve) are also shown.

Therefore, according to this embodiment, since the gas turbine exhaust gas temperature can be kept constant even under partial load of the combined plant, it is possible to sufficiently cope with a rapid load change, and the exhaust gas temperature is lowered. Since it is not present, the heat recovery rate in the steam generator (exhaust heat recovery boiler 5) and the cycle efficiency of the steam turbine can be maintained high even under partial load, and there is an effect that the efficiency under partial load can be made sufficiently high.

FIG. 7 compares the partial load efficiencies of the conventional combined plant and the combined plant according to one embodiment of the present invention with the efficiency of the steam turbine system fixed. It can be seen that

Further, according to this embodiment, the decrease in the combustor outlet temperature at the time of partial load can be made smaller than in the conventional case, and the flow rate of air passing through the combustor can be decreased. Compared with the combined plant, it is possible to reduce changes in the flow velocity and the air-fuel ratio that affect the combustion state of the combustor at partial load, and it is possible to realize a combustor that can perform stable combustion even at partial load.

FIG. 8 shows changes in plant load and combustor inlet flow velocity ratio in comparison between a conventional combined plant and a combined plant according to an embodiment of the present invention. Changes in load and combustor air-fuel ratio are shown by comparing a conventional combined plant and a combined plant according to one embodiment of the present invention, and from these figures, according to the present invention, stable even under partial load. It can be seen that a combustor capable of excellent combustion can be realized.

Further, according to this embodiment, at the time of starting,
Since the compressed air can be supplied to the high pressure compressor 1 by driving the low pressure compressor 25, there is an effect that the starting drive power of the system including the high pressure compressor 1 and the gas turbine 3 can be reduced.

By the way, in the power generation combined plant to which the present invention is applied, it is required to increase the capacity of the single machine in order to reduce the construction cost. However, in order to increase the capacity of the single machine, the air flow rate of the air compressor is increased. Must. On the other hand, it is the length of the first-stage rotor blade that determines the air flow rate of the air compressor, but this length is limited by the tip peripheral speed, and is currently close to the limit. It has become quite difficult to increase.

However, according to this embodiment, the low-pressure compressor 25 is provided in the preceding stage of the high-pressure compressor 1, which increases the pressure of the air introduced into the high-pressure compressor 1 and is proportional to this pressure. Since the flow rate of air passing through the high-pressure compressor 1 can be increased, the single-unit capacity of the combined plant can be further increased even when the first-stage rotor blades of the high-pressure compressor 1 have reached their maximum. .

Next, some of other embodiments of the present invention will be described below. First, FIG. 2 shows a second embodiment of the present invention. The difference between this embodiment and the embodiment shown in FIG. 1 is that the low pressure compressor 25 is driven by a steam turbine instead of being driven by an electric motor. In view of the above, 201 is the steam turbine for driving the low pressure compressor. A low pressure steam bypass pipe 203 having a rotation speed control valve 204 for bypassing steam from the low pressure steam pipe 202 is connected to an inlet of the steam turbine 201. A steam discharge pipe 206 connected to the condenser 23 is provided at the outlet of the steam turbine 201 for driving the low pressure compressor.

Therefore, the steam turbine 201 for driving the low pressure compressor is driven by the steam generated in the exhaust heat recovery boiler 5 and passing through the low pressure steam bypass pipe 203 from the low pressure steam pipe 202 to drive the low pressure compressor 25. To drive. Then, the steam discharged from the steam turbine 201 is returned to the condenser 23 through the steam discharge pipe 206.

A rotation speed control valve 204 installed in the middle of the low-pressure steam bypass pipe 203 is operated by a control signal from the load control device 33, and the rotation speed control valve drive device 205.
Driven by the low pressure compressor 2 depending on the plant load
The rotation speed control of 5 is performed.

According to this embodiment, the low pressure compressor 25 is
Since it is driven by the steam turbine instead of the electric motor, there is an effect that even when the power required to drive the low-pressure compressor 25 increases, the capacity can be easily coped with when the capacity of the plant is increased.

FIG. 3 shows a third embodiment of the present invention. This embodiment is different from the embodiment shown in FIG. 1 in that the low pressure compressor 25 is separately driven instead of being driven by an electric motor. This gas turbine system is composed of a gas turbine compressor 301, a combustor 302, and a gas turbine 303 in that it is driven by the gas turbine system of FIG.

A fuel control valve 304 having a fuel control valve drive device 305 is installed in the fuel pipe of the combustor 302 for driving the low pressure compressor. The fuel control valve drive device 3
A control signal is input to the load control device 33 from the load control device 33. The air whose pressure has been increased by the compressor 301 is introduced into the combustor 302, high temperature and high pressure combustion gas is generated in the combustor 302, and the combustion gas is supplied to the gas turbine 303 to generate motive power. Machine 2
5 is driven. At this time, the fuel control valve 304 is controlled by the fuel control valve drive device 305 which receives the control signal from the load control device 33, and the fuel amount for controlling the rotational speed of the low pressure compressor 25 according to the plant load. To control.

In this embodiment, since the low pressure compressor 25 is driven by the gas turbine, this is the case when the power required to drive the low pressure compressor 25 increases when the capacity of the plant output is increased. However, the peak power is required because the low-pressure compressor 25 is not normally driven and the plant plan is designed to operate the low-pressure compressor 25 when peak power is required. At this time, if the operation of the low-pressure compressor 25 is started, the compressed air is supplied to the high-pressure compressor 1 and the amount of electric power that can be generated by the generator 4 is increased, so that it is possible to easily cope with the peak electric power. effective.

FIG. 4 shows a fourth embodiment of the present invention. This embodiment is different from the embodiment shown in FIG. 1 in that it is replaced by one separately installed low pressure compressor 25. In terms of using a plurality of units, for example, two units, 401 and 402 in FIG.
Are low-pressure compressors. These low pressure compressors 4
01 and 402 are driving electric motors 403 and 404, respectively.
The compressed air from each of them is commonly connected to the input side of the intercooler 26 and supplied to the input of the high pressure compressor 1.

In order to avoid complication, the exhaust temperature detector 31 and the load control device 33 shown in FIG. 1 are omitted in FIG. 4, and the low pressure compressor driving motor 403 is further illustrated. The rotation speed control devices 404 and 404 are also omitted.

According to the embodiment of FIG. 4, since the two low pressure compressors 401 and 402 are used, the low pressure compressor 40 is provided by using them as compressors having different characteristics.
1 and low-pressure compressor 402 are selected, or two low-pressure compressors 401 and 402 are operated at the same time, etc. By selectively using these according to the operating state of the plant, the operation range as a plant can be expanded. There is.

[0055]

According to the present invention, since the exhaust gas temperature of the gas turbine can be kept constant during the partial load operation of the gas turbine, a gas turbine system that can sufficiently cope with a rapid partial load change is easily provided. There is an effect that can be provided to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a gas turbine system according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the gas turbine system according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the gas turbine system according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the gas turbine system according to the present invention.

FIG. 5 is a characteristic diagram of an example of the present invention.

FIG. 6 is a characteristic diagram of an example of the present invention.

FIG. 7 is a characteristic diagram of an example of the present invention.

FIG. 8 is a characteristic diagram of an example of the present invention.

FIG. 9 is a characteristic diagram of an example of the present invention.

[Explanation of symbols]

 1 High Pressure Compressor 2 Combustor 3 Gas Turbine 4 Generator 19 High Pressure Steam Turbine 20 Reheat Steam Turbine 21 Low Pressure Turbine 21 23 Condenser 24 Water Supply Pump 25 Separate Low Pressure Compressor 26 Intercooler 27 Low Pressure Compressor Drive Electric motor 31 Exhaust temperature detector 28 Fuel control valve 29 Fuel drive valve control device 30 Rotation speed converter 33 Load control device

Claims (6)

[Claims] 1. A gas turbine system including at least an air compressor, a combustor, and a turbine, wherein an air supply means for supplying compressed air to an inlet of the compressor is provided, and the gas is supplied by the air supply means. A gaster system configured to control the output of a gas turbine by controlling the pressure of air and the amount of fuel supplied to the combustor. 2. A gas turbine system including at least an air compressor, a combustor, and a gas turbine, and a drive device capable of controlling the rotation speed, and a drive device driven by the drive device to pressurize an inlet of the air compressor. Provided with a separate compressor that supplies air, the load of the gas turbine is controlled by controlling the rotation speed of the drive device, and the exhaust gas temperature of the gas turbine is controlled by controlling the amount of fuel supplied to the combustor. A gaster system characterized by being configured to. 3. The gaster system according to claim 2, wherein the drive device is an electric motor. 4. The gaster system according to claim 2, wherein the drive device is a steam turbine. 5. The gaster system according to claim 2, wherein the drive device is a gas turbine. 6. The gaster system according to claim 2, wherein two or more separate compressors are provided.