JP2657411B2 - Combined cycle power plant and operating method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a combined cycle power plant in which the loads of a gas turbine and a steam turbine are controlled to increase the load drop rate of the power plant as a whole, and a combined power plant therefor. Related to driving method.

[Conventional technology]

In general, a combined cycle power plant has a gas turbine that is rotationally driven by combustion gas, an exhaust heat recovery boiler that generates high-pressure steam from exhaust gas from the gas turbine, and a rotary turbine that is rotationally driven by high-pressure steam from the exhaust heat recovery boiler. And a steam turbine.

In such a combined cycle power plant, it is necessary to control the load on the gas turbine and the steam turbine in accordance with the fluctuation in power consumption. In the conventional combined cycle power plant, only the load on the gas turbine is controlled by adjusting the fuel flow rate, and the load on the steam turbine is not particularly controlled.

There has been proposed a combined cycle power plant in which a pipe that bypasses a steam turbine is provided and a valve is attached in the middle of the pipe (for example, Japanese Patent Application Laid-Open No. Sho 60-125705). However, this pipe is for discharging excess steam at the time of starting / stopping the power plant, relieving the load, and tripping, and is not for controlling the steam turbine.

[Problems to be solved by the invention]

In the conventional technique in which the combustion flow rate is adjusted, it is easy to rapidly reduce the load on the gas turbine, but it is difficult to reduce the load on the steam turbine. This is because the steam turbine uses high-pressure steam generated in the exhaust heat recovery boiler. That is, changes in the generated steam flow rate and temperature are reduced due to the amount of heat stored in the heat transfer tubes, pipes, drums, and the denitration device of the exhaust heat recovery boiler, and the response to the steam turbine is delayed. For this reason, the load drop rate of the steam turbine is reduced, and the load drop rate of the combined power plant as a whole is at most about 5%. Further, it is impossible to increase the load drop rate further by the conventional technology.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combined power plant capable of preventing a response delay of a load drop of a steam turbine with respect to a load drop of a gas turbine when a load is dropped, and increasing a load drop rate of the whole power plant and its operation. Is to provide a way.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a gas turbine that is rotationally driven by a combustion gas, an exhaust heat recovery boiler that generates high-pressure steam by heat of exhaust gas from the gas turbine, and a rotary turbine that is rotationally driven by the high-pressure steam. In a single-pressure combined power plant comprising a steam turbine, and a generator connected to the rotating shaft of the gas turbine and the steam turbine, the output of the generator is less than the required output in response to a load drop request signal. Fuel amount control means for suppressing the amount of fuel to the gas turbine when the amount is large, and high-pressure steam from the exhaust heat recovery boiler on condition that the amount of fuel to the gas turbine is suppressed by the fuel amount control means. A bypass means for releasing all or a part of the steam to the downstream side of the steam turbine.

The present invention also provides a gas turbine that is driven to rotate by combustion gas, an exhaust heat recovery boiler that generates high-pressure steam and low-pressure steam by heat of exhaust gas from the gas turbine, and a high-pressure steam that is driven to rotate by the high-pressure steam. A turbine,
In a mixed-pressure combined power plant including a low-pressure steam turbine rotationally driven by the low-pressure steam, and a generator connected to the rotation shafts of the gas turbine, the high-pressure steam turbine, and the low-pressure steam turbine, a load drop request signal Fuel amount control means for suppressing the amount of fuel to the gas turbine when the output of the generator is greater than the required output in response to the fuel cell; and the fuel amount to the gas turbine is suppressed by the fuel amount control means. And bypass means for releasing all or a part of the high-pressure steam and the low-pressure steam from the exhaust heat recovery boiler to the downstream side of the high-pressure steam turbine and the low-pressure steam turbine.

Further, the present invention provides a gas turbine that is driven to rotate by combustion gas, and a waste heat that generates high-pressure steam by heat of exhaust gas from the gas turbine and generates reheat steam by a reheater provided inside. A recovery boiler, a high-pressure steam turbine rotationally driven by the high-pressure steam, a reheat steam turbine rotationally driven by the reheat steam, and a rotating shaft of the gas turbine, the high-pressure steam turbine, and the reheat steam turbine. Amount control for suppressing a fuel amount to the gas turbine when an output of the generator is larger than a required output in response to a load drop request signal in a reheat-type combined power plant comprising: Means and all or high pressure steam from the exhaust heat recovery boiler on condition that the fuel amount to the gas turbine is suppressed by the fuel amount control means. With escape part to the downstream side of the high pressure steam turbine, in which is provided a bypass means for releasing a portion of the reheated steam to the downstream side of the reheat steam turbine.

The present invention also provides a gas turbine that is driven to rotate by combustion gas, an exhaust heat recovery boiler that generates high-pressure steam by heat of exhaust gas from the gas turbine, a steam turbine that is driven to rotate by the high-pressure steam, In a multi-shaft combined power plant including a generator connected to a rotating shaft of a gas turbine and a generator connected to a rotating shaft of the steam turbine, the generator is configured to respond to a load drop request signal. A fuel amount control means for suppressing the fuel amount to the gas turbine when the output of the exhaust gas is larger than the required output; and the exhaust heat recovery on condition that the fuel amount to the gas turbine is suppressed by the fuel amount control means. A bypass means for releasing all or a part of the high-pressure steam from the boiler to the downstream side of the steam turbine.

Further, the present invention drives the gas turbine by the combustion gas, introduces exhaust gas discharged from the gas turbine into an exhaust heat recovery boiler to generate high-pressure steam, and rotates and drives the steam turbine by the high-pressure steam. When lowering the load in the operation method of the combined power plant that drives the generator by the rotating force of the gas turbine and the steam turbine, when the output of the generator is larger than the required output, the fuel amount to the gas turbine is reduced. While suppressing the amount of fuel to the gas turbine, all or a part of the high-pressure steam from the exhaust heat recovery boiler is directly released to the downstream side of the steam turbine on condition that the fuel amount to the gas turbine is suppressed, thereby reducing the load on the steam turbine. This is to make it descend immediately.

[Action]

According to the above configuration, in the case of a single-pressure combined cycle power plant, the amount of high-pressure steam flowing into the steam turbine is reduced by releasing all or a part of the high-pressure steam to the downstream side of the steam turbine when the load drops. The load on the turbine can be reduced rapidly. At this time, the load on the gas turbine is rapidly reduced by reducing the fuel flow rate. The same applies to the case of a multi-shaft combined cycle power plant.

In the case of a mixed-pressure combined cycle power plant, when the load drops, all or part of the high-pressure steam and the low-pressure steam is released to the high-pressure steam turbine and the downstream side of the low-pressure steam turbine, thereby reducing the load on the high-pressure steam turbine and the low-pressure steam turbine. Can be rapidly reduced.

Furthermore, in the case of a reheat-type combined cycle power plant, when the load drops, all or a part of the high-pressure steam is released to the downstream side of the high-pressure steam turbine, thereby rapidly reducing the load on the high-pressure steam turbine and reducing the reheated steam. Relieving all or part of the reheat steam turbine downstream allows the load on the reheat steam turbine to be rapidly reduced.

〔Example〕

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

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. This is a schematic system diagram of a single-pressure combined cycle power plant. As shown in the figure, the air 5 compressed by the gas turbine compressor 4 is sent to a combustor 6 where it is mixed with fuel 7 and burned.
It becomes high temperature and high pressure combustion gas. This combustion gas is introduced into the gas turbine 1 and expands to drive the gas turbine 1 to rotate. The gas turbine exhaust gas 10 that rotationally drives the gas turbine 1 is sent to the exhaust heat recovery boiler 2 disposed downstream thereof, where heat exchange with the feedwater 12 is performed. Then, the thermal energy (sensible heat) held in the gas turbine exhaust gas 10 is recovered, and is released as low-temperature gas 11 to the atmosphere.

Further, feed water 12 supplied to the exhaust heat recovery boiler 2 becomes high-temperature and high-pressure steam 13 in the gas turbine exhaust gas 10, is sent to the steam turbine 3, and drives the steam turbine 3 to rotate.
After that, the steam 13 becomes low-temperature, low-pressure steam 14 and the condenser 15
Is exchanged with seawater 16 and condensed to form condensate, which is stored in the condenser 15. Further, the condensed water is boosted in pressure by a water supply pump 17 provided at an outlet of the condenser 15, and is condensed by the exhaust heat recovery boiler 2.
Supplied to

Further, the gas turbine 1 and the steam turbine 3 that are rotationally driven drive the generator 9 to obtain an electric output.

In such a single-pressure combined cycle power plant, when it is necessary to rapidly reduce the load, the flow rate of the fuel 7 is suppressed by narrowing the fuel flow control valve 18, and the flow rate / temperature of the combustion gas 8 decreases. As a result, the driving force of the gas turbine 1 decreases. Further, by reducing the flow rate and temperature of the gas turbine exhaust gas 10 from the gas turbine 1, the sensible heat given to the exhaust heat recovery boiler 2 decreases, and the generated steam amount, temperature,
As the pressure decreases, the driving force of the steam turbine 3 also decreases.
However, there is a response delay in the drive reduction of the steam turbine 3. Therefore, in the present embodiment, when the load drops, the turbine bypass valve 19 is opened, so that all or a part of the steam 13 flowing into the steam turbine 3 is directly bypassed to the condenser 15, and the driving force of the steam turbine 3 is reduced. Let it. as a result,
The load on the steam turbine 3 can be rapidly reduced,
The load drop rate of the combined power plant as a whole can be increased more than before.

Second Embodiment FIG. 2 shows a second embodiment of the present invention. This is a schematic system diagram of a mixed-pressure combined cycle power plant. Only differences from FIG. 1 will be described.

A part of the feed water 12 supplied to the exhaust heat recovery boiler 2 is pressurized to a high pressure by a transfer pump 21 provided in the exhaust heat recovery boiler 2, sent as high-pressure steam 22 to a high-pressure steam turbine 24,
The high-pressure steam turbine 24 is rotationally driven. Meanwhile, transfer pump
The feedwater that does not pass through 21, ie, the feedwater that is not pressurized, is sent to the low-pressure steam turbine 25 as low-pressure steam 23, and drives the low-pressure steam turbine 25 to rotate. And high-pressure steam turbine
High-pressure steam 22 and low-pressure steam turbine 25 that rotationally drive 24
The low-pressure steam 23 rotationally driven is turned into low-temperature, low-pressure steam 14 and sent to the condenser 15.

In such a mixed-pressure combined cycle power plant, when it is necessary to rapidly reduce the load, the load on the gas turbine is reduced by narrowing the fuel flow control valve 18 as in the first embodiment. Further, by opening the high-pressure turbine bypass valve 26 and bypassing all or a part of the high-pressure steam 22 to the condenser 15, the load on the high-pressure steam turbine 24 decreases. At the same time, by opening the low-pressure turbine bypass valve 27 and bypassing the low-pressure steam 23 to the condenser 15, the load on the low-pressure steam turbine 25 decreases. In this way, it is possible to increase the load drop rate of the entire combined cycle power plant.

Third Embodiment FIG. 3 shows a third embodiment of the present invention. This is a schematic system diagram of a reheat type combined cycle power plant. Here, only the features of the present embodiment will be described.

The high-pressure steam 28 from the exhaust heat recovery boiler 2 drives the high-pressure steam turbine 29 to rotate, and then becomes low-pressure, low-temperature steam 30, which is heated by the reheater 31 in the exhaust heat recovery boiler 2, It becomes steam (reheated steam) 32. The reheat steam 32 flows into the reheat turbine 33 and drives the reheat turbine 33 to rotate.

In such a reheat-type combined cycle power plant, when it is necessary to rapidly reduce the load, the load on the gas turbine is reduced by narrowing the fuel flow control valve 18 as in the two embodiments described above. Descend. The high-pressure turbine bypass valve 34 is opened, and the high-pressure steam 28 is
, The load on the high-pressure steam turbine 29 is reduced. In this case, in order to prevent the reheat steam temperature at the outlet of the reheater 31 from excessively rising, a desuperheater 35 is provided on the downstream side of the high-pressure turbine bypass valve 34. 12 is injected via the control valve 36.
Further, by opening the reheat turbine bypass valve 37 and bypassing the reheat steam 32 to the condenser 15, the load on the reheat turbine bypass 33 is reduced. In this way, it is possible to increase the load drop rate of the entire combined cycle power plant.

In the above three embodiments, the gas turbine device, the exhaust heat recovery boiler device, and the steam turbine device are each configured by one unit. However, the gas turbine device, the exhaust heat recovery boiler device, and the steam turbine device are configured by a plurality of units. The present invention can also be applied to a multi-shaft combined power plant configured with a stand. That is, by directly bypassing excess steam generated from the exhaust heat recovery boiler to the downstream side of the steam turbine device, it is possible to reduce the load on the steam turbine device and increase the load drop rate of the combined power plant as a whole. It is possible.

FIG. 4 shows an example of a load control device for the gas turbine / steam turbine when the load of the combined cycle power plant drops.

At the time of load drop, the deviation between the load drop request signal 41 and the load output signal 45 of the generator 9 is read by the control device 40. If the output during operation is larger than the required output, the control device 40 controls the fuel flow control valve 18 to operate. It issues a fuel flow reduction command 42 to be throttled. At that time, if the fuel flow rate control valve 18 of the gas turbine reaches the preset minimum allowable opening based on the opening signal 44 from the opening detector 39, the control device 40 further controls the turbine bypass so as to open the turbine bypass valve 19. The opening command 43 of the valve opening is issued. Thereby, the opening degree of the turbine bypass valve 19 is controlled such that the excess steam from the exhaust heat recovery boiler 2 is bypassed and the load output from the generator 9 matches the required output.

〔The invention's effect〕

As described above, according to the present invention, when a load drop is requested, the amount of fuel to the gas turbine is suppressed, and the steam to the steam turbine is bypassed to the downstream side of the steam turbine. The output of the machine can be quickly lowered to the required output.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a single-pressure combined power plant, and FIG.
The figure is a schematic diagram of a mixed-pressure combined power plant, FIG. 3 is a schematic diagram of a reheat combined power plant, and FIG.
FIG. 2 is a schematic system diagram in a case where a load control device is provided in the single-pressure combined power generation plant of FIG. DESCRIPTION OF SYMBOLS 1 ... Gas turbine, 2 ... Exhaust heat recovery boiler, 3 ... Steam turbine, 4 ... Gas turbine compressor, 6 ... Combustor, 9 ... Generator, 13 ... High temperature and high pressure steam, 15 ... Condenser, 17 ... Water supply pump, 18 ... Fuel flow control valve, 19 ...
Turbine bypass valve, 22 high pressure steam, 23 low pressure steam, 24 high pressure steam turbine, 25 low pressure steam turbine, 26 high pressure turbine bypass valve, 27 low pressure turbine bypass valve, 28 high pressure Steam, 29 High pressure steam turbine, 31 Reheater, 32 Reheat steam, 33 Reheat turbine, 34 High pressure turbine bypass valve, 37 Reheat turbine bypass valve, 40 Control device.

Claims (6)

(57) [Claims] A gas turbine rotatably driven by a combustion gas; an exhaust heat recovery boiler for generating high-pressure steam by heat of exhaust gas from the gas turbine; a steam turbine rotatably driven by the high-pressure steam; A single-pressure combined power plant comprising a turbine and a generator connected to a rotating shaft of a steam turbine, wherein the output of the generator is greater than the required output in response to a load drop request signal, Fuel amount control means for suppressing the fuel amount of the fuel gas, and all or part of the high-pressure steam from the exhaust heat recovery boiler provided that the fuel amount to the gas turbine is suppressed by the fuel amount control means. A combined cycle power plant comprising a bypass means for escaping to a downstream side of a turbine. 2. The combined cycle power plant according to claim 1, wherein said bypass means includes a pipe connecting a condenser provided downstream of said steam turbine and said waste heat recovery boiler, and a pipe of said pipe. A combined cycle power plant, comprising: a turbine bypass valve disposed in the middle of a road; and control means for opening the turbine bypass valve in response to a load request signal. 3. A gas turbine rotatably driven by combustion gas, an exhaust heat recovery boiler for generating high pressure steam and low pressure steam by heat of exhaust gas from the gas turbine, and a high pressure steam turbine rotatably driven by the high pressure steam And a low pressure steam turbine rotatably driven by the low pressure steam; and a generator connected to the rotating shafts of the gas turbine, the high pressure steam turbine, and the low pressure steam turbine. Fuel amount control means for suppressing the fuel amount to the gas turbine when the output of the generator is larger than the required output in response to the request signal; and the fuel amount to the gas turbine is suppressed by the fuel amount control means. All or a part of the high-pressure steam and the low-pressure steam from the exhaust heat recovery boiler Combined cycle power plant, characterized by comprising a bypass means for releasing to the downstream side of the turbine. 4. A gas turbine rotationally driven by combustion gas, and exhaust heat recovery for generating high-pressure steam by heat of exhaust gas from the gas turbine and generating reheat steam by a reheater provided in the gas turbine. A boiler, a high-pressure steam turbine rotationally driven by the high-pressure steam, a reheat steam turbine rotationally driven by the reheat steam, and a rotating shaft of the gas turbine, the high-pressure steam turbine, and the reheat steam turbine. A regenerative combined power plant comprising: a fuel amount control means for suppressing a fuel amount to the gas turbine when an output of the generator is larger than a required output in response to a load drop request signal And removing all or part of the high-pressure steam from the exhaust heat recovery boiler on condition that the fuel amount to the gas turbine is suppressed by the fuel amount control means. With escape to the downstream side of the high pressure steam turbine, combined cycle power plant, characterized by comprising a bypass means for releasing a portion of the reheated steam to the downstream side of the reheat steam turbine. 5. A gas turbine rotatably driven by a combustion gas, an exhaust heat recovery boiler for generating high-pressure steam from heat of exhaust gas from the gas turbine, a steam turbine rotatably driven by the high-pressure steam, and the gas turbine. In a multi-shaft combined power plant including a generator connected to a rotating shaft of a turbine and a generator connected to a rotating shaft of the steam turbine, in a multi-shaft combined power plant, the generator Fuel amount control means for suppressing the amount of fuel to the gas turbine when the output is greater than the request signal; and the exhaust heat recovery boiler on condition that the amount of fuel to the gas turbine is suppressed by the fuel amount control means. And a bypass means for releasing all or a part of the high-pressure steam from the steam turbine to a downstream side of the steam turbine. 6. A gas turbine is rotationally driven by the combustion gas, exhaust gas discharged from the gas turbine is introduced into an exhaust heat recovery boiler to generate high-pressure steam, and the high-pressure steam drives and rotates the steam turbine. In the method of operating a combined power plant that drives a generator by the rotational force of the gas turbine and the steam turbine, when lowering a load, a fuel amount to the gas turbine is reduced when an output of the generator is larger than a required output. Control and
On condition that the amount of fuel to the gas turbine is suppressed, all or part of the high-pressure steam from the exhaust heat recovery boiler is directly released to the downstream side of the steam turbine, and the load on the steam turbine is quickly reduced. A method for operating a combined cycle power plant, comprising: