JPH02140405A - Operating method for steam-gas complex cycle power generating plant and power generating plant thereof - Google Patents

Abstract

PURPOSE:To prevent a low pressure turbine and a reheater from being overheated by starting a plant with a steam turbine which is driven by starting steam fed from a steam feed device for starting. CONSTITUTION:In a plant starting process, steam is introduced from a steam feed device 44 for starting to a low temperature reheat pipe 19, and a low pressure turbine 24 is driven by the steam so as to start a gas turbine 4 thereby. Therefore, when a power train system is in rotation, steam flows always to a reheater 7 and the low pressure turbine 24 passing through the low temperature reheater pipe 19, and the heating pipe of the reheater 7 is not heated to be damaged by exhaust gas of the gas turbine 4, and the low pressure turbine 24 is not set to a high temperature by a windage loss. On the other hand, in the case that the reheater 7 is not well heated, the low pressure turbine 24 is not driven by low temperature steam since the steam is fed switchingly to the low pressure turbine 24 after being passed through a high temperature reheat pipe 20.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention provides a method for operating a steam-gas combined cycle power plant that combines a heat recovery boiler with a reheater and a steam turbine; Regarding the device.

(Conventional technology) The number of steam-gas combined cycle power generation plants has been increasing in recent years as a promising high-efficiency power generation technology. Countermeasures such as reheating the cycle are being considered.

That is, FIG. 3 is a system diagram showing a typical example of the above steam-gas combined cycle power generation plant, in which air pressurized by the air compressor 1 is combusted together with fuel supplied via the fuel control valve 2. The gas is supplied to the vessel 3, where it is combusted and becomes high-temperature, high-pressure combustion gas.

This combustion gas is introduced into the gas turbine 4, where it is expanded to perform work, and is sent to the exhaust heat recovery boiler 5 as exhaust gas.

This exhaust gas has a sufficiently high temperature, and includes a superheater 6, a reheater 7, a high-pressure steam generator 8, a high-pressure economizer 9, and an intermediate-pressure steam generator 10, which are installed in the exhaust heat recovery boiler 5, respectively.
The medium-pressure economizer 11, low-pressure steam generator 12, and low-pressure economizer 13 are exhausted while being heated, forming a gas cycle.

On the other hand, the steam generated in the high-pressure steam generator 8 passes through the main steam pipe 14 via the superheater 6, and is sent to the high-pressure turbine 17 via the main steam stop valve 15 and the main steam control valve 16, where it is expanded. The exhaust gas is sent to the 14-heater 7 through the check valve 18 and the low-temperature reheat pipe 19. The exhaust gas from the high-pressure turbine 17 is heated in the 11f heater 7, becomes high-temperature reheat steam, passes through the high-temperature reheat pipe 20, passes through the reheat steam stop valve 2] and the reheat steam control valve 22, and then passes through the medium-pressure The water is guided to the turbine 23, expands and performs work in the intermediate pressure turbine 23 and the low pressure turbine 24, and then exchanges heat with the cooling water sent by the circulating water pump 26 in the condenser 25 to become condensed water.

The condensate that has become condensed water in the condenser 25 is transferred to the condensate pump 27
The steam is sent to the low-pressure economizer 13 of the waste heat recovery boiler 5, heated there, and then returned to the low-pressure steam generator 12. The low-pressure steam generated by the low-pressure steam generator 12 passes through the low-pressure steam pipe 28 and is sent to the low-pressure turbine 24 together with the exhaust from the intermediate-pressure turbine 23 via the low-pressure steam stop valve 29 and the low-pressure steam control valve 30.

By the way, the canned water remaining in the low pressure steam generator 12 is
The pressure is increased by the boost pump 31, and part of the canned water in the middle of the boost pump 31 is heated by the medium pressure economizer 11 and then sent to the medium pressure steam generator 10, and the rest is heated by the high pressure economizer 9 and then sent to the high pressure steam generator. Sent to 8. Medium pressure steam generator 1
The intermediate pressure steam generated at 0 is sent to the low temperature reheat pipe 19 through the intermediate pressure steam pipe 32, the check valve 33, and mixed with the high pressure turbine exhaust gas.

Note that the main steam pipe 14 includes a turbine bypass valve 34.
A turbine bypass pipe 35 that branches to the condenser 25 via
The low-temperature reheat pipe 19 is branched, and in the middle of the low-temperature reheat pipe 19, a line that can extract air is connected via an air extraction valve 36 for use as other units or plant auxiliary steam. Further, the main steam pipe 14 is provided with a drain valve 37, the intermediate pressure steam pipe 32 is provided with a drain valve 38, the low pressure steam pipe 28 is provided with a drain valve 39, and the high pressure reheat pipe 20 is provided with a drain valve 40, respectively. In this way, one cycle for the water-steam system is constructed.

On the other hand, a gas turbine 4, an air compressor 1, a high pressure turbine 1
7. The intermediate pressure turbine 23 and the low pressure turbine 24 constitute a power train system with one shaft, and a generator 41 and a starting motor 42 are connected to the shaft.

By the way, when starting up a steam-gas combined cycle power plant with the above configuration, there is a possibility that fuel may leak during shutdown and flow into the gas turbine body, or that unburned fuel that leaks out due to a gas turbine failure remains. If ignition occurs under such conditions, there is a risk of explosion or fire, and to prevent this, it is necessary to replace the gas turbine system with safe air before starting a gas turbine.

Therefore, at the time of plant startup, the power train system is rotated up by the startup generator 42 and the rotation speed is maintained at approximately 30%, so that the air from the air compressor 1 is used to air the inside of the combustor 3 and gas turbine 4. Replace.

This air replacement operation is called purge operation. After the purge operation is completed, the combustor 3 is ignited, the gas turbine 4 is ignited, and the power train system is again sped up by the starting motor 42 to maintain approximately 50% rotational speed.

By maintaining the above rotational speed, the heat recovery boiler 5 is heated by the gas turbine exhaust gas, and the high pressure steam generator 8
, intermediate pressure steam generator 10, and low pressure steam generator 12, but each of these steams is at high pressure, intermediate pressure, and low pressure until the pressure conditions can be reached for the steam turbine. While draining the drain generated in each steam pipe 14, 32.28 from each drain valve 37, 38.39, each steam pipe is warmed.

After that, when the steam of the low-pressure steam generation S12 rises to a predetermined pressure, the drain valve 39 is closed and the steam is guided to the low-pressure turbine 24 via the low-pressure steam control valve 30 for cooling the low-pressure turbine 24. Similarly, when the steam in the intermediate pressure steam generator 10 rises to a predetermined pressure, the drain valve 38 is closed.
It is guided to the low-temperature reheat pipe 19 via the check valve 33 for cooling the reheater 7 . At this time, the check valve 18 on the high-pressure turbine exhaust side is fully closed, and the reheat steam stop valve 21 and the reheat steam control valve 22 are fully open, so normally the intermediate pressure steam generator 10
A separate pressure regulator (not shown) is provided to control the steam pressure to a predetermined pressure. On the other hand, when the steam from the high-pressure steam generator 8 rises to a predetermined pressure, the drain valve 37 is closed, and the steam from the high-pressure steam generator 8 is guided to the condenser 25 via the turbine bypass valve 34. .

Therefore, during this time, the power train system is increased in speed while increasing the amount of fuel supplied to the gas turbine 4, and when the speed reaches approximately 70%, the gas turbine 4 is operated by the combustion gas combusted with the air sent from the air compressor 1. Since the rotational speed of the power train system can be maintained by this, the starting motor 42 is stopped. Subsequently, the amount of fuel is increased to increase the speed of the power train system by the gas turbine 4, and at the rated speed, the generator 41 is added to take the initial load. Furthermore, the load increase by the gas turbine 4 continues,
When the steam from the high-pressure steam generator 8 reaches a temperature suitable for the rotor temperature of the high-pressure turbine 17, the turbine bypass valve 34 is closed and the steam is guided to the high-pressure turbine 7 via the steam control valve 16. After that, the load on the plant is increased while increasing the load on the gas turbine 4 and the high-pressure turbine 17.

(Problem to be solved by the invention 17) However, in such a start-up, a long period of time is required from the time when the power train system first increases in rotation until the steam from the low-pressure steam generator 12 is introduced into the low-pressure turbine 24. Wings H
The low-pressure turbine 24 becomes idle and becomes high temperature due to the frictional energy caused by the rotation, and the low-pressure turbine 24
There are problems such as placing the parts used in the process in unfavorable conditions. In addition, after the gas turbine ignites, until the steam from the single-pressure steam generator 10 is guided to the low-temperature reheating pipe 19, it continues to be heated by the exhaust gas of the gas turbine 4 without steam flowing into the +1 heater 7. As a result, it is expected that the heating tube of the reheater 7 will burn out.

Further, during operation of the steam-gas IM combined cycle power plant as described above, the pressure in the low temperature reheat pipe 19 changes approximately in proportion to the artificial steam flow rate of the intermediate pressure turbine 23. Therefore, when extracting air through the extraction valve 36 for use in other units or plant auxiliary steam, the pressure inside the low-temperature reheating pipe will be lower than the pressure during normal operation. in this case,
There is no problem if the amount of extracted air is small compared to the artificial steam flow rate of the intermediate pressure turbine, but if the amount is large, such as exceeding approximately 20%, the pressure drop in the low temperature reheating pipe becomes large.

In such a state, the high pressure of the exhaust heat recovery boiler 5,
The heat absorption balance in each medium-pressure and low-pressure steam generator differs greatly from the planned conditions, and the amount of steam generated deviates significantly from the planned value, which not only contributes to performance deterioration, but also causes excessive pressure on the final stage blades of the high-pressure turbine. There are problems such as the generation of stress.

In view of these points, the present invention aims to provide a method and apparatus for operating a steam-gas combined cycle power plant that prevents overheating of a low-pressure turbine and a reheater at the time of plant start-up. Another object of the present invention is to reduce the performance deterioration as much as possible when extracting air from a low-temperature reheating pipe during plant operation, and to avoid generating excessive stress on the final stage blades of a high-pressure turbine. An object of the present invention is to obtain a method for operating a combined cycle power plant and an apparatus therefor.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a gas turbine, an air compressor, a steam turbine including a high-pressure side turbine and a low-pressure side turbine operated by steam generated by exhaust heat from the gas turbine, and a power generator. Each arranged on the same axis,
In a method of operating a steam-gas combined cycle power plant that operates a power train system, steam from a steam supply device for starting the plant is guided to a low-pressure turbine through a reheater to increase the speed of the power train system, and then the speed is increased. Replaces the air in the gas turbine equipment with air from the air compressor (
-1 After that, the gas turbine is rejuvenated, and the power train system is subsequently increased in speed with steam from the plant startup steam supply device, and after the gas turbine reaches a rotational speed at which it can become self-sustaining, Steam is secured for cooling the reheater and low-pressure turbine, and the reheat steam control valve controls the inlet steam pressure of the low-pressure turbine, while the fuel control valve controls the speed-up of the power train system. It is characterized by doing the following.

In addition, the reheater is not sufficiently warmed during cold startup, and when the startup steam is passed through the reheater, the steam is cooled too much, which is rather unfavorable for the startup condition of the low-pressure side turbine inlet. Therefore, in such a case, starting steam is introduced to a high temperature reheating pipe on the downstream side of the reheater to enable starting.

Furthermore, after the steam from the heat recovery boiler is introduced into the high-pressure turbine, the low-pressure turbine inlet pressure is controlled by the reheat steam control valve via the generator load. It's okay.

Furthermore, the device according to the present invention includes a gas turbine, an air compressor, a steam turbine consisting of a high-pressure side turbine and a low-pressure side turbine operated by steam generated by exhaust heat from the gas turbine, and a generator on the same axis. A steam-gas combined cycle power generation plant having a power train system arranged and configured, characterized in that a starting steam supply device is connected to a low temperature +Ii heat pipe on the exhaust side of a high pressure side turbine.

(Function) In the plant startup process, steam is introduced from the startup steam supply device into the low-temperature reheat pipe, and the steam drives the low-pressure side turbine, thereby starting the gas turbine. Therefore, while the powertrain system is rotating, steam always flows to the reheater and low-pressure turbine through the low-temperature reheat pipe, and the reheater's heating pipe is never heated to the point where it is damaged by the gas turbine exhaust gas. The low-pressure turbine does not become hot due to wind damage. Furthermore, if the reheater is not sufficiently warmed up, the steam is switched and fed to the low pressure turbine through the high temperature reheat pipe, so the low pressure turbine is not operated with low temperature steam.

Further, after the steam from the exhaust heat recovery boiler is introduced into the high pressure side turbine, the low pressure side turbine inlet pressure is controlled by the reheat steam control valve via the load of the generator. Therefore, even if air is extracted to other units or plant auxiliary steam during plant operation, the pressure inside the low-temperature reheat pipe will not drop below the pressure that changes depending on the generator load during normal operation. Therefore, the heat absorption balance in the intermediate pressure steam generator changes stably according to the load of the generator, the amount of intermediate pressure generated steam can be obtained almost as planned, and the steam applied to the final stage blades of the high pressure turbine The load or stress will not exceed the planned value, and the performance during plant operation and the stress applied to the final stage blade of the high-pressure turbine will be maintained approximately as planned.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the same parts in FIG. 1 as in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, starting steam (!
(A supply device 44 is connected. The startup steam supply device 44 is also connected to the high temperature reheat pipe 20 on the downstream side of the reheater 7 via a valve 45.

Therefore, when starting up the plant, first the check valve 18
．． 33 and reheat steam control valve 22 are fully closed, valve 4
3 is opened and starting steam is introduced from the starting steam supply device 44 into the low-temperature IL heat tube 19. Then, the reheat line consisting of the low temperature reheat pipe 19, the reheater 7, and the high temperature reheat pipe 20 is gradually warmed by this steam, and the drain generated during this time is discharged from the drain valve 40. In addition, when starting the starting steam without passing it through the reheater 7, the valve 45 is opened with the valve 43 closed, and the starting steam from the starting steam supply device is introduced into the high-temperature reheating pipe 20. .

When condensate is no longer generated and the steam pressure in the reheat line reaches a predetermined pressure, the reheat steam control valve 22 is slightly opened to guide the steam to the intermediate pressure turbine, and then the reheat steam control valve 22
The rotational speed of the powertrain system is controlled to be constant.

Therefore, the rotational speed of the power train system is maintained at 30% rotational speed and purge operation of the gas turbine equipment is performed, and after the completion of this purge operation, the rotational speed of the power drain system is lowered to approximately 16%. Summon a gas turbine. Thereafter, the speed of the power train system is increased again by the steam from the startup steam supply device 44, and the rotation speed is maintained at approximately 50%.

During this time, the reheater 7, the low pressure turbine 24, etc. are maintained cooled by the steam supplied from the startup steam supply device 44, and the exhaust heat recovery boiler 5 is warmed by the gas turbine exhaust gas. Then, a high pressure steam generator 8, an intermediate pressure steam generator 10. The drain generated in each of the high pressure steam pipe 14, intermediate pressure steam pipe 32, and low pressure steam pipe 28 is removed from each drain until the steam generated in the low pressure steam generator 12 reaches a pressure condition that can be used by the steam turbine. Valve 3
7, 38. Perform warm pipe operation for each steam pipe while discharging from 39.

Thereafter, when the steam in the low-pressure steam generator 12 rises to a predetermined pressure, the three drain valves are closed, and the steam is led to the low-pressure turbine 24 via the low-pressure steam control valve 30 for heat recovery. Similarly, when the steam in the intermediate pressure steam generator 10 rises to a predetermined pressure, the drain valve 38 is closed, and the steam from the intermediate pressure steam generator 10 is guided to the low temperature reheat pipe 19 via the check valve 33. Heat is recovered. Furthermore, when the steam in the high-pressure steam generator 8 rises to a predetermined pressure, the drain valve 3
7 is closed and the condenser 2 is connected via the turbine bypass valve 34.
5.

Meanwhile, during this period, the power train system is increased in speed while increasing the total fuel supply to the gas turbine 4, and when the speed reaches approximately 70%, the combustion gas combusted by the air sent from the air compressor 1 is transferred to the gas turbine 4. After this, the steam from the startup steam supply device 44 is used to keep the inlet pressure of the intermediate pressure turbine constant by the reheat steam control valve 22. controlled by. Therefore, the fuel is subsequently increased by the fuel control valve 2, the power train system is increased in speed by the gas turbine 4, and then, at the rated speed, the generator 4 is connected to take the initial load.

Furthermore, when the load increase by the gas turbine 4 continues and the steam from the high-pressure steam generator 8 reaches a temperature suitable for the rotor temperature of the high-pressure turbine 17, the main steam + l valve 15
is fully opened and the steam is guided to the high pressure turbine 17 via the main steam control valve 16. At the same time, turbine bypass valve 34 is closed.

After this, the load of the plant is increased while increasing the load of the gas turbine 4 and the high pressure turbine 17, and the artificial pressure of the intermediate pressure turbine is controlled by the reheat steam control valve 22 via the negative 6:I of the generator. I'll do what I do.

Figure 2 is a diagram showing an example of the relationship between the intermediate pressure turbine population pressure and the generator load. Since the valve 22 is speed controlled, the intermediate pressure turbine population pressure is determined by this control. Thereafter, the reheat steam control valve 22 is used for constant pressure control of the intermediate pressure turbine population pressure. Then, when steam from the high-pressure steam generator is introduced into the high-pressure turbine, the population pressure of the intermediate-pressure turbine increases as the load on the generator increases.

〔Effect of the invention〕

As explained above, in the present invention, the plant is started by the steam turbine using the starting steam supplied from the starting steam supply device, so that cooling steam is always ensured in the reheater and the low-pressure turbine. is possible,
It is possible to prevent damage to the heating tube of the reheater or problems caused by abnormally high temperatures of the low pressure turbine. Also,
If the inlet pressure of the low-pressure turbine is controlled according to the load of the generator, the performance during plant operation and the stress applied to the final stage blades of the high-pressure turbine can be maintained almost as planned, while other units or Air can be extracted to blunt auxiliary steam, etc.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of the steam-gas combined cycle power plant of the present invention, Fig. 2 is an explanatory diagram showing the relationship between the intermediate pressure turbine population pressure and the generator load in the method of the present invention, and Fig. 3 is a diagram of the conventional steam-gas combined cycle power generation plant. FIG. 1 is a system diagram of a gas combined cycle power generation plant. 1... Air compressor, 3... Combustor, 4... Gas turbine, 5... υ heat recovery boiler, 7... Reheater,
8... High pressure steam generator, 10... Medium pressure steam generator,
12...Low pressure steam generator, 16...Main steam control valve,
17... High pressure turbine, 19... Low temperature reheat pipe, 22
... Reheat steam control valve, 23 ... Intermediate pressure turbine, 24
...Low pressure turbine, 34...Turbine bypass valve,
44...Steam IJl for startup, supply device. Applicant's agent Vr, Fujio Figure 2

Claims (1)

[Claims] 1. A gas turbine, an air compressor, a steam turbine consisting of a high-pressure side turbine and a low-pressure side turbine operated by steam generated by exhaust heat from the gas turbine, and a generator, each on the same axis. In a method of operating a steam-gas combined cycle power plant having a power train system arranged and configured, steam from a steam supply device for starting the plant is guided to a low-pressure turbine through a reheater to speed up the power train system, and then While maintaining that speed, the air in the gas turbine equipment is replaced with air from the air compressor, and then the gas turbine is ignited, and the power train system is subsequently sped up using steam from the plant startup steam supply device. After the gas turbine reaches a rotational speed that allows it to stand on its own, the steam from the plant startup steam supply system is secured for cooling the reheater and low-pressure turbine, and the reheat steam control valve controls the low-pressure turbine population. It is characterized by controlling the speed up of the power train system using the fuel control valve while controlling the steam pressure at a constant level.
A method of operating a steam-gas combined cycle power plant. 2. After the steam from the heat recovery boiler is introduced into the high-pressure turbine, the low-pressure turbine inlet pressure is controlled by the reheat steam control valve via the generator load. Item 1. A method of operating a steam-gas combined cycle power plant according to item 1. 3. Steam from the plant startup steam supply device is guided to the low-pressure turbine through the reheater when the reheater is warmed up, and through the reheater when the reheater is cold. 2. The method of operating a steam-gas combined cycle power plant according to claim 1, wherein the steam-gas combined cycle power generation plant is guided directly to the low-pressure turbine. 4. A power train system in which a gas turbine, an air compressor, a steam turbine consisting of a high-pressure side turbine and a low-pressure side turbine operated by steam generated by exhaust heat from the gas turbine, and a generator are arranged on the same axis. A steam-gas combined cycle power generation plant having a steam-gas combined cycle power generation plant, characterized in that a startup steam supply device is connected to a low-temperature reheat pipe on the exhaust side of a high-pressure side turbine. 5. The steam according to claim 4, characterized in that the startup steam supply device is connected to the high temperature reheat pipe on the downstream side of the reheater, thereby making it possible to switch to the connection line to the low temperature reheat pipe. Gas combined cycle power plant.