JP2558855B2 - Method of operating steam-gas combined cycle power plant and its power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method for operating a steam-gas combined cycle power plant in which an exhaust heat recovery boiler having a reheater and a steam turbine are combined, and Regarding the device.

(Prior Art) In recent years, the number of steam-gas combined cycle power generation plants constructed as a leading high-efficiency power generation technology is increasing, and on the other hand, in order to further improve the efficiency, the temperature of the gas turbine inlet is increased and the steam cycle is increased. Measures such as reheat of 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, and the air compressor 1
The air whose pressure has been increased by is supplied to the combustor 3 together with the fuel supplied through the fuel control valve 2, and is burned there to become high-temperature high-pressure combustion gas. This combustion gas is introduced into the gas turbine 4, expanded there to perform work, and is sent to the exhaust heat recovery boiler 5 as exhaust gas.

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

On the other hand, the steam generated by the high-pressure steam generator 8 is the superheater 6
Through the main steam pipe 14 and the main steam stop valve 15 and the main steam control valve 16 to the high-pressure turbine 17, where it expands and performs work. Heat tube
It is sent to the reheater 7 through 19. The exhaust gas from the high-pressure turbine 17 is heated by the reheater 7, becomes high-temperature reheat steam, passes through the high-temperature reheat pipe 20, and passes through the reheat steam stop valve 21 and the reheat steam control valve 22 to generate the intermediate pressure turbine. After being guided to 23, it expands and performs work in the intermediate-pressure turbine 23 and the low-pressure turbine 24, and then in the condenser 25, it exchanges heat with the cooling water sent by the circulating water pump 26 to become condensed water.

The condensate that has been condensed by the condenser 25 is sent to the low pressure economizer 13 of the exhaust heat recovery boiler 5 by the condensate pump 27,
After being heated there, it is returned to the low pressure steam generator 12. The low-pressure steam generated by this low-pressure steam generator 12 is the low-pressure steam pipe 28.
Through the low pressure steam stop valve 29 and the low pressure steam control valve 30 and is sent to the low pressure turbine 24 together with the exhaust gas from the intermediate pressure turbine 23.

By the way, the can water remaining in the low-pressure steam generator 12 is
The booster pump 31 boosts the pressure, and part of the water in the middle of the booster pump 31 is heated by the medium-pressure economizer 11 and then sent to the medium-pressure steam generator 10. The rest is heated by the high-pressure economizer 9 and is heated by the high-pressure steam generator 9. Sent to 8. The intermediate-pressure steam generated by the intermediate-pressure steam generator 10 passes through the intermediate-pressure steam pipe 32, the check valve 33 and the low-temperature reheat pipe 19, and is mixed with the high-pressure turbine exhaust.

A turbine bypass pipe 35 that branches to a condenser 25 via a turbine bypass valve 34 is branched to the main steam pipe 14, and another unit or a plant auxiliary steam is provided in the middle of the low temperature reheat pipe 19. A line capable of being bleed is connected via a bleed valve 36 for use in such as. Further, a drain valve 37 for the main steam pipe 14, a drain valve 38 for the medium-pressure steam pipe 32, a drain valve 39 for the low-pressure steam pipe 28, and a drain pipe for the high-pressure reheat pipe 20.
40 are provided respectively. In this way, one cycle for the water-steam system is constructed.

On the other hand, gas turbine 4, air compressor 1, high pressure turbine
17, the medium-pressure turbine 23, and the low-pressure turbine 24 constitute a power train system with a single shaft, and the generator 41 and the starter motor are arranged on the shaft.
42 are connected.

By the way, in the start-up of the steam-gas combined cycle power generation plant having the above-mentioned configuration, a state in which the fuel should leak and flow into the gas turbine body during a stop, or a state in which the unburned fuel that has flowed out due to the gas turbine ignition failure remains There is a danger of causing an explosion or a fire if ignited by, and in order to prevent this, it is necessary to replace the gas turbine system with safe air before igniting the gas turbine.

Therefore, when the plant is started up, the power train system is rotated and raised by the start-up generator 42 and the rotation speed of approximately 30% is maintained, so that the air from the air compressor 1 causes the air inside the combustor 3 and the gas turbine 4 to rise. Replace. Such an air replacement operation is called a purge operation. And
After the completion of the purge operation, the combustor 3 is ignited, the gas turbine 4 is ignited, and the power train system is accelerated again by the starting electric motor 42 to maintain the rotation speed of about 50%.

By maintaining the rotation speed, the exhaust heat recovery boiler 5 is warmed by the gas turbine exhaust gas, and steam is generated in each of the high pressure steam generator 8, the intermediate pressure steam generator 10, and the low pressure steam generator 12, Each of these steams is at high pressure until pressure conditions are available for the steam turbine,
The drain generated in the medium-pressure and low-pressure steam pipes 14, 32, 28 is discharged from the drain valves 37, 38, 39 to warm the steam pipes.

After that, when the steam of the low-pressure steam generator 12 rises to a predetermined pressure, the drain valve 39 is closed and 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 of the medium-pressure steam generator 10 has risen to a predetermined pressure, the drain valve 38 is closed, and 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 in the fully open state. A pressure adjusting device (not shown) is separately provided for controlling the temperature. 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, when the power train system is accelerated while increasing the fuel supply amount to the gas turbine 4 and reaches approximately 70% speed, the operation of the gas turbine 4 by the combustion gas burned by the air sent from the air compressor 1 As a result, the rotation speed of the power train system can be maintained, so that the starting electric motor 42 is stopped. Then, subsequently to this, the fuel is increased to accelerate the power train system by the gas turbine 4, and the generator 41 is inserted at the rated speed to take the initial load. When the load from the gas turbine 4 is further increased 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 turbine bypass valve
34 is closed, the steam is guided to the high pressure turbine 17 through the steam control valve 16, and thereafter, the load of the plant is increased while increasing the loads of the gas turbine 4 and the high pressure turbine 17.

(Problems to be Solved by the Invention) However, in such a start-up, from the time when the power train system first rises until the steam from the low-pressure steam generator 12 is introduced into the low-pressure turbine 24, However, there is a problem that the low-pressure turbine 24 having the above condition becomes idle and becomes high in temperature due to frictional energy due to rotation, and is placed in a state unfavorable for parts used in the low-pressure turbine 24. Further, after the gas turbine is ignited, until the steam from the medium pressure steam generator 10 is guided to the low temperature reheat pipe 19, the steam is continuously heated by the exhaust gas of the gas turbine 4 while the steam is not flowing to the reheater 7. Therefore, it is expected that the heating pipe of the reheater 7 will be burned.

Further, during the operation of the steam-gas combined cycle power plant as described above, the pressure of the low temperature reheat pipe 19 is set to the intermediate pressure turbine 23.
Changes substantially in proportion to the inlet steam flow rate. For this reason, the bleed valve should be used for other units or for plant auxiliary steam.
When bleeding through 36, the pressure in the low temperature reheat pipe will be lower than the pressure during normal operation. In this case, there is no problem when the extraction amount is small with respect to the medium-pressure turbine inlet steam flow rate, but when the extraction amount is large, for example, more than approximately 20%, the pressure drop in the low temperature reheat pipe becomes large.

In such a state, the heat collection balance in each of the high-pressure, medium-pressure, and low-pressure steam generators of the exhaust heat recovery boiler 5 is greatly different from each planned condition, and the generated steam amount largely deviates from the planned value, resulting in performance deterioration. There is a problem that not only the above-mentioned problem is promoted but also excessive stress is generated in the last stage blade of the high pressure turbine.

In view of such a point, the present invention has an object to obtain a method 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 startup, and an apparatus thereof. Further, another object of the present invention is to reduce the performance deterioration as much as possible when extracting air from the low temperature reheat pipe during plant operation, and to prevent excessive stress from being generated in the final stage blades of the high pressure turbine. (EN) A method of operating a combined cycle power plant and an apparatus therefor.

[Structure of Invention]

(Means for Solving the Problems) The present invention provides a gas turbine and an air compressor, a steam turbine including a high-pressure side turbine and a low-pressure side turbine that are operated by steam generated by exhaust heat from the gas turbine, and a generator. In a method of operating a steam-gas combined cycle power plant having a power train system, each of which is arranged on the same axis, the steam from the plant start steam supply device is introduced to the low pressure side turbine through the reheater, and the power train system is provided. The speed is increased, and then the speed is maintained to replace the air in the gas turbine equipment with the air from the air compressor, after which the gas turbine is ignited and the power from the plant start steam supply device is subsequently used to power the steam. After accelerating the train system and reaching the rotation speed at which the gas turbine can be self-sustaining, start the steam supply system for plant The steam from the plant is secured for cooling the reheater and the low-pressure side turbine, and while controlling the inlet steam pressure of the low-pressure side turbine by the control of the reheat steam control valve, the fuel control valve controls the power train system. It is characterized by performing speed-up control.

Also, at the time of cold start, the reheater is not sufficiently warm, and when the starting steam is passed through the reheater, the steam is cooled too much, which is not preferable for the starting state of the low pressure side turbine inlet. Therefore, in such a case, it is characterized in that the starting steam is guided to the high temperature reheat pipe on the downstream side of the reheater so as to be started.

Further, in the present invention, 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. May be.

Further, the apparatus according to the present invention includes a gas turbine and an air compressor, a high-pressure side turbine operated by steam generated by exhaust heat from the gas turbine, a steam turbine including a low-pressure side turbine, and a generator on the same axis. In the steam-gas combined cycle power generation plant having the power train system arranged as described above, the starting steam supply device is connected to the low temperature reheat pipe on the exhaust side of the high pressure side turbine.

(Operation) In the plant starting process, steam is introduced from the starting steam supply device to the low temperature reheat pipe, and the low pressure side turbine is driven by the steam, thereby starting the gas turbine. Therefore, during the rotation of the powertrain system, the steam always flows through the low temperature reheat pipe to the reheater and the low pressure side turbine, and the exhaust pipe of the gas turbine does not heat the heating pipe of the reheater to the extent that it is damaged. The low pressure turbine does not become hot due to wind loss. Further, when the reheater is not sufficiently warmed, steam is switched and sent to the low pressure side turbine through the high temperature reheat pipe, so that the low pressure side turbine is not operated by the 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 when the other unit or the plant auxiliary steam is extracted during the operation of the plant, the low temperature reheat pipe internal pressure does not drop below the pressure that changes according to the generator load during the normal operation. Therefore, the heat collection balance in the medium-pressure steam generator changes stably according to the load on the generator, and the amount of medium-pressure generated steam can be obtained almost as planned. The load or stress does not become excessive with respect to the planned value, and the performance during the plant operation and the stress applied to the final stage blades of the high-pressure turbine are maintained almost as planned.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, a low-temperature reheat pipe 19 connected to the exhaust side of the high-pressure turbine 17 is provided with a starting steam supply device via a valve 43.
44 is connected. In addition, the starting steam supply device 44
Is also connected via a valve 45 to a high temperature reheat pipe 20 downstream of the reheater 7.

Then, when starting the plant, first check valve 1
8,33 and the reheat steam control valve 22 are fully closed, the valve 43 is opened and the start steam is supplied from the start steam supply device 44 to the low temperature reheat pipe 19
To be introduced. Then, this steam gradually warms the reheat line consisting of the low temperature reheat pipe 19, the reheater 7, and the high temperature reheat pipe 20, and the drain generated during this time is discharged from the drain valve 40. Moreover, when starting steam without passing 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 reheat pipe 20. .

When drainage is eliminated and the steam pressure in the reheat line reaches the specified 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 is used to power train. The rotation speed of the system is controlled to be constant.

Therefore, the rotational speed of the powertrain system is maintained at 30% to carry out the purge operation of the gas turbine equipment, and after the completion of the purge operation, the rotational speed of the powertrain system is temporarily reduced to about 16% and the gas is cooled. Ignite the turbine.
After that, the power train system is accelerated again by the steam from the starting steam supply device 44 to maintain the rotation speed at about 50%.
During this time, the reheater 7, the low-pressure turbine 24, etc. are kept cooled by the steam supplied from the starting steam supply device 44, and the exhaust heat recovery boiler 5 is warmed by the gas turbine exhaust gas. The high-pressure steam pipe 14, the medium-pressure steam pipe 32, and the medium-pressure steam generator 10 until the steam generated in the low-pressure steam generator 12 and the low-pressure steam generator 12 reach the pressure conditions that can be used in the steam turbine. , And low-pressure steam pipe 28
The drain pipe 37, 38, 39 discharges the drain generated in each of the above, while warming up the steam pipe.

After that, when the steam of the low-pressure steam generator 12 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 and heat is recovered. Similarly, when the steam of the medium pressure steam generator 10 rises to a predetermined pressure, the drain valve 38 is closed and the steam from the medium pressure steam generator 10 is guided to the low temperature reheat pipe 19 via the check valve 33. Heat is recovered. Also, the steam of the high-pressure steam generator 8
When the pressure rises to a predetermined pressure, the drain valve 37 is closed and the water is guided to the condenser 25 via the turbine bypass valve 34.

On the other hand, during this period, when the power train system is accelerated while increasing the fuel supply amount to the gas turbine 4 and reaches approximately 70% speed, the combustion gas burned by the air sent from the air compressor 1 is generated in the gas turbine 4. Since it becomes possible to work and maintain the rotation speed of the powertrain system, after that, the steam from the starting steam supply device 44 is controlled by the reheat steam control valve 22 so that the inlet pressure of the intermediate pressure turbine becomes constant. Controlled. Therefore, the fuel is continuously increased by the fuel control valve 2 and the power train system is accelerated by the gas turbine 4,
After that, the generator 41 is inserted at the rated speed to take the initial load.

Further, the load increase by the gas turbine 4 is continued, and 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 main steam stop valve 15 is fully opened and the main steam control valve 16 is opened. This steam through a high pressure turbine
Lead to 17. At the same time, the turbine bypass valve 34 is closed.

After that, the load of the plant is increased while increasing the loads of the gas turbine 4 and the high pressure turbine 17, and the inlet pressure of the intermediate pressure turbine is controlled by the reheat steam control valve 22 via the load of the generator. To do.

FIG. 2 is a diagram showing an example of the relationship between the intermediate pressure turbine inlet pressure and the generator load. From the start of the plant until the rotational speed of the powertrain system reaches approximately 70% speed, reheat steam control is performed. Since the speed of the valve 22 is controlled, the medium pressure turbine inlet pressure is determined by this control. After that, the reheat steam control valve 22 is used for constant pressure control of the intermediate pressure turbine inlet pressure. Then, when the steam of the high-pressure steam generator is introduced into the high-pressure turbine, the inlet pressure of the intermediate-pressure turbine rises as the load on the generator rises.

〔The invention's effect〕

As described above, in the present invention, the plant is started by the steam turbine using the starting steam fed from the starting steam supply device, so that the cooling steam is always secured in the reheater and the low pressure turbine. Therefore, it is possible to prevent damage to the heating pipe of the reheater, or to prevent inconvenience caused by abnormally high temperature of the low-pressure turbine. When the inlet pressure of the low-pressure side turbine is controlled according to the load of the generator, the performance of the plant and the stress on the last stage blades of the high-pressure turbine are maintained almost as planned while other units. Alternatively, it can be extracted into plant auxiliary steam.

[Brief description of drawings]

FIG. 1 is a system diagram of a steam-gas combined cycle power plant of the present invention, FIG. 2 is an explanatory diagram showing a relationship between an intermediate pressure turbine inlet pressure and a generator load in the method of the present invention, and FIG. 3 is a conventional steam- It is a system diagram of a gas combined cycle power generation plant. 1 ... Air compressor, 3 ... Combustor, 4 ... Gas turbine, 5 ...
Exhaust 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 ... Medium pressure turbine, 24 ... Low pressure turbine , 34 ...
Turbine bypass valve, 44 ... Steam supply device for starting.

Claims (5)

(57) [Claims] 1. A power system in which a gas turbine and an air compressor, a steam turbine including a high-pressure side turbine and a low-pressure side turbine which are operated by steam generated by exhaust heat from the gas turbine, and a generator are arranged on the same shaft. In a method of operating a steam-gas combined cycle power plant having a train system, steam from a plant start steam supply device is introduced to a low pressure side turbine through a reheater to accelerate a power train system and then maintain the speed. Then, the air in the gas turbine equipment is replaced with the air from the air compressor, and then the gas turbine is ignited, and then the power train system is accelerated by the steam from the steam supply device for starting the plant. After reaching the self-sustaining rotation speed, the steam from the plant start steam supply unit is reheated and the low pressure side. It is ensured for cooling of the turbine, and while controlling the inlet steam pressure of the low pressure side turbine by the control of the reheat steam control valve, the fuel control valve controls the speedup of the power train system. A method of operating a steam-gas combined cycle power plant. 2. 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. The method of operating a steam-gas combined cycle power plant according to claim 1. 3. The steam from the steam supply device for starting the plant is led to the low-pressure side turbine through the reheater when the reheater is in the warm state, and reheated when the reheater is in the cold state. The method of operating a steam-gas combined cycle power plant according to claim 1, characterized in that the steam-gas combined cycle power plant is directly led to the low-pressure side turbine without passing through the reactor. 4. A gas turbine and 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 generator are arranged on the same shaft. In a steam-gas combined cycle power plant having a power train system, a starting steam supply device is connected to a low temperature reheat pipe on an exhaust side of a high pressure side turbine,
Steam-gas combined cycle power plant. 5. The steam supply device for start-up is connected to a high temperature reheat pipe on the downstream side of the reheater to enable switching to a connection line to the low temperature reheat pipe. Steam-gas combined cycle power plant.