JP2604082B2 - Combined cycle power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined cycle power plant in which a gas turbine section and a steam turbine section are combined, and more particularly to a combined cycle power plant using high-pressure superheated steam as a cooling medium for blades of the gas turbine section.

[0002]

2. Description of the Related Art In recent years, power consumption has been increasing at an accelerating rate, and it is no longer possible to cope with existing power plants using steam turbines alone. As alternative technologies, power plants using gas turbines and power plants using steam turbines have become available. We are seeing the emergence of so-called combined cycle power plants that skillfully combine

[0003] This combined cycle power plant is preferred because it is much higher than the cycle efficiency of a steam turbine alone, and is also preferred in that quick start / stop, which is a characteristic of a gas turbine, is superior to that of a steam turbine alone. Have been.

Conventionally, in this type, exhaust gas discharged from a gas turbine is sent to an exhaust heat recovery boiler having two or three drums, where high-pressure, high-temperature steam is generated, and the superheated steam is generated. The rotating torque is sent to a steam turbine, and the rotating torque is given to a generator to generate an electric output. The cycle efficiency is high in that the exhaust heat gas is skillfully used.

[0005] However, even with this type in which the cycle efficiency is further increased, day and night research is being conducted with the aim of increasing the output from the power plant and further improving the cycle efficiency one step further. There is a problem of guaranteeing the material strength of gas turbine blades.

In general, it is well known that in this type of motor, the higher the temperature of the working gas, the higher the output that can be obtained. The higher the temperature of the working gas, the lower the rotational torque. The material strength of the gas turbine blades that it produces has a problem that cannot withstand the ultra-high temperatures.

To cope with such a problem, a part of high-pressure air from an air compressor is sent to a gas turbine blade, and a part of steam is extracted from a steam generator such as a so-called air-cooled blade or boiler. The so-called steam-cooled blades, which send air to gas turbine blades, have been studied.

[0008]

By the way, the recent development of the gas turbine is to increase the working gas temperature (gas turbine inlet temperature) from the 1100 ° C class to the 1300 ° C class as one step, and extend it to the 1500 ° C class or more. So
Even at such ultra-high temperatures, the air-cooling method of the blades has not been able to achieve the expected results of cycle efficiency more than expected, and the desire for steam-cooling methods for vibrating blades is increasing. In this case, the steam source is desirably steam extracted from the medium-pressure drum.According to trial calculations, when taking the stationary blade of the first stage of the gas turbine as an example, the gas turbine passes through the combustor from the air compressor compared to the air-cooled type. The amount of working gas sent to the tank can contribute to expansion work by more than 40%, and the cycle efficiency is relatively 1.7%.
It has been calculated that the above improvement is obtained.

However, when the steam from the medium-pressure drum is taken out as a steam source of the steam cooling system, although the steam is superior to the air cooling system as described above, the steam consumption by the steam cooling increases, but the steam consumption increases. Therefore, the amount of superheated steam sent from the high-pressure system drum to the steam turbine unit decreases, and eventually the output of the steam turbine unit tends to decrease. Therefore, when the steam consumption increases, it is not always preferable to withdraw the steam from the drum of the medium pressure system, even if it is a fixed amount.

Therefore, the present invention seeks a dramatic development in this kind of technical field, and provides a combined cycle power plant in which even if steam is used for cooling gas turbine blades, the cycle efficiency is further increased. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION The present invention has a gas turbine section, a steam turbine section, and an exhaust heat recovery boiler. The exhaust heat recovery boiler is provided along the flow direction of the exhaust gas discharged from the gas turbine section. The high pressure drum, the medium pressure drum, and the low pressure drum are provided in this order, and the steam from the high pressure drum is sent to the high pressure turbine of the steam turbine section via the first superheater and the second superheater, and the steam that has performed expansion work is discharged there. In a combined cycle power plant that superheats again with the reheater and sends out the superheated steam to the medium-pressure turbine and the low-pressure turbine of the steam turbine section, the combined-cycle section of the high-pressure steam cooling pipe and the auxiliary steam pipe extending from the first superheater is used. A cooling steam pipe that branches and connects to the blades of the gas turbine section is provided, while the outlet side of the blades of the gas turbine section is connected to the inlet of the high-pressure turbine of the steam turbine section. It is those with a.

[0012]

The present invention focuses on the fact that when the blades of the gas turbine section are cooled by steam, the consumption of the superheated steam is relatively small due to the high temperature and pressure of the steam. (1) The superheated steam is sent to the gas turbine blades via a high-pressure steam cooling pipe extending from the superheater, and the steam after cooling the blades is sent to the high-pressure turbine of the steam turbine via the recovery pipe. It contributes to the expansion work of the high pressure turbine. Therefore, the waste of the steam is relatively small, and the steam used for the cooling is returned to the high-pressure turbine of the steam turbine section, so that the cycle efficiency is further increased.

Shortly after startup, the steam from the auxiliary steam pipe is used because the superheated steam passing through the first superheater has not reached the predetermined temperature and pressure.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a combined cycle power plant according to the present invention will be described below with reference to the accompanying drawings in connection with the prior art.

FIG. 1 shows a schematic system which is a typical example of a combined cycle power plant according to the present invention. In this plant, a generator GEN, a steam turbine section ST, a gas turbine section GT, a waste heat Recovery boiler H
While having the RSG, the generator GEN and the steam turbine section S
T, the gas turbine unit GT is connected in tandem with a common shaft.

The gas turbine section GT includes an air compressor 2 having an intake chamber 1, a combustor 3, and a gas turbine 4. The air after dust removal in the intake chamber 1 is pressurized by the air compressor 2, and the high-pressure air To the combustor 3, where a high-pressure and high-temperature working gas is produced together with the fuel, and the working gas is sent to the gas turbine 4 to perform expansion work and convert heat energy into rotational energy.

The working gas used for consuming the rotational energy is sent as an exhaust gas to an exhaust heat recovery boiler HRSG,
Here, steam is generated.

The exhaust heat recovery boiler HRSG is of a type having three drums. The exhaust heat recovery boiler HRSG includes a second high-pressure superheater HPSH-2 and a second high-pressure superheater HPSH-2. Second reheater RH-2, first reheater RH-
1. The first high pressure superheater HPSH-1 is provided. Further, the exhaust heat recovery boiler HRSG has a high-pressure drum 5 directly connected to the first high-pressure superheater HPSH-1, and the high-pressure drum 5 includes a high-pressure evaporator HPEVA.

The intermediate-pressure evaporator IPSH, the low-pressure superheater LPSH, and the second high-pressure economizer HPECO-2 are provided downstream of the exhaust gas from the high-pressure evaporator HPEVA.
A medium pressure drum 6 provided with A is provided.

The intermediate-pressure drum 6 is provided for recovering the heat energy of the exhaust heat gas without exhaustion. The intermediate-pressure drum 6 includes an intermediate-pressure economizer IPECO,
Low pressure evaporator LPE with high pressure economizer HPECO-1
It is tied to a low pressure drum 7 provided with VA. Further, a low-pressure economizer LPECO is disposed on the downstream side of the exhaust heat gas of the low-pressure drum 7, and the low-pressure economizer LPECO is provided in the steam turbine section S.
They are receiving water from T.

The steam turbine section ST includes an exhaust heat recovery boiler H
In order to receive the steam from the RSG and convert the steam energy to rotational energy, the high-pressure turbine 8,
An intermediate pressure turbine 9 and a low pressure turbine 10 are provided. That is, the high-pressure turbine 8 is connected to the second heat recovery boiler HRSG.
The superheated steam from the high-pressure superheater HPSH-2 is received and expanded there, and the steam whose pressure and temperature are reduced is reheated through the first reheater RH-1 and the second reheater RH-2.
The reheated steam is sent to the medium-pressure turbine 8 where expansion work is performed again, and the steam after the expansion work is also expanded in the low-pressure turbine 10. The steam after the expansion work is thus
The water is cooled by a condenser 11 and returned to a low-pressure economizer LPECO of an exhaust heat recovery boiler HRSG via a pump 12 and a ground steam heat exchanger 13 as feed water.

The operation based on the above configuration will be described.

Atmospheric air sucked through the intake chamber 1 is sent to a combustor 3 together with fuel after being pressurized by an air compressor 2 to produce working gas. The working gas drives the gas turbine 4 to rotate by its expansion force, and is sent to the waste heat recovery boiler HRSG as waste heat gas. The exhaust gas flows in the direction of the arrow, during which time the preheating of the feedwater, the separation of water and water, and the evaporation are repeated, and finally superheated steam is generated. That is, the feed water guided from the steam turbine section ST is supplied to the low-pressure economizer LP.
ECO is preheated, and the preheated water is partially diverted to the low-pressure drum 7 through the first valve 24, where it is separated into water and water, and evaporated in the low-pressure evaporator LPEVA. It is delivered to the low pressure turbine 10.
In addition, part of the remaining preheated water is the first high pressure economizer HPEC
O-1 flows to the high-pressure drum 5 via the second high-pressure economizer HPECO-2 and the third valve 26, while the second high-pressure superheater HPS
It has been sent to H-2. Further, another part of the remaining preheated water flows to the intermediate pressure drum 6 via the intermediate pressure economizer IPECO and the second valve 25, and is also sent out to the second reheater RH-2.

The medium pressure drum 6 receives a part of the preheated water and separates water and water, and during this time, evaporates in a medium pressure evaporator IPEVA.
From medium pressure superheater IPSH to first reheater RH as medium pressure steam
-1.

The superheated steam extracted from the exhaust heat recovery boiler HRSG by repeating the preheating, steam-water separation and evaporation in this way is subjected to the above-mentioned expansion work and reheating in the steam turbine section ST, and is supplied from the generator GEN. Electrical energy is being extracted.

In contrast to the conventional example described above, according to the present invention, during operation of the gas turbine 4, cooling steam for supplying cooling steam to each blade from the outlet side to the inlet side in order to compensate for a decrease in material strength of the gas turbine moving and stationary blades. The feature is that the line is provided. That is, the gas turbine 4 is provided with a cooling steam pipe 14 for supplying cooling steam to each blade.
14 is the first high-pressure superheater HPS of the waste heat recovery boiler HRSG
A high-pressure steam cooling pipe 15 extending to a point C on the outlet side of H-1 and having a cooling high-pressure steam stop valve 27 interposed therebetween, and an auxiliary steam pipe 16 connected to an auxiliary boiler (not shown) with an auxiliary steam source valve 28 interposed therebetween. And it is forked.

The cooling steam pipe 14 includes a flow valve 32, a mist separator 33, a bypass valve 17, and an inlet valve 18, and a recovery pipe 19 for returning steam having cooled each blade to the high-pressure turbine 8 of the steam turbine section ST. Prepare. The recovery pipe 19 has a pressure adjusting valve 20 for adjusting the pressure of the return cooling steam, a first processing valve 21 for processing drain water and residual gas before and after start-up, and a blocking valve 22 for stopping the recovered cooling steam. I have.

On the other hand, the air compressor 2 of the gas turbine section GT
Is provided with a purge pipe 23.
Is connected via a purge valve 29, a cooling steam pipe 14, and a high-pressure steam cooling pipe 15 to a vent pipe 31 in which a second processing valve 30 is interposed.

Prior to the description of the steam cooling to each blade of the gas turbine according to the above configuration, the drain processing and the warming processing of each pipe system as a preceding stage are divided into steps before starting, after starting, and after stopping. I will explain.

(1) Before start-up Drain water and impurities remain in each pipe system, and if these are left untreated, the gas turbine blades suffer from thermal stress on the blades due to the generation of oxide scale and clogging. Since excess is generated, each pipe system is purged with steam. During this purge, the auxiliary steam source valve 28 is open, the flow valve 32 is open, the bypass valve 17 is open, the pressure regulating valve 20 is open, and the first processing valve 21 is opened.
Is open, second processing valve 30 is open, inlet valve 18 is closed, check valve
22 is closed, the cooling high-pressure steam stop valve 27 is closed, and the purge valve 29 is closed. Steam is sent from the auxiliary steam pipe 16 to the cooling steam line that has gone through such a procedure, and drain water and air remaining in each pipe system are sent to the outside.

(2) After start-up (2-1) Initial start-up After the above-mentioned purging, the inlet valve 18 is opened, the bypass valve 17 is closed, and the steam from the auxiliary steam pipe 16 is sent out to each pipe system. Warm inside each wing. (2-2) Middle period of start-up When the warming is completed, the auxiliary steam source valve 28 is closed, the first processing valve 21 is closed, the second processing valve 30 is closed, and the cooling high-pressure steam stop valve 27 is opened. 1 High pressure superheater HPSH-1
The cooling of each blade of the gas turbine 4 is started using the steam from the gas turbine. In this case, although the exhaust heat gas is sent from the gas turbine 4 to the exhaust heat recovery boiler HRSG, the steam discharged from the first high-pressure superheater HPSH-1 has a pressure and a pressure required to cool each blade of the gas turbine 4. When steam conditions such as temperature have not been reached, steam from the auxiliary steam pipe 16 is used. When each blade of the gas turbine 4 is cooled using steam from the auxiliary steam pipe 16, the opening and closing of each valve is performed by opening the auxiliary steam source valve 28, opening the first processing valve 21, and opening the second processing valve.
30 is open, the cooling high pressure steam stop valve 27 is closed, the flow valve 32 is open, the bypass valve 17 is closed, the inlet valve 18 is open, the blocking valve 22 is closed, and the purge valve 29 is closed. The operation of each valve starts cooling of each blade. (2-3) Late Startup At this time, the output of the gas turbine 4 rapidly increases, and the steam discharged from the first high-pressure superheater HPSH-1 reaches steam conditions such as pressure and temperature required for cooling each blade. Has reached. For this reason, the steam from the auxiliary steam pipe 16 is switched and the first
The steam from the high pressure superheater HPSH-1 is used. In this switching, each valve is opened and closed by closing the auxiliary steam source valve 28 and closing the first steam.
The processing valve 21 is closed, the second processing valve 30 is closed, and the blocking valve 22 is opened. The operation of each valve preferably cools each blade.

(3) At Shutdown When the operation of the gas turbine 4 is completed and each pipe system is left as it is, it is affected by the drainage of the residual steam, and air flows into the pipe while being left. Tubing causes oxidation and corrosion. Therefore, an operation of purging the residue in each pipe system to the outside using the high-pressure air from the air compressor 2 is performed. In this case, each valve is opened and closed by closing the auxiliary steam source valve 28,
The first processing valve 21 is open, the second processing valve 30 is open, the cooling high-pressure steam stop valve 27 is closed, the blocking valve 22 is closed, the purge valve 29 is open, and the inlet valve 18 is closed. This purges the residue in each pipe system to the outside. During the purging, the mist in each pipe system is separated and removed by the mist separator 33.

In the combined cycle power plant according to the present invention, cooling steam is supplied to each blade of the gas turbine 4 after the opening and closing operation of each valve.

First, the steam from the auxiliary steam pipe 16 is sent out to each blade of the gas turbine 4 via the cooling steam pipe 14, where it is cooled and then discharged to the outside via the recovery pipe 19 and the first processing valve 21. During this period, the process waits until the steam discharged from the first high-pressure superheater HPSH-1 reaches a pressure / temperature equal to or higher than a predetermined value.

When the steam of the first high-pressure superheater HPSH-1 reaches a certain value or more, the above-mentioned valves are opened and closed, and the superheated steam of the first high-pressure superheater HPSH-1 is supplied to the high-pressure steam cooling pipe 15, the cooling steam pipe. Through 14, it is sent to each blade of the gas turbine 4. After cooling each blade of the gas turbine 4, the steam is returned to the inlet of the high-pressure turbine 8 of the steam turbine section ST via the recovery pipe 19,
It is used here for expansion work.

As described above, the superheated steam of the first high-pressure superheater HPSH-1 is used for cooling each blade of the gas turbine 4 and the recovered steam after cooling is returned to the high-pressure turbine 8 as shown in FIG. As can be seen, the cycle efficiency is improved by about 2% compared to cooling the steam extracted from the medium pressure drum to each blade of the gas turbine. This is due to the fact that the temperature and pressure are higher than the steam withdrawn from the medium-pressure drum, and the steam after cooling is returned to the high-pressure turbine 8 and used for expansion work.

Therefore, the improvement in cycle efficiency contributes to the saving of fuel as well as the relatively low steam consumption required for cooling each blade of the gas turbine 4, and is an air pollution factor accompanying the saving of fuel. The generation of NOx and CO is relatively small.

[0038]

In the combined cycle power plant according to the present invention, while providing a cooling steam pipe which branches off from the junction of the high pressure steam cooling pipe from the first superheater and the auxiliary steam pipe and connects to the blades of the gas turbine section, The gas turbine unit is provided with a recovery pipe connected to the high-pressure turbine of the steam turbine unit from the blades. According to the present invention, there are excellent effects such as improvement of cycle efficiency and suppression of pollution problems due to fuel saving. .

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a combined cycle power plant according to the present invention.

FIG. 2 shows the existing cycle efficiency, the cycle efficiency when steam from an intermediate pressure drum of an exhaust heat recovery boiler is used to cool the blades of a gas turbine unit, and the blade of a gas turbine unit using superheated steam according to the present invention. FIG. 4 is a characteristic diagram for comparing cycle efficiencies when steam is cooled.

[Explanation of symbols]

 GT Gas turbine section HRSG Exhaust heat recovery boiler ST Steam turbine section 4 Gas turbine 5 High pressure drum 6 Medium pressure drum 7 Low pressure drum 8 High pressure turbine 14 Cooling steam pipe 15 High pressure steam cooling pipe 16 Auxiliary steam pipe 19 Recovery pipe HPSH-1 First Superheater HPSH-2 Second superheater

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-16109 (JP, A) JP-A-62-67239 (JP, A) JP-A-63-309731 (JP, A) 40244 (JP, B2)

Claims (1)

(57) [Claims] 1. A gas turbine section, a steam turbine section, and an exhaust heat recovery boiler. The exhaust heat recovery boiler includes a high pressure drum, a medium pressure With a drum and a low-pressure drum, the steam from the high-pressure drum is sent to the high-pressure turbine of the steam turbine section via the first superheater and the second superheater, and the steam that has been expanded is heated again by the reheater, In a combined cycle power plant that sends out the superheated steam to a medium-pressure turbine and a low-pressure turbine of a steam turbine section, a branch from a junction of a high-pressure steam cooling pipe and an auxiliary steam pipe extending from the first superheater is provided. A cooling steam pipe connected to the steam turbine section, and an outlet side of the blades of the gas turbine section is provided with a recovery pipe connected to an inlet of a high-pressure turbine of the steam turbine section. Unbound cycle power plant.