JPH09170407A - Steam turbine cooling device for uniaxial complex cycle power generation plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce start-up time without generation of overheat caused by windage loss and surely have cooling steam preventing the generation of overheat by providing a cooling steam control system giving a valve opening/closing signal to a flow control valve in a cooling steam system so that the quantity of cooling steam does not exceed a specified value. SOLUTION: There are provided a low pressure steam system LS guiding steam from a low pressure drum 14 of an exhaust heat recovery boiler HRSG to a steam turbine low pressure part 6 and a cooling steam system CS guiding steam from a separate steam source to the steam turbine low pressure part 6 as cooling steam. The total flow is obtained according to an output signal of a flow meter 23 of the low pressure steam system LS and a flow meter 26 of the cooling steam system CS. A cooling steam control system CSC giving a valve opening/closing signal to a flow control valve 27 of the cooling steam system CS is provided so that the ratio of cooling steam quantity from the cooling steam system CS to the total qauantity does not exceeds a specified value. It is thus possible to surely have cooling steam required for prevention of generation in overheat caused by windage loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine cooling device for a single-shaft combined cycle power plant, and particularly effectively cools an overheated state that occurs in the final stage of the steam turbine low pressure section during start-up operation. The present invention relates to a steam turbine cooling device for a single-shaft combined cycle power plant.

[0002]

2. Description of the Related Art A single-shaft combined cycle power plant includes a single shaft, a compressor, a gas turbine, a steam turbine high pressure section,
The steam turbine middle pressure part and steam turbine low pressure part are arranged in a skewer, and because the arrangement is axial, the installation area is relatively small, and the quick start provided in the gas turbine can be used. Furthermore, since exhaust heat generated from a gas turbine can be effectively used as a heat source for steam generation, it has recently been favored and adopted in large numbers due to its high thermal efficiency as compared with the thermal efficiency of a gas turbine alone or a steam turbine alone.

In this type of power plant start-up operation, a low pressure portion of the steam turbine is evacuated through a condenser by a vacuum pump, and when a prescribed vacuum degree is reached, a single shaft (rotating shaft) is driven by a driving force of a starting motor. ) Is rotated to accelerate each pressure part of the compressor, gas turbine, and steam turbine, and then fuel is injected into the gas turbine combustor to generate combustion gas, and the gas turbine is started by generation of this combustion gas. ing.

After starting, the gas turbine performs expansion work by the combustion gas and sends the exhaust heat after the expansion work to the exhaust heat recovery boiler for steam generation as a heat source. During this period, no steam is obtained from the exhaust heat recovery boiler in each pressure section of the steam turbine, so there is so-called no-ventilation / no-load operation, and only the air in the turbine casing of each pressure section is agitated. It is in a state.

Among the pressure portions of the steam turbine under such an agitated state, especially in the low pressure portion of the steam turbine, since the moving blades in the final stage portion have a length of 1 m or more,
Wind loss (power loss due to air agitation in the steam turbine casing) occurs, and the frictional heat causes the components in the final stage to fall into an overheated state, resulting in a problem of reduced strength of the material.

As a workaround for such a problem,
For example, as seen in Japanese Patent Publication No. 6-78724,
Empirically, the rotational speed at which the wind loss occurs in the final paragraph is empirically known, and the exhaust heat recovery is performed on the condition that the rotational speed for this wind loss and the low-pressure drum internal pressure of the exhaust heat recovery boiler have reached a given value It was already known to supply low pressure steam to the low pressure section of a steam turbine from a low pressure drum of a recovery boiler to cool the final stage of the low pressure section of the steam turbine and to protect its components from overheating.

[0007]

However, in the prior art as described in the above publication, it takes time for the internal pressure of the low-pressure drum of the exhaust heat recovery boiler to reach a given pressure, and during this period, the rotating shaft loses windage. Therefore, the rotation speed must be kept lower than before so that the start-up operation can be shortened. In particular, unlike a hot start, a cold start requires more than 2 hours for start-up time, which detracts from the advantage of shortening start-up, which is one of the selling points of this type of power plant.

In addition, the output of a recent power plant is increasing, and the start-up time tends to increase as the output increases, and the start-up time is shortened if the rotation speed is held at a level at which windage loss does not occur. In addition to this, it has become impossible to protect the components in the final paragraph from the overheated state only with the low-pressure steam amount supplied from the low-pressure drum of the exhaust heat recovery boiler to the low-pressure part of the steam turbine. Furthermore, when the load is cut off, the steam supplied to each pressure section of the steam turbine is inevitably cut off, but there are still cases where it is required to maintain the rotation speed of the rotating shaft at a constant speed or higher. , In this case as well, steam from the low pressure drum is required to avoid overheating due to windage loss,
Since the amount of steam is increasing, it is not possible to cover it with the conventional amount of steam alone, and some measures have to be taken.

The present invention has been made in view of the above circumstances, and it is possible to prevent overheating due to windage loss without holding the rotation speed of a single shaft (rotating shaft) lower than the conventional rotation speed. In order to shorten the start-up time by avoiding the above, it is possible to provide a steam turbine cooling device for a single-shaft combined cycle power plant that can reliably secure the cooling steam necessary for avoiding overheating due to windage loss. To aim.

[0010]

In order to achieve the above object, a steam turbine cooling device for a single-shaft combined cycle power plant according to the present invention has a single shaft, a compressor, and a gas. Turbine, steam turbine high pressure part,
A steam turbine intermediate pressure part and a steam turbine low pressure part are provided, and high pressure air from the compressor is sent to a combustor, where fuel is added to generate combustion gas, and the generated combustion gas is sent to the gas turbine to perform expansion work. The exhaust heat of the combustion gas after expansion work is used as a heat source to generate steam by a separate heat recovery steam generator, and the generated steam causes expansion work in the steam turbine high pressure section, steam turbine intermediate pressure section, and steam turbine low pressure section. In the single-screw combined cycle power generation plant that performs the steam from the low-pressure drum of the exhaust heat recovery boiler, a low-pressure steam system that guides the steam turbine low-pressure section, and is connected to this low-pressure steam system, from a separately placed steam source. A cooling steam system for guiding steam to the low-pressure part of the steam turbine as cooling steam is provided, while an output signal of the low-pressure steam system flow meter and an output of the cooling steam system flow meter are provided. A cooling steam control system that gives a valve opening / closing signal to the flow control valve of the cooling steam system so that the proportion of the amount of cooling steam from the cooling steam system in the total flow rate sum with the signal does not exceed a given value. It is provided.

The present invention described in claim 2 is the same as the claim 1.
A cooling steam control system for giving a valve opening / closing signal to the flow control valve of the cooling steam system described above, an adding unit for adding the output signal of the flow meter of the low-pressure steam system and the output signal of the flow meter of the cooling steam system,
It has a comparing section for matching a given value from the setter with the output signal from the adding section, and an adjusting section for giving a valve opening / closing signal to the flow rate control valve of the cooling steam system based on the deviation from the comparing section. It is configured.

Further, according to the present invention as set forth in claim 3, a given value of a setter of the cooling steam control system for giving a valve opening / closing signal to the flow control valve of the cooling steam system according to claim 2 is obtained from the condenser. It is determined by the output signal of the function generator that calculates the amount of cooling steam commensurate with the degree of vacuum.

Further, the steam turbine cooling device for a single-shaft combined cycle power plant according to the present invention according to claim 4 has, in a single shaft, a compressor, a gas turbine, a steam turbine high pressure section, a steam turbine intermediate pressure section, and a steam turbine. A low-pressure part is provided, and high-pressure air from the compressor is sent to a combustor, where fuel is added to generate combustion gas, and the generated combustion gas is sent to the gas turbine to perform expansion work and combustion after expansion work. Single-screw combined cycle power generation plant in which steam is generated by a separately placed exhaust heat recovery boiler using the exhaust heat of gas as a heat source, and the generated steam performs expansion work in the steam turbine high pressure section, steam turbine intermediate pressure section, and steam turbine low pressure section. In, the steam from the low-pressure drum of the exhaust heat recovery boiler, a low-pressure steam system for guiding to the steam turbine low-pressure portion, connected to this low-pressure steam system, A cooling steam system that guides the steam from the stationary steam source to the steam turbine low-pressure section as cooling steam, and the reheated steam from the reheater of the exhaust heat recovery boiler, the steam through the steam turbine intermediate pressure section. While having a reheat steam system to guide to the turbine low pressure section, while providing a flow meter to this reheat steam system, when detecting that this flow meter can cover the cooling of the steam turbine low pressure section only with reheat steam, A cooling steam control system for giving a valve closing signal to the cooling steam supply valve of the cooling steam system is provided.

According to a seventh aspect of the present invention, there is provided a single-shaft combined cycle power plant steam turbine cooling device in which a single shaft is provided with a compressor, a gas turbine, a steam turbine high pressure section, a steam turbine intermediate pressure section, and a steam turbine. A low-pressure part is provided, and high-pressure air from the compressor is sent to a combustor, where fuel is added to generate combustion gas, and the generated combustion gas is sent to the gas turbine to perform expansion work and combustion after expansion work. Single-screw combined cycle power generation plant in which steam is generated by a separately placed exhaust heat recovery boiler using the exhaust heat of gas as a heat source, and the generated steam performs expansion work in the steam turbine high pressure section, steam turbine intermediate pressure section, and steam turbine low pressure section. In the above, a low pressure steam system for guiding the steam from the low pressure drum of the exhaust heat recovery boiler to the low pressure part of the steam turbine and a low pressure steam system connected to the low pressure steam system, The cooling steam system that guides the steam from the steam source to the low pressure part of the steam turbine as cooling steam, and the main steam from the superheater of the exhaust heat recovery boiler, the high pressure part of the steam turbine and the reheat of the exhaust heat recovery boiler. Heater, while having a main steam system for guiding to the steam turbine low-pressure portion via the steam turbine intermediate pressure portion, provided with a valve lift detector for detecting the valve opening of the high-pressure control valve of the main steam system, When the valve lift detector detects that only the main steam can cover the low pressure part of the steam turbine, a cooling steam control system for providing a valve closing signal to the cooling steam supply valve of the cooling steam system is provided. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In order to easily understand a steam turbine cooling device for a single-shaft combined cycle power plant according to the present invention, a first embodiment, a second embodiment and a third embodiment will be described below. I will explain separately.

(First Embodiment) FIG. 1 is a schematic system diagram showing a steam turbine cooling device of a single-shaft combined cycle power plant according to the present invention.

As shown in FIG. 1, a steam turbine cooling device of a single-shaft combined cycle power plant has a prime mover section G.
T, an exhaust heat recovery boiler HRSG, a low pressure steam system LS,
It has a configuration including a cooling steam system CS and a cooling steam control system CSC.

The prime mover section GT has a single shaft (rotating shaft) in which a gas turbine 1, a compressor 3, a steam turbine high pressure part 4, a steam turbine intermediate pressure part 5, and a steam turbine low pressure part 6 are arranged in a skewed shape in an axial shape. It has a long stretch.

The inlet end A of the exhaust heat recovery boiler HRSG is separated from the prime mover GT by a distance, and is connected to the outlet end A of the gas turbine 1. This exhaust heat recovery boiler HRSG
Receives the exhaust heat of the combustion gas of the gas turbine 1, and along the flow thereof, the superheater 8, the reheater 9, the high-pressure evaporator 11 communicating with the high-pressure drum 10, and the medium-pressure evaporator communicating with the intermediate-pressure drum 12. 13, a low-pressure evaporator 15 communicating with the low-pressure drum 14 and a economizer 16. The steam generated from the low-pressure evaporator 15 and the economizer 16 are used for the steam turbine high-pressure section 4, the steam turbine intermediate-pressure section 5, and the steam turbine high-pressure section 4.
The configuration is such that the steam turbine low-pressure portion 6 is fed. That is, the steam turbine high pressure section 4 is connected to the superheater 8 via the high pressure control valve 17 of the main steam system MS, and the outlet end B thereof is connected to the inlet end B of the reheater 9. The reheater 9 is for generating so-called reheated steam that recovers the steam condition (pressure / temperature) of the steam expanded by the steam turbine high-pressure unit 4 to the original steam condition, and has its outlet end. C and the inlet end C of the steam turbine intermediate pressure section 5
Is provided with a reheat system RHS for connecting the intermediate block valve 18 via the intermediate block valve 18. Further, the inlet end of the steam turbine low-pressure portion 6 is provided with a low-pressure control valve 21 to the low-pressure steam system LS, and the outlet end thereof is provided with a condenser 19 and a condensate pump 20 to provide an exhaust heat recovery boiler. Each is connected to the HRSG economizer 16.

The low pressure steam system LS comprises a steam turbine low pressure section 6
Is connected to the low-pressure drum 14 of the exhaust heat recovery boiler HRSG, and has a pipeline structure including a low-pressure control valve 21, a check valve 24, and a flow meter 23. This low-pressure steam system LS has
A cooling steam system CS is additionally attached.

The cooling steam system CS is provided with a steam source 22, and is provided with a flowmeter 26, a flow rate control valve 27, and a cooling steam supply valve 25 along the flow of the cooling steam sent from the cooling steam system CS. It is connected to the inlet side of the low pressure control valve 21 of the low pressure steam system LS. The vapor source 22 is
Even though a large amount of cooling steam is consumed in order to avoid overheating due to windage loss of the steam turbine low-pressure part 6, it is a good idea to keep it at the minimum necessary limit in view of economic efficiency. In consideration of the property, it is desirable to use, for example, another low-pressure steam system of the existing combined cycle power plant or a house boiler exclusively used in the power plant.

The low-pressure steam system LS and the cooling steam system CS are both provided with a common cooling steam control system CSC. The cooling steam control system CSC controls the amount of cooling steam fed from the steam source 22 to the steam turbine low pressure section 6 to a minimum required limit, and is an output signal of the flow meter 23 of the low pressure steam system LS. In addition, an adder 28 for adding the output signal of the flow meter 26 of the cooling steam system CS and the output signal of the adder 28 are matched with the output signal as a given value predetermined by the setter 30. It is configured to include a comparison unit 29 and an adjustment unit 31 that produces a valve opening / closing signal of the flow rate adjustment valve 27 by performing proportional / integral calculation on the deviation from the comparison unit 29.

Next, the operation based on the above configuration will be described.

Before starting, the condenser 19 is evacuated by a vacuum pump (not shown), and when the specified vacuum degree is reached, a starting motor (not shown) causes the prime mover GT to rotate and the combustor 2 The ignition of the gas turbine 1 and the compressor 3 starts the parallel operation.

The compressor 3 sucks in atmospheric air to increase its pressure and sends the high-pressure air to the combustor 2 for producing combustion gas. In the combustor 2, fuel such as L
NG or kerosene is added to produce hot combustion gas. The gas turbine 1 causes the combustion gas to perform expansion work,
The combustion gas after the expansion work is sent to the exhaust heat recovery boiler HRSG as a heat source for generating steam. During this period, the engine department G
The steam turbine high-pressure part 4, the steam turbine medium-pressure part 5, and the steam turbine low-pressure part 6 of T are in a so-called no-ventilation / no-load state in which steam from the exhaust heat recovery boiler HRSG is not obtained. In the casings 4, 5 and 6, air is continuously stirred by rotating the moving blades. In particular, the rotor blades in the final stage of the steam turbine low-pressure section 6 are
Since the blade is longer than that of No. 5, a large amount of rotational frictional heat is generated during agitation of air, and the rotational frictional heat causes the components in the final paragraph to fall into an overheated state. At this time, the low-pressure drum 4 of the exhaust heat recovery boiler HRSG is open and is at a given pressure, so that the low-pressure steam from this is passed through the low-pressure control valve 21 of the low-pressure steam system LS to the steam turbine low-pressure section 6. The steam turbine low pressure portion 6 is prevented from being overheated.

However, when the start-up time becomes longer than before with the increase in output, the low-pressure steam amount supplied from the low-pressure steam system LS to the low-pressure steam turbine section 6 alone is enough to drive the low-pressure steam turbine section 6. It is no longer possible to cover for avoiding overheating. Therefore, in the low pressure steam system LS,
A cooling steam system CS is provided that backs up the cooling steam from the steam source 22 as a shortage of low-pressure steam. This cooling steam system CS is just a low pressure steam system LS
Since it is for backup of the above, it is necessary to keep the amount of cooling steam at the minimum necessary limit without excess or deficiency with respect to the above shortage of low pressure steam.

The amount of cooling steam sent from the steam source 22 of the cooling steam system CS to the low pressure steam system LS is the cooling steam control system CSC.
Is controlled by That is, the low pressure steam of the low pressure steam system LS is detected by the flow meter 23, and the cooling steam of the cooling steam system CS is detected by the flow meter 26. The output signals detected by the flow meters 23 and 26 are
Each is sent to the adder 28, where it is sent to the comparator 29 as an addition signal. The comparison unit 29 compares the addition signal with the output signal from the setter 30 as a predetermined given value, and when a deviation occurs, sends the deviation signal to the calculation unit 31, where A valve opening / closing signal is generated by proportional / integral operation, and the valve opening / closing signal is used as the cooling steam system C.
It is given to the flow rate control valve 27 of S to control the amount of cooling steam from the steam source 22.

Therefore, in the steam cooling device for a single-shaft combined cycle power plant according to the present invention, even if the steam turbine low-pressure portion 6 falls into an overheated state due to windage loss during start-up, the flow control valve 27 of the cooling steam system CS is operated. By controlling the flow rate, the amount of steam required to avoid the overheated state can be reliably ensured, and the start-up time can be shortened.

When the gas turbine 1, the steam turbine high pressure section 4, the steam turbine medium pressure section 5 and the steam turbine low pressure section 6 all reach the rated speed and only the gas turbine 1 enters the parallel operation, the combustion gas temperature is increased. As the steam pressure of the high pressure drum 10 of the exhaust heat recovery boiler HRSG approaches a given pressure, the high pressure steam control valve 1 of the main steam system MS 1
7. Open the intermediate blocking valve 18 of the reheat steam system RHS to ventilate the high pressure steam from the high pressure drum 10 to each pressure section 4, 5, 6 of the steam turbine, and increase the load of the gas turbine 1 after the ventilation operation. Together with steam turbine pressure parts 4, 5, 6
Also enters the load operation, and thus the electric output from the generator 7 is obtained.

FIG. 2 is a schematic system diagram showing a modified example of the first embodiment according to the present invention, particularly a cooling steam control system. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this modified example, a given value of the setter 30 of the control system CSS that gives a valve opening / closing control signal to the flow rate control valve 27 of the cooling steam system CS is obtained as the degree of vacuum of the condenser 19.

It is generally known that when the degree of vacuum of the condenser 19 becomes higher, the influence of overheating due to windage loss of the steam turbine low-pressure portion 6 becomes smaller. It directly affects the increase / decrease in the amount of steam guided in No. 6. In this case, changes in the degree of vacuum affect the influence of the amount of exhaust steam guided from the steam turbine low-pressure portion 6 to the condenser 19, the cooling water source to the condenser 19, for example, the amount of seawater and the temperature of seawater guided from the ocean. However, it is considered that the amount of seawater maintains the design value, so it is ultimately affected by the seawater temperature. In other words, if the seawater temperature is high,
The degree of vacuum has a relationship of decreasing. Since the temperature of seawater cannot be adjusted, it is necessary to determine the amount of steam guided to the steam turbine low-pressure section 6 in the end, corresponding to changes in the degree of vacuum.

The first example of the first embodiment of the present invention focuses on such a point, and as shown in FIG. 2, the condenser 19 is provided with a vacuum gauge 32. , The output signal of the vacuum gauge 32 is obtained from the function generator 33 in which the characteristic diagram of the relationship between the amount of steam guided to the steam turbine low-pressure section 6 and the vacuum degree shown in FIG. 3 is input. The output signal determined here is passed through the setting unit 30 to the comparison unit 2
9 is input to the flow control valve 27 of the cooling steam system CS by a deviation calculation signal from the output signal from the adding unit 28 to control the cooling steam from the steam source 22.

Therefore, the vapor source 22 of the cooling vapor system CS
The cooling steam from the can be backed up to the low pressure steam of the low pressure steam system LS without excess or deficiency so as to correspond to the change in the degree of vacuum of the condenser 19, so that the steam turbine low pressure portion 6 is accompanied by windage loss. It is possible to avoid overheating.

(Second Embodiment) FIG. 4 is a schematic system diagram showing a second embodiment according to the present invention. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

During the aeration operation, the main steam of the high pressure drum 10 flows through the superheater 8, the main steam system MS, the high pressure regulator valve 17, and the steam turbine high pressure section 4, and when passing through the reheater 9, it becomes reheated steam. The reheat steam system RHS and the intermediate stop valve 18 are used to sequentially flow to the steam turbine intermediate pressure portion 5 and the steam turbine low pressure portion 6. However, in the present embodiment, reheat flowing to the steam turbine low pressure portion 6 is performed. The steam (which is not yet at a given force at this point) is used to avoid overheating associated with windage loss. That is, before the ventilating operation, the low-pressure steam of the low-pressure steam system LS is guided to the steam turbine low-pressure section 6 together with the cooling steam of the cooling steam system CS, but since this cooling steam has a usage limit, When the amount of reheated steam exceeds the amount of cooling steam of the cooling steam system CS, the supply of cooling steam to the steam turbine low pressure portion 6 is stopped.

A description will be given below with reference to FIG.

An outlet end C of the reheater 9 of the exhaust heat recovery boiler HRSG and an inlet end C of the steam turbine intermediate pressure portion 5 are connected by a reheat steam system RHS having an intermediate blocking valve 18 interposed therebetween. A flow meter 34 is provided in the reheat steam system RHS. The output signal of the flow meter 34 is the cooling steam control system CS.
It has been sent to C. The cooling steam control system CSC is a setter 3
5 and a comparison calculation unit 36, and supplies a valve closing signal to the cooling steam supply valve 25 of the cooling steam system CS to stop the supply to the cooling steam turbine low-pressure unit 6. That is, the reheated steam guided from the reheater 9 to the steam turbine intermediate pressure section 5 is detected by the flow meter 34, and this detection signal is sent to the comparison calculation section 36 of the cooling steam control system CSC. . Here, when a deviation (when the amount of reheat steam exceeds the cooling steam of the cooling steam system CS) is collated with the output signal as a given value from the setter 35, the deviation is calculated and the valve is closed. A signal is generated and the valve closing signal is given to the cooling steam supply valve 25 of the cooling steam system CS to cut off the supply of the cooling steam.

As described above, in the present embodiment, when the reheated steam of the reheated steam system RHS guided to the steam turbine low pressure section 6 exceeds the cooling steam amount of the cooling steam system CS, Since the supply can be automatically cut, the steam source 22 of the cooling steam system CS does not excessively consume the cooling steam and can maintain a stable steam amount and steam pressure.

FIG. 5 is a schematic system diagram showing a modification of the second embodiment according to the present invention. The same components as those of the second embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

In the present modification, a pressure gauge 37 is provided in place of the flow meter 34 of the reheat steam system RHS in the second embodiment shown in FIG. This is because we paid attention to the fact that the steam flow rate and the steam pressure are in a proportional relationship. in this case,
It has been empirically known that the overheated state due to the windage loss of the steam turbine low-pressure part 6 can be avoided if the steam pressure reaches a given value. Therefore, the pressure detected by the pressure gauge 37 of the reheat steam system RHS is If the output signal from the setting device 35 of the cooling steam control system CSC is exceeded, a valve closing signal can be given to the cooling steam supply valve 25 of the cooling steam system CS, and the cooling steam is supplied to the steam turbine low pressure section 6. Can be cut. Therefore, the vapor source 22 of the cooling vapor system CS can maintain a stable vapor amount and vapor pressure.

(Third Embodiment) FIG. 6 is a schematic system diagram showing a third embodiment according to the present invention. The same components as those of the second embodiment are designated by the same reference numerals, and the description thereof will be omitted.

During the ventilating operation, the steam of the exhaust heat recovery boiler, as described in the second embodiment, includes the high pressure drum 10, the steam turbine high pressure section 4, the reheater 9, the steam turbine intermediate pressure section 5, and the steam. The turbine low pressure portion 6 flows in this order, but in the present embodiment, attention is paid to the main steam from the high pressure drum 10 serving as a ventilation steam source, and this main steam cools the cooling steam system CS. When it exceeds the amount of steam,
The supply of cooling steam to the steam turbine low-pressure section 6 is stopped. That is, the main steam is the main steam system M.
This is because it has been noted that the amount of steam flowing to the steam turbine high-pressure part 4 via the high-pressure control valve 17 for S and the amount of steam flowing to the low-pressure part 6 of the steam turbine have a substantially equal relationship.

A description will be given below with reference to FIG.

Exhaust heat recovery boiler HRSG high-pressure drum 10
Main steam is generated from the main steam (the main steam being ventilated is not at a given pressure), and this main steam is the superheater 8 and the main steam system MS.
After flowing through the high pressure control valve 17 of the steam turbine to the steam turbine high pressure section 4, where each component is heated, it flows to the reheater 9 to recover the original steam conditions (pressure / temperature), and as reheated steam, The amount of steam passing through the steam turbine high-pressure part 4 and the amount of steam flowing into the steam turbine low-pressure part 6 because the steam turbine intermediate pressure part 5 and the steam turbine low-pressure part 6 flow in this order from the intermediate blocking valve 18 of the reheat steam system RHS. And are almost equal.

Therefore, in the third embodiment according to the present invention, the valve lift detector 3 is attached to the high pressure control valve 17 of the main steam system MS.
8 is provided. The output signal of the valve lift detector 38 is sent to the control system CSC. Control system CSC
Has a setter 39 and a comparison calculation unit 40, and supplies a valve closing signal to the cooling steam supply valve 25 of the cooling steam system CS to stop the supply of cooling steam to the steam turbine low-pressure unit 6. That is, the amount of main steam guided from the high-pressure drum 10 to the steam turbine high-pressure unit 4 is determined by the opening of the high-pressure regulator valve 17, and the valve lift detector 38 detects this opening. The output signal of the valve lift detector 38 is sent to the comparison calculation unit 40 of the cooling steam control system CSC, where it is collated with the output signal from the setter 39 to generate a deviation (the main steam amount is the cooling steam of the cooling steam system CS). Is exceeded), the deviation is calculated to generate a valve closing signal, and the valve closing signal is supplied to the cooling steam supply valve 25 of the cooling steam system CS to cut off the supply of cooling steam.

As described above, in this embodiment, when the main steam guided to the steam turbine low pressure portion 6 exceeds the cooling steam amount of the cooling steam system CS, the supply of the cooling steam can be automatically cut. As a result, as in the second embodiment described above, the steam source 22 of the cooling steam system CS can keep the amount of steam and the steam pressure in a stable state.

FIG. 7 is a schematic system diagram showing a modification of the third embodiment according to the present invention. The same components as those in the third embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present modification, a flow meter 41 is provided in the main steam system MS in place of the valve lift detector 38 of the high pressure regulator valve 17 in the third embodiment shown in FIG. This is because the amount of steam obtained by the valve lift, that is, the valve opening, and the amount of steam of the flow meter match.

Therefore, in the present embodiment, as in the third embodiment, when the main steam exceeds the cooling steam of the cooling steam system CS, the cooling steam of the cooling steam system CS is cut by the cooling steam control system CSC. Therefore, the steam source 22 of the cooling steam system CS can be maintained under a stable steam condition.

[0051]

As described above, in the steam turbine cooling device of the single-shaft combined cycle power plant according to the present invention, the low steam system connecting the low pressure drum of the exhaust heat recovery boiler and the low pressure part of the steam turbine is cooled. Added steam system,
With this cooling steam system, the low-pressure steam system backs up the shortage of the amount of steam required to avoid overheating due to wind damage in the low-pressure part of the steam turbine, and the control system keeps this backup steam amount to the minimum required limit. Since it is equipped with the above, it is possible to avoid overheating due to windage loss and to shorten the start-up time without keeping the rotation speed of a single shaft (rotating shaft) low as in the conventional case. The cooling steam required for heating can be reliably secured, and the cooling steam from the steam source of the cooling steam system can be stably supplied to the low-pressure part of the steam turbine.

Further, in the steam turbine cooling device of the single-shaft combined cycle power plant according to the present invention, in order to keep the cooling steam of the cooling steam system supplied to the low pressure part of the steam turbine to the minimum necessary limit, Since reheated steam or main steam in the main steam system is used to avoid overheating due to windage loss, it is possible to reduce the consumption of cooling steam from the steam source in the cooling steam system, and the steam source has a stable steam amount and The vapor pressure can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing an embodiment of a steam turbine cooling device of a single-shaft combined cycle power generation plant according to the present invention.

FIG. 2 is a schematic system diagram showing a modified example of the first embodiment according to the present invention.

FIG. 3 is a graph showing the relationship between the degree of vacuum of the condenser and the amount of cooling steam.

FIG. 4 is a schematic system diagram showing a second embodiment according to the present invention.

FIG. 5 is a schematic system diagram showing a modified example of the second embodiment according to the present invention.

FIG. 6 is a schematic system diagram showing a third embodiment according to the present invention.

FIG. 7 is a schematic system diagram showing a modified example of the third embodiment according to the present invention.

[Explanation of symbols]

 1 Gas turbine 2 Combustor 3 Compressor 4 Steam turbine high pressure part 5 Steam turbine medium pressure part 6 Steam turbine low pressure part 7 Generator 8 Superheater 9 Reheater 10 High pressure drum 11 High pressure evaporator 12 Medium pressure drum 13 Medium pressure evaporation 14 low pressure drum 15 low pressure evaporator 16 economizer 17 high pressure regulator valve 18 intermediate blocking valve 19 condenser 20 condensate pump 21 low pressure regulator valve 22 steam source 23, 26, 34, 41 flow meter 24 check valve 25 cooling Steam supply valve 27 Flow rate control valve 28 Addition section 29 Comparison section 30, 35, 39 Setter 31 Control section 32 Vacuum gauge 33 Function generator 36, 40 Comparison calculation section 37 Pressure gauge 38 Valve lift detector GT Motor section HRSG Discharge Heat recovery boiler MS Main steam system RHS Reheat steam system LS Low pressure steam system CS Cooling steam system CSC Cooling steam control system

Claims (9)

[Claims] 1. A single shaft is provided with a compressor, a gas turbine, a steam turbine high pressure section, a steam turbine medium pressure section, and a steam turbine low pressure section, and high pressure air from the compressor is sent to a combustor where fuel is supplied. In addition, combustion gas is generated, and the generated combustion gas is sent to the gas turbine for expansion work, and exhaust heat of the combustion gas after expansion work is used as a heat source to generate steam by a separate heat recovery steam generator, and the generated steam In the single-shaft combined cycle power plant that performs expansion work in the steam turbine high pressure section, the steam turbine intermediate pressure section, and the steam turbine low pressure section, the steam from the low pressure drum of the exhaust heat recovery boiler is guided to the steam turbine low pressure section. And a cooling steam system which is connected to the low pressure steam system and which guides the steam from the separately placed steam source to the low pressure part of the steam turbine as cooling steam. On the other hand, in the total flow rate sum of the output signal of the low-pressure steam system flow meter and the output signal of the cooling steam system flow meter, the proportion of the amount of cooling steam from the cooling steam system does not exceed a given value. As described above, the steam turbine cooling device for a single-shaft combined cycle power plant, comprising a cooling steam control system for providing a valve opening / closing signal to the flow control valve of the cooling steam system. 2. A cooling steam control system for giving a valve opening / closing signal to a flow control valve of the cooling steam system adds a signal output from the flow meter of the low pressure steam system and an output signal of the flow meter of the cooling steam system. And a comparison unit that compares a given value from the setter with the output signal from the addition unit, and a control unit that gives a valve opening / closing signal to the flow control valve of the cooling steam system based on the deviation from the comparison unit. 2. The structure according to claim 1, wherein
A steam turbine cooling device for a single-shaft combined cycle power plant according to the description. 3. A function generator for calculating a cooling steam amount commensurate with a degree of vacuum obtained from a condenser, for a given value of a setter of a cooling steam control system for giving a valve opening / closing signal to a flow control valve of the cooling steam system. 3. The output signal according to claim 2, wherein
A steam turbine cooling device for a single-shaft combined cycle power plant according to the description. 4. A single shaft is provided with a compressor, a gas turbine, a steam turbine high pressure section, a steam turbine medium pressure section, and a steam turbine low pressure section, and high pressure air from the compressor is sent to a combustor where fuel is supplied. In addition, combustion gas is generated, and the generated combustion gas is sent to the gas turbine for expansion work, and exhaust heat of the combustion gas after expansion work is used as a heat source to generate steam by a separate heat recovery steam generator, and the generated steam In the single-shaft combined cycle power plant that performs expansion work in the steam turbine high pressure section, the steam turbine intermediate pressure section, and the steam turbine low pressure section, the steam from the low pressure drum of the exhaust heat recovery boiler is guided to the steam turbine low pressure section. Low pressure steam system, a cooling steam system that is connected to the low pressure steam system and guides steam from a separately placed steam source to the low pressure part of the steam turbine as cooling steam, and the exhaust heat The reheated steam from the reheater of the recovery boiler is provided with a reheated steam system that guides the steam turbine low pressure part through the steam turbine intermediate pressure part, while providing a flow meter in the reheated steam system, When it is detected that the flow meter can cool the low-pressure part of the steam turbine only with reheated steam, a cooling steam control system for providing a valve closing signal to the cooling steam supply valve of the cooling steam system is provided. A steam turbine cooling system for a single-shaft combined cycle power plant. 5. A cooling steam control system for giving a valve closing signal to a cooling steam supply valve of the cooling steam system, wherein the output signal of the flow meter of the reheat steam system and a given value predetermined by a setter are used. When the output signal of the above flowmeter exceeds the output signal,
The steam turbine cooling device for a single-shaft combined cycle power plant according to claim 4, further comprising a comparison calculation unit that generates a valve closing signal. 6. The steam turbine cooling device for a single-shaft combined cycle power plant according to claim 4, wherein a pressure gauge is provided in place of the flow meter provided in the reheat steam system. 7. A single shaft is provided with a compressor, a gas turbine, a steam turbine high pressure section, a steam turbine medium pressure section, and a steam turbine low pressure section, and high pressure air from the compressor is sent to a combustor where fuel is supplied. In addition, combustion gas is generated, and the generated combustion gas is sent to the gas turbine for expansion work, and exhaust heat of the combustion gas after expansion work is used as a heat source to generate steam by a separate heat recovery steam generator, and the generated steam In the single-shaft combined cycle power plant that performs expansion work in the steam turbine high pressure section, the steam turbine intermediate pressure section, and the steam turbine low pressure section, the steam from the low pressure drum of the exhaust heat recovery boiler is guided to the steam turbine low pressure section. Low pressure steam system, a cooling steam system that is connected to the low pressure steam system and guides steam from a separately placed steam source to the low pressure part of the steam turbine as cooling steam, and the exhaust heat A main steam system for guiding the main steam from the superheater of the recovery boiler to the steam turbine high pressure section, the reheater of the exhaust heat recovery boiler, and the steam turbine low pressure section via the steam turbine intermediate pressure section On the other hand, a valve lift detector for detecting the valve opening of the high pressure control valve of the main steam system is provided, and when the valve lift detector detects that the steam turbine low pressure part can be cooled by the main steam alone, A steam turbine cooling device for a single-shaft combined cycle power plant, comprising a cooling steam control system for giving a valve closing signal to a cooling steam supply valve of the cooling steam system. 8. A cooling steam control system for giving a valve closing signal to a cooling steam supply valve of a cooling steam system is predetermined from an output signal of a valve lift detector of a high pressure control valve of a main steam system and a setter. 8. The single-axis combined cycle power generation according to claim 7, further comprising: a comparison calculation unit that produces a valve closing signal when the output signal of the valve lift detector exceeds the output signal of a given value. Plant steam turbine cooling system. 9. The steam turbine cooling device for a single-shaft combined cycle power plant according to claim 7, wherein a flow meter is provided in place of the valve lift detector provided in the steam control valve of the main steam system.