JP2002221007A - Thermal power generation plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal power generation plant with improved high output and high plant thermal efficiency. SOLUTION: This thermal power generation plant is provided with an existing steam turbine plant 26 and is newly provided with a steam turbine 27 capable of supplying high-temperature and high-pressure steam to a high-pressure turbine of the steam turbine plant 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal power plant, and more particularly, to a thermal power plant in which an existing turbine plant is combined with a new turbine.

[0002]

2. Description of the Related Art In recent thermal power generation plants, there is a demand for a high-efficiency plant that effectively utilizes energy to increase the output, and in response to these demands, an existing steam turbine plant (conventional) is called repowering. The plant is combined with a newly installed gas turbine plant, and the combined cycle power plant of the exhaust heat recovery type and the combined cycle power plant of the exhaust heat refueling type are operated as practical units.

As shown in FIG. 8, the former exhaust heat recovery type combined cycle power plant is provided with a newly installed gas turbine plant 1 as a so-called topping cycle, and a newly installed waste heat recovery boiler 2 as a so-called bottoming cycle. And a steam turbine plant 3.

The gas turbine plant 1 comprises an air compressor 4, a gas turbine combustor 5, a gas turbine 6, and a generator 7.
The air sucked by the air compressor 4 is compressed to high pressure, fuel is supplied to the gas turbine combustor 5 together with the high-pressure air to generate combustion gas, and the generated combustion gas is expanded by the gas turbine 6. The generator 7 is driven by the power (rotation torque) generated at the time of expansion.

The exhaust heat recovery boiler 2 uses the exhaust gas (gas turbine exhaust) supplied from the gas turbine 6 of the gas turbine plant 1 as a heat source, and
Is supplied to the steam turbine plant 3 to perform heat exchange as a heated source to generate steam.

On the other hand, the steam turbine plant 3 includes a high-pressure turbine 8, a medium-pressure turbine 9, a first low-pressure turbine 10, a second low-pressure turbine 11, and a generator 12. After performing the expansion work, the heat is returned to the reheater (not shown) of the exhaust heat recovery boiler 2 as turbine exhaust and heat is again applied thereto. The turbine exhaust after the expansion work is supplied to the first low-pressure turbine 10 and the second low-pressure turbine 1.
1 to perform expansion work again, and the generator 12 is driven by power generated during the expansion work. The turbine exhaust that has completed expansion work in each of the first low-pressure turbine 10 and the second low-pressure turbine 11 is supplied to the exhaust heat recovery boiler 2 as feedwater via a condenser, a feedwater heater, or the like (both not shown). Will be returned.

[0007] As shown in FIG. 9, when the exhaust gas from the gas turbine 6 of the gas turbine plant 1 is supplied to the boiler 13, the latter combined-cycle power generation plant of the exhaust gas recirculation type uses a forced air blower (FDF). ), Fuel is added to the boiler 13 to reburn the exhaust gas from the gas turbine 6, and a part of the combustion gas is supplied to the high-pressure gas feed water heater 24 and the low-pressure gas feed water heater 23 to heat the feed water. Is what you do. That is, this type of power plant includes a newly-installed gas turbine plant 1, a high-pressure gas feed water heater 24, and a low-pressure gas feed water heater 2
3. Chimney 25, existing boiler 13, reheater 14, high-pressure turbine 8, medium-pressure turbine 9, low-pressure turbine 15, generator 16, condenser 17, condensate pump 18, low-pressure water supply of steam turbine plant 3 This is a combination of a heater 19, a deaerator 20, a water supply pump 21, and a high-pressure water heater 22.

[0008] The combined cycle power plant of the exhaust gas reburning type having such a configuration assists the combustion by adding fuel to the exhaust gas supplied from the gas turbine 6 of the newly installed gas turbine plant 1 to the existing boiler 13, and a part thereof is assisted. It is used for generating steam and the rest for heating feedwater.

The steam generated from the boiler 13 performs expansion work in the high-pressure turbine 8, is heated as turbine exhaust by the reheater 14, and is supplied as reheated steam to the medium-pressure turbine 9 and the low-pressure turbine 15, respectively, for expansion. It does work and drives the generator 16 with the power generated by the expansion work.

The turbine exhaust leaving the low pressure turbine 15 is:
The condensed water is condensed by the condenser 17 to be condensed water, and the condensed water is pressurized by the condensate pump 18. , High pressure feed water heater 22, high pressure gas feed water heater 24
To the boiler 13 after deaeration and preheating (regeneration).
To return to. In addition, the high pressure feed water heater 22,
As the heat source of the low-pressure feed water heater 19, extracted steam from the medium-pressure turbine 9 is used, and the high-pressure gas feed water heater 24 and the low-pressure gas feed water heater 23 use combustion gas obtained by burning the exhaust gas from the gas turbine 6 with the boiler 13. Is used as a heat source, and after preheating the feed water, it is discharged from the chimney 25 to the atmosphere.

As described above, an exhaust heat recovery type combined cycle power generation plant and an exhaust gas reburning type combined cycle power generation plant are used. And the thermal efficiency of the plant was increased. In addition, this type of power plant has a high quality fuel such as liquefied natural gas (LN) in consideration of pollution problems such as NOx.
G) is used.

[0012]

The existing steam turbine plant 3 shown in FIG. 8 and FIG.
It is designed based on handling supercritical vapor state quantities of kg / cm ² or more and temperature of 538 ° C. or more.

However, the temperature of the exhaust gas discharged from the newly installed gas turbine plant 1 is about 600 ° C. to 700 ° C. For this reason, the state quantity of the steam generated from the exhaust heat recovery boiler 2 is significantly different from the design plan value of the existing steam turbine plant 3, and the performance of the existing steam turbine plant 3 is exhibited as designed. Is difficult.

When a new gas turbine plant 1 is combined with an existing steam turbine plant 3, the existing boiler 13 and a pure water device (not shown) for supplying water are removed, and the gas turbine is replaced with a gas turbine. It is necessary to install new equipment such as the plant 1 and the control device, so that much labor is required for workers at the site.

The existing boiler 13 uses coal, heavy oil, or the like as a fuel. However, if a new gas turbine plant 1 is installed, a high-quality fuel, for example, LNG is required, and the fuel cost increases.

The present invention has been made in view of the above circumstances, and a new steam turbine is installed in front of an existing steam turbine plant so that a steam of a state quantity corresponding to a supercritical condition which is a design condition can be supplied to an existing steam turbine plant. It is an object of the present invention to provide a thermal power plant that is selected as a turbine and that achieves higher output and higher plant thermal efficiency.

[0017]

In order to achieve the above object, a thermal power plant according to the present invention has an existing steam turbine plant installed therein, and the steam turbine plant has the same structure as the steam turbine plant. The steam turbine capable of supplying high-temperature, high-pressure steam that satisfies the inlet steam condition of the high-pressure turbine is newly installed on the upstream side of the lower plant.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, the newly installed steam turbine is a back pressure turbine, as described in claim 2.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above-mentioned object, as described in claim 3, the back pressure turbine is installed separately in a first back pressure turbine and a second back pressure turbine.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, as described in claim 4, in the back pressure turbine, the first stage is configured as a Curtis stage, and the rest is configured as a normal stage.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, as set forth in claim 5, the Curtiss stage has a speed ratio U / C of 0.2 ≦ C, where C is the theoretical steam speed and U is the peripheral speed of the blade. U / C ≦ 0.
4 is set.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above-mentioned object, as described in claim 6, the normal paragraph section has a speed ratio U / C of 0.4 when the theoretical steam speed is C and the peripheral speed of the blade is U. ≦ U / C ≦ 0.
6 is set.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, as described in claim 7, the back pressure turbine has a Ni content of 3 in a turbine component.
5% or more of the Ni-based alloy steel is used.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, the newly installed steam turbine is a high-speed steam turbine.

Further, the thermal power plant according to the present invention comprises:
In order to achieve the above object, an existing steam turbine plant is installed as described in claim 9,
A high-pressure, high-pressure, high-pressure steam that satisfies the inlet steam conditions of the high-pressure turbine is installed in the high-pressure turbine of the steam turbine plant. The steam turbine plant further includes a reheater that joins and heats the turbine exhaust of the back-pressure turbine and heats the combined heat to supply the reheated steam to a medium-pressure turbine of the steam turbine plant.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a thermal power plant according to the present invention will be described with reference to the drawings and reference numerals attached to the drawings.

FIG. 1 is a schematic system diagram showing a first embodiment of a thermal power plant according to the present invention.

In the thermal power plant according to the present embodiment, as a repowering of the existing steam turbine plant (conventional turbine) 26, the steam turbine plant 26 with the inlet steam condition upstream of the existing steam turbine plant 26 is used. Back pressure turbine 2 at a higher temperature and pressure higher than the above and the turbine exhaust conditions are matched with the inlet steam conditions of the existing steam turbine plant 26.
7 is installed together with the generator 28 as a new turbine.

A steam turbine plant 26 as an existing turbine includes a high-pressure turbine 29, a medium-pressure turbine 30, a reheater 31, a first low-pressure turbine 32, and a second low-pressure turbine 3
3. A configuration including a generator 34 is provided.

In the thermal power plant having such a configuration, the high-temperature and high-pressure steam generated in the boiler 35 is
The back pressure turbine 27 performs expansion work, and the power generator 28 is driven by power (rotation torque) generated during the expansion work.

Turbine exhaust from the back pressure turbine 27 is supplied to a steam turbine plant 2 as an existing turbine.
The high-pressure turbine 29 flows into the high-temperature and high-pressure steam conditions required by the high-pressure turbine 29.

The turbine exhaust having completed the expansion work in the high-pressure turbine 29 is heated in the reheater 31 and the reheated steam is expanded in the medium-pressure turbine 30, and then the first low-pressure turbine 32 and the second low-pressure turbine The turbine 33 also performs expansion work, and the generator 34 is driven by the power generated at that time.

As described above, in the present embodiment, the back pressure turbine 27 as a new turbine is installed in the steam turbine plant 26 as an existing turbine, and steam of higher temperature and pressure generated in the boiler 35 than the conventional one is newly installed. The expansion work is performed by the back pressure turbine 27 to drive the generator 28, and the high-temperature and high-pressure turbine exhaust from the newly installed back pressure turbine 27 is supplied to the existing steam turbine plant 26 as the turbine to perform the expansion work. As a result, high-temperature and high-pressure steam can be supplied to the existing steam turbine plant 26, and the existing steam turbine plant 26 can be operated at the highest efficiency point to realize operation with high output and high plant thermal efficiency. Can be.

FIG. 2 is a schematic system diagram showing a second embodiment of the thermal power plant according to the present invention.

The thermal power plant according to this embodiment heats the turbine exhaust from the back-pressure turbine 27 installed as a new turbine and the turbine exhaust from the high-pressure turbine 29 in the steam turbine plant 26 as an existing turbine, and reheats it. It is provided with a reheater 31 for supplying the intermediate pressure turbine 30 as hot steam.

As described above, in the present embodiment, the turbine exhaust of the back pressure turbine 27 as the newly installed front turbine and the turbine exhaust of the high pressure turbine 29 in the steam turbine plant 26 as the existing turbine are merged. Since the reheater 36 is provided to reheat the turbine exhaust thus heated and supply the reheated steam to the intermediate pressure turbine 30, the steam turbine plant 26 as an existing turbine has a high temperature
High-pressure steam can be supplied, and the existing steam turbine plant 26 can be operated at the highest efficiency point to realize high output and high plant thermal efficiency.

If the steam condition flowing into the existing steam turbine plant 26 is a high temperature of about 600 ° C. and the steam condition flowing into the back pressure turbine 27 as the new turbine is even higher, the back pressure Turbine 2
No. 7 requires the use of Ni-based alloy steel having a Ni content of 35% or more for turbine components such as nozzles, rotors, and turbine blades. As shown in FIG. 6, the Ni-based alloy steel having a Ni content of 35% or more is based on the fact that a high-temperature creep strength higher than that of a conventional heat-resistant steel can be secured.

When the steam condition flowing into the existing steam turbine plant 26 is a high temperature of about 600 ° C. and the steam condition flowing into the back pressure turbine 27 as the new turbine is even higher, for example, As shown in FIG. 3, a back pressure turbine 27 as a newly installed turbine is provided with a first back pressure turbine 27a having a first generator 28a,
The second back pressure turbine 27b provided with the second generator 28b may be installed as two units.

FIG. 4 is a schematic system diagram showing a third embodiment of the thermal power plant according to the present invention.

In the thermal power plant according to the present embodiment, a back pressure turbine 27 is installed as a new turbine, a steam turbine plant 26 is installed as an existing turbine, and the first stage of the back pressure turbine 27 as a new turbine is installed. The section ST1 is a Curtiss stage (high-load blade section), and the rest is a normal paragraph section ST2.

In the Curtiss stage (high-load blade stage), when the theoretical steam speed is C and the peripheral speed of the blade is U, the speed ratio U / C
Is set in the range of 0.2 ≦ U / C ≦ 0.4, as shown in FIG. The remaining normal paragraph ST2 sets the speed ratio U / C to 0.4 ≦ U / C ≦ 0,0 as shown in FIG.
6 is set. The reason why the first stage section ST1 of the newly installed back pressure turbine 27 is a Curtiss stage (high-load blade stage) is as follows.
Assuming that the thermal head is HR, the theoretical steam velocity C is C = 91.
Since it is 5 ° (HR), it is based on the fact that the thermal head HR can be increased if the blade peripheral speed is the same.

As described above, in this embodiment, the first stage ST1 of the back pressure turbine 27 installed as a newly installed turbine is a Curtis stage, and the rest is a normal stage ST2. When the ratio U / C is 0.2 ≦ U / C
≦ 0.4, and the speed ratio U / C of the remaining normal paragraph ST2 was set within the range of 0.4 ≦ U / C ≦ 0.6 to reduce the number of turbine stages. , High-temperature and high-pressure steam can be supplied to the existing steam turbine plant 26.
At a high efficiency point to achieve high output and high plant thermal efficiency.

FIG. 7 is a schematic system diagram showing a fourth embodiment of the thermal power plant according to the present invention.

In the thermal power plant according to the present embodiment, the high-speed steam turbine 37 is installed as a new turbine, the steam turbine plant 26 is installed as an existing turbine, and the high-speed steam turbine 37 as the new turbine is rotated at a rotational speed. Is set in the range of 5000 to 6300 rpm, and a speed reducer 38 is provided between the power generator 28 and the generator 28.

As described above, in this embodiment, the high-speed steam turbine 37 is installed as a new turbine, the rotation speed of the high-speed steam turbine 37 is set in the range of 5000 to 6300 rpm, and the number of turbine stages is reduced. High-temperature and high-pressure steam can be supplied to the existing steam turbine plant 26, and the existing steam turbine plant 26 can be operated at a high efficiency point to achieve high output and high plant thermal efficiency.

[0046]

As described above, in the thermal power plant according to the present invention, a steam turbine as a newly installed turbine is selected so that high-temperature and high-pressure steam can be supplied to an existing steam turbine plant. Therefore, the existing steam turbine plant can be operated at a high efficiency point, and an operation with high output and high plant thermal efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing a first embodiment of a thermal power plant according to the present invention.

FIG. 2 is a schematic system diagram showing a second embodiment of the thermal power plant according to the present invention.

FIG. 3 is a schematic system diagram showing a modification of the second embodiment of the thermal power plant according to the present invention.

FIG. 4 is a schematic system diagram showing a third embodiment of the thermal power plant according to the present invention.

FIG. 5 is a graph of blade efficiency showing the relationship between turbine stage efficiency and speed ratio.

FIG. 6 is a graph showing the relationship between creep rupture stress and temperature, comparing the strength of a conventional heat-resistant steel with that of a Ni-based alloy steel.

FIG. 7 is a schematic system diagram showing a fourth embodiment of a thermal power plant according to the present invention.

FIG. 8 is a schematic system diagram showing a conventional combined cycle power plant.

FIG. 9 is a schematic system diagram showing another conventional combined cycle power plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas turbine plant 2 Exhaust heat recovery boiler 3 Steam turbine plant 4 Air compressor 5 Gas turbine combustor 6 Gas turbine 7 Generator 8 High pressure turbine 9 Medium pressure turbine 10 First low pressure turbine 11 Second low pressure turbine 12 Generator 13 Boiler 14 Reheater 15 Low-pressure turbine 16 Generator 17 Condenser 18 Condenser pump 19 Low-pressure feedwater heater 20 Deaerator 21 Feedwater pump 22 High-pressure feedwater heater 23 Low-pressure gas feedwater heater 24 High-pressure gas feedwater heater 25 Chimney 26 Steam turbine plant 27 Back pressure turbine 27a First back pressure turbine 27b Second back pressure turbine 28 Generator 28a First generator 28b Second generator 29 High pressure turbine 30 Medium pressure turbine 31 Reheater 32 First low pressure turbine 33 2 Low-pressure turbine 34 Generator 35 Boiler 37 High-speed steam Turbine 38 speed reducer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01K 7/10 F01K 7/10 13/02 13/02 G

Claims (9)

[Claims] 1. An existing steam turbine plant is installed, and a steam turbine capable of supplying high-temperature, high-pressure steam satisfying inlet steam conditions of the high-pressure turbine to a high-pressure turbine of the steam turbine plant is provided upstream of the steam turbine plant. A thermal power plant that is newly installed on the side. 2. The thermal power plant according to claim 1, wherein the newly installed steam turbine is a back pressure turbine. 3. The thermal power plant according to claim 2, wherein the back pressure turbine is divided into a first back pressure turbine and a second back pressure turbine. 4. The thermal power plant according to claim 2, wherein the first stage of the back pressure turbine is formed in the Curtiss stage, and the rest is formed in the ordinary stage. 5. The Curtis stage has a theoretical steam velocity of C,
When the peripheral speed of the wing is U, the speed ratio U / C is 0.2 ≦ U
The thermal power plant according to claim 4, wherein / C is set in a range of 0.4 or less. 6. The normal paragraph section is defined as a theoretical vapor velocity of C,
When the peripheral speed of the blade is U, the speed ratio U / C is 0.4 ≦ U
5. The thermal power plant according to claim 4, wherein /C≦0.6. 7. The thermal power plant according to claim 2, wherein the back pressure turbine uses a Ni-based alloy steel having a Ni content of 35% or more for a turbine component. 8. The thermal power plant according to claim 1, wherein the newly installed steam turbine is a high-speed steam turbine. 9. An existing steam turbine plant is installed, and a back-pressure turbine capable of supplying high-temperature, high-pressure steam satisfying the inlet steam condition of the high-pressure turbine to the high-pressure turbine of the steam turbine plant is provided upstream of the lower plant. A reheater that combines and heats the turbine exhaust of the high-pressure turbine and the turbine exhaust of the back-pressure turbine, and supplies it as reheated steam to the medium-pressure turbine of the steam turbine plant. A thermal power plant.