JPS5838308A - Gas turbine-steam turbine composite plant - Google Patents

Abstract

PURPOSE:To prevent erosion of a moving vane through evaporation of moisture in wet steam of a steam turbine, by a method wherein a part of gas from a waste heat boiler at an exhaust gas flow path of a gas turbine is introduced to the stationary vane of the low-pressure stage of the gas turbine. CONSTITUTION:A composite cycle consists of a gas turbine 4 and steam turbines 13, 17 and 19. A waste heat boiler 5 is installed to the exhaust gas flow path of the gas turbine 4, a part of waste heat gas 100, being exhausted from a chimney 6 of the boiler 5 and having high calory, is sucked through a waste heat gas outlet 103 by a suction blower 102, it is introduced to a stationary vane of a low-pressure trubine 19 located at a wet steam area, and it is exhausted to the chimney 6 after heating the stationary vane. This enables to reduce wetness of a low-pressure stage of a steam turbine, and permits the prevention of erosion of a moving vane. Additionally, the reduction in energy loss due to wet steam permits the improvement of a plant efficiency of a turbine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low pressure stage of a steam turbine, and more particularly to an improvement in a low pressure turbine operated in a wet steam region in a gas turbine, a steam turbine, or a combined cycle steam turbine.

A low-pressure turbine of a thermal power plant is operated in a wet steam region in two to three stages before the final stage by repeating expansion within the turbine. When a turbine is operated in such humid steam, the turbine rotor blades are eroded and damaged by water droplets in the humid steam. Furthermore, it causes many problems in terms of reliability and performance, such as a decrease in turbine internal efficiency due to moisture loss.

Conventionally, to prevent erosion, techniques such as protecting the rotor blades with materials with good erosion resistance or using centrifugal force to remove water droplets attached to the rotor blades from the flow path have been used to prevent the harmful effects of wet steam flow. are dealing with.

An object of the present invention is to prevent rotor blades of a low-pressure turbine operated in wet steam, reduce energy loss due to wet steam, and improve turbine stage efficiency and plant efficiency.

The target area is the gas turbine/steam turbine combined cycle, which has recently been attracting attention for improving plant efficiency. Cycle waste heat is used to heat the stationary blades of the steam turbine stage that operates in the wet steam region. The purpose is to suppress the amount of moisture in the turbine flow path.

Embodiments of the present invention will be described with reference to the drawings.

The first example is a gas turbine and a steam turbine combined cycle.
As shown in the figure. Air compressed by compressor 1 and fuel 2 are transferred to combustor 3
The gas turbine 4 is driven and the generator 22 takes the load. The waste heat gas expanded by the gas turbine 4 and having a high calorific value is led to the boiler 5, where the heat is recovered by the boiler feed water, and then discharged from the chimney 6.

On the other hand, boiler heat exchanger tube 11 by boiler feed pump 10!
The generated high-temperature and high-pressure steam 12 is expanded in the high-pressure turbine 13, and the steam 14 from the expansion stage of the high-pressure turbine 13 becomes reheated steam 16 in the boiler reheater 15, and expanded in the low-pressure turbine 19 from the intermediate-pressure turbine 17. It is configured to drive a generator 22' to obtain electrical output.

In a turbine plant having such a configuration, the main steam 18 that has entered the stage of the low-pressure turbine 19 is repeatedly expanded within the stage, and is led to the condenser 21 via the exhaust chamber 20. During the process in which this steam expands within the stages, generally two to three stages before the final stage are operated in a wet steam region. For this reason,
The rotor blades are damaged by erosion due to water droplets contained in the wet steam. On the other hand, it causes energy loss due to wet steam, lowers stage efficiency, and ultimately deteriorates power plant efficiency. In order to suppress the amount of moisture in the turbine stage inner passage, a part of the waste heat gas 100 having a high calorific value discharged from the chimney 6 of the boiler 5 is passed through a waste heat gas outlet 103 provided in the chimney. The steam is taken out by the suction blower 102, guided to the turbine stationary blades in the wet steam region, and after heating the stationary blades is discharged to the chimney. Furthermore, if the waste heat gas is corrosive, clean air 104 shown in FIG. 2 can be introduced to the turbine stator blades via a heat exchanger 103' as a gas for heating the turbine stator blades.

A method of heating stator blades in a turbine stage will be explained with reference to FIGS. 3 and 4. FIG.

The rotor blade 51.51' which is a rotating body is a disk, 52.52
', rotor shaft 53, stationary body 11s4.5
Diaphragm 55°55' supporting 4', 56.5
6' and a casing 57.

The waste heat gas 100 having a high calorific value enters the diaphragm outer peripheral pocket 31 through the inlet pipe 30.degree. At this time, each stator blade is heated by the high-temperature waste gas guided into the hollow part 32 of the stator blade 54, and the moisture in the steam that adheres to the surface of the stator blade and forms a water film is evaporated. In this way, the gas that heated the stator blades is collected in the inner peripheral pocket 33 of the diaphragm, and is heated in the hollow part 32 of the stator blade 54a.
The exhaust pipe 35 is connected to the suction blower 102 as exhaust gas 101 through the exhaust pipe 35a. Note that the hollow parts 32, 32a
An internal structure (not shown) for promoting heat transfer to the stationary blades 54, 54a is provided.

In the gas turbine steam turbine combined cycle of the present invention, the humidity in the steam can be reduced by heating the stationary blades in the wet steam region of the low pressure stage of the steam turbine, and the turbine movement due to water droplets in the wet steam can be reduced. It is possible to prevent r-o-john. Moreover, energy loss due to wet steam can be reduced, and the flint efficiency of the turbine can be improved.

In the present invention, the amount of waste heat gas required to heat the stationary blades of the stage in the wet steam region can be calculated using the following equation. G
g=(Gs-X-r)/(GpgΔt), where Gg=
Amount of waste heat gas, Gpg=specific heat of waste heat gas at constant pressure, Δt=temperature required for heating, Gs 22-stage smoke amount X=humidity.

For example, in a power generation plant with a steam turbine with an electric output of 250 MW, the steam temperature υ
The amount of waste gas required to reduce the temperature by about 2 inches is about the same amount as the amount of waste gas discharged from the boiler, and the humidity in the steam turbine stage can be reduced without requiring much power for the suction blower 102. can be destroyed. Moreover, since there is an inversely proportional relationship between an increase or decrease in humidity and an increase or decrease in stage efficiency, the amount of reduction in steam humidity according to the present invention is directly linked to the amount of improvement in stage efficiency. Generally speaking, a decrease of 1 inch in humidity means 1% of the stage efficiency.
Since the electric output of the steam turbine increases, the plant efficiency shown in FIG. 1 improves.

The above effect will be specifically explained with reference to FIG.

Conventionally, expansion is repeated within the stage from low-pressure turbine inlet condition A, until the turbine final stage exhaust condition B is reached. In this expansion process, under the inlet condition C2 of the second stage stator blade before the final stage, 2
% humidity, and the humidity at the final stage stator blade inlet condition is 5.
It is Chi. In such a step thermal expansion diagram, 0 point is 07
The stator blade is heated to a point D' to reduce the humidity, and further heated to E at the final stage stator blade inlet D' to reduce the humidity and expand to the final stage rotor blade outlet F. As a result, by utilizing a quantity of waste gas of several inches, it is possible to reach a point F' in which the steam wetness is reduced by 3 to 5 inches compared to point B, which is the conventional final point of expansion. Therefore, it is possible to prevent water droplets contained in wet steam and water droplets generated in the stator blade flow path, and to prevent erosion of the final stage rotor blade.

Furthermore, when the humidity is reduced, energy loss due to wet steam is reduced, making it possible to improve the turbine internal efficiency, and thus the plant efficiency.

As described above, the present invention can provide a gas turbine/steam turbine combined cycle with high efficiency and reliability.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a gas turbine steam turbine combined cycle of the present invention, FIG. 2 is a schematic diagram of an air preheater of the present invention,
3 and 4 are structural diagrams of turbine stationary blades of the present invention in a steam turbine stage, and FIG. 5 is an i-s diagram showing an embodiment of the present invention.
It is a line diagram. 4...'i'1xp-hin, 5 river waste heat boiler, 6...
・Chimney, 19...Steam turbine low pressure section, 1oo...
Waste heat gas, ¥ 1 item 0 / 4 Figure 63 Atsushi Figure 4

Claims (1)

[Claims] 1. In a gas turbine/steam turbine complex plant, a part of the gas discharged from the waste heat boiler installed in the exhaust gas flow path of the gas turbine is guided to a low-pressure turbine that operates on the wet steam of the steam turbine to generate wet steam. A gas turbine/steam turbine combined plant characterized by being configured to serve as a heating source for evaporating moisture inside.