Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2001-09-27
2004-01-20
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S806000
Reexamination Certificate
active
06679047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a combined cycle gas turbine system and, more particularly, to a combined cycle gas turbine system in which the temperature and flow rate of cooling steam are efficiently controlled and the heating of fuel and the cooling of gas turbine blade cooling air are carried out by steam generated at a waste heat recovery boiler.
2. Description of the Prior Art
FIG. 10
is a diagram of a steam cooled type combined cycle gas turbine system in the prior art. In
FIG. 10
, the prior art steam cooled gas turbine system is constructed by a gas turbine
8
, a waste heat recovery boiler
9
and a steam turbine
29
. In the gas turbine
8
, suction air is taken into a compressor
2
to be compressed to a predetermined pressure, and while the compressed air is partially used for cooling a gas turbine blade, the greater part thereof is led into a combustor
3
to be mixed with fuel
7
for generation of a high temperature gas. The high temperature gas enters a turbine
6
to expand for work, and the turbine output, after deduction of the compressor output, is converted into electric power at a generator
1
. On the other hand, outlet steam of a high pressure turbine
21
flowing through piping
101
is partially taken to be supplied into the turbine
6
for cooling the gas turbine blade via the cooling steam supply piping
101
. This steam is heated by cooling a steam cooled blade
51
and is recovered into an inlet of an intermediate pressure turbine
22
via cooling steam recovery piping
102
. Thus, for cooling the gas turbine blade, the air bled from the compressor
2
and a portion of the outlet steam of the high pressure turbine
21
are used.
While outlet air of the compressor
2
is partially used for blade cooling in the turbine
6
, this air, being of a high temperature, is cooled to a predetermined temperature at a blade cooling air cooler
4
a
using a cooling fan
5
and is then used for the turbine blade cooling. Thus, the air so led from the compressor
2
is first cooled at the blade cooling air cooler
4
a
using the cooling fan
5
to be then supplied into the turbine
6
.
In the waste heat recovery boiler
9
, outlet steam of a low pressure turbine
23
is converted into water from steam at a condenser
25
. Then, the water is pressurized at a feed water pump
26
and heated at a feed water heater
10
to become saturated water. This saturated water is separated into three systems of water. The first one becomes saturated steam at a low pressure evaporator
11
, becomes superheated steam at a low pressure superheater
15
and is then supplied to an inlet of the low pressure turbine
23
. The second one is pressurized to a predetermined pressure at an intermediate pressure pump
28
, becomes saturated water at an intermediate pressure economizer
12
, becomes saturated steam at an intermediate pressure evaporator
14
, becomes superheated steam at an intermediate pressure superheater
16
and is then supplied to an inlet of a reheater
20
. And the third one is pressurized to a predetermined pressure at a high pressure pump
27
, becomes saturated water at a first high pressure economizer
13
and a second high pressure economizer
17
, becomes saturated steam at a high pressure evaporator
18
, becomes superheated steam at a high pressure superheater
19
and is then led into the high pressure turbine
21
. The mentioned superheated steam enters the high pressure turbine
21
, the intermediate pressure turbine
22
and the low pressure turbine
23
, respectively, to expand for generating an output, and this output is converted into electric power at a generator
24
.
With respect to the abovementioned cooling by steam, it is impossible to use the steam in a quantity in excess of that of the steam obtainable at the outlet of the high pressure turbine
21
. Hence, in order to secure a spare quantity of the available steam, it is preferable to reduce the flow rate of the cooling steam to the extent possible. Also, if the cooling steam is made less in quantity, it becomes possible to control the temperature of the steam, after being used for cooling, with less variation in the quantity of the cooling steam. Especially, if the temperature of the cooling steam heated by cooling is maintained to a predetermined level, it will not only enhance the reliability and life of the cooled blade, rotor, pipings, etc. of the gas turbine, but it will also ensure an operation that does not damage the enhanced combined efficiency. In order to reduce the quantity of the cooling steam, it is necessary to reduce the temperature of the cooling steam.
Thus, while the temperature of the cooling steam is necessary to be maintained lower for enhancing the reliability of the cooled blade or the like, in the system shown in
FIG. 10
, the cooling steam supply temperature is decided by the outlet conditions of the high pressure turbine
21
, and it is difficult to further reduce the cooling steam temperature in this system.
Also, the air bled from the compressor for cooling the gas turbine blade is once cooled at the blade cooling air cooler
4
a
using the cooling fan
5
to be supplied into the turbine
6
, as mentioned above, and the heat obtained by such cooling is discharged outside without use. This causes a reduction in the thermal efficiency (gas turbine efficiency and combined efficiency) of the gas turbine and of a combined cycle system using this gas turbine. Moreover, the fuel
7
is supplied into the combustor
3
without being heated (preheated).
SUMMARY OF THE INVENTION
In view of the mentioned problems in the prior art, therefore, it is an object of the present invention to provide a steam cooled type combined cycle gas turbine system in which the system is made such that the cooling of a turbine blade is done by steam partially taken from an outlet of a high pressure turbine, and the temperature of this steam is adjusted by cooling water taken from a waste heat recovery boiler or by water taken from a condenser. A cooling steam supply system is made such that a moving blade, a stationary blade and a combustor transition piece are supplied with steam via their respective separate systems so that the steam supplied to the stationary blade and the combustor transition piece may be of a temperature higher than that supplied to the moving blade to thereby obtain a higher effect of cooling by steam in the respective steam systems. Preheating of fuel is done to thereby enhance the combined efficiency.
In order to achieve the abovementioned object, the present invention provides the following inventions (1) to (8).
(1) A combined cycle gas turbine system comprises a steam turbine having a high pressure turbine, an intermediate pressure turbine and a low pressure turbine. A condenser condenses exhaust steam of the low pressure turbine of the steam turbine. A gland steam condenser is connected to the condenser. A gas turbine has a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor and a turbine for expanding high temperature combustion gas coming from the combustor for driving a generator. A cooling steam system cools the combustor and a blade of the turbine and a waste heat recovery boiler has components of a feed water heater, an intermediate pressure superheater, a reheater, etc., and is fed with exhaust gas of the gas turbine so that condensed water coming from the condenser via the gland steam condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. The cooling steam system is constructed to comprise a moving blade cooling system having a water spray rate control valve for leading high pressure water from the feed water heater, a demineralizer connected to the water spray rate control valve and a water sprayer connected to the demineralizer for spraying the high pressure water into a passage for leading cooling
Hyakutake Yoshinori
Sugishita Hideaki
Uematsu Kazuo
Casaregola Louis J.
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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