Power plants – Combustion products used as motive fluid
Reexamination Certificate
2001-05-30
2002-05-28
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039190, C060S039182, C060S039780
Reexamination Certificate
active
06393822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combined cycle power generation plant capable of setting a steam generated from an exhaust gas heat recovery boiler to a proper temperature and supplying the steam to a steam turbine plant while supplying the steam generated from the exhaust gas heat recovery boiler to a gas turbine plant as a cooling steam, and also relates to a cooling steam supply method for the combined cycle power generation plant.
2. Description of the Related Art
In recent years, a study and development for obtaining high power and achieving high heat efficiency has been made in a combined cycle power generation plant. With the study and development, there has been made a plan to raise a combustion gas temperature of at least a portion of a gas turbine inlet from a temperature of 1300° C., obtained in the prior art, to a temperature of 1500° C. or more.
In the case of creating a high temperature of the combustion gas of the gas turbine inlet, for example, a high chromium steel has been conventionally used as a component of a gas turbine plant, and part of the compressed air from an air compressor has been supplied to the component of the gas turbine plant as a cooling medium. However, in the prior art as described above, the strength of the component has been close to its limit. For this reason, in order to discover a cooling medium substituting for the compressed air used in the prior art, it has been attempted to study and develop a new cooling medium to be supplied to the components of the gas turbine plant, and steam has been selected as one of the cooling medium. A combined cycle power generation plant which takes advantage of steam cooling has been already disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 5-163960 and 6-93879.
Steam has a higher specific heat as compared with compressed air and is adapted to an absorption of heat generated in components, for example, in a gas turbine stationary blade and a movable blade, accompanying with high temperature of the gas turbine plant. However, each of the gas turbine stationary blade and the movable blade has a structure in which a complicatedly meandering narrow passage is defined in the interior of these blades. For this reason, if impurities such as silica or the like are contained in a steam passing through the above passage, unbalanced cooling occurs because of the possibility of clogging the passage with silica or the like. As a result, these blades are broken down due to thermal strain accompanying the unbalanced cooling. Therefore, cooling steam is required having a high cleanliness factor.
Further, in the case where a cooling steam is supplied to components of the gas turbine plant, it is necessary to provide a steam supply source which can supply a steam of proper temperature. If not so, the component of the gas turbine plant generates an excessive thermal stress resulting from the difference in temperature between a combustion gas as a driving fluid and these components, which difference may result in a possibility that these components are broken down. For this reason, in the components of the gas turbine plant, a steam supply source, which can supply a steam of proper temperature, is securely required.
On the other hand, with a temperature of the gas turbine plant being high, a steam supplied from the exhaust gas heat recovery boiler to a steam turbine plant also has a high temperature. In this case, if the steam temperature is too high, an excessive thermal stress is generated in the steam turbine plant, and as a result, it becomes difficult to maintain a material strength of the components of the steam turbine plant. For this reason, in the steam turbine plant, it is necessary to provide a steam supply source which can supply a steam of a proper temperature.
As described above, in the combined cycle power generation plant, a first high pressure superheater of the exhaust gas heat recovery boiler is selected and set as a steam supply source, taking into consideration the cleanliness of cooling steam, supply of proper temperature steam, and technical matters indispensable to the gas turbine and steam turbine plant. As one example, a combined cycle power generation plan as shown in
FIG. 6
has been already proposed.
The combined cycle power generation plant shown in
FIG. 6
has an arrangement in which a gas turbine plant
1
and a steam turbine plant
2
are combined by a common rotary shaft
3
and an exhaust gas heat recovery boiler
4
is located independently from these plants.
The gas turbine plant
1
includes a generator
5
, an air compressor
6
, a combustor
7
and a gas turbine
8
. Air AR sucked by the air compressor
6
is made into a high pressure compressed air, and is guided to the combustor
7
. In the combustor
7
, a fuel is added to the compressed air so that a combustion gas is generated, and then, the combustion gas is expanded by the gas turbine
8
, thus the generator
5
is driven by the power generated in the above manner.
The steam turbine plant
2
includes a high pressure turbine
9
, an intermediate pressure turbine
10
, a low pressure turbine
11
and a condenser
12
. An exhaust steam, after being expanded by the high pressure turbine
9
, is led to a reheater
13
of the exhaust gas heat recovery boiler
4
and is superheated therein. Then, the exhaust steam is led to the intermediate pressure turbine
10
and is expanded as a reheat steam. Further, the exhaust steam is again expanded by the low pressure turbine
11
, and thereafter, is condensed into a condensate by the condenser
12
. The condensate is supplied as a feed water to the exhaust gas heat recovery boiler
4
via a pump
100
.
Meanwhile, the exhaust gas heat recovery boiler
4
is provided with a third high pressure superheater
14
, the reheater
13
, a second high pressure superheater
15
, a first high pressure superheater
16
, a high pressure evaporator
18
including a high pressure drum
17
, an intermediate pressure superheater
19
, a high pressure economizer
20
, a low pressure superheater
21
, an intermediate pressure evaporator
23
including an intermediate pressure drum
22
, an intermediate pressure economizer
24
, a low pressure evaporator
26
including a low pressure drum
25
, and a low pressure economizer
27
. These components or elements are arranged in order from an upstream side toward a downstream side along a flow of an exhaust gas G of the gas turbine plant
1
, and steam is generated through the heat exchanging operation between each heat exchanger and the exhaust gas G.
Specifically, in the exhaust gas heat recovery boiler
4
, a feed water supplied from the condenser
12
of the steam turbine plant
2
via the pump
100
is preheated by the low pressure economizer
27
and is led to the low pressure drum
25
. Then, by taking advantage of a difference in density of drum water, the feed water is circulated through the low pressure evaporator
26
to generate steam, and the generated steam is supplied to the low pressure turbine
11
via the low pressure superheater
21
.
The low pressure economizer
27
leads part of the feed water, which is diverted (divided) on an outlet side of the economizer
27
, to the low pressure drum
22
by a low pressure pump
28
and the intermediate pressure economizer
24
. Due to a difference in density of drum water, a part of the saturated water is circulated through the low pressure evaporator
23
to generate steam, and then, the generated steam is supplied to the gas turbine plant
1
via the intermediate pressure superheater
19
so as to cool the components of the gas turbine
8
.
Further, the low pressure economizer
27
leads the remaining feed water to the high pressure drum
17
by a high pressure pump
29
and the high pressure economizer
20
. Then, the remaining saturated water is circulated through the high pressure evaporator
18
to generate steam, and the generated steam is led to the first high pressure superheater
16
.
This first high pressure superh
Kabushiki Kaisha Toshiba
Kim Ted
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