Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
1999-04-28
2001-06-12
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S730000
Reexamination Certificate
active
06244039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combined cycle plant comprising a heat exchanger which uses steam as a high temperature side working medium for recovering heat into compressed air or gas turbine fuel to be supplied into a gas turbine.
2. Description of the Prior Art
As a first prior art example for carrying out this type of heat recovery, a regenerative type gas turbine combined cycle plant will be described with reference to FIG.
4
.
In a combined cycle plant formed using a regenerative type gas turbine shown in
FIG. 4
, a regenerative type gas turbine
01
constitutes a topping cycle of the combined cycle plant and comprises a compressor
1
, a generator
2
connected to the compressor
1
via a shaft, a regenerator
3
for recovering heat into compressed air discharged from the compressor
1
, a combustor
4
for burning fuel (supplied from outside the cycle plant) using heated air supplied through the regenerator
3
, a turbine
5
operated by combustion gas sent from the combustor
4
, an exhaust gas duct
6
for supplying therethrough exhaust gas from the outlet of the turbine
5
to a heating side of the regenerator
3
, and an exhaust gas duct
7
for supplying therethrough the exhaust gas from the regenerator
3
to a waste heat recovery boiler
02
.
In the waste heat recovery boiler
02
supplied with the exhaust gas from the turbine
5
, heat recovery is done sequentially at a high pressure steam generator
29
, an intermediate pressure steam generator
28
and a low pressure steam generator
27
to generate a saturated steam of high pressure, intermediate pressure and low pressure, respectively.
The high pressure saturated steam is led into a high pressure superheater
33
via a high pressure steam pipe
34
to be elevated in temperature to a predetermined level, and is then led into a high pressure turbine
22
of a steam turbine plant constituting a bottoming cycle of the combined cycle via a high pressure steam pipe
32
to expand there to generate power.
On the other hand, the intermediate pressure saturated steam is led through an intermediate pressure steam pipe
31
to be mixed on the way with steam from the outlet of the high pressure turbine
22
and to be elevated in temperature to a predetermined level at a reheater
26
, and is then led into an intermediate pressure turbine
23
to expand there to generate power.
Also, the low pressure saturated steam is led through a low pressure steam pipe
30
to be mixed on the way with steam from the outlet of the intermediate pressure turbine
23
, and is then led into a low pressure turbine
24
to expand there to generate power. The steam is thereafter condensed into water at a condenser
25
to be then supplied into the waste heat recovery boiler
02
.
A second prior art example for carrying out this type of heat recovery will be described with reference to FIG.
5
.
In a steam cooled type gas turbine shown in
FIG. 5
, the system is so constructed that steam from a high pressure turbine outlet is directly used for cooling of the gas turbine blades, and is then recovered into an intermediate pressure turbine. Meanwhile, air from compressor outlet is used for cooling of a combustor tail tube.
That is, in
FIG. 5
, numeral
01
designates a gas turbine, numeral
02
designates a waste heat recovery boiler, numeral
57
designates a high pressure turbine, numeral
58
designates an intermediate pressure turbine and numeral
59
designates a low pressure turbine. In the gas turbine
01
, air taken into a compressor
55
is compressed to a predetermined pressure, and this compressed air from the compressor
55
is mixed with fuel for combustion at a combustor
56
. In this process, the flow rate of the fuel is adjusted so as to attain a predetermined at the inlet of a turbine
54
.
Combustion gas of high temperature and high pressure generated at the combustor
56
is expanded at the turbine
54
to work for power generation at a generator
70
, and exhaust gas from the turbine
54
is supplied into the waste heat recovery boiler
02
via an exhaust gas duct
60
.
High pressure exhaust steam from the outlet of the high pressure turbine
57
is supplied into the turbine
54
as cooling steam for cooling of the stationary blades and the moving blades thereof via a blade cooling steam supply pipe
61
. The cooling steam heated through this cooling process is supplied into the inlet of the intermediate pressure turbine
58
via a blade cooling steam recovery pipe
62
.
In the waste heat recovery boiler
02
, high pressure steam generated at a high pressure drum
53
is led into the high pressure turbine
57
via a high pressure steam pipe
63
to expand there to generate power.
Outlet steam from the high pressure turbine
57
is bifurcated so that a first portion is led as blade cooling steam for the stationary blade and moving blade of the turbine
54
via the blade cooling steam pipe
61
, as mentioned above, and so that a second portion is led into a reheater
74
of the waste heat recovery boiler
02
.
Intermediate pressure steam generated at an intermediate pressure drum
52
is mixed with the second portion of the high pressure exhaust steam (which is the portion of the outlet steam from the high pressure turbine
57
to be supplied into the reheater
74
) to be heated there and is then mixed with the blade cooling steam led through the blade cooling steam recovery pipe
62
to be supplied into the intermediate pressure turbine
58
.
The steam so mixed and supplied into the intermediate pressure turbine
58
expands there to generate a predetermined power. The intermediate pressure exhaust steam, or the outlet steam from the intermediate pressure turbine
58
, is mixed with low pressure steam generated at a low pressure drum
51
and supplied through a low pressure steam pipe
65
and is then supplied into the low pressure turbine
59
for generating a predetermined power.
Low pressure exhaust steam coming out of the low pressure turbine
59
is condensed into water at a condenser
71
to then be pressurized to a predetermined level at a pressure pump
72
to be fed into the waste heat recovery boiler
02
via a feed water pipe
73
.
In the first prior art example of the combined cycle plant constructed as described above, the regenerative type gas turbine plant acting as the topping cycle of the combined cycle plant comprises the regenerator
3
, as compared with a conventional simple gas turbine, so that the exhaust gas heat is recovered into the inlet of the combustor
4
. Thus, the inlet temperature of the combustor
4
is elevated and an advantage is obtained of reducing the fuel flow rate and thus enhancing the gas turbine efficiency and the combined efficiency.
In order to obtain this advantage, however, it is necessary to provide a piping of the exhaust gas duct
6
, which has a large size, from the outlet of the turbine
5
to the regenerator
3
. It is also necessary to provide a piping of the exhaust gas duct
7
, which is downstream thereof, from the regenerator
3
to the waste heat recovery boiler
02
. Thus, the cost of the plant increases because the cost of the exhaust ducts
6
,
7
is high.
Also, as the exhaust gas from the turbine
5
is first supplied into the regenerator
3
to pass therethrough, there occurs a large pressure loss of the exhaust gas. This reduces the turbine pressure ratio to hinder the original intent of the regenerative type gas turbine to enhance the turbine efficiency and the combined efficiency.
Furthermore, the heat exchange at the regenerator
3
is between the exhaust gas on the high temperature side and the compressed air on the low temperature side, and the heat transfer coefficient of the high temperature side heat transfer surface of the regenerator
3
is smaller as compared with the heat exchange with steam. As a result, the heat transfer area of the regenerator
3
becomes larger as compared with the heat exchanger of the waste heat recovery boiler in which the high temperature side is the exhaust gas
Akita Eiji
Sugishita Hideaki
Tsukuda Yoshiaki
Uematsu Kazuo
Freay Charles G.
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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