Title: Combined cycle plant
Abstract: In a combined cycle plant that combines a conventional thermal power plant and a gas turbine plant, there is provided a dump system 1 that connects a main steam pipe 60 with the condenser 25 and dumps the steam generated by the boiler 10 into the condenser 25, bypassing the steam turbine; and HRSG HP turbine bypass system 2 and HRSG LP turbine bypass system 3 which connect the HP pipe 70 and LP pipe 71 of the heat recovery steam generator, respectively.
Patent Number: 6,983,585 Issued on 01/10/2006 to Hattori, et al.
| Inventors:
|
Hattori; Youichi (Higashiibaraki, JP);
Inui; Taiji (Hitachi, JP)
|
| Assignee:
|
Hitachi, Ltd. (Tokyo, JP);
Hitachi Engineering Co., Ltd. (Hitachi, JP)
|
| Appl. No.:
|
636756 |
| Filed:
|
August 8, 2003 |
Foreign Application Priority Data
| Aug 09, 2002[JP] | 2002-232270 |
| Current U.S. Class: |
60/39.182; 60/39.3 |
| Current Intern'l Class: |
F02C 6/00 (20060101); F02G 1/00 (20060101); F02G 3/00 (20060101) |
| Field of Search: |
60/39181,391.82,391.83,772-775,778,779,786,393
|
References Cited [Referenced By]
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| 5737912 | Apr., 1998 | Krakowitzer.
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| 5755089 | May., 1998 | Vanselow.
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| 6105362 | Aug., 2000 | Ohtomo et al.
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| 6109020 | Aug., 2000 | Liebig.
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| 6397575 | Jun., 2002 | Tomlinson et al.
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| 6578352 | Jun., 2003 | Morikawa et al.
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| 6598399 | Jul., 2003 | Liebig.
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| 6615575 | Sep., 2003 | Liebig.
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| 6644011 | Nov., 2003 | Cheng.
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| 6679047 | Jan., 2004 | Uematsu et al.
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| 6782703 | Aug., 2004 | Dovali-Solis.
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| 6829898 | Dec., 2004 | Sugishita.
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| 6851266 | Feb., 2005 | Liebig.
| |
| Foreign Patent Documents |
| 19849740 | Jan., 2000 | DE.
| |
Primary Examiner: Rodriguez; William H.
Attorney, Agent or Firm: Antonelli, Terry, Stout and Kraus, LLP.
Claims
What is claimed is:
1. A combined cycle plant equipped with a conventional thermal power plant having
a boiler, boiler pipe including main steam pipe, cold reheat pipe and hot reheat
pipe, steam turbine; condenser; and condensate water/feedwater system, and
a gas turbine plant having a gas turbine, heat recovery steam generator recovering
heat from the gas turbine exhaust, and heat recovery steam generator pipe supplying
the generated steam from the heat recovery steam generator to the steam turbine,
the combined cycle plant further comprising:
a dump system connecting the boiler pipe with the condenser and dumps the steam
generated by the boiler into the condenser, bypassing the steam turbine; and
a pipe connecting the heat recovery steam generator pipe with the dump system
into the condenser, wherein the dump system into the condenser is a turbine bypass
system equipped with a flash tank and the point of connection between the heat
recovery steam generator and the dump system into the condenser is located on the
flash tank of the turbine bypass system or on a pipe near the flash tank.
2. A combined cycle plant equipped with a conventional thermal power plant having
a boiler, boiler pipe including main steam pipe, cold reheat pipe and hot reheat
pipe, steam turbine; condenser; and condensate water/feedwater system, and
a gas turbine plant having a gas turbine, heat recovery steam generator recovering
heat from the gas turbine exhaust, and heat recovery steam generator pipe supplying
the generated steam from the heat recovery steam generator to the steam turbine,
the combined cycle plant further comprising:
a dump system connecting the boiler pipe with the condenser and dumps the steam
generated by the boiler into the condenser, bypassing the steam turbine; and
a pipe connecting the heat recovery steam generator pipe with the dump system
into the condenser,
wherein the dump system into the condenser is equipped with a turbine bypass
valve and attemperator and the point of connection between the heat recovery steam
generator and the dump system into the condenser is located on a pipe between the
turbine bypass valve and the attemperator.
3. A combined cycle plant equipped with a conventional thermal power plant having
a boiler, boiler pipe including main steam pipe, cold reheat pipe and hot reheat
pipe, steam turbine; condenser; and condensate water/feedwater system, and
a gas turbine plant having a gas turbine, heat recovery steam generator recovering
heat from the gas turbine exhaust, and heat recovery steam generator pipe supplying
the generated steam from the heat recovery steam generator to the steam turbine,
the combined cycle plant further comprising:
a dump system connecting the boiler pipe with the condenser and dumps the steam
generated by the boiler into the condenser, bypassing the steam turbine;
a pipe connecting the heat recovery steam generator pipe with the dump system
into the condenser and
a valve that is installed in the dump system into the condenser and a control
unit that employs state variables of the valve as input and controls the start
timing of the gas turbine plant.
4. A combined cycle power plant including a combustion boiler, a steam turbine
driven by the steam generated by the combustion boiler, and a combustion boiler
steam pipe supplying the steam generated by the combustion boiler to said steam
turbine, a condenser which condenses the steam discharged from the steam turbine,
and including a gas turbine plant having a gas turbine, a exhaust heat recovery
boiler which uses the gas turbine as a heat source and a exhaust heat recovery
boiler steam pipe which supplies the steam generated bys aid exhaust heat recovery
boiler to the combustion boiler steam pipe, the combined cycle power plant further comprising:
a first turbine bypass system which bypasses the steam of the combustion boiler
steam flowing through the combustion boiler steam pipe;
a second turbine bypass system which bypasses the steam of the exhaust heat recovery
boiler supplied to the steam turbine through the combustion boiler steam pipe and
flown through the combustion boiler steam pipe;
wherein the first and second bypass systems are shared partially and the generated
steam of the combustion boiler and/or the exhaust-heat recovery boiler are dumped
to the condenser through the shared first and second bypass systems.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a combined cycle plant that combines a conventional
thermal power plant and a gas turbine plant.
In a well-known combined cycle plant combining a conventional thermal power plant
comprising a boiler, steam turbine, condenser, etc. and a gas turbine plant comprising
a gas turbine and heat recovery steam generator, the steam generated by the boiler
of the conventional thermal power plant and the steam generated by the heat recovery
steam generator of the gas turbine plant are put together to drive the steam turbine.
A prior art relating to this type of power plant is disclosed, for example, in
the Japanese Laid-open Patent Publication No. 2000-220412.
SUMMARY OF THE INVENTION
A power plant is equipped with a system for dumping the steam generated by the
boiler into the condenser at the time of start, stop and load rejection. Since
the prior art mentioned above relates to a power plant that combines a conventional
thermal power plant and a gas turbine plant and so the plant is equipped with two
steam generators, i.e. boiler and heat recovery steam generator, it is necessary
to install two dump systems for dumping the generated steam into the condenser.
Consequently, the system layout becomes complicated and multiple inlet ports need
to be installed on the condenser.
The present invention provides a means for constructing a dump system for dumping
the generated steam into the condenser without increasing the number of inlet ports
on the condenser of an existing plant.
A combined cycle plant according to the present invention is equipped with a
dump
system that connects the boiler pipe with the condenser and dumps the steam generated
by the boiler into the condenser, bypassing the steam turbine, and a pipe that
connects the heat recovery steam generator pipe with the dump system into the condenser.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of the combined cycle plant according to the embodiment
1 of the invention;
FIG. 2 is a schematic diagram of the combined cycle plant according to the embodiment
2 of the invention;
FIG. 3 is a schematic diagram of the combined cycle plant according to the embodiment
3 of the invention;
FIG. 4 is a schematic diagram of the combined cycle plant according to the embodiment
4 of the invention;
FIG. 5 is a schematic diagram of the combined cycle plant according to the embodiment
5 of the invention; and
FIG. 6 is a schematic diagram of the combined cycle plant according to the embodiment
6 of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention are described hereunder, using FIG.
1 to FIG. 6.
<Embodiment 1>
A preferred embodiment of a combined cycle plant according to the present invention
is described hereunder, using FIG. 1.
The power plant is equipped mainly with two plants: a conventional thermal power
plant comprising a boiler
10, a boiler pipe including a main steam pipe
60, cold reheat pipe
61 and hot reheat pipe
62, high-pressure
(HP), intermediate-pressure (IP) and low-pressure (LP) turbines
21,
22
and
23, respectively, a condenser
25, and a condensate water/feedwater
system; and a gas turbine plant comprising a gas turbine
40, a heat recovery
steam generator
50 that recovers heat from the exhaust of the gas turbine
40, and a heat recovery steam generator pipe including a HP pipe
70
and LP pipe
71.
In FIG. 1, feedwater supplied to the boiler
10 is heated by an economizer
12 and steam is generated by an evaporator
13. The generated steam,
while being superheated through a primary superheater
14 and a secondary
superheater
15, is directed as superheated steam into the HP turbine
21
through the main steam pipe
60 connecting the evaporator
13 with
the HP turbine
21.
On the other hand, the steam generated by the heat recovery steam generator
50
is joined into the main steam pipe
60 through the HP pipe
70 connecting
a HP drum
51 with the main steam pipe
60 and also directed as superheated
steam into the HP turbine
21.
After having driven the HP turbine
21, the steam flows through the cold
reheat pipe
61 and is directed to a reheater
11 of the boiler
10.
The steam superheated by the reheater
11 is supplied to the IP turbine
22
through the hot reheat pipe
62. On the other hand, the steam generated by
the heat recovery steam generator
50 is joined into the hot reheat pipe
62 through the LP pipe
71 connecting the LP drum
52 with the
hot reheat pipe
62 and also directed as superheated steam into the IP turbine
22.
After having driven the IP turbine
22, the steam is led into the LP
turbine
23 through a crossover pipe
63. The steam, after having driven
the LP turbine
23, is then led into the condenser
25 and turns to
condensate water.
The condensate water condensed by the condenser
25 is then pressurized
by a condensate pump
30 and heated by a gland steam condenser
31,
and then branched into the condensate for the conventional thermal power plant
and the feedwater for the heat recovery steam generator
50 of the gas turbine plant.
A condensate pipe
65 connecting the condenser
25 with a deaerator
34 is installed in the condensate water system of the conventional thermal
power plant. The condensate water in the conventional thermal power plant is heated
by the LP heater
32, deaerated by the deaerator
34, and then turned
to feedwater. Besides, a feedwater pipe
66 connecting the deaerator
34
with the boiler
10 is installed in the feedwater system of the conventional
thermal power plant. The feedwater in the conventional thermal power plant is pressurized
by the feedwater pump
36, heated by the HP heater
37, and then returned
to the boiler
10.
On the other hand, the feedwater in the gas turbine plant is led through a feedwater
pipe
72 into the heat recovery steam generator
50, which recovers
heat from the exhaust of the gas turbine
40, and turned to steam by heat
exchange with the gas turbine exhaust, and then joined into the main steam pipe
60 through the HP pipe
70 connecting the HP drum
51 with the
main steam pipe
60, and serves as superheated steam to drive the HP turbine
21.
Besides, the feedwater, having branched inside the heat recovery steam generator
50 and directed to the LP drum
52, is turned to steam by heat exchange
with the gas turbine exhaust, and then joined into the hot reheat pipe
62
through the LP pipe
71 connecting the LP drum
52 with the hot reheat
pipe
62, and serves as superheated steam to drive the IP turbine
22.
In normal operation, power generation cycle is repeated as above and the electric
energy is generated by the steam turbine generator
24, which is driven by
the directly-connected HP, IP and LP steam turbines
21,
22 and
23,
and also by the gas turbine generator
44, which is driven by the directly-connected
gas turbine in this power plant.
While the plant continues operation in the above cycle under normal condition,
the conventional thermal power plant is equipped with a system for dumping the
generated steam into the condenser in case of start, stop and load rejection where
the generated steam cannot be directed into the steam turbine. In this embodiment,
there is provided a turbine bypass system
1 that is branched from the main
steam pipe
60 and connected to the condenser
25 through the turbine
bypass valve
8 and relevant pipe. With this turbine bypass system
1,
the steam generated by the boiler
10 can be dumped into the condenser
25.
On the other hand, there is provided another turbine bypass system for the steam
generated by the heat recovery steam generator
50: a HRSG HP turbine bypass
system
2 that is branched from the HP pipe
70 and connected to the
turbine bypass system
1 and a HRSG LP turbine bypass system
3 that
is branched from the LP pipe
71 and connected to the turbine bypass system
1.
That is, in this embodiment, the HRSG high pressure turbine bypass system
2
(HRSG low pressure turbine bypass system
3) which is the second turbine
bypass system is connected in the middle of the first turbine bypass system
1.
Furthermore, the turbine bypass system
1 from the connecting point of the
HRSG high pressure turbine bypass system
2 (HRSG low pressure turbine bypass
system
3) to a steam condenser
25 is shared as a bypass system of
the generating steam of the combustion boiler
10 and the exhaust heat recovery
boiler
50.
When building the parallel power generation system composed of the steam power
generation plant, the gas turbine, and the exhaust heat recovery boiler, by sharing
a part of turbine bypass system
1 also as a turbine bypass system in the
exhaust heat recovery boiler
50 such as this embodiment, enlargement and
complication of a steam condenser
25 is avoided, and it is able to reduce
the cost of a steam condenser or a turbine bypass system considerably.
Moreover, when carrying out the re-powering by adding the gas turbine plant
to an established steam power generation plant, large reconstruction of a steam
condenser may be needed and it may not be able to do in reconstruction depending
on the case. However, it becomes possible to solve these problems by constituting
a turbine bypass system as mentioned above.
To start this power plant, the conventional thermal power plant is started first,
and then the gas turbine plant is started. Accordingly, the boiler
10 is
started first and the steam generated by the boiler
10 is discharged into
the condenser
25 through the turbine bypass system
1 in the beginning,
and then, when the pressure and temperature of the steam generated by the boiler
10 become high enough to be supplied to the steam turbine, the steam is
led into the steam turbine.
Then, when the turbine bypass system
1 becomes not in operation or the
amount of steam from the boiler
10 into the turbine bypass system
1
becomes lower than a specified amount after the steam generated by the boiler
10
is all directed into the steam turbine, the gas turbine plant is started. The steam
generated by the heat recovery steam generator
50 is directed, through the
HRSG HP turbine bypass system
2 and HRSG LP turbine bypass system
2,
into the turbine bypass system
1 and then discharged into the condenser
25.
When the pressure and temperature of the high-pressure steam from the heat recovery
steam generator
50 become high enough to be mixed into the main steam, and
when the pressure and temperature of the low-pressure steam from the heat recovery
steam generator
50 become high enough to be mixed into the hot reheat steam,
each steam from the heat recovery steam generator
50 is mixed into the main
steam pipe
60 and hot reheat pipe
62, respectively, and the turbine
bypass system
1 becomes not in operation.
As the turbine bypass system
1 of the boiler
10 is put into service
for the boiler
10 and heat recovery steam generator
50 in turn as
explained above, the turbine bypass systems
2 and
3 from the heat
recovery steam generator can be connected each to the turbine bypass system
1
of the boiler
10.
The above operation is maintained so far as the control unit
80 monitors
the opening state of the turbine bypass valve
8 and permits to start the
gas turbine
40 only when the above operating condition is met.
In an event of load rejection or steam turbine tripping, generated steam can
no
longer be directed into the steam turbine either in the conventional thermal power
plant or in the gas turbine plant, and so the generated steam cannot be handled
only by the turbine bypass system
1. Because of the above, it is recommended
that each boiler pipe and HRSG pipe is equipped with a release valve
64
for releasing the steam generated in the conventional thermal power plant and gas
turbine plant into the air.
With the combined cycle plant according to this embodiment, because it is not
necessary to install a system for dumping the generated steam into the condenser
in each conventional thermal power plant and gas turbine plant, the generated steam
can be dumped into the condenser without increasing the number of inlet ports on
the condenser of an existing plant.
Besides, because the operating state of the gas turbine plant and conventional
thermal power plant is monitored and each plant is started in turn accordingly,
it no longer happens that the steam generated in the gas turbine plant and in the
conventional thermal power plant is dumped into the condenser at the same time.
Thus, the capacity of the dump system can decrease.
A typical embodiment of the present invention is as explained above. However,
since
there are different constructions available for the system for dumping the generated
steam into the condenser, some more are described hereunder.
<Embodiment 2>
FIG. 2 shows a preferred embodiment 2 of a combined cycle plant according to
the present invention. The same devices and components as in FIG. 1 are denoted
the same and no more explanation is given on them. Description hereunder covers
differences only. In the figure, the control unit
80 is not shown.
The plant is equipped with the turbine bypass system
1 as a system for
dumping the generated steam into the condenser. The turbine bypass system of this
embodiment is branched from the main steam pipe
60 at the outlet of the
primary superheater
14, directed through the pipe and the flash tank
4,
and then piped and connected to the condenser
25. With this turbine bypass
system
1, the steam generated at the start of the boiler
10 is dumped
into the condenser
25.
The plant is also equipped with another turbine bypass system for dumping the
steam generated by the heat recovery steam generator
50: the HRSG HP turbine
bypass system
2 that is branched from the HP pipe
70 and connected
to the flash tank
4, and the HRSG LP turbine bypass system
3 that
is branched form the LP pipe
71 and connected to the flash tank
4.
The point of connection of each turbine bypass system from the heat recovery steam
generator
50 can be located not only on the flash tank
4 but also
on the pipe near the flash tank
4.
<Embodiment 3>
FIG. 3 shows a preferred embodiment 3 of a combined cycle plant according to
the present invention. The same devices and components as in FIG. 1 and FIG. 2
are denoted the same and no more explanation is given on them. Description hereunder
covers differences only. In the figure, the control unit
80 is not shown.
As the turbine bypass system for the boiler
10, the plant is equipped
with
the HP turbine bypass system
1a that is branched from the main steam
pipe
60 and connected to the cold reheat pipe
61 and the LP turbine
bypass system
1b that is branched from the hot reheat pipe
62
and connected to the condenser
25. Besides, a main steam pipe drain system
5 connecting the main steam pipe
60 with the condenser
25
is also installed. The main steam pipe drain system
5 and LP turbine bypass
system
1b serve as a system for dumping the generated steam into
the condenser.
The HRSG HP turbine bypass system
2 is connected to the main steam pipe
drain system
5 and the HRSG LP turbine bypass system
3 is connected
to the LP turbine bypass system
1b so as to serve as the turbine
bypass system for the steam generated by the heat recovery steam generator.
<Embodiment 4>
FIG. 4 shows a preferred embodiment 4 of a combined cycle plant according to
the present invention. The same devices and components as in FIGS. 1 to 3 are denoted
the same and no more explanation is given on them. Description hereunder covers
differences only. In the Figure, the control unit
80 is not shown.
The plant of this embodiment is equipped with the secondary superheater bypass
system
6 connecting the main steam pipe
60 with the condenser
25.
The secondary superheater bypass system
6 and LP turbine bypass system
1b
are installed to serve as the system for dumping the generated steam into the condenser.
The HRSG HP turbine bypass system
2, branched from the HP pipe
70
and connected to the secondary superheater bypass system
6, and HRSG LP
turbine bypass system
3, branched from the LP pipe
71 and connected
to the LP turbine bypass system
1b, are installed to serve as the
turbine bypass system for the steam generated by the heat recovery steam generator
50.
<Embodiment 5>
FIG. 5 shows a preferred embodiment 5 of a combined cycle plant according to
the present invention. The same devices and components as in FIGS. 1 to 4 are denoted
the same and no more explanation is given on them. Description hereunder covers
differences only. In the Figure, the control unit
80 is not shown.
The plant of this embodiment is equipped with the superheater inlet dump system
7 connecting the main steam pipe
60 with the condenser
25.
The superheater inlet dump system
7 and turbine bypass system
1 serve
as the system for dumping the generated steam into the condenser.
The HRSG HP turbine bypass system
2, branched from the HP pipe
70
and connected to the turbine bypass system
1, and HRSG LP turbine bypass
system
3, branched from the LP pipe
71 and connected to the superheater
inlet dump system
7, are installed to serve as the turbine bypass system
for the steam generated by the heat recovery steam generator
50.
<Embodiment 6>
FIG. 6 shows a preferred embodiment 6 of a combined cycle plant according to
the present invention. The same devices and components as in FIGS. 1 to 5 are denoted
the same and no more explanation is given on them. Description hereunder covers
differences only. In the figure, the control unit
80 is not shown.
In the plant of this embodiment, an attemperator
9 is installed on the
turbine bypass system
1, and both HRSG HP turbine bypass system
2
and HRSG LP turbine bypass system
3 are connected to the turbine bypass
system
1. The point of connection is located on a pipe from the turbine
bypass valve
8 to the attemperator
9.
Assuming that a combined cycle plant is to be constructed, there may be
several different cases available in addition to a case where a new combined cycle
plant is constructed from the scratch as above: for example, a case where a gas
turbine plant is newly added to the existing conventional thermal power plant or
a case where boiler and gas turbine plant are newly installed but the existing
steam turbine is put into use.
When a new power plant according to the present invention is to be constructed,
installing respective dump systems for dumping the steam generated in the conventional
thermal power plant and gas turbine plant into the condenser is not necessary.
Even in the case where a gas turbine plant is to be added to an existing conventional
thermal power plant, no additional inlet port needs to be installed on the condenser
to receive a dump system for the steam generated by the heat recovery steam generator,
and so large-scale remodeling of the condenser is not needed.
The meaning of Reference signs in Figs. are as follows:
1 . . . Turbine bypass system,
2 . . . High pressure turbine bypass
system of HRSG,
3 . . . Low pressure turbine bypass system of HRSG,
4
. . . Flash tank,
5 . . . Drain system of main steam pipe,
6 . .
. Bypass system of secondary superheater,
7 . . . Dump system at superheater
inlet,
8 . . . Turbine bypass valve,
9 . . . Attemperator,
10
. . . Boiler,
11 . . . Reheater,
12 . . . Economizer,
13 .
. . Evaporator,
14 . . . Primary superheater,
15 . . . secondary
superheater,
21 . . . HP (high-pressure) turbine,
22 . . . IP (intermediate-pressure)
turbine,
23 . . . LP (low-pressure) turbine,
24 . . . Steam turbine
generator,
25 . . . Condenser,
30 . . . Condensate pump,
31
. . . Gland steam condenser,
32 . . . LP (low-pressure) heater,
34
. . . Deaerator,
36 Feedwater pump,
37 . . . HP (high-pressure) heater,
40 . . . Gas turbine,
41 . . . Compressor,
42 . . . Turbine,
43 . . . Combustor,
44 . . . Gas turbine generator,
50 . .
. Heat recovery steam generator,
51 . . . HP drum,
52 . . . LP drum,
60 . . . Main steam pipe,
61 . . . Cold reheat pipe,
62 .
. . Hot reheat pipe,
63 . . . Crossover pipe,
64 . . . Release valve,
70 . . . HP pipe,
71 . . . LP pipe,
72 . . . Feedwater pipe,
80 . . . Control unit.
According to the present invention, because installing respective dump
systems for dumping the steam generated in the conventional thermal power plant
and gas turbine plant into the condenser is not necessary, a system for dumping
the generated steam into the condenser can be constructed without increasing the
number of inlet ports on the condenser of an existing plant.
*
