Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2001-11-19
2003-08-12
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S039163, C060S772000
Reexamination Certificate
active
06604354
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a combined cycle power plant, which is a combination of a steam turbine power facility with a gas turbine power facility.
In recent years, there has been a greater increase in demand for an improved thermal efficiency in a thermal power facility. Especially, there has recently been a demand for development of a high thermal efficiency system utilizing the existing facilities in view of difficulty in acquiring the site of a new facility and decrease in construction costs. It is said that conversion of a conventional power plant into a combined cycle power generation system is the most effective way in order to provide such a high thermal efficiency.
With respect to measures for remodeling the existing conventional thermal power facility into the combined cycle power system, there have been known an exhaust gas re-combustion type power plant as shown in
FIG. 10 and a
heat recovery type power plant as shown in FIG.
11
.
In the exhaust gas re-combustion type power plant as shown in
FIG. 10
, a combustion boiler, which is applied in an existing steam turbine power unit, is utilized as it is. More specifically, the existing steam turbine power unit A is provided generally with a steam turbine power facility
3
having a steam turbine
1
and a generator
2
, a combustion boiler
4
for supplying steam to the steam turbine
1
, a steam condenser
5
(which may be called merely condenser hereinlater) for condensing an exhaust gas from the steam turbine
1
, a condenser pump
6
for supplying condensed water (i.e., condensate) to the combustion boiler
4
and the other components. A gas turbine power unit B, which is additionally provided in the above-mentioned steam turbine power unit A, is provided with a gas turbine power facility
10
having a combustor
7
, a gas turbine
8
, a generator
9
and the other components. A high-temperature gas, which still contain sufficiently large amounts of oxygen and unburned fuel discharged from the gas turbine
8
in sufficient amounts, is introduced as air for boiler combustion into a furnace of the combustion boiler
4
to burn fuel “F” and an exhaust gas after combustion is discharged from a stack
11
. Such an exhaust gas re-combustion type power plant has advantageous features of permitting to enhance a boiler-efficiency and achieve heat recovery of a boiler-exhaust gas through heat exchange between the boiler-exhaust gas and a boiler-feedwater.
In the heat recovery type power plant as shown in
FIG. 11
, a heat recovery steam generator (HRSG)
12
is provided in place of the combustion boiler used in the existing steam turbine power unit so as to cause production of steam in the existing steam turbine power unit with the use of an exhaust gas from the gas turbine
8
. The structural components as shown in
FIG. 11
are identical to those in FIG.
10
. Accordingly, the same reference numerals as in
FIG. 10
are given to the identical components in FIG.
11
and description thereof is omitted. Such a heat recovery type power plant has advantageous features of permitting to introducing a high-temperature gas discharged from the gas turbine
8
into the heat recovery steam generator
12
to generate steam so as to drive the steam turbine
1
by the thus generated steam.
The above-described types of the power plant, however, has provided the following problems.
The exhaust gas re-combustion type power plant as shown in
FIG. 10
provides a low improvement-value in efficiency of about 5% as a relative value. For example, there is assumed that a single 240 MW gas turbine of 1300° C. class is provided in an existing 500 Mw boiler/turbine facility to remodel such facility into a combined cycle power generation system having the same plant power output. The thermal efficiency of the existing plant is assumed as 40%. When the existing system is remodeled into the exhaust gas re-combustion power plant under such conditions, although the combination of the gas turbine as additionally provided and the existing steam turbine ensures the plant power output of 500 MW, the thermal efficiency is about 42%, thus leading to improvement merely of about 5% as a relative value.
When the existing system is remodeled into the heat recovery type power plant as shown in
FIG. 11
, there are problems of small power output and impossibility of an independent operation only by the existing boiler/turbine facility. More specifically, the system is composed of the gas turbine as additionally provided, the heat recovery steam generator as additionally provided and the existing steam turbine, and in such arrangement, the existing combustion boiler is removed. In such a case, the thermal efficiency is about 50%, leading to increase in a relative value by 25%, while the power output of 380 MW can merely be ensured, leading to decrease in power output by about 30%. The impossibility of the independent operation only by the existing boiler/turbine facility makes it impossible to carry out a power generation operation during a regular inspection of the gas turbine. Coal, fuel oil and the like are applied as fuel for the existing combustion boiler. Continuous application of such fuels cannot cope with demands for an improved high-thermal efficiency and reduced costs.
SUMMARY OF THE INVENTION
An object of the present invention, which was made in view of such circumstances, is to provide a combined cycle power plant, which permits, when an existing steam turbine power facility is remodeled to the combined cycle type, to ensure plant power output that is equal to that of the existing steam turbine power facility prior to remodeling, provide a remarkably improved thermal efficiency and carry out an independent operation of the existing facility with the use of the existing conventional boiler and steam turbine.
This and other objects of the present invention can be achieved according to the present invention by providing, in one aspect, a combined cycle power plant, comprising:
a gas turbine power facility;
a heat recovery steam generator into which an exhaust gas is introduced from the gas turbine power facility;
a steam turbine power facility having a steam turbine mounted to a shaft different from a shaft on which the gas turbine power facility is mounted;
an existing boiler for supplying steam to the steam turbine power facility;
a system for introducing steam, which is generated in the heat recovery steam generator and the existing boiler, into the steam turbine of the steam turbine power facility through steam lines, which extend from the heat recovery steam generator and the existing boiler and are then joined together; and
a system for causing a line, which is arranged on a downstream side of a steam condenser provided in the steam turbine power facility, to branch off into feedwater lines, and supplying condensate condensed by the condenser into the heat recovery steam generator and the existing boiler.
In this aspect, the steam lines extending from the heat recovery steam generator and the existing boiler to the steam turbine and the feedwater lines extending from a condensed water pump of the steam condenser to the heat recovery steam generator and the existing boiler are provided with valves, respectively, to permit selection of any one of three operation patterns of: a simultaneous power generation operation of the gas turbine power facility and the steam turbine power facility utilizing the steam generated in both the steam generator and boiler; a simultaneous power generation operation of the gas turbine power facility and the steam turbine power facility utilizing only the steam generated in the heat recovery steam generator, while the existing boiler not being in operation (shut-down); and a single power generation operation of only the steam turbine power facility utilizing only the steam generated in the existing boiler, while shutting down the operation of the gas turbine.
The heat recovery steam generator is provided with a low-pressure economizer and there is provided a system for returning at le
Isu Takehiro
Oda Ryou
Oto Chikako
Shibuya Sachio
Sugimori Yoichi
Freay Charles G.
Kabushiki Kaisha Toshiba
Liu Han L
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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