U.S. patent application number 14/315786 was filed with the patent office on 2014-10-16 for method for starting up a gas and steam turbine system.
The applicant listed for this patent is SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Edwin Gobrecht, Rainer Newald, Erich Schmid.
Application Number | 20140305132 14/315786 |
Document ID | / |
Family ID | 34979175 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140305132 |
Kind Code |
A1 |
Gobrecht; Edwin ; et
al. |
October 16, 2014 |
METHOD FOR STARTING UP A GAS AND STEAM TURBINE SYSTEM
Abstract
A method for starting a gas and steam turbine system which
includes a gas turbine system which includes at least one gas
turbine, in addition to at least one steam turbine system which
includes at least one steam turbine and at least one steam system
is provided. Heat produced by the working fluid and which is
released in the gas turbine is guided to the steam system in order
to produce steam which drives the steam turbine. During starting,
the gas turbine is started prior to the steam turbine and the steam
turbine is started in the presence of the first steam in the system
and is impinged upon by said steam.
Inventors: |
Gobrecht; Edwin; (Ratingen,
DE) ; Newald; Rainer; (Erlangen, DE) ; Schmid;
Erich; (Nurnberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SIEMENS AKTIENGESELLSCHAFT |
Munchen |
|
DE |
|
|
Family ID: |
34979175 |
Appl. No.: |
14/315786 |
Filed: |
June 26, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11887868 |
Feb 4, 2009 |
8800297 |
|
|
PCT/EP2006/061217 |
Mar 31, 2006 |
|
|
|
14315786 |
|
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Current U.S.
Class: |
60/778 |
Current CPC
Class: |
F01K 23/108 20130101;
F01K 23/10 20130101; F01K 23/101 20130101 |
Class at
Publication: |
60/778 |
International
Class: |
F01K 23/10 20060101
F01K023/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2005 |
EP |
05007416.0 |
Claims
1. A method for starting up a gas and steam turbine system which
has a gas turbine system comprising a gas turbine; a steam turbine
system comprising a steam turbine and a steam system and in which
the waste heat of a working medium expanding in the gas turbine is
supplied to the steam system for the purpose of generating steam
driving the steam turbine, the method comprising: supplying a waste
heat of a working medium of the gas turbine to the steam system to
produce steam for driving the steam turbine; and starting up the
steam turbine when the first steam is present in the steam system
and is impinged upon by steam, wherein the gas turbine system
experiences a load increase at maximum load ramp during the entire
startup operation
2. The method as claimed in claim 1, tuning the steam system during
the startup operation in such a way that during the acceleration of
the steam turbine the steam temperature increases at a low
gradient.
3. The method as claimed in claim 1, tuning the steam system during
the startup operation in such a way that the steam pressure
increases continuously.
4. The method as claimed in claim 3, wherein the steam system
comprises a steam diverter station, and wherein the tuning includes
opening a steam diverter station of the steam system only so wide
that a minimum steam quantity required for accelerating and
synchronizing the steam turbine is generated by a part of the waste
heat of the working medium and an increase in pressure is produced
in the steam system by the remainder of the waste heat of the
working medium.
5. The method as claimed in claim 3, wherein no diverter station
leading to a bypassing of the steam turbine is opened in the steam
system.
6. The method as claimed in claim 1, wherein the load increase is
maintained until the base load of the gas turbine system has been
reached.
7. The method as claimed in claim 1, wherein the gas and steam
turbine system is switched over into the gas and steam turbine
operating mode during the increase in load.
8. The method as claimed in claim 3, tuning the steam system during
the startup operation in such a way that the steam pressure
increases continuously.
9. The method as claimed in claim 8, wherein the steam system
comprises a steam diverter station, and wherein the tuning includes
opening a steam diverter station of the steam system only so wide
that a minimum steam quantity required for accelerating and
synchronizing the steam turbine is generated by a part of the waste
heat of the working medium and an increase in pressure is produced
in the steam system by the remainder of the waste heat of the
working medium.
10. The method as claimed in claim 8, wherein no diverter station
leading to a bypassing of the steam turbine is opened in the steam
system.
11. The method as claimed in claim 2, wherein the load increase is
maintained until the base load of the gas turbine system has been
reached.
12. The method as claimed in claim 2, wherein the gas and steam
turbine system is switched over into the gas and steam turbine
operating mode during the increase in load.
13. The method as claimed in claim 3, wherein the load increase is
maintained until the base load of the gas turbine system has been
reached.
14. The method as claimed in claim 3, wherein the gas and steam
turbine system is switched over into the gas and steam turbine
operating mode during the increase in load.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This a continuation application which claims benefit of the
U.S. National Stage application 11/887,868 filed Oct. 4, 2007. The
US National Stage application claims benefit to International
Application No. PCT/EP2006/061217, filed Mar. 31, 2006. The
International Application claims priority to European application
No. 05007416.0 filed Apr. 5, 2005. All of the applications are
incorporated by reference herein in their entirety.
FIELD OF INVENTION
[0002] The present invention relates to a method for starting up a
gas and steam turbine system, and in particular a method for a fast
startup of a system of said kind.
BACKGROUND OF THE INVENTION
[0003] In a gas turbine system a gaseous or liquid fuel, for
example natural gas or crude oil, is mixed with compressed air and
combusted. The pressurized combustion exhaust gases are supplied to
the turbine of the gas turbine system as the working medium. The
working medium sets the turbines under expansion into rotation,
with thermal energy being converted into mechanical work, i.e. the
rotation of the turbine shaft. When the expanded working medium is
discharged from the gas turbine system said medium typically still
has a temperature of 500-600.degree. C.
[0004] In a gas and steam turbine system the expanded working
medium, also called flue gas, from the gas turbine system is used
to generate steam for driving a steam turbine. Toward that end the
working medium is supplied to a heat recovery steam generator
connected downstream of the gas turbine system on the exhaust gas
side, in which steam generator heating surfaces are arranged in the
form of pipes or pipe bundles. Said heating surfaces are in turn
connected into a water-steam cycle of the steam turbine system
which has at least one, but mostly a plurality of pressure stages.
The pressure stages differ from one another in that the water
supplied to the heating surface for the purpose of generating steam
has different pressure levels. A gas and steam turbine system
comprising a water-steam cycle having only one pressure stage is
described in DE 197 36 888 A1, and such a system comprising three
pressure stages, namely a high-pressure stage, a medium-pressure
stage and a low-pressure stage, is described in DE 100 04 187
C1.
[0005] Currently, in order to start a gas and steam turbine system,
the gas turbine system is usually started up and the expanded
working medium is supplied to the heat recovery steam generator of
the steam turbine system. Initially, however, the steam generated
in the heat recovery steam generator is not fed to the turbine part
of the steam turbine system, but is directed past the turbine via
diverter stations and supplied directly to a condenser which
condenses the steam to water. The condensate is then supplied to
the steam generator again as feedwater. In many embodiment variants
of gas and steam turbine systems the diverted steam is also
conveyed to the atmosphere.
[0006] The steam turbine is only switched into the cycle when
certain steam parameters in the steam lines of the water-steam
cycle or in the steam lines leading to the turbine part of the gas
turbine system, for example certain steam pressures and
temperatures, are complied with. Complying with said steam
parameters is designed to keep potential stresses in thick-walled
components at a low level.
[0007] After the startup of the gas turbine system there is a power
increase which leads to an increase in pressure in the steam
system. The load gradient at which the gas turbine system is
started up, i.e. the power increase of the gas turbine system per
time unit, is critically dependent on the implementation and mode
of construction of the heat recovery steam generator as well as on
the structural limitations within the steam turbine. As the gas
turbine load and consequently the temperature or, as the case may
be, the volume flow rate of the exhaust gas emitted from the gas
turbine system increase, the steam temperature and the pressure in
the steam system are also increased.
[0008] Before the steam turbine starts up, the gas turbine is
typically kept at a specific partial load until stationary states
have come about in the gas turbine system and in the steam system.
As soon as stable steam production has been reached, the steam
contained in the steam system is channeled to the steam turbine,
thereby accelerating the steam turbine. The turbine speed is then
increased to nominal speed. Following synchronization of the
generator coupled to the steam turbine with the power supply
system, or in the case of single-shaft systems, following the
engagement of the overrunning clutch, the steam turbine is
subjected to further load as a result of an increase in the steam
supply. At the same time the diverter stations close more and more
in order to keep the steam pressure roughly constant and minimize
level fluctuations in the heat recovery steam generator.
[0009] As soon as the diverter stations are closed and the steam
produced in the heat recovery steam generator is channeled in its
entirety to the steam turbine, a further increase in the gas
turbine power output takes place when there is a higher power
requirement on the part of the system which is now operating in the
gas and steam turbine mode.
[0010] By definition, the startup operation of a gas and steam
turbine system is terminated only when the gas turbine has reached
the base load and all diverter stations are closed.
SUMMARY OF INVENTION
[0011] The object of the present invention is to provide a method
for starting up a gas and steam turbine system which enables a
faster startup operation than the method described in the
introduction.
[0012] This object is achieved by means of a method for starting up
a gas and steam turbine system as claimed in the claims. The
dependent claims contain advantageous embodiments of the
method.
[0013] According to the invention, a method is provided for
starting up a gas and steam turbine system, in particular for fast
starting up of a gas and steam turbine system which has a gas
turbine system comprising at least one gas turbine as well as a
steam turbine system having at least one steam turbine and at least
one steam system and in which the waste heat of a working medium
expanding in the gas turbine is supplied to the steam system for
the purpose of generating the steam driving the steam turbine.
[0014] In the method according to the invention, at startup time
the gas turbine is started first, before the steam turbine is
started. The steam turbine is then already started up when the
first steam is present in the steam system and is impinged upon by
steam.
[0015] In the method according to the invention, the steam turbine
is started up at the earliest possible time and accelerated by
means of the first steam from the heat recovery steam generator,
without waiting for stationary states in the steam system. This
measure enables the startup operation of the gas and steam turbine
system to be shortened considerably.
[0016] In contrast to the usual startup method, the steam
temperature in the steam system at the time of starting the steam
turbine can be less than the material temperature of the steam
turbine or of its housing. The early channeling of the steam to the
steam turbine can therefore lead to a cooling down of the
components and to thermal stresses. However, a certain compensation
can be achieved if the gradients are kept correspondingly low
during the following increase in the steam temperatures.
[0017] Advantageously, the tuning of the steam system during the
startup operation is chosen in such a way that the steam pressure
increases continuously. This can be achieved, for example, by
opening a steam diverter station of the steam system only so wide
that a minimum steam quantity required for accelerating and/or
synchronizing the steam turbine is generated using a part of the
waste heat of the working medium and a pressure increase in the
steam system is produced by means of the remaining part of the
waste heat of the working medium.
[0018] In addition to a pressure increase in the steam system, the
comparatively small opening of the steam diverter station leads to
a reduction in the steam production in the heat recovery steam
generator. As a result the thermal load to the condenser is reduced
and the diverter station can close more quickly.
[0019] In a special embodiment of the method according to the
invention the diverter station is not opened at all.
[0020] The method according to the invention can be embodied in
particular in such a way that the gas turbine system experiences a
load increase during the entire startup operation, in particular
until the base load is reached. In other words, the method
dispenses with keeping the gas turbine system at a certain partial
load and waiting until the gas turbine system and the steam system
of the steam turbine system have settled into stationary states.
This measure also leads to a reduction in the startup time of the
gas turbine system and thus enables a fast startup.
[0021] In a special embodiment the gas turbine system's load is
increased at maximum load ramp, which is to say that there is a
maximum increase in the gas turbine power output per time unit.
[0022] The gas and steam turbine system during the starting up of
the gas turbine system to base load is preferably switched over
into the gas and steam turbine operating mode, with the result that
the startup operation is, by definition, terminated when the gas
turbine base load is reached. The switchover into the gas and steam
turbine operating mode can include in particular the
synchronization of a generator coupled to the steam turbine with
the power supply system or, in the case of single-shaft systems,
the engagement of the automatic overrunning clutch.
[0023] The described method according to the invention for starting
up a gas and steam turbine system shortens the startup time of the
system considerably. Compared with the method described in the
introduction, a reduction in the starting time by approximately 50%
is achievable. A gas and steam turbine operator can therefore
respond very flexibly to short-term requirements, as a result of
which the revenues from the purchase of power can be increased. As
a result of the early steam takeover of the steam turbine and the
reduced thermal load in the condenser, which leads to smaller power
losses, there is also an increase in the averaged efficiency of the
gas and steam turbine system, which is a significant factor in
particular in the case of frequent starts and increases the
cost-effectiveness of the system.
[0024] Moreover, the lower steam production in the method according
to the invention for starting up a gas and steam turbine system
also enables smaller diverter stations to be installed, thereby
reducing investment costs.
[0025] The described startup method enabling a fast startup of a
gas and steam turbine system can essentially be realized by means
of software modifications. It is therefore also possible to convert
existing gas and steam turbine systems to the startup method
according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Further features, characteristics and advantages of the
present invention will emerge from the following description of an
exemplary embodiment with reference to the accompanying figure.
[0027] FIG. 1 shows a schematic diagram for a gas and steam turbine
system.
DETAILED DESCRIPTION OF INVENTION
[0028] The gas and steam turbine system 1 represented schematically
in FIG. 1 comprises a gas turbine system 1a as well as a steam
turbine system 1b. The gas turbine system 1a is equipped with a gas
turbine 2, a compressor 4, and at least one combustion chamber 6
connected between the compressor 4 and the gas turbine 2. By means
of the compressor 4, fresh air L is drawn in, compressed and
supplied via the fresh air line 8 to one or more burners of the
combustion chamber 6. The supplied air is mixed with liquid or
gaseous fuel B fed via a fuel line 10 and the mixture ignited. The
resulting combustion exhaust gases form the working medium AM of
the gas turbine system 1a, which working medium AM is supplied to
the gas turbine 2, where it produces work under expansion and
drives a shaft 14 coupled to the gas turbine 2. The shaft 14 is
coupled not only to the gas turbine 2 but also to the air
compressor 4 as well as to a generator 12 in order to drive the
latter. The expanded working medium AM is conducted via an exhaust
gas line 34 to a heat recovery steam generator 30 of the steam
turbine system 1b.
[0029] In the heat recovery steam generator 30 the working medium
output by the gas turbine 1a at a temperature of approx.
500-600.degree. C. is used for generating and superheating
steam.
[0030] In addition to the heat recovery steam generator 30, which
can be embodied in particular as a once-through, forced-flow
system, the steam turbine system 1b comprises a steam turbine 20
having turbine stages 20a, 20b, 20c and a condenser 26. The heat
recovery steam generator 30 and the condenser 26, in combination
with condensate lines and feedwater lines 35, 40 as well as steam
lines 48, 53, 64, 70, 80, 100, form a steam system which, together
with the steam turbine 20, forms a water-steam cycle.
[0031] Water from a feedwater reservoir 38 is supplied by means of
a feedwater pump 42 to a high-pressure preheater 44, also known as
an economizer, and from there is forwarded to an evaporator 46
which is designed for once-through operation and is connected to
the economizer 44 on the output side. For its part, the evaporator
46 is in turn connected on the output side to a superheater 52 via
a steam line 48 into which a water separator 50 is inserted. The
superheater 52 is connected on the output side via a steam line 53
to the steam input 54 of the high-pressure stage 20a of the steam
turbine 20.
[0032] In the high-pressure stage 20a of the steam turbine 20, the
superheated steam from the superheater 52 drives the turbine before
it is passed on via the steam output 56 of the high-pressure stage
20a to an intermediate superheater 58.
[0033] After being superheated in the intermediate superheater 58,
the steam is forwarded via a further steam line 81 to the steam
input 60 of the medium-pressure stage 20b of the steam turbine 20,
where it drives the turbine.
[0034] The steam output 62 of the medium-pressure stage 20b is
connected via an overflow line 64 to the steam inlet 66 of the
low-pressure stage 20c of the steam turbine. After flowing through
the low-pressure stage 20c and the driving of the turbine
associated therewith, the cooled and expanded steam is output via
the steam output 68 of the low-pressure stage 20c to the steam line
70, which leads it to the condenser 26.
[0035] The condenser 26 converts the incoming steam into condensate
and forwards the condensate by means of a condensate pump 36 to the
feedwater reservoir 38 via the condensate line 35.
[0036] In addition to the already mentioned elements of the
water-steam cycle, the latter also comprises a bypass line 100,
what is referred to as the high-pressure diverter line, which
branches off from the steam line 53 before the latter reaches the
steam inlet 54 of the high-pressure stage 20a. The high-pressure
bypass line 100 bypasses the high-pressure stage 20a and flows into
the feed line 80 to the intermediate superheater 58. A further
bypass line, referred to as the medium-pressure bypass line 200,
branches from the steam line 81 before the latter flows into the
steam inlet 60 of the medium-pressure stage 20b. The
medium-pressure bypass line 200 bypasses both the medium-pressure
stage 20b and the low-pressure stage 20c and flows into the steam
line 70 leading to the condenser 26.
[0037] Incorporated into the high-pressure bypass line 100 and the
medium-pressure bypass line 200 are the shutoff valves 102, 202, by
means of which said lines can be shut off. Shutoff valves 104, 204
are also included in the steam line 53 and in the steam line 81, in
each case between the branching-off point of the bypass line 100
and 200, respectively, and the steam inlet 54 of the high-pressure
stage 20a and the steam inlet 60 of the medium-pressure stage 20a,
respectively.
[0038] Incorporated into the medium-pressure bypass line 200 is a
shutoff valve 202 by means of which said line can be shut off. A
shutoff valve 104 is also included in the steam line 53, namely
between the branching-off point of the bypass line 100 and the
steam inlet 54 of the high-pressure stage 20a of the steam turbine
20.
[0039] The bypass line 100 and the shutoff valves 102, 104 are used
during the starting up of the gas and steam turbine system 1 to
divert a part of the steam for the purpose of bypassing the steam
turbine 2. It is possible for at least one diverter station 100,
102, 200, 202 to be opened only so wide that a minimum steam
quantity required for accelerating and/or synchronizing the steam
turbine 20 is generated by a part of the waste heat of the working
medium and an increase in pressure is produced in the steam system
by the remainder of the waste heat of the working medium It is
further possible that no diverter station 100, 102, 200, 202
leading to a bypassing of the steam turbine is opened in the steam
system.
[0040] An exemplary embodiment of the method according to the
invention for starting up a gas and steam turbine system is
described below based on the system 1 described with reference to
FIG. 1.
[0041] At the start of the method the gas turbine system la is
started and the working medium AM being discharged from the system
is supplied to the heat recovery steam generator 30 via an input
30a. The expanded working medium AM flows through the heat recovery
steam generator 30 and exits the latter via an output 30b in the
direction of a vent stack (not shown in FIG. 1). As the working
medium AM flows through the heat recovery steam generator 30, heat
is transferred from the working medium AM to the water or steam in
the water-steam cycle.
[0042] After the gas turbine system has been started up, the waste
heat of the working medium in the heat recovery steam generator 30
leads to the start of steam production in the steam system.
[0043] In this early phase of the startup operation the shutoff
valves 102 and 104 or 202 and 204 are set in such a way that only a
small part of the generated steam flows through the bypass lines
100, 200 and already in this phase of the startup operation the
majority of the steam is supplied to the steam turbine 20. The part
of the steam supplied to the steam turbine 20 accelerates the steam
turbine and preheats the latter insofar as the steam is hotter than
the material of the turbine and the steam lines.
[0044] Since only a small amount of steam flows directly to the
condenser 26 via the medium-pressure bypass line 200, the waste
heat not used during the acceleration and preheating of the steam
turbine 20 leads to a pressure increase in the steam system. In the
further course of the startup operation the steam pressure
therefore increases continuously in the steam system, as a result
of which steam production in the heat recovery steam generator is
reduced. This leads to a reduction in the heat input into the
condenser 26 and as a result the shutoff valves 102 and 202, which
are not fully open anyway, can be closed quickly compared to prior
art starting methods.
[0045] Once the gas turbine system 1 a has been started, the load
of the gas turbine system is increased preferably at maximum load
ramp until the base load is reached.
[0046] If the steam temperature is less than the material
temperature of the turbine 20 at the start of the introduction of
steam into the steam turbine 20, the steam temperature will
steadily increase during the startup of the load of the gas turbine
system and relatively soon exceed the material temperature of the
steam turbine and the lines leading thereto. If the rapid rise from
a relatively cool temperature of the turbine components to a high
temperature would exceed a certain predefined limit of the thermal
stresses in the material due to the starting up of the gas turbine
system at maximum load ramp, the power output of the gas turbine
system can also be increased at a lower ramp than the maximum load
ramp, with the result that the steam temperatures rise more
slowly.
[0047] Since the bypass lines 100, 200 are closed at an early stage
in the startup method according to the invention and the gas and
steam turbine system 1 is switched over into the gas and steam
turbine operating mode already during the starting up of the gas
turbine system 1a to base load, the startup operation is terminated
when the gas turbine base load is reached.
[0048] Even if the steam turbine load were to reach only a
magnitude of approximately 80-90% when the gas turbine base load is
reached, the startup operation is deemed to be completed according
to the definition whereby the startup operation is terminated when
the base load of the gas turbine system is reached and the bypass
lines are closed. Depending on the dynamic characteristics of the
heat recovery steam generator, a further pressure increase will
take place over several minutes and will be completed after
approximately 10-20 further minutes. The amount of steam will
increase accordingly, and steam turbine power output ratings in
excess of 95% will be achieved as a function of steam
temperature.
[0049] The startup method according to the invention has been
described with reference to a gas and steam turbine system
comprising a water-steam cycle which has only one pressure stage.
It should, however, be pointed out at this juncture that the method
according to the invention can also be applied in the case of gas
and steam turbine systems which have more than one pressure stage
in the water-steam cycle. A gas and steam turbine system comprising
three pressure stages, namely a high-pressure stage, a
medium-pressure stage and a low-pressure stage in the water-steam
cycle, for which the startup method according to the invention can
also be used, is described for example in DE 100 04 187 C1, to
which reference is made in relation to the embodiment of a gas and
steam turbine system comprising a plurality of pressure stages.
* * * * *