U.S. patent application number 14/356158 was filed with the patent office on 2014-11-27 for method for operating a gas and steam turbine installation for frequency support.
This patent application is currently assigned to SIEMENS AKTIENGESELLSCHAFT. The applicant listed for this patent is Siemens Aktiengesellschaft. Invention is credited to Andreas Pickard, Erich Schmid.
Application Number | 20140345278 14/356158 |
Document ID | / |
Family ID | 47115955 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140345278 |
Kind Code |
A1 |
Pickard; Andreas ; et
al. |
November 27, 2014 |
METHOD FOR OPERATING A GAS AND STEAM TURBINE INSTALLATION FOR
FREQUENCY SUPPORT
Abstract
A method for operating a gas and steam turbine system having a
gas turbine, a steam turbine and a waste heat steam generator is
provided herein, wherein steam for the steam turbine can be
generated in the exchange of heat with exhaust gas from the gas
turbine. Absorption capacity of the steam turbine can be increased
and pressure in the waste heat steam generator can be lowered to
utilize storage reserves in the waste heat steam generator for
increased generation of steam to assist the frequency in the power
system starting from a steady-state operating mode. Thermal energy
is fed to the waste heat steam generator wherein a power profile of
the gas and steam turbine system is greater than or equal to a
preceding power level of the steady-state operating mode to
increase the absorption capacity of the steam turbine and reduce
pressure in the waste heat steam generator.
Inventors: |
Pickard; Andreas;
(Adelsdorf, DE) ; Schmid; Erich; (Nurnberg,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Aktiengesellschaft |
Munich |
|
DE |
|
|
Assignee: |
SIEMENS AKTIENGESELLSCHAFT
Munich
DE
|
Family ID: |
47115955 |
Appl. No.: |
14/356158 |
Filed: |
October 30, 2012 |
PCT Filed: |
October 30, 2012 |
PCT NO: |
PCT/EP2012/071478 |
371 Date: |
May 4, 2014 |
Current U.S.
Class: |
60/645 |
Current CPC
Class: |
F01K 23/101 20130101;
F01K 3/04 20130101; F01K 27/02 20130101 |
Class at
Publication: |
60/645 |
International
Class: |
F01K 27/02 20060101
F01K027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2011 |
EP |
11188956.4 |
Claims
1. A method for operating a gas and steam turbine installation,
having a gas turbine, a steam turbine and a waste heat steam
generator, in which steam for the steam turbine can be generated by
heat exchange with exhaust gas from the gas turbine, wherein the
method comprises, for frequency support in the power grid, starting
from steady-state operation, increasing the absorption capacity of
the steam turbine and decreasing the pressure in the waste heat
steam generator in order to use storage reserves in the waste heat
steam generator for increased steam generation, and supplying heat
energy to the waste heat steam generator at such a rate that, as a
consequence of increasing the absorption capacity of the steam
turbine and decreasing the pressure in the waste heat steam
generator, a power profile of the gas and steam turbine
installation is greater than or equal to an immediately previously
available power of the steady-state operation.
2. The method as claimed in claim 1, wherein, in order to increase
the absorption capacity of the steam turbine, at least one valve in
a bypass duct is opened in order to bypass a steam turbine stage or
a steam turbine module.
3. The method as claimed in claim 2, wherein steam is fed via the
bypass duct into the steam turbine downstream of a high-pressure
intake.
4. The method as claimed in claim 2, wherein steam is fed via the
bypass duct into the steam turbine downstream of an intermediate-
pressure intake.
5. The method as claimed in claim 1, wherein, in order to increase
the absorption capacity of the steam turbine, at least one valve of
a control wheel on a high-pressure turbine and/or an
intermediate-pressure turbine is opened.
6. The method as claimed in claim 1, wherein the heat energy is
supplied by means of increased power from the gas turbine and thus
an increased flow of exhaust gas.
7. The method as claimed in claim 1, wherein the heat energy is
supplied by an auxiliary firing means.
8. The method as claimed in claim 1, wherein, during steady-state
operation, a steam drum pressure is accumulated by means of a valve
which is opened for frequency support.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2012/071478 filed Oct. 30, 2012, and claims
the benefit thereof. The International Application claims the
benefit of European Application No. EP11188956 filed Nov. 14, 2011.
All of the applications are incorporated by reference herein in
their entirety.
FIELD OF INVENTION
[0002] The invention relates to the frequency support operation of
a gas and steam turbine installation.
BACKGROUND OF INVENTION
[0003] The energy market increasingly requires highly flexible
power station installations which, in addition to short startup and
shutdown times, can also cover a large power range and are well
prepared for frequency support operation.
[0004] This also includes, inter alia, the ability to free up
additional power in the event of high electricity demand (what is
termed peak load operation). In this context it will be expected in
the future that power stations which are operated at their setpoint
also participate in peak load coverage and frequency support.
[0005] Present solutions focus on the use of power reserves within
the components or rely on technologies which can make only a very
small power reserve available. Both for frequency support and for
peak load coverage, the gas turbine can be overfired, the
compressor guide vanes can be opened beyond the base load setting,
or water can be injected into the intake air duct. Requirements
which relate only to peak load coverage can be satisfied by
injecting steam into the gas turbine combustor, by cooling the gas
turbine intake air, for example by means of evaporative coolers or
using refrigeration machines (what are termed chillers), or by
equipping the waste heat steam generator (WHSG) with an auxiliary
firing means in order to raise the steam turbine power. For the
purpose of frequency support, the fresh steam or the steam from the
reheating (modified sliding-pressure operation) can be accumulated
and the turbine control valves can subsequently be opened quickly.
EP 1 164 254 B1 describes a gas and steam turbine installation
having steam bypass lines for peak load coverage, i.e. for
auxiliary power at full load. In that context, part of the steam
generated in the waste heat steam generator is fed via bypass ducts
past the turbine inlets and into further inlets, arranged
downstream of these turbine inlets, to the turbine parts, whereby
the pressure in the waste heat steam generator can be kept
substantially constant and the absorption capacity of the steam
turbine--and thereby also the power output--can be increased.
SUMMARY OF INVENTION
[0006] It is an object of the invention to provide a method for the
frequency support operation of a gas and steam turbine
installation, which method makes an improved power reserve
available.
[0007] Embodiments of the invention achieve this object by
providing that, during the operation of a gas and steam turbine
installation having a gas turbine, a steam turbine and a waste heat
steam generator, in which steam for the steam turbine can be
generated by heat exchange with exhaust gas from the gas turbine,
for frequency support in the power grid, starting from steady-state
operation, the absorption capacity of the steam turbine is
increased and the pressure in the waste heat steam generator is
decreased in order to use storage reserves in the waste heat steam
generator for increased steam generation, and that heat energy is
supplied to the waste heat steam generator at such a rate that, as
a consequence of increasing the absorption capacity of the steam
turbine and decreasing the pressure in the waste heat steam
generator, a power profile of the gas and steam turbine
installation is greater than or equal to an immediately previously
available power of the steady-state operation.
[0008] Embodiments of the invention are accordingly based on the
idea of using storage reserves in the waste heat steam generator in
order to generate additional steam by abruptly opening the valves.
As a consequence of the pressure drop in the waste heat steam
generator, steam is in addition generated and an adequately
dimensioned and rapid supply of heat energy should prevent the
common dip in the power profile. By means of this method, control
power can be provided at partial load and full load.
[0009] By means of a method according to an embodiment of the
invention, the flexibility and profitability of the power station
installation can be substantially increased, since at high power
demand additional energy is available which, in particular through
high electricity sales in electricity markets, leads to increased
revenue and makes the operation of the installation more profitable
(peak load ability). This holds for frequency support operation, in
particular for secondary and tertiary support. It is thus not
necessary for primary frequency support or peak load operation to
configure the high-pressure part and also the reheating part with
higher pressure than for rated operation. In addition, it is not
necessary to run the installation in what is termed modified
sliding-pressure operation which, as a consequence of throttling
back the steam turbine control valves, causes losses in power and
efficiency during standby operation of the installation. By means
of the method according to an embodiment of the invention, the load
range of the power station can be extended, as the low load
operation can also be adjusted more flexibly.
[0010] Advantageously, in order to increase the absorption capacity
of the steam turbine, at least one valve in a bypass duct is opened
in order to bypass a steam turbine stage or a steam turbine
module.
[0011] In this context, it is expedient if steam is fed via the
bypass duct into the steam turbine downstream of a high-pressure
intake.
[0012] It is particularly advantageous if, alternatively or
additionally, steam is fed via the bypass duct into the steam
turbine downstream of an intermediate-pressure intake.
[0013] Alternatively or complementarily, it can be advantageous if,
in order to increase the absorption capacity of the steam turbine,
at least one valve of a control wheel on a high-pressure turbine
and/or an intermediate-pressure turbine is opened.
[0014] Preferably, the heat energy is supplied by means of
increased power from the gas turbine and thus an increased flow of
exhaust gas.
[0015] It can furthermore be advantageous if the heat energy is
supplied by an auxiliary firing means. This must, however, be
dimensioned accordingly.
[0016] In order to further increase the storage capacity, it is
expedient if, during steady-state operation, a steam drum pressure
is accumulated by means of a valve which is opened for frequency
support.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention will be explained in more detail by way of
example with reference to the drawings, which are schematic and not
to scale, and in which:
[0018] FIG. 1 is a simplified circuit diagram of a gas and steam
turbine installation having high- and intermediate-pressure
overload introduction and control wheels in the steam turbine and
an auxiliary firing means in the waste heat steam generator,
[0019] FIG. 2 shows a steam turbine power profile for overload
introduction into the high-pressure turbine for various fresh steam
pressure to introduction pressure ratios and
[0020] FIG. 3 shows a steam turbine power profile for overload
introduction into the intermediate-pressure turbine for various
fresh steam pressure to introduction pressure ratios.
DETAILED DESCRIPTION OF INVENTION
[0021] FIG. 1 shows a gas and steam turbine installation 1 which
comprises a gas turbine 2 and a steam turbine 3. A rotor of the gas
turbine, a rotor of a generator 5 and a rotor of the steam turbine
3 are coupled to one another by means of a shaft 4, wherein the
rotor of the steam turbine 3 and the rotor of the generator 5 can
be rotationally separated from one another and coupled to one
another by means of a coupling 6. The rotors of the generator 5 and
of the gas turbine 2 are fixedly interconnected. A flue gas outlet
from the gas turbine 2 is connected, by means of an exhaust gas
line 7, to a waste heat steam generator 8 which is provided for
generating the working steam of the steam turbine 3 using waste
heat from the gas turbine.
[0022] When the gas and steam turbine installation 1 is in
operation, the rotating rotor of the gas turbine 2 drives, via the
shaft 4, a compressor 9 by means of which combustion air is drawn
in from the surroundings and fed to a combustor 10. There, the
combustion air is mixed with fuel supplied by a fuel feed 11 and is
burnt, and the hot, pressurized exhaust gases are fed to the gas
turbine 12 where they are expanded, performing work. The exhaust
gases, still at a temperature of 500 to 600.degree. C., are then
fed via the exhaust gas line 7 to the waste heat steam generator 8
which they flow through until they pass into the environment by way
of a chimney 13. On their path through the waste heat steam
generator 8, they supply their heat to a high-pressure superheater
14, then to a high-pressure reheater 15, to a high-pressure
evaporator 16, to a high-pressure preheater 17, then to an
intermediate-pressure superheater 18, to an intermediate-pressure
evaporator 19, to an intermediate-pressure preheater 20, then to a
low-pressure superheater 21, to a low-pressure evaporator 22 and
finally to a condensate preheater 23.
[0023] Steam superheated in the high-pressure superheater 14 is fed
through a steam takeoff line 24 to a high-pressure stage 25 of the
steam turbine 3 where it is expanded, performing work. With the
work--as with the work performed in the gas turbine--the shaft 4
and thus the generator 5 are moved to generate electrical energy.
The hot steam partially expanded in the high-pressure stage 25 is
then fed to the high-pressure reheater 15 where it is once again
heated, and is fed through a takeoff line 26 to an
intermediate-pressure stage 27 of the steam turbine 3 where it is
expanded, performing mechanical work. The steam partially expanded
there is fed via an overflow line 28 to a low-pressure stage 29 of
the steam turbine 3 where it is further expanded, providing
mechanical energy.
[0024] The expanded steam is condensed in the condenser 30 of the
steam turbine 3 and the resulting condensate is fed by means of a
condensate pump 31 directly to a low-pressure stage 32 of the waste
heat steam generator 8, or by means of a feed pump 33--by which it
is provided with appropriate pressure--to an intermediate-pressure
stage 34 or to a high-pressure stage 35 of the waste heat steam
generator 8, where the condensate is evaporated. After steam
generation and superheating, the steam is fed via the relevant
takeoff lines 24, 26, 36 of the waste heat steam generator 8 back
to the steam turbine 3 to be expanded and to perform mechanical
work.
[0025] Shut-off fittings 37 and 38 are arranged in the steam
takeoff lines 24 and 26. A bypass duct 39 having a shut-off fitting
40 for bypassing the high-pressure stage 25 branches off from the
steam takeoff line 24 leading to the high-pressure stage 25 of the
steam turbine 3. A bypass duct 41 having a shut-off fitting 42 for
bypassing the intermediate-pressure stage 27 branches off in
similar fashion.
[0026] A first control wheel 43 is attached to the rotor of the
steam turbine 3 upstream of the high-pressure part 25 as seen in
the flow direction. A second control wheel 44 is similarly attached
to the rotor of the steam turbine 3 upstream of the
intermediate-pressure part 27 as seen in the flow direction. A
control wheel comprises nozzles which are controlled by valves and
by means of which in each case segments of a turbine can be acted
upon. Depending on how many valves are open, a greater or lesser
quantity of auxiliary steam flows via the nozzles into the
turbine.
[0027] Furthermore, FIG. 1 shows, at the entrance to the waste heat
steam generator 8, an auxiliary firing means 45 in which fuel is
added to the gas turbine exhaust gas, which still contains a lot of
oxygen, and the mixture is burnt. In this way, the fresh steam can
be heated above the temperature of the gas turbine exhaust gas or
for generating process steam if the steam generation is to be
decoupled from the electricity generation of the gas turbine 2. In
particular, an auxiliary firing means 45 can be of interest in
order to increase the output of electrical power at peak demand
times.
[0028] The method according to an embodiment of the invention
provides that the mass flow rate of steam through the steam turbine
is increased at short notice by opening an overload valve 40, 42 or
a turbine bypass 39, 41 and, in connection therewith, the power of
the steam turbine 3 rises rapidly (in seconds).
[0029] The overload introduction may, according to an embodiment of
the invention, be used both on the high-pressure turbine 25 for
raising the mass flow rate of fresh steam and on the
intermediate-pressure turbine 27 for raising the mass flow rate of
reheat steam, and also upstream of each further turbine stage (e.g.
low-pressure turbine 29).
[0030] As an alternative, the absorption capacity of the steam
turbine can be increased by means of a control wheel 43, 44 on the
high-pressure turbine 25, and/or on the intermediate-pressure
turbine 27, by opening corresponding valves.
[0031] In this context, storage reserves from all pressure stages
32, 34, 35 of the waste heat steam generator 8 (e.g. also
intermediate- and low-pressure system, where present) can be
released. By accumulating the drum pressure, e.g. by means of a
pressure regulating valve 46 in the intermediate-pressure steam
system 34, the storage capacity can in this context be increased.
This increase in the mass flow rate of steam is based on an
increase in the absorption capacity of the steam turbine and,
associated therewith, a drop in pressure in the system.
[0032] This drop in pressure leads to a storing of thermal reserves
(hot water, steel masses in the waste heat steam generator) and
thus to a short-term increase in power of the steam turbine, as
FIGS. 2 and 3 show for the power profile in the event of overload
introduction for various ratios of fresh steam pressure to
introduction pressure in the high- or intermediate-pressure
turbine. The horizontal line indicates the value for steady-state
operation.
[0033] Since the thermal storage reserves are limited, the
decreasing storage effect is compensated for or further increased,
according to an embodiment of the invention, either by a
self-igniting auxiliary firing means 45 in the waste heat steam
generator 8, an auxiliary firing means 45 operating at a continuous
minimum load or by means of available power reserves in the gas
turbine 2 (opening the compressor guide vanes, overfiring, steam
injection or water injection into the compressor 9 or combustor
10).
* * * * *