U.S. patent application number 10/168686 was filed with the patent office on 2003-08-07 for method for operating a steam turbine installation and a steam turbine installation that functions according thereto.
Invention is credited to Noelscher, Christoph.
Application Number | 20030145596 10/168686 |
Document ID | / |
Family ID | 7933670 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030145596 |
Kind Code |
A1 |
Noelscher, Christoph |
August 7, 2003 |
Method for operating a steam turbine installation and a steam
turbine installation that functions according thereto
Abstract
During the operation of a steam turbine installation (1), flue
gas (RG) produced by combusting a fossil fuel (B) is firstly guided
in a high-temperature heat exchanger (3) while exchanging heat with
water vapor (WD) which flows in the water-steam circuit (6) of a
steam turbine (7) and which is fed to the steam turbine (7) as
fresh steam (FD) having a fresh steam temperature (T.sub.FD) of
preferably greater than 800 .degree. C. The flue gas (RG) that is
cooled down in the high-temperature heat exchanger (3) is
subsequently guided in a waste heat stem generator (4) while
exchanging heat with feed water (SW), which flows in the
water-steam circuit, whereupon inducing the production of water
vapor (WD).
Inventors: |
Noelscher, Christoph;
(Nuernberg, DE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O.BOX 8910
RESTON
VA
20195
US
|
Family ID: |
7933670 |
Appl. No.: |
10/168686 |
Filed: |
June 21, 2002 |
PCT Filed: |
December 8, 2000 |
PCT NO: |
PCT/DE00/04373 |
Current U.S.
Class: |
60/670 |
Current CPC
Class: |
F01K 7/22 20130101; F22B
31/00 20130101; Y02E 20/18 20130101 |
Class at
Publication: |
60/670 |
International
Class: |
F01K 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 1999 |
DE |
199 61 808.9 |
Claims
1. A method of operating a steam turbine installation, in which
method combustion gas (RG) generated by combustion of a fossil fuel
(B) is guided so as to exchange heat with a medium (SW, WD) flowing
in the water/steam cycle (6) of a steam turbine (7), in which the
hot combustion gas (RG) is first supplied to the primary side of a
high-temperature heat exchanger (3) and is there guided so as to
exchange heat with steam (WD), which is supplied to the secondary
side of the high-temperature heat exchanger (3) and flows in the
water/steam cycle (6), the steam heated by this means being
supplied to the steam turbine (7) as live steam (FD), and in which
the combustion gas (RG) cooled in the high-temperature heat
exchanger (3) is subsequently guided in a waste-heat steam
generator (4) so as to exchange heat with feed water (SW) flowing
in the water/steam cycle (6), the steam (WD) being generated by
this means.
2. The method as claimed in claim 1, in which the steam (WD) is
heated in the high-temperature heat exchanger (3) to a live steam
temperature (T.sub.FD) greater than or equal to 800.degree. C.
3. The method as claimed in claim 1 or 2, in which the steam
turbine (7) is cooled by the steam (WD) extracted from the
water/steam cycle (6).
4. The method according to one of claims 1 to 3, in which the steam
(WD) generated in the waste-heat steam generator (4) is supplied to
a separate steam turbine (15) and the steam (WD) expanded
there--with work output--is supplied to the high-temperature heat
exchanger (3).
5. A steam turbine installation having a combustion installation
(1) for a fossil fuel (B) for the generation of combustion gas
(RG), which is guided in a high-temperature heat exchanger (3) and
in a waste-heat steam generator (4) connected downstream on the
combustion gas side of the high-temperature heat exchanger (3) so
as to exchange heat with a medium (SW, WD) flowing in the
water/steam cycle (6) of a steam turbine (7), and in which the
steam side of the high-temperature heat exchanger (3) is connected
between the waste-heat steam generator (4) and the steam turbine
(7).
6. The steam turbine installation as claimed in claim 5,
characterized in that the steam turbine (7) is connected to a
cooling steam line (13) by means of which the steam (WD) extracted
from the water/steam cycle (6) can be supplied to the steam turbine
(7) as cooling steam (KD).
7. The steam turbine installation as claimed in claim 6,
characterized in that the cooling steam line (13) is connected to a
steam line (9) connecting the high-temperature heat exchanger (3)
to the waste-heat steam generator (4).
8. The steam turbine installation as claimed in one of claims 5 to
7, characterized by a separate steam turbine (15) connected on the
steam side between the waste-heat steam generator (4) and the
high-temperature heat exchanger (3).
9. The steam turbine installation as claimed in claim 8,
characterized by a steam line (17) connecting the separate steam
turbine (15) with heating surfaces (8) of the high-temperature heat
exchanger (3), to which steam line (17) is connected a cooling
steam line (18) for supplying cooling steam (KD) to the steam
turbine (7) connected downstream of the high-temperature heat
exchanger (3) on the steam side.
10. The steam turbine installation as claimed in one of claims 5 to
9, characterized in that an ash separator (2) is connected
downstream of the combustion installation (1).
Description
[0001] The invention relates to a method of operating a steam
turbine installation, in which method combustion gas generated by
combustion of a fossil fuel is guided so as to exchange heat with a
medium flowing in the water/steam cycle of a steam turbine. It also
relates to a steam turbine installation operating according to this
method.
[0002] In power stations employed for electricity generation, in
which a fossil fuel, in particular coal, is employed as the primary
energy carrier, various so-called combined processes can be applied
which have in common the combined employment of a gas turbine
installation and a steam turbine installation. In the case of
so-called pressurized coal gasification (Integrated Gasification
Combined Cycle--IGCC) for example, coal is gasified with the supply
of oxygen generated in an air separation plant and the gaseous fuel
generated is burnt in a combustion chamber after gas cleaning has
taken place. The hot combustion gas generated during the combustion
is expanded in a gas turbine at an inlet temperature of between
1000.degree. C. and 1400.degree. C. The combustion gas,
expanded--with work output--and cooled to approximately 540.degree.
C., is guided in a waste-heat steam generator so as to exchange
heat with a medium flowing in the water/steam cycle of a steam
turbine in the form of a water/water/steam mixture. The live steam
generated in the process is expanded--with work output--at an inlet
temperature of approximately 540.degree. C. in the steam
turbine.
[0003] Further combined processes are pressurized fluidized bed
combustion (PFBC) and pressurized pulverized coal combustion
(PPCC), in which coal is likewise burnt as the primary energy
carrier and the cleaned combustion product is supplied as hot
combustion gas directly to the gas turbine. In these combined
processes also, the combustion gas expanded--with work output--and
cooled to approximately 500.degree. C. to 550.degree. C. in the gas
turbine is guided in a waste-heat steam generator or heat exchanger
so as to exchange heat with the medium flowing in the water/steam
cycle of the steam turbine. The steam generated in the process is
superheated either in the waste-heat steam generator itself or in
the combustion installation and again supplied as live steam to the
steam turbine.
[0004] Just as in a purely fossil-fired steam turbine installation,
the steam expanded--with work output--in the steam turbine is again
condensed in its combined processes, in a condenser connected
downstream of the steam turbine and is supplied anew as feed water
to the water/steam cycle.
[0005] In addition to these combined processes, the so-called
externally fired combined cycle (EFCC) is described in the article
"EFCC--Ein zukutnftiges Konzept fur Kohle-Kombi-Kraftwerk
(EFCC-Afuture concept for combined coal power station)?", in VGB
Kraftwerkstechnik 77 (1997), Volume 7, Pages 537 to 543. In this
combined process, a high-temperature heat exchanger is employed in
which hot combustion gas generated by the combustion of coal is
guided so as to exchange heat with compressed air. The air heated
in this process to a temperature of approximately 1400.degree. C.
is supplied to the gas turbine as the working medium. The
combustion gas which has been cooled by heat exchange with the
compressed air is again supplied to a waste-heat steam generator.
Subsequent to the heat exchange taking place there with the medium
guided in the water/steam cycle of a steam turbine, the cooled
combustion gas is cleaned in an installation which removes oxides
of nitrogen and/or sulfur (DENOX, REA plant) before it is exhausted
to the surroundings through a chimney.
[0006] The hot combustion gas generated in the case of the EFCC
process in a so-called slag tap firing process is first cleaned by
ash separation and subsequently supplied to the high-temperature
heat exchanger. The parts of the latter exposed to the high
combustion gas temperature, for example tube bundles through which
the compressed air flows and around which the hot combustion gas
flows, consist of a ceramic or a metallic material involving a
special high-temperature resistant alloy.
[0007] This new concept promises an increase in the installation
efficiency, at between 51% and 53%, relative to the combined
processes with integrated gasification combined cycle(IGCC),
pressurized fluidized bed combustion (PFBC) or pressurized
pulverized coal combustion (PPCC). A disadvantage in this combined
process with externally fired combustion cycle (EFCC) is, however,
the fact that the air used as working medium for the gas turbine
must be mechanically compressed. Although the compression energy
necessary for this is reused, in part, by expansion in the gas
turbine, the overall process is subject to loss, particularly as
the mechanical energy necessary is only used in an unfavorable
manner for the generation of electricity.
[0008] The invention is based on the object of providing a method
of operating a steam turbine installation in which, in a simple
manner, as high as possible an installation efficiency is achieved
by a live steam inlet temperature, for the steam turbine, which is
as high as possible. A particularly suitable steam turbine
installation for carrying out the method is, in addition, to be
provided.
[0009] With respect to the method, the object is achieved according
to the invention by the features of claim 1. For this purpose, the
hot combustion gas generated by combustion of a fossil fuel is
first guided as the primary medium in a high-temperature heat
exchanger so as to exchange heat with steam, flowing in the
water/steam cycle of the steam turbine, as the secondary medium.
The steam heated in the process to a temperature of preferably more
than 800.degree. C. is supplied as live steam to the steam turbine.
The combustion gas cooled in the high-temperature heat exchanger is
subsequently guided in a waste-heat steam generator so as to
exchange heat with feed water flowing in the water/steam cycle in
order to generate the steam.
[0010] In the combustion of problematic fuels, such as in refuse
combustion, it is in fact known from DE 693 16 634 T2 to use, for
steam generation, hot exhaust gas which has been generated with the
application of a high-temperature heat exchanger. In this
arrangement, however, the high-temperature heat exchanger and a
waste-heat boiler are connected in parallel on the waste-gas side
and air, for example, as an additional energy carrier, flows
through a superheater connected downstream on the steam side of the
waste-heat boiler and the high-temperature heat exchanger in a
closed cycle.
[0011] The invention, then, is based on the consideration that the
mechanical compression energy for the electricity generation
necessary in the EFCC process can be more favorably used if,
instead of air, a liquid is compressed and subsequently thermally
evaporated. The heating of steam, which is extracted from a
conventional water/steam cycle of a steam turbine, is then
particularly favorable. This steam can then be heated in the
high-temperature heat exchanger to a temperature of between
1200.degree. C. and 1400.degree. C. and subsequently expanded in a
cooled high-temperature steam turbine. The latter then drives a
generator or also a feed-water pump.
[0012] In this way, the energy extracted from the high-temperature
heat exchanger can be exergetically better used, as compared with
the EFCC process. Even in the case where the efficiency is the
same, a smaller installation volume can, in the case of the heating
of steam for a steam turbine, be achieved for the same useful
mechanical energy as compared with the EFCC process. On the one
hand, this is based on the fact that, for the same transmission of
high-temperature heat, the fuel utilization is higher as compared
with the EFCC process because, in the latter, the gas turbine waste
heat is usually supplied to the combustion process. On the other
hand, the high-temperature heat exchanger can have a smaller
configuration as compared with the EFCC process because the fuel
utilization must, for the same effectiveness, be the same for the
same useful mechanical energy. For the same electrical power, the
more efficient utilization of the high-temperature heat by the
steam turbine additionally permits a reduction in the conventional
steam constituent as compared with the EFCC process. Furthermore,
the air compressor necessary with the latter is dispensed with.
[0013] In order to deal with the high live steam temperatures of
more than or equal to 800.degree. C., it is expedient to cool the
steam turbine. Steam extracted from the water/steam cycle is
advantageously used for this purpose.
[0014] In an advantageous embodiment, the steam produced in the
waste-heat steam generator is first expanded--with work output--in
a separate (conventional) steam turbine before this expanded steam
is heated in the high-temperature heat exchanger to the live steam
temperature of the steam turbine connected downstream of the
high-temperature heat exchanger on the steam side. The two steam
turbines, together with a generator, can then be seated on a common
shaft (single-shaft embodiment) and can operate on a common
condenser, which is connected upstream of the heating surfaces of
the waste-heat steam generator within the water/steam cycle. The
steam turbine connected down-stream of the high-temperature heat
exchanger on the steam side then forms, so to speak, the
high-temperature part of the steam turbine connected upstream of
the high-temperature heat exchanger on the steam side.
[0015] With respect to the steam turbine installation, the object
is achieved, according to the invention, by the features of claim
5. Advantageous configurations are the subject matter of the
sub-claims which refer back to claim 5.
[0016] A high-temperature heat exchanger connected upstream of the
waste-heat steam generator on the combustion gas side and
downstream on the steam side--with heat-exchanger heating surfaces
in, for example, ceramic material--is connected upstream, on the
steam side, of a preferably steam-cooled high-temperature steam
turbine. In order to cool the steam turbine, a cooling steam line,
by means of which steam extracted from the water/steam cycle can be
supplied as cooling steam to the steam turbine, is guided to the
latter. In this arrangement, the cooling steam line is expediently
connected to a steam line connecting the high-temperature heat
exchanger to the waste-heat steam generator. The cooling steam line
is, in the case of the embodiment with a separate steam turbine
which [lacuna] expediently connected to a steam line connecting the
latter to the high-temperature heat exchanger, by means of which
steam line the steam to be heated or to be superheated is also
guided.
[0017] Embodiment examples of the invention are explained in more
detail below using a drawing. In this:
[0018] FIG. 1 shows, diagrammatically, a steam turbine installation
with a high-temperature heat exchanger for the generation of live
steam for a cooled high-temperature steam turbine and
[0019] FIG. 2 shows, in a representation corresponding to FIG. 1, a
steam turbine installation with two steam turbines in single-shaft
embodiment.
[0020] Mutually corresponding parts in the two figures are provided
with the same designations.
[0021] The steam turbine installation shown in FIG. 1 comprises a
combustion installation 1 in the form, for example, of an
atmospheric pulverized coal firing with liquidized ash removal in a
separator 2 (slag tap firing), together with a high-temperature
heat exchanger 3 and a waste-heat steam generator 4 connected
downstream of it on the combustion gas side. The heating surfaces 5
of the waste-heat steam generator 4 are connected into the
water/steam cycle 6 of a steam turbine 7. The high-temperature heat
exchanger 3 is connected, on the steam side, downstream of the
waste-heat steam generator 4 and upstream of the steam turbine 7.
For this purpose, heating surfaces 8 of the high-temperature heat
exchanger 3, consisting for example of ceramic material or of a
special high-temperature resistant metal alloy, for example an
oxide dispersion strengthened (ODS) alloy, are connected
downstream, by means of a steam line 9, to the heating surfaces 5
of the waste-heat steam generator 4 and upstream, by means of a
high-temperature steam line 10, to the steam turbine 7.
[0022] During operation of the steam turbine installation, fuel B,
in particular coal, is burnt in the combustion installation 1 with
the supply of air L. The hot combustion product generated by this
is supplied, after a cleaning process in the ash separator 2, to
the high-temperature heat exchanger 3 on the primary side as
combustion gas RG with a combustion gas temperature T.sub.RG of,
for example, 800.degree. C. to 1400.degree. C. In the
high-temperature heat exchanger 3, an exchange of heat takes place
between the hot combustion gas RG and steam WD guided over the
secondary-side heating surfaces 8 of the high-temperature heat
exchanger 3. The steam heated by this process is supplied to the
steam turbine 7 as live steam FD with a live steam or inlet
temperature T.sub.FD greater than or equal to 800.degree. C. The
steam turbine 7, in which the live steam FD expands--with work
output drives a generator 11 for the generation of electricity.
[0023] The live steam FD expanded--with work output--in the steam
turbine 7 is condensed in a condenser 12 connected downstream of
the steam turbine 7. The resulting condensate or feed water SW is
supplied, by means of a feed-water pump 13, to the heating surfaces
5 of the waste-heat steam generator 4, in the form for example of a
preheater and an evaporator connected downstream of it. The steam
WD generated in the waste-heat steam generator 4 is guided via the
steam line 9 to the steam side of the high-temperature heat
exchanger 3.
[0024] The steam turbine 7 is cooled by means of cooling steam KD
and is therefore preferably embodied as a high-temperature steam
turbine. In the embodiment example, the cooling steam KD is
extracted from the water/steam cycle 6 from the steam line 9. For
this purpose, a cooling steam line 14 is connected to the steam
line 9 connecting the high-temperature heat exchanger 3 to the
waste-heat steam generator 4.
[0025] In the exemplary embodiment shown in FIG. 2, the steam
turbine installation comprises, in addition to the high-temperature
steam turbine 7, a further steam turbine 15, which drive the
generator 11 via a common shaft 16 (single shaft). The generation
of the hot combustion gas RG takes place in a manner analogous to
the exemplary embodiment of FIG. 1. In this arrangement, the hot
combustion gas RG is again guided in the high-temperature heat
exchanger 3 so that it exchanges heat with steam WD, which is
extracted from the further steam turbine 15 in this case. For this
purpose, the steam turbine 15 is connected on the steam side
between the waste-heat steam generator 4 and the high-temperature
heat exchanger 3. The further steam turbine 15 is again connected
on the exhaust steam side to the condenser 12, into which the
high-temperature steam turbine 7 also opens on the exhaust steam
side.
[0026] In the exemplary embodiment of FIG. 2, therefore, the actual
high-temperature part of the separate steam turbine 15 is embodied
in the form of a high-temperature steam turbine 7, whereas this
high-temperature part is integrated into the steam turbine 7 in the
exemplary embodiment of FIG. 1. In the steam turbine installation
of FIG. 2, the steam turbine 7, operating as the high-temperature
part, is again cooled by means of cooling steam KD. The latter is
extracted from a steam line 17 connecting the further or separate
steam turbine 15 to the heating surfaces 8 of the high-temperature
heat exchanger 3 and is guided by means of a cooling steam line 18,
which is connected to the steam line 17, to the high-temperature
steam turbine 7.
[0027] The operating pressure of the steam turbine installation 1
is, in practice, approximately limited to between 15 bar and 30 bar
at an operating temperature of 1400.degree. C., by the strength of
the high-temperature heat exchanger. The operating pressure p in
the water/steam cycle 6, at 30 bar, is therefore relatively low in
comparison with a conventional water/steam cycle at approximately
250 bar. The operating pressure can be increased to 150 bar in the
case of an operating temperature of 1000.degree. C.
* * * * *