U.S. patent application number 09/761243 was filed with the patent office on 2001-08-30 for gas and steam turbine plant.
Invention is credited to Hannemann, Frank, Schiffers, Ulrich.
Application Number | 20010017030 09/761243 |
Document ID | / |
Family ID | 7874482 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017030 |
Kind Code |
A1 |
Hannemann, Frank ; et
al. |
August 30, 2001 |
Gas and steam turbine plant
Abstract
In a gas and steam turbine plant with a waste-heat steam
generator, a fuel gasification device is located upstream of the
combustion chamber of the gas turbine via a fuel line. The
after-heat steam generator is located downstream of the gas turbine
on the flue-gas side and the heating surfaces of which are
connected into the water/steam circuit of the steam turbine for the
integrated gasification of a fossil fuel. For especially high plant
efficiency, a heat exchanger is connected on the primary side into
the fuel line between the gasification device and a saturator. In
addition to a mixing device for admixing nitrogen, the heat
exchanger likewise is connected on the secondary side into the fuel
line between the saturator and the combustion chamber.
Inventors: |
Hannemann, Frank; (Spardorf,
DE) ; Schiffers, Ulrich; (Eckental, DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
POST OFFICE BOX 2480
HOLLYWOOD
FL
33020-2480
US
|
Family ID: |
7874482 |
Appl. No.: |
09/761243 |
Filed: |
January 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09761243 |
Jan 17, 2001 |
|
|
|
PCT/DE99/02106 |
Jul 8, 1999 |
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Current U.S.
Class: |
60/39.12 ;
60/39.182 |
Current CPC
Class: |
F02C 3/28 20130101; Y02E
20/18 20130101; Y02P 80/15 20151101; Y02T 10/12 20130101; Y02E
20/16 20130101; F02C 6/18 20130101; F01K 23/068 20130101 |
Class at
Publication: |
60/39.12 ;
60/39.182 |
International
Class: |
F02C 006/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 1998 |
DE |
198 32 293.3 |
Claims
We claim:
1. A gas and steam turbine plant, comprising: a gas turbine having
a flue-gas side and a combustion chamber; a steam turbine with a
water/steam circuit; a fuel line connected to said combustion
chamber; a saturator connected to said fuel line; a waste-heat
steam generator located downstream of said gas turbine on said
flue-gas side, said waste-heat generator having heating surfaces
connected into said water/steam circuit of said steam turbine, and
said waste-heat generator having a fuel gasification device located
upstream of said combustion chamber of said gas turbine on said
fuel line; a heat exchanger having a primary side and a secondary
side, said heat exchanger connected on said primary side into said
fuel line between said gasification device and said saturator, said
heat exchanger connecting on said secondary side into said fuel
line between said saturator and said combustion chamber; and a
mixing device admixing nitrogen in said fuel line between said heat
exchanger and said saturator.
2. The gas and steam turbine plant according to claim 1, including:
a crude-gas waste-heat steam generator upstream of said saturator,
preceding said heat exchanger in said fuel line.
3. The gas and steam turbine plant according to claim 1, including:
a further heat exchanger having a primary side and a secondary
side, said secondary side of said further heat exchanger connected
into said fuel line between said saturator and said combustion
chamber.
4. The gas and steam turbine plant according to claim 3, wherein
said further heat exchanger is heated by feedwater.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application No. PCT/DE99/02106, filed Jul. 8, 1999,
which designated the United States.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a gas and steam turbine plant with
a waste-heat steam generator which is located downstream of a gas
turbine on the flue-gas side and the heating surfaces of which are
connected into the water/steam circuit of a steam turbine, and with
a fuel gasification device located upstream of the combustion
chamber of the gas turbine via a fuel line.
[0004] A gas and steam turbine plant with integrated gasification
of fossil fuel conventionally includes a fuel gasification device.
The gasification device is connected on the outlet side to the
combustion chamber of the gas turbine via a number of components
provided for gas purification. The gas turbine may, in this case,
be followed on the flue-gas side by a waste-heat steam generator,
the heating surfaces of which are connected into the water/steam
circuit of the steam turbine. A plant of this type is known, for
example, from UK Patent Application GB-A 2 234 984.
[0005] Furthermore, German Published, Non-Prosecuted Patent
Application DE 33 31 152 A1 discloses a method for operating a gas
turbine plant combined with a fuel gasification plant. In this
case, nitrogen can be supplied to the fuel gas directly upstream of
the combustion chamber.
[0006] In this plant, a saturator is connected into the fuel line
between the gasification device and the combustion chamber of the
gas turbine. In the saturator, the gasified fuel is laden with
steam. Such a plant reduces pollutant emission during the
combustion of the gasified fossil fuel. For this purpose, the
gasified fuel flows through the saturator, countercurrent to a
water stream. The water stream is carried in a water circuit
designated as a saturator circuit. For especially high efficiency,
heat can be fed from the water/steam circuit into the saturator
circuit.
[0007] By coming into contact with the heated water stream in the
saturator, which is carried in the saturator circuit, the gasified
fuel is saturated with steam and to a limited extent undergoes
heating. In this case, for thermal and also operational reasons,
further heating of the fuel may be necessary before the fuel is
supplied into the combustion chamber of the gas turbine.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
gas and steam turbine plant that overcomes the
herein-aforementioned disadvantages of the heretofore-known devices
of this general type and that has especially high plant
efficiency.
[0009] With the foregoing and other objects in view, there is
provided, in accordance with the invention, a gas and steam turbine
plant. The gas and steam turbine plant includes a gas turbine, a
steam turbine, a waste-heat steam generator, a heat exchanger, and
a mixing device. The gas turbine has a flue-gas side and a
combustion chamber. The steam turbine has a water/steam circuit.
The waste-heat steam generator is located downstream of said gas
turbine on said flue-gas side. The waste-heat generator has heating
surfaces connected into the water/steam circuit of said steam
turbine. The waste-heat generator has a fuel gasification device
located upstream of the combustion chamber of the gas turbine on a
fuel line. The heat exchanger has a primary side and a secondary
side connected on the primary side into the fuel line between the
gasification device and a saturator. The heat exchanger connects on
the secondary side into the fuel line between the saturator and the
combustion chamber. The mixing device admixes nitrogen in the fuel
line between the heat exchanger and the saturator.
[0010] In accordance with another feature of the invention, the gas
and steam turbine plant includes a crude-gas waste-heat steam
generator upstream of the saturator. The crude-gas waste-heat steam
generator precedes the heat exchanger in the fuel line.
[0011] In accordance with another feature of the invention, the gas
and steam turbine plant includes a further heat exchanger. The
further heat exchanger has a primary side and a secondary side. The
secondary side of the further heat exchanger connects into the fuel
line between the saturator and the combustion chamber.
[0012] In accordance with another feature of the invention, the
further heat exchanger is heated by feedwater.
[0013] In accordance with this object, a heat exchanger is
connected on the primary side into the fuel line between the
gasification device and the saturator, in addition to a mixing
device for admixing nitrogen, and is likewise connected on the
secondary side into the fuel line between the saturator and the
combustion chamber.
[0014] In a plant of this type, the admixing of nitrogen to the
gasified fossil fuel, also designated as synthesis gas, is intended
for maintaining particularly low NO.sub.x limit values in the
combustion of the synthesis gas. The mixing device provided for
admixing the nitrogen is connected into the fuel line upstream of
the saturator on the fuel side. The heat exchanger is, in this
case, connected into the fuel line upstream of the mixer and
saturator on the primary side and downstream of the saturator on
the secondary side. The heat exchanger thus transmits heat from the
synthesis gas, also designated as crude gas, flowing into the
saturator into the synthesis gas, also designated as mixed gas,
flowing out of the saturator. The heat exchanger (also designated
as a crude-gas/mixed-gas heat exchanger) thus gives rise to an at
least partial heat-side bypass of the saturator. Thereby, the
thermodynamic losses of the overall process are kept particularly
low due to the heating of the synthesis gas by the crude gas. The
fuel-side arrangement of the mixing device upstream of the
saturator at the same time ensures that the crude-gas/mixed-gas
heat exchanger transmits the heat from the crude gas to a
particularly large mass stream. Thus, by virtue of an arrangement
of this type, a particularly favorable heat exchange can be
achieved, since, under the boundary condition of a constant final
temperature, a comparatively large quantity of heat can be
transmitted to the mixed gas flowing out of the saturator.
[0015] For especially high plant efficiency, in an advantageous
development, the crude-gas/mixed-gas heat exchanger is preceded in
the fuel line by a crude-gas waste-heat steam generator upstream of
the saturator. The crude-gas waste-heat steam generator precools
the synthesis gas or crude gas generated in the gasification
device. This precooling is beneficial for material reasons. At the
same time, the heat extracted from the crude gas can be utilized in
an especially beneficial way for steam generation. In steam
generation, in a plant designed for the gasification of coal as
fossil fuel, a so-called gas quench may be provided, in which
so-called quench gas, branched off from the fuel line at a point
between the crude-gas/mixed-gas heat exchanger and the saturator,
is supplied to the synthesis gas before the latter enters the
crude-gas waste-heat steam generator. In an arrangement of this
type, the crude-gas mass flow is approximately comparable to the
mixed-gas mass flow, so that the mixed gas can be preheated by heat
exchange with the crude gas to temperatures of well above three
degrees Celsius (>300.degree. C.) under customary operation
conditions.
[0016] Expediently, a further heat exchanger is connected on the
secondary side into the fuel line between the saturator and the
combustion chamber. The further heat exchanger can be heated, for
example, with a medium-pressure feedwater. In this arrangement,
even in the case of only limited cooling of the crude gas, for
example because of boundary conditions set by a crude-gas dedusting
device, reliable preheating of the mixed gas, along with especially
high plant efficiency, is ensured. A concept of this type for
mixed-gas preheating is also particularly suitable for a plant that
is designed for the gasification of coal as fossil fuel and in
which gas quench is not provided or for a plant designed for the
gasification of oil as fossil fuel. Particularly in the case of a
plant designed for the gasification of coal and without gas quench,
the crude-gas mass flow is usually approximately half the mixed-gas
mass flow. This limits the mixed-gas preheating by the
crude-gas/mixed-gas heat exchanger to a temperature range of about
200.degree. C. to 230.degree. C. Therefore, in a plant of this
type, additional mixed-gas preheating via a further heat exchanger
is especially beneficial. The further heat exchanger can be heated
with high-pressure feedwater.
[0017] Advantages of the invention include, that the
crude-gas/mixed-gas heat exchanger, provided in addition to the
mixing device connected into the fuel line upstream of the
saturator, allows the heat exchanger to have an especially
favorable transmission of heat from the crude gas flowing into the
saturator to the mixed gas flowing out of the saturator, by
bypassing the saturator. Therefore, thermodynamically unfavorable
cooling and reheating of the synthesis gas are necessary only to a
limited extent, so that the efficiency of the gas and steam turbine
plant is especially high.
[0018] Other features that are considered as characteristic for the
invention are set forth in the appended claims.
[0019] Although the invention is illustrated and described herein
as embodied in a gas and steam turbine plant, the invention is
nevertheless not intended to be limited to the details shown,
because various modifications and structural changes may be made
therein without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
[0020] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0021] FIG. 1A is a schematic and block diagram of a gas turbine
plant portion of a gas and steam turbine plant; and
[0022] FIG. 1B is a schematic diagram of a steam turbine plant
portion of the gas and steam turbine plant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In all the figures of the drawing, sub-features and integral
parts that correspond to one another bear the same reference symbol
in each case.
[0024] Referring now in detail to the single figure of the
drawings, there is seen a gas and steam turbine plant 1 that
includes a gas turbine plant 1a and a steam turbine plant 1b. The
gas turbine plant 1a includes a gas turbine 2 with a coupled air
compressor 4 and a combustion chamber 6 that is located upstream of
the gas turbine 2 and that is connected to a compressed-air line 8
of the compressor 4. The gas turbine 2 and the air compressor 4 and
also a generator 10 are seated on a common shaft 12.
[0025] The steam turbine plant 1b includes a steam turbine 20 with
a coupled generator 22 and, in a water/steam circuit 24, a
condenser 26 located downstream of the steam turbine 20 and also a
waste-heat steam generator 30. The steam turbine 20 has a first
pressure stage or high-pressure part 20a, of a second pressure
stage or medium-pressure part 20b and of a third pressure stage or
low-pressure part 20c, which drive the generator 22 via a common
shaft 32.
[0026] In order to supply working medium AM or flue gas, expanded
in the gas turbine 2, into the waste-heat steam generator 30, an
exhaust-gas line 34 is connected to an inlet 30a of the waste-heat
steam generator 30. The expanded working medium AM from the gas
turbine 2 leaves the waste-heat steam generator 30 via its outlet
30b in the direction of a chimney which is not illustrated in any
more detail.
[0027] The waste-heat steam generator 30 comprises a condensate
preheater 40 that can be fed on the inlet side with condensate K
from the condenser 26 via a condensate line 42, into which a
condensate pump unit 44 is connected. The condensate preheater 40
is connected on the outlet side to a feedwater tank 46 via a line
45. Moreover, in order to bypass the condensate preheater 40, as
required, the condensate line 42 can be connected directly to the
feedwater tank 46 via a bypass line which is not illustrated. The
feedwater tank 46 is connected via a line 47 to a high-pressure
feed pump 48 with medium-pressure extraction.
[0028] The high-pressure feed pump 48 brings the feedwater S
flowing out of the feedwater tank 46 to a pressure level suitable
for a high-pressure stage 50 of the water/steam circuit 24. The
high-pressure stage is assigned to the high-pressure part of the
steam turbine 20. The feedwater S, which is under high pressure,
can be supplied to the high-pressure stage 50 via a feedwater
preheater 52. The feedwater preheater 52 is connected on the outlet
side to a high-pressure drum 58 via a feedwater line 56 capable of
being shut off by means of a valve 54.
[0029] The high-pressure drum 58 is connected to a high-pressure
evaporator 60 arranged in the waste-heat steam generator 30, in
order to form a water/steam cycle 62. For the discharge of fresh
steam F, the high-pressure drum 58 is connected to a high-pressure
superheater 64 which is arranged in the waste-heat steam generator
30 and which is connected on the outlet side to the steam inlet 66
of the high-pressure part 20a of the steam turbine 20.
[0030] The steam outlet 68 of the high-pressure part 20a of the
steam turbine 20 is connected via a reheater 70 to the steam inlet
72 of the medium-pressure part 20b of the steam turbine 20. Its
steam outlet 74 is connected via an overflow line 76 to the steam
inlet 78 of the low-pressure part 20c for the steam turbine 20. The
steam outlet 80 of the low-pressure part 20c of the steam turbine
20 is connected via a steam line 82 to the condenser 26, so that a
closed water/steam circuit 24 is obtained.
[0031] Moreover, a branch line 84 branches off from the
high-pressure feed pump 48 at an extraction point at which the
condensate K has reached a medium pressure. This branch line is
connected via a further feedwater preheater 86 or medium-pressure
economizer to a medium-pressure stage 90 of the water/steam
circuit. The medium-pressure stage is assigned to the
medium-pressure part 20b of the steam turbine 20. For this purpose,
the second feedwater preheater 86 is connected on the outlet side
to a medium-pressure drum 96 of the medium-pressure stage 90 via a
feedwater line 94 capable of being shut off by means of a valve 92.
The medium-pressure drum 96 is connected to a heating surface 98
arranged in the waste-heat steam generator 30 and designed as a
medium-pressure evaporator, in order to form a water/steam cycle
100. For the discharge of medium-pressure fresh steam F', the
medium-pressure drum 96 is connected via a steam line 102 to the
reheater 70 and therefore to the steam inlet 72 of the
medium-pressure part 20b of the steam turbine 20.
[0032] A further line 110 provided with a low-pressure feed pump
107 and capable of being shut off by means of a valve 108 branches
off from the line 47 and is connected to a low-pressure stage 120
of the water/steam circuit 24. The low-pressure stage is assigned
to the low-pressure part 20c of the steam turbine 20. The
low-pressure stage 120 includes a low-pressure drum 122 that is
connected to a heating surface 124 arranged in the waste-heat steam
generator 30 and designed as a low-pressure evaporator, in order to
form a water/steam cycle 126. In order to discharge low-pressure
fresh steam F", the low-pressure drum 122 is connected to the
overflow line 76 via a steam line 128, into which a low-pressure
superheater 129 is connected. The water/steam circuit 24 of the gas
and steam turbine plant 1 thus comprises three pressure stages 50,
90, 120 in the exemplary embodiment. Alternatively, however, fewer,
in particular two, pressure stages may also be provided.
[0033] The gas turbine plant la is designed to operate with a
gasified synthesis gas SG that is generated by the gasification of
a fossil fuel B. The synthesis gas provided may be, for example,
gasified coal or gasified oil. For this purpose, the combustion
chamber 6 of the gas turbine 2 is connected on the inlet side to a
gasification device 132 via a fuel line 130. Coal or oil can be
supplied as fossil fuel B to the gasification device 132 via a
charging system 134.
[0034] In order to provide the oxygen O.sub.2 required for
gasifying the fossil fuel B, the gasification device 132 is
preceded via an oxygen line 136 by an air separation plant 138. The
air separation plant 138 is capable of being loaded on the inlet
side with a part stream T of the air compressed in the air
compressor 4. For this purpose, the air separation plant 138 is
connected on the inlet side to an extraction air line 140 which
branches off from the compressed-air line 8 at a branch point 142.
Moreover, a further air line 143, into which an additional air
compressor 144 is connected, issues into the extraction air line
140.
[0035] In the exemplary embodiment, therefore, the entire air
stream L flowing into the air separation plant 138 is composed of
the part stream T branched off from the compressed-air line 8 and
of the air stream conveyed from the additional air compressor 144.
A connection concept of this type is also designated as a partly
integrated plant concept. In an alternative embodiment, the
so-called fully integrated plant concept, the further air line 143,
along with the additional air compressor 144, may also be dispensed
with, so that the air separation plant 138 is fed with air
completely via the part stream T extracted from the compressed-air
line 8.
[0036] The nitrogen N.sub.2 obtained additionally to the oxygen
O.sub.2 in the air separation plant 138 during the separation of
the air stream L is supplied, via a nitrogen line 145 connected to
the air separation plant 138, to a mixing device 146 and is admixed
with the synthesis gas SG there. In this case, the mixing device
146 is designed for particularly uniform and strand-free mixing of
the nitrogen N.sub.2 with the synthesis gas SG.
[0037] The synthesis gas SG flowing out from the gasification
device 132 first passes via the fuel line 130 into a crude-gas
waste-heat steam generator 147, in which cooling of the synthesis
gas SG takes place by heat exchange with a flow medium.
High-pressure steam generated during this heat exchange is supplied
to the high-pressure stage 50 of the water/steam circuit 24 in a
way not illustrated in any more detail.
[0038] A dedusting device 148 for the synthesis gas SG and a
desulfurating plant 149 are connected into the fuel line 130
downstream of the crude-gas waste-heat steam generator 147 and
upstream of the mixing device 146, as seen in the direction of flow
of the synthesis gas SG. In an alternative embodiment, instead of
the dedusting device 148, a soot scrubber device may also be
provided, particularly when the gasified fuel is oil.
[0039] For especially low pollutant emission during the combustion
of the gasified fuel in the combustion chamber 6, the gasified fuel
with steam can be loaded prior to entry into the combustion chamber
6. This may be accomplished in a saturator system, which is
advantageous in thermal terms. For this purpose, a saturator 150 is
connected into the fuel line 130. In the saturator, the gasified
fuel is carried in countercurrent to the heated saturator water. In
this case, the saturator water circulates in a saturator circuit
152 that is connected to the saturator 150. Into the saturator
circuit 152, a circulating pump 154 and a heat exchanger 156 for
preheating the saturator water are connected. In this case, the
heat exchanger 156 is loaded on the primary side with preheated
feedwater from the medium-pressure stage 90 of the water/steam
circuit 24. In order to compensate for the losses of saturator
water that occur during the saturation of the gasified fuel, a feed
line 158 is connected to the saturator circuit 152.
[0040] A heat exchanger 159 acting as a crude-gas/mixed-gas heat
exchanger is connected on the secondary side into the fuel line 130
downstream of the saturator 150, as seen in the direction of flow
of the synthesis gas SG. In this case, the heat exchanger 159 is
likewise connected into the fuel line 130 on the primary side at a
point upstream of the dedusting plant 148. This configuration
allows the synthesis SG to flow into the dedusting plant 148 and
transmit part of its heat to the synthesis gas SG flowing out of
the saturator 150. The routing of the synthesis gas SG via the heat
exchanger 159 prior to entry into the desulfurating plant 149 may
also be provided, in this case, with regard to a connection concept
which is modified in terms of the other components. Particularly
when a soot scrubber device is incorporated, the heat exchanger may
be arranged preferably on the crude-gas side downstream of the soot
scrubber device.
[0041] A further heat exchanger 160, which on the primary side may
be feedwater-heated or else steam-heated, is connected on the
secondary side into the fuel line 130 between the saturator 150 and
the heat exchanger 159. In this case, the heat exchanger 159,
designed as a crude-gas/pure-gas heat exchanger, and the heat
exchanger 160 ensure particularly reliable preheating of the
synthesis gas SG flowing into the combustion chamber 6 of the gas
turbine 2, even when the gas and steam turbine plant 1 is in
different operating states.
[0042] Furthermore, in order to load the synthesis gas SG flowing
into the combustion chamber 6 with steam, as required, the fuel
line 130 has connected into it a further mixing device 161.
Medium-pressure steam can be supplied to the further mixing device
via a steam line, not illustrated in any more detail. The
medium-pressure steam ensures that the gas turbine operates
reliably in the event of operational incidents.
[0043] In order to cool the part stream T of compressed air to be
supplied to the air separation plant 138 and also designated as
extraction air, the extraction air line 140 has connected into it
on the primary side a heat exchanger 162 which is designed on the
secondary side as a medium-pressure evaporator for a flow medium
S'. The heat exchanger 162 is connected, to form an evaporator
cycle 163, to a water/steam drum 164 designed as a medium-pressure
drum. The water-steam drum 164 is connected via lines 166, 168 to
the medium-pressure drum 96 assigned to the water/steam cycle 100.
Alternatively, however, the heat exchanger 162 may also be
connected directly on the secondary side to the medium-pressure
drum 96. In the exemplary embodiment, therefore, the water/steam
drum 164 is connected indirectly to the heating surface 98 designed
as a medium-pressure evaporator. Moreover, a feedwater line 170 is
connected to the water/steam drum 164 for the refeed of evaporated
flow medium S'.
[0044] Connected into the extraction air line 140 downstream of the
heat exchanger 162, as seen in the direction of flow of the part
stream T of compressed air, is a further heat exchanger 172 which
is designed on the secondary side as a low-pressure evaporator for
a flow medium S". In this case, to form an evaporator cycle 174,
the heat exchanger 172 is connected to a water/steam drum 176
designed as a low-pressure drum. In the exemplary embodiment, the
water/steam drum 176 is connected via lines 178, 180 to the
low-pressure drum 122 assigned to the water/steam cycle 126 and is
thus connected indirectly to the heating surface 124 which is
designed as a low-pressure evaporator. Alternatively, however, the
water/steam drum 176 may also be connected in another suitable way.
The steam extracted from the water/steam drum 176 can be supplied
as process steam and/or as heating steam to a secondary consumer.
In a further alternative embodiment, the heat exchanger 172 also
may be connected directly on the secondary side to the low-pressure
drum 122. Moreover, the water/steam drum 176 is connected to a
feedwater line 182.
[0045] The evaporator cycles 163, 174 may in each case be designed
as a positive cycle. The cycle of the flow medium S' or S" is
ensured by a circulating pump. The flow medium S', S" at least
partially evaporates in the heat exchanger 162 or 172 designed as
an evaporator. In the exemplary embodiment, however, both the
evaporator cycle 163 and the evaporator cycle 174 are each designed
as a natural cycle. The cycle of the flow medium S' or S" is
ensured by the pressure differences established during the
evaporation process and/or by the geodetic arrangement of the
respective heat exchanger 162 or 172 and of the respective
water/steam drum 164 or 176. In this embodiment, in each case, only
one circulating pump (not illustrated) of comparatively small
dimension is connected into the evaporation cycle 163 or into the
evaporator cycle 174 for the purpose of starting up the system.
[0046] For feeding heat into the saturator circuit 152, there is
provided, in addition to the heat exchanger 156 which is capable of
being loaded with heated feedwater branched off downstream of the
feedwater preheater 86, a saturator water heat exchanger 184. The
saturator water heat exchanger 184 is capable of being loaded on
the primary side with feedwater S from the feedwater tank 46. For
this purpose, the saturator water heat exchanger 184 is connected
on the primary side to the branch line 84 via a line 186 on the
inlet side and to the feedwater tank 46 via a line 188 on the
outlet side. For reheating the cooled feedwater S flowing out of
the saturator water heat exchanger 184, an additional heat
exchanger 190 is connected into the line 188 and on the primary
side is located downstream of the heat exchanger 172 in the
extraction air line 140. This configuration achieves especially
high heat recovery from the extraction air and therefore especially
high efficiency of the gas and steam turbine plant 1.
[0047] A cooling-air line 192 branches from the extraction air line
140 between the heat exchanger 172 and the heat exchanger 190, as
seen in the direction of flow of the part stream T, and a part
quantity T' of the cooled part stream T can be supplied to the gas
turbine 2 via the cooling-air line as cooling air for cooling the
blades.
[0048] The arrangement of the mixing device 146 on the fuel side
upstream of the saturator 150 enables, in the heat exchanger 159,
especially favorable heat transmission from the synthesis gas SG
flowing into the saturator 150 and also designated as crude gas to
the synthesis gas SG flowing out of the saturator 150 and also
designated as mixed gas. In this case, heat exchange is promoted.
In particular, the heat exchanger 159 promotes heat exchange by
transmitting the heat from the crude gas to a particularly high
mass flow of the mixed gas. Thus, even in the case of a limited
final temperature, a comparatively large amount of heat can be
transmitted to the mixed gas flowing out of the saturator 150. The
gas and steam turbine plant 1 therefore has especially high plant
efficiency.
* * * * *