U.S. patent application number 09/761238 was filed with the patent office on 2001-09-27 for gas and steam-turbine plant.
Invention is credited to Hannemann, Frank, Schiffers, Ulrich.
Application Number | 20010023579 09/761238 |
Document ID | / |
Family ID | 7874483 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023579 |
Kind Code |
A1 |
Hannemann, Frank ; et
al. |
September 27, 2001 |
Gas and steam-turbine plant
Abstract
A gas and steam-turbine plant includes a heat-recovery steam
generator which is connected downstream of a gas turbine on the
flue-gas side and has heating surfaces connected in a water/steam
circuit of a steam turbine. A gasifier is connected upstream of a
combustion chamber of the gas turbine for integrated gasification
of a fossil fuel. Oxygen can be fed to the gasifier from an
air-separation unit, to which in turn a partial flow of air
compressed in an air compressor associated with the gas turbine can
be admitted on the inlet side. In such a gas and steam-turbine
plant, reliable cooling of the bleed air, in an especially simple
type of construction, is to be ensured in all operating states,
irrespective of the integration concept which is taken as a basis.
Therefore, a heat exchanger for cooling the partial flow of
compressed air is connected on the primary side in a bleed-air line
connecting the air compressor to the air-separation unit. The heat
exchanger is constructed on the secondary side as an evaporator for
a flow medium.
Inventors: |
Hannemann, Frank; (Spardorf,
DE) ; Schiffers, Ulrich; (Eckental, DE) |
Correspondence
Address: |
LERNER & GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7874483 |
Appl. No.: |
09/761238 |
Filed: |
January 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09761238 |
Jan 17, 2001 |
|
|
|
PCT/DE99/02058 |
Jul 2, 1999 |
|
|
|
Current U.S.
Class: |
60/39.12 ;
60/39.182 |
Current CPC
Class: |
Y02E 20/18 20130101;
Y02E 20/16 20130101; F01K 23/068 20130101; Y02P 80/15 20151101 |
Class at
Publication: |
60/39.12 ;
60/39.182 |
International
Class: |
F02C 003/28; F02C
006/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 1998 |
DE |
198 32 294.1 |
Claims
We claim:
1. A gas and steam-turbine plant, comprising: a steam turbine
having a water/steam circuit; a gas turbine having a flue-gas side;
a combustion chamber associated with said gas turbine; an air
compressor associated with said gas turbine for supplying a partial
flow of air compressed in said air compressor; a bleed-air line
connected to said air compressor; an air-separation unit supplying
oxygen and having an inlet side connected to said bleed-air line
for receiving said partial flow of air compressed in said air
compressor; a heat-recovery steam generator connected downstream of
said gas turbine on said flue-gas side, said steam generator having
heating surfaces connected in said water/steam circuit; a gasifier
for fuel, said gasifier connected upstream of said combustion
chamber and receiving oxygen from said air-separation unit; a
water/steam drum; and a heat exchanger constructed as an
evaporative cooler for cooling said partial flow of compressed air,
said heat exchanger having a primary side connected to said
bleed-air line and a secondary side connected to said water/steam
drum to form an evaporator circuit for a flow medium.
2. The gas and steam-turbine plant according to claim 1, wherein
said heat exchanger is a first heat exchanger and is constructed as
an intermediate-pressure evaporator, a second heat exchanger has a
secondary side constructed as an evaporator for a flow medium and
is connected to said bleed-air line downstream of said first heat
exchanger, and said second heat exchanger is constructed as a
low-pressure evaporator.
3. The gas and steam-turbine plant according to claim 2, including
another water/steam drum, said second heat exchanger having a
secondary side connected to said other water/steam drum to form an
evaporator circuit.
4. The gas and steam-turbine plant according to claim 3, wherein at
least one of said water/steam drums is connected to a number of
said heating surfaces of said heat-recovery steam generator.
5. The gas and steam-turbine plant according to claim 1, wherein
said heat exchanger is a first heat exchanger, a feedwater tank is
associated with said heat-recovery steam generator, a second heat
exchanger is connected to said bleed-air line downstream of said
first heat exchanger, and said second heat exchanger has a
secondary side connected to said feedwater tank.
6. The gas and steam-turbine plant according claim 1, including a
cooling-air line branching off from said bleed-air line downstream
of said heat exchanger in a direction of flow of said partial flow
of air compressed in said air compressor, said cooling-air line
feeding a partial quantity of a cooled partial flow as cooling air
to said gas turbine for cooling blades of said gas turbine.
7. The gas and steam-turbine plant according claim 2, including a
cooling-air line branching off from said bleed-air line downstream
of said first and second heat exchangers in a direction of flow of
said partial flow of air compressed in said air compressor, said
cooling-air line feeding a partial quantity of a cooled partial
flow as cooling air to said gas turbine for cooling blades of said
gas turbine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application No. PCT/DE99/02058, filed Jul. 2, 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
having a heat-recovery steam generator, which is connected
downstream of a gas turbine on the flue-gas side and which has
heating surfaces that are connected in a water/steam circuit of a
steam turbine. A gasifier for fuel is connected upstream of a
combustion chamber of the gas turbine.
[0004] A gas and steam-turbine plant having integrated gasification
of fossil fuel normally includes a gasifier for the fuel. That
gasifier is connected on the outlet side to the combustion chamber
of the gas turbine through a number of components provided for gas
cleaning. In that case, a heat-recovery steam generator has heating
surfaces connected in the water/steam circuit of the steam turbine
and may be connected downstream of the gas turbine on the flue-gas
side. Such a plant has been disclosed, for example, by UK Patent
Application GB 2 234 984 A.
[0005] Furthermore, German Published, Non-Prosecuted Patent
Application DE 33 31 152 A1 discloses a method of operating a
gas-turbine plant having a fuel-gasification plant. In that method,
low-oxygen air collecting in an air-separation unit is admixed to
fuel of medium calorific value delivered to the fuel-gasification
plant and the fuel/air mixture of low calorific value is fed to a
combustion chamber of the gas-turbine plant. In that case, the
compressor of the gas-turbine plant, in addition to supplying the
combustion chamber with air, also supplies the air-separation unit
with air. It is known from U.S. Pat. No. 4,677,829 and U.S. Pat.
No. 4,697,415 to cool compressed air from an air compressor through
the use of heat exchangers.
[0006] A device for removing sulphurous constituents is provided in
that plant in order to provide reliable cleaning of the gasified
fossil fuel. A saturator is connected downstream of that device in
a feed line, opening into the combustion chamber, for the gasified
fuel. The gasified fuel is loaded with steam in the saturator in
order to reduce pollutant emission. To that end, the gasified fuel
flows through the saturator in counterflow to a water flow, which
is directed in a water circuit referred to as a saturator circuit.
In order to provide an especially high efficiency, provision is
made for an input of heat from the water/steam circuit into the
saturator circuit.
[0007] In addition to the fossil fuel, oxygen required for the
gasification of the fuel can also be fed to the gasifier of such a
gas and steam-turbine plant. In order to obtain that oxygen from
air, an air-separation unit is normally connected upstream of the
gasifier. In that case, a partial flow, also referred to as bleed
air, of air compressed in an air compressor associated with the gas
turbine, may be admitted to the air-separation unit.
[0008] As a result of the compression process, the air flowing off
from the compressor has a comparatively high temperature level.
Cooling of the partial flow of the compressed air, also referred to
as bleed air, is therefore normally necessary before it enters the
air-separation unit. The heat extracted from the bleed air in the
process is normally transferred to the saturator circuit for heat
recovery and thus for achieving a high plant efficiency. Depending
on the operating state of the plant, only residual cooling of the
bleed air through the use of cooling water before it enters the
air-separation unit is then necessary in such a structure.
[0009] However, such a concept for cooling the bleed air assumes
that the heat supply during the air cooling and the heat demand in
the saturator circuit are matched to one another in a sufficiently
effective manner. Depending on the integration concept, that is
depending on the type of air supply for the air-separation unit and
the components used in the process, such bleed-air cooling
therefore cannot be used universally and is only reliable to a
limited extent in some operating states of the gas and
steam-turbine plant.
SUMMARY OF THE INVENTION
[0010] It is accordingly an object of the invention to provide a
gas and steam-turbine plant, which overcomes the
hereinafore-mentioned disadvantages of the heretofore-known devices
of this general type and in which, irrespective of an integration
concept taken as a basis, reliable cooling of bleed air, in an
especially simple type of construction, is ensured in all operating
states.
[0011] With the foregoing and other objects in view there is
provided, in accordance with the invention, a gas and steam-turbine
plant, comprising a steam turbine having a water/steam circuit, a
gas turbine having a flue-gas side, a combustion chamber associated
with the gas turbine, an air compressor associated with the gas
turbine for supplying a partial flow of air compressed in the air
compressor, and a bleed-air line connected to the air compressor.
An air-separation unit supplying oxygen and having an inlet side
connected to the bleed-air line receives the partial flow of air
compressed in the air compressor. A heat-recovery steam generator
is connected downstream of the gas turbine on the flue-gas side.
The steam generator has heating surfaces connected in the
water/steam circuit. A gasifier for fuel is connected upstream of
the combustion chamber and receives oxygen from the air-separation
unit. A heat exchanger is constructed as an evaporative cooler for
cooling the partial flow of compressed air. The heat exchanger has
a primary side connected to the bleed-air line and a secondary side
connected to a water/steam drum to form an evaporator circuit for a
flow medium.
[0012] The invention is thus based on the concept that, for
bleed-air cooling which can be used irrespective of the integration
concept and the fuel to be gasified and is reliable in all
operating states, the heat extracted from the bleed air should be
capable of being drawn off irrespective of a firmly preset heat
demand. The bleed-air cooling should therefore be isolated from the
heat supply into the saturator circuit. The bleed air is instead
cooled by heat exchange with a flow medium. In this case,
evaporation of the flow medium is provided for especially high
operational stability in a simple type of construction and for
favorable input of the heat extracted from the bleed air into the
plant process.
[0013] In accordance with another feature of the invention, in
order to provide especially flexible bleed-air cooling which can be
adapted to various operating states in a simple manner, a further
heat exchanger, constructed on the secondary side as an evaporator
for a flow medium, is connected downstream of the heat exchanger in
the air-bleed line. The heat exchanger is constructed as an
intermediate-pressure evaporator and the further heat exchanger is
constructed as a low-pressure evaporator.
[0014] The heat exchanger constructed as an intermediate-pressure
evaporator is expediently connected on the flow-medium side to a
heating surface, associated with an intermediate-pressure stage of
the steam turbine, in the heat-recovery steam generator. In an
analogous configuration, the heat exchanger constructed as a
low-pressure evaporator may be connected on the flow-medium side to
a heating surface, associated with a low-pressure stage of the
steam turbine, in the heat-recovery steam generator. However, the
heat exchanger constructed as a low-pressure evaporator is
expediently connected on the flow-medium side to a secondary steam
consumer, for example to the gasifier or to a gas-processing system
connected downstream of the latter. In such a configuration,
reliable feeding of the secondary consumer with process steam or
with heating steam is ensured in an especially simple manner.
[0015] In accordance with a further feature of the invention, at
least one of the heat exchangers is connected on the secondary side
to a water/steam drum in order to form an evaporator circuit.
[0016] In this case, the evaporator circuit may be constructed with
forced circulation. However, in an especially advantageous
development, the respective evaporator circulation is constructed
with natural circulation. Circulation of the flow medium is ensured
by pressure differences occurring during the evaporation process
and/or by a geodetic configuration of the evaporator and the
water/steam drum. In such a configuration, only a circulating pump
with a comparatively low rating is required for starting the
evaporator circulation. In accordance with an added feature of the
invention, the respective water/steam drum is expediently connected
to a number of heating surfaces disposed in the heat-recovery steam
generator.
[0017] In accordance with an additional feature of the invention,
there is provided an additional heat exchanger connected downstream
of the heat exchanger in the bleed-air line. The additional heat
exchanger is connected on the secondary side to a feedwater tank
associated with the heat-recovery steam generator. With such a
configuration, an especially favorable input of heat into the
saturator circuit can be achieved, with the input of heat being
independent of the integration concept. This is because, in this
case, the input of heat into the saturator circuit can be effected
through a heat exchanger, through which preheated feedwater
extracted from the feedwater tank can flow on the primary side. The
feedwater leaving this heat exchanger and cooled down by the input
of heat into the saturator circuit can then be fed to the
additional heat exchanger connected in the bleed-air line, where it
heats up again due to the further cooling of the bleed air. An
input of heat into the saturator circuit can therefore be achieved
without greater heat losses in the feedwater.
[0018] In accordance with a concomitant feature of the invention,
there is provided a cooling-air line which branches off from the
bleed-air line downstream of the heat exchanger or downstream of
the heat exchangers, as viewed in the direction of flow of the
partial flow, for reliable cooling of blades of the gas turbine. A
partial quantity of the cooled partial flow can be fed through the
cooling-air line to the gas turbine as cooling air in order to cool
the blades.
[0019] The advantages achieved with the invention reside in
particular in the fact that a flexible adaptation of the gas and
steam-turbine plant to different integration concepts while
achieving an especially high plant efficiency is made possible by
the cooling of the bleed air in a number of heat exchangers
constructed as evaporators for a flow medium. In this case, the
extraction of heat from the bleed air through the heat exchanger
constructed as an evaporator is independent of the input of heat
into the saturator circuit. The gas and steam-turbine plant can
therefore be used in an especially reliable manner even in various
operating states. Furthermore, the structure of the respective heat
exchanger as an evaporator permits an especially simple supply of
secondary consumers with process steam or with heating steam. In
particular, the gasifier or a gas-processing component connected
downstream of the latter is suitable as such a secondary consumer.
In this case, due to the comparatively high storage capacity of the
respective evaporator circuit, even fluctuating tapped quantities
of process steam or heating steam by the respective secondary
consumers do not lead to operational malfunctions.
[0020] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0021] Although the invention is illustrated and described herein
as embodied in a gas and steam-turbine plant, it is nevertheless
not intended to be limited to the details shown, since 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.
[0022] 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
[0023] FIGS. 1A and 1B are respective left and right halves of a
schematic and block diagram of a gas and steam-turbine plant
according to the invention, in which roman numerals I-VIII indicate
connections between the figures that are described below.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Referring now in detail to the single FIGURE of the drawing,
there is seen a gas and steam-turbine plant 1 which includes a
gas-turbine plant la 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, which is disposed upstream of the gas
turbine 2 and is connected to a compressed-air line 8 of the
compressor 4. The gas turbine 2 and the air compressor 4 as well as
a generator 10 sit on a common shaft 12.
[0025] The steam-turbine plant 1b includes a steam turbine 20 with
a coupled generator 22. The steam-turbine plant 1b also includes a
condenser 26 disposed downstream of the steam turbine 20 as well as
a heat-recovery steam generator 30, in a water/steam circuit 24.
The steam turbine 20 is formed of a first pressure stage or
high-pressure part 20a, a second pressure stage or
intermediate-pressure part 20b as well as a third pressure stage or
a low-pressure part 20c, which drive the generator 22 through a
common shaft 32.
[0026] An exhaust-gas line 34 is connected to an inlet 30a of the
heat-recovery steam generator 30, in order to feed working medium
AM expanded in the gas turbine 2, or flue gas, into the
heat-recovery steam generator 30. The expanded working medium AM
from the gas turbine 2 leaves the heat-recovery steam generator 30
through an outlet 30b in the direction of a non-illustrated
stack.
[0027] The heat-recovery steam generator 30 includes a condensate
preheater 40, which can be fed on the inlet side with condensate K
from the condenser 26 through a condensate line 42, in which a
condensate pump unit 44 is connected. The condensate preheater 40
is connected on the outlet side through a line 45 to a feedwater
tank 46. In addition, in order to bypass the condensate preheater
40 as and when required, the condensate line 42 may be connected
directly to the feedwater tank 46 through a non-illustrated bypass
line. The feedwater tank 46 is connected through a line 47 to a
high-pressure feed pump 48 having intermediate-pressure
extraction.
[0028] The high-pressure feed pump 48 brings feedwater S flowing
off from 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 50 is associated with the high-pressure part
20a of the steam turbine 20. The feedwater S under high pressure
can be fed to the high-pressure stage 50 through a feedwater
preheater 52. A feedwater line 56, which can be shut off with a
valve 54, connects the outlet side of the feedwater preheater 52 to
a high-pressure drum 58. The high-pressure drum 58 is connected to
a high-pressure evaporator 60 disposed in the heat-recovery steam
generator 30, in order to form a water/steam circuit 62. The
high-pressure drum 58 is connected to a high-pressure superheater
64 in order to draw off live steam F. The high-pressure superheater
64 is disposed in the heat-recovery steam generator 30 and is
connected on the outlet side to a steam inlet 66 of the
high-pressure part 20a of the steam turbine 20.
[0029] A steam outlet 68 of the high-pressure part 20a of the steam
turbine 20 is connected through a reheater 70 to a steam inlet 72
of the intermediate-pressure part 20b of the steam turbine 20. A
steam outlet 74 of the intermediate-pressure part 20b is connected
through an overflow line 76 to a steam inlet 78 of the low-pressure
part 20c of the steam turbine 20. A steam outlet 80 of the
low-pressure part 20c of the steam turbine 20 is connected through
a steam line 82 to the condenser 26, so that the closed water/steam
circuit 24 results.
[0030] In addition, a branch line 84 branches off from the
high-pressure pump 48 at an extraction point at which the
condensate K reaches an intermediate pressure. The branch line 84
is connected through a further feedwater preheater or
intermediate-pressure economizer 86 to an intermediate-pressure
stage 90, which is associated with the intermediate-pressure part
20b of the steam turbine 20 of the water/steam circuit. To this
end, a feedwater line 94, which can be shut off with a valve 92,
connects the outlet side of the further feedwater preheater 86 to
an intermediate-pressure drum 96 of the intermediate-pressure stage
90. The intermediate-pressure drum 96 is connected to a heating
surface 98 disposed in the heat-recovery steam generator 30 and
constructed as an intermediate-pressure evaporator, in order to
form a water/steam circuit 100. In order to draw off
intermediate-pressure live steam F', the intermediate-pressure drum
96 is connected through a steam line 102 to the reheater 70 and
thus to the steam inlet 72 of the intermediate-pressure part 20b of
the steam turbine 20.
[0031] A further line 110 which branches off from the line 47 and
is provided with a low-pressure feed pump 107, can be shut off with
a valve 108 and is connected to a low-pressure stage 120 of the
water/steam circuit 24. The low-pressure stage 120 is associated
with the low-pressure part 20c of the steam turbine 20. The
low-pressure stage 120 includes a low-pressure drum 122, which is
connected to a heating surface 124 disposed in the heat-recovery
steam generator 30 and is constructed as a low-pressure evaporator,
in order to form a water/steam circuit 126. In order to draw off
low-pressure live steam F", the low-pressure drum 122 is connected
through a steam line 128 to the overflow line 76. A low-pressure
superheater 129 is connected in the steam line 128. Therefore, the
water/steam circuit 24 of the gas and steam-turbine plant 1
includes three pressure stages 50, 90, 120 in the exemplary
embodiment. Alternatively, however, fewer, in particular two,
pressure stages may be provided.
[0032] The gas-turbine plant la is constructed for operation with a
gasified synthetic gas SG, which is produced by the gasification of
a fossil fuel B. For example, gasified coal or gasified oil may be
provided as the synthetic gas. To this end, the combustion chamber
6 of the gas turbine 2 is connected on the inlet side through a
fuel line 130 to a gasifier 132. Coal or oil can be fed through a
feed system 134 to the gasifier 132, as fossil fuel B.
[0033] In order to provide oxygen O.sub.2 required for the
gasification of the fossil fuel B, an air-separation unit 138 is
connected upstream of the gasifier 132, through an oxygen line 136.
A partial flow T of the air compressed in the air compressor 4 can
be admitted to the air-separation unit 138 on the inlet side. To
this end, the air-separation unit 138 is connected on the inlet
side to a bleed-air line 140, which branches off from the
compressed-air line 8 at a branch point 142. In addition, a further
air line 143, in which an additional air compressor 144 is
connected, opens into the bleed-air line 140. Therefore, in the
exemplary embodiment, a total air flow L flowing to the
air-separation unit 138 is composed of the partial flow T branched
off from the compressed-air line 8 and the air flow delivered by
the additional air compressor 144. Such a circuit concept is also
referred to as a partly integrated plant concept. In an alternative
configuration, a so-called fully integrated plant concept, the
further air line 143 together with the additional air compressor
144 may also be omitted. In that way, the feeding of the
air-separation unit 138 with air is effected completely through the
partial flow T bled from the compressed-air line 8.
[0034] Nitrogen N.sub.2 which is obtained in the air-separation
unit 138 in addition to the oxygen O.sub.2 during the separation of
the air flow L is fed through a nitrogen line 145 connected to the
air-separation unit 138 to a mixing device 146 and is admixed there
to the synthetic gas SG. In this case, the mixing device 146 is
constructed for especially uniform and strand-free mixing of the
nitrogen N.sub.2 with the synthetic gas SG.
[0035] The synthetic gas SG flowing off from the gasifier 132
passes through the fuel line 130 and first of all into a crude-gas
heat-recovery steam generator 147, in which the synthetic gas SG is
cooled down by heat exchange with a flow medium. High-pressure
steam generated during this heat exchange is fed to the
high-pressure stage 50 of the water/steam circuit 24 in a
non-illustrated manner.
[0036] A deduster 148 for the synthetic gas SG and a
desulphurization unit 149 are connected in the fuel line 130
downstream of the crude-gas heat-recovery steam generator 147 and
upstream of the mixing device 146, as viewed in the direction of
flow of the synthetic gas SG. In an alternative configuration, a
soot scrubber may also be provided instead of the deduster 148, in
particular during gasification of oil as fuel.
[0037] In order to provide an especially low pollutant emission
during the combustion of the gasified fuel in the combustion
chamber 6, provision is made for loading the gasified fuel with
steam before entry into the combustion chamber 6. This may be
effected in an especially advantageous manner in a saturator
system, from a thermal point of view. To this end, a saturator 150,
in which the gasified fuel is directed in counterflow to heated
saturator water, is connected in the fuel line 130. In this case,
the saturator water circulates in a saturator circuit 152, which is
connected to the saturator 150 and in which a circulating pump 154
and a heat exchanger 156 for the preheating of the saturator water,
are connected. In this case, preheated feedwater from the
intermediate-pressure stage 90 of the water/steam circuit 24 is
admitted to the heat exchanger 156 on the primary side. A feeder
line 158 is connected to the saturator circuit 152 in order to
compensate for losses of saturator water which occur during the
saturation of the gasified fuel.
[0038] A heat exchanger 159, acting as a crude-gas/pure-gas heat
exchanger, is connected downstream of the saturator 150 in the fuel
line 130 on the secondary side, as viewed in the direction of flow
of the synthetic gas SG. In this case, the heat exchanger 159 is
likewise connected in the fuel line 130 on the primary side at a
point upstream of the deduster 148, so that the synthetic gas SG
flowing to the deduster 148 transfers some of its heat to the
synthetic gas SG flowing off from the saturator 150. The directing
of the synthetic gas SG through the heat exchanger 159 before entry
into the desulphurization unit 149 may also be provided in a
circuit concept which is modified with regard to the other
components.
[0039] A further heat exchanger 160 is connected between the
saturator 150 and the heat exchanger 159 in the fuel line 130 on
the secondary side. The further heat exchanger 160 may be heated on
the primary side by feedwater or by steam. In this case, even
during different operating states of the gas and steam-turbine
plant 1, the heat exchanger 159, which is constructed as
crude-gas/pure-gas heat exchanger, and the heat exchanger 160,
ensure especially reliable preheating of the synthetic gas SG
flowing to the combustion chamber 6 of the gas turbine 2.
[0040] A further mixing device 161 is also connected in the fuel
line 130 in order to admit steam as and when required to the
synthetic gas SG flowing to the combustion chamber 6.
Intermediate-pressure steam can be fed through a non-illustrated
steam line to the further mixing device 161, in particular in order
to ensure reliable gas-turbine operation in the event of
operational malfunctions.
[0041] In order to cool the partial flow T of compressed air or
so-called bleed air to be fed to the air-separation unit 138, a
first heat exchanger 162, which is constructed on the secondary
side as an intermediate-pressure evaporator for a flow medium S',
is connected in the bleed-air line 140 on the primary side. In
order to form an evaporator circuit 163, the heat exchanger 162 is
connected to a water/steam drum 164 that is constructed as an
intermediate-pressure drum. The water/steam drum 164 is connected
through lines 166, 168 to the intermediate-pressure drum 96
assigned to the water/steam circuit 100. Alternatively, however,
the heat exchanger 162 may also be connected on the secondary side
directly to the intermediate-pressure drum 96. Therefore, the
water/steam drum 164 is connected indirectly to the heating surface
98 which is constructed as an intermediate-pressure evaporator, in
the exemplary embodiment. In addition, a feedwater line 170 is
connected to the water/steam drum 164 for the subsequent feeding of
evaporated flow medium S'.
[0042] A second heat exchanger 172 is connected downstream of the
heat exchanger 162 in the bleed-air line 140, as viewed in the
direction of flow of the partial flow T of compressed air. This
second heat exchanger 172 is constructed on the secondary side as a
low-pressure evaporator for a flow medium S". In this case, the
heat exchanger 172 is connected to a water/steam drum 176 that is
constructed as a low-pressure drum, in order to form an evaporator
circuit 174. In the exemplary embodiment, the water/steam drum 176
is connected through lines 178, 180 to the low-pressure drum 122
associated with the water/steam circuit 126 and is therefore
indirectly connected to the heating surface 124 which is
constructed as a low-pressure evaporator. Alternatively, the
water/steam drum 176 may also be connected in another suitable
manner, in which case steam bled from the water/steam drum 176 can
be fed to a secondary consumer as process steam and/or as heating
steam. In a further alternative configuration, the heat exchanger
172 may also be connected on the secondary side directly to the
low-pressure drum 122. In addition, the water/steam drum 176 is
connected to a feedwater line 182.
[0043] The evaporator circuits 163, 174 could each be constructed
with forced circulation. In that way the circulation of the flow
medium S' and S" would be respectively ensured by a circulating
pump, and the flow medium S', S" would be at least partly
evaporated in the heat exchanger 162 or 172 that is respectively
constructed as an evaporator. In the exemplary embodiment, however,
both the evaporator circuit 163 and the evaporator circuit 174 are
each constructed for natural circulation. The circulation of the
flow medium S' or S" is respectively ensured by pressure
differences occurring during the evaporation process and/or by a
geodetic configuration of the respective heat exchanger 162 or 172
and the respective water/steam drum 164 or 176. In this
configuration, in each case only a non-illustrated circulating pump
with a comparatively low rating for starting the system is
connected in the evaporator circuit 163 or in the evaporator
circuit 174, respectively.
[0044] In order to provide for the input of heat into the saturator
circuit 152, a saturator-water heat exchanger 184 is provided in
addition to the heat exchanger 156 to which heated feedwater
branched off downstream of the feedwater preheater 86 can be
admitted. Feedwater S can be admitted to the saturator-water heat
exchanger 184 on the primary side from the feedwater tank 46. To
this end, the primary side of the saturator-water heat exchanger
184 is connected on the inlet side through a line 186 to the branch
line 84 and on the outlet side through a line 188 to the feedwater
tank 46. In order to reheat the cooled feedwater S flowing off from
the saturator-water heat exchanger 184, an additional or second
heat exchanger 190 is connected in the line 188. This heat
exchanger 190 is connected on the primary side downstream of the
heat exchanger 172 in the bleed-air line 140. Especially high heat
recovery from the bleed air and thus an especially high efficiency
of the gas and steam-turbine plant 1 can be achieved by such a
configuration.
[0045] A cooling-air line 192 branches off from the bleed-air line
140 between the heat exchanger 172 and the heat exchanger 190, as
viewed in the direction of flow of the partial flow T. A partial
quantity T' of the cooled partial flow T can be fed through the
cooling-air line 192 as cooling air to the gas turbine 2 in order
to cool the blades.
[0046] Due to the structure of the respective heat exchangers 162
and 172 as an intermediate-pressure evaporator and a low-pressure
evaporator, reliable cooling of the bleed air is ensured even
during various operating states of the gas and steam-turbine plant
1 and even in the case of different integration concepts for the
gasification of the fossil fuel B. The concept of the bleed-air
cooling by connecting the heat exchangers 162 and 172, constructed
as evaporator coolers, in the bleed-air line 140, is therefore also
especially suitable for various fossil fuels B. In particular, due
to the multiplicity of adjustable steam parameters in the
evaporator circuits 163 and 174, such bleed-air cooling can be
adapted in an especially flexible manner to various requirements
during the operation of the gas and steam-turbine plant 1.
* * * * *