U.S. patent application number 13/953143 was filed with the patent office on 2013-11-28 for combined cycle power plant with co2 capture plant.
This patent application is currently assigned to ALSTOM Technology Ltd. The applicant listed for this patent is ALSTOM Technology Ltd. Invention is credited to Francois DROUX, Frederic Zenon KOZAK, Hongtao LI, Christoph RUCHTI, Manfred WIRSUM, Alexander ZAGORSKIY.
Application Number | 20130312386 13/953143 |
Document ID | / |
Family ID | 44246132 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130312386 |
Kind Code |
A1 |
WIRSUM; Manfred ; et
al. |
November 28, 2013 |
COMBINED CYCLE POWER PLANT WITH CO2 CAPTURE PLANT
Abstract
A combined cycle power plant includes a CO2 capture system
operatively integrated with a liquefied natural gas LNG
regasification system, where cold energy from the regasification
process is used for cooling processes within the CO2 capture system
or processes associated with it. These cooling systems include
systems for cooling lean or rich absorption solutions for the CO2
capture or the cooling of flue gas. The LNG regasification system
is arranged in one or more heat exchange stages having and one or
more cold storage units. The power plant with CO2 capture can be
operated at improved overall efficiencies.
Inventors: |
WIRSUM; Manfred;
(Rheinfelden, DE) ; RUCHTI; Christoph; (Uster,
DE) ; LI; Hongtao; (Aarau, DE) ; DROUX;
Francois; (Oberrohrdorf, DE) ; KOZAK; Frederic
Zenon; (Knoxville, TN) ; ZAGORSKIY; Alexander;
(Wettingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALSTOM Technology Ltd |
Baden |
|
CH |
|
|
Assignee: |
ALSTOM Technology Ltd
Baden
CH
|
Family ID: |
44246132 |
Appl. No.: |
13/953143 |
Filed: |
July 29, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/051267 |
Jan 26, 2012 |
|
|
|
13953143 |
|
|
|
|
Current U.S.
Class: |
60/39.182 |
Current CPC
Class: |
F01K 23/10 20130101;
Y02C 20/40 20200801; F25J 3/04593 20130101; Y02E 20/18 20130101;
F25J 2270/904 20130101; F25J 2230/02 20130101; B01D 2252/102
20130101; F01K 23/064 20130101; Y02E 20/16 20130101; F25J 3/04266
20130101; F25J 2210/70 20130101; F25J 2240/82 20130101; F01K 13/00
20130101; F25J 2210/62 20130101; B01D 53/1475 20130101; F25J
3/04533 20130101; Y02E 20/14 20130101; F01K 23/068 20130101; F25J
2230/80 20130101; Y02E 20/32 20130101; Y02E 20/326 20130101; F22B
1/1815 20130101; F25J 2260/80 20130101; Y02C 10/06 20130101; F25J
3/04018 20130101; B01D 53/1425 20130101 |
Class at
Publication: |
60/39.182 |
International
Class: |
F01K 23/10 20060101
F01K023/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2011 |
EP |
11152823.8 |
Claims
1. A combined cycle power plant comprising a gas turbine (GT), a
steam turbine (ST), a heat recovery steam generator (HRSG), a
liquefied natural gas (LNG) regasification system, and a CO2
capture system arranged to process exhaust gases exhausted by the
heat recovery steam generator (HRSG) wherein the liquefied natural
gas regasification system comprises heat exchangers operatively
connected with heat exchangers within the CO2 capture system,
wherein one or more heat exchangers arranged in a cascaded way,
configured for the operation at temperatures of the natural gas
form an LNG inlet temperature up to at least -10.degree. C. and of
which at least one heat exchanger is configured and arranged for
heat exchange between the liquefied natural gas and a heat exchange
medium, where that heat exchange medium has cryogenic temperatures
or chilling temperatures at the output from that at least one heat
exchanger.
2. The combined cycle power plant according to claim 1 wherein the
CO2 capture system is a system arranged for a chilled ammonia
process and the power plant comprises lines to direct the heat
exchange medium from this regasification heat exchanger to one or
more of the following refrigeration systems within the CO2 capture
system a cooler integrated in a cooling circuit of a flue gas
direct contact cooler (DCC), a water cooler prior to a flue gas
water wash apparatus (WW), a cooler for the cooling of CO2 rich
absorption solution within the CO2 capture system.
3. The combined cycle power plant according to claim 1 wherein the
CO2 capture system is a system arranged for an amine process for
the removal of CO2 from flue gases and the liquefied natural gas
regasification system comprises one or more heat exchangers
arranged in a cascaded way, configured for the operation of the
natural gas from an LNG inlet temperature up to at least 0.degree.
C. and of which at least one heat exchanger is configured and
arranged for heat exchange between the liquefied natural gas and a
heat exchange medium, where that heat exchange medium has cryogenic
temperature or chilling temperatures at the output from that at
least one heat exchanger.
4. The combined cycle power plant according to claim 3 wherein the
power plant comprises lines to direct the heat exchange medium from
this regasification heat exchanger to a system (LSC) for cooling a
CO2 lean solution within the CO2 capture amine process system.
5. The combined cycle power plant according to claim 1 wherein the
at least one heat exchanger, which is configured and arranged for
heat exchange between the liquefied natural gas and a heat exchange
medium that has a cryogenic temperature or a chilling temperature
at the output from the heat exchanger, is operatively connected to
a system for cooling the inlet air to the gas turbine (GT) of the
combined cycle power plant.
6. The combined cycle power plant according to claim 5 wherein the
one or more heat exchangers of the liquefied natural gas
regasification system are additionally operatively connected to one
or more of the following systems of the combined cycle power plant:
a system for flue gas cooling prior to its entry to the CO2 capture
system, a system for flue gas chilling prior to its entry to the
CO2 capture system. a cooling water system for the steam turbine
condenser, a system for the cooling of flue gas recirculated after
the HRSG back to the gas turbine inlet, a system for the chilling
of flue gas recirculated after the HRSG back to the gas turbine
inlet, a system for cooling of CO2 extracted by the CO2 capture
system. a system for drying CO2 by means of chilling.
7. The combined cycle power plant according to claim 1 wherein the
heat exchangers of the liquefied natural gas regasification system
are arranged either in series or in parallel.
8. The combined cycle power plant according to claim 7 wherein each
of the heat exchangers of the LNG regasification system are
configured and arranged for heat exchange within a given
temperature range, where each one of the heat exchangers can
comprise one or more heat exchange apparatuses, which can be
arranged either in series or in parallel to one another.
9. The combined cycle power plant according to claim 5 wherein the
liquefied natural gas regasification system comprises one or more
cold storage units for the storage of liquefied natural gas
arranged in parallel to its heat exchangers.
10. The combined cycle power plant according to claim 1 wherein the
system for liquefied natural gas regasification comprises a heat
exchanger configured and arranged for the liquefaction of CO2
extracted by the CO2 capture system.
11. The combined cycle power plant according to claim 6 wherein a
line leads from the system for drying and cooling CO2 to the heat
exchanger for CO2 liquefaction and a line for liquefied CO2 leads
from this heat exchanger to a transport facility (T) or pump.
12. The combined cycle power plant according to claim 1 wherein the
liquefied natural gas regasification system comprises a heat
exchanger configured and arranged for heat exchange between
liquefied natural gas and a medium having cryogenic temperatures at
the output of said heat exchanger and a line for said heat exchange
medium that leads to an air separation unit, and a line leads from
said air separation unit (ASU) back to said heat exchanger.
13. The combined cycle power plant according to claim 5 wherein the
liquefied natural gas regasification system is additionally
operatively connected to the cooling system for the steam turbine
(ST) condenser.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to PCT/EP2012/051267 filed
Jan. 26, 2012, which in turn claims priority to European
Application 11152823.8 filed on Feb. 1, 2011, both of which are
hereby incorporated in their entirety.
TECHNICAL FIELD
[0002] The present invention pertains to a combined cycle power
plant for the generation of electric power having a gas turbine, a
steam turbine, and a heat recovery steam generator, and furthermore
a plant for the capture and compression of carbon dioxide. The
invention pertains in particular to an integration of a liquefied
natural gas processing system with the power plant.
BACKGROUND ART
[0003] Combined cycle power plants for the generation of
electricity are known to include a gas turbine, a steam turbine,
and a heat recovery steam generator utilizing the hot flue gases
emitted by the gas turbine to generate steam to drive the steam
turbine. In order to reduce emissions that contribute to the
greenhouse effect, various measures have been proposed to minimize
the amount of carbon dioxide emitted into the atmosphere. Such
measures include the arrangement of systems in the power plant that
capture and process CO2 contained in the flue gases exhausted by a
heat recovery steam generator HRSG or a coal-fired boiler. Such CO2
capture processes operate for example on the basis of chilled
ammonia or amine processes. In order to work effectively, both of
these processes require that the flue gases are cooled to
temperatures below 10.degree. C. Furthermore, for the captured CO2
to be transported and stored economically, it is purified,
separated from water, chilled, compressed, and liquefied. For this,
among others, sufficiently cold heat exchange media need to be
provided at economical conditions. A CO2 capture plant of this type
requires a given amount of energy, which reduces the overall
efficiency of the power plant. In order to design a combined cycle
power plant with CO2 capture more energy efficiently, it has been
proposed to use the cold energy from the LNG regasification for
some power plant processes.
[0004] JP2000024454 discloses the use of vaporization heat of LNG
to cool waste gases and solidify carbon dioxide contained in the
waste gases. JP60636999 discloses the use of cold heat generated
upon the evaporation of LNG to recover carbon dioxide from exhaust
gas as liquefied carbon dioxide. WO 2008/009930 discloses the use
of such cold energy in an air separation unit to produce nitrogen
and oxygen.
[0005] U.S. Pat. No. 6,367,258 discloses the vaporization of
liquefied natural gas for a combined cycle power plant, where the
cold energy of the vaporization is utilized for the chilling of gas
turbine intake air, steam turbine condenser cooling water, or a
first heat transfer fluid intended to cool components in the gas
turbine.
[0006] Velautham et al., <<Zero emission combined Power cycle
using LNG cold>>, JSME International Journal, Series B, Vol.
44, No. 4, 2001, discloses the use of liquefied natural gas cold
for cooling air in heat exchange with air in view of separating
oxygen from the air for further use in a combined cycle power
plant. The use of liquefied natural gas cold reduces the energy
consumption of the oxygen-air-separation process. The use of
liquefied natural gas cold energy in heat exchange with CO2 for its
liquefication is also disclosed.
[0007] The WO2007/148984 discloses a LNG regasification plant in
which natural gas is burned in pure oxygen. The plant also
comprises a boiler and a steam turbine to generate electricity from
the hot combustion gases. From the resulting flue gas CO2 is
separated by condensation of water vapor. Further, CO2 is cooled
against LNG for liquefaction.
[0008] The U.S. Pat. No. 5,467,722 discloses a combined cycle power
plant with a subsequent CO2 capture system and a LNG regasification
plant. The CO2 capture system comprises heat exchangers, which cool
the flue gas for cryogenic CO2 capture using liquid LNG as a heat
sink.
SUMMARY
[0009] It is an object of the present invention to provide a
combined cycle power plant operating with a CO2 capture plant
having increased power plant efficiency over known power plants of
this type.
[0010] A combined cycle power plant comprises a gas turbine, a
steam turbine, and a heat recovery steam generator (HRSG), both
turbines driving a generator. The power plant comprises furthermore
a CO2 capture system operating on the basis of a chilled ammonia or
an amine process and arranged to process exhaust gases from the
HRSG. According to the invention the combined cycle power plant
comprises a liquefied natural gas regasification system, which
comprises heat exchangers operatively connected with one or more
heat exchangers within the CO2 capture system.
[0011] The regasification of the liquefied natural gas LNG provides
the cold energy necessary to operate cooling processes in the CO2
capture system. The heat gained by the heat exchange medium in that
cooling process is in turn used to support the regasification
process of the LNG. The LNG regasification system and the cooling
systems of the CO2 capture system are integrated in a closed
circuit system. This integration reduces the amount of energy
needed to operate the CO2 capture system and LNG system, which
otherwise would to be provided by other means, for example by steam
extraction and electricity from the power plant. It therefore
mitigates the efficiency reduction due to the CO2 capture process
and LNG regasification processes.
[0012] In an embodiment of the invention, the LNG regasification
system comprises one or more heat exchangers, configured for the
operation at a specific temperature range of the natural gas in a
cascaded arrangement, form a LNG inlet temperature up to ambient
temperature, for heat exchange between the LNG on the cold stream
side and a heat exchange medium on the hot stream side of the heat
exchanger. The heat exchange medium on the hot stream side has
cryogenic or chilling temperatures at the output of the heat
exchanger depending on the cold requirements of the process. The
chilling temperatures can be for example in the range from above a
cryogenic temperature (cryogenic temperatures are temperatures
below -150.degree. C.) up to 10.degree. C. or even up to ambient
temperature, or in an embodiment in a range from 5.degree. C. to
2.degree. C. for chilled ammonia process applications.
[0013] In a further embodiment, the CO2 capture system is arranged
for the chilled ammonia process. In order to support this process,
the power plant comprises lines to direct the heat exchange medium
from this regasification heat exchanger generating a medium having
cryogenic or chilling temperatures to one or more refrigeration
systems within the CO2 capture system, where the refrigeration
systems are [0014] a cooler in a cooling circuit of a flue gas
direct contact cooler, [0015] a water cooler arranged prior to a
flue gas water wash apparatus, [0016] a cooler for cooling part of
a rich absorption solution flow for the purpose of regulating the
temperature thereof.
[0017] In a further embodiment of the invention, the CO2 absorption
system is a system for the removal of the CO2 from flue gases by
means of an amine process and the system for the LNG regasification
is operatively connected to cooling systems within this CO2
absorption system. This amine process system requires a heat
exchange medium for cooling the absorption lean solution to
temperatures of about 45.degree. C. As is the case in the
embodiments above, the use of cooling power from the LNG system
mitigates the efficiency reduction due to the CO2 capture process.
In a particular embodiment of the invention, lines lead from the
heat exchanger of the LNG system to a cooler for amine process lean
solution and back to the heat exchanger.
[0018] The heat exchangers are arranged in a cascaded way (the
natural gas output temperature of a heat exchanges is the input
temperature of the subsequent heat exchanger, and the natural gas
is heated up form an LNG inlet cryogenic temperature up to
-10.degree. C. or more, preferably up to 0.degree. C. or up to
ambient temperature), and each of the heat exchangers of the LNG
regasification system is configured and arranged for heat exchange
within a specific temperature range based on load and temperature
requirements of the cold utilities (such as an air separation unit,
a CO2 liquefaction process, a chilled ammonia CO2 capture process,
cooling requirements in combined cycle power plants, etc) optimized
via process integration. More specifically in one exemplary
embodiment the natural gas temperature range in the first heat
exchanger is defined by the cryogenic inlet temperature of the LNG
as well as the requirements of the cold utility and heat exchange
medium on the hot stream side of this first heat exchanger. The
boiling temperature of the LNG at the regasification pressure can
be used as the natural gas outlet design temperature for this first
heat exchanger. In order to reduce equipment size the natural gas
outlet temperature of the first range can be higher, typically
10.degree. C. to 50.degree. C. higher that the LNG boiling
temperature This first heat exchanger will provide cryogenic cold
or very low temperature chilling power to the cold utility which
requires extremely low temperature cold such as an air separation
unit, etc. The natural gas inlet temperature of the second
temperature range is the outlet temperature of the first range and
the output temperature of the second range is the inlet temperature
of the third range. This heat exchanger can be designed to provide
very low temperature chilling power, at a temperature higher than
the first heat exchanger.
[0019] The natural gas inlet temperature of the third temperature
range is the outlet temperature of the second range. This heat
exchanger can be designed to provide chilling power, which has a
higher temperature than the second heat exchanger.
[0020] In such a cascaded arrangement, the energy losses of the LNG
chilling power is minimized when providing cold to different cold
utilizes.
[0021] Specifically the following temperature ranges are used in an
exemplary embodiment: First natural gas temperature range:
-165.degree. C. to -120.degree. C., second temperature range:
-120.degree. C. to -80.degree. C., and third temperature range:
-80.degree. C. to 0.degree. C.
[0022] Each one of these heat exchangers can comprise one or more
heat exchange apparatuses, which can be arranged either in series
or in parallel to one another. Such arrangements allow flexibility
in flow and temperature control of the heat exchange medium and
allow flexibility in control in different operation modes of the
power plant.
[0023] In a further embodiment of the invention, the LNG
regasification system comprises cold storage units for the storage
of LNG, which are arranged for providing cold heat exchange media
to the above-mentioned cooling systems within the power plant. In
case of non-operation of LNG regasification or regasification, the
cold energy contained in these cold storage units can be used for
the CO2 liquefication process, thereby enabling reduction of power
consumption of the CO2 absorption system.
[0024] In a further embodiment of the invention, the LNG
regasification system, in particular a heat exchanger arranged for
operation with a heat exchange medium having chilling temperatures
at its output, is additionally operatively connected with a system
for cooling the inlet air to the gas turbine of the combined cycle
power plant. The chilling temperatures of the medium can be in a
range of 10.degree. C. or less, or in a range from 5.degree. C. to
2.degree. C.
[0025] In a further exemplary embodiment of the invention, the LNG
regasification system is additionally operatively connected with
one or more of the following systems associated with the process of
the capture of CO2 from the flue gas from the combined cycle power
plant: [0026] a system for flue gas cooling and/or chilling prior
to its entry to the CO2 capture system in order to fulfill
temperature requirement for the CO2 capture process, [0027] a
system for the cooling of flue gas recirculated after the HRSG back
to the gas turbine inlet, [0028] a system for the chilling of flue
gas recirculated after the HRSG back to the gas turbine inlet,
[0029] a system for cooling of CO2 extracted by the CO2 capture
system. [0030] a system for drying CO2 by means of chilling.
[0031] The recirculation of flue gas increases the CO2
concentration in the flue gas and thereby increases the CO2 capture
process efficiency.
[0032] In a further exemplary embodiment of the invention, the LNG
regasification system is additionally operatively connected with a
cooling water system for the steam turbine condenser. This further
increases the overall efficiency by effectively using the cold
energy available for cooling and in turn using the low-level heat
available from the condensation for the LNG regasification
process.
[0033] From all of the above-mentioned cooling systems, the return
heat exchange medium is directed back to the heat exchanger within
the LNG regasification system.
[0034] The LNG regasification system can thereby be operated with
the heat provided by the cooler and chiller systems of the combined
cycle power plant. In return, the cooler and chiller systems can be
operated with the cold energy provided by the LNG.
[0035] The use of the cold energy available from the LNG
regasification system in any of the above cooling systems increases
the overall power plant efficiency as these cooling systems no
longer have to be operated with energy taken from other sources of
the power plant. The heat taken back from the above-mentioned
cooling systems on the other hand provide a heat source for the LNG
regasification. Therefore, no or less steam extraction from the
combined cycle power plant will be needed to operate the LNG
regasification. The power plant's performance (efficiency and power
output) can be improved.
[0036] In a further exemplary embodiment of the invention the
system for LNG regasification comprises a heat exchanger configured
and arranged for the liquefication of CO2 extracted by the CO2
capture system. The power plant with such LNG system requires no,
or fewer, compressors for the liquefaction of the CO2. In addition,
that heat exchanger of the LNG regasification system is provided
with heat from the CO2 liquefaction process.
[0037] In a further embodiment, the power plant comprises lines to
direct the heat exchange medium from the first heat exchanger of
the liquefied natural gas regasification system to an air
separation unit. The heat exchange medium has cryogenic
temperatures (temperatures below -150.degree. C.) at the output of
that heat exchanger and is used for the operation of the air
separation process thereby reducing the energy required to operate
that unit. A further line for the return heat exchange medium from
the air separation unit leads back to that first heat exchanger and
provides its heat to the liquefied natural gas regasification
process.
[0038] In an alternative embodiment the chilling power from the
first heat exchanger of the liquefied natural gas regasification
system is exchanged to the inlet air of the air separation unit and
the chilling power from a second heat exchanger of the liquefied
natural gas regasification system is used to cool the outlet air of
the first compressor of the air separation unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 shows a schematic of the combined cycle power plant
with CO2 capture system according to the invention and in
particular the operative connections between the LNG regasification
system and the cooling systems within the power plant.
[0040] FIG. 2 shows a detailed schematic of a CO2 capture system,
in particular of chilled ammonia system and the operative
connections between the LNG system and this CO2 capture system.
[0041] FIG. 3 shows a detailed schematic of a CO2 capture system,
in particular of a system based on an amine process and the
operative connections between the LNG system and this CO2 capture
system.
[0042] FIG. 4 shows a schematic of the combined cycle power plant
with CO2 capture system according to a further embodiment of the
invention and in particular the operative connections between the
LNG regasification system and the cooling systems within the power
plant.
DETAILED DESCRIPTION
[0043] FIG. 1 depicts a combined cycle power plant 10 for the
generation of electricity with a gas turbine GT provided with
ambient air A, a heat recovery steam generator HRSG, which
generated steam using the hot exhaust gases from the gas turbine,
and steam turbine ST driven by steam generated in the HRSG. A
condenser 1 condenses the expanded steam and the condensate is
directed as feedwater to the HRSG thereby completing the
water/steam cycle of the steam turbine. The power plant furthermore
comprises a CO2 capture system 5A, 5B, which can be either a system
operating on the basis of a chilled ammonia process (as shown in as
5A in FIG. 2) or a system based on a amine process (as shown as 5B
in FIG. 3).
[0044] The gas turbine of power plant 10 is operated with natural
gas supplied by the liquefied natural gas LNG regasification plant
20. The power plant 10 is operatively connected with a LNG
processing system 20 having one more stages, which vaporizes
cryogenic liquefied natural gas LNG for use in the gas turbine
combustion chamber CC. According to the invention, the LNG
regasification processes in system 20 is integrated with one or
more cooling and chilling systems within the power plant 10 in
order to optimize the overall power plant efficiency. For this, the
LNG system 20 comprises several stages 21-23, which are arranged in
series, where each stage is dedicated to the regasification of the
LNG within a range about a specific temperature level. In
particular, the cooling or chilling systems within the CO2 capture
system are integrated in closed heat exchange circuits with the LNG
regasification system 20.
[0045] A first embodiment comprises a power plant with a CO2
capture system 5a, which is a system operating on the basis of a
chilled ammonia process, as shown in FIG. 2. The system 5a
comprises a CO2 absorption column A preceded by a direct contact
cooler DCC, which cools the flue gas directed from the HRSG via
line G1 from a temperature in the range from 120.degree. C. to
80.degree. C. down to a temperature of 10.degree. C. or less, as it
is required to successfully operate the chilled ammonia process. A
cooler 31 is arranged in cooling circuit of the direct contact
cooler DCC and is configured to use the cold energy from heat
exchanger 23 of the LNG regasification system 20. The heat
exchanger 23 generates a chilled flow medium of 10.degree. C. or
less, for example from 2-5.degree. C., which is used in a cooler 33
to cool the flue gas to a temperature of less than 10.degree.
C.
[0046] Gas that is free of CO2 exits from the column A via line G5
and is directed to a water wash WW, from which a gas line G6 for
cleaned flue gas extends to the direct contact cooler DCC2.
Finally, the cleaned flue gas is directed from the direct contact
cooler DCC via line G7 to a stack S and the atmosphere.
[0047] The water wash W W is operatively connected to a stripper St
and a water cooler 32 via water lines W. A line for a pure CO2 flow
leads from the stripper St to a regenerator RG. The CO2 captured
from the flue gas is finally released at the top of the regenerator
RG, from where it is directed to further processing, for example
compression, drying, or chilling.
[0048] The CO2 absorption column A is connected with a system for
the regeneration of the chilled ammonia, its absorption solution.
The CO2-rich absorption solution RS is reheated by means of a
regenerator RG in order to release the CO2 and produce a CO2-lean
solution LS to be reused in the absorption column A. The absorption
solution regeneration system comprises additionally a cooler 33 for
the rich solution RS.
[0049] Each of the above-mentioned coolers 31, 32, 33 within the
chilled ammonia CO2 capture system 5A require chilling water as
cooling medium having temperatures of less than 10.degree. C.,
which can be provided by the heat exchanger 23 of the LNG system
20. Each of these coolers is connected in a closed circuit with
heat exchanger 23 by means of lines 25 and 26.
[0050] According to a further embodiment of the invention, the CO2
capture system can also be a system 5B based on an amine process,
as shown FIG. 3. It includes a CO2 absorber B, which is provided
with a flow of water via line W and lean absorption agent flow LS'.
Flue gas from the HRSG is directed to the bottom of the absorber B
and raises up through the apparatus in counter-current to the lean
solution LS'. Clean flue gas exits at the top of the apparatus and
is directed to the atmosphere via a stack S. The rich solution
resulting from the absorption process is directed via line RS' and
a heat exchanger LRX to an amine regenerator column ARC. There the
CO2 is released from the solution and directed via a condenser C'
to facilities for further processing or storing. The absorption
column ARC is further connected with a circuit containing a
reboiler RB, from which a lean solution flow is directed via line
LS' to the heat exchanger LRX, where the lean solution LS'
exchanges heat with the rich solution RS' thereby preheating the
rich solution prior to its entry to the amine regenerator column
ARC. The lean solution LS' needs to be further cooled prior to its
use in the absorber column B. For this, it is directed through a
heat exchanger LSC, which is configured to cool the lean solution
by means of chilling water in line 25 from stage 23 of the LNG
system. The heated water from the heat exchanger LSC is directed
back to stage 23 for chilling again in stage 23, thereby closing
the circuit.
[0051] The CO2 extracted from the flue gas exits from the
regenerator column ARC and is directed to further processing such
as compression, drying, or chilling.
[0052] Depending on the type of CO2 capture system installed, the
flue gas from the HRSG should be cooled to specific temperature
ranges prior to its processing within that system. In the case of
chilled ammonia process, the flue gas has a preferred temperature
from of less than 10.degree. C. prior to entering the absorber. In
the case of an amine process, the flue gas should have a
temperature of ca. 50.degree. C. in order to assure optimal
operation. For such flue gas cooling, the power plant comprises a
flue gas cooler 3A, or if necessary, additionally a flue gas
chiller 3B arranged in the flue gas line for cooling or chilling
the flue gas prior to its processing in the CO2 capture processing.
The cold energy therefore may be entirely drawn from the LNG
system. The cooler/chiller system 3A, 3B in turn supports the LNG
system with heat gained from the flue gas and directed to the LNG
system via line 26.
[0053] The power plant comprises several further cooling systems
connected or associated with the CO2 capture system, which can be
integrated with the LNG system, in addition to the cooling systems
of the CO2 capture system itself.
[0054] The CO2 capture system 5A, 5B is connected to a CO2 drying
and cooling system 6 for processing the captured CO2, which has
been separated from the flue gas in the CO2 capture system. An
optional compressor for CO2 compression may be arranged following
the cooling system 6.
[0055] In order to enhance the efficiency of the CO2 capture
process by means of increasing the CO2 concentration in the flue
gas, the power plant 10 can furthermore comprise a flue gas
recirculation system, which can include a line branching off the
exhaust line from the HRSG, which directs untreated flue gas back
to the gas turbine inlet via a flue gas cooler 4a followed by an
optional flue gas chiller 4b. Cooled or chilled flue gas exiting
from the flue gas cooler or flue gas chiller respectively is
directed and admixed to the inlet air flow A intended for the gas
turbine compressor.
[0056] For a further power plant capacity increase, the power plant
can comprise an inlet air chilling system 2, which cools the inlet
air for example in case of high ambient air temperatures using a
chilled medium from heat exchanger 23 via line 25. The heated
medium is returned to heat exchanger 23 via line 26.
[0057] The power plant is operatively connected with the liquefied
natural gas processing system 20, which vaporizes cryogenic
liquefied natural gas LNG for use in the gas turbine combustion
chamber CC and/or for export via a gas pipeline. The regasification
processes and the various cooling and chilling systems within the
power plant 10 are integrated in a manner to optimize the overall
power plant efficiency. The LNG system 20 comprises for example
several stages 21-23, which are arranged in series, where each
stage vaporizes the LNG to a different temperature level. A first
stage 21 is configured and arranged to vaporize the LNG and is
operatively connected in a closed circuit to an air separation unit
ASU within power plant 10 via lines 27 and 28. Line 27 directs
cryogenic cold via a flow medium to operate the ASU, where a line
28 directs the heat generated in the ASU back to vaporizer stage 21
to vaporize the LNG.
[0058] The air separation unit ASU is arranged in a line for
ambient air, which branches off the inlet airflow line A for the
gas turbine compressor. Pure oxygen extracted from ambient air is
directed either back to the ambient air line to the compressor,
and/or the combustion chamber CC of the gas turbine, and/or the
heat recovery steam generator HRSG to support supplementary
firing.
[0059] A second heat exchanger 22 of the LNG system 20, as shown in
FIG. 1, is operatively connected with the CO2 drying and cooling
system 6. The cold energy of the LNG heat exchanger 22 is used to
liquefy the CO2 captured from the gas turbine exhaust gas after the
CO2 has been compressed sufficiently in a compressor 37. The
liquefied CO2 may be directed to a transportation facility T or any
other facility for processing or storing CO2.
[0060] The integration of the second heat exchanger 22 of the LNG
vaporizer into the CO2 processing of the power plant allows a
liquefaction of the CO2 without the need of additional CO2
compressors and intercoolers to compress the CO2 to higher
pressures. This arrangement allows a significant savings in
investment and operating cost as well as plant efficiency.
[0061] The third heat exchanger 23 of the LNG regasification system
20 is operatively connected by means of lines 25 and 26 with cooler
systems of the CO2 capture system 5A or 5B. In order to
additionally optimize the overall power plant efficiency, further
cooling systems within the power plant 10 can be integrated in
similar manner. These systems include for example the cooling
system for the steam turbine condenser 1.
[0062] Each one of the heat exchangers 21-23 may in themselves
comprise one or more vaporizer units, where in the case of several
units, the units can be arranged in series or in parallel. Such
arrangements allow for flexible control of the LNG and heat
exchange flows and the respective temperatures.
[0063] Additionally, the last heat exchanger 23 may be combined
with a cold storage unit 24, which is also connected by lines to
lines 25 and 26. Also heat exchanger 22 may be connected with a
cold storage unit 35, which is connected with lines to compressor
37 and the transport facility T. Similarly, the heat exchanger 21
may be combined with a cold storage unit 36, which is connected via
lines to lines 27 and 28. This configuration allows the operation
of the cooling and chilling systems within the power plant during a
shut-down of the LNG regasification process or insufficient cold
available from the process.
[0064] FIG. 4 shows a further exemplary embodiment of the power
plant 10 with a variant of the LNG regasification plant 20'. This
variant comprises two heat exchangers 21 and 23 for LNG
regasification with optional cold storage units 24 and 36. Instead
of having a heat exchanger 22 used for CO2 liquefaction, the power
plant comprises a system of compressors 37 with an intercooler 34
arranged after the drying and chilling system 6. The intercooler is
supplied with cold via line 25 from heat exchanger 23.
* * * * *