METHOD FOR REDUCING C0 2 EMISSIONS IN A COMBUSTION STREAM
AND INDUSTRIAL PLANTS UTILIZING THE SAME
BACKGROUND
[0001] This application relates reducing CO2 emissions in combustion
streams.
[0002] Air pollution concerns worldwide have led to stricter emissions
standards. These standards regulate the emission of oxides of nitrogen (NOx),
unburned hydrocarbons (HC), carbon monoxide (CO), and carbon dioxide (C0 2),
generated by the power industry. In particular, carbon dioxide has been identified as a
greenhouse gas, resulting in various techniques being implemented to reduce the
concentration of carbon dioxide being discharged to the atmosphere.
[0003] There are three generally recognized ways currently employed for
reducing CO2 emissions from such power stations. The first method is to capture CO2
after combustion with air from the exhaust gas; wherein the CO2 produced during the
combustion is removed from the exhaust gases by an absorption process, adsorption
process, membranes, diaphragms, cryogenic processes or combinations thereof. This
method, commonly referred to as post-combustion capture, usually focuses on
reducing CO2 emissions from the atmospheric exhaust gas of a power station. A
second method includes reducing the carbon content of the fuel. In this method, the
fuel is first converted into H2 and CO2 prior to combustion. Thus, it becomes possible
to capture the carbon content of the fuel before entry into the gas turbine and the
formation of CO2 is hence avoided. A third method includes an oxy-fuel process. In
this method, pure oxygen is used as the oxidant as opposed to air, thereby resulting in
a flue gas consisting of carbon dioxide and water.
[0004] The main disadvantage of the post-combustion CO2 capture processes
is that the CO2 partial pressure is very low in the flue gas (typically 3-4% by volume
for natural gas fired power plants). Although the CO2 concentration at the stack and
thus the partial pressure could be increased by partial recirculation of the flue gas to
the compressor of the gas turbine (in this respect see, for example, U.S. Pat. No.
5,832,712 and WO 2009/098128), it still remains fairly low (about 6-10% by
volume). And, due to somewhat lower isentropic exponent (also known as ratio of
specific heat) of the flue gas compared to pure air, penalties in power and efficiency
are expected for natural gas fired power plants when exhaust gas recirculation is
employed. For the same reason, it is less than ideal to compress a mixture of flue gas
and air in the gas turbine compressor. These factors significantly increase the cost of
electricity generation. In fact, the cost of CO2 capture is generally estimated to
represent three-fourths of the total cost of a carbon capture, storage, transport, and
sequestration.
[0005] As a result, there is a continuing need for cost-effective CO2 removal
technologies.
BRIEF DESCRIPTION
[0006] In one embodiment, a method for reducing CO2 emissions in an
exhaust stream is provided. The method comprises generating an exhaust stream, and
compressing the stream. A first flow path of the compressed exhaust stream is
recirculated back to the generating step. A second flow path of the compressed stream
is provided to a separator where CO2 is then separated from the compressed exhaust
stream to provide a substantially CO2 free exhaust stream and a stream of liquid CO2.
[0007] An industrial plant is also provided. The plant comprises a
manufacturing assembly for producing a product and an exhaust stream comprising
CO2 and further comprises a compressor, recirculation line and carbon dioxide
separation system. The compressor receives the exhaust stream comprising CO2 and
generates a compressed exhaust gas. The compressor comprises a first conduit
configured to recirculate a first flow path of the compressed exhaust gas to an
upstream point in the manufacturing assembly. The compressor further comprises a
second conduit configured to provide a second flow path of the compressed exhaust
gas to the CO2 separation system. The CO2 separation system is configured to receive
the compressed exhaust gas and generate a substantially CO2 free exhaust stream and
stream of liquid CO2.
[0008] A natural gas combined cycle power plant is also provided. The plant
comprises a semi-open combustion cycle and a closed steam cycle and in operation
generates an exhaust stream comprising CO2. The plant further comprises at least one
compressor downstream of the combustion cycle and steam cycle, as well as a CO2
separator. The compressor is coupled to a recirculation line that fluidly connects the
compressor with the open combustion cycle. The compressor is also fluidly
connected to the C02 separator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other features, aspects, and advantages of the present
invention will become better understood when the following detailed description is
ead with reference to the accompanying drawings in which like characters represent
like parts throughout the drawings, wherein:
[0010] Figure 1 is a schematic illustration of a natural gas combined cycle
power plant in accordance with one embodiment;
[001 1] Figure 2 is a schematic illustration of a natural gas combined cycle
power plant in accordance with another embodiment;
[0012] Figure 3 is a schematic illustration of a natural gas combined cycle
power plant in accordance with another embodiment;
[0013] Figure 4 is a schematic illustration of a natural gas combined cycle
power plant in accordance with another embodiment; and
[0014] Figure 5 is a schematic illustration of a cascade plant in accordance
with yet another embodiment
DETAILED DESCRIPTION
[0015] Any compositional ranges disclosed herein are inclusive and
combinable (e.g., ranges of "up to about 25 wt%", or, more specifically, "about 5 wt%
to about 20 wt%", are inclusive of the endpoints and all intermediate values of the
ranges). Weight levels are provided on the basis of the weight of the entire
composition, unless otherwise specified; and ratios are also provided on a weight
basis. Moreover, the term "combination" is inclusive of blends, mixtures, reaction
products, and the like. Furthermore, the terms "first," "second," and the like, herein
do not denote any order, quantity, or importance, but rather are used to distinguish
one element from another.
[0016] The terms "a" and "an" herein do not denote a limitation of quantity,
but rather denote the presence of at least one of the referenced items. The modifier
"about" used in connection with a quantity is inclusive of the stated value, and has the
meaning dictated by context, (e.g., includes the degree of error associated with
measurement of the particular quantity). The suffix "(s)" as used herein is intended to
include both the singular and the plural of the term that it modifies, thereby including
one or more of that term (e.g., "the stream(s)" may include one or more streams).
[0017] Reference throughout the specification to "one embodiment", "another
embodiment", "an embodiment", and so forth, means that a particular element (e.g.,
feature, structure, and/or characteristic) described in connection with the embodiment
is included in at least one embodiment described herein, and may or may not be
present in other embodiments. In addition, it is to be understood that the described
inventive features may be combined in any suitable manner in the various
embodiments.
[0018] Provided herein are methods and systems for reducing CO2 in
emissions streams, e.g., of power plants. The present methods not only make use of
exhaust gas recirculation, but also, compression of the exhaust gas. Importantly, the
compression of the exhaust gas is done prior to the introduction thereof into the gas
turbine compressor and/or its mixture with pure air. And so, penalties in power and
efficiency that may otherwise be expected for natural gas fired power plants that
employ exhaust gas recirculation due to lower ratio of specific heat of the exhaust gas
as compared to pure air, can be minimized, or even eliminated.
[0019] The compression of the exhaust gas also serves to increase the pressure
and thus, decrease the volume, of the exhaust gas. Recirculation of the compressed
exhaust gas increases the concentration of C02 in the exhaust gas. As a result,
removal of CO2 from the exhaust gas is thus simplified, and the capital and energy
expenditures required to do so reduced as compared to those associated with CO2
removal from a non-compressed exhaust gas, since less energy may be required to
freeze out the CO2 from a compressed exhaust gas stream as compared to a noncompressed
exhaust stream. Finally, the CO2 is cryogenically separated at pressures
greater than or equal to ambient pressure, but lower than the pressure at the triple
point of C02. And so, the recovered CO2 can be pumped to its final pressure, rather
than compressed.
[0020] As a result, the methods and plants disclosed herein may use at least
10% less energy, or at least 20% less, or even at least 30% less, than conventional
methods and plants that provide from the removal of C02 from an exhaust stream.
These energy savings can be further maximized in those embodiments of the methods
and/or plants wherein heat is recovered from the hot exhaust gas.
[0021] The present methods comprise generating an exhaust stream
comprising CO2. The exhaust stream is compressed and recycled to increase the CO2
concentration therein. Generally speaking, any amount of compression that will
provide even a minimal increase in pressure in the exhaust stream may be used, and
the exact amount may be dictated by the initial concentration of CO2, the other
components in the exhaust stream, the CO2 separation mechanism desirably
employed, and the like. On the other hand, in those embodiments wherein the CO2
separation mechanism desirably comprises a cryogenic separator, the exhaust gas will
desirably not be compressed to a pressure greater than the triple point of CO2, i.e.,
about 5 atmospheres.
[0022] A first flow path of the compressed exhaust stream is recirculated back
to the generating step. The particular amount of the compressed exhaust stream
recirculated in the first flow path can be selected based upon the increase in CO2
concentration in the exhaust gas desired. Generally speaking, increases in CO2
concentration in the exhaust stream may be expected to be seen when at least about
10%, or about 20%, or about 30%, or about 40%, or even up to about 50% of the
compressed exhaust stream is recirculated to the generating step.
[0023] A second flow path of the compressed exhaust stream is provided to a
separator where CO2 is then separated from the compressed exhaust stream to provide
a substantially CO2 free exhaust stream and liquid CO2. The separator desirably
comprises a cryogenic separator, also commonly referred to as a "CO2 freeze out
unit", either used alone, or in combination with other CO2 separation processes such
as CO2 selective membrane technologies, sorption processes (adsorption and/or
absorption), diaphragms, and the like. Such methods, as well as the parameters for
their operation, are well known to those of ordinary skill in the art. Examples of
suitable membrane technologies and details of their use are disclosed in US Patent
Publication Nos. 2008/0104958 and 2008/0127632 to Finkenrath, which publications
are hereby incorporated herein by reference to the extent that they do not conflict with
the teachings herein.
[0024] In some embodiments, one or more cryogenic separators are used to
remove CO2 from the exhaust stream. Cryogenic separators for the removal of CO2
are known in the art, many are commercially available, and any of these may be
utilized in the methods. As is known to those of ordinary skill in the art, cryogenic
separators operate by "freezing out" the CO2 as a solid from the compressed exhaust
stream. The CO2 "snow" is then collected, compressed and melted. The melted CO2
is then pumped to its final pressure for storage or use.
[0025] Because of the cost and energy savings they provide, the present
methods are advantageously incorporated into industrial processes and plants that
generate exhaust streams comprising CO2. Further, the methods are easy to
implement on all existing and future power plants, as no integration with the main
power system is required. In some embodiments, such industrial plants may
incorporate a heat exchanger, which may be integrated with the main power system, if
desired. Such integration could lead to a reduction of the power requirement needed
to drive the other components of the industrial plant, or even help to make the CO2
separation components energy self-sustainable.
[0026] Examples of industrial plants that could benefit from incorporation of
the principles described include combustion processes, such as coal fired power
plants, oil-fired boilers, cement or steel factories, etc. Generally speaking, such plants
will comprise a manufacturing assembly for producing a product and an exhaust
stream comprising CO2. Such plants will further desirably comprise a compressor,
recirculation line and carbon dioxide separation system. The compressor receives the
exhaust stream comprising CO2 and generates a compressed exhaust gas. The
compressor comprises a first conduit configured to recirculate a first flow path of the
compressed exhaust gas to an upstream point in the manufacturing assembly. The
compressor further comprises a second conduit configured to provide a second flow
path of the compressed exhaust gas to the CO2 separation system. The CO2 separation
system is configured to receive the compressed exhaust gas and generate a
substantially CO2 free exhaust stream and stream of liquid CO2.
[0027] One particular class of industrial plants that could benefit from
incorporation of the methods and principles described herein includes natural gas
power plants, e.g., natural gas combined cycle power plants. FIG. 1 is a schematic
illustration of one embodiment of natural gas combined cycle power plant.
[0028] Plant 100 includes a semi-open combustion cycle 101, comprising first
second compressor 102, natural gas inlet 134, combustor 104 and expander 106, and a
closed steam cycle 103, comprising steam turbine 108, and generator 110. Semi-open
combustion cycle 101 and closed steam cycle are mounted on the same shaft, and so,
as shown in FIG. 1, are mechanically connected, but are not fluidly connected.
[0029] Plant 100 further comprises heat exchanger 116. Heat exchanger 116
is in flow communication with expander 106 and steam turbine 108. In operation, the
relatively hot exhaust stream discharged from expander 106 is channeled through heat
exchanger 116. The heat energy from the hot exhaust stream is transferred to the
working fluid flowing through heat exchanger 116, e.g., in some embodiments a heat
recovery steam generator, or HRSG, to generate steam that is used to produce further
power in steam turbine 108. In some embodiments, heat exchanger 116 is a noncontact
heat exchanger, i.e., in which water or steam from closed steam cycle 103 is
provided to and passed through tubes (not shown) in heat exchanger 116 via conduit
120 and exhaust gas from semi-open combustion cycle 101 is provided to and passes
around the tubes (not shown) within heat exchanger 116 via conduit 118.
[0030] A condenser 112 can be located downstream from steam turbine 108 to
convert the stream discharged from steam turbine 108 to water by lowering the
temperature. A pump 114 may also be employed downstream of the condenser 112 to
increase the pressure of the water prior to entry into the heat exchanger 116.
[0031] Cooled exhaust gas exits heat exchanger 116 and is provided to first
compressor 118. In the embodiment shown in Figure 1, downstream of first
compressor 118, a first flow of the compressed exhaust gas is recirculated through
conduit 120 back and to semi-open combustion cycle 101, and more particularly, to
second compressor 102. In some embodiments, up to about 20 volume %, or about 30
volume %, or about 40 volume %, or even up to about 50 volume % of the
compressed exhaust stream can be recycled to enter open combustion cycle 101 with
air at second compressor 102. Compressing the exhaust stream prior to the inlet of
first compressor 102 increases the CO2 concentration in the working fluid, thereby
increasing the driving forces for the CO2 separation in CO2 separation unit 122.
[0032] A second flow of compressed exhaust gas is provided to CO2
separation unit 122 from first compressor 118 via conduit 124. In some
embodiments, CO2 separation unit 122 comprises a CO2 cryogenic separator, either
used alone, or in combination with other CO2 separation processes such as CO2
selective membrane technologies, sorption processes (adsorption and/or absorption),
diaphragms, and the like. CO2 membrane technologies are disclosed, for example, in
US Patent Publication Serial No. 2008/0134660, hereby incorporated herein by
reference in its entirety.
[0033] CO2 separation unit 122 produces a substantially CCVfree exhaust gas,
discharged out conduit 126, and the frozen out CO2 collected, compressed, melted and
delivered to pump 128 where it is pumped to supercritical pressure for transport via
conduit 130.
[0034] Natural gas combined cycle plant 100 is operated as known in the art,
and as such, produces an exhaust stream having a temperature of from about 600
degrees Fahrenheit (°F) (316 degrees Celsius (°C)) to about 1,300°F (704°C). The
exhaust stream discharged from open combustion cycle 101 is channeled through heat
exchanger 116 wherein a substantial portion of the heat energy from the exhaust
stream is transferred to the closed steam cycle 103, with the working fluid channeled
therethrough to generate steam that can be utilized to drive steam turbine 108 and
generator 110. In other embodiments, the exhaust stream can be simply cooled
without utilizing the heat rejected to useful purpose, and/or it can be linked to another
process to provide heat in the form of steam or hot water.
[0035] Heat exchanger 116 facilitates reducing the operational temperature of
the exhaust stream to a temperature that is between about 75°F (24°C) and about
248°F (120°C). In some embodiments, heat exchanger 116 facilitates reducing the
operational temperature of the exhaust stream to a temperature that is approximately
100°F (38°C).
[0036] The relatively cool dry exhaust stream is then compressed in first
compressor 118. If desired, prior to providing the exhaust stream to first compressor
118, the temperature thereof may be further reduced by passing the exhaust stream
through a heat exchanger, wet scrubber, or the like (not shown). In some
embodiments, such a heat exchanger/wet scrubber (not shown) can be used to
condense the water present in the exhaust gas as well as to reduce the temperature of
the exhaust stream, e.g., to about 40°C, so that the compression power required is
reduced.
[0037] First compressor 118 will desirably be utilized to increase the
operating pressure of the exhaust stream channeled there through to a pressure that is
up to about four or five times greater than the operating pressure of the exhaust stream
discharged from heat exchanger 116. Moreover, channeling the exhaust stream
through first compressor 118 causes the temperature of the exhaust stream to increase.
And so in some embodiments, once discharged from first compressor 118, the exhaust
stream may optionally be passed through heat exchanger or wet scrubber to reduce the
temperature thereof.
[0038] Such a heat exchanger may be operatively disposed relative to conduit
124 or conduit 120, as desired. When operatively disposed relative to conduit 124,
such a heat exchanger or wet scrubber may facilitate reducing the operational
temperature of the exhaust stream, which in turn, may be advantageous for operating
CO2 separation unit 122.
[0039] The CO2 rich exhaust stream discharged from first compressor 118
enters the CO2 separation unit 122 via conduit 124. As described above, CO2
separation unit 122 comprises a CO2 freeze out unit, either used alone, or in
combination with other CO2 separation processes such as CO2 selective membrane
technologies, sorption processes (adsorption and/or absorption), diaphragms, and the
like.
[0040] The CO2 freeze out unit comprises an advanced refrigerant process,
preferably a mixed-refrigerant cycle, which is able to reduce the temperature of an
exhaust stream down to -150°C and frost CO2 at pressures greater or equal to
atmospheric, but lower than the pressure at the triple point of CO2. As the CO2
freezes, it is separated from the substantially CO2 free exhaust stream. Subsequently
the solid CO2 is collected and melted, using for instance the low-temperature heat
from the exhaust stream. Once the CO2 is in liquid state, it is pumped to a
supercritical pressure, which is required for transport, sequestration and reinjection
purposes.
[0041] Figure 2 is a schematic illustration of an exemplary natural gas
combined cycle plant 200 according to another embodiment. In addition to those
components described above in connection with Figure 1, plant 200 comprises
additional, third compressor 230 to further compress the exhaust gas in recirculation
line 220. And, the compressed, recycled exhaust gas is combined with compressed air
at an inlet to expander 206.
[0042] The introduction of compressed air at an inlet to expander 206 process
can act to cool down the blades of the expander, reducing or eliminating to divert air
from compressor. That is, since the pressure of the exhaust gas exiting first
compressor 218 is limited by the pressure acceptable within CO2 separation unit 222
to the pressure at the triple point of CO2, or to about 5 atmospheres, the pressure of
the exhaust gas recirculated and added to semi-open combustion cycle 201 after
combustor 204 and prior to expander 206 must be raised to substantially equivalent to
the pressure within expander 206, e.g, to about 20 to 40 atmospheres, or flow in the
conduit 220 will reverse. Compressed exhaust gas can also cool down the blades of
expander 206, and reduce or eliminate the need to divert air from compressor 202 for
this purpose. As a result, this embodiment can provide further reductions in penalties
to semi-open combustion cycle 201.
[0043] Figure 3 is a schematic illustration of an exemplary natural gas
combined cycle plant 300 according to another embodiment. In addition to those
components described above in connection with Figure 1, plant 300 comprises
additional compressor 332 to compress inlet air to a pressure substantially equivalent
to that of the compressed, recycled exhaust gas. The compressed air and compressed
recycled exhaust gas are combined at valve 336, prior to introduction into semi-open
combustion cycle 301 at compressor 302.
[0044] Figure 4 is a schematic illustration of an exemplary industrial plant
according to another embodiment. In addition to those components described above
in connection with Figure 3, plant 400 comprises intercooler 438. In operation,
compressed air and compressed recycled exhaust gas are combined at valve 436, prior
to introduction into intercooler 438. Intercooler 438 operates to decrease the
temperature of the low-pressure compressed gas mixture prior to further compression
in second compressor 402. As the temperature of the gas mixture decreases, so does
the compression work of second compressor 402. Thus, an intercooled gas turbine
cycle might have higher efficiency than non intercooled gas turbine cycles for the
same compression ratio. In the exemplary embodiment, the plant 400 may comprise
an LMS100 available from General Electric Aircraft Engines, Cincinnati, Ohio.
[0045] Figure 5 is a schematic illustration of another embodiment. More
particularly, Figure 5 shows cascade plant 500, wherein two gas turbine power plants,
upstream plant 540 and downstream plant 542, are configured in series. In the
embodiment shown, downstream plant 542 is provided with first compressor 518,
conduit 520 and CO2 separation unit 522. The advantage of this configuration is that
the concentration of CO2 and partial pressure in the exhaust stream of downstream
plan 542 increases relative to that of a single natural gas combined cycle plant, which
facilitates the CO2 separation process.
[0046] Upstream plant 540 is operated as known in the art, and as such,
produces an exhaust stream having a temperature of from about 600 degrees
Fahrenheit (°F) (316 degrees Celsius (°C)) to about 1,300°F (704°C). The exhaust
stream discharged from semi-open combustion cycle 501 is channeled through heat
exchanger 516 wherein a substantial portion of the heat energy from the exhaust
stream is transferred to the closed steam cycle 503. More particularly, Heat
exchanger 516 facilitates reducing the operational temperature of the exhaust stream
to a temperature that is between about 75°F (24°C) and about 248°F (120°C), or to a
temperature of about 100°F (38°C). The exhaust stream from upstream plant 540, and
more particularly, heat exchanger 516, is provided to downstream plant 542, which
then operates substantially as described above in connection with Figure 1.
[0047] While the invention has been described with reference to a preferred
embodiment, it will be understood by those skilled in the art that various changes can
be made and equivalents can be substituted for elements thereof without departing
from the scope of the invention. In addition, many modifications can be made to
adapt a particular situation or material to the teachings of the invention without
departing from essential scope thereof. Therefore, it is intended that the invention not
be limited to the particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include all embodiments falling
within the scope of the appended claims.

WHAT IS CLAIMED IS:
1. A method for reducing CO2 emissions in an exhaust stream,
comprising:
generating an exhaust stream;
compressing the exhaust stream;
recycling a first flow path of the compressed exhaust stream to the generating
step; and
separating CO2 from a second flow of the compressed exhaust stream to
produce a liquid CO2 stream and a substantially CO2 free exhaust stream.
2. The method of claim 1, wherein the exhaust stream is generated by a
combustion process.
3. The method of claim 2, wherein the exhaust stream is generated by a
coal or natural gas fired power plants, an oil-fired boiler, or a cement or steel factory.
4. The method of claim 3, wherein the exhaust stream is generated by a
natural gas fired power plant.
5. The method of claim 1, wherein the CO2 is separated from the second
flow of the compressed exhaust stream using a cryogenic separator, a CO2 selective
membrane technology, an adsorption process, an absorption process, a diaphragm, or
combinations of these.
6. The method of claim 1, wherein the CO2 is separated from the second
flow of the compressed exhaust stream using a cryogenic separator.
7. The method of claim 6, wherein the exhaust stream is compressed to a
pressure of less than about 5 atmospheres.
8. The method of claim 7, wherein the exhaust stream is compressed to a
pressure of from about 1 atmospheres to about 4 atmospheres.
9. The method of claim 1, wherein up to about 50% of the compressed
exhaust stream is recycled in the first flow path.
10. An industrial plant for producing a product and an exhaust stream
comprising CO2 comprising:
A manufacturing assembly for producing a product and an exhaust
stream comprising CO2;
A compressor;
A recirculation line operatively coupling the compressor to the
manufacturing assembly; and
a CO2 separator.
11. The industrial plant of claim 10, wherein the manufacturing assembly
produces power.
12. The industrial plant of claim 11, wherein the manufacturing assembly
produces power via a combustion process.
13. The industrial plant of claim 12, wherein the process combusts natural
gas.
14. The industrial pant of claim 10, wherein the CO2 separator comprises a
cryogenic separator, a CO2 selective membrane technology, an adsorption process, an
absorption process, a diaphragm, or combinations of these.
15. The industrial plant of claim 14, wherein the CO2 separator comprises
a cryogenic separator.
16. A natural gas combined cycle power plant that generates an exhaust
stream comprising CO2, the plant comprising
A semi-open combustion cycle;
A closed steam cycle;
A CO2 separator; and
At least one compressor operatively disposed downstream of the open
combustion cycle and the closed steam cycle and coupled to (i) a
recirculation line that fluidly connects the compressor with the semiopen
combustion cycle and (ii) a conduit that fluidly connects the
compressor to the CO2 separator.
17. The plant of claim 16, further comprising at least a second compressor
operatively disposed relative to the recirculation line.
18. The plant of claim 17, wherein the semi-open combustion cycle
comprises a combustor and an expander, and wherein the recirculation line is fluidly
connected to an inlet of the expander.
19. The plant of claim 16, further comprising an inlet air compressor
operatively disposed upstream of the open combustion cycle, and wherein the
recirculation line is fluidly connected to a valve operatively disposed between the air
compressor and the open combustion cycle.
20. The plant of claim 19, further comprising an intercooler operatively
disposed between the valve and the open combustion cycle.
1. The plant of claim 16, further comprising at least one heat exchanger.
22. The plant of claim 21, wherein the at least one heat exchanger is
operatively disposed relative to the recirculation line.
23. The plant of claim 21, wherein the at least one heat exchanger is
operatively disposed relative to the first compressor, the CO2 separator, or both.
24. The plant of claim 16, operatively disposed relative to at least one
other natural gas combined cycle power plant.