U.S. patent application number 14/487985 was filed with the patent office on 2015-01-01 for systems and methods for treating carbon dioxide.
The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Mehmet Arik, Douglas Carl Hofer, Vitali Victor Lissianski, Stephen Duane Sanborn, Roger Allen Shisler, Paul Brian Wickersham, Jalal Hunain Zia.
Application Number | 20150000333 14/487985 |
Document ID | / |
Family ID | 46939484 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150000333 |
Kind Code |
A1 |
Zia; Jalal Hunain ; et
al. |
January 1, 2015 |
SYSTEMS AND METHODS FOR TREATING CARBON DIOXIDE
Abstract
A heat exchange assembly for treating carbon dioxide (CO.sub.2)
is described. The heat exchange assembly includes a housing that
includes an inlet, an outlet, and an inner surface that defines a
cavity extending between the inlet and the outlet. The housing is
configured to receive solid CO.sub.2 through the inlet. At least
one heat exchange tube extends through the housing. The heat
exchange tube is oriented to contact solid CO.sub.2 to facilitate
transferring heat from solid CO.sub.2 to a heat exchanger fluid
being channeled through the heat exchange tube to facilitate
converting at least a portion of solid CO.sub.2 into liquid
CO.sub.2. The heat exchange assembly is configured to recover a
refrigeration value from the solid CO.sub.2 and transfer at least a
portion of the recovered refrigeration value to a flue gas.
Inventors: |
Zia; Jalal Hunain;
(Niskayuna, NY) ; Hofer; Douglas Carl; (Clifton
Park, NY) ; Lissianski; Vitali Victor; (Schenectady,
NY) ; Sanborn; Stephen Duane; (Copake, NY) ;
Arik; Mehmet; (Alemdag, TR) ; Shisler; Roger
Allen; (Ballston Spa, NY) ; Wickersham; Paul
Brian; (Schenectady, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
SCHENECTADY |
NY |
US |
|
|
Family ID: |
46939484 |
Appl. No.: |
14/487985 |
Filed: |
September 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13285375 |
Oct 31, 2011 |
|
|
|
14487985 |
|
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Current U.S.
Class: |
62/602 |
Current CPC
Class: |
B01D 2258/0283 20130101;
B01D 2257/504 20130101; F25J 1/0027 20130101; F28D 7/16 20130101;
F28D 7/082 20130101; F28F 1/24 20130101; B01D 53/002 20130101 |
Class at
Publication: |
62/602 |
International
Class: |
F25J 1/00 20060101
F25J001/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH &
DEVELOPMENT
[0002] This invention was made with Government support under
Contract No. DE-AR0000101, awarded by the Department of Energy. The
Government has certain rights in this invention.
Claims
1. A gas treatment system for use in treating carbon dioxide
(CO.sub.2) in a flue gas, said gas treatment system comprising: a
cooling system coupled to a source of flue gas and configured to
receive a flow of flue gas from the source, said cooling system
configured to cool CO.sub.2 within the flue gas to form solid
CO.sub.2; and a heat exchange assembly coupled to said cooling
system for receiving a flow of solid CO.sub.2 from said cooling
system, wherein said heat exchange assembly is configured to
recover a refrigeration value from the solid CO.sub.2 and transfer
at least a portion of the recovered refrigeration value to the flue
gas, said heat exchange assembly comprising: a housing comprising
an inlet, an outlet, and an inner surface that defines a cavity
extending between said inlet and said outlet, said housing
configured to receive solid CO.sub.2 through said inlet; and at
least one heat exchange tube extending through said housing, said
heat exchange tube oriented to contact solid CO.sub.2 to facilitate
transferring of heat from solid CO.sub.2 to a heat exchange fluid
being channeled through said heat exchange tube to facilitate
converting at least a portion of solid CO.sub.2 into liquid
CO.sub.2.
2. A gas treatment system in accordance with claim 1, wherein said
housing is configured to maintain said cavity within a predefined
range of pressures to prevent re-sublimation of solid CO.sub.2 to
gaseous CO.sub.2.
3. A gas treatment system in accordance with claim 1, wherein said
housing inner surface extends between an upper portion and a lower
portion extending below said upper portion, said lower portion
configured to contain liquid CO.sub.2 therein.
4. A gas treatment system in accordance with claim 3, wherein said
at least one tube includes an outer surface and a plurality of fins
extending outwardly from said tube outer surface, each fin of said
plurality of fins is configured to support solid CO.sub.2 within
said upper portion.stf
5. A gas treatment system in accordance with claim 4, wherein each
fin of said plurality of fins is at least partially submerged
within liquid CO.sub.2.
6. A gas treatment system in accordance with claim 4, wherein
adjacent fins are oriented such that a plurality of openings are
defined between adjacent fins, each opening is sized to channel
liquid CO.sub.2 from said upper portion to said lower portion.
7. A gas treatment system in accordance with claim 1, further
comprising a lockhopper assembly coupled between said cooling
system and said heat exchange assembly for receiving solid CO.sub.2
from said cooling system, said lockhopper assembly configured to
enable solid CO.sub.2 to be gravity fed into said housing
cavity.
8. A gas treatment system in accordance with claim 1, further
comprising a CO.sub.2 sequestration system coupled to said heat
exchange assembly for receiving a flow of liquid CO.sub.2 from said
heat exchange assembly.
9. A method of treating carbon dioxide (CO.sub.2), said method
comprising: channeling a flue gas containing CO.sub.2 to a cooling
system to cool the flue gas to form solid CO.sub.2; channeling the
solid CO.sub.2 to a heat exchange assembly, wherein the heat
exchange assembly includes a housing configured to receive solid
CO.sub.2 therein, and at least one heat exchange tube extending
through the housing; adjusting a pressure within the housing to
maintain the housing pressure within a predefined range of
pressures to prevent re-sublimation of solid CO.sub.2; channeling a
flow of heat exchange fluid through the at least one heat exchange
tube to facilitate a transfer of heat from solid CO.sub.2 to the
heat exchange fluid to convert at least a portion of solid CO.sub.2
into liquid CO.sub.2 and to recover a refrigeration value from the
CO.sub.2; and transferring at least a portion of the recovered
refrigeration value to the flue gas to facilitate cooling the flue
gas.
10. A method in accordance with claim 9, further comprising
channeling the heat exchange fluid to a pre-cooling system to
facilitate transferring the recovered refrigeration value to the
flue gas to facilitate cooling the flue gas.
11. A method in accordance with claim 9, further comprising
channeling solid CO.sub.2 from a lockhopper assembly to the heat
exchange assembly, wherein the lockhopper assembly is configured to
enable solid CO.sub.2 to be gravity fed into the housing
cavity.
12. A method in accordance with claim 9, further comprising
channeling liquid CO.sub.2 from the heat exchange assembly to a
CO.sub.2 sequestration system.
Description
[0001] This Application is a Division of patent application Ser.
No. 13/285,375, filed on Oct. 31, 2011, the contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] The subject matter described herein relates generally to gas
treatment systems and, more particularly, to gas treatment system
for use in treating carbon dioxide (CO.sub.2).
[0004] At least some known power generation systems include a
combustor and/or boiler to generate steam that is used in a steam
turbine generator. During a typical combustion process within a
combustor or boiler, for example, a flow of combustion gases, or
flue gases, is produced. Known combustion gases contain combustion
products including, but not limited to, carbon, fly ash, carbon
dioxide, carbon monoxide, water, hydrogen, nitrogen, sulfur,
chlorine, arsenic, selenium, and/or mercury.
[0005] At least some known power generation systems include a gas
treatment system for use in reducing an amount of combustion
products within the flue gases. Known gas treatment systems include
a low-temperature cooling system for separating CO.sub.2 from the
flue gases. During operation, the low-temperature cooling system
cools a flue gas stream to form solid CO.sub.2 from gaseous
CO.sub.2 suspended within the flue gas stream. In addition, at
least some known gas treatment systems include a low-temperature
solids pump for use in transporting the solid CO.sub.2 from the
low-temperature cooling system to a CO.sub.2 sequestration system
for sequestration and deposition of the CO.sub.2. During operation,
the low-temperature cooling system transfers a refrigeration value
to the flue gas stream to form solid CO.sub.2. As the
low-temperature solids pump conveys the solid CO.sub.2 from the
cooling system, at least some of the refrigeration value may be
lost to heat generated from operation of the solids pump. The loss
of refrigeration value through the solids pump increases the cost
of operating the gas treatment system by increasing an amount of
energy required to cool the flue gas stream.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In one aspect, a heat exchange assembly for treating carbon
dioxide (CO.sub.2) is provided. The heat exchange assembly includes
a housing that includes an inlet, an outlet, and an inner surface
that defines a cavity extending between the inlet and the outlet.
The housing is configured to receive solid CO.sub.2 through the
inlet. At least one heat exchange tube extends through the housing.
The heat exchange tube is oriented to contact solid CO.sub.2 to
facilitate transferring heat from solid CO.sub.2 to a heat
exchanger fluid being channeled through the heat exchange tube to
facilitate converting at least a portion of solid CO.sub.2 into
liquid CO.sub.2. The heat exchange assembly is configured to
recover a refrigeration value from the solid CO.sub.2 and transfer
at least a portion of the recovered refrigeration value to a flue
gas.
[0007] In another aspect, a gas treatment system for use in
treating carbon dioxide (CO.sub.2) in a flue gas is provided. The
gas treatment system includes a cooling system coupled to a source
of flue gas and configured to receive a flow of flue gas from the
source. The cooling system is configured to cool gaseous CO.sub.2
suspended within the flue gas to form solid CO.sub.2. A heat
exchange assembly is coupled to the cooling system for receiving a
flow of solid CO.sub.2 from the cooling system. The heat exchange
assembly is configured to recover a refrigeration value from the
solid CO.sub.2 and transfer at least a portion of the recovered
refrigeration value to the flue gas. The heat exchange assembly
includes a housing that includes an inlet, an outlet, and an inner
surface that defines a cavity extending between the inlet and the
outlet. The housing is configured to receive solid CO.sub.2 through
the inlet. At least one heat exchange tube extends through the
housing. The heat exchange tube is oriented to contact solid
CO.sub.2 to facilitate transferring heat from solid CO.sub.2 to a
heat exchanger fluid being channeled through the heat exchange tube
to facilitate converting at least a portion of solid CO.sub.2 into
liquid CO.sub.2.
[0008] In yet another aspect, a method of treating carbon dioxide
(CO.sub.2) is provided. The method includes channeling a flue gas
containing CO.sub.2 to a cooling system to cool the flue gas to
form solid CO.sub.2, and channeling solid CO.sub.2 to a heat
exchanger assembly. The heat exchanger assembly includes a housing
that is configured to receive solid CO.sub.2 therein, and at least
one heat exchange tube extending through the housing. A pressure
within the housing is adjusted to maintain the housing pressure
within a predefined range of pressures to prevent re-sublimation of
solid CO.sub.2. A flow of heat exchange fluid is channeled through
the at least one heat exchange tube to facilitate a transfer of
heat from solid CO.sub.2 to the heat exchange fluid to convert at
least a portion of solid CO.sub.2 into liquid CO.sub.2, and to
recover a refrigeration value from the CO.sub.2. At least a portion
of the recovered refrigeration value is transferred to the flue gas
to facilitate cooling the flue gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of an exemplary power generation
system.
[0010] FIG. 2 is a schematic view of an exemplary heat exchanger
assembly that may be used with the power generation system shown in
FIG. 1.
[0011] FIGS. 3-4 are schematic views of alternative embodiments of
the heat exchanger assembly shown in FIG. 2.
[0012] FIG. 5 is an alternative embodiment of the power generation
system shown in FIG. 1.
[0013] FIG. 6 is another embodiment of the power generation system
shown in FIG. 1.
[0014] FIG. 7 is a flow chart of an exemplary method that may be
used to treat carbon dioxide generated during operation of the
power generation system shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The exemplary systems and methods described herein overcome
at least some disadvantages of known gas treatment systems by
providing a gas treatment system that includes a heat exchange
assembly that is configured to transfer heat from a heat exchange
fluid to solid CO.sub.2 to facilitate recovering a refrigeration
value from solid CO.sub.2. Moreover, the heat exchange assembly is
configured to maintain CO.sub.2 in solid-liquid phase equilibrium
to enable the heat exchange assembly to transfer heat to solid
CO.sub.2 to facilitate forming liquid CO.sub.2 for use in
pre-cooling a flue gas. By providing a gas treatment system that
includes a heat exchange assembly configured to recover a
refrigeration value from solid CO.sub.2, the cost of treating
CO.sub.2 suspended within a flue gas is reduced as compared to
known gas treatment systems.
[0016] FIG. 1 is a schematic view of an exemplary power generation
system 10. FIG. 2 is a schematic view of an exemplary heat exchange
assembly 12 that may be used with power generation system 10. In
the exemplary embodiment, power generation system 10 includes a
combustor assembly 14, a steam generation assembly 16 downstream of
combustor assembly 14, and a steam turbine engine 20 coupled to
steam generation assembly 16. Combustor assembly 14 includes at
least one combustor 22, a fuel supply system 24, and an air supply
system 26. Fuel supply system 24 is coupled to combustor 22 for
channeling a flow of fuel such as, for example, coal to combustor
22. Alternatively, fuel supply system 24 may channel any other
suitable fuel, including but not limited to, oil, natural gas,
biomass, waste, and/or any other fossil and/or renewable fuel that
enables power generation system 10 to function as described herein.
In addition, air supply system 26 is coupled to combustor 22 for
channeling a flow of air to combustor 22. Combustor 22 is
configured to receive a predetermined quantity of fuel and air from
fuel supply system 24 and air supply system 26, respectively, and
ignite the fuel/air mixture to generate combustion or flue gases.
Moreover, combustor 22 channels a flow of flue gases 28 to steam
generation assembly 16 to generate steam that is channeled to steam
turbine engine 20 for use in generating a power load.
[0017] In the exemplary embodiment, steam generation assembly 16
includes at least one heat recovery steam generator (HRSG) 30 that
is coupled in flow communication with a boiler feedwater assembly
32. HRSG 30 receives a flow of boiler feedwater 33 from boiler
feedwater assembly 32 to facilitate heating boiler feedwater 33 to
generate steam. HRSG 30 also receives flue gases 28 from combustor
assembly 14 to further heat boiler feedwater 33 to generate steam.
HRSG 30 is configured to facilitate transferring heat from flue
gases 28 to boiler feedwater 33 to generate steam, and channel
steam 34 to steam turbine engine 20. Steam turbine engine 20
includes one or more steam turbines 36 that are rotatably coupled
to a power generator 38 with a drive shaft 40. HRSG 30 discharges
steam 34 towards steam turbine 36 wherein thermal energy in the
steam is converted to mechanical rotational energy. Steam 34
imparts rotational energy to steam turbine 36 and to drive shaft
40, which subsequently drives power generator 38 to facilitate
generating a power load.
[0018] In the exemplary embodiment, power generation system 10
includes a gas treatment system 42 that is downstream from
combustor assembly 14 and steam generation assembly 16. Gas
treatment system 42 is configured to receive flue gases 28
exhausted from combustor assembly 14 and/or steam generation
assembly 16 to facilitate removing combustion products including,
but not limited to, carbon, fly ash, carbon dioxide, carbon
monoxide, water, hydrogen, nitrogen, sulfur, chlorine, arsenic,
selenium, and/or mercury from the flue gases.
[0019] In the exemplary embodiment, gas treatment system 42
includes a flue gas pre-cooling system 44, a low-temperature
cooling system 46 downstream of flue gas pre-cooling system 44, a
CO.sub.2 separator 48 downstream of cooling system 46, heat
exchange assembly 12 downstream of cooling system 46, and a
CO.sub.2 utilization system 52 downstream of heat exchange assembly
12. Flue gases 28 including gaseous CO.sub.2 and nitrogen (N.sub.2)
are channeled to flue gas pre-cooling system 44 from combustor
assembly 14 and/or steam generation assembly 16. Flue gas
pre-cooling system 44 facilitates a heat transfer from flue gases
28 to a heat exchange fluid 54 being channeled through flue gas
pre-cooling system 44 to facilitate reducing a temperature of flue
gases 28. Pre-cooling system 44 channels the cooled flue gases 28
to cooling system 46.
[0020] Cooling system 46 is configured to treat flue gases 28 to
cool gaseous CO.sub.2 within flue gases 28 to form solid CO.sub.2.
Cooling system 46 channels cooled flue gases 28 and solid CO.sub.2
to CO.sub.2 separator 48 to facilitate separating solid CO.sub.2
and N.sub.2 from flue gases 28. CO.sub.2 separator 48 channels
solid CO.sub.2 56 to heat exchange assembly 12 to facilitate
transferring heat from heat exchange fluid 54 to solid CO.sub.2 56.
Moreover, heat exchange assembly 12 is configured to facilitate
transferring of heat from solid CO.sub.2 56 to heat exchange fluid
54 being channeled through heat exchange assembly 12 to facilitate
converting solid CO.sub.2 56 to liquid CO.sub.2 58. Moreover, heat
exchange assembly 12 is configured to recover a refrigeration value
from solid CO.sub.2 56 and transfer at least a portion of the
recovered refrigeration value to the flue gases 28 to facilitate
cooling flue gases 28. In addition, heat exchange assembly 12 is
configured to channel liquid CO.sub.2 58 to CO.sub.2 utilization
system 52 for utilization of rich CO.sub.2. In one embodiment,
CO.sub.2 utilization system 52 includes a sequestration system for
sequestration of rich CO.sub.2. Alternatively, utilization system
52 may include any system configured to use CO.sub.2 for any
purpose. In the exemplary embodiment, heat exchange assembly 12 is
also configured to adjust a temperature and a pressure within heat
exchange assembly 12 such that CO.sub.2 within heat exchange
assembly 12 is in solid-liquid phase equilibrium.
[0021] Heat exchange assembly 12 includes a heat exchanger 60 and a
lockhopper assembly 62. Lockhopper assembly 62 is coupled between
heat exchanger 60 and CO.sub.2 separator 48 for channeling solid
CO.sub.2 56 from CO.sub.2 separator 48 to heat exchanger 60.
Lockhopper assembly 62 includes a tank 64 that is configured to
receive solid CO.sub.2 56 from CO.sub.2 separator 48, and a valve
assembly 66 coupled between tank 64 and heat exchanger 60 to enable
solid CO.sub.2 56 to be selectively channeled to heat exchanger 60
from tank 64. Lockhopper assembly 62 is configured to adjust a
pressure within tank 64 such that a pressure within tank 64 is
within a range of pressures such that solid CO.sub.2 56 remains in
the solid phase. In addition, lockhopper assembly 62 is configured
to enable solid CO.sub.2 56 to be gravity fed from tank 64 into
heat exchanger 60. In the exemplary embodiment, lockhopper assembly
62 is configured to maintain an interior pressure equal to about 7
atm.
[0022] Heat exchanger 60 includes a housing 68 and at least one
heat exchange tube 70 that extends through housing 68. Housing 68
includes an inlet 72, an outlet 74, and an inner surface 76 that
defines a cavity 78 extending between inlet 72 and outlet 74.
Housing 68 is configured to maintain a pressure within cavity 78
within a predefined range of pressures to facilitate preventing
re-sublimation of solid CO.sub.2 56 to gaseous CO.sub.2 within
cavity 78. In the exemplary embodiment, housing 68 is configured to
maintain an internal pressure of about 7 atm. In one embodiment,
housing 68 is configured to maintain an internal pressure between
about 1 atm to about 10 atm. Moreover, lockhopper assembly 62
channels a flow of pressurized fluid to housing cavity 78 through
valve assembly 66 to pressurize housing 68 to a predefined
pressure. In the exemplary embodiment, inner surface 76 includes an
upper portion 80, and a lower portion 82 that extends below upper
portion 80. Inlet 72 extends through upper portion 80 and is
coupled to lockhopper assembly 62 for receiving solid CO.sub.2 56
from lockhopper assembly 62. In addition, housing lower portion 82
is sized and shaped to contain liquid CO.sub.2 58 therein. Outlet
74 extends through lower portion 82, and is coupled to CO.sub.2
utilization system 52. More specifically, heat exchange assembly 12
includes a liquid CO.sub.2 pump 84 that is coupled between heat
exchanger 60 and CO.sub.2 utilization system 52 for channeling
liquid CO.sub.2 58 from lower portion 82 to CO.sub.2 utilization
system 52.
[0023] In the exemplary embodiment, heat exchange tube 70 extends
though housing cavity 78, and is configured to channel a flow of
heat exchange fluid 54 through housing cavity 78. Heat exchange
tube 70 extends along a centerline axis 85 between a first end 86,
and a second end 88. Heat exchange tube 70 is oriented within
cavity 78 such that an outer surface 90 of heat exchange tube 70
contacts solid CO.sub.2 56 to facilitate transferring heat from
heat exchange fluid 54 to solid CO.sub.2 56 to increase a
temperature of solid CO.sub.2 56 and facilitate converting at least
a portion of solid CO.sub.2 56 to liquid CO.sub.2 58.
[0024] Heat exchange assembly 12 also includes a plurality of fins
92 that extend outwardly from tube outer surface 90. Each fin 92
includes an outer surface 94 that is configured to contact solid
CO.sub.2 56 to facilitate transferring heat from heat exchange
fluid 54 to solid CO.sub.2 56 to facilitate forming liquid CO.sub.2
58 from solid CO.sub.2 56, and to cool heat exchange fluid 54 to
recover a refrigeration value from solid CO.sub.2 56. Each fin 92
is oriented within cavity 78 such that solid CO.sub.2 56 is at
least partially supported by heat exchange tube 70 within housing
upper portion 80. Moreover, each fin 92 is oriented to channel
liquid CO.sub.2 58 formed within cavity 78 from upper portion 80 to
lower portion 82 such that liquid CO.sub.2 58 is collected within a
pool 96 formed within lower portion 82. In the exemplary
embodiment, each fin 92 is oriented substantially perpendicular to
centerline axis 85. In addition, each fin 92 is at least partially
submerged within liquid CO.sub.2 58 to facilitate transferring heat
from liquid CO.sub.2 58 to heat exchange fluid 54. In one
embodiment, heat exchange tube 70 includes a plurality of pipes 98
that are each coupled to one or more fins 92. Each pipe 98 is
oriented within cavity 78, and extends between first end 86 and
second end 88. One or more pipes 98 are at least partially
submerged within liquid CO.sub.2 58 to facilitate transferring heat
from liquid CO.sub.2 58 to heat exchange fluid 54.
[0025] During operation of system 10, combustor 22 receives a
predefined quantity of fuel from fuel supply system 24, and
receives a predefined quantity of air from air supply system 26.
Combustor 22 injects the fuel into the air flow, ignites the
fuel-air mixture to expand the fuel-air mixture through combustion,
and generates high temperature flue gases. Combustor 22 channels
flue gases 28 to HRSG 30 to facilitate generating steam from flue
gases 28. In addition, boiler feedwater assembly 32 channels a flow
of boiler feedwater 33 to HRSG 30. HRSG 30 transfers heat from flue
gases 28 to boiler feedwater 33 to facilitate heating boiler
feedwater 33 to generate steam 34. HRSG 30 discharges steam 34
towards steam turbine 36 wherein thermal energy in the steam is
converted to mechanical rotational energy. HRSG 30 and/or combustor
22 discharge flue gases 28 toward gas treatment system 42 to
facilitate treating carbon dioxide CO.sub.2 suspended within flue
gases 28.
[0026] In the exemplary embodiment, HRSG 30 and/or combustor 22
channel flue gases to pre-cooling system 44. Pre-cooling system 44
transfers heat from flue gases 28 to heat exchange fluid 54 to
reduce a temperature of flue gases 28. Pre-cooling system 44
discharges flue gases 28 towards cooling system 46 to facilitate
generating solid CO.sub.2 from gaseous CO.sub.2 suspended within
flue gases 28. In addition, pre-cooling system 44 channels heat
exchange fluid 54 towards heat exchange assembly 12. Cooling system
46 cools flue gases 28 to generate solid CO.sub.2 and channels
cooled flue gases 28 and solid CO.sub.2 56 to CO.sub.2 separator 48
to facilitate separating solid CO.sub.2 and N.sub.2 from flue gases
28. CO.sub.2 separator 48 discharges solid CO.sub.2 towards
lockhopper assembly 62. In addition, CO.sub.2 separator 48 channels
a flow of CO.sub.2 lean gas 100 that includes a mixture of CO.sub.2
and N.sub.2 to cooling system 46 and/or lockhopper assembly 62. In
one embodiment, CO.sub.2 lean gas 100 discharged from CO.sub.2
separator 48 is divided into a first sub-stream 102 and a second
sub-stream 104. First sub-stream 102 is discharged to atmosphere.
Second sub-stream 104 is compressed in a compressor 106 and
channeled to lockhopper assembly 62 at a predefined pressure to
facilitate adjusting a pressure within lockhopper assembly 62.
[0027] Lockhopper assembly 62 channels solid CO.sub.2 56 towards
heat exchanger 60 to transfer heat from solid CO.sub.2 56 to heat
exchange fluid 54 being channeled through heat exchanger 60. Solid
CO.sub.2 56 is gravity fed to heat exchanger 60 to transfer heat
from heat exchange fluid 54 to solid CO.sub.2 56 to convert at
least of portion of solid CO.sub.2 58 to liquid CO.sub.2 58, and to
cool heat exchange fluid 54 to recover a refrigeration value from
solid CO.sub.2 56. Heat exchanger 60 discharges liquid CO.sub.2 58
to CO.sub.2 utilization system 52. In addition, heat exchanger 60
channels heat exchange fluid 54 towards pre-cooling system 44 for
use in cooling flue gases 28.
[0028] In the exemplary embodiment lockhopper assembly 62 and heat
exchanger 60 each include an internal pressure equal to about 7 atm
to facilitate preventing re-sublimation of solid CO.sub.2 56 to
gaseous CO.sub.2 within cavity 78, and to maintain CO.sub.2 in
solid-liquid phase equilibrium. Lockhopper assembly 62 channels
solid CO.sub.2 56 having a temperature equal to about -102.degree.
C. towards heat exchanger 60. Heat exchange fluid 54 is channeled
into heat exchanger 60 includes a temperature equal to about
-51.degree. C. As solid CO.sub.2 56 contacts of heat exchange tube
70, at least a portion of solid CO.sub.2 56 is converted to liquid
CO.sub.2 58. Liquid CO.sub.2 58 discharged from heat exchanger 60
includes a fluid temperature equal to about -51.degree. C. Heat
exchange fluid 54 discharged from heat exchanger 60 includes a
fluid temperature equal to about -80.degree. C.
[0029] FIGS. 3-4 are schematic views of alternative embodiments of
heat exchange assembly 12. Identical components shown in FIGS. 3-4
are labeled with the same reference numbers used in FIG. 2. In an
alternative embodiment, heat exchange tube 70 extends between a
first section 108 and a second section 110. First section 108 is
oriented within lower portion 82 such that first section 108 is at
least partially submerged within liquid CO.sub.2 58. Second section
110 is oriented within upper portion 80, and is configured to
support solid CO.sub.2 56 such that solid CO.sub.2 56 is oriented
above liquid CO.sub.2 pool 96. Fins 92 are coupled to heat exchange
tube 70 and are oriented obliquely with respect to centerline axis
85 to facilitate channeling liquid CO.sub.2 58 from upper portion
80 to lower portion 82. One or more fins 92 are coupled to tube
first section 108, and are at least partially submerged within
liquid CO.sub.2 58.
[0030] Referring to FIG. 4, in another embodiment, each fin 92 is
coupled to second section 110 of heat exchange tube 70 such that
each fin 92 is oriented within upper portion 80. Each fin 92 is
oriented with respect to an adjacent fin 92 such that a plurality
of openings 112 are defined between adjacent fins 92. Each opening
112 is sized and shaped to channel liquid CO.sub.2 58 from upper
portion 80 to lower portion 82.
[0031] FIG. 5 is another embodiment of power generation system 10.
Identical components shown in FIG. 5 are labeled with the same
reference numbers used in FIG. 1. In an alternative embodiment,
heat exchanger 60 channels cold liquid CO.sub.2 58 to flue gas
pre-cooling system 44 for use in pre-cooling flue gases 28. More
specifically, liquid CO.sub.2 pump 84 channels liquid CO.sub.2 58
from heat exchanger 60 to flue gas pre-cooling system 44. In
addition, flue gas pre-cooling system 44 channels liquid CO.sub.2
58 to CO.sub.2 utilization system 52. In one embodiment, liquid
CO.sub.2 pump 84 is configured to channel liquid CO.sub.2 58
through flue gas pre-cooling system 44, and to CO.sub.2 utilization
system 52.
[0032] FIG. 6 is an alternative embodiment of power generation
system 10. Identical components shown in FIG. 6 are labeled with
the same reference numbers used in FIG. 1. In an alternative
embodiment, power generation system 10 includes a top cycle or gas
turbine engine assembly 114 and a bottom cycle or steam turbine
engine 20. Gas turbine engine assembly 114 includes a compressor
116, a combustor 118 downstream of compressor 116, and a turbine
120 downstream of combustor 118 and powered by gases discharged
from combustor 118. Turbine 120 drives an electrical generator 122.
In addition, turbine 120 discharges flue gases 28 to HRSG 30 for
generating steam from flue gases 28.
[0033] In the exemplary embodiment, heat exchanger 60 is coupled
downstream of pre-cooling system 44 for receiving a flow of flue
gases 28 from pre-cooling system 44. During operation HRSG 30
and/or turbine 120 discharge flue gases 28 to pre-cooling system 44
to transfer heat from flue gases 28 to liquid CO.sub.2 58.
Pre-cooling system 44 channels flue gases 28 to heat exchanger 60
to transfer heat from flue gases 28 to solid CO.sub.2 56 to form
liquid CO.sub.2 58 from solid CO.sub.2 56 to facilitate cooling
flue gases 28, and to recover a refrigeration value from solid
CO.sub.2 56. Heat exchanger 60 channels cooled flue gases 28 to
cooling system 46 to cool flue gases 28 to form solid CO.sub.2 from
gaseous CO.sub.2 suspended within flue gases 28. Cooling system 46
channels solid CO.sub.2 and flue gases 28 to CO.sub.2 separator 48
to separate solid CO.sub.2 from flue gases 28, and discharge solid
CO.sub.2 to lockhopper assembly 62. Lockhopper assembly 62
discharges solid CO.sub.2 56 to heat exchanger 60 to transfer heat
from solid CO.sub.2 56 to flue gases 28 being channeled through
heat exchanger 60, and to form liquid CO.sub.2 58 from solid
CO.sub.2 56. Heat exchanger 60 channels liquid CO.sub.2 58 to
pre-cooling system 44 to facilitate transferring heat from flue
gases 28 to liquid CO.sub.2 58. In addition, pre-cooling system 44
channels liquid CO.sub.2 58 to CO.sub.2 utilization system 52.
[0034] FIG. 7 is a flow chart of an exemplary method 200 that may
be used to treat CO.sub.2 that is generated during an operation of
power generation system 10. In the exemplary embodiment, method 200
includes channeling 202 solid CO.sub.2 from lockhopper assembly 62
to heat exchange assembly 12, and channeling 204 a flow of heat
exchange fluid 54 through heat exchange tube 70 to facilitate a
transfer of heat from solid CO.sub.2 to heat exchange fluid 54 to
form liquid CO.sub.2 from solid CO.sub.2, and to recover a
refrigeration value from solid CO.sub.2 and liquid CO.sub.2. Method
200 also includes adjusting 206 a pressure within housing 68 to
maintain a housing pressure within a predefined range of pressures
to prevent re-sublimation of solid CO.sub.2 to gaseous CO.sub.2.
Heat exchange fluid 54 is channeled 208 from heat exchange assembly
12 to pre-cooling system 44 to pre-cool flue gases 28. Liquid
CO.sub.2 is channeled 210 from heat exchange assembly 12 to a
CO.sub.2 utilization system 52 to facilitate utilization of rich
CO.sub.2.
[0035] The above-described systems and methods overcome at least
some disadvantages of known gas treatment systems by providing a
gas treatment system that includes a heat exchange assembly
configured to transfer heat from a heat exchange fluid to solid
CO.sub.2 to facilitate recovering a refrigeration value from solid
CO.sub.2. In addition, the gas treatment system includes a heat
exchange assembly that is configured to maintain CO.sub.2 in
solid-liquid phase equilibrium to enable the heat exchange assembly
to transfer heat from solid CO.sub.2 to a heat exchange fluid to
facilitate forming liquid CO.sub.2 for use in pre-cooling a flue
gas. By providing a gas treatment system that includes a heat
exchange assembly that recovers a refrigeration value from solid
CO.sub.2, the cost of treating CO.sub.2 suspended within a flue gas
is reduced as compared to known gas treatment systems.
[0036] Exemplary embodiments of systems and methods for treating
carbon dioxide are described above in detail. The systems and
methods are not limited to the specific embodiments described
herein, but rather, components of systems and/or steps of the
method may be utilized independently and separately from other
components and/or steps described herein. For example, the systems
and method may also be used in combination with other gas treatment
systems and methods, and are not limited to practice with only the
gas treatment system as described herein. Rather, the exemplary
embodiment can be implemented and utilized in connection with many
other gas treatment system applications.
[0037] Although specific features of various embodiments of the
invention may be shown in some drawings and not in others, this is
for convenience only. In accordance with the principles of the
invention, any feature of a drawing may be referenced and/or
claimed in combination with any feature of any other drawing.
[0038] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
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