U.S. patent application number 13/110322 was filed with the patent office on 2012-11-22 for liquid carbon dioxide refrigeration system.
Invention is credited to Kenneth L. Burgers, John M. Girard, Yeu-Chuan Simon Ho, Balazs Hunek, Bryce M. Rampersad, Jeffrey R. Wallace.
Application Number | 20120291480 13/110322 |
Document ID | / |
Family ID | 47173906 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120291480 |
Kind Code |
A1 |
Girard; John M. ; et
al. |
November 22, 2012 |
LIQUID CARBON DIOXIDE REFRIGERATION SYSTEM
Abstract
A liquid carbon dioxide refrigeration system is provided. The
refrigeration system may include a storage tank arranged for
storing liquid carbon dioxide, and a vessel arranged to separate
carbon dioxide into a vapor carbon dioxide portion and a liquid
carbon dioxide portion. A first conduit is coupled to the storage
tank and the first vessel such that liquid carbon dioxide can pass
from the storage tank to the first vessel. A second conduit is
coupled to the first vessel such that the liquid carbon dioxide
portion can pass into a refrigeration device, and a third conduit
is coupled to the first vessel and the first conduit to recycle the
vapor carbon dioxide portion back to the first conduit. The third
conduit may include a refrigeration package to compress and liquefy
the vapor carbon dioxide portion
Inventors: |
Girard; John M.; (Downers
Grove, IL) ; Wallace; Jeffrey R.; (Naperville,
IL) ; Rampersad; Bryce M.; (Bloomingdale, IL)
; Burgers; Kenneth L.; (East Amherst, NY) ; Ho;
Yeu-Chuan Simon; (Naperville, IL) ; Hunek;
Balazs; (Chicago, IL) |
Family ID: |
47173906 |
Appl. No.: |
13/110322 |
Filed: |
May 18, 2011 |
Current U.S.
Class: |
62/617 ; 62/430;
62/435 |
Current CPC
Class: |
F25B 19/005 20130101;
F25B 9/008 20130101 |
Class at
Publication: |
62/617 ; 62/430;
62/435 |
International
Class: |
F25J 3/00 20060101
F25J003/00; F25D 17/02 20060101 F25D017/02 |
Claims
1. A method of delivering liquid carbon dioxide to a refrigeration
device, the method comprising: releasing carbon dioxide from a
storage tank into a fluid conduit and toward a refrigeration
device; separating the carbon dioxide into a vapor carbon dioxide
portion and a liquid carbon dioxide portion; recycling the vapor
carbon dioxide portion into the fluid conduit; and introducing the
liquid carbon dioxide portion near its triple point into the
refrigeration device.
2. The method of claim 1, wherein the act of recycling the vapor
carbon dioxide portion into the fluid conduit includes a
refrigerating package for the vapor carbon dioxide portion.
3. The method of claim 1, wherein the act of separating the carbon
dioxide includes reducing the pressure of the carbon dioxide.
4. The method of claim 3, wherein the act of separating the carbon
dioxide includes introducing the carbon dioxide into a first
vessel, and wherein the pressure of the first vessel is maintained
below the pressure of the introduced carbon dioxide.
5. The method of claim 3, wherein the act of separating the carbon
dioxide includes introducing the carbon dioxide into a first
vessel, and wherein the pressure of the carbon dioxide is reduced
after the carbon dioxide is introduced into the first vessel.
6. The method of claim 1, wherein the carbon dioxide is released
into a primary fluid conduit extending between the storage tank and
the refrigeration device, and the act of separating the carbon
dioxide includes transferring the carbon dioxide into a secondary
flow circuit for additional conditioning.
7. The method of claim 1, wherein the act of introducing the liquid
carbon dioxide portion into the refrigeration device includes
pumping the liquid carbon dioxide portion into the refrigeration
device.
8. The method of claim 1, wherein the act of separating the carbon
dioxide includes introducing a first portion of the carbon dioxide
into a first vessel and introducing a second portion of the carbon
dioxide into two or more vessels.
9. A liquid carbon dioxide refrigeration system secondary flow
circuit configured to be coupled to a primary fluid conduit
extending between a carbon dioxide storage tank and a refrigeration
device configured to receive carbon dioxide from the storage tank,
the secondary flow circuit comprising: a first vessel constructed
and arranged to separate carbon dioxide into a vapor carbon dioxide
portion and a liquid carbon dioxide portion; a downstream conduit
coupled to the first vessel and constructed and arranged such that
the liquid carbon dioxide portion can pass either into the
refrigeration system or into the primary fluid conduit; a recycle
conduit coupled to the first vessel, the recycle conduit
constructed and arranged to recycle the vapor carbon dioxide
portion back to the primary fluid conduit; and wherein the recycle
conduit comprises a refrigeration package configured to compress
and liquefy vapor carbon dioxide portion.
10. The liquid carbon dioxide refrigeration system secondary flow
circuit of claim 9, further comprising: a second vessel constructed
and arranged to separate the carbon dioxide into a vapor carbon
dioxide portion and a liquid carbon dioxide portion, wherein the
secondary flow circuit is configured to cycle between separating
carbon dioxide in the first vessel and two or more vessels.
11. The liquid carbon dioxide refrigeration system secondary flow
circuit of claim 9, further comprising a pressure reducing element
positioned upstream of the first vessel and configured to lower the
pressure of the carbon dioxide.
12. The liquid carbon dioxide refrigeration system secondary flow
circuit of claim 9, wherein the downstream conduit comprises a
pump.
13. A liquid carbon dioxide refrigeration system comprising: a
storage tank constructed and arranged for storing liquid carbon
dioxide; a primary fluid conduit having a first end coupled to the
storage tank and a second end configured to be coupled to a
refrigeration device, wherein the primary fluid conduit is
configured to allow carbon dioxide to pass from the storage tank
and into the refrigeration device; a secondary flow circuit coupled
to the primary fluid conduit, the secondary flow circuit
comprising: a first vessel constructed and arranged to separate
carbon dioxide into a vapor carbon dioxide portion and a liquid
carbon dioxide portion; a secondary conduit coupled to the primary
fluid conduit and the first vessel, the secondary fluid conduit
constructed and arranged such that the carbon dioxide can pass from
the primary fluid conduit and into the first vessel; a downstream
conduit coupled to the first vessel and constructed and arranged
such that the liquid carbon dioxide portion can pass either into
the refrigeration system or into the primary fluid conduit; and a
recycle conduit coupled to the first vessel and the primary fluid
conduit, the recycle conduit constructed and arranged to recycle
the vapor carbon dioxide portion back to the primary fluid
conduit.
14. The liquid carbon dioxide refrigeration system of claim 13,
wherein the recycle conduit comprises a refrigeration package
configured to compress and liquefy the carbon dioxide vapor
portion.
15. The liquid carbon dioxide refrigeration system of claim 13
wherein the secondary fluid conduit is coupled to the primary fluid
conduit at a first location on the primary fluid conduit and the
recycle conduit is coupled to the primary fluid conduit at a second
location on the primary fluid conduit, wherein the second location
is upstream of the first location.
16. The liquid carbon dioxide refrigeration system of claim 13,
wherein the secondary flow circuit further comprises a second
vessel constructed and arranged to separate the carbon dioxide into
a vapor carbon dioxide portion and a liquid carbon dioxide portion,
and wherein the secondary flow circuit is configured to cycle
between separating carbon dioxide in the first vessel and in the
second vessel.
17. The liquid carbon dioxide refrigeration system of claim 16,
wherein the secondary flow circuit further comprises a conduit
coupling the first vessel to the second vessel and configured to
adjust the pressure between the first vessel and the second vessel.
Description
FIELD OF INVENTION
[0001] The present invention is directed to a liquid carbon dioxide
refrigeration system, and in particular to systems and methods for
delivering liquid carbon dioxide to a refrigeration device which
recycles carbon dioxide vapor back into the system reducing carbon
dioxide released to the atmosphere.
BACKGROUND OF INVENTION
[0002] Carbon dioxide (CO.sub.2) is conventionally used as a
refrigerant. For example, solid carbon dioxide (also known as "dry
ice") is routinely used for its cooling properties. Liquid carbon
dioxide is also a common refrigerant and has many applications, for
example, in the food chilling and freezing industry.
[0003] Carbon dioxide is commonly captured from suitable industrial
processes such as refinery and fermentation that would otherwise
release it directly to the atmosphere. The CO.sub.2 stream is
purified, liquefied and stored for use in other industrial
processes.
[0004] It is industry standard for liquid carbon dioxide to be
supplied in a tank or vessel. At room temperature and pressure,
carbon dioxide is in a gaseous state. To keep the carbon dioxide in
a substantially liquid state, the storage tanks are typically
maintained at a temperature between approximately -15.degree. F.
and approximately 0.degree. F. and at a pressure between
approximately 250 psia and approximately 300 psia. The carbon
dioxide may be stored in these tanks until needed.
[0005] As shown in FIG. 1, a conventional liquid carbon dioxide
refrigeration system includes a carbon dioxide storage tank 10
coupled to a refrigeration device 20 (such as a freezer) via a
fluid conduit 40. A first fluid conduit 42 delivers liquid carbon
dioxide into the refrigeration device where it is sprayed onto
items to be cooled. A second fluid conduit 44 may also be provided
to introduce vapor carbon dioxide from the storage tank and into
the refrigeration device. The carbon dioxide vapor may be used to
pressurize the line, to move the liquid carbon dioxide through the
fluid conduit, and/or to prevent the liquid carbon dioxide from
turning into a solid and freezing and/or clogging the fluid conduit
40. As the carbon dioxide passes through the refrigeration system
and provides refrigeration, the carbon dioxide converts into vapor
which is removed from the system via an exhaust 46.
[0006] One alternative to supplying CO2 to remote locations is
described by Tyree in U.S. Pat. No. 4,693,737. Tyree found that
providing sub-cooled liquid CO2 to the work stations resulted in
less CO2 being expended for a given cooling requirement. Tyree also
attempts to conserve CO2 vapor generated during the production of
the near triple point CO2 used to cool the storage cabinets. Tyree
describes returning the vapor to a solid CO2 bunker where it would
condense into a solid and could later be returned to the main
storage vessel by a compressor for reuse. While the present
invention takes advantage of the additional refrigeration available
from near triple point CO2, it provides a direct method of
re-liquefying the CO2 vapor generated during the sub-cooling
process through the use of an in-line compressor and heat
exchanger. While the invention described by Tyree could be used for
low refrigeration demand applications, the equipment needed for
large demand requirements would be prohibitively large and
expensive.
[0007] An alternative to recycle CO2 for large refrigeration
applications is described in U.S. Pat. No. 5,966,946 by Girard et
al. Girard describes a method of recapturing CO2 vapor generated in
a refrigeration enclosure. Girard ensures a suitably high CO2 vapor
concentration, compresses it and re-liquefies it for reuse in the
refrigeration enclosure. The present invention utilizes the
additional refrigeration capacity of sub-cooled CO2 and recycles
and re-liquefies generated vapor with a less complex process. The
less complicated process stems from the fact that the present
invention provides a closed loop vapor recycle process.
SUMMARY OF INVENTION
[0008] In one illustrative embodiment, a method of delivering
liquid carbon dioxide to a refrigeration device is provided. The
method includes releasing carbon dioxide from a storage tank into a
fluid conduit and toward a refrigeration device, separating the
carbon dioxide into a carbon dioxide vapor portion and a liquid
carbon dioxide portion, reliquefying and recycling the vapor carbon
dioxide portion into the supply fluid conduit or storage tank, and
introducing the separated liquid carbon dioxide portion into the
refrigeration device.
[0009] In another illustrative embodiment, a liquid carbon dioxide
refrigeration system provides a secondary flow circuit which is
configured to be coupled to a primary fluid conduit extending
between a carbon dioxide storage tank and a refrigeration device
configured to receive carbon dioxide from the storage tank. The
secondary flow circuit includes a first vessel constructed and
arranged to separate carbon dioxide into a vapor carbon dioxide
portion and a liquid carbon dioxide portion, and a downstream
conduit coupled to the first vessel and constructed and arranged
such that the liquid carbon dioxide portion can pass either into
the refrigeration system or into the primary fluid conduit. The
secondary flow route further includes a recycle conduit coupled to
the first vessel, the recycle conduit constructed and arranged to
recycle the vapor carbon dioxide portion back to the primary fluid
conduit; and the recycle conduit includes a refrigeration package
configured to compress and cool the vapor carbon dioxide
portion.
[0010] In yet another illustrative embodiment, a liquid carbon
dioxide refrigeration system is provided. The refrigeration system
includes a storage tank constructed and arranged for storing liquid
carbon dioxide, a first vessel constructed and arranged to separate
carbon dioxide into a vapor carbon dioxide portion and a liquid
carbon dioxide portion, and a first conduit coupled to the storage
tank and the first vessel and constructed and arranged such that
carbon dioxide can pass from the storage tank to the first vessel.
The system further includes a second conduit coupled to the first
vessel and constructed and arranged such that the liquid carbon
dioxide portion can pass into a refrigeration system, and a third
conduit coupled to the first vessel and the first conduit, the
third conduit constructed and arranged to recycle the carbon
dioxide vapor portion back to the first conduit, and wherein the
third conduit comprises a refrigeration package configured to
compress and liquefy the vapor carbon dioxide portion.
[0011] In a further illustrative embodiment, a liquid carbon
dioxide refrigeration system is provided. The refrigeration system
includes a storage tank constructed and arranged for storing liquid
carbon dioxide, and a primary fluid conduit having a first end
coupled to the storage tank and a second end configured to be
coupled to a refrigeration device, where the primary fluid conduit
is configured to allow carbon dioxide to pass from the storage tank
and into the refrigeration device. The refrigeration system further
includes a secondary flow circuit coupled to the primary fluid
conduit, the secondary flow circuit including a first vessel
constructed and arranged to separate carbon dioxide into a carbon
dioxide vapor portion and a liquid carbon dioxide portion, and a
secondary fluid conduit coupled to the primary fluid conduit and
the first vessel, the secondary fluid conduit constructed and
arranged such that the carbon dioxide can pass from the primary
fluid conduit and into the first vessel. The secondary fluid
circuit also includes a downstream conduit coupled to the first
vessel and constructed and arranged such that the liquid carbon
dioxide portion can pass either into the refrigeration system or
into the primary fluid conduit, and a recycle conduit coupled to
the first vessel and the primary fluid conduit, the recycle conduit
constructed and arranged to comprise a refrigeration package
configured to compress and liquefy the vapor carbon dioxide portion
to recycle the liquefied carbon dioxide portion back to the primary
fluid conduit.
[0012] Various embodiments of the present invention provide certain
advantages. Not all embodiments of the invention share the same
advantages and those that do may not share them under all
circumstances.
[0013] Further features and advantages of the present invention, as
well as the structure of various embodiments that incorporate
aspects of the invention are described in detail below with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0014] The foregoing and other objects and advantages of the
invention will be appreciated more fully from the following
drawings, wherein like reference characters designate like
features, in which:
[0015] FIG. 1 is a schematic diagram of a prior art liquid carbon
dioxide refrigeration system;
[0016] FIG. 2 is a schematic diagram of a liquid carbon dioxide
refrigeration system according to one embodiment of the present
invention;
[0017] FIG. 3 is a schematic diagram of a liquid carbon dioxide
refrigeration system according to another embodiment of the present
invention; and
[0018] FIG. 4 is a schematic diagram of a liquid carbon dioxide
refrigeration system according to yet another embodiment of the
present invention.
DETAILED DESCRIPTION
[0019] The cooling capacity of liquid carbon dioxide increases as
liquid carbon dioxide approaches its triple point (i.e. the
temperature and pressure at which a substance simultaneously exists
in a solid phase, a liquid phase and a gas phase). It is thus
desirable for liquid carbon dioxide to be near its triple point in
a refrigeration system, because when the temperature is near the
triple point, liquid carbon dioxide provides the greatest increase
in cooling capacity per unit mass.
[0020] In particular, in a refrigeration system, such as the one
illustrated in FIG. 1, once in the refrigeration device 20, the
liquid carbon dioxide expands to form a solid phase and a vapor
phase. On a mass basis, about half of the liquid carbon dioxide
converts to solid, the other half to vapor. Applicant recognized
that a majority of the refrigeration results from the solid phase
and minimal refrigeration occurs from the vapor phase. Applicant
further recognized that when the carbon dioxide is close to its
triple point, the percentage of the solid phase increases, thus
increasing the available refrigeration. Applicant also recognized
the difficulty in moving the near triple point liquid carbon
dioxide due to its tendency to flash from the liquid state directly
into the vapor and solid states due to pressure drops from valves
and piping and liquid head.
[0021] One aspect of the present invention is directed to a
refrigeration system that is able to recover a portion of the
carbon dioxide vapor and recycle it back into the system. It is
contemplated that this may improve the efficiency of a
refrigeration system and may, for example, increase the cooling
capacity for a carbon dioxide storage tank 10 on a mass basis. In
particular, the recycled vapor carbon dioxide recovered from the
system may be converted into liquid carbon dioxide which can be
used to cool the refrigeration device. As shown in FIG. 1, this
vapor carbon dioxide would otherwise not be used and would be
vented off to atmosphere via the exhaust 46. It is contemplated
that this increase in efficiency may decrease the total amount of
carbon dioxide consumption for a particular refrigeration device
20.
[0022] Another aspect of the present invention is directed to a
refrigeration system that is able to produce liquid carbon dioxide
near its triple point in an on-going process for immediate use in
the refrigeration device. As mentioned above, as carbon dioxide
approaches its triple point, the cooling capacity increases which
may improve the efficiency of the refrigeration system.
[0023] One or more of the above aspects of the present invention
may be achieved by separating the carbon dioxide into a vapor
carbon dioxide portion and a liquid carbon dioxide portion. The
liquid carbon dioxide portion may be near its triple point and can
pass on to the refrigeration system, and the vapor carbon dioxide
portion can be recycled back into the refrigeration system. As set
forth in greater detail below, the refrigeration system may include
a vessel 62 that is configured to separate carbon dioxide into a
vapor carbon dioxide portion and a liquid carbon dioxide portion.
As discussed below, the vessel 62 may be part of a secondary flow
circuit 60 which is configured to be coupled to the primary fluid
conduit 40 which extends between the carbon dioxide storage tank 10
and the refrigeration device 20. It should be appreciated that for
purposes herein, the phrase "liquid carbon dioxide" is used to
refer to carbon dioxide in which a majority of the mass and/or
volume of the carbon dioxide is in a liquid state. One of skill in
the art would recognize that some amount of vapor carbon dioxide
may exist in liquid carbon dioxide. A change in temperature and/or
pressure may cause the state or phase of the carbon dioxide to
change. For example, carbon dioxide which is approximately 100% in
a liquid state may exit the storage tank 10, and at a downstream
location in the conduit 40, vapor carbon dioxide may form in the
conduit. This may be caused by the pressure drop in the pipe and/or
may be caused by a heat gain. Likewise, the phrase "carbon dioxide
vapor" is used to refer to carbon dioxide in which a majority of
the mass and/or volume of the carbon dioxide is in a gaseous state.
One of skill in the art would recognize that some amount of liquid
carbon dioxide and/or solid carbon dioxide may exist in carbon
dioxide vapor under the proper circumstances. Furthermore, the
phrase "solid carbon dioxide" is used to refer to carbon dioxide in
which a majority of the mass and/or volume of the carbon dioxide is
in a solid state. One of skill in the art would recognize that some
amount of carbon dioxide vapor and/or liquid carbon dioxide may
exist in solid carbon dioxide.
[0024] When separating the carbon dioxide vapor portion from the
liquid carbon dioxide portion, the liquid carbon dioxide portion
may reach a temperature and a pressure approaching its triple
point. And, by removing some of the vapor from the carbon dioxide,
the cooling capacity of the carbon dioxide may increase. As
mentioned above, in a refrigeration system, such as the one
illustrated in FIG. 1, once in the refrigeration device 20, the
liquid carbon dioxide expands to form a solid phase and a vapor
phase. When using liquid carbon dioxide from a conventional carbon
dioxide storage tank at conventional storage conditions
(approximately 0.degree. F. and at a pressure of approximately 300
psia), once the liquid carbon dioxide enters the refrigeration
device 20, the carbon dioxide may expand into approximately 54%
vapor and approximately 46% solid carbon dioxide by mass. In
contrast, in one embodiment, after the carbon dioxide is separated
in first vessel 62, the liquid carbon dioxide portion may be at a
temperature and pressure such that it is closer to its triple point
such that once the liquid carbon dioxide enters the refrigeration
device 20, the carbon dioxide may expand into approximately 42%
vapor and approximately 58% solid carbon dioxide by mass. Turning
to FIG. 2, one embodiment of a refrigeration system 100 with a
first vessel 62 for separating carbon dioxide is illustrated.
Similar to the conventional refrigeration system shown in FIG. 1,
this system 100 includes a carbon dioxide storage tank 10 coupled
to a refrigeration device 20 (such as a freezer) via a primary
fluid conduit 40. The primary fluid conduit 40 includes a first
fluid conduit 42 for delivering liquid carbon dioxide into the
refrigeration device and a second fluid conduit 44 for introducing
vapor carbon dioxide into the refrigeration device. As mentioned
above, the vapor carbon dioxide may be used to pressurize the line,
to move the liquid carbon dioxide through the fluid conduit, and/or
to prevent the liquid carbon dioxide from turning into a solid and
freezing and/or clogging the fluid conduit 40 and/or the
refrigeration device.
[0025] In the embodiment of FIG. 2, the vessel 62 is part of a
secondary flow circuit 60 which branches off from the primary fluid
conduit 40. As illustrated, the secondary flow circuit 60 includes
a secondary fluid conduit 70 which is coupled to the primary fluid
conduit 40 and the first vessel 62 and is arranged such that the
carbon dioxide can pass from the primary fluid conduit 40 and into
the first vessel 62 to separate the carbon dioxide into a vapor
carbon dioxide portion and a liquid carbon dioxide portion. As
discussed below, in the vessel 62, the pressure of the carbon
dioxide may be decreased and the temperature of the carbon dioxide
may be decreased such that the carbon dioxide approaches its triple
point. It is also contemplated that such a change in temperature
and pressure may help to separate the vapor portion from the liquid
portion.
[0026] The secondary flow circuit 60 may also include a downstream
conduit 80 coupled to the first vessel 62 and arranged such that
the liquid carbon dioxide portion can pass into the refrigeration
system 20. It should be appreciated that the downstream conduit 80
may be configured such that the liquid carbon dioxide portion
passes to another conduit, such as the primary conduit 40 before
passing into the refrigeration system, as the invention is not so
limited. As illustrated, the secondary flow circuit 60 further
includes a recycle conduit 90 coupled to the first vessel 62 and
the primary fluid conduit 40 and arranged to recycle the vapor
carbon dioxide portion back to the primary fluid conduit 40 or the
storage vessel 10.
[0027] As illustrated, the secondary fluid conduit 70 may include a
pressure reducing element 72 which is configured to lower the
pressure of the carbon dioxide. It is contemplated that the
pressure of the carbon dioxide may be lowered to a point close to
its triple point. As mentioned above, the carbon dioxide may exit
the storage tank 10 having a pressure of approximately 300 psia. In
one embodiment, the pressure reducing element 72 lowers the
pressure of the carbon dioxide down to at least approximately 78-80
psia. It should be recognized that lowering the pressure of the
carbon dioxide removes energy from the carbon dioxide which may
help to facilitate the separation of the liquid carbon dioxide
portion from the vapor carbon dioxide portion. The pressure
reducing element 72 may be a valve or other pressure regulator
which would be readily apparent to one having ordinary skill in the
art.
[0028] As shown in FIG. 2, the recycle conduit 90 includes a
refrigeration package 92 downstream of the first vessel 62 which is
configured to compress and cool the vapor carbon dioxide portion.
As mentioned above, the pressure of the carbon dioxide may be
lowered, for example, down to approximately 80 psia before the
carbon dioxide is separated into a vapor portion and a liquid
portion. Thereafter, the refrigeration package 92 may compress the
vapor portion to increase its pressure before being introduced back
to the primary fluid conduit 40. Furthermore, the temperature of
the carbon dioxide may be decreased in the first vessel 62 during
separation. For example, in one embodiment, the carbon dioxide may
exit the storage tank 10 having a temperature of approximately
0.degree. F. The vessel 62 may be configured to lower the
temperature of the carbon dioxide down to approximately -67.degree.
F. to -68.degree. F. (the triple point temperature of carbon
dioxide is approximately -69.9.degree. F.). The refrigeration
package 92 may be configured to compress and liquefy the vapor
carbon dioxide portion before being introduced back to the primary
fluid conduit 40.
[0029] The secondary flow circuit 60 may be positioned such that
the recycled vapor portion of the carbon dioxide exits the vessel
62 and the refrigeration package 92 and flows back into the primary
fluid conduit 40. As shown, carbon dioxide may enter the secondary
flow circuit 60 through the secondary fluid conduit 70 which is
coupled to the primary fluid conduit 40 at a first location on the
primary fluid conduit. The recycled vapor portion of the carbon
dioxide may flow back into the primary fluid conduit 40 at a second
location on the primary fluid conduit 40 which is upstream from the
first location where primary fluid conduit 40 meets secondary fluid
conduit 70. Alternatively, the recycled vapor portion of the carbon
dioxide may flow directly to the storage vessel 10.
[0030] It is contemplated that the vessel 62 may be positioned
proximate the refrigeration device 20 such that once separated in
the vessel 62, the liquid portion of the carbon dioxide may pass
through the downstream conduit 80 and into the refrigeration device
20 due to gravity. For example, the vessel 62 may positioned on top
of or in an elevated position with respect to the refrigeration
device 20.
[0031] As illustrated, in another embodiment, the downstream
conduit 80 includes a pump 82. It should be appreciated that the
pump 82 may be used to drive the liquid portion of the carbon
dioxide into the refrigeration device 20. It should also be
appreciated that the pump 82 may assist in increasing the pressure
of the liquid carbon dioxide portion. For example, in one
embodiment, the pump 82 is configured to raise the pressure of the
liquid carbon dioxide, preferably to a range between 150 psia to
300 psia and most preferably between 200 psia to 250 psia. The pump
82 may be configured to turn the liquid carbon dioxide portion into
a subcooled liquid.
[0032] It should be appreciated that the secondary flow circuit 60
may be configured such that the loop components may be retrofitted
to an existing refrigeration system, such as the one shown in FIG.
1. It is also contemplated that the secondary flow circuit 60 may
be configured as part of a new refrigeration system, as the
invention is not so limited.
[0033] Turning now to FIG. 3, another embodiment of a refrigeration
system 200 is illustrated. This refrigeration system includes many
of the same components discussed above and shown in FIG. 2, and
thus like components are given like reference numbers. The system
200 disclosed in FIG. 3 includes a secondary flow circuit 66
configured to separate carbon dioxide into a vapor carbon dioxide
portion and a liquid carbon dioxide portion. This particular
embodiment includes a first vessel 62 and a second vessel 64, where
each vessel is configured to separate the carbon dioxide into a
vapor portion and a liquid portion. The refrigeration system 200
may be configured to cycle between separating carbon dioxide in the
first vessel 62 and separating carbon dioxide in the second vessel
64. It should be appreciated that the present invention further
contemplates three, four or more vessels 62, 64, as the invention
is not so limited. The refrigeration system 200 shown in FIG. 3 may
be configured to produce liquid carbon dioxide near its triple
point in an on-going process for immediate use in the refrigeration
device.
[0034] Liquid carbon dioxide may be introduced into the secondary
flow circuit 66 through the secondary fluid conduit 70 and as
shown, may pass into either the first vessel 62 or the second
vessel 64. The secondary fluid conduit 70 may include one or more
pressure reducing elements 72 which are configured to lower the
pressure of the carbon dioxide delivered to the vessels 62, 64. It
is also contemplated that one vessel may be filled with carbon
dioxide and thereafter, the pressure within that vessel 62, 64 may
be reduced to facilitate the separation of the vapor portion from
the liquid portion. It may take a period of time to fill,
depressurize, pressurize and/or evacuate a vessel 62. Thus, a
plurality of vessels 62, 64 may be provided so that a second vessel
64 may be separating carbon dioxide, and thus producing a liquid
portion of the carbon dioxide near the triple point condition to
introduce into the refrigeration device 20 while the first vessel
62 is being filled with carbon dioxide, depressurized, pressurized,
and/or evacuated. In one embodiment, the plurality of vessels 62,
64 are configured such that a substantially continuous stream of
liquid carbon dioxide near the triple point can flow into the
conduit 80 as the system cycles between the first vessel 62 and the
second vessel 64.
[0035] As shown, the first and second vessels 62, 64 may be coupled
to the second primary fluid conduit 44 such that vapor carbon
dioxide from the storage tank 10 may be introduced into the first
and second vessels 62, 64. It is contemplated that fluid conduit 44
may be used to adjust the pressure within the vessels 62, 64. For
example, fluid conduit 44 may be used to increase the pressure
within the vessels 62, 64 from approximately 80 psia to
approximately 300 psia resulting in a false head pressure to assist
fluid movement in conduit 80 into the refrigeration device 20. In
one embodiment, a conduit 68 couples the first vessel 62 to the
second vessel 64 via valve 30 and is configured to adjust the
pressure between the first and second vessels.
[0036] Once the carbon dioxide is separated in one of the vessels
62, 64, the liquid portion is introduced into the downstream
conduit 80 to pass into the refrigeration device 20. The vapor
portion that is removed from the vessel 62, 64 during the
separation process is introduced into the recycle conduit 90 to
recycle the vapor portion back into the primary conduit 40. As
discussed above, the recycle conduit 90 may include a refrigeration
package 92 downstream of the vessels 62, 64 and is configured to
compress and warm the vapor carbon dioxide portion before being
introduced back into the primary conduit 40.
[0037] Turning now to FIG. 4, another embodiment of a refrigeration
system 300 is disclosed. The refrigeration system 300 is similar to
the systems 100, 200 discussed above, except this system 300 does
not have a separate secondary flow circuit that branches out from
the primary conduit. This refrigeration system 300 has a liquid
carbon dioxide storage tank 10 and a refrigeration package 20
positioned downstream of the storage tank 10 and configured to
receive carbon dioxide from the tank. The system 300 further
includes a first vessel 62 arranged to separate carbon dioxide into
a vapor carbon dioxide portion and a liquid carbon dioxide portion.
A first conduit 40 (similar to primary conduit 40 discussed above)
is coupled to the storage tank 10 and the first vessel 62 such that
liquid carbon dioxide can pass from the storage tank and into the
first vessel 62. The first conduit 40 may include a pressure
reducing element 72 which is configured to lower the pressure of
the carbon dioxide. A downstream conduit 80 (similar to downstream
conduit 80 discussed above) is coupled to the first vessel 62 and
arranged such that the liquid carbon dioxide portion can pass into
a refrigeration system 20. A recycle conduit 90 (similar to recycle
conduit 90 discussed above) is coupled to the first vessel 62 and
the first conduit 40 and is arranged to recycle the vapor carbon
dioxide portion back to the first conduit 40. As shown, the recycle
conduit 90 may include a refrigeration package 92 configured to
compress and cool the vapor carbon dioxide portion before being
introduced back into the first conduit 40. The refrigeration system
300 shown in FIG. 4 may be configured to produce liquid carbon
dioxide near its triple point in real-time.
[0038] A method of delivering liquid carbon dioxide to a
refrigeration device in accordance with the present invention may
include one or more of the following acts of: releasing carbon
dioxide from a storage tank into a fluid conduit and toward a
refrigeration device, separating the carbon dioxide into a vapor
carbon dioxide portion and a liquid carbon dioxide portion,
recycling the vapor carbon dioxide portion into the fluid conduit,
and introducing the liquid carbon dioxide portion into the
refrigeration device.
[0039] For the purposes of simplifying the figures, some
lines/connections to the vessels and tanks that are routinely
provided in the carbon dioxide industry and more specifically in a
refrigeration system have been omitted, such as, but not limited to
fill or transfer lines, auxiliary liquid or vapor lines, surge
tanks, safety relief valves, filters, vents, purge valves, and
pressure gauges. System monitoring devices, controls and
programmers may be included if desired. Valves may, for example, be
electric or pneumatic, and may be either remotely controlled or
manually controlled, as the invention is not so limited.
[0040] It should be appreciated that various embodiments of the
present invention may be formed with one or more of the
above-described features. The above aspects and features of the
invention may be employed in any suitable combination as the
present invention is not limited in this respect. It should also be
appreciated that the drawings illustrate various components and
features which may be incorporated into various embodiments of the
present invention. For simplification, some of the drawings may
illustrate more than one optional feature or component. However,
the present invention is not limited to the specific embodiments
disclosed in the drawings. It should be recognized that the present
invention encompasses embodiments which may include only a portion
of the components illustrated in any one drawing figure, and/or may
also encompass embodiments combining components illustrated in
multiple different drawing figures.
[0041] It should be understood that the foregoing description of
various embodiments of the invention are intended merely to be
illustrative thereof and that other embodiments, modifications, and
equivalents of the invention are within the scope of the invention
recited in the claims appended hereto.
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