U.S. patent application number 11/150895 was filed with the patent office on 2005-12-15 for cryogenically producing oxygen-enriched liquid and/or gaseous oxygen from atmospheric air.
Invention is credited to Corey, John A..
Application Number | 20050274142 11/150895 |
Document ID | / |
Family ID | 35459088 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050274142 |
Kind Code |
A1 |
Corey, John A. |
December 15, 2005 |
Cryogenically producing oxygen-enriched liquid and/or gaseous
oxygen from atmospheric air
Abstract
A system and method are disclosed for the production of
oxygen-enriched liquid and purified gaseous oxygen from local
atmospheric air. In one embodiment, the system includes an air
mover for generating a local atmospheric air stream; a cryocooler
including a cooling element thermally coupled to a condensing
separator; a heat exchanger having a first path for receiving a
cold gaseous exhaust stream from the condensing separator and a
second path for chilling and removing readily-condensible
contaminants from the local atmospheric air stream to form a
purified gas mixture stream via heat transfer to the cold gaseous
exhaust stream; and a receiver for the oxygen-enriched liquid that
condenses from the purified gas mixture stream in the condensing
separator, leaving the gaseous exhaust stream.
Inventors: |
Corey, John A.; (Melrose,
NY) |
Correspondence
Address: |
HOFFMAN WARNICK & D'ALESSANDRO, LLC
75 STATE STREET
14TH FL
ALBANY
NY
12207
US
|
Family ID: |
35459088 |
Appl. No.: |
11/150895 |
Filed: |
June 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60579276 |
Jun 14, 2004 |
|
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|
Current U.S.
Class: |
62/643 ;
62/615 |
Current CPC
Class: |
F25J 3/04278 20130101;
F25J 2215/50 20130101; F25J 2290/62 20130101; F25J 3/04981
20130101; F25J 2205/24 20130101; F25J 2270/90 20130101 |
Class at
Publication: |
062/643 ;
062/615 |
International
Class: |
F25J 001/00; F25J
003/00 |
Claims
What is claimed is:
1. A system for producing an oxygen-enriched liquid from local
atmospheric air, the system comprising: an air mover for generating
a local atmospheric air stream; a cryocooler including a cooling
element thermally coupled to a condensing separator; a heat
exchanger having a first path for receiving a cold gaseous exhaust
stream from the condensing separator and a second path for chilling
and removing readily-condensible contaminants from the local
atmospheric air stream to form a purified gas mixture stream via
heat transfer to the cold gaseous exhaust stream; and a receiver
for the oxygen-enriched liquid that condenses from the purified gas
mixture stream in the condensing separator, leaving the gaseous
exhaust stream.
2. The system of claim 1, wherein the heat exchanger further
includes a third path for transferring heat to the oxygen-enriched
liquid to transform at least a part of the oxygen-enriched liquid
into purified gaseous oxygen.
3. The system of claim 2, further comprising a selector valve for
controlling dispensing of the oxygen-enriched liquid and the
purified gaseous oxygen.
4. The system of claim 2, further comprising a humidifier for
adding moisture to the purified gaseous oxygen.
5. The system of claim 1, further comprising a system controller
for controlling the air mover, the heat exchanger, the cryocooler
and a reversing valve.
6. The system of claim 5, wherein the system controller adjusts
output based on a status of the receiver.
7. The system of claim 1, further comprising a reversing valve for
directing the local atmospheric air through the first path and the
exhaust stream through the second path.
8. The system of claim 1, wherein the cryocooler is selected from
the group consisting of: a Stirling type and an orifice pulse tube
type.
9. The system of claim 1, wherein an output of the system is less
than approximately 10 liquid liters per day.
10. The system of claim 1, wherein the system operates on one of
approximately 110 V and 220 V electricity.
11. The system of claim 1, wherein the system is portable by an
individual person.
12. The system of claim 1, wherein an output of the system includes
a coupling adapted to interface with at least one of standard
medical oxygen storage and standard oxygen dispensing
equipment.
13. The system of claim 1, wherein the receiver includes an
insulated dewar for storing the oxygen-enriched liquid.
14. The system of claim 1, wherein the heat exchanger is oriented
to enable gravity assist.
15. The system of claim 1, further comprising an auxiliary
defroster.
16. A system for selectively isolating a liquid purified component
of a gaseous mixture, the system comprising: a flow generator for
generating a gas mixture stream; a cryocooler including a cooling
element extending into a condensing separator; a heat exchanger
having a first path for receiving a cold exhaust stream from the
condensing separator and a second path for chilling and removing
contaminants from the gas mixture stream to form a purified cold
gas mixture stream via heat transfer to the cold exhaust stream;
and wherein the cooling element condenses the liquid purified
component from the purified cold gas mixture stream, leaving the
cold gaseous exhaust stream, which exits through the first path of
the heat exchanger.
17. The system of claim 16, wherein the heat exchanger further
includes a third path for transferring heat to the liquid purified
component to transform the liquid purified component into another
gaseous mixture.
18. The system of claim 16, further comprising an insulated dewar
for storing the liquid purified component and a system controller
for adjusting output based on a status of the insulated dewar.
19. A method for producing oxygen-enriched liquid from local
atmospheric air, the method comprising the steps of: forming an
input stream of the local atmospheric air; using cold exhaust from
a closed-cycle cryogenic cooler to remove readily-condensible
contaminants from the input stream to form a purified gas stream;
and cryogenically cooling the purified gas stream with a
closed-cycle refrigerator to condense oxygen to form the
oxygen-enriched liquid.
20. The method of claim 19, further comprising forming gaseous
oxygen from the oxygen-enriched liquid by using heat from the input
stream to warm a portion of the oxygen-enriched liquid.
21. A system for producing purified gaseous oxygen from local
atmospheric air, the system comprising: an air mover for generating
a local atmospheric air stream; a cryocooler including a cooling
element thermally coupled to a condensing separator; a heat
exchanger having a first path for receiving a cold gaseous exhaust
stream from the condensing separator, a second path for chilling
and removing readily-condensible contaminants from the local
atmospheric air stream to form a purified gas mixture stream via
heat transfer to the cold gaseous exhaust stream, and a third path
for transferring heat to an oxygen-enriched liquid that condenses
from the purified gas mixture stream in the condensing separator to
transform the oxygen-enriched liquid into the purified gaseous
oxygen.
22. The system of claim 21, further comprising a receiver for the
oxygen-enriched liquid that condenses from the purified gas mixture
stream in the condensing separator, leaving the gaseous exhaust
stream.
23. The system of claim 22, further comprising a selector valve for
controlling dispensing of the oxygen-enriched liquid and the
purified gaseous oxygen.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/579,276, filed Jun. 14, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates to cryogenic gas separation, and more
particularly, to a system and method for cryogenically producing
oxygen-enriched liquid and/or purified gaseous oxygen from
atmospheric air, on demand, at or near the point of use.
[0004] 2. Related Art
[0005] A growing number of aging persons require oxygen therapy,
typically in the range of 1-5 liters per minute of purified oxygen
introduced to their breathing air to compensate for reduced lung
capacity. Many of these people remain mobile and moderately active
for many months or years while requiring such therapy. Presently,
most of these people are served in their homes by use of an oxygen
concentrator, which pressurizes the air and preferentially passes
oxygen through a separator (e.g., membrane or pressure-swing
absorber), delivering purities in the 90-98% range. In case of
power loss, such patients also keep a large pressurized oxygen
cylinder on hand. For mobile patients, smaller pressure cylinders
are typically used to supply oxygen gas. These bulky, heavy tanks
must be pulled by the individual on wheeled carts, which is a
difficult and awkward process, especially for elderly people with
breathing difficulties.
[0006] An alternate approach for supporting mobile oxygen users
exists, using unpressurized liquid oxygen (LOX) in small
(sub-liter) lightweight portable dewars that are easily carried in
belt or backpack. Liquid oxygen is almost 1000 times the density of
its atmospheric gaseous equivalent, so the required volume is 5
times smaller than even high-pressure gas (typically at 3000 psi).
In addition, LOX eliminates the need for heavy pressurized
containment. Present LOX therapy is achieved only at much higher
cost than typical gaseous oxygen therapies. LOX therapy is also
unavailable to many people, insured or not, because such treatment
requires the regular, periodic delivery of large, insulated dewar
tanks of LOX to the patients home, solely to allow refilling of the
lightweight mobile supply. Accordingly, a concentrator is still
used for stationary support because the cost of delivered LOX is
too high for stationary use. In this case, only the very
inexpensive larger pressure cylinder for back-up supply is avoided.
There is also a safety concern with storage of large amounts of
LOX, a powerful oxidizer (fire accelerant). Consequently, LOX
therapy today is restricted to a minority of relatively wealthy
individuals even though many more would benefit by its advantages
in comfort and effectiveness if a cost-effective means to provide
it can be developed.
[0007] In one approach, LOX generation is provided in homes by
combining a cryocooler (a closed-cycle cryogenic refrigeration
device) with a standard concentrator. One example of this approach
is disclosed in U.S. Pat. Nos. 5,803,275 and 6,212,904. A
disadvantage of this approach, however, is that a standard
concentrator is still required, which adds complexity and cost.
[0008] There are also many standard air separation plants in
existence, the basic principles of cryogenic air separation having
been established in the early 20.sup.th century. See for example,
Universal Industrial Gases, Inc., "General Process
Description-Cryogenic Air Separation," from their website, June
2004. However, these plants are vastly too large because they
necessarily employ industrial-scale structure that is impractical
for home production of oxygen-enriched liquid in individual-use
quantities. For example, standard plant-size systems use cracking
towers that are many feet tall and process many tons of product per
day or hour. In addition, older large mass production plants use
reversing heat exchangers, but always require pre-separation of
water vapor (H.sub.2O) and carbon dioxide (CO.sub.2) to delay the
requirement for reversing with the required high internal volume
and consequent reversing losses. Furthermore, efficiency is
considered tantamount to these systems, which necessitates many
features that add costs to the systems, making them impractical for
a mass market.
[0009] In view of the foregoing, there is a need in the art for an
improved solution for efficiently producing oxygen-enriched liquid
and/or purified gaseous oxygen from local atmospheric air.
SUMMARY OF THE INVENTION
[0010] A system and method are disclosed for the production of
oxygen-enriched liquid and purified gaseous oxygen from local
atmospheric air. In one embodiment, the system includes an air
mover for generating a local atmospheric air stream; a cryocooler
including a cooling element thermally coupled to a condensing
separator; a heat exchanger having a first path for receiving a
cold gaseous exhaust stream from the condensing separator and a
second path for chilling and removing readily-condensible
contaminants from the local atmospheric air stream to form a
purified gas mixture stream via heat transfer to the cold gaseous
exhaust stream; and a receiver for the oxygen-enriched liquid that
condenses from the purified gas mixture stream in the condensing
separator, leaving the gaseous exhaust stream.
[0011] A first aspect of the invention is directed to a system for
producing an oxygen-enriched liquid from local atmospheric air, the
system comprising: an air mover for generating a local atmospheric
air stream; a cryocooler including a cooling element thermally
coupled to a condensing separator; a heat exchanger having a first
path for receiving a cold gaseous exhaust stream from the
condensing separator and a second path for chilling and removing
readily-condensible contaminants from the local atmospheric air
stream to form a purified gas mixture stream via heat transfer to
the cold gaseous exhaust stream; and a receiver for the
oxygen-enriched liquid that condenses from the purified gas mixture
stream in the condensing separator, leaving the gaseous exhaust
stream.
[0012] A second aspect of the invention includes a system for
selectively isolating a liquid purified component of a gaseous
mixture, the system comprising: a flow generator for generating a
gas mixture stream; a cryocooler including a cooling element
extending into a condensing separator; a heat exchanger having a
first path for receiving a cold exhaust stream from the condensing
separator and a second path for chilling and removing contaminants
from the gas mixture stream to form a purified cold gas mixture
stream via heat transfer to the cold exhaust stream; and wherein
the cooling element condenses the liquid purified component from
the purified cold gas mixture stream, leaving the cold gaseous
exhaust stream, which exits through the first path of the heat
exchanger.
[0013] A third aspect of the invention relates to a method for
producing oxygen-enriched liquid from local atmospheric air, the
method comprising the steps of: forming an input stream of the
local atmospheric air; using cold exhaust from a closed-cycle
cryogenic cooler to remove readily-condensible contaminants from
the input stream to form a purified gas stream; and cryogenically
cooling the purified gas stream with a closed-cycle refrigerator to
condense oxygen to form the oxygen-enriched liquid.
[0014] A fourth aspect of the invention is directed to a system for
producing purified gaseous oxygen from local atmospheric air, the
system comprising: an air mover for generating a local atmospheric
air stream; a cryocooler including a cooling element thermally
coupled to a condensing separator; a heat exchanger having a first
path for receiving a cold gaseous exhaust stream from the
condensing separator, a second path for chilling and removing
readily-condensible contaminants from the local atmospheric air
stream to form a purified gas mixture stream via heat transfer to
the cold gaseous exhaust stream, and a third path for transferring
heat to an oxygen-enriched liquid that condenses from the purified
gas mixture stream in the condensing separator to transform the
oxygen-enriched liquid into the purified gaseous oxygen.
[0015] The foregoing and other features of the invention will be
apparent from the following more particular description of
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The embodiments of this invention will be described in
detail, with reference to the following figures, wherein like
designations denote like elements, and wherein:
[0017] FIG. 1 shows one embodiment of a system for producing
oxygen-enriched liquid and/or purified gaseous oxygen from local
atmospheric air according to the invention.
DETAILED DESCRIPTION
[0018] With reference to the accompanying drawings, the present
invention includes a miniature oxygen separation and liquefaction
system and method, intended for providing oxygen-enriched liquid
and/or purified gaseous oxygen for both stationary and mobile
patients (or for any other purpose requiring small amounts of
oxygen-enriched liquid or purified gaseous oxygen on demand and
on-site).
[0019] FIG. 1 shows one embodiment of a system 8 for selectively
isolating a liquid purified component of a gaseous mixture
according to the invention. In accordance with the invention, in
one preferred embodiment, system 8 is especially advantageous for
producing an oxygen-enriched liquid 10 from local atmospheric air.
System 8 includes an air mover 12 (or flow generator) for
generating a local atmospheric air stream 14. It should be
recognized that the position of air mover 12 may be changed, e.g.,
to the exhaust side to draw rather than push the flow. Air stream
14 enters a heat exchanger 20 having a first path 22 for receiving
a cold exhaust stream 24 from a condensing separator 40 and a
second path 26 for receiving air stream 14 and for removing
readily-condensible contaminants by condensation, freezing, and
(de)sublimation to form a purified gas (mixture) stream 46 from air
stream 14. Condensation, etc., occurs in second path 26 via heat
transfer to cold exhaust stream 24 in first path 22. As will be
described below, readily-condensible contaminants may include, for
example, carbon dioxide (CO.sub.2) and water (H.sub.2O). Heat
exchanger 20 may be oriented to enable gravity assist, if desired
(e.g., slanted or vertical). Once cold exhaust stream 24 passes
through heat exchanger 20, it may be released to the atmosphere as
exhaust 30. Alternatively, exhaust 30 may be re-routed to a
cryocooler 50, described below, for its heat rejection purposes
(not shown). Conversely, air stream 14 may be drawn over the cooler
rejection surfaces of cryocooler 50 prior to entering heat
exchanger 20, thereby increasing the temperature difference between
exchanger 20 paths to allow a smaller exchanger and lower cost.
[0020] Purified gas stream 46 enters condensing separator 40.
System 8 also includes a cryocooler 50 that includes a cooling
element 52 that extends into condensing separator 40. Cryocooler 50
can be, for example, of the Stirling type or an orifice pulse tube
type. However, cryocooler 50 preferably includes a sealed,
closed-cycle and maintenance-free cryogenic cooler so that it is
practical for the preferred application, i.e., on-site oxygen
generation without skilled operators. "Closed-cycle" means that the
cryocooler contains a separate working fluid and does not use
expansion of the process fluid itself (here, air or its purified
derivatives) as a cooling medium to enable cryogenic separation of
that process fluid, which would necessitate provisions for
power-consuming compression before condensation, distillation and
rectification. In addition, the lack of a high pressure requirement
on the process fluid makes use of a reversing valve 92 possible, as
will be described in more detail below. This situation is in
contrast to conventional larger scale devices that use large-scale
motors, e.g., using a 1000 HP or more, to spin compound
turbo-compressors and expanders that are entirely inappropriate and
impossible to scale down to the sizes of interest of the preferred
application. Even known larger, on-site liquefier products use
mechanical (kinematic) Stirling machines or Gifford-McMahon
refrigerators that are incompatible with the low-maintenance and
small-scale requirements of home use liquid oxygen production. To
this end, cryocooler 50 may be, for example, of the type available
from Clever Fellows Innovation Consortium, Inc. (CFIC) of Troy,
N.Y., which are smaller, sealed, closed-cycle cryocoolers that have
no regular maintenance requirement over a multi-year service
life.
[0021] When purified gas stream 46 encounters cooling element 52,
oxygen (O.sub.2) preferentially condenses (at approximately 84K.)
in condensing separator 40 from purified gas stream 46 into
oxygen-enriched liquid 10, leaving cold exhaust stream 24. A
receiver 60, preferably in the form of an insulated dewar, may be
provided to store oxygen-enriched liquid 10 collected from
condensing separator 40. A second, portable dewar (not shown) may
also be provided with system 8, rather than just an oxygen-enriched
liquid tap 84 from receiver 60.
[0022] As also shown in FIG. 1, in an alternative embodiment, heat
exchanger 20 may further include a third path 28 for transferring
heat to oxygen-enriched liquid 10 (drawn from receiver 60) to
transform oxygen-enriched liquid 10 into a purified gaseous oxygen
70 for immediate breathing by a user. A selector valve 80 may be
provided for controlling dispensing of oxygen-enriched liquid 10
and/or purified gaseous oxygen 70. However, where oxygen-enriched
liquid 10 is the only desired product, this structure can be
omitted. Conversely, where only purified gaseous oxygen 70 is
required (e.g. for welding), receiver 60 may be omitted from system
8, retaining only a small condensing chamber to separate
oxygen-enriched liquid 10 from other gases before re-vaporizing it
in third path 28 of heat exchanger 20. In another alternative
embodiment, a humidifier 82 may be provided for adding moisture to
purified gaseous oxygen 70. In addition, an output of system 8 may
also include a coupling 84 adapted to interface with a standard
medical oxygen storage and/or standard oxygen dispensing
equipment.
[0023] A system controller 90 may also be provided for controlling
air mover 12, heat exchanger 20, cryocooler 50 and a reversing
valve 92 (discussed below). In one embodiment, system controller 90
adjusts output based on a status of receiver 60. For example,
system controller 90 may reduce or stop output if receiver 60 is
substantially full. System controller 90 may also control air
stream 14 flow rate relative to the available cooling capacity and
operating temperatures, to minimize the mass of air that is cooled
and re-heated.
[0024] System 8 may also include a reversing valve 92 for reversing
a flow direction. That is, periodically switching the flow
direction such that local atmospheric air 14 passes through first
path 22 and exhaust stream 24 passes through second path 26, which
may be advantageous periodically to remove build up within system 8
when connected as shown. In particular, because of the freezing of
moisture and some trace compounds like carbon dioxide (CO.sub.2),
the pressure drop or flow rate may be monitored by system
controller 90. When the frozen accumulation has diminished the flow
to some predetermined level, reversing valve 92 is switched to the
alternate position, reversing the flow of air stream 14 and exhaust
30. Exhaust 30 then becomes a re-vaporizing stream that carries
away the frozen materials. In this way, the frozen accumulation is
never excessive and is managed without costly air separators or
concentrators that pre-purify the gas stream before cooling.
[0025] In an alternative embodiment, materials captured from the
clean out process can be captured as liquids and combined with the
dry purified gaseous oxygen 70 to humidify that stream for more
comfortable breathing support, e.g., via humidifier 82. Although
shown separately, reversing valve 92 may be integrated with heat
exchanger 20, for example, by making a rotary heat exchanger 20
that slowly turns against an inlet manifold (partly connected to
inlet and partly to exhaust on one end) to bring each of many paths
sequentially into contact with the inlet and exhaust on one end,
and always in connection with condensing separator 40 on the other
end. An auxiliary defroster 94 may also be provided, if desired, to
assist in cleaning. The position of auxiliary defroster 94 may vary
from that shown.
[0026] Turning to further alternative embodiments of the invention,
condensing separator 40 can include various elements of known
separation means, including but not limited to, distillation
columns, rectifiers, vapor-liquid contact surfaces, and other like
means of enhancing the preferential condensation-based separation
of a component fluid, like oxygen from an air-based mixture.
Further, it is within the scope of the invention to conjoin the
functions of heat exchanger 20 and condensing separator 40 such
that an un-separated liquid exits heat exchanger 20 into condensing
separator 40, which may cooperate with receiver 60, cryocooler 50
and such known elements, to provide a distillation column for the
un-separated liquid. In addition, as known by those with skill in
the art of cryocooler-liquefiers, the pre-cooling heat exchanger 20
may be positioned in parallel with and in thermal contact with the
cryocooler cold element 52, thereby sharing thermal gradients with
common structure and insulation and thereby achieving
correspondingly higher efficiency.
[0027] Turning more specifically to the operation of system 8, air
mover 10 provides a continuous fresh local atmospheric air stream
14. Local atmospheric air may include, for example, nitrogen
(N.sub.2), oxygen (O.sub.2), and traces of argon (Ar), water vapor
(H.sub.2O), carbon dioxide (CO.sub.2) and other minor elements.
Local atmospheric air stream 14 is directed into second path 26 of
heat exchanger 20, where it gives up heat to first path 22 (and
possibly third path 28), which contains cold exhaust stream 24
(third path 28 would include cool gaseous oxygen 70 forming from
oxygen-enriched liquid 10). As air stream 14 loses heat in second
path 26, its temperature drops. Some of the air stream's components
(particularly water (H.sub.2O) and carbon dioxide (CO.sub.2)) are
condensed or frozen out of the stream early during the cooling
process because their temperatures of phase-change are
significantly higher than those of the main components, i.e.,
nitrogen (N.sub.2), oxygen (O.sub.2) and argon (Ar). Typical trace
pollutants like carbon monoxide (CO), hydrocarbons (e.g.,
CH.sub.4), and other more complex compounds also are readily
condensible. Normal condensation temperatures for the major
constituents of air and their fraction in a standard atmosphere
are: water (H.sub.2O) at 273K.: 0.1 to 2.8%; carbon dioxide
(CO.sub.2) at 195K.: 0.035% (CO.sub.2 directly freezes and
sublimes, no liquid phase at atmospheric pressure); oxygen
(O.sub.2) at 90.2K.: 20.95%; argon (Ar) at 87.3K.: 0.93%; and
nitrogen (N.sub.2) at 77.4K.: 78.1%. The remaining cooled gases
(i.e., nitrogen (N.sub.2), oxygen (O.sub.2) and argon (Ar) and
traces) form purified gas stream 46, which passes into condensing
separator 40 (and receiver 60), where they are exposed to cooling
element 52 maintained in the range of approximately 80-90 K. by
cryocooler 50. The heat extracted from purified gas stream 46 by
heat transfer to cooling element 52 preferentially condenses oxygen
(O.sub.2) and argon (Ar) (and a fraction of nitrogen (N.sub.2) in
solution), forming oxygen-enriched liquid 10. Uncondensed nitrogen
(N.sub.2) (with traces of oxygen (O.sub.2), argon (Ar) and other
minor constituents) exits condensing separator 40 and reenters
first path 22 of heat exchanger 20 as cool exhaust stream 24, where
it absorbs heat from air stream 14 in second path 26, then passes
through selector valve 92 and exits as exhaust 30. The liquid,
oxygen-enriched condensate 10 is partially accumulated in receiver
60 and partially directed through third path 28 of heat exchanger
20 (when provided), exiting, as needed, as purified gaseous oxygen
70 for consumption. Oxygen-enriched liquid 10 is stored until
needed (as for mobile patient support), when it can be drawn off as
a liquid for use in that form.
[0028] As the warmer condensates in heat exchanger 20 accumulate
from continuing flow of incoming air, the pressure required to
maintain flow will rise. This, or the reduction of flow at fixed
pressure, or even passage of a preset interval of time, can be used
by system controller 90 to switch reversing valve 92 to its
alternate position, reversing connections of first path 22 and
second path 26, respectively, between inlet air 14 and exhaust 30.
That reversal enables the re-entrainment of warmer condensates,
maintaining open paths and free air flow through heat exchanger 20,
as described above.
[0029] The invention also includes a method for producing
oxygen-enriched liquid 10 from local atmospheric air. The method
includes forming an input stream 14 of local atmospheric air; using
cold exhaust 24 from a closed-cycle cryogenic cooler 50 to remove
readily-condensible contaminants from input stream 14 to form a
purified gas stream 46; and cryogenically cooling purified gas
stream 46 with a closed-cycle refrigerator to condense oxygen to
form oxygen-enriched liquid 10. A purified gaseous oxygen 70 may be
formed from oxygen-enriched liquid 10 by using heat from input
stream 14 to warm a portion of oxygen-enriched liquid 10, e.g., via
third path 28.
[0030] System 8 provides a number of advantages compared to the
prior art. For example, system 8 can be implemented on a much
smaller scale. For example, depending on size, an output of system
8 may be less than approximately 10 liquid liters per day. System 8
preferably operates using approximately 110 V electricity, i.e., US
household electricity, or 220 V, i.e., European and Japanese
household electricity, and is portable by an individual person.
System 8 also removes the need for pre-separation of
readily-condensible contaminants, including water vapor (H.sub.2O)
and carbon dioxide (CO.sub.2), before cooling by using heat
exchanger 20 as a purifier. That is, pre-separation by non-cooling
means is not required. Also, no concentrator or other source of
previously-separated gas feed stream is required. In addition,
oxygen-enriched liquid 10 capacity of receiver 60 can be sized to
assure continuous oxygen support through a power outage of any
duration. System 8 is particularly useful for cost-effective
on-site treatment of emphysema and other disorders requiring
continual administration of oxygen, and especially for mobile
patients who can receive the gaseous product directly when resting,
and use oxygen-enriched liquid 10 as a portable source of gaseous
oxygen when mobile. As a result, system 8 provides lower cost
oxygen-enriched liquid therapy that can benefit a large number of
users that now must use less satisfactory, but cheaper treatments.
In particular, insurance-dependent users (notably Medicare
subscribers in the US) can receive the preferred treatment while
reducing health care cost to insurers. System 8 makes no attempt to
separate the argon (Ar) from the oxygen (O.sub.2) because the argon
is too little to resell and does no harm as a small impurity in the
oxygen for most applications.
[0031] While this invention has been described in conjunction with
the specific embodiments outlined above, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, the embodiments of the
invention as set forth above are intended to be illustrative, not
limiting. Various changes may be made without departing from the
spirit and scope of the invention as defined in the following
claims. For example, system 8 may be used to purify other species
from other mixtures than air such as isolating butane from a
mixture of hydrocarbons in natural gas. In this case, a similar
sequential condensation with reversing flow-re-entrainment for
warmer condensates, and an isolated collection chamber and outlet
stream for the desired pure condensate would be used.
* * * * *