U.S. patent application number 10/358411 was filed with the patent office on 2003-10-23 for life support oxygen concentrator.
This patent application is currently assigned to QuestAir Technologies Inc.. Invention is credited to Keefer, Bowie G., McLean, Christopher.
Application Number | 20030196550 10/358411 |
Document ID | / |
Family ID | 4164843 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030196550 |
Kind Code |
A1 |
Keefer, Bowie G. ; et
al. |
October 23, 2003 |
Life support oxygen concentrator
Abstract
Gas separation by pressure swing adsorption (PSA) and vacuum
pressure swing adsorption (VPSA), to obtain a purified product gas
of the less strongly adsorbed fraction of the feed gas mixture, is
performed with an apparatus having a plurality of adsorbers. The
adsorbers cooperate with first and second valve means in a rotary
PSA module, with the PSA cycle characterized by multiple
intermediate pressure levels between the higher and lower pressures
of the PSA cycle. Gas flows enter or exit the PSA module at the
intermediate pressure levels as well as the higher and lower
pressure levels, under substantially steady conditions of flow and
pressure. The PSA module comprises a rotor containing laminated
sheet adsorbers and rotating within a stator, with ported valve
faces between the rotor and stator to control the timing of the
flows entering or exiting the adsorbers in the rotor. Feed gas is
compressed prior to entry to the first valve means. Exhaust is
passed either directly or through a vacuum pump to the
atmosphere.
Inventors: |
Keefer, Bowie G.;
(Vancouver, CA) ; McLean, Christopher; (Vancouver,
CA) |
Correspondence
Address: |
KLARQUIST SPARKMAN, LLP
121 SW SALMON STREET
SUITE 1600
PORTLAND
OR
97204
US
|
Assignee: |
QuestAir Technologies Inc.
|
Family ID: |
4164843 |
Appl. No.: |
10/358411 |
Filed: |
February 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10358411 |
Feb 4, 2003 |
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09733606 |
Dec 8, 2000 |
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6514319 |
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Current U.S.
Class: |
95/96 |
Current CPC
Class: |
B01D 53/047 20130101;
B01D 2259/40069 20130101; B01D 2259/40075 20130101; Y02C 10/08
20130101; B01D 2259/40003 20130101; Y02P 20/151 20151101; B01D
2259/4541 20130101; B01D 2253/108 20130101; C01B 13/0259 20130101;
B01D 53/053 20130101; C01B 2210/0046 20130101; B01D 53/0476
20130101; Y02C 20/40 20200801; B01D 2259/4533 20130101; B01D 53/06
20130101; B01D 2256/12 20130101; B01D 2259/40005 20130101; Y02P
20/152 20151101; B01D 2257/504 20130101; B01D 2259/40052
20130101 |
Class at
Publication: |
95/96 |
International
Class: |
B01D 053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 1999 |
CA |
2,292,054 |
Claims
What is claimed is:
1. Process for pressure swing adsorption separation of a feed gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers within a rotor and
equally spaced angularly about the axis defined by rotation of the
rotor relative to a stator, and rotating the rotor so as to
generate within each adsorber cyclic variations of pressure and
flow at a cyclic period defined by the frequency of rotation along
a flow path contacting the adsorbent material between first and
second ends of the adsorber, the cyclic variations of pressure
extending between a higher pressure and a lower pressure of the
process; rotating the rotor so that the first ends of the adsorbers
successively communicate to feed and exhaust ports provided in a
first valve surface between the rotor and the stator, and the
second ends of the adsorbers successively communicate to a light
product port, to light reflux exit ports and to light reflux return
ports provided in a second valve surface between the rotor and the
stator; the process including for each of the adsorbers in turn:
(a) supplying feed gas mixture at a feed pressure through the feed
port to the adsorber over a feed interval which is substantially
{fraction (1/3)} of the cycle period so as to pressurize the
adsorber to substantially the higher pressure, and then to deliver
light product gas from the light product port at substantially the
higher pressure less flow frictional pressure drops, (b)
withdrawing light reflux gas enriched in the less readily adsorbed
component from the light reflux exit ports, in part to depressurize
the adsorber after the feed interval, (c) withdrawing second
product gas at an exhaust pressure through the exhaust port from
the adsorber over an exhaust interval which is substantially
{fraction (1/3)} of the cycle period so as to depressurize the
adsorber to substantially the lower pressure while delivering the
second product gas, (d) returning light reflux gas enriched in the
less readily adsorbed component from the light reflux return ports
so as to purge the adsorber in the latter part of the exhaust
interval and then to partially repressurize the adsorber prior to
the next feed interval, so that feed gas is continuously supplied
to substantially one adsorber at time, and exhaust gas is
continuously removed from substantially one adsorber at a time.
2. The process of claim 1, with a number of steps (b) for
withdrawing light reflux gas from an adsorber, and an equal number
of steps (c) for returning that light reflux gas to an
adsorber.
3. The process of claim 2, further comprising the step of
performing pressure let-down on each light reflux gas after being
withdrawn and before being returned.
4. The process of claim 2, further comprising the step of
withdrawing light reflux gas from an adsorber and directly
returning that light reflux gas to another adsorber whose cyclic
phase is 120.degree. apart.
5. The process of claim 2, further comprising the step of
withdrawing light reflux gas from an adsorber, delivering that
light reflux gas to a buffer chamber, and then later returning that
light reflux gas from the buffer chamber to another adsorber whose
cyclic phase is 120.degree. apart.
6. Process for pressure swing adsorption separation of a feed gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers within a rotor and
equally spaced by 120.degree. angular separation about the axis
defined by rotation of the rotor relative to a stator, and rotating
the rotor so as to generate within each adsorber cyclic variations
of pressure and flow at a cyclic period defined by the frequency of
rotation along a flow path contacting the adsorbent material
between first and second ends of the adsorber, the cyclic
variations of pressure extending between a higher pressure and a
lower pressure of the process; rotating the rotor so that the first
ends of the adsorbers successively communicate to feed and exhaust
ports provided in a first valve surface between the rotor and the
stator, and the second ends of the adsorbers successively
communicate to a light product port, to first, second and third
light reflux exit ports and to first, second and third light reflux
return ports provided in a second valve surface between the rotor
and the stator; the process including for each of the adsorbers in
turn the following cyclical steps in sequence: (a) supplying feed
gas mixture at a feed pressure through the feed port to the
adsorber over a feed interval which is substantially {fraction
(1/3)} of the cycle period so as to pressurize the adsorber to
substantially the higher pressure, and then to deliver light
product gas from the light product port at substantially the higher
pressure less flow frictional pressure drops, (b) withdrawing a
first light reflux gas enriched in the less readily adsorbed
component from the first light reflux exit port at about the end of
the feed interval, (c) withdrawing a second light reflux gas
enriched in the less readily adsorbed component from the first
light reflux exit port to depressurize that adsorber after the feed
interval, (d) withdrawing a third light reflux gas enriched in the
less readily adsorbed component from the first light reflux exit
port to further depressurize that adsorber, (e) withdrawing second
product gas at an exhaust pressure through the exhaust port from
the adsorber over an exhaust interval which is substantially
{fraction (1/3)} of the cycle period so as to further depressurize
that adsorber to substantially the lower pressure while delivering
the second product gas, (f) returning third light reflux gas from
the third light reflux return port which is receiving that gas
after pressure letdown from another adsorber (whose phase is
leading by 120.degree.), so as to purge the adsorber in the latter
part of the exhaust interval, (g) returning second light reflux gas
from the second light reflux return port so as to partially
repressurize the adsorber prior to the next feed interval, (h)
returning first light reflux gas from the first light reflux return
port which is receiving that gas after pressure letdown from
another adsorber (whose phase is lagging by 120.degree.), so as to
further repressurize the adsorber prior to the next feed interval,
and (i) cyclically repeating the above steps, so that feed gas is
continuously supplied to substantially one adsorber at time, and
exhaust gas is continuously removed from substantially one adsorber
at a time.
7. Process for pressure swing adsorption separation of a feed gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers, and generating within
each adsorber cyclic variations of pressure and flow at a cyclic
period defined by the frequency of rotation along a flow path
contacting the adsorbent material between first and second ends of
the adsorber and with the cyclic phase 120.degree. staggered for
each adsorber, the cyclic variations of pressure extending between
a higher pressure and a lower pressure of the process; the process
including for each of the adsorbers in turn the following cyclical
steps in sequence: (a) supplying feed gas mixture to the first end
of the adsorber over a feed interval which is substantially
{fraction (1/3)} of the cycle period so as to pressurize the
adsorber to substantially the higher pressure, and then to deliver
light product gas from the second end of the adsorber at
substantially the higher pressure less flow frictional pressure
drops, (b) withdrawing a first light reflux gas enriched in the
less readily adsorbed component from the second end of the adsorber
at about the end of the feed interval, (c) withdrawing a second
light reflux gas enriched in the less readily adsorbed component
from the second end of the adsorber to depressurize that adsorber
after the feed interval, and delivering the second light reflux gas
to a buffer chamber, (d) withdrawing a third light reflux gas
enriched in the less readily adsorbed component from the second end
of the adsorber to further depressurize that adsorber, (e)
withdrawing second product gas at an exhaust pressure from the
first end of the adsorber over an exhaust interval which is
substantially {fraction (1/3)} of the cycle period so as to further
depressurize that adsorber to substantially the lower pressure
while delivering the second product gas, (f) supplying third light
reflux gas from another adsorber (whose phase is leading by
120.degree.) to the second end of the adsorber, so as to purge the
adsorber during the latter part of the exhaust interval, (g)
supplying second light reflux gas from the buffer chamber to the
second end of the adsorber, so as to partially repressurize the
adsorber prior to the next feed interval, (h) supplying third light
reflux gas from another adsorber (whose phase is leading by
120.degree.) to the second end of the adsorber, so as to further
repressurize the adsorber prior to the next feed interval, and (i)
cyclically repeating the above steps, while feed gas is
continuously supplied to substantially one adsorber at time, and
exhaust gas is continuously removed from substantially one adsorber
at a time.
8. Apparatus for pressure swing adsorption separation of a gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the gas mixture by an
adsorbent material under increase of pressure between a lower
pressure and a higher pressure, so as to separate from the gas
mixture a heavy product gas enriched in the more readily adsorbed
component and a light product gas depleted in the more readily
adsorbed component; the apparatus including an adsorber rotor
cooperating with a stator mutually defining the rotational axis of
the rotor and with rotor drive means to rotate the rotor at a
rotational period which defines a pressure swing adsorption cycle
period, the rotor containing a cooperating set of three adsorbers
equally angularly spaced about the rotational axis, each adsorber
having a flow path contacting the adsorbent material between first
and second ends of the adsorber, the first ends of the adsorbers
communicating by first apertures to a first valve surface between
the rotor and the stator, and the second ends of the adsorbers
communicating by second apertures to a second valve surface between
the rotor and the stator; the first valve surface having feed and
exhaust ports engaging successively in fluid communication with the
first apertures, and the first valve surface having a light product
port, and first, second and third light reflux exit ports and first
second and third light reflux return ports engaging successively in
fluid communication with the second apertures; the apparatus
further including feed supply means communicating to the feed port
and second product exhaust means communicating to the exhaust port;
the first and third light reflux exit ports communicating to
directly to the first and third light reflux return ports
respectively, and the second light reflux exit port communicating
to a buffer chamber communicating in turn to the second light
reflux return port; and the angular positions and widths of the
ports and apertures being configured so that for each adsorber in
sequence the following steps are performed: (a) the first aperture
of the adsorber is opened to the feed port through which feed gas
mixture is supplied by the feed supply means over a feed interval
of substantially {fraction (1/3)} of the cycle period so as to
pressurize the adsorber to substantially the higher pressure, while
the second aperture of the adsorber is then opened to the light
product port in the feed interval so as to deliver light product
gas at substantially the higher pressure less flow frictional
pressure drops, (b) the second aperture of the adsorber is opened
sequentially to the first, second and third light reflux exit ports
so as to deliver light reflux gas enriched in the less readily
adsorbed component and to depressurize the adsorber after the feed
interval, (c) the first aperture of the adsorber is opened to the
exhaust port through which second product gas is exhausted by the
second product exhaust means at an exhaust pressure over an exhaust
interval which is substantially {fraction (1/3)} of the cycle
period so as to depressurize that adsorber to substantially the
lower pressure and to deliver the second product gas, (d) the
second aperture of the adsorber is opened sequentially to the
third, second and first light reflux return ports so as to purge
the adsorber in the latter part of the exhaust interval and then to
partially repressurize the adsorber prior to the next feed
interval.
9. The apparatus of claim 8, further including sealing means in the
first and second valve surfaces of the stator so as to limit gas
leakage from and between the ports in those valve faces.
10. The apparatus of claim 8, in which the adsorber rotor includes
a central core which is cylindrical and concentric with the
axis.
11. The apparatus of claim 10, in which the central core is hollow
and contains the buffer chamber which communicates to the second
light reflux exit and return ports.
12. The apparatus of claim 8, in which the adsorbers are provided
from layered adsorbent sheets, the sheets being formed of adsorbent
material and a reinforcement material, with spacers between the
sheets to establish flow channels between adjacent pairs of
sheets.
13. The apparatus of claim 12, the adsorbers being installed as
angularly spaced adsorber packs within the rotor and between the
first and second valve faces, with the adsorbent sheets as sheets
layered with flow channels therebetween to form the pack, and with
the width of the sheets being not more than about {fraction (1/3)}
of the circumference of the central core.
14. The apparatus of claim 13, in which the adsorber rotor includes
a central core which is cylindrical and concentric with the axis,
and with the three adsorber packs positioned at equal angular
intervals around the central core of the rotor, and with sealing
partitions between the packs.
15. The apparatus of claim 8, in which the adsorber rotor includes
a central core which is cylindrical and concentric with the axis,
an adsorbent sheet formed of adsorbent material and a reinforcement
material is rolled with spacers in a spiral roll about the central
core so that the spacers define flow channels between adjacent
layers of the roll, and lateral sealing means are provided at
120.degree. angular intervals in the spiral roll so as to define
the three adsorbers within the spiral roll.
16. The apparatus of claim 15, in which the lateral sealing means
are provided by impregnating the spiral rolls with an inert sealant
at 120.degree. angular intervals.
17. The apparatus of claim 8, with means for light reflux pressure
let-down of gas withdrawn from a light reflux exit port before
return that gas to a light reflux return port.
18. The apparatus of claim 17, in which the means for light reflux
pressure let-down is an orifice.
19. The apparatus of claim 8, in which the feed supply means is a
compressor.
20. The apparatus of claim 19, in which the compressor supplies
feed gas at a pressure which varies in accordance with
pressurization of each adsorber during the feed interval.
21. The apparatus of claim 20, in which the compressor has two
compression chambers in opposed phase, the volume of the
compression chambers is cyclically varied by operation of a
compressor drive means at a cyclic period which is {fraction (2/3)}
of the rotational period of the adsorber rotor, and the compressor
drive means is synchronized with the adsorber rotor drive means so
that one compression chamber supplies feed gas to an adsorber over
its feed interval, and the other compression chamber supplies feed
gas to the next adsorber over its feed interval.
22. The apparatus of claim 20, in which the compressor drive means
and the adsorber rotor drive means are operated by a single
motor.
23. The apparatus of claim 8, in which the exhaust means includes
an orifice cooperating with the exhaust port so as to achieve
pressure letdown to approximately the lower pressure of second
product gas from a depressurizing adsorber during the early part of
the exhaust interval for that adsorber.
24. The apparatus of claim 8, in which the exhaust means is a
vacuum pump.
25. The apparatus of claim 24, in which the vacuum pump has two
pump chambers in opposed phase, the volume of the pump chambers is
cyclically varied by operation of a vacuum pump drive means at a
cyclic period which is {fraction (2/3)} of the rotational period of
the adsorber rotor, and the vacuum pump drive means is synchronized
with the adsorber rotor drive means so that one pump chamber
exhausts second product gas from an adsorber over its exhaust
interval, and the other pump chamber exhausts second product gas
from the next adsorber over its exhaust interval
26. The apparatus of claim 25, in which the vacuum pump drive means
and the adsorber rotor drive means are operated by a single
motor.
27. The apparatus of claim 21 and 25, in which the compressor drive
means, the vacuum pump drive means and the adsorber rotor drive
means are operated by a single motor.
28. The apparatus of claim 27, in which the motor is operated at
variable speed to adjust the light product flow and purity
according to demand.
29. The apparatus of claim 21 and 25, in which the compressor drive
means, the vacuum pump drive means and the adsorber rotor drive
means are operated by a manual or pedal crank.
30. The apparatus of claim 21 and 25, in which the cyclic phases of
the compression chambers and pump chambers are separated by
90.degree..
31. The apparatus of claim 27, in which the feed gas mixture is
air, the adsorbent material includes a nitrogen-selective zeolite,
and the light product is enriched oxygen.
32. Process for pressure swing adsorption separation of a feed gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily component being
preferentially adsorbed from the feed gas mixture by an adsorbent
material under increase of pressure, so as to separate from the
feed gas mixture a heavy product gas enriched in the more readily
adsorbed component and a light product gas enriched in the less
readily adsorbed component; providing for the process a
co-operating set of three adsorbers within an adsorber housing body
(AHB) and equally spaced angularly about the axis defined by
relative rotation between the AHB and first and second valve bodies
relative to a stator, and establishing relative rotation so as to
generate within each adsorber cyclic variations of pressure and
flow at a cyclic period defined by the frequency of rotation along
a flow path contacting the adsorbent material between first and
second ends of the adsorber, the cyclic variations of pressure
extending between a higher pressure and a lower pressure of the
process; establishing the relative rotation so that the first ends
of the adsorbers successively communicate to feed and exhaust ports
provided in a first valve surface between the AHB and the first
valve body, and the second ends of the adsorbers successively
communicate to a light product port, to light reflux exit ports and
to light reflux return ports provided in a second valve surface
between the AHB and the second valve body; the process including
for each of the adsorbers in turn: (e) supplying feed gas mixture
at a feed pressure through the feed port to the adosrber over a
feed interval which is substantially {fraction (1/3)} of the cycle
period so as to pressurize the adsorber to substantially the higher
pressure, and then to deliver light product gas from the light
product port at substantially the higher pressure less flow
frictional pressure drops; (f) withdrawing light reflux gas
enriched in the less readily adsorbed component from the light
reflux exit ports, in part to depressurize that adsorber after the
feed interval; (g) withdrawing second product gas at an exhaust
pressure through the exhaust port from the adsorber over an exhaust
interval which is substantially {fraction (1/3)} of the cycle
period so as to depressurize that adsorber to substantially the
lower pressure while delivering the second product gas; and (h)
returning light reflux gas enriched in the less readily adsorbed
component from the light reflux return ports so as to purge the
adsorber in the latter part of the exhaust interval and then to
partially repressurize the adsorber prior to the next feed
interval, so that feed gas is continuously supplied to
substantially one adsorber at time, and exhaust gas is continuously
removed from substantially one adsorber at a time.
Description
FIELD OF THE INVENTION
[0001] The invention relates to gas separations conducted by
pressure swing adsorption (PSA), and particularly to air separation
to generate concentrated oxygen or to air purification to remove
carbon dioxide or vapour contaminants. In particular, the present
invention relates to a rotary valve gas separation system having a
plurality of rotating adsorbers disposed therein for implementing a
pressure swing adsorption process for separating out the gas
fractions.
[0002] Four possible applications of the present invention are:
[0003] (a) Home use medical oxygen concentrators;
[0004] (b) Portable oxygen concentrators;
[0005] (c) Ultra low power oxygen concentrators, e.g. for third
world medical clinics; and
[0006] (d) Manually operated oxygen concentrator or air purifier
for survival life support.
BACKGROUND OF THE INVENTION
[0007] Gas separation by pressure swing adsorption is achieved by
coordinated pressure cycling and flow reversals over an adsorber
that preferentially adsorbs a more readily adsorbed component
relative to a less readily adsorbed component of the mixture. The
total pressure is elevated during intervals of flow in a first
direction through the adsorber from a first end to a second end of
the adsorber, and is reduced during intervals of flow in the
reverse direction. As the cycle is repeated, the less readily
adsorbed component is concentrated in the first direction, while
the more readily adsorbed component is concentrated in the reverse
direction.
[0008] A "light" product, depleted in the more readily adsorbed
component and enriched in the less readily adsorbed component, is
then delivered from the second end of the adsorber. A "heavy"
product enriched in the more strongly adsorbed component is
exhausted from the first end of the adsorber. The light product is
usually the desired product to be purified, and the heavy product
often a waste product, as in the important examples of oxygen
separation over nitrogen-selective zeolite adsorbents and hydrogen
purification. The heavy product (enriched in nitrogen as the more
readily adsorbed component) is a desired product in the example of
nitrogen separation over nitrogen-selective zeolite adsorbents.
Typically, the feed is admitted to the first end of a adsorber and
the light product is delivered from the second end of the adsorber
when the pressure in that adsorber is elevated to a higher working
pressure. The heavy product is exhausted from the first end of the
adsorber at a lower working pressure. In order to achieve high
purity of the light product, a fraction of the light product or gas
enriched in the less readily adsorbed component is recycled back to
the adsorbers as "light reflux" gas after pressure letdown, e.g. to
perform purge, pressure equalization or repressurization steps.
[0009] The conventional process for gas separation by pressure
swing adsorption uses two or more adsorbers in parallel, with
directional valving at each end of each adsorber to connect the
adsorbers in alternating sequence to pressure sources and sinks,
thus establishing the changes of working pressure and flow
direction. The basic pressure swing adsorption process makes
inefficient use of applied energy, because of irreversible
expansion over the valves while switching the adsorbers between
higher and lower pressures. More complex conventional pressure
swing adsorption devices achieve some improvement in efficiency by
use of multiple "light reflux" steps, both to achieve some energy
recovery by pressure equalization, and also desirably to sequence
the light reflux steps so that lower purity light reflux gas
reenters the second end of the adsorbers first, and higher purity
light reflux gas reenters the second end of the adsorbers last, so
as to maintain the correct ordering of the concentration profile in
the adsorbers.
[0010] The conventional method of supporting the adsorbent is also
problematic. There is a need for rigid high surface area adsorbent
supports that can overcome the limitations of granular adsorbent
and enable much higher cycle frequencies. High surface area
laminated adsorbers, with the adsorbent supported in thin sheets
separated by spacers to define flow channels between adjacent
sheets, formed either as stacked assemblies or as spiral rolls,
have been disclosed by Keefer (U.S. Pat. No. 4,968,329 and U.S.
Pat. No. 5,082,473).
[0011] U.S. Pat. No. 4,968,329 discloses related gas separation
devices with valve logic means to provide large exchanges of fresh
feed gas for depleted feed gas. Such large feed exchanges may be
required when concentrating one component as a desired product
without excessively concentrating or accumulating other components,
as in concentrating oxygen from feed air containing water vapour
whose excessive concentration and accumulation would deactivate the
adsorbent.
[0012] Siggelin (U.S. Pat. No. 3,176,446), Mattia (U.S. Pat. No.
4,452,612), Davidson and Lywood (U.S. Pat. No. 4,758,253), Boudet
et al (U.S. Pat. No. 5,133,784), and Petit et al (U.S. Pat. No.
5,441,559) disclose PSA devices using rotary adsorber
configurations. Ports for multiple angularly separated adsorbers
mounted on a rotor assembly sweep past fixed ports for feed
admission, product delivery and pressure equalization. In this
apparatus, the relative rotation of the ports provides the function
of a rotary distributor valve. All of these prior art devices use
multiple adsorbers operating sequentially on the same cycle, with
multiport distributor rotary valves for controlling gas flows to,
from and between the adsorbers.
[0013] The prior art includes numerous examples of pressure swing
adsorption and vacuum swing adsorption devices with three adsorbers
operating in parallel. Thus, Hay (U.S. Pat. No. 4,969,935) and
Kumar et al (U.S. Pat. No. 5,328,503) disclose vacuum adsorption
systems which do not achieve continuous operation of compressors
and vacuum pumps connected at all times to one of the three
adsorbers. Such operation is achieved in other three adsorber
examples provided by Tagawa et al (U.S. Pat. No. 4,781,735), Hay
(U.S. Pat. No. 5,246,676), and Watson et al (U.S. Pat. No.
5,411,528), but in each of these latter examples there is some
undesirable inversion of the ordering of light product withdrawal
and light reflux steps so that process efficiency is
compromised.
SUMMARY OF THE INVENTION
[0014] The present invention is intended to enable high frequency
operation of pressure swing and vacuum swing adsorption processes,
with high energy efficiency and with compact machinery of low
capital cost. The invention applies in particular to air
separation.
[0015] The invention provides an apparatus for PSA separation of a
gas mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the gas mixture a heavy product gas enriched in the
more readily adsorbed component, and a light product gas enriched
in the less readily adsorbed component and depleted in the more
readily adsorbed component. The apparatus includes compression
machinery cooperating with three adsorbers mounted in a rotary PSA
module.
[0016] Each adsorber has a flow path contacting adsorbent material
between first and second ends of the flow path. The adsorbers are
mounted at equal angular spacings in an adsorber housing, which is
engaged in relative rotation with first and second valve bodies to
define rotary sealing faces of first and second valves adjacent
respectively the first and second ends of the adsorber flow paths.
In some preferred embodiments, the adsorber housing is a rotor (the
"adsorber rotor") which rotates while the first and second valve
bodies together form the stator. In other preferred embodiments,
the adsorber housing is stationary, while the first and second
valve bodies achieve the valving function. Fluid transfer means are
provided to provide feed gas to the first valve body, to remove
exhaust gas from the first valve body, and to deliver product gas
from the second valve body.
[0017] The first valve admits feed gas to the first end of the
adsorbers, and exhausts heavy product gas from the first end of the
adsorbers. The second valve cooperates with the adsorbers to
deliver light product gas from the second end of the adsorbers, to
withdraw light reflux gas from the second end of the adsorbers, and
to return light reflux gas to the second end of the adsorbers. The
term `light reflux" refers to withdrawal of light gas (enriched in
the less readily adsorbed component) from the second end of the
adsorbers via the second valve, followed by pressure let-down and
return of that light gas to other adsorbers at a lower pressure via
the second valve. The first and second valves are operated so as to
define the steps of a PSA cycle performed sequentially in each of
the adsorbers, while controlling the timings of flow at specified
total pressure levels between the adsorbers and the compression
machinery.
[0018] The PSA process of the invention establishes the PSA cycle
in each adsorber, within which the total working pressure in each
adsorber is cycled between a higher pressure and a lower pressure
of the PSA cycle. The higher pressure is superatmospheric, and the
lower pressure may conveniently either be atmospheric or
subatmospheric. The PSA process also provides intermediate
pressures between the higher and lower pressure. The compression
machinery of the apparatus in general includes a feed gas
compressor and a heavy product gas exhauster. The exhauster would
be a vacuum pump when the lower pressure is subatmospheric. When
the lower pressure is atmospheric, the exhauster could be an
expander, or else may be replaced by throttle means to regulate
countercurrent blowdown.
[0019] In the present invention, the feed compressor will typically
supply feed gas for feed pressurization of the adsorbers to the
first valve means. The exhauster will typically receive heavy
product gas for countercurrent blowdown of the adsorbers from the
first valve means.
[0020] A buffer chamber is provided to cooperate with the second
valve. The buffer chamber provides the "light reflux" function of
accepting a portion of the gas enriched in the second component as
light reflux gas from a adsorber at the higher pressure and during
concurrent blowdown to reduce the pressure from the higher
pressure, and then returning that gas to the same adsorber to
provide purge at the lower pressure and then to provide light
reflux pressurization to increase the pressure from the lower
pressure. The light reflux function enables production of the light
product with high purity.
[0021] The present invention performs in each adsorber the
sequentially repeated steps within the cycle period as follows:
[0022] (A) Feed pressurization and production. Feed gas mixture is
admitted to the first end of the adsorber during a feed time
interval over approximately {fraction (1/3)} of the cycle period
(0T-T/3), commencing when the pressure within the adsorber is a
first intermediate pressure between the lower pressure and the
higher pressure, pressurizing the adsorber to the higher pressure
(step A1), and then delivering light product gas from the second
end (step A2) at a light product delivery pressure which is
substantially the higher pressure less minor pressure drops due to
flow friction.
[0023] (B) Withdraw from the second end a first light reflux gas
enriched in the second component (preferably following step A2 of
light product delivery) at approximately the higher pressure during
a brief time interval at or near the end of step A (T/3).
[0024] (C) Equalization to buffer chamber. While flow at the first
end of the adsorber is stopped during a concurrent blowdown time
interval following step B, withdraw a second light reflux gas
enriched in the second component as light reflux gas from the
second end of the adsorber into the buffer chamber, and
depressurizing the adsorber toward a second intermediate pressure
between the higher pressure and the lower pressure.
[0025] (D) Withdraw a third light reflux gas from the second end as
purge flow for another adsorber, during a brief time interval at
approximately the end of step C (T/2).
[0026] (E) Countercurrent blowdown and exhaust. Exhaust a flow of
gas enriched in the first component from the first end of the
adsorber during an exhaust time interval (T/2-5T/6), in step E1 to
depressurize the adsorber from the second intermediate pressure to
the lower pressure, and then in step E2 transferring a flow of
third light reflux gas from the second end of another adsorber
undergoing step D to purge the adsorber at substantially the lower
pressure while continuing to exhaust gas enriched in the first
component as a heavy product gas.
[0027] (F) Equalization from buffer chamber. While flow at the
first end of the adsorber is stopped, supply second light reflux
gas from the buffer chamber to the second end of the adsorber. This
increases the pressure of the adsorber from substantially the lower
pressure to the second intermediate pressure.
[0028] (G) Admit a flow of first light reflux gas from the second
end of another adsorber as backfill gas to increase adsorber
pressure to the first intermediate pressure for the beginning of
step A of the next cycle.
[0029] It will be appreciated by those skilled in the art that
alternative light reflux flow patterns may be used. For example,
delete steps B and G, or delay step B to follow step A rather than
overlap step A so it acts as a pressure equalization step. With
appropriate porting of the second valve, the apparatus of this
invention may be used to implement the process steps of prior art
cycles with three adsorbers, for example as prescribed in any of
the above cited U.S. Pat. Nos. 4,781,735; 4,969,935; 5,246,676;
5,328,503; and 5,411,528.
[0030] The process may be controlled by varying the cycle frequency
so as to achieve desired purity, recovery and flow rates of the
light product gas. Alternatively, the feed flow rate and the light
product flow rate may be adjusted at a given cycle frequency, so as
to achieve desired light product purity. Preferably, light product
flow rate is adjusted to maintain delivery pressure in a light
product receiver, by simultaneously varying feed compressor drive
speed and the rotational frequency of the PSA module.
[0031] In vacuum embodiments, the first intermediate pressure and
second intermediate pressure are typically approximately equal to
atmospheric pressure, so that the lower pressure is subatmospheric.
Alternatively, the lower pressure may be atmospheric. In air
purification applications, the first component is an impurity gas
or vapour, the gas mixture is air containing the impurity, and the
light product is purified air. In air separation applications, the
first component is nitrogen, the second component is oxygen, the
adsorbent material includes a nitrogen-selective zeolite, the gas
mixture is air, and the light product is enriched oxygen.
[0032] In preferred embodiments of the invention, the adsorbent is
supported in the form of layered adsorbent or "adsorbent laminate,"
formed from flexible adsorbent sheets. The adsorbent sheets are
thin sheets of adsorbent with a composite reinforcement, or as an
inert sheets or foil coated with the adsorbent. Flow channels are
established by spacers forming parallel channels between adjacent
pairs of sheets. The channel width between adjacent adsorbent
sheets of the experimental adsorbers has been in the range of 50%
to 100% of the adsorbent sheet thickness. This "adsorbent laminate"
configuration has much lower pressure drop than packed adsorbers,
and avoids the fluidization problem of packed adsorbers. The
adsorbent sheets are typically in the range of 100 to 175 microns
thick. The sheet-laminate provides desirable compliance to
accommodate stacking or rolling errors, and spacer systems provide
the necessary stability against unrestrained deflections or
distortions that would degrade the uniformity of the flow channels
between adjacent layers of adsorbent sheet.
[0033] According to one aspect of the invention there is provided
process for pressure swing adsorption separation of a feed gas
mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers within a rotor and
equally spaced angularly about the axis defined by rotation of the
rotor relative to a stator, and rotating the rotor so as to
generate within each adsorber cyclic variations of pressure and
flow at a cyclic period defined by the frequency of rotation along
a flow path contacting the adsorbent material between first and
second ends of the adsorber, the cyclic variations of pressure
extending between a higher pressure and a lower pressure of the
process; rotating the rotor so that the first ends of the adsorbers
successively communicate to feed and exhaust ports provided in a
first valve surface between the rotor and the stator, and the
second ends of the adsorbers successively communicate to a light
product port, to light reflux exit ports and to light reflux return
ports provided in a second valve surface between the rotor and the
stator; the process including for each of the adsorbers in
turn:
[0034] (a) supplying feed gas mixture at a feed pressure through
the feed port to the adsorber over a feed interval which is
substantially {fraction (1/3)} of the cycle period so as to
pressurize the adsorber to substantially the higher pressure, and
then to deliver light product gas from the light product port at
substantially the higher pressure less flow frictional pressure
drops;
[0035] (b) withdrawing light reflux gas enriched in the less
readily adsorbed component from the light reflux exit ports, in
part to depressurize that adsorber after the feed interval;
[0036] (c) withdrawing second product gas at an exhaust pressure
through the exhaust port from the adsorber over an exhaust interval
which is substantially {fraction (1/3)} of the cycle period so as
to depressurize that adsorber to substantially the lower pressure
while delivering the second product gas; and
[0037] (d) returning light reflux gas enriched in the less readily
adsorbed component from the light reflux return ports so as to
purge the adsorber in the latter part of the exhaust interval and
then to partially repressurize the adsorber prior to the next feed
interval,
[0038] so that feed gas is continuously supplied to substantially
one adsorber at time, and exhaust gas is continuously removed from
substantially one adsorber at a time.
[0039] According to another aspect of the invention there is
provided process for pressure swing adsorption separation of a feed
gas mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers within a rotor and
equally spaced by 120.degree. angular separation about the axis
defined by rotation of the rotor relative to a stator, and rotating
the rotor so as to generate within each adsorber cyclic variations
of pressure and flow at a cyclic period defined by the frequency of
rotation along a flow path contacting the adsorbent material
between first and second ends of the adsorber, the cyclic
variations of pressure extending between a higher pressure and a
lower pressure of the process; rotating the rotor so that the first
ends of the adsorbers successively communicate to feed and exhaust
ports provided in a first valve surface between the rotor and the
stator, and the second ends of the adsorbers successively
communicate to a light product port, to first, second and third
light reflux exit ports and to first, second and third light reflux
return ports provided in a second valve surface between the rotor
and the stator; the process including for each of the adsorbers in
turn the following cyclical steps in sequence:
[0040] (a) supplying feed gas mixture at a feed pressure through
the feed port to the adsorber over a feed interval which is
substantially 1/3 of the cycle period so as to pressurize the
adsorber to substantially the higher pressure, and then to deliver
light product gas from the light product port at substantially the
higher pressure less flow frictional pressure drops;
[0041] (b) withdrawing a first light reflux gas enriched in the
less readily adsorbed component from the first light reflux exit
port at about the end of the feed interval;
[0042] (c) withdrawing a second light reflux gas enriched in the
less readily adsorbed component from the first light reflux exit
port to depressurize that adsorber after the feed interval;
[0043] (d) withdrawing a third light reflux gas enriched in the
less readily adsorbed component from the first light reflux exit
port to further depressurize that adsorber;
[0044] (e) withdrawing second product gas at an exhaust pressure
through the exhaust port from the adsorber over an exhaust interval
which is substantially {fraction (1/3)} of the cycle period so as
to further depressurize that adsorber to substantially the lower
pressure while delivering the second product gas;
[0045] (f) returning third light reflux gas from the third light
reflux return port which is receiving that gas after pressure
letdown from another adsorber (whose phase is leading by
120.degree.), so as to purge the adsorber in the latter part of the
exhaust interval;
[0046] (g) returning second light reflux gas from the second light
reflux return port so as to partially repressurize the adsorber
prior to the next feed interval;
[0047] (h) returning first light reflux gas from the first light
reflux return port which is receiving that gas after pressure
letdown from another adsorber (whose phase is lagging by
120.degree.), so as to further repressurize the adsorber prior to
the next feed interval; and
[0048] (i) cyclically repeating the above steps,
[0049] so that feed gas is continuously supplied to substantially
one adsorber at time, and exhaust gas is continuously removed from
substantially one adsorber at a time.
[0050] According to a further aspect of the invention there is
provided process for pressure swing adsorption separation of a feed
gas mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the feed gas mixture
by an adsorbent material under increase of pressure, so as to
separate from the feed gas mixture a heavy product gas enriched in
the more readily adsorbed component and a light product gas
enriched in the less readily adsorbed component; providing for the
process a cooperating set of three adsorbers, and generating within
each adsorber cyclic variations of pressure and flow at a cyclic
period defined by the frequency of rotation along a flow path
contacting the adsorbent material between first and second ends of
the adsorber and with the cyclic phase 120.degree. staggered for
each adsorber, the cyclic variations of pressure extending between
a higher pressure and a lower pressure of the process; the process
including for each of the adsorbers in turn the following cyclical
steps in sequence:
[0051] (a) supplying feed gas mixture to the first end of the
adsorber over a feed interval which is substantially {fraction
(1/3)} of the cycle period so as to pressurize the adsorber to
substantially the higher pressure, and then to deliver light
product gas from the second end of the adsorber at substantially
the higher pressure less flow frictional pressure drops,
[0052] (b) withdrawing a first light reflux gas enriched in the
less readily adsorbed component from the second end of the adsorber
at about the end of the feed interval;
[0053] (c) withdrawing a second light reflux gas enriched in the
less readily adsorbed component from the second end of the adsorber
to depressurize that adsorber after the feed interval, and
delivering the second light reflux gas to a buffer chamber;
[0054] (d) withdrawing a third light reflux gas enriched in the
less readily adsorbed component from the second end of the adsorber
to further depressurize that adsorber;
[0055] (e) withdrawing second product gas at an exhaust pressure
from the first end of the adsorber over an exhaust interval which
is substantially {fraction (1/3)} of the cycle period so as to
further depressurize that adsorber to substantially the lower
pressure while delivering the second product gas;
[0056] (f) supplying third light reflux gas from another adsorber
(whose phase is leading by 120.degree.) to the second end of the
adsorber, so as to purge the adsorber during the latter part of the
exhaust interval;
[0057] (g) supplying second light reflux gas from the buffer
chamber to the second end of the adsorber, so as to partially
repressurize the adsorber prior to the next feed interval;
[0058] (h) supplying third light reflux gas from another adsorber
(whose phase is leading by 120.degree.) to the second end of the
adsorber, so as to further repressurize the adsorber prior to the
next feed interval; and
[0059] (i) cyclically repeating the above steps,
[0060] while feed gas is continuously supplied to substantially one
adsorber at time, and exhaust gas is continuously removed from
substantially one adsorber at a time.
[0061] According to another aspect of the invention there is
provided an apparatus for pressure swing adsorption separation of a
gas mixture containing a more readily adsorbed component and a less
readily adsorbed component, with the more readily adsorbed
component being preferentially adsorbed from the gas mixture by an
adsorbent material under increase of pressure between a lower
pressure and a higher pressure, so as to separate from the gas
mixture a heavy product gas enriched in the more readily adsorbed
component and a light product gas depleted in the more readily
adsorbed component; the apparatus including an adsorber rotor
cooperating with a stator mutually defining the rotational axis of
the rotor and with rotor drive means to rotate the rotor at a
rotational period which defines a pressure swing adsorption cycle
period, the rotor containing a cooperating set of three adsorbers
equally angularly spaced about the rotational axis, each adsorber
having a flow path contacting the adsorbent material between first
and second ends of the adsorber, the first ends of the adsorbers
communicating by first apertures to a first valve surface between
the rotor and the stator, and the second ends of the adsorbers
communicating by second apertures to a second valve surface between
the rotor and the stator; the first valve surface having feed and
exhaust ports engaging successively in fluid communication with the
first apertures, and the first valve surface having a light product
port, and first, second and third light reflux exit ports and first
second and third light reflux return ports engaging successively in
fluid communication with the second apertures; the apparatus
further including feed supply means communicating to the feed port
and second product exhaust means communicating to the exhaust port;
the first and third light reflux exit ports communicating to
directly to the first and third light reflux return ports
respectively, and the second light reflux exit port communicating
to a buffer chamber communicating in turn to the second light
reflux return port; and the angular positions and widths of the
ports and apertures being configured so that for each adsorber in
sequence the following steps are performed:
[0062] (a) the first aperture of the adsorber is opened to the feed
port through which feed gas mixture is supplied by the feed supply
means over a feed interval of substantially {fraction (1/3)} of the
cycle period so as to pressurize the adsorber to substantially the
higher pressure, while the second aperture of the adsorber is then
opened to the light product port in the feed interval so as to
deliver light product gas at substantially the higher pressure less
flow frictional pressure drops;
[0063] (b) the second aperture of the adsorber is opened
sequentially to the first, second and third light reflux exit ports
so as to deliver light reflux gas enriched in the less readily
adsorbed component and to depressurize the adsorber after the feed
interval;
[0064] (c) the first aperture of the adsorber is opened to the
exhaust port through which second product gas is exhausted by the
second product exhaust means at an exhaust pressure over an exhaust
interval which is substantially {fraction (1/3)} of the cycle
period so as to depressurize that adsorber to substantially the
lower pressure and to deliver the second product gas; (d) the
second aperture of the adsorber is opened sequentially to the
third, second and first light reflux return ports so as to purge
the adsorber in the latter part of the exhaust interval and then to
partially repressurize the adsorber prior to the next feed
interval.
[0065] Further objects and advantages of the invention will become
apparent from the description of preferred embodiments of the
invention below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] The preferred embodiments of the present invention will now
be described, with reference to the drawings, in which:
[0067] FIG. 1 shows a simplified schematic of a rotary vacuum
oxygen concentrator with three adsorbers, a feed air compressor,
and an exhaust vacuum pump.
[0068] FIG. 2 shows a schematic of a rotary positive pressure
oxygen concentrator with three adsorbers, with each adsorber
communicating to a feed air compressor.
[0069] FIG. 3 shows a more detailed schematic of a rotary vacuum
oxygen concentrator apparatus with three adsorbers, with each
adsorber communicating to a feed air compressor, and an exhaust
vacuum pump.
[0070] FIG. 4 shows the gas flow pattern and pressure pattern
associated with an adsorber of the apparatus of FIG. 1.
[0071] FIG. 5 shows the pressure pattern for all three adsorbers,
in the format to which the invention shall be applied.
[0072] FIG. 6 shows a cross section of a rotary module of an oxygen
concentrator, with each of the two valve ends being shown at a
different point in the cycle.
[0073] FIGS. 7 to 10 show closer views of the stator and rotor
valve faces.
[0074] FIG. 11 shows an embodiment similar to FIG. 1 but with the
adsorber housing stationary while the first and second valve bodies
rotate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0075] FIGS. 1, 2 and 3
[0076] An oxygen concentrator according to the invention has three
adsorbers 1, 2 and 3 in apparatus 4 (the rotary PSA module); the
adsorbers having respectively first ends 5, 6 and 7, and second
ends 8, 9 and 10. The PSA cycle is performed in the three
adsorbers, with a phase shift of 120.degree. between the adsorbers
in the sequence of adsorbers 1, 2 and then 3. FIGS. 1 and 3 show
vacuum assisted embodiments, while FIG. 2 shows a positive pressure
embodiment without vacuum assist.
[0077] Compressor 11 is provided to draw feed air through inlet
filter 12 from feed 201 and conduit 614, and to supply compressed
feed air to the adsorbers through first ends 5, 6 and 7. In FIGS. 1
and 3, an exhauster 202 as vacuum pump 13 is provided to exhaust
nitrogen enriched air waste along piping 615 from second ends 8, 9
and 10. Motor 14 is provided to drive compressor 11 by shaft 15 and
vacuum pump 13 by shaft 16. Product 203 is expelled from piping 616
leading from second ends 8, 9 and 10.
[0078] FIG. 2 shows a rotary positive pressure PSA oxygen
concentrator. In this embodiment, the vacuum pump 13 is replaced
with exhaust conduits incorporating throttle orifices 17 and 18 for
controlled pressure release during countercurrent blowdown, and a
low pressure exhaust conduit 19 exhausting directly to
atmosphere.
[0079] Apparatus 4 includes a rotary adsorber module 20 including a
stator 21, first stator valve face 22, rotor 23 and second stator
valve face 24. Product delivery valve 25 delivers product. Purge is
recycled through conduit 26, while backfill is transferred through
conduit 27. Equalization occurs through conduit 28 and through
buffer chamber 29.
[0080] In this embodiment and those shown FIGS. 2 and 3, the
adsorber housing body rotates and is referred to as the rotor,
while the first and second valve bodies are the stator and are
referred to as the first and second valve faces.
[0081] FIG. 3 shows a specific example of a two-cylinder double
acting piston machine with the two pistons operating in opposite
phase. It shows a more detailed look at the compressor and vacuum
pump assemblies. The filtered air from inlet air filter 12 travels
through the inlet check valve 45 and enters the feed chamber 41. It
then is expelled through discharge check valve 40, making its way
to the stator 21. Compressor intake manifold 44 collects the air to
be used for compression. Compressor exhaust manifold 43 provides
the piping for the exhaust air from the compressor.
[0082] Exhaust chamber 42 collects the exhaust from the PSA unit.
Pump intake manifold 47 and pump exhaust manifold 46 are the piping
assemblies that accomplish the air transfer for the pump. Inlet
check valve 49 regulates the flow of exhaust into the exhaust
chamber 42. Discharge check valve 48 regulates the exiting
stream.
[0083] If the pistons are reciprocating at a frequency much greater
than the frequency of the rotor, then the system is simply a piston
compressor embodiment as in FIG. 1. However, an alternative is to
synchronize piston reciprocation in both frequency and phase with
the PSA cycle so that a complete feed step "A1" is accomplished by
a simple stroke of a compressor piston, and an exhaust step "E1" is
accomplished by a single stroke of a vacuum pump piston. The
reciprocating frequency of the compressor and vacuum is set to be
exactly 1.5 times the frequency of the cycle. Pressure variations
within the PSA cycle are thus coordinated with those within the
compressor and vacuum pump cylinders, enabling an improvement in
efficiency and substantially eliminating pressure and flow
pulsations extraneous to the PSA cycle itself.
[0084] These actions are facilitated by reciprocating crank drives
50 and 51. This is useful for use in manual drives (manual or foot
pedal power with a pulley linkage between the motor and the rotor).
The manual apparatus could be used in emergency situations such as
at altitude or in confined spaces such as in submarines or in mine
shafts.
[0085] Furthermore, power consumption is reduced since the
compressor 11 and vacuum pump 13 each follow the changing pressure
of the adsorber for respectively feed pressurization and
countercurrent blowdown steps. Thus, the average working pressure
across each of the compressor 11 and vacuum pump 13 is much less
than the maximum working pressure.
[0086] FIGS. 4 and 5
[0087] FIGS. 4 and 5 show the 360.degree. position variation of the
gas flow over a cycle period in the adsorbers of the apparatus of
FIGS. 1 and 3. FIG. 4 shows the cycle for adsorber 1, while FIG. 5
shows the cycle for all three adsorbers. Note that the three
adsorbers charted in FIG. 5 are 120.degree. out of phase from each
other.
[0088] The horizontal axis 100 of FIG. 4 represents position, in
30.degree. fractions of the cycle period. The vertical axis 101
represents the working pressure in adsorber 1.
[0089] Curve 102 shows the position variation of the flow path
through the valve face plates, with the system pressure cycling
between higher pressure 104 and the lower pressure 103, 105 and 110
are the intermediate pressures in the cycle.
[0090] The cycle is divided into six process steps.
[0091] 1. The feed pressurization step extends over the feed time
interval from positions 0.degree. degrees to 120.degree. of the
cycle period on horizontal axis 100. At the beginning of the cycle
(0.degree.), feed gas is fed through inlet filter 12 to compressor
11 and the first end of the adsorbers, bringing the system to its
higher pressure 104. The feed step includes feed from first
intermediate pressure 105 to the higher pressure 104. Typically,
the first intermediate pressure is nominally atmospheric
pressure.
[0092] 2. A and B: Feed with production and production for backfill
(pressurization with gas enriched in the second component). In step
A, between 60.degree. and 90.degree., light product gas is
withdrawn from the second end of adsorber 1 through the light
product port. Between 90.degree. and 120.degree. (step B), light
reflux is withdrawn from the second end of adsorber 1 to backfill
adsorber 2.
[0093] 3. C and D: The concurrent blowdown step extends over the
concurrent blowdown interval from 120.degree. to 180.degree..
Between 120.degree. and 150.degree. (step C), light reflux gas is
withdrawn from the second end of adsorber 1 to equalize the buffer
chamber 29. During 150.degree. to 180.degree. (step D), light
reflux gas is removed from the second end of adsorber 1 to purge
adsorber 3. The concurrent blowdown step begins at substantially
the higher pressure 104 and ends at a second intermediate pressure
110, which typically may be approximately equal to the first
intermediate pressure 105.
[0094] 4. E1: The countercurrent blowdown (to exhaust) interval E1
extends from 180.degree. to 300.degree., bringing the system down
from second intermediate pressure 110 to its lower pressure
103.
[0095] 5. E2: Purge to exhaust. During step E2, gas is removed
between 270.degree.-300.degree. from the second end of adsorber 2
to purge adsorber 1. Exhaust is removed from the first end of
adsorber 1 from 270.degree.-300.degree..
[0096] 6. F and G: The countercurrent re-pressurization step
extends from 300.degree. to 360.degree.. The cycle between
300.degree.-330.degree. (step F) equalizes the second end of
adsorber 1 from the buffer chamber 29. The cycle between
3300-360.degree. (step G) is applied to backfilling adsorber 1 from
adsorber 3.
[0097] The following sequence table illustrates the above sequence
description.
1TABLE 1 Sequence Table Adsorber 1 Adsorber 2 Adsorber 3 1st
2.sup.nd 1st 2.sup.nd 1st 2.sup.nd Stator Stator Stator Stator
Stator Stator Step Time valve Valve State valve Valve State valve
Valve State 1 0-30 F to H1 Closed Feed Closed L2 to B Provide
buffer H3 to E Closed Exhaust pressurization gas 2 30-60 F to H1
Closed Feed Closed L2 to L3 Provide purge H3 to E L2 to L3 Purge
pressurization 3 60-90 F to H1 L1 to P Production H2 to E Closed
Exhaust Closed B to L3 Pressurization from buffer 4 90-120 F to H1
L1 to L3 Provide H2 to E Closed Exhaust Closed L1 to L3 Product
product pressurization pressurization 5 120-150 Closed L1 to B
Provide buffer H2 to E Closed Exhaust F to H3 Closed Feed gas
pressurization 6 150-180 Closed L1 to L2 Provide purge H2 to E L1
to L2 Purge F to H3 Closed Feed pressurization 7 180-270 H1 to E
Closed Exhaust Closed B to L2 Pressurization F to H3 L3 to P
Production from buffer 8 210-240 H1 to E Closed Exhaust Closed L3
to L2 Product F to H3 L3 to L2 Provide pressurization product
pressurization 9 240-270 H1 to E Closed Exhaust F to H2 Closed Feed
Closed L3 to B Provide buffer pressurization gas 10 270-300 H1 to E
L3 to L1 Purge F to H2 Closed Feed Closed L3 to L1 Provide purge
pressurization 11 300-330 Closed B to L1 Pressurization F to H2 L1
to P Production H3 to E Closed Exhaust from buffer 12 330-360
Closed L2 to L1 Product F to H2 L1 to L2 Provide H3 to E Closed
Exhaust pressurization product pressurization
[0098] FIG. 6
[0099] FIG. 6 shows a cross section of a rotary module of an oxygen
concentrator. The bottom left of the figure shows a motor 206
attached to a gear 209, which is in turn attached to drive coupling
210. Rotation of the assembly is about axis 211.
[0100] The left side of the diagram shows the first stator valve
face plate 22, while the right side of the diagram shows the second
stator valve face plate 24. Rotor valve face plates are represented
by 37 and 38 and are described in FIGS. 7 and 10. Note that the two
sides of the drawing are shown at different stages of the cycle.
Piping connects three laminate adsorbers 204 to buffer chamber 29.
Feed is input through feed port 201. Exhaust is released through
exhaust port 202. Product is sent through product port 203. Outer
housing 207 contains the rotor assembly 208. Cross sections 212,
213 and 214 are described in FIGS. 7 through 10.
[0101] FIG. 7 and b (Both Figures are Taken at the Cross Section
212 of FIG. 6.)
[0102] FIG. 7a shows the first rotor valve face 37. Apertures 250
(H1), 251 (H2) and 252 (H3) on the face plate facilitate the flow
action of gases from one adsorber to another corresponding to the
sequencing defined in the FIGS. 4/5 description. H1, H2 and H3
correspond to the first rotor valve openings for adsorbers 1,2 and
3, respectively.
[0103] FIG. 7b shows the first stator valve face 22. Feed enters
through feed port aperture 201 and exhaust exits through exhaust
port aperture 202.
[0104] Both figures can are taken at the cross section 212 on FIG.
6.
[0105] FIGS. 8a and 8b
[0106] FIGS. 8a shows the rotor laminate adsorber cross section. It
is a cross section located at the 213 position on FIG. 6. Note that
it is a single spiral wound with spacers separating the layers. The
three adsorber sections 1, 2 and 3 are shown separated by sealant
separators 301 that are impregnated in the laminate adsorber.
Buffer chamber 29 is located in the center of the rotor apparatus
208. Arrow 302 shows the direction of rotation of the adsorber
assembly.
[0107] FIG. 8b shows multiple sheets of laminate with physical
plugs as separators 301.
[0108] FIG. 9
[0109] FIG. 9 shows the rotor valve face cross section. It is a
cross section located at the 213 position on FIG. 6. The dashed
slots 401 correspond to the relative positions of the adsorbers in
the rotor assembly. 402, 403 and 404 represent the rotor port
apertures 501, 502 and 503 (as seen in FIG. 10a) or 250, 251 and
252 (as seen in FIG. 7a), depending on which rotor face is being
described.
[0110] FIG. 10
[0111] FIG. 10a shows the second rotor valve face 38. FIG. 10b
shows the second stator valve face 24. Both figures are taken at
cross section 214 on FIG. 6. Each of the apertures 501 (L1), 502
(L2) and 503 (L3) on the face plate facilitate the flow action of
gases from one adsorber to another corresponding to the sequencing
defined in the FIGS. 4/5 description. L1, L2 and L3 correspond to
the second rotor valve openings for adsorbers 1,2 and 3,
respectively.
[0112] Reference numerals 504, 505, and 506 indicate first, second
and third light reflux exit ports, respectively, and numerals 507,
508, and 509 indicate first, second and third light reflux return
ports, respectively. Reference numeral 29 indicates the buffer
chamber.
[0113] FIG. 11
[0114] FIG. 11 shows and embodiment 600 similar to FIG. 1, but with
the adsorber housing body stationary while the first and second
valve bodies rotate.
[0115] The adsorbers are mounted at equal angular spacings in an
adsorber housing body 23, which is engaged in relative rotation
with first and second valve bodies 611 and 613 to define rotary
sealing faces of first and second valve adjacent respectively the
first and second ends of the adsorber flow paths. There is fluid
sealing engagement between the adsorber housing body and
respectively the first and second valve bodies. The adsorber
housing body 23 is stationary, while the first and second valve
bodies 611 and 613 rotate to achieve the valving function. Fluid
transfer means are provided to provide feed gas to the first valve
body 611, to remove exhaust gas from the first valve body 611, and
to deliver product gas from the second valve body 613.
[0116] In this embodiment, the first valve body has fluid seals 604
and 605 which define the feed fluid transfer chamber 601 as fluid
transfer means to provide feed gas to the first valve body between
the first valve body 611 and the casing 612. Feed gases are
conducted through conduit 614.
[0117] The first valve body also has fluid seal 605 and 606 which
define the exhaust fluid transfer chamber 602 between the first
valve body 611 and the casing 612. Chamber 602 is fluid transfer
means to remove exhaust gas from the first valve body. Exhaust
gases are conducted through conduit 615.
[0118] The second valve body 613 has fluid seals 608 that defines
the product fluid transfer chamber 610 between the second valve
body 613 and the casing 612. Chamber 610 is fluid transfer means to
provide product gas from the second valve body. Product gases are
conducted through conduit 616.
[0119] These is a shaft for each valve body that drives rotation of
the body, with shaft 603 driving first valve body 611 and shaft 609
driving second valve body 613. An option exists for these shafts to
be engaged as a single shaft to drive the valve bodies. The shafts
are driven to rotate by valve drive means 607, such as a motor.
[0120] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
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