Patent Application
20070289445
In the following description, numerous specific details are set forth in order to provide a more thorough description of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail so as not to obscure the invention.
In general, the invention comprises gas separation systems, gas separators and methods of separating gas. One aspect of the invention is a system including a gas separator. The separator includes multiple sieve beds and a rotary valve. The rotary valve is configured to selectively deliver gas to the sieve beds for separation, and to de-pressurize, purge and then pre-pressurize the beds for the next adsorptive cycle. The rotary valve is configured so that each of the beds in the system are offset from one another in the cycle. In a preferred embodiment, at least two beds are in the adsorptive phase at all times.
One embodiment of the invention will be described with reference first to
A compressor 24 obtains air from an intake 26 and provides that air at high pressure to the system 20. In a preferred embodiment, the air 26 is atmospheric or “room” air. Of course, other sources of product, such as air or other gas to be separated, may be utilized. The air may be filtered, such as with a 0.3 micron filter 28, to remove particulate matter such as dust and fume. A silencer (not shown) may also be used to lower the in-take noise.
A fan coil 30 may be used to remove moisture from the compressed air. The fan coil 30 may be utilized to lower the temperature of the incoming air, causing moisture to condense from the air for collection. The compressed air may be delivered to a storage tank 32. Additional moisture may be condensed and collected from the air at the storage tank 32.
The compressed air is then introduced to the separator 22. One or more embodiments of a separator 22 in accordance with the invention is detailed below. In a preferred embodiment, the separator 22 is utilized to separate oxygen from the air. In this process, substantially pure oxygen is delivered as the desired output or product. Nitrogen and other gases are generated as exhaust or waste product. As indicated above, the separator of the invention could be utilize to separate or concentrate other product from an incoming product supply.
The oxygen may be collected in a reservoir (not shown in
The oxygen may be delivered through a one-way valve 38 which ensures that the sieve beds of the separator 22 are sealed from atmospheric moisture and pollution when the system is not in operation. The separated or generated oxygen then goes through the regulator valve 40 to lower the output pressure, such as to about 0.04-0.05 MPa. The oxygen may also pass through a filter 42, such as a 0.2 micron filter, to further remove any unwanted particles and ensure the oxygen is clean.
A flow-meter 44 may be used to regulate the oxygen output to a desired flow rate. For example, as detailed below, the oxygen may be delivered to a breathing unit associated with a respiratory patient. The flow-meter or flow regulator may be used to regulate the flow to the patient. Lastly, the oxygen may be passed through a humidifying device 46 to add moisture thereto (so that it is not so dry, such as in the case where it is being delivered directly to the lungs of patient), before the oxygen is delivered to an output 48. The output 48 might be tube, port or the like, such as might be connected to a supply line leading to a respiratory device or the like.
One embodiment of a concentrator or separator 22 in accordance with the invention will now be described in greater detail with reference to
The sieve beds 50 are preferably of any type now known or later developed which are useful in separating oxygen or other desired product from an incoming product supply, preferably atmospheric or room air. Preferably, the sieve bed 50 comprises a material which readily absorbs nitrogen, but not oxygen, thereby permitting oxygen to pass there through.
Preferably, the separator 22 includes five (5) sieve beds 50. As illustrated, the sieve beds 50 are preferably located in a pentagonal orientation around a centerline C or center of the separator 22, thereby providing a small profile or size for the separator 22.
The sieve beds 50 have a top or proximal end and a bottom or distal end. The bottom or distal end of each bed 50 is located at the module base 57. As detailed below, air is provided to the bottom end of each sieve bed 50. The air is then separated, with oxygen (or other desired product) being delivered to the top end of each sieve bed 50. The top ends of the beds 50 correspond to the module top or cover 56. Oxygen passing through the beds 50 is delivered to the reservoir 58.
The separator 22 includes means for selectively delivering air or other product to each bed 50 for separation. In a preferred embodiment, the means comprises the control valve 52. In that the control valve is, in a preferred embodiment, a rotating valve, the control valve is also referred to herein as a rotating valve 52. One embodiment of the rotating valve 52 of the invention will be detailed with reference to
In general, the valve 52 comprises five (5) main elements or portions. The valve 52 includes a housing. In a preferred embodiment, the housing comprises an upper housing 60 and a lower housing 62. The valve 52 also comprises a static plate or stator 64, a rotating plate or rotor 66, and means for moving the rotating plate 66. In one embodiment, as illustrated in
As illustrated, the lower housing 62 has a top and a bottom. In one embodiment, the lower housing 62 is generally cylindrical in shape and is a generally solid body. The lower housing 62 may have a variety of configurations, however. In a preferred embodiment, the lower housing 62 defines a depression or inset in the top thereof. As illustrated, the static plate 64 preferably sits within this depression. When the static plate 64 is generally cylindrical in shape, the inset or depression is preferably similarly shaped, so that the static plate 64 fits tightly within the lower housing 62.
A waste gas exhaust passage 68 extends through the lower housing 62 from the top to the bottom thereof. As illustrated, the waste passage 68 terminates at the inset and is preferably arranged to align with a mating passage in the static plate 64 (described below). As illustrated, a nipple 70 may be located at the exit of the waste gas exhaust passage 68 from the bottom of the lower housing 62, such as to permit connection of a gas line thereto.
The lower housing 62 also defines an air passage 72 corresponding to each of the sieve beds 50. Thus, in the embodiment where the separator 22 includes five (5) sieve beds, there are preferably five (5) air passages 72. As illustrated, each air passage 72 leads from the inset through the lower housing 62 to a side or peripheral portion thereof. In this orientation, each air passage 72 turns ninety (90) degrees along its path. A nipple 74 or other connector may be located at the exit of each air passage 72 from the lower housing 62.
As described above, the static plate 64 sits at least partially within the inset in the top of the lower housing 62. In one embodiment, the static plate 64 is a disc-like (generally circular peripheral shape) member. As illustrated, one or more seals 76, such as O-rings, may be located between the static plate 64 and the lower housing 62 to form an air-tight seal there between.
Referring also to
Referring again to
The upper housing 60 defines a chamber 78. The chamber 78 extends inwardly from the bottom thereof, such than when the upper housing 60 is mounted to the lower housing 62, the chamber 78 is generally closed.
An air intake passage 80 leads from the exterior of the upper housing 60 there through to the chamber 78. In one embodiment, this passage 80 is a generally straight, horizontally positioned passage. A nipple 82 or other fitting may be located at the exterior of the upper housing 60, such as for connection to an air pipe. Preferably, compressed air is delivered through the passage 80 to the chamber 78.
As illustrated, the chamber 78 is preferably sized to accept the rotating plate 66 therein. In one embodiment, the chamber 78 is generally positioned about a centerline C through the valve 52. The rotating plate 66 is designed to rotate about this centerline C within the chamber 78.
The rotating plate 66 is a generally disc-shaped member. The rotating plate 66 is located in the chamber 78 and positioned adjacent the static plate 64, and more preferably is placed on top of the static plate 64 in direct and sealing contact therewith. The rotating plate 66 is designed to cooperate with the static plate 64 to selectively open and close the air and waste gas passages 68b, 72b through the static plate 64 which leads to the corresponding passages 68, 72 through the lower housing 62. Additional details of the rotating plate 66 will be provided with reference to
As indicated, means are provided for selectively rotating the rotating plate 66. In one embodiment, this means comprises a motor 84. The motor 84 is preferably located above the upper housing 60. In one embodiment, the upper housing 60 defines a drive rod passage 86 from the top thereof through to the chamber 78. The passage 86 is preferably positioned along the centerline C.
The motor 84 is preferably an electrically-powered, synchronous motor. The motor 84 moves a drive rod 88 which is connected to the rotating plate 66. The drive rod 88 extends from the motor 84 through the drive rod passage 86.
In one embodiment, one or more seals 90, such as O-rings, are located between the drive rod 88 and the upper housing 60 to seal the space there between. In addition, one or more bearings 94 may be located around the drive rod 88, such as near the top of the chamber 78 in the upper housing 60, to rotationally support the drive rod 88.
Biasing means, such as a spring 92, preferably provide a pre-loading force to hold the rotating plate 66 in place. As illustrated, the spring 92 is a coil-spring which is located at least partially between the drive rod 88 and the rotating plate 66.
In one embodiment, at least the static plate 64 and rotating plate 66 are constructed of ceramic. This has the advantage that the plates are air-tight, hardwearing and self lubricating.
The rotating plate 66 will now be described in more detail with reference to
As illustrated, the second and fourth areas 98, 102 are defined by generally solid portions of the rotating plate 66 which effectively block air or waste gas flow. In one embodiment, the first area 96 comprises an inset area at the periphery of the rotating plate 66 (inset relative to the shape of the rotating plate 66 if it were entirely circular or cylindrical in shape). The third area 100 comprises an inset or depression formed in the bottom of the rotating plate 66.
As illustrated, as the rotating plate 66 rotates, the third area 100 selectively aligns with one or more of the air passages 72b through the static plate 64. When this occurs, the air passage 72b through the static plate 64 is placed in communication with the waste passage 68b, thereby allowing waste gas to flow from the one or more sieve beds 50 (corresponding to the air passage(s) 72(b)) to the waste gas exhaust from the valve 52. As detailed below, one advantage of the invention is the simplicity of the valve and passage configuration. As indicated, the same passages which are utilized to deliver gas for separation are used to deliver waste gas back to the valve for routing to the exhaust.
In addition, as the rotating plate 66 rotates, the first area 96 selectively aligns with one or more of the air passages 72b through the static plate 64. When this occurs, compressed air which is delivered to the chamber 78 (see
Operation of the separator 52 will now be described in more detail. In general, each sieve bed 50 undergoes a PSA cycle which includes the following phases.
One phase is the “adsorption” phase. In accordance with this phase, high pressure gas or other product is delivered to a sieve bed for separation. The gas or other product is separated by the sieve bed. As detailed above, where the gas is atmospheric or room air, the sieve bed may be configured to separate the oxygen from the remaining gasses (primarily nitrogen). The separated gas is delivered through the one or more delivery holes or passages, such as to the product gas reservoir.
This phase will be described relative to one of the sieve beds 50 of the system 20 described above. With specific reference to the embodiment separator 22 detailed above, in this step, compressed air is delivered through the air passage 80 to the chamber 78 of the valve 52. When the first area 98 of the rotating plate 66 is aligned with the air passage 72b in the static plate 64, pressurized air flows through the static plate 64, through the corresponding air passage 72 in the lower housing 62, to the sieve bed 50.
Another phase is “co-current de-pressurization” phase. In this phase, the source of compressed air or other product is removed from the sieve bed. Separated product, such as oxygen, continues to be generated and be released from the sieve bed through a top regulating exit hole. The gas pressure within the sieve bed will gradually decrease down to very close to atmospheric pressure.
This phase will be described relative to one of the sieve beds 50 of the system 20 described above. With specific reference to the embodiment separator 22 detailed above, in this step, the rotating plate 66 is oriented so that the second portion 98 covers the air passage 72b which leads through the static plate 64 and thereon to the sieve bed 50. As such, the supply of compressed air is cut off from that sieve bed. The already delivered air, which is at a high pressure, continues to be separated as it passes through the sieve bed 50. As oxygen is separated and delivered from the sieve bed, the gas pressure in the sieve bed decreases.
Another phase is the “counter-current pressurization” phase. During this phase, the remaining gas in the sieve bed is released back through the entry hole, thus further lowering the internal gas pressure. At this time, adsorptive gas element starts to release from sieve bed.
This phase will be described relative to one of the sieve beds 50 of the system 20 described above. With specific reference to the embodiment separator 22 detailed above, in this step, the rotating plate 66 is oriented so that the third portion 100 the air passage 72 from the sieve bed 50 (which connects with the air passage 72b through the static plate 64) with the waste gas passage 68b which leads through the static plate 64 and the waste gas passage 68 through the lower housing 62, to the waste gas outlet. At this time, gas which was delivered but not separated, and waste product (i.e. product remaining after separation) can flow from the sieve bed 50 to the waste gas outlet, thus lowering the pressure within the sieve bed 50.
Another phase is the “purge” phase. During this phase, a small portion of the product gas enters or flows back into the sieve bed to help re-generate the molecule sieve and prepare the sieve for the next cycle. As this product gas flows back, it purges waste and unseparated gas.
This phase will be described relative to one of the sieve beds 50 of the system 20 described above. With specific reference to the embodiment separator 22 detailed above, in this step, the rotating plate 66 remains oriented in a position where the waste gas can escape or exhaust from the sieve bed 50. However, some product gas re-enters the sieve bed (essentially flowing backwardly, as from the top to the bottom of the sieve beds of the valve 52 as described). This product gas purges nitrogen and other separated gas from the sieve bed from that bed back through the valve 52.
Lastly, another phase is the “pre-pressurization” phase. During this phase, the air or product entry to the sieve bed is again closed. A small portion of the less adsorptive gas element (such as oxygen) enters from the regulating hole to start pressurizing the sieve bed and ready the bed for the next adsorption in the next cycle.
This phase will be described relative to one of the sieve beds 50 of the system 20 described above. With specific reference to the embodiment separator 22 detailed above, in this step, the rotating plate 66 is oriented so that the fourth portion 102 again covers the air passage 72 which leads through the static plate 64 and thereon to the sieve bed 50. As this time, as product gas continues to enter the sieve bed, the gas pressure in the sieve bed increases.
In the preferred embodiment of the invention, the separator 22 has five (5) sieve beds 50. The rotating plate 66 is rotated so that each of the sieve beds 50 goes through the above-described five phase cycle each time the rotating plate 66 makes a full cycle (i.e. full 360 degree rotation). Because various cycles are defined by the areas of the rotating plate 66, the sieve beds are simultaneously in different of the phases, depending upon the relative position of the rotating plate 66 to the stator 64 (and thus relative to the delivery passages leading to the sieve beds).
One example of the cycle sequence of each sieve bed according to time is shown in the following table:
This configuration has a number of benefits. First, there are always two sieve beds in the adsorption phase, and only one sieve bed has a bigger difference in pressure at switching time. This ensures that the stability of output gas pressure of the system. Hence the flow, as well as the concentration, of the product gas remains stable.
In accordance with the invention, the cycle time may be adjusted by changing the speed of the rotating plate. Notably, the time of each step or phase of the PSA cycle can be adjusted by the position and/or angular extent of the portions of the rotating plate (i.e. the “absorption” phase can be extended by increasing the size of the cut-away portion 96 of the plate). As one example, to deliver a flow rate of 5 LPM of the product gas, the cycle time may be around 15-30 seconds, which corresponds to a rotating plate rotational speed of about 2-4 rpm.
The system, separator and method of the invention have a number of additional features and advantages. One advantage is that air is well filtered and passed through a silencer to the compressor. The compressor then generates a stream of high pressure compressed air. This compressed air may be cooled and passed through a container for condensation to remove excess moisture before entering the separator. Inside the separator, the rotating plate always exposes two air passages leading through the static plate to two corresponding sieve beds. Nitrogen, water and carbon dioxide (or other products, as desired) are adsorbed on the molecule sieve. Oxygen, the less adsorbed gas element, will be produced through the regulator hole at top of the sieve bed as the product gas. The product gas will be collected at the oxygen reservoir (pressure at about 0.1 MPa) and further regulated to about 0.04-0.05 MPa before passing out for patient use.
Other advantages of the system and method is that providing a stable production gas (such as oxygen) output pressure and flow rate. The system and method also have a high gas separation efficiency, such that a smaller mass of adsorpt, such as molecule sieve, needs to be used to produce the same volume and concentration of oxygen than prior systems and devices. The system and method are also very responsive to change—such as when the desired output is changed from a lower volume to higher volume oxygen output.
The system and method operate with small compressor pressure variation (in the range of +/−0.02 MPa) as compared to traditional 2 bed systems (+/−0.05 MPa). This reduction in pressure variation prolongs the life of compressor as well as reduces noise level of the entire system, which is crucial for patients under medical treatment.
It will be appreciated that the system and method of the invention may have other configurations than specifically illustrated and described. For example, the separator of the invention might be utilized with a system which differs from that illustrated in
The separator of the invention may also have configurations other than as specifically illustrated while still being configured to implement the method of product separation. Various aspects of the invention, including aspects of the separator, may have applicability to other products or methods. For example, the control valve might be used with separators otherwise having other configurations.
The separator might be configured, for example, with multiple product gas reservoirs or a separate product gas reservoir. The control valve might be used with a separator having other numbers of sieve beds. The sieve beds might be configured other than as illustrated (for example, be cross-sectionally square rather than circular).
In one embodiment, the stator might be integral with the lower housing, rather than being a separate element which is mounted in an inset thereof. The passages may have a variety of shapes, and the passages might comprise tubes, pipes or other members defining generally closed or contained flow paths.
One advantage of the embodiment separator described and illustrated is its simplicity. The separator employs a minimal number of components and has few moving components. The passage configuration of the separator allows for five distinct sieve bed phases, even though only a single passage leads to each sieve bed. Instead of multiple passages like in prior art designs, the configuration of the invention allows the separator to have a less complex and more compact configuration. As detailed above, for example, waste gas is routed back from the sieve beds to the control valve (and there beyond to an exhaust point) using the same passages as which deliver product to be separated. In addition, the control valve can be located at the bottom of the separator close to the bottom of the beds, and the product gas can be stored at the top of the beds, providing a compact configuration (since cross-passages and the like, as are common in other designs, do not need to be provided between the ends of the beds).
The rotor/stator combination is particularly advantageous in that it allows the sieve beds to cycle through the five phases merely by rotating the rotor relative to the stator. No other valves or other elements are needed to control the gas flow (of delivery or waste gas).
It will be understood that the above described arrangements of apparatus and the method there from are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.
