Patent Application
20080028933
Features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though not necessarily identical components. For the sake of brevity, reference numerals or features having a previously described function may not necessarily be described in connection with other drawings in which they appear.
Embodiment(s) of the radial sieve module (and method(s) of using the same) disclosed herein may advantageously be used for the extraction of nitrogen (or other undesirable gases) to provide substantially high concentrations of oxygen for medical purposes. Furthermore, embodiment(s) of the radial sieve module may integrate one or more beds of adsorbent into one continuous, radial bed. Further, an embodiment of the radial sieve module is adapted to minimize (i.e., shorten) the adsorbent bed size and/or minimize (i.e., reduce) the number of device components. Still further, an embodiment of the radial sieve module may be used in a system incorporating a pressure swing adsorption (PSA) process and may advantageously promote a fast response PSA cycle. It is believed that the shorter bed lengths may increase the efficiency of the modules when used with appropriately timed pressurization/flow cycles.
Referring to
In an embodiment, the housing 14 generally has a substantially cylindrical shape. However, it is contemplated as being within the purview of the present disclosure that the housing 14 may be configured in any suitable shape, including, but not limited to other regular geometric shapes, or irregular geometric shapes. It is to be understood that the housing 14 is formed of a material that does not allow gas to flow through the outer wall(s) of the housing 14. Generally, the housing 14 is formed of any material that is not reactive with the gas(es) flowing in the module 10, and is able to withstand the pressure cycles that may be used. Non-limitative examples of suitable housing 14 materials include aluminum (e.g., extruded aluminum), engineering grade thermal plastics that are designed taking into account the requirements of a pressure vessel (e.g., projected pressures, etc.), or the like, or combinations thereof.
The housing 14 is sealed with two end caps 42, 42′ located adjacent the opposed ends 18, 22. In an embodiment, each of the end caps 42, 42′ is formed integrally with the housing 14. As such, the end caps 42, 42′ may be formed from the same material as the housing 14. In another embodiment, specifically shown in
It is to be understood that the seal member 16 may be formed from any suitable sealing material(s). In an embodiment, the seal member 16 includes at least one of O-rings, non-permeable die cut or molded gaskets, and/or the like, and/or combinations thereof. The end caps 42, 42′ may alternatively be designed to have a press fit with the housing 14, or they may be welded to the housing 14 and the tubes 26, 30 to form a seal therebetween. Still another option for sealing the end caps 42, 42′ to the housing 14 includes solvent bonding and/or using adhesives.
Embodiments of the radial sieve module 10 also include a seal between each of the respective tubes 26, 30 and the respective end caps 42, 42′. It is to be understood that a seal member 16, or any other suitable sealing means may be used, thereby substantially preventing gas from leaking outside of the respective tube 26, 30. In a non-limitative example, a press fit may allow enough of a seal between the inner porous tube 26 and the respective end caps 42, 42′ and between the outer porous tube 30 and the respective end caps 42, 42′.
The housing 14, and any integral end cap(s) 42, 42′ may be formed via any suitable method. One non-limitative example of such a method is molding using a mold having a predetermined shape. The predetermined shape of the mold depends, at least in part, on whether one or both of the end caps 42, 42′ are being formed integrally with housing 14.
It is to be understood that the end caps 42, 42′ may be adapted to direct gas flow. Generally, one end cap 42, 42′ may direct gas flow into the inner porous tube 26, and the other of the end caps 42′, 42 may collect gas flow as it exits the hollow channel 34. Thus, gas may be directed into the module 10 at the inner porous tube 26 via one end cap 42, 42′ at one opposed end 18, and may be directed out of the module 10 at the hollow channel 34 via another end cap 42′, 42 at the other opposed end 22.
In an alternate embodiment, one end cap 42, 42′ may direct gas flow into the hollow channel 34, and the other of the end caps 42′, 42 may collect gas flow as it exits the inner porous tube 26. Thus, gas may be directed into the module 10 at the hollow channel 34 via one end cap 42, 42′ at one opposed end 22, and may be directed out of the module 10 at the inner porous tube 26 via another end cap 42′, 42 at the other opposed end 18.
In still another alternate embodiment, one of the end caps 42, 42′ is adapted to direct gas flow and collect gas flow, while the other of the two end caps 42′, 42 acts as a sealant. As such, in this embodiment, gas flow may be directed into the inner porous tube 26 and out of the hollow channel 34 through one end cap 42, 42′.
Embodiments of the end caps 42, 42′ that allow gas to flow therethrough include one main aperture 43, 43′, and may also include additional smaller apertures 44. In a non-limitative example, the end cap 42, 42′ suitable for gas collection includes the additional smaller apertures 44. Furthermore, as shown in
The radial sieve module 10 also includes an adsorbent material 38 (shown in
It is to be understood that the bed length B is determined as a direct function of the PSA cycle used. This length B is proportional to the flow time of the gas. Shorter bed lengths are believed to drive shorter flow cycles (i.e., shorter flow times). In a non-limitative example, the bed length B is limited by a nitrogen wave front that moves through the bed (in the case of purifying oxygen) during the PSA process.
Typical cycles for PSA range from about 8 seconds to about 15 seconds. For such cycles, the bed length B may range from about 100 mm to about 400 mm. A non-limitative example embodiment of the radial sieve module 10 disclosed herein is configured to utilize PSA cycles less than about 2 seconds and have a bed length B ranging from about 5 mm to about 40 mm. This advantageously reduces the required volume of adsorbent material 38, and the total volume of the sieve module 10.
In an embodiment, the adsorbent material 38 is selected from zeolites, activated carbon, silica gel, and combinations thereof. In a further embodiment, the adsorbent material 38 is selected from Li-LSX beads; zeolite X; zeolite Y; zeolite LSX; MCM-41 zeolites; activated alumina; and/or silicoaluminophosphates (SAPOS); and/or combinations thereof. Generally, the adsorbent material 38 includes a plurality of particles. As the adsorbent material 38 is established between two porous tubes 26, 30, it is to be understood that each of the plurality of pores of the porous tubes 26, 30 has a maximum diameter smaller than a minimum diameter of each of the plurality of particles of the adsorbent material 38. This substantially ensures that the adsorbent material 38 will be maintained between the porous tubes 26, 30. As such, the size (i.e., diameter) of the adsorbent material 38 particles may depend, at least in part, on the material selected for the inner and outer porous tubes 26, 30. In some embodiments, any diameter may be suitable. As non-limitative examples, the diameter of the adsorbent material 38 particles ranges from about 100 μm to about 800 μm; or from about 400 μm to about 800 μm.
The adsorbent material 38 is capable of selectively trapping some fluid(s) (e.g., gas molecule(s), contaminants, water molecules, or the like), while allowing other fluid(s) to pass therethrough. Generally, the adsorbency rates are specific to the material 38 selected. In an embodiment, the gas flow contains at least oxygen and another gas. As a non-limitative example, the gas flow may be air, whereby an adsorbent material 38 may trap nitrogen and oxygen from the air at significantly different rates, thereby allowing the oxygen to become substantially purified. In other embodiments, the adsorbent material 38 may be designed for the purification of other gas(es) by targeting specific contaminants. In still another embodiment, the adsorbent material 38 may be used as a desiccant drying device.
In yet a further embodiment, a relatively thin (e.g., from about 1/100 of the bed length B to about 1/50 of the bed length B) skin layer of the adsorbent material 38 is converted or deactivated to act as a desiccant layer for water separation when exposed to humid gas. Once subjected to this humid gas, this adsorbent material 38 skin layer is generally incapable of separating nitrogen (or gases with a molecular size substantially similar to nitrogen), but will continue to separate the water molecules from the incoming gas and purge back out with every cycle of the PSA. The radial sieve module 10 according to embodiment(s) herein offers more surface area for converting or deactivation of the adsorbent material 38 for this desiccant filtration layer than traditional bed designs, which may prove advantageous in many instances, one example of which is in humid climates.
In an embodiment, the inner porous tube 26 and/or the outer porous tube 30 is/are formed of a porous polymeric material. As previously stated, the pores of the tubes 26, 30 are smaller than the minimum size of the adsorbent material particles. As a non-limitative example, any non-hydroscopic engineering grade thermoplastic material having a pore size smaller than a smallest diameter of the adsorbent material 38 particles may be used. In an embodiment using adsorbent material 38 particles having diameters greater than about 300 μm, the pore size of the inner and/or outer porous tubes 26, 30 is about 300 μm or less. It is to be understood, however, that if the adsorbent material 38 particles have larger diameters, the inner and outer porous tube 26, 30 pore sizes may be increased accordingly; and if the adsorbent material 38 particles have smaller diameters, the inner and outer porous tube 26, 30 pore sizes may be decreased accordingly.
Designing the bed length B with the inner and outer porous tubes 26, 30 substantially reduces the number of pieces for making the module 10. Some conventional modules have a multiple bed design in which many short beds are laid out in a linear fashion (one next to the other). This linear design substantially increases the total volume of the module; due, at least in part, to the spacing required from one bed to another, and the manifold required to distribute the gas to the multiple flow paths. In contrast, embodiment(s) of the module 10 disclosed herein advantageously have a decreased volume, while maintaining or increasing its efficiency.
The radial sieve module 10 (or a plurality of radial sieve modules 10) may be utilized in an oxygen concentrator system, which may be used to supply patients with high concentrations of oxygen for extended periods of time. Embodiments of the module 10 may also be used in a desiccant drying system. Still further, the module(s) 10 may be utilized in a system incorporating a PSA cycle/process, where one or more modules 10 may be utilized to produce, concentrate, or separate a gas.
An embodiment of a method for concentrating oxygen includes directing a gas flow through the main aperture 43, 43′ of one of the end caps 42, 42′ to the center of the inner porous tube 26 or to the hollow channel 34. It is to be understood that, initially, the gas flow travels parallel to the length of the tube 26 or channel 34. In an embodiment, the gas is pressurized (typically with a compressor) and controlled into one or more of the modules 10 by a series of valves. The valves may be controlled by a microprocessor, which takes into account the timing for the pressurization, and the flow and exhaust of the bed (i.e., the area between the inner and outer porous tubes 26, 30 where the adsorbent material 38 is located). The timing, and the bed flow/exhaust may be determined, at least in part, by the adsorbent material 38 used and the bed length B. It is to be understood that the valve design may be developed with a control algorithm to provide the proper flows based on the system design.
In an embodiment, the method also includes causing pressure in the inner porous tube 26 to increase, thereby redirecting the gas flow radially (substantially perpendicular to the initial gas flow through the tube 26) through pores of the inner porous tube 26. In another embodiment, the method includes causing pressure in the hollow channel 34 to increase, thereby redirecting the gas flow radially (substantially perpendicular to the initial gas flow through the channel 34) through pores of the outer porous tube 30. In either embodiment, an increase in pressure may be caused by a compressor. After the gas flows radially through the inner porous tube 26 or the outer porous tube 30, it contacts the adsorbent material 38, whereby (undesirable) gas molecules of the gas flow are adsorbed, thereby forming an adsorbed gas flow. It is to be understood that the adsorbed gas flow is the gas flow that continues to flow through the adsorbent material 38, and has the undesirable molecule(s) removed therefrom.
In the embodiment where gas is initially introduced into the module 10 via the inner porous tube 24, the method further includes directing the adsorbed gas flow through pores of the outer porous tube 30 and into the hollow channel 34. As the housing 14 is formed of a non-gas permeable material, the adsorbed gas flow is directed toward an end cap 42, 42′ where the gas is collected. In the embodiment where gas is initially introduced into the module 10 via the hollow channel 34, the method further includes directing the adsorbed gas flow through pores of the inner porous tube 26 and out toward an end cap 42, 42′ where the gas is collected.
It is to be understood that the dimensions disclosed herein may vary depending, at least in part, on the adsorbent material 38 utilized, and/or the capacity of the entire module 10 or system in which it is used. The diameter between the porous tubes 26, 30 (defining the bed length B) may also be determined by the adsorbent material 38 used. Still further, the length L, 50 of the tubes 26, 30 may be altered, depending, at least in part, on the output capacity required by the module 10 or the system in which it is incorporated.
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting.
