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.

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° 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° 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° 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°), 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°), 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° 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°) 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°) 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° 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° 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°.  
     
     
         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.