Flow regulated pressure swing adsorption system

Abstract

Pressure swing adsorption (PSA) separation of a gas mixture is performed in an apparatus with a plurality of adsorbent beds. The invention provides rotary multiport distributor valves to control the timing sequence of the PSA cycle steps between the beds, with flow controls cooperating with the rotary distributor valves to control the volume rates of gas flows to and from the adsorbent beds in blowdown, purge, equalization and repressurization steps.

We claim:  
     
       1. Process for separating first and second components of a feed gas mixture, the first component being more readily adsorbed under increase of pressure relative to the second component which is less readily adsorbed under increase of pressure over an adsorbent material, such that a gas mixture of the first and second components contacting the adsorbent material is relatively enriched in the first component at a lower pressure and is relatively enriched in the second component at a higher pressure when the pressure is cycled between the lower and higher pressures at a cyclic frequency of the process defining a cycle period; providing for the process a number “N” of substantially similar adsorbent beds of the adsorbent material, with said adsorbent beds having first and second ends; and further providing for the process a first rotary distributor valve connected in parallel to the first ends of the adsorbent beds and a second rotary distributor valve connected in parallel to the second ends of the adsorbent beds, with flow controls cooperating with the first and second distributor valves; introducing the feed gas mixture at substantially the higher pressure to the first distributor valve; and rotating the first and second distributor valves so as to perform in each adsorbent bed the sequentially repeated steps within the cycle period of: 
       (A) supplying a flow of the feed gas mixture at the higher pressure through the first distributor valve to the first end of the adsorbent bed during a feed time interval, withdrawing gas enriched in the second component from the second end of the adsorbent bed, and delivering a portion of the gas enriched in the second component as a light product gas,  
       (B) withdrawing a flow of gas enriched in the second component as light reflux gas from the second end of the adsorbent bed through the second distributor valve, so as to depressurize the adsorbent bed from the higher pressure toward an equalization pressure less than the higher pressure, while controlling the flow so that the pressure in the bed approaches the equalization pressure within an equalization time interval,  
       (C) withdrawing a flow of light reflux gas enriched in the second component from the second end of the adsorbent bed through the second distributor valve, so as to depressurize the adsorbent bed from approximately the equalization pressure to an intermediate pressure less than the equalization pressure and greater than the lower pressure, while controlling the flow so that the pressure in the bed reaches approximately the intermediate pressure within a cocurrent blowdown time interval,  
       (D) withdrawing a flow of gas enriched in the first component from the first end of the adsorbent bed through the first distributor valve, so as to depressurize the adsorbent bed from approximately the intermediate pressure to approach the lower pressure, while controlling the flow so that the pressure in the bed approaches the lower pressure within a countercurrent blowdown time interval,  
       (E) returning a flow of light reflux gas enriched in the second component from the second distributor valve to the second end of the adsorbent bed at substantially the lower pressure, while withdrawing gas enriched in the first component from the first end of the adsorbent bed and through the first distributor valve over a purge time interval, said flow of gas enriched in the second component from the second distributor valve being withdrawn from another of the adsorbent beds which is undergoing cocurrent blowdown step (C) of the process,  
       (F) returning a flow of light reflux gas enriched in the second component from the second distributor valve to the bed, so as to repressurize the adsorbent bed from approximately the lower pressure to approach the equalization pressure, while controlling the flow so that the pressure in the bed approaches the equalization pressure within an equalization time interval, said flow of gas enriched in the second component from the second distributor valve being withdrawn from another of the adsorbent beds which is undergoing equalization step (B) of the process,  
       (G) admitting gas to the adsorbent bed, so as to further repressurize the adsorbent bed from the equalization pressure toward the higher pressure, while controlling the flow so that the pressure in the bed approaches the higher pressure within a repressurization time interval,  
       (H) cyclically repeating steps (A) to (G).  
     
     
       2. The process of  claim 1 , further varying cycle frequency so as to achieve desired purity, recovery and flow rate of the light product gas. 
     
     
       3. The process of  claim 1 , in step (G) returning a flow of light reflux gas enriched in the second component from the second distributor valve to the bed, so as to repressurize the adsorbent bed to approach the higher pressure, while controlling the flow so that the pressure in the bed approaches the higher pressure within a repressurization time interval, the flow of gas enriched in the second component from the second distributor valve being withdrawn from another of the adsorbent beds which is undergoing feed step (A) of the process. 
     
     
       4. The process of  claim 1 , in step (G) admitting feed gas from the first distributor valve to the bed, so as to repressurize the adsorbent bed to approach the higher pressure, while controlling the flow so that the pressure in the bed approaches the higher pressure within a repressurization time interval. 
     
     
       5. The process of  claim 1 , supplying the feed gas mixture during the initial part of step (A) to the first end of the adsorbent bed, and then supplying a second feed gas with a greater concentration of he first component during the later part of step (A) to the first end of the adsorbent bed. 
     
     
       6. The process of  claim 5 , recompressing a portion of the gas enriched in the first component withdrawn from the first end of an adsorbent bed during step (D) or preferably (E) to substantially the higher pressure, and supplying this portion of the gas enriched in the first component as the second feed gas through the first distributor valve to the first end of the adsorbent bed in the latter part of the feed time interval in step (A). 
     
     
       7. The process of  claim 6 , providing a feed selector valve to alternatingly direct the feed gas mixture or the heavy reflux gas through the first distributor valve to the first end of the adsorbent bed, and switching the feed selector valve at a frequency “N” times the cycle frequency. 
     
     
       8. The process of  claim 1 , exchanging light reflux gas enriched in the second component between a bed undergoing step (B) and another bed undergoing step (F) directly through the second distributor valve in substantially identical equalization time intervals for those steps (B) and (F). 
     
     
       9. The process of  claim 8 , in which the cycle period is approximately the sum of the feed time interval, twice the equalization time interval, the cocurrent blowdown time interval, the purge time interval, and the repressurization time interval. 
     
     
       10. The process of  claim 1 , further providing adjustable orifices interposed between the second end of each adsorbent bed and the second distributor valve as flow controls cooperating with the second distributor valve, one adjustable orifice being provided for each bed and the orifices being adjusted simultaneously so as to have substantially identical settings at any time, and adjusting the orifices so as to control the flow at the second ends of the adsorbent beds in steps (B), (C), (E), (F) and (G). 
     
     
       11. The process of  claim 10 , further providing a product delivery check valve for each adsorbent bed communicating from the second end of that adsorbent bed to a light product manifold, and delivering the light product through the product delivery check valves. 
     
     
       12. The process of  claim 10 , in which the time intervals of steps (B), (C) and (F) are substantially equal, so that the intermediate pressure remains substantially constant as the orifices are adjusted. 
     
     
       13. The process of  claim 10 , in which the orifices are adjusted by switching between discrete settings. 
     
     
       14. The process of  claim 1 , further delivering the light product gas through the second distributor valve. 
     
     
       15. The process of  claim 1 , further providing an adjustable orifice in the second distributor valve as a flow control cooperating with the second distributor valve, and adjusting the orifice so as to control the flow in step (C). 
     
     
       16. The process of  claim 1 , further providing adjustable orifices in the second distributor valve as flow controls cooperating with the second distributor valve, and adjusting the orifices so as to control the flow at the second ends of the adsorbent beds in steps (B), (C), (E), (F) and (G). 
     
     
       17. The process of  claim 1 , further providing a flow control cooperating with the first distributor valve to control the flow in step (D) so as to establish the intermediate pressure relative to the higher and lower pressures, such that the ratio of the difference between the intermediate pressure and the lower pressure to the difference between the higher pressure and the lower pressure is in the range of approximately 0.15 to 0.25. 
     
     
       18. The process of  claim 1 , further controlling the flow in step (A) by establishing the volumetric flow of the feed gas mixture at the higher pressure. 
     
     
       19. The process of  claim 1 , further controlling the flow in step (A) by regulating the pressure at which the product gas is withdrawn. 
     
     
       20. The process of  claim 1 , further controlling the flow in each step so as to avoid damaging the adsorbent by transient high flow velocity in the adsorbent bed. 
     
     
       21. The process of  claim 1 , further controlling the flow velocities in steps (B), (C), (D), (F) and (G) so that the ratio of the peak flow velocity to the average flow velocity in those steps will not exceed approximately 2:1. 
     
     
       22. Apparatus for separating first and second components of a feed gas mixture, the first component being more readily adsorbed under increase of pressure relative to the second component which is less readily adsorbed under increase of pressure over an adsorbent material, such that gas mixture of the first and second components contacting the adsorbent material is relatively enriched in the first component at a lower pressure and is relatively enriched in the second component at a higher pressure when the pressure is cycled between the lower and higher pressures at a cyclic frequency of the process defining a cycle period, the apparatus including 
       (a) a number “N” of substantially similar adsorbent beds of the adsorbent material, with said adsorbent beds having first and second ends defining a flow path through the adsorbent material;  
       (b) light product delivery means to deliver a light product flow of gas enriched in the second component from the second ends of the adsorbent beds;  
       (c) a first rotary distributor valve connected in parallel to the first ends of the adsorbent beds; the first distributor valve having a stator and a rotor rotatable about an axis; the stator and rotor comprising a pair of relatively rotating valve elements, the valve elements being engaged in fluid sealing sliding contact in a valve surface, the valve surface being a surface of revolution coaxial to the axis, each of the valve elements having a plurality of ports to the valve surface and in sequential sliding registration with the ports in the valve surface of the other valve element through the relative rotation of the valve elements; one of the valve elements being a first bed port element having N first bed ports each communicating to the first end of one of the N adsorbent beds; and the other valve element being a first function port element having a plurality of first function ports including a feed port, a countercurrent blowdown port and a purge exhaust port; with the bed ports spaced apart by equal angular separation between adjacent ports; and with the first function ports and first bed ports at the same radial and axial position on the valve surface so that each first function port is opened in sequence to each of the N first bed ports by relative rotation of the valve elements;  
       (d) a second rotary distributor valve connected in parallel to the second ends of the adsorbent beds and cooperating with the first distributor valve; the second distributor valve having a stator and a rotor rotatable about an axis; the stator and rotor comprising a pair of relatively rotating valve elements, the valve elements being engaged in fluid sealing sliding contact in a valve surface, the valve surface being a surface of revolution coaxial to the axis, each of the valve elements having a plurality of ports to the valve surface and in sequential sliding registration with the ports in the valve surface of the other valve element through the relative rotation of the valve elements; one of the valve elements being a second bed port element having N second bed ports each communicating to the second end of one of the N adsorbent beds; and the other valve element being a second function port element having a plurality of second function ports including a plurality of light reflux withdrawal ports and light reflux return ports, with each light reflux return port communicating through the second function element to a light reflux withdrawal port; with the bed ports spaced apart by equal angular separation between adjacent ports; and with the function ports and bed ports at the same radial and axial position on the valve surface so that each function port is opened in sequence to each of the N bed ports by relative rotation of the valve elements;  
       (e) drive means to establish rotation of the rotors, and hence relative rotation of the bed port elements and the function port elements of the first and second distributor valves, with a phase relation between the rotation of the rotors and angular spacing of the function ports of the first and second distributor valves so as to establish for each adsorbent bed communicating to corresponding first and second bed ports the following sequential and cyclically repeated steps at a cycle frequency for those bed ports:  
       (i) the first bed port is open to the feed port, while light product gas is delivered by the light product delivery means,  
       (ii) the second bed port is open to a light reflux withdrawal port,  
       (iii) the first bed port is open to the countercurrent blowdown port,  
       (iv) the first bed port is open to the purge exhaust port, while the second bed port is open to a light reflux return port;  
       (f) countercurrent blowdown flow control means cooperating with the first distributor valve;  
       (g) light reflux flow control means cooperating with the second distributor valve;  
       (h) feed supply means to introduce the feed gas mixture to the feed port of the first distributor valve at substantially the higher pressure; and  
       (i) exhaust means to remove gas enriched in the first component from the purge exhaust port of the first distributor valve.  
     
     
       23. The apparatus of  claim 22 , in which the second function ports of the second distributor valve include light reflux withdrawal ports to withdraw light reflux gas enriched in the second component from beds undergoing feed, equalization depressurization and cocurrent blowdown steps; light reflux return ports to supply gas enriched in the second component to beds undergoing purge, equalization pressurization and repressurization steps; and each light reflux withdrawal port communicates to a light reflux return port through an orifice; so as to establish by rotation of the distributor valve rotors the following sequential and cyclically repeated steps for the adsorbent bed of: 
       (A) the first bed port is open to the feed port, while the second bed port is open to a light reflux withdrawal port communicating through an orifice to a light reflux return port open to repressurize another bed undergoing step (F) below, and light product gas is delivered from the second end of the adsorbent bed by a light product delivery valve;  
       (B) the second bed port is open for pressure equalization to a light reflux withdrawal port communicating through an orifice to a light reflux port open to another bed undergoing step (F) below, so as to equalize the pressures of the beds;  
       (C) the second bed port is open for cocurrent blowdown to a light reflux withdrawal port communicating through an orifice to a light reflux port open for purging to another bed undergoing step (E) below;  
       (D) the first bed port is open to the countercurrent blowdown port, so as to depressurize the bed to the lower pressure;  
       (E) the first bed port is open to the purge exhaust port, while the second bed port is open to a light reflux return port so as to receive light reflux gas from another bed undergoing step (C) above;  
       (F) the second bed port is open to a light reflux return port so as to receive light reflux gas from another bed undergoing step (B) above for pressure equalization; and  
       (G) the second bed port is open to a light reflux return port so as to receive light reflux gas from another bed undergoing step (A) above for repressurization.  
     
     
       24. The apparatus of  claim 23 , in which the first bed port is opened to the feed port before light product gas is delivered from the second end of the adsorbent bed by the light product delivery valve, so that repressurization of the adsorbent bed is achieved at least in part by feed gas. 
     
     
       25. The apparatus of  claim 23 , in which each light reflux withdrawal port communicates to a light reflux return port through an orifice which is an adjustable orifice, provided as light reflux flow control means. 
     
     
       26. The apparatus of  claim 23 , in which the first bed port element is the stator, and the first function port element is the rotor, of the first distributor valve; and the second bed port element is the stator, and the second function port element is the rotor, of the second distributor valve. 
     
     
       27. The apparatus of  claim 26 , in which each light reflux withdrawal port communicates to a light reflux return port through an orifice which is an adjustable orifice within the rotor, provided as light reflux flow control means. 
     
     
       28. The apparatus of  claim 26 , with actuator means to control the adjustable orifice from outside the rotor while the rotor is revolving. 
     
     
       29. The apparatus of  claim 28 , in which the adjustable orifice is provided as a throttle valve within the rotor, and the actuator means is coupled to the throttle valve through a mechanical linkage. 
     
     
       30. The apparatus of  claim 26 , in which each light reflux withdrawal port communicates to a light reflux return port through an adjustable orifice which is a throttle valve external to the rotor, with transfer chambers having rotary seals providing fluid communication between the throttle valve and the light reflux withdrawal port, and between the throttle valve and the light reflux return port. 
     
     
       31. The apparatus of  claim 26 , in which the light reflux control means includes an adjustable orifice or throttle valve interposed between the second end of each adsorbent bed and the second distributor valve, and means to adjust the orifices or throttle valves simultaneously such that each of the adjustable orifices will have substantially identical settings at each time. 
     
     
       32. The apparatus of  claim 31 , in which each of the adjustable orifices is provided by at least two fixed orifices in parallel, with one of the fixed orifices always open to flow, and another orifice being opened or closed to flow by a selector valve so as establish respectively less restrictive and more restrictive discrete settings of the adjustable orifice. 
     
     
       33. The apparatus of  claim 31 , in which the light product delivery means for each adsorbent bed is provided as a check valve enabling flow from the second end of that adsorbent bed to a product delivery manifold. 
     
     
       34. The apparatus of  claim 31 , in which the light product delivery means is the second distributor valve, provided with a light product delivery port; and a check valve is provided in parallel with each adjustable orifice or throttle valve so as to permit unrestricted flow from the second end of each bed to the second distributor valve. 
     
     
       35. The apparatus of  claim 22 , with the drive means being a variable speed drive controlled by a cycle frequency controller. 
     
     
       36. The apparatus of  claim 22 , with the drive means including angular velocity variation means to vary the angular velocity of the rotor of the first distributor valve at a multiple “N” times the cycle frequency, so as to extend the time interval during which a function port is substantially fully open to each bed port, and to reduce the time interval during which that function port is substantially closed to any bed port, while maintaining the minimum angular velocity of the rotor during the cycle to be greater than zero. 
     
     
       37. The apparatus of  claim 36 , in which the angular velocity variation means is provided as a pair of noncircular gears in the drive train to the first distributor valve. 
     
     
       38. The apparatus of  claim 22 , in which a function port is shaped so as to provide a gradually opening orifice so as to impose relatively intensive throttling at the beginning of a blowdown, pressurization or equalization step. 
     
     
       39. The apparatus of  claim 22 , in which the valve surface of a distributor valve is a flat disc normal to the axis of that valve, and with loading means to establish fluid sealing sliding contact between the stator and rotor of that distributor valve. 
     
     
       40. The apparatus of  claim 39 , in which the loading means is in part provided by compression springs. 
     
     
       41. The apparatus of  claim 39 , in which the loading means includes a plurality of axially aligned loading pistons disposed in a coaxial annulus within the valve rotor at substantially the radius of the function ports, with each piston communicating to the local gas pressure at its axially projected position in the valve surface, and the pistons reacting against a rotating thrust plate so as to achieve approximate radial balance. 
     
     
       42. The apparatus of  claim 39 , in which the loading means to establish fluid sealing contact between the rotor and stator is provided by axially aligned fluid transfer sleeve for each bed port of the stator and providing sealed fluid communication to the corresponding adsorbent bed of each bed port, with the fluid transfer sleeves having enough axially projected area so as to thrust the stator against the rotor in sealing contact, with optional assistance of compression springs. 
     
     
       43. The apparatus of  claim 42 , in which a clearance space between stator and the fluid transfer sleeves may be used as a fluid flow passage to achieve enhanced convective cooling of the valve. 
     
     
       44. The apparatus of  claim 39 , in which the loading means to establish fluid sealing contact between the rotor and stator is provided by a thrust slipper reacting against a stationary thrust plate and engaged by axially compliant sealing means to the valve rotor so as to define a chamber pressurized by feed fluid to thrust the rotor against the valve sealing surface. 
     
     
       45. The apparatus of  claim 44 , in which the thrust slipper provides fluid transfer means to convey feed fluid from a stationary housing to the rotor. 
     
     
       46. The apparatus of  claim 44 , in which the thrust slipper is eccentrically positioned and radially offset from the axis of said rotor toward the high pressure feed port and away from the low pressure exhaust port, so as to balance approximately the pressure distribution in the valve sealing surface. 
     
     
       47. A rotary pressure swing adsorption process for separating a first component from a second component of a feed gas mixture where the first component is more readily adsorbed by an adsorbent material at increased pressure relative to the second component, comprising: 
       
         providing a rotary PSA device having a rotor for rotation relative to a stator and a plurality of adsorbent beds, each bed having a flow path through adsorbent material from a first end to a second end;  
       
       
         supplying a feed gas mixture comprising at least the first component and the second component to a first end of a first adsorbent bed at a higher pressure relative to a lower pressure of a pressure swing cycle;  
       
       
         withdrawing a gas from the first adsorbent bed; and  
       
       
         providing a control mechanism operating to control flow of at least a portion of a withdrawn gas for supply to a second adsorbent bed, thereby substantially depicting the second adsorbent bed of the component having a substantially reduced concentration in the withdrawn gas to a level substantially equal to that prior to introducing the feed gas mixture to the second bed.  
       
     
     
       48. The process according to  claim 47  where the adsorbent beds are rotated by the rotor.  
     
     
       49. The process according to  claim 47  where the adsorbent beds are relatively rotating with respect to the rotor.  
     
     
       50. The process according to  claim 47  where the component having a substantially reduced concentration in the withdrawn gas is the first component.  
     
     
       51. The process according to  claim 47  where the withdrawn gas is light reflux gas.  
     
     
       52. The process according to  claim 47  where the control mechanism is a control valve in a fluid path between the first and a second adsorbent bed to control the flow of the portion of withdrawn gas to the second adsorbent bed.  
     
     
       53. The process according to  claim 52  where the withdrawn gas is drawn from one end of the first adsorbent bed and a portion of the withdrawn gas is delivered to a corresponding end of the second adsorbent bed.  
     
     
       54. The process according to  claim 53  where the withdrawn gas is light reflux gas.  
     
     
       55. The process according to  claim 54  where the light reflux gas is withdrawn from the second end of the first adsorbent bed and a portion of the light reflux gas is delivered to the second end of the second adsorbent bed.  
     
     
       56. The process according to  claim 52  where the gas flow is controlled so that the pressure in the second adsorbent bed is substantially the same pressure as in the first adsorbent bed before the end of an equalization time interval.  
     
     
       57. The process according to  claim 47  where the pressure in the second adsorbent bed is increased to an equalization pressure higher than the lower pressure by supplying a sufficient amount of the withdrawn gas to increase the pressure in the second adsorbent bed to the equalization pressure.  
     
     
       58. The process according to  claim 47  and further comprising withdrawing gas enriched in the first component from the first end of the first adsorbent bed to further depressurize the adsorbent bed.  
     
     
       59. The process according to  claim 47  and further comprising returning a portion of the withdrawn gas as purge gas to the second end of the first adsorbent bed at substantially a lower pressure of the pressure swing cycle, thereby desorbing at least a portion of the first component from the first adsorbent bed while withdrawing gas enriched in the first component from the first end of the first adsorbent bed.  
     
     
       60. The process according to  claim 59  further comprising controlling a flow of the portion of the withdrawn gas, thereby purging the adsorbent material of the first component to a level substantially equal to that prior to supplying feed gas to the first end to initiate a pressure swing cycle.  
     
     
       61. The process according to  claim 47  and further comprising storing at least a portion of a withdrawn gas as stored gas in a surge chamber.  
     
     
       62. The process according to  claim 61  and further comprising supplying stored gas to an adsorbent bed.  
     
     
       63. The process according to  claim 62  where stored gas is supplied to the second end of the first adsorbent bed, the second end of the second bed, or both.  
     
     
       64. The process according to  claim 47  and further comprising withdrawing at least a portion of the first component from a first end of the first adsorbent bed and returning the portion to the first end of a second adsorbent bed.  
     
     
       65. The process according to  claim 47  and further comprising providing a distributor valve fluidly coupled to the second ends of the adsorbent beds, whereby light reflux gas is withdrawn through the distributor valve.  
     
     
       66. The process according to  claim 65  where the adsorbent beds are stationary.  
     
     
       67. The process according to  claim 65  and further comprising providing a distributor valve fluidly coupled to the first ends of the adsorbent beds, whereby feed gas supply and exhaust gas withdrawal occurs through the distributor valve.  
     
     
       68. The process according to  claim 67  where the adsorbent beds are rotating.  
     
     
       69. The process according to  claim 67  where the adsorbent beds are stationary.  
     
     
       70. The process according to  claim 47  comprising purging the adsorbent material of the second adsorbent bed of the first component by providing a light reflux flow at a pressure controlled by an inline valve.  
     
     
       71. The process according to  claim 47  further comprising: 
       
         withdrawing light reflux gas enriched in the second component from the second end of the first adsorbent bed;  
       
       
         supplying a portion of the light reflux gas to the second end of the second adsorbent bed; and  
       
       
         controlling flow of the portion of light reflux gas supplied to the second end of the second adsorbent bed to reduce pressure in the first adsorbent bed to an equalization pressure less than the higher pressure.  
       
     
     
       72. The process according to  claim 47  where the lower pressure of the pressure swing cycle is below atmospheric pressure.  
     
     
       73. The process according to  claim 47  where the second component of the feed gas comprises hydrogen gas.  
     
     
       74. The process according to  claim 73  where the withdrawn gas is enriched in hydrogen gas relative to the feed gas, and wherein at least a portion of the withdrawn gas is utilized as fuel for a fuel cell.  
     
     
       75. A pressure swing adsorption process for separating a first component from a second component of a feed gas mixture where the first component is more readily adsorbed by an adsorbent material at increased pressure relative to a second component, comprising: 
       
         providing a plurality of adsorbent beds, each bed having a flow path through adsorbent material from a first end to a second end;  
       
       
         providing a first rotary distributor valve connected in parallel to first ends of the adsorbent beds and a second rotary distributor valve connected in parallel to second ends of the adsorbent beds;  
       
       
         supplying a feed gas mixture comprising the first component and the second component at a higher pressure to a first end of a first adsorbent bed through a feed port defined by the first rotary distributor valve;  
       
       
         withdrawing a first gas enriched in the second component from a second end of the first adsorbent bed;  
       
       
         withdrawing a second gas from the second end of the first adsorbent bed thereby depressurizing the first adsorbent bed to an equalization pressure lower than the higher pressure;  
       
       
         providing a portion of the first gas, the second gas, or both to the second end of an adsorbent bed at substantially a lower pressure of a pressure swing cycle while withdrawing gas enriched in the first component from the first end of the adsorbent bed, and controlling flow of the provided portion of the first gas, the second gas, or both to desorb an adsorbed component from the adsorbent material in the bed to a level substantially equal to that prior to supplying feed gas to the first end to initiate a pressure swing cycle; and  
       
       
         repressurizing the adsorbent bed.  
       
     
     
       76. The process according to  claim 75  and further comprising withdrawing a third gas from the second end of the first adsorbent bed thereby depressurizing the first adsorbent bed to an intermediate pressure less than the equalization pressure.  
     
     
       77. The process according to  claim 75  comprising cyclically repeating each process step at a cycle frequency.  
     
     
       78. The process according to  claim 77  where the adsorbent beds are rotating while process steps are cycled.  
     
     
       79. The process according to  claim 77  comprising controlling the cycle frequency.  
     
     
       80. The process according to  claim 79  where the cycle frequency is controlled to produce product gas at a desired rate.  
     
     
       81. The process according to  claim 79  where the cycle frequency is controlled to produce product gas at a selected purity of the second component.  
     
     
       82. The process according to  claim 79  where the cycle frequency is controlled to produce product gas at a selected recovery of the second component from the feed gas mixture.  
     
     
       83. The process according to  claim 79  further comprising withdrawing an exhaust gas from the first adsorbent bed during the desorption of the first component from the adsorbent material, wherein the cycle frequency is controlled to produce exhaust gas at a desired purity of the first component.  
     
     
       84. The process according to  claim 75  where the lower pressure of the pressure swing cycle is below atmospheric pressure.  
     
     
       85. The process according to  claim 75  where the second component of the feed gas comprises hydrogen gas.  
     
     
       86. The process according to  claim 85  where at least a portion of the product gas is utilized as fuel for a fuel cell.  
     
     
       87. The process according to  claim 75  comprising cyclically repeating each process step at a cycle frequency.  
     
     
       88. The process according to  claim 87  where the adsorbent beds are rotating while process steps are cycled.  
     
     
       89. The process according to  claim 87  comprising controlling the cycle frequency.  
     
     
       90. The process according to  claim 89  where the cycle frequency is controlled to produce product gas at a desired rate.  
     
     
       91. The process according to  claim 89  where the cycle frequency is controlled to produce product gas at a selected purity of the second component.  
     
     
       92. The process according to  claim 89  where the cycle frequency is controlled to produce product gas as a selected recovery of the second component from the feed gas mixture.  
     
     
       93. The process according to  claim 89  further comprising withdrawing an exhaust gas from the first adsorbent bed during the desorption of the first component from the adsorbent material, where the cycle frequency is controlled to produce exhaust gas at a desired purity of the first component.  
     
     
       94. A pressure swing adsorption apparatus for separating a first component from a second component of a feed gas mixture where the first component is more readily adsorbed by an adsorbent material at increased pressure relative to a second component, comprising: 
       
         plural adsorbent beds having first and second ends, each adsorbent bed comprising an adsorbent material and defining a flow path through the adsorbent material from the first end to the second end;  
       
       
         a rotary distributor valve fluidly coupled in parallel to the first ends, second ends, or the first and second ends of the adsorbent beds, the rotary distributor valve having a stator and a relatively rotatable rotor;  
       
       
         drive means for rotating the rotor;  
       
       
         feed gas supply means for supplying feed gas to the first ends of the adsorbent beds;  
       
       
         product withdrawal means for withdrawing product enriched in the second component;  
       
       
         control means to control flow of a gas withdrawn from a first adsorbent bed and delivered to a second adsorbent bed, thereby depleting the second adsorbent bed of the component having a substantially reduced concentration in the withdrawn gas to a level substantially equal to that prior to introducing the feed gas mixture; and  
       
       
         exhaust withdrawal means for withdrawing exhaust gas enriched in the first component.  
       
     
     
       95. The apparatus according to  claim 94  further comprising a rotary distributor valve fluidly coupled in parallel to the first end of the adsorbent beds, the rotary distributor valve having a stator and a rotor, whereby feed gas mixture is supplied to the first end of the adsorbent beds through at least one port defined by the rotary distributor valve.  
     
     
       96. A rotary pressure swing adsorption apparatus, comprising: 
       
         plural adsorbent beds having first and second ends, each adsorbent bed having an adsorbent material and defining a flow path through the adsorbent material from the first end to the second end;  
       
       
         a rotor and a stator manually defining a rotary distributor valve fluid coupled in parallel to the first ends, the second ends, or the first and second ends of the adsorbent beds; and  
       
       
         a valve defining an adjustable orifice fluidly communicating with, and in a fluid path between, the rotary distributor valve and the second end of an adsorbent bed.  
       
     
     
       97. The apparatus according to  claim 96  further comprising plural valves defining adjustable orifices communicating in parallel with, and in a fluid path between, the rotary distributor valve and the second ends of the adsorbent beds.  
     
     
       98. A rotary pressure swing adsorption apparatus, comprising: 
       
         plural adsorbent beds having first and second ends, each adsorbent bed having an adsorbent material and defining a flow path through the adsorbent material from the first end to the second end;  
       
       
         a rotor and a stator mutually defining a rotary distributor valve fluidly coupled in parallel to the first ends, the second ends, or the first and second ends of the adsorbent beds, the rotary distributor valve defining plural fluid ports; and  
       
       
         loading means fluidly connected to a source of variable pressure to apply a sealing force to the rotary distributor valve.  
       
     
     
       99. The apparatus according to  claim 98  further comprising a control mechanism operating to control flow of at least a portion of a gas withdrawn from a first adsorbent bed for supply to a second adsorbent bed.  
     
     
       100. The apparatus according to  claim 98  further comprising a conduit providing a fluid path between at least two ports, the conduit having an adjustable orifice in the fluid path.  
     
     
       101. The apparatus according to  claim 98 , where the rotor and stator mutually define a valve surface, and the valve surface is configured as a surface of revolution.  
     
     
       102. The apparatus according to  claim 101 , where the surface of revolution is a flat disc.  
     
     
       103. The apparatus according to  claim 101 , where the surface of revolution is a conical frustum.  
     
     
       104. The apparatus according to  claim 101 , where the surface of revolution is a cylinder.  
     
     
       105. The apparatus according to  claim 98 , where the loading means comprises a pressure chamber.  
     
     
       106. The apparatus according to  claim 98  where the loading means comprises at least one piston.  
     
     
       107. The apparatus according to  claim 98  where the source of variable pressure comprises an adsorbent bed.  
     
     
       108. A rotary pressure swing adsorption apparatus, comprising: 
       
         plural adsorbent beds having first and second ends, each adsorbent bed having an adsorbent material and defining a flow path through the adsorbent material from the first end to the second end;  
       
       
         a rotor and a stator mutually defining a rotary distributor valve fluidly coupled in parallel to the first ends, the second ends, or both ends of the adsorbent beds; and  
       
       
         control means to control flow of a gas withdrawn from a first adsorbent bed and delivered to a second adsorbent bed.  
       
     
     
       109. The apparatus according to  claim 108 , where the rotor and stator mutually define a valve surface, and the valve surface is configured as a surface of revolution.  
     
     
       110. The apparatus according to  claim 109 , where the surface of revolution is a flat disc.  
     
     
       111. The apparatus according to  claim 109 , where the surface of revolution is a conical frustum.  
     
     
       112. The apparatus according to  claim 109 , where the surface of revolution is a cylinder.