Rotary sequencing valve with flexible port plate

Rotary sequencing valve comprising a rotor having a rotor face rotatable about an axis perpendicular to the rotor face, wherein the rotor face has a plurality of openings, one or more of which are disposed at a selected radial distance from the axis, and wherein the rotor includes at least one passage connecting at least one pair of the plurality of openings. The valve includes a flexible port plate having a first side and a second side, wherein the first side faces the rotor and engages the rotor such that the flexible port plate can be rotated coaxially by the rotor and can move axially with respect to the rotor, wherein the flexible port plate has a plurality of ports between the first and second sides, which ports are aligned with the openings in the rotor face. The valve also includes a stator having a stator face disposed coaxially with the rotor and the flexible port plate, wherein the second side of the flexible port plate is in sealable, slidable rotary contact with the stator face, wherein the stator face has a plurality of openings, some of which are disposed at the selected radial distance from the axis, and wherein the plurality of openings extend as passages through the stator. The valve may be used in pressure or temperature swing adsorption systems.

BACKGROUND OF THE INVENTION

Rotary valves are widely used in the process industries for directing fluids from one or more process sources to one or more process destinations in repeatable cyclic process steps. These valves, also called rotary sequencing valves, are used in cyclic or repeatable processes such as gas separation by pressure or temperature swing adsorption, liquid separation by concentration swing adsorption, gas or liquid chromatography, regenerative catalytic processes, pneumatic or hydraulic sequential control systems, and other cyclic processes.

One type of rotary valve has a cylindrical configuration in which inner or outer cylinders with properly positioned ports and seals rotate relative to one another such that ports in the inner and outer cylinders are aligned and/or blocked in a predetermined cyclic sequence. Another type of rotary valve has a flat circular configuration in which a flat ported rotor rotates coaxially on a flat ported stator such that ports in the stator and rotor are aligned or blocked in a predetermined cyclic sequence. Sealing typically is provided by direct contact of the flat rotor face sliding over the flat stator face. A high degree of precision is required in the fabrication of these flat surfaces to prevent excessive leakage at the mating surfaces. Rigid materials such as metal, carbon, or ceramic typically are used for rotors and stators, and wear of the parts or distortions caused by temperature differentials will cause changes in the shape of the surfaces, thereby allowing leakage across the seal formed between the surfaces. A sheet of deformable material may be bonded to the rotor or stator face to improve the seal between the rotor and stator.

Rotary circular valves with a flat circular configuration are particularly useful in pressure swing adsorption systems utilizing multiple parallel adsorber beds operating in overlapping cyclic steps which include feed, pressure equalization, depressurization, purge, and repressurization steps. As the size and throughput of an adsorption system increases, the diameters of the circular rotary valves also increase. As these valves increase in diameter, typically above about six inches, it becomes increasingly expensive to machine rotor and stator surfaces with the high degree of flatness required for proper fluid sealing between the rotor and stator faces. In addition, larger valve sizes magnify the problem of deviations from flatness caused by wear between the surfaces, thermal distortion of the mating parts, internal manufacturing stresses, or stresses from the pressure of the fluid flowing through the valve.

These problems are addressed by embodiments of the present invention, as described below and defined by the claims which follow, providing an improved rotary valve that alleviates sealing problems caused by flatness deviations due to rotor and stator fabrication, and also compensates for wear and thermal distortion during valve operation.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to a rotary sequencing valve comprising a rotor having a rotor face rotatable about an axis perpendicular to the rotor face, wherein the rotor face has a plurality of openings, one or more of which are disposed at a selected radial distance from the axis, and wherein the rotor includes at least one passage connecting at least one pair of the plurality of openings. The valve includes a flexible port plate having a first side and a second side, wherein the first side faces the rotor and engages the rotor such that the flexible port plate can be rotated coaxially by the rotor and can move axially with respect to the rotor, wherein the flexible port plate has a plurality of ports between the first and second sides, which ports are aligned with the openings in the rotor face. The valve also includes a stator having a stator face disposed coaxially with the rotor and the flexible port plate, wherein the second side of the flexible port plate is in sealable, slidable rotary contact with the stator face, wherein the stator face has a plurality of openings, some of which are disposed at the selected radial distance from the axis, and wherein the plurality of openings extend as passages through the stator.

The rotary sequencing valve may further comprise flow restricting means disposed in the passage connecting the pair of openings for restricting the flow of fluid through the passage.

In an embodiment of the invention, one rotary position of the rotor and the port plate about the axis places a pair of openings in the stator in flow communication with a pair of openings in the flexible port plate, the pair of openings in the rotor face, and the passage in the rotor that connects the pair of openings in the rotor face. Another rotary position of the rotor and the port plate about the axis places another pair of openings in the stator in flow communication with the pair of openings in the flexible port plate, the pair of openings in the rotor face, and the passage in the rotor that connects the pair of openings in the rotor face.

One or more of the ports extending through the port plate may be arcuate slots, each of which forms a circumferential passageway for fluid flow between an opening in the rotor face and an opening in the stator face.

Another embodiment of the invention includes a rotary sequencing valve comprising:(a) a rotor equipped to rotate about an axis, wherein the rotor includes a rotor face perpendicular to the axis, a plurality of openings in the rotor face, one or more of which are disposed at a selected radial distance from the axis, and a passage extending between a pair of the openings in the rotor face that places the pair of openings in flow communication;(b) a flexible port plate having a first surface, a second surface, a plurality of ports extending through the port plate from the first surface to the second surface, wherein the ports in the port plate are aligned with the openings in the rotor;(c) axially slidable connecting means extending between the rotor and the first surface of the flexible port plate such that the rotor and port plate can rotate together about the axis;(d) elastic sealing means in sealable contact with the rotor face and in sealable contact with the first surface of the flexible port plate, wherein the elastic sealing means provides a seal surrounding each opening in the rotor face and a seal surrounding each port on the first surface of the flexible port plate so that each opening in the rotor face is in flow communication with each port aligned with that opening;(e) a stator having a stator face disposed coaxially with the rotor and the flexible port plate, wherein the second side of the flexible port plate is in sealable, slidable rotary contact with the stator face, a plurality of openings in the stator face, some of which are disposed at the selected radial distance from the axis, and a plurality of passages extending through the stator, each passage extending through the stator from each of the openings in the stator face, respectively.

In this embodiment, one rotary position of the rotor and port plate about the axis aligns a pair of ports with a pair of openings in the stator face, another rotary position of the rotor and port plate about the axis aligns the pair of ports with another pair of openings in the stator face, and yet another rotary position of the rotor and port plate about the axis blocks one or more of the openings in the stator face.

The rotary sequencing valve typically comprises rotary drive means for rotating the rotor and port plate. The rotary drive means can be operated to drive the rotor and port plate continuously at a constant rotational speed or to position the rotor and port plate discontinuously in a repeatable rotational cycle.

The axially slidable connecting means extending between the rotor and the first surface of the flexible port plate may comprise cylindrical drive pins on the rotor face which fit into cylindrical drive pin sockets in the first surface of the port plate. The rotary sequencing valve may include means for pressing the rotor face against the elastic sealing means.

The elastic sealing means may be selected from the group consisting of(a) grooves surrounding each opening in the first surface of the port plate and elastic O-rings inserted in the grooves, wherein the O-rings protrude beyond the first surface and sealaby contact the rotor face surrounding each opposing opening in the rotor face;(b) grooves surrounding each opening in the rotor face and elastic O-rings inserted in the grooves, wherein the O-rings protrude beyond the rotor face and sealably contact the first surface of the port plate surrounding each opposing opening in the port plate;(c) a sheet of elastic material having a first side adjacent to the first surface of the port plate and a second side adjacent to the rotor face, wherein the sheet has openings which are similar in shape and size to the ports in the port plate, and the first and second sides of the sheet each have raised regions surrounding each opening therein that sealably contact the rotor face surrounding each opposing opening therein and sealably contact the first surface around opposing ports in the port plate;(d) raised regions of elastic material attached to the first surface of the port plate around each port in the port plate; and(e) raised regions of elastic material attached to the rotor face around each opening in the rotor face.

Embodiments of the invention include a port plate for use between the rotor and the stator of a rotary sequencing valve, the port plate comprising flexible material having a first surface, a second surface, an axis perpendicular to the second surface, and a plurality of ports extending through the port plate from the first surface to the second surface, wherein one or more of the ports are disposed at a selected radial distance from the axis. The port plate may further comprise grooves in the first surface thereof, wherein each groove surrounds a closed region on the first surface, some or all of the grooves surround ports, elastic O-rings are inserted in the grooves, and the O-rings protrude beyond the first surface of the port plate. The port plate may include at least two drive pin sockets for axially and slidably receiving drive pins to rotate the port plate around the axis.

Various embodiments of the invention also include a rotor and port plate assembly for use in a rotary sequencing valve. The assembly comprises a rotor equipped to rotate about an axis, wherein the rotor includes a rotor face perpendicular to the axis, a plurality of openings in the rotor face including a first opening and a second opening, and a passage extending between the first opening and the second opening that places them in flow communication, wherein one or more of the openings in the rotor face are disposed at a selected radial distance around the axis. The assembly includes a flexible port plate having a first surface, a second surface, a plurality of ports extending through the port plate including a first port and a second port, wherein the first opening in the rotor face is aligned with the first port in the port plate and the second opening in the rotor face is aligned with the second port in the port plate. The assembly also comprises axially slidable connecting means extending axially between the rotor and the first surface of the flexible port plate such that the rotor and the port plate can rotate together about the axis, and elastic sealing means in sealable contact with the first surface of the flexible port plate and with the rotor face.

Other embodiments of the invention include a rotary sequencing product valve for use at the product ends of four parallel adsorber vessels in a four-bed pressure swing adsorption process, wherein each vessel has a feed and a product end. The valve comprises:(a) a rotor equipped to rotate about an axis, wherein the rotor includes a rotor face perpendicular to the axis; seven openings in the rotor face wherein a first opening intersects the axis and the other six openings are disposed at a selected radial distance from the axis; a passage extending between the first opening and a second opening, a passage extending between the first opening and a third opening, a passage extending between a fourth opening and a fifth opening, and a passage extending between a sixth opening and a seventh opening, respectively, thereby placing the first, second, and third openings in flow communication, the fourth and fifth openings in flow communication, and the sixth and seventh openings in flow communication;(b) a flexible port plate having a first surface, a second surface, and six ports extending through the port plate, wherein the ports in the port plate and the openings in the rotor face are aligned and in flow communication as follows: a first port with the first opening, a second port with the second and seventh openings, a third port with the third opening, a fourth port with the fourth opening, a fifth port with the fifth opening, and a sixth port with the sixth opening;(c) axially slidable connecting means extending between the rotor and the first surface of the flexible port plate such that the rotor and the port plate can rotate together about the axis;(d) elastic sealing means in sealable contact with the first surface of the flexible port plate and the rotor face, wherein the elastic sealing means seals the first port to the first opening, the second port to the second and seventh openings, the third port to the third opening, the fourth port to the fourth opening, the fifth port to the fifth opening, and the sixth port to the sixth opening, respectively; and(e) a stator having a stator face in sealable and slidable contact with the second surface of the flexible port plate and disposed coaxially relative to the rotor and port plate; five openings in the stator face wherein a first opening intersects the axis and the other four openings are disposed at the selected radial distance from the axis; and five passages extending through the stator from each of the five openings in the stator face, respectively, wherein the first opening in the stator face is in flow communication via a first passage with a product delivery line, and wherein each of the other four openings in the stator face is in flow communication via each of the other passages with the product end of a first, a second, a third, and a fourth adsorber vessel, respectively.

This rotary sequencing product valve may be operated such that(1) in a first rotary position of the rotor and port plate about the axis, the openings in the rotor, ports in the port plate, and openings in the stator are aligned to place the product end of the first adsorber vessel in flow communication with the product delivery line and with the product end of the second adsorber vessel, and to place the product ends of the third and fourth adsorber vessels in flow communication; and(2) in a second rotary position of the rotor and port plate about the axis, the openings in the rotor, ports in the port plate, and openings in the stator are aligned to place the product end of the first adsorber vessel in flow communication with the product delivery line and with the product end of the second adsorber vessel, and to place the product ends of the second and fourth adsorber vessels in flow communication.
The rotary sequencing product valve may further comprise a drive shaft equipped to rotate the rotor about the axis, a valve housing sealably attached to the stator wherein the valve housing surrounds the rotor, port plate, and elastic sealing means, wherein the drive shaft passes through the valve housing and is rotatably sealed to the housing so that the housing has a fluid-tight interior.

In a related embodiment, the invention includes a rotary sequencing feed valve for use at the feed ends of four parallel adsorber vessels in a four-bed pressure swing adsorption process, each vessel having a feed and a product end. The valve comprises:(a) a rotor equipped to rotate about an axis, wherein the rotor includes a rotor face perpendicular to the axis, two openings in the rotor face wherein a first opening intersects the axis and a second opening is disposed at a selected radial distance from the axis, and a passage that extends between the first and second openings to place the first and second openings in flow communication;(b) a flexible port plate having a first surface, a second surface, and three ports extending through the port plate, wherein a first port in the port plate is aligned and in flow communication with the first opening in the rotor face and a second port in the port plate is aligned and in flow communication with the second opening in the rotor face;(c) axially slidable connecting means extending between the rotor and the first surface of the flexible port plate such that the rotor and the port plate can rotate together about the axis;(d) elastic sealing means in sealable contact with the first surface of the flexible port plate and the rotor face, wherein the elastic sealing means seals the first port to the first opening and the second port to the second opening, respectively; and(e) a stator having a stator face in sealable and slidable contact with the second surface of the flexible port plate and disposed coaxially relative to the rotor and port plate; five openings in the stator face wherein a first opening intersects the axis and the other four openings are disposed at the selected radial distance from the axis; and five passages, each passage extending through the stator from each of the five openings in the stator face, respectively, wherein the first opening in the stator face is in flow communication via a first passage with a waste discharge line and wherein each of the other four openings in the stator face is in flow communication via each of the other passages with the feed end of a first, a second, a third, and a fourth adsorber vessel, respectively.

The rotary sequencing feed valve may further comprise a drive shaft equipped to rotate the rotor about the axis, a valve housing sealably attached to the stator wherein the valve housing surrounds the rotor, port plate, and elastic sealing means, wherein the drive shaft passes through the valve housing and is rotatably sealed to the housing so that the housing has a fluid-tight interior, and a feed inlet line connected to the housing in flow communication with the fluid-tight interior.

In the rotary sequencing feed valve, the port plate may be circular and a third port in the port plate may be formed by removing a portion of a sector of the port plate extending from the periphery of the port plate to a radial distance from the axis which is less than the selected radial distance, and wherein the third port is in direct flow communication with the interior of the valve housing.

The rotary sequencing feed valve may be operated such that(1) in a first rotary position of the rotor and port plate about the axis, the openings in the rotor, ports in the port plate, and openings in the stator are aligned to place the feed end of the first adsorber vessel in flow communication with the feed inlet line and to place the feed end of the third adsorber vessel in flow communication with the waste discharge line; and(2) in a second rotary position of the rotor and port plate about the axis, the openings in the rotor, ports in the port plate, and openings in the stator are aligned to place the feed end of the second adsorber vessel in flow communication with the feed inlet line and to place the feed end of the fourth adsorber vessel in flow communication with the waste discharge line.

Another embodiment of the invention includes a rotary sequencing valve assembly for a pressure swing adsorption system which uses a plurality of parallel adsorber vessels, each vessel having a feed end and a product end, wherein the rotary sequencing valve assembly comprises:(1) a rotary sequencing feed valve comprising(a) a rotor having a rotor face rotatable about an axis perpendicular to the rotor face and a coaxial drive shaft, wherein the rotor face has a plurality of openings, one or more of which are disposed at a selected radial distance from the axis, and wherein the rotor includes a passage connecting a pair of the openings;(b) a flexible port plate having a first side and a second side, wherein the first side engages the rotor such that the flexible port plate can be rotated coaxially by the rotor and can move axially with respect to the rotor, wherein the flexible port plate has a plurality of ports between the first and second side, and wherein two of the ports are aligned with the openings in the rotor face; and(c) a stator having a stator face disposed coaxially with the rotor and the flexible port plate, wherein the second side of the flexible port plate is in sealable, slidable rotary contact with the stator face, wherein the stator face has a plurality of openings, some of which are disposed at the selected radial distance from the axis, wherein the openings extend as passages through the stator, wherein one of the openings in the stator face is in flow communication with a waste discharge line, and wherein each of the other openings in the stator face is in flow communication with the feed end of each of the plurality of adsorber vessels, respectively;(2) a rotary sequencing product valve comprising(a) a rotor having a rotor face rotatable about an axis perpendicular to the rotor face and a coaxial drive shaft, wherein the rotor face has a plurality of openings, one or more of which are disposed at a selected radial distance from the axis, and wherein the rotor includes a passage connecting a pair of the openings;(b) a flexible port plate having a first side and a second side, wherein the first side engages the rotor such that the flexible port plate can be rotated coaxially by the rotor and can move axially with respect to the rotor, wherein the flexible port plate has a plurality of ports between the first and second side, and wherein the ports are aligned with the openings in the rotor face; and(c) a stator having a stator face disposed coaxially with the rotor and the flexible port plate, wherein the second side of the flexible port plate is in sealable, slidable rotary contact with the stator face, wherein the stator face has a plurality of openings, some of which are disposed at the selected radial distance from the axis, wherein the openings extend as passages through the stator, wherein one of the openings in the stator face is in flow communication with a product delivery line, and wherein each of the other openings in the stator face is in flow communication with the product end of each of the plurality of adsorber vessels, respectively; and(3) rotary drive means to rotate the drive shaft of the rotary sequencing feed valve and the drive shaft of the rotary sequencing product valve.

The rotary drive means may comprise a motor-driven system that turns the drive shafts of both the rotary sequencing product valve and the rotary sequencing feed valve. The motor-driven system may turn the drive shafts of both the rotary sequencing product valve and the rotary sequencing feed valve at the same speed. The drive shafts of both the rotary sequencing product valve and the rotary sequencing feed valve may form a single drive shaft. The rotary sequencing feed valve may further comprise a drive shaft equipped to rotate the rotor about the axis, a valve housing sealably attached to the stator wherein the valve housing surrounds the rotor, port plate, and elastic sealing means, wherein the drive shaft passes through the valve housing and is rotatably sealed to the housing so that the housing has a fluid-tight interior, and a feed inlet line connected to the housing in flow communication with the fluid-tight interior.

DETAILED DESCRIPTION OF THE INVENTION

Rotary sequencing valves, in which a flat ported rotor rotates coaxially on a flat ported stator wherein ports in the stator and rotor are aligned or blocked in a predetermined cyclic sequence, are used for directing fluids in cyclic processes having a number of repeatable steps. Embodiments of the present invention are directed to rotary sequencing valves which utilize a flexible port plate disposed between the stator and rotor of the rotary sequencing valve. The flexible port plate, which is made of flexible material, is connected to the rotor and is turned by the rotor such that a flat face on one side of the port plate rotates slidably and sealably on the flat stator face. The other side of the port plate contacts the rotor face such that openings or ports in the rotor face are aligned with and in sealable fluid flow communication with ports in the port plate. The ports in the port plate align sequentially with openings in the stator face as the rotor and port plate rotate together, and sealing at the interface between the port plate and stator face is provided by contact between the flexible material of the port plate and the stator as the two parts slide relative to one another.

FIG. 1shows an exploded sectional view illustrating a center cross section of an exemplary embodiment of the rotary sequencing valve. Rotor1is attached to drive shaft3that rotates the rotor around axis5. The rotor may be made of metal, ceramic, carbon, or other rigid material that is compatible with the fluid flowing through the valve. Rotor face7has opening9that intersects axis5and has opening11at a selected radial distance from axis5. Vertical bore13, vertical bore15, and horizontal bore17form an internal passageway that connects openings9and11and places them in fluid flow communication. Plug16may be used to close the outer end of horizontal bore17. The passage formed by horizontal bore17may include flow restricting means (not shown) such as an orifice assembly to restrict or control the flow of fluid through the bore. Other alternative flow restricting means may be used to control fluid flow through the passage such as, for example, an adjustable flow control valve. The rotor may have additional openings and passages (not shown) as discussed later, and these also may include flow restricting means. In one embodiment, at least two drive pins18project from rotor face7.

Rotor face7is perpendicular to shaft3and axis5and preferably is essentially flat, which means that the face is fabricated to be as flat as practical using conventional machining and grinding methods. Advanced fabrication methods such as lapping or other highly specialized and expensive processes are not required to provide extreme flatness. The rotor face should have a sufficiently smooth finish so that fluid-tight seals can be formed around openings in the rotor face as described later.

As an alternative embodiment to the internal passage formed by vertical bore13, vertical bore15, and horizontal bore or passage17to connect openings9and11, the rotor can be designed and fabricated such that bore11and bore13pass through the top of the rotor, horizontal bore or passage17is not used, and bore11and bore13are connected by an external passage or pipe. This alternative may be desirable if the number and orientation of internal passages complicates the machining steps in rotor fabrication. This alternative external passage or pipe may include flow restricting means such as an orifice assembly to control the flow of fluid through the bore. Other alternative flow restricting means may be used to restrict or control fluid flow through the passage such as, for example, an adjustable flow control valve.

Port plate19is disposed adjacent to rotor face7and has central port21passing through the port plate from first side or surface23to second side or surface25. Port21intersects axis5and is axially opposite or aligned with opening9. Port27, disposed at a selected radial distance from axis5, extends through the port plate from first side or surface23to second side or surface25. This port may be arcuate in shape as described later. Port27is opposite or aligned with opening11. A port and an opening in the rotor face are aligned by definition when they are in flow communication, that is, when fluid can flow directly between an aligned port and opening.

Flexible port plate19engages rotor1such that the port plate can be rotated about axis5by rotor1and the port plate can move axially with respect to the rotor. Any engaging means may be used to engage port plate19with rotor1or rotor face7as long as the engaging means allows axial movement of the port plate with respect to the rotor. The engaging means also may be defined as axially slidable engaging means, one of which is illustrated inFIG. 1, wherein surface23of port plate19may have at least two drive pin sockets29positioned to slidably receive drive pins18when rotor face7is moved axially towards first surface23of port plate19. These pins rotate the port plate while allowing the port plate to move axially with respect to rotor1. Other axially slidable engaging means can be envisioned which are within the scope of the embodiments of the present invention. For example, the port plate may be attached to the rotor using recessed screws that do not clamp the port plate tightly to the rotor, but allow the port plate to move axially with respect to the rotor and prevent the port plate from becoming disengaged from the rotor.

Port plate19preferably is made of a material with a low modulus of elasticity and has a thickness such that it is flexible relative to the rotor and stator materials. The port plate material also should have a low coefficient of friction relative to the stator material and should be compatible with the fluid flowing through the valve. A suitable material for the port plate may be selected from materials such as, for example, polytetrafluoroethylene (PTFE), carbon- or bronze-filled PTFE, polyoxymethylene or acetal (for example, Delrin®), nylon, or polyetheretherketone (PEEK). The port plate should have an appropriate degree of flexibility so that it can conform to any deviations from flatness of the stator face as described below. The degree of flexibility of the port plate is a function of the modulus of the port plate material and the thickness of the port plate. In a typical embodiment, the thickness of the port plate may be in the range of {fraction (1/16)} inch to ½ inch.

Each of the port openings in first surface23of port plate19is surrounded by elastic sealing means which seals the port opening to an opposite opening in rotor face7. The elastic sealing means preferably comprises elastic material which sealably contacts rotor face7and may be sealably attached to or in sealable contact with port plate19. The elastic material preferably allows a slight axial motion of port plate19relative to rotor face7when first surface23and rotor face7are pressed together in contact with the elastic sealing means. First surface23of port plate19typically does not contact rotor face7.

In one embodiment of the elastic sealing means shown inFIG. 1, grooves are cut into first surface23around ports21and27in port plate19. O-rings31and33are inserted into the grooves around ports21and27, respectively, and the depth of the grooves is less than the diameter of the O-ring cross section such that the O-rings protrude above or beyond first surface23as shown. Rotor face7is pressed against O-rings31and33(and optionally against other O-rings not shown here), which in turn presses flat second surface25of port plate19against flat stator face35. The compression of the O-rings is on the order of tens of thousandths of an inch, so it is much greater than the size of any deviation from the flatness of stator face35. The flexible material of the port plate19conforms to any out-of-flatness imperfections in stator face35as it slides in rotary motion over stator face35, thereby maintaining a fluid seal. While this embodiment has been described for O-rings having a circular cross-section, rings having other cross-sectional shapes may be used as desired.

The O-rings can be made of any appropriate material with sufficient elasticity and compatible with the fluid flowing through the valve. Exemplary materials that can be used for the O-rings include, for example, nitrile rubber, neoprene, ethylene propylene, and fluoroelastomers such as Viton®.

O-rings31and33serve several functions because of their elastic properties. First, they force second surface25of port plate19against stator face35; second, they maintain a seal on first surface23around the ports in the port plate and on rotor face7around openings9and11; third, they prevent leakage between rotor face7and first surface23of port plate19as the port plate flexes relative to stator face35; and fourth, they allow port plate19to move slightly in the axial direction relative to stator37to compensate for wear of second surface25as port plate19rotates against stator face35. This axial movement also can compensate for distortion of stator face35that may be caused by thermal gradients or fluid pressure loads.

In an alternative embodiment, the grooves could be cut into rotor face7around openings9and11(not shown) rather than being cut in port plate19as described above. The O-rings then would ride in the rotor and press against first surface23of port plate19. Drive pins18would fit into drive pin sockets29as described above. In another embodiment, the elastic sealing means may comprise a sheet of elastic material having a first side adjacent to first surface23of the port plate and a second side adjacent to rotor face7. The sheet in this embodiment would have openings which are similar in shape and size to the ports in the port plate, and the first and second sides of the sheet each would have raised regions surrounding each opening that sealably contact rotor face7surrounding each opposing opening in the rotor face and sealably contact first surface23around opposing ports in the port plate. Alternatively, the elastic sealing means may comprise raised regions of elastic material bonded or attached to the first surface23of port plate19around each port in the port plate or raised regions of elastic material bonded or attached to rotor face7around each opening in the rotor face.

There are also other types of elastic sealing means which may be used for sealing service between rotor face7and first surface23of port plate19. For example, seals containing internal springs to provide elasticity could be used, which would provide a seal between the rotor and port plate, and also to provide force to push the port plate against stator face35. This force should not be affected significantly by flexing of port plate19and the flexing of the port plate should be significantly less than the compression of the seals.

Stator face35preferably is essentially flat, which means that the face is fabricated to be as flat as practical using conventional machining and grinding methods. Advanced fabrication methods such as lapping or other highly specialized and expensive processes are not required to provide extreme flatness. Stator face35and second surface25of port plate19preferably are smooth to minimize abrasive wear during rotary operation. Stator face35has holes or openings39,41, and43which lead to passages45,47, and49, respectively, through the body of stator37. Opening41and passage47typically intersect axis5. Openings39and43are disposed at approximately the same selected radial distance from axis5as are port27in port plate19and opening11in rotor face7. Opening41, port21, and opening9are always aligned and in fluid flow communication when the rotor, port plate, and stator are pressed sealably together. In a first orientation as shown inFIG. 1, opening39, port27, and opening11are aligned and are in fluid flow communication with opening41, port21, and opening9by way of bore13, bore17, and bore15. As rotor1and port plate19rotate to a second orientation (not shown) 180 degrees from the first orientation, opening43, port27, and opening11are aligned and are in fluid flow communication with opening41, port21, and opening9by way of bore13, bore17, and bore15.

Rotor1and stator37may have other multiple openings and passageways (not shown) for other fluid flow functions as described below. Port plate19likewise may have additional ports (not shown) for other fluid low functions as described below.

Rotary sequencing valves of the type described above are particularly useful in pressure swing adsorption (PSA) systems utilizing multiple parallel adsorber beds operating in overlapping cyclic steps that include feed, pressure equalization, depressurization, purge, and repressurization steps. Embodiments of the rotary sequencing valve illustrated above may be used in the exemplary four-bed PSA process illustrated in the cycle chart of FIG.2A and the schematic bed flow diagrams ofFIGS. 2B and 2C.

FIG. 2Ashows the overlapping cycle steps for each of beds A, B, C, and D wherein each bed proceeds in turn through the cycle steps during the time periods as shown. Bed A, for example, proceeds through (a) a feed step during time t0to t2in which a feed gas is introduced into a feed end of the bed while a product gas is withdrawn from a product end of the bed; (b) an equalization step during time t2to t3in which the bed is depressurized through the product end to provide pressurization gas to another bed; (c) a provide purge step during t3to t4in which the bed is further depressurized to provide purge gas to yet another bed on the purge step; (d) a waste blowdown step during t4to t5in which the bed is further depressurized from the feed end; (e) a purge step during t5to t6in which the bed is purged by introducing into the product end a purge gas provided by another bed; (f) a repressurization step during t6to t7via the product end with gas from another bed undergoing equalization and with product gas; and (g) a final repressurization step with product gas during t7to t8.

FIG. 2Bshows the flow configuration for beds A, B, C, and D during time t0to t1. Feed flows through line201into the feed end of bed A while final product gas is withdrawn via line203from the product end of bed A. A portion of the product gas from bed A via line205is used to repressurize bed B. Equalization gas flows via line207from bed D to bed B. Waste depressurization gas is withdrawn via waste discharge line209from bed C.

FIG. 2Cshows the flow configuration for beds A, B, C, and D during time t1to t2. Feed flows via line201into the feed end of bed A while final product gas is withdrawn via line203from the product end of bed A. A portion of the product gas from bed A via line205is used to repressurize bed B. Purge gas flows via line211from bed D to bed C and waste purge gas is withdrawn via waste discharge line213(the same line as line209) from bed C.

Beds A, B, C, and D cycle in turn through similar bed flow configurations during time periods t2to t4, t4to t6, and t6to t8. The flow of gas among the four beds may be controlled by a rotary sequencing feed valve at the feed ends of the beds and rotary sequencing product valve at the product ends of the beds. An exemplary rotary sequencing product valve for this service is illustrated in the exploded perspective drawing ofFIG. 3. Acutaway view of the body of rotor301illustrates the openings and internal passages which direct gas at the product ends of the beds. There are six outer holes in the rotor face (not visible here) which are disposed at a selected radial distance from the rotor axis and a single center hole in the rotor face intersecting the axis. The first and second of these outer holes are connected by internal passage303; the first and second outer holes are connected to the left and right ends, respectively, of internal passage303. The third of these outer holes is connected to the center hole by internal passage305. The fourth and sixth of these outer holes are connected by internal passage307and bores309and311respectively. The fifth of these outer holes, which is located in the lower rear area of rotor301and is not visible here, is connected to the center hole by passage313, which passes beneath passage305. The center hole, the third hole, and the fifth hole therefore are all connected and can be in fluid communication. The face of rotor301has at least two drive pins, one of which is visible as drive pin315. One or more of passages303,305,307, and313may have internal orifices (not shown) to regulate the flow of fluid through the passages.

Port plate317has center hole319opposite the center hole in rotor301and at least two drive pin sockets321and323, which are disposed such that the drive pins in the rotor slide into and engage the drive pin sockets when the rotor and the port plate are pressed together axially and disengage when the rotor and the port plate are pulled apart axially. The drive pins and drive pin sockets thus provide disengagable and axially slidable connecting means extending between the rotor face and the flexible port plate. The drive pins rotate port plate317in concert with the rotation of rotor301and also allow the port plate to move axially with respect to the rotor. This allows the port plate to move slightly in the axial direction to compensate for deviations from flatness of the stator face and from eventual wear of the port plate as it slides rotatably on the stator face. Other types of disengagable and axially slidable connecting means between the rotor and port plate may be envisioned, and are within the scope of the present invention, as long as they provide the dual functions of rotating the port plate and allowing the port plate to move axially with respect to the rotor.

Port plate317also has arcuate slots or ports324,325,327,329, and331which are located at approximately the same radial distance from the axis as the six outer holes in the face of rotor301. The first hole in the rotor face is opposite port331, the second hole is opposite port324, the third and fourth holes are opposite port325, the fifth is opposite port327, and the sixth is opposite port329.

Stator face333of stator335has center hole337and holes339,341,343, and345located 90 degrees apart and at approximately the same radial distance from the axis as the ports in port plate317. Each of the holes on the stator face lead to passages through the stator to the underside of the stator (not shown). In the alignment of rotor301, port plate317, and stator335ofFIG. 3, lines and arrows show fluid flow paths through the valve components. For example, it is shown that fluid can flow from hole345, through port331, the first hole in the face of rotor301, passage303, the second hole in the face of rotor310, port324, and hole339. Also, fluid can flow through hole343in the stator face, through arcuate slot327, through the fifth hole in the rotor face (not seen in this view), and through passage313. This fluid stream then splits and a portion flows through passage305, through the third hole in the face of rotor301, circumferentially through arcuate slot or port325, and through hole341. The remaining portion flows through port319and through center hole337in the face of stator335.

As rotor301and port plate317rotate together, with the port plate in contact with stator face333, the ports in the port plate pass sequentially over the holes in the stator face and direct fluid flow in turn to different combinations of the holes in the stator. The passages from holes339,341,343, and345can be connected with the product ends of adsorbent beds C, B, A, and D, respectively, ofFIG. 2C. Amore detailed description of the fluid flow through the rotary sequencing valve during the segments of the PSA cycle is given below.

A more detailed view of the exemplary rotary sequencing product valve is illustrated in the exploded perspective drawing of FIG.4. Rotor301is shown with the holes and interior passages drawn in phantom lines. The first, second, third, fourth, fifth, sixth, and center holes in the face of rotor301discussed in reference toFIG. 3are shown inFIG. 4as holes401,403,405,407,409,411, and412respectively. Also shown inFIG. 4are passages303,305,307, and313.

An alternative embodiment is possible in which interior passages303,305,307, and313within rotor301are not used. Instead, passages extend from holes401,403,405,407,409,411, and412through the rotor to the top surface of the rotor. External piping is used to connect the holes at the top surface of the rotor to give the same fluid flow paths among the holes as described above using the interior passages. In this alternative, the passage from center hole412would have to be set at an angle from the axis to avoid the axial drive shaft (not shown inFIG. 3but seen in FIG.1). Alternatively, the drive shaft could be connected to rotor301by a hollow spacer and the center passage could be axial.

Grooves are cut in first surface413of port plate415to contain O-rings as earlier described. Specifically, grooves417,419,421,423,425,427are cut into first surface413surrounding ports429,431,433,435,437, and439, respectively. Drive pin sockets321and323are shown which receive drive pin315and a second drive pin316disposed 180 degrees opposite. O-rings441,443,445,447,449, and451fit into grooves417,419,421,423,425,427, respectively. Stator335was described above with reference to FIG.3.

The O-rings are inserted into the grooves and the face of rotor301is pressed against the O-rings while drive pins315and316are inserted slidably and axially into drive pin sockets321and323. The O-rings contact the rotor face and form seals around the holes in the rotor face. O-ring441seals around hole403, O-ring443seals around holes405and407, O-ring445seals around hole411, O-ring447seals around hole409, O-ring449seals around hole401, and O-ring451seals around center hole412. The second surface of port plate415contacts and seals against stator face333as earlier described.

In an alternative embodiment, the grooves could be cut into the face of rotor301around openings therein (not shown) rather than being cut in port plate415as described above. The O-rings then would ride in the rotor and press against first surface413of port plate415. Drive pins315and316would fit into drive pin sockets321and323as described above.

In another embodiment, the sealing means may comprise a sheet of elastic material having a first side adjacent to first surface413of the port plate and a second side adjacent to the face of rotor301. The sheet has openings which are similar in shape and size to the ports in the port plate, and the first and second sides of the sheet each have raised regions surrounding each opening that sealably contact the face of rotor301surrounding each opposing opening in the rotor face and sealably contact first surface413around opposing ports in the port plate.

There are also a number of other types of plastic seals which may be used for sealing service between the face of rotor301and first surface413of port plate415. For example, seals containing internal springs to provide elasticity could be used, which would provide a seal between the rotor and port plate, and also to provide force to push the port plate against stator face333. This force should not be affected significantly by flexing of port plate415and the flexing of the port plate should be significantly less than the compression of the seals.

The assembled rotary sequencing product valve is installed in a sealed housing (described later) including a drive shaft seal. Any slight leakage of gas through the rotary seal between the port plate and the stator will accumulate in the housing, thereby raising the pressure within the housing. This pressure, acting on the rotor, will force it against the stator, since the pressure at the stator ports is less than the housing pressure. This additional force will further minimize leakage.

A rotary sequencing valve having similar features to the product end rotary valve described above can be designed for the feed end of the adsorber beds. An exemplary rotary sequencing feed valve is illustrated in the exploded perspective drawing of FIG.5. The face of rotor501has two holes or openings503and505connected by interior passage507shown in phantom. Hole505is located at the center of the rotor and intersects the axis of the rotor, and hole503is located at a selected radial distance from hole505. At least two drive pins509and511are mounted on the rotor face. The top of rotor501has a drive shaft (not shown) which turns the rotor about a central axis (not shown) which passes through hole505.

An alternative embodiment of the rotor is possible in which interior passage507within rotor501is not used. Instead, an external pipe is extended from hole503to505above the top surface of the rotor to give the same fluid flow paths between the holes as described above using the interior passage. In this alternative, the passage from center hole505would have to be set at an angle from the axis to avoid the axial drive shaft (not shown inFIG. 5but seen in FIG.1). Alternatively, the drive shaft could be connected to rotor501by a hollow spacer and the center passage could be axial.

Port plate513has first surface515and a second surface (not seen in this view) on the reverse side. The port plate has three ports or openings passing from the first surface to the second surface. Port517is in the center of the port plate and intersects the axis, and is surrounded by groove519. Port521, generally arcuate in shape, is located approximately at the same selected radial distance as hole509in rotor501and is surrounded by groove523. Port525is formed by removing a partial segment of the port plate as shown and is open at the circumference of the port plate. The inner edge of port525is located at approximately the same radial distance as the inner edge of port521. First surface515has at least two drive pin sockets527and529which are located to mate with drive pins511and509, respectively, in the face of rotor501. The first surface of port plate513also has two grooves531and533disposed between ports521and525. Grooves531and533do not surround ports and may be located at approximately the same radial location as port521. O-rings535,537,539, and541are sized for insertion into grooves519,523,531, and533, respectively, in first surface515of port plate513.

In an alternative embodiment, the grooves could be cut into the face of rotor501around openings therein (not shown) rather than being cut in port plate513as described above. The O-rings then would ride in the rotor and press against first surface515of port plate513. Drive pins509and511would fit into drive pin sockets529and527as described above.

In another embodiment, the sealing means may comprise a sheet of elastic material having a first side adjacent to first surface515of the port plate and a second side adjacent to the face of rotor501. The sheet has openings which are similar in shape and size to the ports in the port plate, and the first and second sides of the sheet each have raised regions surrounding each opening that sealably contact the face of rotor501surrounding each opposing opening in the rotor face and sealably contact first surface515around opposing ports in the port plate.

There are also a number of other types of plastic seals which may be used for sealing service between the face of rotor501and first surface515of port plate513. For example, seals containing internal springs to provide elasticity could be used, which would provide a seal between the rotor and port plate, and also to provide force to push the port plate against stator face543. This force should not be affected significantly by flexing of port plate515and the flexing of the port plate should be significantly less than the compression of the seals.

Stator face543of stator545has center hole547and holes549,551,553, and555located 90 degrees apart at approximately the same radial distance from the axis as the ports in port plate513. Each of the holes on the stator face lead to passages through the stator to the underside of the stator (not shown). The O-rings are inserted into the grooves and the face of rotor501is pressed against the O-rings while drive pins509and511are inserted into drive pin sockets529and527, respectively. The O-rings contact the rotor face and form seals around the holes in the rotor face. O-ring535seals around hole505and O-ring537seals around hole503. There is no port in the area surrounded by grooves531and533. O-rings539and541contact the rotor face and provide the necessary force to the port plate so that the second surface of the port plate maintains sealing contact with the stator face.

The second surface of port plate513contacts and seals against stator face543as the port plate rotates slidably and sealably against stator face543. As rotor501and port plate513rotate, center hole547in stator545remains aligned with port517, port521is aligned in turn with holes549,551,553, and555in stator face543, and port525uncovers in turn each of holes549,551,553, and555. The passages through stator545from holes549,551,553, and555can be connected with the feed ends of adsorbent beds B, C, D, and A, respectively, ofFIG. 2C. Amore detailed description of the fluid flow through the rotary sequencing feed valve during the segments of the PSA cycle is given below.

The assembled rotary sequencing feed valve is installed in a sealed housing similar to that of the rotary sequencing product valve; the housing includes a drive shaft seal for the drive shaft that rotates the rotor. The feed fluid to be distributed by the rotary sequencing feed valve is introduced directly into the valve housing. As port525in rotating port plate513uncovers in turn each of holes549,551,553, and555in stator face543, the feed fluid is directed into the feed ends of adsorbent beds B, C, D, and A, respectively, of FIG.2C.

The operation of the rotary sequencing product valve of FIG.4and the rotary sequencing feed valve ofFIG. 5is illustrated inFIGS. 6A,6B,7A, and7B for the pressure swing adsorption cycle ofFIGS. 2A,2B, and2C.FIGS. 6A and 7Aare views of section1—1through port plate415of FIG.4andFIGS. 6B and 7Bare views of section2—2through port plate513of FIG.5. These views thus include partial views of the stator face. In order to aid the viewer, dashed lines are included to indicate the flow passages in the rotor which connect the ports in the port plate.

A schematic flow diagram showing the relationship among the adsorbent beds and the rotary sequencing valves is given in FIG.8. Rotary sequencing feed valve801is connected to the feed ends of beds A, B, C, and D by feed lines803,805,807, and809, respectively. Feed gas line811is connected to the housing of rotary feed valve801as earlier described. Waste blowdown line813is connected to a center opening in the stator of this valve as earlier described. Bed product lines815,817,819, and821connect the product ends of beds A, B, C, and D, respectively, with rotary sequencing product valve823. Final product line825is connected to a center opening in the stator of this valve as earlier described. Rotary drive means827drives shafts829and831which rotate the rotors of valves801and823, respectively. Rotary drive means827typically includes an electric motor and a reduction gear drive to rotate shafts829and831at the speed required by the specific process cycle in which fluid flow is controlled by valves801and823. Valves801and823typically operate at the same constant rotational speed, but may be operated if desired at a non-constant rotational speed or discontinuously in a repeatable cycle by means of on-off control of the electric drive motor.

FIG. 6Aillustrates the relationship of port plate600to the stator of the rotary sequencing product valve for the PSA cycle steps ofFIG. 2Bthat occur between times t0and t1of FIG.2A. The port plate has center port601and arcuate ports603,605,607,609, and611. The stator has center opening613and radially-located openings615,617,619, and621. Passage623in the rotor connects ports609and603in the port plate; passage625in the rotor connects ports601and603in the port plate; passage627in the rotor connects ports605and607in the port plate; and passage629in the rotor connects ports601and611in the port plate. Openings615,617,619, and621in the stator are connected to the product ends of adsorber beds A, B, C, and D, respectively, of FIG.2B. Opening613is connected to final product line825(FIG.8).

FIG. 6Billustrates the relationship of the port plate to the stator of the rotary sequencing feed valve for the PSA cycle step ofFIG. 2Bthat occurs between times t0and t1of FIG.2A. Port plate630has center port631, arcuate port633, and sector port635. The stator has center opening637and radially-located openings639,641,643, and645. Passage647in the rotor connects ports631and633in the port plate. Openings639,641,643, and645in stator646are connected to the feed ends of adsorber beds A, B, C, and D, respectively, of FIG.2B. Opening637is connected to a waste blowdown line. Feed is introduced into the valve housing (not shown) as earlier described.

At the product end of the adsorbent beds between times t0and t1ofFIG. 2A, the rotary product valve ofFIG. 6Aallows product to flow from the outlet of bed A through product line815(FIG.8), opening615in the stator, port611in the port plate, passage629in the rotor, port601in the port plate, and opening613in the stator to final product line825(FIG.8), and also through passage625in the rotor, port603in the port plate, opening617in the stator, and line817to pressurize the product end of bed B. The rotary product valve also allows depressurization gas to flow from the product end of bed D through line821, opening621in the stator, port609in the port plate, passage623in the rotor, port603in the port plate, and opening617in the stator to provide repressurization gas to the inlet of bed B via line817. Opening619in the stator is blocked by the port plate, and ports605and607in the port plate are blocked by the stator face.

At the feed end of the beds, during the same time period t0to t1, rotary sequencing feed valve801ofFIG. 8allows feed gas to flow from feed line811into the housing of the feed valve, through sector port635(FIG.6B), through the uncovered opening639in the face of stator646, and through feed line803(FIG. 8) into the feed end of adsorber bed A. Simultaneously, the rotary valve allows blowdown waste gas to flow from the feed end of bed C, through opening643in the stator face, through arcuate port633, through passage647in the rotor, through port631, and through opening637in stator646to waste line813(FIG.8). Openings641and645in stator646are blocked by port plate630.

As port plates600and630rotate clockwise as shown, the PSA cycle ofFIG. 2Aproceeds through the time period between t1and t2. The flow relationship among the adsorbent beds during this period is shown inFIG. 2C, wherein feed continues to bed A, product gas continues to repressurize bed B, depressurization gas from the product end of Bed D countercurrently purges bed C, and waste purge gas is withdrawn from the feed end of bed C.

At the product end of the adsorbent beds between times t1and t2ofFIG. 2A, the rotary product valve ofFIG. 7Aallows product to flow from the outlet of bed A through product line815(FIG.8), opening615in the stator, port611in the port plate, passage629in the rotor, port601in the port plate, and opening613in the stator to final product line825(FIG.8), and also through passage625in the rotor, port603in the port plate, opening617in the stator, and line817to pressurize the product end of bed B. The rotary product valve also allows depressurization gas to flow from the product end of bed D through line821(FIG.8), opening621in the stator, port607in the port plate, passage627in the rotor, port605in the port plate, and opening619in the stator to provide purge gas to the product end of bed C via line819(FIG.8). Port609is blocked by the face of the valve stator.

At the feed end of the beds, during the same time period t1to t2, rotary sequencing feed valve801ofFIG. 8allows feed gas to flow from feed line811into the housing of the feed valve, through port635(FIG.7B), through the uncovered opening639in the face of stator646, and through feed line803(FIG. 8) into the feed end of adsorber bed A. Simultaneously, the rotary valve allows blowdown waste gas to flow from the feed end of bed C via feed line807(FIG.8), through opening643in the stator face, through arcuate port633, through passage647in the rotor, through port631, and through opening637in stator646to waste line813(FIG.8). Openings641and645in stator646are blocked by port plate630.

Thus during the time periods t0to t1and t1to t2, the rotary valve positions ofFIGS. 6A and 6Bcontrol gas flow for the feed step of bed A, the equalization and feed pressurization steps of bed B, the waste blowdown and purge steps of bed C, and the equalization and provide purge steps of bed D. As the rotary sequencing feed valve801and product valve825continue their rotation, this combination of steps proceeds in turn through beds B, C, D, and A during time period t2to t4, through beds C, D, A, and B during time period t4to t6, and through beds D, A, B, and C during time period t6to t8. One full revolution of rotary sequencing feed valve801and product valve825drives one full cycle of the four-bed PSA system. A typical cycle time t0to t8may be in the range of 6 to 120 seconds; the corresponding rotational speed of rotary sequencing feed valve801and product valve825would be between 10 and 0.5 RPM.

The rotary sequencing valves and parts described above may be assembled into a valve housing using known mechanical sealing methods to ensure fluid-tight operation. An exemplary method of assembling the valve described inFIG. 1is illustrated in the valve assembly cross-section of FIG.9. Rotor901is driven by drive shaft903about axis905and its face is in sealable contact with the upper surface of port plate907as earlier described, for example, by using representative O-rings909. The upper surface of port plate907and the face of rotor901are not in direct contact, and are separated by O-rings909and optionally other O-rings not visible in this cross-section view. The lower surface of port plate907rotates sealably and slidably on the face of stator913. Plug915may be used to close the outer end of horizontal bore917and may include an orifice assembly (not shown) which extends into bore917to control the flow of fluid through the bore. The rotor may have additional openings and passageways (not shown) as discussed earlier.

The face of rotor901is perpendicular to drive shaft903and axis905, and the face preferably is essentially flat, which means that the face is fabricated to be as flat as practical using conventional machining and grinding methods. Advanced fabrication methods such as lapping or other highly specialized and expensive processes are not required to provide extreme flatness. The rotor face should have a sufficiently smooth finish so that fluid-tight seals can be formed around openings in the face. In one embodiment, at least two drive pins (not seen in this view) project from the rotor face and slidably engage in an axial direction with drive pin sockets in the upper surface of port plate907. Rotor901is attached to the end of drive shaft903by threaded stud or bolt919.

Rotor901, drive shaft903, port plate907, and the face of stator913are sealed within a housing formed by the body of stator913, wall section921, head923, and shaft seal and bearing housing925. Stator913is sealed to wall section921by seal927and wall section921is sealed to head923by seal929. Shaft seal and bearing housing925is sealed to head923by seal931. Drive shaft903is sealed into shaft seal and bearing housing925by rotary seal933and shaft903is supported radially by bearing935. Stator913may be joined to wall section921by threaded bolt assemblies937, head923may be joined to wall section921by threaded bolt assemblies939, and bearing housing925may be joined to head923by bolt assemblies941.

Axial force may be generated between seal housing925and rotor901by spring washer943which slidably engages with the rotating upper face of rotor901by means of roller bearing945. This force pushes the lower face of rotor901against the O-rings in the upper face of port plate907. Other known means to generate axial force between seal housing925and rotor901, for example by wave springs or helical springs, may be used as desired and are considered within the scope of the embodiments of the present invention.

The features illustrated inFIG. 9may be used for rotary feed valves as well as rotary product valves. Rotor901is representative of product valve rotor301of FIG.4and feed valve rotor501of FIG.5. Stator913is representative of stator335of FIG.4and stator545of FIG.5. The rotary valve illustrated inFIG. 9can be operated in any orientation; when used in the configuration ofFIG. 8, for example, the orientation shown inFIG. 9would be used for the feed valve and an orientation rotated 180 degrees would be used for the product valve.

In the embodiments described above and illustrated inFIGS. 1-9, the rotor, port plate, and stator have a center hole intersecting the axis for either product delivery (product valve) or waste gas discharge (feed valve). In an alternative embodiment, for example in a valve configuration in which the rotor drive shaft passes through the stator, the product gas or waste gas passage through the stator would be offset from the axis. In this embodiment, the product delivery or waste gas discharge passage through the stator would be disposed at a different radial location than the passages connected to the adsorbent beds. A circular channel formed in the port plate at a similar radial location as the product delivery or waste gas discharge passage would rotate over the opening to this passage in the stator such that the opening and the circular channel would always be aligned in flow communication. An opening in the rotor would be aligned with the circular channel in the port plate, and this opening would be connected through a passage in the rotor to a port in the port plate which rotates over the face of the stator. This port would align in turn with each passage through the stator leading to each adsorber bed to allow gas flow to or from the bed. Alternatively, a circular channel could be placed in the stator or the rotor to serve the same function as a circular channel in the port plate.

While the rotary valve embodiments described above are illustrated for use in a four-bed pressure swing adsorption process, they may be used with any number of adsorption beds in a PSA system. These rotary valve embodiments are not limited to use in PSA systems, and may be used in any process applications which require the unique characteristics and operating advantages of rotary valves. The embodiments of described herein are particularly useful in larger rotary valves in which the required degree of flatness for rotors and stators operating in direct rotary sliding contact would be difficult or expensive to attain and difficult to maintain during operation.