Abstract:
A multiport rotary valve is described providing the interconnection of a plurality of conduits with a predetermined cycle. The valve uses a stack of plates defining channels and ports to form the fluid circuits.

Description:
FIELD OF THE INVENTION 
     The invention is related to multiport rotary valves. In particular this invention relates to valves which are capable of accomplishing the simultaneous interconnection of a plurality of conduits having a predetermined periodic sequence. 
     BACKGROUND OF THE INVENTION 
     The separation of an individual component from a mixture can be performed by adsorption separation. To perform the separation using an adsorption separation process in a continuous manner, the process utilizes a simulated moving bed (SMB). A simulated moving bed is a technology that connects the inlet flows, or feeds, and outlet flows, or extract and raffinate, to a series of adsorption beds in sequence. These beds may be considered to be portions of a single large bed whose movement is simulated. As the separation proceeds, the inlet flows and outlet flows are shifted from one bed to the next bed in the sequence. The moving bed simulation may be simply described as dividing the bed into a series of fixed beds and moving the points of introducing and withdrawing liquid streams from the series of beds instead of moving the beds past the inlet and outlet ports. 
     One method of accomplishing the change of position of the inlets and outlets is the use of a complex multi-port stopcock, or multi-port valve, having four or more inlet and outlet flow lines and which are connected to a plurality of other lines leading to specific points in the adsorption bed. One type of these multi-port valves is known as a “rotary valve.” 
     Rotary valves are known in the art, and are described in U.S. Pat. Nos. 3,040,777; 3,192,954; 3,422,848 and 4,632,149. Processes utilizing a rotary valve in a simulated moving bed adsorption process are described in U.S. Pat. Nos. 3,201,491 and 3,291,726. 
     The problem with the usual rotary valves is that the valves are designed for large scale processing and are large and expensive. There is room for improvement in producing a small scale rotary valve. 
     SUMMARY OF THE INVENTION 
     The present invention is a rotary valve assembly for use in an adsorption separation system. The assembly comprises a first rotary plate having a surface for contact with a stationary plate, an inlet port and outlet port in fluid communication with each adsorbent bed inlet and outlet ports, and a plurality of secondary ports equal to the number of inlet and outlet ports; and a second rotary plate where the second rotary plate defines a plurality of channels and where each channel creates fluid communication between one secondary port and one of either the inlet port and outlet port of the first plate. The first rotary plate and second rotary plate form a rotary plate stack, where the ports extend through the plates, and the channels are bounded to form conduits within the stack. The assembly further comprises a first stationary plate having a plurality of ports with each port in fluid communication with one of an adsorbent bed inlet port, adsorbent bed outlet port, and a net flow port; a second stationary plate having a plurality of ports corresponding to each port on the first stationary plate, and a plurality of channels defined within the second plate equal to one less than the number of adsorbent beds; and a third stationary plate having a plurality of ports corresponding to the number of ports on the first rotary plate. The first stationary plate, second stationary plate and third stationary plate form a stationary plate stack, where the ports extend through the plates, and the channels are bounded to form conduits within the stack. The rotary plate stack rotates against the stationary plate stack and creates a series of simultaneous interconnections to permit the flow of fluid through a series of adsorption beds. The invention is a stack of plates that forms a compact and inexpensive rotary valve for use in small scale applications of adsorption separation. 
     In one embodiment, the rotary valve is an assembly of plates, wherein the plates are chemically etched, stamped, or machined to provide channels and ports. The ports and channels create an interconnection of conduits for creating the continuous flow paths directing fluids to and from a series of adsorbent beds. The ports also provide for attachment to external lines allowing for the addition of fluids and drawoff of product streams. 
     Other objects, advantages and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a first rotary plate of the rotary valve assembly for use with a four adsorbent bed system; 
         FIG. 2  is a second rotary plate of the rotary valve assembly; 
         FIGS. 3   a ,  3   b ,  3   c  are the channel patterns for the second rotary plate for an 8 adsorbent bed system, a 12 adsorbent bed system and a 16 adsorbent bed system respectively; 
         FIG. 4  is a first stationary plate of the rotary valve assembly for use with a four adsorbent bed system; 
         FIG. 5  is a second stationary plate of the rotary valve assembly for use with a four adsorbent bed system; 
         FIG. 6  is a third stationary plate of the rotary valve assembly for use with a four adsorbent bed system; 
         FIG. 7  is a smear plate design for use in the rotary valve assembly; 
         FIG. 8  is a design of the third stationary plate with lubrication grooves; and 
         FIG. 9  is a design of the third stationary plate with lubrication grooves and smear channels. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention comprises a rotary valve for use in an adsorption separation process. The rotary valve is used in an adsorption separation process where individual components from a mixture are separated through selective adsorption and it is necessary to connect at least one feed stream to a series of beds in sequence. This process is a simulated moving bed process and is described in U.S. Pat. No. 2,985,589 (Broughton et al.), which is incorporated by reference in its entirety. These beds may be individual beds, or portions of a single large bed. In the simulated moving bed process, when the feed stream inlet is shifted from one bed to the next, it is necessary to change the origin and destination of at least three additional streams. The additional streams to be shifted are a desorbent stream (an inlet), an extract stream (an outlet), and a raffinate stream (an outlet). The origins and destinations are the entry points and drawoff points for the streams from the beds. 
     Selective adsorption separation has become important for numerous small scale operations and reducing the expense associated with the equipment can enable the economical production of specialty chemicals. 
     A low cost rotary valve design is an assembly comprising a stack of plates and enables inexpensive production of a small rotary valve. The rotary valve assembly comprises a stack of rotary plates that interface with a stack of stationary plates. The valve is demonstrated in one embodiment with four adsorbent beds. The stack of rotary plates includes a first plate  10 , or interface plate, as shown in  FIG. 1 , which has a smooth surface for providing a sealing contact with a matching stationary surface. The first plate  10  includes a plurality of primary ports  12 , where the number of primary ports is equal to the number of fluid connections, or conduits, leading to and from adsorption beds, or the number of inlet and outlet ports for the adsorption beds. The first plate  10  further includes a plurality of secondary ports  14 , where the number of secondary ports  14  is equal to the number of primary ports  12 . The ports  12 ,  14  extend through the first plate  10  to a second side opposite the smooth surface. 
     The stack of rotary plates includes a second plate  20 , or channel plate, as shown in  FIG. 2 . The second plate  20  has a first side that matches the second side of the first plate  10 . The second plate  20  has a plurality of channels  26  defined within the second plate  20 , with each channel  26  having a first end  22  and a second end  24 . The channels  26  are formed through any method for producing grooves. Possible methods include, for example, chemical etching methods and other well known methods for micro-machining. In addition, depending on the materials of manufacture for the plates, the plates can be formed in molds where the channels  26  are defined in the mold. This is especially true for plastic materials. When the first plate  10  and the second plate  20  are stacked, the first end  22  of each channel  26  is aligned with a primary port  12  providing fluid communication between the first end  22  and the primary port  12 . Also, the second end  24  of each channel  26  is aligned with a secondary port  14  providing fluid communication between the second end  24  and the secondary port  14 . In addition, no channel  26  intersects another channel  26 . In this embodiment, the primary ports  12  are arrayed around an axis of rotation at a constant distance from the axis of rotation, and the secondary ports  14  are arrayed around the axis of rotation at a second constant distance from the axis of rotation. 
     Alternate designs for the rotating plates include forming the second plate  20  with channels  26  that extend all the way through the plate  20 . In this alternate design, a third plate (not shown) seats against the second plate  20  on the side opposite the side that interfaces with the first plate  10 . In another alternative, the second plate  20  has ports extending though the plate  20  at the channel ends  22 ,  24 , and the channels are on the side of the plate away from the first plate  10 , and a third plate (not shown) covers the channels  26  to form enclosed conduits. 
     This rotary valve design is expandable to any number of adsorption beds, and the channel pattern for the second rotating plate  20  is shown for 8, 12, and 16 bed systems in  FIGS. 3   a  to  3   c.    
     The rotary valve assembly further comprises a stack of stationary plates. The stack of stationary plates includes a first stationary plate  30 , as shown in  FIG. 4 . The first stationary plate  30 , or connection plate, includes a plurality of adsorbent bed ports  32  wherein each port  32  is in fluid communication with an inlet or an outlet to an adsorbent bed, therefore the number of adsorbent bed ports is two times the number of adsorbent beds. The first stationary plate  30  further includes a plurality of net flow ports  34 . The number of net flow ports  34  is equal to the number of inlet flow lines to the system and outlet flow lines from the system. In the present embodiment, there are two inlets, a desorbent inflow and a feedstream, and two outlets, an extract outflow and a raffinate outflow, for a total of four net flow ports  34 . The ports  32 ,  34  extend through the first stationary plate  30 , where a first side of the plate  30  provides for fluid communication to the adsorbent beds and the net flow lines, and a second side for a sealing contact with a second stationary plate  40 . 
     The second stationary plate  40 , or channel plate, is shown in  FIG. 5  and has a plurality of primary ports  42  that extend through the plate  40 . The primary ports  42  are in fluid communication with the adsorbent bed ports  32  of the first stationary plate  30 . The second stationary plate  40  includes at least two ports  44  in fluid communication with two of the net flow ports  34  of the first stationary plate  30  and extend through the plate  40 , and a first side for a sealing contact with the first stationary plate  30 . The second stationary plate  40  defines at least two channels  46  in the plate  40 , wherein the channels  46  each have a first end  47  and a second end  48 , and wherein at least one of the channels is in fluid communication with a net flow port  34  of the first stationary plate  30 . The channels  46  are formed with any method for producing grooves and may extend through the thickness of the second stationary plate  40 . When the channels  46  do not extend through the second stationary plate  40 , at least one of the channels  46  must have a port that extends through the plate  40  to provide fluid communication with at least one of the net flow ports  34  of the first stationary plate  30 . The second stationary plate  40  also has a second side opposite the first side for a sealing contact with a third stationary plate  50 , or contact plate for the stationary plate assembly. 
     The third stationary plate  50  is shown in  FIG. 6  and has a plurality of primary ports  52  that extend through the plate  50 , and has a first surface that forms a sealing contact with the second stationary plate  40 . The primary ports  52  are in fluid communication with the primary ports  42  of the second stationary plate  40 , and the number of primary ports is equal to the number of adsorbent bed ports  32 . The third stationary plate  50  further includes a plurality of secondary ports  54  that extend through the plate  50 , and the number of secondary ports  54  is equal to the number of primary ports  52 . The third stationary plate  50  is positioned against the second stationary plate  40  such that the primary ports  52  are in fluid communication with the primary ports  42  of the second stationary plate  40 . In addition, the secondary ports  54  are positioned such that each of the channels  46  provide fluid communication between a pair of secondary ports  54 , and that two of the secondary ports are in fluid communication with the two ports  44  in the second stationary plate  40 . The ports  52 ,  54  are arrayed around the axis of rotation around which the rotary plate stack turns, and are disposed in a manner to periodically be in fluid communication with the ports  12 ,  14  of the first rotary plate  10 . 
     The five plates are stacked in the order  20 ,  10 ,  50 ,  40 , and  30 . The rotating plates  10 ,  20  can be permanently held together, or held together by means that enables disassembly. The stationary plates  30 ,  40 ,  50  can be permanently held together, or held together by means that enables disassembly also. The rotating plate stack and the stationary plate stack are held together by means that provides a seal and allows the rotating plate stack to move against the surface of the third stationary plate  50 . In general, the first rotary plate  10  and the third stationary plate  50  are much thinner than the other plates  20 ,  30 ,  40 . 
     An alternate embodiment of the stationary plate stack is made of only the first stationary plate  30  and the third stationary plate  50  with the channels  46  defined either in the first stationary plate  30  in the surface facing the third stationary plate, or in the third stationary plate  50  in the surface facing the first stationary plate  30 . In this embodiment the first stationary plate  30  is the connection plate for making fluid connections to the adsorption beds, and the third stationary plate  50  is a contact plate for making the interface contact with the rotary plate assembly. 
     Although the above example is presented to serve as an exemplary example, and there are many variations that one skilled in the art would be able to design upon reading the description, it is intended that the invention covers the many variations of plate stacks of this invention. 
     The materials of construction can be any durable and rigid material, such as stainless steel or other corrosion resistant material. Alternatively, the materials of construction can be some durable and rigid material with an impermeable and corrosion resistant coating applied to the plates. The first rotary plate  10  and the third stationary plate  50  are preferably made of a lubricious polymeric material to provide a seal as well as allowing the first rotary plate  10  to slide against the third stationary plate  50 . A preferred material is Teflon™, or other polyfluorinated polymeric material. In an alternative, either one or both of the surfaces of the first rotary plate  10  and the third stationary plate  50  that slide against each other can be coated with a lubricious polymeric material. 
     In one embodiment, the invention includes channels  56  in the third stationary plate  50 . The channels  56  convert the third stationary plate  50  to a smear plate, as shown in  FIG. 7 . A smear plate extends the fluid communication during the rotation of the rotating plates  10 ,  20 . The channels  56  extend from the third stationary plate ports  52 ,  54  along a path that will be followed by the ports  12 ,  14  of the rotating plates  10 ,  20 . As the rotating plates  10 ,  20  move, the ports  12 ,  14  on the first rotating plate  10  establish fluid communication with the smear channels  56  as the ports  12 ,  14  pass over a first end  57  of the channels  56 . Fluid flows through an inlet port  54 , along a smear channel  56  and into a rotating plate port  14 . Fluid also flows from a rotating plate port  12  into the smear channel  56  beginning at the first end  57 , along the channel to the second end  58 , and out the stationary plate port  52 . During the rotation of the rotating plates  10 ,  20 , fluid communication is maintained as the ports  12 ,  14  move along the channels  56 , until the ports  12 ,  14  pass over the second end  58  of the channels  56 . As rotation continues, there is a break in fluid communication for the short interval that the ports  12 ,  14  pass over a gap  59  between the channels  56 . The gap  59  is sized to be at least the diameter of the ports  12 ,  14 . After passing over the gap  59 , fluid communication is reestablished and the sequence is advanced. The channels  56  are in fluid communication with the ports  52 ,  54  at the second end  58  of the channels  56 , and the channels  56  are purged of residual fluid from the prior sequence to minimize backmixing. In an alternate embodiment, the smear channels  56  are on the first rotary plate  10  of the rotary plate stack. 
     In another embodiment, the invention includes lubrication grooves  66  defined in the third stationary plate  50 , as shown in  FIG. 8 . The lubrication grooves  66  provide for access to an appropriate lubricant to reduce friction between the surface of rotating plate  10  and the surface of stationary plate  50 . The grooves  66  are circular with the center at the axis of rotation for the rotating plates  10 ,  20 , and the grooves  66  do not intersect any of the ports  52 ,  54  on the stationary plate  50 , nor do any of the ports  12 ,  14  of the rotating plate  10  pass over the grooves. This limits that amount of lubricant that may enter the system. A preferred lubricant is the desorbent used in the separation process. Use of the desorbent as a lubricant prevents cross-contamination between the ports of the valve. When the desorbent is the lubricant, a groove  68  is provided for fluid communication between the lubrication grooves  66  and the desorbent inlet  64 . The desorbent inlet  64  is also one of the secondary ports  54  of the third stationary plate  50  and is the high pressure point of the system. This provides for positive pressure on the lubrication system and prevents other streams in the system from cross-contamination. Optionally, a separate port for lubricant can be added to the valve when it is desired to use a lubricant other than the desorbent. This separate port would have no fluid communication with the rest of the adsorption separation system. 
     Another embodiment of the invention incorporates the prior two embodiments and is shown in  FIG. 9 . In this embodiment, the third stationary plate  50  of the rotary valve incorporates lubrication grooves  66  and smear channels  56 . The grooves  66  and channels  56  are as described above. 
     While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications of the plates, combinations of plates, and equivalent arrangements included within the scope of the appended claims.