WO2010002383A1

WO2010002383A1 - Flow distribution apparatus

Info

Publication number: WO2010002383A1
Application number: PCT/US2008/068754
Authority: WO
Inventors: William J. Koves; Jeffrey M. Borek; Hadjira Iddir
Original assignee: Uop Llc
Priority date: 2008-06-30
Filing date: 2008-06-30
Publication date: 2010-01-07

Abstract

A flow distribution apparatus located above the top-most bed of solid particles in an adsorbent vessel of a simulated moving bed adsorptive separation process having a vertical axis having a lower boundary substantially perpendicular to the vertical vessel axis. A top grid plate defines a lower volume between the top grid plate and a lower fluid distributing boundary. A passageway having walls through the top grid plate provides fluid communication between (a) an inlet pipe having a diameter and a central axis parallel to the vertical vessel axis and (b) the lower volume. A perforate distribution plate provides fluid communication between the inlet pipe and the lower volume, has an imperforate area to reduce vertical momentum of the fluid, and has perforations sized and spaced apart to achieve a pressure drop across the distribution plate sufficient to adequately diffuse the incoming flow from the inlet pipe.

Description

FLOW DISTRIBUTION APPARATUS

FIELD OF THE INVENTION

[01] The subject invention relates to apparatus used to distribute fluid. More specifically, the invention relates to an apparatus that distributes fluid flowing in a vessel containing solid particles. In an exemplary application, this invention finds use above the top-most bed in simulated moving bed (SMB) adsorptive separation processes.

DESCRIPTION OF RELATED ART

[02] Various apparatus that mix and/or distribute fluid as it flows through a vessel containing solid particles are well known in the art. One or more such devices may be positioned within a vessel and divide the solid particles into two or more beds. The use of such fluid distributing devices can increase the efficiency of operations by providing more uniform fluid properties across the cross-sectional area of the vessel. For example, they can minimize or eliminate flow rate variations or channeling; temperature differences; and variations in the fluid composition. These apparatus may also include a wide variety of means to introduce a fluid stream into the vessel and/or withdraw a fluid stream from the vessel. Such devices will be called "mixer- distributor-collectors".

[03] Many variations of mixer-distributor-collectors are well known in the art. For example, their use in adsorptive separation or chromatography processes such as SMB adsorptive separations are exemplified in U.S. Pat. Nos. 3,214,247; 3,789,989; 4,378,292; and 6,024,871 each of which is incorporated by reference in its entirety. The following are common components of such apparatus: 1) an upper boundary comprising a means for retaining the bed of solid particles above the apparatus and permitting the flow of fluid downward through the apparatus; 2) a fluid deflection plate located below and spaced apart from the upper boundary; 3) a fluid distributor located below and spaced apart from the deflection plate; and 4) a passageway through the fluid deflection plate which provides fluid communication between the upper boundary and the fluid distributor. Myriad other components and extensive variations for them as well as the common components listed above are also well known in the art. [04] Desirable characteristics of such mixer-distributor-collectors are also well known in the art. Examples include: 1) having a minimal volume; 2) preventing back mixing; 3) collecting the liquid flowing through the vessel and thoroughly mixing it to minimize localized concentration gradients; 4) providing for the introduction and thorough mixing of another fluid stream when called for; 5) providing for the removal of a fluid stream from the vessel when called for without negatively impacting the operation; and 6) minimizing the pressure drop through the apparatus. Finally, the mixer- distributor-collector is to provide uniform redistribution of the fluid across the cross sectional area of the vessel while precluding high velocity jet streams and/or other fluid turbulence from disturbing the downstream bed of solid particles. The terms "upstream" and "downstream" are used herein in their normal sense and are interpreted based upon the overall direction in which fluid is flowing in the vessel. Thus, downstream is equivalent to a downward or lower location in the vessel.

[05] Perry's Chemical Engineers' Handbook, 7th Edition, edited by D. W. Green et al., published by McGraw-Hill, New York, in 1997, pages 6-33 to 6-34 describe the well known use of adding sufficient uniform resistance across the flow channel to smooth out a non-uniform velocity profile through channels or process equipment. Detailed studies of various fluid flow manipulators and combinations thereof are given by J. Tan-Atichat, H. M. Nagib, and R. I. Loehrke, "Interaction of free-stream turbulence with screens and grids: a balance between turbulence scales", J. of Fluid Mech., (1982), vol. 114, pp. 501-528. The use of fluid flow manipulator devices such as honeycombs, screens, perforated plates, porous solids such as fritted material and mesh blankets, grids, and combinations thereof having sufficient uniform resistance and providing a more uniform redistribution (more uniform velocity profile) at the downstream or outlet boundary of a mixer-distributor-collector is well known in the art. Herein, this component of the mixer-distributor-collector will be referred to as the "fluid distributor".

[06] It has been found that mixer-distributor-collector apparatus of the prior art can create high velocity jet streams and/or turbulence which cause significant movement of the particles in the contact bed immediately below the apparatus even at a relatively low average linear fluid velocity through the vessel. The mixer-distributor-collector application of US 7,314,551 reduces the fluid jets and/or turbulence to eliminate disturbances to the lower solid particle bed at the low average linear fluid velocity in the vessel, and significantly reduces or eliminates disturbances to the particle bed beneath even when the average linear fluid velocity is increased by a factor of about four to about seven. However, the vertical velocity of the liquid is greater at the top grid, because all liquid flow enters from a single pipe. Therefore, there exists a need for an improved flow distribution apparatus for the top grid.

SUMMARY OF THE INVENTION

[07] In a first embodiment, the present invention provides a flow distribution apparatus for the top bed of a SMB apparatus that minimizes or eliminates attrition and disturbance of the particles in the bed by minimizing or eliminating high velocity jets and/or other turbulence that disturbs the downstream particle beds.

[08] In a second embodiment, a perforate distribution plate is interposed between an inlet pipe and a lower fluid distributing boundary. The perforate distribution plate has an imperforate area to abate the velocity of the incoming fluid.

[09] It has been found that the performance of mixer-distributor-collector apparatus of the prior art can be improved for the top-most grid by use of embodiments of the flow distribution apparatus of this invention. These embodiments reduce attrition and disturbance of the top-most particle bed by reducing high liquid velocities jets into the top-most bed.

BRIEF DESCRIPTION OF THE DRAWINGS

[10] Figure 1 is a sectional side view of a vessel containing a plurality of superposed particle beds having intermediate mixer-distributor-collectors of the prior art.

[11] Figures 2A-2C show overhead sectional views depicting mixer-distributor-collectors of the prior art in a vessel.

[12] Figures 3 A and 3B are sectional side views taken along the section lines of Figures 2 A and 2B, respectively, of additional prior art embodiments.

[13] Figures 4A and 4B illustrate side and section views, respectively, of an embodiment of the flow distribution apparatus of the invention. DETAILED DESCRIPTION

[14] Embodiments of the invention are suitably used in any process where fluid is contacted with solid particles disposed in a plurality of beds arranged vertically in a vessel. The cross-section of most such vessels is circular, but is not so limited. More than one such vessel may be used.

[15] Fluid flows downwardly through the vessel typically from an inlet pipe, through the solid particle beds separated by mixer-distributor-collectors. Non-limiting examples of the diverse types of materials include particles of adsorbents, resins, catalysts, and inert materials. The fluid may be a vapor, a liquid, or a supercritical fluid. The fluid may contain many compounds or be a mixture of many fluid streams.

[16] Embodiments of the invention are not intended for multiple phases, although small amounts of a second phase can be present. Therefore, in one embodiment, the fluid is of one phase. As used herein, the terms "substantially of one phase" and "substantially single fluid phase" mean that at least 95 weight percent is of one phase. Likewise, when it is stated herein that the fluid is substantially liquid, it means that at least 95 weight percent of the fluid is liquid.

[17] Many such processes are well known in the refining, petrochemical, and chemical processing industries, including for example various reaction and separation processes. In one embodiment, the process is an adsorptive separation process.

[18] For ease of description, this invention will be described as it relates to an adsorptive separation process practiced in a simulated moving bed apparatus.

[19] A detailed description and various embodiments of the subject invention will now be given by reference to the accompanying drawings. The drawings are simplified schematic views, not to scale; only showing components necessary for an understanding of the invention. The drawings are presented to illustrate some embodiments of the invention and are not intended to limit the scope of the invention as set forth in the claims.

[20] FIG. 1 illustrates a prior art vertically positioned vessel 1 adapted to hold a plurality of vertically spaced superposed particle beds 2. There may be two to twelve or more particle beds in a single vessel. The beds are separated by mixer-distributor-collectors 3, which are intended to be used between beds 2. One or more fluid streams are introduced to the upper portion of the vessel 1 by way of an inlet port 4. The fluid flows downwardly through the vessel contacting each particle bed 2 and mixer- distributor-collector 3 in sequence and is removed from the lower portion of the vessel by way of an outlet port not shown. An optional mixer-distributor-collector may also be located below the lowest particle bed in the vessel. As shown, upper boundary 5 for intermediate apparatus, fluid distributor 6, and optional flow manipulator 7 are components of the mixer-distributor-collector apparatus 3 and are arranged substantially parallel with respect to each other and substantially perpendicular to the vertical axis or major centerline of the vessel represented by imaginary line 13.

[21] "Substantially parallel" as used herein refers to the overall spacing of the components of the apparatus so that they are essentially parallel in construction. Flexing or distortions of the components such as from construction, installation, or load bearing may occur. For example, the solids retaining screen (upper boundary) may exhibit some major deflections when supporting a significant weight of particles. This will not preclude reference to components as being in substantially parallel arrangement with respect to each other.

[22] "Substantially perpendicular" as used herein shall refer to an approximate normal positioning of various components of the apparatus. In some instances slight variations may occur in various components of the apparatus in construction, installation, or by virtue of their bearing weight which may cause deflections. This may cause the components to lie in planes which are not exactly perpendicular to a given axis. Thus, the term "substantially perpendicular" as used herein shall include angles within the range from about 85 to about 95 degrees.

[23] For intermediate apparatus, upper boundary 5 may be similar to any of the well known means used in the art for retaining the solid particles above the apparatus while permitting the downward flow of fluid through the apparatus. The fluid distributor 6 is located below and spaced apart from the solids retaining screen (upper boundary) to define the volume of the mixer-distributor-collector between the upper boundary 5 and the fluid distributor 6. Fluid deflection plate 8 is located between and spaced apart from the upper boundary 5 and fluid distributor 6. The substantially imperforate fluid deflection plate 8 is located within the volume of the mixer-distributor-collector and divides the volume into an upper volume 14 located between the upper boundary 5 and the deflection plate 8 and a lower volume 15 located between the deflection plate 8 and the fluid distributor 6. The deflection plate 8 contains a passageway 9 which is defined as an opening in the plate providing fluid communication between the upper volume 14 and lower volume 15 of the apparatus. This fluid deflection plate 8 serves to collect the fluid across the cross sectional area of the vessel below the upper particle bed and to thoroughly mix the fluid as it is forced through passageway 9.

[24] The apparatus volume will usually be partially occupied by one or more other component(s). For example, there may be one or more supporting members such as braces or spacers that help maintain the separation between the solids retaining screen (upper boundary) and the fluid distributor. Supporting members may also be used to provide separation between these components and the deflection plate. There may also be load bearing bars or a support grid extending across the column to reinforce and support the solids retaining screen. Other optional but common components located within the apparatus volume will be detailed later herein.

[25] Fluid distributor 6 provides for the distribution or redistribution of the fluid across the cross sectional area of the vessel to maintain a uniform velocity profile or plug flow of the fluid in the vessel. This function is important for example to maintain a uniform residence time of the fluid when contacting a catalyst bed to achieve a desired reaction, or to maintain a sharp composition profile in the mobile fluid phase when contacting with an adsorbent to achieve a desired separation of components in an adsorptive separation process. The design of devices such as perforated plates, screens, grids, porous solids, honeycombs, and combinations thereof to improve and/or maintain a uniform velocity profile (plug flow) of fluid is well known by those of ordinary skill in the art as evidenced by the previously referenced pages of Perry's Chemical Engineers' Handbook wherein the number of velocity heads of pressure drop (K) is on the order of 10. For example, the fluid distributor comprises a perforated plate and an adjacent screen, or is a profile wire screen. [26] Optional flow manipulator 7 is spaced apart from and located below the fluid distributor 6. As used herein the term flow manipulator means any device used to alter the manner in which fluids travel through a vessel or conduit, such as in affecting the mean and fluctuating components of velocity. Examples of flow manipulators include: screens; grids; perforated plates; honeycombs; porous solids such as fitted materials and mesh blankets; and combinations thereof. The flow manipulator 7 improves fluid flow characteristics by minimizing or eliminating fluid velocity jets and/or other turbulence that can disturb the downstream particle bed.

[27] Mixer-distributor-collector apparatus may be fabricated and installed by any means known by those of ordinary skill in the art. Thus, the apparatus may be constructed from any material which can withstand the operating conditions such as the temperatures and pressures of the specific process intended. The materials must also be compatible with the fluids they will contact. Usually the same material will be used for all the components of the apparatus but this is not required. Typically in larger vessels at least some of the components are made of a suitable metal to provide the strength needed to support the upper bed of particles. The apparatus may be supported in the vessel by any known means such as support rings on the inner wall of the vessel; support beams extending from the vessel shell; and/or vertical support members such as hubs. The apparatus can be installed in a variety of well known ways. Smaller vessels such as laboratory or bench scale units may have vertical portions with fittings such that the mixer-distributor-collector apparatus can be inserted whole between the portions. In commercial scale vessels, the apparatus is usually designed and fabricated in segments that fit through a manway or port in the vessel shell and are assembled within the vessel. Each component of the apparatus can be assembled individually from multiple pieces and the apparatus built up by layers. Often, the apparatus is designed in segments where each segment comprises all layers and components of the apparatus. These segments are arranged and assembled to form the apparatus across the cross section of the vessel.

[28] FIGS. 2A-2C illustrate three examples of such prior art segmental arrangements as viewed looking down the vessel at an elevation just below the upper boundary of the apparatus. That is, the solids retaining screen is not shown in FIGS. 2A-2C in order to provide a clear view of how segments of the apparatus may be arranged. In FIG. 2A, the vessel is cylindrical as indicated by the circular cross section, vessel shell 12 and vertical axis 13. The ribs 10 define the side boundaries between adjacent segments. The apparatus segments may be supported by any well known means such as support beams or a grid which are attached, usually in a removable manner, to the inner surface of the vessel shell. In the ten central segments and the right chordal segment the passageways 9 are illustrated as a single rectangular opening through and surrounded by the fluid deflection plates 8. The chordal segment on the left side of FIG. 2A shows that the passageway 9 may be curved to follow the vessel shell.

[29] FIG. 2B depicts another possible configuration of a known mixer-distributor-collector in a cylindrical vessel or column. Support hub 11 is located in the center of the column. This hub is typically a pipe which is aligned with the major centerline or vertical axis 13 of the vessel. The ribs 10 define the side walls of the segments and radiate out from the support hub 11 extending to the outer edges of the particle beds at the inner surface of the vessel shell. The ribs rest on a support ring attached to the support hub and inner surface of the vessel. The ribs 10 are sufficiently strong to support the mixer-distributor-collector and the weight of the particle bed, together with the pressure drop experienced across the bed. In FIG. 2B, the passageway 9 of each segment is a narrow rectangular opening that completely traverses between the ribs 10. The fluid deflection plate may be considered as being comprised of an inner portion extending from the hub to the passageway and an outer portion extending from the passageway to the vessel shell.

[30] Passageways 9 typically are placed to provide efficient distribution of fluid in the particle beds. Typically, the ratio of the distance of the passageway from the central support hub to the distance of the passageway from the inner surface of the vessel is within the range from about 2.9 to about 1.3. Thus, multiple portions may be used to define the fluid deflection plate 8 and passageway 9. Alternatively, passageway 9 may be defined by two arcs that traverse the fluid deflection plate between the ribs (not shown).

[31] FIG. 2C illustrates the arrangement of apparatus segments within a vessel having a square cross sectional area with shell 12 and centerline 13. Each segment may have the same configuration to simplify fabrication and assembly. However, this is not required. One or more segments of the apparatus may differ as is illustrated by examples of various passageway 9 configurations shown on the left side of FIG. 2C. The units or segments of the apparatus may be designed in any manner such that they can be assembled to form the apparatus across the cross section of the vessel below the particle bed. Each segment of the apparatus may be of a unique cross sectional shape; however, it is usually more efficient to design the apparatus minimizing the number of different segment designs.

[32] FIGS. 3A and 3B illustrate additional details of prior art mixer-distributor-collectors. The views in FIGS. 3A and 3B correspond to the section lines marked in FIGS. 2A and 2B respectively. However, the additional components shown in FIGS. 3 A and 3 B represent different arrangements than those previously discussed. In FIG. 3A, the upper boundary 5 comprises a wire screen 16 which overlays a perforated plate 17. Each segment is fabricated with its own ribs 10 such that adjoining segments will meet along the outer surfaces of the adjoining ribs as illustrated in FIG. 3A. Alternatively, a single rib 10 may be used between each adjoining segment. In such arrangements, the ribs may be secured to the vessel and be sufficient to support the apparatus. For example, the segments, preassembled from the remaining components, can be set on a bottom ledge of the ribs. In these and other embodiments, the ribs 10 or walls defining the segments may be solid as illustrated, while in other arrangements they may have openings to permit the mixing of fluid between the segments arranged in the same plane.

[33] Other optional components illustrated in FIG. 3 A and 3B include the conduit 18 and mixing box 19. The conduit 18 serves as a means to introduce or withdraw fluid from the volume of the mixer-distributor-collector apparatus when this act is required by the process. The connection of single as well as multiple conduits to mixer- distributor-collectors is well known. It is also known that each segment may have its own conduit or conduits and these may be connected to a distribution manifold within the vessel to minimize the number of perforations required through the vessel shell. Thus, the conduits provide fluid communication between the volume of the apparatus and other equipment outside the vessel shell. Although the conduit 18 may simply be in open communication with the volume of the apparatus, it is common for the conduit 18 to be connected to a mixing chamber or box 19 which is located at least partially within the volume of the apparatus. The mixing box serves to mix fluid that has passed through the particle bed above with any fluid introduced through conduit 18.

[34] Another optional component of the apparatus is splash plate 20. Splash plate 20 is an imperforate surface which may be used to reduce the vertical momentum of the fluid before it passes through the fluid distributor 6 which in this embodiment is a perforated plate.

[35] Embodiments of the flow distribution apparatus of this invention are improvements over the optional use of the mixer-distributor-collector illustrated in Figures 1-3 for distribution of flow to the uppermost particle bed.

[36] In Figs. 4A and 4B, parts corresponding to or analogous with parts identified in Figs. 1-3 are identified with like reference numerals. A side view of an embodiment of the flow distribution apparatus 103 is illustrated in Fig. 4A. A top view of the embodiment of the flow distribution apparatus 103 illustrated in Fig. 4B is a part of a wedge-shaped portion analogous to the shape illustrated in prior art Fig. 2B for a mixer-distributor-collector.

[37] In Fig. 4A, optional flow manipulator 7 is shown above and optionally spaced apart from a particulate bed. Fluid distributor 6 is above and spaced apart from flow manipulator 7. Splash plate 20 is an imperforate surface that may be used to further reduce vertical momentum of the fluid before it passes through fluid distributor 6. Line 5 indicates the top of rib plate 10.

[38] Top grid plate 8 is spaced apart from fluid distributor 6 and defines a lower volume 15 between the two. Top grid plate 8 preferably has a slope downward from passageway 9 to the shell 12 of the vessel and from passageway 9 to hub 13. The purpose of this slope is to maintain a constant velocity head across the fluid distributor 6. Therefore, when the volume of fluid is greatest, the distance between top grid plate 8 and fluid distributor 6 is greatest. In an alternative embodiment, top grid plate is essentially flat and essentially parallel to fluid distributor 6.

[39] Note that because all fluid enters through passageway 9 from inlet pipe 101, there is no need to identify an 'upper volume 14' in embodiments of this invention. The height of distribution box 19 is set by the need to ensure thorough fluid distribution with minimum pressure drop. There is no need for an upper volume in which to mix fluids.

[40] Top grid plate 8 includes passageway 9 therethrough for flow of fluid into the particulate bed. Passageway 9 has walls 109 substantially perpendicular to fluid distributor 6 and extending through top grid plate 8. Preferably walls 109 do not extend beyond the bottom of top grid plate 8. A preferred embodiment is illustrated in Figure 4A. If the walls 109 extend into lower volume 15, the fluid velocity at splash plate 20 is likely to be increased as fluid flows off splash plate 20 and on to fluid distributor 6. Also, eddys that may lead to bed disturbance may be created.

[41] Walls 109 form distribution box 19 in cooperation with inlet pipe 101 and, if necessary, transition surface 110, which serves to ensure that the fluid is introduced to distribution box 19, through passageway 9, and into the uppermost particulate bed. Distribution box 19 does not function as a mixer of fluid collected from top grid plate 8 with fluid from inlet pipe 101. There is no fluid on fluid deflector plate 8 at the top of the vessel.

[42] Inlet pipe 101 is connected to inlet port 4 by a conduit or pipe not shown. Inlet pipe 101 typically is one of a plurality of distributor pipes from a manifold at inlet port 4. As the skilled practitioner recognizes, it is preferred to minimize the volume of the vessel dedicated to such flow-distribution apparatus. However, as noted above, the primary design characteristic is that distribution box 19 has sufficient vertical height to ensure good distribution of fluid flow to achieve minimum pressure drop. Therefore, distribution box 19 preferably has a vertical height (parallel to the axis of inlet pipe 101) sufficient to minimize pressure drop in distribution box 19 and across perforate distribution plate 50 while ensuring good flow distribution. The skilled practitioner recognizes that the height of distribution box 19 and the size and distribution of perforations 52 in perforate distribution plate 50 affect the pressure drop across those devices. As it is preferred to minimize this pressure drop while ensuring that the downward velocity fluid from inlet pipe 101 is abated to minimize velocity jets and other disturbances of top-most particulate bed 2, it is not practical to identify dimension for these features. Rather, the dimensions depend upon the velocity of the fluid, the size of perforate plate 50, and the size and distribution of perforations 52 therein. For example, fewer or smaller perforations 52 will increase the pressure drop. The height of distribution box 19 and the distance between the end of inlet pipe 101 and perforate distribution plate 50 are established to allow for abatement of fluid velocity while minimizing the pressure drop across distribution box 19.

[43] As shown in Fig. 4A, in one embodiment, transition surface 110 can be a fiat surface (plate) essentially parallel with fluid distributor 6. In another embodiment not shown, transition surface 110 can be disposed at an angle between inlet pipe 101 and wall 109 that is neither essentially parallel with nor essentially perpendicular to upper boundary 5.

[44] Perforate distribution plate 50 distributes fluid introduced into distribution box 19 by inlet pipe 101 to a lower volume 15. Perforate distribution plate 50 extends to each wall 109 to form a complete perforate bottom to distributor box 19 and to fill passageway 9. Perforate distribution plate 50 can be secured in place in any suitable way within the skill of the practitioner. For example, perforate distribution plate 50 can be welded to walls 109. In view of the preference to minimize the height of distribution box 19, perforate distribution plate 50 most preferably is located at the bottom of walls 109. However, perforated distribution plate 50 can be located at any height on walls 109 preferably at a height consistent with minimizing the pressure drop while abating the vertical velocity of the fluid.

[45] Perforate distribution plate 50 has an imperforate area 51 having a diameter at least equal to, and preferably greater than, the diameter of inlet pipe 101. Imperforate area 51 serves to further reduce vertical momentum of fluid introduced to the uppermost particulate bed. Therefore, imperforate area 51 preferably in slightly larger than inlet pipe 101 to ensure that the entirety of the fluid jet impacts the imperforate area 51. As the skilled practitioner recognizes, the dimension of a jet of fluid flowing out of inlet pipe 101 will increase as the distance between the end of inlet pipe 101 and imperforate area 51 on perforate distribution plate 50 increases. Therefore, the skilled practitioner, with the guidance provided herein, will be able to determine the preferred size of imperforate area 51. Typically, the dimensions of imperforate area 51 will be 5 percent greater than the dimensions of inlet pipe 101, more typically 10 percent greater. The imperforate area 51 is centered below the central axis 102 of the inlet pipe 101. [46] The side and location of the perforations 52 in perforate distribution plate 50 are selected to achieve a pressure drop across perforate distribution plate 50 sufficient to adequately diffuse the incoming flow from inlet pipe 101. Typically, the perforations 52 have a diameter of 5 mm, and are spaced apart to achieve the desired flow diffusion. Typically, the perforations 52 are spaced apart in a regular pattern, and, for the embodiment shown in Fig. 4B, the pattern is triangular. Perforations 52 typically extend over the entirety (except the imperforate area) of perforate distribution plate 50.

[47] Imperforate area 51 can be formed in a manner known to the skilled practitioner. For example, in the embodiment illustrated in Fig. 4A, imperforate area 51 comprises a solid disc attached to the upper surface of the perforate distributor plate 50. In an alternative embodiment not shown, a region of perforate plate 51 is not perforated to form the imperforate area 51. In another embodiment not shown, the entirety of the perforate distribution plate 50 is perforated, and the perforations in the imperforate area are plugged or otherwise filled.

[48] Figure 4B is a top view through section B-B of Fig. 4A of a pie- or triangular shaped embodiment of a flow distribution apparatus of the invention. As can be seen, rib plate 10 forms opposite walls 109 of distribution box 19. Vertical axis of the vessel 13 is located to the left of this segment.

[49] Fig. 4B also illustrates walls 109 and clearly illustrates that ribs 10 from opposite walls 109 in this embodiment. The perforations in perforated plate 50 extend over the entire surface thereof, if imperforate area 51 is a separate piece attached to the top or the bottom (undersurface) of perforate distributor plate 50. Otherwise, imperforate area 51 simply is devoid of perforations.

[50] Fig. 4B also illustrates, in the embodiment depicted, imperforate area 51 is located with its center at the intersection of the center lines A and B. Centerline A is the centerline for both imperforate area 51 and perforate distributor plate 50 and centerline B is the longitudinal centerline of the segment depicted. Imperforate area 51 is centered under inlet pipe 101.

[51] In one embodiment, the subject invention is used above the top particle bed in a SMB adsorptive separation process. The practice or use of embodiments of the subject invention is not believed to be related to or limited to the use of any particular type of SMB process or any particular adsorbent/desorbent combination. The general technique employed in the performance of a simulated moving bed (SMB) adsorptive separation is well described in the literature. For instance, a general description directed to the recovery of para-xylene is presented at page 70 of the September 1970 edition of Chemical Engineering Progress (Vol. 66, No 9). The simulated moving bed technique is also described in R. A. Meyers, Handbook of Petroleum Refining Processes, pages 8-85 to 8-87, McGraw-Hill Book Company (1986) and in the Adsorption, Liquid Separation section of the Kirk-Othmer Encyclopedia of Chemical Technology, 2002, John Wiley & Sons, Inc. Countercurrent SMB systems are described in many available references, such as U.S. Pat. No. 2,985,589, incorporated herein by reference in its entirety. Equipment utilizing these principles can vary in size from the pilot plant scale shown in U.S. Pat. No. 3,706,812 to commercial petrochemical plant scale, with flow rates ranging from a few cc per hour to many thousands of gallons per hour. Large scale plants normally employ rotary valves having a port for each conduit while small scale and high pressure units tend to use valves having only two or three ports. The invention may also be employed in a SMB adsorptive separation process which simulates cocurrent movement of the adsorbent, like that disclosed in U.S. Pat. Nos. 4,402,832 and 4,478,721. The functions and properties of adsorbents and desorbents in the chromatographic separation of liquid components are well-known, and reference may be made to U.S. Pat. No. 4,642,397, which is incorporated herein by reference, for additional description of these adsorption fundamentals. In an embodiment, the fluid is substantially a liquid.

[52] Existing SMB process units may be readily adapted to operate under the claimed invention. Practice or use of embodiments of the subject invention requires no significant changes in the operating conditions of the unit. The changes could be made any time the SMB process is halted, such as for a scheduled or unscheduled turnaround, unit revamp, or adsorbent reloading. After the SMB process unit is safely brought to an idle state, the adsorbent would be unloaded and any existing mixer- distributor-collector would be removed. New flow distribution apparatuses according to embodiments of the subject invention could be available for immediate installation. Alternatively, an existing mixer-distributor-collector could be easily modified by adding features. With the guidance provided herein, the skilled practitioner will be able to install a flow distribution apparatus embodiment of the invention.

[53] While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.

Claims

CLAIMSWe Claim:

1. A flow distribution apparatus (103) located above the topmost bed of solid particles (2) in an adsorbent vessel (1) of a simulated moving bed adsorptive separation process having a vertical axis (13), said apparatus comprising: a lower fluid distributing boundary (6) being substantially perpendicular to the vertical vessel axis (13); a top grid plate (8) defining a lower volume (15) between the top grid plate (8) and the lower fluid distributing boundary (6); a passageway (9) having walls (109) substantially parallel to the vertical axis (13) through the top grid plate (8), the passageway (9) providing fluid communication between (a) an inlet pipe (101) having dimensions and a central axis (102) parallel to the vertical vessel axis (13) and (b) the lower volume (15); a perforate distribution plate (50) in the passageway (9) and substantially parallel to the lower boundary (6), below and spaced apart from the end of the inlet pipe (101) and above the lower boundary (6) and providing fluid communication between the inlet pipe (101) and the lower volume (15); the perforate distribution plate (50) having ah imperforate area (52) having dimensions at least equal to the diameter of the inlet pipe (101) located coaxially therewith in the passageway (9), the remainder of the perforate distribution plate (50) having perforations (52); wherein the perforations (52) are sized and spaced apart to achieve a minimum pressure drop across the perforate distribution plate (50) sufficient to adequately abate the vertical velocity of the incoming flow from the inlet pipe (101) and provide more uniform velocity distribution entering the lower volume (15).

2. The apparatus of claim 1 wherein the walls (109) do not extend below the lower surface of the top grid plate (8).

3. The apparatus of any preceding claim wherein the perforate deflection plate (50) is at the lower end of the walls (109).

4. The apparatus of any preceding claim wherein the dimensions of the imperforate area (51) are 5 percent greater than the dimensions of the end of the inlet pipe (101).

5. The apparatus of claim 4 wherein the dimensions of the imperforate area (51) are 10 percent greater than the dimensions of the end of the inlet pipe (101).

6. The apparatus of any preceding claim wherein the top grid plate (8) slopes downwardly from passageway (9) toward vessel shell (12) and toward the vertical axis (13).

7. The apparatus of any preceding claim wherein the imperforate area (51) is a solid disc (53) fixed to a surface of the perforate distribution plate (50).

8. The apparatus of any preceding claim wherein the imperforate area (51) is coplanar with the perforate distribution plate (50).

9. The apparatus of any preceding claim wherein the perforations (52) have a diameter of 5mm.

10. The apparatus of any preceding claim wherein the perforations (52) are arranged in a triangular pattern.