Abstract:
A separations tray assembly for use in a fluid-fluid exchange column. The separations tray assembly is of the type where a first fluid, in a continuous phase, is directed across successive trays in a serpentine flow path. A second fluid, in a dispersed phase ascends through apertures in the tray thus inducing interaction and mass transfer with the first fluid. In accordance with one aspect of the present invention, the separations tray further includes a diffuser skirt, having apertures disposed therein, operatively coupled to a fluid channel. The diffuser skirt is operable to direct the first fluid to cover substantially an entire volumetric cross-flow window between successive separations trays and to induce stirring and mixing of the first fluid and the second fluid to effect efficient mass transfer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and incorporates by reference the entire disclosure of, U.S. patent application Ser. No. 13/101,638, filed May 5, 2011. U.S. patent application Ser. No. 13/101,638 claims priority from and incorporates by reference the entire disclosure of U.S. Provisional Patent Application No. 61/345,439, filed May 17, 2010. Additionally, the present application incorporates by reference the entire disclosure of U.S. patent application Ser. No. 12/408,333, filed Mar. 20, 2009, U.S. patent application Ser. No. 12/109,781, filed Apr. 25, 2008, and U.S. Provisional Patent Application No. 61/178,676, filed May 15, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mass-transfer trays for chemical process columns and, more particularly, but not by way of limitation, to an improved liquid-liquid contactor tray for facilitating increased mass transfer efficiency. 
     2. History of Related Art 
     Distillation columns have been developed and used for many decades to separate selected components from a multicomponent stream. The major “separations” process is commonly known in the art as “fractionation.” Successful fractionation in a distillation column depends upon intimate contact between a heavier fluid and a lighter fluid. Some contact devices, such as, for example, trays, are characterized by relatively high pressure drop and relatively high fluid hold-up. One type of contact apparatus utilizes fluid in a vapor phase to contact fluid in a liquid phase. Another type of contact apparatus is structured packing. Structured packing is energy efficient as it exhibits low pressure drop and low fluid hold-up. However, these very properties at times make columns equipped with structured packing difficult to operate in a stable, consistent manner. Moreover, many applications simply require the use of trays. 
     A particularly effective tray in process columns is a sieve tray. Typically, the sieve tray is constructed with a plurality of apertures formed in a deck surface. The plurality of apertures permit ascending lighter fluid to flow into direct engagement with heavier fluid that is flowing across the sieve tray. When there is sufficient lighter-fluid flow upwardly through the sieve tray, the heavier fluid is prevented from running downwardly through the plurality of apertures (referred to as “weeping”). A small degree of weeping is normal in sieve trays while a larger degree of weeping is detrimental to the capacity and efficiency of the tray. Such trays may be either single-pass or multi-pass. In addition, such trays may incorporate serpentine flow, orbital flow, or uni-directional flow. 
     Another type of “separations” process involves mass transfer between two fluids which are both in a liquid state. This is commonly referred to as “fluid-fluid exchange.” The primary advantage of fluid-fluid exchange over fluid-vapor exchange is an amount of process energy required. In the fluid-vapor exchange, substantial energy must be provided and consumed to boil a fluid into a vapor state and maintain the fluid in the vapor state for the duration of the process. In contrast, most fluid-fluid exchange processes operate at temperatures slightly above ambient temperature such as, for example, 90° F. resulting in significant energy savings. 
     In cases involving fluid-fluid exchange, there are specific performance issues that impact efficiency. In typical fluid-fluid exchange columns, a first fluid is in a continuous phase and a second fluid is in a dispersed phase. In one arrangement, the heavier fluid, in a continuous phase, is passed downwardly in a circuitous path across a series of horizontally disposed trays spaced in a vertical relationship, one to the other. The heavier fluid forms a fluid layer on the trays. Droplets of the lighter fluid, in a dispersed phase, ascend through the plurality of apertures and interact with the continuous fluid. This arrangement may be used, for example, in re-capture of an acid where the heavier fluid is water containing the acid and the lighter fluid is a selected solvent. In another arrangement, the heavier fluid is the dispersed phase and the lighter fluid is the continuous phase. In this arrangement, the heavier fluid forms droplets which fall downwardly through the plurality of apertures. The heavier fluid droplets fall through the lighter fluid, in continuous phase, flowing upwardly in a circuitous path across an underside of the trays. This arrangement may be used, for example in solvent recovery of Benzene from aromatics process streams. 
     In conventional fluid-fluid contactor trays, velocities of the continuous-phase fluid are very low relative to fluid-vapor columns. The low velocities in the continuous-phase fluid result in the continuous-phase fluid having minimal head pressure thereby inducing re-circulation and stagnation. Recirculation and stagnation reduces mass-transfer driving force. Tray areas where no mass transfer between the continuous-phase fluid and the dispersed-phase fluid occurs are referred to as “dead zones.” Dead zones form in locations where the continuous-phase fluid stagnates thus exhausting the solvent absorption capability. Furthermore, the low velocities of the continuous-phase fluid result in the continuous-phase fluid tending to not cover an entire surface of a tray. Such incomplete tray coverage lessens an area of effective mass transfer and reduces an efficiency of the tray. These problems are generally present regardless of whether the heavier fluid or the lighter fluid is used as the continuous phase. 
     U.S. Pat. No. 7,556,734, assigned to AMT International Inc., teaches an exchange column for contacting liquid in a continuous phase with liquid in a dispersed phase. Contact between liquid in the continuous phase and liquid in the dispersed phase is enhanced by providing upstanding baffles on lower trays interspersed with depending baffles from trays above. In addition, flow distribution partitions extend along a flow path, between the baffles, to distribute liquid flow across the trays. 
     U.S. Pat. No. 4,247,521, assigned to Union Carbide Corporation, teaches a liquid-liquid contacting tray having a channelized liquid transfer means for transferring continuous phase liquid from a contacting zone on one side of the tray to a contacting zone on the other side of the tray. The channelized liquid transfer means includes a settling section operable to allow disengagement of the discontinuous phase liquid from the continuous phase liquid, and a pressure drop section. 
     U.S. Pat. No. 2,752,229 assigned to Universal Oil Products Company, teaches a tower for effecting countercurrent contacting of fluid streams, particularly liquid-liquid contacting. The tower includes a plurality of vertically spaced perforated liquid distributing decks extending across a confined chamber. Sloping liquid downpipe assemblies extend from a liquid receiving well on one deck to a liquid seal reservoir of the next lower deck. Use of the sloping downpipe ensures that the continuous-phase liquid moves in the same direction across successive trays thus creating a uni-directional flow path. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a separations tray assembly for use in a fluid-fluid exchange column. The separations tray assembly is of the type where a first fluid, in a continuous phase, is directed across the tray in a cross-flow path. A second fluid, in a dispersed phase, ascends through apertures in the tray thus inducing interaction and mass transfer with the first fluid. In accordance with one aspect of the present invention, the separations tray further includes a diffuser skirt, having apertures disposed therein, operatively coupled to a fluid channel. The diffuser skirt is operable to direct the first fluid to cover substantially an entire surface of the separations tray and to induce stirring and mixing of the first fluid and the second fluid to effect efficient mass transfer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the method and system of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a side-elevational cross-sectional view of a prior art fluid-fluid exchange column; 
         FIG. 2  is a side-elevational cross-sectional view of a prior-art fluid-fluid exchange column; 
         FIG. 3  is a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment; 
         FIG. 4  is a top-plan, diagrammatic view of a tray according to an exemplary embodiment; 
         FIG. 5  is a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment; 
         FIG. 6  is a top-plan, diagrammatic view of a tray according to an exemplary embodiment; 
         FIG. 7A  is a perspective view of a diffuser skirt according to an exemplary embodiment; 
         FIGS. 7B-7E  are top-plan views of diffuser skirts according to exemplary embodiments; 
         FIG. 7F  is a top-plan, diagrammatic view of a tray according to an exemplary embodiment; 
         FIG. 8  is a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment; 
         FIG. 9A  is a top-plan, diagrammatic view of a tray according to an exemplary embodiment; 
         FIG. 9B  is a top-plan, diagrammatic view of a tray according to an exemplary embodiment; and 
         FIG. 10  is a is a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Referring now to  FIG. 1 , there is shown a side-elevational cross-sectional view of a prior-art fluid-fluid exchange column. A fluid-fluid exchange column  10  includes a continuous-fluid-feeder line  12  and a first draw-off line  14 . Also included are a dispersed-fluid feeder line  16  and a second draw-off line  18 . A plurality of trays  20 ( 1 )- 20 ( 7 ) are disposed within the fluid-fluid exchange column  10 . Typically, the fluid-fluid exchange column  10  is used in extraction processes such as, for example, extraction of an acid from water using a solvent. 
     Still referring to  FIG. 1 , the plurality of trays  20 ( 1 )- 20 ( 7 ) generally comprise a solid tray or deck having a plurality of apertures  22  disposed therein. The plurality of apertures  22  may include, for example, holes, slots, floating valves, or any other appropriate type of aperture. Separation trays such as, for example, the plurality of trays  20 ( 1 )- 20 ( 7 ) comprise at least one of cross-flow trays with downcomers and counter-flow trays without downcomers. In cross-flow trays, a lighter fluid  30  ascends through the plurality of apertures  22  and contacts a heavier fluid  24  moving across the plurality of trays  20 ( 1 )- 20 ( 7 ). In an active area, the heavier fluid  24  and the lighter fluid  30  mix and fractionation occurs. In counter-flow trays, both the lighter fluid  30  and the heavier fluid  24  pass through the plurality of apertures  22 . 
     Still Referring to  FIG. 1 , in cross-flow operation, the heavier fluid  24 , in a continuous phase, is introduced to, and substantially fills, the fluid-fluid exchange column  10  via the continuous-fluid-feeder line  12 . The heavier fluid  24  is directed onto one of the plurality of trays  20 ( 1 )- 20 ( 7 ) such as, for example, the tray  20 ( 2 ) by means of a fluid channel  26  from the tray  20 ( 1 ) above. The fluid channel  26  is referred to as a “downcomer.” The heavier fluid  24  moves across the tray  20 ( 1 ) and enters the fluid channel  26  through a downcomer entrance  28 ( a ) and then leaves through a downcomer exit  28 ( b ). At the same time, the lighter fluid  30  in a dispersed phase is introduced to the fluid-fluid exchange column  10  via the dispersed-fluid feeder line  16 . The lighter fluid  30  forms bubbles that rise through the heavier fluid  24 . Typically, the bubbles of the lighter fluid  30  are approximately ¼ of an inch or smaller. The lighter fluid  30  rises through the fluid-fluid exchange column  10  and forms a coalesced layer on an underside of each of the plurality of trays  20 ( 1 )- 20 ( 7 ). The plurality of apertures  22  facilitate passage of the lighter fluid  30  through each of the plurality of trays  20 ( 1 )- 20 ( 7 ) allowing interaction with the heavier fluid  24 . Remaining heaver fluid  24  is removed from the fluid-fluid exchange column  10  via the first draw-off line  14 . Likewise, remaining lighter fluid  30  is removed from the fluid-fluid exchange column  10  via the second draw-off line  18 . 
     For example, in the case of an extraction column, heavier fluid  24  such as, for example, water containing acetic acid is pumped into the fluid-fluid exchange column  10  in a continuous phase, via continuous-fluid feeder-line  12 . The heavier fluid  24  comprising the water-acid mixture descends through the fluid-fluid exchange column  10  in a circuitous route passing over each of the plurality of trays  20 ( 1 )- 20 ( 7 ) in alternating directions. Simultaneously, lighter fluid  30  such as, for example, a solvent containing an alkyl acetate is introduced via the dispersed-fluid feeder line  16 . The lighter fluid  30  comprising the solvent-alkyl acetate mixture bubbles up through the water-acid mixture and coalesces on the underside of each of the plurality of trays  20 ( 1 )- 20 ( 7 ). The solvent interacts with the water-acid mixture and gradually absorbs the acetic acid. Thus, the concentration of acetic acid is greatest in water-acid mixture moving across the tray  20 ( 1 ). The concentration of acetic acid in the water decreases as the water-acid mixture moves across each successive tray of the plurality of trays  20 ( 1 )- 20 ( 7 ) until, finally, residual water (also referred to as “raffinate”) is removed from the fluid-fluid exchange column  10  via the first draw-off line  14 . In similar fashion, the concentration of acetic acid in the solvent increases with each successive tray until acetic acid extract is removed from the fluid-fluid exchange column  10  via the second draw-off line  18 . 
     Referring now to  FIG. 2 , there is shown a side-elevational cross-sectional view of a prior-art fluid-fluid exchange column. A fluid-fluid exchange column  32  includes a continuous-fluid-feeder line  34  and a first draw-off line  36 . Also included are a dispersed-fluid feeder line  38  and a second draw-off-line  40 . A plurality of trays  42 ( 1 )- 42 ( 7 ) are disposed within the fluid-fluid exchange column  32 . A fluid-fluid exchange column such as, for example, the fluid-fluid exchange column  32  may be used in a process such as, for example, extraction of benzene from water. 
     Still referring to  FIG. 2 , the plurality of trays  42 ( 1 )- 42 ( 7 ) generally comprise a solid tray or deck having a plurality of apertures  44  disposed therein. The plurality of apertures  44  may include, for example, holes, slots, floating valves, and other appropriate types of apertures. In operation, a lighter fluid  46 , in a continuous phase, is introduced to, and substantially fills, the fluid-fluid exchange column  32  via the continuous-fluid-feeder line  34 . The lighter fluid  46  is directed onto a tray such as, for example, the tray  42 ( 6 ) by means of a fluid channel  48  from the  42 ( 7 ) tray below. The fluid channel  48  is referred to as an “upcomer.” The lighter fluid  46  moves across the tray  42 ( 7 ) and enters an upcomer entrance  50 ( a ). The lighter fluid  46  then exits the fluid channel  48  via an upcomer exit  50 ( b ). A heavier fluid  52 , in a dispersed phase, is simultaneously introduced to the fluid-fluid exchange column  32  via the dispersed-fluid feeder line  38 . The heavier fluid  52  forms bubbles that descend through the lighter fluid  46 . Typically, the bubbles of the heavier fluid  52  are approximately ¼ of an inch or smaller. The heavier fluid  52  descends through the fluid-fluid exchange column  32  and forms a coalesced layer on a top surface of each of the plurality of trays  42 ( 1 )- 42 ( 7 ). The plurality of apertures  44  facilitate passage of the heavier fluid  52  through each of the plurality of trays  42 ( 1 )- 42 ( 7 ) allowing interaction with the lighter fluid  46 . Residual lighter fluid  46  is removed from the fluid-fluid exchange column  32  via the first draw-off line  36 . Likewise, residual heavier fluid  52  is removed from the fluid-fluid exchange column  32  via the second draw-off line  40 . 
       FIG. 2  is included herein to demonstrate that either a heavier fluid or a lighter fluid may be used in operation as the continuous phase with appropriate modifications to a structure of the fluid-fluid exchange column. For ease and clarity of discussion, the following exemplary embodiments will be described by way of example as having a heavier fluid in the continuous phase. However, one skilled in the art will recognize that, alternatively, each of the embodiments below could function with a lighter fluid as the continuous phase and flow redirected in accordance therewith. 
     Referring now to  FIG. 3 , there is shown a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment In various embodiments, a fluid-fluid exchange column  300  includes a plurality of trays  302 ( 1 )- 302 ( 5 ) and a plurality of fluid channels  304 . In various embodiments, the plurality of fluid channels  304  may include, for example, a downcomer or an upcomer as described hereinabove. In a typical embodiment, a tray such as, for example, the tray  302 ( 2 ), allows fluid to enter and exit via the fluid channels  304 . In a typical embodiment, the fluid channels  304  include a plurality of orifice constrictions  306 ( a )- 306 ( c ) disposed therein. The plurality of orifice constrictions  306 ( a )- 306 ( c ) may utilize a variety of pressure-drop control devices such as, for example, an envelope-pipe reducer  306 ( a ), a perforated plate  306 ( b ), a plurality of baffles  306 ( c ), and the like. In a typical embodiment, plurality of the orifice constrictions  306 ( a )- 306 ( c ) restrict the flow of fluid moving through the fluid channels  304  and prevent backflow of either a continuous-phase fluid  308  or a dispersed-phase fluid  310  therethrough. In a typical embodiment, the plurality of trays  302 ( 1 )- 302 ( 5 ) include a diffuser skirt  312 ( a ). The diffuser skirt  312 ( a ) includes a diffuser body and plurality of apertures  314  therein. The diffuser skirt  312 ( a ) depends from an underside of the fluid channel  304 . As shown by way of example in  FIG. 3 , the diffuser skirt  312 ( a ) extends entirely between two trays such as, for example, the trays  302 ( 1 ) and the tray  302 ( 2 ); however, one skilled in the art will recognize that the diffuser skirt  312 ( a ) may not extend entirely between the two trays  302 ( 1 ) and  302 ( 2 ) leaving a clearance space. Although the plurality of apertures  314  are shown by way of example in  FIG. 3  as perforations, one skilled in the art will recognize that, in alternative embodiments, the plurality of apertures  314  may include slots, louvers, and the like. The plurality of apertures  314  are illustrated by way of example in  FIG. 3  as being evenly spaced around the diffuser skirt  312 ( a ); however, the plurality of apertures  314  may alternatively be grouped to direct the continuous-phase fluid  308  in a desired direction. By way of example, the fluid-fluid exchange column  300  is shown in  FIG. 3  as containing five trays  302 ( 1 )- 302 ( 5 ); however, one skilled in the art will recognize that, in alternative embodiments, any number of trays may be utilized. 
     Referring still to  FIG. 3 , in various embodiments, the fluid-fluid exchange column  300  includes a first conduit  312 ( b ). In a typical embodiment, the first conduit  312 ( b ) includes a plurality of apertures  315  disposed therein. In various embodiments, the first conduit  312 ( b ) depends from an underside of the fluid channel  304 . As shown by way of example in  FIG. 3 , the first conduit  312 ( b ) does not extend entirely between two trays such as, for example, the tray  302 ( 3 ) and the tray  302 ( 4 ); however, one skilled in the art will recognize that, in alternative embodiments, the first conduit  312 ( b ) may extend entirely between the two trays  302 ( 3 ) and  302 ( 4 ). Although, the plurality of apertures  315  are shown by way of example in  FIG. 3  as perforations; one skilled in the art will recognize that, in alternative embodiments, the plurality of apertures  315  may include slots, louvers, or the like. The plurality of apertures  315  are illustrated by way of example in  FIG. 3  as being evenly spaced around the first conduit  312 ( b ); however, the plurality of apertures  315  may alternatively be grouped to direct the continuous-phase fluid  308  in a desired direction. 
     Referring still to  FIG. 3 , in certain embodiments, the plurality of apertures  315  are disposed on both an interior face and an exterior face of a second conduit  312 ( c ). Such an arrangement facilitates mixing of the continuous-phase fluid  308  and the dispersed-phase fluid  310  on the exterior side of the second conduit  312 ( c ). Additionally, this arrangement allows an active area, where mixing of the continuous-phase fluid  308  and the dispersed-phase fluid  310  occurs, to extend entirely to the outer wall  301  of the fluid-fluid exchange column  300 . 
     Referring still to  FIG. 3 , in certain embodiments, a coalescing element  316  may be included on any of the plurality of trays  302 ( 1 )- 302 ( 5 ) to facilitate coalescing of the dispersed-phase fluid  310 . Although the coalescing element  316  is shown in  FIG. 3  as being disposed on an underside of the plurality of trays  302 ( 1 )- 302 ( 2 ), one skilled in the art will recognize that the, in alternative embodiments, coalescing element  316  may be located on a top surface of the plurality of trays  302 ( 1 )- 302 ( 2 ) in cases where the dispersed-phase fluid  310  is heavier than the continuous-phase fluid  308 . 
     Still referring to  FIG. 3 , during operation, the continuous-phase fluid  308  moves across a tray such as, for example, the tray  302 ( 1 ), into the fluid channel  304 , and through at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ). As the continuous-phase fluid  308  moves through at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ), flow of the continuous-phase fluid  308  is restricted resulting in increased velocity of the continuous-phase fluid  308 . The added velocity further facilitates stirring and mixing of the continuous-phase fluid  308  and the dispersed-phase fluid  310  forcing the continuous-phase fluid  308  to be spread entirely across a cross-flow volumetric window between successive trays such as, for example, the trays  302 ( 1 ) and  302 ( 2 ) preventing stagnation and reducing recirculation (also referred to as “eddy current”) in the continuous-phase fluid  308 . Additionally, according to an exemplary embodiment, thrust tabs (not explicitly shown in  FIG. 3 ) may be incorporated in conjunction with the plurality of apertures  314  or  315  to direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window between each of the plurality of trays  302 ( 1 )- 302 ( 5 ). 
     Referring now to  FIG. 4 , there is shown a top-plane, diagrammatic view of a tray according to an exemplary embodiment. In a typical embodiment, a tray such as, for example, the tray  302 ( 2 ) includes a diffuser skirt  312 ( a ), a plurality of baffles  408 , and a plurality of vanes  412 . In a typical embodiment, the diffuser skirt  312 (a) forms a chord across a surface of a tray such as, for example, the tray  302 ( 2 ). As illustrated in  FIG. 4 , a plurality of tabs  404  may be incorporated with the plurality of apertures  314  (shown in  FIG. 3 ) to direct the continuous-phase fluid  308  in a desired direction thus further inducing the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  302 ( 2 ). The plurality of baffles  408  may be incorporated within the fluid channel  304  to direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  302 ( 2 ). Additionally, the plurality of vanes  412  may be incorporated to impart additional velocity to the continuous-phase fluid  308  and to further direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  302 ( 2 ). 
     Referring now to  FIG. 5 , there is shown a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment. In a typical embodiment, a fluid-fluid exchange column  500  includes a plurality of trays  502 ( 1 )- 502 ( 5 ). By way of example, the fluid-fluid exchange column  500  is illustrated in  FIG. 5  as having five trays  502 ( 1 )- 502 ( 5 ); however, one skilled in the art will recognize that, in alternative embodiments, any number of trays could be utilized. In a typical embodiment, a tray such as, for example, the tray  502 ( 2 ) allows fluid to enter and exit via fluid channels  504 . In various embodiments, the plurality of fluid channels  504  may include, for example, a downcomer or an upcomer as described hereinabove. In various embodiments, the fluid channels  504  include at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ) (shown in  FIG. 3 ) disposed therein. The plurality of orifice constrictions  306 ( a )- 306 ( c ) are described above with respect to  FIG. 3 . In a typical embodiment, a plurality of diffuser skirts  506 ( a )- 506 ( c ), each having a diffuser body and a plurality of apertures  508  disposed therein, depends from an underside of the fluid channels  504 . As shown by way of example in  FIG. 5 , the plurality of diffuser skirts  506 ( a )- 506 ( c ) extends substantially between two trays such as, for example, the tray  502 ( 1 ) and the tray  502 ( 2 ); however, one skilled in the art will recognize that, in alternative embodiments, the plurality of diffuser skirts  506 ( a )- 506 ( c ) may not extend entirely to, for example, the tray  502 ( 2 ) leaving a clearance space between the plurality of diffuser skirts  506 ( a )- 506 ( c ) and the tray  502 ( 2 ) for additional flow. 
     Still Referring to  FIG. 5 , in contrast to  FIG. 3 , the plurality of diffuser skirts  506 ( a )- 506 ( c ) are, in a typical embodiment, angled towards an outer wall  510  of the fluid-fluid exchange column  500  thereby inducing turbulence in the continuous-phase fluid  308 . Although, the plurality of apertures  508  are shown by way of example in  FIG. 5  as perforations; one skilled in the art will recognize that the plurality of apertures  508  could include slots, louvers, and other configurations. The plurality of apertures  508  are illustrated by way of example in  FIG. 5  as being evenly spaced around the plurality of diffuser skirts  506 ( a )- 506 ( c ); however, the plurality of apertures  508  may alternatively be grouped to create a specific fluid flow Additionally, in various embodiments, at least one of inlet weirs  512 ( a )- 512 ( c ) may be disposed on a top surface of a tray such as, for example, the trays  502 ( 2 )- 20 ( 4 ) medially of the plurality of diffuser skirts  506 ( a )- 506 ( c ). In some embodiments, a diffuser skirt such as, for example, the plurality of diffuser skirts  506 ( b ) may extend entirely to the outer wall  510  of the fluid-fluid exchange column  500 . In this arrangement, the plurality of diffuser skirts  506 ( b ) also performs the function of at least one of the orifice constrictions  306 ( a )- 306 ( c ). Such an arrangement also allows an active area associated with a tray such as, for example, the tray  502 ( 4 ) to extend entirely to the outer wall  510  of the fluid-fluid exchange column  500 . In addition, in some embodiments, a diffuser skirt  506 ( c ) may seal upon a floor of an adjacent tray such as, for example, the tray  502 ( 5 ). 
     Still Referring to  FIG. 5 , in certain embodiments, the coalescing element  316  may be included on any of the plurality of trays  502 ( 1 )- 502 ( 5 ) to facilitate coalescing of the dispersed-phase fluid  310 . Although the coalescing element  316  is shown in  FIG. 5  as being disposed on an underside of a tray such as, for example, the trays  502 ( 1 )- 502 ( 2 ), one skilled in the art will recognize that, in alternative embodiments, the coalescing element  316  could be located on a top surface of a tray such as, for example, the trays  502 ( 1 )- 502 ( 2 ) in those flow configurations where the dispersed-phase fluid  310  is heavier than the continuous-phase fluid  308  and the flow is redirected in accordance therewith. 
     Still referring to  FIG. 5 , during operation, the continuous-phase fluid  308  moves across a tray such as, for example, the tray  502 ( 1 ), into the fluid channel  504 , and through at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ). As the continuous-phase fluid  308  moves through the plurality of diffuser skirts  506 ( a )- 506 ( c ). In a typical embodiment, the diffuser skirts  506 ( a )- 506 ( c ) are angled towards an outer wall  510  of the fluid-fluid exchange column  500 . In a typical embodiment, flow restriction imposed by the plurality of apertures  508  results in additional velocity being imparted to the continuous-phase fluid  308 . The added velocity further facilitates stirring and mixing of the continuous-phase fluid  308  and the dispersed-phase fluid  310 . Such added velocity also forces the continuous-phase fluid  308  to be spread entirely across a volumetric cross-flow window between successive trays such as, for example, the trays  502 ( 1 )- 502 ( 2 ) thus preventing stagnation and reducing recirculation of the continuous-phase fluid  308 . In addition, the continuous-phase fluid  308  passes through the plurality of apertures  508  at right angles to the plurality of diffuser skirts  506 ( a )- 506 ( c ). In various embodiments, some of the continuous-phase fluid  308  will pass over, for example, a solid inlet weir  512 ( a ). In an alternative embodiments, some of the continuous-phase fluid  308  could pass through a perforated inlet weir  512 ( b ). The interaction of the plurality of diffuser skirts  506 ( a )- 506 ( c ) and the perforated inlet weir  512 ( b ) introduce turbulence to the continuous-phase fluid  308 . The directional turbulence causes stirring of the continuous-phase fluid  308  thus facilitating interaction with the dispersed-phase fluid  310 . Additionally, thrust tabs (not explicitly shown in  FIG. 5 ) may be incorporated in conjunction with the plurality of apertures  508  of the plurality of diffuser skirts  506 ( a )- 506 ( c ) or the perforated inlet weir  512 ( b ) to direct the continuous-phase fluid  308  to cover an entire volumetric cross-flow window of the plurality of trays  502 ( 1 )- 502 ( 5 ). 
     Referring now to  FIG. 6 , there is shown a top-plane, diagrammatic view of a tray according to an exemplary embodiment. In a typical embodiment a tray such as, for example, the tray  502 ( 2 ) includes a diffuser skirt  506 ( a ) and a plurality of vanes  602 . The diffuser skirt  506 ( a ) forms a chord across a surface of the tray  502 ( 2 ). As illustrated in  FIG. 6 , thrust tabs (not explicitly shown in  FIG. 6 ) may be incorporated with the plurality of apertures  508  to direct to the continuous-phase fluid  308  (not shown in  FIG. 6 ) in a desired direction thereby inducing the continuous-phase fluid  308  to cover an entire volumetric cross-flow window of a tray such as, for example the tray  502 ( 2 ). Additionally, at least one or a plurality of vanes  602  may be disposed on a tray such as, for example, the tray  502 ( 2 ) to impart additional velocity to the continuous-phase fluid  308  and to further direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  502 ( 2 ). According to exemplary embodiments, the vanes  602  may be curved, angled, or straight to reduce eddy currents in the continuous-phase fluid  308  and the dispersed-phase fluid  310  (not shown in  FIG. 6 ). Reducing eddy currents prevents recirculation of either the continuous-phase fluid  308  or the dispersed-phase fluid  310  and improves efficiency of the plurality of trays  502 ( 1 )- 502 ( 5 ). The plurality of apertures  508  are illustrated by way of example in  FIG. 6  as being evenly spaced around the diffuser skirt  506 ( a )- 506 ( c ); however, the plurality of apertures  508  may alternatively be grouped to create a specific fluid flow. 
     Referring now to  FIG. 7A , there is shown a perspective view of a diffuser skirt according to an exemplary embodiment. In a typical embodiment, a diffuser skirt  700  comprises a plurality of apertures  702 . The plurality of apertures  702  are illustrated by way of example in  FIG. 7A  as being evenly spaced around the diffuser skirt  700 ; however, the plurality of apertures  702  may, in alternative embodiments, be grouped to create a specific fluid flow. In a typical embodiment the diffuser skirt  700  is substantially convex shaped. The diffuser skirt  700  may be, for example, roughly infundibular or quasi-frustoconical in shape. 
       FIGS. 7B-7E  illustrate various exemplary shapes of the diffuser skirt  700 .  FIG. 7B  illustrates the diffuser skirt  700  as chevron shaped.  FIG. 7C  illustrates the diffuser skirt  700  as pentagon-shaped,  FIG. 7D  illustrates the diffuser skirt  700  as open hexagon-shaped.  FIG. 7E  illustrates the diffuser skirt  700  as an open polygon or any other appropriate shape. 
     Referring specifically to  FIG. 7F , there is shown a top-plane, diagrammatic view of a tray according to an exemplary embodiment. In a typical embodiment, a tray  704  includes a diffuser skirt  700  having a plurality of apertures  702  therein. In a typical embodiment, the diffuser skirt  700  is substantially arc-shaped. In a typical embodiment, the diffuser skirt  700  may be, for example, roughly infundibular or quasi-frustoconical in shape. During operation, the continuous-phase fluid  308  moves through the plurality of apertures  702  at an approximate right angle to the diffuser skirt  700 . The roughly arcuate profile of the diffuser skirt  700  facilitates directing the continuous-phase fluid  308  over the entire volumetric cross-flow window between successive trays such as, for example, the tray  704 . In various embodiments, tabs  64  (shown in  FIG. 4 ) may be incorporated with the plurality of apertures  702  to direct the continuous-phase fluid  308  in a desired direction thereby inducing the continuous-phase fluid  308  to cover the entire volumetric cross-flow window between the successive trays such as, for example, the trays  502 ( 1 )- 502 ( 2 ) (shown in  FIG. 5 ). Additionally, at least one or a plurality of vanes  706  may be incorporated to impart additional velocity to the continuous-phase fluid  308  and to further direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  704 . The vanes  706  may be curved, angled, or straight to reduce eddy currents in the continuous-phase fluid  308  and the dispersed-phase fluid  310  (not explicitly shown in  FIG. 7 ). The plurality of apertures  702  are illustrated by way of example in  FIG. 7F  as being evenly spaced around the diffuser skirt  700 ; however, the plurality of apertures  702  may, in alternative embodiments, be grouped to direct the continuous-phase fluid  308  to cover an entire volumetric cross-flow window of the tray  704 . 
     Referring now to  FIG. 8 , there is shown a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment. A fluid-fluid exchange column  800  includes a plurality of trays  802 ( 1 )- 802 ( 4 ). In a typical embodiment, a tray such as, for example, the tray  802 ( 2 ) allows fluid to enter and exit via fluid channels  804 . In various embodiments, the plurality of fluid channels  804  may include, for example, a downcomer or an upcomer as described hereinabove. In a various embodiments, the fluid channels  804  include at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ) (shown in  FIG. 3 ) discussed above with respect to  FIG. 3  disposed therein. A downspout  806 , having a plurality of apertures  808  therein, depends from an underside of the fluid channel  804 . As shown by way of example in  FIG. 8 , the downspout  806  extends substantially between two successive trays such as, for example, the tray  802 ( 1 ) and the tray  802 ( 2 ) leaving a clearance gap  810  between the downspout  806  and the tray  802 ( 2 ); however, one skilled in the art will recognize that, in alternative embodiments, the downspout  806  may extend entirely to the tray  802 ( 2 ) leaving no clearance space. Although, the plurality of apertures  808  are shown by way of example in  FIG. 8  as perforations; one skilled in the art will recognize that, in alternative embodiments, the plurality of apertures  808  could include slots, louvers, or the like. The plurality of apertures  808  are illustrated by way of example in  FIG. 8  as being evenly spaced around the downspout  806 ; however, the plurality of apertures  808  may alternatively be grouped to create a specific fluid flow. By way of example, the fluid-fluid exchange column  800  is illustrated as including four trays  802 ( 1 )- 802 ( 4 ); however, one skilled in the art will recognize that, in alternative embodiments, any number of trays could be utilized. 
     Still Referring to  FIG. 8 , in certain embodiments, the coalescing element  316  may be included on the any of the plurality of trays  802 ( 1 )- 802 ( 4 ) to facilitate coalescing of the dispersed-phase fluid  310 . Although the coalescing element  316  is shown in  FIG. 8  as being disposed on an underside of the plurality of trays  802 ( 1 )- 802 ( 4 ), one skilled in the art will recognize that, in alternative embodiments, the coalescing element  316  could be located on a top surface of the plurality of trays  802 ( 1 )- 802 ( 4 ) in cases where the dispersed-phase fluid  310  is heavier than the continuous-phase fluid  308 . 
     Still referring to  FIG. 8 , during operation, a continuous-phase fluid  308  moves across a tray such as, for example, the tray  802 ( 1 ), into the fluid channel  804 , and through at least one of the orifice constrictions  306 ( a )- 306 ( c ). As the continuous-phase fluid  308  moves through the downspout  806 , the flow restriction imposed by the plurality of apertures  808  results in velocity being imparted to the continuous-phase fluid  308 . The added velocity also facilitates stirring and mixing of the continuous-phase fluid  308  and the dispersed-phase fluid  310 . Such added velocity also forces the continuous-phase fluid  308  to be dispersed across an entire volumetric cross-flow window between successive trays such as, for example, the tray  802 ( 1 ) and the tray  802 ( 2 ) thus preventing stagnation and recirculation. Additionally, thrust tabs (not explicitly shown in  FIG. 8 ) may be incorporated in conjunction with the plurality of apertures  808  to direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of the plurality of trays  802 ( 1 )- 802 ( 4 ). 
     Referring now to  FIGS. 9A and 9B , there is shown a top-plane, diagrammatic view of a tray according to an exemplary embodiment. In a typical embodiment a tray such as, for example, the tray  802 ( 2 ) includes the fluid channel  804  and the downspout  806 . In a typical embodiment, the downspout  806  can be seen disposed within the fluid channel  804 . As shown in  FIG. 9A , in certain embodiments, a single downspout  806  may be included in the fluid channel  804 . However, as illustrated in  FIG. 9B , in certain alternative embodiments, multiple downspouts  807 ( 1 )- 807 ( 5 ) may be included in the fluid channel  804 . As previously illustrated in  FIG. 4 , thrust tabs (not explicitly shown in  FIGS. 9A and 9B ) may be incorporated with the plurality of apertures (not explicitly shown in  FIGS. 9A and 9B ) to direct the continuous-phase fluid  308  in a desired direction thereby inducing the continuous-phase fluid  308  to cover the entire volumetric cross-flow area of a tray such as, for example, the tray  802 ( 2 ). Additionally, at least one or a plurality of vanes  902  may be incorporated to impart additional velocity to the continuous-phase fluid  308  and to further direct the continuous-phase fluid  308  to cover the entire volumetric cross-flow window of a tray such as, for example, the tray  802 ( 2 ). The vanes  902  may be curved, angled, or straight to reduce eddy currents in the continuous-phase fluid  308  and the dispersed-phase fluid  310  (not explicitly shown in  FIG. 9 ). 
     It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. Although the method and apparatus shown or described has been characterized as being preferred it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims. For example, most embodiments are described herein as having a heavier fluid in a continuous phase; however, one skilled in the art will recognize that a lighter fluid could comprise the continuous phase with minimal change to the structure of the fluid-fluid exchange column. By way of further example, the principles disclosed herein are applicable to various types of separations trays including, for example, valve trays, sieve trays, and the like. Furthermore, the features discussed above with respect to  FIGS. 1-9  may be combined and rearranged in numerous advantageous ways that will be apparent to one of ordinary skill in the art. For example, although specific embodiments are discussed herein that have various features such as lighter fluid slots, ridges, and thrust tabs, it is fully contemplated that other advantageous embodiments may have any combination of or even multiple instances of these features. Finally, specific embodiments are illustrated herein as pertaining to single-pass trays with a serpentine flow path; however, one skilled in the art will recognize that the principles disclosed herein could be applicable to separations trays having numerous types of flow paths including, for example, dual-pass, multiple pass, orbital flow, and uni-directional flow. 
       FIG. 10  is a is a diagrammatic, side-elevational, cross-sectional view of a fluid-fluid exchange column according to an exemplary embodiment. In a typical embodiment, a fluid-fluid exchange column  1000  is constructed similar to any of, for example, the fluid-fluid exchange columns  300 ,  500 , or  800  shown in  FIGS. 3, 5, and 8 . In a typical embodiment, a continuous-phase fluid  1008  is a light fluid and thus flows from a bottom portion to a top portion of the fluid-fluid exchange column  1000 . Likewise, a dispersed-phase fluid  1010  is a heavy fluid and thus flows from a top portion to a bottom portion of the fluid-fluid exchange column  1000 . In a typical embodiment, during operation, the continuous-phase fluid  1008  moves across a tray such as, for example, the tray  1002 ( 1 ), into a fluid channel  1004 , and through at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ). As the continuous-phase fluid  1008  moves through at least one of the plurality of orifice constrictions  306 ( a )- 306 ( c ), flow of the continuous-phase fluid  1008  is restricted resulting in increased velocity of the continuous-phase fluid  1008 . The added velocity further facilitates stirring and mixing of the continuous-phase fluid  1008  and the dispersed-phase fluid  1010  forcing the continuous-phase fluid  1008  to be spread entirely across a cross-flow volumetric window between successive trays such as, for example, the trays  1002 ( 1 ) and  1002 ( 2 ) preventing stagnation and reducing recirculation (also referred to as “eddy current”) in the continuous-phase fluid  1008 . Additionally, according to an exemplary embodiment, thrust tabs (not explicitly shown in  FIG. 10 ) may be incorporated in conjunction with a plurality of apertures  1014  or  1015  to direct the continuous-phase fluid  1008  to cover the entire volumetric cross-flow window between each of the plurality of trays  1002 ( 1 )- 1002 ( 5 ).  FIG. 10  is included herein to demonstrate that either a heavier fluid or a lighter fluid may be used in operation as the continuous phase with appropriate modifications to a structure of the fluid-fluid exchange column. 
     Although various embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth herein.