Abstract:
A collector is used to collect and mix liquid from an overlying zone in a mass transfer column in which fluid streams are processed, such as to obtain fractionation products. The collector has two or more liquid collection regions and two or more sumps positioned about the perimeter of the liquid collection regions. A plurality of channels and deflectors are spaced apart within each liquid collection region and vapor passages are formed in the spacings between adjacent channels. The deflectors direct descending liquid into the channels and shield the vapor passages from the descending liquid. The channels within each liquid collection region are arranged into interspersed sets, with one set of channels preferentially directing collected liquid into one sump and another set of channels preferentially directing collected liquid into another sump. Preferably, roughly equal amounts of liquid from each liquid collection region are deliver to the two sumps so that liquid in the sumps is of a more uniform concentration and composition. One or more of the sumps includes a downcomer for directing the liquid from the sump to an underlying zone. By mixing the liquid within the collector, the use of a separate mixing device can be avoided. As a result, vertical space in the column that would normally be occupied by the mixing device can be filled with packing or other internals to increase the efficiency of the column.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of provisional application Serial No. 60/460,966 filed Apr. 7, 2003. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates generally to mass transfer columns and, more particularly, to apparatuses and methods for collecting and mixing descending liquid for more uniform distribution to an underlying bed of packing or other devices within such columns.  
           [0003]    Mass transfer columns, including heat exchange columns, typically include an upright shell and a plurality of zones within the shell where packing and/or horizontally disposed trays are used to facilitate mass or heat transfer between fluid streams flowing within the column. The fluid streams are normally one or more downwardly flowing liquid streams and one or more ascending vapor streams, although other combinations of fluid streams are possible. Liquid exiting the bottom of one zone may have different concentrations and compositions at different locations across the horizontal cross section of the zone. In order to reduce these concentrational and compositional maldistributions, the liquid is often collected and mixed before it is then distributed to an underlying zone. Separate components are frequently used to effect the desired collection, mixing and distribution of the liquid as it descends from one zone to another. The use of separate components, however, can be undesirable because the vertical spacing occupied by these components reduces the available area within the column for other processing of the fluid streams and may require that a taller column be utilized to provide the spacing needed to effect the desired processing operations.  
           [0004]    A combined collector and mixer has been utilized in columns of the type described above in order to reduce the number of components and the vertical spacing required to collect and mix the liquid exiting from a zone within the column. This combined collector and mixer utilizes a plurality of rows of upwardly extending vanes that collect the descending liquid and feed it into sumps that in turn feed the liquid into a center downcomer. While this device is an effective mixer because all of the collected liquid flows to a single downcomer, mixing efficiency would be greatly reduced in applications where high liquid flow rates and/or large column diameters require the use of two or more downcomers. In such applications, liquid, which is fed from one area of the collector into one downcomer, can have a different composition than liquid flowing from the remaining area of the collector into the other downcomer. As a result, a need has developed for a combined collector and mixer that is not only capable of handling high liquid flow rates using two or more downcomers but is also effective in mixing liquid from different areas of the collector so that liquid entering the downcomers is of substantially uniform composition.  
         SUMMARY OF THE INVENTION  
         [0005]    In one aspect, the present invention is directed to a liquid collector that more uniformly mixes the liquid collected from an overlying zone in a mass transfer column prior to discharging the collected liquid into an underlying zone. As used herein, the term “mass transfer column” is intended to encompass those columns in which only heat exchange occurs. The liquid collector comprises at least first and second sumps, one of which may be an annular sump and the other or both of which may be chordal sumps. The sumps divide the collector into two or more liquid collection regions, each of which contains a first set of spaced apart liquid collection channels and an interspersed second set of spaced apart liquid collection channels. A plurality of upwardly extending deflectors having surfaces for directing descending liquid into the liquid collection channels are positioned in the liquid collection regions. Drain openings are positioned in the liquid collection channels to allow liquid in the first set of channels to preferentially drain into the first sump and liquid in the second set of channels to drain into the second sump. The preferential flow from the liquid collection channels can be achieved in a variety of ways, such as by partially or completely blocking the flow of liquid from one end in the first set of liquid collection channels and partially or completely blocking the flow of liquid from the opposite end in the second set of liquid collection channels, by tilting the liquid collection channels downwardly in the desired direction of flow, and by aligning the drain openings with different sumps. The first and second sets of liquid collection channels preferably deliver roughly equal amounts of liquid from each liquid collection region into the first and second sumps. In this manner, liquid in the first sump will preferably have roughly the same concentration and composition as liquid in the second sump. One or more openings, such as a downcomer inlet, are provided in at least one of the sumps to allow liquid to exit the sump for delivery to an underlying zone in the column.  
           [0006]    In one embodiment of the collector, one of the sumps is an annular sump and the other sump is a chordal sump. In other embodiments, two or more chordal sumps are used with or without an annular sump. The liquid collection regions in some embodiments are hemispherical and can optionally include one or more center regions. In other embodiments, the liquid collector regions are pie-shaped quadrants. More than two sets of liquid collection channels can also be used.  
           [0007]    In a preferred embodiment, two spaced apart chordal sumps and an annular sump are utilized in the collector. The chordal sumps divide the collector into three regions; two hemispheric liquid collection regions of roughly equal areas and a center liquid collection region of roughly twice the area of each hemispheric liquid collection region. Both of the chordal sumps include a downcomer inlet that drains liquid into a downcomer for delivery to an underlying liquid distributor. Flow restriction devices are positioned along the sumps in a manner to cause a portion of the liquid in each hemispheric region to bypass the adjacent sump and be delivered to the remote sump. Preferably, the collected liquid in each of the liquid collection regions is delivered in roughly equal amounts to both of the chordal sumps so that the mixed liquid within one chordal sump is of generally the same concentration and composition as the mixed liquid in the other chordal sump. In this manner, the collector is able to deliver two or more liquid streams of more uniform concentration and composition to an underlying zone even if the liquid when received by the collector from the overlying zone is of varying composition across the cross section of the column. The amount of liquid may be the same in the two or more liquid streams or greater amounts of liquid may be present in one or more of the liquid streams than in the other liquid streams. Ascending vapor flow channels are preferably formed in the spacings between adjacent liquid collection channels to allow vapor to pass upwardly through the collector in countercurrent relationship to the descending liquid.  
           [0008]    In another aspect, the invention is directed to a method of using the described collector to collect liquid from an overlying zone in a mass transfer column and mix it to obtain one or more liquid streams of a more uniform composition. The liquid streams are then delivered to an underling zone for further processing within the column. The method comprises the steps of collecting descending liquid within a plurality of channels positioned within two or more liquid collection regions of the collector. The channels within each liquid collection region are arranged into two or more interspersed sets, with one set of channels preferentially delivering the collected liquid to one sump and another set of channels preferentially delivering the collected liquid to another sump. The first and second sets of channels preferably deliver roughly equal amounts of liquid to the two sumps. The liquid in the sumps is then delivered to an underlying zone within the column where further processing of the liquid can occur. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0009]    In the accompanying drawings which form part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:  
         [0010]    [0010]FIG. 1 is a top plan view of a column taken in horizontal cross section and containing a collector constructed in accordance with the present invention, the collector being shown somewhat schematically with arrows illustrating the direction of liquid flow within the collector;  
         [0011]    [0011]FIG. 2 is a fragmentary top plan view of the collector shown on an enlarged scale from that shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is a fragmentary side elevation view of the collector taken in vertical section along line  3 - 3  of FIG. 2;  
         [0013]    [0013]FIG. 4A is a fragmentary side elevation view of the collector within the area designated by the number  4 A in FIG. 3 and shown on a still further enlarged scale;  
         [0014]    [0014]FIG. 4B is a perspective view of a group of vanes of the collector in accordance with an embodiment of the present invention;  
         [0015]    [0015]FIG. 5 is an enlarged fragmentary end elevation view of the collector taken in vertical section along line  5 - 5  of FIG. 2 and showing further details of a chordal sump;  
         [0016]    [0016]FIG. 6 is an enlarged fragmentary end elevation view of the collector taken along line  6 - 6  of FIG. 2 and showing a downcomer extending between the chordal sump and a parting box of an underlying distributor;  
         [0017]    [0017]FIG. 7 is a fragmentary top plan view of the collector showing the chordal sump and downcomer on an enlarged scale from that shown in FIG. 2;  
         [0018]    [0018]FIG. 8 is a side elevation view of a downpipe used with the collector;  
         [0019]    [0019]FIG. 9 is a top plan view of the collector with center portions removed to illustrate the flow of liquid along the annular or ring sump;  
         [0020]    [0020]FIG. 10 is a fragmentary top plan view of the collector taken within the area designated by the number  10  in FIG. 9 and showing further details of the area where the annular sump feeds into an end of one of the chordal sumps;  
         [0021]    [0021]FIG. 11 is a fragmentary top plan view of the collector taken within the area designated by the number  11  in FIG. 9 and showing further details of the area where the annular sump is blocked from feeding into the corresponding end of the other chordal sump.  
         [0022]    [0022]FIGS. 12-18 are top plan views of a column containing collectors constructed in accordance with different embodiments of the present invention and shown somewhat schematically to illustrate the direction of liquid flow within the collector. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Turning now to the drawings in greater detail and initially to FIG. 1, a column of the type in which fluid streams are processed to obtain fractionation products and/or otherwise to cause mass transfer and heat exchange between the fluid streams is designated broadly by the numeral  20 . Column  20  comprises a rigid upright shell  22  having a cylindrical, polygonal or other suitable configuration and constructed from metal or other materials compatible with the fluids and conditions within the column. Shell  22  has a diameter and height selected for permitting the desired processing of fluid streams in an open internal area  24  defined by the shell  22 .  
         [0024]    A collector  26  of the present invention is mounted within the shell  22  in a substantially horizontal orientation and is sized to fill substantially the entire horizontal cross section of the open internal area  24  so that the collector  26  captures substantially all of the liquid descending from an overlying zone. The overlying zone contains any of various devices commonly found within mass transfer or heat exchange columns that cause lateral distribution of the liquid. For example, the overlying zone can contain a bed of random or structured packing. The specific nature of the devices within the overlying zone is unimportant to an understanding of the present invention.  
         [0025]    As best shown in FIG. 1, the collector  26  comprises an annular sump  28  and two chordal sumps  30  and  32  that extend in parallel and spaced apart relationship. The chordal sumps  30  and  32  are of a length to extend completely across the cross section of the column  20  with their ends interconnected with the annular sump  28 . Downcomer inlets  34  and  36  are centrally positioned along the horizontal length of the chordal sumps  30  and  32 , respectively. As will be discussed below, the present invention can be utilized with different arrangements and numbers of sumps, as well as different numbers and locations of downcomer inlets.  
         [0026]    The chordal sumps  30  and  32  are positioned to divide the surface of the collector  26  into a center and two side regions,  38 ,  40  and  42  respectively, with the area of the center region  38  being roughly twice the area of each of the two side regions  40  and  42 . Turning additionally to FIGS. 2-4B, a plurality of parallel rows of upright liquid collecting vanes  44  are positioned within and substantially fill these regions  38 ,  40  and  42 . As best illustrated in FIG. 4A and FIG. 4B, the vanes  44  each comprise a channel  46  and a deflector  48  that extends upwardly from the channel  46  at an angle to the vertical. The channel  46  and deflector  48  of the vane  44  are illustrated as an integral, one-piece construction, but they may instead be formed as separate components. Preferably, the various parts of each vane  44  are formed by simply bending a single piece of metal or other material into the desired configuration, although other forms of construction can be used if desired. The channel  46  is formed from longitudinally extending side walls  50  and  52  that are spaced apart and interconnected by a bottom panel  54 . The channel  46  has a width that is less than the spacing between adjacent vanes  44  so that an open vapor passage  56  is formed between the vanes  44  to permit upward passage of vapor designated by arrows  57  through the collector  26 .  
         [0027]    The deflector  48  extends upwardly at an angle from side wall  50  and has a downwardly angled flange  58  at its upper end. The angled nature of the deflector  48  and the flange  58  positioned at its upper end forms a shield over the adjacent vapor passage  56  to block descending liquid from entering the vapor passage  56 . The descending liquid is instead funneled into the channel  46  by the angled surface of the associated deflector  48  and by the flange  58  carried by the adjacent vane  44 . The spacing between adjacent vanes  44  is maintained by spacer plates  60  that extend transversely across the upper ends of groups of adjacent vanes  44  and have cutouts for receiving the upper ends of the deflectors  48 . In a similar manner, a plurality of laterally spaced apart bolting plates  62  extend transversely under the lower ends of groups of vanes  44  and have cutouts for receiving the channels  46 .  
         [0028]    The vanes  44  are longitudinally oriented so that they extend horizontally between the chordal sumps  30  and  32  in the center region  38  and between the chordal sumps  30  and  32  and the annular sump  28  in the side regions  38  and  40 , respectively. The vanes  44  preferably extend perpendicularly to the horizontal longitudinal axis of the chordal sumps  30  and  32 , but can alternatively extend at other angles. At least one end of the channel  46  in each vane  44  is open to act as a drain opening to permit fluid to flow from the channel  46  into the adjacent annular sump  28  or chordal sump  30  or  32 . The other end in at least some or all of the channels  46  is completely or partially blocked by a flow restrictor in the form of a plate  64  (FIGS. 4B and 5) to prevent or impede liquid from exiting the channel  46  through the blocked end. In this manner, some of the channels  46  within center region  38  preferentially feed liquid into chordal sump  30  while others of channels  46  preferentially feed liquid into the other chordal sump  32 . Still others of the channels  46  within the center region  38  can be open on both ends to feed liquid into both chordal sumps  30  and  32 . For example, in one arrangement, every other channel  46  is blocked at one end and the remaining channels  46  are blocked at the opposite end by plates  64  so that adjacent channels  46  preferentially feed liquid into different chordal sumps  30  and  32 . In another arrangement, every third channel  46  is open at both ends to feed both sumps  30  and  32  while the remaining channels  46  are blocked at alternating ends. It will be appreciated that other arrangements can be used so long as the flow of liquid from the center region  38  is divided into roughly equal portions that are fed into the two chordal sumps  30  and  32 . It is also important that adjacent channels  46  or groupings of channels feed different chordal sumps  30  and  32  so that liquid in one sump is of substantially the same composition as the liquid in the other sump. In this manner, liquid captured by the vanes  44  across the cross section of the center region  38  is well mixed and is of uniform composition prior to entering the separate downcomer inlets  34  and  36 .  
         [0029]    In a similar manner, the channels  46  in the vanes  44  in the side regions  40  and  42  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  30  or  32 . In this manner, the liquid captured by the vanes  44  in both of the side regions  40  and  42  is fed in roughly equally amounts to the annular sump  28  and the chordal sumps  30  and  32 .  
         [0030]    The annular sump  28  feeds its liquid into selected ends of the chordal sumps  30  and  32  that in turn feed the collected liquid into the downcomer inlets  34  and  36 . As can best be seen in FIGS. 9-11, a hemispheric portion of the annular sump  28  feeds liquid into one end of chordal sump  30  and the other hemispheric portion feeds liquid into the opposite end of the other chordal sump  32 . An annulus blocking plate  66  is positioned in the annular sump  28  just downstream from the inlet end of the chordal sump  30  and another annulus blocking plate  68  is positioned just downstream from the inlet end of the other chordal sump  32 . The opposite ends of the chordal sumps  30  and  32  are blocked by end plates  70  and  72  respectively to prevent or impede liquid from entering the blocked ends of the sumps  30  and  32  from the annular sump  28  and to prevent or impede liquid in the chordal sumps  30  and  32  from entering the annular sump  28 . As can be seen in FIG. 1, the annulus blocking plates  66  and  68  and sump end plates  70  and  72  thus serve to divide the annular sump  28  into the hemispheric portions that feed liquid from side region  40  into chordal sump  32  and also feed liquid from the other side region  42  into the other chordal sump  30 . In this manner, some of the liquid captured by the vanes  44  in side region  40  is mixed with the liquid in the other side region  42  prior to entry into the downcomer inlets  34  and  36 . In a preferred arrangement, one portion of the liquid captured in side region  40  is delivered through one end of the associated channels  46  directly into the chordal sump  30  while the other, preferably equal, portion of the captured liquid is directed through the other end of the channels  46  into one hemispheric portion of the annular sump  28  where it is carried in the direction of flow arrows  74  to the other chordal sump  32 . In the same manner, one portion of the liquid captured in the other side region  42  is delivered directly to chordal sump  32  while the other portion is directed to the other hemispheric portion of the annular sump  28  and is carried in the direction of flow arrows  76  to the other chordal sump  30 . This arrangement ensures that equal parts of the liquid captured by the collector  26  are fed to the downcomer inlets  34  and  36  and that the liquid entering one inlet is of substantially the same composition as liquid entering the other inlet. In order to facilitate the desired directional flow of the liquid along the sumps  28 ,  30  and  32 , the floors of the sumps can optionally be inclined downwardly in the direction of flow. Similarly, rather than using end plates  64  to impede liquid flow from ends of the channels  46 , the channels can simply be tilted downwardly in the direction of the desired flow of liquid from the channels  46 .  
         [0031]    Turning now to FIGS. 6-8, a downcomer  78  extends downwardly from each downcomer inlet  34  and  36  and is received within a parting box  80  of an underlying distributor. The downcomer  78  preferably extends vertically downward, but may also be inclined as illustrated in FIG. 6. Downpipes  82  are also provided in both chordal sumps adjacent the ends of the rectangular downcomer inlets  34  and  36 . The underlying distributor is used to effect a uniform lateral distribution of the liquid to an underlying zone containing devices such as beds of packing. The specific details of the distributor and devices in the underlying zone are not important to the present invention that resides in the design of the collector  26 . The use of two downcomers  78  allows the collector  26  to handle high liquid flow rates while the design of the collector  26  ensures that the flow rate and composition of liquid in one downcomer is roughly the same as that in the other downcomer.  
         [0032]    Referring next to FIG. 12, another embodiment of a collector  126  comprising an annular sump  28  and a single chordal sump  32  is shown. The chordal sump  32  extends completely across the center cross section of the column  20  with its ends interconnected with the annular sump  28 . Downcomer inlet  36  is centrally positioned along the horizontal length of the chordal sump  32 .  
         [0033]    The chordal sump is positioned to divide the surface of the collector  126  into two side regions  40  and  42 , of roughly equal area. A plurality of parallel rows of upright liquid collecting vanes  44  of the type previously described are positioned within and substantially fill regions  40  and  42 .  
         [0034]    At least one end of the channel  46  of each vane  44  is open to form a drain opening that permits fluid to flow from the channel  46  into the adjacent annular sump  28  or chordal sump  32 . In this embodiment, every other channel is blocked at one end and the remaining channels  46  are blocked at the opposite ends by plates, such as plates  64  previously described, so that adjacent channels  46  preferentially feed liquid into the chordal sump  32  or annular sump  28 . Annulus blocking plates  66  and  68  are positioned in the annular sump  28  at opposite ends of the chordal sump  32  to divide the annular sump  28  into hemispheric portions that separately feed liquid into opposite ends of the chordal sump  32 . Liquid that enters the annular sump  28  from liquid collection region  40  is thus delivered to one end of the chordal sump  32  while liquid entering the annular sump  28  from the other liquid collection region  42  is delivered to the opposite end of the chordal sump  32 . In this manner, some of the liquid captured by the vanes  44  across the cross section of the side regions  40  and  42  is mixed in different hemispheric portions of the annular sump  28  before reaching the chordal sump  32  and is of a more uniform composition prior to entering the downcomer inlet  36 . The annulus blocking plates  66  and  68  can also be omitted if so desired. The design variations previously described with respect to collector  26  can be used with collector  126 . For example, instead of flow liquid out of the opposite ends of adjacent channels  46 , the channels  46  may be grouped together such that two or more adjacent channels  46  discharge liquid at the same end. Similarly, the desired directional flow from channels  46  can be achieved by sloping the channels  46  downwardly in the desired direction of flow.  
         [0035]    Referring next to FIG. 13, another embodiment of a collector of present invention is shown and is designated by the numeral  226 . The collector  226  includes an annular sump  28  and three chordal sumps  30 ,  32  and  33  that extend in a parallel and spaced apart relationship. Downcomer inlets  34 ,  36 , and  37  are centrally positioned along the horizontal length of the chordal sumps  30 ,  32 , and  33 , respectively.  
         [0036]    The chordal sumps  30 ,  32 , and  33  are positioned to divide the surface of the collector into two center regions  38  and  39 , and two side regions  40  and  42 . A plurality of parallel rows of upright liquid collecting vanes  44  are positioned within and substantially fill regions  38 ,  39 ,  40 , and  42 . The vanes  44  are longitudinally orientated so that they extend between the chordal sumps  30  and  32  in the center region  38  and between the chordal sumps  32  and  33  in the center region  39 . The vanes  44  are also longitudinally orientated so that they extend between chordal sump  33  and annular sump  28  in side region  40  and between chordal sump  30  and annular sump  28  in side region  42 . At least one end of the channel  46  in each vane  44  is open to permit fluid to flow from the channel  46  into the adjacent annular sump  28  or chordal sump  30 ,  32 , or  33 . The other end of at least some of the channels  46  is completely or partially blocked, such as by plate  64  previously described, to prevent or impede liquid from exiting the channel  46  through the blocked end. In this manner, liquid preferentially flows in one direction from some channels  46  and preferentially flows in the opposite direction from others of the channels  46 .  
         [0037]    The annulus blocking plates  66  and  68  and sump end plates  70 ,  71 ,  72  and  73  serve to divide the annular sump  28  into hemispheric portions. One hemispheric portion of the annular sump  28  feeds liquid into one end of the chordal sump  33  and the other hemispheric portion feeds liquid into the opposite end of the other chordal sump  30 . An annulus blocking plate  66  is positioned in the annular sump  28  just downstream from the inlet end of the chordal sump  33 , and another annulus blocking plate  68  is positioned just downstream from the inlet end of the chordal sump  30 . The opposite ends of the chordal sumps  30  and  33  are blocked by end plates  71  and  72  respectfully, to prevent or impede liquid from entering the blocked ends of sumps  30  and  33  from annular sump  28  or prevent or impede liquid in chordal sumps  30  and  33  from entering annular sump  28 . Both ends of chordal sump  32  are blocked by end plates  70  and  73  to prevent or impede liquid from entering the blocked ends of sump  32  from the annular sump  28  and to prevent or impede liquid in sump  32  from entering annular sump  28 . However, in another embodiment, the ends of chordal sump  32  are not blocked by end plates or they are perforated, or are of a reduced height to act as weirs, or are otherwise constructed to allow portions of the liquid in annular sump  28  to be fed into the center chordal sump  32  and liquid in the chordal sump  32  to flow into annular sump  28 .  
         [0038]    Channels  46  in the vanes  44  in side region  42  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump and adjacent chordal sump  30 . In this manner, one portion of the liquid captured by the vanes  44  in side region  42  is delivered directly to chordal sump  30  while the other portion is directed into the annular sump and is carried to chordal sump  33 .  
         [0039]    Similarly, channels  46  in the vanes  44  in side region  40  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump and adjacent chordal sump  33 . In this manner, one portion of the liquid captured by the vanes  44  in side region  40  is delivered directly to chordal sump  33  while the other portion is directed into the annular sump  28  and is carried to chordal sump  30 .  
         [0040]    The channels  46  in the vanes  44  in center regions  38  and  39  are open at one or both ends in an alternating or other manner to feed liquid into center chordal sump  32  and adjacent sumps  30  and  33  respectively. This arrangement ensures that liquid captured by the collector  226  is fed to the downcomer inlets  34 ,  36  and  37  in proportional amounts and that the liquid entering one downcomer inlet is of substantially the same composition as the liquid entering the other downcomer inlets. Design variations and features previously described with respect to the other collector embodiments can also be used with collector  226 .  
         [0041]    In a variation of collector  226  illustrated in FIG. 17, the single center chordal sump  32  is replaced with two adjacent chordal sumps  32   a  and  32   b  and the associated downcomer  36  is eliminated. One end of chordal sump  32   a  is in fluid flow communication with one portion of the annular sump  28  so that liquid entering chordal sump  32   a  from liquid collection region  39  preferentially flows into the annular sump  28  and then into chordal sump  30 . Similarly, the opposite end of chordal sump  32   b  is in fluid flow communication with another portion of the anular sump  28  so that liquid entering chordal sump  32   b  from liquid collection region  38  preferentially flows into the annumlar sump  28  and then into chordal sump  33 . Flow restrictor plates  70  and  73  are positioned in the other ends of chordal sumps  32   a  and  32   b , respectively, to block or impede flow of liquid out of or into those ends of the chordal sumps  32   a  and  32   b.    
         [0042]    Referring next to FIG. 14, a still further embodiment of a collector is illustrated and is designated by the numeral  326 . Collector  326  includes an annular sump  28  and two chordal sumps  30  and  32  that intersect to divide the surface of the collector  26  into four pie-shaped quadrant regions  86 ,  88 ,  90  and  92 , of roughly equal area. Downcomer inlets  34 ,  36 , and are positioned along the horizontal length of one of the chordal sumps  30  or  32 . A plurality of parallel rows of upright liquid collecting vanes are positioned within and substantial fill regions  86 ,  88 ,  90  and  92 . The vanes  44  are longitudinally oriented so that they extend between one of the chordal sumps  30  or  32  and the annular sump  28 . At least one end of the channel  46  of each vane  44  is open to permit fluid to flow from the channel  46  into the adjacent annular sump  28  or chordal sump  30  or  32 .  
         [0043]    An annulus blocking plate  66  is positioned in the annular sump  28  just downstream from the first end of chordal sump  32  and another annulus blocking plate  68  is positioned just downstream from the second end of chordal sump  32 . The first and second ends of chordal sump  30  are blocked by end plates  70  and  72  respectively to prevent or impede liquid from entering the blocked ends of sump  30  from the annular sump  28  or to prevent or impede liquid in sump  30  from entering annular sump  28 . A central plate  84  is placed diagonally between (quadrants regions)  90  and  88  such that liquid flowing along one half chordal sump  30  is redirected into one portion of chordal sump  32  to reach the downcomer inlet  36  and liquid flowing in the opposite direction along the other half of the chordal sump  30  is redirected into the other portion of chordal sump  32  to reach the other downcomer inlet  34 . It can be seen that the central plate  84  in effect divides both chordal sumps  30  and  32  into two smaller sumps and the downcomer inlets  34  and  36  are positioned only in the two smaller sumps created from sump  32 .  
         [0044]    Channels  46  in the vanes  44  in quadrant regions  86  and  88  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  30 . In this manner, one portion of the liquid captured by the vanes  44  in regions  86  and  88  is delivered directly to chordal sump  30  and eventually into downcomer  36  in chordal sump  32  while the other portion is directed into the annular sump  28  and is carried to the first end of chordal sump  32  and downcomer  34 .  
         [0045]    In quadrant regions  90  and  92 , channels  46  in the vanes  44  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  30 . In this manner, one portion of the liquid captured by the vanes  44  in regions  90  and  92  is delivered directly to chordal sump  30  and eventually into downcomer inlet  34  in chordal sump  32  while the other portion is directed into the annular sump and is carried to the second end of chordal sump  32  and downcomer inlet  36 . This arrangement ensures that substantially equal parts of the liquid captured by the collector  326  are fed to the downcomer inlets  34  and  36  and that the liquid entering one inlet is of substantially the same composition as the liquid entering the other inlet. Liquid entering downcomer inlet  36  flows downwardly and is discharged into one parting box, such as parting box  80  previously described, liquid entering downcomer inlet  34  flows into another parting box.  
         [0046]    Referring next to FIG. 15, another collector embodiment is shown and is designated by the numeral  426 . A collector  426  includes an annular sump  28  and two chordal sumps  30  and  32  that intersect to divide the surface of the collector  26  into four pie-shaped quadrant regions  86 ,  88 ,  90  and  92 , of roughly equal area. Downcomer inlets  34 ,  35 ,  36 , and  37  are positioned along the horizontal length of the chordal sumps  30  and  32 . A plurality of parallel rows of upright liquid collecting vanes are positioned within and substantially fill regions  86 ,  88 ,  90  and  92 . The vanes  44  in regions  88  and  90  are longitudinally oriented so that they extend between chordal sump  30  and the annular sump  28 . The vanes  44  in regions  86  and  92  are rotated from the position illustrated in FIG. 14 and are oriented so that they extend between chordal sump  32  and annular sump  28 . At least one end of the channel  46  of each vane  44  is open to permit fluid to flow from the channel  46  into the adjacent annular sump  28  or chordal sump  30  or  32 .  
         [0047]    An annulus blocking plate  66  is positioned in the annular sump  28  just downstream from the first end of chordal sump  32  and another annulus blocking plate  68  is positioned just downstream from the second end of chordal sump  32 . The first and second ends of chordal sump  30  are blocked by end plates  70  and  72  respectively to prevent or impede liquid from entering the blocked ends of sump  30  from the annular sump  28  or to prevent or impede liquid in sump  30  from entering annular sump  28 . A center plate  84  is placed diagonally between quadrant regions  88  and  90  such that liquid flowing along a portion of chordal sump  30  is redirected into chordal sump  32  to reach the downcomer inlets  35  and  36 .  
         [0048]    Channels  46  in the vanes  44  in quadrant region  86  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  32 . In this manner, one portion of the liquid captured by the vanes  44  in region  86  is delivered directly to chordal sump  32  and eventually into downcomer inlets  36  while the other portion is directed into the annular sump and is carried to the first end of chordal sump  32  and downcomer  35 .  
         [0049]    Channels  46  in the vanes  44  in quadrant region  88  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  30 . In this manner, one portion of the liquid captured by the vanes  44  in region  88  is delivered directly to chordal sump  30  and into downcomer inlet  37  while the other portion is directed into the annular sump  28  and is carried to the first end of chordal sump  32  and downcomer  35 .  
         [0050]    Channels  46  in the vanes  44  in quadrant region  90  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  30 . In this manner, one portion of the liquid captured by the vanes  44  in region  90  is delivered directly to chordal sump  30  and into downcomer inlet  34  while the other portion is directed into the annular sump  28  and is carried to the second end of chordal sump  32  and downcomer  36 .  
         [0051]    Channels  46  in the vanes  44  in quadrant region  92  are open at one or both ends in an alternating or other manner to feed liquid into the annular sump  28  and adjacent chordal sump  32 . In this manner, one portion of the liquid captured by the vanes  44  in region  92  is delivered directly to chordal sump  32  and into downcomer inlet  35  while the other portion is directed into the annular sump  28  and is carried to the second end of chordal sump  32  and downcomer  36 .  
         [0052]    The arrangement described above ensures that substantially equal parts of the liquid captured by the collector  426  are fed to the downcomer inlets  34  and  35  as are fed to the downcomer inlets  36  and  37  and that the liquid entering each inlet is of a more uniform, although not completely uniform, composition. Liquid entering downcomer inlets  34  and  35  flows downwardly and, to achieve more complete and uniform mixing, is preferably delivered into one parting box of the type previously described. Likewise, the liquid entering downcomer inlets  36  and  37  flows downwardly into a different parting box  80 .  
         [0053]    Referring next to FIG. 16, a collector  526  is illustrated and differs from the embodiments previously described in the manner in which liquid exits the channels  46 . Collector  526  includes chordal sumps  30 ,  32  and  33  that extend in a parallel and spaced apart relationship. Downcomer inlets  34 ,  36 , and  37  are centrally positioned along the horizontal length of the chordal sumps  30 ,  32 , and  33  respectively. The chordal sumps  30 ,  32 , and  33  are positioned to divide the surface of the collector into two center regions  38  and  39 , and two side regions  40  and  42 . A plurality of parallel rows of upright liquid collecting vanes  44  are positioned within and substantially fill these regions  38 ,  39 ,  40 , and  42 . The vanes  44  are longitudinally orientated so that they extend across all or most of the column  20 .  
         [0054]    In a preferred embodiment, the floor and/or side walls of the channels  46  in the vanes  44  have at least one drain opening  94  to feed liquid into one or more of the sumps  30 ,  32 , and  33 . The channels  46  of adjacent vanes  44  have drain openings  94  positioned in an alternating or other manner to feed liquid into sumps  30 ,  32  and  33 . In this manner, one portion of the liquid captured by the vanes  44  in regions  38 ,  39 ,  40  and  42  is delivered directly to chordal sump  30  and into downcomer inlet  34  while the other portions of the liquid captured in region  40  is delivered directly to chordal sumps  32  and  33  and into downcomer inlets  36  and  37  respectively.  
         [0055]    The number and arrangement of sumps and downcomer inlets can be varied in collector  526 . As but one example, the collector  526  can include an annular sump of the type previously described, in addition to chordal sumps  30 ,  32  and  33 . When an annular sump is utilized, at least one end of the channel  46  of each vane  44  is open to permit fluid to flow from the channel  46  into the adjacent annular sump or each channel has at least one drain opening  94  to feed liquid into one or more of the sumps  30 ,  32 , and  33 . In this embodiment, end plates may be used to prevent or impede liquid from flowing from the annular sump  28  into the chordal sumps  30 ,  32  and  33 . The end plates may be perforated, of differing heights, or otherwise constructed to control the amount of liquid fed from the annular sump into the chordal sumps  30 ,  32  and  33 . The end plates may be of a height to prevent any liquid from flowing from the annular sump into one or more of the chordal sumps  30 ,  32  and  33  or vice-versa or may be perforated, of differing heights, or otherwise constructed to allow a controlled amount of liquid to enter and exit one or more of the chordal sumps  30 ,  32  and  33 .  
         [0056]    In still further embodiments, the single annular sump  28  is replaced by two or more concentric annular sumps to deliver liquid from different liquid collection areas into different chordal sumps. A collector  626  employing such concentric annular sumps is illustrated in FIG. 18. In collector  626 , an annular region is partitioned into a first outer annular sump  28   a  that extends around a portion of the circumference of the annular region and a second outer annular sump  28   b  that extends around the remaining portion of the circumference. A concentric first inner annular sump  28   c  is positioned radially inwardly from and preferably adjacent to the first outer annular sump  28   a  and extends around a smaller portion of the annular region circumference. A similar second inner annular sump  28   d  is positioned radially inwardly from the second outer annular sump  28   b  and extends around another smaller portion of the annular region circumference. The first outer and inner annular sumps  28   a  and  28   c  feed liquid into one end of chordal sump  30  and center chordal sump  32 , respectively, with the opposite end of chordal sump  30  being closed by a flow restrictor plates  72 . In a similar manner, the second outer and inner annular sumps  28   b  and  28   d  feed liquid into the opposite end of the chordal sump  33  and center chordal sump  32 , respectively. The other ends of the chordal sumps  33  and  30  are closed by flow restrictor end plates  71  and  72 , respectively, to block or impede liquid flow between those ends of the chordal sumps  33  and  30  and the inner annular sumps  28   c  and  28   d , respectively. Liquid collection channels  46  in each of liquid collection regions  38 ,  39 ,  40  and  42  drain the collected liquid into two or more of the sumps  28   a - d ,  30 ,  32  and  33 . For example, the liquid collection channels  46  in liquid collection region  40  divide the collected liquid proportionally among the outer annular sump  28   a , inner annular sump  28   c , and center chordal sump  32 . The outer annular sump  28   a  in turn delivers the liquid to chordal sump  30  and the inner annular sump  28   c  delivers the liquid to center chordal sump  32 . In a similar manner, the liquid collection channels  46  in liquid collection region  42  divide the collected liquid proportionally among the outer annular sump  28   b , inner annular sump  28   d , and chordal sump  30 . The outer annular sump  28   b  in turn delivers the liquid to chordal sump  33  and the inner annular sump  28   d  delivers the liquid to the center chordal sump  32 . The liquid collection channels  46  in liquid collection region  38  divides the collected liquid equally between the chordal sumps  30  and  32  and the liquid collection channels  46  in liquid collection region  39  likewise divides the collected liquid equally between the chordal sumps  33  and  32 .  
         [0057]    The collector  626  also illustrates two of the different types of drain openings that have been previously described for allowing liquid to preferentially drain from the liquid collection channels  46  into the desired sump. In one embodiment, drain openings  94  are formed in the floor of the liquid collection channels, while in the other embodiment the liquid simply drains through the drain opening formed by an open end of the liquid collection channel  46 .  
         [0058]    From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.  
         [0059]    It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.  
         [0060]    Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.