Historv of the Related Art Distillation columns are utilized to separate selected components from a multi component stream. Successful fractionation in the column is dependent upon intimate contact between the light, ascending liquid and the heavy, descending liquid within the column. Some columns use liquid-liquid contact devices such as trays.

Such trays are generally installed on support rings within the tower and have a solid tray or deck with a plurality of apertures in an"active"area. Such trays may be utilized to provide liquid-liquid contact when the descending, heavy liquid is the continuous phase within the tower and the ascending, light liquid is the dispersed phase within the tower. In towers exhibiting such flow, the descending, heavy liquid is directed onto the top surface of a tray by means of a vertical channel from the tray above. This channel is referred to as the downcomer. The descending liquid moves across the active area and exits through a similar downcomer. The location of the downcomers determine the flow pattern of the liquid. The light liquid ascends through the apertures in the active area of the tray and contacts the descending liquid moving across the tray. Such trays may also be utilized to provide liquid-liquid contact when the ascending, light liquid is the continuous phase and the heavy, descending liquid is the dispersed phase. In towers exhibiting such flow, ascending, light liquid is directed onto the bottom surface of a tray by means of a vertical channel from the tray below. This channel is referred to as the upcomer. The ascending liquid moves across the active area and exits through a similar upcomer. The location of the upcomers determine the flow pattern of the liquid. The heavy liquid descends through the apertures in the active area of the tray and contacts the ascending liquid moving across the tray. In either case, the light, ascending liquid and the heavy, descending liquid mix in the active area and fractionation occurs.

Maximum efficiency of the active area of a tray is an important consideration to chemical process tower design. Regions of the tray which are not effectively used for

liquid-liquid contact can reduce the fractionation capacity and efficiency of the tray. One such problem that reduces such fractionation capacity and efficiency is the existence of retrograde flow on a tray.

Referring now to FIG. 1, there is shown a flow diagram across a conventional tray 950. Tray 950 is illustrated herein as a round tray having a first conventional downcomer (not shown) for feeding a heavy, descending liquid (the continuous phase) upon a solid, underlying tray inlet area 952 and then over an inlet weir 954 to an active area 956.

Liquid flows across active area 956, over weir 958, and down downcomer 960, away from tray 950. A plurality of arrows 962 illustrate the non-uniform flow 964 of liquid across tray 950. Non-uniform flow 964 produces retrograde flow on tray 950, as manifested by recirculation cells 966.

Recirculation cells 966 are shown to be formed on both sides of tray 950 lateral to the direction of flow of liquid across the tray. These recirculation cells are the result of retrograde flow near the wall 968 of the tower, and this backflow problem becomes more pronounced as the diameter of the column increases. The formation of these retrograde flow areas, or recirculation cells 966, decreases the efficiency of tray 950.

More specifically, it is well known that the concentration-difference between the light, ascending liquid and the heavy, descending liquid is the driving force to effect mass and/or energy transfer within a liquid-liquid chemical process tower. With the increase in retrograde flow and the resultant stagnation effect from recirculation cells 966, this concentration-difference driving force for mass and/or energy transfer is reduced. The reduction in this concentration-difference driving force results in more contact or height requirement for a given separation in the column.

From the above, it may be appreciated that the efficiency of the active area of a fractionation tray is influenced by the flow of the continuous phase liquid across the active area of the tray. At the initial point of contact of the continuous phase liquid from a downcomer or upcomer onto a surface of the tray, the liquid typically does not exhibit a flow characteristic that provides optimum efficiency for the active area of the tray.

Therefore, a need exists in the chemical process tower industry for devices and methods that optimize the flow characteristic of this continuous phase across a surface of a fractionation tray.

Summarv of the Invention The present invention relates to a tray assembly for maximizing the efficiency of mass and/or energy transfer in a chemical process tower. More particularly, one aspect of the present invention may be incorporated into a chemical process tower for contacting a continuous phase liquid with a dispersed phase liquid. The chemical process tower comprises a tower having an inner wall and a first tray supported horizontally in the tower.

The first tray includes a first inner weir vertically coupled to the first tray, a first outer weir vertically disposed in the tower radially outwardly of the first inner weir, a second inner weir vertically coupled to the first tray on an opposite side of the tower from the first inner weir, a second outer weir vertically disposed in the tower radially outward of the second inner weir, and a first active area having a plurality of apertures disposed between the first and second inner weirs. The tray also has a first channel defined by the first inner weir and the first outer weir, and a second channel defined by the first outer weir and the inner wall of the tower. The tray further includes a third channel defined by the second inner weir and the second outer weir, and a fourth channel defined by the second outer weir and the inner wall of the tower.

In another aspect, the present invention comprises a tray for a chemical process column. The tray includes a generally planar member having an active area with a plurality of apertures therethrough, a first inner weir coupled to and disposed perpendicularly with the planar member, and a first outer weir coupled to the first inner weir and disposed perpendicularly with the planar member. A first channel is defined by the first inner weir and the first outer weir, and a second channel is defined at least partially by the first outer weir.

In a further aspect, the present invention comprises a method of interacting a continuous phase liquid and a dispersed phase liquid in a chemical process tower. A first tray is disposed horizontally in the tower. The tray includes a first inner weir vertically coupled to the tray, a first outer weir vertically disposed in the tower radially outwardly of the first inner weir, and a first active area having a plurality of apertures. The tray also includes a first channel defined by the first inner weir and the first outer weir, and a second channel defined by the first outer weir and an inner wall of the tower. A dispersed phase liquid flows through the plurality of apertures in the first active area, and a continuous phase liquid flows across the active area and through the first and second channels.

Brief Description of the Drawings For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a schematic, sectional view illustrating the flow of a heavy, descending, continuous phase liquid across the top surface of a conventional fractionation tray; FIG. 2 is a schematic, side elevation, sectional view of a tray assembly according to a first, preferred embodiment of the present invention and illustrating the flow of a light, ascending, dispersed phase liquid and a heavy, descending, continuous phase liquid through a chemical process column; FIG. 3 is an enlarged, sectional, top view of one of the trays of the tray assembly of FIGS. 2 and 7; FIG. 4 is an enlarged, sectional, top view of a second one of the trays of the tray assembly of FIGS. 2 and 7; FIG. 5 is a schematic, sectional view illustrating the flow of a continuous phase liquid across a surface of the tray of FIG. 4; FIG. 6 is a schematic, sectional view illustrating the flow of a continuous phase liquid across a surface of the tray of FIG. 3; and FIG. 7 is a schematic, side elevation, sectional view of a tray assembly according to a second, preferred embodiment of the present invention and illustrating the flow of a light, ascending, continuous phase liquid and a heavy, descending, dispersed phase liquid through a chemical process column Detailed Description of the Preferred Embodiments The preferred embodiments of the present invention and their advantages are best understood by referring to FIGS. 2-7 of the drawings, like numerals being used for like and corresponding parts of the various drawings.

Referring first to FIG. 2, a schematic, side elevation, sectional view of a tray assembly 100 according to a first, preferred embodiment of the present invention is illustrated in a liquid-liquid chemical process column 10. Column 10 comprises a cylindrical tower 12. Although not shown in FIG. 2, tower 12 has a variety of conventional structures found in a liquid-liquid chemical process column, such as an

ascending liquid side stream feed line, an ascending liquid outlet, a descending liquid side stream feed line, and a descending liquid outlet. Tower 12 may also have additional conventional structures found in a liquid-liquid chemical process column, such as a descending liquid side stream draw offline, a descending liquid side stream feed line, and a plurality of manways for facilitating access to the internal region of tower 12.

In operation, a light, ascending liquid 15 flows upwardly through column 10, and a heavy, descending liquid 13 flows downwardly through column 10. In its downward flow, heavy liquid 13 is depleted of some material which is gained by light liquid 15 as they pass through tray assembly 100 of column 10, and light liquid 15 is similarly depleted of some material which is gained by heavy liquid 13. Heavy liquid 13 may be the continuous phase and light liquid 15 may be the dispersed phase, or light liquid 15 may be the continuous phase and heavy liquid 13 may be the dispersed phase.

As shown in FIG. 2, tray assembly 100 includes four trays, three of which, trays 102,104, and 104', are numbered for illustration. As may be appreciated from FIG. 2, trays 102 and 104 have different, but cooperating structures. Therefore, trays 102 and 104 are preferably disposed within tower 12 in an alternating manner. Of course, the number of trays within the tray assembly 100 is dependent on the specific process being run in column 10, and tray assembly 100 can thus be formed with fewer or greater than four trays. Consistent with the above-described scheme of alternating trays 102 and 104 within tower 12, tray 104'has an identical structure to tray 104.

Tray 102 is a generally planar member having two tray-to-tray transfer devices (TTTD) 106 and 108 disposed on opposite sides of the tray. TTTD 106 provides a flow path for a heavy, descending, continuous phase liquid 13 from tray 102 to tray 104.

TTTD 106 comprises a vertical, inner weir 110 and a vertical, outer weir 112. Inner weir 110 and outer weir 112 each extend above a top surface 102a of tray 102. Inner weir 110 and outer weir 112 each extend below a bottom surface of tray 102, and outer weir 112 preferably extends farther below tray 102 than inner weir 110. for example, in a tower 12 having an inner diameter of 457 mm and a spacing between trays of approximately 250 mm, outer weir 112 preferably extends approximately 100 mm below tray 102, and inner weir 110 preferably extends approximately 60 mm below tray 102. The specific dimensions that inner weir 110 and outer weir 112 extend below tray 102 may vary with the size of tower 12, the spacing between trays in tower 12, and the specific process being

run in column 10. In addition, although not shown in FIG. 2, the lower end of inner weir 110 is preferably notched. Such notching preferably utilizes a"saw-tooth"cross-sectional geometry, although"square-tooth"or other cross-sectional geometries may also be used.

Inner weir 110 and outer weir 112 define an inner downcomer 114. Outer weir 112 and the inner wall of tower 12 define an outer downcomer 116.

Tray-to-tray transfer device (TTTD) 108 provides a second flow path for a heavy, descending, continuous phase liquid 13 from tray 102 to tray 104. Similar to TTTD 106, TTTD 108 comprises an inner weir 118 and an outer weir 120. The structure of inner weir 118 and outer weir 120 is substantially identical to inner weir 110 and outer weir 112 of TTTD 106, respectively. Inner weir 118 and outer weir 120 define an inner downcomer 122, and outer weir 120 and the inner wall of tower 12 define an outer downcomer 124.

Tray 104 is a generally planar member having a tray-to-tray transfer device (TTTD) 109 disposed proximate the center of the tray. TTTD 109 provides a flow path for heavy, descending, continuous phase liquid 13 from tray 104 to the immediately underlying tray in tower 12. TTTD 109 comprises a vertical weir 126 and an opposing, vertical weir 128. Weirs 126 and 128 each extend above a top surface 102a of tray 102, and weirs 126 and 128 each extend below a bottom surface of tray 102. Weirs 126 and 128 define a central downcomer 130.

FIG. 3 shows a detailed, top view of TTTD 106, TTTD 108, and tray 102. Inner weir 110 of TTTD 106 preferably comprises plates 1 l0a-f that are connected together in the configuration shown in FIG. 3. Inner weir 110 is preferably coupled to tray 102 by conventional means such as brackets or welding (not shown), and inner weir 110 may also be coupled to the inner wall of tower 12 by such conventional means (not shown). Outer weir 112 preferably comprises plates 112a-f that are connected together in the configuration shown in FIG. 3. Outer weir 112 is preferably coupled to inner weir 110 by conventional means such as welding (not shown) or brackets 117, and outer weir 112 may also be supported by the inner wall of tower 12 via brackets 119 and 119a. Inner downcomer 114 is characterized by portions 114a, 114b, 114c, and 114d, with the size of portions 114a-d increasing from a center line of the downcomer near bracket 119a to one end portion 114a, and from the center line of the downcomer to the other end portion 114d. inner downcomer 114 also preferably completely chokes the downward flow of

liquid 13 at its center line near bracket 119a. In contrast, outer downcomer 116 is characterized by an unchoked, downward flow of liquid 13. In addition, the size of each of the end portions of outer downcomer 116 near plates 1 lova and 112a, and near plates 11 Of and 112f, is preferably larger than the remaining portion of outer downcomer 116.

Brackets 117,119, and 119a preferably extend the entire height of outer downcomer 116.

Inner weir 118 of TTTD 108 preferably comprises plates 118a-fthat are connected together in the configuration shown in FIG. 3. Inner weir 118 is preferably coupled to tray 102 by conventional means such as brackets or welding (not shown), and inner weir 118 may also be coupled to the inner wall of tower 12 by such conventional means (not shown). Outer weir 120 preferably comprises plates 120a-f that are connected together in the configuration shown in FIG. 3. Outer weir 120 is preferably coupled to inner weir 118 by conventional means such as welding (not shown) or brackets 121, and outer weir 120 may also be supported by the inner wall of tower 12 via brackets 123 and 123 a. Inner downcomer 122 is characterized by portions 122a, 122b, 122c, and 122d, with the size of portions 122a-d increasing from a center line of the downcomer near bracket 123a to one end portion 122a, and from the center line of the downcomer to the other end portion 122d. Inner downcomer 122 also preferably completely chokes the downward flow of liquid 13 at its center line near bracket 123a. In contrast, outer downcomer 124 is characterized by an unchoked, downward flow of liquid 13. In addition, the size of each of the end portions of outer downcomer 124 near plates 118a and 120a, and near plates 118f and 120f, is preferably larger than the remaining portion of outer downcomer 124.

Brackets 121,123, and 123a preferably extend the entire height of outer downcomer 124.

Although in FIG. 3 six plates are connected to form each of inner weir 110 and outer weir 112, the weirs can be formed with fewer or greater numbers of plates. In addition, the weirs can be formed with plates disposed at different angles relative to each other and the inner wall of tower 12 than shown in FIG. 3. Furthermore, each of the weirs could alternatively be formed with a single, arcuate or curved plate instead of a plurality of segmented plates connected together as shown in FIG. 3.

As shown in FIG. 3, tray 102 preferably also comprises two active areas 132a and 132b containing a plurality of apertures 134 allowing the flow of the dispersed phase liquid through tray 102. Although only selected groupings of apertures 134 are shown in FIG. 3, such groupings are for purposes of illustration only, and apertures 134 are

preferably disposed throughout the entire area of active areas 132a and 132b. Apertures 134 may comprise holes, valve structures, or other conventional fractionation tray apertures. Active areas 132a and 132b preferably do not extend into the area of tray 102 generally beneath the central downcomer of the tray disposed in tower 12 immediately above tray 102. Thus, an unperforated tray inlet area 133 is defined between active areas 132a and 132b. The outer sides of active areas 132a and 132b preferably mirror the construction of inner weirs 110 and 118, respectively. Although not shown in FIG. 3, the outer sides of active areas 132a and 132b may extend all the way to inner weirs 110 and 118, respectively.

FIG. 4 shows a detailed, top view of TTTD 109 and tray 104. Weirs 126 and 128 preferably each comprise a single plate disposed within tower 12 in a chordal manner.

Tray 104 preferably comprises unperforated tray inlet areas 144a and 144b disposed on opposing sides of tray 104 generally below TTTD 106 and TTTD 108, respectively. Tray 104 also preferably comprises two active areas 136a and 136b containing a plurality of apertures 138 allowing the flow of a dispersed phase liquid through tray 104. Although only selected groupings of apertures 138 are shown in FIG. 4, such groupings are for purposes of illustration only, and apertures 138 are preferably disposed throughout the entire area of active areas 136a and 136b. Apertures 138 may comprise holes, valve structures, or other conventional fractionation tray apertures. As shown in FIG. 4, active area 136a preferably extends from weir 126 to tray inlet area 144a, and active area 136b preferably extends from weir 128 to tray inlet area 144b.

Having described the structure of tray assembly 100, the operation and advantages of tray assembly 100 are now described in greater detail. Referring generally to FIGS.

2-4, heavy, descending, continuous phase liquid 13 generally flows across the top surface 102a of tray 102 in two directions, from tray inlet area 133 to inner weir 110, and from tray inlet area 133 to inner weir 118. As liquid 13 flows across tray 102, it crosses the active areas 132a and 132b and engages light, ascending, dispersed phase liquid 15 flowing from apertures 134. Inner weir 110 controls the flow of liquid 13 that passes from active area 132a into inner downcomer 114, and outer weir 112 controls the flow of liquid 13 that passes from active area 132a into outer downcomer 116. Similarly, inner weir 118 controls the flow of liquid 13 that passes from active area 132b into inner

downcomer 122, and outer weir 120 controls the flow of liquid 13 that passes from active area 132b into outer downcomer 124.

Liquid 13 exiting inner downcomer 114 and outer downcomer 116 first contacts tray 104 in tray inlet area 144a, and liquid exiting inner downcomer 122 and outer downcomer 124 first contacts tray 104 in tray inlet area 144b. Liquid 13 generally flows across the top surface 104a of tray 104 in two directions, from tray inlet area 144a to weir 126, and from tray inlet area 144b to weir 128. As liquid 13 flows across tray 104, it crosses the active areas 136a and 136b and engages light, ascending, dispersed phase liquid 15 flowing from apertures 138. Weirs 126 and 128 control the flow of liquid 13 that passes from active areas 136a and 136b, respectively, into central downcomer 130.

Dispersed phase liquid 15 accumulates into coalesced regions beneath the trays within tower 12, and these coalesced regions are generally formed by the bottom surfaces of the trays, their respective weirs, and the inner surface of tower 12. For example, a coalesced region 142 of light liquid 15 is formed by tray 102 and inner weirs 110 and 118, and coalesced regions 140a and 140b of light liquid 15 are formed by tray 104, weirs 126 and 128, and the inner wall of tower 12.

Referring now to FIGS. 2,3, and 5 in combination, the uniform, optimized flow of heavy liquid 13 across the top surface 104a of tray 104 provided by TTTD 106 and TTTD 108 of tray 102 is illustrated. For TTTD 106, one may appreciate that the amount of liquid 13 allowed to flow through inner downcomer 114 is determined by the geometry of inner downcomer 114, including the complete choking of flow near the center line of inner downcomer 114 near bracket 119a; the relative size of downcomer portions 114a-114d; and the height of weir 110 above and below tray 102. Similarly, the amount of liquid 13 allowed to flow through outer downcomer 116 is determined by the geometry of outer downcomer 116, including the unchoked flow of downcomer 116; the size of outer downcomer 116 relative to inner downcomer 114; and the height of weir 112 above and below tray 102. Of course, given its identical structure, the same factors determine the amount of liquid 13 allowed to flow through inner downcomer 122 and outer downcomer 124 of TTTD 108.

As shown in FIG. 5, the above-described structural characteristics of TTTD 106 and TTTD 108 result in a uniform, optimized flow of liquid 13 across the top surface 104a of tray 104. More specifically, liquid 13 exiting from TTTD 106 flows in a uniform

manner from tray inlet area 144a to central downcomer 130, as illustrated by arrows 146a and uniform flow line 148a. Liquid 13 exiting from TTTD 108 flows in a uniform manner from tray inlet area 144b to central downcomer 130, as illustrated by arrows 146b and uniform flow line 148b. This uniform flow essentially eliminates the recirculation cells and retrograde flow areas present on conventional fractionation trays, as illustrated by FIG.

1. The elimination of such retrograde flow increases the efficiency of the mass and/or energy transfer occurring between liquid 13 and liquid 15 on the top surface 104a of tray 104, and thus increases the efficiency of column 10.

Referring now to FIGS. 2,4, and 6 in combination, the uniform, optimized flow of heavy liquid 13 across the top surface 102a of tray 102 provided by TTTD 109'of tray 104'is illustrated. As noted previously, tray 104'has an identical structure to tray 104, and therefore, in the description below, reference numerals referring to tray 104 and TTTD 109 in FIGS. 2 and 4 will also be used for tray 104'and TTTD 109'. For TTTD 109', one may appreciate that the amount of liquid 13 allowed to flow through central downcomer 130 is determined by the geometry of central downcomer 130, including the unchoked flow of the downcomer; the width of downcomer 130; the height of weirs 126 and 128 above and below tray 104; and the location of TTTD 109'relative to TTTD 106 and TTTD 108 of tray 102.

As shown in FIG. 6, the above-described structural characteristics of TTTD 109' result in a uniform, optimized flow of liquid 13 across the top surface 102a of tray 102.

More specifically, a first portion of liquid 13 exiting from TTTD 109'flows in a uniform manner from center line 150 of tray inlet area 133 to inner downcomer 114 and outer downcomer 116, as illustrated by arrows 152a and uniform flow line 154a. In addition, a second portion of liquid 13 exiting from TTTD 109'flows in a uniform manner from center line 150 of tray inlet area 133 to inner downcomer 122 and outer downcomer 124, as illustrated by arrows 152b and uniform flow line 154b. This uniform flow essentially eliminates the recirculation cells and retrograde flow areas present on conventional fractionation trays, as illustrated by FIG. 1. The elimination of such retrograde flow increases the efficiency of the mass and/or energy transfer occurring between liquid 13 and liquid 15 on the top surface 102a of tray 102, and thus increases the efficiency of column 10.

Referring now to FIG. 7, a tray assembly 200 according to a second, preferred embodiment of the present invention is shown disposed within tower 12. As shown in FIG. 7, tray assembly 200 includes four trays, three of which, trays 202,204, and 204', are numbered for illustration. As may be appreciated from FIG. 7, trays 202 and 204 have different, but cooperating structures. Therefore, trays 202 and 204 are preferably disposed within tower 12 in an alternating manner. Of course, the number of trays within tray assembly 200 is dependent on the specific process being run in column 10, and tray assembly 200 can thus be formed with fewer or greater than four trays. Consistent with the above-described scheme of alternating trays 202 and 204 within tower 12, tray 204' has an identical structure to tray 204.

As may be appreciated by one skilled in the art with reference to FIGS. 2 and 7, the structure of tray assembly 200 is substantially identical to tray assembly 100, except that tray assembly 100 must be inverted, or turned"upside down", to form tray assembly 200. Therefore, in the description below, reference numerals referring to the various components of tray 102, TTTD 106, TTTD 108, tray 104, TTTD 109, tray 104', and TTTD 109'in FIGS. 2 through 6 will also be used for the various components of tray 202, TTTD 206, TTTD 208, tray 204, TTTD 209, tray 204', and TTTD 209', respectively, in FIGS. 3-7.

As shown in FIG. 7, tray 202 is a generally planar member having two tray-to-tray transfer devices (TTTD) 206 and 208 disposed on opposite sides of the tray. TTTD 206 provides a flow path for a light, ascending continuous phase liquid 15 from tray 202 to tray 204. TTTD 206 comprises a vertical, inner weir 110 and a vertical, outer weir 112.

Inner weir 110 and outer weir 112 each extend below a bottom surface 102a of tray 202.

Inner weir 110 and outer weir 112 each extend above a top surface of tray 202, and outer weir 112 preferably extends farther above tray 202 than inner weir 110. For example, in a tower 12 having an inner diameter of 457 mm and a spacing between trays of approximately 250 mm, outer weir 112 preferably extends approximately 100 mm above tray 102, and inner weir 110 preferably extends approximately 60 mm above tray 102.

The specific dimensions that inner weir 110 and outer weir 112 extend above tray 202 may vary with the size of tower 12, the spacing between trays in tower 12, and the specific process being run in column 10. In addition, although not shown in FIG. 7, the upper end of inner weir 110 is preferably notched. Such notching preferably utilizes a

"saw-tooth"cross-sectional geometry, although"square-tooth"or other cross-sectional geometries may also be used. Inner weir 110 and outer weir 112 define an inner upcomer 114. Outer weir 112 and the inner wall of tower 12 define an outer upcomer 116.

TTTD 208 provides a second flow path for a light ascending, continuous phase liquid 15 from tray 202 to tray 204. Similar to TTTD 206, TTTD 208 comprises an inner weir 118 and an outer weir 120. The structure of inner weir 118 and outer weir 120 is substantially identical to inner weir 110 and outer weir 112 of TTTD 206, respectively.

Inner weir 118 and outer weir 120 define an inner upcomer 122, and outer weir 120 and the inner wall of tower 12 define an outer upcomer 124.

Tray 204 is a generally planar member having a tray-to-tray transfer device 209 disposed proximate the center of the tray. TTTD 209 provides a flow path for light, ascending, continuous phase liquid 15 from tray 204 to the immediately overlying tray in tower 12. TTTD 209 comprises a vertical weir 126 and an opposing, vertical weir 128.

Weirs 126 and 128 each extend below a bottom surface 104a of tray 204, and weirs 126 and 128 each extend above a top surface of tray 204. Weirs 126 and 128 define a central upcomer 130.

FIG. 3 shows a detailed, top view of TTTD 206, TTTD 208, and tray 202. As mentioned previously, the structure of TTTD 206, TTTD 208, and tray 202 are preferably identical to, but inverted from, TTTD 106, TTTD 108, and tray 102 of tray assembly 100.

FIG. 4 shows a detailed, top view of TTTD 209 and tray 204. As also mentioned previously, the structure of TTTD 209 and tray 204 are preferably identical to, but inverted from, TTTD 109 and tray 104 of tray assembly 100.

Having described the structure of tray assembly 200, the operation and advantages of tray assembly 200 are now described in greater detail. Referring generally to FIGS. 3, 4, and 7, light, ascending, continuous phase liquid 15 generally flows across the bottom surface 102a of tray 202 in two directions, from tray inlet area 133 to inner weir 110, and from tray inlet area 133 to inner weir 118. As liquid 15 flows across tray 202, it crosses the active areas 132a and 132b and engages heavy, descending, dispersed phase liquid 13 flowing from apertures 134. Inner weir 110 controls the flow of liquid 15 that passes from active area 132a into inner upcomer 114, and outer weir 112 controls the flow of liquid 15 that passes from active area 132a into outer upcomer 116. Similarly, inner weir 118 controls the flow of liquid 15 that passes from active area 132b into inner upcomer

122, and outer weir 120 controls the flow of liquid 13 that passes from active area 132b into outer upcomer 124.

Liquid 15 exiting inner upcomer 114 and outer upcomer 116 first contacts tray 204 in tray inlet area 144a, and liquid exiting inner upcomer 122 and outer upcomer 124 first contacts tray 204 in tray inlet area 144a. Liquid 15 generally flows across the bottom surface 104a of tray 204 in two directions, from tray inlet area 144a to weir 126, and from tray inlet area 144b to weir 128. As liquid 15 flows across tray 204, it crosses the active areas 136a and 136b and engages heavy, descending, dispersed phase liquid 13 flowing from apertures 138. Weirs 126 and 128 control the flow of liquid 13 that passes from active area 136aand 136b, respectively, into central upcomer 130. Dispersed phase liquid 13 accumulates into coalesced regions above the trays within tower 12, and these coalesced regions are generally formed by the top surfaces of the trays, their respective weirs, and the inner surface of tower 12. For example, a coalesced region 142 of heavy liquid 13 is formed by tray 202 and inner weirs 110 and 118, and coalesced regions 140a and 140b of heavy liquid 13 are formed by tray 204, weirs 126 and 128, and the inner wall of tower 12.

Referring now to FIGS. 3,5, and 7 in combination, the uniform, optimized flow of light liquid 15 across the bottom surface 104a of tray 204 provided by TTTD 206 and TTTD 208 of tray 202 is illustrated. For TTTD 206, one may appreciate that the amount of liquid 15 allowed to flow through inner upcomer 114 is determined by the geometry of inner upcomer 114, including the complete choking of flow near the center line of inner upcomer 114 near bracket 119a; the relative size of upcomer portions 114a-114d; and the height of weir 110 above and below tray 202. Similarly, the amount of liquid 15 allowed to flow through outer upcomer 116 is determined by the geometry of outer upcomer 116, including the unchoked flow of upcomer 116; the size of outer upcomer 116 relative to inner upcomer 114; and the height of weir 112 above and below tray 202. Of course, given its identical structure, the same factors determine the amount of liquid 15 allowed to flow through inner upcomer 122 and outer upcomer 124 of TTTD 208.

As shown in FIG. 5, the above-described structural characteristics of TTTD 206 and TTTD 208 result in a uniform, optimized flow of light liquid 15 across the bottom surface 104a of tray 204. More specifically, liquid 15 exiting from TTTD 206 flows in a uniform manner from tray inlet area 144a to central upcomer 130, as illustrated by arrows

146a and uniform flow line 148a. Liquid 15 exiting from TTTD 208 flows in a uniform manner from tray inlet area 144b to central upcomer 130, as illustrated by arrows 146b and uniform flow line 148b. This uniform flow essentially eliminates the recirculation cells and retrograde flow areas present on conventional fractionation trays, as illustrated by FIG. 1. The elimination of such retrograde flow increases the efficiency of the mass and/or energy transfer occurring between liquid 13 and liquid 15 on the bottom surface 104a of tray 204, and thus increases the efficiency of column 10.

Referring now to FIGS. 4,6, and 7 in combination, the uniform, optimized flow of light liquid 15 across the bottom surface 102a of tray 202 provided by TTTD 209'of tray 204'is illustrated. As noted previously, tray 204'has an identical structure to tray 204, and therefore, in the description below, reference numerals referring to tray 204 and TTTD 209 in FIGS. 4 and 7 will also be used for tray 204'and TTTD 209'. For TTTD 209', one may appreciate that the amount of liquid 15 allowed to flow through central upcomer 130 is determined by the geometry of central upcomer 130, including the unchoked flow of the upcomer; the width of upcomer 130; the height of weirs 126 and 128 above and below tray 204; and the location of TTTD 209'relative to TTTD 206 and TTTD 208 of tray 202.

As shown in FIG. 6, the above-described structural characteristics of TTTD 209' result in a uniform, optimized flow of liquid 15 across the bottom surface 102a of tray 202. More specifically, a first portion of liquid 15 exiting from TTTD 209'flows in a uniform manner from center line 150 of tray inlet area 133 to inner upcomer 114 and outer upcomer 116, as illustrated by arrows 152a and uniform flow line 154a. In addition, a second portion of liquid 15 exiting from TTTD 209'flows in a uniform manner from center line 150 of tray inlet area 133 to inner upcomer 122 and outer upcomer 124, as illustrated by arrows 152b and uniform flow line 154b. This uniform flow essentially eliminates the recirculation cells and retrograde flow areas present on conventional fractionation trays, as illustrated by FIG. 1. The elimination of such retrograde flow increases the efficiency of the mass and/or energy transfer occurring between liquid 13 and liquid 15 on the bottom surface 102a of tray 202, and thus increases the efficiency of column 10.

From the above, it may be appreciated that incorporating the tray assemblies of the present invention into a chemical process tower improves the efficiency of the mass

and/or energy transfer between a light, ascending liquid and a heavy, descending liquid in the tower. Such improvement is obtained by optimizing the flow characteristics of a continuous phase liquid across the active areas of the trays comprising the tray assemblies.

The tray assemblies of the present invention are applicable in towers in which the descending liquid is the continuous phase and the ascending liquid is the dispersed phase, and in towers in which the ascending liquid is the continuous phase and the descending liquid is the dispersed phase.

The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, numerous geometries and/or relative dimensions could be altered to accommodate specific applications of a chemical process tower.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. While 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.