WO1999024135A1

WO1999024135A1 - Vapor-liquid contact tray assembly

Info

Publication number: WO1999024135A1
Application number: PCT/US1998/023810
Authority: WO
Inventors: Michael J. Binkley; Gary W. Gage
Original assignee: Koch-Glitsch, Inc.
Priority date: 1997-11-10
Filing date: 1998-11-10
Publication date: 1999-05-20
Also published as: AU1314099A

Abstract

A downcomer tray assembly (10) is provided for a vapor-liquid contact process column, wherein the tray assembly defines a liquid flow direction in which liquid is directed across the tray assembly and downwardly therefrom, and directs vapor flow upward through the liquid. The tray assembly (10) includes a peripheral ring (14) adapted to be secured to the column, and a tray (16) supported on the ring (14) and presenting an inner area disposed inside the periphery of the ring and an outer peripheral area overlying the ring (14). A first set of valves (22) are formed in the inner area of the tray (16) to define an active vapor-liquid contact area, and a second set (24) are provided which overlap the central and peripheral area of the tray to increase the active vapor-liquid contact area. Each valve (24) of the second set includes a top wall (34), a pair of depending side walls (36), and a valve aperture (38) between the tray (16) and the top wall (34) for defining a vapor flow path, and the valve aperture (38) are disposed in the outer peripheral area of the tray (16) to promote flow in that area and to increase the active area of the tray (16).

Description

VAPOR-LIQUID CONTACT TRAY ASSEMBLY

BACKGROUND OF THE INVENTION

The present invention relates generally to vapor-liquid contact trays for use in a fluid treatment vessel, and more particularly to an apparatus for improving the performance of such trays by extending the active area thereof.

Fractionation column trays generally come in one of two configurations: cross-flow and counter flow. The trays generally consist of a solid tray or deck having a plurality of apertures and are installed on support rings within the tower. In cross-flow trays, vapor ascends through the apertures and contacts the liquid moving across the tray through an "active" area thereof. In the active area, liquid and vapor mix and fractionation occurs. The liquid is directed onto the tray by means of a vertical channel from the tray above. This channel is referred to as the inlet downcomer. The liquid moves across the tray and exits through a similar channel referred to as the exit downcomer. The location of the downcomers determines the flow pattern of the liquid. If there are two or more inlet downcomers and the liquid is split into a plurality of streams over each tray, it is called a multiple-pass tray. If there is only one inlet and one outlet downcomer on opposite sides of the tray, it is called a single pass tray. The number of passes generally increases as the required liquid rate increases. It is the active area of the tray, however, which is of critical concern.

Not all areas of the tray are active for vapor-liquid contact. For example, the area along the perimeter of the tray directly overlying the support ring is generally solid. Likewise, when cross members or other support structures are employed to provide additional support for the tray assembly in the column, the areas of the tray overlying the support structures are solid. As such, these areas are "inactive", meaning that vapor is not directed through the liquid flowing across these areas, and little or no vapor-liquid contact is induced. In order to gain more active area for vapor-liquid contact, it is known to provide a construction in which a support ring includes a peripheral area spanning the space between the tray and the walls of the column, and the peripheral area includes a plurality of apertures such that the area between the tray and the column walls is rendered active for vapor-liquid contact. However, such a construction requires the use of a specially constructed support ring, substantially increasing the cost of the assembly, and the improved construction fails to provide for active liquid-vapor contact in the region of overlap of the tray and support ring.

It is known to provide an inverted, cup-shaped active washer for securing the tray to the support ring, wherein the washer includes a hollow interior space and presents apertures that permit an ascending flow of vapor therethrough. The washer is constructed of any desired shape, and includes a mounting aperture sized for the receipt of a securing member that passes through an oversized slot or aperture in the tray and engages a clamp secured beneath the support ring. The slot in the tray is oversized to permit vapor to pass up through the active washer into contact with liquid being directed across the tray, rendering the area around the securing member active. Although the use of an active support ring and active washers increase the active area of the tray to include the areas outside of the tray and around the members used to secure the tray on the support ring, the circumferential area of the tray overlapping the support ring remains inactive. It would be beneficial to extend the active area of the tray into this outer circumferential area of the tray to any extent possible.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a vapor-liquid contact tray having valves in the outer peripheral area thereof overlapping the support ring of the column such that more valve area is available, increasing the capacity of the tray.

It is another object of the present invention to provide an improved vapor- liquid contact tray that minimizes dead areas adjacent the column wall, improving efficiency and reducing fouling of the tray during use.

In accordance with these and other objects evident from the following description of a preferred embodiment of the invention, a downcomer tray assembly is provided for a vapor-liquid contact process column, wherein the tray assembly defines a liquid flow direction in which liquid is directed across the tray assembly and downwardly therefrom, and vapor is directed to flow upward through the liquid. The tray assembly includes a peripheral ring adapted to be secured to the column, and a tray supported on the ring and presenting an inner area disposed inside the periphery of the ring and an outer peripheral area overlying the ring. A first plurality of valves is preferably formed in the inner area of the tray to define an active vapor-liquid contact area, and a second plurality of valves is formed in the tray, each of which overlaps the central and peripheral areas of the tray to increase the active vapor-liquid contact area of the tray assembly.

In accordance with one aspect of the invention, the tray includes a plurality of tray apertures that each span both the inner and outer areas, and valves are supported in the apertures. Each of the valves includes a top wall, a pair of depending side walls, and a valve aperture extending between the tray and the top Wall for defining a vapor flow path, wherein the valve apertures are disposed in the outer peripheral area of the tray. Preferably, the valves are directional, meaning that they direct vapor flow relative to the liquid flow path to promote vapor-liquid interaction. For example, by angling the valves relative to the liquid flow path by angles of 15°, 30°, 40°, and so on, flow is promoted for capacity and efficiency, and retrograde flow is prevented.

By providing a construction in accordance with the present invention, numerous advantages are realized. For example, by providing a vapor-liquid contact tray having valves in the outer peripheral area thereof overlapping the circumferential flange of the vessel, more area of the tray is available for vapor-liquid contact, increasing the capacity of the tray. In addition, by providing a construction that minimizes dead areas adjacent the vessel wall, efficiency is improved and fouling of the tray is reduced. The inventive construction also acts as a froth initiator to reduce weepage at the perimeter of the tray. Another aspect of the invention relates to the use of a construction in which some of the valves extending over the outer peripheral area of the tray include top walls presenting apertures, the assembly further including clamps extending beneath the support ring, and securing members sized for receipt in the apertures for securing the peripheral ring between the tray and the clamps. By providing this type of construction, the valves in the peripheral region of the tray can be used as support holes for receiving the securing member to secure the tray to the flange while doubling as a valve. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

A detailed description of the preferred embodiment of the present invention is provided in detail below with reference to the attached drawing, wherein: Fig. 1 is a perspective view of a downcomer tray assembly constructed in accordance with the preferred embodiment of the present invention;

Fig. 2 is a fragmentary perspective view of the tray assembly, illustrating an active circumferential region thereof;

Fig. 3 is a fragmentary top plan view of an alternate embodiment of the vapor-liquid contact tray; Fig. 4 is a sectional view taken through line 4-4 of Fig. 3, illustrating a fixed peripheral valve forming apart of the tray assembly, the peripheral valve being used as a location for a fastener for securing the contact tray to the support ring; and

Fig. 5 is a fragmentary plan view of an alternate construction of the support ring.

DETAILED DESCRIPTION OF THE INVENTION

A downcomer tray assembly 10 constructed in accordance with the present invention is illustrated in Fig. 1, and is adapted for use on a vapor-liquid contact column 12 such as that described in U.S. Patent No. 5,453,222, issued September 25, 1995, and incorporated herein. As such, the column is conventional, and is preferably constructed of metal or any other suitable material that is resistant to corrosion and wear when exposed to the fluids to be handled therein.

The downcomer tray assembly 10 broadly includes a peripheral support ring 14 adapted to be secured to the column by welding or the like, a vapor-liquid contact tray 16 supported on the ring, a downcomer 18 through which liquid passes from the tray to an underlying tray, and an inlet region 20 into which liquid flows from an overlying tray. In addition, a plurality of valves 22, 24 are supported on the tray, and provide an active area on the tray within which vapor is directed transverse to the liquid flow path such that the vapor and the liquid in the column are brought into cross-flow contact with one another. The support ring 14 is preferably formed of the same metal or material as the column, and is in the shape of an annular ring, presenting opposed upper and lower planer surfaces, and radially opposed inner and outer circumferential edges. As shown in Fig. 2, the outer circumferential edge is secured to the inner wall of the column 12, preferably by welding, and the tray 16 is supported on the upper surface thereof. Turning to Fig. 5, an alternate construction of the support ring is illustrated, wherein the ring 26 includes an inner circumferential edge that is scalloped or cut away at a plurality of locations there along in order to accommodate at least some of the valves on the tray. By reducing the radial dimension of the support ring at selected locations along the circumference thereof, it is possible to extend the active area of the contact tray, improving the capacity and efficiency thereof. As an alternative to cut a ways along the inner circumferential edge of the support ring, holes can be utilized in the support ring.

Returning to Fig. 1, the contact tray 16 of the assembly 10 is formed from a sheet or plate of metal or any other suitable material that is resistant to corrosion and wear when exposed to the fluids to be handled in the column. As such, the tray is a planer panel of generally circular shape, being truncated on diametrically opposed sides thereof to accommodate the downcomer 18 and the inlet region 20. The tray presents an upper liquid support surface, and defines an outer diameter that is smaller than the outer diameter of the support ring 14 but larger than the inner diameter of the ring. As shown in Fig. 3, an inner area 28 of the tray 16 is defined by the area of the tray that is located radially inside of the support ring, and an outer area 30 of the tray extends along the periphery of the tray overlying the ring. In other words, the inner area of the tray is the area that does not overlie the ring, while the outer peripheral area does.

The tray 16 is slotted or perforated to accommodate the valves 22, 24, and the perforations extend over the inner area 28 of the tray and at least a radially inner portion of the outer area 30. The valves 22 supported in the inner area of the tray need not be of the same type as valves 24 used in the outer area, and make up a first plurality of valves that define an active vapor-liquid contact area of the tray. The second plurality of valves 24 are supported in the outer area of the tray, and also define the active area of the tray such that the active area extends radially beyond the inner area 28 of the tray at least partially into the outer peripheral area 30. As shown in Fig. 4, each of the perforations 32 in the outer area of the tray overlap the inner area such that when the tray 16 rests on the support ring 14, the perforations 32 extend partially over the ring. Preferably, each perforation is generally circular, defining a center point that is located in the inner area of the tray. As such, the valves 24 supported in the perforations at the inner circumferential edge of the support ring 14 overlap the ring so that the active area defined by the tray extends completely to the inner circumferential edge of the ring, and beyond. The valves 22, 24 provide for the flow of gases or vapor up through the liquid that is directed across the tray in order to provide mixing of the vapor and liquid. The valves are of conventional construction, and can either be fixed or moveable as is understood to a person of ordinary skill in the art of designing such contact trays. In the illustrated embodiment, the valves 22, 24 are fixed, and each valve 22, 24 includes a top wall 34 and a pair of diametrically opposed depending side walls 36 that extend between and connect the top wall and the tray. Such valves can be constructed by punching or otherwise deforming the metal of the tray to shape the valve from the material displaced by the formation of the perforation. As such, each valve 22, 24 presents diametrically opposed, laterally extending openings or apertures 38 that are generally semi-circular is shape, and extend between the depending side walls 36 of the valve. The effect created by this construction of the valve is that vapor is directed through the valve in a generally horizontal direction laterally of the valve.

As shown in Fig. 3, by orienting the valves 24 in a particular orientation along the periphery of the tray, it is possible to provide a construction having improved flow promotion relative to conventional tray constructions. For example, the valves 24 can be oriented parallel to the direction of liquid flow across the tray between the inlet region and the downcomer, or can be angled relative to the direction of liquid flow. If the valves are angled, any desired angle can be chosen. Preferably, each valve 24 is individually oriented to promote mixing of vapor and liquid on the tray, wherein the valves are oriented at 15°, 30°, 40°, etc., relative to the direction of liquid flow across the tray. In addition to improving liquid-vapor contact, this construction also prevents retrograde flow across the tray.

As shown in the tray variation illustrated in Figs. 3 and 4, at least some of the valves 24 can be used as both valves and as points of securement between the tray and the support ring. The valves that are to be used for this purpose are provided with holes through the top wall thereof such that the top wall can receive a securing member 40. The securing member preferably includes a threaded bolt or the like, and a clamp 42 is provided beneath the tray and ring for receiving the bolt. A washer 44 and nut 46 are secured to the upper threaded end of the bolt to tighten the clamp against the bottom of the support ring and the tray to secure the tray in place. Because the perforation 32 in the tray is larger than the diameter of the securing member 40, the valve remains able to function as a valve in allowing vapor to pass up through the contact tray for mixing with the liquid supported on the tray. Thus, although the securing member 40 occupies a portion of the area of the valve, a percentage of the area remains open for use as a valve. In addition to providing the valves 24 along the circumferentially outer region of the contact tray, it is also possible to provide such valves overlapping tray joints, seams, beams and the like which extend parallel to the direction of flow, or to other similar areas that are normally inactive in conventional contact tray constructions. As such, these seams and beams can be rendered active by the provision of valves that overlap them in the manner described herein.

The subject of the present invention can also be employed with sieve, perforated or other types of trays including moveable valves, conventional, small scale valves, miniature valves, and the like. The invention also applies to the use of tabs, hoods, scoops and shapes of directional flow promoters that overlap the support ring, flange, joints or other beam or support structures. In all of these applications, the subject of the invention is employed to increase or extend the active area of the contact tray by employed peripheral valves, preferably fixed, that extend beyond or overlap the support structure.

Thus, although the invention has been described with reference to the preferred embodiment illustrated in the drawing, it is noted that substitutions may be made and equivalents employed herein without departing from the scope of the invention as recited in the claims.

Claims

1. A downcomer tray assembly for a vapor-liquid contact process column, wherein the tray assembly defines a liquid flow direction in which liquid is directed across the tray assembly and downwardly therefrom, and directs vapor flow upward through the liquid, the tray assembly comprising: a peripheral ring adapted to be secured to the column; a tray supported on the ring and presenting an inner area disposed inside the periphery of the ring and an outer peripheral area overlying the ring; a first plurality of valves formed in the inner area of the tray to define an active vapor-liquid contact area; and a second plurality of valves formed in the tray, each of the second valves overlapping the central and peripheral areas of the tray to increase the active vapor-liquid contact area of the tray assembly to include a fraction of the outer peripheral area of the tray.

2. The tray assembly as recited in claim 1, wherein the second plurality of valves are fixed relative to the tray.

3. The tray assembly as recited in claim 1, wherein the second plurality of valves are movable relative to the tray.

4. The tray assembly as recited in claim 1 , wherein at least one of the second plurality of valves includes a top wall presenting an aperture, the assembly further comprising a clamp extending beneath the support ring, and a securing member sized for receipt in the aperture for securing the peripheral ring between the tray and the clamp.

5. The tray assembly as recited in claim 1, wherein the second plurality of valves each include a top wall, a pair of depending side walls, and an aperture between the tray and the top wall for defining a vapor flow path.

6. The tray assembly as recited in claim 5, wherein the aperture is disposed in the outer peripheral area of the tray.

7. The tray assembly as recited in claim 5, wherein the side walls of each of the second plurality of valves are diametrically opposed to one another relative to the top wall of the valve, the direction of separation of the side walls defining a longitudinal axis of the valve.

8. The tray assembly as recited in claim 7, wherein the longitudinal axes of the second plurality of valves are parallel to one another.

9. The tray assembly as recited in claim 7, wherein the longitudinal axes of at least two of the second plurality of valves are angled relative to one another.

10. The tray assembly as recited in claim 7, wherein the longitudinal axes of at least some of the second plurality of valves are angled relative to the direction of liquid flow across the tray by an angle of between about 15┬░ and 45┬░.

11. The tray assembly as recited in claim 7, wherein the top wall of each of the second plurality of valves is circular in shape, defining a center point that is disposed in the central area of the tray.

12. The tray assembly as recited in claim 4, wherein the aperture formed in the top wall of each of the second plurality of valves is disposed at a location in the central area of the tray.

13. A downcomer tray assembly for a vapor-liquid contact process column, wherein the tray assembly defines a liquid flow direction in which liquid is directed across the tray assembly and downwardly therefrom, and directs vapor flow upward through the liquid, the tray assembly comprising: a peripheral ring adapted to be secured to the column; a tray supported on the ring and presenting an inner area disposed inside the periphery of the ring and an outer area overlying the ring, the tray including a plurality of tray apertures that each span both the inner and outer areas; a plurality of valves supported in the apertures of the tray, each of the valves including a top wall, a pair of depending side walls, and a valve aperture between the tray and the top wall for defining a vapor flow path, the valve apertures being disposed in the outer peripheral area of the tray.

14. The tray assembly as recited in claim 13, wherein the plurality of valves are fixed relative to the tray.

15. The tray assembly as recited in claim 13 , wherein the plurality of valves are movable relative to the tray.

16. The tray assembly as recited in claim 13, wherein at least one of the plurality of valves includes a top wall presenting an aperture, the assembly further comprising a clamp extending beneath the support ring, and a securing member sized for receipt in the aperture for securing the peripheral ring between the tray and the clamp.

17. The tray assembly as recited in claim 13, wherein the side walls of each of the plurality of valves are diametrically opposed to one another relative to the top wall of the valve, the direction of separation of the side walls defining a longitudinal axis of the valve.

18. The tray assembly as recited in claim 17, wherein the longitudinal axes of the plurality of valves are parallel to one another.

19. The tray assembly as recited in claim 17, wherein the longitudinal axes of at least two of the plurality of valves are angled relative to one another.

20. The tray assembly as recited in claim 17, wherein the longitudinal axes of at least some of the plurality of valves are angled relative to the direction of liquid flow across the tray by an angle of between about 15┬░ and 45 ┬░ .

21. The tray assembly as recited in claim 17, wherein the top wall of each of the plurality of valves is circular in shape, defining a center point that is disposed in the central area of the tray.

22. The tray assembly as recited in claim 16, wherein the aperture formed in the top wall of each of the plurality of valves is disposed at a location in the central area of the tray.