US2376940A - Fractionation column - Google Patents

Description

May 29, 1945- R. H. RlElvlElvscI-uuEIDER 2,376,940

. I FRACTIONATION COLUMN Filed June 28, 1945 Z/WQ'J' 4 17 l I J0 15A i 6 J6 f 9 J\; 19 l H1 20 I I 4 .5- Z el 14 5, 7 Je J3 3- mja E .3 .5J/ZZ EZ3\34 J0 l 17. 'I6 J5 l1-' I I I i J9 y en 2 J3 g 127` I4 9 7 2l 4 f5 AGENT I Pascua May '29.1945

' '2slasso Fics Faaca'iona'nois COLUMN Ralph Eitlmcnsohneider, -Pleasantville. N. YV..

alslgnor to The Lummus Company, `N. Y.; a oorporationofDelawai-e appussusnsune ze, ma. semi a. 492,569

: claim. (ci. ssi-'114) The 'present invention relates to fractionation columns and particularly to improvements in the construction of the liquid downfiow means andthe internal reinforcing column.. Y It is common to provide for internal reinforcementl of a fractionation .column by securing to means of a 'fractionation the inner wall thereof a series of vertically spaced sign of the bubble cap reinforcing rings. ylior adequatestrength, such rings` are generally made quite wide radially so that they project a considerable distance into the interior of the column. In the case of a column ble cap deck area. This improved liquid downflow means may be used with particular advantage in a vacuum fractionation column.

Anotherl important object of theginvention is to provide for a fractionation column Lan improved construction and downfiow means and the internal reinforcing means which enables the downpipes to be placed in such a position as to intersect the reinforcing rings without weakening thereof whereby the downpipes may be located closer to the inner wall of the column and the decks may consequently which isto bcoperated under vacuum conditions,

the rings are usually made particularly wide in order` to enable the column to .withstand the external atmospheric pressure. Such wide rings occupy much ofthe cross-sectional area of the space-within the column and. heretofore. have placed objectionable limitations upon the positioning of the liquid downpipes and upon the dedecks therein.

According to one standarddesign, a bubble cap deck extends from one side of the column across the interior thereof and terminates short of the opposite side of the column to provide the deck with an overi'iow edge. A weir is` provided at `'tliis-'edga .and o ne or more downpipes are arranged to receive the liquid flowing over the weir and to conduct it downwardly within the column generally to the next lower deck. It is that the `deckextend as far as possible across the interior ofthe column in order to provide a relativelyV large deck area for the accommodation ofrbubble caps.

Heretofore, the wide reinforcing rings vprojecting inwardly from the wall of a column such as one used in vacuum fractionation have formed obstructions to advantageous placing of the downpipes and have necessitated placing of the latter entirely inwardly of the rings. Such placing of the downpipes necessitates narrowing of the deck in order to bring the overflow edge vthereof in proper` relation to the downpipes and thereby entails the sacrifice of much precious deck area. The deck area thus sacrificed may reduce the area available for bubble caps to such a degree as to require the elimination of an entire row or more of'bubble caps.. Thereby, the fractionation capacity of a column of a given diameter is objectionably limited.-

An important object of the present invention is to provide for a fractionation column an, im-

l'proved construction and arrangement ofthe liqdesirable v i Another object of the be extended farther across the column to afford greater area for the accommodation of bubble caps. Y

invention is to provide an -improved `construction and arrangement of the liquid downnow means and the internal reinforcing rings so `devised as to define i'orv each bubble deck a suitable space for disengagement of vapor from the liquid before passage of the latter into the downpipes.

Other objects and advantages of the invention will appear hereinafter.

In the drawing,

Fis. l is a vertical central sectional view of a portion of a fractionation .column embodying the invention;

Fig. 2 is ahorizontal section through said column, one of the bubble cap decks and associated parts appearing in plan and a portion of the deck being broken away to disclose the underlying structure; and Y.

Figs. 3 'and 4 are detail vertical sectional views of modified features of construction.

A portion of a fractionation column embodying the invention is indicated at I. This column is reinforced .internally by vertically spaced rings l ring is rigidly secured to the inner wall ofthecolumn as bywelding therearound as indicated at l. 'I'he dimensions of the ring will vary according to the diameter of the column and the nature of the fractionation process in which the column is employed. For a process performed under vacuum conditions, for instance, a column', having an internal diameter of ten feet may require reinforcing rings fof approximately six to eight inches radial width, measured from the outer periphery of the ring lto the inner edge of the horizontal flanged, Such a wide ring will arrangement of the liquid deck I reinforce the column to the extent necessary to withstand the'extcrnal atmospheric pressure.

tachably -secured thereto. They support thedeck at, a suitable elevation above the ring for a purpose which will be explained hereinafter.

In the present instance, the deck comprises qthree sections or plates including a large central plate 9, a margin plate 9 of segmental Aform at i one edge of the central plate. and a margin plate III at the opposite edge of the central plate. The edges of these plates opposed to the inner wall of the column are shaped to conform to the cur'- vature of such wall and are desirably formed y with upstanding arcuate flanges. Suitable packing I I lis interposed between these flanges and the column wall. The opposed edges of' plates 8` 'and 9 extend along the upper side of one of thev beams, and the opposed edges of the plates 8 and III extend along the upper side of the other beam. Rows of studs lI2 detachably secure the plates along the opposed edges thereof to the crossbeams. the shanks of the studs extending between the opposed edges and havingA nuts screwed upon their upper ends to engage both of the adjacent plates. One or more brackets I3 resent instancepeach deck is supported.

thercaround to the flange andthe plate. l downpipes extend downwardly into a sealing well l I'I, and the liquid flows over weir I 9 into the preliminary downilow space defined by the inner wall of the column, the apron 20, and the bottom structure formed by the reinforcing ring and the plate. Thence. the liquid ilows through the downpipes to the sealingmell of the next lower deck.

It will be seen that the construction disclosed provides for advantageous arrangement of the downpipes close to the inner wall of a fractionation column regardless of the radial width of the reinforcing rings so that the decks can be made wide enough to afford deck area sumcient for a required bubble cap capacity. This advantage is obtained without weakening of the re- -inforcing rings since each ring is reinforced by are secured to the inner wall of the column in position to afford under-support for the outer edge of the margin plate 9.

The central deck plate bears a plurality of rows of bubble -cap risers I4, over which are mounted caps I5. Margin plate 8 has an up-l standing rib I9 upon which a weir I1 is mounted for vertical adjustment thereof, 'and margin plate III has an upstanding rib I9 upon which a Weir I9 is also adjustably mounted. These ribs and weirs are arranged parallel to the opposed edges of the deck plates. Margin plate I0 is formed with aA vertical depending portion 20 reaching to l a level below that oi' the flange 4 of the reinforcing ring and forming a downilow apron.

The total width of the three deck plates is such that, the apron is located in a suitably spaced relation to the opposed portion of the column wall to ailord therebetween a liquid downow space of a desired capacity. Between the lower edge portion of the downflow apron 20 and the adjacent reinforcing ring 2, there is a bottom plate 2| of segmental form. This plate is horizontally disposed in the same plane as the flange 4 of the ring, and its outer edge is shaped to conform'to the curvature of the inner edge of the flange andfis welded continuously thereto as at 22 to form a sealed, rigid connection; Along its s inner edge, plate 2| is formed with a depending flange 29 bolted, as at 24, to the lower margin of the downilow apron.

In the present instance, two downpipes 25 are shown as provided for each bubble cap deck. However, the number of downpipes per deck may be varied. In order to locate the downpipes close to the inner wall of the column, the flange 4 of eachV reinforcing ring associated with a respective deck vand the bottom plate 2I welded to this flange are formed respectively at their opposed edges with two pairs of registering recesses 28 and 21. The registering recesses define circular apertures of. a size to snugly receive the downpipes, and the upper ends of the downpipes are tted respectively in these apertures and welded the welded-on plate, which compensates for the recessing of the rings to accommodate the downpipes. In addition, the construction provides the desirable preliminary downilow space of greater capacity than the downpipes to permit retained vapors to disengage from the liquid before the latter enters the downpipes.

Fig. 3 shows a modified construction wherein a larger bottom plate 2Ia for the downflow space is substituted for the plate 2I. Plate 2Ia is of segmental form and overlies the associated reinforcing ring. The outer edge of the plate conforms to the column'wall, and the plate is welded around this edge to the wall as at .5a. Welding 22a also secures the plate to the inner edge of the ring flange 4; and, if desired, the plate and the flange may be welded' together face-to-face for maximum reinforcement of the ring. At its inner edge the plate is formed with an upturned flange 29 bolted to the apron 29 as 'at' 29.- As in the first-described form of the bottom structure, the ring ange 4 is recessed as at 29 to partially receive the downpipes. The plate 2Ia, however, lhas complete apertures for fully receiving the upper ends of the downpipes, and the latter are welded to the plates around these apertures. The downpipes may also be welded to the flange 4 around the recesses 20.

Fig. 4 shows a modification of the bottom plate and the downflow apron. Here, the apron, designated at 20a, has an out-turned flange along its lower edge, and the plate, designated at 2lb, has a flat inner margin underlying this ange and bolted thereto as at 3l.

It will be appreciated that my invention is also applicable to a bubble-deck construction wherein n0 provision is made for disengagement of retained vapor from the downflowing liquid. In such case the plate I Il is not provided with'the downwardly extending portion 20.

Although my invention has been more particularly described in connection with a vacuum fractionation column wherein the reduction of the cross-sectional area is most desirable because of the accompanying decrease in construction l cost, it is not necessarily limited thereto and may also be used in .connection with a column operatf ing at atmospheric or superatmospheric pressure.

While I have disclosed several satisfactory forms of embodiment of my invention, the invention is not limited to these specific embodiments and to the details disclosed but includes such changes as come within the scope of the appended claims.

I claim: 1. In a fractionation co1umn,an internal reinforcing ring for the column secured to theinner wall ot the latter, a bubble cap deck within the column and having an edge thereof spaced from said column wall and provided with a downow weir, crossbeams borne by said ring and supporting said deck in a position spaced above the ring. a downflow apron extending J`downwardly from said deck edge and disposed with relation to the opposed portion of said column wall to afford therebetween a downilow space substantially segfmentalin horizontalsection for disengagement of vapor from liquid ilowing over said weir, a plate extending from the lower portion oi' said apron outwardly to said ring to form a bottom for said space, 'and a downpipe leading downwardly from the bottom 01' said space and of small downflow capacity in comparison with the flow capacity of said space, said ring and said plate being both recessed to receive the upper end of said pipe therethrough and said plate being secured to the` ring vto reinforce the latter and compensate for such recessing oi the` ring. v

2. In a fractionation column having a bubble cap deck, a plurality of downpipes eccentrically located within the column and arranged to receive liquid from said deck and conduct the liquid downwardly within the column, an internal reinforcing `ring for the column and secured to the inner wall thereof and having an inwardly extending annular flange, and a segmental plate disposed inwardly of said ilange and with its outer edge in opposition to the inner edge of the f/ v inner wall of the column and provided at said edge with a downilow weir, an internal reiniorc-` in g ring for the column secured to said inner walland disposed at a level spaced below that of the deck, ,a downilow apron extending downi y wardly from said deck edge and disposed in relation to the opposed portion of the column wall to aiord therebetween a ldowniiiow space segmental in cross section for disengagement of vapors from liquid iiowing over said weir, a plate extending outwardly from the lower portion of -said apron to said ring to form a bottom for said space, and a downpipe leading downwardly from said bottom and of small downnow capacity in comparison with the iiow capacity of said space.

RALPH H. mmmNscrmmnna.

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