US2711307A

US2711307A - Contacting tray construction

Info

Publication number: US2711307A
Application number: US283430A
Authority: US
Inventors: Oswald H Milmore
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1952-04-21
Filing date: 1952-04-21
Publication date: 1955-06-21
Anticipated expiration: 1972-06-21

Description

June 21, 1955 Q. H. WLMORE 2,711,307

CONTACTING TRAY CONSTRUCTION Filed April 21, 1952. 2 sheets-sheet 1 3l WV: .n -F` 5o 21/ 1- 29 fb N1 \L 5l O /l 'L l 2 ,I 19 1 1 *2 15 1.

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1 1s 2a- 12a J 1Q 15 Y 11 n- 1% "mfnvznJror June 21, 1955 o.v H. MILMORE 2,711,307

CONTACTING TRAY CONSTRUCTION Filed April 21, '1952 2 Sheets-Sheet 2 M V f if la nveni'or liquid and gas. These spaces are, for best results, made high enough to permit disengagement of the liquid droplets, so that the gas can ascend through the next higher tray without carrying over any appreciable quantity of liquid. Too close a vertical tray spacing limits the permissible gas flow rate and also the load point, i. e., the rate of gas ow at which liquid is prevented from descending through the slots in sufficient amount to maintain the necessary ow of liquid and at which the column therefore becomes inoperative due to flooding. In general, it is desirable to space such trays apart by distances at least about three times the bar widths, and spacings of from three to thirty inches are typical, The trays may be oriented as shown, whereby the grid bars of each tray extend at right angles to those of the adjacent trays.

- The several contacting trays have two or more subjacent beams 15 extending transversely to the directions of the grid bars and the bars are welded to the upper parts thereof whereby each tray forms a unitary structure that may be fabricated outside of the column and lowered through the interior. One or more trays are supported in any suitable manner, e. g., on the bottom of the column or on a suitable truss, (not shown) and higher trays are stacked successively, as shown. Thus, the beams 15 of each tray may rest on the upper surfaces of the adjoining lower trays and may be bolted thereto by bolts 16 extending through flanges 17. When the grid bars on adjoining trays are 90 out of orientation, as shown, the beams 15 on successive trays will likewise extend in alternate directions, forming a shaft-like structure at the center of the column. This central part vmay be utilized as an access passage by using interrupted bars 12a at the center of each tray so as to leave a central man-way and providing a central grid having grid bars 12b for closing the man-way. As shown in Figure 3, the ends of the bars 12a are supported on and welded to bars 18 that are, in turn, welded to the sides of the beams 15 away from the center, with the top faces ilush. The ends of the bars 12b rest on the upper edges of the beams; these barsv are welded to horizontal spacer bars 19, which extend transversely along the under sides of the bars and spaced inwardly from the ends, whereby the assembly of all bars 12b forms a removable section of the tray. These removable sections are detachably connected to the other parts of the trays by any suitable fastening means. I prefer in many applications to arrange the fastening means to permit the sections to be loosened either from the top or from the bottom, and to this end bracket plates 2i? having vertical holes 21 are welded to the beams 15 a short distance below the top thereof (Figures 3 and 4). These brackets have slots 22 milled in their upper faces. Bolts 23, having transverse pins 24 resting in the slots 22 so as to prevent rotation of the bolts, extend through the holes 21 and through registering holes in the spacer bars 19 and grid bars 12b. These bolts have top and

bottom nuts

25, 26. It is evident that it is possible to secure or remove the removable man-way sections either from the top or bottom of the tray by manipulation of the

nuts

25 or 26. When a section has been loosened, it can be pushed upward and then slid horizontally onto the grid bars 12a, between the beams 15 of the next higher tray, permitting a man to climb through the may-way. Handholes 27 are cut at intervals into the beams 15 to permit inspection of the sections of the grid trays beyond the beams and access toV the bolts 16.

A frusto-conical, downwardly diverging ring 28 is welded to the lower face of each spray grid tray, the lowermost part having an external diameter only slightly smaller than the interior diameter of the column so as to permit the tray to be moved vertically within the column despite the usual shape irregularities of the latter. The ring thus forms an inclined llange that forms a trough together with the column wall. The grid bars terminate access to the top of the trough. It may be noted that this ring further serves as a structural member in positioning the outer ends of the interrupted grid bars 12a. A limp closure member is placed into this trough to span the gap by its weight. In the embodiment shown, this member is a cable 29 (Figures l, 2, 5 and 6) having a sleeve 30 receiving the cable ends so as to form a hoop. At least one of the cable ends preferably has a sliding t within the sleeve, while the other end is secured, e. g., by crimping, so as to permit the circumference of the hoop to vary to adapt itself to the requirement of the trough. The sleeve has a perforated lug 31 to facilitate grasping the cable for removing it from the trough. While I have shown a limp closure member comprising a single turn of cable, and have provided for variations in the length of the cable by means of the slide sleeve 3), the invention is not restricted to this speciiic arrangement. The cable descends by the weight thereof to different depths in the trough at different circumferential positions thereof, depending upon the horizontal distance between the ring 28 and the column wall, thereby substantially closing the annular gap. To prevent the cable from becoming displaced in the event of sudden pressure surges a plurality of slotted positioning lugs 32 are clamped to each tray by bolts 33, extending across the trough above the cable.

In operation, liquid descends through the column, passing through the slots 13, and gas ascends through the same slots. For example, in fractional distillation the gas may be provided by supplying heat to a lower part of the column. The upward gas velocity is usually maintained suiciently high to interfere with the free drainage of liquid through the slots, whereby a body of liquid is built up on each tray and the ascending gas entrains some of this liquid and throws it up into the contact space 14 as an intense spray, thereby eiecting intense atomization.

It is evident that the trays are adequately placed in how-restrictive relation to the column wall if the leakage path is smaller than the width of the slots, and this requirement is met by the closure arrangement shown. By placing the ring 28 below the tray a body of water collects in each annular trough, which effectively prevents the upward by-passing llow of gas. A minor amount of liquid may seep through, down from the trough, but seepage is opposed by the pressure of the gas and the amount thereof is small in relation to that descending through the wider slots 13.

It is also possible to locate the inclined ange at a different height in relation to the tray surface and to use other types of limp closure members. Both variants are shown in Figure 7, it being understood that either may be applied individually. In this embodiment, the frustoconical flange 28a is fixed to the upper faces of the grid bars 11, and the limp closure member is a chain 29a that is placed in the trough formed by the ring and the column wall 11. The chain may be retained by slotted positioning lugs 32a, which are clamped by nuts 33 on studs held by base plates 34 welded at intervals to the top of the ring. The operation of this embodiment is similar to that described above, with the diiference that the hydrostatic head of the liquid in the trough will vbe somewhat less.

As previously indicated, the invention is notlimited to columns using spray grid trays without downcomers, but may be used with other types of trays. Thus, Figure 8 shows the invention applied to a conventional bubble tray 35 having vapor risers 36 and bubble caps 37 forV the upow of gas and for effecting contact between the gas and liquid on the tray. The tray may be provided with a conventional overow weir and liquid downcomer (not shown) as understood in the distillation art. The tray has the frusta-conical ring 28 welded to the bottom and is supported through this ring by angle clips 38 thatV are welded or otherwise tixed at intervals to the column at or near the smaller, upper part of the ring so as to afford 15 wall 11. The closure cable 29 is placed into the resulting annular trough and retained by the positioning lugs 3,2, as previously described.

Figures 9 and 10 illustrate a variant wherein the tray is made up of sections and the inclined peripheral ange isdiscontinuous. Such a construction is desirable particularly in columns that do not have llanged heads, but having, instead, openings in the side near the top and bottom, such openings having diameters less than the internal column diameter. For introducing the prefabricated trays through such side openings, it is advantageous to construct the trays, in sections andto mount the sections on tmsses extending across the column. As shown in the drawing, the column 11 has transverse beams or trusses 40 fixed thereto and extending from wall to wall for supporting the trays, again represented by spray grid trays having grid bars 12. The trays are formed in sections, of which two

sections

41 and 42 are shown, with their contiguous margins both over the truss 40 and supported thereon through spacer bars 43 and 44 that are welded to the lower faces of the grid bars that lie above the truss. The tray sections are bolted downby nuts45 and 46, respectively, on bolts xed to the truss and extending through holes in the grid bars. g Each tray section has welded thereto at the arcuate periphery thereof a sec-y tion of a frusto-conical ange, indicated at 47 and 48. The closure cable 29 with its sleeve 30 is placed in the trough formed between the ange and the column wall and retained by slotted lugs 32, as previously described.

I claim as my invention:

1. A gas-liquid contacting column comprisingan upright shell; a plurality of gas-liquid contacting trays positioned at different levels within the shell having openings and positioned by the weight thereof at'each part of the tray perimeter at a height that is determined solely by t the local horizontal distance between saidv flange and wall.

2. The column according to claim 1 wherein the limp closure material is` an annular member that is substantially incompressible. Y

3. The column according to claim 2 wherein the annular member is a chain.

4. The column according to claim 2 wherein the annular member, is a cable.

5. The column accordingV to claim 4 wherein the cable has a length less than the circumference of the trough and the ends of the cable are in alignment and axially movable relatively to one another.

6. The column according to claim 4 wherein the cable I has a length less than the circumference of the trough and Y be engaged for removal from the trough.

for the passage of gas and liquid therethrough; land an annular closure between a tray and the wall of the shell, said closure comprising a downwardly and outwardly inclined ange at the periphery of the tray forming an annular trough with the said wall, and limp closure material within the trough in engagement with said flange and wall 7.Y The columnY according to yclaim 1 wherein the tray is made of several separate sections each of which includes a part of the perimeter thereof, and the said inclined ange is discontinuous, with aA portion thereof on each of said separate sections of the tray.

References CitedV in they le of this patent UNITED jSTATES PATENTS "France Dec; 1l, 1943