US2551016A - Bubble cap and downspout unit - Google Patents

Description

May l, 1951 l w. R. KINNAIRD BUBBLE CAP AND DOWNSPOUT UNIT Filed March 26, 1949 Patented May l, 1951 UNITED STATESy PATENT oFFicE BUBBLE CAPAN'D DOWNSPOUT UNIT William R. Kinnaird, Riverside, Ill., assignor to Universal Oil Products Company, Chicago, Ill.,V a corporation of Delaware Application March 26, 1949, Serial No. 83,640

6 Claims. (Cl. 2.61-114) This invention relates to an improved' type of bubble cap and downspout unit for liquid and vapor contacting towers, such as fractionating columns, strippingV towers, and the like. In particular, the invention provides a bubble deck or unit which attains improved vapor and liquid contacting at each deck by utilizing both the direct bubble type of' contact between the vapor and liquid, as Well as the passage of' the rising vapor stream through falling liquid iilms or streams, and thus obtain an eii'lcient contacting between the concurrently moving streams. f

In other than packed columns, counter-currently moving streams of liquidv and vapor are normally caused to contact` one another by means of barile plates or conventional types of bubble decks. The usual form and type of bubble deck ortrayy provides an arrangement where the vapoi; isv forced to bubble through a bath of liquid maintained on each tray, While in general the various baille arrangements used, such as disc and donut pans, provide that the liquidl fall in a series of films or streams and the rising vapor stream pass upwardly through them. For purposes of efficiency, various types of cross-ow bubble decks are mostv commonly used in fractionating columns, even though they are in general rather expensive` to build and maintain as compared with packed beds and some of the baffle arrangements of simple construction.

It is a principal object of this invention to provide a liquid and vapor contacting deck which combines both the direct bubbling contact between the liquid and vapor streams and the fall'- ing stream type of contact, whereby to obtain an eflicient counter-current liquid and vapor contact.

It is also an object of the invention to provide a single'large bubble cap having a specially designed top portion which provides a liquid reservoir thereon permitting indirect heating from the rising vapor stream, as well as means for effecting the free fall of the liquid therefrom through which the rising vapor stream may subsequently pass.

It is a still further object of the presentinvention to provide a relatively simple type of construction and arrangement that attains a high eiciency of contact between the vapor andliquid streams without the necessity of a large number of vapor risers and bubblel caps at each deck.

Briefly, this improved bubble deck or contacting tray and downspout unit for a'liquid-Vapor contacting chamber comprises, a deck plate having an upturned continuous inner walll forming a centrally positioned vapor opening, with a second-wall extending upwardly from the plate forming an overilow Weir and an annular liquid retaining trough encompassing the central vapor opening and a liquid downspout section adjacent the wall vof the column or chamber, a vapor defiecting bubble cap positioned over the central vapor opening with a perforate depending wall extending into the annular-shaped liquid retaining trough, an upwardly projecting Wall from the top of the cap forming a liquid reservoir on the upperv surface thereof and providing a continuous weir suitable for discharging liquid in a substantially uniform and free falling stream to the annular trough on the deck plate, liquid downspout means depending from the downspout section with liquid sealing and distributing means. at the. lower end thereof suitable to distribute and discharge liquid to the liquid reservoir of thecap on the next lower deck.

Inv a preferred embodiment, the liquid sealing and distributing means provides a substantially continuous pan or trough around the. inner wall of the contacting chamber and is spaced a short distance above the `top of4 the bubble cap on the next lower deck such that a substantially continuous andA cylindrically shaped -stream of liquid falls to the liquid reservoir of the lower cap. Thus, the rising vapor stream is bubbled through a liquid bath on the deck plate, subsequently passes through a continuous stream or film of liquid from the bubble cap at that deck, and then subsequentlyI passes through a second lm or stream falling from the liquid distributing means of the deck thereabove, which as noted hereinabove, is positioned a short distance above the bubble cap, and discharges liquid to the liquid reservoir on the capv in a free falling stream. There is thus provided two contacts between the rising vapor stream and the descending liquid stream at each, of the contacting decks or units in addition to the bubbling contact. A preferred form of the apparatus also utilizes a plurality of downspouts or downpipes from the liquid withdrawal Section at each deck, such that the liquid is withdrawn uniformly from each deck and distributed uniformly into a continuous annular distributing pan at the bottom of the downspouts.

It is a particular advantage of this arrangement to obtain not only the multiple liquidV and vapor contacts at each deck, but the advantage of a heating and distilling operation on the body of. liquid which is maintained on each oi the bubble caps at each of the decks. Preferably, the upper surface of the single large bubble cap is substantially flat and the upwardly projecting wall which provides a weir for the liquid spilling over from that reservoir is relatively short, so

- that a shallow reservoir of liquid is maintainedl on the cap and may be readily heated by indirect heat exchange from the rising vapor stream. The rising vapors are deiiected by the inner roof andA Wall of the bubble cap through the submerged perforations, which in turn provide abubbling of the vapor stream through the liquid retained on the deck plate.

The present construction which provides a single large bubble cap is also of advantage in that the cost of construction, as well as for assembly, is substantially less than for many conventional decks having a large number of vapor risers and bubble caps. However, as with previous forms of bubble trays, the deck plate may be removable from the column or tower, and may be of cast iron, steel or alloy or other material, suitable to withstand the temperature and the nature of the fluid materials handled.

Reference to the accompanying drawing and the following description thereof will serve to clarify the arrangement and construction of the improved deck, as well as further illustrate additional advantages and features attained by this construction.

Figure 1 of the drawing is a sectional elevation view of a portion of a liquid and vapor contacting tower having a preferred embodiment of the improved contacting tray of this invention.

Figure 2 of the drawing is a partial plan view, indicating the arrangement of walls and downspouts, as indicated by the line 2-2 in Figure 1 of the drawing.

Figure 3 of the drawing is a sectional plan view, indicating an alternate embodiment of the deck with a modified arrangement of the overflow weir and downspouts.

Referring now to Figures l and 2 of the drawing, there is indicated a chamber wall which, as has been noted, may be the wall of a fractionator, treating tower, stripping chamber, or other column, wherein there is a countercurrent contacting of fluid streams and in which a plurality of baffles or bubble trays are normally used. At each tray or deck, there is a substantially horizontal deck plate 2, which in turn is preferably supported in a removable manner on an angle 3, or other supporting means attached to the wall of column l. Preferably, a continuous shelf angle, such as 3, is utilized with a packing material 4 placed between the outer upturned wall 5 f of the deck plate and the inner wall surface of the chamber I, such that the liquid and vapor streams are passed through each of the decks without by-passing or channelling themselves next to the wall of the chamber. At the center of the deck 2, there is an upturned wall B encompassing a large centrally positioned vapor opening, and spaced intermediately between the inner wall 6 and the outer wall 5 of the deck is a continuous wall or weir 1. The weir I provides an annular-shaped liquid retaining section between it and the inner wall 6. The outer annular section on the deck, between the weir 'I and the outer wall 5, forms a liquid withdrawal and downspout section suitable to receive the liquid overflowing from the Weir 'I and discharge it downwardly through a plurality of liquid downspouts, conduits, or downpipes 8.

Positioned over the central vapor opening and concentrically around the inner wall 6, is a bubble cap 9, which in turn is preferably constructed in a manner to have a substantially flat upper surface and a continuous downturned wall or skirt section Iii, which in turn has a plurality of slots or openings II around the lower periphery thereof. These slots or openings II provide a multiplicity of passageways for the rising vapor stream which is deflected downwardly therethrough by the top surface of the bubble cap, with aresultingbubbling contact between the vapor and the liquid bath, which is maintained on the upper surface of the deck plate. The present invention is not limited to any particular shape or form of slots or perforations II in the skirt IIl of the bubble cap but such openings must be adequate to transmit the vapor stream at a desired rate and velocity as may be desired in the design of the column, without causing an undue pressure drop.

Also, the top of the weir or wall 'I must be sufficiently above the top of the slots I I to insure maintaining a body of liquid for the rising vapor stream to bubble through.

The upper and outer periphery of each bubble cap has an angularly projecting wall or weir I2 which forms a liquid reservoir on the upper portion of each cap, and in addition provides an overflow weir which projects outwardly from and beyond the lower wall portion of the cap, such that with a circular cap, as liquid spills over the wall I2 from the liquid reservoir, it passes in a substantially continuous and cylindrical falling film or stream into the body of liquid maintained on the deck plate 2. The arrangement and spacing of the wall I2, with respect to the weir 1 on the deck plate, as well as with the lower skirt I0 of the bubble cap, is such that the vapor stream after bubbling through the body of the liquid on the deck then passes through the cylindrical falling stream of liquid prior to passing upwardly and around the top of the bubble cap.

In the drawing, and in a preferred embodiment of the apparatus, a continuous sealing pan or trough I3 is placed below each of the downspouts 8 and adjacent the wall of the chamber I, so that an overspilling body of liquid is maintained in an annular-shaped trough and rising vapors are prevented from passing upwardly through the downspout section. Like the deck plate 2, the annular trough YI3 may be removably supported on lugs or a continuous angle, which attaches to the wall of the chamber, and likewise a packing material 4 may be'used between the outer wall of the pan and the wall of the chamber. The inner periphery of the trough is arranged and constructed such that it projects over the liquid reservoir on the bubble cap 9 of the next lower deck, so that as the liquid spills from the angular trough,it will provide a substantially'continuous cylindrical stream of liquid as it falls to the liquid' reservoil` below. Thus, as the vapors pass upwardly through the column, a second contact is made with a falling stream or film at each deck or unit. The annular trough I3 may be spaced only a short distance above the top of the next lower deck and bubble cap, providing only space necessary for the passage of the rising vapor stream. A short fall for the liquid stream is also preferable in order to reduce the amount of foaming or frothing within the liquid reservoirs of the bubble caps 9.

The two overow weirs, such as provided by the projecting wall I2 on the bubble cap and the inner periphery of the sealing trough I3, may if desired; have notched or serrated edges which in turn provide for a multiplicity of small streams falling from the periphery thereof and effect an eicient contact with the rising vapors. The wall I2 on the bubble cap is indicated in the drawing as having a serrated edge of this type.

Although not shown in the drawing, the bubble cap 9 may be bolted or otherwise removably fastened to the deck plate 2 such that it will hold its position on the deck under operating conditions. Means may also be provided for leveling the deck plate 2, the bubble cap 9, and the sealing and distributing trough I3, such that substantially uniform overflow of the liquid is obtained around their peripheries at each deck.

Figure 2 of the drawing indicates the plurality of downspouts 3 to be substantially and uniformly placed around the liquid withdrawal section, Such that the liquid passes uniformly to the seal and distributing pan I3 at the lower end oi the downspouts. The number and size of the downspouts 8 will, of course, depend upon the quantity of liquid handled within each column and the desired rate of now through the column. While the present drawing indicates the downspouts to be a part of or connected to the deck plate 2, it is not intended to limit the present unit to that construction only, for obviously, the various downspouts 8 may be and preferably are detachably or removably connected to each deck plate. Also, while the trough I3 has been indicated as supported by the wall of the chamber, Lit may be removably attached to and suspended from the various downspouts. Alternately, a plurality of sealing and liquid distributing trays may be used, rather than a single annular-shaped trough, a single distributing tray being used for each of the plurality of downspouts.

In Figure 3 of the drawing, there is indicated a modied form of the contacting deck, having an overflow Weir l', which forms a liquid withdrawal and downspout section on only a portion of the tray and a lesser number of elongated downspout conduits or passageways 8' are provided from the liquid Withdrawal zone, to pass the liquid from that deck to a suitable distributtrough I3 in Figure 1, so that a continuous cylini drically shaped stream of the liquidfalls to the bubble cap on the next lower tray and vapor rising upwardly through the column does not bypass this second falling iilm of liquid in any portion of the column.

In the foregoing description, the various walls and members of the trays have been described as being of a circular or cylindrical shape, although preferably circular, it is not intended to limit the construction and arrangement to that only, for

obviously, rectangular vapor openings, bubble caps, downspouts, etc., may well be used within the scope of the present invention, which obtains both a bubbling contact and a multiple spraying or falling film contact between the Vapor and liquid streams.

I claim as my invention:

1. A contacting tray and downspout unit for a vapor-liquid contacting column comprising in combination, a deck plate having an upturned and continuous inner wall forming a centrally positioned vapor opening, a second wall spaced from said inner wall and extending upwardly from said plate forming an annular liquid retaining trough with said inner wall, an outer wall extending upwardly from said deck plate and forminga liquid downspout section with said second wall, a bubble cap positioned over said Vapor opening and said inner wall, said cap having a depending perforate skirt extending into said annular liquid retaining trough, an angularly projecting wall extending upwardly and outwardly from the periphery of said bubble cap and forming a liquid reservoir on the top of said cap, said angularly projecting Wall terminating over said annular trough, liquid downspout means depending from said downspout section, and liquid sealing and distributing means at the lower end of said downspout means.

2. The contacting tray and downspout unit of claim 1 further characterized in that said downspout means comprises a plurality of downpipe conduits depending from said downspout section and terminating in said liquid sealing and distributing means.

3. The contacting tray and downspout unit of claim 2 still further characterized in that said liquid seal and distributing means comprises an annular trough positioned below and in vertical alignment with said liquid retaining trough and downspout section.

4. A vapor-liquid contacting apparatus comprising a column having a plurality ci superimposed contacting trays therein; each tray comprising a substantially horizontal deck plate removably supported from the inner wall of the column and having a continuous upturned inner wall forming a single centrally positioned vapor opening, a second wall extending upwardly from said plate and spaced concentrically around said inner wall, said second wall forming an annular liquid retaining trough with said inner wall and a liquid downspout section adjacent the Wall of the column, a bubble cap extending over said central vapor opening, a perforate skirt extending downwardly from said cap into said annular liquid retaining trough, a continuous angularly projecting wall extending upwardly and outwardly from the periphery of said cap and forming a liquid reservoir thereon, said angularly projecting wall terminating over said annular liquid trough on said deck plate, a plurality of liquid down spouts depending from said downspout section; an annular-shaped liquid sealing and distributing trough positioned below said downspouts and adjacent the Wall of said column, said liquid distributing trough having an overflow wall extendingl over and spaced above the liquid reservoir on the bubble cap of the next lower tray in said column.

5. The contacting column of claim 4 further characterized in that said plurality of downspouts from said downspout section and from each tray are uniformly spaced around the entire periphery of each tray.

6. The contacting column of claim 4 further characterized in that said plurality of downspouts from said downspout section depend from only a portion of said tray, with the downspouts of adjacent trays placed with respect to one another and providing a partial crossiiow of liquid at each deck.

WILLIAM R. KINNAIRD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,480,888 Marshall Jan. 15, 1924 1,635,440` Shay July 12, 1927 1,651,354 Alexander Dec. 6, 1927 1,765,087 Mase June 17, 1930 1,981.343 De Florez Nov. 20. 1934

Images