US3105862A

US3105862A - Jet tray tabs

Info

Publication number: US3105862A
Application number: US55981A
Authority: US
Inventors: Jr Felix F Doering
Original assignee: Esso Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1960-09-14
Filing date: 1960-09-14
Publication date: 1963-10-01
Anticipated expiration: 1980-10-01

Description

06L 1963 F. F. DOERING, JR $10 JET TRAY TABS Fild Sept. 14. 1960 I 2 Sheets-Sheet 1 REB'CHLER EFFLUENT BOTTOMS FIG-7 Felix F. Doering, Jr. Inventor By WA]. W1 4 M Patent Attorney Oct. 1, 1963 F. F. DOERING, JR

JET TRAY TABS 2 Sheets Sheet 2 Filed Sept. 14. 1960 %%M 4 4 hhmxAox mTO hAOXAOy AOXAOXAOXAOXAOXAOXA OXAOXAOXAQXAOXAOXAO XAOXA4 X%OVAAQXA XAOXAOXAOXAOXAOXAO/I Felix E Doering, Jr. Inventor By WJJWH Patent Attorney United States Patent O 3,105,862 JET TRAY TABS Felix F. Doering, Jr., Scotch Plains, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 14, 1960, Ser. No. 55,981 1 Claim. (Cl. 261-114) The present invention is concerned with an improved apparatus for countercurrently contacting liquids with vapors. More particularly, the invention is concerned with an improved fractionating tray whereby etfioient contacting is obtained over a broad range of operation. In its particular aspects, the present invention is concerned vn'th a fractionating tray in which eflicient contacting is maintained over a broad range of liquid and vapor loadings by using tabs of various weights pivotably mounted on the tray, covering vapor slots, the tabs being forced into an open position by the gaseous pressure below the tray. The rear edge of each tab is secured to the tray. A stop prevents the tab from pivoting beyond a 45 angle to the tray so that a horizontal velocity component is thus imparted to the vapor rising through the slots in the tray. High liquid rates are obtainable on this tray with no loss in tray efficiency because of the pumping action of the vapor as it rises through the liquid.

It is known to the art to use fractionating devices that have punched tabs, inclined at an angle to the tray, over vapor slots in the tray. As vapor rises through the slots it is given a horizontal velocity component in the direction of liquid flow. This momentum interchange aids liquid in getting across the tray.

However, fraotionating devices of this nature have an extremely limited range of operation. At low vapor rates liquid dumps through the slots and the vapor-liquid contacting device becomes considerably less efiicient. To overcome this difiiculty, whole rows of vapor slots are blanked by passing a sheet metal strip under the tabs and bolting it to the tray. This practice results in a reduced plate efiiciency because the bubble area, i.e. the area of the tray over which vapor-liquid contacting occurs, is reduced. Therefore, it is an object of the present invention to provide a means for maintaining the bubble area over the whole area of the tray available for vaporliquid contacting over a range of vapor-liquid loadings far exceeding that capable under the prior art.

This object is accomplished in the present invention by using tabs that are pivotably mounted to the tray and by using tabs of various weights. By uniformly interspersing tabs of various weights a self-blanking tray is obtained. At low vapor rates only one series of tabs may be open. At higher vapor rates, a moderate increase in the pressure drop through the tray will cause another series to open up, allowing the greater quantity of vapor to how through the slots. Thus, the vapor pressure drop across the tray is maintained within the range of best efiiciency, even with vapor and liquid rates varying over an extremely broad range of operating conditions. Further, by uniformly interspersing tabs of various weights over the tray, the bubble area will remain substantially constant from the lowest operable vapor rate to the highest.

The present invention thus contemplates the use of several series of tabs. The Weight of the tabs in each 7 3,105,862 Patented Oct. 1, l$63 series as well as the number of series depends on economic considerations as well as the range of liquid and vapor loadings expected.

The tabs may be given various weights by any number of satisfactory methods. One method is to punch each series of tabs from a different gage sheet metal.

Another method is to bolt, solder, weld or otherwise attach by any suitable means -a weight to a standard tab. The shape of the weight is not critical and may have a circular or rectangular cross section. The weight is suitably attached to either the bottom or top of the tab. However, the position of the weight must be such that the pivotal movement of the tab is not restricted.

It is also known to use elongated hinged members in fractionating devices which tend to give the vapor a horizontal velocity component as it rises through the tray. These devices have proved to be unsatisfactory in that the vapor rises through the liquid in sheets, i.e., in extremely large elongated bubbles, thus yielding an ineflicient mass transfer mechanism. Furthermore, in tractionating devices of this kind there is no provision for blanking the vapor passageways at extremely low vapor rates to avoid chattering of the hinged members.

Therefore, it is an object of the present invention to provide a pivot-ably mounted tab which has extremely simple construction, installation and maintenance characteristics, and at the same time provide a small tab, thus retaining the mass transfer advantages of having small bubbles of vapor rising through liquid on the tray. Furthermore, by using two or more series of tabs, each series being responsive to a different gaseous pressure beneath the tray, a self blanking fractionating device is obtained which operated at maximum efliciency over a broader range of liquid and vapor loadings than anything currently known to the art.

Further objects of the present invention will become apparent by referring to the drawings which show an embodiment of the same.

FIG. '1 is a top view of a tab element in the open position on a tray.

FIG. 2 is a sectional view 2-2 of the tab element in FIG. 1.

FIG. 3 is a side view of a tab element as it is punched out of sheet metal.

FIG. 4 is a top view 'of the tab element of FIG. 3.

FIG. 5 is a top view of, a punched tray vapor slot.

FIG. 6 is a top view of a tray showing a method of uniformly interspersing three series of weights of tabs.

FIG. 7 is an illustration of a fractionating tower using the pivotably mounted tab elements of the present invention.

Referring now to FIGS. 1 and 2 in more detail, 1 is a tray on which a tab element 16 is shown in the open position. Tab element 16 consists of tab 4, clamp 5 and tab stop 6. Tab 4 is retained on tray 1 by bending clamp 5 through clamp hole 3 and under tray 1. The angular displacement B of tab 4 is governed by the position of tab stop 6. The angular displacement B is between 5 and 45 preferably 20. Clamp 5 is formed in a shape to retain tab 4 on tray 1, by using any suitable means, such as a pliers or a jig specifically adapted to such purpose. The purpose of clamp '5 is merely to retain tab 4 on tray 1 and thus should not be tightly formed against tray 1 to bind or restrict the pivotal movement of tab 4. Also, clamp holes 3 should be slightly larger than clamps so that that pivotal movement of tab 1 will not be restricted.

It is also desirable to have tab 4 slightly overlap vapor slot 2. Thus, the edges of tab 4 should overlap vapor slot 12, hie- A inch. The preferred overlap is /s inch.

FIGS. 3, 4, and 5 show tab element '16 and tray 1 as each appears after being punched from sheet metal.

Tab element 116 is thus of unitary construction and is simply installed on tray 1 by bending clamps 5 into clamp holes *3.

Tab stop 6 is shown formed to the desired angular displacement B when tab element 16 is punched from sheet metal. The angular displacement B of tab stop 6 can be adjusted by any suitable means.

Since tray 1 is made of sheet metal, the openings for vapor slot 2 and clamp holes 3 can be readily punched, out or formed by any suitable means.

It may thus be seen that the fractionating device of the present invention is easily assembled.

The shape of tab 4- shown in FIGS. 1-5 is rectangular With a radius of curvature on the forward edge equal to /z the width of rear edge. However, this is merely one embodiment of the present invention and the particular shape of the tab 4 or vapor slot 2 is not intended to be limited. The cross sectional area of vapor slot should be from 0.25 to 9.0 square inches depending on the particular fractionating service. The preferred range for the cross sectional area of vapor slot 2 is from 1 to 4 square inches.

FIG. 6 is an illustration of three series of tabs 4 of different weights, tab 4a being the lightest, 412 an intermediate weight tab, and 40 being the heaviest tab. The tabs, 4a, 4b and 4c are depicted symbolically to facilitate the illustration of uniform interspersion of three series of

tabs

4a, 4b and 4c, across tray =1. The tabs are arranged in rows parallel to the recessed inlet 7 which provides a liquid seal so that vapor cannot pass up the downcomer associated with the tray above. As shown, the

tabs

4a, 4b, and 4c are uniformly interspersed over the entire tray in a recurring series, i.e., 4a, 4b and 40, 4a, 4b and 40, etc. In this way there is obtained a distribution of 4a tabs throughout the tray bubble area. Similarly,

tabs

4b and 4c are distributed throughout the total bubble area. Thus, even at very low vapor rates, the bubble area is maintained at a maximum. Since bubble area is related to tray efficiency, it is important to keep the bubble area as large as possible.

To realize the objects of the present invention to the fullest extent, it is necessary to layout tabs 4 on tray 1 in such a manner to avoid channeling of liquid across tray 1. To do this, tabs '4 of one row (a row being normal to the direction of liquid'flow) are offset-with respect to tabs -4 of the adjacent rows. The offset would normally be one-half the distance between tabs in a row.

This particular arrangement, as shown in FIGURE 6, results in a tab 4 layout having an isosceles triangle pattern.

The distance between tabs 4 in one row is in the range of from -1 to 5 inches. Also, the distance between rows of tabs 4- is in the range of from 1 to 5 inches. The distances between the tabs 4 in a row and the rows of tabs 4 will depend, in each instance, on the size and number of vapor slots 2 and the overall dimensions of tray '1. Insofar as possible, the triangular pitch of tabs 4 should be maintained even when different weights of tabs 4 are used, as in FIGURE 6. As it may be seen from FIG URE 6, it is difiicult to maintain a triangular pitch of open tabs when operating at vapor velocities such that tabs 4a and lb are open. However, this feature of the invention should be retained and a layout of tabs 4 other than that shown in FIGURE 6 can be used to do so.

It should be noted that the present invention does not rely solely on the use of differently weighted tabs to obtain a broader range of operation than with the prior .ferent weights. It is not intended that the present inven- 9 tion should be limited to tray designs using three Weights of tabs, but rather that the number of different weights of tabs should be another variable in selecting the optimurn tray design in a given situation.

FIG. 7 illustrates a fractionating tower 9 with tabs 4 in the open position on tray v1 due to the gaseous pressure beneath tray 1.

The feed, which may be liquid, vapor, or a mixed vapor-liquid stream, enters tower 9 through line 10'. Overhead vapor is taken from tower 9 through line 1d. Liquid reflux is sent back to tower 9 through line 13.

Radio plate 15 prevents the liquid reflux from line 13 from shooting across the top tray 1 and thus a liquid level is maintained on top tray 1. v

The liquid in tower 9' passes across each tray *1 in a countercurrent flow pattern as it passes down tower 9 through downcomers 8. Recessed inlets 7 prevents vapor from flowing upwardly through downcomers 3; A liquid bottoms is removed from tower 9 through liquid bottoms line 12. Heat is supplied to the tower by means of a neboiler (not shown). The fluid from the re boiler enters tower 9 through reboiler effluent line '14.

As shown in 'FIG. 7, tabs 4 open so that vapor passing upwardly through tray !1 is given a horizontal velocity component in the direction of liquid flow across the tray, i.e. toward downcomer 8.

The purpose of FIG. 7 is to show a working embodiment of the present invention and is not intended to restrict the use of the present invention to any particular fractionating tower design.

The figures have shown one particular tab element design which is the preferred embodiment of the present invention. However, the tabs could be pivotably mounted to the tray by means of a pinned hinge arrangement. The design shown in the figures is preferred because of its simplicity of construction and installation. Other designs can be used which retain this feature of the present invention.

Having described this invention, what is sought to be protected by Letters Patent is set forth in the following claim.

What is claimed is:

In a vapor-liquid contacting device including at least one vapor-liquid contacting tray, means to supply liquid to said tray from above, andmcans to supply vapor to said tray from below, the improvement which comprises providing said contacting device with a contacting tray comprising in combination the following:

(a) liquid introduction means on at least one location on the tray and liquid withdrawal means on at least one location on the tray,

(b) at least one row of vapor apertures on said tray with an individual cross sectional area of 1 to 4 square inches,

(c) at least one row of tab elements on said tray,

(d) said row of tab elements containing at least two groups of tab elements of different weights,

(e) said tab elements each comprising in combination a tab, integral clamps, and an integral tab stop,

(f) said tray having clamp holes adjacent to and spaced from each said vapor aperture,

.( g) said tabs being above and overlapping each said vapor aperture,

(h) said clamps extending from said tab through said clamp holes thereby providing means for pivotably mounting said tab element on said contacting tray,

(2') said tab stop being located between said integral 6 clamps and being angularly displaced from the plane References Cited in the file of this patent of said tab element at an angle not exceeding 45 UNITED STATES PATENTS 581d tab element being freely pivotable on said contacting tray, within the angular displacement be- 948,432 Rudeen 1910 tween the tab stop and plane of said tab to direct 5 2718900 Nutte? Sept- 1955 upflowing vapor in the direction of liquid flow on 2,772,080 HPggms et 1956 the tray, I 2,787,453 Hibshrnan et al Apr. 2, 1957 (k) said tab stop engaging the upper surface of said 2,809,821 CPnStannkeS 1957 tray when said pivotably mounted tab is lifted from 2,846,204 Gllmore 51 1958 said tray to an angle equal to the angular displace- 10 2,853,231 Hlbshman et a Sept. 23, 1958 ment between said tab stop and the plane of said 310191003 "Glitsch 30, 1962 tab element FOREIGN PATENTS 1,237,299 France June 20, 1960