US2778621A - Entrainment-obviating bubble cap - Google Patents

Description

J n- 2 1 7 M. u. ZIMMERMAN, JR 2,778,621

ENTRAINMENT-OBVIATING BUBBLE CAP Filed Dec. 8, 1953 I I I I I 1 I I I z 7 F Illlllll ENTRAINMENT-OBVIATIN G BUBBLE CAP Marlin U. Zimmerman, Jr., Cleveland, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio Application December 8, 1953, Serial No. 396,847

3 Claims. (Cl. 261114) In bubble cap type fractionating apparatus, entrainment of liquid mist particles in the up-sweep of the vapor current is a condition which inherently occurs, and this diminishes the elliciency of fractionation in proportion as it is permitted to occur. Attempts have been made to diminish the evil by installing a partition of a layer of wire-mesh packing between the trays in the tower. This however, requires special supports and special mounting and is difficult to install, and in the case of old towers is sometimes impractical. In accordance with the present invention, entrainment-prevention means may be had which is not only particularly effective, but is of a character easily installed in old and new towers. Other objects and advantages will appear from the following description.

To the accomplishment of the foregoing and related ends, said invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

Fig. l is a fragmentary vertical section of a bubblecap fractionating tower in accordance with the invention;

Fig. 2 is a a detail vertical section, on larger scale, of an individual bubble cap; and

Fig. 3 is a similar View of a modification.

in general, the invention provides entrainment-preventing means which is localized to the individual bubble cap. Thus. a unit is possible which is pre-assembled and which needs only to be set in place on the vapor-riser on the plates.

As seen in Fig. l, a bubble cap tower T thus is furnished with bubble caps B, each of which has its own entrainment-preventing means; and as shown in detail in Fig. 2 this involves a vapor-riser 2 through the plate P, and a cap 3 is positioned over the riser and having a downwardly-directed flange 4 which dips into the liquid on the plate, as in usual form. Suitable means for positioning and holding the cap from displacement are provided, and may include support means 5 projecting downwardly from the cap to seat on the upper edge 6 of the vapor-riser, and a stem or bolt 7 with head 8 against the top of the cap, engages in a hold-down member 9 below, which bears against the undersurface of the plate cxteriorly of the vapor-riser, the stern having a nut 10 to set up against the hold-down member. Within the vapor-riser, a freely pervious filling 12 is arranged, and while this may in some cases be of metallic filamentary material without definite structure, preferably a plurality of wire mesh layers are employed. These are held between two spiders .13 which bear on the upper and lower surface of the mesh assembly, and are held to the stem 7 suitably, by threading, or set screws, or pins, etc. Thus, the structure forms a unit in which the cap carries the 2,778,621 Patented Jan. 22, 1957 assembly of mesh layers, and is anchored in place by the hold-down member 9.

Ordinarily, pieces of mesh work, as cut for instance in discs, mis-match in their interstitial openings sufliciently to present adequate surfaces upon which droplets of liquid swept along in the vapor stream may impinge and capillarily spread out and adhere. And with adequate size mesh, the liquid can drain off in drops and fall free from the mesh work. In some cases however it is advantageous to employ wire-mesh pieces of nonuniform or different mesh dimension. Thus, alternate layers or pieces may be of smaller mesh.

Ordinarily, the wire thickness may be in the range of 0011410035 in. and desirably with a free volume of about 97.7%. And if alternate layers or pieces are in different mesh dimension, these may be for example pieces of finer mesh alternating with pieces of coarser mesh. The metal of which the wire mesh is made can vary in accordance with the material which is being fractionated. lf presence of water introduces a rust factor, instead of using ordinary ferrous metal wire mesh, such metals as nickel alloys, Monel, brass, etc., may be employed. In some cases coated or plated iron base wire mesh may be applied.

in some instances instead of fitting the mesh work assembly in the lumen of the vapor-riser, an assembly of layers of wire mesh 12, as shown at Fig. 3 may be more simply clamped across the lumen of the vapor-riser, and the mesh work assembly then serve as a hold-down member in conjunction with the stem 7' with its head 8 against the top of the cap 3, and again a nut 10 below.

The manner of operation of the device is seen from the foregoing. Vapors rising from below find exit through the risers of the bubble caps on each plate, and in passing through the entrainment-preventing filamentous or mesh work mass, the rising small liquid droplets strike the metal surfaces and adhere and spread out and coalesce and ultimately form drops which fall clear and are thus eliminated from the stream, without filling the interstitial. spaces and thereby interposing corresponding obstruction to flow.

Not only is a convenient and easily applied construction here realized, but a higher efficiency over screen partitions between plates is found to result. The reason is not wholly clear, but apparently the abrupt changes in direction and velocity of the vapor stream incurred at the bubble-cap convergence favor impingement of the traveling mist particles against the multiplied metal surfaces and thus promote shake-out.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. in a bubble-cap fractionator, entrainment-preventing means comprising a bubble-cap with a plurality of Wire mesh discs of non-uniform mesh dimension in its vapor-riser, spiders between which such are held, a stem extending centrally through the whole, a hold-down member held by the lower end of said stem to engage against the bottom of the plate beyond the vapor-riser, and a nut on the upper end of. the stern bearing against the top of the bubble-cap.

2. in a bubble-cap fractionator, entrainment-preventing means comprising a bubble-cap with a plurality of layers of wire mesh in its vapor-riser, spiders between which such are held, a stern extending centrally through the whole, a hold-down member held by the lower end of said stem to engage against the bottom of the plate 3 beyond the vapor-riser, and a nut on the upper end of the stem bearing against the top of the bubble-cap.

3. A bubble-cap assembly for use in fractionating apparatus including a plate equipped with a vapor-riser, a cap adapted to be mounted on the free end of such riser, a stem carried by said cap for projection into the riser, a mass of filamentary material on the stem at such location as to be positioned Within the riser, such mass being eifective when thus positioned to close the lumen of the riser, clamping members carried by the stem at either side of the mass to hold the same therebetvt'een, the stem being of such length as to extend through the riser and beneath such plate, and a hold-down member mounted on the lower end of thestem for engagement with the underside of the plate.

References Cited in the file of this patent UNITED STATES 'PATENTS Little July 4, Cooke Feb. 25, Levin Aug. 23, Bottoms Feb. 28, Myers Jan. 15, Puls Sept. 22, Rousseau June 26, Dunn Dec. 18,

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