US3039750A - Contact plate structure for use in a rectifying or contacting column - Google Patents

Description

June 19, 1962 w. KITTEL 3,039750 CONTACT PLATE STRUCTURE FOR USE IN A RECTIFYING 0R CONTACTING COLUMN Filed Aug. 16, 1956 INVENTOR 14644 7-5.? A7 7751.

BY ow mu ATTORNEYS United States Patent Oflfice 3,939,75i3 Patented June 19, 1962 3,639,759 CQNTACT PLATE STRUCTURE FGR USE IN A RECTIFYING R CGNTACTING (IOLUMN Walter Kittel, Gertengasse 12, Grnunden, Austria Filed Aug. 16, 1956, Ser. No. 604,555 Claims priority, application Switzerland Mar. 7, 1952 2 Claims. (Cl. 261114) This application is a continuation-in-part application of my patent application Ser. No. 340,583 filed on March 5, 1953 for A Contact Plate Structure, now abandoned.

This invention relates to rectifying or contacting columns, wherein a liquid and a gaseous medium are brought into intimate contact, and more particularly to a contact plate structure for use in this type of rectifying or contacting colun'ins.

A contact plate structure substantially comprises a plane plate mounted in a cylindrical vertical container, the so-called column, said plate having one or several round or elongated openings surrounded by an upwardly extending flange for the passage of the ascending gases or vapors respectively. Said openings are covered by deflecting devices or so-called bells placed over them. Said deflecting devices corresponding in shape to the shape of said openings likewise are of round or elongated shape.

The desired contact between the gases or vapors and the liquid is obtained in the following manner: The gases or vapors discharged from the openings at a level above the plane of the plate are returned to the plane of the plate by the bells. The liquid flowing in horizontal direction along the plate from an inlet to an outlet arranged above the plane of the plate is dammed so as to form a layer of predetermined thickness. The gases or vapors are discharged from the edges of the bells into said flowing layer of liquid at a level immediately above the plane of the plate so that they infiltrate said liquid.

A contact plate of the bell-type has the advantage over other types of contact plates, that the necessary layer of liquid, caused by the above mentioned arrangement of the gas inlet and liquid outlet, is obtained under all conditions of operation, even at a very low load; therefore at least from a theoretical point of view, the mode of operation of such a contact plate of the bell-type is fully maintained, whatever the condition of operation may be.

As, in practice, during the operation of a rectifying column it becomes quite often necessary to reduce ternporarily the throughput, contact plates of the bell-type are still used in most cases owing to said far reaching independence of such contact plates from variations in the load, although the construction of such contact plates is rather complicated and many suggestions for different constructions have been made. It has been found out for quite some time that the contact proper between the gases or vapors and the liquid is unsatisfactory, as, as a matter of fact, said contact is limited to the short distance between the edge of the bell and the level of the layer of liquid through which the gases or vapors discharged from the bells pass in a more or less vertical direction.

As experiments show, an appreciable increase in the effect cannot be obtained by bringing the level of the liquid to a higher point above the plate for enlarging said path of contact, notwithstanding the mechanical disadvantages resulting therefrom, especially the increase in the resistance to flow of the gases or vapors; therefore it has been suggested to improve the intensity of contact between the gases or vapors and the liquid by giving the edges of the bells a particular shape, for example by providing the edges with teeth or slots or perforations whereby a better and finer distribution of the flow of the gas is obtained.

Disregarding a certain stabilization of the state of flow on the contact plate, said modifications, however, do not produce a substantial success with respect to the efiect to be obtained by the contact plate, as-especially for higher loads caused by the gases or vaporsa great amount of the gas or vapor passes through the liquid in the shape of channels so that it contacts the liquid only at the marginal Zones of the channels thus formed.

Only an insuflicient improvement of this phenomenon can be obtained by the use of recently proposed so-callecl sieve-bells having a sieve-like shaped lower rim.

It has been found out, though, that the above mentioned formation of channels may be avoided in principle and at the same time an intensification of the contact between liquid and gas or vapor respectively may be obtained by subjecting the liquid to rotation by a suitably oriented introduction of the gases or vapors respectively.

Therefore, above thoughts applied to the principle characterizing the contact plates of the bell-type, bell-caps have been proposed, wherein the hitherto customary lower rim with purely radially oriented slots has been replaced by a lower rim with slots having a more or less tangential direction of discharge, this being taken in a uniform sense in relation to the vertical axis of the bell.

In making this proposal, however, it has been overlooked entirely that the liquid being in the immediate surrounding of the individual bells provided with the slots described above and being subjected to rotation in above mentioned manner moves away from the edges of the bells owing to the centrifugal forces caused by the rotation, so that an effect just contrary to the desired effect is obtained by the device.

Although the supply branches for supplying the gaseous medium and the discharge branches for discharging the liquid to and from the contact plate structure according to the invention are likewise arranged at an elevated level above the bottom surface of the contact plate structure for maintaining a coherent layer of liquid, in contrast to hither-to known devices the deflection or introduction respectively of the gaseous medium into the liquid according to the inventive device does not occur by means of the customary bell-caps, i.e. it does not take place in a radial outwardly oriented sense around a centrally located gas supply branch. According to the invention, however, the gases or vapors are subjected to a reversed direction of flow by means of a suitable deflecting device, as said gases or vapors must pass in an inwardly oriented direction through an annular edge of the deflecting device, i.e. the gases or vapors are forced to pass through said deflecting device in a radial direction relative to the latter towards the center. Thus, the deflecting device according to the invention representingwith respect to its shape a reversed form of a customary bellcap will be called hereinafter a hollow bell. If furthermore, the lower circumferential edge of said hollow bell is provided with a series of inclined slots, the inwardly flowing gases or vapors hit in a more or less tangentially oriented manner the liquid being within the space formed by the hollow bell.

in contrast to its behavior in the hitherto known bell caps with edges having inclined slots, the liquid is led by the centrifugal forces associated with the rotation in a straight manner to the edge of the hollow bell according to the invention so that a very intimate contact between the liquid and the gases or vapors is obtained.

Moreover, as a result of the rotation or the centrifugal force caused thereby, this arrangement according to the invention provides for the fact that the thorough mixing of liquid with gas or vapor taking place at the lower edge of the hollow bell is followed in the next higher zone by a just as eifective segregation or centrifugal separaof the drops of liquid carried over, so that the danger of carrying over liquid in the flow of gas or vapors is substantially reduced, whereby a reduction of the distances between the contact plate structures and thus of the total height of the column becomes possible.

. shown having a plurality of round gas outlets 11 arranged in a plane above the plane of the collecting tray, said gas outlets being mostly arranged in areas or" triangular or square shape uniformly distributed over the contact plate structure.

Furthermore, in such a case, the hollow bells, necessary for obtaining the desired effect, being provided with inclined slots along the circumference of their lower edge as described above, extend downwardly into the space between the gas chimneys on the collectin tray and rest on the free area of the surface of the collecting tray between said chimneys. The upper ends of the hollow bells can be connected with each other so as to form a unitary deflecting body. Thus, the necessary deflection of the gases may be obtained in a simple manner.

The arrows show the deflection of the gases or vapors passing through the chimneys 114 arranged on the collecting tray or plate 181; said deflection is caused by a system of hollow bells 116 arranged above the collecting plate 101. In fact, the system of hollow bells constitutes a body 102 in the shape of an inverted collecting plate offset relative to the arrangement of the gas chimneys. The gases or vapors are discharged in a tangential direction from the edges of the hollow bells 102 resting on the collecting plate 101 through the non-radial slots a arranged along the circumference of said edges, whereby the above mentioned effect of flow is again assured.

Furthermore, as indicated in the drawing, it is also possible to combine the collecting plate 101 and the system 116 of hollow bells to one and the same element of construction so that the gases or vapors discharged from the chimneys are rotated already at this point by the non-radial slots of said element. In this case, the above described effect, thus obtainable in the liquid, is very advantageous and desirable, as the liquid shall not rain through the chimneys.

Other modifications, depending on the special requirements of the case, may be made without departing from the scope of the invention.

What 1 claim is:

l. A contact plate structure for use in a rectifying or contacting column wherein a liquid and a gaseous medium are brought into contact, said structure comprising in combination: a first plate having a plurality of first spaced openings arranged in accordance with a predetermined pattern, a plurality of chimneys on said first plate, the number of chimneys being equal to the number of openings in said first plate, each chimney being associated with one of said openings, a second plate having a plurality of second spaced openings, said second openings being offset to said first openings of the first plate, and a plurality of annular elements arranged on said second plate on the surface thereof facing said first plate, the number of annular elements being equal to the number of openings in said second plate, each annular element being associated with one of said openings of said second plate, said annular elements extending into the space bet een the gas chimneys of said first plate, and the walls of said annular elements being provided with a plurality of uniformly oriented nonradially extending slots for leading the gaseous medium towards the center of the annular element, so that the gases and liquid, due to the resulting rotation and centrifugal force of the liquid, will be pressed by the liquid against said element.

2. In a contact plate structure as claimed in claim 1, said first plate with its chimneys and said second plate with its annular elements being combined so as to form a unit.

References (Zited in the file of this patent UNITED STATES PATENTS 1,480,888 Marshall Jan. 15, 1924 2,136,139 Kuhni Nov. 8, 1938 FOREIGN PATENTS 164,250 Austria Oct. 25, 1949 301,425 Switzerland Nov. 16, 1954 497,599 Belgium Sept. 15, 1950 629,086 Germany Apr. 22, 1936

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