US3266786A

US3266786A - Two-phase disk contactor

Info

Publication number: US3266786A
Authority: US
Inventors: Patrick G Grimes; Marvin C Raether
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1963-11-22
Filing date: 1963-11-22
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16

Description

l, @966 F, G, GRn/|55 ETAL 3,266,785

TWO'PHASE DISK CONTACTOR Filed Nov. 22, 1963 OX Gf/V )ad MKM United States Patent 3,266,786 TWG-PHASE DESK CNTACTR Patrick G. Grimes, Milwaukee, and Marvin C. Raetlier,

lirookiieid, Wis., turing Company, Milwaukee, Wis.

Filed Nov. 22, 1963, Ser. No. 325,592 2 Claims. (Cl. 261-92) This invention relates generally to two-phase contactors. More specifically, this invention relates to disks used in two-phase contactors.

The two-phase contactor generally utilizes a plurality of elements which are dipped into a liquid, exposed to gas and then returned into the liquid. This device is also applicable when two immiscible liquids are used. The twophase contactor is used as a means to selectively absorb into or remove from a fluid certain elements or gases. Examples of successful applications of this type of a device are: removing dust particles from an air stream and oxygenating liquids.

Two-phase contactors frequently utilize a plurality of disks which are rotated into a liquid and then exposed to a gas. As they are being rotated, the surface of the disks picks up a thin film of liquid. These disks usually rotate slowly to avoid throwing the liquid film olf the disk by centrifugal force. As a result, the surface of the liquid film is usually saturated with the gas passing over the exposed portion of the disk within a very short time after the hlm emerges from the liquid. It has been recognized that a greater amount of gas can be absorbed in the film on these disks if the amount of liquid retained on the disks and exposed to the gas is increased.

It has been suggested `that roughing the surface of the disk would provide a large surface area to which the liquid would adhere and thereby expose a greater surface Y area of liquid to the gas so as to absorb more of the gas. While this is true, roughing the surface of the disks has proved relatively inefhcient.

This invention concerns a unique way of exposing7 a greater amount of liquid film to the gas so as to absorb a greater volume of gas and thereby improve the efficiency of the two-phase contactor. The liquid film on the disk tends to liow along the surface of the disk as it is rotating. It is believed that if the flow path of the liquid film on the disk is elongated, a greater area of liquid film surface will be exposed to the gas and a greater volume of gas will be absorbed into the liquid being treated.

Generally, there are -two forms of fiow which can occur on the film. The first being the laminar flow in which the top surface of the liquid flows faster than the lower layers and hence exposes the second or lower layer of film to the gas phase. The other form being a turbulent tiow where there is a type of rolling of the lilm of liquid as it tio'ws off of the contactor. This also exposes more surface of the film to the gas phase. Hence, elongating the flow distance with either type of fiow will increase the tilm surface exposed to the gas phase.

To elongate the iiow of liquid on the disk, the diskv of this invention has a plurality of projections which are arranged on the flat surface of the disk to be in a generally horizontal position as they emerge from the liquid to be treated to lif-t a greater amount of liquid on the disk than would be lifted by mere film adhering to the disk surface. During the rotation of the disk, the projections assume a vertical position so as to cause the liquid to flow along the disk surface due to gravitational force.

Therefore it is the object of this invention to provide a new and improved two-phase contactor.

Another object of this invention is to provide a new and improved disk for use in a twophase contactor.

assignors to Allis-Chalmers Manufac- Another object of this invention is to provide a disk for use in a two-phase contactor that elongates the flow of liquid on the disk.

Another object of `this invention is to provide a new and improved two-phase contactor which increases the volume of gas absorbed in the liquid film on the surface of the two-phase contactor disk.

Other objects and advantages of this invention will be lapparent from the following description when read in connection with the accompanying drawings, in which:

FIG. 1 is an isometric view of a two-phase contacter having disks of this invention;

FIG. 2 is a front View of a disk showing the preferred embodiment of this invention;

FIG. 3 is an end View of the disk of FIG. 2;

FIG. 4 is a front view of a disk showing an alternate embodiment of this invention;

FIG. 5 is a partial section view of the disk of FIG. 4 taken along lines V-V;

FIG. 6 is a front view of a disk showing still another embodiment of this invention;

FIG. 7 is an end View of the disk of FIG. 6; and

FIG. 8 is a partial cross section View of a disk showing a modified form of a projection used on a disk of this invention.

Referring more specifically to the drawing by characters of reference, the two-phase contactor 10 of this invention is illustrated as a liquid gas contactor having a tank 11 with bulk liquid 12 to be -treated owing in the lower portion of the tank. A horizontally disposed shaft 13 is rotatably mounted in a pair of spaced apart bearings 14 and a plurality of disks 16 are mounted on the shaft 13 for rotation therewith in a substantially vertical plane. About one-half of each disk is submerged in the bulk liquid 12 to obtain maximum results. A suitable source of power such as the illustrated electric motor 18 is provided for rotating the shaft. Preferably the shaft is rotated at a relatively slow speed to avoid throwing liquid off of the disks by centrifugal force.

As the disks are rotated through the bulk liquid to be treated, a film of liquid adheres to the surface of the disks and is carried through and is exposed to the gas phase of the contactor. As the portion of the disk out of the water is being rotated, the liquid film on the surface tends to flow downward slightly due to gravitational force. Naturally the amount of flow depends on the thickness of the film and its natural adherence to the material which forms the surface of the disk. If the amount of liquid picked up on the disk exceeds that amount which would naturally adhere to the disk surface through surface tension, the excess portion of that liquid flows downward along the surface of the disk more easily than the film adhering to the disk. Since flow on the disk surface is desired in this invention, an attempt is made to lift as much liquid as possible on the disk. Also, the speed of the disk has to be kept slow enough so that the gravitational force will overcome any tendency of centrifugal force o-f the disk to throw this liquid radially outward or to neutralize it so that the liquid does not ow at all.

It hasbeen found by experimentation that the surface area exposed to the gas in this type of contactor is saturated with the gas within a very short time after the disk emerges from the bulk liquid. Hence, to increase the amount of gas absorbed in the liquid a larger surface area must be exposed to the gas.

As the liquid film on the surface of the disk tiows along the disk, it exposes additional film surface to the gas phase and more gas is absorbed into the liquid. This is a continuing process and hence the greater distance the film flows on the disk before re-entering the liquid in the tank,

the greater the amount of surface exposed to the gas and the greater the amount of gas absorbed in the liquid.

As mentioned above, there are basically two types of flow which occur in this film which cover the surface of the disk. One is what is known as the laminar flow in which the outer surfaces of theliquid flow downward at a faster rate than the inner layers of liquid which have a greater adhesion to the surface of the disk. The other type of flow is called the turbulent flow in which the liquid tumbles down the surface of the disk and as it tumbles and rolls it exposes previously submerged surface areas to the gas. In the contactor such as illustrated in the drawing both types of flow occur. For example, some of the liquid tends to cascade over the ribs or projections and cause a turbulent type of flow, whereas some of the fluid tends to llow along the surface of the disk in the trough formed between adjacent projections. In this case a laminar type flow occurs. In either case though, new unsaturated film surface is being constantly developed for exposure to the gas and more gas is correspondingly absorbed into the film.

The disk 16 illustrated in FIGS. l and 2 is the preferred embodiment of this invention. The disk 16 has a plurality of arcuately spaced outwardly extending projections 21 mounted on the surface thereof. Adjacent projections form troughs 22 therebetween. These projections 21 extend generally toward the center of the disk and are specifically arranged so that when a projection 21 emerges from the bulk liquid in the tank 11, it is in a substantially horizontal position so as to entrap on the disk a greater amount of liquid than would normally adhere to the surface of the disk by surface tension alone. As the disk 16 continues to rotate, these projections 21 gradually assume and pass through a substantially vertical position. As the projection is rotating toward the vertical position, gravitational forces tend to draw the liquid downward through the trough 22 between projections 21 toward the center of the disk. This type of llow is laminar. However, some of the liquid in the disk 16 cascades over the projections 21 thereby causing a turbulent flow. As the projection 21 assumes a vertical position, all of the liquid adjacent the projection is flowing downward in laminar flow. As the projection passes the vertical midpoint, any liquid which has -not flowed all the way to the center of the disk and back to the bulk liquid starts to flow across the trough 22 to the projection 21 on the other side of the trough. As the projection rotates further to near a horizontal position just prior to re-entry into the bulk liquid in the tank 11, the liquid on the disk tends to ride up slightly on the projection. Other of the liquid on the disk still flows toward the center of the disk. The net effect is to elongate the flow path of the liquid on the disk and cause it to remain on the disk for a longer period of time continually exposing new unsaturated film surfaces and thus more and more of the liquid to the gas. Hence, more gas is absorbed into the film and returned to the bulk liquid in the tank.

The size and shape of the troughs or projections on the disk may be varied to accommodate various types of liquids and materials of the disk. Furthermore, the shape of the specific projections can be different such as the example illustrated in FIG. 8 in which the projection 25 on disk 26 is designed to have an inclined leading surface 27 extending downward from the outer part of the projection toward the surface of the disk at an angle o less than 90 so as to form a somewhat of a V-shaped trough 28 to entrap more liquid between the projection and surface of the disk as the disk is being rotated upward through the bulk liquid. This provides a greater amount of liquid to be treated by the gas. Furthermore, the trailing surface 29 of the projection 25 can be inclined in the same direction to Iform an obtuse angle with the disk surface as compared with the acute angle formed between the disk surface and the leading surface 27. This configuration induces turbulent or cascading flow over the projection 25 as it moves downward from its vertical position toward the bulk liquid.

FIGS. 4 and 5 illustrate a modified disk 32 of this invention in which the troughs 33 between projections 34 all terminate in groove 3S formed `by an annular projection 36 spaced radially outward from the center of the disk and radially inward from the ends of the projections 34. This particular arrangement is intended to prevent as much as possible liquid flowing off the disk into the bulk liquid before the disk has passed entirely through the gas phase. A further modification of that type of a disk is illustrated in FIGS. 6 and 7 in which a number of cordlike bridging members 40 are positioned on disk 41 between adjacent radial projections 42 to form pockets 44. This further retards the flow of liquid in a radial inward direction and causes the liquid to flow down one projection across the cordlike member and then over a second projection 42. This construction also induces more turbulent type flow.

Experiments using the disks of this invention as cornpared with a plain disk with a roughed surface show that the amount of oxygen absorbed in the liquid film on the disk and hence dissolved into the bulk liquid in a given length of time can be increased by as much as 50 percent.

In operation, the liquid such as water to be treated flows through the tank 11 by means of the inlet and outlet pipes. If a gas such as atmosphere is used, it is not necessary to enclose the disks. However, if a gas other than atmosphere is to be used, the contacter should be enclosed as by tank 11 and the gas, for example oxygen, injected into the enclosure by suitable means. During operation the disks 16 are rotated slowly with preferably 40 to 60 percent of their surface in the liquid. As one of the projections 21 emerges from the bulk liquid 12, it is in a substantially horizontal position and traps liquid between the projection 21 and the surface of the disk in an amount which exceeds that which would naturally adhere to the disk by surface tension alone. As the disk continues to rotate, the projection 21 gradually assumes a vertical position. During this time, some of the liquid on the disk is flowing radially inward along the projection and other of the liquid is cascading over the projection. When the projection 21 is in the vertical position, all of the gravitational force is downward and all the liquid tends to flow downward in the trough between adjacent projections. As the projection passes through the vertical position into the next quadrant the liquid on the disk tends to flow across the bottom of the trough 22 to the next projection. By the time the projection is about to re-enter the bulk liquid, it is again approaching a substantially horizontal position and the liquid from the trough 22 is tending to flow over the projection 21 again toward the bulk liquid. Thus, the flow of a molecule of water could be described as being picked up between projections, flowing radially inward along the project1on across the bottom of the trough, and then down the adjacent projection again radially inward toward the center of the disk and possibly flowing over a projection. By comparison, if there were no projections the liquid would tend to flow directly to the bulk liquid immediately upon emerging from the liquid and would find the shortest path to the liquid. As was pointed out above, the increased path of travel of the liquid causes a greater surface area of liquid film to be exposed to the gas resulting in a much higher volume of gas absorbed in the liquid film and returned to the bulk liquid being treated.

Although the operation was explained in detail in relation to the disk 16 of FIGS. 1 and 2, the operation in connection with the other illustrated disks would be substantially the same. This is also true if the phases were two immiscible liquids rather than the liquid-air illustrated.

Although only a few embodiments of this invention have been illustrated and described, it will be apparent to those skilled in the art that various modications and changes can be made therein without departing from the spirit of the invention or scope of the appended claims.

Having now particularly descri'bed and ascertained the nature of our said invention and the manner in which it is to be performed, we declare that what we claim is:

1. A two-phase contactor comprising a plurality of disks mounted `for rotation, said disks being located so as to `be partially submerged in a liquid to be treated, at least one surface of each of said disks having a plurality of arcuately spaced inwardly extending radial projections formed thereon, adjacent radial projections cooperating with the intermediate disk surface to form llow contr-0l troughs therebetween, said troughs terminating in a groove formed by an annular projection spaced radially outward from the center of the disk and radially inward from the inner ends of the radial projections, said projections being arranged to entrap liquid in said troughs upon emerging from said liquid and direct the flow of said liquid in an elongated path along the surface of said disk as said disk is being rotated.

2. A two-phase contactor comprising a plurality of disks mounted for rotation, said disks being located so as to be partially submerged in a liquid to be treated, at

References Cited by the Examiner UNITED STATES PATENTS 844,466 2/1907 Prott 261-84 X 1,619,286 3/1927 Burks 103-96 2,698,287 12/1954 Bowden et al 202-175 X FOREIGN PATENTS 21,708 1891 Great Britain.

HARRY B. THORNTON, Primary Examiner.

E. H. RENNER, Assistant Examiner.

Claims

1. A TWO-PHASE CONTACTOR COMPRISING A PLURALITY OF DISKS MOUNTED FOR ROTATION, SAID DISKS BEING LOCATED SO AS TO BE PARTIALLY SUBMERGED IN A LIQUID TO BE TREATED, AT LEAST ONE SURFACE OF EACH OF SAID DISKS HAVING A PLURALITY OF ARCUATELY SPACED INWARDLY EXTENDING RADIAL PROJECTIONS FORMED THEREON, ADJACENT RADIAL PROJECTIONS COOPERATING WITH THE INTERMEDIATE DISK SURFACE TO FORM FLOW CONTROL TROUGHS THEREBETWEEN, SAID TROUGHS TERMINATING IN A GROOVE FORMED BY AN ANNULAR PROJECTION SPACED RADIALLY OUTWARD FROM THE CENTER OF THE DISK AND RADIALLY INWARD FROM THE INNER ENDS OF THE RADIAL PROJECTIONS, SAID PROJECTIONS BEING ARRANGED TO ENTRAP LIQUID IN SAID TROUGHS UPON EMERGING FROM SAID LIQUID AND DIRECT THE FLOW OF SAID LIQUID IN AN ELONGATED PATH ALONG THE SURFACE OF SAID DISK AS SAID DISK IS BEING ROTATED.