US3536453A - Apparatus for mass-transfer processes in liquid-liquid systems - Google Patents

Description

APPARATUS FOR MASS-TRANSFER PROCESSES IN Oct. 7 J. F. SOKOV ETAL 3,536,453"

LIQUID-LIQUID SYSTEMS Original Filed Dec. 6, 1966.

United States Patent 3,536,453 APPARATUS FOR MASS-TRANSFER PROCESSES IN LIQUID-LIQUID SYSTEMS Jury Fedorovich Sokov, Ulitsa Kosmouanton 18, kv. 52, and Zoya Dmitrievna Putilova, Ulitsa Pervomaiskaya 3, kv. 14, both of Ufa, U.S.S.R. Continuation of application Ser. No. 599,551, Dec. 6, 1966. This application June 28, 1968, Ser. No. 752,422 Int. Cl. B01d 11/04 U.S. Cl. 23270.5 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for mass-transfer in a liquid-liquid system in which rings and discs are mounted in succession on a rotor in a shell and wherein the rings have a diameter somewhat smaller than the internal diameter of the shell for mixing light liquid droplets with a stream of heavy liquid and the discs have a diameter slightly smaller than the rings for collecting light liquid beneath the discs to break the liquid into droplets. The heavy liquid with a dissolved traction of the light liquid is discharged at the bottom of the shell, while the remaining fraction of the light liquid passes upwardly through a jacket separated from the rotor for discharge from an outlet at the top of the shell.

This application is a continuation of U.S. application 599,551 filed Dec. 6, 1966, now abandoned.

This invention relates to apparatus for mass transfer in a liquid-liquid system which find application in the petroleum processing, petrochemical, and chemical industries.

Known in the art are apparatus for mass transfer in a liquid-liquid system which comprise a cylindrical vertical shell incorporating a rotor with discs (Netherlands Pat. No. 67,932, cl. 12cI).

In these apparatus, the mixing of liquids is effected in the central part of the apparatus due to rotation of discs mounted on a shaft, while the settling of liquids takes place under rings affixed to the inner wall of the apparatus somewhat below the discs.

However, the apparatus as designed provides no effective utilization of power applied to the liquids being mixed, as mixing takes place in the central part of the apparatus between the discs and rings, i.e. in the zone of 'low velocities, whereas settling takes place close to the apparatus walls under the stator rings, i.e. in the zone of maximum velocities under these conditions, the coalescence of droplets of a light liquid is impeded, so that the efficiency of mass-transfer processes in the above ap paratus will be low.

It is an object of the present invention to provide an apparatus for effecting mass-transfer processes in liquidliquid systems that will have high capacity and efficiency.

It is another object of the present invention to employ a rotor provided with discs and rings for effecting the mixing of liquids.

It is a further object of the present invention to provide in the apparatus conditions that are conducive to vigorous mixing of the heavy and the light liquid in the vicinity of the apparatus walls due to ring rotation, as well as conditions that favor the enforced coalescence of droplets of the light liquid due to centrifugal force which arises as a result of ring rotation and throws out the heavy liquid to the walls of the apparatus shell, while the light liquid is caused to collect in the apparatus center under the discs.

It is a further object of the present invention to reduce the consumption of power while providing adequate Contact between the liquids and vigorous mass transfer.

With these and other objects in view, the present invention resides in that the rotor shaft of the apparatus, apart from the discs, carries rings whose outer diameter is slightly smaller than the inner diameter of the apparatus shell and which are intended for mixing droplets of the light liquid with a heavy liquid stream as well as for preventing the longitudinal circulation of the liquids along the shell walls, and the diameter of the rotor discs is somewhat smaller than the outer diameter of the rings, this arrangement being instrumental in causing the light liquid to collect under the discs and thereafter breaking said liquid into droplets by means of said discs.

It is expedient to mount the rings on stops rigidly connected to the shaft, so as to dispose the rings inbetween and coaxially with the discs.

Other objects and advantages of the present invention will become apparent from the description and appended drawing, which shows a longitudinal section of the present apparatus for mass transfer in a liquid-liquid system.

In the description of the specific embodiment of the present invention, shown in the appended drawing, recourse is had, for the sake of clarity, to definite terminology. However, the narrow terms used in no way limit the invention, and it should be remembered that every narrow term embraces all the equivalent elements that function in a similar manner and find application for the solution of analogous problems.

The apparatus comprises vertical cylindrical shell 1 and rotor 2, which consists of shaft 3- with discs 4 and rings 5 mounted in the middle part of said shaft.

In shell 1 of the apparatus provision is made for cover 6 in the top part, while the middle part of shell 1 incorporates heavy liquid inlet union 7 and light liquid inlet union 8.

Incorporated in the bottom part of shell 1 is a heavy liquid outlet union 9 and a union 10, through which bottom spraying is effected. In cover 6 provision is made for light liquid outlet union 11.

Disposed in the top and the bottom parts of shell 1 are brackets 12, 12 which respectively carry grates 13 and 14 intended for damping the rotary motion of the liquids.

Shaft .3 of rotor 2 is mounted in top bearing 15 and bottom bearing 16. To eliminate vibrations, provision is made in the central part of shaft 3 for intermediate bearings 17 with rollers 18.

Because of its considerable length, shaft 3 consists of several parts joined together by means of couplings 19.

To tighten shaft 3 and eliminate its vibrations, the top and the bottom parts of shaft 3 are furnished with top coupling 20 and bottom coupling 21, respectively, while top articulated joint 22 and bottom articulated joint 23 are intended for facilitating the centering of shaft 3.

Due to the provision of jacket 24, the rotation of shaft 3 exerts no effect on the liquid in the upper settling zone.

Discs 4 are welded to sleeves 25, which are mounted on shaft 3 by means of keys (not shown in the drawing). Also welded to sleeves 25 are stops 26, to the free ends of which are welded rings 5.

Subsequent sleeves 25 with discs '4 and rings 5 disposed on them are fastened on shaft 3 at some distance from one another. Other known techniques of fastening discs 4 and rings 5 are likewise feasible.

The diameter of discs 4 is somewhat smaller than the outer diameter of rings 5 which, in its turn, is slightly smaller than the inner diameter of shell 1.

Discs 4 are mounted on shaft 3 coaxially with rings 5, the distance between adjacent discs and rings being adequate for the passage of liquid streams.

Discs 4 are intended for collecting the light liquid underneath and for breaking the liquid into droplets.

It is the function of rings 5 to mix the light liquid drops with a heavy liquid stream and to prevent the longitudinal circulation of liquid streams along the apparatus Walls.

The number of discs 4 and rings 5 in the apparatus,

their position in relation to one another and geometrical relations may be varied depending upon the properties of the liquids being brought into contact with one another, upon the desired capacity of the apparatus, and also upon the efiiciency of the mass-transfer process in question.

Shaft 3 is driven in rotation by shaft 27 of a drive which consists of an electric motor and a reducing gear (not shown in the drawing).

The bottom part of shell 1 rests, via mantle 29, on supporting ring 28.

Mass-transfer processes in the liquid-liquid systems are carried out in the apparatus of the present invention as follows.

A liquid solvent, e.g. diethylene glycol is fed into the apparatus from the top via union 7, while a liquid feed stock, e.g. platformate, enters the apparatus through bottom union 8.

Diethylene glycol, a heavier liquid, sinks to the bottom of the apparatus, in which the gasoline flows upwards counter-currently to the diethylene glycol stream.

The feed stock is a disperse phase, while diethylene glycol is a continuous phase and fills the entire volume of the apparatus below the liquid interface, which is maintained slightly under top grate 13.

The rotation of rotor 2 causes diethylene glycol, the heavy continuous phase, to be thrown by discs 4, due to centrifugal force, against the walls of the apparatus from whence underlying rings 5 direct diethylene glycol to the next discs disposed in the direction of liquid flow.

The stream of gasoline, the light phase, is displaced by the heavy phase from the apparatus walls towards the center, where it collects under discs 4 in the form of a cone with the base directed upwards. The light phase flows from under disc 4 in the form of jet, is broken into droplets and thrown towards the apparatus walls.

Because of the rotation of rings 5, there occurs vigorous mixing of gasoline droplets with the diethylene glycol stream at the apparatus walls. Then the gasoline droplets are displaced by the heavy phase (diethylene glycol) towards the apparatus center and collect under the next higher discs 4. Thus, the process of consecutively breaking the gasoline into droplets and mixing the droplets obtained with the diethylene glycol stream is repeated on passage from one pair of discs 4 and ring 5 to another, and so on.

In view of the fact that in the apparatus having a limited number of mixing stages, the process of mass transfer cannot yield a sufficiently high concentration of the product compound (extract), provision is made for bottom spraying through union 10 to attain this goal.

In bottom spraying, use is made of either the extract, which is partly recycled to the apparatus, or some other solvent, having a limited dissolving power with respect to the extractable material.

Due to countercurrent mass transfer in the present apparatus, diethylene glycol dissolves the bulk of aromatic hydrocarbons contained in platformate, passes through the settling zone (below grate 14) and leaves the apparatus through union 9. In the apparatus, the dearomatized gasoline rises, passes through the upper settling zone (above grate 13) and leaves the apparatus through union 11.

In case the apparatus is employed for effecting mass transfer processes wherein the specific gravity of the solvent used is lower than that of the feed stock, it is expedient to feed the solvent into the apparatus via bottom union 8 while the supply of the feed stock is carried out through top union 7.

It is also feasible to have the liquid interface in the bottom part of the apparatus, i.e., below grate 14. In this case, the liquid that enters the apparatus through bottom union 8 will be the continuous phase, whereas the disperse phase will be the liquid entering the apparatus through top union 7.

The present apparatus for effecting the process of mass transfer in a liquid-liquid system has the following advantages.

At a comparatively modest energy consumption, rotor rotation breaks the feed stock stream into minute droplets and effects a vigorous mixing of the droplets thus produced with the solvent stream.

Rotary motion of the continuous phase stream (solvent) and feed stock droplets provides a prolonged contact between the solvent and feed stock, thereby intensifying extractable material transfer from the feed stock phase into the solvent phase.

Centrifugal force that arises as a result of rotor rotation provides favorable conditions for settling and delamination of the liquids as the solvent, being the heavier liquid, is thrown towards the apparatus Walls, and the feed stock, being the lighter liquid, collects under the discs at the apparatus center.

The above advantages of the apparatus for mass transfer processes in a liquid-liquid system make it possible to attain a high capacity and vigorous mass transfer in the apparatus according to the present invention.

For example, for the system diethylene glycol-platformate the capacity of the apparatus amounts to 70 111. per m? per hour, and the efiiciency of the apparatus, expressed as the height of the apparatus (in meters) corresponding to a theoretical mixing stage, equals 1 to 1.2 m., so that performance of the apparatus of the present invention is much superior to that obtained with the equipment of other types employed in analogous mass transfer processes.

Although the present invention has been described with reference to a specific embodiment thereof, it will be readily understood by those skilled in the art that various modifications and changes may be resorted to without deviating from the spirit and scope of the invention. Such changes and modifications shall be considered as falling within the spirit and scope of the present invention as disclosed hereinabove and in the appended claims.

What is claimed is:

1. An apparatus for carrying out mass-transfer in a liquid-liquid system by multiple successive conversion of one liquid into the dispersed phase and from the dispersed phase into the continuous phase in the presence of another immiscible or partly miscible and counterflowing liquid and by subsequent stepwise contacting of said two liquids, which comprises a cylindrical vertical shell; an inlet for a first liquid in the upper region of the shell; an inlet for a second liquid in the lower region of the shell; an outlet at the top of the shell for a fraction of the second liquid; an outlet at the bottom of the shell for a mixture of the first liquid and the remainder of the second liquid which is dissoved therein; a rotor mounted in said shell including a vertical shaft coaxially mounted in said shell, means for driving the shaft in rotation, rings mounted coaxially on said shaft for rotation therewith, said rings each having a large circular central coaxial opening and an outer diameter slightly smaller than the inner diameter of said shell for mixing droplets of second liquid with a stream of first liquid at the periphery of the rings and for preventing the longitudinal circulation of liquid along the walls of said shell, discs mounted on said shaft for rotation therewith, said discs being positioned beneath respective rings, said discs having a diameter about equal to the inner diameter of said rings and being imperforate for collecting second liquid under said discs in the center region of the shell and subsequently breaking said second liquid into droplets which are fed to adjacent rings whereby the rings and discs form a plurality of individual mixing and settling zones, stops rigidly connected to said shaft and including a plurality of radially and upwardly extending arm portions attached to each of said rings to support said rings, said stops being attached to said shaft adjacent the respective discs beneath said rings to form vertically spaced ring and disc units, the spacing between the ring and disc in each of said units being substantially less than the spacing between adjacent units, means in said shell defining a region above the uppermost ring for settling of the fraction of second liquid prior to discharge thereof through the outlet therefore, and means in said shell defining a region below the lowermost disc for settling of the first liquid and the second liquid dissolved therein prior to discharge thereof through the outlet therefore.

2. An apparatus according to claim 1 comprising impervious jacket means surrounding said shaft at a level between the inlet for the first liquid and the outlet for the fraction of the second liquid for defining a passage externally of the jacket means between said jacket means and said shell for the flow of the fraction of said second liquid in isolation from the shaft.

3. An apparatus according to claim 2 wherein said jacket means is a cylindrical impervious jacket surrounding the shaft.

4. An apparatus according to claim 3 including a grate supported by the shell beneath said jacket in the region between the jacket and shell.

5. An apparatus according to claim 2 including an inlet beneath the second liquid inlet for a bottom spray of liquid directly into the shell.

6. An apparatus according to claim 4 including a second grate supported by the shell at a level between the first liquid inlet and the outlet at the bottom of the shell.

References Cited NORMAN YUDKOFF, Primary Examiner S. J. EMERY, Assistant Examiner US. Cl. X.R. 23310; l96-14.52

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