US 3285705 A
Description (OCR text may contain errors)
Nov. 15, 1966 F. J. ZUIDERWEG ETAL 3,
CONTACTOR WITH ROTOR AND SECTOR STATORS 2 Sheets-Sheet 1 Filed May 22, 1963 FIG.
INVENTOR S2 FREDERIK J. ZUIDERWEG STEVEN STEMERDING BY: M/JW M FIG.
THEIR ATTORNEY 1966 F. J. ZUIDERWEG ETAL 3,285,705
CONTACTOR WITH ROTOR AND SECTOR STATORS 2 Sheets-Sheet 2 Filed May 22, 1963 FIG. 3
FREDERIK J. ZUIDERWEG STEVEN STEMERDING THEIR ATTORNEY United States Patent The invention relates to a contactor for bringing into intimate. contactftwo or more flowable phases that are at least partially immiscible with each other, e.g., immiscible or partially miscible, suitable, for example, for the "extraction of liquid mixtures such as mineral or fatty or essential oils. with the aid of one or more selective solvents, or for carrying out chemical, reactions, such as reactions between olefins and. sulphuric acid.
Thephases to be brought into contact with each other are, as a rule, fluid phases, in particular liquid-liquid or liquid-gas, and. have different specific gravities. One of the phases may also consist of. or contain finely distributed solids. The two phases may flow counter-currently through the contactor or one. phase mayflow through a substantially stationary body of the other phase; in some applications, moreover, the phases may flow'concurrently.
From the -U.S. Patent No. 2,601,674, issued June 24, 1952, it is known to effect intimate contact between flowable phases in a series of stages defined by annular stator baffles mounted at vertical intervals within. a vertical cylindrical housing which contains a rotor having circular batliesor discs fixed thereto for rotation at locations midway between the stator baflles. The stator baffles define compartments which intercommunicate only through the openings at the centers of the stator baffles.
When the contactor described in the said US. patent is constructed for large capacities and, therefore, with large housing diameters, certain difficulties are. encountered; Thus, when the compartment height is left the same as with smaller diameters, the operation of the contactor becomesless effective, whichmust be attributed to incomplete formation of the:vortexpattern that should be set up in the apparatus during its operation. Thus undesirable effect. can be substantially counteracted by increasing the compartment height. This modification, however, promotes mixing of the phases, and results in a reduction of the number of theoretical contacting stages per unit length. of the column; consequently, the length of the column must be increased. This, however, presents difficulties both of a mechanical and of an operational nature, arising from the greater length of the rotor and increased diameter of the-rotor. discs, for then a considerable mass has to be driven; this mayleadtoobjectionable vibrations, so that; special and. costly constructions are required for the; drive mechanism, for horizontal and verticalpositioning,andfor the support of the rotor.
It is the object of thisinvention to provide an improved oont'actor, suitable for up-scaling to largerdiameters, wherein the abovementioneclv drawbacks are avoided. or minimized.
In summary, according to; the invention the contactor vessel is provided with statorswhich are formed by one or by a plurality-of flat. ring sectors, which stators define compartments that are in direct intercommunication in the annular region'occupied; by the sectors, and the rotor which extends through the several compartments issituated in-the central part, i.e.,. centrallywith respect to The said-annular'region.
It is evident that the; rotor sweepszoutr a solid having a surface of revolution, herein called the effective surface, and the diameter of that surface is herein called the effective diameter of the rotor. The rotor may take any of several forms, among which are a substantially smooth cylinder, a cylinder having fixed thereto one or more strips which extend radially outwards, and a cylinder having fixed thereto a plurality of plates.
In the preferred arrangement according to any of these rotor constructions the effective. surface is cylindrical: when the rotor is cylindrical (without any projections) the rotor surface is the same as the effective surface; when one or more, e.g., two to ten, strips, preferably distributed uniformly, are applied, the effective surface is the cylindrical surface swept by said strips; and when plates are provided, the effective surface is that swept out by the radial extremities of the plates, which may be. circular. A rotor having an effective cylindrical surface is simple from the point of view of constructon; one of the reasons for this is that no special attention need be devoted to centering. the rotor with respect to the stators.
The stationary ring. sectors are preferably thin plates mounted at vertically spaced positions in planes situated perpendicularly'to the rotor axis, i.e., they are preferably horizontal. At each said position there may be one sector which occupies an are less than about 225 e.g., 180, or a plurality of sectors which together preferably occupy an are less than about 225, e.g., 180, and together form one stator. The sectors are, in 'either arrangement, staggered so that the sector or sectors at each position at least in part overlap the gap or gaps'in adjacent stators.
In one embodiment, using a single sectorper position, the sectors are semi-annular plates (180 sectors of rings), sectors at successive positions being staggered by 180. In another embodiment, using a plurality of sectors per position, the several, e.g., four, sectors are of such. circumferential dimensions that, together, they occupy less than the stated arc, and are preferably equal in size and'distributed uniformly about the circumference; the sectors in adjacent positions are preferably of like size and number and are staggered to lie opposite the gaps between the former sectors. When the sectors at each position together occupy exactly 180 of arc, the staggering is. advantageously equal to an angle of 180 dividedby the number of sectors at each position.
The space within the housing is divided into compartments by the said stators, the word compartment being herein used to denote the spaces bounded vertically by the said positions, viz.,. by horizontal planes in which the adjacent stators are situated.
Asa result of the staggering of the stationary sectors a particularly good. flow of the. phases and excellent mass transfer are realized. When the diameter of'the housing or shell' is increased it is, in principle, not necessary to increase the compartment height significantly because with the rotor according to the invention,,especially when it has a cylindrical effective surface, a flow pattern is created that is, within limits, virtually independent of the vertical distance between the stators. Therefore, with equal capacity and efficiency, the length of the contactor according'to the invention can be less than in the case of known constructions, especially when larger housing diameters are used.
It" is observed that, nevertheless, with larger diameters of the housing the. distance between adjacent stators will generally be chosen somewhat greater than with smaller diameters. Thus, the stator spacing at small housing. diameters, less than 50 cm., is generally 3-5 cm., and at greater diameters, above 50 cm., gene-rally- 5-20 cm.
The effective diameter of the rotor. should'preferably be'l'arge in relation to the ring sectors, e.g.,.only about 035- to 2.0% less than the internal diameter of the stationary ring sectors, so that there is only a narrow slit between the rotor and the stator.
The effective diameter ofthe rotor is generally between 0.2 and 0.5, preferably not over 0.33 of the housing or shell diameter. The free passage through the stator is preferably at least 45% of the horizontal cross sectional area of the housing, which is of importance for attaining a large throughput.
The invention will be further described with reference to the accompanying drawings three specific embodiments by way of illustration, wherein:
FIGURE 1 is a vertical sectional view through a contactor according to a first embodiment;
FIGURE 2 is a transverse sectional view taken on the line 2-2 of FIGURE 1;
FIGURE 3 is a fragmentary vertical sectional view showing a second embodiment;
FIGURE 4 is a transverse sectional view taken on the line 4-4 of FIGURE 3, and
FIGURE 5 is a fragmentary vertical sectional View showing a third embodiment.
Referring to FIGURES 1 and 2, the contactor comprises a vertical cylindrical shell 6 forming a housing having vertically spaced inlets 7 and 8, which may be arranged tangentially. The housing has end closures 9 and 10 and may contain, between the inlets and the closures, suitable structures 11 and 12, mounted on supports 13 and 14, for preventing turbulence in the main part of the shell from being transmitted into the end zones adjoining the closures while permitting free flow of fluid through the structures; they may take the form of grids of flat vertical plates to form egg-crate structures.
The shell carries a plurality of stationary sectors 15, 15a, which are, in this embodiment, semi-annular. The sectors 15 age staggered 180 in relation to the sectors 15a. At the E e ntral axis is a rotor 16, in the shape of a cylinder of diameter close to that of the radially inner margins of the sectors 15, 15a, so as to leave only narrow intervening slits 17. The rotor is mounted for rotation by terminal shafts 18 and 19 which extend through the structures 11 and 12 and are rotatable in bearings 20 and 21 carried by the end closures. The shaft 18 extends out through the top closure and is driven by suitable means, such as a pulley 22 and a belt 23, in the direction of the tangential inlets. The lower bearing 21, which is a combined radial and thrust bearing, may, if desired, be lubricated by admitting a small part of the feedstream from the inlet 8 via a branch duct 24. This is desirable when the stream admitted at the bottom is oil, and particularly useful when the contactor contains an aggressive, viz., a corrosive fluid which is flushed out of the bearing by the lubricating stream. A hood 25, carried by hte shaft 19, in this case preferably encloses the bearing 21. The branch stream to the bearing is, naturally, kept as small as possible.
The vessel has outlets 26 and 27 communicating with the end zones. Settling occurs in both of these zones, and an interface level is maintained in one of them, e.g., in the upper one as indicated at 28. Suitable means for controlling the feed and/ or discharge rates so as to maintain the interface level are known in the art, e.g., from the above cited US. patent, and are for this reason not described herein.
In operation, either the heavier or the lighter phase may be dispersed, and this may be controlled by the start-up procedure, as described in the above-cited US. patent. For example, when the lighter phase, such as lubricating oil, admitted through the inlet 8 is to be dispersed, the column is initially filled with the other liquid, e.g., a selective solvent such as furfural or phenol, which is admitted through the inlet 7; thereafter both liquids are introduced continuously while the rotor 16 is driven at a speed sufficient to disperse the oil in the solvent and to establish vortex patterns within the compartments. The solvent moves downwards, flowing through successive compartments and through the lower structure 12, below which there exists a quiescent zone in which entrained oil droplets settle upwards; the extract phase (solvent containing extracted, e.g., aromatic compounds in solution) is withdrawn through the outlet 27. The oil is dispersed into droplet-s which move upwards through the compartments and through the upper structure 11, and settle within the quiescent upper end zone to form an oil layer above the interface 28. The extracted oil, from which compounds such as aromatics have been removed, is discharged through the outlet 26.
Referring to FIGURES 3 and 4, there is shown a part of an embodiment incorporating two features which may be applied individually to the previous embodiment, namely, the use of a plurality of sectors for each stator and the use of strips on the rotor. The cylindrical shell 29 contains a plurality of stators 30, 30a, arranged in alternation and of like construction save for circumferential staggering by angles of 45. As appears in FIGURE 4, the stator 30 comprises four sectors of a ring 31, 32, 33 and 34, each sector having an arc of 45. The sectors are distributed uniformly about the circumference. At the central axis is a rotor which comprises a cylindrical shaft 35 and a plurality, e.g., four vertical strips 36 which project radially outward. The number and radial dimensions of these strips may be varied and are selected so as to provide the desired influence or grip on the liquid. The shaft is mounted for rotation as for the first embodiment. The effective diameter of the rotor is twice the radial distance from the axis of rotation to the outermost part of the strip (of the largest strip when not all are of the same radial dimension). Advantageously, this effective diameter is made only slightly less than the diameters ofinner edges of the sectors, so as to leave only a narrow slit 37, preferably of the size previously stated.
In the embodiment shown in FIGURE 5 the shell .29 is fitted with stators 30 and 30a, as previously described. The rotor comprises a shaft 38, mounted for rotation, and a plurality of plates 39 fixed for rotation with the shaft at the levels of the stators. The plates 39 may have circular outlines, although this is not essential. The effective diameter of the plates (being the same as the actual diameter when they are circular) is only slightly smaller than the diameter of the inner edges of the sectors which constitute the stators. The function of this embodiment 1s very similar to that of the first, save that the rotor has a reduced diameter in the regions bet-ween stators.
The apparatus described attains high contacting efficiency, e.g., when used for solvent extraction or other purposes. This high efliciency can probably be accounted for by the fact that the dispersed phase, as it is transported from one compartment to the next, has a tendency to coalesce against the stators which, in the radial directron, are relatively wide, thus forming larger drops; these are then again dispersed into smaller drops in the next compartment, to which they flow by passage through the open areas adjoining the sectors, in the annular, outer region of the shell. For it is known that during and imrnediately after the dispersion of one phase into another phase the rate of mass transfer between the phases is higher than when the dispersed phase is merely maintained in the dispersed state. Therefore, in certain cases, the effectiveness of the present apparatus can be further increased by providing the stators, at the location where the dispersed phase tends to coalesce, with a structure and/or with material which promotes such coalescence. pf course, this should not, at least to any important extent, interfere with the total flow of fluid. Suitable materials promoting coalescence are fibrous materials, such as steel wool and synthetic fibers, such as polypropylene fibers.
The coalesence-promoting material is illustrated in FIG- URE 5, wherein layers 40 of fibrous material areapplied to the under surfaces of the stator ring segments and, optional-ly, at the open spaces between the ring sectors, to
promote coalescence of the dispersed phase flowing between compartments.
The contactor may be operated at atmospheric pressure, e.g., for extracting lubricating oils with a normally liquid or a normally solid but molten selective solvent; however, superatmosphe'ric pressure may be used, e.g., in the extraction of kerosene with sulphur dioxide to remove aromatics. Operation under superatmospheric pressure requires the vessel tobe sealed and operation is then facilitated by driving the rotor magnetically or by an electric motor contained within the shell instead of extending the rotor shaft out through the closure. An example of such a construction is described in US. Patent No. 3,013,866, issued December 19, 1961. However, in most instances a direct mechanical drive, as illustrated herein, is preferred. The contactor may also be used to carry out chemical reactions, for instance, the preparation of isopropyl alcohol from propene and sulphuric acid. In deasphalting residual oil with light parafiinic hydrocarbons, the residual oil is introduced at the top and the precipitating agent, e.g., propane, at the bottom. The precipitate is discharged at the bottom. Such de-asphalting may be carried out as described by Thegze, Wall, Train and Olney in an article Rotating Disk Contactors Perform Well in Propane De-asphalting of Lube Oil in the Oil and Gas Journal of May 8, 1961, pages 90-94. The heating coils described therein maybe applied to the contactor according to the invention.
The apparatus may also be used in processes in which solids occur in one or both of the phases. Thus, one or more components can be separated from a liquid mixture by adsorption; the mixture then constitutes one phase and a finely divided adsorbent the other. An example of an application of this type is the separation of benzene from a mixture of C hydrocarbons with the aid of silica gel. In ion-exchange processes the apparatus may be similarly applied.
Sometimes one of the phases consists of a suspension of solids in a liquid. This is the case, for example, when a suspension of polypropylene particles in a hydrocarbon is washed in order to remove, for example, catalyst remnants, hydrochloric acid and/ or alcohols. This suspension can be purified by a countercurrent treatment with water as the washing liquid. The suspension to be purified is introduced at the bottom of the contactor, the washing liquid at the top, and the purified suspension is discharged continuously at the bottom.
The contactor can also be used for carrying out a twosolvent extraction. The mixture to be separated is then introduced through an auxiliary inlet 41 (FIGURE 1) at a level between the principal inlets and the two solvents through the inlets 7 and .8, respectively. An example of such an extraction is the treatment of volatile or essential oils with pentane and alcohol.
During the contacting, mass transfer occurs between the dispersed and the continuous phase. Sometimes-as in the case of a chemical reaction-a new substance is formed.
Because one of the phases is dispersed throughout the several contacting compartments, which are in direct intercommunication, while the other phase is everywhere continuous, the instant apparatus does not involve a series of successive mixing and settling stages.
Example Comparative tests were carried out in three forms of contactors A. An apparatus acording to the invention as shown in FIGURES 1 and 2, consisting of a vertically arranged cylindrical housing with an internal diameter of 30 cm., containing a coaxial, smooth cylinder having a diameter of 10 cm. as the rotor. Against the inside of the housing horizontal, semi-annular stators had been installed, each staggered 180 in relation to the next; the width of the stators was 9.5 cm. The distance between two adjacent semiannular stators was 5 cm.
B. An apparatus described. in A, but with a rotor consisting of a cylinder having a diameter of 10 cm., provided with four axially arranged strips, each with a width of 20 mm., as shown for the rotor of FIGURES 3 and 4; the width of the stators was 7.5 cm.
C. A device according to the cited US. Patent No. 2,601,674, consisting of a vertically arranged cylindrical housing having an internal diameter of 30 cm, containing a shaft with rotor discs (diameter of the discs 19 cm.), horizontal annular stators (diameter of the opening 21 cm.) being fitted against the inside of the housing midway between the rotor discs; the distance between two adjacent rotor discs was 10 cm.
In these apparatus countercurrent extractions were carried out under comparable conditions, n-butylamine being extracted from kerosene with the aid of water; the phase ratio applied was as 1:1. From the experimental results it appeared that in apparatus A, B and C the heights of one theoretical extraction stage were 40, 26 and 60 cm., respectively. The determinations were preformed by the method described in L. Alders Liquid-Liquid Extraction (Elseviers Publishing Co., 2nd ed. (1959) 128).
We claim as our invention:
1. A rotor contactor for contacting at least two flowable phases which comprises:
an upright, elongated vessel having vertically spaced inlet and outlet means;
upright rotor means centrally mounted within :said vessel so as to define an annular region between said rotor means and the interior surface of said vessel;
a series of stationary, flat ring sectors aflixed to the interior surface of said vessel in substantially horizontal planes at vertically spaced positions between said inlet and outlet means within said annular region, each of said sectors having a sector are of not more than 225, each of said sectors being in positions that are angularly displaced one from another in vertically displaced horizontal sector planes;
the portion of said annular region between vertically displaced ring sectors forming compartments, said compartments communicating within said annular region along radial boundaries of said compartments, said radial boundaries extending between said vessel interior surface and said rotor means;
said rotor means extending adjacent each of said compartments; and
means for driving said rotor means.
2. A contactor as defined in claim 1 wherein said rotor is a smooth cylinder.
3. A contactor as defined in claim 1 wherein said rotor comprises a shaft and at least one longitudinal strip extending radially therefrom and fixed thereto.
4. A contactor as defined in claim 1 wherein said rotor comprises a shaft and a plurality of plates extending radially therefrom at the positions of the said stationary ring sectors and fixed to the shaft to be in planes perpendicular to the rotor axis.
5. A contactor as defined in claim 1 wherein the distance between said vertically spaced positions of the sector i between about 3 and 20 centimeters.
6. A contactor as defined in claim 1 wherein said stationary ring sectors consist of semi-annular plates regularly staggered on opposite sides of the vessel axis.
7. A contactor as defined in claim 1 wherein, at each of said vertically spaced positions, there is a plurality of stationary ring sectors which are regularly distributed circumferentially about the rotor and together occupy not more than an arc of about 225, the ring sectors situated in adjacent positions being staggered so that at least parts of the sectors in one of a pair of adjacent positions are opposite the intervals between sectors in the other position of the pair.
8. A contactor as defined in claim 1 wherein the maximum diameter of the rotor at said positions is between 0.2 and 0.5 of the internal diameter of the vessel.
7 v g 9. A contactor as defined in claim 1 wherein the max- References Cited by the Examiner irnum diameter of the rotor at said positions is between UNITED STATES PATENTS 0.5 and 2.0 percent less than the inner diameter of the 2,601,674 6/1952 Reman 23 2705 said stationary ring sectors, 'Whereby only a narrow slit 729,544 1/1956 Pieters 27 5 is formed between said sectors and the surface swept by 5 2912310 11 1959 w ll et 1 23 270.5 the rotor. 2,941,871 6/1960 Geller et a1 23-2705 10. In COIHbIDRtIOHWI'th the contactor defined 1n clalm HARRY B. THORNTON Primary Examinen 1 coalescing means Within at least some of said compartments for coalescing dispersed phase near said stationary 10 RONALD WEAVER RENNER sectors. Assistant Examiners.