|Publication number||US2601674 A|
|Publication date||Jun 24, 1952|
|Filing date||Jun 13, 1949|
|Priority date||Jun 18, 1948|
|Publication number||US 2601674 A, US 2601674A, US-A-2601674, US2601674 A, US2601674A|
|Inventors||Gerrit H Reman|
|Original Assignee||Shell Dev|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (27), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 24, 1952 G, H, REMAN 2,601,674
LIQUID CONTACT APPARATUS WITH ROTATING DIsKs Filed June 13, 1949 2 sHEETs-SHEET 1 June 24, 1952 G, H, REMAN 2,601,674
LIQUID CONTACT APPARATUS WITH ROTATING DISKS Filed June 13, 1949 2 SHEETS-SHEET 2 Patented June 24, 1,952
` VUNITED :STATES PATIENT `olii-fici;
LIQUID coNTAcT APPARATUS WITH RoTATING nIsKs VGerrit H. Reman, Amsterdam,'Netherlands, `assgnor to Shell Development Company, San Francisco, Calif., a corporation of Delaware.
Application June 13, 1949, Serial No.98,793 Inthe Netherlands June V18,` 1948 .14 claims. (c1. `ca -4270.5)
The `invention"relates`to a Acontactor 'for intimately `contacting two or more liquids that are at leastpartiallyimmiscible, 4 e. g., immiscible lor partially miscible, so as "to 'form `two liquid'phases when in contact `with `each other, the contactor being of "the `type having "a plurality of discs mounted on V'a rotatingjs'haft within a station- Lary shell "having fixed baffles. Such vapparatus .issuitable `for effecting intimate contact `be V'tween `.liquids flowing through the shell in the same direction or in `countercurrent Aand may be applied, "for example, for the solvent extrac- "tion of liquid mixtures, "such asmineral orfatty o rressential oils with one or `more selective solvents. or 'for causing intimate contact `between 4reagents when carrying out chemical reactions,
such as reactions between .higher `olefins and s ulfuric acid. Y 1
The contacter of the. present inventiombriefly,
comprises a stationary tubeor `shell `of `which the part 'forming the actual contacting `fzoneisV subdivided into a plurality of compartments, preferably.substanta1ly identicalinsize and shape,
by stationary annular baffles or ringshaving cen- `trai openings. Further, there are `rotor discs,
one.` in each compartment, fixed on a 'rotor shaft `coaxial with the stationary tube, the discs being, located approximately" halfway between the stationary bales. The liquids to be contacted y,are `fed `into the contactor to traverse the several compartmentssuccessively, either in a common direction or in countercurrent to one another. When used: for countercurrent ow `of liquids, .the .tube is at` leastpartly upright,. e. g., .,vertical, .and )the liquids are of different densities ...this results `in ,thev formation of two liquid phases of differentdensites which traverse the `successive compartments lin, opposite directions.
The rotation of therotor discsi imparts afurther,
i` even more important,.movement Ato the liquid,
causing intimate contacting, as will appear 'from .thefollowing description. The important novel features of `the device according to ,theinvention reside inthe ,arrangementofthe discsand stators. The diameter of 'the rotor discs is smaller` than thediameter of 'the opening in the stator baffles. Further optional improvements reside' in the `relationship .between the. diameter :of `the-stationarytube andthe diameter of the rotor discs fand lthe axialinterval :between the i-,baiilespandalso inthe shapes of thelstator baf- `fles and discs, as will be described.
Itisfalready known that extractionscan be carried out in a vertical column 4"containing a `vertical `rotor shaft fitted -with .a number of rotor discs or balesfandrannular stator-rings Y According to the iknownuconstructions the diameter of thefrotorf baffles` isfap- 2 preciably greater than the inner diameter of the stator rings to bring the surfaces of the rings androtor batlles facing eachother, Whichhas heretofore been regarded asimportant for creating `shearbetween the liquids for effective `contacting. rlhis arrangement made it `diflicult to `assemble and disassemble the apparatusbecause the `rotoriand the attached rotor bailies could not `be moved through the I central holes in the stat- `or rings. TMoreover, contacting eiiiciencieswere notlas great as can be realized with the con- `tactor `ofthe present invention.
Also, in such prior contactorsthe rotor Adiscs `were :provided with irregularities, such as perforations,stirrers, and radial `fins or ribs for the purposes of insuring a more `positive agitation of the liquids when the discs were rotated; further, `the edges of the rotor and/or `stator 'rings were flanged. These arrangements resulted initurbulence and random eddy currents, wherebyamarked divergenceinthe sizes of the dispersed droplets of the liquid was brought about. `Thus, when the liquids are subjected to `theagitating action of the `irregularly-sl'iaped rotatingdiscs andthe stator, resultingin the dispersioniof one liquid in the other, the particles of fthe dispersed liquid vary greatly in sizes; this `results in an unsatisfactory extraction.
`Itis an object of `the present invention `to provide an improved rotating disc contactor whichhas a higher contactingefficiency than `those fknown heretofore, and which can bezmore diameters `smaller than the diameter of the hole in the stator bafes, so that the surfaces of `the rotor and stator baffles are not opposite each other.
Further. it was found to be advantageous to 'formthese `baffles with smooth, preferably plane surfaces, toavoid random turbulence.
thereby, promoting homogeneity in the sizesof `the dispersed droplets.
The `contacter' according to the present invention comprises'an outer shell whichshould, when countercurrent extraction is to be practiced, be
`atleast :partially upright, e. g., vertical; preferably, it is circular in cross-section and has cylindrical walls, although the invention contemplates within its scope the use of shells of other shapes. The shell or column has fitted within it a series of annular, stationary, transverse stator bafes bailies of other outlines, e. g., frusto-conical sur-V faces of revolution, is possible. They may be permanently fixed to the shell wall or removably mounted in any desired manner, e; g.,'by being xed t'o a removable cage or frame, and spaced axially with respect to the shell. The intervals between the baiiles, i. e., the lengths of the `compartments, may be uniform, but may be varied in certain cases, as to take care of peak liquid loads as will be explained. These stator bales are provided throughout the part of" the shell that is to serve as the actual contacting'or` extraction zone; this may but need not extend over the full length of the shell. Liquid inlet and discharge ports are provided at suitable points, e. g., at the ends of the shell; if desired,.additional ports may be provided at one or more intermediate points for the admission or discharge of liquid.
A rotor shaft is rotatably mounted substantially coaxially with the shell, and is provided with suitable drive means for rotation at a high speed. It extends through theV openings in the stator bales, and carries a plurality of rotor ameter than the diameter of the opening in the stator baliles. By this arrangement the extraction elciency is improved, and the above-mentioned diiliculties in assembling and dismantling the apparatus are avoided,'it being possible to remove the rotor` shaft and rotor baffles through the openings in the stators. When the stators are not all of the same size, they may be arranged with openings becoming progressively larger toward one end, thereby still permitting free movement of the shaft and rotor ballles through the openings.
The invention, further, comprises other features bringing about added and marked improvement in the contacting efliciency, such features Y being of utility when applied in conjunction with the contactor described above, but which may be separately applied to such a contactor. The first 'of these features relates to the relative dimenh sions of the shell'and rotor baffles. It was found that best results are obtained when the ratio of the internal diameter of the shell to the diameter of the rotor bales is from about 1.5 to and including about 3.0.v According to a second feature, it lwas found that best results are obtained when the ratio of the internal diameter 0f the The stator bafesare prefer- 4 shell to the axial interval between the baffles is from about 2` to and including vabout 8. Summarizing the three optimum dimensional relations:
d2 d1 (l) D 2gb-S8 (3) where D is the internal diameter of the shell; d1
and dz are the diameters of the central opening in-the stator baffles and the diameter of the rotor baiiies, respectively; and a is the interval between the baffles, all as indicated in Fig. 3. These relations'should', preferably, apply lthroughout the contactor, even when the dimensions are not uniform throughout the column,exceptin compartments wherein the diameter of the rotor` is decreased and/ or the interval a is increased to take care of peak liquid loads as will be explained.
According to still another feature, the rotor baliles and statorfrbaffles are preferably both formedof comparatively thin, sheet material, e. g., metal or plastic, without irregularities, ribs, flanges, or -the like, thereby providingfeachV of these baffles with twosubstantially smooth faces. This results in an operation-which dilersinan important respect from that of prior devices, wherein random turbulence was eiiected by irregularities or periorations in these baffles, and the dispersed` droplets had widely different sizes. By the preferred arrangement according to theV invention a far more uniform dispersion of one liquid in the other1 is effected, andthe extraction lis materiallyimproved. One aspectof this improvement is a better relation between degree of contacting, rateof throughput and flooding Thus, as the speed of the rotor is increased, the particles become more finely dispersed and tend to settle more slowly, so that there `results improved contacting and` decreased capacity. If the speed of the'rotor is `too high orV the liquids are Vfed into thel column too rapidly. the contactor will nood .It is evident that the flooding condition is largely determined by the presence of many small dispersed droplets, which forman emulsion incapable vof settling. vIf the particle sizes are not uniform there willv be comparatively large dispersed droplets, .which are not properly `contacted with the. other liquid, while the contactor is already near to Vits flooding condition.l By bringing about a greater homogeneity in particle sizes the incidence of these large droplets rjust prior to flooding is avoided, and the contacting eiciency is improved.
The contactor may be lemployed for contacting l liquids, either concurrently or countercurrently.
In countercurrent extractions the liquid to be separated may be passedin countercurrent to a single solvent or a solvent mixture yadmitted at the opposite end of the contactor; it may also be subjected toV double countercurrent extraction, i. e., extracted with two partially immiscible solvents which are caused to now countercurrently to one another by introduction at spaced points in the contactor, the liquid to be separated being introduced either with one of the solvents (usually the one with which it is most miscible) or at a point intermediate to the points of`introduction of the two solvents.
The construction of the contactor according to the invention will be further illustrated with reference to the accompanying drawing forming a -partei. thisispecication and illustrating .certain preferredembodiments, wherein: l
Fig. 1 `is a section on a vertical plane;
Fig. V3 A-is waf` diagram indicating `the important dimensions; l
1Fig..4 is a schematic diagram.Y illustratingfthe `contacter inisection `with auxiliary'equipment usedwtherewith;
Fig. "5 isa fragmentary` sectional .view of ra =modiiication; and
Figs. i6- Aand? `are schematic ,diagrams showing further modifications.`
iReferringto Figs. land l2, theapparatusfcon- `sistsoica-closedvertical column Izoffcireular p cross section and cylindricalshapehaving-a fco- `axialrotorshaft '2 journalled --at its ends for rotation and having a pulley Zw bywhich` it may be'rotated by a drive' belt, notshown. 4A plurality `of circular, imperforate baffles 3,'made of *.thin, `flat sheetfmetal, arexed tothe` rotor shaftfor rotation `therewith `with their plane `surfaces ,perpendicular to the shaft'axis. `The inner1wall of the column `is equipped with'lannular horii Zontal stator ringsv 4 likewise-made of i thin, Vflat sheet metaLbut having circular central` openings concentric With the rotorbaffles-and shaft@ they are arranged perpendicular tol the fshaftiaxis-and `located `so that they are approximately 1in' the centers of `the spaces between adjacentroton battles. The stator'bales thereby subdividetthe `columninto a vertical series. of compartments, the height of which is determined bythe vertical interval between fbailles. ,This :interval may be uniform `throughout the heightof thercolumn, but also may benon-uniform as 'will be'explained. According to the inventiontheinner diameterdi of: .the -stators'is greaterthan .dal-the diameter of the rotor baiileswhereby it is possible to insert the rotor assembly, consisting of the rotor `shaft and rotor baffles, `throughthe `openings-inthe stators, and, if necessary, torremove'` this assembly after removing the lid 'of `the column. It fwill .be noted that the` ratio of D, theinternal diameter of the column, to the diameter of thelrotor baiiles \.is,. in theY embodiment-according -to Figs. l and .2, 2.5'7,.i.e., between v1.5 Land, ,and that thefratio of. the column diametery tothe vertical interval betweenlike baiiies is 3.48, i.-e.,.ubetween 2 and 8.
The stators ..aremounted only in thecentral r and discharge arrangements may be` used, as for example, external settlers aslare shown inrFigi.
in using the coni-,actor `the liquids to beV :contacted be admitted and :contactedeither `intermittently or continuouslypthe latter 'being more generally employed. is desired bothliquids `are introduced'at one end (either top` or bottom) either. through `the same or diierent port-sof the columnandtwithdrawn at the opposite `end. 'In-operating the 'contacter for countercurrent `extraction heavy 44and flight `When coneurrentflow ,t
=' ."phase l is dispersed.
*5,6 `liquids 'are` introduced.continuously or intermittentlysat-the-.top and bottom, respectively, and the ycontactor can be operated either so' that the flight. liq-.uidphase or so that the heavy liquid phase isythefcontinuousphase. When the light liquid .ilphase iste-"be -fcontinuous the column is. initially illedx with light liquid; thereafter the heavy liquid fisvfintroducedand dispersed by the rotor discs, `passing .downwardlyzby gravity and collecting at the bottom ofthe column .to form a layer of heavy liquidzbelcwt'the level A. By'regulating the rates of lfeed Aand-.dravvofi1ofheavy liquid the interface -between` -li'ght and heavy liquids is .maintained at :the zlevelrA. Oni the other hand, when the light Pliquidphase-is lto'be .dispersed the column is finitiallyilledfwith heavy. liquid and the interface is maintainedY at `the levelB near the top of the `columniby vregulating the rate of flow oi heavy fliquid.
It .'is'ipre'ferred to `operatethe contacter With thelinterface-at thelower level A, with the heavy liquidphaseidispersed, because in most cases a `Shigher maxim`umload `can be` attained for `any givcnrotorspeed than when the lighter liquid 4 Load denotes the total .ia-'mount ofilight" and` heavy liquid phases passing ithrou'gha 'compartment in unit time, and maxif'mufmtload denotes! the load at which ilooding `*occurs at agiven"rotor speed. With a contacter Tof the"type describeiwherein all compartments arefof identical constructionand when the liquids are such that @there is no `substantial change in tthevolunlesandl compositions of the phases, the ilooding' limit is reached practically simultaneously in all compartments as the load is increased, flkeeping 4the phase-ratio vand the rotor speed constant) AVVlWhen light and heavy partially immiscible iliquidsvarelintroduced into the column they form .light 'and heavy "liquid phases, consisting pre- -:.tlininantly of' the light and heavy initial liquids, respectively, but one `or both of these phases con- 'tainssome solute dissolved out from the other liquid. =In countercurrent extractions it is defsira-ble thatthe'seresulting liquid phases have a si 11i-mum densi-ty difference of 0.02 gram per cubic lfoentin'ieter to permit countercurrent flow by .'.gravityfiatireasonableload;however, it is easier tofoperatefthe"column'lvvith liquid phases having -fg'reaterfdensity differences, e. g., 0.08 gram per 1 cubic centimeter; and operations with such higher Idensitydifierencesare more common.
EitherA the light or the heavy liquidmay be the ts'olvenu tlieotherliquid beingthe liquid being fextracted. rliioreover, either the solvent or the liquid being extracted may form `the continuous phase, the other forming the dispersed phase, the choice beingl usually `made -aiter considering the filow ratioof the feed liquids. Both liquids are -usiially'fedinto thetcontactor continuously, but interlmittentfflow is also possible. For example, Awhen theliquid forming the continuous phase is Afa=solventorltreating agent capableof treating a .largervolume ofthe other liquid, theformer may be introduced orreplenished only intermittently, and yaifstrea/m.: of l the latterliquid may be flowed fithroughan unchanging body of the former.
'The operation of `the contacter Will nowbe `de- -scribedtasfiapplied to the counter-current extrac- Ltioniof al light hydrocarbon oil forming thecon- :tinuousphase -witl1 a heavier solvent,` such as furfural or aqueous phenol, forming the dispersed A'extract-phase. The column having been initially "filled with; oil, l the lheavier solvent is introduced `Acontinuously-Lat .the top'fandoil is intro'duc'edpontinuously at the bottom while rotating the rotor, resulting in a fine dispersion of the solvent in the oil, particularly at the levels of the rotating bailles. The finely dispersed droplets constitute the extract or solvent phase, which is collected and coalesced at the bottom and withdrawn through the port 'I at a controlled rate to maintain the interface at the level A, suitable flow control and level-indicating means being provided, such as valve and level controller as shown in Fig. 4. The continuous oil phase rises through the column and dispersed extract phasesettles' from it at the level above the inlet port 5. It is then discharged through the port 3 which is preferably fully open to permit outflow of oil at a rate determined by the oil feed rate. This contacted oil is often called the raffinate phase.
rThe mechanism of dispersion and intimate contact within the contacter may be described'as follows. When the contactor is in operation there is, in the first place, a countercurrent flow through the column of light and heavy phases. This flow is caused by the difference in densities of the phases. The rotation of the rotor discs imparts a further and even more important movement to the phases which may be explaiined as follows, neglecting, for the moment, the countercurrent lio-w: The centrifugal forces caused by the rotation of the rotor discs induce flow of liquid from a rotor shaft radially outwards toward the column wall; this causes a flow of liquid from the column walls radially inwards toward the rotor shaft in the neighborhood of the stationary baffles. In addition, there is a rotation of the liquid around the rotor shaft. Thus, the motion of the liquid phase, apart from the countercurrent flow of the phases, is toroidal, as indicated by the lines T in Fig. l. The flow of the liquid resulting from the rotation of the rotor discs causes one of the liquid phases to become reduced to a very une state and dispersed because of the shearing stresses accompanying this flow. Both movements of the liquid described are superimposed. Hence, for the schematic picture of the flow of the phases in the extraction Zone we have a gravity settling of heavy drops in an ascending stream of light phase superimposed on a toroidal ilow, which is for the greater part in a horizontal direction. This toroidal flow causes local recirculation of both liquids within each compartment,
and only portions of the liquid taking part in this flow pass on to the next compartment by gravity. The path of the dispersed droplets of the heavier extract or solvent phase which pass on to the next compartment. is indicated in Fig. l by the line marked S.
It is evident that the stream of dispersed solvent phase S is, in each compartment, caused to move in a direction toward the column wall, where there is less turbulence; there this stream shows a tendency to become more coarsely dispersed. However, the stream is forced by the stator baflles to change its direction and is eventually-partly owing to the pumping action of the rotating baflles-once again sucked to the center of the column, to be again driven to the wall of the column by the next lower rotor baille. From the drawing it is evident that the dispersed extract phase crosses the ascending stream of oil both at the level of the rotor discs and near the stator baliles, thereby causing intensive extraction.
The speed of rotation of the rotor baflles is preferably such that the extract phase remains dispersed throughout thecolumn, inthe less turbulent parts near the column wall as Well as near the rotor baflles, except, of course, in the settling zonesV at the ends of the column. The contractor is, therefore, not of the type having a number of successive mixing and settling stages.
However, coalescence and redispersion of the dispersed droplets may occur at one or more intermediate compartments under certain conditions, and the invention is not limited to operations wherein such coalescence is avoided. It is desirable to op'erate the rotor at the maximum speed that can be attained without causing flooding.
A further example of the'use of the contacter, involving double countercurrent extraction with two solvents is the exraction of lemon or orange oil to separate terpene hydrocarbons therefrom. In this case, pentane is fed in at the bottom as the light liquid solvent and methanol containing 10% water is the heavy solvent which is fed in at the top and dispersed in the pentane. The lemon or orange oil is introduced at an intermediate point and occurs predominantly in the continuous phase. Methanol extract phase is coalesced and drawn off at the bottom and pentane, together with the residue of the lemon or orange oil, ilows 01T at the top. It was found Vthat this extraction proceeded smoothly although these oils are known to give emulsion troubles.
Another common feature in the extraction of essential oils is the coagulation of proteinic bodies from the oil by the alcohols; these bodies combine at the interface in conventional equipment using successive mixing and settling zones. With I the apparatus according to the invention, however, these bodies are discharged from the extraction zone with the methanol phase, which is the dispersed phase, and collect outside of the extraction zone, i. e., in the lower settler, where they do not interfere with the coalescence of the methanol drops.
The contactor may be advantageously employed together with certain auxiliary equipment, indicated diagrammatically in Fig. 4, wherein the contactor column I, provided with rotor baffles 3 and stator baflles 4 as previously described, is provided with liquid feed pumps I 0 and I I for the heavy and light liquid. It is sometimes difficult to utilize the spaces at the ends of the column to settle out the dispersion because this necessitates taking measures to avoid too high a turbulence in these end zones, such as operating the rotor shaft at a speed lower than that desirable for effective contacting. Moreover, this necessitates the use of sight gauges and/or liquid level controllers within the column. To avoid these difficulties it is often preferable to use external settlers. Thus, as shown, the dispersion is drawn off from the top and bottom of the column via lines I2 and I3 and passed into settlers I4 and I5, respectively. Settled heavy phase is returned from the settler I4 via line I6, clear light liquid being drawn off through outlet line I'I. Similarly, settled light phase is returned from the settler I5 via line I8, clear heavy liquid being drawn olf through outlet line I9, controlled by valve 20 and liquid level controller 2| to maintain the interphase at the level A.
In the extraction according to the foregoing paragraph the heavy phase was the dispersed phase, and the valve 22 in the light liquid outlet line was fully open, When the light liquid phase is to be dispersed the interface is maintained at the upper level B by regulating the rate of flow of heavy liquid by the valve 20 and liquid level controller 23, the controller 2l,beingjnthisrcase unnecessary. 4
i As was indicated above, the haines, need lnot, in every case be flat, but `may lbe ,surfacesn of; revolution.` Avmodied embodimenti using` frusta-conical baffles isyshown in` Fig.5j,.. whereinA the column l a, hasy a shaft 2c,` withl frusta-conical bafles da, and` the, stator` bafflesjlrt are, also frustofconicah It is evident that ,the dat 'baffles cit-Fig. lform, a special (andpreferred), caseof bafiies l which` are surfaces of revolution, the,` gen eratrixA in Athis case` being perpendiculark to4 the axisl of revolution. While Figi V5 shows both the rotor and stator baffles to be frustofconical, itis evident thatreithenonelcould be` flat t A, further modication shown in Fig. 5 Ais, in., themanner,` of mounting` the,V stator rings in thecolurnn. Infstead of beingY permanently fixed to thecolumn, thestators 4a are xedto vertical-rods 24,; form,- ing ya frame-work whichcanbe,removedfromthe top of the column.
, The efficiency,l of thecohtactor accordingto-,the present `invention will, he` apparentfrom, the data inthe follow-ingexamplesk 1,
EXAMPLE i The @Xpaliments,A ,were r Qarried; out with V61.- tial GQ11111121 having minimiert??? nlm `C911.- taining Hat h,orizontal` stator rings with Central circular holes having diameters of;V 5 01 mm., and spacedwvertically ati2v2lmrn.` Eour diiferentroy tors, having; 11st rotor bailes, 0f diameters., dioatedin tllatable., and. all@ tad; @91500, revolutions per minute, Wereud IliSlQQQSSii/e funs to: extract, acetic arid, from-,a mixture 0il @satis acidand, methyl isobntyl ketone,` using water .as a solvent. The methyl isobiityl ketone `iormechtlie` lighter, continuous phase, and water formed the heavier, dispersed extract phase.` Y
`In each `run, the column AvilasloadedI to` the maximum, withoutinducingi houding, and1 the total eiiiciencyvwas"determined,` By total eil-` c ienQY. is meantherein" th product 'or .the maxi-` mum` load (aslpreviouslyd lined), inliters/hour and the efficiency of, the e, ractipnexpr'esssd as, a' percentage. `(lin efiiciencyor 100%` denotes that the extractiveaction, of a, complmllt Of the Column. is, squali@ that (0f la, theoreicaltep or stage; for al deunition'of 'the theoretical stage, ses. Perrrs Clflemical.` Engineers t Handbook., 2d edition, 19.41 page 1215;) The resultaat the rims are tabulated Tablel ciencies than those, of run f1 wouldresult, showing the known constructionsto be less 4fai/.oitable than that according ,to the ,inventicinA As to the width ofgthe stator ringsit can, be remarked that with decreasing width the maximum load of the column increases and the eiliciency decreases. Especially in the case of columns with a small diameter the width of the stator rings can be small, even very small, since the pumping action caused by the rotor baiiles is so powerful that the presence of the stator rings is notior hardly required for reversing the radially outward liquid stream asindicated at S in Fig, 1';
As regards the `distance a between the stator bafes it can be remarked that the maximum load asa `function of1 this distance at first increases about nroportionately tothe distance of,` the bai',- es andl-as `soon, as the distance between the baies becomes equal to the diameter of the tube-remains practically constant; that -when the distance between the baiiles is increased the efficiency per compartment (hence for each bafes) first risesslightly to become practically constant immediatelylafter; and `that the efciency of a; column of l@certain length decreases accordingly, as,` there are fewer compartments., (stator baf-` fies). In viewof these,considerationsthe,ratioof the diameter ofvthe, column tcrtlie,distancebe,n tween` the `rotor bailiesis. preferably,v chosen` be.- tween 2` andl.V i
In orderto determinethemost favorable value of the speed of rotation ofthe rotorbafs the above extraction experiments were repeated with diilerent speeds of rotation and* various Yloadsfof the column.' The diameter offthe rotor baiiles was4 3 0 mm.; the inner diameter of the stator rings was mm.; andthe distance betweenV the baiileswas22mm. Y
4Q The results arelisted in Table II.`
Tabled] Eiicency inwPer. 45 Speed 0151` Cet htaldm lEiliciency fMaximum Total rotation at themavxipermissible Em# 11.1?. mumloadf load 1./h. Aciency` `4o eo s o 10o- 15 l ',15 16l 18 24 143` 3,430 21` a2` ,24 `26 31; lazy 3,780 24 25 27 30` 33 114, 3,760 27 28 `30 `34` 35 1041 3,'640 sa ,33" 35 37, 9o` 1 3,330
TheI data `clearly show-that ,the best results are obtained when the ratio of the `column diameter to the rotor baille diameter is `frornabout 1.5 to 3.0. Thecurve` of totaleiliciency for this series of runs has a maximumlin the vicinity of` aratio 2.63, and the total-efficiencydecreases` as the ratio isV increased or decreased. In` the case Aofknown constructionsL of... rotating disc contactora-r in which the diameter of the rotor baiiles. exceeds the inner Adiameterofrthe stator rings, the diameterof` the rotor baleswouldabegreater than `50 mm3., andI a lowerratio, with even lowertotaljer- EXAMPLE 1H The above l advantage is apparent from, there: sults, of-experiments listed in .'I'ableIIlI.-` These Iexperiments werecarried out with, theaforemem tioned column, in which the diameterof. the, rotor fbaies., was 3,0 mm., thev inner,` diameter, ot the stator` rings50` mm., and .the distance between the rotortbaiies 22` mm. The load amounted1 to 1l 60-80 liters/hour. `rThe phase ratio is the ratio of the quantity of extracting agent (water) to the quantity of the mixture to be treatedy (methyl isobutyl ketone-i-acetic acid).
Table III Elicicncy in per cent at a phase ratio i Speed of rotation R. P. M.
A spindle oil with a Viscosity of 50 centistokes at the extraction temperature was extracted in countercurrent with furfural (1 part by volume of oil to `2.6 parts Iby Volume of furfural) in an extraction column according to the invention. The diameter of ythe column was 79 mm., the diameter of the rotor bailies the inner diameter of the stato-r rings mm., the distance between the rotor baiiles 22 mm., and the number of revolutions per minute 1200.
At a total throughput of 36 liters/hour (10 liters of oil and 26 liters of furfural) the eiliciency per compartment of the column was found to be approximately 32%.
When comparing the present apparatus with a similar apparatus of the same capacity (150 liters/hour) which, however, Vhad no stator rings and in which the rotor consisted of a rotating cylinder without bales, it appeared that in the latter apparatus the Volume for a theoretical step is 11/2-2 times as large, in other words the eiciency of this apparatus is 11/2-2 times less than that of the device according to the invention.
It is Well known in the extraction art that, under certain operating conditions, greater liquid loads occur at certain points of a countercurrent extraction zone than at other points of the zone; Such load differences may be due to volume changes or to the shuttling of solute between the liquid phases, fluid being trapped so to speak; such peaks in the liquid load may be caused .by the use of temperature gradients. Further, loading peaks may result from introduction of solvent or of a liquid mixture to be'extracted at an intermediate point in the column. A commonly encountered load peak occurs near the point of introduction ofthe liquid to be extracted, particularly in the case where a double countercurrent extraction is used, i. e., an extraction wherein two at least partially immisci=ble solvents are flowed countercurrently through the contactor and the mixtureto be extracted is introduced into the ccunterilowing solvent system, as in the extraction of lemon or orange oil, as previously described. In such situations it may occur that if all compartments are of identical construction most of them will be under-loaded when the compartment carrying the peak load is near the flooding condition.
4'-Ihe contactor according to the present invention lcan be easily adapted to increase the permissible maximum liquid load at whatever compartment or compartments loading peak occurs'. Either of two, or both expedients in conjunction, can be employed: (a) The diameter d2 of the rotor baille can be decreased somewhat under the diameter of the rotors in the other compartments. (b) The spacing a between baiiies can be increased somewhat above that in the other compartments. The for-mer results in a slight drop in stage efficiency in the modied compartment, while the latter reduces the stages per length of column. These expedients, however, result in an increase in the over-all total efciency of the contactor in situations wherein peak loadings occur.
The modication of the rotor baille diameter and/or compartment length may in some cases result in using ratios for D/dz and D/a which fall outside of the preferred ranges. Thus, the former ratio may have values from about 3 to 5, while the latter ratio may be as low as 1 or less.
The rst of these expediente is shown in Fig. 6 wherein the lowermost rotor baie 3b, near the inlet port 6 through which the liquid to be treated is introduced, has a smaller diameter than the other rotor baiiies 3.
The second expedient is shown in Fig. 7, vwherein the vertical distance between the two lowermost stationary baies 4b and 4c (and also' the distance between the two lowermost rotor baffles yd and 3e), near vthe inlet port E for the liquid to be extracted, is greater than that between the baiiles higher up in the column.
It is evident that the number of compartments may be selected as desired, considering the stage efficiency and the number of theoretical stages required. For example, contactors having from about 15 to 100 compartments are typical.
I claim as my invention:
1. A rotating disc contactor comprising a tubular shell; a plurality of annular, stationary bales xed vwithin said shell extending from the shell wall to a central opening and dividing said shell into a series of compartments; a rotor shaft extending axially with respect to said shell through said openings; a plurality of disc-like rotor baiiles xed to said shaft, each rotor baile being wholly within one of said compartments and displaced a substantial distance axially from the stationary baffles thereof and extending outwardly toward the wall of said shell, each of said rotor bafes being smaller than the openings in the stationary baies toward one end of the shell from the respective roto-r baille. whereby said shaft and rotor baflies can be moved through said openings toward the said end of the shell; means for introducing and 'discharging fluid at axially displaced points in said shell; and means for rotating said rotor shaft and rotor baies.
2. A rotating disc contactor according to claim 1 wherein in at least the majority of the compartments the rati-o of the internal diameter of the tubular shell a't said compartment to the diameter of the rotor baffle in said compartment is at least about 1.5 and not greater than about 3.
3. A rotating -disc contactor according to claim 1 wherein in at least the majority of the compartments the rati-o of the internal diameter of the tubular shell at said compartment to the distance .between the stationary baffles of said compartment is at least about 2 and not greater than about 8.
4. A rotating disc contactor according to claim 1 wherein said tubular shell is cylindrical and circular in cross section and all Stationary baffles have circular yopenings with diameters greater than the diameters of the rotor baffles.
5. A contactor according to claim 1 wherein the stationary baiiies and the rotor loa-illes have smooth surfaces of revolution, substantially free from surf-ace irregularities.
6. A contacter according to claim 5 wherein the stationary baffles and the rotor baffles have plane surfaces vdisposed perpendicular to the axis of the shaft. l
7. A rotating disc contactor for countercurrently contacting at least partially immiscible liquids comprising an at least partially upright column; a plurality of annular, static-nary bailles xed within said column vextending from the column wall to a central opening and dividing said shell into a series of compartments; a rotor shaft extending axially with respect to said column through said openings; a plurality of disc-like rotor baiiies fixed to said shaft and extending outwardly toward the wall of said column, each of said rotor bailies being located approximately in the center of a compartment between the stationary baiiles thereof, said rotor bailes having diameters less than the diameters of the openings in the stationary bailes of the respective compartments; inlet means for introducing liquids at different levels into the column; outlet means for discharging liquids at different levels from the column; and means for rotating said rotor shaft and rotor baiiles.
8. A rotating disc contacter according to claim 7 wherein the rotor bames are formed of at sheet material disposed perpendicular to the shaft axis.
9. A rotating disc contactor according to claim 7 wherein the stationary `baffles are formed of ilat sheet material disposed perpendicular to the shaft axis.
10. A rotating disc contacter according to claim 7 wherein the column is cylindrical, the stationary baliles are of substantially the same size throughout the column7 and the diameter of the rotor baiiles near the inlet means for the liquid to be treated is smaller than the diameter of the rotor baies in other parts of the column.
11. A rotating disc contacter according to claim 7 wherein the distance between stationary baliies near the inlet means for the liquid to be treated is greater `than the distance between stationary balies at other .parts yof the calumn.
12. A rotating disc contacter for countercurrently contacting at least partially immiscible liquids comprising an at least partially upright column; a plurality of annular, stationary baflies iXed within said column extending from 'the column wall to a central opening and dividing said shell into a series of compartments; a rotor shaft extending axially with respect to said column through said openings; a plurality of disc-like rotor baffles fixed to said shaft and extending outwardly toward the wall of said column, each of said rotor bales being located approximately in the center of a compartment between the stationary baiiles thereof, the ratio of the internal diameter of the tubular shell to the diameter of the rotor baffles being, in at least Ithe majority of the compartments, at least about 1.5 and not greater than about 3; inlet means for introducing liquids at different levels into the column; outlet means for discharging liquids at different levels from the column; and means for rotating said rotor and rotor baflles.
13. A rotating disc contactor for countercurrently contacting at least partially immiscible liquids comprising an at least partially uprightV column; a plurality of annular, stationary bailles fixed within said column extending from the column wall to a central opening and dividing said shell into a series of compartments, the ratio of the internal diameter of the tubular shell to the distance between the stationary bailies being, in"` at least the majority of the compartments, at least about 2 and notgreater than about 8; a rotor shaft extending axially with respect to said column through said openings; a plurality of disc-like rotor baffles xed to said shaft and extending outwardly toward the wall of said column, each of said rotor baffles being loc-ated approximately in the center of a compartment between the stationary baffles thereof; inlet means for introducing liquids at diiierent levels into the column; outlet means for discharging liquids at different levels from the column; and means for rotating said rotor and rotor baffles.
14. A rotating disc extraction column for countercurrently contacting at least partially immiscible liquids of dierent densities comprising: a vertical, cylindrical column of substantially circular cross section having an internal diameter D; an outlet opening at each end of the column for the discharge of contacted liquids; an inlet opening near each end of the column for the introduction of liquids to be con tacted, said inlet openings being spaced vertically from the outlet openings away from the ends of the column to provide a settling zone between the inlet and outlet openings at each end of the column; a series of annular, stationary bailies of thin, flat sheets with 'plane upper and lower surfaces disposed horizontally within .the column, `each baffle extending from the column Wall radially inwardly to a central circular opening of diameter d1, said baiiles being imperforate except for said circular opening and being spaced at substantially uniform vertical intervals a and located between said inlet openings; a. rotor shaft substantially coaxial with the column mounted for rotation and extending through said openings in the baliles; and a plurality of circular, imperforate rotor baffles with diameters d2 of thin, flat sheets with plane upper and lower surfaces iixed to the shaft for rotation therewith with their surfaces perpendicular to the shaft, said rotor baflles being spaced along the rotor shaft at substantially uniform vertical intervals a and located to cause one rotor baffle to lie substantially at the center of each space between adjacent stationary baiies; the relations between the dimensions stated in at least the majority of said compartments being such that:
Ld-DZSS), .2S-ggg, and d2 d1 GERRIT I-I. REMAN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,081,241 Lynn Dec. 9, 1913 1,845,128 Coahran Feb. 16, 1932 2,091,645 McConnell Aug. 3l, 1937 2,273,660 Poole Feb. 17, 1942 2,316,769 Chilson Apr. 20, 1943 2,474,006 Maycock June 2l, 1949 2,474,007 Maycock June 21, 1949 FOREIGN PATENTS Number Country Date 82,433 France Sept. 15, 1868
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|U.S. Classification||422/257, 422/106, 208/311, 208/327, 422/259, 366/303|