US2116428A - Process and apparatus for treating mineral oils - Google Patents

Description

y 3, 1 M. R. FENSKEY 2,116,428

PROCESS AND APPARATUS FOR TEEATING MINERAL OILSv Filed June 29, 1935 2 Sheets-Sheet 1 mmM/zme May '3, 1938. M. R. FENSKE 2,116,423

PROCESS AND APPARATUS FOR TREATING MINERAL OILS Filed June 29, 1935 2 Sheets-Sheet 2 E 32 as awe/MM llppiicntion .lunc 2t,

This inycntion pcrtains gcnlcrsily to a method sud spparctus ior contscting liquid phases.

in copcnding application. Serial No. 10,932 by lii crrcll R. li cnshe and Wilbert E. McClucr filed 5 March 113, i935 there is described sud claimed a mcthocl cud apparatus of the foregoing character "wherein high emcicncics arc obtaimcd by chem tivcly contacting the liquid phases without serious .chuunelinu. This is accomplished generally speaking by causing thcliquicls to flow through thc sons of contact over one or more attenuatcd packing members.

This invention relates to an improvement over a ccrtnin spccics of said above-mentioned appliimmiscible or only partially miscible solvents are' counterfiowed by virtue of a dificrence in their densities, the liquid under treatment such as lubricating oil, is introduced intermediate the counter-flow and selectively dissolved in the two solvents, and the less soluble portions of the material' dissolved in each solvent are thrown out I of solution and 'fcd back into tho zone of contact; When a plurality of packing members are employcd they may or may not be separately onwhen they are not scparutcly cncloscd and are oi'tha same dimensions, said packing members 5 are usually substantially uniformly distributed laterally of the counterflow, and substantially the same amount of liquid is caused to how over each. Thus substantially the same conditions are caused to oust throughout any lateral cross section of tho counterflow when the process is in operation. Should the packing members be of different dimensions, the necessaryadjustments as to distribution of packing members and/or of liquid flow may be made to accomplish the same results. When the packing members are separately enclosed, for instance by tubes having relatively small ,cross sections oi any desired geometrical shape, the countercurrently flowing liquids are 1 brought into afllcient contact in a plurality of 50 separate groups of countercurrently flowing streams or in other words in a plurality of separate phase contacting units. In. this case each liquid is preferably metered into each unit in a manner so that at least substantially the same results are produced by each unit. 7

a. M smothers, rs, p strut Petroleum Becca-ch ilorporation, as corporation oi bouncy r v I (m. ltd-13) Y m. 2am

It has been observed that wetting of the pncls ins member or members by one and perhaps in some cases more than one phase plays an impor-= taut part in the e'mciency of contsct and the pre= ventionof channeling. This is par icularly truc of longitudinally srranged attenuated packing members which appear to not us guiding elements for at least one phase (and possibly more) as it flows through the tower keeping ssid phase distrlbutcd laterally of its flow. The sttcnuatlons m are preferably of sumciently small cross section to avoid presenting a path oi least rcsistuncc oi any practicable conscuucncc upon (which term includes through) itself.

The wetting feature msitcs it possiblc to dis-- is perse the wetting phase (or phases) by virtue oi its spreading out into films on the surfaces of the packing member or members. in some cuscs these films collect in drops at points on the pscls ing and become detached only to rccontact the m packing and spread out into films again. This kneading actiomwhenpresent, assists in bringing the phase particles to the 'surfacc tor contact Purposes.

While the capacity of a tower having longitudig5 nally arranged attenuated packing members m be increased somewhat by increasing the cross sections of the packing members to avoid serious channeling due to too large a cross section, the capacity preferably will be increased and de- 30 creased by increasing and decreasing the number or packing members. The periphery oi the tower is then adjusted to conform thereto.

When tubes are not employed, the individual longitudinally arranged packing members may be of any suitable character. For instance, they may comprise rods of any geometrical cross scc-= tion, strips oi? jaclr chain etc. Such members may carry spaced laterally extending protuberances such as discs, spheres, irustums oi cones, i'rustums of double cones. rain drop shapes, or any other surface of revolution to increase the surface. The protuberances on each attenuated packing member may overlap the protuberanccs on adjacent attenuated packing members so that any c5 drops leaving any protuberance will at oncc contact another protuberance further downstream to re-form into a film. This arrangement of the protuberances also causes the liquids to flow in'a circuitous course through the tower.

When tubes nclose individual longitudinally arranged packing members, these members may be constructed as set forth in the preccdln paragraph or they may be made up of a large number of separate elements such as raschlg rings or similar packing. The separate elements may or may not be connected together since the packing may acquire its shape by virtue of the tube wall.

By making the tube walls perforated or reticular, for instance by forming the tube walls of wire cloth, the constructions of the two previous paragraphs might be combined, that is the reticular tubes may be packed as suggested in the first preceding paragraph and may carry on their outer surfaces protuberances of the character and arrangement as set forth in the second preceding paragraph. It should be noted that the rods and protuberances of said second preceding paragraph need not be solid but may be perforated or reticular or of other like construction.

Other features of the invention reside 'in the construction, arrangement and combination of parts and in the steps, combinations of steps and sequences of steps, all of which,together with other features, will become more apparent to persons skilled in the art as the specification proceeds and upon reference to the drawings in which:

Figure 1 is a sectional elevation of a tower illustrating one form of theinvention;

Figure 2 is a section on line 2-2 of Figure 1;

Figures 3a and 3b comprise a broken sectional elevation illustrating another form of the invention; and

Figure 4 is a section on line H of Figure 30.

Referring now more particularly to Figures 1 and 2, at l0 isshown a tower comprising a plurality of tubes H Joined at their ends by tube sheets I! and I3 and surrounded by a plurality of superimposed heat exchange chambers ll. Tower It also includes segregating chambers II and It respectively at opposite ends of tubes II as well as feeding chambers i1 and II also respectively at said opposite ends.

Chamber ll communicates with the upper ends of tubes l I through metering tubes Ill and chamber l8 communicates with the lower ends of tubes ll through metering tubes II.

Tubes l I preferably contain suitable phase contacting means illustrated at 20, for instance, any of the packing materials referred to in said copending application. However, when tubes II are of small inner diameter, packing materials may not be required. I

Communication is had with tubes I I at any intermediate point through any suitable means, for instance, by means of a member 22 which is illustrated ascomprising a conduit 23 and a pluby heat exchange jacket 28 and chamber i8 is illustrated as being surrounded by a heat exchange jacket 21.

Chamber I5 is illustrated as containing a heat exchange coil 89 and chamber I8 is illustrated as containing a heat exchange coil II.

Anysuitable means (not shown) may beem- I ployed for circulating heat exchange fluid through any of the chambers ll, 26 and/or 21 and through coils 69 and/or ll.

Chamber I! has an outlet pipe II at its upper I endand an outlet pipe 12 at its lower end and chamber l6 has an outlet pipe 73 at its upper end and an outlet pipe I4 at its lower end.

Tubes II are illustrated as extending up into chamber I! to form a well 15 with which outlet I2 communicates.

Tubes II are illustrated as also extending down into chamber It to form a well It with which outlet l3 communicates.

-which is illustrated Tubes Il may have-a cross section of any desired geometrical configuration and, within certain preferred limits, any desired area. The cross section of tubes II is preferably limited to an area sufficiently small to prevent serious channeling after the contacting means, for instance packing 28, has been arranged therein.

The preferred limiting cross sectional area for tubes Ii will be not only a function of the type of packing employed since certain types of packing will as a rule permit the use of a larger cross section without an inordinate falling off of efiiciency than other types, but also of the degree of .uniformity of distribution of packing in the tubes.

cannot be given but may be readily determined,

for instance, by testing the emciency of single tubes of diflerent sizes when packed with the packing which is to be employed.

It may-be stated as' a general rule that one should proceed with caution after exceeding a cross sectional area; equivalent to that of a circular tube in the neighborhood of three inches in diameter although, with the proper selection of packing and a careful distribution in each tube, it is possible that larger cross sectional areas may be employed while inother cases smaller cross sections may be required.

Therefore, the term "relatively small cross sectional area" when employed in this specification and in the claims is intended to mean a cross section which' when taken in conjunction with the contactingmeans (if any) therein is sufficiently small to materially increase the contacting emciency because of the constriction of its area.

In those cases in which it is desired to cause heat transfer through the tube walls, consideration should be given to the effect of cross sectional area upon emcient heat transfer.

In the operation of tower l I the heavier solvent is introduced into tubes H through chamber l1 and metering tubes 2|, and the lighter solvent is introduced into tubes ll through chamber is and metering tubes 2|. Due to the difference in density these solvents flow countercurrently to each other through the tubes and, since they are immiscible or only partially miscible, two liquid phases are present.

The oil may be introduced into the tubes ll through a member 22, for instance member 21d midway of the length of tubes H.

If one of the solvents is selective as to nonparamnlc constituents and the other selective as to paraflinic constituents, the oil components will divide between the two phases more or less according to this selectivity.

The lighter phase flows intochamber I! wherein its temperature is reduced by means of a cooling fluid in coil 69 causing separation of the less soluble constituents which collect in well II and the rest of this phase leaves the tower through D D The separated components as they collect in well 15 are withdrawn throughpipe 1i and are fed back into the tubes II, for instance at 116,

2,1 races materials inlprocess are of thesamecomposition.

Thus the precipitatedcomponents are refluxed.

, The heavier phase flows into chamber l6 wherein its temperature isreduced by cooling fluid in coil 10 thereby separating lesssoluble components which collect in -well l6 and the rest of this phase flows out through 14. V

The separated components as they collect in well Hi are withdrawn through pipe "I3 and are fed back into the tubes H, for instance at 22g, 22f, or 22c and preferably at a point at which the materials in process are ofthe samecomposition. Thus the precipitated components are refluxed.

The result of setting up reflux conditions in tower i is a much sharper separation between paraflinicand non-paraflinic material.

Should the material separated in chamber l proveto be lighter thanthe phase from .which it is separated, it will comprise the upper layer and can be withdrawn through pipe 1| instead of 12, the phase from which this material is separated being then withdrawn through pipe 12.

' Likewise, should the material separated in chamber l6 be heavier than the phase from which it is separated so as to form the lower layer it might be withdrawn through pipe I4 and the phase from which it is separated withdrawn at 13.

Separation of less soluble materials from the two phases might be efifected by other means, for instance by extending metering tubes 20 and 2| as indicated in dotted lines and employing heat exchange chambers Ma and Nb for cooling purposes. In this case tubes II can, be made flush with headers l2 and i3 and pipes 12 and 13 might be omittedgparticularly when the material separated is of a density such as to flow, countercurrently to the phase from whichit is separated.

If the opposite is true separation might take place in chambers i5 and I8 and the separated material fed back through members 22 as before.

It is, of course, understood that heat exchange chambers I4 may be of any number, that is one or more. The same applies to members 22 and tubes .Tubes Il may be of any desired length.

Separation might be efiected by other means, for instance, by the use of a third solvent which is capable of forming a solvent mixture of lower solvent capacity for theoil with the solvent or solvents of the phase; or by reducing the solvent concentration in the phase; or by reducingthe temperature by any other means; or by a combination 'of any two or more of the foregoing or otherwise.

The desiderata in the operation of tower in are (1) that the lighter phase leaving any individual contacting unit shall be of'the same composition as the lighter phase leaving any other contacting unit; (2) that the same shall apply with respect to the heavier phase; and (3)- that the phases shall bemixed at any cross section in any contacting unit.-

In substantially approaching the foregoing it is simpler to make tubes of the same cross sec} tion and length; to provide the same character of contacting means in each tube; to feed the oil undertreatment at substantially the same rate into each tube; to divide each solvent sub; 'stantially equally between the tubes; and to divide each separated material substantially equally between the tubes.

However, the individual contacting units may diifer without departing from the spirit of the invention. Such differences may be as to construction, for instance as to size, length, contacting meansor otherwise.

.any other unit.

For instance,'the individual contacting units may vary as to construction but may be matched so that each will deliver lighter phase of substantially the same composition, and heavierphase of substantially the same composition when oil is fed at substantially the same rate to each, and each solvent is substantially equally divided between the tubes. y

On the other hand, the individual contacting units may be of the same and/or of different construction but may difier as to capacity. In this case adjustments of oil feed and/or of solvent feed may be made to cause the respective phases from any unit to be of substantially the same composition as the respectivephases from The useof metering tubes 20 makes it possible to adjust the feeding rate of the heavier solvent to any contacting unit by employing a, metering 'tube for that unit of the desired capacity. like- The precision of this balance will, of course, depend upon the results desired and, therefore, may

be rough or close according to requirements.

Any other means may be adopted for feeding the various liquids into the tubes Ii.

While the invention has been described in connection with one or more tubes of. "relatively small cross sectional area in its broad phases it extends to setting up reflux conditions at the opposite ends of a tower of any diameter even though the high efficiencies resulting from the use oi'one or more" tubes of the character described may not be obtained.

A construction in which the attenuated packing members are not enclosed in tubes is illustrated in Figures 3 and 4 in which tower 30 is shown as comprising a. plurality of rods 3| carrying spa'ced protuberances 32, a plurality of shells 33 having jackets 34, a feeding chamber 35,,a' segregating chamber 36, a combined feeding and segregating chamber 31, and a plurality of intermediate feedingsections 50. Rods 3| may be supported in tower 30 in any suitable manner, for instance as illustrated.

Extending downwardly from feeding chamber 35 about each rod 3| is a metering tube 39 which is arranged so that the metered liquid will .be deposited onthe rod. i Tubes 39 are of sufflcient length to form with their supporting plate Ill-and the upper end of the uppermost shell 33 a segregating chamber 36.

The lower end of each rod 3| is illustrated as being surrounded by a segregating tube M'which forms with the rod an annular space for the downward flow of liquid adhering to the rod. The lower end of each tube 40 is provided with a plurality of apertures 42 to permit said liquid to flow into chamber 31. i

Each tube 4| is illustrated as extending beyond the upper end of chamber 31 and with its upper end surrounded by a tube 43 in such a manner as toafford an annular space 44 between the tubes for metering purposes.

overlapping the discs 32 on adjacent rods 3|.

Feeding chamber 35 has an inietpipe 45, segregating chamber 36 has an outlet pipe 46, and combined feeding and segregating chamber 81 has an inlet pipe 41 and an outlet pipe 48. i

Each feeding section III comprises a chamber II formed by tube sheets I! and "between which extend a plurality of imperforate tubes ll and a plurality of perforate tubes 56.

Imperforatetubes 54 are free from any ob 1 r the tower, for instance in case said liquid does not preferentially wet the attenuated packing members.

Each feeding section 50 has an inlet pipe S'l. In describing the operation of tower 30 it will be assumed that the heavier solvent phase preferentially wets the rods ii and discs 32 in prefer-' ence to the lighter solvent phase. It the reverse is true, tower Ill might be constructed up-side-- down.

The heavier liquid flows'from feeding chamber 35 down through metering tubes 39 onto the respective rods 3|, continues on down through the tower, collects in tubes ll, drains out through apertures 42. to form a layer in chamber 31 and is withdrawn through pipe 48.

. The lighter liquid enters chamber 31 through pipe I and occupies the upper part of chain This liquid is metered up through anber' 31. nular spaces M and thus is distributed laterally of tower I0. a

As the lighter phase flows up through the tower it intimately contacts the descending heavier.

phase.

- The lighter phase'collects insegregating chamber 36 and is withdrawn through 48..

The liquid under treatment, for instance pe troleum oil dissolved or not in a solvent, is fed into tower 30 through feeding sections 50, fresh oil being fed in at feeding section 5012 and partiaily'treatedoil at feeding section a and/or feeding section 50b.

The fresh oil fed into the tower through feeding section 80b is selectivelydissolved in the two counter-flowing solvents, one part of the oilbeing carried down into feeding and segregating chamber 31, dissolved in the-heavier solvent and the other part being carried up'into segregating chamber "in solution in the lighter solvent.

The heavier solvent with oil in solutionis' pumped into separating chamber '59 wherein a part of the dissolved oil is separated from the solvent, for instance by cooling, and is fed back into the tower through feeding section Etc. The rest of the oil dissolved in the heavier solvent is withdrawn from separating chamber It at".

The .lighter solvent with oil in solution flows into separating chamber I wherein a part of the oil is separated from solvent, for instance by cool- The separated oil is fed .back into tower 30 through feeding section "a. The rest of the oil dissolved in solvent is'removed from separating chamber OI through. pipe 82.

. In'the foregoing. description, it hasbeen assumed-that the oil separated from the heavier 'solvent is lighter than the solvent and that the oil separated from the lighter solvent isheavier than the-lighter solvent. If the reverse isitrue in the case of either or both solvents, it is merely necessary to turn separating chambers I and/or tl'up-si'de-down as required.

Any other means for separating oil from solution may be employed. I

Any other suitable means may be provided for metering thev liquids into the tower'and/or for separating the phases. For instance, tubes 4! and I! -might be eliminated. The separation of lighter solvent from the heavier solvent '(with oil in solution) would then be by simple layer formation, and the lighter solvent would be distributed laterally of the tower by virtue of its layer. This arrangement might be preferred in certain cases particularly if the differential in wetting ability is' small between the heavier solvent (with oil in solution). and thelighter solvent.

For the purpose of clearness, a limited'number of attenuated packing members has been shown in the drawings with the. volume of free space fairly large compared to the surface area of the packing. It is to be understood, however, that a part of the the attenuated packing members" may be as.

densely grouped as desired and may be provided with any desired number of protuberances.

If one or more of the liquids should find a path of least resistance along the inner walls of .shells 33, baflles might be attached to these walls to causesuchliquid or liquids'to iiow back to-" become re-distributed.

While the metering onto the individual packward the attenuated packing members and toing members of the liquid which preferentially wets the packing may .be preferredfit is not an indispensable feature and other constructions may be employed, for instance in case there should be no clearly defined differential between wetting ability of the variousphass.

While heat exchange jackets ll have not beenillustrated as being divided into a number of sections, such construction may be adopted.

While in the description *of the attenuated Y packing members, it has been inferred that they have .uniform wetting features throughout. it is to be understood that the packing members may have surfaces of at least two different-types, said surfaces differing from each other in that they" are preferentially wetted' by diflerent phases as described and claimed in copending application",

Serial No. 29,159, filed June 29, 1935.

These different .types 'of surfaces maylbe dissired way, for-instance (1 alternately in circumferential bands, (2) longitudinal bands, (3)

spiral bands, (4) mottling, (5) checker work and/or (6) .in any other suitable manner particularly when applied to longitudinally arranged attenuated packing-members of solid or similar design. However, when said packing member or such as by the use of raschig rings, jack chain or tributed over the packing members in any de-' members are made up in the form of a net-work,

other packing materials, the same arrangement of surfaces maybe adopted when, practical, or

any other suitable arrangement} may be adopted.

With such an arrangement'any phase may be positively conducted through any portion of the zone of contact by virtueof the preferential wetting feature, or the phases may be caused .to in j Having particularly described, the invention, it

is to be understood that changes, omissions, ad-

ditions, substitutions, and/or modifications might be made within the scope of the claims without departing from the spirit thereof.

I claim:

1. In a process for contacting a mineral oil and two solvents capable of forming two liquid phases whereinsaid solvents are caused to-fiow countercurrently to each other by virtue of a difference'. in density and said oil is introduced intermediate the ends of the counterfiow for solution in said solvents, thesteps of dividing each of said solvents into a plurality of relatively small streams, contacting said streams so that each stream or eachsolvent contacts one stream of the other solvent in a separate phase contacting path of relatively small cross sectional area and of substantial length, feeding said oil into said 'separate phase contacting paths intermediate the ends of the counterflow of solvents, precipitating components from the final phases thus produced, flowing a separate stream of each of; said precipitates through each of said phase-contacting paths for re-solutio'n in said solvents, uniting the streams of the lighter of the resultant phaws at' the tops ofsaid phase contacting paths, and uniting the streams of the heavier of said resultant phases at the bottoms of said phase contacting paths. 1

2. In a process involving the contacting of 'a mineral oil and at least two solvents in a common path wherein said solvents are caused to flow countercurrently to each other byvvirtue of a difierence in their densities and wherein said oil is fed into said path at an intermediate point, thesteps of causing at least one-of said liquids to flow throughsaid common path in a widely distributed form by conducting said liquid through said common path over a plurality of vertically arranged packing mediums each of which has a relatively long and narrow shape, said packing mediums being wetted by said liquid, separating dissolved oil from the lighter solvent, feeding said separated oil back into said common path at. a point above the feeding point of fresh oil, separating dissolved oil .from the heavier solvent, and feeding said last-mentioned separated oil back into said common path at a point below the'ieedingpoint of fresh oil.

3. In a process involving the contacting of -a mineral oil and at least two solvents in a common path wherein said solvents are caused to flow countercurrently to each other. by virtue of a difierence in their densities and wherein'said oil is fed into said path at an intermediate point,

,the steps of causing at least one of said liquids to flow through said common path in a widely distributed form by conducting said liquid through said common path over a plurality of vertically arranged packing mediums each or which has a relatively long and narrow shape, said packingmediums being wetted by said liquid, separating dissolved oil ,from the lighter solvent, feeding said separated oil back into said common path at a point above the feeding point of fresh oil, separating dissolved oil from theheavier solvent, feeding said last-mentioned separated oil back into said common path at a point below the feeding point of fresh oil, and separately encasing eadh of said packing mediums to confine said counterflow to said packing mediums.

'4. A process for treating liquid phases of incomplete and partial miscibility such as in the solvent treatment of petroleum oil fractions with two solvents comprising countercurrently flowing said solvents by means of a ,difierence in their densities through a plurality of phase contacting paths of relatively small cross sectionalarea and of said paths with said last-mentioned separated oil by subjecting said last-mentioned separated oil to contact with said solvents, maintaining the proportions of said phases at least substantially identical in said phase contacting paths, uniting the streams of the lighter of the resultant phases at the tops of said phase contacting paths,

and uniting the streams of the heavier of the resultant phases a the bottoms of said phase contacting paths.

5. A process for treating a mineral oil with two solvents which are capable of forming two solvent'phases with said oil in solution and in which said phases are caused to move countercurrently to. each other through a phase contacting zone by virtue of a diflerence in density, comprising introducing said solvents and oil into said phase contacting zone at vertically spaced points to form said two solvent phases with said oil in solution, maintaining at least one phase ina widely distributed form by causing said relative movement between said phases to take place in the presence of a group of attenuated packing members arranged in the zone of contact side byside and longitudinally of the flow of said phases with each packing member of suihcient length to extend throughout at least a substantial portion of said zone of contact, spacing the points of entry of said solvents from each other and from the point of entryof said .011. with the points of entry of said solvents on opposite. sides of the point of entry of said oil, choosing said solvents as to density so that said phases will flow through said phase contacting zone in opposite directions, precipitating oil from the lighter phase,. bringing phases in said phase contacting zone above the point of entry of said oil, precipitating oil irom the heavier phase, and bringing said last mentioned precipitated oil intocontact with the two phases in said phase contacting zone below the point of entry of said oil.

6. A process for treating a mineral oil with two solvents which are capable of forming two solvent phases with said oil in solution and in which said phases are caused to move countercurzone by virtue of a difference in density, comprising introducing said solvents and oil into said phase contacting zone at vertically spaced points to form said two solvent phases with said oil in solution, maintaining at least one phase for atleast the most part in a plurality of separate rel- 7 said precipitated oil into contact with the two rently to each other through a phase contacting atively small streams, spacing the points of entry j of said solvents from each other and from the point of entry 'otsaid oil with the points of entry of saidsolvents on opposite sides of the point of entry of said'oil, choosing said solvents as to density so that said phases will flow through said phase contacting zone in opposite directions, preprecipitated. oil into contact with the two phases .in saidphase contacting zone above the point of cipitating oil from the lighter phase, bringing said Y is tacting course'oisubstantial length with a sep- 6 entry of said on, precipitating oil; from the heavier phase and bringing said last mentioned precipitated oil into, contact with the two'phases in said phase contacting zone entry or saidoil. a '7. Apparatus comprising a column, means for below the point of introducing liquids into said column at at least threevertically spaced points to cause at least two oi" said liquids to ilow countercurrently toeach other through said column by virtue of a diiierenccin density-such as in the treatment of mineral "oils, means at each oi said points for dividing the fed liquid into a plurality of separate streams, means for contacting each separate stream-oi each liquid in a segregated phase'conarate stream of each oi the other liquids, and

means for maintaining the temperature at oppo-.

site ends of said phase contacting courses lower 20' than the temperature oi. the main portions 0 said phase contacting courses.

8. Apparatus comprising a column, means for introducing liquids into said column at at least three vertically spaced points, to cause at least 2 two of said liquids to flow countercurrently to each other through said column by virtue oia difference in density such as in the treatment of mineral oils, means at each'oi said points". for

dividing the fed liquid into a plurality of separate streams, means for contacting each separate stream of each liquid in a segregated phase contacting course of substantial length with a separate stream of each of the other liquids, means for maintaining the temperature at opposite ends of said phase contacting courses lower than the temperature of the main portions of said phase contacting courses, means atsaid opposite ends for separating liquid phases produced by said reduction in temperature, and means for- 1 feeding one of the phases separated at each end gated phase contact paths, means ior feeding liquids into said column at at least three vertically spaced points to cause at least two of said liquids to flow countercurrently to each other by virtue of a. difference in density such as in the solvent treatment of mineral oils, means for re-.

moving solutions of said .liquids, means for separating solute from said solutions, and means for feeding said separated solute back into said

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