US2029688A - Process and apparatus for contacting two materials - Google Patents

Description

Feb. 4,v 'I L EfgvvlLsoN y 2,029,688

1 PROCESS ANDIAPPARATUS RoR oNmAcT-INGTWO 'MATERIALS Filed nec. s. 1932 y 'ATTORNEY Patented Feb. 4, 1936 -g raoonss AND APPARATUS Fon ooN'rAc'rme 'rwo MATERIALS neben E. wilson, emes", n1., einer te standard Oil Company, Chicago, Ill., a corporation of Indiana Application December Vs, 1932, serial 1m64.553s

6 Claims,

My. invention relatesto processes and apparatus for the continuous counter-current con-- tactlng of two materials, particularly two substantially liquid materials. More particularly it relates to processes and apparatus for the continuous counter-current extraction of a mineral lubricating oil stock with a selective solvent.

It is an object of my invention to provide a e more eficient, effective and economical process 10 and apparatus for' continuous counter-current contacting of this type than any heretofore available. In particular it is my object to provide a novel and advantageoustype yof process and apparatus for the continuous counter-current extraction of a mineral lubricating'oil stock with a selective solvent. The various detailed objects of my invention will lbecome apparent as the description thereof proceeds.

Mineral lubricating Aoil stocks, particularly `20 mixed base stocks, as produced by distillation processes from crude mineral oils contain a great variety of chemical constituents most of which.

have never been indlviduallyidentiiied but which may be roughly classied as relatively parafdnic" 35 thenic constituents and will be referred to herein as a relatively naphthenic fraction. In general, the'relatively paramnic fraction can be identitled as having a high ratio of hydrogen to carbon,.a low temperature coelcient of-viscosity,

40 and a high resistance to sludging as compared -with the relatively naphthenic fraction.-

Itis well known that the relatively parailinic constituents are preferable to either the relatively'` naphthenic constituents or the original 45 mineral lubricating oil stock for use as an ordinary lubricant. For this reason many attempts have been made to'separate these relatively paraflinic constituents from the accompanying relatively naphthenic constituents in order to produce 50 a superior lubricating oil. jIn the past this has frequently beendone by extracting the mineral lubricating oil .stock with a selectivesolvent for either the relatively paramnic constituents or the relatively naphthenic constituents, generally the 66 letter.

The principal procedures which have been used in this type of process to date have been:

1. More or less completely dissolving the lubricating oil stock in a solvent at an elevated temperature and then lowering the temperature so 5 as to throw a relatively parainic fraction out of solution as a separate liquid phase; and

2. Agitating .the mineral lubricating oilstock with a solvent in a tank or similar vessel at such a temperature vthat a fraction (generally the 10 relatively naphthenic fraction) is dissolved and the remaining fraction is left as a separate liquid phase.

The process and apparatus of my invention improve on these prior art practices by passing 15 the` mineral lubricating oil stock and a selective solvent in counter-current relationship to each other and in continuous or preferablyintermittent contact with each other, coagitating them throughout an intermediate portion of their contact zone and removing the resultant materials, which are, in general: (l) the bulk of the selective solvent carrying with it in solution a rela*- -tively naphthenic fraction of the original mineral lubricating oil stock, and (2) the residual g5 relatively paratllnic fraction carrying with it some dissolved solvent and generally some entrained material. My process has the advantage of continuity. requires very little equipment for a plan of large capacity, is very cheap as compared with former processes, is much more ilexible andecontrollable than the prior art batch processes and accomplishes a more eilicient extraction, i. e., there is more divergence in properties between the relatively parafllnic and the relatively naphthenic fractions as I produce them than between the corresponding fractions as pro.- duced by the prior art processesl with which I f am familiar.

Reference will now be had more particularly 40 to the drawing in which: Figure 1 represents a longitudinal view of my apparatus, partly'in section; and Figure 2 represents a partial trans- -described later. An upwardly elongated settling chamber similar to sump I2 may, if desired, be used at the end of chamber Il opposite sump I2 and the pipe controlled by valve 29 may suitably lead o!! from a point near the top of said up- Il tal, as indicated in the drawing. Chamber Il.

may be of any suitable cross section, for instance circular (as shown), U -shaped or elliptical with the vertical axis longer than the horizontal. At

the end of the chamber II, which carries the sump I2, a pipe I3 enters the chamber and is upturned to permit the introduction oi a fluid material to chamber II in an upwardly-directed stream. 'I'he uptumed end oi' pipe I3 is shown as carrying a perforated baule I4 adapted to'distribute the incoming material. At the opposite end of chamber Il a pipe I8 enters .the chamber at the' bottom thereof and a pipe I1 enters at the top, one or both of which are used for the introduction of the second material to be contacted. M; I

As a specic embodiment of my invention, I utilize my process and apparatus to extract a mineral lubricating oil stock, namely, a waxbearing cut made by distillation of a Mid- Continent crude oil and having a viscosity of 74 seconds Saybolt at 210 F., with a selective solvent, namely, dichlorethylether. Since the solvent has a higher specific gravity than the lubricating oil stock it flows through my apparatus as a lower stratum and the lubricating oil stockilows in the opposite direction as an upper stratum.

If my process is operatedk without rotation of shaft I8 carrying paddles I9 the operation is as follows: The dichlorethylether is introduced through pipe I E, is deflected by baiile 20 and passes along the bottom of chamber I I through passages f 23 which are formed by chamber Illand bailles 24. Dichlorethylether may also, or alternatively, be admitted through pipe I1 by means of pipe 21| and valve 22 and if so it ilows downwardly through the outgoing stream of extractedlubri` eating oil stock, thereby Washing out at least a portion of the entrained dirty dichlorethylether carried by said extracted lubricating oil stock, passing to the bottom of chamber II and ilowing through passages 23 in succession along with the dichlorethylether, if any, admitted through pipe I6. The dichlorethylether (carrying extractedrelatively naphthenic constituents of the original lubricating oil stock) ows out through the last passage 23 on the right and comes in contact with the incoming lubricating oil stock introduced through pipe I3. 'Ihis is desirable since this incoming stock is often highly viscous and by allowing it to dissolve a portion of the solvent its viscosity is reduced and it flows through the apparatus more readily than would otherwise be the case. The spent" dichlorethylether then passes into sump I2 which is elongated to permit entrained undissolved oil to settle out and the settled dichlorethylether `with the dissolved Vrelatively naphthenic fraction is removed from sump I2 through pipe 25 and valve 26. The material removed through pipe 25 is then subjected to a fractional distillation operation to remove the dichlorethyletherA from the relatively naphthenic fraction of the lubricating oil stock dissolved therein. The dichlorethylether, after purification, if desired, is then returned to the process through pipe I6 and/or pipe I1 .andthe relatively naphthenic fraction is available as a by-product.

Simultaneously with the introduction of dichlorethylether through pipe I6 and/or pipe I1, lubricating oil stock is introduced through pipe ,oaaessv I3, preferably at about one-half the rate at which the dichlorethvlether is introduced. lThe lubrieating oil stock, after picking up some ofthe spent dichlorethylether as previously described, flows upwardly through compartment -2l I`and thence in succession through passages 21 formed by chamber II and bailes 24. Flowing out oi' the last passage 21. on the left it comes in contact with liresh dichlorethylether introduced through pipe I1, passes under bame 23 (which is used to preserve qulescence in the vicinity ofthe outlet) and is continuously removed from chamber Il through valve 23. y

Bames 24 in their preferred form extendtransversely across chamber II a'nd serve to divide it into a series of compartmentsv including end compartments 2 9 and intermediate compartments 30. As hereinbefore mentioned, bales 24 do not extend to the top or bottom of chamber II but are cut oil to form segmental passages 23 and 21 at the bottom and top respectively. In other suitable forms of my apparatus, these passages may be formed by openings located near the top and bottom of baiiles 24 and may be staggered so that passages in adjacent baiiles are not in alignment and material owing through them must therefore pursue a circuitous course.4 When working with highly viscous materials,it is sometimes desirable to use circular passages and to place a small screw conveyor in each passage, or in certain of them to expedite the dow of material. y

In the center of each compartment 3l are located two secondary bailies 3l extending downwardly from the top of chamber I I and upwardly from the bottom thereof. respectively. These baiiies 3l are preferably circular segments as shown and it is preferred that they extend to points considerably closer to the axis of chamber II than do passages 23 and 21. The purpose of baffles 3| is to force the materials flowing through chamber II to pass into the central portion of chamber II at intervals throughout their flow. Extending throughout the length of chamber II and approximately axially disposed therein is shaft I8 which is carried by bearings 32 as shown. Shaft I8 is driven through pulley wheels 33 and belt 34 by means of drive shaft 35 which is rotated by means not shown. The speed of rotation of shaft I8 can be varied at will by changing the position of belt 34 on pulley wheels 33. Any suitable means for selectively adjusting the speed of rotation of shaft 35 can be used but it is highly important that some such means be provided. Within each half of each of compartments 33, shaft I8 carries a paddle I3 suitably mounted to rotate with shaft I8. Paddles I9, as shown,

` and slightly reduced agitation at points progressively nearer to the periphery of chamber Il. It is preferred that the blades of paddles I3, when in vertical/position, extend somewhat closer to the top and bottom of chamber II than do the inner edges of bailles 3l but not as close as do the outer edges of bailies 24.

Various modifications can be made in paddles I3. In some cases it is desirable to perforate them so as to obtain an increased emulsifying effect. A still higher degree of agitation can, when desired, be obtained by using a greater number of blades on each Wheel and/ or by making the blades cup-'shaped rather than nat.

Having now described the principal characteristics of my process and apparatus with the exception of the centrifugal'separation feature to be described later, I will turn now to a more detailed discussion ofthe flow of materials through chamber Il. scribed above I have indicated the iiow of materials when no agitation is used, i. e., when shaft Il and paddles I 9 are stationary. Under such conditions, however, there is little effective extraction because thecontact between the dichlorethylether. andthe lubricating oil stock is entirely inadequate. By rotating paddles ilat a moderate speed, generally within Vthe range 8 to 50 R.. P. M., it is possible to create a well mixed emulsiiied stratum in the central part ofthe apparatus, quite adequate to give eifective contact, and yet by having the paddles fairly short, as shown, continuous separation of the two materials in each of compartments lll can be obtained. The result of operating under such conditions is that there is always a stratum ofsubstantially unemulsified lubricating oil stock at the top of each of the compartments, 'a stratum of substantially unemulsiiied dichlorethylether at the bottom ofeach of the compartments and an intermediate well-mixed or emulsiiled layer. As

. aforementioned, the upper limit of the emulsiiied layer should be above the lower edges of the upperfbaiiles 3i and below the upper edges of batlies 24 and the corresponding lower limit should be below the upper edges of bailles 3| and above the 'lower edges of the lower bames 2l. By adjusting the speed of rotation of shaft i8v in order to achieve this result it is possible to prevent any lubricating oil stock and dichlorethylether in each contact zone of my process(i. e., in each of compartments 30)' by soV adjusting the rate of introduction of the starting materials as to make the time of contacting Lin each stage about two to four minutes. By using 5 or 6 stages I obtain an extremely efilcient countercurrent extraction such as could be secured only by a great many separate and time-consuming lsteps when. using Y the old prior art processes.

\'.I'he.rate of rotation of shaft I8 which will accomplish this desired optimum degree of emulsiiication will vary greatly with such factors as the character of the materials being contacted, the temperature, the design of the paddles, etc. butin typical cases it will be within the range 5 to 60 R. P. M.

My apparatus can` be designed to have any number of compartments 30 from one up. However, in order to take full advantage of the counter-current principle, I prefer ,to use atleast three compartments 3l, and preferably four or iive of them in addition vto the two end compartments 29. In general .it is not-desirable to use ymore than six compartments since the advantage lgained by theaddition of further compartments is not sufficient to ofiset the additional cost.

A further feature of my process and apparatus, which has not heretofore been discussed, is a method for removing entrained material from one or both of the resultant materials withdrawn from chamber I i. yThe drawing shows this .re-

`In the specific embodiment de'- moval of entrained material as operating on the lighter of the two resultant materials leaving chamber II. In the speciiic embodiment heretofore referred to, this lighter material is the extracted lubricating oil stock, i. e., the relatively parafiinic fraction together with some dissolved dichlorethylether and some entrained material. Rather than subject this whole system, as withdrawn from chamber II, to distillation to separate dichlorethylether from oil as would normally be done, I prefer to rst remove the entrained vmaterial since this is composed for the most part of dirty dichlorethylether carrying some of the relatively naphthenic constituents of the original lubricating oil stock which it is desired to segregate from the relatively paramnic constituents constituting the bulk of the material removed through valve 28; According to my process, this separation of entrained material is done bythe use of centrifuge $6 operated through pulley Il by means of a motive source not shown. 'I'he relatively paralnic fraction produced inf` chamber il carrying some dissolved solvent and some entrained dirty" solvent is withdrawn from casing I I through valve 29 and passed to centrifuge 36 'where' the entrained material is separated from the relatively parafiinic fraction containing dissolved solvent and said entrained material is returned by means of pipe 38, and, if necessary, a suitable pump not shown, to casing il through valve 39 and/or valve 40. The relatively paraiiinic fraction carrying dissolved solvent passes out of centrifuge 36 through pipe 4I and is then, in general, subjectedI to fractional distillation, by means not shown, to separate the dichlorethylether from the relatively paraillnic vfraction whichconstitutes the principal final product of my process. The dichlorethylether removed from this relatively parafllnic fraction,

after purification if required, is returned to the process by means of pipe 2| along with the solvent recovered from the relatively naphthenic fraction and fresh "make-up solvent.

As aforementioned, the entrained matter, i. e.,

" dirty solvent separated by centrifuge 36 is returned tcchamber ii through valve 39 or III. In order to preserve equilibrium conditions inA chamf ber II and to achieve maximum eiilciency it is desirable that this dirty solvent be returned to chamber Il ata point at which its composition,

-containing solvent and relatively naphthenic .lubricating oil constituents without materially disturbing the equilibrium which exists at the point of introduction between solvent, relatively paraiilnic constituents and relatively naphthenic constituents. This can be done by admitting the ,dirty solvent through valve 39 and/or valve III,

depending on which point corresponds more closely. to the compositionof the dirty solvent. Further alternative points of admission can. of course, be provided as required.

It will be understood that my process can vreadl admitting it to my process.

In the foregoing speciilc embodiment I have described the use of dichlorethylether in my process and apparatus as a desirable selective solvent. It will readily be comprehended, however, that a variety of other solvent materials can satisfactorily be used, the main requirement being a selective solvent power for the relatively parafnic constituents or for the relatively naphthenic constituents of the original lubricating oil stock and a. specific gravity substantially different from that of the. lubricating oil stock to be treated. In

general, it is the relatively napnthenic constituents which are selectively dissolved. As alternatives to the use of dichlorethylfr ther, I i'lnd that nltrobenzene and phenol, a* Jong other substances, are very satisfactory in a solvent extraction process of this type. When operating on a wax-bearing lubricating oil stock I can either remove the wax before the'solvent extraction or solvent extract the wax-bearing oil. In thelatvter cases it is sometimes lnecessary to expedite lubricating oil stock, my apparatus can readily be modified to permit this, the onlyessential difference being that the relative positions of the two strata are reversed.

Although in general the introduction of and removal of material from my apparatus should be such as to keep the interface -between the two counter-current streams substantially in the center of chamber Il, it will be apparent that this can be adjusted to any other level if desired. Thus, for instance, if one of the two materials separates more readily from the central emulsifled stratum than does the other, it is desirable to have at any given time in chamber il less of the'material'which separates more readily and more of the material which separates less readily, the result being that the separation of the latter is promoted. Therelative amounts of the two materials in chamber Il at any given vtime can readily be controlled by an adjustable float-controlled mechanism operating on one or more of the valves controlling the admission and/or removal of materials from my apparatus. Suitably this may consist of a device intermediate in density between the two materials in sump I2 which will oat at the interface and control the operation of say, valve 26 so as to keep the interfacial level at any desired point.

Although I have described my invention with particular reference to the solvent extraction of mineral lubricating oil stocks it will readily be understood that it may in whole or in part be applied to any process in which it is desired to contact `two immiscible or' partially miscible liquids, or other materials which can be owed. Thus, for example, my process and apparatus can be used in the solvent extraction of vegetable oils, solvent extraction of motor fuels, the chemical treatment of various liquids with various reagents, the washing of liquids, etc. I do not, therefore, desire to be limited by my specic disclosure but only by the appended claims in which I have defined the novel features of my I claim:

1. A process for the counter-current contacting of ,two liquids comprising introducing one of said two liquids into an end contact zone forming one'of a series of at least ilve adjacent linearly disposed contact zones, introducing the other of said two liquids intolthe end contact zone of said series of contact zones located opposite said rstmentioned end contact zone, iiowing each. of said two liquids through each of said Contact zones in succession in a direction opposed to the direc` tion of flow of the otherof said two materials,

separating said two liquids from each other at.

eachof the borders between each adjacent pair ofv said contact zones, partially emulsifying all of the liquid passing through each of the intermediate contact zones, and separately withdrawing two resultant liquids from opposite end contact zones.

2. A process forjthe counter-current extraction of a mineral lubricating oil stock comprising relatively paraiiinic constituents and relatively naphthenic constituents with a'selective solvent for said relatively naphthenic constituents, comprising flowing said lubricating oil stock and said. selective solvent in counter-current relationship to each other, washing the extracted lubricating oil stock by admitting at least a part of said selective solvent at a point near the point of withdrawal of, said extracted lubricating oil stock, separately withdrawing the selective solvent after extraction of said relatively naphthenic constituents, separating said relatively naphthenic constituents from said selective solvent and returning said selective solvent to the process, centrifuging the resultant lubricating oil stock to remove entrained dirty solvent and returning said dirty solvent to the process at a point at which the degree of extraction is approximately that represented by the composition of the dirty solvent.

3. In apparatus for the countercurrent contacting of two liquids, a generally horizontal elongated chamber, a series of transverse baiiles provided with openings at their tops and bottoms, said bafilespartially dividing said chamber into two end'compartments and a plurality of intermediate compartments, said passages which permit liquid strata at the top andA bottom of said chamber to flow from one of said compartments to the next, a second series of transverse bailles, thev members thereof located between the members of said first mentioned series of baiiles and extending upward from the bottom of said chamber and downward from the top of said chamber, agitation means located within and confined to said intermediate compartments, means for introducing one of said two liquids into one of said end compartments, means for introducing the other of said two liquids into the other of said end compartments and means for withdrawing a resultant liquid from each of saidend compartments.

4. In apparatus for the countercurrent contacting of two liquids a generally horiontal elongated chamber, a series of bailles, the members thereof extending downward from the top of said chamber at intervals along its length, passages located in the upper portions of the members of said series of bailies, a second series of bailles, the members thereof located in staggered relation to the members of said first-mentioned series of bailles at intervals along the length of said chamber and extending upward from the center of said chamber to points above the lowest points to which the members of said first-mentioned series of baiiies extend, but not extending to the top of said chamber, a third series of bailles, the members thereof extending upward from the bottom of said chamber at intervals along its length, passages located in the lower portions of the members of said third series of baiiles, a fourth series of bailles, the members thereof located in staggered relation to the members of said third series of battles at intervals along the length of said chamber and extending downward from the center oi said chamber to points below the highest points to which the members of said third series of baiiies extend, but not extending to the bottom of said chamber, agitation means located within at least some of the spaces between said various baiiles and means for introducing said two liquids near opposite ends of said chamber and means for withdrawing a resultant liquid near each end of said chamber.

5. In apparatus for theA counter-current contacting of two liquids, a generally horizontal elongated chamber, a series of transverse baiiles provided with openings at their tops and bottoms,

said batiles dividing said chamber into two end compartments and at least three intermediate compartments, said compartments communicat- `ing with each other through said passages which chamber, the members of said last-mentioned series of baffles located between the members of said first-mentioned series of bailies, rotary agitation means located within and conned to said intermediate compartments, means for selectively adjusting the rate of rotation of said agitation means, means for introducing one of said two liquids into one of said end compartments, means for introducing the other of said two liquids into the other of said end compartments, and means for withdrawing a resultant liquid from each of said two end compartments.

6. A process for the counter-current extraction of an oil stock comprising relatively parainic constituents and relatively naphthenic constituents with a selective solvent for said relatively naphthenic constituents, comprising flowing said oil stock and said selective solvent in countercurrent relationship to each other, washing the extracted oil stock by admitting at least a part of said selective solvent at a point near the point of Withdrawal of said extracted oil stock, separately withdrawing the selective solvent after extraction of said relatively naphthenic constituents, separating said relatively naphthenic constituents from said selective solvent and returning said selective solvent to the process, separating the resultant oil stock from entrained dirty solvent and returning said dirty solvent tothe process at a point at which the degree of extraction is approximately that represented by the composition of the dirty solvent.

ROBERT E. WILSON.

s'R'rnrrcuvr4 or CORRECTION.

'atent No. 2,029,688. j February 4, 1936.

ROBERT E, WELSON,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, second column, line 48, claim 3, after the comma and before "said" insert the words said compartments communicating with each other through; and lines 68, 69 and 70, claim 4, strike out the words and comma "passages located in the upper 4,portions of the members of said series of baffles, page 5, first column, lines 5 ,6 and '7, claim 4, strike out the words and comma "passages located n the lower portions of the members of said third series of baffles, and

that thel said Letters Patent should be read with these corrections therein that the' same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day or April, A. D. 1936.

Leslie Frazer Seal) Acting Commissioner of Patents.

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