US2037316A - Method of and apparatus for fractionating - Google Patents

Description

M. R. FENSKE Filed June 26, 1933 IW Y / i &

METHOD oF AND APPARATUS 'FOR FRACTIONATING 1l l1 lillllllIllillllllillllf/a.

April 14, 1935..

FIG. IA.

April' 14, 1936.

M. R. FENSKE METHOD oF AND APPARATUS FOR FRAGTIONATING Filed June 26, 1933 5 Sheets-Sheet 2 FIG. 2A',

WATER -ql/ I I f April 14, 1936. M. R. FENSKE METHOD OF AND APPARATUS FOR FRACTIONATING Filed June 26, 1935 5 Sheets-Sheet 3 M. R. FENsKE l 2,037,316- METHOD 0F AND APPARATUS FOR FRAQTIONATING' April l14, 1936'.

Filed June zes. 1935 5 sneemeg-sluml 4 April14, 1936. A M n FENsKE I I 2,037,316

METHOD OF AND APPARATUS FOR FRACTIONATING 5 Sheets-Sheet 5 Filed June 26, 1955 Patented Apr. 14, 1936 UNITED STATES 4METHOD 0F AND APPARATUS FOR FRACTIONATING Merrell Robert Fenske, State College, Pa., as-

signor to The Pennsylvania State College, State' College, Pa., a corporation of Pennsylvania Application June 26, 1933, Serial No. 677,754

14 Claims. (Cl. 196-139) This inventionrelates to a method of and apparatus for fractionating, and with regard to certain more specific features, to fractionating towers for separating mixed vapors into their. components.

Among the several objects of the invention may be noted the provision of a fractionating tower of the class described which has a greatly improved fractionating eiiiciency for its height, a fractionatingl tower providing improved means l for contacting, within a short space, a maximum of ascending vapors with a maximum of descending scrubbing liquid, such contact being accomplished in a manner leading to optimum intimacy of contact; a fractionating tower of the packed" type wherein such diiculties as channeling of the reflux, liquid stream are obviated; a fractionating method wherein a plurality of evenly constituted, relatively small streams of reflux liquid are maintained separately against the vapors being scrubbed, and including means for forming said small streams of reiiux liquid in such manner that all streams will contain substantially identical quantities of liquid; a

fractionating tower having a greatly reduced pressure drop between its ends, as compared with prior types of fractionating towers; and the pro- .vision of fractionat-ng towers 'of the class described which are relatively simple in construction and operation. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, f'eatures of construction, and arrangements of parts, and steps and sequence of steps, which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

`In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention, v

Figures 1A and 1B together constitute a longitudinal section of a fractionating tower embodying the present invention, Fig. 1A being the bottom section, and Fig. 1B the top section, of the tower;

' FiguresZA and 2B together constitute a longitudinal section of a tube or column comprising part of the tower of Figs. 1A'1B; i

Fig. 3 is a horizontal cross-section of the tower of Fig. 1B, taken substantially along-line 3 3 of Fig. 1B;

F'g. 4 'is a side elevation of a fractionating tower similar to that of Figs. 1A-1B, but of relatively greater length;

Fig. is a horizontal cross-section of the tower of Fig. 4, taken substantially along line 5-5 of Figures 4 and 6;

Fig. 6 is a vertical section of a distributor section comprising part of the tower of Fig. 5, taken 5 substantially along line 6-6 of Fig. 5;-

Fig. 7 shows a number of types of packing elements suitable for use in the towers of Figures 1 through 6;

Figures 8A and 8B together constitute a longil0 tudinal section of an alternative embodiment of the invention, suitable particularly` for vacuum distillations; Fig. 8A being the bottom section, and Fig. 8B the top section, of the tower; l

Fig. 9 is a longitudinal enlarged section of a 15 single tube and rod comprising part of the tower of Figs. 8A--8B;

Fig. 10 is a horizontal cross-section of the tower of Fig. 8A, taken substantially along line lli-I0 of Fig. 8A;

Fig. ll is a horizontal cross-section of the tower of Fig. 8A, taken substantially along line ll-Il of Fig. 8A;

Fig. l2 is a horizontal crow-section of the tower of Fig. 8B, taken substantially along line 25 l2-I2'of Fig. 8B; and,

Fig. 13 is an enlarged, somewhat distorted /view of the packing elements of the tower oi' Figs. 8A-8B.-

Similar reference characters indicate correspending parts throughout the several views of the drawings.

The process of fractionating mixed vapors, such as those which come off a petroleum still or the like, consists essentially inscrubbing an ascending current of the mixed vapors witha descending liquid, commonly called the reux liquid. As the vapors come into contact with the liquid, the heavier of the higher boiling components of the vapor are condensed in the liquid and so 40 washed on down the tower. If the tower is thermally insulated, so that there is no considerable heat loss (i. e., the process is adiabatic), then the condensation of'the Vapor to a liquid gives o heat, which is in turn utilized to vaporize the lighter components of the reflux liquid, the vapors thus formed joining the primary vapors and proceeding upwardly in the tower. Thus, as the fractionating continues, the vapors, as they -rlse in the tower, become progressively richer in low boiling components, while the liquid reflux, as it descends in the tower,`becomes progressively richer in high boiling components. The ultimate result is that the low boiling components allaccumulate at the top of the tower, while the high boiling components accumulate at the bottom, and thus fractionation is achieved.

Two factors contribute to the effectiveness of the separation. First, the larger the ratio of descending reux to ascending vapors, the more probable it is that the vapors will be effectively scrubbed of theirhigher boiling fractions. Second, the effectiveness depends upon the degree of intimacy of contact between the reflux and the vapors, for without thorough contact no sepa-l ration whatever is possible.

The customary, and most widely-used type of fractionating tower heretofore, was the bubble plate tower which comprised a series of plates arranged in vertical order, each plate carrying a liquid level of reflux thereon, and each plate being provided with means for bubbling the ascending vapors through the redux liquid thereon. Provision was also made for draining the reux liquid progressively downwardly. Fractionating towers of this type, which will not be described in great detail, usually consist of from ten to sixty plates. If the vapor-liquid contact on each plate were perfect, that is, if equilibrium were actually established during the time that the bubble of vapor was in contact with the reflux liquid, there would be Aaccomplished one perfect distillation, and the tower would be said to have a "perfect or theoretical plate. However, in actual use, equilibrium conditions are by no means reached, andan eiiiciency factor is adopted to express the ratio of actual to theoretical enrichment. In ordinary towers of this type, the eillciency is from 50 to 80 per cent., averaging about 60 percent. This means (say, when the eiiiciency is but 56%), that two plates are actually needed to do the work that one could theoretically do.

Coupled with this factor requiring an excessive number of plates is the fact that compara tively wide spacing between the plates is necessary. This is because of liquid entranment incident to the turbulence created as the vapors bubble through a plate, and the entrained liquid must be given suiicient space to settle out before the vapors are bubbled through another plate. Another reason for wide spacing is found in the back-pressure on individual plates occasioned by an increased rate of throughput, which backpressure lmight, if the-plates were too close together, cause the redux liquid to back up through the overow pipe to the plate above,l and thus spoil Athe fractlonating conditions.

For these reasons, plates are, on the average, spaced apart :trom l to 2 feet. So'with an average plate ehciency of 66%, a vertical height of 20 to 41.0 inches ia required to achieve a fractionation eqnivalent'to one theoretically perfect plate. This height, to l0 inches, represents the height equivalent to a theoretical plate factor, hereinafter referred to as the H. E. T. PJ. For a bubble plate type fractionating tower, therefore, the H. E. T. P. is large, 4and a very high tower is required for any degree of perfect separation. The present invention is concerned primarily with reducing the H. E. T. P. factor, so that a tower of high fractionating ability can be made in a relatively short length.

Another type of fractionating tower comprises a column of the packedf type, in which a tube is' lled 'with packing material and the reflux liquid allowed to trickle slowly downwardly over this material against the upward flow of the vapers. The packing material, which is of many slider-ent shapes and types, causes a high degree of intimacy of contact between the reux liquid and the vapors, and the efllciency of such materials as fractionating means is considerably more nearly perfect than that of the bubble plate. Further, no liquid entrainment or back-f pressure difliculties are found in this type of tower, as there is no turbulence of contact as in the bubble plates and no liquid levels to set up back-pressures. In small-scale operations, such as laboratory-scale fractionations, therefore, the emciency of a packed column tower is immensely greaterl than that of a bubble plate tower. For instance, with the separation, of benzene and carbon tetrachloride in a packed column about 28 inches long and 3A inch in diameter, an

` H. E. T. P. factor of ll/z'inches was obtained.

It is when the simple type of packed column tower is enlarged in diameter to a commercial size -(to accommodate a large throughput) that the diiiculties commencea nd.the fractionation eiliciency ldrops off rapidly.' I`h islls due to the channeling vof the reflux liquid streams as they progress downwardly throughI the packing. It will be apparent that for a packed column to operate with maximum eflciency, the liquid stream must be broken up into as large an area as possible for greater contact withthe vapors. But the normal tendency is for a liquid to reduce its surface area for a given mass, and not to increase its area as desired. So the distributed liquid streams in a large-diameter column naturally come together, exposing the vaporsto less and less area per unit mass of liquid. This coalescing of the liquid streams is called channeling, and the greater the diameter and height of thecolumn, the more pronounced is such channeling.

To reduce the channeling effect in packed col-s umns it has heretofore been proposed to'redistribute' the liquid stream periodically at certain levels in the tower. That is, the channeling is conceded', but the stream is freshly subdivided at frequent intervals by means of distributors, as they are called. A system of distributors considerably increases the eiliciency of the packed type of tower for commercial sizes, but as larger diameter towers are needed the redistribution problem becomes increasingly complicated, so that it becomes apparent that redistribution is not the ideal solution to the problem of making a large diameter packed tower as edicient as a small diameter packed column. The present 'invention departs from previous developments along the line of redistribution in packed towers and proceeds upon a new line. In-

stead of attempting redistribution with its attendant diihculties, the present invention provides a Ylarge-diameter tower that is made up of individual units comprising the highly eicient small diameter columns. Large throughput' is thus accomplished by multiplying the number of small capacity, small-diameter columns, rather than by increasing the diameter of a single column, in this way preserving the high efciency of the small-diameter column and obviatingthe difficulties of channeling. Proceeding in this manner, there is practically no end to the capacity whch may be achieved, for to increase the capacity, all that is necessary is to increase the number of unit columns.

The design' of vsuch a tower `made up of a large number of unit columns is not, however, without its difllculty. To achieve a uniform fractionation in each of a large number of small columns (which is necessary in order to obtain uniform quality products from all of the columns),

vidual columns, and equal reflux ratiosin eachv of the columns. 4This latter in turn requires an equal amount of reflux liquidrin each column. The accompanying drawings illustrate towers l `which conform to these, conditions.

Referring now more particularly to Figures 1Ak andV 1B,` it will be seen that .the fractionating towi er of the present invention comprises cylindrical outer jacket sections I, 3, and 5, which are each provided with suitableilariges and bolts whereby they may be assembled as a single tower. Below the lower section I is a bottom section 1, which is in the form of an inverte'd'dome and terminates in a relatively large-diameter .vapor entrance conduit 9. .Abovethe upper section is a similar dome-shaped top II. 'Ihe bottom and top sections 1 and I I are provided with flanges to match the flanges of the sections I and 5, respectively.'l

The bottom flange I3, and' top flange I5 of the section I continueas plates across each end of the section I, which plates are drilled--to accommodate a large number of parallel unit column tubes I1 (see also Fig. 3). The tubes I1 are secured firmly in place in the plates I3 and I5 by expanding their ends, in the same manner as heat exchangers have heretofore been constructed. A spacer plate I9 (see Fig. 1A) may also be provided, if the tubes I1 are unusually long and require additional support, but in general v the tubes I1 are sufficiently rigid to maintain themselves in the desired spaced relation and no spacer plate I9 is required. The space exterior to the tubes I1 is dead air space, and serves excellently as heat insulating means to give the tower as a whole its adiabaticcharacteristics.

The tubes I1 are open at each end. They are each filled to within a few inches of the top (see Figures 2A and 2B) with packing material 2|, which may comprise any suitable material having a high ratio of surface area to free space (the surface area determining the area of liquid surface) for the liquid-vapor contact, while the free space permits the flow of the vapors without'too great'obstruction and without too great pressure 1 drop in the tube. Various types of packing material, as shown in. Fig. 7, are suitable. Referring to Fig. 7,'A indicates `a chain packing',.B va simple wire carding tooth, ,C a bent wire carding tooth, D a crimped wire, E a single turn, open wire helix, F a crossed-wire unit, G a multi-turnf wire helix, and H an ordinary copper rivet, all of which are more or less suitable for present purposes. The problems of the choice of a sult-` able packing material are treated with more detail, in my copending application for Letters Patent Ser. No. 677,755 filed June 26, 1933 to which reference is-hereby directed. At the lower end of each tube I`1 a grating 22 (Fig. 2B) may be provided, if ,necessary, to hold the packing material in place.

Between the vtop flange I5'of the lower section I and the bottom flange 23 ofthe intermediate section 3 '(Fig. 1B) is clamped a ring 25, which includes 'four outlet pipes 21' arranged ninety degrees apart (see also Fig. 3) IThe ninety degree spacingvpermits even withdrawal of the vapors,

as will fbeindicated. hereinafter, and the take-off system in this respect resembles. a piezorneter.A a.- rangementfor gas pressure measurement.; -v i .',The intermediate section rhas. the aforemem. tioned bottom flange 23 and a top flange :29 as f well.v

for a plurality'of outer-' ':ondenser tubes 3|. The f 'condenser tubes`3l` are equal in number tothe vfractiormting units' I1, and are sospaced-'that they are located each directly above a 'corresponding fractionating tube I1 when the column asia whole is assembled.

Also clamped between thev sections I and 3 is a. plate .33 which comprises ,the support for a plurality of connecting tubes 35 (Figures v1B and 2B) The connecting tubes 35 project a few inches into the fractionating columns or tubes I1, and are `cut off 'slopingly on their lower ends within the tubes 'I1-` The upper ends of the tubes 35 are positioned directly beneath the condenser tubes 3l so as to deliver vapor thereto and receive condensed 'liqu'id therefrom.

Between the top flange 29 of the intermediate sectibn'3 and the bottom flange 31 of the top section 5 is clamped another ring 39 which is in all respects similar to the ring 25. A plate 4I on the upper end of the ring-39 supports inner condenser tubes 43, which project downwardly into the I outer condenser tubes 3I (Fig. 2A) throughout substantially the entire length of said outer tubes 3I. Thel tubes 43 have closed ends which terminate in rods 45, which in turn project downwardly through the remainder of tubes 3l, and a part of connecting tubes 35. The ring 39 has gas outlet pipes 41 (Fig; 1B).

The ltop section'. 5 which is the shortest of the ing therethrough, and an overflow pipe 5I which terminates close to the top of said Section 3.

`'Between the top flange 53 of the top section 5 and the'flange 55 of the dome-top Il is clamped a plate'. 51, iwhich plate 51 supports innermost condenser tubes 59. The innermost tubes 59 ex- `several sectionahas. a water inlet pipe 49 leadtend downwardly into the tubes 43 nearly to the l bottom thereof. At the top of the dome II is a water outlet pipe 6 I.

When. assembling the various parts, all parts not stated to communicate arc presumed to be sealed together in a leak-proof manner with gaskets or the like. v

All'of the tubes 3| are equal in length, as are the tubes'43,and 59, respectively. This is to provide equal condensing surfaces in each of the individual condensers.

The operation of` this embodiment of the in- Yvention'is as follows: u

Water for condensingpurposesis admitted through the pipe 49, and it immediately establishes a level in the uppersection 5. The condensing'water'then flows, in equal streams. downwardly into tubes 43, filling said. tubes. and overflows by rising -in tubes 59 to the dome I I, whence,

after a suitablelevel has been built up it discharges through pipe 5I.A This system. provides for an equal condensingcapacity in each of the.

be rememberedt-,was .one of the conditions heretoyforepointed 'outas desirable for the proper operati'onofthe tower. A Vaporsentering the column'through pipe 9 are in arelative stateof` equilibriumdue to the large., diameter-of pipe f Theythereforeimpinge upon and divide themselveagintofequalt streams flowing -1 f into `each of the fractionating tubes I1. It is assumed that reflux liquid is already travelling downwardly in the tubes I1. The fractionation of the vapors now goes on in the described manner through the packed columns I1, each column operating in exactly the same manner because it is receiving the 4same amount of vapor and of reflux liquid and because it contains the same amount of packing material.

When the vapors reach the to`p of tubes I1 they have been scrubbed effectively. Here they divide into two paths. The largerportion of the vapors pass out through the top of tubes I1, into the ring and thence through outlets 21 to the usual condensing apparatus. The remainder of the vapors pass through the lower ends of connecting tubes and into the condensers, where they are condensed by contact with the water-cooled inner tubes 43. Such non-condensible gases and the like as are present pass from the top of the condenser tubes 3| and out through outlets 41. The condensed vapors constitute replenishments of the reflux liquid, and fall downwardly with gravity and are distributed into the fractionating tubes I1.

It will be seen that the ratio of vapors passing out of the tubes I1 entirely, to those passing into the condensing systems, are equal in all of the tubes, for this is controlled by the area of the opening of the connecting tubes 35, which are all equal.

Thus, a tower is provided which is made up of a plurality of unit columns, each of which carries an identical amount of vapor, fractionates it to an identical extent, and distributes identical proportions to the product outlet and to the individual condenser systems, wherein identical condensing conditions prevail, so that identical volumes of reflux liquid are delivered into each of thc individual fractionating columns for treatment of further vapors. f

The reflux liquid remaining at. the bottom of the fractionating columns flows back through the pipe 9 to the still or other suitable device for effecting vaporization. Or, a trap may be provided for collecting these heavier residues.

In certain cases, it is desired to take off or cut distillate fractions intermediate to those issuing from the top of the tower, and/or to add vapors to be fractionated. This is provided for by the arrangement shown in Figs. 4, 5, and 6. Referring to Fig. 4, it will be seen that the fractionating section is broken up into a plurality of sections la, Ib, and Ic, all of which are identical to the section heretofore described. Between these sections are provided sections 63 (see also Figures 5 and 6) which are also vapor redistribution sections. Each section 63 has an upper flange 65 and a lower flange 61, the upper flange G5' extending across the section as a supporting plate for tubes 69 whichv llt. against the tubes I1 of the fractionating vsection next above. 'Ihe tubes 69 are constricted at their lower ends into smaller delivery tubes 1| which extend a short distance below the lower flange 61, so as to fit into the upper ends of the fractionatingtubes I1 in the section next below. Holes 12 are provided near ,the ends of the tubes 69. Into the sections 63 project vapor tubes 13, 15, and 11. Tube 13 is the largest in diameter and has spaced holes 19` therein. Tube 15 is smaller, but extends nearly to the center of the section. Tube 11 does not project into the section at all, but merely constitutes a peripheral opening or outlet from the section. The arrangement of the tubes 13, 15, and 11 is such that substantially equal quantitles of vapor are drawn from or added to all parts of the section, so that no vapor surging results to cause faulty redistribution of the vapor into-the fractionating tubes I1 of the next section above.

In operation, the sections 63 serve to gather together the vapors from all of the tubes I1, persets up a vacuum condition which results in drawing more vapors from the column.

The redistribution sections may be established at as many places as may be desired. Further, the' intermediate fractionating sections can be made equal in length, or of different length, depending `upon the character of the intermediate products desired. While the pressure drop from top to bottom in the apparatus .thusfar...dlsclosed is not prohibitivelyhigh,` it is in some..instances (such as the vacuum distillation of lubricating oils) too high for ready accommodationl ofithexoils being distilled. This is occasioned by the frictional resistance offered to the vapors by the closely confined packing material in the tubes I1. The embodiment of the invention shown in Figures 8A through 13 is designed particularly to secure a minimum pressure drop, and is thus adapted particularly for vacuum distillations. This embodiment follows the same general principles as the embodiment heretofore described, but instead of drawing thevapors through confined packing material in a narrow tube, the tube is replaced by a rod which carries elements to effect a devious flow of the reflux liquid, and the vapors are not sepa-K rated into several streams but are passed in a single stream in contact with the several reflux liquid streams (which are maintained separate) on the rods. Identical condensing systems of the same type as in the previous embodiment provide for equal volumes of reflux liquid on each of the rods,

Referring now more particularly to Figures 8A and 8B, numerals |0|, |03 and |05 indicate bottom, intermediate, and top shell sections, each provided with suitable joining flanges. Below the bottom section |0| =is a connecting section |01 which connects the tower, preferably, directly to the'still |09. A top dome section is attached to the top section |05. I

The lower flange ||3 of the `lower section |0| extends across said section as a plate, as shown insection in Fig. 11, and serves to support the lower ends of a plurality of parallel, closely spaced rods ||5. Holes ||1 between the rods ||5 permit entrance of vapors into the fractionating section in a uniformly distributed manner, and also permit egress of reflux liquid reaching the lower ends of the rods.

The top flange ||9 of the section |0| is joined directly to the bottom flange |2| of the section |03. Neither of these flanges extends across its section as a plate.

Near the bottom of intermediate section |03 is Aprovided a portion |23. of increased diameter,

which portion houses a condensing ccil |25. An annular channel or trough |21 vdownwardly terminates the portion |23, and a drain |29 leads .9and 13).

from said channel."ffearlthe top offthe' section |03 is provided an outlet pipe |3|, by which the vacuumfor the 'distillationis drawn. i

The top flangev|33 `of ,the section ID3k extends across said section as a plate, and ysupports the upper end of outer condenser tubes |35. The lower ends of the tubes |35 (see Fig., 9) are closed, and to them are welded the 'upper ends of the rods ||5.v Thus therods I are, in effect, supported by the outer condenser'tubes |35.

Upper section |05 is similar toA its corresponding section in the'first'e'rnbodiment of the invention, and carries water inlet pipe |31 and Water overflow pipe |39. The, upper Vflange IM of this section extends across the section, and serves. to support inner condenser tubes |43 which are concentric with the outer condenser tubes |35, and extend downwardly therein for the majority of their length.

The top dome section I l| 4is provided at its top with a water outlet pipe |45.

Each of the rods I5 carries thereon a plurality of flow-breaking elements, which in the present embodiment comprise discs |41 (see also Figures The discs |4`|` are arranged at different heights onthe various rods and are of such diameter that they touch no rod except the one to which they are aixed. They constitute elements tending to give the descending reflux liquid a devious path, and at the same time keep the streams on the several rods entirely separatem In this manner the area for liquid-to-vapor contact is increased. Fig. 13 is purposely exaggerated as to the number of discs and the 'closeness with which they are spaced in order to show how they are t ing section in a single stream, but contact with a large area of reflux liquid on the rods I5, with their attached discs. When they reach the top of the fractionating section IUI, they have been effectively scrubbed and are free of heavier prod-` ucts. In the lower part of the section |03, a part of the vapors come into contact with the ooling coil| and are condensed,.to fall into the annular channel' |21'whence they arefwithdrawn through the outlet |29 .as the product. The remainder of the vapors continue upwardly to come in contact with the 'water-cooled tubes |35. As the iiow of-vapors is even across the column, the' i indensation on each of thev tubes |35 is equal, and the condensed 'vapors' (now comprising the reux liquid) rundown the tubes |35 and onto the rods |`5 to commence their downward travel through the fractionating section. The water flow. inthe condensing system is equal foreach t1'.be and takes place in the same manner as that set forth in connectionjwith the description of he first embodiment. v t f Residual iiXed gases, if any, pass from the ,ap-

paratus through the outlet |3|;' y y t while the embodiment just described., yisfnot in tre strictest sense a packed type of lfractionating` power; it will be'seenfthati "has been fo order offene millimeter of mercl'lfy.L

,v It will "understoodl hat` flux liquid streams down through"` theiractionating tower is but one offthe many methods that could ,be used with equal success'. For example,-

'to have a-r pressurejdropof theI the rods might be replaced by lengths of chains, y

ortherods might be retained but given a highly irregular `surface to increase the area of reflux liquid in contact with the ascending vapor stream.

It will `be readily seen that the .fundamental characteristicof similarity between the vseveral embodiments of/the invention is found in the y separate formation andseparate maintenance of a plurality of reflux liquid streams ofl equal size and surface area, and the separate streams being brought into intimate contact with a counterow of vapors to be fractionated,-and the streams being formed from a portion of. thefractionated vapors reaching the top of the tower.

Throughout this specification, the separate fractionating units (small diameter columns or rods, as the case may be) have been described as of equal diameter or as carrying equal streams of reiiux liquid, and the condens-ers have likewise been described as of equal condensing capacity. This equality has been provided for the/purpose of securing equal ratios of vapors to reuxing liquid at each of the units. Such equal ratiosof vapors to refluxing liquid may likewise be achieved by so proportioning the apparatus that if` one column or rod, for example, is of a. greater diameter and carries a greater volume of reflux liquidl obtained from a condenser' of greater condensing capacity, then that column or rod shall receive a proportionately greater volume of vapors than smaller diameter columns or rods.

vIn view of they above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be .a unit stream, into intimate contact with aplurality of substantially separately maintained flowing countercurrent to the vapors, whereby Athe vaporsv are scrubbed of their heavier components, bringing scrubbed vapors into contact with aplurality of separate condensing means,A

thereby separately forming each of said plurality of separate streams of refluxing liquid, and

maintaining at all times at each of said sep'arate streams a substantially equal ratio of vapors-` to refluxing liquid. t y QV V 2. The method of fractionating, vapors which comprises introducingsaidfvapors, originally'iny f a` unit stream, into intimate contactwith apluf-` rality of substantiallyseparately vmaintained f streamspof vrefluxing liquid, vthereiiuxingf liquid I iiowing. counter toxthegvapors,wherebyzthe vapors i l 'are scrubbed of their' heaviercomponents, bring-1 #ing scrubbed vapors into lcontact with a plural- "'ity of separate *condensing means, .tlnreby-` sparately forming each of said plurality of separate streams of refluxing liquid, the refluxing liquid 5,5'

sesl

streams of refiuxing liquid-maintaining at all times at each of said separate streams a substantially equal ratio of vapors to refiuxing liquid, and withdrawing a product portion after' said vapors are scrubbed but before the condensed scrubbed vapors are Vformed into said vapors are scrubbed of heavier components, re-

combining said scrubbed vapors into a `unit stream and from said unit stream of scrubbed vapors, withdrawing a portion as product vapors, while bringing the remainder of said scrubbed vapors into contact with a plurality of separate condensing means, thereby separately forming each of said plurality of separate streams of refiuxing liquid, and maintaining at all times at each of said separate streams a substantially equal ratio of vapors to refluxing liquid.

4. The method of fractionating vapors which comprises introducing said vapors, originally in a unit stream, into intimate contact with a plu-I rality of substantially separately maintained streams of refiuxing liquid of substantially equal size, the reflux liquid flowing countercurrent to the vapors, whereby the vapors are scrubbed of heavier components, recombining the scrubbed vapors into a unit stream, and from said unit stream of scrubbed vapors, withdrawing a portion as product vapors, while bringing the remainder of said scrubbed vapors into contact with a plurality of separate, substantially equal, balanced condensing means, thereby separately forming each of said plurality of equal separate streams of reiluxing liquid.

5. VThe method asset forth in claim 4, in which each separate stream of reflux liquid is maintained as a unit packed fractionating column.

6. The method as set forth in claim 4, in which the vapor stream is maintained as a single stream, in contact with said plurality of reux streams throughout the fractionating step.

'7 Fractionating apparatus comprising a tower made up of a plurality of relatively small-diameter packed fractionating columns, means including a jacket confining said columns in parallel relationship in said tower with dead air spaces surrounding the said columns, said jacket 'andsaid air spaces maintaining said columns under substantially equal temperature conditions, and a plurality of individual condensers arranged t0 deliver one into each of said columns.

8. Fractionating apparatus comprising a plurality of relatively small-diameter packed fractionating columns, a tower confining said columns in parallel relationship, and a separate condenser delivering into the top of each of said packed columns, each of said columns having substantially the same fractionating characteristics and each of the condensers having substantially the same condensing capacity, means for distributing the vapors to .be fractionated substantially equally into said plurality of columns, means for. withdrawing from each of said columns a substantially equal proportion of the fractionated vapors therein, and means conducting the remaining fractionated vapors into -the condensers associated with the respective columns. l

' claim 8 in which all of said condensers are arranged in yparallel relationship,l and unitary conjdenser feeding means and discharging means for all of'said condensers.

f 10. liractionatng apparatus as set forth in `claim 8" in which at least one redistributing secpacked columns, 'said redistributing section including means for combining `the vapors in all of said columns and redistributing the vapors equally to each of said columns, but without combining the reflux liquid streams in the separate columns, and means for adding vapors to bottom of said tower, means for admitting vapors to be fractionated to said tower and conducting said vapors upwardly in said tower, and means for withdrawing a product portion from said tower at a point just below said condensers, al-

lowing the remainder of said vapors to strike said condensers to be condensed thereon, the said means extending downwardly from said condensers being constructed Ato compel the liquid flowing thereon to take a devious path exposing a relatively large surface area of liquid.

13. Fractionating apparatus comprising a plurality of separate fractionating units, a tower enclosing said units and maintaining said units in parallel relationship, said units comprising parallel condensers of substantially equal condensing capacity disposed near the top of said tower, means extending downwardly from each of said condensers adapted to conduct the liquid condensed thereon in separate streams to the bottom of said tower, means for admitting vapors to be fractionated near the bottom of said tower and conducting said vapors upwardly in said tower, and means for withdrawing a portion of said vapors from said tower at a point just below said condensers, allowing the remainder of said vapors to strike said condensersto' be condensed thereon, the said means extending downwardly from said condensers, comprising parallel rods with spaced discs attached thereto.

14. Fractionating apparatus comprising a plurality of separate fractionating units, a tower4 enclosing said units and maintaining said units in parallel relationship, said units comprising parallel condensers of substantially equal condensing capacity disposed near the top of said tower, means extending downwardly from each of said condensers adapted to conduct the liquid condensed thereon in separate tortuous-path streams to the bottom of said tower, means for admitting vapors tosbe fractionated near the bottom of saidtower and conducting said vapors upwardly in said tower, and means for withdrawing a portion of said vapors from said tower at a point just below said condensers, allowing the remainder of said vapors to strike said condensers to be condensed thereon, the said means for withdrawing a portion of the vapors comprising a separate condenser in the form oi' a coil surrounding said, units near the top thereof, said coil being adapted to condense a portion of the vapors, and a. trough concentric with and beneath said coil for removing the condensed va- 5 pors from the tower.

- MERREIL ROBERT FENSKE.

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