US2370462A - Vacuum distillation process and apparatus - Google Patents

Description

' Feb. 2 7, 1945. J. c. HECKEIIQ VACUUM DISTILLATION PROCESS AND APPARATUS Filed June 4, 19414 2 Sheets-Sheet 1 FIG.- I.

' JOHN C. HEEKE INVENT OR WW Q m A TTORNEYS Feb. 27, 1945.

J. c. HECI ER 2,370,462

. VACUUM DISTI-LLATIQN PROCESS AND APPARATUS Filed June 4, 1941 2 sheets-sheet 2 JOHN n. HEEKER INVENTOR ATTORNEYS "Patentecl Feb.' 2'7,-1945 2,370,462 1 VACUUM nIs'rrLLA'rIoN mocnss AND 1 APPARATUS John 0. Becker,

Rochester, N. Y assignor'to Distillation Products, Inc Rochester, N. Y a corporation ofDela'ware:

Appl'leation'June 4. 1941,. sefrial'no. 396,570

9 Claims. 01. 20 2552) a This invention relates .to a'process stand to apparatus for effecting evaporation of a distilland 4 and more particularly to the process of and to" apparatus for high vacuum distillation.

Inprior molecular stills and especially in -evaporatorsin which there is no ebullition, it

has beencustomary to effect evaporation by" that the oil is hot and obviates the need for transfer tubes and pipes wherein thermal decomposition takes place and wherein heat i lostby radiation. Another feature of the invention relates to an evaporating unit, the temperature\ of' which can means of heated plates. Such plates are expenof their necessary mass, are subject to consider able heat lag which wastes much "time during the starting and stopping of the apparatus. In-

addition, such evaporating plates must be provided with means to prevent the distilland from channeling'that is, the formation of rivulets' of distilland on the evaporating surface with bare spaces in between. -Also,-such evaporating plates effect considerable heat radiation and, therefore, cause considerable thermal losses.

The main feature of the present invention-re-- lates to a still having an inexpensive evaporating 'sive as well as'difilcult to fabricate and. because element which. is simple inconstruction and. in

which there is negligible thermal lag wherebyv the loss of time in starting and stopping evaporation is reduced to a minimum.

Another feature of the invention relates to an I evaporating element which has small radiating I evaporation can take place during the entire time 55 the evaporating coil. I When the still is in opit serves as a complete evaporator.

' area for thermal losses and in which the thermal emoien'cy' will be high since the. total amount of heat is applied. directly to the distillan'd. In ad-' dition, the evaporating element will never be much above the evaporating temperature so that radiation losses will be small.

A further feature of the invention relates to a simple arrangement for altering the tempera.-

' ture gradient of the evaporating element. Since the evaporating element is in the form of a coil the heat supplied to the several unit lengths of the coil can easily be changed by varying the number of coil turns per unit length to satisfy the heat requirements in any given situation.

Instead of varying the space between the turns of the coil, electrical taps can be connected to the coil at various lengths thereof to aiiordindi- .vidual temperature adjustments to selected zones of the coil. By this arrangement, the heat input of the coil,- near the top thereof. can be of higher value where the oil is cold and requires a quick temperature rise.

to the use of one long heating coil adjacent various condensing zones spaced-along its path so that Thus, a single distilling unit will have the advantage that An additional feature of the invention relates of the distilland thereon;

.be easily controlled, Since the evaporating ele- I mentisin the form of a coil of. wire, the 're- For a clearer understanding of the inventioln reference is made to the detailed description and claims when taken with the drawings in which:

, Fig. 1 is a vertical section through a still made in accordance with the present invention;

Fig. 2 iS'B, cross section ofthis still taken on the line 2'-'-2 of Fig. 1; e

Fig. 3 is an enlarged view of a piece of the evaporating element illustrating the distribution Fig. 3A is a fragmentary view of a modified form of evaporating element;

Fig. 4 is a vertical section thru a modified I form of still incorporating the present invention; while Fig. 5 is a cross section of this modified form taken substantially on line 5- -5 of Fig. 4; and

Fig. 6 is a perspective view of a further modified formof the invention.

Referring to the still of Fig. 1, the numeral 5 designates a-closed cylindrical chamber, the inner wall of which provides a condensing surface.

The chamber is provided with an'ewiporatlng element 6 in the'form' of a helically wound, elec-' trical heating coil of nichrome resistance wire or the like, which is insulatedly mounted at the top and bottom of chamber in such a manner that the coil extends along the principal axis of the chamber. As herein illustrated, the upper end of the coil is suspended'fromthe tension spring I which tends to keep the coil taut at its axial position in-the chamber. The space between the inner wall of the chamber and the heating coills such that short path distillation can be effected in accordance with -'the disclosures of the Hick-- 'm'an & Hecker Patent 2,126,467 granted Aug. 9, 1938, and Hickman Patent 2,221,691 granted Nov. 12, 1940.

The upper portion 'of the chamber is provided with an inlet pipe 8 by which degassed oil or other distilland is supplied to the upper end of oration, a rarefied atmosphere maintained within the chamber thru a conduit 9 which is connected to a suitable vacuum pump (not vidual' temperature adjustment for any selected shown). While the invention is. not. limited to any particular degree of evacuation, it is pri-- marily related to devices commonly referred to as high vacuum unobstructed path stills of the character disclosed in the mentioned patents.

In the arrangement of Fig. 1 the still is assum ed to be of the multi-stage type wherein the- 1 evaporating element 6 has two zonesiA and B to be maintained at'difierent temperatures during the operation of the stills The side wall of the cylindrical chamber is formed with annular gutters I and l-l located atqthe lower boundaries of the heating zones 6A and B-respectively. Thus, the distillates condense on the wall of the chamber and accumulate in the respective gutters to flow away thru discharge pipes I2 and l3 1 communicating therewith. Theibottom of the chamber is provided with an outlet pipe 14 through which the residue is discharged.

Although the invention is not;1imited to any particular diameter or length of coil; a-satisfactory heating element has been madeof #22 gauge zone.

Where it is desired to gain increased capacity,

,the evaporating coils can be arranged in parallel relation according to a cylindrical pattern, in a modified form of the still shown in Figs. 4 and 5.

still is providedwith an upright cylindrical *chamber 2| generally annular in cross section,

the chamber being defined by an outer cylindrical vcasing 2| and a smaller cylindrical casing 22 coaxiallyposltioned therein. Thetops 23 and 24 of these cylindrical casings are, closed and mounted in'spaced relation to provide space for -a radial distributor. The inner casing is open at j the bottom forreceiving cooling medium there in from pipe P but the lower edges or the inner andoilter casings are-sealed together by an annular plate 25.. Provision is made for evacuating the annular chamber in the form voffa pipe 30 nichrome resistance wire helically wound into a coil one-eighth of an inch in diameter and twentyfour inches long, the coil being stretched so that adjacent turns thereof were not in contact. -With such a construction, the oil or other distilland flows down the coil in the form of a compact cent turns as shown in Fig. 3 and at least twentyfive percent of the space within the coil'should preferably be occupied.

During operation or the 'stilL'the chamber 8 is evacuatedto a very low value thru the pipe 9. Theevaporatlng element 6 is included in series with' a source of'heat'in'g current, a suitable rheostat (not shown) being preferably included in series with this circuit so that the temperatures or the zones iA'and 6B of'the heating element 8 can be closely regulated." Oil or other distilland is introduced through the pipe 8 to theheating coil l on which it flows down slowly'because of capillary action due to the narrow spaces between the adjacent turns of the coil. The heatedoil, as it flows down the coil, evaporatesand the: fractions of the distillate condense on the inner wall of the chamber where they accumulate and flow down into the respective gutters l0 and II being discharged therefrom through the dis- Y chargepipes' l2 and IS. The fraction ofthe distilland which 'does'not evaporate at the prevail-.-

ing temperatures flows down to the bottom of the chamber where it accumulates as'a residue which is discharged through the outlet pipe II.

In the formof the invention Just described,

the diil'erent heating zones 6A and BB 01' the evaporating element are obtained by a different amount ofspacing between the turns of the .0011.

coils are. arranged in vertical parallel relation accordin to a cylindrical pattern which is coaxial with the chamber 20. While these coils of the inner casing 22.

communicating with the chamber and connected .to a suitablevacuum pump not shown). The distributor/dis: 24' may be mounted for rotation in any suitable manner such as by being concentrically secured to-the lower end of a shaft 35. This shaft extends coaxially of the inner casing thru astumng box." and terminates in a driven pulley 31. The inner-walls of the chamber 20 near the lower portion thereof are provided with "gutters 39 and in which the distillate collectsbeing discharged thru the pipe 4| and 42 respectively.

It has been mentioned that the' evaporating may be thus arranged in various ways, it is preferred to suspend these coils from the lower edge of an annular or funnelasha'ped conducting mem-. ber 26. This conducting member is insulatedly mounted on the inner wall of the casing 2| with the edge ofthe member on .a level with the top A power lead 21 extends from the member 26' thru an insulating bushing. 2. to the exterior of the chamber. Similarly, the lower. ends of the coils 8 are secured ,to an annular conducting member 29 which is Y insulatedly' mounted on the bottom plate 25 of f the chamber. A second power lead 3| extends from member .29 thru an insulating bushing 32 in the wall of the outer casing;

The oil or other distilland is introduced into the chamberthru an inlet pipe 33. This pipe discharges the oil on a rotating, horizontal disc 34 serving to distribute the oil uniformly on the funnel-shaped member 28 from which the oil flows down the coils 6. The operation of this still will be obvious from the foregoing description.

In the modified form of the invention illustrated in Fig. 6', the still '50 is generally oblong in shape with-its side walls 5| spaced apart a distance appropriate for short unobstructed path distillation. In this arrangement, the evaporat- In-the case of the zone A, theindividual turns are closer together and, therefore, have a higher overall heating effect than where the spacing is farther apart as in the case of the zone GB. In-

stead of varying the spacing between the coil turns to obtain the several temperature zones, the coil may be provided with one or more electrical taps T along its length (Fig. 3A) to give indilug coils '8 are mounted in a vertical plane parallel to and preferably midway between the side walls SI of the still. The coils are conductively joined at their upper ends to the horizontal conducting. rod 52 insulatedly mounted in the end Walls 53 of the stil1.- Similarly the lower ends of the coils '6 are electrically connected to the horizontal conducting rod 54 insulatedly mounted in the end walls '53. The rods 52 and 54 are connected thru the power leads 55 and 56 to a source of electric current while the still is in operation.

The oil or other distilland is supplied to the still thru supply pipe 58 to a metering device 59 from which it fiows to branch feed pipes 60 sealed into the top of the still and discharging on, the upper ends of the coils 6.

The lower parts of the side and end walls of the still have a continuous gutter 62 formed therein in the region of the lower ends of the coils 6. This gutter has a discharge pipe 63 for distillate while the bottom ofthe still has apipe 64 thru which residue is discharged.

Since this form ofthe still is intended for high vacuum distillation, the space within the still is evacuated thru pipe 65. I

The operation of this modified still will be obvious from the description of the operation of the still disclosed inFig. 1.-

It should be appreciated that the evaporatingcoils are inexpensive to manufacture and can be easily replaced by fresh units if the need arises.

Since each evaporating coil ha small mass, it

responds promptly to changes in heating current so that the temperature within the still can be easily regulated asdesired. It will also be appreciated that radiation of heat is reduced to a minimum since each coil is'surrounded by the flowing oil. i

What I claim is:

1. The method of effecting distillation which comprises causing a distilland to flow slowly as I a column with its entire outer surface exposed to a rarefied atmosphere, introducing heat into said column along an internal, line-like, helical I path for the most part completely immersed in said column and extending lengthwise thereof, a substantial portion of the space within said path being filled with distilland, condensing the I distillate adjacent 'said column, and discharging the distillate.

2. The method of effecting distillation which comprises causing a distilland to flow slowly in a substantially straight course as a column with its entire outer surface exposed to a rarefied atmosphere, introducing heat into said column along an internal line-like helical path for the most part completely immersed therein and extending lengthwise thereof, a substantial portion of the space within said path being filled with distilland, condensing the distillate adjacent said column, and discharging the distillate.

3. In an unobstructed free path distillation device, a downwardly extending coreless, helical coil of wire, said coil having'its'inner and outer surfaces completely exposed for the flow of distilland thereover, means for heating said coil,

means for applying a stream of distilland to the upper endof said coil, a condensing surface extending in generally parallel short path relation 'to said coil, means for maintaining a rarefied atmosphere betweensaid coil and said surface, andmeans for accumulating distillate and residue at spaced points in said device.

. '4. In a device of the class described, a closed, elongated, vertical chamber, means for maintaining a rarefied atmosphere in said chamber, a hellcal electrical heating coil extending along the principal axis of said chamber, said 0011 being coreless whereby distilland can flow over the inner surface and over the outer surface thereof, and means tor applying a streaxnof distilland and. means for'applying electric heating currents of different values to said taps, means for to the upper portionof said coil, said chamber having one portion to accumulate distillate and a second portion to accumulate residue.

5. In a device of the class described, at least one downwardly extending coreless, helical heating coilof wire suspended by its ends, means for heating difierent portions of said coil to different temperature values, means for "applying a stream of distilland to the upper end of said coil, a condensing surface extending in generally parallel short path relation to said coil, means for maintaining a rarefied atmosphere between said coil and said surface, and means for accumulating distillate and residue at spaced points in said device.

6. In a device of the class described, at least one coreless, helical coil of resistance wire extending downward with its inner and outer suriaces exposed for the flow of distilland thereover, said coil having at least two zones, the spacing of the turns of said coil in one-zone being diflerent from thespacing of the turns in the other zone, means for applying an electric heating current .to said coil, means for applying a stream of distillandto the upper end of saidcoil, a condensing surface extendingin generally parallel short path relation to said coil, means for maintaining a rarefied atmosphere between said coil and said surface, and means for accumulating distillate and residue at spaced points in said device.

7. In a device of the class described at least one helical, coreless, resistance-type heating coil extending downward, said coil having electrical taps dividing the same into at least two zones applying a stream of distilland to the upper end of said coil, a condensing surface extending in generally parallel short path relation to said coil,

means for maintaining a rarefied atmosphere between saidcoil and said surface, and means for accumulating distillate and residue at spaced points in said device.

8. In a device of the class described, an upwardly extending chamber provided with spaced condensing walls, upwardly extending helical,

. coreless coils of the resistance heating type havingtheir principal axes displaced from one anotherin side by 'side relation, said walls being spaced in condensing relation to said coils, means for maintaining a rarefied atmosphere in said chamber, means for applying electric heating currents to said coils, means for applying a distilland tosaid coils, and means for accumulating a distillate condensed on said walls.

9. In a device of the class described, an upwar'dly extending cylindrical chamber provided with condensing walls, coreless heating-coils of 'wire mounted withinthe chamber with their principal axes extending in spaced. upright relaticn according to a cylindrical pattern coaxial with said chamber, means for maintaining a rarefled atmosphere in said chamber, means for applying electric heating currents to said coils, means for applying a distilland to said coils, and means for accumulating distillate condensed on the walls of said chamber.

JOHN c. nncxna.

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