US2210928A

US2210928A - Vacuum distillation apparatus

Info

Publication number: US2210928A
Application number: US309646A
Authority: US
Inventors: Kenneth C D Hickman
Original assignee: Distillation Products Inc
Current assignee: Distillation Products Inc
Priority date: 1936-07-06
Filing date: 1939-12-16
Publication date: 1940-08-13
Anticipated expiration: 1957-08-13
Also published as: BE470122A; US2180053A; NL52045C; GB482883A; DE968391C; FR49278E; US2210927A; US2180050A; GB500195A; FR834937A

Description

Aug. 13, 1940. w K. c. D. HxcKMAN VACUUM DISTILLATION APPRATUS Original Filed Sept. 5 1936 FIG.1.

r.- n f. I

H ich'man INYENTOR.

KennelhCD.

/h/wn ;72- f BY W ATTORNEYS o temperature and on Patented Aug. 13, 1940 UNITED STATES Z,Zl0,928

PATENT OFFICE signor, by mesne assignments, Products, Inc., Rochester, Y.,

of lDelaware to Distillation a corporation Original application Septcmbei' 5, 1936, Serial No.

Divided and this application December 16, 1939, Serial No. 309,646

3 Claims. (Cl. 202-205) This invention relates to improved apparatus for the high vacuum unobstructed path distillation of relatively non-volatile heat labile substances.

It is well known that when thermally unstablev phlegmatic organic compounds are subjected to distillation, much harmful decomposition takes place. The spoiling is caused by heat and the quantity decomposed is dependent both on the the length of time the material is exposed to the high temperature. n order to minimize decomposition, it has been customary to reduce the pressure at which distillation takes place or to reduce the mass of material held in the heated zone. This has been done by admitting the material in small quantities at a time to boilers heated under vacuum and withdrawing the material immediately after treatment. The method of operation has reached a natural limit in molecular distillation apparatus Where the material is spread in a thin film by gravity over a hot surface and the constituents are allowed to evaporate into a space substantially empty of residual gas. The temperature for a given rate of distillation per unit area of surface exposed is thus reduced to the lowest possible limit and the quantity of material exposed in unit time is likewise made small.

This invention has for its object to provide improved vacuum distillation apparatus which will avoid the above difiiculties. Another object is to provide improved vacuum distillation ap paratus which substantially lowers the amount of decomposition heretofore encountered. A further object is to provide high vacuum, unobstructed path distillation apparatus in which the film of distilling liquid is formed by forces greater than gravity and as a consequence the films are substantially thinner than the natural limit discussed above. Other objects will appear hereinafter. f

These and other objects are accomplished by my invention which includes high vacuum unobstructed path distillation apparatus provided with a moving vaporizing surface over which the distilland travels by centrifugal force. v

In order to enable a clear understanding of the principles of my invention I have 'illustrated in the accompanying drawing various embodiments thereof.

Referring to the drawing:

Fig. 1 illustrates a sectional elevation of a centrifugal vacuum stil1.` w

Fig. 2 illustrates an elevation in section of a modification of the type of still of Fig. 1.

Referring to Fig. 1 reference numeral l designates a cylindrical still casing provided with an integral base 2 and a removable top plate 3 which is kept in gas tight contact with the upper edge of l by a gasket 4. The wall of casing l is 5 provided with a large conduit 5 which connects with high vacuum pumps (not shown).

Annular gutters

6, 1 and 8 are formed in the walls of casing I, gutters 'l and 8 draining into withdrawal conduits 9 and ID and gutter 6 into conduit II. A drive shaft |2 provided with a pulley |6 extends the length of the still and is housed in, and supported by bearings |3 and |4 the latter being provided with a packing gland to prevent entry of gas.

The upper portion of bearing l|4 is provided with a small reservoir |5 filled with a low vapor pressure liquid which further insures against leakage of gas. Any oil leaking through the bearing falls onto disk 20, fixed on shaft 12 and is thrown by centrifugal force into the annular trough of reservoir 2|. A conically-shaped plate 22 is fastened upon shaft |2 at 23. the upper periphery of the plate being on a substantially horizontal line with gutter 6. A conically-shaped plate 24 is fastened to the shaft |2 at 25 and the upper periphery thereof is on a horizontal line with gutter 8. Plate 24 supports a similarly shaped plate 26, the upper curved portion 21 of which is integral with the periphery of plate 24 as shown. A conically-shaped plate 28 positioned substantially equidistant from

plates

24 and 26 is supported in the position shown by welded spacers 29. The periphery of plate 28 does not extend to the curved portion 21, so that there is an open passage from the space between

plates

24 and 28 and that between

plates

26 and 28. A collarshaped cone 30 is mounted in the position shown upon plate 24 and is rigidly malntained in that position by spacers 3l. The upper periphery of plate 30 being opposite to the annular openingr of gutter 1. The force of rotation transmitted from shaft |2 to plate 24 is in turn transmitted to

plates

28, 26 and 30, and the entire assembly is thereby rotated as a unit. The lower portion of plate 28 dips into a heating fluid 32, the rotation of the entire body of which is prevented by a collar-shaped baffle 33. The lower section of the still containing the heating fiuid is separated from the remainder by a circular baflie 34. The section of the still thus isolated is evacuated byl conduit 35 connecting with high vacuum pumps (not shown). A conduit 31 serves to introduce material to be distilled onto the upper central portion of plate 22. Annular-shaped projections 55 22 as shown.

38 and 38 are positioned the intemal walls of which are provided with annular gutters 8|, 82 and 88,.draining into

conduits

84, 85 and 88, respectively. A shaftv 81 provided with a driving pulley 88 is vertically positioned in the still as shown and has mounted upon it

disks

88, 80 and 8|. Tl'ese disks are spaced on shaft 81 in such a manner that their peripheries are on a horizontal plane with the openings of gutters 8|, 82 and 83, respectively.

Disks

89 and 8| are of such diameter that 'their periphery approaches or extends into the openings of the gutters. Disk 80 is of considerably less diameter. A capillary conduit 82 extends into the still and is provided with an electrical heating unit 83 which is heated by electricity introduced through lead '

wires

84 and 85, the latter being provided with a rheostat or similar means for controlling the current input. Conduit 82 is bent at right angles and the end 88 is flared and extends into close proximity with the upper surface of disk 80. The still is evacuated by means of high vacuum pumps connected to

conduits

81, 88, 88 and |00. Conduits 88 and |00 being fan shaped as shown in order to provide a larger portal for diffusing gases.

In Operating the .apparatus illustrated in Fig. 1, the heating fluid 32 is brought to an elevated temperature by application of external heating means such as electrical resistance colls or gas burners. The still is evacuated through conduits 5 and 38. When a high vacuum has been produced, shaft |2 is caused to rotate at a high speed usually above 1000 R. P. M. The hot fluid 32 is drawn up the surface of plate 28 by centrifugal force and fills the space between plate 28 and plate 28. It is returned through the space formed between

plates

28 and 28. In this manner the rotation of the entire assembly is caused to heat plate 24 to any desired distillation temperature. Material to be distilled and preferably in a degassed condition is introduced through conduit 31 on to the upper rotating surface of cone-shaped disk 22. The material is thrown by centrifugal force to the periphery of disk 22 and is shot into annular gutter 8. T'he material drains into conduit and is conveyed to the central portion of plate 24. On falling onto the upper surface of plate 24 the liquid is shot by centrifugal force to the periphery and into gutter 8. The temperature of plate 24 is so regulated that the desired amount of distillation takes place during the short period of travel over its surface, complete distillation in the short time being a result of the extreme thinness of the film and/or high degree of turbulence. Molecules distilling from'the surface of 24 travel to the surface of cone-shaped disk 22. The condensate .is thrown by centrifugal force to the projection 38 and is shot into collar-shaped disk 30 and travels upon the surface thereof and is thrown into gutter 'I and withdrawn through conduit 8. Small amounts of condensate which are not thrown from th disk at 38 are eliminated at projection 38 and are likewise thrown into gutter 1. By introducing the material to be distilled onto the upper surface of disk 22 the distillant is caused to maintain the condensing surface at a suitable low temperature. Since convection of heat in a high vacuum is very low this troublesome difiiculty of cooling is overcome in a simple manner. 'I'he false roof 38 formed of a disk-shaped 2,2io,eaa on the surface of plate plate rigidly mounted on shaft |2 serves to throw any condensate dripping from the walls and top of the still onto the horizontal walls of the still casing down which it flows into gutter 8.

operation employing the apparatus of Fig. 2, the vacuum pumps connected to

conduits

81, 88, 88 and |00 are put into operation and a vacuum of the proper value produced and maintained in the still. Shaft 81 is caused to rotate at a suitable high rate and heating unit 83 is brought to a suitable elevated temperature. Material to be distilled is forced through tube 82 and is sprayed in heated condition on/the upper surface of disk by the flared distributing head 88. The heated distilland is shot by centrifugal force in the form of a curtain or sheet of droplets into gutter 82. The dotted lines indicating the path of travel. Material evaporating from the sheet or curtain is condensed on

plates

88 and 8|. The condensate is thrown by centrifugal force into gutters 8| and 83 and is withdrawn through

conduits

84 and 86. The upper surface of condensing plate 88 and the lower surface of condensing plate 8| are blackened in order to increase radiation and thus help to maintain the disks at a suitable condensing temperature. This heat is dissipated by radiation to the top 10 and base 1| of the still which are jacketed as shown for the circulation of cooling `'fiuid by introduction through

conduits

12 and 13` and withdrawal through

conduits

14 and 15. If desired, these disks can be cooled by a cooling fluid in the manner described in connection with Fig. 1. The material to be distilled is introduced through the capillary tube 92 in such a way that it is raised to distillation temperature during its path of travel through the heating element 83. The heater 83 is at such a temperature that with the particular rate selected the material is brought to distillation temperature. The length of the capillary tube, the diameter and the rate of flow can all be adjusted to give practically instantaneous heatingto distillation temperature and the material can then be immediately disposed on the plate 80, the heating and distillation taking place if desired in less than a small fraction of a second.

The heating and cooling fiuids used in the apparatus of Figs. 1 and 2 must have a sufliciently low vapor pressure at the temperature at which they are used that they will not give off vapors and thus destroy the vacuum in the still or pollute the distillate and distilland. The selection of materials for this purpose obviously depends upon the vacuum used and the temperature which they have during their passage through the still. For high vacuum work, such as for instance at pressures below .1 of a mm., materials such as vegetable and animal oils, non-volatile hydrocarbon fractions, phthalate esters, etc., have been found to be very suitable. Speeds of rotation may be varied greatly depending upon the size of the apparatus and the material distilled. For most purposes speeds of 500 to 10,000 R. P. M. will be found to be suitable.

Many changes can be made in the above described apparatus without departing from the spirit or scope of my inventiori. For instance, it is possible to employ any number of condensing and evaporating disks in one still unit and such procedure would usually be preferable in large commercial installations. In the apparatus of Fig. 2, heating may be brought about by heating the disk 80 instead of preheating the material before introduction on the disk. In this manner the short space of time elapsing between the heating and actual distillation is eliminated. It is, of course, apparent that many stills can be connected in series and different fractions removed in each still or, if desired, incomplete distillation in one still can be made complete in a subsequent still when it is at substantially the same temperature. t

The distance between the vaporizing and condensing surfaces can be varied considerably as described in my copending application 64,178 filed 2/ 15/36. The'only important requirement is that the vaporizing and condensing surfaces be separated by substantially unobstructed space so that the passage of vapors, from the vaporizing to the condensing surface is not substantially interfered with. Obstructions which materially prevent this passage, cause the pressure in the still to rise and greatly increase thermal decomposition. In many cases the effect is to completely prevent distillation. Obstructions which are of small extent or which are arranged so as not to substantially interfere in this passage are not harmful. Distances of less than 12 inches and especially less than six inches such as 1/2 to 3 inches in general give best results. However it is to be understood that my'invention is not restricted to these preferred examples.

The apparatus described herein is of particular value for use in the high vacuum distillation of organic substances which are relatively non volatile and/or thermally unstable. The pressure during distillation should be maintained at a low value to avoid thermal decomposition and should generally be below approximately 1 mm. such as for instance pressures of .1 mm. to .0001 mm.

Temperatures to be used vary according to lthe material to be distilled and the amount of impurities present. With vitamins temperatures between 70 and 300 C. can be used although those between 100 and 250 C. are most generally employed.

While my invention is of particular value in distilling vitamins from vegetable and animal oils such ascod and halibut liver, tuna, menhaden, etc. fish oils, it is applicable to the distilw lation of difiicultly volatilizable, heat labile organic compounds in general. Thus it may be employed to distill hormones, sterols, sterol derivatives, enzymes, animal and vegetable oils, highly unsaturated glycerides, etc. which are easily decomposed by heating to an elevated temperature. Normally solid materials can be distilled by melting or by dissolving in a low vapor pressure liquid solvent in the manner described in my co-pending application 64,178 referred to above.

I have found when distilling under these conditions, that for every elevation in temperature of. about C. the distillation rate is doubled. It has been impossible to take advantage of this discovery using prior known distillation methods, because using a higher temperature would greatly increase the rate of decomposition. However by Operating in accordance' with my lnvention these higher temperatures can be used without increasing decomposition. This result being due to the practically instantaneous vaporizatlon which results by Operating in the manner described. My discovery in fact makes it possible to distill materials at temperature above what has previously been considered to be their decomposition temperature. Most decompositlonrrtemperatures have been determined by static methods which involved heating a body of 'the material over a space of time. However this value is entitled to consideration in most cases only if the period of heating is also given. If the heating period were less than a minute, to a fraction of a second as it is in my process, the value would have been found to be much higher. The heating periods described herein are intended to define the time of heating, i. e. the interval between the time that the distilland is fed onto the distilling surface and the time that the .undistilled residue leaves the edge thereof.

Non-volatile, easily decomposable substances which could not be distilled without decomposition can be separated with ease employing the principles of my invention. For instance it has not been commercially feasible or possible to separate the high boiling form of Vitamin D (dis-v closed in my copending application Serial NoV 99,631, filed September 5, 1936) from fish oils by 0 conventional methods of molecular distillation. This is due to its high boiling point and extreme thermal'instability. In order to separate the material without undue decomposition it is necessary to have a heating period of less than -30 seconds at 240-220 C. Distillation within this short period with commercial gravity flow methods is impossible. However by Operating as'described above distillation can be efiected with ease in that length of time and in many cases in a second or less where the expedient .of high temperature distillation is used.

This application is a division of my application 99,632 filed September 5, 1936.

' What I claim is:

1. Centrifugal high 'vacuum distillation apparatus characterized by a rotatable vaporizing surface, means for introducing distilland onto, and means for removing undistilled residue from the vaporizing surface, a condensingsurface lo- V cated within the still so that it is separated from the vaporizing surface by substantially unobstructed space, means for cooling distilling vapors so that they are condensed upon the condensing surface, and means for removing condensate from the condensing surface.

2. Centrifugal high vacuum distillation apparatus characterized by an approximately circular vaporizing surface which is adapted to be rotated about its central axis, means for introducing distilland onto the central portion of the vaporizing surface, means for removing undistilled residue from the periphery of the vaporizing surface, a condensing surface located within the still so that it is separated from the vaporizing surface by substantially unobstructed space, means for cooling distilling vapors so that they will be condensed on the condensing surface and means for removing condensate from the condensing surface.

3. Centrifugal high vacuum 'distillation apparatus characterized by a rotatable vaporizing surface, means for introducing distilland onto the vaporimng surface, means for removing undistilled residue from the vaporizjng surface. a rotatable condensing surface located within the still so that itis separated from the vaporizing surface by substantially unobstructed space, means for cooling distilling vapors so that they are condensed upon the condensing surface, and means for collecting condensate from the condensing surface during rotatlon thereof.

KENNETH C. D. HICKMIAN.