US2224621A

US2224621A - High vacuum distillation

Info

Publication number: US2224621A
Application number: US214682A
Authority: US
Inventors: Voorhees Vanderveer
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1938-06-20
Filing date: 1938-06-20
Publication date: 1940-12-10
Anticipated expiration: 1957-12-10

Description

Dec. 10, A1940. V, VOORHEES 2,224,621

HIGH VACUUM DISTILLATION Filed June 20, 1958 To Vacuunz B ATTORNEY Patented Dec. 10, v1940 HIGH VACUUM DISTILLATION Vanderveer Voorhees, Hammond, Ind., alsignor to Standard Oil Company, Chicago, lll., a corporation of Indiana Application June 20, 1938, Serial N0. 214,682

19 Claims.

This invention relates to a process and apparatus for distilling oils, and particularly for distilling heavy high boiling petroleum oils and lubricating oils. One object of the invention is to distill high boiling substances under high vacuum without decomposition. Another object is to distill high boiling substances under so-called mo' lecular distillation conditions without ebullition and without entrainment and contamination of the distillate bythe undistilled oil. Still another object of the invention is to provide ameans for Refemngto the drawing, Figure 1', a. sneu It is connected to an exhausting vacuum pump or pumps not shown by means of largevacuum connections II and- I2. Alternative or supplementary connections to the exhausting means may be made on other parts of the shell, for example to the sides thereof. Within the gas tight shell I is located stationary condenser element I3 suitably formed of a perforated cylinder provided with a cooling coil I4 in heat conductive contact therewith. The cooling coil, for example, may be aQPPel' tube spiral soldered to the interior surface of the condenser cylinder. The surface I5 of the condenser I3 is provided with openings I6 to permit free passage of gases and liquids from the exterior to the interior thereof. Collector bafiies I1 and I8 serve to direct liquid condensate away from the interior surface of the condenser and into the receiving funnel I9 whence the liquids ilow by line 20 to suitable receiver not shown. Connections 2| and 22 serve to supply cold water, oil, brine or other-suitable cooling fluid to the coil` I 4. The direction lof ow of the cooling fluid may be either to the top of the condenser or to the bottom.

Surrounding condenser I3 is evaporator 23 which is 1supported by spider V24 and bearing 25 providing for free rotation about its axis. Power for rotating cylinder 23 is provided' by motor 26 through the geared pulley 2l and belted pulley 28. Obviously, various other means may be employed for providing rotation. In the arrangement shown a packing gland 29 prevents ingress of air through the shell I0 to the evacuated space within, although I may'mount the motor inside casing I0 and 'thusavoid any possibility of air leakage whatever.

Heat is -supplied to thesurface of'evaporator 23 preferably by electrical induction heater or electrical resistance winding, the latter being illustrated in the drawing. A current of electricity supplied by lead wires 30 and 3l passes through the shell III by'

insulated conductors

32 and 33.

Brushes

34 and 35 bearing on suitable collector rings 36 and 3l conduct the electric current to resistance winding I8 which is suitably disposed along the outer surface of evaporating cylinder 22 to provide the heat necessary for distilling oil or other liquid on the interior surface thereof. Additional electrical connections may be provided to facilitate regulation of the heat supplied to evaporator 23. Thus separate coils may be provided at intervals along the surface of the evaporator to separately control thetemperature in different sections as indicated by suitable temperature indicating means notshown. Thus the temperature may be graduallyincreased as one progresses from the upper end 20 to the lower end of the evaporator 23 or,if desired, the temperature may be held substantially constant throughout.

The oil to be distilled is supplied by line 39,

- controlled by valve 4l leading to preheater chamber 4I. The oil may be preheated in chamber 4I by heating element 42 to a suitable temperature well below its decomposition pointffor example 500 to 650 F. in the case of heavy mineral oils. Any vapors evolved from the oil in the preheater 4I are exhausted by line 43 connected to a vacuum pump not shown. It is preferred to exhaust the preheater 4I to a pressure as low as that within the shell I0. A From .4I the oil flows by line 44 to sight vfeed 45 and thence by line 46 to'the upper en'd of evaporator 23. The oil is suitably introduced into the evaporator by allowing it to iiow into channel member 4l where-it collects by virtue of the action of the centrifugal force resulting from the rotation of evaporator 23 hereinbefore mentioned. From channel 41 the oil flows in a uniformly thin iilm downward over the inner surface of evaporator 23, finally passing out at the bottom over lip 43. Trough 43 collects the residual oil from which it is conducted by outlet line III.

' Various other means may be employed for supporting the evaporating and condensing surfaces 23 and I4.l For example, in Figure 2 the hollow 50 stationary shaft 80 supports condensing surface 6I by spiders, and evaporating suace I3 is rotated thereabout on bearings 64 and Il. Cooling water for the -condenser is supplied through the hollow shaft 80 entering at one end and passing by connection l0 to coil l1 and thence by connection 63 to the supporting shaft Il and out at the other end.

, Referring again to Figure 1 the inner surface of the revolving evaporator 2l is preferably pol- U rosion resistant alloy, such as stainless steel.

'I'he exterior surface-I5 of the condenser I3 is likewise preferably polished to prevent absorption of radiant heat. The surface of the evaporator 23 may be truly cylindrical throughout its length or, if desired, it may be slightly conical with the apex in eitherV direction, but preferably toward the top, thus providing more rapid flow of liquid downward along the surface. In that caseLthe condenser I3 should likewise be conical to correspond therewith. v

'I'he distance separating the condensing surface I5 from the evaporating surface 23 is preferably very short, in order to provide a minimum distance for evaporated oil molecules to travel from the heated surface to the cold condensing element 23 of my vacuum distillation'apparatus surface. It is preferred to adjust the surfaces so that the distances between the evaporator and condenser approximate the mean free path of the oil molecules under the conditions of temperature and pressure prevailing. However, much larger distances may be employed, for example, up to fifty or even one hundred times the mean free path of the molecules. Thus, distances of 0.05 to 0.4 inch are contemplated.

It is not necessary to rotate the evaporating at veryt high speeds in order to maintain a uniform lm of oil on the interior surface thereof.

For example, I may operate with speeds of only 200 to 600 revolutions per minute. At such speeds of rotation the oil is distributed'in a uniform film over the inner surface making it possible to adjust the space between the evaporator and the condenser very closely and accurately without contamination of the distillate on the condenseroccurring as a result of physical contact between irregularities on the distilling surface. The rotating motion also serves to provide agitation of the oil, thus exposing continually new' illm surface to evaporation. ,l

Gases dissolved in the oil and any-vaporous decompositionproduct.thereof Awhich may be liberated at the distunng surface andy s ready l may be employed, asuitablepressure for most purposes being 0.01 mm. of mercury. One of the important advantages of my vacuum stillation apparatus lies inthe equalization of pressure therein by use of unobstructed gas passages from evaporatingsurface to vacuum pump, thus providing substantially the same pressure at the evaporating surface as atthe vacuum pump.

If desired, I may rotate the evaporating element of-my apparatus at sufficient speed to build up by centrifugal action, increased pressure within the oil film adjacent the surface of the evaporator 23 thus retarding ebullition of the oil and permitting the use of somewhat higher temperatures without entrainrnent dimculty. By this means the development of 'a vapor phase within the oil lm in contact with the metallic heating surface is avoided and superheating 'of the body of oil within the oil film, above its boiling point at the low pressure prevailing, is made possible. v

Although I have described my invention with respect to certain embodiments thereof lt should be understood that various modincations may be employed without departing from the spirit thereof. Thus I- may employ in a series two or more distillation units, as described, conducting theoll from one unit to the next to produces series of fractions of increasing molecular weight. I may 'also segregate the distillate from succeeding sections of the condenser in a single unit for the same purpose. JI'may charge the apparatus with crude oil residue, for example, a 40% residue from Pennsylvania or Mid-Continent crude oil. I may also apply my distillation process todistillation of'other materials, such as c oal tara, vegetableand animal oils, fats and waxes, foi' example, degras, olive oil, chaulmoogra oil, tung oil, etc. I may also apply my distillation method to the recovery of vitamines from various products, such as fish liver oils, e. g.,.menhaden,-c od,4 halibut liver oils, irradiated fats, etc. In general,

the method may be applied to the distillation of any liqueilable substances whose separation is desired without decomposition. The method is particularly valuable for the distillation of lubricating oils where loss of viscosity from decomposition is a serious objection to the use of ordinary.`distillation methds.

I claim: v- 1. The lprocess of distilling liquids under high vacuum without ebullition which comprises main- Ataining a cooled, substantially cylindrical, con.

densing surface positioned to Vpermit withdrawal of condensate and surrounding said condensing surface in close proximity thereto and concentric therewith, a heated, rotatable, substantially cylindrical, evaporating surface, introducing a stream of said liquid at a point on the interior of said evaporating surface, rotating said evaporating surface at a speed adapted to subject the liquid to a suicient centrifugal force to uniformly distribute it over the 'surfacethereoL collecting and withdrawing distillate from said condensing surface and discharging unevaporated liquid from said evaporating surface at a point remote from said point of introduction.

2. The process of claim 1 wherein said distillation is conducted under a. pressure of 0.1-to .00001 mm. mercury pressure. a

3. The process of claim 1 wherein the distillation is conducted under a low pressure of the order of .01 mm. mercury, gases evolved from said liquid undergoing distillation are permitted to pass through' openings in said cylindrical condensing surface leading to the interior thereof and thence are discharged from the end thereof.

4. The process of claim 1 wherein said liquid is a petroleum lubricating oil.

v5. The process of claim 1 wherein said liquid is an animal fat.

6. In a molecular distillation process wherein a nquld is disuned without bomng by maintaining'a heated surface thereof in close proximity .to a cooled, condensing surface at alow pressure lof the order of .0.01 mm. mercury, the improwe- -ment comprising distributing saidliquidon the interior surfaceof a heated'revolving cylinder, condensing the vapors on a cooled, condensing,

surface positioned to permit withdrawal of condensate and located within said revolving cylinder and in close proximity to the surface thereof and causing said cylinder to revolve at a rate of speed suicient to subject the said liquid retained therein to centrifugal force sumcient to retard ebullition of said liquid.

7. In a molecular still wherein a crude, liquid material is distributed over a heated, evaporating surface in closeproximity to a cooled, condensing surface, the improvement comprising a gas-tight shell, a connection leading from said shell to a gas exhausting means, a rotatable, heated, cylindrical, evaporating surface within said shell, a' cooled, cylindrical, condensing surface positioned to permit withdrawal of condensate and located within said evaporating surface and in close proximity thereto, means for rotating said evaporating surface, mean-s for introducing a stream of liquid onto said evaporating surface within the space between it and the said condensing surface, means for withdrawing unevaporated residue from said evaporating surface and means for withdrawing distillate from said condensing surface. f

8. A molecular still as described in claim 'Iv further characterirfied dn.' that the evaporating and condensing surfaces are vertical.

9. In a molecular still wherein a crude, liquid material is distributed over a heated, evaporating sufacein close proximity to a cooled, condensing surface, the improvement comprising a gas-tight shell, a connection leading from said lshell to a gas exhausting means, a rotatable,

heated, evaporating surface within said shell, a cooled, condensing surface positioned to permit withdrawal of condensate and located in close proximity to said evaporating surface and nearer to the axis of rotation of the evaporating surface than is the evaporating surface itself, means for 'rotating said evaporating surface, means for introducing a liquid onto said evaporating surface -within the space between it and said condensing surface, means for discharging unevaporated residue from said evaporating surface and means for collecting and withdrawing distillate from said condensing surface. i

10. The apparatus of claim 9 wherein means are provided for heating said liquid at a low pressure on the order of .01 mm. mercury before i11- troducing it onto said evaporating surface and means for maintaining a pressure 'within said shell of the order of .01 mm.

11. The apparatus of claim 9 wherein said evaporating surface is heated by electrical means.

v12. In a molecular still wherein a crude liquid material is distributed over a heated, evaporating surface in close proximity to a cooled, condensing surface, the improvement comprising a cylindrical, gas-tight shell, a substantially cylindrical, rotatable, heated, evaporating surface within said shell, a substantially cylindrical condenser providing a cooled, condensing surface positioned to permit withdrawal of condensate and located within said evaporating surface, means for introducing a. liquid onto said evaporating surface be- .01 mm. mercury.

gases from said evaporatinir surface through said condensing surface thence through the end of said cylindrical condenser and through said gastight shell to said gas exhausting means.

13. In a molecular distillation process wherein a liquid is distilled from an evaporating surface to a condensing surface without ebullition, the improvement which comprises maintaining the evaporating liquid under a centrifugal pressure in a direction away from .the condensing surface.

14. The process of claim 13 wherein said distillation is conducted under. a pressure of 0.1 to .00001 mm. mercury pressure.

15. The process of claim 13 is a petroleum lubricating oil.

wherein said liquid 16. The process of distilling liquids under high f vacuum without ebullition which comprises inheated, evaporating surface which is in close proximity to a cooled, condensing surface posi- 'tioned to permit withdrawal of condensate and located so that a centrifugal force produced by rotation of the evaporating surface operates in a direction away from said condensing surface, maintaining the space between the said surfaces under a' high vacuum, rotating said evaporating surface at a speed adapted to subject the liquid to a sumcient, centrifugal force to uniformly distribute said liquid over the surface thereof, and collecting and withdrawing distillate from said condensing surface.

17. In a molecular still wherein a crude, liquid material is distributed over a heated, evaporating surface in close proximity to a cooled, condensing surface,'the` improvement comprising a gas-tight shell, a connection leading from said shell to a gas exhausting means, a rotatable, heated, cylindrical, evaporating surface within said shell, a cooled, cylindrical, condensing surface positioned to permit withdrawal of condensate and located within said evaporating surface and in close proximity thereto, means for rotating said evaporating surface, means for introducing a stream of liquid onto said evaporating surface within the space between it and the said condensing surface, and means for withdrawing distillate from said condensing surface.

18. In a molecular still wherein a crude liquid material is distributed over a heated, evaporating surface in close proximity to a cooled, condensing surface, the improvement comprising a gas-tight shell, a connection leading from said shell to a gas exhausting means, a rotatable, heated, evaporating surface within said shell, a cooled condensing surface positioned to permit Withdrawal vspace between it and said condensing surface,

and means for collecting and withdrawing distillate from said condensing surface.

19. ,The apparatus of claim 18 wherein means are provided for heating said liquid at a low pressure on the order of .01 mm. mercury before introducing it onto said evaporating surface and wherein means are also provided for maintaining a pressure withinl said shell of the order of VANDERVEER VOORHEES.