US2575051A - Process for purifying oil by distillation - Google Patents

Description

1951 c. J. EGGER ETAL PROCESS FQR PURIFYING OIL BY DISTILLATION 2 SHEETS-Sl-IEET 1 Filed July 9, 1945 I N VEN TORS MT- Wmw ,QAMJLM- M M Nov. 13, 1951 Filed July 9, 1945 C. J. EGGER ET AL PROCESS FOR PURIFYING OIL BY DISTILLATION 2 SHEETSSHEET 2 m? BYWH- 1N VEN TORS "d lation "a d p-s ce nequipment f for carrying out "the processes, have Patented Nov. 13, 1951 UNITED :STIAT ES PATENT OF success :FQIR mrrrmo some) .DIS MI QN Charles J. *Egger and Robert H. 'Webster, Gleveland, Ohio"; assignors to The Buokeye Laborae tories Corporation, a corporation .ofJOhio .JippiicationJuljB, 194'5,"Sei'ial'No. 603,856 7 I l claim.

Qu i vent on rel e ineen ra it d t l I and v more 'p;articu1arly to apparatus and process for separating iiuids of divergent "boiling points.

.iIn recent ear he as e velopment of 'iiaslh-distillation and allied processes "for handling easily decomposable fiuid in Processes, and

bss l tieve qp d' ee hw rsi c ur as recovering of hy-prodrsct organic compound; cleaning-'andrecovery ofused and contaminated oils as lubricating "and rol-lingoils; and the dehydrating and d egasifying of fluids. *-Manyof these processesand the eguipment for the proc- -esseshhave operatedwith only apart o'ff-the system employing -the-fiash-disti1lation principle while others were directed almost in-their-en- -tirety to t-he "flash-distillation principle. Further, although at first analysis they=may appear quite similan-two wide 1y divergent principles are followed in operating various-types of flash-distillation equipment. First of these,=is--theprocess which attempts 1:0 vaporize all but the extremely high :boiling point :constituents and sol-i'dsf Ihis process -=attempts--to turn I all --of the fluids enteri-ng the still into gases l for subsequent .selective condensation. In this type-of equip- .mentiand-sprocess, the gases leaving ithe still are .generally :.strained :through a ;.scrubbing :medium of .loose materials in order :to :retain .:.any entrained solid matter and aunvaporized heavy liquid material. i- I he second method, isto apply only enough heat to vaporize unwanted constituents and permit -the remaining constituents to be removed fromthe still as a liquid.

Itis-the second mode of-operation to which-our invention relates. In the past, many' -attempts have been made to se parate fluids of Widely diavergent boiling points'by pumping them at fa .high pressure into a low pressure zone and atomizing the fluids-in order that a maximum :amount ofasurfacearea might bespresented to the infiuence ofthelow pressure zone, and thereby =.thr ow the more volatile f constituent into gaseous phase and thus be removed from the higher boiling point constituents. =-Hdwever, fit

is always found that a considerable"percentagepf "the "material desired to 'be separated out was alway found t fin she r osiu t whe us n the-standard equipment -for this process.

After id r blezsiud a deve menthwe have discovered: that he weakness of the present k QthPQ hQs QI the ia u i resq riiz "t n d IfQ- im yi g 321. extreme 331156 amount of sensibleheatabsorbed"by liquid ma- 'terials-when volatilized 'cally as the heat of vaporization. a found, thatthe amountof heat absorbed loythe -constituentsheing volatilized is so great-that fthe rne ii9 .Fi flui s 91 ,isl versn tor the removal of contaminants f 2 i h and expanded. Thefheat absorbed 'by the volatilization is known techni- 'We have temperature within the still was oftentimesfre- 'duced to 'a' temperature insufiicient to --cause v olatilization of the incoming impurities. Therefor, these impurities remain with the treated materials leaving the still. Further, it

has been found that after 'a-tomizing the contaminated or mixed materialja complete separatio n has "not loeen 5 accomplished by the *time the spray is recollected; and therefore requires a longer exposure to the" ifeduced pressure of the still. However, while beingiurther exposed to the reduced pressure area, 'the newsman be maintained at a high temperature lever iri'order tooontinue to supply the latent l eat'of 'i'apori- "z'ation required for 7 the remaining volatile constituents." That is, if the atomized fluids are allowed to contact a cold-surface,'orreturnover cold surf-aces to-asumpfor collection, "the volatilecons'tituent's 'haveno chance to volatilize "and therefor remain with the tre'ated materials; We have-found that-inorder toeffeta complete and satisfactory separation of these volatile inaterials from 4 the less volatile materials, the distillation zone into which the materials areato'rnized, must be maintained at substantially the same'temperaturelevel at allftimes, and the walls of the ohaniber, andcther surfaces which'the fiuids'might strikeor touch -must also be maintaine'd at-substantially the -same constant' te'r'n- "perature.

Also, we have discovered that in separating YTlier Q m pom; Q l fi isf t g t ro v .aproces Lfq th Subs ntiall ther object of Q "additional *heat "to Mia/mussrleated conglomeration of fluids of divergent boiling points while being distilled at sub-atmospheric pressures and while in the finely dispersed state to obtain complete vaporization of all the volatile components of the conglomeration desired to be removed, and to prevent condensation of the vaporized volatile components within the distillation chamber.

Another object of our invention is the provision of spray atomizing a conglomeration of fluids of divergent boiling points into a sub-atmospheric pressure chamber and thereafter interrupting the spray by means of a fluid film exposing device capable of collecting the atomized spray and dispersing same over a multitude of tortuous path surfaces to increase the length of time which the conglomeration of materials is exposed to the action of the sub-atmospheric pressure.

Another object of our invention is the provision of supplying heat of vaporization and thermal energy of expansion by direct heat to the vaporization area in which the expansion is carried out.

Another object of our invention is to provide a-process and apparatus for isothermal flashdistillation to separate a conglomeration of materials of divergent boiling points.

Other objects and a fuller understanding of our invention may be had by referring to the following description and claim taken in conjunction with the accompanying drawings, in which;

Figure 1 is a cross-sectional view taken along the line I-l of Figure 2;

Figure 2 is a longitudinal cross-sectional view taken along the line 22 of Figure l;

Figure 3 is a cross-sectional view taken along the line 33 of Figure 4; and

Figure 4 is a longitudinal cross-sectional view taken along the line 44 of Figure 3.

To achieve a separation of fluids of divergent boiling points mixed together in a conglomeration, such for example, as fluid dissolved in fluid,

, gases dissolved in fluid, and mixtures of fluid, or -any combination or combinations of the aforesaid types, it is necessary to use some convenient form of distillation, and all known methods of commercial treatment contemplate the use of this type of physical action. Many means have been devised to accomplish this separation rapidly, completely, and effectively, but all have comprehended the separation being done by distillation of considerable quantities of the conglomeration. Conesquently, an appreciable time interval elapses between the introduction of heat and pressure change, and the completion of the removal of the volatile portion. Also, to accomplish final removal of the last traces of the vola- .tile portion from a quantity of the original conglomeration, thermal energy is applied at an increasing rate. While this is being done, conditions exist in the conglomeration frequently favorable to breaking down some of the desirable constituents, with formation of additional undesirableconstituents and products of lower molecular weights. These break-down products are of lower boiling points, usually sufficient in degree ing mixtures will frequently cause the final product to be considered not totally satisfactory in regard to desirable physical characteristics.

If, however, a comparatively small amount of the conglomeration be subjected to a distillation process at sub-atmospheric pressure, and if this quantity be extended to present the greatest possible surface to this sub-atmospheric action, it is found that the separation is achieved with a degree of completeness not previously possible, and in a period of time which does not permit any observable degradation of the desirable constituent of the conglomeration. In order to present maximum surface, it is necessary either to present a continuous film of negligible thickness, or to disperse the conglomeration in exceedingly fine globules. The existence of either of these forms must exist for a period of time sufiicient to assure the separation of the lower boiling point constituents from the higher boiling point constituents of the conglomeration. From the standpoint of control of operating conditions, it has been found to be more satisfactory to present discreet globular particles to the combined action of heat and reduced pressure, than to extend a continuous film, only one surface of which can be presented to the sub-atmospheric pressures and spaces.

One of the features of our invention is the provision of heat for the walls of the chamber independently of theheating of the conglomeration to be treated. For example, we have found that if the conglomeration is first raised to a temperature sufliciently high to assure enough heat energy for the heat of vaporization for the volatile portion, it is entirely possible that the volatilization of the more volatile constituents by distillation will be practically complete even though the vaporization is carried out in a chamber that is not supplied with our improved heated wall condition. If however, the vaporized portions have occasion to come in contact with the walls of the chamber which are at a much lower temperature, condensation occurs on the walls and an appreciable amount of the volatile constituents will flow down the sides of the chamber and combine with the less volatile constituents which have been freed from the more ,volatile constituents by the fractional distillation which has already occurred. The final result is therefor that the volatile portions are removed from the conglomeration being treated, and subsequently reincorporated to some degree.

We have found that by maintaining the walls of the chamber in the area of the spray and evaporation, and preferably by maintaining all of the walls of the chamber at an elevated temperature, we have contributed substantially to the efliciency of the process. We have found that the walls of the chamber should be maintained substantially equal to, or slightly above, the temperature of the conglomeration of fluids at the point of introduction into the chamber. By maintaining the walls at atemperature as thus described, we have fulfilled two conditions necessary for successful operation. In the first place, for successful operation, there must be no flow of heat from the conglomeration, or from the vaporized volatile portion, to the wall. To allow such flow of heat would result in condensation of the volatilized portion with the result that the vaporized portion would be returned to the treated material. Secondly, because a large amount of heat is required to supply energy for expansion of the conglomeration within the chamber and to supply the latent heat of vaporization for the removal of the volatile portion,

fore entering into the chamber. original conglomeration may be heated to a react on supplying additional heat through the walls'of the chamber to the conglomeration attheapoint .of the spraying and the volatilization reduces the need for heating theoriginal conglomeration to an unduly high temperature in an effort to supply the heat directly to the conglomeration be- That is, the

vthe chamber as it is required.

Our invention comprehends the application of the principles explained in a manner whichis;

eflicient and economical. The preferred apparatus employed is shown in the drawings andthe process will be understood when reference is made to them while the'oper'ationis explained.

As will be seen, the reguisites for carrying out our process employ a means of supplying the conglomeration through a supply line 14. The conglomeration is pre-heated by passing through a heat exchanger l and is placed under a relatively high pressure by a pump I6. The conglomeration then progresses to a heater H which may be conveniently heated by electrical heating elements of any suitable design, or by steam or other suitable devices if desired. The conglomeration is then introduced into an evacuated expansion chamber II byspray atomizing the same through a spray nozzle It whereby it is dispersed into exceedingly fine globular particles projected into the space enclosed by the chamber II. The chamber ii is maintained at sub-atmospheric pressure by means of a vacuum pump Hi. It is desirable in many applications to use a condenser as illustrated connected between the chamber l and the vacuum pump H in order to condense the volatilized portions of the conglomeration which are carried off by the action of the vacuum pump 29. 1

The chamber H is surrounded by an insulated housing IE to provide an air space 12 which may be heated to any suitable desirable temperature by heater meanssuch as heater rods IS. The heater rods 13 may be connected to any suitable electrical outlet and they warm the air in the space I2 and thus maintain the walls of the chamber H at a temperature at least as high ized material is indicated by the reference character 29 and is so directed by the sprayino'zzle Is that it impingesagainst a fluid=:s'urface .exposingdevice 22 where the atomizedmater'ial .collectedtas a thin. film and is 'outwardly dispersed to collect in a collecting gutter 25. The collecting gutter 25 is perforated at its lower edge as illustrated by the reference character 26 in the Figure 1. .-.The fluid material thus collected in the gutter 25 may drip freely through the openings 25 and drip downwardly in a direction countercurrent to the direction of the spray 29 and is intercepted in the lower portion of the chamber II by a baffle arrangement 28. The baflle arrangement 28 permits the returning components to flow in a thin film surface for an extended period of time as it progresses to the lower level of expansion chamber II which will serve as a fluid sump. The treated components are removed from the chamber I I through a conduit 33 and passed through the heat exchanger [5 ai relatively low sub-atmospheric pressure, and

fluid deposited -upon. a .surface.

where the sensible Zheat soontained therein i'is -transferredrto a'o'ertain extent to the incoming 'iconglomeration ias previously described. The treatewmaterials' may be maintained at :.a scon- -stant level in the sump :p'o'rtion of "the :chamber l l (by means of a constant level cap 32 .positioned atthe intakeend of the conduit-3,3.

The cap 32 thus maintains a-constant level the sump portion of thecchamber .l l to seal the conduit .33 from the action of arvacuum withinzthe cham- -ber *H, but affords immediate removal of ithe .excess materialfromithe chamber *1.

Lhu's, no accumulation is present beyond theidesired: seal- =-ingi level at any-time inithe chamber *H ItoidecreaseL-its defective sspace'or capacity. The rprocessma-y bezcarried outxcontinu'ously without interrupti'on, and "tests show that ''the process -a-n'd equipmentwafford substantially a complete separatiomas desired.

.It ;-is :of course understood, that "theJgreatest amoun't ofsurface maybe obtained-in a fluid material'by sprayatoniizingithe material rather than providing a thin film-surface. However, 'achamber'suitable for spray atomizing a liquid from .a relatively high pressure into the chamber held at which would be large enough to'permit the :spray to ascend as far as possible-without striking -.any surface; would be unduly large and impractical.

Therefor, the fluid surface exposing device 22 is employed, against which the spray 29 may impinge andibe interrupted in its upward direction. In our apparatus, "this devicel'2'2, we have found, produces the. greatest amount of surface area for The device 22 comprisestwoscreen holders 24 positioned one above'the other andcontaining a 'multitudezof small particles :such as raschig rings, beryl saddlesyglass beads,.or other loose materials in- :cluding; glass wool, mineral-wool and steel wool. The device 22 is substantially cone' shaped'with itsvapexcextending upwardly in the 'center and theside descending therefromtowards the gutter 25. .Thus, the spray 29impingesagainst the .device 22 and is there interrupted in its upward 7 path of travel by the multitude of .smallparticles -23. The fluid. portion of theconglomeration is thus collected upon the surface of the particles 23 andvis continuously moved from one particle to the :other "outwardly and downwardly :by the forceof theoncoming spray 29. During the time when .the fluid portion of the conglomeration is thus deposited upon the-surface of theyparticles 23, it is in a very thin 'film stage and is :continuously exposed to the action 'Idf the vacuum within the chamber l l Thus, any small amount of material to be volatilized which has not already been removed during theatomized state between the nozzle l8 and the fluid surface exposing device 22, will be given an opportunity to volatilize and escape. Also, the small particles 23 provide a ready path for the volatilized constituents to pass therethrough and be exhausted through the condenser 20 and vacuum pump l9. Further, the remaining fluid portion which is collected in the trough 25 and allowed to drip countercurrently to the spray 29 as described, is further exposed for a period of time to the action of the vacuum within the chamber ll while running over the baflle device 28 to the fluid pump portion of the chamber ll.

Another suitable apparatus to carry out the process is illustrated in the Figures 3 and 4 of the drawing, and comprises a vacuum chamber 35 of substantially cone shaped cross-section.

Thus, the remaining liquid components of the original contaminated material are returned to the sump portion of the chamber 35 by running in a thin surface area from the openings 26 of the trough 25 along the tapering heated surfaces of the cone shaped chamber 35. Thus, it will be seen, that the cone shaped chamber 35 replaces and eliminates the need for the baflle means 28. In fact, the cone shaped chamber 35 provides a warm surface upon which the returning fluid may flow in order to assure a supply of sensible heat to cause complete volatilization of the volatile impurities.

In both the straight and the cone shaped devices, we usually provide at least'one vision port 3| in order that the operator may visually inspect the condition existing within the chamber.

The process and apparatus described herein has not been limited to any specific fluid or conglomeration of fluids, because we have found that the device and process is equally successful with a large number of various fluids. For example, this process and equipment has been used successfully for restoring various contaminated oils such as heat transfer oil used for quenching purposes in hardening of steel, electrical insulating oil, engine oil, lubricating oil for vacuum pumps and the like, refrigerator lubricating oils, for degasifying beverage Waters, and for degasifying and dehydrating various fluids. That is, the process and equipment is equally successful for removing undesirable constituents, for dehydrating, and for degasifying. Also, it has been found that each fluid treated requires a different temperature, pressure, and vacuum. Thus, whereas one fluid may require a relatively high preheat temperature, another fluid may actually require refrigeration before being atomized within the expansion chamber. In all cases, however, the walls of the expansion chambers are easily adjusted in temperature to maintain them at exactly the proper temperature to conduct sensible heat therethrough to'maintain the interior of the chamber at exactly the desirable degree of temperature while in operation.

Although we have described our invention with a certain degree of particularity in its preferred form, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is: Process for fractionally separating 'contaminating materials of unlike boiling points in oils, comprising the steps of preheating a conglomeration of oil having said materials to an elevated temperature, providing a chamber having side I walls'and top and bottom end walls sealed vacuum'tight, and having a fluid surface exposing means near the top end wall of the chamber, evacuating said chamber to a sub-atmospheric pressure by withdrawing vapors from the area of the chamber between the said fluid surface exposing means and the top end wall, said elevated preheat temperature being sufficiently high toj'vaporize at said sub-atmospheric pressure the highest boiling point material to be removed, but said temperature being below the vaporization and decomposition temperature at said sub-atmospheric pressure of the oil to be retained as a liquid, spray atomizing said preheated conglomeration in said chamber from a position near the bottom end of the chamber in an upward direction toward said fluid surface exposing means and Y simultaneously supplying sensible heat through said side wall of said chamber, said sensible heat being suflicient in value to maintain the side wall of said chamber at a tempera ture at least as high as the boiling point within the chamber of the highest boiling point constituent to be removed to prevent condensation thereof, and being sufficient in value to supply the heat of vaporization absorbed by volatilization of the constituents to be removed, which sensible heat value together with the heat units in the heated oil itself provide full separation of the contaminants from the oil without overheating and destroying the oil, intercepting the remaining liquid oil portion of said conglomeration on said fluid surface exposing means, said intercepted liquid oil portion thereby being exposed to the action of said sub-atmospheric pressure and to said sensible heat for a period of time as a thin film upon the fluid surface exposing means, returning the intercepted liquid oil by gravity in a countercurrent direction to the original spray direction to the bottom end of the chamber, and withdrawing from the chamber the collected liquid oil in the bottom of the chamber.

CHARLES J. EGGER. ROBERT H. WEBSTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,824,498 Rodman Sept. 22, 1931 1,836,338 Rodman Dec. 15, 1931 1,951,739 Rodman Mar. 20, 1934 2,278,543 French Apr. 7, 1942 2,332,215 French Oct. 19, 1943 2,357,829 Ittner Sept. 12, 1944

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