US1707448A - Process of distilling mineral oil - Google Patents

Description

April 2, 1929. A. E. PEw, JR 1,707,448 f PROCESS OF DISTILLNG MINERAL OIL Filed Dec. 22, 1926 /4 fra/iwf Vs.

Patented Apr.l 2, 1929.

uNrrEu STATES PATENT OFFICE.

" ARTHUR E. PEW`,.JR., oF BRYN MAWR, PENNSYLVANIA, AssIGNoR '.ro sUN on. com- PANY, or PHILADELPHIA, PENNSYLVANIA, A CORPORATION oF NEW JERSEY.

PROCESS 0F DISTIIIJIITNG MINBAL OIL.

Application illed December 22, 1926. Serial No. 156,289.

The use of steam in stills for distilling hydrocarbon mixtures, and particularly mineral oil, for the purpose of agitation and consequent turbulence, with lowered vapor tension due to the presence of the steam, has long been known andpracticed, both in stills operating at substantially atmospheric pressure and inLstills operating under vacuum. ,There are many plants today operating at quite high vacuums which use steam as a means for agitating the oil in the stills, thus preventing accumulation of dirt on the bottom sheets and incidentally lowering the boiling point of the oils by lowering the vapor tension. The turbulence.

obtained in a still by the use of steam materially increases the capacity of the still, since the heat transfer is much greater than when the still isrun dry,

However, it lias'long been thought that the use of steam" necessarily results in the overhead distillate 4being of inferior color as compared with such oils obtained in high vacuum distillation without the use of steam. In the course of my experimental work,l I distilled Various oils under vacuums ranging from 28 to 29 inches. In order to lower the boiling points of'the oil under thisvacuum and in order to get good agitations to prem vent burning and local overheating, steam was admitted beneath the surface of the oil.

, The steam was generated in a still under a vacuum slightly lower than the vacuum in the stilL This was necessary in -order to generate enough pressure in the steam still vto push steam through the oil in the oil still. The distillates thus obtained were of better quality than were obtained from the distillation of the same oil under a vacuum of from 3 to 4 mm. without the presence of steam. The reasons for this result I believe to be as follows:

The volume of one poundofsteam at atmospheric pressure is 26.79 cubic feet. The volume of one pound of steam at 28.5 inches of vacuum is 469 cubic feet. By the process of generating steam under vacuum, the steam has fully expanded, or substantially so, when it Venters the oil in the still.. This makes it necessary to use less steam than would be required in a still operating at atmospheric pressure with steam at ordinary pressure, the agitating effect of steam being largely volumetric. Steam could be admitted to the still from a line operating at. any pressure, but the instant the steam leaves the nozzles and is injected into the oil in the stills when such still is operating under high', vacuum, it is subject to the absolute pressure which is on the still, namely, a very high vacuum. The steam expands instantaneously according to the difference of pressure at the injector and that on the still. This rapidl expansion has a tendency to cause entrainment as the steam passes upward through the oil. This entrainment would have a bad effect on the color of the distillates. However, when steam is generated under substantially the same vacuum as is applied to the oil still, the steam is a1- relady expanded at the instant it hits the o1 As a matter of operatingeconomy, it is quite eiiicient to use steam generated under vacuum, since on all vacuum plants it is necessary to have a vacuum pump or steam ejector, and the exhaust steam from such apparatus can be used through coils in the boiler for the generation of steam under vacuum. For example,v the boilingv point of water at 27.3 inches ot' vacuum is only 110 F.,v whereas the temperature of steam at two pounds gauge pressure is 218 F., giving a difference in temperature of 108, which is ample for the transfer of heat from steam to water economically.

However, the reasons which have just been outlined do not fully explain the great benefit to be derived from the present process. Ordinary boiler feed Water contains from 1% to 4% ofl airby Volume. Air is 78% nitrogen by volume and approximately 21% oxygen, the balance vbein argon. ien such water is distilled an the steam used in any oil still, the air enters the hot oil along with the steam in more than suflicient quantities to cause substantial oxidation of the distillates. Evidence of this is comparatively poor color and noticeable acidity.

The fact that air in water causes corrosion is well known in boiler practice, corrosion being the result of oxidation. The last decribed operation ai'ords definite proof that the oxygen in the air does act as an oxidiz- #ing agent.

er methods. For example, advantage cany be taken of known laws of partial pressures by bubbling exhaust steam through the water in such quantities that the resultant tot-al pressure would be very great in proportion to the partial pressure due to the air in the water. By removing air from water by any suitable method, and then converting such air-free water into steam, and injectin the steam into a body of oil being ldistille under vacuum, distillates are obtained that are satisfactory as to color as well as to general quality. l

This last described process'v constitutes, broadly, my invention, although the process embodies other important features, which canbest be understood by an explanation of the apparatus shown in the accompanying drawing. Although the process is not de-4 pendent for its execution on any particular apparatus, that herein illustrated and described has been found eiiicient.

The ligure is a diagrammatic view of apparatus wherein my invention may be practice Water is pumped through line 8, at a temperature of ap roximately 120 F., into an evaporator tan 10. Here the water flows at hi h velocities and in turn films over incline plates 9. Tank 10`is maintained under a vacuum of (say) 28 inches. At 28 inches of vacuum, the boiling point of water is 100 F. and at 26.4 inches ofvacuum it is ,120 F. Hence, due to the vacuum in the Vthrough line 4 to brinev cooler 2. Cooled brine 1s pumped throu h tubes in this cooler, thereby extracting t e heat from .the water vapor and air, and thus condensing the y water. The air is sucked to a vacuum pump Water substantially free of air then ilowsf.

from the kbottom 'of evaporator 10 into line lthe feed Y 11 and lthence into boiler12. Difference in elevation between vaporizer 10 andfboile'r 12',` 4 ,v l or a seal on line 11, compensatesrfor the difference in pressure between 'boiler 12 and i vaporizer 10.- On the assumption'fthat still 19 operates at 28.9 inches of vacuiii'nand.has1V 4 feet of oil in the still, thisjhead' of oilis equivalent to a-pressure of about min. Q which is equivalent to 3 inches'of mercury.

Hence, in order to get the steam from boiler 12 into still 19 there must be a vacuumin boiler 12 of 25.9 inches or a `littleffless,"de-

pending on line friction, say 25175,inches. .I Under this vacuum, water boils at"130."F.

Summarizing: vaporizer 10 is maintainedat 28 inches of vacuum, water entering at `120" F. and leaving at 100 F.; boiler 12 is malin tained at 25.5 inches of vacuum andthe water. is heated therein to 130 F.; `still 19 is maintained at 28.9 linches of vacuum and containsl oil having a depth of fourfeet Stem is admitted through pipe 13Y tothe` I steam coil in the boiler. This steam may be the exhaust from the vacuum pump `The 95 condensed steam is run out as water through pipe 14. A drain 15 is appended 'tothe'V boiler. l

Still 19 is charged through line 18 and may be drained through line 17. The 'still may be run continuously or intermittently. Steam from boiler 12 passes through'line 16 and into distributor pipes 20, whence it flows through the main body of oil in still 19. i t

`Oil vapors and steam leave still` 'y19-.1651

through pipe 21 and pass into tower `22.

This tower is surroundedv by an insulated air f. Jacket 23, air-being admitted through :fines I 24 and passing upwards through-"passages- 23 and past damper 31 into the atmosphere.

The described passage of air cools the mix-,z ture yof oil vapors .and steam,toanyfdesired In 'the illustrated apparatusjihe degree.

vapors',v are cooled suiilcientlyto'gcondense the lubricating'oil fractons,'which pass-out through line 25 and condenser 26 v'int'olre-l ceiving tank .27, and lthrough lin`eff-z29 yto pump and storage. A vacuum` is maintained on this tank through lines 28 and 40 to afp vacuum pump (not shown). .Y

The uncondensed steam and lighter 'oils pass out thetop of tower 22 I line 32'to separator 3ft- 35. v .v

This separator is constructedwith 'an air 22. A mixture of oil vapors and 'steam passes downward through the annular chamber 34 and thence u ward through the inner or central cham r- 35. In traversing vby means i l jacket 33 similar -to the-air jacket int-awel'.

1o harometric -injection condenser 46.

these chambers the oil vapors are condensed, transferring their heat to the air in jacket 33. Thecondensed oil runs out through line 36, cooler 37 and line 38 to tank 41, and thence through line 42 to storage. A vacuum is maintained by means of lines 39 and 40 to the last mentioned vacuum pump. y

The steam, still uncondensed, passes out the top of chamber 35 through line 45 to a Here waterlis injected through line 47 into condenser 46, which condenses the steam, the condensate and the injected water passing downstand pipe 48 to a barometric seal 55, which has an overflovvthro'gh line 53, and

a drain 54. Watervapors and non-oondenfv sable still gases pass into an ejector or a wet orl dry vacuum pump 49.r If this is an ejec," tor, steam is admitted through line "56 and exhausted through line 50. l v j There are substantial advantages in ada t inv the invention to other processes of isti ing oil, such asthose disclosed in the applications filed by Pew and Thomas March 5,

1925, Serial N o. 13,040, and by me May 29,v

1926,A Serial No'. 112,485; but the describedv application of the invention to a simple and Well known type of oil still (19) .discloses the invention in a simple form. It will be understood, however,'that the process is applicable vto any known method of vacuum distillation. 1

Having now fully described my invention,

what I claim and desire to protect lby Let? ters Patent is:

1; The process of vaporizing oilk which comprises removing air from water, generating ste-am from` such water and mixing such steam with ythe oil. .v

2. The process of 'vaporizing oil which comprises removing air from water, vgen. erati'ng steam from such water under a partial vaCuUm, mixingsuch steam with the oil, and maintaining a higher vacuum on the oil during its vaporization.v 3. The process of Yvaporizing oil which comprises owing Water in shallow streams over extended surfaces while'subjecting it to a high vacuum and thereby deaerating the water, generating steaml from such Water under a substantial vacuum, mixing said steam with the oil, and maintaining the'oil under a higher vacuum than that under which the steam is generated.r f i 4. The process of distilling oil which comprises flowingv Water in a 'shallow stream over extended surfaces' while subjecting it to a high vacuum: andA thereby removing most of the'- air from the water, heating. the des aerated water-to convert itinto steam substantially devoid ofI air, injecting said steam into the oil while ymaintaining the oil under vacuum, andcondensing the oil vapors thereby enabling vthe production of ,anv oi distillate substantially free from the decomseparating them from uncondensed `by heat exchangeof the oil vapors and steam position products produced by high temperature and substantially free from the oxidation products produced by the contact of the oil with oxygen.l

y 5. The process 'of 'distilling oil which comprises removing air from Water, generating steam from such-water, mixing such steam With the oil, and by'heat exchange with a4 exchange of Atheoil vapors and steam With' a current of air, and passing uncondensed steam-v and lighter-'oil vapors into heat exchange with a current of air and thereby condensing such lighter oil vapors and separatl ing them from nncondensed steam.

r, 7. The process of distilling oil which comprises removing air from water, gen-- erating steam from such water, mixingsuch.

steamy-with the oil, condensing oil vapors and steam with a current of air, and condensing the steam fromn which the condensed yoil has separated. v

8. The process of distilling oil to produce distillates of high quality and good color notwithstanding the injection of steam into the oi1,'which comprises substantially avoid` ing oxidation of the distillates'by mixing with the oil steam from which a greatlyv predominant proportion of its content of airv has been removed.

9. The process of distilling oil which comprises maintaining the oil under a low subatmospheric ressurev and mixing .with the oil steam un er a sub-atmospheric pressure suihciently higher than the pressure on the oil to enable the steam to be forced into the oil and sufficiently low to minimize; thev volumetric expansion of the steam when admitted to the oil and the resultantl entrainrl ment as the steam travels through the oil.

removed and forcing the deaerated' steam.

.into the oil under a sub-atmosphericpressureyl vabove that to which the oil `is sub'ected but l suiciently low to minimize the e ect of its f expansion and the resultant entrainment ,as

the steam travels through the oil.

1 1. ';[`11e process of vaporizing oil which comprises removing air from water, generatingfsteam from such water, maintaining'y von. 'the 011 a low subfatxnosphericv absolute pressure'lower than the absolute pressure under which the steam Wes generated, end Inxing' the steam, as it is generated, with the o1 12. rThe process' of veporizing oil which comprises removing air from Water by Howin the Water over yen extended surface while su jectng it to e, 10W sub-atmospheric pressure, v generating steam from said Water 1Q under e, higher sub-atmospheric pressure,

merma mixing such steam with the oii, and mainmining on the oil e sub-atmospheric' absolute pressure lower than the absolute pressure under which the steam was generated.

In testimony of which invention, I have hereunto set my henci, at Philadelphia, Pennsylvania, on this 15th dey of Becember, 1926.

ARTHUR n. PEW, en.

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