US1963888A - Method of distilling heavy petroleum oils - Google Patents

Description

June 19, 1934. G. B. COUBROUGH 1,963,883

METHOD OF DiSTILLING HEAVY PETROLEUM OILS Filed OCT 5, 1932 26 ias Patented June 19, 1934 I METHOD OF DISTILLING HEAVY PETROLEUM OILS George B. Coubrough; Long Beach, Calif., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application October 5, 1932, Serial No. 636,347

15 Claims. (01. 196-77) The present invention relates to methods of of the oils being furnished by a part of their own distilling heavy petroleum oils, particularly heavy sensible heat as well as by a part of the sensible oils which are associated with only small quanheat of the unvaporized residue. Inasmuch as titles of unvaporizable residuum the latent heat of the oils is accompanied by a It is well-mow that the most valuable lubrireduction Of the sensible heat of the entire mix- 0 cating oils are those of highest viscosity and high ture, a temperature differential necessarily exboiling point which are also the oils most susists tw n t ater d the flas n zone. ceptible to injury when it is attempted to distill According to the present invention, the 11011- them from intimate solution with non-volatile Volatile aterial added t0 t e Original mixture 10 components, such as asphaltum. In particuaffords a large store of sensible heat at a low 65 lar, high viscosity oils of Pennsylvania and other temp 0 t at t e nversio t latent crudes having only a m ll cont t of h t, heat may be accomplished without an excessive cannot ordinarily be obtained by distillation, ifi n i f perature between the heater but must be stripped of lighter oils and collected and the flash ZOIie- Practical s, the as a residuum requiring expensive acid tr atadded non-volatile material is preferably as- 7 merit methods to purify the oils to suitable comp This p in mixture W y 1111- mercial standards, vaporizable material originally present, is con- The present invention provides a method for iiihiiOuSiy recovered as residue, and all P the continuous distillation and concentration of thereof y be continuously u a d to be heavy lubricating oils from crudes having only m ed with the bottoms entering the heater. a. small content of unv riz ble id The more volatile or lighter materials added I have discovered that heavy petroleum oils to t original m x u p ra y comprise a that are highly susceptible t decomposition or kerosene or light gas oil fraction with a narrow cracking by overheating may be distilled withrange of boilin DOihiiS t a y lower than the 25 out injury at minimum temperatures if heated boiling Point Of t heavy Oil 130 be distilledand flashed from mixt hi h h b l. The purpose of this material is to form a mixture tered to contain certain favorable proportions of with the heavy Oils Such that W fl d under lighter oils and also of unvaporizable residuum. Vacuum, the collective flesh p u e wi be My improved method takes advantage of this dismaterially lower than that Of the heavy Oils 30 oovery and consists essentially of altering the themselves. composition of the material to be distilled so as The vy s to be d s d ar t r f r subto form a mixture of favorable proportions for .i d t0 e influence of two factors, e O distilling at a temperature below that at which Which Controls the temperature at which fle h decomposition or cracking can occur, vaporization can occur at the pressure employed,

35 The process is carried out in apparatus of the and the other of Which Controls the pp y of general type used for continuous distillation. heal? required fer vaporization Without t y The materials are first heated under conditions exceeding that temperature 1 in which no opportunity for gradual or progres- I have found that a temperature of about sive vaporization is present, as in a pipe still, 720 F. is the maximum that need be reached in 40 d are then released into a vaporizing zone the heater to vaporize all of the heaviest oils unmaintained undervacuum wherein the oils under a moderate vacuum to produc espheitie dergo a collective or flash vaporization due to residues substantially free of oils and a distillate the pressure drop between the heater and the vapor mixture containing substantially all the vaporizing zone. I heavy oils of the original material.

45 In order that suificient heat may be imparted With a View to the sharpest possible separation to the starting mixture to effect flash. vaporizaof the high viscosity lubricating or heavy oils tion of all of the oils, but without the necessity from the lighter diluent oils contained in the of heating to an unsafe temperature at any distillate vapor mixture, I prefer that the startpoint, I alter the composition of the original maing material, which can be selected for its favor- 5o terial by adding thereto materials having both able content of heavy lubricating oils, shall have non-volatile components and other components been subjected to a preliminary" distillation to more volatile than the oils to be distilled. eliminate oils of closely related composition and It w'll be understood that flash vaporization of only moderately lower boiling point such, for of the oils occurs entirely under the heat preexample, as wax distillate. Then the altered 55 viously imparted in the heater, the latent heat mixture which is subjected to the final distillation will consist of a mixture of (1) heavy lubricating oils such as cylinder stock, (2) added lighter oils such as kerosene, which will flash with the heavy oils at a mean collective boiling point but are yet of sufl'iciently unrelated character and low boiling point to be readily separable from the heavy oils by rectification, and (3) asphaltum or asphaltic residuum.

The accompanying drawing is a diagram of the preferred form of apparatus for practising the present invention.

The invention is herein illustrated and described as embodied in the process of obtaining cylinder stock as distillate. The crude is first subjected to preliminary distillation steps to eliminate therefrom oils more volatile than the cylinder stock and the final residue of such steps, consisting of cylinder stock in mixture with a small amount of asphalt is then mixed with the lnore volatile and non-volatile materials to be subjected to the final flash vaporization.

In the apparatus shown in the drawing, the crude oil which has been preferably subjected to a preliminary treatment to remove a part of the gasoline, as well as impurities, is introduced through a pipe 2 and a heater 4 to a column 6, wherein gasoline is obtained as an overhead vapor product at 8 and kerosene and gas oil are obtained as side products from the draw-off pipes 10 and 12 respectively. The residue of the column 6 is withdrawn by the pipe 14 and is introduced through a heater 16 into a second column 18 to obtain gas oil as an overhead product through the pipe 20 and pre'ssable wax distillate as a side product at the draw-off 22. Preferably, this column operates at atmospheric pressure under steam distillation by steam introduced at the bottom through a pipe 24. A slop cut consisting of a mixture of wax distillate and cylinder stock may be taken off as a side product at 25. By this preliminary.distillation, the bottoms are reduced to a mixture of asphalt with cylinder stock of substantially any desired specifications.

The residue from the column 18 is withdrawn by the pipe 26. This residue comprises the starting material for the main process, namely, a mixture containing only cylinder stock and asphalt. To this starting material is continuously added a mixture of materials, consisting of both light gas oil and asphalt. The gas oil is conducted from the draw-off 12 of column 6 through a pipe 28 by a pump 29, the pipe 28 connecting with the pipe 26. Asphalt is introduced into the pipe 26 through a pipe 30, which may lead either from a storage receptacle or from the final column, as will presently be explained. The entire mixture,

comprising the residue from column 18, the gas oil and the asphalt, is continuously pumped through a heater 31 to be elevated to a high temperature (but below the cracking point), and is then released into a final column 32 having a flashing zone 33. This last column is maintained under vacuum. Steam may be introduced at 34,

in which case only a moderate vacuum need be employed. The use of a moderate vacuum in conjunction with steam is preferred, since a very high vacuum may promote entrainment or distillation of asphalt with a corresponding contamination of the distillates.

The asphaltic residue is withdrawn from the bottom of the column at 35. If desired, a portion thereof may be taken ed as a product, and the remainder returned through a pipe 36 and pump 37 to the line 30.

The mixed vapors of gas oil and cylinder stock ing chamber.

which have vaporized as a unit from the asphalt pass upwardly through entrainment catchers 38 and thence through a vapor pipe 40 which rises from a deck 42. The deck 42 is imperforate, except for the vapor passage, it being essential to prevent passage of reflux condensate into contact with the initial vapors which would result in a diminution in the temperature of the flashing zone, and would therefore require a compensating increase in the temperature of heating.

The overhead vapors are conducted by a pipe 44 to a condenser 46 which is connected with any suitable vacuum pump or jet. When steam is used, the condensate is collected in a decanter 48, the water is drawn off at 50, and a part of the oil condensate, is returned through the pipe 52 to a reflux section 53 in the upper part of the column, the remainder being drawn 01? through the valved pipe 54 as a product. This condensate is of the same composition as the gas oil introduced through the pipe 28. The gas oil reflux condenses the cylinder stock vapor which is collected as a liquid on the deck 42 and is withdrawn at 56. The

the cylinder stock and the diluent oil can be effected by a minimum of reflux.

The character and amount'of the added materials are not critical. The light or diluent oil should be of suiflciently related properties to the heavy oils so that it may be collectively flashed with them, and is preferably a fraction of the,

same series obtained from the crude oil; on the other hand, it .should have unrelated or nonadjacent properties with respect to boiling point and vapor pressure and is preferably of a character to vaporize completely under conditions of pressure and temperature at which vaporization of the cylinder stock would be negligible. is to say, the light oil should be of materially lower boiling point than the cylinder stock to insure collective vaporization at a low temperature and also to facilitate separation in the portion 53 of the column. Moreover, it should be stable at any temperature encountered in the process and should be readily condensable at temperatures obtainable with ordinary cooling water. A gas oil or kerosene cut is satisfactory, particularly if it has 'narrow limits of initialand end 'points, such as 450-550 F., at atmospheric ing temperature, and the quantity of added heat storage material, together with such asphalt as is present in the starting material, should be sufficient to provide the heat of vaporization of the vapors without an excessive difierential of temperature between the pipe still and the vaporiz- With average bottoms, the best quantity of volatile oil will be about equal to the quantity of heavy oils in the mixture, and the total quantity of asphalt, including that contained in the starting material, will be about equal to the quantity of heavy oils. Under such conditions, when an absolute pressure of 50 to 100 min.

That

- of asphalt and heavy oils.

the addition of a diluent is maintained in the flashing zone, distillation can be efiected with a maximum pipe still temperature not in excess of 700 F.

As a specific example of my process, I may take a Pennsylvania crude which contains approximately 20 of lubricating stock and about 1% of unvaporizable asphaltic residuum. The crude is reduced to 10% bottoms by distillation of 90% by volume of lighter materials in the preliminary columns. This 10% figure is illustrative only, and the crude may be reduced to bottoms of any specifications, ranging from 10 to approximately 20% depending on the character of the final product desired. The 10% bottoms, constituting the starting material for the final process, therefore comprise 9 parts of lubricating stock and 1 part of asphalt by volume. With this starting material are mixed 8 parts of asphaltifor example, asphalt of 100 penetration previously obtained from a Smackover crude) and 9 parts by volume of gas oil or kerosene. The starting material composition thus altered to provide substantially equal parts of asphalt, lubricating stock and diluent, is then heated to about 700 in the pipe still 31 and introduced into the column 32 which is maintained under an absolute pressure of about '75 mm. The actual pressure and temperature are interdependent, and the temperature may be reduced by increasing the vacuum, and vice versa. In any event, the vacuum is such that complete vaporization of the oils occurs without exceeding the cracking point.

The operation results in recovery of the diuent as the overhead product, all of the lubricating stock as a sde product, and a residue consisting of the asphalt of the original crude, together with that mixed therewith. After the process is started, the m'xing of asphalt with the starting material may be carried out as above described, or. a portion of the asphalt may be recirculated, as illustrated in the drawing. It will be evident that the proportion of recirculated asphalt will be such as to maintain the de-' sired proport'ons in the starting mixture.

In the specific example given above, it will be noted that the oils are recovered as a pure Pennsylvant'a overhead stock. If blended lubricating oils are desired, the blending may be carried out prior to the final vaporizing operations. For example, a blend of 10% Pennsylvania bottoms may be made with, say, 25% bottoms of smackover crude, which has a high asphalt content, the proportion of the blended bottoms being such as to give approximately equal parts of asphalt and lubricating stock. To th s blended mixture, the diluent, such as kerosene or gas oil, is added, and the distillation is carried out as above descr'bed.

The present invention is of greatest value in refining crude oils having only a small asphalt content. When the crude has more than a certan minimum, generally about 6% of asphalt, it can be reduced in the prelim-nary columns to obtain bottoms having about equal proportions Such bottoms form a favorable mixture for flash vaporization upon thereto, in accordance with the principles described in my Patent No. 1,905,156.

When the original crude contains less than the minimum of about 6% asphalt, the crude cannot usually be reduced in the preliminary columns to bottoms having the desired quantity of asphalt unless at some point a cracking temperature is reached. Accordng to the present invention, as typified in the above example, it is not necessary to reduce any crude to less than about 10% in the preliminary stages, final operations being carried out by adding both asphalt and diluent, followed by flashing in the final column.

Having thus described the invention, what is claimed is:

1. The method of recovering oils and residuum from petroleum bottoms containing primarily lubricating oils with a small amount of non-volatile residuum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible, adding to the mixture a quantity of non-volatile heat storage medium, subjecting the oils to flash vaporization by continuously heating the mixture in a confined stream and releasing the heated mixture into a vaporizing zone maintained under vacuum to vaporize all of the oils as a unit from the residuum under the contained heat of the m'xture, con densing the vapors, and withdrawing non-volatile residue.

2. The method of recovering oils and asphalt from petroleum bottoms containing primarily lubricating oils with a small amount of non-volatile asphaltic resduum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible, adding to the mixture a quantity of asphalt as a heat storage medium, subjecting the oils tofiash vapor.zation by continuously heating the ,mxture in a confined stream and releasing the heated mixture into a vaporizing zone maintained under vacuum to vaporize all of the oils, as a unit from the asphalt under the contained heat of the mixture, condensing the vapors, and withdrawing asphalt as residue.

3. The method of recovering oils and asphalt from petroleum bottoms containing primarily lubricating oils with a small amount of nonvolatile asphaltic residuum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible,

subjecting oils to flash vaporization by continuously heating the mixture in a confined stream and releasing the heated mxture into a vaporizing zone maintained under vacuum to vaporize all of the oils as a unit from the asphalt under the contained heat of the mixture, condensing the vapors, withdrawing asphalt as residue, and recirculating a portion of the withdrawn asphalt to be mixed and heated with the original mixture to increase the heat content of the mater'al supplied to the vaporizing zone.

4. The method of separately recovering cylinder stock as an overhead product and asphalt as residue from a mixture thereof having only a small content of asphalt which consists in adding to the mixture a mater'al at least as volatile as gas oil, continuously heating the mixture, releasing the heated mxture into a vaporizing zone at a pressure low enough to vaporizethe oils by the contained heat of the mixture, condens'ng the vapors, and recirculating a part of the asphalt residue to be added to the original der stock as' an overhead product and asphalt as residue from a mixture thereof substantially free of wax distillate having only a small asphalt content which consists in adding to the mixture a material at least as volatile as gas oil, adding asphalt as a heat storage medium, continuously heatingthe mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the oils by the contained heat of the mixture, condensing the vapors, and withdrawing asphalt as residue. v 1

6. The method of separately recovering cylinder stock as an overhead product and asphalt as residue from a mixture thereof substantially free of wax distillate and having only a small quantity of asphalt which consists in adding to the mixture a low-boiling petroleum fraction, at least as volatile as gas oil, continuously heating the mixture, releasing the heated mixture into'a vaporizing zone at a pressure low enough to vaporize the combined oils by the contained heat of the mixture, withdrawing the vapors, and recirculating a part of the asphalt residue to be added to the mixture'to act as a heat storage medium in the vaporizing zone.

7. The method of dividing petroleum oils which consists in fractionally distilling from the oil several fractions of increasing boiling points including wax distillate, leaving a residual mixture consisting of a mixture of cylinder stock and a small quantity of asphalt, adding to the residual mixture a petroleum fraction at least as volatile as gas oil, adding asphalt as a heat storage medium, continuously heating the mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the combined oils by the contained heat of the mixture, withdrawing the vapors, and leaving asphalt as residue.

8. The method of dividing'petroleum oils which consists in fractionally distilling from the oil several fractions of increasing boiling points including wax distillate, leaving a residual mixture consisting of cylinder stock and a small quantity of asphalt, adding to the residual mixture a diluent at least as volatile as gas -oil, continuously heating the mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the combined oils by the contained heat of the mixture, withdrawing the vapors and leaving asphalt as residue, recirculating a portion of the asphalt to the mixture to be heated,

. and separately condensing the cylinder stock and the diluent.

' I 9. The method of recovering oils and residuum from petroleum bottoms containing primarily lubricating oils with a small amount of non-volatile residuum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible, adding a quantity of asphalt as a heat storage medium, the total quantities of diluent, lubricating oils and asphalt in the mixture being in approximately equal proportions, subjecting the oils to flash vaporization by continuously heating the mixture in a confined stream and releasing the heated mixture into a vaporizing zone maintained under vacuum to vaporize all of the oils as a unit from the residuum underthe contained heat of the mixture, condensing the vapors, and withdrawing non-volatile residue.

10. The method of recovering oils and asphalt from petroleum bottoms containing primarily lubricating oils with a small amount of non-volatile asphaltic residuum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible, adding to the mixture a quantity of asphalt as a heat storage medium, subjecting the oils to flash vavaporizing zone, condensing the vapors, and with--' drawing asphalt as residue.

. 11. The method of recovering oils and asphalt from petroleum bottoms containing primarily lubricating oils with a small amount of non-volatile asphaltic residuum which consists in adding to the bottoms a diluent which can be completely vaporized under conditions at which vaporization of the bottoms would be negligible, subjecting oils to flash vaporization bycontinuously heating the mixture in a confined stream and releasing the heated mixture into a vaporizing zone maintained under vacuum to vaporize all of the oils as a unit from the asphalt under the contained heat of the mixture, introducing steam into the residue from the vaporizing zone, condensing the vapors, withdrawing asphalt as residue, and recirculating a portion of the withdrawn asphalt to be mixed and heated with the original mixture to increase the heat content of the material supplied to the vaporizing zone.

12. The method of separately recovering cylinder stock as an overhead product and asphalt as residue from a mixture thereof having only a small content of asphalt which consists in adding to the mixture a material at least as volatile as gas oil, continuously heating the mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the oils by the contained heat of the mixture, introducing steam into the residue from the vaporizing zone, condensing the vapors, and recirculating a part of the asphalt residue to be added to the original mixture to act as a heat storage medium in the vaporizing zone.

13. The method of separately recovering cylinder stock as an overhead product and asphalt as residue from a mixture thereof substantially free of wax distillate and having only a small quantity of asphalt which consists in adding to the mixture 2:. low-boiling petroleum fraction, at least as volatile as gas oil, continuously heating the mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the combined oils by the contained heat of the mixture, introducing steam into the residue from the vaporizing zone, withdrawing the vapors, and recirculating a part of the asphalt residue to be .added to the, mixture to act as a heat storage medium in the vaporizing zone.

14. The method of dividing petroleum oils which consists in fractionally distilling from the oil several fractions of increasing boiling points including wax distillate, leaving a residual mixture consisting of cylinder stock and a small quantity of asphalt, adding to the residual mixture a diluent at least as volatile as gas oil, continuously heating the mixture, releasing the heated mixture into a vaporizing zone at a pressure low enough to vaporize the combined oils by the contained heat of the mixture, introducing steam into the residue from the vaporizing zone, withdrawing the vapors and leaving asphalt as residue, recirculating a portion of the asphalt to the mixture to be heated, and separately condensing the cylinder stock and the diluent.

15. The method of recovering oils and residuum from petroleum bottoms containing primarily lubricating oils withsa small amount of nonin a confined stream and releasing the heated mixture into a vaporizing zone maintained under vacuum to vaporize all of the oils as a unit from the residuum under the contained heat of the mixture, introducing steam into the residue from the vaporizing zone, condensing the vapors, and withdrawing non-volatile residue.

GEORGE B. COUBROUGH.

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