US1905156A - Method of dividing petroleum bottoms - Google Patents

Description

April 25, 1933- G. B. coLlBRouGH 1,905,156

, METHOD OF DIVIDING PETROLEUM BOTTOMS Filed March 8, 1932 Witness Iwenivr 6. W WW9? '1 W Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE GEOBGE B. COUIBROUGH, F LONG B EACH, CALIFORNIA, ASSIGKOB TO THE LmUS COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE METHOD OF DIVIDING Application filed March 8,

The present invention relates to methods of dividing asphaltic petroleum bottoms. This application is a continuation in part of my application SerialNo. 573,446, filed November 6, 1931. I a

The recovery of asphalt from petroleum bottoms is of great importance commercially necessity of heating beyond the cracking tem:

perature is not avoided even by distillation under the highest practicable vacuum.

The objectof the present invention is to provide a method of dividing petroleum bottoms to obtain asphalt of high grade as residue and an oil stock as an overhead product without cracking.

lVith this object in view, the principal feature of the invention consists in adding to the bottoms a diluent oil non-adjacent to the bottoms, that is. an oil which can be completely vaporized under conditions of pressure and temperature at which vaporization of the bottoms is negligible, heatingthe mixture in a confined stream, as in a pipe still, to a. temperature'below the cracking point, and then releasing the heated mixture into a flashing or vaporizing zone maintained under a sufficiently high vacuum to effect complete vaporization of all of the oils as a unit or blanket cut under the contained heat of the mixture. The separation of the oils ,from asphalt is accomplished entirely by flash vaporization without rectification of the initially formed vapors.

The residue of the flashing operation comprises substantially pure asphalt. The initial vapors which comprise, as a unit, all of the oils of the original bottoms, together with the diluent, may then be condensed and collected in any desired manner. The diluent, being non-adjacent to the oils, may be easily separated therefrom by any simple process of condensation. Theremaining oils may be PETROLEUM no'r'rous 1932. Serial no. 597,51s.

collected as a unit. The nature of these remaining oils depends upon the composition of the original bottoms. For example, if the original bottoms comprise only cylinder stock and asphalt, the resulting overhead product, after the diluent has been separated therefrom, consists of an exceptionally high grade cylinder stock which may be used in the'manufacture of lubricating oils. If the original bottoms contain not only asphalt and cylinder stock, but wax distillate components as well, the asphalt is obtained as residue in the same way and the vapors comprise a mixture of cylinder stockand wax distillate with the diluent.

n the original bottoms comprise both wax distillate and cylinder stock in mixture with the asphalt, it is frequently desirable to collect the wax distillate and the cylinder stock as products separate from each other, as well as from the asphalt. The present invention permits separating the oils as a unit from the asphalt in accordance with the roc ess above described, followed by fractionation between the cylinder stock and wax distillate vapors, so long as no reflux is permitted to pass into contact with the initially flashed vapors in the flashing z one. However, due to the considerable number of fractionating decks required for this fractionation, and the consequent resistance created by these decks, the vacuum in the flashing zone may be lowered to such a point that complete vaporization cannot take place under the contained heat of the mixture. Accordingly, another feature 'of the present invention contemplates a primary reduction of the bottoms by fractional distillation to a predetermined point to obtain, for example, wax distillate as an initial overhead product and a residual mixture of asphalt and cylinder stock. This residue of the primarydistillation isthen used as the starting mate rial of the process above described, being mixed with the diluent and then subjected to heating and flash vaporization to obtain an overhead cylinder stock and an asphalt residue. In any case, whatever the startin material may be, an asphalt of exceptiona grade may be prepared and an overhead product of any predetermined composition may be obtained.

lthough it hasbeen proposed to use a light oil in mixture with heavier oils in. various distillation processes, the essential feature of the present invention comprises the use of a diluent in combination with a vaporization step that involves only flashing of the vapors from the asphalt, without controlling the composition thereof bythe introduction of reflux into the flashing zone.. An attempt at fractional distillation of the initial vapors by the use of a reflux condensate introduced into the flashing zone would result in a diminution in the temperature of the flashing zone and require a compensating increase in the temperature of initial heating drawn by the pipe 26.

to a point above the cracking point.

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

The invention is herein described as embodied in a process for dividing petroleum bottoms to obtain cylinder stockas an overhead product and completely reduced asphalt as a residue. p

r In the apparatus shown in the drawing, the crude oil which has been preferably sub ected 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 kero-' sene and gas oil are obtained as side products from the draw-off pipes 10 and 12 respectively. The residue of the column- 6, consisting of 45% bottoms, is withdrawn by the pipe 14 and is introduced through a heater 16 intofa second column 18 to obtain gas oil as an overhead product through the pipe 20 and pressable wax distillate as a side product at the draw-0E 22. Preferably, this column operates 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.

column 18 is with- This residue com prisesthe starting material for the main process, namely, a mixture containing only cylinder stock and asphalt. A part of the gas oil, used as the diluent for the starting material, is led from the draw-oil 12 of the first column through a pipe 28. which leads directly to the residue pipe 26 of the second column. Themixture of gas oil, cylinder stock, and asphalt thus formed, is passed through a heater 30, to be elevated to a high temperature (but below the cracking point), and is then released into a final column hav ing a flashing zone 32. This last column is The residue from the ers 38 and drawn at 56. The annular-space around suitable,

maintained under vacuum. Steam may be introduced at 34, in which case, only a moderate vacuum need be employed. The asphaltic residue is withdrawn from the bottom of the column at 36. The mixed vapors of gas oil and cylinder stock which have vaporized as a unit from the cylinder stock pass upwardly through entrainment catche 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, an

crease in the temperature of heating, so that cracking would occur.

The overhead vapors are conducted by a pipe 44 to a condenser 46 which is connecte 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 parts of the column, the remainder being drawn .ofi' 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 witlllit e vapor pipe 40 is preferably provided with decks 58 forming a restripping section into which steam is introduced at 60 for distilling off any remnant of gas oil which may pass downwardly toward the deck 42. The upper section of the column is only of small size and requires only a few decks, since a complete separation between the cylinder stock and the non-adj acent diluent can be effected by a minimum of reflux.

Neither the composition nor the quantity of the oil introduced as a diluent at 28 is critical. This oil should vaporize completely under conditions of pressure and temperature at which vaporization of cylinder stock is negligible, which will ensure ease of separation from the cylinder stock. It should be stable atany temperature normally encountered, and should be readily condensible at the pressures employed in the process and at temperatures attainable with ordinary cooling water. Substantially any fraction non-adjacent to the cylinder stock satisfies the conditions of stability and convenient separation. Gas oil, particularly the lighter gas oil fractionfrom the first column, is not only because of the properties referred to above, but also because it may be readily condensed, thereby permitting holding of a high vacuum in the column 32. Kerosene may also be used. It has been found that with gas oil as a diluent, the process d would therefore require a compensating in- In operation of the process, the diluent oilaccomplishes two functions-first, it lowers the maximum temperature to which the mixture must be heated to apoint at which sufiicientcontained heat can be supplied for the subsequent vaporization without exceeding the cracking temperature, and second, it prevents cracking of any of the components due to local overheating in the pipe still,

because it sufiiciently lowers the viscosity of the mixture so that formation of heavy oil films adjacent to the hot tube wall is eliminated, The oil is preferably heated in the still to a temperature of about 700 F.

The use of the diluent forms only a step in the complete process. The invention in its broader aspects contemplates the separation of an oil group from asphalt by an unrecti fied flash cut'under the contained heat imparted in the pipe still.

The process is not limited to the recovery of cylinder stock as a separate product, but

may be employed to eflect a separation of any or all of the oils from the asphalt residue. For example, it may be desired to obtain from the bottoms an overhead product consisting of a mixture of other oil groups with cylinder stock. The present invention is also used for this purpose and as in the case above described, the same high grade of asphalt is obtained. In this instance, there is-no necessity of effecting any separation between the wax distillate and the cylinder stock, especially if all of the overhead product is to be later subjected to a cracking operation. The process is carried out in exactly the same manner by taking a blanket out between the asphalt residue on the one hand and the overhead product on the other. This overhead product may be used in any suitable manner, for example, as a cracking stock.

It will be noted that whatever the final products may be, the essential features of the present invention are (1) the addition to the starting material of a fraction non-adjacent thereto and being completely vaporizable under conditions of pressure and temperature at which vaporization of the starting material is negligible; (2) the heating of the entire mixture in a confined stream wherein no separation or segregation of the oils is permitted; and (3) the release of the heated mixture into a flashing zone under vacuum wherein all of the di ls vaporize as an unrectified blanket out under the contained heat of the mixture, there being no attempt at control of vapor composition by passage of reflux below the deck 42. A small quantity of asphalt may go over with the vapors, but

be obtained,'.the startingmaterial preferabl comprises only a mixture/ofcylinder stoc and asphalt, substantially free of wax distillate. The principal reason for eliminating the wax distillatefronrthe original mixture is that the cylinder stock and wax distillate must eventually be separated from each other. If the cylinder stock and wax distillate are collected as a single product, wax removal is very diflicult, if not impossible, because of the difference in physical properties of waxes occurring in wax distillate and cyllinder stock, and in the correspondingly different methods employed for theirremoval. The Wax distillate and the cylinder stock migh be separated from each'other, by rectification of the vapors in the reflux zone. 53, except that such rectification between these adjacent fractions would ordinarily require so many decks that with existing apparatus, 7 the vacuum in the flashing zone could be maintained only with difiiculty, if at all.- For lubricating oil cuts, it is therefore preferable to reduce theoriginal bottoms by a primary operation in the column 18.

It has beenproposed in some instances to employ a light oil in connection with heavier oils for distillation purposes. For example; one proposed method employs a diluent oil' for fractional distillation of vWax distillate from cylinder stock. Such a process, however, does not accomplish the purpose of effecting separation between oils and asphalt andeven if workable, it presents cracking difficulties owing to the fact that very high 100 initial temperatures are necessarily employed to compensate for the necessary rectification between the cylinder stock and the distillate.

It has also been proposed to bubble gas oil I vapors through heated bottoms. process, however, results in a progressive vaporization of oils ofincreasing boiling points tending to establish an ultimate equilibrium prior to complete reduction of the asphalt.

, In the present invention,,the flash va'poriza- 1m tion of the oils under reduced pressure in the presence of the diluent results in direct and immediate recovery of the oil compo nents. i

In the final analysis, the success of thepres process, no separation of the components oc 4 curs until the mixture reaches the flashing chamber because the intimate turbulent contact obtained in the heating coil insures com- Such a plete equilibrium between the vaporized and unvaporized portions of the mixture. en the necessary heat hasbeen imparted to the mixture, it is released into the flash chamber where'the pressure maintained is such that equilibrium conditions is accomplished largecontinuous ly by the preliminary removal from the starting material of fractions adjacent to the starting material. It will be understood that the original bottoms comprise a practically chain of components'having pro- 'gressive gradations in boiling points. Such a continuous chain conduces to theequilibrium' by which the-heavier components of the cylinder stock are inextricably locked up with the asphalt. By the present process, however, the material introduced into the flash column comprises a broken chain of components, so that theaffinity of the oils for the asphalt is destroyed. The oil mixture comprising the starting material and the diluent vaporizes as a unit from theresidue. In practice, it is unnecessary to heat the oil to a temperature much in excess of 700 F., the pressure being suflicient to force the oil through the pipe still. At this temperature, no appreciable cracking occurs and flash vaporization can take place under a moderate vacuum such as an absolute pressure of 50 to 100 millimeters of mercury. Vaporizar tion is enhanced with some oils by the use of steam, but steam is not ordinarily essentiaL.

The use of steam does not change the character of flash vaporization of the body of oils from the residual material.

The present invention provides for ractically complete recovery of the valuab e lu bricating components as well as direct recovery of asphalt in its most valuable form. Asphalt, with a'penetration as low as 2, measured by the standard enetration test, has been obtained. It is to e noted that the re covery of such exceptionally high grade asphalt is not, only important in ltself, but is also of importance in indicating the substantially complete recovery of the valuable components of the oil.

Whereas exlsting processes of treating asphalt bottoms to obtain lubricating oils ordinarily result in a loss of as much as 40% of the cylinder stock components, the present invention operates with a practically negligible .loss. Moreover, there is a decided advantage in the economy of subsequent acid treatment of the oils. Under the usual processes,

suflicient cracking'takes place to form a considerable quantity of unsaturates which are first acted upon by the acid. In the present invention, wherein substantially complete revaporization from mixture into a vaporizing zone densing the vapors 0 some cases only one-half, than the amount required in the usual processes.

Having thus described the invention, is claimed is:

1. The method of separating lubricating oils from asphalt which consists in taking a starting mixture containing lubricating oils and non-volatile asphaltic residuum, adding thereto a diluent oil which is completely vaporizable under conditions at which vaporwhat ization of the starting material would be negligible, continuously subjecting all of the oils to flash vaporization from the asphaltic residuum by first heating the entire mixture in a confined stream under pressure and then releasing the mixture into a vaporizing zone maintained under a sufliicent vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heating bemg condensing the vapors while preventing e turn of any condensate to the vaporizing zone, and withdrawing asphaltic residue.

2. The method of separating lubricating oils from asphalt which consists in taking a starting mixture containing lubricating oils and non-volatile asphaltic residuum,-adding thereto a diluent oil which is completely vaporizable under conditions at which vaporization of the starting material is negligible, continuously subjecting all of the oils to flash the asphaltic residuum by insuificient to crack any of the materials,

first heating the entire mixture in a confined stream under pressure and then releasing the mixture into a vaporizing zone maintained under a suflicient vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heatingbeing insuflicient to crack any of the materials, separately condensing the vapors of the lubricating oils and the diluent while preventing'return of any condensate to the vaporizing .zone, and withdrawing asphaltic residue.

3. The-method of separating lubricating oils from asphalt which consists in takinga starting mixture containing lubricating oilsand non-volatile asphaltic residuum,'adding thereto a diluent oil which is completely vaporizable under conditions at which vapori- K zation of the starting material is negligible, continuously subjecting all of the oils to flash vaporization from the asphaltic residuum by first heating the entire mixture in a confined stream under pressure and then releasing the maintained under a suin'icent vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heating being insuflicient to crack any of the materials; introducing steam into contact with the unvaporized residue from the vaporizin zone, separately conthe lubricating oils and the diluent while preventing return of any condensate to the vaporizing zone, and withdrawing asphaltic residue.

4. The method of separating cylinder stock from asphalt which consists in taking a starting mixture containing cylinder stock and non-volatile asphaltic residuum, adding thereto a diluent oil comprising a fraction at least as volatile as gas oil, subjecting all of the oils to flash vaporization from the asphaltic residuum by first heating the entire mixture in a confined stream under pressure and then releasing the mixture into a vaporizing zone maintained under a suflicient vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heat ing being insuificient tocrack any of the materials, separately condensing the cylinder stock and the diluent while preventing return of any condensate to the vaporizing zone, and withdrawing asphaltic residue.

5. The method of separating cylinder stock from asphalt which consists in taking a starting mixture containing cylinder stock and; non-volatile asphaltic residuum, adding thereto a diluent oil comprising a fraction at least as volatile as gas oil, subjecting all of the oils'to flash vaporation from the asphaltic residuum by first heating the entire mixture consists in distilling from the crude apluresiduum by first heating the entire mixture in a confined stream under pressure and then releasing the mixture into a vaporizing zone maintained under a sufficient vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heating being insufl'icient to crack any of the materials, separately condensing the vapors of the cylinder stock and the diluent while preventing return of any condensate to the vaporizing zone, and withdrawing asphaltic residue.

In testimony whereof I have signed my name to this specification.

GEORGE B. COUBROUGH.

in a confined stream under pressure and then releasing the mixture into a vaporizing zone maintained under a suflicient vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heating being insuificient to .crack any of the materials, introducing steam into contact with the unvaporized residue from the vaporizing zone, separately condensing the cylinder stock and the diluent while preventing return of any condensate to the vaporizing zone,

and withdrawing asphaltic residue.

6. The method of dividing crude oil which consists in stripping from the crude aplurality of fractions including some lubricating components and all lighter fractions to leave an uncracked bottoms mixture consists ing of. lubricating stock and non-volatile asphaltic residuum, adding to said bottoms mixture a light diluent oil fraction which is completely vaporizable under conditions at which vaporization of the bottoms would be negligible, subjecting all of the oils to flash vaporization from the asphaltic residuum by first heating the entire mixture in a confined stream under pressure and then releasing the mixture-into a vaporizing zone maintained under a suflicient Vacuum to vaporize the oils under the contained heat of the mixture, the temperature of heating being insufficient to crack any of the materials, separately condensing the vapors of the lubricating stock and the diluent while preventing return of any condensate to the vaporizing zone, and

- withdrawing asphaltic residue.

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