US2010008A - Method for treating oils - Google Patents

Description

Aug. 6, 1935. u. B. BRAY METHOD FOR TREAT ING OILS Filed March 6, 1933 mm hm INVENTOR. Ulrzc B. Bray M Mr ATTORNEY.

Patented Aug. 6, 1935 UNITED STATES METHOD FOR TREATING OILS Ulric B. Bray, Los Angclcs, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application March 6, 1933, Serial No. 659,855

13 Claim.

This invention relates to a method for separating asphalt and wax from oils containing the same and is a continuation, in part, of my copending application Serial No. 466,189, filed July 7th, 1930.

In my co-pending application, Serial No. 466,- 189, filed July '7, 1930, I disclosed a process for producing lubricating oils and separating asphalt from asphaltic base crudes or cr'udes containing both asphalt and wax. In this process, the crude oil containing asphalt was topped to leave a residue which contains fractions having a viscosity above 400 to 500 seconds Saybolt Universal at 100 F. In other words, the degree of distillation was such that a minimum deterioration of the desirable temperature viscosity characteristics of the oil resulted. The topped residue was then mixed with a solvent in which the lubricating oil fractions are soluble but in which the asphalt is insoluble. This caused precipitation of the asphalt.

As a particular feature of the invention, I disclosed the use of hydrocarbon solvents to precipitate the asphalt which are volatile at atmospheric temperatures and pressures. Such hydrocarbon solvents include propane, isobutane, butane, ethane, methane or mixtures thereof and are obtainable by rectification of casinghead gasoline bythe so-called stabilizing method now conventional in the natural gasoline industry. They comprise the overhead gaseous fractions of the stabilizing process. The gaseous fractions are liquefied by compression and cooling in the conventional manner and are drawn oil into pressure chambers where they are maintained in the liquid state until they are used. A typical analysis of such a fraction is 6.72% ethane, 72.20% propane, 19.91% isobutane and 1.17% normal butane. The necessary pressure to maintain this fraction in a liquid state at 75F. is approximately 125 pounds per sq. in. gauge. For purposes of simplicity, I will refer to this fraction or solvent as propane or liquid propane in thefurther discussion of my invention.

As stated, the lubricating oil stock containing asphalt was mixed with this liquid solvent under pressure suflicient to maintain the solvent in the liquid state and the mixture was allowed to settle under this pressure to permit the precipitation of the asphalt. The solution of lubricating oil in the liquid solvent was withdrawn from the pressure precipitator or decanter and expanded through heating coils to vaporize the solvent, leaving behind the lubricating oil substantially free of asphalt. The gaseous vapors were recompressed and cooled to ellect liquefaction and were returned to the system. The asphalt was removed as a slurry of propane and bitumen which was then heated to remove the propane which was also re-liquefled.

If the lubricating 011 stock was produced from a mixed base crude, i. e. crude containing both asphalt and wax, it was treated for wax removal subsequent to the de-asphaltizing step.

This was accomplished by evaporative refrigeration, that is, use was made of the refrigerative effect of the liquefied normally gaseous hydrocarbon solvent by release of pressure and evaporation of a. portion of the solvent. The chilling eflect on the oil precipitated the wax from the propane solution. The pressure was reduced to substantially atmospheric which caused the oil to be chilled to 40 F. The precipitated wax was separated from the oil and from the residual solvent as by centrifuging. The wax-free solution was then heated'to evaporate the solvent leaving behind a lubricating oil free from both asphalt and wax.

In the foregoing process, the precipitated as-' phalt separated from the pressure precipitator was described as comprising a slurry of asphalt and propane from' which the latter was separated by distillation to leave behind a substantially 'pure asphalt or bitumen.

I have now discovered that asphalt may be separated from oils containing asphalt either as a liquid fraction or as a solid asphalt, depending upon the ratio of solvent to oil. If the ratio of solvent to oil is high, the asphalt separated is a granular solid or a substantially pure bitumen.

If this ratio is low, the asphalt may be separated from the remaining oil solvent solution as a liquid. By referring to the asphalt as a liquid it will be understood that the asphalt separated in the decanter when an asphaltic oil is mixed. with solvent comprises a substantially homoge neous solution of asphalt, oil and propane which is liquid at atmospheric temperatures. It comprises a liquid fraction as distinguished from a slurry of asphalt and propane or a heterogeneous mixture of asphalt and propane containing some oil from which the asphalt may be separated fromthe remaining solution by simple decantation or filtration.

There are certain critical volumetric ratios below which no separation of an oil phase from the asphalt phase can take place. This ratio will vary with the type of crude or residuum; for example, with a Poso Creek residuum topped to an on-stream viscosity of 67 seconds Saybolt Universal at 100 F., no separation of phases" was observed until the volumetric ratio exceeded one and one-half volumes of propane to one volume of oil. On a McKittrick residuum, there was no separation of phases until the volumetric ratio exceeded 0.6 volume of solvent to one volume of oil. At slightly above these critical volumetric ratios, a maximum recovery of oil is obtained. Further increase in the volumetric ratio shows a steady decrease in percent recovery of lubricating oil, while the character of the oil is increasingly better in regard to color. Thus, on a Poso Creek residuum, a volumetric ratio of propane to oil of Izl showed a maximum oil recovery of approximately 85%. This amount gradually decreased to approximately 75% as the volumetric ratio increased to Illzi. The

amount of asphalt recovered showed a steady increase. The probable explanation of this decrease in oil recovery as the volumetric ratio increased is the residual solubility of the asphalt in the propane oil solution, this solubility being greater the higher the concentration of the lubricating oil in the propane. With high proportions of propane, therefore, less asphalt is dissolved in the solution layer and a cleaner product is obtained, the recovery being less by this decreased amount of asphalt.

In the following table, I have tabulated the signiiicant data of the operation of the process on a. Poso Creel: residuum which was topped to an onstream viscosity of 67 seconds Saybolt Universal at 100 l., showing the variation of percent recovery of lubricating oil and asphalt with variation of the volumetric ratio of propane to residuum. It will be observed that the percent loss is within experimental error. However, a greater proportion of this loss may be attributed to incomplete removal of precipitated asphalt from the experimental apparatus. Therefore, a greater proportion of the loss should be added to the percent of asphalt recovered to give approximately the true amount of asphalt recovered. It will be noted that the experiments on asphalt precipitation or separation from the oil we'recarried out at aproximately 80 F.

Influence of volumetric ratio of propane on re covery of lubricating oil V 1 ti P t me re 0 recover Percent Percent pro to lubricating mitifim oil from what he residuum l:l No separation 1. :1 No separation 2:1 84. 0 15. 6 0. 6 3:1 82. 2 l6. 5 1. 3 3. 5:1 80. 0 16. 7 8. 3 6:1 79. 0 Bi. 5 0. 6 6:1 79. 2 2o. 7 0. l 'm 7a 0 2o. 0 2. 0 :1 77. 5 21. 8 0. 7 :1 76. 6 23. 4 l. 0 :1 76. 8 20. 0 3. 0

The character of asphalt separated also varies with variation of volumetric ratio of propane to oil. In general, with low volumetric ratios and high. percentages of oil recovery, the asphalt separated by startiflcation is liquid asphalt, i. e. liquid at ordinary temperatures. Also, when freed of solvent it has a low melting point and a high penetration. with increasing volumetric ratios,

the character of the asphalt stratified passes from the liquid state to a solid asphalt or substantially pure bitumen in finely divided form. The penetration will correspondingly become lower and the melting point higher, when freed of solvent, as the volumetric ratio increases.

I have discovered that there is a critical volumetric ratio for each oil below which asphaltmay be separated from the oil as a liquid and above which the asphalt is separated as a granular solid or as a substantially pure bitumen. In general, a volumetric ratio of six or less of propane to one of oil will result in the separation of the asphalt as a liquid fraction, whereas a ratio above 6 z 1 will cause separation of the asphalt from the oil as a solid. I do not wish to be limited to this exact ratio since the upper limit of volumetric ratio for separation of asphalt as a liquid fraction will depend entirely upon the character of residuum operated on and the degree to which it is topped. With certain asphaltic stocks, the upper limit of volumetric ratio will be less than 6:1, particularly in cases where the asphaltic content of the residuum is high. On a Poso Creek residuum topped to an on-stream viscosity of 67 seconds Saybolt Universal at i00 F., I have noted that the asphalt is a liquid fraction when the separation is effected at a volumetric ratio of 6:1 or less. However, I may state that a. liquid asphalt may be separated from every asphaltic oil at a ratio within the range of approximately 0.616 volumes of propane to one volume of the oil. Consequently, the limitation of ratios must be determined for each particular residuum. One method for accomplishing the determination is by performing a series of experiments on the particular residuum employing gradually increasing volumetric ratios and noting the ratio Where the asphalt stratified from the oil solvent solution passes from the liquid state to the granular bitumen. This may be readily understood by anyone skilled in the art.

Thus it will be observed that by controlling the proportions of propane, it is possible to cause the oil, propane and asphalt mixture to separate into two liquid phases, one containing the bulk of the oil dissolved in propane and perhaps a small amount of asphalt and a. lower layer of asphalt dissolved in propane containing a more or less limited amount of oil. In the above experiment when the volumetric ratio of propane to residuum was less than approximately 6:1, such separation occurred.

I have shown above that it is possible to control the characteristics .of the recovered asphalt by controlling the volumetric ratio. Thus by decreasing the amount of solvent, I may obtain a liquid asphalt and by increasing the amount of solvent, I may obtain a solid asphalt. It is possible to obtain a solid asphalt from the above liquid asphalt by commingling the asphalt with additional solvent. Thus the liquid asphalt recovered by treating Poso Creek residuum with a 6:1 or less volumetric ratio of solvent to residuum may be treated with additional amounts of solvent to precipitate solid asphalt. This can be done conveniently in a counter-current system as will be described below.

The foregoing discussion has been made with reference to the use of liquid propane as the solvent for asphalt separation or stratification from the asphalt containing oil. While propane is perhaps a preferred solvent to obtain the best commercial results, I do not wish to be limited solely to the use of propane, since other solvents may be employed with varying results and in employing such other solvents, the range of volumetric ratios for effecting stratification of the two liquid phases may also change, depending upon the solvent power or ability of the solvent to throw the asphalt from solution.

I have further discovered that one may use to advantage the unstratified and unseparated as-- material will precipitate at the low temperatures prevailing in a dewaxing apparatus and thus will act as nuclear or gathering bodies for the wax during crystallization by chilling. In other words. I prefer to separate the asphalt from an asphalt and wax containing 011 as a liquid i'raction and thus leave asphaltic material in the bulk of the oil containing solvent and then reduce the temperature on this oil solvent solution by reducing the pressure and evaporating a portion the solvent to chill the oil and precipitate the asphalt and wax and then separate the precipitated wax and asphalt from the asphalt. and wax-free lubricating oil dissolved in solvent.

With the'above discussion in mind, it will be perceived that it is an object of my invention to separate asphalt from an asphalt containing oil by means of a liquefied normally gaseous hydrocarbon solvent under pressure suiilcient to maintain the solvent in a liquid state and in an amount sufilcient to separate the contained asphalt as a liquid fraction. A particular object of my invention resides in the use of liquid propane 'as a preferred solvent for accomplishing this result.

A further object of my invention resides in eflecting separation of asphalt from an asphalt and wax containing 011 by means of propane in an amount sumcient to cause stratification of two liquid layers, one containing the bulk or oil and propane and a small amount of unstratified asphalt and the other layer containing asphalt and propane together with a small amount of oil and subsequently chilling the upper layer in the presence of such unstratifled asphalt to cause precipitation oi. the wax and asphalt, then separating the oil solvent solution irom the precipitated wax and asphalt and then separating residual solvent from the oil solvent solution to produce a lubricating oil substantially free of asphalt and wax. It is another object to accomplish a chilling eflect by releasing the pressure on the oil solvent solution to evaporate a portion of the solvent.

Other objects and advantages of my invention will be apparent from the following description of my invention taken from the drawing which represents a schematic arrangement for carrying out my invention.

Referring to the drawing, an asphalt contain= ing oil is taken from tank i and is passed into line 2 by pump 3 where it meets a propane solution of lubricating oil coming through line 2a. The propane solution and residuum passed through turbulence coil or mixing coil 4 and then into decanter or asphalt precipitator 5. The asphalt in the residuum is separated by the propane and settles to the bottom of the decanter 5 as an asphalt containing some propane which is passed by pump 6 into line 1 controlled by valve 8 where it is mixed with fresh propane taken from storage tank 9 via line it, pump II and line It controlled by valve I3. Fresh propane may also be introduced into line 2 via line H controlled by valve 15. The amount of propane introduced into the residuum will depend upon whether it is desired to remove the asphalt at the. bottom of the decanter 5 as a slurry oi asphalt and propane, i. e. as a mixture of substantially pure bitumen and propane or as a liquid fraction containing asphalt and propane'with some oil. If it is desired to separate the asphalt in decanter b as a. liquid fraction, the volumetric ratio oi propane to oil in decanter 5 will be within a range of 0.6:6 to one depending upon the character of the residuum and the degree to which it was topped. Higher volumetric ratios will precipitate the aspect as aslurry 01' substantially pure bitumen and propane. The asphalt and. propane mixture is then passed into mixing coil I6 and then into decanter or asphalt precipitator ll provided with scrapers or agitating paddles l8 operated by belt l9 from any suitable source or power not shown. Decanters 5 and I1 and propane storage tank 8 are maintained at the same pressure by means of equilibrium lines 23 controlled by valves 24 and 28'. This pressure should be sulllcient to maintain the solvent in the liquid state at ordinary temperatures. For the solvent given above, 1. e., propane, this pressure is about 125 lbs. per sq. in. a

The clear overflow from decanter I 1, consisting of liquid propane in which is dissolved a small amount of residual lubricating oil from the asphalt separated in decanter 5, is passed into line 20 controlled by valve 2! by means of pump 22 which forces it into line 2 where it is mixed with incoming residuum and passed through turbulence coil 4 in decanter 5, as described above.

The asphalt precipitated in decanter l1 settles to the bottom of the decanter and is removed as a slurry oi substantially pure bitumen and. propane. Scrapers or vanes it prevent the asphalt from adhering to the walls of the decanter and aid in passing the asphalt slurry to a screw conveyor 25 driven by motor 28. The asphalt slurry is passed into line ti to pump 28 which forces it through valve 29 into line at controlled by valve 32, valve 36 on line 35 being closed. The asphalt slurry is passed through valve 32 under pressure into heating coil 36 where it is heated to a sufiiciently high temperature to melt the asphalt and vaporize the residual propane. The heated mixture is then flashed through pressure reduction valve 38 on line 31 into evaporator it which operates at a lower pressure. Steam superheated in coil 42 is introduced into 48 to supply additional heat and to reduce the asphalt to proper speciilcation, generally only as regards flash and fire points. The overhead from evaporator til passing through mist extractor ii is sent through line 43 to cooler 44 and then to separator 45. The uncondensed propane from separator 45 is sent through line 46 controlled by valve ll to line 48 to the suction of compressor 69 where its pressure is raised to that in the high pressure system and sent to cooler 50 where it liquefies and runs down into the propane storage tank 9. Any uncondensed light oil in separator 55 is withdrawn through line 5! and condensed water through a The asphalt is taken from the bottomflow from decanter 5 may be sent through line 51 by pump 58 into line 59 controlled by valve 60 and passed to acid treatment and neutralization with alkali in accordance with the method described in my aforementioned copending application. The countercurrent washing of the separated asphalt illustrated by the above method of operation may be extended to as may steps as desired but in general two decanters giving two .wax to precipitate from solution.

countercurrent washings will be suflicient to produce an asphalt substantially free of wax and oil.

However, if the residuum from which the lubricating oil is produced also contains wax, the wax will be dissolved in the overflow from decenter 5, in which case I prefer to close valve 89 and pass the solution into line 8! controlled by pressure reduction valve 82 into a low pressure chilling column or evaporator 89. In column 88, suflicient propane vaporizes to reduce the temperature of the remaining material to a predetermined dewaxing temperature which causes The desired dewaxing temperature is obtained by controlling the pressure in column 69 by the proper operation of valves on line 84 and compressor 49 which is connected to the evaporator by lines 84, 66,81 and 49. The pressure to be maintained in column 63 will be generally about 0 lbs. gauge which corresponds to a temperature of approximately -40 F.

As the propane solution passes through valve 82, its pressure is reduced so that a portion of the propane evaporates in column 83 and the vapors pass out of the top through line 64 controlled by valve 65, then through lines 86 and Bl into line 48 and compressor 49 where the vapors are compressed, liquefied in cooler 58 and passed a to propane storage tank 9.

The chilledoil dissolved in propane carrying the precipitated wax is removed from the evapo-, rator or chilling column 69 through line 10 controlled by valve H by pump i2, which forces it into the vapor tight wax separator or settler 13. In order to prevent ebullition in the wax separator during the wax settling operation, pressure is imposed upon the solution of oil. This is accomplished by maintaining pressure within the separator by pump I2. As the chilled mass in the wax separator remains in a non-ebullient state, the wax settles out and is collected by vanes 14 operated by pulley 15 connected to a suitable source of power not shown. The wax-free oil dissolved in propane is withdrawn from the separator l3 and pumped by pump 16 through line H and valve 18 into heater [9 provided with mist extractor 80 where the propane present is vaporized by the aid of steam circulated through the closed steam coil 8i. The vaporized propane passes out of the heater through line 82 controlled by valve 83, cooled in cooler 84 and then passes through lines 95, 86, 61 and 48 to compressor 49, cooler 50 into storage tank 9. The dewaxed propane free oil passes from heater 19 by means of line 86 controlled by valve 81, through heat exchanger 98, line 89 into tank 90.

The precipitated wax slurry settling at the bottom of the wax separator 13 is removed from the separator through line 9| and is passed through heat exchanger 88 where it extracts heat from the dewaxed oil from heater 19. The wax slurry is then pumped by pump 92 into line 93,

through heater 94 and line into separator 96.

.of asphalt and propane containing some oil. In

carrying this out, valves 8, I3, M, 29 are closed and valves I8 and 94 are open. Valve 24' connecting the equilibrium line 29 to decanter i1 is closed while valve 24 connecting the equilibrium line to decanter 5 is open. Thus decanter I1 is cut out of the system and the process will be operated employing only one decanter, i. e., decanter 5. Crude oil residuum as before is introduced into line 2 and is mixed under pressure with liquid propane from storage tank 9 passed through lines 05 and ii. The quantity of liquid propane introduced into line 2 should be sufiicient to cause stratification in decanter 5 into two liquid layers; the lower layer being a liquid asphalt fraction dissolved in propane and containing some oil and the upper layer comprising the bulk of the oil dissolved in propane and containing dissolved asphalt. The amount added will depend upon the character of the crude oil from which the residuum is produced and the degree of topping, but in general will be within a volumetric ratio of approximately 0.6:6 of propane to one of residuum. The mixture is then passed through turbulence coil 4 into decanter 5. The liquid asphalt solution containing a quantity of propane settles to the bottom of the decanter and is removed by pump 6 which forces it into lines 35 and 30 and valve 32, through heating coil 36 and is then flashed through pressure reduction valve 81 into evaporator 40 which operates at a lower pressure. superheated steam maybe introduced into the bottom of the evaporator to aid in reducing the asphalt.

The overflow i'rom decanter 5 consisting of the bulk of lubricating oil and propane and containing a small amount of unseparated asphalt material is pumped through line 51 into line 59 from which it is passed to acid and alkali treatment to remove the remaining asphaltic material, valve 62 on line H being closed. However, if the overflow contains wax I prefer to close valve 68 and open valve 62 and pass the overflow to the dewaxing unit prior to any acidtreatment. The asphaltic material which will precipitate at lower temperatures due to its limited solubility in the oil propane solution at the dewaxing temperatures will then act as nuclear or gathering bodies during wax crystallization and thus aid in the separation of the wax from the oil.

The overflow from decanter 5 is then passed through pressure reduction valve 82 into low pressure chilling column or evaporator 63 where sufllcient propane vaporizes to reduce the temperature of the remaining material to a predetermined dewaxing temperature, 1. e. 40 F. which causes the wax and asphalt to precipitate from solution. If the overflow did not contain a sufficient amount of propane to effect the proper reduction in temperature of the oil or the proper precipitation of wax or asphalt, further quantities of liquid propane may be mixed therewith prior to passage through valve 62. The mixture in the chilling column 83 is then passed into wax separator 19 from which dewaxed oil and solvent is passed into heater 19 wherein residual solvent is evaporated while the precipitated wax and asphalt slurry is removed from the separator, passed through heat exchanger 88 through heater 94 into separator 98 in which propane is vaporized and passed to storage tank 9. The mass collecting in separator 96 is then passed to storage tank I05 while the dewaxed and de-asphaltized lubricating oil free from propane is passed through heat exchanger 88 into tank 90. 7

If desired,. the overflow from decanter 5 and containing wax may be acid and alkali treated prior to dewaxing in the manner described in my aforementioned co-pending application.

It is to be understood that the above is merely illustrative of preferredembodiments of my invention of which many variations may be made by those skilled in the art without departing from the spirit thereof. 7

I claim: Y

1. A method for separating asphalt from oil which comprises mixing an asphalt containing 011 with a liquefied normally gaseous hydrocarbon solvent in an amount suflicient to separate asphalt as a liquid fraction and separating and removing said liquid asphalt from the oil solvent solution. 3 x

2. A method for separating asphalt from asphalt containing oil which comprises mixing said oil with a liquefied normallygaseoushydrocarbon solvent under temperatures and pressures sufllcient to maintain said solvent liquid, separating said mixture into two liquid fractions, one of said fractions comprising substantially solvent and oil and the other comprising solvent and liquid asphalt, separating said asphalt and solvent mixture from said oil solvent mixture and separating the .solvent from the asphalt.

3. A method for separating liquid asphalt from asphalt containing oil which comprises commingling said oil with a liquefied normally gaseous hydrocarbon under temperatures and pressures sufficient to maintain said solvent liquid, separating said mixture into two liquid fractions, one of said fractions comprising substantially solvent and oil and the other comprising liquid asphalt containing solvent, separating said liquid asphalt from the oil solvent solution and separating the solvent from the liquid asphalt.

4.A method-for separating asphalt from oil which comprises mixing an asphalt containing oil with a liquefied normally gaseous hydrocarbon solvent under superatmospheric pressure in an amount sufllcient to precipitate asphalt as a liquid fraction and separating and removing said liquid fraction from the oil solvent solution under super-atmospheric pressure.

5. A method for separating asphalt from oil which comprises mixing an asphalt containing oil with a liquefied normally gaseous hydrocarbon solvent under superatmospheric pressure in the proportions of 0.6-6 volumes of said solvent to one volume of said oil to effect separation of the asphalt as a liquid fraction, separating and removing said liquid fraction from the oil solvent solution.

6. A method for separating asphalt from oil which comprises commingling an asphalt containing oil with a liquefied normally gaseous hydrocarbon solvent; in an amount sumcient to separate asphalt as a liquid traction, separating and removing said asphalt liquid fractionfrom the oil solvent solution and washing said asphalt liquid fraction with further quantities of solvent to produce a solid asphalt.

'l. A method for separating asphalt and wax from oils containing the same which comprises mixing an oil containing asphalt and wax with a liquefied normally gaseous hydrocarbon solvent to separate asphalt as a liquid fraction and to leave asphaltic material in the remaining oil solvent solution, separating and removing said liquid fraction from the remaining oil solvent solution and chilling said oil solvent solution to precipitate said asphaltic material and wax from the oil solvent solution.

8. A method for separating asphalt and wax from oils containing the same which comprises mixing an oil containing asphalt and wax with a liquefied normally gaseous hydrocarbon solvent, stratifying the resultant mixture into two layers, one containing the bulk ofoil and solvent and containing asphaltic material and wax and the other containing a liquid asphalt and solvent and containing some oil, separating the two layers, chilling the layer containing the bulk of oil and solvent and containing asphaltic material and wax to precipitate said asphaltic material and wax and separating said precipitated asphaltic material and wax from the remaining oil and solvent.

9. A method for separating asphalt and wax from oils containing the same which comprises commingling an oil containing asphalt and wax with a liquefied normally gaseous hydrocarbon solvent under superatmospheric pressure in an amount suflicient to separate asphalt as a liquid fraction and to leave a portion of the asphaltic material in solution in the oil solvent solution containing wax to act as nuclear bodies for wax crystallization in a subsequent dewaxing operation,\, separating and removing the oil solvent solution from the asphaltic liquid fraction, releasing the pressure on the oil solvent solution to vaporize a portion of the solvent and thus chill the oil to precipitate wax and contained asphaltic material and separating said precipitated wax and asphaltic material from the remaining oil solvent solution.

10. A process for separating asphalt from oil containing the same which comprises commingling said oil with a solvent to separate liquid asphalt from the oil, separating said liquid asphalt together with a quantity of oil from the oil solvent solution, commingling said separated asphalt andoil with a liquefied normally gaseous hydrocarbon solvent to separate the oil from said separated asphalt and separating the oil and solvent from said separated asphalt.

11. A processfor separating asphalt from oils containing the same which comprises commingling said oil with a liquefiednormally gaseous hydrocarbon solvent to separate liquid-asphalt from the oil, separating and removing liquid asphalt with a quantity of oil from the oil solvent solution, commingling said separated asphalt and oil with further quantities of said liquefied normally gaseous hydrocarbon solvent to separate the oil from said separated asphalt and separating and removing the oil and solvent from said separated asphalt.

12. A process as in claim 11 in which the solvent comprises liquid propane.

13. A method for separating asphalt from asphalt containing oil which comprises mixing said oil with a liquefied normally gaseous hydrocarbon solvent in an'amount sumcient to separate the asphaltic oil and solvent into two liquid fractions comprising an upper liquid layer oi. oil dissolved in solvent and a lower liquid. layer of asphalt dissolved in oil and solvent, separating the lower liquid layer from the upper liquid layer ULRIC B. BRAY.

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