US2081734A - Method for treating oils - Google Patents

Description

- May 25, 1937. u. B. BRAY METHOD FOR TREATING OILS Original Filed Aug. l, 1935 n. m T T V.A b.

Patented May 25, 15937 )PATENT oFFic-Ei METHOD FOR TREATING OILS Ulric B. Bray, Palos Verdes Estates, Calif., as-

signor to Union Oil Company ofv California, Los Angeles, Calif., a corporation of California Original application August 1, 1933, Serial No. 683,187. Divided and this application December 14, 1935, Serial No. 54,503

20 Claims.

This invention relates to a method for'separating asphalt and wax from oils containing the same. The invention relates particularly to a method for removing the asphalt from oils containing the same in a plurality of stages. The present invention is a division \of Serial No.

683,187, filed August 1st, 1933 now U. S. Patentv 2,041,276, which is a continuation, in part, of my co-pending -applications Serial No. 466,189, led

July 7th, 1930, and Serial No. 659,855, led March 6th, 1933 now U. S. Patent No. 2,010,008.

In my co-pending application Serial No.

466,189,1iled July 7th, 1930, I disclosed a process for producing lubricating oils and for separating asphalt and/or wax from oils containing the same. In this process a crude oil residuum.con.

taining asphalt which was topped so that the residue contained fractions having a viscosity from 400 to 500 seconds Saybolt universal at 100 F. was commingled with a iiqueed normally gaseous hydrocarbon solvent such as propane under pressure suilicient to maintain the solvent in the liquid state. This permitted precipitation of asphalt. The solution of lubricating oil in the liquid solvent and precipitated asphalt was permitted to settle in order to stratify the precipitated asphalt from the oil solvent solution. The latter was expanded through heating coils to vaporize the solvent and thus leave behind a lubrieating' oil substantially free from asphalt. The precipitated asphalt in the decanter was removed as a slurry of propane and bitumen which was also heated to remove residual propane. The propane in each case was recovered by compression and cooling and returned to the system for further use.-

If the lubricating oil 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 deasphaltizing step. This was accomplished by evaporative refrigeration, that is, the pressure on the solution was released and a portion of the solventA was evaporated by the release in pressure which effectedgchillirng of the oil and precipitation of the wax from the propane solution. By reducing the pressure to substantially atmospheric, the temperature of the solution was reduced to approximately 40 F. The precipitated wax was separated from the oil and from the residual solvent by settling, ltration, or centrifuging. The wax-free solution was heated to evaporate the solvent and thus to produce a lubricating oil free from both asphalt and wax.

As a. particular feature of the invention, the

use of such hydrocarbon solvents which are volatile at atmospheric temperature and pressure was disclosed to precipitate the asphalt. Such hydrocarbon solvents include propane, iso-butane, ethane, methane or mixtures thereof and are obtainable by rectification of casinghead gasoline by the'so-called stabilizing method now conventional in the natural gasoline industry. 'I'hey comprise the overhead gaseous fractions'of the stabilizing process. The ygaseous fractions are liquefied by compression and cooling in the conventional manner and are drawn offinto 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, 19.19% iso-butane and 1.17% normal butane. The necessary pressure to maintain this fraction in a liquid state at approximately 75 F., is about 125 lbs. per sq. in. gauge. In the present invention, I intend to include the use of the foregoing liqueed normally gaseous hydrocarbon solvents.

In the foregoing process, the precipitated asphalt separated from the pressure precipitator comprised a slurry of asphalt and propane from which the latter was separated by distillation to leave a substantially pure asphalt or bitumen. This type of asphalt seriously handicaps the efcient operationv of the process due to the fact that it must kbe heated to a uid consistency before it can 'be easily pumped and handled.

In my co-pendirg application Serial No. 659,855, led'March 6th, 1933 now U. S. Patent 2,010,008, I disclosed a process for the separation` quantity of asphalt in the oil solvent solution.

The oil solvent solution was then chilled to precipitate wax and also the remaining asphalt which were separated from the oil solvent solution by settling. v

By the present invention I propose to separate the asphalt present inthe residuum from the oil in a plurality of stages. In the first stage of the process, the oil orresiduum is commingled with a solvent in such ratio as to separate the asphalt as a liquid fraction. This is accomplished by providing a low volumetric ratio of propane to oil. If the ratio of solvent to oil is high, the asphalt is separated as a granular solid or as a substantially pure bitumen containing propane. On the be separated from the oil solvent solution as a liquid fraction. By referring to the asphalt as a liquid fraction, it will be understood that the asphalt separated in the decanter when the residuum containing asphalt is mixed with solvent comprises `a substantially homogeneous solution of asphalt, oil and propane which is liquid at atmospheric temperature. It comprises a liquid fraction as distinguished from a slurry of asphalt and propone or a heterogeneous mixture or asphalt and propane containing oil from which the asphalt may be separated from themixture by simple deeantation or nltration.

The amount oi propane mixed with the oil will depend to a large extent on the character o! the crude or residuum treated. Also the amount of asphalt recovered in this stage will depend upon the propane-oil ratio. For example, a treatment on Poso Creek residuum topped to an on-stream viscosity of 67 seconds Saybolt universal at 100 F., the minimum amount oi' propane that can be used to leffect a separation of phases will exceed approximately 1% volumes of propane to one volume ol oil. 0n a McKittrick residuum, a separation of phases can be obtained when the volumetric ratio exceeds 0.6 volume of solvent to one volume of oil. A further increase in the volumetric ratio of the respective oils indicates a steady decrease in percentage recovery oi the lubricating oil, while the character of the oil is increasingly better as to color. The amount o! asphalt recovered will also increase with an increase in the propane to oil ratio. However, the character of the asphalt recovered varies with variation oi this ratio'. In general, with low volumetric ratios and high percentage of oil recovered, the asphalt separated by stratication is a liquid asphalt. When free of solvent it has a low melting point and a high penetration. By increasing the volumetric ratio, the character of the asphalt stratified and recovered passes from the liquid stage to a solid asphaltl or a substantially pure bitumen in iinely divided form. The penetration will correspondingly become lower and the melting point higher as the volumetric ratio is increased. In other words, it appears that there is a critical volumetric ratio below which asphalt may be separated from the oil as a liquidv traction and above which the asphalt comprises a granular solid or substantially pure bitumen. In general, the volumetric ratio o! 6 or less of propane to one of oil will result in the separation of the asphalt as a liquid lfraction, whereas a ratio above this will cause the asphalt to be separated as a solid. Ido notwish to belimitedto this exact ratio since the upper limit of volumetric ratio for the separation of asphalt as a'liquid fraction will depend entirely upon the character oi.' the residuum treated and the degree to which it is topped. With certain stocks, the upper llimit o! volumetric ratio will be less than 6 to 1, perticularly in `cases where the asphaltic content of the residuum is high. On a Poso Creek residuum' topped to an on-stream viscosity oi 67 `seconds Saybolt universal at 100 F., the separation of asphalt as a volumetric ratio of 6 to 1 or less. However, I may state that liquid asphalt may be separated from any asphaltic oil at a ratio within the lrange ol approximately 0.6 to 6 volumes of propane to one volume of the oil.

When the process oi the ilrst stage is operated to eilect removal of asphalt as a liquid fraction,

the oil solvent` solution ls dark and its viscosity ls solution is treated liquid fraction may be effected at a v relatively high which indicates that a substantial amount'of asphalt remains in solution. This oil in the second stage of the process forming the subject oi my invention. I have discovered that when the propane solution oi the ilrst stage is mixed with additional propane at the same or at a lower temperature, additional precipitation of asphalt is eilected. In most cases.

the second precipitate of asphalt will settle as a lliely divided material or asphaltic slurry of bitumen and propane. The amount ofasphalt separated in the second stage will depend upon the amount of asphalt removed in the llrst stage which will, of course. depend upon the volumetric ratio of propane to oil employed in the rst stage. The amount of asphalt separated in the second stage will also depend upon the volumetric ratio oi propane to oil employed in the second stage. In general, this amount will comprise from 2 to 4% of additional asphalt'based on the residuum entering the process. This additional amount may be removed by settling or filtration. The propane-oil solution may then be chilled to a temperature between 40 F. and 404li'. to eilect a still further precipitation of asphalt or to 'eifect a simultaneous precipitation of asphalt and wax where the oil treated contains wax. It de'- sired.v the temperature may be reduced to the cloud point of the wax to separate pseudo asphal-` tic bodies prior to carrying out the dewaxing operation. l l

With the above discussion in mind, it will be perceived that it is an object oi' my invention to separate asphalt from asphalt containing oil by means of a liqueiied normally gaseous hydrocarbon solvent under pressure sufficient to maintain the solvent in a liquid Astate and inan lamount sunlcient to, separate the, contained asphalt as a liquid fraction and then adding a further quantity of tolvent to the all solvent solution and separating a further quantity of asphalt at the same or at a lower temperature than the temperature employed in the first stage or a portion may be removed at the same temperature after the addition of further quantities of solvent and the remainder removed at a lower temperature. A. particular object of my invention resides in the usel ot liquid propane as a preierred solvent for accomplishing the above resuits.

Another object o! my invention resides in effecting separation of asphalt from an asphalt and wax containing oil by means of a solvent such as propane in an amount sufficient to cause stratification oi two liquid layers. one containing the bulk o! o'il, propane and wax, together with a small amount of unprecipitat'ed asphalt and the other layer containing asphalt and propane together with a small amount oi. oil, in separating these two liquid layers, in adding a further quantity of propane to the solution oi oil and propane containing wax and unseparatedasphalt to precipitate said asphalt,. in separating the precipitated asphalt from the oil, solvent and wax. in chilling the oil solvent solution containing wax to precipitate the wax, in separating the precipitated wax from the oil solvent solution and in then separating the residual solvent from the oil to produce a lubricating oil substantially tree of asphalt and wax.

It is another object of the invention to accomplish chilling of the oll solvent solution by re- .stantially pure bitumen and propane.

Other objects and advantages of my invention will be apparent from the following description' .propane coming from propane storage tank 8 via line i0, pump I I and line I2 controlled by valve I3. `The propane and residuum is passed through turbulence or mixing coil 4 and then into decanter or asphalt precipitator 5. The amount of propane introduced into residuum will depend upon whether it is desired to remove the asphalt at the bottom of decanter 5 as a slurry of asphalt and propane. i. e. as a mixture o1 substantially pure bitumen and propane or as a liquid fraction of asphalt and'propan'e containing some oil. In the preferred operation, it is desirable to Iseparate the asphalt in decanter 5 as a liquid fraction in which case the volumetric ratio of propane to oil employed will be within a range of 0.6 to 6 of propane to one volume of oil, depending upon the character of the oil or residuum treated and the degree to which it was topped. Volumetric ratios higher than those specified will eiIect precipitation. and settling of the asphalt as a slurry of sub,-

'I'he asphalt settling to the bottom of decanter 5 is withdrawn by means of pump 6 and line 1 controlled by valve 8 to further treatment as'will be hereinafter described.

The clear overflow from decanter 5 consisting of liquid propane and the bulk of the oil is passed into line I4 by means of pump I5 where it meets a stream of liquid propane passed from storage tank 9, line I and pump II into line I2' controlled by valve I 3'. The mixture is then passed into turbulence coil I6 and then into decanter or asphalt precipitator I1 provided with Scrapers or agitating paddles I8 operated by belt I 5 from any suitable source of power not shown. Decanters and I1 and propane storage tank 5 are maintained at substantially the same pressure by means of equilibrium lines 23 controlled by valves 24 and 24'. This pressure should be su'cient to maintain the solvent in the liquid stage at ordinary temperatures of approximately 75 F. For the solvent given above, that is, propane, this pressure is about 125 to 175 lbs. per sq. in. gauge. If desired, the pressure in decanter I1 may be maintained lower than that in decanter 5 so that a lower temperature may be provided in decanter I1.I For example, the temperature in decanter I1 may be reduced to approximately 40 F. to 40 F. depending upon whether the oil contains wax or not. If the oil is substantially free from wax, the temperature may be reduced to approximately 0 F. to 40 F. If the oil contains wax, it is preferable to reduce the temperature to not substantially below that temperature at which wax begins to precipitate. This temperature is approximately 35 F. to 45 F. The temperature reduction in decanter I1 may be eiected by closing valve 24 and regulating valve |22 online |23 which connects ,to line 1I and the compressor 54. The wax may then be separated in the manner hereinafter described.

'I'he amount of propane introduced into the solution of oil and propane removed from decanter 5 will depend upon the amount of propane y already present-infthe solution and also on the Y amount of unseparated asphalt i'ro'm the first stage. As an example. Santa Fe Springs long residuum topped to approximately 100 viscosity (Baybolt universal at 100 F.) on the overhead stream was extracted in the first stage with three volumes of propane to give a yield of 23% oi recovered asphalt based on the residuum which appears as a liquid phase containing approximately 30% propane when equilibrium is reached between three volumes of propane and the residuum under pressure. The clear propane solution is decanted and mixed with 4 additional volumes of propane also at atmospheric temperature and allowed to settle. Approximately 2% to 4% of additional asphalt based on the residuum precipitated and settled to the bottom of the second decanter I1. This asphalt'was recovered as a slurry oi' nely dividedsubstantially pure bitumen and propane at the bottom of -decanter I1. Scrapers or vanes I8 preventthe asphalt from adhering to the Walls of the decanter and aid in passing the asphalt slurry to a screw conveyor 25 driven by motor 26. The asphalt slurry is passed into line 21 to pump 28 which forces it through valve 29 into lines 30 and 3| to further l treatment as will be describedhereinafter.

The asphalt settling to the bottom of decanters 5 or I1 as described above may be separately treated for removal of propane or may be treated in admixture. If it is desired to separately treat the asphalt from decanter 5, it is withdrawn from the bottom oi the decanter by means of pump 6 and line 1 controlled by valve 8 and passed into lines 30 and 3| where, if desired, it ls mixed with a preheated uxing oil coming from line 40 which is obtained from storage tank 33, pumped by pump 34 through line 35 to heater 36 where itis preheated and is then passed through line 31 into line 38 controlled by valve 38 and thence into line 40 controlled by valve 4I and introduced into line 3| controlled by .valve 32.

The mixtureof preheated fluxing oil and asphalt removed from decanter 5 containing propane is passed through valve 32 and heating 44 on line 43 into evaporator 45 which is operatedv at w, lower pressure. If the iluxing oil has been preheated to a suiliciently high temperature toux the asphalt in line 3|, heater 42 may be a omitted and the mixture ilashed through valve 44 into evaporator 45. Steam superheated in coll 46 is introduced into 45 to supply additional heat and to reduce the mixture to proper speciflcation generally, only as regards ash and re points. The overhead from evaporator 45 passing through mist extractory 41 is sent through line 48 to cooler 49 and then to separator 50. The uncondensed propane from separator 50 is sent through line 5| controlled by valve 52 to line 53 to the suction of compressor 54 where its pressure is raised to that in the high pressure system and is then sent to cooler 55 Where it is liqueiiedand runs down into propane storage If desired, the asphalt from decanter 5 may be.

mixed with that of decanter |1 and treated in admixture in the'evaporator 45.

If it is desired to recover the asphalt in either l decanter 5 or |1 in substantially pure form, i. e.

without cutting back with a iiuxing oil of lower viscosity, a small amount of oil passing throughv line 40 may be introduced through line 3| to start the process and the valve 4| is closed. Then a portion of the asphalt recovered in the evaporator 45 may be continuously circulated via line |20 controlled by valve |2| and pump |22 through a heater |23 and line |24 into line 3| to supply heat for fluxing and evaporation of residual propane in the precipitated asphalt. Heater 42 may be omitted. The introduction of hot uxing oil into the asphalt recovered from the bottom of decanter 5 is not entirely necessary since this asphalt is substantially liquid and can be readily passed or pumped through the lines connecting decanter 5 with evaporator 45. However, it is preferable to commingle the asphalt settling to the bottom of decanter l1 with hot iiuxing oil since this asphalt is heavy and cannot be efiiciently handled.

The overflow from decanter i1 consisting of propane and deasphaltized lubricating oil stock is sent through line 6| by pump 62 and then through line 53 controlled by valve 64 to acid treatment and neutralization with alkali in accordance with the method described in my aforementioned co-pendng application Serial No. 466,189. However, if the residuum from which the lubricating oil is produced also contains Wax, the wax would be dissolved in the overow from decanter l'l in which case I prefer to close valve @d and pass the solution into line 55 controlled by pressure reduction valve dfi into low pressure chilling column or evaporator 5l. In column 61,

sufcient propane vaporizes to reduce the temperature o the remaining material to a predetermined dewaxing temperature which causes Wax to precipitate from solution. The fiesired 'dewaxing temperature is obtained by controlling the pressure in column tl by the proper operation of valve 59 on line t8 and compressor 55 which is connected to the evaporator by lines 59, 30, "li, and 53. The pressure to be maintained in column 51 will be generally about 0 lbs. gauge which corresponds to a temperature of approximately 40 F.

As the propane solution passes through valve G6, its pressure is reduced so that a. portion of the propane evaporates in column (ill and the vapors pass out of the top through line 553 controlled by valve te, then through lines lli and "ll into line 53 and compressor 5d where the vapors are liqueiied, cooled in 55 and passed to propane storage tank 5.

The chilled oil dissolved in the propane carryn ing the precipitated wait is removed from the evaporator or chilling column l through line 12 controlled by valve '13 by pump iid, which forces it into the vamp-tight wax separator or heater 8|.

settler 15. In order to prevent ebullition or boiling in the wax separator during the. wax settling operation, pressure is imposed upon the solution of oil. This is accomplished by malntaining pressure within the separator by pump 14. As the chilled mass in the wax separator remains in a non-ebullient state, the wax settles out and is collected by vanes 16 operated by belt 11 connected to a. suitable source of power not shown. The wax-free oil dissolved in propane 1s withdrawn from the separator 15 and pumped by pump 18 through lines 19 and valve 80 into heater 8| provided with mist extractor 82 where the propane present is vaporized by the aid of steam circulated through the closed steam coll 83. The vaporized propane passes out of the heater through line 84 controlled by valve 85, cooled in cooler 86 and then passes through lines 81, 10, 1|, and 53 to compressor 54, cooler 55 into storage tank 9. The dewaxed propanefree oil passes from heater 8| by means of line 88 controlled by valve 89, through heat exchanger 9|, line 92 into tank 93.

The precipitated `wax slurry containing propane settling at the bottom of the wax separator 15 is removed from the separator through line 94 and is passed through heat exchanger 9| where it extracts heat from the dewaxed oil from the l The wax slurry is then pumped by pump 95 into line 96 Where it is mixed with a hot fluxlng oil coming from line 81 controlled by valve 98. This oil may comprise a portion of the fiuxing oil passed from tank 33, heated in heater 36 and by-passed into line 91. The mixture of hot fiuxing oil and wax slurry is then introduced into line Sil, heater |90 and then passed'through line iti into separator |02. Vaporized propane is passed to propane` storage tank 9 via line |03 controlled by valve |04, cooler |05, lines |06, 1 i, and 53, compressor 5d and cooler i 55. The mixture of propane-free luxing oil and rwax comprising a fuel oil is Withdrawn from separator |02 through line |01 and pumped by pump |00 into line it@ controlled by valve H0 into storage tank til. if desired, a portion of this mixture may be lay-passed and. sent through line ||2 controlled by valve H3 to pump llil which 'forces it through heater H5 into line H5 and then into line d@ Where it meets further quantities of wax slurry from settler l5.

1f it is desired to recover the Wax' in settler l5 as a crude petrolatum which may then be puried according to methods now conventional, the uxing material may comprise an initial amount of petrolatum preheated to a temperature of approximately 350 F. and introduced into line 99 which is mixed with the wax slurry in the proportions of two Volumes of preheated petrolatum to one volume of wax slurry. The mixture is then passed into separator |02 where propane lis vaporized. Heater i0@ may be omitted. The crude petrolatum is withdrawn from separator |02 at a temperature of approximately v200" F. which is sufciently high above the melting point of the petrolfitum to permit efficient pumping and handling and is then passed through line l0'l and pump |08, one volume ci the material passing into tank i li and the other two volumes are recirculated into line 59 via line ii' and pump im which forces the material through heater H5 where the temperature is again raised to 350 F. and passed into lines lit and 99. The cyclic circulation through line il?, heater H5, line H5 into line 99 is carried on continuously.

lso

-If desired, the initial amount of preheated petrolatum introduced into line 99 may be substituted by an initial volume of preheated petroleum residuum which is circulated through the apparatus in themanner described above, one volume being withdrawn into tank while the -remainder is recirculated into the wax slurry comingfrom separator 15. After a number of such circulations, the material'passing into line |01 will be suillciently free from petroleum residuum and will comprise a crude petrolatum. Consequently, the material collecting in tank and the portion recirculated through heater -will also comprise a crude petrolatum.

If it is desired to convert the wax into fuel oil, 'it is preferable to mix the wax slurry coming from settler 'i5 with a cracked residuum lcon-- tinously introduced into line 9@ via line 91, said cracked vresiduum possessing a pour point depressant. If the cracked residuum is at a sufciently high temperature, say about 500 F., heater |00@ may be -omitted or by-passed and the mixture passed directly into separator |02 to permit vaporization of propane. The mixture from separator |02 comprising a fuel oil is then passed to storage tank or a portion thereof may be recirculated into line 99 vvia heater IIS.

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

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

I claim:

1. A process for separating the diluent from solidified impurities removed from oils by the aid of such diluent which comprises mixing the solidifled impurities containing the diluent with a preheated oil and evaporating the diluent from the l mixture. 2. A process for-separating the diluent from soliditled impurities removed from oils -by the aid of a light liquid hydrocarbon which comprises mixing the solidiiled impurities containing the diluent with a preheated oil and iluxing the same. and evaporating the diluent from the mixture.

3. A process for treating oils which comprises mixing the oil with a liquid capable oiA precipitating impurities solidiilable at ordinary temperatures from the oil, separating said impurities containing a portion vof said liquid from the oil, mxing said separated impurities and liquid with a preheated oil and evaporating the liquid from the mixture. 4. A process as in claim 3 in which the liquid is normally gaseous.

5. A process asin claim 3 in which a normally gaseous hydrocarbon.

6. A processas in claim 3 in which the liquid the liquid is .is propane.

' 7. A process for the separation of asphalt from oils containing the same'which comprises mixing the oilwith aliquid capable of precipitating the asphalt from the oil, removing the precipitated asphalt containing a small amount of said liquid, mixing said separated asphalt and diluent with heated oil and uxing the asphalt and evaporating the liquid from the mixture.v l

8. A process for the separation of asphalt from oils containing the same which comprises mixing the oil with an asphalt precipitating liduidamixing vthe precipitated asphalt containing a small amount of said liquid with an oil heated to a suirlciently elevated temperature to ilux the asphalt and removing evaporated liquid from the iluxed asphalt.

9. A process for the separation of asphalt from oils containing the same which comprises mixing the oil with an asphalt, precipitating liquid, separating the precipitated asphalt containing a small amount of said liquid from the remaining oil-and liquid, commingling the separated asphalt and liquid with hot asphalt and evaporating the liquid from the mixture.

l0. A process for the separation of asphalt from oils containing the same which comprises mixing the oil with an asphalt precipitating liquid, separating the precipitated asphalt containing a small amount' of said liquid -from the remaining oil and I liquid, iluxing the separated asphalt and liquid with oil, evaporating said liquid from the mixture and recirculating preheated asphalt to said asphalt containing asphalt precipitating liquid separated from oil containing asphalt.

11. A process for the separation of wax from oils containing the same which comprises mixing ythe oil with a diluent, chilling the mixture to precipitate wax and separating the precipitated Awax containing a small amount of diluent from theoil and remaining diluent, mixing'saidl separated wax and diluent with preheated ,oil and evaporating A the diluent from the mixture.

. 12. A process for removing diluent from wax slurry separatedfrom oils inthe presence of diluent which comprises mixing the separated wax slurry containing diluent with a hot oil to iiux the vwax and evaporate diluent and separating the diluent from the mixture.

13. A process for treating wax slurry contain ing diluent which comprises commingling the wax slurry with hot wax and evaporating diluent from the mixture.

14. A process for treating wax slurry containing diluent which comprises commingling the wax slurry in the preheated wax and evaporating diluent from the mixture and recirculating a portion of said mixture from which diluent has been evaporated for admixture with further quantities of wax slurry.

' 15. A process as in claim 13 in which the wax mixed with the wax slurry is petrolatum.

16. A process as in claim 14 in which the preheated wax initially mixed with the wax slurry is I l petrolatum. l

17. A'process for treating wax slurry vwhich comprises mixing the wax slurry with preheated petroleum residuum at an elevated temperature and circulating a portion of the mixture for admixture with further quantities of wax slurry.

18. A process as in claim 17 in which the preheated petroleum residuum is a cracked residuum.

19. A'process for treating wax slurry containing a small quantity of diluent which comprises iiuxing the wax slurry with hot oil at a temperature sunicient to evaporate the diluent, passing the mixture into avaporizer wherein the diluent is removed from the mixture, withdrawing the iluxed mixture from' the vaporizer, heating a portion of said withdrawn mixture and mixing said heated portion with further amounts of wax slurry containing diluent.

20. A process as in claim 19 in which the hot oil is petrolatum.

A ULRIC B. BRAY.

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