US2040056A - Dewaxing hydrocarbon oil - Google Patents

Description

May5, 1936. R. E. MANLEY DEWAXING HYDROCARBON OIL Filed June 13, 1932 @a5/5er E MHA/LEY INVENTOR BY W ATTORNEY Las lPatented May 5, 1936 UNITED *STATI-:s

vP .MEN'I OFFICE 2,040,053 DEWAXIN G -IIYDROGARBON OIL tion of Delaware Application June 1a, 1932, semi No. 616,865

This invention relates to dewaxing hydrocarbon oil and more particularly to a process of removing parailin wax from waxl-bearing petroleum all for the production of low pour test lubricating o The invention broadly contemplates a process cf dewaxing hydrocarbon. oil wherein the cycle of operation comprises diluting wax-bearingfoil with a low boiling hydrocarbon liquid having properties characteristic of propane, for example, and which may be gaseous under ordinary conditions of temperature and pressure, chilling this mixture to precipitate the wax constituents, separating the precipitated wax by filtration in the presence of a substantially dehydrated lter-aid material, separating from the filter-aid material the wax and moisture absorbed during dewaxing, and mixing' this substantially moisture-'free iiiter-aid material, advantageously after chilling,A

with further wax-bearing oil.

My invention contemplates diluting wax-beary ing oilwith a light hydrocarbon liquid composed of such constituents as propane, propylene, bun tane, 'and the like, and .in suitable proportion with the oil to produce a solution from which the wax constituents may be readily precipitated upon cooling. The cooling may be effected by refrigeratively evaporating a--portion of the low boiling hydrocarbon liquid directly from the mixture undergoing cooling. If'desired, partial cooling .of the mixture may be effected in this way while the final chilling maybe accomplished by passing the partially cooled mixture in indirect heat exchange relationship with a refrigerant material. A part dof the cooling may be effected by flowing the fresh wax-bearing mixture in heat exchange relationship with the outgoing cold dilute dewaxed mixture. In this latter case, a

part or all of the low boiling diluent'liquid mayv be evaporatedwith refrigerative effect from the dewaxed mixture during the exchange, and subsequently be recovered for use in diluting fresh 1 wax-bearing oil, as described, for example, in my ccpending application, Serial No. 553,084, filed July 25, 1931, for Dewaxing hydrocarbon oil.

When the wax-bearing mixture has been cooled to eiIect precipitation of the wax constituents, it is mixed with a substantially dehydrated filteraid material of the type such as diatomaceous earth of other similar porous or brous filter-aid material,r and which has advantageously been first subjected to cooling or chilling before ad' mixing with'the oil, as will subsequently bmdescribed inmore detail.

The precipitated waxand solid'fllt'er-aid mateadmlxed.

turejfree lter-aid material.

11 Claiml. (Cl. 196-17) The -precipitated wax and solid filter-aid material, which is thus separated from the liquid hydrocarbons, is mixed with a liquid material adapted to displace the wax, as well asabsorbed moisture, from the filter-aid material. Petroleum naphtha, for example, is particularly suitable for this purpose, although other wax solvents may be used. The removal'of this moisture is necessary since, otherwise, its accumulation de'- stroys theeii'ectiveness of the material as a nlteraidmedium, particularly in dewaxing operations where low temperatures prevail. This moisture is originally absorbed from the incoming oil and the surroundings. It must be continually removed, otherwise it accumulates in the material, forms ice during the dewaxing step, and thus reduces the porosity of the material andmaterially de- 2 4creases its effectiveness as a nlteraid. 5

from the slurry by filtration while maintaining the mixture in a hot condition. The separated filter-aid material may be washed with fresh 3,5 warm solvent liquid to remove remaining oil or wax, following which the recovered material, now

in a substantially completely dehydrated state,` is subjected to cooling and chilling before mixing with further wax-bearing oil. This cooling, 40 may be accomplished, for example, by spraying the material with some of the low boiling hydrocarbon liquid-which is refrigeratively evaporated in direct contact with the iilter-aid material to thus cool it to a temperature approaching that of the chilled wax-bearing oil with which it is to be My invention, therefore, comprises a cyclic process of dewaxing oils which involves diluting the oil with a liquid combining the properties of a wax-precipitating liquid medium with those of a refrigerating medium.l The precipitated wax is then separated from this chilled mixture by filltrationl in the presence of a substantially mois- The resulting filter cake is removed and the wax and the moisture, absorbed during the dewaxing operation, separated from the filter-aid material to thereby condition it for use in dewaxing further oil.

In order to more fully describe the invention, reference will now be made to the accompanying iiow diagram, illustrating diagrammatlcally an arrangement of flow adapted to carry out my invention.

Wax-bearing oil from a tank I i delivered to a mixer 2 wherein it is dil ted with low boiling hydrocarbon liquid, such s propane, butane, etc., delivered from a tank 3. The mixer 2 is provided with a stirring mechanism and is also adapted to withstand pressure. If desired, a portion of the diluent liquid may be evaporated from the mixture with refrigerative eiect at. this point in order to bring about preliminary chilling of the mixture. The resulting vapor is led o3 through a vent l to be recovered by compressing.

The resulting mixture of wax-bearing oil and diluent liquid is drawn off from the mixer 2 through a chilling coil or heat interchanger 5 wherein the mixture may be brought into heat exchange relationshipwith a stream of cold mixture from which the wax has been removed.

-The cooling effect may be further augmented by refrigeratively evaporating a portion or all of the diluent liquid from the dewaxed mixture during passage through the exterior shell of the interchanger5.

'I'he preliminarily cooled wax-bearing mixture is then introduced to a vessel 5 wherein further' cooling is advantageously effected by causing a portion'of the diluent liquid to evaporate from vthe mixture. This evaporation may be\effected by reducing'the pressure or by applying'a-vacuum to the vessel, 4as the case may be.` Liquidpropane may be introduced to the bottom of this vesselv from the tank 3 through a pipe and a branch pipe 0 to produce this internal `cooling eect. The vapor evolved within the vessel is removed through a vent pipe and delivered vto compressing means to be liquefiedv and cooled for further use. The wax-bearing mixture may thus, for example, be cooled to a temperature of around +i5 F. or lower within the vessel 6. Where materially lower temperatures are desired, it may beI preferable to conduct this cold mixture through a subsequent chiller 9, wherein the mixture fiowsin indirect heat exchange relationship witha refrigerant material; The refrigerant material may, for example,- be propane, which is allowed to expand directly around` the coils or pipes through which the wax-bearing mixture is flowing. y

The iinally chilled dilute wax-bearing mixture is withdrawn from the chiller 9 through a pipe I0 and delivered to a mixer Il wherein it is wd mixed with dehydratedfilter-aid materiaL'separated from the wax removed in a previous dewaxing cycle. The recovered.. filter-aid4 material, preferably after chilling or cooling, is introduced to the mixer through a chute l2. suitable stirring means are provided within the mixer for.

effecting complete mixing of the'lter-aid material with the wax-bearing solution. If desired, additional propane liquid may be introduced to the mixer Il through a pipe I3, either to increase the degree of dilution, or for. the purpose of supplying additional refrigeration by causing evaporation of such propane within the mixer in indirect contact with the wax-bearing mixture, the vaporized material being drawn ofi from the mixer to compressing means for further use,

The chilled mixture containing suspended wax and filter-aid material is removed from the mixer Il by a pump` Il and delivered to a pressure filter I5 which may be, for example, of the pressure leaf or rotating drum type. Additional propane or diluent liquid may be mixed with the mixture as it enters the filter, or may be introduced into the filtering liquid within the filter shell or bowl, and caused to vaporize therein to obtain a chilling eii'ect immediately adjacent the filtering surfaces therein. The refrigeration supplied immediately adjacent the filtering surfaces in this way serves to maintain the filtering mixture at thedesired lowtemperature and prevent softening or re-solution of the wax. Propane vaporized within the filter shell is drawn off through a pipe I6 either to a compressor or to a gasometer.

At the end of a filtering cycle, the lter contents may be displaced and the filter cake dried by introducing additional propane to the filter wherein it is converted into gas and thus serves as a. displacing and cake-drying medium.

The filtrate removed from the filter is conducted through a pipe I9 to a stripper 20. However, all or a portion of this dewaxed filtrate may be first conducted through a pipe 2| to the exterior shell of the chilling coil 5 for the purpose of cooling the fresh incoming charge, as already described. From the shell of the chilling coil 5, it is returned through a pipe 22 to the stripper 20.

The stripper 2li comprises a column containing suitable packing material, such as bubble trays, and is provided with a heating coil through which heat may be supplied to the bottom of the stripper. It is also provided with a cooling coil near its top for supplying reiiux thereto.

'Ihe dewaxed filtrate is introduced to this stripper wherein the diluent liquid is removed.

'I'he strippeddewaxedoil is removed from the y The filter cake formed during the filteringoperation is removed from the filter shell by a.

scroll 24 and discharged into a closed hopper or receiver 25. The receiver 25 communicates, by means of a chute 26, with the Abottom of a closed vessel 21 into which the lter rcake is introduced for treatment with a wax soivent or displacing liquid. 'I'he vessel 21 is provided with suitable stirring mechanism as well as a heating coil. Naphtha is introduced tothe vessel 21 through pipe 28 and mixed with the filter cake to form a slurry or suspension. The contents of the vessel are maintained at a temperature of around to 200 F. or higher if necessary. It is contemplated that higher temperatures may be maintained as, for example, where it is desired to vaporize or distill off volatile matter in- 'cluding moisture. Und'er these conditions of temperature, the naphtha exerts a solvent effect .on the oil and the wax. The wax is thus displaced from the pores of the filter-aid material, i

and removed from the non-condensible portion. 'I'he condensed naphtha withdrawn from the tower 3U may be returned through pipe 3l to the vessel 21. 'Ihe uncondensed vapors removed from the top of this tower, composed substantially of propane,` are conducted through a pipe 32 to the gasometer I8.

The hot suspension of oil and wax and separated iilter-aid material is withdrawn from the bottom of the vessel 21 by a pump 21a and conducted to the bowl of a rotating drum lter 33, adapted to operate under pressures either above or below atmospheric pressure. The mixture is advantageously maintained at a temperature of around 160 F. or 180 F. while in the lter bowl, and subjected to filtration under these conditions so that the wax is maintained in a liquid condition. The filter-aid material is deposited upon the exterior surface of a rotating drum 34 while the solvent naphtha and dissolved oil and wax are drawn through the surface into the interior of the drum as a filtrate. This ltrate is removed from the interior of the drum through a pipe 35 leading to a receiver 36. The filter-aid material is deposited on the surface of the rotating drum as a iilter cake, and as the drum rotates is passed out of the ltering mixture through successive zones wherein it is dried to remove adhering ltering liquid. washed with fresh naphtha, dried to remove adhering naphtha, following which it is chilled and discharged from the lter, or discharged from the lter and then" chilled prior to reuse. During passage through the cake Washing zone, petroleum naphtha is introduced through a pipe 31 and. heating coil38, to a spray 39 positioned within the hood of the filter. By means of this spray, it is sprayed against the lter cake and drawn through the cake along with dissolved oil and wax to the interior of the drum 34. From the interior of this drum, it is withdrawn through pipe 4U to a receiver 4I. The contents of the receiver 4I advantageously form the wax solvent supplied through pipe28 to the vessel 21 for treating further filter cake.

The drying gas drawn through the filter cake during passage through the delivering zo'ne is supplied to the hood of the lter through a pipe 42 from the gasometer I8.

The dried cake then passes into the chilling zone. This chilling or cooling is effected by introducing liquid propane through a pipe 43 from the tank 3 to a spray 44 within the hood of the filter. Propane is thus sprayed directly on to the filter cake, whereupon evaporation with refrigerative effect occurs, the evaporated propane being drawn through the cake into the interior of the drum from which it is removed through the pipe 40. The evaporation of the propane, in direct contact with the filter-aid material, not only cools and chills it but also materially aids in removing remaining particles of naphtha solvent as well as moisture.

The cake is then removed from the surface of the drum and discharged into the chute I2 leading to the mixer II, previously referred to. 1f desired, the step of spraying the filter-aid material with refrigerant liquid while still on the ltering surface may be omitted. Instead, the filter-aid material may be chilled after being discharged into the chute I2 as, for example, 'by introducing liquid propane into the chute near its lower end and from which point the propane vaporizes and passes upwards through the chute in countercurrent contact with the descending lter-aid material.

top of the stripper vpipe 55 to a compressor 51.

The receivers 35 and 4I are provided with vapor f outlets 45 and 46, respectively, leading to a knockout box or trap 41. Trap 41 is advantageously provided with a barometric leg 48 by which means entrained liquid or foam is removed. Vapor or gas is'removed from the trap 41 through a pipe 49 leading to a compressor 50 advantageously of the two-stage type.

Theeompressor 50 serves to reduce the pressure through the receiving drums to the interior of the rotating drum of the lter 33, and also takes care of excess propane vapor accumulating in the gasometer I8. The compressed vapors are delivered by the compressor 50 to a stripper 5I substantially similar to the stripper 2U already described.

The solution of oil and wax accumulating in the receiver 36'contains a certain amount .of naphtha and propane. When vacuum is applied to the receiver through the pipe 46 vaporization of a substantial proportion of this propane and naphtha occurs, the vaporized material being drawn off to the compressor 50. A heating coil is advantageously provided within the bottom of the receiver 36 to supply heat which may be used to facilitate the separation of as much prop-ane aspossible at this point, as well as to maintain the wax in a liquid condition during the evaporation of the propane and naphtha. The wax solution .is withdrawn from the bottom of the ref ceiver 36 by a pump 52 and delivered through a pipe 53 to the stripper 5I.

Heat is supplied to the bottom of the stripper in order to boil off the propane and naphtha which rises through the stripping column, and

in doing so is subjected to rectication to effect separation between the propane and the higher boiling naphtha. The naphtha so separated is removed from a mid-point of the stripper through a pipe 54 to a receiving drum 55. This naphtha may berreturned to the system either as a Wash solution tothe lter 33, or as a wax solvent to the vessel 21.

. The separated propane is removed from the in vapor form through the The compressed vapor is then conducted through a cooling coil 58 wherein it is liqueiied and from there returnedv through the pipe 59 to the storage tank 3.

The combined operation of dewaxing, recovering and reconditioning of filter-aid material is advantageously carried out in a closed system to avoid loss of prop-ane, inltration of air from the.warm surroundings into the system, and to facilitate operations generally. In the practice of this invention, for example, about one part of wax-bearing lubricating distillate derived from Mid-Continent crude by vacuum distillation and having a viscosity of about 60 Saybolt universal seconds at 210 F. is mixed with about two parts of propane in the mixer 2, under a pressure sufficient to maintain the propane in a liquid condition. This mixture at a temperature of around 90 F. is then advantageously passed through the chilling coil 5 wherein it is cooled to a temperature of about +45 F. by heat interchange with the outgoing cold dilute dewaxed mixture.

The preliminarily cooled mixture is then de;- livered into the vessel 6 wherein it is cooled to about +15 org-20 F. by causing a portion of the diluent liquid to vaporize from the mixture or by introducing additional propane liquid into the mixture, which 'is allowed to vaporize with refrigerative effect. The mixture is maintained at a dilution of from 50% to -10% of propane liquid. 'Ihe final chilling of this mixture is then effected by passing the mixture through the chiller 9 wherein the temperaturefis reduced to about 30 F. At this temperature, the mixtlne is introduced to the mixer Il and admixed with dehydrated and conditioned filter-aid material -to separate the suspendedsolid material. The

filtrate` is withdrawn and the diluent liquid removed therefrom by stripping, in the stripper 20, to produce a dewaxed oil having a pour test 'I'he wax cake is removed 'from the filter and subjected to treatment, as already described, to separate therefrom the filter-aidA material which is reconditioned for mixing with further wax-bearing oil.

'I'he invention is not restricted to dewaxing` viscous distillate wax-bearing stocks, but is also adapted to the treatment of various types of wax-bearing oilsor fractions, including residual cylinder stocks, wax concentrates, and so forth.

While certain operating conditions have been described in the foregoing example, it is contemplated that these conditions, particularly as regards temperature and pressure, may be varied to suit different requirements, and depending upon the nature of the wax-bearing oil undergoing treatment. Also, while the useof propane has been specifically described, it is contemplated that variousv other hydrocarbon fractions of somewhat -similar nature, including other liquid refrigerants which are gaseous under normal temperatures and pressures, and which are suitable as wax-precipitating media, may be emplOyed.

Obviously, many modiications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limita-l tions should be imposed as are indicated in the appended claims.

I claim:

l. In a process of dewaxing hydrocarbon oil by filtration at low temperature in'the presence of hot naphtha, and refrigeratively evaporating a volatile solvent liquid in direct .contact with the 'washed filter-aid material to dissolve and remove adhering naphtha and to chill the filter-aid material prior `to admixing with the cold waxbearing oil.

2. In a yprocess of dewaxing. hydrocarbon oil by filtration at low temperature in the presence ci' a substantially dehydrated inertV comminuted solid lter-aid material, the method of reconditioning and dehydrating the filter-aid material for reuse comprising forming a suspension of the resulting illter cake in a wax solvent, heating the suspension to displace wax, oil and moisture from the filter-aid materiaLseparating the iilter- 0 F. or below suitable for eid materies while het from the displaced metter,

' washing the separated filter-aid material with hotsolvent, and refrigeratively evaporating a volatile solvent liquid in direct contact with the washed filter-aid material to dissolve and remove adhering wax solvent and to chill the filteraid material prior to with the cold wax-bearing oil.

3. In the process of dewaxing wax-bearing oil wherein the wax-bearing oil is chilled to '0 F. or

below by direct vaporization therefrom of a volatile refrigerant and solvent liquid, and the wax thus precipitated separated therefrom in the presence of an inert solid comminutedillter-aid material, the method of recovering and reconditioning the filter-aid material for reuse, comprising treating the mass of filter-aid material and adhering waxy matter with a wax solvent liquid at elevated temperature adapted to dissolve the waxy matter and displace it from the filter-aid material, separating the filter-aid material from the resulting mixture while maintaining the mixture at elevated temperature, washing the separated filter-aid material with hot solvent to remove remaining impurities, and vaporizing a portion of the volatile refrigerant in a direct contact with the washed lter-aid material to dissolve and remove adhering solvent liquid and to thereby cool the lter-aid material to a temperature of around admixing with further cold wax-bearing mixture.

4. In the process of dewaxing wax-bearing oil wherein the wax-bearing 011 is chilled to 0 F. or

below, by direct vaporization therefrom of a refrigerant material comprising essentially propane, and the wax thus precipitated separated therefrom in the presence of an inert solid comminute'd filter-aid material, the method of recovering and reconditioning the filter-aid material-,for reuse,

. comprising mixing the mass of filter-aid material and adhering waxy matter with a solvent liquid adapted to dissolve the waxy matter-and displace it from the filter-ald, heating the resulting mixture whereby propane contained in the wax and filter-aid material is vaporized and recovered,

vseparating the lter-aid material from the remaining hot mixture, washing the separated filteraid material with fresh solvent liquid, and vaporizing propane in direct contact with the washed filter-aid material to dissolve and remove adhering solvent and to thereby chill the filter-aid material to a temperature around 0 F.l or below suitable for'admixing with further cold waxbearing mixture. v

5. In the process of dewa'xing wax-bearingoil,

wherein the wax-bearing oil is chilled to 0 F. or below, by direct vaporization therefrom of a refrigerant comprising essentially propane, and thev wax thus precipitated separated therefrom in the presence of an inert solid comminuted filter-aid material, the method of recovering and reconditioning the filter-aid material for reuse, comprising mixing the mass of filter-aid material and adhering waxy matter with naphtha adapted to dissolve the waxy matterand displace it from the lter-aid, heating the`resulting mixture to a temperature of from about to about 200 F. whereby propane contained in the wax "and filter-aid material is vaporized and recovered, l

separating the filter-aid material fromthe remaining hot mixture, washing the separated ill ter-aid material with fresh naphtha, and then further washing it with vaporizir'ig propane to disl solve and Aremove adhering naphtha and to cool' the filter-aid material for admixing with further col-d wax-bearing mixture;

6. In the process of dewaxing wax-bearing oil wherein the wax-bearing oil is'chilled to 0 F. or below, by direct vaporization therefrom of a refrigerant material comprising essentially propane, and the wax thus precipitated separated therefrom in thepresence of aninert solid comminuted filter aid material, the method of recovering and reconditioning the filter-aid material for reuse.

comprising mixing the filter-aid material and ad.

hering waxy matter with'naphtha, heating the resulting mixture whereby propane contained in the waxy matter and filter-aid material is vaporized and recovered, subjecting the remaining mixture to filtration at a temperature of from 160 to 200 F. to remove the dissolved waxy material and form a filter cake of filter-aid material, washing the resulting filter cake with hot naphtha to remove adhering impurities, and spraying the washed cake with a liquid hydrocarbon compris-V ing essentially propane to remove adhering naphtha and to-cool the filter-aid material for admixing with further cold wax-bearing oil.

'7. In dewaxing waxb,earing oil wherein solidified wax is separated from the oil in the presence of a solid inert comminuted'filter-aid material,

the wax dissolved and removed from the filter-aid materalb-y treating the filter-aid material and adhering Iwax with a solvent liquid for.wax, 'and the filter-aid material -conditioned for reuse, the steps consisting in contacting the solvent-treated filter-aid materialwith a volatile solvent liquid v and refrigeratively evaporating a portion of said liquid in direct contact with said filter-aid mate.- rial thereby washing retained -Wax solvent liquid from the lter-aid material and precooling it for reuse with fresh'wax-bearing charge.

8. In the process :of dewaxing I wax-bearing mineral oil wherein thewa:7 is separated from cold dilute wax-bearing oilin the presence of a solid inert. comminuted filter-aid material, the

'methodof cooling the filter-aid material prior to its addition to t-he wax-bearing oil,` comprising refrigeratively vaporizing a low-boiling hyd rocarbon liquid comprising, propane 'in direct contact with the filter-aid material whereby it is chilled to substantially' the temperature desired for dewaxing the oil.

9. In a dewaxing process wherein a wax-bearing mixture is chilled by direct vaporization therefrom of a volatile refrigerant material of the character of a light low-boiling petroleum fraction and the wax thus precipita-ted separated from the cold mixture in the presence of an inert solid comminuted wax-adherent material, the method of cooling the Wax-adherent material priorto its addition to the wax-bearing mixture comprising refrigerativelyevaporating a portion of the refrigerant material in direct contact with the wax-adherent material whereby it is chilled to substantially the temperature desired for dewaxing the oil.

10. In the processv of dewaxing wax-bearing oil wherein the Wax-bearing oil is chilled to 0 F. or below by direct vaporization therefrom ofy -direct contact with said filter-aid material there- 'by washing retained wax solvent liquid from the filter-aid material and precooling it for reuse with fresh wax-bearing charge.

' 11. In' the process of dewaxing wax-bearing oil in whichthe wax-bearing oil is chilled to 0 F. or below by direct vaporization therefrom of' a liquefied normally gaseous hydrocarbon, and the wax thus precipitated separated therefrom in the lpresence ofI an. inert solid comminuted filter-aid material, the steps consisting in 4contacting the filter-aid material with some ofthe liquefied normally gaseous hydrocarbon, refrigeratively evaporating at least a portion of said liquid in direct contact with said lter--aid ma-v terial to 4thereby cool the same, and admixing the cooled filter-aid material with the previously chilled wax-bearing mixture.

ROBERT E. MANIEY.

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