US1782028A - Process and apparatus for dewaxing oils - Google Patents

Description

New; 18, 1930.

E. F. BURCH PROGESS AND APPARATUS FOR DEWAXING OILS Filed March 14. 1927 iln! I l M 2",. rgr zi iiii 4 i l 1 Svwehtoz L/ [BURCH 331% M15 Gummy trifu Patented Nov. 18, 1930 UNITED STATES l ATE 'NT orricl-z ELI r. nuacrr,- on L UREL SPRINGS, NEW JERSEY, ASSIGNOR 'ro CREW LEVICK cou- PANY, on :PniLADnLrnI'A, PENNSYLVANLA, A CORPORATION or PENNSYLVANIA PROCESS AND APPARATUS FOR DEWAXING oILs Application filed Mai-ch 14, 1927. Serial No. 175,022.

The present invention relates to a process and apparatus for separating wax from oils.

vAccording to recent developments in the art of dewaxing petroleum distillates or residuums the wax is separated with the aid of centrifugal force by passing the chilled stock containing the wax in suspension through an apparatus known as a centrifuge. In present methods however it has been found necessary to mix with the chilled stock some foreign liquid such as water in order to aid in the discharge of the Wax from the apparatus. And because of the clogging of the apparatus with cold wax it has also been proposed to introduce hot water into the bowl of the centrifuge in order to melt the wax and carry it out, particularly if the wax is crystalline. Furthermore it has been proposedto heat the wax being discharged by means of electrical heating elements mounted in the upper portion of the bowl of the cen ge. It is evident that when a foreign liquid is introduced into the separator the capacity is correspondingly reduced and if this liquid is heated in order to melt the wax the oil-wax mixture will also be heated and therefore a certain amount of the precipitated wax will be redissolved in the oil.

Depending on the previous treatment of the oil the wax may separate out on chilling in either one of two different forms; crystalline or amorphous. Under present commercial methods the separation of crystalline wax from oil by use of the centrifuge has met with considerable ditficulty probably because of the harder character of the wax deposit made in the machine. In fact, its discharge from the centrifuge has heretofore been made possible only by the use of a heated liquid such as water.

The present invention relates generally to improvements in processes and apparatus of the type referred to, the principal object being to overcome the defects inherent in 7 these processes.

A further object of the invention is to.-

the commercial separation of wax, either crystalline or amorphous, from oils containparent from the following detailed description taken in connection with the accompanying drawing in which The figure is a vertical view partly in section of a portion of a centrifugal separator c'onstructed in accordance with the invention and adapted to carry out the novel process.

The separator as shown is of the type known as the De Laval with certain important im rovements which renders it particularly a apted for the separation of wax from oils.

The oil from which the wax is to be sepa-i a rated is delivered from a refrigerating plant after having been cooled suflicientl (10 to 10 F.) to throw the wax out 0 solution and is passed by means of a conduit 2 into a separator 3. To the conduit 2 is attached an automatic float valve feed regulator which comprises a T-head 4 inside of which a tube .6 slides to regulate the flow from pipe 2.

The tube 6 is mounted centrally-of and extends through a float 8 which is placed in the feed cup 10 of the separator 3. The oilwax mixture flows from the pipe 2 into the a head 4 then through conduit 6 into the feed cup 10 in which the fluctuation of the liquid level operates the tube 6 by means of the float 8 to increase or decrease the flow of mixture from the pipe 2 in accordance with the capacity of the separator. The outer surface of the upper vend of conduit 6 and the inner surfaceof the head 4 are machined so that perfect functioning of the valve is assured at all times. The oil-wax mixture passes from the-feed cup '10 downthrough feed conduit '12 which discharges into a central conduit 14 ofa separator bowl 16.

.From the conduit 14 themixture "discharges :radially into the bottomof the bowl by con- 7 the bowl 16. In the case of oil and wax the oil, being of less specific gravity than the wax, flows inward in the narrow chambers between the discs, then flows upwardly in the space provided between the discs 20 and the outer wall of conduit 14, finally discharging from the bowl over a weir 22. The separated oil discharging over the weir 22 is re covered in the usual manner by means of a pan 24 and led awayto storage by the conduit 26. The wax is thrown by the centrifugal force of the rotating bowl onto the inner surface thereof and forms a wax zone extending into the outer ends of the chambers between the discs 20. As the wax accumulates it flows upward along the inner Wall of the bowl into a conduit formed by the bowl cover 31 and the disc-like extension 28 of the weir 22. The wax is finally discharged from the bowl'around an annular plate 32 and over the capv of the bowl into the wax pan 34 from which it flows by the conduit 36.

In order to avoid the difficulty heretofore experienced by having the wax harden or pack on the inner. walls of the bowl, in the passage 30 and pan 34, provision is made to introduce steam into the pan 34 by a valved steam pipe 38 in order to keep the wax in a melted condition therein. The steam introduced by the pipe 38 melts the wax in pan 34 and Ipasses around its inner edge adjacent the how 16 so that the outer surface of the bowl including the cover 31 is heated by the steam to a degree suflicient to melt the wax coming in contact therewith. If desirable steam or a similar heating gas may be passed by an appropriate pipe directly into the space around the bowl from which'a portion may be allowed to flow into the pan 34, but all that is necessary is to keep the outer surface of the bowl at.a temperature slightly above the melting point of the wax. By the pres-- ent method of heating, the heat 1s confined entirely to the outer layer of the wax zone in the bowl so that as soon as this layer is melted it immediately passes upward and out of the bowl, in other words, the central zone in the bowl is at the temperature of the refrigerated mixture and as the wax separates in the intermediate zone and passes outward it advances to the outer surface of the bowl and then out, thus preventing any re-solution of warmed wax in the oil. The melted wax being discharged may tend to heat the oil inside the weir 22 but thisis of no,importance since the wax has already been separated therefrom and this cold oil now serves as an insulation between the inflowing' mixture and the discharging wax.

In cases in which the refri erated mixture of oil and wax is found to e very viscous so that the capacity of the separator would be materially affected, a quantity of naphtha, gasoline or other similar thinning agent is mixed therewith in order to break the viscosity and thus increase the through-put of oil. The adding of the diluent may be done either'before or after the refrigeration but i done after, the diluent should be coole to the temperature of the wax oil mixture.

phous wax, however, the use of steam on the outside of the bowl may be limited or dispensed with entirely because amorphous wax or petrolatum is much more plastic and therefore .flows more readil than crystalline wax.. The use of steam 1s advantageous in any case and should at least be used in the wax pan to aid in the wax removal.

The apparatus which forms an important part of the present invention differs from other apparatus of this type in that the wax and oil discharge openings in the bowl are brought closer together both vertically and horizontally by shortening the weir 22 and by using a plate 32 having a smaller diameter than usual. The specific gravity of wax is only a few hundredths greater than that of the oil from which it is separated and if it were not for the possibility of amplifying this difference by the use of centrifugal force a gravity separation of the two would be practically impossible. Therefore in the apparatus shown the height of the weir 22 with respect to the height of the wax discharge has been adjusted in accordance with the rela the densities of the wax and oil so that the zone of separation will be held more nearly the mid-vertical zoneof the discs 20. Likewise the decrease in the inner diameter of the ring 32 is an adjustment in this same diree- 4 tion and gives a wax discharge at a point .with respect to the-oil discharge comparable to their respective specific gravities and quantities in the mixture. With the treatment of distillates or residuums which differ widely in the specific gravity of the oil or wax content, smaller or larger rings may be substituted in the place of the ring 32 in order to give the desired relation between the flow of oil and wax through-the apparatus. The

height of the weir 22 may be made adjustable in any convenient manner.

An important phase of the present mvention is the separation and recovery of wax from oil by centrifugal separation without the aid of a high gravity liquid such as water or brine to carry the wax out of the separator as is used in present commercial processes.

The apparatus described, by being operated without a carrier liquid gives a much greater through-put of oil per unit than otherwise would be obtained and therefore the total investment in separators for the treatment of a given quantity of oil per day is correspondingly reduced.

The float valve 8 as referred to above permits the operation of the apparatus at its maximum capacity at all times regardless of the variation due to the change in velocity of the bowl or to viscosity of the oil. With an ordinary faucet such a separator must always be run at a safe capaclty or an operator must be constantly changing the valve. By the use of the automatic float valve described above a constant liquid head is also maintained in the apparatus which naturally avoids the changing of the various vertical separating zones existing on the interior of the bowl.

The separator as shown is understood to be mountedin the usual manner so that the bowl may be rotated at the usual rate. An upper pan is also shown by which overflow'o'il from the pipe 12 in case of a sudden stoppage or from pan 24 may be taken care of.

Instead of heating the bowl in the manner referred to, heat may be supplied to the separated wax by means of a small steam coil or jacket mounted around the inner eriphery of the separator bowl and supplied with steam from suitable conduits in the bottom of the bowl which may connect through the bowl spindle with a suitable supply of steam or other heating agent. If this type of heating is adopted the heating agent could be discharged into the passage 30 to be discharged with the wax into the'pan 34. Warm water or steam would be a suitable heating agent in this case.

The steam.which condenses in the wax pan can be run off with the wax and se arated by gravity or by cooling. The wax 0 take 36 is preferably bent so as to form a liquid seal to prevent the escape of steam. The small amount of steam which may pass from pan 34 into pan 24 will do no damage in heating the separated oil but as good a fit as practicable should be secured between pain 24 and weir 22. l

The term wax as used in this specification and appended claims unless otherwise qualified is understood to include any form of crystalline or amorphous wax-like material which may be precipitated in an oil on cooling.

While the invention has been particularly described with respect to the separation of for the separation of precipitates from oils or other liquids for example the separation of precipitated organic compounds from solvents or liquors or the separation of stearin from oleo.

Having described the preferred form of the invention what is claimed as new is:

1. The process of separating wax from chilled mineral oil containing wax in suspension. which comprises continuously introducing the mixture of oil and wax into a centrifugal separator bowl whereby the wax is separated from the oil in an outer layer surrounding the oil, applying gaseous heating medium to the outer surface ofthe separator bowl whereby said layer of wax is melted and separately discharging said separated oil and melted wax from said sepa-- rator.

2. The process of separating wax from oil in a chilled mixture in which the wax is thrown out of solution and in suspension in the oil, which comprises continuously feeding such a mixture into a centrifugal separator where the constituents of the mixture are separated in accordance with their specific gravities, automatically feeding said mixture at a rate corresponding to the maximum capacity of the separator and increas ing the fluidity of the separated wax in said separator while maintaining the capacity of the separator and while maintaining the mix ture being separated at substantially its inlet temperature, by passing a hot gaseous heating medium in contact with the outer surface of said separator."

3. The process of separating wax from oil after the mixture has been chilled to precipitate the wax in the oil, which comprises continuously introducing the chilled mixture into the central portion of a centrifugal separating device whereby the wax collects in an outer zone and the oil collects in an inner zone, discharging the separated ingredients upwardly into respective receiving chambers,

introducing a heating medium into the wax receiving chamber to melt the wax and simultaneously indirectly heating a portion of the wax collecting in said outer zone by passing a gaseous heating medium in contact with said separating device whereby the fluidity of said wax is increased.

4. The process of centrifugally separating a mixture of substances of different specific gravity the heavier of which isin a state of suspension in the lighter, which comprises subjecting the mixture to centrifugal force whereby the substances are stratified in concentric zones in accordance with their respective specific gravities the heavier constituent forming a zone surrounding the lighter, continually supplying the mixture to be sepa-.

rated, indirectly heating the outer portion of the zone containing the heavier constituent to increase its fluidity by applying a gaseous heating medium to the outer surface of the 5 container in which said substances are stratified and continually discharging the separated constituents from their respective zones.

5. The process of centrifugally separating 1o wax from oils, which comprises continuously supplying to the separating zone of a centrifugal separator a chilled mixture of oil and suspended wax, automatically regulating the supply of said mixture so as to maintain said separator at maximum capacity, stratiing said wax and oil in concentric zones in accordance with their respective specific gravities, continually discharging separated wax and oil from their respective zones into separate receiving pans and introducing steam into the wax receiving pan to increase the fluidity of the wax therein.

6. A centrifugal separator for separating mixtures of ingredients the heavier of which is relatively viscous at the temperature of the mixture, which comprises a centriflwal bowl adapted to be rotated at high speeds, auto- 'matic means for feeding a regulated quan- "tity of said mixture to said bowl, outlet ports in said bowl for the lighter and heavier constituents of said mixture and means for applying a regulated quantity of a gaseous heat-' ing medium to the outer surface of said bowl to decrease the viscosity of said heavier constituent.

7. A centrifugal separator adapted for sep arating wax from oil, which comprises a centrifugal bowl having a cylindrical body portion and a frustro-conical cover, automatic 40 means for supplying a mixture of oil and wax centrally of said bowl in accordance with the capacity of said separator, separate outlets above said cover for oil and wax, a separate collecting pan for said oil and wax, and means for passing a heating gas into said wax pan and downwardly on the exterior of said bowl cover and bod 8. A centri ugal separator adapted for the j separation of a readily meltable solid con stituent from a chilled mixture -containing said solid in suspension in a liquid solvent of said solid, which comprises a centrifugal bowl, means for feeding said mixture centrally of said bowl, a discharge for said liquid near the central portion of said bowl, a discharge passage from the inner peripheral part of said bowl for said meltable solid constituent and means for heating the outer zone of solid constituent in said bowl and dis no charge passage, said heating means comprising means for passing a gaseous heating agent into contact with the' outer surface of said bowl and discharge passage.

9. Acentrifugal separator adapted for sep- 05 arating wax from oil, which comprises a centrifugal separator bowl adapted to be rotated I at high speeds, means for feeding wax-oil mixture to said bowl, separate discharge passages from said bowl for wax and oil, a collecting pan for discharged .oil, a collecting pan for discharged wax and means in said in specific gravity of said lighter and heavier constituents to be separated.

.11. The method of operating a centrifugal separator for the separation of a readily meltable solid or semi-solid materiahfrom a J chilled mixture comprising said material in suspension in a liquid solvent of said mate- I rial, which comprises introducing said chilled mixture into the separating chamber of a centrifugal separator, rotating said separating.

chamber at arelatively high speed to stratify said constituents in accordance with their respective specific gravities, heating the wall of the separating chamber against which the readily meltable solid material collects in said chamber by applying a gaseous heating medium to the opposite side of said wall, thereby to melt said material and facilitate its discharge from said chamber, and separately discharging said melted material and said liquid from said separating chamber.

In testimony whereof I aflix my signature.

' ELI F. BURCH.

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