US1994485A - Treatment of oil-wax mixtures - Google Patents

Description

March 19, 1935. l. M. PERKINS ET AL TREATMENT 0F OIL WAX MIXTURES Filed June 20, 1931 2 Sheets-Sheet 1 w w n w n g March 19, 1935. Ml PERKlNs Er AL 1,994,485

TREATMENT OF OIL WAX MIXTURES m1 attain,

Patented Mar. 1,9, 1935 UNITED STATES PATENT OFFICE TREATMENT OIL-WAX MIXTURES Application June 20, 1931, Serial No.545,813

=15 claims.

The present invention relates to the separation of a mixture of wax and hydrocarbon oil into its respective solid and liquid components, and more particularly, to the treatment of that type of oilwax mixture which is adapted to be separated into such components by the well-known process of sweating.

Typical of those oil-wax mixtures which are adapted to be subjected to a process of sweating and therefore adapted to be treated by our process, is the wax cake, commonly known as slack wax, which remains in the filter press when petroleum fractions, such as those known as paraiiin distillates, are subjected to a pressing operation. Such oil-wax mixtures usually contain y less than 50% of oil.

As is well recognized, sweating processes require prolonged periods of time, large and cumbersome apparatus, and the utilization of considerable heat. An object ofthe present invention, which is based upon an 'entirely different principle from that upon which sweating is based, is to replace sweating, thereby to overcome, among others, the objections above stated. By our process, oilwax mixtures of the type aforesaid may be separated efliciently, economically and rapidly into their respective solid and liquid components.

Furthermore, our process and apparatus are capable of separating a composite wax mixture intol a. series of wax fractions of progressively higher melting points. f i

If an oil-wax mixture is completely liquefied, then maintained in a static condition and cooled, those components thereof which become solid as a result of the cooling, form as one large mass or cake which occludes substantial quantities of those components which under prevailing conditions Aare still liquid; the solid components, in forming, apparently becoming so interwoven as to prevent substantial movement of the liquid components occluded therein. It is well known that if such a solid mass is comminuted it will become ofa more o less liquid consistency, presumably because the occluded liquid components are then free to move. The present invention, however, is not-based upon nor does it include anyl step of comminuting a previously solidifiedoil-wax mixture.

According to our invention, the oil-wax mixture is first raised to a temperature sufficient to completely liquefy the solid portion thereof, thereupon the mixture in a completely liquid state is uniformly cooled to a temperature at which at least a portion thereof will solidify, while simultaneously and continuously, during such cooling operation, thoroughly agitating the mixture. This procedure, which in each case is properly regulated to the particular oil-wax mixture being treated, results inthe formation of distinct agglomerates, eaclrof which may be the size of grains of rice;J or of that order, or somewhat larger. a Such agglomerates may then be readily separated from that portion of the mixture which remainsliquid, by any suitable method adapted4 to the separation of solids from liquids, as for example, by draining the liquids from the solids. We have found that agglomerates so formed entrain or occlude very little, if any, of that portion of the mixture which remains liquid during their formation; By treating the agglomerates so formed one or more times, for example, under successively higher temperature v conditions, a series of solids of progressively higher melting-points may be produced. Thus by our process a substantially oil-free wax may be produced and/or there may be effected a fractional l separation of the solid components of an oil-wax mixture into two or more fractions of different melting points.k f

. Hereinafter, for convenience, the term wax will be used to indicate that material which forms as a solid during the agglomerating step of our process, and the term oil will be used to indicate"that material which remains liquid during and immediately after such step. It is to be understood, however, that in some cases, depending lupon the particular operating conditions and/or the materials or mixture being treated. what may be called oil" herein, in fact may be a liquid wax.

There are two primary factors upon which the success of our process depends, rst, control of the temperature during the cooling step or our process; and second, the rate Yof agitation during such step. Each of these factors may vary dependingl upon the particular oil-wax mixture being treated. A given oil-wax mixture if cooled too rapidly or' shock-chilled may not produce the desired solid agglomerates. The usual effect of cooling too rapidly or shock-chilling the oil-wax mixture is the formation of that portion thereof which becomes solid into a fibrous mass, quite unlike the distinct agglomerates formed by our process Vwhich `may be easily separated from the portion of the mixture which remains liquid. Cooling too slowly causes that portion which solidies to form as very small particles, from which the liquid portieri is dimcultly removable.

As to the agitation, if the mixture is agitated too. slowly during the cooling step, the desired formation of agglomerates does not occur, but on the other hand, that portion which becomes solid forms as a mass in which substantial quantities of the portion which remains liquid is occluded; whereas, when the mixture is too vigorously agitated during the co`oling operation, the desired agglomeration is not effected, since the solids form as minute particles from which it is difficult to separate that portion of the mixture which remains liquid. Agitation in accordance with our process is such as to cause that portion of the mixture which becomes solid duringour agglomerating step to form as distinct aggregatesl or agglomerates of the size of grains of rice or of that order, or even larger, as for example, of the size of peas. Herein, and in the appended claims the term thorough as applied to agitation, will be used to indicate an intensity of agitation sumcient to cause this desired formation of agglomerates.

For a better understandingof our invention, reference is had to the accompanying drawings in which:

Fig. 1 is an elevational view in section of one type of apparatus in which our process may be carried out;

Fig. 2 is a ow chart showing the various steps I involved in our process; yand Fig. 3 is anelevational view in section of a modified form of our apparatus.

Referring to Fig. 1, A designates an agitator comprising a container c having a jacket :i thereabout. A feed line 1 having valve 2 communicates with the bottom of container c for furnishing a let "pipes 8 and 9 controlled respectively by valves 8' and 9'. A spout or trough 10 leads from a point adjacent the upper end of container c to tank l2, and delivers onto an endless belt 11,'

supported internally of said tank by rollers 13 and 14 on shafts 13 and 14 respectively. Through gears 15, shaft 14 is connected with and rotated by motor M', and such rotation is transmitted'to endless belt 11 to cause it to move in the direction indicated by the arrow. 'I'here is a pipe 16 with nozzle arranged adiacent the end of the forward path of travel of the endless belt l1 so that steam may be directed thereupon. The belt 11 is constructed of perforated material such as wire screen or equivalent.

A partition or dam 17 is provided in the tank 12 to separate it into two compartments 18 and 19, the partition being arranged adjacent the end of the forward path of travel of the belt l1. The compartments 18 and 19 are provided respectively with drawoff pipes 23 and 24, having valves- 23 and 24' respectively. Compartment 18 is equipped with a steam coil 20, the inlet and outlet ends of which are provided with Valves 21 and 22 respectively.

In carrying out our process, the steps of which are shown in the ow chart (Fig.2), the oil-wax mixture is first completely liquefied by heating, then is run into container c through pipe l. Where slack wax is to be treated, a temperature of the order of F. is generally sufficient to cause complete liquefaction. A cooling medium, such as water, is circulated through the jacket i by way of inlet 8 and outlet 9. During the entire cooling operation, blades` 3 are continuously rotated to cause uniform cooling of the mixture, the Scrapers# serving to prevent sticking of portions of the mixture which upon coming into direct contacty with the cooled container walls, tend to cause solidiiication of wax whereupon it would adhere to said walls. 'I'he rate of rotation of the blades 3 depends somewhat upon the particular mixture being treated, but generally the desired speed lies between 30 and 60 R. P. M, for

an agitator having a diameter of the order of 20 inches. We regulate the rates of cooling and agitation so that upon reaching the temperature at which the wax will solidify and agglomerate,

the result will be the formation of agglomerates4 latter becomes filled `with the oil-wax mixture 525 to the level of the dotted line a, by which time that portion thereof which is at such level has.

been reduced to a temperature, as for example, of' about 80 F., when treating slack wax to obtain an ultimate wax of the order of 116 F. melting point. As a result of the gradual cooling and thorough agitation of the mixture during its passage through the container c, the agglomeration is completed, and the wax in the desired form results.

The mixture of oil and wax then passes through the spout 10 onto the endless belt 11 through which liquid may readily pass, but upon which wax particles will beretained. During the time the belt 11 is traveling fromy one end of the tank 12 to the other, almost all of the liquid gravitates -to compartment 18, whereby the wax upon reaching the end of the forward path of travel of said belt is substantially free from liquid. The wax is then melted by steamffrom the pipe 16, and in such condition passes into compartment 19. There is a tendency for a certain amount of oil to adhere to the outer surface of the wax agglomerates, perhaps in the form of a film, and it is helpful to wash the agglomerates, for instance, while traveling along the endless belt, with a de- .tergent liquid, such as water, sodium silicate or soap solution, to effect removal of this oil. The detergent liquid may bestbe employed to Wash the agglomerates during passage of the latter along the forward path of travel of the endless belt. For example, a series of spray nozzles (not shown) may be arranged above and along the length of the belt, and the liquid may be supplied to the nozzles by suitable pipe connections".

Compartment 18 is kept warm by means of steam coil 20 thereby to maintain the liquid in the compartment suiiiciently fluid to permit ready withdrawal through line 23; usually a temperature of from 80 F. to`95 F. is suflicient for this purpose. Compartment 19 as a result of the direct steam heating from pipe 16 is at a temperature above the melting point of the wax, consequently,

the waxin said compartment is aliquld.

Referring to the apparatus shown in Fig. 3,

wherein wax separation is also accomplished by uniformly and gradually cooling a liquid oil-wax mixture with thorough agitation, the cooling,

exchange contact with a cooling liquid. It is possible to use a large number of liquids for this purpose, the requirements being that with respect to the oil-wax mixture the liquid used be immiscible, chemically inactive, and of different specific gravity; these requirements being met, fory instance, by water, alcohols, soap solution and/or saltv solution. Certain suitable liquids have a more pronounced detergent action on the wax agglomerates than others, tending to break down the oil lm adhering to the wax, and are preferred for that reason. A dilute sodium silicate solution has been found quite satisfactory in this respect.

In the drawings, molten slack Wax is supplied to the constant level tank B from supply tank C through valve controlled pipe 101, by means of a pump P. A substantially constant level in tank B is insured by the overflow pipe 102. A continuous supply of molten slack wax enters the crystallizer A from tank B through valve controlled pipe 103 at a point 104 intermediate the bottom and top'of the crystallizer, the molten slack wax traveling upwardly within the crystalli'zer. The oil-wax mixture may be maintained molten in tanks C- and B by means of steam coils or other suitable heating means, such as burners; the heating means is not shown in the drawings, it being considered a conventional element.

The cooling solution is continuously supplied in` the form of a stream or spray through lthe opening 105 in the top 106 of the crystallizer, and, being heavier than the molten slack wax, sinks in direct counter current heat exchange relation therethrough to the bottom of the crystallizer, forming a layer, in which any resulting emulsion may separate.

During the intermixture of the molten slack wax and the cooling liquid a thorough agitation is edected by stationary blades 108 extending horizontally from the crystallizer wall, and blades 109 carried by a rotating shaft 110 mounted within the crystallizer above the layer 107 and driven through suitable gears 111 by motor M.

It will be seen that in continuous operation, the oil-wax mixture is gradually cooled, since at the point of initial contact of the molten oil-wax mixture with the cooling liquid, the latter is at its highest temperature, whereas, at the point of nal contact in the top of the crystallizer A, the cooling solution is at its lowest temperature. Dining this gradual cooling and thorough agitation, as the molten oil-wax mixture progresses to the top of the crystallizer, the wax is cooled to its point oi solidiflcation and separates from the oil in the form of crystals which combine to form agglomerates which contain substantially no occluded oil. It is possible to control the purity and size of these agglomerates to a considerable extent by controlling the rates of cooling and agitation.

Due to the continuous addition of molten slack wax at the inlet 104, a mixture containing unsolidified oil, agglomerated wax, and a certain amount of cooling liquid reaches the level of the spout 112 and is transferred thereby to the inlet 113 of a washer D. Valve controlled pipe 131 directs a small stream of cooling liquid into the spout 112 to act as a liquid medium for the transfer of the liquid-oil, agglomerated-wax mixture through the washer inlet. This inlet discharges the mixture within a perforated or screen-covered cylinder 114 rotatably mounted within the washer D and at an inclined angle from the point of communication with the inlet 113, where the mixture is held in uid-free relation with the washing liquid. The central shaft 115 of the cylinder is conveniently mounted at its upper and lower ends respectively in journal boxes 116 and 117, and is caused to rotate by motor M2 through belt 118 attached to pulleys 127 and 128. The perforated cylinder 114 is submerged in a body of the `same liquid that is employed as the cooling agent in the crystallizer A, and the cooling-liquid portion of the mixture entering the cylinder from the crystallizer` immediately intermingles therewith. As the mixture of oil and agglomerated wax is lighter than the wash liquid in which it is submerged,

the mixture rises to the top of the cylinder, where the liquid oil percolates through the openings therein, rising to the surface of the wash liquid to form a well dened layer. The wax retained within the cylinder is carried downwardly by longitudinal vanes 119 in contact with the inner wall of the cylinder, upon rotation of the latter. 1n its circular travel toward the bottom of the cylinder the wax reaches an angle of repose with respect to the vanes 119 at which it is released, again rising to the upper inner surface of the cylinder. The constant repetition of this operation causes the wax to receive a thorough separation from the oil in traveling to the discharge end 120 of the cylinder. Being liberated from th'e cylinder at 120 the wax rises to the surface of the washing liquid, is melted, and passes into container F through the spout 121.

As both the liquid oil and agglomerated wax eventually rise to the surface of the washing liquid, it is necessary to provide a partition 122 transversely mounted within the washer D at a point near the discharge end of the cylinder, to form separate surface chambers, 123, and 124 for the oil and wax respectively. As oil accumulates at surface chamber 123. it is conveniently drawn off to tank E by pipe 125.

The liquid in washer D is preferably the same as that which is used as a cooling liquid yin crystallizer A, and -as before stated, it is advantageous to employ a liquid such as sodium silicate solution which has a detergent action on the wax agglomerates. The employment of such a liquid is conductive to substantial separation of the oil and wax. Removal of the separated wax from the surface chamber 124 of the washerD is expedited by steam coil 126 which heats the floating wax to a molten condition. Steam coil 133, connected in parallel with coil 126 is used to insure easy withdrawal of the floating layer of separated oil from surface chamber 123.

To obtain the necessary constant circulation of the cooling medium through the crystallizer the liquid settling into the layer 107 of crystallizer A is transferred through pipe 132 by pump P' to washer D. Also, a certain amount of the cooling liquid flows into this washer along with the mixture of liquid oil and agglomerated wax. Continuous flow is effected by transferring a constant stream of liquid into the crystallizer A through inlet 105. As this liquid is substantially above the temperature required for cooling, it is passed through heat exchanger 130 to restore it to the proper cooling temperature prior to its introduction into the crystallizer. In operating, using apparatus as above described, it will be seen that within the crystallizer A there is a continuous counter flow of cooling liquid to molten wax. Upon entering the crystallizer the molten oilwax mixture contacts in heat exchange relation the descending cooling liquid and is cooled there-n by. The cooling liquid having contacted the oil'- wax mixture during its descent through the crystallizer is only slightly cooler than the moltenwax mixture at this point, thereby preventing shock-chilling; and as the molten oil-wax mixture rises it contacts cooling liquid having a progressively decreasing temperature, being slowly cooled thereby to the point of wax crystallization. Continuous thorough agitation during the cooling period causes the crystalline wax to form into agglomerates. By the time the slack wax reaches the level of the outl'et, substantially all of the higher melting constituents which crystallize at the temperature involved have formed into agglomerates.

The sodium silicate solution or other washing liquid travels in a cycle through the crystallizer into the washer, and back to the crystallizer, performing the dual functions of cooling agent and washing and separating medium.

The following experimental run is given as an illustration of the results which may be obtained by our process.

Slack waxwith a melting point of l03 F. and containing 35 percent oil was charged into the crystallizer at 130 F., cooled, with thorough agitation, to 80 F. by countercurrent contact with a 2 B. solution of sodium silicate, and passed through the washer D of the system last described. `Of the original charge, 60 percent was taken o as wax having l2 percent oil content and melting at 113 F. This material was remelted and recharged through the apparatus under the same conditions as in the iirst run, and 35 percent of the original charge was separated as wax having a melting point of 120 F. and containing 1.5 percent oil, a product similar to the ordinary yellow crude scale Wax produced by sweating in periods of usually 48 to 75 hours. By one additional crystallization substantially oil-free Wax having a melting point of 124 F. was obtained, and subsequent operation with the oil fractions at lower temperatures produced a total i 56 percent of the original charge as yellow crude scale wax, while 44 percent of the charge was recovered as an oil having a pour-point of 65 F.

By similar operations when starting with an oil-free wax and properly controlling the temperature to which the material is cooled', fractions having any desired melting-point, up to the .highest melting-point of any component present in the oil-free Wax, may be separated, since wax will crystallize from a liquid composed of molten, lower-melting waxes as well as from an oily mixture.

While our invention has been-described in some detail, we do not intend to be restricted to the specific modification disclosed. We have dis.- covered that slowly cooling and thoroughly agitating a molten oil-wax mixture of the type adapted to be sweated results in the formation of agglomerates of wax whichare easily separated from constituents of the mixture which remain liquid.

What we claim is:

l. A process for separating the constituents of an oil-wax mixture which is adapted to be sweated, which comprises liquefying said mixture, slowly cooling the liquid mixture to a temperature at which at least a portion of the Wax solidifles, and thoroughly agitating said mixture at such rate that the solidid portions'agglomerate into the form of globules.

2. A process for separating wax from an oilwax mixture which is adapted to be sweated,

.which comprises melting the oil-wax `mixture,

slowly cooling the molten mixture to a temperature at which at least part of the wax contained in the mixture solidies, thoroughly agitating the mixture during the cooling period at such rate that globular shaped agglomerates of the solidified particles form, and separating said agglomerates from the constituents of the mixture which remain liquid.

3. A process for separating wax from an oil- Wax mixture which is adapted to be sweated,

which comprises melting the oil-wax mixture, slowly cooling the molten mixture'to a temperature at which the desired cut of wax crystallizes, thoroughly agitating the cooling mixture, at such rate that the wax crystals agglomerate into globular shaped masses, and separating said masses from the constituents of the mixturewhich remain liquid.

4. A process for separating wax from an oilwax mixture which is adapted to be sweated, which comprises melting the oil-wax mixture, slowly cooling the molten mixture to a temperature at which the desired cut of waxes crystallizes, thoroughly agitating the cooling mixture at such rate thatA the wax crystals agglomerate into masses, separating said agglomerated masses from the constituents of the mixture which remain liquid, and washing said agglomerated masses with a detergent liquid 'which is substantially immiscible with wax and oil.

5. A. process for separating wax from an oilwax mixture which is adapted to be sweated, which comprises melting said mixture, uniformly cooling the molten mixture to a temperature at which at least a portion of the wax content therein crystallizes, `agitating the mixture during thecooling process to form agglomerates of the crystallized wax, separating said agglomerates from the constituents of the mixture which-remain liquid, and washing said agglomerates with a detergent alkaline solution.

6. A process for separating wax from an oilwax mixture which is adapted to be sweated, which comprises melting said mixture, gradually cooling the molten mixture to a temperature at which at least a portion of the wax contained in the mixture crystallizes, thoroughly agitating the mixture during said cooling at such a rate as to cause said wax crystals to agglomerate in the form of globular masses substantially continuously witlr their formation, separating said Aagglomerates from the constituents of ther mixture which remain liquid,` and repeating the treatment upon the separated agglomerates.

7. A process for removing wax from an oil--wax mixture which is adapted to be sweated, which'V comprises umelting said mixture, passing the molten mixture in heat exchange relation to a cooling agent to gradually cool said mixture to a temperature at which at least part o1 the wax contained therein crystallizes, agitating the cooling mixture to the extent necessary to cause said wax crystals to combine in the form of globular shaped agglomerates, and separating said agglomerates from the constituents oi the mixture which remain liquid.

8. A process for removing Wax from an oil-wax mixture which is adapted to be sweated, which comprises melting said mixture, passing the molten mixture in indirect countercurrent heat exchange relation with a cooling liquid to progressively cool the mixture to a" temperature at which at least a portion of the wax contained in the mixture solidies, agitating the cooling mixture to the extent necessary to cause the solidified wax to agglomerate in the form of globular masses continuously with its solidification, and separating said agglomerates from the remaining liquid.

9. A process for removing wax from an oil-wax mixture which is adapted to be sweated, which comprises melting said mixture, passing the molten mixture in direct heat exchange contact with a. cooling fluid which is substantially immiscible with said mixture to cool the mixture to a temperature at which at least a portion of the wax content thereof crystallizes, agitating the cooling mixture to the extent necessary to cause the wax crystals to agglomerate, and separating said agglomerates from the constituents of the mixture which remain liquid and from the cooling fluid.

10. A process for removing wax from an oilwax mixture which is adapted to be sweated, which comprises melting said mixture, passing the molten mixture in direct heat exchange contact with a cooling fluid, consisting of a solution of alkaline silicates or soap, to cool the mixture to a temperature at which at least a portion of the wax content thereof solidies, agitating the cooling mixture tothe extent necessary to cause the solidified Wax to agglomerate, separating said agglomerates from the constituents of the mixture which remain liquid and from the cooling fluid.

11. A process for removing wax from an oilwax mixture which is adapted to be sweated, which comprises melting said mixture, passing the molten mixture in direct countercurrent heat exchange contact with a cooling fluid immiscible with said mixture and having av diierent specific gravity therefrom to slowly cool said mixture to a temperature at which at least a portion of the Wax contained therein crystallizes, agitating the cooling mixture tocause said wax crystals to combine into a plurality of agglomerates, and separating said agglomerates from the constituents of the oil-wax mixture which remain liquid and from the cooling fluid.

12. A process for removing waxfrom an oilwax mixture which is adapted to be sweated, which comprises melting said mixture, passing the molten mixture in direct countercurrent heat exchange contact with a solution of sodium silicate to slowly cool said mixture to a temperature at which at least a portion of the wax content therein crystallzes, agitating the cooling mixture to cause said wax crystals to combine into a pluing liquid by draining the liquid constituents therefrom through a perforated screen.

Y 13. A process for separating the higher melting constituents from the lower melting constituents of an oil-wax mixture which is adapted to be sweated, which comprises melting said oil-wax mixture, progressively cooling said molten mixture to a temperature between substantially 10 F. and 25 F. below the melting point of said mixture, whereby at least a portion of the higher melting constituents of said mixture solidify, agitating at a controlled rate the progressively cooling mixture to cause said solidified constituents to combine into a plurality of globular shaped agglomerates, and separating said agglomerates from the constituents which remain liquid.

14. A process for separating the higher melting constituents from the lower melting constituents of an oil-wax mixture which is adapted to be sweated, which comprises melting said oil-wax mixture, passing the lmolten mixture in direct heat exchange contact c'ountercurrent to a cooling fluid, immiscible with said mixture and having a different specific gravity therefrom, to cool said mixture to a temperature between 10 F. and

25 F. below the melting point thereof, whereby at least a portion of the high melting constituents crystallize, continuously agitating the cooling mixture to cause the crystallized constituents tocombine into a plurality of agglomerates, and separating said agglomerates from the constituents which remain liquid by draining and washing with a detergent liquid.

l5. A process for removing wax from an oil- `wax mixture which is adapted to be sweated, which comprises melting said mixture, passing the'molten mixture in direct heat exchange contact countercurrent to a cooling fluid, immiscible with said mixture and having a different specific gravity therefrom, to slowly cool said mixture to a temperature at.which at least a portion of the wax containedtherein crystallizes, agitating the cooling mixture to the extent necessary to cause said wax crystals to combine into a plurality of agglomerates, and separating said agglomerates from the constituents of the oil-wax mixture which remain liquid and from the cooling fluid by submerging the substances to be separated in contact with a wash liquid, immiscible with the oil-wax mixture and having a different specific gravity therefrom, whereby the liquid constituents of the oil-wax mixture are removed from the wax agglomerates.

IVAN M. PERICINS. FLOYD B. HOBART.

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