US1831433A - Process for the removal of solid oils and waxes from liquid oils and similar materials - Google Patents

Description

Nov. 10, 1931.

C. PROCESS FOR THE REMOV V. ZOUL AL OF SOLID OILS AND WAXES FROM LIQUID OILS AND SIMILAR MATERIALS Filed July l, 1924 ATTORNEY.

i Patented Nov 10, i

UNITED STATES MT1-:NT ori-ICE 'CHARLES v. lzouL. vor sAN'rA moNIcA, CALIFORNIA, AssIoNoR, :BY IIEsNE AssIoN- MENTS, TO GEIJTE YORK c rnocnss Foa THE-REMOVAL or soLID oILs ANn wAxEs smILAn xATEaIAIs CORPORATION, 0F NEW YORK, N. Y., A. GORPOBATION OF NEW 'Applicationmea my 1,1924. 'serial Navassse.

This invention relates to a process of -rel moving solid fats, .oils and waxes such asV is tov provide 'abprocess by means of, which mineral,'vege marine, and animal oils containing only small percentages of solid fats or oils, may beeconomically treated for. their removaltherefrom and whereby 'the removal of such solid constituents may be effected more rapidly, thorou hly, and 'ef' ficiently than has heretofore n possible. Heretofoie in order to remove solid oils or fats from oils or liquids containing them, it has been found desirable to keep such oils at a low temperature for certain minimum lengths of time so that the solid constituents, such as waxes, paraffin, steari-n, orthe like, crystallize out of solution. Thetemperature to which oils are cooled depends not only on the melting point of the constituent being removed, but also its amount, solubilityin the mother liquor and; various otherV factors. Rapid cooling has never been successful as the crystal formation forms'on the cooling coils or other suitable cooling means and insulates them thermally so that the main body of oil is not cooled thoroughly and evenly.- Rapid cooling can be'used if the oil is kept in active circulation so as to prevent the formation of crystals on the cooling-means, but ythis procedure results in the formation of n very iinelv divided crystals which are extremely difficult to separate from the oil either by gravitational separation or by filter pressing. For this reason the separation of solid oils orats is accomplished in practice by cooling slowly', but'the maintenance of a large body ofoil at a low temperature -for a long time' is not economical.

My process makes it possible lto cool oils Enom LIQUID oILs AND containing small amounts of solid'fats or oils i rapidly, so 'that' circulation or agitation of the cooling liquid may be' used and although small crystals are formed,I have devised a means of separating them from the. oils s0 that no diiiiculty `is encountered in making the separatiom- Many vegetable oils suchv as eottonseed, corn oil,` sesame' oil, linseed loil and othersl contain small percentages of stearin, palmitin, arachine, cholesterol, sitosterol, brassicasterol, bombicesterol stigmasterol,coproster ol, clionasterol, and the like which are diiiicultly removable. My process as hereinafter described makes it possible to remove these constituents very efectively and conomically.

Mineral-oils contain `solid waxes and paralins, both protoparaiin and pyroparailin; some mineral oils also contain a wax similar to Montan wax, while others contain small quantities of ceresin. The presence of any one or more of these paraifins or waxes or similar matter is more or less dependent upon the treatment given the oil during refining and distillation, but in all cases these waxes and paraifins are difiicult to remove and for this reason my process is of great commercial value when applied to this type ofoil.

Fish oils and animal oils such as tallows, lards, neats foot oils, and the-like, all contain small quantities 'of stearin andsome of the above mentioned solid oils.

As mentioned above, diiiiculty, has been experienced heretoforein that if it is desired to cool a large'quantity of `oil rapidly, the waxy matter and solid oils notonly crystallize on the cooling surfaces and insulate the main body of oil, but'usually crystallize in the soft, mushy, finely divided condition, especially if the solid constituent'is only present in small amounts so that the chilled oil after crystallization has taken lace, presents a difficult problem'to the oil re ner. Settling and decantation are not satisfactory in that large amounts of liquid oil are left in the solidconstituent. While filtration through cloth or in hydraulic presses has been most generally adopted, slimingof the cloth very often occurs, preventing filtration and making the removal of such solid oils from the cloth very difficult.

In the accompanying sketch I show in diagrammatic elevation an apparatus Which may be used in the operation of my invention. The oil or fat to be treated, is supplied to tank 1 through pipe means 6. Tank 1 is equipped with brine coils 2 or with other suitable means of reducing the temperature of the oil or fat in said tank, with an agitating mechanism 3 of suitable design, and with means for introducing finely divided diatomaceous earth or other solidI finely divided filtering material from a hopper 4, such means comprising screw conveyor 5 or any other means appropriate for the purpose. The chilled untreated oil from tank 1 may pass through valve 7 and pipe 8 to a pump 9 which then forces it through pipe 34 and valve 17 into a filter press or other filtering apparatus of suitable design 18. The treated oil then passes through valve 21 and pipe 35 to storage or for further treatment by any other process.

A precoating tank 10 is also supplied With brine coils 11 or if desirable, with a brine jacket or With any other appropriate means of reducing the temperature of the liquid contained therein, Withan agitating mechanism 12, and With means for gradually supplying thereto finely divided diatomaceous earth or other finely divided solid filtering material from a hopper 13. On the drawing I have shown the use of a screw conveyor 14 for gradually moving the material used in my process from hopper 13 into precoating tank 10. The discharge 15 from the precoating tank conducts the oil through valve 16 into the pump 9 from which it is forced through pipe 34 and valve 17 into the filter press 18 and may be discharged from said filter press through valve 20 and pipe means 19 back into the precoating tank 10. Means for introducing clean destearinizing or devvaxed oil into precoating tank 10 other than that obtained from the filter press 18 through valve 2O and pipemeans 19 are not shown but may be used when desirable.

Tank 22 represents a receptacle used for collecting the cake from filter press 18 and may be eouipped with steam coils 23 or with a steam jacket not shown.

Tank 22 discharges through pipe 36 and valve y24 into a pump 25 which in turn discharges through pipe 37 and valve 26 into a filter press or other filtering' apparatus 27. Valve 28 and discharge pipe 38 mav be provided at the discharge end of the filtering apparatus. Pipe means 29 and 30 entering the filtering apparatus 18 may be provided for introducing steam, air, or a solvent for Washing purposes commercial scale.

to prepare the ltering apparatus 18 for discharging its cake into the tank 22. Pipe means 31 and 32 may also be provided for introducing steam, air, or a solvent into the filtering apparatus 27 for Washing or cleaning said apparatus.

As an illustration of my process I shall describe the treatment ofcottonseed oil on which I have done very successful Work on Cottonseed oil is obtained by expressing dehulled cottonseed, the crude oil being usually refined by treating with alkali. The refined oil is further treated when desirable by bleaching with a decolorizing agent such as fullers earth, carbon or acid clay and the bleached oil is usually deodorized.

`When it is desirable to produce a Winter oil or an oil suitable for salad oil, the stearin and palmitin present is removed according to the usual practice by cooling the refined oil for a period of about one Week, from an initial temperature .averaging F. through a mean temperature of about 57 F. to a final temperature of 44 to 46 F. and then filtering through cloth at a lovv pressure in large filter presses of suitable design in rooms kept at a temperature of not over 48 F.

The temperature to which the oil is chilled must be carefully regulated s o that Well formed crystals of palmitic and stearic glycerides are formed in the mother liquor. Sudden cooling tends to form amorphou-s crystals which are mushy, soft, exceedingly fine and difcult to separate from the main body of oil. This separation of stearin and palmitin must be very thorough, as the usual cold test consists in placing the finished oil in cracked ice for a period of five hours, at the end of which time no crystallization of stearin or palmitin should have taken place.

In applying my invention to the treatment of cottonseed oil I prefer to add a small percentage, say from one-fourth of one per cent to one per cent of diatomaceous earth (either raw or calcined) from hopper 4, to the body of oil being treated, just before or during the time of cooling in tank 1. I have found that best results are obtained by adding diatomaceous earth to oil after cooling had started, but before any stearin has begun to separate. Diatomaceous earth usually, in this manner, act-s as a nucleus and stearin crystals appear to form much more rapidly after the addition of this materia. The period of cooling, heretofore extended over a period of about one week, may be reduced to one or tivo days, depending upon the amount of oil, type of cooling apparatus, and other factors. After rapidly cooling the oil down to a sufficiently low temperature to cause crystallization of the stearin, for example, to about 44 F. the oil is allowed to stand in tank 1 for approximately three hours at 44to 48A F., but frequently stirred for example by agitator 3. The stearin by this time is completely out of solution and may be separated in the hereinafter described manner.

aSeparation of solid oils such as stearin from an oil, is preferably carried out in plcate and frame or recessed plat type of filters in-'.

dicated at 18 in rooms chilled to a temperature of from 48 to 50 F. Rapid chilling produces fine crystals which when pressed through a filter press, slime and elo the cloths to such an extent that filtration 1s impossible. In the operation of my process, however, I prefer to form an oil wetted coating of diatomaceous earth upon the filtering surfaces of the filtering apparatus before passing therethrough the chilled oil.

To form the coating of oil-.wetted diatomaceous earth upon the filtering surfaces I have utilized, usually, a de-stearinized cold salad oil as a medium by which the diatomaceous earth is carried into the press and built up on the filtering surfaces in the form.

of an oil-wetted coating. The operation in detail consists of placing a volume of destearinized cold salad oil, having a volume in excess of the volumetric capacityof the pump, piping and filter press being used, in a suitable tank 10 provided with mechanical agitation and cooling coils as above described.

This de-stearinized oil is first pum d through the filter press so as to thoroughly oil VWet the filtering surfaces, displace all entrappedair and reduce the temperature of the press to that of the oil. This circulation of the oil takes place through pipe means 145, valve16, pump 9, pipe 34, and valve 17 into filter press Y18 and thence through valve 20 and plpe means 19 back to tank 10, and the temperature of the oil is meanwhile reduced or kept sufficiently low to cool the. filtering apparatus to the desired temperature. Diatomaceous earth in' suitable quantity is then gradually added to the oil at the agitating tank 10, by any suitable means such as for example hopper 13 and the screw conveyor 14.- and the recirculation continued until the required amount of diatomaceous earth, now thoroughly oil wetted, is formed as a precoat or coating upon the filtering surfaces of the filter press. The cooling of the contents of tank 10 is continued during this time. so

that the precoat and any oil remaining therein are kept at the desired low temperature. Only a small amount of diatomaceous earth is required for this purpose and I have found that from 2 to 6 ounces of this material per square foot of filtering surface is ample. The precoat oil after all the diatomaceous earth has been retained in the filter press is pumped back into tank 10, or into suitable storage tanks, and the chilled oil from tank l containing stearin crystallized on the diatomaceous earth nuclei is then passed through valve 7, pipe means 8, pump 9, pipe 34,* and valve v17, into and through the precoated filter press 18, valves 16 and 20 having been i closed and valve 21 opened. A cake is thus formed on the outside of the previously formed diatomaceous earth precoat on the filter surface, containing the stearin together with the diatomaceous earth, While the clear, liquid oil flows out through valve 21 and pipe 35 and is collected for shipment or for subsequent treatment. When a batch of oil is finished, or the cake spaces in the filter press are filledwith cake, the passage of oil is discontinued.

By performing the operation in the above described manner the. removal of stearin is accomplished with great rapidity and very thoroughly. The cake separates from the cloth very easily after completion of a run and is sent to tank 22 or to any other suitable heating chamber and the stearin may then be separated from the diatomaceous earth by heating the cake. by steam coil 23 or other heating means to a sufficient temperature tov melt the stearin and refiltering the resulting liquid so that only the diatomaceous earth is retained on the filter cloths and the pure stearin in liquid form passes through, which upon chilling, solidifies into a hard White solid. This .warm filtration is preferably carried out ina separate. filter press 27, or

other suitable filtering apparatus, which may be of much smaller capacity than the first press. The diatomaceous earh is thus recovered, substantially free from stearin and other material and may if desired be re-used in place of, or in addition to, fresh diatomaceous earth in another cycle of the above.

process, such recovered earth being used either informing the oil-wetted coating on the filtering surfaces, or by adding it to the main body of oil to be treated, during chilling, or in both of the above ways. This reuse ofthe diatomaceous earth constitutes' an important advantage of my invention, and is dependent upon the fact that the solid constituent, which is removed from the oil by the low temperature filtration, may itself be separated from the diatomaceous earth by a' -quired amount. A great saving of the diatomaceous earth is-thus effected.

Although in the above described operaJ ion I have rep tedly mentioned diatomaecous earth, also (liown as kieselguhr, infusor'ial earth, tripoli or-fossil fiour, other finely divided, solid, porous materialsmay. be utilized for this purpose.` In general, however, the material used should be chemically inert toward the oil so as to neither affect the character of the oil nor be itself changed in composition during the process, although in some cases the material may have a bleaching or decolorizing effect on the oil. Some examples of other suitable materials are tufa, pumice, volcanic ash, various carbons, or the like. The diatomaceous earth may be reduced to any suitable state of division and may be calcined either ybefore or after grinding or crushing, such calcination being done either with or without the use of salts or other chemicals. At certain times an additional bleaching effect is desirable and for this purpose a carbon, bonechar or charcoal may be utilized in the same m'anner as above described, the bleaching and destearinizing operation being carried out at the same time, although because of the low temperatures employed the decolorizing action is not as effective.

And although in the above example I have repeatedly made reference to the removal of stearin from cotonseed oil, attention is called to the fact that the solid oil is formed almost entirely of palmitin, the word stearin being used in plant technology for almost any solid oil obtained from` a liquid oil by chilling to a low temperature. Other solid constituents may also be removed from other oils, fats, and waxes by my process, and it will be understood that the term so-lid constitu-ents is used in the same sense in which it is used technically in the treatment of any particular oil or other liquid. In general by solid constituents, I mean any materials which crystallize or separate from a liquid .peratures below atmospheric.

oil, fat, or wax upon chilling thereof to tem- Such materials, after separation, are generally solids themselves at ordinary temperatures, but do not separate from the liquid oil at such temperaures because of their solubility therein. In some cases, however, materials may be separated from liquids by such chilling processes, which are themselves liquids at ordinary temperatures, Aand the term solid constituents as here used is to be understood to include such materials.

Sesame seed oil and corn oil are also difficultly refined, whenever absolute removal of solid oils and waxes is desired.L Both of these oils are high in olein and linoleic content, and contain some sterols or waxes. Sesame oil contains palmitin and stearin also. The refining operations for the removal of these solid oils and waxes is carried out in practically the same manner as for cottonseed oil, described above, the temperatures to be employed being determined by test, as these oils change in composition, depending upon locality from which they are obtained and other factors.

Y The dewaxing of mineral oils or the rem'oval of paran therefrom may be accomplished in much the same manner. There are two types of paraffin, protoparaiin occurring naturally in the oils, and pyroparaffin, formed during heating or distillation'. Paraffn is markedly more soluble in mineral oil than in gasoline and in order to get a better precipitation of paraiiin from a mineral oil, a dilution of the mineral oil with gasoline or light distillate has been found beneficial. This dilution, however, involves an expensive step in the refining operation and necessitates a recovery process. By using diatomaceous earth in the manner indicated above with vegetable oils and chilling rapidly with circulation and agitation of the oil, the paraffin may be precipitated in a very satisfactory manner.

Precoating of the press is done by means of a cold, dewaxed mineral oil to which diatomaceous earth is added during circulation through the press, so that a coating of `oil wetted diatomaceous earth is formed on the filtering surfaces. The vamount of diatomaceous earth used in applying such precoat may be approximately the same as used in the above described treatment of vegetable oil, say from 2 to 6 oz. or more per square foot of filter area. The main body of mineral oil from which paraiiin is to be removed is chilled to a sufficiently low temperature to cause crystallization of the solid constituents. Such temperature varies between rather wide limits, depending on the character of the oil and the character and amount of the solid constituents present, and has been found, in different cases to range from 10 F. to 30 F. The temperature required, in general, is `slightly above that to which it is necessary to chill the oil without the use of diatomaceous earth to aord nuclei for crystallization, and the time of chilling is also greatly reduced although suchfperiod also varies rather widely. As in the previously described example, diatomaceous earth is preferably added to the main body of mineral oil at ,the start of, or during, the chilling, and preferably before crystallization of the solid constituents has begun. The proportion of diatomaceous earth used for this purpose has in some cases been 2 or 3 per cent of the weight of oil, although in some cases as low as 1% is sufficient, and in other cases as much as 7 or 8% may be required.

The resulting 'oil is particularly adaptable for lubricating purposes as it is entirely free from all solids, paraffin, wax, or the like, as it has been shown that paraffin has no lubricating value and tends to reduce the viscosity of oils at high temperatures. The paraiiin which is removed by filtration through such oil wetted coatings of diatomaceous earth, may be recovered by melting and refiltering at a higher temperature so -as to give a clean product. The diatomaceous earth may thus be recovered and re-used as above described, if desired.

This invention therefore in its preferred embodiment comprises a method of removing solid fats, oils and waxes from liquid o1ls by chilling them sufficiently to cause solidlfication of the maerial to be removed in the presence of diatomaceous earth or otherfinely divided porous material, and then passmg such chilled oils through a precoat of diatomaceous earth or other finely divided material placed upon the filtering surfaces and wetted initially with a clean destearinized or dewaxed oil of the same character as that being treated, said precoat having also been chilled below the solidification point of said solid material.

What I claim is:

l. In the process of removing from liquid vegetable oils certain oleaginous constituents that are solids at temperatures below atmospheric, by mixing the oil with diatomaceous earth and chilling the mixture to solidify such solid constituents of the oil and filtering the resultant mixture at the said temperatures, the steps of preparing a pre-coated filtering medium for use in filtering such resultant mixture, comprising flowing into a filter press at temperatures below the solidification temperatures of said solid constituents of the oil, a mixture of diatomaceous earth and oil of the kind being treated but substantially free from said solid constituents whereby a coating of oil-wetteddiatomaceous earth is formed on the filtering surfaces of the filter press.

2. In the process of removing from cottonseed oil, certain oleaginous constituents that are solids at temperatures below atmospheric by mixing the oil with diatomaceous earth and chilling the mixture to solidify such solid constituents of the oil and filtering the resultant mixture at the said temperatures, the steps of preparing a pre-coated filtering medium for use in filtering such resultant mixture, comprising flowing into a filter press at temperatures below the solidification temperatures of said solid constituents of the oil, a mixture of diatomaceous earth and oil of the kind being treated but substantially free from said solid constituents, whereby a coating of oil-wetted diatomaceous earth `is formed on the filtering surfaces of the filter press.' i

3. In the process of removing from liquid oils and fats, certain oleaginous constituents that are solid at temperatures below atmospheric, by mixing the liquid with diatomaceous earth and chilling the mixture to solidify such solid constituents ofthe liquid and filtering the resultant mixture atjhe said temperatures, the steps of preparing a pre-coated filtering medium for use in filtering such rewhereby a coating of diatomaceous earth wetted with the liquid being treated is formed on the filtering surfaces of the filter press.

In testimony whereof I have hereunto subscribed my name this 19th day of June, 1924.

CHARLES V. ZOUL.

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