US2305619A - Refining of oils - Google Patents

Description

Dec. 22, 1942. w, KELLEY ETAL K 2,305,619

f' K REFINING OF OILS Filed July 14, 1958 2 Sl'leeLS-Sheeil l Gum ludkge Separating Dec. 22, 1942. w. KELLEY ETAL 2,305,619

REFINING OF OILS Filed July 14, 1938 2 Sheets-Sheet 2 1 n. 7 l Y 63 i WQSZLLqwLd Z/galL il 61 (16J Ei Z 1: zulfrzj,

Separata? OFFICE alumno or ons Calif.. zsaldxelieyasslgnor,

bymeaneasaignmentato'l'helnmmnsoom- -panmacomrationoflbeiaware application .my 14,19, serial No. nasse s' claim.

This invention relates to improvements in the process of refining fatty oils such as vegetable and animal oils, and particularly oils which include. as naturally occurring undesirable conlstituents, albuminous, mucilaginous, colloidal and coloring matters, and also substantial amounts of free fatty acids.

One of the principal objects of this invention isA to provide an improved method for the removal of the free fatty acids from oils of the character described which is particularly characterized by completeness of removal of the deleterious materials and the reduction of the shrinkage due to such removal.

Another object of the invention is to provide an improved method of rening such oils to produce superior commercial end products, particularly the improved acid free oil and improvedy soaps.

Another and more specific object of the invention is -to treat a fatty acid containing oil with an alkali for the neutralization of the fatty acids in the oil, such treatment being carried out in the presence of a soap solvent other than, or in addition to, water to facilitate separation of the soaps from the oil, without the usual requirement of adding heat, thereby affording economies in the apparatus required and in the time needed for treatment.

Another object of the invention is to provide an improved method of neutralizing the free fatty acids in edible oils of the character described and quickly separating the soaps therefrom in the presence of ethyl alcohol which dissolves the soap and renders the separation sharp and quick, such alcohol having no harmful eil'ect on the edible quality of the oil and being readily recovered without substantial expense or loss,

Further objects and advantages of. the invention will appear from the following disclosure of a representative form of the process and one embodiment of our invention taken in connection with the attached drawings illustrative thereof, and in which:

Figure 1 is a diagrammatic flow arrangement for the treatment of fatty acid containing oils in accordance with one embodiment of our invention; and

Figure 2 is a similar form of diagram for a modified flow arrangement.

Broadly stated this invention comprises the refinement of fatty oils and particularly vegetable oils for the purpose of removing certain undesirable naturally occurring constituents thereof, particuiaru the aibummcus, muclminous, colloidal and coloring matters and the free fatty acids, all this being accomplished without detrimentally affecting the other characteristics of the oil, in some cases actually improving the same.

In detail, the process comprising our invention may be divided into the several steps of first removing the. aforementioned mucilaginous material; second, removal of the coloring matter: and third, a removal of the free fatty acids.

In general, the varioussteps of the process will be performed in the order named for best results. It is not essential, however, that the step of removing the coloring matter be performed prior to the step of removalof the free fatty acids. It is preferable, however, to remove the mucilaginous material prior to the removal of the free.

fatty acids in practicing the process of our invention. The mucilaginous material above referred to is sometimes described as lipoids," and wherever the term "mucilaginous material" is use d herein, it is meant to include the substances ordinarily included by the term lipolds.

The removal of the lipoids may be most conveniently accomplished by water washing the oil. This water washing step consists of adding to the oil on the order of about 10% of the weight of the voil of water at room temperature. The water may be introduced to the oil by spraying the sameon the surface of the oil, while the latter is gently agitated, the gentle agitation of the oil taken in conjunction, with the passage of the water down through the oil being eii'ective to remove most of the lipoids present. 'I'he general process of water washing oil of this character is disclosed in U. 11,725,895, issued to W. S. Baylis on August 27. 1929. A

After the water washed oil has been substantially freed from the water layer containing the lipoids in a well known manner, the oil will then be conveniently treated with a'.decoloring material such as clay, for example that available on the market under the commercial trade name of FlltroL In general relatively small amounts of such decoloring material will be found sumcient,for example, from 1-5%` of the amount of oil being treated, the nature of the decoloring material, of course, governing the amount used. The treatment with the decoloring material, such as clay. is preferably carried on at an elevated temperature, the upper limit of which is the temperature at which the oilwould be adversely aected, and the lower temperature being gen- S. `Patent No..

F. Ordinarily.

alkali solution,

' ing a solvent erally onthe order of about 1004 when treating cottonseed oil. the decolorizing or clay treatment step may advantageously be carried on at a temperature of about 140 F.

The mixture of oil and decolorizing or treatment material is thoroughly agitated for a period of about minutes, after which it is filtered and a clear oil drawn of! from which the lipoids and the majority of the coloring material has now been removed, .but which still contains most of the free fatty acids.

In view of/the particular nature of the step of the present prcess during which the free fatty acid is removed and which is likewise effective to remove a substantial amount of the coloring matter present; the decolorizing step Just described need not be carried on to such a complete removal of all of the coloring matter as is necessary with the prior art processes. As previoisly indicated, it is within the contemplation oi' our invention to carry on the decolorizing step as such subsequent to the step of removing the free fatty acids, although in general, at least partial decolorization of the oil prior to the step of removing the free fatty acids w'ill be found preferable.

The step of removing the free fatty acids is accomplished by treating the oil with an alcoholic which solution will usually also ycontain substantial amounts of water. kali i's of course added for the purpose of neutralizing or saponifying the free fatty acids. The alcohol, or alcohol and water if the solution contains water, v

for the soap thus formed as well as for such coloring matter as may be removed by the alcoholic soap solution and to facilitate separation of the soap from the oil being treated.

Sodium hydroxide is a convenient alkali which may be used for this purpose, although other alkalies, which will saponify the free fatty acids vand are not incompatible with the oil and other constituents in the mixture at this stage of the process may be employed.

Ii' the oil being treated is an edible oil, the alcohol employed should of course be a non-toxic alcohol and therefore ethyl alcohol will preferably be used. Wherev it is possible to steam distill, for example. and completely remove the alcohol employed as a solvent, `the other alcohols, such as methyl, may be employed. If. the employment of a toxic alcohol is not objectionable,- as in the case of non-edible oils, then any alcohol, such as any of the lower aliphatic alcohls, which are good solvents remain substantially all inthe oil phase, may be used The amount of alkali employed will be determined of course by the free fatty acid content of Ithe oil being treated. It will be generally desirable to employ, as nearly as practicable, the theoretical amount necessary to neutralize or saponify the free fatty acids. A slight excess of. for example, 20% of such theoretical amount will usually be employed. At this point it may be well to note that the prior art processes of rening oils of the character to which this invention relates, have employed amounts of alkali Y equivalent to several times the theoretical amount necessary to neutralize or saponify the free fatty acids. In practicing the process of our invention, the excess of alkali employed will generally fall between 5-and 50% of the theoretical amount required to neutralize the free fatty acids.

The amount of alcohol employed may be varied for the soap and will not is added vfor the purpose of providu limits, for example, from v.through a centrifuge.

over a .very wide range, `f or example, from l to 200% of the wei'ght of the oil being treated. The relative proportions of the amount of alcohol and water present may likewise vary over very wide l i a ratio of from 1 part by 4 weight of a1coho1 to 1o to 20 parts by weight weight of water.-

The foregoing ranges of percentages and proportions are representative but are not to be construed as flimiting the percentages and proportions within which the named constituents may be employed.

The treating materials mentioned above, namely alkali, alcohol, and in most cases also water, will preferably first be mixed. The oil and mixture of treating materials will then be combined, preferably afterveach has been raised to an elevated temperature, likewise usually lying between F. on the low side and the temperature at which the oil deteriorates on the high side. Usually a temperature lying between and F. will be found most satisfactory for cottonseed oil. Where the alcohol is used in re1- atively high proportion as compared with the water, for example in the ratio of 4 to 1, it is not necessary and sometimes not desirable to treat at elevated' temperatures.

After the oil and treating materials are combined in the m er above explained, they should be agitated for a period varying from 5 to 30 minutes. When cottonseed oil is being treated, the period of agitation need not continue longer than about 20 minutes. When the alcohol-alkali or alcohol-water-alkali mixture is added to the oil being treated by 'means of apparatus such as is illustrated for example in U. S. Patent No. 2,042,880, further y found unnecessary. Upon the addition of the treating material to the oil, reaction immediately takes place whereby the soap is formed and, as the agitation is continued with the temperature maintained, and particularly when the mixture maintained at an elevated temperature, the soap solution lcontained in the oil will be noticed to appreciably darken as the same absorbs coloring matter from the oil.

`parts by weight of water, of alcohol to 1 part by At the completion of the reaction, the oil andl the soap solution contained therein, may be separated either by gravity or bypassing the same In the case of the use of an alcohol of relatively low speciiic gravity and in large proportions relative to the amount of water used, the soap solution will have a speciic gravity less than that of the oil being treated, and in such case, when settling takes place, will form a. layer at the top of the mixture. In the case of the use of ethyl alcohol in proportions of about four times that of the amount of water used,

lseparation of `the two liquid layers takes place rapidly when cottonseed oil, for example, is treated, to form a.y complete layer at the top of the -mixture containing the soap and a considerable 'portion of the coloring matter of the oil.

' When a large proportion of water relative to the amount of alcohol is used, for example equal amounts by weight, the soap solution will have a higher specific gravity than the oil, and in this case. the soap solution settlesv to form a layer at the bottom of the mixture. It will Vusually be found desirable to avoid such proportions of alcohol and water as will produce a soap containing layer having the same specific gravity as the oil. as in this case it would be more diiilcult to agitation after blending will be Likewise, in`

cover the alcohol.

cause separation ofzthetwo Aiayel'sexcept by other methods vauch as nltration.

The following are two specific examples of embodiments of ,our invention in the rednement ofcottonseed oil. Theoil treated in veach case' very much smaller amount lof alcohol with respect tof the amount' of water `was employed. the liirst example, the amount of alcohol was considerable -with respect to the amount of oil treated. whereas inthe second example, the amount of alcohol-water solution for the soapwas `Arelatively small with respect to the total amount of oil treated. f

parts of. 95% ethyl alcohol. 24 parts by weight. of .a 12% aqueous solution of caustic'- sodawere` then added. `It had previously been determined by analysis-that parts by weight of this caustic lsolution would be required to neutralize `the free* fatty acid contained in 1000'parts of the oil: the amount addedtherefore represented a `20% excess.

In the `first specific example hot water at a temperature of 170 F. 'by` .stirring the mixture ofoii andfwater for ilve minutes. The washwater, having settled to `the bottom at the `end of minutes, was drawn oi! and the oil dried.' The wash water was added to the alcoholic soap mixture and acidulated `with a slight excess of acid, the clear fatty acids going to the top; the alcohol-.water solution was drawn on, neutralized and distilled-The fatty acids were washedand then dried. l

' Thefollowing is a description ofthe function ofthe illustrated apparatus which'shows one manner in which the previously described process comprising our invention may be'carrie'd out.

The oilI which maybe'of a typical commercial gradepis first introduced at-il intoa mixing After the caustic solution wasadded to the alcohol-oil mixture, `the wholel was thoroughly agitated at room temperature in 'a closed conapproximately 5 minutes. The mixture was-allowed tostand and at the end of 8 xrlinutes there was a substantially complete separation ofthe oil and the alcoholv solution containing the saponied free fatty acids. .The slightly turbidoil, which constituted the lower layer, wasd'rawn off down to the clear solution of the alcohol. The oil .was then washed at a temperature-of 170 F., with 100 partslby weight of hot water, the mixture being stirred quite vigorously for several minutes. f The settled wash water was drawn oif from the mixture and the oil dried. The wash water was added to the alcohol solution and thefatty `acids were separated 'out by adding sufficient acid' until the mix-y ture gave an acid reaction. The layer of fatty acids separated out as a clear layer at the vtop and the lower solution consisting of alcohol and water was taken oif. This alcohol-water mixture was neutralizedand the whole distilled to ref- The fatty acids were washed and then dried.` l

Examplell 1000x partsby weightof the same water washed and clay treatedl cottonseed oil as used in Example I were heated toMO-F.- To thiswere added 24.` parts gby- 1,weight` of a, 12% aqueousycaustic soda solution (equivalent,tothefreefatty acid, plus a 2 0% excess) contained in a of .5 0 parts'of `water and-,70 cohol. This mixture of alcohol, caustic soda and waterA had first been mixture `was thoroughly stirred forflve minutes. It was then allowed@ the en dv -of-4 which time the Ydarlrred alcoholic soap solution; had settled to .the bottom and `.cleanly v separated :from .the oil. This -soap-containing layer was separated from the oiland the i with 100 parts by weight of oil was then washed stand `for 30 minutes at` in the mixer 2|.

purpose.

tank i2 wherein it is mixed with wash liquid at Il as by the propeller II and, if desired, in the presence of heat through the steam coil li. The amount of wash liquid depends upon the initial amount of gums and other impurities in the oil and with a typical grade of oil having 1% of such impurities, approximately 1% of' wash liquid is added. The wash liquid is preferably water.

which 'is efficient and inexpensive. The mixing -is done with a very'- gentle stirring of the water 'and oil and 'after a few minutes of stirring. the

mixture may be drawn oi! at l1 into aseparator I8 which mayzbe aldecantingtank orany other type of apparatus which will allow the gum and sludge to settle out at l0 so that the washed oil may be removed at 20. v

' The water washed oil removedat 2l is-improved in color somewhat, but still contains the larger part of the color impurities. As the sec- 'ond step in the process. it is therefore preferable to clay treat this oil which may be 'accomplished The oil is intimately mixed in the' mixer 2l with clay such asFiltrol from a suitable supply 22, and preferably the clay and oil are introduced in exactly proportioned quantities through proportionating device 21 such as described in Cornell U. S. Patent 2,109,331. The clay may be of any suitable type and is preferably in the orderv of approximatelyi to 3% of the oil. l

The mlxing device 2l is adapted not only to intermix the oil and clay, but to do so in a relatively flnely attenuated stream` and under suitable operating conditions, such as under a vacuum obtained in line 2l and at an elevated temperature which may be obtained in any desired manner. While thespecic form of `attenuating apparatus is not essential totheproces's, 4it is found that one as described in Cornell U. S. Patent 2,043,880` is particularly efficient for this In such" apparat the introduced mixture is passedthrough a suitable manifold onto a rotatingf'disk 25 revolved at relatively high speed and'with the `mixture spread thin by the collar 26. The. attenuated stream of oil and .clay is" very intimately and ,quickly'fmixedxand the mixture `is ,collected in ythe bottom .from which it is `withdrawn bythe pump 21 andintroduced into -the lter28. v

The illterv2l may be of any suitable type and is preferably a Yvacuum ory pressure `filterA so that eiective -lter rates can be obtained.v `".lhe lter cake, whichis removed at-29, includes the clay with a substantial portion of the :color impurities in the voil,-p1us-a veryV small .proportion v`of oil. `The foill. contained inthe filter cakerepresents vabout 1% "ofl-theoriginal chargeA or '25%' of the cake and this may be treated in any desired manner to recover the oil duced at of desired.

The filtrate from the filter 28 is a light colored oil from which the mechanical impurities have been removed, but it still contains the free fatty acids which are removed in the mixing device 32. This device may be similar to the previous mixing device 2l and in such case is also preferably operated under vacuum obtained by the line 33. We find, however, that neutralization of the free fatty acids in the oil by the alkali from line 34 can be greatly improved if alcohol is introduced at the same time. The amount of alcohol is based upon the nature ofthe oil and the amount of free fatty acids, and due to the fact that the proportion should be precisely adjusted, 'we prefer to use proportionating devices 36, which are similarY to the proportionating device 23 heretofore mentioned.

Each of the proportionating devices will accurately gauge the amount of material including the alkali from the line 34,' the alcohol from the line 35 and the oil from the line 31. While the alcohol and the oil may be introduced through the same manifold, it is preferable that the alkali be introduced separately because of the small amount of alkali necessary to neutralize the free fatty acid. Normally commercial oils have from 1 to 3% free fatty acids and the amount of alkali necessary is very small in proportion to the amount of oil. The amount of alcohol may be in the range of 5 to 100% of the oil treated. I

Instead of following the procedure above outlined it is within'the contemplation of our invention to introduce the water by means of a which can be reintrol separate proportionating device or the water and alkali may be introduced in one proportionating device and the alcohol in another, or the alcohol, water and alkali may be pre-mixed in predetermined proportions and introduced by means of a single proportionating device.

By the use of the mixing device 32, we obtain a highly attenuated stream of alkali, alcohol and oil mixture which assures a very positive neutralization of all the free fatty acids. Only a slight excess of alkali is needed beyond the theoretically 4required amounts and by operation under vacuum, there is no oxidation which can take place and there is no true emulsion formed. l

This is of great importance as heretofore it has been necessary to employ heat to break the emulsion and we nd that not only do we not need heat, but that in some cases neutralization works better cool, that is in the range of normal room temperature.

The mixture which is removed by the pump 40 may beintroduced into a separating and decanting .tower 4l, and within a few minutes it will be found that the alcoholic solution of soap may be drawn oi sequentially through the lines 42 and 43. A sight gage 44 is useful for this purpose. The oil in the line 42 may be introduced into a tank 46 provided with a heating means 4l to drive oi any possible alcohol carried therein. `The alcohol can be condensed at 48 and collected at 49. The oil removed at 5u. preferably after water washing and drying is a commercial product, superior in color and free of fatty acids and salable at a premium.

rl'he alcohol and soap solution drawn oi in the line 43 may be introduced into column 5I, heated by a suitable source at 52 to drive oif the alcohol. The vapors are condensed at 53 and collected at 54. such alcohol being suitable for reuse in line 35 or for other purposes.

The soap stock drawn on at 58 is'a pure white material suitable for any desired commercial purpose and is of a premium grade. An alternative method of treating the soap solution is to acidify and remove the fatty acids before recovery of the alcohol.

We find that the operation of the process as set forth involves a relatively low shrinkage as compared toprior processes and, if desired, the shrinkage due to the oil carried in the illter cake can be eliminated as the oil can be economically recovered. There is practically no shrinkage unaccounted for except in the gum and sludge. 'I'he soap stock of course accounts for substantially all of the free fatty acids as one impurity, but as this is a superior premium product, the economic loss is very small. i

Pure grain alcohol is a preferred solvent because it contains no impurities, traces of which may be left in the oil. This is essential Where the oil is used for edible purposes. Furthermore, the soap is readily soluble in such alcohol and the alcohol can be easily recovered by distillation. If the recovered oil is not used for edible purposes, it is apparent that other solvents may be used, provided they are economically satisfactory, and such solvents include methyl alcohol.

While it is preferable to initially remove the gum and sludge by water washing and to then 'decolorize the oil before the fatty acids are removed, this is not an essential sequence in the refining of the oil. It is possible to remove the fatty acids and subsequently decolorize the oil, or to eliminate the decolorizing treatment altogether if it is not required. It is preferable, however, to rst wash the liquidto remove the gums and sludge as it greatly facilitates the subsequent separation of the neutralized fatty acids from the oil.

In accordance with this arrangement, which is disclosed in Figure 2, the oil which `enters at 60 is mixed with wash liquid at 6I in tank 62 as by propeller 63, after which the oil is withdrawn at 64 into separator tank 65, from which the gum and sludge will settle out at $6 from the clear oil removed at 6l.

The oil is then passed through one of a series of proportionating devices l0 into the mixing device ll into which alkali is introduced from the line l2 through a proportionating device 'I0 for intimate mixing on the rotating disk 13 as heretofore described. The alkali and oil are separately introduced as near to the disk as possible because of the relatively small amount of alkali required. Furthermore. the mixing devi-ce 1I is preferably operated under a vacuum in line 14.

As in the prior arrangement, we have shown the introduction of alcohol from line 15 through a third proportionating device for mixture with the oil and alkali. It is possible, however, to eliminate the alcohol, but it gives a better color separation and a more rapid separation of the neutralized acids from the oil.

The separation of the neutralized acids from the oil is accomplished in the separating and decanting tower 'l1 into which the mixture is pumped by pump 18 from the bottom of device ll. 'I'he oil and the neutralized acid or If alcohol and will color oil.

The oil and soap solutions are removed from the bottom of the separating tower 11 through sight gage 88 with the oil being drawn off rst through the line 8| into the distilling column 82 which is provided with a steam coil 88 to drive oi! the alcohol condensed at 84 and removed in the line 85. The sharp stratification of oil and soap makes it possible to draw oi all of the oil after which the soap (and alcohol) can be withdrawn in the line 88 and introduced into the distilling column 81 which is similarly provided with aheating coil 88 to drive off the alcohol condensed at 89 and removed in line 90. The soap stock is removed in the line 8l and is suitable for commercial purposes.

The oil which is removed from the column 82 through the line 92, is free of gums, sludge and fatty acids and has been partially decolorized. If further decolorizing is desired, it may be introduced into the mixing device 93 through the proportionating device 94 with clay from line 95, and similarly pass through another proportioning device 94 with the resultantintimate mixture of clay and oil accomplished by means of the mixing disk 86. As above mentioned, the decolorizing mixer 83 is preferably operated under a vacuum as by line 91 and is preferably operated atA an elevated temperature in the neighborhood of 140" F. which is found to accelerate the decolorizing treatment. The mixture is removed in line 88, enters the illter 99 with the ltrate removed at |88 as a clear, substantially colorless, acid-free oil. The illter cake removed at I Iii'contains a small proportion of the original charge of oil and may be subsequently treated for recovery of the oil.

While we have shown preferred forms of embodiment of our invention, we are aware that other modifications may be made thereto and we therefore desire a broad interpretation of our invention within the scope and spirit .of the description herein and of the claims appended herev inafter.

We claim:

l. In the method of refining animal and vegetable oils containing free fatty acids and other deleterious materials from which the deleterious materials are removed by a water washingand gum removal step and the oil is decolorized, the improvement which comprises neutralizing the free fatty acid content of the partially puriiled oil with an alcohol solution of an alkali neutralizing material, such neutralization step being carried out under a vacuum with the oil and neutralizing solution being finely attenuated without subdivision of the oil stream, whereby, on settling at normal room temperatures, the alcohol solution itself will sharply separate from the neutralized oil. v

2. Themethod of refining animal and vegetable oils as claimed in claim l, in which the alcohol concentration is sumcient to form an alcohol and soap solution which is relatively heavier than the oil.

3. The method of refining animal and vegetable oils as claimed in claim 1, in which the alcohol concentration is suilicient to form an alcohol and soap solution which is relatively lighter than the 011. r

4. 'I'he method of neutralizing the free fatty acid content of cottonseed oil which has been water washed and from which the gums and sludge have been removed and in which the fatty acid content is in the range of 1 to 3%, which comprises mixing with said oil a non-saline alcoholic solution of an alkali in which the alkali corresponds. in amounts to the range not to exceed 20% in excess of that theoretically required for the neutralization of the acid, passing such oil and alkali solution through a chamber in a finely attenuated, rapidly moving, continuous stream in the presence of a substantial vacuum, subsequently collecting the neutralized oil and alcoho1- soap solution. separating the alcohol-soap solution from the neutralized oil, and thereafter separating the alcohol from the soap to provide'a relatively pure soap stock.

5. A process of reflningva glyceride-type oil, which process includes the steps of:A removing gums and mucilaginous matter from said oil;

y mixing in a connned space under vacuum in a fatty acids, and a de-emulsifyins'and inhibiting agent comprising a lower aliphatic alcohol added in such amount as to minimize the saponiilcation and entrainment of neutral oil; separating the foots from the refined oil, and removing the deemulsifyingand inhibiting agent by vaporizing the same.

W'ILIJAM KELLEY. MEAD CORNELL.

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