US2878275A - Miscella refining - Google Patents

Description

R. O. SCHMITT MISCELLA REFINING Filed Oct. 1l, 1957 March 17, 1959 INVENTOR ATTORNEYS 40 .fa 60 ed l ide/ cffw',

BY wmweem coa/am' United States Patent O MISCELLA REFINING Robert O. Schmitt, Cincinnati, Ohio, assignor to The Buckeye Cellulose Corporation, Cincinnati, Ohio, a corporation of Ohio p v Application Gctober 11, 1957, Serial No. 689,713

5 claims. (C1. 26o- 426) This invention relates to the refining of solvent extracted vegetable oilsand more particularly to the refining of Stich oils in the presence of the extraction solvent.

Refining processes involving the addition of anaqueons alkaline refining agent to a solvent solution 'of extracted oil are well known to the art and are characterized by the phase miscella refining. When contacted with the alkali, the fatty acids present are converted into soap; mucilaginous material such `as phosphatides, proteins and gums are precipitated; and coloring matter and other undesirable impurities are removed from the oil, along with any soap which has been formed. The precipitate thus formed is commonly referred to` in the art as foots The oil solvent serves to minimize the loss of neutral oil by emulsification with the foots.

In the refining of oil-solvent solutions (hereinafter referred to -as miscellas) removal of color to meet edible standards is difficult but may be effected by continued agitation of the miscella with the refining lye over a long period of time or by agitation with large excesses of the refining lye. However, either of these expedients is-conducive to excessive oil saponiiication and an attendant increase in oil loss.

` The point in miscella refining at which the process of color removal has proceeded to substantial completion is designated by those skilled in the art las the color break.` This color Upon admixture of lye with the miscella, the foots which are formed initially contain only minor `amounts of color. lf a small amount of this "mixture of miscella and foots is placed on a piece of filter paper, the `:foots appear as colored, immobile masses; and the dark colored miscella is absorbed by the filter paper and spreads to form adark colored circle. 4After further agitation and during the latter stages `of miscella refining, however, the foots particles form dispersed aggregates containing most break is determined as follows.

of the colored constituents originally present in the oil."

The point of fcolor break is that point at which removal of color has proceeded to the `extent that when a portion of the mixture of foots and miscella is placed on filter paper, the foots particles appear as dark colored immobile masses, and clear refined miscella is'absorbed by the filter paper and spreadsto form a substantially colorless circle. i i i The primary `object in miscella refining is to obtain a `thorough dispersion of the refining lye in the miscella so that maximum contact in the oil occurs, therebyenabling an earlier color break and more `complete color removal.` Whenthe suspended foots coalesce and agglomerato to form large foots aggregates at a point early in the refining operation, a substantial amount of the refining lye is entrapped `within the aggregates; and the quantity of available refining lye is insufficient to effect satisfactory color reduction. In such a case it is often necessary to subject the recovered oil to a second refining in order that its color may be sufficiently light to meet current standards for edible us`e,'

as in shortenings for example. Moreover, when the colorl break is delayed, valuable time is lost, costs of operation 4are increased, and neutral oil recovery is` diminished through increased saponitication of the'oil.

" Since saponification of neutral oil is minimized under betweenthe lye and color bodies 2,878,275 Patented Max".l 1.77, 1959 conditions which promote an earlyk color break, refining procedures which lessen the time necessary to achieve this color break are highly desirable. One such procedure hasbeen described in Folzenlogen U. S. Patent 2,563,327, wherein the desired results are achieved by agitation of the refining lye and miscella in the presence of certain non-ionic ethers. These ethers, however, constitute an expense .item of some importance, and a process enabling substantial reduction in the required amount `of the ethers, accompanied by an earlier color break and reduced operating, costs, would constitute a genuine advance in the art.

It is an object of the present invention to provide an improved process for refining solvent extracted vegetable oils in thepresence of the extraction solvent, whereby color removal from the oil is effected in a greatly reduced time, at reduced cost, and with a minimum of saponification of neutral oil.

It is a further object to provide an improvement on the processes` described and claimed in U. S. Patent 2,563,327. l

In one of its aspects, this invention .is based on the discovery that seedlng Vcrude miscella with a portion of the foots which have been separated from miscella in a previous refining, such seeding to be conducted prior to the addition of the refining lye and in the presence of `a minor amount of any of the non-ionic ethers described and claimed in U. S. Patent 2,563,327, unexpectedly through a synergistic action promotes a` color break in a much shorter time than has heretofore been possible throughthe use of such ethers alone. In the complete absence of the above mentioned non-ionic ethers, the seeding of crude miscella with a portion of the foots lwhimhave been separated from miscella in a previous refining will reduce the color break time substantially. It hasjbeen observed that such seeding of crude miscella with recirculated-foots and particularly with non-ionic etherspresent results inthe formation of foots which in the presence of conventional agitation remain `uniformly dispersed in the miscella throughout the entire color removal operation, thereby promoting an early color break and substantially complete4 color removal.

As will be noted from ythe following detailed description, the essential distinguishing'features` of the refining procedure 4offthis inventionover those procedures heretofore employed inthe art residesin the recirculation of a portion of the foots from a previous refining and particularlyin the presence of much smaller quantities of thermen-ionic ethers of U. S. Patent 2,563,327 than have heretofore been required, resulting in a consistently early color break.

The invention `will be better understood by reference to the drawings, wherein: i

Figure 1 is a ow chartof a preferred method of practicing the invention whereinl nou-ionic-ethers are employed, and i Figure `2 is .agraph which shows `the effect of recirculating foots, with and without non-ionic ether, on color break time. i

Referring tothe drawings, Figure l depicts atypical commercial batchmiscella .refining operation in which crude Voottonseed oil .in hexane solution is refined with sodium hydroxide in large vented closed kettles 10. The kettles have a capacity of about 500 cubic feet, are cylindrical in shape andhave a domedtop and a conical bottom. -Each kettle is provided with an internal steam coil `for heatingrthe charge and an, agitator for mixing.

In av conventional refiningl operation, aqueous refining lyeI from storage" 12 is `introduced into a charge of `crude miscella `in such a vrefining kettle, and the agitators are set to revolve at about 70 revolutionsper minute or at such speed as may be required' to effect adequate dspersion of the lye. It will be understood, of course, that the degree of agitation is not a critical limitation and will, 1n fact, vary depending upon kettle construction and the type, size and shape of the agitator. The agitation is continued until' the undesirable color has been removed from the oil, i. e. until a color break is noted, at which time the mixture of refined miscella and suspended foots is dropped t-o a drop tank agitation to keep the foots in uniform suspension, prior to passage to a centrifugal separator. From this drop tank the mixture passes through a'"pump` 14 to a closed centrifuge 15 which separates the refined miscella from the foots. The refined miscella goes to a surge tank 16 and is then separated into solvent-and neutral oil fractions by conventional methods. The foots mixture is collected in a surge tank 17 and heated by passage through a heat exchanger 18. The solvent is then separated from the foots-water-sol'vent mixture in a flash evaporator 19 and condenser 20. The foots are subsequently processed in a conventional manner, and the solventis returned to the system.

In the practice of the invention the crude miscella is seeded by returning a portion of the foots discharged from evaporator 19 through pipe 21 by metering pump 22 to kettle 10, and non-ionic ethers are introduced from tank 11, the seeding being accompanied by sufficient agitation to effect a uniform dispersal of the foo'ts and ethers throughout the miscella prior to the addition of the aqueous refining lye. The foots which are employed for seeding may also come from the surge tank 17, and the heat exchanger 18 and the lines connecting these points.

The miscella coming from the extraction step usually contains more solvent than oil',`but the refining procedure of this invention does not require large quantities of solvent and itmay be desirable from the standpoint of economy in handling, storage, etc., to remove a portion of the solvent before performing the refining operation.

Such reductions in the amount of solvent can be achieved by the usual evaporation facilities known in the art. It is preferred that the refining procedure be carried out on miscellas containing from about 25 percent to about 60 percent oil.

In practices involving refining substantially immediately after extraction or miscella concentration, the temperature of the miscella may be well above 100 F., as it is charged to the refining equipment. If necessary the temperature of the miscella can be adjusted before the addition of the recirculated fonts', non-ionicethers if employed and refining lye. In thel practice of the present invention, ordinarily the refining is'conducted at tempera tures of from about 100 F., to v140 F. Temperatures substantially above 140 F., generally tend to induce the formation of large foots aggregates rather than the desirable fine foots dispersion, thereby causing a delayed color break and incomplete color removal. The rate of reaction between the refining lye and the color bodies in the oil is slowed appreciably at temperatures substantially below 100 F. Preferably the refining is con-` ducted at temperatures from 115 F., to 125 F., when the miscella is constituted of about 40 to 60 percent oil in commercial hexane.

The advantages of this invention are also realized 13 equipped with adequate when the miscella is constituted of volatile oil-extraction solvents other than hexane. Thus improved results in color reduction arealso noted inthe case of miscellas formed by the use of extraction solvents such as benzene,

heptane, commercial mixtures containing such hydrocarbons, and other volatile aliphatic'l and aromatic hydrocarbon oil extraction solvents and'solvent mixtures known in the art. The invention is of 'particular advantage, of course, in the refining of those miscellas formed in the use of solvents which dissolve aff' considerable quantity of high colored constituents from the oil-bearing meats.

`It has been found that yaqueous solutions containing from about 5% to about 20% sodium hydroxide may be used, final choice depending on the refiners judgment, arrived at after consideration of the nature of the miscella being refined.

The amount of aqueous alkali used in the miscella relining techniques of this invention will normally be -175 percent of the maximum percent sodium hydroxide prescribed by the rules of the National Cottonrseed Products Association in the regular refining of hydraulic cottonseeed oils of the same free fatty acid content, figured as oleic acid (percent NaOH=percent F. F. A./5.2+.54). Under normal conditions and with normal hexane miscellas, obtained in the extractionv of cottonseed oil for example, 12S-150 percent of maximum will suice. However, amounts below 125%, such as k50%, and amounts in excess of 150%, such as 225%,

can be employed, depending on the nature and amount of impurities in the oil of the miscella being refined.

The recircuated foots which are added to the refining kettle in the practice of this invention can be removed from the refining system at any point, although for convenience the foots are preferably obtained just after the evaporation of the solvent. It will be apparent, of course, that there may be mechanical means for pumping the foots directly to the refining kettle from the removal 4point in the system or that the foots can be manually 'manner and with the results set forth in the preceding sentence `and amounts of foots substantially in excess of 50 pounds per 6000 pounds of oil in the form of a 50% ,miscella have resulted in a substantially reduced color break time.

As stated hereinbefore, any of the non-ionic ethers described in Folzenlogen, U. S. Patent 2,563,327, can be employed in the practice of this invention. VThese nonionic ether compounds are liquid at about 80 F., and are of the group consisting of (1) ethers of polyhydric alcohols, said alcohols containing from two to three hydroxyl groups and having from two to eight carbon atoms in the carbon skeleton, and (2) non-ionic derivatives of such of said ethers as contain unreacted hydroxyl groups. Of these non-ionic ethers set forth in the Folzenlogen patent, polypropylene glycol having a molecular weight of about 400 is preferred -for use in the present invention. An amount yas small as about 0.05 pound of non-ionic ether is sufficient in combination with recirculated foots to substantially reduce the color break time of miscellas containing 6000 pounds of oil. The use of greater quantities of the non-ionic ethers is, of course, permissible, and no adverse effects have been observed when such greater quantities have been employed. However, the use of non-ionic ethers in quantities substantially greater than the 0.05 pound set forth above only increase the cost of the refining operation to an extent which is disproportionate to the benefit gained from the increased usage. i

Example l The following table exemplifies the results obtained in a series of several batch relinings of cottonseed oil hexane miscella at F., and the data reported therein designate clearly the beneficial effect of seeding with foots from a previous refining, both with and without the presence of non-ionic ethers. The particular non-ionic ether 4employed is a polypropylene glycol having an average molecular weight of 400 (hereinafter designated P-400), and hexane is the solvent. Foots containing 70% by weight of water =and 30% by weight of nonvolatile material comprising soap; neutral oil; mucilaginous material such as phosphatides, proteins, gums; colorweight of oil, 10 pounds of foots from a previous refining, 0.1 pound of dipropylene glycol when used, :a premixing time of 3 minutes, an amount of sodium hydroxide suicient to provide 125% of the maximum prescribed by ing matter, and alkali) from a flash evaporator are added 5 the National Cottonseed Products Associati-on and a titrato the refining kettle along with a charge of 1600 gallons tion value (as explained hereinbefore) of 31.1. of the designated crude miscella and the P-400 When The above description of the invention has been conused. Continuous agitation `is used during the filling fined specifically to miscellas obtained in the extraction cycle and for the designated periods of time after comof cottonseed oil and soybean oil, and the invention is pletion of the filling cycle. After this premixing period, of particular importance in the case of cottonseed oil Water and `a sodium hydroxide solution are `added miscellas. However the advantage of greatly reduced simultaneously in the amounts designated in the following color break time, at reduced cost, and with a minimum table. The titration values in the ta'ble below represent of saponification of neutral oil, is realized in the refining the milliliters of 0.25 N. sodium hydroxide required to of miscellas obtained in the solvent extraction of other neutralize the acidic material in 50 ml. of the crude 15 oleaginous materials. miscella. In these refinings, as in all refinings Within However, although the specific description of the inthe scope of this invention, a premixing time of 'about vention has been related to batch refining, it is to be two minutes prior to the addition of the lye is required understood that the advantages of the invention may also to completely disperse the foots, P-400 when used and be realized by recirculating separated foots in the presany accompanying water in the crude cottonseed miscella. 20 ence of non-ionic ethers in continuous refining procedures With adequate premixing the crude miscella darkens con employing continuous mixing of miscella and alkali residerably, indicating the presence of a very fine disperfining agent followed by continuous centrifugal separasion. After the lye is added there is produced a very tion of the refined miscella and precipitated foots. fine grain foots which settles very slowly in the absence Having thus described my invention, what I claim is: of agitation and contributes to good centrifuge operation. 1. In the process of refining vegetable oils in solution If there is insuicient premixing, the color break time in volatile solvents, the steps which comprise seeding such will increase and large foots particles will be produced, solution with foots which have been separated from resulting in excessive `neutral oil losses in the foots. The miscella in a previous refining, premixing the combinapremixing may extend for an indefinite period of time tion of solution and recirculated foots to obtain a uni- Without adverse effect on refining, form diSpeTsiOn prior to the addition 0f alkali refining Batch Gallons Percent 'lltra- Gallons Lbs. Lbs. Premix, Break No. H2O O11 tion 20% P400 Foots Minutes Time Miseella NaOH Prior to the discovery of the advantageous action of agent, and then agitating this premixed combination with l recirculating foots from a previous refining and nonan aqueous solution of an alkali refining agent. ionic ethers in reducing break time, it was necessary to 2. In the process of refining vegetable oils in solution continue vagitation of the miscella-lye mixture for an in volatile solvents, the steps which comprise seeding such average time of about 20 minutes, with even longer times 50 solution with foots which have been separated from often being required. The use of the non-ionic ethers miscella in a previous refining and with a minor amount described in U. S. Patent 2,563,327 was an unquestioned of at least one non-ionic compound, liquid at about advance in the art and lowered the break time to an F., and of the group consisting of (l) ethers of polyaverage of about 15 minutes, although variation still prehydi'iC alcohols, Said alCOhOlS Contaiilihg from tWO t0 sented some problems. Seeding the crude miscella with 55 three hydroxy groups and having from two to eight carfoots from a previous refining and non-ionic ethers has bon atoms in the carbon skeleton thereof., and (2) nonreduoed the rior-mal break time to from 2 to 8 minutes, ionic organic derivatives of such said ethers as contain and the consistency of 'break time which has been uhreactd hydi'OXy groups; PremiXing the COmbinaton achieved allows a much smoother remrig operation, of solution, recirculated foots and non-ionic ethers to Furthermore, the recirculation of foois has riot only roo0 obtain a uniform dispersion prior to the addition of alsulted ina consistently low break time but, has reduced kali refining agent; and then agitatihg this premixed 60mnon-ionic ether usage from 200-500 ml. per 1600 gallon bination with an aqueous solution of an alkali refining batch of miscella containing 6000 pounds of oil to as little agent as 25 ml. per batch 3. The process of claim 2 in which said vegetable oil Substantially identical results are observed when soy- 55 iS COttODSeFCl Oil, Said Solvent iS all aliphatic hYdfOCafbOH bean oil is substituted for the cottonseed oil employed in OileXti'aCtiOIi Solvent and Said alkali liihing agent iS this example SOdium hydroxide.

Example Il The procltlesshof claim 3 in which said solvent comprises essentia y exane.

The graphical rpresentauon Set folth m Flgllre 2 1S 70 5. The process of claim 2 in which said vegetable oil the result 'of a Set-les if Separate rentngs anti 1t Shows is cottonseed oil, said solvent comprises essentially .hex- Cle'ady th? reducllons il Color b reak tlmeffvhlch can be ane, said alkali refining agent is sodium hydroxide, and uhm/.ed by reclrculatmg varying quantum? (if foots said non-ionic compound is polypropylene glycol having both 1n the presence and absence of non-ionic ether. amolecular weight of 4O0 Experimental conditions include 1600 gallons of a cottonseed oil hexane miscella at F., containing 40% by 75 No references cited.

Claims (1)

1. IN THE PROCESS OF REFINING VEGETABLE OILS IN SOLUTION IN VOLATILE SOLVENTS, THE STEPS WHICH COMPRISE SEEDING SUCH SOLUTION WITH FOOTS WHICH HAVE BEEN SEPARATED FROM MISCELLA IN A PREVIOUS REFINING, PREMIXING THE COMBINATION OF SOLUTION AND RECIRCULATED FOOTS TO OBTAIN A UNIFORM DISPERSION PRIOR TO THE ADDITION OF ALKALI REFINING AGENT, AND THEN AGITATING THIS PREMIXED COMBINATION WITH AN AQUEOUS SOLUTION OF AN ALKALI REFINING AGENT.

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