US2410926A - Fatty oil desliming process - Google Patents

Description

Patented Nov; 12, 1946 I mm on. nnsmumc raocass William A. Bush and Edward A. Lasher, Los

Angeles, 05111.,

assignors to California Flaxseed Products Company, Los Angeles, Calif., a corporation of Califo No Drawing. Application April 4, 1944, Serial no. 529,551'

4 Claims. '(01. 260 24) This invention relates to a method for de-slim-' ing fatty oils.

One object of the invention is to provide a simple method for refining fatty oils which will produce oil with such high purity that for many purposes further purification processes are unnecessary. Another object is to provide a method of refining fatty oils which produces 011 of such purity that any subsequent bleaching treatments are greatly facilitated. Another object is to remove materials which inhibit decolorizing by bleaching clays. Still another object is to provide a simple method for producing break-free oil. Another object is to provide a slime-removing process for fatty oils which requires no subsequent steps of water washing.

- We have discovered that fatty oils maybe readily refined and freed from dispersed colloidal phosphatides and mucilaginous suspensions by mixing with the impure oils a relatively small amount of both water and a watersoluble solid acid, followed by anaddition of a filter-aid material such as diatomaceous silica powder, and subsequent separation of the purified oil from the residue. It is an important part of this process that the amount of added water shall be not more than will be absorbed and held by the filter-aid material and will thus be separated from the oil in the filtering step. It is also important that the solid acid shall be sufiiciently soluble in the selected limited amount of water, at the operating temperature,'

that a strong acid solution will result, to effect the separation of the slime from the oil.- The addition of water is necessary since solid acid particles alone do not effect the desired de'sliming It is practically impossible to remove all of the slime in pressed or expelled fatty oils by filtration methods alone. The'slimes are so completely dispersed that they tend to pass through the filter cloth for a time and then eventually the cloth becomes blocked so that no oil can be forced through under ordinary working pressures. These conditions remain essentially-the same even when fairly large amounts oi filteraid powder are added, the-filteraid serving only to slightly prolong the filtering cycle. In any case some slime goes through into the filtered oil unless some steps are taken to change the nature of the slimes so that they may be filtered out. In practice, the freshly pressed or partly refined oils are allowed to age in tanks, and the top oil only is withdrawn for refining, the foots being left and treated separately. Unless the aging has been for quite a prolonged time, even 2 a yearor more, the slimes are to some extent still present as dispersed-colloids in the main body of the oil, and are difllcult to remove com-- pletely.

Many methods have heretofore been proposed and used for de-sliming pressed fatty oils, which involve treatment withstrong acids followed by repeated washings with large amounts of water,

an also sometimes involvingneutralization of residual acid by an alkali treatment, followed by further water washings. Various salt solutions have been used for washing oils to aid in the removal of the slimes, followed by repeated water washings to remove the salt. All of these methods require repeated handling of the oil, with significant losses in oil in the form of emulsions, and muchtime is consumed in the treatments.

' These methods seemingly merely cause the slimes to become less finely dispersed in the oil but do not greatly change their slimy or non-filtering character, and even after repeated washings by acid solutions and with water, or with salt solutions and water, the slime may not be filtered out so. completely as to give a "break-free oil. It is only when the oils have settled or matured by very long standing, followed by'separation from the roots, by drawing on the top oil that break-free oils may be produced by these older methods. Av "break-free oil in the trade is one which does not form a cloud or precipitate when heated as in varnish making or in forming heatbodied oil. The "break material may or may not of itself be colored, and the refining steps of this invention relate to removal of slime and suspended matter and not directly to removal of color as treatment with bleaching clays. We have found, however, that oils refined by our rocess are much more easily bleached by bleaching clay treatment, following the removal of slimes.

Our method will be understood-by the following illustrative examples.

To about 21,000 pounds of prime coldpressed linseed oil, previously warmed to about F.,

was added with'vigorous stirring, a solution of 6 pounds of oxalicacid crystals dissolved in three gallons of hot water. This solution was sprayed into the vigorously agitated oil and intimately mixed with it for a period of 5 to 15 minutes. About pounds of diatomaceous silica filteraid was then added and the vigorous stirring continued for another 10 to 15 minutes, followed by a period of about an hour during which the stirring was only enough to keep the fllteraid suspended. The entire batch was then pumped through a plate and frame filter press which had previously been pre-coated with filteraid. All of the slime, filteraid, water and any precipitated solid acid particles if any, were retained in the press-cake, together with a little occluded clean oil. After the batch had been filtered, the filter press was blown with air, and the recovered oil added to the main batch. ll 'he linseed oil so produced is clear and lighter in color than a similar oil treated by conventional methods, and it forms no break when heated for heatbodying or varnish making,

Dark colored oils de-slimed by our process are I noticeably improved in color probably by removalof the colored suspensoids, and furthermore, the oil is rendered much more amenable to bleaching by bleaching clays for subsequent reduction of color. In one case, a dark'green mustard oil, deslimed by our process, was improved in color by this process of desliming from a color of 14 to one of 12 on Gardner colorstandards 1933 scale, and when subsequently further bleached by heating with decolorizing clay, required only 2 percent of clay to give a bleached oil of about 8 on the same color scale.

Sulfamic acid maybe used in place of oxalic acid. For example, crude linseed oil containing three percent foots (as determined by the heated oil method, A. S. T. M. D234-28 method) in the amount of 21,000 pounds, heated to about 80 F. was charged into an oil refining kettle equipped with variable speed stirrers. A solution of 6 pounds sulfamic acid gallons of distilled water was then sprayed into the rapidly stirred batch of oil. The violent agitation was continued for about minutes, then 150 pounds of diatomaceous silica filteraid powder was added and the agitation continued for crystals dissolved in three a fifteen more minutes. The stirring rate was then lowered to that required to keep the filteraid powder in suspension, for about an hour longer. Then the batch was filtered through a precoated filterpress; The water, filteraid, acid in solution and as solid particles if any, and all of the slimes,

were retained in the press, with some occluded oil which was blown out with air at the end of the cycle. The break-free oil was of quality suitable for the paint trade.

Crude soy bean oil produced by pressing or expelling is usually contaminated withv higher percentages of slimes than crude linseed oil. Yet our process yielded a break-free oil from soy bean oil, which at the same time was improved in color from 12 to 11 on the Gardner Color Standards of 1933. In one case, 21,000 pounds of the crude soy bean oil were treated as in the above example for linseed oil with 47 pounds of oxalic acid dissolved in gallons of distilled water. In this case 3'70 pounds of diatomaceous silica filteraid were used to pick up the slimes, the acid and the water, 55 pounds of the filteraid being used to precoat the filterpress. The treated oil exhibited no break when heated to 500 F. in 5 minutes.

Bottoms from oil storage tanks, containing as high as 30 percent break" have been cleaned up and purified to a break-free oil. In one case, 42 pounds of sulfamic acid in 26 gallons of water,

with 1460 pounds of diatomaceous silica filteraid;

in 21,000 pounds of "bottoms treated as in the above example for linseed oil, gave a saleable, break-free paint oil.

One important advantage of our process is that no water washing after desliming is required, and consequently much time is saved, less equipment is required, and much less oil is lost by the emulsification inherent in the processes involving large volumes of treating and washing liquids.

Other solid acids having sufllcient solubility to form moderately concentrated water solutions comparable to those of oxalic acid and sultamic acid, may be employed, for examples citric acid, picric acid, maleic acid, etc., have been found to be satisfactory in our process. Any solid acid which is insoluble in the oil, and which is sufllciently solubl in water to give in concentrated or saturated solution a strong aqueous acid, and at least is moderately strongly ionized, may be used. The strong mineral acids such as sulfuric and hydrochloric, are not suitable because they combine chemically with the oil or dissolve in it, and if used would require much waterwashing to remove acidity from the filtered oil. We have successfully used sulfamic, oxalic, citric, picric and maleic acids. These acids are insoluble in fatty oils such as linseed, soy bean, mustard, perilla, tung, sardine, and similar oils, and do not chemically combine with this type of oil. These acids range in solubility at room temperatures from about 1.4 to 130 parts by weight to 100 parts of water, and have ionization con'stantsranging from about 10* to 10 These acids are solids, so that any excess acid above that which will dissolve in the small amount of available water at any stage of our refining process will be retained in the filter cake, and therefore will not pass with the refined oil as would excess liquid acids. Other acids having similar properties to those described are believed to be equivalent in our process.

In using the solid acids, we find it desirable to dissolve the acid in the small amount of water used in our process, using hot water if necessary. When this solution is violently mixed into the oil batch, minute particles are dispersed throughout the oil, along with, in some cases, the precipitated solid particles of acid. Violent agitation of the mixture is required in order to bring all parts of the oil in contact with the acid.

The amount of water, as previously stated, is

small and is selected as an amount which will 1 space, and the cycle is shortened. On the other hand, if too little filteraid is used, the filter cloths become clogged with slime and the cycle of operations is too short for economical operation. An additional advantage of smaller amounts of filteraid is the smaller amount of oil absorbed in the filter cake, which absorbed oil cannot all be economically removed, and a smaller amount absorbed means a smaller loss. An optimum quantity of filteraid may be selected for any set of conditions and materials which will give economical operation and at the same time give clear filtrates. The amount of filteraid used by us in our method has varied from 0.7 to 7.0 percent weight of filteraid based on the weight of oil treated, and the amount of water has varied from 16 to percent by weight of the filteraid. The amounts of acid, filteraid, and water, will of course, vary with the kind of oil, the amount and nature of the slime. and the completeness of slime removal desired, and the range of proportions here given is illustrative.

The type of filteraid used by us in a processed diatomaceous silica of the type known in the trade as Hyfio and "Speedex which are natural diatomaceous silica powders calcined with a fluxing material as described in U. S. Patent No.

The completeness of the de-sliming process depends upon the amount of water, solid acid, and filteraid used, and if a completely break-free oil is desired, the larger amounts of acid and filteraid may be used. For purposes where break-free oil is not required, lesser amounts of acid and filteraid may be employed.

The temperature of the oil during our desliming process is not critical but is selected to give the required fluidity of the oil for facility in mixing and handling, and for shortening the time of treatment.

While our process is directed to removing the colloidally dispersed and fine suspended mucilaginous and protein materials, it usually reduces the color slightly because these suspensoids themselves may be colored and the oil darkened thereby. Therefore the oil usually is lightened by our process. In addition, because of the complete removal of these extraneous materials, it is found that the oils so treated, when heated alone. are

somewhat bleached, and if furtherlightening of the color is required or desired, the oils treated, by our process are much easier to bleach by treat ment with bleaching clays, requiring shorter times and less clay. w

It will be seen that our process has many advantages because it is simple, direct, requires no after washing, gives .break-free" oil, and a mini-,

mum of losses of 011 during treatment. The process may be used on oils having excess slimes such as tank bottoms, which do not clean up readily y. y other n n m hod.

We claim: 1. The process of de-sliming a fatty oil comprising mixing into said oil a substantially saturated water solution of a solid acid selected from the group consisting of sulfamic acid, oxalic acid, citric acid, picric acid and maleic acid in an amount suflicient to break the slime dispersion,

mixing into said mixture a solid filteraid powder in amount sufiicient to absorb all of said water solution remaining after mixing with the fatty oil, and filtering out said filteraid, acid and water with the slime from the purified oil.

2. The process of de-sliming a fatty oil comprising mixing into said oil a substantially saturated water solution of sulfamic acid in an amount sufiicient to break the slime dispersion, mixing into said mixture a filteraid powder in amount suflicient to absorb all of said water solu tion remaining after mixing with the fatty oil, and filtering out said filteraid, acid and water with the slime from the purified oil.

3. The process of de-sliming a fatty oil comprising mixing into said- 011 a substantially satu rated water solution of oxalic acid in an amount suflicientto break the slime dispersion, mixing into said mixture a fllteraid powder in amount filtering out said filteraid, acid and water with the slime from'the purified oil.

WILLIAM A. BUSI-L EDWARD A, LASHER.