US 3102898 A
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United States Patent 3,102,398 PROCESS FOR THE PURIFICATION OF GLYCERIDE OILS Robert O. Schmiti, Wyoming, Ohio, assi'mor to The Procter & Gamble Company, Qineinnati, Ohio, a corporation of Ohio No Drawing. Filed Nov. 14, 1960, Set. N 68,642
4 Claims. (Cl. 260-425) This invention relates to a novel process for purifying glyceride oils, and more specifically, it relates to a process for refining certain soybean oils.
Crude glyceride oils, as they are obtained from their sources by the appropriate removal process, contain substances other than the triglyceride itself. These nonglyceride substances include gross material from the source of fat, such as xanthophyll, chlorophyll, and so on; products obtained by the breakdown of the glycerides during treatments, such as fatty acids; and other substances which are chemical derivatives of the glyoerides, such as phosphatides and sterol derivatives. Some of these impurities are desirable in that they help to protect the oil from oxidation or other adverse processes, but by far the greater amount of these substances must be removed during processing for edible purposes because they are deleterious to the appearance, taste, keeping qualities, and other properties of the oil.
The removal of gross impurities, gummy or mucilaginous material, and the free fatty acids from the glyceride oil is commonly referred to as refining and as herein used the term excludes bleaching (color removal) and odor removal. Known methods of refining include contacting the glyceride oil with strong or dilute alkaline materials followed by separation of impurities, by liquidliquid extraction of impurites from the glyceride oils, by some form of steam distillation, and by contacting the glyceride oils with acids. Each of these methods is said to have its advantages for use in refining oils of one type or another for a certain ultimate utility.
The ultimate objective of a refining operation is to remove every undesirable impurity completeiy, while at the same time maintaining intact all of the desirable glyceride oil. The particular process used with a given oil is determined by the foregoing consideration of maximum impurity removal with a minimum of glyceride oil loss. Since a good part of the refining cost arises from losses of glyceride oil, much work has been done to increase the elficiency of refining, and many processes have been developed for this purpose.
In the art of alkali-refining of glyceride oils, sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide, magnesium hydroxide, ammonia, and even organic alkalies, such as monoethanolamine, have been used. Some processes also use minor amounts of other substances such as inorganic phosphates or sodium silicates. Substances with cations other than sodium being generally more costly, the most popular processes have used either sodium hydroxide or sodium carbonate as the refining agents. Each of these two reagents has its advantages and disadvantages. Sodium hydroxide, for instance, is said to give excellent color removal, but is such a strong alkali that it also attacks the neutral oils and increases the cost of the process through conversion of some of the glyceride oils to the relatively less desirable soap stocks. Sodium carbonate, on the other hand, attacks the glyceride oils little or not at all, but generally lacks the degree of impurity-removal which sodium hydroxide is capable of achieving.
Today much of the glyceride oil is refined in a con tinuous process. This process involves the steps of bringing the oil and alkali to the proper temperature,
3,102,898 ?atented Sept. 3, 1963 mixing these two materials, adjusting the temperature if necessary, providing a suliicient hold time, subjecting the mixture to degasification or such other steps as are necessary, and continuously centrifuging the mixture to separate the refined glyceride oil from the impurities. In the case of refining soybean oil, the use of sodium hydroxide as the refining agent and the use of continuous processing engenders further problems which contribute to high losses. These losses arise chiefly during centrifugation of the mixture. The nature of the impurities, or Toots, phase largely controls the degree of separation effected during the centrifugation. Sometimes these foots entrap large quantities of the relatively more valuable neutral glyceride oils in the soaps obtained from neutralization of the fatty acids with the refining alkali. In other cases, the foots become exceedingly hard and will not flow properly from the bowl of the continuous centrifuge. Not only does this result in high losses as [cots are carried into the neutral oil (necessitating another physical separation), but there is also the attendant inconvenience and production loss in having to shut down a centrifuge and clean out the bowl or discs. This cieanin g operation is quite time-consuming since it necessitates partial disassembly of the centrifuge.
This problem of intractable foots is especially acute when sodium hydroxide is used to refine degummed soybean oils. This difficulty inevitably shows up as higher refining losses. It has been said that it is possible to overcome this problem through the use of additional water metered into the centrifuge, commonly called bowl flush. The use of bowl flush, however, requires quantities of water and modifications to the centrifuge, and presents the problem of disposing of large quantities of water contaminated with the impurities removed from the glyceride oil.
Soybean oils contain quantifies of phosphatides (mixed esters of substituted phosphoric acid and fatty acids with a polyhydric alcohol). Some of these phosphatides have commercial value, and when the economic considerations are favorable, i.e., equipment is available and the market price is attractive, may advantageously be removed from the oil before the oil is refined. This operation is accomplished by adding a quantity of water to the crude soybean oil and then centrifuging the mixture, and as commercially practiced, it removes most of the water-precipitatable phosphatides (lipoid A). Because these phosphattides are rather sticky, gummy materials, this treatment is known as degumming.
The degumming operation, however, does not remove all of the phosphoruscontaining lipoids from the crude oil. There remains a non-water-precipitatable fraction lipoid B). These lipoid B constituents are very powerful emulsifiers and make maximum centrifugal separation of refined oil from the foots phase very diflicult.
When sodium carbonate is used as the refining agent, the neutral glyceride oils are not saponified, and as a result, refining loses are lower. Moreover, the facts tend to become softer. However, the carbonate will not precipitate lipoid B. The remaining lipoid B may cause considerable difficulty during centritugat-ion and also result in the oils darkening in color during subsequent addition of sodium hydroxide to remove lipoid B.
Subsequent to the refining of the oil, its color is redu'm by an operation called bleaching. This comprises mixing diatomaceous earth or a similar material with the refined oil and passing the oil through a filter. The filters must be taken apart and cleaned from time to time when the throughput rate falls below the desired minimum. More eflicient refining and more complete removal of foots from the oil increases the length of time between shutdowns to clean out the filters. The economies of fewer shutdowns for cleanout are obvious.
It is an object of this invention to provide an improved process for obtaining highpurity soybean oil from crude dcgummed or non-degummcd soybean oil.
Another object of the instant invention is the elimination of bowl flush in the refining of dcgummed soybean oil, with the attendant elimination of the need for water, more costly modified equipment, and waste water disposal prob] ems.
It is a further object of this invention to minimize refining loses.
Yet another object of the instant invention is lowering the amount of alkali reagents necessary fully to refine a crude soybean oil.
A further object of the instant invention is the prevention of stratification, or phase separation, in the centrifuge bowl regardless of what grade of dcgummed or non-degummed soybean oil is refined.
An additional object of the invention is the production of higher clarity oil which will permit a more efficient bleaching operation with fewer shutdowns for filter cleanout.
Other and further objects of the instant invention will be readily apparent to those skilled in the art after they have read and become familiar with the following description.
The instant invention is essentially a sodium carbonate process with the addition of a critical amount of sodium hydroxide solution mixed into the carbonate solution before it contacts the crude oil. If just sufi'icient sodium hydroxide is added to the sodium carbonate to remove essentially all of the lipoid B contained in the crude oil, the carbonate is able to produce a high-purity oil with very low refining losses. In order to refine the crude oil continously it is necessary that at least a minimum amount of agitation be given to the oil and carbonatc hydroxide mixture.
When the amount of hydroxide in the carbonate is controlled according to the teachings of the instant invention, less reagent is required and lower refining losses are obtained for a given refined oil quality than if the carbonate and hydroxide were added to the oil singly or sequentially in any order. The process of this invention will produce a pure refined oil more economically than with any other process known for refining oils which contain significant quantities of lipoid B.
Briefly described, the process of the instant invention comprises the steps of continuously adding to a. stream of crude lipoid B-containing oil a sodium carbonate solution containing a controlled amount of sodium hydroxide, subjecting the oil and alkalies to at least short period of mixing above a minimum intensity, holding the oil with or without further mixing of either highor low-intensity until the reaction is sufficiently complete, and centrifuging the mixture to separate the refined oil from the foots. The amount of sodium hydroxide solution which is to be added to the sodium carbonate solution is critical and is determined from the properties of the crude oil to be refined.
This process is in general applicable to lipoid B-containing crude oils which are light in color. As used herein, the term lipoid B-contnining crude oil means one which has not been refined to any degree and therefore contains free fatty acids and other deleterious impurities in addition to lipoid B. For said light-colored crude oils, sodium carbonate refining is inadequate because of the lipoid B content of said oils.
The fatty acid content of the oil and many other of the acidic impurities are fairly completely removed by sodium carbonate alone. The lipoid A content of an oil presents little or no roblem generally, because it precipitatable by water along and no soda ash is required to remove lipoid A rather completely from the crude oil. The lipoid B component, not being precipitated by water,
poses more of a problem. This problem was especially acute in the case of degummcd oils, since the relatively higher proportion of lipoid B in the oil tends to act as an emulsifier. This resulted in either a very poor separation of the refined oil from the fonts or else very high losses of the neutral glyccride oils.
An example of an oil containing significant quantities of the lipoid 5 component is soybean oil. It is considered to be light-colored because the color bodies are rather easily removed by sodium carbonate refining alone. Many of the dark-colored oils require the use of much larger quantities of sodium hydroxide than those contemplated by the instant invention and, if treated. by the process of this invcntion, would require a re-refining with lye to secure adequate color removal. The process of this invention will be described in terms of refining soybean oils.
The principal refining agent used in this process is so dium carbonate. It removes the bulk of the free fatty acids and much. of the other material, except for lipoid B. It has been found that to secure adequate refining completeness while attaining the low refining losses possible with this invention, it is necessary that the amount of sodium carbonate by itself be sufficient to permit of no carbon dioxide evolution during the refining operation. The amount of sodium carbonate required. is more than two equivalents for each mole of free fatty acid present in the crude oil, and preferably, in the range of 3 to 5 equivalents. So long as the quantity of sodium carbonate present is sutlicicnt to suppress all evolution of carbon dioxide gas, the upper limit of sodium carbonate usage is set only by economic considerations and the amount of water which one wishes to introduce into the crude oil during the refining operation. In general, the less water which is introduced into contact with the oil during the refining operation, the better are the results obtained. It has been found that 3 or 4 molecular equivalents of sodium carbonate are generally satisfactory.
The concentration of sodium carbonate solution is not critical in the practice of this invention. In general, the concentration may range from 16 Baum to a saturated solution. The lower limit of concentration of the sodium carbonate solution is set by the desirability of keeping the amount of water in the system as low as possible consistent with good centrifugal separation. The preferred range is from about 16 to about 28 Eaum. It has been found convenient to use a 24 Baum sodium carbonate solution in the practice of this invention. A constant amount of sodium carbonate solution is metered into the oil, and a quantity of sodium hydroxide solution is variably metered into the sodium carbonate solution before admixture with the oil, as discussed hereinafter. So long as the fatty acid content of the crude oil remains approximately the same, there is no need to vary the amount of 24 Baum sodium carbonate solution which is added thereto.
The process of this invention requires that the quantity of sodium hydroxide metered into the soda ash stream be very carefully controlled. If too little sodium hydroxide is used in the process. insutficient removal of the lipoid B component will result. This will affect the keeping properties adversely and may result in darkening of the oil when it is subsequently deodorized. Especially in the case of degummed soybean oil, failure to use sufficient sodium hydroxide will result in much poorer refined oil quality. On the other hand, the use of a greater quantity of sodium hydroxide than called for by the instant invention will result in hard foots, that is, in foots which will not flow and will remain in the bowl necessitating centrifuge shutdown, and in attack of the glyceride oil by the hydroxide.
The amount of sodium hydroxide required for adequate refining and minimum loss in this process is that which will produce a phosphatide content, expressed as phosphorus pcntoxide, of from about 3 to about 30 parts per million in the refined oil. This amount of P may c nveniently be determined by any desired method, one method being AOCS test Cu 12-155 from which the P 0 content can be calculated. The preferred range is from about 5 to about parts per million of the refined oil. The amount of sodium hydroxide added will generally lie between about 00004- times to about 0.004 times the weight of the crude oil.
A fairly close approximation of the amount of sodium hydroxide which must be added to the sodium carbonate to refine a given oil can be calculated from the formula where W equals the weight of sodium hydroxide to be added for each unit weight of crude oil and A is the weight of acetone insolubles per unit weight of oil. The amount of acetone insolubles in the oil is readily determined by AOCS method Ja 446.
It is pointed out that some discretion must be exercised in the use of the above formula. If the amount of acetone insolulbles is zero, then one would have a gum-free oil which would not require refining by the process of this invention (nor probably, any refining). There have been no cases studied in connection with the perfection of this invention Where less than 50% of the W value given by the above formula was required, nor are there any known instances where more than 1.5 times the W" value was required adequately to refine an oil. The above formula has been derived from work with degummed and Iron-degumrned soybean oils. Those skilled in the art will realize that soybean oils obtained under unusual extraction conditions may behave anomalously and that adjustments will probably have to be made in the above formula for such oils.
When used in conformity with the teachings of the invention, the carbonate and hydroxide somehow so coast that the glyceiide oils are not attacked by the high alkalinity. When sodium hydroxide alone is added to a glyceride oil, saponification (and, of course, high losses) result. If a refining system in which sodium hydroxide solution is added directly to the oil is allowed to stand, the saponification of neutral oil. will deposit soaps in the lines, and some diificulty will be experienced in cleaning the system in preparation for further use. Illustrative of the above-mentioned ooaction, it has been found th at when this invention is used to refine oil, the system can be shut down and restarted at will. No hard foots form to clog the lines, even though the sodium hydroxide remains in contact with the oil. It should again be emphasized, however, that the amount of hydroxide added to the carbonate solution must be very carefully controlled, as hereinbefore discussed, to secure these results.
When the sodium hydroxide is added as a solution to the sodium carbonate solution, the concentration of the hydroxide solution is not particularly critical. The range of concentrations from about 16 Baum to the saturation point of the sodium hydroxide solution may be used in the practice of the instant invention. The preferred concentration of sodium hydroxide is from about 18 to about Baurn. As is the case with the sodium carbonate solution, too weak a sodium hydroxide solution will introduce excessive water into the oil. While concentrations above 50 Baum can be obtained with sodium hydroxide solutions, it is undesirable to use a very high concentration because of the relatively small quantities of sodium hydroxide which must be metered into the sodium carbonate. As the concentration of sodium hydroxide increases, increasingly smaller amounts of the solution must be metered into the sodium carbonate stream. It has been found convenient to use a concentration of about 24 Baum in the practice of this invention.
In general, mixing temperatures of from about 70 to about 160 F. have been found satisfactory in carrying out the process of this invention. As the temperature of the process is varied, a point will be noted which gives the highest purity of oil for the conditions used. Whether or not the oil has been degummcd affects the optimum temperature required for the mixing operation. It has been found that for non-degummed soybean oils a mixing temperature in the range of about 70 to about 120 F. gives adequate results and the preferred range is from about to about F. For degummcd oil a somewhat higher temperature range, on the order of to 160 F. is indicated, with optimum results between about 130 and about 140 F.
After the carbonate-hydroxide stream is introduced into the crude oil, at least a short period of high-shear mixing is required to achieve the results of this invention. Mixing may be continued during the entire time that the oil and carbonate-hydroxide are in contact, or the initial mixing may be followed by a period of relatively more quiescent contact. At least about 15 seconds high-shear mixing time is required when a turbine mixer is used at the turbine tip speeds discussed below. An advantage which accrues from the use of a high-intensity mixing action is that very short hold times are required, on the order of about four minutes.
While a minimum turbine tip speed of 850 feet per minute is needed to complete the refining in a reasonable time, higher completeness for a given chemical usage and minimum hold times are attained at higher turbine speeds. For this reason, it is preferable to maintain turbine tip speeds of 1500 or more feet per minute. Very satisfactory results have been obtained with a battery of mixers, in which a high-shear mixer is followed by a number of lower speed mixers. While much of the work involved in perfecting this invention has used high-speed turbine mixers, other highshear mixers adapted to continuous operation can be used. For smallscale work, a Dispersator type of mixer was used and gave satisfactory results. Any high-shear mixer which will give shear forces equivalent to a turbine tip speed of at least 850 feet per minute is adaptable to this process.
Even with very highshear mixing. a minimum of about one minute of contact time has been found desirable to permit the refining action to go toward completeness. Not only does high-shear mixing reduce the hold time (and hence the size of the system), but it also results in lower refining reagent usage and lower refining losses.
When the reagent has had adequate time to react with the impurities in the oil, the mixture is introduced into a continuous centrifuge. Any type of continuous cen trifuge known in the art is adequate to separate the refined oil from the foots. The more recent hermetic centrifuges give excellent results in this process, and the older bowland disc-type centrifuges are also quite satisfactory. The temperature at which the fluid is introduced into the centrifuge should be sulliciently high so that the glyceride oil phase has a low viscosity. In general, the lower the viscosity of the oil phase, the easier will be the separation of the two phases. While increased lluidity of the oil phase is beneficial, the temperature must not be raised high enough to cause thermal and oxidative decomposition or alteration to the glyceride oil. In general, the fluid should be introduced into the centrifuge at a temperature in the range of from about to 160 F. Best results with both degummed and nondegumrned soybean oils have been obtained when the temperature during the centrifugation is maintained between about and about F.
The centrifugation is an operation which frequently causes a great deal of difiiculty in the oil refining art. Dilficulties arise with hard foots in that they plug the bowl, and with foots containing large amounts of natural emulsifiers the foots are carried over into the finished glyceride oil and, conversely, glyceride oil is lost in the foots. The foots produced by this process are very tractable, fiow from the centrifuge quite easily. permit low refining losses, and are removed to such an extent that in actual operation over a 10-week period a reduction of more than 25% was obtained in the number of filter cleanings required during the bleaching operation.
It was also found in the actual operation with this process that capacities of centrifuges are increased over the capacity attained with a sodium hydroxide refining process. In some cases, increases in centrifuge throughput of greater than 25% were obtained.
It should be remarked that some of the prior art refining processes, when used for degummed soybean oil, required the introduction of a stream of water into the centrifuge in order to obtain separation of the foots phase from the refined oil. This Water addition, commonly called bowl flush, required special centrifugal equipment and large quantities of water. The process of this invention is adequate to refine even degummed soybean oils without necessity of adding Water at the centrifuge.
The following examples are given to illustrate the practice of this invention.
Example I A non-degummed crude soybean oil was found to have a free fatty acid content of 0.64%, a water content of 0.08%, and an acetone insoluble content of 1.39% of which 0.13% was lipoid B. The standard cup refining loss was determined to be 4.01% by AOCS method Ca 9b-52.
The oil was introduced at the bottom of a hereinafterdescribed high-shear mixer at a temperature of 82 F. and a rate of 225 pounds per hour. A stream of 24 Baum sodium carbonate was added to the oil in an amount which was 3.1% of the weight of the crude oil. Before the sodium carbonate was introduced into the oil, 1.45 rs by weight of the crude oil of a 24 Baum sodium hydroxide solution was added to the sodium carbonate solution. The crude oil and alkali materials remained in the mixer for four minutes average and the emerging stream had a temperature of 106 F., the temperature rise being primarily due to mechanical work in the mixer.
The high-shear mixer used was constructed from a 25- inch length of S-inch Schedule 40 steel pipe. The pipe was mounted vertically, and l s-inch nipples were placed close to the top and to the bottom on the wall of the pipe to provide for the incoming and outgoing streams of fluid. The pipe was divided into five compartments by ila-inch annular .baflle plates mounted coaxially in the pipe. A shaft was mounted coaxially with the pipe and battles and driven by a 1 hp. electric motor. Mounted on the shaft were five 2 /2-inch -bladed turbine impellers so placed that one was in each of the five compartments delimited by the four aforesaid baffle plates. The stream of oil and refining alkalies was introduced into the bottom of this high-shear mixer and removed at the top. The turbine impeller blades were operated at a tip speed of 1500 feet per minute.
After the residence time of four minutes average, the mixture of oil and alkali was continuously removed from the top fitting on the mixer and introduced into a heat exchanger where the temperature was raised to 140 F. The foots were then separated from the refined oil by a continuous centrifugation in a DeLaval VO-224 hermetic centrifuge.
The refined oil was found to contain 0.002% soap, 0.01% lipoid B, 0.006% free fatty acid, and 5.2 parts per million P The refining loss was 2.83%, or 70.5% of the official cup loss.
Example II A non-degummed crude soybean oil was refined in the equipment described in Example I. The oil was introduced into the mixer at a temperature of 88 F. at a rate of about 225 pounds per hour. The crude oil contained 0.75% free fatty acid, 0.16% water, and
8 .8696 acetone insolubles of which 0.11% was lipoid B. The standard cup refining loss for this oil was 4.42%.
A mixture of 2.92% of 24 Baum sodium carbonate solution and 0.94% of 24 Baum sodium hydroxide solution. both weights being based on the weight of the crude oil, were introduced into the crude oil stream. Residence time in the high-shear mixer at a turbine tip speed of 1500 feet per minute averaged four minutes and the temperature of the ei'lluent was 109 F. The stream was then brought to F. and introduced at that term pcrature into the DeLaval centrifuge.
The refined oil was found to contain 0.001% soap, 0.23% water, 0.011% free fatty acid, and 19.7 parts per million P 0 The refining loss was 3.21%, or 72.7%, of the official cup loss.
Example III A dcgurnmed soybean oil was refined according to the teachings of this invention using the equipment of Example I. This degummed soybean oil analyzed 0.51% free fatty acid, 0.05% water, and 0.27% acetone insoluble of which 0.15% was lipoid B. The refining loss was determined to be 1.61 by AOCS method Ca 9e-52.
he oil was introduced into the mixer at a temperature of 124 F. and at the rate of about 225 pounds per hour. A mixture of 1.32% 24 Baum sodium carbonate solution and 0.65% 24 Baume sodium hydroxide solution, based on the weight of the crude oil, were introduced into said crude oil. The average residence time of the stream in the mixer was four minutes at a turbine tip speed of 1500 feet per minute. The effluent from the mixer was at a temperature of 140 F. and was centrifuged in the DeLaval at this temperature to separate the fonts from the refined oil.
The refined oil was found to contain 0.015% soap 0.12% water, 0.007% free fatty acid, and 24.9 parts per million P 0 The refining loss was 1.03%, or 64.1% of the olficial cup loss.
This invention is not limited to any particular degree of mixing intensity beyond the minimum intensity discussed above. Excellent results in commercially refining millions of pounds of soybean oil have also been obtained by introducing the mixture of oil and alkali into a mixture with a turbine tip speed of 1500 feet per minute and a hold tinte of about 15 to about 30 seconds. From this mixer the stream was introduced into a battery of lower-speed mixers at a turbine tip speed of 900 feet per minute and maintained there for three to four minutes.
The foregoing examples, while illustrative of the practice of this invention and some of its preferred embodiments are not intended to be limitative. When said examples are considered in the light of this disclosure, the permissible variations in operating conditions will be obvious to those skilled in the art.
The advance over the art having been described, what is claimed is:
1. The process of continuously refining lipoid B- containing crude soybean oils which comprises the steps of (1) continuously adding a mixture of aqueous sodium carbonate and sodium hydroxide solutions to a stream of said crude oil, said sodium carbonate being added in an amount sufficient to suppress any evolution of carbon dioxide gas and greater than 2 molecular equivalents for each mole of free fatty acid present in said crude oil, and said sodium hydroxide being added in an amount sufficicnt to reduce the phosphatide content, expressed as phosphorus pentoxide, of the refined oil to between about 3 and about 30 parts per million and in the range of from about 0.0004 to about 0.004 times the weight of said crude oil, (2) subjecting the combination of said crude oil and the said mixture of sodium carbonate and sodium hydroxide to shearing forces equivalent to turbine tip speeds in excess of about 850 feet per minute for at least 15 seconds, (3) maintaining said combination in contact for at least about one minute, whereby the major portion of the impurities is removed from the said crude oil to form a refined oil and a foots phase, and (4) separating said refined oil from said foots phase by centrifugation.
2. The process of continuously refining lipoid B-containing crude soybean oils which comprises the steps of (1) continuously adding to said crude oil a mixture of an aqueous solution of sodium carbonate having a concentration of more than about 16 Baum and an aqueous sodium hydroxide solution having a concentration of more than about 16 Baum, said sodium carbonate being added in an amount which will completely suppress any evolution of carbon dioxide gas and greater than 2 molecular equivalents for each mole of free fatty acid present in said crude oil and said sodium hydroxide being added in an amount sufficient to reduce the phosphatide content, expressed as phosphorus pentoxide, of the refined oil to between about 3 and about 30 parts per million and in the range of from about 0.0004 to about 0.004 times the Weight of the said crude oil, (2) subjecting the combination of said crude oil and the said mixture of sodium carbonate and sodium hydroxide to shearing forces equivalent to turbine tip speeds in excess about 850 feet per minute for at least 15 seconds, (3) maintaining said combination in contact for at least about one minute, whereby the major portion of the impurities is removed from said crude oil to form a refined oil and a foots phase, and (4) separating the refined oil from said foots phase by centrifugation.
3. The process of continuously refining lipoid B-containing non-degummed crude soybean oil which comprises the steps of l) continuously adding to said crude oil a mixture of aqueous sodium carbonate solution having a concentration of more than about 16 Baum and aqueous sodium hydroxide solution having a concentration of more than about 16 Baurn, said sodium carbonate being added in an amount which will completely suppress any evolution of carbon dioxide gas and greater than 2 molecular equivalents for each mole of free fatty acid present in said oil and said sodium hydroxide being added in an amount suflicient to reduce the phosphatide content, expressed as phosphorous pentoxide, of the refined oil to between about 3 and about 30 parts per million and being from about 0.0004 to about 0.004 times the weight of the said crude oil, (2) subjecting the combination of said crude oil and the said mixture of sodium carbonate and sodium hydroxide to shearing forces equivalent to turbine tip speeds in excess of about 850 feet per minute for at least 15 seconds at a temperature in the range of from about to about 120 F., (3) maintaining said combination in contact for at least about one minute at a temperature in the range of from about 70 to about 120 F., whereby the major portion of the impurities is removed from the said crude oil to form a refined oil and a foots phase, and (4) separating said refined oil from said foots phase by centrifugation at temperatures of from about 120 to about 160 F.
4. The process of continuously refining lipoid B-containing degummed crude soybean oils which comprises the steps of (l) continuously adding to said crude oil a mixture of aqueous sodium carbonate solution having a concentration of more than about 16 Baum and aqueous sodium hydroxide solution having a concentration of more than about 16 Baum, said sodium carbonate being added in an amount which will completely suppress any evolution of carbon dioxide gas and greater than two molecular equivalents for each mole of free fatty acid present in said crude oil and said sodium hydroxide being added in an amount sufiicient to reduce the phosphatide content, expressed as phosphorus pentoxide, of the refined oil to between about 3 and about 30 parts per million and being from about 0.0004 to about 0.004 times the Weight of said crude oil, (2) subjecting the combination of said crude oil and the said mixture of sodium carbonate and sodium hydroxide to shearing forces equivalent to turbine tip speeds in excess of about 850 feet per minute for at least 15 seconds at a temperature of from about to about 160 F., (3) maintaining said combination in contact for at least about one minute at a temperature in the range of from about 100 to about 160 F., whereby the major portion of the impurities is removed from the said crude oil to form a refined oil and a foots phase, and (4) separating said refined oil from said foots phase by centrifugation at temperatures of from about to about F.
References Cited in the file of this patent UNITED STATES PATENTS 2,686,796 Markley et \al. Aug. 17, 1954 2,733,252 Milbers et al. Jan. 31, 1956 2,991,178 Clayton July 4, 1961