US2683155A - Refining of vegetable, marine, and animal oils containing phosphatides - Google Patents

Description

July 6, 1 954 CAUSTIC D. W. DRON REFINING OF VEGETABLE, MARINE, AND ANIMAL OILS CONTAINING PHOSPHATIDES Filed May 24, 1951 MIXER HEATER MIXER BUFFER SOLUTION HOT WATER EJECTOR HEATER CRUDE //v VE/V 70/? Douglas W. Dron Patented July 6, 1954 REFINING OF EGETABL ANIMAL' OILS GONTAINING' Piles- PHATID'ES Douglas W. Dron, Poughkeepsie, N. Y., assignor to The Be Laval Se York, N.- Y., a corpora parator Company, New tion of New J ersey,

Application May '24, 1951, Serial-No.--227,987-

6 Claims.

This invention relates to'therefining of Vegetable, marine 'andanimal oils-which in their crudeform, contain gums or phosphati'des.- It has for its principal-obiect theprovision ofwan improved process by which such oil's can be treated in a continuous operation to obtain a refined oil having-a high degree of purity,v with the-smallest possible loss of neutral oil and with a minimum consumption-of refining agent, by mean of a refining .plant having a low equipment cost.

In the'refining of fatty oils, the gums which are normally present .inthe crude oil are commonly extracted in a preliminary or degumming operation, wherein the crude oil is first mixed with: ahydrating agent'so that the gums are hydrated and precipitated as slimy substances, which are then removed from the oil by centrifugal separation. In this way, emulsion-forming bodie'share removed from the oil at the outset, so that the subsequent operations in the neutralization stage can be carried out more efficiently and with lower losses.

The neutralizati'on stage 'comprisesessentially the'steps of mixing the degummed oil with a caustic refining agent to neutralize the free fatty acids in the oil, and centrifuging themixture to separate the resulting soap-stock from the purified oil. The latter is then fed to a washing stage where it is mixed with water and recentrifuged, the washed oil then being dried, if necessary, as by means'of-avacuum'drier.

According to the present invention, thecrude oil is fed from a supply source in a stream into which a medium for hydrating the'phosphatides is continuously injected, whereupon the oil is passed through a reaction zone while maintainingithe oil in a turbulent state; In this way, the phosphatides or gums are formed into slimy bodies or agglomerates'suspended in'the'oil and thereby are conditioned for more eifective centrifugal separation from the oil. Thereafter, free fatty acids in the oil are neutralized by intimately mixing with the oil a caustic refining agent, this neutralizing operation being effected either before or after centrifugal separation of the previously conditioned gums from the oil. The'mixture of thecaustic'reagent with the oil is effected extremely rapidly, preferably during the lapse of from 2 to 5 seconds, during which short time complete neutralizing is effe'cted, and the mixture is'then fed promptly to acentrifuge where the soapst'ock'is separated quickly from "the oiland also tlie hydrated "gums,

fromthe oi1,-if the latter (gum-s) have-not pre- 2V viously been extracted, themaximumv lapse of time from themoment the oil is mixed with the caustic reagent until the refined oil is discharged from the centrifuge-beingapproximately 40 seconds, preferably about 20-seconds. These steps of hydrating the gums, neutralizing the-free fatty acids, and centrifugally'separatingthe soapstock from the oil are effected continuously, and the process is characterized principally by maintaining the oil stream outof contact withthe atmosphere during the entire course of its passage from the crude oil-source, which supplies .the stream into which the hydrating medium isuinjected, to and through the centrifuge whereithe soapstock is separated from the purified oil. This exclusion of atmospheric air from the oil may be effected by the use of enclosed: mixing Zones for mixing the oil with. the hydrating medium and the caustic reagent, respectively, an enclosed reaction zone for conditioning the dehydrated gums, and arcentrifugal separator or separators of the hermetic (.closedl type for separating the gums andsoapstock from the 011, the piping of the system havingair-ti'ght connections with these various operating zones and the centrifuge or centrifuges.

By maintaining the oil out of contact with the atmosphere through the hydrating, neutralizing, and separating stages, as previously described, the occlusion of oil in the gum agglomerates and the soapstock is greatly reduced, so that a higher yield of refined oil is obtained. Also, the degumming is accomplished more readily. The exclusion of air from the oil through the hydrating or degumming stage not only promotes'the conditioning of the gum agglomerates for their centrifugal separation from, the oil, butalso has the effect of resisting or retarding emulsification of the oil in the neutralization stage during the violent mixing of the oil and caustic reagent. Moreover, due to passage of the oil to and through the neutralization stage free from entrained air and the effects of air contact,- the neutralization can be-carried out during the extremely short period of contact between the oil and reagent, as 'mentioned heretofore, which is highly important in preventing saponiiication of oil. In other words, the exclusion of air from the oil passing through the hydrating'and neutralizing stages has the indirect effect of reducing saponification in that it'enables the neutralization to take place during a much shorter oil-reagent contact period with a given degreeof mixing Due to super-atmospheric' pressure in the hermetic type separator bowl, the'emulsion is broken and the soapstock separated much sooner than is the case with an open type machine. In an open type separator, extended contact time is necessary to prepare the oil-soap mixture for separation, this being determined by the break in the oil which must become plainly visible to the naked eye in order to effect separation. In a hermetic type bowl where fairly high pressures of 85 to 90 lbs. are employed in its operation, the oil-soap mixture can be separated before the break is visible to the eye although the neutralizing is complete, thus preventing excessive saponification while waiting for the visible break to occur. The hermetic separator also permits neutralizingwith a higher temperature without danger of oxidation, due to the absence of contact with air. Color setting is prevented because of the short contact time at elevated temperatures and the absence of contact with air.

In many instances, the neutralization of the free fatty acids can be carried out effectively in a single stage wherein the caustic reagent is mixed intimately with the oil, before separation of the previously conditioned gums, and the gums and soapstock are centrifugally separated from the oil after the brief oil-reagent contact period. However, with some oils, particularly expeller cottonseed crudes, it is advantageous to carry out the neutralization in two stages, the first of which comprises mixing the caustic reagent with the oil to a point where the free fatty acids are close to neutralization, and then promptly centrifuging the oil to remove the gums and soap and any other centrifugally separable impurities. In the second stage of the neutralization, additional reagent is mixed with oil to complete the neutralization and decolorizing, after which the oil is promptly centrifuged to separate the resulting soapstock and color bodies. Preferably, the reagent used in the second neutralizing stage is a buffer solution of caustic and a non-saponifying alkali. When the neutralizing is effected in two stages, an hermetic or closed centrifuge is used at the end of each stage, to prevent contact of the oil with the atmosphere.

The temperature control of the oil during the hydration, neutralization and centrifuging is an important factor in the new process, since the exclusion of air from the oil in its passage through these various stages evidently affects the optimum temperature at each stage. Preferably, the oil is preheated to a temperature of 80 to 120 F. prior to injection of the hydrating medium, and the latter may be introduced and mixed in the form of steam or vapor, by means of an injector or atomizer. This not only promotes the hydration and conditioning of the gums, but also is in keeping with the objective of preventing contact of the oil with air. The mixture of oil and hydrated gums from the reaction or gumconditioning zone is preferably further heated to a temperature of 180-2l0 F., and the caustic reagent is injected into the hot oil. By reason of this high temperature during the neutralization, the soapstock acquires a relatively low viscosity so that it entrains very little neutral oil.

In the accompanying drawing, the single illustration is a schematic view of a plant suitable for use in practicing the new process, and this plant will now be described in connection with a preferred practice of the invention.

Referring to the drawing, the crude oil is delivered from a supply source or pipe ID to a pump II, from which it passes through a preheater l2 where the oil is heated to a temperature of to F. The oil then passes through a hydrating injector I3 where the hydrating agent from a pipe 13a is continuously injected into the stream of crudeoil. By injecting the hydrating medium in'this manner, a thorough mixing of the medium with the oil is obtained and at the same time the oil is maintained free from entrained air. From the injector l3, the oil passes to the bottom of a reaction zone formed by reactor [4, the reaction zone being enclosed by the reactor to exclude air from the oil during the hydration or reaction for conditioning the gums. During the passage of the oil upward through the reaction zone I4, it is maintained in a turbulent state by means of an agitator (not shown) extending into the reaction zone and driven by a variable speed motor Ma mounted on top of the tower. This agitation of the oil in the reaction zone prevents settling of the gum agglomerates in the reaction zone and assists in the conditioning of the gums for their effective centrifugal separation from the oil.

The oil with its hydrated gums is discharged from the top of the reaction zone 14 and passes through a pipe 15 either directly to the separator 22 (if the gums are of value) or to a heater I6, where it is heated to a temperature of l802l0 F. The oil then passes through a pipe H to a mixer [8 where it is mixed intimately with a stream of a caustic refining agent supplied to the mixer through a pipe [9. The mixer 18 forms a mixing zone where the reagent and oil are subjected to a brief but violent agitation over a. period of 2 to 5 seconds, to obtain a thorough mixing of the caustic solution in the form of fine droplets in the oil. Since mixers suitable for this purpose are known in the art, it is unnecessary to describe the mixer in further detail.

The discharge from the mixer 18 is fed through a pipe 2| to a hermetic centrifuge 22 having an air-tight seal 22a between the pipe 2| and the centrifuge inlet. The centrifuge also has outlets 22b and 220 having sealed connections to pipes 23 and 24 for the separated impurities and the refined oil phase, respectively. Centrifuges of this hermetic type are well known, an example of this type being disclosed in U. S. Patent No. 2,107,035.

As previously indicated, the caustic reagent may be introduced into the mixer la in an amount suiiioient only to bring the free fatty acids in the oil to a point close to neutralization, whereby the discharge from the centrifuge outlet 2% will be gums and soap. The interval between the introduction of the oil into the mixer l8 and its discharge through the centrifuge outlet 220 is restricted to approximately 20 seconds, so that the period of contact between the oil and the reagent is within this range.

The degummed and semi-neutralized oil from centrifuge 22 passes through pipe 24, pump 25, and pipe 26 to another mixer '2! similar to the mixer I8, where it is mixed intimately with a buffer solution introduced through pipe 28. The buffer solution may comprise a non-saponifying alkali, and its function is to complete the neutralization of the free fatty acids and the decolorizing of the oil. After a mixing period of 2-5 seconds in the mixer 21, the oil passes from the mixer through a pipe 30 to a second centrifuge 3| of the hermetic type. This centrifuge has a sealed inlet 3m and sealed outlets Nb and 310,

corresponding to the inlet 22a. and the outlets 22b and 220, respectively, of the first stage centrifuge 22. In the centrifuge 3|, the soapstock resulting from the neutralizing and decolorizing operation is separated from the oil and discharged through outlet 3|?) and pipe 32. The refined oil discharged from the centrifuge outlet Sic passes through pipe 33, pump 34 and pipe 35 to a mixing zone 3'6 where it is mixed with water fed from a pipe 37. This water, which is used for washing the oil, is heated and delivered through pipe 31 by a pump 38. From the mixing zone 36, the water and oil mixture passes upward through a reactor 39, where it is agitated by a mixer driven from a vari-speed motor 39a. The mixture is discharged from the top or" the tower 39 and passes through pipe 40 to another hermetic centrifuge 4| having a sealed inlet Ha. In the centrifuge 4|, the wash water is separated from the oil, the water passing through a sealed outlet 4lb and the washed oil discharging through a sealed outlet Me. The oil may then be delivered through a pipe 42 to a vacuum dryer. The discharge temperature from the vacuum dryer is from 140 to 195 F. If the 011 goes directly to a bleaching operation, it goes through a heat exchanger to increase the temperature for bleaching. If the oil is to go to storage, the heat exchanger is used as a cooler to reduce the oil temperature and thereby prevent oxidation through contact with air on the hot oil in storage.

As in the case of the first stage of neutralization, the mixing period in the mixer 2! is approximately 2-5 seconds, and the maximum time from the introduction of the oil to this mixer to its discharge through outlet 3lc is approximately 20 seconds. When the neutralizing is to be effected in a single stage, as previously mentioned, the caustic reagent is delivered to. mixer l8 at a rate suificient to effect complete neutralization of the free fatty acids and decolorizing of the oil, so that the discharge from centrifuge outlet 22b will comprise the soapstock as well as the gums. The purified oil from outlet 220 may then be fed directly to the pump 34 and the washing stage.

I claim:

1. In the refining of vegetable, marine and animal oils containing phosphatides, the process which comprises continuously feeding the crude oil in a stream from a supply source, continuously injecting a hydrating medium into the stream of the crude oil for hydration of the phosphatides, passing the oil, after the injection of said medium, through a reaction zone while maintaining the oil in a turbulent state, to condition the phosphatides for centrifugal separation from the oil, intimately mixing the crude oil from said reaction zone with a caustic refining agent in an amount sufficient only to bring the free fatty acids in the oil to a point somewhat less than complete neutralization, then promptly centrifuging the incompletely neutralized oil to extract the phosphatides therefrom, intimately mixing the oil from said centrifuging with a further amount of caustic refining agent sufficient to complete the neutralization of the free fatty acids in the oil, promptly feeding the oil and said last agent, after said last mixing, to a re-centrifuging operation and there separating the oil quickly from the impurities contained therein following said neutralization, separately discharging the oil and said impurities from the re-centrifuging operation, and maintaining the oil out of contact with the atmosphere during the entire course of its passage from said source to and through the centrifugin and re-centrifuging operations.

2. A process according to claim 1, in which said hydrating medium is steam.

3. A process according to claim 1, in which said first centrifuging is efiected at a temperature of -210 F.

4. A process according to claim 1, in which said further caustic refining agent is a buffer solution of a non-saponifying alkali.

5. A process according to claim 1, in which the mixture of oil, phosphatides and said first agent is heated to a temperature of 180-210 F. and subjected to a strong but brief agitation prior to said first centrifuging.

6. A process according to claim 1, in which the elapsed time between the start of each mixing operation and the completion of the subsequent centrifuging operation is no greater than 20 seconds.

References Cited in the file of this patent UNITED STATES PATENTS Number

Claims (1)

1. IN THE REFINING OF VEGETABLE, MARINE AND ANIMAL OILS CONTAINING PHOSPHATIDES, THE PROCESS WHICH COMPRISES CONTINUOUSLY FEEDING THE CRUDE OIL IN A STREAM FROM A SUPPLY SOURCE, CONTINOUSLY INJECTING A HYDRATING MEDIUM INTO THE STREAM OF THE CRUDE OIL FOR HYDRATION OF THE PHSOPHATIDES, PASSING THE OIL, AFTER THE INJECTION OF SAID MEDIUM, THROUGH A REACTION ZONE WHILE MAINTAINING THE OIL IN A TURBULENT STATE, TO CONDITION THE PHOSPHATIDES FOR CENTRIFUGAL SEPARATION FROM THE OIL, INTIMATELY MIXING THE CRUDE OIL FROM SAID REACTION ZONE WITH A CAUSTIC REFINING AGENT IN AN AMOUNT SUFFICIENT ONLY TO BRING THE FREE FATTY ACIDS IN THE OIL TO A POINT-SOMEWHAT LESS THAN COMPLETE NEUTRALIZATION, THEN PROMPTLY CENTRIFUGING THE INCOMPLETELY NEUTRALIZED OIL TO EXTRACT THE PHOSPHATIDES THEREFROM, INTIMATELY MIXING THE OIL FROM SAID CENTRIFUGING WITH A FURTHER AMOUNT OF CAUSTIC REFINING AGENT SUFFICIENT TO COMPLETE THE NEUTRALIZATION OF THE FREE FATTY ACIDS IN THE OIL, PROMPTLY FEEDING THE OIL AND SAID LAST AGENT, AFTER SAID LAST MIXING, TO A RE-CENTRIFUGING OPERATION AND THERE SEPARATING THE OIL QUICKLY FROM THE IMPURITIES CONTAINED THEREIN FOLLOWING SAID NEUTRALIZATION, SEPARATELY DISCHARGING THE OIL AND SAID IMPURITIES FROM THE RE-CENTRIFUGING OPERATION, AND MAINTAINING THE OIL OUT OF CONTACT WITH THE ATMOSPHERE DURING THE ENTIRE COURSE OF ITS PASSAGE FROM SAID SOURCE TO AND THROUGH THE CENTRIFUGING AND RE-CENTRIFUGING OPERATIONS.

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