US2437075A - Glyceride oil refining with foots softening agent - Google Patents

Description

B. CLAYTON March 2, 1948;

GLYCERIDE OIL REFINING WITH FOOTS SOF TENING AGENT.

Filed Jan. 5, 1945 altar/"44,6

This invention relates Patented Mar. 2, 1948 enronama on. name wrrn Foo'rs SQFTENING AGENT Benjamin Clayton, Houston Text, assignor by to' Benjamin Clayton, Houston, Tex., doing business'as Refining mesne assignments,

Unincorporated Continuation of application Serial No. 398.489, June 17,1941, which is adivision of application Serial No. 298,685, September 26, 1939. This application January 5, 1945, Serial No. 571,509

":11 Claims. 1 1 1 z y or partially refining animal and vegetable oils.

Caustic alkalies in amounts providing large excesses havet been conventionally employed in the I complete alkali refining of animal and vegetable oils to neutralize the free fatty acids thereof and form separable soap stock. Such excesses of caustic alkalies saponify neutral oil. to produce reflninglosses. Also, substantial amounts of neutrai oil are ,lost by'entra'mment in the soap stock a process of refining,

will be had to the accompanying drawings of which: i l

' Figure 1 is a schematic diagram of apparatus in when this soap stock is separated from the oil;

The employment of caustic alkalies in excess as the neutralizing agent has been considered necessary for complete refining in order to produce a separable soap stock and also in order to reduce the color of certain oils. r

In accordance with the present invention, it

has been found that n'on-saponifying neutralizing agents may be employed for complete refining so as to substantially eliminate lossesby saponification of neutral oil and also that the proper employment of softening or diluting agents for soap stock or other foots provides efllcient separation of the soap stock from the oil and reduces entrainment of neutral oil. The present invention also contemplates the employment or oil solvents during a refining operation together with a partial or complete dehydration step to remove the solvent, the dehydration step being employed after adding the refining agent and prior to sepa ration. The dehydration step is preferably followed b a rehydration step prior to separation. Certain of the steps of the present invention may be employed in combination with the use of caustic alkalies as neutralizing reagents to reduce refining losses; even if the conventional excesses of such caustic alkalies are employed; The

present invention also enableslower excesses or no excess of caustic alkalies to be employed in the'neutralization step'so as to reduce or' elim inate losses due to saponification 01' neutral 011 while still providing effective separation of the soap stock and adequate color reduction. Furthermore, certain steps of the present invention ar efiective to reduce refining losses in acid refining processes or in partial refining or degumming operations employed to' condition the oil for more effective alkali refining or for the pro- I duction of non-break oil.

The object of the present invention is to providea process of refining .or partially refining vegetable and animal oils in which refining losses are markedly reduced.

In describing the present invention, reference invention may be performed; and

Figure 2 is' a similar diagram of a' modified apparatus.

Referring more particularly to Figure 1: l0 indicates a tank for oil to be refined, I I indicates a tank which may contain either a refining agent or a diluting or softening agent for the soap stock or other foots, and I2 indicates a tank for an additional refiningor other agent. The oil may be brought to a predetermined temperature by a heating coil l3 positioned in the tank ill, and may be withdrawn from the tank by a pump 14 and passed-through a heat exchange device ii to a flow mixer l6. The heat exchange device may include a coil l1. through which the oil is passed, which coil is positioned in a casing 1 l8 through whichany desired heating medium may be circulated. Neutralizing or other refining agent may be heated in the tank If, withdrawn .by a pump 20 and delivered to the flow mixer It, The flow mixer l6 may be of any desired type of closed mixing device such as a closed mechanlcal agitator or colloid mill. In many cases the mixer may merely be a means for injecting a flowing, stream of the agent into a flowing stream of the oil.

The mixture of oil and agent may be passed through a second heat exchange device 2|, and then delivered to a second flow mixer 22. Additional agent may be brought to a desired mixing temperature in the tank, withdrawn by a pump 24 and delivered to the flow mixer 22. For alkali refining, at least one oi. the agents added in the mixers IE or 22 containssufficient neutralizing agent to neutralize the free fatty acids and form soap stock. The pumps I4, 20 and 24 are preferably arranged to deliver accurately proportioned streams of the various materials. One way of accomplishing this is to drive the pumps by a variable speed electric motor 25 with variable speed devices 26 and 21 positioned between the motor and the pumps 20 and 24. r The resulting mixture may be passed through another heat exchange device 28. As discussed below, the continuous mixing steps just described can be employed to deliver a mixture to a vapor separating chamber described below with reference to Figure 2 and, if continuous centrifugal separation is to be employed. the mixture from the vapor separating chamber can be rehydrated and delivered to a continuous centrifugal separatorv the light efiluent into a receiver 33. If the neua.

tralized oil is too highly colored, it may be withdrawn from the receiver 33 by a, pump 34 and passed through a heat exchange device 35 to a flow mixer 36. A color reducing agent heated to a desired temperature may be withdrawn from a tank 31 by a pump 38 and delivered to the flow mixer 36. Pumps 34 and 38 may also be arranged to deliver accurately proportioned streams by driving the pumps with a variable speed electric motor 40 and providing a variable speed device 4l between the motor 40 and the pump 38. The mixture of oil and color reducing agent may then be passed through one or more heat exchange devices 42 and 43 and delivered to a continuous centrifugal separator 44 in which the color impurities are separated from the oil and discharged as the heavy efliuent into a receiver 46. The oil is discharged as the light effluent into a receiver 48. The color reduction step may be omitted if the color of the neutralized oil in the receiver 33 is sufficiently low and is not ordinarily employed with acid refining or partial refining.

Following alkali or acid refining, the oil discharged into the receiver 48, or, if the color reduction step is omitted, the oil discharged into the receiver 33, is desirably washed and vacuum dried by withdrawing a stream of the oil by a pump 49, passing the same through a heat exchanger 50 to bring the oil to a desired mixing temperature, which is usually between 120 and 200 F., and delivering the stream into a flow mixer A stream of water heated to the desired mixing temperature may be withdrawn from a tank 52 by a pump 53 and delivered to the mixer 5|, in amounts ranging between 5 and 30% of the oil and usually about 15%. ture may then be passed through a heat exchanger 54and delivered to a continuous centrifugal separator 55. The temperature for most.

effective separation ordinarily ranges between 140 and 200 F. The water containing dissolved impurities is discharged as the heavier efiluent into a receiver 56 and the washed oil is discharged as the light eflluent into a receiver 51. The washed oil may then be withdrawn from the receiver 5'! by a pump 58, passed through a heat exchanger 59 and delivered into a vacuum chamber 60 at a temperature which is preferably be tween 160 and 210 F. The vacuum chamber is preferably provided with an agitator GI and with a heating coil 63. It may also be provided with a steam distributor 64 so that steam, preferably superheated, may be introduced to agitate the oil and assist in carrying off water and other vapors. Vapors may be withdrawn from the vacuum chamber into a condenser 65 provided with a receiver 66, by a vacuum pump 61. A relatively high vacuum, for example between 27 and 29 inches of mercury, is preferably maintained in the vacuum chamber. Temperatures in the vacuum chamber will usually range between 160 and 200 F. for drying the oil, although the temperature may be increased up to 350 F. and the oil treated with superheated steam in order to deodorize the oil. The washed and dried oil may be removed from the vacuum chamber and discharged from the process by a pump 68.

Non-saponifying neutralizing agents, that is, agents which will not saponify neutral oil but The resulting mixwhich will react with free fatty acids present in the oil to form separable reaction products, are particularly useful in the process of the present invention for complete refining, although caustic alkalies can also be employed as the neutralizing agent under certain conditions, as described hereinafter. Soda ash is, however, a preferred nonsaponifying neutralizing agent.

1 While continuous flow mixing of the oil and agents under pressure and out of contact with the air is preferred, it is possible to mix a body of oil with a soda ash solution in a mixing receptacle such as shown in Figure 2, as the soda ash will not saponify neutral oil even upon prolonged contact. Thus, oil can be introduced into a receptacle 69 through .a pipe 10 and soda ash solution introduced through the pipe 'H. The receptacle may be provided with an agitator l2 driven from any suitable source of power so that a thorough admixture of the oil and neutralizing agent can be produced. The receptacle may also be provided with a heating coil 14 for heating thev mixture during or subsequent to mixing. The mixture of oil and resulting soap stock may be withdrawn from the receptacle by a pump 15 and passed through a heat exchange device 18. The mixture may then be introduced into a vacuum chamber 11 provided with a heating coil 18 and an agitator 19. With some oils it has been found preferable to substantially completely dehydrate the mixture in the vacuum chamber by withdrawing water vapors into a condenser 82 in which the water is condensed and delivered as liquid water to a receiver 83. However, with other oils it has been found sufllcient to merely remove gaseous materials such as air and carbon dioxide while removing only a portion of the water. The employment of very dilute solutions of soda ash in conjunction with dehydration is particularly effective with some oils, as the dilute solution modifies the gums to produce more effective separation and the dehydrator may be employed to bring the water content of the mixture to that producing most effective separation. -The solution initially added may even be sufficiently dilute that neutralization does not take-place until after partial dehydration. A vacuum pump 84 maybe connected to the receiver to maintain a vacuum in the vacuum chamber. The vacuum chamber may also be provided with a steam distributor 85 through whichsteam, preferably superheated, may be introduced into the oil to assist in carrying off the vapors and agitating the oil.

A dehydrated or partially dehydrated mixture of oil and soap stock may be withdrawn from the vacuum chamber by a pump 86 and passed through a heat exchanger 81 into a mixer 88. If the mixture of oil and soap stock withdrawn from the vacuum chamber contains less water or soap stock softening agent than that providing effective separation, it may be rendered separable by admixing therewith a stream of rehydrating or diluting agent withdrawn from a tank 89 by a pump 90 and delivered'to the mixer 88. The preferred rehydrating agent is an aqueous solution of soda ash, although other agents may be employed as hereinafter described. The rehydrated mixture may then be passed through another heat exchange device 9|. If desired, additional rehydrating agent of the same or different kind or concentration may be withdrawn from a tank 82 by a pump 93 and delivered into a mixer 94,into which the mixture fromthe heat exchange device 9| may also be delivered. The resulting mixture may then be passed through another heat '5 exchange device DI and delivered to a continuous centrifugal separator 88. With certain oils sufil- -cient rehydrating agent of the correct concentration may be introduced into the mixer .80 so that the mixer 94 and heat exchange device .95

usually enable a lesser amount to be employed.

' Thin liquid soap stock is separated from the refined oil and discharged as the heavy eilluent into a receiver 98 and neutralized oil is charged as the light eilluent into a receiver I 00. If necessary, for

further color reduction, the oil may be withdrawn from the receiver I 00 and subjected to a color reduction step similar to that described with reference to Figure 1 after which it may be washed and dried-or. if the color of theoil is sufiiciently low, it may be immediately subjected to a washing and drying step.

In carrying out the process of. Figure 2, the 'oilin the mixingreceptacle 09 is usually maintained at a relatively low temperature, for example,'temperatures between 70 and 100 F as heating the oil prior to admixing with neutralizing agent to a temperature much above 100 1 may damage the oil. Suiilcient soda ash or other non-saponifyingneutralizing'agent is preferably introduced into the receptacle to neutralize the free fatty acids. when employing soda ash, it will in some cases be necessary to add at least twice as much soda ash as that necessary to neutralize the free fatty acids in order to prevent violent foaming in v the receptacle. This is particularly true if the mixture is heated in thgrecep'tacle. By employing a large excess of soda ash, or very dilute solutions thereof, the mixture may be heated torelatively high temperatures, for example 120 to 140 F., in' the receptacle without excessive foaming. The materials in the tank 69 are preferably agitated at a relatively highspe'ed until a thorough admixture is obtained. The agitation may then be slowed and a stream of the mixture withdrawn from the receptacle by the pump 15. It is usually desirable to employ'the heat exchanger 18 to inportion of the water is withdrawn and the mix- In the process abovedescribed employing nonsaponifying alkalies; substantially no neutral oil is lost by saponiflcation thereof. The n'on-saponifying neutralizing agents 0 not. attack the oil and, even though caustic alkaliesare employed in the color reducing step, the small amount and the short time of contact with the oil. as well as the emcient separation obtainable in the absence of soap stock, enables color reduction to be carried on with no substantial saponification of neutral oil. The losses during the color reduction crease the temperature of the mixture to between 160 and 210 F. Upon discharging the heated mixture into the vapor separating chamber I1, water and'other v'aporizable impurities are withdrawn therefrom to'form a partially or substantially completely dehydrated mixture. If a substantially completely dehydrated mixture is found desirable for a given 01], the employment of concentrated solutions or slurries in the mixer 69 reduces the amount of water removed in the vapor separating chamber. Even'dry' soda ash or other non-saponifying agent may sometimes be employed. Any carbon dioxide formed as a result of admixing sodaash with the oilis withdrawn from the mixture even if dry soda ash is employed and, if neutralization of the oil has not been completed in. the receptacle 89, substantially complete neutralization is effected in the vapor s'eparating chamber".

The treatment of the mixture of oil and soap stock in the chamber 11 appears to modify the nature of the soap stock so thatbetter separation maybe accomplished in theseparator 88, and this is particularly true if the treatment therein is 'sufliciently drastic that at least a substantial condensing the vapor step are usually not greater than 'ro' of 1%. The losses in the neutralizing step are\ due substan"-. tially entirely to entrainment of neutral oil in the soap stock and are usually less than half those ordinarily encountered in the best prior processes. All of the steps of the process may be rapidly performed so that the oil is not subjected to high temperatures for extended periods of time.

, It'is apparent that the continuous step of mixing oil and neutralizing agent shown in Figure 1 may be employed with the dehydration step of Figure 2 as stated above.

The dehydration step including vapor and gas separation shown in .Figure 2 is particularly adaptable to refining oils containing 011 solvents, as such solvents are removed from the oil in the vacuum chamber ll. Thus, such solvents as hexane, benzene, gasoline, benzol and other petroleum solvents employed to extract the oil from the seeds may bepresent in the oil so that it is unnecessary to remove the same prior to refining. The presence of such solvents is often desirable. as the solvent vapors separated from the oil assist in removing vaporizable impurities from the oil and if caustic alkalies are employed for neutralization such solvents inhibit saponification of neutral oil thereby. It is, therefore, sometimes desirable to add such solvents even if not originally present in the oil. Also, other vaporizable materials such as ethyl or isopropyl alcohol, or other fatty acid or soap solvents, may be added to the oil either alone or in combination with the petroleum solvents above referred to. Such solvents also inhibit saponification of neu- The various solvents appear to modify the nature of the gums and soap stock so that more eifective separation is accomplished in the separator 90. The solvents removed in the vacuum chamber may be recovered thereof and may be again used in "the process.

Instead of employing a separate color reduction step suc as that disclosed in Figure 1 when non-saponifyng neutralizing agents are employed, it is'sometimes possible to secure suiilcient color reduction. of the oil by adding a small amount of caustic alkali solution tow the oil and soap stock mixture prior to the separation of the soap stock from the oil. Thus the mixer 22 of Figure 1 and the mixer 94 of Figure 2 may be employed for'this purpose. A small amount of caustic alkali solution may thus be added alone or in admixture with soda ash or other diluting solution. Thus with certain oils, even when employing non-saponifying agents for neutralization, the subsequent color reduction step may be I eliminated, without substantial increase of refining losses even though the oil being refined is rather highly colored, by adding caustic alkali after neutralization but before separation of the soap stock.

It is also possible to admix a small amount of caustic alkali such as caustic soda with the soda ash solution initially admixed with the oil so that less soda ash solution is necessary to neutralize the free fatty acids while preventing the formation of carbon dioxide. This operation is par-,- ticularly useful when refining oils containing large amounts of free fatty acids. If the amount of caustic alkali thus added is not greater than that necessary to; neutralize the free fatty acids in the oil, no saponiflcationof neutral oil takes place during the neutralizing step. Just sufficient caustic alkali solution to neutralize the free fatty acids may also be employed as the neutralizing agent in the absence ofsoda ash, even when the mixture is dehydrated, without materially increasing refining losses if sufficient soda ash or equivalent soap stock softening solution is added prior to separation'to soften the soap stock and provide effective separation.

The process of the present invention has been particularly described with reference to the employment of soda ash solutions, since such solutions, if employed in suificient amount and of proper concentration, effectively soften the soap stock and produce an extremely liquid soap stock. Also, such soda ash solutions effectively drive the oil out of the soap stock phase so that very little 7 oil is retained in the soap'stock. However, other non-saponifying neutralizing agents such as trisodium phosphate, disodium phosphate, sodium silicate, equivalent potassium salts and other alkaline. salts of alkali earth metals are also effective. Also, amines such as ammonia, trieth anolamine, etc., may be employed as neutralizing agents in any process not involving dehydration, as they also produce softened soap stock and do not saponify neutral oil. It is not necessary that 2.11 of the agent present during separation be basic in nature, as certain substantially neutral sodium thiocyanate, etc., and equivalent potassium, ammonium and alkali earth metal salts which also soften the soap stock may be substituted in part for the soda ash or other neutralizing agent, so long as sumcient neutralizing agent is present to substantially completely neutralize the free fatty acids. The equivalent potassium salts are usually even more effective than sodium salts but are relatively expensive. Even a small amount of acidic materials such as naphthenic acid which react with alkalies to form very liquid soaps may be employed. Abietlc acids, such as those found in rosin, may also be employed for the same purpose. The resulting solutions of salts of these acids function as soap stock softening agents and reduce the amount of other solutions such as soda ash necessary for effective separation. The acids may also be converted into soap prior to introduction into the process. The acids or soaps may be added prior or after neutralization of the soap or may be added with the neutralizing agent. Small amounts, for example, 1 to 3% of the naphthenic acid or rosin relative to the weight of the soap stock, are usually suiiicient for effective separation even in the absence of soap stocks containing large amountsmf salts other than soap. Sufficient neutralizing agent should be employed to neutralize the free fatty acids or any other acidic material present.

Potassium soaps are usually more liquid than sodium soaps, and it is many times advantageous to have such soaps present during separation. This can be accomplished by substituting potassium carbonate for a part or all of the sodium carbonate as the neutralizing agent. Potassium hydroxide can also be substituted for caustic soda wherever caustic soda is disclosed herein. Also, a potassium soap solution may be added as a rehydrating or soap stock softening solution. Certain other bases such as urea also produce very i liquid soaps and can be employed as neutralizing agents either alone or in combination with other agents to soften the soap stock, or soaps of urea or similar bases may be added either before or after neutralization as a soap stock softening agent. In many cases, however, the soap stock softening agent may consist in whole or in part of substantially neutral salts which have a softening effect upon the soap stock. Various mixtures of such salts, other soap stock softening agents and neutralizing agents may be present during, centrifugal separation so long as the amount and concentration ofthe solution is suflicient to produce aliquid soap stock containing salts such as sodium sulfate, sodium thiosulfate,

substantial excesses of soda ash or other nonvery little neutral oil. The amount and concentration of such solutions will vary with different oils and agents employed but will usually fall within'the range of concentrations and amounts given with respect to soda ash solutions. The employment of such soap stock softening agents in relatively large amounts is particularly important when refining oils such as palm oils, which form soaps which are hard and relatively insoluble. With some oils it is sometimes possible to employ relatively large amounts of water alone as the diluting agent. Certain salts, for example, chlorides such as sodium chloride, are not effective to produce the improved separation of the present invention, as they harden instead of soften the soap stock.

While continuous centrifugal separation produces much better results than settling operations, improved results over prior batch processes are obtained by employing large amounts of solutionsof the non-saponifying neutralizing agents, salt solutions, or other soap .stock softening agents, above discussed during a batch settling operation. The soap stock layer is more compact and contains less neutral oil and there is a sharp line of division between the oil and the soap stock after settling. The amounts and concentrations of neutralizing agents and other agents given with respect to continuous centrifugal separation are usually effective for batch settling operations. Thus continuous mixing of the neutralizing agent may be combined with a batch settling operation, a batch mixing operation may be combined with a continuous centrifugal separation, or both separation and mixing may be continuous or batch. Color reduction and separation of color impurities as well as washing and drying may also be continuous or batch.

In fact, an entire refining operation, including mixing, dehydrating, rehydrating or diluting,

soap stock separating, color reduction and washingand drying, or anyselected number of these steps may be carried out in a single kettle if de- I gummed. The soap stock-oil mixture has a tendency to stratify into three layers either in a centrifugal or settling step, that is to say, into an oil layer, a layer containing a mixture of oil and soap, and a soap layer, so that either the separated oil contains substantial amounts of soap or the separated soap stock contains large amounts of oil. The softening agents prevent this stratification. The dehydration treatment also aids in preventing this stratification.

In any case, the employment of large. amounts of non-saponifying neutralizing agents during separation, or the employment of, diluting or soap in a more complete separation of the oil from the soap stock. When non-saponifying neutralizing agents are employed, there is substantially no loss arising from saponification of neutral oil. Color reduction steps performed on the oilfrom which the soap stock has been removedQalso produce negligible refining losses. The large amount of solutions present during soap stockseparating and the washing step remove substantial amounts of color impurities even if no caustic alkalies or separate color reduction step is employed. The oil resulting from the process is of high quality and, if desired, of low color. One, of the major advantages of the present process is its adaptahave been previously removed. The term animal oils is intended to include fish oils, such as sardine, menhaden, herring, etc.

The employment of the dehydrating step of the present invention, even when caustic alkalies, such as caustic soda, with the conventional large excesses are used as the neutralizing agent, pro duces improved results. Continuous mixing as disclosed in Figure 1, either with stream preheatins to temperatures between 100 to 160 F. orv

subsequent stream heating, is preferable as the mixture can be; delivered into the dehydrating chamber of Figure 2 before substantial saponification of neutral oil takes place. Also, rapid and substantially complete dehydration is also preferred as removal of substantially all of the water stock softening agents mentioned herein, results and are many times necessary if amounts of caustic soda chemically equivalent to the free fatty acids are employed. In such cases, the soap stock softening. agents may be present during neutralization or added in solution before separation. The interposed dehydration and rehydration steps also have the advantage of making theconcentration of the solutions employed for neutralization independent of the separation step. Thus, very dilute solutions can be employed for neutralization for certain oils and separation carried out in the presence of more concentrated solutions.

The dehydration and rehydration steps or the employment of softening agents for the acid foots also reduce refining losses in acid refining proc- Such acid refining processes involve the mixing oi' solutions of strong mineral acids, such as 's'ulfuric or phosphoric, with the animal or vegetable oils in orderto render separable impurities otherthan free fatty acids. Acid refined oils are chiefly employed in the paint and varnish industries for uses where the presence of free fatty acids is desirable or at least unob- ,iectionable. Such acid refining processes are preferably carried out by employing the continuous mixing steps described with reference to Figure 1. ,Relatively concentrated solutions are usually employed and the acid will not only cause splitting of the glycerides in the presence of vwaterbut will also attack the oil .to cause sulfonation, e'tc., depending upon-the acid employed. By rapidly dehydrating the mixture after the acid refining reagent has been mixed therewith,

these reactions are arrested and the acid foots rendered more easily separated. after rehydration. After again rehydrating' the foots, and

' separating them from the oil, the amount of oil prevents or'sub'stantially retards further saponification of neutral oil. The dehydrated soap stock can, however, continue to act as a color adcases it is not necessary to completely dehydratev the oil-foots mixture, as-improved results are sesorbing agent in, the presence of excess caustic.

By rehydrating the mixture and promptly centrifugally separating, a more eflective separation can be produced. Thus, both the amount of neu-' tral oil saponified and the amount thereof entrained in the soap stock is reduced. As stated above, the dehydration treatment appears to modify the soap stock so that separation is more easily accomplished and the oil more easily and more completely removed from the soap stock. Ill 3 6! the solvents above mentioned may be 15resent during the neutralization step to further retard saponification of neutral oil during saponification, and are removed in the dehydrating step for reuse. in the process, if desired.

When employing the usual excess of caustic neutralizing agents, water alone may be used as entrained in the foots is reduced over processes in which no dehydration step is employed, so that the dehydration and rehydration stepsresult in less destruction of neutral oil.

It has also been found that the soap stock softening agents disclosed above are, in general, ef-

fective to also soften the acid foots so that even less oil is entrained therein when separated. The foots softening agents are preferably added after dehydration, as a part of the rehydrating agent, but in some cases it has been found desirable to add these agents in part or all prior to dehydration, in which case water or solutions containing less of the agents can be added after dehydration as part oi the rehydrating solution. In many cured by partial dehydration. The softening agents are efiective to improve separation even though no dehydration step is employed. By addingthe agents in solution, preferably'after the acid is added, the mixture may be rapidly and substantially completely separated into oil and foots so that entrainment of oil in the foots is minimized. The softening agents selected for use in acid refining will to some extent be controlled by the reactions which may occur between the acid and the agent as well as the desired properties of the refined oil. If alkaline softening agents are employed, sufficient acid refining agents should be used to combine with the alkali and still leave sufficient acid to render the acid foots separable. The reaction products of the acid and alkali then constitute the softening agents. If carbonates are employed in this manner, it is usually necessary to use a dehydration step and add the carbonates before dehydration in order to remove carbon dioxide and prevent it from interfering with separation. Neutral salts and acidic softening agents above disclosed can be employed without necessitating an increase in the amount of acid refining agent.

The dehydrating step and foots softening agents are also applicable to partial refining or degumming processes employing weak acids or bases or substantially neutral solutions or even water to precipitate foots. Water alone, weak solutions of strong acids or strong alkalies, and more concentrated solutions of weak acids or bases or of substantially neutral salts will render separable impurities generally referred to as gums. A dehydration step, even though water alone is employed to precipitate the gums prior to dehydration, renders the gums more easily separable when again precipitated even though removal of water during dehydration may cause some of the gums to again disperse in the oil. Again, adding water either alone or carrying a softening agent provides an improved separation over that when the dehydration step is omitted. The presence of softening agents during separation further improves the separation so as to reduce the oil entrained in the foots. This is true even if the dehydrating step is omitted. It is apparent that the softening agents employed in demming processes should be neither strong alkali nor strong acid. However, substantially neutral salts of alkali metals, including the potassium soaps of fatty or other acids, the sodium or potassium soaps of naphthenic or rosin acids,

formamide, urea, sodium and ammonium sulphamates, are particularly suitable and solutions thereof are preferably added after the gums have been precipitatedand prior to separation.

In connection with the alkali refining of animal andvegetable oils, the dehydration step described makes it possible to employ other methods-of separation than those depending upon diflerence of specific gravity. For example, the soap stock can be filtered out of the oil. This is preferably accomplished by a continuous vacuum filter in which the soap deposited upon the filter member is continuously scraped therefrom. When substantially all of the water has been rapidly withdrawn while the soap stock is suspended in the oil, as is the case in the continuous dehydration step disclosed, the soap stock collecting uponthe filter member has a granular or open structureand the oil is more easily withdrawn therefrom. The soap stock after filtration stillcontains some oil which can be recovered by mixing an oil solvent such as benzene with the dehydrated and filtered soap stock and again filtering. Alternatively, the soap stock can be washed with solvent while on the filter member. It is preferred, however, to continuously scrape the filtered soap stock from the filter member and deliver it to a mixing device concurrently with a stream of solvent, withdrawing a stream of the mixture from the mixer and delivering it to a second continuous filter in which the mixture is continudensed and reused. A more desirable operation is to return the oil-solvent mixtureto the oil to be refined, for example, by proportioning a stream of the same into a stream of the oil prior to mixing the refining reagent therewith or, less desirably, just after mixing the refining reagent with the oil. The solvent is then present during neutralization or immediately thereafter and to inhibit any saponification of neutral oil, the solvent is removed in the dehydration step and may easily-be condensed'and separated from the water for reuse in removing oil from the filtered soap stock. A similar series of steps can also be employed with respect to dehydrated acid foots filtered from the oil in a manner similar to that described in relation to acid refining. A basket type of centrifugal separator may also be employed for separating foots from a dehydratedvmixture and is substantially equivalent to a filter. Provision can be made for continuously removing the. facts deposited in the basket, for example, by a'scraping mechamism, and the foots can be treated to remove residual oil in the same manner as the foots separated from the oil by filtration. Also, a continuousv centrifugal separator can be used to separate the foots from'the dehydrated mixture by introducing a stream of water or a solution containing softening agents into the bowl of the separator adjacent the periphery thereof so as to cause the foots to be continuously discharged as a stream without the diluting or softening liquid coming into contact with the oil. Any soap left in the oil can be removed in a subsequent color reduction or washing step.

As stated above, non-saponifying alkalies, particularly soda ash, are the preferred neutralizing and soap stock softening agents for alkali refining. Soda ash not only effects a low loss refining operation but the resulting soap stock is a valuable detergent. The soda ash is less destructive to the gums contained in the oil and soap stock than caustic alkalies, so that a better quality soap stock is produced even when refining undegummed oil. The decomposition products of gummy materials such as proteins and phosphatides are amine-like, evil smelling compounds and are largely avoided when soda ash or in a'quick continuous process.

be separated in substantially undecomposed form other non-saponifying alkalies are employed for refining, particularly when refining is carried on The gums may from soap stock and recovered as valuable byproducts by washing or solvent treatment of the soap stock, although for some detergent purposes it is desirable to leave the gums in the soap stock.

When refining degummed oil, a good quality filled soap is directly produced. By controlling the amount of water employed in the rehydrating or soap stock softening agents, a neat soap, i. e., one containing approximately 30% water, can be directly produced so as to be capable of being converted into any type of soap product by known commercial methods. Other types of nonsaponifying alkali refining agents or soap stock ously separated into a solvent oil phase, and sub stantlally oil free soap stock. The oil can then be freed of solvent by volatilization, for example, by heating a stream of oil-solvent mixture softening agents which will function as soap fillers may be substituted in part or wholly for the soda ash in the refining process to produce the detergents discussed above.

This application is a continuation of my a plication Serial No. 398,489, filed June 17, 1941, now Patent No. 2,37%,924, which in turn is a division of my co-pending application Serial No. 296.685, filed September 26, 1939, Patent No.

2,249,701, reissued Jan. 6, 1942, as Patent N- Re.21,992. a

While I have described the preferred embodiments oi. my invention, it is understood that the details thereof may be varied within the scope oi. the following claims. 7

I claim: 7 1. In the art of refining animal and vegetable qils wherein impurities are removed in the form of aqueous foots by centrifugal separation, the improvement which comprises the step of se;)- arating the foots bycentrifugalseparation in the presence of a softening agent for-said roots selected from the group'consisting of abietic acid, naphthenic acid, and water soluble soaps of such acids, the amount of said agent bein suflicient to substantially soften said foots. I i

2. The process as defined in claim 1 in which the softening agent comprises naphthenic acid. 3. The process as defined in claim lj-i'n which the softening agent comprises abietic acid.

4. The process asvdefined in claim 1 in which the softening agent comprises rosin soap.

Q5. The process as defined in claim 1 in which the softeningagent comprises 1 to 3% of naph- -.thenic acid relative to the weight of said roots.

6. The process as defined in claim '1 in which the softening agent comprises 1 to 3% of rosin relative to the weight of said foots.

"l. The process as defined in claim 1 in which the softening agent comprises na'phthenic acid which is added to the oil prior to refining.

anon 14 resultant soapstock, and centrirugally separating the soapstock thus produced from a refined oil. 10. The process of refining animal and vegetable oils containing free fatty acids which comprises the steps of introducing a neutralizing agent for the free fatty acids contained in said oil and also introducing abietic acid, .the amount of neutralizing agent being suflicient to react with the free fatty acids and also with the abietic acid and the amount of abietic acid being suffi- .cient to substantially soften the resultant soapstock,,-an'd cntrifugaliy separating ,the'-. soap-' it stock thus produced from a refined oil.

11. The process of refining animal and vegeftable oils which have previously been degummed and which contain free fatty acids, which cqmprises the steps of neutralizing the free fatty acids contained in said oil by adding a neutralizing' agent for said free fatty acids thereby b-securing a. soapstock-oil'mixture which has a 8. The process as defined in claim 1 in which 1 the softening agent comprises abietic acid which is added to the oil prior to refining.

tendency to stratify, thusinterfering with cert trifugal separation, facilitating said centrifugal separation by incorporating into said mixture group consisting of abietic acid. naphthenic acid and water soluble soaps-of such acids,-the amount of said agent being suflicient to substantially soften said soap stock;

' BENJAMIN CLAYTON.

\ REFERENCES CITED The following references are of record the filelof this patent:

UNITED STATES PATENTS Number Name Date 2,205,971 Clayton et a]. i June 25, 1940 2,126,334 Langedjk Aug. 9, 1938 2,115,668' James Apr. 26, 1938. 1,692,226 Schwarcman Nov. 20, 1928 1,548,838 Harvey Aug. 11, 1925 1,169,154 Holbrook Jan. 25, 1916 2,271,621

Brown Feb, 3, 1942 a. softening agent preventing such stratificatiomg .said softening agent being selected from the

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