US2374924A - Refining of animal and vegetable oils - Google Patents

Description

May 1, 1945.

B. CLAYTON REFINING OF ANIMAL AND VEGETABLE OILS Original Filed Sept. 26, 1939 lutomm b Patented May 1, 1945 Q 2,374,924 DEFINING OF 511131115? AND VEGETABLE Benjamin Olayton, Houston, Tex assignor, by

meme assignments, to Befinin g, Unincorporated, a Texas partnership Original application September 26. 1939, Serial No. 296,685. Divided and this 17, 1941, Serial No. 398,189

application June 6 Claims. (Cl. 200-426) This invention relates to a Process of refining or partially refining animal and vegetable oils.

Caustic alkalies in amounts providing large excesses have been conventionally employed in the 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 refining losses. Also, substantial amounts of neutral oil are lost by entrainment in the soap stock when this soapv 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.

In accordance with-the present invention, it has been found that non-saponifying neutralizing agents may be employed for complete refining so as to substantially eliminate losses by saponification of neutral oil and also that the proper employment of softening or diluting agents for soap stock or other foots provides efilcient separation of the soap stock from the oil and reduces entrainment of neutral oil. The present invention also contemplates the employment of 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 separation. The dehydration step is preferably followed by 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 enables lower excesses or no excess of caustic alkalies to be employed in the neutralization step so as to reduce or eliminate losses due to saponification oi neutral oil while still providing effective separation of the soap stock and adequate color reduction. Furthermore, certain steps of the present invention are effective to reduce refininglosses in acid refining processes or in partial refining or degumming operations employed to condition the oil for more effective alkali refining or for the production of non-break oil.

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

In describing the present invention, reference will be had to the accompanying drawing of which:

Figure l is a schematic diagram of apparatus in which certain steps of the process of the present invention'may be performed; and

Figure 2 is a similar diagram of a modified apparatus.

Referring more particularly to Figure 1: i0 indicates a tank for oil to be refined, ll indicates a tank which may contain either a refining agent or adiluting or softening agent for the soap stock or other foots, and I2 indicates a tank for an additional refining or other agent. The oil may a be brought to a predetermined temperature by a heating coil l3 positioned in the tank I0, and may be withdrawn from the tank by a pump [4 and passed through a heat exchange device I5. 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 i8 through which any desired heating medium may be circulated. Neutralizing or other refining agent may be heated in the tank ll, withdrawn by a pump 20 and delivered to the fiow mixer IS. The fiow mixer l6 may be of any desired type of closed mixing device such as'a closed mechanical agitator or colloid mill. In many cases the mixer may merely be a means for injecting a flowing stream of the agent into a fiowingstream of the oil.

The mixture or oil and agent may be passed through a second heat exchange device 2|, and then delivered to a second fiow mixer 22. Additional agent may be brought to a desired mixing temperature in the tank I2, withdrawn by a pump 24 and delivered to the fiow mixer 22. For alkali refining, at least one of the agents added in the mixers It or 22 contains sufiicient 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. 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 sepainto a receiver 3|.

centrifugal separator as a liquid heavy ei'liuent as the light eiliuent into a receiver I3. If the neutralized 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 I! 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 II 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 I1 and delivered to a continuous centrifugal separator 44 in which the color impurities are separated from the oil Neutralized oil is discharged agent under certain conditions, as described hereinafter. Soda ash is, however, a preferred nonsaponifying neutralizing agent. a

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 7 ash will not saponify neutral oil even upon proand discharged as the heavy efliuent into -a receiver 48. The oil is discharged as the light emuent into a receiver 40. The color reduction step may be omitted if the color of the neutralized oil in the receiver ll is sufficiently low and is not ordinarily employed with acid refining or partial refinin Following alkali or acid refining, the oil discharged into the receiver 40, 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 ill 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 ii. 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 ii, in amounts ranging between and 30% of the oil and usually about The resulting mixture may then be passed through a centrifugal separator 55. The temperature for most effective separation ordinarily ranges belonged contact. Thus, oil can be introduced into a receptacle 6-9 through a pipe 10 and soda ash solution introduced through the pipe 1|. The receptaclemay be provided with an agitator 12 driven from any suitable source of power so that a thorough admixture of the oil and neutralizingv agent can be produced. The receptacle may also be provided with a heating coil II for heating the mixture during or subsequent to mixing. The

I 'mixture of oil and resulting soap stock may be withdrawn from the receptacle by a pump 15 and passed through a heat exchange device 16. 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 I which the water is condensed and delivered as liquid water to a receiver 83. However, with other oils it has been found sufflcient 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 heat exchanger 54 and delivered to a continuous tween 140 and 200 F. The water containing dissolved impurities is discharged as the heavier eiluent into a receiver 6 and the washed oil is discharged as the light efliuent into a receiver 51.

The washed oil may then be withdrawn from the receiver 51 by a pump 50, passed through a heat exchanger I! and delivered into a vacuum chamber at a temperature which is preferably between 160 and 210 F. The vacuum chamber is preferably provided with an agitator ti and with a heating coil 63. It may also be provided with a steam distributor 0| so that steam, preferably superheated, may beintroduced to agitate the oil and assist in carrying oflf water and other vapors. Vapors may be withdrawn from the vacuum chamber into a condenser provided with a receiver 66, by a vacuum pump 61. A relatively high vacuum, for example between 2'! 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 Bl.

NOII-SBIDODHYHIK neutralizing agents, that is. agents which will not saponify neutral oil but which will react with free fatty acids present in of soda ash in conjunction with dehydration is particularly effective with some oils, as the dilute solution modifies the gums'to produce more eilec- I tive 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 sufliciently dilute that neutralization does not take place until after partial dehydration. A vacuum pump 84 may 'be connected to the receiver to maintain a vacuum in the vacuum chamber. The

vacuum chamber may also beprovided with a steam distributor 85 through which steam, preferably superheated, may be introduced into the oil to assist in carrying of! 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 06 andpassed through a heat exchanger 81 into a mixer 88. If the mixture of oil and soap stock withdrawn y 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 r diluting a ent withdrawn from a tank 09 by a pump and delivered to the mixer 00. 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 92 by a pump 93 and delivered into a mixer 94,

into which the mixture from the heat exchange device 0| may also be delivered. The resulting mixture may then be passed through another heat exchange device 9! and delivered to a continuous centrifugal separator 98. With certain oils sufiicient rehydrating agent of the correct concentration may be introduced into the mixer 88 so that the mixer 84 and heat exchange device 95 may be eliminated. If sufllcient soda ash or other agent was admixed with the oil prior to dehydration, the rehydrating agent may be water alone. In any case, the amount and concentration of soda ash or other solution present during separation in the separator 96 will be similar to the amount specified with reference to the process of Figure 1, although the dehydration treatment will usually enable a lesser amount to be employed. Thin liquid soap stock is separated from the refined oil and discharged as the heavy effluent into a receiver 98 and neutralized oil is discharged as the light effluent into a receiver Hill. If necessary. for further color reduction. the oil may be withdrawn from the receiver I 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 the oil is sufficiently low, it may be immediatel subjected to a washing and drying step.

In carrying out the proces of Figure 2, the oil in the mixing receptacle 69 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 F. may damage the oil. Suillcient soda Mb or other non-saponifying neutralizing 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 the receptacle. This is particularly true if the mixture is heated in the receptacle. By employing a large excess of soda ash, or very dilute solutions thereof. the mixture may be heated to relatively 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 high speed 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 I6 to increase the temperature of the mixture to between160 and 210 F. Upon discharging the heated mixture into the vapor separating chamber .11, water and other vaporizable 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 oil. 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 soda ash with the oil is withdrawn from the mixture even if dry soda ash is employed andif neutralization of the oil has not been completed in the receptacle 69. substantially complete neutralization is effected in the vapor separating chamber 11.

The treatment of the mixture of oil and soap stock in the chamber 11 appears to modify the nature of the soap stock so that better separation may be accomplished in the separator 98,

and this is particularly true if the treatment therei is sufficiently drastic that at least a substantial portion ofthe water is withdrawn and the mixture then dehydrated. Also, other porizable impurities are withdrawn from the In the process above described employing nonsaponifylng alkalies, substantially no neutral oil is lost by. saponification thereof. The nonsaponifying neutralizing agents do not attack the oil and, even though caustic alkalies are employed in the color reducing step, the small amount and the short time of contact with the oil, as well as the efficient separation obtainable in the absence of soap stock, enables color reduction to be carried on with no substantial saponiflcation of neutral oil. The losses during the color reduction step are usually not greater than of 1%. The losses in the neutralizing step are due substantially 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 thedehydration 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 oil" solvents. as such solvents are removed from the oil in the vacuum chamber 11. Thus. such solvents as hexane, benzene, gasoline, benzol and other petroleum solvents employed to extract the oil from the seeds may be present 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 saponiflcation 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 neutral oil by caustic alkalies. The various. solvents appear to modify the nature of the gums and soap stock so that more efiectisve se aration is accomplished in the separator 9 ber may be recovered by condensing the vapor thereof and may be again used in the process.

Instead of employing a separate color reduction step such as that disclosed in Figure 1 when non-saponifying neutralizing agents are employed. it'is sometimes possible to secure suflicent color reduction of the oil b adding a small amount of caustic alkali solution to the oil and soap stock mixture prior to the separation of the soap stock from the oil. Thus the mixer 22 of Figure l 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 the treatment in the The solvents removed in the vacuum chamlarge amounts of free solution. Thus with certain oils, even when employing ncn-saponifying agents for neutralize-- tion, the subsequent color reduction step may be eliminated, without substantial increase of refining losses even though 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 sodaash 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 particularly useful when refining oils. containing fatty acids. If the amount of caustic alkali thus added is not greater than that necessary to neutralize in the oil, no saponification of neutral oil takes place during the neutralizing step. Just suflicient caustic alkali solution to neutralize the free fatty acids may also be employed as the neutralizing agent in the absence of soda ash, even when the mixture is dehydrated, without materially increasing refining losses if sufllcient 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 sufllcient amount and of proper concentration, effectively soften the soap stock and produce an extremely liquid soap stock. Also, such soda ash solutions eifectively drive the oil out of the soap stock phase so that very little 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, triethanolamine, etc., may be employed as neutralizing agents in any process not involving dehydration, as they not saponify neutral oil. It is not necessary that also produce softened soap stock and do all of the agent present during separation be basic in nature, as certain substantially neutral salts such as sodium sulfate, sodium thiosulfate, 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 ing 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. Abietic 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 ecessary for effective separation. The acids may also be converted into soap prior to introduction into the proc the 011 being refined is the free fatty acids soda ash or other neutralizthese acids, particularly the rosin soap,

or other non-saponifying alkalies. The salts of have the advantage of increasing the value of the soap stock over soap stocks containing large. amounts of salts other than soap. Sufllcient 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 lwdroxide 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 pro-.

duce very 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 stock softening agents and neutralizing agents maybe present during centrifugal separation so long as the amount and concentration of the solution is sufllcient to produce a liquid soap stock containing very 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 centrifuga1 separation produces much better results than settling operations, improved results over prior batch processes are obtained by employing large amounts of solutions of 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 usually effective for batch settling operations.

Thus continuous mixing of the neutralizing agent may be combinedwith a batch settling 0peration, a batch mixing operation may be comess. The acids or soaps may be added prior or I v the absence of substantlal-excesses of soda ash bined 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 bat'chr In fact, an entire refining operation, including mixing, dehydrating, rehydrating or diluting, soap stock separating, color reduction and washing and drying, or any selected number of these steps may is employed. The oil resulting from can, however, continue 2,874,994 be carried out in a single kettle if desired. The

soap stock softening vention agents of the present inor settling step,

a layer containing a mixture of oil and soap, and

tion. The dehydration treatment also aids in preventing this stratiflcation.

In any case, the employment oi large amounts of non-saponifying neutralizing agents during separation, or the employment of diluting or soap stock softening agents mentioned herein, results 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 oil from which the soap stock has been removed also produce negligible refining losses. amount of solutions present during soap stock separating and the washing step remove substantial amounts of color impurities even if no caustic alkalies or separate color reduction step the process is of high quality and, if desired, of low color. One of the major advantages of the ess is its adaptability to substantially all types of vegetable and animal oils. Thus, vegetable oils such as cottonseed, corn, sesame, soya bean, linseed, etc., can be treated. Even tung oil, which is extremely difiicult to refine because of emulpresent procsion difliculties, may be satisfactorily refined, particularly in a process involving dehydration, as such dehydration completely breaks emulsions formed during neutralization. The vegetable oils may be either crude oils containing gums, or may be so-called degummed oils from which the ummy materials have been previously removed. The term "animal oils" is intended to include fish oils, suchas sardine, menhaden, herring, etc.

The employment of the dehydrating step of the present invention, even when caustic alkalies, such as caustic soda, withthe conventional large excesses are used as the neutralizing agent, produces improved results. Continuous mixing as disclosed in Figure 1, either with stream preheat-v ing to temperatures between .100 to 160 F. or 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 prevents or substantially retards further saponification of neutral oil.

to act as a color adsorbing agent in the presence of excess caustic. By rehydrating the mixture and promptly centrifugally a more efiective separation can be saponification of neutral oilduring saponiflcation, v

The dehydrated soap stock and are removed in use in the process, if desired.

When employing the usual excess of caustic neutralizing agents, water alone may be used as tion 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 ioots also reduce refining losses in acid refining processes. Such acid refining processes involve the mixing of solutions of strong mineral acids, such as sulfuric or phosphoric, with the animal or vegetable oils in order to render separable impurities other than free fatty acids. Acid refined in the paint and varnish industries for uses where the presence of free fatty acids is desirable or at least unobjectionable. Such acid refining processes are preferably carried out by employing the continuous mixing steps described 1. Relatively concentrated solutions are usually employed and the acid will not only cause splitting ofthe glycerides in the presence of water but will also-attack the oil to cause sulfonation, etc.,

depending upon the acid employed. By rapidlyv dehydrating the mixture after the acid refining therewith, these reactions erties of the refined oil.

the dehydrating step for rewith reference to Figure impurities generally referred soaps of naphthenic or rosin vto a second continuous agents should be used to combine with the alkali and still leave sumcient 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. Y

The dehydrating step and facts softening agents are also applicable'to partial refining or degumming processes employing weak acids or bases or substantially neutral so utions or even water to precipitate foots. Water alone, weak solutions of strong acids or strongalkalies, and more concentlated solutions of weak acids or bases or of substantially neutral salts will render separable 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' degummin 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 acids, formamide, urea, sodium and ammonium sulphamates, are particularly suitable and solutions thereof are preferably added after the gums have been precipitated and prior to separation.

In connection with the alkali refining of animal and vegetable oils, the dehydration step described makes it possible to employ other methods of separation than those depending upon difference of specific gravity. For example, the soap stock can be filtered out of the oil. This is preferably accomplished by acontinuous 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 hydration step disclosed, the ing upon the filter member soap stock collecthas a granular or open structure and the oil is more easily with- The soap stock after filtration still contains 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 soapv 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 memher 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 filter in which the mixture is continuously separated and substantially oil free soap stock. The oil can then be freed of solvent by volatilization, for example, by heating a stream of oil-solvent mixture and delivering the heated mixture into the continuous demanner as the filtration. Also, a continuous into a solventoil phase,

a vapor separating chamber such as that shown in Figure 2. The vaporized solvent can then be condensed and reused. A more desirable operation is to reutm the 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 aftermixing the refining reagent with the oil. \The solvent is then present during neutralizatlonl 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 A basket can be treated to centrifugal separater can be used to separate the foots from the dehydrated mixture by introducing a stream of water or a solution containing softening agents int .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 ,leftin the oil can be removed in a subsequent color reduction or washing step.

As stated above, non-saponifying alkalie particularly soda ash, are the preferred neutralizing and soap stock softening agents for alkali refining. Soda ash not only 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 materials such as proteins and phosphatides are amine-like, evil smelling compounds and are largely avoided when soda ash or other non-saponifying employed for refining, particularly a a quick continuous process. separated in substantially undecomposed form from soap stock and recovered as valuable byproducts by washing or solvent treatment of the soap stock, although for some detergent purposes I quality filled soap is directly produced. By controlling the amount of water employed in the rehydrating or soap stock softening agents, a neat soap, 1. 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 non-saponifying alkali refining agents or soap stock softening agents which will funuction 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 division of copending application Serial No. 296,685 filed September 26, 1939, now issued as Patent No. 2,249,701.

While I have described the preferred embodi oil-solvent mixture to the I effects a low loss refining operation but the resulting soap stock is a 2,374,924 ments of my invention, it is understood that the details thereof may be varied within the scope of the followin claims.

I claim:

1. The process of refining table oils which comprises neutralizing free fatty said filter with from.

4. The process of refining animal and vegebl ta e oils which comprises mixing a proportioned stream oi said oil and portioned stream of an aqueous alkaline refining and thereafter continuously centrifugally separating said soap stock from said oil.

and soap stock, vaporizing volatile substances including substantially all of'said solvent from said mixture, and separating said soap stock from said oil.

6. The process of refining animal and vegetable oils BENJAMIN CLAYTON.

CERTIFICATE OF CORRECTION.

Patent ms. 2, 7h,92l

BENJAMIN CLAYTON.

ond column, line I for column, line 14,, for "reutrn" read --function--,- drated" 6, after "oil" insert --solvent--,- be read with this correction ther-ei 0rd oi the case Signed read (Seal) dehydra ted n in the Patent Office.

and sealed this 7th day of August, A. o. 1915.

read --rehydrated--; --return--; line 68, second column, insert -resulting mixture of said oil and said--; line 21;, claim and that the said letters Patent should that the sane may conform to Page 5, secpage 6, second for "funuetion" line 8, claim 14., after "dehythe rec- Leslie Frazer 2,374,924 ments of my invention, it is understood that the details thereof may be varied within the scope of the followin claims.

I claim:

1. The process of refining table oils which comprises neutralizing free fatty said filter with from.

4. The process of refining animal and vegebl ta e oils which comprises mixing a proportioned stream oi said oil and portioned stream of an aqueous alkaline refining and thereafter continuously centrifugally separating said soap stock from said oil.

and soap stock, vaporizing volatile substances including substantially all of'said solvent from said mixture, and separating said soap stock from said oil.

6. The process of refining animal and vegetable oils BENJAMIN CLAYTON.

CERTIFICATE OF CORRECTION.

Patent ms. 2, 7h,92l

BENJAMIN CLAYTON.

ond column, line I for column, line 14,, for "reutrn" read --function--,- drated" 6, after "oil" insert --solvent--,- be read with this correction ther-ei 0rd oi the case Signed read (Seal) dehydra ted n in the Patent Office.

and sealed this 7th day of August, A. o. 1915.

read --rehydrated--; --return--; line 68, second column, insert -resulting mixture of said oil and said--; line 21;, claim and that the said letters Patent should that the sane may conform to Page 5, secpage 6, second for "funuetion" line 8, claim 14., after "dehythe rec- Leslie Frazer

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