US2450235A

US2450235A - Fractional separation of fatty oil substances

Info

Publication number: US2450235A
Application number: US739541A
Authority: US
Inventors: William P Gee
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1947-04-05
Filing date: 1947-04-05
Publication date: 1948-09-28
Anticipated expiration: 1965-09-28

Description

y t. 28, 1948. w. P. cal-:E

.FRACTIONAL SEPARATION 0F FATTY OIL SUBSTANCES 2 Sheets-Sheet 1 Filed April 5, 1947 Sept. 28, 1948. w. P. GEE

FRCTIONAL SEPARATION OF FATTY OIL SUBSTANCES Filed April 5, 1947 2 Sheets-Sheet 2 INVENTOR.

W L. z, /AM P GEE ATT RNEY Patented Sept. 28, 1948 FRACTIONAL SEPARATION F FATTY OIL SUBSTANCES william P. Gee, Plainfield, N. J., assigner a Texaco Development Corporation, New York, N. Y., a corporation of Delaware Application April 5, 1941, serial No. '139,541

9 claims. (ci. 26o-428.5)

This invention relates to the fractional separation of fatty oil substances such as the fatty oil mixtures derived from vegetable, land and marine animal or other sources.

Such oils usually comprise fatty acids having from about 12 to 18 carbon atoms per molecule and, in the natural state, are largely in the form of glycerides, although they frequently include the free fatty acids. In some instances, as for example, in the case of sperm oil, the fatty acids are largely combined as esters of the higher aliphatic alcohols although they may be present as glycerides to the extent of 12 to 30% of the fatty oil.

This invention is a continuation-in-part of my copending application S. N. 615,886 filed September 12, 1945, now abandoned which in turn is a continuation in part of my application S. N. 454,- 666 filed August 13, 1942. The present invention involves separation of fatty substances contained in the fatty oil, into fractions of different melting point or different solidification point range by continuous filtration in the presence of a polar solvent liquid such as acetone, methylethyl ketone, benzene, di and tri-chlorethylenes, nitrparaiiins such as nitroethane, and non-polar solvents such as low boiling petroleum hydrocarbons, namely propane, butane, pentane, etc, or compatible mixtures of any of these solvents. The fatty substance to be treated may be any particular por-tion of a raw oil, such as a mixture consisting essentially of free fatty acids obtained by acidulation of the saponified acids separated from the oil.

The term fatty substance as used herein is intended to mean the fatty acids, whether occurring naturally or synthetically or derived from natural products by conventional procedures; the glycerides of the fatty acids, most frequently the triglycerides, but also the equivalent mono or diglycerides and mix-tures thereof; and the other esters of the fatty acids, that is to say esters with either the lower aliphatic alcohols such as the ethyl and methyl esters through the complete range including esters of fatty acids and long chain aliphatic alcohols such as cetyl palmitate and the like. The term fatty acids includes not only the typical saturated and unsaturated members having from about 12 to 18 carbon atoms, but also the known fatty acids having a greater number -of carbon atoms, as well as the shorter chain fatty acids down to about eight carbon atoms. The present invention permits fractional separation of the foregoing from each other whether in relatively pure mixtures or in admixture with other and non-saponiable mate- Y for example, be operated at a lower temperature A level. In this wayvthe original fatty oil feed may be separated into a series of separate, substanvrials which may sometimes occur in the fatty oil substances and mixtures .referred to above.

The solvent liquids contemplated are organic solvents from which the fatty substances may be crystallized without alteration in their essential state.

The fatty oil substance to be filtered is mixed with the solvent liquid in an amount and under conditions of temperature such as to obtain a mixture composed of a liquid phase comprisingfatty oil substance dissolved in solvent liquid and a solid phase consisting essentially of fatty constituents of predetermined and relatively narrow melting point or solidiflcation point range. This phase mixture with the solid phase dispersed substan-tially uniformly throughout the liquid phase is passed in a continuous stream to a continuous filter advantageously of the rotating leaf or drum type wherein the filter surface passes through y tially pure fractions.

An important feature of the invention involves maintaining the proper relation between the solid and liquid phases in the phase mixture passing to the filter. It is advantageous that the volume of such liquid phase bein the ratio of about 16 to 50 volumes per unit volume of solid phase. Expressed in terms 'of percent solids it is desirable Athat the solids lcontained in the phase mixture passing to the filter be in therange about 2% to 6% by volume of the phase mixture and not substantially in excess of this value.

Optimum results, within this range, are obtained when the solids ln the phase mixture are about 5 to 6% of the volume of the phase mixture.

If the solid phase is rpresent inthe feed mixture to a larger extent than this a filter cake is obtained which is too thick to permit effective displacement of liquid phase from the filter cake during the washing step and under such circum- 'stances sharp separation between component fractions of the fatty oil feed is not realized.

The ratio of solid phase to liquid phase can be controlled Iby correlating the amount and character of the solvent liquid employed with the temfperature at which the Imixture is filteredand also by recycling either filtrate or solids 'to the mixture passing to the filter. Recycling of filtrate increases the ratio of liquid to solids and is advantageous from the standpoint of exerting a beneficial modifying action on the crystalline structure of the solid phase whereby more eflicient filtration and more c1ose-cut fractionation may be realized. On the other hand, solids may be recycled so as to maintain Ithe solid content witihin the aforesaid 2 to 6% of the feed mixture, particularly where the solvent content in the liquid phase cannot be reduced without an excessive increase in the viscosi-ty of the liquid phase.

As already intimated liquid p'hase retained in the filter cake is displaced by washing' prior to discharge from the filter. This washing is accomplished =by applying a further quantity of the solvent liquid to the filter cake, in situ, in such manner as 4to displace the retained liquid phase as filtrate. Effective displacement is secured by applying .the wash solvent liquid to the filter cake in the form of an unbroken film or -sheet of solvent liquid maintained over the cake for a period of time subsequent lto its emergence from the filtering mixture. To facilitate realizing complete displacement of' retained liquor the filter cake should not exceed about one-quarter inch in thickness. On lthe other hand, the cake should be not less than about one-eighth inch in thi-ckness; otherwise difficulty is encountered in discharging it from the filter surface.

An important advantage of the present invention is that it provides a continuous method of effecting fractional separation of these fatty substances, such separation heretofore Ihaving been effected yby pressing, usually involving a succession of pressing operations applied to the same fraction.

A further advantage is that the present invention permits realizing a sharper lseparation between individual fractions of the feed oil.

For example, when treating an oil derived from soya bean and consisting essentially of free fatty acids. in orde-r to separate therefrom a fraction consisting essentially of .palmit-ic and stearic acids, in accordance with lthe process of this invention, a filter cake is obtained in a. single ltering operation which, after removal of :the solvent, will have an iodine number of 5 or less indicating the substantial absence of the unsaturated acids which are of lower melting point. By prior art methods involving pressing, about the best that can be expected is a product having an iodine number of about 15.

In order to describe the invention further reference will now be made to the figures of the accompanying drawing.

As indicated in Figure 1, fatty oil from a source not shown is conducted through a pipe to a mixer 2 while solvent from a source not shown is conducted through a pipe 3 to the mixer. The solvent may be, for example, a low molecular weight ketone such as acetone or methylethyl ketone or a mix-ture of such ketones with benzol or other aromatic hydrocarbons. 'llhe solvent may be mixed with the fatty oil in the proportion of about 2 to 5 parts of solvent to 1 part by volume of fatty oil although the actual proportions used will depend upon the character of the fatty oil feed and also upon the degree of fractionation desired.

'I'he resulting mixture may be conducted from the mixer 2 to a heater l wherein the mixture is warmed or heated sufficiently to effect complete solution of the fatty oil in the solvent liquid. If

desired, the mixture may -be raised to a tempera- -ture A25 to 50 F. Yabove the temperature of oomplete solution in order to condition the mixture.

The solution is then passed from the heater I to a chiller or cooler 5 wherein the temperature of the solution is reduced to the desired point so as to effect crystallization of the constituent of the fraction desired to be separated. A solid phase is obtained containing fatty oil constituents of predetermined melting point or solidioation Ipoint range.

If desired, only a portion of the total solvent liquid may be mixed initially with the fatty oil and this partially diluted mix-ture chilled to approximately the filtering temperature, the remainder of the solvent liquid prechilled to the filtering temperature being added -to the partially diluted mixture prior to filtration. l

In any case, the mixture brought to the desired filtering temperature is passed to a filter 6 advantageously -comprising a hollow rotating cylinder or hollow rotatin-g leaves covered with filter cloth with means for creating vacuum within the interior of the filter element or for exerting positive pressure upon the exterior thereof.

The liquid phase is separated from the feed mixture as filtrate which is discharged through a pipe l to a receiver 8, while the solid phase is retained on the filter cloth as a filter cake and discharged from the filter through a conduit 9 rto a receiver III.

As will be explained later, the filter cake is washed in situ with additional solvent liquid which m-ay be introduced to the filter through the pipe I I. The resulting wash filtrate is usually removed from the filter as a separate stream through a pipe I2 discharging into a receiver I3. This wash filtrate is advantageously used for mixing with fresh fatty oil feed to the system.

The interior of the filter 6 is maintained at approximately the same temperature as that of the entering feed mixture. This is accomplished by circulating gas through the filter. Thus, an inert gas such as flue gas is drawn from a storage tank I4 by means of a blower I5 and passed through a heat exchanger I6 wherein the gas is brought to the desired temperature. From the heat exchanger I6 the gas is passed through a pipe I1 into the hood of the filter 6 and is discharged from the interior of the lter through the filtrate discharge pipes 1 and I2. The discharged gas is removed from the receivers 8 and I3 and may be returned to the suction side of the blower I5 as indicated.

If necessary the circulating gas may be scrubbed with a suitable liquid medium to remove moisture. Moreover, the scrubbing medium may also serve in the capacity of a cooling agent when it is desired to reduce the temperature of the gas.

The filtrate drawn of from the receiver 8 may be discharged through a pipe 2li leading to a solvent recovery unit 2l. This unit may comprise a still and other auxiliary apparatus adapted for stripping the solvent liquid from the fatty oil.

On the other hand, the filtrate may be conducted through a pipe 22 to a. succeeding stage ent solvent or in the presence of the same solvent f but in different proportion so as to effect precipitation of another fraction consisting of constituents of the fatty oil feed.

As indicated, a portion of the filtrate may be recycled through a pipe 23 to theL feed mixture. The recycled material may be mixed with the feed after passage of the feed through the chilling system. or may be mixed therewith at any other point, as for example with the feed entering the mixer 2, or with the stream entering the heater l.

The filter cake discharged into the receiver I may be drawn off through a pipe 24 to a solvent recovery unit 25 substantially similar to the unit 2I wherein solvent liquid is recovered from the fatty oil products.

Figure 2 shows diagrammatically and in outline a rotary vacuum continuous filter of the type used in Figure 1 with the filtering cycle indicated thereon. The filter surface is shown at 50 and is divided by division strips 5I into a plurality of longitudinal segments about the periphery of the filter. The customary filter valve which controls the application of suction and the supply of pressure blowback gas to the interior of the filtering segments at various stages in the cycle of rotation of the filter is indicated at 52.

Numeral 53 indicates the liquid level of the mixture within the filter bowl. This liquid level may be such as to provide from about 40 to 50% submergence of the filter drum. y

The filter drum rotates in the direction of the arrow 5I and cake formation starts at 55. At this point the filter valve opens to communicate suction to the filtering surface, which suction continues throughout the extent of the immersed portion of the filter to provide the pick up" or cake forming area 56.

The filtrate from this section isr discharged through the filtrate line as previously described. As the filter segments consecutively emerge from the filtering mixture their communication with filtering outlet is cut oil' at 58; and after a short rotation, communication with the washing and drying discharge port of the valve is initiated at 59. The action of the vacuum then creates a pressure differential on the filtering surface which causes a chilled gaseous atmosphere surrounding the filter to act upon the cake during the drying stage 60 to drain or strip retained liquid phase from the cake. The washing of the drained cake then commences as indicated at 5 I The wash solvent liquid is introduced to a Weir trough or pipe 62 which is mounted to extend longitudinally throughout the length of the filter, being supported in any suitable manner corresponding approximately to the zenith of rotation of the filter drum. Wash solvent is continuously supplied to the Weir through the previously mentioned pipe I I so as to maintain a continuous overflow at the Weir 53. Additional wash solvent may also be supplied to the cake by means of sprays. Hence an unbroken sheet or film of wash liquid is caused to flow over the filter cake in a direction opposite to the direction of the filter rotation. -Suflicient wash liquid is supplied so as to maintain this thin liqud film over the exposed portion of the filter cake substantially throughout the extent of the washing zone indicated at 65.

The pressure differential existing upon opposite sides of the cake and liquid film causes the wash liquid to ow into the cake and displace remaintity of wash liquid supplied and the extent of the washing zone is such as to obtain substantially complete displacement of retained liquid fatty oil solution from the filter cake.

Following the washing zone the cake is sub- Jected to further pressure differential during the drying stage 58 at which time cold gas from the atmosphere surrounding the filter and supplied from the previously mentioned heat exchanger I5 is drawn through the filtering surface to displace Wash solvent as well as to maintain the filtering surface at approximately the same temperature as the feed mixture entering the filter from the previously mentioned chiller 5.

The liquids and gases drawn through the filter during passage from 59 to 81, at which latter point the discharge passage is closed by the valve, are discharged through the wash filtrate pipe I2.

A full block 8B separates the termination of the vacuum and initiation of the pressure blowback at 69. At this point chilled gas under pressure is discharged through the passage in the valve to the interior of the segments of' the filter causing a slight distention and movement of the filter cloth indicated at 10. This assisted by the scraper 'II serves to remove the formed and dried filter cake.

The reverse flow of chilled gas or blowback terminates at l2 and the full block indicated at 13 separates the termination of the cake discharge zone from the beginning of the cake forming zone at 55 whereupon the cycle is repeated.

Operation of the invention will now be described by reference to the following example in which an acidulated soya bean oil having an API gravity of 25.4, titer test of about 70 F. and iodine number (Wijs) of about 135 is subjected to successive filtrations.

One volume of oil is mixed with between 2 and 3 parts of acetone and the resulting mixture chilled at a rate of about 1.5 to 2 F. per minute to a temperature level of about 0 to plus 5 F. thereby crystallizing out solids consisting essentially of the saturated acids, stearic and palmitic.

After or during chilling suiiicent filtrate from the subsequent primary filtering operation is added to the mixture in order that the solid content is adjusted to permit formation of not more than a one-quarter inch cake Within the cake forming time on the continuous filter when allowing suiiicient time to supply the amount of wash solvents specified below. Under this condition, which is most important for successful operation of the process, the mixture is passed to a continuous rotary filter as described in connection with Figures 1 and 2 so as to separate the liquid phase as filtrate and the solid phase as filter cake. The filter cake is washed in situ with additional acetone, chilled to about 0 to plus 5 F. temperature, in the proportion of about 1.5 to 2 volumes of wash solvent per volume of fatty oil charged to the filter.

The filter cake discharged from the filter and after removal of the solvent -liquid amounts to 'about 10.0% by volume of fatty oil feed and is characterized by having a titer of about F. and an iodine number of' about 3.

The filtrate on the basis of being free from solvent will thus amount to about 90.0% by volume of the initial charge oil and is characterized by having a titer of about 24 F. and an iodine value of about 150.

A portion of the filtrate is recycled to control per cent of solids as previously described. The remainder of the filtrate, without removal of solvent, is then passed to a second stage wherein it is chilled to a temperature of about minus 35 to minus 45 F. following the same procedure as previously described. In this operation a second filter cake amounting to about 41% by weight of the original fatty oil feed isobtained. It will consist essentially of oleic acid and is characterized by having a titer of about 65 F. and an iodine number of 70. The second filtrate on the basis of being solvent free will thus amount to about 49% of the original fatty oil feed and will consist of oil having a titer in the range minus 4 to plus 3 F. and having an iodine value in the range 164 to 170. Recycling of filtrate may also be necessary to control per cent solids in the feed to the second stage filtration.

While the first filter cake and filtrate and also the second precipitate have been described as having specific values for titer and iodine number nevertheless it is contemplated that the operation may be regulated so as to produce fractions having tests varying somewhat from those specified. For example, the'filter cake produced in the first filtration may consist of fatty oil material having a titer in the range 115 to 125 F. and an iodine number in the range to 25; while the filtrate produced in the initial filtration may contain oil having a titer in the range to 24 F. and an iodine number in the range 140 to 160.

Likewise the filter cake produced in the second filtration may have a titer in the range 59 to 95 F. and an iodine number in the range 50 to 100.

The solidication point or titer of the fatty oil substances comprising the filter cake is materially affected by the presence of small amounts of either lower or higher melting point constituents of the fatty oil, particularly in view of the fact that mixed fatty acids apparently form eutectic mixtures in which the melting point of the mixture of any two acids may be considerably lower than the melting points of the individual acids. For example, the mixture of palmitic and stearic acids obtained in the lter cake from the first filtration described in the above example may have a, melting point of about 125 F. whereas the melting points of palmitic and stearic acids are about 145 to 157 F. respectively.

Accordingly, it is important to realize effective displacement washing of the filter cake prior to discharge from the filter and for this additional reason it is desirable to form on the filter a filter cake which is susceptible to effective washing in situ. As mentioned earlier the forming of such cake is dependent upon controlling the ratio of solids to liquids in the liquid and solid phase mixture passing to the filter. One method of adjusting this ratio is by recycling of filtrate as previously disclosed. In some instances the recycled filtrate may amount to as much as 2 to 3 volumes per volume of fatty oil feed to the process.

Although soya bean oil has been referred to in the foregoing example, nevertheless it is contemplated that the procedure of this invention is applicable to treatment of other vegetable and animal oils including corn oil, palm oil, cocoanut oil, rape oil, walnut oil and sardine oil. The process may be Aapplied to the crude oil or to any desired portion thereof. As previously intimated the crude oil or a fraction thereof may be saponified by treatment with caustic. the resulting saponified acid constituents separated, and thereafter treated with mineral acid so as to obtain a free fatty acid mixture. The free fatty acid mixture may be subjected to fractionation by the process of the present invention. Alternately essentially free fatty acids may be obtained by the well known pressure splitting of fats.

It may be applied to fatty acid mixtures prepared from any source as by the oxidation of paraffin hydrocarbons, an example of which would be the products obtained by oxidizing petroleum wax.V

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the separation of solidifiable constituents from fatty substances contained in fatty oil by continuous vacuum filtration in the presence of a solvent liquid from which solidifiable constituents can be crystallized .without substantial alteration in their essential state, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a filter cake of solids in a continuous recurring cycle, the steps comprising chilling said fatty substance mixed with a solvent comprising aliphatic ketone to a filtering temperature lat which crystallization of def sired solidifiable constituents occurs, forming at said filtering temperature a chilled mixture comprising a liquid phase of noncrystallized fatty constituents dissolved in solvent and a solid 'phase of crystallized fatty constituents, said solid phase amounting to from about 2 to not in excess of about 6% by volume of the liquid phase at said filtering temperature, passing a stream of said mixed phases, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum drum filter with the filter drum about 40 to 50% submerged in the filtering mixture, separating liquid phase as filtrate and forming a filter cake of solid phase. washing said filter cake in situ to displace retained liquid phase, continuously discharging filtrate from said filter, and continuously discharging washed filter cake from the filter substantially free from fatty constituents solidifying below and above said filtering temperature,

2. In the separation of saturated fatty acids from a mixture of saturated and unsaturated fatty acids having from about 12 to 18 carbon atoms per molecule by continuous vacuum filtration in the presence of a solvent liquid, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a filter cake or solids in a continuous recurring cycle, the steps comprising chilling said fatty acid feed mixed with a solvent comprising an aliphatic ketone to a'filtering temperature at which crystallization of desired solidifiable constituents occurs, forming at said filtering temperature a mixture comprising a liquid phase of saturated fatty acids dissolved in solvent and a solid phase of crystallized saturated acids, said solid phase amounting to from .about 2% to not in excess of about 6% by volume of the liquid phase at said filtering temperature, passing a stream of said phase mixture, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum filter with the filter drum about 40 to 50% submerged in the filtering mixture, separating liquid phase as filtrate and forming a filter cake of solid phase, continuously discharging flltrate from said filter and continuously discharging the washed filter cake -comprising saturated acid substantially free from unsaturated acids.

3. The method according to claim 2 in which the solvent comprises a low molecular weight aliphatic ketone and the filtration is eected at a temperature of about F.

4. In the separation of solidiiiable constituents from a fatty oil mixture by continuous vacuum filtration in the presence of a solvent liquid, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a lter cake of solids in a continuous recurring cycle, the steps comprising mixing soybean fatty acids with from about 3 to 5 .volumes of a low molecular weight ketone, heating the mixture to effect complete solution of oil in the solvent, chilling the solution to a filtering temperature in the region of about 0 F. so as to form a mixture of fatty oil and solvent comprising a liquid phase of fatty oil dissolved in the solvent and a solidA phase consisting essentially of stearicv and palmitic acids, said solid phase amounting to about 2 to 6% by volume of the liquid phase at said filtering temperature, passing a stream of said mixed phases, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum drum filter with the filter drum about 40 to 50% submerged in the filtering mixture, separating liquid phase as filtrate and forming a filter cake of solid phase, washing said filter cake in situ with additional solvent at about said filtering temperature to displace retained liquid phase, continuously discharging filtrate from said filter and continuously discharging Washed filter cake from the filter substantially free from fatty oil constituents other than said stearic and palmitic acids.

5. In the separation of solidifiable constituents from a fatty oil mixture by continuous vacuum filtration in the presence of a solvent liquid, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a filter cake of solids in a continuous recurring cycle, the steps comprising mixing soybean fatty acid with about 4 volumes of acetone, heating the mixture to eect complete solution of oil in the solvent, chilling the solution to a filtering temperature in the region of about 0 F.

so as to form a mixture of fatty oil and solvent comprising liquid phase of fatty oil dissolved in the solvent and a solid phase consisting essentially of stearic and palmitic acids, said solid phase amounting to about 2 to 6% by volume of the liquid phase at said filtering temperature, passing a stream of said mixed phases, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum drum filter with the filter drum about 40 to 50% submerged in the filtering mixture, separating liquid phase as filtrate and forming a filter cake of solid phase, washing said filter cake in situ with additional acetone at about said filtering temperature in the proportion of about ll/l to 2 volume of acetone per volume of soy-bean oil charged to the filter to displace retained liquid phase, continuously discharging filtrate from said filter and continuously discharging washed filter cake from the filter substantially free from fatty oil constituents other than said stearic and palmitic acids` 6. In the separation of solidiiiable constituents from a mixture of fatty substances contained in fatty oil by continuous vacuum filtration in the presence of a solvent liquid from which solidifiable constituents can be crystallized without substantial alteration in their essential state, said ltration involving forming, washing, drying on,

and discharging from a rotating drum fllter surface a filter cake of solids in a continuous recurring cycle, the steps comprising dissolving said mixture of fatty substances in a solvent comprising an aliphatic ketone, chilling the solution to a filtering temperature such as to effect crystallization from the solution of fatty constituents of desired relatively narrow solidiflcation point range, passing the resulting chilled mixture of solid and liquid phases to a continuous rotary drum vacuum filter with the filter drum about 40 to 50% submerged in the filtering mixture, maintaining the solid phase uniformly dispersed throughout the liquid phase and in the proportion of about 2 to 6% by volume of the liquid phase in the mixture undergoing filtration such that a filter cake is formed which is not less than about M; inch and not more than about 5/4 inch in thickness, separating liquid phase as filtrate, washing said filter cake in situ with additional solvent at about said filtering temperature to displace retained liquid phase, continuously discharging filtrate from said filter and continuously discharging washed filter cake from the filter substantially free from fatty constituents solidifying below and above said filtering temperature.

7. In the separation of solidiflable constituents from fatty substances contained in fatty oil by continuous vacuum filtration in the presence of a solvent liquid from which solidiable constituents can'be crystallized without substantial alteration in their essential state, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a filter cake of solids in a continuous recurring cycle, the steps comprising chilling said fatty substance mixed with said solvent to a filtering ternperature at which crystallization of desired solidifiable constituents occurs, forming at said filtering temperature a chilled mixture comprising a liquid phase of non-crystallized fatty constituents dissolved in solvent and a solid phase of crystallized fatty constituents, said solid phase amounting to about 2 to 6% by volume of the liquid phase at said filtering temperature, passing a stream of said mixed phases, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum drum filter, separating liquid phase as filtrate and forming a filter cake of solid phase, washing said filter cake in situ to displace retained liquid phase, continuouslv discharging filtrate from said filter, and continuously discharging washed filter cake from the filter substantially free from fatty constituents solidifying either below or above said filtering temperature,

8. In the separation of solidiflable constituents from a mixture of fatty substances contained in fatty oil by continuous vacuum filtration in the presence of a solvent liquid from which solidiflable constituents can be crystallized without substantial alteration in their essential state, said filtration involving forming, washing, drying on, and discharging from a rotating drum filter surface a filter cake of solids in a continuous recurring cycle, the steps comprising dissolving said mixture of fatty substances in said solvent, chilling the solution to a filtering temperature such as to effect crystallization from the solution of fatty constituents of desired relatively narrow solidiflcation point range, passing the resulting chilled mixture of solid and liquid phases to a continuous rotary drum vacuum filter, maintaining the solid phase uniformly dispersed throughout the liquid phase in the proportion of about 2 to 6% by volil ume of the liquid phase in the mixture undergoing filtration such that afilter cake is formed which is not less than about Va inch and not more than about V4 inch in thickness, separating liquid phase as nitrate, washing said iilter cake in situ with additional solvent at about said filtering temperature to displace retained liquid phase, continuously discharging nitrate from said filter and continuously discharging Washed filter cake from the filter substantially free from fatty constituents solidifying below and above said filtering temperature.

9. In the separation of solidifiabie constituents from a fatty oil mixture by continuous vacuum nltration in the presence of a solvent liquid from which solidiiiable constituents can be crystallized without substantial alteration in their essential state, said filtration involving forming, washing, drying on and discharging from a rotating drum filter surface a filter cake of solids in a continuous recurring cycle, the steps comprising chilling said fatty oil mixed with said solvent to a ltering temperature at which crystallization of desired solidiiable constituents occurs, forming at said illtering temperature a mixture of fatty oil and said solvent liquid comprising a liquid phase of fatty oil dissolved in solvent and a solid phase of crystallized fatty constituents, said solid phase amounting to about 2 to 6% by volume of the liquid phase at said filtering temperature, passing a stream of said mixed phases, the solid phase being uniformly dispersed throughout the liquid phase, to a continuous rotary vacuum drum filter with the i'llter drum about 40 to 50% submerged in the filtering mixture, separating liquid phase as filtrate and forming a filter cake of solid phase, washing said filter cake in situ to displace retained liquid phase, continuously discharging filtrate from said filter, and continuously discharging washed filter cake from the filter substantially free from fatty constituents soiidifying below and above said filtering temperature.

WILLIAM P. GEE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,974,542 Parkhurst Sept. 25, 1934 2,107,664 Gee Feb. 8, 1938 2,166,891 Gee July 18, 1939 2,228,040 Voogt et ai. Jan. 7, 1941 2,288,441 Ewing June 30, 1942 2,248,668 Gee July 8, 1941 2,293,676 Myers et al Aug. 18, 1942 2,356,346 Packie et al. Aug. 22, 1944