US3239547A - Process for deodorizing fats and oils by distillation with steam under vacuum conditions - Google Patents

Description

March 8, 1966 D. J. BRION ETAL 3,239,547

PROCESS FOR DEODORIZING FATS AND OILS BY DISTILLATION WITH STEAM UNDER VACUUM CONDITIONS Filed Aug. 1, 1961 United States Patent O PROCESS FOR DEODORIZING FATS AND OlLS BY DISTILLATION WITH STEAM UNDER VACUUM CONDITIONS Denis J. Brion, Richmond, Va., and Richard I. Fiala, Decatur, Ill., assignors to A. E. Staley Manufacturing Company, Decatur, Ill., a corporation of Delaware Filed Aug. 1, 1961, Ser. No. 128,443 4 Claims. (Cl. 260-428) This invention relates, generally, to an improved method of controlling the content of oil and fat deodorizer distillates in condensate water and to the recovery of such distillates therefrom. The invention relates more particularly to the recovery of vegetable oil distillates (e.g., `soybean oil distillates) which form emulsions in the condensate water used in removing and recovering such distillates from deodorizer vapors. The use of water-soluble proteins, notably corn steep water, to break such emulsions and effect the recovery of the distillates therefrom constitutes an important feature of the invention.

Large quantities of vegetable oils are deodorized during the refining thereof in the vegetable oil industry. Such oils include soybean oil, corn oil, peanut oil, and cottonseed oil. In general, the deodorization of such oils is accomplished by introducing steam into them while they are maintained under vacuum. The high vacuum, steam deodorization of vegetable oils may be carried out either as a batch operation or in a continuous manner, the trend in the industry being toward installation of continuous deodorizers which operate under very high vacuums.

The vapors which come oit lduring deodorization (i.e., treatment with steam and under vacuum) whether -a batch or continuous process, contain so-called vegetable oil distillates (VOD) which are valuable by-products and, which it not recovered, often pose problems from the standpoint of waste disposal and stream polution. While the vege- -table oil distillates -are relatively easily condensed, they have posed a problem in the industry in that they form oil land water emulsions which become highly viscous and difficult to handle when the concentrations of the distillate in water exceeds about 2%. This problem of removal and recovery of vegetable oil distillates from condensate water or scrubber water is discussed by R. I. Piala in a paper entitled A Commercial Process for the Recovery of Deodorizer Distillates, appearing in the September, 1959 issue of the Journal of the American Oil Chemists Society and in his Patent 3,061,622, dated October 30, 1962. In that `article a commercial type of vapor scrubber was referred to which has found good acceptance in the industry for scrubbing the vapors from Vacuum deodorizers so as to remove 99-l% of the vegetable oil distillates therefrom. This vapor scrubber is known by lthe l,trade name Convactor and is manufactured by Groll-Reynolds Co., Inc., of New York, New York. This particular apparatus includes -a scrubber section wherein eluent deodorizer vapors are intimately mixed with cool scrubber water with complete condensation occurring, followed by flashing of water, equivalent to the steam content of the deodorizer vapors, and subsequent delivery of the clean steam into a barometric condenser. The scrubber water has condensed therein the organic materials evolved during deodorization, referred to as vegetable oil distillates and comprised for the most part of sterols, tocopherols, free fatty acids (5S-65%) and neutral oils. Other vapor scrubbing apparatus of known type may also be used in lieu of the so-called Convactors.

While the Convactors or other distillate scrubbing and condensing equipment provides for eicient removal of the vegetable oil distillates from the deodorizer vapors, heretofore it has been not practical to operate such apparatus except at very low concentrations of the distillates 3,239,547 Patented Mar. 8, 1966 ICC in the condensate or scrubber water. As long as the concentrations of the vegetable oil distillates in the condensate water remains low, e.g., not over about 1%, the emulsions which forms are highly fluid, pumpable liquids very much resembling ordinary milk in appearance and iluidity, but containing a small amount of curd-like flocs of the organic material. However, as the concentration of the organic material increases toward 2%, the curd-'like flocs become thicker and the emulsion lbecomes less fluid and increasingly less pumpable. Finally, when the concentration of the distillates or oil organic material rises above about 2%, the lloc becomes so thick that the emulsion no longer exhibits Newtonian tlow but instead it resem-bles a material like mayonnaise which does not exhibit ordinary lluidity and cannot be pumped and circulated in the usual manner that water and similar lluids can.

If the emulsion its allowed to approach or reach this mayonnaise-like stage, then operation of the Convactor or other scrubbing equipment has to cease and the contents cleaned out before operation can be resumed with fresh water.

In the above mentioned technical paper of R. I. Fiala, a practical method of controlling the concentration of vegetable oil distillates or organic material in the Convactor circulating water is described which has served to avoid excessive build up of the distillate concentration in the scrubber water and to keep it at a safe operating level. Briefly, the Fiala method involves bleeding olf a stream of the scrubber water from the circulating system of the Convactor and after heating the stream to a temperature sufficient to break the emulsion, passing it into a separator such as a centrifuge. The vegetable oil distillate separates out as the non-aqueous or oil phase and is collected while the clean water phase that separated out as the aqueous phase is returned back to the Convactor system. However, since it is not safe to permit the vegetable oil distillate content to build up in excess ot about 1.5% by weight in the scrubber or Convactor water, the success of the Fiala method depends on diverting a large enough quantity of the Convactor w-ater to the centrifuge to keep the organic level below about 1%.

It was discovered in accordance with the present invention that substantial improvements could be obtained in the treatment procedure described in the Fiala paper by incorpo-rating in the scrubber or condensate water of the Convactor or similar apparatus a small amount of a water-soluble protein material, `corn steep water being a preferred such material. Thus, by maintaining a concentration of from 0.1 to 0.2% water soluble protein in the scrubber or condensate water of the Convactor or other vapor scrubber apparatus the build-up of vegetable oil distillates in the scrubber water can be permitted to rise substantially above the prior safe level of 1.5% to 2%, even up to as much as 25% before the pumpable klluidity is interfered with. Furthermorea with this minor content of water soluble protein being maintained a true emulsion does not form and the vegetable oil distillate is readily separated -and recovered from the condensing water.

One of the principal advantages of the present invention is that the concentrations of the vegetable oil distillates in the scrubber water can be satisfactorily maintained at or below a safe level simply by subjecting only a small stream of the condensate water to the separation treatment of 4this invention for say only six hours out of twenty four hours of continuous operation. Of course, with separating equipment of larger `capacity this time could be 'further reduced. Conversely, by operating smaller equipment for longer periods the safe level can also be readily maintained.

While the present invention is particularly useful in connection with controlling the vegetable oil distillate content and build-up in condenser or scrubber water and recovering the same therefrom, it has application to the control and recovery of deodorizer distillates of other oils and fats, including animal oilsand fats.

The object of the present invention, generally stated, is the provision of an improved meth-od of controlling the content and build-up of oil and fat ydeodorizer distillates in condensate or scrubber waters, and the recovery of the same therefrom.

An important object of the invention is the provision of such a method of control and recovery which is more efficient than prior methods in that: (l) higher levels of concentration of the oil and fat deodorizer distillates may be allowed to accumulate in the condensate or scrubber waters without endangering the operation Iof the scrubber apparatus because of an increase in the viscosity of the scrubber water beyond the pumpable stage; (2) smaller volumes of the scrubber water need to be treated for shorter periods; and (3) the cost of treating material (i.e., water soluble protein) is so small as to be almost negligible; and (4) heating costs are reduced.

For a more complete understanding of the nature and scope yof the invention reference may now be had to the following detailed description thereof taken in connection with the accompanying drawing wherein, the single figure constitutes a flow diagram in connection with which one working example or embodiment of the invention will be described.

Referring to the flow diagram, the left-hand portion thereof illustrates a known type of deodorizer which operates continuously under a high vacuum, such as a Girdler semi-continuous deodorizer. Oil to be deodorized is delievered into the top portion of the deodorizer through a line and is subjected to steam treatment under varying temperature conditions as it ows into and through a series of troughs 11 into each of which live steam is delivered through a series of pipes 12. The deodorized `oil is taken olf at the bottom of the deodorizer through a line 13.

The distillates and steam mixture constituting the effluent from the deodorizer is discharged therefrom through a connection 14 and moves through a first stage booster jet 15 in the form of a venturi operated by steam injected through the line 16. The vapors then move through a second stage booster jet 17 which is operated by steam injected thereinto through a line 18. The steam injected into the booster jets 15 and 17 aid in maintaining the high vacuum under which the deodorizer is operated and in this manner the eluent vapors of the deodorizer including incondensables, organic condensables and steam are delivered into the distillate condenser through an inlet 19.

The distillate condenser illustrated is of the Convactor type described above and, by way of example, consists of a 33t-foot black iron tower which is designed for a dual purpose. The first purpose of the tower is to remove the non-volatile organic material from thedeodor-l izer efuent vapors and the second purpose is to condensate and discharge the jet exhaust steam and deodorizer blowing steam. The tower is divided into two specific.

sections, an upper barometric condenser section and a lower vapor scrubber section. These two sections are joined by a vapor balance line which allows steam and high volatile organic compounds in the scrubber section to Hash to the barometric condenser.

The deodorizer eiuent vapors enter the upper portion of the scrubber condenser section and are deected downwardly through a curtain of relatively cool scrubber condensing water `delivered into the scrubber section through a line 20. The condensing water is maintained in a closed-circuit system to provide for continuous recirculation thereof through the scrubber section of the tower. This section at the bottom thereof includes a reservoir containing a supply -of condensing water the level of which is maintained by a level control operating a valve 21 disposed in a make-up water supply linel 22 ;which feeds fresh water into the reservoir for level maintenance pur-y poses. In recycling, the condensing water is taken out from the bottom of the reservoir through a line 23 by a pump 24 placedtherein and delivered through a line 25 the Yrelatively cool condensing water, the organic material and steam is condensed resulting in a raising. of the temperature of the condensing watervby the transfer :of .latent heat. The heated condensing water then falls through a water collecting cone 26 constitutingy the bottom portion of the upper section of the scrubber and in communication at the base thereof with a flash chamber.- plate 27 is located at the base `of the conet26l in the flash chamber to provide for ecient flashing of the more volatile materials from the condensing water. The Iflash chamber is in communication withv the` upper barometric condenser section through the vapor balancev line isthus at a slightly reduced pressure as the barometric condenser operates at a slightly reduced pressure relative to the scrubber section. The more yvolatile materials including the incondensables will flash from the condensing water until thermodynamic equilibrium has once more been attained. Thisy procedure, therefore, leaves only the nonvolatile organics in the once. again cool condensing water with this water falling into the reservoir for recirculation through the tower., The heat-picked up bythe condensing water is immediately dissipated by lrapid evaporation orr flashing of the volatilestherefrom, this evaporation taminants andk rise throughY the vapor balance line to be.

condensed in the barometric condenser. The ashed material is approximately equalr to the sum ofthe deodorizer blowing steam plus the jetfexhaust steanrdelivered through the lines 16 and 18. Condensing Water is supplied through line 28 to the barometric condenser section and is removed through line 29 as waste or for any suitable treatment. The vacuum in the barometricI condenser section is drawn by theutilization of a booster jet 30 voperated by steam delivered through a line 31 and any effluent vapors taken from the barometric. condenser section ofthe tower are ,delivered intoa smaller condenser connected to the discharge end of thej'et30 from which liquid discharge to a vdrain is handled through a line 32. Vacuum is maintained on the smaller dischargefcondenser by a booster jet 33 operated by steam delivered thereinto through a line 34 with the subsequent steam and vapors being discharged vin any suitable `manner through a line:

35, normally to the atmosphere.4

The net result of the foregoing operation ispthe removal of the organic distillates from the deodorizer vapors and i concentration of these distillates in the condensing water in the scrubber section of the tower. These distillates, Including the physical entrained solids, consist of varying amounts of fatty acids, glycerides, sterols, and; tocopherols. As these materials are relatively immiscible;

with the water in which they arecondensed, the accumulation in the-condensing water'takes the form of an oilin-water emulsion. Several distinct phases occur in the condensing water as the concentration of organic dis-y dride degummed soybean oil which is break-'free but conf A iflash This excess flashis continuously' tains about 0.2% to 0.3% free fatty acids, such as produced according to the method disclosed in Patent No. 2,782,216.

With the type of oil described, t-his being generally representative of various types of fatty oils, the condensing water becomes a turbid w-hite, resembling milk, with between 0% and 0.15% organic ydistillates condensed therein. The fluidity characteristics, as measured by viscosity, are not greatly different from pure Water during this phase. Between 0.15 and 1.0% concentration, the organic materials begin to associated, forming solidaggregates or ocs which fioat on the condensing water. This phase is characterized by a gradually increasing viscosity although the thickening does not materially affect the ilow properties of the water. Within the concentration range of about 1.0% to 1.5%, the flocculent organic solids become dense causing the water viscosity to increase more than a 100%. In this phase the fluidity characteristics of the water are greatly reduced. With a concentration exceeding 1.5% a gelling action occurs and the water cannot be pumped with the result that the tower becomes inoperative.v

As indicated above, the present invention provides a new and improved met-hod of controlling the concentration of organic distillates in the condensing or condensate Water so as to prevent the organic distillate content from resulting in an increase in viscosity to the point that the scrubber or condensing water cannot be readily recirculated. Basic to the improved method of the present invention is the addition and maintenance of a small per cent of a water soluble protein material in the scrubber or condensing water.

Referring again to the flow diagram, a small portion of the scrubber or condensing water which is being continuously recirculated through line 25 is periodically bled off through line 36 to the inlet connection of a pumpg37 which feeds a centrifuge 38. The pump 37 discharges through a line 40 to the feed inlet of the centrifuge 38. Line 40 is provided with a rotarneter, other flow measuring device 41 connected in a by-pass line 42. A steam injection line 43 having a control valve 44 is also connected in line 40 upstream from an indicating thermometer 45. The oil phase discharge connection 46 of the centrifuge 38 ydischarges through a line 47 into an organic distillate storage tank. If line 47 is exposed to cold temperatures it should be provided with an external heater so that the stream of organic distillates may be maintained fluid at all times.

Clean water discharging from the aqueous discharge connection 48 passes downwardly through line 50 into a water surge tank 51 provided with a liquid level control means such as the conventional oat control indicated 49 operatively connected with flow control valve 56 in the return line 54. A clean water recycle pump 52 has its inlet connection connected with the bottom of the tank 51 by way of a line 53. The discharge connection of the pump 52 communicates by way of the line 54 to an inlet connection 55 in the bottom of the reservoir portion of the Convactor. The flow control valve 56 in line 54 is regulated by the float 49 or other liquid level sensing means in the tank 51 s-o as to maintain the water level in tank 51 between predetermined operating levels.

The following working example will more fully inform those skilled in the art of the nature of the invention and a preferred embodiment thereof.

Example vThis example is a description of a satisfactory operating procedure for the plant described in the accompanying llow diagram wherein the deodorizer is being utilized on a round-the-clock basis to deodorize soybean oils which has already been degummed so as to be breakfree, by treatment with acetic anhydride in accordance with the method disclosed in Patent No. 2,782,216.

The distillate condenser tower of the Convactor operates with the condensing water in the lower scrubber section in equilibrium wit-h the barometric condenser portion at a temperature within the range of to 105 F. The body of condensing or scrubber water (e.g., 15,000-16,000 lbs.) is recirculated through the line 25 at an average rate of about 1075 gallons per minute (g.p.m.). By means of prior addition and occasional make-up as periodic (e.g., weekly) tests indicate to be necessary, a concentration in the range of from 0.1 to 0.2% by weight of protein is maintained in the condensing or scrubbing water. The occasional addition of make-up protein can be conveniently made either at the water surge tank 51 or With makeup water through line 22. A highly satisfactory source of water soluble protein for this purpose has been found to be corn steep water or corn steep liquor, a well known material in the corn wet milling industry and described, for example, in a paper by R. Winston Liggett and H. Koi-ller entitled, Corn Steep Liquor in Microbiology, in Bacteriological Reviews, vol. 12, No. 4, December 1948. So-called heavy pure steep water contains about 12.5 to 15% protein and has been used with complete success in the practice of the present invention.

By maintaining a level of concentration of from 0.1 to 0.2% of the water soluble protein in the condensing or scrubber water, it is necessary to only operate the centrifuge 38 siX hours out of every twenty-four hours of operation of the Convactor. In starting up the 6- hour treatment of the condensing or scrubber water, the centrifuge 38 is rst brought up to full speed. In the case of a Sharples D2 centrifuge this requires about 10 minutes time. When the centrifuge 38 is up to speed then the centrifuge feed pump 37 is started and the ilow of Water through the line 40 is adjusted by means of observing the rotameter 41 until it equals approximately 10-15 g.p.m. Steam is added through line 43 until the steam temperature obtains a value between 15G-160 F. as indicated by the thermometer 45. Good separation of fatty material and water is readily obtained in the centrifuge 38.

During operation, the centrifuge discharges the oil or fatty material consisting of the organic distillates through the connection 46 into the line 47 so that they accumulate in the storage tank provided therefor. The pump 52 operates to return the separated clean Water to t-he Convactor as it accumulates in the tank 51, the flow rate being controlled by means of the valve 56. The heat content of the clean water is thus dissipated in the Convactor unit.

It Will be seen that a number of variations can be made in the above described example, in practicing the present invention. The following specific variations or changes will be mentioned with the understanding that still others will be suggested to, and occur to, those skilled in the art:

(a) Instead of adding steam line 43, the liquid steam going to the centrifuge may be heated by means of a heat exchanger disposed in line 40.

(b) The temperature of the liquid steam going to the centrifuge may be adjusted within the operable range of to 250 F. The narrower range of 150-160 F. is preferred in that heating costs are low and the temperature is sufficient to keep the vegetable oil distillate melted so that separation in the centrifuge is facilitated.

(c) A centrifuge of less capacity than that of centrifuge 38 may be used to control the concentration or buil-d-up of organic distillates in the condenser or scrubber water within proper operating range by running it for longer periods, including continuous operation if necessary.

(d) Conversely, by using a centrifuge of increased capacity, proper control over the concentration and buildup of the organic distillates in the condensate or scrubber water may be maintained while operating for shorter periods of time.

(e) Instead of operating the centrifuge 38 `for 6 -hours out of every three shifts, it could be operated l2 hours continuously during every siX shifts.

(f) While the preferred range of concentration of water soluble protein the condensate or scrubber water is from 0.1 to 0.2% as above mentioned, it is possible to` operate satisfactorily with as little las 0.05%. It is also possible to operate the system with higher concentrations, such .for example as 0.5% water soluble protein. i

(g) Instead of using corn steep water as the source of water soluble proteins, other source materials therefore could be used including egg albumen, gelatin, and pep tone. Also water soluble proteins can be inexpensively obtained from such materials as casein and soybean meal.

The foregoing and other modifications and variations may be adopted in practicing the invention without departing from the spirit and scope of the invention as indicated in the appended claims.

What is claimed as new is:

1. In the process of deodorizing fats and oils by distillation with steam an-d under vacuum wherein the organic distillates are condensed in a scrubber in recirculating water in which ocs form that are emulsionsof said distillates in water, said ocs -decreasing the liuidity of the condenser water substantially as the concentration of distillates increases toward a value on the order of 2%,` the improvement for suppressing the effect of said flocs on the tluidity of the condenser water as the concentration of distillates approaches and exceeds said 2% value 'that comprises incorporating and maintaining in said condenser water a concentration of water-soluble protein in the range of 0.05% to 0.5%and `permitting the concentration of said distillates in said recirculating water to build up to values several times greater than 2%. v

2. The method of claim 1 wherein the water from said diverted portion is returned to the condenser water.

3. In the process of deo'dorizing soybean oil with steam 8L and under vacuum wherein organic distillates from ,a deodorizer are condensed in ai-scrubberl in vrecirculated condenser Water in which rsaid ldistillates form viscous emulsions at vlow concentrations in the order of about 2%, the improveinentfor controlling the formation of such emulsions and for recovering the distillates fromrsaid condenserA water kwhich comprises introducing and main-v taining a concentration'of water soluble protein in the range of from about 0.05% to 0.5 in the yrecirculated condenser water to permit a build-up of up to about 25% of condensed distillates in the recirculated condenser water heating at least a portion ofrecirculated condenser' water and condensed distillates to facilitate separation ofy distillate material @from the water, separating the distillateI .material from the water,and returning theseparated .water to the scrubberas condenser water.

4. -The method of claim 3 `wherein cornsteep water is used as the source of water soluble proteins.

References Cited by theiExamin'er` UNITED .STATES yPATENTS v OTHER REFERENCES American Oil Chemists Society Journal, v01. 36, September 1959 Fiala; R'. J. (pp. 375-379relied on NORMAN YUDKOFF, Primary Examiner.

ALPHONSO D. SULLIVAN', y Examiner.

Claims (1)

1. IN THE PROCESS OF DEODORIZING FATS AND OILS BY DISILLATION WITH STEAM AND UNDER VACUUM WHEREIN THE ORGANIC DISTILLATES ARE CONDENSED IN A SCRUBBER IN RECIRCULATING WATER IN WHICH FLOCS FORM THAT ARE EMULSIONS OF SAID DISTILLATES IN WATER,SAID FLOCS DECREASING THE FLUIDITY OF THE CONDENSER WATER SUBSTANTIALLY AS THE CONCENTRATION OF DISTILLATES INCREASES TOWARD A VALUE ON THE ORDER OF 2%, THE IMPROVEMENT FOR SUPPRESSING THE EFFECT OF SAID FLOCS ON THE FLUIDITY OF THE CONDENSER WATER AS THE CONCENTRATION OF DISTILLATES APPROACHES AND EXCEEDS SAID 2% VALUE THAT COMPRISES INCORPORATING AND MAINTAINING IN SAID CONDENSER WATER A CONCENTRATION OF WATER-SOLUBLE PROTEIN IN THE RANGE OF 0.05% TO 0.5% AND PERMITTING THE CONCENTRATION OF SAID DISTILLATES IN SAID RECIRCULATING WATER TO BUILD UP TO VALUES SEVERAL TIMES GREATAER THAN 2%.

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