US2110789A

US2110789A - Process of bleaching oils

Info

Publication number: US2110789A
Application number: US150824A
Authority: US
Inventors: Clayton Benjamin; Benjamin H Thurman
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-06-28
Filing date: 1937-06-28
Publication date: 1938-03-08
Anticipated expiration: 1955-03-08

Description

yMarch 8, 1938. la.l CLAYTON ET AL APROCESS oF BLEACHING ons Filed June 28, 193'/ Patented Maa-'8, i938 UNITED STATES.

PROCESS BLEACRING OILS Benjamin clama, nousmn,.rex., alla Benjamin Il. Thurman, Bronxville, N. Y,

' Application June 2.8, 1937, Serial ldd-150,824

' 9 claims.

Crude glyceride oils, such as animal, vegetable anddish oils, usually contain various impurities, l for example, fatty acids, coloring matter, and gums. The fatty acids and gums can be almost completely removed by refining processesemploying caustic soda or other alkaline refining agents.

lSuch reilning processes ordinarily includeyth'e mixing of proper proportions o f a caustic soda solution with the loil so that alkali reacts with the free fatty acldsto form soap and the separation of the Aresultant soapfrom the oil. Most of the-gums present separate with the soap and if the refining process is properly conducted a large part of the coloring matter is likewise lseparated with the soap. The refining process may be continuous or batch and the' soap, along with other impurities, separated from the reiined oil by vcentrifugal separation '-or settling.

usually contains small amounts of soap, water, and free alkali. If the soap and free .alkali are present in appreciable quantities they can be removed by washing with water, as by mixing water with 4the oil either in abatch or continuous process and. then separating the water in which thealkali and soap are dissolved by either a centrifugal or settling operation. 1

In many instances the reilning operation leaves the oil, too highly colored -for an acceptable commercial product and it has been the practice in the art to treat this oil With/a bleaching agent .as by mixing such bleaching agents as fullers earth, acid treated clay or nely divided carbon with the oil and then filtering the bleaching agent 4from the oil. 'I'his method of bleaching or removing ythe nal coloris expensive as large filter presses and large quantities of bleaching agents are required. Also a considerable .proportion of the oil is lost by being retained in the bleaching agent andv discarded therewith. The\present in-l vention provides a process which may be employedin lieu of the conventional processes emplaying bleaching agents or in case the oil is extremely highly colored, it may be employed in addition to treatment with'bleaching agents. In .the latter 'case both the amount oi' bleaching agent and the amount'ofv oil lost in the process lare markedly reduced. n 4

The reiined oil from the above described processv Bassum l Also, in addition to the impurities discussed above, glyceride oils, in many cases, contain volaltile and other impurities which are no t removed by the above described r'e'ning process or in the washing and bleaching steps of the prior art. 5 Certain of these impurities. give the resultant oil an objectionable odor and ilavor or deleteriously aifect the keeping qualities or the oil. These impurities can be removed by vaporization in thepresent process or broken down into other coml0 pounds, which are not objectionable by the temperatures employed. Thus, the oil may be deodorized and improved in flavor and keeping qualities, as well as bleached, by the present invention. If a crude oil is relatively pure or the l5 nature of its intended use does not require a highly refined oil, the present invention may be applied tosuch a crude oil to reduce its color and remove other objectionable impurities, but the invention findsA its greatest utility in bleaching 20 previously refined oils. 7

It is, therefore, an object ofthe present invention to provide an improved process of bleaching glyceride oils.v l

Another object of the invention is to provide 25 an improved process of bleaching previously refined glyceride oils. 1

Another object of the invention is to provide an' improved process of bleaching glyceride oils in which no bleaching agents are required.

A further object of the invention is lto provide a. continuous process of bleaching glyceridev oils in which the oil is subjected to elevated temperatures out of contact with the air and cooled before being brought again in contactwith the air.

A still further object of the invention is toprovide an improved process of bleaching glyceride voils and at the same time removing vaporlzable and other impurities. y

In` accordance with the present invention, the 40 glyceride oil is passed continuously through a heating zone where its temperature-isfrapidly raised 'and wherein it is maintained out of contact with the atmosphere. The temperatures contemplated ,by the present invention are, in general sumciently high that contact with the atmosphere by the heated oil would cause deterioration of the oil. When the desired temperature of the oil has been reached, the oil is quickly cooled to a -temperature at which it will not be deleteriously ailected by contact with the atmosphere by being passed through a cooling zone before it is discharged into contact with the atmosphere, f

The temperatures to which the oil is subjected cannot be precisely stated since they will vary with the type of oil being treated and the amount of bleaching necessary for a particular oil. For

a linseed oil or soya bean oil this temperature may reach 500 to 600 F. while for cottonseed, corn, sesame or other of the more edible oils, temperatures between 420 and 500 F. are usually sufficient. If a slight bleaching only is required, it will be apparent that the temperature to which a -given oil is subjected may be somewhat lower.

The bleaching of the oil .appears to be a function of the temperature reached and it is not necessary to maintainl the oil at the high tem; perature over a period of time. If the oil is4 maintained at such high temperature for an extended period of time, polymerization, as well as cracking, may occur with an increase of fatty acid content and the production of an undesirable flavor and darkening of the oil so that satisfactory bleaching. is not accomplished. It is, therefore, desirable to heat the oil as rapidly as possible and then cool the oil .as rapidly as possible.

The pressure in the heating zone will ordinarily be only that-necessaryto force the oil through the zone since 'high pressure is not necessary for the present bleaching process and it is furthermore not necessary to prevent vaporization of 'all of the more volatile constituents pressure than theheating zone-and in some instances the employment of a vacuum chamber is found to be desirable. Even if vaporization has been allowed to occur in the heating zone, discharging the heated oil into a lower pressure or vacuum chamber will cause further vaporization of volatiles and expansion of those already formed so as to cool the oil. With certain oils it has been found that a better bleach is produced by entirely preventing vaporization in the heating zone while with other'oils it has been fou`nd desirabletoemploy a suiiiciently low pressure in the heating zone to provide for vaporization therein. Aside from the cooling effect of vaporization'in cooling the oil after it is discharged from the heating zone, a portion of the coloring matter appears to be removed with the l vapor -along with other vaporizable impurities contained in oil so that it is -desirable to withdraw vapors from the oil while it is in a heated condition or during cooling thereof. urated or superheated steam may be introduced into the expansion 'chamber to assist in the vaporization of the volatilesA and with certain oils it has been found that a better bleach is proa duced by the presence ofY small proportions of Water inthe oil when it is introduced into the heating zone. remaining in the oil after the oil has been refined or after being washed as above described, oradditional Water may be introducedinto the oil before it is heated. Thus, with cerating oils the present process may also Operate to dry the Either sat- This water may either be that oils and it is unnecessary to employ a separate drying step. With other oils it has beenfound desirable to heat them in the absence of moisture in which case a dry oil is employed or the oil is dried before it is heated.

The oil may be further cooled before discharg- Ving the same to the atmosphere by being passed in heat exchange relation with alcooling medium either in the expansion chamber orin an additional chamber so that the temperature of the oil is below that at which oxidation or other deleterious action occurs when it is again contacted with the atmosphere.

A diagrammatic drawing of an apparatus suitable for carrying out the present process is shown in the single figure of *the attached drawing and the process will be described in more detail in connection therewith.

Referring more particularly to the drawing, I indicates a tank for receiving the oil to be bleached, which oil ma be either a crude oil or a previously refined oi As stated above, this oil may be either dry or may contain small portions of water depending upon the type of oil being treated. The oil is withdrawn from tank `I through a pipe 2 in which is positioned a control valve 3 and is forced by a pump 4 through a pipe 5 connected to the .inlet of a heating coil 1 positioned in a heater casing 8. The oil leav- II secured to lthe closed endl'I2 of the hollow member I0. The other end I3 of the tube II is open landis slitted and spread so that the ends of the spread portions contact with the 'inside surface of the hollow member III leaving openings for the'oil to pass through the tube II into an annular space Il between the tube Illand the interior surface of the hollow member I0. The oil is vdischarged from the hollow member I through pipe`I which leads from the heat regulator 9 to the exterior of the heater casing 2.

One end of' the .heat regulator 9 is held in adjusted position by the thread support I 6 passing through a correspondingly threaded opening in the wall of the heater casing 8. A hand wheel II i's provided at the outer end of the support I6 and tlie interior end of the support I6 terminates in an enlargement `-I8 rotatable in a recess I9 provided therefor in the closed end I2 of the hollow member IU. By turning the hand wheel I'I lthe heat regulator 9 can be moved lon- -Igitudinally to adjust the temperature i' the oil leaving the heating oil 1 as will be hereinafter described.

The end of the hollow member IB opposite the support I6 is provided with a stem or extension which extends through van opening 2| in the wall of the heater casing- 8. VA fuel valve 22 is xed on the outer end of the stem 20 and is positioned in the Valve housing 23 attached to the wall of the heater casing 8. The valve housing l amount of fuel delivered to the heater is controlled by the valve 22 and the controlled amount of fuel is conducted by a pipe 21 to a burner 28 positioned below the heat regulator or thermostat assembly 9 so that products of combustion Imm the burner. 28 contact with both the heat perature of the hollow member I0. and therefore the amount of fuel fed to the burner 28 def pends both upon the temperature of the products of-combustion and the temperature of the oil leaving the 4coil 1. It has been found `thfat this arrangement automatically maintains an extremely uniform discharge temperature of the oil leaving the coil 1 and that this uniform discharge temperature may be predetermined., by

adjustment of the hand wheel I1. Also in case of failure of the oil supply to coil 1, the hollow member I9 is rapidly heated to shut off supply Y o! fuel before damage vdue to high temperature occurs to the heater casing 9 `or the elements enclosed therein@ Pipe I5 delivers the oil Vdischarged from the heat regulator. 9 to an evaporating or expansion chamber 29 and terminates thereinvin a discharge nozzle 30. A valve 3l may be positioned in the pipe I5 so that anydesired pressure in theheating coil may be imposed by the pump 4 and main- -tained by partially closing this valve.. Alternatively the nozzle 30 may be, made replaceable so that nozzles having .diil'erent sized ldischarge openings may be substituted to maintain theden sired pressure or the diameter of the pipe 1 of the coil may be made sufficiently small so that the desired pressure is maintained without the necessity of a restricted discharge. Af steam supplypipe 32 may be providedfor introducing 'either saturated or superheated steam into the expansion chamber 29 to assistin va orization or add additional heat in the pansion chamber 29. Vapors are withdrawn Ifr m the expansion chamber 29 by a pipe 3 g to a condenser 34. 'I'he condenser may be of any suitable type and may include a cooling coil 35 connected to pipe 33 and positioned ina casing 34, through which a cooling medium may be circulated. The vcondenser coil 35 maydischarge into a receiver 31 to 'which a vacuum pump 38 ist,v connected by a pipe 39. "If evaporation and con densationat atmospheric pressure is desired, the receiver 31 may be vented directly to the atmosphere by opening the valve 40 in the pipe 4I. Condensate may be rembved from the receiver 31 through a pipey 42 and a pump (not shown) may be employed for this purpose, when a vacuum is maintained in receiver 31,A

` A valved dischargepipe 43 leads from the bottom of the expansion chamber 29 and is con- 'vice 46 which may include nected to a pump 44 for withdrawing the treated oil'from the expansion chamber and discharging the same through a pipe 45 to a cooling del la coil 41 positioned in a chamber 4 t hrough which a cooling medium may be passed. An'eective manner of conserv- `ing heat in the process is to employ the oil being delivered tothe heating coil 1 as a cooling medium for cooling the oil inthe expansion chamber 29. 'I'his `can lbe accomplished when high temperatures in the expansion chamber are not required by owing all orjaportion of the oil entering the process through the pipe 50 provided with a` valve 5I and connected to the pipe 2 between the tank I andthe valve 3 and then through a cooling coilv 52 positioned in the exp'ansion` chamber 429 and returning the oil through a pipe 53 and valvev54 to the pipe 2 bel tween the. valve 3 and the pump 4. By closing or partially closing the valve 3 and opening or partially opening the valves 5I and 54 any desired portion of the oil from the tank I can be run through the cooling coil 52 so as to preliminarily heat the oil entering the. coil 1 and cool the oil in the expansion chamber 29.

'I'he rate at which the oil is passed throughthe coil 1 as well as the amount of heat applied to the coil will usually'bediil'erent for diierent oils being treated since the temperatures suitable for diierent oils will vary as above discussed. By setting the hand wheel I1, the discharge temperature of the oil is maintained substantially 'f constant by the automatic neatrgulator s at any desired temperature. Itis, of course, understood that any other means of. rapidly heating the oil such as a steam or liquid heating bath may be employed instead of using products of combustion directly in contact with the heating coil. By this invention, glyceride oils aretreated-in such a way that they arebleached very eifectively and eiiiciently and in an economical manner. It requires only a very few minutes, for example, four to ten minutes, to increase the `temperature of the il from room temperature or the temperature atwhich it is discharged from the previous refining or other steps to the tem-- pera'ture required to bleach the oil. This short time of heating and the fact that the oil is maintained out of contact with the atmosphere while it is in a highly heated condition prevent injuring the oil. Also thefvelocity ot the oil through the tir coil 1 is such that substantially uniform heating a specific example of the present invention, a

previously refined cottonseed oil having an original colqrpf 37 yellow, 'I red was bleached in a -few minutes to a color of 30 yellow, 3 red without employing any bleaching agents, l By testing samples of the oil to be treated, the art can readily ascertain whether to heat t'heoil in a dry condition or with small proportions of water and also the necessary temperature reached in the heating coii. With extremely diiiicult oils to bleach, the present process may be preceded-- or followedby a conventional bleaching stepv employing bleaching agents suchas fullers earth or carbon. However, even in such casca-the loss f of oil as well as the amount of bleaching agent required is markedly reduced by employing the present invention Aas a part of thebleaching operation. Volatile impurities are removed by expanding the heated oil into the closed chamber 29.' Such volatile impurities can be condensed and,collected in the receiver 31 and in many cases constitute valuable by-products. When it is not desired to operate the expansion chamber 291m'- der vacuum conditions or t recover the volatile impurities the condenser 34 and receiver 31 can `be omitted.' l'

Although the present invention has particular utility in bleachingglyeeride oils 'which have 'been previously refined there are certain glyceride oils whichybecauseof the nature of their use ora their excellent quality in a crude state, do not require refining-but nevertheless should have their color reduced. The present invention 20 animal 'a is applicable to such oils ev n though they have not been previously refined. nd is effective to reduce the color thereof. No reagents such asalkali or bleaching agents are required and the oil 5 is subjected merely to heating and cooling out of ,contact with the atmosphere. For example, linseed oil which has been cold pressed and which has not been neutralized and refined with alkali aswell as linseed oils which have been refined v may be bleache'd to colors of 20 yellow, 2 red or less.

Although we have described the preferred embodiment of our invention, it is to beunderstood that thepresent invention is not to be limited to the precise details of the process herein disclosed but may be varied within the scope of the following claims.

What w claim is:

1. 'I'he process of bleaching previously refined v'e'getable oils which are substantially free of free fatty acids, which comprises, passing said oils under pressure and out of 'contact with the air through .a heated zone of such dimensions that the oil is substantially uniformly heated, raising the temperature of said oil in said zone sufficient to reduce the color of said oil and cause volatile constituents to pass into vapor when' th pressure is lowered, cooling said oil before the viscosity characteristics thereof have been materially changed by suddenly lowering the pressure and withdrawing said volatile constituents. n. 2. The process of bleaching previously refined animal and vegetable oils which are substantially free of free fatty acids, which comprises, passing said oils at an elevatedpressure and out of contact with the air through a heated zone of such dimensions that the oil is substantially uniformly heated, raising the temperature of said oil in said zone suicient to reduce the color of said oil and cause volatile constituents to pass into vapor when the pressure is released, cooling said oil before the viscosity characteristics thereof have been materially changed by suddenly releasing said pressure and withdrawing said volatile con-Y stituents and further cooling said oil before bringing the same into contact withthe air. 3. 'I'he process of bleaching previously refined aniral and vegetable oils which are substantially free of free fattyfacids, which comprises, passing said oils under pressure through a heated zone and out of contact with the air, maintaining suicient velocityof vsaid oil in said )zone to cause the oil to be substantially uni- 65. formly heated-raising the temperature of the oil in said zone sufcient to reduce the'color of said oil and cause volatile constituents thereofto ,pass into vapor when the pressure is reduced, sud'den- :y releasing saidA pressure to cool said oil 'before the viscosity characteristics of said oil have been materially changed by delivering the oil Vinto a lower pressure zone and withdrawing said volatile constituents. f

4. The process .of bleaching previously refined g5 animal and vegetable oils which are substantially free of free fatty acids, which comprises, passing said oils at an elevated pressure and out of contact with the air through a'heated zoneo'f such dimensions that the oil is substantially unifam- 7`0 ly heated, raising the temperature of 4said oil in said zone to approximately .500 F., cooling said oil before the viscosity characteristics thereof have beenmaterially changed by suddenly'releasing the pressure and withdrawing volatile 16' products therefrom.

.5. VThe process -of bleaching previously refined animal and vegetable oils which are substantially free of free `fatty acids, which comprises, passing said oils through an elongated 'curved heated zone at a temperature sufficient to reduce der pressure and out of contact with the air through a heated zone of such dimensions that the oil is substantially uniformly heated, raising the temperature of said oil in said zone suflicient to reduce the color of said oil and cause volatile impurities to pass into vapor when the pressure 'is lowered, cooling said oil before the viscosity lcharacteristics thereof have been materially changed by suddenly lowering the pressure and withdrawing said volatile impurities.

'1. The process of bleaching previously refined -glyceride voils which are substantially free of free fatty acids and removing volatile impm'ities therefrom, which comprises, passing said oils under pressure and out of contact with the air through a heated zone of such dimensions that the oil is substantially uniformly heated, raising the temperature of said oil in said zone suflicient to reduce the color of said oil and causev volatile impurities to pass into vapor when the pressure is lowered, cooling said oil before the viscosity charactertistics thereof have been materially changed by suddenly discharging said oil into a vacuum zone and withdrawing said volatile impurities from said vacuum.

8. The process ofv bleaching previously refined glyceride oilswhich 'are substantially free of free fatty acids and removing volatile impurities therefrom and recovering the same, which comprises, passing said "oils under pressure and out of contact with the air through a heated zone of such dimensions that the oil'is substantially uniformly heated, raising theV temperature of said oil in said zone sumcient to reducethe color of said oil and cause volatile impurities to 'pass vinto vapor when the pressure is lowered, cooling said oil before the viscosity characteristics thereof have been materially changed by suddenly lowering the pressure and withdrawing said volatile impurities 'and condensing the same. f.

9. The process of bleaching previously refine glyceride oils which are substantially free of free fatty acids, which comprises, passing said oils containing a small, proportion of'water under pressure and out of contact with the air through a heated zone of such dimensions that the oil is substantially uniformly heated, raising the temperature of Said oil in said zone sufficient to reduce the color of .said oil and cause volatile 1 constituents, including said water, to pass into y vapor when the pressure is'lowered, cooling said oil before the viscosity characteristics thereof 'havebeen materially changed by! suddenly low- ,ering the pressure and withdrawing said volatile constituents.

v BENJAMIN'- CLAYTQN- BENJAMIN H.