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Dec. 10, 1946.
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.
B. CLAYTON
'
PURIFICATION OF 011.
2,412,251
‘
Filed April 21, 1945'
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' b’eqjamin Waylon
(MM m?tm 4W
. Patented Dec. 10, 1946
‘ 42,412,251
‘ vum'rau STAT as
PATENT OFF-ICE _
. 2,413,281
PURIFICATION OF OIL
Benjamin Clayton. Houston, Tex, unis-nor,
meme assignments, vto Benjamin Clayton,
Houston. Ten, doing business as Refining, Un
_ incorporated
, Application April :1, 1943, Serial No. 483,953
'
13 Claims‘.
(01. zoo-42s)
This invention relates to the puri?cation of oil
and more particularly to a process for the re
moval of small amounts of impurities from glyc
eride oils, such as ‘animal and vegetable oils,
which oils are substantially free of fatty acids
and gums.
-
'
It is frequently necessary to purify glyceride
.oils which are low in free fatty acid content, for
example, oils having free fatty acid content below
25% and which are also low in materials com
monly referred to as gums, namely, phosphatides,
2
continuous re?ning as strong caustic solutions
cause the small amount of soap‘ formed during
the re-re?ning operation to be salted out of the
caustic solution and to separate with the neutral
oil in the centrifugal separator. By employing
a strong caustic solution for color removal and
then diluting the caustic immediately before or
during separation of the oil from the decolor
izing reagent, soap and precipitated impurities, it
has been vfound that the bene?cial effects of
-.the strong caustic solution can be obtained while’ ,
separation difficulties are obviated. Di?iculties
similar to those described above are encountered
‘ties required to be removed may‘ be coloring‘
with various other oils which are low in free fatty
matter or materialswhich impart to the oil "a ‘deleterious. taste or odor. Or it may be desired 15 acid and gum content and the employment of
strong caustic solutions to precipitate or remove
to treat an oil which has naturally occurring
impurities from the oil, ‘followed by dilution of
, impurities in very limited quantities.
the caustic solution during or just prior to separa
An example of a glycedle oil which requires
tion, has also been found applicable in the treat
color removal is a cottonseed oil which has been
re?ned with non-s'aponifying alkalies such as 20 ment of such oils.
It is therefore an object of the present inven
soda ash or has been re?ned with insumcient
tion to provide an ‘improved process for removing.
caustic alkali to lower the color of the oil to the
impurities from glyceride oils which are low in
required extent. The employment of non-caustic
free fatty acid and gum content.
alkali adequately removes the free fatty acid con
proteinaceous materials, resins, etc. The impuri
,Another object of the invention is to provide
tent and also removes substantially all of the 25
gums but the resulting oil is usually of darker ' an improved process of ‘removing small amounts
' color than that desired. The losses resulting from
of impurities from glyceride oils having low free
fatty acid and gum content in which process
the re?ning of vegetable oils in a continuous‘
strong caustic alkali solutions are employed but
process using soda ash or other non-saponifying
alkalies are much less than in processes in which 80 are diluted prior to the separation operation.
v Another object of the invention is to provide
su?lcient caustic alkali is employed in the ?rst
a process of re-re?ning g1yceride.-oiis contain
instance to not only remove fatty acids and gums
ing only a small amount of impurities in which
~ from the oil but to produce a low colored oil.
re?ning losses are reduced.
,
'
'
It is, however, necessary to re-reflne the oil
A further object of the invention is to pro
using a caustic alkali or similar color reducing‘
vide an improved process of e?ectively remov
material to produce a low colored oil.
ing impurities from glyceride oils which contain
Cottonseed oils vary widely in their charac- ,
small amounts only of such impurities so as to
teristics from year to year and in accordance with
. overcome separation dif?culties.
production areas. It has been found possible to
re-re?ne certain types of cottonseed 011. after 40 A still further object of the invention-is to‘
provide an improved process of reducing the color
they have been re?ned by a continuous soda
of refined glyceride oils by chemical treatment
ash process, by using small amounts ofrelatively
and with substantially no re?ning losses.
dilute caustic alkali in a continuous process to
obtain a properly decolorized oil with exceedingly -
Other objects and advantages of the invention
smallylosses. However, it has alsov been found 45 will appear in the following description of pre
ferred embodiments thereof given with reference
that many and perhaps most cottonseed oils, are
not capable of , being re-re?ned with small
amounts vof relatively dilute caustic alkali. Such
dilute alkali not only fails to reduce. the color of
to the attached drawing'in which: ,
.
Fig. l is a schematic diagram of an apparatus
' suitable for carrying out the present invention,
,_
the oil but produces di?icultly separable emul 50 and
Fig. 2 is a somewhat diagrammatic vertical sec
sions which are not properly separated in a‘
tional view through a centrifugal separator bowl, _
continuous centrifugal separator.
particularly applicable for use in the , present
In accordance with the present invention, it
has been found that emulsion di?iculties may be
Referring to Fig; 1, the process of the present
obviated and an adequate reduction of the color 55
invention
is preferably carried out in apparatus
of the oil can be obtained by employing small
invention.
amounts of relatively concentrated caustic soda,
_
_
_
in which an. oil is treated with a reagent for pre
cipitating the impurities and then'delivered into
for example, concentrations between 20 and 50°
a centrifugal separator ill for separation, of the
Baumé. The use‘ of such concentrated solutions,
however, has heretofore been found impossible in 60 precipitated material or foots from the oil. The
2,412,901
‘impurities and'soap flow outwardly and then up
oil to be treated may be withdrawn from a source
of supply shown as a tank II by means of a Pro
wardly along the periphery of the bowl and are
portioning pump l2 and delivered through a heat- '
ing coil I! of a heat exchange device M to a mixer ,
discharged through the port 48, the imperforate
88 preventing admixture of the heavy emu
ent with the oil being discharged through the
l8. The tank ll may be provided with a heatingv
coil l‘l or similar heating means for maintaining
the oil in the tank H in ?uid condition in case
oils or fats solid at ordinary temperatures are
port 44.
~~
'
-
Water or other diluting agent is introduced into
I the bowl by" the pipe :2 which extends down
being treated. The reagent for precipitating im
wardly through the pipe 28 so as to terminate
purities may be withdrawn from a tank l8 and 10 within‘ a circular bame member 84 which-main
delivered by a proportioning pump I! through a
tains the water separate from the incoming oil
heating coil 2| of the heat exchanger 22 to the
reagent mixture and directs the diluting agent
mixer M. The mixer IB'may be of any suitable
to the lower periphery of the bowl. The diluting
type such as a closed mechanical agitator but is
agent admlxes with the heavy emuent'to' dilute
preferably of the flow mixer type disclosed in the 15 the same and cause any soap present in the mixpatent to Thurman 2,142,062 granted December
ture to be retained insolution or dissolved in the
2'7, 1938.
,
'
heavy eiiluent. so as to be ‘discharged therewith
A thorough mixture of the reagent and oil pro
duced in the mixer i8 is then passed through a
through the port 48.
'
,
In treatment of oils such as those contemplated
in the present invention, namely, oils which are
low in free fatty acid and gum content, the heavy
effluent is predominantly an aqueous solution of
' heating coil 23 of the heat exchanger 24 and de
liveredinto the centrifugal it through the pipe
28. A diluting agent for the reagent in the mix
ture entering the centrifugal in may be with
' the reagent even before dilution with the diluting
drawn from tank 21 by means of a proportioning
pump 28 and delivered through the coil 29 of the
heat exchanger 8| and a pipe 82 so as to be ad
mixed with the oil reagent mixture at the en
agent. This aqueous solution contains excess re
agent and‘small amounts of soap. 'Attempts to
employ dilute precipitating agents result not only
in lne?ective removal of impurities from the oil
tranceof the centrifugal separator iii. The dilut
ing agent which, in most instances, is water,
but in the formation of tight emulsions which
are not effectively separated in the centrifugal
dilutes the mixture so that soap formed in the 30 even though the mixture is separated atrela=
reaction is retained in solution in the aqueous
'tively high temperatures. In such cases, substan
‘phase or heavy emuent and discharged through
tial amounts of reagent are carried out with the
the spout 88 into a receiver 84 while the puri
puri?ed oil discharged from the port st, requir
?ed oil is discharged through a spout 88 into
ing extensive washing or other treatment to re
a receiver 81. The proportioning pumps i2, i9 '
move the included reagent from the oil. More
and 28 may be driven by a variable speed electric
importantly, a very substantial amount of the
motor 88 connected directly to the oil pump l2
oil is entrained with and discharged with the
and through variable speed devices 39 and M be
heavy e?luent through the port 48, resulting in
, tween the motor 38 and the proportioning pumps
high re?ning losses. In many instances also the
is and 28, respectively. Other types of propor
impurities are not adequately removed from the
tioning apparatus may, however, be employed, for
example, that shown in patent to Thurman above
,
oil.
By employing strong precipitating reagents
such as caustic soda solutions-ranging between
Instead of delivering the diluting agent into
20 to 50° Baumé, such emulsions are not encoun
the oil-reagent mixture as the mixture enters the v tered and in accordance with the present inven
centrifugal separator, it is preferred to admix
tion re?ning losses are reduced to a very_low
the diluting agent with the heavy effluentv in the
?gure. However, small amounts of soap are
centrifugal after separation has-been largely ac
formed by reaction of the caustic alkali with
complished. This avoids substantially all con
residual free fatty acids in the oil or by reaction
tact between the oil and a dilute reagent so that ‘ 50 with the oil itself and this soap is grained out of
emulsion di?iculties are entirely overcome. A
the heavy e?luent in the centrifugal. Three
[suitable type of centrifugal separator for accom
layersor strata tend to be built up in the cen
plishing this operation is shownin Fig. 2. Such
trifu'gal bowl: an inner oil layer, an intermediate
a separator may include a bowl 42 mounted upon,
soap layer, and an outer aqueous layer. These
a shaft 48 for rotation .at high speed and may 55 layers are not. de?nitely defined and any attempt
also include an outlet port 44 for the light e?iuent
to‘ adjust the centrifugal to separate the soap
and anoutlet 48 for the heavy e?iuent. The oil
with the aqueous layer causes high re?ning losses
and reagent mixture containing precipitated im
whereas failure to separate the soap with the
purities, as well as a small amount of soap, is de
aqueous layer produces an impure oil requiring
livered into the centrifugal through a stationary
extensive further purification treatment.
This difficulty can be overcome by diluting the
pipe 41 and then delivered into a tubular inner
mixture Just prior to centrifugal separation, for
bowl member ‘.8 by means of a distributor 49.
The inner bowl member 48 divides the separation
example, by introducing a diluting agent such
zone of the bowl from the inlet portion ‘thereof
as water into the mixture entering the centrif
and directs the incoming mixture downwardly
ugal but a slight amount of difilcultly separable
and outwardly into the lower portion of the bowl.
emulsion may be formed due to contact between
The separation zone of the bowl may be provided
the oil and diluted reagent and it is found thatv
with a plurality of conical baiiie members 8|
the precipitation of impurities such as coloring
which are apertured at 82 adjacent the neutral
matter is not as effective 6.515 the case when
‘ referred.
‘zone of separation.
Material to be separated
?ows upwardly through the apertures 82, the
light effluent comprising the oil ?owing inwardly
in the bowl and being discharged through the
outlet port 44. The heavier materials comprising
separation is substantially complete prior to dilu
tion of the mixture. In the centrifugal separa- _'
tor shown in Fig. 2, diluting of the heavy eiiluent
‘ after complete or substantially complete separa
vtion thereof from the oil causes the soap layer
the aqueous phase containing the precipitated 75 above referred to, to remain in solution or go
9,419,251
as high as the temperature of' separation and
preferably is somewhat higher. Thus the tem
into solution in the aqueous layer so that it
separates cleanly from the oil.
4
perature of the diluting agent will range be- >
Reaction of color impurities, with a precipitat
ing reagent such as caustic soda usually takes
tween approximately 100 and 200° F.
The material discharged from the centrifuge’
place more rapidly and more completely at low
is in most cases largely water containing excess
caustic soda anda small amount of soap. In
general the amount of soap will not exceed 2%
temperatures, for example, temperatures be
tween 70 and 100° F._ The oil in the tank ll of
Fig. 1 is therefore preferably maintained be
tween these temperatures except in cases where '
and is usuall between .2% and 1% of thema
exchanger I4 is therefore notv employed when
the oil is at the correct temperature for admix
ture with the precipitating reagent but may
the losses when employing equivalent. amounts of
the oil is delivered to the tank from a priorlre ii) terial discharged. By employing strong caustic
alkali solutions and diluting the same just prior
?ning or similar process at a high temperature
to or during separation, the losses rarely exceed
or the oil or fat requires heating to a higher
_'.2% and usually do not exceed .15% whereas
temperature to render the same ?uid. The heat
dilute caustic soda in the ?rst instance may run
as high as 2% or higher. It has been found
that even increasing the amount of caustic
solution does not measurably increase the losses
be employed to either cool or heat the oil in
order to bring it to the desired temperature for
mixing with the reagent. Similarly the heat
in the process provided su?icient diluting agent
exchanger 22 may be employed to either heat or 20 is introduced to carry the concentration of the
reagent in the centrifugal below that at which
cool the reagent to a desired mixing tempera
soap‘ tends to separate with the oil.
ture. In general the temperature of the re
, While the present process is particularly adapt
agent will usually be adjusted to substantially
able to the re-refining of cottonseed oil previ
that of the oil entering the mixer l8. .
ously refined by a continuous soda ash process,
such as oil refined by the processes disclosed
in my Patents Nd. 2,249,701 and No. 2,249,702,
granted July 15, 1941, certain vegetable or ani
Properly proportioned amounts of the oil and
reagent are thus delivered to the mixer l8 by
means of proportioningpumps l2 and I8 and
passed through the reaction coil 23 in the heat
mal oils in the form they are recovered from the
raw material are naturally low in free fatty acids
and gumsand the present process may be advan
tageously employed for removal of small amounts
of impurities therefrom. Also substantially com
pletely re?ned oils intended for edible purposes
exchanger 24. Since . the temperature giving
most e?’ective separation is usually considerably -
above the most emcient reaction temperature,
any desired heating medium may be circulated
through the heat exchanger 24 to raise the tem
perature of the mixture to that required for
effective centrifugal separation. These tem
peratures will usually range between 120 and
180° F., depending upon the type of oil being
treated, the impurities desired to be removed
and the melting temperature of the oil. The
oils being treated will ordinarily contain not
more than approximately 25% free fatty acid
are frequently processed under conditions which
somewhat increase their free fatty acidvcontent
and impart deleterious tastes or odors thereto.
Such oils or fats are advantageously subjected
to the process of the present invention for re
40 moval of the small amounts of impurities con
tained therein. Furthermore, certain light col
ored oils, such as corn oil, requiring no treatment _
and only slight amounts or traces of gums. The
for color reduction after re?ning in continuous
preferred reagent is a concentrated aqueous solu
soda ash, processes, are benefited by, treatment
tion of caustic soda, for example, solutions rang—
ing from 20° Baumé up to 50° Baumé. A con 4. in accordance with the present invention as in
some instances such oils are extremely difficult
siderable excess of caustic soda over that re
to wash without excessive re?ning losses. It has
quired to neutralize any free fatty acids present
been found that treatment in accordance with
is usually employed. Thus the amounts of
’ the present invention in conjunction with a sub
caustic solution will usually range between ap
proximately 1/2 and 4%, the quantity most gen
' erally used being in the ‘neighborhood of 2%.
As stated above, the temperature of mixing is
preferably between '70 and 100° F. although for
removing certain types of impurities this tem
perature may be as high as 130 to 140° F. The
' temperature of separation will, however, usually
sequent water washing operation produces ‘much
lower losses than direct washing of the oil from
the primary re?ning operation. Thus the pres
ent process conditions the oil for a washing op
eration with low losses.
While caustic soda is a preferred reagent in the
present invention, it is also possible to employ
range between 120 and 180° F., although this
temperature may at times be as low as 100° F.
Water is the preferred diluting agent and the
amount of water will.ordinari1y range between
approximately 2.5 and ten times the amount of
sodium peroxide which liberates caustic soda
while admixed with water and should be used
in sufficient amounts to produce the concentra
tion of caustic soda contemplated in the pres
ent invention. The sodium peroxide additionally
reagent employed. In general, it has been found .
desirable to reduce the concentration of the ex
cess reagent in the centrifugal to at least 8°
the oil.
liberates oxygen which materially assists in re
moving coloring matter and other impurities from
An advantageous operation is to em
ploy a reagent consisting predominantly of caus
Baumé although in some instances higher con
centrations up to 10 or 12° Baumé have been
found operable and lower concentrations rang
tic soda but containing a small amount of so
dium peroxide or other oxygen liberating mate
ing down to approximately 4° Baumé may'some
times be found advantageous in the centrifugal
such as potassium‘ compounds are also suitable. I
separator.
In any event, the amount of water *
or other diluting agent employed in the centrif
ugal separator should be sufficient to cause the
soap to separate in solution or in dispersed form
in the aqueous phase. Also the temperature of
the diluting agent should in general, be at least
rial.
Other equivalent alkali metal compounds
This application is a continuation-in-part of
my copending application Serial N0..398,489, ?led
June 17, 1941, which is in turn a division of Se
rial No. 296,685, ?led September 26, 1939, now
Patent No. 2,249,701, granted July 15, 1941.
'
While I have disclosed the preferred embodi
2,412,051 ,
,
7
_
ment of my invention, it is understood that the
details thereof may be varied within the scope
of the following claims.
I claim:
'
I
aqueougphase and said soap have been at least
partially separated from said oil, to reduce the
concentration of said aqueous. phase to at-least
8° Bé..whereby said soap discharges from said
1. The process of purifying a glyceride oil which 5 centrifugal with said aqueous phase.
,
is low in free fatty acid and gum content and
5. The process of purifying a glyceride oil
contains small amounts of other impurities, which 1
which is low in free fatty acids and gum content,
‘process comprises, mixing with saidoil a caus
which process comprises mixing with said oil a
tic soda solution having a concentration between
caustic alkali solution having a concentration
approximately 20 and 50° Bé., said reagent being 10 between approximately 20 and 50° Bé. to pre
added in sufficient amount to precipitate said im
cipitate said- impurities and to form a small
purities and prevent'the formation of an emul-'
amount of soap, and of suiiicient concentration
sion in said oil and said reagent, whereby the
to stratify the mixture into an oil phase, a soap
resulting mixture will separate into an oil layer,
phase and an aqueous phase when the same is sub
a' soap layer, and an aqueous layer containing 15 jected to centrifugal separation, thus interfering
said impurities when subjected to centrifugal sep- '
aration, subjecting the resulting mixture to cen
with such separation, subjecting the resulting
mixture to centrifugal separation and condition
trifugal separation and diluting said mixture prior
ing such stratified mixture for centrifugal sepa
to complete separation in the centrifugal‘ to lower
ration by adding su?icient water to said aqueous
the concentration of the aqueous layer to be 20 phase in said centrifugal to reduce the concen
tween approximately 4 and 10° Bé., whereby said
tration thereof to such an extent that said strat
soap discharges with said aqueous layer‘ from
said centrifugal.
' i?cation is overcome and said soap is discharged
- with the said aqueous phase.
_ 6. The process as de?ned in claim 5 in which
.
2. The process of purifying a glyceride oil which
is low in free fatty acid and gum content and 25 the concentration of said aqueous phase is re
contains small amounts of other impurities, which
duced to between approximately 4 and 10° Bé.
process comprises, mixing with said all a caustic
I
7. The process of purifying vegetable and ani
soda solution having a concentration between ap
mal oils containing impurities, including free
proximately 20 and 50° Bé., said reagent being
fatty acids, which comprises, mixing therewith an
added in su?icient amount to precipitate said im 30 alkaline re?ning reageant capable of reacting
purities and prevent the formation of ,an- emul
with said impurities to precipitate the same and
sion of said oil and said reagent, whereby the
, produce soap, said reagent being added in suf
resulting mixture will separate into an oil layer, ' ficiently high concentration to produce a strat
a soap layer, and an aqueous layer containing
i?ed mixture including an oil phase, a soap phase,
said impurities when subjected to centrifugal sep 35 and an aqueous phase when the mixture is sub-v
aration, subjecting the resulting mixture to cen
jected to centrifugal separation, thus interfering
trifugal separation and diluting said reagent prior
with said separation, reducing concentration by
to complete separation in the centrifugal so as
adding an aqueous diluent to said mixture in sum
to produce a concentration in said aqueous layer
quantity to overcome such strati?cation,
not substantially greater than 8° Bé., whereby 40 cient
whereby to permit said soap to be‘discharged with
said soap discharges with said aqueous layer from
said aqueous layer, and centrifugally separating
said centrifugal.
~
_
the thus conditioned mixture.
3.- The process of purifying a glyceride oil which
8. The process as defined in claim 7 in which
is low in free fatty acid and gum content and con- ‘
the dilution produces a separation of the heavier‘
tains small amounts of other impurities, which 45 ei?uenthaving a Baumé between approximately
process comprises, mixing with said oil a caustic
4 and 10°.
alkali solution having a concentration between
9. The process as defined in claim 7 in which
approximately 20 and 50° Bé. to precipitate said
the dilution is effected after the soap has been at
impurities‘ and form a small amount of soap,
whereby the resulting mixture strati?es into an
oil phase, a soap phase and an aqueous phase
least partially separated from the oil in the cen-‘ .
50' trifugai apparatus.
. when the same is subjected to centrifugal separa
10. The process as de?ned in claim 7 in which
the dilution occurs prior to complete separation in
tion, subjecting the resulting mixture to cen
the centrifugal.
.
>
trifugal separation, and adding sufficient water
11. The process as de?ned in claim '7 in which
to said aqueous phase in said centrifugal after 55 the impurities separatedfrom the oil in the cen
said aqueous phase and soap have been at least
partially separated from said oil to reduce the
concentration of said aqueous phase to between
trifugal are diluted in the centrifugal after sub
stantial separation from the oil.
12.“ A‘ re-re?ning process for oils of low im
purity content which process comprises the treat
approximately 4 and 10° Bé. whereby said soap
discharges from said centrifugal with said aque 60 ment of said oils with a caustic solution in a con
ous phase.
’
4.. The process of purifying a glyceride oil which
is low in free fatty acid and gum content and con- _‘
tains small amounts of other impurities, which
process comprises, mixing with said oil a caustic
alkali solution having a concentration. between
approximately 20 and 50° 36. to precipitate said
impurities and form a, small amount of soap,
whereby the resulting mixture stratifies into an,
oil phase, a soap phase and an aqueous phase when 70
the same is subjected to centrifugal separation,
‘subjecting the resulting mixture to centrifugal
separation,'and adding sumcient water to said
aqueous phase in said centrifugal after said:
centration su'mciently high to cause strati?cation
into an ‘oil phase, a soap phase and an aqueous
phase'when the'mixture is subjected to centrifugal
separation, introducing water to said mixture in
su?icient quantity to convert the mixture from its
thus strati?ed condition to a sufficiently non
strati?ed condition to permit the soapstocl-r to be
discharged with the aqueous phase, - and cen
trifugally separating the thus conditioned mix
ture. '
,
.
13. The process as defined in claim 12 in'which'
the water is introduced at the point of separation
inthe centrifugal.
i
I BENJAMIN CLAYTON.
MN
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