Note: Descriptions are shown in the official language in which they were submitted.
I ~ fi3~2~
This invention relates to methods for refining oils
and fats.
Various methods have been developed for refining oils
and fats. The alkali refining method is widely used and an im-
portant method of refining oils and fats, since it has many
advantages over the other methods. An important problem which
recently becomes noticeable from the point of view of environ-
mental pollution and saving materials is that the alkali refin-
ing method produces a large amount of waste water.
In the conventional alkali refining method, crude or
degummed oils and fats of animal and vegetable origin are con-
tacted wi-th an aqueous alkaline solution. The free fatty acid
in the oils and fats reacts with the alkaline solution and the
oils and fats are deacidified to form soapstock consisting
mainly of a fatty acid soap which is separated by centrifugation
as illustrated in the flow sheet A.
After separating the soap from the oil the deacidified
oil is then mixed and stirred with a large amount of hot water
to achieve a sufficient contact of the oil with hot water.
The soap which is still present in the oil in an amount
of about 100 - 1,000 ppm depending on the type and capacity of
the centrifuge is shifted to the li~uid phase and is again
centrifuged. To carry out this washing process only once is not
enough, thus the operation must be repeated more than twice in
order to remove soap exhaustively from the oil.
i il 6~28
FLOW SHEET A
Crude or degummed oils and fats
o animal and vegetable origin
¦ ~ an aqueous alkaline
¦ solution
deacidification
centrifugation
¦ ~ soapstock
¦~ hot water
mixing, stirring
centrlfugation
waste water ~
~ ~ hot water
treatment for mixing, stirring step of washing
discharge , ~ I ~ ~ith water
centrifugation
~aste water ~ ¦
¦~ adsorbent
decolorization
- deodorization
refined oil
~S - 2 -
~ ~ fi~2~
Therefore a very large amount of waste water is produced in the
washing process.
Since this waste water contains a considerable amount
of impurities including soap and entrained oils, it is not per-
mitted to discharge the waste water without treatment by the
pressure floatation method or by the activated sludge process.
Therefore a large inves-tment is required for the equipment to
treat the waste water.
A centrifuge or mixing and stirring apparatus requir-
ed in the washing process is very expensive and the number of
these apparatuses required depends on the number of times the
washing treatment is carried out. Washing twice requires two
sets of these apparatuses. Even the washing process which is
used only in the oil refineries requires a large investment
and it is a large economical burden to the processors. It is
undesirable to use such a large amount of water from the point
of view of saving materials and this is the first item to be
reduced. Thus the conventional alkali refining method is be-
coming gradually more disadvantageous.
The object of the present invention is to provide an
economical method for the refining of oils and fats.
Another object of the invention is to provide a method
for the refining of oils and fats which eliminates the washing
step, thus avoiding the production of waste water and the accom-
panyin~ environmental pollution.
A further object of the invention is to provide a
method for refining oils and fats which eliminates the invest-
ment for the apparatus required to wash the neutralized oils
and fats with water and to treat the waste water.
Briefly, these objects and other objects of the inven-
tion can be attained by providing a method of refining oils and
fats wherein washing process is eliminated after the separation
J I ~32~
of soapstock from the neutralized oils and fats.
This invention relates to a method of refining animal
and vegetable oils and fats, and more particularly to a method
of refining crude oils and fats of animal and vegetable origin
or oils and fats which have been subjected to a conventional
pre-treatment. Tne invention is characterized by deacidifying
said oils and fats with an aqueous solution of alkaline compounds,
separating the soapstock thus formed from the deacidified oils
and fats by centrifuge, admixing said deacidified oils and fats
directly with an aqueous solution of acids without washing the
deacidified oils and fats with water after the separation of
soapstock, drying if required, the resulting mixture, treating
the mixture with an adsorbent and subjecting the oils and fats
to a steam distillation treatment.
The inventors have studied oil refining methods which
eliminate the washing steps after deacidification in the con-
ventional alkali refining method, thus avoidin~ the production
of waste water and realizing the present invention.
~ ~ 6~28
FLOW SHEET B
Crude or degummed oils and fats
of animal and vegetable origin
an aqueous alkaline solution
deacidification
I
centrifugation
soapstock
¦~ an a~ueous acid solution 1
mixing, stirring step of treatment
with acids
<- adsorbent
decolorization
deodorization
I
refined oil
As lllustrated in Flow Sheet B, the method of refining
animal and vegetable oils and fats according to the present in-
vention omits the washing step which is used in the conventional
alkali refining method, and replaces the washing step with a
simple step of acid treatment. Therefore the refining process
itself is simplified significantly. Since the centrifugal
separation of oils from washing water which is carried out in
the conventional washing step is eliminated in the refining
method of the present invention, an expensive centrifugal mach-
ine is not needed and no waste water is produced.
The method of refining oils and fats according to the
invention comprises the following steps:
J ~ 6~2~
~1) treating the oils and fats with an alkaline
solution (deacidification),
(2) separating the insoluble matter,
(3) treating the oils and fats with an aqueous
~olution of acids,
(~) treating the oils and fats with an adsorbent
(decolorization),
(5) treating the oils and fats by steam distilla-
tion (deodorization
More specifically, according to the invention, there
is provided a method of refining an animal or vegetable oil or
fat which comprises:
(a) mixing said oil or fat with an aqueous solution
of an alkaline substance,
(b) separating the insoluble matter in the oil or
fat from the resulting mixture'
(c) directly admixing the deacidified separated oil
or fat from step (b) with an aqueous solution
of an acid,
(d) treating the resulting admixture with an adsor-
bent to adsorh coloring matter, impurities and
salts formed during step (c),
(e) separating said adsorbent from said oil or fat
and
(f) treating said oil or fat after step (e) by steam
distillation.
The particulars of these steps are described below.
1. Alkali treatment.
This step is a conventional deacidification step which
is self-explanatory. The oils and fats of animal and vegetable
origin are, if required, subjected to a pre-treatment such as
physical removal of impurities from the oil by filtration or
sedimen-tation, degumming with water, acids, alkalis and other
che~micals. Gum conditioning with acids such as phosphoric acid
I ~ ~3~8
may also be carried out in the conventional manner. This pre-
treatment step is an optional one.
The alkali treatment is carried out by contacting oils
and fats with an aqueous alkaline solution to neutralize the
free fatty acid, to saponify, hydrate and coagulate the gummy
substance and to decolorize the coloring matter in the oils
and fats. ~lkali compounds such as caustic soda and soda ash
are usually added to the oil. Soaps and coagulated gurnmy sub-
stancesare suspended in the mixture as insoluble matter.
2. Separation of insoluble matter.
This step is a commonly used one in the conventional
allcali refining method. The insoluble matter in the oil formed
in the preceding step of alkali treatment is removed from the
oil in the form of soapstock by means of centrifugation. This
soapstock consists mainly of soap and contains entrained neutral
oil and impurities such as gummy substance.
3. Treatment with an aqueous solution of acids.
In the usual alkali refining method, after step (2),
the oil (hereinafter called as deacidified separated oil) is
washed with a large amount of water. It is the characteristic
of the present invention that step (3) be carried out directly
without washing the deacidified separated oil with water.
The deacidified separated oil usually contains soap
as described before in an amount of 100 to 1,000 ppm and a small
amount of impurities such as mucilages. The deacidified sep-
arated oil is treated with an aqueous solution of acids in this
step (3) to hydrolyze the soap contained in the oil to form
free fatty acid and salts. Impurities such as mucilages con-
tained in the oil in a small amount are coagulated simultan-
eously in the oil as the insoluble matter. Thus free fattyacid so formed dissolves in the oil and the impurities and salts
remain in the oil as insoluble matter.
~ ~ 63228
The acids used in this step are organic or inorganic
acids such as hydrochloric acid, sulfuric acid, phosphoric
acid, oxalic acid, acetic acid, acetic anhydride, citric acid
and tartaric acid or the combination of more than two kinds
of these acids. Phosphoric acid is the most suitable consider-
ing the influence on the material of the equipment and from an
economical point of view. These acids are added to the de-
acidified separated oil at a suitable concentration and the
mixture is mixed or stirred at a temperature from room tempera-
ture to 100C for a period of time varying from several secondsto several hours. If phosphoric acid is used, the concentration
of the aqueous solution of acid is preferably about 75 - 85%,
and if citric acid is used~ the concentration is preferably
about 73-80%. Lower concentration of acids can also be used
in this step but the con~entration of the acid solution is
possibly as high as possible in view of subsequent step 4.
The wide interval of contact time is due to the differences
of contact efficiencies among the mixers which are used. In
short, it is necessary to establish an even and intimate
contact between acids and soaps or mucilages in order to make
sure that the reaction between them is rapid and sufficient.
The e~uipment or apparatus ~sed in the alkali refining method
wherein oils are contacted with an alkali or water can also
be used in this step. The contact between acids and soaps or
mucilages can be accelerated by using a homogenizer.
The amount of an aqueous solution of acid to be added
is calculated mainly from the amount of acid required to de-
compose the soap contained in the deacidified separated oil
and is established considering the amount of impurities such
as mucilages in the oil. When the soap content in the oil is
1000 ppm or 100 ppm, the amount of 85% phosphoric acid re-
quired is preferably about 380 ppm or 38.0 ppm and if 10~/o
f
- ~1 832?J8
acetic acid is used, preferably about 197 ppm or 19.7 ppm
is required to decompose the soap. The amount of impurities
should also be considered.
After the treatment involved in this step, if
required, the oil is dried through a suitable drier to
remove excess water from the oil before the treatment of
the following step.
4. Treatment with adsorbent (decolorization).
This step is a conventional decolorization process.
The oil which is treated with acids in step (3) or the oil which
is dried after the treatment of step (3) is treated with an ad-
sorbent such as activated clay or activated carbon. The impuri-
- 8a -
,1
~ 1 63228
ties which remain in the oil such as mucilages, salts formed by
the reaction of acids with soaps and the coloring matter in the
oil are substantially entirely adsorbed on the adsorbent and
are removed from the oil. The manner of treatment, the condi-
tions and the apparatus used for the conventional decoloriza-
tion step can be applied to this step.
5. Treatment by steam distillation (deodorization).
This step is also a conventional deodorization pro-
cess. The fatty acid which became free by the acid treatment
in step (3) is distilled entirely away from the oil accompanied
by the odorous matter. The coloring matter in the oil is decom-
posed simultaneously due to the heat and the oil is changed to
lightly colored. Since the impurities such as mucilages have
already been removed entirely from the oil, the oil does not
color due to the presence of impurities. The conventional steam
distillation method, apparatus and the conventional conditions
can be applied to this step.
The above constitutes an embodiment of -the invention.
The effects and advantages of the present invention are that
the washing step of the conventional al]cali refining method is
eliminated and consequently expensive equipment and apparatus
such as centrifuge are not required in this procedure. The im-
purities and soaps which are removed from the oil by the conven-
tional washing process are treated with acid in the deacidified
separated oil and are removed entirely from the oil in the fol-
lowing decolorization and deodorization steps~
In order to treat the oil with an aqueous solution of
acids according to the present invention, only one mixing
apparatus is required in a series of oil refining apparatus.
Two sets of apparatus such as centrifuge and mixer in a series
of conventional oil refining apparatus is required for washing
twice in the washing step. This means that the method of refin-
ing oils and fats according to the invention is far superior to
g _
~ :~ 6:~2~
the conventional alkali refining method from an economical
point of view.
The reduction of cost for the apparatus was estimated
to be more than 100,000,000 yen in 1979, since the apparatus
and the equipment for the washing step such as the centrifuge
and the mixer became useless. This amount was calculated for
an oil refinery having an average capacity in Japan, such as
200 tons per day. Moreover the running cost such as the cost
for operation and maintenance of the apparatus and the cost
for fixed assets such as space and building for these appara-
tus are not necessary. Therefore, the method of the invention
has an inestimable economical superiority over the usual methods.
The method of the invention is not accompanied by the
generation of waste water and is a clean method which is effect-
ive in protecting the environment from pollution. The method of
the invention can reduce the comsumption of water, heat energy
for heating washing water and the ener~y for the operation of
the apparatus during the washing step. This method is highly
suitable for the oil refining industry. The quality of the re-
fined oils and fats produced by the method of the invention issubstantially the same as that of the oil produced by the con-
ventional alkali refinin~ method and the yield of oil is superior
to that produced by the conventional method.
If the washing process of the conventional alkali re-
fining method is omitted and the amount of adsorbent is increas-
ed to remove the soaps, impurities and coloring matter still
present in the oil without treating the deacidified oil with an
acid, the fact of omitting the washing step is still recommended
in this method as in the method of the present invention. How-
ever, this method requires a very large amount of adsorbentcompared with the method of the inven-tion. Therefore, a large
amount of -the oil is lost with -the adsorbent and the disadvantage
-- 10 --
~J ~ ~322~
caused by the increase of the cost of the adsorbent and by the
decrease of the yield of the oil cancels the advantage of omitt-
ing -the washing step. This method is not an economically signi-
ficant method which is, as a matter of course, far inferior to
the method of the invention.
The method of the present invention can be applied
favourably to the refining of all kinds of vegetable and animal
oils and fats such as soybean oil, rape seed oil, rice oil,
corn oil, cotton seed oil, sunflower oil, safflower oil, sesame
oil, peanut oil, palm oil, coconut oil, linseed oil, lard, beef
tallow, mutton tallow, fish oil and the oils and fats of marine
animals.
IIaving generally described this invention, a further
understanding can be obtained by reference to certain specific
examples which are provided herein for purposes of illustration
only and are not intended to be limiting unless otherwise speci-
fied.
EXAMPLE 1
Soyb~an oil was treated by the conventional al]cali
refining method. A deacidified separated oil was obtained by
separating soapstock from the oil using a centrifuge. The oil
was divided into four samples and was used for the following
tests. The characteristics of the deacidified separated oil is
shown in Table 1.
Test 1 (Method of the present invention (1~)
40 ppm by weight of 85% phosphoric acid was added to
the deacidified separated oil and the acid treatment was carried
out by stirring the mixture for 5 minutes at a temperature of
80C. Then 0.3% by weight of activated clay was added to the
oil treated with acid, and the oil was decolorized under reduced
pressure at 105C for 15 minutes and the activated clay was
separated from the mixture. The decolorized oil thus obtained
~ :~ 83228
was subjected to deodorization under vacuum at 250C for 45
minutes to give the refined oil.
Test 2 (Method accordinq to the present invention (2))
This test was carried out under the same conditions
as in Test 1 except that the amount of phosphoric acid was
changed to 80 ppm.
Test_3 (Comparison test (1): conventional method)
The deacidified separa-ted oil was washed with 20%
of hot water against the oil and centrifuged. After the wash-
ing a double decolorization and deodorization were carried outunder the condition described in Test 1.
Test 4 (Comparison test (2))
The deacidified separated oil was directly decolorized
and deodorized under the conditions described in Test 1 without
acid treatment and washing.
- 12 -
~ 1~3~2~
, ___ . . _ .. ~
~s ~
~ ~ ~ ,~
o ~ a ~ ~ ~J
vl ~ a) ~-- ~D ~ ~ O
.,, ~ ~ ~ 5~ o . ,~ o .
h `-- ~ C~ ~ u~ r1 ~ O
d~ 1~ O rl O X X tl)
Q~ O
E~ ~ r~ O
O O ~ d~
t) ~ ;~ 3 ~11 ~ rl
_ .__.
~) ~ . I
~ ~ rJ
O rl
u~ ~D r~ ~ ~) X r~
~r( rl ~' O O ~t~) O (r) co O
~- O ~ ~ ~ ~ ~ ~ r~ O
r~ O ~ ~ O X rl O O
Q, ~ ~ t~l ~ X
~ O ~
~ ~r~cO ~0 ~
. O rl r-l . ._ . __
O~ (~I r~
,r,~
~_ ~U r ;~
rl t) ~ ;~ p; r
O u~ O ~1 O ~ O O tY') O
a)rl~ O Q, ~) ~D (I) ~ X r~l O
a) ~: ~ o X ~ o
O ~ ~ .IJ Q, O O ~ rl
D ~ 0,1:: O
a) ~ ~ o~
~0
~1
, -~
_ r~ ,~
E~ ,, ~ ~ S ,1
_ ~ ~ IY
3 U 3 o7 ~o ~ ~
0 1/~ 0 ~ O ` ~: O O ~ O
a) ,~ ~ 1~ ~) ~ ~D O ~ X ~1 0
~ ~ ~ a),~ o X ~ o
r-l O ~ ~ ~ ~, Q~ O :~ ,1
a) ~ O
a~ ~ a) o o
E~ ~ ~ ~ ~0
/ _ ._ ..
O / ~ ,,~
/ ,1 -,1 .,
/ ~ ~ Q. aJ ~ ,, ~ ^ a) ,P~
U~ / ~ ~ ~ ~ ~ ~ ,~
a) / ~ ~, o ~ ~ ~ o ~ ~ Q~ ~ o
/ ~ ~ ~- ~ ~ ~ ~
/ ~ ~ ~ ~ ~o
/ ~ ~ ~ ~ ~ O ~ '~ O
/ O rl 11~ 0 rl d O ,1 ~-1 (d ,1 rl O ~d
/ ~) ~.) O ~ t) O rS~ c) O O O O
/ ~1 ~ I ~ 4 f~ U u~ ~ U Ql ~1
~ ... .__
,1 ~ O O N a)
~1 O ~: ~) .,1 N
-,1 ~ o~ (~ ~ ,1
U S~ 3 ~ ,o
,~ ~ U ~ O
o (1~ rlrl-rl a~ ~ O rl
0 3 ~ O ~ O
.
O O
rl
I :~ 63228
The characteristics of the oil at each step in the
tests 1 - 4 are shown in Table 1.
As evident from the results of the tests shown in
Table 1, the refining method of the invention (in the tests 1
and 2) can give a refined oil having substantially the same
characteristics and quality as that of the oil obtained by
the conventional method (test 3) by treating merely the deacid-
ified separated oil with phosphoric acid without washing with
water. As the conditions of decolorization and deodorization
in the method of the invention need not be changed from that
of the conventional method, they have no influence on the yield
of refined oil. The method of the invention is rather superior
to the conventional method in the yield of refined oil, since
the latter loses neutral oil entrained in the washing water.
When the deacidified separated oil is directly decolor-
ized and deodorized without acid treatment and washing with
water (in test 4), soaps and phospholipids are not sufficient-
ly removed. Therefore the quality of the refined oil is bad.
It was found in the test that activated clay was re-
quired in an amount of 0.8% which was more than twice the clayrequired in the method of the invention, in order to improve
the quality of the refined oil in test 4 to the level of the
quality of the oil obtained in tests 1 and 2. The increase of
the cost for refining the oil by this method compared with that
of the method of the invention was about 1000 yen per ton of
the oil.
EXAMPLE 2
Rape seed oil was treated conventionally with the
alkaline solution and the soap stock was centrifuged. 431 ppm
by weight of 30% aqueous solution of citric acid was added to a
deacidified separated oil having an acid value of 0.06, a soap
content of 205 ppm and a phospholipid content of 283 ppm. The
- 14 -
~ I ~322~
mixture was stirred for 30 minutes at a temperature of 50C.
Then 0.6% by weight of activated clay was added to the oil, and
the oil was decolorized at 105~C for 15 minutes. The activated
clay was separated from the oil. The oil was deodorized under
reduced pressure at 250C for 45 minutes to give a refined oil.
It has an acid value of 0.05, a color of 6Yx0.5R and a phos-
pholipid content of 5 ppm. The quality of the refined oil was
substantially the same as that in a conventionally refined oil.
EXAMPLE 3
Corn oil was deacidified by the conventional alkali
treatment and the soap stock was centrifuged to obtain the de-
acidified separated oil. 604 ppm by weight of a 20% aqueous
solution of hydrochloric acid was added to the deacidified
separated oil having an acid value of 0.08, a soap content of
990 ppm, and a phospholipid content of 368 ppm. Tne mixture was
stirred for 5 minutes at a temperature of 80C. Then 0.6% by
weight of activated clay was added to the oil, and the oil was
decolorized at 105C for 15 minutes. After the activated clay
was separated from the oil, the oil was deodorized under reduc-
ed pressure at 260C for 60 minutes to give a refined oil. It
has an acid value of 0~07, a color of 6Yx0.6R and a phospholipid
content of 13 ppm. The quality of the refined oil was substan-
tially the same as that of conventionally refined oil.
EXAMPLE 4
. _
Beef tallow was deacidified by the conventional alkali
treatment and the soap stock was separated from the tallow to
give a deacidified separated tallow having an acid value of 0.06,
a soap content of 205 ppm and a phospholipid content of 54 ppm.
45 ppm by weight of 98% acetic acid was added to the tallow
and the mixture was agitated at high speed by a Dispermill
(made hy Hosokawa Iron Works) for 30 seconds at a temperature of
90C. 2% by weight of activated clay was added to the oil, and
* Trademark
- 15 -
I ~ 63~2P~
was decolorized under reduced pressure at a temperature of
100C for 30 minutes. The oil was deodorized under vacuum at a
temperature of 250C for 90 minutes. The refined oil obtained
had an acid value oE 0.02, a color of lYxO.lR and a trace of
phospholipid.
The refining method of the invention can eliminate
the washing step after deacidification and separation of soap
stock from the deacidified oil in the usual alkali refining
method as clearly shown in the examples and can give a refined
oil with a good yield having the same quality as that of the
conventionally refined oil.
Since the economical burden to the processors is very
small for the acid treatment of the present invention compared
with the advantage of omitting the washing step, the method of
the invention is far superior to the conventional method. The
refining method of the invention does not produce waste water
and saves the consumption of valuable water, thus making an
important contribution to the oil refining industry.
- 16 -
