Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION:
The present invention relates to an improvement in the
treatment of crude oils by means of ultrafilters.
A crude oil generally contains phospholipids and other
S impurities which must be removed in a purification step
before the oil is used as a food or for industrial purposes.
The phospholipids are generally removed in the first stage
in the purification step. This treatment is generally
called l~degummingll. A known, most common method of degumming
~ comprises adding water to a crude oil to insolubilize the
phospholipids dissolved in the crude oll and then removing
the same by centrifugal separation or the like. In this
method, a re-degumming step wherein phosphoric acid or the
like is added is required, since the removal of the phos-
I ~ pholipids ls insufficient, However, a sufficient removal ofthe phospholipids cannot still be attained by the method
including said re-degumming step.
Further, phospholipid contents of the oil meal or
waste water formed in a deacidification step which follows
O the re-degumming step are high and, cansequently, the
workability is reduced and the load is increased in -the
treatment of the waste water disadvantageously.
On the other hand, lecithin usable as food or usable
industrially can be obtained from the phospholipids by-
~S produced in the degumming step. Therefore, the above
defects of the degumming method wherein water and phosphoricacid are used are undesirable also from the viewpoint of
lecithin production.
There have been known other methods such as a method
disclosed in the specification of Japanese Patent Laid-Open
No. 153010/1975 wherein a solution of crude oil in a solvent
is passed through an ultrafilter to divide the same into
phospholipids having higher molecular weights and crude
oil having lower molecular weights. By this method, the
~0 defects of the above method wherein water and phosphoric
acid are added can be substantially wholly overcome.
However, if this method is carried out on a commercial
basis, other defects are caused such as increase in viscosity
of the solution to be treated and deposition of the phos-
pholipids on the surface of the ultrafilter to seriously
reduce the filtration velocity of the ultrafilter. Thus,
the concentration of the phospholipids is not effected
sufficiently, As a result, lt is difficult to obtain leci-
thin of a high quality, This method is also still unsatis-
O fctory,
On the other hand, phospholipids by-produced in the
degumming step of oils are added to various oil meals to
improve the efficiencies of the oil meals used as feed or
~ertilizer,
Said phospholipids are generally cassed "oil foots"
and usually obtained in the step of degumming oils by the
ll~;i4S8
addition of water. The oil foots have a water content of
around 50 % and, therefore9 a drylng step is required for
removing the water from the oil foots after they are
incorporated in the oil meals Further, it is difficult
to obtain a homogeneous mixture of the oil foots having a
high viscosity with the oil mea~ and the mixture is apt
to form lumps, whereby evaporation efficiency of the water
in said drying step is low.
SUMMARY OF THE INVENTION:
~O An ob~ect of the present invention is to provide an
lmproved method of degumming a crude oil by means of
ultrafilters on a commercial scale.
Another object of the present invention is to provide
oil meàl feeds and fertilizers containing a concentrated
phospholipid solution separated out by means of ultrafilters.
According to the present lnvention, an impr~ved method
of treating an oil by means of ultrafllters is provided
wherein a solution of crude oll in a solvent is successively
contacted with at least two ultrafilters arranged in
O series and a part of the solvent, solution or filtrate
which passed through the ultrafilters is fed into at least
one connecting part between the ultrafilters to divide the
solution into a filtrate from which phospholipids have been
removed and a concentrated phospholipid solution, the
degummed oil is obtained from the filtrate and lecithin is
~ 5 8
obtalned from the concentrated solution.
The concentrated phospholipid solution is added to an
Oil meal and the solvent is removed to obtain a feed or
fertilizer of a high efficiency.
S DETAILED DESCRIPTION OF THE INVENTION:
The ultrafilter used in the present invention is
preferably of a solvent-resistant, oil-resistant, tubular
module made of a polysulfone or polyimide high molecular
membrane. Fractional molecular weight of the membrane is
J~ preferably in the range of 6,000-20,000.
As the crude oils which can be treated by the method
of the present invention, there may be mentioned oils
obtained from soy beans, rapeseeds, cotton seeds, linseeds,
~unflower, safflower and sesame seeds.
J5~ As the solvents, there may be used hydrocarbons such
as alcohols (for example, ethanol), petroleum benzine,
trichloroethylene and particularly preferably hexane.
The suitable crude oil concentration in a solution of
crude oil in a solvent (hereinafter referred to as miscella)
O to be fed to the ultrafilters is 20-40 %. A higher concen-
tration is impractical, since the filtrating velocity of
the membrane is reduced.
A crude oil obtained by solvent extraction method is
in the form of the miscella having a concentration generally
a~ in the above range and, therefore, lt may be used in the
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process of the present invention as ~t is.
By feeding a part of the solvent, mescella or filtrate
which passed through the ultrafilters in at least one
connecting part between the ultrafilters~ the viscosity
and concentration of the miscella to be treated can be
reduced, whereby the treating efficiency is improved.
Suitable quantity of the liquid to be fed is 5-10 wt. %
based on the miscella to be treated. The liquid may be fed
ln all or a part of the connecting parts for the ultra-
filters. In the latter case, lt is preferred to feed the
same in a connecting part positioned before the last
ultrafilter in which viscosity and concentration of the
miscella to be treated are high.
A device used for carrying out the present invention
~S is provided with ultrafilters; a pump, pipes and tank
for circulating a miscella through the ultrafilters under
pressure; and a pump and pipes for feeding a part of the
solvent, miscella or ~iltrate into the ultrafilter-
co~necting parts. The miscella circulating in the ultra-
~o filters and the tank is successively contacted with theultrafilters under pressure, thereby increasing phsopho-
lipid concentration in the circulating liquid which has
not been passed through the ultrafilters. On the other
hand, the miscella from which the phospholipids have been
removed is collected as the filtrate A part of the solvent,
1~ 45~
miscella or filtrate is fed into at least one ultrafilter-
connecting part and sent towards a downstream ultrafilter
together with the miscella to be treated.
In the operation, temperature of the miscella is
S preferably 40-65C and pressure is 5-20 Kg/cm2. If a
lower temperature or pressure is employed, the filtration
;.
velocity of the filters is lowered and the amount treated
i 9 reduced.
The degummed miscella is thus obtained, from which
~ the solvent is then removed and it is purified by ordinary
methods. On the other hand, the solvent is removed from
the concentrated phospholipid solution to obtain lecithin
of a high purity.
According to the process of the present inventlon,
I ~ the increase in viscosity and concentration of the liquid
to be treated can be controlled and the phospholipids
deposited on the surface of the ultrafllters can be washed
away by feeding the solvent or miscella into the ultra-
filter-connecting part(s). Accordingly, the filtration
velocity of the ultrafilters ls not reduced and a high
treatment efficiency can be obtalned. Thus, the degumming
by means of ultrafilters can be carried out on a commercial
scale and the process is simplified and costs are reduced
a ~ as compared with the conventional degumming method wherein
water and phosphoric acid are used. In addition, a higher
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rate of removal of the phospholipids than that of the above
conventional degumming method can be obtained by the method
of the present invention. A crude oil to be degummed by
the method of the present invention does not always
S necessitate the deacidification treatment by alkali
purification but steam purification may be employed wherein
the crude oil is discolored with china caly and then
deodorized and deacidified by the steam distillation.
The oil foots obtained by the alkali purification of
1~ the degummed crude oil have a low phospholipid content (less
than o.l~ by weight) and, therefore, the emulsification
hardly occurs in the step of decomposing the oil foots into
fatty acids, thereby improving the workability. Further,
weste waters discharged in the alkali purification step and
decomposition step are not so highly soiled and can be easily
treated. The treated water has an improved quality.
For the regeneration of the ultra-filters, a known method
such as back wash method may be employed to increase the
treatment efficiency. On the other hand, the circulating
liquid obtained by the degumming contains highly concentrated
phospholipids. After the removal of the solvent, light-colored
lecithin having a purity equivalent or superior to that of
commercially available lecithin is obtained directly.
In another aspect of the present invention, the
concentrated phospholipid solution is added as it is to
1161~58
an oil cake suitably in an amount of 1-5 wt. % based on
the oil meal.
As the oil meals, there may be used those used as
feeds or fertilizers in the prior art such as oil meal5
S obtained from soy beans, rapeseeds, cotton seeds, linseeds,
sunflower and safflower.
After the addition of the concentrated solution
followed by the removal of the solvent in an ordinary
manner, an oil meal of the present invention is obtained.
~O Since the above phospholipids have substantially the same
composition as that of oil foots added to oil meals in the
conventional method, the oil meal of the present invention
is substantially the same as oil meals obtained by the
conventional method and has a high efficiency as feed or
IS fertilizer. The oil meal obtained by the solvent extraction
method still contains a small quantity of solvent and
requires an additional step of removing the same.
However, if the solvent is thus removed after the addition
of the concentrated solution to the oil meal from which
the solvent has not been removed yet, the solvent in the
oil meal and the solvent in the concentrated solution can
be distilled out at once to simplify the steps.
Unlike the conventional oil foots, the concentrated
phospholipid solution of the present invention is free of
S water and, consequently, drying step after the addi-tion
~ 45~
thcreof to tilC oil mcal is unnccessary. Further, the
concentrated solution having a low ~iscosity can be mixcd
with t~le oil mcal to form a homogeneous mixtur~ without
forming lumps unlike the oil foots obtained in the prior
art.
The following examples further illustrate the present
invention.
Exampl e 1
A miscella [ oil content: 22~, phospholipld content
of the oil: 2.5%(as acetone-insoluble matter) (The same
shall apply hereinafter)] obtained from rapeseeds by the
extraction method using hexane as solvent was treated in
a device comprising three non-aqueous membranes for ultra-
filtration NTU-4220 (fractional molecular weight: 20,000)
P-l8 module arranged in serles. The membrane areas of the
respective modules were 9.2 m2, l.8 m2 and 0.8 m2 in order.
The miscella was fed into the modules at a rate of 1550
~/hr. under conditions comprising a pressure at the inlet
of the membrane of lO Kg/cm2, a temperature of 5UOC and a
linear velocity in the membrane of 2-4 m/sec. The
miscella circulating in the modules was con~acted with the
ultrafilters. l'he phospholipids were concentrated in the
circulating liquid which had not been passed through the
untrafilters. The miscella from which the phospholipids
had been removed was collected as the filtrate. 69~/hr.
45~
of hexane was fed in a connecting part between the second
module and the -third rnodule. Flow rates in the respec-tive
modules are shown in Table 1.
Table 1
S First Second Third
stage stage stage
Concentrated solution
~circulating solution) 222 61 60
(~hr.)
~g Filtrate (~/hr.)1333 161 70
Filtrate (B/m2-hr.)90 60 100
The resulting filtrate had a phospholipid content of
less than 0.1 wt. % and an acid value of 1.6. The filtrate
was treated in an ordinary manner to remove the solvent
JS therefrom and then subjected to the alkali purification
(deacidification, dlscoloration and deodorization) to obtain
the intended oil. The oil had a chromaticity of 3.4Y/0.3R
r~ (determined with Lovibond colorimeter with 133.4 mm cell)
(The same shall apply hereinafter), acid value of 0.04,
AOM stability of 21.0 (peroxide value: 2.2) and a good
flavor.
For comparison, the s~ne procedure as above was repeated
except that hexane was no-t fed into the module-connecting
part. In this case, the filtration velocity of the membrane
~ began to lower about five minutes after the start of the
operation. Ten minutes after the start of the operation,
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458
filtration flow was reduced from 100 ~/m2 to 30 ~/m2
and the workability was deteriorated.
A crude rapeseed oil obtained by removing the solvent
from said miscella was treated by the conventional
S degumming method wherein water and phosphoric acid were
used. The resulting degummed oil had a phospholipid
content of 0.2 o6 which was higher than that observed
after carrying out the method of the present invention
and a degumming rate lower than that of the present
~0 invention. Phospholipid contents (excluding the solvent)
of the circulating liquid were 20 %, 40 % and 65 % in
the respective sta~es, The solvent was then removed
therefrom by means of a film evaporator (100C/20 Torr) to
obtain highly pure, light-colored rapeseed lecithin. This
JS product had a chrornaticLty of G14 (determined with Cardner
colorimeter) (The same shall apply hereinafter), acid value
of 22, water content of 0.1 % and phospholipid content of
65 %.
~xample 2
ao A miscella (oil content: 21 ~, phospholipid content:
2.5 %) obtained from soy beans by the extraction method
using hexane as solvent was treated by means of ultrafilters
in the same manner as in Example 1 to obtain a filtrate from
which the phospholipids had been removed and a circulating
a~ liquid containing the concentrated phospholipids. The
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4~B
solvent was removed from the former by an ordinary method
and the residue was subjected to the steam purification
(discoloration, steam distillation) to obtain the intended
oil. The product had a chromaticity of 2.9Y/0,2R, acid
value of 0.03, AOM stability of 17.5 (peroxide value: 1.9)
and a good flavor.
The solvent was removed from the latter in the same
marner as in Example 1 to obtain highly pure, light-
colored soybean lecithin. Thls product had a chromaticity
1~ of G13, acid value of 25, water content of 0.1 ~ and phos-
pholipid content of 64 96.
Example 3
A miscella [oil content: 22 %, phospholipid content
of the oil: 2.5 % (as acetone-insoluble matter)] obtained
from rapeseeds by the extraction method using hexane as
solvent was treated by means of the same ultrafiltration
device as in Example 1 under the same conditions as in
Example 1. The mlscella circulating in the modules was
contacted with the ultrafilters. The phospholipids were
~o concentrated in the circulating liquid which had not
been passed through the ultrafilters. Hexane was fed at a
rate of 69 ~/hr. into a connecting part between the
second module and the third module. Phospholipid contents
(excluding the solvent) of the circulating liquid were 20
S %, 40 % and 65 % in the respective stages. The final
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451!~
phospholipid concentration in the third stage reached 65 %.
220 Kg of the product was added to 7,500 Kg of soy bean
oil meal to obtain a homogeneous mixture easily. The
solvent was removed from the mixture in an ordinary manner
S to obtain the oil meal having a high efficiency as feed.
For comparison, oil foots obtained by treating a
crude rapeseed oil (obtained by removing the solvent
from said miscella) by the conventional degumming method
wherein water was used in an ordinary manner were added
/O to a soy bean oil meal. It was difficult to mix them
homogeneously and lumps were formed, since the oil foots
had a high viscosity. Further, a drying step was required
for removing water from the oil foots after the mixing.
The water evaporation efficiency in the drying step was
1~ low due to the lumps.
