Note: Descriptions are shown in the official language in which they were submitted.
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METHODS FOR DEGUMMING OILS
FIELD
[0001] The present invention relates to methods for improving the refining of
oils, and in
particular, to improving the degumming of vegetable oils having free fatty
acids ad phospholipids.
BACKGROUND
[0002] Vegetable oils are generally pressed or extracted oil from a vegetable
source.
Vegetable oils can contain phospholipids, commonly known as gums, which can be
hydratable or
non-hydratable. For example, the following oils can contain gums, in weight
percent, soybean 1 to
3, corn 0.6 to 0.9, sunflower oil 0.5 to 0.9 and canola oil (crude) 1 to 3.
Gums can be partially
removed from vegetable oils through know degumming processes, such as water
degumming, acid
degumming, caustic refining and enzymatic degumming. Such processes can be
found in U.S.
Patent Nos. 4,049,686; 5,239,096; 5,264,367; 5,286,886; 6,001,640; 6,033,706;
7,494,676 and
7,544,820. Further references include U.S. Pat. App. Pub. Nos. 2007/0134777;
2008/0182322 and
2012/0258017.
[0003] Other degumming processes include high shear mixers, for example, the
processes
disclosed in U.S. Patent Nos. 4,240,972; 4,698,185; 6,172,248 and 8,491,856.
It has been proposed to
refine vegetable oil using cavitation, such as that disclosed in U.S. Pat.
App. Pub. Nos. 2009/0314688;
2011/0003370 and 2014/0087042.
[0004] The existing methods are not sufficient to efficiently remove non-
hydratable
phospholipids present in the oil because the non-hydratable phospholipids are
not available to be
hydrated or reacted to enable their removal. Thus, there is a need for
alternative degumming
processes for treating vegetable oil that can provide cost- effective removal
of phosphorous,
preferably to levels of 5 ppm to 10 ppm or below, depending on applications,
and of metallic
impurities such as calcium, magnesium and/or iron. The present invention
focuses on such process
for degumming vegetable oils.
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SUMMARY
[0005] The present invention provides a process for hydrating the non-
hydratable
phospholipids in vegetable oil. A vegetable oil is mixed with an acid to form
an emulsion. The
emulsion can be mixed with a base to form a pretreated mixture. The pretreated
mixture can
have emulation droplets containing an acid and base. The process includes
compressing the
pretreated mixture to reduce the volume of the droplets containing an acid and
the droplets
containing base to form of compressed mixture. The compressed mixture is
explosively
decompressed in a decompression step. The explosive decompression of the
compressed
mixture is carried out in the range of 1 x 105 MPa per second to about 3 x 106
MPa per second.
The decompression step causes the droplets containing the acid and the base to
burst and form
smaller droplets containing an acid and droplets containing a base.
[0006] In one embodiment, the process can include subjecting the pretreated
mixture to a
compression step and at least two decompression step intervals. The
decompression step
intervals can be each carried out at a decompression rate in the range of 1 x
105 MPa per second
to about 3 x 106 MPa per second.
[0007] In another embodiment, the explosive decompression can be carried out
at a
decompression rate such that cavitation bubbles are not formed, for example,
in the range of 1 x
105 MPa per second to about 3 x 106 MPa per second.
[0008] In another embodiment, the explosive decompression can be carried out
at a
decompression rate such that the compressed mixture remains in entirely liquid
form during the
explosive decompression.
[0009] In another embodiment, the pretreated mixture can be compressed to a
level of at
least 3 MPa and the volume of the droplets containing an acid and base can be
reduced by at
least 0.1%.
[0010] In another embodiment, the device used to compress the pretreated
mixture can be
a plunger, centrifugal or gear pump. The device used to decompress the
compressed mixture can
be a throttle device, such as an orifice, nozzle or pressure loss fluid
control device, which can be
adjustable or non-adjustable.
[0011] In a further embodiment, the process can include multiple compression
and
decompression devices, the compression and decompression devices can be
positioned in series
to form a consecutive compression and decompression intervals for processing
the pretreated
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mixture. Alternatively, the compression and decompression devices can be
arranged in parallel
for processing the pretreated mixture.
[0012] In yet another embodiment, the vegetable oil can be a crude oil or a
previously
water degummed oil.
[0013] The present invention provides a vegetable oil degumming system. The
system
can include a tank for mixing a vegetable oil and an acid to form an emulsion
and a base tank.
The base from the base tank can be mixed with the oil and acid emulsion to
form a pretreated
mixture. The system further includes a compression device having an inlet for
receiving the
pretreated mixture. The compression device is capable of compressing the
pretreated mixture to
form a compressed mixture having a pressure of at least 3 MPa. The system
further includes a
decompression device having an inlet for receiving the compressed mixture. The
decompression
device is capable of decompressing the compressed mixture at a rate in the
range of 1 x 105 MPa
per second to about 3 x 106 MPa per second without subjecting the mixture to
cavitation to form
a degummed vegetable oil.
[0014] In an embodiment, the system can include a pre-filter device for
filtering the
pretreated mixture prior to compression with the compression device. The pre-
filter device can
be connected to the inlet of the compression device.
[0015] In another embodiment, the device used to compress the pretreated
mixture can be
a plunger, centrifugal or gear pump. The device used to decompress the
compressed mixture can
be a throttle device, such as an orifice, nozzle or pressure loss fluid
control device, which can be
adjustable or non-adjustable.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The following figures illustrate various aspects of one or more
embodiments of
the present invention, but are not intended to limit the present invention to
the embodiments
shown.
[0017] FIG. 1 shows a process for degumming vegetable oil by use of
compression and
decompression steps.
DETAILED DESCRIPTION
[0018] As used herein, when a range such as 5-25 is given, this means at least
or more
than 5 and, separately and independently less than or not more than 25.
[0019] The present invention relates to processes and systems for degumming
vegetable
oils, such as plant-derived oils. The processes and systems use the energy
released from
explosive decompression to achieve effective degumming of vegetable oils,
which allows for the
removal of phospholipids, metals and other impurities.
[0020] Turning to FIG. 1, a vegetable oil 1 and an acid 2 can be mixed 4 in a
mixing or
holding tank 6 to form an acid in oil emulsion 8. The vegetable oil 1 can be
any oil derived,
produced or extracted from a vegetable, seed or vegetable plant, such as acai
oil, almond oil,
babassu oil, blackcurrent seed oil, borage seed oil, canola oil, cashew oil,
castor oil, coconut oil,
coriander oil, corn oil, cottonseed oil, crambe oil, flax seed oil, grape seed
oil, hazelnut oil,
hempseed oil, jatropha oil, jojoba oil, linseed oil, macadamia nut oil, mango
kernel oil,
meadowfoam oil, mustard oil, neat's foot oil, olive oil, palm oil, palm kernel
oil, palm olein,
peanut oil, pecan oil, pine nut oil, pistachio oil, poppy seed oil, rapeseed
oil, rice bran oil,
safflower oil, sasanqua oil, sesame oil, shea butter, soybean oil, sunflower
seed oil, tall oil,
tsubaki oil walnut oil. The vegetable oil can be in any condition, for
example, the vegetable oil
can be crude, refined, pressed, extracted, filtrated, dcwatered or water
degummcd.
[0021] The vegetable oil 1 can have a phosphorus content in the range of 15 to
1,200
ppm. For example, a crude vegetable oil can have a phosphorus content in the
range of 200-
1,200 ppm whereas a water degummed vegetable oil can have a lower phosphorus
content in the
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range of 15 to 200 ppm. The processes and systems described herein can reduce
the phosphorus
content of the vegetable oil, for instance, the phosphorus content can be
reduced by at least 50,
60, 70, 80, 85, 90, 92.5, 95, 96, 97, 98 or 99 percent.
[0022] The acid 2 can be added to the vegetable oil to aid in the hydration of
the non-
hydratable phospholipids. The acid 2 can be organic or inorganic, for example,
phosphoric acid,
hydrochloric acid, sulfuric acid, ascorbic acid, acetic acid, citric acid,
fumaric acid, maleic acid,
tartaric acid, succinic acid, glycolic acid or any combination thereof. The
acid is preferably
added to the vegetable oil in an aqueous solution. For example, the aqueous
acid can have any
concentration of acid such that when added to the vegetable oil the acid
content, excluding the
water, is at least 0.005 weight percent of the total weight of the oil. The
amount of aqueous acid
added to the vegetable oil can be in the range of 0.1 to 0.3 weight percent of
the oil. The
aqueous acid can have an acid concentration of 50 to 90 weight percent or 60,
70, 80 or 85
weight percent acid.
[0023] The vegetable oil 1 and acid 2 can be combined 4 in line by a static
mixer or the
like or be combined or individually added to a mixing tank 6 to form an acid
in oil emulsion as
known in the art. The emulsion 8 can have droplets in the vegetable oil. The
droplets can
contain water and acid.
[0024] The emulsion 8 can be combined with a base 10 to form a pretreated
mixture 14.
A base 10 can be added to achieve neutralization of free fatty acids in the
vegetable oil. The
base 10 can be sodium hydroxide, potassium hydroxide, sodium silicate, sodium
carbonate,
calcium carbonate, or any combination thereof. The base is preferably added to
the emulsion 8
in an aqueous solution. For example, the aqueous base can have any
concentration of base such
that when added to the emulsion the base content, excluding the water, is at
least 0.005 weight
percent of the total weight of the vegetable oil. The amount of aqueous base
added to the
emulsion 8 can be in the range of 0.1 to 0.5 weight percent of the oil. The
aqueous base can have
an base concentration of Ito 30 weight percent or 5, 10, 15, 20 or 25 weight
percent base.
[0025] The emulsion 8 and base 10 can be combined in line by a static mixer or
the like
or be combined or individually added to a mixing apparatus 12, such as a
mixing tank, to form a
pretreated mixture 14. The pretreated mixture 14 can have droplets in the
vegetable oil. The
droplets can contain water and acid, water and base or a combination of water,
acid and base.
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[0026] The pretreated mixture 14 can be processed at a temperature in the
range of 20 to
100 C, or 30, 40, 50, 60, 70, 80 or 90 C. Preferably, the pretreated mixture
is maintained at a
processing temperature in the range of 40 to 95 C.
[0027] The pretreated mixture 14 is subjected to a compression step. The
compression
step can include passing the pretreated mixture 14 through a compression
device 16 to form a
compressed pretreated mixture 18. The compression device 16 can include, for
example, a
pump, such as a plunger, centrifugal or gear pump. The compression device 16
can increase the
pressure of the pretreated mixture 14 to at least 3 MPa to form the compressed
pretreated mixture
18. For example, the pressure of the pretreated mixture 14 can be increased to
a pressure in the
range to 3 to 10 MPa, or 3.5, 4, 4.5, 5, 6, 7, 8 or 9 MPa.
[0028] The compressed pretreated mixture 18 is subjected to a decompression
step.
Preferably, the The decompression step, or multiple decompression steps,
operates to degum the
compressed pretreated mixture 18. The decompression step can include passing
the compressed
pretreated mixture 18 through a decompression device 20. The decompression
device 20 can
include, for example, a throttling device, which can be adjustable or non-
adjustable, a local
constriction, an orifice, pressure loss fluid control valve, nozzle, baffle or
aperture. in one
embodiment, the orifice or nozzle can have an opening diameter less than or
equal to 2 mm, or
preferably less than or equal to 0.5 mm. The decompression device 20 can have
a sharp edged or
squatted edge surface for creating more shear and at a reduced pressure drop
time.
[0029] The decompression device 20 can decompress or reduce the pressure in
the
compressed pretreated mixture 18 at a rate in the range of 1 x 105 MPa per
second to about 3 x
106 MPa per second. The pressure drop created by the decompression device can
be in the range
of 0.1 to 3 MPa, or at least 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2,
2.2, 2.4, 2.6 or 2.8 MPa. The
decompression device reduces the volume of the compressed droplets containing
acid and base.
The compressed droplets containing acid, base or a combination thereof can be
increased in
volume in the range of 0.1 percent to 0.4 percent after being decompressed
with the
decompression device 20. Likewise, the droplets containing acid, base or a
combination thereof
can be reduced in volume in the range of 0.1 to 0.4 percent after being passed
through the
compression device 16. For example, the compression device 16 can reduce the
volume of the
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droplets by 0.1 percent when the pressure of the pretreated mixture 14 is
increased to 3 MPa and
the volume can be reduced by 0.3 percent when the pressure is increased to 7
MPa.
[0030] The decompression step can reduce the pressure or decompress the
compressed
pretreated mixture at a rate that can cause the droplets containing acid, base
or a combination
thereof to burst explosively into smaller droplets or increase the volume of
the droplets to a
precompressed state. Without being bound by any particular theory, it is
believed that the acid in
the smaller burst droplets of the decompressed mixture can react with the non-
hydratable
phosphatides in the oil and decompose them. The finer dispersion of droplets
in the
decompressed mixture promotes and enhances the reaction because both reagents,
acid and base,
are added to the oil in a diluted solution. A very fine dispersion of droplets
can enhance the
reaction when it has to be substantially completed and the oil requires low
residual phosphatides
content. Preferably, the dispersion of droplets is so fine that the reaction
between the acid and the
non-hydratable phosphatides in the oil is substantially instantaneous or at
least completed within
seconds of the decompression step or steps. A fine dispersion of droplets can
also enhance a
neutralization reaction with the base. After decompression, the aqueous base
droplets can burst
to create smaller diameter droplets, which in turn increases the surface
interface of the droplets
with the oil, and then diffusion distances can decrease and the reaction is
enhanced. The
decompression step or steps can also promote self-oscillations in the droplets
containing acid,
base or a combination thereof, which can improve heat and mass transfer
processes.
[0031] The compressed pretreated mixture 18 can be decompressed in one pass
through
the decompression device 20. Alternatively, the compressed pretreated mixture
18 can be passed
through the decompression device 20 multiple times, such as at least 2, 3, 4,
5, 6, 7 or 8 passes.
In another embodiment, two or more decompression devices 20 can be in series
to carry out
successive decompression steps, such as at least 2, 3, 4, 5, 6, 7 or 8
decompression intervals.
Each decompression step or interval or pass can result in a reduction in
pressure in the range of
0.1 to 3 MPa, or at least 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2,
2.4, 2.6 or 2.8 MPa.
Between each decompression step, interval or pass, the decompressed mixture
can have a
residence period before being subjected to the next decompression. For
example, the residence
period can be in the range of 0.1 to 3 seconds.
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[0032] The residence time period can provide time to allow the non-hydratable
phospholipids within a lipid matrix of the oil to migrate to an oil-water
interface with the
droplets. In same time, aqueous acid and base droplets can coalesce, and the
interface can
decrease, wherein diffusion distances will increase and all this will slow
down the mass transfer
processes. As such, at least a second explosive decompression step can promote
further reaction
and can impart additional treatment of the emulsion for reaction completion.
Compression and
explosive decompression steps can be repeated 2, 3, 4, or 5 and more times if
needed. This action
promotes gum formation, adsorption of metal-containing compounds and other
reactions and
processes.
[0033] The decompressed mixture 22 can be transferred to a holding tank or
container 24
to allow the mixture to settle and, to the extent possible, separate into
phases, e.g., oil and water.
The holding tank 24 can be used for storing the decompressed mixture 22 for
further processing.
The decompressed mixture 26 can be sent to one or more separation steps. A
separation device,
28, as shown, can be used to separate the gums from the oil. The separation
device 28 can be a
device known in the art, for example a filter or centrifuge. Preferably, the
separation device 28
separates the decompressed mixture 22, 26 into a purified oil 32 and a waste
stream 30, such as
the aqueous component of the mixture. The oil can be subjected to other
processing steps as
known in the art, such as bleaching or deodorizing. Such steps can be
desirable depending on
the intended use of the purified oil product.
[0034] In order to promote a further understanding of the invention, the
following
examples are provided. These examples are shown by way of illustration and not
limitation.
[0035] Example 1
[0036] 300 g water degummed soybean oil with a measured residual phosphorus
content
of 46 ppm was heated to a temperature of approximately 70 C and mixed with
0.01 weight
percent aqueous phosphoric acid (85 wt%) to form an acid/oil emulsion having
0.0085 weight
percent phosphoric acid. The acid/oil emulsion was for 2 minutes with a
magnetic stirrer and
0.35 weight percent of aqueous caustic soda (9.5 wt%) was added to the
acid/oil emulsion to
form a pretreated mixture. The pretreated mixture was compressed and
subsequently
decompressed in three decompression intervals. The compression step included
passing the
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pretreated mixture through a plunger pump to form a compressed mixture having
a pressure of 9
MPa. The overall pressure drop after three decompression intervals was 7.88
MPa.
[0037] The decompression intervals were carried out with three throttle
orifice devices
positioned in series and connected to the discharge pipe of the plunger pump.
The compressed
mixture was decompressed in the first throttle device using an explosive
decompression rate was
1.4 x 106 MPa per second. The second throttle device, downstream of the first,
carried out an
explosive decompression at the rate of 3.2 x 105 MPa per second. The third
throttle device,
downstream of the second, carried out an explosive decompression at the rate
of 1.1x 105 MPa
per second to form a decompressed vegetable oil having a pressure of 1.12 MPa
that was further
processed to separate the aqueous acid and base to form a degummed vegetable
oil. The
degummed vegetable oil was analyzed for phosphorus and other trace elements. A
residual
phosphorus content of 2.3 ppm was measured and the iron, Fe, content had
decreased from the
initial value of 0.8 ppm to 0.05 ppm. The concentrations of calcium, Ca, had
decreased to 2 ppm
from 35 ppm and the magnesium, Mg, had decreased to 0 ppm from 8 ppm. Thus,
the
degumming process resulted in a soybean oil having a 95 percent reduction in
phosphorus, a 93.8
percent reduction in iron, a 94.3 percent reduction in calcium and a 100
percent reduction in
magnesium.
[0038] Example 2
[0039] A portion of the pretreated mixture from Example 1 was subjected to a
compression step and two consecutive decompression steps in intervals. The
compression step
was carried out by passing the pretreated mixture through the plunger pump of
Example 1 to for
a compressed mixture having a pressure of 5.8 MPa. The overall pressure drop
after two
decompression intervals was 4.87 MPa.
[0040] The decompression intervals were carried out with two throttle orifice
devices
positioned in series and connected to the discharge pipe of the plunger pump.
The compressed
mixture was decompressed in the first throttle device using an explosive
decompression rate was
1.7 x 106 MPa per second. The second throttle device, downstream of the first,
carried out an
explosive decompression at the rate of 7.8 x 105 MPa to form a decompressed
vegetable oil
having a pressure of 0.93 MPa that was further processed to separate the
aqueous acid and base
to form a degummed vegetable oil.
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[0041] The degummed vegetable oil was analyzed for phosphorus and other trace
elements. A residual phosphorus content of 3.4 ppm was measured and the iron,
Fe, content had
decreased from the initial value of 0.8 ppm to 0.07 ppm. The concentrations of
calcium, Ca, had
decreased to 4 ppm from 35 ppm and the magnesium, Mg, had decreased to 2 ppm
from 8 ppm.
Thus, the degumming process resulted in a soybean oil having a 92.6 percent
reduction in
phosphorus, a 91.3 percent reduction in iron, a 88.6 percent reduction in
calcium and a 75
percent reduction in magnesium.
[0042] Example 3
[0043] Crude soybean oil with a residual phosphorus content of 530 ppm was
mixed with
with 0.03 weight percent aqueous phosphoric acid (85 wt%) to form an acid/oil
emulsion having
0.0255 weight percent phosphoric acid. The acid/oil emulsion was for 2 minutes
with a
magnetic stirrer and 0.6 weight percent of aqueous caustic soda (9.5 wt%) was
added to the
acid/oil emulsion to form a pretreated mixture. The pretreated mixture, at 90
C, was
compressed and subsequently decompressed in three intervals. The compression
step included
passing the pretreated mixture through a plunger pump to form a compressed
mixture having a
pressure of 3.4 MPa. The overall pressure drop after three decompression
intervals was 3.19
MPa.
[0044] The decompression intervals were carried out with four throttle orifice
devices
positioned in series and connected to the discharge pipe of the plunger pump.
The compressed
mixture was decompressed in the first throttle device using an explosive
decompression rate was
4.2 x 105MPa per second. The second throttle device, downstream of the first,
carried out an
explosive decompression at the rate of 2.8 x 105 MPa per second. The third
throttle device,
downstream of the second, carried out an explosive decompression at the rate
of 1.9 x 105 MPa
per second. The fourth throttle device, downstream of the third, carried out
an explosive
decompression at the rate of 1.4 x 105 MPa per second to form a decompressed
vegetable oil
having a pressure of 0.21 MPa that was further processed to separate the
aqueous acid and base
to form a degummed vegetable oil. The degummed vegetable oil was analyzed for
phosphorus
and other trace elements. A residual phosphorus content of 8 ppm was measured.
Thus, the
degumming process resulted in a soybean oil having a 98.5 percent reduction in
phosphorus.
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[0045] While various embodiments in accordance with the present invention have
been
shown and described, it is understood the invention is not limited thereto,
and is susceptible to
various changes and modifications as known to those skilled in the art.
Therefore, this invention
is not limited to the details shown and described herein.
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