U.S. patent application number 10/619833 was filed with the patent office on 2004-05-06 for substantially fat free products from whole stillage resulting from the production of ethanol from oil-bearing agricultural products.
Invention is credited to Hammond, Neal, Prevost, John.
Application Number | 20040087808 10/619833 |
Document ID | / |
Family ID | 32107162 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040087808 |
Kind Code |
A1 |
Prevost, John ; et
al. |
May 6, 2004 |
Substantially fat free products from whole stillage resulting from
the production of ethanol from oil-bearing agricultural
products
Abstract
A process for obtaining substantially fat free products from
whole stillage produced during ethanol production from agricultural
products, such as cereal grains. More particularly, at least a
portion of the fat is removed from both the thin stillage stream
and the wet distillers grains that result from whole stillage.
Inventors: |
Prevost, John; (Baton Rouge,
LA) ; Hammond, Neal; (Galt, CA) |
Correspondence
Address: |
HENRY E. NAYLOR & ASSOCIATES
P.O. BOX 86060
BATON ROUGE
LA
70879-6060
US
|
Family ID: |
32107162 |
Appl. No.: |
10/619833 |
Filed: |
July 15, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10619833 |
Jul 15, 2003 |
|
|
|
10281490 |
Oct 28, 2002 |
|
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Current U.S.
Class: |
554/9 |
Current CPC
Class: |
C12P 7/06 20130101; Y02E
50/10 20130101; C11B 1/00 20130101; Y02E 50/17 20130101 |
Class at
Publication: |
554/009 |
International
Class: |
C11B 001/00 |
Claims
What is claimed is:
1. A process for recovering an oil stream from the whole stillage
produced in the production of ethanol from an oil-bearing
agricultural product, which process comprises: separating the whole
stillage in a solids rich stream referred to as the wet distillers
grains stream and a water rich stream referred to as the thin
stillage stream, both streams containing oil from the cereal
grains; conducting the wet distillers grains stream, the thin
stillage stream, or both, to an oil removal stage wherein at least
a portion of the oil is removed from the one or both streams, and
wherein the oil is removed by centrifugation or solvent
extraction.
2. The process of claim 1 wherein centrifugation is used to
separate the oil from the one or more streams, thereby resulting in
an oil and water stream, which oil and water stream is sent to a
separation zone.
3. The process of claim 2 wherein the separation zone is a
distillation stage wherein water is distilled from the oil.
4. The process of claim 2 wherein the separation zone is a
decanting stage wherein the oil and water stream is allowed to sit
in a suitable vessel until a two phase system develops, an oil
phase and a water phase.
5. The process of claim 4 wherein the oil phase is decanted from
the water phase.
6. The process of claim 1 wherein only the thin stillage stream is
subjected to oil removal.
7. The process of claim 6 wherein centrifugation is used to remove
oil from the thin stillage stream.
8. A process for recovering an oil stream from the thin stillage
that results in the production of ethanol from cereal grains, which
process comprises: drying the thin stillages stream so that its
water content is less than about 15 wt. %; passing the dried thin
stillage into an extraction zone; contacting said dried thin
stillage with a normally gaseous solvent for in effective amount of
time thereby extracting oil from said dried thin stillage and
resulting in a substantially oil free dry thin stillage and an oil
in solvent solution; conducting said oil in solvent solution to a
separation zone wherein the solvent is evaporated from the oil;
collecting the substantially oil free thin stillage and the
oil.
9. The process of claim 8 wherein the solvent is selected from the
group consisting of butane, propane, and mixtures thereof.
10. The process of claim 8 wherein the oil removal is performed in
batch mode.
11. The process of claim 8 wherein the oil removal is performed in
continuous mode.
12. In a process wherein a cereal grain is milled, formed into a
mash and fermented to produce an ethanol stream and a whole
stillage stream, which whole stillage stream is centrifuged to
produce: a) a wet distiller grains stream, which is dried to
produce a dried distiller grains stream; and b) a thin stillage
stream, which is evaporated to produce a syrup stream; and wherein
all of said streams contain oil from the cereal grain, the
improvement which comprises removing at least a portion of the oil
from one or more of the stream selected from the wet distiller
grains stream, the dried distiller grains stream, the thin stillage
stream, and the syrup stream.
13. The process of claim 12 wherein only the thin stillage stream
is subjected to oil removal.
14. The process of claim 13 wherein the oil is removed from the
thin stillage stream by centrifugation.
15. The process of claim 14 wherein centrifugation results in a
stream containing a mixture of oil and water.
16. The process of claim 15 wherein the mixture of oil and water
stream is conducted to a decanting vessel wherein the mixture is
allowed to sit until an oil phase is formed on top of a water
phase.
17. The process of claim 16 wherein the oil phase is decanted from
the water phase.
18. The process of claim 15 wherein the mixture of oil and water
stream is conduced to a distillation stage wherein the water is
distilled from the oil.
19. The process of claim 12 wherein the thin stillage stream is
conducted to an evaporator to produce a syrup stream containing
less than about 15 wt. % water, which syrup stream is itself
conducted to an oil removal stage wherein at least of the oil is
removed from the syrup.
20. The process of claim 19 wherein the oil is removed from the
syrup by centrifugation to produce a mixture of oil and water
stream.
21. The process of claim 20 wherein the mixture of oil and water
stream is conducted to a decanting vessel wherein the mixture is
allowed to sit until an oil phase is formed on top of a water
phase.
22. The process of claim 21 wherein the oil phase is decanted from
the water phase.
23. The process of claim 20 wherein the mixture of oil and water
stream is conduced to a distillation stage wherein the water is
distilled from the oil.
24. The process of claim 12 wherein the thin stillage is conducted
to an evaporator to produce a solids rich syrup stream, then to a
drier to produce a free-flowing solids stream, which free-flowing
solids stream is conducted to an oil removal zone wherein at least
a portion of its oil is removed by use of solvent extraction.
25. The process of claim 24 wherein the free-flowing solids stream
is subjected to oil removal process comprising: introducing the
free-flowing solids into an evaporation vessel; removing air from
the extraction vessel; introducing a normally gaseous solvent into
the extraction vessel at a rate and under a pressure to cause the
normally gaseous solvent to convert to a liquid; causing the
free-flowing solids and solvent to have an effective residence time
to allow at least a portion of the oil to dissolve in the solvent;
passing the oil and solvent to a separation zone wherein the
solvent is separated from the oil.
26. The process of claim 25 which is a continuous process.
27. The process of claim 25 which is a batch process.
28. The process of claim 25 wherein the normally gaseous solvent is
selected from butane, propane, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of U.S. Ser. No.
10/281,490 filed Oct. 28, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates a process for obtaining substantially
fat free products from whole stillage produced during ethanol
production from agricultural products, such as cereal grains. More
particularly, at least a portion of the fat is removed from both
the thin stillage stream and the wet distillers grains that result
from whole stillage.
[0004] 2. Description of Related Art
[0005] In a conventional ethanol production process utilizing corn
as the starch containing feedstock, the corn is ground to produce a
milled corn. This is typically achieved by the use of a hammer mill
or other suitable milling equipment. Water and enzymes are added to
the milled corn and heated to form a mash. The mash is then mixed
in a fermentation vessel with water, yeast and optionally minerals
and nutrients to enhance the fermentation of the mash. The
resulting fermented product, commonly referred to as the "beer", is
then distilled to produce an ethanol rich stream (about 95% ethanol
and 5% water by weight) and whole stillage. The whole stillage
comprises water, as well as the solids left over from the
fermentation. The whole stillag is typically centrifuged to remove
a substantial portion of the water to form a solids rich fraction
commonly referred to as wet distillers grains and a substantially
liquid fraction commonly referred to as thin stillage. The wet
distillers grains fraction includes most of the protein-containing
solids from the whole stillage. It also contains about 8 to 12 wt.
% fat. The thin stillage fraction, after evaporation to form a
syrup, will typically contain from about 8 to 15 wt. % a fat. This
syrup is also referred to as condensed distillers solubles (CDS),
and is typically combined with the wet distillers grains and sent
to a dryer to produce a dry protein containing animal feed called
distiller dried grain solubles (DDGS).
[0006] Conventional ethanol processes have several significant
problems. One problem is the energy costs to remove water from the
whole stillage to produce a low economic value DDGS. A second
problem is the environmentally unacceptable amount of volatile
organic compounds (VOC), air toxics, and combustion pollutants,
such as CO, NO.sub.x, and particulate matter, released into the
atmosphere during conventional drying methods. To achieve an
acceptable levels VOC, air toxics, and combustion pollutants
release amount requires large capital investments in thermal
oxidizers and other equipment to capture the VOC, air toxics, and
combustion pollutants released during conventional drying methods,
as well as expensive equipment maintenance. Another problem,
depending on the end use of the stream, is that the fat content for
both the thin stillage fraction and the wet distillers grains
fraction can be considered too high. These problems have hampered
the commercial success of ethanol production processes that have to
date, remained economically viable due only to governmental
subsidies.
OBJECTS AND SUMMARY OF THE INVENTION
[0007] One object of the present invention is to provide an
improved ethanol production process that results in value added
flavor enhancing, nutritional, nutraceutical, and/or pharmaceutical
by products.
[0008] Another object of the present invention is to provide an
improved ethanol production process that minimizes the amount of
VOC and other pollutants released to the atmosphere during the
treatment of the whole stillage.
[0009] Still another object of the present invention is to provide
an improved ethanol production process resulting in an oil stream,
which oil stream is obtained from dried distillers grains, thin
stillage, syrup resulting from thin stillage, or a mixture
thereof.
[0010] Other objects and advantages of this invention shall become
apparent from the ensuing descriptions of the invention.
[0011] Accordingly, an improved ethanol producing process is
disclosed wherein a starch-containing feedstock, preferably a
cereal grain such as corn, is processed to produce ethanol and
whole stillage. The whole stillage comprises solids, nutrients,
yeast and water remaining after the ethanol has been distilled off.
The whole stillage is centrifuged, filtered or otherwise separated
by any suitable technique to produce a substantially solids stream
and a substantially liquid stream. The substantially solids stream
is referred to as wet distillers grains and contains most of the
protein-containing solids, from about 8 to about 12 wt. % fat or
oil, and water. The substantially liquid stream, referred to as the
thin stillage will comprise the nutrients, yeast and most of the
water from the whole stillage. The thin stillage is typically
subjected to an evaporation step remove water and produce a syrup
that will contain about 7 to about 15 wt. % oil or fat. It is to be
understood that no distinction is made herein between the terms
"oil" and "fat" and the words can be used interchangeably
herein.
[0012] The wet distillers grains are dried under conditions that do
not denature the proteins contained in the distillers grains, and
more preferably, under conditions that minimize volutizing organic
components in the wet distillers grains. The drying conditions used
will depend on a variety of factors. For example, when utilizing
spray drying, these factors include the ease at which the wet
distillers grains can be atomized, the humidity of the air in the
drying environment, the temperature of the hot air used to dry the
wet distillers grains, the temperature of the wet distillers grains
when they enter the spray drier, and the contact time between the
hot air and the atomized wet distillers grain. In a preferred
embodiment, these factors are controlled to produce a protein-rich
product having a water content of less than about 15% by weight.
More preferably a protein-rich product is produced that is
substantially free of oil, but that will require an oil removal
step. It has been found that setting the temperature and contact
time to achieve a hot air exhaust temperature between about
140.degree. F. and about 170.degree. F. will result in a
protein-rich product containing less than about 15% water by weight
and whose proteins have not been denatured. Under normal humidity
conditions and using conventional spray drying technology an
exhaust temperature in the above range should result in an inlet
hot air temperature of less than about 450.degree. F., and a
contact time of less than about three minutes. Utilization of the
above drying conditions will also reduce the VOC emissions to the
atmosphere. In a preferred embodiment the drying conditions are set
to maintain the temperature of the wet distillers grains at an
effective temperature that is low enough so that the amount of VOCs
emitted will be less than the environmental regulations permit. It
is preferred that a temperature be used wherein substantially no
VOCs are emitted. It is further preferred that any VOC that is
volatized pass through a cold trap and then filtered to remove
water to produce a VOC product. The VOC product can then be
utilized as a supplement to flavor enhance other products.
[0013] The dried distillers grains can be subjected to an oil
removal step. It is preferred that an oil removal technique be used
that will remove substantially all of the oil from the dried
distillers grains. Non-limiting examples of oil removal techniques
that can be used include centrifugation, pressing with and without
the use of a solvent, and solvent extraction without the use of
pressing. The preferred solvent for solvent extraction is a
normally gaseous solvent, more preferably butane, propane, or
mixtures thereof. By normally gaseous we mean a solvent in which
the oil is soluble and being in the gas phase at atmospheric
pressure and at room temperature (approximately 75.degree. F.).
[0014] The syrup can be added to the wet distillers grain prior to
the drying step and be processed under the same conditions as the
wet distillers grains as described above. An oil removal step can
be performed on either the thin stillage before evaporation or on
the syrup after evaporation. If performed prior to evaporation, an
oil removal process such as centrifugation is preferred whereas
after evaporation a solvent extraction process is preferred to
extract at least a portion of the oil from the syrup.
[0015] In another alternate embodiment the thin stillage stream is
not subjected to oil removal and is passed through a
microfiltration unit utilizing a filter size to form a carotenoid
containing retentate and a nutrient rich permeate. A filter having
a pore size of about 0.1 to 1.0 micron can be used. The carotenoid
containing retentate is then dried to produce a carotenoid rich
product having less than about 15% water by weight. It has been
found that setting the temperature and contact time to achieve a
hot air exhaust temperature between about 140.degree. F. and about
170.degree.F. will result in a carotenoid rich product containing
less than about 15% water by weight. Under normal humidity
conditions and using a conventional spray dryer an exhaust
temperature in the above range should result in an inlet hot air
temperature of less than about 450.degree. F., and a contact time
of less than about three minutes. In a preferred embodiment any
volatized VOC is passed through a cold trap and filter to produce a
liquefied VOC product.
[0016] In yet another alternate embodiment the nutrient rich
permeate is passed through an ultrafiltration unit utilizing a
filter size to form a protein and yeast containing retentate and
vitamin and mineral containing permeate. A filter having a pore
size of less than about 0. I microns is preferred. The protein and
yeast containing retentate is dried to produce a protein and yeast
rich product having less than 15% water by weight. It has been
found that setting the temperature and contact time to achieve a
hot air exhaust temperature between about 140.degree. F. and about
170.degree. F. will result in a protein and yeast rich product
containing less than about 15% water by weight and whose proteins
have not been denatured. Under normal humidity conditions and using
a conventional spray dryer an exhaust temperature in the above
range should result in an inlet hot air temperature of less than
about 450.degree. F., and a contact time of less than about three
minutes. The vitamin and mineral containing permeate can also be
dried under the same conditions as the protein and yeast containing
retentate to produce a vitamin and mineral rich product having less
than 15% water by weight. It is preferred that any volatized VOC's
be passed to a cold trap and filter to produce a liquid VOC
product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings illustrate a preferred embodiment
of this invention. However, it is to be understood that this
embodiment is not intended to be exhaustive, nor limiting of the
invention. They are but examples of some of the forms in which the
invention may be practiced.
[0018] FIG. 1 is a schematic illustrating a conventional ethanol
production process, but with oil removal steps on products
resulting after centrifugation of the whole stillage.
[0019] FIG. 2 is a schematic illustrating a preferred embodiment of
this invention to treat the wet distillers grain to produce a
non-denatured protein rich product.
[0020] FIG. 3 is a schematic illustrating a preferred embodiment of
this invention to treat the thin stillage through use of
microfiltration to produce a carotenoid rich product.
[0021] FIG. 4 is a schematic illustrating a preferred embodiment of
this invention to treat the permeate stream from the
microfiltration through use of ultrafiltration to produce a
protein/yeast rich product and/or a vitamin/mineral rich
product.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Without any intent to limit the scope of this invention,
reference is made to the figures in describing the preferred
embodiments of the invention utilizing corn as the starch
containing feedstock. The process described herein can also be used
with other starch containing feedstocks such as bagasse, sugar
cane, grains, and other oil-bearing starch or sugar based
materials.
[0023] In a typical ethanol production process as illustrated in
FIG. 1, a starch-containing feedstock 1, such as corn, is fed to a
grinder 2 to produce a milled corn 3. The milled corn 3 is then
sent to a mixer 4 where water 5, as well as enzymes 6, are added to
produce a liquid mash 7. The liquid mash 7 is then sent to a
fermentation vessel 8 where the desired yeast and additional
enzymes 9, as well as the minerals and nutrients 10 if necessary
for efficient fermentation, are added. After an effective amount of
fermentation time a "beer" is produced and is sent to distillation
unit 12 where an ethanol rich (about 95% ethanol by weight) stream
13 is separated from the remaining fermented solids and water. The
remaining fermented solids and water is generally known as the
whole stillage 14. The whole stillage 14 is processed to produce an
animal feed commonly known as DDGS. The conventional method of
treating whole stillage 14 is conduct it to a centrifuge 15 to form
two separate streams, a substantially solids stream and a
substantially liquid stream. The substantially solids stream is
referred to as the wet distillers grains fraction 16. The
substantially liquid stream is referred to as the thin stillage
fraction 17. The wet distillers grains fraction 16 is comprised of
most of the solids, protein, water, and about 8 to 12 wt. % oil.
The thin stillage stream 17 is substantially all water with some
oil and up to about 10 wt. % solids. It includes the minerals,
nutrients, yeast and the remaining water that was found in the
whole stillage 14. In a typical process, the thin stillage stream
17 is sent to evaporator 18 where water 19 is removed and the
remaining solids or syrup 20 are combined with the wet distillers
grain 16 and sent to a dryer 21. In the improved process of the
present invention oil can removed at various stages of the process.
For example, the wet distillers grains can be passed to oil removal
step 16A wherein at least a portion of the oil is removed. Since
the wet distillers grains still contain a significant amount of
water, it is preferred to remove the oil by a centrifugation
process wherein the wet distillers grains are introduced into a
centrifuge apparatus and centrifuged at an effective speed and
amount of time to cause oil to be removed from the wet distillers
grains. The resulting liquid products from centrifugation will be
predominantly comprised of water and oil, which can be separated
from each other by any suitable oil/water separation technique. For
example, the oil/water mixture can be conducted to a decanting tank
and allowed to sit for an effective amount of time to allow phase
separation to occur. That is for an oil phase and a water phase to
form. The oil phase can then be easily decanted. It is also within
the scope of this invention that the oil/water mixture be passed
through a countercurrent vessel containing one or more suitable
vertically disposed distribution trays wherein a solvent, such a
C.sub.2 to C.sub.6 alkane is passed counter to the flow of the
oil/water mixture. The oil will be taken up in the solvent and be
carried with the solvent to a separation vessel wherein the solvent
can be flashed or distilled from the oil and recycled.
[0024] The wet distillers grains can also be dried via dryer 21 to
produce a dried distillers grains fraction which can then be
subjected to oil removal via 24A. Oil removal step 24A can be any
suitable oil removal process including centrifugation, but solvent
extraction is preferred. The dried distillers grains can be first
pressed before solvent extraction. That is, the dried distillers
grains can be put in a suitable press and a substantial amount of
oil removed via pressing. At least a portion of the remaining oil
can be removed by subjecting the pressed grains to a suitable
solvent, preferably a normally gaseous solvent, more preferably one
selected from butane, propane and mixtures thereof. Since the
solids of the wet distillers grains originate from the milling of
the cereal grain, it is unlikely that pressing will be needed to
remove the oil.
[0025] Dryer 21 is typically operated with hot air having an inlet
temperature at about 1000.degree. F.-1200.degree. F. The hot air
will remain in contact with the wet distillers grain 16 and syrup
20 for an effective amount of time, which will typically be from
about 3 to 10 minutes, more preferably from about 4 to 6 minutes
before exiting the dryer 20 having an exhaust temperature at about
200.degree. F.-225.degree. F. At these conditions the protein
contained in the dried solids 24 are denatured and are only good
for use in animal feed known as DDSG. In addition any water vapor
22 and VOC 23 in the wet distillers grain 16 and syrup 20 is
volatized and either released to the atmosphere or passed through
expensive conventional thermal oxidizers (not shown).
[0026] Both the thin stillage and syrup can each be individually,
or a mixture thereof, conducted to an oil removal step, 17A and
20A. For example, the thin stillage can be centrifuged in a similar
manner as the wet distillers grains and the resulting oil/water
mixture sent to a separation zone wherein the water is separated
from the oil. As mentioned previously, separation can be done by
simple decanting, by distilling the water from the oil, or by
passing a solvent, in which the oil is at least partially soluble
or misible, can be run counter current with the flow of mixture,
which solvent will pickup the oil and carry it in the opposite
direction than the water. If using solvent extraction it is
preferred that the material being oil-extracted be substantially
dry. For example, it is preferred to dry the syrup by any suitable
means, preferably by spray drying, before subjecting it to a
solvent.
[0027] As previously mentioned, the preferred solvent for solvent
extraction is a normally gaseous solvent. As previously mentioned,
butane, propane, and mixtures thereof are preferred with propane
being the more preferred. Non-limiting examples of other solvents
that can be used include: methane, ethane, ethylene, propylene,
butylene, sulfur dioxide, carbon dioxide, CHF.sub.3, CClF.sub.3,
CFBr.sub.3, CF.sub.2.dbd.CH.sub.2, CF.sub.3--CF.sub.2--CF.sub.3,
CF.sub.4, CF.sub.4, CH.sub.3--CF.sub.3, CHCl.sub.2, ammonia,
methane, dimethylether, methyl fluoride, and halogenated
hydrocarbons that are normally gaseous as indicated.
[0028] If solvent extraction is used it can be conducted in either
batch, semi-batch or continuous mode, with continuous mode being
preferred. By semi-batch we mean that the process unit will contain
several extraction vessels, wherein there will always be one
extraction vessel off line and being emptied of treated product
while the other one or more extraction vessels will remain on line.
When it is time to unload treated product from one of the reactors
on line, such extraction vessel will be taken off line and the
extraction vessel that was off line will take its place on line. In
one preferred method for practicing batch solvent extraction, the
material to be extracted is introduced into a suitable extraction
vessel. Air is removed from the vessel and a normally gaseous
solvent is introduced wherein it is pressurized, preferably by
continuing to introduce solvent into the closed vessel until the
normally gaseous solvent is converted to the liquid state. The oil
will then dissolve in the liquid solvent and the solution of oil
and solvent will be conducted from the extraction vessel to a
separation vessel where the solvent will be removed from the oil by
flashing or distillation. It is preferred that the oil in solvent
solution be passed from the extraction vessel to the separation
vessel while the solvent is still in the liquid state. It is also
preferred that a vacuum be used to remove remaining solvent from
the deoiled material as well as being used to aid in the removal of
air from the extraction vessel prior to introduction of
solvent.
[0029] Any suitable continuous solvent extraction mode can be used
in the practice of the present invention. For example, the material
(syrup) to be extracted can continuously be fed at an effective
rate, into a pressure sealed extraction vessel by any suitable
means, such as by use of an auger feeding mechanism. Solvent can
continuously be added to contact fresh syrup to be extracted and
the resulting oil in solvent solution can continuously be removed
and the solvent separated from the oil as previously mentioned.
[0030] In one preferred embodiment, the process of this invention
involves improved treatment of the whole stillage 14 to produce
products each having greater economic value than DDGS, as well as
significantly reduce the costs of treatment of the emissions from
the process. In particular the amount of VOC emissions can be
reduced while at the same time producing a flavor enhancement
supplement product. Turning now to FIG. 2, the whole stillage 14 is
again separated into two product streams by centrifuge 15. Other
known separating equipment such as filters could be used. These two
streams include the wet distillers grains 16 containing oil and
most of the protein compounds found in the whole stillage 14 and
the thin stillage stream 17 also containing oil, as well as most of
the carotenoid, yeast, vitamin, mineral, and remaining protein
compounds.
[0031] The wet distillers grain 16 is sent to a drying step 21 that
is operated at conditions controlled to produce a protein rich
product having a water content of less than about 15% by weight.
Non-limiting examples of suitable drying means include spray
drying, fluidized bed drying, single and double drum dehydrating,
use of ring drier or other suitable means to produce a
substantially free flowing solid. It is preferred that the drier
can be a spray drier. It has been found that setting the
temperatures of the hot air and the wet distiller grain 16, as well
as their contact time to achieve a hot air exhaust temperature of
between about 140.degree. F. and about 170.degree. F. will result
in the production of a protein rich product 23 having a water
content of less than about 15% by weight. Under normal humidity
conditions a hot air exhaust temperature in the above range would
likely require an inlet hot air temperature of less than about
450.degree. F., and a contact time of less than about three
minutes. Within these drying conditions the wet distillers grain
temperature should remain below the temperature to volatize most,
if not all, of the VOC contained in the wet distillers grain. Thus,
a significant portion of the VOC will remain in the protein rich
product 23. This has the result of not only reducing the VOC that
are volutized, but maintaining more of the flavor enhancing
compounds in the protein rich product 23. It is also preferred that
the protein rich product 23 be cooled upon leaving dryer 21 to
prevent any further volutization of the VOC that is contained in
the protein rich product 23. One method of cooling the protein rich
product 23 is through the use of a fluidized bed wherein cool or
ambient temperature air is used to fluidize the bed. Other known
cooling techniques could be employed. This protein rich product 23
can also be subjected to an oil removal step (not shown) as
previously mentioned.
[0032] The water and any VOC vapor 22 removed during drying can be
recycled to the mixer 4. Depending on the dryer operating
conditions some VOC may be volatized. Because the volume of the
volutized VOC is substantially less than in a conventional whole
stillage treatment process, the water and VOC vapor 22 can be sent
through a conventional and less expensive cold trap 24 to produce a
liquid VOC product 25. Water 26 in the liquid VOC product 25 can be
removed, such as by filter 26 or other known separating equipment,
to produce a dry VOC product 28 that can be sold as a flavor
enhancing additive.
[0033] Turning now to FIG. 3 in another preferred embodiment the
thin stillage 17, without oil removal, is passed through a
microfiltration unit 29 having a filter size of about 0.1 to 1.0
micron to form a retentate stream 30 and a permeate stream 31. In a
more preferred embodiment the filter size is set to capture in the
retentate stream 30 the carotenoid compounds. Carotenoid compounds,
particularly Lutien and Zeaxantin, have been found useful in
reducing various serious eye diseases such as age related macular
degeneration and cataracts. The retentate stream 30 containing the
carotenoid compounds is sent to dryer 32. If desired, this
carotenoid rich product can also be subjected to an oil removal
step (not shown) as previously mentioned. In a preferred embodiment
dryer 32 will be operated at a temperature to minimize the
denaturing of any protein contained in the retentate stream 30, as
well as to prevent volatization of the VOC's in the retentate
stream 30 during the period that the retentate stream 30 is
contained in the dryer 32. This can be achieved if the retentate
stream 30 is retained in dryer 32 for a period of less than about
three minutes, and the dryer 32 is operated with a hot air exhaust
temperature less than about 170.degree. F. to remove the water.
Operated in this manner sufficient water can be removed to form a
carotenoid rich product 34 having less than 15% water by weight.
Depending on the dryer operating conditions and the retention time
of the retentate stream 30 in the dryer 32 some VOC may be
volatized. Because the volume of the VOC is substantially less than
in a conventional whole stillage treatment process, the water and
VOC vapor 33 can be sent through a conventional and less expensive
cold trap 35 to produce a liquid VOC stream 36. Stream 36 can be
recycled to mixer 4 or preferably the liquid VOC can be separated
from the water 38 in stream 36 by a filter 37 to produce VOC
product 39 that can be sold as a flavor enhancing additive.
[0034] Turning now to FIG. 4 in another preferred embodiment the
permeate 31 is passed through an ultrafiltration unit 40. The
filter size is selected to be less than about 100,000 molecular
weight to produce a protein and yeast rich retentate 41 and a
vitamin and mineral rich permeate 42. By less than 100,000
molecular weight we mean that the filter is one that components
less than about 100,000 molecular weight will pass. The protein and
yeast rich retentate 41 is sent to dryer 43 to remove at least a
substantial portion of the water from the retentate 41. It is
preferred that the dryer 43 be operated to minimize the
volalization of any VOC's in the retentate 41. This can be achieved
by utilizing the same operating conditions as described above for
dryer 32. Operated in this manner sufficient water can be removed
to form a protein and yeast rich product 45 having less than 15%
water by weight. Depending on the dryer operating conditions and
the retention time of the protein and yeast retentate 41 in the
dryer 43 some VOC may be volatized. Because the volume of the VOC
is substantially less than in a conventional whole stillage
treatment process, the water and VOC vapor 44 can be sent through a
conventional and less expensive cold trap 48 to produce a liquid
VOC stream 49. Stream 49 can be recycled to mixer 4 or preferably
the water 51 in stream 41 can be separated by filter 50 to form a
VOC product 52 that can be sold as a flavor enhancing additive.
[0035] In another preferred embodiment the vitamin and mineral rich
permeate 42 is sent to the dryer 46 to remove at least a
substantial portion of the water in permeate 42. It is preferred
that the dryer 46 be operated to minimize the volalization of any
VOC's in the permeate 42. This can be achieved by operating dryer
46 under the same conditions as dryer 43. Operated in this manner
sufficient water can be removed to form a vitamin and mineral rich
byproduct 47 having less than 15% water by weight. Depending on the
dryer operating conditions and the retention time of the permeate
42 in the dryer 46 some VOC may be volatized. Because the volume of
the VOC is substantially less than in a conventional stillage
treatment process, the water and VOC vapor can be sent through a
conventional and less expensive cold trap 48 to produce a liquid
VOC stream similar to stream 49. This stream can also be recycled
to mixer 4 or passed through a filter, such as filter 50, to form a
VOC product that can be sold as a flavor enhancing additive.
[0036] Thus, as shown in the FIGS. 2-4, the whole stillage 14 can
be processed to produce a protein rich product 23, a carotenoid
rich product 34, a protein and yeast rich product 45, and a vitamin
and mineral rich product 47 with minimum or no VOC's released to
the atmosphere. The VOC's produced do not have to be treated by
expensive thermal oxidizers or similar equipment, but can be sent
to a less expensive cold trap and filter to produce yet another
value added product, liquid VOC's. Each of these five product
streams has significantly greater commercial value than the
currently produced animal feed DDGS.
[0037] It is not necessary that separate cold traps be used for
each of the product streams. Depending on the amount of VOC
volatized, the different VOC streams volatized can be combined and
sent to one or more of the cold traps, thus further reducing
capital expense. Depending on the product desired it is also
possible to direct various streams to a common dryer. There are of
course other alternate embodiments that are obvious from the
foregoing descriptions of the invention which are intended to be
included within the scope of the invention as defined by the
following claims.
[0038] In another preferred embodiment of the present invention the
thin stillage is dried to a substantially free flowing powder by
any suitable drying means. Non-limiting examples of suitable drying
means include spray drying, fluidized bed drying, single and double
drum dehydrating, use of ring drier or other suitable means to
produce a substantially free flowing solid. It is preferred that
the drier can be a spray drier. It is preferred that the water
content of the thin stillage be first reduced by one or more
dewatering steps, such as evaporation, prior to being subjected to
the drying means. The dewatering step(s) is distinguished from the
drying step since the drying step is performed at elevated
temperatures and the dewatering is done by lower temperature
operations that include gross water separation, such as by
pressing, evaporation, etc. After drying, the resulting free
flowing powder will contain 15 wt. % or less water, based on the
total weight of the final dried product. It is preferred that the
water content of the final product be from about 10 wt. % to about
15 wt. %. It is also preferred that the drying be done at an
effective temperature and for an effective amount of time. By
effective temperature we mean that temperature that is effectively
low so that desirable ingredients, such as proteins, are not
destroyed but not so low that drying takes an uneconomical amount
to time. Such temperatures will be less than about 170.degree. F.,
typically from about 140.degree. F. to about 170.degree. F. An
effective amount of an additive can be introduced into the thin
stillage stream prior to drying or it can be introduced into the
drying means simultaneously with the thin stillage. The additive
can be any ingredient in an amount that is needed to produce a
final dried product having the desired properties for its intended
end use. Non-limiting end uses can be an ingredient for a pet food
or for human consumption. Non-limiting examples of such additives
are selected from vitamins, minerals, amino acids, proteins,
flavors, phytochemicals, pharmaceuticals, nutraceuticals, binders
and fillers, other streams resulting from the treatment of cereal
grains, and mixtures thereof. It is to be understood that the free
flowing syrup powder can also be subjected to an oil removal step
as previously described.
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