U.S. patent application number 10/395547 was filed with the patent office on 2004-04-29 for treatment of thin spillage resulting from the production of ethanol from cereal grains.
Invention is credited to Hammond, Neal, Prevost, John.
Application Number | 20040082044 10/395547 |
Document ID | / |
Family ID | 32107162 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040082044 |
Kind Code |
A1 |
Prevost, John ; et
al. |
April 29, 2004 |
Treatment of thin spillage resulting from the production of ethanol
from cereal grains
Abstract
A process for recovering a substantially free flowing product
from thin stillage which contains a substantial amount of water,
which thin stillage is obtained from the distillation of beer
produced in a fermentation zone to produce ethanol, which process
comprises conducting said thin stillage into a drying zone to
produce a product having a water content of 15 wt. % or less.
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.: |
10/395547 |
Filed: |
March 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10395547 |
Mar 24, 2003 |
|
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10281490 |
Oct 28, 2002 |
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Current U.S.
Class: |
435/161 |
Current CPC
Class: |
C12P 7/06 20130101; Y02E
50/17 20130101; Y02E 50/10 20130101; C11B 1/00 20130101 |
Class at
Publication: |
435/161 |
International
Class: |
C12P 007/06 |
Claims
What is claimed is:
1. A process for recovering a substantially free flowing product
from thin stillage which contains a substantial amount of water,
which thin stillage is obtained from the distillation of beer
produced in a fermentation zone to produce ethanol, which process
comprises conducting said thin stillage into a drying zone to
produce a product having a water content of 15 wt. % or less.
2. The process of claim 1 wherein beer is produced from corn as a
feedstock.
3. The process of claim 1 wherein the water content of the
substantially free flowing product is from about 10 wt. % to about
15 wt. %.
4. The process of claim 1 wherein the drying zone includes a
technique selected from spray drying, fluidized bed drying, single
and double drum dehydrating, use of ring drier,
5. The process of claim 1 wherein the thin stillage is subjected to
at least one dewatering stages to drive off at least a portion of
the water prior to drying.
6. The process of claim 1 wherein prior to drying an effective
amount of an additive is introduced with the thin stillage.
7. The process of claim 6 wherein the additive is selected from the
group consisting of vitamins, minerals, amino acids, proteins,
flavors, phytochemicals, pharmaceuticals, nutraceuticals, binders
and fillers, other streams resulting from the treatment of cereal
grains, and mixtures thereof.
8. The process of claim 7 wherein the additive is selected from
amino acids, proteins and mixtures thereof.
9. The process of claim 7 wherein the additive is selected from
vitamins, minerals, and mixtures thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Ser. No.
10/281,490 filed Oct. 28, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates a process for recovering a
substantially free flowing product from thin stillage which
contains a substantial amount of water, which thin stillage is
obtained from the distillation of beer produced in a fermentation
zone to produce ethanol, which process comprises conducting said
thin stillage into a drying zone to produce a product having a
water content of 15 wt. % or less.
[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 similar conventional milling equipment. Water and enzymes
are added to the milled corn and heated to form a liquefied mash.
The liquefied mash is then mixed in a fermentation vessel with
water, yeast and selected minerals and nutrients to enhance the
fermentation of the mash. The 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 a whole
stillage. The whole stillage comprises water, as well as the solids
resulting from the fermentation. It is typical to centrifuge the
whole stillage to remove a substantial portion of the water to form
a wet distillers grain. The wet distillers grain includes most of
the protein containing solids that is found in the whole stillage.
The removed water containing nutrients and other solids generally
known as the thin stillage is sent to an evaporator to remove a
substantial portion of the water. The remaining nutrients and
solids called the syrup are then combined with the wet distillers
grain. The combined syrup and wet distillers grain is sent to a
dryer to produce a dry protein containing animal feed called
distiller dried grain solubles (DDGS).
[0006] These prior art ethanol processes have several significant
problems. One problem is the energy costs to remove the water from
the whole stillage to produce a low economic value DDGS. A second
problem is the environmentally unacceptable amount of VOC's, air
toxics, and combustion pollutants, such as CO, NO.sub.x, and
particulate matter, released into the atmosphere during the drying
process. To achieve an acceptable 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 the drying
process, as well as expensive annual equipment maintenance. 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] Therefore, one object of this invention is to provide an
improved ethanol production process that results in value added
flavor enhancing, nutritional, nutraceutical, and/or pharmaceutical
byproducts.
[0008] Another object of this 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 this invention is to provide an
improved ethanol production process requiring reduced capital
equipment investment and reduced maintenance costs.
[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 is hydrolyzed to
produce ethanol and a whole stillage. The whole stillage comprises
the remaining solids, nutrients, yeast and water remaining after
the ethanol has been removed during the hydrolysis step. The whole
stillage is centrifuged, filtered or otherwise separated by other
known techniques to produce wet distillers grain and a thin
stillage stream. The wet distillers grain, also known as thick
stillage, includes most of the protein containing solids and some
of the water comprising the whole stillage. The thin stillage will
comprise the nutrients, yeast and most of the water in the whole
stillage. The wet distillers grain is dried under conditions that
do not denature the proteins contained in the thick stillage, and
more preferably, under conditions that minimize the volutizing of
the VOC contained in the wet distillers grain. The drying
conditions depend on a variety of factors. When utilizing a spray
dryer, these factors include the ease in which the wet distillers
grain can be atomized, the humidity of the air in the drying
environment, the temperature of the hot air used to dry the wet
distillers grain, the temperature of the wet distillers grain when
it enters 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. 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
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. Utilization of the above drying conditions will also
reduce the VOC emission to the atmosphere. In a preferred
embodiment the drying conditions are set to maintain the
temperature of the wet distillers grain below the temperature
required to volatize most of the VOC's. 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.
[0012] If desired the thin stillage stream can be sent to an
evaporator to remove most of the water to produce the syrup. 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 grain as described above.
[0013] In another alternate embodiment the thin stillage stream 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.
[0014] In 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 0.1 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
[0015] 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.
[0016] FIG. 1 is a schematic illustrating a conventional prior art
ethanol production process.
[0017] 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.
[0018] 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.
[0019] 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
[0020] 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 starch containing materials.
[0021] In a conventional 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 necessary for
efficient fermentation, are added. After the desired amount of
fermentation has been completed the resulting product 11 commonly
referred to as the "beer" is sent to a 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 treated to produce an
animal feed commonly known as DDGS. The most common method to treat
the whole stillage 14 is to separate the whole stillage 14 by
centrifuge 15 to form two separate streams. The first is known as
the wet distillers grain 16. The wet distillers grain 16 includes
most of the solids and some of the water found in the whole
stillage 14. The second stream is known as the thin stillage stream
17. 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. The dryer 21 is
typically operated with the 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
approximately five 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).
[0022] 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
grain 16 containing most of the protein compounds found in the
whole stillage 14 and the thin stillage stream 17 containing most
of the carotenoid, yeast, vitamin, mineral, and remaining protein
compounds.
[0023] 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.
[0024] 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.
[0025] Turning now to FIG. 3 in another preferred embodiment the
thin stillage 17 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. 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
* * * * *