U.S. patent application number 10/072219 was filed with the patent office on 2002-06-13 for integrated processing of biomass and liquid effluents.
Invention is credited to Pye, Edward Kendall.
Application Number | 20020069987 10/072219 |
Document ID | / |
Family ID | 27154755 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020069987 |
Kind Code |
A1 |
Pye, Edward Kendall |
June 13, 2002 |
Integrated processing of biomass and liquid effluents
Abstract
An integrated process for the combined fermentation and the
conversion of liquid and solid residues generated by the cane sugar
industry into a variety of useful products. The process also
relates to the treatment of other biomass materials. The process
combines elements of alcohol-based organosolv pulping with
fermentation in a fully integrated operation. This process
eliminates the need for separate costly facilities, thus reducing
capital and operating costs, providing opportunities for heat and
energy reduction and a high degree of internal process recycle. The
process would replace costly waste and residue treatment operations
with revenue generating operations.
Inventors: |
Pye, Edward Kendall; (Media,
PA) |
Correspondence
Address: |
Edward Kendall Pye
210 Timber Jump Lane
Media
PA
19063-1134
US
|
Family ID: |
27154755 |
Appl. No.: |
10/072219 |
Filed: |
February 9, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60307712 |
Jul 26, 2001 |
|
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Current U.S.
Class: |
162/77 ; 162/91;
162/99 |
Current CPC
Class: |
A23J 1/005 20130101;
C12P 7/06 20130101; Y02A 40/209 20180101; Y02P 20/125 20151101;
Y02P 60/87 20151101; C05F 5/00 20130101; A23K 10/33 20160501; Y02P
60/871 20151101; D21C 5/00 20130101; A23K 10/12 20160501; Y02P
20/10 20151101; Y02E 50/17 20130101; Y02E 50/10 20130101; Y02A
40/20 20180101 |
Class at
Publication: |
162/77 ; 162/91;
162/99 |
International
Class: |
D21C 003/20; D21C
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2000 |
AU |
51888/00 |
Claims
What I claim as my invention is:
1. An integrated process performing fermentation of low value
(molasses) and waste sugars together with the conversion of biomass
residues from the cane sugar industry (bagasse) for the production
of multiple useful products. Such process combines the elements of
alcohol-based organosolv pulping and ethanol fermentation into a
single integrated process.
2. A process, as in claim 1, in which the useful products are any
combination, or number, of products including unbleached
papermaking pulp, bleached papermaking pulp, high alpha-cellulose
pulp, organosolv lignin, furfural, acetic acid, ethyl acetate,
sodium acetate, xylose, xylan, butanol, acetone, high-protein
animal feed, plant fertilizer, uronic acids and ethanol.
3. A process for delignifying biomass fibrous residues comprising,
digesting biomass fibrous residues in a mixture of ethanol and
water in a digester at elevated temperature and pressure,
continually exposing the mixture of ethanol and water to the
fibrous residues in a suitable digester, or by circulating the
mixture of ethanol and water between the digester and a holding
tank for a time sufficient to at least partially delignify the
biomass fibrous residues and form a pulp, draining the mixture to a
spent liquor tank at the end of the circulation time, causing the
remaining liquor and partially delignified biomass to transfer from
the digester to a blow tank by opening the valve to the blow
tank.
4. A process according to claim 3, wherein the process includes the
step of recovering lignin and other chemicals from the mixture of
ethanol and water contained in the spent liquor tank.
5. A process according to claim 3 or claim 4, wherein the mixture
of ethanol and water in the digester is maintained at a temperature
in a range from 170 to 205.degree. C.
6. A process according to claim 5, wherein the pressure in the
digester and the holding tank is maintained at a level sufficient
to prevent the mixture of water and ethanol from vaporizing.
7. A process according to any one of claims 3 to 6, wherein the
mixture of ethanol and water in the digester contains ethanol and
water in a ratio in a range from 35% to 70% by weight ethanol to
water.
8. A process according to any one of claims 3 to 7, wherein the
circulation time lies in a range from 30 minutes to 3 hours.
9. A process according to claim 8, wherein the circulation time
lies in a range from 1 to 2 hours.
10. A process according to any one of claims 3 to 9, wherein the
process includes transferring the contents of the spent liquor tank
to a flash tank to enable volatile material to evaporate thereby
leaving a lignin-rich condensed liquor, lowering the pH of the
condensed liquor to a level below 3, diluting the condensed liquor
with an aqueous stream and cooling the condensed liquor to cause
lignin to precipitate from the mother liquor and separating lignin
from the mother liquor.
11. A process according to claim 10, wherein the process includes
the steps of distilling the diluted mother liquor to recover
ethanol and furfural therefrom leaving an aqueous stillage.
12. A process according to claim 11, including the steps of
concentrating the aqueous stillage by evaporation, allowing a
liquid lignin fraction to settle, removing the liquid lignin
fraction from an upper layer of the aqueous stillage thereby
leaving an aqueous layer containing xylose, xylan and other sugars.
Description
RELATED APPLICATIONS
[0001] Australian Patent Application No: 51888/00; Filing Date:
Aug. 8, 2000; Relationship: Equivalent claims
[0002] U.S. Provisional Patent Application No. 60/307,712; Filing
Date: Jul. 26, 2001; Relationship: Equivalent claims
BACKGROUND OF INVENTION
[0003] This invention relates to a process for the manufacture of
multiple valuable products from various wastes generated during the
production and recovery of cane sugar, as well from other
agricultural cellulosic biomass materials.
[0004] The cane sugar industry generates vast quantities of liquid
wastes and solid residues during the production of its primary
product. These include sugar cane bagasse and liquor streams
containing large quantities of low-grade sugars. Bagasse is usually
burned inefficiently in boilers to generate steam and power. The
liquid waste streams, mostly molasses, are usually sold as
low-grade cattle feed additives.
[0005] The cane sugar industry is normally a highly competitive,
low profit industry. One approach to improve profitability is to
convert these wastes and residues into saleable products that can
add to the revenues of the industry. The value of this approach has
been recognized for a number of years and considerable research and
commercial development has been undertaken to identify useful
products, such as furfural and papermaking pulp that can be
generated from these wastes.
[0006] A new type of pulping technology, known as organosolv
pulping, has distinct advantages for the cane sugar industry. It
has almost no environmental problems, is less capital intensive
than kraft, it produces multiple co-products, is ideally suited to
pulping non-wood biomass that contain high levels of inorganic
materials, and can be profitably operated on a much smaller scale
than conventional pulping processes. Organosolv pulping has been
described in numerous patents and publications including U.S. Pat.
No. 3,585,104 Kleinert, U.S. Pat. No. 4,100,016 Diebold et al.,
U.S. Pat. No. 4,496,426 Baumeister et al. Although organosolv
pulping has numerous advantages over conventional chemical pulping
methods, such as the kraft, sulfite and the soda processes, in the
pulping of wood and other woody biomass resources, it suffers from
a disadvantage of significant losses of the relatively costly
organic solvent from the process. If the solvent employed is
ethanol the environmental consequences of this loss is minor, but
the economic consequences can be important, since they can make the
operating costs of an organosolv process higher than those for
conventional chemical pulping processes. This requires the
provision of substantial quantities of expensive make-up solvent to
the process. This higher operating cost is one major reason that
has held back the commercial acceptance of organosolv pulping
processes.
[0007] One approach to reducing the cost of make-up solvent
required by an organosolv pulp mill, to make it economically
attractive, is to produce the required make-up solvent on site. For
an ethanol-based organosolv pulp mill a fermentation facility can
be constructed adjacent to the pulp mill for this purpose. However,
if constructed on a small size sufficient for the make-up needs of
a small pulp mill, the relative capital costs of such a
fermentation facility would make it economically unattractive.
Furthermore, if the pulp mill uses wood as a raw material, the
fermentation plant would need to purchase fermentation feedstock,
such as sugar or starch, at considerable cost. This problem can be
overcome for an ethanol-based organosolv pulp mill processing
agricultural residues, such as bagasse. Such a pulp mill processing
bagasse would ideally be situated adjacent to a cane sugar mill,
since the bagasse is a low value product of these mills. Therefore
no transportation costs would be incurred for the raw material.
Another low value by-product of the sugar mill is molasses, a high
sugar content liquid by-product. It is well recognized that
molasses can be readily fermented commercially to yield ethanol. It
therefore represents a low cost fermentation feedstock present at
the sugar mill.
[0008] Even more attractive for the cane sugar industry is that
ethanol-based organosolv pulping is highly compatible with an
agricultural economy. Its primary process chemical is ethanol,
which can be easily produced by fermentation of waste sugars and
starch. Furthermore, many of the co-products of the process find
immediate use and value in agriculture, such as animal feed
supplements and slow release fertilizer and pesticides. This
invention solves the problem of the high capital cost of a
dedicated small fermentation plant to provide make-up ethanol by
physically integrating the fermentation of molasses into the
process equipment of an organosolv pulp mill. A single mill
consisting of organosolv pulping of biomass residues integrated
with the processing and fermentation of aqueous waste streams will
result in major profits for the cane sugar industry. At the same
time such a strategy will result in a high degree of environmental
protection and support for the development of adjacent industrial
activities based on the co-products of this process.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention provides a process for delignifying
biomass fibrous residues comprising digesting biomass fibrous
residues in a mixture of ethanol and water in a digester at
elevated temperature and pressure.
[0010] The process would include the step of treating spent liquor
to recover lignin, acetic acid, furfural, xylose and other
co-products, as well as recovering alcohol for re-use in the
process and subjecting various liquid sugar waste streams of the
process and from a cane sugar mill to fermentation in order to
produce ethanol and other fermentation products which may be used
in the process. The recovery of ethanol from the spent cooking
liquors and the recovery of ethanol from the fermentation liquors
would be accomplished in the same process equipment. These two
processes, the organosolv pulping and the fermentation of waste
sugar streams, would be accomplished in the same plant, which would
allow equipment, heat and energy integration providing considerable
economic advantages. This process concept is applicable to other
biomass residues as well as cane-sugar residues. The potential
advantages of integrating these two formerly separate activities
into a single operating unit are numerous. They include lower total
capital costs, combining different liquor streams for common
product recovery, opportunities for process heat and energy
reduction, internal process chemical production, reduced
transportation costs, substantial environmental improvement and the
potential for the use of larger, more efficient equipment in a
shared operation. Separate facilities operating in isolation may
not be economic. This identifies the unit processes and the product
flows in an integrated total process that would provide these
advantages to the cane sugar industry.
[0011] The distillation tower in the process could recover not only
ethanol for recycle, but also furfural and ethyl acetate, two
valuable products that are generated during the bagasse cooking
stage. Both can be sold, probably as crude products suitable for
upgrading at a centralized facility. Such activities would
encourage the formation of additional local industries designed to
support the sugar cane processors using the technology described in
this invention. Other local industries could take the lignin
produced in these mills and convert it to value-added products,
such as concrete admixtures and dye dispersants. Other options
presented by this invention include the recovery of xylose (a sugar
present in large quantities, mostly as xylan, in bagasse). This
could be sold in the world market for pure xylose that is used as a
starting material in the production of the anti-caries sweetener,
xylitol. Xylose can also be converted to furfural. If market prices
support this option then xylose recovery could be maximized by
extended steaming of the bagasse prior to cooking. Xylose would be
recovered from the steaming condensate.
[0012] Utilizing this invention could lead to higher value pulps
which would have high alpha-cellulose content and therefore be
suitable for rayon production. The result for the cane sugar
industry of practicing this invention would be the elimination of
costly environmental control operations and the production of
significant revenues from the sale of several value-added products.
These products would in turn create opportunities for the
introduction of ancillary industries.
DESCRIPTION OF THE DRAWING
[0013] In the accompanying drawing, which illustrates by way of
example the embodiment of this invention,
[0014] FIG. 1 is a flow diagram identifying the unit process steps
of an integrated process for the production of pulp and several
useful by-products from bagasse, a biomass residue of the cane
sugar industry. While not every unit process is essential for the
economic success of the invention, the combination of all these
unit processes provides maximum utility of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The present invention is directed at a single integrated
process that converts biomass residues from the cane sugar
industry, sometimes referred to as bagasse, into a series of
valuable products including, but not limited to, papermaking pulps.
The process is integrated with the element of fermentation of waste
and low-grade molasses to produce ethanol, other fermentation
products and high protein animal feed. Other sources of low grade,
but fermentable carbohydrate may be substituted for molasses in
this invention. A key element incorporated into the process is
organosolv delignification of bagasse. This element utilizes some
of the alcohol generated in the fermentation element. The
organosolv element generates products such as lignin, xylose,
furfural, acetic acid and pulp for use in papermaking, dietary
fibre, or as chemical cellulose. Much utility is gained by
integrating these several elements into a single process. The
advantages include heat and energy reduction through process
integration, capital reduction through the co-processing of various
process streams and waste minimization opportunities through the
combining of several process streams. These elements and advantages
are illustrated in the process flow diagram, FIG. 1.
[0016] The process starts with the preparation of the bagasse into
a form suitable for packing into a pressure vessel, identified in
FIG. 1 as a digester. The preferred form is into stem sections of
approximately ten centimeters in length, but any similar form is
appropriate. A compressed pellet is also appropriate as feed for
the digester. As illustrated the digester is one of a series of
batch digesters that may be rotating spheres, or a continuous
conveyed inclined or horizontal tube configuration, but could also
be a vertical tubular batch or continuous design. In FIG. 1 a
preferred configuration of a rotating globe batch digester
configuration is illustrated. The operations described below for
one digester are identical to those for the additional digesters
that are operated sequentially at appropriate intervals to allow
optimal use of the remaining equipment in the process.
[0017] Following preparation of the fibrous residue (bagasse) into
the useful form described above it is conveyed by conveyer, 41, to
the top of the digester for loading into the digester. Once the
digesters, is filled with a pre-determined amount of bagasse, the
conveyer is stopped and the digester is closed. An exhaust valve,
46, located behind a screen, 42, in the bottom of the digester is
now opened and low-pressure steam (less than 50 psi) is allowed to
enter the top of the digester through a pipe, 45. This steaming,
which is required to displace air in the fibre bed, continues until
temperature sensors in the exhaust line indicate that steam is
exiting from the bottom of the digester. Any condensate of the
steaming exits through the same line. Alternatively, if the
moisture content of the bagasse is too high, nitrogen gas may be
substituted for steam for the air displacement. All valves are now
closed and the pump, 43, in the line exiting the 2.sup.nd liquor
tank is turned on. The 2.sup.nd liquor tank is full of aqueous
alcohol at the desired concentration and temperature. This liquor
was used as a wash liquor from a previous digester cook and was
retained between cooks in the 2.sup.nd Liquor Tank, 3. The
preferred alcohol concentration in water is in the range of 35%-70%
(w/w) and the preferred temperature is in the range of
170.degree.-205.degree. C. This liquor is pumped through a heat
exchanger, 44, to maintain its desired temperature and then into
the top of the digester through the top liquor line. Once the
digester starts to fill, liquor exits the bottom of the digester
from behind a screen, 42, constructed around the outlet line at the
bottom of the digester, from where it is returned to the top of the
2.sup.nd Liquor Tank, 3. This hot liquor circulation is continued
for the appropriate time necessary to raise the contents of the
digester to the desired cooking temperature. At this point the
liquor exit valve, 46, is closed and the desired weight of hot
liquor, usually 2 to 5 times the dry weight of the bagasse, is
Pumped into the digester from the 2.sup.nd Liquor Tank. Liquor flow
is then stopped, steam is continually sent to a jacket surrounding
the digester to maintain its temperature at the desired cooking
temperature and the globe digester is rotated for the desired
cooking time. This time is normally between 30 minutes and 3 hours,
with the preferred time being between one and two hours. At the end
of this time the rotation of the digester is stopped with the
liquor outlet line and surrounding screen at the bottom of the
digester. Part of the hot black liquor is then flashed into a Flash
Tank, 6. The valve at the top of the 2.sup.nd Liquor Tank is then
closed and the return liquor is diverted to the Spent Liquor Tank.
Residual liquor in the 2.sup.nd Liquor Tank is pumped down to a
level sufficient to keep the suction side of the pump flooded.
Liquor remaining in the Digester is drained through the lower
screens into a drain line from where it is also pumped to the Spent
Liquor Tank. Next, clean aqueous alcohol at the concentration and
temperature previously described is pumped from the 1.sup.st Liquor
Tank, 2, into the top and bottom lines of the Digester and returned
to the 2.sup.nd Liquor Tank, 3, using the appropriate valves and
pumps. After the 1.sup.st Liquor Tank has been almost emptied
liquor flow to the Digester is stopped and the remaining liquor in
the Digester is drained down and pumped to the 2.sup.nd Liquor Tank
through the appropriate lines and valves. The Digester is now
depressurized by opening the valves in the top line and the vapors
passed to a Blow-Down Condenser, 35. The alcohol-rich vapors are
condensed and returned to the Recovery Alcohol Tank, 9, for re-use
in the process. The partially-delignified fibres are now sluiced
from the Digester through the bottom valve, using water or
preferably condensate from the evaporator. This sluiced pulp is
sent to a tank, 51, from which it is pumped continuously to
conventional pulp refining, washing, screening, cleaning and
bleaching operations. The liquor from these operations can be
processed by conventional means for alcohol recovery and sodium
acetate recovery.
[0018] The spent liquor under pressure in the Spent Liquor Tank, 4,
is flashed into a Flash Tank, 6, and the vapors condensed through
the Blow-Down Condenser, 35, and returned to the Recovery Alcohol
Tank, 9, for re-use. The condensed liquor in the Flash Tank,
containing the extracted lignin, is then pumped to the Lignin
Precipitation Tank, 7, where it is mixed rapidly with stillage from
the Distillation Tower, 14, and the pH adjusted to below 3.0 with
acid and the mixture cooled to about 17.degree.. Lignin
precipitates from the mixture and forms a slurry. This is pumped to
a suitable filtering device, such as a drum filter, 13, where the
lignin is removed as a wet cake that is sent to an appropriate
drier, while the filtrate is pumped to a Recovery Feed Tank, 54.
From this tank the filtrate is pumped to an appropriately designed
Distillation Tower, 14. Such a tower would have a lower steam
stripping section and an upper rectifying section, or be composed
of two columns having these functions. In this tower alcohol,
together with some esters, is recovered as an overhead condensate
and returned to the Recovery Alcohol Tank for re-use in the
process. Furfural, which is present in the filtrate, accumulates at
one of the lower trays in the rectifier section where it is drawn
off, cooled and mixed with water before being sent to the Decanter.
The lower liquid phase in the decanter is crude furfural, which is
upgraded to merchant furfural in a commercially available system.
The upper layer is aqueous alcohol, which is passed back to the
Distillation Tower to recover the alcohol by mixing with the tower
feed stream. Steam to power the stream stripping section is
provided by Reboilers at the bottom of the tower.
[0019] Aqueous stillage from the bottom of the Distillation Tower
containing sugars, some lignin and minerals, is sent to an
appropriately designed multi-stage evaporator, 19, where it is
concentrated to about 25% solids. This concentrate is pumped to an
Evaporator Concentrate Decanter, 23, where a lower layer of oily
lignin is recovered and dried. The upper aqueous layer containing
xylose, xylans, other sugars and minerals, is sent to a
commercially available xylose recovery unit, 24, for production of
purified xylose. The effluents from this unit include waste hexose
sugars, which are passed to the fermentation operations for alcohol
production, and an aqueous solution of minerals, which are returned
to the cane fields as fertilizer.
[0020] The aqueous condensate from the Evaporator is passed to a
commercially-available solvent extraction unit, 21, such as those
employing tri-octyl phosphine oxide, (TOPO), for recovery of acetic
acid, formic acid, furfural and ethanol as separate marketable
products. The clean water that exits this unit is useful in the
pulp washing and bleaching operations.
[0021] Molasses is used as the fermentation raw material in a
fermentation plant, 26, employing yeast to produce ethanol and
other fermentation products. This medium may be supplemented with
additional sugars from acid-hydrolysis products of waste cellulose,
as required for maximum productivity. Additional minerals that may
be required at this stage can be supplied from the waste liquor
stream of the xylose recovery plant. After fermentation is complete
in a sequential battery of batch Fermenters, the beer is pumped to
a Filter, 31, where yeast and other solids are removed and dried
for sale as high-protein animal feed supplement. The clarified beer
is then passed to the Recovery Feed Tank, 54, mixed with the
filtrate from the Lignin Recovery Filter and pumped to the
Distillation Tower for recovery of ethanol and other
components.
[0022] By this invention a range of valuable products is produced
from the solid and liquid residues of the cane sugar industry.
* * * * *