U.S. patent application number 17/511465 was filed with the patent office on 2022-02-17 for efficient methods and compositions for recovery of products from organic acid pretreatment of plant materials.
This patent application is currently assigned to Pierson Capital Environmental (Beijing) Limited. The applicant listed for this patent is Pierson Capital Environmental (Beijing) Limited. Invention is credited to Feng LING.
Application Number | 20220049421 17/511465 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-17 |
United States Patent
Application |
20220049421 |
Kind Code |
A1 |
LING; Feng |
February 17, 2022 |
EFFICIENT METHODS AND COMPOSITIONS FOR RECOVERY OF PRODUCTS FROM
ORGANIC ACID PRETREATMENT OF PLANT MATERIALS
Abstract
The invention is directed to compositions and processes
concerning efficient downstream processing of products derived from
organic acids pretreatment of plant materials.
Inventors: |
LING; Feng; (Jilin,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pierson Capital Environmental (Beijing) Limited |
Beijing |
|
CN |
|
|
Assignee: |
Pierson Capital Environmental
(Beijing) Limited
Beijing
CN
|
Appl. No.: |
17/511465 |
Filed: |
October 26, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17058595 |
Nov 24, 2020 |
11186950 |
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PCT/CN2018/088698 |
May 28, 2018 |
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17511465 |
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International
Class: |
D21C 11/00 20060101
D21C011/00; B01D 1/00 20060101 B01D001/00; B01D 1/26 20060101
B01D001/26; B01D 3/14 20060101 B01D003/14; B01D 3/38 20060101
B01D003/38; B04B 11/02 20060101 B04B011/02; B04B 11/08 20060101
B04B011/08; C05F 5/00 20060101 C05F005/00; C07G 1/00 20060101
C07G001/00; C08B 1/08 20060101 C08B001/08; C08L 5/14 20060101
C08L005/14; C12F 3/10 20060101 C12F003/10; D21C 9/00 20060101
D21C009/00 |
Claims
1. A method of producing a lignin composition, the method
comprising the steps of: a) separating lignin from a lignin
suspension produced from organic acids pretreatment of plant
material by centrifugation, and b) cleaning the lignin in the
centrifuge by multiple applications of wash solution onto the
lignin during centrifugation, to form multiple centrifugates, and
c) recovering a first centrifugate and a second centrifugate for
use in hemicellulosic juice concentration, and d) recycling a third
centrifugate for separating the lignin in the concentrated
extraction liquor in the separating step of the process, and e)
discharging the lignin from the centrifuge.
2. The method according to claim 1, wherein the centrifuge is a
scraper centrifuge.
3. The method according to claim 1, wherein the centrifuge is
equipped with a spraying device for delivering wash solution.
4. The method according to claim 1, wherein the centrifuge rotates
continuously through the entire process.
5. The method according to claim 1, wherein the wash solution
comprises formic acid, acetic acid, and water.
6. The method according to claim 1, wherein the wash solution
consists solely of water.
7. The method according to claim 1, wherein the multiple
applications of wash solution comprise a first application of a
wash solution comprised of high organic acids content washing
water, a second application of a wash solution comprised of low
organic acids content washing water, and a final application of a
wash solution comprised of fresh water.
8. The method according to claim 1, wherein the wash solution has a
content of formic acid of 0% to 30% by weight.
9. The method according to claim 1, wherein the wash solution has a
content of acetic acid of 0% to 20% by weight.
10. The method according to claim 1, wherein the first centrifugate
is comprised of the liquids separated from the lignin suspension
applied to the centrifuge.
11. The method according to claim 1, wherein the second
centrifugate is comprised of the first wash solution applied to the
lignin in the centrifuge.
12. The method according to claim 1, wherein the first and second
centrifugates are collected and used for hemicellulosic juice
production.
13. The method according to claim 1, wherein the third centrifugate
is comprised of the second and any subsequent wash solutions
applied to the lignin in the centrifuge.
14. The method according to claim 1, wherein the third centrifugate
is recycled to the lignin precipitation step.
15. The method according to claim 1, wherein first centrifugate
comprises 10% to 60% of the total centrifugates.
16. The method according to claim 1, wherein the second
centrifugate comprises 10% to 30% of the total centrifugates.
17. The method according to claim 1, wherein the third centrifugate
comprises 10% to 50% of the total centrifugate.
18. The method according to claim 1, wherein the lignin is 90% to
99% pure, based on the total weight of the cleaned lignin.
19. A lignin composition obtained by a method according to claim
1.
20. The lignin composition according to claim 19, wherein the
lignin is 90% to 99% pure, based on the total weight of the cleaned
lignin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 17/058,595 filed Nov. 24, 2020, which is a 35 U.S.C. 371
national stage of International Application Number
PCT/CN2018/088698 filed May 28, 2018, the full disclosure of each
of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention is related to compositions and processes
concerning; (i) recovery of organic acids from a cellulosic pulp
derived from organic acids pretreatment of plant materials, (ii)
treatment of cellulose recovered from a cellulosic pulp derived
from organic acids pretreatment of plant materials prior to
conversion to glucose, (iii) separating and cleaning lignin from a
lignin suspension derived from organic acids pretreatment of plant
materials, (iv) recovery of organic acids from the aqueous phase of
organic acids pretreatment of plant materials, (v) recovery of
residual organic acids from hemicellulose-containing fractions
derived from organic acids pretreatment of plant materials, and
(vi) organic fertilizer produced from cellulose and hemicellulosic
juice derived from organic acid pretreatment of plant
materials.
BACKGROUND OF THE INVENTION
[0003] The invention relates in a first aspect to a method for
recovering organic acids from cellulosic pulp by a combined
application of dryer and desolventizer. This aspect of the
invention increases efficiency of existing organic acids
pretreatment process by allowing recovery and reuse of the organic
acids used to dissolve the hemicellulose and lignin contained in
lignocellulosic plant materials. After the dissolving step of
organic acids pretreatment of plant materials, a mixture of soluble
and insoluble parts is obtained. After separating the mixture into
soluble and insoluble fraction, a cellulosic pulp and extraction
liquor are obtained. The cellulosic pulp represents about 62% of
the soluble fraction primarily composed of organic acids and water
and 38% of the insoluble fraction primarily comprised of
undissolved cellulose.
[0004] Organic acids pretreatment processes suitable to application
of the present invention are described in international patent
publications WO 2011/154293 and WO 2010/006840, the contents of
which are hereby incorporated in their entirety. The present
invention may also concerns recovery of organic acids from an
organic acids pretreatment process step involving partial
elimination of lignins to obtain a residual overall level of
lignins of 0.3% to 4%. Such step is described in international
patent publication WO 2012/049054, the contents of which is hereby
incorporated in its entirety.
[0005] In such processes, the lost organic acids represent not only
a significant portion of the unit operational costs, but the
unrecovered organic acids also have an impact on environmental
considerations. Thus, efficient recovery of organic acids from the
cellulosic pulp produced by organic acids pretreatment of plant
materials provides both economic and environmental advantages over
existing methods.
[0006] In another aspect, the invention further relates to a
process for treating cellulose by a combination of neutralization
and alkalization, wherein the cellulose is derived from existing
processes for producing bioethanol or other products, comprising
organic acids pretreatment of plant materials. Such existing
processes are described in U.S. patent publication 2013-0183733,
the contents of which is hereby incorporated in its entirety.
[0007] Production of bioethanol via processes including the steps
of organic acids pretreatment, involves an initial step to
destructure lignocellulosic plant material by subjecting it to a
mixture of formic acid, acetic acid and water, the next step
involves separating cellulose from the other materials. In order to
achieve the best possible yield of enzymatic hydrolysis of the
separated cellulose, a partial elimination of lignin prior to the
enzymatic hydrolysis step is disclosed, such a treatment of the
cellulose, so as to eliminate the lignins in order to achieve a
preferred lignin level, wherein the residual overall level of
lignins is equal to approximately 1.65%, is carried out by means of
treating cellulose with sodium hydroxide, followed by a washing
step intended to eliminate the residual sodium hydroxide before
enzymatic hydrolysis.
[0008] Typically, treatment of cellulose derived from organic acids
pretreatment of plant materials is carried out by adding sodium
hydroxide into the cellulose directly to adjust the pH to pH 10 to
pH 12, subsequently a separation step is carried out to separate
the mixture into the treated cellulose and the filtrate (mainly
contain the sodium hydroxide and other soluble fractions). The
cellulose produced by the existing organic acids pretreatment
process, contains residual organic acids from the pretreatment
process ranges between 0.5% to 5% of the dry cellulose by weight.
Neutralization of these residual acids consumes large quantities of
sodium hydroxide which directly result a cost increases for
bioethanol production and indirectly results in cost increases for
treatment of the filtrate. Thus, a method for minimizing the amount
of sodium hydroxide required to reach the operational pH range
prior for subsequent treatment of cellulose represents a
particularly important advantage over existing methods.
[0009] In another aspect the invention relates to a process for
separating and cleaning lignin from a lignin suspension derived
from organic acid pretreatment of plant materials by use of
centrifugation.
[0010] The organic acids pretreatment process uses an organic acids
solution as reagent to dissolve the hemicellulose and lignin
contained in plant materials, after separation, the extracted
liquor is separated from the mixture. The extracted liquor which is
composed primarily of cellulose, dissolved hemicellulose, lignin,
minerals, organic acids, water and the others is concentrated by an
evaporation system to remove part of the organic acids and water to
a dry matter content of 55% to 65%, calculated from the total
weight of the concentrated extraction liquor. The existing
processes are described in international patent publications WO
2000/068494, WO 2009/092749, WO 2011/154293, and WO 2015/185639,
the contents of each which are incorporated by reference in their
entirety.
[0011] In such processes, a lignin suspension is typically obtained
by dispersing the lignins in the mixture of concentrated extraction
liquor and water and the separation of the lignin and sugars
present in the lignin suspension are separated via a filter press.
After separating the lignin, a pressed cake of lignin and
sugar-comprising liquor are obtained. The pressed lignin cake is
washed with water, or by a combination of air and water, to obtain
a final washed lignin and washing liquor.
[0012] However, the filter press cannot run continuously throughout
the entire process, and therefore washing the cake using a filter
press cannot produce a homogeneous product due to structural
limitations of the device. The filtered cake of lignin is a
rectangle so that the wash path across the lignin cake is variable
and generally inconsistent. The present disclosure provides methods
for centrifugal recovery of lignins thereby reducing water usage
and thus reducing energy consumption while improving recovery of
lignin from lignin suspensions.
[0013] In another aspect the invention relates to a process for
producing hemicellulosic juice by a combination of evaporation and
stripping from the hemicellulosic mixture produced by organic acids
pretreatment of plant materials which is comprised largely of
dissolved hemicellulose, organic acids and water. The organic acids
pretreatment process use the organic acids solution as a reagent to
dissolve the hemicellulose and lignin contained in the
lignocellulosic raw material in a relatively low temperature and
atmospheric pressure, even in the following extraction liquor
treatment process are carried out in a relatively low temperature
and at an atmospheric or vacuum pressure so as to prevent furfural
to be created.
[0014] Typically, the extraction liquor which consists of dissolved
hemicellulose, lignin, organic acids and water is concentrated by
the multi-effect evaporation system to remove part of the organic
acids and water to a dry matter content of 55% to 65%, calculated
from the total weight of the concentrated liquor. The lignin
contained in the concentrated liquor is separated by an existing
process for the separation of lignins and sugars from an extracted
liquor, in this process, prior to separation of lignins and sugars,
mixing the concentrated liquor with water in equal parts by weight,
the separated lignin must be washed by water to remove the residual
sugars, organic acids, the whole soluble materials and waters are
collected together to form the hemicellulosic mixture of dissolved
hemicellulose, organic acids and water produced in this process.
Such processes are described in international patent publications
WO 2011/154293 and WO 2010/006840, the contents of each which are
incorporated in their entirety.
[0015] Dissolved hemicellulose in the hemicellulosic mixture mainly
comprises xylose and arabinose which can be used to produce ethanol
and other industrial products. However, organic acids present in
the hemicellulosic mixture will inhibit conversion of xylose and
arabinose to ethanol and other industrial products. Thus, efficient
removal of organic acids from the hemicellulosic mixture to produce
the hemicellulosic juice is particularly important for maximizing
yield of ethanol from the available sugars within the
hemicellulosic juice.
[0016] In another aspect the invention relates to recovering
organic acids from the high water content organic acids solutions
produced by organic acids pretreatment of plant materials
processes. Typically the content of organic acids in such processes
are higher than 83% of the total weight of the solution. The
organic acids serve as reagent to dissolve the hemicellulose and
lignin contained in the lignocellulosic raw materials in a
relatively low temperature and atmospheric pressure to avoid
production of furfural during the pretreatment process. After
separation, the liquor containing dissolved hemicellulose, lignin,
organic acids, water and other constituents. The water, constituted
of the waters in the organic acids solution and in the raw
material, is concentrated by an evaporation system to remove part
of the organic acids with water which form the first stream of high
water content organic acids solution.
[0017] The lignin contained in the concentrated liquor is separated
by an existing process for the separation of lignins and sugars
from extracted liquor in this process, prior to the separation of
lignins from the concentrated liquor, mixing the concentrated
liquor with water precipitates the lignins in the concentrated
liquor, in equal parts by weight of the concentrated liquor.
Subsequently, the separated lignin is washed with water to remove
residual sugars, organic acids and other water soluble
components.
[0018] The whole soluble materials with the waters, the water
remained in the concentrated liquor, the water mixed in the
concentrated liquor for precipitating the lignin, and the water
used as washing water, are collected together to form a mixture
consisting primarily of dissolved hemicellulose, organic acids, the
water (remained and added in the process) and other minor
components. Such processes are described in international patent
applications WO 2011/154293 and WO 2010/006840, the contents of
each which are incorporated in their entirety.
[0019] In order to efficiently remove the organic acids from the
high water content organic acid solutions regardless of their
source, a process a combination of evaporation with stripping is
disclosed. The disclosed process comprises a first pass
multi-effect evaporator to evaporate the organic acids with water
from the mixture partially, the condensate of the evaporator which
mainly comprises organic acids and the water, forms the second
stream of high water content organic acids solution.
[0020] The concentrated organic acids mixture from evaporator is
fed to a stripping column wherein the organic acids are further
removed to a content of less than 2%, the condensate from the
stripping column forms the third stream of high water content
organic acids solution.
[0021] The fourth stream of high water content organic acids is
derived from recovery of organic acids from the cellulosic pulp
which contains about 62% of the soluble part (which largely
consists of organic acids and water), and about 38% of the
insoluble part (which consists mainly of cellulose) by use of a
desolventizer adapted to utilize steam to remove the residual
organic acids from dried cellulosic pulp. In this aspect of the
present invention the condensate from the desolventizer forms the
fourth stream of high water content organic acids solution.
[0022] In order to recycle the organic acids and the waters to the
organic acids pretreatment process, the additional waters of these
four streams of high water content organic acids solution need to
be removed from these four streams of high water content organic
acids solution to meet the requirement of water content for
extraction and delignification step.
[0023] In another aspect the invention relates to a method for
producing organic fertilizers by utilizing stillage from cellulose
and hemicellulosic juice.
[0024] This invention is based on organic acid pretreatment plant
materials wherein the plant materials, particularly grain straw,
serve as raw material. The separation of lignocellulosic raw
materials into cellulose, hemicellulosic juice and lignin by the
organic acid pretreatment process, hydrolysis and fermentation of
cellulose and hemicellulosic juice, and conversion of most of the
cellulose and hemicellulosic juice into ethanol are described in
international patent application WO 2015/185639, the contents of
which is hereby incorporated in its entirety.
[0025] Typically, in processes for producing fuel ethanol after
fermentation, the mixture of fermented cellulose and hemicellulosic
juice is fed to a mash column of distillation system, where the
ethanol is extracted to produce the fuel ethanol. In such processes
the residue is released from the bottom of the mash column. One
consequence of the organic acid pretreatment process is that most
of the nutritional constituents of the lignocellulosic raw material
(protein, potassium, phosphate, etc.) is separated into the
hemicellulosic juice, and mixed with the fermentation material
(yeast, glycerol, etc.) as stillage. Use this stillage becomes a
key problem, without a productive use, the stillage will be treated
as waste, and treatment of such waste is costly. Under existing
processes, there is no good method being proposed. This aspect of
the present invention provides a process for decanting and
evaporating the stillage solids to form the basis of a valuable
organic fertilizer while simultaneously contributing vapor derived
from the stillage liquid as a thermocouple to the to the stillage
solids evaporation system thereby producing a thermodynamically
efficient method of recovering and processing otherwise
unproductive stillage.
SUMMARY OF THE INVENTION
[0026] A first aspect of the present invention discloses methods
and compositions for efficient, thorough and economic recovery of
organic acids from cellulosic pulp by a combination of dryer and
desolventizer. The method comprises a first step which uses the
dryer to reduce the organic acids to a content of 5% to 12%,
calculated from the total weight of the dried cellulosic pulp. At
this level it is difficult to further remove organic acids by
continued drying. To overcome this defect, the invention comprises
a second step wherein a desolventizer is used to further remove the
organic acids using direct steam as the desolventizing medium to
reduce the organic acid content to less than 2%, relative to the
total weight of the desolventized cellulosic pulp.
[0027] Another aspect of the present invention is to provide a
process and compositions for treating cellulose by a combination of
neutralization and alkalization that uses the minimum of sodium
hydroxide possible to prepare cellulose for enzymatic digestion and
means of recycling the sodium hydroxide liquor from the
alkalization step to the neutralization step, using the minimum
sodium hydroxide to decrease the cost of bioethanol production and
treatment of the attendant wastes.
[0028] Another aspect of the present invention provides lignin
separation and cleaning process and compositions, using
centrifugation which further comprises recycling specific portions
of centrifugate and online washing to obtain pure lignin to
decrease overall water consumption and obtain high quality
lignin.
[0029] Another aspect of the invention is a process to efficiently
and economically remove organic acids from the hemicellulosic
mixture of dissolved hemicellulose, organic acids, and water by
combining evaporation with stripping to produce a hemicellulosic
juice composition. The process comprises in a first step a
multi-effect evaporation system to partially evaporate the organic
acids with water to a dry matter content of 40% to 70%, calculated
from the total weight of the concentrated hemicellulosic juice. The
process further comprises a second step wherein the concentrated
hemicellulosic juice is fed to a stripping column wherein the
organic acids are further removed to a content of less than 2%,
calculated from the total weight of the hemicellulosic juice.
[0030] Another aspect of the present invention is a process for
efficient and economic removal of water from high water content
organic acids solutions by a process comprising multi-column
distillation to produce a composition suitable for subsequent
recycling within the organic acids pretreatment process. The
process is characterized by a) adopting a two to five columns
distillation system to recover the organic acids, and b) feeding
fresh steam only into the first column of the multi-column
distillation system, and c) providing the vapors released from
previous columns to the subsequent columns as the thermal energy
sequentially, and d) feeding one or more streams of high water
content organic acids solutions into different columns within the
multi-column system to balance the energy requirements for the
columns comprising the distillation system, and e) adjusting the
content of the organic acids in the condensate of the first column
to minimize fresh steam consumption, and f) recycling the total
organic acids and the total waters discharged from the multi-column
distillation system into the overall process constituting organic
acid pretreatment of plant materials, which can maximally reduce
the energy, i.e., steam consumption for recovering of the organic
acids, meantime can recycle the total organic acids and waters to
the pretreatment process.
[0031] In another aspect of the present invention is a method to
utilize the stillage of fermentation of cellulose and
hemi-cellulosic juices to produce an organic fertilizer composition
efficiently and economically. Stillage is rich in organic matter
and nutrients which meet the requirements as an organic fertilizer.
The organic fertilizer can improve quality of the soil as well as
providing nutrients to plants e.g. grains. In contrast, chemical
fertilizers can damage soil even while providing nutrients to the
plants. Organic fertilizer is an important emerging direction for
agriculture. This aspect of the present invention is characterized
by the use of the stillage (fermentation by products) to produce
valuable organic fertilizer by an efficient and economic method.
The method comprises separating stillage by decanting to obtain a
solid fraction of stillage and a thin stillage comprising more
dilute fraction of stillage. The method further comprises
concentrating the thin stillage by multi-effects evaporation system
to obtain a concentrated stillage, mixing the solid fraction and
concentrated stillage to obtain a mixture, drying said mixture by
dryer to obtain the organic fertilizer, the vapor released from the
dryer as the thermal energy of the multi-effect evaporation system,
the fresh steam is fed to the multi-effect evaporation system as
the supplementary thermal energy.
DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a process diagram illustrating how organic acids
are recovered from cellulosic pulp by combination of dryer and
desolventizer units. Cellulosic pulp (21) is introduced into the
dryer unit (101) to obtain dried cellulosic pulp (22) and vapor
(23). The vapor (23) is used to provide thermal energy to the
extraction liquor concentration system as well as other operational
units within the overall system. Dried cellulosic pulp (22) is fed
to the desolventizer (103) to further remove organic acids by
utilizing direct steam (23) as the desolventizing medium to obtain
desolventized cellulosic pulp (24). The vapor (25) from the
desolventizer unit is fed to condenser I (104). Non-condensing
vapor (26) from condenser I (104) is fed to condenser II (105). The
condensed vapor solution (27) from condenser I and the condensed
vapor solution (28) from condenser II (105) may be combined to form
the organic acids solution (13).
[0033] FIG. 2 is a schematic illustrating the structure of the
desolventizer (103). Dried cellulosic pulp (22) is fed into the top
of the desolventizer (103) through a feed inlet (106). The direct
steam (23) sprays out from the holes of the plate (109) then goes
out through the layer of the dried cellulosic pulp, meantime the
direct steam brings the residual organic acids which is contained
in the dried cellulosic pulp to form the organic acids vapor, the
organic acids vapor is released from the vapor outlet (107) of the
desolventizer (103). The released organic acids vapor is fed into
condenser I (104) and the uncondensed vapor within Condenser I
(104) is fed into condenser II (105). The condensates of condenser
I (104) and condenser II (105) form the organic acids solution
(13). After desolventizing, the desolventized cellulosic pulp (24)
is discharged by a rotary discharger (108).
[0034] FIG. 3 is a schematic illustrating the treatment of
cellulose by a combination of neutralization and alkalization
wherein the cellulose (21) is fed to the neutralization tank (101)
where sodium hydroxide (23) and recycled sodium hydroxide liquor
(22) are added to form the neutralized cellulose mixture (24). The
neutralized cellulose mixture (24) is fed into press I (102) to
obtain a filtrate (25) and the neutralized cellulose (26). The
filtrate (25) is discharged to a waste water treatment system
(103), while the neutralized cellulose (26) is fed to the alkalized
reactor (104). Within the alkalized reactor (104) sodium hydroxide
(27) is added to obtain an alkalized cellulose mixture (28). The
alkalized cellulose mixture (28) is fed into press II (105) to
obtain the sodium hydroxide liquor (22) to recycle to the
neutralization tank and the final alkalized cellulose (29)
product.
[0035] FIG. 4 is a process diagram illustrating a process for
producing pure lignin. In this process the third centrifugate (21)
mixes with concentrated extraction liquor (22) to form the mixture,
the mixture is emulsified in the suspension tank (102) by using the
continuous or batch emulsifier (101) to form stable lignin
suspension (23). The lignin suspension (23) is then fed into a
centrifuge (103) where the lignin suspension is separated into a
lignin layer and a first centrifugate (25). The first centrifugate
(25) is delivered to a multi-effect evaporation system (104) for
hemicellulosic juice production. A first wash water (27) is
introduced to wash the lignin layer to produce a second
centrifugate (26). The first wash water may be the high acid
content water from condenser I of the acids distillation unit (5)
of FIGS. 10-13. The second centrifugate (26) is also delivered to
the multi-effect evaporation system (104) for hemicellulosic juice
production. A second wash water (28) is introduced to the lignin
layer to produce at least a third centrifugate (21). The second
wash water may comprise the low acids content wash water from the
other condensers except condenser I of the acids distillation unit
(7) of FIGS. 10-13, or fresh water (29), or a mixture of both. The
third and any subsequent centrifugates may be combined and
reintroduced into the suspension tank (102) to suspending the
lignin. The washed lignin is discharged from the centrifuge as pure
lignin (24).
[0036] FIG. 5 illustrates the sequence of steps involved in
producing hemicellulosic juice. Raw hemicellulosic juice (21)
separated from extraction liquor by lignin precipitation,
filtration, and washing is fed into a multi-effect evaporation
system (101). A concentrated hemicellulosic juice (22) and
condensed organic acids (23) are produced by the multi-effect
evaporator system. Fresh steam (26) and the concentrated
hemicellulosic juice (22) are introduced into the stripping column
(102) to further remove organic acids and obtain the stripped
hemicellulosic juice (24) with an organic acid content of less than
2% of the total weight of the stripped hemicellulosic juice and the
newly condensed acids (25).
[0037] FIG. 6 graphically details a 2-effect evaporation and
stripping system. Internal labels are described in Example 4.
[0038] FIG. 7 graphically details a 3-effect evaporation and
stripping system. Internal labels are described in Example 4.
[0039] FIG. 8 graphically details a 4-effect evaporation and
stripping system. Internal labels are described in Example 4.
[0040] FIG. 9 is a flow diagram of the process for recovering
organic acids from high water content organic acids solutions by
multi-column distillation. Raw lignocellulosic plant materials (11)
are fed to the extraction step (101). Organic acids (12) are added
to the plant material at the extraction step (101) to dissolve the
hemicellulose and lignin from the raw plant material (11) to obtain
an extraction mixture (13). An extraction liquor (14) is produced
by separation (102) of soluble and suspended particles from the
extraction mixture wherein the insoluble and unsuspended residue
comprise the cellulosic pulp (15). The cellulosic pulp (15) is
dried in a dryer (109) to produce a dried cellulosic pulp (27) and
the condensate from the dryer, including organic acids may be
recycled in the extraction step (101). In this process, the
extraction liquor (14) is fed into the evaporation system (103) to
partially remove residual organic acids and water to form a first
stream of high water content organic acids solution (1) and obtain
concentrated liquor (16). The concentrated liquor (16) is fed into
the lignin separation (104) step, in this step the addition of
water (17) precipitates the lignin, allowing separation of the
lignin from the concentrated liquor (16), obtaining the separated
lignin (18) and the soluble materials with the waters (19). The
lignin requires washing with various wash waters (20) in a series
of lignin washing steps (22) to remove residual sugars, organic
acids and other water soluble constituents. The water from the
lignin washing step (105) and the soluble materials with the wash
water (19) are pooled to form a mixture of hemicellulose, organic
acids, water and other water soluble constituents (23). To remove
the organic acids from this mixture (23) and reduce the water
content the mixture (23) is subject to multi-effect evaporation
(106) The condensate of the multi-effect evaporator forms a second
stream of high water content organic acids solution (2). Following
the multi-effect evaporation (106) the concentrated mixture (24) is
fed into a stripping column (107) wherein the organic acids are
further removed to a content of less than 2%, the condensate from
the stripping column forms a third stream of high water content
organic acids solution (3) and the hemicellulosic juice (25). To
remove organic acids from the dried cellulosic pulp (15) a
desolventizer (108) is adapted to use direct steam (26) to remove
the residual organic acids. The condensate from the desolventizer
forms a fourth stream of high water content organic acids solution
(4) and the desolventized cellulosic pulp (28). The four streams of
high water content organic acids solutions are fed into the
multi-column distillation system (110) to reduce the water content.
An aqueous acid solution (5) is obtained with an acid content of
0.5 to 10% in the condensate discharge from the top of the first
column. Subsequent columns produce condensate (7) discharge with
acid content of 0.2% to 1%. Aqueous acid solutions (6) with an acid
content of 5% to 15% comprise the bottom output of the first
column. Where all acid percentages are calculated by weight.
[0041] FIG. 10 illustrates the details of a 2 column distillation
system. Internal labels are described in Example 5.
[0042] FIG. 11 illustrates the details of a 3 column distillation
system. Internal labels are described in Example 5.
[0043] FIG. 12 illustrates the details of a 4 column distillation
system. Internal labels are described in Example 5.
[0044] FIG. 13 illustrates the details of a 5 column distillation
system. Internal labels are described in Example 5.
[0045] FIG. 14 is a process diagram illustrating production of an
organic fertilizer from fermentation stillage (21) from the bottom
of a mash column (100) of an ethanol distillation system. The
stillage (21) is fed into a decanter (101) to obtain a solid
fraction (22) and a thin stillage (23). The thin stillage (23) is
fed to the multi-effect evaporation system (102) to generate a
concentrated stillage (24). The solid fraction (22) and the
concentrated stillage (24) are fed into a mixer (103) wherein the
two fractions are mixed to obtain a mixture (25). The mixture (25)
is fed into a dryer (104) to obtain a dried mixture (26) and this
dried mixture (26) represents a high quality organic fertilizer.
The vapor (27) released from the dryer (104) may be fed into the
multi-effect evaporator (102) to provide thermal energy for the
evaporation process, the fresh steam (28) is fed to the
multi-effect evaporation system (102) as the supplementary thermal
energy.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Recovery of Organic Acids from Cellulosic Pulp
[0047] The first aspect of the present invention discloses methods
and compositions for efficient, thorough and economic recovery of
organic acids from cellulosic pulp by a combination of dryer and
desolventizer. The organic acids and desolventized cellulosic pulp
are produced by a process comprising the steps of: [0048] a) drying
a cellulosic pulp produced from organic acids pretreatment of plant
material in a dryer to remove the organic acids to a content of 3%
to 18%, calculated from the total weight of the dried cellulosic
pulp, and, [0049] b) capturing the vapor released from the dryer
for use in the extraction liquor concentration system and other
organic acids pretreatment operational systems as a source of
thermal energy, and [0050] c) condensing the vapor in the
extraction liquor concentration system and other organic acids
pretreatment operational systems to form a first phase of the
organic acids solution of the organic acids pretreatment process,
and [0051] d) using direct steam in a desolventizer to further
remove the organic acids from the cellulosic pulp, to a content of
less than 2%, and [0052] e) condensing the organic acids vapor
released from the desolventizer, to obtain a second phase of
organic acids solution of the organic acids pretreatment
process.
[0053] This aspect of the invention relates to a method for
recovering organic acids from cellulosic pulp derived from the
organic acids pretreatment process of plant material by a
combination of dryer and desolventizer. The organic acids
pretreatment process uses the organic acids as a reagent to
dissolve the hemicellulose and lignin contained in the
lignocellulosic plant materials. After separating the cellulosic
pulp from the mixture of the soluble part and insoluble part, the
residue which includes the insoluble part is the cellulosic
pulp.
[0054] The existing organic acids pretreatment process may include
a step of partial elimination of the lignins to obtain a residual
overall level of lignins of 0.3 to 4% of the total cellulosic pulp
by dry weight. The content of the organic acids in the cellulosic
pulp may be 35% to 65%, calculated from the total weight of the
cellulosic pulp. The content of the cellulose in the cellulosic
pulp may be 30% to 50%, calculated from the total weight of the
cellulosic pulp.
[0055] As shown in FIG. 1 the cellulosic pulp from the organic
acids pretreatment process is fed to the dryer. The dryer reduces
the organic acids to a content of 3% to 18%, calculated from the
total weight of the dried cellulosic pulp, once the content of the
organic acids is lower than 3%, the dryer cannot efficiently
further remove organic acids, if the content of the organic acids
is higher than 18%, the consumption of direct steam by the
desolventizer is inefficient.
[0056] Drying of the cellulosic pulp is carried out by many forms
of dryers which may include tube dryers, pneumatic dryers, spray
dryers, rotary disc dryers, and other dryer technologies known to
those in the art; it is particularly preferable to utilize a tube
dryer. The dryer step may be carried out at a temperature of
90.degree. C. to 150.degree. C. After drying, the dried cellulosic
pulp discharged from dryer is fed to the desolventizer.
[0057] The vapor which released from the dryer may be used for the
extraction liquor concentration system as well as provide other
systems with thermal energy. The condensates of the vapor from the
dryer which is condensed in the extraction liquor concentration
system and other systems form the first phase of organic acids
solution and may be reused in the organic acids pretreatment
process.
[0058] In the desolventizer shown in FIG. 2, the organic acids are
further removed from the dried cellulosic pulp to a content of less
than 2%, calculated from the total weight of desolventized
cellulosic pulp. The desolventizer may utilize direct steam as the
desolventizing medium to remove the organic acids furtherly from
the dried cellulosic pulp. The desolventizer may further remove the
organic acids by using direct steam as the desolventizing medium in
step d) carried out at a temperature of 90.degree. C. to
150.degree. C.
[0059] After the desolventization step, the desolventized
cellulosic pulp can be used to produce ethanol and other
products.
[0060] The organic acids vapor also contains water released from
the desolventizer is recovered by the condensation system of the
organic acids distillation system, wherein the organic acids are
recovered for use in the organic acids pretreatment process. The
condensation system is carried out by 1 to 3 condensers, preferably
by 2 condensers.
Production of Alkalized Cellulose
[0061] This aspect of the invention relates to a process for
treating cellulose by a combination of neutralization and
alkalization to produce an alkalized cellulose comprising the steps
of: [0062] a) neutralizing the organic acids contained in the
cellulose produced from organic acids pretreatment of plant
material with sodium hydroxide liquor recycled from step d) of the
process to form a neutralized cellulose mixture, and [0063] b)
separating neutralized cellulose from the neutralized cellulose
mixture with a press, the filtrate is directly released to waste
water treatment system, and [0064] c) alkalizing the neutralized
cellulose by addition of a sodium hydroxide solution in a reactor
to form an alkalized cellulose mixture, and [0065] d) separating
the alkalized cellulose from the alkalized cellulose mixture with a
press, wherein the sodium hydroxide liquor (filtrate of the
alkalized cellulose mixture) comprises sodium hydroxide for reuse
in step a) of the process.
[0066] In this aspect of the invention, the cellulose produced from
cellulosic pulp derived from the organic acid pretreatment
processes and stripped of residual organic acids by the drying and
desolventizing steps described above may still contain a residual
level of organic acids representing is 0.5% to 5% of the total
weight of the cellulose. In this aspect of the invention such
cellulosic pulp is further treated to form an alkalized cellulose
by a process comprising neutralization and subsequent
alkalization.
[0067] As illustrated in FIG. 3, in step a) of the process residual
organic acids contained in the cellulose are neutralized by adding
sodium hydroxide liquor recycled from separating the alkalized
cellulose from the alkalized cellulose mixture in step d). The pH
of the sodium hydroxide liquor is pH 10 to pH 12. After addition of
the sodium hydroxide liquor to the cellulose, the pH of the
cellulose mixture is adjusted to a range of 5 to 8 by addition of
more sodium hydroxide as necessary. Use of sodium hydroxide liquor
recycled from the last steps of the process for producing alkalized
cellulose can decrease the overall consumption of sodium hydroxide
from 30% to 65% by weight, relative to current treatment
processes.
[0068] In step b) the neutralized cellulose is separated from the
neutralized cellulose mixture by use of a press. The press may be a
screw press or other type of press known to those of skill in the
art. In this separation step, the neutralized cellulose mixture
formed in step a) is separated into two streams, one comprises the
neutralized cellulose, the other comprises the filtrate. The
neutralized cellulose has a dry solid content of 30% to 45%. The
filtrate is directly released to a waste water treatment system,
the pH of the filtrate is pH 5 to pH 8, so there is no need to
adjust the pH by titration as in existing treatment processes.
[0069] In step c), the neutralized cellulose is alkalized by adding
a sodium hydroxide solution to the neutralized cellulose in a
reactor to a pH of pH 10 to pH 12, at a temperature of 50.degree.
C. to 100.degree. C. Under these conditions the content of the
lignin contained in the cellulose can be reduced to a level of 1%
to 2.5%, calculated from the total weight of the cellulose.
[0070] In step d), the alkalized cellulose mixture is separated by
use of a press. In this separation step, the alkalized cellulose
mixture is separated into two streams, one stream comprises the
alkalized cellulose, the other stream comprises the sodium
hydroxide liquor.
[0071] The alkalized cellulose contains a dry solid content of 30%
to 45%, calculated from the total weight of the alkalized
cellulose. After a washing step, this alkalized cellulose can be
hydrolyzed by cellulase with a high conversion rate of cellulose to
glucose.
[0072] The sodium hydroxide liquor may be recycled for neutralizing
the organic acids in step a).
Production of Pure Lignin
[0073] This aspect of the invention relates to a process for
separating and cleaning lignin from a lignin suspension by
precipitation and centrifugation, comprising the steps of: [0074]
a) separating lignin from a lignin suspension produced from organic
acids pretreatment of plant material by batch or continuous
centrifugation, and [0075] b) cleaning the precipitated lignin in
the centrifuge by multiple applications of wash solution onto the
lignin layer during centrifugation, to form multiple centrifugates,
and [0076] c) recovering a first centrifugate and a second
centrifugate for use in hemicellulosic juice concentration, and
[0077] d) recycling a third centrifugate for precipitating the
lignin in the concentrated extraction liquor into lignin suspension
of the organic acids pretreatment process. [0078] e) discharging
the lignin from the centrifuge.
[0079] The extraction liquor of this aspect of the invention is
obtained from existing organic acids pretreatment processes wherein
the hemicellulose and lignin contained in plant materials are
dissolved in the organic acids solutions from which the extraction
liquor is derived. The extracted liquor is separated from the
mixture, the extracted liquor which comprises cellulose, dissolved
hemicellulose, lignin, minerals, organic acids, water and the other
minor constituents is concentrated by the evaporation system to
remove part of the organic acids and water to a dry matter content
of 55% to 65%, calculated from the total weight of the concentrated
extraction liquor.
[0080] Accord to the present invention, the separating equipment is
a centrifuger, preferable a scraper centrifuger, which may be run
in continuous or batch mode. The centrifuger is equipped with a
spraying device which can evenly spray washing water onto the
lignin layer to obtain a pure lignin.
[0081] As illustrated in FIG. 4, the third centrifugate from step
d) mixes with concentrated extraction liquor to form the mixture,
the mixture is fed to the suspension tank in which the mixture is
emulsified by using the continuous or batch emulsifier to form the
stable lignin suspension. The lignin suspension is then
successively fed to the centrifuge, the centrifuge then separates
the lignin suspension to obtain the first centrifugate and a lignin
layer. The first centrifugate which comprises 10% to 60% of the
total centrifugate volume is recovered for subsequent processing by
the hemicellulosic juice production unit.
[0082] The spraying device delivers washing water which may include
a mixture of formic acid, acetic acid and water to provide an
online wash of the lignin layer. In a preferred embodiment the
centrifuge is continuously rotating. Under continuous rotation, the
washing water can be evenly sprayed on the lignin layer to provide
homogeneous cleaning of the lignin. During spraying, impurities are
washed out by the washing water, the recovered washing water and
the impurities form the second centrifugate which comprises 10% to
30% of the total centrifugate by volume. The centrifuge continues
to operate while subsequent washes are applied to produce third and
possible more centrifugates. The third and subsequent centrifugates
may comprise 10% to 50% of total centrifugate by volume. Once the
final centrifugate is removed the lignin layer is discharged from
the centrifuger to obtain a pure lignin comprising 90% to 99%
lignin by weight.
[0083] The washing water may comprise water or a mixture of formic
acid, acetic acid and water, wherein the formic acid content of the
mixture is 0% to 30%, calculated from the total weight of the
mixture, and the acetic acid content of the mixture is 0% to 20%,
calculated from the total weight of the mixture. The mixture of
formic acid, acetic acid and water may derive from the recovered
organic acids from high water content organic acids solutions by
acids distillation unit. In a preferred embodiment the initial
washing water introduced into the centrifuge are derived from the
high organic acids content washing water. In some embodiments the
second washing water introduced into the centrifuge are derived
from the low organic acids content washing water. In some
embodiments fresh water comprises the washing water for the third
and any subsequent wash procedures for cleaning the lignin layer to
obtain the pure lignin.
[0084] The first centrifugate and the second centrifugates may be
recovered and delivered to the subsequent hemicellulosic juice
production unit, while the third and any subsequent centrifugate
may be recycled to the lignin suspending step to decrease water
consumption for the initial lignin precipitation step which
consequently decreases energy consumption of the hemicellulosic
juice production and organic acids recovery unit.
Production of Hemicellulosic Juice
[0085] This aspect of the invention relates to a process for
producing hemicellulosic juice by a combination of evaporation and
stripping, comprising the steps of: [0086] a) introducing a
hemicellulosic mixture comprised of dissolved hemicellulose,
organic acids, water and others produced by organic acids
pretreatment of plant material into a multi-effect evaporation
system, and [0087] b) evaporating the hemicellulosic mixture within
the multi-effect evaporator to form a concentrated hemicellulosic
juice with a dry matter content of 40% to 70% (w/w), and [0088] c)
removing organic acids from the concentrated hemicellulosic juice
in a stripping column to form a hemicellulosic juice, wherein the
hemicellulosic juice comprises less than 2% (w/w) organic
acids.
[0089] This invention is based on the existing organic acids
pretreatment of plant materials process, wherein a mixture of
formic acid and acetic acid or formic acid only are used to
dissolve hemicellulose and lignin from the lignocellulosic raw
plant materials, after an initial separation step, the extraction
liquor which comprises dissolved hemicellulose, lignin, organic
acids, water and other minor constituents is separated from the
remaining insoluble material (mainly comprising cellulose).
[0090] After lignin precipitation, filtration and washing steps,
the lignin is removed from the extracted liquor, the remainder
known as hemicellulosic juice is comprised of dissolved
hemicellulose, organic acids, water and other minor water soluble
constituents.
[0091] The dissolved hemicellulose in the hemicellulosic juice is
mainly comprised of xylose and arabinose, which can be used to
produce ethanol and other industrial products. Organic acids
remaining in the hemicellulosic juice may inhibit the conversion of
xylose and arabinose to ethanol and other industrial products. In
addition, such organic acids represent a loss of a costly reagent
in the overall organic acids pretreatment process. This aspect of
the invention specifically concerns producing hemicellulose
suitable for optimal conversion to ethanol with minimal residual
organic acids by a process that can simultaneously recover such
organic acids present in hemicellulosic juice for use in the
organic acids pretreatment process.
[0092] The content of dissolved hemicellulose in hemicellulosic
juice is 2% to 20%, calculated from the total weight of the
hemicellulosic mixture. The content of organic acids in the
hemicellulosic juice is 10% to 30%, calculated from the total
weight of the hemicellulosic mixture. Step a) of the present
invention is characterized in that the multi-effect evaporation
system partially evaporates the organic acids with water to a dry
matter content of 40% to 70%, calculated from the total weight of
the concentrated hemicellulosic juice.
[0093] The multi-effect evaporation can decrease the steam/energy
consumption for removing the organic acids and concentrating the
hemicellulosic juice. In some embodiments the multi-effect
evaporation is characterized by use of 2 to 4 effects evaporation
systems as shown in FIGS. 6-8. In a preferred embodiment the
process uses a 3 effects evaporation system.
[0094] In some embodiments the multi-effect evaporation of organic
acids with water is carried out at a temperature of 60.degree. C.
to 160.degree. C. in the first effect evaporator. In some
embodiments the multi-effect evaporation of organic acids with
water is carried out at a temperature of 25.degree. C. to
60.degree. C. in the last effect evaporator.
[0095] The first evaporator of the multi-effect evaporation system
may utilize the vapor output from the top of the stripping column
as the complete source or as a partial source of thermal energy. In
each step of the multi-effect evaporation system, the vapor output
from the top of the previous evaporator may be utilized for thermal
energy to drive the following column to reduce the overall energy
required by the multi-effect evaporation system.
[0096] As shown in FIGS. 6-8 the hemicellulosic mixture is fed in
the first evaporator and discharged from the first evaporator
sequentially.
[0097] After the concentration of the hemicellulosic juice by the
multi-effect evaporation system, the dry matter content of
concentrated hemicellulosic juice which is discharged from the
first evaporator is 40% to 70% of the total weight of the
concentrated hemicellulosic juice, the viscosity of the
concentrated hemicellulosic juice is 200 mPas to 1000 mPas, if the
viscosity is higher than this range, the concentrated
hemicellulosic juice it is too difficult to further remove the
organic acids by evaporation.
[0098] This invention is further characterized by combining the
multi-effect evaporation system with a stripping column. The
concentrated hemicellulosic juice discharged from the multi-effect
evaporation system is fed to the top plate of the stripping column.
The stripping column utilizes direct steam as the stripping medium
to remove the organic acids further to a content of less than 2% of
the total weight of the stripped hemicellulosic juice.
[0099] The vapor output from the top of the stripping column may be
used as the thermal energy of the first evaporator of the
multi-effect evaporation system.
[0100] The stripped hemicellulosic juice discharged from the bottom
of the stripping column is used as the final product, i.e. the
hemicellulosic juice, which can be used to produce ethanol and
other industrial products.
Removal of Water from High Water Content Organic Acids
Solutions
[0101] This aspect of the invention relates to a process for
recovering organic acids from high water content organic acids
solutions by multi-column distillation, comprising, [0102] a)
adopting a two to five columns distillation system to recover the
organic acids, and [0103] b) feeding fresh steam only into the
first column of a multi-column distillation system, the others
columns utilize the vapor released from the previous column as the
thermal energy sequentially, and [0104] c) directing the vapors
released from previous columns to the subsequent columns as the
thermal energy, so that the vapor released from the first column
will be fed into the second column and the vapor released form the
second column will be fed into third column and so on through each
column of the distillation system, and [0105] d) feeding one or
more streams of high water content organic acids solutions into
different columns within the multi-column system to balance the
energy requirements for the columns comprising the distillation
system, and [0106] e) adjusting the content of the organic acids in
the condensate of the first column to minimize fresh steam
consumption, and [0107] f) recycling the total organic acids and
the total waters discharged from the multi-column distillation
system.
[0108] In this aspect of the invention, the high water content
organic acids solutions derived from organic acids pretreatment
process of plant material. Typically the content of the organic
acids comprises more than 83% of the total weight of the solution.
Typically, during the organic acids pretreatment process, and as a
consequence of the downstream steps of cellulosic pulp processing
and lignin and hemicellulosic sugar production in a relatively low
temperature and atmospheric pressure, which lead to that there is
no furfural created during the whole pretreatment process, as well
as four streams of high water content organic acids solutions are
generated. In order to recycle the organic acids in the high water
content organic acids streams into the organic acids pretreatment
process the water content must be reduced.
[0109] Recovering organic acids from the high water organic acids
solution by distillation requires very high energy inputs.
Therefore, reducing the energy required to recover and recycle
organic acids is essential for commercializing the organic acids
pretreatment process.
[0110] In one embodiment the invention is characterized in that
recovering organic acids from high water content organic acids
solution by use of a two to five column distillation system to
maximize energy efficiency. A preferred embodiment uses a four
column distillation system.
[0111] The greater the number of columns, the less steam/energy is
consumed by the distillation system. However, the number of columns
comprising the distillation system is limited by the difference of
temperature between the columns of the distillation system.
Surprisingly, we have empirically discovered that if the system
includes more than five columns the difference in temperature
between the columns is too small to use the vapor released from the
previous column as the steam/energy for the following column in
series.
[0112] After scientific analysis, two to five columns distillation
system can be suitable for recovering organic acids from high water
content organic acids solution in this process, four columns
distillation is the most suitable from the view of efficiency and
economy.
[0113] Typically, organic acids pretreatment processes create four
streams of high water content organic acids solutions as described
above. The term "high water content organic acids solution" means
the water content is higher than the required water content in the
organic acids solution used for dissolving plant materials in the
organic acids pretreatment process. Thus, to recycle the organic
acids from the four high water content organic acids streams, the
additional water added throughout the various process steps needs
to be removed. In order to minimize the amount of steam/energy
required for recovering organic acids from high water content
organic acids solutions by multi-column distillation it is
necessary to regulate the steam/energy used for each column so that
it is suitable to the level of organic acids within the individual
column within the series.
[0114] The invention adopts two methods to accomplish this. First
by feeding the highest water content organic solution to the last
column of the distillation system and feeding the lowest water
content organic acids solution to the first column of the
distillation system the energy input into the entire system is
directed appropriately. Second, by regulating the organic acids
content in the condensate discharged from the top of first column
from 0.5% to 10% of the total weight of the condensate by adjusting
the quantity of the steam/energy introduced into the first column
allows the consumption of the steam/energy across the whole
distillation system to be balanced. The condensate of the first
column organic acids content of 0.5% to 10% can be diverted for use
in the lignin precipitation step of the lignin production
process.
[0115] In the system described here other columns in the series
typically produce condensates with an organic acids content of 0.2%
to 1% of the total weight of the input condensates. These
condensates can be recycled to the pretreatment process for washing
lignin and other steps in the lignin production process.
[0116] In order to maintain an optimal temperature differential
between the columns, the first column is operated out at a
temperature of 120.degree. C. to 175.degree. C., the last column is
operated at a temperature of 50.degree. C. to 95.degree. C.
[0117] The organic acids solution discharged from the bottom of the
first column has a water content of 5% to 15%, calculated from the
total weight of the organic acids solution, these organic acids
solution can be directly reused to the organic acids pretreatment
process at the initial step of solubilizing the raw plant
material.
Organic Fertilizer
[0118] This aspect of the invention depicted in FIG. 14 relates to
a method for producing organic fertilizer from stillage created
from cellulose and hemicellulosic juice, comprising the steps of:
[0119] a) separating stillage from cellulose and hemicellulosic
juice produced by organic acids pretreatment of plant material
using a decanter to obtain a solid fraction of the stillage and a
thin stillage, and [0120] b) concentrating the thin stillage with a
multi-effect evaporation system to obtain a concentrated stillage
wherein the steam for the multi-effect evaporation system is
supplied from vapor released from the dryer in step d) of the
process optionally supplemented with fresh steam, and [0121] c)
mixing the solid fraction and concentrated stillage to obtain a
mixture, and d) drying the mixture to obtain the organic
fertilizer, wherein the vapor released from the dryer is fed to the
multi-effect evaporation system as thermal energy for the
multi-effect evaporation system of the process.
[0122] This invention is based on the existing organic acids
pretreatment process. In the pretreatment process, the organic
acids solution is used as the extraction reagent to dissolve most
of the lignin, hemicellulose, salts (mainly salts of potassium and
the phosphate), protein and the other components of the
lignocellulosic plant materials. The pretreatment mixture is
separated into the insoluble cellulosic pulp and a mixture of
hemicellulosic juice and lignin. The cellulosic pulp is dried to
obtain cellulose. The hemicellulosic juice and lignin mixture is
separated into hemicellulosic juice (containing hemicellulose,
salts, protein and the other soluble constituents) and lignin.
After hydrolysis and fermentation of cellulose and hemicellulosic
juice, most of the cellulose and the hemicellulose included in the
hemicellulosic juice are converted into ethanol. After extraction
of ethanol from the fermented cellulose and hemicellulosic juice by
distillation, residues of fermented cellulose and hemicellulosic
juice are discharged from the bottom of the mash column of the
distillation system. The residues are the stillage (by-product of
the process).
[0123] The stillage contains many of the nutritive components
(protein, potassium, phosphorus, calcium, magnesium, sodium,
aluminum, etc.) from the lignocellulosic raw materials as well as
additional nutritive components comprising yeast, secondary
metabolites produced by growth of the yeast during the
fermentation, and residual yeast growth media including significant
amounts of nitrogen, potassium, phosphorus and organic substances.
Such material represents all the requirements of an organic
fertilizer. Organic fertilizers are fertilizers derived from animal
matter, animal excreta (manure), human excreta, and vegetable
matter (e.g., compost and crop residues), in contrast, the majority
of fertilizers used in commercial agriculture are chemical
fertilizers extracted from minerals (e.g., phosphate rock) or
produced industrially (e.g., ammonia). Organic agriculture, as a
system of farming, allows for use of certain fertilizers and
amendments and disallows others. Both organic and chemical
fertilizers can provide significant boosts in plant yields however,
organic fertilizers have more complete mineral profiles and cannot
cause the kind of soil damage that can be inflicted by chemical
fertilizers. Organic fertilizers are an important developing
direction for agriculture.
[0124] This process disclosed here in one embodiment uses
agriculture residues as the raw materials and the stillage produced
in part by hydrolysis of cellulose and hemicellulose recovered from
the agriculture residues and fermentation of the sugars released by
hydrolysis of cellulose and hemicellulose by yeast to produce an
organic fertilizer.
[0125] The method is characterized in that the stillage is obtained
from the bottom of the mash column of an ethanol distillation
system. The dry matter content is 2% to 20%, calculated from the
total weight of the stillage. In one embodiment a centrifuge is
used to separate the stillage into a solid fraction and a thin
stillage fraction. In a preferred embodiment the centrifuge is a
decanter centrifuge.
[0126] After separation, the dry matter content of the solid
fraction is 20% to 45%, calculated from the total weight of the
solid part of stillage. The dry matter content of the thin stillage
fraction is 1% to 15%, calculated from the total weight of the thin
stillage.
[0127] The thin stillage may be concentrated by a multi-effect
evaporation system. The multi-effect evaporation system may include
4 to 6 effects evaporation system. In a preferred embodiment the
multi-effect evaporation is a 5 effects evaporation system. In the
multi-effect evaporation system, the vapor released from the top of
the previous evaporator is utilized as the thermal energy of the
following evaporator to minimize the total energy for the
multi-effect evaporation system. The thin stillage is fed into the
last evaporator of the multi-effect evaporation system and
discharged from the first evaporator of the multi-effect
evaporation system. The multi-effect evaporation system is carried
out at a temperature of 30.degree. C. to 150.degree. C.
[0128] After the concentrating, the dry substance content of the
concentrated stillage is 28% to 45%, calculated from the total
weight of the concentrated stillage.
[0129] The condensate of the vapor separated in the multi-effect
evaporation system, which is obtained in step b), may be reused as
process water.
[0130] The solid part and concentrated stillage are fed to a mixer,
wherein the two parts are mixed to obtain the mixture of the solid
fraction and the concentrated stillage. The mixture of the solid
part and the concentrated stillage is dried by the dryer,
preferably the tube dryer, to obtain the organic fertilizer. The
dryer is operated at a temperature of 80.degree. C. to 160.degree.
C. The dry solid content of the organic fertilizer is 50% to 80%,
calculated from the total weight of the organic fertilizer. The
vapor released from the dryer may be fed to the stillage
multi-effect evaporation system to provide thermal energy to the
multi-effect evaporation system. After drying, the mixture of the
solid part and the concentrated stillage is dried and this dried
mixture can be used as the organic fertilizer.
[0131] The organic fertilizer contains the organic matter, protein,
potassium salts, phosphate, the mineral substance and others. The
organic matter content of the organic fertilizer is 30% to 65%,
calculated from the total dry matter of the organic fertilizer.
Total nutrient (calculated based on the formula that the
nutrient=Nitrogen+Phosphorus pentoxide+potassium oxide) content of
the organic fertilizer is 5% to 30%, calculated from the total dry
matter of the organic fertilizer. The pH value of the organic
fertilizer is 5.5 to 8.5. The water content of the organic
fertilizer is 20% to 50%, calculated from the total weight of the
organic fertilizer.
EXAMPLES
Example 1
[0132] Organic Acid Recovery from Cellulosic Pulps
[0133] Corn straw was used as the lignocellulosic raw material.
Cellulosic pulp was obtained according to the organic acid
pretreatment process. The organic acids composition is formic acid
26%, acetic acid content 59%, and 15% water, the temperature is
103.degree. C., the solvation time is 240 min. After separation,
the cellulosic pulp is separated from the liquid fraction.
[0134] Approximately 5 kg of cellulosic pulp was recovered, the dry
matter content was 38.0%, the content of the organic acids was
49.5% and the content of water was 12.5%, calculated from the total
weight of the cellulosic pulp. The cellulosic pulp was fed to the
dryer to obtain the dried cellulosic pulp, the drying temperature
was 120.degree. C. After drying, the organic acids content of the
dried cellulosic pulp was 5.5%.
[0135] The dried cellulosic pulp was introduced into the
desolventizer at a feed flowrate is 200 g/min, direct steam is
introduced into the bottom of the desolventizer, the temperature of
the steam was 120.degree. C., and the flowrate of the direct steam
feed to the desolventizer was 14.1 g/min. The desolventized
cellulosic pulp was discharged from the desolventizer.
[0136] The organic acids content of the desolventized cellulosic
pulp was 1.8%, calculated from the total weight of the
desolventized cellulosic pulp.
[0137] A second cellulosic pulp derived from corn straw was
prepared under the similar conditions as described above. In this
trial however the dryer temperature was slightly lower (110.degree.
C.) while the flowrate of steam in the desolventizer was increased
to 26.3 g/min. The desolventized cellulosic pulp produced under
these conditions had an organic acids content of 1.95%.
[0138] In a third study wheat straw was used as the lignocellulosic
raw material and a cellulosic pulp was obtained according to the
organic acid pretreatment process described above.
[0139] Approximately 5 kg of cellulosic pulp was recovered, the dry
matter content was 37.5%, the content of organic acids was 50.2%
and the content of water was 12.3%, calculated from the total
weight of the cellulosic pulp. The cellulosic pulp was fed to the
dryer to obtain the dried cellulosic pulp, the drying temperature
was 115.degree. C. After drying, the organic acids content of the
obtained dried cellulosic pulp was 6.7%.
[0140] The dried cellulosic pulp was introduced into the
desolventizer at a feed flowrate is 200 g/min, direct steam is
introduced into the bottom of the desolventizer, the temperature of
the steam was 120.degree. C., and the flowrate of the direct steam
feed to the desolventizer was 16.8 g/min. The desolventized
cellulosic pulp is discharged from the desolventizer.
[0141] The desolventized cellulosic pulp produced under these
conditions had an organic acids content of 1.91%.
[0142] Table 1 summarizes these data.
TABLE-US-00001 TABLE 1 Organic acid content of cellulosic pulps
Dried Desolventized Cellulosic pulp cellulosic pulp cellulosic Dry
Organic Organic pulp matter acids Water acids Organic acids Direct
steam content content content content content Flowrate (%) (%) (%)
(%) (%) (g/min) Corn straw 38 49.5 12.5 5.5 1.80 14.1 Corn straw 38
49.5 12.5 8.0 1.95 26.3 Wheat straw 37.5 50.2 12.3 6.7 1.91
16.8
Example 2
Neutralization and Alkalization Treatment of Cellulose.
Sample 1
Method A:
[0143] Initially, 0.4 kg cellulose (lignin content was 4.1% and
organic acids content was 1.56%) was fed to the reactor, the
agitator was started and the pH adjusted to 12 with a sodium
hydroxide solution, which added 3.34 L of additional water. The
temperature of the reactor was maintained at 80.degree. C. and the
reaction continued for 60 minutes.
[0144] When the reaction is ended, 9.16 g sodium hydroxide was
consumed and the lignin content of the treated cellulose was
1.89%.
Method B:
[0145] In the initial neutralization step of a first processing
run, 0.4 kg cellulose (lignin content was 4.1% and organic acids
content was 1.56%) was fed to the reactor, the agitator was started
and the pH adjusted to pH 6.5 with a sodium hydroxide solution,
which added 3.34 L of additional water. The temperature of the
reactor was maintained at 80.degree. C. and the reaction continued
for 30 minutes. Following this reaction, the cellulose mixture was
filtered and pressed.
[0146] In the alkalizing step the neutralized cellulose is added to
an alkalization reactor, the agitator is started, and the pH
adjusted to pH 12 with a sodium hydroxide solution, which added
3.34 L of additional water. The temperature of the reactor was
maintained at 80.degree. C. and the reaction continued for 30
minutes. Sodium hydroxide was added as necessary to maintain the pH
at pH 12. After 30 minutes the alkalized cellulose mixture was
filtered and pressed to obtain the sodium hydroxide liquor and the
alkalized cellulose. The sodium hydroxide liquor may be reused in
the neutralization step in a second (subsequent) processing
operations.
[0147] In a second processing run 0.4 kg of cellulose (with a
lignin content of 4.1% and an organic acids content of 1.56%) is
fed into the neutralization reactor, the agitator is started, and
the sodium hydroxide liquor recovered from the alkalizing step of
the first processing run is used to adjust the pH to pH 6.8, the
temperature of the reactor is maintained at 80.degree. C. and the
reaction continued for 30 minutes. Following this reaction, the
cellulose mixture was filtered and pressed.
[0148] The alkalizing step of the second (and subsequent)
processing runs comprise the same as the steps described in the
first round. Importantly, the sodium hydroxide liquor recovered
after filtering and pressing the alkalized cellulose may be reused
in the neutralization step in the next processing operation. In the
second round of processing utilizing sodium hydroxide recovered
from the first round the total sodium hydroxide consumed was 4.58
g, the lignin content of the treated cellulose was 1.85%.
Sample 2
Method A:
[0149] Initially, 0.4 kg cellulose (lignin content was 3.6% and
organic acids content was 2.68%) was fed to the reactor, the
agitator was started and the pH adjusted to 12 with a sodium
hydroxide solution, which added 3.34 L of additional water. The
temperature of the reactor was maintained at 80.degree. C. and the
reaction continued for 60 minutes.
[0150] When the reaction is ended 12.4 g sodium hydroxide was
consumed and the lignin content of the treated cellulose was
1.56%.
Method B:
[0151] In the initial neutralization step of a first processing
run, 0.4 kg cellulose (lignin content was 3.6% and organic acids
content was 2.68%) was fed to the reactor, the agitator was started
and the pH adjusted to pH 6.5 with a sodium hydroxide solution,
which added 3.34 L of additional water. The temperature of the
reactor was maintained at 80.degree. C. and the reaction continued
for 30 minutes. Following this reaction, the cellulose mixture was
filtered and pressed.
[0152] In the alkalizing step the neutralized cellulose is added to
an alkalization reactor, the agitator is started, and the pH
adjusted to pH 12 with a sodium hydroxide solution, which added
3.34 L of additional water. The temperature of the reactor was
maintained at 80.degree. C. and the reaction continued for 30
minutes. Sodium hydroxide was added as necessary to maintain the pH
at pH 12. After 30 minutes the alkalized cellulose mixture was
filtered and pressed to obtain the sodium hydroxide liquor and the
alkalized cellulose. The sodium hydroxide liquor may be reused in
the neutralization step in subsequent processing operations.
[0153] In a second processing run 0.4 kg of cellulose (with a
lignin content of 3.6% and an organic acids content of 2.68%) is
fed into the neutralization reactor, the agitator is started, and
the sodium hydroxide liquor recovered from the alkalizing step of
the first processing run is used to adjust the pH to pH 6.8, the
temperature of the reactor is maintained at 80.degree. C. and the
reaction continued for 30 minutes. Following this reaction, the
cellulose mixture was filtered and pressed.
[0154] The alkalizing step of the second (subsequent) processing
run comprises the same steps described in the first round.
Importantly, the sodium hydroxide liquor recovered after filtering
and pressing the alkalized cellulose may be reused in the
neutralization step in the next processing operation. In the second
round of processing utilizing sodium hydroxide recovered from the
first round the total sodium hydroxide consumed was 7.87 g, the
lignin content of the treated cellulose was 1.58%.
Sample 3
Method A:
[0155] Initially, 0.4 kg cellulose (lignin content was 3.8% and
organic acids content was 4.52%) was fed to the reactor, the
agitator was started and the pH adjusted to pH 12 with a sodium
hydroxide solution, which added 3.34 L of additional water. The
temperature of the reactor was maintained at 80.degree. C. and the
reaction continued for 60 minutes.
[0156] When the reaction is ended 17.9 g sodium hydroxide was
consumed and the lignin content of the treated cellulose was
1.66%.
Method B:
[0157] In the initial neutralization step of a first processing
run, 0.4 kg cellulose (lignin content was 3.8% and organic acids
content was 4.52%) was fed to the reactor, the agitator was started
and the pH adjusted to 6.5 with a sodium hydroxide solution, which
added 3.34 L of additional water. The temperature of the reactor
was maintained at 80.degree. C. and the reaction continued for 30
minutes. Following this reaction, the cellulose mixture was
filtered and pressed.
[0158] In the alkalizing step the neutralized cellulose is added to
an alkalization reactor, the agitator is started, and the pH
adjusted to pH 12 with a sodium hydroxide solution, which added
3.34 L of additional water. The temperature of the reactor was
maintained at 80.degree. C. and the reaction continued for 30
minutes. Sodium hydroxide was added as necessary to maintain the pH
at pH 12. After 30 minutes the alkalized cellulose mixture was
filtered and pressed to obtain the sodium hydroxide liquor and the
alkalized cellulose. The sodium hydroxide liquor may be reused in
the neutralization step in subsequent processing operations.
[0159] In a second (subsequent) processing run 0.4 kg of cellulose
(with a lignin content of 3.8% and an organic acids content of
4.52%) is fed into the neutralization reactor, the agitator is
started, and the sodium hydroxide liquor recovered from the
alkalizing step of the first processing run is used to adjust the
pH to pH 7.1, the temperature of the reactor is maintained at
80.degree. C. and the reaction continued for 30 minutes. Following
this reaction, the cellulose mixture was filtered and pressed.
[0160] The alkalizing step of the second (subsequent) processing
run comprises the same steps described in the first round.
Importantly, the sodium hydroxide liquor recovered after filtering
and pressing the alkalized cellulose may be reused in the
neutralization step in the next processing operation. In the second
round of processing utilizing sodium hydroxide recovered from the
first round the total sodium hydroxide consumed was 13.3 g, the
lignin content of the treated cellulose was 1.63%.
[0161] Table 2 summarizes these sample data.
TABLE-US-00002 TABLE 2 Sodium hydroxide consumption for treating
cellulose Cellulose Sodium hydroxide consumption Acid Lignin Lignin
Sodium Sodium content content content hydroxide hydroxide before
before after consumption consumption Reduced treatment treatment
treatment of Plan A of Plan B ratio (%) (%) (%) (g) (g) (%) Sample
1 1.56 4.1 1.85 9.16 4.58 50.0% Sample 2 2.68 3.6 1.56 12.4 7.87
36.5% Sample 3 4.52 3.8 1.63 17.9 13.3 25.7%
Example 3
Lignin Production
[0162] Extraction liquor was obtained from the organic acid
pretreatment process, wherein the composition of the organic acids
in the pretreatment comprises formic acid 26%, acetic acid content
59%, and water 15%. The pretreatment temperature was 103.degree. C.
and the pretreatment extraction duration was 240 min. After
separation, the extraction liquor was separated from the solid
fraction, the extraction liquor was concentrated by evaporation,
and the concentrated extraction liquor obtained. The dry matter
content of the concentrated extraction liquor was 60.1%, and the
lignin content was 29.5% (the other components of the concentrated
extraction liquor are listed in Table 3).
[0163] 1.40 kg of concentrated extraction liquor was combined with
an equal weight of the fresh water (1.40 kg) and an emulsifier
(SHW300R lab emulsifier, Shanghai Shenghaiwei Electric Instruments
Co., Ltd) operated at 7500 rpm for about 30 min was used to produce
a lignin suspension. The lignin suspension was introduced into a
centrifuge, centrifuged for 5 mins, and the first centrifugate
(2.05 kg of liquid) and a solid lignin layer obtained. The first
centrifugate is removed from the centrifuge.
[0164] 1.94 kg of wash water was fed into a spray device to wash
the lignin layer within the centrifuge. The washing water in the
procedure includes water and mixtures of formic acid, acetic acid
and water. When feeding the washing water to the centrifuge, an
initial feed of 0.54 kg of high organic acids content washing water
comprising an organic acid content of 5.92% was used, the second
wash comprised 1.00 kg of low organic acids content washing water
wherein the organic acid content was 0.8%, and a finally wash
comprising 0.40 kg of fresh water was found to wash the lignin
layer sufficiently to obtain pure lignin.
[0165] Following the initial centrifugation and discharge of the
initial centrifugate, the centrifuge continued to operate for 5
min, during this time the first wash with high organic acids water
was performed and the second centrifugate (0.54 kg) obtained. The
centrifuge was operated for another 5 mins during which time the
second wash with low organic acids water was performed and the
third centrifugate 1.40 kg was obtained. After a subsequent third
wash with fresh water a lignin layer comprising 0.75 kg was
obtained. The first centrifugate and the second centrifugate were
recovered and may be incorporated in subsequent hemicellulosic
juice production unit operations. The dry lignin was discharged
from the centrifuge, and the purity of the lignin determined to be
98.1% (the components of the lignin at each stage of operation are
shown in Table 3).
TABLE-US-00003 TABLE 3 Components of concentrated extraction
liquor, washing waters, and lignin (I) Concentrated Washing water
Purity of extraction liquor H-water L-water H.sub.2O Lignin dry
lignin Lignin 29.54% 55.00% 98.1% H.sub.2O 5.11% 94.09% 99.20%
100.00% 43.96% Cellulose 3.00% 0.03% Xylan 8.70% 0.10% Mineral
6.07% 0.07% Others 12.75% 0.14% Acetic acid 23.75% 5.87% 0.80%
0.57% Formic acid 11.08% 0.05% 0.13% Total Impurity 65.35% 5.92%
0.80% 1.04% Note: impurities include cellulose, xylan, trace
mineral, acetic acid and formic acid.
[0166] The third centrifugate (1.40 kg) from above was recycled for
use as diluent of the concentrated extraction liquor to produce a
lignin suspension using the SHW300R lab emulsifier as described
above. The obtained lignin suspension was introduced into the
centrifuger and the centrifuger was operated as described above to
yield a lignin layer of about 0.75 kg.
[0167] In this operation the first wash comprised 0.54 kg of high
organic acids content wash water in which the organic acid content
was about 10%. The second wash comprised 1.00 kg the low organic
acids content wash water in which the organic acid content was
about 2%, and a final wash comprising 0.40 kg of fresh water. All
centrifuge operations and conditions were carried out as described
above. As before, the first and second centrifugates may be
recycled for use in subsequent hemicellulosic juice production unit
operations. At the end of the operation the lignin is discharged
from the centrifuge. In this instance the purity of the lignin was
97.2% (the components of the lignin at each stage of operation are
shown in Table 4).
TABLE-US-00004 TABLE 4 Components of concentrated extraction
liquor, washing waters, and lignin (II) Concentrated Purity
extraction Washing water of dry liquor H-water L-water H.sub.2O
Lignin lignin Lignin 29.54% 55.00% 97.2% H.sub.2O 5.11% 90.00%
98.00% 100.00% 43.40% Cellulose 3.00% 0.04% Xylan 8.70% 0.12%
Mineral 6.07% 0.08% Others 12.75% 0.17% Acetic acid 23.75% 9.92%
2.00% 1.03% Formic acid 11.08% 0.08% 0.15% Total Impurity 65% 10%
2% 0% 2% Note: impurities include cellulose, xylan, trace mineral,
acetic acid and formic acid. H-water indicates high organic acids
content wash water and L-water indicates low organic acids content
wash water.
[0168] Once again, the third centrifugate (1.40 kg) from the
operation described above was recycled to dilute the concentrated
extraction liquor to produce a lignin suspension by treatment with
the SHW300R lab emulsifier. The obtained lignin suspension was
introduced into the centrifuger and the centrifuger was operated as
described above to yield a lignin layer.
[0169] In this operation the first wash comprised 0.54 kg of high
organic acids content wash water in which the organic acid content
was 5.92. The second wash comprised 1.00 kg of low organic acids
content washing water in which the organic acid content was 0.8%,
and a final wash comprising 0.79 kg of fresh water. All centrifuge
operations and conditions were carried out as described above. As
before, the first and second centrifugates may be recycled for use
in subsequent hemicellulosic juice production unit operations. At
the end of the operation the lignin is discharged from the
centrifuge. In this instance the purity of the lignin was 98.8%
(the components of the lignin at each stage of operation are shown
in Table 5).
TABLE-US-00005 TABLE 5 Components of concentrated extraction
liquor, washing waters, and lignin (III). Concentrated extraction
Washing water Lignin Purity liquor H-water L-water H.sub.2O lignin
of dry Lignin 29.54% 55.00% 98.8% H.sub.2O 5.11% 94.09% 99.20%
100.00% 44.34% Cellulose 3.00% 0.02% Xylan 8.70% 0.06% Mineral
6.07% 0.04% Others 12.75% 0.09% Acetic acid 23.75% 5.87% 0.80%
0.36% Formic acid 11.08% 0.05% 0.08% Total Impurity 65.35% 5.92%
0.80% 0.66% Note: impurities include cellulose, xylan, trace
mineral, acetic acid and formic acid. H-water indicates high
organic acids content wash water and L-water indicates low organic
acids content wash water.
Example 4
Hemiceullulosic Juice Processing
[0170] A concentrated hemicellulosic mixture was obtained from an
initial hemicellulosic mixture comprising dissolved hemicellulose,
organic acids water, and other soluble constituents (16.4% dry
matter content, 6.0% formic acid, 14.4% acetic acid, and 63.2%
water) by use of an evaporator (100 mm diameter, 2 m height), using
indirect steam to heat the evaporator to evaporate the organic
acids and water from the hemicellulosic mixture.
[0171] The flowrate of the hemicellulosic mixture into the
evaporator was 10.0 kg/h, with an indirect steam flowrate of 6.2
kg/h, and an evaporation temperature of 90.degree. C., which
produced a flowrate of the concentrated hemicellulosic mixture of
2.96 kg/h. The dry matter content of the concentrated
hemicellulosic mixture produced under these conditions was 55.6%.
The acids content of the concentrated hemicellulosic mixture was
16.5%.
[0172] Feeding the resulting concentrated hemicellulosic mixture
into the top of a stripping column (100 mm diameter, 2.5 m height),
and feeding the direct steam into the bottom of the stripping
column, served to partially strip the organic acids present in the
concentrated hemicellulosic into the direct steam. This produces
the stripped hemicellulosic mixture. Adjusting the stripping
specifications to a direct steam flowrate of 1.51 kg/h and a direct
steam temperature of 105.degree. C. produced a flowrate of the
stripped hemicellulosic mixture of 2.46 kg/h. The dry matter
content of the stripped hemicellulosic mixture was 60.4%. The acids
content of the stripped hemicellulosic mixture was 1.64%.
[0173] Modeling the evaporation and stripping process with Aspen
Plus software (Aspen Technology, Inc., Massachusetts, USA) allowed
a number of different operational parameters to be explored based
on regression of the vapor-liquid equilibrium with experimental
data described above.
[0174] Using the model parameters described above, conditions and
performance for 2, 3 and 4 effects evaporation and stripping
systems were simulated for concentration of hemicellulosic mixture
comprising dissolved hemicellulose, organic acids, and water and
other constituents.
[0175] The flowsheets for the 2, 3, and 4 effects evaporation and
stripping system are constructed for use by the Aspen Plus
software, are shown in FIGS. 6-8, respectively. In these models the
hemicellulosic mixture (21) comprising dissolved hemicellulose,
organic acids, water and other constituents is evaporated by
evaporator II and evaporator I and the concentrated hemicellulosic
juice (22) is obtained. The concentrated hemicellulosic juice (22)
is fed to the top of the stripping column (102), fresh steam (26)
is fed to the bottom of the stripping column (102) and the stripped
hemicellulosic juice (24) is obtained. The vapor discharged from
the top of the stripping columns and the additional fresh steam
(27) is used as a heat resource for evaporator I and the vapor
discharged from the top of the stripping column and the additional
fresh steam (27) that is condensed within evaporator I is recovered
as condensed acid II (25). The vapor from evaporator I is used as a
heat source for evaporator II, while the vapor from evaporator I
that condenses in evaporator II serves as condensed acid I (23).
The same scenario involving use of vapor initially recovered from
the stripping column into evaporator I and vapor recovered from
evaporator I serving as a heat source for evaporator II extends to
systems that include additional multi-effect evaporator units as
illustrated in FIG. 7 for a 3-effect evaporator system and FIG. 8
for a 4-effect evaporator system, there is no need of fresh steam
in FIG. 7 for a 3-effect evaporator system, the more vapor (28)
from the stripping column than the vapor needed for the 4-effect
evaporator system is discharged from the top of the stripping
column is used to the other system.
[0176] The tables below present many of the observed and predicted
parameters of each of the multi-effect evaporator systems described
herein.
TABLE-US-00006 TABLE 6 Observed inputs to the evaporation system
models Dry matter Formic acid Acetic acid Water Flowrate content
content content content (t/h) (%) (%) (%) (%) The 12.0 16.4% 6.0%
14.4% 63.2% hemicellulosic mixture
TABLE-US-00007 TABLE 7 Observed specification of the stripped
hemicellulose juice Dry matter Total acids Evaporation Flowrate
content content Water content effects (t/h) (%) (%) (%) 2 3.27
60.2% 0.53% 39.27% 3 3.25 60.5% 1.65% 37.85% 4 3.27 60.1% 0.93%
38.97%
TABLE-US-00008 TABLE 8 Predicted steam consumption of evaporation
and stripping systems 2 effects 3 effects 4 effects Steam
consumption of stripping (t/h) 3.85 2.75 3.23 Steam consumption of
evaporation (t/h) 3.85 2.63 2.01 Surplus steam (t/h) 0 0.12
1.22
TABLE-US-00009 TABLE 9 Predicted heat exchange surface area of
evaporation systems 2 effects 3 effects 4 effects Total heat
exchange surface (m.sup.2) 887 1377 2269
Example 5
[0177] Recovering Organic Acids from High Water Content Organic
Acids Solutions
[0178] A high water content organic acids solution (27.6% formic
acid, 51.5% acetic acid, and 20.9% water) was fed into a
distillation column (90 mm diameter, 3 m height, packing column)
operating with a heat duty of 12.6 MJ/h, a reflux ratio of 13.0, 1
atmosphere pressure, at a flow rate of 4.0 kg/h. Under these
conditions the condensate of the vapor released from the top of the
column is produced at a flow rate of 0.41 kg/h which comprises
0.27% formic acid, 4.07% acetic acid, and 95.66% water. The
distilled organic acids solution, which is discharged from the
column bottom, is obtained at a flow rate of 3.59 kg/h and
comprises 30.7% formic acid, 56.9% acetic acid, and 12.4%
water.
[0179] Modeling this process with the Aspen Plus software using the
parameters described above allows simulation of distillation
systems comprising 2, 3, 4, and 5 columns for separating water from
high water content organic acids solutions. The flow sheets
produced by the modelling software are shown in FIGS. 10-13 for
2-column, 3-column, 4-column, and 5-column distillation systems,
respectively.
[0180] The organic acids composition of the various input streams
of high water content organic acids solutions originating from
organic acids pretreatment processes are listed in Table 10.
TABLE-US-00010 TABLE 10 Organic acid composition of inputs to
multi-column distillation systems Flowrate Formic acid Acetic acid
Water content Stream (kg/h) content (%) content (%) (%) 1 471.3
27.6% 49.1% 23.3% 2 270.7 5.8% 15.2% 79.0% 3 80.6 7.6% 17.4% 75.0%
4 12.8 9.9% 18.9% 71.2% Note: The stream designation matches those
depicted in FIG. 10 and described below.
[0181] The basic distillation process for a 2 column distillation
system is illustrated in FIG. 10. Three of the four input streams
are fed into are fed into the first distillation column (201).
These streams are derived from the hemicellulosic juice evaporation
step (2), the hemicellulosic juice stripping step (3), and the high
water organic acids solution from the desolventizer step of
cellulosic pulp processing (4). The condensate of vapor (7)
discharged from the top of the first column (201) may be recovered
for other unit operations. The concentrated mixture (301) is
discharged from the bottom of the first column (201) and fed into
column 2 (202). The remaining input stream (1) derived from the
extracting liquor evaporation step of lignin production is also fed
into column 2 (202). The condensate of vapor (5) discharged from
the top of the second column (202) may be recovered for other unit
operations. The distilled organic acids solution (6) is discharged
from the bottom of the second column (202). The organic acid
content of the various output streams of a two-column distillation
system are presented in Table 11.
TABLE-US-00011 TABLE 11 Organic acid composition of outputs of a
2-column distillation system Flowrate Formic acid Acetic acid Water
content Stream (kg/h) content (%) content (%) (%) 5 129.8 0.0% 0.8%
99.2% 6 477.8 32.0% 60.0% 8.0% 7 227.8 0.0% 0.8% 99.2% Note: The
stream designation matches those depicted in FIG. 10 and described
above.
[0182] A similar process representing the process flow within a 3
column distillation system is depicted in FIG. 11. In this case the
operation is similar in terms of input and output streams of the
two column system described above. However, in this case the vapor
condensates of the first two columns are pooled to form a single
output stream (7 of FIG. 11) and the distilled organic acids
solution discharged from column 2 (302) is fed into a third column
(203) where the vapor condensate (5) is recovered and the further
distilled organic acids solution (6) is discharged from the bottom
of the third column (203). The organic acid content of the various
output streams of a two-column distillation system are presented in
Table 12.
TABLE-US-00012 TABLE 12 Organic acid composition of outputs of a
3-column distillation system Flowrate Formic acid Acetic acid Water
content Stream (kg/h) content (%) content (%) (%) 5 78.4 0.0% 0.8%
99.2% 6 477.8 32.0% 60.0% 8.0% 7 279.3 0.0% 0.8% 99.2% Note: The
stream designation matches those depicted in FIG. 11 and described
above.
[0183] Similarly, the process representing the process flow within
a 4 column distillation system is depicted in FIG. 12. The organic
acid content of the various output streams of a two-column
distillation system are presented in Table 13.
TABLE-US-00013 TABLE 13 Organic acid composition of outputs of a
4-column distillation system Flowrate Formic acid Acetic acid Water
content Stream (kg/h) content (%) content (%) (%) 5 49.8 0.0% 0.8%
99.2% 6 477.8 32.0% 60.0% 8.0% 7 307.8 0.0% 0.8% 99.2% Note: The
stream designation matches those depicted in FIG. 12.
[0184] The process representing the process flow within a 5 column
distillation system is depicted in FIG. 13. The organic acid
content of the various output streams of a five-column distillation
system are presented in Table 14.
TABLE-US-00014 TABLE 14 Organic acid composition of outputs of a
5-column distillation system Flowrate Formic acid Acetic acid Water
content Stream (kg/h) content (%) content (%) (%) 5 37.5 0.0% 0.8%
99.2% 6 477.8 32.0% 60.0% 8.0% 7 320.2 0.0% 0.8% 99.2% Note: The
stream designation matches those depicted in FIG. 12.
[0185] According to the simulation flow sheets steam consumption
can be significantly reduced by the number of distillation columns
present in the system. The data supporting this observation is
presented in Table 15.
TABLE-US-00015 TABLE 15 Steam consumption profiles of 2-, 3-, and
4-column distillation systems Heat duty Reduced ratio Type (MJ/h)
(%) 2 column distillation 1188 27.6% 3 column distillation 860.4 3
column distillation 860.4 20.0% 4 column distillation 687.6
[0186] The indicated reduction in the thermal requirements of a two
column system relative to three column system is 27.6%, while the
reduction in the thermal requirements of a four column system are
an additional 20% lower than those of three column system, with an
overall reduction to 42% of the thermal requirements of a two
column system required for a four column system.
[0187] Interestingly, additional columns provide minimal energy
improvements. See Table 16.
TABLE-US-00016 TABLE 16 Steam consumption profiles of 4- and
5-column distillation systems Heat duty Reduced ratio Type (MJ/h)
(%) 4 column distillation 687.6 4.97% 5 column distillation
653.4
Example 6
Organic Fertilizer
[0188] In an initial experiment, corn straw was used as the
lignocellulosic plant material source for organic acids treatment
using formic acid and acetic acid to extract the hemicellulose and
the lignin. The mixture of hemicellulose and lignin was separated
to obtain a cellulosic pulp fraction and an extraction liquor. The
cellulosic pulp was treated to partially eliminate lignin and
washed with water to obtain cellulose. The extraction liquor was
concentrated to separate the lignin, after the separation of the
lignin, the residue was concentrated and stripped to obtain the
hemicellulosic juice. The cellulose and hemicellulosic juice
mixture was hydrolyzed and fermented of by adding cellulose enzymes
and yeast, respectively, to produce ethanol. The ethanol was
separated from the fermentate by distillation, the residual matter
of the distillation constitutes the stillage.
[0189] Stillage (2113 g comprising 9.23% dry matter content) was
fed into a decanter to produce a solid fraction 61.4 g (comprising
38.0% dry matter content) and a thin stillage 2051.6 g (comprising
8.37% dry matter content) after decanting. The thin stillage was
evaporated (in an evaporator operated at 110.degree. C.) to obtain
the concentrated stillage 451.6 g (comprising 38.0% dry matter
content). The solid fraction and concentrated stillage were
combined to obtain a mixture (513.0 g). The mixture was dried in a
dryer operated at a temperature of 120.degree. C. to obtain 335.1 g
of a final organic fertilizer; with a dry matter content of organic
fertilizer of 58.2% and a pH of 6.1. The organic fertilizer has a
dry matter content of 58.2%, an organic matter content of 47.8%,
and a total nutrient content of 5.86% (calculated based on a
formula wherein Nutrient=Nitrogen+Phosphorus pentoxide+Potassium
oxide), calculated from the total dry matter.
[0190] In a second trial to produce an organic fertilizer from
stillage using corn straw as an initial input to the organic acids
treatment process, stillage (2113 g comprising 9.23% dry matter)
was fed into the decanter. After decanting a solid fraction 67.1 g
(35.5% dry matter content) and a thin stillage 2046 g (8.37% dry
matter content) were obtained. The thin stillage was evaporated (in
an evaporator operated at 105.degree. C.) to produce 456.7 g of a
concentrated stillage with 37.5% dry matter content. The solid
fraction and the concentrated stillage were combined to produce
523.8 g of a mixture. The mixture was dried in a dryer operated at
130.degree. C. to produce 297.7 g of the final organic fertilizer
with a dry matter content of 65.5% at pH 6.0. The organic
fertilizer contains 47.3% organic matter with a total nutrient
content of 5.81%, calculated from the total dry matter.
[0191] In a third experiment to produce organic fertilizer from
stillage, wheat straw was used as an initial input to the organic
acids treatment process, stillage (1940 g comprising 9.38% dry
matter) was fed into the decanter. After decanting a solid fraction
59.5 g (37.0% dry matter content) and a thin stillage 1880.5 g
(8.51% dry matter content) were obtained. The thin stillage was
evaporated (in an evaporator operated at 115.degree. C.) to produce
438.3 g of a concentrated stillage with 36.5% dry matter content.
The solid fraction and the concentrated stillage were combined to
produce 497.8 g of a mixture. The mixture was dried in a dryer
operated at 140.degree. C. to produce 244.3 g of the final organic
fertilizer with a dry matter content of 74.5% at pH 6.2. The
organic fertilizer contains 48.5% organic matter with a total
nutrient content of 6.12%, calculated from the total dry
matter.
* * * * *