U.S. patent application number 15/420153 was filed with the patent office on 2017-07-20 for processes for producing cellulose pulp and pulp-derived products from lignocellulosic biomass.
The applicant listed for this patent is API Intellectual Property Holdings, LLC. Invention is credited to Vesa PYLKKANEN, Theodora RETSINA, Steven R. RUTHERFORD.
Application Number | 20170204563 15/420153 |
Document ID | / |
Family ID | 50431817 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170204563 |
Kind Code |
A1 |
RETSINA; Theodora ; et
al. |
July 20, 2017 |
PROCESSES FOR PRODUCING CELLULOSE PULP AND PULP-DERIVED PRODUCTS
FROM LIGNOCELLULOSIC BIOMASS
Abstract
The GreenBox+ technology is suitable to extract hemicellulose
sugars prior to pulping of biomass into pulp products. The revenue
obtainable from the sugar stream can significantly improve the
economics of a pulp and paper mill. An initial extraction and
recovery of sugars is followed by production of a pulp product with
similar or better properties. Other co-products such as acetates
and furfural are also possible. Some variations provide a process
for co-producing pulp and hemicellulosic sugars from biomass,
comprising: digesting the biomass in the presence of steam and/or
hot water to extract hemicellulose into a liquid phase; washing the
extracted solids, thereby generating a liquid wash filtrate and
washed solids; separating the liquid wash filtrate from the washed
solids; refining the washed solids at a refining pH of about 4 or
higher, thereby generating pulp; and hydrolyzing the hemicellulose
to generate hemicellulosic fermentable sugars.
Inventors: |
RETSINA; Theodora; (Atlanta,
GA) ; PYLKKANEN; Vesa; (Atlanta, GA) ;
RUTHERFORD; Steven R.; (Peachtree City, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
API Intellectual Property Holdings, LLC |
Minnetrista |
MN |
US |
|
|
Family ID: |
50431817 |
Appl. No.: |
15/420153 |
Filed: |
January 31, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15098383 |
Apr 14, 2016 |
9556557 |
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15420153 |
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14044784 |
Oct 2, 2013 |
9347176 |
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15098383 |
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61842356 |
Jul 2, 2013 |
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61781635 |
Mar 14, 2013 |
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61709960 |
Oct 4, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21C 3/02 20130101; D21C
3/222 20130101; D21C 3/26 20130101; D21B 1/021 20130101; Y02E 50/10
20130101; D21C 1/02 20130101; D21B 1/02 20130101; D21C 3/20
20130101; D21C 3/08 20130101; C08B 37/0057 20130101; C12P 7/10
20130101; D21H 11/00 20130101; Y02E 50/16 20130101; C08B 1/00
20130101; D21C 3/22 20130101; C12P 7/56 20130101; C12P 19/14
20130101; D21C 11/0007 20130101; C12P 7/54 20130101; C12P 7/16
20130101; C13K 1/02 20130101; C08H 8/00 20130101; D21C 9/02
20130101 |
International
Class: |
D21C 3/22 20060101
D21C003/22; D21C 11/00 20060101 D21C011/00; C08B 37/00 20060101
C08B037/00; C13K 1/02 20060101 C13K001/02; C12P 7/56 20060101
C12P007/56; C12P 19/14 20060101 C12P019/14; C12P 7/10 20060101
C12P007/10; C12P 7/16 20060101 C12P007/16; C12P 7/54 20060101
C12P007/54; D21C 9/02 20060101 D21C009/02; D21H 11/00 20060101
D21H011/00 |
Claims
1. A process for producing pulp from biomass, said process
comprising: (a) providing lignocellulosic biomass comprising
cellulose, hemicellulose, and lignin; (b) digesting said biomass in
the presence of steam and/or hot water to extract at least a
portion of said hemicellulose into a liquid phase, thereby
generating extracted solids, wherein step (b) does not include a
chemical pulping method; (c) washing said extracted solids with
water at a washing pH of about 7 or less, thereby generating a
liquid wash filtrate and washed solids; (d) refining said washed
solids at a refining pH of 4 to 6.5, thereby generating pulp; and
(e) recovering or further processing said pulp.
2. The process of claim 1, wherein said lignocellulosic biomass is
selected from the group consisting of hardwoods, softwoods, forest
residues, industrial wastes consisting essentially of
lignocellulosic material, consumer wastes consisting essentially of
lignocellulosic material, and combinations thereof.
3. The process of claim 1, wherein step (b) is conducted at a
digestor temperature selected from about 140.degree. C. to about
220.degree. C.
4. The process of claim 1, wherein step (b) is conducted at a
digestor residence time selected from about 1 minute to about 60
minutes.
5. The process of claim 1, wherein step (b) is conducted at a
digestor pH from about 2 to about 6.
6. The process of claim 1, wherein the pulp yield on biomass is
from about 75% to about 95% by weight.
7. The process of claim 1, wherein said washing in step (c)
utilizes fresh water.
8. The process of claim 1, wherein said washing in step (c)
utilizes alkali-free recycled water.
9. The process of claim 1, wherein steps (b) and (c) are carried
out in a single unit.
10. The process of claim 1, wherein said liquid phase and said
liquid wash filtrate are separately processed.
11. The process of claim 1, wherein said pulp is characterized by a
concora of about 25 lbf or higher.
12. The process of claim 1, wherein said pulp is characterized by a
ring crush strength of about 25 (lbf/6 in) or higher.
13. The process of claim 1, wherein said pulp is characterized by a
breaking length of about 2.0 km or higher.
14. The process of claim 1, wherein during step (e), at least a
portion of said pulp is hydrolyzed to generate glucose.
15. The process of claim 1, wherein at least a portion of said pulp
is converted to corrugated medium or paper.
Description
PRIORITY DATA
[0001] This patent application is a continuation of U.S. Pat. No.
9,556,557, issued Jan. 31, 2017, which is a continuation of U.S.
Pat. No. 9,347,176, issued May 24, 2016, which claims priority to
U.S. Provisional Patent App. No. 61/709,960, filed Oct. 4, 2012;
U.S. Provisional Patent App. No. 61/781,635, filed Mar. 14, 2013;
and U.S. Provisional Patent App. No. 61/842,356, filed Jul. 2,
2013. Each of these patent applications is hereby incorporated by
reference herein.
FIELD
[0002] The present invention generally relates to improved
processes for producing cellulose pulp while recovering fermentable
sugars from lignocellulosic biomass.
BACKGROUND
[0003] In recent years, the GreenPower+ technology has been
developed by American Process, Inc. (API). GREEN POWER+ is a
registered trademark of API, Registration No. 4062241. GreenPower+
technology is a patented technology for the production of low-cost
sugars from the hemicelluloses of any type of biomass, including
hardwoods, softwoods, and agricultural residues. The GreenPower+
process produces low-cost C.sub.5 and C.sub.6 sugars from the
hemicelluloses of biomass feedstocks. These sugars are co-produced
along with biomass power, pellets, or pulp. Essentially, sugars are
extracted from the solids which are then utilized for existing
applications, in synergy with pulp mills, pellet mills,
biomass-based renewable power plants, and many other existing
sites. Value is added while minimizing capital costs for commercial
implementation, which may be retrofits, capacity additions, or
greenfield sites. When applied to a pulping operation, the
GreenPower+ technology is also known as GreenBox+.TM. technology.
GREENBOX+ is a trademark of API, Serial No. 86000173.
[0004] It would be desirable to retrofit existing pulp mills with a
GreenBox+ process. The revenue obtainable from the sugar stream can
significantly improve the economics of a pulp and paper mill.
Ideally, an initial extraction and recovery of sugars is followed
by a pulping process that produces a pulp product with equivalent
or similar properties, or potentially even better properties for
certain downstream products. Besides sugars, other co-products
become possible, in particular acetates since hemicellulose has a
high concentration of acetyl groups that are released as acetic
acid during sugar extraction.
[0005] In addition to the potential for higher revenue, there is
also potential for reduced costs. For example, if the GreenBox+
process can replace a chemical pulping method, the chemical
recovery cycle may be eliminated. There may also be environmental
compliance benefits and reduced costs for compliance.
[0006] To date, there has been limited commercial success in
extracting hemicellulose prior to pulping. Further improvements are
needed to establish an economic process.
SUMMARY
[0007] Some variations provide a process for co-producing pulp and
hemicellulosic sugars from biomass, the process comprising:
[0008] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0009] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0010] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0011] (d) washing the extracted solids with water at a washing pH
of about 7 or less, thereby generating a liquid wash filtrate and
washed solids;
[0012] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0013] (f) refining the washed solids at a refining pH of about 4
or higher, thereby generating pulp; and
[0014] (g) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0015] In some embodiments, step (b) is conducted at a digestor
temperature selected from about 140.degree. C. to about 220.degree.
C., such as from about 170.degree. C. to about 190.degree. C. In
some embodiments, step (b) is conducted at a digestor residence
time selected from about 1 minute to about 60 minutes, such as from
about 2 minutes to about 10 minutes.
[0016] In some embodiments, step (b) is conducted at a digestor pH
from about 2 to about 6, such as from about 3 to about 5. In
various embodiments, the refining pH is selected from about 5 to
about 9, such as about 6 to about 8, or about 6.5 to about 7.5. The
refining pH will generally be higher than the digestor pH,
following pH adjustment with a suitable base. It is possible,
however, for the digestor pH to be higher than the refining pH, or
for the digestor pH and refining pH to be similar.
[0017] In certain embodiments, step (b) comprises introducing a
sulfur-containing compound selected from the group consisting of
sulfur dioxide, sulfurous acid, sulfuric acid, lignosulfonic acid,
and combinations or derivatives thereof.
[0018] The pulp yield on biomass may vary from about 75% to about
95% (or higher) by weight. In some embodiments, the pulp yield on
biomass is at least 85% or at least 90% by weight. In certain
embodiments that achieve only mild extraction of hemicelluloses,
the pulp yield on biomass is higher than 95%, such as about 96%,
97%, 98%, or 99% by weight.
[0019] In some embodiments, the washing in step (d) utilizes fresh
water. In these or other embodiments, the washing in step (d) may
utilize recycled water, which is preferably alkali-free recycled
water to reduce or avoid alkaline degradation of sugars.
[0020] In some embodiments, steps (b) and (d) are carried out in a
single unit. For example, a continuous countercurrent unit may be
configured for both digestion and washing of solids.
[0021] When step (c) is carried out, the liquid phase and the
liquid wash filtrate may be separately processed. Alternatively,
the liquid phase and the liquid wash filtrate may be combined for
the hydrolyzing in step (g). When step (c) is not carried out, the
liquid phase (from digestion) forms part of the liquid wash
filtrate, which also includes wash water.
[0022] In some embodiments, the hydrolysis catalyst comprises one
or more compounds selected from the group consisting of sulfur
dioxide, sulfurous acid, sulfuric acid, lignosulfonic acid, and
combinations or derivatives thereof. In other embodiments, the
hydrolysis catalyst comprises hemicellulase enzymes.
[0023] Some variations of the invention provide a process for
co-producing pulp and hemicellulosic sugars from biomass, the
process comprising:
[0024] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0025] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0026] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0027] (d) washing the extracted solids with water at a washing pH
selected from about 7 or less, thereby generating a liquid wash
filtrate and washed solids;
[0028] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0029] (f) further digesting the extracted solids and/or the washed
solids using a chemical pulping method, thereby generating digested
solids;
[0030] (g) refining the digested solids at a refining pH selected
from about 4 or higher, thereby generating pulp; and
[0031] (h) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0032] In some embodiments, the chemical pulping method is selected
from the group consisting of Kraft pulping, sulfite pulping, soda
pulping, and organosolv pulping. In certain embodiments, soda
pulping is employed to further digest the extracted solids, the
washed solids, or both of these.
[0033] Some variations of the invention provide a process for
co-producing pulp and hemicellulosic sugars from biomass, the
process comprising:
[0034] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0035] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0036] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0037] (d) washing the extracted solids with water at a washing pH
selected from about 7 or less, thereby generating a liquid wash
filtrate and washed solids;
[0038] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0039] (f) refining the washed solids at a refining pH selected
from about 4 or higher, thereby generating pulp;
[0040] (g) further digesting the pulp using a chemical pulping
method; and
[0041] (h) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0042] In some embodiments, the chemical pulping method is selected
from the group consisting of Kraft pulping, sulfite pulping, soda
pulping, and organosolv pulping. In certain embodiments, soda
pulping is employed to further digest the pulp.
[0043] In some variations, a process for producing pulp from
biomass comprises:
[0044] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0045] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0046] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0047] (d) washing the extracted solids with water at a washing pH
of about 7 or less, thereby generating a liquid wash filtrate and
washed solids;
[0048] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0049] (f) refining the washed solids at a refining pH of about 4
or higher, thereby generating pulp; and
[0050] (g) recovering or further processing the pulp.
[0051] The pulp from any of the disclosed processes may be combined
with a second source of cellulose fiber prior to downstream
processing of the pulp. The second source of cellulose fiber may be
selected from, but is not limited to, OCC pulp, Kraft pulp, sulfite
pulp, soda pulp, NSSC pulp, and organosolv pulp.
[0052] The pulp from any of the disclosed processes may be
characterized by a concora of about 25 lbf or higher, such as about
32 lbf or higher. The pulp from any of the disclosed processes may
be characterized by a ring crush strength of about 25 (lbf/6 in) or
higher, such as about 40 (lbf/6 in) or higher. The pulp from any of
the disclosed processes may be characterized by a breaking length
of about 2.0 km or higher, such as about 3.6 km or higher.
[0053] Optionally, at least a portion of the pulp may be hydrolyzed
to generate glucose.
[0054] In some embodiments, the process further comprises
recovering an acetate co-product (using e.g. reverse osmosis), such
as potassium acetate or sodium acetate.
[0055] Some variations provide a process for producing
hemicellulosic sugars from biomass, the process comprising:
[0056] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0057] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0058] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0059] (d) washing the extracted solids with water at a washing pH
of about 7 or less, thereby generating a liquid wash filtrate and
washed solids; and
[0060] (e) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0061] Preferably, the process (in any embodiment) includes process
integration of mass and/or energy involving at least two steps of
said process. In some embodiments, the process includes process
integration of mass and/or energy involving at least three steps of
said process. Several examples of process integration are disclosed
in the detailed description below.
[0062] For example, process integration may include recycling
evaporator condensates may be recycled for use in step (b);
recycling evaporator condensates may be recycled for use in one or
more washing steps; integration with downstream operations
involving the pulp, during or after step (g); concentrating
fermentable sugars, recovering a condensate stream therefrom, and
introducing the condensate stream to another location with a water
requirement; sterilizing a fermentor or fermentor feed stream with
a vapor take-off from one or more evaporators; and/or concentrating
a fermentation product in a non-externally-heated effect of a
multiple-effect evaporation unit.
[0063] The invention provides pulp intermediates or products
produced by processes as described. The invention also provides
consumer products (e.g., paper or corrugated medium) produced from
the pulp intermediate or product. Also provided are hemicellulosic
sugar intermediates or products produced by the disclosed
processes. Fermentation products may be produced from the
hemicellulosic sugar intermediates or products.
BRIEF DESCRIPTION OF THE FIGURES
[0064] FIG. 1 is a high-level block-flow diagram according to some
retrofit embodiments of the invention.
[0065] FIG. 2 is a simplified process-flow diagram for the
production of pulp, hemicelluloses, and acetates, in some
embodiments.
[0066] FIG. 3 is a simplified process-flow diagram for the
production of pulp, sugars, and acetates, in some embodiments.
[0067] FIG. 4 is a simplified process-flow diagram for the
production of pulp, acetates, and furfural, in some
embodiments.
[0068] FIG. 5A summarizes pulp physical properties measured from
laboratory-scale experiments for a range of hot-water-extraction
pulping conditions.
[0069] FIG. 5B summarizes pulp physical properties measured from
laboratory-scale experiments for a range of hot-water-extraction
pulping conditions.
[0070] FIG. 6 summarizes data collected with respect to the
hemicellulose stream extracted during experimental
hot-water-extraction pulping.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0071] This description will enable one skilled in the art to make
and use the invention, and it describes several embodiments,
adaptations, variations, alternatives, and uses of the invention.
These and other embodiments, features, and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following detailed description
of the invention in conjunction with any accompanying drawings.
[0072] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly indicates otherwise. Unless defined otherwise,
all technical and scientific terms used herein have the same
meaning as is commonly understood by one of ordinary skill in the
art to which this invention belongs. All composition numbers and
ranges based on percentages are weight percentages, unless
indicated otherwise. All ranges of numbers or conditions are meant
to encompass any specific value contained within the range, rounded
to any suitable decimal point.
[0073] Unless otherwise indicated, all numbers expressing reaction
conditions, stoichiometries, concentrations of components, and so
forth used in the specification and claims are to be understood as
being modified in all instances by the term "about." Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the following specification and attached claims are
approximations that may vary depending at least upon a specific
analytical technique.
[0074] The term "comprising," which is synonymous with "including,"
"containing," or "characterized by" is inclusive or open-ended and
does not exclude additional, unrecited elements or method steps.
"Comprising" is a term of art used in claim language which means
that the named claim elements are essential, but other claim
elements may be added and still form a construct within the scope
of the claim.
[0075] As used herein, the phrase "consisting of" excludes any
element, step, or ingredient not specified in the claim. When the
phrase "consists of" (or variations thereof) appears in a clause of
the body of a claim, rather than immediately following the
preamble, it limits only the element set forth in that clause;
other elements are not excluded from the claim as a whole. As used
herein, the phrase "consisting essentially of" limits the scope of
a claim to the specified elements or method steps, plus those that
do not materially affect the basis and novel characteristic(s) of
the claimed subject matter.
[0076] With respect to the terms "comprising," "consisting of" and
"consisting essentially of," where one of these three terms is used
herein, the presently disclosed and claimed subject matter may
include the use of either of the other two terms. Thus in some
embodiments not otherwise explicitly recited, any instance of
"comprising" may be replaced by "consisting of" or, alternatively,
by "consisting essentially of."
[0077] Some variations of the present invention are premised on the
surprising discovery that steam or hot-water extraction of biomass
is an effective pulping step to produce a pulp product, such as a
chemical or semi-chemical pulp material, while also producing a
hemicellulose sugar stream. Through experimentation, the inventors
have determined suitable conditions for hot-water extraction as
well as suitable downstream conditions and overall process
configurations for co-producing pulp and sugars.
[0078] The biomass feedstock may be selected from hardwoods,
softwoods, forest residues, industrial wastes, consumer wastes, or
combinations thereof. Exemplary biomass feedstocks include maple,
birch, and aspen. Some embodiments utilize agricultural residues,
which include lignocellulosic biomass associated with food crops,
annual grasses, energy crops, or other annually renewable
feedstocks. Exemplary agricultural residues include, but are not
limited to, corn stover, corn fiber, wheat straw, sugarcane
bagasse, rice straw, oat straw, barley straw, miscanthus, energy
cane, or combinations thereof.
[0079] Some variations provide a process for co-producing pulp and
hemicellulosic sugars from biomass, the process comprising:
[0080] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0081] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0082] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0083] (d) washing the extracted solids with water at a washing pH
of about 7 or less, thereby generating a liquid wash filtrate and
washed solids;
[0084] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0085] (f) refining the washed solids at a refining pH of about 4
or higher, thereby generating pulp; and
[0086] (g) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0087] In some embodiments, step (b) is conducted at a digestor
temperature selected from about 140.degree. C. to about 220.degree.
C., such as from about 170.degree. C. to about 190.degree. C. In
some embodiments, step (b) is conducted at a digestor residence
time selected from about 1 minute to about 60 minutes, such as from
about 2 minutes to about 10 minutes.
[0088] In some embodiments, step (b) is conducted at a digestor pH
from about 2 to about 6, such as from about 3 to about 5. In
various embodiments, the refining pH is selected from about 5 to
about 9, such as about 6 to about 8, or about 6.5 to about 7.5. The
refining pH will generally be higher than the digestor pH,
following pH adjustment with a suitable base. It is possible,
however, for the digestor pH to be higher than the refining pH, or
for the digestor pH and refining pH to be similar.
[0089] In certain embodiments, step (b) comprises introducing a
sulfur-containing compound selected from the group consisting of
sulfur dioxide, sulfurous acid, sulfuric acid, lignosulfonic acid,
and combinations or derivatives thereof. In these embodiments, the
digestor pH may be less than 2, such as about 1.5, 1, 0.5, 0 or
less.
[0090] The pulp yield on biomass may vary from about 75% to about
95% (or higher) by weight. The yield is the fraction of starting
solids remaining after pulping and washing, on a dry basis. In some
embodiments, the pulp yield on biomass is at least 85% or at least
90% by weight. In certain embodiments that target mild extraction
of hemicelluloses, the pulp yield on biomass is higher than 95%,
such as about 96%, 97%, 98%, or 99% by weight. When the biomass
yield is high, relatively little hemicelluloses are extracted. It
can nevertheless be advantageous to extract a small quantity of
hemicelluloses under mild conditions.
[0091] In some embodiments, the washing in step (d) utilizes fresh
water. In these or other embodiments, the washing in step (d) may
utilize recycled water, which is preferably alkali-free recycled
water to reduce or avoid alkaline degradation of sugars.
"Alkali-free recycled water" means that no alkali metal, or a base,
salt, or derivative thereof (e.g., sodium hydroxide or potassium
chloride) is introduced into the recycled water prior to use for
washing. If desired, the pH of the wash water may be adjusted or
maintained in the range of about 4 to 9, such as about 4.5, 5, 5.5,
6, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 8, or
8.5. For example, a fresh water source at a pH of about 8 may be
adjusted with an acid to a pH of about 6 for washing. Or a recycled
water stream at a pH of about 4 may be adjusted to a pH of about 7
for washing.
[0092] In some embodiments, steps (b) and (d) are carried out in a
single unit. For example, a continuous countercurrent unit may be
configured for both digestion and washing of solids. Multiple units
may be employed in parallel, where each unit is configured for both
digestion and washing. Or, a first unit may be configured for only
digestion, with a downstream unit configured for both digestion and
washing. Or, a first unit may be configured for both digestion and
washing, followed by a downstream washing-only unit. Many
variations are possible.
[0093] When step (c) is carried out, the liquid phase and the
liquid wash filtrate may be separately processed. Alternatively,
the liquid phase and the liquid wash filtrate may be combined for
the hydrolyzing in step (g). When step (c) is not carried out, the
liquid phase (from digestion) forms part of the liquid wash
filtrate. That is, the digestor liquor is fed forward, without
solid-liquid separation, to washing. Additional wash water is
added, depending on the desired amount of washing and the washing
efficiency of the washing unit. The digestor liquor therefore
becomes combined (and diluted) with the added wash liquid.
[0094] Step (g) is desirable to increase the yield of fermentable
sugars, by hydrolyzing (with water) the soluble oligomers into
monomers. In some embodiments, the hydrolysis catalyst comprises
one or more compounds selected from the group consisting of sulfur
dioxide, sulfurous acid, sulfuric acid, lignosulfonic acid, and
combinations or derivatives thereof. In other embodiments, the
hydrolysis catalyst comprises hemicellulase enzymes or other
enzymes capable of catalyzing hydrolysis of hemicellulose. In
certain embodiments, step (g) is not performed and the
hemicellulose oligomers (with some monomers typically present)
recovered for sale or later processing.
[0095] Some variations of the invention provide a process for
co-producing pulp and hemicellulosic sugars from biomass, the
process comprising:
[0096] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0097] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0098] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0099] (d) washing the extracted solids with water at a washing pH
selected from about 7 or less, thereby generating a liquid wash
filtrate and washed solids;
[0100] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0101] (f) further digesting the extracted solids and/or the washed
solids using a chemical pulping method, thereby generating digested
solids;
[0102] (g) refining the digested solids at a refining pH selected
from about 4 or higher, thereby generating pulp; and
[0103] (h) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0104] Some variations of the invention provide a process for
co-producing pulp and hemicellulosic sugars from biomass, the
process comprising:
[0105] (a) providing lignocellulosic biomass comprising cellulose,
hemicellulose, and lignin;
[0106] (b) digesting the biomass in the presence of steam and/or
hot water to extract at least a portion of the hemicellulose into a
liquid phase, thereby generating extracted solids;
[0107] (c) optionally separating at least some of the liquid phase
from the extracted solids;
[0108] (d) washing the extracted solids with water at a washing pH
selected from about 7 or less, thereby generating a liquid wash
filtrate and washed solids;
[0109] (e) separating at least some of the liquid wash filtrate
from the washed solids;
[0110] (f) refining the washed solids at a refining pH selected
from about 4 or higher, thereby generating pulp;
[0111] (g) further digesting the pulp using a chemical pulping
method; and
[0112] (h) hydrolyzing the hemicellulose contained in the liquid
phase and/or in the liquid wash filtrate, in the presence of a
hydrolysis catalyst, to generate hemicellulosic sugars.
[0113] In some embodiments, the chemical pulping method is selected
from the group consisting of Kraft pulping, sulfite pulping, soda
(sodium hydroxide) pulping, sodium carbonate pulping, and
organosolv pulping. In certain embodiments, soda pulping is
employed to further digest the extracted solids, the washed solids,
or both of these.
[0114] The pulp from any of the disclosed processes may be combined
with a second source of cellulose fiber prior to downstream
processing of the pulp. The second source of cellulose fiber may be
selected from, but is not limited to, OCC pulp, Kraft pulp, sulfite
pulp, soda pulp, NSSC pulp, or organosolv pulp.
[0115] The pulp from any of the disclosed processes may be
characterized by a concora of about 25 lbf or higher, such as about
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 lbf or higher. The
pulp from any of the disclosed processes may be characterized by a
ring crush strength of about 25 (lbf/6 in) or higher, such as about
40 (lbf/6 in) or higher. The pulp from any of the disclosed
processes may be characterized by a breaking length of about 2.0 km
or higher, such as about 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8,
2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6 km or higher.
[0116] The invention provides pulp intermediates or products
produced by processes as described. Using well-known techniques,
consumer products (e.g., paper or corrugated medium) may be
produced from the pulp intermediate or product. See, for example,
Twede and Selke, "Cartons, crates and corrugated board: handbook of
paper and wood packaging technology," DEStech Publications, pages
41-56, 2005; and Foster, "Boxes, Corrugated" in The Wiley
Encyclopedia of Packaging Technology, 1997, eds. Brody A and Marsh
K, 2nd ed.
[0117] Optionally, at least a portion of the pulp may be hydrolyzed
to generate glucose. For example, pulp having inferior properties
(such as fiber length or strength) may be hydrolyzed to glucose
using cellulase enzymes or an acid catalyst (e.g., sulfuric acid).
In some embodiments, the entire pulp product is hydrolyzed to
glucose to maximize sugar production, either as a transient
operation or as a steady-state operation.
[0118] The hemicellulosic sugars may be recovered in purified form,
as a sugar slurry or dry sugar solids, for example. Any known
technique may be employed to recover a slurry of sugars or to dry
the solution to produce dry sugar solids. Thus the invention
provides hemicellulosic sugar intermediates or products produced by
the disclosed processes. In certain embodiments, the extracted
hemicellulose stream is combusted for energy, or discarded.
[0119] Fermentation products may be produced from the
hemicellulosic sugar intermediates or products. In some
embodiments, the hemicellulose sugars are fermented to ethanol,
1-butanol, isobutanol, acetic acid, lactic acid, succinic acid, or
any other fermentation product. A purified product may be produced
by distillation, which will also generate a distillation bottoms
stream containing residual solids. A bottoms evaporation stage may
be used, to produce residual solids. Residual solids (such as
distillation bottoms) may be recovered, or burned to produce energy
for the process.
[0120] In some embodiments, the process further comprises
recovering an acetate co-product, such as potassium acetate or
sodium acetate. The process may include evaporation of hydrolysate
to remove some or most of the volatile acids. The evaporation step
is preferably performed below the acetic acid dissociation pH of
4.8, such as about 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, or 4.5. In
certain embodiments, the process further comprises combining, at a
pH of about 4.8 to 10 or higher, a portion of the vaporized acetic
acid with an alkali oxide, alkali hydroxide, alkali carbonate,
and/or alkali bicarbonate, wherein the alkali is selected from the
group consisting of potassium, sodium, magnesium, calcium, and
combinations thereof, to convert the portion of the vaporized
acetic acid to an alkaline acetate. The alkaline acetate may be
recovered by reverse osmosis or other membrane separation or
filtration (see, for example, U.S. Pat. No. 8,211,680 which is
incorporated by reference). If desired, purified acetic acid may be
generated from the alkaline acetate. Acetic acid and acetate salts
have a number of known commercial uses.
[0121] Some embodiments also recover a furfural co-product. When
furfural is desired, the conditions of the initial extraction
and/or the hemicellulose hydrolysis may be more severe (compared to
sugars production) so that C.sub.5 sugars are converted to
furfural. Under conditions of heat and acid, xylose and other
five-carbon sugars undergo dehydration, losing three water
molecules to become furfural (C.sub.5H.sub.4O.sub.2). Hydrogenation
of furfural provides furfuryl alcohol, which is a useful chemical
intermediate and which may be further hydrogenated to
tetrahydrofurfuryl alcohol. Furfural is used to make other furan
chemicals, such as furoic acid, via oxidation, and furan via
decarbonylation.
[0122] In some embodiments, additional evaporation steps may be
employed. These additional evaporation steps may be conducted at
different conditions (e.g., temperature, pressure, and pH) relative
to the first evaporation step.
[0123] Some embodiments employ reaction conditions and operation
sequences described in U.S. Pat. No. 8,211,680, issued Jul. 3,
2012; and/or U.S. patent application Ser. Nos. 13/471,662;
13/026,273; 13/026,280; 13/500,917; 61/536,477; 61/612,451;
61/612,453; 61/624,880; 61/638,730; 61/641,435; 61/679,793;
61/696,360; 61/709,960. Each of these commonly owned patents and
patent applications is hereby incorporated by reference herein in
its entirety. In some embodiments, the process is a variation of
the GreenPower+ or GreenBox+ process technology which is commonly
owned with the assignee of this patent application.
[0124] Effective "hot-water extraction" (or "HWE") conditions may
include contacting the lignocellulosic biomass with steam (at
various pressures in saturated, superheated, or supersaturated
form) and/or hot water. In some embodiments, the HWE step is
carried out using liquid hot water at a temperature from about
140-220.degree. C., such as about 150.degree. C., 160.degree. C.,
170.degree. C., 175.degree. C., 180.degree. C., 185.degree. C.,
190.degree. C., 200.degree. C., or 210.degree. C. In some
embodiments, the HWE step is carried out using liquid hot water
with a residence time from about 1 minute to about 60 minutes, such
as about 2, 2.5, 3, 3.5, 4, 5, 7.5, 10, 12.5, 15, 20, 25, 30, 35,
40, 45, 50, or 55 minutes.
[0125] FIG. 1 is a high-level block-flow diagram according to some
embodiments. Wood is fed to one or more digestors, which may be
existing digestors in a retrofit of an existing pulp mill, for
example. Existing washer(s) and evaporator(s) may also be utilized.
In the embodiments depicted in FIG. 1, pulp is the primary product
and acetate and furfural are co-products.
[0126] FIG. 2 is a simplified process-flow diagram for the
production of pulp, hemicelluloses, and acetates, in some
embodiments. FIG. 3 shows a simplified process-flow diagram for the
production of pulp, sugars, and acetates, in some embodiments. FIG.
4 shows a simplified process-flow diagram for the production of
pulp, acetates, and furfural, in some embodiments. These figures by
no means limit the invention and are meant to be exemplary only.
Additional unit operations may be included. For example, additional
digestors for HWE pulping may be employed anywhere in the processes
depicted.
[0127] In some embodiments, washing of HWE pulp is performed using
fresh water. In some embodiments, washing of HWE pulp is performed
using recycled water that does not contain significant quantities
of alkali. The absence of significant quantities of alkaline
components reduces or avoids caustic degradation of sugars.
[0128] HWE pulping typically will produce digested solids in liquid
with a pH of about 3 to 5, such as from about 3.5 to 4.5. In some
embodiments, following HWE pulping, the pH of the pulp is adjusted
prior to refining of the solids. In certain embodiments, the pH is
adjusted to neutral or near-neutral pH, such as pH selected from
about 5 to about 9, preferably about 6.5-7.5, more preferably about
6.8-7.2. The pH adjustment may be accomplished by any known means,
such as (but not limited to) treatment with sodium hydroxide or
ammonia.
[0129] In some embodiments, following HWE pulping, an additional
pulping step is employed, such as soda pulping. In some
embodiments, the hydrolysate (containing hemicelluloses) from HWE
pulping is separated from the solids prior to introducing soda to
the solids.
[0130] FIGS. 5A and 5B summarize pulp physical properties measured
from laboratory-scale trials for a range of HWE pulping conditions.
In these figures, LHW is "liquid hot water." Soda cooks were
performed for comparison. The results in FIG. 5A were used to
adjust and optimize conditions for the experiments in FIG. 5B. Note
that in FIG. 5B, the refining pH is about 7 to 7.3, compared to a
refining pH range of about 3.8 to 4.2 in the HWE experiments. FIG.
6 summarizes the data collected with respect to the hemicellulose
stream extracted during HWE pulping.
[0131] The HWE pulp obtained may be combined with another biomass
source prior to downstream processing. For example, the HWE pulp
may be combined with recycled fiber (e.g., OCC or old corrugated
container pulp) and then fed to a paper machine, in some
embodiments. Or, the HWE pulp may be combined with a NSSC pulp,
soda pulp, sulfite pulp, Kraft pulp, or another pulp for further
processing.
[0132] In some embodiments, the process further comprises removing
a vapor stream comprising water and vaporized acetic acid from the
extract liquor in at least one evaporation stage at a pH of 4.8 or
less, to produce a concentrated extract liquor comprising the
fermentable hemicellulosic sugars. At least one evaporation stage
is preferably operated at a pH of 3.0 or less.
[0133] The process may further comprise a step of fermenting the
fermentable hemicellulosic sugars to a fermentation product. The
fermentation product may be ethanol, 1-butanol, isobutanol, or any
other product (fuel or chemical). Some amount of the fermentation
product may be growth of a microorganism or enzymes, which may be
recovered if desired.
[0134] In some embodiments, the fermentable hemicellulose sugars
are recovered from solution, in purified form. In some embodiments,
the fermentable hemicellulose sugars are fermented to produce of
biochemicals or biofuels such as (but by no means limited to)
ethanol, 1-butanol, isobutanol, acetic acid, lactic acid, or any
other fermentation products. A purified fermentation product may be
produced by distilling the fermentation product, which will also
generate a distillation bottoms stream containing residual solids.
A bottoms evaporation stage may be used, to produce residual
solids.
[0135] Pentose sugars can react to produce furfural. Under
conditions of heat and acid, xylose and other five-carbon sugars
undergo dehydration, losing three water molecules to become
furfural (C.sub.5H.sub.4O.sub.2). Furfural is an important
renewable, non-petroleum based, chemical feedstock. Hydrogenation
of furfural provides furfuryl alcohol, which is a useful chemical
intermediate and which may be further hydrogenated to
tetrahydrofurfuryl alcohol. Furfural is used to make other furan
chemicals, such as furoic acid, via oxidation, and furan via
decarbonylation. Generally speaking, process conditions that may be
adjusted to promote furfural include, in one or more reaction
steps, temperature, pH or acid concentration, reaction time,
catalysts or other additives (e.g. FeSO.sub.4), reactor flow
patterns, and control of engagement between liquid and vapor
phases.
[0136] In some embodiments, the process further comprises
recovering the lignin as a co-product, either in combination with a
salt such as gypsum, or in substantially pure form.
[0137] Process integration may be carried out for any of the
disclosed processes or configurations. In some embodiments, process
integration includes pinch analysis and energy optimization
involving one or more steps (including all steps) in the
process.
[0138] For example, evaporator condensates may be recycled for use
in one or more washing steps, and/or as part of the digestor
cooking liquor. In some embodiments, evaporator condensates may be
recycled to a reverse osmosis unit configured for recovering
alkaline acetates. Process integration may also be conducted with
downstream papermaking operations.
[0139] In some embodiments, process integration includes
concentrating fermentable sugars, recovering a condensate stream
therefrom, and introducing the condensate stream to another
location with a water requirement, such as washing, filter
regeneration, or fermentation. The other location may be upstream
or downstream of the condensate stream, or may even be at a
co-located site.
[0140] In some embodiments, process integration includes
sterilizing a fermentor or fermentor feed stream with a vapor
take-off from one or more evaporators used for concentrating the
fermentable sugars and/or one or more evaporators used for
concentrating the fermentation product. In some embodiments,
process integration includes pre-cooling a fermentor feed stream
with a product stream comprising the fermentation product.
[0141] In some embodiments, process integration includes
concentrating the fermentation product in a non-externally-heated
effect of a multiple-effect evaporation unit, such as the last
effect of the multiple-effect evaporation unit. In some
embodiments, process integration includes using vapor recompression
and vacuum pumping to concentrate the fermentation product, to
minimize cooling water requirements.
[0142] In some embodiments, process integration includes
concentrating one or more organic waste streams and combusting the
one or more organic waste streams with lignin or another
biomass-derived material.
[0143] In some embodiments, process integration includes utilizing
a rectifier reflux condensor to pre-evaporate stillage from a
fermentation product distillation column. The process integration
may also include preheating dimineralized water or preheating
turbine condenser condensate, for example.
[0144] When lignosulfonic acid is utilized, either to assist the
initial extraction or for hydrolysis of hemicellulose oligomers to
monomers, the lignosulfonic acid may be provided by another
biorefining process. For example, the AVAP.RTM. process employs
sulfur dioxide and a solvent for lignin to fractionate biomass,
which produces lignosulfonic acids during digestion.
[0145] The present invention, in various embodiments, offers
several benefits including but not limited to (i) increased yield
of pulp, (ii) recovery of hemicelluloses which may be converted to
value-added products, (iii) removal of chemicals from the pulping
process, (iv) elimination of chemical-recovery plant operations,
(v) reduction in number of evaporation stages required, and (vi)
reduced environmental footprint.
[0146] The present invention also provides systems configured for
carrying out the disclosed processes, and compositions or products
produced therefrom. Biorefineries may be configured to carry out
the processes disclosed using known equipment. The biorefineries
may be retrofits to existing mills, or new sites.
[0147] Any stream generated by the disclosed processes may be
partially or completed recovered, purified or further treated,
and/or marketed or sold.
[0148] In this detailed description, reference has been made to
multiple embodiments of the invention and non-limiting examples
relating to how the invention can be understood and practiced.
Other embodiments that do not provide all of the features and
advantages set forth herein may be utilized, without departing from
the spirit and scope of the present invention. This invention
incorporates routine experimentation and optimization of the
methods and systems described herein. Such modifications and
variations are considered to be within the scope of the invention
defined by the claims.
[0149] All publications, patents, and patent applications cited in
this specification are hereby incorporated by reference in their
entirety as if each publication, patent, or patent application were
specifically and individually put forth herein.
[0150] Where methods and steps described above indicate certain
events occurring in certain order, those of ordinary skill in the
art will recognize that the ordering of certain steps may be
modified and that such modifications are in accordance with the
variations of the invention. Additionally, certain of the steps may
be performed concurrently in a parallel process when possible, as
well as performed sequentially.
[0151] Therefore, to the extent there are variations of the
invention, which are within the spirit of the disclosure or
equivalent to the inventions found in the appended claims, it is
the intent that this patent application will cover those variations
as well.
* * * * *