U.S. patent application number 13/464453 was filed with the patent office on 2012-11-08 for lignin production from lignocellulosic biomass.
This patent application is currently assigned to RENMATIX, INC.. Invention is credited to Krishnan V. Iyer, Kiran Kadam, Michel A. Simard.
Application Number | 20120282466 13/464453 |
Document ID | / |
Family ID | 47090420 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120282466 |
Kind Code |
A1 |
Iyer; Krishnan V. ; et
al. |
November 8, 2012 |
Lignin Production From Lignocellulosic Biomass
Abstract
Methods are disclosed for providing lignin product of a small
particle size for improving burning efficiency and for avoiding
typical equipment fouling problems while maximizing energy
recovery.
Inventors: |
Iyer; Krishnan V.;
(Philadelphia, PA) ; Simard; Michel A.; (Berwyn,
PA) ; Kadam; Kiran; (Golden, CO) |
Assignee: |
RENMATIX, INC.
Kennesaw
GA
|
Family ID: |
47090420 |
Appl. No.: |
13/464453 |
Filed: |
May 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61482425 |
May 4, 2011 |
|
|
|
Current U.S.
Class: |
428/402 ;
106/802; 523/456; 524/72; 530/500 |
Current CPC
Class: |
Y02P 20/544 20151101;
C07G 1/00 20130101; D21C 11/0007 20130101; Y02P 20/54 20151101;
Y02P 70/24 20151101; Y02P 70/10 20151101; C08H 6/00 20130101; Y10T
428/2982 20150115; C04B 24/18 20130101; Y02P 30/20 20151101; C08H
8/00 20130101; C10G 2300/1014 20130101 |
Class at
Publication: |
428/402 ;
530/500; 524/72; 523/456; 106/802 |
International
Class: |
C08H 7/00 20110101
C08H007/00; C04B 16/04 20060101 C04B016/04; C08K 5/13 20060101
C08K005/13 |
Claims
1. A method of preparing lignin from lignocellulolosic biomass,
comprising: providing lignocellulosic biomass under a first
pressure of at least about 220 bar and at a first temperature of at
least about 360.degree. C., comprising: a first solid fraction
comprising: insoluble lignin; and a first liquid fraction
comprising: soluble C.sub.6 saccharides; and soluble lignin;
gradually reducing said first pressure of said lignocellulosic
biomass to a second pressure while substantially simultaneously and
gradually reducing said first temperature of said lignocellulosic
biomass to a second temperature at least about 1.degree. C. above
the glass transition temperature of lignin at said second pressure;
wherein said first liquid fraction is not substantially gasified;
and optionally, substantially simultaneously reducing said second
pressure and said second temperature to a third pressure and a
third temperature in a time less than about 1 second to precipitate
said soluble lignin in said first liquid fraction and form a
mixture comprising: a second solid fraction comprising: insoluble
lignin; and precipitated lignin; and a second liquid fraction
comprising: soluble C.sub.6 saccharides.
2. A method of claim 1, wherein said first temperature is about
360.degree. C. to about 380.degree. C.
3. A method of claim 1, wherein said second temperature is at least
about 5.degree. C. above the glass transition temperature of lignin
at said second pressure.
4. A method of claim 1, wherein said second temperature is about
110.degree. C. to about 120.degree. C.
5. A method of claim 1, wherein said third temperature is about
20.degree. C. to about 100.degree. C.
6. A method of claim 1, wherein said first pressure is about 220
bar to about 250 bar.
7. A method of claim 1, wherein said second pressure is greater
than atmospheric pressure.
8. A method of claim 1, wherein said second pressure is about 50
bar to about 150 bar.
9. A method of claim 1, wherein said second pressure is atmospheric
pressure.
10. A method of claim 1, further comprising: recovering at least a
portion of heat.
11. A method of claim 1, further comprising: permitting said
insoluble lignin and said precipitated lignin to separate out by
gravity.
12. A method of claim 1, further comprising: separating said second
solid fraction and said second liquid fraction.
13. A method of claim 1, wherein said method is continuous.
14. A method of claim 1, wherein said method employs multiple
pressure down valves and multiple heat exchangers.
15. A method of claim 1, wherein said lignocellulosic biomass is
fractionated to remove at least a portion of C.sub.5 saccharides
prior to said providing step.
16. A method of claim 1, wherein the average particle size of said
insoluble lignin and precipitated lignin is less than about 500
microns.
17. A lignin product produced by the method of claim 1.
18. A lignin product of claim 17, wherein said lignin product is
used as a fuel, tackifier, phenol formaldehyde resin extender in
the manufacture of particle board and plywood, in the manufacture
of molding compounds, urethane and epoxy resins, antioxidants,
controlled-release agents, flow control agents, cement/concrete
mixing, plasterboard production, oil drilling, general dispersion,
tanning leather, road covering, vanillin production, dimethyl
sulfide and dimethyl sulfoxide production, phenol substitute in
phenolic resins incorporation into polyolefin blends, aromatic
(phenol) monomers, additional miscellaneous monomers, carbon
fibers, metal sequestration in solutions, basis of gel formation,
polyurethane copolymer, and combinations thereof.
19. A method of reducing lignin fouling during processing of
lignocellulolosic biomass, comprising: providing lignocellulosic
biomass under a first pressure of at least about 220 bar and at a
first temperature of at least about 360.degree. C., comprising: a
first solid fraction comprising: insoluble lignin; and a first
liquid fraction comprising: soluble C.sub.6 saccharides; and
soluble lignin; gradually reducing said first pressure of said
lignocellulosic biomass to a second pressure while substantially
simultaneously and gradually reducing said first temperature of
said lignocellulosic biomass to a second temperature at least about
1.degree. C. above the glass transition temperature of lignin at
said second pressure; wherein said first liquid fraction is not
substantially gasified; and optionally, substantially
simultaneously reducing said second pressure and said second
temperature to a third pressure and a third temperature in a time
less than about 1 second to precipitate said soluble lignin in said
first liquid fraction and form a mixture comprising: a second solid
fraction comprising: insoluble lignin; and precipitated lignin; and
a second liquid fraction comprising: soluble C.sub.6
saccharides.
20. A method of claim 19, wherein said first temperature is about
360.degree. C. to about 380.degree. C.
21. A method of claim 19, wherein said second temperature is at
least about 5.degree. C. above the glass transition temperature of
lignin at said second pressure.
22. A method of claim 19, wherein said second temperature is about
110.degree. C. to about 120.degree. C.
23. A method of claim 19, wherein said third temperature is about
20.degree. C. to about 100.degree. C.
24. A method of claim 19, wherein said first pressure is about 220
bar to about 250 bar.
25. A method of claim 19, wherein said second pressure is greater
than atmospheric pressure.
26. A method of claim 19, wherein said second pressure is about 50
bar to about 150 bar.
27. A method of claim 19, wherein said second pressure is
atmospheric pressure.
28. A method of claim 19, further comprising: recovering at least a
portion of heat.
29. A method of claim 19, further comprising: permitting said
insoluble lignin and said precipitated lignin to separate out by
gravity.
30. A method of claim 19, wherein said method is continuous.
31. A method of claim 19, wherein said method employs multiple
pressure down valves and multiple heat exchangers.
32. A method of claim 19, wherein said lignocellulosic biomass is
fractionated to remove at least a portion of C.sub.5 saccharides
prior to said providing step.
33. A method of claim 19, wherein the average particle size of said
insoluble lignin and precipitated lignin is less than about 500
microns.
34. A lignin product produced by the method of claim 19.
35. A lignin product of claim 34, wherein said lignin product is
used as a fuel, tackifier, phenol formaldehyde resin extender in
the manufacture of particle board and plywood, in the manufacture
of molding compounds, urethane and epoxy resins, antioxidants,
controlled-release agents, flow control agents, cement/concrete
mixing, plasterboard production, oil drilling, general dispersion,
tanning leather, road covering, vanillin production, dimethyl
sulfide and dimethyl sulfoxide production, phenol substitute in
phenolic resins incorporation into polyolefin blends, aromatic
(phenol) monomers, additional miscellaneous monomers, carbon
fibers, metal sequestration in solutions, basis of gel formation,
polyurethane copolymer, and combinations thereof.
36. A composition, comprising: lignin; wherein said lignin is
processed from lignocellulosic biomass using supercritical or near
critical fluid extraction.
37. A composition of claim 36, wherein said lignin has an average
particle size is less than about 500 microns.
38. A composition of claim 36, wherein said lignin has a heating
value as measured by ASTM-D240 of at least about 5,000 BTU/lb at
30% moisture content.
39. A composition of claim 36, wherein said lignin has a heating
value as measured by ASTM-D240 of at least about 7,500 BTU/lb at
15% moisture content.
40. A composition of claim 36, wherein said lignin has a heating
value as measured by ASTM-D240 of at least about 8,000 BTU/lb at 5%
moisture content.
41. A composition of claim 36, wherein said composition is
substantially free of organic solvent.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This applications claims the benefit of U.S. application No.
61/482,425 filed May 4, 2011, the entire disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to methods of
preparing lignin from lignocellulosic biomass. More particularly,
it relates to methods of preparing lignin from lignocellulosic
biomass using coordinated reductions in pressure and temperature to
separate and to pulverize the lignin without fouling the equipment
and with improved energy recovery.
BACKGROUND OF THE INVENTION
[0003] Existing processes delignify lignocellulosic biomass before
entering the cellulose conversion process using solvents or other
chemicals. In such delignification processes, complex equipment is
typically required and is expensive to operate because of the
solvent or chemical usage and lack of recovery methods. In other
existing processes, the solid conversion of lignocellulosic biomass
in pre-treatment (fractionation) and cellulose hydrolysis requires
high temperatures to fully or partially solubilize the lignin
present. Upon cooling, the lignin precipitates from solution. The
lignin may be recovered from the process and burned for thermal
energy. The particle size of the recovered lignin may be variable
and too large for efficient burning, thus requiring a separate
pulverizing step. Furthermore, as the lignin in solution cools, it
becomes sticky (typically in the glass transition temperature range
of lignin, which is about 100.degree. C. under ambient pressure)
and tends to foul the process equipment to the point of making the
process inoperable. It would be useful to have methods for
providing lignin of a substantially uniform, small particle size
for improving burning efficiency, for enhanced properties for the
use of lignin as a feedstock for the production of other chemicals,
and for avoiding typical equipment fouling problems. Furthermore,
it would be desirable to maximize energy recovery in the process.
The methods and compositions of the present invention are directed
toward these, as well as other, important ends.
SUMMARY OF THE INVENTION
[0004] In one embodiment, the invention is directed to methods of
preparing lignin from lignocellulolosic biomass, comprising: [0005]
providing lignocellulosic biomass under a first pressure of at
least about 220 bar and at a first temperature of at least about
360.degree. C., comprising: [0006] a first solid fraction
comprising: [0007] insoluble lignin; and [0008] a first liquid
fraction comprising: [0009] soluble C.sub.6 saccharides; and [0010]
soluble lignin; [0011] gradually reducing said first pressure of
said lignocellulosic biomass to a second pressure while
substantially simultaneously and gradually reducing said first
temperature of said lignocellulosic biomass to a second temperature
at least about 1.degree. C. above the glass transition temperature
of lignin at said second pressure; [0012] wherein said first liquid
fraction is not substantially gasified; and [0013] optionally,
substantially simultaneously reducing said second pressure and said
second temperature to a third pressure and a third temperature in a
time less than about 1 second to precipitate said soluble lignin in
said first liquid fraction and form a mixture comprising: [0014] a
second solid fraction comprising: [0015] insoluble lignin; and
[0016] precipitated lignin; and [0017] a second liquid fraction
comprising: [0018] soluble C.sub.6 saccharides.
[0019] In another embodiment, the invention is directed to methods
of reducing lignin fouling during processing of lignocellulolosic
biomass, comprising: [0020] providing lignocellulosic biomass under
a first pressure of at least about 220 bar and at a first
temperature of at least about 360.degree. C., comprising: [0021] a
first solid fraction comprising: [0022] insoluble lignin; and
[0023] a first liquid fraction comprising: [0024] soluble C.sub.6
saccharides; and [0025] soluble lignin; [0026] gradually reducing
said first pressure of said lignocellulosic biomass to a second
pressure while substantially simultaneously and gradually reducing
said first temperature of said lignocellulosic biomass to a second
temperature at least about 1.degree. C. above the glass transition
temperature of lignin at said second pressure; [0027] wherein said
first liquid fraction is not substantially gasified; and [0028]
optionally, substantially simultaneously reducing said second
pressure and said second temperature to a third pressure and a
third temperature in a time less than about 1 second to precipitate
said soluble lignin in said first liquid fraction and form a
mixture comprising: [0029] a second solid fraction comprising:
[0030] insoluble lignin; and [0031] precipitated lignin; and [0032]
a second liquid fraction comprising: [0033] soluble C.sub.6
saccharides.
[0034] In yet other embodiments, the invention is directed to
lignin products produced by the methods of the invention.
[0035] In further embodiments, the invention is directed to
compositions, comprising: [0036] lignin; [0037] wherein said lignin
is processed from lignocellulosic biomass using supercritical or
near critical fluid extraction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. In the drawings:
[0039] FIG. 1 is a schematic diagram of the method of producing
lignin from cellulosic biomass in one embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0040] As employed above and throughout the disclosure, the
following terms, unless otherwise indicated, shall be understood to
have the following meanings.
[0041] As used herein, the singular forms "a," "an," and "the"
include the plural reference unless the context clearly indicates
otherwise.
[0042] While the present invention is capable of being embodied in
various forms, the description below of several embodiments is made
with the understanding that the present disclosure is to be
considered as an exemplification of the invention, and is not
intended to limit the invention to the specific embodiments
illustrated. Headings are provided for convenience only and are not
to be construed to limit the invention in any manner. Embodiments
illustrated under any heading may be combined with embodiments
illustrated under any other heading.
[0043] The use of numerical values in the various quantitative
values specified in this application, unless expressly indicated
otherwise, are stated as approximations as though the minimum and
maximum values within the stated ranges were both preceded by the
word "about." In this manner, slight variations from a stated value
can be used to achieve substantially the same results as the stated
value. Also, the disclosure of ranges is intended as a continuous
range including every value between the minimum and maximum values
recited as well as any ranges that can be formed by such values.
Also disclosed herein are any and all ratios (and ranges of any
such ratios) that can be formed by dividing a recited numeric value
into any other recited numeric value. Accordingly, the skilled
person will appreciate that many such ratios, ranges, and ranges of
ratios can be unambiguously derived from the numerical values
presented herein and in all instances such ratios, ranges, and
ranges of ratios represent various embodiments of the present
invention.
[0044] As used herein, the phrase "substantially free" means have
no more than about 1%, preferably less than about 0.5%, more
preferably, less than about 0.1%, by weight of a component, based
on the total weight of any composition containing the
component.
[0045] A supercritical fluid is a fluid at a temperature above its
critical temperature and at a pressure above its critical pressure.
A supercritical fluid exists at or above its "critical point," the
point of highest temperature and pressure at which the liquid and
vapor (gas) phases can exist in equilibrium with one another. Above
critical pressure and critical temperature, the distinction between
liquid and gas phases disappears. A supercritical fluid possesses
approximately the penetration properties of a gas simultaneously
with the solvent properties of a liquid. Accordingly, supercritical
fluid extraction has the benefit of high penetrability and good
solvation.
[0046] Reported critical temperatures and pressures include: for
pure water, a critical temperature of about 374.2.degree. C., and a
critical pressure of about 221 bar; for carbon dioxide, a critical
temperature of about 31.degree. C. and a critical pressure of about
72.9 atmospheres (about 1072 psig). Near-critical water has a
temperature at or above about 300.degree. C. and below the critical
temperature of water (374.2.degree. C.), and a pressure high enough
to ensure that all fluid is in the liquid phase. Sub-critical water
has a temperature of less than about 300.degree. C. and a pressure
high enough to ensure that all fluid is in the liquid phase.
Sub-critical water temperature may be greater than about
250.degree. C. and less than about 300.degree. C., and in many
instances sub-critical water has a temperature between about
250.degree. C. and about 280.degree. C. The term "hot compressed
water" is used interchangeably herein for water that is at or above
its critical state, or defined herein as near-critical or
sub-critical, or any other temperature above about 50.degree. C.
(preferably, at least about 100.degree. C.) but less than
subcritical and at pressures such that water is in a liquid
state
[0047] As used herein, a fluid which is "supercritical" (e.g.
supercritical water, supercritical CO.sub.2, etc.) indicates a
fluid which would be supercritical if present in pure form under a
given set of temperature and pressure conditions. For example,
"supercritical water" indicates water present at a temperature of
at least about 374.2.degree. C. and a pressure of at least about
221 bar, whether the water is pure water, or present as a mixture
(e.g. water and ethanol, water and CO.sub.2, etc). Thus, for
example, "a mixture of sub-critical water and supercritical carbon
dioxide" indicates a mixture of water and carbon dioxide at a
temperature and pressure above that of the critical point for
carbon dioxide but below the critical point for water, regardless
of whether the supercritical phase contains water and regardless of
whether the water phase contains any carbon dioxide. For example, a
mixture of sub-critical water and supercritical CO.sub.2 may have a
temperature of about 250.degree. C. to about 280.degree. C. and a
pressure of at least about 225 bar.
[0048] As used herein, "continuous" indicates a process which is
uninterrupted for its duration, or interrupted, paused or suspended
only momentarily relative to the duration of the process. Treatment
of biomass is "continuous" when biomass is fed into the apparatus
without interruption or without a substantial interruption, or
processing of said biomass is not done in a batch process.
[0049] As used herein, "resides" indicates the length of time which
a given portion or bolus of material is within a reaction zone or
reactor vessel. The "residence time," as used herein, including the
examples and data, are reported at ambient conditions and are not
necessarily actual time elapsed.
[0050] As used herein, the term "substantial free of" refers to a
composition having less than about 1% by weight, preferably less
than about 0.5% by weight, and more preferably less than about 0.1%
by weight, based on the total weight of the composition, of the
stated material.
[0051] As used herein, the term "saccharification" and
"saccharified" refers to the breakdown of polysaccharides to
smaller polysaccharides, including oligosaccharides, and
monosaccharides, whether through hydrolysis, the use of enzymes, or
other means, generally into a liquid fraction and a solid
fraction.
[0052] As used herein, the term "glass transition temperature" or
"Tg" means the temperature at which an amorphous regions of a
semi-crystalline material change from a glassy, brittle state to a
rubbery or plastic state. It is dependent upon the composition of
the material being tested, including moisture content, and the
extent of annealing. Glass transition temperature may be measured
by differential scanning calorimetry, thermomechanical analysis,
dynamic mechanical analysis, and the like.
[0053] As used herein, the term "pulverize" means providing a small
particle size, such as through spraying or atomizing, or reducing
the particle size of a given material, whether or not through the
use of mechanical means.
[0054] As used herein, the term "gradually" or "gradual" used with
respect to a pressure or temperature reduction refers to
incremental changes of the pressure or temperature, respectively.
The incremental changes per unit time may be the same or different.
Preferably, an individual increment is less than about 50%, more
preferably less than about 25%, even more preferably less than
about 20%, yet even more preferably less than about 10%, or even
less than about 5% or 1%, of the range to be covered from the
initial to final pressure or temperature.
[0055] As used herein, the term "simultaneously" or "simultaneous"
used with respect to a temperature reduction refers to incremental
changes of the temperature that substantially match the
corresponding pressure reduction.
[0056] As used herein, the term "gasified" or "gasification" means
that a material changes from the liquid state to the gaseous
state.
[0057] As used herein, "lignocellulosic biomass or a component part
thereof" refers to plant biomass containing cellulose,
hemicellulose, and lignin from a variety of sources, including,
without limitation (1) agricultural residues (including corn stover
and sugarcane bagasse), (2) dedicated energy crops, (3) wood
residues (including sawmill and paper mill discards), and (4)
municipal waste, and their constituent parts including without
limitation, lignocellulose biomass itself, lignin, C.sub.6
saccharides (including cellulose, cellobiose, C.sub.6
oligosaccharides, C.sub.6 monosaccharides, and C.sub.5 saccharides
(including hemicellulose, C.sub.5 oligosaccharides, and C.sub.5
monosaccharides).
[0058] Generally, the methods of the invention utilizes the
relationship between glass transition temperature (T.sub.g) and
pressure to eliminate lignin fouling in the processing equipment
while decreasing heat losses. Rather than cooling the slurry as it
exits, for example, from the cellulose hydrolysis reactor, the
methods of the invention cools the slurry in such a fashion that
simultaneous depressurizing and cooling takes places so there is no
gasification of the components of the slurry mixture, i.e., no
flash cooling at high temperatures. This results in higher heat
recovery, using, for example, heat exchangers. As the slurry is
gradually depressurized while cooling, the Tg of lignin gradually
decreases toward the Tg at atmospheric pressure (i.e., about
100.degree. C.). Thus, the temperature of the slurry is always kept
above the T.sub.g, thereby preventing fouling and sticking within
the processing equipment at higher temperatures. Optionally, the
slurry may be subjected to flash cooling from a temperature above
the T.sub.g to precipitate out and pulverize (provide as a small
particle size) lignin. This is accomplished by cooling the stream
containing the lignin to just above its glass transition
temperature (T.sub.g) to prevent sticking and then rapidly dropping
the pressure so that the lignin is well below its T.sub.g at the
new pressure when it precipitates out of solution at a small
particle size. While this optional step results in some heat loss
of low heat, it comes with the advantage of more concentrated
product liquor as well as improved lignin quality.
[0059] Accordingly, in one embodiment, the invention is directed to
methods of preparing lignin from lignocellulolosic biomass,
comprising: [0060] providing lignocellulosic biomass under a first
pressure of at least about 220 bar and at a first temperature of at
least about 360.degree. C., comprising: [0061] a first solid
fraction comprising: [0062] insoluble lignin; and [0063] a first
liquid fraction comprising: [0064] soluble C.sub.6 saccharides; and
[0065] soluble lignin; [0066] gradually reducing said first
pressure of said lignocellulosic biomass to a second pressure while
substantially simultaneously and gradually reducing said first
temperature of said lignocellulosic biomass to a second temperature
at least about 1.degree. C. above the glass transition temperature
of lignin at said second pressure; [0067] wherein said first liquid
fraction is not substantially gasified; and [0068] optionally,
substantially simultaneously reducing said second pressure and said
second temperature to a third pressure and a third temperature in a
time less than about 1 second to precipitate said soluble lignin in
said first liquid fraction and form a mixture comprising: [0069] a
second solid fraction comprising: [0070] insoluble lignin; and
[0071] precipitated lignin; and [0072] a second liquid fraction
comprising: [0073] soluble C.sub.6 saccharides.
[0074] In another embodiment, the invention is directed to methods
of reducing lignin fouling during processing of lignocellulolosic
biomass, comprising: [0075] providing lignocellulosic biomass under
a first pressure of at least about 220 bar and at a first
temperature of at least about 360.degree. C., comprising: [0076] a
first solid fraction comprising: [0077] insoluble lignin; and
[0078] a first liquid fraction comprising: [0079] soluble C.sub.6
saccharides; and [0080] soluble lignin; [0081] gradually reducing
said first pressure of said lignocellulosic biomass to a second
pressure while substantially simultaneously and gradually reducing
said first temperature of said lignocellulosic biomass to a second
temperature at least about 1.degree. C. above the glass transition
temperature of lignin at said second pressure; [0082] wherein said
first liquid fraction is not substantially gasified; and [0083]
optionally, substantially simultaneously reducing said second
pressure and said second temperature to a third pressure and a
third temperature in a time less than about 1 second to precipitate
said soluble lignin in said first liquid fraction and form a
mixture comprising: [0084] a second solid fraction comprising:
[0085] insoluble lignin; and [0086] precipitated lignin; and [0087]
a second liquid fraction comprising: [0088] soluble C.sub.6
saccharides.
[0089] A schematic of one embodiment of the invention is shown in
FIG. 1. The lignin slurry exits the hydrolysis process 1 at a first
temperature and a first pressure. It is first cooled to a first
intermediate temperature using a pre-cooler heat exchanger 2 and
depressurized to a first intermediate pressure using pressure
letdown valve 3. It is next cooled to a second intermediate
temperature using a pre-cooler heat exchanger 4 and depressurized
to a second intermediate pressure using pressure letdown valve 5.
It is further cooled to a third intermediate temperature using a
pre-cooler heat exchanger 6 and depressurized to a third
intermediate pressure using pressure letdown valve 7. It is further
cooled to a fourth intermediate temperature using a pre-cooler heat
exchanger 8 and depressurized rapidly using pressure letdown valve
9, and subsequently the liquid (i.e., water) content in the slurry
is flash evaporated. This results in the sudden precipitation of
the soluble lignin into fine particles inside the lignin pulverizer
11. In certain embodiments, the pulverizer is of relatively small
volume to keep the slurry moving and avoid lignin settling. In
other embodiments, it may be of a large volume to permit settling
of the lignin, which may be recovered by mechanical means,
especially when using full flash. The inlet pipe to the pulverizer
may either be above, below, or to either side of the pulverizer.
Atmospheric pressure for full pressure reduction, or an
intermediate pressure in the case of a partial pressure reduction,
is maintained in the pulverizer by the back pressure control valve
10. In embodiments using full flash to atmospheric pressure, no
back pressure control is needed. Any recovered steam enters a
condenser 12 (not shown) for heat recovery. Following the
pulverizer, the slurry flows through flow control 14 and then is
further cooled to recover more heat in a heat exchanger 16, and is
reduced to atmospheric pressure, if not yet a atmospheric
temperature, via a pressure letdown valve 18 in the settling tank
20. In the tank, the lignin is permitted to settle to the bottom.
Finally, the slurry may be passed through a solid/liquid filtration
apparatus 22 for final separation of liquor 24 and lignin 26.
[0090] Advantages of the methods of the invention are that the
pulverization (preparation of small particles and/or reduction in
average particle size) of soluble and insoluble lignin improves
handling, accelerates the drying, and improves combustion of the
lignin. Another advantage of the methods of the invention is that
the glass transition phase of the lignin, both soluble and
insoluble, is avoided, which in turn avoids fouling of the process
equipment.
[0091] In certain embodiments of the method, lignocellulosic
biomass is fractionated to remove at least a portion of C.sub.5
saccharides by any suitable means, including, but not limited to,
hydrothermal treatment (such as hot compressed water, subcritical,
near critical, or supercritical water, which may contain other
fluids, including alcohol, acid, or base), enzymatic treatment, and
the like.
[0092] In certain embodiments of the method, the average particle
size of said insoluble lignin and precipitated lignin is less than
about 500 microns.
[0093] The methods of the invention are preferably run
continuously, although they may be run as batch or semi-batch
processes.
[0094] The methods of the invention may be carried out in any
suitable reactor, including, but not limited to, a tubular reactor,
a digester (vertical, horizontal, or inclined), and the like.
Suitable digesters include the digester system described in U.S.
Pat. No. 8,057,639, which include a digester and a steam explosion
unit, the entire disclosure of which is incorporated by
reference.
[0095] In certain embodiments, methods employ multiple pressure
down valves and multiple heat exchangers.
[0096] In certain embodiments of the methods, the first temperature
is about 360.degree. C. to about 380.degree. C., preferably, about
360.degree. C. to about 377.degree. C., and more preferably, about
365.degree. C. to about 377.degree. C.
[0097] In certain embodiments of the methods, the second
temperature is at least about 5.degree. C. above the glass
transition temperature of lignin at said second pressure. In
certain embodiments of the methods, the second temperature is at
least about 10.degree. C. above the glass transition temperature of
lignin at said second pressure. In certain embodiments of the
methods, the second temperature is about 110.degree. C. to about
150.degree. C., preferably, about 110.degree. C. to about
135.degree. C., and more preferably, about 110.degree. C. to about
120.degree. C.
[0098] In certain embodiments of the methods, the third temperature
is about 20.degree. C. to about 100.degree. C., preferably, about
20.degree. C. to about 80.degree. C., and more preferably, about
20.degree. C. to about 60.degree. C.
[0099] In certain embodiments of the methods, the first pressure is
about 220 bar to about 300 bar, preferably, about 220 bar to about
250 bar, and more preferably, about 240 bar to about 250 bar.
[0100] In certain embodiments of the methods, the second pressure
is greater than atmospheric pressure. In certain embodiments of the
methods, the second pressure is about 50 bar to about 150 bar,
preferably, about 50 bar to about 125 bar, and more preferably,
about 50 bar to about 100 bar. In certain embodiments of the
methods, the second pressure is atmospheric pressure.
[0101] In certain embodiments, the methods may further comprise the
step of recovering at least a portion of heat added to the system,
for example, through the use of at least one heat exchanger.
[0102] In certain embodiments, the method further comprises the
step of reducing the pressure on said mixture to a third pressure.
Pressure control impacts temperature in the flashing process where
the saccharified lignocellulosic biomass is cooled in a very short
period of time (e.g., less than one second). The inlet pressure
must be equal to or greater than the saturation pressure at the
given temperature so that the liquid components of fraction remain
as liquids. With respect to processing of lignocellulosic biomass,
it is preferably to avoid the temperature range of about
180.degree. C. and about 240.degree. C., the glass transition
temperature range of lignin under typical processing conditions.
Thus, if the inlet temperature is at least the 240.degree.
C.+1.degree. C., then the minimum inlet pressure needs to be about
34 bar but may be much higher. For example, it is typical to have
the inlet pressure at 40 bar. The exit temperature is determined
and dependent upon the exit pressure. If, for example, there is
flash cooling of the saccharified lignocellulosic biomass down to a
temperature of 180.degree. C., then the exit pressure needs to
equal to the saturation pressure at 180.degree. C., which about 10
bar. The exit pressure is controlled by the back pressure valve,
and the exit temperature is determined by the exit pressure. If the
exit pressure is changed, the exit temperature will also change.
The exit temperature is the saturation temperature at the selected
pressure.
[0103] In certain embodiments, the method further comprises the
step of permitting said insoluble lignin and said precipitated
lignin, where the lignin has been pulverized (provided as a small
particle size or reduce the particle size) to separate out by
gravity.
[0104] In certain embodiments, the method further comprises the
step of separating said second solid fraction and said second
liquid fraction. Suitable separation methods including filtration
methods well known to those skilled in the art, such decanter
filters, filter press, reverse osmosis and nanofiltration,
centrifuge decanters, and the like.
[0105] In another embodiment, the invention is directed to lignin
products produced by the methods of the invention, including fuels,
such as those used in a process heat boiler. The lignin product may
also be used as a functional replacement for phenol, as a
functional replacement for polyol, or as a building block for
carbon fiber. In certain embodiments, the lignin product is used as
a fuel, tackifier, phenol formaldehyde resin extender in the
manufacture of particle board and plywood, in the manufacture of
molding compounds, urethane and epoxy resins, antioxidants,
controlled-release agents, flow control agents, cement/concrete
mixing, plasterboard production, oil drilling, general dispersion,
tanning leather, road covering, vanillin production, dimethyl
sulfide and dimethyl sulfoxide production, phenol substitute in
phenolic resins incorporation into polyolefin blends, aromatic
(phenol) monomers, additional miscellaneous monomers, carbon
fibers, metal sequestration in solutions, basis of gel formation,
polyurethane copolymer, and combinations thereof.
[0106] In another embodiment, the invention is directed to
compositions, comprising: [0107] lignin; [0108] wherein said lignin
is processed from lignocellulosic biomass using supercritical or
near critical fluid extraction. In preferred embodiments, the
composition is substantially free of organic solvent. In preferred
embodiments, the lignin has an average particle size less than
about 500 microns, more preferably 300 microns, even more
preferably, less than about 250 microns, and yet even more
preferably less than about 50 microns. The particle size of the
lignin may be measured by standard sieve shaker, microscopy,
infrared spectroscopy, and other standard size analysis
techniques.
[0109] In a preferred embodiment, the lignin has a heating value as
measured by ASTM-D240 of at least about 5,000 BTU/lb at 30%
moisture content. In a preferred embodiment, the lignin has a
heating value as measured by ASTM-D240 of at least about 7,500
BTU/lb at 15% moisture content. In a preferred embodiment, the
lignin has a heating value as measured by ASTM-D240 of at least
about 8,000 BTU/lb at 5% moisture content.
[0110] The present invention is further defined in the following
Examples, in which all parts and percentages are by weight, unless
otherwise stated. It should be understood that these examples,
while indicating preferred embodiments of the invention, are given
by way of illustration only and are not to be construed as limiting
in any manner. From the above discussion and these examples, one
skilled in the art can ascertain the essential characteristics of
this invention, and without departing from the spirit and scope
thereof, can make various changes and modifications of the
invention to adapt it to various usages and conditions.
EXAMPLES
Example 1
[0111] The methods of the invention may be carried out using the
following pressure and temperature changes using the apparatus
shown in FIG. 1:
TABLE-US-00001 Temperature (.degree. C.) Pressure (bar) Starting
Point .gtoreq.~365 .gtoreq.~250 1. From starting pressure,
.gtoreq.~365 .fwdarw. ~250 .gtoreq.~250 .fwdarw. ~150 reduce
temperature to about 250.degree. C. and then reduce pressure to 150
bar 2. Reduce temperature to ~250 .fwdarw. ~210 ~150 .fwdarw. ~50
about 210.degree. C. and then reduce pressure to 50 bar 3. Reduce
temperature to ~210 .fwdarw. ~145 50 .fwdarw. 20 about 145.degree.
C. and then reduce pressure to 20 bar 4. Reduce temperature to ~145
.fwdarw. ~120 20 .fwdarw. atmospheric about 120.degree. C. and then
flashed off
[0112] Conventional processes suffer a major disadvantage because
of the heat loss due to flashing that reduces heat recovery. In
contrast, the methods of the present invention cool and
depressurize simultaneously so that there is no flashing. In other
words, all the heat put into the system may be recovered as there
is no steam formation. Even if there is some flashing, it would be
very minimal with little heat loss. Accordingly, the method of the
present invention reduces heat loss through the system.
[0113] When ranges are used herein for physical properties, such as
molecular weight, or chemical properties, such as chemical
formulae, all combinations, and subcombinations of ranges specific
embodiments therein are intended to be included.
[0114] The disclosures of each patent, patent application, and
publication cited or described in this document are hereby
incorporated herein by reference, in their entirety.
[0115] Those skilled in the art will appreciate that numerous
changes and modifications can be made to the preferred embodiments
of the invention and that such changes and modifications can be
made without departing from the spirit of the invention. It is,
therefore, intended that the appended claims cover all such
equivalent variations as fall within the true spirit and scope of
the invention.
* * * * *