U.S. patent application number 12/717833 was filed with the patent office on 2010-09-09 for systems and processes for producing bio-fuels from lignocellulosic materials.
This patent application is currently assigned to WASHINGTON STATE UNIVERSITY. Invention is credited to Shulin Chen, Oisik Das, Manuel Garcia-Perez, Robert L. Johnson, Jieni Lian, Shi-Shen Liaw, Zhouhong Wang, Shuai Zhou.
Application Number | 20100223839 12/717833 |
Document ID | / |
Family ID | 42676998 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100223839 |
Kind Code |
A1 |
Garcia-Perez; Manuel ; et
al. |
September 9, 2010 |
SYSTEMS AND PROCESSES FOR PRODUCING BIO-FUELS FROM LIGNOCELLULOSIC
MATERIALS
Abstract
A selective pyrolysis process for the production of bio-oils
enriched in pyrolytic sugars and phenols and conversion of these
compounds into second generation bio-fuels is disclosed herein. One
embodiment of the process comprises pre-treating a biomass with
superheated steam or gases in a selected range of temperatures,
followed by fast pyrolysis using synthesis gas as a carrier, and a
two-step condensation operation. The aqueous phase from the second
condenser can then be reformed to produce hydrogen or can be
gasified together with the charcoal to produce syngas.
Inventors: |
Garcia-Perez; Manuel;
(Pullman, WA) ; Johnson; Robert L.; (West St.
Paul, MN) ; Liaw; Shi-Shen; (Taipei City, TW)
; Chen; Shulin; (Pullman, WA) ; Lian; Jieni;
(Pullman, WA) ; Zhou; Shuai; (Pullman, WA)
; Das; Oisik; (Pullman, WA) ; Wang; Zhouhong;
(Pullman, WA) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
P.O. BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
WASHINGTON STATE UNIVERSITY
Pullman
WA
|
Family ID: |
42676998 |
Appl. No.: |
12/717833 |
Filed: |
March 4, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61157338 |
Mar 4, 2009 |
|
|
|
Current U.S.
Class: |
44/313 ;
44/451 |
Current CPC
Class: |
Y02E 50/17 20130101;
C13K 1/02 20130101; Y02E 50/10 20130101; C12M 43/00 20130101; C10J
2300/0909 20130101; C10J 2300/1681 20130101; C12P 7/06 20130101;
C12M 21/12 20130101; C01B 2203/0233 20130101; Y02E 50/14 20130101;
C10J 2300/094 20130101; C10J 2300/165 20130101; Y02E 50/32
20130101; C10J 3/66 20130101; Y02E 50/15 20130101; C10J 2300/0956
20130101; C10L 9/083 20130101; C10B 57/02 20130101; C10J 2300/1671
20130101; F02C 3/28 20130101; C12M 45/20 20130101; Y02E 50/12
20130101; Y02E 50/30 20130101; C10B 53/02 20130101; C10K 3/006
20130101; C10J 2300/1846 20130101; C10B 47/44 20130101; C01B 3/34
20130101 |
Class at
Publication: |
44/313 ;
44/451 |
International
Class: |
C10L 1/18 20060101
C10L001/18; C10L 1/182 20060101 C10L001/182 |
Claims
1. A process for processing a biomass, comprising: treating a
biomass by heating the biomass at a first temperature; thermally
converting the treated biomass into a product having an oil portion
and an aqueous portion via pyrolysis at a second temperature, the
first temperature being lower than the second temperature; and
selecting the first temperature based on a correlation between the
first temperature and a desired anhydrosugar content in the oil
portion of the product.
2. The process of claim 1 wherein thermally converting includes
using a synthesis gas as a carrier gas in a pyrolysis reactor.
3. The process of claim 1, further comprising producing an oil
phase in a first condenser and producing an aqueous phase in a
second condenser, the first and second condensers are in a
series.
4. The process of claim 1, further comprising separating sugars
from phenols in the oil phase via liquid-liquid extraction with a
solvent.
5. The process of claim 1, further comprising converting at least a
fraction of sugars in the oil phase to ethanol.
6. The process of claim 1 wherein the oil phase contains sugars,
and wherein the process further comprising converting at least a
fraction of the sugars into lipids.
7. The process of claim 1 wherein treating a biomass includes
treating a biomass by heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C.
8. The process of claim 1 wherein treating a biomass includes
treating a biomass by heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C. for a period of time
of about 3 minutes to about 10 hours.
9. The process of claim 1 wherein treating a biomass includes
treating a biomass by heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C. for a period of time
of about 1 minutes to about 10 hours, and wherein the first
temperature is inversely related to the period of time.
10. A process for processing a biomass, comprising: providing a
biomass having a first crystallinity; modifying a structure of
cellulose in the biomass to have a second crystallinity higher than
the first crystallinity; and thermally converting the biomass with
the increased crystallinity into a pyrolysis product containing
anhydrosugar via pyrolysis.
11. The process of claim 10 wherein: the first crystallinity of the
biomass corresponds to a first anhydrosugar content of the
pyrolysis product; and modifying the structure of cellulose
includes modifying the structure of cellulose to have a second
crystallinity and/or a degree of polymerization corresponding to a
second anhydrosugar content higher than the first anhydrosugar
content of the pyrolysis product.
12. The process of claim 10 wherein: the first crystallinity of the
biomass corresponds to an anhydrosugar content of the pyrolysis
product; and modifying the structure of cellulose includes
enhancing the anhydrosugar content of the pyrolysis product.
13. The process of claim 10 wherein modifying the structure of
cellulose includes heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C.
14. The process of claim 10 wherein modifying the structure of
cellulose includes heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C. for a period of time
of about 1 minute to about 10 hours.
15. The process of claim 10 wherein modifying the structure of
cellulose includes heating the biomass at a first temperature of
about 200.degree. C. to about 300.degree. C. for a period of time
of about 3 minutes to about 10 hours, and wherein the first
temperature is inversely related to the period of time.
16. A process for processing a biomass, comprising: heating a
biomass at a first temperature; thermally converting the heated
biomass into a product via pyrolysis at a second temperature, the
first temperature being lower than the second temperature; and
wherein the first temperature is selected to enhance an
anhydrosugar content in the product from thermally converting the
heated biomass.
17. The process of claim 16 wherein the first temperature is
selected to be about 200.degree. C. to about 300.degree. C.
18. The process of claim 16 wherein the first temperature is
selected to be about 200.degree. C. to about 300.degree. C., and
wherein a heating period of time is also selected to enhance the
anhydrosugar content in the product from thermally converting the
heated biomass.
19. The process of claim 16 wherein the first temperature is
selected to be about 200.degree. C. to about 300.degree. C., and
wherein a heating period of time is also selected to enhance the
anhydrosugar content in the product from thermally converting the
heated biomass, the heating period of time being about 1 minute to
about 10 hours.
20. The process of claim 16 wherein the first temperature is
selected to be about 200.degree. C. to about 300.degree. C., and
wherein a heating period of time is also selected to enhance the
anhydrosugar content in the product from thermally converting the
heated biomass, the heating period of time being about 1 minutes to
about 10 hours and inversely related to the first temperature.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 61/157,338, filed on Mar. 4, 2009, the disclosure
of which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] This disclosure relates to systems and processes for
producing liquid fuels from lignocellulosic materials (e.g.,
agricultural and forestry residues and energy crops).
BACKGROUND
[0003] Biomass is an attractive feedstock to offset fossil fuels
because it is carbon neutral (or negative), renewable, and may be
domestically produced. One conversion platform uses a
thermo-chemical process (commonly referred to as "pyrolysis") to
convert biomass into bio-oil. Bio-oils are similar in appearance
and color as crude oil though bio-oil contains considerably more
oxygenated and functional compounds.
[0004] Although bio-oil can be used directly for stationary diesel
engines, bio-oil may be too corrosive and viscous as a transport
fuel. There is however great potential to use bio-oil as a
feedstock for centralized refineries to produce chemical products
and/or transportation fuels. However, several technical challenges
exist for the utilization of bio-oil as a feedstock. First,
bio-oils are highly acidic and may be corrosive to pipes and
storage vessels. Secondly, bio-oils can be unstable when stored for
prolonged periods of time. Third, bio-oils typically contain a wide
variety of molecules including a substantial amount of small
molecules, which are difficult to upgrade. Accordingly, several
improvements in converting biomass to bio-oils are needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic flow diagram illustrating a system for
converting biomass into bio-oils in accordance with embodiments of
the technology.
[0006] FIG. 2 is a schematic diagram illustrating a system for
performing bio-oil refining in accordance with embodiments of the
technology.
[0007] FIGS. 3A and 3B are schematic diagrams illustrating a
reactor in accordance with embodiments of the technology.
[0008] FIG. 4 is a graph showing ratios of peaks in Py-GC/MS
chromatogram assigned to levoglucosan and to hydroxyacetaldehyde in
accordance with embodiments of the technology.
[0009] FIG. 5 shows the changes of levoglucosan/furfural ratios as
a function of pyrolysis temperature in accordance with embodiments
of the technology.
[0010] FIGS. 6 and 7 show the ratio of levoglucosan and other
products of oxidation reactions in accordance with embodiments of
the technology.
[0011] FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a
function of pretreatment temperature in accordance with embodiments
of the technology.
[0012] FIG. 9 shows levoglucosan/hydroxyacetaldehyde ratios as a
function of pyrolysis temperature in accordance with embodiments of
the technology.
[0013] FIG. 10 shows a glucose content as a function of
fermentation time in accordance with embodiments of the
technology.
[0014] FIG. 11 shows a rate of microbial growth in solutions
derived from bio-oils and in control solutions produced with
glucose in accordance with embodiments of the technology.
[0015] FIG. 12 shows ethanol concentration as a function of
fermentation time in accordance with embodiments of the
technology.
[0016] FIG. 13 shows sugar consumption and production of fatty
acids as a function of fermentation time in accordance with
embodiments of the technology.
DETAILED DESCRIPTION
[0017] Specific details of several embodiments of the disclosure
are described below with reference to systems and processes to
selectively convert lignocellulosic materials into a bio-oil that
is rich in anhydrosugars (e.g., levoglucosan and cellobiosan) and
phenols as well as the further conversion of the anhydrosugars to
ethanol and/or lipids. The term "lignocellulosic materials"
generally refers to materials containing cellulose, hemicelluloses,
and lignin. Examples of lignocellulosic materials include wood
chips, straws, grasses, corn stover, corn husks, weeds, aquatic
plants, hay, paper, paper products, recycled paper and/or paper
products, and other cellulose containing biological materials or
materials of biological origin. Several embodiments can have
configurations, components, or procedures different than those
described in this section, and other embodiments may eliminate
particular components or procedures. A person of ordinary skill in
the relevant art, therefore, may understand that the technology may
have other embodiments with additional elements, and/or may have
other embodiments without several of the features shown and
described below with reference to FIGS. 1-13.
[0018] FIG. 1 is a schematic flow diagram illustrating a system 100
for converting biomass into bio-oils in accordance with embodiments
of the disclosure. As shown in FIG. 1, the system 100 includes a
drier 102, a torrefaction unit (with an optional grinder) 104, a
pyrolysis reactor 106, a first condenser 108, a second condenser
110, and a combustor 112 operatively coupled in series. The system
100 also includes an evaporator 114, a steam reformer 116, and a
gasification reactor 118 operatively coupled to one another as well
as to the pyrolysis reactor 106 and the second condenser 110. Even
though only particular components are shown in FIG. 1, other
embodiments of the system 100 can also include washers, decanters,
filters, and/or other suitable components in addition to or in lieu
of the foregoing components of the system 100.
[0019] The dryer 102 can include a direct-contact dryer, an
indirect-contact dryer, and/or other suitable types of dryer. In
the illustrated embodiment, the dryer 102 includes a direct-contact
dryer configured to receive and contact the biomass 1 with a hot
combustion gas 6 from the combustor 112. The exhaust from the dryer
102 is vented to atmosphere. In other embodiments, the dryer 102
can also be coupled to an optional hot gas source (e.g., hot air,
not shown) for start-up, supplementing the hot combustion gas 6,
and/or other suitable purposes. After drying, the dryer 102
provides a dried biomass 2 to the torrefaction unit 104. In further
embodiments, the dryer 102 and the torrefaction unit 104 can be
integrated in a single unit (not shown).
[0020] The torrefaction unit 104 can be configured to pre-treat the
dried biomass 2 before subjecting the dried biomass 2 to pyrolysis.
The torrefaction unit 104 can include any vessel capable of
controllably heating the dried biomass 2 to a desired temperature.
Optionally, the torrefaction unit 104 can also include a grinder
and/or other suitable components to reduce the size of the dried
biomass 2. For example, in one embodiment, the torrefaction unit
104 can include an auger reactor configured to controllably heat
the dried biomass 2 while reducing the size of the dried biomass 2,
as described in more detail below with reference to FIG. 4. In
other embodiments, the torrefaction unit 104 may also use a
synthesis gas 16 from the reformer 116 as a carrier gas for the
pretreatment reactions.
[0021] The pyrolysis reactor 106 can include a fluidized bed, a
fixed bed, an ablative reactor, vacuum pyrolysis reactor, auger
pyrolysis reactor, and/or other suitable types of pyrolysis
reactors. In one embodiment, the pyrolysis reactor 106 can include
embodiments of the auger reactor shown in FIG. 3. In other
embodiments, the pyrolysis reactor 106 can include other types of
reaction vessels. Even though the torrefaction unit 104 and the
pyrolysis reactor 106 are shown as separate components in FIG. 1,
in certain embodiments, the torrefaction unit 104 and the pyrolysis
reactor 106 can be combined into a single component. In further
embodiments, a single component (e.g., the reactor of FIG. 3) may
perform the function of both the torrefaction unit 104 and the
pyrolysis reactor 106. As a result, the torrefaction unit 104 and
the pyrolysis reactor 106 may be integrated into a single unit.
[0022] The first and second condensers 108 and 110, the boiler 114,
and the reformer 116 can individually include a plate-and-frame,
tube-and-shell, brazed aluminum, and/or other types of heat
exchanger. In one embodiment, the first condenser 108 can be an
empty scrubber. In other embodiments, the first condenser 108 can
operate in other suitable fashion. Even though the first and second
condensers 108 and 110 are shown as separate components in FIG. 1,
in certain embodiments, the first and second condensers 108 and 110
may be combined into a single heat exchanger. In further
embodiments, one of the first and second heat exchangers 108 and
110 may be omitted.
[0023] The combustor 112 can be configured to react a combustible
gas with air and/or oxygen to produce electrical, heat, and/or
other forms of energy. In the illustrated embodiment, the combustor
112 includes a gas turbine coupled to an electrical generator. In
other embodiments, the combustor 112 can also include a gasoline
engine, a diesel engine, a ramjet, and/or other suitable combustion
components. In further embodiments, the combustor 112 may be
omitted.
[0024] The gasification reactor 118 can be configured to convert a
carbonaceous material into a combination of hydrogen, carbon
monoxide, carbon dioxide, and/or other suitable gaseous components.
The gasification reactor 118 can include a counter-current fixed
bed gasifier, a co-current fixed bed gasifier, a fluidized bed
reactor, an entrained flow gasifier, and/or other suitable types of
gasifier.
[0025] In operation, the biomass 1 is provided to drier 102. The
drier 102 dries the biomass 1 with, for example, the combustion gas
6 from the combustor 112. The dried biomass 2 then enters the
torrefaction unit 104 to be pre-treated prior to pyrolysis. In
certain embodiments, the torrefaction unit 104 heats the dried
biomass 2 to a desired temperature (e.g., about 200.degree. C. to
about 300.degree. C.) for a treatment period (e.g., 3 min to about
10 hours) with a portion of the synthetic gas 15 from the reformer
116 as a carrier gas.
[0026] The pre-treatment temperature and time may depend on each
other. For example, a high pre-treatment temperature may require a
short treatment time and vice versa. Without being bound by theory,
it is believed that pre-treating the biomass 1 in the torrefaction
unit 104 can (1) remove at least part of the hemicellulose and
acetic acid from the solid matrix; (2) reduce the degree of
polymerization of cellulose and increase crystallinity of the
cellulose; (3) de-polymerize at least part of the lignin; and (4)
weaken biomass fibrous structure for ease of grinding.
[0027] The pre-treated biomass is then provided to the pyrolysis
reactor 106 in which the biomass is thermally converted at
temperatures between 400 and 500.degree. C. into a vapor phase
pyrolysis product 3 and bio-char 8. In certain embodiments, the
pre-treated biomass provided to the pyrolysis reactor 106 may
contain additives (e.g., H.sub.2SO.sub.4, (NH.sub.4).sub.2HPO.sub.4
and (NH.sub.4).sub.2SO.sub.4) at concentrations of about 0.1 mass %
or other suitable concentration values. The additional of such
additives are believed to enhance the production of anhydrosugars
from biomass. In other embodiments, the pyrolysis reactor 106 may
contain other suitable compositions.
[0028] In the illustrated embodiment, the first and second
condensers 108 and 110 may then condense the pyrolysis product 3
with ambient air 17 (and/or other suitable coolant) to separate and
collect different fractions from the pyrolysis product 3 and
produce heated air streams 18 and 19, which is provided to the
combustor 112. In other embodiments, the first and second
condensers 108 and 110 may both cool the pyrolysis product 3 with
ambient air.
[0029] The temperature in the first condenser 108 can be controlled
to separate heavier compounds (e.g., phenols and sugars) from light
compounds (e.g., acetic and formic acid). A bio-oil 9 can be
separated via solvent extraction (e.g., with ethyl acetate) and/or
other suitable techniques to produce a stream rich in phenols and
pyrolytic sugars. A first fraction of the bio-oil 9, which is rich
in sugar can then be hydrolyzed, detoxified and fermented to
produce ethanol and/or can be subject to other types of suitable
processing to produce other hydrocarbons. A second fraction of the
bio-oil 9, which is rich in phenols can be converted into green
gasoline via hydro-treatment and/or other suitable processes, as
described in more detail below with reference to FIG. 2.
[0030] The second condenser 110 can then receive an output stream 4
from the first condenser 106 and collect an aqueous stream 10 from
the pyrolysis product 3. The aqueous stream 10 is then supplied to
the reformer 116 via the boiler 114 to produce a synthetic gas 20.
The synthetic gas 20 is then provided to the combustor 112 for
conversion into electricity and/or other forms of energy.
Optionally, the aqueous stream 10 can be gasified with the bio-char
8. The gasification reactor 118 can convert at least a portion of
the bio-char 8 into a synthetic gas 14 provided to the reformer 116
and output the rest of the bio-char 8 as char and ash. In other
embodiments, the bio-char 8 may be provided to the combustor 112
and/or otherwise processed. In further embodiments, the bio-char 8
may form a final product of the process.
[0031] Several embodiments of the technology utilize pretreatment
with specific temperatures to produce the bio-oil 9 that is more
enriched in sugars, less corrosive, more stable than conventional
bio-oils. Without being bound by theory, it is believed that
biomass degradation via pyrolysis may be classified into three
general categories: de-polymerization, fragmentation, and
polycondensation. Depolymerization reactions are believed to yield
primarily monomers that are greater than five carbons. Such
monomers may be either carbohydrodrate (from
cellulose/hemicellulose) or aromatic (from lignin). Fragmentation
reactions are believed to lead to the formation of small molecules
that are typically smaller than five carbons. Poly-condensation
reactions are believed to result in the formation of charcoal.
Pyrolysis reactors can reduce the formation of char by having very
high heating rates which may reduce the time the material is in the
temperature range of 270-350.degree. C. in which dehydratation and
crosslinking reactions are favored.
[0032] Several embodiments of the system 100 can alter the
structural properties of the biomass 1 for improving the
selectivity to favor depolymerization reactions and improve the
bio-oil quality produced during pyrolysis. Several factors are
believed to influence whether degradation proceeds via
fragmentation or de-polymerization reactions. The presence of
alkaline is believed to strongly catalyze fragmentation reactions.
Other factors such as degree of polymerization, crystallinity, and
the interactions lignin/cellulose are also factors that can be
adjusted to improve reaction selectivity toward de-polymerization
(formation of precursors of transportation fuels). Thus, by
increasing the crystallinity and reducing the degree of
polymerization via heating in the temperature range of about
200.degree. C. to about 300.degree. C. (in the presence or absence
of steam), the reaction selectivity to de-polymerization may be
improved.
[0033] Several embodiments of the systems and processes can also
have substantial energy savings as a result of pretreatment for
grinding operations. The pretreatment not only removes components
of the material, it may also attenuate the physical integrity and
reduce the energy required to reduce particle sizes to what is
required for the pyrolysis reactor. It should be noted that
grinding can contribute to as much as 10% of the total energy in
the biomass.
[0034] FIG. 2 is a schematic diagram illustrating a process 200 for
performing bio-oil refining in accordance with embodiments of the
disclosure. As shown in FIG. 2, the process 200 can include
separating a phenolic fraction from an aqueous fraction in the
bio-oil 9. Techniques suitable for this separation can include
liquid-liquid extraction with water, an organic solvent, and/or
other suitable materials. The phenolic fraction can then be
hydro-treated with hydrogen to produce green gasoline. The aqueous
fraction can be (1) hydro-treated under high pressure to produce
green diesel; (2) hydrolyzed, neutralized, and detoxified to
produce lipids; and/or (3) hydrolyzed, neutralized, detoxified, and
fermented to produce alcohol.
[0035] FIG. 3A is a schematic diagram illustrating an reactor 300
in accordance with embodiments of the technology. As shown in FIG.
3A, the reactor 300 includes a feeder 302 coupled to a treatment
zone 304 having a first end 303a and a second end 303b. The feeder
302 can include a screw pump and/or other suitable material moving
components. The treatment zone 30 can include a generally helical
auger (or screw) 307 and/or other suitable structures inside a
housing 305 and a motor 320 operatively coupled to the auger
320.
[0036] The reactor 300 also includes a heat exchanger 306 and a
furnace 308 on the housing 305 and a power supply/controller 310
operatively coupled to the furnace 308. The reactor 300 further
includes a solid container 312 and a condenser 314 proximate to the
second end 303b of the treatment zone 304. Optionally, the reactor
300 includes a plurality of cooling traps 316 coupled to the
condenser 314 for collecting condensed materials.
[0037] In operation, the feeder 302 forces biomass (shown as
separate spheres in FIG. 3A for illustration purposes) to enter the
treatment zone 304 via the first end 303a along with an optional
carrier gas. The heat exchanger 306 and the furnace 308 then heats
the biomass to a desired temperature while the auger 307 moves the
biomass toward the second end 303b and reduces the size of the
biomass. Solid portions of the biomass are then collected at the
solid container 312 while volatile portions are collected at the
condenser 314 and/or the cooling traps 316.
[0038] A single reactor 300 may be used for both pre-treating and
pyrolysis of the biomass. For example, the biomass may be processed
in the reactor 300 at a first temperature (e.g., about 200.degree.
C. to about 300.degree. C.). The collected solid portions may then
be returned to the feeder 302 to be provided to the auger 304 and
processed at a second temperature (e.g., about 500.degree. C. to
about 600.degree. C.).
[0039] In other embodiments, as shown in FIG. 3B, the reactor 300
may include more than one treatment zones (e.g., by having more
than one furnaces) such that the pre-treatment and pyrolysis
operations may be performed in a continuous fashion. Several
components shown in FIG. 3B are generally similar in structure and
function as those shown in FIG. 3A. As a result, common acts and
structures are identified by the same reference numbers.
[0040] As shown in FIG. 3B, the reactor 300 can include a first
treatment zone 304a coupled to a second treatment zone 304b. The
first treatment zone 304a can include a first auger (or screw) 307a
inside a first housing 305a having a first end 303a and a second
end 303b. The first auger 307a can be operatively coupled to a
first motor 320a. The first treatment zone 304a also includes a
first furnace 308a proximate to the first housing 305a and
operatively coupled to a first power supply/controller 310a. The
first treatment zone 304a also includes a carrier gas inlet 324a
and a carrier gas outlet 324b in fluid communication with the auger
307a.
[0041] Optionally, the first treatment zone 304a can also include a
grinder 322 and/or other suitable components configured to reduce a
physical size of the biomass in the first treatment zone 304a. In
the illustrated embodiment, the grinder 322 is proximate to the
second end 303b of the first treatment zone. In other embodiments,
the grinder 322 may be at other locations of the first treatment
zone or may be omitted.
[0042] The second treatment zone 304b can have generally similar
components as the first treatment zone 304a. For example, the
second treatment zone 304b can include a second auger 307b in a
second housing 305b and operatively coupled to a second motor 320b.
The second treatment zone 304b can also include a second furnace
308b proximate to the second housing 305b and operatively coupled
to a second power supply/controller 310b.
[0043] In operation, the feeder 302 forces biomass to enter the
first treatment zone 304a via the first end 303a along with an
optional carrier gas via the carrier inlet 324a. The heat exchanger
306 and the first furnace 308a then heats the biomass to a first
temperature (e.g., about 200.degree. C. to about 300.degree. C.)
while the auger 307 moves the biomass toward the second end 303b.
The optional grinder 322 can then reduce the biomass from the first
treatment zone 304a to particle sizes less than about 2 mm before
the biomass is provided to the second treatment zone 304b. The
second furnace 308b can then heat the biomass to a second
temperature (e.g., about 500.degree. C. to about 600.degree. C.) to
thermally convert the biomass via pyrolysis. Solid portions of the
biomass are then collected at the solid container 312 while
volatile portions are collected at the condenser 314 and/or the
cooling traps 316.
[0044] Even though embodiments of the reactor 300 are shown in
FIGS. 3A and 3B as being carried by a cart, in other embodiments,
various components of the reactor 300 may be separately and/or
fixedly installed. In other embodiments, the reactor 300 may
utilize other components for conveying and/or reducing size of the
biomass. For example, in certain embodiments, at least one of the
first and second augers 307a and 307b may be omitted in the reactor
300 shown in FIG. 3B. Instead, the reactor 300 may carry the
biomass through the treatment zones 304a and 304b pneumatically,
hydraulically, and/or via other suitable means. In further
embodiments, the biomass may be treated in at least one of the
first and second treatment zones 304a and 304b in a batch mode. In
yet further embodiments, the reactor 300 can include three, four,
and/or other suitable number of treatment zones with similar or
different configurations.
EXAMPLES
[0045] Tests were conducted to understand the effect of
torrefaction conditions (temperature and presence of oxygen) and
pyrolysis temperatures on the selectivity of pyrolysis reactions
towards the production of anhydrosugars were carried out in our
Py-GC/MS. The pretreatment was performed at temperatures ranging
from 200 to 320.degree. C. Pyrolysis tests were conducted at
temperatures between 350 and 550.degree. C. The tests were carried
out with Avicel (crystalline cellulose with low degree of
polymerization), .alpha.-cellulose (a blend of cellulose and
hemicellulose), wheat straw and the woody fraction of Douglas Fir
(containing cellulose, hemicelluloses and lignin). Before
conducting the Py-GC/MS studies, the alkalines in all the samples
were removed with hot water (at 120.degree. C.).
[0046] The Py-GC/MS tests were carried using a CDS pyro-probe 5000
connected in-line to an Agilent GC/MS. Samples were loaded into a
quartz tube and gently packed with quartz wool prior to pyrolysis.
The samples were kept for 3 minutes at the pretreatment temperature
before the oven temperature was reduced to 210.degree. C. The
samples were kept in these conditions for 1 minute. Samples were
pyrolysed by near instantaneous heating to the final temperature
and held at this temperature for 3 minutes.
[0047] The GC/MS inlet temperature was maintained at 250.degree. C.
and the resulting pyrolysis vapors were separated by means of a 30
m.times.0.25 .mu.m inner diameter column. The column was heated at
3.degree. C./min from 40 to 280.degree. C. The gas was then sent
into a mass spectrometer and the spectra of the most important
peaks were compared to an NBS mass spectra library to establish the
identity of each compound.
[0048] FIG. 4 shows the ratio of the area of the peaks in the
Py-GC/MS chromatogram assigned to levoglucosan (a product of
cellulose depolymerization reactions) and to hydroxyacetaldehyde (a
product of cellulose fragmentation reactions). This ratio can be
used as an index of the selectivity of thermochemical reactions
towards the production of anhydrosugars. FIG. 4 shows that a mild
torrefaction in the range of temperature between 200 and
320.degree. C. can enhance the production of levoglucosan for
.alpha.-cellulose, wheat straw and the wood fraction of Douglas
Fir.
[0049] The presence of oxygen during torrefaction had a positive
effect on wheat straw. For all the other biomasses, the presence of
oxygen during pretreatment is detrimental to the yield of sugar
obtained. In the case of Wheat Straw the highest selectivity
towards the production of anhydrosugars was obtained for samples
pretreated at temperature over 270.degree. C. in the presence of
oxygen. For Douglas Fir the best results were achieved for samples
pretreated in the absence of oxygen at temperatures over
230.degree. C. It is noteworthy that a drastic increase in the
selectivity towards the production of levoglucosan was also
observed when the Douglas Fir wood was heated in the presence of
oxygen at temperatures over 310.degree. C.
[0050] FIG. 5 shows the changes of levoglucosan/furfural ratios as
a function of pyrolysis temperature in accordance with embodiments
of the technology. The pretreatment temperature does not have any
effect on the Levoglucosan/furfural ratios for the Avicel. This
result suggests that Avicel was not dehydrated in the pretreatment
conditions tested. In the case of .alpha.-cellulose, an increase in
the levoglucosan/furfural ratio was observed as the pretreatment
temperature increases. The presence of oxygen during pretreatment
of .alpha.-cellulose and Avicel causes a reduction in the
levogluocan/Furfural ratio for most of the materials but not for
the wheat straw. The conditions improving the ratio
levoglucosan/furfural are very similar to those improving the ratio
levoglucosan/hydroxyacetaldehyde.
[0051] FIGS. 6 and 7 show the ratio of levoglucosan and other
products of oxidation reactions in accordance with embodiments of
the technology. With the exception of wheat straw, the shapes of
the curves describing the evolution of the levoglucosan/carbon
dioxide and levoglucosan/acetic acid ratio are similar to those
shown in FIGS. 4 and 5. For the wheat straw there is a maximum for
samples pretreated in the presence of oxygen. This maximum could
indicate the temperature at which oxidation reactions responsible
for the formation of CO.sub.2 and acetic acid accelerate.
[0052] FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a
function of pretreatment temperature. The conditions improving this
ratio were similar to those improving the levoglucosan/CO2 and
levoglucosan/acetic acid ratios. But, pre-treating biomass in the
presence of oxygen considerably increases the production of
mono-phenols due to the oxidation of lignin linkages. According to
our results the levoglucosan/2-methoxy phenol ratio can be improved
if the wheat straw is pretreated at a 270.degree. C. in the
presence of oxygen. The presence of oxygen was detrimental for the
Douglas Fir.
[0053] The effect of pyrolysis temperatures on the selectivity of
thermochemical reactions towards the production of levoglucosan in
unpretreated samples is shown in FIG. 9. The results indicate that
as the pyrolysis temperature increases the fragmentation reactions
responsible for the formation of hydroxyacetaldehyde are favored
over the depolymerization reactions responsible for the formation
of anhydrosugars. Although this behavior was observed for all the
samples, the effect of temperature was more pronounced for the
Avicel and for the .alpha.-cellulose. Materials containing lignin
show a much less pronounced effect.
[0054] Tests on auger pyrolysis were also conducted. Douglas Fir
wood was pre-treated at select conditions identified by Py-GC/MS
and was subject to pyrolysis in the Auger Pyrolysis reactor built
at Washington State University (generally similar to that shown in
FIG. 3A). During testing, 200 g of Douglas Fir samples were added
into 3 L of deionized water. The biomass and the water were heated
in an autoclave (Consolidated Stills & Sterilizers) at
120.degree. C. for 20 min.
[0055] The water and the solid were separated by filtration. The
solid was dried overnight at 105.degree. C. For every 200 g of
biomass 175 g of pre-treated samples were obtained (87.5 mass %).
These samples were further subject to a mild torrefaction in the
same Auger reactor but using lower wall temperatures (e.g.,
270.degree. C.). The reactor was operated under a nitrogen
atmosphere (flow rate of nitrogen: 3 l/min) and the biomass
particles were conveyed through the Auger at 5.2 rpm (Pretreatment
time: 2.5 minutes).
[0056] Pyrolysis tests on the pre-treated samples were carried out
in the same Auger Pyrolysis reactor. The reaction conditions were
the following: Auger speed: 13 rpm (residence time of particles in
the reactor: 1 minute), hopper feeding rate: 43.6 rpm, pressure
inside the reactor: 1 atm., carrier gas: N2, flow rate: 10 l/min,
temperature in the wall of the reactor: 500.degree. C., post-oven
temperature 420.degree. C.; estimated heating rate: (4-7.degree.
C./s or 240-420.degree. C./min). Although the heating rates
achieved are lower than the 10-1000.degree. C./s needed for fast
pyrolysis reactors it is still faster than the 10.degree. C./min
typically reported for slow pyrolysis. The yield of products
obtained with Douglas Fir as received and after hot water and
thermal pretreatment at 270.degree. C. for 3 minutes are shown in
Table 1. The oil produced in our system is a single phase oil very
similar to those produced in fast pyrolysis reactors.
TABLE-US-00001 TABLE 1 Hot Water Hot Water + Oven Original Douglas
Fir Pretreatment Pretreatment Bio-oil 55.4 .+-. 4.6 57.1 .+-. 1.1
56.8 .+-. 3.6 Char 22.7 .+-. 5.0 17.4 .+-. 0.5 19.5 .+-. 4.8 Gas
21.7 .+-. 0.6 25.5 .+-. 1.6 23.7 .+-. 1.3
[0057] Production of ethanol from pyrolytic sugars was also
investigated. Two bio-oils were used to produce ethanol. The first
bio-oil produced from a hardwood provided by Dynamotive. The second
bio-oil studied was produced in a fast pyrolysis reactor at Monash
University (Australia) using as a feedstock a softwood bark. The
name and the content of each of the species quantified by GC/MS and
by Karl Fischer Titration are listed in Table 2.
TABLE-US-00002 TABLE 2 Softwood Bark Dynamotive Compound Oil
(Monash) Oil 1 Water 13.92 29.35 2 Glycolaldehyde 1.41 1.62 3
Acetic Acid 1.17 3.30 4 Acetol 1.56 2.67 5 Toluene 0.003 0.001 6
Cyclopentanone 0 0.002 7 2-Furaldehyde 0 0.52 8
2-Cyclopenten-1-one, 2-methyl- 0 0.04 9 2(5H)-Furanone 0 0.36 10
2-Furanethanol, b-methoxy-(S)- 0.35 0.83 11 Phenol 0.58 0.29 12
O-Cresol 0.28 0.14 13 p-Cresol and m-Cresol 0.55 0.18 14 Phenol,
2-methoxy- 1.81 1.07 15 Phenol, 2,4-dimethyl- and 0.31 0.12 Phenol,
2,5-dimethyl- 16 Phenol, 4-ethyl- 0.26 0.08 17 Phenol,
3,4-dimethyl- 0.22 0 18 Phenol, 2-methoxy-4-methyl- 0.80 0.29 19
Pyrotechol 1.14 0.67 20 1,2-Benzenediol, 3-methyl- 0.71 0 21
Phenol, 4-ethyl-2-methoxy- 0.43 0.17 22 1,2-Benzenediol, 4-methyl-
1.56 0 23 Syringol 0 1.11 24 Eugenol 0.31 0.13 25 Phenol,
2-methoxy-4-propyl- 0.21 0.09 26 4-Ethylcatechol 0.16 0 27 Vanillin
0.45 0.30 28 Phenol, 2-methoxy-4-(1- 0.76 0.05 propenyl)-, (E)- 29
1,6-Anhydro-b-D-Glucose 3.61 4.07 30 2-Propanone, 1-(4-hydroxy-3-
0.52 0 methoxyphenyl)- 31 Syringaldehyde 0 0.50 32 Phenanthrene,
1-methyl-7- 0.003 0 (1-methylethyl)- Total 33.09 47.9
[0058] As shown in Table 2, the softwood bark derived oil produced
at Monash contains significantly less water than the oil provided
by Dynamotive. The content of phenols in the softwood bark derived
oil is higher than in the oil provided by Dynamotive.
[0059] Table 3 shows the content of sugars in the oil produced by
Dynamotive. The glucose quantified in this oil was derived from the
hydrolysis of levoglucosan, cellobiosan and other
oligo-anhydrosugars. The content of glucose (a fermentable sugar)
in these oils is approximately 5.02 mass %. This concentration of
sugar is suitable for fermentation. The other sugars derived from
hemicelluloses (fucose, arabinose, galactose, mannose/xylose,
fructose, ribose) accounted for 1.08 mass % of this oil.
TABLE-US-00003 TABLE 3 Sugars Content (mass %) Fucose 0.058
Arabinose 0.105 Galactose 0.197 Glucose 5.028 Mannose/Xylose 0.586
Fructose 0.115 Ribose 0.019 Total sugars 6.108
[0060] Although the bulk of the phenolic compounds from bio-oil can
be extracted with the ethyl acetate, small concentrations of these
toxic compounds remain in the aqueous phase together with most of
the sugars. The nature and the range of lethal concentrations of
many of these toxic compounds was not well known. Thus, we carried
out tests with model compounds to identify which of them were toxic
to yeasts.
[0061] The toxic effects of selected bio-oil compounds (acetic
acid, propanoic acid, cyclopentanone, 2-furaldehyde, furfuryl
alcohol, phenol, eugenol, acetol, 2-(5H)-furanone, stilbene,
vanillin, syringaldehyde, o-cresol) on Saccharomyces cerevisiae
were studied. The concentration of each of the compounds tested was
25, 50, 75 and 100% of the concentration found in bio-oils (CFBO)
for a fast pyrolysis oil derived from Mallee which was produced at
a pyrolysis temperature of 500.degree. C. The inhibition rate
estimated for the compounds studies is shown in Table 4.
TABLE-US-00004 TABLE 4 25% of 50% of 75% of 100% of N.sup.o
Compound CFBO CFBO CFBO CFBO 1 Acetic acid 97.75 97.75 97.96 98.24
2 Propanoic acid 97.01 97.54 97.82 98.00 3 Cyclopentanone -22.07
-5.26 -4.41 21.73 4 2-furaldehyde 7.81 7.98 11.03 95.89 5 Furfuryl
alcohol 5.94 6.90 7.81 7.81 6 Phenol 76.95 96.95 97.45 97.67 7
Eugenol 97.04 97.22 96.64 97.04 8 Acetol 44.17 77.80 78.93 80.07 9
2-(5H)-Furanone 3.057 5.89 8.83 10.42 10 Stilbene 9.17 32.62 37.89
45.07 11 Vanillin 81.54 82.45 81.77 81.88 12 Syringaldehyde 71.68
79.95 81.54 81.99 13 O-cresol 2.61 14.16 23.38 31.22 14 O-xylol
5.01 5.23 5.33 5.44 15 Pyrocatechol 84.53 90.48 91.67 92.10 16
Palmitic acid 2.63 0.36 -2.02 -4.19 17 Toluene -0.72 1.00 1.66 2.09
18 Tetradecane 1.11 4.68 10.53 10.64 19 Petadecane 4.68 7.39 8.90
9.78
[0062] As shown in Table 4, the carboxylic acids (acetic acid and
propanoic acid) and the phenols (phenol, eugenol, vanillin,
syringaldehyde, pyrocatechol) are the most lethal compounds
inhibiting yeast growth. The furans (furaldehyde, furfuryl alcohol,
2-(5H)-furanone) and the alkanes (tetradecane, pentadecane) are
also inhibitors but their inhibition rate is much lower.
[0063] Extraction of phenols, hydrolysis, detoxification and
fermentation of pyrolytic sugars were also tested. Ethyl-acetate
was the solvent used for the extraction of compounds from the
bio-oil. The method employed to separate the phenols is similar to
the one patented by NREL for the production of resins. Briefly,
blends of ethyl acetate/bio-oil with mass ratio of 1:1 were
prepared. The blends were shaken for 10 minutes at 30.degree. C.
and were left to equilibrate for over 6 hours. The organic phase
rich in ethyl acetate which contains most of the phenols was
separated by decantation and the ethyl acetate solubilised in the
aqueous phase removed with a rotary evaporator at 80.degree. C.
[0064] The sugars in the aqueous phase (levoglucosan, cellobionsan)
were hydrolysed using H.sub.2SO.sub.4 as catalyst to produce
glucose. The phenols remaining in the aqueous phase were removed by
adsorption on activated carbon. An activated carbon/aqueous
solution volume ratio of 1:1 was employed. The aqueous solution was
left overnight at 4.degree. C. in the refrigerator and the slurry
formed was filtrated to obtain a colorless liquid. The aqueous
solution containing the sugars was then neutralized to pH 7 with
solid barium hydroxide. Under these conditions the free sulfuric
acid and the acetic acid present in the aqueous phase are removed
as precipitated salts.
[0065] The content of sugars in the detoxified solution was
quantified by Ion Exchange Chromatography and the detoxified
aqueous phase rich in sugars was then fermented. Briefly, YPD media
was prepared by taking 25 ml of the detoxified solution obtained in
the previous step, 2 mass % yeast extract and 1% mass peptone. 10
vol of Saccharomyces cerevisiae seed culture media was then
inoculated in the YPD media. The media was cultured at 30.degree.
C. and the micro-organism growth, sugar consumption and ethanol
production were monitored by UV-Vis, ion exchange chromatography,
and GC-FID. The initial content of glucose in the detoxified
aqueous phases from the Dynamotive oil and from the oil produced in
Monash University were 2.6 and 2.0 mass % respectively. Clearly the
solvent extraction method should be further improved. Control
solutions containing the same concentrations of glucose were also
fermented.
[0066] FIG. 10 shows a glucose content as a function of
fermentation time. Based on the consumption of glucose it appears
that the fermentation process happened mainly during the first 5
hours. No major difference was observed between the behavior of the
control and the solutions derived from pyrolysis oils.
[0067] FIG. 11 shows a rate of microbial growth in solutions
derived from bio-oils and in control solutions produced with
glucose. As shown in FIG. 11, most of the growth happened in the
first 5 hours and that the growth in the solution derived from
bio-oil was comparable with the growth obtained with the control
solution prepared with glucose. Very little microbial growth was
observed after the first 5 hours.
[0068] FIG. 12 shows ethanol concentration as a function of
fermentation time. High concentrations of ethanol were produced
(12-16 g/L) during the first 5 hours. The production of ethanol
slowed down after almost the same time that the content of glucose
in the solution was depleted. The production of ethanol from the
solutions derived from bio-oils was comparable to the production of
ethanol from the control. The effect of any inhibitor remaining in
the solution was negligible.
[0069] Fatty acids were produced from glucose using oleaginous
yeasts (Cryptococcus curvatus and Rhodotorula glutinis yeasts).
These yeasts were cultured for periods varying between 24 and 144
hours on a mixture rich in xylose and glucose which were derived
from pyrolysis oils. The initial content of glucose in the solution
was 6.8 mass %.
[0070] FIG. 13 shows sugar consumption and production of fatty
acids as a function of fermentation time in accordance with
embodiments of the technology. Microorganisms with fat content
ranging from 28 to 68 mass % were obtained with the Cryptococcus
curvatus. Lower fat contents (between 13 and 45 mass %) were
obtained with Rhodotorula glutinis. The most important fatty acids
found in Cryptococcus curvatus were: palmitic (C16:O) (20 mass %),
stearic (C18:O) (20 mass %) and oleic (48 mass %) acids. A slightly
different fatty acid profile was observed for the Rhodotorula
glutinis: palmitic (15 mass %), stearic (20 mass %) and oleoic: (51
mass %).
[0071] From the foregoing, it will be appreciated that specific
embodiments of the technology have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the technology. Many of the elements of
one embodiment may be combined with other embodiments in addition
to or in lieu of the elements of the other embodiments.
Accordingly, the technology is not limited except as by the
appended claims.
* * * * *