U.S. patent application number 13/856443 was filed with the patent office on 2013-08-29 for systems, methods and compositions relating to combustible biomaterials.
This patent application is currently assigned to Agni Corporation (Cayman Island). The applicant listed for this patent is Agni Corporation (Cayman Island). Invention is credited to Nicholas Carlin, Sumer Johal, John J. McNamara, Pauravi Shah.
Application Number | 20130219780 13/856443 |
Document ID | / |
Family ID | 44814572 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130219780 |
Kind Code |
A1 |
Johal; Sumer ; et
al. |
August 29, 2013 |
SYSTEMS, METHODS AND COMPOSITIONS RELATING TO COMBUSTIBLE
BIOMATERIALS
Abstract
A composition of biomass material is disclosed. The composition
includes: (i) a lignocellulosic material; and (ii) at least one
member selected from a group comprising of potassium, sodium and
chlorides, wherein said at least one member comprising not more
than about 0.01% (by weight) of said composition. The composition
may not include more than 10% of water.
Inventors: |
Johal; Sumer; (Concord,
CA) ; Carlin; Nicholas; (Bay Point, CA) ;
Shah; Pauravi; (San Francisco, CA) ; McNamara; John
J.; (El Sobrante, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Agni Corporation (Cayman Island); |
|
|
US |
|
|
Assignee: |
Agni Corporation (Cayman
Island)
Grand Cayman
KY
|
Family ID: |
44814572 |
Appl. No.: |
13/856443 |
Filed: |
April 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12941023 |
Nov 5, 2010 |
8425635 |
|
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13856443 |
|
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61326998 |
Apr 22, 2010 |
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Current U.S.
Class: |
44/605 |
Current CPC
Class: |
Y02E 50/30 20130101;
Y02E 50/10 20130101; Y02E 50/15 20130101; B08B 3/04 20130101; C10L
9/083 20130101; C10L 5/445 20130101; C10L 5/363 20130101; C10L 5/44
20130101 |
Class at
Publication: |
44/605 |
International
Class: |
C10L 5/44 20060101
C10L005/44 |
Claims
1. A composition of biomass material, comprising: a lignocellulosic
material; and chlorides comprising not more than about 0.1% (by
weight) of said composition.
2. The composition of biomass material in claim 7, wherein said
composition comprises not more than 10% of water.
3. The composition of claim 7, wherein a heat value of said biomass
material is between about 15,000 kJ/kg and about 20,000 kJ/kg.
Description
RELATED APPLICATION
[0001] The application is a divisional application of U.S. patent
application Ser. No. 12/941,023, filed Nov. 5, 2010, which further
claims priority from U.S. Provisional Application having Ser. No.
61/326,998, filed on Apr. 22, 2010, which is incorporated herein by
reference for all purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to production of
combustible biomaterials. More particularly, the present invention
relates to novel systems, methods, and compositions relating to
production of combustible biomaterials from one or more different
types of agricultural residue.
[0004] 2. Background of the Invention
[0005] High demand for fuel and energy, and a decrease in
conventional energy supplies, such as oil and natural gas, are
driving exploration of renewable energy sources such as biofuels.
Renewable energy sources are desirable because they are available
long after conventional energy supplies have been depleted.
Specifically, biomass, a resource abundantly and renewably present
in nature, is the source for production of biofuels.
[0006] In an attempt to harness energy from biomass, conventional
systems and methods attempt to burn biomass in biomass-fired
combustors at industrial-grade temperatures, typically ranging from
800.degree. C. to 1200.degree. C. Unfortunately, such attempts are
futile because biomass treated in this manner simply does not burn.
Moreover, high-temperature treatment of biomass according to
conventional attempts suffers from certain drawbacks. By way of
example, high-temperature treatment of biomass produces ash, which
typically includes alkali and alkaline earth chlorides, sulfates,
carbonates, and complex silicates, which accumulate on various
combustor components, such as tubes carrying solvents for
heating.
[0007] As another example, at high temperatures inside the
combustion chamber, the silicates combine with potassium and sodium
to form silica glass chunks, which also accumulate on and clog the
provisions for ash disposal.
[0008] Such undesirable accumulations of ash and silica glass
chunks result in fouling and slagging inside the combustion
chamber, eventually leading to a decline in combustor efficiency
and capacity. Specifically, heat efficiency during the attempted
combustion process is significantly diminished, and restricted flow
through the combustor causes mechanical damage. To this end,
premature shutdown of the system for maintenance and removal of the
accumulated undesired deposits is necessary. As a result,
conventional systems and processes realize lower throughput for
energy production. More than that, there may well be permanent
damage to the combustor (e.g., it may undergo corrosion, or require
significant repair, or even replacement). This translates into
increased capital costs for the conventional systems and processes,
which rely on biomass for energy production.
[0009] What is therefore needed are novel systems, methods, and
compositions that harness energy from biomass without suffering
from the drawbacks encountered by the conventional systems and
processes of biomass treatment.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, in one aspect, the present
invention provides a method for making combustible biomaterial. The
method includes: (i) receiving one or more types of biomass, each
of which includes a combustion-retarding material; (ii) rupturing
lignocellulose in the one or more types of biomass to produce
ruptured biomass including the combustion-retarding material; (iii)
washing the ruptured biomass with solvent to drive
combustion-retarding materials from the ruptured biomass into the
solvent to produce a combustion-retarding-material-enriched solvent
and a combustion-retarding-material-depleted ruptured biomass; and
(iv) pyrolyzing the combustion-retarding-material-depleted ruptured
biomass to produce a combustible biomaterial. At least one of the
one or more types of biomass may include at least one member
selected from a group consisting of rice straw, sugar cane leaves,
cotton stalks, mustard stalks, pine needles, coffee husks, coconut
husks, rice husks, mustard husks, weed straw, corn stover, sugar
cane bagasse, millet stalks, pulses stalks, sweet sorghum stalks,
nut shells, animal manure, guar husk, acacia totalis, julia flora,
jatropha residue, wild grass, pigeon beans, pearl millet, barley,
dry chili, gran jowar, linseed, maize/corn, lentil, mung bean,
sunflower, til, oil seed stalks, pulses/millets, black gram, sawan,
soybean stalks, cow gram, horse gram, finger millet, turmeric,
castor seed, meshta, sannhamp, and hemp. In certain embodiments of
the present invention, rupturing is carried out by crushing or
chopping the lignocellulose in the biomass. Preferably, the
ruptured biomass including the combustion-retarding material is
washed for a time that is between 20 minutes and 60 minutes.
[0011] In one embodiment of the present invention, the solvent
includes H.sub.2O. In preferred embodiments of the present
invention, the solvent includes H.sub.2O or H.sub.2SO.sub.4.
Preferably, the solvent has a pH that is between about 4 and about
7. In preferred embodiments of the present invention, the solvent
is maintained at a temperature that is between about 30.degree. C.
and about 70.degree. C., and in more preferred embodiments of the
present invention the solvent is maintained at about 50.degree.
C.
[0012] In preferred embodiments of the present invention, the
washing includes washing ruptured biomass using recycled solvent.
Preferably, recycled solvent is maintained at a temperature of
between about 30.degree. C. and about 70.degree. C., and more
preferably, the recycled solvent is maintained at a temperature of
about 50.degree. C.
[0013] In preferred embodiments of the present invention,
pyrolyzing is carried out at temperature that is between about
100.degree. C. and about 500.degree. C., and more preferably,
pyrolyzing is carried out at a temperature that is between about
250.degree. C. and about 350.degree. C. Pyrolyzing may be carried
out in the absence of oxygen. Preferably, pyrolyzing is carried out
for a time that is between about 10 minutes and about 24 hours.
Inventive methods may further include densifying the combustible
biomaterial to produce biocoal. Densifying may be carried out using
a pelletizer to produce biocoal pellets.
[0014] Inventive methods may further still include soaking the
ruptured biomass in the solvent before the washing the ruptured the
biomass. Preferably, soaking is carried out at a temperature that
is between about 30.degree. C. and about 70.degree. C. Also,
preferably, soaking is carried for a duration that is between about
30 minutes and about 60 minutes. Also, preferably, the solvent has
a pH that is between about 4 and about 7.
[0015] In preferred embodiments, inventive methods also include
screw-pressing the combustion-retarding-material-depleted ruptured
biomass to squeeze out the residual solvent after washing the
ruptured biomass. Other preferred embodiments of the present
invention, further still include drying the
combustion-retarding-material-depleted ruptured biomass after screw
pressing. Drying may include air drying the
combustion-retarding-material-depleted ruptured biomass or drying
the combustion-retarding-material-depleted ruptured biomass using
syngas produced from pyrolyzing, and wherein the syngas includes
one member selected from a group consisting of CO.sub.2, CO,
CH.sub.4, and H.sub.2.
[0016] In another aspect, the present invention provides a method
for washing biomass. The method includes: (i) receiving a first
discrete amount of biomass; (ii) receiving a second discrete amount
of biomass; (iii) washing the first discrete amount of biomass with
solvent to produce a first effluent stream enriched with
combustion-retarding material; and (iv) washing the second discrete
amount of biomass with the first effluent stream to produce a
second effluent solvent stream. In one embodiment, the present
invention further provides a step of washing the second discrete
amount of biomass with the solvent after washing the first discrete
amount of biomass with the solvent. Inventive methods may further
include washing a third discrete amount of biomass with the second
effluent stream to produce a third effluent stream, such that the
third effluent stream has a higher concentration of
combustion-retarding material than the second effluent stream.
[0017] In preferred embodiments of the present invention, the
method includes washing different discrete amounts of biomass
ranging from a first discrete amount of biomass to an N discrete
amounts of biomass, and washing the Nth discrete amount of biomass
with an (N-1)th effluent stream, which results from washing (N-1)
discrete amounts of biomass, wherein N is a whole number that is
greater than 2. Preferably, washing the Nth discrete amount of
biomass produces an Nth effluent stream, which has a higher
concentration of combustion-retarding material than the (N-1)
effluent stream. The Nth effluent stream may be conveyed for
effluent treatment.
[0018] Inventive methods for producing combustible materials may
further still include collecting the first effluent stream in a
first collection chamber after washing the first discrete amount of
biomass. Further, such methods may include pumping the first
effluent stream to a position from where the first effluent stream
can be dispensed to wash the second discrete amount of biomass.
Similarly, inventive methods may further still include collecting
the second effluent stream in a second collection chamber after
washing the second discrete amount of biomass. Like the first
effluent stream, these methods may further still include pumping
the second effluent stream to a position from where the second
effluent stream can be dispensed to wash a third discrete amount of
biomass.
[0019] Unloading the first discrete amount of biomass after the
washing the first discrete amount of biomass with the solvent may
also be carried out as part of the inventive methods. Further, such
methods may include advancing the second discrete amount of biomass
to a position, from where washing of the second discrete amount of
biomass is carried out, and wherein the step of advancing is
performed after washing the first discrete amount of biomass.
[0020] In yet another aspect, the present invention provides a
method for washing biomass. The method includes: (i) receiving N
discrete amounts of biomass, wherein N is a whole number and is
greater than 2; (ii) conducting a first washing cycle, which
includes washing a first of N discrete amounts of biomass using a
solvent to produce a first effluent stream associated with the
first washing cycle, washing a second of N discrete amounts of
biomass using the first effluent stream associated with the first
washing cycle to produce a second effluent stream associated with
the first washing cycle and washing other discrete amounts of
biomass to satisfy a condition of washing the Nth discrete amount
of biomass using an (N-1)th effluent stream associated with the
first washing cycle; and (iii) conducting a second washing cycle,
which includes washing a second of N discrete amounts of biomass
using a solvent to produce a first effluent stream associated with
the second washing cycle, washing a second of N discrete amounts of
biomass using the first effluent stream associated with the second
washing cycle to produce a second effluent stream associated with
the second washing cycle and washing other discrete amounts of
biomass to satisfy a condition of washing the Nth discrete amount
of biomass using an (N-1)th effluent stream associated with the
second washing cycle.
[0021] Inventive methods of washing biomass may further include
conducting an Xth washing cycle, which includes washing an Xth of N
discrete amounts of biomass using a solvent to produce a first
effluent stream associated with the Xth washing cycle, washing an
(X+1)th of N discrete amounts of biomass using the first effluent
stream associated with the Xth washing cycle to produce a second
effluent stream associated with the Xth washing cycle and washing
other discrete amounts of biomass to satisfy a condition of washing
the Nth discrete amount of biomass using an (N-X)th effluent stream
associated with the Xth washing cycle, where X is a whole number
ranging from 3 to N.
[0022] In preferred embodiments of the present invention, each of N
discrete amounts of biomass is washed with the solvent. Preferably,
washing the first discrete amount of biomass is carried out by
spraying the solvent on the first discrete amount of biomass.
Preferably, the Nth discrete amounts of biomass is washed with a
volume of solvent that is between about 0.5 liters and about 4
megalitres. Preferably, the solvent is maintained at a temperature
that is between about 30.degree. C. and about 70.degree. C., and
more preferably, the solvent is maintained at a temperature that is
about 50.degree. C.
[0023] In preferred embodiments of the present invention, washing
the N discrete amount of biomass includes washing a total of the
biomass which weighs between about 1 metric ton and about 1000
metric tons. Preferably, each of the N discrete amounts of biomass
weighs between about 1 kg and about 100 metric tons. In preferred
embodiments of the present invention, each of the N discrete
amounts of biomass is washed with a volume of solvent that is
between about 0.5 liters and about 4 mega-liters. Preferably,
washing the first discrete amount of biomass occurs for a time that
is between about 20 minutes and about 60 minutes.
[0024] In preferred embodiments of the present invention, the first
effluent stream associated with the first washing cycle is
maintained at a temperature that is between about 30.degree. C. and
about 70.degree. C. More preferably, the first effluent stream
associated with the first washing cycle is maintained at a
temperature that is about 50.degree. C. In these embodiments,
inventive methods further include draining the first effluent
stream associated with the first washing cycle into a first
collection chamber. Inventive methods may further include a step of
pumping the first effluent stream associated with the first washing
cycle such that it is dispensed above the second of the N discrete
amount of biomass to produce the second effluent stream associated
with the first washing cycle. Collecting the second effluent stream
into a second collection chamber may be part of the inventive
methods of washing biomass.
[0025] In one embodiment of the present invention, receiving a
first discrete amount of biomass includes receiving in a first bin,
the first discrete amount of biomass and receiving a second
discrete amount of biomass includes receiving in a second bin, the
second discrete amount of biomass.
[0026] In yet another aspect, the present invention provides a
method for producing combustible biomaterial. The method includes:
(i) receiving one or more types of biomass, each of which includes
a combustion-retarding material; (ii) washing the biomass with a
solvent to drive combustion-retarding materials from the biomass
into the solvent to produce a
combustion-retarding-material-enriched solvent and a
combustion-retarding-material-depleted biomass; (iii) pyrolyzing
the combustion-retarding-material-depleted biomass to produce a
combustible biomaterial and carbon dioxide; and (iv) drying the
combustion-retarding-material-depleted biomass using the carbon
dioxide to produce a dried-combustion-retarding-material-depleted
biomass. The biomass may include at least one member selected from
a group consisting of rice straw, sugar cane leaves, cotton stalks,
mustard stalks, pine needles, coffee husks, coconut husks, rice
husks, mustard husks, weed straw, corn stover, sugar cane bagasse,
millet stalks, pulses stalks, sweet sorghum stalks, nut shells,
animal manure, guar husk, acacia totalis, julia flora, jatropha
residue, wild grass, pigeon beans, pearl millet, barley, dry chili,
gran jowar, linseed, maize/corn, lentil, mung bean, sunflower, til,
oil seed stalks, pulses/millets, black gram, sawan, soybean stalks,
cow gram, horse gram, finger millet, turmeric, castor seed, meshta,
sannhamp, and hemp. Preferably, drying is performed at a
temperature that is between about 20.degree. C. and about
50.degree. C.
[0027] In preferred embodiments of the present invention, the
solvent includes H.sub.2O and in more preferred embodiments the
solvent includes H.sub.2O or H.sub.2SO.sub.4. The solvent may have
a pH that is between about 4 and about 7. Inventive methods may
further include a step of rupturing lignocellulose in one or more
types of biomass to produce ruptured biomass including the
combustion-retarding material, and the rupturing step is performed
before the step of washing the biomass.
[0028] Certain embodiments of the present invention may further
include a step of air drying the
combustion-retarding-material-depleted biomass that is performed
before the pyrolyzing step. Drying may be carried out by simply
using air, and therefore, drying in some instances may refer to air
drying. In preferred embodiments, drying the
combustion-retarding-material-depleted biomass further includes a
step of conveying the carbon dioxide produced from the pyrolyzing
step.
[0029] In yet another aspect, the present invention provides a
system for producing combustible biomaterial. The system includes:
(i) a lignocellulose rupturing device for rupturing lignocellulose
in biomass to produce a ruptured biomass material, the ruptured
biomass material having a combustion-retarding material; (ii) a
washing subassembly designed to wash the ruptured biomass material
having a combustion-retarding material with a solvent and produce a
combustion-retarding-material-enriched solvent and a
combustion-retarding-material-depleted ruptured biomass; and (iii)
a pyrolyzing subassembly for pyrolyzing the
combustion-retarding-material-depleted ruptured biomass to produce
a combustible biomaterial. In preferred embodiments, the inventive
system may further include a densifier that is designed to densify
the combustible biomaterial to produce biocoal. Preferably, the
densifier is a pelletizer designed to produce biocoal pellets.
[0030] Inventive systems may further include: (i) a soaking chamber
for soaking ruptured biomass in a solvent to produce
soaked-ruptured biomass; and (ii) a first connection for conveying
the soaked-ruptured biomass to the washing subassembly. In
accordance with a preferred embodiment of the present invention,
systems may further still include: (i) a drying chamber designed to
dry the combustion-retarding-material-depleted ruptured biomass and
produce dried-combustion-retarding-material-depleted ruptured
biomass; and (ii) a second connection for conveying
combustion-retarding-material-depleted ruptured biomass from the
washing subassembly to the drying chamber. In certain of these
preferred embodiments, inventive systems may further still include
a third connection for conveying the
dried-combustion-retarding-material-depleted ruptured biomass to
the pyrolyzing subassembly.
[0031] In yet another aspect, the present invention provides a
biomass washing sub-assembly. The biomass washing sub-assembly
includes: (i) a plurality of bins, each of which is designed to
hold a single discrete amount of biomass; (ii) a solvent dispenser
for dispensing solvent at a location from where the solvent washes
a first discrete amount of biomass when the first discrete amount
of biomass is inside a first of the plurality of bins, to produce a
first effluent stream; and (iii) a first pump for pumping the first
effluent stream to a location from where the first effluent stream
washes a second discrete amount of biomass when the second discrete
amount of biomass is inside a second of the plurality of bins, to
produce a second effluent stream. Preferably, the second effluent
solvent stream has a higher concentration of combustion-retarding
material than the first effluent stream. In certain preferred
embodiments of the present invention, the solvent dispenser is a
spray. Inventive systems may further include a first effluent
dispenser connected to the first pump and configured to dispense
the first effluent stream. An interior of each of the bins may be
coated with an acid resistant material. Systems of the present
invention may further still include a conveyer belt that is
designed to advance the plurality of bins after concluding washing
of at least one of the discrete amount of biomass contained inside
one of the plurality of bins.
[0032] In accordance with one embodiment of the present invention,
systems further still include a plurality of sieves, each of which
is located below one of the plurality of bins or fitted to bottom
of the one of the plurality of bins. Preferably, inventive systems
further still include a plurality of collection chambers, each of
which is disposed below one of the plurality of bins and each of
which is designed to collect an effluent stream produced from
washing of the single discrete amount of biomass. Such inventive
systems may further still include a plurality of heaters which are
located below some of the plurality of collection chambers, and
each of the plurality of heaters are designed to heat the effluent
stream produced from washing of the single discrete amount of
biomass.
[0033] In yet another aspect, the present invention provides a
biomass composition derived from rice straw. The composition
includes a lignocellulosic material containing no more than about
0.01 weight percent of potassium. In one embodiment, the inventive
composition contains no more than about 10 weight percent of
water.
[0034] In yet another aspect, the present invention provides
another biomass composition derived from rice straw. The
composition includes a lignocellulosic material containing no more
than about 0.01 weight percent of sodium. In one embodiment, the
inventive composition contains no more than about 10 weight percent
of water.
[0035] In yet another aspect, the present invention provides a yet
another biomass composition derived from rice straw. The
composition includes a lignocellulosic material containing no more
than about 0.01 weight percent of chlorides. In one embodiment, the
composition contains no more than 10 weight percent of water.
[0036] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof,
will be best understood from the following descriptions of specific
embodiments when read in connection with the accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 shows a cross-sectional view of biomass, which is
processed according to one embodiment of the present invention.
[0038] FIG. 2 shows a schematic of a system, according to one
embodiment of the present invention, for producing a combustible
biomaterial from biomass.
[0039] FIG. 3 shows a side-sectional view of a washing subassembly,
according to one preferred embodiment of the present invention, for
washing biomass to remove combustion-retarding materials
therefrom.
[0040] FIG. 4 is a flowchart of a process, according to one
embodiment of the present invention, for producing a combustible
biomaterial from biomass.
[0041] FIG. 5 is a flow chart showing a washing step, according to
one preferred embodiment of the present invention, described in the
process of FIG. 4.
[0042] FIG. 6 shows a side-sectional view of a part of washing
subassembly of FIG. 3, which may be implemented to carry out the
washing step of FIG. 5.
[0043] FIG. 7 is a flowchart showing a washing step, according to
another preferred embodiment of the present invention, that is
described in the process of FIG. 4 and that implements multiple
washing cycles to wash a discrete amount of biomass.
[0044] FIG. 8 shows a side-sectional view of a part of washing
subassembly of FIG. 3, which may be implemented to carry out the
washing step of FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] In the following description, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. It will be apparent, however, to one skilled in
the art that the present invention may be practiced without
limitation to some or all of these specific details. In other
instances, well-known process steps have not been described in
detail in order to not unnecessarily obscure the invention.
[0046] The present invention recognizes that biomass, as used in
conventional systems and processes, is not combustible at high
enough temperatures that are necessary for generating energy,
because it contains certain combustion-retarding materials. To this
end, the present invention provides novel systems, methods, and
compositions in connection with the removal of such
combustion-retarding materials from the biomass before subjecting
it to combustion. By timely and proper removal of such materials,
the present invention circumvents the drawbacks of slagging and
fouling of the combustors encountered by the conventional systems
and processes. As a result, the present invention provides the
advantages of significantly higher throughputs and lower capital
costs, which are not realized by the conventional systems and
methods.
[0047] FIG. 1 shows a typical biomass material 100, which includes
a lignin sheath 116, consisting of a rigid non-carbohydrate
polymer. Sheath 116 is tightly bound to hemicellulose 114, composed
of polysaccharides. Deeper inside biomass 100 and after
hemicellulose 114, cellulose 112, also composed of polysaccharides
(that can be broken down into glucose), is found. Housed inside
barrier 112 is at least one combustible material, and other
components such as alkali compounds (e.g., alkali and alkaline
earth chlorides, sulfates, carbonates, and complex silicates),
potassium and sodium, which the present invention recognizes as
non-combustibles or, in the alternative, referred to as
combustion-retarding materials 120.
[0048] In biomass 100, lignin sheath 116 comprises the outer
portion of the plant cell wall, providing a strong protective
coating and making inaccessible hemicellulose 114, cellulose 112,
combustible glucose 118, and combustion-retarding materials 120.
Both hemicellulose 114 and cellulose 112 fortify the protection
provided by lignin sheath 116 and make it even more difficult to
access the combustible and non-combustible components inside
biomass 100. The term "lignocellulose," as used in this
specification, refers collectively to lignin sheath 116,
hemicellulose 114, and cellulose 112. Thus, lignocellulose houses
both combustible and non-combustible components. The present
invention provides systems and methods which effectively rupture
the lignocellulose to access the combustible 118 and
non-combustible 120 components inside biomass 100. By making the
combustible 118 and non-combustible 120 components inside biomass
100 accessible, the present invention uses a solvent to effectively
remove the non-combustible components 120 from biomass 100. The
resulting biomaterial is a combustible product.
[0049] The present invention recognizes that in a process designed
to remove the non-combustible components 120 from biomass 100, mass
transfer, i.e., transfer of non-combustible components 120 that
exist in the solid phase inside biomass 100 to an aqueous phase in
the solvent, is the rate-limiting step. Relying on conventional
wisdom regarding use of solvents to remove soluble components,
those skilled in the art may well conclude that in such a removal
process, not mass transfer, but solubility limits of
non-combustible components 120 in the solvent, is the rate-limiting
step. The present invention therefore represents a significant
departure from such conventional wisdom. Furthermore, sequence of
certain steps in preferred embodiments of the present invention
described below are designed to serve the recognition that mass
transfer is the rate-limiting step.
[0050] In accordance with one embodiment of the present invention,
a system 200 for producing a combustible biomaterial is shown in
FIG. 2. System 200 may be implemented to process one or more
different types of biomass. As shown in FIG. 2, a first type of
biomass 202, a second type of biomass 204, and a third type of
biomass 206, are one at a time or are contemporaneously fed inside
a biomass rupturing apparatus 208. Inside rupturing apparatus 208,
lignocellulose inside biomass is ruptured to produce ruptured
biomass. In its ruptured form, the combustible and non-combustible
components inside the biomass are no longer confined inside the
barrier created by lignocellulose, but are accessible for
treatment. The ruptured biomass is conveyed to a washing
sub-assembly 210, where it contacts a solvent, which dissolves the
non-combustible components and produces a
combustion-retarding-material-enriched solvent and a
combustion-retarding-material-depleted biomass. It is noteworthy
that significant portion of the lignocellulose is not soluble in
the solvent. The resulting combustion-retarding-material-depleted
biomass, which is still wet from the residual solvent, advances to
drying. In certain embodiments,
combustion-retarding-material-depleted biomass of the present
invention has a consistency of a sludge-like material before it
advances to drying.
[0051] In a first pass of the
combustion-retarding-material-depleted biomass through a drying
chamber 212, the biomass is air dried to produce a dried
combustion-retarding-material-depleted biomass, which prepares it
for pyrolysis. In a pyrolyzing subassembly 214, the dried
combustion-retarding-material-depleted biomass is subject to heat
treatment in the absence of oxygen to produce a combustible
biomaterial and syngas. The syngas includes at least one member
selected from a group consisting of CO, CO.sub.2, CH.sub.4, and
H.sub.2. A connection 218 between pyrolyzing subassembly 214 and
drying chamber 212 is designed to convey the syngas to drying
chamber 212. In subsequent passes of the
combustion-retarding-material-depleted biomass through drying
chamber 212, connection 218 allows the syngas to participate in the
drying step. In other words, syngas is conveyed from pyrolyzing
subassembly 214 through connection to drying chamber 212 to
facilitate drying of combustion-retarding-material-depleted
biomass. Of particular importance is the ability of this connection
to recycle CO.sub.2, which is one of the components of syngas.
Instead of releasing CO.sub.2into the atmosphere, the present
invention uses the CO.sub.2 byproduct, which is greenhouse gas
whose emission requires high capital expenditure for
environmentally compliant remediation. As a result, the systems and
processes of the present invention not only provide a combustible
biomaterial at high throughputs, they also provide a low cost
combustible bio-based product whose production minimizes reduction
of harmful greenhouse gases.
[0052] In preferred embodiments of the present invention, the dried
sludge undergoes densification. By way of example, a densifier 216,
as shown in FIG. 2, is used to densify the combustible biomass and
produce a densified combustible biomaterial. Preferably, densifier
216 is a pelletizing apparatus, which is capable of densifying a
combustible biomaterial having a consistency of a dried-sludge
material, used to produce combustible biomaterial in the form of
pellets, which are easily transported and stored and used as an
energy source.
[0053] Although system 200 shows an input of three different types
of biomass, alternative embodiments of the present invention may
similarly process less than three or more than three different
types of biomass. It is noteworthy that the present invention
therefore advantageously produces combustible biomaterial using
different types of agricultural residue. Furthermore, regardless of
the type of agricultural residue used, the present invention
provides consistent gross calorific values for the ultimately
produced combustible biomaterial. Thus, the present invention
provides systems and methods to generate consistent and predictable
amounts of energy from a very diverse range of agricultural
residues, which are available in a geographic area during a
particular season.
[0054] Biomass 202, 204, and 206 may be any type of agricultural
residue containing combustion-retarding materials confined within a
barrier created by lignocellulose. System 100 is designed to
process biomass which includes at least one member selected from a
group consisting of rice straw, sugar cane leaves, cotton stalks,
mustard stalks, pine needles, coffee husks, coconut husks, rice
husks, mustard husks, weed straw, corn stover, sugar cane bagasse,
millet stalks, pulses stalks, sweet sorghum stalks, nut shells,
animal manure, guar husk, acacia totalis, julia flora, jatropha
residue, wild grass, pigeon beans, pearl millet, barley, dry chili,
gran jowar, linseed, maize/corn, lentil, mung bean, sunflower, til,
oil seed stalks, pulses/millets, black gram, sawan, soybean stalks,
cow gram, horse gram, finger millet, turmeric, castor seed, meshta,
sannhamp, and hemp. Wood or certain derivatives of wood are
combustible and, therefore, do not contain combustion-retarding
material, as contemplated by the present invention. Furthermore,
wood is not agricultural residue, as that term is used in the
specification.
[0055] Biomass rupturing apparatus 208 may be a commercially
available chopper, crusher, smasher, pulverizer, or the like, well
known to those skilled in the art. Although preferred embodiments
of the present invention contemplate using mechanical means,
chemical means may well be employed to attack and rupture the
lignocelluloses in biomass. So long as the lignocelluloses are
ruptured and a greater surface area of the combustible and
non-combustible components is exposed, any means, whether
mechanical or chemical is acceptable. In more preferred embodiments
of the present invention, however, rupturing takes place along the
lignocellulose fiber, as opposed to rupturing across those fibers,
to expose even a greater surface area of the biomass.
[0056] Washing sub-assembly 210 is designed to remove
combustion-retarding materials from the biomass during washing.
Non-combustible components or combustion-retarding materials, as
these terms are used interchangeably herein, include at least one
member selected from a group consisting of alkali and alkaline
earth chlorides, sulfates, carbonates, and silicates. Washing can
be accomplished by any technique that contacts the ruptured biomass
with a solvent. By way of example, washing can be accomplished by
submerging or soaking the biomass in a solvent. In preferred
embodiments of the present invention, however, washing is carried
out using a subassembly 300 shown in FIG. 3, which is explained in
greater detail below.
[0057] Drying chamber 212 is a chamber which is configured to dry
combustion-retarding-material-depleted biomass with air and syngas.
In a first pass of combustion-retarding-material-depleted biomass
through drying chamber 212, when syngas has not yet been produced
in pyrolyzing subassembly 214,
combustion-retarding-material-depleted biomass is air dried to
remove moisture. During a subsequent pass or subsequent passes of
combustion-retarding-material-depleted biomass through the
pyrolyzing sub-assembly 214, however, syngas produced in pyrolyzing
subassembly 214 is conveyed to drying chamber 212 for removing
moisture as part of the drying process.
[0058] A pyrolyzing sub-assembly 214 is capable of heating dried
combustion-retarding-material-depleted biomass in the absence of
oxygen to produce a combustible biomaterial. Pyrolyzing subassembly
214 can be any apparatus that effectively degrades long-chain
polymers of hemicellulose and cellulose into a simpler form (e.g.,
glucose), which can be converted to energy under high-temperature
conditions disclosed by the present invention. By way of example,
the pyrolyzing sub-assembly 214 may be a boiler or a combustor well
known to those skilled in the art and operating at a temperature
that is between about 100.degree. C. and about 500.degree. C. In
the absence of oxygen, pyrolysis, according to the present
invention, ensures that the carbon content in the resulting
combustible biomaterial will not react with oxygen to form
hydrocarbon or ash. Rather, the biomass undergoing pyrolysis
creates activated carbon bonds, which provides for an energy-dense
end product and increases the gross calorific value of the
combustible biomaterial. According to the present invention, the
gross calorific value of the combustible biomaterial after
pyrolyzing goes up by a factor that is between about 7 and about 10
times compared to before pyrolyzing.
[0059] Furthermore, pyrolyzing sub-assembly 214 is configured to
drive away moisture from the combustible biomaterial to produce
combustible material that is hydrophobic. Energy-dense and
hydrophobic biomaterials represent preferred embodiments of the
inventive biomaterials because they are stable, well-suited to
transport over long distances, and lend themselves to being
conveniently stored for long periods of time.
[0060] In certain preferred embodiments, inventive biomass systems,
such as system 200, include a soaking chamber, which is disposed
between rupturing apparatus 208 and washing sub-assembly 210.
Ruptured biomass is soaked in a solvent contained inside this
chamber before the ruptured biomass undergoes washing.
[0061] In accordance with certain preferred embodiments of the
present invention, system 208 also includes a screw-press, which is
positioned after washing sub-assembly 210 for pressing out the
residual moisture remaining in
combustion-retarding-material-depleted biomass, to prepare that
biomass for drying inside drying chamber 212.
[0062] In a preferred embodiment, inventive washing sub-assemblies,
an example of which is denoted by reference numeral 210 as shown in
FIG. 2, include a multiple bin sub-assembly 300 as shown in FIG. 3.
Sub-assembly 300 includes a plurality of bins 302 (e.g., a
representative number of them are shown as 302a, 302b, 302c, 302d,
302e). Each bin is designed to receive a discrete amount of biomass
(e.g., ruptured biomass as discussed in connection with FIG. 1).
According to this embodiment of the present invention, a large
amount of biomass is processed by dividing and processing it in
relatively smaller discrete amounts, with each such amount
contained inside a bin (e.g., bin 302a). Bins 302 are driven on a
conveyer belt 320 from a loading point 322 to an unloading point
324 and then back to loading point 322. Washing of biomass by a
solvent takes place when bins traverse from loading point 322 to
unloading point 324. A solvent reservoir pump 308 pumps a solvent
to a solvent spray 304, from where it is dispensed for washing a
discrete amount of biomass contained within a bin. By way of
example, when bin 302a is traversing from loading point 322 to
unloading point 324 and it arrives at a location under spray 304,
the solvent is dispensed from spray 304 for washing a discrete
amount of biomass contained inside bin 302a. After washing of the
biomass inside bin 302a has concluded, bin 302b advances to a
position under spray 304 so that the biomass contained inside that
bin can similarly undergo washing by solvent. In this manner,
biomass contained inside each bin is washed by the solvent.
[0063] An effluent stream resulting from solvent washing of a
discrete amount of biomass contained in a bin, as described above,
flows through an effluent drain 208 and is used for subsequent
washing of another discrete amount of biomass contained inside
another bin. By way of example, after biomass in bin 302a undergoes
washing, the resulting effluent stream is collected inside a
collection chamber 312, from where it is pumped using an effluent
pump 314 to an effluent spray 306, which dispenses the effluent for
washing the biomass in bin 302b. In this manner, biomass inside a
bin located downstream is washed with the effluent produced from
washing of biomass inside a bin located upstream. In preferred
embodiments of the present invention, not all, but certain ones of
collection chamber 312, come fitted with heaters to make sure that
the effluent stream is maintained at a desirable temperature for
effective washing of biomass. According to the embodiment shown in
FIG. 3, the last collection chamber conveys the effluent stream for
effluent treatment through an opening 318.
[0064] Bin 302 may be any commercially available receptacle capable
of holding a discrete amount of biomass. Bin 302 comes fitted with
or has disposed below its bottom surface a sieve. The sieve has
appropriately sized pores that hold back sufficiently large biomass
particles that may hinder the operation of a downstream effluent
pump 314. Although bin 302 is made from any rigid material strong
enough to hold relatively large quantities of biomass, it is
preferably made from a material that is also unreactive to an
acidulated solvent (e.g. stainless steel). In more preferred
embodiments of the present invention, however, an interior portion
of bin 302 is coated with a material that is unreactive to an
acidulated solvent, as this provides a more cost-effective solution
than manufacturing entire bin 302 from an expensive material, such
as stainless steel.
[0065] Solvent reservoir 308, in accordance with one embodiment of
the present invention, stores solvent. In preferred embodiments of
the present invention, solvent inside reservoir 308 is acidulated
water having a pH that is between about 4 and about 7. As such, in
these embodiments, solvent reservoir, like the bins described
above, may be composed of any material that will not react with the
acidulated water. The acidulated water composition preferably
includes H.sub.2SO.sub.4, as it is relatively easily neutralized
compared to other acidic compounds.
[0066] The use of bins to separate solvent from the treated biomass
represents a marked improvement over conventional techniques of
effecting such a separation. Specifically, well-known techniques,
such as reverse osmosis or filtration, which may be employed to
separate treated biomass and solvent, are labor-intensive and
time-consuming. Use of bins, according to the present invention,
treats the biomass with the solvent and contemporaneously separates
the treated biomass form the solvent, without incurring the high
costs associated with conventional techniques of effecting such a
separation.
[0067] Washing Subassembly 310, as shown in FIG. 3, can be
implemented in a variety of different ways. FIG. 4 shows a process
400, according to one preferred embodiment of the present
invention, for washing (which can be carried out in subassembly
310) one or more types of agricultural residue or biomass (as these
terms are used interchangeable in this specification). Agricultural
residue or biomass referred to in this specification includes
combustion-retarding materials. Process 400 begin when in a step
402, one or more types of biomass containing combustion-retarding
materials is received. By way of example, step 402 includes one or
more types of different agricultural residue being delivered in
trucks.
[0068] Next, step 404 includes rupturing lignocellulose in the
biomass to produce ruptured biomass. By way of example, biomass
rupturing apparatus 108, as shown in FIG. 1, is used to rupture and
produce ruptured biomass. As described above, in this step, surface
area of the biomass is increased by rupturing, resulting in
exposure of active sites for solubilization of combustion-retarding
materials in the subsequent washing step 306.
[0069] In step 406, the present invention provides a step of
washing ruptured biomass with a solvent to drive
combustion-retarding materials from ruptured biomass to solvent
(e.g., the same solvent described in solvent reservoir 308) and
produce combustion-retarding-material-depleted biomass and
combustion-retarding-material-enriched solvent.
[0070] The present invention recognizes that temperature, residence
time, and pH are important parameters to consider for effectively
performing step 406. In preferred embodiments of the present
invention, washing step 406 preferably uses a solvent and effluent
streams maintained (e.g., using heaters 316 of FIG. 3) at a
temperature that is between about 30.degree. C. and about
70.degree. C., and more preferably, at about 50.degree. C. At these
temperatures, combustion-retarding materials undergo a phase shift
that facilitates their leaching from a solid phase, as they exist
in biomass, into an aqueous phase, as they are found in the solvent
after washing.
[0071] In certain embodiments of the present invention, the
parameters of washing step 306 are set to account for the type of
biomass material washed. In particular, lignin-enriched biomass
material (e.g., cotton stalks, rice stalks, or mustard stalks)
requires a higher concentration of acidic solvent. If the solvent
is too acidic, however, then the lignocellulosic material will
dissolve along with the combustion-retarding material. Should this
happen, it is extremely difficult and expensive to separate the
combustion-retarding material from the lignocellulosic material. As
a result, the present invention recognizes the need to strike a
delicate balance in selecting the proper pH of the solvent for
effective washing of the biomass.
[0072] Temperature impacts rate of mass transfer of the
combustion-retarding materials from the solid phase in the biomass
to the aqueous phase in the solvent. Higher temperatures agitate
the combustion-retarding material, making it more mobile to
facilitate mass transfer. If the temperature is not high enough,
then the transfer of the combustion-retarding materials from the
solid phase to the aqueous phase is relatively slow and does not
provide maximum throughput. On the other hand, if the temperature
is too high, then process 400 runs the risk of converting the
hemicellulose and cellulose fibers into simple sugars, like
glucose, that become soluble in water, and therefore does not
provide the desired yield. Similar to the above-discussion
regarding selection of the proper pH, the present invention
recognizes that it is also important to strike a balance when
setting the temperature of the solvent during washing step 406. By
way of example, the temperature of solvent can be any value that is
between about 30.degree. C. and about 70.degree. C. In preferred
embodiments of the present invention, however, the temperature is
about 50.degree. C.
[0073] During step 406, biomass should contact the solvent for
sufficiently long periods of time to facilitate mass transfer, but
so long as to break down the hemicellulose and cellulose fibers to
simple sugars, which are soluble in the solvent. In this context,
the present invention recognizes that an appropriate residence time
of the biomass in the solvent that maximizes mass transfer depends
on the amount of lignin present in the biomass. The present
invention recognizes that a lignin-rich biomass, such as cotton
straws, should have a residence time that is between about 2 hours
and about 4 hours to breakdown the hemicellulose and cellulose
layers and allow for mass transfer. Rice or mustard straws, which
are not as lignin rich as cotton straws, should have a residence
time of between about 1 hour and about 1.5 hours. Against this
backdrop, rice and mustard husk, which may be thought of as
lignin-poor, have a residence time that is about 30 minutes. As a
result, depending on the amount of lignin present in the biomass,
residence times according to the present invention can be a value
that is between about 30 minutes and about 4 hours.
[0074] Referring back to process 400 in FIG. 4, after washing step
406 concludes, a step 408 of pyrolysis is carried out on the
resulting combustion-retarding-material-depleted biomass to produce
a combustible material. At this stage of process 400, the
combustion-retarding-material-depleted biomass, which may have the
consistency of sludge-like material, undergoes pyrolysis in the
absence of oxygen. Pyrolysis drives away moisture from the
combustion-retarding-material-depleted biomass to produce an
energy-dense and hydrophobic combustible biomaterial.
[0075] The present invention recognizes that both temperature and
treatment time are important parameters during pyrolysis to achieve
a high throughput and the requisite yield. By way of example, the
temperature during pyrolysis is a value that is between about
100.degree. C. and about 500.degree. C., and preferably a value
that is between about 250.degree. C. and about 350.degree. C. The
time of treatment is a value that is between about 10 minutes and
about 24 hours.
[0076] In certain preferred embodiments, inventive biomass
processes, such as process 400, include a step of soaking that is
carried out after rupturing step 404 and before washing step 406.
In this step, ruptured biomass is soaked in a solvent before it
undergoes washing. The ruptured biomass may soak in the solvent for
a duration that is between about 30 minutes and about 60
minutes.
[0077] In accordance with certain preferred embodiments of the
present invention, process 400 also includes a pressing step, which
is performed after washing sub-assembly 210. In the pressing step,
the residual moisture remaining in
combustion-retarding-material-depleted biomass is pressed out to
prepare that biomass for a subsequent drying step. Drying of the
combustion-retarding-material-depleted biomass takes place at a
temperature that is between about 20.degree. C. and about
50.degree. C. and for a duration that is between about 10 minutes
and 48 hours.
[0078] The present invention also recognizes that rupturing step
404 plays a significant role, not only in facilitating mass
transfer during washing step 406, as mentioned above, but also
during the subsequent pyrolyzing step 408. Specifically, the
biomass with increased surface area, resulting from rupturing step
404, undergoes pyrolysis to create a uniform distribution of
moisture-retardant sites from moisture-absorbent sites. As a
result, the present invention not only produces a biomaterial that
is combustible, but also one that undergoes combustion in a
homogeneous manner. The combustible biomaterial, according to the
present invention, therefore, combusts in a predictable manner and
realizes higher yields, both of which make it a desirable renewable
fuel source.
[0079] Furthermore, the increased surface area of the ruptured
biomass also facilitates heat transfer during pyrolyzing step 408.
Heat is more easily transferred inside ruptured biomass during
pyrolyzing step 408 to effectively remove moisture. In the absence
of a previous rupturing step, a significant amount of heat is
wasted on rupturing the lignocellulosic structure in the biomass
during pyrolysis. The present invention avoids such waste, and
instead utilizes a significant amount, if not almost all, of the
heat available during pyrolysis to effectively produce a
combustible biomaterial. Consequently, a rupturing step, which
precedes a washing step and a pyrolysis step, serves both to
facilitate mass transfer and heat transfer.
[0080] Not only does the present invention conserve energy, it also
conserves solvent. To this end, FIG. 5 shows a flowchart depicting
a process 500 for washing relatively large amounts of biomass with
a relatively small amount of solvent. In accordance with one
embodiment of the present invention, a large amount of biomass is
divided into small, discrete amounts of biomass. Specifically, step
502 includes receiving "N" discrete amounts of biomass, where N is
a whole number and the biomass includes a combustion-retarding
material. In a next step 504, a first of N discrete amounts of
biomass undergoes washing with a solvent to produce a
combustion-retarding-material-depleted biomass and a first effluent
that is enriched with combustion-retarding materials. Then, in step
506, a second of N discrete amounts of biomass undergoes washing by
the first effluent to produce a second effluent, which is used to
wash the third of N discrete amounts of biomass. In this manner,
the effluent stream produced from washing one discrete amount of
biomass is used for subsequently washing another discrete amount of
biomass and so on until the washing proceeds to washing the Nth
discrete amount of biomass. According to step 508, the Nth discrete
amount of biomass is washed with the (N-1)th effluent stream to
produce an Nth effluent stream, which in certain preferred
embodiments of the present is sent for effluent treatment. Process
500, starting from step 502 to step 508, can be thought of as a
single washing cycle. According to step 510, a single washing
cycle, as described above, produces N discrete amounts of biomass
depleted of combustion-retarding materials.
[0081] FIG. 6 shows a subsystem 600, which is a portion of system
200 of FIG. 2. Subsystem 600 is configured to carry out a single
washing cycle for an exemplar embodiment, where N equals to 5. In
FIG. 6, each of five bins 202a, 202b, 202c, 202d and 202e receive a
discrete amount of biomass. When first discrete amount of biomass
inside bin 202a is positioned under spray 204, a solvent pump 208
pumps solvent and dispenses it through a first spray 204a to wash
the first discrete amount of biomass. A resulting first effluent
exits bin 202a through opening 210a and is pumped by a pump 214a to
a second spray 204b, which then dispenses the first effluent to
wash a second discrete amount of biomass inside second bin 202b.
Using similar components, as used in the configuration to wash a
first discrete amount of biomass, a second opening 210b and a pump
214b transport the resulting second effluent to a third spray 206c.
In this manner, effluents resulting from prior washings are used to
wash subsequent discrete amounts of biomass in bins 206c, 206d, and
206e. These effluent streams are guided to perform such washings
using openings 210c, 210d, and 210e, and pumps 214c, 214d, and
214e. Washing discrete amounts of biomass in each of five bins
202a, 202b, 202c, 202d, and 202e in this manner can be thought of
as a single washing cycle.
[0082] It is noteworthy that when one effluent stream washes a
discrete amount of biomass to produce another effluent stream,
which in turn washes another discrete amount of biomass to produce
a yet another effluent stream, it is reasonable to conclude that
the effluent streams resulting from successive downstream washing
steps are progressively more enriched with combustion-retarding
materials. In other words, it is reasonable to conclude that the
second effluent stream is enriched with combustion-retarding
materials to a greater extent than the first effluent stream.
Similarly, the third effluent stream may be enriched with
combustion-retarding materials to a greater extent than the second
effluent stream. However, the present invention recognizes that
with each washing of a discrete amount of biomass, the drained
effluent becomes progressively more enriched with
combustion-retarding materials. Those skilled in the art will
recognize that the inventive washing process does not result in
diminished washing efficiency (i.e., inability of the solvent to
extract combustion-retarding materials from biomass); rather, the
progressively enriched effluent streams still maintain the ability
to solubilize combustion-retarding materials.
[0083] Although a single washing cycle, such as the one described
above, provides an effective way to remove combustion-retarding
materials, multiple washing cycles as described below represent a
more preferred embodiment of the present invention. FIG. 7 is a
flowchart of a process 700, in which multiple washing cycles are
performed. As it is described below, this figure reflects an
understanding that if discrete amounts of biomass contained inside
downstream bins are washed with effluents that are progressively
more enriched with combustion-retarding materials, then biomass
inside downstream bins are not going to be washed as effectively as
the biomass in upstream bins because it is likely that the biomass
in downstream bins will absorb some of the combustion-retarding
materials previously leached out from washing of biomass in
upstream bins. Multiple washing cycles, as envisioned in the
present invention, ensure that such absorption of
combustion-retarding materials by biomass in downstream bins is
avoided. In multiple washing cycles, each of a plurality of
discrete amounts of biomass is washed with effluents, which are
relatively less enriched with combustion-retarding materials, and
then is ultimately washed with a solvent.
[0084] In one embodiment, process 700 of the present invention
begins at step 702 when N discrete amounts of biomass are received
and the biomass contains combustion-retarding materials. In step
704, a first washing cycle is performed. The first washing cycle is
substantially similar to steps 504, 506, and 508, as described with
respect to FIG. 5. Thus, N discrete amounts of biomass undergo
washing in the first cycle. The various resulting effluent streams
(e.g., from the first effluent to the (N-1)th effluent) are
associated with the first washing cycle.
[0085] Next, step 706 includes a second washing cycle, which is
substantially similar to the first washing cycle, except instead of
washing first of N discrete amounts of biomass with the solvent,
the second of N discrete amounts of biomass undergoes washing with
the solvent. Consistent with this understanding, the various
resulting effluent streams (e.g., from the first effluent to the
(N-1)th effluent) are associated with the second washing cycle.
[0086] According to step 708, an Xth washing cycle is performed so
that the Xth of N discrete amounts of biomass undergoes washing
with the solvent, where X is a whole number that ranges from 3 to
N. In this step, a resulting first effluent associated with the Xth
washing cycle is used for washing (X+1)th of N discrete amount of
biomass to produce a second effluent associated with the Xth
washing cycle. Furthermore, washing is performed in successive
discrete amounts of biomass in this manner in this step until the
Nth discrete amount of biomass is washed with (N-X)th effluent
associated with the Xth washing cycle, where X is a whole number
ranging from 1 to N. Finally, step 710 results in N discrete
amounts of biomass depleted of combustion-retarding materials.
[0087] FIG. 8 shows a subsystem 800, which is a portion of system
300 of FIG. 3, and is simplified to facilitate discussion.
Subsystem 800 is configured to carry out a single washing cycle for
an exemplar embodiment where N equals to 5. In FIG. 8, each of five
bins 302a, 302b, 302c, 302d, and 302e receive a discrete amount of
biomass and each such bin leads a first washing cycle 802. As shown
in FIG. 8, bin 302(a) undergoes washing by a solvent and leads the
first washing cycle. Similarly, when bins 302(b), 302(c), 302(d),
and 302(e) undergo washing by a solvent, they lead a second 804, a
third 806, a fourth 808, and a fifth 810 washing cycle,
respectively. The term "washing cycle," as used in this
specification, does not refer to a discrete washing cycle, rather
it is a continuous process designed to ensure that biomass in
downstream bins is washed with effluents that are progressively
less enriched with combustion-retarding materials, and biomass in
these bins is ultimately washed by the solvent.
[0088] Regardless of whether single or multiple washing cycles are
used, the combustion-retarding-material-depleted biomass is sent to
pyrolysis to produce a combustible material as explained above. In
accordance with one embodiment, a single washing cycle of the
present invention washes between about 1 metric ton and about 1000
metric tons of biomass. In this embodiment, between about 1000
liters and about 40 mega-liters of solvent is used. Biomass, which
undergoes washing in a single washing cycle, may be divided into
between about 10 discrete amounts of biomass and about 1000
discrete amounts of biomass. Each such discrete amount of biomass
may be washed with a volume of solvent that is between about 0.5
liters and about 4 mega-liters.
[0089] Relying on conventional wisdom, those skilled in the art
would recognize that to wash significantly large amounts of
biomass, a proportionately large amount of solvent is necessary.
However, based on the recognition that mass transfer is the
rate-limiting step for removal of combustion-retarding materials
from biomass, the present invention represents a marked departure
from such wisdom and recognition as it provides systems (e.g.,
system 300 shown in FIG. 3) and processes (e.g., processes 500 and
700 shown in FIGS. 5 and 7, respectively) that allow significantly
large amounts of biomass to be washed with relatively small amounts
of solvent. Dividing a significantly large amount of biomass into
smaller discrete amounts that are contained inside bins and
successively washing such discrete amounts of biomass with effluent
streams resulting from numerous previous washing steps consumes a
relatively small amount of solvent. Conservation of resources, such
as conserving large volumes of solvent, translates into an
inexpensive solution to meet the growing demand for energy.
[0090] The present invention also offers biomass compositions
(i.e., containing a lignocellulosic material) that are combustible.
By way of example, before a washing step (e.g., washing step 406 in
FIG. 4) is carried out, a composition of ruptured rice straw
includes about 0.2 weight percent potassium and has no more than
about 10 weight percent water. After the washing step concludes,
the amount of potassium in the washed rice straw is reduced by a
factor of 20 compared to the amount of potassium in the rice straw
before washing. In other words, the rice straw includes about 0.01
weight percent of potassium. At this stage, however, the rice straw
content is moisture rich and includes about 50 weight percent
water.
[0091] After a drying step (e.g., which is carried out in a drying
chamber 212 of FIG. 2) is performed on the washed rice straw
composition, the potassium content remains substantially similar to
the potassium content in the rice straw before the drying step, but
the moisture content reduces to about 10 weight percent.
[0092] In the methods and systems according to the present
invention, the amount of other non-combustible biomass components
other than potassium, such as sodium and chlorides, may well be
reduced. By way of example, before a washing step (e.g., washing
step 406 in FIG. 4) is carried out, a composition of ruptured rice
straw includes about 0.1 weight percent. After the washing step
concludes, the amount of sodium in the washed rice straw is reduced
by a factor of 10 compared to the amount of sodium in the rice
straw before washing. In other words, the rice straw includes about
0.01 weight percent of sodium. As another example, after washing
the rice straw, the amount of chlorides in the washed rice straw is
similarly reduced by a factor of 10 compared to the amount of
chlorides in the rice straw before washing. In other words, the
rice straw includes about 0.01 weight percent of sodium.
[0093] Although illustrative embodiments of this invention have
been shown and described, other modifications, changes, and
substitutions are intended. By way of example, the present
invention discloses removal of combustion-retarding materials;
however, it is also possible to remove a single
combustion-retarding material using the systems, processes, and
compositions of the present invention. Accordingly, it is
appropriate that the appended claims be construed broadly and in a
manner consistent with the scope of the disclosure, as set forth in
the following claims.
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