U.S. patent application number 13/618528 was filed with the patent office on 2013-09-26 for particle for gasification containing a cellulose core with a coating of lignin.
This patent application is currently assigned to SUNDROP FUELS, INC.. The applicant listed for this patent is Robert S. Ampulski, Joel K. Monteith, John T. Turner. Invention is credited to Robert S. Ampulski, Joel K. Monteith, John T. Turner.
Application Number | 20130248760 13/618528 |
Document ID | / |
Family ID | 49210896 |
Filed Date | 2013-09-26 |
United States Patent
Application |
20130248760 |
Kind Code |
A1 |
Ampulski; Robert S. ; et
al. |
September 26, 2013 |
PARTICLE FOR GASIFICATION CONTAINING A CELLULOSE CORE WITH A
COATING OF LIGNIN
Abstract
A biomass composition of matter to be used in a torrefaction
process or a biomass gasification reaction is described. The
biomass in a particle form is created in a pretreatment step that
occurs prior to the torrefaction process or the biomass
gasification reaction. A bulk structure of the biomass is 1)
stripped apart to at least partially separate an outer layer of
lignin in the biomass from the cellulose fibers, 2) internally
blown apart to create fragments of the fiber bundle, and 3) any
combination of the two in the pretreatment step. The biomass in
particle form has a length to thickness aspect ratio on average of
less than 300 to 1, a thickness on average of less than 100 microns
thick and a length on average of less than 3000 microns.
Inventors: |
Ampulski; Robert S.;
(Fairfield, OH) ; Turner; John T.; (West Chester,
OH) ; Monteith; Joel K.; (Bethel, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ampulski; Robert S.
Turner; John T.
Monteith; Joel K. |
Fairfield
West Chester
Bethel |
OH
OH
OH |
US
US
US |
|
|
Assignee: |
SUNDROP FUELS, INC.
Longmont
CO
|
Family ID: |
49210896 |
Appl. No.: |
13/618528 |
Filed: |
September 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13429847 |
Mar 26, 2012 |
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13618528 |
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13531318 |
Jun 22, 2012 |
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13429847 |
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Current U.S.
Class: |
252/183.11 ;
162/21 |
Current CPC
Class: |
D21B 1/36 20130101; D21H
11/08 20130101; D21B 1/02 20130101; D21C 1/02 20130101 |
Class at
Publication: |
252/183.11 ;
162/21 |
International
Class: |
D21B 1/36 20060101
D21B001/36; D21H 11/00 20060101 D21H011/00 |
Claims
1. A biomass composition of matter to be used in 1) a biomass
gasification reaction where larger organic molecules making up the
biomass are decomposed into smaller molecules to create syngas
components, including hydrogen (H2) and carbon monoxide (CO), as a
product of the biomass gasification reaction, 2) a torrefaction
process, or 3) any combination of the two, comprising: biomass in a
particle form created in a pretreatment step that occurs prior to
the biomass gasification reaction or torrefaction process, where
the biomass initially has a bulk structure including organic
polymers of lignin that surround a plurality of cellulose fibers in
a fiber bundle, where the bulk structure of the biomass is 1)
stripped apart to at least partially separate an outer layer of
lignin in the biomass from the cellulose fibers, 2) internally
blown apart to create fragments of the fiber bundle, and 3) any
combination of the two in the pretreatment step that uses at least
moisture, pressure, and heat to liberate and expose the cellulose
fibers to be able to react in a two-stage sequence during the
biomass gasification reaction or torrefaction process rather than
react in a repeating cycle of multiple layers of lignin followed by
the cellulose and hemicelluloses, and where the biomass in particle
form has a length to thickness aspect ratio on average of less than
300 to 1, a thickness on average of less than 100 microns thick and
a length on average of less than 3000 microns.
2. The biomass composition of matter of claim 1, where the biomass
particle created in the pretreatment step includes both 1) chunks
of pure lignin, from the layer of lignin surrounding any
hemi-cellulose and cellulose in the cellulose fibers, that have
been separated from the cellulose fibers as well as 2) cellulose
fibers now freestanding from the fiber bundle where the
freestanding cellulose fibers have some lignin still attached to
the surface of the fiber, where the biomass particle when fed into
the biomass gasifier is allowed a more rapid exposure to directly
react the cellulose and hemi-cellulose as well as substantially
eliminating having to react layer after layer of lignin surrounding
the cellulose and hemi-cellulose, followed by another layer of
lignin surrounding cellulose and hemi-celluloses that would have to
be sequentially reacted through if the pretreatment step did not at
least partially separate the lignin from the cellulose fibers.
3. The biomass composition of matter of claim 1, wherein the
pretreatment step is a Thermo Mechanical Pulping process using two
or more stages to pretreat the biomass for subsequent supply to the
biomass gasifier, where the stages are configured to use a
combination of heat, pressure, moisture, and mechanical agitation
that are applied to the biomass to degrade bonds between the lignin
from the cellulose fibers, then mechanically strip fibers from the
fiber bundle to separate an outer layer of lignin in the biomass
from the cellulose fibers, and then supply the biomass particles in
a pulp form from an outlet stage of the Thermo Mechanical Pulping
process.
4. The biomass composition of matter of claim 3, wherein the
biomass particle formed after the pretreatment step of the Thermo
Mechanical Pulping process is 1) an individual cellulose fiber
having some lignin on the cellulose fiber while other areas of the
individual cellulose fibers have no lignin adhering to the surface
of the cellulose fiber, 2) a group of several fibers adhering
together but at least ten times less than in the amount of
plurality of fibers making up the fiber bundle, and 3) any
combination, where the average dimensions of the biomass in
particle form produced from the Thermo Mechanical Pulping process
is approximately 10 to 100 microns thick with a length of fifty
microns to three mm, and an aggregate amount of biomass in particle
form supplied from the outlet stage of the Thermo Mechanical
Pulping process has an increased exposed surface area of at least
twenty times the surface area compared to the surface area of a
same amount of biomass supplied to an input stage of the TMP
process.
5. The biomass composition of matter of claim 1, wherein the
pretreatment step is a Thermo Mechanical Pulping that uses two or
more stages that include a steam tube stage and a refiner unit
stage, where the steam tube stage has an input cavity to receive
biomass in chip form and a steam supply input to apply steam into a
vessel containing the biomass in chip form to elevate temperature
in the vessel to between 130 to 200 degrees C. at a pressure
between 70 and 110 PSI, where the biomass in chip form with
softened lignin is then fed from the steam tube stage to the
refiner unit stage, which is at the same pressure as the steam tube
stage, and where in the refiner unit stage a mechanical separator
is configured to further to cooperate with the steam to separate
the plurality of cellulose fibers in the fiber bundle into biomass
in particle form consisting of 1) individual strands of fibers 2) a
group of no more than three individual fibers in the group of
fibers 2), and 3) any combination of both.
6. The biomass composition of matter of claim 1, wherein the
pretreatment step is a steam explosion process that uses a
combination of heat, pressure, and moisture that are applied to
biomass in two or more stages to make the biomass in particle form,
where the biomass is created in a moist fine particle form, where
the steam explosion process applies steam to biomass in chip form
received in an input stage from a lower pressure steam supply input
to begin degrading bonds between the lignin and cellulose fibers of
the biomass and increase a moisture content of the biomass in chip
form, and then in another stage, apply a higher pressure steam at
at least ten times atmospheric pressure to heat and pressurize any
gases and fluids present inside the biomass in order to internally
blow apart the bulk structure of the biomass via a rapid
depressurization of the biomass with the increased moisture content
and degraded bonds, where the biomass produced into the moist fine
particle form from the stages has average dimensions of less than
50 microns thick and less than 500 microns in length.
7. The biomass composition of matter of claim 6, wherein the
biomass particle formed after the pretreatment step of the steam
explosion process is a fragment of one to several cellulose fibers
adhering to each other with having some lignin on each fiber but
merely a portion of these fibers from the fiber bundle remain
intact, and where the average dimensions of the particles of
biomass produced from the steam explosion process are approximately
10 to 100 microns thick with a length of less than 200 microns, and
the produced biomass in fine particle form has a length to
thickness aspect ratio on average of less than 10 to 1, and an
aggregate amount of biomass in fine particle form produced after
the steam explosion process has an increased exposed surface area
of at least twenty times the surface area compared to a surface
area of a same amount of biomass supplied to an input stage of the
steam explosion process.
8. The biomass composition of matter of claim 6, wherein the
biomass composition formed after the SEP pretreatment step is
multiple fragments of the individual cellulose fibers or even
several cellulose fibers clumped together; however, merely a
portion of the original cellulose fibers remain intact, which makes
the mass smaller and flow characteristics of the biomass in fine
particle form to flow like a grain of sand rather than like a fiber
stalk; and where the two or more stages includes a mechanical
agitation step of the biomass prior to forming the biomass
composition of multiple fragments of the individual cellulose
fibers or even several cellulose fibers clumped together.
9. The biomass composition of matter of claim 1, wherein the
decomposition of the large organic molecules in the biomass
gasification reaction occurs due exposure of the biomass
composition to elevated heat of greater than 700 degrees C. but not
with exposure to a flame or other combustion source, and where the
two-stage sequence of almost all of the lignin reacting and then
the cellulose and hemi-cellulose reacting during the biomass
gasification reaction produces a reaction product of resultant
stable ash formation, a complete amelioration of tar to less than
500 milligrams per normal cubic meter, and a yield of at least 90%
of the biomass to hydrogen, carbon dioxide, and carbon monoxide
gaseous products.
10. The biomass composition of matter of claim 1, wherein the
pretreatment step is SEP that uses two or more stages including a
thermally hydrating stage and a steam explosion stage, where the
thermally hydrating stage has steam applied to biomass received in
chip form in order to soften and elevate a moisture content of the
biomass so at least the cellulose fibers and surrounding lignin of
the biomass in the steam explosion stage can be internally blown
apart, and in the steam explosion stage, the softened and hydrated
biomass are exposed to 160 to 850 PSI and temperature between
160-270.degree. C. for a set time period to create high pressure
steam inside the partially hollow cellulose fibers and other porous
areas in the bulk structure of the biomass material, and then an
amount of pressure at an exit in the steam explosion stage is
dropped rapidly in less than three seconds by extruding the bulk
structure of the biomass through an orifice sized in proportion to
the fibers passing through it into a tube at normal atmospheric
pressure to cause an internal explosion, which internally blows
apart the biomass into minute fine particles of biomass, where
internally blowing apart the bulk structure of biomass in the fiber
bundle into pieces and fragments of cellulose fiber and lignin
results in 1) an increase of a surface area of the biomass in fine
particle form compared the received biomass in chip form, and 2)
the creation of the two-step reaction in the biomass gasification
reaction of any of lignin adhering cellulose fiber as well as any
loose chunks of lignin and then a reaction of the cellulose fibers
as opposed to a multistep cycling reaction of lignin and then the
cellulose fibers followed by lignin and more cellulose fibers.
11. A method to create a biomass composition of matter to be used
in 1) a biomass gasification reaction where larger organic
molecules making up the biomass are decomposed into smaller
molecules to create syngas components, including hydrogen (H2) and
carbon monoxide (CO), as a product of the biomass gasification
reaction, 2) a torrefaction process, or 3) any combination of the
two, comprising: creating biomass in a particle form in a
pretreatment step that occurs prior to the biomass gasification
reaction or torrefaction process, where the biomass initially has a
bulk structure including organic polymers of lignin that surround a
plurality of cellulose fibers in a fiber bundle, where the bulk
structure of the biomass is 1) stripped apart to at least partially
separate an outer layer of lignin in the biomass from the cellulose
fibers, 2) internally blown apart to create fragments of the fiber
bundle, and 3) any combination of the two in the pretreatment step
that uses at least moisture, pressure, and heat to liberate and
expose the cellulose fibers to be able to react in a two stage
sequence during the biomass gasification reaction or torrefaction
process rather than react in a repeating cycle of multiple layers
of lignin followed by the cellulose and hemi-cellulose; and where
the biomass in particle form has a length to thickness aspect ratio
on average of less than 300 to 1, a thickness on average of less
than 100 microns thick and a length on average of less than 3000
microns.
12. The method of claim 11, biomass particle created in the
pretreatment step includes both 1) chunks of pure lignin, from the
layer of lignin surrounding any hemi-cellulose and cellulose in the
cellulose fibers, that have been separated from the cellulose
fibers as well as 2) cellulose fibers now freestanding from the
fiber bundle where the freestanding cellulose fibers have some
lignin still attached to the surface of the fiber, where the
biomass particle when fed into the biomass gasifier is allowed a
more rapid exposure to directly react the cellulose and
hemi-cellulose as well as substantially eliminating having to react
layer after layer of lignin surrounding the cellulose and
hemi-cellulose, followed by another layer of lignin surrounding
cellulose and hemi-celluloses that would have to be sequentially
reacted through if the pretreatment step did not at least partially
separate the lignin from the cellulose fibers.
13. The method of claim 11, wherein the pretreatment step is a
Thermo Mechanical Pulping process using two or more stages to
pretreat the biomass for subsequent supply to the biomass gasifier,
where the stages are configured to use a combination of heat,
pressure, moisture, and mechanical agitation that are applied to
the biomass to degrade bonds between the lignin from the cellulose
fibers, then mechanically strip fibers from the fiber bundle to
separate the outer layer of lignin in the biomass from the
cellulose fibers, and then supply the particles in a pulp form from
an outlet stage of the Thermo Mechanical Pulping process.
14. The method of claim 13, wherein the biomass particle formed
after the pretreatment step of the Thermo Mechanical Pulping
process is 1) an individual cellulose fiber having some lignin on
the cellulose fiber while other areas of the individual cellulose
fibers have no lignin adhering to the surface of the cellulose
fiber, 2) a group of several fibers adhering together but at least
ten times less than in the amount of plurality of fibers making up
the fiber bundle, and 3) any combination, where the average
dimensions of the biomass in particle form produced from the Thermo
Mechanical Pulping process is approximately 10 to 100 microns thick
with a length of three mm or less, and an aggregate amount of
biomass in particle form supplied from the outlet stage of the
Thermo Mechanical Pulping process has an increased exposed surface
area of at least twenty times the surface area compared to the
surface area of a same amount of biomass supplied to an input stage
of the TMP process.
15. The method of claim 11, wherein the pretreatment step is a
Thermo Mechanical Pulping that uses two or more stages that include
a steam tube stage and a refiner unit stage, where the steam tube
stage has an input cavity to receive biomass in chip form and a
steam supply input to apply steam into a vessel containing the
biomass in chip form to elevate temperature in the vessel to
between 130 to 200 degrees C. at a pressure between 70 and 110 PSI,
where the biomass in chip form with softened lignin is then fed
from the steam tube stage to the refiner unit stage, which is at
the same pressure as the steam tube stage, and where in the refiner
unit stage a mechanical separator is configured to further to
cooperate with the steam to separate the plurality of cellulose
fibers in the fiber bundle into biomass in particle form consisting
of 1) individual strands of fibers 2) a group of no more than three
individual fibers in the group of fibers 2), and 3) any combination
of both.
16. The method of claim 11, wherein the pretreatment step is a
steam explosion process that uses a combination of heat, pressure,
and moisture that are applied to biomass in two or more stages to
make the biomass in particle form, where the biomass is in a moist
fine particle form, where the steam explosion process applies steam
to biomass in chip form received in an input stage from a lower
pressure steam supply input to begin degrading bonds between the
lignin and cellulose fibers of the biomass and increase a moisture
content of the biomass in chip form, and then in another stage,
apply a higher pressure steam at at least ten times atmospheric
pressure to heat and pressurize any gases and fluids present inside
the biomass in order to internally blow apart the bulk structure of
the biomass via a rapid depressurization of the biomass with the
increased moisture content and degraded bonds, where the biomass
produced into the moist fine particle form from the stages has
average dimensions of less than 50 microns thick and less than 500
microns in length.
17. The method of claim 16, wherein the biomass particle formed
after the pretreatment step of the steam explosion process is a
fragment of one to several cellulose fibers adhering to each other
with having some lignin on each fiber but merely a portion of these
fibers from the fiber bundle remain intact, and where the average
dimensions of the particles of biomass produced from the steam
explosion process are approximately 10 to 100 microns thick with a
length of less than 200 microns, and the produced biomass in fine
particle form has a length to thickness aspect ratio on average of
less than 10 to 1, and an aggregate amount of biomass in fine
particle form produced after the steam explosion process has an
increased exposed surface area of at least twenty times the surface
area compared to a surface area of a same amount of biomass
supplied to an input stage of the steam explosion process.
18. The method of claim 16, wherein the biomass composition formed
after the SEP pretreatment step is multiple fragments of the
individual cellulose fibers or even several cellulose fibers
clumped together; however, merely a portion of the original
cellulose fibers remain intact, which makes the mass smaller and
flow characteristics of the biomass in fine particle form to flow
like a grain of sand rather than like a fiber stalk; and where the
two or more stages includes a mechanical agitation step of the
biomass prior to forming the biomass composition of multiple
fragments of the individual cellulose fibers or even several
cellulose fibers clumped together.
19. The method of claim 11, wherein the decomposition of the large
organic molecules in the biomass gasification reaction occurs due
to the exposure of the biomass composition to elevated heat of
greater than 700 degrees C. but not with exposure to a flame or
other combustion source, and where the two-stage sequence of almost
all of the lignin reacting and then the cellulose and
hemi-cellulose reacting during the biomass gasification reaction
produces a reaction product of resultant stable ash formation, a
complete amelioration of tar to less than 500 milligrams per normal
cubic meter, and a yield of at least 90% of the biomass to
hydrogen, carbon dioxide, and carbon monoxide gaseous products.
20. The method of claim 11, wherein the pretreatment step is SEP
that uses two or more stages including a thermally hydrating stage
and a steam explosion stage, where the thermally hydrating stage
has steam applied to biomass received in chip form in order to
soften and elevate a moisture content of the biomass so at least
the cellulose fibers and surrounding lignin of the biomass in the
steam explosion stage can be internally blown apart, and in the
steam explosion stage, the softened and hydrated biomass are
exposed to 160 to 850 PSI and temperature between 160-270.degree.
C. for a set time period to create high pressure steam inside the
partially hollow cellulose fibers and other porous areas in the
bulk structure of the biomass material, and then an amount of
pressure at an exit in the steam explosion stage is dropped rapidly
in less than three seconds by extruding the bulk structure of the
biomass into a tube at normal atmospheric pressure to cause an
internal explosion, which internally blows apart the biomass into
minute fine particles of biomass, where the exit is an orifice
sized in proportion to the fibers passing through it to cause a
violent interaction of the fibers with neighboring fibers, the
edges of the exit orifice, and any combination of both, where
internally blowing apart the bulk structure of biomass in the fiber
bundle into pieces and fragments of cellulose fiber and lignin.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of and is a continuation
in part of US application titled "Pretreatment of biomass using
thermo mechanical methods before gasification," Ser. No.
13/429,847, filed on Mar. 26, 2012 as well as US application titled
"Pretreatment of biomass using steam explosion methods," Ser. No.
13/531,318 filed on Jun. 22, 2012.
FIELD
[0002] The invention generally relates to pre-treatment of biomass
using steam explosion methods, thermal mechanical pulping
processes, and others to condition the biomass particle before
torrefaction or gasification.
BACKGROUND
[0003] Medium density fiberboard is made with dry wood chips and
uses fibers of trees in the fiberboard. Other processes require
multiple steps of grinding the wood chips, drying the chips,
re-grinding the chips, moisturizing the fibers, densifying the
fibers, and then densifying the wood chips (such as in the form of
pellets). These processes are complex, capital intensive and
require large amounts of energy. Some other typical processes need
to dry the chips of biomass and then grind the chips to very small
dimensions before sending them to a subsequent heating/processing
unit. This drying and grinding takes a lot of energy and capital
costs. These processes produce small fibers but ones that are many
times the size of the fine powder particles produced in the biomass
particle and none have been used a biomass gasification reaction.
Likewise, some processes have produced fuel compositions from
ethanol but not through torrefaction or biomass gasification.
SUMMARY
[0004] A biomass composition of matter to be used in a torrefaction
process or a biomass gasification reaction. The biomass in a
particle form is created in a pretreatment step that occurs prior
to the torrefaction process or the biomass gasification reaction. A
bulk structure of the biomass is 1) stripped apart to at least
partially separate an outer layer of lignin in the biomass from the
cellulose fibers, 2) internally blown apart to create fragments of
the fiber bundle, and 3) any combination of the two in the
pretreatment step. The biomass in particle form has a length to
thickness aspect ratio on average of less than 300 to 1, a
thickness on average of less than 100 microns thick and a length on
average of less than 3000 microns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The multiple drawings refer to embodiments of the
disclosure. While embodiments of the disclosure described herein
are subject to various modifications and alternative forms,
specific embodiments thereof have been shown by way of example in
the drawings and will herein be described in detail.
[0006] FIG. 1 illustrates a diagram of example biomass in chip form
exploded into biomass in fine particle form.
[0007] FIG. 2 illustrates a diagram of example biomass in chip form
having a bundle of fibers that are frayed or partially separated
into individual fibers.
[0008] FIGS. 3-5 illustrate diagrams of different levels of
magnification of an example chip of biomass having a fiber bundle
of cellulose fibers surrounded and bonded together by lignin.
[0009] FIG. 6 illustrates a flow schematic of an embodiment of a
steam explosion unit having an input cavity to receive biomass as a
feedstock, two or more steam supply inputs, and two or more stages
to pre-treat the biomass for subsequent supply to a torrefaction
unit and/or biomass gasifier.
[0010] FIG. 7 illustrates a flow schematic of an embodiment of a
Thermo Mechanical Pulping unit having an input cavity to receive
biomass as a feedstock, a steam supply input, and two or more
stages to pre-treat the biomass for subsequent supply to a
torrefaction unit and/or biomass gasifier.
[0011] While the disclosure is subject to various modifications and
alternative forms, specific embodiments thereof have been shown by
way of example in the drawings and will herein be described in
detail. The disclosure should be understood to not be limited to
the particular forms disclosed, but on the contrary, the intention
is to cover all modifications, equivalents, and alternatives
falling within the spirit and scope of the disclosure.
DETAILED DISCUSSION
[0012] In the following description, numerous specific details are
set forth, such as examples of specific chemicals, named
components, connections, types of heat sources, etc., 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
disclosure may be practiced without these specific details. In
other instances, well known components or methods have not been
described in detail but rather in a block diagram in order to avoid
unnecessarily obscuring the present disclosure. Thus, the specific
details set forth are merely exemplary. The specific details may be
varied from and still be contemplated to be within the spirit and
scope of the present disclosure.
[0013] In general, a number of example processes for and
apparatuses associated with a pre-treatments of biomass are
described. The following drawings and text describe various example
implementations for biomass particle created by the pre-treatments
of biomass. In an embodiment, a method creates a biomass
composition of matter to be used in 1) a biomass gasification
reaction where larger organic molecules making up the biomass are
decomposed into smaller molecules to create syngas components,
including hydrogen (H2) and carbon monoxide (CO), as a product of
the biomass gasification reaction, 2) a torrefaction process, or 3)
any combination of the two. Biomass in a particle form is created
in a pretreatment step that occurs prior to the biomass
gasification reaction or torrefaction process. The biomass
initially has a bulk structure including organic polymers of lignin
that surround a plurality of cellulose fibers in a fiber bundle.
The bulk structure of the biomass is 1) stripped apart to at least
partially separate an outer layer of lignin in the biomass from the
cellulose fibers, 2) internally blown apart to create fragments of
the fiber bundle, and 3) any combination of the two in the
pretreatment step that uses at least moisture, pressure, and heat
to liberate and expose the cellulose fibers to be able to react in
a two stage sequence during the biomass gasification reaction or
torrefaction process rather than react in a repeating cycle of
multiple layers of lignin followed by the cellulose and
hemi-cellulose. The produced biomass in particle form has a length
to thickness aspect ratio on average of less than 300 to 1, a
thickness on average of less than 100 microns thick and a length on
average of less than 3000 microns.
[0014] One skilled in the art will understand parts and aspects of
many of the designs discussed below within this illustrative
document may be used as stand-alone concepts or in combination with
each other.
[0015] FIG. 1 illustrates a diagram of example biomass in chip form
exploded into biomass in fine particle form. Likewise, FIG. 2
illustrates a diagram of example biomass in particle form just
starting to have the cellulose fibers separated from the bundle of
fibers.
[0016] A pretreatment step may create a biomass composition of
matter, such as those examples shown in FIGS. 1 and 2, to be used
in a subsequent torrefaction process or a biomass gasification
reaction where larger organic molecules making up the biomass are
decomposed into smaller molecules to create syngas components,
including hydrogen (H2) and carbon monoxide (CO), as a product of
the biomass gasification reaction, 2) a torrefaction process, or 3)
any combination of the two. The biomass in a particle form 153 is
created in the pretreatment step that occurs prior to the
torrefaction of the biomass particle or the biomass gasification
reaction of the biomass particle.
[0017] The biomass in chip form 151 initially has a bulk structure
including organic polymers of lignin that surround a plurality of
cellulose fibers in a fiber bundle. The bulk structure of the
biomass may be 1) stripped apart to at least partially separate an
outer layer of lignin in the biomass from the cellulose fibers, 2)
internally blown apart to create fragments of the fiber bundle, and
3) any combination of the two in the pretreatment step. The
pretreatment step, such as Thermo Mechanical Pulping (TMP), Steam
Explosion Process (SEP) or similar process, may use at least
moisture, pressure, and heat to liberate and expose the cellulose
fibers to be able to react in a two stage sequence during the
biomass gasification reaction or torrefaction process rather than
react in a repeating cycle of multiple layers of lignin followed by
the cellulose and hemi-cellulose. The biomass in particle form 153
may have a length to thickness aspect ratio on average of less than
300 to 1, a thickness on average of less than 100 microns thick,
and a length on average of less than 3000 microns.
[0018] In an embodiment, woody biomass can arrive at the
pretreatment process in the form of chips 151 that can range in
size from 0.5 to 3'' in length. (See chip 351 in FIG. 3 and the
example chips 151 in FIG. 1) This size is too large to be easily
gasified in most processes. Further, the chips contain cellulose
fibers and hemi-cellulose polymers that are held together with
lignin and essentially surrounded by a layer of lignin. In normal
operations, the biomass in chip form 151 may be ground into smaller
sizes so they can be gasified or torrefied. The fibers in these
chips 151 are stacked in bundles and layers much like soda straws
in a box. (See FIG. 5) The lignin surrounds the individual straws
(fibers) and binds the straws (fibers) together. (See FIG. 4) When
a chemical reaction is used to convert the biomass in chip form 151
to a fuel, the reaction must generally start on the outside of the
chip and work its way to the center. In these types of
arrangements, there are multiple repeated layers that the chemical
reaction process must peal through to completely convert the chip
to useful fuel. For example, the chemical reaction must first react
the lignin in an outer layer, then the hemi-cellulose and cellulose
(carbohydrate), then go to the next layer of lignin surrounding
carbohydrate, and so on until the entire chip is consumed. The
system could grind the chips to a finer size, which could speed up
the kinetics but the process would still be one of reacting lignin
followed by carbohydrate, lignin followed by carbohydrate, and so
on.
[0019] The pretreatment system advantageously strips apart and/or
internally blows apart the fibers in the fiber bundle from each
other leaving the lignin that was in the middle lamella (See FIG.
4) in either free standing chunks of lignin or a small amount left
on the surface of the individual fibers. The produced biomass in
particle form 153 has all of the fiber bundle separated into
individual components. If the TMP process has been used as the
pretreatment step then biomass in particle form 753 will be
individual or small groups of fibers as shown in FIG. 7. If the
steam explosion process has been used as the pretreatment step then
biomass in particle form 153, 653 will merely be fragments of the
fibers as shown in FIGS. 6 and 1. The outer layer of lignin gluing
together and binding the cellulose fiber bundle is generally peeled
away or blown apart allowing much more rapid exposure to the
carbohydrates as well as substantially eliminates having to react
layer after layer of lignin surrounding carbohydrates, followed by
another layer of lignin surrounding carbohydrates. Chunks of pure
lignin will be created as well as lignin that is exposed on the
outside of the cellulose fiber for rapid reaction. After the lignin
is reacted, the cellulose fiber is then exposed and the remaining
carbohydrate and lignin in the fiber are reacted. In this manner,
almost all of the lignin would be exposed and reacted at about the
same time and then the carbohydrate components can be reacted.
Thus, the individual fibers or fragments of fibers with the lignin
on the surface can now be reacted. Since the lignin is on the
surface it should react first and then the carbohydrates of
cellulose and hemi-cellulose. Some lignin still resides inside the
fiber but should react quickly as the carbohydrate is removed. This
makes the biomass gasification reaction more like a two step
process than a multistep cycling reaction. The biomass gasification
reaction does not need to peal through the biomass in chip form 151
to gasify it--cycling from lignin to carbohydrate to lignin to
carbohydrate--etc.
[0020] Note, the lignin-coated fibers could be first processed
using torrefaction and or extractive removal, and then followed by
biomass gasification, or gasified directly or only torrefied.
[0021] Thus in an embodiment, the biomass particle 153 created in
the pretreatment step includes both 1) chunks of pure lignin, from
the outer layer of lignin surrounding any hemi-cellulose and
cellulose in the cellulose fibers, that have been separated from
the cellulose fibers as well as 2) cellulose fibers now
freestanding from the fiber bundle. The freestanding cellulose
fibers generally will have some lignin still attached to the
surface of the fiber. The biomass particle when fed into the
biomass gasifier is allowed a more rapid exposure to directly react
the cellulose and hemi-cellulose as well as substantially
eliminating having to react layer after layer of lignin surrounding
the cellulose and hemi-cellulose, followed by another layer of
lignin surrounding cellulose and hemi-celluloses, etc. that would
have to be sequentially reacted through if the pretreatment step
did not at least partially separate the lignin from the cellulose
fibers. The produced particles of biomass 153 are fed downstream to
the biomass gasifier for the rapid biomass gasification reaction in
a reactor of the biomass gasifier because they create a higher
surface to volume ratio for the same amount of biomass compared to
the received biomass in chip form 151, which allows a higher heat
transfer to the biomass material and a more rapid thermal
decomposition and gasification of all of the molecules in the
biomass.
[0022] Referring to FIG. 2, the example fiber bundle 252 is
starting to have cellulose fibers separated from the bundle of
fibers to create multiple discrete pieces of biomass in particle
form. This is also shown as the middle step in FIGS. 6 and 7 where
the tubular fibers are starting to separate in the fiber bundle
652, 752.
[0023] The pretreatment step of Thermo Mechanical Pulping process
can make the biomass in particle form. Thus, Thermo mechanical
pulping is one method that actually separates the fibers from each
other in the fiber bundle leaving the lignin and hemi-cellulose at
least partially intact on the outside of the cellulose fiber.
[0024] Referring to FIG. 7, the biomass in particle form 753 after
the pretreatment step of the Thermo Mechanical Pulping process is
1) an individual cellulose fiber having some lignin on the
cellulose fiber while other areas of the individual cellulose
fibers have no lignin adhering to the surface of the cellulose
fiber, 2) a group of several fibers adhering together but at least
ten times less than in the amount of plurality of fibers making up
the original fiber bundle in the chip of biomass 751, and 3) any
combination. The average dimensions of the biomass in particle form
produced from the Thermo Mechanical Pulping process is generally
approximately 10 to 100 microns thick and preferably 20-50 microns
thick with a length of three mm or less. An aggregate amount of
biomass in particle form 753 supplied from the outlet stage of the
Thermo Mechanical Pulping process have an increased exposed surface
area of at least twenty times the surface area compared to the
surface area of a same amount of biomass in chip form 751 supplied
to an input stage of the TMP pretreatment step.
[0025] In general, the Thermo Mechanical Pulping process can use
two or more stages to pretreat the biomass for subsequent supply to
the biomass gasifier. The stages are configured to use a
combination of heat, pressure, moisture, and mechanical agitation
that are applied to the biomass to degrade bonds between the lignin
from the cellulose fibers, and then mechanically strip fibers from
the fiber bundle to separate an outer layer of lignin in the
biomass from the cellulose fibers. The stages then supply the
biomass particles in a pulp form from an outlet stage of the Thermo
Mechanical Pulping process to one of a densification unit, a
torrefaction unit 712, a dryer, or a biomass gasifier 714.
[0026] In an embodiment, the multiple stages of Thermo Mechanical
Pulping are configured to loosen and strip fibers from the lignin
in the biomass. The two or more stages may include a steam tube
stage 706 and a refiner unit stage 708. The steam tube stage 706
has the input cavity to receive biomass in chip form 751 and a
steam supply input to apply steam into a vessel containing the
biomass in chip form 751 to elevate temperature in the vessel to
between 130 to 200 degrees C. at a pressure between 70 and 110 PSI.
In an embodiment, chips 751 are pretreated with steam in the steam
tube's pressure vessel 706 at about 160.degree. C. and about 90 psi
for approximately 2 minutes. These conditions are sufficient to
soften the lignin. The biomass in chip form 751 with softened
lignin is then fed from the steam tube stage 706 to the refiner
unit stage 708, which is at the same pressure as the steam tube
stage 706. In the refiner unit 708, a mechanical separator is
configured to further to cooperate with the steam to separate the
plurality of cellulose fibers in the fiber bundle into biomass in
particle form 753 consisting of 1) individual strands of fibers 2)
a group of no more than three individual fibers in the group of
fibers 2), and 3) any combination of both. A conveying system
coupled to a collection chamber at an outlet stage of the refiner
unit stage supplies particles of biomass in pulp form. A majority
of the initial lignin and cellulose making up the biomass received
in the receiver section of the thermally decomposing stage remains
in the produced particles of biomass but is now substantially
separated from the fibers in pulp form.
[0027] FIGS. 3-5 illustrate diagrams of different levels of
magnification of an example biomass in chip form having a fiber
bundle of cellulose fibers surrounded and bonded together by
lignin.
[0028] FIG. 3 shows a cross section of a cut tree. The figure
illustrates the bark on the outside and the annual rings of the
example biomass in log form. There is also a microscopic
illustration of an example wood chip from that log. The annual
rings are visible as alternating high and low density areas. Thus,
a chemical reaction of molecules of this chip of biomass entails
progressively working away--one layer of fibers at a time--from the
outside of the biomass in chip form 353 to the inside of the chip
until the entire chip is consumed. However, typically, the outer
layers of the biomass chip fully react; whereas, the inner layers
do not fully react and this tends to cause excessive char and tar
as products of the chemical reaction verses higher yields of
gaseous products and resultant ash.
[0029] FIG. 5 shows an enlargement of the example piece of biomass
in chip form 551. The fibers extend in the vertical direction.
Three growth regions are shown, an outer low density (fast growing
spring wood), a high-density region (slow growing summer wood), and
another low-density region. This corresponds to, for example, one
and a half year's growth. The straight standing fibers are `bonded`
or `glued` together by lignin that is deposited between the
fibers.
[0030] FIG. 4 shows an even greater magnification of the biomass in
chip form 451 with the lignin in the space between the cellulose
fibers in the fiber bundle. FIG. 4 illustrates a chip of biomass
451 having a fiber bundle of cellulose fibers surrounded and bonded
together by lignin. The space between the fibers is called the
middle lamella (ML).
[0031] Generally, biomass may contain a cellulose core with a
coating of hemi-cellulose and lignin.
[0032] Cellulose is a principal chemical constituent of the cell
walls of higher orders of plants. Cellulose is a complex
carbohydrate, such as (C6H10O5), occurring in the form of polymer
chains, primarily Glucose molecules joined together end to end.
Cellulose contains linear polysaccharides in the cell walls. The
multiple groups of glucose molecules form a chain held firmly
together side-by-side and forming microfibrils with high tensile
strength. Lignin and hemi-cellulose can also be found between the
microfibrils bonding them together and contributing to the strength
of the fiber. Microfibrils can be grouped together to form fibrils
and the fibrils can be grouped together to form the cellulose
fibers. Lignin and hemi-cellulose can be found between each of
these components providing additional strength to the fiber. The
cellulose molecules form the fibers. Note, the SEP explosion
pretreatment step can even separate some of the microfibril bonds
making a frayed strand of fiber.
[0033] Hemi-cellulose is a group of carbohydrates found in or
bonded to the cell wall, in more or less intimate association with
cellulose. This group of carbohydrates generally includes those
less-resistant substances in the cell wall, which though insoluble
in hot water can be removed with either hot or cold dilute alkalis
or readily hydrolyzed into sugars and constituent acids by means of
hot dilute acids. It may be produced from `other` products of
photosynthesis: [0034] 6-carbon sugars (glucose, galactose,
mannose) [0035] 5-carbon sugars (xylose and arabinose) [0036] Sugar
derivatives (glucuronic acid) [0037] branched polymers with low DP
(.about.200) [0038] contributes to bonding between cellulose and
lignin
[0039] Thus, the hemi-cellulose may be an amorphous group of
branched polysaccharides that surrounds the cellulose fibers and is
a linkage between the cellulose fibers and the lignin. The
cellulose is typically a homogeneous polymer while the
hemi-cellulose is typically a heterogeneous chemical group of
polymers.
[0040] Lignin is a complex and high molecular weight polymer built
upon phenyl propane units, such as (C10H1203), bound together by
ether and carbon-carbon bonds. Lignin surrounds and occurs between
cell walls making up the fibers acting as a binding agent to hold
cells together. Lignin adheres between the outer layers of the
cellulose fibers giving structural rigidity to the biomass made up
bundles of cellulose fibers and holds those cellulose fibers
together.
[0041] Referring to FIG. 1, several pieces of biomass in chip form
151 are exploded into a plurality of pieces of biomass in fine
particle form 153.
[0042] FIG. 6 illustrates a flow schematic of an embodiment of a
steam explosion unit having an input cavity to receive biomass as a
feedstock, two or more steam supply inputs, and two or more stages
to pre-treat the biomass for subsequent supply to a biomass
gasifier and/or torrefaction unit.
[0043] Referring to FIG. 6, the steam explosion process 608 applies
steam to the biomass in chip form 651 received in an input stage
from a lower pressure steam supply input to begin degrading bonds
between the lignin and cellulose fibers of the biomass and increase
a moisture content of the biomass in chip form 651. Next, in
another stage, the SEP process 608 applies a higher pressure steam
at at least ten times atmospheric pressure to heat and pressurize
any gases and fluids present inside the biomass in order to
internally blow apart the bulk structure of the biomass via a rapid
depressurization of the biomass with the increased moisture content
and degraded bonds.
[0044] In an embodiment, the thermally hydrating stage has low
pressure steam applied to the biomass received in chip form 651 in
order to soften and elevate a moisture content of the biomass so at
least the cellulose fibers and surrounding lignin of the biomass in
the steam explosion stage can be internally blown apart in the next
stage. The biomass in chip form 651 in the thermally hydrating
stage is heated to greater than 60.degree. C. using the low
pressure steam, and in the steam explosion stage, the softened and
hydrated biomass is exposed to 160 to 850 PSI and temperature
between 160-270.degree. C. for a sufficient time period to create
high pressure steam/fluid inside the partially hollow cellulose
fibers and other porous areas in the bulk structure of the biomass
material. In an embodiment, chips of biomass are heated to
temperatures over 200.degree. C. and pressures over 23 bar (325
psi). The higher the pressure tends to create smaller fragments of
lignin and cellulose fibers. In addition, when mechanical agitation
is applied to the biomass as the biomass proceeds through the SEP
process 608, this factor also tends to create smaller fragments of
lignin and cellulose fibers when the biomass composition exits the
steam explosion stage.
[0045] The pressure at an exit in the steam explosion stage is
dropped rapidly in less than three seconds by extruding the bulk
structure of the biomass into a tube at normal atmospheric pressure
to cause an internal explosion, which internally blows apart the
biomass into minute fine particles of biomass 653.
[0046] As shown in the diagram on the bottom of the figure, the
biomass in fine particle form 653 formed after the pretreatment
step of the steam explosion process is a fragment of one to several
cellulose fibers adhering to each other with having some lignin on
the fiber while other areas of the individual cellulose fibers have
no lignin adhering to the surface of the cellulose fiber. Note, the
biomass composition formed after the pretreatment step is generally
individual cellulose fibers or even several cellulose fibers
clumped together; however, merely a portion of the cellulose fibers
remain intact, which makes the mass of each biomass particle
smaller. The biomass composition formed after the SEP pretreatment
step is multiple fragments of the individual cellulose fibers or
even several cellulose fibers clumped together. The flow
characteristics of these fragments of biomass in particle form 653
is more like that of grains of sand rather than like fiber
stalks.
[0047] The biomass produced into the moist fine particle form 653
from the stages may have average dimensions of less than 50 microns
thick and less than 500 microns in length. In an embodiment, the
average dimensions of the particles of biomass produced from the
steam explosion process are approximately 5 to 100 microns thick
preferably 5-50 microns thick with a length of less than 200
microns (outliers may be up to 500 microns long), and the produced
biomass in a particle form 653 has a length to thickness aspect
ratio on average of less than 10 to 1. An aggregate amount of
biomass in particle form 653 produced after the SEP pretreatment
step has an increased exposed surface area of at least 20 times the
surface area compared to a surface area of a same amount of biomass
in chip form 653 supplied to an input stage of the SEP pretreatment
step. The thickness of a single cell of biomass depending on the
plant species is around 20 to 40 microns thick. Thus, the steam
explosion process is generally blowing apart each cell in the
biomass creating a small thickness of 5 to 20 microns thick for the
resulting fine particles of biomass produced from the SEP.
[0048] Note, the lower the pressure in the steam explosion reactor
vessel, such as (6 bar), the bigger the particles of biomass are
formed almost like fiber particles; and likewise, the higher the
pressure in the steam explosion reactor vessel, such as (16 bar),
the smaller the particles of biomass are formed almost like fine
grains of sand or finely ground up coffee grounds.
[0049] The increased surface area of the resulting fine particles
of biomass formed as a product of the SEP also can improve the
downstream biomass gasifier's performance. The SEP produces a
higher amount of surface area for a same starting quantity of
biomass than the TMP process on the biomass. The higher amount of
surface area makes a higher throughput of biomass material
attainable through the same biomass gasifier design. The reaction
rate of biomass particles passing through the biomass gasifier in
the biomass gasification reaction seems to be a mathematical
function of the surface area of those fine particles biomass. A
steam oxidation of the biomass occurs in the biomass gasification
reaction. The steam oxidation of the biomass affects the reaction
rate of the biomass particles in the biomass gasification reaction.
Thus, a higher throughput is attainable with the increased reaction
rate due to the greater surface area of the produced fine particles
of biomass from SEP. The higher throughput results in any of 1) a
lower residence time is needed in the biomass gasifier for a same
amount of SEP biomass particles compared to a TMP biomass particle
size; and alternatively, 2) a higher quantity of SEP biomass
particles can be reacted in the biomass gasifier compared to a TMP
biomass particle size for a same amount of residence time in the
biomass gasifier.
[0050] Those produced moist fine particles of biomass 653 can be
subsequently fed to a feed section of the biomass gasifier 614, the
torrefaction unit 612, a densification unit, a dryer, or any
combination of these. Note, the produced moist fine particles of
biomass 653 can be directly fed to a feed section of the biomass
gasifier 614 after passing through a dryer/low temperature 300
degree C. torrefaction unit and obtaining the desire moisture
content for the biomass gasifier.
[0051] The internally blowing apart the bulk structure of biomass
in a fiber bundle into pieces and fragments of cellulose fiber,
lignin and hemi-cellulose results in all three 1) an increase of a
surface area of the biomass in fine particle form compared the
received biomass in chip form 651, 2) a creation of the two step
reaction in the biomass gasification reaction of any of lignin
adhering cellulose fiber as well as any loose chunks of lignin and
then a reaction of the cellulose fibers as opposed to a multistep
cycling reaction of lignin and then the cellulose fibers followed
by lignin and more cellulose fibers, and 3) a change in viscosity
of the resulting produced biomass in fine particle form 653 to flow
like grains of sand rather than like fibers.
[0052] TMP and SEP are two methods discussed for producing the
biomass in particle form 653, 753. Other methods for producing
these chunks of lignin and lignin-coated fibers are generally
regarded as high yield pulping processes. One of these includes
what is known as CTMP--Chemi-thermo mechanical pulp. In this
process sodium sulfite is added to help loosen the lignin. Grinding
the chips in a stone mill may also be used. These fibers are known
as stone ground wood.
[0053] Moisture values in the incoming biomass in chip form 651 can
vary from about 15% to 60% for biomass left outside without extra
drying. Chips of biomass may be generated by a chipper unit 604
cooperating with some filters with dimensions to create chips of
less than about one inch and on average about 0.5 inches in average
length and a 1/4 inch in thickness on average. (See for example
FIG. 3 a chip of biomass 351 from a log of biomass) Chips of
biomass are fed on a conveyor or potentially placed in a pressure
vessel in the thermally decomposing stage in the steam explosion
unit 608 that starts a decomposition, hydrating/moistening, and
softening of the chips of biomass using initially low-pressure
saturated steam. The low-pressure saturated steam may be at 100
degrees C. The system may also inject some flow aids at this point,
such as recycled ash from the biomass gasifier 614, to prevent
clogs and plugging by the biomass chips.
[0054] Both the steam explosion unit 608 and the TMP process 706,
708 are configured to receive two or more types of biomass feed
stocks, where the different types of biomass include 1) soft woods,
2) hard woods, 3) grasses, 4) plant hulls, and 5) any combination
that are blended. The steam explosion process or TMP turns them
into a homogenized feedstock that is subsequently collected and
then fed into the biomass gasifier 614, 714 or torrefaction unit
612, 712. The torrefaction unit 612, 712 and biomass gasifier 614,
714 are designed to be feedstock flexible without changing out the
physical design of the feed supply equipment or the physical design
of the biomass gasifier or torrefaction unit via at least particle
size control of the biomass particles produced from steam explosion
stage or TMP process.
[0055] Thus, in an embodiment, the thermally hydrating stage may
receive the biomass in chip form 651 including leaves, needles,
bark, and wood. The thermally hydrating stage applies the
low-pressure saturated steam to the biomass at a temperature above
a glass transition point of the lignin in order to soften and
elevate the moisture content the biomass so the cellulose fibers of
the biomass in the steam explosion stage can easily be internally
blown apart from the biomass in chip form 651. In an embodiment,
the chips of biomass are heated to greater than 60.degree. C. using
the steam. The low pressure steam supply input applies low-pressure
saturated steam into a vessel containing the chips of biomass at an
elevated temperature of above 60 degrees C. but less than 120
degrees C. at a pressure around atmospheric PSI, to start a
decomposition, hydrating, and softening of the received biomass in
chip form 651. The low pressure supply input may consist of several
nozzles strategically placed around the vessel. The chips stay in
the thermally hydrating stage long enough to saturate with
moisture.
[0056] The thermally hydrating stage feeds chips of biomass that
have been softened and increased in moisture content to the steam
explosion stage, which is at a pressure 10 to 40 times the pressure
as is present in the thermally hydrating stage and an elevated
temperature, such as a temperature of 160-270.degree. C.,
223.degree. C. preferably. The pressure may be at 180-850 Pound per
Square Inch (PSI) (400 PSI preferably). The steam explosion stage
further raises the moisture content of the plug of biomass to at
least 40% by weight and preferably 50 to 55% moisture content by
weight. The % moisture by weight may be the weight of water divided
by a total weight consisting of the chips of biomass plus a water
weight. In the steam explosion stage, the softened and hydrated
chips of biomass are exposed to high temperature and high-pressure
steam for a sufficient time period, such as 3 minutes to 15
minutes, to create high pressure steam inside the partially hollow
cellulose fibers and other porous areas in the bulk structure of
the biomass material. (See for example FIG. 5 illustrating a chip
of biomass having a fiber bundle of cellulose fibers surrounded and
bonded together by lignin but under magnification having numerous
porous areas.)
[0057] Note, the Steam Explosion Process (SEP) on the biomass chips
uses no mechanical refiner to separate fibers; rather, the biomass
chip is internally exploded in SEP. Also, no chemical acid
additives are added in SEP, such as added acid; and thus, a yield
of 88% or greater may be achieved.
[0058] After the thermally hydrating stage, the softened biomass in
chip form 651 are any combination of 1) crushed and 2) compressed
into a plug form, which is then fed into a continuous screw
conveyor system, which these provide a mechanical agitation to the
biomass to be combined with the high pressure steam explosion used
in this SEP process. The continuous screw conveyor system moves the
biomass in plug form into the steam explosion stage. The continuous
screw conveyor system also uses the biomass in plug form to prevent
blow back backpressure from the high-pressure steam present in the
steam explosion stage from affecting the thermally hydrating stage.
Other methods could be used such as 1) check valves and 2) moving
biomass in stages where each stage is isolatable by an opening and
closing mechanism.
[0059] The steam explosion stage can operate at pressures up to 850
psi. The plug screw feeder conveys the chips along the steam
explosion stage. High-pressure steam is introduced into the plug
screw feeder in a section called the steam mixing conveyor. The
high pressure supply input may consist of several nozzles
strategically placed around the steam mixing conveyor. Retention
time of the biomass chip material through the steam explosion stage
is accurately controlled via the plug screw feeder. In the steam
explosion stage, the biomass in plug form is exposed to high
temperature and high pressure steam at at least 160 degree C. and
160 PSI from the high pressure steam input for at least 5 to 15
minutes and preferably around 10 minutes until moisture penetrates
porous portions of the bulk structure of the biomass and all of the
liquids and gases in the biomass are raised to the high
pressure.
[0060] The continuous screw conveyor system feeds the biomass in
plug form through the steam explosion stage to an exit.
[0061] In an embodiment, a small opening forms the exit, such as
1/2 to 3/4 inch opening, and goes into a tube that is maintained at
around atmospheric pressure and any internal fluids or gases at the
high pressure expand to internally blow apart the biomass. The
pressure at the exit in the steam explosion stage is dropped
rapidly by extruding the bulk structure of the biomass at between
160 to 850 PSI into a tube at normal atmospheric pressure to cause
an internal "explosion" rapid expansion of steam upon the drop in
pressure or due to the "flashing" of liquid water to vapor upon the
drop in pressure below its vapor pressure, which internally blows
apart the biomass in chip form 651 into minute fine particles of
biomass 653. In another embodiment, the steam explosion reactor
portion of the steam explosion stage contains a specialized
discharge mechanism configured to "explode" the biomass chip
material to a next stage at atmospheric pressure. The discharge
mechanism opens to push the biomass from the high-pressure steam
explosion reactor out this reactor discharge outlet valve or door
into the feed line of the blow tank.
[0062] Thus, the pressurized steam or super-heated water out of the
steam explosion reactor in this stage is then dropped rapidly to
cause an explosion, which disintegrates the chips of biomass into
minute fine particles. (See for example FIG. 1 illustrating chips
of biomass exploded into fine particles of biomass 153.) The
original bundle of fibers making up the biomass is exploded into
fragments making discrete particles of fine powder. (See for
example FIGS. 4A-C illustrating different levels of magnification
of a chip of biomass having a fiber bundle of cellulose fibers
surrounded and bonded together by lignin and compare to FIG.
1.)
[0063] The moisture and biomass chips get extruded out the reactor
discharge to a container, such as the blow line, at approximately
atmospheric pressure. The size of the exit orifice effects factors
such as exit velocity, a depressurization time constant, and even
whether every fiber exiting mechanically interacts with an edge of
the orifice or has enough space to violently interact with the
other mass around that fiber but not too much to space such as a 3
inch exit orifice to allow many fibers to exit without violently
interacting with a neighboring fiber or edge of the exit orifice
line. Thus, the size of the exit orifice is controlled relative to
the size of the fibers passing through that exit orifice. The
high-pressure steam or water conversion to vapor inside the
partially hollow fibers and other porous areas of the biomass
material causes the biomass cell to explode into fine particles of
moist powder. The bulk structure of the biomass includes organic
polymers of lignin and hemi-cellulose that surrounds a plurality of
cellulose fibers. The bulk structure of the biomass is internally
blown apart in this SEP step that uses at least moisture, pressure,
and heat to liberate and expose the cellulose fibers to be able, as
an example, to directly react during the biomass gasification
reaction rather than react only after the layers of lignin and
hemi-cellulose have first reacted to then expose the cellulose
fibers. The high temperatures also lowers the energy/force required
to breakdown the biomass' structure as there is a softening of
lignin that facilitates fiber separation along the middle
lamella.
[0064] The morphological changes to the biomass coming out of SEP
reactor can include: [0065] a. No intact fiber structure exists
rather all parts are exploded causing more surface area, which
leads to higher reaction rates in the biomass gasifier; [0066] b.
Fibers appear to buckle, they delaminate, and cell wall is exposed
and cracked; [0067] c. Some lignin remains clinging to the cell
wall of the cellulose fibers; [0068] d. Hemi-cellulose is partially
hydrolyzed and along with lignin are partially solubilized; [0069]
e. The bond between lignin and carbohydrates/polysaccharides (i.e.
hemi-cellulose and cellulose) is mostly cleaved; and [0070] f. many
other changes discussed herein.
[0071] The created moist fine particles may be, for example, 20-50
microns thick in diameter and less than 100 microns in length on
average. Note, 1 inch=25,400 microns. Thus, the biomass comes from
the chipper unit 104 as chips up to 1 inch in length and 0.25
inches in thickness on average and go out as moist fine particles
of 20-50 microns thick in diameter and less than 100 microns in
length on average, which is a reduction of over 2000 times in size.
The violent explosive decompression of the saturated biomass chips
occurs at a rate swifter than that at which the saturated
high-pressure moisture in the porous areas of the biomass in chip
form can escape from the structure of biomass.
[0072] Note, no external mechanical stripping of the fiber bundles
is needed in SEP rather the process uses steam to explode cells
from inside outward and potentially uses some mechanical agitation
of the biomass to create smaller fragments as a resultant product.
Use of SEP on the biomass chips produces small fine particles 653
of cellulose and hemi-cellulose with some lignin coating. (See FIG.
1 illustrating example chips of biomass, including a first chip of
biomass 151, exploded into fine particles of biomass 153.) The FIG.
1 SEP resultant biomass fragments can be compared to just a stalks
of fibers being produced in FIG. 2. This composite of lignin,
hemi-cellulose, and cellulose in fine form has a high surface area
that can be moved/conveyed in the system in a high density.
[0073] The produced fine particles of biomass are fed downstream to
the biomass gasifier 614 for the rapid biomass gasification
reaction in a reactor of the biomass gasifier 614 because they
create a higher surface to volume ratio for the same amount of
biomass compared to the received biomass in chip form 651, which
allows a higher heat transfer to the biomass material and a more
rapid thermal decomposition and gasification of all the molecules
in the biomass.
[0074] The produced particles of biomass loses a large percentage
of the moisture content due to steam flashing in the blow line and
being vented off as a water vapor. The produced particles of
biomass and moisture are then separated by a cyclone filter and
then fed into a blow tank. Thus, a water separation unit is inline
with the blow line. A collection chamber at an outlet stage of the
steam explosion stage is used to collect the biomass reduced into
smaller particle sizes and in pulp form and is fed to the water
separation unit. Water is removed from the biomass in fine particle
form in a cyclone unit or a flash dryer.
[0075] A moisture content of the fine particles of biomass 653 is
further dried out at an exit of the blow tank by a flash dryer that
reduces the moisture content of fine particles of biomass 653 to
5-20% by weight preferably and up to 35% in general. A goal of the
fiber preparation is to create particles of biomass with maximum
surface area and as dry as feasible to 5-20% moisture by weight of
the outputted biomass fine particle. The flash dryer merely blows
hot air to dry the biomass particles coming out from the blow tank.
The flash dryer can be generally located at the outlet of the blow
tank or replace the cyclone at its entrance to make the outputted
biomass particles contain a greater than 5% but less than 35%
moisture content by weight.
[0076] The resulting particles of biomass differs from Thermal
Mechanical Pulping (TMP) in that particles act more like crystal
structures and flows easier than fibers which tend to entangle and
clump.
[0077] The reduced moisture content of 5% to about 35% by weight of
the biomass in fine particle form is fed by a conveying system, as
an example, to a torrefaction unit 612 to undergo torrefaction or
pyrolysis at a temperature from 100 to 700 degrees C. for a preset
amount of time.
[0078] A conveyor system supplies the biomass in particle form to a
torrefaction unit 612 to process the biomass at a temperature of
less than 700 degrees C. for a preset amount of time to create off
gases to be used in a creation of a portion of the syngas
components that are collected by a tank and may be eventually fed
to the methanol synthesis reactor.
[0079] The fine particles of biomass 653 out of the blow tank and
flash dryer has a low moisture content already due to the steam
flashing, further air drying, and are a composite of fragments of
cellulose fibers with a lignin coating, pieces of lignin,
cellulose, and hemi-cellulose, etc. The biomass gasifier 614 has a
reactor vessel configured to react the biomass in moist fine
particle form with an increased surface area due to being blown
apart by the steam explosion unit 608. The biomass gasifier 614 has
a high pressure steam supply input and one or more heaters, and in
the presence of the steam the biomass in fine particle form 653 are
reacted in the reactor vessel in a rapid biomass gasification
reaction between 0.1 and 5.0 second resident time to produce at
least syngas components, including hydrogen (H2) and carbon
monoxide (CO). When the biomass in fine particle form 653 produced
are supplied in high density to the biomass gasifier 114, then the
small particles react rapidly and decompose the larger hydrocarbon
molecules of biomass into the syngas components more readily and
completely. Thus, nearly all of the biomass material, lignin,
cellulose fiber, and hemi-cellulose, completely gasifies rather
than some of the inner portions of the chip not decomposing to the
same extent as that fine particle. These fine particles compared to
chips create less residual tar, less carbon coating and less
precipitates. Thus, breaking up the integrated structure of the
biomass in a fiber bundle tends to decrease an amount of tar
produced later in the biomass gasification. These fine particles
also allow a greater packing density of material to be fed into the
biomass gasifier 614. As a side note, having water as a liquid or
vapor present at at least 10 percent by weight may assist in
generating methanol CH3OH as a reaction product in addition to the
CO and H2 produced in the biomass gasifier 614.
[0080] The torrefaction unit 612 and biomass gasifier 614 may be
combined as an integral unit.
[0081] In the alternative, the moist blown apart particles of
biomass may be fed in slurry form from the output of the steam
explosion reactor directly, or after drying, to a densification
unit. The densification unit may densify the biomass from form into
pellets of biomass, which those pellets are then fed into the
biomass gasifier 614. This direct feed and conversion of biomass
from form to pellet form saves multiple steps and lots of energy
consumption involved in those eliminated steps. Alternatively, the
pellets may be transported to facilities for further processing to
liquid fuel, heat/power, animal feed, litter, or chemicals.
[0082] In an embodiment, the biomass gasifier 614 is designed to
radiantly transfer heat to particles of biomass flowing through the
reactor design with a rapid gasification residence time, of the
biomass particles of 0.1 to 10 seconds and preferably less one
second. The biomass particles and reactant gas flow through the
radiant heat reactor. Primarily radiant heat from the surfaces of
the radiant heat reactor and particles entrained in the flow heat
the particles and resulting gases to a temperature in excess of
generally 700 degrees C. and preferably 1300.degree. C. to produce
the syngas components including carbon monoxide and hydrogen, as
well as keep produced methane at a level of .ltoreq.1% of the
compositional makeup of exit products, a resultant stable ash
formation, complete amelioration of tar to less than 500 milligrams
per normal cubic meter, and the production of the hydrogen and
carbon monoxide products. In some embodiments, the temperature
range for biomass gasification is greater than 800 degrees C. to
1400 degrees C. In some embodiments, the temperature range for
biomass gasification is greater than 700 degrees C. to 1450 degrees
C. In some embodiments, the temperature range for biomass
gasification is greater than 1000 degrees C. The biomass in
particle form used as a feed stock into the radiant heat reactor
conveys the beneficial effects of more effective heat transfer of
radiation to the biomass particles and increased gasifier yield of
generation of syngas components of carbon monoxide and hydrogen for
a given amount of biomass fed in, and improved process hygiene via
decreased production of tars and C2+ olefins compared to chips of
biomass. A control system for the radiant heat reactor matches the
radiant heat transferred from the surfaces of the reactor to a flow
rate of the biomass particles to produce the above benefits.
[0083] The biomass in particle form produced for fuel production
breaks apart a larger piece of biomass into the particle sizes to
increase an exposed surface area of the particles compared to the
larger piece of biomass. The particle sizes compared to the larger
piece of biomass increases surface area, improves flow
characteristics because it flows more like grains of sands/coffee
rather than like fibers, results in less tar and char formation in
downstream torrefaction or gasifier process and rather decomposes
more completely into constituent gases including CO, H2, CO2 and
ash.
[0084] Another possible biomass gasifier 614 implementation has a
high temperature steam supply input and one or more regenerative
heaters. In the presence of the steam, the particles of the biomass
broken down by the pretreatment step are reacted in the reactor
vessel in a rapid biomass gasification reaction at a temperature of
greater than 700 degrees C. in less than a one second residence
time in the biomass gasifier to create syngas components, including
hydrogen (H2) and carbon monoxide (CO). The biomass gasifier 614
can typically feed to a methanol (CH3OH) synthesis reactor.
[0085] An example Particle Size Analysis to determine the particle
size can be a Digital Image Processing Particle Size and Shape
Analysis System such as a Horiba Camsizer XT particle size
analyzer. Such a system uses one or more cameras to provide rapid
and precise particle size and particle shape distributions for dry
powders bulk material in the size range, for example, from 30 .mu.m
to 30 mm. The measurements from the digital image processing system
allows a correlation to existing data from techniques as diverse as
sieving and sedimentation, which in some instances may also be used
to measure particle size. In an embodiment, the particle size of
the steam exploded wood chips is measured using a Horiba Camsizer
XT particle size analyzer. The sample to be measured is mixed in a
resealable bag by kneading and agitating the material in the bag by
external manipulation. After mixing, a sample amount, such as
approximately 3 cm 3, is loaded into the sample hopper of the
instrument. The target is to run and analyze enough sample size,
such as at least 2 million particles from each sample, so the
sample volume is only important insofar as it corresponds to an
adequate number of particles. Example settings on the instrument
can be as follows 0.2% covered area, image rate 1:1, with X-Jet,
gap width=4.0 mm, dispersion pressure=380.0 kPa, xFe_max [and
xc_min, accordingly]. Feed rate is controlled to yield a target
covered area so that the computer can process the images quickly
enough. The camera imaging rate is fixed, and both "basic" and zoom
images are obtained for every run. A single value for average
particle size, such as the diameter is less than 50 microns, may be
the objective measurement standard. In an embodiment, a three point
value for both Fe-max and xc-min is more complete. So that's like a
6 point value. The particle size distribution (PSD) may be defined
as Fe-Max D10, D50, D90 and Xc-min D10, D50, D90. The measurement
then can use multiple values such as input 6 values to determine
the measurement. Other similar mechanisms may be used.
[0086] Calculations can be made using Fe max and xc min on a volume
basis. Two models can be used to analyze the particle images:
xc-min, which yields results comparable to those obtained by
physically screening/sieving samples, and Fe-max, which is similar
to measuring the longest dimension of a given particle with a
caliper. Raw data, frequency plots, binned results, and particle
images are obtained for all samples. D10, D50, and D90 may be
calculated on a volume basis, as is the average aspect ratio. D90
describes the diameter where ninety percent of the distribution has
a smaller particle size and ten percent has a larger particle size.
The D10 diameter has ten percent smaller and ninety percent larger.
A three point specification featuring the D10, D50, and D90 is
considered complete and appropriate for most particulate materials.
In an embodiment, the particle size distribution PSD may be defined
as D50 (.mu.m) Model Fe-max.
TABLE-US-00001 TABLE 1 Particle size distributions for steam
exploded wood Particle size indices for SEP-processed samples
generated from xc-min and Fe-max models. D10 D50 D90 Avg. Example
Model (.mu.m) (.mu.m) (.mu.m) Aspect SEP White Pine #1 xc- 20.4
59.8 176 0.47 min SEP White Pine #2 xc- 23.9 71.7 213 0.48 min SEP
White Pine #2-a xc- 21.7 65.3 197 0.49 min SEP White Pine #3 xc- 23
59.5 182 0.47 min SEP Mixed Hardwood #4 xc- 39.3 175.0 404.1 -- min
SEP Black Spruce #5 xc- 25.6 94.4 320 0.45 min SEP White Pine #1
Fe- 34.5 158 541 0.47 max SEP White Pine #2 Fe- 41.4 186 660 0.45
max SEP White Pine #2-a Fe- 39.2 176 584 0.46 max SEP White Pine #3
Fe- 42.9 186 629 0.45 max SEP Mixed Hardwood #4 Fe- 37 168 397 --
max SEP Black Spruce #5 Fe- 44.7 238 878 0.44 max
[0087] The examples in Table 1 were produced with a Steam Pressure
of 16 bar and a reaction time of 10 minutes.
[0088] As discussed, the decomposition of the large carbohydrate
and other organic molecules in the biomass gasification reaction
occurs due exposure of the biomass composition to elevated heat of
greater than 700 degrees C., but not to an internal flame other
combustion source. Thus, an external heater heats the biomass in
particle form. The exposure of the cellulose fibers to be able to
directly react during the biomass gasification reaction rather than
merely reacting only in a repeating cycle of the layer of lignin
first reacting to then expose the cellulose fibers, and then a next
layer of lignin followed by cellulose fibers reacting causes a
biomass gasification reaction product of resultant stable ash
formation, a complete amelioration of tar to less than 500
milligrams per normal cubic meter, and a yield of at least 90% of
the biomass to hydrogen, carbon dioxide, and carbon monoxide
gaseous products.
[0089] The biomass gasifier feeds a gas clean up section to clean
ash, sulfur, water, and other contaminants from the syngas gas
stream exiting the biomass gasifier 614. The syngas is then
compressed to the proper pressure needed for methanol synthesis.
The syngas from the catalytic converter may connect upstream or
downstream of the compression stage.
[0090] The synthesis gas of H2 and CO from the gasifier is sent to
the common input to the one or more methanol synthesis reactors.
The methanol produced by the one or more methanol synthesis
reactors is then processed in a methanol to gasoline process.
[0091] The liquid fuel produced in the integrated plant may be
gasoline or another such as diesel, jet fuel, or some alcohols.
[0092] FIG. 7 illustrates a flow schematic of an embodiment of a
Thermo Mechanical Pulping unit having an input cavity to receive
biomass as a feedstock, a steam supply input, and two or more
stages to pre-treat the biomass for subsequent supply to a
torrefaction unit and/or biomass gasifier. Thermo Mechanical
Pulping, also known as TMP, is one such thermo mechanical method
that can be used where the pulp is produced by processing wood
chips using heat (thus thermo) and a mechanical refining movement
(thus mechanical).
[0093] The TMP process can use chips of wood, needles, bark,
leaves, fiber crops, or waste paper. Wood pulp comes from softwood
trees, such as spruce, pine, fir, larch and hemlock, and hardwood
trees, such as eucalyptus, aspen and birch. Wood and other plant
materials used to make pulp contain three main components (apart
from water): cellulose fibers (used in other technologies for paper
making), lignin (a three-dimensional polymer that binds the
cellulose fibers together, which is chemically removed in the paper
making field) and hemi-celluloses, (shorter branched carbohydrate
polymers). The biomass contains cellulose fibers and hemi-cellulose
that are held together with lignin. The aim of pulping is to break
down the bulk structure of the fiber source, be it chip form, stem
form, or other plant parts, into the small groups of fibers or even
into individual constituent fibers.
[0094] The TMP unit can be configured to receive two or more types
of biomass feed stocks, where the different types of biomass
include 1) soft woods, 2) hard woods, 3) grasses, 4) plant hulls,
and 5) any combination that are blended and thermo mechanically
processed into a homogenized torrefied feedstock within the TMP
unit 708 that is subsequently collected and then fed into the
biomass gasifier 714. The torrefaction unit 712 assists in making a
biomass feed system that is feedstock flexible without changing out
the physical design of the feed supply equipment or the physical
design of the biomass gasifier via at least particle size control
of the biomass particles produced from refiner unit stage 708.
[0095] The thermo mechanical pulping process breaks down a bulk
structure of the received biomass, at least in part, by applying
steam from the steam supply input to soften the lignin and make it
easier to degrade bonds between the lignin and the hemi-cellulose
from cellulose fibers of the biomass. Strength of the fibers is
further impaired with the gasification's use of thermo mechanical
pulping because the fibers are separated to potentially individual
fibers and also cut to small dimensions. A lack of concern exists
to maintain the strength of the fibers in the woody biomass chips
compared to the paper pulping industry. The traditional TMP process
tries to maintain the strength of the fibers to make particle
board, newspapers, etc. In the current application of using the
fibrous biomass in pulp form as a chemical reactant feedstock, the
steam in connection with the mechanical force can be used to weaken
the fibers and the fibers can then be cut to small dimensions
because the fibers, lignin, and cellulose will eventually be
thermally decomposed into syngas components. This process of TMP
for gasification is less costly than producing paper with TMP
because the gasification process does not require full length
strong fibers as required for making paper or the traditional extra
steps used to keep the strength of the fibers.
[0096] The Thermo Mechanical Pulping process also reduces the
amount of energy required to produce particles of biomass compared
to mechanical treatment alone. A major issue in the paper industry
is that mechanical pulp mills use large amounts of energy, mostly
electricity to power motors that turn the grinders. Steam treatment
significantly reduces the total energy needed to make the pulp and
eases the separation of the fibers. Thus, many advantages exist to
the gasification of woody and other fibrous biomass to strip apart
the fibers from the lignin.
[0097] There are a number of different mechanical processes that
can be used to separate the wood fibers. For example, manufactured
grindstones with embedded silicon carbide or aluminum oxide or
metal discs called refiner plates can be used to grind the biomass
chips. Thus, the chips are steamed while being refined by the
grindstones or metal discs to create the pulp. These chips of
biomass have a large moisture content, are thermally heated from
the steam, expanded by the elevated temperature and pressure, and
then a mechanical force may also be applied to the wood chips in a
crushing, shearing, vibrating, or grinding action, which generates
additional heat and shredding action, which aids in separating the
individual fibers from each other and the lignin.
[0098] The TMP unit reduces the biomass into smaller particle sizes
that should be more easily and rapidly gasified. Fibers are long
tubular strings of material, whereas chips are irregular spheres.
The fibers compare to angel hair spaghetti, whereas chips are more
like ravioli. Torn and shredded fibers may be preferred for the
gasification process because they create a higher surface to volume
ratio for the same amount of biomass. The higher surface area of
the fibers traveling through the biomass gasifier 714 compared to a
chip allows higher heat transfer to the biomass material and a more
rapid thermal decomposition and gasification of all the molecules
in the biomass. Thus, nearly all of the biomass material lignin,
fiber, and cellulose completely gasify rather than some of the
inner portions of the chip not decomposing to the same extent to
that the crusted shell of a char chip decomposes.
[0099] A collection chamber at an outlet stage of the refiner unit
stage 708 is used to collect the biomass reduced into smaller
particle sizes and in pulp form, which should be more easily and
rapidly gasified. The produced particles of biomass in pulp form
include fibers in the form of long tubular strings of material that
are torn and/or shredded. The biomass particles separated into
fibers are preferred for the biomass gasification reaction in the
biomass gasifier 714 because they create a higher surface to volume
ratio for the same amount of biomass compared to chips of biomass,
which allows higher heat transfer to the biomass material and a
more rapid thermal decomposition and gasification of all the
molecules in the biomass. The refiner unit stage 108 has a knife
stage in the fiber separation unit that initially separates the
fibers from the chips and may chop the fibers of the biomass to
shorter lengths of 1-3 mm and then a high pressure steam fiber
separation stage furthers the blowing apart of the loosely grouped
fibers in the particles of biomass. The refiner unit produces fiber
particles that on average are approximately 20-50 .mu.m thick and
1-3 mm in length. In another embodiment, the fibers may have an
equivalent spherical diameter of less than 3 mm.
[0100] The biomass gasifier 714, torrefaction unit 712, and
chipping unit 704 may operate similar as described in FIG. 6.
[0101] While some specific embodiments of the disclosure have been
shown the invention is not to be limited to these embodiments. For
example, the recuperated waste heat from various plant processes
can be used to pre-heat combustion air, or can be used for other
similar heating means. Regenerative gas burners or conventional
burners can be used as a heat source for the furnace. Alcohols C1,
C2 and higher as well as ethers that are formed in the torrefaction
process may be used as a high value in boosting the octane rating
of the generated liquid fuel, such as gasoline. Biomass gasifier
reactors other than a radiant heat chemical reactor may be used.
The Steam Methane Reforming may be/include a SHR (steam hydrocarbon
reformer) that cracks short-chained hydrocarbons (<C20)
including hydrocarbons (alkanes, alkenes, alkynes, aromatics,
furans, phenols, carboxylic acids, ketones, aldehydes, ethers, etc,
as well as oxygenates into syngas components. The disclosure is to
be understood as not limited by the specific embodiments described
herein, but only by scope of the appended claims.
* * * * *