Note: Descriptions are shown in the official language in which they were submitted.
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METHODS FOR PRODUCING 13IOMASS-BASED FUEL
WITH PULP PROCESSING EQUIPMENT
RELATED APPLICATION
[0001] This application claims the benefit of the filing date and priority to
I.T.S.
Provisional Application 61/152,556, filed February 13, 2009, the entirety of
which is hereby
incorporated by reference.
BACKGROUND
[0002] The present disclosure relates to processing energy resources, and,
more
particularly, to methods for producing biomass-based fuel with pulp processing
equipment.
[0003] Biomass of various types may be used to manufacture densified fuel.
Biomass may take the form of wood, woody biomass, or other biomass such as,
without
limitation, sugarcane bagasse, straw, switchgrass, or other agricultural
Material when; biomass
may be a byproduct of other processes or where biomass may be a feedstock
grown for the
purpose of making directly or indirectly, a fuel.
[0004] The terms "pellets" and "briquettes" commonly refer to fragments of
biomass, treated biomass, coal, or some or all in combination that have been
compacted to form
a densified fuel produced in various sizes and shapes. For example, various
size feedstocks, such
as sawdust or chips ranging in size from less than 1" to over 3" along the
longest dimension, may
be processed and pelletized. Material may be dried and extruded through dies
sized for the
desired cross-sectional area and of varying lengths. Floor-mounted machines or
presses with
dyes may receive prepared feedstock and discharge extruded pellets sized
(e.g., by cutting or
trimming) to desired lengths at the outlet of the machines or presses. The
term "white pellet"
may refer to the use of suitably sized and pelletized wood that has had
minimal if any treatment
beyond chipping and grinding prior to being introduced into the pellet machine
or press. White
pellets may be used in residential heaters, in district heating, and/or in
industrial power
generation, including coal-fired power generation plants.
[0005] Industrial use of white pellets may be limited by the white pellets'
inherent
properties including sensitivity to water, low hardness, and lack of
durability, leading to the
production of dust as the pellets abrade through handling and/or as a result
of moisture
absorption. These properties, independently and together, may cause the
pellets to rapidly
disintegrate. Due to such limitations, white pellets require specific storage
and handling
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accommodations to protect the pellets from the elements and to mitigate dust
concentrations that
may create an explosion hazard. Consequently, using white pellets in coal-
fired power
generation plants in concentrations from 1% to 100% may require significant
adaptations to both
plant operating procedures and capital equipment considering, for example,
that coal may be
typically stored and handled outdoors with exposure to the elements.
[0006] The term "black pellet" may refer to a pellet with a lignin binder
and/or
coating induced by processing the biomass feedstock prior to introducing the
biomass into the
pellet machine or press. Steam explosion may be used in manufacturing
densified fuel as a
means to free lignin from cellular structures of biomass, thereby allowing the
lignin to
commingle with the fiber portion of the biomass and, when compacted by the
pellet machine or
press, forming both a waterproof or water-resistant internal binder as well as
a waterproof or
water-resistant protective surface coating that enhances the durability of
pellets and briquettes.
As a result, pellets and briquettes may have improved abrasion properties and
may be stored
outdoors in a manner similar to outdoor storage of coal. Having physical
characteristics similar
to coal may facilitate the introduction of pellets into coal handling
processes of conventional coal
plants, resulting in both capital cost and operating cost savings as compared
to the use of white
pellets.
[0007] Providing a manufacturing and processing plant for densified biomass-
based fuel poses a number of challenges for the energy industry. These
challenges may entail
complications and expenses including one or more of the purchase and
preparation of land,
coordination with governmental zoning restrictions and other regulations,
coordinating
expectations with a surrounding community, design and construction of
facilities, design and
assembly of complex equipment and procedures, purchase of new equipment, and,
generally,
large upfront expenses in time, capital and other resources. Therefore, it may
be desirable to
have methods that mitigate the challenges associated with manufacturing and
processing
densified biomass-based fuel.
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SUMMARY
[0008] The present disclosure relates to processing energy resources, and,
more
particularly, to methods for producing biomass-based fuel with pulp processing
equipment.
[0009] In one embodiment, a method of manufacturing biomass-based pellets
includes liberating lignin from biomass-based feedstock via pulp digester. The
method may
include pelletizing the biomass-based feedstock and the liberated lignin to
form the biomass-
based pellets.
[0010] In one embodiment, a method for converting a pulp processing plant to a
biomass-based pellet manufacturing plant includes installing a pellet mill in
the pulp processing
plant. The method may include re-routing output from a pulp digester, such
that the output
enters the pellet mill and bypassing unnecessary equipment.
[OO11] In one embodiment, a method for mitigating the costs of establishing a
biomass-based pellet manufacturing plant includes identifying an existing pulp
processing plant,
obtaining permission to access and convert the pulp processing plant, and
converting the pulp
processing plant for manufacture of biomass-based pellets.
[0012] The features and advantages of the present disclosure will be readily
apparent to those skilled in the art. While numerous changes may be made by
those skilled in
the art, such changes are within the spirit of the invention.
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BRIEF DESCRIPTION OF TIRE DRAWINGS
[0013] A more complete understanding of the present embodiments and
advantages thereof may be acquired by referring to the following description
taken in
conjunction with the accompanying drawings, in which like reference numbers
indicate like
features.
[0014] Figure 1 illustrates a block diagram indicating a method of mitigating
the
costs of establishing a biomass-based pellet manufacturing plant in accordance
with certain
embodiments of the present invention.
[0015] Figure 2 illustrates a block diagram indicating a method for converting
a
pulp processing plant to a biomass-based pellet manufacturing plant in
accordance with certain
embodiments of the present invention.
10016] Figure 3 illustrates a block diagram indicating a converted pulp
processing
plant in accordance with certain embodiments of the present disclosure.
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DETAILED DESCRIPTION
[0017] The present disclosure relates to processing energy resources, and,
more
particularly, to methods for producing biomass-based fuel with pulp processing
equipment. For
purposes of this disclosure, a biomass-based pellet may include without
limitation a fragment or
piece of any shape, size, or division, including a briquette. A biomass-based
pellet, and biomass-
based material may include, at least in part and without limitation, material
consisting of or
derived from wood, woody biomass, or any other biomass such as bamboo,
sugarcane bagasse,
straw, switchgrass, husks, or other agricultural material where biomass may be
a byproduct of
other processes or where biomass may be a feedstock grown for the purpose of
manufacturing a
fuel.
[0018] In certain embodiments of the present disclosure, existing pulp making,
papennaking, and/or cellulosic ethanol equipment may be used to produce
biomass-based
exploded or otherwise treated product that may be ready for densification to
achieve a biomass-
based pellet. In some instances, this type of pellet is called a "high-
density" or "black" pellet. In
certain embodiments of the present disclosure, existing technology, e.g.,
equipment widely used
for preprocessing wood in the pulp and paper industry, may be adapted to
accomplish the
liberation of lignin present in biomass-based feedstock. An existing pulp
processing plant may
be used with some or all equipment intact and, with the addition of
pelletizing equipment, may
produce a steam-exploded biomass-based pellet without building new steam
explosion facilities.
Conversion of conventional pulp processing plant digestion technology may be
adapted to so that
chemical treatment, which may be typical to pulping processes, may not be
necessary in a
converted pulp processing plant. Existing equipment may be converted to steam
explosion
equipment and coupled with densification processes to manufacture biomass-
based pellets.
[0019] Referring now to Figure 1, in one exemplary embodiment, the costs
associated with establishing biomass-based pellet manufacturing may be reduced
by first
identifying 100 an existing pulp processing plant. This identification may
include researching
several pulp processing plants and determining whether any of them is in
financial distress
and/or in need of financial stimulation. In some embodiments, the existing
pulp processing plant
may be a paper mill, a freestanding pulp processing facility, or any other
pulp processing source.
[0020] Once an existing pulp processing plant has been identified 100,
permission
105 may be obtained to access and convert the pulp processing plant to a
biomass-based pellet
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manufacturing facility. This permission 105 may be obtained through contract
agreement,
purchase of assets, merger, acquisition, lease agreement, or any other grant
of rights to access
and conversion, including altering intended use of an asset already owned.
[0021] Once an existing pulp processing plant has been identified 100 and
permission 105 obtained, it may be converted 110 for manufacture of biomass-
based pellets.
This conversion 110 is described in detail below with reference to Figure 2.
[0022] In some embodiments, costs may be further reduced by identifying 115 an
existing source of biomass-based feedstock, before, after, or in conjunction
with identification
100 of pulp processing plant. Some examples of sources of biornass-based
feedstock may
include nearby forests, grasslands, or any of a number of other renewable
biomass-based
feedstock sources. After identification 115 of an existing source of biomass-
based feedstock,
permission 120 may be obtained to access and use the biomass-based feedstock
for manufacture
of biomass-based pellets. This permission 120 may be obtained through contract
agreement,
purchase of assets, merger, acquisition, lease agreement, or any other grant
of rights to access
and use, including altering intended use of an asset already owned. If the
existing source of
biomass-based feedstock is remote from the pulp processing plant, an
additional step of
obtaining permission 125 to transport the biomass-based feedstock from the
existing source to
the pulp processing plant may be included either in addition to, or in place
of the step of
obtaining permission to access and use the biomass-based feedstock. For
example, this
permission may include a contract for purchase of goods, including quantities
requirements and
term of contract provisions.
[0023] Referring now to Figure 2, in one exemplary embodiment, a pulp
processing plant may be converted for use in biomass-based pellet
manufacturing. Such a
conversion may involve converting 200 an existing pulp digester for use in the
manufacture of
biomass-based pellets, installing 205 a pellet mill in the pulp processing
plant, re-routing 210
output from the pulp digester, such that the output enters the pellet mill,
and/or bypassing 215
unused components in the pulp processing plant.
[0024] Converting 200 an existing pulp digester may involve removal of some or
all equipment used for chemical treatment and/or lignin removal. Installing
205 a pellet mill
may involve leasing, purchasing, or otherwise acquiring a pellet mill of the
type described below
with reference to Figure 3, and ensuring that it is delivered to the pulp
processing plant for
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installation in a location suitable for use with the rest of the equipment
useful for biomass-based
pellet manufacture. Re-routing 210 the output from the pulp digester may not
require physical
changes to equipment, and may be as simple as moving a conveyor, or may
involve complex
movements of equipment. In some instances, re-routing 210 the output from the
pulp digester
may include re-routing and/or bypassing intermediate equipment, such as, for
example, a blow
tank. Bypassing 215 unused components may include bypassing particular
equipment useful in
pulp processing plant operations but unnecessary in biomass-based pellet
manufacture. When
bypassed equipment is unnecessary, the method may further include removing 220
and/or selling
225 the bypassed equipment.
[0025] Referring now to Figure 3, converted pulp processing plant 300 is
illustrated in accordance with certain embodiments of the present disclosure.
Biomass-based
feedstock may be collected from a location near converted pulp processing
plant 300. For
example, biomass-based feedstock may be timber collected from forestland
adjacent to converted
pulp processing plant 300. Alternatively, biomass-based feedstock may be
delivered to pulp
processing plant 300 from a remote location. For example, biomass-based
feedstock may be
bamboo grown in another country and delivered to pulp processing plant 300,
either intact, or
pre-processed to some extent. Any of a number of other sources for biomass-
based feedstock
may also be suitable. Depending on the source and condition of the biomass-
based feedstock, it
may undergo additional treatment in existing facilities 305 prior to entry
into pulp digester 325.
Existing facilities 305 may include any number and variety of existing
papermaking and/or
cellulosic ethanol production equipment. For example without limitation,
existing facilities 305
may include one or more of storage yard 310, debarking equipment 315, chipping
equipment
320, pulp digester 325, and blow tank 330, which may or may not be coupled
together by any
conveying equipment or other means of transferring material. Depending on the
particular
biomass-based feedstock, one or more of the units of existing facilities 305
may be modified or
even omitted.
[0026] Upon delivery to converted pulp processing plant 300, biomass-based
feedstock may be stored in storage yard 310 for some time prior to use.
Storage yard 310 may be
a location, with certain equipment if desired, adapted for one or more of
receiving, storing, and
preparing biomass-based material for processing. In some embodiments, storage
yard 310 is a
wood yard suitable for use with wood-based materials.
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[0027] Depending on the type of biomass-based feedstock, it may pass through
debarking equipment 315, which may be any equipment and/or machinery
configured to
prepared biomass-based material for farther processing by removing material,
for example, by
removing bark from surfaces of logs.
[0028] Biomass-based feedstock may pass through flume shower 360 or other
equipment suitable to wash off dirt or other impurities in biomass-based
feedstock, when using
unprocessed biomass-based feedstock. Flume shower 360 may be part of existing
facilities 305,
or flume shower 360 may be added to existing facilities 305 for use in biomass-
based pellet
manufacture. In some instances, flume shower 360 may be modified or omitted,
depending on
the particular application.
[0029] If the size of biomass-based feedstock is larger than desirable for use
in
pulp digester 325, it may pass through chipping equipment 320 prior to entry
into pulp digester
325. Chipping equipment 320 may be any equipment and/or machinery configured
to reduce
biomass-based material into smaller parts. In some instances, a grinder (not
shown) may be used
for further reduction in size of biomass-based feedstock.
[0030] Biomass-based feedstock may pass through dryer 365, if desired, to
reduce
moisture content to a level suitable for use in pulp digester 325. For
example, dryer 365 may be
used to obtain moisture content between 0% and 15% by weight. Dryer 365 may be
a rotary
dryer, steam dryer, superheated steam dryer, low temperature dryer, or any of
a number of other
devices for adjusting moisture content.
[00311 Existing pulp processing plants may typically use pulp digester 325 in
a
cooking process, along with significant amounts of chemicals and/or enzymes
sometime referred
to as "cooking liquor." The cooking process may be used to separate lignin
and/or sugars from
fiber and maintain separation in dilute slurry. The lignin and fiber are
typically moved to
separate vessels in existing pulp processing plants, with no further
comingling of fiber and
lignin. In some embodiments of converted pulp processing plant 300, chemicals
and/or enzymes
may be added to biomass-based feedstock in a chemical treatment operation (not
shown) to
produce a biomass-based slurry for use in pulp digester 325. In other
embodiments, chemicals
and enzymes may be omitted.
[00321 Biomass-based feedstock (or slurry) may enter pulp digester 325 through
an opening sized accordingly. Pulp digester 325 may include any vessel and
associated
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equipment configured to receive biomass-based feedstock (or slurry) and
process it under desired
pressures and at desired temperatures. Pulp digester 325 may include one or
more vessels
configured to operate in a batch manner, in a multi-batch or semi-continuous
manner, or in a
continuous manner. Examples of other existing pulp digesters 325 may include,
but are not
limited to, Masonite guns, standard Kraft digesters, standard sulfite
digesters,
chemithermomechanical pulping, thermomechanical pulping, groundwood pulping,
and
pressurized groundwood pulping.
[0033] If the operation is batch-type, the supply of biomass-based feedstock
(or
slurry) may cease and the pulp digester 325 may be closed off. In a continuous
operation, the
supply of biomass-based feedstock (or slurry) may be continuous. At a
predetermined
temperature and temperature, pulp digester 325 will, over a predetermined
amount of time, treat
or cook the bioinass-based feedstock (or slurry), using steam, either with or
without chemical
additives and/or water, to liberate lignin from the biomass-based feedstock by
steam explosion.
Once the cooking is suitably complete, pulp digester 325 may be opened to
adjacent blow tank
330, allowing removal of cooked biomass-based material, which includes the
biomass-based
feedstock and the liberated lignin, from pulp digester 325 via explosion into
blow tank. Cooked
biomass-based material may transferred to the blow tank 330 on a batch and/or
continuous basis.
Blow tank 330 may include any vessel and associated equipment configured to
receive treated,
or cooked biomass-based material, which may be in a slurry state with cooking
liquor and/or
steam, from pulp digester 325.
[0034] Existing pulp processing plants may not be designed to use such pulping
technologies to steam explode fibers, but may be designed to use pulping
technologies under
various conditions. For example, pulping technologies may involve pressures
below 150 psi
(pounds per square inch), chemical additives, one or more cooking processes,
and a dilute slurry
that may comprise approximately 50% dry solids.
[0035] Conventional high-density pellet manufacturing, on the other hand,
typically involves higher temperatures and pressures and smaller chambers than
pulp digester
325. Operating pressures may exceed 150 psi in certain implementations, such
as where a
Masonite gun may be employed, where operating pressures may reach or exceed
1,000 psi.
Thus, in certain instances, converted pulp processing plant 300 may employ
longer cook times
than found in conventional high-density pellet manufacturing.
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[0036] Steam explosion may be used at normal operating pressures to soften
biomass-based fibers in preparation for re-entry at atmospheric conditions,
thus exploding the
fibers at a lower pressure or, in the case of a Masonite gun, a significantly
higher pressure.
Certain embodiments may accomplish steam explosion at pressures in approximate
ranges of 225
psi to 375 psi and/or may produce a product of 85% to 92% dry solids, while
keeping lignin with
fiber for pellet processing. Steam impregnating raw fuel may pre-soften the
material. Certain
embodiments may use chemicals with the steam impregnation to further soften or
accelerate
softening raw fiber prior to cooking. Such chemicals may include sodium
sulfite, caustic soda,
or any other suitable chemical, as would be appreciated by one of ordinary
skill in the art having
the benefit of this disclosure. Other embodiments may include addition of
supplementary lignin
and/or omit steam explosion from the process of liberating lignin.
[00371 Cooked biomass-based material may pass from blow tank 330 through
dryer 370, if desired, to reduce moisture content to a level suitable for use
with pelletizing
equipment 340. For example, dryer 370 may be used to obtain moisture content
between 0% and
15% by weight. Dryer 370 may be a rotary dryer, steam dryer, superheated steam
dryer, or any
of a number of other devices for adjusting moisture content.
[0038) Cooked biomass-based material may be transferred, either directly, or
via
one or more of blow tank 330 and dryer 370, from pulp digester 325 to
pelletizing equipment
340, which may include one or more of a pellet mill 345, pellet cooling
equipment 350 and pellet
storage 355. Cooked biomass-based material may be processed by pellet mill 345
to form
biomass-based pellets. Pellet mill 345 may be any device suitable for
extrusion or other
compression of cooked biomass-based material to create biomass-based pellets.
After exiting
pellet mill 345, biomass-based pellets may pass through or otherwise encounter
pellet cooling
equipment 350 for cooling. Pellet cooling equipment 350 may be any equipment
or means for
cooling biomass-based pellets, including, but not limited to, air circulation
or water quenching.
In some embodiments, pellet cooling equipment 350 may not be needed, and
biomass-based
pellets may be cooled during storage. Biomass-based pellets may then be stored
at pellet storage
355. Because high-density biomass-based pellets are moisture and abrasion
resistant, pellet
storage 355 may be, for example, indoor storage, outdoor storage, covered
storage, or uncovered
storage, Additionally biomass-based pellets may be used in standard coal
handling equipment,
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including railcars, conveyors, storage, and other processing facilities,
eliminating the need for
significant capital investment in order to coal fire biomass-based pellets
with coal.
[00391 In addition to existing facilities 305, a typical existing pulp
processing
plant may include balance of the existing plant 335, which may constitute
equipment that may
not be needed in manufacturing and processing biomass-based pellets. Balance
of the existing
plant 335 may be removed or left in place, as desired or as needed to
accommodate pellet
equipment 340.
[0040] As would be appreciated by one of ordinary skill in the art having the
benefit of the present disclosure, any number of modifications, adaptations,
and alternatives may
be employed to convert an existing pulp processing plant. For example, "steam"
may refer not
only to water vapor, but may also include other vapors useful in the
applications indicated above.
[0041] Thus, the methods disclosed herein provide the potential for
significantly
lowering costs of producing biomass-based fuel and initiating large-scale
manufacturing and
processing of biomass to make biomass-based feedstock for power generation
units such as
cogeneration, boilers and other types of power plants. Conversion of existing
pulp processing
plants according to the present disclosure offers significant economies
compared to new
construction of high-pressure steam explosion. Methods according to the
present disclosure may
be applied to existing pulp and feedstock production sites in any number of
various wood and
pulp and paper countries to facilitate business related to manufacturing,
processing and
delivering biomass-based fuel. Other technical advantages will be apparent to
those of ordinary
skill in the art in view of the specification, claims, and drawings.
[0042] Therefore, the present disclosure is well adapted to attain the ends
and
advantages mentioned as well as those that are inherent therein. The
particular embodiments
disclosed above are illustrative only, as the present disclosure may be
modified and practiced in
different but equivalent manners apparent to those skilled in the art having
the benefit of the
teachings herein. Furthermore, no limitations are intended to the details of
construction or
design herein shown, other than as described in the claims below. It is
therefore evident that the
particular illustrative embodiments disclosed above may be altered or modified
and all such
variations are considered within the scope and spirit of the present
disclosure. In addition, the
terms in the claims have their plain, ordinary meaning unless otherwise
explicitly and clearly
defined by the patentee.
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