Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FUEL PELLET COMPRISING AN AGRICULTURAL BIOMASS
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority of U.S. Provisional Application Serial
No.
60/845,339, filed September 18, 2006, which is incorporated herein by
reference in its
entirety.
BACKGROUND
[0002] Oil and coal are commonly used for heating. However, increasing costs
and
environmental concerns related to fossil fuels have led to an increased demand
for
alternative heating fuels.
[0003] One such alternative is pelleted hardwood fuel. Hardwood pellets can
provide
sufficient heat to be an efficient fuel. However, pelleted hardwood fuels face
some of the
same limitations as fossil fuels. For instance, hardwood trees that are
harvested take years
to replace with new growth. Also, the increased efficiencies achieved in the
lumber and
paper industries place constraints on the amount of hardwood scrap that is
available for
pelleting. Hardwood also has a high lignin contents (e.g., typically at least
about 25 wt.%).
High lignin contents can result in the production of tar-like residues when
the fuel is burned.
This may necessitate processing of hardwood materials to remove a portion of
the lignin
content prior to being used to form a fuel pellet. Accordingly, there is a
continuing need for
alternative fuels that are renewable and in adequate supply.
SUMMARY
[0004] The present application is directed to fuel pellets formed from a
mixture which
includes an agricultural biomass. Typically, the fuel pellets include
substantial amounts of
agricultural biomass having a relatively low lignin content, e.g., about 60
wt.% (dry basis)
or more of the agricultural biomass. The fuel pellets may have a low ash
content, good
pellet durability (e.g., as determined by their pellet durability index) and
heating values
comparable to conventional hardwood fuel pellets. The fuel pellet may be
formed by
pelleting a mixture comprising agricultural biomass which includes whole corn,
corn cobs,
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corn stover, wheat, wheat middlings, wheat straw, soy beans, soy bean hulls,
soy cotyledon
fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp
and/or sunflower hulls.
Other suitable agricultural biomass materials which may be used to form the
present fuel
pellets include co-products from corn milling processes (e.g. corn gluten
feed, white fiber),
oat hulls, rice hulls, rapeseed meal, rapeseed fractions, bagasse, empty palm
fruit bundles,
almond hulls, walnut meal, and the like. In some embodiments, it may be useful
to
formulate the fuel pellet such that it has an ash content with composition
and/or
characteristics comparable to that of fly ash. Additional agricultural biomass
materials
which may be used to form the present fuel pellets include ground barley,
cottonseed hulls,
whole cottonseed, ground milo, oatmeal, oat flour, rye and/or broken rice. The
agricultural
biomass may be used "as is" or may have undergone some physical or chemical
process(es)
prior to being used to produce the present fuel pellets. For instance, the
agricultural
biomass is to produce the fuel pellet may have has undergone a pretreatment
process such as
size reduction, homogenization, thermal pretreatment or the like.
[0005] The fuel pellet typically has an ash content of no more than about 5
wt.%,
desirably, no more than about 4 wt.% and, more desirably, no more than about 3
wt.%, a
PDI of at least about 90, and a heating value of at least about 6000 BTU/lb
(dry basis),
desirably at least about 6500 BTU/lb (dry basis), more desirably at least
about 6800 BTU/lb
(dry basis) and, preferably, at least about 7000 BTU/lb (dry basis). In some
embodiments,
the fuel pellets may have a heating value of about 7,500 BTU/lb (dry basis) or
higher.
Typically the agricultural biomass will have a lignin content of no more than
about 10 wt.%
(on a dry basis). In many embodiments, the mixture desirably includes at least
about 60
wt.%, suitably at least about 75 wt.% and, often, at least about 90 wt.% of
such agricultural
biomass. Suitably, the lignin content of the fuel pellets is no more than
about 10 wt.%, and,
desirably no more than about 5 wt.% (on a dry basis).
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[0006] In one embodiment the fuel pellet comprises an agricultural biomass
selected from
the group consisting of corn (e.g. cracked corn and/or whole corn), corn cobs,
corn stover,
wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon
fiber, alfalfa,
dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof.
The fuel pellet may have an ash content of no more than about 3 wt.%, a PDI of
at least
about 90, and a heating value of at least about 6000 BTU/lb (dry basis),
desirably at least
about 6500 BTU/lb (dry basis), more desirably at least about 6800 BTU/lb (dry
basis) and,
preferably, at least about 7000 BTU/lb (dry basis).
[0007] Another embodiment relates to a fuel pellet formed by pelleting a
mixture
comprising about 40 to 90 wt.% corn; and about 10 to 60 wt.% of an
agricultural biomass
selected from the group consisting of corn cobs, corn stover, wheat, wheat
middlings, wheat
straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried
distillers grain, oats, oat
straw, sugar beet pulp, sunflower hulls and mixtures thereof. The fuel pellet
may have an
ash content of no more than about 3 wt.%, a PDI of at least about 90, and a
heating value of
at least about 6000 BTU/lb (dry basis), desirably at least about 6500 BTU/lb
(dry basis),
more desirably at least about 6800 BTU/lb (dry basis) and, preferably, at
least about 7000
BTU/lb (dry basis).
[0008] Yet another embodiment relates to a method of producing heat comprising
burning
a fuel pellet wherein the fuel pellet comprises an agricultural biomass
selected from the
group consisting of cracked corn, whole corn, corn cobs, corn stover, wheat,
wheat
middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber,
alfalfa, dried
distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof. The
fuel pellet may have an ash content of no more than about 3 wt.%, a PDI of at
least about
90, and a heating value of at least about 6000 BTU/lb (dry basis), desirably
at least about
6500 BTU/lb (dry basis), more desirably at least about 6800 BTU/lb (dry basis)
and,
preferably, at least about 7000 BTU/lb (dry basis).
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DETAILED DESCRIPTION
[0009] Biomass fuel pellets for use in stoves and boilers should conform to a
variety of
requirements. The pellets should have a sufficient heating value when burned
to be an
efficient source of energy. The pellets should also have a low ash content to
prevent
equipment fouling. To avoid unsafe burning conditions, the pellets should also
have a
sufficient integrity such that the amount of fine particles is kept low.
[0010] To be economical, a fuel pellet should desirably have a heating value
of at least
about 6000 BTU/lb (dry basis), desirably at least about 6500 BTU/lb (dry
basis), more
desirably at least about 6800 BTU/lb (dry basis) and, preferably, at least
about 7000 BTU/lb
(dry basis) when burned. In an exemplary embodiment the present fuel pellets
may have a
heating value of about 7200 BTU/lb (dry basis) or even higher. Conventional
hardwood can
have a heating value as high as about 7900 BTU/lb.
[0011] Another requirement for a heating fuel is a low ash content. Ash
produced by
burning fuel may result in fouling of equipment. In some embodiments, an
adequate ash
content may be no more than about 5 wt.%, suitably no more than about 4 wt.%.
and, more
suitably, no more than about 3 wt.%. In other applications, it may be
desirable to provide a
biomass fuel pellet with an ash content of no more that about 2.5 wt.%. In yet
other
embodiments, the ash content may be no more than about 2.0 wt.% or no more
than about
1.7 wt.%. For certain applications, fuel pellets with an ash content up to
about 15 wt.% may
be quite suitable.
[0012] Biomass fuel pellets must also have a sufficiently high integrity to
limit the
presence of fine combustible particles. A pellet's integrity can be measured
by its pellet
durability index ("PDI") as measured via a procedure similar to that described
in Feed
Manufacturing Technology III (American Feed Industry Association, Arlington
VA.
McEllhiney, R. R. (technical Editor). 1985. Appendix G Wafers, Pellets, and
Crumbles -
Definitions and methods for determining specific weight, durability, and
moisture content;
Section 6 Durability; Paragraph 2, Pellets and crumbles) the disclosure of
which is herein
incorporated by reference. The procedure includes the following steps:
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1) Obtain a composite product sample by obtaining several samples at regular
intervals throughout production. The samples should be mixed together for
testing.
2) Screen sample with the appropriate screen as set forth on the Screen Sizes
for
Pellet and Crumbles Durability Tests, by shaking it 30 times.
3) Place a 500-gram sample (+/- 10 grams) in a tumbler compartment. An
exemplary tumbler may be 25 x 12.5 x 12, including four chambers and
tumble at about 54 rpm.
4) Tumble sample for 10 minutes.
5) Screen sample with the appropriate screen as set forth on the Screen Sizes
for
Pellet and Crumbles Durability Tests by shaking it approximately 30 times.
6) Document the amount of sample and the amount of screened product.
[0013] Biomass fuel pellets desirably have a PDI of at least about 90 and more
desirable
at least about 95. The biomass fuel pellets may be generally cylindrical in
shape and have a
diameter of about 2/16 of an inch to 6/16 of an inch. More desirably, the fuel
pellets may
have a diameter of about 3/16 of an inch to 5/16 of an inch. The fuel pellets
may have an
aspect ration (i.e. diameter : length) of about 1:1 to 5:1.
[0014] Other properties, such as sulfur and moisture content have effects on
pellet fuel
performance. High sulfur contents can lead to pollution causing combustion
products.
Also, high moisture content in a fuel may reduce efficiency. Table 1 shows the
reported
values for properties of a conventional hardwood pellet as well as those for a
variety of
agricultural biomass fuels. Other agricultural biomass based-fuels may be
suitable as well.
Table 7 lists a number of other potential ingredients. The predicted BTU/lb
for these
materials was derived from standard feed analyses of the nutrient components
in a particular
ingredient.
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Table 1
Fuel Property As Is Dry Basis
Moisture 7.08 wt.%
BTU / lb. 7955 8573
Hardwood Pellet
Ash wt.% 0.34 wt.% 0.36 wt.%
Sulfur wt. % 0.01 0.01
Moisture 12.25 wt.%
Alfalfa BTU / lb. 6934 7729
(leaf and stem) Ash wt.% 7.94 wt.% 9.06 wt.%
Sulfur wt.% 0.195 0.22
Moisture 6.02 wt. %
BTU / lb. 7786 8501
Aspen
Ash wt.% 2.48 wt.% 2.67 wt.%
Sulfur wt. % 0.02 0.02
Moisture 12.06 wt.%
BTU / lb. 7199 8097
Corn Gluten Feed
Ash wt.% 3.78 wt.% 4.30 wt.%
Sulfur wt.% 0.33 0.375
Moisture 13.43 wt.%
Corn - shell
BTU / lb. 6924 8100
54.5 lb/bu. T.W.
Ash wt.% 1.13 wt.% 1.23 wt.%
13 wt. % moist.
Sulfur wt. % 0.11 0.13
Moisture 12.49 wt.%
Corn - high oil
BTU / lb. 7398 8480
56.21b/bu T.W.
Ash wt.% 1.17 wt.% 1.34 wt.%
12.9 wt.% moist.
Sulfur wt.% 0.095 0.11
Moisture 139 wt.%
Corn - waxy
BTU / lb. 7073 8113
56.6 lb/bu. T.W.
Ash wt.% 1.26 wt.% 1.44 wt.%
13 wt. % moist.
Sulfur wt.% 0.12 0.135
Moisture 7.12 wt. %
BTU / lb. 7369 7911
Corn Cob
Ash wt.% 2.16 wt.% 2.32 wt.%
Sulfur wt.% 0.04 0.04
Corn Stover/Stalks Moisture 9.14 wt.%
BTU / lb. 7057 7768
Ash wt.% 6.81 wt.% 7.64 wt.%
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Sulfur wt.% 0.035 0.04
Moisture 9.27 wt. %
Dried Distillers
BTU / lb. 8459 9422
Grain with solubles
Ash wt. % 4.16 wt. % 4.13 wt. %
(DDGS)
Sulfur wt.% 0.4 0.45
Moisture 13.35 wt.%
Dried Distillers Grain
BTU / lb. 8473 9848
with out solubles
Ash wt.% 1.96 wt.% 2.24 wt.%
(DDG)
Sulfur wt.% 0.34 0.4
Moisture 12.49 wt.%
BTU / lb. 7143 8242
Oats
Ash wt.% 3.17 wt.% 3.58 wt.%
Sulfur wt. % 0.135 0.16
Moisture 10.25 wt.%
BTU / lb. 8783 10230
Soybeans
Ash wt.% 5.19 wt.% 6.22 wt.%
Sulfur wt.% 0.29 0.33
Moisture 11.38 wt.%
BTU / lb. 6660 7570
Soybean Hulls
Ash wt.% 4.17 wt.% 4.22 wt.%
Sulfur wt.% 0.07 0.08
Moisture 8.26 wt. %
BTU / lb. 6839 7375
Straw - wheat
Ash wt.% 10.40 wt.% 11.33 wt.%
Sulfur wt.% 0.07 0.075
Moisture 6.91 wt. %
BTU / lb. 7153 7626
Straw - oat
Ash wt.% 7.90 wt.% 8.49 wt.%
Sulfur wt.% 0.05 0.055
Moisture 9.70 wt.%
BTU / lb. 6597 7345
Sugar Beet Pulp
Ash wt.% 3.80 wt.% 4.31 wt.%
Sulfur wt. % 0.14 0.16
Moisture 8.65 wt.%
BTU / lb. 8474 9654
Sunflower Hulls
Ash wt.% 2.86 wt.% 3.13 wt.%
Sulfur wt. % 0.14 0.15
Wheat Middlings Moisture 12.58 wt.%
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BTU / lb. 7228 8415
Ash wt.% 5.18 wt.% 6.00 wt.%
Sulfur wt. % 0.15 0.17
Moisture 10.38 wt.%
Wheat BTU / lb. 7159 8063
(Hard Red Spring) Ash wt.% 2.08 wt.% 2.28 wt.%
Sulfur wt. % 0.20 0.22
[0015] During combustion of the fuel pellets, if materials containing
potassium, sulfur
and/or chlorine are present, K, S, and Cl can vaporize and deposit on metal
surfaces. The
resulting deposited layer may eventually melt and become sticky, which can
result in the
trapping of nonvolatile materials, containing elements such as Si, Ca, and Mg.
Such
elements may react with alkali metals, sulfur and/or chlorine The products of
such reactions
(e.g., alkali silicates) and/or chloride salts can lead to breakdown of the
protective oxide
layer on metal surfaces and ultimately contribute to accelerating corrosion.
It can be
advantageous to have low levels of inorganic compounds incorporating the
elements listed
above in the present fuel pellets. Example, for residential appliances, the
Pellet Fuel
Institute has a maximum limit on water soluble Na in fuel pellets of 300 ppm.
[0016] The following examples are presented to illustrate the present
invention and to
assist one of ordinary skill in making and using the same. The examples are
not intended in
any way to otherwise limit the scope of the invention.
EXAMPLE S
Example 1 -
[0017] Six batches of biomass fuel pellets were made. Table 2 shows the weight
percents
for each component of the fuel pellet. The fuel pellet formula was weighed out
and mixed
in a ribbon mixer for 3 minutes. Once the mixing is complete, the loose mix
was
conditioned with steam. The conditioned mixture was then pelleted at a
temperature of 140
- 180 F utilizing a 1/4 inch die then cooled using a counter flow cooler. The
cooled pellets
were then screened to remove any remaining fine material.
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Table 2
Sample 1 2 3 4 5 6
Cracked Corn 75 50 50 55 75
Whole Corn 50
Wheat Middlings 25 25 25 25 35 25
Soy Hulls 25 25 25
DDGS 10
[0018] Samples from each batch were tested for Moisture content, heating
value, and ash
content. All but one sample was tested for sulfur content as well. Table 3
includes the
results of the testing wherein sample numbers correspond to the samples in
Table 2.
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Table 3
Sample Property
Moisture 12.37 wt.%
BTU / lb. 7028
Ash wt.% 2.63 wt.%
Sulfur wt.% 0.15
Moisture 11.68 wt.%
BTU / lb. 6987
2
Ash wt.% 33 wt.%
Sulfur wt.% 0.14
Moisture 11.09 wt.%
BTU / lb. 7015
3
Ash wt.% 3.37 wt.%
Sulfur wt.% 0.15
Moisture 11. 14 wt. %
BTU / lb. 7059
4
Ash wt.% 3.50 wt.%
Sulfur wt.% Not Tested
Moisture 13.7 wt.%
BTU / lb. 7175
Ash wt.% 2.67 wt.%
Sulfur wt.% 0.17
Moisture 14.49 wt.%
BTU / lb. 7435
6
Ash wt.% 1.7 wt.%
Sulfur wt.% 0.11
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Example 2 -
[0019] Table 4 shows the weight percents for each component of six exemplary
fuel pellet
formulations. The fuel pellet formula may be weighed out and mixed in a ribbon
mixer for
3 minutes. Once the mixing is complete, the loose mix may be conditioned with
steam.
The conditioned mixture will then be pelleted at a temperature of 140 - 180 F
utilizing a 1/4
inch die then cooled using a counter flow cooler. The cooled pellets were then
screened to
remove any remaining fine material.
[0020] A variety of materials may be used in place of and/or together with the
agricultural
biomass materials listed above. For example, corn, corn byproducts, oats, oat
byproducts,
wheat, wheat byproducts, rice, and rice byproducts. Also, oilseeds and oilseed
materials
may be used. Such material include soy beans, soy bean byproducts, sunflower
seeds,
sunflower byproducts, rapeseeds and rapeseed byproducts.
ILLUSTRATIVE EMBODIMENTS
[0021] A number of illustrative embodiments of the present methods and
compositions are
described below. The embodiments described are intended to provide
illustrative examples
of the present methods and compositions and are not intended to limit the
scope of the
invention.
[0022] The present fuel pellets may be formed from a mixture which includes
substantial
amounts of agricultural biomass having a relatively low lignin content, e.g.,
about 60 wt.%
(dry basis) or more of the agricultural biomass. The fuel pellets desirably
have a low ash
content, good pellet durability (e.g., as determined by their pellet
durability index) and
heating values comparable to conventional hardwood fuel pellets. In some
instances, the
fuel pellets may have an ash content as high as about 15 wt.%, although lower
ash contents,
e.g., no more than about 5 wt.% and, more desirably, no more than about 3
wt.%, are
commonly suitable for many applications. The fuel pellets may be formed by
pelleting a
mixture comprising agricultural biomass which includes whole corn, corn cobs,
corn stover,
wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon
fiber, alfalfa,
dried distillers grain, oats, oat straw, sugar beet pulp and/or sunflower
hulls. Other suitable
agricultural biomass materials which may be used to form the present fuel
pellets include
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co-products from corn milling processes (e.g. corn gluten feed, white fiber),
oat hulls, rice
hulls, rapeseed meal, rapeseed fractions, bagasse and/or empty palm fruit.
[0023] The fuel pellets may comprise an agricultural biomass having a lignin
content of
no more than about 10 wt.%. Typically, the fuel pellet itself has a lignin
content of no more
than about 10 wt.% and, often, no more than about 5 wt.%. The pellet may have
an ash
content of no more than about 3 wt.%, a PDI of at least about 90 and a heating
value of at
least about 7000 BTU/lb (dry basis). In some embodiments, the fuel pellet will
have a
heating value of at least about 7200 BTU/lb (dry basis) and more desirably
7500 BTU/lb
(dry basis).
[0024] In some of these embodiments, the agricultural biomass may be selected
from the
group consisting of cracked corn, whole corn, corn cobs, corn stover, wheat,
wheat
middlings, wheat straw , soy beans, soy bean hulls, soy cotyledon fiber,
alfalfa, dried
distillers grain, oats, oat straw, sugar beet pulp, rapeseed hulls, sunflower
hulls and mixtures
thereof. The fuel pellet may have a PDI of at least about 90 and more
preferably at least
about 95.
[0025] In some of embodiments, the agricultural biomass may comprise at least
about 40
wt.% cracked corn, whole corn, or a mixture thereof and preferably at least
about 40 wt.%
cracked corn.
[0026] In some instances, the present fuel pellets may include up to about 30
wt.%
triacylglyceride material (i.e., have a "triacylglyceride content" of no more
than about 30
wt.%). Typically, the fuel pellet has a triacylglyceride content of no more
than about 5
wt.% and, more desirably, the fuel pellet has a triacylglyceride content of no
more than
about 3 wt.%.
[0027] In some embodiments, the fuel pellet further comprises a sugar alcohol
component,
which may comprise glycerol. Typically, the fuel pellet contains no more than
about 5
wt.% of the sugar alcohol but in certain embodiments, may contain up to about
30 wt.% of
the sugar alcohol. Optionally, the fuel pellet further comprises a processing
aid. The
processing aid may comprise paraffin wax, hydrogenated triacylglyceride,
tallow, and/or a
thermoplastic polymer (which may optionally be densified).
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[0028] In some embodiments, a fuel pellet may be formed by pelleting a mixture
comprising about 40 to 85 wt.% cracked corn, about 20 to 60 wt.% wheat
middlings, and
optionally up to about 5 wt.% glycerol. In many embodiments, the inclusion of
3 wt.%
glycerol or less as a pelleting aid may be quite suitable.
[0029] Other suitable pelleting aids may encompass both lubricants and
binders. For
example, glycerol may have functionality as both. Examples of suitable binders
would
include, but are not limited to, lignin sulfonates, starches of various
grains, gelatins, or
alginates with inclusion levels as low as 0.1%. or as high as 40-50% in case
of starches.
Super Lube (Uniscope), Lube Aid (Ag Research), Pelltech (Borregaard Ligno
Tech) are
non-limiting examples of lubricants.
[0030] In some embodiments, a fuel pellet may comprise an agricultural biomass
selected
from the group consisting of cracked corn, whole corn, corn cobs, corn stover,
wheat, wheat
middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber,
alfalfa, dried
distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof. The
fuel pellet may have an ash content of no more than about 3 wt.%, a PDI of at
least about
90, and a heating value of at least about 7000 BTU/lb (dry basis).
[0031] A fuel pellet may be formed by pelleting a mixture comprising about 40
to 90
wt.% corn, and about 10 to 60 wt.% of an agricultural biomass selected from
the group
consisting of corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy
beans, soy
bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat
straw, sugar beet pulp,
sunflower hulls and mixtures thereof. The fuel pellet may have an ash content
of no more
than about 3 wt.%, a PDI of at least about 90, and a heating value of at least
about 7000
BTU/lb (dry basis).
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[0032] A method of producing heat may comprise burning a fuel pellet
comprising an
agricultural biomass. In some instances, the agricultural biomass may include
material
selected from the group consisting of cracked corn, whole corn, corn cobs,
corn stover,
wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon
fiber, alfalfa,
dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof.
In some of these embodiments, the fuel pellet may have an ash content of no
more than
about 3 wt.%, a PDI of at least about 90, and a heating value of at least
about 7000 BTU/lb
(dry basis). In other embodiments, the fuel pellet may have an ash content of
no more than
about 2.5 wt.% ash, desirably no more than about 2.0 wt.% ash, and more
desirably no more
than about 1.7 wt.% ash. The fuel pellet commonly has a density of at least
about 35 lbs/ft3
and desirably no more than about 45 lbs/ft3. Suitably, the pellets have a
density of about 40-
43 lbs/ft3.
[0033] A fuel pellet may comprise an agricultural biomass wherein the pellet
has an ash
content of no more than about 3 wt.%, a PDI of at least about 90, a sulfur
content of no
more than about 0.2 wt.%, a moisture content of no more than about 15 wt.%
(more
desirably no more than about 13 wt.%), a triacylglyceride content ("TAG
content") of no
more than about 5 wt.% and a heating value of at least about 7000 BTU/lb (dry
basis). In
some embodiments the agricultural biomass may have a lignin content of no more
than
about 10 wt.% and desirably no more than about 5 wt.%.
[0034] In some embodiments, the fuel pellet may comprise from 0.1 to 5 wt.%
glycerol.
In other embodiments, the fuel pellet may comprise at least about 0.5 wt.%
glycerol. In yet
other embodiments, the fuel pellet comprises about 1 to 3 wt.% glycerol.
[0035] In some embodiments, the fuel pellet may have a generally cylindrical
shape. The
fuel pellet may have a diameter of about 2/16 of an inch to 6/16 of an inch.
More desirably,
the fuel pellet may have a diameter of about 3/16 of an inch to 5/16 of an
inch. The fuel
pellet may have an aspect ratio of about 1:1 to 5:1.
[0036] In some embodiments the fuel pellet may comprises a processing aid.
Pellets
containing such a processing aid may suitably include about 0.1 to 3 wt.%
glycerol.
[0037] In some embodiments, a fuel pellet may be formed by pelleting a mixture
comprising about 40 to 90 wt.% corn, and more desirably about 40 to 80 wt.%
corn. The
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mixture may further comprise wheat, wheat middlings, soy hulls, sunflower
hulls, rapeseed
hulls, oats, dried distillers grains, beet pulp, corn cob, or mixtures
thereof.
[0038] In yet another embodiment, the fuel pellet comprises an agricultural
biomass
having a lignin content of no more than about 10 wt.% (dry basis), wherein the
pellet has an
ash content of no more than about 3 wt.%, a PDI of at least about 90, and a
heating value of
at least about 7000 BTU/lb (dry basis).
[0039] In yet another embodiment, the fuel pellet comprises at least about 60
wt.% (dry
basis) of an agricultural biomass selected from the group consisting of
cracked corn, whole
corn, corn cobs, corn stover, wheat, wheat middlings, soy beans, soy bean
hulls, soy
cotyledon fiber, dried distillers grain, oats, sugar beet pulp, sunflower
hulls, co-products
from corn milling processes, oat hulls, rapeseed meal, rapeseed fractions,
bagasse, rice
hulls, ground barley, cottonseed hulls, whole cottonseed, ground milo,
oatmeal, oat flour,
rye, broken rice, empty palm fruit bundles and mixtures thereof. The fuel
pellet typically
has an ash content of no more than about 3 wt.%, a PDI of at least about 90,
and a heating
value of at least about 6800 BTU/lb (dry basis), more suitably at least about
7000 BTU/lb
(dry basis) and, more desirably, at least about 7200 BTU/lb (dry basis).
[0040] In yet another embodiment, the fuel pellets are formed from a mixture
which
includes corn, corn byproducts, oats, oat byproducts, wheat, wheat byproducts,
rice, and/or
rice byproducts. Also, oilseeds and oilseed materials may be used. Such
materials include
soy beans, soy bean byproducts, sunflower seeds, sunflower byproducts,
rapeseeds and
rapeseed byproducts. Commonly, the fuel pellet comprises at least about 60
wt.% (dry
basis) of agricultural biomass, such as the materials described in this
paragraph.
[0041] In yet another embodiment, the fuel pellets comprise at least about 60
wt.% (dry
basis) of an agricultural biomass selected from the group consisting of
cracked corn, whole
corn, corn cobs, corn stover, wheat, wheat middlings, soy beans, soy bean
hulls, soy
cotyledon fiber, dried distillers grain, oats, sugar beet pulp, sunflower
hulls, co-products
from corn milling processes, oat hulls, rapeseed meal, rapeseed fractions,
bagasse, rice
hulls, empty palm fruit bundles and mixtures thereof. Such fuel pellets
typically have an
ash content of no more than about 3 wt.%, a PDI of at least about 90, and a
heating value of
at least about 6800 BTU/lb (dry basis), more suitably at least about 7000
BTU/lb (dry basis)
and, more desirably, at least about 7200 BTU/lb (dry basis).
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WO 2008/036605 PCT/US2007/078655
[0042] In yet another embodiment, the fuel pellets are formed by pelleting a
mixture
comprising about 40 to 90 wt.% corn; and about 10 to 60 wt.% of an
agricultural biomass
which includes corn cobs, corn stover, wheat, wheat middlings, wheat straw,
soy beans, soy
bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat
straw, sugar beet pulp,
sunflower hulls, co-products from corn milling processes, oat hulls, rapeseed
meal, rapeseed
fractions, bagasse, rice hulls, ground barley, cottonseed hulls, whole
cottonseed, ground
milo, oatmeal, oat flour, rye, broken rice, empty palm fruit bundles or a
mixture thereof.
Such fuel pellets typically have a PDI of at least about 90. Such fuel pellets
typically have a
heating value of at least about 6800 BTU/lb (dry basis), more suitably at
least about 7000
BTU/lb (dry basis) and, more desirably, at least about 7200 BTU/lb (dry
basis). Such fuel
pellets suitably have an ash content of no more than about 3 wt.%.
[0043] In some embodiments, a fuel pellet may comprise an agricultural biomass
selected
from the group consisting of cracked corn, whole corn, corn cobs, corn stover,
wheat, wheat
middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber,
alfalfa, dried
distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof. The
fuel pellet may have an ash content of no more than about 3.0%, a PDI of at
least about
90%, and a heating value of at least about 7000 BTU/lb.
[0044] In some embodiments, a fuel pellet may comprise an agricultural biomass
selected
from the group consisting of cracked corn, whole corn, corn cobs, corn stover,
wheat, wheat
middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber,
alfalfa, dried
distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof. The
fuel pellet may have an ash content of no more than about 3 wt.%, a PDI of at
least about
90, and a heating value of at least about 7000 BTU/lb.
[0045] A fuel pellet may be formed by pelleting a mixture comprising about 40
to 90
wt.% corn, and about 10 to 60 wt.% of an agricultural biomass selected from
the group
consisting of corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy
beans, soy
bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat
straw, sugar beet pulp,
sunflower hulls and mixtures thereof. The fuel pellet may have an ash content
of no more
than about 3 wt.%, a PDI of at least about 90, and a heating value of at least
about 7000
BTU/lb.
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WO 2008/036605 PCT/US2007/078655
[0046] A method of producing heat may comprise burning a fuel pellet
comprising an
agricultural biomass. In some instances, the agricultural biomass may include
material
selected from the group consisting of cracked corn, whole corn, corn cobs,
corn stover,
wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon
fiber, alfalfa,
dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and
mixtures thereof.
In some of these embodiments, the fuel pellet may have an ash content of no
more than
about 3 wt.%, a PDI of at least about 90, and a heating value of at least
about 7000 BTU/lb.
In other embodiments, the fuel pellet may have an ash content of no more than
about 2.5
wt.% ash, desirably no more than about 2.0 wt.% ash, and more desirably no
more than
about 1.7 wt.% ash. The fuel pellet commonly has a density of at least about
35 lbs/ft3 and
desirably no more than about 45 lbs/ft3. Suitably, the pellets have a density
of about 40-43
lbs/ft3.
[0047] Yet another embodiment is directed to a method of producing heat
comprising
burning fuel pellets formed by pelleting a mixture comprising an agricultural
biomass
which includes whole corn, corn cobs, corn stover, wheat, wheat middlings,
wheat straw,
soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers
grain, oats, oat straw,
sugar beet pulp, sunflower hulls, co-products from corn milling processes, oat
hulls,
rapeseed meal, rapeseed fractions, bagasse, rice hulls, empty palm fruit
bundles and
mixtures thereof. The fuel pellets commonly have a PDI of at least about 90
and a heating
value of at least about 7000 BTU/lb (dry basis).
[0048] Yet another embodiment is directed to a method of producing heat
comprising
burning fuel pellets formed from a mixture which includes substantial amounts
of
agricultural biomass having a relatively low lignin content, e.g., about 60
wt.% (dry basis)
or more of the agricultural biomass. The fuel pellets desirably have a low ash
content,
good pellet durability (e.g., as determined by their pellet durability index)
and heating
values comparable to conventional hardwood fuel pellets. In some instances,
the fuel
pellets may have an ash content as high as about 15 wt.%, although lower ash
contents, e.g.,
no more than about 5 wt.% and, more desirably, no more than about 3 wt.%, are
commonly
suitable for many applications.
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WO 2008/036605 PCT/US2007/078655
[0049] Unless expressly stated otherwise, all percentages referred to herein
are on a
weight to weight basis (i.e., "wt.%"). In some instances, the percentages are
expressed on a
dry weight to total dry weight basis (i.e., "wt.% (dry basis)").
[0050] References to specific examples, use of "e.g.," use of the word
"invention," etc.,
are not meant to restrict the scope of the recited claim terms. Accordingly,
the claims are
not tied and should not be interpreted to be tied to any particular
embodiment, feature, or
combination of features other than those explicitly recited in the claims,
even if only a
single embodiment of the particular feature or combination of features is
illustrated and
described herein. Thus, the appended claims should be read to be given their
broadest
interpretation in view of the prior art and the ordinary meaning of the claim
terms.
[0051] As used herein (i.e., in the claims and the specification), articles
such as "the," "a,"
and "an" can connote the singular or plural. Also, as used herein, the word
"or" when used
without a preceding "either" (or other similar language indicating that "or"
is unequivocally
meant to be exclusive - e.g., only one of x or y, etc.) shall be interpreted
to be inclusive
(e.g., "x or y" means one or both x or y). Likewise, as used herein, the term
"and/or" shall
also be interpreted to be inclusive (e.g., "x and/or y" means one or both x or
y). In
situations where "and/or" or "or" are used as a conjunction for a group of
three or more
items, the group should be interpreted to include one item alone, all of the
items together, or
any combination or number of the items. Moreover, terms used in the
specification and
claims such as have, having, include, and including should be construed to be
synonymous
with the terms comprise and comprising.
[0052] Unless otherwise indicated, all numbers or expressions, such as those
expressing
dimensions, physical characteristics, etc. used in the specification are
understood as
modified in all instances by the term "about." At the very least, and not as
an attempt to
limit the application of the doctrine of equivalents to the claims, each
numerical parameter
recited in the specification or claims which is modified by the term " about"
should at least
be construed in light of the number of recited significant digits and by
applying ordinary
rounding techniques. Moreover, all ranges disclosed herein are to be
understood to
encompass any and all subranges subsumed therein.
-18-
CA 02663750 2009-03-18
WO 2008/036605 PCT/US2007/078655
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21
CA 02663750 2009-03-18
WO 2008/036605 PCT/US2007/078655
Table 7
Predicted Heating Value (BTU/Ib)
for Various Agricultural Materials
Predicted Predicted
MOISTURE ASH Sulfur BTU/Ib (As- BTU/Ib (Dry
Is Basis) matter Basis)
Alfalfa - Dehydrated 8.9 10.3 0.25 6774 7435
Bakery By-Product <10%
Fat 9.7 4.24 0.16 7573 8387
Barley Ground 12.40 2.35 0.15 6888 7863
Barley Hulls 6.37 5.98 0.13 7197 7687
BARLEY MIDDS 12 5 0.17
Barley Screening/Malt 8.66 5.24 0.16 7209 7893
Sprout Pellets
Barley Straw 10.00 8.82 0.15 6677 7419
Beet Pulp 8.2 6.44 0.22 6853 7466
Citrus Pulp 11.9 5.97 0.06 6586 7475
Cocoa Hulls <5% Fat 10.50 8.19 6959 7775
Cocoa Hulls >5% Fat 8.27 5.96 7829 8534
Coconut - Copra Meal 6.60 6.08 0.30 8039 8607
Corn DDGS 9.07 4.35 0.42 8250 9073
Corn Germ Meal -
Solvent 10.90 1.93 0.37 7400 8306
Corn Gluten Feed 8.70 6.10 0.38 7266 7958
Corn Gluten Feed - MCP 57.50 2.55 0.11 3336 7849
Corn Gluten Feed -
Sweet Bran 39.85 3.24 0.26 4829 8028
Corn Gluten Feed - Wet 57.50 2.60 0.10 3366 7921
Corn Gluten Meal 60%
Protein 10.60 1.66 0.50 8189 9160
Cottonseed - Whole 8.36 3.50 0.23 8652 9441
Cottonseed Hulls 10.20 2.74 0.20 7209 8028
Cottonseed Meal - 10.70 6.22 0.40 7505 8404
Dehulled Expeller
Malt Sprouts 5.57 5.78 0.61 7520 7963
Milo - Fine Ground 14.10 1.34 0.09 6863 7989
Oat Flour 7.85 1.83 0.17 7704 8361
Oat Hulls 9.70 5.38 0.06 6900 7641
Oat Straw 8.00 6.62 0.21 6959 7564
-22-
CA 02663750 2009-03-18
WO 2008/036605 PCT/US2007/078655
Table 7 (Cont'd)
Predicted Predicted
MOISTURE ASH Sulfur BTU/Ib (As- BTU/Ib (Dry
Is Basis) matter Basis)
Oatmeal - Feed Grade 8.90 2.18 0.19 7570 8310
Oats - Whole 10.5 2.81 0.12 7314 8172
Oil - Corn 0.02 0 0 16624 16628
Oil - Cottonseed 0.99 0.00 0.00 16591 16756
Oil - Rice Bran 0.66 0.00 0.00 16248 16356
Oil - Soybean 0.02 0 0 16634 16637
Palm Kernel Meal -
Expeller 8.54 4.12 0.25 7895 8632
Palm Kernel Meal - 5.25 20.86 0.00 7034 7424
Expeller/Extruded
Palm Kernel Meal -
Solvent 11.70 5.41 0.00 6964 7886
Peanut Meal - Beef 10 5.47 0.31 7634 8482
Peanut Meal 45% Protein 8.38 6.86 0.31 7561 8253
Peanut Meal 50% Protein 7.79 4.92 0.25 8021 8698
Rapeseed Meal 0 8.20 8.39 0.64 7312 7965
Rice - Broken 13.77 0.68 0.06 6709 7780
Rice Bran - Defatted 20% 10.80 12.75 0.19 6482 7267
NDF
Rice Bran - Hi Fat 8.50 9.03 0.18 8174 8933
Rice Hulls 8.70 16.69 0.09 6030 6605
Rice Straw 4.15 14.28 0.27 6607 6893
Rice Straw - NH3 Treated 7.11 10.44 0.27 6817 7338
Rye 12.58 1.60 0.12 6844 7829
Rye Distillers 25% NDF 11.43 4.27 0.43 7436 8396
Rye Distillers 50% NDF 7.91 2.41 0.44 8042 8733
Rye Straw 10.00 4.50 0.10 6897 7663
Safflower Meal 7.3 4.71 0.18 7568 8164
Sesame Meal - Solvent 6.57 5.54 0.7 7909 8465
Sorghum Stover 12 9.68 0.0968 6382 7252
Soybean Germ 10.4 4.5 0.22 8371 9343
Soybean Hulls 13.30 4.65 0.18 6855 7906
Soybean Meal - 48%
Protein 12 6.1 0.4 7358 8361
-23-
CA 02663750 2009-03-18
WO 2008/036605 PCT/US2007/078655
Table 7 (Cont'd)
Predicted Predicted
MOISTURE ASH Sulfur BTU/Ib (As- BTU/Ib (Dry
Is Basis) matter Basis)
Soybean Meal - 10.27 5.46 0.39 8125 9055
Expeller/Extruded
Soybean Screenings 10.58 13.02 0 7115 7957
Sunflower Hulls 10.8 4.72 0.11 7669 8597
Sunflower Meal -
Expeller 6.67 6.47 0 8973 9614
Walnut Meal 9 3.59 0.13 7977 8766
Wheat - Ground 8-
14% NDF 11.8 1.6 0.18 6970 7903
Wheat Germ 12.64 3.45 0.31 7331 8392
Wheat Germ Meal 12.92 3.84 0.31 7732 8879
Wheat Gluten Feed 11.27 6.4 0.25 7022 7914
Wheat Gluten Meal 8.17 4.06 0.25 8384 9130
Wheat Midds By-
Product 27-34%
NDF 12.3 4.94 0.19 7064 8055
Wheat Straw 11.00 6.94 0.17 6651 7473
Wheat Straw - NaOH
Treated 8.28 8.03 0.27 6751 7360
-24-
