Note: Descriptions are shown in the official language in which they were submitted.
,
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HYDROPHOBIC STARCH COMPOSITIONS AND
USES OF STARCH AS FUEL
[0001]
FIELD OF THE lNVENTION
10002] Fuels and fuel components comprising starch are provided, as well as
methods for operating a combustor such as a boiler or an internal combustion
engine
by feeding a starch fuel to the combustor. The starch may be a common starch
or a
modified starch, such as a free-flowing, hydrophobic starch having a near-
neutral dry
product pH. The starch may be provided as a solid fuel such as a powdered fuel
or as
a fuel slurry. The fuels can include a starch as the primary combustible
component
and/or may include other fuel components such as gasoline, diesel, kerosene,
jet fuel,
and alcohols. Methods are also provided for making a free-flowing hydrophobic
starch by preparing an aqueous mixture comprising a starch, a siliconate, and
an acid,
where the aqueous mixture has a near-neutral pH, and drying the starch solids
to
obtain a hydrophobic starch having a near-neutral dry product pH.
BACKGROUND OF THE INVENTION
[00031 The public's interest in renewable energy sources such as biofuels
is
higher than ever. A lot of this interest in biofuels can be attributed to the
desire to
lessen America's dependence on imported crude oil. The price of crude oil has
fluctuated at a high level recently, and there axe frequent tensions with many
oil-
producing countries. During 2005, U.S. crude oil reached highs of nearly $71 a
barrel
in August, up from $43 at the beginning of the year. It appears unlikely that
prices
will stabilize in 2006, given the continued unrest in Iraq and simmering
tensions with
Iran. Iran is the second largest crude oil producer in OPEC and holds 10% of
the
world's proven oil reserves. At one point, Iran warned that crude oil prices
would
soar if Iran were subjected to economic sanctions in response to its nuclear
program.
Gasoline has become relatively expensive for American drivers, recently
reaching
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prices of over three dollars per gallon. American motorists have been
frustrated by
these relatively high gasoline prices, especially during the summers of 2004
and 2005.
[0004] Interest in biofuels can also be attributed to public awareness
regarding
pollution and environmental hazards from the consumption of fossil fuels. The
burning of fossil fuels such as petroleum-based fuels, coal and natural gas
causes a
release of pollutants that may increase global climate change, acid rain, and
ozone
problems. Fossil fuels are not considered renewable energy sources, as they
are the
result of organic material being covered by successive layers of sediment over
the
course of millions of years.
[0005] Most cars and trucks on the road today are fueled by gasoline and
diesel
fuels. These fuels are produced from crude oil, which is a non-renewable
fossil fuel.
Non-renewable fuels depend on resources that will eventually run out.
Renewable
energy sources, in contrast, are constantly replenished and will not run out.
One type
of renewable resource is biomass, which includes plants and organic wastes
that can
be converted to fuels, chemicals, and other materials. Biomass can be used as
solid
fuels, or can be converted into liquid or gaseous forms, for the production of
electric
power, heat, chemicals, or fuels.
[0006] Government agencies and corporations in the energy and
transportation
industries continue to search for and develop renewable energy sources. The
U.S.
Department of Energy Biomass Program develops technology for conversion of
biomass (plant-derived material) to fuels, chemicals, materials and power, so
as to
reduce dependence on foreign crude oil and foster growth of biorefineries.
Biomass
can provide a renewable alternative for liquid transportation fuel. The use of
biomass
would aid rural economies, decrease America's dependence on imported crude oil
and
reduce pollution.
[0007] Ethanol is currently used as a biofuel, most commonly as a fuel
component
with gasoline for automotive use. In fact, a significant proportion of gas
purchased at
the pump contains about 10 or 15% ethanol. Ethanol has been widely used as a
fuel
component in gasoline for about 30 years. Its use as a fuel component was
initially
motivated by problems with petroleum supplies in the 1970's, as well as
political
pressure to reduce American dependence on imported crude oil. The use of
ethanol
was also motivated by a desire to increase the demand for agricultural
products such
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as corn. Ethanol can be obtained by fermentation of hydrolyzed starch, which
is
obtained by the processing of corn and other agricultural crops.
[0008] One of the
challenges in getting biofuels to replace fossil fuels has been
that the cost of creating biofuels has been higher than the cost of
traditional petroleum
exploration, production and refining. Another challenge has been that
significant
energy is required to create a BTU of biofuel, perhaps more than biofuel
itself
produces in some cases. However, such challenges may be met or reduced (at
least in
part) by increased crop yield due to biotechnology, improved biomass refinery
methods, and increased petroleum costs.
[0009] Despite
those challenges, use of biofuels in the United States has steadily
increased, and the U.S. Depaiti ___________________________________ lent of
Energy has set goals to promote the further
development and use of biofuels. Among those goals are that by the year 2020,
ten
percent of transportation fuel will be supplied by biomass, and five percent
of
industrial and utility power demands will be supplied by biopower.
[0010] Ethanol is
not the only biofuel that is used commercially. Another is
biodiesel, which is currently used in diesel engines. Biodiesel is made by
transforming animal fat or vegetable oil with alcohol and can be directly
substituted
for diesel, either as neat fuel (B100) or as an oxygenate additive (typically
20%-B20).
B20 earns credits for alternative fuel use and does not require the purchase
of a new
vehicle. In Europe, biodiesel is usually made from rapeseed (canola) oil,
while in the
United States, biodiesel is usually made from soybean oil.
[0011] Despite
advances in the development of ethanol and biodiesel as biofuels,
there remains a need for continued development of biofuels and fuel components
from
biomass which can be produced relatively easily and inexpensively. It would be
highly desirable to identify new fuels and fuel components developed from
biomass,
including fuels and fuel components having a cost advantage with respect to
existing
biofuels.
BRIEF SUMMARY OF THE INVENTION
[0012] As one
aspect of the present invention, novel fuels and fuel components
are provided that include starch, a biomass that can be obtained from corn,
potatoes,
and other agricultural products. The starch can be a common starch or a
modified
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starch, such as a free-flowing hydrophobic starch having a near-neutral dry
product
pH. Starch fuels or fuel components can be used for operating internal
combustion
engines or other combustors. As such, starch fuels and fuel components provide
a
feasible and sensible alternative or addition to petroleum-based fuels and to
currently
available biofuels. Moreover, fuels and fuel components can be obtained from
the
relatively inexpensive processing of starch and the formation of starch
slurries and/or
starch powders produced during existing processing operations for milling corn
or
other crops. The present fuels and fuel components can include starch, such as
a
hydrophobic starch. Preferably, the present fuels and fuel components include
a
common starch or a free-flowing, hydrophobic starch having a near-neutral dry
product pH.
[0013] As another aspect, methods are provided for fueling an internal
combustion engine or another combustor which comprises feeding to the engine
under
combustion conditions a fuel comprising a starch. As yet another aspect,
methods are
provided for operating an internal combustion engine or another combustor
using a
starch as a fuel or a fuel component. For example, the engine can be a diesel
engine
or an engine that has a spark plug. The methods can include introducing a fuel
comprising a starch, such as a common starch, or a free-flowing, hydrophobic
starch
into a combustion chamber of the engine. The methods can also include
introducing
sufficient air to the chamber for combustion, and igniting the starch as a
fuel for the
engine. The fuel or fuel component can be a common starch, or a free-flowing,
hydrophobic starch having a near-neutral pH, or a highly alkaline or highly
acidic
free-flowing, hydrophobic starch, or another modified starch.
[0014] As another aspect of the present invention, methods are provided for
operating or fueling various types of combustors by feeding starch to the
combustor,
preferably as a powder or a slurry. The methods can be used with a variety of
combustors, such as steam generating boilers, various types of kilns, rotary
driers,
blast furnaces and other types of combustors. As another example, the
combustor can
be an internal combustion engine such as a diesel engine or an engine that has
a spark
plug. The methods can include feeding or introducing a fuel comprising starch
(such
as a common starch or a free-flowing, ,hydrophobic starch having a near
neutral dry
product pH) as a slurry or powder into the combustion area of the combustor.
The
fuel can be fed gravimetrically by conveyor belts, screw conveyors, pneumatic
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injection systems (such as for starch powders), or hydraulic injection systems
(such as
for starch slurries). The methods can also include feeding an oxidant such as
air to
the combustor for combustion, and combusting the starch to provide heat or
perform
work. The methods can also include creating or maintaining combustion
conditions
in the combustor or a combustion area.
[0015] As yet another aspect of the present invention, novel methods are
provided
for preparing a hydrophobic starch having a near-neutral dry product pH. The
new
hydrophobic starch can be used as a fuel or fuel component, or put to another
use.
The method comprises preparing an aqueous mixture comprising a starch, a
siliconate, and an acid, wherein the aqueous mixture has a near-neutral pH.
The near-
neutral pH can be achieved in the aqueous mixture by including a suitable
amount of
acid in the aqueous mixture. Starch solids in the aqueous mixture can be
separated by
filtering or other means, preferably without washing. Starch solids from the
aqueous
mixture are dried to form a hydrophobic starch. The dried starch solids can be
subjected to grinding or another powderizing step.
[0016] An aqueous mixture having a near-neutral pH and comprising the
starch
and the siliconate can be prepared in a number of ways. For example, the
starch and
the siliconate can be combined in the aqueous mixture before combining with an
acid.
An acid can then be added to the aqueous mixture in an amount sufficient to
adjust the
pH of the aqueous mixture to a near-neutral pH. As another example, the
siliconate
and the acid can be combined to form an aqueous solution before combining with
the
starch. The aqueous solution can have a near-neutral pH when the starch is
combined.
[0017] As another aspect of the invention, novel hydrophobic starch
compositions
are provided which are free-flowing, hydrophobic, and have a near-neutral dry
product pH. Yet another aspect of the invention includes reaction products
from the
manufacturing methods described herein. For example, a novel hydrophobic
starch
composition comprises the reaction product of a starch, a siliconate, and an
acid,
mixed at a near-neutral pH, filtered, and dried to a desired moisture.
Preferably, the
reaction product is obtained without washing. The dry product pH of the novel
starch
compositions and reaction products can be between about 6.9 and about 7.6 or
another
desirable pH range.
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[0018] The novel free-flowing hydrophobic starch compositions described
herein
may be used in the conventional ways or in new ways, as described in detail
herein.
For example, the free-flowing, hydrophobic starch compositions having near-
neutral
dry product pH can be used as dusting materials, dry lubricants, and
detackifying
agents. As another example, the free-flowing, hydrophobic starch compositions
are
useful as fuels or fuel components for internal combustion engines and other
combustors. As such, the free-flowing, hydrophobic starch compositions
constitute a
feasible and sensible alternative to petroleum-based fuels, since a fuel or
fuel
component can be obtained from the inexpensive starch slurry produced during
the
routine processing operation of conventional wet corn milling. Additionally,
the low
production cost and lack of free acidity or alkalinity of the novel
hydrophobic starch
compositions having a near-neutral dry product pH reduces potential
corrosiveness.
This makes it a superior choice to the prior hydrophobic free-flowing starches
in
applications such as rubber dusting, dry lubrication, or detackifying.
Moreover, the
combustion products of the novel hydrophobic starch composition, being of near-
neutral pH, will have little or no corrosivity.
[0019] An object of the present invention is the use of starch, such as
modified
starch or common (unmodified) starch, as a solid fuel or a fuel slurry for
various types
of combustors including internal combustion engines and boilers. Another
object is to
provide a fuel or fuel component in which the energy and/or cost used to
produce the
fuel is minimized. For example, it is desirable to produce a biofuel such as a
starch
fuel having equal or more energy content for less cost and energy used to
produce
another biofuel such as ethanol. Another object is to provide a fuel or fuel
component
which would be price-competitive with petroleum-based fuels. Another object is
to
provide a fuel or fuel component which does not depend on tax subsidies that
presently support the use of ethanol as a fuel. Another object is to provide a
biofuel in
which the energy for producing the fuel is minimized. Still another object of
the
present invention is to provide a fuel or fuel component comprising starch.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Common starch or modified starch can be used as a fuel or a fuel
component for a combustor such as a boiler, kiln, dryer or furnace. Other
examples of
combustors are internal combustion engines such as vehicle engines or
generators,
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including gasoline engines, diesel engines, jet engines, and others. The
starch may be
in granule form or in particulate form and may be provided as a fuel slurry or
solid
fuel.
[0021] A fuel for a combustor may consist essentially of a starch.
Alternatively, a
starch can be the primary combustible component in a fuel. Alternatively, a
fuel may
comprise a starch as one fuel component along with other fuel components such
as
gasoline, diesel, kerosene, or jet fuels. In such fuels, the starch is one
combustible,
and one or more other combustibles may be included in the fuels. Other
possible fuel
components are alcohols. The present fuels and fuel components may also
include
detergents, and deposit control agents, as well as various other fuel
additives known
in the automotive field.
[0022] When used in a boiler or other combustor, a fuel is fed to a furnace
or
combustion area, where the fuel is ignited by a flame or other ignition
source. The
fuel may be a solid biofuel consisting essentially of starch in granule or
particulate
form, or other fuel components or other materials can be included in the fuel.
Preferably a solid fuel has a relatively low moisture content so that energy
is not used
to evaporate moisture from the fuel. The fuel can be mixed with an oxidant
such as
air in the combustion area or before being fed to the combustion area. The
fuel is then
combusted, such as by igniting the fuel with a flame and creating or
maintaining
combustion conditions. Heat from the combusted starch is used, such as to turn
water
into steam or to provide heat for drying another material. A device for
atomizing a
starch powder or converting a starch slurry to an aerated suspension can be
provided
in connection with boilers and other types of combustors.
[0023] When used in a gasoline internal combustion engine, a fuel
comprising a
starch is mixed with air in a carburetor and passed to the cylinder, or is
introduced by
an injector into the cylinder, where a spark plug is timed to generate a spark
to ignite a
fuel/air mixture. A piston in the cylinder moves axially in a stroke,
providing
rotational motion to a crank shaft via a connecting rod.
[0024] When used in a diesel engine, a fuel comprising a starch is injected
into
compressed air in an engine cylinder, and the heat of the compressed air
ignites the
fuel (although a glow plug or other ignition device may be used under some
circumstances, such as when the engine is cold). Diesel engines use direct
fuel
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injection -- the diesel fuel is injected directly into an engine cylinder by
an injection
system. Injection systems are known in the art for providing fuel powders to
engines.
[0025] When used in a jet engine, a fuel comprising a starch is combined
with air
drawn in at the front which has been compressed. The fuel combined with air is
typically ignited by a flame in the eddy of a flame holder, and burned as an
atomized
mixture. The combustion greatly increases the energy of the gases which are
then
exhausted out of the rear of the engine. The jet engine generates thrust
because of the
acceleration of the air through it¨the equal and opposite force this
acceleration
produces is thrust.
[0026) Combustors include various types of engines, heaters and other
equipment
and machinery that employ the combustion of a fuel to provide heat or perform
work.
For example, internal combustion engines for vehicular applications combust
fuel to
perform work by moving piston, turbines or other apparatus to provide motion
to a
vehicle. Internal combustion engines include gasoline engines, diesel engines,
jet
engines and others. Other examples of combustors are boilers, rotary kilns,
dryers,
and blast furnaces which produce heat.
[0027] Combustors fueled by starch can be used in a wide variety of
vehicles and
equipment. For example, internal combustion engines fueled by the present
fuels and
fuel components can power automobiles, trucks, lawn mowers, tractors, farm
machinery, trains, marine engines, fire pumps, power generators, jet engines,
industrial equipment such as chippers and air compressors, locomotives, mining
machinery, and others. This is not an exhaustive list, and it is contemplated
that fuels
comprising a starch are suitable for any use or application of an internal
combustion
engine or other combustor.
[00281 Starch fuels in slurry or solid form can be used in internal
combustion
engines or other combustors, or an engine or its associated equipment (for
example,
ignition devices or fuel injectors) which may be modified using routine
engineering
principles to be more suitable for operation using a starch powder or slurry
as a fuel.
For example, an agitator or mixer can be located upstream of the internal
combustion
engine or other combustor so as to maintain the fuel slurry in a homogenous
state and
to prevent starch particulates from settling and separating from the liquid
component
of the slurry. The use of powdered or particulate fuels for internal
combustion
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engines has been described in the public literature such as, for example, U.S.
Patent
No. 3,981,277 (Abom), U.S. Patent No. 4,052,963 (Stieger), U.S. Patent No.
4,070,997 (Stieger), U.S. Patent No. 4,359,970 (Wolters), and U.S. Patent No.
5,056,469 (Kimberley). Furthermore, powdered or particulate fuels of
appropriate
size can be used in existing common-rail injection systems, which are
currently used
with diesel engines and may also be used with gasoline engines.
[0029] The present fuels may be in the form of a powder, such as a solid
fuel
powder that comprises or consists essentially of a common starch or a modified
starch. Alternatively, the present fuels may be in the form of a fuel slurry,
which has
solid particles within a liquid phase. In these fuels, the starch may be
included in the
fuel in granule form or in particulate form. Where a fuel is in solid or
slurry form, it
is desirable that the fuel has particles having an appropriately small
particle size. A
finely divided particulate form is preferred when the starch is to be used in
an internal
combustion engine such as a common rail injection system. In general, it is
desirable
to provide a fuel powder in very finely divided form, such as of a size to
pass through
a 325 mesh screen, a 200 mesh screen or a 150 mesh screen. Alternatively, the
fuel
powder can have a mean particle size less than about 100 micrometers,
alternatively
less than about 90 micrometers, alternatively less than about 75 micrometers,
alternatively less than about 60 micrometers.
[0030] A fuel powder or slurry can be aspirated into a combustion cylinder
of an
internal combustion engine on a suction stroke. At the end of the compression
stroke,
the fuel powder or slurry can be ignited, such as by the heat of a compression
or by a
spark generating element, and thereby the fuel is caused to burn and produce a
power
stroke of the engine's piston. In a diesel engine, the fuel is generally
ignited by the
heat of the compressed air, though a glow plug is used when the engine is
cold.
[0031] Alternatively, the present fuels or fuel components can be provided
in
slurry, solid, or gel form. Such fuels may be provided in fluid form, such as
by
suspending a starch in a liquid component. For example, starch may be combined
with a liquid component to form a fuel slurry. Alternatively, starch may be
combined
with a liquid component to form a gel, such as a gelled gasoline or kerosene.
For
example, a starch may be included as a fuel component in a gelled fuel for a
jet engine
and could provide a significant proportion of the heat of combustion of the
fuel.
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[0032] Fuels and fuel components comprising starch may have various
advantages over other fuels in terms of cost and convenience in handling and
manufacture. Additionally solid fuels can be easier to handle than liquid
fuels. A fuel
provided as a free-flowing powder or in a particulate slurry may be used in
place of or
in combination with a liquid fuel in an internal combustion engine such as a
diesel
engine.
[00331 It is contemplated that it may be desirable to provide maximum or
minimum concentrations of a starch (such as a common starch or a modified
starch) in
a fuel. For example, the present fuels can have a starch content of more than
about
0.5 weight percent (wt %). Alternatively, the present fuels may comprise at
least
about 1 wt % starch, at least about 2 wt % starch, at least about 5 wt %
starch,
alternatively at least about 6 wt % starch, alternatively at least about 7 wt
% starch,
alternatively at least about 8 wt % starch, alternatively at least about 9 wt
% starch,
alternatively at least about 10 wt % starch, alternatively at least about 11
wt % starch,
alternatively at least about 12 wt % starch, alternatively at least about 13
wt % starch,
alternatively at least about 14 wt % starch, alternatively at least about 15
wt % starch,
alternatively at least about 16 wt % starch, alternatively at least about 17
wt % starch,
alternatively at least about 18 wt % starch, alternatively at least about 19
wt % starch,
alternatively at least about 20 wt % starch, alternatively at least about 22
wt % starch,
alternatively at least about 25 wt % starch, alternatively more than 25 wt %
starch,
alternatively at least about 30 wt % starch, alternatively at least about 35
wt % starch,
alternatively at least about 40 wt % starch, alternatively at least about 45
wt % starch,
alternatively at least about 50 wt % starch, alternatively at least about 55
wt % starch,
alternatively at least about 60 wt % starch, alternatively at least about 65
wt % starch,
alternatively at least about 70 wt % starch, alternatively at least about 75
wt % starch,
alternatively at least about 80 wt % starch, alternatively at least about 85
wt % starch,
alternatively at least about 90 wt % starch, alternatively at least about 95
wt % starch.
[0034] It is also contemplated that it may be desirable to provide a
maximum
content of starch in the present fuels, such as at most about 5 wt % starch,
alternatively at most about 10 wt % starch, alternatively at most about 15 wt
% starch,
alternatively at most about 16 wt % starch, alternatively at most about 17 wt
% starch,
alternatively at most about 18 wt % starch, alternatively at most about 19 wt
% starch,
alternatively at most about 20 wt % starch, alternatively at most about 25 wt
% starch,
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alternatively at most about 30 wt % starch, alternatively at most about 35 wt
% starch,
alternatively at most about 40 wt % starch, alternatively at most about 45 wt
% starch,
alternatively at most about 50 wt % starch, alternatively at most about 55 wt
% starch,
alternatively at most about 60 wt % starch, alternatively at most about 65 wt
% starch,
alternatively at most about 70 wt % starch, alternatively at most about 75 wt
% starch,
alternatively at most about 80 wt % starch, alternatively at most about 85 wt
% starch,
alternatively at most about 90 wt % starch, alternatively at most about 95 wt
% starch.
10035] The weight percentages of starch are calculated on a dry basis by
excluding the moisture content of the starch from the percentage. Any of the
minimum and maximum concentrations of starch set forth above may be combined
to
define a concentration range of starch in a fuel.
[0036] For an automotive fuel, it is contemplated that desirable minimum
and
maximum concentrations of starch may be provided, such as for example, an
automotive fuel having a concentration of from about 5 wt % to about 50 wt %
starch,
alternatively from about 10 wt % to about 45 wt %, alternatively, from about
25 wt %
to about 35 wt %, alternatively from about 8 wt % to about 16 wt % starch.
[0037] An automotive fuel may be provided that comprises a starch and
gasoline
and/or another hydrocarbon. For example, a desirable automotive fuel may
include
starch and gasoline as the only combustibles or may include other
combustibles. As
another example, a fuel may be provided which consists essentially of starch
and
gasoline. An automotive fuel may also include methyl tertiary butyl ether
(MTBE)
and/or ethanol, as well as one or more other fuel additives such as
detergents, anti-
corrosion agents, and other additives used in automotive applications.
Alternatively,
an automotive fuel can include starch and gasoline and be substantially free
of MTBE
and/or ethanol.
[0038] A jet engine fuel may be provided that comprises starch and jet
fuel. Such
a jet fuel may be a solid fuel or a gel and may comprise, for example, less
than about
20 wt % starch, alternatively less than about 15 wt % starch.
[0039] A fuel slurry may be provided that comprises, for example, more than
0.5
wt % starch, and/or less than about 55 wt % starch. A fuel slurry can be
prepared by
mixing free-flowing starch with a liquid component. Suitable liquid components
include gasoline, diesel, kerosene, jet fuel, and alcohols. Preferably the
free-flowing
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starch has a moisture content of about 8% or less, more preferably about 5.5%
or less.
The starch can be dried or re-dried to a desired moisture level and combined
with a
liquid component before absorbing a substantial amount of water from the air.
The
starch can be provided in granule or particulate form.
[0040] A fuel for an internal combustion engine or other combustor may
consist
essentially of a common or modified starch composition. In such a fuel, the
starch
composition is the main source of combustion. Alternatively, a fuel may
comprise a
starch composition as one fuel component along with other fuel components such
as
gasoline, diesel, kerosene, or jet fuels. In such a fuel, the starch is one
combustible,
and one or more other combustibles.
[0041] Starches suitable for use herein include corn starch, potato starch,
tapioca
starch, wheat starch, rice starch, sorghum starch, and the like, as well as
combinations
of any of the foregoing. The starch may be a modified starch or common
(unmodified) starch. The starch may be in its original granule form, or it may
be
milled to reduce its particle size and/or homogenize its particle size and/or
shape. The
starch may have any suitable pH, though a starch having a near-neutral dry
product
pH will usually be preferred to avoid corrosiveness.
[0042] Starches are polymeric chains of glucose units. Natural starches
from
plants are mixes of two types of polymeric chains called amylose and
amylopectin, in
which the monomers are glucose units joined to one another head-to-tail
forming
alpha-1,4 linkages. Amylose is a linear polymer of glucose linked with a(l-4)
bonds. Amylopectin is a highly branched polymer of glucose found in plants.
Its
glucose units are linked in a linear way with a(1--34) bonds, but branching
takes place
with a(1--).6) bonds occurring each 24 to 30 glucose units. The relative
content of
amylose and amylopectin varies between different species of starch.
[0043] Starch is generally produced by milling an agricultural product that
is a
source of starch (for example, corn, potatoes, tapioca, wheat, rice, sorghum,
and the
like). The product of milling is processed to remove fibers, proteins, and
soluble
material.
[0044] Modified and unmodified starches are products routinely produced in
conventional corn wet milling plants, and as such, constitute a feasible and
sensible
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alternative to petroleum-based fuels. The production of these type starches is
not
limited to corn wet milling operations but can include dry milling operations.
[0045] If the starch slurry produced by the corn wet milling process is
simply
dried, it is referred to as common, regular or unmodified starch. It is
available in
various physical forms and pH ranges. Treating common starch with various
chemicals such as acids and various oxidizing agents can produce modified
starches
with various physical properties. Dry product pH of common and modified
starches
tend to vary between 4.0 to 8Ø In the present methods and compositions, the
dry
product pH of the starch used in the fuels and fuel components will generally
be in the
range of from about 4 to about 11, alternatively from about 4 to about 8,
preferably from about 6.5 to about 7.5. The dry product pH of starch refers to
the pH
of an aqueous mixture when the starch is mixed in water at a concentration of
10 g of
the starch in 50 ml of distilled water.
[0046] The moisture content of common and modified starches may vary
between
4.5% to 13%. For the present invention, for a powdered starch fuel, it is
preferred to
dry or re-dry starch to obtain a starch having a moisture in the range of from
about 4%
to about 11%, alternatively from about 4.5% to about 8%, alternatively from
about
4.5% to about 5.5%.
[0047] Starch can be less expensive than ethanol as a fuel, in terms of
energy
produced divided by cost of production. The preparation of ethanol from starch
requires processing steps which add to costs. In the overall reaction of
starch to
produce ethanol (C61-11005) 2C2H5OH + 2õCO2, there is a 3% decrease in
enthalpy
(heat content). Additionally, the large scale production of ethanol from
starch still
experiences some loss, generally attaining about 93% of the theoretical yield.
More
particularly, the overall enthalpy yield of starch converted to ethanol can be
calculated
as follows:
7120 cal per g x 2 moles (46g) ethanol = 96.73% enthalpy yield.
4180 cal per g x 1 mole (162g) starch
96.73 x 93% large-scale production yield = 89.96% overall yield.
Thus the overall enthalpy yield is about 90%.
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[0048] This loss of energy stored in starch and the amount of energy
required for
converting starch to ethanol in a large-scale production process make ethanol
less
attractive as a fuel alternative. In order to make ethanol more attractive in
the U.S.
fuel market, federal tax subsidies have been implemented. This reduces the
direct
price that is charged to the consumer for fuels containing ethanol, but tax
revenue is
reduced to promote the production and use of ethanol for transportation fuels.
It
would be desirable to provide a biofuel requiring fewer or no tax subsidies.
[0049] In addition to the use of common starch in the present fuels and
fuel
components, starches can be modified in several ways to change their
characteristics.
For example, starches can be modified by increasing cross-linking, or by
heating to
break long amylose and amylopectin chains down into smaller molecules like
dextrin,
polydextrin, and malto-dextrin. As another example, starches can have a
hydrogen
replaced by something else, such as a carboxymethyl group, carboxyethyl
groups, or
carboxypropyl groups. Such groups make the starch more hydrophilic, and aid in
cross-linking. Oxidized starch, usually oxidized with sodium hypochlorite, is
whiter
than unmodified starch, has increased clarity, and a lower viscosity.
[0050] Another example of a modified starch is a hydrophobic starch. A
hydrophobic starch can be prepared by combining a starch with an alkyl
siliconate. It
is contemplated that a free-flowing, hydrophobic starch preferably having near-
neutral
dry product pH, can be used as a fuel or a fuel component.
[0051] The hydrophobic starch has polymerized siliconate on the starch
surface
which tends to maintain low moisture content as well as mobility. Thus, a free-
flowing, hydrophobic starch has less tendency to absorb moisture which would
decrease mobility. A composition will be considered free-flowing when it has
equal
or better mobility than finely ground starch. An impalpable powder having a
sufficiently low moisture content will generally be free-flowing.
[0052] Free-flowing, hydrophobic starches are known in the art and have
been
used as dusting materials, dry lubricants, and detackifying agents. U.S.
Patent No.
2,961,339 (Wolff et al.) discloses a free-flowing modified starch and methods
for
preparing the starch by treating with alkyl siliconates. Wolff '339
purportedly
discloses a siliconated granular starch which is water-repellant and
completely free of
undesirable alkalinity. Wolff '339 states that an improved starch is made by
drying
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the starch before washing, so the water-repellant or hydrophobic quality is
fixed but
the alkalinity is not fixed and may be removed by washing.
[0053] U.S. Patent No. 3,071,492 (Satterly) discloses a free-flowing
hydrophobic
starch and methods of manufacturing the starch by treating starch in a water
slurry
with a water-soluble silicone such as monosodium methyl siliconate. Satterly
'492
states that its resultant product has dry flow characteristics not found in
any raw starch
or other starch product, and the flow characteristics resemble those of a
fluid rather
than a solid.
[0054] Wolf '339 and Satterly '492 do not expressly discuss the alkalinity
of the
slurry or resulting product. In the methods described by both Wolff '339 and
Satterly
'492, the aqueous mixture of the starch and sodium methyl siliconate would
have a
highly alkaline pH (e.g., a pH of 12 or higher) due to the siliconate. The
free-
flowing, hydrophobic starches would have a highly alkaline dry product pH.
[0055] Canadian Patent No. 726,667 (Speakman) describes free-flowing,
hydrophobic starch and methods of preparation. Speakman '667 discusses a
method
of treating granule starch with an alkali metal alkyl siliconate to produce a
powdered
product having high mobility and hydrophobicity and possessing free acidity.
Speakman '667 states that a highly mobile, hydrophobic starch product can be
produced by mixing an aqueous solution of an alkali metal alkyl siliconate
with an
aqueous suspension of granular starch, adjusting the pH of the mixture to a
low value
by the addition of an acid, filtering off the starch without washing, drying
the starch
cake, and grinding to reduce the product to a powder.
[0056] Speakman '667 teaches that Wolff '339 and Satterly '492 operated at
a
highly alkaline pH and produced highly alkaline starch products. In discussing
Wolff
'339, the Speakman '667 patent states, "Even after washing and redrying, the
products exhibit a high alkalinity." In discussing Satterly '492, the Speakman
'667
patent states, "Finally, the free-flowing hydrophobic products made by this
method
have appreciable alkalinity, as shown by pH values of 10 or greater of
mixtures of the
product and water after vigorous shaking."
[0057] The Speakman '667 patent discloses adjusting the pH of an aqueous
mixture of siliconate and starch to a low value by the addition of an acid. In
a specific
example, the pH of the mixture was adjusted to 2.5 using hydrochloric acid.
The
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resulting starch had a dry product pH of 2.6. The Speakman '667 patent states,
"It is
possible to provide free-flowing hydrophobic starches having acidic or
alkaline levels
anywhere in a wide range by intimately mixing finely powdered alkaline
products
made by the methods of the prior art and acidic products made by the present
invention."
[0058] The known methods of preparing free-flowing hydrophobic starch
products result in starch products which are highly alkaline or highly acidic
when
dispersed in water. The high alkalinity or high acidity of known starch
products when
dispersed in water poses the possibility that these starch products might,
under some
conditions, corrode some materials with which they come into contact. The
potential
for corrosion limits the desirability of these known methods and compositions
where
corrosivity is a concern.
[0059] While the methods listed above are useful for preparing free-flowing
hydrophobic starch, there is a need for a free-flowing hydrophobic starch
whose dry
product pH is near-neutral. The present disclosure provides compositions and
methods relating to the novel preparation of a free-flowing, hydrophobic
starch
having near-neutral dry product pH.
[0060] Near-neutral pH is neither highly acidic nor highly alkaline. For
example,
near-neutral pHs include pHs between about 6 and about 8. The dry product pH
of a
composition refers to the pH of an aqueous mixture when the composition is
mixed in
water at a concentration of 10 g of the composition in 50 ml of distilled
water. The
present disclosure provides techniques for making hydrophobic starch
compositions
having dry product pHs greater than 6 or about 6, alternatively greater than 5
or about
5, alternatively greater than 4 or about 4, alternatively greater than 3 or
about 3,
alternatively greater than 2.6. The present disclosure provides techniques for
making
hydrophobic starch compositions having dry product pHs less than 8 or about 8,
alternatively less than 9 or about 9, alternatively less than 10 or about 10,
alternatively
less than 11 or about 11, alternatively less than 12. Any of the minimum and
maximum pHs set forth above may be combined to define a pH range.
[0061] The present techniques for making hydrophobic starch compositions
use
starches, siliconates and acids. Starches suitable for use in preparing
hydrophobic
starches include the types of starches mentioned above (corn starch, potato
starch,
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tapioca starch, wheat starch, rice starch, sorghum starch, and the like, as
well as
combinations of any of the foregoing).
[0062] The unmodified or common starch is generally produced by milling an
agricultural product that is a source of starch (for example, corn, potatoes,
tapioca,
wheat, rice, sorghum, and the like). The product of milling is processed to
remove
fibers, proteins, and soluble material. The milled common starch can be
modified to
' impart hydrophobicity, such as by combining with a siliconate.
[0063] Alkyl siliconates, in the form of the alkali metal salt, have been
known as
agents for imparting water resistance or water repellency to a wide variety of
substrates such as masonry, water-based paint ingredients, powdered materials
such as
limestone, gypsum, and the like, paper, paperboard, and various textiles.
Siliconates
are sometimes referred to as silanolates or salts or siliconic acids.
[0064] Sineonates include organosiliconates such as alkyl siliconates and
phenyl
siliconates, and salts thereof. The preferred salts are sodium and potassium
salts.
Alkali metal alkyl siliconates include those, defined by the general formula:
OH
I
R-Si-O X
I
OH
where R is an alkyl group containing 1 or more carbons and X is an alkali
metal. The
preferred alkali metal alkyl siliconate is sodium methylsiliconate, where R is
a methyl
group and X is sodium or potassium. Exemplary species of alkali metal
organosiliconates include sodium methylsiliconate, sodium ethylsiliconate,
sodium
propylsiliconate, potassium methylsiliconate, potassium ethylsiliconate and
potassium
propylsiliconate.
[0065] Suitable acids include hydrogen-donating acids, for example,
hydrochloric,
sulfuric, nitric, phosphoric, and acetic acids. A preferred acid is
hydrochloric acid.
[0066] The starches, siliconates and acids can be used in the following
methods to
make free-flowing, hydrophobic starch compositions. An aqueous mixture of
starch,
siliconate and acid is prepared in any suitable manner. For example, an
aqueous
slurry of corn starch can be prepared from dry substance granule corn starch,
and a
siliconate can be combined to form an aqueous mixture comprising the starch
and the
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siliconate. The aqueous mixture can be adjusted to a desired near-neutral pH
with the
addition of a suitable amount of an acid. Alternatively, the aqueous mixture
can be
made by a method where a siliconate, preferably sodium methylsiliconate, is
combined with an acid in an aqueous solution before combining the starch to
form an
aqueous mixture. In other words, an aqueous solution can be made from a
siliconate
and an acid, and the solution can be adjusted to a desired near-neutral pH
with a
suitable amount of acid.
[0067] Typical concentrations of starch in an aqueous slurry include the
range of
about 30% to about 39% by weight. Any appropriate starch may be used, though
untreated corn starch is often preferred for reasons of economy or
availability. The
slurry can then be agitated by any suitable means. For example, variable or
high
speed propeller agitators or other types of mixing equipment can be used to
agitate the
slurry.
[0068] As mentioned above, the siliconate can be added to an aqueous slurry
comprising starch to form an aqueous mixture of starch and siliconate, or the
starch
can be added to an aqueous solution comprising the siliconate. The siliconate
can be
combined with the starch slurry by itself or in combination with an acid. The
amount
of siliconate can be selected as a proportion of the amount of starch. For
example, the
concentration of the metal alkyl siliconate preferably will be approximately
0.05% to
5%, alternatively about 0.5 % to 1.0%, alternatively about 0.8% by weight
compared
to the starch.
[0069] The pH of the aqueous mixture is adjusted to a desired pH by adding
an
acid. The pH can be adjusted to a near-neutral pH. The pH can be adjusted to a
pH
greater than 4 and less than about 10, alternatively between about 5 and about
9,
alternatively between about 6 and about 8, alternatively between about 6.5 and
about
7.5, alternatively between about 6.8 and about 6.9, using an acid which
dissociates
sufficiently in water to produce the desired pH.
[0070] The aqueous mixture having a near-neutral pH and comprising the
starch
and the siliconate is agitated for a suitable period, for example at least 30
minutes,
although agitation can continue for longer or shorter periods. The starch can
then be
separated from the aqueous mixture by any effective means, such as by
filtration, to
obtain starch solids (the wet filter cake resulting from filtration).
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[0071] The wet filter cake (the starch solids) is then dried to a suitable
moisture
content to obtain dried starch solids. For example, the filter cake may be
dried to a
minimum moisture content, such as a moisture content of at least about 6%,
alternatively at least about 7%, alternatively at least about 8%,
alternatively at least
about 9%, alternatively at least about 10%. As another example, the filter
cake may
be dried to a maximum moisture content, such as at most about 11%,
alternatively at
most about 12%, alternatively at most about 13.5%. The foregoing minimum and
maximum moisture contents may be combined to form ranges.
[0072] Drying promotes polymerization of the siliconate, which provides
and/or
contributes to free-flowing and hydrophobic attributes. Therefore, it is
contemplated
:that the present methods may comprise polymerizing (by a technique other than
drying) at least some of the siliconate on at least some of the starch to form
a
hydrophobic starch. However, drying is the most convenient and practical
technique
for polymerizing at least some of the siliconate and for obtaining a starch
composition
having a desired moisture content. Drying temperatures in the range of 160 to
210
degrees Fahrenheit are preferred for drying, though other suitable
temperatures,
pressures and conditions can also be used and are easily determined.
[0073] The dried filter cake (dried starch solids) can then be powderized,
such as
by grinding or pulverizing, or by sieving the dried starch solids to remove
oversize or
non-powder material. The wet filter cake before powderizing does not have to
be
washed, nor does the powder have to be washed. The powder is hydrophobic and
free-flowing, and has a near-neutral dry product pH. The method can also
include the
steps of adjusting the pH of the aqueous mixture with one or more acids,
filtering off
the starch without washing, drying the starch, then grinding and screening the
resulting starch product through a sieve.
[0074] The free-flowing, hydrophobic starch compositions are especially
contemplated for use as a fuel or a fuel component for an internal combustion
engine
such as a vehicle engine or a generator, including gasoline engines, diesel
engines, jet
engines, and others. A fuel for an internal combustion engine may consist
essentially
of a free-flowing, hydrophobic starch, preferably having a near-neutral dry
product
pH. In such a fuel, the hydrophobic starch is the main source of combustion.
Alternatively, a fuel may comprise a hydrophobic starch as one fuel component
along
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with other fuel components such as gasoline, diesel, kerosene, or jet fuels.
In such a
fuel, the hydrophobic starch is one combustible, and one or more other
combustibles.
Other possible fuel components are alcohols. The foregoing fuels and fuel
components may also include detergents, and deposit control agents, as well as
various other fuel additives known in the automotive field.
[0075] Specific examples of various aspects of the invention are provided
below
solely for information and education and are not intended to delineate the
scope of the
invention nor limit the claims. In the examples and throughout this
specification,
percentages are intended to refer to percent by weight, unless otherwise
indicated.
EXAMPLE 1
[0076] Dry unmodified corn starch was suspended in water to create a slurry
of
500 mL total volume, containing 210.7 g of starch and 375 g of water.
[0077] 3.29 g of an aqueous solution of sodium methylsiliconate was added
to the
starch slurry to create an aqueous mixture. The added solution contained 1.053
g of
siliconate solids. The sodium methylsiliconate was provided as 0.5% siliconate
solids
by weight compared to the dry starch. The pH of the mixture was adjusted to
6.88
using hydrochloric acid.
[0078] The mixture was agitated at room temperature for 30 minutes. The pH
was
measured again to verify that the mixture was in a near-neutral pH range. The
pH
was 6.68 at the second measurement. The wet starch solids were recovered by
filtration on a Buchner funnel. The wet starch solids were not washed.
[0079] The filter cake was then dried in a conventional oven at about 180
F for
approximately 4 hours. After drying, the dried starch solids were ground in a
roller
mill to pass a 150 mesh copper wire screen. A free-flowing, hydrophobic starch
having a near-neutral dry product pH was obtained.
EXAMPLE 2
[0080] Ten grams of the free-flowing, hydrophobic starch composition
prepared
in Example 1 was placed in 50 mL of distilled water and shaken vigorously for
10
minutes. The pH of this mixture was measured and found to be 6.90. The pH
determined in this manner is the "dry product pH" of the hydrophobic starch
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composition. Thus, the free-flowing, hydrophobic starch from Example 1 had a
dry
product pH of 6.90.
EXAMPLE 3
[0081] A hydrophobic starch is used as a fuel for an internal combustion
engine.
A free-flowing hydrophobic starch is introduced to the fuel tank of a diesel
vehicle.
The Siemens VDO common-rail injection system for diesel engines has injectors
that
would permit injection of a powder passed through a 150 mesh screen. A free-
flowing, hydrophobic starch composition that is a powder with particle sizes
less than
150 mesh is used as a fuel with such a system. The free-flowing, hydrophobic
starch
composition is used as a fuel for an internal combustion engine. The fuel is
provided
to the engine in free-flowing form and is aspirated into a cylinder on a
suction stroke.
The fuel is heated by compression to a point at which the finely divided
material is
ignited by the heat of compression, or by an ignition source such as a glow
plug when
the engine is cold.
EXAMPLE 4
[0082] Fuels were made as follows. Commercial grade gasoline was obtained
and
mixed with starch to form fuel slurries having various starch contents. The
starch
used to prepare those fuels was a corn starch having approximately 11%
moisture.
[0083] A first fuel slurry was prepared comprising about 34% by weight
starch on
a dry basis by mixing the starch with gasoline. The fuel slurry had excellent
flowability characteristics. A second fuel slurry was prepared comprising
about 44%
by weight starch in gasoline, and this fuel slurry also had good flowability.
A third
fuel slurry was prepared comprising about 52% by weight starch in gasoline.
This
fuel slurry was more viscous than the first two slurries but exhibited
acceptable
flowability for use.
[0084] The foregoing starch contents were calculated on a dry basis. The
moisture of the starch was factored into the calculation of the starch content
of the
fuel by multiplying the measured weight of the starch by 0.89 to determine the
actual
weight of the starch on a dry basis added to the gasoline. The weight of the
gasoline
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was calculated based on the volume of gasoline used, based on a specific
gravity for
gasoline of 0.74 g/ml.
[00851 As another example of a fuel according to the present invention, a
solid
fuel comprising starch is prepared as follows. Corn starch is prepared by a
wet
milling process and dried to yield a starch having a moisture content of about
11%.
This starch is re-dried to reduce the moisture content to about 5%, and the re-
dried
starch is milled or comminuted to yield a finely divided particulate material.
For
example, the particulate material can be of a size that passes through a 200
mesh
screen or a 150 mesh screen. The particulate starch is suitable for use as a
fuel
powder for a boiler. A fuel consisting essentially of the starch powder at
about 5%
moisture is free-flowing and can be fed to a boiler or another combustor and
combusted to provide heat to water or another fluid in the boiler.
100861
[0087] While the present invention has been described and illustrated by
reference
to particular embodiments, it will be appreciated by those of ordinary skill
in the art
that the invention lends itself to many different variations not illustrated
herein. For
these reasons, then, reference should be made solely to the appended claims
for
purposes of determining the true scope of the present invention.
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