Note: Descriptions are shown in the official language in which they were submitted.
CA 02587025 2007-04-13
COMPRESSED FUEL PRODUCT USING FLAX STRAW DERIVATIVE
FIELD OF THE INVENTION
The present invention relates to a compressed fuel product, for example
a firelog, fuel pellets, briquettes or wafers and the like, and more
particularly relates to
a compressed fuel product which comprises a flax straw derivative.
BACKGROUND
It is known to modify natural fuels such as wood products and the like to
improve the burning characteristics thereof. For example it is known to
manufacture a
fire log comprising various wood products which are densified and compressed
into a
solid body using waxes, resins or other additives other than natural cellulose
material
to both improve the burning of the material and the bonding of the finished
compressed product. Known additives are typically costly and in addition are
generally considered to be not environmentally friendly.
US patents 6,113,662 to Sprules and 4,478,601 to Stephens disclose
examples of compressed fuel products in which combustible materials are
compressed into a solid body requiring bonding agents to form the finished
product.
US 4,553,978 to Yvan discloses an example of a fuel product which does not
make
use of additional waxes or binders, however the resulting product is instead
highly
friable as it may be broken up by hand due to its small specific gravity in
the order of
0.25. Due to the characteristics of the finished product according to the
techniques of
Yvan, the resulting product is unusable as a fire log as the product is not
sufficiently
durable. US 2,177,557 discloses a further example of fuel product, however the
product relies on alcohols and other additives in order to function properly
so that the
product is both costly to manufacture and results in undesirable fumes.
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SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a
compressed fuel product comprising a material compressed into a solid body,
the
material comprising a flax straw derivative.
According to second aspect of the present invention there is provided a
method of forming a compressed fuel product comprising providing a material
comprising a flax straw derivative and compressing the material into a solid
body.
Use of a flax straw derivative for forming a compressed fuel product
results in the product being formable into a fire log or other compressed
solid body
without the addition of any other waxes, resins or bonding type agents being
required
as the natural lignins in the flax straw derivative are sufficient to effect
bonding of the
log into the desirable solid body. The resulting composition of the log is
therefore
environmental friendly while being both simple and low cost to manufacture.
The material may primarily comprise a flax straw derivative as a majority
thereof, but preferably the material consists only of a flax straw derivative.
Preferably, the flax straw derivative consists only of flax shives in which
the shives consist of the remainder of flax straw once the fibrous material
has been
removed. The flax straw derivative used in the present invention however may
comprise flax straw in its entirety, with or without the flax seeds, and with
or without
fibrous material known to be extracted from the flax straw. The flax straw
derivative
may further comprise parts of flax seed, for example seed hulls or other
remnants
resulting from the removal of flax oil from the flax.
The method of forming the compressed fuel product preferably includes
bonding the material together in the solid body solely by natural lignin in
the flax straw
derivative.
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Preferably the material is compressed until the solid body has a specific
gravity greater than 1, and more preferably approximately 1.25.
The method may include extruding the material through an extruder
having a screw press and heating the material as it is extruded solely by
friction
generated from rotating the screw press.
Preferably the solid body comprises a firelog.
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a compressed fuel product according to
the present invention.
Figure 2 is a schematic view of the process for forming the compressed
fuel product.
Figure 3 is a plan view a site for effecting the process of Figure 2.
Figure 4 is an enlarged plan view of a portion of the site plan according
to Figure 3.
Figure 5 is an enlarged plan view of a cooling section of the site plan
according to Figure 3.
Figure 6 is a partly sectional side schematic view of one of the extruders
for forming the compressed fuel products.
In the drawings like characters of reference indicate corresponding parts
in the different figures.
DETAILED DESCRIPTION
Referring to the accompanying figures there is illustrated a compressed
fuel product generally indicated by reference numeral 10. In the illustrated
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embodiment, the product 10 is formed in the shape of a fire log and consists
solely of
flax shives so that the completed compressed fuel product has a specific
gravity in the
order of 1.25. No additional waxes or bonding agents are included as the
natural
lignin in the flax shives provides sufficient bonding to maintain the fuel
product
compressed as a single body once heated and compressed under considerable
pressure.
Prior to formation of the compressed fuel product 10, harvested flax is
first processed to remove the seeds and is then subsequently processed at a
plant 12
to remove fibrous material from the straw so that only the shives remain. The
flax
shives are then transported from the processing plant 12 to the site
illustrated in figure
3. The flax shives are transported by trailers 14 which feed the flax shives
into an
unloading hopper 16 at the site. An auger 18 carries the flax shives from the
unload
hopper to a blower 20 which conveys the shives into a wet storage bin 22 on
the site.
When it is desirable to form the compressed fuel product, the flax shives
are carried from the storage bin 22 by an auger 24 to a dryer 26 which dries
the
shives to a moisture content of approximately 4% to prepare it for subsequent
processing. The dryer 26 is heated by raw flax material being burned in a
suitable
burner 68. A cyclone 28 assists in subsequently carrying the material from the
dryer
26 to a dry storage area 70.
A plurality of feed augers 32 in the dry storage area 70 feed the flax
shives into a series of extruders 30 supported in parallel with one another
where the
compressed fuel product is extruded therefrom to respective log cutters 34
which cut
the compressed fuel product into individual logs deposited on a conveyor belt
36.
Once formed into individual logs, the compressed fuel product is
delivered by the conveyor belt 36 to an outdoor cooling building 38 prior to
packaging.
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The cooling building 38 includes a cooling belt 40 which conveys the product
10 along
multiple passes in front of cooling fans 42 which cool the product. The
product is then
returned indoors for being deposited on a receiving table 44.
From the receiving table 44, the product 10 is either loaded onto bulk
5 pallets 46 or the product is placed in cardboard grocery trade boxes 48 in
quantities of
six per box. When packaged in grocery trade boxes, fire starter 50 is packaged
with
the logs with the boxes being subsequently taped by an automatic taper 52
before
being loaded onto pallets 54 which are subsequently wrapped by a suitable
wrapper
56 for placement either in storage 58 on the site or onto carrier trucks 60
for delivery.
The bulk pallets 46 are also wrapped by a suitable automatic wrapper
62 for either being placed in storage 64 or for being loaded onto carrier
trucks 66 for
subsequent delivery.
Turning now to the extruders 30 in more detail as shown in Figure 6,
each extruder 30 includes an inlet hopper 70 which receives the flax shives
for
distribution to the inlet of a screw press 72. The screw press 72 feeds the
flax shives
through a surrounding barrel 74 to force the shives under pressure through a
die 76
which continuously extrudes the compressed fuel product consisting solely of
flax
shives therefrom. The screw press 72 is tapered to be reduced in diameter
towards
the die 76. An internal cooling jacket is provided surrounding the barrel
prior to the
die 76.
Sufficient pressure is generated by the screw press 72 which in turn
provides sufficient heat by friction that the natural lignins in the flax
shives cause the
flax shives to be bonded together to form the finished compressed fuel
product. The
cutters 34 form the individual fire logs from the continuously extruded
material exiting
the extruder.
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As described above flax straw derivative, comprising either whole flax
straw including both shives and fiber or just flax shives, is bonded into a
compressed
fuel product using pressure, heat and natural lignins of the flax to effect
the bonding.
To begin the process, the raw, screened material is first received in a
walking floor
trailer with a moisture content of about 10 to 12 %.
The unloading hopper receives the bulk flax straw at a rate of about one
tonne per minute.
The raw material is augured out of the bin and deposited into either a
blower or a screw auger that carries the straw up to the top of the 100 tonne
" wet "
bin. The raw flax straw is metered out of the 100 tonne bin at a consistent
rate of
approximately six tonnes per hour. The material is fed into a horizontal
continuous run
dryer. The dryer is fueled by a bio-fuel burner 68 that is supplied with dried
flax straw
that has already passed through the dryer.
A suction fan that is creating negative pressure in the dryer actually pulls
the flax straw through the dryer & then through a cyclone. The cyclone is used
to
separate the flax straw from the air created by the fan.
The dried flax straw now falls to the bottom of the cyclone through a
rotary gate & drops in to an auger that will carry the dried material into a
dry bin 70
inside the building.
The dry bin 70 in the manufacturing plant has a live bottom floor. This
means that the bottom of the bin is mostly covered with the screw feed augers
32 to
draw the product out at a very precise & even rate. This is the metering
system that
controls the flow of raw, dried material into the densified log extruder. Once
the
product is augured out of the dry bin it is transferred via another screw
auger to the
hopper on to of the extruder.
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The raw, dried material is now gravity fed from the extruder hopper
down into the extruder itself.
The extruder, powered by a 100 horse power electric motor, consists of
a receiving chamber, screw, barrel, and forming die.
The receiving chamber is the area around the tail end of the extruder
screw that allows the initial course flights of the screw to pick up material.
The flax
straw is then forced into the barrel of the extruder. The material is starting
to pack in
the barrel. The screw, turning at about 300 rpm continuously pushes more
material
into the barrel and then forces it into the die. The die forms the material
into a round
log about 4 inches in diameter with diametrically opposed flat sides of
approximately
1.5 inches in width.
The screws of the extruders are operated to generate heat to achieve
temperatures in the range of 300 to 350 degrees Fahrenheit by friction alone.
This
heat is sufficient to effectively melt the natural lignins in the flax straw
to successfully
glue the logs together without the addition of any glues, waxes, or resins of
any kind.
The end product is a densified, all natural 4 inch diameter fire log, ten to
twelve inches long weighing about 5 pounds with a specific gravity of around
1.25.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
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