Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to improvements
in fuels, and more particularly to an improved coal
fuel product and a method for producing it.
With the ever increasing cost of petroleum fuels
and dwindling oil reserves, the users of domestic and
industrial fuels have been converting to alternative
fuels. Such alternatives include natural gas, electricity,
wood and coal. Natural gas, because of its gaseous state,
is not readily transportable, and is therefore only practical
for those users within easy access to a natural gas pipeline.
Likewise, electricity is only a viable alternative when
produced hydroelectrically. Otherwise, it must be produced
using conventional fuels such as oil, nuclear or bituminous
coal. Hydroelectric power is limited as to the distance
from its source. Wood as fuel is presently limited to a
cottage-trade distribution and can be expensive.
Coal, which is very abundant and relatively
inexpensive, can be easily transported in bulk by rail.
However, coal suffers from several disadvantages. Most
2Q coals have varying degrees of sulphur content. When burnt,
coal gives off sulphur dioxide which combines with moisture
in a chimney or smoke stack to produce sulphuric acid.
This acid is released to the atmosphere and comes down
as acid rain.
me best coal, that is, the cleanest having
the highest calorific value and lowest sulphur content,
is anthracite coal. m is coal, however, is also the most
expensive, and the hardest to ignite (a disadvantage
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as a domestic fuel).
Furthermore, all coals are handled or distri-
buted in a very inconvenient manner. It may be
delivered by truck to one's home, but a bin must be
provided to store up to 3 tons of bri~uettes of anywhere
from pellet size ~l cm) to chunks of several centimeters
in size. Coal i9 also dusty and dirty.
It is an aim of the present invention to
provide coal ai a fuel, suitable for domestic and commer-
cial use, which overcomes many of the above disadvantages.
It is an aim of the present invention to
utilize lower grade and thus cheaper coals, while
neutralizing their sulphur content and presenting the
coal fuel in a package which is clean and easily
distributed and handled.
A fuel product in accordance with the presen~
invention comprises a composite log consisting of a
mixture of betw~een 90% and 98~ coal particles having a
size of up to -4 mesh, cellulosic fibers in the range
of 2~ to 10%, grounded limestone particles in the range
of 1% to 15% by weight, and a moisture content of less
than 30%, the so-formed log being contained in a
hermetically sealed envelope, with the envelope made
of non-toxic combustible material.
, In a more specific embodiment, the composite
log consists of 90 to 94% coal particles and 6 to 10%
used newqiprint fibers and a supplement of 1% to 5% by
' weight of limestone is present in the mixture. The
moisture content is 10% or less, and the hermetic
~ 30 envelope is made of polyethylene.
`~ In another embodiment of the present invention,
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a composite log includes 90% of coal particle9, 5%
of shredded bark, preferably from conifer trees, and
5% of paper fibers, preferably of used newsprint, and
a quantity of powdered limestone in an amount of 3%
to 5% by weight.
More specifically, the bark utilized would be
selected from a group including pine, spruce, balsam
and hemlock. More specifically, the coal is a highly
volatile bituminous coal and is preferably ground to a
size of -8 mesh.
A method of making a composite fuel log in
accordance with the present invention includes the steps
of preparing a slurry of water and paper fibers, grind-
ing coal to a mesh size of between ~0 microns and 3 mm,
adding the coal particles to the slurry to a proportion
of between 2% and 10% paper fibers and 90~ to 98% coal
particles, mixing the slurry, adding powdered limestone to
the slurry in an amount of 1% to 15% by weight, pouring
the slurry into an open-ended mold, applying suction
at least to the open end of the mold to reduce the
water content to at least 50% moisture content, removing
- the so-formed log from the mold and drying the log to
reduce the moisture content to below 3~% moisture content
- and placing the log in a hermetically sealed envelope.
In a more specific version of the method in
accordance with the present invention, the used paper
fiber content is 6 to 10% and the coal particles are
94% while the limestone is added to an amount of 3%
- to 5% by weight thereof. The slurry is poured into
a cylindrical mold, and a porous tube is inserted
~- along the central axis of the cylindrical mold, and
suction is applied through the porous tube to ~ithdraw
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water from the so-formed log to below 50% moisture
content, removing the porous tube therefrom, leaving a
concentric cylindrical bore in the log, removing the log
from the mold and drying the log to reduce the moisture
content 30% or less and enveloping the so-formed log in
a polyethylene envelope and hermetically sealing the
envelope.
Having thus generally described the nature of
the invention, refererce will now be made to the
accompanying drawings, showing by way of illustration,
a preferred embodiment thereof, and in which:
Figure 1 is a schematic view of an embodiment
of an apparatus for making logs in
accordance with the present invention,
Figure 2 is a perspective view of a coal log in
accordance with the present invention,
Figure 3 i9 a perspective view of another embodiment
of the present invention, and
Figure 4 is a longitudinal cross-section thereof.
In a specific example, 200 grams of newsprint
was pulped in 3 liters of water by a 1 gallon Waring
blender, a further 200 grams of shredded bark and 3
kilograms of coal were added into the slurry, and the
heavy paste was beaten with a household mixer. me coal
had been ground to 1 mm, and a bituminous coal from Minto,
New Brunswick was selected. m e slurry so formed was poured
into a cylindrical mold, 12 inches in length and 6 inches
in diameter. A one-and-a-half inch diameter "Porex" tube
~ was inserted centrally of the cylinder, and suction was
-~ 30 applied to the "Porex" tube for withdrawing water from the
mold.
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When removed from the mold, the logs contained about
25% water.
The log was then air dried for one week in
a laboratory with no application of external heat.
Virtually, all of the water was removed in this matter.
The bark utilized was a mixture of spruce
and pine bark from a lumber mill in Doaktown, ~ew
Brunswick. The bark was shredded in a laboratory
Waring blender, then it was partially dried. It is
contemplated that the bark can be successfully shredded
by using a carding mill utilized for separating
asbestos fibers and wool fibers. It has been found
through experimentation that the fibrous material can
be made solely from waste newspaper or with a mixture
of newspaper and bark. However, the fibrous material
cannot be composed solely of bark fibers. At least a
small percentage of paper fiber is necessary in the
mixture.
Most of the coals being utilized contain, as
described previously, sulphur which, when burnt, will
produce sulphur dioxide which can, upon contact with
moisture, produce sulphuric acid or acid rain. In
order to neutralize the sulphur, it has been found
satisfactory to add crushed limestone in the slurry
before being molded. The limestone can be in a ratio
of up to 15% of the weight of the coal and fibers, but
is preferably between 3% and 5% by weight. This
apparently is sufficient to neutralize most of the
sulphur in the coal when it is being burned.
The log described above was found to ignite
quite readily and combustion was sustained. Other
experiments have been made, and- it has been found that
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a suitable size of log is of 4 inches in diameter and
15 inches in length with a central bore of 1 inch.
The polyethylene sealed envelope maintains
the log dry and prevents the log from being in contact
- with oxygen which might cause spontaneous combustion.
Other examples of the log have been made
using -8 mesh particle size in terms of the coal, and it
has been found that these logs burn quite readily.
The density of the logs has been found to be between
.5 to .9 indicating that the logs are quite porous
and, therefore, quite well adapted to sustain
combustion.
A further embodiment for making the log is
illustrated in Figure 1. The apparatus shown in Figure
1 is an extruder having a cone-shaped feeder 10 and a
worm screw ~2 on a shaft 14 for advancing the paste of
coal and fibers 16. An elongated tube 18 having perfora-
tions 20 and being closed at one end is aligned concen-
trically with the shaft 14 and extends axially of the
extruder. The tube 18 is connected to a suction pump,
not shown. The extruder also includes a die 22 and a
molding tube 24. A cutting saw 26 is provided at the
end thereof for cutting predetermined lengths of the
so-formed log 28.
As can be seen from the drawing, the paste of
coal and fibers is advanced by the screw 12 through the
die 22 and the molding tube 24 and is then cut off by
the saw 26 ~nto predetermined lengths. While the
material is advancing in the die 22 and the tube 24,
suction is applied so as to withdraw water from the
so-formed log 28. The log 28 is then advanced on a
conveyor for room temperature drying, and it can then
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be passed into a drying room to reduce the moisture
content of the log to below 10%~ The log is then
packaged and shipped. It has been found that a
preferred shape of the log is octagonal.
A further embodiment is illustrated in Figures
3 and 4. As shown in these drawings, a trough-shaped
feeder 110 is provided having a worm screw 112 passing
through the bottom thereof. The worm screw 112 is added
on a shaft 114 which is rotated by a motor 115 to pass
the slurry or paste through an extruder pipe 124a and
124b. The pipes 124a and 124b are connected by a coupling
125. The end of pipe 124b is slit longitudinally to
- allow a degree of expansion and the segments
of the pipe so-formed 124b include holes 127. A coil
spring 130 surrounds the end of the pipe 124b to provide
radial pressure on the slit end of the pipe.
The coupling 125 is provided to allow different
sizes of pipe 124b depending on the size of log to be
supplied. As the slurry is passed by the worm screw 112,
it advances through the extruder pipe 124a and 124b and
is finally discharged in order to be processed with the
log shown in Figures 1 and 2.
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