Note: Descriptions are shown in the official language in which they were submitted.
2~9~47
F I E I.D OF THE I NV EN T I ON
The invention relates to a so-called fireplace log of
the type macl~ of waste wood chips, and a hydrocarb~n wax
binder, and in particular to a fireplace log having a low
wax content in comparison to the wood content, and to a
method of producing such a low wax high wood content log.
BACKGROUND OF THE I NVENT I O~l
Fireplace logs manufactu-ed of waste wood products such
as wood chips, saw dust and the like, are very well known
and are in wide use. Customarily, these fireplace logs
consisting of waste wood chips and saw dust are bound
together by hydrocarbon wax, and so-called "pitch" which is
in fact an organic resin waste product. The waxes used are
typically heavy hydrocarbons, which are themselves waste
residues from the processing of petroleum products. Such
wax residues are substantially solid at normal temperatures,
and will melt at elevated temperatures. Pitch is a waste
product from the production of paper, and also acts as an
additional binder. Tn the manufacture of such well known
fireplace log products, the waste wood chips and saw dust
are mixed with the wax and pitch at an elevated temperature,
and are then extruded through a tubular die, and allowed to
cool. Typically, the logs will have a diameter of somewhere
between four and six inches. After cooling they are then
wrapped in a suitable paper wrapper
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usually printed with directions for use. Typically the
paper wrapper also contains a certain wax content. The
directions for use usually include directions to tear the
paper and light it with a match. The burning of the paper
wrapper will then ignite the log. Once ignited the log will
then burn for a considerable length of time providing a
steady flame, and a certain limited degree of heat. In this
way, persons wishing to use a fireplace may simply purchase
these logs, and use them one at a time or more if required
to provide at least the appearance of an open haarth fire.
Such fireplace logs are usually employed more for their
appearance, and the feeling of general hospitality, than the
actual generation of heat. However, they have the great
advantage that ~he logs are readily available, can be stored
safely indoors, and are available for use more or less
instantaneously. In this way, problems encountered using
conventional hardwood fuel in open fireplaces are
substantially avoided. Hardwood fuels are, in many cases,
difficult to start so that they require kindling wood,
newspaper, and a certain amount of care before a fire is
established. Once ~stablished the fire requires regular
attention and the addition of further wood in order to
maintain an attractive flaming appearance.,
The storage of such hardwood products indoors is generally
speaking undesirable. Hardwood products frequently contain
insects, or insect eggs, and once brought indoors, the
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insects are liable to escape and eventually infest the home.
For this reason, hardwood fuels are usually left
outside and only brought ~n on "as needed" basis. This
means that when starting a fire from typical hardwood, it
will usually be at the outdoor temperature, which may be
extremely cold and must, therefore, be subjected to high
heat in order to ignite it. The storing of wood products
out of doors also presents a problem. If they become wet,
or covered with snow, they cannot be used. Accordingly,
they must be stored under cover. This, therefore, creates
further problems.
Nonetheless, in spite of all of these problems, a great
many persons prefer a genuine hardwood fire, to a fire made
of fireplace logs using waste wood products. One of the
main reasons for this preference is the fact that typical
fireplace logs of the type described above contain a
relatively high proportion of wax and pitch. As much as 50
per cent of the weight of a typical fireplace log may be wax
and pitch. Consequently, when burning, the typical
fireplace log gives off a flame with a blueish tinge, and
may also give off an odour which is not characteristic of
the burning of hardwood by itself. For these reasons,
therefore, in spite of their great convenience, there is
some resistance amongst customers tb the actual use of
fireplace logs made of waste wood products.
Another factor leading to the disfavour of fireplace
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logs made of wood chips and wax is the fact that persons are
increasingly conscious of environmental problems created by
certain types of fuel, and in particular petroleum waxes.
The burning of petroleum products in general is regarded as
undesirable by many people and consequently persons
concerned with the environment are prejudiced against the
use of fireplace logs of the type described.
The industry has recognized this problem, and in recent
years has developed a proposed standard for fireplace logs,
under which logs with a certain minimum wax content may
carry a "green" label as being "environmentally friendly".
The industry has more or less arbitrarily concepted a
prospective standard of 65 per cent wood and 35 per cent wax
and pitch. A fireplace log made up with this content it is
hoped, would burn with less odour, and also the flame would
not carry the blueish tinge of the typical fireplace log, to
the same extent. Thus, it would be, to the customer, more
appealing as an environmentally friendly product and, at the
same time, less objectionable in that it would not display
the typical blueish flame and odour of the conventional
fireplace log.
However, attempts to make a conventional fireplace log
using wood chips, saw dust, wax and pitch" in the
proportions of 65 per cent to 35 per cent, have been
unsuccessful. The 35 per cent figure for wax and pitch
content simply will not bind the wood chips together and
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produce an acceptable log. The log will not solidify and
hold together when it is extruded and consequently does not
function as a log.
A careful study of the problem of the actual content of
fireplace logs in the process of manufacture has revealed
that the reason for this appears to be that the wood chips
and saw dust, during mixing with the heated wax and pitch,
actually absorb a considerable quantity of wax and perhaps
pitch into the cells of the wood. The wood chips and
sawdust are cellular products and are relatively spongy, and
the wax being hot and liquid easily penetrates the cells and
fills them. Consequently, until enough wax has been added
to the waste wood product to fill the cells in the wood
chips, and then excess wax is added, there will not be
sufficient wax to act as a binder to hold the wood chips
together.
Clearly, one solution would be simply to use
alternative forms o~ adhesive binders to hold the wood chips
together. However, this would not be acceptable, because
most adhesives would be more harmful to the environment than
hydrocarbon waxes, when burnt at the relatively low
temperatures in the typical open hearth domestic fireplace.
Consequently, binders having a greater binding power or
adhesion, cannot be used. It is, therefore, clearly
desirable to provide a fireplace log having a higher wood
content and a lower wax binder content, so as to overcome
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the various problems noted above.
BR I EF SUMMARY OF THE I NV EN T I ON
With a view to providing a solution to the foregoing
problems, the invention comprises a low wax high wood
content fireplace log, in turn, comprising a first quantity
of waste wood products, said first quantity of waste wood
products being densified, in volume in proportions of,
between about 1:5 and 1:10, in volume as compared with the
volume of said wood products prior to densification and in
which the densified wood products are characterized by an
absence of open cell voids, a quantity of heavy hydrocarbon
wax binder compounds, which contact the exterior of the
densified wood products without substantially penetrating
them, and in which the quantity of densified wood products
and the quantity of wax products are in a proportion of
between about 60:40 and 80:20 by weight.
The invention further comprises such a low wax high
wood content fireplace log and wherein the densified wood
products comprise at least 50 per cent of wood products
having a maximum dimension of between 0.25 and 0.125 of an
inch, and a second quantity of approximately 25 per cent of
wood products having a dimension between 0.125 and 0.01 of
an inch, and the remainder having a dimens~on less than .01
of an inch.
The invention further comprises such a low wax high
wood content fireplace log, wherein said wax product are
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characterized by an absence of penetration into said wood
products, and extend between said wood products, as a
binder, but without penetration of said wood products.
The invention also further comprises a process for the
manufacture of a low wax high wood content fireplace log and
comprising the steps of forming a mixture of wood products
comprising wood chips having an average dimension of between
0.25 and 0.125 of an inch, and wood chips of 0.125 to 0.01
of an inch, and wood dust of 0.01 of an inch or less,
compressing said mixture whereby to densify wood products by
a factor of between 5:1 and 10:1, breaking up said densified
wood products into a loose mixture of densified wood
products, adding a quantity of heavy hydrocarbon wax
material at an elevated temperature in a liquid phase to
said densified loose wood product mixture, and extruding
said mixture of densified wood products and wax through an
extrusion die, and allowing said wax to cool and harden,
thereby forming elongated homogenous masses of densified
wood products and wax.
The invention further comprises such a process wherein
said wood products are compressed so as to substantially
eliminate the cellular structure and voids in said wood
products, whereby to prevent the penetrat~on of said wax
into said wood products.
The invention further comprises such a process wherein
said wood products are in a proportion of between 65 per
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cent and 80 per cent by weight, and wherein said wax
products are within a proportion of between about 35 per
cent and 20 per cent by weight.
The invention further comprises such a process wherein
said wax products include heavy hydrocarbon wax material and
pitch.
The various features of novelty which characterize the
invention are pointed out with more particularity in the
claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating
advantages and specific objects attained by its use,
reference should be had to the accompanying drawings and
descriptive matter in which there are illustrated and
described preferred embodiments of the intention.
I N THE DRANINGS
Figure 1 is a perspective illustration of a typical
fireplace log, shown with the paper wr`apping partially
opened up;
Figure 2 is a greatly enlarged schematic sectional
section of a typical prior art fireplace log, and labelled
'Prior Art".
Figure 3 is a greatly enlarged schematic sectional
illustration of a low wax fireplace log in accordance with
the invention;
Figure 4 is a schematic illustration illustrating the
steps in the process of forming a low wax fireplace log,
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Figure 5 is a schematic illustration showing an
apparatus suitable for compressing and densifying the wood
products prior to manufacture into a low wax fireplace log
in accordance with the invention, and,
Figure 6 is a schematic illustration showing an
apparatus suitable for mixing the separated densified wood
products and wax, and extruding the same.
DESCRIPTION OF A SPECIFIC EMBODIMENT
Referring now to Figure 1, a fireplace log is there
illustrated comprising a manufactured homogenous log-like
block 10, and a paper wrapper 12. The block 10 consists of
a mixture of waste wood chips and waste wood products such
as saw dust, and heavy hydrocarbon waxes and usually some
so-called "pitch" an organic resin waste product. The paper
wrapper 12 is fabricated so as to incorporate a certain
amount of wax, in most cases, so as to form a flammable fire
starter, by ~.Pans of wh.ich the log 10 itself may be ignited.
In this manner, the use of such logs is highly
convenient, and a fire of one or more such logs requires
substantially no attention once the paper is ignited. The
logs usually burn continuously, giving off a flame, so as to
provide the hospitable appearance of an open hearth wood
fire. However such logs burn with a bluei$h flame and have
a characteristic odour.
As best shown in Figure 2, such logs 10 as known and
used heretofore, have comprised a plurality of wood chips of
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various si~es, and some saw dust, essentially being waste
wood products from various types of woodworking machinery
and from wood processing factories. Such waste wood
products are bound together with a mixture of heavy
hydrocarbon waxes (waste products from petroleum oil
distillation) and organic resin, a waste products from paper
mills. One variety of such organic resins is commercially
available under the name "Pamak", (trade mark) from Hercules
Incorporated of Wilmington, Del.
In Figure 2, the wood chips and other waste materials
are indicated generally as 14, and the wax and "organic
resin wastes" mixture is indicated by dots 16. The wax and
"organic resin wastes" mixture in Figure 2 is shown as
penetrating and permeating through the cells of the wood
chips 14, and also filling the spaces between them so as to
provide a binder to bind the loose wood chips and saw dust
into an homogeneous log. It will thu4 be apparent that
there is a considerable proportion of the entire log which
consists of wax and "organic resin wastes". Not all of the
wax and "organic resin wastes" is acting as a binder. The
proportion of the wax and "organic resin wastes" which has
penetrated and permeated into the fibres and cells of the
wood itself is not acting as a binder, and is essentially
unnecessary. However, wood chips and other wood waste
products are of such a nature that the cells are open and
spongey and are easily penetrated by the hot liquid wax
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during the conventional manufacturing process used to
manufacture such logs. Consequently, such wax once it has
penetrated the wood cells and filled them, is not available
to act as a binder to hold the wood chips and waste products
together. In this respect, such wax and "organic resin
wastes" which has penetrated the cells of the wood products
is essentially unnecessary to the formation of the log, and
is in fact undesirable. Further quantities of wax and
"organic resin wastes" must then be added to fill the spaces
between the wood chips, and bind them into an homogenous
log-like mass.
In accordance with the invention, there is provided a
modified form of fireplace log in which the wood chips and
wood waste products such as saw dust are first compressed
and densified so as to substantially close up and eliminate
the cells in the wood after which wax, and some "organic
resin wastes", are added as a binder. It will thus be seen
that as shown in figure 3, the wood chips indicated
generally as 20 are shown to be essentially flattaned, and
the saw dust and other finer waste products are essential~ly
squeezed flat into flakes similar to the flattened wood
chips 20. In this condition, the cells are substantially
closed up, and are incapable of taking up any significant
guantity of wax. -
In this log, made in accordance with the invention, the
wax and 'lorganic resin wastes" is indicated generally as 22
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and it will be seen that it extends simply between the wood
chips and waste products, but does not penetrate or permeate
into them to any significant extent.
Conseguently, the log of flgure 3 has a much higher
quantity of wood and a lower quantity of wax and "organic
resin wastes" than the fireplace log of figure 2. In fact,
given suitable densification techniques, it is possible to
compress the waste wood chips and saw dust to an extent of
between 5:1
and 10:1 by volume. When mixed with hot wax and "organic
resin wastes", such densified wood and waste products will
thus produce a log which has a much higher wood content and
a lower wax and "organic-resin wastes" content, and thus
will be more desirable to the consumer, and will also
substantially meet the industry standards for a "green"
fireplace log product.
In accordance with the invention it is thus possible to
achieve a ~ireplace log as shown in figure 3 having a wood
content of at least 65 per cent, with a wax and "organic
resin wastes" content of 35 per cent, and in many cases,
depending upon the type of waste material and the source of
the wood products, it is possible to achieve a better wood
to wax ratio than this.
It will of course be appreciated that the wood to wax
ratio will vary from time to time depending upon the wood
waste material which is supplied to the processing plant
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turning it into fireplace logs. Wood waste products which
contain a hi~h proportion of saw dust and a lower proportion
of chips may require a somewhat higher content o~ wax, and
conversely wood products which contain a higher quantity of
wood chips, preferably hardwoocl chips, and a lower quantity
of saw dust, may require a lower proportion of wax and
"organic resin wastes".
The process in accordance with the invention will
proceed essentially as illustrated in figure 4 with
apparatus as shown schematically in figures and 5 and 6.
As illustrated in the schematic process diagram of
figure 4, tha wood waste products are first of all processed
by continuous compression in a densifier 30(Fig 5).
Typically a densifier 30 will have a cylinder 32,
piston 34, extrusion die 36, and hopper 38. Piston 34 is
driven by motor 40.
These densified wood products will usually be produced
in an essentially solid form in the form of a continuous
solid billet 42 of densified wood. This is because the
densification process usually is carried out by forcing the
wood products through extrusion die 36. The resulting end
product is a continuous generally substantially cylindrical
billet of densified wood, in which the wood products are
compressed and densified by proportions of between about 5:1
and 10:1.
This billet of densified wood is then passed to the
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second stage of the process in which it is broken down in a
separator 44 into loose particles of densified wood. This
may be done by passing it through a mill, such as a
conventional hammer mill(not shown). However, such a hammer
mill may result in the breaking up of wood chlps into finer
wood particles such as saw dust and other fine wood
fragments. This is generally speaking undesirable from the
view point of the invention. Fine dust like wood products
will tend to take up a greater quantity of wax than will
wood chips having dimensions in the region of between and
about 0.25 and 0.125 of an inch.
In addition, such fine wood products will tend to break
apart during combustion, and may rise up the chimney as wood
particles rather than burning, and passing up as products of
combustion. This is undesirable since it results in
excessive emissions of particulate matter into the
atmosphere. Accordingly, whatever techniques are used to
separate and break up the solidified billets of densified
wood should be preferably such as to minimize the creation -
of additional wood dust products.
One technique which is particularly suitable is passing
such densified wood billets through a system of rollers,
which simply shred and break up the wood billets, but do not
grind them up in the same way as a milling davice.
Accordingly, the separator 44 step as illustrated in
figure 4 is preferably although not exclusively a roller
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crushing device (not shown) of a type well known in the
art.
From the separator 44, the broken up loose densified
wood particles are then passed to a mixer and extruder 46.
In the mixer the densified wood products from hopper 48 are
mixed by an auger 50 with a mixture of hot heavy hydrocarbon
waxes, preferably mixed with a proportion of "organic resin
wastes", supplied by suitable heated supply means indicated
as 52, having any suitable heating means 54.
From the mixing device 46, the mixed wood products
together with wax, and "organic resin wastes", if included,
: are forced through an extrusion die 56 of a type well knownin the art, thereby producing a continuously extruded log-
shaped formation, typically having a dimension of between
about 4 and 6 inches in across, and having in same cases a
cylindrical shape, and in others an irregular rectangular
shape. The waxes in the extruded product rapidly cool and
harden, binding the product in an homogeneous product.
The log formations are then cut up into suitable
lengths, and wrapped in paper, and packaged ready for sale.
In this way it is possible to produce fireplace logs
having a much higher wood content and lower wax content than
previously known fireplace logs. The resulting low wax high
wood content logs will burn cleaner with a lesser degree of
blue flame ancl a lesser degree of undesirable odour than
prior art logs and a higher wax content. In addition they
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will be more environmentally friendly, and will thus have a
greater degree of consumer acceptance, than was the case
with conventional prior art fireplace logs having a higher
wax content since the heavy hydrocarbon wax, as a raw
material, is somewhat more costly than waste wood products,
the improved low-wax densified wood fireplace logs will have
a slightly lower raw material cost, than prior art high wax
content logs, which is an addecl benefit.
Typical product data for the heavy hydrocarbon waxes is
1-0 as follows:
Density Boiling
~at 15 c 0.81-0.85 kg/L Range(at 1 atm): 3160C
(wide
range)
Vapour Pressure N/A
Percent Volatile
(at 25 c ) (at 20 c) o%
Vapour Densisty N/A Evaporation ~ate: NjA
(at 20 c~
Solubility in Water Negligible Drop Melting Point: 46-86c
Viscosity: 2,8,4,7,4.2,20.3,7.8 Appearance & Odour:
Color less
- to yellow
solid with
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hydrocarbon
odour.
(Kinematic) 20,7 c5t (0)100 c
(typical respectively)
Their chemical formations are complex, and variable,
but but will typically include various hydrocarbons in the
range of C 20 and up.
Typical product data for t:he oranic resin wastes is as
follows:
They are typically obtained by the distillation of
crude tall oil.
Viscosity, os
120 8~ ......... ,........................... 425-470
210 F ....................................... 20-30
Ash, % ..................................... 0.3-0.8
Water % ................................... 0.02-0.03
Density,lbs/gal................... 8.4-8.8
API gravity, 60 ................. 9.5-10.6
Specific ~ravity, 26............. 1.01-1.06
Pour Point, ...................... 105-115
BTU/lb ........................ 17,000-18,000
Bulfur, % ........................ 0.15-0.25
Flashpoint, ...................... 470-520
Saponification number ............ 80-120
Aold number
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CWTP and TP ....................... 30-50
NTF ............................... 15-25
Iodine number ..................... 90-120
The foregoing is a description of a preferred
embodiment of the invention which is given here by way of
example only. The invention is not to be taken as limited
to any of the specific features as described, but
comprehends all such variations therefore as come within the
scope of the appended claims.
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