Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR TREATING LIGNOCELLULOSIC MATERIAL, AND
APPARATUS FOR CARRYING OUT THE SAME
Field of the invention:
The present invention relates to a process for treating lignocellulosic
material, such as wood and the like, and also relates to an apparatus for
carrying
out the process. More particularly, the present invention relates to a process
for
improving the quality of wood to be treated by roasting the wood with a multi-
step
process, including treatment at a high temperature gradient.
Background of the invention:
Torrefaction is an artisanal technique that has been used for centuries to
enhance the esthetic and physical features of wood. Since torrefaction
compares
favourably with chemical treatment of wood, there is ever increasing interest
in the
many industrial applications for this process.
Torrefaction involves heating wood at relatively high temperatures to
improve the properties of the wood without the addition of chemicals or toxic
substances.
This natural process increases the durability and stability of wood, while
enhancing the esthetic value of individual wood species. Torrefaction is a
type of
heat treatment that increases the density of the wood, improves its
dimensional
stability and gives it rich, balanced overtones similar to the look of exotic
wood
species.
There exist also several technologies for the curing, roasting and/or
stabilizing of wood, and some of these inventions date back several years as
well.
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-
Indeed, known in the art are the followin US g patents and patent
applications: 4,233,752; 4,345,384; 4,787,917; 5,123,177; 5,555,642;
5,678,324;
5,901,463; 5,926,968; 5,992,043; and 6,374,513.
Also known in the art are the following CA patents and patent applications:
356,430; 684,915; 1,091,871; 1,109,251; 1,133,205; and 1,159,643.
However, many problems still continue to persist despite recent advances in
the technology, deterring wood manufacturers from using such inventions for
the
fabrication of floors, furniture, decks, etc.
Such problems include staining, where the resin/acid drawn out of the wood
during the roasting process remains on the surface of the wood until cool
down,
causing stains on the wood. In other instances, uniformity has been identified
as a
substantial problem, where the wood becomes darker on the ends and lighter in
the middle of the planks, leaving wood manufacturers to stockpile a variety of
unwanted colors. Beyond the problem of uniformity of color, there seems to be
a
problem with roasting devices being unable to offer customers a customization
option for roasting color. In other instances, roasting of wood is found to be
very
time consuming and thus, very costly. In other instances, fire hazards appear
to be
at the heart of the matter, forcing operators to introduce inert gases or
operate
entirely with a negative pressure. Finally, key to the problems faced by
current
wood roasting devices and/or methods: the lack of automation in the roasting
process, forcing operators to make intuitive decisions regarding the outcome
within the roasting apparatus, further affecting the lack of uniformity of the
wood.
Hence, in light of the above-discussed, there is a need for an improved
process and/or apparatus which would be able to overcome some of the
aforementioned prior art problems.
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Summary of the invention:
The object of the present invention is to provide a process for treating
lignocellulosic material which, by virtue of its features and steps, satisfies
some of
the above-mentioned needs, and which is thus an improvement over other related
processes known in the prior art.
In accordance with the present invention, the above object is achieved by a
process for treating lignocellulosic material, the process comprising the
steps of:
a) providing lignocellulosic material;
b) evaluating parameters of the lignocellulosic material;
c) preparing the lignocellulosic material;
d) heating the lignocellulosic material in a treatment chamber following a
given profile based on parameters of the lignocellulosic material;
e) stabilizing the lignocellulosic material; and
f) cooling down the lignocellulosic material.
According to another aspect of the present invention, and as will be easily
understood, there is also provided an apparatus such as the one briefly
described
herein and such as the one exemplified in the accompanied drawings.
According to yet another aspect of the present invention, there is also
provided a treatment plant provided with the above-mentioned apparatus.
~ According to yet another aspect of the present invention, there is also
provided a method of operating the above-mentioned apparatus, and a
corresponding operating software.
According to yet another aspect of the present invention, there is also
provided a material having been treated with the above-mentioned process,
apparatus and/or method.
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The objects, advantages and other features of the present invention will
become more apparent upon reading of the following non-restrictive description
of
preferred embodiments thereof, given for the purpose of exemplification, only
with
reference to the accompanying drawings.
Brief description of the drawings:
Figure 1 is a front view of an apparatus according to a preferred
embodiment of the present invention, the apparatus being shown provided with a
door where material to be treated is entered.
Figure 2 is a top view of what is shown in Figure 1.
Figure 3 is a side view of a water basin of the apparatus according to a
preferred embodiment of the present invention.
Figure 4 is a side view of a combustion chamber of the apparatus according
to a preferred embodiment of the present invention.
Figure 5 is a rear view of what is shown in Figure 1, the opposite end from
the door being shown.
Figure 6 is a graph illustrating the preferred four phases of roasting wood
with a process and/or apparatus according to the present invention.
Figure 7 is a preferred graph illustrating the area of coloration, obtained
during "phase 3" of the roasting process according to the present invention.
Figure 8 is a preferred graph illustrating the area of coloration during the
roasting process according to the present invention, where preferably, every
four
seconds, the software calculates the anticipated area by calculating the
acquired
area.
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.
Figure 9 is a preferred graph illustrating the positive and negative pressure
during the roasting process according to the present invention.
5 Detailed description of preferred embodiments of the invention:
In the following description, the same numerical references refer to similar
elements. The embodiments shown in the figures, and the physical dimensions
exemplified herein, are preferred.
Moreover, although the present invention was primarily designed for use
with lignocellulosic material, such wood for example, it may be used with
other
types of objects and in other fields, as apparent to a person skilled in the
art. For
this reason, expressions such as " lignocellulosic", "wood", etc. used herein
should
not be taken as to limit the scope of the present invention and includes all
other
kinds of items with which the present invention could be used and may be
useful.
Moreover, in the context of the present invention, the expressions
"machine", "apparatus", "device", and any other equivalent expression known in
the art will be used interchangeably. Furthermore, the same applies for any
other
mutually equivalent expressions, such as "lignocellulosic material" and
"wood",
"treating", "processing", "torrefying", "coloring" and "roasting", as well as
"method",
"process" and "operation" for example, as also apparent to a person skilled in
the
art.
In addition, although the preferred embodiment of the present invention as
illustrated in the accompanying drawings comprises various components and
although the preferred embodiment of the apparatus as shown consists of
certain
geometrical configurations as explained and illustrated herein, not all of
these
components and geometries are essential to the invention and thus should not
be
taken in their restrictive sense, i.e. should not be taken as to limit the
scope of the
present invention. It is to be understood, as also apparent to a person
skilled in the
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art, that other suitable components and cooperations thereinbetween, as well
as
other suitable geometrical configurations may be used for the apparatus and
corresponding parts according to the present invention, as briefly explained
and
inferred herein, without departing from the scope of the invention.
Broadly described, the apparatus according to the present invention, as
shown in the accompanying drawings, is used for carrying out a process for
stabilizing wood such that it remains stable over time. Also disclosed is a
method
for coloring wood by heat treatment of lignocellulosic material where the
material is
pre-heated at an elevated temperature. Preferably, this includes clamping down
wood to be treated in a chamber prior to a 4-step roasting process at a pre-
determined temperature in an electric chamber to extract the water and
acidity/resin by destroying part of the hemicellulose of the wood. Preferably
also,
the method comprises the calculation of a theoretical "area of coloration" of
the
wood. Uniformity of color is preferably achieved by providing wood with a
transverse air-flow as well as a positive pressure upon heating and a negative
pressure upon cooling.
The present invention also relates to a method of improving the quality of
wood, by roasting wood with a high temperature treatment. Different degrees of
roasting provide a selection of colors. The present invention also relates to
the
ventilation, evacuation and pressure systems, insuring a stain-free product, a
short
duration of process, as well as a fire safe process.
According to the preferred embodiment of the present invention, the
process for roasting wood preferably includes the following steps: a)
evaluation of
wood; b) preparation of wood; c) preparation of stabilization software
program; d)
phase 1: heating (part 1); e) phase 2: heating (part 2); f) phase 3:
stabilization of
wood; and g) phase 4: cool down.
Prior to roasting lignocellulose materials, a few steps are required.
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First, said material, in this case "wood", is preferably identified by type,
thickness, length and humidity level. Humidity level is evaluated. For optimal
operation of apparatus, a maximum of about 10% of humidity in the wood ensures
uniformity of coloration.
Then, said wood is prepared, where load of wood is preferably stacked with
hollow tubing spacers. This ensures that wood in the middle of the pile can
benefit
from air circulation and heat equal to wood at the top of the stack, as can be
easily
understood by a person skilled in the art.
Referring now to Figure 1, there is shown a front view of the apparatus
according to a preferred embodiment of the invention. It preferably comprises
rounded external walls 1, and a sealable door 2, where the load is entered. A
ceiling 3, internal walls 7 and a floor 8 ensure the possible preferred volume
of
about 8.2 meters that can be roasted at once. Legs 6 and 6' keep the apparatus
off the floor by about 0.35 meters. Preferably, when loading the apparatus
with
said wood, thermocouples are entered into ends of the wood, dispersed
throughout the load to measure average temperature. The software uses these
sensors to make further decisions about the desired roasting. A pressure is
automatically applied throughout the load with preferably 50-75kg
approximately
throughout the process. This compressing jack 4 minimizes warping and bending
in the process. When the load has been properly entered in the apparatus, the
door is sealed.
Once the load is properly placed in the treatment chamber, the roasting
program is set up. The variables for the said wood load are entered in the
program
interface, for example: type of wood, thickness, length, humidity level and
desired
color. Unlike other similar inventions, this apparatus provides the choice of
a
specific level of wood roasting, from lighter color to darker color.
The program is launched, using the required data. The program is
automated based on the input data and continuous temperature monitoring by the
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thermocouples in the wood and by measuring the temperature of the ambient air
inside said treatment chamber.
Referring now to Figure 2, there is shown a top view of the apparatus. The
wood load is placed in treatment chamber 28. Surrounding the treatment chamber
is preferably a variety of components that enable proper roasting of the said
wood.
Preferably, a heater 23 made up of three (3) elements enables heating. It
should
be noted that three (3) elements offer over-capacity, in the case of
breakdown,
thus ensuring no loss in productivity. A fan 22 is positioned next to the
heating
elements. This fan ensures a transverse airflow throughout the load.
Deflectors 21
and 21' are located at angle on both sides of the load. These deflectors are
preferably perforated with holes that are proportional to their distance from
the
heater and fan, insuring equal airflow everywhere in the treatment chamber. A
louver 25, gas pipe 24 and water basin 26 ensure the required air pressure, as
can
be easily understood by a person skilled in the art. These will be discussed
in
further detail hereinbelow. Finally, water sprinklers 27 and 27' enable to re-
inject
water into the treatment chamber during cool down to accelerate the process.
During the roasting process, the resins in coniferous wood and acids in
deciduous wood are drawn to the surface. Because of transverse circulation
through the apparatus (processing/wood stack) area, these by-products are
channeled to the outside walls of the chamber instead of being left to deposit
on
the wood. This transverse circulation through the apparatus is central to the
process as it ensures that the resins and acids do not stain the wood, leaving
an
even color throughout the product.
Referring now to Figure 3, there is shown a side view of the water basin 26.
A gas pipe 36 joins the treatment chamber to the water basin. Although low
near
the ground the gas pipes, it preferably opens near the top of the treatment
chamber. The reason the gas pipe opens near the top of the treatment chamber
is
to eliminate the chance that the water from the water basin will flow back
into the
treatment chamber when cooling occurs and the apparatus moves into a state of
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negative pressure. The water basin is filled with a certain volume of water 30
meant to maintain preferably a 0.5kg (approx.) of pressure inside the
treatment
chamber during heating and roasting.
During heating and roasting, gases evaporate from the wood. These gases
are being circulated inside the treatment chamber by the fan. Some of the
gases
end up clinging to the walls of the apparatus, falling to the floor. Others
are
evacuated by the gas pipe when the pressure inside the treatment chamber
becomes greater than 0.5kg.
Through the pipe, the gases are led to the water basin, where dust and
particles are left in the water itself. Res-.dual gases continue onward to a
vertical
evacuation pipe 29.
Referring now to Figure 4, there is shown the combustion chamber. Gases
enter the chamber from the evacuation pipe 29. The gases are preferably burnt
by
a suitable gas, such as propane 32, reducing gas emissions before being
released
out into the atmosphere by suitable evacuating means, such as chimney 31, for
example.
Referring now to Figure 5, there is shown the back view of the apparatus. A
louver 25 is located half way up from the floor. Sprinklers 27 and 27' are
located
on both sides. When the said material is finished roasting, cool down begins.
As
the said wood contairis practically no more moisture and the temperature is
decliriing within the treatment chamber, a negative pressure automatically
forms
inside the treatment chamber. This negative pressure is confirmed by the water
level in the water basin, which lowers, as the gas pipe 36 begins to fill
towards the
treatment chamber. Louver 25, which weighs approximately 0.25 to 0.5kg, is
installed inside the treatment chamber. As such, when the negative pressure
within the treatment chamber becomes greater than 0.5kg, the louver opens for
a
moment, allowing the treatment chamber to calibrate back. This calibration to
a
light negative pressure ensures that the apparatus does not collapse inward or
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that the water from the basin spills dust and particle filled water back into
the
chamber, as can be easily understood by a person skilled in the art. Further,
it
keeps the wood apparatus from getting too much oxygen, thus, causing a risk of
ignition within the treatment chamber. Water sprinklers 27 and 27' accelerate
the
5 cool down period of the wood. In addition, it provides the wood with some
humidity, ranging from about 0.5% to about 3.0%. This re-humidification is
made
possible as the inside of each piece of wood is itself in negative pressure
compared to the ambient pressure inside the treatment chamber, a state which
naturally takes place as a result of the high temperature treatment of the
wood.
10 This immediate re-humidification further stabilizes the wood, which is
clamped
down into the chamber by compression jack 4.
Referring now to Figure 6, there is shown a preferred graph of the four (4)
phases of roasting. The X-axis, split in four (4) phases, measures time, while
the
Y-axis measures the temperature in degrees Celsius. This graph shows the
treatment chamber temperature line 50, the wood temperature line 51, the
critical
temperature line 52 and the area of coloration 53. During Phase 1, the wood is
preferably heated from its original temperature to approximately 120 C. During
this
phase, the software calculates the necessary differential in temperature
between
the chamber and the wood. This differential is based on an algorithm taking
account of wood's humidity, type and thickness, the required minimum
difference
being approximately 75 C. This differential prevents cracking of the wood.
Phase 2
begins when the wood has reached the intermediate temperature of approximately
120 C. At this point, the program calculates a reduction in differential
between
wood temperature and treatment chamber, as the wood is now safe from cracking.
Phase 2 has the purpose of further reducing the humidity within the wood,
bringing
wood moisture down to about 0-2%. This takes place within the preferred range
of
about 120 C and 180 C. Roasting occurs in Phase 3 and cooling in Phase 4.
These are further explained in reference to the next figures.
Referring now to Figure 7, there is shown a close up view of Figure 6,
showing the intersection of the wood temperature line 51 with the critical
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temperature line' 52, together forming the area of coloration 53. As such, the
third
phase begins when the wood has reached the required critical temperature.
During this stage the wood begins to roast, hemicellulose being broken down
and
polymerized. Once the wood temperature line 51 crosses over the critical
temperature line 52, the program begins calculating the "area of coloration"
53
every four (4) seconds, preferably.
Referring now to Figure 8, there is shown another view of Figure 7, adding
the element of time. Again, looking at the area of coloration, this time it is
split up
between the time line 56, dividing the "acquired area" 54 and the "anticipated
area" 55. As such, we find that the "area of coloration" 53 is the sum of the
"area
already acquired" + the "anticipated area". The program calculates what total
"area
of coloration" will give the desired color based on the algorithm taking into
account
wood type, wood thickness, temperature of the wood temperature line 51 and
treatment chamber temperature line 50. The software makes a different
calculation
when the temperature of the treatment chamber intersects with the wood
temperature line. This intersection 57 provides a ceiling to the temperature
of the
wood and allows further calculation of the "area of coloration" ensuring that
the
wood does not exceed approximately 225 C while meeting the desired color.
The critical temperature varies based on the type of wood. In addition, it
should be noted that the area called "area of coloration" varies based on the
aforementioned variables, notably: desired color, type of wood and thickness.
As
such, the software running the said apparatus creates a heating profile for
the
wood such that the "area of coloration" provides the desired wood color of
final
product. The greater the "area of coloration", the darker the coloration.
When the wood crosses the critical temperature line 52, cool down officially
begins. The heating elements are stopped. Air is allowed to circulate without
added heat. External radiators are engaged to speed up the cooling process of
the
wood. To speed up the cooling process, water is sprayed inside the chamber. As
the wood lowers substantially in temperature, water vapors begin to be
absorbed
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by the wood. By the time Phase 4 of cooling is finished, wood has typically
reabsorbed about 1 to 5% of moisture.
It should be noted that at this stage of the process, it is possible to inject
stain, paint, perfume, plastic, protective liquid to coat the wood/or be
absorbed by
the wood during the cool down phase.
Referring now to Figure 9, there is shown a graph showing the X-axis,
representing time. The Y-axis represents the temperature in Celsius while the
Z-
axis represents the pressure scale, divided by a dotted line 58, for zero
being
equal to the ambient atmosphere. This graph shows the relationship between the
roasting process and the positive and negative pressure within the treatment
chamber. More specifically, the wood temperature line 51 against the pressure
line
59. As the temperature inside the treatment chamber rises, so does the
pressure
line. The said pressure line stabilizes at approximately 0.5kg, due to the
water
basin system that is linked to the treatment chamber by a gas pipe. During
cool
down, the pressure line crosses the zero mark, descending into negative
pressure
and stabilizing at negative 0.5kg, due to the louver on the back wall of the
treatment chamber. Such a pressure system enables the apparatus to provide
wood that is free from stains, informally roasted and safe from re-igniting.
Hence, it may now be better appreciated that according to the present
invention, there is provided a method of roasting material such as wood by
heating
at high temperatures'which preferably comprises the following steps: a)
creating a
roasting profile for the wood using an algorithm that calculates temperature
curves
required to obtain the final color desired, these calculations being
preferably based
on wood type, thickness, length and average humidity level; b) subjecting the
material such as wood to be roasted in an electric apparatus at very high
temperature, based on the roasting profile, subjecting the wood to reach the
"area
of coloration"; c) interrupting the roasting treatment as soon as the
program's
calculated "anticipated area" gives the customer the desired color; and d)
cooling
and re-humidifying of wood.
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Preferably, the atmospheric pressure during heating and roasting is
maintained at about a positive 0.5kg, thus enabling the pressure to evacuate
through a water basin.
Preferably also, the atmospheric pressure during the cooling phase is
controlled and maintained at approximately 0.25 to 0.5 kg of negative
pressure.
Preferably also, the extracts drawn from the wood during the heating
phases is removed from the surface of the wood by transverse airflow.
Preferably also, water is injected into the treatment chamber to aid in
cooling and re-humidifying the wood.
Preferably also, the water basin is linked to the said treatment chamber by a
gas pipe located at the upper part of the treatment chamber.
Preferably also, a specific volume of water in the water basin regulates the
0.5kg of positive pressure.
Preferably also, the water basin acts as a dust and particle collector during
the period where the apparatus operates with a positive pressure.
Preferably also, gases that exit through the water basin is combusted,
before being released into the atmosphere.
Preferably also, during the cooling phase, a negative pressure is maintained
at approximately 0.25 to 0.5kg by an inward louver.
Preferably also, inward louver is approximately 2 to 10cm in diameter and
about 0.25 to 1.0kg in weight.
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----
--- Preferably also, transverse airflow circulates through the wood, enabling
angled deflectors and scaled perforations to achieve a balanced airflow
circulation
throughout the pile of wood.
Preferably also, the balanced airflow due to perforated deflectors enable
extracts drawn from the wood to collect on the walls and floor of the
apparatus,
rather than on the wood.
Preferably also, the wood is roasted without any resin or acid stains.
Preferably also, the area of coloration is determined by the operating
software based on desired color.
Preferably also, the software automates the process based on the variables
inputted and by measuring the temperature of the wood and air within the
treatment chamber.
Preferably also, the software calculates the temperature curve necessary to
roast at the desired color, using the shortest and most time efficient path,
without
risking cracking or burning said material.
Preferably also, the material is selected from the group consisting of aspen
wood ("tremble" in French); maple wood ("erable" in French); birch wood
("bouleau" in French);*and cherry wood ("merisier" in French). Preferably
also, the
material is any other soft or hard wood.
The process for stabilizing wood according to the present invention is
particularly advantageous in that it enables the wood treated to remain stable
over
time.
As aforementioned, the process preferably includes the following steps: a)
evaluation of wood; b) preparation of wood; c) preparation of stabilization
software
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program; d) phase 1: heating (part 1); e) phase 2: heating (part 2); f) phase
3:
stabilization of wood; g) phase 4: cool down; and h) phase 5: cool down and re-
humidification.
5 According to the preferred embodiment of the present invention in regards
to the evaluation of wood: the wood is identified by type, thickness, length
and
humidity level. Humidity level is evaluated as follows: wood chip samples are
weighed. Then, the chips are microwave treated in two-minute increments and
weighed again after each microwave session until the wood chip provides three
(3)
10 equal readings in a row. This indicates that there is no more moisture in
the wood.
From that, the moisture level is calculated using the original weight of the
chips of
wood and the weights after microwave treatments. Wood should contain no more
than about 10% humidity, using the present machine, to ensure good quality
wood
that remains stable over time.
According to the preferred embodiment of the present invention in regards
to the preparation of wood: load of wood is prepared for the machine with
hollow
spacers of approximately '/z' square cross section. The load in put in
machine.
Three (3) thermocouples are entered 5" deep into ends of the wood, one near
the
top of the load, one near the middle and one near the bottom. With the help of
a
compressing jack, a preferred 11000-Ibs load is applied to the top of the wood
pile.
This load is measured by a gage. This compressing jack minimizes warping and
bending in the process. The door is sealed.
According to the preferred embodiment of the present invention in regards
to the preparation of the roasting program: the variables for the wood load
are
entered in the program interface: type of wood, thickness, length, humidity
level
and desired color (desired color level, is directly proportional to
dimensional
stability of the end product). These factors are entered in the program
interface
before the machine is set into motion. Unlike other wood roasting apparatus,
this
one enables customers to specify a requirement for a specific level of wood
stability, from lighter color to darker color. The program is launched, using
the
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-- -- --------- - ------
.---
required data. The program is automated based on the input data and continuous
temperature monitoring by the three thermocouples in the wood and one that
measures ambient air temperature inside the machine.
According to the preferred embodiment of the present invention in regards
to Phase 1: heating (part 1): during heating up, temperature slowly raised in
the
machine maintaining an approximate 75 C difference between the treatment
chamber temperature and the wood temperature. This process begins the
dehumidification of the wood in a way that ensures it will not be ruined by
cracking.
According to the preferred embodiment of the present invention in regards
to Phase 2: heating (part 2): when the wood has reached the approximate
intermediate temperature of about 180 C, the program reduces the gap between
the chamber and the wood temperature, bringing the wood to the critical
temperature.
According to the preferred embodiment of the present invention in regards
to the Phase 3 (roasting): the third phase begins when the wood has reached
the
required critical temperature. During this stage, the wood begins to roast,
hemicellulose being broken down and polymerized. Once the wood temperature
curve crosses over the temperature line the program begins calculating the
"area
of coloration" every four (4) seconds. The "area of coloration" is the sum of
the
"area of coloration" already acquired + the "anticipated area". The program
calculates what total "area of coloration" will give the desired color and
then, with
the "area already acquired", calculates when to start cool down so that total
"area
of coloration" does not exceed the desired value to achieve customer specified
color. The critical temperature varies based on the type of wood. In addition,
it
should be noted that the area called "surface of coloration" varies based on
the
aforementioned variables, notably: desired color, length and thickness. The
software running the machine creates a heating profile for the wood such that
the
surface of coloration will provide the desired wood color of final product.
The
greater the "area of coloration", the darker the coloration, irrelevant of the
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thickness of the wood. Taking into consideration the total "area of
coloration"
desired and the "area already acquired" at any given second/time, the program
starts the cool down in such a way that the "anticipated area" + the "acquired
area"
gives the desired surface of coloration.
According to the preferred embodiment of the present invention in regards
to Phase 4 (cooling and re-humidification): the heating elements are stopped.
Air
is allowed to circulate without added heat. External radiators are engaged to
speed up the cooling process of the wood.
When the wood temperature has initially gone below the initial critical
temperature, re-humidification begins. Water is sprayed inside the chamber,
until
the wood has reached approximate moisture content of about 0.5% to about 3.0%.
This step aids in the cooling process (making cooling more efficient) and
allows
the wood to re-absorb moisture while it remains clamped in the compression
jack.
This step improves stability of the wood because it reaches near hygroscopic
equilibrium while being maintained in a dimensionally stable clamp. As
aforementioned, it should be noted that at this stage of the process, it is
possible
to inject stain, paint, perfume, plastic, protective liquid to coat the
wood/or be
absorbed by the wood during the cool down phase. When wood is taken out of the
apparatus without re-injecting moisture the wood reaches hygroscopic
equilibrium
with its ambient environment, absorbing moisture from the air and potentially
warping or bending. Therefore, the present process maximizes the stability of
the
end product by allowing the wood to reabsorb water in a controlled
environment.
External radiators continue working until the wood has cooled sufficiently to
be
taken out of the machine without any danger of re-igniting.
During all phases of the process according to the present invention, the
following preferred considerations should be taken into account, as can be
easily
understood by a person skilled in the art.
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18
--------- - - -
In regards to atmospheric pressure and water valve: atmospheric pressure
in the chamber is maintained at about 11b. The evacuation set up enables gases
to
escape the chamber through water while providing the apparatus with internal
pressure control. The escaped gases are taken to a separate chamber where they
are combusted.
In regards to calculated wood temperature (i.e. with thermocouples): the
program is preferably calibrated to calculate the temperature in the center of
the
wood pile based on wood dimension using the temperature reading of a given
distance (preferably, five (5) inches) from the end of the three different
pieces of
wood, one from the top of the pile, one from the middle and one from the
bottom.
The program takes an average value of the three (3) thermocouples, then
applies
a dimensional adjustment factor to approximate the temperature at the center
of
the pile.
In regards to air and exhaust flow: there is one deflector on each side of the
chamber, normalizing flow across the stalk of wood, from the wood nearest the
fans to furthest away. Exhaust gases and by-products (e.g. resins, acids,
etc.) flow
out to the sides of the chamber, directed by the ventilation. Gases then
escape
through the water valve. These deflectors are set at an angle, such that the
wood
furthest away from the heat source and fan have a greater amount of space for
the
air to circulate in. The deflectors are perforated with holes that increase in
size
further away from the fans. This allows for a balanced airflow in the
transverse
direction., through the spaces between rows of wood all along the length of
the
machine. This even balanced airflow further contributes to the assurance of a
uniform product, clear of deposit residue.
In regards to resin and acid deposits: during the roasting process, the resins
in coniferous wood and acids in deciduous wood are drawn to the surface.
Because of transverse circulation through the chamber (processing/wood stack)
area, these by-products are channeled to the outside walls of the chamber
instead
of being left to deposit on the wood. This transverse circulation through the
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19
chamber is central to the process as it ensures that the resins and acids do
not
stain the wood, leaving an even color throughout the product.
Hence, as may now be better appreciated from the above description, the
present invention is a substantial improvement over the prior art in that, by
virtue
of its design and components, the apparatus represents important advantages
over other related apparatuses known in the prior art, in terms of
performance,
applications, safety and costs.
Indeed, the present invention enables namely to: a) avoid for operators to
make decisions regarding the outcome within the roasting apparatus and thus
adversely affecting the uniformity of the wood to be treated because according
to
the present invention, there is provided a software use to automate the
operations
in the manner described hereinabove; b) the software used according to the
present invention enables the machine to use the shortest possible route for
roasting without danger of cracking; c) have angled and perforated deflectors
combined with the fan thus creating a transverse airflow which enables to
roast the
wood with a uniform color from end to end; and d) avoid fire hazards.
The process according to the present invention is also advantageous in that
not only does it enable to treat the wood in order to have improved physical
properties, as discussed herein, but also enables to color the material being
treated. This coloring of the material is preferably carried out by an
injection of a
very fluid dye. The carrying out of this application is preferably done as
follows: the
process applies itself only after the stabilizing period of the wood but does
not
require any torrefaction. The process enables for a multitude of choices of
colors.
Preferably, the process is applied during the normal period of required re-
humidification, the application of the product being carried out preferably by
the
sprinkler system used for humidifying and/or cooling the wood, everything
being
preferably controlled by a corresponding operating software, in which case,
this
operating software will require a slight modification of the normal
torrefaction and
cooling time for the application of the product.
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As also may now be better appreciated from the above-discussed, the
process according to the present invention is also advantageous in that it
enables
the impregnation of previously scented water into the lignocellulosic material
to be
5 treated. Indeed, the process offers the possibility of treating with wood
essences
such as grey pine, white pine, fir or spruce. This application is preferably
carried
out as follows: after having torrefied the essence of the wood to the desired
color
(e.g. cedar), one only has to re-humidify with the scented water to the
desired
scent level (e.g. cedar). This step preferably applies itself after the normal
10 torrefaction period of the wood and may be part of the required re-
humidifying
period, the application of the product being carried out preferably by the
sprinkler
system used for cooling the wood and controlled by the operating software, in
which case the latter would preferably require a slight modification of the
normal
cooling time for the application of the product.
As also may now be better appreciated, the present invention is also
advantageous in that the resulting treated material is a totally natural
product, and
in that the process according to the present invention, as explained above,
enables to deliver predictable and consistent results, in terms of physical
properties, color, scent, and the like.
The apparatus according to the present invention is preferably provided with
precision controls, and designed to produce high quality, pollution free,
competitively priced wood products for which new applications are poised to
compete in the market place.
The process according to the present invention is also advantageous in that
it is different from conventional heat treatments because it is done in an
oxygen-
deprived environment to prevent the wood from igniting, which means it is
possible
to heat the wood to high temperatures of between about 160 C and 245 C. At
these temperatures, the molecular structure of the wood is altered, enhancing
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21
-- - - - - ---- - - - - --- - ---
_
some of the wood's physical properties, specifically its colour, dimensional
stability
and resistance to fungal decay, which is also very desirable.
More efficient than drying, the process according to the present invention
eliminates the water'and sap present in the wood, along with the absorbed
water
contained in the wood cells, reducing the moisture content of wood to
practically
0%.
The apparatus according to the present invention is preferably devised to
maximize productivity, while being easy to use and safe. The apparatus
preferably
comprises the following components, features and/or resulting advantages: a)
high
capacity wood load, preferably ranging from about 3,000 to about 5,000'fbm
depending on the thickness of the wood; b) a durable construction in a
preferred
304 grade stainless steel resisting corrosion and inclement weather, while
delivering exceptional durability; c) efficient thermal insulation for
improving
working conditions and minimizing workplace accidents; d) a high performance
centrifugal fan for preventing steam and smoke from infiitrating the
workplace; e) a
track loading system which facilitates loading and unloading; f) a
computerized
control system ensuring precision quality control; g) an off-gas burner for a
safer,
more environmentally friendly unit that helps minimize air emissions; h) a
rapid
treatment cycle (a 6- to 10-hour treatment cycle processes up to 20,000 fbm in
24
hours); i) low-cost energy (Quebec's low power prices leads to highly
competitive
global product); j) improved ventilation grille especially designed to ensure
perfectly . balanced air flow; k) readily accessible mechanical and electrical
components for easy maintenance and emergency operations; I) an exhaust
steam filtration for reducing fumes discharged into the atmosphere, minimizing
environmental risks; m) an innovative press system for eliminating warping of
upper rows of planks during the process; and n) an interior or exterior
installation
option, preferably with its stainless steel construction and high performance
thermal insulation, for enabling the apparatus to be installed and operated
outside
all year round.
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-- - -------- ------ -- ------- --- ----- -
The process according to the present invention is also advantageous in that
unlike chemical treatment processes, which alter the natural appearance of
wood
(for example the greenish tinge of treated wood), the present process actually
enhances the natural intrinsic beauty of wood, giving added value to less
popular
species, because it*gives everyday species a richer hue, similar to that of
exotic
wood species.
Other advantages resulting from material being treated with a process
according to the present invention are the following: a) practically
inexistent
moisture content because treated wood has practically no (close to 0%)
internal
moisture and will not reabsorb moisture from the air or surface runoff since
its
hygroscopic properties are altered by the heating process; b) dimensional
stability
because the treated wood will not shrink, swell or warp with changing weather
and
moisture conditions - it is therefore ideal for precision applications such as
furniture, doors and windows; c) resistance to biodegradation because treated
wood is resistant to fungi and moulds, which mark and degrade wood, because
fungi and moulds require a moisture content of at least 20% to develop; d)
resistance to insect pests because the present process kills the cells on
which
wood insects and parasites feed, treated wood is thus much less likely to be
attacked by pests, an important feature for the North American and European
markets, where termite damage is a major concern; e) chemical free treatment
process because the present process uses no chemicals or toxic substances -
the
production and use of treated wood is therefore safe and in compliance with
the
most stringent environmental and export standards. Moreover, wood treated
according to the present process, unlike chemically treated wood, can be
safely
handled, transported and processed immediately; f) treated through to the core
because unlike, chemical treatment, which protects only the surface layer of
the
wood, the present process affects the entire piece of wood through to the core
-
treated wood can, therefore, be processed, cut or sanded, without loosing any
of
its properties: cut ends remain protected, and scratches and cracks are
essentially
invisible; and g) a great variety of hues and consistent colour because the
present
process can enrich the hue and appearance of practically all species, which
opens
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23
up new possibilities for many species that have never been considered
aesthetically pleasing.
Being more durable, more stable and aesthetically more pleasing than
natural and chemically treated wood, wood treated according to the present
invention is an ideal choice for a broad range of applications: a) outdoor
structures
(e.g. fences; garden furniture; patios and pergolas; and wood siding); b)
finishes
(e.g. floors; cabinetry; mouldings; kitchen cabinets; and components and
furniture); and c) specialty products (e.g. caskets; educational and
recreational
toys; resonance chambers for musical instruments; and clock components).
Of course, numerous modifications could be made to the above-described
embodiments without departing from the scope of the invention, as defined in
the
appended claims.
