Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROCESS AND APPARATUS FOR USE IN RECYCLING COMPOSITE MATERIALS
This application is a division of application number
2,612,598, filed in Canada on January 9, 2007.
BACKGROUND OF THE INVENTION
[0001] The invention relates to processes and apparatus for
recycling. More particularly, the invention relates to
processes and apparatus for recycling composite materials.
[0002] There are several types of packaging used for food
products or for different industrial products in general. Most
food and industrial product packaging is typically constructed
in one of the following forms: a) paper board, for example,
cardboard; b) plastic, for example, polyethylene terephtalatic
(PET); c) paper/plastic, for example, beverage cartons;
d) plastic/aluminum laminates, for example, packaging for
coffee, dry soups, dog food, chocolates, cereals, etc.; and,
e) paper/plastic/aluminum, for example, beverage cartons for
orange juice, milk, etc.
[0003] When the food and industrial product packaging contains
only paper (as in (a)) or paper/plastic (as in case (c)), the
public has already discovered processes to recycle such
packaging materials. For example, paper packaging is fed into
hydro-pulping equipment to desegregate the paper fibers. The
separated paper fibers are then removed with water and dried
in a paper machine. The resulting recycled paper may then be
reused, for example, to make cardboard boxes for instance. In
the case where the food and industrial product is a composite
material such as paper/plastic (as in case (c)), the plastic
is separated automatically in the hydro-pulping, and normally
discarded since the plastic is (1) rarely made of only one
type
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of plastic and (2) contains contaminants, which makes it
difficult to reuse the plastic rejects.
[0004] When the food and industrial product packaging contains
only plastic such as bottles, the recycling process involves
washing, drying and grinding the plastic packaging, and
extruding and melting the ground plastic packaging in order to
form a new, recycled plastic product.
(0005] The recycling of food or industrial packaging becomes
challenging where plastic/aluminum laminates and
paper/plastic/aluminum composite materials are concerned. For
example, both types of packaging typically contain a very thin
piece of aluminum foil, for example, less than 10 microns thick,
intimately joined with a plastic component, for example, a
plastic sheet less than 100 microns thick, and paper. The paper
can be recycled using recycling processes already described.
However, the plastic and aluminum rejects cannot be recycled.
(0006] There are no commercial recycling processes for recycling
plastic and aluminum rejects from plastic/aluminum packaging and
paper/plastic/aluminum packaging due to the difficulties
associated with separating the plastic from the aluminum.
Moreover, whereas paper/plastic/aluminum contains one type of
plastic, plastic/aluminum packaging generally utilizes more than
one type of plastic. For example, the plastic component
typically contains polyethylene (PE), with minor amounts of
polypropylene (PP) and polyethylene terephtalatic (PET) also
present. These factors contribute to the present inability to
effectively recycle plastic/aluminum and paper/plastic/aluminum
packaging.
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[0007] Plastic/aluminum food and industrial packaging and the
plastic/aluminum rejects, for example, factory wastes, spent
packaging, etc., are not being properly recycled; most of these
materials are being dumped into landfills or incinerated.
Although incineration sounds like an efficient process,
incineration possesses some operating difficulties due to the
presence of the aluminum. Aluminum does not "burn" and generate
gas, rather aluminum oxidizes and generates aluminum oxide, a
solid waste, which needs to be periodically removed from the
incinerators.
[0008] At the present time, Corenso United Oy Ltd. of Finland
utilizes a pyrolysis process to recycle paper/plastic/aluminum
packaging once the paper component is removed. Pyrolysis is
conducted for generating a combustible gas that can be used to
generate energy. However, the remaining aluminum foil, in
pieces, cannot be recycled or reused. During pyrolysis, the
aluminum partially oxidizes and the oxidized aluminum becomes
difficult to melt. Aluminum oxide will form from the outside to
the inside of the aluminum foil. Aluminum oxide melts at
temperatures above 1,700 C and does not melt at temperatures of
700 C, the melting point of aluminum. Since the aluminum foil is
very thin to begin with, even a thin oxide layer becomes a
significant obstacle and prevents successfully melting the
aluminum foil. In addition, the pyrolysis process creates
aluminum/aluminum oxide residues and generates a considerable
amount of burnt gases. Hence, pyrolysis is not an
environmentally friendly process and fails to effectively
recycle aluminum from paper/plastic/aluminum food and industrial
packaging.
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SUMMARY OF THE INVENTION
[0009] In accordance with the present invention, a process for
recycling composite materials broadly comprises feeding a
quantity of composite material broadly comprising at least one
polymer and aluminum into at least one first reactor; heating
said composite material in a non-oxidizing environment at a
temperature sufficient to volatilize the at least one polymer
and form a hydrocarbon by-product and aluminum in the at least
one first reactor; feeding the aluminum free of the at least one
polymer into a second reactor; and heating the aluminum in a
non-oxidizing environment at a temperature sufficient to melt
the aluminum in the second reactor.
[0010] In accordance with the present invention, a system for
recycling composite materials broadly comprises at least one
first reactor comprising an external heating element disposed
about a mixing cavity containing at least two screws comprising
a shaft and at least two internal heating elements disposed
therein; and a second reactor comprising a plasma heating system
disposed proximate to a melt bath.
[0011] In accordance with the present invention, a reactor
broadly comprises an external heating element disposed about a
mixing cavity containing at least two screws comprising a shaft
and at least two internal heating elements disposed therein.
[0012] In accordance with the present invention, a reactor
broadly comprises a plasma heating system disposed proximate to
a melt bath coated with a material having refractory properties.
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[0013] The details of one or more embodiments of the
invention are set forth in the accompanying drawings and
the description below. Other features, objects, and
advantages of the invention will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. la is a representation of a lateral view of a
system for recycling composite materials;
[0015] FIG. lb is a representation of a top view of the
system of FIG. 1;
[0016] FIG. 2a is a representation of a top view of a first
reactor of the system of FIGS. la and lb;
[0017] FIG. 2b is a representation of a lateral view of the
first reactor of FIG. 2a;
[0018] FIG. 2c is a representation of a cross-sectional
view of the first reactor of FIG. 2b;
[0019] FIG. 3a is a representation of a top view of a
second reactor of the system of FIGS. la and lb; and
[0020] FIG. 3b is a representation of a cross-sectional
view taken along lines B-B of FIG. 3a of the second
reactor.
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(0021] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0022] As used herein, the term "hydrocarbon by-product" means a
hydrocarbon composition comprising a plurality of hydrocarbon
chain compositions each having about 6 to about 10,000 carbon
atoms per chain, preferably about 6 to about 1000 carbon atoms
per chain, most preferably about 6 to about 100 carbon atoms per
chain, and existing in one or more of the following states of
matter: as a solid, solid-liquid, liquid, liquid-gas or gas.
[0023] As used herein, the term "hydrocarbon product" means a
hydrocarbon composition that at room temperature exists in one
or more of the following states of matter: solid, solid-liquid,
liquid, liquid-gas or gas.
[0024] As used herein, the term "aluminum by-product" means a
by-product composed of aluminum that is free of any oxides of
aluminum.
(0025] As used herein, the term "at least one first reactor"
means one or a series of reactors connected together that
maintain a non-oxidizing environment and operate at a
temperature sufficient to volatilize polymers and form at least
one hydrocarbon by-product.
[0026] As used herein, the term "a second reactor" means a
reactor that maintains a non-oxidizing environment and receives
aluminum free of at least one polymer.
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[0027] Referring now to FIGS. la-lb, a system 10 of the present
invention is shown. The system 10 of the present invention
maintains a non-oxidizing environment through the entire
process. The non-oxidizing environment ensures the aluminum
oxide layer present upon the aluminum does not increase in
thickness and the polymer does not react to form CO, CO2, H2O and
other undesirable by-products during the process of the present
invention. The system 10 for recycling composite materials may
comprise a means for feeding 11 a quantity of composite material
(not shown) into an injection port 12 of at least one first
reactor 14. During a first phase of the process for recycling
composite materials, a composite material generally comprising
at least one polymer and aluminum is introduced into the first
reactor 14 through the injection port 12. An inert gas is
preferred in order to maintain the desired non-oxidizing
environment. The composite material may be processed at a
temperature sufficient to volatilize the polymer component and
form a condensable, gaseous hydrocarbon by-product and aluminum
free of at least one polymer. The hydrocarbon by-product may be
removed from the first reactor 14 through a hydrocarbon by-
product outlet 16. The hydrocarbon by-product outlet 16 may be
connected to a means for condensing 18 where the hydrocarbon by-
product is condensed to form at least one hydrocarbon by-
product. The outlet for processed materials may be in
communication with another first reactor 14 in order to further
process any remaining polymer component of the composite
material, or may be in communication with an injection port 22
of a second reactor 20.
[0028] During the second phase of the process for recycling
composite materials, the aluminum free of at least one polymer
may be transported from an outlet for processed materials 19 of
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the first reactor 14 through a means for feeding 21 and into the
injection port 22 of the second reactor 20. In the second
reactor 20, the aluminum is heated at a temperature sufficient
to melt the aluminum. Due to the absence of oxygen the aluminum
oxide layer does not grow and increase in thickness. The
aluminum free of at least one polymer may then be removed
through an outlet 24 and cooled to form at least one aluminum
by-product.
[0029] Referring now to FIGS. 2a-2c, at least one first reactor
14 may comprise a shell 30 disposed about a mixing cavity 32.
The mixing cavity 32 has an interior surface 31 and is in
communication with both the injection port 12 and outlets 16,
19. A quantity of thermal insulating material 35 may be disposed
upon the external surface of the shell 30. The thermal
insulating material may comprise, but is not limited to, fibrous
ceramic materials, silica, alumina, combinations comprising at
least one of the foregoing, and the like, and preferably a
mixture of silica and alumina where the amount of silica present
is greater than the amount of alumina present. An external
heating element 33, such as an electrical heating element, may
be disposed between the interior surface 31 and shell 30. The
external heating element 33 serves to heat the composite
material of the mixing cavity 32 during operation. The external
heating element 33 may sustain a temperature sufficient to
volatilize the at least one polymer component and form the
condensable, gaseous hydrocarbon by-product. In addition, the
external heating element 33 may also be provided outside the
first reactor 14. For example, a heat source (not shown) may
provide a heated fluid, such as oil, gas, water, steam,
combinations comprising at least one of the foregoing fluids,
and the like, via a conduit (not shown) to the first reactor 14.
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The conduit may enter the first reactor 14 and be disposed
between the interior surface 31 and the shell 30 so that the
fluid may circulate and heat the mixing cavity 32 to a
temperature sufficient to volatilize the at least one polymer
component and form the condensable, gaseous hydrocarbon by-
product.
[0030] To process the composite material, the first reactor 14
includes at least two screws 34, 36 comprising a first screw 34
mounted on a first shaft 38 and a second screw 36 mounted on a
second shaft 40 disposed within the mixing cavity 32. Each shaft
38, 40 contain an internal heating element 42, 44 disposed
therein. Like the external heating element 33, each internal
heating element 42, 44 of the first reactor 14 may also heat the
composite materials of the mixing cavity 32 during operation.
The internal heating elements 42, 44 may comprise an electrical
resistance heating element known to one of ordinary skill in the
art. The internal heating elements 42, 44 may sustain a
temperature sufficient to volatilize the polymer component and
form the hydrocarbon by-product. Suitable electrical resistance
heating elements includes, but are not limited to, nickel
chrome, and the like.
[0031] Throughout the process, both internal heating elements
42, 44 are operated to ensure a uniform temperature is
maintained throughout the entire volume of each first reactor
14. In addition, the external heating element 33 and both
internal heating elements 42, 44 are all operated to ensure a
uniform temperature is maintained throughout the entire volume
of each first reactor 14. The heating elements 33, 42, 44
placement within the mixing cavity 32 provide a favorable heat
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transfer to the composite material and ensures the composite
material heats uniformly while being processed. In addition, the
thermal insulating material 35 helps prevent heat loss, or at
the very least provides for minimal heat losses, from the mixing
cavity 32 and further ensures temperature control, favorable
heat transfer conditions and uniform heating of the composite
material.
[0032] The operating temperature throughout the entire volume of
each first reactor 14 may be a temperature range of about 300 C
to about 700 C, and preferably a range of about 400 C to about
600 C. The process of the present invention may be operated
under a vacuum, rather than at atmosphere. However, whether
operating the process under a vacuum or at atmosphere, the
operating temperature is no less than at least about 400 C, as
this temperature is necessary to volatilize the at least one
polymer component present within the composite materials. These
operating temperature ranges prevent the polymer component from
deteriorating while being processed, and also promotes the
generation of condensable, gaseous hydrocarbon by-products. When
processing the polymer component(s) at a temperature below or
above the ranges indicated, the polymer component can volatilize
and form non-condensable, gaseous hydrocarbon by-products or
both non-condensable, gaseous hydrocarbon by-products and soot.
Soot, in turn, will contaminate the aluminum that remains after
the polymer component(s) have been volatilized and removed
during the first phase of the process carried out by the system
of the present invention.
[0033] The screws 34, 36 may driven by a means for driving 46
disposed externally to the first reactor 14. The means for
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driving 46 may comprise any type of mechanical device capable of
causing the screws 34, 36 to rotate simultaneously in the same
direction and at the same speed about their shafts 38, 40. For
example, the first screw 34 may rotate at the same speed in a
first direction indicated by an arrow 48 and the second screw 36
may rotate in a second direction indicated by an arrow 50 as
depicted in FIG. 2c. One of ordinary skill in the art will
recognize the screw operating conditions may be altered yet
still accomplish the desired effects of the process of the
present invention.
[0034] The screws 34, 36 are disposed adjacent to each other
such that the screws 34, 36 are parallel to each other and do
not make contact with one another. Each screw 34, 36 include a
blade disposed along their shaft 38, 40, respectively, such that
the blade is concentrically disposed about each shaft like a
corkscrew and forms a plurality of blades and channels between
each blade. Generally, the corkscrew orientation of the blade is
commonly referred to as the helix of the screw. Being helically
shaped, the blade(s) of each screw 34, 36 are curved from the
tip to the shaft such that the surface of each blade is concave
in nature. During operation, the first screw 34 rotates about
the shaft 38 and the first helix of the first screw 34 enters
the channels of the second helix of the second screw 36. The
movement and orientation of the first helix through the channels
of the second helix remove any molten polymer composition(s)
from the screw 34 and shaft 40 and effectively clean screw 34
and shaft 40. The continual movement of the first, second screws
34, 36 effectuate the continual movement of the molten polymer
component(s) along each screw 34, 36 and prevent the molten
polymer component(s) from agglomerating within the mixing cavity
32 and along either screw 34, 36. Typically, as the polymer
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component(s) melt, the layers of polymer may form a thicker
layer which can form a ball of molten polymer component(s) while
rotating within a mixing cavity. The movement and orientation of
the screws 34, 36 effectively prevent such agglomeration of
molten polymer component(s) from occurring.
[00351 More specifically, as the first and second screws 34, 36
rotate simultaneously at the same speed and in the same
direction, at least one first blade of the first screw rotates
through at least one second channel of the second screw. As the
first blades rotates, the first blade moves back and forth
axially relative to a position of the second shaft of the second
screw. The curvature of each first blade's surface facilitates
this back and forth axial movement within each second channel
relative to the position of the second shaft of the second
screw. In contrast, a blade having no curvature, that is a flat
shaped blade, and disposed perpendicularly to a second screw
would not move axially back and forth within a channel of the
second screw relative to a position of the second shaft of the
second screw. Throughout the rotation of the screws and this
back and forth axial motion of the first and second blades, the
composite material is being processed by the first and second
screws 34, 36 within the reactor 14. At the same time, the tip
of the first blade is also removing the processed composite
material from the shaft of the second screw and effectively
cleaning the second shaft 40 and second screw 36. As the first
blades of the first screw 34 clean the second screw 36, the
second blades of the second screw 36 are also operating in the
same manner to remove the processed composite material from the
shaft of the first screw 34 and effectively clean the first
shaft 38 and first screw 34.
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[0036] For purposes of example, and not to be taken in a
limiting sense, the dimensions of the first reactor may be sized
accordingly with the intended processing conditions and
industrial purpose. For example, each screw may have a length of
about 1 meter to about 30 meters. Each screw may have a
diameter of about 10 centimeters to about 150 centimeters. Each
first blade of the first screw may be disposed about 1
millimeter to about 50 millimeters from each second blade and
the second shaft of the second screw. And, each second blade of
the second screw may be disposed about 1 millimeter to about 50
millimeters from each first blade and the first shaft of the
first screw. A tip of each first blade may be positioned about 1
millimeter to about 50 millimeters from the second shaft of the
second screw. And, a second tip of each second blade may be
positioned about 1 millimeter to about 50 millimeters from the
first shaft of said first screw.
[0037] Prior to volatilization, the polymer component(s) begin
as large hydrocarbon chain compositions having more than about
100,000 carbon atoms per chain. During volatilization, the
polymer component(s) begin breaking down into smaller
hydrocarbon chain compositions each having less than about
100,000 carbon atoms per chain. As volatilization nears
completion, the polymer component(s) break down into a plurality
of small hydrocarbon chain compositions each having about 6 to
about 10,000 carbon atoms per chain, preferably about 6 to about
1,000 carbon atoms per chain, most preferably about 6 to about
100 carbon atoms per chain, which forms the hydrocarbon by-
product.
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[0038] The hydrocarbon by-product preferably comprises
hydrocarbon chains comprising no less than 6 carbon atoms per
chain and no more than 100 carbon atoms per chain. Hydrocarbon
chain compositions falling within the enumerated carbon atoms
per chain range form condensable, gaseous hydrocarbon by-
products under the operating conditions maintained within the
first reactors 14. Such condensable, gaseous hydrocarbon by-
products may be condensed to form hydrocarbon by-products
desired by the market, for example, paraffinic compounds; a
commodity that commands high market value. In contrast,
hydrocarbon chain compositions containing less than 6 carbon
atoms per chain form non-condensable, gaseous hydrocarbon by-
products such as methane, ethane, propane and butane, which as
commodities command far lower market value. Hydrocarbon chain
compositions containing more than 100 carbon atoms per chain are
unlikely to be generated in a gas form.
[0039] Throughout processing the composite material, the
hydrocarbon by-product may be removed through the outlet 16
during the process. The hydrocarbon by-product may be condensed
into a hydrocarbon product using a means for condensing 18. The
means for condensing 18 may comprise any device capable of
condensing hydrocarbons as known to one of ordinary skill in the
art. when performing the process of the present invention, at
least one hydrocarbon product is formed upon condensing the
hydrocarbon by-product. For example, the hydrocarbon product
may comprise a paraffin composition that contains paraffin in
part (solid) and paraffinic oil in part (liquid) at room
temperature. Depending upon the operating conditions of the
means for condensing 18, any number of hydrocarbon products may
be produced using the process of the present invention as the
paper/plastic/aluminum and plastic/aluminum food and industrial
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packaging being recycled may each contain one or more different
polymers.
[0040] Once the polymer component(s) of the composite material
have been volatilized and only aluminum remains, the pieces of
aluminum coated with a thin film of aluminum oxide are
transported into an injection port 61 of the second reactor 20
using a means for transporting 21 as known to one of ordinary
skill in the art. Referring now to FIGS. 3a and 3b, the second
reactor 20 preferably maintains a non-oxidizing environment and
may comprise a shell 60 disposed about a cavity 62. The cavity
62 houses a melt bath 64 having a coating disposed thereupon.
The coating comprises at least one material possessing
refractory characteristics. Suitable materials possessing
refractory characteristics for use herein may include, but are
not limited to, silica, alumina, combinations comprising at
least one of the foregoing, and the like, and preferably a
mixture comprising about 70% by weight to 90% by weight of
alumina and silica in the remainder. A quantity of thermal
insulating material 65 may be disposed upon the external surface
of the shell 60 in order to prevent heat loss, or at the very
least provides for minimal heat losses, from the cavity 62.
Suitable thermal insulating materials include, but are not
limited to, fibrous ceramic materials, silica, alumina,
combinations comprising at least one of the foregoing materials,
and the like, and preferably a mixture of silica and alumina
where the amount of silica present is greater than the amount of
alumina present.
[0041] A plasma heating system 66 may be mounted to the shell 60
such that a plasma heating device 68 is disposed within the
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cavity 62. The plasma heating device 68 may be disposed
proximate to and above the melt bath such that the device 68 can
move back and forth across the surface of the melt bath and melt
the aluminum free of at least one polymer component. A suitable
plasma heating device 68 for use herein may comprise a swivable,
transferable or non-transferable plasma torch capable of moving
in any and all directions across the surface of the melt bath,
for example, a sweeping motion, and capable of generating at
least enough heat to break the aluminum oxide film and melt
aluminum. Any number of inert gases as known to one of ordinary
skill in the art may be utilized as the plasma gas. An inert
gas, such as Ar, is preferred in order to maintain the non-
oxidizing environment within the second reactor 20. The plasma
heating device 68 may generate an electric arc having a
temperature above about 10,000 C (18,032 F) which far exceeds
the temperature of about 660 C (1220 F), the melting point of
aluminum or about 1,700 C (3,092 F), the melting point of
aluminum oxide. The aluminum oxide film melts and releases the
aluminum contained within the oxide shell. Due to the absence of
oxygen, the resulting aluminum liquid should be free of any
oxides of aluminum.
[0042] As pieces of aluminum enter the melt bath 64, the plasma
torch moves in a sweeping motion above the aluminum. The plasma
torch arc strikes the aluminum and forms molten aluminum
droplets and a layer of dross forms atop the molten aluminum. As
additional aluminum enters the melt bath 64 and melts, a layer
of dross forms and floats atop the molten aluminum. The dross
layer insulates the molten aluminum from the high temperatures
generated by the plasma torch. At the very surface of the dross
layer having a thickness of about 1 millimeter to about 2
millimeters, the temperature reaches between about 2,000 C to
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about 3,000 C. However, the temperature drops considerably below
the dross surface such that the dross layer effectively
insulates the molten aluminum. As a result, the molten aluminum
can be maintained at a temperature of no more than about 800 C
during the process. Throughout the process, a graphite tool (not
shown) may be used to periodically skim the surface of the melt
bath 64 and remove the layer of dross. One of ordinary skill in
the art will recognize any tool may be incorporated to achieve
this purpose as well. As pieces of aluminum continually enter
the second reactor 20, molten aluminum is also tapped in order
to maintain a constant melt bath level. When tapping the molten
aluminum, the molten aluminum may be cooled to a temperature of
about 600 C. The resulting melted aluminum may be removed from
the cavity 62 via an outlet 70 to form at least one aluminum by-
product.
[0043] As discussed, paper/plastic/aluminum and plastic/aluminum
packaging materials are not being recycled and/or not being
recycled completely due to the intrinsic difficulties in
separating plastic and aluminum as well as each component's
physical and chemical properties. Common thermal separation
(e.g., pyrolysis) of the two components is very difficult due to
the heat transfer limitations caused by the plastic component
and the insufficient weight of the aluminum in order to break up
the aluminum oxide layer. Other prior art recycling processes,
including chemical separation, have not succeeded either
economically or environmentally.
[0044] The system and process of the present invention
successfully recycles both paper/plastic/aluminum and
plastic/aluminum packaging materials. Plastics composed of one
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or more polymers and aluminum of any thickness may now be
separated and recycled rather than disposed as waste material.
The system and process of the present invention possesses
several advantages in carrying out this successful endeavor.
[0045] The process of the present invention is environmentally
friendly. The process does not generate any type of
environmentally harmful residue or toxic gaseous or liquid
effluents. Throughout the process, the composite material is
processed in sealed reactors and the release of the hydrocarbon
by-product and aluminum by-product is controlled. And, unlike
prior art methods for recycling plastic, plastic/aluminum or
paper/plastic/aluminum composite materials, the process of the
present invention does not require additional reagents to
effectuate processing the composite materials.
[0046] The process of the present invention avoids the most
common obstacle that has, until now, prevented recycling
plastic/aluminum and paper/plastic/aluminum packaging. By
maintaining non-oxidizing atmospheres and controlling the
temperature throughout the process, aluminum oxide cannot form
and prevent the recycling process. As a result, the hydrocarbon
by-product and aluminum by-products in turn exhibit homogeneity,
which equals quality.
[0047] The process of the present invention employs specially
designed sealed reactors to ensure the composite materials are
processed efficiently. The use of a specially designed sealed
vessel and double self-cleaning screws permits the uniform
heating and continuous processing of the polymer(s) in the
composite material. This ensures the plastic does not
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deteriorate during the process. The use of a specially designed
plasma system permits the melting of aluminum of any size and
thickness, even when they are very thin. As a result, any
aluminum oxide existing previously from the shell, the plasma
system melts the aluminum oxide layer and releases the molten
aluminum.
[0048] The process of the present invention is not only
successful over failed attempts by the prior art but also
efficient. The prior art processes typically lose at least forty
percent (40%) of the aluminum when recycling plastic/aluminum
and paper/plastic/aluminum composite materials. As a result,
prior art processes cannot recover more than sixty percent (60%)
of the aluminum when recycling these composite materials. The
process of the present invention recovers at least approximately
90% of the aluminum. The overall energy efficiency of the
process of the present invention is greater than approximately
seventy-five percent (75%). The high efficiency is due in part
to the intrinsic characteristics of the heating sources, that
is, the external and internal heating sources and plasma torch,
and also in part to the orientation of the heating sources and
thermal insulation material within and about each reactor.
[0049] One or more embodiments of the present invention have
been described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are
within the scope of the following claims.
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