U.S. patent application number 13/462201 was filed with the patent office on 2012-08-30 for separation of materials comprising super absorbent polymers using reduced water.
This patent application is currently assigned to KNOWASTE INTERNATIONAL LLC. Invention is credited to David B. Grimes.
Application Number | 20120217326 13/462201 |
Document ID | / |
Family ID | 45769960 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120217326 |
Kind Code |
A1 |
Grimes; David B. |
August 30, 2012 |
SEPARATION OF MATERIALS COMPRISING SUPER ABSORBENT POLYMERS USING
REDUCED WATER
Abstract
Embodiments of the present disclosure include a method for
separating a material comprising a super absorbent polymer, a fiber
and a plastic to separate the material into components thereof, one
method comprising shredding the material, adding salt to the
material, and agitating the material, wherein the material does not
comprise a slurry.
Inventors: |
Grimes; David B.;
(Greenfield, MA) |
Assignee: |
KNOWASTE INTERNATIONAL LLC
West Bromwich
GB
|
Family ID: |
45769960 |
Appl. No.: |
13/462201 |
Filed: |
May 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13304208 |
Nov 23, 2011 |
8177151 |
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13462201 |
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12780293 |
May 14, 2010 |
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13304208 |
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61216342 |
May 16, 2009 |
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61216363 |
May 16, 2009 |
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Current U.S.
Class: |
241/15 ; 241/22;
241/23 |
Current CPC
Class: |
B29B 2017/0224 20130101;
C08J 11/06 20130101; Y02W 30/701 20150501; B29L 2031/4878 20130101;
Y02W 30/52 20150501; Y02W 30/62 20150501; B29K 2001/00 20130101;
C08J 2300/14 20130101; Y02W 30/622 20150501; Y02W 30/523 20150501;
B29B 17/02 20130101 |
Class at
Publication: |
241/15 ; 241/22;
241/23 |
International
Class: |
B02C 23/08 20060101
B02C023/08; B02C 23/18 20060101 B02C023/18; B02C 23/06 20060101
B02C023/06 |
Claims
1. A method for separating the component parts of a material
comprising a super absorbent polymer (SAP), a fiber component and a
plastic component, the method comprising: shredding the material;
adding a salt to the material; and agitating the material, wherein
the material is not a slurry or part of a slurry.
2. The method of claim 1, further comprising: heating the
material.
3. The method of claim 2, wherein heating comprises heating with
steam.
4. The method of claim 2, further comprising: pressurizing the
material; and depressurizing the material.
5. The method of claim 4, wherein the heating, pressurizing and
agitating are performed in an autoclave.
6. The method of claim 1, wherein the salt comprises aluminum
sulfate.
7. The method of claim 1, wherein the salt comprises a salt
solution.
8. The method of claim 1, wherein less than 10% water by weight of
material is added to the material.
9. The method of claim 1, wherein less 200 liters of water per ton
of material is added to the material.
10. The method of claim 9, wherein the material comprises
substantially no free water.
11. The method of claim 1, further comprising: using a dry process
to separate the material into: a fiber and SAP component, and a
plastic component.
12. A method for separating the component parts of a material
comprising a super absorbent. polymer (SNP), a fiber component and
a plastic component, the method comprising: heating the material;
and pressurizing the material, wherein the material is not a slurry
or part of a slurry.
13. The method of claim 12, further comprising: shredding the
material.
14. The method of claim 13, further comprising: agitating the
material.
15. The method of claim 14, further comprising: depressurizing the
material.
16. The method of claim 15, wherein the heating, pressurizing,
depressurizing and agitating are performed in an autoclave.
17. The method of claim 12, further comprising: separating the
material into: a fiber and SAP component, and a plastic component.
Description
CROSS REFERENCE
[0001] This application is a continuation-in-part of U.S. utility
application Ser. No. 12/780,293, filed May 14, 2010, which claims
priority from provisional application 61/216,342, filed May 16,
2009 and provisional application 61/216,363, filed May 16, 2009,
the entire contents of both applications which are incorporated
herein by reference, including any references cited therein,
FIELD OF THE INVENTION
[0002] The invention relates to methods of separating products
containing super absorbent polymers into their constituent parts,
including a plastic component, super absorbent polymers, and
cellulosic fibers, and further refinement of said constituent
parts. Examples of such products include absorbent sanitary
products, for example diapers.
BACKGROUND
[0003] As used herein, absorbent sanitary paper products include,
for example, but not limited to, disposable diapers, incontinence
products, feminine hygiene products, bedpads and other related
absorbent and adsorbent products ("products" or "material"). These
products typically consist of (i) a non-woven sheet formed from a
liquid permeable material, for example a liquid permeable membrane
formed from polypropylene, polyethylene, or woven products formed
from cotton or rayon, (ii) a liquid impermeable back sheet formed
from, for example, polyethylene, polypropylene, starch based
degradable plastic films, woven cloth or rubber, and (iii) an
adsorbent or absorbent core of air laid wood pulp fluff, commonly
referred to as air felt, and/or synthetic pulp including
polypropylene or polyethylene filaments that may be bonded or
unbonded, hemp or other adsorbent fibrous material. The core is
typically wrapped or encased in a creped envelope of wet strength
tissue paper or a material with similar characteristics, The
wrapping on the core may or may not be breathable, biodegradable,
odour degradable or degradable or dissolvable by other means. The
core usually also contains a super absorbent polymer (SAP)
material, which is typically a polyacrylate, polyacrylamide,
crosslinked starch or other hydrophilic component, which may be
synthetic, and may be in granular, fibrous or laminate form,
possessing the ability to bond with water, urine or other body
fluids or retain them without substantial release or discharge from
the absorbent portion. Diapers and incontinence products typically
utilize pressure sensitive adhesives or refastenable tape tabs or
similar closure mechanisms. Feminine hygiene pads and incontinence
products often use pressure sensitive adhesives for glue lines to
attach the pad or liner to the user's undergarments. Diaper and
incontinence products typically utilize elastic, polyurethane,
puckering and welding or adhesives to create close fitting cuffs
around the leg and waist openings to provide a more leakproof
fit.
[0004] Absorbent sanitary paper products are normally disposed of
along with garbage generated by households, institutions, hotels
and the like, by incineration or in landfill disposal sites.
Incineration tends to result in air or other pollution being
generated. Landfill disposal results in an accumulation of such
products. Thus, the consequences of the convenience or necessity of
use of absorbent sanitary paper products include problems relating
to disposal of such products. in addition, use of either
incineration or landfill disposal results in loss or destruction of
the components of the absorbent sanitary paper products, rather
than recycling some or all of those components to the same or other
end-uses. The disposal problems are of ever increasing concern to
environmental and governmental authorities, and means are required
for effective disposal and utilization of used absorbent sanitary
products. Additionally the disposal of the scraps and defective
product post industrial diapers puts a burden on manufacturers and
wastes valuable resources.
SUMMARY OF THE INVENTION
[0005] Embodiments of this disclosure include a method for
separating the component parts of a material comprising a super
absorbent polymer (SAP), a fiber component and a plastic component.
in certain embodiments, this method comprises shredding the
material, adding a salt to the material and agitating the material,
wherein the material does not comprise a slurry. Other embodiments
include heating the material. In some embodiments, the heating
comprises heating with steam.
[0006] In some embodiments of this disclosure, the material is
pressurized and then depressurized. In further embodiments, the
heating, pressurizing and agitating are performed in an autoclave.
In certain embodiments, the salt comprises aluminum sulfate. in
other embodiments, the salt comprises a salt solution.
[0007] In some embodiments of this disclosure, less than 10% water
by weight of material is added to the material. In other
embodiments, less 200 liters of water per ton of material is added
to the material. In still other embodiments, the material comprises
substantially no free water. I certain embodiments, using a dry
process, the material is separated into a fiber and SAP component,
and a plastic component.
[0008] Some embodiments of this disclosure include a method for
separating the component parts of a material comprising a super
absorbent polymer (SAP), a fiber component and a plastic component,
the method comprising heating the material and pressurizing the
material. Other embodiments include shredding the material. Still
further embodiments include agitating the material. Some
embodiments include depressurizing the material. In certain
embodiments, the heating, pressurizing, depressurizing and
agitating are performed in an autoclave.
[0009] Some embodiments of this disclosure include further
separating the material into a fiber and SAP component, and a
plastic component.
DESCRIPTION OF THE FIGURES
[0010] FIG. 1 depicts a flow diagram of one embodiment of the
methods described herein for separating a product containing a
super absorbent polymer (SAP), a fiber and a plastic into its
component parts; and
[0011] FIG. 2 depicts a flow diagram of one embodiment of the
methods described herein for separating a product containing a
super absorbent polymer (SAP), a fiber and a plastic into its
component parts, and highlighting yet another embodiment of the
methods herein for deactivating any SAP remaining in a plastics
component (circled portion).
[0012] FIG. 3 depicts a flow diagram of one embodiment of the
methods described herein for separating a product containing a
super absorbent polymer (SAP), a fiber and a plastic into its
component parts using an autoclave and salt.
[0013] FIG. 4 depicts a flow diagram of one embodiment of the
methods described herein for separating a product containing a
super absorbent polymer (SAP), a fiber and a plastic into its
component parts using an autoclave, but without adding salt in the
autoclave,
DETAILED DESCRIPTION
[0014] Numbers in the present disclosure are rounded to the nearest
significant figure using conventional rounding techniques. Ranges
of numbers contained herein are understood to contain the numbers
on the upper and lower limits, unless otherwise indicated. For
instance, a range "from 1 to 10" is understood to include a range
including the number "1" and up to and including the number
"10."
[0015] The present disclosure includes methods of separating a.
product including a super absorbent polymer (SAP), a fiber and a
plastic into components thereof. This disclosure also includes
methods of deactivating SAP in a plastic recovered from a product
including SAP. In addition, this disclosure includes methods of
producing reusable plastic and SAP from the treatment of a product
including SAP. Further, this disclosure includes methods of
treatment of a wet SAP such that the SAP is reusable and/or does
not comprise alum, As used herein, "alum" refers to KAl(SO4)2.
Other names for alum include kalinite (the mineral form), potash
alum, potassium alum dodecahydrate or KAl(SO4)2.about.12H2O.
Aluminum sulfate (Al2(SO4)3 or Al2O12S3) is sometimes incorrectly
referred to as alum, however, under the definition of alum herein,
alum does not include aluminum sulfate. Finally, this disclosure
includes methods of recycling SAP for use as an agglomerating
agent.
[0016] Previous methods of separating absorbent sanitary paper
products continue to produce byproducts having their own disposal
issues. U.S. Pat. No. 5,558,745, incorporated by reference herein,
describes one such method. This method includes shredding the
products and adding a crosslinking agent to harden the SAP. The
hardened SAP is then separated from the plastic and fiber. The
process uses rotating multi-shell drums and centrifugal cleaners to
achieve separation. While the process may achieve separation, there
are disadvantages to the separated components. The plastic
component, for example, still contains SAP and cellulosic material.
The recovered SAP, in it's hardened, granulated state, no longer
retains its super absorbent function. This function may possibly be
recovered by the addition of large amounts of NaOH (at a pH of 11,
for example), for example, but the necessary processing makes the
SAP much more expensive than virgin SAP. The granulated SAP is also
unsuitable for agricultural and landfill applications, since the
crosslinking salts that remain with the SAP, especially alum, are
environmentally unfriendly and detrimental to plant growth.
Additionally, if Alum is used as the crosslinking agent, any
byproducts from this process may be environmentally unfriendly as
alum may have a negative impact on plant and animal life.
[0017] The benefits of the methods of the present disclosure
include cost savings due to reduced use of chemicals, for example,
alum. In addition, any residual SAP in the plastic stream is
deactivated, making the plastic more attractive as a recycled
material. Any composted fiber and/or alum resulting from this
process may be more desirable due to reduced or eliminated alum
content. And finally, because alum may not be used on the bulk of
the SAP, the SAP may have increased options for recycling and
increased market value.
[0018] Absorbent sanitary paper products ("products" or "material")
typically consist of (i) non-woven sheet formed from a liquid
permeable material, for example a liquid permeable membrane formed
from polypropylene, polyethylene, or woven products formed from
cotton or rayon, (ii) a liquid impermeable back sheet formed from
for example polyethylene, polypropylene, starch based degradable
plastic films, woven cloth or rubber, and (iii) an adsorbent or
absorbent core of air laid wood pulp fluff, commonly referred to as
air felt, and/or synthetic pulp including polypropylene or
polyethylene filaments that may be bonded or unhanded, hemp or
other adsorbent fibrous material ("fiber component"). Components
(i) and (ii), typically both made of a thermoplastic, may be
referred to herein as the "plastic component." The core is
typically wrapped or encased in a creped envelope of wet strength
tissue paper or a material with similar characteristics. The
wrapping on the core may or may not be breathable, biodegradable,
odour degradable or degradable or dissolvable by other means. The
core usually also contains a super absorbent polymer (SAP)
material, which is typically a polyacrylate, polyacrylamide,
crosslinked starch or other hydrophilic component, which may be
synthetic, and may be in granular, fibrous or laminate form,
possessing the ability to bond with water, urine or other body
fluids or retain them without substantial release or discharge from
the absorbent portion. Diapers and incontinence products typically
utilize pressure sensitive adhesives for refastenable tape tabs or
similar closure mechanisms. Feminine hygiene pads and incontinence
products often use pressure sensitive adhesives for glue lines to
attach the pad or liner to the user's undergarments. Diaper and
incontinence products typically utilize elastic, polyurethane,
puckering and welding or adhesives to create close fitting cuffs
around the kg and waist openings to provide a more leakproof
fit,
[0019] Absorbent sanitary paper products are usually fabricated
using SAPs. Such polymers facilitate wetting and wicking properties
of the products, especially the cellulosic core usually present in
the products, and in particular increase the liquid retention
capacity of the absorbent sanitary paper products. Super-absorbent
polymers tend to be acrylic polymers and starch-based polymers. At
least SAP's made from acrylic polymers are usually cross-linked in
the manufacturing process in order to give them compressive and
tensile strength along with their super absorbent properties.
Further cross-linking may occur in steps in embodiments of the
methods of the present disclosure.
[0020] As a result of the inherent water absorption properties of
SAP, SAP tends to swell on contact with aqueous solutions. Products
containing SAP may swell to 2-5 times or more its dry (feed) volume
on contact with an aqueous solution. Chemical steps including
cross-linking of the SAP in situ or adding agents that reduce the
swelling of SAP and/or change the shape and specific gravity of
particles of SAP may reduce swelling. In some instances, reduction
of swelling, i.e. shrinkage, of SAP should be carried out prior to,
or substantially simultaneously with cross-linking of the SAP if
cross-linking is desired. Water-soluble alkali and alkaline earth
metal compounds are believed to cause shrinkage of the SAP whereas
the aluminum, copper, iron and zinc compounds, for example, alum,
are believed to cause cross-linking The treatment of the SAP should
be carried out in acidic or substantially neutral solutions,
especially at a pH of about 3-8, which limits the alkali and
alkaline earth metal compounds that may be used. Examples of
chemical compounds that may be added, usually in the form of
mixtures, to effect cross-linking of SAP, especially SAP formed
from acrylic polymers, include soluble salts of at least one of an
alkali metal, an alkaline earth metal, aluminum, copper (II), iron
(III), and zinc. Examples of such salts include calcium chloride,
calcium nitrate, calcium sulphate, magnesium chloride, magnesium
nitrate, magnesium sulphate, disodium phosphate, barium chloride,
sodium carbonate and bicarbonate, trisodium phosphate, sodium
silicate, potassium sulphide, aluminum sulphate, sodium bisulphate,
zinc sulphate, aluminum chloride, sodium sulphate and alum.
Aluminum salts e.g. sulphate and chloride, are preferred.
[0021] The present disclosure includes methods of separating
products that include a super absorbent polymer (SAP), a fiber and
aplastic. FIG. 1 depicts one embodiment of this method. This
embodiment includes first shredding the products. In addition to
shredding, this may also be accomplished by otherwise releasing the
SAP and fiber component from the nonwoven and plastic layers by
some form of cutting or tearing. All separation processes will be
referred to herein as "shredding."
[0022] Next, water, an aqueous solution, or another solvent is
added to the shredded product, causing the SAP to swell. The
product is then moved to a press. Enough water must be added such
that separation of the components is maximized in the press, while
at the same time attempting to minimize the total amount of water
needed. Preferably, this amount includes not more than enough water
to saturate the SAP. In some embodiments, water is added in about a
10 to 1 ratio of water to dry product by weight. In other
embodiments, the water is added in a range of about from 10:1 to
20:1 water to dry product by weight. Caustic aqueous solution may
speed the absorption process, making this portion of the method
fluster.
[0023] The press may include, for example, but not limited to, a
screw press. One example of such a press is the Model SP-23-2 (HDS
Dewatering Corp., Montreal, Quebec, Canada). Other types of presses
may include, for example, but not limited to, hydraulic presses,
for example, a ram press (MENA, Sweden), pneumatic presses,
magnetic presses, knuckle-joint presses, rolling presses and
centrifuges.
[0024] Once inside the press, the method includes pressing the
product against a screen. The press applies pressure by pressing
the wet product and forcing the product against a screen. As used
herein, the term "pressing" means to act upon through force, for
example pushing or thrusting force, or to move by means of
pressure. As used herein, the term "screen" means a body having at
least one opening against which the press forces the wet product.
Examples of a screen include, but are not limited to, a plate with
holes, a sieve, wire mesh, a screen cylinder, and a "basket." The
openings in the screen may include perforations, holes, slots,
grating, mesh, or the like. Preferably, the openings include holes
between 0.049 inches and 0.25 inches in diameter. More preferably,
the openings are between 0.0625 inches and 0.125 inches. Most
preferably, the openings are about 1/16 inch. In general, the
openings are big enough such that the SAP and some of the fiber is
pressed through the openings. Preferably, the openings are small
enough such that the majority or substantially all of the plastic
component remains in the press. in the end, the press separates the
product into a plastics component (plastics component) remaining in
the press and a SAP and fiber component (SAP and fiber component)
pushed out of the press. Up to about 50% of the fiber content may
exit the press in the SAP and fiber component. The remaining fiber
remains in the press with the plastic, in addition to any residual
SAP. In a screw press, for example, the press applies pressure via
a screw flight, forcing the wet product against a screen cylinder
or "basket," This forces the SAP through the screen plate openings,
while the plastic remains in the press.
[0025] The benefits of this particular method of separation
involving a press is that no salt is required. Salts may he harmful
or at least undesirable to the environment. When certain components
of the products are used in the environment, for example as
compost, salts included in those components may have deleterious
effects such as changing the pH of the water in the surrounding
ecosystem, and/or killing, injuring or disrupting plant and animal
life. Alum, a salt commonly used in separation of SAP from these
products, is particularly undesirable in the environment.
Therefore, in the methods involving the use of a press, the
products preferably do not include a salt, and the steps of adding
water and pressing does not include the addition of a salt. In
particular, the products and these steps do not include a material
that cross-links SAP. Preferably, the products do not include alum
and these steps do not include the addition of alum.
[0026] The plastics component that remains in the press includes
substantially plastic, but also includes some SAP and fiber.
Plastic products made from this plastic component may still swell,
form a gel, and/or retain water when exposed to water due to the
residual amounts of SAP. This result is particularly
disadvantageous for recycled products including the plastic
component, such as, for example, plastic lumber, which will likely
be exposed to water. This result (gelling of residual SAP) may
occur even after the plastic/SAP is melted and extruded into a
finished product. Thus, it is preferable to remove as much SAP as
possible from the plastic component, and deactivate any remaining
SAP in the plastic before recycling the plastic composition. As
used herein, "deactivate" refers to rendering the SAP substantially
unable to swell or retain water. This may be accomplished by either
crosslinking the SAP to the point where swelling is minimized or
eliminated, or exposing the SAP to a substance that breaks the
existing crosslinks. In one embodiment of this disclosure, the
method further includes adding a composition that substantially
deactivates SNP to the plastics component. In another embodiment,
the method further includes substantially separating the remaining
SAP from the plastics component. In still further embodiments, the
method further comprises both adding a composition that
substantially deactivates SAP to the plastics component and
substantially separating the remaining SAP from the plastics
component. Any combination of these steps yields a purified
plastics component and a secondary component which may include
water, fiber and SAP. As used herein, a purified plastics component
is substantially comprised of plastic, and any remaining SAP in the
purified plastics component is substantially deactivated.
[0027] In a preferred embodiment, a composition comprising alum is
added to the plastics component and then water, fiber and SAP is
removed to yield a purified plastics component and a secondary
component including the water, fiber and SAP. One of the benefits
of the embodiments of the present disclosure is that the alum is
only added after the plastic has been substantially separated from
the other components, for example by a press as described above.
This may require the use of less alum than other prior art methods.
In some embodiments, the amount of alum measured in dry weight
added to the plastics component is about equivalent to the dry
weight of SAP remaining in the plastics component.
[0028] The alum composition may also include additional water. The
alum may serve two purposes when used after pressing. First, the
alum may act as a washing agent to break the bonds between the SAP
and the surrounding solids after the pressing adheres them. Second,
the alum acts as an agent to sequester the SAP by dewatering,
densifying and deactivating the SAP. The alum crosslinks the SAP to
a point where swelling and water retention is minimized or
substantially eliminated. Then, any secondary components such as
water, loose solids such as SAP particles, and fiber (secondary
component) are separated from the purified plastics component. The
separation can be accomplished using a pulper and a washer, as is
known in the art. In one embodiment, the plastic with some
contamination is ground into smaller pieces using a single rotor
plastics grinder that reduces the plastic to less than about 20 mm
diameter pieces. The material exits the grinder and drops into a
pulper or agitator tank containing an impeller for separating the
components in a slurry.
[0029] In an embodiment including a pulper and a washer, the salt,
for example, alum, is introduced to the plastics component and
agitated. The salt can be added in liquid solution or granulated
form. The liquid alum is pumped in at a controlled rate to match
approximately equal to the dry weight of SAP in the incoming
solids. In one embodiment, the dosing pump includes a positive
displacement gear pump. Water may also added to the mix until the
suspension is about 1-5% solids by weight.
[0030] The plastic and remaining SAP, paper fiber and waste
(plastics component) are sent to a coarse screen with openings of
about 1-6 mm such as a "friction washer" similar to a
FW-560/3000-SP type (REKO Technologies, Putte, Belgium). The
mixture is drained and agitated, removing more of the paper fiber,
SAP, and waste. The remaining plastic may travel through a washer
to flush with clean water further removing impurities, for example
an 1W 1004-SP type intensive washer (REKO Technologies, Putte,
Belgium). After exiting the washer the plastic may go to a screw
press for removal of some of the water bringing the solids to about
20-60% solids by mass. For example, a suitable press may include a
dewatering screw press type AKUPRESS A 200 (Andritz Kufferath GmbH,
Dueren, Germany). In one embodiment, the press may include 3 mm
screen openings
[0031] After separating the secondary component (fiber, SAP, waste)
from the plastic component, the plastic component may be recycled.
In some embodiments, the plastic component is dried before being
recycled into another product.
[0032] The secondary component may be further separated using a
sidehill screen, for example. Water and any accompanying small
particles of fiber (water and fiber component) is separated from
any SAP and larger sized fiber particles (SAP and fiber component)
by the sidehill screen, for example a 24 inch inclined screen with
about 0.25 mm slotted screen surface with about a 380 liters per
minute flow rate (GL&V, Montreal, Quebec, Canada). The result
of this separation is the water and fiber component and the SAP and
fiber component.
[0033] The water and fiber component may be further subjected to
dissolved air filtration. Dissolved air flotation (DAF) is a water
treatment process that clarifies wastewaters (or other waters) by
the removal of suspended matter such as oil or solids, or in this
instance, fiber and/or SAP. The removal is achieved by dissolving
air in the water or wastewater under pressure and then releasing
the air at atmospheric pressure in a flotation tank or basin. The
released air forms tiny bubbles which adhere to the suspended
matter, causing the suspended matter to float to the surface of the
water where it may then be removed by a skimming device. In
general, any wastewaters from the methods of the present disclosure
may be subjected to DAF.
[0034] The SAP and fiber component may also be further separated by
a press, a centrifugal drum, or other means into a substantially
water component (water component) and a fiber sludge component
(fiber sludge component) including any remaining SAP and fiber. The
water component may be subjected to DAF or other wastewater
treatment techniques. The fiber sludge component may be disposed in
a landfill or used as compost or any other suitable use. The fiber
sludge component may be combined with the super absorbent polymer
and fiber component from the initial press operation (the component
that exited the press) before being disposed, landfilled,
composted, disposed in some other manner, or recycled as another
product.
[0035] The SAP and fiber component that leaves the press during the
initial pressing operation (described above) may be recycled in
that form, or it may be further processed and/or separated. In
certain embodiments, the SAP and fiber may be subjected to a
further separation step, including separating the SAP and fiber
component into a SAP component (SAP component), which may include
substantially SAP, and a fiber component (fiber component), which
may include substantially fiber.
[0036] In some embodiments, the SAP may be dried, either as part of
the SAP and fiber component, or after being separated into the SAP
component. These methods include drying the SAP component or SAP
and fiber component by salt assisted dehydration. The SAP and fiber
component may also be used for compost, or recycled for other
products.
[0037] One of the products that the SAP and fiber component may be
used for is a seeding or reseeding composition for growing
vegetation on freshly excavated or fire-damaged ground. In this
embodiment, the human waste may or may not be removed from the SAP
and fiber component. If it is retained, the human waste may be
sanitized by techniques known in the art, for example, but not
limited to, radiation, autoclaving and/or pasteurization. Seeds may
be added to the SAP and fiber component, and the mixture is
distributed on the ground. The seeds sprout into new vegetation.
The SAP holds water and slowly releases it, providing a.
time-release source of water for the seeds. This effect is
especially beneficial in arid climates or in fire-damaged areas. In
addition, the SAP and fiber remains near the surface of the soil
allowing oxidation and sunlight degradation, allowing the SAP to
decompose while at the same time establishing ground cover. The
fiber in the mixture typically and preferably includes long strings
of fiber that interweave, Typically, the fibers are about 1-3 mm
long and 50 microns in diameter. The interlaced fibers prevent
migration of the SAP, seeds, and underlying soil. This may be
especially beneficial in fire-damaged ground or on hillsides.
Finally, the waste, if present, may act as a fertilizer.
Additionally, any beneficial salts such as potassium salts that
remain from the salt assisted dehydration may act as fertilizers.
Additional fertilizers known in the art may also be added to the
seeding composition.
[0038] In another embodiment. SAP recovered from the methods
described in this disclosure may be used in fire prevention. The
SAP may be wet and sprayed onto houses, barns, fuel tanks and other
structures in the face of an oncoming fire. The wet SAP may provide
protection from nearby heat and flames,
[0039] In yet another embodiment, SAP with or without fiber may be
used for the sequestering/collection/removal of toxic waste,
hazardous chemicals and heavy metals from water and soil. In one
embodiment, dehydrated or partially hydrated SAP is spread across
an area of soil. Water and contaminants may be absorbed into the
SAP gel, preventing the water from penetrating into the ground
water until the material can be moved as a solid. Retention in the
SAP may also eliminate the hazard of dripping water and
contaminants until the now contaminated SAP is moved to safe
location for disposal. Wet SAP in a "gel" state also has a blocking
property. Wet SAP swells to block the passage of water and other
fluids. This "blocking" is prevented in diapers, for example, by
mixing the SAP with fibers that provide a liquid passageway. When
there is no passageway, however, SAP can effectively block liquid
flow. Thus, a layer of SAP on contaminated ground may prevent more
water falling onto the soil and getting contaminated, In another
embodiment, SAP may be added to a leaking vessel containing a
contaminant. If the SAP settles in the leak, it would block further
leakage.
[0040] Salt assisted dehydration is a method for drying SAP, or in
this case, an SAP and fiber component. This method is much faster
than air-drying, and uses less energy than using heat alone to dry
the SAP. The method first includes contacting wet or dry super
absorbent polymer with a salt or aqueous salt solution, Preferably,
the salt used does not cause further crosslinking of the SAP. The
salt serves to draw water out of the wet SAP, This method also
includes decanting at least a portion of the salt water and water
extracted from the wet super absorbent polymer. The remaining
portion of the salt water and water extracted from the wet super
absorbent polymer may be evaporated. As the water evaporates, the
salt remains on the surface of the SAP, drawing even more water out
of the SAP particles. Finally, the dried salt may be removed from
the super absorbent polymer.
[0041] In some embodiments, about 2 grams of salt by dry weight may
be added for every gram of SAP dry weight. The initial dewatering
is driven by concentration of salt, and therefore more salt will
increase water removal before evaporation starts. Once the salt
water initially removed from the SAP is decanted, the remaining
process will evaporate the water and reach an equilibrium with the
salt concentrated on the surface of the SAP. Salt concentration may
be adjusted depending on whether a faster dehydration is desired,
or whether less salt is used to reduce cost.
[0042] In certain embodiments, removing the dried salt from the SAP
comprises placing the super absorbent polymer and salt in a dry
state into a rotating drum. The inside of the drum may include a
screen, or may have holes, slots or other openings or apertures.
The openings are large enough that the salt particles can pass
through, but small enough so that substantially all of the SAP and
fiber, if present, remain in the drum. The SAP may include
particles from 1/10 to 1/2mm. Consequently, it is preferred that
the holes in the drum are about 0.1 mm, or 0.0039 inches. The salts
used for salt assisted dehydration may include, for example, but
not limited to, NaCl, sea salt, calcium chloride, and potassium
salts. The potassium salts may include, for example, but not
limited to Potassium Chloride, Potassium Nitrate and potassium
carbonate.
[0043] Potassium salts are preferable because unlike other salts,
potassium salts may actually be beneficial to plants. Indeed,
potassium salts are a component of some fertilizers. Thus, when
potassium salts are included in a component including SAP that is
used as compost or some other agricultural product, the potassium
salts may benefit the environment, Further, the decanted water from
the salt assisted dehydration product may be used as a liquid
fertilizer because of its potassium salt content. Finally, it is
preferred that the salt used in salt assisted dehydration does not
include alum, or any other salt that causes further crosslinking or
irreversible contraction of the SAP, or is environmentally
unfriendly.
[0044] The methods of the present disclosure also provide a method
of producing both a reusable plastic and a reusable SAP from
separation of a product containing SAP, a fiber and a plastic into
its component parts. Examples of this method is described above
using a press and the embodiment depicted in FIG. 1. In these
methods, the products are first separated into components including
a plastics component including substantially plastic, but also some
SAP and fiber (plastic component), and an SAP and fiber component
(SAP and fiber component) including substantially SAP, waste and
fiber, but also some plastic. In these methods, water may be
removed SAP/fiber component with a method comprising salt assisted
dehydration, yielding a reusable SAP. Salt assisted dehydration is
described, above. The method may further include treating the
plastics component with a composition comprising alum in order to
remove or deactivate any residual alum in the plastic. In these
methods, the initial separation step may include shredding the
product, adding water to the product, and pressing the product
against a screen as described above. The press separates the
products into components including a plastics component, and a
super absorbent polymer and fiber component in these methods,
treating the plastics component further with a composition
including alum includes adding a composition including alum to the
plastic component as described above. One of the benefits of the
methods described in this disclosure is that any water recovered
may be used in a composting and biogas facility to adjust the
moisture of incoming materials.
[0045] Further embodiments of this disclosure include methods of
deactivating super absorbent polymer in a plastic component as part
of the separation of a product comprising a super absorbent
polymer, a fiber and a plastic. One of these embodiments is
depicted in FIG. 2. Initially, separating the products including a
super absorbent polymer may be achieved in a substantially dry
environment, unlike the method described above using a press.
[0046] One dry separation method uses a drum type filter separator,
for example, the Model FS-75 fluff separator (Ibis Company,
Hoschton, Ga., USA). This device uses a rotating filter with air
blowers and a vacuum system to draw the paper fiber away from the
plastic after they have been run through a shredder and a "buster
fan" that loosens and separates the diaper scraps. Air cyclones can
further separate the larger SAP particles from the fluff fiber
using the different densities and geometry to separate SAP and
fiber. These devices will only remove a percentage of the SAP, None
of the separated components have purity.
[0047] This process may yield a substantially dry super absorbent
polymer component, and a substantially dry fiber component, and a
substantially dry plastic component. Alum or a similar salt can be
introduced to these streams to condition either the fiber stream
with small amounts of SAP still carried with the paper fiber, or to
condition the plastics stream which also may include residual
SAP.
[0048] The fiber may be sent to an agitator tank and combined with
water and alum. Low levels of alum can be used to reflect the low
levels of SAP in the remaining fiber stream. The fiber stream can
now be partially dewatered to isolate the salt and water. The
dewatered pulp with small amounts of deactivated SAP can be added
to the pulp stream of a typical low end recycled paper mill without
any further separation being required. The remaining SAP particles
would be incorporated into the paper without seriously degrading
the final product. Without the SAP deactivation step, the expanding
SAP in the pulp would stick to the surface of the paper machine
felts and wires, plugging the surface and preventing water from
draining. The active SAP even in small amounts would create spots
in the paper commonly called "stickies" in the paper industry.
[0049] In the case of the plastics stream, a composition including
alum is added to the plastic component, as described above. This
method includes adding a composition comprising alum to the plastic
component.
[0050] Certain other embodiments of this disclosure include a
plastic product including the plastic component of any of the
methods described herein. Because any remaining SAP in the plastic
is deactivated, the plastic may be suitable for recycling into
other products including products that may be exposed to water. In
certain embodiments, the plastic component is recycled into a
plastic product including a product selected from the group
consisting of plastic lumber and roofing shingles, or any other
suitable plastic product. Other plastic products may be extruded,
cast, or molded into useful articles. Another embodiment of this
disclosure includes a method of making a plastic product including
using any of the plastic components described herein to make the
plastic product.
[0051] Certain other embodiments of the present disclosure include
a method of using recycled super absorbent polymer as an
agglomerating agent. This method may include treating the super
absorbent polymer with heat and/or a chemical in order to break the
crosslinking bonds to form substantially uncrosslinked super
absorbent polymer. This method may further include using the
substantially uncrosslinked super absorbent polymer as an
agglomerating agent. The agglomerating agent may be used in a
dissolved air flotation (DAF) process.
[0052] In other embodiments of this disclosure, separation of a
material containing SAP, a fiber component and a plastic component
includes shredding the material, adding a salt to the material and
agitating the material. In certain embodiments, the material is not
a slurry, as discussed below. One embodiment demonstrating this
process is depicted in FIG. 3. The material may be shredded before
agitating, or the material may be shredded through the act of
agitation itself, Shredding may occur during agitation merely by
the agitation of the material, or the shredding may occur as a
result of physical contact with the apparatus that is performing
the agitation, for example, but not limited to a rotating vessel.
The rotating vessel may have fins, blades, or other components to
assist in shredding the material.
[0053] As mentioned above, agitating the material may be
accomplished by a rotating vessel. Agitating may also be
accomplished by other methods, for example, but not limited to,
shaking, vibrating, stirring, blowing and cycloning.
[0054] In some embodiments, the salt dries or removes water from
the SAP through salt-assisted dehydration, as discussed above.
Water removed from the SAP and fiber is removed from the material.
Removal may occur by various methods, including draining,
decanting, pumping, and evaporating the water.
[0055] In certain embodiments, no water or very little additional
water is added to the material during salt-assisted dehydration
aside from the water already contained in the material. In certain
embodiments, less than 20% water by weight of the material is
added, In other embodiments, less than 15% water by weight of the
material is added. In still further embodiments, less than 10%
water by weight of the material is added. And in other embodiments,
less than 5% water by weight of the material is added.
[0056] In some embodiments, the material is heated during
salt-assisted dehydration. The heat may serve to evaporate the
water, such that it may be removed from the material as water
vapor. This may help to dry the SAP and material faster.
Evaporating water may increase the concentration of salt on the
surface of the SAP, which serves to draw more water out of the SAP
driven by the concentration gradient. In certain embodiments, the
material is heated in a vessel that is heated by a jacket or other
heat exchanger. In other embodiments, the material is heated by
injecting steam into a vessel that contains the material. In some
embodiments, the amount of water added as steam is from 1-10% by
weight of the material. In other embodiments, water added as steam
is about 5% by weight or less of the material. In certain
embodiments, water added as steam is about 50 liters per ton of
material or less.
[0057] In some embodiments, the salt being added to the material
may be in aqueous form to allow the use of dosing pumps to control
the amount of salt being added. In some embodiments, the amount of
salt solution added is from 1-10% by weight of the material. In
other embodiments, salt solution added is about 5% by weight or
less of the material. In certain embodiments, salt solution added
is about 50 liters per ton of material or less.
[0058] In certain embodiments, the combined amount of water added
as steam and as a salt solution is less than 500 liters per ton of
material. In other embodiments, the combined amount of water added
as steam and as a salt solution is less than 250 liters per ton of
material, in some embodiments, the combined amount of water added
as steam and as a salt solution is less than 100 liters per ton of
material. In other embodiments, the amount of total water added is
less than 75 liters per ton. In still other embodiments, the total
amount of water added may be less than 50 liters per ton or 25
liters per ton of material. In some embodiments, substantially no
additional water is added to the material.
[0059] In some embodiments, the amount of water added to the
material before separating is only as much as is required to heat
the material with steam and/or add a salt solution to the material
in metered doses. In these and other embodiments, the material does
not form or comprise a slurry.
[0060] A slurry may be described as "a thin, watery suspension . .
. " Lewis, Richard J., Hawley's Condensed Chemical Dictionary, Van
Nostrand Reinhold Co. (12.sup.th Ed., 1993). Another description is
"a thin mixture of an insoluble substance . . . with a liquid . . .
to prepare a suspension of (a solid in a liquid)." Random House
Webster's College Dictionary, Random House (2.sup.nd Ed., 1999). A
slurry is also described as a suspension or a "soupy" material,
possibly containing significant quantities of interstitial water
between the particles of solid matter. A slurry may be described as
a suspension of solids in a liquid. The solids in a slurry are
enveloped in the liquid phase of the suspension. Suspended solid
particles vary in size from very fine colloidal particles to
sedimentable coarse particles, with solid concentration affecting
the viscosity. Usui, Hiromoto, Powder Technology Handbook, 299, CRC
Press (3.sup.rd Ed., 2006), Fluid behavior, however, is the
hallmark of a slurry. Id. Thus, in some embodiments, less water is
added to the material than would be required to make it flow or
exhibit fluid behavior.
[0061] In embodiments of this disclosure, the solids are not
suspended in a liquid. There is little or no "free water" in the
solids mass. In some embodiments where salt is added to the
material, the salt requires the mechanical agitation to bring the
salt into direct contact with the surface of the SAP gel.
[0062] In other embodiments, the material is not submerged or put
in a bath of water or aqueous solution. In still other embodiments,
the material is not saturated by, or immersed in, water or aqueous
solution. In some embodiments, after adding water or aqueous
solution, the material cannot be poured like a liquid, sludge or
slurry. In some embodiments, the material does not comprise a
slurry, sludge or suspension from the addition of any water to the
material. In certain embodiments, the amount of water added to the
material is less than what would be added to a washing machine type
device. These types of devices typically use a perforated basket or
mesh cage inside, which may not be present in the vessels of
certain embodiments herein. In certain embodiments, water or "free
water" does not circulate through the material during
agitation.
[0063] In other embodiments, the material does not form or comprise
a sludge. A sludge may be described as a "thick, viscous mass."
Lewis, Richard J., Hawley's Condensed Chemical Dictionary, Van
Nostrand Reinhold Co. (12.sup.th Ed., 1993).
[0064] In some embodiments, the range of salt concentration in the
salt solution added to the material is from about 2% by weight to
15-20% by weight. In certain embodiments, the concentration depends
on the quantity of SAP in the process, which can vary. In some
embodiments, the amount of dry (non-aqueous) salt added to the
material in either dry or aqueous form is roughly equal to the dry
weight of the SAP. In some embodiments, the purity of the salt may
be as low as 17% by weight of industrial grade granulated alum. In
one embodiment, a weight of dry salt of about from 3% to 5% of the
weight of the material is added to the material in either dry form
or in a solution. In another embodiment salt in the amount of about
5% by weight of the incoming material is added.
[0065] In still further embodiments, the material may be
pressurized during salt-assisted dehydration, with or without heat.
The pressurization may occur naturally as a result of heat causing
water to evaporate while contained in a pressure vessel. In another
embodiment, the material may be pressurized in a pressure vessel
using a compressed fluid, for example, steam.
[0066] In some embodiments, the material undergoes salt-assisted
dehydration in an autoclave. The autoclave may heat, pressurize,
agitate and/or shred the material. In some embodiments, water is
only removed from the autoclave at or near the end of the
salt-assisted dehydration process. At this point, the pressure in
the autoclave is released and existing water vapor escapes. Liquid
water may also flash to vapor while pressure is being released.
Remaining liquid water may be removed, as described above, from the
autoclave. In other embodiments, water vapor is removed from the
autoclave while it is pressurized. In certain embodiments this is
done with a vacuum pump system.
[0067] The temperature of the autoclave may depend on the final use
of the material. In embodiments where the material needs to be
sterilized, the material may be held at 121.degree. C. for fifteen
minutes. In other embodiments, the material is heated to a
temperature that allows for sterilization, and kept at that
temperature for an effective amount of time. If sterilization is
not required, the process may be operated at ambient temperatures,
allowing the material to air-dry or vacuum dry. In some
embodiments, the autoclave should not heat the material to the
melting point of the plastic. If the plastic melts, it can bind to
the fiber and SAP making separation more difficult. In some
embodiments, the autoclave heats the plastic to a temperature less
than the melting point of the lowest-melting component of the
material. In other embodiments, the autoclave heats the material up
to from 125.degree. C. to 130.degree. C.,
[0068] In some embodiments, the autoclave is operated at
temperatures of from 100.degree. C. to 130.degree. C. in other
embodiments, the autoclave is operated at temperatures of from
121.degree. C. to 125.degree. C. In still other embodiments, the
autoclave may be operated at a temperature of about 121.degree.
C.
[0069] In some embodiments, the autoclave is operated at pressures
of from atmospheric pressure (about 1 bar) to over 4 bar. In other
embodiments, the autoclave is operated at pressures of from 1-3
bar. In other embodiments, the autoclave is operated at pressures
of from 2-2,3 bar, In still other embodiments, the autoclave may be
operated at a pressure of about 2.1 bar. In some embodiments, the
pressure in the autoclave is generated by merely heating the
material, which evaporates the water in the material. In other
embodiments, the autoclave is heated and pressurized by adding
steam. In certain embodiments, the steam may be at a pressure of
2.0-2.2 bar and a temperature of 121.degree. C.; to 125.degree.
C.
[0070] In some embodiments, the autoclave and/or salt-assisted
dehydration process removes from 30-99% of the water from the SAP
and other components of the material. In other embodiments, the
autoclave and/or salt-assisted dehydration process removes from
90-95% of the water from the SAP and other components of the
material. In still other embodiments, the autoclave and/or
salt-assisted dehydration process removes at least about 95% of the
water from the SAP and other components of the material.
[0071] In some embodiments, the material is subjected to a
separation process after leaving the autoclave. In some
embodiments, the separating process separates the material into a
component comprising mostly fiber and SAP with some plastic (fiber
and SAP component), and a component comprising mostly plastic with
some fiber and SAP (plastic component). In some embodiments, the
separation process is a dry separation process, meaning that the
material separated by the process is not a. slurry, or meaning that
no additional water is added for the separation process. In one
embodiment, this separation process includes a dry screen with
approximately one inch openings. In other embodiments, the openings
may range from 0.25''-2.0''. The screen retains most of the
plastics with a small amount of fiber, waste and SAP ("plastic
component"). In some embodiments, the plastics are sent to a
pulper/washer with approximately 0.06 inch openings, which adds
water to the plastic component to clean and further separate the
material. In other embodiments, the openings may range from
0.004''-0.5''. In some embodiments, the plastics may then be
recycled. In still further embodiments, the plastic may be further
reduced in size before or after washing. The reduced particle size
may range from 0,25''-0.5''.
[0072] In certain embodiments, fiber, waste and SAP removed in the
pulper/washer ("fiber and SAP component") is sent to a sidehill
screen with 0.03 inch openings. In other embodiments, the openings
may range from 0.10''-0.125''. Wastewater from the sidehill screen
is subjected to dissolved air filtration in some embodiments. In
other embodiments, the SAP, fiber and waste from the sidehill
screen is pressed to remove additional water. The SAP, fiber and
waste may then be recycled for use in energy production,
incineration, landfill, or other use.
[0073] In some embodiments, the SAP, fiber and waste that is
separated from the plastics and passes through the dry screen may
also be recycled for use in energy production, incineration,
landfill, or other use. In other embodiments, this dry material may
be used to make paper products.
[0074] In some embodiments, the salt used in the process may be any
salt discussed in this disclosure. In one embodiment, a salt that
causes shrinkage or dehydration, but no cross-linking may be used.
In other embodiments, a salt that causes cross-linking may used. In
certain embodiments, aluminum sulfate is used in the autoclave. One
benefit of using aluminum sulfate is that the SAP is deactivated so
that the fiber and plastic may be recycled.
[0075] Generally, the benefits of using this system where little to
no water is added are that since the components are deactivated and
separated in a substantially dry manner, the resulting separated
components are lighter and require less energy to process, dry and
ship. The process also consumes less water compared to a system
using wet pulping and other wet separation methods involving liquid
suspensions and/or slurries. Even when wet separation methods are
used in these embodiments, they are used further downstream and use
much less water than if water was added initially. In some
embodiments, other separation processes, including those described
in this specification, may be used to further separate and refine
the material.
[0076] FIG. 4 depicts an example of another embodiment of a dry
separation system. In this embodiment, the material is shredded
before being added to an autoclave or by the autoclave itself. The
material is subject to heat, pressure and agitation, but salt is
not added while the material is in the autoclave. In further
embodiments, the material is depressurized after heating and
agitating. In certain embodiments, the material does not comprise a
slurry. In some embodiments, the dehydrated material is separated
by a dry screen as described above. In certain embodiments, the
plastic from the dry screen with small amounts of fiber, SAP and
waste is also separated by a pulper/washer. However, in these
embodiments, salt may be added in addition to water in the
pulper/washer in order to deactivate the SAP.
[0077] In certain of these embodiments, the SAP, fiber and waste
from the dry screen may be composted or recycled in that form. In
other embodiments, however, salt and/or water may be added to the
SAP, fiber and waste. In some embodiments, the salt dehydrates the
SAP, but does not deactivate it. This stream may be placed in
containers, pasteurized or dried. The SAP, fiber and waste may then
be recycled by methods disclosed herein, for example, by combining
with seed. In these embodiments, the SAP is active for recycled
materials where retaining water is desired. This process has
benefits similar to the ones described above, but also may use less
salt. In some embodiments, other separation processes, including
those described in this specification, may be used to further
separate and refine the material.
EXAMPLE 1
[0078] FIG. 3 represents the process used in a pilot plant that has
been created to separate material containing SAP, a fiber component
and a plastic component. First, the material is shredded. Then, the
material is added to a rotating autoclave. Aluminum sulfate is
added to the autoclave either in dry form or by a salt solution
using a dosing pump. The salt helps to dehydrate and/or crosslink
the SAP during the process.
[0079] The material is heated during in the autoclave during
agitation. The heat disinfects the material and also speeds up the
dehydration of the SAP. The heat may also serve to evaporate the
water, which is removed from the material as water vapor.
Evaporating water may increase the concentration of salt on the
surface of the SAP, which serves to draw more water out of the SAP
driven by the concentration gradient. The autoclave is heated by a
jacket or other heat exchanger. In order to speed up the heating
process, steam is sometimes injected into the autoclave. The water
added as steam is about 50 liters per ton of material or less. When
salt is added as a solution, the water making up the solution is
about 50 liters per ton of material or less. Thus, the combined
amount of water added as steam and as a salt solution is less than
100 liters per ton of material.
[0080] The amount of water added is such that the material does not
form a suspension, slurry or sludge. The material is not agitated
in a bath like a washing machine. Instead, the water inherent in
the material is dried by the autoclave with only minimal addition
of other water
[0081] The amount of dry (non-aqueous) salt added to the material
in either dry or aqueous form can be roughly equal to the dry
weight of the SAP, but mostly the weight of dry salt is about from
3% to 5% of the weight of the material is added to the material in
either dry form or in a solution.
[0082] The autoclave is pressurized while agitating. The
pressurization occurs from a combination of the water native to the
material evaporating and injected steam. When the agitation is
complete, the pressure in the autoclave is released and existing
water vapor escapes. Some liquid water also flashes to vapor while
pressure is being released. Remaining liquid water, which is
minimal, is removed from the autoclave. In the future, a vacuum
pump will be installed to vent water vapor while the autoclave is
under pressure.
[0083] The material is held at 121.degree. C. for at least fifteen
minutes in the autoclave. The autoclave is operated at a pressure
of about 2.1 bar. The steam is at a pressure of about 2.0-2.2 bar
and a temperature of about 121.degree. C. to 125.degree. C.
[0084] The autoclave removes at least about 95% of the water from
the SAP and other components of the material with the addition of
only a minimal amount of water in the beginning of the process.
Overall, this process uses significantly less water than "washing
machine" style processes.
[0085] After leaving the autoclave, the material is subjected to a
dry separation process using a dry screen with approximately one
inch openings. The screen retains most of the plastics with a small
amount of fiber, waste and SAP ("plastic component"). The plastics
are sent to a pulper/washer with approximately 0.06 inch openings.
The plastics are then further reduced in size by a conventional
shredder and then recycled. The final particle size of the plastic
is about 0.25''-0.5''.
[0086] The fiber, waste and SAP removed in the pulper/washer
("fiber and SAP component") is sent to a sidehill screen with 0.03
inch openings. Wastewater from the sidehill screen is subjected to
dissolved air filtration. The SAP, fiber and waste from the
sidehill screen is pressed to remove additional water. The SAP,
fiber and waste is then recycled.
[0087] The present invention may be embodied in other specific
forms without departing from its essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not as restrictive. The scope of the present
invention is, therefore, indicated by the appended claims rather
than by the foregoing description. All changes which come within
the meaning and range of the equivalence of the claims are to be
embraced within their scope.
* * * * *