U.S. patent application number 12/814391 was filed with the patent office on 2010-12-02 for system for recycling plastics.
This patent application is currently assigned to Plas2Fuel Corporation. Invention is credited to Kevin C. DeWhitt.
Application Number | 20100305372 12/814391 |
Document ID | / |
Family ID | 42332595 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100305372 |
Kind Code |
A1 |
DeWhitt; Kevin C. |
December 2, 2010 |
SYSTEM FOR RECYCLING PLASTICS
Abstract
One embodiment of a method of recycling a plastic material
includes heating a plastic material in a treatment chamber in
incremental steps through a series of graduated temperature set
points wherein each graduated temperature set point corresponds to
a vaporization temperature of an individual by-product of said
plastic material, and pulling a vacuum of inert gas on the
treatment chamber at each temperature set point to selectively
remove an individual by-product corresponding to the temperature
set point.
Inventors: |
DeWhitt; Kevin C.;
(Longview, WA) |
Correspondence
Address: |
STOEL RIVES LLP - SLC
201 SOUTH MAIN STREET, SUITE 1100, ONE UTAH CENTER
SALT LAKE CITY
UT
84111
US
|
Assignee: |
Plas2Fuel Corporation
Tigard
OR
|
Family ID: |
42332595 |
Appl. No.: |
12/814391 |
Filed: |
June 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11510489 |
Aug 24, 2006 |
7758729 |
|
|
12814391 |
|
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Current U.S.
Class: |
585/241 ;
422/116 |
Current CPC
Class: |
C10B 53/07 20130101;
C10G 1/10 20130101; Y02P 20/143 20151101; C10B 47/18 20130101 |
Class at
Publication: |
585/241 ;
422/116 |
International
Class: |
C10G 1/10 20060101
C10G001/10; G05B 17/00 20060101 G05B017/00 |
Claims
1. A method of recycling a plastic material, comprising: heating a
treatment chamber including a plastic material to a first
predetermined temperature; pulling a vacuum on said treatment
chamber to remove a first gaseous product from said plastic
material; heating said treatment chamber to a second predetermined
temperature greater than said first predetermined temperature; and
pulling a vacuum on said treatment chamber to remove a second
gaseous product from said plastic material.
2. The method of claim 1 further comprising maintaining an oxygen
level in said treatment chamber below a combustion level of liquid
or gaseous products from said plastic material.
3. The method of claim 1 wherein said treatment chamber is held at
said first predetermined temperature until a sensor detects the
presence of said first gaseous product in an exiting stream from
said treatment chamber in an amount below a first predetermined
amount of said first gaseous product.
4. The method of claim 1 wherein said treatment chamber is held at
said second predetermined temperature until a sensor detects the
presence of said second gaseous product in an exiting stream from
said treatment chamber in an amount below a second predetermined
amount of said second gaseous product.
5. The method of claim 1 wherein said treatment chamber is held at
said first predetermined temperature for a time period determined
by a control system.
6. The method of claim 1 wherein said vacuum is pulled on said
treatment chamber utilizing an inert gas.
7. The method of claim 1 wherein a finished product of said method
comprises petroleum oil.
8. The method of claim 7 wherein said petroleum oil is removed in
liquid form from a bottom of said treatment chamber.
9. The method of claim 1 wherein said first and second gaseous
products are sequentially condensed in a condensation tank to
sequentially produce separated, liquified first and second
by-products.
10. The method of claim 1 wherein said first predetermined
temperature is less than a boiling point of a
highest-boiling-point-contaminant in said plastic material.
11. The method of claim 1 wherein said plastic material comprises
waste plastic containers including waste milk jugs and waste soda
bottles.
12. The method of claim 1 wherein said first predetermined
temperature is in a range of 270 to 330 degrees Celsius and said
first gaseous product comprises vaporized hydrochloric acid, and
said second predetermined temperature is in a range of 300 to 375
degrees Celsius and said second gaseous product comprises vaporized
bromine.
13. A system for recycling plastic material, comprising: a
treatment chamber for receiving plastic material therein; a heating
system that heats said treatment chamber; a vacuum system that
pulls a vacuum on said treatment chamber utilizing an inert gas;
and a control system including computer operable instructions that
control said heating system to heat said treatment chamber in
incremental steps through a series of graduated temperature set
points.
14. The system of claim 13 further comprising a sensing system that
detects an amount of a plurality of gaseous products pulled by said
vacuum system from said treatment chamber, wherein said control
system automatically controls said heating system based on
information received by said control system from said sensing
system.
15. The system of claim 14 wherein said sensing system detects when
an amount of a first gaseous product pulled by said vacuum system
from said treatment chamber falls below a predetermined first
value, and wherein said control system thereafter controls said
heating system to heat said treatment chamber from a first
predetermined temperature to a second predetermined
temperature.
16. The system of claim 15 wherein said sensing system detects when
an amount of a second gaseous product pulled by said vacuum system
from said treatment chamber falls below a predetermined second
value, and wherein said control system thereafter controls said
heating system to heat said treatment chamber from said second
predetermined temperature to a third predetermined temperature.
17. The system of claim 13 wherein said heating system comprises a
gas manifold that heats ambient air and a duct system that
circulates said heated ambient air around said treatment
chamber.
18. The system of claim 13 further comprising a vapor treatment
vessel connected to said treatment chamber, said vapor treatment
vessel including a vapor exit port and a liquid exit port.
19. The system of claim 18 further including a scrubber connected
to said vapor exit port of said vapor treatment vessel.
20. A method of recycling a plastic material, comprising: heating a
plastic material in a treatment chamber in incremental steps
through a series of graduated temperature set points wherein each
graduated temperature set point corresponds to a vaporization
temperature of an individual by-product of said plastic material;
and pulling a vacuum of inert gas on said treatment chamber at each
temperature set point to selectively remove an individual
by-product corresponding to said temperature set point.
Description
[0001] The creation of a mounting surplus of waste plastics has
increasingly negative environmental, economical and political
implications. Recycling waste plastic into usable end products has
heretofore been commercially unviable due to the production of a
blend of undesirable by-products that is difficult to further
separate or process, and the large energy costs associated with the
recycling process itself. It may be desirable to provide a system
and method of recycling plastics that reduces the problems
associated with undesirable by-products and that reduces the energy
costs of the recycling process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] FIG. 1 represents a schematic view of a recycling system
according to one embodiment of the present invention.
[0003] FIG. 2 is a plan view of the recycling system.
[0004] FIG. 3 is a cross sectional view of the system of FIG. 2
taken along section lines 3-3.
DETAILED DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 represents a schematic view of a recycling system 10
according to one embodiment of the present invention. System 10 may
be described generally as a system for recycling waste plastic
materials that provides dynamic, real-time process control. The
system allows the user to easily process commingled sources of
mixed waste plastic that may contain trace levels of non-plastic
contamination such as foodstuffs, labeling, soil, and the like. The
system uses a controllable energy system and vacuum (negative
pressure) to control a third variable, namely, dwell time within
the treatment chamber, to completely control the recycling
process.
[0006] In particular, the system provides a process for separately
removing individual by-products of the waste plastic such that the
by-products themselves are marketable end products. Some of the
individual by-products removed by the present system include
chlorine (found in polyvinylchloride plastics), bromine (utilized
as a flame retardant in many plastics), water (found on wet
feedstock), and the like.
[0007] System 10 (shown schematically in this figure) includes a
recirculating energy system 12 that may include a gas
manifold/burner system 14, ductwork 16 to direct the flow of heated
air, damper vents 18 capable of introducing or dispersing fresh
air, exhaust air and supply air, and a variable-supply air fan 20
capable of metering the amount of air heated by burner system
14.
[0008] System 10 may further include an air-tight process reactor
22 with the ability to hold a vacuum, and which may be completely
contained within the recirculating air system. Accordingly, the
energy contained in the air from burner system 14 may be
transferred to the contents of the reaction chamber of reactor 22.
The reactor 22 may include a vapor exit port 24 connected directly
to a vapor treatment vessel 26, such as a reflux heat exchanger,
via piping 25. The reactor 22 may also include a valved solid-waste
material port 28 at the bottom of the chamber. A waste material
container 30 may be connected to the valved process reactor 22
solid waste material port 28.
[0009] Vapor treatment vessel 26 may be directly linked to process
reactor 22 via piping 25. The internal temperature of vessel 26 may
be controlled by energy system 12 or a thermal fluid medium within
the vessel, which may control the temperature of vessel 26 by
transferring energy either into or out of vessel 26. The vapor
treatment vessel 26 may be equipped with two exit ports, a top exit
port 32 and a bottom exit port 34.
[0010] Top exit port 32 of vapor treatment vessel 26 may be
connected to a vapor scrubbing system 36 via a valved pipe train
38. A bulk oil collection vessel 40 may be connected via a valved
pipe train 42 to bottom exit port 34 of vapor treatment vessel 26.
A source of negative pressure, such as a pressure system, namely a
vacuum system 44, may be connected to vapor scrubber 36.
[0011] A process control system 46 may include computer operable
instructions that may utilize the output 49 from chemical process
feedback sensors 48 which may be connected to each of processor
reactor 22, to treatment vessel 26, and to scrubber 56. These
sensors 48 may generate process feedback loops 50 that provide
information to recirculating energy system 12, vapor treatment
vessel 26 and to vacuum system 44, in order to control and modify
the process on a real-time basis. Much of the equipment utilized in
this process will be well known to chemical or process engineers
skilled in the art.
[0012] The method of the invention will now be described in detail.
In particular, the invention provides for the pyrolytic cracking of
plastic materials which involves heating the plastic material in
the absence of oxygen so as to prevent combustion (as a potential
reaction pathway) from occurring. First, ground or chipped plastic
material 54 is introduced into process reactor 22. Plastic material
54 may be introduced by any means, such as by a screw auger (not
shown) or the like. After material 54 is placed within reactor 22
the reactor is sealed and vacuum-tested for seal integrity. The
reactor may then be purged with an inert gas, such as nitrogen, and
then a vacuum pressure pulled thereon by use of vacuum system
44.
[0013] Energy system 12 is then activated, and the air surrounding
reactor 22 is slowly heated as it circulates around the reactor
through ductwork 16 and returns to the burner chamber of burner
system 14. Controlling the amount of fresh air entering energy
system 12, the amount of hot exhaust air leaving energy system 12,
the intensity of burner 14, and the flow rate of air through energy
system 12 utilizing damper vents 18, allows reactor 22 to be
subjected to a precise temperature profile. Additionally, as
reactor 22 is heated, a variable pressure (positive or negative
pressure) may be applied to the reactor chamber using a pressure
system, such as vacuum system 44. During heating of reactor 22,
plastic materials 54 within the reactor may be agitated by any
means, such as by a paddle 74 (see FIG. 3) positioned within
reactor 22.
[0014] In this manner, three variables may affect the plastic
material 54 inside reaction chamber 22, namely, temperature,
pressure and dwell time. Together, these three parameters
constitute a processing profile, which may be either static or
dynamic. The processing profile may contain several sets of
discrete predetermined set points which may govern the temperatures
and pressures encountered by the bulk plastic material 54 during
the course of processing. A change in set point conditions may
include precise rates of change (versus time) in both the
temperature and pressure parameters. An analogous example would be
a gas chromatograph, which uses temperature rate programming and
flow rate (of an inert gas) through a columnar material to achieve
its objectives.
[0015] After sealing plastic material 54 in reactor 22 and
initiating energy system 12, the bulk plastic material 54 may then
be subjected to the initial, predetermined processing profile
conditions, which may include a discrete temperature and pressure,
as well as a temperature ramping rate, to move from the current
(ambient) temperature to the first predetermined temperature and
pressure set point in the processing profile. The ramping rate of
the reactor temperature through several vaporization set point
conditions may be chosen to be slow enough such that a particular
chemical component will be completely vaporized and removed from
reactor 22 prior to the next vaporization set point being reached.
Accordingly, such a slow ramp rate of the reactor temperature may
be defined herein as a discrete stepwise increase in temperature
within reactor 22 because complete vaporization of one component is
achieved before vaporization of the next component begins.
[0016] If the bulk plastic material 54 is composed of mixed plastic
waste, contaminants are likely to be present in the mixture.
Contaminants may include trace levels of water, food stuffs, paper
or cellulose waste, chemical or biological wastes, and the like.
Contaminants may also include specific molecules present in the
polymer such as chlorine in the case of polyvinylchloride plastic,
or bromine in the case of flame retardant materials embedded in the
plastic. As the temperature in reactor 22 increases, specific
chemical species reach their boiling point and begin to enter the
vapor phase. Once these individual contaminants reach their boiling
point, they will exit the reactor through piping 25 and move to
vapor treatment vessel 26.
[0017] The processing profile may allow for this elemental or
molecular speciation or separation of components of plastic
material 54 by ramping to particular predetermined temperature and
pressure set points and then maintaining these conditions for a
finite length of time before moving forward in the profile. As an
example, an initial set point from ambient conditions may be 100
degrees Celsius (.degree. C.) and 0.95 atmospheres (atm), which may
slightly exceed the boiling point conditions for water. At this
first set point condition, any moisture in the form of water
adhering to plastic 54 in reactor 22 will begin to boil and exit
the reaction chamber due to the vacuum pressure pulled on reactor
22 by vacuum system 44. The vacuum system may pull the individual
vaporized components from reactor 22 and into vessel 26 and
thereafter into a fume scrubber 36. In another embodiment, a slow
and steady temperature increase ramp rate may be utilized thereby
allowing one component to be fully vaporized and removed before
vaporization of a second component begins.
[0018] Referring again to the previous example, the water vapor
will exit reactor 22 and will enter vapor treatment vessel 26, with
the bulk plastic 54 and any other higher-boiling point materials
remaining behind in a solid, semi-solid or liquid phase in reactor
22. In this manner, the undesirable contaminant water is separated
from the remainder of bulk plastic material 54 without allowing
other contaminants to be removed with the water. In other words,
substantially pure water is removed from bulk plastics 54 such that
the substantially pure water may become a usable by-product instead
of an unseparated, undesirable by-product of the reaction. By
"substantially pure" Applicants mean that a trace amount of other
material may be included in the water, wherein the trace amount
does not chemically alter the properties of the separated
by-product removed during the process.
[0019] As the water vapor enters vapor treatment vessel 26, the
water vapor will encounter a controlled temperature environment.
The environment within the treatment vessel 26 may be controlled,
such as by energy system 12, in a manner to substantially ensure
that the substance entering the vessel either remains in the gas
phase or condenses from the gas to the liquid phase, as desired. In
the case of the water vapor, the environment within treatment
vessel 26 may ensure that the water vapor remains in the gas phase.
In other words, vessel 26 may be heated to a temperature above the
vaporization point of water, and/or the vacuum pressure increased,
such that the water vapor from reactor 22 remains in the vapor
phase as it is pulled through vessel 26 by vacuum system 44.
[0020] The water vapor may then exit treatment vessel 26 and enter
fume scrubber 36, which may be a vessel containing a liquid, or
aqueous media 56, such as pH adjusted or buffered water. Aqueous
and inorganic species that are pyrolyzed to a gas phase in reactor
22 and then move through fume scrubber 36 may be absorbed and/or
neutralized by aqueous media 56. In contrast, gaseous organic
species that move through fume scrubber 36, such as either
non-condensable gases (such as C.sub.1-C.sub.4 species) or higher
molecular-weight species, may condense upon interaction with
aqueous media 56 present in scrubber 36. Organic species that
condense will form a layer on top of aqueous media 56 present in
the scrubber and can be removed using chemical or mechanical
methods. The non-condensable species may be captured and contained
in an external pressure vessel 58 for use as an energy source in
conjunction with energy system 12.
[0021] Chemical sensors 48 within system 10 may monitor the
presence and/or absence, and the corresponding concentration of
chemical species, such as chloride, bromide, or the like, and
provide process feedback loops 50 to energy system 12, treatment
vessel 26, and vacuum system 44. For example, when the amount of
water vapor in pipe 32 falls to a predetermined set point or rate
according to sensor 48 and control system 46, the next set point in
the processing profile may be initiated, in which both the
temperature and/or vacuum pressure are increased by modifying
energy system 12 and vacuum system 44. These new set point
conditions could be imparted to reactor 22 in a discrete, stepwise
fashion, or in a linear gradient that gradually moves from set
point to set point such that there is some dwell time corresponding
to each predetermined set point.
[0022] One advantage of system 10 described herein is that the
entire processing profile may be programmable and can be changed
dynamically by control system 46 using feedback signals provided by
sensors 48. Further, if a particular set of conditions comprising a
processing profile exists or is developed that enables the end user
to optimize the pyrolytic process, those conditions could easily be
replicated for other reactors at the site.
[0023] Referring again to the system as shown, after the water
vapor has left the system 10, the processing profile may be changed
to a second set of predetermined conditions in which the
predetermined temperature may be, for example, in a range of 270 to
330.degree. C., such as a temperature of 300.degree. C., with the
pressure unchanged. At this temperature and pressure set point,
chlorine in the polyvinylchloride (PVC) polymer chain will
dehydro-dechlorinate, and chlorine gas and hydrochloric acid vapor
will be released from reactor 22. These species will encounter
vapor treatment vessel 26 and will, at this point in the processing
profile, remain in the gas phase and continue as vapor until
reaching fume scrubber 36. After the vapor enters fume scrubber 36
the species will be absorbed in scrubbing medium 56, with or
without neutralization.
[0024] When process feedback sensors 48 indicate to process control
system 46 a lack of new hydrochloric acid formation from reactor
22, or a level of hydrochloric acid below a predetermined minimum
threshold, the processing profile may then be moved by control
system 46 to the next set of predetermined processing conditions,
which may target, for example, the elimination of bromine in the
bulk plastic materials. Accordingly, for example, a third
predetermined set point, may be a temperature of 325.degree. C.
with an unchanged pressure, i.e., 0.95 atm, wherein the temperature
in a range of 300 to 375.degree. C., such as a temperature of
325.degree. C., may be slightly above a vaporization temperature of
bromine. Accordingly, in this manner, chlorine and bromine and/or
other contaminants within original bulk plastic materials 54 may be
separately removed from the original bulk plastic materials 54 such
that the separated by-products may themselves become desirable end
products, instead of unseparated, undesirable system by-products
that may require further separation.
[0025] After several of these "chromatographic speciation steps" in
the processing profile, the remaining materials in reactor 22 may
include only plastic polymer molecules in the liquid state and
carbon solids that are non-volatile. At this point, the processing
profile conditions in reactor 22 may be modified in order to begin
cracking the polymeric backbone of the remaining bulk materials. At
well defined temperature and pressure settings, the next molecules
to enter the vapor phase may be large, targeted, carbon chains, for
example, hydrocarbon chains having a length of C.sub.20-C.sub.60.
These may exit reactor 22 and encounter vapor treatment vessel 26,
where the environment of the treatment vessel 26 may cause the
higher molecular weight hydrocarbons to condense into liquid form
and exit vessel 26 gravimetrically through bottom exit port 34 to
tank 40.
[0026] This path of hydrocarbon condensate may be facilitated by
closing valve 38 on upper exit port 32, thereby preventing any
large hydrocarbon molecules from entering fume scrubber 36. The
processing profile would then be complete, and reactor 22 may be
allowed to cool to ambient conditions of temperature and pressure.
Any residual liquid and solid materials remaining in reactor 22 may
then be removed from reactor 22 by opening port 28 and allowing the
material(s) to enter waste solids container 30.
[0027] In this manner, waste plastic materials 54 may be treated
and useful end products generated, such as cracked hydrocarbon
material that may be utilized as petroleum fuel, water, chlorine
and bromine, each individually separated from one another. The
inventive system described may have a relatively low energy
consumption, and may utilize relatively low pressures, compared
with the methods of the prior art which typically use high
temperatures and/or high pressures. Such high temperatures and
pressures often lead to the formation of undesirable hydrocarbon
species such as aromatic compounds and solid carbon waste. By
avoiding such high temperatures and pressures, the inventive system
described herein employs lower pyrolytic temperatures and longer
exposure times, resulting in the formation of fewer undesirable
hydrocarbons like aromatic species. This change in the temperature
and time parameters also provides the system with the ability to
crack plastic wastes only to the point that the resulting heavy oil
may be further refined and/or modified using standard refinery
technology, with no need for elaborate condensation systems.
Moreover, the low temperatures and pressures utilized allow for a
great deal of enhanced flexibility, because the oil produced may be
further refined on-site or may be sold/transported to an offsite
small-scale refining operation.
[0028] Accordingly, the inventive system 10 has the following
advantages. The system provides a method of recycling mixed-waste
and single source plastics 54 into immediately usable products. The
system provides a method of isolating and removing volatile
contaminants, such as chlorine, from the plastic feedstock before
rendering the cracked plastics into usable products. The system
provides a programmable system/method that adjusts to various
blends or single-sources of feedstock so as to optimize the process
and the resultant products, such as processing polystyrene to
styrene monomer. Moreover, the use of a vacuum pulled on reactor 22
allows for complete elimination of separated vaporized components
from the reactor prior to the next component being vaporized and
removed from reactor 22.
[0029] FIG. 2 is a plan view of the recycling system 10. In
particular, energy system 12 is shown including a recirculation fan
20 and a burner 14. The energy source utilizes ductwork 16, dampers
18, cooling fan 6, and exhaust fan 7 to control temperature in the
reactor 22 and the vapor treatment vessel 26.
[0030] FIG. 3 is a cross sectional view of system 10 taken along
section lines 3-3 of FIG. 2. Scrubber 36 is shown as drums
positioned adjacent a vacuum pump 88 of vacuum system 44. Bulk
storage tank 40 is shown as a drum positioned below vapor treatment
vessel 26 and container 30 is shown as a tank positioned below
reactor 22. Reactor 22 includes a stirring paddle 74, attached by a
shaft coupling 76 to a motor 78.
[0031] The foregoing description of embodiments of the invention
have been presented for purposes of illustration and description.
It is not intended to be exhaustive or to limit the invention to
the precise form disclosed, and modifications and variation are
possible in light of the above teachings or may be acquired from
practice of the invention. The embodiments were chosen and
described in order to explain the principles of the invention and
its practical application to enable one skilled in the art to
utilize the invention in various embodiments and with various
modification as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
claims appended hereto and their equivalents.
* * * * *