Patent Description:
In a first aspect the invention provides a method according to claim <NUM>. In a second aspect the invention provides a system according to claim <NUM>.

The written disclosure herein describes illustrative embodiments that are non-limiting and non-exhaustive. Reference is made to certain of such illustrative embodiments that are depicted in the figures, in which:.

The systems and methods described herein are configured for efficient recycling of waste plastics. Some systems and methods can quickly and simply convert waste plastics into one or more purified organic molecular species, which can be considered a hydrocarbon oil product. The hydrocarbon oil product may be readily stored, transported, and/or refined into fuel or other commercially relevant materials.

In some embodiments, waste plastic feedstock can be fed continuously through the systems disclosed herein. The feedstock may be pre-melted via a mixing, heating and compacting apparatus prior to introduction into a pyrolysis reactor, which then heats the pre-melted feedstock such that the feedstock transitions into a vapor (e.g., one or more gases) for further processing. In some instances, the vapor can be introduced into a condenser and directly contacted with a pH adjusted solution (or other process solution), which can, in some instances, absorb a portion of the vapor and condense another portion thereof. The condensed material can comprise one or more organic molecular species that can be termed herein as a hydrocarbon oil product. The hydrocarbon oil product can be separated from the other portions of the vapor that are absorbed into the pH adjusted solution, and thus the hydrocarbon oil product can be of a clean or purified quality such that it may be readily refined from a crude state. In other instances, other condensing apparatuses or methodologies may be used to condense out desirable products from the vapor discharged from the pyrolysis reactor or reactors.

In some instances, the feedstock may comprise waste plastics including an appreciable amount of halide compounds or heteroatoms from one or more sources of contamination and the system may be configured to recover a hydrocarbon oil product therefrom. The system may include a mixing, heating and compacting apparatus configured to receive a supply of the waste plastic feedstock and to output a densified melt of plastic material. An amendment comprising or consisting of alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum may be mixed, heated and compacted with the waste plastic based feedstock in the mixing, heating and compacting apparatus to form a densified melt of plastic material including the amendment. The system may further comprise a pyrolysis reactor configured to receive the densified melt of plastic material including the amendment, pyrolyze the densified melt of plastic material including the amendment, and output a hydrocarbon gas stream and a solids residue stream, the solid residue stream including a substantial portion of the halide compounds or heteroatoms of the waste plastic based feedstock via interaction of the halide compounds or heteroatoms with the amendment. Additionally, one or more condensers may be provided to condense out a hydrocarbon oil product from the hydrocarbon gas stream output from the pyrolysis reactor. In some instances, the system may be configured to condense out a tars product from the hydrocarbon gas stream output from the pyrolysis reactor with a quenching apparatus. The system may be further configured to route the tars product to a secondary pyrolysis reactor to generate a secondary hydrocarbon gas stream and a secondary solids residue stream. The secondary hydrocarbon gas stream may be further processed and combined with an altered hydrocarbon gas stream output from the quenching apparatus for subsequent processing by the one or more condensers to recover a hydrocarbon oil product.

Various systems and methods will now be described. Advantages of the systems and methods, as well as features and steps thereof, respectively, will be apparent from the disclosure that follows, including the Figures.

<FIG> provides a schematic diagram of a plastic recycling system <NUM> falling outside the scope of the invention, but which may be useful for understanding the invention. The plastic recycling system includes a heating system <NUM> that is configured to deliver heat to a plastic feedstock <NUM>. The heating system <NUM> can comprise any suitable heating mechanism, such as, for example, a combustion burner, a fluidized bed burner, a retort, or any other such heating system. In some instances, the heating system comprises a pyrolysis recovery unit (PRU). The PRU may include a dual screw feed mechanism to receive the plastic feedstock and simultaneously transport and pyrolyze the feedstock, and to output a hydrocarbon gas stream <NUM> and a solids residue stream <NUM>. The PRU may include multiple successive zones of heating along a length thereof.

The plastic feedstock <NUM> can comprise waste plastics of one or more varieties (e.g., mixed plastics), and may include trace amounts of non-plastic contamination or impurities. For example, the impurities may be of an external nature (e.g., water, foodstuffs, labeling, soil, paper, or cellulose waste) or may result from internal amendments of the waste plastics, such as fillers, plasticizers and other amendments, introduced at the time of manufacture of the waste plastics (e.g., glass, metal, iron, bromine, and/or chlorine). The plastic feedstock <NUM> may be provided in a ground, chipped, or other form that can promote the transfer of heat thereto.

The plastic feedstock <NUM> may be fed to the system in a continuous manner. A feed apparatus can include bins, hoppers, conveyors, mixers, heaters and compactors designed to provide a continuous material feed. The feed apparatus may comprise a mixing, heating and compacting apparatus <NUM> and may include a compactor and a pre-melter, such as a mixer designed to receive the feedstock and output a continuous stream of densified plastic melt. In other instances, the feedstock may be fed directly into the heating system (e.g., PRU) <NUM> without being subjected to pre-melting.

The heat provided by the heating system (e.g., pyrolysis recovery unit) <NUM> can be sufficient to crack or depolymerize the plastic feedstock <NUM> and convert at least a portion thereof into a vapor. The vapor can include one or more gaseous organic species, one or more gaseous inorganic species, and/or one or more varieties of entrained particles. In particular, the vapor can include depolymerized non-polar organic gases, which may be desirable for collection and refinement, and which can be mixed with impurities. The organic gases can include, for example, one or more paraffins, olefins, naphthenes, aromatics, and/or other classes of hydrocarbon materials. The mixed-in impurities can include, for example, inorganic acids (e.g., hydrochloric acid, hydrobromic acid), entrained metals or metalloids (e.g., cadmium, iron, antimony); and/or organic acids (e.g., terephthalic acid). The vapor may include additional molecular species, such as polar organic molecules, which may or may not be collected with the non-polar organic molecules. For example, the vapor can include one or more alcohols, ketones, ethers, phenols, carboxylic acids, or other polar organic molecules.

The plastic feedstock may be heated under vacuum conditions, or under negative pressure. The plastic feedstock may be heated under positive pressure. The plastic feedstock may be heated under atmospheric pressure conditions, or under any suitable combination of the foregoing (e.g., the pressure may be varied during a heating event).

The vapor can be delivered to a vapor treatment system <NUM> that effects a phase change of at least a portion of the vapor such that certain molecules transition from a gaseous state to a liquid state. The vapor treatment system <NUM> may also be referred to as a vapor treatment unit or a vapor treatment vessel. The vapor treatment system <NUM> may include a pH adjusted solution (or other process solution) that is used to effect the condensation. Moreover, the pH adjusted solution can be configured to absorb at least a portion of the impurities from the vapor. The solution may be able to readily absorb organic acids, inorganic acids, metals, metalloids, and/or certain polar organic molecules. The term "pH adjusted solution" is used in a broad sense and includes solutions that are not pH neutral and that exhibit any or all of the various properties described herein. For example, a pH adjusted solution can be formulated to remove impurities from the vapor, and can sometimes be immiscible with condensed oils so as to be readily separated therefrom. For example, the pH adjusted solution can comprise an acidic solution, which may, in some cases, be strongly acidic. The pH adjusted solution can comprise a buffered aqueous solution adjusted to a desired pH value. The pH adjusted solution can have a pH value that is less than <NUM>, less than about <NUM>, less than about <NUM>, less than about <NUM>, less than about <NUM>, less than about <NUM>, or less than about <NUM>.

The pH adjusted solution can include one or more chemical amendments of any suitable variety to achieve the desired properties of the solution. Such properties can include, for example, the ability to remove one or more impurities from the vapor and/or a high immiscibility with oil. Adjustment or optimization of one or more of foregoing properties may be achieved by altering the concentration of the one or more chemical amendments within the pH adjusted solution. For example, the presence, combination, and/or concentration of one or more materials within the pH adjusted solution can optimize removal of contaminants from the vapor as it interacts with the pH adjusted solution. The pH adjusted solution can include strong and/or weak inorganic acids (e.g., hydrochloric acid, acetic acid), one or more pH buffer solutions (e.g., acetic acid+sodium acetate), one or more chelating agents (e.g., ethylenediaminetetraacetic acid (EDTA)), and/or one or more coagulants and/or flocculants (e.g., calcium hydroxide, polyacrylamide).

The vapor treatment system <NUM> can be configured to effect direct contact between the vapor received therein and the pH adjusted solution (or other process solution). For example, as further discussed below, the pH adjusted solution may be sprayed into contact with the vapor, whereas sometimes the vapor may be bubbled through the solution. The pH adjusted solution can absorb or dissolve portions of the vapor (e.g., organic acids, inorganic acids, metals, metalloids, and/or certain polar organic molecules). The pH adjusted solution also can be provided at a lower temperature than that of the vapor such that the solution condenses at least those portions of the vapor that are immiscible therein (e.g., non-polar organic molecules).

Those portions of the condensed vapor that are immiscible in the pH adjusted solution (i.e., the hydrophobic portions) can be readily separated from the solution. The separation (or at least one or more stages thereof) takes place within the vapor treatment system, whereas sometimes, the separation (or at least one or more stages thereof) takes place within a separator <NUM> that is independent of the vapor treatment system <NUM>.

The immiscible portions may be removed from the vapor treatment system as a form of crude oil <NUM>. The crude oil <NUM> thus can have few or no impurities, as the impurities that were present in the plastic feedstock are dissolved or absorbed into the pH adjusted solution. Sometimes at least some of the dissolved or absorbed impurities can remain within the pH adjusted solution within the vapor treatment system <NUM>. For example, in some instances, after the pH adjusted solution has amassed the impurities, it may continue to be used within the vapor treatment system <NUM>, such that the impurities are not removed (at least not immediately) from the vapor treatment system <NUM>. In other or further embodiments, dissolved or absorbed impurities are removed from the vapor treatment system <NUM> separately from the oil <NUM>.

Certain classes of polar organic molecules may only partially (or at least partially) partition into the pH adjusted solution. For example, a portion of certain alcohols, ketones, ethers, phenols, carboxylic acids, and/or other polar organic molecules may partition into the pH adjusted solution and another portion thereof may partition into the crude oil. Accordingly, crude oil that includes a portion of a species of polar organic molecules may be separated from a pH adjusted solution that contains another portion of the species of polar organic molecules.

The vapor may include portions that do not condense within the vapor treatment system <NUM> and are not absorbed by the pH adjusted solution. Such non-condensable gases <NUM> can be removed separately from the vapor treatment system <NUM>, and may be combusted or disposed of in any other suitable manner.

The vapor treatment system <NUM> may operate under vacuum conditions, or under negative pressure. The vapor treatment <NUM> system may operate under positive pressure. The vapor treatment system <NUM> may operate under atmospheric pressure conditions, or under any suitable combination of the foregoing (e.g., the pressure may be varied during a condensing event).

The system can be well suited for quickly cracking or depolymerizing the plastic feedstock. For example, heating of the plastic feedstock and conversion thereof into the vapor can be performed at high temperatures at which a variety of different molecular species may be gasified simultaneously. Such different molecular species might have different vaporization temperatures at a given pressure, and a temperature at which the plastic feedstock is heated can exceed this temperature for some or all of the molecular species. The molecular species can then be separated from each other when the vapor is delivered to the vapor treatment system, as previously described. Accordingly, the system can operate without the heating system slowly heating up and occasionally holding steady at various discreet temperature levels along the way so as to allow for individual molecular species to be gasified sequentially. It is to be appreciated, however, the system may also be used in an operational mode in which the heating system and the plastic feedstock progress through a series of sequential heating steps or levels, as just described.

The system <NUM> can include a vacuum system <NUM> that is configured to maintain a negative pressure within the heating system (e.g., PRU) <NUM> and within the vapor treatment system <NUM>. The vacuum system <NUM> can continuously evacuate gases from the heating system (e.g., PRU) <NUM> such that depolymerization of the plastic feedstock occurs in an oxygen-deprived or oxygen-free environment. The vacuum system <NUM> draws the vapor into the vapor treatment system <NUM>, where it is contacted by the pH adjusted solution, or non-PH adjusted solution, or otherwise processed by a condensing apparatus or device. The vacuum system <NUM> draws the non-condensable gases <NUM> from the vapor treatment system <NUM>, and may distribute them to a combustion unit or other suitable disposal device <NUM> (e.g., emissions control device). In some instances, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger or other apparatus or system for energy recovery purposes. For instance, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger to supply heat for other aspects of the systems and methods of processing waste plastics described herein, such as, for example, supplying heat to the mixing, heating and compacting apparatus <NUM> (e.g., pre-melt extruder) to assist in generating the densified plastic melt for introduction into the heating system (PRU) <NUM>. In other instances, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger or other energy recovery device to supply energy for unrelated purposes.

The system <NUM> may include a coalescer/separator <NUM> that receives an emulsion of condensed material from the vapor treatment system <NUM>. The emulsion can comprise crude oil that includes a small amount of the pH adjusted solution (or other process solution) entrained therein. The coalescer/separator <NUM> can be configured to separate the crude oil <NUM> from the pH adjusted solution (or other process solution) based on the difference in relative density between these materials. For example, the coalescer/separator <NUM> can comprise a settling tank that allows gravitational separation of the solution from the crude oil <NUM>. In other systems or methods the coalescer/separator <NUM> may comprise a centrifuge or other separator device.

The system <NUM> can further include a variety of sensor and control components (not shown). For example, the system <NUM> can include one or more pressure sensors and/or temperature sensors, which can provide to a controller various data regarding the operation of the heating system (e.g., PRU) <NUM> and the amount of heat being delivered to the feedstock. The sensors can communicate with a controller in any suitable manner, such as by wired or wireless connection. The controller can alter operational parameters of the heating system (e.g., PRU) <NUM> in response to data received from the sensors and/or as a result of other programming.

A master control system may be configured to communicate with the controller, and may also be configured to communicate with additional controllers that may each be dedicated to subsystems of the plastic recycling system. For example, separate subsystem controllers may be dedicated to the vapor treatment system <NUM> and the vacuum system <NUM>, respectively. Sometimes, subsystem controllers may be situated locally (e.g., near the various subsystems with which they are associated), whereas the master control system may be situated in a supervisory station in which an operator can monitor the instantaneous status of the subsystems of the system <NUM> and make changes thereto as desired, whether onsite or offsite.

For the sake of convenience, subsystem controller(s) associated with a particular component may not be identified hereafter, nor will it be explicitly stated that a particular subsystem controller and/or the master control system is able to monitor and/or control the operation of a particular component of the plastic recycling system <NUM>, although such is understood. It is also noted that steps or control events discussed herein which can be effected by sub-controllers and/or the master control system may be embodied in machine-executable instructions that are to be executed by a general-purpose or special-purpose computer (or other electronic device). Alternatively, the steps or control events may be performed or instigated by hardware components that include specific logic for performing the steps or control events, or by a combination of hardware, software, and/or firmware. Some or all of the steps may be performed locally (e.g., via a subsystem controller) or remotely.

As the feedstock is heated in the heating system (e.g., PRU) <NUM>, the plastic feedstock eventually gasifies or vaporizes. The vapor can be introduced into the vapor treatment system <NUM> in any suitable manner. For example, the vapor may be introduced into a condensing tower of a condenser substantially without altering a trajectory of the vapor. The vapor may encounter a baffle upon entering the condensing tower.

Those portions of the vapor that are not condensed (i.e., non-condensable gases) may be passed to a caustic scrubber, which passes the remaining vapor through a caustic solution so as to chemically scrub the vapor (e.g., remove mercaptan sulfur species therefrom) and so as to neutralize trace levels of free inorganic acids. The remainder of the vapor may pass from the caustic scrubber through to an emissions control device (ECD) <NUM>. Any suitable vacuum system <NUM> may be used with the plastic recycling system <NUM> to move the vapor accordingly.

Any suitable emissions control device (ECD) <NUM> can be used with the plastic recycling system <NUM>. The emissions control device <NUM> can comprise a burner or other combustion device. Exhaust <NUM> from the emissions control device <NUM> may be vented to atmosphere. The hot exhaust <NUM> may instead be transferred to other portions of the plastic recycling system <NUM>.

The absorbed and condensed portions of the vapor may settle into a tank of the coalescer/separator <NUM> that includes one or more weirs. The pH adjusted solution (or other process solution), which retains the absorbed impurities, may facilitate coagulation of some contaminants which have a greater relative density than the condensed crude oil material <NUM>, and may settle to the bottom of the tank. Accordingly, the condensed crude oil <NUM> rises to the top of the tank and flows over the one or more weirs to be collected for further processing <NUM>, storage <NUM> or use.

In addition, downstream processing may be provided to purify the product streams discussed herein or fractionate said streams into specified hydrocarbon cuts. Process units for this purpose may include, but are not limited to, distillation, solvent extraction, adsorption, and catalyst treatment units.

In some instances, one or more supplemental condensers <NUM> may be provided to condense out light hydrocarbons <NUM> from the quenched pyrolysis gas <NUM>. The one or more streams of light hydrocarbons <NUM> may then be combined with the crude oil product <NUM>, or may be stored as separate hydrocarbon products. In some instances, at least a portion <NUM> of the light hydrocarbons <NUM> may be directed to the vapor treatment system <NUM> to assist in quenching the pyrolysis gases, namely, the hydrocarbon gas stream <NUM> output from the heating system (e.g., PRU) <NUM>. In some instances, at least a portion <NUM> of the light hydrocarbons <NUM> may be directed to the heating system (e.g., PRU) <NUM> to be reintroduced into the heating system (e.g., PRU) <NUM> for further processing.

<FIG> provides a schematic diagram of an embodiment of a plastic recycling system <NUM>, which is particularly well suited for producing one or more hydrocarbon oil products <NUM>, <NUM> from waste plastic feedstock <NUM>. Similar to the aforementioned system, a mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM> may be provided to receive a supply of waste plastic <NUM> and to output a densified melt of plastic material <NUM>. The system <NUM> may further include a pyrolysis recovery unit (PRU) <NUM> that is configured to receive the densified melt of plastic material <NUM> and pyrolyze the densified melt of plastic material <NUM> and output a primary hydrocarbon gas stream <NUM> and a primary solids residue stream <NUM>. The PRU <NUM> may comprise, for example, a dual screw feed mechanism within a reactor shell which is configured to simultaneously transport and heat the feedstock introduced into the PRU <NUM>. The PRU <NUM> may have multiple zones of heating along a length thereof to effectively heat the feedstock to a pyrolysis temperature as the material progresses from one end of the PRU <NUM> to the other.

The system <NUM> may further comprise a primary quenching apparatus <NUM> that is configured to receive the hydrocarbon gas stream <NUM> output from the PRU <NUM> and to condense out a tars product <NUM> for introduction into a supplemental tars pyrolysis reactor <NUM> for further processing, as discussed elsewhere herein. Similar to the PRU <NUM>, the supplemental tars pyrolysis reactor <NUM> may comprise a dual screw feed mechanism within a reactor shell which is configured to simultaneously transport and heat the material introduced into the supplemental tars pyrolysis reactor <NUM>. The supplemental tars pyrolysis reactor <NUM> may have multiple zones of heating along a length thereof to effectively heat the feedstock to a pyrolysis temperature as the material progresses from one end of the supplemental tars pyrolysis reactor <NUM> to the other. The PRU <NUM> and the supplemental tars pyrolysis reactor <NUM> may have different form factors, throughput capacities and/or different heating profiles.

The primary quenching apparatus <NUM> may also be configured to discharge an altered hydrocarbon gas stream <NUM> for further processing. A primary condenser and separator <NUM> may be provided to receive the altered hydrocarbon gas stream <NUM> from the primary quenching apparatus <NUM> and to condense out and separate a hydrocarbon oil product <NUM>. Additionally, a supplemental condenser and separator <NUM> may be provided to receive a discharged gas stream <NUM> from the primary condenser and separator <NUM> and to condense out and separate light hydrocarbons (e.g., methane, ethane, propane) to form a light hydrocarbon product <NUM> or to be combined with other product streams. The primary condenser and separator <NUM> and/or the supplemental condenser and separator <NUM> may be configured to direct a portion of the hydrocarbon oil product <NUM> and the light hydrocarbon product <NUM> upstream to the primary quenching apparatus <NUM> to assist in condensing out the tars product <NUM> from the hydrocarbon gas stream <NUM> output from the PRU <NUM>. In some instances, at least a portion of the hydrocarbon oil product <NUM> and/or at least a portion of the light hydrocarbon product <NUM> may be directed to the heating system (e.g., PRU) <NUM> to be reintroduced into the heating system (e.g., PRU) <NUM> for further processing.

Any remaining non-condensable gasses <NUM> may be processed as described in connection with the aforementioned system, including processing by an appropriate emissions control device <NUM> and under the influence of a vacuum system <NUM>. In some instances, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger or other apparatus or system for energy recovery purposes. For instance, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger to supply heat for other aspects of the systems and methods of processing waste plastics described herein, such as, for example, supplying heat to the mixing, heating and compacting apparatus <NUM> (e.g., pre-melt extruder) to assist in generating the densified plastic melt for introduction into the heating system (PRU) <NUM>. In other instances, the non-condensable gases <NUM> from the vapor treatment system <NUM> may be routed to a heat exchanger or other energy recovery device to supply energy for unrelated purposes.

Although multiple stage condenser/separators are shown and described herein, it is appreciated that the systems and methods described herein are not limited to the use of multiple stage condensing and separating, and may, in other instances, include a single stage condensing and separating apparatus or employ other well know systems and techniques for condensing and separating out one or more desired products, such as via distillation techniques and the like.

The hydrocarbon oil product stream may be filtered and chilled by a product filter <NUM> and a product chiller <NUM> prior to product storage or transport. In addition, downstream processing may be provided in some embodiments to purify the product streams discussed herein or fractionate said streams into specified hydrocarbon cuts. Process units for this purpose may include, but are not limited to, distillation, solvent extraction, adsorption, and catalyst treatment units.

As discussed above, the system <NUM> may comprise a primary quenching apparatus <NUM> that is configured to receive the hydrocarbon gas stream <NUM> output from the PRU <NUM> and to condense out a tars product <NUM> for routing to a tars pyrolysis reactor <NUM> for further processing. A supply of the tars product <NUM> may be temporarily stored in a tars tank <NUM> for subsequent processing or use. A portion of the tars product <NUM> may be bled off from the system <NUM> and routed via a tars bleed line <NUM> to an energy recovery unit or to an appropriate disposal system. At least some of the tars product <NUM> may be routed to the tars pyrolysis reactor <NUM> for pyrolysis of the tars product <NUM> into a secondary hydrocarbon gas stream <NUM> and a secondary solids residue stream <NUM>. The secondary solids residue stream <NUM> may be combined with the primary solids residue stream <NUM> and routed to an appropriate waste disposal system <NUM>.

Advantageously, the system <NUM> may further comprise a secondary quenching apparatus <NUM> that is configured to receive the secondary hydrocarbon gas stream <NUM> output from the tars pyrolysis reactor <NUM> and to condense out a supplemental hydrocarbon product <NUM>. The supplemental hydrocarbon product <NUM> may be combined with the tars product <NUM> output from the primary quenching apparatus <NUM> for reentry into the tars pyrolysis reaction <NUM> for further processing as discussed above. In this manner, a portion of the feedstock can be continuously refined by the tars pyrolysis reactor <NUM> to provide an exceptionally purified hydrocarbon based oil product.

The secondary quenching apparatus <NUM> may also be configured to discharge a supplemental altered hydrocarbon gas stream <NUM>. The supplemental altered hydrocarbon gas stream <NUM> may be combined with the altered hydrocarbon gas stream <NUM> from the primary quenching apparatus <NUM> and routed to the primary and secondary condenser and separators <NUM>, <NUM> for further processing as discussed above. In addition, the secondary quenching apparatus <NUM> may be configured to receive a portion of the hydrocarbon oil product <NUM> and/or the light hydrocarbon product <NUM> from the condenser and separators <NUM>, <NUM> to assist in condensing out the supplemental hydrocarbon product <NUM> from the secondary hydrocarbon gas stream <NUM> output from the tars pyrolysis reactor <NUM>.

In accordance with some aspects of the present invention, a supply of the waste plastic feedstock may include an appreciable amount of halide compounds (e.g., hydrogen chloride) or heteroatoms (e.g., sulfur, phosphorous) from one or more sources of contamination (e.g., halide containing plastics such as PVC, polymer additives, contaminants from food, soil, salt and other environmental sources). Advantageously, embodiments of the systems described herein may include an amendment feed arrangement <NUM> to enable the introduction of an amendment <NUM> to the feedstock to be pyrolyzed with the waste plastic material <NUM> and any contaminants therein. The amendment <NUM> may comprise, for example, alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum. In particular, the amendment <NUM> may comprise, for example, at least one of: calcium oxide (CaO); calcium hydroxide (Ca(OH)<NUM>); ferric oxide (Fe<NUM>O<NUM>); and alumina (Al<NUM>O<NUM>). The amendment <NUM> may be provided in the form of: a homogenous powder or particles; supported material on a solid substrate; or a slurry. For example, the amendment <NUM> may be provided in the form of a slurry having a solvent in the form of water, a hydrocarbon, or a hydrocarbon mixture. The amendment <NUM> may be provided in a concentration of between <NUM>% and <NUM>% by weight of the combined waste plastic feedstock and amendment, or between <NUM>% and <NUM>% by weight of the combined waste plastic feedstock and amendment, or about <NUM>% by weight of the combined waste plastic feedstock and amendment.

Advantageously, the amendment <NUM> may be combined with the waste plastic based feedstock prior to mixing, heating and compacting of the supply of the waste plastic based feedstock <NUM> to form the densified melt of plastic material <NUM>. For example, the supply of the waste plastic based feedstock <NUM> and the amendment <NUM> may be mixed, compacted and heated to at least about <NUM> degrees Celsius prior to introduction in the pyrolysis reactor <NUM> to provide a particularly advantageous densified melt of plastic material having the amendment interspersed therein. In addition, the waste plastic based feedstock <NUM> and the amendment <NUM> may be fed through an airlock <NUM> to substantially reduce or eliminate oxygen from the waste plastic based feedstock <NUM> and the amendment <NUM>. In this manner, the densified melt of plastic material <NUM> may comprise the amendment intermixed throughout the densified melt of plastic material <NUM> prior to supplying of the densified melt of plastic material <NUM> to the pyrolysis reactor <NUM> under oxygen free or low oxygen conditions. Although the airlock <NUM> is illustrated schematically in <FIG> as a separate component or sub-system, the airlock <NUM> may be integrated into the mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM>, when provided, or into the pyrolysis reactor <NUM> to provide oxygen free or low oxygen conditions within the pyrolysis reactor <NUM> during pyrolysis.

The amendment <NUM> may be mixed with the waste plastic based feedstock <NUM> prior to introduction into the mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM>, or may be mixed with the waste plastic based feedstock within the mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM> itself. In other less advantageous instances, the amendment <NUM> may be fed into the pyrolysis reactor <NUM> separate from the densified melt of plastic material <NUM> to be mixed with the plastic material within the pyrolysis reactor <NUM> itself. Still further, in embodiments where the mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM> may be omitted, the amendment <NUM> may be combined with the waste plastic based feedstock <NUM> and may forgo pre-melting prior to introduction of the materials into the pyrolysis reactor <NUM>.

In any event, upon pyrolysis of the waste plastic feedstock <NUM> intermixed with the amendment <NUM>, the pyrolysis reactor <NUM> is configured to output the hydrocarbon gas stream <NUM> for processing (as discussed above) and the solids residue stream <NUM>. Advantageously, in such instances, the solid residue stream <NUM> includes a substantial portion of the halide compounds or heteroatoms of the waste plastic based feedstock <NUM> via interaction of the halide compounds or heteroatoms with the amendment <NUM>. As such, the addition of the amendment <NUM> can assist to provide an exceptionally purified hydrocarbon based oil product by effectively removing halide compounds and heteroatoms from the product streams.

In view of the foregoing, it will be appreciated that various methods of processing waste plastics may be provided.

According to one example embodiment, a method of processing waste plastics may include: mixing, heating and compacting a supply of a waste plastic based feedstock including an appreciable amount of halide compounds or heteroatoms from one or more sources of contamination; providing an amendment comprising alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum to be mixed, heated and compacted with the waste plastic based feedstock to form a densified melt of plastic material including the amendment; supplying the densified melt of plastic material including the amendment to a pyrolysis reactor; pyrolyzing the densified melt of plastic material including the amendment within the pyrolysis reactor to generate a hydrocarbon gas stream and a solids residue stream, the solid residue stream including a substantial portion of the halide compounds or heteroatoms of the waste plastic based feedstock via interaction of the halide compounds or heteroatoms with the amendment; and condensing out the hydrocarbon based product from the hydrocarbon gas stream output from the pyrolysis reactor.

Providing the amendment may include mixing the amendment with the waste plastic based feedstock prior to or during the mixing, heating and compacting of the supply of the waste plastic based feedstock to form the densified melt of plastic material, such that the densified melt of plastic material comprises the amendment intermixed throughout the densified melt of plastic material prior to supplying of the densified melt of plastic material including the amendment to the pyrolysis reactor.

The method may further include, prior to mixing, heating and compacting the supply of the waste plastic based feedstock and the amendment, passing the supply of the waste plastic based feedstock and the amendment through an airlock to substantially reduce or eliminate oxygen from the waste plastic based feedstock and the amendment.

The method may further include routing the supplemental hydrocarbon product from the secondary quenching apparatus to the secondary pyrolysis reactor for further processing.

Furthermore, the method may include: mixing, heating and compacting the supply of the waste plastic feedstock to form a densified melt of plastic material; and supplying the densified melt of plastic material to the primary pyrolysis reactor. In some instances, the method may further include providing an amendment comprising alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum to be mixed, heated and compacted with the waste plastic based feedstock for introduction into the pyrolysis reactor. In yet other instances, the method may further include providing an amendment comprising alkaline earth oxides and/or hydroxides, oxides of iron, and/or oxides of aluminum to be combined with the waste plastic feedstock for pyrolysis treatment within the primary pyrolysis reactor without pre-melting.

It is appreciated that aspects of the systems and methods described herein may be applicable to treating mixed waste plastics comprising a variety of plastics types, or treating a waste plastic feedstock that may be characterized by including predominantly one or more particular waste plastics, such as, for example, a feedstock of predominately waste polystyrene from which a monomer (e.g., styrene) product may be recovered.

It is also appreciated that aspects of the systems and methods described herein may include the aforementioned mixing, heating and compacting apparatus (e.g., pre-melt extruder) <NUM>, <NUM> to receive a supply of waste plastic and to output a densified melt of plastic material, or, in other instances, the feedstock may be fed directly into the heating system or pyrolysis reactor (e.g., PRU) <NUM>, <NUM> without being subjected to pre-melting.

Still further, it is appreciated that various condensed product streams generated throughout the systems and methods described herein, may be routed back to the heating system or pyrolysis reactor (PRU) <NUM>, <NUM> to be reintroduced into the heating system or pyrolysis reactor (PRU) <NUM>, <NUM> for further processing, or may by routed elsewhere or sold as a separate product with or without additional conditioning of said product streams.

Claim 1:
A method of processing a waste plastic feedstock, the method comprising:
pyrolyzing a supply of the waste plastic feedstock within a primary pyrolysis reactor (<NUM>) to generate a primary hydrocarbon gas stream (<NUM>) and a primary solids residue stream (<NUM>);
condensing out a tars product (<NUM>) from the primary hydrocarbon gas stream (<NUM>) output from the primary pyrolysis reactor (<NUM>) with a primary quenching apparatus (<NUM>);
discharging a primary altered hydrocarbon gas stream (<NUM>) from the primary quenching apparatus (<NUM>);
pyrolyzing the tars product (<NUM>) within a secondary pyrolysis reactor (<NUM>) to generate a secondary hydrocarbon gas stream (<NUM>) and a secondary solids residue stream (<NUM>);
condensing out a supplemental hydrocarbon product (<NUM>) from the secondary hydrocarbon gas stream (<NUM>) output from the secondary pyrolysis reactor (<NUM>) with a secondary quenching apparatus (<NUM>);
discharging a supplemental altered hydrocarbon gas stream (<NUM>) from the secondary quenching apparatus (<NUM>);
combining the supplemental altered hydrocarbon gas stream (<NUM>) from the secondary quenching apparatus (<NUM>) with the primary altered hydrocarbon gas stream (<NUM>) from the primary quenching apparatus to form a combined altered hydrocarbon gas stream; and
condensing out a hydrocarbon oil product from the combined altered hydrocarbon gas stream with one or more condensers (<NUM>, <NUM>).