CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63/403,415 filed September 2, 2022, the disclosure of which is incorporated herein by reference.

FIELD

[0002] Systems and methods are provided for recycling of plastic waste in crackers.

BACKGROUND

[0003] Processing of plastic waste is a subject of increasing importance. It would be desirable to have a processing pathway that allowed for conversion of plastic waste into liquid products. The liquid products can potentially be used as fuels, lubes and/or as a feedstock for production of olefin monomers. Although dedicated processing systems could be used for plastic waste conversion, such dedicated systems require substantial initial capital costs and a constant supply of waste plastic feed. Thus, it would be desirable to leverage an existing processing unit to be able to co-process plastic waste.

[0004] Another difficulty with conversion of plastic waste is that the properties of plastic waste can vary widely. Thus, it would be desirable to have a processing system and method that can tolerate variability in the plastic waste feed.

SUMMARY

[0005] Disclosed herein is an example method of processing plastic waste comprising: thermally cracking at least a plastic waste feed and a cracking feedstock to produce at least a cracking product comprising hydrocarbons, wherein the cracking feedstock comprises a T10 distillation point of 343°C or higher; measuring a contaminant concentration; and adjusting the plastic waste feed in response to the contaminant concentration.

[0006] Further disclosed herein is an example method of processing plastic waste comprising: physically processing a plastic waste feed to reduce a maximum particle size of the plastic waste feed; combining the plastic waste feed with a carrier fluid to form a combined feedstock; physically processing the combined feedstock to reduce a maximum particle size of solid particles in the combined feedstock; preheating the combined feedstock to cause solid particles in the combined feedstock to melt; and thermally cracking the combined feedstock to produce at least a cracking product comprising hydrocarbons. [0007] Further disclosed herein is an example method of processing plastic waste comprising: identifying target specifications required for a plastic waste feed; determining a mixture of at least two plastic waste compositions that meet the target specifications; mixing the at least two plastic waste compositions to form the plastic waste feed; and thermally cracking at least the plastic waste feed and a cracking feedstock to produce at least a cracking product comprising hydrocarbons, wherein the cracking feedstock comprises a T10 distillation point of 343°C or higher. [0008] These and other features and attributes of the disclosed methods and systems of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows. BRIEF DESCRIPTION OF THE DRAWINGS [0009] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein: [0010] FIG.1 is an illustrative depiction of a process for pre-treatment of plastic waste in accordance with embodiments of the present disclosure. [0011] FIG.2 is an illustrative depiction of a process for feeding plastic waste to a cracking reactor with a feed system in accordance with certain embodiments of the present disclosure. [0012] FIG.3 is an illustrative depiction of a fluidized bed coking system including a coker, a heater, and a gasifier in accordance with certain embodiments of the present disclosure. [0013] FIG.4 is an illustrative depiction of a fluidized bed coking system including a coker and a gasifier in accordance with certain embodiments of the present disclosure. [0014] FIG.5 is an illustrative depiction of a delayed coking system including a coker and a fractionator in accordance with certain embodiments of the present disclosure. DETAILED DESCRIPTION [0015] In various embodiments, systems and methods are provided for chemical recycling of artificial turf. In some embodiments, a process for chemical recycling of artificial turf includes thermally cracking a plastic waste feed to produce hydrocarbons. In some embodiments, the plastic waste feed is co-processed in the thermal cracking environment with a conventional cracking feedstock, such as petroleum vacuum residuum. While the systems and methods disclosed herein are suitable for thermally cracking the plastic waste feed in a variety of different cracking embodiments, they may be particularly suitable for thermally cracking the plastic waste feed in a coking environment, such as delayed coking and fluidizing coking environments. Cracking Feed [0016] In accordance with present embodiments, a plastic waste feed is cracked to produce hydrocarbons. In some embodiments, the plastic waste feed is co-processed with another cracking feedstock. [0017] The plastic waste feed includes one or more different types of plastic waste compositions. As used herein, the term “plastic waste” refers to a waste material that includes plastic in an amount of at least 50% by weight and can include plastic in an amount of at least 80%, at least 90%, or more by weight. A plastic waste composition is a composition that includes one or more types of plastic waste. Plastic waste compositions may include any of a variety of plastics, including thermoset and thermoplastic polymers. Examples of suitable plastics include polymers, such as polyethylene terephthalates (PET or PETE), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS), and combinations thereof. In some embodiments, the plastic waste composition includes plastic obtained from any source including, but not limited to, municipal, industrial, commercial or consumer sources. In some embodiments, the plastic waste composition includes post-consumer use plastics. Further examples of suitable plastic waste compositions include plastic obtained from a common source or from mixed sources, including mixed plastic waste obtained from municipal or regional sources and/or from waste streams of polyethylene terephthalates (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), and/or polystyrene (PS). Even further, examples of suitable plastic waste compositions include any of various used polymeric articles without limitation. Some examples of the many types of polymeric articles include: films (including cast, blown, and otherwise), sheets, fibers, woven and nonwoven fabrics, furniture (e.g., garden furniture), artificial turf, sporting equipment, bottles, food and/or liquid storage containers, transparent and semi-transparent articles, toys, tubing and pipes, sheets, packaging, bags, sacks, coatings, caps, closures, crates, pallets, cups, non-food containers, pails, insulation, and/or medical devices. Further examples include automotive, aviation, boat and/or watercraft components (e.g., bumpers, grills, trim parts, dashboards, instrument panels and the like), wire and cable jacketing, agricultural films, geomembranes, playground equipment, and other such articles, whether blow molded, roto-molded, injection-molded, or the like. The ordinarily skilled artisan will appreciate that such polymeric articles may be made from any of various polymer and/or non-polymer materials, and that the polymer materials may vary widely (e.g., ethylene- based, propylene-based, butyl-based polymers, and/or polymers based on any C2 to C40 or even higher olefins, and further including polymers based on any one or more types of monomers, e.g., C ₂ to C ₄₀ α-olefin, di-olefin, cyclic olefin, etc. monomers). Common examples include ethylene, propylene, butylene, pentene, hexene, heptene, octene, and styrene; as well as multi- olefinic (including cyclic olefin) monomers such as ethylidene norbornene (ENB) and vinylidene norbornene (VNB) (including, e.g., when such cyclic olefins are used as comonomers, e.g., with ethylene monomers). [0018] In some embodiments, the plastic waste compositions includes one or more plastics classified as plastic identification code (PIC) 1 to 7 by the Society of the Plastics Industry. For example, the examples of suitable plastics include one or more of the following plastics: polyethylene terephthalate classified as PIC 1; high-density polyethylene classified as PIC 2; polyvinyl chloride classified as PIC 3; low-density polyethylene classified as PIC 4; polypropylene classified as PIC 5; polystyrene classified as PIC 6; and polycarbonate and other plastics classified as PIC 7. Combinations of the various plastics classified as PIC 1 to PIC 7 are also suitable in accordance with present embodiments. [0019] In addition to polymers, a plastic waste composition can include a variety of other components. Such other components can include additives, modifiers, packaging dyes, and/or other components typically added to a polymer during and/or after formulation. The plastic waste compositions can further include any components (e.g., paper) typically found in plastic waste. Finally, the plastic waste composition can further be mixed with a carrier fluid so that the feedstock to the thermal cracking process corresponds to a solution or slurry of the plastic waste composition. [0020] In embodiments where the plastic waste feed is introduced into the thermal cracking environment at least partially as solids, having a small particle size can facilitate transport of the solids and/or reduce the likelihood of incomplete conversion. In some embodiments, the waste feedstock includes polymeric waste having a maximum particle size to 0.01 millimeter (“mm”) to 75 mm, 0.01 mm to 50 mm, 0.01 to 25 mm, 0.01 to 10 mm, 1 mm to 50 mm, 1 mm to 25 mm, 1 mm to 10 mm, 5 mm, or 0.1 mm to 5 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 1 mm to 5 mm, or 1 mm to 3 mm. For determining a maximum particle size, the particle size is defined as the diameter of the smallest bounding sphere that contains the particle. Additionally or alternately, the plastic waste in the plastic waste feed can be melted and/or pelletized to improve the uniformity of the particle size of the plastic particles. In some aspects, the plastic waste has a maximum particles size of 75 mm or less, 50 mm or less, 25 mm or less, 10 mm or less, or 5.0 mm or less. Additionally or alternately, bulk density of the plastic waste can be selected, for example, to facilitate transport. In some embodiments, the bulk density can be adjusted, for example, by compaction or pelletizing, among other techniques. In some embodiments, the plastic waste has a bulk density of 10 lb/ft ³ to 35 lb/ft ³ (160 kg/m ³ to 560 kg/m ³ ), or 20 lb/ft ³ to 35 lb/ft ³ (320 kg/m ³ to 560 kg/m ³ ), or 25 lb/ft ³ to 35 lb/ft ³ (400 kg/m ³ to 560 kg/m ³ ). [0021] In some embodiments, the plastic waste feed meets the target specifications for the thermal cracking environment. The target specification can include physical characteristics, chemical characteristics, or both. Examples physical characteristics of the specification may include particle size. Example chemical characteristics of the specification may include contaminant concentration. The contaminant limits on a thermal cracking unit (e.g., a coker unit) can be set by several design and operating factors with the specific limit determined by that specific unit and refining site configuration. For example, the specification may include an upper limit on a concentration of one or more contaminants in the plastic waste, such as total halides (e.g., chlorides, fluorides, bromides). In some embodiments, the specification may include an upper limit of 0.5 wt%, 0.1 wt%, or less on total halides in the plastic waste feed. These limits will broadly be set on the coker by furnace and reactor metallurgy, fractionator and fractionator overhead metallurgy, fractionator top operating temperature and these limits may be further influenced by corrosion risks from other factors. The unit fouling risk may also set limiting contaminant concentrations with specific fouling risks in furnace tubes, feed preheat exchangers, fractionator tower trays and product heat exchangers. The specific configuration of the routing of the coker product streams to downstream units may result in additional contaminant limits set by these downstream processes. The downstream processes could be limited by corrosion or catalyst deactivation concerns. Coker plastic feed composition may also be limited by coker unit yield and quality concerns. A unit may desire to limit the additional production of aromatics such as benzene or olefinic products or overall unit coke make. [0022] Optionally, a carrier fluid can also be included in the plastic waste feed to assist with introducing the plastic waste into the thermal cracking environment. For introduction into a thermal cracking environment, it can be convenient for the feedstock to be in the form of a slurry. If a carrier fluid is used for transporting the plastic waste feed, any suitable fluid can be used. Examples of suitable carrier fluids can include (but are not limited to) a wide range of petroleum or petrochemical products. For example, some suitable carrier fluids include crude oil, naphtha, kerosene, diesel, light or heavy cycle oils, catalytic slurry oil, and gas-oils. Other potential carrier fluids can correspond to naphthenic and/or aromatics solvents, such as toluene, benzene, methylnaphthalene, cyclohexane, methylcyclohexane, and mineral oil. Still other carrier fluids can correspond to refinery fractions, such as a gas oil fraction or naphtha fraction from a coker. As yet another example, a distillate and/or gas oil boiling range fraction can be used that generated by thermal cracking of the plastic waste feed, either alone or with an additional feedstock. [0023] In various embodiments, thermal cracking can be used to co-process a combined feedstock corresponding to a mixture of a conventional cracking feedstock and a plastic waste feed. In some embodiments, the conventional cracking feedstock is used as the carrier fluid for the plastic waste feed. The conventional cracking feedstock can correspond to one or more types of petroleum and/or renewable feeds with a suitable boiling range for thermal cracking, such as processing in a coker. The amount of plastic waste feed in the combined feedstock can correspond to 1% to 50%, 3% to 50%, 10% to 50%, 25% to 50%, 1% to 25%, 3% to 25%, 10% to 25%, or 3% to 15% by weight of the combined feedstock. The conventional cracking feedstock can correspond to 50% to 99% by weight of the combined feedstock to the coker. [0024] In some embodiments, the cracking feedstock for co-processing with the plastic waste feed can correspond to a conventional petroleum feedstock having a relatively high boiling fraction, such as a heavy oil feed. For example, the cracking feedstock portion of the feed can have a T10 distillation point of 343°C or more, or 371°C or more. As used herein, the distillation points are determined in accordance with ASTM D86. In the event that ASTM D86 is unsuitable for characterization of a sample, ASTM 2887 may be used instead. In some embodiments, the cooker feedstock has a T10 distillation point of 343°C to 650°C. Examples of suitable heavy oils for inclusion in the cracking feedstock include, but are not limited to, reduced petroleum crude; petroleum atmospheric distillation bottoms; petroleum vacuum distillation bottoms, or residuum; pitch; asphalt; bitumen; other heavy hydrocarbon residues; tar sand oil; shale oil; or even a coal slurry or coal liquefaction product such as coal liquefaction bottoms. Such feeds will typically have a Conradson Carbon Residue (ASTM D189-165) of at least 5 wt%, generally from 5 wt% to 50 wt%. In some embodiments, the feed is a petroleum vacuum residuum. [0025] Some examples of conventional petroleum feedstock suitable for processing in a delayed coker or fluidized bed coker can have a composition and properties within the ranges set forth below in Table 1. Table 1 Example Coker Feedstock Conradson Carbon 5 to 40 wt.% [0026 biomass having a suitable boiling range can also be used as part of the cracking feed. Such renewable feedstocks include feedstocks with a T10 boiling point of 340°C or more and a T90 boiling point of 600°C or less. An example of a suitable renewable feedstock derived from biomass can be a cracking oil feedstock derived at least in part from biomass. [0027] In some particular embodiments, the plastic waste feed and the conventional cracking feedstock (e.g., coker feedstock) are mixed to form a combined feedstock prior to entering the thermal cracking environment. In other embodiments, the plastic waste feed and the conventional cracking feedstock are separately introduced into the thermal cracking environment. More generally, however, any convenient method for introducing both the plastic waste feed and the cracking feedstock into the coking environment can be used. [0028] Prior to being introduced into the coking environment, the feedstocks (optionally in the form of a combined feedstock) are pre-heated in accordance with one or more embodiments. Pre-heating the feedstocks in one or more heating stages can increase the temperature of the feedstocks to a mixing and storage temperature, to a temperature related to the cracking temperature, or to another convenient temperature. [0029] In some embodiments, a portion of the pre-heating of a plastic waste feed can be performed by mixing the plastic waste feed with a cracking feedstock in a mixing tank and heating the mixture in the mixing tank. For example, a plastic waste feed and a cracking feedstock can be mixed in a heated stirred tank for storage operating at 200°C to 325°C, or 275°C to 325°C. In some embodiments, tank agitation aids in uniform dispersal of the plastic waste feed into resid and maintains slurry suspension. Heating in a mixing tank provides heat to the combined feedstock prior to introducing the combined feedstock into the cracking reaction environment. This can reduce or minimize additional cracking heat duty that would otherwise be required to heat the plastic waste feed to thermal cracking temperatures. In addition to heating, stripping of the combined plastic waste feed and cracking feedstock using a stripping gas can be performed in a mixing tank. Passing a stripping gas through the combined feedstock can assist with removing gases that are entrained in the combined feedstock. [0030] Still another option can be to mix the plastic waste feed with the cracking feedstock after the pre-heater furnace for the coker, in accordance with certain embodiments. In these embodiments, the cracking feedstock can be heated to a higher temperature in the pre-heater, and then the plastic waste feed can be added to the pre-heated cracking feedstock to heat the plastic waste feed. [0031] In some embodiments, the plastic waste in the combined feedstock is re-sized to further reduce particle size after mixing. For example, the combined feedstock from the mixing tank is then physically processed to reduce the particle size of the plastic waste. In some embodiments, the maximum particle size of the combined feedstock is reduced to about 5 mm or less, 2 mm or less, or 1 mm or less. For example, the combined feedstock is reduced to a particle size of 0.1 mm to 5 mm, 0.1 mm to 2 mm, or 0.1 mm to 1 mm. Examples of physical processing can include sizing of the plastic waste, for example, by crushing, chopping, shredding, and grinding (including cryogenic grinding). In some embodiments, the plastic waste is passed through milling equipment, such as a roller mill, to reduce particle size. Physical processing in the roller mill is able to provide particles with a consistent particle size in accordance with one or more embodiments. After the particle sizing the combined feedstock is pumped to the coking environment, such as the thermal cracking reactor. In some embodiments, combined feedstock from the particle size is pumped and then preheated before thermal cracking. [0032] In some embodiments, the plastic waste feed and/or combined feedstock is atomized prior to introduction to the thermal cracking reactor. For example, the plastic waste feed and/or combined feedstock can be atomized using an atomizing apparatus (e.g., nozzle assembly) with a fluid such as steam, nitrogen, fuel gas, or natural gas, among others. The fluid may be introduced in any suitable amount for atomization, including 0% to 5% by weight of the plastic waste feed and/or combined feedstock. Plastic Waste Pretreatment [0033] In various aspects, the plastic waste can be pre-treated prior to delivery into the coker reactor. Methods for pre-treating the plastic waste can include one or more of sorting, contaminant rejection, cleaning, particle sizing, and classification. One or more of these steps can be in equipment on site directly attached to the thermal cracking unit or in an upstream remote facility. [0034] In some embodiments, pretreatment of the plastic waste includes sorting the plastic waste to provide a sorted plastic waste. The sorting includes, for example, removal of non- plastic waste from the plastic waste. As previously noted, plastic waste is not necessarily 100% plastic such that the plastic waste can be sorted to remove non-plastic waste. In some embodiments, at least 5 wt%, at least 10 wt%, or least 50 wt% of the non-plastic waste is removed from the plastic waste. The sorting also includes, for example, sorting the plastic waste to provide two or more different grades of plastic wade. The sorting by grade may be based on chemical and/or physical parameters, including size, weight, density, volume, or a combination thereof. [0035] In some embodiments, pretreatment of the plastic waste includes contaminant rejection from the plastic waste to provide a purified plastic waste composition. Plastic waste can include a variety of contaminants, such as chlorides, metals, and minerals, among others, that can be problematic for subsequent processing. Specific examples of contaminants include, for example, sodium, mercury, bromine, fluorine, calcium, nitrogen, and oxygen. In some embodiments, the thermal cracking may have specifications for one or more of the contaminants, listing the amount of the contaminant that can be present in the plastic waste. Contaminant rejection includes removing at least a portion of the contaminants from the plastic waste to provide purified plastic waste. Contaminant rejection includes use of any suitable technique for removal of contaminants from the plastic waste. An example technique includes use of magnetic fields for removal of metal contaminants from the plastic waste. The magnetic fields may be generated, for example, using magnets or included magnetic fields from eddy current. In some embodiments, the plastic waste may be exposed to a magnetic field to remove at least a portion of the metal contaminants from the plastic waste. Another example for contaminant rejections includes application of centripetal or centrifugal forces for separation of contaminants (e.g., metal contaminants) that vary significantly from the other components of the plastic waste. Another example technique for contaminant rejection includes use of visual inspection or infrared devices. For example, infrared sorting units can apply an infrared light (e.g., in the near infrared spectrum of 0.75 to 1.4 micrometers) and uses a spectrometer to detect reflected light that can be used to identify the material passing through the light, which can then be rejected if it does not meet a preselected criteria. [0036] In some embodiments, contaminant rejection from the plastic waste compositions includes cleaning the plastic waste compositions to provide a cleaned plastic waste composition. For example, the plastic waste composition can be cleaned by washing, rinsing, and/or spraying the plastic waste composition with a solvent to remove at least a portion of the contaminants from the plastic waste composition. In some embodiments, the solvent includes water. The solvent also includes a detergent, caustic, or other solvent to enhance the wash process, in one or more embodiments. The cleaning may also include mechanical agitation and/or scrubbing to remove adherent contaminants on the plastic waste composition. [0037] In accordance with present embodiments, contaminant rejection removes at least a portion of the contaminants from the plastic waste. For example, at least 10 wt% of the contaminants in the plastic waste composition can be removed. In some embodiments, at least 50 wt%, at least 75 wt%, at least 90 wt%, or more of the contaminants in the plastic waste composition can be removed. [0038] In some embodiments, pre-treatment of the plastic waste composition includes sizing of the plastic waste in the plastic waste composition to reduce its particle size. Sizing includes, for example, performing a physical processing step on the plastic waste composition to reduce its particle size in preparation for the thermal cracking environment. For example, having a small particle size can facilitate transport of the solids and/or reduce the likelihood of incomplete conversion in thermal cracking. In some embodiments, the plastic waste composition is sized to enable conveyance into a mixing chamber, for example, by way of pneumatic transport, belt conveyance, or drum conveyance. In some embodiments, the plastic waste composition is sized to meet equipment minimum free path. For example, subsequent equipment may have restrictions that limits the particle size of the plastic waste. In some embodiments, the plastic waste is sized to facility subsequent melting of the solid particle into a slurry. For example, a smaller particle size should have a reduced heat duty required for melting. Examples of physical processing can include sizing of the plastic waste composition, for example, by crushing, chopping, shredding, and grinding (including cryogenic grinding). In some embodiments, the physical processing can be used to reduce the maximum particle size of 0.01 mm to 75 mm, 0.01 mm to 50 mm, 0.01 to 25 mm, 0.01 to 10 mm, 1 mm to 50 mm, 1 mm to 25 mm, 1 mm to 10 mm, 5 mm, or 0.1 mm to 5 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 1 mm to 5 mm, or 1 mm to 3 mm. Optionally, after the physical processing, the plastic waste composition can be sieved or filtered to remove larger particles. In some embodiments, the sieving or filtering can be used to reduce the maximum particle size to 75 mm or less, 50 mm or less, 25 mm or less, 10 mm or less, or 5.0 mm or less. [0039] Another pretreatment can be included melting of the plastic waste in the plastic waste composition, for example, in an extruder. After extruding, the melted plastic waste composition can either be directly mixed with a conventional cracking feedstock and/or a solvent, or the extruded plastic can be pelleted to form a desired particle size for the plastic waste feed. [0040] In some embodiments, pre-treatment of the plastic waste composition includes classification of the plastic waste. Classification includes, for example, analysis of the plastic waste composition by various methods or apparatus to determine characteristics of the plastic waste. The plastic waste composition is then classified based on the determined characteristics. For example, the plastic waste composition may be analyzed to determine chemical composition, size, weight, density, volume, and/or mass. Any suitable techniques may be used for analyzing the plastic waste composition, including spectroscopy that can be used to determine the type or types of plastics in the plastic waste composition. In some embodiments, the plastic waste composition is classified based on size with reject of plastic waste composition that is too large prior to subsequent blending with the conventional cracking feed. [0041] In some embodiments, pre-treatment of the plastic waste composition includes blending plastic waste compositions. For example, two or more different plastic waste compositions can be blended to provide a mixed plastic waste composition, which can then be included a plastic waste feed to a thermal cracking environment. The plastic waste composition can differ based on different physical or chemical parameters, including contaminants, size, weight, density, volume, or a combination thereof. For example, a first plastic waste composition with a concentration of a first polymer in an amount of about 50% by weight of the first plastic waste composition can be blended with a second plastic waste composition with a concentration of a second polymer in an amount of about 50% by weight of the second plastic waste composition. The two or more plastic waste compositions can be selected to provide a mixed plastic waste composition that meets the required specifications for the thermal cracking environment, thus allowing use of plastic waste compositions in the thermal cracking environment that could not otherwise be used due to the required specifications. For example, a plastic waste composition with a contaminant concentration, such as chloride concentration, that exceeds the specification could be blended with another plastic waste composition with a lower contaminant concentration to provide mixed plastic waste composition that is within the specification. [0042] FIG.1 illustrates a process 100 for pre-treatment of plastic waste in accordance with embodiments of the present disclosure. As illustrated, the process 100 includes providing plastic waste composition at block 102. The plastic waste composition from block 102 can be directed to an offsite waste handling facility 104 or shipped to an onsite waste handling facility 106. At the onsite waste handling facility 106, the plastic waste composition is received at an intake unit, such as receiving, at block 118 and then pretreated prior to thermal cracking. At the offsite waste handling facility 104, the plastic waste composition is pretreated prior to shipment to the onsite waste handling facility 106 for thermal cracking. For example, the plastic waste composition may be sorted, cleaned, and/or mixed at the offsite waste handling facility 104 to thermal cracking specifications. The offsite waste handling facility 104 includes a number of different units for pretreatment of the plastic waste composition that are located offsite as shown on FIG.1, but alternatively one or more of the units of FIG.1 can be located onsite. For example, the plastic waste composition may alternatively be sent to the onsite waste handling facility 106 for sorting, cleaning, and/or mixing to meet thermal cracking specifications. [0043] At the offsite waste handling facility 104, the plastic waste composition is first receiving in sorting at block 108. Sorting includes, for example, removal of non-plastic waste from the plastic waste. Sorting also includes, for example, separation of the plastic waste composition based on physical and/or chemical parameters. The sorted plastic waste composition can also have contaminants rejected at block 110. In contaminant rejection, at least a portion of the contaminants are removed from the plastic waste composition in accordance with one or more embodiments. The sorted plastic waste composition from sorting at block 108 can be directed to storage at block 112. In storage, the sorted plastic waste composition can be stored in multiple storage vessels such as a feed silo or other suitable vessel. Alternative, the sorted plastic waste composition from sorting at block 108 can be directed to sizing at block 114 to provide a sized plastic waste that is then directed to storage at block 112. Prior to storage, the sized plastic waste composition may also be cleaned by way of contaminant rejection at block 110. From the storage, the plastic waste composition can be directed to mixing at block 115. In mixing, the plastic waste composition may be mixed, for example, to meeting thermal cracking specifications. For example, two or more different plastic waste compositions may be mixed to meet thermal cracking specifications. From mixing, a mixed plastic waste composition may be packaged at block 116 for shipment to the thermal cracking facility. The mixed plastic waste composition may be packaged using any suitable technique to facilitate shipment, including bags, blocks, boxes, hopper trucks, rail cars, or barges. In some embodiments, the mixed plastic waste is shipped in a container made of recycled material or other material suitable for feed into the thermal cracking environment. For example, the shipping container may be made from polymers, such as polyethylene terephthalates (PET or PETE), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low- density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS), and combinations thereof. In these embodiments, the mixed plastic waste composition would not be removed from the shipping container at the thermal cracking facility but rather the mixed plastic waste composition and the shipping container would be comminuted together to form a plastic waste feed to the thermal cracking environment that includes the comminuted shipping container. In some embodiments, the density of the plastic waste composition is increased, for example, to reduce volume and, thus, maximized shipping. In some embodiments, the density of the plastic waste composition is reduced to 95 kg/m ³ to 1000 kg/ m ³ , 300 kg/m ³ to 1000 kg/ m ³ , or 400 kg/m ³ to 500 kg/ m ³ . [0044] At the onsite waste handling facility 106, the plastic waste composition is received at block 118. The plastic waste composition received at the onsite waste handling facility 106 can be mixed plastic waste from packaging at block 116, plastic waste received directly from block 102, or other suitable source plastic waste. The onsite waste handling facility 106 is onsite at a thermal cracking unit. At receiving, the plastic waste composition can be weighed or otherwise processed for intake into the facility. From receiving at block 118, the plastic waste composition is conveyed by way of particle transport at block 120 for further pretreatment in accordance with one or more embodiments. Any suitable technique for particle transport can be used to convey the plastic waste composition including dry or wet transport. Examples of suitable transport mechanisms include, for example, pneumatic transport, belt conveyance, hoists, and/or drum conveyance. In some embodiments, dry plastic waste composition uses pneumatic transport while wetted plastic waste uses mechanical transport, such as belts, conveyors, drums, and/or hoists. Wet transport includes screws, belts, draw conveyors, bucket elevators, slides, and bins, among others. Wet transport is suitable, for example, where the plastic waste includes a liquid, for example, water or hydrocarbon wetted plastic waste. In the illustrated embodiment, the plastic waste composition is conveyed to storage and blending at block 122. For example, the plastic waste composition may be stored and also blended with additional plastic waste, for example, to meet thermal cracking specifications. The plastic waste composition may be blended with an additional plastic waste composition either before or after storage. From block 122, the plastic waste composition may either be sent to particle sizing and classification at block 124 or contaminant rejection at block 126. In contaminant rejection, at least of a portion of the contaminants may be removed from the plastic waste composition prior to the particle sizing and classification of block 124. In particle sizing and classification, the plastic waste composition is further sized to reduced particle size in accordance with some embodiments. In particle sizing and classification, the plastic waste composition may also be analyzed, for example, to determine characteristics of the plastic waste composition, in accordance with some embodiments. From block 126, at least a portion of the plastic waste can be sent to the thermal cracking environment, in some embodiments. The plastic waste composition can be composition fed directly into the coker and/or mixed with a conventional cracking feedstock. In alternative embodiments, at least a portion of the plastic waste composition can be preheated at block 128. Preheating can reduce or minimize additional cracking duty that would otherwise be required to heat the plastic waste feed. The preheating can, for example, melt or otherwise soften the plastic waste in some embodiments. In some embodiments, the preheating includes melting the plastic in an extruder. After extruding, the melting plastic waste can be fed into the thermal cracking environment, for example, either directly or first mixed with a conventional cracking feedstock. In some embodiments, the preheated plastic waste composition can have further contaminant rejection at block 126 prior to feeding into the thermal cracking environment for removal of at least a portion of the contaminants from the plastic waste composition. [0045] In some embodiments, contaminants are measured and then used for feedback control of the plastic waste feed to the thermal cracking reactor. For example, the plastic waste feed may be adjusted in response to the measured contaminant concentration. Adjustment of the plastic waste feed included, for example, changing the feed rate and/or composition of the plastic waste feed. For example, the amount of one or more plastic waste compositions may be changed (e.g., increased or decreased) in response to the contaminant concentration. By way of example, the feed rate of the plastic waste feed may be reduced in response to the contaminant concentration. Any suitable technique may be used for contaminant measured, including, for example, sampling with lab analysis or on-line analyzers. In particular, embodiments, the contaminants are measured in a cracking product or a particular fraction of the cracking product. For example, the contaminants may be measured in the coker fractionator overhead gas stream (e.g., ethylene and lighter, or pentane and lighter); in the coker liquid products from the fractionator that can include naphtha, kerosene, light coker gas oil and heavy coker gas oil defined by boiling range of the products set by downstream processing; and/or in the sour water condensed from the top of the coker fractionator or in the top pump around after contacting the coker product vapors. Contaminant concentration could also be measured in any scrubbed gas stream from combined coker feedstock before the coker reactor from a pre- treatment step. These potential contaminants could be organic and inorganic halides including chlorine, fluorine, bromine, iodine. It could also include arsenic compounds, mercury or mercury compounds and Aldehydes and organic acids. The contaminants in the coker products may be different compounds in the feed to the coker reactor. Additional contaminants in the cracked products (e.g., cracked gas) that can be related back to feed quality also include NOx, carbon monoxide, and carbon dioxide. In addition, circulating coke can also be measured for sodium accumulation on fluidized cokers and flexicokers, for example. Plastic Waste Cracking [0046] In accordance with one or more embodiments, the plastic waste feed is cracked to produce more valuable cracking products. Thermal cracking is a process in which larger molecules are broken down to produce smaller, more useful molecules. For example, thermal cracking processes include thermally cracking long chain hydrocarbons (or other long chain molecules) into shorter chain molecules. Examples of suitable thermal cracking processes include coking, visbreaking, and pyrolysis. [0047] In some embodiments, the plastic waste feed is heated until melted, for example, to 150°C to 325°C or 275°C to 325°C. Contaminants may then be at least partially removed (e.g., filtered) from the melted plastic waste feed with the melted plastic waste feed then directly injected into a cracking reactor, which receives conventional cracking feedstock by way of a separate feed system. In the cracking reactor, the plastic waste feed and the conventional cracking feedstock are co-processed to generate valuable cracking products. [0048] In some embodiments, the plastic waste feed is heated until melted, for example, to 150°C to 325°C or 275°C to 325°C. Contaminants may then be at least partially removed (e.g., filtered) from the melted plastic waste with the melted plastic waste feed then mixed with conventional cracking feedstock with the combined feedstock injected into a cracking reactor. In the cracking reactor, the plastic waste feed and the conventional cracking feedstock are co- processed to generate valuable cracking products. [0049] In some embodiments, the plastic waste feed is heated until melted, for example, to 150°C to 325°C or 275°C to 325°C. Contaminants may then be at least partially removed (e.g., filtered) from the melted plastic waste feed with the melted plastic waste feed then introduced into a heated mixing chamber with a carried fluid. In the mixing chamber, the melted plastic waste feed and carried fluid are mixed to produce a mixed feedstock. In some embodiments, the mixing chamber is heated. The mixed feedstock may be further heated and/or physically processed for particle size reduction prior to injection into the cracking reactor. [0050] In some embodiments, the plastic waste feed is stored (e.g., at ambient conditions) and then physical transported without melting to a mixing chamber. In the mixing chamber, the plastic waste feed and carried fluid are mixed to produce a mixed feedstock. In some embodiments, the mixing chamber is heated. The mixed feedstock may be further heated and/or physically processed for particle size reduction prior to injection into the thermal cracking reactor. [0051] FIG. 2 illustrates an example system 200 for co-processing of plastic waste. As illustrated, the system 200 includes a plastic waste supply 202 and a conventional cracker feedstock supply 204. The plastic waste supply 202 can provided any suitable plastic waste composition suitable for use as a plastic waste feed, including plastic waste composition from the process 100 shown on FIG. 1. While not shown on FIG.2, the plastic waste feed can be preheated (e.g., block 128 on FIG. 1). As illustrated, a plastic waste feed including a plastic waste composition is provided from plastic waste supply 202 to a mixing chamber 208 by line 206. In some embodiments, the plastic waste feed provided to the mixing chamber 208 is melted or otherwise preheated. Also supplied to mixing chamber 208 is a carried fluid (e.g., a conventional cracker feedstock or other solvent) by line 210. In some embodiments, the carrier fluid is preheated. In some embodiments, the carried fluid is a conventional cracker feedstock supplied from convention cracker feedstock supply 204, which may be supplied, for example, to preheater 213 by line 212 with a preheated conventional crack feedstock then supplied to the mixing chamber 208. In the mixing chamber 208, the plastic waste feed and the conventional cracker feedstock are mixed to form a combined feedstock. In some embodiments, the mixture in the mixing chamber 208 is heated, for example, to 150°C to 325°C or 275°C to 325°C. Tank agitation aids in uniform dispersal of the plastic waste into the mixture and maintains slurry suspension. [0052] In the illustrated embodiment, the combined feedstock of the plastic waste feed and the conventional cracker feedstock is then provided to a particle sizer 216 by line 214. In the particle sizer 216, the particle size of the plastic waste feed is further reduced. The particle sizer 216 uses any suitable technique to size the combined feedstock including, for example, crushing, chopping, shredding, and grinding (including cryogenic grinding). The combined feedstock may be sized to provide a maximum particle size, for example, of 5 mm or less, 2 mm or less, or 1 mm or less. In some embodiments, the particle sizer 216 includes milling equipment, such as a roller mill. The combined feedstock is then pumped with pump 220 through line 218 to a combined feed preheater 222 and then fed to the cracking reactor 226 via line 224. The combined feed preheater 222 heats the combined feedstock, for example, to a temperature of 150°C to 370°C. The combined feed preheater 222 can be any suitable type of heater, including, for example, a heat exchanger or electric heater. In some embodiments, the combined feedstock is preheated by direct injection of hot oil. In some embodiments, the combined feedstock is preheated to melt the plastic waste and provide the combined feedstock with a viscosity of 2000 centipoise, 1000 centipoise, or less. For example, the combined feedstock is preheated such that at least 50 wt% of the plastic waste supplied to the cracking reactor 226 is melted. In some embodiments, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95wt%, or more of the plastic waste supplied to the cracking reactor 226 is melted. In some embodiments, the plastic waste is preheated in the combined feed preheater 222 without melting, for example, with 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95wt%, or more of the plastic waste supplied to the cracking reactor 226 in solid form. [0053] In the illustrated embodiment, a portion of the conventional cracker feedstock is supplied directly to the cracking reactor 226. As illustrated, a portion of the conventional cracker feedstock may be supplied by line 228 from the preheater 213 directly to the cracking reactor 226. In the illustrated embodiment, a portion of the plastic waste feed is also directly supplied to the cracking reactor 226 by line 230. This portion of the plastic waste feed can be in solid form or may be at least partially melted prior to addition to the cracking reactor 226. In some embodiments, at least some of the plastic waste feed is directed via line 232 for combination with conventional cracker feed in line 228 with the combined feed being fed to the cracking reactor 226 via line 228. [0054] In the cracking reactor 226, the plastic waste feed and the conventional cracking feedstock are cracked to produce more valuable cracking products, including various hydrocarbons. In some embodiments, the cracking products include a cracking effluent, which may include a gas, a liquid, or a mixture thereof. In the illustrated embodiment, the cracking effluent is provided via line 234 to a separator 236. Although shown as one unit, separator 236 may include several unit operations such as steam stripping, distillation, and quenching, for example, to separate the effluent from the cracking into various fractions, including, but not limited to, a fuel gas fraction 238, a naphtha fraction 240, a distillate fraction 242, and/or a gas oil fraction 244. The particular fractions produced from the separator 236 can vary as desired for a particular application. [0055] In some embodiments, analyzers 246a-246f are used for feedback control of the plastic waste feed. As illustrated, the analyzers 246a-246f may be placed on one or more feed and/or product lines for measurement of various components in the feed and/or product lines. In the illustrated embodiment, analyzer 246a is placed on line 224 to measure a combined feedstock of the plastic waste and a conventional cracking feedstock while analyzer 246b is placed on line 230 with direct injection of the plastic waste to the cracking reactor 226. In addition, the illustrated embodiment includes analyzers 246d-246g on various product lines, including fuel gas fraction 238, a naphtha fraction 240, a distillate fraction 242, and/or a gas oil fraction 244. While not shown, another analyzer may be placed, for example, to measure contaminants, such as total halides or hydrogen chloride in sour water from a fractionator. [0056] In some embodiments, the analyzers 246a-246f measure contaminants, such as chloride or other halides, such as fluorine and bromine. In response to the measurement of contaminant concentration from the one or more analyzers, for example, the plastic waste feed is adjusted. This adjustment includes one or more of adjusting the plastic waste ratio and/or adjusting the composition of the plastic waste feed. The plastic waste ratio includes the ratio of the plastic waste to the conventional cracking feedstock. For example, if one or more contaminants are high in the analyzers 246a-246f, the plastic waste ratio may be reduced, such that less of the plastic waste with the contaminant is processed. Reducing the plastic waste ratio includes, for example, reducing the feed rate of the plastic waste, for example, reducing the rate of direct plastic waste injection or the rate of plastic waste being combined with the conventional cracker feedstock. In other embodiments, the plastic feed includes one or more plastic waste compositions with the particular composition of the one or more plastic waste compositions being adjusted in response to the measurement of contaminant concentration. For example, if a particular contaminant concentration is too high, a plastic waste composition with that particular contamination can be adjusted such that its feed rate is reduced or potentially even stopped to control the contaminant level. In some embodiments, a concentration in the plastic waste feed of a plastic composition with chlorine can adjusted in response to a measure chlorine concentration, for example, the concentration may be reduced. [0057] One example of thermal cracking of the plastic waste feed includes coking in which longer chain molecules are thermally cracked to produce shorter chain molecules with excess carbon left behind in the form of petroleum coke. Coking processes in modern refinery settings can typically be categorized as delayed coking or fluidized bed coking. Fluidized bed coking is a petroleum refining process in which heavy petroleum feeds, typically the non-distillable residues (resids) from the fractionation of heavy oils are converted to lighter, more useful products by thermal decomposition (coking) at elevated reaction temperatures, typically 480°C to 590°C, and in most cases from 500°C to 550°C. Example heavy oils suitable for processing by the fluid coking process include heavy atmospheric resids, petroleum vacuum distillation bottoms, aromatic extracts, asphalts, and bitumens from tar sands, tar pits and pitch lakes of Canada (Athabasca, Alta.), Trinidad, Southern California (La Brea (Los Angeles), McKittrick (Bakersfield, Calif.), Carpinteria (Santa Barbara County, Calif.), Lake Bermudez (Venezuela) and similar deposits such as those found in Texas, Peru, Iran, Russia and Poland. [0058] Fluidized coking is carried out in a unit with a large reactor containing hot coke particles which are maintained in the fluidized condition at the required reaction temperature with steam injected at the bottom of the vessel with the average direction of movement of the coke particles being downwards through the bed. In particular embodiments, the combined feedstock is heated to a pumpable temperature, typically in the range of 350°C to 400°C, mixed with atomizing steam, and fed through multiple feed nozzles arranged at several successive levels in the reactor. Steam is injected into a stripping section at the bottom of the reactor and passes upwards through the coke particles descending through the dense phase of the fluid bed in the main part of the reactor above the stripping section. Part of the feed liquid coats the coke particles in the fluidized bed and is subsequently cracked into layers of solid coke and lighter products which evolve as gas or vaporized liquid. The residence time of the feed in the coking zone (where temperatures are suitable for thermal cracking) is on the order of 1 second to 30 seconds. Reactor pressure is relatively low in order to favor vaporization of the hydrocarbon vapors which pass upwards from dense phase into dilute phase of the fluid bed in the coking zone and into cyclones at the top of the coking zone where most of the entrained solids are separated from the gas phase by centrifugal force in one or more cyclones and returned to the dense fluidized bed by gravity through the cyclone diplegs. The mixture of steam and hydrocarbon vapors from the reactor is subsequently discharged from the cyclone gas outlets into a scrubber section in a plenum located above the coking zone and separated from it by a partition. It is quenched in the scrubber section by contact with liquid descending over sheds. A pump-around loop circulates condensed liquid to an external cooler and back to the top shed row of the scrubber section to provide cooling for the quench and condensation of the heaviest fraction of the liquid product. This heavy fraction is typically recycled to extinction by feeding back to the coking zone in the reactor. [0059] During a fluidized coking process, the coking feedstock, pre-heated to a temperature at which it is flowable and pumpable, is introduced into the coking reactor towards the top of the reactor vessel through injection nozzles which are constructed to produce a spray of the feed into the bed of fluidized coke particles in the vessel. Temperatures in the coking zone of the reactor are typically in the range of 450°C to 650°C and pressures are kept at a relatively low level, typically in the range of 0 kPag to 700 kPag, and most usually from 35 kPag to 320 kPag, in order to facilitate fast drying of the coke particles, preventing the formation of sticky, adherent high molecular weight hydrocarbon deposits on the particles which could lead to reactor fouling. In some embodiments, the temperature in the coking zone can be 450°C to 600°C, or 450°C to 550°C. The conditions can be selected so that a desired amount of conversion of the feedstock occurs in the fluidized bed reactor. For example, the conditions can be selected to achieve at least 10 wt% conversion relative to 343°C (or 371°C), or at least 20 wt% conversion relative 343°C (or 371°C), or at least 40 wt% conversion relative to 343°C (or 371°C), such as up to 80 wt% conversion or possibly still higher. The light hydrocarbon products of the coking (thermal cracking) reactions vaporize, mix with the fluidizing steam and pass upwardly through the dense phase of the fluidized bed into a dilute phase zone above the dense fluidized bed of coke particles. This mixture of vaporized hydrocarbon products formed in the coking reactions flows upwardly through the dilute phase with the steam at superficial velocities of roughly 1 to 2 meters per second (~ 3 to 6 feet per second), entraining some fine solid particles of coke which are separated from the cracking vapors in the reactor cyclones as described above. In embodiments where steam is used as the fluidizing agent, the weight of steam introduced into the reactor can be selected relative to the weight of feedstock introduced into the reactor. For example, the mass flow rate of steam into the reactor can correspond to 6.0% of the mass flow rate of feedstock, or 8.0% or more, such as up to 10% or possibly still higher. The amount of steam can potentially be reduced if an activated light hydrocarbon stream is used as part of the stripping and/or fluidizing gas in the reactor. In such embodiments, the mass flow rate of steam can correspond to 6.0% of the mass flow rate of feedstock or less, or 5.0% or less, or 4.0% or less, or 3.0% or less. Optionally, in some embodiments, the mass flow rate of steam can be still lower, such as corresponding to 1.0% of the mass flow rate of feedstock or less, or 0.8% or less, or 0.6% or less, such as down to substantially all of the steam being replaced by the activated light hydrocarbon stream. The cracked hydrocarbon vapors pass out of the cyclones into the scrubbing section of the reactor and then to product fractionation and recovery. [0060] In a general fluidized coking process, the coke particles formed in the coking zone pass downwards in the reactor and leave the bottom of the reactor vessel through a stripper section where they are exposed to steam in order to remove occluded hydrocarbons. The solid coke from the reactor, consisting mainly of carbon with lesser amounts of hydrogen, sulfur, nitrogen, and traces of vanadium, nickel, iron, and other elements derived from the feed, passes through the stripper and out of the reactor vessel to a burner or heater where it is partly burned in a fluidized bed with air to raise its temperature from 480°C to 700°C to supply the heat required for the endothermic coking reactions, after which a portion of the hot coke particles is recirculated to the fluidized bed reaction zone to transfer the heat to the reactor and to act as nuclei for the coke formation. The balance is withdrawn as coke product. The net coke yield is only 65 percent of that produced by delayed coking. [0061] For a coking process that includes a gasification zone, the cracking process proceeds in the reactor, the coke particles pass downwardly through the coking zone, through the stripping zone, where occluded hydrocarbons are stripped off by the ascending current of fluidizing gas (steam). They then exit the coking reactor and pass to the gasification reactor (gasifier) which contains a fluidized bed of solid particles and which operates at a temperature higher than that of the reactor coking zone. In the gasifier, the coke particles are converted by reaction at the elevated temperature with steam and an oxygen-containing gas into a fuel gas including carbon monoxide and hydrogen. [0062] The gasification zone is typically maintained at a high temperature ranging from 850°C to 1,000°C and a pressure ranging from 0 kPag to 1000 kPag, preferably from 200 kPag to 400 kPag. Steam and an oxygen-containing gas are introduced to provide fluidization and an oxygen source for gasification. In some embodiments, the oxygen-containing gas can be air. In other embodiments, the oxygen-containing gas can have a low nitrogen content, such as oxygen from an air separation unit or another oxygen stream including 95 vol% or more of oxygen, or 98 vol% or more, are passed into the gasifier for reaction with the solid particles including coke deposited on them in the coking zone. In embodiments where the oxygen- containing gas has a low nitrogen content, a separate diluent stream, such as a recycled CO ₂ or H ₂ S stream derived from the fuel gas produced by the gasifier, can also be passed into the gasifier. [0063] In the gasification zone the reaction between the coke and the steam and the oxygen- containing gas produces a hydrogen and carbon monoxide-containing fuel gas and a partially gasified residual coke product. Conditions in the gasifier are selected accordingly to generate these products. Steam and oxygen rates (as well as any optional CO2 rates) will depend upon the rate at which cold coke enters from the reactor and to a lesser extent upon the composition of the coke which, in turn will vary according to the composition of the heavy oil feed and the severity of the cracking conditions in the reactor with these being selected according to the feed and the range of liquid products which is required. In some embodiments, the fuel gas product from the gasifier contains entrained coke solids and these are removed by cyclones or other separation techniques in the gasifier section of the unit. Suitable cyclones include internal cyclones in the main gasifier vessel itself or external in a separate, smaller vessel as described below. The fuel gas product is taken out as overhead from the gasifier cyclones. The resulting partly gasified solids are removed from the gasifier and introduced directly into the coking zone of the coking reactor at a level in the dilute phase above the lower dense phase. [0064] In some embodiments, the coking conditions can be selected to provide a desired amount of conversion relative to 343°C. Typically, a desired amount of conversion can correspond to 10 wt% or more, or 50 wt% or more, or 80 wt% or more, such as up to substantially complete conversion of the feedstock relative to 343°C. [0065] The volatile products from the coke drum are conducted away from the process for further processing. For example, volatiles can be conducted to a coker fractionator for distillation and recovery of coker gases, coker naphtha, light gas oil, and heavy gas oil. Such fractions can be used, usually, but not always, following upgrading, in the blending of fuel and lubricating oil products such as motor gasoline, motor diesel oil, fuel oil, and lubricating oil. Upgrading can include separations, heteroatom removal via hydrotreating and non- hydrotreating processes, de-aromatization, solvent extraction, and the like. The process is compatible with processes where at least a portion of the heavy coker gas oil present in the product stream introduced into the coker fractionator is captured for recycle and combined with the fresh feed (coker feed component), thereby forming the coker heater or coker furnace charge. The combined feedstock ratio (“CFR”) is the volumetric ratio of furnace charge (fresh feed plus recycle oil) to fresh feed to the continuous fluidized coker operation. Fluidized coking operations typically employ recycles of 5 vol% to 35% vol% (CFRs of 1.05 to 1.35). In some embodiments, there can be no recycle and sometimes in special applications recycle can be up to 200%. [0066] The Flexicoking™ process, developed by Exxon Research and Engineering Company, is a type of fluid coking process that is operated in a unit including a reactor and a heater, but also including a gasifier for gasifying the coke product by reaction with an air/steam mixture to form a low heating value fuel gas. A stream of coke passes from the heater to the gasifier where all but a small fraction of the coke is gasified to a low-BTU gas (˜120 BTU/standard cubic feet) by the addition of steam and air in a fluidized bed in an oxygen- deficient environment to form fuel gas including carbon monoxide and hydrogen. In a conventional Flexicoking™ configuration, the fuel gas product from the gasifier, containing entrained coke particles, is returned to the heater to provide most of the heat required for thermal cracking in the reactor with the balance of the reactor heat requirement supplied by combustion in the heater. A small amount of net coke (1 percent of feed) is withdrawn from the heater to purge the system of metals and ash. The liquid yield and properties are comparable to those from fluid coking. The fuel gas product is withdrawn from the heater following separation in internal cyclones which return coke particles through their diplegs. [0067] In this description, the term “Flexicoking” (trademark of ExxonMobil Research and Engineering Company) is used to designate a fluid coking process in which heavy petroleum feeds are subjected to thermal cracking in a fluidized bed of heated solid particles to produce hydrocarbons of lower molecular weight and boiling point along with coke as a by-product which is deposited on the solid particles in the fluidized bed. References to fluidized cokers are intended to include conventional fluidized cokers as well as flexicokers. The resulting coke can then be converted to a fuel gas by contact at elevated temperature with steam and an oxygen-containing gas in a gasification reactor (gasifier). This type of configuration can more generally be referred to as an integration of fluidized bed coking with gasification. FIGS. 3 and 4 provide examples of fluidized coking reactors that include a gasifier. [0068] FIG. 3 shows an example of a Flexicoker unit (i.e., a system including a gasifier that is thermally integrated with a fluidized bed coker) with three reaction vessels: reactor, heater and gasifier. The coking system 300 includes coker reactor 302 with the coking zone and its associated stripping and scrubbing sections (not separately indicated), heater 304 and gasifier 306. A cracking feedstock, which may be a plastic waste feed (or combined feedstock of plastic waste feed and conventional cracking feedstock) is introduced into the coking system 300 by line 308 and cracked hydrocarbon product withdrawn through line 310. While FIG.3, shows a combined feedstock, example embodiments also include separate introduction of the conventional cracking feedstock and plastic waste feed to the coker reactor 302. Fluidizing and stripping steam is supplied by line 312. Cold coke is taken out from the stripping section at the base of coker reactor 302 by means of line 314 and passed to heater 304. The term “cold” as applied to the temperature of the withdrawn coke is, of course, decidedly relative since it is well above ambient at the operating temperature of the stripping section. Hot coke is circulated from heater 304 to coker reactor 302 through line 316. Coke from heater 304 is transferred to gasifier 306 through line 318 and hot, partly gasified particles of coke are circulated from the gasifier back to the heater 304 through line 320. The excess coke is withdrawn from the heater 304 by way of line 322. In conventional configurations, gasifier 306 is provided with its supply of steam and air by line 324 and hot fuel gas is taken from the gasifier to the heater though line 326. In some alternative embodiments, instead of supplying air via a line 324 to the gasifier 306, a stream of oxygen with 95 vol% purity or more can be provided, such as an oxygen stream from an air separation unit. In such embodiments, in addition to supplying a stream of oxygen, a stream of an additional diluent gas can be supplied by line 328. The additional diluent gas can correspond to, for example, CO2 separated from the fuel gas generated during the gasification. The fuel gas is taken out from the unit through line 330 on the heater; coke fines are removed from the fuel gas in heater cyclone system 332 including serially connected primary and secondary cyclones with diplegs which return the separated fines to the fluid bed in the heater. The fuel gas from line 330 can then undergo further processing. For example, in some embodiments, the fuel gas from line 330 can be passed into a separation stage for separation of CO2 (and/or H2S). This can result in a stream with an increased concentration of synthesis gas, which can then be passed into a conversion stage for conversion of synthesis gas to methanol. [0069] It is noted that in some optional embodiments, heater cyclone system 332 can be located in a separate vessel (not shown) rather than in heater 304. In such aspects, line 330 can withdraw the fuel gas from the separate vessel, and the line 322 for purging excess coke can correspond to a line transporting coke fines away from the separate vessel. These coke fines and/or other partially gasified coke particles that are vented from the heater (or the gasifier) can have an increased content of metals relative to the feedstock. For example, the weight percentage of metals in the coke particles vented from the system (relative to the weight of the vented particles) can be greater than the weight percent of metals in the feedstock (relative to the weight of the feedstock). In other words, the metals from the feedstock are concentrated in the vented coke particles. Since the gasifier conditions do not create slag, the vented coke particles correspond to the mechanism for removal of metals from the coker / gasifier environment. In some embodiments, the metals can correspond to a combination of nickel, vanadium, and/or iron. Additionally, or alternately, the gasifier conditions can cause substantially no deposition of metal oxides on the interior walls of the gasifier, such as deposition of less than 0.1% by weight of the metals present in the feedstock introduced into the coker / gasifier system, or less than 0.01% by weight. [0070] In configurations such as FIG. 3, the system elements shown in the figure can be characterized based on fluid communication between the elements. For example, coker reactor 302 is in direct fluid communication with heater 304. Coker reactor 302 is also in indirect fluid communication with gasifier 306 via heater 304. [0071] As an alternative, integration of a fluidized bed coker with a gasifier can also be accomplished without the use of an intermediate heater. In such alternative aspects, the cold coke from the reactor can be transferred directly to the gasifier. This transfer, in almost all cases, will be unequivocally direct with one end of the tubular transfer line connected to the coke outlet of the reactor and its other end connected to the coke inlet of the gasifier with no intervening reaction vessel, i.e., heater. The presence of devices other than the heater is not however to be excluded, e.g., inlets for lift gas etc. Similarly, while the hot, partly gasified coke particles from the gasifier are returned directly from the gasifier to the reactor this signifies only that there is to be no intervening heater as in the conventional three-vessel Flexicoker™ but that other devices may be present between the gasifier and the reactor, e.g., gas lift inlets and outlets. [0072] FIG.4 shows an example of integration of a fluidized bed coker with a gasifier but without a separate heater vessel. In the configuration shown in FIG. 5, the cyclones for separating fuel gas from catalyst fines are located in a separate vessel. In other aspects, the cyclones can be included in a main gasifier vessel 404. [0073] In the configuration shown in FIG.4, the coker system 400 includes a coker reactor 402, main gasifier vessel 404 and a separator vessel 406. The cracking feedstock is introduced into coker reactor 402 through line 408 and fluidizing/stripping gas through line 410; cracked hydrocarbon products are taken out through line 412. The cracking feedstocks includes a plastic waste feed with optional combination with a conventional cracking feedstock (e.g., heavy oil feed). The plastic waste feed can be separately introduced to the coker reactor 402 or introduced in combination with a conventional cracking feedstock, for example. Cold, stripped coke is routed directly from coker reactor 402 to main gasifier vessel 404 by way of line 414 and hot coke returned to the reactor in line 416. Steam and oxygen are supplied through line 418. The flow of gas containing coke fines is routed to separator vessel 406 through line 420 which is connected to a gas outlet of the main gasifier vessel 404. The fines are separated from the gas flow in cyclone system 422 including serially connected primary and secondary cyclones with diplegs which return the separated fines to the separator vessel. The separated fines are then returned to the main gasifier vessel 404 through return line 424 and the fuel gas product taken out by way of line 426. Coke is purged from the separator through line 428. The fuel gas from line 426 can then undergo further processing for separation of CO2 (and/or H2S) and conversion of synthesis gas to methanol. [0074] The coker and gasifier can be operated according to the parameters necessary for the required coking processes. Thus, the heavy oil feed in the cracking feedstock will typically be a heavy (high boiling) reduced petroleum crude; petroleum atmospheric distillation bottoms; petroleum vacuum distillation bottoms, or residuum; pitch; asphalt; bitumen; other heavy hydrocarbon residues; tar sand oil; shale oil; or even a coal slurry or coal liquefaction product such as coal liquefaction bottoms. Such feeds will typically have a Conradson Carbon Residue (ASTM D189-165) of at least 5 wt%, generally from 5 wt% to 50 wt%. In some embodiments, the cracking feedstock is a petroleum vacuum residuum. [0075] Delayed coking is another coking process for the thermal conversion of heavy oils such as petroleum residua (also referred to as “resid”) to produce liquid and vapor hydrocarbon products and coke. In particular embodiments, delayed coking is performed on a feedstock of a plastic waste feed optionally combined with a conventional cracking feedstock to produce liquid and vapor hydrocarbon products and coke. In some embodiments, the conventional hydrocarbon feedstock includes resids from heavy and/or sour (high sulfur) crude oils. Delayed coking of the feedstock is carried out by converting part of the feedstock to more valuable hydrocarbon products. The resulting coke has value, depending on its grade, as a fuel (fuel grade coke), electrodes for aluminum manufacture (anode grade coke), etc. [0076] Generally, a feedstock is pumped to a pre-heater where it is pre-heated, such as to a temperature from 480°C to 520°C. The pre-heated feed is conducted to a coking zone, typically a vertically oriented, insulated coker vessel, e.g., drum, through an inlet at the base of the drum. Pressure in the drum is usually relatively low, such as 100 kPa-g to 550 kPa-g, or 100 kPa-g to 240 kPa-g to allow volatiles to be removed overhead. Typical operating temperatures of the drum will be between roughly 400°C to 445°C, but can be as high as 475°C. The hot feed thermally cracks over a period of time (the “coking time”) in the coke drum, liberating volatiles composed primarily of hydrocarbon products that continuously rise through the coke bed, which consists of channels, pores and pathways, and are collected overhead. The volatile products are conducted to a coker fractionator for distillation and recovery of coker gases, gasoline boiling range material such as coker naphtha, light gas oil, and heavy gas oil. In an embodiment, a portion of the heavy coker gas oil present in the product stream introduced into the coker fractionator can be captured for recycle and combined with the fresh feed (coker feed component), thereby forming the coker heater or coker furnace charge. In addition to the volatile products, the process also results in the accumulation of coke in the drum. When the coke drum is full of coke, the heated feed is switched to another drum and hydrocarbon vapors are purged from the coke drum with steam. The drum is then quenched with water to lower the temperature down to 95°C to 150°C, after which the water is drained. When the draining step is complete, the drum is opened, and the coke is removed by drilling and/or cutting using high velocity water jets (“hydraulic decoking”). [0077] FIG. 5 illustrates an example delayed coking system 500. In the illustrated embodiment, a feedstock 502 including a plastic waste feed, which may be preheated, is fed into a coker fractionator 504. In some embodiments, the feedstock 502 further includes a conventional cracking feedstock, which may also be separately feed to the coker fractionator 504. In the illustrated embodiment, a fractionator effluent 506 including at least a portion of the plastic waste feed and/or conventional cracking feedstock is withdrawn from the coker fractionator 504 and fed to a coker furnace 508. From the coker furnace 508, the preheated effluent 510 including a preheated plastic waste feed and/or preheated conventional cracking feedstock is passed to a coking reactor 512, which includes, for example, a coking vessel or coking drum. The preheated effluent 510 also includes, for example, tower bottoms (or recycle). The coking reactor 512 is operated at coking conditions such that the preheated plastic waste feed/conventional cracking feedstock thermally cracks over a period of time (the “coking time”) in the coking reactor 512, liberating volatiles composed primarily of hydrocarbon products that continuously rise through the coke bed, which consists of channels, pores and pathways, and are collected overhead as a coker effluent 514, which is passed to the coker fractionator 504. In the illustrated embodiment, the coker effluent 514 is separated in the coker fractionator 504 into various fractions, including, but not limited to, one or more of a coker gas fraction 518, a coker naphtha fraction 520, a coker distillate fraction 522, and a coker gas oil fraction 524. It should be understood that separation of the coking products into various fractions can occur in one or more vessels and/or one or more different operations. As previously mentioned, coke is accumulated in the coking reactor 512 (e.g., coking vessel). A coke product 516 including coke is withdrawn from the coking reactor 512. Cracking Products [0078] Coking of the plastic waste feed either alone or in combination with the conventional cracking feedstock produces cracking products. In some embodiments, the cracking products include a cracking effluent, which may include a gas, a liquid, or a mixture thereof. As discussed above, the cracking effluent can be fractionated or otherwise separated to form desirable product streams, such as fuel gas (e.g., C4 and lighter hydrocarbons), naphtha, distillate, and gas oil. Naphtha typically has a boiling point range of 80°C to 205°C. Distillated typically has a boiling point range of 205°C to 370°C. Gas oil typically has a boiling point range of 370°C to 595°C. In some embodiments, such as coking, the cracking products further include coke. Because many plastic wastes have relatively low sulfur content (as compared to a conventional coker feedstock), the cracking products have reduced sulfur content, in some embodiments, thus reducing the needed severity for any subsequent sulfur removal processes, such as hydroprocessing. [0079] Coke produced in a coking process is typically a carbonaceous solid material of which a majority is carbon. Since the coke is produced from the co-processing of a conventional cracking feedstock in the coker, it can also be referred to as petroleum coke or petcoke, in accordance with one or more embodiments. The coke yield typically is 20 wt% to 40 wt% of the combined coker feedstock. However, since plastic wastes can have substantially higher atomic ratio of hydrogen to carbon, coking with a plastic waste feed can produce a reduced or minimized amount of coke. The particular composition of the coke depends on a number of factors, including the particular coking process, such as a delayed coker or in some embodiments, the coke includes carbon in an amount of 80 wt% to 95 wt% based on a total weight of the coke. Additional components in the coke include hydrogen, nitrogen, sulfur, and heavy metals, such as aluminum, boron, calcium, chromium cobalt, iron, manganese, magnesium, molybdenum, nickel, potassium, silicon, sodium, titanium, and/or vanadium. [0080] In some embodiments, the cracker effluent originates at least in part from polymeric materials in the plastic waste feed, such polyolefins or other polymers (e.g., polystyrene). In some embodiments, monomers and/or polymers in the cracker effluent and/or derived from one or more components of the cracker effluent are considered circular. For example, the cracker effluent includes a circular monomer derived from cracking the plastic waste feed. By way of further example, a circular polymer may be produced from one or more components of the cracker effluent. Advantageously these monomers and/or polymers are considered circular by attributing them to the polymers in the plastic waste feed, for example, by crediting, allocating, and/or offsetting or substituting for other hydrocarbons in a mass or energy balance within the coker system. In some embodiments, the monomers and/or polymers formed can be certified for their circularity by third party certification. One example of such certification is the mass balance chain of custody method set forth by the International Sustainability and Carbon Certification. Additional Embodiments [0081] Accordingly, the present disclosure may provide for the recycling of plastic waste that includes cracking a plastic waste feed to produce hydrocarbons. The methods and systems may include any of the various features disclosed herein, including one or more of the following statements. [0082] Embodiment 1. A method of processing plastic waste comprising: thermally cracking at least a plastic waste feed and a cracking feedstock to produce at least a cracking product comprising hydrocarbons, wherein the cracking feedstock comprises a T10 distillation point of 343°C or higher; measuring a contaminant concentration; and adjusting the plastic waste feed in response to the contaminant concentration. [0083] Embodiment 2. The method of Embodiment 1, wherein the contaminant concentration is measured in a liquid separated from the cracking product. [0084] Embodiment 3. The method of Embodiment 1, wherein the contaminant concentration is measured in a gas separated from the cracking product. [0085] Embodiment 4. The method of Embodiment 1, wherein the contaminant concentration is a concentration of hydrogen chloride measured in sour water produced in a fractionator. [0086] Embodiment 5. The method of Embodiment 1, wherein the contaminant concentration is a concentration of one or more organic halides. [0087] Embodiment 6. The method of Embodiment 1, wherein the contaminant concentration is a concentration of one or more of NOx, carbon monoxide, or carbon dioxide in the cracking product or a separated fraction of the cracking product. [0088] Embodiment 7. The method of Embodiment 1, wherein the contaminant concentration is a measurement of sodium accumulation in coke produced in the step of thermally cracking. [0089] Embodiment 8. The method of Embodiment 1, wherein the adjusting the plastic waste feed comprises adjusting a feed rate of the plastic waste feed to reduce a ratio of the plastic waste feed to the cracking feedstock. [0090] Embodiment 9. The method of Embodiment 1, wherein the adjusting the plastic waste feed comprises changing an amount of one or more plastic waste compositions in the plastic waste feed. [0091] Embodiment 10. The method of Embodiment 1, wherein the plastic waste feed comprises one or more plastics classified as plastic identification code 1 to 7 by the Society of the Plastics Industry. [0092] Embodiment 11. The method of Embodiment 1, wherein the cracking feedstock comprises petroleum vacuum residuum. [0093] Embodiment 12. The method of Embodiment 1, wherein the cracking feedstock comprises a T10 distillation point of 343°C to 650°C. [0094] Embodiment 13. The method of Embodiment 1, wherein the plastic waste feed is fed to a cracking reactor in a combined feedstock of the plastic waste feed and the cracking feedstock in an amount of about 0.1 wt% to about 25 wt%. [0095] Embodiment 14. The method of Embodiment 1, wherein the step of thermally cracking comprises exposing the plastic waste feed and the cracking feedstock to coking conditions. [0096] Embodiment 15. A method of processing plastic waste comprising: physically processing a plastic waste feed to reduce a maximum particle size of the plastic waste feed; combining the plastic waste feed with a carrier fluid to form a combined feedstock; physically processing the combined feedstock to reduce a maximum particle size of solid particles in the combined feedstock; preheating the combined feedstock to cause solid particles in the combined feedstock to melt; and thermally cracking the combined feedstock to produce at least a cracking product comprising hydrocarbons. [0097] Embodiment 16. The method of Embodiment 15, further comprising preheating the plastic waste feed and preheating the carrier fluid. [0098] Embodiment 17. The method of Embodiment 15, wherein the maximum particle size of the plastic waste feed is reduced in the physically processing to about 0.1 millimeter to about 75 millimeters. [0099] Embodiment 18. The method of Embodiment 15, wherein the maximum particle size of the solid particles in the combined feedstock is reduced to about 0.1 millimeter to about 1 millimeter. [0100] Embodiment 19. The method of Embodiment 15, wherein the step of physically processing the combined feedstock to reduce a maximum particle size of solid particles in the combined feedstock comprises passing the combined feedstock through a ball mill. [0101] Embodiment 20. The method of Embodiment 15, wherein the carrier fluid and the plastic waste feed are combined in a heated mixing chamber. [0102] Embodiment 21. The method of Embodiment 15, wherein the carrier fluid comprises a cracking feedstock with a T10 distillation point of 343°C or higher. [0103] Embodiment 22. The method of Embodiment 15, wherein the carrier fluid comprises petroleum vacuum residuum. [0104] Embodiment 23. The method of Embodiment 15, wherein the plastic waste feed comprises one or more plastics classified as plastic identification code 1 to 7 by the Society of the Plastics Industry. [0105] Embodiment 24. The method of Embodiment 15, wherein the plastic waste feed is present in the combined feedstock in an amount of about 0.1 wt% to about 25 wt%. [0106] Embodiment 25. The method of Embodiment 15, wherein the step of thermally cracking comprises exposing the combined feedstock to coking conditions. [0107] Embodiment 26. A method of processing plastic waste comprising: identifying target specifications required for a plastic waste feed; determining a mixture of at least two plastic waste compositions that meet the target specifications; mixing the at least two plastic waste compositions to form the plastic waste feed; and thermally cracking at least the plastic waste feed and a cracking feedstock to produce at least a cracking product comprising hydrocarbons, wherein the cracking feedstock comprises a T10 distillation point of 343°C or higher. [0108] Embodiment 27. The method of Embodiment 26, wherein the at least two plastic waste compositions comprise a first plastic waste composition that does not meet the target specifications and a second plastic waste composition that meets the target specifications. [0109] Embodiment 28. The method of Embodiment 26, wherein the target specifications comprise a contaminant concentration. [0110] Embodiment 29. The method of Embodiment 26, wherein the target specifications comprise an upper limit on a halide concentration. [0111] While the disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the disclosure as disclosed herein. Although individual embodiments are discussed, the present disclosure covers all combinations of all those embodiments. [0112] While compositions, methods, and processes are described herein in terms of “including,” “containing,” “having,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. The phrases, unless otherwise specified, “consists essentially of” and “consisting essentially of” do not exclude the presence of other steps, elements, or materials, whether or not, specifically mentioned in this specification, so long as such steps, elements, or materials, do not affect the basic and novel characteristics of the disclosure, additionally, they do not exclude impurities and variances normally associated with the elements and materials used. [0113] All numerical values within the detailed description are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. [0114] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.