Mixing plastic into a petroleum stream

Abstract

A method of dissolving plastic waste with a petroleum solvent includes mixing the plastic waste and the petroleum solvent at a mixing temperature of greater than a melting point of the plastic waste to form a homogenous mixture. The petroleum solvent includes greater than 50 wt.% aromatics. The mixture may be fed to a downstream processing unit.

Description

MIXING PLASTIC INTO A PETROLEUM STREAMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.FIELD

[0003] The present disclosure relates generally to mixing plastic into a petroleum stream. More particularly, the present disclosure relates to using an impellor and applying heat to dissolve plastic into fuel oil.BACKGROUND

[0004] Plastic recycling plays an important role in reducing the environmental footprint of plastic waste and in conserving natural resources. As industries and consumers increasingly rely on plastic products, generation of plastic waste has escalated, leading to significant environmental concerns, including pollution of oceans and landscapes. Recycling offers a pathway to minimize this impact by reprocessing plastic waste into new materials, thereby reducing the need for virgin plastic production and the associated consumption of petroleum-based resources. Recycling plastic can also be economical depending on the process employed.

[0005] Conventional methods of advanced plastic recycling may include pyrolyzing the plastic in a pyrolysis reactor to produce pyoil, gas, and char. The pyoil can then be fed into steam crackers or refinery units such as the fluid catalytic cracking (FCC). For this step, the pyoil may be blended into the traditional feedstock stream, such as naphtha or vacuum gas oil (VGO). Conversion of mixed plastic waste to pyrolysis oil or lighter may require batch or semi-batch processes that are inefficientand expensive. Additionally, these processes may suffer from poor mixing, which in turn may negatively impact heat transfer and mass transfer and cause equipment fouling and plugging problems.

[0006] Thus, there may be a need for methods for recycling plastics that result in better mixing and that are more cost effective.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0008] FIG. 1 is a schematic diagram of an exemplary system for mixing plastic into a petroleum stream, according to an embodiment of the present disclosure;

[0009] FIG. 2 is a schematic diagram of an exemplary mixing unit for mixing plastic into a petroleum stream, according to an embodiment;

[0010] FIG. 3 A is a perspective view of an exemplary impellor, according to an embodiment;

[0011] FIG. 3B is a side view of an exemplary impeller, according to another embodiment;

[0012] FIG. 4 is a partial cut-away perspective view of an exemplary high shear pump, according to an embodiment;

[0013] FIG. 5 is an optical microscope image of an exemplary mixture of polypipe plastic in fuel oil after mixing with a high-shear mixer;

[0014] FIG. 6 is an optical microscope image of an exemplary mixture of polypipe plastic in fuel oil after mixing with a conventional 4-blade impeller;

[0015] FIG. 7 is a flow diagram of a method for mixing plastic into a petroleum stream;

[0016] FIG. 8 is a photograph of plastic waste material;

[0017] FIG. 9 is a photograph of petroleum solvent;

[0018] FIG. 10 is a photograph of a mixture of plastic waste and petroleum solvent at room temperature;

[0019] FIG. 11 is a photograph of plastic waste and improper petroleum solvent after mixing;

[0020] FIG. 12 is a photograph of plastic waste and improper petroleum solvent after mixing; and

[0021] FIG. 13 is a photograph of a mixture of plastic waste and a petroleum solvent that is added to another petroleum solvent.DETAILED DESCRIPTION

[0022] It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The description that follows includes example systems, methods, techniques, and program flows that embody aspects of the disclosure. However, it is understood that this disclosure may be practiced without these specific details. For brevity, well-known steps, protocols, structures, and techniques have not been shown in detail in order not to obfuscate the description. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents.Overview

[0023] An exemplary method of mixing plastic into a refinery stream may involve refinery integration. Refinery integration may involve using existing refinery equipment such as delayed cokers and fluid catalytic crackers to convert plastic waste to usable liquids (e.g., pyrolysis oils) and gases (ethylene and propylene). For example, polymer films (e.g., agricultural films), which are almost exclusively low-density polyethylene (LDPE), may be used for such refinery integration. Viscosities for LDPE at 300 °C may exceed 300,000 cP, making it difficult for impeller type stirrers to work well. However, the plastics can be mixed into the refinery petroleum stream at elevated temperatures,thereby significantly reducing the viscosity. Effective mixing of the solute (e.g., plastic) and solvent (e.g., a petroleum solvent such as petroleum stream from a refinery processing unit or storage tank) may ensure a homogeneous stream without large plastic agglomerates can be fed to the refinery unit operations. Additionally or alternatively, a multiaxial or coaxial mixing system may be used in order to uniformly disperse, homogenize, or suspend the plastics throughout the petroleum solvent. As described in more detail below, multiaxial or coaxial mixing system may be effective for medium to high viscosity mixtures, thus allowing for high plastic concentration in the plastic / petroleum mixture. Operating the mixing system at elevated temperature (i.e. above the melting point of the plastics) may allow for enhanced solubility of plastics into the petroleum stream. Plastics tend to float in petroleum (because of their lower density relative to petroleum streams) and / or agglomerate (melted particles may stick to one another if not properly agitated). As described in more detail below, the use of heat, a particular solvent (e.g., petroleum stream), a multiaxial mixing system, or combinations thereof according to the present disclosure can minimize these effects.

[0024] In various embodiments, the solvent used to dissolve the plastic waste is a petroleum solvent, for example a petroleum stream. The petroleum stream may be a product stream from one or more parts of a petroleum refinery, for example, a crude oil distillation unit, light ends recovery unit, naphtha hydrotreating unit, catalytic reformer, middle distillates hydrotreating unit, fluid catalytic cracking unit, hydrocracker unit, delayed coking unit, or any other unit of the petroleum refinery. Additionally or alternatively, the petroleum steam may be provided from a product storage tank receiving and storing product from any of the aforementioned refinery units. In some embodiments, the petroleum stream may come from a source outside of the refinery. The petroleum stream’s composition may include a mixture of hydrocarbons such as paraffins, naphthenes, aromatics, and / or olefins having a SARA (Saturates, Aromatics, Resins, and Asphaltenes) distribution as described inmore detail herein. The petroleum stream may also contain sulfur compounds, nitrogen compounds, oxygen compounds like carboxylic acids, metals such as vanadium and nickel, and water and / or salts.

[0025] The plastic to be mixed into the petroleum may include any suitable plastic material. Nonlimiting examples include polyolefins, such as polyethylene (e.g., high-density polyethylene, low-density polyethylene, etc.), polypropylene, polystyrene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyamide, polycarbonate, polyurethane, polyester, natural and synthetic rubber, tires, filled polymers, composites, and plastic alloys. Non-limiting examples of sources of the plastic material to be mixed into the petroleum may include industrial packaging, agricultural film, construction materials, automotive parts, electronic waste, marine debris, commercial fishing gear, industrial containers, bulk transportation bags, pallets, crates, office supplies, medical waste, laboratory equipment, textile fibers, carpeting, signage, and trade show materials, aerospace components, railroad ties, cable insulation, pipelines, safety equipment, protective gear, synthetic turf, playground equipment, outdoor decking, recycling bins, waste containers, street furniture, public transportation components, bicycle racks, bollards, traffic cones, water supply pipes, sewage and drainage pipes, irrigation systems, geomembranes, roofing materials, window frames, door frames, insulation materials, and 3D printing filament, and / or consumer waste. In an aspect, the plastic is a waste material commonly referred to as plastic waste, mixed plastic waste or similar that has been sized (e.g., ground) into a particulate form. Mixed plastic waste streams may be produced, for example, by grinding post-consumer recycled plastic.

[0026] Referring to FIGS. 1-2, an exemplary system 1 for mixing plastic into a petroleum stream is shown. The system 1 may include a mixing unit 10 having a mixing tank 31 and a mixing structure 15; an upstream processing unit (e.g., a fuel oil tank 12) configured to supply a petroleum solvent (e.g., fuel oil) to the mixing unit 10; a pre-heat furnace 14 configured to pre-heat the mixture of plastic and fuel oil from the mixing unit 10; a coke drum 16 configured to receive the pre-heated mixture ofplastic and fuel oil from the pre-heat furnace 14; and a coker fractionator 18 configured to receive the mixture of plastic and fuel oil from the coke drum 16, and output liquid and gas hydrocarbons (e.g., gas oil, light liquids, and gas). The system 1 may further include a heater configured to heat contents of the mixing tank 31. For example, a heating jacket may be applied to mixing tank 31; a heating element may be disposed within mixing tank 31 ; a direct fired heater may be used to heat the mixing tank (e.g., gas fired burners disposed below the mixing tank 31); one or more in-line heaters (e.g., heat exchangers or gas fired heaters) may be used in a solvent feed line to mixing unit 10 and / or in the recirculation loop formed by streams 43 and 17; or combinations thereof. The heater may apply heat to the contents of mixing vessel 31 to maintain a mixing temperature low enough so that no depolymerization occurs during mixing but high enough to enhance the solubility of the plastic. The mixing structure 15 may be configured to mix the plastic into the petroleum solvent by imparting a shear on the contents inside the mixing tank 10 (e.g., a shear of less than 10,000 s'1). In some embodiments, in the system 1, plastic is mixed with petroleum solvent at a concentration of approximately 25 % wt. After the solvated plastic leaves the system 1 , it may be added to a feed stream to a refinery processing unit such as a cracking unit or a coking unit. In some embodiments, the concentration of plastic in the feed stream to the refinery unit will be approximately 0.5 to 1% wt.

[0027] In more detail, the fuel oil tank 12 may be configured to store heavy petroleum products, for example from a refinery distillation column or other processing unit. The fuel oil tank 12 may be designed with materials such as reinforced steel or concrete to withstand the corrosive nature of crude oil and its products. It may feature containment systems, such as double walls and leak detection mechanisms, to prevent spills and environmental contamination. The fuel oil tank 12 may have floating roofs, which may rise and fall with the oil level to minimize air space and thus reduce volatile organic compound (VOC) emissions. Additionally, the fuel oil tank 12 may be equipped with safety systems such as flame arrestors and pressure relief valves to manage the risk of fire or explosion. Thefuel oil tank 12 may have monitoring and / or control systems for measuring and managing tank temperature and contents.

[0028] As understood by a person skilled in the art, typically fuel oil is one of the fractions produced from conventional distillation columns (e.g. distillate fuel oil No. 1 / No. 2, or a diesel fuel). Additionally, heavier / residual fuel oils (referred to as No. 4-6 fuel oils) are produced by blending lighter distillates (e.g. Fuel oils No. 1 or 2, heavy cracked distillate, heavy vacuum distillate) with high viscosity distillation residues from the refinery (typically either (1) the residue from atmospheric tower, (2) vacuum residue (VR), (3) thermally cracked residue, or (4) pyrolysis fuel oil). The particular fuel oil produced (e.g. blending / proportions) is specific to each refinery. It often targets a certain viscosity orboiling point spec, and also depends on market conditions / economics. Often these fuel oils are sold on the open market, allowing end-users or other refiners to purchase the specific grades needed for their operations. In some embodiments, any suitable fuel oil having a SARA distribution of the type disclosed herein may be used as a solvent in the processes described herein.

[0029] The pre-heat furnace 14 may be configured to increase the temperature of the mixture of plastic and petroleum being fed to a refinery processing unit, e.g., a coking unit. It may include a series of burners configured to heat up tubes through which the mixture flows. The pre-heat furnace may be configured to ensure that the mixture reaches a target temperature. Control systems may monitor and control the temperature, flow rates, and combustion process.

[0030] The coke drum 16 (e.g., two or more coke drums 16) may be vertical cylindrical vessels for delayed coking process. It may perform a thermal cracking operation designed to convert the mixture of plastic and petroleum into lighter products and petroleum coke. The coke drum 16 may operate under thermal cycling and high temperatures. It may periodically fill with hot, heavy feedstock which then undergoes cracking. The coke drum 16 may be made from high-grade alloy steels to resist thermal and mechanical stress. The coke drum 16 may include systems for cutting and removing thecoke once the cracking process is complete, such as top and bottom heads that open for coke cutting and removal. High-pressure water jets may be utilized. The coke drum 16 may be monitored by acoustic emission monitoring and real-time thickness measurement.

[0031] The coker fractionator 18 may separate the various hydrocarbon streams produced during coking into distinct fractions based on their boiling points. It may include a distillation column in which the mixture from the coke drum 16 is fractionated into lighter products and coke. The distillation column may include a tower equipped with a series of trays or packing material to facilitate contact between the vapor rising through the column and the liquid descending, thereby enabling the selective condensation and re-evaporation of hydrocarbon components. In some embodiments, vacuum residue VR is fed into the coker fractionator 18. In some embodiments, material is recycled from the coker fractionator 18 into the pre-heat furnace 14. In some embodiments, material is recycled from the coker fractionator 18 into fuel oil tank 12 and / or mixing unit 10. The coker fractionator 18 may output gas oil, light liquids, and gases, which may be further processed and / or transported in the refinery. The coker fractionator 18 may have a control system that may monitor and adjust the operating parameters in real time for efficient and safe separation of products. In some embodiments, the output of the coker fractionator is about 70% wt. liquid and gas.

[0032] Referring to FIG. 2, the mixing unit 10 may include a mixing tank 31. The mixing tank 31 may include a lid 21 for allowing the plastic (e.g., agglomerates, pellets, flakes, or the like) to be loaded into the mixing tank 31. The plastics may be fed through a port or opening in the lid / top of the mixing tank 31. The plastics can be fed into the mixing tank 31 at a controlled rate via systems such as an eductor, an auger / incline screw conveyor (w / shaft or shaftless), or an incline belt conveyor. Examples of plastic materials that can be added to the mixing tank 31 include polyolefins such as polyethylene (such as polyethylene (PE) (e.g., linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE)) and polypropylene (PP), or any othersuitable plastic. The plastic may be, for example, agricultural waste plastic such as films (e.g., ground or crop cover) and / or flexible tubing (e.g., for irrigation). Before being added to the mixing tank 31, the plastic may be pre-processed. For example, plastic films may be densified (e.g., extruded) into pellets or agglomerates and further sized (e.g., ground) as desired. For example, agricultural bales can be shredded, dry-washed, and densified to produce granules suitable for feeding into the mixing tank 31. In some embodiments, the plastic material to be added includes regrinds, pellets, and / or agglomerates. In some embodiments, there is 20-25% wt. of plastic added to the solvent (e.g., fuel oil) to form a stable solvent / plastic mixture within the mixing tank 31. Pyrolyzing the plastic before it is added to the mixing tank 31 may not be performed (e.g., is not required) in many applications (in other words, the present process may be carried out in the absence of and without the need for pyrolysis of the plastic material).

[0033] The mixing tank 31 may be configured to receive petroleum solvent through an inlet. The petroleum solvent may include fuel oil, naphtha, vacuum residue (VR), vacuum gas oil (VGO), or the like. The mixing tank 31 may have an outlet for outputting the mixture of plastic and petroleum solvent. The mixing unit 10 may by cylindrical or any other suitable shape. It may be made of stainless steel, coated carbon steel, or any other suitable material. The mixing unit 10 may include a motor 11 and a mixing structure 15 (e.g., one or more shafts and impellers). In some embodiments, the motor 11 and the mixing structure 15 may be disposed on a longitudinal axis L of the mixing tank 31. In some embodiments, the motor 11 and the mixing structure 15 may be offset from the longitudinal axis L. The motor 11 may drive the mixing structure 15 (e.g., by driving one or more shafts of the mixing structure 15), as discussed in more detail below. In some embodiments, there is more than one motor 11, and each motor 11 drives a shaft of one or more mixing structures 15. In some embodiments, the motor 11 is disposed above the mixing tank 31 (e.g., above the lid 21). The shaft may extend into the mixing tank 31 where the mixing structure 15 is located.

[0034] The mixing unit 10 may further include a high shear mixer 13 in fluid communication with the mixing tank 31 (for example, disposed in a recirculation loop) and configured to impart a shear on the petrol eum / plastic mixture (e.g., outside the mixing tank) of at least 20,000 s'1. In some embodiments, the high shear mixer 13 is in-line, within a pipe connected to an outlet of the mixing tank 31. In some embodiments, the high shear mixer 13 is placed on the bottom of the mixing tank 31. The high shear mixer 13 may break up agglomerates that remain within the vessel and / or reduce the particle or droplet size of the plastics within the solvent (e.g., fuel oil). For example, the high shear mixer 13 may produce droplets or particles that are on the order of 1 micron in diameter. The high shear mixer 13 may include a rotor-stator combination in which the rotor may spin at a high rate of speed (e.g., up to 10,000 rpm). Any suitable stator type is within the scope of the present disclosure. For example, the type of stator may be selected depending on the application, desired shear rate, and / or targeted particle size. To impart maximum shear and produce very fine droplets, a ‘fine emulsor’ type of stator may be used. For other applications, a slotted, circular, or square / rectangular stator may be used. Referring to FIG. 4, the high shear mixer 13 may include an inlet 142 configured to receive the mixture of plastic and petroleum solvent from the first pipe 43. An impeller 141 may apply shear to the mixture to mix and disperse the plastic in the petroleum solvent. The mixture may then exit through the outlet 143 to the second pipe 17.

[0035] As shown in FIG. 2, the first pipe 43 may extend from the mixing tank 31 and into the high shear mixer 13. The second pipe 17 may extend from the high shear mixer 13 into the mixing tank 31. A third pipe 19 may extend from the second pipe 17 and to feed a refinery process unit (e.g., the preheat furnace 14 of a delayed coking unit). A first valve 46 may be disposed on the first pipe 43; a second valve 44 may be disposed on the second pipe 17; and a third valve 20 may be disposed on the third pipe 19. During a mixing phase, the first valve 46 may be open, the second valve 44 may be open, and the third valve 20 may be closed. This may allow petroleum and plastic to recirculatebetween the mixing tank 31 and the high shear mixer 13, which may improve bulk mixing and promote turnover of contents. During an output phase, the first valve 46 may be closed, the second valve 44 may be open, and the third valve 20 may be open, thus allowing the mixture of plastic and petroleum to exit the mixing unit 10 and enter the feed line to a refinery processing unit (e.g., pre-heat furnace 14). During other phrases, fuel oil feed may circumvent the mixing unit 10 (e.g., be directly fed from the fuel oil tank 12 to the pre-heat furnace 14 as shown in FIG. 1).

[0036] Referring to FIGS. 2-3, the mixing structure 15 may include a first impeller 121 configured to sweep a path proximate to a wall 22 of the mixing tank 31 at a first rotational speed, and a second impeller 124 configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed. A direction of rotation of the first impeller 121 may be different from a direction of rotation of the second impeller 124. For example, the first impeller 121 may rotate at a speed of less than 50 rpm, and the second impeller 124 may rotate at a speed of approximately 200 rpm; and / or the first impeller 121 may rotate clockwise, and the second impeller 124 may rotate counterclockwise.

[0037] Referring to FIG. 3A, the first impeller 121 may have a double-helical shape. The first impeller 121 may include first blades 123 disposed at an angle with respect to the wall 22. The second impeller 124 may include second blades 125 configured to pump fluid within the mixing tank 31. The first impeller 121 may include a first shaft 122, and the first blades 123 may extend from the first shaft 122. The second impeller 124 may include a second shaft 126, and second blades 125 may extend from the second shaft 126. The second blades 125 may be pitched (e.g., the second impeller 124 may be a hydrofoil). This may provide high pumping capacity and strong axial flow. The first shaft 122 may be parallel and / or coaxial with the second shaft 126. The first shaft 122 may share a common axis A with the second shaft 126. The common axis A may be coaxial with the longitudinal axis L of the mixing tank 31. The second shaft 126 may extend along a longitudinal axis L of the mixing tank 31, extend parallel to the longitudinal axis L of the mixing tank 31 and spaced apart from the longitudinalaxis L of the mixing tank 31, or extend at an angle with respect to the longitudinal axis L of the mixing tank 31.

[0038] In more detail, the first impeller 121 may include a frame 127 extending from the first shaft 122. The frame 127 may be rectangular or square shaped. The frame 127 may include a first segment 145 extending from the first shaft 122 in a first direction and a second segment 133 extending from the first shaft 122 in a second direction opposite to the first direction. The first segment 145 may be colinear with the second segment 133. The frame 127 may further include a third segment 134 extending from the first segment 145 in a third direction perpendicular to the first direction and a fourth segment 135 extending from the second segment 133 in the third direction. The third segment 134 may be parallel to the fourth segment 135. The frame 127 may further include a fifth segment 136 extending from the third segment 134 in the second direction and a sixth segment 137 extending from the fourth segment 135 in the first direction. The fifth segment 136 may be colinear with the sixth segment 137. The fifth segment 136 and the sixth segment 137 be connected to a rod 128 (e.g., a rod 128 coaxial with the first shaft 122). The first impeller 121 may further include helical blades 130. The helical blades 130 may be connected to (e.g., welded to) the frame 127. For example, there may be two helical blades 130, each being connected to two comers formed by the rectangular frame 127. For example, one of the helical blades 130 may be connected to a comer formed by the first segment 145 and the third segment 134 and a comer formed by the fourth segment 135 and the sixth segment 137; and the other helical blade 130 may be connected to a comer formed by the second segment 133 and the fourth segment 135 and a comer formed by the third segment 134 and the fifth segment 136. Each helical blade 130 may be semicircular. The helical blades 130 may be oriented at approximately 45-degree angles with respect to the common axis A and be approximately perpendicular to each other. The first blades 123 may further include a U-shaped blade 129 extending from the rod 128. The rod 128 may be disposed at a center of the U-shaped blade 129. The U-shaped blade 129 may beoriented perpendicular to the fifth segment 136 and the sixth segment 137. The U-shaped blade 129 may be oriented at approximately a 45-degree angle with respect to the helical blades 130.

[0039] At least part of the mixing structure 15 may be made of metal. An outer edge of the first blades 123 may be disposed closer to the wall than a distance equal to 10% of a diameter of the mixing tank 31. In some embodiments, flexible (e.g., Teflon) scrapers are attached to the helical blades 130 to scrape the interior circumferential surface of the mixing tank 31 so that plastic does not agglomerate on that surface of the mixing tank 31. The U-shaped blade 129 may also have flexible scrappers attached thereto to prevent plastic from agglomerating on the bottom surface of the mixing tank 31. The Teflon material may prevent wear on the mixing tank 31.

[0040] The second impeller 124 may include second blades 125. The second blades 125 may include pitch blades 132 extending from the second shaft 126. There may be any suitable number of pitch blades 132 and / or pitch blade clusters (e.g., pitch blades 132 disposed at a common axial distance along the second shaft 126). In the embodiment shown in FIG. 3 A, there are two clusters each having two pitch blades 132. The angle from which the pitch blades 132 extend from the second shaft 126 in the first cluster may be different from the angle from which the pitch blades 132 extend from the second shaft 126 in the second cluster. For example, the pitch blades 132 in the first cluster may be offset 90-degrees with respect to the pitch blades 132 in the second cluster.

[0041] FIG. 3B shows an alternative embodiment of the mixing structure 15. In the embodiment of FIG. 3B, the first shaft 122 is not colinear with the second shaft 126 but is parallel with the second shaft 126. The first blades 123 may be V-shaped. The first blades 123 may extend from a distal end of the first shaft 122. The first blades 123 may include a first blade segment 138 extending from an end of the first shaft 122 and a second blade segment 139 extending from an end of the first blade segment 138 parallel to the first shaft 122. Although three first blades 123 are shown in FIG. 3B, any suitable number of blades is within the scope of the present disclosure. The second blades 125 mayextend from the second shaft 126 (e.g., at a distal end of the second shaft 126). The longitudinal axis Al of the first shaft 122 may be coaxial with the longitudinal axis L of the mixing tank 31. The longitudinal axis A2 of the second shaft 126 may be offset from the longitudinal axis Al of the first shaft 122 by a distance D. The longitudinal axis Al of the first shaft 122 may be parallel to the longitudinal axis A2 of the second shaft 126. The distance D may be, for example, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4,75, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 feet.

[0042] Referring to FIG. 7, a method 700 of mixing plastic with a petroleum solvent is shown. The method 700 may include the step 702 of adding petroleum solvent (e.g., a solvent having compositional characteristics of the type disclosed herein) and plastic material into a mixing tank, wherein the solvent and / or the contents of the mixing tank are heated to a temperature above a highest melting point of the plastic (e.g., the component of a plastic waste mixture having the highest melting point) and below a lowest depolymerization / thermal degradation temperature of the plastic (e.g., a component of a plastic waste mixture having the lowest depolymerization / thermal degradation temperature). The method 700 may further include the step 704 of mixing the plastic material with the petroleum solvent, for example by inducing a first flow inside the mixing tank proximate to a wall of the mixing tank at a first flow rate, and inducing a second flow inside the mixing tank proximate to a center of the mixing tank at a second flow rate that is greater than the first flow rate, wherein a direction of the first flow is different from a direction of the second flow. The first flow may be a flow that moves in a circle along a circumferential wall of the mixing tank. Alternatively, the first flow may move in a spiral along the circumferential wall of the mixing tank. The second flow may be a flow in a direction of a longitudinal axis of the mixing tank. Alternatively, the second flow may be a flow in a direction at an angle with respect to the longitudinal axis of the mixing tank. A temperature of the solvent / plastic mixture inside the mixing tank may be approximately 170 °C. The petroleum solventmay be fuel oil. The plastic material may have a particle size of 5 to 25 mm before the mixing of the plastic material into the petroleum. The plastic material may have a particle size of 10 microns or less after the mixing of the plastic material with the petroleum. The mixing of the plastic with the petroleum within the mixing tank may include imparting a shear on the plastic / petroleum mixture of less than 10,000 s'1. The mixing of the plastic material with the petroleum solvent may further include diverting the plastic / solvent mixture outside of the mixing tank to a mixer (e.g., a high-shear in-line mixer) that imparts a shear on the mixture of at least 20,000 s'1.

[0043] In an aspect, it has been surprisingly discovered that the combination of the structure of the first impeller 121 and the second impeller 124, the first impeller 121 rotating in a different direction than the second impeller 124, and the first impeller 121 rotating at a lower speed than the second impeller 124 allows plastic to be dissolved when contacted with a heated petroleum solvent without pre-processing the plastic with pyrolysis. Agglomeration of sticky melted plastics may be eliminated by this novel solvent / plastic mixing process. The output of the process may be a soluble, one-phase solution with substantially no chunks nor agglomerates and uniform distribution of plastic (e.g., polymers) throughout the petroleum solvent. With the elimination of the pyrolysis step, the plastic may be directly mixed with the petroleum stream, which may result in significant cost savings and greater process efficiency. For example, cost savings may be achieved through the energy savings of not extruding, depolymerizing, pyrolyzing (e.g., thermally degrading), or otherwise pre-processing to break down the molecular structure of the plastic polymers before adding it to the petroleum. The only pre-processing necessary may be mechanical (e.g., sizing of the plastic, for example via grinding). Heat and mass transfer of when processing the resultant solvated plastic (e.g., solvent / plastic mixture) may also be significantly improved by the method, and a reduction in fouling and plugging may be achieved in refinery process equipment receiving the resultant solvated plastic (e.g., solvent / plastic mixture) as a feed stream.

[0044] In another aspect, it has been surprisingly discovered that petroleum solvents may be selected to effectively solubilize the waste plastic of the type described herein. In particular, the solvent may have SARA distribution effective to solubilize polymers such as polyolefins to a desired degree to produce a desired dissolution outcome (e.g., to produce a homogenous solvent / plastic mixture of the type described in the Examples). Accordingly, the SARA (Saturates, Aromatics, Resins, and Asphaltenes) distribution of the solvent can be selected for optimum plastic solubilization. In particular, the solvent may have sufficient aromatic levels to effectively solubilize polymers such as polyolefins. For example, aromatic levels of the solvent may be greater than 50 wt% (e.g., greater than 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 90% and equal to or less than 100%) in order to produce a desired dissolution outcome (e.g., to produce a homogenous solvent / plastic mixture of the type described in the Examples). Additionally or alternatively, resin and asphaltene levels of the solvent may be greater than 10 wt% (e.g., greater than 10%, 20%, 30%, 40% or 50% and less than 100%) in order to produce a desired dissolution outcome (e.g., to produce a homogenous solvent / plastic mixture of the type described in the Examples). Additionally or alternatively, saturate levels of the solvent may be less than 30 wt% (e.g., less than 30%, 25%, 20%, 15%, 10%, 5%, or 1%, or alternatively 0%) in order to produce a desired dissolution outcome (e.g., to produce a homogenous solvent / plastic mixture of the type described in the Examples).

[0045] Saturates are saturated hydrocarbon compounds, typically non-polar, for example straightchain alkanes (n-alkanes) and branched or cyclic alkanes (isoalkanes and cycloalkanes). The saturates may include, for example, parafins, cyclohexane, or any other suitable saturate. The aromatics may have, for example, one or more (e.g., two) ring structures such as benzene, toluene, xylene, naphthalene, and anthracene. The resins include polar aromatic compounds that are heavier than typical aromatics, and often contain heteroatoms such as nitrogen, sulfur, or oxygen. The resins may include, for example, may include multi aromatic compounds. Asphaltenes are the heaviest, mostpolar, and complex hydrocarbons, consisting of large molecules with multiple aromatic rings, sulfur, nitrogen, and other heteroatoms. Asphaltenes are insoluble in light solvents (e.g., n-heptane) and often precipitate out, contributing to fouling in pipelines and refinery equipment.

[0046] The mixing of plastic with a solvent having a designated SARA distribution may be performed at elevated temperatures (greater than 140 °C, (e.g., greater than 150 °C, 160 °C, 170°C, or 180°C and less than 200°C). The plastic waste and solvent may be mixed at a temperature of at least 140°C. Alternatively, the temperature may be in a range of from about 140 to about 200°C, alternatively from about 160 to about 180°C, or alternatively from about 170 to about 180°C. At processing temperature, the mixture can be viscous, for example, several thousand centipois (up to ten thousand) at 175 °C. In some embodiments, the mixture can flow through a heated line to keep viscosity low enough for it to flow. Operating the mixing system at such temperatures (e.g., above the melting point of the plastics) may allow for enhanced solubility of plastics into the petroleum stream, as it may ensure that the plastics are in the melt phase and that the viscosity of the mixture is reduced. Additionally, a multiaxial or coaxial mixing system of the type described herein can be used to uniformly disperse, homogenize, or suspend the plastics throughout the petroleum solvent and prevent large agglomerates from forming. In some embodiments, the mixer 15 is operated under low shear conditions, e.g., less than about 10,000 s'1.

[0047] In some embodiments, a solvent having a designated SARA distribution may be mixed with a plastic starting material comprising polyethylene and / or polypropylene. The plastic waste may comprise greater than or equal to 70, 75, 80, 85, 90, 95 wt. % polyolefins (e.g., PE and / or PP). The plastic waste may include any one or any combination of any two or more of plastic flakes, plastic agglomerates, and plastic re-grinds. The plastic waste may have an average particle size in a range of from about 1 to about 100 mm, alternatively in a range of from about 1 to about 50 mm, or alternatively in a range of from about 5 to about 25 mm. Additionally or alternatively, the particle size may bedetermined during the a process of reducing the size of the plastic waste, for example grinding the plastic waste in one or more granulators. For example, there may be a specific screen size for the output of the granulators, which are used to produce the re-grinds or agglomerates having a desired size or combination (e.g., distribution) of sizes (e.g. screen sizes of 3 / 8”, ’A”, or 1” are common). For example, output from a granulator can be run through a plurality of screens of differing size to sort the plastic waste particles by size, and then the sorted plastic waste particles can be further blended to achieve a desired particle size distribution (e.g., 50 / 50 blend, 33.3 / 33.3 / 33.3 blend, etc.).

[0048] The solvent having a desired SARA distribution may be obtained from a refinery process unit or a product storage tank of a refinery process unit as described herein. In some embodiments, the petroleum solvent can be from a vacuum residue (residue from the vacuum column). In some embodiments, the petroleum solvent can be vacuum gas oil (e.g., top fraction from the vacuum column). In some embodiments, the petroleum solvent can be from a liquid stream off of a coker (e.g., gas oil produce that comes from a coker and / or naphtha and / or mid cut such as gas oil (e.g., heavy coker gas oil)). The petroleum stream can be any stream or combination of streams that has a desired SARA distribution (e.g., that can be blended to achieve a composition having the desired SARA distribution).

[0049] In some embodiments, the solvent having a desired SARA distribution may be pumped in from a tank or a pipeline. In some embodiments, the plastic may be held in a storage bin or container such as a silo. There may be a conveyer (e.g., an auger) that feeds solids in though the top of the mixing tank 31. The process may be a continuous process in which solids and solvent are metered in mixing tank 31 at a defined rate. In steady state, an output stream may be generated at a mass flow rate about equal to the mass flow rate of the solvent and plastic input streams. The output stream comprises a mixture of solvent / plastic (solubilized plastic) where the plastic has been solubilized anduniformly homogenously mixed. The output stream can be sent to a downstream process unit as described herein.

[0050] While the mixing step (e.g., the plastic being solubilized in the solvent having a desired SARA distribution) itself may not include a chemical reaction, a chemical reaction may take place further downstream according to the application. For example, the solvent / plastic mixture from the mixing unit 10 may be fed into a coker, a FCC, a cracker, or other downstream refining unit for further processing. In the embodiments in which the solvent is from vacuum gas oil, the vacuum gas oil / plastic mixture may be fed from the mixing unit 10 into FCC. In the embodiments in which the solvent is fuel oil and / or vacuum residue, the fuel oil / plastic mixture and / or vacuum residue / plastic mixture may be fed from the mixing unit 10 into a coker. In the embodiments in which the solvent is naphtha, the naphtha / plastic mixture may be fed from the mixing unit 10 into crackers.

[0051] An exemplary method of dissolving plastic waste with a petroleum solvent having a desired SARA distribution may include mixing the plastic waste and the petroleum solvent at a mixing temperature of greater than a melting point of the plastic waste to form a homogenous mixture, wherein the petroleum solvent comprises greater than 50 wt.% aromatics. The petroleum solvent may be any suitable solvent having a desired SARA distribution. The petroleum solvent may comprise aromatics in a range of from about 50 wt% to about 75 wt%, alternatively from about 50 wt% to about 70 wt%, or alternatively from about 50 wt% to about 65 wt.%. The petroleum solvent may comprise less than 20 wt.% resins. The petroleum solvent may include resins in a range of from about 0 wt% to about 20 wt%, alternatively from about 5 wt% to about 20 wt%, or alternatively from about 5 wt% to about 17 wt.%. The petroleum solvent may include less than 15 wt.% asphaltenes. The petroleum solvent may include asphaltenes in a range of from about 0 wt% to about 15 wt%, alternatively from about 0 wt% to about 10 wt%, or alternatively from about 5 wt% to about 10 wt.%. The petroleum solvent may include less than 30 wt.% saturates. The petroleum solvent may include saturates in arange of from about 10 to about 30 wt%, alternatively from about 10 wt% to about 25 wt%, or alternatively from about 15 to about 25 wt.%. The aromatics / saturates ratio may be greater than 1.5, alternatively, in a range of from about 1.5 to about 7.5, alternatively from about 2.5 to about 7.5, alternatively from about 2.5 to 5.0, or alternatively about 3. The amounts of saturates, aromatics, resins, and asphaltenes (e.g., the SARA distribution) may be determined using clay-gel column chromatography. The amounts of saturates, aromatics, resins, and asphaltenes (e.g., the SARA distribution) may be determined according to ASTM D2007.

[0052] The amount of plastic waste present in the homogenous solvent / plastic mixture may be in a range of from about 1 to about 40 wt.%, alternatively from about 5 to about 30 wt.%, alternatively from about 10 to about 25 wt%, alternatively from about 15 to about 25 wt.%, or alternatively about 20 wt.%, based on the total weight of the homogenous mixture.

[0053] The mixing may include a shear rate of less than 10,000 s'1. The mixing may be performed using a coaxial mixer. The plastic waste and the solvent may be contacted before the mixing, during the mixing, or both. The method may be performed as a continuous process (and is not a batch or semi-batch process), wherein the mass flow rate of continuous solvent and plastic feed streams into the mixing unit 10 is about equal to the mass flow rate of a continuous solvent / plastic mixture product stream output from the mixing unit 10. The plastic waste and solvent may be added simultaneously and continuously to a mixing vessel during the mixing and an effluent stream comprising the homogenous mixture is continuously recovered from the mixing vessel. The solvent may be heated to the mixing temperature.

[0054] In some embodiments, the plastic waste does not pyrolyze into the petroleum solvent. The viscosity may be less than 100,000 cP (e.g., at mixing temperatures) or less than 10,000 cP (which is advantageous for mixing).

[0055] An exemplary method of dissolving plastic waste with a petroleum solvent having a desired SARA distribution may include feeding (e.g., continuously feeding) petroleum solvent from an upstream processing unit to a mixing tank; feeding (e.g., continuously feeding) plastic waste into the mixing tank; mixing the plastic waste into the petroleum solvent at a temperature of at least 140°C to dissolve the plastic waste into the petroleum solvent, wherein an aromatic level of the petroleum solvent is greater than 50 wt%; and feeding (e.g., continuously feeding) the mixture of plastic waste and petroleum solvent to a downstream processing unit.

[0056] In some embodiments, the upstream processing unit comprises a vacuum column, a fluidized catalytic cracker (FCC), or a fuel oil tank. The petroleum solvent may be fed to the mixing tank via a fuel oil stream from the fuel oil tank, a naphtha stream from the FCC, a heavy cycle gas oil (HCGO) or slurry oil from the FCC, a vacuum residue stream from the vacuum column, a vacuum gas oil stream from the vacuum column, or combinations thereof. The downstream processing unit may comprise a pre-heat furnace.

[0057] The method may further comprise heating the mixture in the pre-heat furnace; feeding the heated mixture to a coke drum; coking the heated mixture inside the coke drum to produce coke and vaporized hydrocarbons; and feeding the vaporized hydrocarbons to a coker fractionator. The method may be performed as a continuous process (e.g., that is not a batch or semi-batch process).

[0058] An exemplary system for mixing plastic waste and a petroleum solvent having a desired SARA distribution may include a mixing tank configured to receive the petroleum solvent and plastic waste; a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed; and a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, and wherein the petroleum solventcomprises greater than 50 wt.% aromatics. The method may further include a heater configured to heat contents of the mixing tank to a temperature greater than a melting point of the plastic waste.

[0059] An exemplary method of operating a system for mixing plastic waste and a petroleum solvent having a desired SARA distribution may include activating a conveyor (e.g., an auger) to feed petroleum solvent and plastic waste into a mixing tank; providing power to a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed, and to a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, and wherein the petroleum solvent comprises greater than 50 wt.% aromatics

[0060] The systems and methods of the present disclosure yield surprising results. The commonly held belief in the art has been that like dissolves like. Polymers are very long chain saturates, and thus it would be expected that a more saturated or paraffinic solvent would do a better job of solubilizing the polymers. The inventors have surprisingly discovered that certain petroleum solvent having a desired SARA distribution can achieve advantageous results in solubilizing waste plastics. For example, aromatics are more effective at solubilizing polymers than saturated or paraffinic solvents when used according to the specific methods disclosed herein. In particular, the method comprising mixing the plastic waste and a petroleum solvent having a desired SARA distribution at a mixing temperature of greater than a melting point of the plastic waste to form a homogenous mixture, wherein the petroleum solvent comprises greater than 50 wt.% aromatics, is surprisingly effective at dissolving plastic waste, as evidenced by the examples infra.

[0061] The concept of refinery integration, or using existing processes to co-process plastic waste with petroleum streams, offers the potential to realize significant CAPEX savings and significantly improve both heat and mass transfer. The systems and methods disclosed herein can advantageouslybe used to solubilize plastic streams so that the resulting homogenized blend can be processed in refinery units such as FCC or delayed coker.EXAMPLE 1

[0062] Tests have been conducted using an overhead high-shear mixer. Polypipe (LLDPE) plastic flakes or re-grinds of approximately 5 to 25 mm in size were added to fuel oil, and the sample was heated up to a mixing temperature of approximately 170 °C. The high-shear mixer was operated at a stirring speed within the range of 3,000 to 6,000 rpm. At the conclusion of the test, a sample was taken and examined under an optical microscope. An image of this sample is shown in FIG. 5. The image shows the presence of the plastic ‘particles’ dispersed throughout the fuel oil. The plastic was in this form because the material had cooled down to room temperature when the microscope images were taken. The size of these particles was on the order of 10 microns or less, which is a significant reduction from their starting size of 5 to 25 mm. As a comparison, a test was done with a conventional 4-blade impeller. The sample was heated to a temperature of 170 °C and mixed at approximately 250 rpm. FIG. 6 is an image of the results from this test, showing that much larger particles remain (on the order of at least several hundred microns).EXAMPLE 2

[0063] Tests have also been conducted with a paint mixer of a spiral / helical design. The paint mixer was selected as a rough approximation of the first (i.e., outer) mixer of the present disclosure. The diameter ratio of the paint mixer to the vessel was approximately 0.77. In this test, approximately 400 to 600 g of fuel oil was added to the mixing vessel and heated up to a temperature of approximately 170 °C. While the oil was being heated, the material was mixed with the paint mixer at 50 to 100 rpm. Once the desired temperature of 170 °C was achieved, plastic re-grinds of approximately one to two inches in size were added to the vessel at a rate of approximately 1.6 to 2 g / min, until a concentration of 25 wt% of plastics in fuel oil was achieved. As the plastic concentration increased in the mixture throughout the course of the test, the speed was increased to approximately 125 rpm. The gradual addition of the plastics helped to ensure that agglomerates of plastics would not form.EXAMPLE S

[0064] An alternative test was performed similar to Example 2 but all of the plastics were added to the fuel oil at the start of the test at 25 wt%. It was found that the plastics clumped together into a large mass that could not be deagglomerated.EXAMPLE 4

[0065] Referring to FIGS. 8-10, plastic waste was dissolved in a petroleum solvent (i.e., fuel oil) at a concentration of 20 wt% plastics by mixing with a spiral -helical mixer at 175 °C and at 100 rpm. The plastic was added incrementally until it reached a level of 20 wt%. Once the 20 wt% level was reached, the mixing was continued for 15 minutes, and then the mixing was stopped and the temperature was lowered to room temperature. Based on visual observation confirming complete melting and dissolution of the plastics into the solvent (e.g., no agglomerations or chunks of plastic remain), the outcome of the test was a very homogeneous sample, indicating excellent dissolution of the polymers into the solvent. The solvent had the following SARA composition: 21 wt% saturates,66 wt% aromatics, 7 wt% resins, 5 wt% asphaltenes. The aromatic / saturate ratio was 5.5. FIG 8 is a photograph of the starting plastic waste re-grind material. These flakes (or re-grinds) were -5-25 mm in size. FIG. 9 is a photograph of the solvent. FIG. 10 is a photograph of the mixture of plastics in solvent after cooling down to room temperature.EXAMPLE S

[0066] As a comparison, a test was done using a solvent containing significantly less aromatics (and a lower ratio of aromatics to saturates) as compared with Example 4. The solvent had the following SARA distribution: 48 wt% saturates, 47 wt% aromatics, 4 wt% resins, and < 1 wt% asphaltenes. The plastic and the solvent were mixed with a spiral -helical mixer at 175 °C and at 100 rpm for 30 minutes. The plastic was at a 5 wt% concentration. The result is shown in FIG. 11. The plastics were not solubilized, as can be seen in the photograph (i.e., agglomeration and chunks of undissolved plastic are clearly visible). That is, the plastic grinds remained in-tact and did not dissolve into the solvent after the mixing procedure. An additional attempt was made at a higher temperature 190 °C with no change in the results (i.e., again, the plastics were not solubilized).EXAMPLE 6

[0067] As another comparison, a third solvent was tested having the following SARA distribution: 12 wt% saturates, 57 wt% aromatics, 15 wt% resins, and 16 wt% asphaltenes. The aromatic / saturate ratio in this case was 4.75. The plastic and the solvent were mixed with a spiral-helical mixer at 175 °C and at 100 rpm for 30 minutes. The plastic was at a 5 wt% concentration. The result is shown in FIG. 12. The plastic grinds are clearly visible throughout the sample, indicating poor dissolution (i.e., agglomeration and chunks of undissolved plastic are clearly visible). An additional attempt was made at a higher temperature 190 °C with no change in the results (i.e., again, the plastics were not solubilized).EXAMPLE ?

[0068] FIG. 13 is a photograph the result of a plastic and Solvent A mixture (where Solvent A had proper characteristics to allow for dissolution of plastics) having been added to Solvent B (where Solvent B had improper characteristics) at a wt ratio of 1 :2. That is, Solvent A was in accordance with Example 4 and Solvent B was in accordance with Example 6. Thus, it has been shown that if the plastics are mixed with and dissolved into a solvent with suitable properties, and then that mixture is added to a solvent with improper properties, the plastics typically do not precipitate out of the solution (e.g., no agglomerations or chunks of plastic remain or form). This indicates that downstream combination of the mixture of the present disclosure with other petroleum streams can be carried out without concerns of disturbing the dissolved state of the polymers.

[0069] While embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of this disclosure. The embodiments described herein are exemplary only and are not intended to be limiting. Many variations and modifications of the embodiments disclosed herein are possible and are within the scope of this disclosure. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented. Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other techniques, systems, subsystems, or methods without departing from the scope of this disclosure. Other items shown or discussed as directly coupled or connected or communicating with each other may be indirectly coupled, connected, or communicated with. Method or process steps set forth may be performed in a different order. The use of terms, such as “first,” “second,” “third” or “fourth” to describe various processes or structures is only used as a shorthand reference to such steps / structures and does not necessarily imply that such steps / structures are performed / formed in that ordered sequence (unless such requirement is clearly stated explicitly in the specification).

[0070] Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Ri, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Ri +k* (Ru-Ri), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, > 50 percent, 51 percent, 52 percent, , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Language of degree used herein, such as “approximately,” “about,” “generally,” and “substantially,” represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the language of degree may mean a range of values as understood by a person of skill or, otherwise, an amount that is + / -10%.

[0071] Disclosure of a singular element should be understood to provide support for a plurality of the element. It is contemplated that elements of the present disclosure may be duplicated in any suitable quantity.

[0072] Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc. When a feature is described as “optional,” both embodiments with this feature and embodiments without this feature are disclosed. Similarly, the present disclosure contemplates embodiments where this “optional” feature is required and embodiments where this feature is specifically excluded.

[0073] Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as embodiments of the present disclosure. Thus, the claims are a further description and are an addition to the embodiments of the present disclosure. The discussion of a reference herein is not an admission that it is prior art, especially any reference that can have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein.ADDITIONAL DISCLOSURE

[0074] The following are non-limiting, specific embodiments in accordance with the present disclosure:

[0075] In a first embodiment, (I) an apparatus for mixing plastic into a petroleum stream comprises a mixing tank configured to receive petroleum and plastic; a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed; and a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, or (II) an apparatus for mixing plastic into a petroleum stream comprises a mixing tank (e.g., cylindrical) having a central axis and configured to receive petroleum and plastic; a first impeller disposed within the mixing tank and driven by a first impeller shaft having a central axis that is about co-axial with the central axis of the mixing tank; and a second impeller disposed within the mixing tank and driven by a second impeller shaft having a central axis that is offset a distance (e.g., 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4,75, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 feet) from the central axis of the first impeller and / or the central axis of themixing tank, and wherein the first and second impellers are configured to rotate at the same or different speed, in the same or different (e.g., opposite) directions, or both. The apparatus (I) or (II) may further comprise a third impeller disposed within the mixing tank and driven by a third impeller shaft having a central axis that is offset a distance (e.g., 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4,75, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 feet) from the central axis of the first impeller, the central axis of the mixing tank, and / or the central axis of the second impeller, and wherein the first, second and third impellers are configures to rotate at the same or different speed, in the same or different (e.g., opposite) directions, or both. In the apparatus (I) or (II), the central axis of first, second, and / or third impellers may be about coaxial (e.g., parallel and positioned apart by a distance of equal to less than 1, 0.5, 0.1, 0.05, 0.01, 0.005, 0.001, 0.0005, 0.0001, 0.00005, 0.00001, or 0 inches).

[0076] A second embodiment can include the apparatus of the first embodiment, further comprising a heater configured to heat contents of the mixing tank.

[0077] A third embodiment can include the apparatus of the first embodiment, further comprising a mixer in fluid communication with the mixing tank and configured to impart a shear rate of at least 20,000 s'1(e.g., wherein the mixer is located in a pump-around flow loop in fluid communication with the mixing tank).

[0078] A fourth embodiment can include the apparatus of any of the first through third embodiments, wherein the first impeller comprises a double-helical shape.

[0079] A fifth embodiment can include the apparatus of any of the first through fourth embodiments, wherein the first impeller comprises blades disposed at an angle with respect to the wall.

[0080] A sixth embodiment can include the apparatus of any of the first through fifth embodiments, wherein the second impeller comprises blades configured to pump fluid within the mixing tank.

[0081] A seventh embodiment can include the apparatus of any of the first through sixth embodiments, wherein the first impeller comprising a first shaft and first blades extending from the first shaft, and the second impeller comprises a second shaft and second blades extending from the second shaft.

[0082] An eighth embodiment can include the apparatus of any of the first through seventh embodiments, wherein the first shaft is parallel to the second shaft.

[0083] A ninth embodiment can include the apparatus of any of the first through eighth embodiments, wherein the first shaft is coaxial with the second shaft.

[0084] A tenth embodiment can include the apparatus of any of the first through ninth embodiments, wherein an outer edge of the first blades is disposed closer to the wall than a distance equal to 10% of a diameter of the mixing tank.

[0085] In an eleventh embodiment, a method of mixing plastic material into a petroleum stream includes adding petroleum and plastic material into a mixing tank, wherein the petroleum is heated (e.g., heated before being added to the mixing tank, heated while in the mixing tank but before the plastic material is added, heated while in the mixing tank and after the plastic material is added, or combinations thereof); and mixing the plastic material into the petroleum by inducing a first flow inside the mixing tank proximate to (e.g., at and / or near) a wall of the mixing tank at a first flow rate, and inducing a second flow inside the mixing tank proximate to (e.g., at and / or near) a center of the mixing tank at a second flow rate that is greater than the first flow rate, wherein a direction of the first flow is different from a direction of the second flow.

[0086] A twelfth embodiment can include the method the eleventh embodiment, wherein a temperature inside the mixing tank is approximately 170 °C.

[0087] A thirteenth embodiment can include the method of the eleventh or twelfth embodiments, wherein the petroleum is fuel oil.

[0088] A fourteenth embodiment can include the method of any of the eleventh through thirteenth embodiments, wherein the plastic material has a particle size of 5 to 25 mm before the mixing of the plastic material into the petroleum.

[0089] A fifteenth embodiment can include the method of any of the eleventh through fourteenth embodiments, wherein the plastic material has a particle size of 10 microns or less after the mixing of the plastic material into the petroleum.

[0090] A sixteenth embodiment can include the method of any of the eleventh through fifteenth embodiments, wherein the mixing of the plastic into the petroleum comprises imparting a shear on the petroleum of less than 10,000 s'1.

[0091] A seventeenth embodiment can include the method of any of the eleventh through sixteenth embodiments, wherein the mixing of the plastic material into the petroleum further comprises diverting the petroleum and the plastic material outside of the mixing tank to a mixer that imparts of shear on the petroleum of at least 20,000 s'1.

[0092] In an eighteenth embodiment, a system for mixing plastic material into fuel oil (or other petroleum) comprises a mixing tank; a fuel oil tank configured to supply fuel oil (or other petroleum) to the mixing tank; a first impeller configured to sweep a path proximate to a wall of the mixing tank to mix plastic material into the fuel oil; a pre-heat furnace configured to pre-heat the mixture of plastic material and fuel oil from the mixing tank; a coke drum configured to receive the pre-heated mixture of plastic material and fuel oil from the pre-heat furnace; and a coker fractionator configured to receivethe mixture of plastic material and fuel oil from the coke drum, and output liquid and gas hydrocarbons.

[0093] A nineteenth embodiment can include the system of the eighteenth embodiment, further comprising a heater configured to heat contents of the mixing tank.

[0094] A twentieth embodiment can include the system of the eighteenth or nineteenth embodiments, wherein the first impeller is configured to sweep the path proximate to the wall of the mixing tank at a first rotational speed, and wherein the system further comprises a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller.

[0095] A twenty-first embodiment can include the system of any of the eighteenth through twentieth embodiments, wherein the impeller is configured to mix the plastic material into the fuel oil by imparting a shear on the fuel oil inside the mixing tank of less than 10,000 s'1.

[0096] A twenty-second embodiment can include the system of any of the eighteenth through twenty -first embodiments, further comprising a mixer in fluid communication with the mixing tank and configured to further mix the plastic material into the fuel oil by imparting a shear on the fuel oil outside the mixing tank of at least 20,000 s'1.

[0097] In a twenty -third embodiment, a method of mixing plastic material into a petroleum stream includes adding petroleum and plastic material into a mixing tank to form a mixture, wherein the petroleum is heated (e.g., heated before being added to the mixing tank, heated while in the mixing tank but before the plastic material is added, heated while in the mixing tank and after the plastic material is added, or combinations thereof); and subjecting the mixture to counter-directional shear (e.g., shear of the same or different magnitudes), counter-directional flow (e.g., flow of the same or different magnitudes), opposite-directional shear (e.g., shear of the same or different magnitudes),opposite-directional flow (e.g., flow of the same or different magnitudes), or combinations thereof to produce a homogenous product of the plastic material (solute) in solution with the petroleum stream (solvent).

[0098] A twenty-fourth embodiment can include the method of the twenty-third embodiment, further comprising processing the homogenous product in a refinery process unit selected from the group consisting of a crude oil distillation unit, a light ends recovery unit, a naphtha hydrotreating unit, a catalytic reformer, an aromatization unit, a middle distillates hydrotreating unit, a fluid catalytic cracking unit, a hydrocracker unit, a delayed coking unit, and any combination thereof.

[0099] A twenty-fifth embodiment can include the method of the twenty-third or twenty-forth embodiment, wherein the petroleum stream is a product of a refinery process unit selected from the group consisting of a crude oil distillation unit, a light ends recovery unit, a naphtha hydrotreating unit, a catalytic reformer, an aromatization unit, a middle distillates hydrotreating unit, a fluid catalytic cracking unit, a hydrocracker unit, a delayed coking unit, and any combination thereof.

[0100] In a twenty-sixth embodiment, a method of dissolving plastic waste with a petroleum solvent includes mixing the plastic waste and the petroleum solvent at a mixing temperature of greater than a melting point of the plastic waste to form a homogenous mixture, wherein the petroleum solvent comprises greater than 50 wt.% aromatics.

[0101] A twenty-seventh embodiment can include the method of the twenty-sixth embodiment, wherein the petroleum solvent comprises aromatics in a range of from about 50 wt% to about 75 wt%, alternatively from about 50 wt% to about 70 wt%, or alternatively from about 50 wt% to about 65 wt.%, or Alternatively, from about 50-55, 55-60, 50-60, 60-65, 60-70, or 65-80 wt%.

[0102] A twenty-eighth embodiment can include the method of the twenty-sixth or twentyseventh embodiments, wherein the petroleum solvent comprises less than 20 wt.% resins, or alternatively, less than 30, 25, 24, 23, 22, 21, 19, 18, 17, 16, 15 wt.%.

[0103] A twenty-ninth embodiment can include the method of any of the twenty-sixth through twenty-eighth embodiments, wherein the petroleum solvent comprises resins in a range of from about 0 wt% to about 20 wt%, alternatively from about 5 wt% to about 20 wt%, or alternatively from about 5 wt% to about 17 wt.%, or alternatively from 1-30, 0-20, 5-18, 7-10, less and 15, less than 10, or less than 5 wt%.

[0104] A thirtieth embodiment can include the method of any of the twenty-sixth through twentyninth embodiments, wherein the petroleum solvent comprises less than 15 wt.% asphaltenes, or alternatively less than 20, 19, 18, 17, 16, 14, 13, 13, 12, 11, 10 orlesswt%.

[0105] A thirty-first embodiment can include the method of any of the twenty-sixth through thirtieth embodiments, wherein the petroleum solvent comprises asphaltenes in a range of from about 0 wt% to about 15 wt%, alternatively from about 0 wt% to about 10 wt%, or alternatively from about 5 wt% to about 10 wt.%, alternatively from 0-20, 5-25, 0-18, less than 14, less than 11 less than 7 or less than 5, or 0 wt.%.

[0106] A thirty-second embodiment can include the method of any of the twenty-sixth through thirty-first embodiments, wherein the petroleum solvent comprises less than 30 wt.% saturates, or less than 40, 35, 25, 20, 15, 10, 5, or 0 wt.%.

[0107] A thirty-third embodiment can include the method of any of the twenty-sixth through thirty-second embodiments, wherein the petroleum solvent comprises saturates in a range of from about 10 to about 30 wt%, alternatively from about 10 wt% to about 25 wt%, or alternatively from about 15 to about 25 wt.%, alternatively, 10-50, 20-30, 15-30, 20-45, alternatively less than 40, 35, 30, 25, 20, 15, 10, 5, or0wt%.

[0108] A thirty-fourth embodiment can include the method of any of the twenty-sixth through thirty-third embodiments, wherein the aromatics / saturates ratio is greater than 1.5, alternatively, in arange of from about 1.5 to about 7.5, alternatively from about 2.5 to about 7.5, alternatively from about 2.5 to 5.0, or alternatively about 3.

[0109] A thirty-fifth embodiment can include the method of any of the twenty-sixth through thirty-fourth embodiments, wherein the amounts of saturates, aromatics, resins, and asphaltenes (e.g., the SARA distribution) are determined using clay-gel column chromatography.

[0110] A thirty-sixth embodiment can include the method of any of the twenty-sixth through thirty-fifth embodiments, wherein the amounts of saturates, aromatics, resins, and asphaltenes (e.g., the SARA distribution) are determined according to ASTM D2007.

[0111] A thirty-seventh embodiment can include the method of any of the twenty-sixth through thirty-sixty embodiments, wherein the amount of plastic waste present in the homogenous mixture is in a range of from about 1 to about 40 wt.%, alternatively from about 5 to about 30 wt.%, alternatively from about 10 to about 25 wt%, alternatively from about 15 to about 25 wt.%, or alternatively about 20 wt.%, alternatively less 30-50, 25-35, 10-20, less than 50, less than 40, less than 30, less than 20, or less than 10 wt.% based on the total weight of the homogenous mixture.

[0112] A thirty-eighth embodiment can include the method of any of the twenty-sixth through thirty-seventh embodiments, wherein the temperature is at least 140°C, or alternatively 100-200, 130-160, 140-150, 145-170, or at least 160 °C.

[0113] A thirty-ninth embodiment can include the method of any of the twenty-sixth through thirty-eighth embodiments, wherein the temperature is in a range of from about 140 to about 200°C, alternatively from about 160 to about 180°C, or alternatively from about 170 to about 180°C.

[0114] A fortieth embodiment can include the method of any of the twenty-sixth through thirtyninth embodiments, wherein the plastic waste comprises either one or a combination of plastic flakes, plastic agglomerates, and plastic re-grinds.

[0115] A forty-first embodiment can include the method of any of the twenty-sixth through fortieth embodiments, wherein the plastic waste has an average particle size in a range of from about 1 to about 100 mm, alternatively in a range of from about 1 to about 50 mm, or alternatively in a range of from about 5 to about 25 mm, or alternatively about 1-30, 10-40, 20-80, or 30-100 mm. Typically there is a specific screen size for the output of the granulators, which are used to produce the re-grinds or agglomerates (e.g. screen sizes of 3 / 8”, ’A”, or 1” are common).

[0116] A forty-second embodiment can include the method of any of the twenty-sixth through forty-first embodiments, wherein the plastic waste comprises equal to or greater than 70, 75, 80, 85, 90, 95 wt. % polyolefins, or alternatively 70-95, 80-90, 70-80, or 50-70 wt. %.

[0117] A forty -third embodiment can include the method of any of the twenty-sixth through forty -second embodiments, wherein the mixing comprises a shear rate of less than 10,000 s'1.

[0118] A forty-fourth embodiment can include the method of any of the twenty-sixth through forty -third embodiments, wherein the mixing is performed using a coaxial mixer.

[0119] A forty-fifth embodiment can include the method of any of the twenty-sixth through fortyfourth embodiments, wherein the plastic waste and the solvent are contacted before the mixing, during the mixing, or both.

[0120] A forty-sixth embodiment can include the method of any of the twenty-sixth through fortyfifth embodiments, wherein the method is performed as a continuous process (and is not a batch or semi-batch process).

[0121] A forty-seventh embodiment can include the method of any of the twenty-sixth through forty-sixth embodiments, wherein the plastic waste and solvent are added simultaneously and continuously to a mixing vessel during the mixing and an effluent stream comprising the homogenous mixture is continuously recovered from the mixing vessel.

[0122] A forty-eighth embodiment can include the method of any of the twenty-sixth through forty-seventh embodiments, wherein the solvent is heated to the mixing temperature.

[0123] A forty -ninth embodiment can include the method of any of the twenty-sixth through fortyeighth embodiments, wherein the plastic waste does not pyrolyze into the petroleum solvent.

[0124] A fiftieth embodiment can include the method of any of the twenty-sixth through fortyninth embodiments, wherein the mixture has a viscosity of less than 100,000 cP (at mixing temperatures), or less than 10,000 cP.

[0125] In a fifty-first embodiment, a method of dissolving plastic waste with a petroleum solvent comprises feeding (e.g., continuously feeding) petroleum solvent from an upstream processing unit to a mixing tank; feeding (e.g., continuously feeding) plastic waste into the mixing tank; mixing the plastic waste into the petroleum solvent at a temperature of at least 140°C to dissolve the plastic waste into the petroleum solvent, wherein an aromatic level of the petroleum solvent is greater than 50 wt%; and feeding (e.g., continuously feeding) the mixture of plastic waste and petroleum solvent to a downstream processing unit.

[0126] A fifty-second embodiment can include the method of the fifty -first embodiment, wherein the upstream processing unit comprises a vacuum column, a fluidized catalytic cracker (FCC), or a fuel oil tank.

[0127] A fifty-third embodiment can include the method of the fifty-first or fifty-second embodiments, wherein the petroleum solvent is fed to the mixing tank via a fuel oil stream from the fuel oil tank, a naphtha stream from the FCC, a vacuum residue stream from the vacuum column, a vacuum gas oil stream from the vacuum column, or combinations thereof

[0128] A fifty-fourth embodiment can include the method of any of the fifty-first through fifty-third embodiments, wherein the downstream processing unit comprises a pre-heat furnace.

[0129] A fifty-fifth embodiment can include the method of any of the first-first through fiftyfourth embodiments, further comprising heating the mixture in the pre-heat furnace; feeding the heated mixture to a coke drum; coking the heated mixture inside the coke drum to produce coke and vaporized hydrocarbons; and feeding the vaporized hydrocarbons to a coker fractionator.

[0130] A fifty-sixth embodiment can include the method of any of the fifty-first through fiftyfourth embodiments, wherein the method is performed as a continuous process (and is not a batch or semi-batch process).

[0131] In a fifty-seventh embodiment, a system for mixing plastic waste and a petroleum solvent comprises a mixing tank configured to receive the petroleum solvent and plastic waste; a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed; and a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, and wherein the petroleum solvent comprises greater than 50 wt.% aromatics.

[0132] A fifty-eighth embodiment can include the system of the fifty-seventh embodiment, further comprising a heater configured to heat contents of the mixing tank to a temperature greater than a melting point of the plastic waste.

[0133] In a fifty -ninth embodiment, a method of operating a system for mixing plastic waste and a petroleum solvent comprises activating a conveyor to feed petroleum solvent and plastic waste into a mixing tank; providing power to a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed, and to a second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed, wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, and wherein the petroleum solvent comprises greater than 50 wt.% aromatics.

[0134] A sixtieth embodiment can include the method of the fifty-ninth embodiment, wherein the conveyor comprises an auger.

[0135] Use of the phrase “at least one of’ preceding a list with the conjunction “and” should not be treated as an exclusive list and should not be construed as a list of categories with one item from each category, unless specifically stated otherwise. A clause that recites “at least one of A, B, and C” can be infringed with only one of the listed items, multiple of the listed items, and one or more of the items in the list and another item not listed.

[0136] As used herein, the term “or” does not require selection of only one element. Thus, the phrase “A or B” is satisfied by either element from the set {A, B}, including multiples of any either element; and the phrase “A, B, or C” is satisfied by any element from the set {A, B, C} or any combination thereof, including multiples of any element. A clause that recites “A, B, or C” can be infringed with only one of the listed items, multiple of the listed items, and one or more of the items in the list and another item not listed.

[0137] As used herein, the terms “a” and “an” mean “one or more.” As used herein, the term “the” means “the one or more.” Thus, the phrase “an element” means “one or more elements;” and the phrase “the element” means “the one or more elements.”

[0138] As used herein, the term “and / or” includes any combination of the elements associated with the “and / or” term. Thus, the phrase “A, B, and / or C” includes any of A alone, B alone, C alone, A and B together, B and C together, A and C together, or A, B, and C together.

Claims

CLAIMSWhat is claimed is:

1. A method of dissolving plastic waste with a petroleum solvent, comprising:mixing the plastic waste and the petroleum solvent at a mixing temperature of greater than a melting point of the plastic waste to form a homogenous mixture,wherein the petroleum solvent comprises greater than 50 wt.% aromatics.

2. The method of claim 1, wherein the petroleum solvent comprises aromatics in a range of from about 50 wt.% to about 75 wt.%.

3. The method of claim 1, wherein the petroleum solvent comprises less than 20 wt.% resins.

4. The method of claim 1, wherein the petroleum solvent comprises less than 15 wt.% asphaltenes.

5. The method of claim 1, wherein the petroleum solvent comprises less than 30 wt.% saturates.

6. The method of claim 1, wherein an amount of the plastic waste present in the homogenous mixture is in a range of from about 1 to about 40 wt.%.

7. The method of claim 1, wherein the temperature is at least 140°C.

8. The method of claim 1, wherein the plastic waste comprises equal to or greater than 70 wt. % polyolefins.

9. The method of claim 1, wherein the plastic waste and the petroleum solvent are added simultaneously and continuously to a mixing vessel during the mixing and an effluent stream comprising the homogenous mixture is continuously recovered from the mixing vessel.

10. The method of claim 1, wherein the solvent is heated to the mixing temperature.

11. The method of claim 1, wherein the plastic waste does not pyrolyze into the petroleum solvent.

12. A method of dissolving plastic waste with a petroleum solvent, comprising:feeding petroleum solvent from an upstream processing unit to a mixing tank;feeding plastic waste into the mixing tank;mixing the plastic waste into the petroleum solvent at a temperature of at least 140°C to dissolve the plastic waste into the petroleum solvent, wherein an aromatic level of the petroleum solvent is greater than 50 wt%; andfeeding the mixture of plastic waste and petroleum solvent to a downstream processing unit.

13. The method of claim 12, wherein the petroleum solvent is fed to the mixing tank via a fuel oil stream from a fuel oil tank, a naphtha stream from a fluid catalytic cracker, a FCC slurry oil or Heavy Cycle Gas Oil (HCGO) from a fluid catalytic cracker, a vacuum residue stream from a vacuum column, a vacuum gas oil stream from a vacuum column, or combinations thereof.

14. The method of claim 12, further comprising:heating the mixture in the pre-heat furnace;feeding the heated mixture to a coke drum;coking the heated mixture inside the coke drum to produce coke and vaporized hydrocarbons; andfeeding the vaporized hydrocarbons to a coker fractionator.

15. A system for mixing plastic waste and petroleum solvent, comprising:a mixing tank configured to receive petroleum solvent and plastic waste;a first impeller configured to sweep a path proximate to a wall of the mixing tank at a first rotational speed; anda second impeller configured to rotate inside of the path at a second rotational speed that is greater than the first rotational speed,wherein a direction of rotation of the first impeller is different from a direction of rotation of the second impeller, andwherein the petroleum solvent comprises greater than 50 wt.% aromatics.

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