Methods for mixing plastics into petroleum streams

Abstract

An apparatus for mixing plastic into a petroleum stream may include 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. A direction of rotation of the first impeller may be different from a direction of rotation of the second impeller.

Description

METHODS FOR MIXING PLASTICS INTO PETROLEUM STREAMSTECHNICAL FIELD

[0001] 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

[0002] 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.

[0003] 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 inefficient and expensive. Additionally, these processes may suffer from poor mixing, which in turn may negatively impact heat transfer and mass transfer.

[0004] 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

[0005] 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.

[0006] FIG. l is a schematic diagram of an exemplary system for mixing plastic into a petroleum stream, according to an embodiment of the present disclosure;

[0007] FIG. 2 is a schematic diagram of an exemplary mixing unit for mixing plastic into a petroleum stream, according to an embodiment;

[0008] FIG. 3 A is a perspective view of an exemplary impellor, according to an embodiment;

[0009] FIG. 3B is a side view of an exemplary impeller, according to another embodiment;

[0010] FIG. 4 is a partial cut-away perspective view of an exemplary high shear pump, according to an embodiment;

[0011] FIG. 5 is an optical microscope image of an exemplary mixture of polypipe plastic in fuel oil after mixing with a high-shear mixer;

[0012] 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; and

[0013] FIG. 7 is a flow diagram of a method for mixing plastic into a petroleum stream.DETAILED DESCRIPTION

[0014] 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.

[0015] 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, 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., petroleum stream) may ensure a homogeneous stream without large plastic agglomerates can be fed to the refinery unit operations. 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 (becauseof 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 multiaxial system according to the present disclosure can minimize these effects.

[0016] 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. 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. 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.

[0017] The plastic to be mixed into the petroleum may include any suitable plastic material. Nonlimiting examples include polyolefins, such as polyethylene and 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, doorframes, insulation materials, and 3D printing filament, and / or consumer waste.

[0018] 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; a fuel oil tank 12 configured to supply 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 of plastic 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 mayfurther include a heater configured to heat contents of the mixing tank 31 . The heater may apply heat 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 by imparting a shear on the petroleum 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 at a concentration of approximately 25 % wt. After the plastic leaves the system 1, it may be added to a main stream of a refinery. In some embodiments, the concentration of plastic in the main stream of the refinery will be approximately 0.5 to 1% wt.

[0019] In more detail, the fuel oil tank 12 may be configured to store heavy petroleum products. 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. The fuel oil tank 12 may have monitoring and / or control systems for measuring and managing tank temperature and contents.

[0020] The pre-heat furnace 14 may be configured to increase the temperature of the mixture of plastic and petroleum. 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.

[0021] 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 the coke 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.

[0022] 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 thermally cracked 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 be fed into the coker fractionator 18. In some embodiments, material is recycled from the coker fractionator 18 into the pre-heat furnace 14. The coker fractionator 18 may output gas oil, light liquids, and gasses, 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.

[0023] 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 polyethylene (such as linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE)), polypropylene (PP), or any other suitable 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 into pellets or agglomerates. 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 fuel oil. Pyrolyzing the plastic before it is added to the mixing tank 31 is optional and may not be performed in many applications. The mixing tank 31 may be configured to receive petroleum through an inlet. The petroleum 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. 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 someembodiments, the motor 1 1 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.

[0024] The mixing unit 10 may further include a high shear mixer 13 in fluid communication with the mixing tank 31 and configured to impart a shear on the petroleum (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 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 from the first pipe 43. An impeller 141 may apply shear to the mixture to mix and disperse the plastic in the petroleum. The mixture may then exit through the outlet 143 to the second pipe 17.

[0025] 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 into the pre-heat furnace 14. 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 recirculate between 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 allowingthe mixture of plastic and petroleum to exit the mixing unit 10 and enter the 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).

[0026] 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.

[0027] Referring to FIG. 3 A, 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 longitudinal axis L of the mixing tank 31, or extend at an angle with respect to the longitudinal axis L of the mixing tank 31.

[0028] 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 fromthe 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 corners formed by the rectangular frame 127. For example, one of the helical blades 130 may be connected to a corner formed by the first segment 145 and the third segment 134 and a corner 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 corner 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 be oriented 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.

[0029] 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.

[0030] 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.

[0031] 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 secondshaft 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 may extend 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.

[0032] Referring to FIG. 7, a method 700 of mixing plastic into a petroleum stream is shown. The method 700 may include the step 702 of adding petroleum and plastic material into a mixing tank, wherein the petroleum is heated. The method 700 may further include the step 704 of mixing the plastic material into the petroleum 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 inside the mixing tank may be approximately 170 °C. The petroleum may 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 into the petroleum. The mixing of the plastic into the petroleum may include imparting a shear on the petroleum of less than 10,000 s’1. The mixing of the plastic material into the petroleum may further include 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.

[0033] The inventors have 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 thanthe second impeller 124, and the first impeller 121 rotating at a lower speed than the second impeller 124 allows plastic to be dissolved into heated petroleum without pre-processing the plastic with pyrolysis. Agglomeration of sticky melted plastics may be eliminated by this process. The output of the process may be a soluble, one-phase solution with substantially no chunks nor agglomerates and uniform distribution of polymers throughout the petroleum solvent. With the elimination of the pyrolysis step, the plastic may be directly mixed into 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 and depolymerizing the plastic before adding it to the petroleum. The only pre-processing necessary may be mechanical. Heat and mass transfer may also be significantly improved by the method.EXAMPLE 1

[0034] Tests have been conducted using an overhead high-shear mixer. Polypipe 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

[0035] 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 mixturethroughout 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 3

[0036] 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.

[0037] 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).

[0038] 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, Rl, 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=R1 +k* (Ru-Rl), 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 avalue, 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%.

[0039] 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.

[0040] 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.

[0041] 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

[0042] The following are non-limiting, specific embodiments in accordance with the present disclosure:

[0043] 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 thatis 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 the mixing tank, and wherein the first and second impellers are configures 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).

[0044] A second embodiment can include the apparatus of the first embodiment, further comprising a heater configured to heat contents of the mixing tank.

[0045] 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).

[0046] A fourth embodiment can include the apparatus of any of the first through third embodiments, wherein the first impeller comprises a double-helical shape.

[0047] 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.

[0048] 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.

[0049] 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 thefirst shaft, and the second impeller comprises a second shaft and second blades extending from the second shaft.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] A twelfth embodiment can include the method the eleventh embodiment, wherein a temperature inside the mixing tank is approximately 170 °C.

[0055] A thirteenth embodiment can include the method of the eleventh or twelfth embodiments, wherein the petroleum is fuel oil.

[0056] 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 20 mm before the mixing of the plastic material into the petroleum.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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 receive the mixture of plastic material and fuel oil from the coke drum, and output liquid and gas hydrocarbons.

[0061] A nineteenth embodiment can include the system of the eighteenth embodiment, further comprising a heater configured to heat contents of the mixing tank.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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).

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.”

[0071] 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. An apparatus for mixing plastic into a petroleum stream, comprising: 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.

2. The apparatus of claim 1, further comprising a heater configured to heat contents of the mixing tank.

3. The apparatus of claim 1, 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.

4. The apparatus of claim 1, wherein the first impeller comprises a double-helical shape.

5. The apparatus of claim 1, wherein the first impeller comprises blades disposed at an angle with respect to the wall.

6. The apparatus of claim 1, wherein the second impeller comprises blades configured to pump fluid within the mixing tank.

7. The apparatus of claim 1, 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.

8. The apparatus of claim 7, wherein the first shaft is parallel to the second shaft.

9. The apparatus of claim 7, wherein the first shaft is coaxial with the second shaft.

10. The apparatus of claim 7, 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.

11. A method of mixing plastic material into a petroleum stream, comprising: adding petroleum and plastic material into a mixing tank, wherein the petroleum is heated; and mixing the plastic material into the petroleum 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.

12. The method of claim 11, wherein a temperature inside the mixing tank is approximately 170 °C.

13. The method of claim 11, wherein the petroleum is fuel oil.

14. The method of claim 11, wherein the plastic material has a particle size of 5 to 25 mm before the mixing of the plastic material into the petroleum.

15. The method of claim 11, wherein the plastic material has a particle size of 10 microns or less after the mixing of the plastic material into the petroleum.

16. A system for mixing plastic material into fuel oil, comprising: a mixing tank; a fuel oil tank configured to supply fuel oil 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; anda coker fractionator configured to receive the mixture of plastic material and fuel oil from the coke drum, and output liquid and gas hydrocarbons.

17. The system of claim 16, further comprising a heater configured to heat contents of the mixing tank.

18. The system of claim 16, 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.

19. The system of claim 16, wherein the first 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.

20. The system of claim 19, 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.

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