Process for pyrolysis of PVC-containing mixed plastic wastes.

Abstract

A process is provided for the pyrolysis of a mixed plastic stream containing polyvinyl chloride (PVC), in which chlorides from the PVC are removed from an initial melt reactor that melts the mixed plastic stream. The chlorides are removed in a vapor stream from the initial melt reactor, and additional chlorides are removed by the addition of an adsorbent to the pyrolysis reactor and in an adsorption bed downstream of the pyrolysis reactor. The pyrolysis reactor has a configuration including two cylindrical ring structures and an inner cylindrical ring structure within the outer cylindrical ring structure, where a circulating liquid feed stream enters the pyrolysis reactor in a tangential direction to the ring edges of the two cylindrical ring structures, and solid particles move in a downward direction toward the bottom of the pyrolysis reactor.

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority to U.S. Patent Application No. 63 / 132,573, filed December 31, 2020, which is incorporated herein in its entirety.

[0002] FIELD OF THE INVENTION The general field is the pyrolysis of plastic waste streams into hydrocarbons while minimizing the amount of mixed plastic sorting required. Specifically, the present disclosure relates to a low temperature, unstirred, well-mixed pyrolysis reactor. [Background technology]

[0003] Mixed plastic waste originates from curbside waste collection of post-consumer plastic waste. Mixed plastic waste also originates from waste from certain industrial sites, such as construction waste, packaging waste, and agricultural waste, with a wide range of compositions. Chemical recycling by pyrolysis processes is known to convert plastic waste into fuel or petrochemical feedstock alternatives in an air-free atmosphere and under higher temperature conditions, e.g., 350°C to 900°C.

[0004] Despite the variety of mixed plastic feedstocks, the broad definition of mixed plastic waste contains all seven types of plastics: polyethylene terephthalate (PET), low- and high-density polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS), as well as miscellaneous plastics derived from various post-consumer sources, such as e-waste, automotive waste, polyurethane foam packaging, and carpet nylon. Other impurities, such as trace metals from the polymerization process and as formulation additives to improve performance, may be present in the mixed waste feed. Additionally, small amounts of non-plastics, such as paper and wood, may also be present.

[0005] Certain plastics produce higher yields of char, a carbonaceous solid. Char is known to have a significant deactivating effect on heterogeneous catalysts. U.S. Patent No. 6,255,547 (B1) is an example describing a heterogeneous catalyst used to pyrolyze plastics. Heterogeneous catalysts are prone to rapid catalyst deactivation from pyrolysis conditions and deactivating interference from by-products. In particular, interference can occur from coating the catalyst surface or blocking the pores with char. European Patent No. 2,516,592 (B1) describes a method of minimizing interference using a catalyst by employing a batch-mode mechanically stirred reactor. Batch reactors remove char from the bottom of the reactor after each reaction cycle. In many situations, batch operation is undesirable. Operators require multiple reaction trains to avoid production interruptions in batch operation, and schedules become complex. Batch operation can also contribute to fluctuations in product quality over time unless multiple parallel trains are used in a staggered schedule. Operating in this manner adds both capital and operating costs. Pyrolysis without a catalyst is more efficient and economical to carry out continuously.

[0006] The prior art has taught the pyrolysis of plastic waste by using rotary furnaces (US Patent Application Publication Nos. 20170283706(A1) and 201702182786(A1)) or extrusion equipment (US Patent No. 10,233,393). Transport of the char-containing products can involve operating the rotary furnace at a specific rotation speed or utilizing an Auger-type device. Most commonly, heat is transferred indirectly through the reactor wall by fuel gas combustion, electrical heating, or a hot oil medium. Heat transfer to the reactants depends on the conductivity coefficient between the wall and the reactants. This results in a large temperature gradient within the reactor. The process fluid near the wall is much hotter than the process fluid away from the heated wall. The net effect is an excess char yield due to the hotter fluid near the wall. Uniform heat distribution within the reactor should result in a lower char yield and a higher product yield.

[0007] The use of convective heat transfer within a pyrolysis reactor helps avoid the problems associated with indirect heating discussed above. This is typically accomplished by circulating a process stream and heating it with an external heater or exchanger, so that the process stream acts as the heating medium for the reactor (see U.S. Patent Application Publication No. 20140114098(A1)). However, circulating heat transfer media can thermally decompose, complicating the selection of a heating fluid. Plastics themselves also have low thermal conductivity, meaning that large amounts of heat transfer media may be required. U.S. Patent Application Publication No. 20140114098(A1) discloses the use of crude oil as a heat transfer aid to overcome the low thermal conductivity of molten plastic feed. Crude oil and its distillate fractions are known to decompose significantly at temperatures found in pyrolysis reactors. This means that a continuous supply of crude oil is required. This poses a real challenge when such a supply is difficult to obtain and adds extra cost to the process. A process stream is a better choice for the heating medium because it solves this procurement issue. The recycled product stream from the process must be free of large metal solids and large char solids to avoid heater fouling and exchanger fouling. Through a novel reactor design, the pyrolysis pumparound stream can be minimized in its solids content so that the stream does not erode or foul and can provide the heating medium requirements.

[0008] In continuously operated, well-mixed reactor systems, metal species from the feed, such as iron, copper, and aluminum-containing residues in various molecules, any heterogeneous catalyst, or performance-enhancing adsorbents, or larger carbonaceous char particles, can erode, particularly fouling, heater tubes and / or circulation pumps, leading to reduced run times and therefore blockages in transfer lines. It is preferable to remove such solid particles, including metal species from the feed, any heterogeneous catalyst, or performance-enhancing adsorbents, or larger carbonaceous char particles. Metal species, such as iron, copper, and aluminum, are two to three times denser than adsorbent and carbonaceous char particles and therefore can settle to the reactor bottom and leave the process much more easily. However, there is a need to design a system that allows adsorbent and carbonaceous char particles, which can cause blockage problems, to settle to the reactor bottom.

[0009] Therefore, there is a need for a robust process for handling mixed plastics, particularly one that minimizes the amount of sorting of the plastic feed. The reactor system must operate continuously and effectively settle metal and char particles for smooth process operation while maintaining high heat transfer efficiency to the reactor utilizing the process stream. In particular, it can be beneficial to use a reactor that does not need to have a physical mixer, but instead relies on stream velocity to provide the necessary mixing. Summary of the Invention

[0010] Various embodiments contemplated herein relate to processes and apparatus for pyrolyzing mixed plastic waste streams to produce oil products with low chloride content. Exemplary embodiments taught herein provide a process for pyrolyzing mixed plastic waste streams. The embodiments also illustrate novel reactor designs that help enable the aforementioned process.

[0011] According to an exemplary embodiment, a process for pyrolyzing a mixed plastic waste stream is provided. The process involves pyrolyzing a minimally sorted mixed plastic waste stream. The waste plastic is first contacted with a hot liquid stream produced from the process in a melting reactor. This melting reactor melts the waste plastic and produces a vapor stream, which will be described in more detail later in this specification. The bottom liquid from the melting reactor may be pumped or pressurized to a pyrolysis reactor, where the melting reactor bottom stream is decomposed into a vapor stream and a bottom liquid stream. The pyrolysis reactor contains a significant stock of liquid material produced in the polymerization reactor. This liquid mixes with the melting reactor bottom liquid to provide all the heat of reaction and vaporization required for both the melting reactor and the pyrolysis reactor. The hot liquid stream flows through a tangential jet and into the pyrolysis reactor top ring region via a pumping device. The hot liquid stream has a higher temperature than the main reactor because it provides all of the heat required for the pyrolysis reaction. The pyrolysis reaction produces char particles that settle along the circulation wall region to the bottom of the pyrolysis reactor. Any metal particles and large char particles are collected and discharged along the liquid stream at the bottom of the pyrolysis reactor. A portion of the reactor liquid is removed and sent to a pump-around pump. A portion of the circulating liquid is sent through a heater system that provides all the heat needed to sustain the main cracking reaction. At least a portion of the circulating liquid from the heating system is sent directly to the melt reactor to sustain the melt reaction needs.

[0012] The present process utilizes a novel reactor design to provide a method for continuous pyrolysis operation and solids separation, despite using a minimally sorted mixed plastic feed.

[0013] These features, aspects, and advantages of the present disclosure will become better understood upon consideration of the following detailed description, drawings, and appended claims. [Brief explanation of the drawings]

[0014] Various embodiments are described below in conjunction with the following drawings, in which like numbers refer to like elements and in which: [Figure 1] 1 is a schematic diagram of a process and apparatus for pyrolyzing mixed plastic streams according to an exemplary embodiment; FIG. [Figure 2A] 1 is a schematic diagram of a reactor system for pyrolysis of mixed plastic streams in accordance with an exemplary embodiment; FIG. 2 is a schematic diagram showing the feed entering at a vertical angle; [Figure 2B] 1 is a schematic diagram of a reactor system for pyrolysis of mixed plastic streams in accordance with an exemplary embodiment; FIG. 2 is a schematic diagram showing a feed entering at a tangential angle; [Figure 3A] FIG. 1 is a schematic diagram of an alternative reactor system for pyrolysis of mixed plastic streams, including reactors A, B, and C, in conjunction with an exemplary embodiment. [Figure 3B] FIG. 1 is a schematic diagram of an alternative reactor system for pyrolysis of mixed plastic streams, including reactors A, B, and C, in conjunction with an exemplary embodiment. [Figure 3C] FIG. 1 is a schematic diagram of an alternative reactor system for pyrolysis of mixed plastic streams, including reactors A, B, and C, in conjunction with an exemplary embodiment. [Figure 4] FIG. 1 is a schematic diagram of an alternative process and apparatus for pyrolyzing mixed plastic streams according to an exemplary embodiment.

[0015] definition As used herein, the term "reactor" refers to a pyrolysis vessel that provides residence time for the feed polymer. A melt tank reactor is a reactor in which only a portion of the mixed plastic feed is pyrolyzed as the majority of the mixed plastic feed undergoes physical melting to become a viscous liquid. The main pyrolysis reactor types are introduced above, and well-mixed type reactors, which use convective heat transfer, have advantages over the indirect conductive heater transfer provided by furnaces or screw extruders. Well-mixed reactors exhibit an established, uniform temperature distribution throughout the liquid space.

[0016] As used herein, the term "mixed plastic feed" means that more than one polymer is present in the feed.

[0017] As used herein, the term "product" refers to a portion of the mass stream following a pyrolysis reaction. The product can be broad, ranging from a primary product that can be sold for a profit, i.e., a stream that is a by-product when the primary profit product is the intended product. In the present context, the pyrolysis reaction produces a residual gaseous product containing 5-10 wt.% hydrocarbon gases from the molten feed, a liquid with a yield of 70-90 wt.% when condensed to room conditions, and a residue of 2-15 wt.% derived from the reactor discharge as a mixture of liquids and solids that may not have such a high profit margin that they are considered by-products.

[0018] As used herein, the term "residue" refers to the portion remaining after a process step. In the present context, the residue is specifically a stream that leaves the process boundary as a mixture of liquids and solids that has relatively less beneficial use for downstream applications than the main product.

[0019] As used herein, the term "char" refers to the solid material remaining after a plastic feed stream is pyrolyzed. Char is a carbonaceous by-product that is typically embedded in the residue stream. Char is an inevitable by-product of creating the primary product. Reaction strategies can be applied to reduce char, but char cannot be eliminated. Certain plastic compositions produce greater amounts of char than others. It is known that rigid plastics and aromatic-containing plastic compounds, such as PVC, PET, PS, or acrylonitrile butadiene styrene derived from electronic waste, tend to produce more char than polyethylene and polypropylene under comparable processing conditions.

[0020] As used herein, the term "solid" refers to a material in a solid state. As mentioned above, mixed plastics may contain layered additives introduced during the polymer manufacturing process. One example is glass fiber species based on MgO, CaO, and LiO. Another example is metal fillers based on zinc, lead, or cadmium when forming conductive plastics. The metal or alkali metal ultimately becomes a solid residue stream. Another form of solid can come from adsorbents useful for reacting chloride-containing molecules during the reaction. Examples include calcium-based adsorbents in hydroxides, oxides, or carbonates, often derived from natural minerals. Thirdly, there is the aforementioned solid, which is carbonaceous char in an agglomerated form. Large char particles, when conveyed to pumps or heaters, can settle in transfer lines, continually fouling these lines and causing flow interruptions and poor heat transfer. They can also clog pump gears or blades, resulting in long-term interruptions. Large char particles are referred to here by size. Solid / liquid separation is related to their density and particle size. Stokes' law and its derivatives are frequently used to predict the behavior of solids transported in liquids. Metals, alkali metals, and alkaline earth metals are denser than char, a carbonaceous solid, and therefore more likely to settle to the bottom of the reactor for discharge. Selectively settling char presents a more challenging challenge due to its lower density. The difficulty is even more severe when attempting to settle specific, smaller particle size cuts of char. Regarding solid density, particle densities of metals, alkali metals, and alkaline earth metals are frequently 2-5 g / cc. Char particles can have particle densities of 1.25-1.8 g / cc. Char particles larger than about 150 micrometers can be considered more harmful due to their contribution to contamination.

[0021] As used herein, the term "portion" means an amount or portion that is taken or separated from a main stream without any change in composition compared to the main stream. Furthermore, the term "portion" includes dividing the removed or separated portion into multiple portions, each portion retaining the same composition compared to the main stream.

[0022] As used herein, the term "unit" can refer to an area that includes one or more pieces of equipment and / or one or more subunits. Equipment can include one or more reactors or reaction vessels, heaters, separators, drums, exchangers, pipes, pumps, compressors, and controllers. Additionally, equipment such as reactors, dryers, or vessels can further include one or more units or subunits.

[0023] The term "communication" means operatively permitting the flow of material between the listed components.

[0024] The term "downstream communication" means that at least a portion of the material flowing to the object in the downstream communication can operatively flow from the object in communication.

[0025] The term "upstream communication" means that at least a portion of the material flowing from the object in the upstream communication can operatively flow to the communicating object.

[0026] The terms "direct communication" or "directly" mean that the flow from the upstream component enters the downstream component without undergoing a change in composition due to physical fractionation or chemical transformation, the term "settling" as used herein. Sedimentation refers to the separation of solids and liquids, specifically the movement of solids toward or downward within a reaction vessel. For solids to tend to settle, the carrier liquid for the solids must continue to accelerate, and therefore cannot provide velocity or prevent the solids from settling from the continuous spectrum of liquid flow solely through the drag force between the liquid and solids. The critical liquid velocity is often known as "terminal velocity" or "settling velocity." When solids settle, they have a slip velocity, or are delayed, from the liquid average velocity. When this occurs for a group of solids, the solids tend to accumulate in a gradient due to the retardation of solid transport, or to form a precipitate as the liquid moves through a pipe or vessel. Furthermore, when the density difference between the solids and the fluid is smaller, centrifugation principles can be applied to enhance separation. Thus, centrifugal separation devices such as hydrocyclone separation are known to enhance solids separation, apparently enriching the solids concentration along the walls to the very bottom of the device, while the clear, solid-lean liquid returns to the top of the device, thus completing the separation as in solid settling. As used herein, the term "quality." The quality of a pyrolysis product refers to the number of chemical compositions that make the pyrolysis product more or less suitable for downstream applications. In the pyrolysis of mixed plastics, the goal of pyrolysis is often to apply it to downstream refining. The hydrocarbon content of the product is an important measure of quality. In particular, an important quality measure relevant to the present invention is chloride content. Chloride content, whether in organic or inorganic form, tends to lead to metallurgical corrosion. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following Detailed Description is merely exemplary in nature and is not intended to limit the various embodiments or their application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. The figures have been simplified by eliminating many of the devices conventionally used in processes of this nature, such as vessel internals, temperature and pressure control systems, flow control valves, recirculation pumps, etc., that are not specifically required to explain the performance of the process. Furthermore, the illustration of the present process in a particular drawing embodiment is not intended to limit the process to the specific embodiment described herein.

[0028] As shown, the process flow lines in the diagrams may be referred to interchangeably as, for example, lines, pipes, branches, distributors, streams, outflows, feeds, production, sections, catalysts, recovery, recycle, suction, discharge, and caustic.

[0029] A two-stage mixed plastic waste pyrolysis process is provided for pyrolyzing polyvinyl chloride-containing waste streams with metals and char products. The process for pyrolyzing plastic waste streams is addressed with respect to a process and apparatus 100 according to an embodiment as shown in Figure 1. Referring to Figure 1, the process and apparatus 100 includes a melting reactor 101, a pyrolysis reactor 102, separation units 103 and 104, an adsorption bed section 105, a waste gas combustion and oil heat exchanger section (also referred to as an incinerator) 106, a gas cleanup section 107, and finally, a product specification section with optional fractionation and storage 108.

[0030] In one embodiment, the mixed plastic residue stream can include miscellaneous plastic waste, including at least seven types of plastic classifications: polyethylene terephthalate, low-density and high-density polyethylene, polypropylene, polyvinyl chloride, polystyrene, and other miscellaneous plastics. The US Environmental Protection Agency reports in its Advancing Sustainability Material Management: 2016 and 2017 tables and figures that the US average waste plastic mix ending up in landfills in 2017 is shown to be 3% polyvinyl chloride, 13% polyethylene terephthalate, 7% polystyrene, and 11% other plastics and undefined. The relative amounts of each plastic type vary depending on the collection site of the recycled plastic.

[0031] Other miscellaneous plastics can come from various post-consumer products, including acrylonitrile butadiene styrene found in electronic waste, polyurethane foam packaging, carpet nylon, and polysulfone. Mixed plastic residue streams are also commonly known to contain impurities such as paper, wood, aluminum foil, some metallic conductive fillers, or halogenated or non-halogenated flame retardants. During the pyrolysis reaction, some of these impurities may associate with heteroatoms in the product stream. Of all the heteroatoms in the primary product, chlorides from polyvinyl chloride are of greatest quality concern due to their association with metallurgical corrosion. Some contribute to greater char formation due to aromatic structures in the polymer molecules. Some decompose from the plastic molecular matrix, forming particulate by-products containing metals and alkaline earth metals.

[0032] In one embodiment, mixed plastic waste at the end of a mechanical recycling facility (MRF) process that would otherwise be sent to a landfill is used for the pyrolysis feedstock. In Figure 1, the mixed feed stream is minimally classified and received at the MRF site and added to the system as compacted flakes or pellets. Mixed feed stream 1 is added to melt reactor 101. When mixed plastic waste is pyrolyzed, 1 wt. % polyvinyl chloride will theoretically produce about 5800 ppmw of hydrogen chloride, based on the fresh feed rate. Minimally classified mixed feed streams may contain more than 2 wt. % PVC within them. The cold mixed plastic fluff is mixed with hot liquid stream 8 to reach a temperature of 300-350°C.

[0033] The melt reactor 101 functions as a dechlorination reactor and is maintained at a temperature of about 200°C (392°F) to about 350°C (662°F), or preferably about 280°C (536°F) to about 320°C (608°F), a pressure of about 0.069 MPa (gauge) (10 psig) to about 1.38 MPa (gauge) (200 psig), or preferably about 0.138 MPa (gauge) (20 psig) to about 0.345 MPa (gauge) (50 psig), for about 0.1 hours. -1 ~approximately 2 hours -1 , or preferably about 0.2 hours -1 ~approx. 0.5 hours -1 and a nitrogen blanket, or about 1.7 Nm 3 / m 3 (10scf / bbl) ~ approx. 170Nm 3 / m 3 of plastic melt (1,000 scf / bbl), or preferably about 17 Nm 3 / m 3 (100scf / bbl) ~ approx. 850Nm 3 / m 3The melt reactor 101 can operate with a dedicated nitrogen sweep rate of 500 scf / bbl of plastic melt. In the melt reactor 101, polyvinyl chloride is largely pyrolyzed through an "unzip" reaction, in which chloride molecules are readily removed through pyrolytic free radical reactions and hydrogen is removed at nearby sites to form hydrogen chloride. The temperature of the melt reactor 101 is selected to melt most of the plastic components while barely reaching their decomposition temperatures, maximizing the yield of hydrogen chloride and minimizing the amount of reactive olefins formed. The melt reactor is equipped with a mixer to maintain a well-mixed plastic melt until melting is nearly complete. The melt reactor may still retain a fraction of unconverted feed chloride. This chloride requires some downstream processing to meet product quality requirements. A reasonable dechlorination conversion efficiency in the melt reactor is 90%, or about 80 to about 98% within the conditions specified above. Any organic chlorides remaining in the melt reactor bottoms will result in the formation of hydrogen chloride in the pyrolysis reactor, and the organic chlorides and any hydrogen chloride trapped in the pyrolysis oil will be detrimental to downstream processing unit metallurgy, necessitating the addition of additional sorbent. In this invention, the product quality target is less than 10 ppmw chloride or less, regardless of the chloride content in the feed.

[0034] The melt reactor forms a first vapor stream 2 and a first liquid stream 3 from Feed 1. First liquid stream 3 contains a mixed plastic melt, with most of the chlorides removed in vapor stream 2. First liquid stream 3 is sent to a main pyrolysis reactor 102. The main pyrolysis reactor provides a residence time sufficient for all of the mixed plastics to convert first liquid stream 3 into a designated product slate. The main pyrolysis reactor operates at a temperature of about 300°C (572°F) to about 550°C (1022°F), or preferably about 380°C (716°F) to about 450°C (842°F), a pressure of about 0.069 MPa (gauge) (10 psig) to about 1.38 MPa (gauge) (200 psig), or preferably about 0.138 MPa (gauge) (20 psig) to about 0.345 MPa (gauge) (50 psig), and a reaction time of about 0.1 hours. -1~approximately 2 hours -1 , or more preferably about 0.2 hours -1 ~approx. 0.5 hours -1 and a liquid hourly space velocity of the fresh melt feed of about 17 Nm under nitrogen blanket or dedicated nitrogen sweep stream 4. 3 / m 3 (100scf / bbl) ~ approx. 850Nm 3 / m 3 of plastic melt (5,000 scf / bbl), or more preferably about 170 Nm 3 / m 3 (1000scf / bbl) ~ approx. 340Nm 3 / m 3The melt reactor 101 may operate at a rate of 2000 scf / bbl. The nitrogen sweep stream 4 serves as a dilution to the hydrogen chloride partial pressure in the total vapor product. The reduced hydrogen chloride partial pressure significantly reduces the formation of organic chlorides by reducing the equilibrium constant. A finely divided solid sorbent stream 5 may be introduced into the feed at the top of the pyrolysis reactor 102. The sorbent selected may include naturally occurring alkaline materials, such as calcium carbonate, quicklime, or calcium hydroxide. The calcium addition amount is ideally a 2-3 molar ratio relative to the chlorides remaining in the pyrolysis reactor feed. The previous dechlorination step in the melt reactor 101 should have removed at least 80% by weight of the chlorides in the mixed plastics feed. The amount of alkaline sorbent added is based on the feed chloride content and the estimated chloride removal effectiveness. Calcium may also have a flocculating effect, causing carbonaceous char particles to clump around calcium particle seeds. The clumped particles settle more easily in the pyrolysis reactor than unagglomerated char particles. The pyrolysis reactor contains a liquid in phase equilibrium with the vapor product stream. A portion of liquid stream 8 may be sent to a circulation pump. The pumped stream may be split into streams 9 and 10. The mass flow rate of stream 9 may be such that it maintains the melt reactor temperature as described above by mixing with the molten plastic. Stream 9 may also help reduce the polymer melt viscosity. The mass flow rate of stream 10 may be such that it obtains all of the enthalpy requirements via heater 106 as it returns to the pyrolysis reactor 102 through stream 11. The necessary heat transfer is achieved by mixing the hot stream 11 with the cold stream 3 within the primary pyrolysis reactor 102. The pyrolysis reactor 102 may draw a second vapor product stream 6 from the top of the pyrolysis reactor and a second solids-rich product stream 7 from the bottom of the reactor. Convective heat transfer within pyrolysis reactor 102, along with pumped mixing around stream 11, provides uniform heating, an advantage over pyrolysis reaction processes heated by external indirect heating, typically found in extruder or rotary kiln reactors.

[0035] FIG. 1 also shows a vapor product stream 6 containing a range of hydrocarbons carried by the nitrogen stream at a designed vapor linear velocity. In the present invention, the linear vapor velocity is intended to be greater than 0.2 in / sec to avoid secondary cracking. The vapor product stream 6 may be directly or indirectly contacted with a cooling medium and then separated into vapor stream 13 and liquid stream 15. If direct water contact is included as one possible cooling method, a water stream is collected in stream 14. If direct water contact is omitted, stream 14 may not be present. Liquid stream 15 is further heated stream 16 and is flashed in flash drum 104 to produce stabilized liquid stream 18. Vapor stream 17 is at a higher pressure than separator 103 and is pressurized back to separator 103 to increase the recovery of hydrocarbons in the desired products. The stream is mixed with stream 12 to avoid the need for multiple inlet nozzles in separator 103.

[0036] The stabilized liquid stream 19 is further cooled to the desired temperature in stream 19 before entering the adsorber system 105, which serves as a further and final chloride polishing device. Calcium, other alkaline materials, or a range of natural adsorbents can be used to continuously remove a large fraction of the unconverted chloride content in the condensed oil. More preferably, specially designed adsorbents with high adsorbent capacity and activity are used. Adsorbent capacity is defined per unit of adsorbent. Adsorbent activity is defined as the lower temperature required to achieve the desired rate. Furthermore, Honeywell UOP commercial product CLR 204 is particularly suitable for this application. As previously described herein, the present disclosure provides for staged chloride removal. Single-step chloride removal can have efficiency issues in chloride removal when the mixed plastic feed has a high PVC content, e.g., 2% or more. The melt reactor 101 first removes more than 80% by weight of the chlorides in the mixed plastic feed by cracking the PVC in the melt reactor. This chloride is removed as hydrogen chloride. A fraction of the remaining chloride is removed in the pyrolysis reactor 102, where an adsorbent is added to convert a portion of the chloride as a salt. The unconverted hydrogen chloride is further diluted in a sweep nitrogen stream, which minimizes gas-phase recombination reactions between hydrogen chloride and organic molecules. The processes described above in this section can be designed to remove most of the chloride, preferably to less than 200 ppmw in stream 19. The adsorber system 105 is suitable for removing chloride in the final product to near-zero concentrations or 10 ppmw or less. The adsorber system 105 operates with an identical backup bed to avoid chloride breakthroughs. The salt obtained in the adsorber system 105 is considered spent and is removed while other vessels are operating online. This allows the unit to operate continuously, which is advantageous over batch processes. Each chloride control step has an optimum chloride concentration in the feed and an efficiency limit.Adsorbent injection into the gas dilution reactor is known to lead to increasing wastefulness with increasing dosage above a certain efficiency threshold, e.g., when attempting to reduce Cl in the product to levels below approximately 200-400 ppm, and excessive use of adsorbent may be required, resulting in an economic penalty. Adsorbent beds are more suitable and economical only as a final polish, i.e., to reduce the chloride content in the final product from 200-400 ppm to less than approximately 10 ppm. Similarly, any increase in chloride in the adsorbent bed feed may lead to excessive use of large amounts of adsorbent. Therefore, in staged dechlorination, adsorbent injection into the reactor can prove important to reduce the chloride content from several thousand ppm to several hundred ppm. However, the use of adsorbents in the reactor must be designed to remove the adsorbent by settling. The purified product stream 20 is cooled as stream 21 and stored in product storage 108. If desired, stream 21 can be fractionated into two or more streams according to their boiling points before being sent to storage.

[0037] The total vapor stream 13 may contain a variety of gas species. In particular, it may contain nitrogen, residual moisture from the feed, hydrogen chloride, carbon dioxide from the polyethylene terephthalate conversion, methane, ethane, propane, ethylene, propylene, and heavier hydrocarbon vapors from the plastic pyrolysis reaction. The heat content is very high, often on the order of 30,000 KJ / kg. Combustion of the gas is required prior to gas cleaning, but it also provides a useful heat source for the process. The heat of combustion is utilized in a heat exchanger built into unit 106. After incineration, the exhaust gas stream 22 is sent to a cleaning system 107, where dioxins are removed in a carbon bed and hydrogen chloride is scrubbed using either caustic, sodium bicarbonate, or other materials that react with HCl.

[0038] Figure 2, showing the apparatus 200, provides a detailed configuration of the pyrolysis reactor 102, which has several distinct features from prior art pyrolysis reactors. The pyrolysis reactor 102 can be maintained at a constant liquid level. The pyrolysis reactor 102 can have a cylindrical shape with an internal cylinder mechanically designed to fit the reactor's circulation geometry. The internal cylinder can be configured with a portion above the liquid level, but with most of the cylinder submerged within the liquid reactor. In one embodiment, the internal cylinder is eccentric, so that the internal cylinder wall overlaps with the reactor cylinder on one side. In another embodiment, the internal cylinder is concentric, so that the internal cylinder is located at the center of the main reactor. The heat of reaction in the pyrolysis reactor 102 is approximately 2 to 3 times greater than the heat of reaction in the melt reactor. After pyrolysis, the polymer molecules are significantly decomposed into product molecules. The smaller product molecules exit the top of the pyrolysis reactor, mostly as the second vapor stream 6. Product vapor stream 6 exits quickly with the aid of sweep gas 4, which helps induce vaporization of the liquid product to avoid excessive secondary cracking. Sweep gas 4 also helps reduce the partial pressure of light hydrocarbons within the pyrolysis reactor 102. Secondary cracking is a term referring to the primary pyrolysis product undergoing additional residence time under pyrolysis conditions for further cracking. All of the latent heat required to vaporize the product and provide the heat of reaction for the pyrolysis reaction is supplied by heat delivered from stream 11. In one embodiment, as shown in FIG. 2A, stream 11 enters the reactor at a vertical angle. A second solids-rich product stream 7 is shown exiting the bottom of the pyrolysis reactor 102. In another embodiment, shown in FIG. 2B, stream 11 enters the reactor as a tangentially momentum-delivering jet through an annular location between the inner and outer cylinders in the upper section of the reactor. FIG. 2B shows a different perspective view of the interior of the pyrolysis reactor 102, differing only in the angle of entry of stream 11. Polymer melt-rich stream 3 and adsorbent stream 5 are all introduced into the annular region. All feed streams rotate in a spiral and mix as they move downward through the reactor. The feed polymer is also cracked while being mixed in the hot liquid. Adsorbent stream 5 has two main benefits:When the adsorbent is thoroughly mixed within the pyrolysis reactor, it reacts with chloride-containing molecules, forming salts that all pass through the liquid reaction space and are removed at the bottom of the reactor. The adsorbent can act as a flocculant, acting as a seed to bind char particles together to form larger particles. Larger particles separate better under centrifugal force and the long residence time provided by the inner cylinder wall area. All solid particles, including char particles larger than a certain size cut (e.g., 150 micrometers), adsorbent, metals carried from the feed, and metals or alkali metals from plastic additives, move along the wall area, while the liquid redirects upward from the center through the inner cylinder. The entire system behaves like a hydrocyclone separator, but the decomposition reaction occurs. The solid-lean liquid stream bends upward toward the free liquid surface. The liquid stream 8 can be drawn to the heater 106 through a submerged pipe connected to the circulation pump in Figure 1. The vapor stream 6 can be drawn from the vapor space to the separator 103 (see Figure 1), or preferably through an auxiliary gas sweep stream 4 introduced into the vapor space. It is preferable to extend the reactor volume along the lower bottom skirt region of the outer cylinder. An optimal angle range exists between the vertical and inclined walls. An optimal design allows for maximum separation of solids with a minimum density, such as 150 micrometer char, for a particular size cut, achieving the maximum fraction separated at the bottom relative to its total mass in the combined feed stream to the annulus. A total efficiency of 70-80% can be achieved in a typical pyrolysis reactor system using a proprietary calculation method for a 150 micrometer carbonaceous particle size with a density of 1.5 g / cc. The disclosed reactor scheme has remarkable solids separation efficiency compared to any other reactor configuration for the same transport purpose.

[0039] In another embodiment, an alternative option exists. The two-cylinder reactor configuration shown in Figure 3 further discloses that stream 11 can enter the reactor through the inner cylinder wall edge and enter the tapered pipe, further increasing velocity by 2 to 10 times over that seen in the upstream pipe. This momentum is exemplified in the upper split section of the reactor 102. The polymer melt-rich stream 3 and the adsorbent stream 6 are rapidly mixed due to the turbulence created by the tapered pipe. Both the mass and heat flows are vigorously mixed. In the alternative reactor scheme, particles move toward the tip of one side of the inner cylinder or downward toward the conical wall region of the main reactor wall. They are then collected in the reactor bottom stream. In the alternative reactor scheme shown in Figure 3, stream 8 can be pumped as a circulation stream on the side of the pyrolysis reactor 102 between the inner wall and the outer main reactor wall. The draw location is ideally located in the upper liquid level section. When the reactor liquid moves from the lower tip of the inner cylinder, it moves back to the draw location. At the bottom, a taper angle between the inner and outer cylinder walls can be provided to prevent solids in the bottom cone from accelerating to the draw position. Alternative reactor schemes may have separation efficiencies approximately 10-30% lower, depending on the design details. Figures 2 and 3 both represent two-cylinder designs for pyrolyzing waste plastics while separating solid particles. Both have surprisingly high solid separation efficiencies compared to any prior art known to the authors, even for the most difficult-to-separate carbonaceous char particles—e.g., carbonaceous char particles 150 micrometers in size and 1.5 g / cc in density as demonstrated. The present invention is not limited to the two taught configurations; it can encompass a range of dimensional variations along the two-cylinder reactor design.

[0040] In any of the disclosed well-mixed pyrolysis reactor schemes, the solids content is highly concentrated. In one example, there is a char yield of 3-5% based on the freshly fed polymer melt. Char is further concentrated in the bottom solid-liquid discharge mixture as the vapor product is removed from the reactor. Frequently, the solids are concentrated several tens of times compared to the product yield. This applies to any of the types of solids discussed above. Highly concentrated solids in the reactor bottom due to enhanced separation or settling can be further removed by a device that handles streams containing high concentrations of solids. An example of a device is a rotary valve device followed by an auger. The bottom stream may contain highly concentrated solids from inorganic metals, spent adsorbent, chloride salts, and / or carbonaceous char.

[0041] Figure 4 is a variation of the embodiment shown in Figure 1. All element numbers are shown in quotation marks to indicate that, with few exceptions, the element numbers have the same meaning as in Figure 1. The main difference is the presence of a separate fired heater 109' that burns liquefied petroleum gas or natural gas to heat the recycled oil stream 10'. Additionally, fired heater exhaust gas stream 26' may be further combined with incinerator exhaust gas cleaning. Additionally, reactor exhaust gas streams 2' and 13' may be blended and split into substream 27' to compensate for fuel consumption in 109'.

[0042] In one embodiment, the two-cylinder reactor configuration shown in Figure 1 discloses that stream 3 can enter the reactor through the inner cylinder wall edge and enter the tapered pipe, further increasing velocity by 2 to 10 times over that seen in the upstream pipe. This momentum is exemplified in the upper split section of the reactor 102. The polymer melt-rich stream 3 and adsorbent stream 6 are rapidly mixed due to the turbulence created by the tapered pipe. Both the mass and heat flows are vigorously mixed. In an alternative reactor scheme, particles migrate toward the tip of one side of the inner cylinder or downward toward the conical wall region of the main reactor wall. They then collect in the reactor bottom stream. In an alternative reactor scheme shown in Figure 3, stream 8 can be pumped as a circulation stream on the side of the pyrolysis reactor 102 between the inner wall and the outer main reactor wall. The draw location is ideally located in the upper liquid level section. When the reactor liquid migrates from the lower tip of the inner cylinder, it migrates back to the draw location. At the bottom, a taper angle between the inner and outer cylinder walls can be provided to prevent solids in the bottom cone from accelerating to the draw position. Alternative reactor schemes may have separation efficiencies approximately 10-30% lower, depending on the design details. Figures 2 and 3 both represent two-cylinder designs for pyrolyzing waste plastics while separating solid particles. Both have surprisingly high solid separation efficiencies compared to any prior art known to the authors, even for the most difficult-to-separate carbonaceous char particles—e.g., carbonaceous char particles 150 micrometers in size and 1.5 g / cc in density as demonstrated. The present invention is not limited to the two taught configurations; it can encompass a range of dimensional variations along the two-cylinder reactor design.

[0043] In any of the disclosed well-mixed pyrolysis reactor schemes, the solids content is highly concentrated. In one example, there is a char yield of 3-5% based on the freshly fed polymer melt. Char is further concentrated in the bottom solid-liquid discharge mixture as the vapor product is removed from the reactor. Frequently, the solids are concentrated several tens of times compared to the product yield. This applies to any of the types of solids discussed above. Highly concentrated solids in the reactor bottom due to enhanced separation or settling can be further removed by a device that handles streams containing high concentrations of solids. An example of a device is a rotary valve device followed by an auger. The bottom stream may contain highly concentrated solids from inorganic metals, spent adsorbent, chloride salts, and / or carbonaceous char.

[0044] A two-stage mixed plastic waste pyrolysis process is provided for pyrolyzing polyvinyl chloride-containing waste streams with metals and char products. The process for pyrolyzing plastic waste streams is addressed with respect to a process and apparatus 100 according to an embodiment as shown in Figure 1. Referring to Figure 1, the process and apparatus 100 includes a melting reactor 101, a pyrolysis reactor 102, separation units 103 and 104, an adsorption bed section 105, a waste gas combustion and oil heat exchanger section (also referred to as an incinerator) 106, a gas cleanup section 107, and finally, a product specification section with optional fractionation and storage 108.

[0045] In one embodiment, the mixed plastic residue stream can include miscellaneous plastic waste, including at least seven types of plastic classifications: polyethylene terephthalate, low-density and high-density polyethylene, polypropylene, polyvinyl chloride, polystyrene, and other miscellaneous plastics. The U.S. Environmental Protection Agency reports in its Advancing Sustainability Materials Management: 2016 and 2017 tables and figures that the U.S. average waste plastic mix ending up in landfills in 2017 is shown to be 3% polyvinyl chloride, 13% polyethylene terephthalate, 7% polystyrene, and 11% other plastics and undefined. The relative amounts of each plastic type vary depending on the collection site of the recycled plastic.

[0046] Other miscellaneous plastics can come from various post-consumer products, including acrylonitrile butadiene styrene found in electronic waste, polyurethane foam packaging, carpet nylon, and polysulfone. Mixed plastic residue streams are also commonly known to contain impurities such as paper, wood, aluminum foil, some metallic conductive fillers, or halogenated or non-halogenated flame retardants. During the pyrolysis reaction, some of these impurities may associate with heteroatoms in the product stream. Of all the heteroatoms in the primary product, chlorides from polyvinyl chloride are of greatest quality concern due to their association with metallurgical corrosion. Some contribute to greater char formation due to aromatic structures in the polymer molecules. Some decompose from the plastic molecular matrix, forming particulate by-products containing metals and alkaline earth metals.

[0047] In one embodiment, mixed plastic waste at the end of a mechanical recycling facility (MRF) process that would otherwise be sent to a landfill is used for the pyrolysis feedstock. In Figure 1, the mixed feed stream is minimally classified and received at the MRF site and added to the system as compacted flakes or pellets. Mixed feed stream 1 is added to melt reactor 101. When mixed plastic waste is pyrolyzed, 1 wt. % polyvinyl chloride will theoretically produce about 5800 ppmw of hydrogen chloride, based on the fresh feed rate. Minimally classified mixed feed streams may contain more than 2 wt. % PVC within them. The cold mixed plastic fluff is mixed with hot liquid stream 8 to reach a temperature of 300-350°C.

[0048] The melt reactor 101 functions as a dechlorination reactor and is maintained at a temperature of about 200°C (392°F) to about 350°C (662°F), or preferably about 280°C (536°F) to about 320°C (608°F), a pressure of about 0.069 MPa (gauge) (10 psig) to about 1.38 MPa (gauge) (200 psig), or preferably about 0.138 MPa (gauge) (20 psig) to about 0.345 MPa (gauge) (50 psig), for about 0.1 hours. -1 ~approximately 2 hours -1 , or preferably about 0.2 hours -1 ~approx. 0.5 hours -1 and a nitrogen blanket, or about 1.7 Nm 3 / m 3 (10scf / bbl) ~ approx. 170Nm 3 / m 3 of plastic melt (1,000 scf / bbl), or preferably about 17 Nm 3 / m 3 (100scf / bbl) ~ approx. 850Nm 3 / m 3The melt reactor 101 may operate with a dedicated nitrogen sweep rate of 500 scf / bbl of plastic melt. The temperature of the melt reactor 101 is selected to melt most of the plastic components while barely reaching their decomposition temperatures, maximizing the yield of hydrogen chloride and minimizing the amount of reactive olefins formed. The melt reactor is equipped with a mixer to keep the plastic melt well mixed until melting is nearly complete. The melt reactor may still leave a fraction of unconverted feed chlorides. This chloride requires some downstream processing to meet product quality requirements. A reasonable dechlorination conversion efficiency in the melt reactor is 90%, or about 80 to about 98% within the previously specified conditions. Any organic chlorides remaining in the melt reactor bottoms will result in the formation of hydrogen chloride in the pyrolysis reactor. Therefore, the organic chlorides and any hydrogen chloride trapped in the pyrolysis oil are harmful to downstream processing unit metallurgy and require the addition of additional sorbents. In the present invention, the product quality target is less than 10 ppmw chloride or less, regardless of the chloride content in the feed.

[0049] The melt reactor forms a first vapor stream 2 and a first liquid stream 3 from Feed 1. First liquid stream 3 contains a mixed plastic melt, with most of the chlorides removed in vapor stream 2. First liquid stream 3 is sent to a main pyrolysis reactor 102. The main pyrolysis reactor provides a residence time sufficient for all of the mixed plastics to convert first liquid stream 3 into a designated product slate. The main pyrolysis reactor operates at a temperature of about 300°C (572°F) to about 550°C (1022°F), or preferably about 380°C (716°F) to about 450°C (842°F), a pressure of about 0.069 MPa (gauge) (10 psig) to about 1.38 MPa (gauge) (200 psig), or preferably about 0.138 MPa (gauge) (20 psig) to about 0.345 MPa (gauge) (50 psig), and a reaction time of about 0.1 hours. -1 ~approximately 2 hours -1 , or more preferably about 0.2 hours -1 ~approx. 0.5 hours -1and a liquid hourly space velocity of the fresh melt feed of about 17 Nm under nitrogen blanket or dedicated nitrogen sweep stream 4. 3 / m 3 (100scf / bbl) ~ approx. 850Nm 3 / m 3 of plastic melt (5,000 scf / bbl), or more preferably about 170 Nm 3 / m 3 (1000scf / bbl) ~ approx. 340Nm 3 / m 3The melt reactor 101 may operate at a rate of 2000 scf / bbl. The nitrogen sweep stream 4 serves as a dilution to the hydrogen chloride partial pressure in the total vapor product. The reduced hydrogen chloride partial pressure significantly reduces the formation of organic chlorides by reducing the equilibrium constant. A finely divided solid sorbent stream 5 may be introduced into the feed at the top of the pyrolysis reactor 102. The sorbent selected may include naturally occurring alkaline materials, such as calcium carbonate, quicklime, or calcium hydroxide. The calcium addition amount is ideally a 2-3 molar ratio relative to the chlorides remaining in the pyrolysis reactor feed. The previous dechlorination step in the melt reactor 101 should have removed at least 80% by weight of the chlorides in the mixed plastics feed. The amount of alkaline sorbent added is based on the feed chloride content and the estimated chloride removal effectiveness. Calcium may also have a flocculating effect, causing carbonaceous char particles to clump around calcium particle seeds. The clumped particles settle more easily in the pyrolysis reactor than unagglomerated char particles. The pyrolysis reactor contains a liquid in phase equilibrium with the vapor product stream. A portion of liquid stream 8 may be sent to a circulation pump. The pumped stream may be split into streams 9 and 10. The mass flow rate of stream 9 may be such that it maintains the melt reactor temperature as described above by mixing with the molten plastic. Stream 9 may also help reduce the polymer melt viscosity. The mass flow rate of stream 10 may be such that it obtains all of the enthalpy requirements via heater 106 as it returns to the pyrolysis reactor 102 through stream 11. The necessary heat transfer is achieved by mixing the hot stream 11 with the cold stream 3 within the primary pyrolysis reactor 102. The pyrolysis reactor 102 may draw a second vapor product stream 6 from the top of the pyrolysis reactor and a second solids-rich product stream 7 from the bottom of the reactor. Convective heat transfer within pyrolysis reactor 102, along with pumped mixing around stream 11, provides uniform heating, an advantage over pyrolysis reaction processes heated by external indirect heating, typically found in extruder or rotary kiln reactors.

[0050] FIG. 1 also shows a vapor product stream 6 containing a range of hydrocarbons carried by the nitrogen stream at a designed vapor linear velocity. In the present invention, the linear vapor velocity is intended to be greater than 0.2 in / sec to avoid secondary cracking. The vapor product stream 6 may be directly or indirectly contacted with a cooling medium and then separated into vapor stream 13 and liquid stream 15. If direct water contact is included as one possible cooling method, a water stream is collected in stream 14. If direct water contact is omitted, stream 14 may not be present. Liquid stream 15 is further heated stream 16 and is flashed in flash drum 104 to produce stabilized liquid stream 18. Vapor stream 17 is at a higher pressure than separator 103 and is pressurized back to separator 103 to increase the recovery of hydrocarbons in the desired products. The stream is mixed with stream 12 to avoid the need for multiple inlet nozzles in separator 103.

[0051] The stabilized liquid stream 19 is further cooled to the desired temperature in stream 19 before entering the adsorber system 105, which serves as a further and final chloride polishing device. Calcium, other alkaline materials, or a range of natural adsorbents can be used to continuously remove a large fraction of the unconverted chloride content in the condensed oil. More preferably, specially designed adsorbents with high adsorbent capacity and activity are used. Adsorbent capacity is defined per unit of adsorbent. Adsorbent activity is defined as the lower temperature required to achieve the desired rate. Furthermore, Honeywell UOP commercial product CLR 204 is particularly suitable for this application. As previously described herein, the present disclosure provides for staged chloride removal. Single-step chloride removal can have efficiency issues in chloride removal when the mixed plastic feed has a high PVC content, e.g., 2% or more. The melt reactor 101 first removes more than 80% by weight of the chlorides in the mixed plastic feed by cracking the PVC in the melt reactor. This chloride is removed as hydrogen chloride. A fraction of the remaining chloride is removed in the pyrolysis reactor 102, where an adsorbent is added to convert a portion of the chloride as a salt. The unconverted hydrogen chloride is further diluted in a sweep nitrogen stream, which minimizes gas-phase recombination reactions between hydrogen chloride and organic molecules. The processes described above in this section can be designed to remove most of the chloride, preferably to less than 200 ppmw in stream 19. The adsorber system 105 is suitable for removing chloride in the final product to near-zero concentrations or 10 ppmw or less. The adsorber system 105 operates with an identical backup bed to avoid chloride breakthroughs. The salt obtained in the adsorber system 105 is considered spent and is removed while other vessels are operating online. This allows the unit to operate continuously, an advantage over batch processes. Each chloride control step has an optimum chloride concentration in the feed and an efficiency limit.Adsorbent injection into the gas dilution reactor is known to lead to increasing wastefulness with increasing dosage above a certain efficiency threshold, e.g., when attempting to reduce Cl in the product to levels below approximately 200-400 ppm, and excessive use of adsorbent may be required, resulting in an economic penalty. Adsorbent beds are more suitable and economical only as a final polish, i.e., to reduce the chloride content in the final product from 200-400 ppm to less than approximately 10 ppm. Similarly, increased chloride in the adsorbent bed feed may lead to excessive use of large amounts of adsorbent. Therefore, in staged dechlorination, adsorbent injection into the reactor can prove important to reduce the chloride content from several thousand ppm to several hundred ppm. However, the use of adsorbents in the reactor must be designed to remove the adsorbent by settling. The purified product stream 20 is cooled as stream 21 and stored in product storage 108. If desired, stream 21 can be fractionated into two or more streams according to their boiling points before being sent to storage.

[0052] The total vapor stream 13 may contain a variety of gas species. In particular, it may contain nitrogen, residual moisture from the feed, hydrogen chloride, carbon dioxide from the polyethylene terephthalate conversion, methane, ethane, propane, ethylene, propylene, and heavier hydrocarbon vapors from the plastic pyrolysis reaction. The heat content is very high, often on the order of 30,000 KJ / kg. Combustion of the gas is required prior to gas cleaning, but it also provides a useful heat source for the process. The heat of combustion is utilized in a heat exchanger built into unit 106. After incineration, the exhaust gas stream 22 is sent to a cleaning system 107, where dioxins are removed in a carbon bed and hydrogen chloride is scrubbed using either caustic, sodium bicarbonate, or other materials that react with HCl.

[0053] Figure 2, showing the apparatus 200, provides a detailed configuration of the pyrolysis reactor 102, which has several distinct features from prior art pyrolysis reactors. The pyrolysis reactor 102 can be maintained at a constant liquid level. The pyrolysis reactor 102 can have a cylindrical shape with an internal cylinder mechanically designed to fit the reactor's circulation geometry. The internal cylinder can be configured with a portion above the liquid level, but with most of the cylinder submerged within the liquid reactor. In one embodiment, the internal cylinder is eccentric, so that the internal cylinder wall overlaps with the reactor cylinder on one side. In another embodiment, the internal cylinder is concentric, so that the internal cylinder is located at the center of the main reactor. The heat of reaction in the pyrolysis reactor 102 is approximately 2 to 3 times greater than the heat of reaction in the melt reactor. After pyrolysis, the polymer molecules are significantly decomposed into product molecules. The smaller product molecules exit the top of the pyrolysis reactor, mostly as the second vapor stream 6. Product vapor stream 6 exits quickly with the aid of sweep gas 4, which helps induce vaporization of the liquid product to avoid excessive secondary cracking. Sweep gas 4 also helps reduce the partial pressure of light hydrocarbons within the pyrolysis reactor 102. Secondary cracking is a term referring to the primary pyrolysis products undergoing additional residence time under pyrolysis conditions for further cracking. All of the latent heat required to vaporize the products and provide the heat of reaction for the pyrolysis reaction is provided by heat delivered from stream 11. In one embodiment, stream 11 enters the reactor as a tangentially momentum-delivering jet through an annular location between the inner and outer cylinders in the upper section of the reactor. Polymer melt-rich stream 3 and adsorbent stream 5 are all introduced into the annular region. All feed streams rotate in a spiral and mix as they move downward through the reactor. The feed polymer is also cracked while being mixed in the hot liquid. Adsorbent stream 5 has two main benefits: When the sorbent is thoroughly mixed in the pyrolysis reactor, it reacts with the chloride-containing molecules to form salts that all pass through the liquid reaction space and are removed at the bottom of the reactor. The sorbent can act as a flocculating agent, acting as seeds to bind char particles together to form larger particles.Larger particles separate better under centrifugal force, due to the long residence time provided by the inner cylinder wall area. All solid particles, including char particles larger than a certain size cut (e.g., 150 micrometers), adsorbents, metals carried from the feed, and metals or alkali metals from plastic additives, move along the wall area, while the liquid redirects upward from the center through the inner cylinder. The entire system behaves like a hydrocyclone separator, except that the decomposition reaction occurs. The solid-lean liquid stream bends upward toward the free liquid surface. Liquid stream 8 can be drawn from a submerged pipe connected to the circulation pump in Figure 1 to the heater 106. Vapor stream 6 can be drawn from the vapor space to the separator 103 in Figure 1, or preferably through the auxiliary gas sweep stream 4 introduced into the vapor space. It is preferable to expand the reactor volume along the lower bottom skirt area of ​​the outer cylinder. There is an optimal angle range between the vertical and inclined walls. The optimal design allows for maximum separation of solids with minimum density for a particular size cut, e.g., 150 micrometer char, achieving the maximum fraction separated to the bottoms relative to its total mass in the combined feed stream to the annulus. A total efficiency of 70-80% can be achieved in a typical pyrolysis reactor system using a proprietary calculation method for a 150 micrometer carbonaceous particle size with a density of 1.5 g / cc. The disclosed reactor scheme has remarkable solids separation efficiency greater than any other reactor configuration for the same transport purpose.

[0054] Figure 4 is a variation of the embodiment shown in Figure 1. All element numbers are shown in quotation marks to indicate that, with few exceptions, the element numbers have the same meaning as in Figure 1. The main difference is the presence of a separate fired heater 109' that burns liquefied petroleum gas or natural gas to heat the recycled oil stream 10'. Additionally, fired heater exhaust gas stream 26' may be further combined with incinerator exhaust gas cleaning. Additionally, reactor exhaust gas streams 2' and 13' may be blended and split into substream 27' to compensate for fuel consumption in 109'.

[0055] Specific Embodiments While the following is described in conjunction with specific embodiments, it will be understood that this description is illustrative and not intended to limit the scope of the foregoing description and the appended claims.

[0056] A first embodiment of the present invention is a process for the thermal decomposition of mixed plastic waste streams, comprising: melting the mixed plastic waste stream in a melt reactor to produce a molten mixed plastic waste stream containing at least two types of plastics, including chlorine-containing plastics and other plastics, to produce a first chloride-rich vapor stream and a first liquid stream; passing the first liquid stream to a pyrolysis reactor to heat it and produce a second chloride-rich vapor stream and a second liquid stream, the pyrolysis reactor having a configuration including two cylindrical ring structures and an inner cylindrical ring structure within the outer cylindrical ring structure, a circulating liquid feed stream entering the pyrolysis reactor tangentially to the ring edges of the two cylindrical ring structures, and solid particles moving in a downward direction toward the bottom of the pyrolysis reactor; passing the heated stream from the pyrolysis reactor to the melt reactor and the second heated stream from the pyrolysis reactor to be further heated and returned to the pyrolysis reactor; and removing chlorides in multiple steps, thereafter producing a liquid product stream.

[0057] A second embodiment of the present invention is a process for the thermal decomposition of a mixed plastic waste stream, comprising: passing the mixed plastic waste stream to a melting reactor to produce a chloride-rich first vapor stream and a first liquid stream; passing the first liquid stream to a pyrolysis reactor to heat and produce a second vapor stream, a second liquid stream, and solid particles, the pyrolysis reactor being configured with two cylindrical ring structures such that the circulating liquid feed stream enters tangentially to the ring edges of the cylindrical ring structures, the solid particles moving in a downward direction within the pyrolysis reactor; passing the first vapor stream to an incinerator to remove hydrocarbons, hydrogen chloride, and alkyl chlorides and then to a gas cleaning zone to remove chlorine compounds and heat at least a portion of the circulating feed stream as a reaction heat supply for the pyrolysis reactor; cooling and separating the second vapor stream into a third vapor stream and a third liquid stream, and then treating the third liquid stream in at least one adsorption bed to remove chlorine-containing impurities. An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, further comprising passing the sorbent to a pyrolysis reactor to remove chlorine compounds. An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, wherein the melting reactor operates at a temperature of from about 200°C (392°F) to about 350°C (662°F). An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, wherein the pyrolysis reactor device comprises a two-cylindrical ring structure, wherein a hot circulating stream enters the annular region tangentially along the outer ring wall edge, a cold circulating stream exits the top of the central cylinder, a solids-rich stream exits the bottom, and a second vapor exits the top of the central cylinder.An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, where the pyrolysis reactor device includes a two-cylindrical ring structure, with the hot circulating stream entering the inner cylinder alternatively tangentially along the inner ring wall edge, the cold circulating stream exiting the outer cylinder's draw point, the solids-rich stream exiting from the bottom, and the second vapor exiting from the top of the middle cylinder. An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, where the gas purification zone includes a catalyst bed for removing dioxin compounds and a vessel containing a caustic compound for neutralizing HCl. An embodiment of the present invention is one, any, or all of the previous through second embodiments of this paragraph, further including passing an adsorber to the pyrolysis reactor to adsorb chlorine and chlorine-containing compounds. An embodiment of the present invention is one, any, or all of the previous embodiment through the second embodiment of this paragraph, where the sorbent is an alkaline material present in the pyrolysis reactor in about a 2-3 molar ratio to chloride. An embodiment of the present invention is one, any, or all of the previous embodiment through the second embodiment of this paragraph, where the sorbent further functions as an agglomeration material for carbonaceous char particles formed during operation of the pyrolysis reactor ... melting reactor is operated at a pressure of about 0.069 MPa (gauge) (10 psig) to about 1.38 MPa (gauge) (200 psig), and for about 0.1 hours. -1 ~approximately 2 hours -1 One, any, or all of the previous embodiment of this paragraph through the second embodiment of this paragraph, wherein the melt reactor operates at a liquid hourly space velocity of about 1.7 Nm under a nitrogen blanket. 3 / m 3 (10scf / bbl) ~ approx. 170Nm 3 / m 312. One, any, or all of the preceding through second embodiments of this paragraph, wherein the melt reactor operates with a dedicated nitrogen sweep rate of 1,000 scf / bbl of plastic melt. 13. One, any, or all of the preceding through second embodiments of this paragraph, wherein approximately 80-98 wt.% of the chlorides from the melt reactor are removed and sent in a vapor stream. 14. One, any, or all of the preceding through second embodiments of this paragraph, wherein a stream of nitrogen is sent to the pyrolysis reactor to dilute the hydrogen chloride partial pressure in the second vapor stream. 15. One, any, or all of the preceding through second embodiments of this paragraph, further comprising sending the second vapor stream to a cooler and to a separator to produce a third vapor stream and a third liquid stream. An embodiment of the present invention is one, any, or all of the preceding through second embodiments of this paragraph, in which the third liquid stream contains less than about 200 ppmw of chlorides. An embodiment of the present invention is one, any, or all of the preceding through second embodiments of this paragraph, in which the third liquid stream is sent to an adsorption bed to remove chlorides. An embodiment of the present invention is one, any, or all of the preceding through second embodiments of this paragraph, in which the pyrolysis reactor has a cylindrical shape with an internal cylinder mechanically designed to fit the reactor circulation geometry. An embodiment of the present invention is one, any, or all of the preceding through second embodiments of this paragraph, in which the heat of reaction in the pyrolysis reactor is about 2-3 times greater than the heat or reaction in the melting reactor. An embodiment of the present invention is one, any, or all of the preceding through second embodiments of this paragraph, in which the incinerator is replaced by a combustion-based heater.

[0058] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, readily ascertain the essential characteristics of the present invention and make various changes and modifications to the present invention to adapt it to various uses and conditions, all without departing from the spirit and scope of the present invention. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0059] Above, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise stated.

Claims

1. 1. A process for the pyrolysis of mixed plastic waste streams, comprising: a) melting the mixed plastic waste stream in a melt reactor to produce a molten mixed plastic waste stream comprising at least two types of plastics, including chlorine-containing plastics and other plastics, and producing a first chloride-rich vapor stream and a first liquid stream; b. passing the first liquid stream to a pyrolysis reactor to heat and produce a second chloride-rich vapor stream and a second liquid stream; c) passing a first portion of the second liquid stream from the pyrolysis reactor to the melt reactor and a second portion of the second liquid stream from the pyrolysis reactor to a heater for further heating and returning the second liquid stream to the pyrolysis reactor as a circulating liquid feed stream; and (d) removing chlorides from steps (a) and (b) and thereafter producing a liquid product stream. where: The pyrolysis reactor has a configuration including two cylindrical ring structures consisting of an inner cylindrical ring structure and an outer cylindrical ring structure, the circulating liquid feed stream enters the pyrolysis reactor tangentially through an annular location between the inner and outer cylindrical ring structures; and solid particles move in a downward direction towards the bottom of the pyrolysis reactor; process.

2. 1. A process for the pyrolysis of mixed plastic waste streams, comprising: a. passing the mixed plastic waste stream to a melting reactor to produce a first vapor stream and a first liquid stream rich in chlorides; b. passing the first liquid stream to a pyrolysis reactor to heat and produce a second vapor stream, a second liquid stream, and solid particles; c) directing a first portion of the second liquid stream from the pyrolysis reactor to the melting reactor and a second portion of the second liquid stream from the pyrolysis reactor to an incinerator for further heating and returning to the pyrolysis reactor as a circulating liquid feed stream; d. passing the first vapor stream to the incinerator to remove hydrocarbons, hydrogen chloride, and alkyl chlorides and then to a gas clean-up zone to remove chlorine compounds and heat the circulating liquid feed stream as a reaction heat supply for the pyrolysis reactor; e. cooling and separating the second vapor stream into a third vapor stream and a third liquid stream, and then treating the third liquid stream with at least one adsorption bed to remove chlorine-containing impurities; where: The pyrolysis reactor has a configuration including two cylindrical ring structures consisting of an inner cylindrical ring structure and an outer cylindrical ring structure, the circulating liquid feed stream enters the pyrolysis reactor tangentially through an annular location between the inner and outer cylindrical ring structures; and solid particles move in a downward direction within the pyrolysis reactor; process.

3. 1. A process for the pyrolysis of mixed plastic waste streams, comprising: a. passing the mixed plastic waste stream to a melting reactor to produce a first vapor stream and a first liquid stream rich in chlorides; b. passing the first liquid stream to a pyrolysis reactor to heat and produce a second vapor stream, a second liquid stream, and solid particles; c) delivering an adsorbent to the pyrolysis reactor to adsorb chlorine and chlorine-containing compounds and to act as an agglomeration material for carbonaceous char particles, the adsorbent being an alkaline material present in about a 2-3 molar ratio to the chlorine and chlorine-containing compounds remaining in the pyrolysis reactor; d) directing a first portion of the second liquid stream from the pyrolysis reactor to the melting reactor and a second portion of the second liquid stream from the pyrolysis reactor to an incinerator for further heating and returning to the pyrolysis reactor as a circulating liquid feed stream; e. sending the first vapor stream to the incinerator to remove hydrocarbons, hydrogen chloride, and alkyl chlorides, and then to a gas clean-up zone to remove chlorine compounds and heat the circulating liquid feed stream as a reaction heat supply for the pyrolysis reactor; f. cooling and separating the second vapor stream into a third vapor stream and a third liquid stream, and then treating the third liquid stream with at least one adsorption bed to remove chlorine-containing impurities; where: The pyrolysis reactor has a configuration including two cylindrical ring structures consisting of an inner cylindrical ring structure and an outer cylindrical ring structure, the circulating liquid feed stream enters the pyrolysis reactor tangentially through an annular location between the inner and outer cylindrical ring structures; and solid particles move in a downward direction within the pyrolysis reactor; process.

Images