Process for pyrolysis of PVC-containing mixed plastic wastes.

Abstract

A process is provided for the thermal decomposition of mixed plastic streams containing polyvinyl chloride (PVC), in which chlorides from the PVC are removed from an initial melt reactor that heats the mixed plastic stream to a temperature sufficient to produce HCl, but low enough to avoid the production of organic chlorides. While chlorides are primarily removed in the vapor stream from the initial melt reactor, further chloride removal can be achieved downstream from the melt reactor by the use of an adsorbent added to the pyrolysis reactor and subsequent adsorption beds.

Description

[Technical Field]

[0001] (Statement of priority) This application claims priority to Provisional Application No. 63 / 050704, filed July 10, 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 the production of valuable, upgradable pyrolysis oil that meets chloride quality specifications in downstream upgrading facilities. [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. Waste recycling facilities apply a sorting process to recover recyclable plastics. Mixed plastic waste is the waste that remains after sorting. Mixed plastic waste is considered to have reached its end of life and is generally sent to landfills or incineration. Chemical recycling through pyrolysis processes can convert end-of-life plastic waste into fuel or petrochemical feedstock alternatives under air-free atmospheres and higher temperature conditions, e.g., 350°C to 900°C.

[0004] While mixed plastic feedstocks are not homogeneous, the broad definition of mixed plastic waste includes all seven types of plastics: polyethylene terephthalate (PET), low- and high-density polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and other miscellaneous plastics. These plastics originate from various post-consumer products, 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 also be present in the mixed feedstock. Additionally, small amounts of non-plastic materials, such as paper, wood, and food residues, are also present.

[0005] Mixed plastic streams have already undergone a sorting process at material recovery facilities. Typically, mixed plastic streams require further sorting before being processed in chemical processes. The purpose of further sorting is to remove problematic contaminants from the recycling process. Non-plastics, such as metals, dirt, and wood, are clearly undesirable. Not all plastics are suitable for pyrolysis, and PVC is particularly undesirable. This is because, if PVC is left untreated, chloride derivatives of PVC in the product may harm the metallurgy of downstream processes. To achieve high efficiency in contaminant removal, a sorting process may be applied prior to the pyrolysis process, including a combination of common techniques such as shredding, magnetic, eddy current, gravity separation, optical, and / or electrostatic sorting. Sorting can be very complex and expensive. It is desirable to apply process steps to remove contaminants. The objective of the present invention is to achieve contaminant removal during chemical recycling instead of investing heavily in a preliminary sorting process. The present invention focuses on chloride derivatives derived from PVC in the feed. Without an expensive classification step to remove most of the PVC prior to the pyrolysis unit, it is unlikely that chlorides can be treated to acceptable levels using prior art processes. In downstream industries, the goal is preferably less than 10 ppw chlorides in the pyrolysis product. No technology can achieve the 99.999% chloride removal efficiency required in a single step to handle approximately 2% PVC in the feed. The present invention teaches how to process PVC-containing feeds to a low Cl range suitable for petrochemical or refinery feeds, such as less than 10 ppw in the product, using a series of steps that provide synergistic effects, for example, for feeds containing about 1-6 wt.% PVC.

[0006] The gradual chloride removal must be achieved through a feasible reactor type and an efficient heat supply strategy. Prior art has taught the pyrolysis of plastic waste using rotary kilns (U.S. Patent Application Publication Nos. 20170283706A1 and 201702182786A1) or extrusion equipment (U.S. Patent Application Publication No. 10,233,393). Transporting the char-containing product may involve operating the rotary kiln in a specific rotary fryer 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 excessive char deposition resulting from the hotter fluid near the wall and consequent poorer heat transfer. Excessive char deposition further behaves as an insulator, resulting in larger thermal gradients along the wall and wall-layer fluid. Uniform heat distribution within the reactor should result in lower char yields and higher product yields. Such heating systems also limit the size of the pyrolysis process.

[0007] The use of convective heat transfer from within the pyrolysis reactor helps avoid the problems associated with indirect heating, as 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. 20140114098A1). However, circulating heat transfer media can thermally decompose, complicating the selection of heating fluids. Plastics themselves also have low thermal conductivity, meaning that large amounts of heat transfer media may be required. U.S. Patent Application Publication No. 20140114098A1 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. The novel reactor design allows the pyrolysis pumparound stream to have a minimal solids content so that the stream does not erode or foul and can provide the heating medium requirements.

[0008] Therefore, there is a need for a robust process for handling mixed plastics, particularly one that minimizes the amount of pre-sorting of the plastic feed prior to the pyrolysis reactor. The process must handle polyvinyl chloride, a common component in the feed, and minimize chlorides in the products resulting from the pyrolysis of polyvinyl chloride. The reactor system must operate continuously and effectively reject any harmful solids, such as any additives, in the reaction system for smooth process operation, while utilizing the process stream and maintaining high heat transfer efficiency to the reactor. Summary of the Invention

[0009] Various embodiments contemplated herein relate to processes and apparatus for pyrolyzing mixed plastic waste streams derived from high PVC in the feed to produce an oil product with low chloride content. Exemplary embodiments taught herein provide a process for pyrolyzing mixed plastic waste streams. The embodiments also illustrate the necessary step-by-step process that enables the aforementioned process.

[0010] 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 mixed plastic waste stream may contain 1-6% PVC by weight in the feed, with limited efforts to remove chlorides through pre-sorting before entering the pyrolysis process. 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 is 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 broken down into a vapor stream and a bottom liquid stream. The pyrolysis reactor contains a significant stock of liquid material produced in the polymerization reactor. A portion of this liquid mixes with the plastic feed in the melting reactor to provide sensible heat and heat of fusion. The remainder of this liquid is heated to provide any remaining heat of reaction and heat of vaporization in the pyrolysis reactor. The heat source is a gaseous or liquefied fuel that is combusted to provide the heat required for the reaction and the latent heat in the reactor. The heated liquid stream has a higher temperature than the main reactor because it provides all of the heat required for the pyrolysis reaction.

[0011] According to another exemplary embodiment, a process for pyrolysis of PVC-containing feedstocks while minimizing the amount of chlorides in the product is provided. It has been discovered that removal of high chlorides requires a staged process to meet product specification requirements. The staged process requires at least two steps, and may require three steps to achieve low product Cl levels. The first step of the dechlorination process involves partial conversion of polyvinyl chloride to hydrogen chloride in a melting step. The hydrogen chloride from this reaction is contained in the vapor stream of the melting reactor and sent directly to an incinerator for combustion with any hydrocarbon gases and, optionally, to help provide heat to the pyrolysis reactor. The hydrogen chloride-rich gas produced from the pyrolysis reactor is then further removed while the liquid product is gradually condensed. Optionally, a finely divided solid sorbent is added to the reactor to enhance chlorine retention by reacting the sorbent with the hydrogen chloride product. The solid sorbent is an inexpensive, alkali-rich reactant that reacts with residual chlorides. Condensation separates the hydrogen chloride-rich gas from the main pyrolysis oil product. The condensed pyrolysis oil product is sent to a post-treatment bed. A small bed of adsorbent further removes the chloride content of the product to nearly zero percent. The synergistic effect of utilizing a staged approach to process Cl from over 5,800 ppw in the feed to 10 ppw in the product using the process and apparatus described herein is not previously known. The present invention discloses a synergistic method for chloride removal, where the size of the first dechlorination tank can be much smaller than the main cracking reactor. The amount of adsorbent required in these beds is minimized by the other steps described above. A final polish chloride removal step is economical using an adsorbent solution as part of the present invention. The present invention eliminates the need for extensive pre-classification at the feed end when the mixed plastic feed has a high PVC content, e.g., greater than 1 wt.% PVC content. The present invention achieves low chlorine levels in the final pyrolysis oil product, e.g., less than 10 ppwm, or preferably less than 6 ppm in the product, that cannot be achieved on a practical scale with a single technology using the described process and apparatus.

[0012] The process utilizes continuous reactors to provide a method for maintaining heat integration, pyrolysis operation, and solids separation despite using a minimally sorted mixed plastic feed.

[0013] These and other features, aspects, and advantages of the present disclosure will become better understood with consideration of the following detailed description, drawings, and 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 2] 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 while 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 a uniform temperature distribution established throughout the liquid space.

[0016] As used herein, the term "mixed plastic feed" means that more than one type of 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 target. 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 a by-product.

[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 producing the primary product. Reaction strategies can be adapted 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 e-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. An 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 ends up in the residue stream in solid form. Another form of solid can come from an adsorbent useful for reacting chloride-containing molecules during the reaction. An example is calcium-based adsorbents in hydroxides, oxides, or carbonates, often derived from natural minerals.

[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 a stream from an upstream component enters a downstream component without undergoing a change in composition through physical fractionation or chemical conversion.

[0027] The term "chloride" refers to chlorine that is chemically incorporated into the PVC in various forms, either organic or inorganic, in the feed, product oil, or product vapor stream.

[0028] As used herein, the term "settling" refers to the separation of solids and liquids, specifically the movement of solids downward toward or within a reaction vessel. For solids to tend to settle, the solid's carrier liquid must continue to accelerate and cannot provide velocity or prevent the solid from settling from the liquid flow continuum solely through the drag force between the liquid and solid. Critical liquid velocity is often known as "terminal velocity" or "settling velocity." When solids settle, they have a slip velocity, or are retarded, from the liquid average velocity. When this occurs for a group of solids, the solids tend to accumulate in a gradient due to retarded solid transport or to form a precipitate as the liquid moves through a pipe or vessel.

[0029] As used herein, the term "quality." The quality of a pyrolysis product refers to the chemical composition of the pyrolysis product, which makes it more or less suitable for downstream applications. A general goal of mixed plastics pyrolysis is to produce a product that can be used in downstream refineries. The hydrocarbon content of the product is an important measure of quality. In particular, an important quality measure relevant to this invention is chloride content. Chloride content, whether in organic or inorganic form, tends to lead to metallurgical corrosion. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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 this type of process, 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.

[0031] As shown, the process flowlines 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.

[0032] A 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 called an incinerator) 106, a gas cleanup section 107, and finally, a product specification section with optional fractionation and storage 108.

[0033] In one embodiment, the mixed plastic residue stream can contain various plastic waste, including seven types of plastic classifications: polyethylene terephthalate, low-density and high-density polyethylene, polypropylene, polyvinyl chloride, polystyrene, and various other plastics. At least one type of plastic is polyvinyl chloride. The U.S. Environmental Protection Agency, in its Advancing Sustainability Materials Management: 2016 and 2017 tables and figures, reports that, on average, approximately 3% polyvinyl chloride, approximately 13% polyethylene terephthalate, approximately 7% polystyrene, and approximately 11% other plastics and undefined amounts made up the 2017 waste plastic mix that ended up in landfills. The relative amounts of each plastic type vary depending on the collection site of the recycled plastic.

[0034] Other miscellaneous plastics can come from a variety of post-consumer products, including acrylonitrile butadiene styrene found in e-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.

[0035] In one embodiment, mixed plastic waste at the end of a material recovering facility (MRF) process that would otherwise be sent to a landfill is used for the pyrolysis feed. 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 the mixed plastic waste is pyrolyzed, 1 wt. % polyvinyl chloride will theoretically produce approximately 5800 ppmw of hydrogen chloride, based on the fresh feed rate. The minimally classified mixed feed stream may contain more than 1 wt. % PVC therein. The cold mixed plastic material is mixed with hot liquid stream 8 to reach a temperature of 300-350°C. Melt reactor 101 functions as a dechlorination reactor and is operated at a temperature of 200°C (392°F) to 350°C (662°F), or preferably 280°C (536°F) to 320°C (608°F), a pressure of 0.069 MPa (gauge) (10 psig) to 1.38 MPa (gauge) (200 psig), or preferably 0.138 MPa (gauge) (20 psig) to 0.345 MPa (gauge) (50 psig), a liquid hourly space velocity of the fresh melt feed of 0.1 hr-1 to 2 hr-1, or preferably 0.2 hr-1 to 0.5 hr-1, and a nitrogen atmosphere or a flow rate of 1.7 Nm3 / m3 (10 scf / bbl) to 170 Nm3 / m3 of plastic melt (Nm3 / m3). The system 100 may operate under a dedicated nitrogen sweep rate of 1,000 scf / bbl (17 Nm / m3) (100 scf / bbl) to 850 Nm / m3 plastic melt (500 scf / bbl). The system 100 includes a melt reactor 101 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 the feed chloride unconverted. The present invention provides a stepwise dechlorination process that uses a combination of steps to economically enable high chloride removal efficiencies.In the present invention, the product quality target can be less than 40 ppmw chlorine, or less than 10 ppmw chlorine, or preferably less than 6 ppmw chlorine, for mixed plastics containing a high PVC content, e.g., 1-6 wt. %. Such a goal cannot be realistically or economically achieved in a single process step. In the melt reactor 101, polyvinyl chloride is mostly thermally decomposed by an "unzipping" reaction, in which chloride molecules are removed by a free radical reaction and extract hydrogen at a nearby site to form hydrogen chloride. This reaction is also known as a "dechlorination" reaction. The temperature of the melt reactor 101 is selected to melt most of the plastic components but barely reach their decomposition temperatures, maximizing the yield of hydrogen chloride and minimizing the amount of reactive olefins and other organic chlorides formed. Thermal dechlorination involves heating the PVC-containing mixed plastic feed in an oxygen-free environment. The chlorides in PVC thermally decompose at approximately 280°C, and appreciable dechlorination rates occur at approximately 300°C. Chloride-containing free radicals derived from PVC tend to abstract hydrogen and form stabilized molecular forms. Other plastics in the mixed feed also begin to melt at temperatures above approximately 300°C. Polystyrene begins thermal decomposition at approximately 320°C, and other plastic types can begin thermal decomposition at approximately 340°C or higher with significant conversion. Chloride-containing free radicals derived from PVC or newly formed hydrogen chloride tend to combine with olefinic ligands to form chloride-containing molecules. Once formed, chloride-containing molecules result in chloride-contaminated pyrolysis oil products. Careful design of melt tank conditions in the melt tank can minimize the formation of chloride-containing molecules through recombination reactions. As mentioned above, the melt tank temperature is preferably between 280°C (536°F) and 320°C (608°F) to focus solely on dechlorinating PVC and melting other plastics. The dechlorination reaction rate is a function of temperature and residence time. Lower operating temperatures require a larger reactor volume to complete the PVC dechlorination reaction.For example, if the feed contains about 2 wt.% PVC or about 1.16 wt.% chlorides, theoretically, a dechlorination efficiency of 99.999% is required to achieve the target chloride removal in a single step. In practical applications, this is not achievable. In a single-tank reactor, the inventors have found that dechlorination efficiency approximately follows first-order kinetic laws, increasing with reactor size or residence time. However, as is well known from first-order CSTR kinetics, the return on dechlorination conversion with increasing reactor size decreases at higher conversion rates. Therefore, it is not practical for a single-step dechlorination reactor to achieve a dechlorination efficiency greater than 90%. To gauge process feasibility, if the dechlorination reactor is larger in size than the main decomposition reactor, the pretreatment step exceeds the needs of the main reaction and exceeds the threadhold of a "practical" design. Limited by practical constraints, a single dechlorination reactor can have a practical dechlorination removal of 90%, or more practically, about 80% to about 90%. Presumably, additional constraints apply, further reducing the actual Cl conversion rate in the melting tank. For example, heat transfer limitations slow the overall reaction rate, and preferably, instead of externally heating the melting tank through the vessel wall, a stream from the main reactor is circulated to the melting tank reactor, eliminating the thermal conductivity heating barrier. This solves the conduction delay problem and coking caused by hotter walls, but the tradeoff is that the circulating liquid requires more residence time to convert chlorides from the PVC. Consequently, a dechlorination conversion rate of more than 90% in the melting tank is considered impractical. The present invention cannot be limited to the reactor design taught, and the inventors' teachings regarding reactor design enable the present invention to produce low-chlorine products. Further synergistic processes using various technologies to achieve the efficiencies necessary to reach low chlorine in the product are taught below.

[0036] The chlorine in the unconverted PVC or the organic chlorides remaining in the melt reactor bottoms are subsequently further pyrolyzed in the pyrolysis reactor to form hydrogen chloride and their hydrocarbon derivatives. Under the same main reactor conditions, the majority of the plastic mixture is pyrolyzed into a range of hydrocarbon molecules, namely, paraffins, olefins, and aromatics with carbon numbers ranging from 1 to 50 or more. Heteroatom-containing molecules are also present. The remaining chloride molecules remaining after the first low-temperature melting step have a different molecular structure from their parent molecules. The remaining chloride molecules require higher activation energy or higher temperatures to convert to chloride radicals. Two possible pathways exist for the formation of stable organic chloride products. Hydrogen chloride-bound pyrolysis hydrocarbon products are a known pathway for organic chloride molecules in liquid-phase pyrolysis reactors. The newly generated chloride free radicals can also react directly with the cracked hydrocarbons to stabilize the organic chloride molecules that form. The organic chloride formation window is consistent with a wide range of operating conditions, including pyrolysis and condensation conditions, e.g., 50 to 450 °C. As mentioned above, organic chlorides carried by the pyrolysis products are the end product of either reaction mechanism, resulting in a lower product quality. Not all hydrogen chloride is chemically converted to organic chlorides; hydrogen chloride formed in the primary pyrolysis reactor escapes with non-condensable vapors when the product buildup is condensed in liquid form. In some cases, to enhance dechlorination in the primary cracking reactor, a sorbent can be added to further improve dechlorination. When a solid sorbent is introduced into a liquid pyrolysis process, either of the reaction mechanisms is affected. Chloride radicals or hydrogen chloride have an affinity for alkaline earth surfaces. Sodium or calcium molecules block newly generated chloride free radicals that react with hydrocarbons. Sodium or calcium molecules may also react directly with hydrogen chloride intermediates before combining with pyrolysis product molecules. The conditions for using the sorbent are further discussed below. There are optimal conditions for the application of the sorbent.

[0037] 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 sufficient residence time 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 300°C (572°F) to 550°C (1022°F), or preferably 380°C (716°F) to 450°C (842°F), a pressure of 0.069 MPa (gauge) (10 psig) to 1.38 MPa (gauge) (200 psig), or preferably 0.138 MPa (gauge) (20 psig) to 0.345 MPa (gauge) (50 psig), and a reaction time of 0.1 hours. -1 ~2 hours -1 or more preferably 0.2 hours -1 ~0.5 hours -1 and a liquid hourly space velocity of the fresh molten feed of 17 Nm 3 / m 3 (100scf / bbl)~850Nm 3 / m 3 Plastic melt (5,000 scf / bbl), or more preferably 170 Nm 3 / m 3 (1000scf / bbl)~340Nm 3 / m 3 It may operate under a dedicated nitrogen sweep stream 4 at a rate of plastic melt (2000 scf / bbl).

[0038] The present invention applies a second step in the dechlorination process designed around a primary pyrolysis reactor. The primary reactor depolymerizes various polymers. Unconverted PVC melt tank is further converted to hydrogen chloride. A portion of the hydrogen chloride reacts with the olefinic pyrolysis oil to form organic chlorides. A portion of the hydrogen chloride exits as vapor stream 13. A portion of the hydrogen chloride exits as a waste stream carried by reactor bottoms residue stream 7. The dechlorination efficiency, or incremental dechlorination conversion, is defined as the disappearance of chloride in the product chloride mass stream in the liquid product proceeding to the next stage, which enters the boundary of the primary reactor. To achieve higher dechlorination efficiency, it is necessary to concentrate the chloride mass streams in liquid stream 7 and vapor stream 13. Experimentally, the inventors have found that dechlorination efficiency is often 40-80%, i.e., less than 80%.

[0039] To further improve dechlorination efficiency, a finely ground solid sorbent stream 5 may be introduced into the feed at the top of the pyrolysis reactor 102 to increase chloride removal to the liquid stream 7. A suitable particle size may be such that 90% of the particles are in the 1-100 μm size range. The sorbent selected may include naturally occurring alkaline materials, such as calcium carbonate, quicklime, or calcium hydroxide-based minerals or products / by-products from mining processes. The choice of sorbent also depends on its availability, grindability, activity, and therefore use and cost. The use of sorbent in the main decomposition reactor 102 and thermal dechlorination in the melting tank 101 have a synergistic effect. Thermal dechlorination in the melting tank is not suitable for dechlorination conversions of 90% or more. Chloride removal by using sorbent in the main reactor 102 cannot practically exceed incremental conversions above 90% for non-obvious reasons. Essentially, to form CaCl2 as a stable product between the sorbent and chloride-containing molecules, the stoichiometric atomic ratio between calcium and chloride must be much greater than 2. Typically, the dosage is within a 3-6 molar ratio. There is an optimal Ca / Cl molar ratio, and consequently, an optimal chloride conversion in the primary reactor 102. Well-mixed reactors are highly preferred because they thoroughly mix the solid sorbent, the chloride-containing liquid molecules, and the newly formed hydrogen chloride released from the final chain of pyrolysis reactions. Well-mixed reactors offer advantages over unmixed extrusion or furnace reactors due to the liquid / solid mixing alone. While fine grinding increases sorbent dispersion, it can be costly if unrealistic particle size targets, such as those below 10 μm on average, are pursued. According to proprietary information, a ratio of 2.5-4 is considered more optimal, and as a result, chloride conversions of 80-90% are more typical due to reactor mixing and particle size constraints. To further explain, when the liquid-solid and sorbent size are determined, the sorbent utilization ratio (defined as the ratio of the mass of trapped chloride to the mass of introduced calcium) tends to decrease as a function of increasing calcium / chloride molar ratio.The similar trend in sorbent-to-storage ratios for sorbent use is intuitively analogous to a more familiar but similar commercial scenario, where calcium oxide is typically applied to absorb SOx emissions from fossil fuel-fired reactors (see Processing and Utilization of High-Sulfur Coals V: Proceedings of the Fifth ed., edited by BK Parekh and JG Groppo, p. 426, Figure 3). Because of the high chloride content in the system, more sorbent must be introduced. However, adding more sorbent creates another limitation. Essentially, the pyrolysis of waste plastics depolymerizes large polymer molecules with molecular weights (e.g., grams per mole) of several thousand or more into tens or hundreds. Therefore, the pyrolysis products are highly volatile. Assuming a large fraction of the feed is converted to vapor products and remains in stream 6. A much smaller fraction of the feed exits as a residue stream in the liquid phase. The mass ratio between stream 6 and steam 7 may be 2.3 to 9. For the portion of sorbent added to the feed, the concentration factor (defined as the ratio of the weight percent solids in the residue stream 7 to the weight percent solids in the feed to the main reactor 2) is 3.3 to 10 times. Typically, it is necessary to limit the amount of solid sorbent in the reactor residue. As a result, dechlorination via the sorbent-chloride reaction in the main reactor has a conversion limit, e.g., 80 to 90%, due to constraints on calcium use. In one exemplary case, by adding sorbent to the pyrolysis reactor, the ratio of sorbent to removed chloride is 2.5 to 4, and it has been found that it is more preferable to limit the spent sorbent to 5 weight percent in the reactor residue stream. Incremental reactor dechlorination is optimal when approximately 90% of the chloride removal is performed by the melt tank, followed by another 90% removal in the main reactor.

[0040] In practical terms, chloride removal efficiency to achieve less than 10 ppmw, or preferably less than 5 ppmw Cl, requires maximizing the dechlorination efficiency in each reactor step, for example, greater than 90%. Neither melt-heat dechlorination in a melting tank with the main reactor fixed by steam removal and reactor residue elimination, nor melt-heat dechlorination in a melting tank with the main reactor fixed by steam removal and reactor residue elimination with adsorbent enhancement, can achieve chlorides less than 10 ppmw, preferably less than 5 ppmw, in the product. This is increasingly true when the PVC content of the feed is greater than 1%. In this case, a separate removal step is required, as explained below.

[0041] 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 its 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, as commonly found in extruder or rotary kiln reactors. Stream 7 contains chlorides, and if sorbent is introduced, more of it will be contained in stream 7, and the chloride remaining in stream 7 will be considered as a contribution to Cl removal efficiency.

[0042] FIG. 1 also shows a vapor product stream 6 containing a range of hydrocarbons carried by the nitrogen stream at the designed vapor linear velocity. 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 a possible cooling method, the water stream is collected in stream 14. If direct water contact is omitted, stream 14 may not be present. The chlorides carried in streams 13 and 14 are considered as contributions to the Cl removal efficiency. Liquid stream 15 is further heated stream 16 and 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 on separator 103. The stabilized liquid stream 19 is further cooled in stream 19 to the desired temperature before entering adsorber system 105. The adsorber system 105 operates as a final chloride polishing device. Each of the above dechlorination steps operates within its own practical and optimal operating efficiency window. Synergies exist between the two when the combination of the agitated circulating oil-heated dechlorination melt reactor, the main pyrolysis reactor, and optional adsorbent enhancement is not sufficient to achieve the 10 ppmw Cl target, or preferably less than 5 ppmw Cl target. If the feed contains more than 2% PVC and increased Cl removal performance is required, making the melt tank larger, making the main reactor larger, or upgrading the main reactor by introducing more adsorbent into it is unlikely to be economical, and a third continuous step involving the use of an adsorber is required. This third operation uses an adsorber dedicated to chloride polishing. While naturally occurring adsorbers can be applied, modified adsorbers are preferred. Preferably, specially modified adsorbers with high adsorption capacity and activity are used. Adsorber capacity is the maximum cumulative mass of chloride that can be retained relative to the mass of the adsorber being replaced, if no further chloride removal can be achieved.Adsorbent activity is defined by the temperature required to achieve a fixed product chloride content (when both the amount of adsorbent and the feed flow rate are fixed) or by the amount of adsorbent required (when both the temperature and the feed flow rate are fixed). Either a lower temperature is required, or a lower quality of adsorbent is required, indicating higher activity. A range of metal oxides may be suitable solely for adsorbing organic chlorides. More preferably, the adsorbent contains alkaline earth metals impregnated on alumina. This provides an engineering balance between activity and capacity using proprietary test data. The fabrication of modified adsorbents is beyond the scope of this invention. The present invention teaches its suitability in this application. The desired activity is the space velocity of the adsorbent relative to the flow rate of the pyrolysis process. For example, the relative volume of the adsorbent bed may be 1 to 4 times the flow rate of the pyrolysis volumetric stream on an hourly basis for a chloride content range of 10 to 1000 ppw in the product stream to achieve an incremental dechlorination efficiency of approximately 90%.

[0043] If the feed contains a high PVC content, the adsorbent bed must reduce chlorides to 10 ppmw or less. The adsorbent bed size must be minimized to maintain the best practical economics. The adsorbent bed performs best only if approximately 90% efficiency has already been achieved in the dechlorination reactor and / or if approximately 90% incremental efficiency has already been achieved when removing the adsorbent in the primary dechlorination reactor. The adsorbent bed has its own limitations when increased removal efficiency is required. For fixed temperature and feed flow rates, an increase in adsorbent quality is required due to activity limitations. When higher removal efficiency is required, increasing residence time reduces the gain in efficiency or incremental dechlorination conversion, disproportionately increasing quality. Alternatively, for fixed adsorbent quality and feed flow rates, an increase in operating temperature is required due to activity limitations. Increasing the temperature is often prohibitive when higher removal efficiency is required, not only because it reduces the incremental dechlorination conversion gain, but also because of the rapid increase in side reactions, such as carbon deposition on the adsorber, which leads to premature deactivation or a decrease in final capacity. Due to these constraints, the inventors have taught that the operating conditions of the adsorber should be better limited to 97% incremental dechlorination conversion, or preferably 95% or less, or more preferably, even lower values, with the upper limit set at the operating temperature, while maintaining reasonable adsorber quality. From practical design considerations, a reasonable measure of adsorber quality is the weight hourly space velocity, defined as the flow rate per unit time of the mass of the total pyrolysis oil stream relative to the mass of the adsorber replaced after one year of continuous operation. A weight hourly space velocity greater than 0.1, more preferably greater than 0.5, is considered practical. Thus, according to the present invention, by optimizing the use of three steps, i.e., the stirred dechlorination reactor, the adsorbent in the main reactor, and the adsorbent bed, a synergistic effect is found to achieve less than 10 ppmw Cl in the product when the PVC content of the feed is greater than 1%. Using only one technology reduces the efficiency and economics of dechlorination. Simply increasing the size of the dechlorination reactor, increasing the adsorbent usage, increasing the amount of adsorbent, or increasing the operating temperature cannot realistically and economically achieve the same objectives.

[0044] When the selection of the adsorbent bed is in accordance with the teachings of the present invention, the adsorbent reactor is operated at a temperature of from 100°C (212°F) to 300°C (572°F), or preferably from 120°C (248°F) to 200°C (392°F), a pressure of from 0.069 MPa (gauge) (10 psig) to 2.07 MPa (gauge) (300 psig), or preferably from 0.138 MPa (gauge) (20 psig) to 1.38 MPa (gauge) (200 psig), for 0.05 hours. -1 ~5 hours -1 , or more preferably 0.1 hours -1 ~2 hours -1 The melt feed can be operated at a liquid hourly space velocity of 1000 kJ / min.

[0045] As previously described herein, the present disclosure provides for staged chloride removal. Single-step chloride removal can have efficiency issues when the mixed plastics feed has a high PVC content, e.g., 2% or greater. Melt reactor 101 first removes over 90% by weight of the chloride in the mixed plastics 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 pyrolysis reactor 102, where an adsorbent is added to convert a portion of the chloride as a salt. Unconverted hydrogen chloride is further diluted in a sweep nitrogen stream, which minimizes gas-phase recombination reactions between hydrogen chloride and organic molecules. The process described above in this section can be designed to remove the majority of the chloride, preferably to less than 200 ppmw in stream 19. Adsorbent system 105, designated 105A and 105B, 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 salts obtained in the adsorber system 105 are considered spent and are removed while other vessels are running 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. Designing an overly large dechlorination reactor or increasing reactor dechlorination efficiency by using additional adsorbent injection into the reactor or by using gas dilution is known to be uneconomical when exceeding a certain efficiency threshold, such as 90%, for example, when seeking to reduce Cl in the product to levels below 200-400 ppm, as the dosage increases. This leads to economic penalties and difficulties in properly distributing the adsorbent if an overly large dechlorination reactor or a significant increase in adsorbent usage is required. Adsorbent beds are more suitable and economical only as a final polish, i.e., when reducing the chloride content in the final product from 200-400 ppm to less than 10 ppm. Similarly, increased chloride in the bed feed can lead to excessively high adsorbent usage.Thus, in a staged dechlorination, sorbent injection into the reactor can prove important to reduce the chloride content from thousands of ppm to hundreds of ppm. 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.

[0046] 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 substances that react with HCl.

[0047] The heat of reaction in the pyrolysis reactor 102 is two to three times greater than that 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 a second vapor stream 6. The product vapor stream 6 quickly leaves with the aid of a sweep gas 4, which is introduced into the pyrolysis reactor 102. Secondary decomposition is a term that refers to the primary pyrolysis products undergoing additional residence time under pyrolysis conditions and further decomposition. All of the latent heat required to vaporize the products and provide the heat of reaction for the pyrolysis reaction is supplied by the heat carried from stream 11.

[0048] Figure 2 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'. [Example]

[0049] Example 1. A chloride mass balance study is presented. Calculations are based on experimental data collected on melt tank dechlorination, adsorbent performance, and adsorber performance. Experiments were conducted at 320°C, with 1%, 2%, or 3% PVC in the feed, and less than 10 ppmw Cl in the product.

[0050] Three steps are run in series demonstrating melt tank size, adsorbent use, and adsorbent use. This example is scaled to a 1 ton / year feed flow basis. The data shows that if only a single step of chloride removal is used, a very large reactor or large amounts of adsorbent and adsorbent use would be required (see melt tank size vs. reactor size vs. ratio for three steps in series). This example illustrates how using three steps in series provides synergistic benefits compared to using any one or two of the three steps.

[0051] [Table 1]

[0052] [Table 2]

[0053] Example 2. A recycled plastic stream was obtained from a materials recovery facility in Wisconsin. The composition was 2 wt% PVC, 20% PE, 75% PP, with the remainder being PET, paper, organic residues, and metallic species. The Cl measured in the feed was 1.189 wt% Cl.

[0054] Step 1: 100 grams of the feed was heat treated in batches in a 500 cc reactor under approximately 25 psig pressure. The reactor was heated from ambient conditions to 300°C and held for 2 hours. After shutdown, the reactor contents were solidified, collected, and measured (i.e., the liquid product from the first stage).

[0055] Step 2. The same feed was tested under the same test conditions as in Step 1. After holding at 300°C for 2 hours, the reactor continued to ramp to 400°C and held for 1 hour. After cooling, the products produced from the pyrolysis reaction were collected in an ice-cooled condenser. 67 grams of product was recovered (i.e., total pyrolysis product). Step 2 was repeated several times to accumulate approximately 300 gm of liquid product (i.e., total combined pyrolysis product).

[0056] Step 3. The entire pyrolysis product was passed through a continuous fixed bed reactor using 3 cc of proprietary UOP commercial adsorbent. The equivalent volume per hour to the volume of adsorbent was 300 psi at a pressure of less than 200 psig. o The process was carried out at conditions below C. The recovered product (i.e., the final pyrolysis oil product) was measured for Cl. The examples demonstrate the observed dechlorination efficiency for an actual stepwise process to achieve Cl below 10 ppmw or preferably below 6 ppm.

[0057] [Table 3]

[0058] 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.

[0059] A first embodiment of the present invention is a process for producing a low chloride pyrolysis oil from a mixed plastic waste stream, comprising three chloride removal steps operating in series: melting the mixed plastic waste stream with a high temperature product stream in a melting reactor to produce a molten mixed plastic waste stream containing at least two plastics, including a chlorine-containing plastic and another plastic, 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 with the high temperature product stream to produce a second chloride-rich vapor stream, a second liquid stream, and solid particles; adding an adsorbent to the pyrolysis reactor to adsorb chloride-containing molecules; passing a portion of the second liquid stream, including a recycle stream from the pyrolysis reactor, to the melting reactor; passing a portion of the second liquid stream from the pyrolysis reactor to be heated and returned to the pyrolysis reactor; and passing the main pyrolysis condensate through an adsorption bed to remove residual chlorides up to 10 ppmw. An embodiment of the present invention is one, any, or all of the preceding through first embodiments of this paragraph, in which the first chloride-rich vapor stream is sent to a gas purification zone. An embodiment of the present invention is one, any, or all of the preceding through first embodiments of this paragraph, in which the melt reactor is operated at a temperature of 280°C (536°F) to 330°C (626°F), the pyrolysis reactor is operated at a temperature of 380°C (716°F) to 450°C (842°F), and the adsorption bed is operated at a temperature of 100°C (212°F) to 300°C (572°F). An embodiment of the present invention is one, any, or all of the preceding through first embodiments of this paragraph, in which the adsorbent is a ground alkaline material present at less than 3% by weight relative to the plastic melt and in a 2.5 to 4 molar ratio relative to the chloride in the pyrolysis reactor. In one embodiment of the present invention, the melt reactor is maintained at a pressure of 0.069 MPa (gauge) (10 psig) to 1.38 MPa (gauge) (200 psig) and a temperature of 0.1 hours. -1 ~2 hours -1It is operated at a liquid hourly space velocity of 1.7 Nm under a nitrogen atmosphere. 3 / m 3 (10scf / bbl)~170Nm 3 / m 3 Operated at a dedicated nitrogen sweep rate of 1,000 scf / bbl for the plastic melt, the pyrolysis reactor was operated at pressures of 0.069 MPa (gauge) (10 psig) to 1.38 MPa (gauge) (200 psig) and for 0.1 hours. -1 ~2 hours -1 and operated under a nitrogen atmosphere or at a liquid hourly space velocity of 17 Nm 3 / m 3 (100scf / bbl)~850Nm 3 / m 3 The adsorbent bed was operated under a dedicated nitrogen sweep stream at a rate of 5,000 scf / bbl of plastic melt, and the adsorbent bed was maintained at pressures ranging from 10 psig (0.069 MPa gauge) to 300 psig (2.07 MPa gauge) for 0.05 hours. -1 ~5 hours -1

[0023] One, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the melt reactor is operated at a fresh melt feed liquid hourly space velocity of 100 ppmw. An embodiment of the present invention is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising passing 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 embodiments through the first embodiment of this paragraph, wherein 80-95 wt.% of the chlorides from the melt reactor are removed and passed in the vapor stream. An embodiment of the present invention is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the third liquid stream contains less than 200 ppmw of chlorides. An embodiment of the present invention is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the third liquid stream is passed to an adsorption bed to remove chlorides. One embodiment of the present invention is any one, any, or all of the preceding embodiments through the first embodiment of this paragraph, in which the heat of reaction in the pyrolysis reactor is 2 to 3 times greater than the heat or reaction in the melt reactor. One embodiment of the present invention is any one, any, or all of the preceding embodiments through the first embodiment of this paragraph, in which the heat required in the melt reactor is provided by mixing a portion of the second liquid stream. One embodiment of the present invention is any one, any, or all of the preceding embodiments through the first embodiment of this paragraph, in which the heat required in the primary reactor is provided by mixing a portion of the heated second liquid stream. One embodiment of the present invention is any one, any, or all of the preceding embodiments through the first embodiment of this paragraph, in which the circulation of a portion of the heated second liquid stream provides mixing of the liquid and the sorbent. One embodiment of the present invention is any one, any, or all of the preceding embodiments through the first embodiment of this paragraph, in which the gas purification zone includes a catalyst bed for removing dioxin compounds and a vessel containing a caustic compound for neutralizing HCl.

[0060] 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 first vapor stream rich in chlorides and a first liquid stream; passing the first liquid stream to a pyrolysis reactor to heat it and produce a second vapor stream, a second liquid stream, and solid particles, the solid particles moving downward in the pyrolysis reactor; passing the first vapor stream to an incinerator and then to a gas cleaning zone to remove chlorine compounds and heating at least a portion of the recycled feed stream as a reaction heat supply for the pyrolysis reactor; cooling the second vapor stream and separating it into a third vapor stream and a third liquid stream; and then treating the third liquid stream with at least one adsorbent bed to remove chlorine-containing impurities. One embodiment of the present invention is one, any, or all of the previous embodiment of this paragraph through the second embodiment of this paragraph, further comprising passing an adsorbent to the pyrolysis reactor to remove chlorine compounds. One embodiment of the present invention is any one, any, or all of the previous through second embodiments of this paragraph, in which the chlorine-containing plastic is polyvinyl chloride and the other plastic is selected from polyethylene terephthalate, low- and high-density polyethylene, polypropylene, polystyrene, and various other plastics. One embodiment of the present invention is any one, any, or all of the previous through second embodiments of this paragraph, in which the gas cleanup zone includes a catalyst bed for removing dioxin compounds and a vessel containing a caustic compound for neutralizing HCl. One embodiment of the present invention is any one, any, or all of the previous through second embodiments of this paragraph, further including passing an sorbent to the pyrolysis reactor to adsorb chlorine and chlorine-containing compounds. One embodiment of the present invention is any one, any, or all of the previous through second embodiments of this paragraph, in which the sorbent is an alkaline material present in the pyrolysis reactor in a molar ratio of 2 to 3 relative to chloride.An embodiment of the present invention is one, any, or all of the previous embodiment of this paragraph through the second embodiment of this paragraph, wherein the sorbent body further functions as an agglomerate for carbonaceous char particles formed during operation of the pyrolysis reactor.

[0061] 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.

[0062] 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 producing low chloride content pyrolysis oil from a mixed plastic waste stream, comprising: a. melting the mixed plastic waste stream comprising at least two plastics, including a chlorine-containing plastic and another plastic, in a melting reactor to produce a first chloride-rich vapor stream and a first liquid stream; b. passing the first liquid stream to a pyrolysis reactor to produce a second chloride-rich vapor stream, a second liquid stream, and solid particles; c) directing a portion of the second liquid stream, including a recycle stream from the pyrolysis reactor, to the melt reactor and directing a portion of the second liquid stream from the pyrolysis reactor to be heated and returned to the pyrolysis reactor; d. cooling and separating the second chloride-rich vapor stream into a third vapor stream and a third liquid stream, and then passing the third liquid stream through an adsorption bed to remove residual chlorides and produce a pyrolysis oil having a reduced chloride content; The process includes:

2. 10. The process of claim 1 further comprising adding an adsorbent to the pyrolysis reactor to adsorb chloride-containing molecules.

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