Plastic Recycling Methods

Abstract

1. A method for treating mixed plastic waste, comprising: (I) pyrolyzing the mixed plastic waste in a pyrolysis reactor at a temperature of 250-700°C and a pressure of 1.0-100 bar to form pyrolysis oil; (II) transferring the pyrolysis oil directly to a hydrotreating unit, optionally through a filter, and subjecting the pyrolysis oil to catalytic hydrotreatment in the presence of hydrogen at a temperature of 250-700°C and a pressure of 1.0-100 bar to form a hydrotreated pyrolysis oil; (III) directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor. The method comprising:

Description

[Technical Field]

[0001] The present invention relates to the recycling of mixed plastic waste. In particular, the present invention relates to a method and apparatus for recycling mixed plastic waste that allows for direct transfer from a pyrolysis reactor used to depolymerize the mixed plastic waste to a hydroprocessing unit used to hydrogenate the pyrolysis oil formed in the pyrolysis reactor. Importantly, the present invention also uses direct recycle or recirculation from the hydroprocessing unit to the pyrolysis reactor to enable the direct transfer process. [Background technology]

[0002] As environmental concerns continue to grow, recycling of plastic waste is an important consideration for all plastic producers. Chemical recycling of plastics typically requires depolymerization, including but not limited to, by pyrolysis of mixed plastic waste (MPW), to produce pyrolysis oil (also referred to herein as pyoil).

[0003] Generally, raw pyoil is not fed directly to steam crackers to produce monomers suitable for the production of plastics because steam crackers utilize saturated hydrocarbons as a feedstock and pyrolysis oil contains many unsaturated or aromatic components. Therefore, the pyrolysis oil is typically pretreated to remove the high concentration of unsaturated components and impurities therein. This further processing typically occurs in a hydrotreatment unit (HDT), followed by separation of the formed components based on boiling point, i.e., fractionation. A fraction can then be sent for steam cracking.

[0004] The configuration of a system capable of converting MPW into target hydrocarbon fractions can vary widely, depending primarily on the quality of the MPW used. MPW can vary based on the polyolefin content therein, its oxygen content, contaminant content, etc. Also, some MPW can be used to target specific end products, such as LPG-Naphtha, to "heavies."

[0005] Pyrolysis of MPW is typically carried out at low pressure and high temperature to increase the yield of low-boiling components that are typically removed before hydrotreating. Cracked oil is the product from the pyrolysis reactor and is mostly condensed to a liquid state. Thus, pyrolysis oil is a mixture of many components with boiling points ranging from 0 to 600°C, particularly from 50 to 500°C.

[0006] The hydrotreating reactions required to saturate the components of the pyrolysis oil and remove contaminants typically require pressures above 20 bar and temperatures in the range of 350-450°C to increase the activity of the hydrogen.

[0007] Chemical recycling processes using pyrolysis oil typically cool and depressurize the pyrolysis oil before it is sent to a hydroprocessing unit because it is desirable to separate lights before the hydroprocessing unit or because the pressure difference between the pyrolysis reaction and the pressure required for the hydroprocessing unit is high. It is difficult to increase the pressure of pyrolysis oil from the pyrolysis reactor to the hydroprocessing unit when the pyrolysis oil is partially gaseous. Therefore, the pyrolysis oil can be cooled, gaseous lights can be removed, and the pressure and temperature can be increased in the liquid state to the operating pressure and temperature of the hydroprocessing unit.

[0008] As a result, pumps to increase the pressure of the liquid pyrolysis oil, heat exchangers, and furnaces need to be installed to heat the pyrolysis oil for the hydroprocessing unit.

[0009] Therefore, after the mixed plastic waste is pyrolyzed, it is common to separate the pyrolysis oil to recover at least the light (low boiling point) fraction. To this end, pyrolysis is typically carried out at low pressure to facilitate the extraction of lights from the pyrolysis reactor. When the pressure in the pyrolysis reactor is high, these lights are more likely to be in liquid form.

[0010] Therefore, typically, the lights are separated to produce a liquid hydrocarbon stream that requires hydrotreating, i.e., hydrogenation to produce saturates that can be cracked. The lights are removed, and the resulting liquid hydrocarbon stream is then reheated and increased in pressure for entry into the hydrotreating unit, where recycle is required to control the exotherm from the hydrotreating reaction.

[0011] Various MPW recycling processes are known. US Pat. No. 4,642,401 describes a method for producing hydrocarbons from pulverized plastic waste at high temperature and pressure in the presence of a solvent. Some hydrocarbons dissolve in the solvent to produce a solvent phase and a residue phase. The dissolved hydrocarbons are recovered from the solvent phase once separated from the residue phase by reducing the temperature and pressure of this phase and subjecting it to distillation.

[0012] US Patent No. 1,085,309 describes a method for producing propylene and cumene. Plastic waste is converted into a hydrocarbon liquid stream and a pyrolysis gas stream in a thermal cracking unit. The hydrocarbon liquid stream is subjected to hydrotreating in the presence of hydrogen in a hydrotreating unit to produce a C5+ hydrocarbon product and a first gas stream. The hydrocarbon product is subjected to a second separation to produce a C6 aromatics stream and a C5+ hydrocarbon stream. A portion of the saturated hydrocarbons isolated in the second separation are recycled to the thermal cracking unit or HDT. Therefore, there is no direct recycle from the hydrotreating reactor to the thermal cracking reactor. The pressure in the thermal cracking unit is not discussed, and the feed to the hydrotreating reactor is liquid; therefore, the entire pyrolysis oil is not fed.

[0013] International Publication No. WO 2018 / 069794 describes a method for producing olefins and aromatic hydrocarbons from mixed plastics. The mixed plastics are converted into hydrocarbon products containing a gaseous phase and a liquid phase in a thermal cracking unit. These streams are separated, and the liquid stream is further separated into a first low-boiling fraction and a second high-boiling fraction. The second fraction is recycled to the thermal cracking unit, and the first fraction is optionally sent to a liquid steam cracker via a hydrotreating reactor. In a further embodiment, after the mixed plastics are converted into hydrocarbon products containing a gaseous phase and a liquid phase in the thermal cracking unit, the liquid phase is hydrotreated, and the resulting hydrotreated pyrolysis oil is separated into a light fraction and a heavy fraction. The heavy fraction can be recycled to the thermal cracking unit. Therefore, there is no direct recycle from the hydrotreating reactor to the thermal cracking reactor.

[0014] International Publication No. WO 2003 / 89548 describes a method for producing lubricant base oils by blending a Fischer-Tropsch feedstock with waste polyolefins. The mixture is fed to a thermal cracking unit and then fractionated. The middle fraction (350-565°C) is potentially mixed with heavies and processed in a hydrotreating reactor, followed by an isomerization dewaxing unit (IDW). The heavy fraction (>565°C) can be sent to the hydrotreating reactor or recycled to the thermal cracking unit.

[0015] International Publication No. WO2021 / 149590 describes a method in which plastic waste is degassed prior to pyrolysis in the presence of a crude oil fraction to reduce viscosity.

[0016] International Publication No. WO 2022 / 146778 describes a method and system for a desulfurization process for fuel produced from scrap tires. The method requires pyrolysis of scrap tires to produce corresponding pyrolysis oil (i.e., pyoil), which is then hydrotreated to enable desulfurization and then finally distilled to obtain corresponding fuel products, such as kerosene, naphtha, fuel, and diesel. There is no teaching of direct recycling of the hydrotreated product to a pyrolysis device, nor of directly transferring the pyrolysis oil to a hydrotreating unit. Summary of the Invention [Means for solving the problem]

[0017] The inventors have now discovered that pyrolysis oil can be transferred directly from a pyrolysis reactor to a hydrotreating unit when there is a partial recycle or partial recycle from the hydrotreating unit to the pyrolysis reactor. The process in the pyrolysis reactor can be carried out at high pressure and temperature, and the resulting pyrolysis oil can be transferred directly to the hydrotreating unit without separating the fluid components of the pyrolysis oil. It can also be transferred to the hydrotreating unit without significantly cooling or depressurizing the pyrolysis oil to remove light ends.

[0018] Therefore, in the present invention, the MPW thermally cracked in the thermal cracking reactor is diluted with at least recycled hydrotreated pyrolysis oil from the hydrotreating unit. Therefore, the feed to the thermal cracking reactor contains MPW and recycled hydrotreated pyrolysis oil. Importantly, nothing needs to be removed from the recycle from the hydrotreating unit before entering the thermal cracking reactor. Therefore, the resulting pyrolysis oil from the thermal cracking reactor is a mixture of pyrolysis oil produced from MPW and further pyrolysis of the recycle stream.

[0019] No one has previously considered a way to transfer MPW directly from a pyrolysis reactor to a hydroprocessing unit without separating the fluid components, ideally without significantly changing the temperature or pressure between the pyrolysis reactor and the hydroprocessing unit. The ability to reduce the temperature or pressure changes provides a more energy efficient method.

[0020] Without wishing to be bound by theory, it is postulated that the use of a direct recycle stream from the hydrotreating unit to the pyrolysis reactor allows for the direct transfer of the pyrolysis oil from the pyrolysis reactor to the hydrotreating unit, since the hydrogenated fraction, which can be re-cracked in the pyrolysis reactor, also serves as a solvent or medium for dissolving the pyrolysis oil at high pressure.

[0021] In one aspect, the present invention provides a method for treating mixed plastic waste, comprising: (I) pyrolyzing the mixed plastic waste in a pyrolysis reactor at a temperature of 250-700°C and a pressure of 1.0-100 bar to form pyrolysis oil; (II) transferring the pyrolysis oil directly to a hydrotreating unit, optionally through a filter, and subjecting the pyrolysis oil to hydrotreatment in the presence of hydrogen at a temperature of 250-700°C and a pressure of 1.0-100 bar to form a hydrotreated pyrolysis oil; (III) directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor. The method includes:

[0022] Viewed from another aspect, the present invention provides a method for treating mixed plastic waste, comprising: (I) providing a pyrolysis reactor with a feed comprising mixed plastic waste; (II) pyrolyzing the feed comprising the mixed plastic waste in the pyrolysis reactor at a temperature of 250 to 700°C and a pressure of 1.0 to 100 bar to form a pyrolysis oil; (III) transferring the pyrolysis oil directly to a hydrotreating unit, optionally through a filter, and subjecting the pyrolysis oil to catalytic hydrotreatment in the presence of hydrogen at a temperature of 250-700°C and a pressure of 1.0-100 bar to form a hydrotreated pyrolysis oil; (IV) directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor, wherein the weight ratio of the hydrotreated pyrolysis oil recycled to the pyrolysis reactor to the mixed plastic waste fed to the pyrolysis reactor is 10:1 to 1:1, preferably 3:1 to 5:1; The method includes:

[0023] Viewed from another aspect, the present invention provides an installation for the treatment of mixed plastic waste, comprising: (I) Pyrolysis reactor; (II) Hydrotreating units; (III) a recycle conduit directly connecting the hydrotreating unit to the pyrolysis reactor. It is equipped with wherein the pyrolysis reactor is directly connected to the hydrotreating unit via a conduit, and the conduit may be equipped with a filter; The above facilities are provided.

[0024] definition

[0025] Mixed plastic waste is abbreviated as MPW in this specification.

[0026] The pyrolysis reactor is the vessel where MPW and recycled hydrotreated pyrolysis oil are heated under pressure to produce pyrolysis oil. There should be no hydrogen feed to the pyrolysis reactor. The terms "pyrolysis reactor" and "pyrolysis unit" are used interchangeably herein.

[0027] The product formed in the pyrolysis reactor is pyrolysis oil (referred to herein as pyoil).

[0028] The hydrotreating unit is a vessel or series of reactors in which hydrogenation reactions occur to saturate the unsaturated components of the pyrolysis oil. The terms "hydrotreating reactor" or "hydrotreating reactors" and "hydrotreating unit" are used interchangeably herein.

[0029] Transfer from the pyrolysis reactor to the hydroprocessing unit occurs directly, optionally via a filter, which therefore means that the liquid portion of the pyrolysis oil is not removed before transfer to the hydroprocessing unit.

[0030] The recycle from the hydrotreating unit to the pyrolysis reactor occurs directly, optionally via a filter, which means that the liquid portion of the hydrotreated pyrolysis oil is not removed before recycle to the pyrolysis reactor.

[0031] It will be understood that the conveying conduits (typically pipes) comprising the direct conveying conduit from one unit to another in the installation of the present invention may require pumps (if gravity cannot be used) and that any conduits allowing transfer may be equipped with valves to prevent backflow, which will not be further described herein.

[0032] The term "heavies" defines liquid hydrocarbons that typically have a boiling point above 360°C and include hydrocarbon compounds having carbon atoms greater than C20 to C24.

[0033] The light fraction (lights) typically comprises hydrocarbon compounds having a boiling point below 200° C. and having a number of carbon atoms between C10 and C12.

[0034] The medium fraction typically contains hydrocarbon compounds having a boiling point between 200 and 360° C. and having carbon atoms between C10 and C24.

[0035] The hydrotreated pyrolysis oil is recycled or recirculated from the hydrotreating unit to the pyrolysis reactor. The terms "recycle" and "recycle" are used interchangeably herein. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 shows an installation suitable for use in the treatment of mixed plastic waste according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention relates to a method and equipment for recycling mixed plastic waste, which can be obtained from post-industrial or post-consumer plastic waste. The mixed plastic waste can include chlorinated plastics, such as chlorinated polyethylene, polyvinyl chloride (PVC), or polyvinylidene chloride (PVDC); non-chlorinated plastics, such as polyolefins, including polyethylene, polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate, and polystyrene.

[0038] In some aspects, the mixed plastics can include PVC, PVDC, polyethylene terephthalate, polybutylene terephthalate, polyolefins, polystyrene, etc., or combinations thereof. Waste plastics disclosed herein also include post-consumer tires.

[0039] Preferably, the mixed plastic waste is predominantly polyolefin-based, and more preferably, the mixed plastic waste comprises more than 75% by weight of polyolefin components, in particular at least 75% by weight of polyethylene and polypropylene components.

[0040] Ideally, the mixed plastic waste used herein should contain no more than 10% by weight of chlorinated plastics. Therefore, in one embodiment, the present invention may utilize a sorting unit to separate any plastics that are not suitable for pyrolysis, such as chlorinated plastics.

[0041] However, it is understood that even MPW that is nominally free of chlorinated plastics may contain contaminants. Therefore, it is preferred that any MPW be subjected to a dechlorination process before entering the pyrolysis unit. This step is designed to remove chlorine (e.g., in the form of HCl) and other heteroatoms from the hydrocarbons present in the MPW.

[0042] Dechlorination of plastic mixtures from household waste and from other chlorine-containing mixtures, such as electronic scrap, is an important step in the chemical recycling of polymers. To ensure that the pyrolysis procedure is safe, the nature of any combustion process and the emissions from the pyrolysis unit must be known. Therefore, it is preferable that chlorine (and other heteroatoms) be removed before the pyrolysis process occurs, so that chlorine waste gases (and other heteroatom-containing gases) are avoided.

[0043] The dechlorination of MPW can be carried out in a dechlorination reactor, which is a vessel adapted to allow for moderate heating of the MPW and to allow the chlorinated gases (and other heteroatom gases) that are formed to be removed. It is preferred if the dechlorination reactor is carried out in the absence of hydrogen.

[0044] Along with the heteroatom-containing impurities, some light gaseous hydrocarbons may be formed during the dechlorination process. These can be removed by sending the heteroatom-containing impurities and gaseous products to a scrubber. Valuable light hydrocarbons can then be separated and recovered from the scrubber using known processes.

[0045] Dechlorination of chlorinated plastics can be carried out at moderate temperatures prior to the thermal degradation of the polymer. Therefore, low-temperature heating of MPW can convert the chlorine in MPW to hydrogen chloride. Suitable temperatures are 150-350°C, preferably 250-300°C. The dechlorination step is often carried out at a lower temperature than the pyrolysis step, e.g., below 250°C. The temperature should be sufficient to decompose the PVC-generating HCl gas without actually pyrolyzing the MPW.

[0046] The preferred pressure is 1-5 bar. The process can be relatively short compared to actual pyrolysis processes. Typical hourly space velocities for fresh melt are about 0.2 h -1 ~ about 0.5 hours and delivered with a nitrogen blanket or dedicated nitrogen sweeping rate.

[0047] Dechlorination methods (known in the art) can ensure that the chloride level in the MPW fed to the pyrolysis reactor is less than about 10 parts per million weight (ppmw) chloride, alternatively less than about 5 ppmw chloride, or alternatively less than about 3 ppmw chloride, based on the total weight of the MPW.

[0048] After the MPW has been optionally dechlorinated, it is passed to a pyrolysis reactor.

[0049] The feed to the pyrolysis unit includes MPW, optionally screened and dechlorinated as described above, and hydrotreated pyrolysis oil recycle from the hydrotreating unit, which is further described below. It is also possible that heavies separated from the hydrotreated pyrolysis oil after the hydrotreating process can be returned to the pyrolysis reactor. Finally, it is possible that pyrolysis oil or bio-oil from another source can be fed to the pyrolysis reactor as an additional feed. Pyrolysis oil or bio-oil from another source may also be fed to a filter after the pyrolysis reactor to become part of the hydrotreating reaction.

[0050] It is preferred if MPW forms at least 75 wt% of the feed to the pyrolysis reactor.

[0051] pyrolysis

[0052] The pyrolysis reactor may be any suitable vessel configured to convert mixed waste plastics into gas and liquid phase products (e.g., simultaneously). The pyrolysis reactor may contain an inert material (e.g., sand, alumina) or a pyrolysis catalyst, such as a zeolite. However, it is preferred if no catalyst is used and the process involves only heat. The pyrolysis unit may be operated adiabatically, isothermally, non-adiabatically, non-isothermally, or a combination thereof.

[0053] Although two pyrolysis reactors connected in series could theoretically be used, the pyrolysis reaction is ideally carried out in a single pyrolysis reactor. In this scenario, the recycle stream from the hydroprocessing unit should occur in at least one, and preferably both, reactors. If recycling occurs in one unit, it is preferably the first unit in the sequence.

[0054] One such reactor may use a catalyst (thus producing catalytically cracked pyrolysis oil), or may simply use thermal processing to produce thermally cracked pyrolysis oil. Catalysts of interest in this process are known, and any commonly known catalyst can be used. Typical catalysts include zeolites.

[0055] The pyrolysis unit can be configured to thermally decompose (e.g., crack) components of the mixed plastic stream fed to the pyrolysis unit. Examples of reactions that can occur in the pyrolysis unit include isomerization, selective ring opening, cracking of long chain molecules, or combinations thereof.

[0056] The pyrolysis reactor may be operated at a temperature of from 250° C. to 700° C., alternatively from 275° C. to 700° C., or alternatively from 300° C. to 400° C. More preferably, however, the temperature is at least 400° C., for example from 400 to 700° C.

[0057] The pyrolysis reaction is carried out in the range of 1.0 to 100 bar, for example 2 to 100 bar, for example 5 to 50 bar, preferably 10 to 100 bar, in particular 20 to 50 bar or 10 to 25 bar.

[0058] The residence time in the pyrolysis reactor may be from 10 to 180 minutes, preferably from 15 to 60 minutes, depending on the temperature.

[0059] Typically, the pyrolysis process is carried out at higher temperatures and for longer periods of time than any dechlorination process.

[0060] The pyrolysis reactor is preferably operated continuously, so that pyrolysis oil formed is constantly removed from the pyrolysis reactor during operation.

[0061] In conventional thermal cracking processes, the pyrolysis oil formed is separated into a gaseous portion and a liquid portion after the thermal cracking reactor. Therefore, the pyrolysis oil is typically fed to a separation unit that functions as a condenser. A gas stream may be removed, and the formed liquid hydrocarbon stream can then be conveyed to the hydrotreating unit. The liquid hydrocarbon stream is reheated and pressurized to the required conditions in the hydrotreating unit. This method allows for the separation of a light fraction, but it is energy intensive. It would be useful if the pyrolysis oil did not need to be cooled and depressurized after the thermal cracking reaction.

[0062] In this case, the pyrolysis oil produced in the pyrolysis reactor is conveyed directly to the hydrotreating unit without fluid separation. Before the pyrolysis oil enters the hydrotreating unit, a filter is used to filter the pyrolysis oil, but no separation of fluid components occurs. The filter simply removes any solid components present in the pyrolysis oil.

[0063] Because the pyrolysis reaction is an endothermic process and the hydrogenation is an exothermic process, this closed loop between both unit operations allows for good temperature and heat control.

[0064] At this point, the pyrolysis oil contains various components such as paraffins, olefins, naphthenes, and aromatics.

[0065] It is preferred if the pressure and temperature in the pyrolysis reactor are such that substantially all of the fluid components (i.e., liquid and gaseous components) of the pyrolysis oil are in the liquid phase at the end of the pyrolysis reaction. The required temperature and pressure are preferably maintained in any conduits connecting the pyrolysis and hydrotreating units such that no gaseous components are present in any conduits.

[0066] Hydrotreating Unit

[0067] In the hydrotreating unit, hydrogen is fed to saturate the compounds present, thus forming hydrotreated pyrolysis oil. Therefore, preferably, the only feeds to the hydrotreating unit are pyrolysis oil and hydrogen. The hydrotreating unit may be any single vessel or series of vessels configured to contain hydrotreating reactions. The hydrotreating unit may contain one or more beds of hydrotreating catalyst. The hydrotreating unit may be operated adiabatically, isothermally, non-adiabatically, non-isothermally, or a combination thereof.

[0068] The hydrotreating unit is preferably operated catalytically in the presence of hydrogen, so that unsaturated compounds are converted to saturated compounds, such as olefins, aromatics, paraffins, i-paraffins, naphthenes.

[0069] Additionally, reactions in the hydroprocessing unit can cause bonds in organic compounds to break, resulting in the "cracking" of a hydrocarbon molecule into two or more smaller hydrocarbon molecules.

[0070] The hydrotreating catalyst may be any catalyst (e.g., commercially available hydrotreating catalyst) used for the hydrogenation of olefins and aromatic hydrocarbons. The hydrotreating catalyst may include, for example, a cobalt and molybdenum catalyst on an alumina support (Co-Mo catalyst), a nickel and molybdenum catalyst (Ni-Mo catalyst), a tungsten and molybdenum catalyst (W-Mo catalyst), a cobalt and molybdenum oxide on an alumina support, for example, a nickel and molybdenum oxide on an alumina support, for example, a tungsten and molybdenum oxide on an alumina support, for example, a cobalt and molybdenum oxide on an alumina support, for example, a cobalt and molybdenum sulfide on an alumina support, for example, a nickel and molybdenum sulfide on an alumina support, for example, a tungsten and molybdenum sulfide on an alumina support, a zeolite containing one or more metals, or a combination thereof.

[0071] Other catalysts suitable for use as hydrotreating catalysts may include, for example, platinum and palladium catalysts on an alumina support (Pt-Pd catalysts), nickel sulfide suitable for slurry processing, molybdenum sulfide suitable for slurry processing, or combinations thereof. Zeolites may include ZSM-5, ZSM-11, Y, high-silica Y, USY, etc., or combinations thereof. Each metal of the one or more metals of the zeolite may be independently selected from the group consisting of cobalt, molybdenum, tungsten, nickel, titanium, copper, magnesium, tin, iron, zinc, vanadium, gallium, calcium, manganese, ruthenium, and rhenium.

[0072] The hydrotreating unit is preferably operated at a temperature of 250 to 700°C, for example 300 to 550°C, preferably 350 to 450°C, especially 400 to 450°C.

[0073] The hydrotreating unit may operate at a pressure of from 1.0 to 100 bar, for example from 20 to 100 bar, especially from 20 to 50 bar.

[0074] The residence time in the hydrotreating unit is 0.2 to 10 hours, preferably 5 to 10 hours.

[0075] Liquid hour space velocity is 0.1~1 hour -1 The time may be 0.1 to 0.2 hours, preferably 0.1 to 0.2 hours.

[0076] As mentioned above, an important aspect of the present invention is that the pyrolysis oil can be transferred to the hydrotreating unit without a separation step, i.e., without separating the fluid components into gaseous and liquid components. Moreover, it is preferable if the temperature and pressure conditions used in both the pyrolysis unit and the hydrotreating unit are substantially similar. Therefore, ideally, there is no need to cool / heat or pressurize / depressurize between these two steps, and the process reduces energy consumption.

[0077] If the hydrotreating unit comprises a series of hydrotreating reactors in series, there must be a direct recycle from at least one of these reactors, for example, the first or last reactor in the series, typically the last reactor. It is possible to provide a recycle from one or more hydrotreating reactors. Alternatively, the recycle does not originate from the last reactor in the series, and the last reactor is used only to increase the quality of the fraction going further downstream in the process, for example, to a steam cracker, since the fraction recycled to the pyrolysis reactor does not need to be of the same quality. The advantage of this configuration is that the size and investment of the hydrotreating unit can be reduced, since the fraction recycled to pyrolysis does not need to be polished.

[0078] It is preferred if the temperatures in the pyrolysis reactor and hydrotreating unit are similar, i.e., within 300°C of each other, preferably within 200°C of each other, and especially within 100°C of each other. Typically, the temperature in the pyrolysis reactor is 100-150°C higher than the temperature in the hydrotreating unit.

[0079] It is preferred if the pressures in the pyrolysis reactor and the hydrotreating unit are within 25 bar of each other, for example within 20 bar of each other, especially within 10 bar of each other, and most especially within 5 bar of each other. Ideally, the pressure conditions are the same in both the pyrolysis reactor and the hydrotreating unit.

[0080] If there is a difference, it is preferred that the pressure in the hydroprocessing unit is higher and the temperature in the pyrolysis reactor is higher.

[0081] The ability to transfer components directly from the pyrolysis reactor to the hydroprocessing unit is energy efficient because there is no need to completely cool, depressurize, reheat, and repressurize, e.g., below 250°C. The pyrolysis oil can be at or near the appropriate temperature and pressure for the hydroprocessing unit, and therefore the process of the present invention reduces energy usage. Even if some pressure and temperature changes are required between the pyrolysis reactor and the hydroprocessing reactor, the fact that these are reduced compared to conventional operation results in a reduction in energy usage.

[0082] The hydrotreating unit is preferably operated continuously.

[0083] A portion of the hydrotreated pyrolysis oil formed during the hydrotreating step is recycled directly to the pyrolysis reactor, therefore, it is not necessary to remove any components from the hydrotreated pyrolysis oil stream before it is recycled.

[0084] The amount of hydrotreated pyrolysis oil recycled to the pyrolysis reactor can vary. However, typically, the pyrolysis reactor is fed with more recycle by weight than the MPW feed. In one embodiment, the present invention requires directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor, wherein the weight ratio of the hydrotreated pyrolysis oil recycled to the pyrolysis reactor to the mixed plastic waste fed to the pyrolysis reactor is 10:1 to 1:1, preferably 3:1 to 5:1.

[0085] Thus, if there is 1000 kg / h of recycled hydrotreated pyrolysis oil fed to the pyrolysis reactor, the amount of MPW fed to the pyrolysis reactor can be 100-1000 kg / h, preferably 300-500 kg / h.

[0086] It can be envisaged that the recycled hydrotreated pyrolysis oil acts as a kind of solvent in the pyrolysis unit.

[0087] The hydrotreated pyrolysis oil that is not recycled can be removed from the hydrotreating unit and fractionated, as is known. Therefore, the hydrotreated pyrolysis oil can be removed and transferred to a separation unit. The hydrotreated pyrolysis oil can be subjected to a steam stripping reaction to remove any water-soluble impurities, and the resulting sour water can be removed.

[0088] Therefore, the hydrotreated pyrolysis oil can be cooled and depressurized to form a light fraction, a middle fraction, and a heavy fraction. The hydrotreated pyrolysis oil may also contain some unreacted hydrogen, which can be separated and recycled to the hydrotreating unit.

[0089] The light fraction typically contains hydrocarbon compounds with a boiling point below 200° C. The middle fraction typically contains hydrocarbon compounds with a boiling point in the range of 200-360° C. The heavy fraction typically contains hydrocarbon compounds with a boiling point above 360° C.

[0090] Alternatively, the lights fraction may comprise hydrocarbons, e.g., primarily C4 to C12, the middle fraction may comprise hydrocarbons, e.g., primarily C10 to C24, and the heavy fraction may comprise hydrocarbons, e.g., primarily C20 and above.

[0091] The hydrotreated pyrolysis oil can be separated into multiple fractions, for example, three fractions, based on the boiling points of the fractions described above. Ideally, the light fraction is collected overhead and the heavy fraction is removed from the base.

[0092] Any fraction of the hydrotreated pyrolysis oil may be sent to a steam cracker for further cracking, but ideally it is the middle fraction that is steam cracked.

[0093] The components present in the hydrotreated pyrolysis oil are typically saturated at this point and can be easily cracked. In the steam cracker, saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the primary and conventional industrial process for producing lighter alkenes, including ethylene and propylene.

[0094] The steam cracker uses steam in a steam cracking furnace to produce lighter hydrocarbons. Typically, the reaction temperature is very high, about 850°C. Any hydrogen that is discharged can be used in the hydrotreating reaction in the hydrotreating unit. The steam cracker can be operated as is well known in the art.

[0095] The heavies fraction obtained in the hydrotreating unit may be recycled to the thermal cracking unit.

[0096] The present invention further relates to an installation suitable for carrying out the method of the present invention, which installation is further defined in relation to the accompanying Figure 1.

[0097] FIG. 1 shows an installation suitable for use in the treatment of mixed plastic waste according to the present invention.

[0098] Mixed plastic waste can be fed to the pyrolysis unit 30 via the sorting unit 10 and the dechlorination unit 20. Any materials removed during the dechlorination step can be sent for scrubbing in the scrubber 25 where lights can be separated.

[0099] Bio-oil or pyrolysis oil from another source can also be fed to the pyrolysis unit. There is also the option that the heavy fraction recovered downstream after separation of the hydrotreated pyrolysis oil can be recycled to the pyrolysis unit.

[0100] The pyrolysis oil formed in the pyrolysis unit can be filtered in a filter 40 to remove any solid components, and the residue can be recovered. The pyrolysis oil can then be transferred directly to a hydrotreating unit 60 without separating the fluid components (i.e., gas and liquid components) of the pyrolysis oil. Hydrogen is supplied to the hydrotreating unit 60 from a hydrogen reservoir via a compressor 76 (not shown).

[0101] The hydrotreated pyrolysis oil formed in the hydrotreating unit can be transferred to a separation unit 70 where the heavies are separated and any lights can be purged. Water may be used in the separation process to remove any water soluble impurities, and thus any sour water formed.

[0102] The residual fluid, hydrotreated pyrolysis oil, can be sent for cracking in a steam cracking (80) process.

[0103] Importantly, there is a direct recycle stream 50 from the hydroprocessing unit 60 to the pyrolysis reactor 30 .

[0104] The installation of the invention therefore has the following essential characteristics: (I) Pyrolysis reactor; (II) Hydrotreating units; (III) a recycle conduit directly connecting the hydrotreating unit to the pyrolysis reactor. It is equipped with Here, the pyrolysis reactor is directly connected to the hydrotreating unit via a conduit, and the conduit may be equipped with a filter.

[0105] Preferably, the facility comprises: (IV) a dechlorination unit in fluid communication with the pyrolysis reactor; (V) a separation unit in fluid communication with said hydrotreating unit; (VI) a steam cracker in fluid communication with said separation unit; (VII) a recycle conduit connecting the separation unit and the pyrolysis reactor. It is equipped with: [Explanation of symbols]

[0106] 10 Sorting Unit 20 Dechlorination Unit 25 Scrubber 30 Pyrolysis Unit 40 filters 50 recirculation 60 Hydrotreating Unit 70 Separation Unit 75 Hydrogen storage via compressor 76 (not shown) 80 Steam Crackers

Claims

1. 1. A method for treating mixed plastic waste, comprising: (I) pyrolyzing the mixed plastic waste in a pyrolysis reactor at a temperature of 250 to 700°C and a pressure of 1.0 to 100 bar to form pyrolysis oil; (II) transferring the pyrolysis oil directly to a hydrotreating unit, optionally through a filter, and subjecting the pyrolysis oil to catalytic hydrotreating in the presence of hydrogen at a temperature of 250-700°C and a pressure of 1.0-100 bar to form a hydrotreated pyrolysis oil; (III) directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor. The method comprising:

2. 1. A method for treating mixed plastic waste, comprising: (I) providing a pyrolysis reactor with a feed comprising mixed plastic waste; (II) pyrolyzing the feed comprising the mixed plastic waste in the pyrolysis reactor at a temperature of 250 to 700°C and a pressure of 1.0 to 100 bar to form a pyrolysis oil; (III) transferring the pyrolysis oil directly to a hydrotreating unit, optionally through a filter, and subjecting the pyrolysis oil to catalytic hydrotreating in the presence of hydrogen at a temperature of 250-700°C and a pressure of 1.0-100 bar to form a hydrotreated pyrolysis oil; (IV) directly recycling a portion of the hydrotreated pyrolysis oil from the hydrotreating unit to the pyrolysis reactor, wherein the weight ratio of the hydrotreated pyrolysis oil recycled to the pyrolysis reactor to the mixed plastic waste fed to the pyrolysis reactor is 10:1 to 1:1, preferably 3:1 to 5:1; The method comprising:

3. 3. The process according to claim 1 or 2, wherein the pyrolysis step (I) is carried out at a pressure of from 2 to 100 bar, preferably from 5 to 50 bar, more preferably from 10 to 25 bar.

4. 4. The process according to any one of claims 1 to 3, wherein the pyrolysis step (I) is carried out at a temperature of at least 400°C.

5. 5. The process according to any one of claims 1 to 4, wherein the hydrotreatment step (II) is carried out at a temperature of at least 300 to 550°C, preferably 350 to 450°C, especially 400 to 450°C.

6. 6. The process according to any one of claims 1 to 5, wherein the hydrotreating step (II) is carried out at a pressure of from 20 to 50 bar.

7. 7. The method according to any one of claims 1 to 6, wherein the mixed plastic waste is subjected to dechlorination before entering the pyrolysis reactor.

8. The method of any one of claims 1 to 7, wherein all fluid components in the pyrolysis reactor are transferred to the hydrotreating unit.

9. 9. The method according to any one of claims 1 to 8, wherein there is no separation of gaseous and liquid components present in the pyrolysis oil between the pyrolysis reactor and the hydrotreating unit.

10. The method of any one of claims 1 to 9, wherein the pyrolysis reactor operates continuously.

11. 11. The method according to any one of claims 1 to 10, wherein the pyrolysis oil is filtered between the pyrolysis reactor and the hydrotreating unit, or the solid components formed during the pyrolysis step (I) are removed from the pyrolysis reactor and are not sent to the hydrotreating unit.

12. 12. The method according to any one of claims 1 to 11, wherein a portion of the hydrotreated pyrolysis oil is removed from the hydrotreatment unit and subjected to separation into fractions based on the boiling points of the hydrotreated pyrolysis oil in a separation unit.

13. 12. The process of claim 11, wherein the highest boiling fraction (heavy fraction) is separated and at least partially recycled to the pyrolysis reactor.

14. 13. The process according to claim 11 or 12, wherein the liquid non-heavy fraction is separated and subjected to steam cracking.

15. The method of any one of claims 1 to 14, wherein hydrogen is recycled from the separation unit to the hydrotreating unit.

16. 16. The method of any one of claims 1 to 15, wherein the only feeds to the hydroprocessing unit are pyrolysis oil and hydrogen.

17. 1. An installation for the treatment of mixed plastic waste, comprising: (I) Pyrolysis reactor; (II) a hydrotreating unit; (III) a recycle conduit directly connecting the hydrotreating unit to the pyrolysis reactor. It is equipped with wherein the pyrolysis reactor is directly connected to the hydrotreating unit via a conduit, and the conduit may be equipped with a filter. The above-mentioned facilities.

18. (IV) a dechlorination unit in fluid communication, e.g., direct fluid communication, with the pyrolysis reactor; (V) a separation unit in fluid communication with the hydrotreating unit; (VI) a steam cracker in fluid communication with said separation unit; (VII) a recycle conduit connecting the separation unit and the pyrolysis reactor.

18. The facility of claim 17, further comprising:

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