Steam cracker setup for conversion of plastic waste into olefins

Abstract

An integrated cracker setup for the production of C2-C4 olefins is disclosed based on the integrated use of renewable feedstock and at least plastic waste feedstock, this latter being converted in a raw gas with high efficiency.

Description

STEAM CRACKER SETUP FOR CONVERSION OF PLASTIC WASTE INTO OLEFINSFIELD OF THE DISCLOSURE

[0001] This disclosure relates to an integrated cracker setup for the production of C2-C4 olefins. More specifically, this disclosure relates to an integrated cracker setup based on fed with renewable and plastic waste feedstock.BACKGROUND OF THE DISCLOSURE

[0002] Crackers plants are a crucial aspect of the petrochemical industry. By traditionally “cracking” fossil fuel-based materials they perform the first step in producing downstream products such as resins and plastics.

[0003] However, the fossil fuel-based feedstocks generate increased concerns with respect to sustainability aspects.

[0004] Accordingly, attempts to use non-fossil cracker feedstocks are evaluated in order to improve circularity and sustainability.

[0005] Chemical recycling for example, in the version plastic-to-feedstock, includes the steps of collecting plastic waste material, followed by heating the plastic waste material to break down the polymers to obtain smaller organic molecules which are then recirculated in the petrochemical industry.

[0006] Typically, the main effluent from the pyrolysis step is a liquid stream, also called pyrolytic oil, which can be subject to a steam cracking step to generate a gaseous fraction composed by C2- C4 olefins. However, the global yields in olefins, particularly ethylene and propylene, in respect of plastic waste feedstock are still at a level of about 35% which is not entirely satisfactory.

[0007] Moreover, since a substantial amount plastic waste is degraded to pyrolytic oil, the steam cracking step would require a consequent high amount of specific energy for producing the requested olefins.

[0008] In view of the above, it would therefore be important to develop a cracker setup able to produce C2-C4 olefins in high yields deriving from non-fossil feedstock.SUMMARY OF THE DISCLOSURE

[0009] In one aspect, the present disclosure provides a steam cracker setup comprising: at least one electrical furnace for depolymerizing polyolefin based plastic waste said furnace operating with an efficiency of at least 70% raw gas based on polyolefin content in plastic waste and at least one furnace for renewable feedstock having a final boiling point (FBP) of less than 550°C and optionally, a hydrogenation unit.

[0010] More specifically, the cracker set-up can comprise: at least one electrical furnace for depolymerizing polyolefin based plastic waste said furnace operating with an efficiency of at least 70% raw gas based on polyolefin content in plastic waste; at least one furnace for renewable feedstock having a final boiling point (FBP) of < 550°C; and at least one electrical furnace for steam cracking feedstock other than plastic waste and renewable feedstock; a quench / fractionation unit receiving the outputs of said furnaces and generating a light hydrocarbon stream and a heavier liquid stream; a cracker backend separation unit receiving the light hydrocarbon stream from the quench / fractionation unit; optionally a hydrogenation unit fed with the heavier liquid stream from the quench / fractionation unit and an output connected with the electrical furnace for steam cracking feedstock other than plastic waste and renewable feedstock; said set-up being characterized by the fact that the raw gas of the plastic waste furnace is sent to the cracker backend separation unit by-passing the quench / fractionation unit.

[0011] According to a specific embodiment, the cracker setup also include a hydrotreating / hydrocracking unit to upgrade heavy cracker residues as well as pyrolysis oil feed (Pyroil, PFO, HVGO etc).

[0012] As mentioned above, in a specific embodiment, the cracker setup also includes at least a further electrical furnace for feedstock other than plastic waste or renewable feedstock such as for example fossil based feedstock like naphtha or natural gas.BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a block flow diagram showing the integrated steam cracker set-up according to the present disclosure.DETAILED DESCRIPTION OF THE DISCLOSURE

[0014] In a particular embodiment, the electrical furnace for the depolymerization of polyolefin based plastic waste is operated at a temperature ranging from 400 to 750°C with a plastic waste feedstock comprising more than 80% wt of polyolefins based on the polymeric content of the plastic waste feedstock.

[0015] Preferably, the plastic waste feedstock is characterized by: (a) a polyolefin content, in particular a total content of polypropylene (PP) and polyethylene (PE) of more than 85 wt.%, more preferably more than 90 wt.%, especially more than 95 wt.% based on the total weight of the polymeric waste material feedstock.

[0016] Preferably, the upper limit of polyolefin content is 99 wt%, more preferably 98 wt% and especially 97 wt% based on the total amount of plastic waste feedstock.

[0017] Furthermore, the total ash content of the plastic waste feedstock is preferably less than 10 wt.%, more preferably less than 5 wt.%, and most preferably less than 3 wt.%, determined as residue after heating the polymeric waste material feedstock at 800 °C for 120 hours in air. Preferably, the plastic waste feedstock is also characterized by (i) a bulk density from 70 to 500 g / 1, preferably from 100 to 450 g / 1 for cases in which the polymeric waste material feedstock is present in shredded form or a bulk density from 300 to 700 g / 1 for cases in which the polymeric waste material feedstock is in pellet form, the bulk density being determined according to DIN 53466, respectively. It has been found that the above mentioned value of bulk density greatly helps to achieve a continue flawless depolymerization process and to prevent blockage of feeding lines and reactor fouling. Furthermore, it also helps to obtain low amounts of residues and an enhanced depolymerization reaction increasing the yield of desired products.

[0018] In a preferred embodiment, the plastic waste feedstock is additionally characterized by: (i) a content of total volatiles (TV), measured as the weight loss of a 10 g sample at 100°C after 2 hours at 200 mbar, of less than 4%, preferably less than 3%.

[0019] In addition to the polyolefin components mentioned above, the polymeric waste material feedstock employed in the process of the present disclosure may include essentially all polymeric materials, in particular those materials formed from synthetic polymers. Non-limiting examplesinclude polyolefins other than PE and PP, such as polybutene- 1 and ethylene-propylene elastomers etc., polystyrene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyamide, polycarbonate, polyurethane, polyester, natural and synthetic rubber, tires, filled polymers, composites and plastic alloys, plastics dissolved in a solvent, etc.

[0020] However, according to the present disclosure which aims at maximizing the production of light gas olefins, the plastic feedstock preferably consists primarily of polyolefins and the nonpolyolefin polymeric materials may be present only in an amount lower than 10%, preferably lower than 5% based on the total amount of plastic waste feedstock.

[0021] As mentioned above, the polymeric waste material feedstock can be composed of one type of polyolefin waste material or may be a mixture of two or more different polymeric waste materials. The embodiment in which the polyolefin waste material is composed entirely by polyethylene (PE) is particularly preferred.

[0022] The polymeric waste material feedstock may be provided in a variety of different forms. In smaller scale operations, the polymeric waste material feedstock may be in the form of a powder. In larger scale operations, the polymeric waste material feedstock may be in the form of pellets, flakes and powders, such as those having a particle size from 1 to 30 mm counting for at least 80wt% of the feedstock (preferably 85%, 90%), preferably from 2 to 20 mm, and more preferably from 2 to 8 mm, or, when in the form of shredded flakes and / or small pieces of film, preferably having a particle size from 1 to 20 mm. In the context of the present disclosure, having a particles size in a defined range means that 90 wt.% of the particles have a particle size which is in the defined range. The particle size may be determined by sieving or by using a Beckman Coulters LSI 3320 laser diffraction particle size analyzer.

[0023] The plastic waste material disclosed above mostly consists of plastic material and is generally named after the type of polymer which forms the predominant component of the polymeric waste material. Preferably, the plastic waste material employed as feedstock in the process of the present disclosure contains more than 50 wt.% of its total weight of the polymeric material, preferably more than 6 wt.% and more preferably more than 70 wt.%. Other components in the polymeric waste material feedstock may, for example, be additives, such as fillers, reinforcing materials, processing aids, plasticizers, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, inks, antioxidants, pigments etc.

[0024] In a specific embodiment, the polymeric waste materials used in the process of the present disclosure preferably comprises polyolefins and polystyrene, such as high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), ethylene- propylene-diene monomer (EPDM), polypropylene (PP), and polystyrene (PS). Particularly preferred are polymeric waste materials comprising a mixture of polyolefins and polystyrene.

[0025] Other non-polyolefin polymeric waste materials, such as polyamide, polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, polyurethane (PU), acrylonitrile-butadiene- styrene (ABS), nylon and fluorinated polymers can also be employed in the process of the present disclosure. If present in the polymeric waste material, those polymers are preferably present in an amount of less than 10% and especially less than 5% of the total weight of the dry weight polymeric waste material feedstock.

[0026] Preferably, the polymeric waste material is essentially free of thermosetting polymers. Essentially free in this regard is intended to denote a content of thermosetting polymers of less than 10 wt.% and even more preferably less than 5 wt.% of the polymeric waste material feedstock.

[0027] The polymeric waste materials used in the process of the present disclosure are preferably selected from the group consisting of single plastic waste, mixed plastics waste, rubber waste. Single plastic waste, single virgin plastic off spec, mixed plastics waste, rubber waste or a mixture thereof are preferred. Single virgin plastic off-spec, mixed plastics waste or a mixture thereof are particularly preferred.

[0028] The polymeric waste material may also contain limited quantities of non-pyrolysable components such as water, glass, stone, metal and the like as contaminants. "Limited quantities" preferably mean an amount of less than 15 wt.%, and more preferably less than 10 wt.% of the total weight of the dry polymeric waste material feedstock.

[0029] The polymeric waste material can optionally be extruded prior to being employed as feedstock in the process of the present disclosure. In some preferred embodiments, the polymeric waste material is pelletized, and the pellets are employed as feedstock in the process of the present disclosure. In other preferred embodiments, the polymeric waste material is employed in a molten state, for example at temperatures from 200°C to 300°C.

[0030] A particularly preferred type of polymeric waste material employed as feedstock in the process of the present disclosure is characterized by the following features:i) A polyolefin content, in particular the content of polypropylene (PP) and / or polyethylene (PE) in the polymeric waste material of more than 80 wt.%, preferably more than 85 wt.%, and more preferably more than 90 wt.%, especially more than 95 wt.% based on the total weight of the polymeric waste material feedstock; ii) The polymeric waste material is a shredded and optionally compacted polymeric waste material in powder, flakes or agglomerate form having a bulk density from 70 to 500 g / 1, preferably from 100 to 450 g / 1, more preferably 200 to 440g / l, especially 250-400 g / 1. or the polymeric waste material is in pellet, form and has a bulk density from 250 to 700 g / 1, the bulk density being determined according to DIN 53466; iii) A total content of volatiles (TV), measured as the weight loss of a 10 g sample at 100 °C and a pressure of 200 mbar after 2 hours of less than 5%, preferably less than 3%, and more preferably less than 2%, especially less than 1%; iv) An amount of polar polymer contaminants in the polymeric waste material of less than 5 wt.%, and more preferably less than 3 wt.%, based on the total weight of the polymeric waste material; v) An amount of cellulose, wood and / or paper in the polymeric waste material of less than 5 wt.%, and more preferably less than 3%, based on the total weight of the polymeric waste material; vi) A total chlorine content of less than 1.0 wt.%, preferably less than 0.5 wt.%, more preferably less than 0.1 wt.%, based on the total weight of the polymeric waste material; vii) A total ash content of the polymeric waste material feedstock of less than 10 wt.%, more preferably less than 5 wt.%, and most preferably less than 3 wt.%, determined as residue after heating the polymeric waste at 800°C for 120 hours in air. In other preferred embodiments, the ash content is from 0.01 to 2 wt.%, preferred from 0.02 to 1.5 wt.%, and more preferred from 0.05 to 1.0 wt.%.

[0031] In a preferred embodiment of the present disclosure, the polymeric waste materials employed as feedstock in the process of the present disclosure is defined by upper limits of minor components, constituents or impurities expressed as percent by weight. The lower limits for the amounts of these components, constituents or impurities in the preferred polymeric waste materials are preferably below the detection limit, or the lower limits are 0.001 wt.% or 0.01 wt.% or 0.1 wt.%, respectively.

[0032] A variety of techniques are known to separate materials in a polymeric waste stream. Moving beds, drums and screens, and air separators are used to differentiate materials by size, weight and density. Advanced sorting of plastic waste by spectroscopy techniques (MIR, NIR [near-infrared]), X-ray or fluorescence spectroscopy deliver high quality plastic waste streams with high polyolefin content.

[0033] Automatic Separation Techniques of waste plastics comprise dry sorting technique, electrostatic sorting technique, mechanical sorting method (involves centrifugal force, specific gravity, elasticity, particle shape, selective shredding and mechanical properties) as well as wet sorting technique (e.g. sink float sorting method) and chemical sorting methods.

[0034] A suitable feedstock to be employed in the process of the present disclosure may be obtained by applying any of the known sorting techniques, as e.g. summarized in B. Ruj et al: Sorting of plastic waste for effective recycling, Int. J. Appl. Sci. Eng. Res 4, 2015, 564-571.

[0035] Depolymerization

[0036] According to the present disclosure the process for the depolymerization of plastic waste material, comprises pyrolyzing the plastic waste material at a temperature preferably ranging from 350 to 750°C, preferably from 420 to 700°C, more preferably from 460 to 680°C and especially from 500 to 680°C. Particularly when the depolymerization is only thermal, the temperature is preferably kept in the range from 500°C to 700°C more preferably in the range from 500 to 600°C.

[0037] The depolymerization process may be only thermal or thermocatalytic.

[0038] If a catalyst is present, it is chosen from those comprising, as the active component, an acidic compound preferably selected from metal oxides, heteropolyacids, mesoporous silica, aluminosilicates catalysts, such as halloysite and kaolinite, and preferably from zeolites optionally modified. Among them, particularly preferred zeolites are synthetic Y-type zeolite and ZSM-5.

[0039] One preferred specific type of catalyst comprises as the active component an acidic compound deposited on a particulate non-porous support with the aid of a coating agent.

[0040] Preferably, the catalyst of the present disclosure is in particulate form. Preference is given to particulate non-porous support selected from the group consisting of sand, glass beads and metal particles. The particulate non-porous support may have any shape such as spherical, cylindrical or any non-homogenous shape. Apart from being particulate, the support employed in the catalyst of the present invention is also non-porous. Non-porous within the meaning of the present disclosure is to be understood as being not permeable to gases, such as air, or liquids such as water. Thesupport, in order to make the catalyst of the present disclosure particularly designed to be mixed with the polymeric waste material undergoing depolymerization, has preferably an average particle size D50 of 0.2 to 20 mm, preferably 0.5 to 10 mm, more preferably 1 to 8, most preferably from 1 to 6 mm determined according to sieve analysis in accordance with ISO 3310-1 / ASTM El l. The test sieve apparatus of Retsch with woven wire mesh sieves (0 125 mm - 20 pm) is an example of usable sieving device.

[0041] Sand is a preferred type of non-porous particulate support, and preferably, has a particle size distribution of:

[0042] The acidic compound of the catalyst of the present disclosure is preferably selected from the group consisting of Al / Si mixed oxides, AI2O3, aluminosilicates, silica and zeolites. Al / Si mixed oxides, which are particularly preferred in the present disclosure, refer to a material comprising a mixture of AI2O3 and SiO2, having a neutral structure.

[0043] Zeolites, which are particularly preferred, as referred to in the present disclosure are understood to be crystalline microporous aluminosilicates which are built up from corner-sharing SiO4- and AIO4- tetrahedrons having the general structure Mn+x / n [AlO2]-x(SiO2)y]+ ZH2O with n being the charge of the cation M, typically an alkaline or alkaline earth metal or hydrogen ion, preferably an ion selected from the group consisting of H+, Na+, Ca2+, K+and Mg2+, and z defining the number of water molecules incorporated into the crystal structure. Zeolites differ from mixed Al / Si oxides by their defined pore structure and ionic character. In particularly preferred embodiments, the zeolite employed as the acidic compound is selected from the group consisting of Zeolite Y, Zeolite Beta, Zeolite A, Zeolite X, Zeolite L and mixtures thereof, especially Zeolite Y and Zeolite Beta. The listed zeolites are well-known and commercially available. Particularly preferred are zeolites wherein the metal ion M is substituted by a hydrogen. Other specific examples for suitable zeolite-type components to be employed in the present disclosure include but are not limited to ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, TS-1, TS-2, SSZ-46, MCM-22, MCM-49, FU-9, PSH-3, ITQ-1, EU-1, NU-10, silicalite- 1 , silicahte-2, boralite-C, boralite-D, BCA, and mixtures thereof.

[0044] In particular preferred embodiments, the acidic compound is an Al / Si mixed oxide. The composition of the Al / Si mixed oxide employed as carrier may be adjusted according to need. However, especially favorable results of the depolymerization are achieved in cases where the acidic compound contains AI2O3 and SiCh in specific amounts. Therefore, in preferred embodiments, the acidic compound contains AI2O3 in an amount from 20 to 99 wt.%, preferably from 30 to 80 wt.%, and especially from 40 to 70 wt.%, based on the total weight of the acidic compound. Further, the acidic compound preferably contains SiCh in an amount from 1 to 80 wt.%, preferably from 20 to 70 wt.%, and especially from 30 to 60 wt.%, based on the total weight of the acidic compound.

[0045] Preferably, the acidic compound contains an excess of AI2O3 with respect to SiCh. Further preferred are embodiments in which the weight ratio of AI2O3 to SiCh in the acidic compound is from 99: 1 to 30:70, preferably from 9: 1 to 3:2, and in particular from 4:1 to 3:2.

[0046] The determination of the SiCh and AI2O3 content of the acidic compound can be carried out by atomic emission spectroscopy using an inductively coupled plasma (ICP-AES).

[0047] The coating agent employed in the catalyst of the present disclosure is preferably selected from the group consisting of oil, inorganic hydrogel or combinations thereof. As inorganic hydrogel, preference is given to silica hydrogel. With regard to oils employed as the coating agent, preference is given to aromatic-free white mineral oil, preferably based on iso-paraffins. In a preferred embodiment, the oil employed has a kinematic viscosity at 20°C of 140 to 180 mm2 / s, preferably 150 to 170 mm2 / s and / or a kinematic viscosity at 40°C of 40 to 80 mm2 / s, preferably 50 to 70 mm2 / s and / or a kinematic viscosity at 100°C of 5 to 15 mm2 / s, preferably 7 to 10 mm2 / s. The kinematic viscosity can be determined according to ISO 3104.

[0048] The preferred amount of coating agent ranges from 1 to 300% preferably from 2 to 150%wt, more preferably from 5 to 100%wt and most preferably 10-80%wt based on amount of acidic compound. For hydrogels, the amount to be employed is referred to the dry weight.

[0049] In a further preferred embodiment, the active compound is comprised in the catalyst of the present disclosure in an amount of 0.5 to 6 wt.%, preferably 2 to 4 wt.%, based on the total weight of the catalyst.

[0050] The catalyst of the present disclosure is preferably obtained by mixing the particulate non- porous support and the coating agent and then adding the acidic compound in the form of a powder to the obtained mixture. The mixture may be optionally heat treated to obtain the catalyst. The heat treatment may, for example, be carried out at a temperature of 100 to 800°C, preferably 150 to 600°C. In a preferred embodiment, the particulate non-porous support is subjected to a drying step before being mixed with the coating agent.

[0051] In a preferred embodiment, the catalyst is obtained by a process comprising the steps of: (a) mixing the particulate non-porous support and the coating agent; and (b) adding the acidic compound in powder form to the mixture of step (a).

[0052] In an especially preferred embodiment, the catalyst is characterized as follows: (a) sand as a particulate non-porous support; (b) an Al / Si mixed oxide or a zeolite as acidic compound; and (c) mineral oil or silica hydrogel as coating agent.

[0053] In addition to the above catalyst component the catalyst package may include also a cocatalysts, for example a clay, component and / or a solid base component for example a metal hydroxide.

[0054] The gaseous effluent from the pyrolysis reactor is then collected and separated into a gaseous and a liquid depolymerization product.

[0055] The collected gaseous fractions may be separated into liquid and gaseous depolymerization products by condensation. Thus, the liquid depolymerization product and the gaseous depolymerization product may be further processed.

[0056] The process of the present disclosure may generate little to no char. Therefore, in preferred embodiments, the residue of the depolymerization process of the present disclosure has a char content of less than 5 wt.%, preferably less than 2 wt.%, based on the total weight of the product.

[0057] The obtained liquid depolymerization product may be further separated. Therefore, the cracker setup preferably further comprise a step of distilling the liquid depolymerization product.

[0058] The process of the present disclosure yields a depolymerization product with a high gaseous content.

[0059] In particular, the amount of gaseous depolymerization product is at least 70% wt of the total polyolefin content in the plastic waste, preferably more than 75%wt, more preferably higher than 80% wt and especially higher than 85%wt of the total polyolefin content in the plastic waste.

[0060] In a particular embodiment, in the said gaseous depolymerization product the amount of C2-C4 olefins is equal to or higher than 50%wt based on the total amount of hydrocarbons. Preferably, the amount of olefinic C2-C4-compounds is equal to or higher than 55% and preferably higher than 60% and especially higher than 65% based on the total amount of hydrocarbons in the gaseous depolymerization product.

[0061] In a specific embodiment, the percentage of ethylene on the total of olefinic C2-C4 compounds, is higher than 28%wt and preferably higher than 30%wt.

[0062] Moreover, the amount of C2-C4 hydrocarbons in the gaseous fraction of the depolymerization product is preferably higher than 80% preferably higher than 85% and especially higher than 90% based on the total amount of hydrocarbons.

[0063] The gaseous product comprising light olefins and light alkanes can be directly transferred to a separation unit in the cracker backend where olefins are separated from the other hydrocarbon components.

[0064] In a preferred embodiment, before being sent to a separation unit, the gaseous product is sent to a cleaning / purification unit for contaminants removal. Such unit which may be comprised of several sections for the removal of contaminants like HC1, HCN, H2S, H2O, NH3, COS, MeCl, MeSH, NOx, etc. A caustic scrubber section is an example of the conventional units usable for this purpose.

[0065] In an alternative embodiment, not represented in Fig. 1, the gaseous stream coming from the cleaning / purification section can be sent to the quench section of the steam cracker.

[0066] Once separated, olefins and the other hydrocarbon components can be subject to different uses. Olefins like ethylene and propylene can be used in polymerization processes and therefore reintroduced in the plastic cycle. Unsaturated C4 hydrocarbons, can be either used in polymerization or subject to a steam cracker step, preferably after having been subject to a hydrogenation step in a hydrogenation unit.

[0067] Saturated hydrocarbons such as ethane, propane and butanes can be sent directly to the additional steam cracking furnace in the conventional way.

[0068] The liquid depolymerization product obtained from the distillation unit can also be sent to an additional steam cracking furnace. However, subjecting the liquid product to a hydrotreating / hydrocracking step for upgrading the pyrolytic oil is especially preferred.

[0069] Plastic Waste Depolymerization Furnace

[0070] The depolymerization process according to the present disclosure can be carried out in a reactor comprising: (a) feeding devices for introducing polymeric waste material and catalyst into the reactor; (b) a pyrolysis device equipped with heating units, gas discharge units and a solid discharge unit; and (c) a condensation unit.

[0071] In a preferred embodiment, the reactor may comprise more than one pyrolysis unit.

[0072] In principle any type of reactor used for pyrolysis can be used provided that heating is generated by the use of electricity. For example screw type, fluidized bed, circulating gas phase with and without catalyst, slurry loop or stirred tank, fixed bed, ebulliated bed reactors.

[0073] It can be for example an agitated vessel with rotating blades or, preferably, a horizontal reactor a screw equipped with a screw for homogenously mixing the polymeric waste material in the pyrolysis device throughout the depolymerization. In this latter case, the residence time of the solids in the pyrolysis device could be well-defined by adjusting the rotational speed of the screw. An example of screw reactor applicable for the present disclosure is described in WO2017 / 173473, herein enclosed for reference, showing a particular type of screw within which a heating fluid flows.

[0074] In such a reactor, the gas discharge units are distributed throughout the pyrolysis device and are provided with an outlet to discharge the gaseous fraction of the depolymerization and an inlet for introducing cleaning gas into the pyrolysis device.

[0075] Preferably, the gas discharge units are equipped with filter membrane to avoid solids to be present in the gaseous fractions after being discharged from the pyrolysis device. The gas discharge units are preferably made of metallic or ceramic grain or fiber materials.

[0076] In another embodiment, the electric furnace working as a depolymerization reactor is of the type described in WO2022 / 136333 the relevant portion of which is herein enclosed by reference. In particular, the heat to the reactor is provided through a circulating molten salt the fusion of which has been obtained by electric heating.

[0077] In a preferred embodiment, the condensation unit comprises several condensers which are preferably operated at different temperatures. The temperatures of the condensers may be set according to the boiling points of the condensates.

[0078] The polymeric waste feedstock and, if employed, the catalyst are introduced into the pyrolysis unit via at least one feeding device and then heated to achieve depolymerization. The gaseous fractions generated during depolymerization are discharged through the outlet of the gasdischarge units and conveyed to the condensation unit for further processing. Any solid residue of the depolymerization is discharged via the solid discharge unit. Cleaning gas for cleaning the gas discharge units and the pyrolysis unit may be introduced through the inlet of the gas discharge units.

[0079] Depolymerization product

[0080] The gaseous fractions generated during pyrolysis are separated into liquid and gaseous depolymerization products, e.g. by condensation.

[0081] The process of the present disclosure yields a depolymerization product of surprising very high selectivity for the gaseous fraction.

[0082] Liquid depolymerization product

[0083] The obtained liquid depolymerization product, especially when the run is carried out in the presence of a catalyst, shows a surprisingly low content of aromatic compounds and in particular a surprisingly low content of polycyclic aromatic compounds and asphaltanes. The liquid depolymerization product obtained by the process of the present disclosure is accordingly characterized by a low content of aromatic and olefinic components as well as a high degree of purity.

[0084] Preferably, the content of aromatic compounds in the obtained liquid depolymerization product is less than 10 mol%, preferably less than 5 mol%, and in particular no more than 3 mol%, the content of aromatic components being measured as contents of aromatic protons in mol% as determined by 1H-NMR -spectroscopy.

[0085] Further, the liquid depolymerization product obtained by the depolymerization process of the present disclosure is characterized by a low content of olefinic compounds. The content of olefinic compounds in the liquid depolymerization product is preferably less than 7 mol%, more preferably less than 5 mol%, even more preferably less than 3 mol%, based on the total number of hydrocarbon protons; the content of olefinic compounds being determined based on the contents of olefinic protons as determined by 1H-NMR -spectroscopy.

[0086] The liquid depolymerization product obtained in the process of the present disclosure has preferably a boiling range from 30 to 550°C, more preferably from 50 to 250°C. By separation techniques such as distillation, the depolymerization product may be separated into hydrocarbon fractionations of different boiling ranges, for example a light naphtha fraction mainly containing Cs and Ce hydrocarbons having a boiling range from 30°C and 130°C, a heavy naphtha fractionmainly containing Ce to C12 hydrocarbons having a boiling range from 130°C to 220°C, a kerosene fraction mainly containing C9 to C17 hydrocarbons having a boiling range from 220°C to 270°C or into other high boiling point fractions such as diesel fuel, fuel oil or hydrowax.

[0087] Preferably, the liquid depolymerization product contains little to no solid residue. In preferred embodiments, the content of residues of the liquid depolymerization product upon evaporation, determined according to ASTM D381, is no more than 5 ppm (w).

[0088] Gaseous depolymerization product

[0089] The gaseous depolymerization product obtained shows a surprisingly low content of low molecular hydrocarbons such as methane or ethane. Rather, it was surprisingly found that the gaseous depolymerization product contained unusually high amounts of higher olefins such as ethylene, propylene, and butenes which are commonly desired for polyolefin production.

[0090] As mentioned above, the amount of olefinic C2-C4-compounds is preferably equal to or higher than 55% and preferably higher than 60% and especially higher than 65% based on the total amount of hydrocarbons in the gaseous depolymerization product. Accordingly, the gaseous depolymerization product obtained by the process of the present disclosure is characterized by a high content of any of ethylene, propylene, and butenes and also by a low content of saturated low molecular hydrocarbons, in particular hydrocarbons of the general formula CnH2n+2 wherein n is a real number ranging from 1 to 4.

[0091] In a preferred embodiment, the gaseous depolymerization product of the process of the present disclosure is characterized by a content of CO of at most 2 wt.%, preferably at most 1 wt.%, more preferably at most 3 wt.%, most preferably at most 2 wt.%, especially at most 0.1 -0.5 wt.%, based on the total weight of the gaseous depolymerization product after step (e) of the process of the present disclosure.

[0092] In a preferred embodiment, the gaseous depolymerization product of the process of the present disclosure is characterized by a content of CO2 of at most 5 wt.%, preferably at most 3 wt.%, more preferably at most 2 wt.%, based on the total weight of the gaseous depolymerization product after step (e) of the process of the present disclosure

[0093] As already explained, the gaseous fraction could thus be directly used as feedstock for further processing in a cracker downstream, e.g. a raw gas compressor to obtain purified monomer streams, and thereafter for the subsequent production of polymers, allowing bypassing the highly energy consuming stream cracking ovens usually required while at the same time reducing theoutput of CO2. In particular, with the process of the present disclosure, the global yield of C2 / C3 olefins can range from 60 to 70% wt based on the amount of plastic waste feedstock.

[0094] Renewable feedstock Furnace

[0095] The furnace working with the renewable feedstock can be one of those customarily used in the art. The reactor can be the same as that used for the plastic waste furnace, thus for example, also in this case a reactor such as the one disclosed in WO2017 / 173473 can be used.

[0096] In terms of operation, it can be operated in such a way that bio naptha and / or bio diesel are the desired product. As shown in Fig. 1, the liquid output products of this furnace may be merged with the liquid outputs of other furnaces and sent to a fractionation stage. After that the pyrolysis fuel oil fraction (PFO) may be subject to a hydrotreating / hydrocracking stage and then reintroduced into the a conventional naphta furnace where they can be converted into lighter products including olefins.

[0097] The renewable feedstock for the renewable feedstock furnace comes preferably from biomass and may preferably include oils and fats of either or both animal and vegetable origin. Oils and fats may include rapeseed oil, palm oil, palm kernel oil, olive oil, soybean oil, sesame oil, castor oil, jatropha oil, corn oil and other vegetable oils, terpenes, fish oil, pork fat, and beef tallow. Oils and fats collected from certain types of algae such as animal fats and the like, and mixtures thereof can be used. Moreover, waste cooking oils, such as tempura oil, can also be used. Oils and fats such as lard and beef tallow that solidify at room temperature may be melted and liquefied by preheating, so that the oils and fats can be either liquid or solid.

[0098] Although various methods, including transesterifications, of producing biofuels are available, the furnace will preferably operate according to either hydrotreatment or according to a catalyst assisted thermal cracking process.

[0099] The hydrotreating method is a method that applies hydrotreating under high pressure such as 10 MPa. The oxygen in the raw material fat is mainly removed as water, and a unsaturated oil- derived unsaturated bond is saturated to obtain a hydrocarbon oil having a boiling point range of light oil.

[0100] In the catalyst assisted cracking various options are possible. For example, fluidized catalytic cracking apparatus having a reaction zone, a separation zone, a stripping zone and a regeneration zone can be used, and a feedstock containing biomass is added in a reaction zone having an outlet temperature of 480 to 540 °C. In this method, a solid acid catalyst such as ultra-stable Y-type zeolite or silica alumina can be used. In the alternative, using a solid acid catalyst heated to a temperature range of 350 to 450 ° C. allows in a reaction vessel, to use liquid oil which, upon contact with the solid acid catalyst, causes removal of the oxygen-containing components from the oil and the catalytic cracking for the generation of a hydrocarbon mixture mainly composed of olefins and paraffins having 9 to 24 carbon atoms having a final boiling point (FBP) of less than 550°C, preferably less than 450°C, more preferably less than 350°C, even more preferably lower than 300°C and especially lower than 250°C.

[0101] In a preferred aspect, use is made of the decarboxylation / decomposition catalyst described in WO2010050186A1 the relevant part of which is herein included for reference. The catalysts therein disclosed and used are able to crack and decompose fats and oils to produce mainly Cs-C24 hydrocarbons.

[0102] It will be apparent to the skilled in the art that the cracker setup of the present disclosure is able to produce olefins, in particular ethylene and propylene, in very high yields and using a non-fossil feedstock which increases the sustainability of the process.

[0103] As mentioned above, the integrated cracker setup also includes at least a further electrical furnace for feedstock other than plastic waste such as for example fossil based feedstock like naptha or natural gas. With the presence of this further furnace(s), working in a conventional way, the integrated cracker setup is well equipped to treat any type of feedstock thus increasing versatility while, at the same time, combining it with increased sustainability and circularity.

[0104] With reference to the Fig. 1, it can be seen that the plastic waste fed to furnace is coming from a preliminary stage of sorting, washing and pretreatment, such as grinding. These operation can be performed in the same unit which can be placed in the same steam cracker plant site or elsewhere.

[0105] The steam cracker can be equipped several furnaces with dedicated feed. In addition to the plastic waste and the renewable feedstock furnaces, more conventional furnaces for fossil based feedstock such as naphtha and LNG / Butane / propane are present. Also, a recycle gas furnace is present receiving the heavier portion of the cracker backend separation unit.

[0106] All the liquid outputs of said furnaces are directed to a quench / fractionation unit from which two streams are generated: a lighter hydrocarbon stream conveyed to the backend separation unit and a heavier liquid stream (PFO) which, after being subject to a hydrotreating / cracking purification step, is reintroduced into the naphtha furnace.

[0107] In addition to the liquid output, the plastic waste furnace generates the gaseous stream (raw gas) which after having passed the adsorbent columns such as Selexsorb for removing heteroatomic impurities, Cl-guard for removing halogens, and Si-guard for removing silicon compounds. Optionally, the raw gas is also directed to a caustic scrubber for removing acidic components thereby becoming a clean gas stream entering the cracker backend separation unit. As said, this latter unit generates olefins and other products that can readily be used for specific purposes such as polymerization of olefins. A part of the separated products is instead reintroduced into the recycle gas furnace, optionally after a step of hydrogenation.

[0108] Finally, the cracker set-up is also equipped with a system for dislodging, treat and dispose of the solid carbonaceous product (Char) produced in the plastic waste furnace.

[0109] The present disclosure will be explained in more detail with reference to the examples provided below.EXAMPLES

[0110] The following analytical methods were employed:1) GC MS was used for liquid and gas analysis.2) Char residue was determined according to mass balance after decoking the residues of the reactor at 800 °C.3) Liquid contents were characterized using simulated distillation (SimDist) analysis according to ASTM D 7213 : 2012. Final boiling point (FBP), boiling temperature at 50% and initial boiling point (IBP) are taken from SimDist.4) The total content of unsaturated components in the liquid condensates were characterized via Bromine number determination using a 848 Titrino Plus (Metrohm AG, Herisau, Switzerland) equipped with an double PT- wire electrode which has integrated a PT1000 temperature sensor, and a 10 ml buret in accordance with ASTM DI 159-01 as described in Metrohm Application Bulletin 177 / 5e, December 2018. The Bromine number (BrNo.) represents the amount of bromine in grams absorbed by 100 grams of a sample.5) 1H-NMR analysis was conducted by dissolving a sample of the liquid condensate in CDC13 and characterizing the sample using proton NMR spectroscopy. Aromatic, olefinic and aliphatic protons were assigned according to the chemical shifts summarized in Table 1 :Table 1 - Integral Regions in 1H-NMR spectroscopy

[0111] The listed types of olefinic protons are assumed to correspond to the following structures:

[0112] The amount of aromatic, olefinic and aliphatic protons may be determined based on the assigned peak integrals according to the following equations:Mol% Aromatic Protons = [(Ii + 12) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + I9)] %Mol% Olefinic Protons Type 1 = [(I4 + 17) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + Is>)] %Mol % Olefinic Protons Type 2 = [(I3 + Is) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + Is>)] %Mol % Olefinic Protons Type 3 = [(le) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + Is>)] %Mol % Olefinic Protons Type 4 = [(Is) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + Is>)] %Mol% Paraffinic Protons = [(I9) / (Ii + 12 + 13 + 14 + Is + le + 17+ Is + I9)] %6) The water content of the catalyst was determined using a Sartorius MA45 (Sartorius AG, Goettingen, Germany) on a sample of 0.5 to 1 g at 180 °C.7) For the determination of a pH value of the hydrodepolymerization products, by extraction of a liquid sample of the hydrodepolymerization product was extracted with water in a volume ratio water: sample of 1 :5 and the pH value of the aqueous solution was measured.8) Properties of the employed organic waste material feedstock were determined as follows:

[0113] As the composition of the organic waste material may vary, samples from 20 to 100 g of the polymeric waste were milled and analyzed. Alternatively, a pelletized sample of the polymeric waste was analyzed. The following methods are used: i) Total Volatiles (TV) were measured as the weight loss of a 10 g sample at 100 °C and after 2 hours at 200 mbar. ii) Water content was determined by Karl-Fischer titration using an apparatus from Metrohm 915 KF Ti-Touch equipped with a PT100 indicator electrode for volumetric KF titration according to Metrohm Application Bulletin 77 / 3e in compliance with ASTM E203. iii) IR-Spectroscopy was used for a qualitative identification of various polymers (PP, PE, PS, PA, PET, PU, Polyester) and additives such as CaCCh. iv) Standard elemental analysis was used for determination of wt.% of H, C, N (DIN 51732: 2014-07) and S (tube furnace, ELTRA GmbH, Haan, Germany, DIN 51724-3: 2012-07). v) 1 H-NMR was used for determining the composition of polymers soluble in solvents adequate for recording a 1H-NMR spectrum: PE / PP balance (copolymers are also included), PET, PS. vi) Ash Content analysis of plastics was determined at 800 °C according to DIN EN ISO 3451-1 (2019-05). vii) Bulk density of the polymer waste was determined according to DIN 53466. viii) Corrosivity was determined as the pH value of an aqueous solution after a contact time of 3 h (5 g sample in 50 ml distilled water) ix) Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used for quantitative element determination (total chlorine content, content of Si or metals) x) The ash content of a liquid feedstock such as pyrolysis oil, is measured according to ASTM D482-19.

[0114] Feedstock:

[0115] Some of the following organic waste materials were employed as feedstocks: A: Pelletized agricultural and industrial packaging film.

[0116] The properties of the feedstocks averaged on analysis of three samples are summarized in Table 2.Table 2:*) Other content includes inorganic, polymer or organic contaminants and volatile components Ash: ash contentTV : total volatilesBD: bulk densityCl: total chlorine contentPE: polyethylene contentPP: polypropylene contentPET: content of polyethylene terephthalatePS: polystyrene contentPA: polyamide contentOther cont.: content of other contaminants

[0117] In the following examples it is illustrated plastic waste thermal depolymerization in an electrical furnace. It will be apparent that the high amount of gaseous product makes it efficient its separation into individual components in the cracker backend.

[0118] Depolymerization

[0119] The feedstock was introduced into a reactor device equipped with electrical heating units, gas discharge units, solid discharge unit; a condensation device and a screw for homogenously mixing the reactor content during depolymerization. Conditions of the depolymerization conducted are summarized in Table 3. The obtained gaseous fractions were further separated into liquid and gaseous depolymerization products by condensation. The amounts of the obtained fractions are also given in Table 3.

[0120] Table 3: Process parameter and mass balance(a)Amount missing to 100% is due to losses; (b) high amount of waxes flouting in an inhomogeneous liquid * Liquid is the combination of all fractions, may contain some waxy solid particles and agglomerates which disappear upon heating to >50 °C

[0121] The above data show that the catalysts of the present disclosure produce high amounts of gaseous depolymerization products and that are able to maintain good performances even when the feedstock is added with heterogeneous material. The results of the analysis of the gaseous depolymerization product are summarized in Table 4.

[0122] Table 4: mass balance of the gaseous depolymerization productHC: HydrocarbonsOlefins: sum of ethylene, propylene and butenesOlefins / HC: percentage of all olefins over total hydrocarbons

[0123] As can be seen from Table 4, the process of the present disclosure yielded gaseous depolymerization products with high amounts of monomers useful as feedstock for polymerizationafter purification. Any saturated gaseous hydrocarbons can be processed in the usual manner back to the steam cracker ovens.

[0124] The following examples illustrate the plastic waste thermocatalytic depolymerization in an electrical furnace. It will be apparent that the high amount of gaseous product makes it efficient its separation into individual components in the cracker backend.

[0125] Feedstock:

[0126] Some of the following organic waste materials were employed as feedstocks: Al : Pelletized agricultural and industrial packaging film.A2) Shredded Multilayer PEX pipe waste with an Aluminum layer (Particle size <20mm)B) Shredded PEX pipe waste with EVOH (Particle size <20mm)C) Shredded PEX pipe waste with an Aluminum layer (Particle size <20mm)D) Shredded monolayer PEX pipe waste (Particle size <20mm)E) Shredded high voltage cable crosslinked waste (Particle size <20mm)F) shredded and pelletized mixed plastic waste from household packaging (comparison) The properties of the feedstocks are summarized in Table 5.Table 5:*) Other content includes inorganic, polymer or organic contaminants and volatile components

[0127] Catalysts used in the examples using a silica hydrogel coating agent were prepared as follows:25.0 kg of sand were placed into a 60 L steel barrel with screw cap and equipped with a Teflon inlay. 500 ml water were added (corresponding to 2.0 wt% with respect to sand) and the drum was placed on a Drum Hoop Mixer and rotated for 1 hour (about 100 rpm). 24.5 kg of the obtained mixture was placed in another drum and 1000 g of a 1:1 milled free-flowing mixtureof silica hydrogel and the acidic compound (corresponding to a 2 wt% loading) and were added. The drum was placed on a drum hoop mixer and rotated for 1 hour (about 100 rpm). At the end of the mixing process a free-flowing catalyst was obtained with an even distribution of the particles of the acidic compound on the surface of the sand particles. The obtained mixture was dried at 120 °C vacuum for 6 h.

[0128] The silica hydrogel was prepared according to the procedure described in EPl 290042, example 1. The solid content of the hydrogel sample was 20 wt%. The D50 of the milled mixture of silica hydrogel and acidic components were between 80-100 pm in accordance with ASTM D4438.

[0129] Table 6 summarizes the catalysts employed with the amount of the acidic compound given in wt.% with respect to sand.Table 6

[0130] Acidic compounds:Zeolyst Beta (CP81 IE-75) commercially available from PQ Corporation, Malvern, PA, USA

[0131] Depolymerization

[0132] The same apparatus described for the previous set of examples was used. Conditions of the depolymerization conducted are summarized in Table 7. The obtained gaseous fractions were further separated into liquid and gaseous depolymerization products by condensation. The amounts of the obtained fractions are also given in Table 7.Table 7: Process parameter and mass balance(a)(a)Amount missing to 100% is due to losses; (b) high amount of waxes flouting in an inhomogeneous liquid+)Liquid is the combination of all fractions, may contain some waxy solid particles and agglomerates which disappear upon heating to >50 °C*

[0133] The above data show that the process of the present disclosure produces high amounts of gaseous depolymerization products and that is able to maintain good performanceseven when the feedstock is added with heterogeneous material. The results of the analysis of the gaseous depolymerization product are summarized in Table 8.Table 8: mass balance of the gaseous depolymerization productCatalyst which was used in three successive runs maintaining good selectivity and then regenerated by heating up to 800 °C in air and sieving out the smaller particles <500 pm (ashes) HC: HydrocarbonsOlefins: sum of ethylene, propylene and butenesOlefins / HC: percentage of all olefins over total hydrocarbons

[0134] As can be seen from Table 8, the process of the present disclosure yielded gaseous depolymerization products with high amounts of monomers useful as feedstock for polymerization after purification.

Claims

CLAIMSWhat is claimed is:

1. A steam cracker setup comprising: at least one electrical furnace for depolymerizing polyolefin based plastic waste said furnace operating with an efficiency of at least 70% raw gas based on polyolefin content in plastic waste; at least one furnace for renewable feedstock having a final boiling point (FBP) of < 550°C; and at least one electrical furnace for steam cracking feedstock other than plastic waste and renewable feedstock; a quench / fractionation unit receiving the outputs of said furnaces and generating a light hydrocarbon stream and a heavier liquid stream; a cracker backend separation unit receiving the light hydrocarbon stream from the quench / fractionation unit; optionally a hydrogenation unit fed with the heavier liquid stream from the quench / fractionation unit and an output connected with the electrical furnace for steam cracking feedstock other than plastic waste and renewable feedstock; said set-up being characterized by the fact that the raw gas of the plastic waste furnace is sent to the cracker backend separation unit by-passing the quench / fractionation unit.

2. The steam cracker setup of claim 1 further comprising a hydrogenation unit for performing hydrotreating / hydrocracking to upgrade liquid depolymerization product (pyrolysis oil) coming from either or both the plastic waste furnace and the renewable feedstock furnace.

3. The steam cracker setup according to any of the preceding claims in which the plastic waste feedstock is characterized by: (a) a polyolefin content, in particular a total content of polypropylene (PP) and polyethylene (PE) of more than 85 wt.% based on the polymeric content of the plastic waste feedstock.4 The steam cracker setup according to any of the preceding claims in which the upper limit of polyolefin content is 99 wt%, more preferably 98 wt% and especially 97 wt% based on the total amount of plastic waste feedstock.

5. The steam cracker setup according to any of the preceding claims in which the polymeric content of the plastic waste feedstock is composed entirely by polyethylene (PE).

6. The steam cracker setup according to any of the preceding claims in which the depolymerization reaction is carried out in the plastic waste furnace at temperatures ranging from ranging from 350 to 750°C, preferably from 420 to 700°C.

7. The steam cracker setup according to any of the preceding claims in which in the plastic waste furnace the depolymerization reaction is thermocatalytic.

8. The steam cracker setup according to claim 7 in which the catalyst is chosen from those comprising, as the active component, an acidic compound preferably selected from metal oxides, heteropolyacids, mesoporous silica, aluminosilicates catalysts and zeolites.

9. The steam cracker setup according to claim 8 in which the catalyst comprises as the active component an acidic compound deposited on a particulate non-porous support with the aid of a coating agent.

10. The steam cracker setup according to any of the preceding claims in which the plastic waste furnace operates with an efficiency of more than 75%wt, more preferably higher than 80%wt in raw gas production based on polyolefin content in plastic waste.

11. The steam cracker setup according to claim 10 in which in the raw gas depolymerization product, the amount of C2-C4 olefins is equal to or higher than 50% wt based on the total amount of hydrocarbons.

12. The steam cracker setup according to claim 11 in which content of CO2 is of at most 5 wt.%, preferably at most 3 wt.%, more preferably at most 2 wt.%, based on the total weight of the raw gaseous depolymerization product.

13. The steam cracker setup according to claim 1 in which the raw gas before being sent to the cracker backend separation unit is sent to a cleaning / purification unit for contaminants removal.

14. The steam cracker setup according to claim 13 in which the raw gas is directed to adsorbent columns such as Selexsorb for removing heteroatomic impurities, Cl-guard for removing halogens, and Si-guard for removing silicon compounds.

15. The steam cracker setup according to one or more of claims 13 and 14 in which the raw gas is directed to a caustic scrubber for removing acidic components.

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